Sustainable Water Use under Changing Land Use, Rainfall Reliability and Water Demands. in the Volta Basin

Transcription

1 ZEF Bonn Sustainable Water Use under Changing Land Use, Rainfall Reliability and Water Demands Partners: in the Volta Basin GLOWA Project financed by: Ministry of Science and Education (BMBF) of the Federal Republic of Germany Bonn University: Center for Development Research (ZEF) Remote Sensing Research Group Institute for Land and Water Management Fraunhofer Institute for Environmental Atmospheric Research (IFU) Institute for Tropical Medicine and Hygiene, Heidelberg University In cooperation with: Council for Scientific and Industrial Research: Savanna Agricultural Research Institute (SARI) Water Research Institute (WRI) University of Ghana, Legon: Remote Sensing Application Unit (RSAU) Population Impact Project (PIP) Institute of Statistical, Social and Economic Research (ISSER) Institut de l'environnement et de Recherche Agricoles (INERA), Burkina Faso

2 GLOWA Volta 1 CONTENTS 1 THE GLOWA VOLTA-PROJECT PROJECT BACKGROUND STRUCTURE OF THE RESEARCH PROJECT 5 2 GLOBAL CHANGE OF THE HYDROLOGICAL CYCLE (GLOBALER WANDEL DES WASSERKREISLAUFES OR GLOWA) PROJECT SETTING REVIEW 9 3 RESEARCH QUESTIONS RESEARCH CLUSTER ATMOSPHERE Preparation of basic version of MM Validation of SVAT-model Research of feedback mechanisms Impact of intensified land use RESEARCH CLUSTER LAND USE CHANGE Land use and natural resources Land use change and socio-economic development Prediction of land use change Vegetation characterization Soil characterisation, surface runoff and infiltration RESEARCH CLUSTER WATER USE Runoff and hydraulic routing Integrated economic-hydrological optimisation Health and water Communal and household water supply Institutional analysis 20 4 STATE-OF-THE-ART AND RESEARCH NEEDS RESEARCH CLUSTER ATMOSPHERE Global state-of-the-art Research needs RESEARCH CLUSTER LAND USE CHANGE Subproject L1: Land use and natural resources Subproject L2: Land use change and socio-economic development Subproject L3: Prediction of land use change Subproject L4: Vegetation characterisation Subproject L5: Soil characterisation, surface runoff and infiltration RESEARCH CLUSTER WATER USE Subproject W1: Runoff and hydraulic routing Subproject W2: Integrated economic-hydrological optimisation Subproject W3: Health and water Subproject W4: Communal and household water supply Subproject W5: Institutional analysis 38 5 CONCEPTS AND METHODS RESEARCH CLUSTER ATMOSPHERE Subproject A1: Preparation of basic version of MM Subproject A2: Validation of SVAT-model Subproject A3: Research of feedback mechanisms Subproject A4: Impact of intensified land use RESEARCH CLUSTER LAND USE CHANGE Subproject L1: Land use and natural resources Subproject L2: Land use change and socio-economic development Subproject L3: Prediction of land use change Subproject L4: Vegetation characterisation Subproject L5: Soil characterisation, surface runoff and infiltration 57

3 2 GLOWA Volta 5.3 RESEARCH CLUSTER WATER USE Subproject W1: Runoff and hydraulic routing Subproject W2: Integrated economic-hydrological optimisation Subproject W3: Health and water Subproject W4: Communal and household water supply Subproject W5: Institutional analysis 67 LITERATURE 70 TABLE 1 FIGURES 1-9

4 GLOWA Volta 3 SUSTAINABLE WATER USE UNDER CHANGING LAND USE, RAINFALL RELIABILITY AND WATER DEMANDS IN THE VOLTA BASIN 1 THE GLOWA VOLTA-PROJECT 1.1 Project Background The watershed of the Volta River (Figure 1) is one of the poorest areas of Africa. Despite the presence of some precious mineral resources, average annual income is estimated in the region at US $800 per year. For the majority of the population, rainfed and some irrigated agriculture is the backbone in the largely rural societies and the principle source of income. Population growth rates exceed 3%, placing increasing pressure on land and water resources. Improved agricultural production in the West African savannah depends on the development of (near) surface water resources and their effective use. Such water development programs will have an impact on the availability of downstream water resources, in particular on those of the Volta Reservoir on which the urban population of Ghana depends for power generation. Precipitation in the region is characterised by large variability, as expressed in periodic droughts. Unpredictable rainfall is a major factor in the economic feasibility of hydraulic development schemes, as witnessed by the power shortages which plagued Ghana in Any water resource management strategy will have to be based on a thorough understanding of this variability. Given the dependence of land/atmosphere energy and water (vapour) exchange on land use, shifts in land use patterns will result in changes in weather patterns and rainfall characteristics in time and space. Future changes in the West African weather regimes will be affected by global climate change. There is only limited understanding of the impact of global changes on meso-regions such as West Africa, and even less knowledge of the feed-back of these effects on regional weather determining factors such as land-cover changes and the resulting shifts in evaporation and run-off. This complex feed-back system may have disastrous consequences for the region and may affect the availability of water and the strategy for managing this precious resource. Changes in rainfall characteristics affect the residents of the Sahel. In the past, the grave water deficiency during extensive droughts had ruinous consequences for the population concerned, and partially caused irreversible ecological damages. In 1984, the drought in the Sahel concerned about 250 million people from 22 countries (WMO, 1985).Several hundred thousand people died in consequence of the drought during the years 1972, 1973, 1977 and in the period from 1982 to Additionally millions of people migrated to adjoining areas to save their lives (Druyan, 1989). The large rainfall variability turns West Africa into a region with permanent climatic problems. Given the necessity of a sustainable management of the water resources in the Volta basin, we define the central objective of the proposed GLOWA project as the analysis of the physical and socio-economic determinants of hydrologic cycles, and based on this the development of a scientifically sound decision support system for the assessment, sustainable use and development of water resources in the Volta Basin. Integration of climatic, ecological and socio-economic factors and correlations with respect to the hydrologic cycle is the main scientific challenge. The decision support system (DSS) will provide a comprehensive monitoring and simulation framework enabling decision makers to evaluate the impact of manageable (irrigation, primary

5 4 GLOWA Volta water use, land-use change, power generation, trans-boundary water allocation) and less manageable (climate change, rainfall variability, population pressure) factors on the social, economic, and biological productivity of water resources. Decision makers will be able to weigh alternative development strategies and answer questions like: Is there a reduction in rainfall and an increase in rainfall variability? What would be the economic and ecological consequences of such a tendency? How can the limited available resources be reconciled with the present population increase and which water resource management strategy should be pursued? Which feed-back loops between land use intensification and reduced rainfall have to be expected? What are the returns in terms of productivity and downstream availability of water resources yielded by large scale irrigation schemes along major rivers or hydraulic development of small valleys in the upper reaches? What are the ecological and socio-economic consequences of an increased hydro-power production (helping industries around Accra) and/or an improved agricultural productivity through irrigation in the North (reducing rural poverty)? What would be the impact of dam building in Burkina Faso on Lake Volta? Can win-win management strategies be developed which satisfy both countries? The DSS will take the form of a set of models which can readily interchange information with the correct scale and format, and a shell within which the models can be used. The model will be dynamic, which here means that the relations between variables and the rates of change, may vary over time and space. As such, the model does more than extrapolate present trends: it captures the functional relationships between different variables. For technical reasons, it will not be a fully interactive model because to run one climate scenario takes about six months. Instead, a limited set of climate scenarios will be made available on the basis of which the less computationally intensive land use and water use models can run in a more interactive mode. As will be explained in more detail below, not every variable of interest is endogenous to the model set. Technological and institutional development will only partially be explained from within the models. As a first step towards full decision support, the model will be run twice, simulating a period of twenty years. The first run will represent a "business as usual" scenario in which no active measures are taken to improve the productive use of water resources. The second run will simulate an economically optimal use of the water resources with developed irrigation, hydropower, industrial and domestic water use sectors giving the highest overall returns to society. The gaps between the "business as usual" and economically optimal runs will clearly show where investments in new technologies (most likely irrigation projects) and changes in institutional arrangements are most needed. Once the DSS is fully functional, it will be able to calculate the impacts of new technology and institutional policies. Most of the changes in the region affecting the availability of water, such as land conversion, shifts in land use, and developments in infrastructure are related to economic development, population dynamics, migration, education, public health, security and governance. Some of these factors can be reasonably well predicted (e.g. population) but are not easily influenced, others are subject to policy and management decisions. The key of this research project is to identify and quantify the interactions between the various sectors of the society and their impact on the environment and vice versa.

6 GLOWA Volta 5 Shifts in land use due to reservoirs, irrigation systems, agricultural cultivation or technical infrastructure modifies the albedo, the emissivity, roughness lengths, and soil parameters. The thus modified evapotranspiration as well as the modified flows of the sensible and potential heat will affect the atmospheric properties over the Volta Basin. Predictions, however, can only be made, if the complex hydrological system and the complex, non-linear interaction between the soil and the atmosphere in particular are understood. So far, no database is available which would allow calculation of the impact of land use on the precipitation characteristics and on the local climate in the Volta basin. Suitable models for deriving the changes in land use patterns from socio-economic characteristics are lacking as well. Both aspects belong to the basic issues of this proposal. The Volta Project will require between 6 and 9 years to deliver a workable DSS that has been adequately tested. The current project phase covers the first three years of this project and concentrates on: Project establishment and infra-structural arrangement for on-site research Field work phase of the first set of PhD. students (13) as well as the permanent staff Integration of socio-economic models and bio-physical models Initial model runs using primary data to the extent possible, and Demonstration, discussions and planning during the two workshops. The project is conceived as an integral component of the GLOWA Project within the Federal Governments program "Research for a Sustainable Environment", sponsored by BMBF. The project is primarily implemented by scientists at the interdisciplinary orientated Centre for Development Research (ZEF), University of Bonn, and the Fraunhofer-Institute for Atmospheric Environmental Research (IFU), Garmisch-Partenkirchen with expertise in the field of regional climatic modelling. This will be complemented by expertise from the departments "Remote Sensing" and "Land and Water Management", both University of Bonn, and with scientists from the Institute for Tropical Hygiene and Public Health, University of Heidelberg, Tufts University and the International Food Policy Research Institute (IFPRI). With very extensive knowledge of the social and physical environment and experience in landand water research, our partners in Ghana will play a central role in this team. Ghanaian institutes are the primary target group of this project in that they will be the immediate receivers of the technology developed. It would be their task to introduce this tool to policy makers in Ghana so that the population as a whole can derive the benefits from improved water management strategies in the Volta Basin. 1.2 Structure of the Research Project The decision support system depends vitally on the input from many different scientific disciplines and the project is interdisciplinary in nature. The challenge for any interdisciplinary research project is on the one hand the development of a meaningful quantitative exchange of information, and on the other hand a synthesis of the different findings, which goes beyond a mere description of the links between social, economic, agronomic, hydrological and meteorological processes. The means by which the quantitative exchange of information is pursued in this project is a set of dynamic models which capture all first order linkages between relevant processes in atmosphere, soil and water. In fact, it is our main scientific ambition to let the boundaries of our models coincide with physical boundaries of the Volta watershed and not to depend on ad hoc assumptions about population growth, land use change, rainfall variability or hydropower demand. All models will be embedded in one shell which defines common interfaces and access to information pooled in a common database. With the exception of the interfaces, the models are independent enough to be developed, calibrated, verified and tested individually.

7 6 GLOWA Volta The complexity of a dynamic model capturing such a diverse array of processes requires some logistic structuring of the project. A common solution to this is to group scientists according to disciplinary association (for example, earth sciences, bio-agronomy and socio-economy) and to try to connect the different findings in a later, integrative stage. We fear that such an approach may fail, due to structural differences in scale of observations, different acceptable levels of uncertainty, and lack of appreciation of the possibilities and limits of non-familiar disciplines. In order to establish a meaningful dialogue between disciplines, the project is structured in an objective-driven mode where scientists with different backgrounds work towards solving clearly defined goals. In the current project this is addressed by dividing the research activities over three clusters: atmosphere (A1-A4), land use change (L1-L5), and water use (W1-W5) and the definition of interfaces for exchanging information. The research activities within each cluster are undertaken by a small interdisciplinary team. It is expected that by concentrating the information exchange between disciplines in small groups, scientific problems between these disciplines will be addressed and solved at the on-set. Final project integration will take place by connecting the clusters through the well-defined, simply structured interfaces. Each of the three clusters treats one important water redistribution complex, but between the clusters, the levels of manageability differ. The behaviour of the atmosphere can not be managed although it is directly affected by macro-developments world-wide, which are treated as given externalities. Land cover and use, soil surface and vegetation, are managed but usually with the objective to obtain a crop and not with the objective to interfere in the hydrologic cycle. The application of management tools is restricted. Irrigation development, hydro-power dams and groundwater withdrawal are, however, the direct outcome of human intervention in the natural flow of water. Subsequently, the role of the social sciences increases from almost nil in the atmosphere cluster, to supportive in the land use cluster, and to dominant in the water use cluster. Practically, research activities are associated with Ph.D. research and, therefore, fourteen subprojects have been defined, each covering research which can, with good and ample support from senior staff, be finished within three to four years by a graduate student. The sub-projects will be introduced and explained in more detail in the following chapters. The inclusion of each sub-project is the result of scientific needs identified on the basis of the overall objectives. In the remainder, it will not always be possible to stress the interwovenness of all activities, which is why a first qualitative sketch is given here for later reference. The main state variables which have to be modelled over space and time are: 1. Precipitation 2. Actual evapotranspiration (ETa) 3. Agricultural production 4. Land use / land cover 5. Population dynamics (incl. growth and urbanisation) 6. Riverflow 7. Water use 8. Hydroenergy 9. Health 10. Technological development 11. Institutional development Variables 1 through 8 are endogenous variables, which will be modelled within the project. They are a function of other endogenous variables, and give dynamic feedback. Variables 9 through 11 are exogenous, with 9 being an output variable and 10 and 11 input variables. It is

8 GLOWA Volta 7 realised that also the three exogenous variables should ideally be produced and treated as endogenous variables but present state of knowledge inhibits such treatment. Consideration of the exogenous variables is a direct result of the project review (v. chapter 2.2 "Project Review") and gives social meaning to the project as a whole. Each sub-project produces output needed either by other sub-projects as variables for further calculation or as a state variable for the whole model. Figure 2 and Table 1 sketch the general structure and correlations between the sub-projects with each arrow representing a major information input. Two structural features have to be pointed out: 1. The sub-projects A2 "Validation of SVAT-model", A4 "Impact of intensified land-use", L5 "Soil characterisation, surface runoff and infiltration", and L4: "Vegetation characterisation" are closely interrelated. This mirrors the actual complexity of water and energy exchange between the land surface and the atmosphere. The two sub-projects of the research group "Land Use Change" are actually needed to overcome some serious scale problems. In present climate models, all surface parameters are lumped effective parameters, coarsely related to land use- and soil types. The predictive value of such lumped variables is questionable. Therefore land use and soil types (from the sub-projects L1 "Land use and natural resources" and L3 "Prediction of land use change") will be transformed to allow data exchange with sub-project A2 "Validation of SVAT-model". 2. Sub-projects L3 ("Prediction of land use change") and W2 ("Integrated economichydrological optimisation") are central integrative models, processing information from many different sub-projects and producing major state variables. Both sub-projects are interdisciplinary, connecting dynamics from social and physical environment. The main scientific challenges of the project will be met here. The senior staff associated with "Land Use Changes" and "Water Use" will be selected based on previous experience with the issues of these two sub-projects. Figure 2 and Table 1 reflect more detailed features of the project, which may help further reading of the project specification. The flow diagram in figure2 is illustrated by table 1.

9 8 GLOWA Volta 2 GLOBAL CHANGE OF THE HYDROLOGICAL CYCLE (GLOWA) 2.1 Project Setting The importance of water can not be overstated, and concerns are mounting world-wide that this precious resource may be the prime limiting factor in future development. There is little doubt that water resources will be the focus of policy and science efforts in many parts of the world. As much as km 3 of water are yearly deposited on land, corresponding to an average annual rainfall of 850 mm world-wide. However, the distribution of water is far from equitable, varying from 0 to 10m/year dependent on location. In the tropics, annual rainfall and its seasonality is strongly determined by the location with regard to the Hadley cell. At the northern and southern extremes of the Hadley cells, the climates tend to be mono-modal, arid to semi-arid. Towards the equator the climates shift to bi-modal humid and per-humid in the Intertropical Convergence Zone (ITCZ). Few places in the tropics fit this model as well as the African continent. Runoff is also distributed unevenly among the continents, with Asia accounting for 36% of global runoff and South America with 26%, whereas Africa accounts for only 11% and Europe for 8 %. The remainder of the water re-enters the atmosphere via evapotranspiration. Agriculture plays a dominant role in the use of water and is under increasing scrutiny. As other sectors of the economy are gaining in importance, competition for water increases and farming generally loses out. Whereas low-income countries withdraw 91% of their water resources for agricultural use, this fraction declines to 69% in middle-income countries and 39% in highincome countries. Increasingly, governments in West Africa are confronted with situations in which water availability is less predictable and scarcity is jeopardising human health and nutrition. This problematic situation results directly from the enormous increase in population in sub-saharan Africa. The available land and water resources are shared by more people, increasing pressure on the natural resources of the region often to the point of degradation and desertification. The degradation processes not only affect the partitioning and fate of rainwater, but also changes some of the atmospheric conditions that control the weather which in turn may enhance desertification. It is the intimate linkage and feed back system between societal structure, the pressure it exerts on land, its effect on climate and, in turn the effect of climate change on land use patterns and communities ability to cope with these changes, that are the key challenge of the proposed research. The Brundtland Report (UNCED, 1987) recognised this close linkage between natural resource endowment and economic development when it noted: "...not only do many forms of economic development erode the environmental resources upon which they are based, but at the same time environmental degradation can undermine development". In acknowledgement of these cyclical processes, the BMBF founded the framework for the GloWa initiative (Global change of the water cycle). The Centre for Development Research was established in 1997 as a joint action between the Federal Government, the State of Northrhine-Westfalia, and the City of Bonn as a novel, interdisciplinary research institute at the University of Bonn dedicated to environmental, economical, cultural and political issues that affect development, particularly in the tropics. The Centre is part of the overall strategy to create a Forum of International Development in Bonn where national and international institutes related to that task are being concentrated. The centre aims to work in close co-operation with its partners in the developing regions on establishing principles that form the basis for sustainable development and in formulating and implementing policies and programs that will further this goal. ZEF, as a federally funded institute seeks to involve expertise and centres of excellence within Germany, and particularly

10 GLOWA Volta 9 within the research triangle of Aachen, Bonn, and Cologne. Global change and desertification are given high priority within the centre, as these are two processes greatly affecting future development being addressed by the UN institutions based in Bonn. The intricate links between global change, society, and development are given increasing attention world-wide. Global programs such as START, IHDP, LUCC and IPCC have been initiated to address some of these complex dynamics. ZEF, with its multi-disciplinary basis is an active partner in such programs and even houses the IHDP offices. Many of these initiatives are being supported by the Global Environmental Facility (GEF). The concerns about global climate change are also generating national initiatives such as the NASA sponsored Land- Biomass-Atmosphere Program (LBA) in the Brazilian Amazon region. The increasing concerns about water has led UNESCO and the Water Council to declare the year 2000 to be the year for water. The Scientific Council Global Environmental Change of the German Government (WBGU) has dedicated considerable time to the issues surrounding water and made recommendations to the government. The BMBF responded with the GloWa initiative, based on a strategy paper prepared by the National Committee on Global Change Research (NKGCF), which will strengthen the German research in the field of "Research for a Sustainable Environment". ZEF entered the GloWa bidding process with a project based in the Volta Basin in Ghana. The Volta Basin covers the entire spectrum of climatic variation on the North-South gradient. It provides both an excellent comparison as well as contrast with some of the river systems in Europe that are being considered for GloWa. The multi-disciplinary constitution of ZEF provides an opportunity to address some of the primary concerns of the GloWa project. ZEF is able to address the fields of land use and land use change, hydrology, economics, demographics, institutional arrangements and social attitudes towards water and water rights. 2.2 Review The content of this proposal is in principle a worked out version of the previous concept note, with the considerations put forward by the reviewers and GSF/BMBF incorporated. At this point, we would like to point out how the review comments have been included. The review pointed towards two strong aspects of the proposal: the research network and the data availability. The success of the Volta project stands or falls with the network of partners in the target country, Ghana. ZEF has been able to mobilise such a network due to prior involvement with a number of these institutions. During a workshop, attended by 8 representatives of these partner institutes as well as by a potential future partner from Burkina Faso, the programmatic details, distribution of responsibilities and modalities of collaboration were elaborated. The data availability is reflected in the second version of the GloWa-Volta data CD-ROM (attached) which now also includes a consistent spatially distributed rainfall dataset, river flow and lake level data from Ghana, and quantified information about (hydro)power production and demands in rural, industrial and urban sectors. This data collection is a very good starting point and any additional data can only be acquired by new measurements and in situ data-rescue activities. The first point of critique was the need for more analytical work through dynamic modelling instead of the more descriptive GIS-type of work. For each research cluster (atmosphere, land use, water use) one or more dynamic models have now been identified. As physical models, mainly describing movement and redistribution of water, of-the-shelf products have been used which will only need local verification, minor adjustments, and calibration. For atmospheric modelling we have with the latest version of MM5 state-of-the-art with respect to meso- to micro scale weather modelling. The Soil-Vegetation-Atmosphere-Transfer (SVAT) model developed by Chen (Chen, submitted) will be used as the basis for a more extensive model

11 10 GLOWA Volta which can address the particular acute need to calculate the exchange of water and energy between atmosphere and land surface in complex terrain as found in the West African savannah. The data driven IRAS model will be used for routing groundwater and surface water and to model the effects of irrigation schemes and dams. For modelling socio-economic developments there are no "universal" ready-made models, although in some areas important advance is being made. For example, the modelling of land use change following changes in mode of production and population pressure under the LUCC project is showing promise. Below we describe how we hope to capitalise on these developments. Remote sensing and GIS will now more actively and directly support such modelling activities and be no longer end products. The second, very important point of critique concerned the fact that the enormous socioeconomic problems of the region were not clearly addressed. (The presentation and conception was indeed rudimentary in the pre-proposal.) We hope it is clear that as the Centre for Development Research our main concern is indeed the socio-economic development of countries like Ghana and Burkina Faso and that we expect that also a research project sponsored by BMBF will contribute to a sustainable development which reconciles social development and maintenance of the natural resource base. Also the Ghanaian partners were during the workshop very much concerned to ensure that the project was more than a purely academic exercise without relevance to the Ghanaian population. The question was how to include more directly such issues as rural poverty, bad urban living conditions, and poor health. The first issue was that of human health in the Volta Basin. When analysing water issues in West Africa, it seems to be indispensable to look at the water related diseases which were already included in the pre-proposal household water issues. The conceptual difficulty lies in the fact that it is at present state of knowledge difficult to model the complete impact of water on all health related issues and near-impossible to model the impact of health on socioeconomic development, migration, and land use. It was, therefore, decided, to strengthen health related research by including besides a household water component also a malaria subproject, with malaria being the prime example of a water related infectious disease. At the same time it was recognised that health would be an exogenous variable, that is an outcome of water related development and that at best we would be able to sketch (not quantify) general health issues and their feedback on society. Because medical expertise is not available within ZEF, co-operation with Dr. Müller, epidemiologist at Heidelberg University, was established. The household water sub-project W4 "Communal and household water supply" now addresses explicitly drinking water in urban centres. The interaction between land use change and climate and its impact on water resources is, in West Africa, still mainly a diffuse large scale process with the impact of the relatively few large cities being very localised. In its present form, the project addresses three urbanisation issues: 1. the drinking water situation in Accra, Tamale and Ouagadougou, 2. predicting movement of people to the cities from a rural income and demographic point of view, 3. the increasing demand for (hydro)power of people living in urban environments. Most anxieties in Ghana about water seem to focus on the availability of affordable electric energy and any irrigation development will, by the politically influential urban population, be judged through its impact on hydropower. Explicitly mentioned in the review was the need to establish better insight in the interaction between water deficiency and technological change. Technological change has an enormous impact, both in the form of intensification of rainfed agriculture and as extension of irrigated area, but its exact shape (and place) is very difficult to predict. Again, the only way we saw possible to include technological change was by including it as and exogenous variable, be it

12 GLOWA Volta 11 this time an input variable, something to be fed into the other models. Technological change through new crop and cropping systems will enter in the sub-project L3: "Prediction of land use change: Application of the LUCC-Method", mainly by applying diffusion models to the spreading of present trends such as the rise of "new" cash crops (cotton in Burkina Faso, sheabutter in Ghana) and the retreat of sorghum and the advance of maize, the latter mainly through the advances in breeding. With the focus being on water, the extension of irrigated agriculture is of extreme interest and, in a way, the main concern of increased water scarcity in the Volta Basin. This type of technological development is mainly an institutional matter with the actual technologies being readily available in the public domain but impossible to implement without the proper institutional framework. This framework should here be seen as rather broad and to include decision making about investment in water technologies at all levels, from household to government. The sub-project "Institutional Analysis" has been added to the project to explicitly address this issue. The way water based technological change now enters the project is the following: The institutional analysis produces an overview over the backgrounds of the present water supply and distribution policy. This puts certain constraints on the economic optimisation model (Sub-Project W2: "Integrated economic-hydrological optimisation"). These constraints will subsequently be relaxed and the new optimal water use will point towards where institutional improvement and added investments will be most productive. This is then fed back for assessment of institutional feasibility and to actual decision makers. The sub-project "Institutional Analysis" will in this way also design the embedding of the DSS. Strengthening of the institutional and social component within the project was made possible by the arrival of Prof. Dr. Wimmer, who will head the "Development and Cultural Change" department at ZEF. He will backstop the staff member and Ph.D. student who will research the institutional development as well as provide input for predicting rural migration and urbanisation. With regard to the organisation of the project (centre of know-how or interconnected project) we welcome the suggestion by BMBF/GSF of a interconnected project. ZEF and its partners agree with the BMBF assessment that this project does not have as its primary objective the education of scholars but more technology development and transfer.

13 12 GLOWA Volta 3 RESEARCH QUESTIONS 3.1 Research cluster Atmosphere The rainfall pattern in West Africa is characterised by large regional rainfall variation but at the same time also by large seasonal and annual changes in precipitation.(kousky et al., 1998; Long et al., 1998; Gasse, 1998). For the water management in the Volta Basin this is of immense importance. Graph 3 and 5 show historical data on precipitation and river flow for the entire Volta Basin. A slight, although statistically not significant, reduction in precipitation since the seventies can be observed. This reduction is compounded by a natural annual variation. It is obvious how sensitive the amount of river flow, in the Volta Basin considered to be a criterion for economical rainfall use, reacts on slight changes in precipitation. The key question is: Does the regional rainfall pattern change due to an intensified land use (including the water from the dam) as well as due to a global increase of CO 2? This question is of crucial importance regarding the long-term provision of water and energy in the Volta Basin. To study the impact of land use on the rainfall pattern a combined numerical soil-vegetationatmosphere-model is required which could be used for hindcasting real events as well as for performing climate calculations. Feedback mechanisms between the earth surface and the atmosphere can be identified, once it is known where precipitated water originally evaporated in the Volta Basin and where this evaporated water comes down as precipitation. In order to determine the impact of land use on the rainfall pattern, numerical calculations are foreseen. The regional meteorological model MM5v3, a numerical model developed at the National Centre for Atmospheric Research in Boulder (USA), will be used as a first basis. It is based on a non-hydrostatic atmospheric model and coupled to a detailed multiple soil level model (SVAT-Model). In order to achieve the overall objective the following four research goals are defined: Preparation of basic version of MM5 Starting with the elementary version of the MM5v3 Model and its pre-processor programmes a basic version of a linked soil-atmosphere model for West Africa and the Volta Basin will be developed. Comparing measurements and simulation of selected rainfall events will result in finding the optimal parameters which are valid for the region. To enable the exchange of data between models of different research clusters, the development of interfaces is necessary. Details of this research goal will be discussed in the sub-project A1 "Preparation of basic version of MM5v3" Validation of SVAT-model As the SVAT Model of the basic MM5v3 Model does not consider sub grid effects, modifications are required to reflect sub-grid scale effects in the soil-vegetation model which appear in the Volta Basin due to the savannah mosaic. To validate the calculations of the interaction between soil and atmosphere, measurements for the latent and sensitive heat fluxes will be taken. The sensitive heat flux will be measured with a scintillometer, the latent heat flux with a Mk2 Hydra Eddy correlation instrument. Research activities will be discussed under the sub-project A2: "Validation of SVAT Model".

14 GLOWA Volta Research of feedback mechanisms Research of the feedback mechanisms between land use, evapotranspiration and rainfall processes centres around the question where precipitated water originally evaporated in the Volta Basin and where evaporated water finally falls as rain. The interlinked model allows for a spatial and temporal correlation between the evaporated water and the precipitated water. This is possible for the current as well as for the foreseen intensified land use. Research activities will be discussed under the sub-project A3: "Research of feedback mechanisms" Impact of intensified land use The impact of intensified land use on regional climate will be studied by focusing on the question whether (with the help of long term simulations of five to 15 years) changes in the rainfall pattern take place. The sensitivity analysis will include the influence of the Volta Dam as well as the effect of planned reservoirs in Ghana and Burkina Faso. In addition, the effect of double the amount of CO 2 in the atmosphere (envisaged for the middle of the 21 century) on the regional climate will be studied, in order to assess the impact of global climate changes on the water balance in the Volta Basin. The research activities are discussed under the sub-project A4: "Impact of intensified land use". The studies within the third and fourth research goal will use the current as well as the future land use which will result from the future population distribution. These will be identified by the research clusters "Water Use" and "Land Use Change". 3.2 Research cluster Land Use Change Land use and natural resources Land cover is the biophysical state of the earth s surface and immediate subsurface. Land use and land-cover change play a major role in global environmental change, as it leads to significant shifts in the earth-atmosphere interactions. The resultant global climate change may in turn force changes in land use and land cover, a cyclical process that may culminate in desertification and abandonment of land. The social and economic implications of this process have only recently gained recognition. For all its importance to scientists and policy makers confronting the complexities of global environmental change, the dynamics and driving forces behind land use and land-cover change are poorly understood. The long-term character, extent, and rates of change of some land cover and use of land are broadly known, but the level of uncertainty and error remain relatively high (Meyer & Turner 1994). Remote sensing and global positioning systems (GPS) have given rise to the advent of more precise and geographically referenced data on cover and use of land which in turn has created opportunities for improved assessments and analysis. With the aid of these new data, we can now start to unravel the processes which drive the cycle of land use change and resource degradation. The first question to be answered now becomes: To what extent are past and current land cover and land use based on the natural resource endowment in the Volta region? The state-of-the-art and research approach concerning this question will be described under the headings L1 "Land use and natural resources " Land use change and socio-economic development In Sub-Saharan Africa, increased food production, food security, and poverty alleviation will require the intensification of agricultural production (Vlek, 1993). In Ghana, population dynamics, particularly population growth are driving this process in many areas, placing undue

15 14 GLOWA Volta pressure on land and causing rural-urban migration. Increased agricultural and economic development will transform the natural resource base with potentially harmful environmental effects, like soil and water degradation. Expansion of urban areas can also negatively impact upon the natural resource base through a concentration on resource demand and pollution at particular locations. Environmental degradation, in turn, can increase the costs of agricultural production and thus contribute to rural poverty. Thus, there are both complementarities and trade-offs between the goals of poverty alleviation, agricultural and economic growth, and sustainable natural resource use (the so-called 'Critical Triangle'). The challenge will be to develop policies, institutions, and technologies that advance poverty alleviation and agricultural and economic growth while maintaining a sustainable natural resource base in the middle and longer term (Vosti & Reardon, 1997). Technical change plays a key role in the land use/socio-economic development link. Agricultural growth with Green Revolution-type technical change can lead to soil mining and area expansion, for example. This growth might be unsustainable since it has primary and secondary deterioration effects as well as potential health and nutrition effects. Primary environmental effects are deforestation, watershed deterioration, soil erosion, soil fertility decline, and desertification. Secondary effects include drought, floods, and, potentially, climate change (von Braun, 1997). The pressures arising out of the processes of economic development that might induce people to change/intensify agricultural land use and degrade the land are those related to: increases in population, declines in common property resources, property rights (land tenure systems), prices and interest rate changes, and technology transfers. The question to answer is: To what extent can shifts in land use be explained by demographic dynamics and associated infra-structural institutional changes? This is discussed under the subproject headings L2: "Land use change and socio-economic development" Prediction of land use change Land use change can often not be simply explained as the equilibrium result of the present set of driving forces (Foster et al., 1992). The process is driven by developments in three different spheres socio-economic, biophysical, and technological two of which involve adaptive agents and systems that respond to and sometimes anticipate changes in the other spheres. An improved land use change analysis must take into account the path-dependency of system evolution, the possibility of multiple stable states, and multiple trajectories. Current land-cover type may be the result of initial conditions combined with a set of small, essentially random events. Since this combination may lead to very different outcomes, prediction is problematic. The analysis of such differential land use/cover development (LUCC), requires a cross-scale, dynamic and a historical dimension not just of human history, but also of natural history. Global change modellers have only recently begun to deal with this complexity, for instance with regard to biotic feedback (Baskin, 1993). In the GloWa project in Ghana, a forwardlooking modelling approach of the land use/cover change process is needed that integrates these three spheres and can answer questions such as: Where will land-cover and land use change taken place in the future, at what rate and why? What differentiation in land use intensity is likely to take place? What classes of land use are emerging and what role do climate change and water play as a constraint to development of land use systems?

16 GLOWA Volta 15 Modelling the dynamics of land use and land-cover change has been hindered by the large variation in these dynamics across physical and social settings. Global aggregate assessments based on a narrow set of data and broad assumptions generally miss the target for large section of the world, whereas local and regional assessments are too specific to be extrapolated to larger scales. Notorious are the inaccuracies in the estimates of deforestation in the tropics, which lead to widespread abuse of these estimates in accusations and defence of the causal practices. Much work remains to be done to fill these increasingly critical gaps in understanding. The question that thus needs addressing is: Taking the physical and socio-economic information into account, can we identify causal mechanisms in land use/cover change and use these in predicting future change patterns? The research needed to answer this question is in subsequent parts described under the heading L3: "Prediction of land use change" Vegetation characterisation Land use/land cover classification is needed to explain phenomena at the basin scale. In West Africa, each class represents really a mosaic of small patches of grassland, woody grassland, forest, cropped fields, short and long fallow fields, wetlands, and villages. Intensified land use is therefore not a large scale abrupt transition through, for example, reclamation but a gradual shift towards mosaics with less natural terrain, shorter fallow, and more cropped fields. Figure 4 shows NDVI values from Landsat-TM sub-scenes for three villages in the West African savannah zone with different degrees of land use intensity. The image stems from the end of the dry season, right when all arable fields are cleared and sown. All these bare fields have very low NDVI values and show up as brown in the image while vegetation shows up as green and grassy fallow as yellow. The first village is typical for a subsistence farming community and the last village is typical for a very intense land use type where even the wetlands are cropped with irrigated rice during the dry season (bright green linear feature). Although it is possible to classify land use systems on the basis of remote sensing, the interpretation really needs more detailed research at field and village level in order to understand the vegetation characteristics in terms of biomass production (agricultural and natural), soil-nutrient extraction, and, especially, its sensitivity to rainfall variability. In addition, vegetation is the main source of evapotranspiration and vegetation parameters which enter atmosphere models (roughness lengths, root depth over time, etc.) have to be directly linked to land use classes if we are to assess the effect of land use change on local climate. The relatively compounded research question is now: What are, for each major land use class, the vegetation characteristics in terms of biomass production (as a function of rainfall and time) and how does this translate into evapotranspiration parameters such as roughness length and root depth? Under the headings L4: "Vegetation characteristics" will be described what is already known about this question and what remains to be done in order to answer Soil characterisation, surface runoff and infiltration Land is a complex of terrain, soil, vegetation and climate. One of the principal components of the natural resource base is the soil. Soils are not just dead surface materials on which to built or a nutrient containing substrate for plant growth, but the living interface between the parent material, the vegetation cover and the atmosphere an interface in which important ecological processes take place. Soils are therefore am irreplaceable component of terrestrial ecosystems

17 16 GLOWA Volta and an important natural basis for human life. Almost two billion hectares world-wide show signs of soil degradation (Schär et al., 1999), which in turn causes migration and urbanisation. Any effort to capture the effect of global change on changes in the water balance and cycle will need to account for changes in the capacity of the soil to continue to play its role as a water reservoir or conduit, and as substrate to hold and support plant growth. Land use intensification or major changes in land cover may have dramatic consequences regarding this ability of the soil. It will be necessary to capture such changes across a mosaic of land use systems and land covers, in order to estimate effective parameters for these, mostly soil physical parameters. With water being at the core of the project, the focus is on the effects on the redistribution of rainfall at the earth surface: some water may run off over the surface, possibly causing erosion, and the remainder infiltrates. Of the water which infiltrates, some will percolate downwards beyond the reach of plant roots will recharge the groundwater which feeds the rivers. The balance is closed by water taken up from the root zone and transpired by the vegetation. The main challenge is here to aggregate what are usually point measurements to a grid-size of 3 km which is, more or less, the standard resolution for basin-wide analyses throughout the project. Thus, the final question to be addressed in the land use cluster is to develop: A database of effective soil physical parameters, to predict the distribution of rainwater between surface runoff, deep percolation, and water available in the root zone. The steps necessary to arrive at such a database will be described under the subproject heading L5: " Soil Characterisation, Runoff and Infiltration ". 3.3 Research cluster Water Use Enhancing water security and productivity at both the household and community level is a growing challenge in the Volta River Basin. Current development priorities, including household food security and health, poverty alleviation through agricultural and economic growth, and environmental sustainability will be achieved only if adequate water is available for each of these objectives. Yet, these priorities often compete for increasingly scarce water resources, with the demands of rapid urban growth - combined with large electricity demands from hydropower generation and increasing industrialization - impinging on rural water consumption and health, irrigated agriculture, and the maintenance of ecological stability. Efficient (re)use of this liquid resource requires technological and institutional innovation. Figure 5 shows basin-wide rainfall and the water levels of Lake Volta since the construction of the reservoir and hydropower station at Akosombo. In a simple way, it shows how water shortages in the region are actually a combination of variability in river flows and an increase in demand fueled by economic development. In the early days of hydropower production at Akosombo, the demand for hydropower was below the production capacity and the VALCO aluminum factory was the major power customer. The lake level was easily restored even during years with below average rainfall. In the early 1980s, however, three very dry years in a row caused a first power production crisis with the lake level falling below the minimum operational level. Once the lake level had been restored, economic growth resumed placing increasing demands on water uses for hydropower production, particularly from urban consumers and mining operations. This increased demand translated into even larger withdrawals from the lake. This behavior led to a second crisis towards the end of the dry season caused by only one single dry year. In principle, Ghana is well-endowed with water resources, with an average per capita water availability of 3,000 m 3 per year (Sharma et al., 1996). Drier, upstream and more densely populated Burkina Faso is less well off with an availability of 2,500 m³ per capita per year (Sharma et al., 1996). However, water availability varies substantially by region and season. In the White Volta River, for example, flows in the dry season, which lasts six months, account

18 GLOWA Volta 17 for only 11% of total annual flows. In addition, rapid population growth estimated at 3.1%/year - combined with increasing urbanization (more than half of the population is expected to live in urban areas by 2020) and plans for extensive irrigation development will lead to rapidly growing water demands in the next few decades (WRM 1998). At the same time, most of the rural population does not have access to safe drinking water and water-related diseases adversely affect human health and productivity. More recently, water pollution from urban wastes, industrial effluents as well as pollution from mining activities has become a challenge for water policymakers. Nitrate leaching from agricultural chemicals might well affect water quality in the future if plans for increased irrigation development will materialize. The relatively high water quality of the Volta allows at present urban water supplies with minimal treatment costs and a reduction in water quality levels would multiply present supply costs. Within the project, the Water Use Cluster will produce three endogenous model variables (river flow, water use, hydropower) as well as three exogenous variables (human health, technological change and institutional development). There are five major research questions, each of which is associated with one sub-project: River Flows and Hydraulic Routing, Integrated Economic-Hydrologic Optimization, Community and Household Water Use, Water and Health, and Institutional Analysis Runoff and hydraulic routing In 1998, Ghanaian newspapers were filled with stories concerning the power shortages caused by the low water levels behind the Akosombo dam, which were partially caused by less than average precipitation during the 1997 rainy season (New African, 1998). In 1999, on the other hand, torrential rains caused bridges to be washed away in Burkina Faso and Northern Ghana (PANA, 1999). Variability in rainfall clearly causes problems and any comprehensive approach to manage the water resources of the Volta should take the high variability in water availability into account. Figure 3 (see page 8) shows that river flows vary with rainfall and that already small variations in rainfall can cause large fluctuations in river flows. This stresses again the need for accurate rainfall predictions as described under the Atmosphere Cluster. In the Water Use Cluster, the first research question is therefore: What is the water availability over time throughout the Volta River network? This research question is addressed in detail in the chapters on the sub-project "River Flows and Hydraulic Routing." Integrated economic-hydrological optimisation Increasing water demands in all water-using sectors as well as increasing (non-consumptive) uses by the hydropower sector that depend on timely and reliable water availability are fueling increasing competition for water uses across water-using sectors (see also Figure 6). Current water withdrawals in the Volta river basin for agriculture (including livestock) and the domestic and industrial sectors amount to 729 million m 3, but will likely increase to 3,940 million m 3 by The investments needed to achieve Ghana's development goals - increase in irrigated areas by a factor of 20 by 2020; achievement of full urban-industrial water coverage by 2015, and full coverage of the rural population with potable water and electricity by 2020 are enormous. The cost of achieving full urban/industrial coverage alone is estimated at US$ 1,2 billion for the entire country, rural coverage, US$ 1,0 billion by 2020, and the cost of additional irrigation infrastructure by 2020 could reach US$ 3,0 billion. Poverty is pervasive in rural areas as most agricultural production is rainfed, and thus depends on the highly variable rainfall. Input use is very low, with fertilizer application averaging about

19 18 GLOWA Volta 3.6 kg/ha during , compared to the African average of 18,1 kg/ha, and the developedcountry average of 82,5 kg/ha (FAO, 1999). Rainfall insecurity is an important reason for the low fertilizer investment because without proper rainfall, the yield response is not high enough to recuperate investment costs. Fertilizer and labor investment in the region is much higher for irrigated agriculture. In Ghana, currently only a minor share of the agricultural area is irrigated mainly high-value crops, like onions and tomatoes that account for about one percent of national food production. Irrigation development has been identified as an effective means to increase agricultural and economic development and reduce rural poverty. Therefore, irrigation has been projected to expand dramatically from about 4,914 ha in 1995 to 104,590 ha by Livestock production and grazing is an important source of income as well as an activity that relies on large land areas in the Volta River Basin. The livestock population on the Ghanaian side of the Volta River Basin has been estimated at 8,9 million animals in 1995 and 14,6 million animals in Projections indicate that the population might increase to 46 million animals by 2020, with a corresponding livestock density of 276 animals per km 2 up from 88 animals in There is a large and increasing number of smaller surface storage dams in the basin mainly for providing livestock with water. Whereas irrigated agriculture, livestock production, and household water use are the major water-consuming activities, hydropower is the largest non-consumptive water use sector and the main source of energy supply in Ghana. The power is being supplied through the Akosombo dam (833 Megawatt, MW) and the Kpong dam (239 MW). Out of the total power production 7% is exported to Togo, Benin and Côte d'ivoire, 48% is used for domestic supply and 45% is sold to the VALCO Aluminum Company. Ghana also has plans to sell hydropower to Burkina Faso; however, these plans have not been realized so far. In 1990, Ghana earned US$ 118 million through the sales of power, making electricity its fourth largest earner of foreign exchange. Competition is growing among the different power-using sectors. For example, the amount of power consumed by VALCO is more than double the consumption of the mining sector, which is considered to be of higher economic importance for the country. Moreover, the Government of Ghana has ambitious plans to supply the entire country with electricity by 2020 currently few rural areas are supplied with electricity. Another policy aims at recovering the full costs of procuring and delivering energy services to consumers - a goal that has also not been reached so far. To meet the growing demand for electricity, new reservoirs and hydropower stations as well as thermal plants will have to be built. Based on the variety of and increasing pressure on the water resources in the basin, a key question to be answered by this project is: Given both current and future hydrological and institutional constraints to water availability and use, how can water be allocated and used optimally by the various productive sectors? The research to be carried out to answer this question is detailed in the chapters on the subproject W2 on Integrated Economic-Hydrologic Optimisation Health and water The connections between water and health in West Africa are plentiful and complex. Irrigation, for example, is often thought of as a cause of disease, especially malaria. Findings in West Africa, however, suggest that irrigation improves income and thereby the general health status of the population. At the same time, the large incidence of mosquitoes in irrigated areas has forced people to use bednets, with a resulting decline in the incidence of malaria, compared to rainfed areas (MARA, 1998). As a general rule, improved health and economic development go

20 GLOWA Volta 19 hand in hand, but quantified relations between variables like population, water use, income, river flow, land use, rainfall, and health are not known. It is recognised here that health has important feedback effects on essential variables in this project, in particular population, income,and water use. However, due to the complexity of these feedback effects, health is treated as an exogenous variable in the context of this project. In the Volta Basin, major water-related diseases are malaria, diarrhoea, schistosomiasis or bilharzia, and guinea worm. They are endemic in most parts and children are most affected by these diseases. In terms of outpatient clinic attendance, malaria and diarrhoea are the most frequent diseases. Malaria is also the major cause of mortality, especially among children. On average, each attack costs about seven days of work. It is realised that the relation between disease and water in the Volta Basin would warrant a project on its own and that many questions will remain unanswered. We believe, however, that any water-related project in West Africa without a health component would be incomplete given the enormous social significance. The choice made here - to focus on malaria as the major water-related disease and on the availability and use of water at the community and household level reflects this approach. This topic is addressed under the sub-project Water and Health. Many factors affect the choice of malaria control methods in Africa, and these factors are not distributed equally across the continent. Thus accurate information on a local and regional level are required before malaria control activities can be planned and resources allocated properly. As a first step to better disease control, existing but disparate information on the distribution of major malaria vectors, levels of morbidity and mortality, and availability of health services will need to be collected and related to water management and use. Because the project analyses processes at the basin scale, it will then be possible to correlate these health data with waterrelated data at the basin level. The research question to be answered is therefore: What is the distribution of malaria, its vectors, and access to health services and how are these related to surface, irrigation, and drinking water? The chapters on the sub-project Water and Health will detail the research needs as well as details on the methodology to approach this question Communal and household water supply Although the household sector uses only a small share of total water withdrawals in the basin, domestic water use is crucial for the socio-economic development and well-being of the basin population. Water for household usage includes water for drinking, cooking, personal hygiene, laundry, house cleaning and watering of gardens and livestock. The main sources of water for households are piped supply from treated water sources; and untreated piped water from groundwater sources, shallow boreholes, wells, ponds, springs, lakes, rivers, and streams. Household access to water varies between urban and rural areas but also on an intra-urban and interregional scale. Urban water supply is characterised by both indoor and outdoor piping, as well as communal standpipes, wells, private water vending and rainwater collection. The piped water system cannot keep pace with the rapid growth in urban areas leading to wide intra-urban differences in access to water-supply facilities. Both quality and efficiency of urban water supply are low due to a series of institutional constraints. As a result, informal - yet higher priced supply networks have emerged in the cities to supplement the public water supply and to satisfy the growing demand. In rural areas of the basin, many households still rely on traditional water sources such as handdug wells, springs, ponds, and other surface water sources. Investments are currently undertaken to provide rural households with safe groundwater by drilling boreholes. In the central part of the Volta Basin, access to drinking water is a particularly difficult problem because the sedimentary geology shows few well-defined aquifers, generally excluding the

21 20 GLOWA Volta possibility of hand-dug wells and diminishing the success rate of deeper boreholes. In this part of the basin, surface water, usually collected in large ponds to bridge the dry season, is often the only source of water supply. Drinking water quality is therefore highly problematic and known to be related to a series of water-related diseases, like diarrhoea. Throughout the basin, there is a seasonal component to water availability and quality that influences both access and costs of water use. The project will assess how future water demands by the rapidly growing and increasingly urban population will be met while assuring improved access by the poor rural population to water resources for domestic use and agricultural production. The main research question is: What is the nature of availability, access and usage of water resources for urban and rural households and what are the direct and indirect costs of access to water at a specific quality level? The chapters on the sub-project "Community and Household Water Use" describe how this question will be approached Institutional analysis A large number of organisations are involved in water resources management in Ghana. However, inadequate cost recovery measures have contributed to the financial weakness of the major water agencies, the Ghana Water and Sewerage Corporation, the Irrigation Development Authority, and the Volta River Authority. Moreover, the organisations are scattered across various ministries with different levels of authority and little co-operation. The establishment of the Water Resources Commission (WRC) in 1996 as an umbrella organisation will likely facilitate more integrated management of the resource. The WRC is expected to become the knowledge base and co-ordinator for all water-related activities in the country. At the international level, Ghana and Burkina Faso are the main stakeholders in the Volta River Basin. Although there are no open hostilities for water rights and resources at this point, competition for scarcer water resources at the international level might well develop in the future if water is not managed more efficiently in both riparian countries. Burkina Faso announced in 1999 plans to build three additional dams at one of the Volta tributaries, two for hydroelectricity and one to supply the capital city of Ouagadougou with water. This would raise the total active storage of the dams to 149 MCM, or 3,75% of the storage of the Akosombo Dam in Ghana. The Ghanaian Government is concerned that these hydropower projects might reduce the flow of the Volta River and thus negatively affect hydropower production in Ghana, which already experienced serious delivery problems in The final research question of the Water Use Cluster thus is: What are the current institutional rules according to which water is allocated for different uses at the local, national, and international level? Such an analysis is not only necessary to set formal conditions for the optimisation of allocation and use of water but also to establish a basis for the operationalisation of the research results. This research question is further described in the chapters on the sub-project "Institutional Analysis."

22 GLOWA Volta 21 4 STATE-OF-THE-ART AND RESEARCH NEEDS 4.1 Research cluster Atmosphere Global state-of-the-art Global as well as regional reasons could be identified for the high rainfall variability in West Africa. Folland et al. (1986), Druyan (1989) and Rowell et al. (1992) report that there is a correlation between years of drought in the Sahel and temperature anomalies of the sea surfaces (SST, Sea-Surface Temperatures) of the Atlantic and the Indian Ocean. Cook (1999) shows with the help of roughly (approx. 250 km) unravelled GCM (General Circulation Model) 3D simulations, that slight rainfall in the Sahel is related to a strong "African-Easterly-Jet" (AEJ). Its position and strength, depends on the SSTs of the Atlantic and Indian Ocean. Results are primarily due to the formation of a meridian soil moisture and temperature gradient between the Sahara and equatorial Africa. Similar qualitative results were found during the HAPEX- Sahel Experiment (Wai et al., 1997). However, in order to better understand these important results regarding rainfall predictability and variation, detailed soil models are required (Cook, 1999). In West Africa the variation of rainfall is characterised by two additional characteristic circumstances: the so called "Little-Dry-Season" in August and the "Togo-Gap" (Hayward & Oguntoyinbo, 1987; Dickson & Benneh, 1995). The "Little-Dry-Season" is a climatic event characterised by the fact that during the month of August, compared to June, July and September, distinctively less rainfall occurs along the Guinea Coast between Sulima in Sierra Leone and Port Harcourt in Nigeria. It is assumed that the origin of the "Little-Dry-Season" is related to the intra-tropical discontinuity (ITD). The ITD characterises the region where humid air from the Atlantic and dry air from the Sahara come together. West Africa becomes a "weather sensitive" region, as the rainfall pattern depends on the ITD: A slight change of the ITD either due to anthropogenic interference or natural ups and downs may have an enormous impact on the regional rainfall pattern. The "Togo-Gap" is a climatic abnormality in south-eastern Ghana and southern Togo where the mean annual rainfall is significantly less compared to the surrounding areas. There is no convincing explanation for the formation of the "Togo-Gap". Besides coastal topographic effects some explanations given include the SST as well as the destabilising effect of the AEJ on the atmosphere. According to current knowledge, changes in land use in West Africa will result in changes of rainfall patterns. Already Charney (1975) found that a reduction of the vegetation in the Sahel and the related increase of the albedo increases aridity in the Sahel. The influence of land use on precipitation and on the latent and sensitive heat fluxes were demonstrated among others by Chen and Avissar (Chen & Avissar, 1994a; Chen & Avissar 1994b). Findell and Eltahir showed by analysing field data from Illinois (USA) that the water saturation in the soil has a positive correlation with subsequent rainfall (Findell & Eltahir; 1997). Research regarding similar relationship mechanisms in the Volta Basin does not exist. In annex 1 ("MM5") the effect of land use in West Africa on the rainfall pattern is shown using a simple example. As an example for the complexity of the interaction between soil humidity and precipitation, the work carried out by Schär shall be mentioned (Schär et al., 1999). This work shows that for Europe the surplus of rain over humid soils compared to dry soils was not directly related to the evapotranspiration. The surplus rainfall over humid soils rather originated from vapour of atmospheric humidity taken into the area of investigation by advection. The feedback between soil humidity and precipitation is caused by an indirect mechanism where humid soils increase the efficiency of convection processes. The surplus of rain over humid soils would, over dry

23 22 GLOWA Volta soils, simply be transported across the area of interest. The evapotranspiration from regional soil humidity in this case triggers atmospheric humidity, brought from outside the area investigated, to precipitate. The recycling of atmospheric humidity was analysed by Trenberth (1999). Eltahir (1989) and Eltahir and Bras (1996) studied the recycling of rain, i.e. the ratio of local evapotranspiration to local rainfall in Central Sudan. Eltahir and Bras (1994) did this for the Amazon Basin, and Brubaker et al. (1993) for four regions: South and North America, Eurasia and West Africa. Studies regarding the impact of changes in land use on the rainfall recycling ratio are not known. Numeric meteorological models allow a quantitative analysis of the evapotranspiration and precipitation development and the variation of atmospheric humidity. The "Evaporation Tagging Method" used in global GCMs by Koster et al. (1986) and Jouzel et al. (1987) do not only determine rainfall recycling ratio but also provide the possibility to analyse in which regions the rainfall water originally evaporated and in which regions the locally evaporated water precipitates. Druyan and Koster (1989) established that the greatest amount of the July rainfall in the western Sahel comes from the tropical North Atlantic Ocean. The second important rainfall source, contributing almost the same amount, was identified as evapotranspiration from the western Sahel itself. Because of the above mentioned interdependencies we can assume that the soil humidity is an essential factor for the total precipitation in the Volta Basin. By using the information on "isotopic enrichment" it is possible to qualitatively check the simulation results of the "evaporation tagging". In natural water, isotopic heavy molecules H 18 2 O and HD 16 O are found besides the normal water molecules H 16 2 O. The frequency ratio of the different molecules is approximately [H 16 2 O] : [H 18 2 O] : [HD 16 O] 10 6 : 2000 : 320. As the mentioned water categories have different vapour pressure and slightly different diffusion velocities, modification in the isotope frequency ratio occurs during evaporation and condensation. For example, during evaporation from a sufficiently large water reservoir the vapour will be enriched with the heavier molecules. From an isotopic point of view the water vapour is lighter than the original water. The degree of the isotope frequency modification depends on different parameters like temperature and air humidity but also from the previous history. These effects therefore allow to a certain degree a conclusion regarding the meteorological circumstances at the time of air vapour and rainfall formation. (Roedel, 1992). Meso-scale numeric meteorological models like the MM5v3 use the method of finite differences to solve the relevant partial differential equations. The spatial resolution of the simulation is given by the used grid width. This causes difficulties when processes and their describing parameters are given on scales smaller then the grid width. This is specially important for West Africa as the landscape is formed like a mosaic with small patches, each representing different land uses like agricultural fields, fallow, villages and forest (savannah mosaic). In order to consider the subgrid-scale effects of the soil properties in the simulation, it is required to upscale the soil properties of this sample with a real vegetative cover to the grid width of the mesoscale model. The smallest grid width will be approximately 3-10 km, the largest grid width approximately 80 km. Usually, the predominant land use type of one grid element will be considered as the representative one for the grid cell and for the energy and moisture flow calculation at the interface soil-atmosphere (common land use strategy). This common strategy, however, is not appropriate in the case of the savannah mosaic as different types of land use result in different impulse, vapour and heat flows due to different water availability, variation in rainfall, vegetation and soil parameters (Avissar & Pielke, 1989). Several concepts exist which allow to consider in one grid cell the aggregated contribution from all land use types. Firstly, statistical dynamic methods (Wetzel & Chang, 1988; Entekhabi

24 GLOWA Volta 23 & Eagleson, 1989; Avissar, 1991) methods calculating the surface properties average (Dolman, 1992; Lhomme, 1992; Claussen, 1991) and different versions of the mosaic method (Avissar & Pielke, 1989; Leung & Ghan, 1995; Mölders & Raabe, 1996) shall be mentioned and, secondly, explicit sub grid techniques (Seth et al., 1994; Mölders & Raabe, 1996) and mixture techniques (Deardorff, 1978; Sellers et al., 1986; Kramm et al., 1994; Kramm et al., 1996). In this project, explicit sub grid techniques shall be favoured. The precision of the SVAT model can be assessed by comparing simulation results with sensitive and latent heat flow measurements. The latent heat flux can be measured for example with the "Eddy-Correlation Method", whereas the sensitive heat fluxes can be measured with a scintillometer. The "Eddy-Correlation Method" determines the vertical water vapour flow by calculating the fluctuation of the vertical components of the wind velocity w ' and by measuring at the same time with sensors close to the surface the variation ρ ' of the absolute humidity around its average. The evaporation ET is then given as ET = w' ρ v '/ ρw, with ρ w standing for water density. The method is, among others, described by Shuttleworth (Shuttleworth et al., 1997) who used it in a specific area of the Sahel. The scintillometer works with a diode, placed in the focus of a concave mirror, which emits electromagnetic radiation with a peak wave length of approximately 1 µm. The radiation is measured by a receiver placed several hundred meters apart. The receiver consists of an identical mirror where a photo diode placed in the focal point evaluates the signal. With this configuration it is possible to determine the refractive index of the air and with this consequently the sensitive heat flux. Chebouni arrives at values (surface average) for the sensitive heat flux in semi-arid regions with mixed land use types by combining scintillometer measurements with an aggregation approach (Chebouni et al., 1999). The aggregation approach is based on results from Shuttleworth, Raupach, Finnigan and Chebouni and uses for the surface prevailing effective roughness lengths, effective zero point modifications as well as effective shearing stress velocities (Shuttleworth, 1997; Raupach, 1991; Raupach & Finnigan, 1995; Chebouni et al., 1995) Research needs The impact of land use and irrigation but also of technical infrastructure (e.g. dams) on the water budget in the Volta Basin has not yet been studied, neither for selected events nor for climatic relevant periods. In order to study the feedback mechanisms between the surface and the atmosphere a meso-scale, three dimensional atmospheric model linked to a detailed soilvegetation model has to be further developed for the region and subsequently be used. Currently, an operational meso-scale meteorological model for West Africa and the Volta Basin, which gives the possibility to describe the complex interactions between the soil and the atmosphere, does not exist. For our research project the basis for such a model will be the MM5v3. Experiences with a meso-scale model such as the MM5v3 mainly exist for regions in Europe and North America. The successfully used setting of parameters in this model for the mid-latitudes can not be adopted uncritically for the Volta Basin and West Africa due to its proximity to the equator and the resulting reduced Coreolis force, the higher altitude of the tropopause, and the increased relevance of convection. Also for global analysis, which provides the boundary values for the mesoscale model, a detailed study of the data quality is required. In order to validate the soil and boundary layer processes, measurements for the latent and sensitive heat fluxes have to be taken at selected locations. The "Eddy-Correlation Method" and the scintillometer technique will be used for this. As the land use types within the targeted resolution of the model of approximately 3 km x 3 km to 10 km x 10 km do change in the savannah mosaic, more effective parameters have to be found for the model parameters of the SVAT in order to account for the sub-grid scale influences of the mixed land use types. In addition, the applicability of results of other studies on effective parameters of albedo,

25 24 GLOWA Volta roughness lengths and stomata resistance (Raupach, 1995) on the SVAT Model by Chen and Dudhia (1999) has to be studied. While, for example, in case of the albedo the arithmetic mean weighted proportionally by area can be used as an effective value, the stomata resistance should be weighted harmonically (Raupach, 1995; Boulet et al., 1999). Depending on available information regarding the variation of parameters within the grid cell different approaches are possible to determine effective quantities. If, for example, frequency distributions for parameters are available, the expected value for the resulting fluxes, which will be transferred into the atmospheric model, can be calculated by convolution of the function with the frequency distribution of the parameters (e.g.. Famiglietti et al., 1994a; Famiglietti et al., 1994b). Is data on the mean and the variance available, an approximation of the resulting mean fluxes can be calculated with a Taylor-Approximation (Kunstmann & Kinzelbach, 1998). Quantitative figures regarding the rainfall recycling ratio in the Volta Basin are not known. The changes of this ratio due to the intensified land use are also not known. By developing and implementing an "Evaporation-Tagging" module in the mesoscale model, it will be possible to study in detail for West Africa - and specifically for the Volta Basin - from where the rainfall water originates and in which way the proportion of local evapotranspiration in the rainfall will change. An "Evaporation-Tagging" for the region West Africa specifically focussing on the Volta Basin is relevant as 30% of the rainfall in the West Sahel comes from local evaporation (Druyan & Koster, 1989). Due to the high evaporation of the Volta Dam the percentage in the Volta Basin will likely be higher. Whether the water budget of other regions in West Africa is affected by changed land use in the Volta Basin, has to be studied. Furthermore, the question on which spatial and temporal scales a connection between evaporated water and rainfall water exists, has to be addressed and also whether there is a correlation between the spatial patterns of the evaporation region and the rainfall region. In this regard, the role of the Volta Dam with an average surface of approximately km 2 (with an average seasonal fluctuation of approximately km 2 ) is of special interest Results from global climatic models are only to a certain limit meaningful for West Africa as due to their rough resolution of several hundred kilometres they are not able to show the effect of complex orography and land use distribution. Small scale phenomena induced by different terrain properties and surface characteristics influence the climate and the water budget in the region significantly. It is of great importance to clarify whether the rainfall variation is affected due to anthropogenic interference, either due to local changes in the land use or a global CO 2 rise. The complex relations between land use and global warming on the climatic conditions in the Volta Basin can only be understood through numerical simulations. Adequate sensitivity studies have to be carried out to find out whether long term changes in the rainfall pattern are foreseeable if the land use is locally intensified or the atmospheric CO 2 concentration increases as predicted. A high spatial resolution of the results will be required for this to assess whether certain sub-regions run the risk that their water demand is in the long term not covered in a sustainable way by the water supply which is available through surface run off, drainage into the ground water and storage in the upper soil layer.

26 GLOWA Volta Research cluster Land Use Change Subproject L1: Land use and natural resources Global state-of-the-art Land covers and changes in them are sources and sinks for most of the material and energy flows that sustain the biosphere and geosphere, such as the hydrological cycle, the carbon and nitrogen cycles including trace gas emissions (BAHC, 1993). Broad classes of land cover are forests, park landscapes with or without livestock herding, farmlands and urban areas. Because contemporary land cover is changed mostly for human use (Awhitby, 1992), an understanding of land use changes is essential to understanding land-cover change. Land use involves both the manner in which the biophysical attributes of the land are manipulated and the intent underlying that manipulation the purpose for which the land is used. It refers to the specific way in which humans treat vegetation, soil and water for consumptive or productive purposes. Biophysical manipulation can thus be seen as the technical-managerial component influencing land use and land cover. Assessing land use/cover change has been approached in at least three different ways: through field-based case studies of land use, thematic assessments of the patterns (spatial and temporal) of land-cover change, and prognostic, regional and global models of land use change/cover. Unfortunately, estimates generated from case studies are often appended with specific-rich narrative, lacking generalities that can lead to macro-models. Thematic assessments of cover change are considered too labour-intensive, too long on detail, and too short on explanatory power. Prognostic macro-models are criticised for their unrealistic assumptions and simplifications that preclude real-world usefulness, let alone accuracy. These stereotypes are not only unwarranted but miss the critical point that each approach complements, and, if integrated properly, improves the others. Local state-of-the-art and data availability The natural resource endowment of Ghana, documented in existing soil, geomorphologic and climatic maps, provide the basis for the carrying capacity of the land. At different periods over the past 50 years such maps and inventories were undertaken and much of the data lies uncollated in different institutional libraries and documentation centres. Land use studies started in Ghana in the early 1940's but systematic land use surveys began with the establishment of the Soil and Land survey branch of the Department of Agriculture in The initial objective was to identify suitable land for the cultivation of cocoa. A parallel land use survey started in the Upper Region of Ghana with the goal of identifying the land use types and to develop a management system for the control of soil degradation and erosion in this densely populated and intensively cropped area. The result was the development of what used to be called "Land planning areas" in the 1950's. The methodology developed in these studies was ground-based and involved parallel mapping of soils, land cover and land use. Observations and records on soils, land use and vegetation were made at regular intervals (Brammer, 1962). Land use was described in terms of the predominant land rotation cultivation and the estimated intensity of use, related to the frequency and extent of cultivation. A resulting land use map at a scale of 1:2,000,000 was published in 1962 covering the period

27 26 GLOWA Volta The Soil Research Institute was established in 1968 and it carried out routine soil and land use surveys for large river basins and other areas of regional extent, e.g. the Navrongo-Bawku area covering the Upper Region of Ghana (Adu, 1969). The land and water survey of Northern Ghana was also carried out at this time (FAO, 1967). These land use and land cover surveys were compiled with the help of aerial photographs taken in 1960 to support the ground procedures. The classification scheme however, remained the same. Arable land use was classified into (i) Compound farms, (ii) Bush farms and (iii) combined compound and bush farms with the highest land use intensity allocated to compound farms. In the 1970's a large area around the Ghana-Burkina Faso border in the Volta Basin was mapped for soils, geomorphology, land cover and land use using digital LANDSAT MSS (Multi-spectral Scanner) image data and existing aerial photographs. Land use intensity was mapped in terms of the effects of land use on the land cover and the terrain. This mapping was under the onchocerciasis project. A number of soil and land use surveys were carried out more recently. This include the Nasia basin land use survey (Adu, 1995) and other surveys related to specific agricultural development projects. Under the supervision of the Ghanaian Environmental Protection Agency (EPA) a new land suitability map for Ghana is nearing completion by the Soil Research Institute. Other land use studies done within the period confirms the previous findings that land use intensity is higher on compound fields than the bush fields and also higher in Upper East Region than in Northern Ghana e.g., see Fig. 7 (Albert, 1996). Based on the existing soil and climatic maps, the Volta region will be subdivided in ecological zones that may be considered of homogeneous potential in terms of primary production and carrying capacity. This classification and mapping exercise, to be undertaken with our partners from Ghana, will be based on secondary data. Such a map would have to be verified by a field survey, to be conducted once an updated map has been made. Verification will be done in some key locations, particularly around the selected watersheds for hydrological research and using local fly-overs to allow observation from the air. Many years of research, partly with support from GTZ, have further strengthened this secondary database with land use data in Ghana. Many of these studies belong to the grey literature and are accessible to the project through the partnership with Ghanaian Institutions in GloWa. An example is shown in Fig. 7, depicting the greatly different land use intensities (R) observed in 1996 for the three, bio-physically similar northern provinces in Ghana. The highest intensities are found in the Upper Eastern Region (UER), where fallow periods have become rare under the current population pressure. The lowest R-values are found in the Northern Region (NR) where fields are fallow half the time. Moreover, whereas 54% of the farms are compound fields in the UER are intensively cultivated compound fields, 94% of the fields in the NR and 75% in the Upper Western Region (UWR) are bush farms (Albert, 1996). The latest addition in terms of land use data is the detailed, satellite based, land use map developed by the Remote Sensing Application Unit (RSAU) of the University of Ghana at Legon for the Environmental Protection Agency. RSAU is one of the Ghanaian project partners and will make the developed expertise and data available. A description of the new land use map, the methods used, as well as a copy of the map can be found in Appendix II "Land use in the Volta Basin". Land use studies in Burkina Faso are much sparser and there is not yet a complete coverage of the country, let alone a coverage following one standard methodology. At the Cellule de Teledetection of INERA, the Burkina research partner in the project, some small scale local land use change studies have been undertaken for the area Southeast of Bobo-Diolassou based on aerial photographs.

28 GLOWA Volta 27 Research needs Many relatively high-quality land suitability and present land use data are available for the Volta Basin, especially for Ghana. As a first step, these datasets should be expanded to include the complete basin in one consistent database. The land use data should also be extended back in time in order to be able to capture past changes and present trends. Both the spatial and temporal extrapolation needs, point towards automatisation of present classification schemes based on remotely sensed data. Once a complete land use and suitability database is available, the challenge becomes a proper analysis which does more than simply describe discrepancies between suitability and use in a GIS-type manner. The real scientific task at hand is therefore a methodological one because it is recognised that the functional relationship sought here (land use as a function of suitability) can only be a partial explanation of the observed land use change with demography and socioeconomic development forming the remaining explanatory factors Subproject L2: Land use change and socio-economic development Global state-of-the-art Increasingly, land use change is being considered the result of differential development pathways (Pender et al., 1998). Pressures due to spatial and temporal economic and demographic developments are being counteracted by human actions that are in themselves firmly guided by the degrees of freedom that the natural resource base, infra-structural development, markets and human capital permit. Farmers, the principal actors and stakeholders, seek to find the best means of alleviating poverty, and may, under certain conditions, get caught in a spiral of environmental degradation which can undermine the agricultural production potential and contribute to sustained poverty and migration. The same actions under different conditions may actually provide the income for investments in the natural or human resource base. For instance, a household may contribute to environmental degradation through excessive production of charcoal, yet use the profits for improvement of human resources, like investments in clean water and health, and thereby set the stage for repaying the environment. The methodology of identifying such principal development pathways, the externalities conditioning them, and understanding temporal links among natural resources use, technical change, and human resource improvement is currently being refined in a joint ZEF/ IFPRI (International Food Policy Research Institute)-Project in Uganda. These methods will be introduced in Ghana Local state-of-the-art and data availability No studies exist which directly address the mutual effects of land use and socio-economic development for the Volta Basin. The RSAU land use map (see Appendix "RSAU Land use Map") contains some clear qualitative indications between intense land use and population pressure around Bolgatanga and Ho which for the Northeast region are described by Nabila (1997). Most demographic data for Ghana come from the census reports of 1960, 1970, and 1984, and the next census is planned for Burkina Faso has census data for For standardised comparison throughout the basin, the Africa population database developed by Deichmann (1996) for 1960, 1970, 1980, and 1990 is extremely useful (see also attached data CD-ROM). Research needs Rating nearly 3 % p.a., the population growth in Ghana is still extremely high and involves far reaching implications for land and water use in the entire Volta region. The relationship between demographic development and land use is a classic socio-economic research question

29 28 GLOWA Volta (Malthus, von Thünen etc.) and a major subject within modern economic geography. Many research concepts concerned with population-land-relations, however, neglect the importance of the factor water. In regard to the previous subproject and those on rising water demand as a result of the population growth, the interactions between demographic development and changing land and water use will be looked at simultaneously. The scientific challenge of this subproject is to model the interactions between population growth and its spatial distribution in and beyond the Volta region (regarding migration). Unlike traditional demographic analyses or so-called capacity analyses, this subproject understands population dynamics not as an endogenous variable for land use but links demographiceconomic modelling to land use/land cover models to allow an endogenous view on population dynamics, distributions and migration Subproject L3: Prediction of land use change Global state-of-the-art Our approach to understanding land use/cover change involves the use of direct observations from a variety of empirical sources of land-cover change, including satellite remote sensing, national censuses and land-cover inventories, and field-based measurements. These observations include natural resource information as well as socio-economic, demographic and institutional conditions prevailing in the region are collated in a GIS-based database. These observations can be used to directly calibrate empirical, spatially detailed models of land-cover change (Lambin, 1994). It is generally recognised that both the physical and socio-economic environment affect land use changes. To combine physical and socio-economic factors in a model to predict future land use is a relatively new approach which we call here the LUCC methodology after the Land use and Land-Cover Change global change research group of the IGBP and IHDP. It should be understood that this approach is at present a collection of models which produces the first results but which is also still very much evolving. Research needs It may be clear that with the global state-of-the-art still very much in evolution and basically no research activities in this field in the region, the research needs are to integrate the knowledge concerning the physical environment and land use change on the one hand and the knowledge concerning socio-economic development and land use change on the other, into one comprehensive dynamic model. In line with the philosophy of the project, most scientific effort is spent on coupling results from different disciplines. The approaches developed within the LUCC framework will be taken as working hypotheses that need to be tested, adjusted and operationalised Subproject L4: Vegetation characterisation Global state-of-the-art Two types of recent research developments are of interest here: plant/crop growth modelling and derivation of evapotranspiration parameters from satellite imagery. As to the first, the number of crop models and their functionality continues to grow since the first models by de Wit (Bouman et al., 1996). Although the models in themselves are not extremely complex, the parameterisation for different varieties under different climatic conditions, is a costly and time-consuming affair (Carberry & Abrecht, 1991). Commercially interesting crops like maize (Jones & Kiniry, 1986) and rice (Kropff et al., 1984) have, of course, received more attention than more marginal subsistence crops like okra. Modelling systems with different crops in the same field, as is more realistic for West Africa, has also

30 GLOWA Volta 29 received attention but remains more troublesome than single crop modelling (Lowen de-boer et al., 1991). Since the first Landsat satellite became operational in 1972, researchers have tried to link remotely sensed data to evapotranspiration characteristics (Jackson, 1977; Menenti, 1984; Nieuwenhuis, 1993). Clearly, some vegetation parameters are more easily quantified with satellite images than others. The Chen (1999) SVAT, which serves as basis for the land/atmosphere modelling in the project, needs vegetation data like albedo, roughness length, minimal stomata resistance and root depth (Chen, submitted). With the exception of albedo and, possibly, roughness length these parameters can not be remotely observed with acceptable directness. Alternatively, SVATs have been developed which cater to what remote sensing satellites can provide (Feddes, 1995; Bastiaanssen, 1998; Mauser & Schädlich, 1998). Local state-of-the-art and data availability Most vegetation characterisation undertaken in the Volta Basin has been done within the framework of land use/land cover classification activities described above under L1: "Land use and natural resources". Of further interest here is the crop modelling done for maize, cowpea and inter-cropping of maize and cowpea for Tamale and Accra (Adiku, 1995; Adiku et al., 1998) which shows the feasibility of using crop models with data available for the basin. Measurement of vegetation characteristics relevant for evapotranspiration was done during the HAPEX-Sahel experiment in West Africa both through ground measurements (Hanan & Prince, 1997; Braud et al., 1997) and remote sensing (Magagi & Kerr, 1997; Gond et al., 1997). At larger scales, the work done under the Famine Early Warning System (FEWS) should be mentioned as it monitors general rainfall patterns, vegetation growth, and food production in all drought threatened areas in Africa. Research needs The first need in the characterisation of the vegetation in the Volta Basin is to "translate" the land use information derived from satellite images into explicit functional descriptions of the actual vegetation for different parts of the region. This can be seen as a detailed form of agroecological zones. The second research need is to select and, where necessary, parameterise the crop models which are relevant for the actual cropping systems in order to describe the biomass production, root growth, and leaf area over time as a function of soil type and water availability. It may be clear that the amount of detail in the crop model output is limited and should focus on key parameters. The final step is to derive vegetation parameters which enter directly into the SVAT model. To select acceptable aggregation schemes is mainly a task of the subproject A2: Validation of SVAT-model. What is needed here is to calculate the parameters of individual sub-grid vegetation elements such as fields with different crops and fallow of different age. The idea is that this will involve active participation in the SVAT development because it is likely that the SVAT has to be adjusted to include vegetation data that can be made available for the complete basin through a combination of remote sensing and crop-growth modelling Subproject L5: Soil characterisation, surface runoff and infiltration Global state-of-the-art The most general way to relate soil physical parameters to readily available soil maps is through the soil texture classes and this is also the method of choice of Chen (Chen, submitted).

31 30 GLOWA Volta Although this is convenient, it is not very accurate, especially when the very old soils of the African shield are considered which have rather specific water conductivity and retention properties. A much better way is to actually measure soil physical parameters for each relevant soil map unit through pedo-transfer functions (ISRIC, 1998). Such an approach is only valid if proper account is given of the variability of the parameters within the soil units. Different approaches have been suggested to address the effect of soil variability on the actual hydrological behaviour of a watershed (e.g. Blöschl & Sivapalan, 1995). The vertical movement of water through the soil determines the division of infiltrated water over deeppercolation and water available within the root zone. This division is extremely important in our case as it determines how much rain can be used locally for evapotranspiration (and crop growth) and how much becomes available elsewhere, either as groundwater or as surface water. As there is little or no lateral influence, aggregation over space of this vertical movement can be done if the spatial variability is known of the relevant parameters (Kim, 1997). Much more difficult is the integration over space of surface runoff (Rockström et al., 1998; Yair & Lavee, 1985) especially when the heterogeneity of infiltration parameters is not randomly distributed but organised in particular patterns over the landscape (Merz & Bardossy, 1998). Explicitly routing the runoff water over space, incorporating rainfall intensity variability over time is at present the only way to properly address surface runoff (van de Giesen, 1999) although some scaling techniques show promise for a less explicit and measurement-intensive approach (Julien & Moglen, 1990). Local state-of-the-art and data availability For Burkina Faso, pedo-transfer functions have been developed for all soil units. Most soils found in the remainder of the Volta basin are soils which are similar to the soils in Burkina Faso with the exception of some of the Vertisols in the lower Volta. This information is very useful as it will provide all necessary average soil physical parameters for a first basin-wide model. Many soil-water movement studies have been undertaken throughout the Volta basin, but the results are not always easy to find as they are hidden in grey literature and project reports. A welcome exception is Sivakumar et al. (1991) where a large series of papers from francophone as well as anglophone west African countries describes soil physical characterisations, infiltration measurements and surface runoff experiments. Hydrological modelling has, in general, stayed behind the modelling boom which characterises the last two decades of hydrology research in industrialised countries. The models most commonly used are based on empirical rules of thumb used for civil engineering design and developed before the eighties (Rodier & Auvray, 1965; Rodier, 1982). Research needs A first step to arrive at a characterisation of soil physical behaviour in the Volta Basin is to extrapolate the pedo-transfer functions, which are available for Burkina Faso, to the complete watershed. Care should be taken, of course, that verification accompanies this extrapolation exercise and that major gaps are filled in through additional measurements. With the basic, large scale, parameterisation available, the next step is to develop a soilphysical or hydrological model to describe the division of rainfall over surface-runoff, deep percolation, and root zone storage. Many such models already exist. There are black box models with transform inputs into outputs with basically no physics involved and there are purely physical models which assume that everything about the system is known or knowable. A very popular approach in hydrology are conceptual models which capture the basic physics while using empirical (fitted) relations to simplify the measurement problem. A black box model has little predictive power and a first-principle physical model poses insurmountable

32 GLOWA Volta 31 measurement problems because so many parameters are needed. A conceptual model is the logical compromise, but the art lies in incorporating enough physics to make reliable predictions. As soon as non-linear processes are involved, integration over space (our 3x3 km cell) of parameters which are used in conceptual models can no longer be obtained by simply averaging. Instead, effective parameters are used which give good results over the relevant mosaic domain. How the specific needs for effective parameters can be met in the Volta basin is a major challenge of this project which can only be met through extensive measurements at micro- (field) to meso- (small watershed) level. 4.3 Research cluster Water Use Subproject W1: Runoff and hydraulic routing Global state-of-the-art A large number of models exist which simulate the movement of rainwater through a watershed and the river network. It is not unusual for hydrologists to develop a model tailored to a specific need or situation instead of applying an existing model. Here, however, we look for a general model or modelling environment which routes water output from sub-projects A2 "Validation of SVAT-model" and L5 "Soil characterisation, surface runoff and infiltration". Most importantly, the chosen model should allow for tight coupling with the economic optimisation model (see below under W2 "Integrated economic-hydrological optimisation") by accepting updated allocation rules and providing physical limits (Lagrangians). Some of the well-known and widely used models should be mentioned here to point out which criteria were used for sifting through the large supply of models. The HEC-1&2 models which originated at the US Army Corps of Engineers have been the starting point of many other models, but because they all are meant describe single events they are not suitable for the Volta where low flows and long term behaviour is of special interest. River basin quality simulation models such as the Enhanced Stream Water Quality Model (QUAL2E) distributed by the United States Environmental Protection Agency (EPA 1998) and the Water Quality for River- Reservoir Systems (WQRRS) (USACE 1998) are partially based on empirical relations which may not be valid in tropic regions. Other comprehensive river basin simulation systems include "classic" Stanford watershed models (f.e. SWM IV), the Tennessee Valley Authority's (TVA) Environment and River Resource Aid (TERRA) (Reitsma, Ostrowski, and Wehrend 1994), WaterWare (Jamieson and Fedra 1996a and b), and the European Hydrological System (SHE) developed as a joint effort by the Institute of Hydrology in Great Britain, SOGREAH (France), and the Danish Hydraulic Institute (DHI) (Abbott et al. 1986). Physical models, like SHE, have the advantage of being purely process based without need for empirical relations. The data need for such models, however, would be too large for the Volta River. The Interactive River-Aquifer Simulation (IRAS) was specifically developed to route water through a river network while enabling non-specialists to evaluate intervention impacts. In its first (DOS based) version, IRAS introduced advanced graphics capabilities to facilitate user interaction in all stages of system simulation. The current IRAS version simulates flows, storage, water quality, hydropower, and energy for pumping in an interdependent surfacegroundwater system. The water quality component allows up to 10 independent or interdependent constituents with first-order kinetics and one-dimensional advection and dispersion. The new IRAS version is operated under Windows 95/NT, uses a relational database, includes sediment transport, and allows for modular interfacing with a watershed runoff component, or other user-defined modules. IRAS has been applied in India, Canada, the United States, Russia, Germany and Portugal where it has been selected as the model for water resources negotiations with Spain (Loucks, et al. 1995). In first instance, IRAS serves as the model and modelling framework for the Volta Basin, mainly because its previous success in

33 32 GLOWA Volta developing countries, which in turn is related to its flexible data demands, and for its open structure (see also below "Methodological approach"). Local state-of-the-art and data availability Probably the most important hydraulic routing work undertaken in West Africa was done as part of the Onchocercosis Control Program (OCP). For more than twelve years, OCP suppressed the blackflies which carry riverblindness by killing the larvae which are attached to branches hanging in oxygen-rich rivers and streams. It is a good example of a case where models are developed to cater to specific needs. On the basis of water level measurements, which were communicated near-real-time through radio and satellite, riverflows were predicted and larvicide rates calculated accordingly. Although OCP is an important source of highquality flow data, the specific nature of the modelling done would limit its use within the GloWa Volta project. At present, no comprehensive hydraulic of hydrologic model for the Volta basin exists. The release of water from Lake Volta for power production at Akosombo is based on empirical rules of thumb. According to J. Amissah-Arthur, Deputy Chief Executive Engineering and Operations of the Volta River Authority, 90% of the water flows into the lake in a three months period which is too short to adjust releases. At the end of that period, one basically knows how much water is available until the next rainy season and this is divided equally, keeping some water in reserve. This strategy ran into problems in the early eighties and in 1998 when the lake filled up less than expected (see also 3. Research Questions). Historical riverflow data are available throughout the Volta basin for all major contributories. Data at Senchi, close to the delta of the Volta are available from 1930 whereas data from most other gauge stations start in the 1960's. In addition, a much denser observation network is in place since the 1970's to cover the needs of the river blindness or onchocercosis project. All these data are available through WRI and a selection can be found on the Volta/GloWa CD- ROM. The combination of longer time series at major points and shorter time series distributed more closely over space is sufficient for the purposes of this project and no additional riverflow measurements are planned. Geological maps are readily available (f.e. Geological Map of Ghana, 1:1,000,000 of 1988) because the interest in mineral exploitation. Hydrogeological information, however, is relatively scarce and limited to qualitative assessments. Information about aquifers and aquicludes is at present only available from borehole development projects and no central database of standard bore log and pump test data is presently in place. Research needs The research needs with respect to modelling river flow are straightforward. A suitable existing hydraulic model should be selected and calibrated for the Volta basin. Such a model would be able to run longer term simulations (incorporating expected changes in the regional climate) and thereby provide risk assessments for proper reservoir management. Such a hydraulic model is needed for optimisation of water use along the river network (see W2 "Integrated economic-hydrological optimisation"), but even as a stand-alone result the model would be able to make reliable statements about the likelihood of repeated water/power shortages. The current planning of future power generation through hydropower and/or thermal plants should include the associated risks. Although the availability of surface water data is sufficient, the lack of readily interpretable groundwater data poses a problem. It is necessary that for the different geological zones of the basin, quantitative insight is acquired between the relation between recharge as determined under L5 "Soil characterisation, surface runoff and infiltration", regional groundwater levels and aquifer discharge into the rivers.

34 GLOWA Volta Subproject W2: Integrated economic-hydrological optimisation Global state-of-the-art McKinney et al. (1999) provide a recent review of water resources modelling at the river basin scale. According to this review, the two principal approaches to river basin modelling are simulation - to simulate water resources behaviour based on a set of rules governing water allocations and infrastructure operation; and optimisation to optimise allocations based on an objective function and accompanying constraints. The range of river basin simulation models can be classified into flow simulation models, water quality simulation models, water rights simulation models, and comprehensive simulation models. Wurbs (1995) reviews a series of river basin flow simulation models, including some well-known applications such as the Long Range Study (LRS) model for the Missouri River, the Potomac River Interactive Simulation Model (PRISM), and the Colorado River Simulation System (CRSS). One of the earlier operational management models was developed by Loaiza García and Jiménez Ramón (1987) who apply a network flow programming simulation model to assess the potential of constructing several reservoirs to augment the municipal water supply for Monterrey, Mexico. These models were developed for specific applications and are thus not generalizable to other river systems. Models like AQUATOOL (Andreu et al., 1996) and the NERC-ESRC Land-Use Programme (NELUP; Dunn et al., 1996), on the other hand, are flow simulation models that allow for userdefined nodes, links, operating rules, and targets. Wurbs et al. (1993) developed the Texas A&M University Water Rights Analysis Package (TAMUWRAP) that handles the prior appropriation system of legal water rights used in much of the western United States. Comprehensive river basin simulation systems refer to interactive river basin simulation models accompanied by graphical user interfaces for the on-screen configuration of the simulated system and display of results. These models have increasingly become the choice for river basin simulation, and the IRAS simulation package (see sub-project W1 River Flows and Hydraulic Routing ) also fits in this development. Optimisation models are based on an objective function and constraints and can include social value systems in the allocation of water resources. There are two basic types of integrated economic-hydrologic optimisation approaches. The first type could be described as hydrologyinferred optimisation in that the model's objective functions for intra-sectoral allocation are derived primarily from hydrologic specifications. The second type refers to economic optimisation models, which optimise allocations intersectorally based on optimal water allocation. Other criteria, such as equity or environmental quality can also be incorporated (McKinney et al., 1999). Examples for integrated economic-hydrologic optimisation models include Vedula and Mujumdar (1992) and Vedula and Kumar (1996) who describe a stochastic dynamic programming model with numerous simplifications that solves for minimum crop yield reductions caused by water stress. Ponnambalam and Adams (1996) report on the application of the Multilevel Approximate Dynamic Programming (MAM-DP) model for the operation of multiple reservoirs. The mathematical formulation of a strict economic optimisation approach (sans flow simulation) is presented by Babu et al. (1996). The state variables are water table depth, salinity, water availability, and cropping intensity; the control variables are investments in unlined and lined canals, public and private drainage, and private tubewells. Functions, presumably empirical in practice, relate control and state variables. From the (nominal) basinlevel approach adopted for this model, salinity and waterlogging impacts are internalised. McKinney and Cai (1996) and McKinney et al. (1997) develop hydrology-inferred policy

35 34 GLOWA Volta analysis tools to be used for water allocation decision-making at the river basin scale (Amu Darya and Syr Darya in the Aral Sea Basin), using GAMS and ArcView GIS software. Basin-scale optimisation models must be able to characterise the hydrologic regime in order to calculate the objective function. Optimal water allocation must also be feasible, at a minimum from an infrastructure operations perspective, for policymakers and system managers to consider their adoption. Models that integrate simulation and economic optimisation with the goal of policy analysis include MODSIMQ (Labadie et al., 1994), EUREKA-ENVINET INFOSYST (Fedra et al., 1993), and the optimisation model of Tejada-Guibert et al. (1995). Faisal et al. (1994), apply such simulation-optimisation modelling of water resource systems to groundwater basins. According to Young (1995), combined hydrologic and economic studies at the river basin level are best equipped to assess water management and policy issues. Current modelling studies more readily recognise the necessity of integrated approaches, but usually either the economic or the hydrologic component dominates, depending on the researchers and on the set of issues examined. Integrated hydrologic-economic models can be classified into models with a compartment modelling approach and models with a holistic approach. Under the compartment approach there is a loose connection between the economic and hydrologic components, that is, only output data is usually transferred between the components. The various (sub)-models can be very complex but the analysis is often difficult due to the loose connection between the components. Under the holistic approach, there is one single unit with both components tightly connected in a consistent system within an integrated analytical framework. Due to modelsolving complexities, the hydrologic side is often simplified (McKinney et al. 1999). (Sub)-models of the compartment type include the approach of Feinerman and Yaron (1983), Lefkoff and Gorelick (1990a,b) and Lee and Howitt (1996). Booker and Young (1994) and Booker (1995) are examples for the holistic modelling approach. Finally, Rosegrant et al. (1999) develop a balanced economic-hydrologic-institutional optimisation model of the holistic type, with a focus on the competition for water resources between agriculture and municipalindustrial areas in the Maipo River Basin, Chile. The approach developed by Rosegrant et al. (1999) is the approach chosen for water use optimisation within the Volta Basin. Local state-of-the-art and data availability There is little local knowledge available on the costs and benefits of water use in the various water-using sectors, including agriculture, industry and households, as well as on the trade-offs and complementarities in use across these sectors. This can be attributed, in part, to the fragmentation of water policy among different ministries, organisations, and agencies. Moreover, analysis of water availability and use at the basin level is a relatively new approach in the Volta Basin. In addition, little thought as reflected in both low financial means and sometimes lack of political will has been given to the consideration of water as an economic good. However, as was stated earlier, the Water Resources Commission will likely facilitate a more integrated approach to water management and use of the basin water resources. Towards this end, a series of data and information has been collected on the water sector in Ghana, including a recent, comprehensive report (WRM 1998). Moreover, the WRI has both extensive data on and considerable experience in the Ghanaian water sector and the project will be able to draw on these data and experience. Substantial information and data on the energy sector in Ghana is also available (Figure 8). Research needs In order to analyse increasing water demands and competition for water uses across sectors, an existing economic-hydrologic-institutional basin model will be adapted to the unique conditions of the Volta River Basin. To accomplish this, in addition to the data provided by the

36 GLOWA Volta 35 flow simulation model (see sub-project W1 River Flows and Hydraulic Routing ) and the already available secondary data (WRM, 1998) a series of agronomic (crop pattern, crop production, yield response factors, effective rainfall, etc.) and socio-economic data (sectoral water uses, costs and prices in water-using sectors) will need to be collected as input parameters for the optimisation model. In addition to the current major water-using sectors - irrigated agriculture and urban water use - functions need to be developed to account for rural water use, and potentially, livestock water use, fishery production, and other environmental/instream water uses. Moreover, the model will need to be linked with all other modelling efforts of the project, in particular with the flow simulation model of sub-project W1 River Flows and Hydraulic Routing Subproject W3: Health and water Global state-of-the-art Malaria control in Africa has recently been receiving renewed attention at the national and international level (Nabarro 1998). The new Roll back malaria initiative of the World Health Organisation is encouraging in this respect, and new public health technologies are offering real opportunities to reduce the burden of disease on the African continent. Beside more emphasis on a good management of malaria control activities within the frame of improved health services, the employment of insecticide-impregnated bed nets holds promise to largely reduce childhood mortality due to malaria (Lengeler 1998). Water management aspects are however, not considered adequately. The local malaria vectors are playing a key role in the epidemiology and control of malaria. Anopheles funestus and two members of the Anopheles gambiae complex, A. gambiae and A. arabiensis, are the three main malaria vectors in Africa. A. funestus and A. gambiae are anthropophilic and endophilic, and are thus largely associated with humans and their habitations. A. arabiensis, on the other hand, feeds on humans and animals, and may rest inside or outside of houses. Vector importance is determined by the mean longevity of the local mosquito population, and its density in relation to humans. The larval habitat of the respective Anopheles species is of critical importance to vector control. Breeding places vary from fresh to brackish water, from standing water to open streams, from water in open sun to water in deep shade, and from large open marshes to tiny pools of water (Clyde 1987; Service 1993; Onori et al. 1993). From the epidemiological point of view, regions can roughly be classified into regions of endemic or stable and regions of epidemic or unstable malaria. Malaria epidemics are typically caused by an increase in the proportion of non-immune individuals in the population of an endemic region, or by a more intense contact of the population with the vector mosquitoes. Malaria associated with ecological disturbances and project-related population movements has become an increasing problem (Onori et al. 1993). In most of the Volta Region, malaria has high levels of endimicity, with malaria transmission taking place 7 to 12 months in the South and 4 to 6 months in the North. Despite the endemic nature of malaria in West Africa, large variability in vector density occur, often associated with the presence of water bodies (MARA, 1998). Local state-of-the-art and data availability Several approaches have been attempted to control malaria and other water-related diseases in Ghana. The WRI and ISSER, both collaborators in the research project, as well as the Health Ministry of Ghana have been working on the control of the disease for some years. The analysis of the incidence and prevalence of water-related diseases, with a focus on malaria, and the linkage of disease to socio-economic development will benefit from previous research

37 36 GLOWA Volta in The Gambia and Burkina Faso. Moreover, the project will draw upon ongoing activities in Burkina Faso (by the Nouna Health Research Centre, Nouna; the Centre National de Lutte contre le Paludisme in Ouagadougou; and the Centre Muraz in Boba Dioulasso). This component is co-ordinated with the international MARA/ARMA project, which aims at mapping the malaria risk in Africa. In Ghana, activities will be co-ordinated with the Navrongo Health Research Centre in Navrongo, Ghana, where a focus research site will be established which is internationally recognised as a centre of excellence in community-based health research. Research needs Many factors affect the choice of malaria control methods in Africa, and these factors are not distributed equally across the continent. Thus accurate information on a local and regional level are required before malaria control activities can be planned and resources allocated properly. Maps offer an ideal way of displaying complex information on the distribution of major malaria vectors, the existing levels of morbidity and mortality and the availability of health services. In areas of endemic malaria, as in the Volta Basin, the pattern of severe malaria disease is likely to vary according to the intensity of transmission (Snow et al. 1997). In areas of relatively low transmission intensity, the disease pattern is dominated by cerebral disease forms in older children, in areas of high transmission intensity young children and infants are mainly dying of severe anaemia (Müller 1999). This age-dependence of malaria disease according to the intensity of malaria transmission has great practical importance for the establishment of adequate preventive and clinical services. Specific preventive measures such as larviciding might only be viable in highly seasonal or fringe areas where the vector populations are rather unstable, environmental modification and manipulation (for example, filling, drainage, changing water levels) may only be feasible in urban and peri-urban areas, and the effectiveness of insecticide-impregnated bed nets will depend on various factors like season, mosquito density, use of similar insecticides in the agricultural sector, and attitudes of the local population towards disease and control measures (Lines 1988, Müller 1999). Against this background, a comprehensive data base on malaria-related information in Ghana and Burkina Faso will be established at the beginning of the project. Data published in scientific journals, university theses, reports of the health authorities and unpublished work from research institutions will be collected. Moreover existing data from the Health Information Systems of both countries will be evaluated regarding their quality at all levels of the health system. Data collected will include malaria disease incidence and prevalence data, data on malaria transmission intensity as measured through the Entomological Inoculation Rate, and malaria parasite prevalence data. In a second step, specific studies will be undertaken to collect information from areas of the Volta Basin without reliable data and from areas of new developmental projects. Emphasis will be put on the definition and prospective collection of surrogate markers for malaria morbidity and mortality (for example, severe anaemia/cerebral malaria rate in children under 5 years) Subproject W4: Communal and household water supply Global state-of-the-art As far as the household water sector is concerned, Webb and Iskandarani (1998) identify a series of research gaps that are relevant both for developing countries in general, and for Ghana - where household water insecurity is a growing problem - in particular. The problems can be grouped under three main headings: Availability, Access and Usage. The idea of water security allows for water to be considered as a natural resource, as a commodity, and as an entitlement. These are complementary perspectives, not contradictory ones. To improve household water

38 GLOWA Volta 37 security of rural and urban households additional research is particularly needed on water demand behaviour and usage: As water resources provide important benefits to humankind, estimating the economic benefits relating to water management decisions are important for allocation decisions. For physical, social and economic reasons, water is a classic non-marketed resource. Even for commodity uses, market prices for water are seldom available or when observable, often are subject to biases. However, because of the increasing scarcity of water for its commodity benefits, economic evaluation plays an increasing role in public decision on water projects, reallocation and policies (Winpenny 1994). During normal years, water of different quality has changing economic values across time and space. But these values remain practically unknown apart from a few studies relating to urban supply projects and irrigation schemes. Part of any understanding of the topography and timing of price relationships to water has to be a better quantification of demand elasticities relating to income and usage, i.e. the willingness and ability to pay (World Bank 1993, Whittington, Swarna, 1994). The household economics of water consumption and potential trade-offs against food consumption, asset investment, and investments in future natural resource productivity, remain poorly understood in water-stressed environments. As for water usage, much research remains to be done on how actual consumption levels among poorest households can be raised. How high is the demand for the different usage purposes? How do patterns of family usage vary across seasons? Who are the beneficiaries of improved water access? Women, men, or children? The wealthy or the poor? And to what extent do various age, gender, status and income categories benefit or lose out in the change? (Zwarteveen, 1997) What improved patterns of usage would maximise gains to water, food and ecological security simultaneously? (Webb, Iskandarani, 1998) Local state-of-the-art and data availability The connection rate to the public piped system is approximately 76% in the urban areas and 46% in the rural areas (Ministry of Works and Housing, 1998a,b). The available calculations of future drinking water demand is questionable since the used population data are based on a Census from However in 2000 a new Census is planned, which will deliver new information on water demand developments of the future. Lack of rural water supply coverage has been long recognised by Ghana to be a major contributor to human disease and malnutrition. The Community Water and Sanitation Program aims at improving the delivery of water and sanitation services in rural communities by introducing a more demand-responsive approach (UNDP-World Bank Water and Sanitation Programm, 1998). The goal is to decentralise community water supply by making the beneficiary community responsible for selecting options in water and sanitation facilities, cover all repair and maintenance costs, and pay 5-10% of capital costs. The drilling of new wells should help to improve rural drinking water supply. This development is taking place within the context of increasing decentralisation of water resources management. However, costeffective policy measures have yet to be implemented on a large scale to achieve full rural coverage by 2015 as envisioned in the national plans. The water demand of farm households for watering livestock and for irrigation is sometimes traditionally linked to the domestic water demand as the same water resource is used. Resulting interdependencies to health and intra-household allocation processes and decision making are insufficiently known in the Volta basin. Research needs The major research needs on the household and community level include the assessment of availability, access, and usage of ground and surface water in the Volta river basin. Therefore,

39 38 GLOWA Volta an econometric analysis of household water demand as well as an aggregated householdcommunity model with time and water access as constraints need to be developed. Data collection is needed to quantify water demand and needs for domestic and agricultural use. Within the project the level of access to save water within the basin needs to be examined and its economic and social benefits or losses measured (e.g. time requirements for fetching water, productivity gains or losses, health impacts). Data from Sub-Project W1 Riverflow and Hydraulic Routing should provide information about spatial and temporal availability of (shallow) groundwater and surface water. Both community participation in water supply policy and the communities ability and willingness to contribute to the provision of water should be studied. This also includes the (potential) role of women in water planning and decision making. Moreover, knowledge transfer (formal and informal), behaviour change and personal care will be key factors to be studied. In this context one important aspect will be to look at intrahousehold decision-making processes and entitlements according to different socio-cultural environments (Haddad, Hoddinott, Alderman, 1997). Based on the evaluation of household access to water, consumption, usage, and storage patterns need to be examined and variations due to season and geographic location will be outlined. In this regard the question of water quality (and thus the linkage with the health and water quality component) will be of utmost importance. The results from the collected empirical data on effective demand and water prices will be integrated into the economic optimisation model of Subproject W Subproject W5: Institutional analysis Global state-of-the-art A series of theoretic approaches have been carried out regarding the optimisation of the water institutions, both from Top Down (Frederiksen, 1992) and the Bottom Up approach. (Duyne, 1998) Both envisage the optimisation of the existing institutions. The water allocation process with a view to the political economy of water use has been analysed in different case studies, but not in Ghana (Allan, 1996). The water allocation process in legal terms can be again separated in the bottom down and bottom up approach. In the Ghanaian context, the official water allocation process has been analysed in WRM (1998), following the Ghanaian Draft Water Law. The theoretical top down approach claims to implement the Water Law from the national to the local level in order to optimise the allocation process, to introduce restrictions in water use, to pay fees or to issue licences for use or pollution (Burchi, 1994, Frederiksen, 1994). The analysis of traditional allocation systems, local rules and management of water use at the local level would be the basis to reform the water rights from the bottom up as has been shown in some case studies of legal pluralism (Benda-Beckmann, 1997) with ongoing reforms (Woodhouse, 1995 and Whyte, 1996). At the international level, detailed studies are available generally for the principles of international Water Law (Caponera, 1996), about theoretical approaches for Joint management of international water resources, (Dellapenna, 1995) and the political factors impeding or enhancing co-operation (Ohlsson, 1998). Local state-of-the-art and data availability The official water allocation process in Ghana has been analysed in WRM (1998) after the drafting of a Ghanaian water Law. Although some communal management examples have been analysed in Ghana through the Word Bank studies, it rather reflects the "official" institutions which have been installed due to the decentralisation policy and not in depth analysis to the

40 GLOWA Volta 39 existing allocation system in the communities which might differ considerably from the official allocation process. A group of developing agencies, including the CfD (Caisse francaise de Developpement, France), CIDA (Canadian International Development Agency), DANIDA (Danish International Development Agency), DFID (Department for International Development, UK), GTZ (Deutsche Gesellschaft für Technische Zusammenarbeit), UNDP (United Nations Development Programme), and the World Bank conducted, through Nii Consult, and in co-operation with the Ministry of Works and Housing in Ghana a review of the water sector, with a focus on the basin level. The review includes six building blocks, including the Social, Economic, and Political Context; Regulation; Economics and Financing; Institutions and Participation; International Waters; and Information. The review also indicated needs for trans-boundary cooperation in water resources management. As a result, a workshop was held in Ghana at the end of September to better identify the issues relating to trans-boundary water resources management under the auspices of the United Nations Environment Programme (UNEP) and the GEF (Global Environment Facility). The review includes descriptions of the major organisations involved in water resources management in Ghana. Of direct interest for the project is the establishment of the Water Resources Commission (WRC, 1996) as an umbrella organisation for water resources development in Ghana. The WRC will likely facilitate future reforms in the water sector, including a more integrated approach and basin-wide management of natural resources. The WRC will be responsible, in particular, for the overall management and national planning. Research needs The existing institutions of water management and the policy priorities in water use are one major factor to determine the future water use in the country. Research needs are identified in the institutional sector on various levels: The international, national, the regional and the local level. At the international level, the political relations between the riparian states should be analysed in order to find impeding and enhancing factors for co-operation between the states. Possible propositions for water management institutions and legal provisions could be adapted to the prevailing political environment and the economic priorities of the riparian states with a view to Development of the River basin. Until the present, no basin wide institution or legal arrangement on water uses of the riparian states has been established or signed. At the national level, research needs are analysis of the relative importance and political power of the different institutions, and which institutions in the end decide over the water use and allocation processes. So far, political priorities of water use have not been analysed or combined with the institutional part. In-depth studies on the water allocation system at the local level are lacking, as well as the efficiency and the implementation of the national allocation process versus the traditional allocation system and a detailed stake holder analysis at different levels. It should be identified which organisation is responsible for which water uses and if they are de facto or only formally controlled by the WRC in order to secure a proper management. In depth studies about the water allocation system on local level are lacking completely. The effects of national planning on local decision systems (and vice versa) should be analysed within the institutional component, including the interest and stake holder groups on different levels.

41 40 GLOWA Volta 5 CONCEPTS AND METHODS The integration of results from different disciplines is often hampered by the different scales at which observations, processes and models are valid and relevant. Here, we want to be able to make predictions at the level of the Volta River Basin, covering 400,000 km². Remote sensing enables us to observe, say, land use patterns at this level, regional atmospheric models are available to make predictions at this level, and urbanisation and migration are typically processes which take place within areas of this size. The processes connecting these factors, however, can often only be understood by zooming in: trees and crops transpire water, not cropping patterns; water in the rivers comes from the runoff of thousands of small first-order watersheds, etc. This project depends heavily on large scale research instruments such as remote sensing and economic optimisation models, but at the same time it is felt that extensive field study has to be undertaken. Field research is needed to verify locally if the predictions and observations made for the basin are correct, but especially to develop, calibrate, and verify models processes which can best be understood at the level of a small watershed, a village, or even a farm or household. For this reason, three field sites have been selected to facilitate smaller scale research: Navrongo, Tamale, and Kumawu. Each site is representative for a larger area, both in terms of natural resources, land use, and population density. Because the focus here is on water, care has been taken that at each site one area/village/watershed is available with irrigated agriculture and one without. In addition, each site has at least one special advantage. Navrongo represents the densely populated North, with its granite geology. It lies right at the border with Burkina Faso and people here speak Mossi, like most Burkinabe which facilitates the inclusion of Burkinabe researchers in the Volta project. Navrongo is also home of an excellent community health research centre with which the project will collaborate. Tamale represents the less densely populated central part of the basin with a sedimentary geology. Tamale is the seat of SARI, the hosting Ghanaian research organisation which will provide central research facilities such as soil and crop laboratories, as well as office space and communication facilities. Kumawu is easily accessible from Kumasi, the second largest town in Ghana which houses the University of Science and Technology (UST) with which several of our research partners maintain ties. Kumawu is representative for the Greater Afram plains which are the locus of recent population inflow and undergo rapid, and often unsustainable land use changes. The sub-projects A2, L3, L4, L5, W4 and W5 will especially profit from the availability of the field sites. A central database will be maintained at project level and each data set will be accompanied with standard meta-data. The standard grid size for basin wide, geo-referenced data is 3x3 km and all endogenous variables will be presented at this resolution. The connection between different sub-models is not the same throughout the project but depends on needs and possibilities. The atmospheric model, for example, is discretized in very short time-steps and takes very long to run (up to six months for a complete simulation). Land use change is a matter of years or decades and it is not useful (or practical) to update the land use at each time step of the atmospheric model. Instead, a small set of land use change scenarios will be provided to the atmospheric model. To ensure that the most relevant land use change factors are represented in these scenarios, a sensitivity analysis project (A3: "Research of Feedback Mechanisms") has been included to ensure that climate/land use change feedback is properly addressed despite the lack of close coupling. The other extreme is shown by the projects W1 "Runoff and Hydraulic Routing" and W2 "Integrated Economic-Hydrological Optimisation" which are closely coupled and will be designed to exchange information at each time step, each river network node, and for each optimisation iteration. For presentation and embedding in decision making processes, a shell will be developed which connects inputs and outputs of all

42 GLOWA Volta 41 models through a pooled database, and produces spatial representations for standard GIS software. In the following, the research activities for each sub-project are described under the appropriate research cluster. 5.1 Research cluster Atmosphere A more detailed understanding of the complex feedback mechanisms between soil and atmosphere in the Volta Basin is only possible with numerical simulations as explained above in the chapters "Global State-of-the-Art" and "Research Needs". A numeric meteorology/climate model, adapted to the specific problem, is required to analyse the effect of intensified land use on the water balance. The targeted simulation will be carried out on basis of the MM5v3 of the Penn-State University and the National Centre for Atmospheric Research. In order to achieve the set scientific and technical work targets (chapter 3), four sub-projects are required. Their work plan is explained in detail in the following chapters Subproject A1: Preparation of basic version of MM5 (Dr. H. Kunstmann (IFU); Dr. R. Knoche (IFU)) This sub-project will provide a basic version of a meso-scale meteorology model adapted to the Volta Basin based on the studies carried out in the Volta Basin; it will also optimise the model and develop interfaces to other models. The sub-project 1 is the base for the other three sub-projects of the research cluster "Atmosphere". A mesoscale meteorological model, which is coupled to a soil-vegetation model, like the MM5v3 will be used for the first time in the region comprising the Volta Basin and West Africa. The MM5v3 of Penn-State University and the National Centre for Atmospheric Research allows simulations with high resolutions due to its nesting capability. Due to this, a detailed soil model can be used which takes into consideration the effect of different vegetation and soil types on soil humidity and temperature as well as orographic related phenomena. In addition, the non linear correlation between soil humidity and rainfall due to convection can be recorded (Chen & Avissar, 1994a). Research question Experiences with the MM5v3 and similar models mainly stem from applications in Europe and several regions in North America and are not readily transferable to West Africa. The proximity to the equator for example makes it necessary to revise geostrophic approximations. Furthermore, the establishment of parameters for the tropics might be required as the ones for the mid-latitudes might not be applicable. The quality of the data available that should enter the model as external parameters can currently not be estimated critically enough. The close exchange of data with the other two research clusters "Land Use Change" and "Water Use" also requires the development of specific interfaces between the respective computer programmes used by these research clusters. Research goals The overall objective of the sub-project 1 can be divided into three sub-objectives: (1) Provision and implementation of a numeric "West Africa Model" based on the MM5v3 (2) Determination of optimal parameters and optimisation of the model regarding precipitation

43 42 GLOWA Volta (3) Development of interfaces for the exchange of data with the research clusters "Land Use Change" and "Water Use". Methodological Approach During phase 1, land use data, soil data and atmospheric GCM data from all available sources will be compiled. This includes the CD-ROM with the "NCEP/NCAR Reanalysis" with which a so called "Hindcasting" (simulation of the meteorological situation of past events) is possible. In addition, for the simulation of the current meteorological conditions of the actual weather the daily AVN analysis will be used which is accessible through the network every morning from the "National Oceanic and Atmospheric Administration" (NOAA) in Boulder/USA. To get realistic circulation samples over the Sahara an initialisation is decisive (Cunnington & Rowntree, 1986). It can be derived from the "NCEP/NCAR Reanalysis" and the daily AVN analysis. Roughly unravelled land use and soil data will be obtained from NCAR. Later they will be replaced with detailed data from the "Land Use Change" research cluster. Afterwards, the required MM5 pre-processor programmes will be installed. In doing so, particularly the geographic circumstances due to the proximity of the equator will be considered (higher tropopause, use of the Mercator Projection, identification of insufficient geostrophic approximations of the wind field close to the surface). An adequate nesting strategy will be developed and the size of the domain will be selected in collaboration with the other two research clusters. The results from the MM5v3 will be visualised with the latest version "NCAR-Graphics" software, which will be purchased and installed. In Phase 2, optimal parameters for the MM5 will be identified by comparing calculated and measured data from specifically selected rainfall events. In a first sensitivity analysis, adequate parameters for the convective rainfall, the explicit rainfall, the radiation transfer and the planetary boundary layer will be studied. MM5 offers different options for the establishment of parameters. As experiences and recommendations regarding optimal parameters do not exist for West Africa - in contrast to Europe and North America - they will be determined during this phase. After comparing the results and observations of selected periods, decisions will be taken on which parameters are adequate for West Africa and the Volta Basin. Areas with one-sided bias regarding the simulated rainfall will be identified. The available parameters for the subscale, convective rainfall may eventually have to be modified to apply to the specific situation in the tropics. During phase 3, appropriate interfaces will be developed to enable the data exchange between the programmes used by the different clusters. This is of importance, as the results and data from the "Land Use Change" research cluster will be used in the soil model of MM5 and because results from MM5 like surface runoff, drainage and evapotranspiration will be passed on to other research clusters. Transformations of co-ordinates and conversions of in- and output data of the model to GIS based formatted displays are required for the development of interfaces. Expectations At the end of the sub-project A1 an efficient and optimised West Africa Model based on the MM5v3 will be available. It can be used and expanded for specific problems in the subsequent three sub-projects. The quality of the data base will then be assessed and the optimal parameterisation can be determined. The model will have interfaces to the other models of the other two research clusters permitting a direct data transfer or exchange. The MM5 Model will be at the disposal of the sub-project A2 "Validation of SVAT Model", A3 "Research of Feedback Mechanisms" and A4 "Impact of Intensified Land Use".

44 GLOWA Volta Subproject A2: Validation of SVAT-model (Dr. N. van de Giesen; Dr. H. Kunstmann (IFU); NN PhD Student) The SVAT Model (Chen & Dudhia, 1999) with which the MM5v3 was equipped has to be adapted to the conditions in the Volta Basin. Sub-project 2 will therefore focus on the extension of the soil model and its validation. Detailed databases on soil characteristics and vegetation will be provided by the research cluster "Land Use Change". Research question The SVAT Model (Chen & Dudhia, 1999), which is usually installed in the MM5v3, uses for each grid cell as representative land use type the land use type which dominates. For this representative land use type, energy and humidity fluxes are measured at the soil-atmosphere boundary layer. For West Africa and the Volta Basin, however, the strategy of the dominant land use type is not adequate as it does not consider the land use variation of the "Savannah Mosaic", which varies in scales smaller than the grid resolution. The effective parameters for the description of soil and vegetation that are related to the respective grid resolutions are not known and have to be determined. Direct measurements have to be taken in order to validate the heat fluxes which have been calculated through effective parameters. This requires specific measuring equipment. A scintillometer is required for sensitive heat flux measurements weighted proportionally by area. For the spot measurements of the latent and sensitive heat fluxes an instrument is required which works with the "Eddy Correlation Method". Research goals The objectives of sub-project 2 can be divided into two elements: (1) Validation of the SVAT model through measurements of latent and sensitive heat fluxes (2) Extension of the SVAT-model to consider sub grid scale effects. Methodological Approach Three test regions for taking measurements will be selected during phase 1. Within each of these test regions two smaller test areas (< 10 km 2 ) will be surveyed and equipped with measuring instruments: one with predominantly intensive land use, one with extensive land use. During two measuring campaigns latent and sensitive heat fluxes will be measured at specific points within each catchment area. The latent heat flux will be measured using the "Eddy Correlation Method" with a "Mark Hydra" measuring instrument (Shuttleworth et al., 1988) of the Institute for Hydrology in Wallingford (UK), which has been used already successfully in the Niger (Blyth & Harding, 1995). The measurements will then be compared to the simulation results of the SVAT-Model. In the periods lying outside the campaigns the evapotranspiration will be estimated on the basis of micro meteorological observations (Bowen-Ratio). The sensitive heat flow will be measured with a scintillometer. The measured heat flows and the surface temperatures measured by satellite will ultimately be compared to those calculated with the model. For each of the six catchment areas a water budget will be estimated whereas precipitation and surface runoff will be measured directly. The relation between hydraulic conductivity and soil humidity as well as suction and soil humidity will be determined in situ with a neutron probe and a tensiometer. Familiarisation with the method will take about 6 months, the measurement campaigns approximately one year. During phase 2 a method will be developed which makes it possible to consider in the SVAT- Model the subgrid scale heterogeneity resulting in a better reproduction of the observed circumstances. Effective parameters for the soil and vegetation parameters of mixed land use types have to be determined. Furthermore, algorithms for the soil model have to be

45 44 GLOWA Volta implemented which allow a transfer from the mixed land use resulting heat flows to the atmospheric model. The sub-project L4 "Vegetation Characterisation" of the research cluster "Land Use Change" will provide a detailed description and characterisation of the vegetative cover. It will also contain the seasonal variation of the root depth. Thereafter, effective parameters for the vegetation will be determined using the available data which have a high resolution. Different aggregation approaches for albedo, roughness longitudes, minimal stomata resistance, root depth, etc. will be applied. The comparison of the measured heat flows with those produced by the model makes a selection of the adequate aggregation method possible. The dependence of the hydraulic conductivity and the suction from the soil humidity is described in the SVAT Model of Chen and Dudhia (1999) through the parameterisation of Cosby (Chen & Dudhia, 1999; from Cosby et al. 1984). For this, the required parameters are firmly tied up with the respective soil type and are primarily adjusted to soil conditions in the mid-latitudes. It is well known that soils in Africa behave differently than soils at mid-latitudes (van Wambeke, 1992). It is also part of this phase to study to which extent the calculated fluxes will change, if, instead of the usually given parameterisation, pedo transfer functions are used for the solution of the Richard Equation that are determined by the sub-project L5 " Soil Characterisation, Surface Runoff and Infiltration". The calculated soil humidity and surface temperature will ultimately also be compared with values of coarse resolution imagery from the NASA-Goddard-Space-Flight-Center which were derived from satellite data and which will be accessible to the project (Jasinski, 1999). This will enable a further verification of how meaningful the soil model is. Expectations A calibrated and validated SVAT Model for the Savannah Mosaic of the Volta Basin will be at the project's disposal at the end of the sub-project. With this model it will be possible to draw a balance of the energy and water budget between the soil and the atmosphere for all foreseen land use levels. The validated SVAT Model will directly be part of the sub-projects A3 "Research of Feedback Mechanisms" and A4 "Impact of Intensified Land Use". It will also provide the determined actual evapotranspiration (ETa) to the sub-projects A1 "Preparation of Basic Version of MM5", A4 "Impact of Intensified Land Use", L4 "Vegetation Characterisation" and L5 "Soil Characterisation, Surface Runoff and Infiltration" Subproject A3: Research of feedback mechanisms (Dr. H. Kunstmann (IFU); Dr. R. Knoche (IFU); NN PhD Student (IFU)) In order to investigate the impacts of land use on the water supply in detail, the interaction of precipitation and evaporation is of basic interest - either as evaporation over vegetation free soil and water surfaces or as transpiration plants. By means of the 'Evaporation-Tagging' method, the numerical model allows the tracking of the water's course as precipitation from its evaporation beyond its interactions with the different atmospheric processes up to its return to the earth's surface. Research question So far, the basic model MM5v3 does not provide the option of "Evaporation-Tagging". In order to implement the required techniques into the model, massive interventions regarding the program structure are necessary. Subsequently, particular arid and humid periods have to be analysed in order to find out on which temporal and spatial scales there is a relation between evaporated water and precipitated water, and if there is a correlation of the spatial patterns of the evaporation area and the corresponding rainfall area. The question has to be raised how

46 GLOWA Volta 45 changes of land use affect these temporal and spatial correlations. A qualitative validation of the "Evaporation-Tagging" can be made by the distribution of deuterium and 18 O-isotopes. Research goals The objectives of sub-project 3 can be sub-divided into two issues: (1) Model instruction for the 'Evaporation-Tagging': Improvement of methods, implementation of algorithms and the setting up of assessment and presentation cycles, and test. (2) Implementation of the 'Evaporation-Tagging' and sensitivity analysis for particular arid and humid years. Methodological Approach In phase 1 the basics of the "Evaporation-Tagging" will be developed, and particular algorithms will be implemented into the code of the West Africa Model. In the case of the "Evaporation- Tagging", control variables will be implemented in addition to the components water vapour, cloud water, cloud ice or precipitation considered in the model. These quantities represent very specific subsets of the mentioned components and are subject to the same physical processes. The definition of these control terms depends on certain problems. Thus, a variable might for example be implemented into the model by defining a certain area of grid points as a swelling zone and starting the evaporation at the calculated evaporation rate. The distribution of the control variables on the surface at a later date finally shows the effect that the water evaporated in the swelling zone has on the precipitation of the adjoined zones. In phase 2 the method of "Evaporation Tagging" implemented in the West Africa Model is applied to specific scenarios. Therefore, particular arid and humid periods of the past are simulated. The required global driving data derive from the "NCEP/NCAR reanalysis". It will be ascertained where the rainfall in the Volta Basin derives from, which share the local evaporation has and which share derives from other areas. In this way the rate of the precipitation-recycling can be quantified. Deuterium and O 18 isotope data (Brunel et al., Mathieu & Bariac 1996) give reference to the origin of the rainfall water. Since there is very few isotope data available for West Africa, a quantitative validation of the "Evaporation- Tagging" can only be made by a correlation of a quantified isotope distribution and the simulated distribution of the precipitation's origin. Further calculations are made about the impacts of changes in land use predicted by the research cluster "Land Use Change" on the dispersion of the evaporated water as well as on the relationship of the precipitation-recycling. Additionally, the sensitivity of several soil parameters on the results from the "Evaporation-Tagging" will be analysed in order to specify the feedback mechanisms. The impacts of the varying surface of the Volta Dam will also be part of the analysis. Later, the research group "Water Use" will track the further course of the surface run-off and the soil drainage by routing-algorithms. Research on the spatial correlation between the evaporation area and the corresponding precipitation area helps to identify those areas within the Volta Basin and in West Africa where intensified land use and land use changes including the construction of further reservoirs have specific impacts on the regional water cycle. Furthermore, it will be assessed if typical periods between evaporation and precipitation can be identified and how these time scales vary depending on an intensified land use. Expectations By means of the "Evaporation-Tagging" those areas in the Volta Basin will be identified where the rainfall correlates with the land use in other areas.

47 46 GLOWA Volta Thus the planning authorities will have insight into the spatial and temporal interactions of intended land use changes and therefore expected changes in precipitation. In consideration of the further differentiation into surface run-off, storage in the non-saturated zone and soil drainage, a more detailed tableau of the regional water cycle might be the result from the cooperation with the research cluster "Water use". The sub-project A4 "Impact of Intensified Land Use" will benefit from the information given on "sensitivity" Subproject A4: Impact of intensified land use (Dr. H. Kunstmann (IFU); Dr. R. Knoche (IFU); NN PhD Student, scholarship holder NRW) Results from global climate models have only a very limited significance for specific regions, since, due to their limited resolution in the scale of a hundred kilometres, they cannot reflect the impact of a complex terrain and a multiple land use as detailed as required. Furthermore, the parameterisations are optimised globally. Therefore regional variables for precipitation and temperature often vary from observed climatologic variables. The comparison of historical precipitation data of the Climate Research Unit of the University of East Anglia (New et al., 1999a, 1999b) with findings of the global climate model ECHAM 4 of the Max-Planck-Institut für Meteorologie during the years from 1930 to 1990 showed an average overestimate of precipitation in the Volta Basin of nearly 40 % due to the model. The significance of global models declines very quickly as soon as phenomena below the continental scale are concerned. This is valid also for the African continent, which shows a variety of regional climate features and therefore might be hit by very different climate changes on different regional levels. Besides the impacts of the global CO 2 increase, it is the effects of the several anthropogenic interferences in land use and infrastructure in West Africa, following a rapid population growth, that are unknown. Since the scheduled regional West Africa Model maps only a limited section of the earth's surface, it can be run with a much higher resolution. The large scale structures simulated in the General Circulation Model (in this case the climate model of the Max-Planck-Institute for Meteorology in Hamburg) provide the boundary conditions at the edge of the MM5v3 domain. Thus, small scale phenomena can be registered, induced by terrain and land use, which influence the climate in the mentioned region because of their geographic position. In this sub-project the impact of intensified land use as well as the effects of the global CO 2 increase on the water supply in the Volta Basin will be analysed. Research question The West Africa Model, developed in the previous sub-projects, is based on the current version 3 of MM5 released by NCAR in July Since MM5v3 is conceived rather as a regional episode model than as a climate model, it has to be adapted in order to use it for long-time climate simulations. After the required adaptation the model should be able to reproduce realtime climate conditions, and provide reliable records on the regional climate under the condition of a future intensified land use and atmospheric CO 2 concentration. The climate simulation, which needs much capacity regarding the calculating time and memory, will answer the question about the impact of land use on the precipitation variability in the Volta Basin and how the increasing atmospheric CO 2 concentration affects the water supply for that region. For water management planning purposes it is of significant importance to know if the water demand calculated by the research cluster "Water Use" under assumed future land use respectively future climatic settings can be satisfied in a sustainable manner by rainfall water, surface run-off and storage in the unsaturated soil zone.

48 GLOWA Volta 47 Research goals The objectives of the sub-project can be subdivided into three items: (1) Model preparation of the West Africa Model code for climate cycles (2) Implementation of climate cycles (a) Comparison with climatologic data (b) Survey of the impact of the regional land use (c) Survey of the impact of global warming (3) Analysis of the long term water availability Methodological Approach In phase 1 the West Africa Model will be adapted in order to apply it for climate cycle simulations. Therefore, the input of ECHAM 4 data sets as a boundary condition has to be made possible, and the internal time counting, which is different from episode simulations, has to be modified. The date formats have to be co-ordinated with the global input data sets, and the different aspects of the year's length implied in certain parameterisations have to be adapted. In long term simulations, different from episode simulations, deeper soil layers also have to be considered and the lower boundary conditions for the temperature and humidity flows have to be modified. In phase 2a the problem whether the climatologic phenomena of the "Togo-Gap" and the "Little-Dry-Season" can be reproduced in long term simulations of five to 15 years will be studied. Therefore, a "1xCO 2 " ECHAM 4 data set of the Max-Planck-Institut für Meteorologie in Hamburg will be used, which should represent the current climatologic conditions. Sensitivity analyses will then provide clarification regarding the origin of the "Togo Gap" and "Little-Dry-Season". The impact of land use on the regional climate will be analysed. Analogue climate cycles will be carried out for the intensified land use ascertained by the research group "Land Use Change", and will be compared with the model results from the before ascertained contemporary setting. Similar to the sub-project A3 "Research of Feedback Mechanisms" the sensitivity of different soil parameters will be analysed in order to identify the feedback mechanisms between soil and atmosphere (phase 2b). The impacts of the Volta Reservoir and the planned dams in Ghana and Burkina Faso will be included in the analysis. The calculations will answer the question whether intensified land use causes a change in precipitation variability, and whether extreme events like droughts will increase. Answer will also be sought to the question whether the dependence of the AEJ and the occurrence of droughts on a meridianal soil temperature and soil moisture gradient and on an anomaly in the SST can be verified by the model. In phase 2c the impact of the global climate change on the water supply in the Volta Basin will be studied. Therefore ECHAM 4 data sets from global simulations will be used, which reflect the climatologic conditions in the middle of the 21st century. Thus the combined impact of land use change and global climate warming on the water supply in the Volta Basin can be assessed. In the final phase 3 the long term average availability of rainfall water will be analysed including its variability. Furthermore it will be assessed if an intensified land use is sustainable with regard to a balanced water supply during a certain period, and if the water demand will exceed the water availability. On the basis of the water-deficiency-index (Moran et al., 1994, Wang & Takahashi, 1999) desertification imperilled areas will be identified. The analysis of the calculated water demand will be supplied by the research cluster "Water Use".

49 48 GLOWA Volta Expectations The results from the highly dissolved climate simulation in sub-project 4 will describe the complex relationship between land use, global warming and regional climatologic conditions in the Volta Basin. The sensitivity surveys will show which long term changes in precipitation have to be anticipated under the conditions of a regional intensification of land use and an increase in the atmospheric CO 2 concentration as predicted by the global climate models. Thus an analysis of the long term water availability can be provided for policymakers. The ascertained data on the expected precipitation will be communicated to subproject A2 "Validation of the SVAT Model", L4 "Vegetation Characterisation" and L5 "Soil Characterisation, Surface Runoff and Infiltration". 5.2 Research cluster Land Use Change The research cluster Land Use Change consists of 5 subprojects. The central sub-project would be L3: "Prediction of land use change" which has as relatively ambitious goal to understand the interactions between social and natural environment on the one hand and land use on the other. For this, we use what we call the LUCC approach which has been applied with some success in Cameroon and Zambia (Lambin & Mertens, 1997). This approach is not a set of universal rules but rather an analytical framework which depends on careful local assessment of the natural resource base and social developments. The results from subprojects L1: Land use and natural resources and L2: Land use change and socio-economic development are meant to provide exactly this for the complete Volta Basin. L1: Land use and natural resources looks at the relation between land suitability and actual land use, assuming that in some areas intensified land use is caused by a richer resource base (for example a flood plain). In areas where such a correlation between intensified land use and richness of resources does not exist, social economic development and especially population increase is expected to be the driving force, and this will be researched in L2: Land use change and socio-economic development. A land use type is typically a geographical variable, denoting a characterisation of a relatively complex situation. In West Africa, this is very much true as the land cover is made up of a mosaic of different landscape elements. One land use type corresponds to a certain patchwork of fields, forests, single trees, villages, and wetlands. It is therefore important to use a detailed and small-scale approach for remote sensing and the classification of land use types. Because the major "global change" factor within the Volta Basin is land use change and because it is the ambition of this project to model its effects on (local) climate and weather patterns, it is necessary to translate land use types into elements which enter directly into the equations which govern the exchange of water and energy between the atmosphere and the land surface. For this reason, two more subprojects have been formulated: L4: Vegetation Characterisation and L5: Soil Characterisation, Surface Runoff and Infiltration. These subprojects characterise soil and vegetation respectively in such a way that the resulting parameters can be used directly in subproject A2: Validation of SVAT-model, where reaggregation at the standard 3 x 3 km level will take place. L4: Vegetation Characterisation produces at the same time enough information to run crop growth simulation models to calculate agricultural production in different parts of the basin. L5: Soil Characterisation, Surface Runoff and Infiltration calculates the movement of water through the soil and thereby also surface runoff and groundwater recharge which are inputs necessary for W1: " Runoff and Hydraulic Routing".

50 GLOWA Volta Subproject L1: Land use and natural resources (Prof. Dr. G. Menz, Dr. F. Vescovi, S.E.K. Duadze (RSAU), Ph.D. candidate, NN co-ordinator Ghana) Research question Land suitability deals with the classification of land into units on the basis of their individual capabilities to perform a given function or a combination of functions. Land suitability classification for crop production takes into account soil chemical and physical parameters, climatic, topographic and sometimes economic factors. The land suitability map of Ghana produced by the Soil Research Institute of Ghana was done for crop production, using the Agro-Ecological Zone (AEZ) model of the Food and Agriculture Organisation (FAO). A land use map simply gives an indication of the use to which a particular piece of land is put at a given time. Land use may not be in consonance with the recommended suitability due to various socioeconomic reasons. On the one hand, socio-economic pressures often lead to inadequate soil utilisation (soil degradation) by the population, on the other hand water supply and soil quality (land suitability) are driving forces and spatial determinants of recent and future settlement and migration patterns. To better understand the different feedback loops between socio-economic development, land use and resource base, the relation between the actual land use and the suitability of the land needs to be investigated. Once this is established, areas with sustainable and unsustainable development can easily be outlined. Research goals Partial objectives of the subproject are to assess the land use and land cover of the Volta Basin over the past twenty-five years (1975, 1984, 1995 and 2000), to investigate where there have been changes, and the direction of the change. The final objective is to assess the relationship between land use/land cover and the land suitability in different parts of the Volta Basin. Methodological Approach For the land use classification of a given year, images of about the same period or season of the year will be used to permit meaningful comparisons. Other data types that will be used directly or indirectly (ancillary data) will include the Soil Research Institute land suitability map, historical rainfall maps (CRU-East Anglia), topographic maps (drainage, settlements, etc), Digital Elevation Model (DEM), and meteorological data. All these are already available in electronic or paper formats. The land cover and land use analysis will be based on the land cover and land use classification scheme of Ghana developed by the Remote Sensing Applications Unit of the University of Ghana (see Appendix "Land use Map of Ghana"). Adjustments may be needed to fit the specific needs of the project. The idea is to automate the classification procedure on the basis of the existing map and to produce maps for the complete basin and for 1975 (first Landsat data), 1984 (census data available), 1990, and 2000 (new census). The interpretation will be verified in the field and accuracy assessment undertaken before final maps are composed. Each map will be accompanied by a database and a bulletin. To analyse the development of land use change over time, different change detection 1 methods will be applied which recognise and define spatial processes within a certain area by analysing 1 Remotely sensed change detection is the theory and methodologies of extracting, delineating, and attributing the temporal variations in the state of an object or phenomenon by observing it at different times using multitemporal imagery. (Dai & Khorram, 1998).

51 50 GLOWA Volta changes between different points in time (Jensen & Toll, 1982; Singh, 1989; Jensen, 1996; Dai & Khorram, 1998). The analysis of multitemporal changes uses approved statistical methods and digital image processing algorithms such as image differencing (Jensen & Toll, 1982; Green et al., 1994), image rationing (Howarth & Wickware, 1981; Nelson, 1983), principal component analysis (Byrne et al., 1980; Fung & Ledrew, 1987) or change vector analysis (Malila, 1980; Michalek et al., 1993). A different approach applies digital pattern recognition methods to already classified satellite images. By the application of the software metrics developed by Gasper and Menz (1999), changes can be detected by means of pattern recognition (dominance, fractal dimension and change of the complexity of the form of the land cover and land use classes). High-resolution time series of NOAA-NDVI data will be used to investigate how the changes of vegetation pattern correlate with the changes in rainfall. With principal component analysis, the multi-temporal NOAA-NDVI time series are sub-divided into single components for different time periods (e.g. single years, rainy season, and phenologic phases). The application of the principal component analysis method will yield meaningful results on the study of the land cover change. Land suitability maps are already present for the whole of Ghana at the scale of 1:250,000 in both paper and electronic formats as produced by Soil Research Institute. Rainfall is an important determinant of land suitability and of special interest in this water project. Therefore, maps with different weights for rainfall will be produced for the correlation analysis in order to measure the extent to which the correlations depend on rainfall or on other land suitability factors (soil physico-chemical properties, slope, etc.). Finally, to examine the correlation between land use and land suitability geo-statistical techniques will be applied. It is to be expected that patterns will be present in both land use and in land suitability which is why a geo-statistical (co-kriging) approach is preferable to a standard pixel-to-pixel correlation measure. Because the correlation will not be the same throughout the basin and for the different years, cluster analysis of the four-dimensional feature space (land use on axis one, land suitability on axis two, and longitude and latitude on the remaining two axes) will proceed the co-kriging. The cluster analysis will in first instance be based on unsupervised classification techniques which divide the pixels in groups with similar features, followed by visual inspection and supervised clustering. Each cluster will then represent a typical area for which the correlation functions will be established through geostatistics. Expectations In this project, the result of the correlation could be positive or negative. That is to say the result may agree with the land suitability classification or not. Land suitability classification aims at the optimum use of the land for production. Apparently, the use of land in accordance with its suitability classification tends to suggest its sustainable use. Therefore a positive correlation between land use and land suitability of the land of the Volta Basin will mean only an improvement in the practices associated with that use and not a switch over to another type of use. On the other hand, a negative correlation between the actual land use and the assessed land suitability will mean a possible switch to another use that is more likely to be less suitable and sustainable. When agriculture is intensified, people tend to use better endowed land more intensively then meagre soils. Positive correlations are also an indication that the physical environment is an important determinant in observed land use change (opportunity-driven intensification). Negative correlation, however, indicates that in these areas, socio-economic developments force people to make land use changes (need-driven intensification). It is expected, therefore,

52 GLOWA Volta 51 that the output of this subproject will provide an important input in subproject 3 "Predicting future land use" Subproject L2: Land use change and socio-economic development (Prof. Dr. J. von Braun, Dr. T. Berger, Dr. F. Vescovi, S.O. Kwankye, PIP, NN PhD. Student) Research question In the face of a rapidly growing population, much pressure is brought to bear on the land and its resources in developing countries. This is especially true for the West African region despite the relatively low population densities. To consider only the population densities (persons per square kilometre) of the Volta basin might be misleading. An integrated approach is more relevant for the rural areas in order to take into account the long term carrying capacity of land and water use and to study the interrelationships between population density and population growth. Nevertheless, it has to be taken into consideration that very rapid population growth can lead to a degradation of the natural resource base. Different hypotheses exist, however, whose empirical test results have not proven satisfactory yet: Investments in land and water use improvements on marginal lands do not off, since the costs for resource improvements and output commercialisation are too high. A contrary, yet unsettled point of view states: Since investments in marginal locations were lacking within the previous decades, substantial potential for productive resource improvements can be assumed due to the expected high marginal return. Still it remains scientifically unclear if The rate of poor population groups at locations with a high potential return is lower than at marginal locations. According to the latest scientific surveys by the Consultative Group for International Agricultural Research (CGIAR), statistical results still don t exist. In order to arrive at substantiated conclusions, empirical studies have to seek answers to the following questions: What is the pattern of population growth and distribution within the Volta basin? To what extent are the land use changes a function of population growth and distribution in the study area? To what extent is population growth and distribution influenced by land use changes, infrastructural developments or institutional changes within the study area? This includes especially the infrastructure development, institutional change and technological improvements which interact with the intensity of land and water use and the demographic consequences. In the face of the still insufficient knowledge about the connections between land and water use, population growth and socio-economic development, research activities have to pursue new methodical approaches which can seek answers to the above mentioned questions and hypotheses. In this context the concept of the "critical triangle of development objectives" which is proposed by Vosti and Reardon (Vosti & Reardon, 1997) seems to be useful. In the long run the generally approved development objectives "Growth", "Overcoming Poverty" and "Sustainable Resource Management" are indeed complementary, at short notice, however, competition is likely to occur particularly between the objectives growth and environment as well as between overcoming poverty and sustainable resource management. According to the authors, the trade-offs between these objectives vary in relation to their political context and their agro-ecological setting. In agro-climatic deprived areas, where an intensified agriculture is expensive, overcoming poverty might require the expansion of the agriculturally used area

53 52 GLOWA Volta unless there are other income sources. This might end in further soil degradation, and thus be inconsistent with the objective of overcoming poverty. In agro-climatic fostered areas, however, where a land use intensification can more easily be run sustainably, there might be a growth potential which can be used without falling back on erosion exposed hillsides, forests or public grasslands. Therefore, it can be stated that not so much disregard of environmental issues causes the deficient resource conserving practices in the rural households, but that the resource degradation is a result of surviving under difficult conditions. Based on the socio-economic and ecological factors which need to be classified on the household and communal level, the scientific challenge exists in analysing the interdependence between the different critical development objectives with regard to a long-term correspondence of the objectives in assessing different policy options as well as institutional and technological alternatives Research goals The sub-project has the overall objective of analysing the interrelationships that exist between land use changes and population within the Volta basin, and research the possible trade-offs and synergies between critical development objectives. This has basically the purpose of obtaining more information for policy makers on the specific socio-economic aspects of changes in land and water use, and assist them in achieving practical and more sustainable political instruments and technological options. Overcoming the monocausal interrelationships between land use and population growth is an important feature of the basic research. Instead, land use and population are seen as endogenous and concurrent problems which have to be taken into consideration in a complex socio-economic-demographic model. The considered "system outputs" can be subdivided into three basic components following the concept of the "critical triangle": 1. Profitability on an individual economic level and income generation 2. Impacts on the natural resource stocks (i.e. soil erosion, nutrient equilibrium) 3. Impacts on food security The "system inputs" can be subdivided into the following groups: 1. Agro-ecological variables (soil types, precipitation etc.) 2. Socio-economic factors (access to infrastructure and markets, household-working capacity and capital resources) 3. Individual economic management variables (factor input amount, technology options) Some of the basic features, i.e. infrastructure or allocation of public services, can be modified by policy makers (federal or local governments, non-governmental organisations). Since the land and water use and its intensity cannot be understood without knowing the demographic development, i.e. migration and other features of population movements, these features have to be particularly considered within the model. Methodological Approach The Project will rely on demographic data from the 1960, 1970 and 1984 Population Censuses of Ghana. The study will also benefit immensely from the Population Census that is planned to take place in March-April, 2000, the preliminary results of which are expected to be published by December the same year. Data on land use will be provided by the information systems of the other sub-projects. On the other hand, detailed surveys will be done within the three main ecological pilot sites that have been selected for the project in order to analyse - besides the demographic analysis - the

54 GLOWA Volta 53 socio-economic factors of land use on a regional level (household- and communal level). Therefore, the following methodology is chosen: Implementation of cascade models for the demographic revision of the population pyramid, including net in- and outflow of the different age groups; Descriptive (statistical) and partial-economic analyses (break-even analyses) for the socioeconomic and agro-ecological characterisation of the prevalent land use and animal farming systems, including the employment of labour apart from agriculture, i.e. factor intensity, profitability, share in sales products, indicators for a sustainable resource management etc. Causality analyses of the studied production- and investment behaviour of the rural households in order to analyse the underlying socio-economic and agro-ecological influencing factors. Assumed are behaviour patterns from a subsistent economy with multiple objectives. Models for representative operating households in order to reproduce physical input-outputrelations (including "ecological outputs" like nutrient release, soil erosion etc.) as well as economic relations. Based on this, analyses of policy options and technological and institutional alternatives for a more sustainable resource management with a parallel enhancement of survival security according to the "critical triangle". In this policy and technology analysis, possible discrepancies between individual economic and common objectives have to be taken into account, i.e. income and food security on the household level, the overall economic growth as well as impacts on the natural resource stocks. Different econometric and programming models will be combined for demographic and socioeconomic land use analyses on the household and aggregated level. Special programming approaches allow the simulation of different policy and technology scenarios as well as of institutional changes regarding a sustainable resource management, income generation and food security (Barbier, 1998). The obtained results can provide predictions of land use changes within sub-project L3 "Prediction of land use change". Expectations Methodical approaches for modelling complex relationships between land and water use and between population and socio-economic growth will be obtained. This will help to classify complex interactions between the above mentioned factors, and to assess them with regard to the critical development objectives. The relationships stated between the population growth and land use patterns in the Volta basin, will be directly taken into account in the sub-project L3 "Prediction of land use change". The predictions made in sub-project L3 can be extended for the whole basin as soon as the data of sub-project L1 "Land use and natural resources" and L2 "Land use change and socio-economic development" are available. The latter will be of basic importance for sub-project W2 "Integrated economic-hydrological optimisation", since the urban growth is closely related to the increasing demand for energy, agricultural products from irrigated soils.

55 54 GLOWA Volta Subproject L3: Prediction of land use change (Prof. Dr. P.L.G. Vlek, Dr. T. Berger, Dr. F. Vescovi, NN Koordinator Ghana, NN PhD Student) Research question General or statistical relationships between the natural resource base on the one hand and the land use changes on the other hand are unlikely to provide the necessary knowledge to project land use patterns in the future, since reliable modelling of climate change requires spatial resolutions between 3 and 5 km. This subproject foresees the analysis of the processes governing land use change within six representative land units of around 10 km 2 in the 3 Pilot Areas, and possibly in some selected satellite areas, and to extrapolate from those areas to principal regions within the Volta Basin. Research goals The primary objective is to provide the project with in-sight into the principal factors driving land use and land cover change within representative areas of the main ecological zones of the Ghanaian Volta basin. These studies will serve as a basis for up-scaling for the SVAT and MM5 models within the basin. They will also provide the basis for studying some of the land and soil-based attributes of the land units, needed for the modelling effort. The predictive capacity for land use change will in itself be a powerful policy instrument. It will, however, gain in power when it is fully integrated with the atmospheric modelling effort. Methodological Approach Six land units of around 3 x 3 km will be chosen, two at each pilot site, and satellite images will be obtained with the desired high resolution for detailed analysis of the land cover and use. All current images will be carefully ground-truthed. All the images will be of about the same period or season of the year so as to permit meaningful comparisons. Other data types that will be used directly or indirectly (ancillary data) will include land suitability information, historical rainfall maps (CRU-East Anglia), topographic maps (drainage, settlements, etc), Digital Elevation Model (DEM) map, meteorological data etc. of the regions, based on existing Ghana data basis and the detailed studies that have been conducted by previous projects in these areas. Information obtained from the surveys that will be conducted by other groups will be added as well. All this information will be assembled in a GIS based data compilation facility to be set up at SARI. The intensive field studies proposed here are seen as a follow-up to the broad scale fast-track approaches applied in L1: Land use and natural resources and should lead to the identification of generic trajectory processes of change (Lambin, 1997). The field studies involving the social-economists in L2: Land use change and socio-economic development, by themselves may fail to provide the spatial dimension of land use change. The challenge of these pilot studies is to combine the human and spatial dimension by analysis of the landscape dynamics through spatial-statistical models. The analysis involves the pinpointing of locations of land cover and land use change in relation to maps of natural and cultural landscape variables. Multivariate statistics are used to determine the variables most closely associated in space with land use change patterns (Lambin, 1994). Algorithms will be developed describing the rate and direction of land cover and land use change as a function of such factors as population dynamics, agricultural activity, proximity and access to water, markets and roads, land tenure, off-farm opportunities for income generation, etc. These methodologies have been largely developed and are being tested worldwide in the LUCC program, of which the GloWa Volta project is a member. These algorithms

56 GLOWA Volta 55 will be tested in satellite locations in order to allow up-scaling and projections of land use and cover for 2010, 2020, and possibly Expectations The subproject will create the ability to project future developments and pressures on land under various scenarios and would allow the analysis of the impact of policy decisions related to population control measures and infra-structure development. The effects on climate and its feed-backs will be realised through coupling with the Research Cluster Atmosphere Subproject L4: Vegetation characterisation (Prof. Dr. P.L.G. Vlek, Dr. F. Vescovi, Dr. M. Fosu (SARI), NN PhD Student, NRW scholarship candidate) Research question Land use change in the Volta Basin usually means intensification of the agricultural use of the land. Agriculture is intensified through reduction of the land under fallow and increased inputs in the form of labour, chemicals and irrigation. Changes in the vegetation are, of course, the first and foremost result of land use intensification. In turn, changes in vegetation may have desirable outcomes (increased food security and rural income) but also negative ones (diminishing of soil nutrient status, erosion). As most evapotranspiration in the Volta Basin in fact consists of plant transpiration and as vegetation also determines to a large extent the exchange of latent heat and momentum between the atmosphere and the earth surface, it is of great importance to have a thorough knowledge of the vegetative cover if one is to know the relations between land use and climate. The Volta Basin covers 400,000 km², which roughly corresponds with 400,000 NOAA/AVHRR pixels or 400 million Landsat pixels. Clearly, for all information to be manageable at all, the spatial resolution has to be reduced. As a rough standard, a pixel size of 3 x 3 km is the resolution at which basin-wide modelling and information exchange will take place. On this scale, land is covered by a mosaic of different vegetations, that each exhibit their own interactions with the atmosphere an with the underlying soil, so care has to be taken that this variability is properly accounted for. The vegetation characterisation should work towards solving two problems associated with upscaling the highly variable savannah mosaic: one is to provide agricultural production figures throughout the basin, and the second is to provide the MM5-SVAT model (see subprojects A1 and A2 and Chen, submitted) with functional vegetation parameters (root depth, roughness length, etc.). Research goals This subproject will analyse the vegetation cover under different land use types in all different ecological zones and develop a classification, capturing the significant fractions of land cover, that can be used for modelling purposes. The classification will be the basis for reaching two objectives: biomass production model capable of reproducing agricultural production as a function of rainfall, soil type, and fertiliser input level basin-wide provision of vegetative parameters needed in the MM5-SVAT model, such as root depth, Leaf Area Index (LAI), and roughness length over the growing season Methodological Approach Detailed survey information from subproject L1: "Land use and natural resources" will be the starting point for this project. With the aid of high resolution satellite imagery and, especially,

57 56 GLOWA Volta the expert opinions of SARI and INERA field personnel, a descriptive database of the vegetative cover and different farming systems will be developed. This database should include major crops, fallow lengths, cropping calendar, rotation schemes and natural vegetation. Similar farming systems will be pooled and dissimilar ones placed into categories that can be distinguished on the basis of geographic location and remote sensing signatures. Different agro-ecological regions will thus be mapped at a grid size of 3 x 3 km. For each major crop, an existing crop-growth model will be selected. The expectation is that little structural adjustment would be needed, but model verification and parameterisation will be performed in each of the three test areas. A somewhat coarser and more general model will be used to describe the development of the fallow vegetation. With the aid of the validated crop and fallow models, simulations will be run based on actual or modelled rainfall and input levels. The first output of these simulations would be distributed agricultural production over the basin. One of the output variables of crop models is the Leaf Area Index (LAI). During important parts of the year, there is a clear correlation between LAI, aggregated by aerial averaging, and the remotely sensed Normalised Difference Vegetation Index (NDVI). By comparing modelled LAI and measured NDVI, a large scale verification/calibration will be undertaken. The output of the crop growth models needs to be translated into parameters which enter directly into the MM5-SVAT. The starting point is the SVAT as described by Chen (submitted) which needs albedo, roughness length (assuming that momentum and sensible heat roughness lengths have a fixed ratio), minimal stomatal resistance, generalised canopy resistance, soil cover, and root depth. These variables are not modelled directly and most are also not directly observable through remote sensing techniques. Through measurements at the test-sites, some of these vegetation parameters will be directly linked to crop-growth-model outputs of the major crops: rootdepth to underground biomass, roughness length to above-ground biomass and albedo to LAI. It is very possible that some parameters (especially those concerning canopy resistance) which now are demanded by the SVAT will actually be replaced with more directly calculated (or remotely sensed) parameters and that the SVAT will be adjusted accordingly. Although developing correct aggregation schemes for the savannah mosaic falls in principle under subproject A2: "Validation of SVAT-model", close co-operation is needed in order to assure that we only work with parameters which indeed are directly linked with the vegetation covers associated with the different land uses. Expectations Besides the inherent value of understanding the differences in vegetative cover throughout the basin and the ecosystem functioning of vegetation types, this subproject has two important service functions to the project as a whole. First, it provides the biophysical basis for estimating biomass and agricultural production, needed to understand the productivity of the land as a measure for agricultural income, and to simulate the effect of rainfall variability on productivity. The second important function is to provide the MM5-SVAT model with the vegetation parameters which govern the actual evapotranspiration.

58 GLOWA Volta Subproject L5: Soil characterisation, surface runoff and infiltration (Prof. Dr. P.L.G. Vlek, Dr. N. van de Giesen, Dr. M. Fosu (SARI), Dr. Thiombiano (INERA), NN PhD Student, NRW scholarship candidate) Research question Water is among the most important limiting production factors in the upper sections of the Volta basin where agriculture is rain fed. The fraction of precipitation that is used for in situ evapotranspiration is of great agronomic importance as it is the prime determinant for yield. In natural eco-systems it determines primary production and often eco-system functioning. However, for the Volta basin as a whole, rain which does not evapotranspire where it falls is also of great importance because this is the water which feeds the rivers, either directly as surface runoff or by recharging the groundwater which then feed the rivers. The subproject A2: "Validation of SVAT-model" focuses on actual evapotranspiration but depends heavily on accurate soil physical parameters. At present, these parameters are only available for a part of the basin (Burkina Faso) and complete basin coverage is needed. The distribution of rainfall over infiltration and runoff is, at watershed level, a relatively complex process which can not be understood by calculating the vertical water movement by simply integrating Richard's equation and assuming that a 3 x 3 km pixel can be seen as single point. Instead, the spatial and temporal dynamics have to be properly accounted for by more detailed measurements and modelling. In addition, only a (small) part of the water which infiltrates will percolate deep enough to become groundwater recharge. From a water resource management point of view, groundwater recharge is extremely important because it is a source of drinking water and feeds the rivers, especially during the dry season when surface water is at a premium. Detailed soil physical research is also needed to model how much groundwater recharge takes place where and when. Research goals There are three objectives which this subproject needs to achieve: a basin-wide database which describes the soil physical parameters of each soil-map unit calculation of the amount of rainwater which runs off over the surface (as a function of these soil physical parameters) calculation of the amount of infiltrated water which percolates beyond the reach of plant roots and thereby becomes groundwater recharge. These objectives are more than mere service functions towards other subprojects. To understand how rainwater is distributed at the soil surface has direct operational value for erosion prevention and water harvesting techniques. Methodological Approach Pedo-transfer functions for all soil types in Burkina Faso have been developed by the International Soil Reference and Information Centre (ISRIC) in Wageningen. With some minor exceptions in the delta of the Volta river, all soils found elsewhere in the Volta basin are also found in Burkina Faso. The first step is to extrapolate the pedo-transfer functions to cover the complete basin and to fill in the remaining holes. Care will be taken to verify the functionality of the pedo-transfer functions, especially through checks at all trial sites. The next step is to examine how, with the aid of the soil-physical parameters, surface runoff and infiltration can be calculated at the level of 3 x 3 km grid cells. In all three test areas, small, well-defined first to second order watersheds will be selected and characterised in detail. All watersheds will be provided with raingauges and measuring weirs to obtain some first

59 58 GLOWA Volta quantitative insight in the fraction of rainfall which runs off during rainstorms. It is expected that on sandstone and granite geologies, the runoff percentage at watershed level is much less than the percentage runoff at point level because of infiltration further down the slope (van de Giesen et al., 1999). It is the runoff at point level which is calculated by standard SVATs, so more detailed research using runoff plots of different lengths will be needed to correctly model surface runoff at the level at which are interested. Erosion and sedimentation tend to be localised problems in the Volta basin and the surface runoff studies will therefore also enhance our capacity to find those regions which are most sensitive to erosion, especially under increased land use intensities. The water which infiltrates into the soil becomes available for uptake by plant roots. A fraction of the infiltrated water will percolate beyond the reach of the roots and recharge the groundwater. In the semi-arid and sub-humid tropics this fraction is usually much smaller (<10%) than in more temperate climates, but nevertheless this fraction is of great importance here because it feeds the groundwater and thus indirectly rivers as well. Recharge measurements are difficult, non-standard measurements. Here, the approach is to install access tubes for neutron probe or TDR-probe (the use of TDR-probes in access tubes would be preferable because of costs and transportation problems of the radioactive neutron probes, but it is, for lack of experimental data, at present unclear if the TDR probes will indeed be the method of choice for the Volta Basin). Around each access tube, a battery of tensiometers will be installed at different depths and existing water movement models will be used to deduce hydraulic conductivity functions, K(θ), and water retention curves, θ(h), and to calculate recharge (Belmans et al., 1983; van Genuchten, 1987; Šimuneth & van Genuchten, 1995; Šimuneth et al., 1998). In addition, at least one of the experimental watersheds will be on a granite geology and have a typical impermeable layer at shallow depth under the slopes (Diatta, 1996) which makes it possible to directly measure recharge through the monitoring of shallow groundwater which is collected locally and discharges locally. An important advantage at all sites will be that direct actual evapotranspiration measurements (subproject A2: Validation of SVAT-model ) will be made which will make it possible to actually close the water balance at the level of the experimental watersheds. Expectations The results from this subproject will provide important insights in the exact mechanisms in which rainfall is divided over in situ evapotranspiration, surface runoff, and groundwater recharge. Through the use of pedo-transfer functions, it is expected that the results at the research sites can be extrapolated throughout the basin. Without this research, it would be difficult to link the impact of land use change on water resources at a process level. Intensified land use is often associated with reduced low flows and/or increased floods and peakflows but examples from Côte d'ivoire show that in the West African savannah the inverse can be true as well. With process studies at three representative sites, more definitive insights will be produced. Subproject A2: Validation of SVAT-model" directly profits from this subproject as the basinwide soil physical parameter database and the modelling outputs (water available in rootzone, deep percolation and surface runoff) will be used there. Finally, subproject W1: Runoff and hydraulic routing needs the groundwater recharge and surface runoff figures in order to calculate the amount of water available in the river network

60 GLOWA Volta Research cluster Water Use Subproject W1: Runoff and hydraulic routing (Prof. Dr. H. Eggers; Dr. N. van de Giesen; Dr. W.E.I. Andah (WRI); NN Koordinator Ghana; NN PhD Student NRW scholarship candidate) Research question In order to optimise water use of the Volta river, the water availability over time along the river network needs to be known. Sub-project A1 "Preparation of basic version of MM5" will determine rainfall and evapotranspiration and L5 "Soil characterisation, surface runoff and infiltration" calculates how rainfall becomes available as river flow through surface runoff and groundwater recharge. What remains to be modelled is the delivery of groundwater to the rivers over time, the hydraulic routing of the river network, and rainfall and evapotranspiration in the riparian zones (including reservoirs). In W2 "Integrated economic-hydrological optimisation", the return on consumptive use of water along the river network will be optimised under different constraints and objective functions. This optimisation can best be achieved through so-called close coupling between the hydraulic and the economic model which ensures that any downstream effects of water consumption is accounted for directly. In order to facilitate such close coupling, the hydraulic modelling should allow for the off-take of river water for drinking water, irrigation, reservoir storage, etc. Although the hydraulic routing through the river system is not expected to pose serious scientific problems, the modelling of groundwater flow in a data sparse environment is. A complete hydrogeological model based on measured aquifer/aquiclude property distributions is beyond the scope of this project. The problem at hand is to accurately model the relation between groundwater recharge from L5 "Soil characterisation, surface runoff and infiltration" and general groundwater levels and the delay between recharge and delivery to the river network. For this purpose, a grey-box model will suffice and the scientific problem now becomes one of parameter estimation through non-linear inversion. Research goals The three research goals are: construction of a comprehensive hydraulic database including the distribution of the river network, existing groundwater level measurements, reservoirs, floodplain characteristics, and gauge and river flow data; operationalisation of a hydraulic river network routing model including flow parameterisation and modelling of rainfall/runoff and evapotranspiration from the (close to) saturated riparian zones and reservoirs; development of conceptual (reservoir type) groundwater models for each major geological zone of the basin, parameterised on the basis of calculated recharge, available groundwater levels, and measured river flows and stages. Methodological Approach Development of hydraulic database Although data in Ghana and Burkina Faso will be made available against reproduction costs given the participation of national scientific organisations in this GloWa project, the collection of some data poses a logistic and administrative problem. The river network and river flow data have already been collected for Ghana with the aid of WRI and through GRDC for the larger gauge stations throughout the basin (see also the Volta/GloWa CD-ROM). What remains to be done here is conversion of the data into standard georeferenced formats.

61 60 GLOWA Volta Data concerning groundwater (levels, bore logs, pump test results) are mainly available through executive agencies involved in borehole development for rural water supplies. In Ghana and Burkina Faso, these activities are often undertaken by private firms under contract with nongovernmental and donor organisations (GTZ, for example, consults GWSC on rural water supply, and the rural water supply project in the Volta Region). Data are not gathered with future scientific analysis in mind and format, completeness, availability and quality will differ enormously. The most efficient way to gather these data is through a contract with a local consultant. River network model Many models exist which can be used to meet the objectives of the study (Wurbs, 1995). The preliminary choice made here is for the Interactive River and Aquifer Simulation model or IRAS ( a relatively simple stage/discharge-based model. Without claiming that other models would be unsuitable, IRAS was mainly chosen for four reasons: the interactive structure enables non-technical users to evaluate the impact of changes in water use, which will help operationalisation of the results within different institutional contexts the open structure makes direct coupling of the hydraulic model with the economic model possible IRAS is data driven which means that also in situations where only few data are available the model is able to simulate river flow; as more data become available the model predictions become more precise IRAS has a proven record of successful application in developing countries (as well as in developed countries) IRAS is provided with a genetic parameter optimisation package which enables model calibration on the basis of existing flow, gauge and well data. It is expected that a first version of IRAS for the Volta will become available shortly after the inception of the GloWa project. This will involve the detailed mapping of stream nodes, segments and reservoirs and establishing stage/discharge parameters for each segment. This activity does not involve original research warranting a PhD and will therefore be executed by the hydrology staff involved (Prof. Eggers, Project Co-ordinator Tamale, Dr. W.E.I. Andah of WRI) supported by two MSc students and the ZEF GIS Lab. It is likely that during the project, more complex questions may become relevant concerning, for example, sediment transport or reactive solute dispersion. As a research tool, more complex hydrological and hydraulic models such as MIKE-SHE will be used to address these questions. Groundwater Given the objectives of the sub-project it is not necessary to develop a full-fledged geohydrological model for the basin. Instead, aquifers are considered as non-linear reservoirs with a storage coefficient (to relate water depth to water volume stored) and at least two parameters describing the stage/discharge behaviour. The scientific question now becomes to optimally estimate the coefficient and parameters and the basis of relatively sparse data. The idea is to adjust existing genetic algorithms to estimate the parameters for each major river segment and geological zone. The genetic algorithm is needed to find global optima for this non-linear inverse problem. Recharge calculations and borehole data will both have associated uncertainties and a Bayesian analysis will therefore be included. The combination of nonlinear inversion, and sparse and uncertain data warrants a full Ph.D. study.

62 GLOWA Volta 61 Data and information from other sub-projects as well as the hydraulic database have to be available before the groundwater model can be parameterised which is why this activity will start in year three of the project. Expectations This sub-project will produce an essential endogenous variable namely Riverflow. Using input from L5: "Soil characterisation, surface runoff and infiltration" it will calculate how much water will be available throughout the river network during the simulation period. Groundwater availability throughout the basin will be described, which is of importance for W4: "Communal and household water supply". A very close connection will be built with W2: "Integrated economic-hydrological optimisation" in the sense that the downstream consequences of any off-take from the rivers "suggested" by W2 will immediately be calculated and fed back to W2 so that direct optimisation can take place Subproject W2: Integrated economic-hydrological optimisation (Prof. Dr. J. von Braun; Prof. Dr. W.K. Asenso-Okyere (ISSER); Dr. T. Berger; C. Ringler; NN Sozioökonom; NN PhD Student) Research question Currently, water withdrawals in Ghana total about 729 million m 3, with urban water demand accounting for about 9% of total demand, rural domestic demand, 10%, irrigation, 77%, and livestock production, 4%. However, both irrigation expansion and population and economic growth are likely to fuel rapid increase in water demand, which is expected to increase more than five-fold by 2020, to 3,940 million m 3. Moreover, the major non-consumptive water use, hydropower, which depends on the level of the Volta Lake, might well be increasingly in competition with upstream consumptive irrigation water demands. The large projected increases in water demand will likely fuel the competition among water-using sectors. The likely increase in land intensification and changes in the hydrologic cycle (precipitation events and variability) will also influence the future competition for water uses in the Volta Basin. The impacts of these developments on hydropower production, water quality, the ecological balance, and the livelihoods in the Volta River Basin are so far unknown. To allocate future investments in technology, infrastructure or capacity building in the water sector wisely, it will be necessary to account for the costs and benefits of the individual investments in both economic and qualitative terms based on an analysis of the trade-offs and complementarities among water-using sectors. In addition, accompanying policy reforms in water management geared towards integrated river basin management will be needed to improve the efficiency, sustainability, and equity of potential investments. Research goals The major objective of the study is to evaluate the costs and benefits as well as the trade-offs and complementarities across water-using sectors in the Volta River Basin. Issues addressed include the impacts of increased irrigation development on hydropower production as well as the implications of increased hydropower development on future irrigated agricultural production and other water-using sectors. A particular focus will be on the implications of new technology development and other means to increase the efficiency of water use on future water demands and the competition across water-using sectors. The study will also contribute to the assessment of the effects of alternative water management and allocation mechanisms, policies, and technologies in the Volta Basin.

63 62 GLOWA Volta Methodological Approach An existing integrated economic-hydrologic optimisation model will be adapted to the Volta River Basin. The prior institutional analysis as well as the results of the household and community and the water and health analyses will contribute to both structure and parameters of the modelling framework. In addition, the economic optimisation model will be linked with the flow simulation model IRAS. The model incorporates water-using sectors, linked through water allocation rules and flow and mass balance equations, which describe the movement, diversion, consumptive use, and return flows of water through a river basin. The model specifies the structure of production and the demand for water and other inputs in each of the sectors, and the rules for optimisation of production, investment, and consumption activities. The development of the empirical model will integrate the hydrological-institutional characteristics of water allocation in the river basin; and analyse the economic costs and benefits of water use in the various sectors. Decision variables are water diversion and consumptive use of water at all basin locations and across sectors, groundwater extraction, and reservoir releases. Flow and water quality levels, reservoir storage, return flows, and economic impacts are the state variables that describe the resulting system. The model will be formulated as an optimisation problem, non-linear in the objective function and constraints. Two alternative approaches to the optimisation problem can be examined. In the first, maximisation of direct economic returns to water use is the objective function, with hydrologic characteristics, institutional rules, and environmental goals (such as maximum allowable salinity levels and minimum allowable instream flows) included as constraints. Alternatively, the objective function can be defined as maximising the direct and indirect economic returns, including full costing of negative and positive environmental effects and externalities. The first approach may prove to be the most feasible, given the difficulties inherent in costing some of the important environmental variables, such as instream flows. At each beneficial use site (agriculture, rural and urban households, mining and hydropower) water withdrawals and consumptive use (if applicable) as well as return flows (and the benefits and environmental externalities, if feasible) generated by water use will be determined. The allocation of water through the node-link network is governed by three kinds of constraints: physical constraints (results of the sub-project W1 River Flows and Hydraulic Routing ); policy constraints such as upper and lower bounds on variables that represent water allocation rules and existing water rights; and system control constraints to maintain feasibility. Water delivered to demand site nodes generates economic benefits from crop production, household uses, or power production. The various benefit and profit functions of water use will be estimated for the different demand sites and sectors in the basin. The river basin model allows the analysis of alternative policy scenarios. The baseline scenario integrates the current physical and technical conditions in the basin, including existing water availability and quality levels, as well as existing institutions and water policies, such as water rights structure, current water allocation, water prices, as well as taxes and subsidies on water, and levels of investment. Alternative scenarios can then systematically vary the physical, technical, institutional and water policy conditions in the basin, in order to analyse the impacts of changes on agricultural productivity, economic benefits, and environmental consequences. The changes in the cost-benefit relationship will then be compared with the investment and transaction costs necessary to achieve these alternatives. In addition, the institutional context and reforms in water policy necessary for these changes will be examined. Moreover, investment functions can directly be integrated into the objective function of the river basin model, either at the household, community, or industry level at the various demand sites (see also Figure 6, page 20) or at the basin level. In addition to the river basin analysis, a separate, dynamic investment analysis should be carried out.

64 GLOWA Volta 63 Expectations The outcome will be an integrated economic-hydrologic-institutional optimisation model for the Volta River Basin that allows for the estimation of the value of water in different uses, and the analysis of the trade-offs and complementarities in use across water-using sectors. The outcomes on potentially optimal water uses - from an economic point of view - will also be transferred back to the sub-project W1 River Flows and Hydraulic Routing, in order to take account of potential consequences of these withdrawals on the hydrologic system operation Subproject W3: Health and water (Dr. O. Müller (University Heidelberg); Dr. N. van de Giesen; NN Sozioökonom; NN PhD candidate) Research question About 90% of the global morbidity and mortality attributed to malaria are in Sub-Saharan Africa, where malaria-deaths mainly occur among young children of remote rural areas with little access to health services. Overall, some 40% of all fever episodes in Africa are caused by malaria (Brinkman and Brinkman 1991). It has been estimated that around one quarter of deaths in children aged one to four years in The Gambia are directly caused by malaria, but malaria is also considered a major indirect cause for mortality in young African children (Greenwood et al. 1987, Molineux 1997). Malaria thus remains a major contributor to the vicious circle of poverty and ill-health in Sub-Saharan Africa. The economic costs of malaria include its effects on the individual, the household, the community, and the economic development. Such effects vary with the age distribution of malaria-attributed morbidity and mortality in different endemic regions. In Africa, where disease and death is concentrated among young children, the effects are different from other areas where disease and deaths occur mainly among the breadwinners or primary caretakers of families. Being the most prevalent disease in the poorest rural areas of Africa, malaria produces much loss of productivity during the rainy seasons, when there is a peak demand for agricultural work (Sauerborn et al. 1996). It is common to find the parameter of seven days of work lost to disability per bout of malaria (Over 1992). Moreover, a significant impairment of the education of children in endemic regions has been attributed to malaria (MacDonald 1950). Political, social and economic changes, including population movements and ecological disturbances, contribute to a worsening of the malaria problem in many malaria endemic countries. Moreover, with rapid urbanisation, urban malaria is likely to become a more serious problem in the near future. The epidemiological situation is worsening with the spread of drug resistance in the parasite and insecticide resistance in the vector. Since the end of the 1970s, resistance to chloroquine is spreading rapidly on the African continent (Kean 1979, Wernsdorfer 1994, Müller et al. 1996). Together with the already huge impact of the AIDS epidemic, the spread of chloroquine resistance is leading to increasing childhood mortality rates in Africa (Marsh 1998, Müller and Garenne 1999). Research goals The objective of this study will be to examine the distribution of malaria-related factors and their relation with water and water-based development. Methodological Approach The methodology applied to achieve the research objectives is three-fold. In a first step, the existing published and unpublished literature on malaria in the Volta Basin will be reviewed, and the quality of existing routine malaria information at all levels of the health system in Ghana and Burkina Faso will be assessed. In areas without reliable data, random sample

65 64 GLOWA Volta surveys will be carried out to get a basin-wide picture of the disease. GIS technology will be applied for the production of malaria risk maps in the Volta Basin. These maps will be made available to national and regional organisations. Based on these maps, in a second step, malaria risk categories in terms of climatic and environmental data will be defined and models able to predict malaria risk in the Volta Basin will be developed. Epidemiological surrogate markers for malaria disease will be developed and field-tested and specific tools, which are helpful in monitoring malaria risks at peripheral health facilities of the countries of the Volta Basin, will be developed. Data collection and map productions will be undertaken in close collaboration with the malariologists from Ghana and Burkina Faso. Thirdly, to establish the relationship between water quality and health and socio-economic development and to gain deeper insights into the health impacts of water, water-based development, and usage and consumption of water of different quality, a survey will be carried out at the research sites (combined with the surveys as described under Sub-project Community and Household Water ). Based on the collected information, detailed benefit functions will be developed that link the returns of improved water quality (and quantity) to health and nutritional outcomes. Expectations The expectation is that this research will provide insight in larger scale distribution of malaria and malaria related factors. Such output will have direct relevance for local health-related activities and programs like WHO s Role Back Malaria Program as it will help select the most appropriate strategies to reduce malaria for different areas. Despite the complexity of the issue at hand, it is also expected that a first step will be made in the assessment of the overall effects of water related development, malaria, and general health status Subproject W4: Communal and household water supply (Prof. Dr. P. Webb; Dr. T. Berger; M. Iskandarani, Doktorandin; NN Koordinator Ghana; NN Socio-Economist; NN PhD candidate) Research question Ideally, the price of a good corresponds to its value and the easiest way to determine the value is to use the market mechanism. However, very few water markets exist world-wide, and traditionally water has been regarded as a public good. In most countries, it has been provided for free or at highly subsidised prices. Therefore it is a scientific challenge to estimate the real price of water. Demand for water (w) as a private consumption good is related to residential water use. Household water demand is site-specific and influenced by a range of natural and socioeconomic factors. The demand relationship is represented by the following demand curve: Q w = Q w (P w, P a, P;Y;Z) Where Q w refers to the individual s level of consumption of water in a specific time period; P w refers to the price of water; P a denotes the price of an alternative water source; P refers to an average price index representing all other goods and services; Y is the consumer s income, and Z is a vector representing other factors, such as climate and consumers preferences (Young 1996). Consumers are hypothesised to adjust water consumption behaviour and to modify water-using appliances in response to changes in the domestic water price. Domestic water consumption thus varies inversely to price changes. The general approach is to apply statistical regression analysis to estimate the parameters of a demand equation. Sufficient numbers of accurate observations on prices and water use for developing reliable demand functions have been difficult to obtain. And these limited data are mainly available through (public) suppliers

66 GLOWA Volta 65 using meters. The main scientific problem is the lack of data on water demand behaviour of consumers obtaining their water from other sources than the public supply system in rural and urban areas. Research goals The major objective of the study is to assess water security at the community and household level and thereby help manage water quality, quantity and its use for human health. The assessment of drinking water demand will be an essential input into the economic optimisation model and will also be informed by the outcomes of the hydraulic modelling. The household water demand analysis will: (1) serve as a demand and cost variable for the integrated economic-hydrological-institutional water allocation model; (2) provide a planning basis and tool for future adequate demand responsive household water supply. Methodological Approach The analysis will basically follow two complementary approaches: Econometric analysis of the determinants of water demand and water price Development of a community and household model for maximising utility of water consumption for domestic and agricultural use with time and water access as constraints. Actual data on expenditure for water of different source and across seasons will be collected based on a household survey. As a large part of the rural population still relies on traditional water sources and fetches water from river and ponds no direct monetary expenditure can be measured. However, time expenses for fetching water (especially of women) and transportation costs involved, can serve as a proxy for the water price (travel cost method) and show the opportunity cost of water (Young 1996). The underlying assumption of the travel cost approach is that observable household behaviour as related to increasing costs of travel reflects the changes in demand for the activity which would occur if prices were actually charged. The travel cost approach involves two steps: the first is to estimate the individual/household demand for the resource, and the second is to statistically derive the relevant aggregate resource demand curve. The households must be questioned regarding the number of visits, the distance travelled to the site and their actual travel expenditures. Regarding the estimation of travel cost, the calculation of opportunity cost of time becomes relevant. In many communities within the Volta river basin, households obtain their water by walking to traditional sources (river, ponds, wells) and carrying water home. If an improvement of water supply reduces the amount of time households spend fetching water, an estimate of the cost savings could be calculated by multiplying the amount of time saved by an estimate of the monetary value of that time. The wage rate of an unskilled labourer in the project area can be used as a proxy. Secondary data collection: Secondary data will be collected from the Ghana Water and Sewage Corporation (GWSC), the Community Water and Sanitation Agency (CWSA), Office Nationale de l Eau et de l Assainissement (ONEA) in Ouagadougou, Burkina Faso and other governmental agencies on the structure of the formal water supply system, consumption and expenditures for water through the piped system and water losses. Community survey and socio-economic assessment of regions: The community survey will provide an overview of household access to water in the river basin. The survey will provide knowledge about the type of access to water of different sources (e.g. borehole, hand-dug well, surface water), quality and basic socio-economic information. Based on this analysis communities will be selected from the three research sites (upper Volta river basin - Navrongo,

67 66 GLOWA Volta central Volta basin Tamale/Datoyili and Lower Volta basin Kumawu/Drabonso) and in addition to that in the coastal plains behind the dam, as access to water is expected to differ there. The selected communities will be stratified into those with good and poor access to water. The criteria for stratification into good and poor will be based on the type of water source a community relies on. The community would be considered to be with good access when the community is connected to the piped system, has access to a borehole or hand-dug well, respectively. Communities that rely on traditional water sources such as river, streams and ponds are classified as having poor access. In parallel, two cities along the Volta will be surveyed in terms of their patterns of intra-urban access to water from different sources and supply systems. Survey will be undertaken in Tamale (mid Volta basin) and Accra (main water consumer of water from the lower Volta basin and capital of Ghana). Household survey: Six household surveys (sample size of 100 / 200 at each site) will be conducted at two points in time (dry and rainy season). One in each selected urban area and one at each rural research site. The survey will help to provide estimates on water demand, usage and expenditures on water according to household composition, type of access, water quality, water price, household income, location, and season. This will help to obtain a better understanding of the economics of household water demand and supply for the different water sources across seasons and level of access and to gain insights into intra-household usage patterns and their health impacts. The urban sample will be drawn randomly after selecting clusters according to the water distribution areas. The urban sample size will be 200 households, 100 for each urban survey site. Survey sites Sample size Tamale (GH) 100 Accra (GH) 100 The rural sample will be composed of a total of 800 randomly sampled households after clustering and stratifying according to the type of access to water: Survey area (District) Upper Eastern Region Northern region Afram plain / Kumawu No. of communities Sampling and stratification 4 2 communities with good access (survey of 2 x 50 HH) 2 communities with poor access (survey of 2 x 50 HH) 4 2 communities with good access (survey of 2 x 50 HH) 2 communities with poor access (survey of 2 x 50 HH) 4 2 communities with good access (survey of 2 x 50 HH) 2 communities with poor access (survey of 2 x 50HH) Coastal region 4 2 communities with good access (survey of 2 x 50 HH) 2 communities with poor access (survey of 2 x 50 HH) Expectations Within the project the urban formal and informal supply system will be analysed and assessed and determinants of water access and water demand examined. Actual data on expenditure for water of different source and across seasons and location will be collected and a demand function derived by estimating income and price elasticities. A

68 GLOWA Volta 67 household-community model with market failure conditions will be developed to explain consumption decisions assuming utility maximisation. Moreover the results help to derive a net benefit function from household water use, which then will serve as a variable in sub-project W2 Integrated economic-hydrologic optimisation Subproject W5: Institutional analysis (Prof. Dr. A. Wimmer; A. van Edig; NN Koordinator Ghana; NN Sozioökonom; NN PhD candidate) Good water management at national level is the condition for any efficient and sustainable water management. Political factors often hinder the reform of the institutions or legal systems and therefore impede an efficient water management. An in-depth analysis of the institutional, political and legal environment should be the basis for any scientific proposition in order to avoid a pure Top Down approach, which might not be implemented at the lower management level due to the lack of participation of the involved communities. Research question In Ghana, a large number of organisations are involved in water resources management. Inadequate cost recovery measures have contributed to the financial weakness of the major water agencies, the Ghana Water and Sewerage Corporation, the Irrigation Development Authority, and the Volta River Authority. Moreover, the organisations are scattered in different ministries with different levels of Authority and little co-operation. However, the establishment of the Water Resources Commission (WRC) in 1996 as an umbrella organisation will likely facilitate more integrated management of the resource. The WRC is expected to become the knowledge base and co-ordinator for all water-related activities in the country. The grant of water rights is one important and crucial example for the need of research and implementation: The WRC is responsible for granting water rights. Until its establishment, the institutions in the different water use sectors were responsible for the granting of water rights (the GWSC for drinking water, the IDA for Irrigation water, the VRA for hydropower). It will be of basic interest how these water grants will be handled in the future, a question which is related to proper institutional management, but also to social and economic questions, like water pricing, efficient water use, priority of drinking water, water quality and water pollution At the international level, Ghana and Burkina Faso are the main stakeholders in the Volta River Basin. Although there are no open hostilities at this point, competition for scarcer water resources at the international level will likely develop in the future if water is not managed more efficiently in both riparian countries. Burkina Faso announced this year to build three dams at one of the Volta tributaries, two for hydro-electric purposes and one to supply the capital city of Ouagadougou with water. This would raise the total active storage of the dams to 149 MCM, or 3,75% of the storage of the Akosombo Dam in Ghana. The Ghanaian Government is concerned that these hydropower projects might reduce the flow of the Volta River and negatively affect hydropower production in Ghana, which already experienced serious delivery problems in The national governments have made the first steps to ameliorate the institutional framework in view of the competition for water resources. The consequences of these developments are still unclear - especially at the local level. Research goals In order to define the institutional framework in which the water allocation takes place the three following research goals have been identified: Analysis of the existing institutions, their efficiency and relative political power

69 68 GLOWA Volta In depth stake holder analysis Overview over the actual international co-ordination efforts as well as incentives and obstacles for international co-operation Methodological Approach The first step of the institutional analysis will be an in-depth analysis of the existing institutions at the international, national and regional level. In-depths interviews will be carried out with the staff members of the institutions, the water use sectors (household water, energy supply, agricultural water) as well as the NGO`s involved in the sector and international organisations. It is hoped, that in the frame of the GLOWA project a conference can be held in Ghana with the different institutions involved in the sector, so that contacts can be made through the Ghanaian counterparts. Close co-operation is envisaged from the beginning with the key policy makers and especially the members of the Water Resources Commission, which started to work 1996 and is supposed to be the overall water management body in Ghana. The second step will be an analysis of the local institutions, water allocation system, and community approaches in water management at the local level at three defined research sites (Tamale, Navrongo and Kumawoi). The existing systems and needs at the community level will be analysed and compared. The third step will be in-depth interviews of the existing institutions. The different institutions at different levels will be examined according to the existing decentralised system (Unit Committee, Zonal Committee, District Assembly and Central government). As faced with concrete needs at the local community level in the water use sector, the methodology will serve both as an efficiency and a political indicator of the institutions at the various level. In-depth interviews with the key actors up to the Central government who will be faced with concrete needs of the communities at the local level which will give evidence about how local systems and problems influence the national institutions and policies and vice versa: Do the formulated national water policies and laws reach the local level at all? An efficient information and implementation system in both ways is crucial to secure the data collection and pollution control, but also the influence and adaptation of the existing traditional allocation systems to the formulated policy processes. Fourth, a detailed stake-holder analysis and the allocation systems at different levels and an analysis of the institutions will be formulated. The efficiency of the institutions, the information flow and the relative political power will be the outcome of the stake holder analysis. By the analysis the question which political factors lead to the current institutional situation will be an integral part of the research. The outcome will not be a model, although the institutional data will be integrated in the Economic optimisation model. The research is rather done in order to understand the political rationality behind the national water policies, the role of the institutions and the role of the water-allocation system at different levels. The same analysis with the same working plan will be done in Burkina Faso, but the analysis will concentrate on institutions and decision systems for the Irrigation systems. Fifth, on the international level, the study will concentrate on the existing and future development priorities of the riparian countries and potential conflicts in the uses. An analysis of the existing institutions responsible for international co-operation will be conducted in Burkina Faso and Ghana as well as the priorities in the Volta basin development of both countries. In this study area the development priorities will be evaluated and possible alternatives for the respective uses will be proposed, if conflicts over the respective use has been identified. Some of these proposals can be win-win situations in the development of projects.

70 GLOWA Volta 69 Sixth, a comparison of the existing national legal water systems which will focus on licensing systems will help to enhance co-operation at least in exchanging data. Political factors which impede the co-operation between the riparians will be analysed and evaluation of water claims of the riparians in the Volta Basin will be conducted on the basis of international Water Law. Expectations The stakeholder analysis will serve as a basis for the political, social, economic and institutional decisions in the water sector. The results will furthermore improve the scientific knowledge about institutions, policy and legislation. The subproject will serve furthermore data collection for the subproject W2: Integrated economic-hydrologic optimisation. It will give subproject W4: Communal and household water use realistic parameters with a view to the allocation of water resources on different economic sectors, integrating the relative power and influence of the different interest groups on the respective government agencies. Finally, the co-operation between the projects and the national institutions will be strengthened through this sub-project.

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80 GloWa Volta Code Keyword Name Variable Input Output A1 MM5 Preparation of basic version of MM5 Actual evapotranspiration (ETa) A2 MM5 MM5 A2 SVAT Validation of SVAT-model Actual evapotranspiration (ETa) MM5 Rainfall Vegetation parameters (Veg Param) Soil parameters (Soil Param) A3 Feedback Research of feedback mechanisms A4 Impact Impact of intensified land use L1 L2 Land Ressources Soc.ec. Develop. Land use and natural resources Land use change and socioeconomic development Rainfall A1 A4 L4 L5 MM5 ETa ETa ETa ETa MM5 A1 Sensitivity L3 MM5 ETa Vegetation parameters (Veg Param) A1 A2 L4 Rainfall Rainfall Rainfall Extrapolation (Extrapol) L3 Ress pattern Soil map Population Extrapolation (Extrapol) L3 Develop pattern Urbanization A2 A3 A4 A1 A4 L4 L5 A2 L4 L5 L3 L5 L3 W2 L3 Prediction Prediction of land use change Table 1: Subprojects, Variables, Inputs, Outputs. Landuse Technology Sensitivity Basic model land resources (Ress pattern) Basic model development (Develop pattern) Production L4 Vegetation Vegetation characterization Production Actual Evapotranspiration (ETa) Rainfall Cropping system (Crop sys) Soil Parameter (Soil Param) L5 Soil Soil characterization, surface runoff and infiltration W1 Runoff Runoff and hydraulic routing W2 Optimization Integrated economichydrological optimization Riverflow Hydroenergy Water use Technology Actual Evapotranspiration (ETa) Rainfall Soil map Vegetation Parameters (Veg Param) Surface runoff and recharge (Recharge) Extraction Urbanization Riverflow Demand Restrictions W3 Health Health and water Health Runoff W1 W4 Household Communal and household water supply Income Health Ground water Restrictions W1 W5 W5 Institutions Institutional analysis Institutional Development (Instit. Developm.) A3 L1 L2 L4 A2 A4 L3 L5 A2 A4 L1 L4 L5 W2 L2 W1 W4 W5 Extrapol Extrapol Crop sys Veg param Veg param Production Veg param Soil param Soil param Recharge Riverflow Riverflow Ground water Extraction Demand Restrictions Restrictions L1 L2 L4 A2 A4 L3 L5 A2 L4 W1 W2 W3 W4 W1 W2 W2 W4

81 GloWa Volta MALI NIGER N BURKINA FASO 0 100km Navrongo GHANA Tamale BENIN TOGO COTE D'IVOIRE Kumawu Akosombo Gulf of Guinea Figure 1: Simple map of the Volta basin

82 GloWa Volta ETa MM5 ETa rain MM5 MM5 A2 SVAT ETa A4 impact rain A3 feedback A1 MM5 ETa soil param veg param ETa rain rain veg param production cropping system atmosphere L5 soil veg param soil param L4 vegetation production sensitivity develop. pattern extrapol land use L1 land resources L3 prediction land use technology L2 soc.-ec. develop. population soil map extrapol ress. pattern drain extraction urbanization water flow W1 riverflow riverflow W2 optimization hydroenergy water use technology W5 institutions instit. developm. restriction W3 health health W4 household income health water use drain ground water demand restriction Figure 2: Structure of the project

83 GloWa Volta Annual Runoff and Rainfall in the Volta Basin Runoff at Senchi [km³/yr] Year Rainfall in the Basin [km³/yr] Runoff Rainfall Figure 3: Water balance of the Volta basin, Runoff at Senchi (Akosombo) and Rainfall

84 GloWa Volta Angolokaha 5,18 W / 8,52 N Karakpo 5,69 W / 9,23 N Lamekaha 5,65 W / 9,27 N km N Source: Landsat TM Scene ( ) Figure 4: Savanna mosaic, villages in the Westafrican savanna with different landuse intensities

85 GloWa Volta Water level Lake Volta 90 Water level [m] Rainfall Jahr 0 Water level Operation level Rainfall Average rainfall Figure 5: Average water level and annual rainfall

86 GloWa Volta Institutional, political, legal Framework Runoff Health MS Navrongo Tamale HH HH HH HH MS COMMUNAL Demand Health COMMUNAL Demand HH HH HH HH Population Households, Production Industry/ HH (Accra) Runoff Runoff MS HH HH Kumawu COMMUNAL Demand Hydroenergy Population HH HH In- and Outflow Nodes Health Households, Production Akosombo-Dam MS Mode of supply Figure 6: Relation between the different components of the Water use cluster in the Volta Basin

87 GloWa Volta Landuse intensity in northern Ghana Landuse intensity [ha/ha] Northern Region Upper Western Region Upper Eastern Region peripheral fields fields close to settlements Figure 7: Landuse intensity in northern Ghana

88 GloWa Volta Electric Power Use Ghana Energy [TWh] Year Valco Urban Mines Export Rural Figure 8: Electric Power Use in Ghana in 1980, 1985, and

89 Figure 9: Interactivity of the IRAS-Model GloWa Volta