GROUNDWATER IN THE VOLTA BASIN

Transcription

1 GROUNDWATER IN THE VOLTA BASIN 1.0 Introduction The Volta is a transboundary river, which is shared by six countries in West Africa; Bénin, Burkina Faso, Cote d Ivoire, Ghana, Mali and Togo. It stretches from north to south over a distance of 1850 km with a basin covering an area of approximately 400,000 km 2 (Fig. 1). The basin area in the six countries varies. It ranges from 2.48% in Cote d Ivoire to 42.9% in Burkina Faso. On the other hand, while the Volta basin covers 70.1% of the land area of Ghana, it dwindles to 1.0 % in Mali. 2.0 Hydrogeology The geology of the main Volta (Fig. 2) is dominated by the Voltaian system, which together with the basement complex dominate the hydrogeological systems (Barry et al., 2006). In Ghana for example, the basement complex covers 54 % of the land area and contributes 50% of groundwater resources. The sedimentary formation underlies about 45% of the country and provides 39 % of groundwater (Fig. 3). 3.0 Transboundary Groundwater At a recent UNESCO Workshop on Inventory of Transboundary Aquifers in West Africa, in Cotonou, Benin, from 30 May to 01 June 2007, the following shared basins were identified in the Volta basin (Table 1). Table 1 Transboundary Groundwater in the Volta Basin Shared Basin Characteristics Countries Iullimeden 3 aquifer basins with River Niger as the southern limit. Mali, Niger, Nigeria Bénin, Algeria Taoudéni Various types of sandstone. The basin is virtually unknown Burkina, Mali, Mauritania, Algeria Tano Coastal sedimentary basin located in the Cote d Ivoire, Ghana lower reaches of the Tano River in Ghana. 3 aquifer horizons with potential to supply Abidjan. Not much information available. Keta Coastal sedimentary basin, which includes Ghana, Togo, Bénin and Nigeria the Volta estuary. 3 transboundary aquifers, which supply water to key coastal urban centres including Lome, Cotonou, Lagos and Port Harcout Volta Information is very scanty. The basin is Burkina, Bénin, Togo virtually unknown. Liptako Gourma* Crystalline basement aquifer Burkina Faso, Niger *Not included in workshop list but could occur in the Volta basin (Fig. 4) While some of the aquifers were virtually unknown, information on the others was scanty. From available information, inconsistencies occur in data and information on groundwater in the Volta basin as a result of inadequate knowledge on the resources. For example, the aquifers identified during the above workshop did not include the Liptako Gourma, which is shared by Burkina Faso and Niger. In spite of this, it can be inferred that all the six riparian countries of the Volta share, at least, one groundwater basin with another country (Table 2). Benin shares as many as four basins with the other riparian countries. Two basins, the Tano and Volta are shared solely by the riparian countries of the Volta while four basins are shared with other non-riparian countries (Fig. 4).

2 Table 2 Shared Groundwater Basins No. of Shared Groundwater Basins Country With Riparian Countries With Non-Riparian Countries Benin 3 2 Burkina Faso 2 2 Cote d Ivoire 1 - Ghana 2 1 Mali 2 2 Togo Utilization and Problems Groundwater resources in the Volta basin are used mainly for domestic water supply in both urban and rural areas. Key cities such as Ouagadougou, Cotonou and Lomé all rely on groundwater for a significant proportion of their water supplies. In many rural areas, groundwater is the only source of safe portable water supply. Groundwater is also used for watering of livestock and crop irrigation but on a comparatively limited scale. In general many groundwater sources are untapped although the rate of use is rapidly increasing (ECOWAS-SWAC/OECD, 2006). The major problems associated with utilization of groundwater in the Volta basin include: Over exploitation as a result of population pressure; Contamination and pollution problems from poor domestic and industrial waste disposal practices; Deforestation and creation of irrigation dams resulting in reduced aquifer recharge; Intrusion of saline waters and high fluoride and iron concentrations affecting water quality; Impacts of reduced rainfall and global climatic change. 5.0 Management of Groundwater in the Volta Basin The management of groundwater occurs at different levels in the various countries. While some countries including Burkina Faso, Cote d Ivoire and Benin have established systems to monitor shared aquifers, others such as Ghana and Togo do not have such systems in place. Monitoring is mainly by the use of networks of piezometers. However, in all cases, installed monitoring systems are not adequate. Data and information are not sufficient to neither map out the aquifers nor assess their recharge. Also, both public and private sector institutions continue to operate sectorally, with little coordination. At the transboundary level, there is virtually no contacts or cooperation between the various national institutions responsible for the management of groundwater resources. Legislation for the management of groundwater resources is not common. It usually forms part of general codes for protection of water resources or the environment and is not specific to ground water. However, efforts are being made to improve the situation as in Ghana, which has recently passed Drilling License and Groundwater Development Regulations in attempt to control drilling and improve data collection. 6.0 Way Forward Many recommendations exist for improved management of groundwater resources in West Africa of which the Volta basin is a part. These include the following: Tripoli June 2002 UNESCO/ISARM Workshop on Managing Shared Aquifers Resources in Africa, which highlighted the need to: Conduct inventories of African shared aquifers; Prepare guidelines for sound and sustainable development of shared aquifers; Initiate activities with the support of partners within the framework of ISARM Africa; 2

3 Include the NEPAD and AMCOW process Groundwater Capacity Building Initiative in Africa (BGR/Cap-Net/WA-Net/Waternet), whose survey resulted in key recommendations for improvement in groundwater management as follows: Groundwater assessment and development; Institutional and legal arrangements; Groundwater protection; Groundwater education and training Cotonou June 2007 UNESCO/ISARM Workshop on Inventory of Transboundary Aquifers in West Africa, which made recommendations to: Prepare an atlas of shared aquifers in West Africa; Conduct case studies for selected aquifer basins; Increase participation of decision makers in management of shared basins All the above recommendations are still valid and relevant and the Volta Basin Authority supports them as providing the right direction for improving management of shared groundwater resources. The VBA therefore wishes to participate fully in these activities. Although VBA, just as other basin organizations in West Africa, is named on the basis of the more obvious Volta River, its Statutes indirectly take into consideration the management of groundwater resources, with references to development of natural resources and adoption of integrated water resources management. At this stage, due to the need to minimize duplication and conserve resources, it is not necessary to create new institutions within the Volta basin or in West Africa specifically for management of groundwater resources. Also, since all water resources should be managed together, VBA and other existing basin organizations as well as institutions such as ECOWAS Water Resources Coordination Unit should be strengthened to integrate management of groundwater resources into their scope of activities. This can be achieved through the modification or expansion of activities such as the operation of observatories and implementation of the HYCOS projects. The Statutes or other relevant international agreements of the basin organizations can also be modified to specifically include groundwater. While it is urgent to improve the management of groundwater resources in the area of the Volta basin, with particular emphasis on shared aquifer basins, repeating the mistake of management of water resources on a sectoral basis should be avoided, even though it appears to be an easier option. In addition to the required cooperation among the riparian countries of the Volta basin, is is important to strengthen inter-basin cooperation since majority of the riparian countries share aquifer basins with some non-volta countries. Also, in view of the growing importance of groundwater to the improvement of livelihoods in the Volta basin, more reliable data and information should be generated to support sustainable management of the resources. The VBA therefore wishes to solicit the support of its international technical and financial partners to undertake a case study of the transboundary aquifers of the Volta basin. 8.0 REFERENCES Barry, B. Obuobie, E., Andreini, M., Andah, W. and Pluquet, M., The Volta River Basin ; Comparative study of river basin development and management. IWMI, Comprehensive Assessment of Water Management in Agriculture ECOWAS-SWAC/OECD Volta HYCOS, Project Document 3

4 Fig. 1 Map of the Volta Basin and Riparian Countries (Volta HYCOS, 2003) Fig.2 Geological Map of the Volta Basin (Barry et al., 2006) 4

5 Fig. 3 Hydrogeological Provinces and River Systems of Ghana (Geological Survey of Ghana 1969) Source: ISARM Africa 3. Taoudéni 4. Iullimeden 12. Liptako Gourma 13. Tano 14. Keta The Volta aquifer is not represented Fig. 4 Shared Aquifer Basins in the Volta Basin 5