9.1 Floods in combination with key drivers Droughts in combination with key drivers Current and future hotspots regarding floods

Transcription

1 Published by: Comparison of key drivers regarding their significance for hydro-meteorological extremes and their impacts on selected hotspots within the Mekong River Basin

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3 Comparison of key drivers regarding their significance for hydro-meteorological extremes and their impacts on selected hotspots within the Mekong River Basin Lars Ribbe, Alexandra Nauditt, Dominic Meinardi, Matthias Morbach, Rike Becker Institute for Technology and Resources Management in the Tropics and Subtropics (ITT), Cologne University of Applied Sciences

4 Table of Content 1 Introduction Motivation and background Objectives and research questions Concept, methodology and structure of the study Study region: Basin Overview and Drivers of Change in the Mekong River Basin (MRB) Geo-physical Characteristics Socio-economic Characteristics Flood Hazards and Vulnerability Introduction Causes and impacts of floods Summary of major floods and their damages Conclusion Drought Hazards and Vulnerability Drought risk assessment and management Drought Vulnerability and socioeconomic impacts Conclusion Key Drivers and Pressures 1: Climate change Introduction and overview of literature Current Situation and Tendencies Current and potential CC hotspots Conclusion and recommendations Key Drivers and Pressures 2: Socio-economic developments Introduction and overview of literature Current situation and tendencies Current and potential hotspots Conclusion and recommendation Key Drivers and Pressures 3: Land use change Introduction and overview of literature Current Situation and tendencies of land use changes in the MRB Current and potential hotspots Conclusion and recommendations Key Drivers and Pressures 4: Hydropower development Introduction and overview of literature Hydropower development: current situation and planning Hydropower development: Impacts on hydro-meteorological extreme events / hotspots Conclusion and recommendations Summary: comparative evaluation and hotspot analysis... 96

5 9.1 Floods in combination with key drivers Droughts in combination with key drivers Current and future hotspots regarding floods and droughts Conclusion and recommendations for further studies and projects References

6 List of Figures Figure 1: The DPSIR approach... 2 Figure 2: Basic concepts related to disaster risk management... 3 Figure 3: Cause-effect relationships of hydro-meteorological extremes... 4 Figure 4: Physical map of the Mekong River Catchment... 5 Figure 5: Mekong at Kratie - the bi-variate distribution of annual flood peak and volume, 1924 to The estimated recurrence interval of the 2011 event in terms of the joint distribution of the two variables is just 1 : 10 years. That of :20 years Figure 6: Potential Effects of Increased Flood-related Vulnerability in the MRB Figure 7: Regional distribution of major Flood impacts Figure 8: Main Effects of Increased Drought-related Vulnerability in the MRB Figure 9: Regional distribution of major observed droughts Figure 10- Inundation map of the Mekong Delta in 2100 at 65cm of sea level rise under B1 emissions scheme Figure 11- Inundation map of the Mekong Delta in 2100 at 75 cm of sea level rise under B2 emissions scheme Figure 12- Inundation map of the Mekong Delta in 2100 at 100cm of sea level rise under A1FI emissions scheme Figure 13: Possible climate change hotspots as identified in the reviewed literature Figure 14: Population density in provinces within the LMB Figure 15 Regional distribution of socio-economic vulnerability Figure 16: Major Land uses in the lower Mekong River Basin Figure 17: Areal changes in land use types in Xishuangbanna region from Figure 18: Change in land use from in Menglun township, SW China Figure 19: Vegetation Cover Changes in Lao PDR Figure 20: Land use/land cover for Sisaket, Thailand and Ordar Mean Chey, Cambodia Figure 21: a) Land Use in 1997; b) Predicted Land Use in 2050 for the Srepok River basin Figure 22: Relationship shrimp farm and mangrove forest in Tra Vinh Figure 23: Land use change at the Ca Mau Peninsula, Vietnamese Mekong Delta Figure 24: Projected land use in Can Tho, Vietnam delta Figure 25: summary of hotspots regarding land use changes Figure 26: Hydropower projects on the Mekong mainstream and tributaries in the LMB Figure 27: Daily hydrograph of Chiang Saen gauging station during filling of Xiowan Dam in 2009 (left) and in 2010 (right) showing a considerable noise due to operation of Chinas mainstream hydropower projects Figure 28: location and size of reservoirs in the MRB Figure 29: status of reservoir construction in the MRB... 94

7 List of Tables Table 1: Flood types in the Lower Mekong Basin with a risk and hazard... 9 Table 2: Ranking of years with highest discharge rates ( ) in the LMB (Source: MRC 2006) Table 3: Information on main causes, effects and impacts of Mekong transboundary flood issues Table 4: Socio-economic impacts of floods in Cambodia ( ) Table5: Socio-economic impacts of floods in Lao PDR ( ) Table 6: Socio-economic impacts of floods in Vietnam ( ) Table 7: Socio-economic impacts of floods in Thailand within the MRB ( ) Table 8: Summary of mentioned and considerable events during the flood seasons 2005 until 2011 based on the Annual Mekong Flood Reports published by the Mekong River Commission Table 9: Floods in Cambodia - major characteristics, socio-economic impacts and areas affected Table 10: Floods in Lao PDR- major characteristics, socio-economic impacts and areas affected.. 25 Table 11: Floods in Vietnam - major characteristics, socio-economic impacts and areas affected.. 26 Table 12: Floods in Thailand - major characteristics, socio-economic impacts and areas affected.. 28 Table 13: Drought types and their characteristics Table 14: Frequency of Droughts in the Mekong Region Table 15: Some of the Potential Impacts of Droughts in the Mekong Region Table 16: Economic Impacts of Droughts in Thailand Table 17- Identifying Drought Hotspots in Vietnam Table 18- Percentage of area at risk of inundation according to the different sea level rise scenarios Table 19: Percentage of Forest Cover of the Mekong countries Table 20: Changes in land use types in Xishuangbanna region from Table 21: Changes in land use/cover from in Menglun township, SW China Table 22: Change in NDVI for whole Lao PDR PDR and the Sayabouri Province Table 23: Changes in area harvested of selected crops (ha) in Lao PDR PDR ( ) Table 24: LULC diversity as response to road distance, at different scales and different timesteps at Sisatek province in Thailand (1989, 1994, 2000 and 2005) Table 25: Results of Land Use/Land Cover change detection analysis (edited by Author) (Senevirathene et al.2011) Table 26: Changes in mangrove forest in Tra Vinh (-: reduction; +: increase) Table 27: Number of existing, planned and under construction hydropower projects in the Lower Mekong Basin on the Mekong mainstream and its tributaries per country and in total Table 28: Installed capacity of existing, under construction and planned hydropower projects (in MW) in the Lower Mekong basin on the Mekong mainstream and its tributaries per country and in total Table 29: Proposed capacity on mainstream hydropower projects in the Greater Mekong Basin Table 30: Monthly discharge anomalies and the range of hydrological variability of the 6 dam cascade scenario compared to the baseline scenario Table 31: Average flood pulse parameters of Baseline, 3 Dam and 6 Dam scenarios at Chiang Saen Table 32: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects on the Mekong mainstream and its tributaries in Lao PDR... 85

8 Table 33: Summary of impacts for dams featured in power surge cases studies Table 34: Sub-catchments with a total live storage greater than m 3 in Lao PDR Table 35: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects in Thailand Table 36: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects on the Mekong mainstream and its tributaries in Cambodia Table 37: Flood parameters in Kratie as an average of 10 year discharge data ( ) Table 38: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects in the 3S River System Table 39: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects in Vietnam... 92

9 Abbreviations ADB AGCMs AOGCMs CRU DHI DMP DPSIR DRI DVI EIA ESCAP FAO FMMP GCMs GDP GFDRR GMS HDI HME ICEM IFRM IPCC JICA LMB LULCC MRB MRC NDVI POM PRECIS SRES SST UMB UNEP UNISDR VIC WFP Asian Development Bank Atmosphere General Circulation Models Atmosphere Ocean General Circulation Models Climate Research Unit Drought Hazard Index Drought Management Program Driving forces, Pressures, States, Impacts and Responses Drought Risk Index Drought Vulnerability Index Environmental Impact Assessment Economic and Social Commission for Asia and the Pacific Food and Agriculture Organization Flood Management and Mitigation Programme General Circulation Models Gross Domestic Product Global Facility For Disaster Reduction And Recovery Greater Mekong Subregion Human Development Index International Center for Environmental Management Integrated Flood Risk Management Intergovernmental Panel on Climate Change Japan International Cooperation Agency Lower Mekong Basin Land Use and Land Cover Change Mekong River Basin Mekong River Commission Normalized Differenced Vegetation Index Princeton Ocean Model Providing Regional Climates for Impacts Studies Special Report on Emissions Scenarios Sea Surface Temperature Upper Mekong Basin United Nations Environment Programme United Nations International Strategy for Disaster Reduction Variable Infiltration Capacity World Food Programme

10 1 Introduction 1.1 Motivation and background The Mekong River Basin is facing huge pressures due to economic and population growth, combined with land use changes and hydropower development. Climate change and its impacts are adding an additional threat. These pressures are expected to intensify the severity of impacts of hydro-meteorological extreme events as floods and droughts. Following the definition of IPCC, the term climate extremes refers to extreme weather and climate events and depicts the occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable (IPCC 2012). Floods lead to direct deaths, damage of infrastructure, harvest losses, epidemics, pests and landslides. Droughts cause crop failures, famines, migration, epidemics, pests, forest fires and salt water intrusion. Furthermore droughts endanger sectors which depend on safe water supply like settlements, industry or hydropower (World Bank 2010). Although their damages are a result of natural climate variability, it seems that the influence of anthropogenic factors on these natural disasters is indeed high. Observing and predicting the intensity of floods it is problematic to separate climate variability or change from other human impacts. Many rivers, for example, are not in their natural status any more, leading to huge alterations of flood patterns, independent of climate factors (IPCC, 2012). It remains largely unclear to what extent extreme events can be attributed to these anthropogenic factors or to natural variability or to a combination of both. Looking at the impacts of extreme events on humans, infrastructure or ecosystems they are often occurring due to increased vulnerabilities rather than a higher hazard level. An important fact is that the economies of many developing countries rely heavily on agriculture, dominated by small-scale and subsistence farming. People s livelihoods in this sector are especially exposed to and impacted by weather extremes. In order to develop effective policies and measures regarding combating hazards and their impacts it is necessary to be clear about the causes. Furthermore, it is important to understand in which geographic areas future impacts of extreme events will likely be the highest. This would allow determining priority areas and possible themes for future projects. Thus, explaining the causes of climate related disasters in terms of hazards and vulnerabilities is a crucial issue and is representing a significant knowledge gap in most river basins worldwide including the Mekong River. 1.2 Objectives and research questions In line with the above mentioned motivation this study aims at analyzing natural and human induced factors which determine the severity of hydro-meteorological extremes and their impacts in the Mekong River Basin. It aims at identifying and quantifying the key drivers of change and evaluates their dynamics in order to be able to estimate their individual relevance for floods and droughts in the region. The study analyses geographical hotspots and evaluates the role of the different drivers which are impacting the severity of climate related disasters. In particular the following research questions are addressed by this study: What is extent and impact of past floods and droughts in the MRB? What can be deduced from Global Circulation Model scenarios regarding changes in the hydrology of the Mekong Basin? 1

11 Which socio-economic developments are relevant in order to understand current or future vulnerabilities regarding hydro-meteorological extremes? What is the recent dynamics of land use changes and which relationships can be drawn regarding a changing hydrology? Which are the recent dynamics of hydropower development and how could they impact the consequences of hydro-meteorological extremes in the future? How can the dynamics of drivers and pressures to hydro-meteorological extremes be related to future hotspots of their potential impacts? Which demands exist for further studies? 1.3 Concept, methodology and structure of the study The study uses the DPSIR (Driving Forces, Pressures, State, Impact and Response) framework as an underlying concept. DPSIR is adopted by several agencies (e.g. EEA, UNEP) as an approach to describe cause and effect relationship in environmental studies in a systematic way. Social and economic developments exert pressure on the environment and, as a consequence, the state of the environment changes. This leads to impacts on e.g. human health and ecosystems. The responses can be designed to target Driving Forces, Pressure, State or Impacts through adaptive or curative measures. Source: Kristensen, 2004 Figure 1: The DPSIR approach Driving Forces considered in this study are those which play a role in view of climate related disasters (in particular floods and droughts), namely climate change, socio-economic change, land use change, and hydropower development. It should be noted that the DPSIR approach also has weaknesses. In particular, it does not follow a clear system approach in the sense that several feedback loops exist between Drivers, Pressures, State and Impacts. Regarding flood and drought risk, the conceptual model used for this study is that proposed by IPCC (2012) depicted in Figure 2: The hazard (weather and climate events) in combination with vulnerability and exposure determines the impacts and likelihood of disasters (disaster risk). This model emphasizes the close link between climate and society. In the context of the present study a weakness of this model is that it does not refer to the multiple causes of climate related hazards. A flood usually has causes beyond the climate system, for example in land use changes, hydropower development or other infrastructural interventions as the building of levees or roads. 2

12 Source IPCC, 2012:4 Figure 2: Basic concepts related to disaster risk management Following this concept and considering the scope of this study a hotspot can be defined as a geographic area which is characterized by a high disaster risk, which means where a combination of high levels of hazard, vulnerability and exposure are observed or are expected to be significant in the future as a result of the current dynamics of drivers and pressures. Thus hotspot is used in this study as a short term for hydro-meteorological disaster hotspot The hotspot analysis involves the identification of drivers and pressures, which influence the disaster risk in certain areas as well as the vulnerability and exposure of societies, infrastructure and (agro)ecosystems exposed to these disasters. Vulnerability, on the other hand can be understood as a composite of sensitivity and resilience. In a first approximation it can be stated that poorer people tend to be more vulnerable. People prepared for a certain disaster are more resilient. This is the fact in areas that recurrently experience a certain hazard. The following figure combines the idea of the DPSIR framework with the Hazard-Vulnerability- Exposure concept applied to the situation in the Mekong River Basin. Obviously, this figure is a simplification of the real situation. As a conceptual model derived from a preliminary system analysis, it serves as a starting point for the subsequent analysis. 3

13 Own concept Figure 3: Cause-effect relationships of hydro-meteorological extremes Regarding the methodology the study is based on an extensive review of published literature, predominantly from peer-reviewed journals from recent years ( ) with relevance to the above mentioned research questions. Furthermore the study will analyze and interpret the literature and summarize key findings in tables, figures and maps. The key literature will be annexed to this study in an annotated bibliography table. Based on the conceptual model and the above mentioned research questions, the following structure for the study was chosen: 1. Summary description of the key features of the basin (chapter 2) 2. Analysis of the past and present extent of flood and drought hazard and vulnerability in the Mekong River Basin and specifying their causes, extent and impacts of floods and droughts (chapters 3+4) 3. Evaluation of four key drivers and pressures with relevance to flood and drought risk: Climate change, socio-economic change, land use change, and hydropower development. Each chapter focuses on those elements of the drivers and pressures which have an impact on flood and drought risk and identifies hotspots (chapters 5-8) 4. Summary analysis on floods and droughts with the determined drivers and pressures in order to identify hotspots (chapter 9) 5. Identifying knowledge gaps and recommend future focal activities (chapter 10) 4

14 2 Study region: Basin Overview and Drivers of Change in the Mekong River Basin (MRB) 2.2 Geo-physical Characteristics The Mekong River arises on the Tibetan Plateau in the Thang Hla Mountains at approximately meter above sea level (Kite, 2001). From the Himalayan Mountains it drains southward until it reaches the South China Sea. On its way it crosses the countries of China (Upper Mekong River /Lancang Jiang) as well as Myanmar, Lao PDR, Thailand, Cambodia and Vietnam (Lower Mekong River (LMR)), covering a catchment area of km 2 (MRC 2005). On its first transect, the Mekong and its tributaries flow through narrow and steep gorges of which many of them are inaccessible. Therefore, the exact estimation of total river length is difficult. Estimates range from 4.100km to 4.900km river length, making the Mekong the largest and most important river in South East Asia (Johnson and Kummu, 2012; Kiem et al., 2008). The Upper Mekong River Area is characterized by tundra vegetation and montane, semi-desert ecosystems Figure 4: Physical map of the Mekong River Catchment (Thompson, 2013), which limit any agricultural expansion on the steep slopes. Further downstream, the river leaves the Himalayan mountain area and most parts of the Lower Mekong River are surrounded by evergreen and deciduous forest (Ishidaira et al., 2008). Clear impacts of demographic and economic development like the expansion of agriculturally used areas and large deforested areas can be seen in this region (Thompson, 2013). Main tributaries, which contribute to as much as one third of the total Mekong River discharge (MRC, 2005), are the Chi and Mun rivers draining into the Mekong from the eastern riverside as well as the Se Kong and Srepok draining the highlands of Vietnam on the western river side further downstream. 5

15 Regarding the mean annual discharge at the river delta of 475 km 3 /a, the Mekong River ranks 10 th among the world largest rivers (MRC, 2005). However the discharge of the Mekong varies significantly with climate conditions and local precipitation events along its tributaries. The Upper Mekong River flow can be described as a nival runoff flow regime, depending on snow fall and snow melt on the Tibetan Plateau; whereas the LMR and its tributaries show a pluvial regime with clear high and low flow periods according to monsoonal events. Especially those last mentioned monsoonal rainfalls, which are dominated by the wet southwest and the dry northeast monsoon, lead to a complex hydrology of the Mekong basin. The annual, intra-annual and high spatial variability of weather conditions in the Mekong catchment generate locally very different runoff flows, since the weather systems are often not large enough to affect the whole basin (MRC 2010a). The southwest monsoon (May-October) entails about 90% of the yearly rainfall, with mean annual precipitation rates between 1.000mm in northeast Thailand and 3500mm in Laos. From October to March the northeast monsoon causes dry climate conditions (Kite 2001). Depending on these seasonal precipitation patterns the river level varies significantly throughout the year. Peak flows of about m 3 /s are reached during wet season in September/October (near Phnom Penh) whereas the Mekong River level drops down to 1.500m 3 /s in March/April during dry season (Kite, 2001). According to Kummu and Sarkkula (2008), it is important to maintain this annual flood pulse for the Mekong River ecosystem. Especially the Cambodian floodplain and the Mekong River Delta, some of the most productive ecosystems in the Mekong region, depend on the discharge and sediment yield from upstream. The Tonle Sap Lake ecosystem is likewise regulated by the natural hydrological patterns. While the Mekong River provides water for the lake system during wet season, the flow direction changes during dry season and the Tonle Sap drains into the Mekong, generating a unique natural phenomenon. This brief description of the main hydrological and climate characteristics of the Mekong basin shows that they must be studied carefully since they are complex and above all highly important for the socio-economic development in the region. For example, flood and drought events depend on rainfall patterns which are spatially highly variable, as mentioned above. Therefore they hardly ever occur in the whole basin at the same time (Adamson & Bird 2010) and must be addressed in their specific natural and socio-economic environment. 2.3 Socio-economic Characteristics The Mekong River Basin (MRB) is the prevailing geo-hydrological structure on the Southeast Asian mainland. Consequently, the people living within this region have adapted their production techniques and their way of life to the given and seasonal varying natural condition of the Mekong and its tributaries. Moreover, they are extremely dependent on the river`s resources (e.g. fish, water, sediments) and thus highly vulnerable, if the water or flow regime is changing as a consequence of natural (e.g. floods, droughts) or human made factors (e.g. hydropower generation or population pressure) ( Menniken 2008; Nuorteva et al ). Great ethnic, religious and cultural heterogeneity characterizes the human geography of the MRB and creates a number of opportunities but also threats for the socio-economic development within this region (ADB 2012; MRC 2011c). Even though estimations about the range of demographic development of the Mekong region are varying, there is a consensus in the scientific discussion about a continuously growing population in the near future. These uncertain forecasts are a result of an often inconsistency in census data collection in the six different countries with their various administrative areas (Eastham et al., 2008). Accordingly, the population of the MRB is expected to grow from currently approximately 70 million people (see Menniken 2008; MRC 2010a; Pech and Sunada 2008) to more than 90 to 100 million by 6

16 2025 (Eastham et al., 2008; Menniken 2008; MRC 2003). In this context it is also noteworthy that millions of people outside the MRB are currently dependent on products, which have their origins in the MRB. For instance, the Vietnamese Mekong Delta is also called the rice bowl of Vietnam as it contributes about 50% to the total rice production in 2012 (43.4 MT) of which 7.7 Mt were exported in of this country ( In terms of socio-economic aspects, the riparian states of the MRB are extremely heterogeneous and differ significantly from each other in their geographical size, number of inhabitants, types of economy, level of education, standard of living, political system or in relation to their cultural traditions and social practices. However, all countries of the LMB have high average economic growth rates from 6% up to 10% per year in common (2010) (UNstats 2013). But besides these positive economic dynamics, large portions of the basin population remain among the poorest in the world and their associated level of socio-economic development thus has to be described as rather low. In Cambodia and Lao PDR, about one third of the population lives below the poverty line (WFP 2008; JICA 2009) and gross national income per capita in 2011 was US$830 in Cambodia and US$1,130 in Lao PDR (ADB 2012). Notwithstanding, all riparian countries of the MRB put a priority on achieving economic growth in order to decrease or break the spiral of poverty and low development. Together with a considerable population growth, which correlates with the prevalent poverty in this region, this economic growth will significantly increase future demand of natural resources such as water. Therefore, an intense competition as well as an increasingly unequal distribution of natural resources is expected (Menniken 2008). This strain on the Mekong River and its related ecosystems could reach a point in the future when key indicators of ecological health (e.g. forest cover, biodiversity, fish stocks, soil quality etc.) are going to be reduced thus far that recovery may not be possible anymore (Kirstensen 2004). Resulting from the socio-economic heterogeneity of the Mekong`s riparian states, the potential and range in utilizing the water resources of the river are differing from country to country. China is primarily interested in hydropower generation, whereas Thailand and Vietnam mainly need water for irrigation (Hirsch 2006). Cambodia heavily depends on fisheries and Laos combines all of these uses. The two latter countries can be characterized as the hydro-politically weakest riparian states, because they are the poorest and at the same time most dependent on the resources of the Mekong. However, Vietnam is in a vulnerable position, too, as it is located in the Mekong Delta region, an area highly affected both by maritime influences and all proceedings further upstream. In addition, Vietnam and Cambodia receive more than two-thirds of their required water resources from international watercourses, which are originating outside their borders, whereas Thailand imports only 40% of its water. With a hydro-electricity rate of 90%, Laos is increasingly vulnerable because the country develops its upcoming electricity supply solely on hydropower (Grumbine et al. 2012). As a consequence of these dependencies, it does not surprise that all four countries consider themselves as downstream riparian states. Resulting from their position, none of these countries is fully sovereign in hydro-politics: China as the upstream state has by its socio-economic, military and geo-physical hegemony the potential to limit the access to the Mekong water resources to an extent that it can significantly impact the future water supply, as well as the given and natural conditions of the entire Mekong region (Hirsch 2006; Menniken 2008; MRC 2010a). 7

17 3 Flood Hazards and Vulnerability 3.1 Introduction Around 80 % of the total mean annual Mekong runoff of 470 km³ reaches the South China Sea during flood season from June to October making floods a recurrent event in the MRB (MRC, 2005; Pham Trong et al., 2009). Depending on type, frequency, duration and severity, the socioeconomic costs of extreme floods in the MRB are similar to other great and heavily populated basins in Asia (e.g. Indus, Ganges etc.), where the river basin is principally used for agricultural purposes. However, one aspect must be paid particular attention to: Even though floods can impose large socio-economic costs to the people of the Mekong (e.g. loss of lives and property, loss of livelihoods, decrease of purchasing and production power etc.), the environmental, social, and economic benefits of flooding (e.g. fish production, provision of nutrient rich sediments, recharge groundwater tables etc.) by far outweigh the costs related to damages. In the Lower Mekong Basin, for example, it is estimated, that the annual costs of flooding amount on average to US$60 70 million a year, whereas the average flood benefits are accounted to up to US$8 10 billion per year (MRC 2010a). Nevertheless, these benefits should not hide the fact that the damages, which are caused by floods, are still substantial in the Mekong region. In this chapter we will firstly present summary information about the main causes, effects and impacts of transboundary flood issues which have the potential to considerably affect or interfere in the socio-economic performance of the Mekong riparian states (see Table 1). Subsequently, the most significant negative socioeconomic impacts of floods are outlined with specific reference to the individual countries and sub-regions (tables 4-12), while the last part analyses in detail the vulnerability to flood hazards as the key reason for recurrent flood related damages. In 2005, the Mekong River Commission released its first Annual Mekong Flood Report based on the national flood reports and data of the LMB Countries. The report has been updated annually to supply a reliable source of data for a sound understanding of the system and the opportunity for an enhanced future management in flood related affairs like land use planning (MRC 2006) Types of Floods Several options exist to classify flood types according to their causes or their typical form of occurrence. Typically, riverine or floodplain floods, flash floods, coastal and estuarine or delta floods are distinguished but also urban floods, dam or dike breach related floods can be distinguished (often called man-made floods). The Mekong River Commission (2005) distinguishes furthermore combined floods where tributary floods meet high water level in the mainstream which prevents drainage. Due to the significance and specific characteristics, the Cambodian floodplain and the Mekong Delta are usually treated separately at MRC publications. Joy (2007) differentiates eight distinct types of flood to arise in the LMB in the Best Practice Integrated Flood Risk Management (IFRM) Guidelines in 2007 (see Table 1). 8

18 Table 1: Flood types in the Lower Mekong Basin with a risk and hazard Flood Category Name Cause Characteristics Risk and Hazard Rainfall Manmade Maritime Mainstream Tributary Local Dam release Dam break Dike breach Storm surge Tsunami Source: Joy, 2007 Excessive rainfall over basin catchment Excessive rainfall over tributary catchments Excessive rainfall over small local catchments Excessive release of water from dams Structural failure of dams Structural failure or overtopping of dikes Tropical cyclones, depressions and storms Undersea earthquakes Generally slow onset and slow moving, especially in lower reaches where flooding can last for 2-4 months Rapid onset and fast moving because of small, steep catchments. Duration typically several days to 1 week Rapid onset, nuisance flooding. Duration typically hours to 1 day Onset can be rapid and unexpected, especially for emergency releases Immediate onset with rapid increase in water levels and destructive velocities. Unexpected flooding of protected areas Slow onset, high water levels. Flood, wind and saltwater damage can occur. Immediate onset. Extreme and immediate increase in water levels, very destructive. Mainstream flooding in Cambodia and the Vietnam delta clearly has the highest risk and hazard. Risk and hazard of mainstream flooding in Lao PDR and Thailand are an order of magnitude less. Tributary flooding in Lao PDR, Thailand and Cambodia, especially flash floods and landslips, are hazardous, but risk and hazard are an order of magnitude less than mainstream flooding in Cambodia and the Vietnam delta. Risk and hazard of local flooding are low; at least an order of magnitude less than tributary flooding. Likelihood of dam release flooding is small, but potentially hazardous and destructive. Likelihood of dam break flooding is very small, but potentially extremely hazardous and destructive. Likelihood of dike breach flooding is small to moderate. Water levels and hazard are significantly lower than for dam break flooding. Likelihood of significant storm surge flooding is low, but potentially hazardous and destructive. Limited to coastal areas of Vietnam delta. Likelihood of significant tsunami flooding is small, but potentially hazardous. Limited to coastal areas of the Vietnam delta, but orientation of coast provides some sheltering Hydrology of Floods While during dry season at Vientiane the largely snow-melt driven part of discharge originating in China (Yunnan component) plays a significant role (75 % of generated runoff) this flow component is getting less important further downstream and it is generally not significant during the flood season (share of contribution of less than 15 % at Kratie during wet season; compare 9

19 MRC 2005). Thus, the major causes of flood hazard are torrential rainfalls associated either with the southwest monsoon (May-September) or later in the year with tropical cyclones. The magnitude of flood pulses can vary significantly from year to year (MRC 2005). Figure 5 provides the recurrence intervals of flood events for the Kratie station. It emphasizes the huge inter-annual variability of peak flood ( to m³/s) and flood volume (50 km³ km³). Source: Adamson MRC, 2005 Figure 5: Mekong at Kratie - the bi-variate distribution of annual flood peak and volume, 1924 to The estimated recurrence interval of the 2011 event in terms of the joint distribution of the two variables is just 1 : 10 years. That of :20 years. Next to the temporal variability of flood events there is a significant spatial variability of floods related to regional patterns of runoff generation. Snowmelt and rainfall on the Upper Mekong Basin generate the first case while the second case is dominated by excessive rainfall events in the highlands of Thailand, Lao PDR and Vietnam. Both cases originate from two different atmospheric processes and hence show a distinct behavior (Delgado et al. 2010). 10

20 To classify the severity of a flood and create a basis for future assessments, historical flood events have been taken into account. The 1966 flood was the worst in the upper part of the LMB, 1978 was the worst flood so far around Kratie. In 1996 a severe flood has been recorded in the area around Stung Treng at the confluence with the Mekong River, the Mekong Delta suffered most during the floods in 1961, 1966 and was the most devastating for the central area of Lao PDR and Thailand. Also the floods in 1971, 1974, 1984, 1991, 1995, 2001and 2002 can be considered as severe for several sections of the LMB. Thus, a severe flood in the LMB is quite a common situation, but the location of the severe impacts is varying within the basin from year to year - see also Table 2 and related map. The flood in 2011 is not considered in the following table, but it ranks among the highest discharge rates in the LMB (MRC 2011b). Years with highest discharge (rank) Station Chiang Saen Luang Prabang Vientiane Nakhon Phanom Mukdahan Pakse Stung Treng Kratie Kampong Cham Tan Chau na Can Tho na Moc Hoa na Table 2: Ranking of years with highest discharge rates ( ) in the LMB (Source: MRC 2006) While peak discharge and total wet season flood volume are useful approximations to quantify the flood hazard, there are other hydrological characteristics which play a role in determining the severity of a flood in terms of impact or damage; these are: The area and depth of inundation The time of occurrence of the flooding (e.g. delayed floods, season and cropping stage; frequency) The speed the water rises (time for humans and animals to react to flood) The stream velocities of the flood water (destructive force, bank erosion etc.) The duration of the flooding (e.g. complete crop yield failure after prolonged flood) 11

21 3.1.3 Flood hazard trends In their study about flood trends and variability in the Mekong River, Delgado et al. (2010) analyzed the annual maximum discharge of the Mekong River from 1925 until 2000 with data of four gauging stations downstream of Vientiane. They found that the average magnitude of floods show a negative trend but the variability is increasing. Hence, very large floods are likely to increase in frequency, while the frequency of average floods decreases. However, causes for the detected increases in variability are yet unknown and could originate from climate oscillations, climate change or changes in land or water uses Flood Vulnerability According to the aforementioned information and neglecting the positive effects of floods, it becomes obvious that almost every year the severity of flooding damage has been substantial within the riparian countries of the MRB. As a consequence of the human-induced drivers of environmental change (population dynamics and migration, agricultural practices and associated land-use changes etc.) it therefore can be supposed that the degree to which socioeconomic and ecological systems are exposed to these flood hazards will be growing in the future. In this relation, the Mekong River Commission also shares the assumption that the vulnerabilities of people and water-related resource systems to severe flood conditions have increased. In the Annual Mekong Flood Report 2010, the MRC points to the following fact: Significant, and to a much greater degree, extreme flood season conditions expose the vulnerabilities of the regional ecology, environment and socio-economy to hydrological surplus and deficit beyond the normal range (MRC, 2011a: 5). Here it is crucial to recognize that there are a variety of factors persistent in the MRB which are contributing to increased vulnerabilities. Some of these factors often work in combination and can change over time, but also vary by location. However, the Flood Preparedness Program of the Mekong River Commission (MRC 2009c) has identified some of these factors, which are considered to cause growing vulnerabilities to flood events: 1) Development of squatter communities on marginal land such as on embankments, riverbanks and within river channels 2) Poverty is typically associated with poor housing and unplanned development with poor drainage and sanitation which increases the risk of water borne diseases 3) Inadequate flood preparedness 4) Lack of awareness about the flood hazards 5) Climate change effects over a particular area 6) Environmental and geographical vulnerabilities The increasing vulnerabilities of people and water-related resource systems to severe flood conditions in parts of the MRB, which are considered to take place in this region, consequently could considerably affect the social, economic and environmental conditions of the riparian states. In addition, the following three impacts could emerge from this situation. Their associated potential effects are presented in Figure 6. 1) Increased poverty resulting from financial losses and a recession in local economies 2) Reduced sustainability and productivity of natural resource utilization and the environment. 3) Adverse effects on social and institutional stability of concerned population 12

22 Source: Own Figure Figure 6: Potential Effects of Increased Flood-related Vulnerability in the MRB In particular poverty is one of the most important factors which aggravate the vulnerability of people regarding floods because it can be seen as the largest barrier to build up sufficient adaptive capacities (e.g. financial resources to compensate agricultural and/or livestock losses) that have the potential to cope and adapt to floods and other natural hazards. It further can be seen as an important reason, why people are forced to live in flood-prone areas, as well as in poor housing conditions with poor drainage and sanitation, which in turn increases the probability to be affected by water borne diseases (Nguyen, 2007; ADB, 2011). Within the MRB the agricultural sector, especially for Myanmar (50%) and Lao PDR (43.4%) is a major contributor to the country s GDP. It further involves 45-80% of the total labour force (Singh, 2007). Flood events with destructive impacts on agriculture consequently are able to create various significant adverse effects to the socio-economic conditions of the riparian states and its population. A decreasing agricultural and livestock production, for instance, which results from extreme floods, is able to reduce incomes and food supply in a manner that a growing number of people are going to be threatened by poverty. This situation would also affect the food processing industry because their facilities may face underutilization Furthermore, floods in the MRB are able to obstruct transport and can cause severe damages to roads, buildings and contents, especially in urban areas. Depending on the frequency and magnitude of flooding, the growing vulnerability of infrastructure potentially will subsequently increase the likelihood of revenue losses, which result from commerce and business interruptions (Douven et al., 2011) 13

23 Besides human-induced activities, severe flood events, like flash floods, have the potential to accelerate land degradation processes (e.g. increased erosion of riverbanks and sediment removal etc.) along the Mekong and its tributaries, too. They, therefore, may create adverse effects on the maintenance of ecosystem services (e.g. damages to plant growth) and increase the chance of further flooding. A reduced sustainability and productivity of natural resource utilization and the environment could be the consequence. Extreme flood conditions disrupt drainage systems in cities and are able to overwhelm sewer systems etc. As a result, pollutants, like chemicals and toxins, and raw sewage are spreading and likely damage the downstream water quality and the sustainability and productivity of the environment (Huong/Pathirana 2011). The release of these materials into the local environment further increase the vulnerability of people, because they contaminate drinking water supplies and create conditions where the risk of outbreaks of water-borne diseases is growing (Nguyen 2007). The environmental and socio-economic impacts of flooding might create adverse effects on the social and institutional stability of the population concerned, especially in areas, which are characterized by a high flood hazard potential and where people, infrastructure and natural resources systems are extremely vulnerable to floods. Dun (2011) concludes that impacts of regular flooding of the Mekong Delta can trigger migration decisions and are a cause for government-initiated resettlement of households. However, the author stresses that regular flooding alone is not sufficient to explain migration - there is rather a general trend in the Mekong Delta of migration from rural to urban areas due to other socio-economic reasons. The population which does not have sufficient capacities (e.g. poor flood preparedness) to cope with extreme flood events further might face a loss of trust in authorities and governmental institutions. This situation, therefore, could provide a breeding ground for public discontent and social unrest (Manuta et al., 2005, MRC, 2010d). In order to determine systematically areas of high vulnerability to floods and their dynamics, spatially distributed socio-economic data needs to be analyzed over longer time periods. These data sets are not available or at least not reported in literature. 3.2 Causes and impacts of floods The Mekong River Basin depends on its flooding events that characterize the region and formed the everyday life and the yearly rhythm of the people living with the Mekong. As mentioned above, the flood season is a normal and recurrent event and the difference from an essential to a hazardous event is defined by the amount of water flowing per time. MRC (2011a) and ADB (2011) used the terms good and bad mainstream floods. Bad mainstream floods are characterized by reducing the rice crop yield due to one or more factors like early onset, high water level and delayed recession of the flood. Good or normal floods are considered to outweigh any negative effect, carrying along fertile sediments, water for irrigation and a lot of fish. Table 3 classifies the causes and impacts of typical floods occurring in the Mekong basin. 14

24 Table 3: Information on main causes, effects and impacts of Mekong Transboundary flood issues Issues Main causes Main effects Main impacts Group 1: Issues related to floodplain developments within the Mekong Delta Expansion of agriculture/ irrigation systems Development and operation of flood protection and control systems road network Industrialization and urbanization along river and canal Sand exploitation Change hydraulic and hydrological condition of flow and water level in flood plain and channel system Change of inundation area and duration Change of water quality, sedimentation, nitrate and pesticide loads Increased risks for loss of lives and damage to property of millions of people Reduction of fish production Degradation of water quality Increment of bank erosion of Mekong and Bassac Group 2: Issues related to impacts of LMB upstream developments on the Mekong Delta Construction, management and operation of hydropower projects on tributaries (mainly Lao PDR and Vietnam) Upstream deforestation Change of flow pattern due to regulation Change of water quality Reduction of sedimentation Increased risks for loss of lives and damage to property Reduction of fish production Increment of dam break risk Group 3: Issues related to impacts of upstream hydropower development in the upper Mekong Basin on the LMB Construction, management and operation of hydropower plants in the upper parts of the MRB (mainly Lancang river) Transition from wet to dry season flows Reduced flood volume and duration Reduction of sedimentation Blockage of fish migration routes Potential impact on floodplain along the mainstream, Tonle Sap and Mekong Delta Group 4: Issues related to hydropower development and operation in the Se San, Srepok and Se Kong river basins Construction, management and operation of hydropower projects Change of flow pattern in the river and water levels Damage of property and human life Increment of dam break risk Group 5: Issues related to bank protection and port development, sand excavation, dam Bank protection and port development Sand excavation Communication of Change of flow pattern and water levels (uncertain cause-effect relations) Bank erosion and loss of land Disruption of fisheries 15

25 operation communications in the upper reaches of the Mekong mainstream Group 6: Issues related to increased floods on tributaries in northwest Cambodia dam operations Enhanced turbidity Flash floods with uncertain causeimpact relations Source: MRC, 2008a, edited by author 3.3 Summary of major floods and their damages Hazardous floods impacts are quantified by affected and killed people, damaged crops (ha), and damaged and destroyed infrastructure. Nowadays, floods cause much higher damage then decades before. This is related to the growing number of people living in affected areas as well as more built infrastructure and growing agricultural areas within flood prone areas. These continuing processes increase the exposure of people and economically viable assets to floods and thus raise the potential for disaster. The Asian Disaster Preparedness Center et al. (2012) depicted in their national risk profile of Lao PDR that agriculture and housing are the most vulnerable sectors to floods. For instance, paddy rice production faces an overall loss of 100 % after being inundated 20 days or more. The more agricultural areas and households are being established in flood prone areas, the higher are the losses in case of hazardous flooding. Main losses in agriculture affect mostly rice crops. Farmers in flood prone areas have adapted their crop patterns over generations and significant deviations of the flood in terms of its extend, shifted timing and longer durations cause flood damages (ADB, 2011). According to De Bruijn (2005) not only the maximum peak discharge defines the level of damage of a flood event but also the timing of the flood and the duration. Tables 4-7 summarize the socio- economic impacts of floods in Cambodia, Lao PDR, Vietnam and Thailand. Table 8 contains the most significant information from to the Annual Mekong Flood Reports from 2005 to 2010 and the Flood Situation Report 2011 (MRC 2011b). Tables 9-12 provide details of important flood events in the four LMB counties. Not only mainstream floods have hazardous characteristics but also flash floods on the tributaries have a huge potential to destroy and cause loss of life. Even in the years with many destructive events in tributaries, the mainstream flood level can be below average (such as 2006 and 2007). As tributary and flash floods happen every year in Thailand, Lao PDR and the upper Se San and Sre Pok Basin in Vietnam, it is difficult to find general conclusions on effects which could be attributed to climate change and infrastructure development. According to the Annual Mekong Flood Reports some years show an average flood situation, some suffered from floods and some suffered from droughts. It therefore must be mentioned that even in cases of regional flooding with record water level, other regions further up- and/or downstream are not affected necessarily as, for example, MRC (2009a) explains for the flood year The MRC (2010b) compared the three flood seasons of 2000, 2006 and 2008 to underscore that the behavior of flood events depend on flood producing rain events in different areas of the Mekong basin and other causative factors Cambodia 16

26 Longer duration of higher floods, reduced fish productivity that is triggered by a drop of migration and a loss of deep pools, increased dam breaking risks and significant damages to property and human life have been identified to be some of the country s most important transboundary flood issues. In this connection, it can be assumed that these impacts are at least partially caused by the development of flood-control systems and resident protection areas along the Vietnamese-Cambodian border; hydropower stations in the Se Kong, Se San and Srepok river basins; hydropower facilities on the Mekong`s main tributaries; but also by floodplain encroachment (e.g. flood-protected areas) that affect upstream areas on Cambodian territory (MRC 2008a). The annual negative socio-economic impacts of Mekong floods in Cambodia can be found in Table 4. Table 4: Socio-economic impacts of floods in Cambodia ( ) Year Cost in US$ (mil.) People killed People affected Damaged crops (ha) (a) (a) (a) Damage in 2007/2008 in Cambodia was almost solely related to flash flooding. Source: MRC 2010a; MRC 2010b; Sopharith 2012; World Bank 2010; Yang 2011, edited by author) Lao PDR Within the boundaries of Lao PDR, there are three transboundary water flood issues, which have been identified by national reports as important challenges to be addressed: the loss of cultivated land, which is resulting from the left bank erosion of the Mekong, the long-term disappearance of islands and houses. In this relation, it is expected that these impacts may result from port construction and bank protection, sand and gravel extraction in Thailand and Lao PDR, but also from not previously announced or insufficient communicated dam releases (e.g. Pak Mun dam/thailand). Here it should be noticed, that dam releases have the potential to significantly change the river`s water flows, as well as it`s hydraulic conditions (MRC 2008a). The socio-economic impacts of Mekong floods in Lao PDR are presented below. 17

27 Table 5: Socio-economic impacts of floods in Lao PDR ( ) Year Cost in US$ (mil.) People killed People affected Damaged crops (ha) (a) (a) Vientiane accounted for 45% of the total damage. Source: Government of Lao PDR 2009; MRC 2010a; MRC 2011a; PDC Weather Wall 2011; UNESCAP 2012, edited by author Vietnam The country has identified six flood issues that can be held responsible for potentially impacting the natural and socio-economic conditions of Mekong Delta and the Eastern Highlands of Vietnam in a negative way (see Table 6). These impacts encompass wetland degradation, decreases in fish production, increasing bank erosion, risks which may result from dam breaking, disappearance or deterioration of fish migratory routes and degradation of water quality, quantity and turbidity. The aspects mentioned above, are perceived to be a result of upstream hydropower development projects; agriculture and irrigation measures, mainly in the Prey Veng and Takeo provinces of Cambodia; and industrialization and urbanization along the mainstream and tributaries. Flood control, road and infrastructure developments in the flood plain of Cambodia, deforestation further upstream and rising exploitation of sand also need to be considered (MRC 2008a). Table 6: Socio-economic impacts of floods in Vietnam ( ) Year Cost in US$ (mil.) People killed People affected Damaged crops (ha) >

28 > > Source: Dang 2012; IRFC 2012; JICA 2009; MRC 2010a; MRC 2010b, edited by author Thailand Resulting from the growing pressure on natural resources and the expansion of human activities (mainly irrigated agriculture) especially in hazard-prone areas, losses from flash floods and associated hazards (e.g. landslides, debris flows) have considerably increased in recent years (MRC 2008b). In this relation it is important to point out, that the resultant annual socioeconomic damages of flooding (see Table 5) were generally confined to the rural areas and the agricultural sector of the Thai Mekong region, mainly in the northeastern parts of Thailand (MRC 2009b). Table 7: Socio-economic impacts of floods in Thailand within the MRB ( ) Year Cost in US$ (Mio) People killed People affected Damaged crops (ha) billion billion > Source: MRC 2008a; MRC 2009a; MRC 2010a; MRC 2010b; MRC 2011a; World Bank 2012, edited by author 19

29 3.3.5 Myanmar and China (Yunnan) The substantial lack of information about floods issues, which can be related to the Mekong region, makes it very difficult to adequately assess the associated socio-economic impacts for these countries. The hazard profile of Myanmar, for instance, which has been published by the Myanmar government in 2009, points to the fact that Shan, the only province, which is located within the Mekong Basin, is threatened by flash floods, inundation and landslides. However, no indications about the resultant socio-economic impacts have been made (Government of Myanmar 2009). The same holds true for China (Yunnan). Resulting from insufficient language skills in Chinese and the restrained information policy of the Chinese government, no sufficient or adequate information about the socio-economic impacts of floods in this region could be accumulated during the desk study. As a consequence, flood information about China (Yunnan) and Myanmar has not been taken into consideration in the subsequent part of this section. 20

30 Details on major recent floods and their socio-economic impacts Table 8: Summary of mentioned and considerable events during the flood seasons 2005 until 2011 based on the Annual Mekong Flood Reports published by the Mekong River Commission. Year Thailand Lao PDR Cambodia Tonle Sap Mekong Delta Tributaries and special events 2005 Comparable to 2002 flood but below Flooding around Ubon Ratchatani and Pakse. Normal flood situation. Heavy rainfall caused severe long lasting flash floods in tributaries of Northern Lao PDR and Chiang Rai, Thailand. Heavy rainfall led to water release from Nam Ngum Dam caused damaging floods around Vientiane (Lao PDR) Average rainfall in Lao PDR far above average, generating several flash floods in central and southern Lao PDR tributaries Affected by several tropical storms, most particular Xangsane and Prapiroon., causing severe flash floods. Scattered flash floods Below average (the lowest flood peak in 80 or more years). Maximum water level nearly as 2000, an extreme flood year. Below average (late flood peak caused unfavorable conditions for agriculture). Flash floods occurred in northern Thailand causing considerable damages 2007 Flash floods caused by tropical storm Lekima. The flood in NE and Central Thailand was the worst in 40 years. Below average, similar to Annual flood was a month late and below average. Higher losses in rice crop then in 2006 in the central and southern Lao PDR provinces due to tropical storms Lekima, also affecting southern Thailand provinces. Seven Typhoons and three tropical depressions caused major flash floods in the upper Se San and Sre Pok Basins in Vietnam Tropical storm Kammuri and Mekkhala caused over Highest water level recorded ever in Vientiane (August 15 th ) Peak discharge: Significantly below normal. Flood volume: Widespread but brief inundation of large areas by spring tide in Tropical storm Kammuri and flash floods in the northern and central Lao PDR caused the major damages and losses in (Strong La Niña year) 21

31 bank flooding of considerable areas. near average. Oct Severe flash floods due to heavy rainfall. Mainstream water level and discharge below average. Maximum water level in the first week of July, which is unusually early. Water level general in average, maximum water level occurred one to two weeks later than usual. Tropical storm Ketsana caused mm precip. Within 3 days causing severe flash floods in the upper Se San and Sre Pok basin (Vietnam) 2010 Two flood events due to tropical storm Mindulle and a tropical depression. Flood damages by flash floods, mainstream water level on record low level. Mainstream water level far below average. Severe drought. Flooding with 6 weeks delay and latest ever since recording. Peak water level below average. Lowest flood volume ever since data recording. Flood season one to two month shorter than average. Considerable noise in the discharge hydrograph of Chiang Saen station probybly due to operation of Chinese dams (compare chapter 8.3.1) 2011 Major mainstream flood inundated large areas in the Cambodian floodplain and the Mekong Delta. Sources :MRC, 2006;MRC, 2007;MRC, 2008;MRC, 2010a;MRC, 2011a;MRC, 2011b 22

32 Table 9: Floods in Cambodia - major characteristics, socio-economic impacts and areas affected Type of Year Most important flood details (major) floods Socio-economic impacts Provinces / Cities affected 2005 Backwaters created in the lowest areas and in tributaries in Stung Treng and Kratie provinces making drainage even harder. Flooding in Kandal and Prey Veng considered to be normal Mekong Flood & Flash Flood 19 deaths, 4805 people required evacuation. Nearly 6000 houses affected and required repair. 309 km of roads flooded with 7km totally destroyed after flooding. 4,138 rice fields flooded, data on yield losses not available. A total loss of US$ 3,8 million was calculated Stung Treng, Kratie, Kompong Cham & Kandal 2006 Below average in terms of flood peak and volume. The flood peak was amongst the lower record over 80 or more years. As a result, no significant losses and damages occurred. Mekong Flood 11 persons killed, 70 km roads lost, bridges and dams lost in many sites and around 13,700 ha of crops damaged. The total flood damage was above US$11,8 million Kampong Cham, Kratie, Stung Treng 2007 Events were mostly a result of the tropical storm Pabuk in the northern and coastal areas of the country. Pabuk caused widespread flash floods and extensive inundation. Flash Flood persons affected, 59 people killed, 750 km of rural roads destroyed, some damages to roads buildings, temples and more than 1500 residential houses destroyed, erosion and increased sediment deposition of dykes and irrigation canals, ha. fish ponds damaged, around ha of crops damaged causing a loss of 252 tons of food production, total flood damage was US$ 9 million. Kampong Thom, Prash Vihear, Ratanakiri, Siem Reap, Battambang, Phnom Penh, Sihanouk-ville, Kampong Cham, Kratie, Stung Treng 2008 One of the least damaging years for the country and the annual financial loss has been below the average. However, as a result from tropical storms, some flood losses arose from flash flooding. Flash Flood ha of crops damaged, total flood costs were accounted to be US$ 5.8 million. Prash Vihear, Kampong Thom, Bantay Meanchey 2009 (a) Events were mostly caused by the tropical storm Ketsana. It solely little affected the water levels along the Mekong but caused significant impacts at the Sre Pok, Se San and Se Kong as a consequence of extreme flash floods and Mekong Flood & Flash Flood Significant impacts on the production sector (agriculture, livestock and fishery = US$ 56,5 million, Industry and commerce US$ 3,5 million), people affected (directly and indirectly), death of 43 persons, ha of damaged crops, damages on infrastructure were severe (mainly roads 23

33 inundation. and bridges) A total of US$ 132 million in damage and losses in infrastructure, Social, production and cross cutting sectors was estimated. Costs for reconstructions were estimated up to US$ 191 million (56% infrastructure, 31% production sector) (b) Meteorological and hydrological conditions were far below long-term average. Water levels were lowest on record. However, heavy rains in October caused flash flooding and urban flooding, as well as, damages on infrastructure and agriculture. Flash Flood properties affected, 62 properties damaged, 8 people killed and 5 injured, 1179 schools damaged, ha of rice and other crops damaged Takeo, Kandal, Pursat, Battambang, Bantay Meanchey, Siem Reap, Kpg Speu, Phnom Penh 2011 Resulting from tropical storms (mostly Haima and Nock- Ten) and low pressure, a series of heavy monsoon rains made 2011 the worst flood season since Mekong Flood & Flash Flood persons and families affected, 250 people killed, houses flooded, ha of rice ( ha were totally destroyed) and ha of other crops affected. Economic damage was estimated up to US$ 161 million. Affected 18 out of 24 provinces, Kampong Thom, Battambang, Banteay Meanchey, Siem Reap were the most affected Source: Care, 2012; MRC 2008b; MRC 2009a; MRC 2010a; MRC 2010b; MRC 2011a; Sopharith 2012; World Bank, 2010; Yang 2011; edited by author 24

34 Table 10: Floods in Lao PDR- major characteristics, socio-economic impacts and areas affected Year Flood Details Type of Flood Socio-economic Impacts Provinces/Cities affected 2005 Many provinces affected with infrastructure being heavily Mekong 480,000 people directly affected. Estimated total damage at Luangnamtha, Oudomxay, damaged. The most affected provinces are located in central and the southern part of Lao PDR where both flood Flood over US$ 18 million for agriculture and forestry sector. Another US$ 8 million registered as damaged to roads Luangprabang, Xayabuli, Huaphan, Vientiane, form the tributaries and backwater from Mekong are Borikhamxay, Khammouan, present. Savanakhet, Saravane, Champassak, Sekong, Attapeu 2006 Only localized flooding in Luang Namtha and Attapeu Mekong Affected 400 villages and 13,500 households. Five people Luang Namtha, Attapeu provinces are the more significant events. Flash flooding in Flood & reported dead and up to 7 million ha of rice and other crops Luang Namtha was in response to orographically induced monsoonal storms. Flash flooding in Attapeu was Flash Flooding damaged. Direct economic losses estimated at US$ 3 million. attributable to the incursion of Severe Tropical Storm Xangsane 2007 Events can be mostly related to the tropical storm Lekima, Flash Flood 614 villages, households and persons Khammuane, Savannakhet, which caused flash floods and consequent inundation in affected, ha of crops damaged, ha of rice field Saravane, Luangnamtha the central and southern parts of the country. Heavy rainfall in Luangnamtha province and a local storm in Vientiane affected, 136 fish ponds damaged, 2 people killed, some damages to infrastructure (e.g. 11 primary schools, 70 m. also caused some damages. roads, 29 irrigation systems). Total costs were estimated up to US$ 18 million Flood situation was dominated by the flood conditions of the Mekong mainstream and the tropical storm Kammuri, Mekong Flood & 754 villages, households and people affected, ha of rice and other crop damaged, 355 ha. Luang Prabang, Vientiane, Bolikhamxay, Khammuane which both had significant impacts at the local and Flash Flood Aquaculture damaged, 7 people killed, significant livestock provincial level, especially between Luang Prabang and Vientiane. losses (702heads) and damages to infrastructure, especially roads (314 km), schools (63 sites), bridges (3sites) and irrigation systems. Costs were estimated up to US$ 56 million. 25

35 2009 (a) Events were mostly a result of the tropical storm Ketsana, which caused flash floods and widespread inundation across the country. Flash Flood people affected, 28 deaths, significant above US$19,7 million damages in agriculture (aggravating rice shortages) and US$ 21,2 million damages in infrastructure (roads, bridges etc.), ha of rice and other crops damaged and US$ 10,1 million damage in social sectors (housing, health and education). Total costs were US$ 58 million. Investments for reconstruction were estimated up to US$ 52 million. Attapeu, Salavan, Xekong, Savannakhet, Champassak 2010 (b) Socio-economic loss and damages mainly resulted from flash flooding because the annual Mekong flood season conditions were far below average. Flash Flood persons and 357 villages affected, 7 deaths, ha of rice crop damaged, several impacts on livestock (179 fish ponds sites, 141 cattle and poultry heads lost) and infrastructure (33 houses, 65 water well and 20 school sites affected), estimated total damage was US$ 20 million. Luang Namtha, Xaignabouli, Vientiane, Khammuane, Savannakhet 2011 Haima and Nock Ten, which both caused widespread flooding and serious erosion, dominated the flood situation of LAO PDR. Flash Flood ha of farmland destroyed, people affected, 42 people killed, severe damages to infrastructure, irrigation systems, roads and bridges, total costs were estimated to be US$ 220 million. Affected 12 of Lao PDR`s 18 provinces, Borikhamxay and Vientiane were the most affected Source: MRC 2008b; MRC 2009a; MRC 2010a; MRC 2010b; MRC 2011a, PDC Weather Wall 2011; UNESCAP 2012; edited by author Table 11: Floods in Vietnam - major characteristics, socio-economic impacts and areas affected Year Most important Flood Details Type of Flood Socio-economic Impacts Provinces/Cities affected 2005 Considered as a balanced flood. Nine provinces reported to be affected by flooding. The rainy season arrived days later than normal in the Delta, started in the end of May and finished in the end of November. Hence, the flood arrived late by the end of October. Mekong Flood 77 deaths, a number of lost and damaged properties. Registered damage to be at US$ 3.5 million. An Giang, Dong Thap, Long An classified as under deep inundation (more or equal to 2m of water) 26

36 2006 Over the Se San and Sre Pok River basins, little flooding was observed. In the Mekong Delta, water rise rapidly in the start of the flooding season. The initial flood peak was followed by 20 days of declining water level. A second peak was created due to Sever Tropical Storm Xangsane. Mekong Flood Damage not widespread due to the average flooding nature. In the Se San and Sre Pok river basins, 1400 properties inundated, 8000 household required evacuation. Crops damage registered at 5800 ha which mostly comprise of rice and coffee. In the Mekong Delta region, 55 deaths reported. Total damage value estimated to be US$ 15 million Dak Nong, Dak Lak, 2007 Seven typhoons and three tropical depressions impacted the Vietnamese regions of the LMB, of which two caused major flash floods and inundation, as well as associated natural hazards (e.g. landslides, debris flows) especially in the Se San and Sre Pok basins. Flash Flood people and families affected, 59 people killed, properties inundated, 166 properties lost, ha of crops damaged, ha.of crops lost, 70 water control projects destroyed. Estimated total damage was US$ 52,3 million. Several impacts on infrastructure (roads, bridges etc.). Dak Lak, Kon Tum, Kon Plong, Can Tho 2008 Flood events caused insignificant flood damages in the Mekong Delta but some local flash floods impacted the central Highlands, especially in the Se San and Sre Pok river basins. Mekong Flood & Flash Flood Compared to other years, socio-economic impacts and the total damages were insignificant and were accounted up to US$ 1 million, ha of crops damaged, 5 provinces affected and 14 people killed Kon Tum, Dak Nong 2009 Like in the other riparian countries, flood events were dominated by the tropical storm Ketsana that generated severe flash floods and extreme water levels. Ketsana was the most intense in recent years. Flash Flood 163 people killed, houses destroyed, houses damaged, ha of rice crop damaged, ha of other crops damaged. Kon Tum, Quang Ngai, several provinces within the Mekong Delta, several provinces in the Central Highlands 2010 (a) Flood damages of the country were mostly limited to the upper Se San region and were cause by storm events. Flash Flood 4 people killed, families affected, of agricultural land damaged, some impacts on infrastructure (56,66 km roads, 6 bridges and 2180 m irrigation canals) with a total cost estimate of US$ Dak Lak, Dak Nong 2011 Like the other LMB countries, Vietnam experienced the worst flooding since eleven years. Significant damages occurred in the Mekong Delta because slow onset floods, that inundated large areas, lasted longer than 3 month. Mekong Flood & Flash Flood Over people and families affected, 85 people killed, Long inundation period seriously impacted the livelihoods of the Mekong population, ha of rice paddies, ha of secondary crops and ha of fruit trees areas and ha of industrial crops were damaged, An Giang, Dong Thap, Long An, Can Tho, Vinh Long, Hau Giang and Kien Giang. An Giang, Dong Thap and Long An were the most affected 27

37 total cost were estimated to be US$ 209 million. Source: Dang 2012; IRFC 2012; MRC 2008b; MRC 2009a; MRC 2010a; MRC 2010b; MRC 2011a; PDC Weather Wall 2011; edited by author Table 12: Floods in Thailand - major characteristics, socio-economic impacts and areas affected Year Flood Details Type of Flood Socio-economic Impacts Provinces/Cities affected 2005 Flash flooding occurred in Chiang Rai. Heavy rain together with backwater from the Mekong led to heavy inundation in Nong Khai, Nakkon Phanom and Mukdahan provinces. Mekong Flood & Flash flood Estimated that damage levels reached US$ 170 million. In 63 Provinces, 600 sections of roads were damaged with a value of almost US$ ha. of fishponds with a value of US$ and ha of rice fields destroyed added to the ha. of total damaged crop fields. Nong Khai, Nakhon Phanom, Mukdahan, Ubon Ratchani, Chang Rai 2006 Rainfall intensity highest in 30 years. Flooding initiated due to Tropical Storm Prapiroon that passed over the East Sea to the northern part of Thailand. Flash flooding occurred in Chiang Rain and Nan provinces Mekong Flood & Flash Flood Large area of inundation in 47 Provinces. Flash flooding event caused heavy damage with the flooding of 500 houses, US$ in roads, US$ in fish ponds and inundation of 800 ha. of farmland in Chiang Rai alone and ha. of total agriculture field. Temporary migration of people from rural family members to Bangkok to find work after the flooding event and 5,1 million people affected. Chiang Rai, Pa-yaw, Nong Khai, Udon Thani, Chaiyaphum, Koonkaen, Masarakam, Roi-et, Yason Thon, Nakhonarchasima, Buriram, Surin Srisakes, Udon Ratchathani, Nan 2007 Like in Lao PDR, major flood damages were caused by the tropical storm Lekima, but also by other flash floods and significantly affected the northeastern and central parts of Thailand. Flash Flood villages in 46 provinces and 3.6 million people affected, 62 people killed, around ha of crops damaged, US$ in fish ponds, severe damages to infrastructure (e.g. US$8.330 in roads, US$309 in bridges, US$ 591 in hydraulic structures and buildings). Total economic costs were US$ 48 million. Loei, Mukdahan, Roi-et Yasothon, Ubonrachatani 2008 Two major events dominated the flood situation of the Thai- Mekong region, the tropical storms Kammuri and Mekkhala. Flash Flood Socio-economic losses and damages concentrated mainly on 65 provinces in rural areas villages and 4.5 million people affected, 97 people killed, ha of agricultural land damaged and US$ lost in fish ponds. Severe Nan, Chiang Rai, Nakhon Phanom, Sakon Nakhon, Nong Khai, Mukdahan, Phetchabun, Khon Kaen, Loei 28

38 damages to infrastructure (e.g. US$ in roads, US$ 573 in bridges, US$ 595 in hydraulic structures and buildings). Total economic costs were US$ 72 million The tropical storm Ketsana was the major flood event and Flash Flood No detailed information about the damages and impacts of caused flash floods and inundation. Ketsana are available for Thailand. It was estimated that the total economic costs of Ketsana was US$ 21 million and well below the long-term average Flood situation was dominated by the tropical storm Mindulle in the northern and northeastern parts of the Flash Flood 5 million people and 1 million families affected, 79 deaths of property damaged ha of crops Mae Hong Son, Chiang Mai, Lamphun, Lampang, Phrae, Nan, country and by local storm rainfalls and flash flooding damaged. Total damages were estimated up to US$ 1.2 Uttaradit, Phetchabun, Phichit, billion. Phitsanulok, Saraburi, Mukdahan, Nakhon Nayok 2011 Unusually heavy rainfall form successive, powerful Flash Flood Flood crisis impacted around 4 million households and 66 out of 76 provinces were (a) monsoons has resulted in the worst flooding in more than five decades affected 13.4 million people, 680 people killed, 2329 houses were destroyed and were partially damaged. Total affected. Phichit, Nakhonsawan, Chainat, Lopburi, Singburi, Phra costs were US$ 46.5 billion. Floodwaters inundated 90 billion Nakhon Si, Pathum Thani, square kilometers of land more than two thirds of the country ha of crops and ha of fishery and Nonthabuiri, Nakhonnayok, Prachinbuiri and Bangkok were of livestock (heads) were affected. severely affected (a) World Bank 2012 provides very detailed information about the 2011 flood impacts for Thailand Source: Morgan Stanley Research 2011; MRC 2008b; MRC 2009a; MRC 2010a; MRC 2010b; MRC 2011a, PDC Weather Wall, 2011; Thaiwater 2011; World Bank 2012; edited by author 29

39 3.4 Conclusion Figure 7 summarizes the frequency of floods in recent years and highlights the most severe flood events. While floods are recurrent in most parts of the MRB and people learned to adapt to them, some extreme events have devastating impacts accompanied with high death tolls, loss of agricultural yields as well as damages to houses and other infrastructure. While immediate damages of floods can be significant subsequent impacts on public health, transport, energy supply and ultimately socio-economic impacts like increase of poverty are often even more damaging. The long term effects can include migration (from rural to urban areas) and political and social instability. Associated with population growth and associated spread of settlements and increased agricultural area often in flood prone areas where the exposure to flood hazards increases. 30

40 The following figure summarizes the years of major flood events and their impacts: Source: Own concept of author based upon MRC flood reports (compare tables 8-12) Figure 7: Regional distribution of major Flood impacts 31

41 4 Drought Hazards and Vulnerability The severe drought impacts from the years 1992, 1993, 1998, 1999 and 2003 until 2006 (Son et al., 2012) show that droughts pose a serious threat to the Mekong region and require a more thorough consideration in future management strategies. According to Terink et al. (2011), negative impacts of droughts in the Mekong region might be more severe than impacts of floods, Navuth (2007) states that they might even be the most costly. 4.1 Drought risk assessment and management Drought risks are considered as a combination of drought hazards and drought vulnerability: drought risks = drought hazards + drought vulnerability (IPCC 2012 (SREX); UN-ISDR, 2009). According to the UN-ISDR Terminology on Disaster Risk Reduction 2009, drought is categorized as a hydro-meteorological hazard which can be described quantitatively by the likely frequency of occurrence of different intensities for different areas, as determined from historical data or scientific analysis (UN-ISDR, 2009). Droughts can be understood from different disciplinary perspectives: while meteorological droughts are defined by a precipitation deficiency over a pre-determined period of time, hydrological droughts depend on certain surface and groundwater availability thresholds (Tallaksen and Lanen, 2004). An agricultural drought is defined by the lack of soil moisture to support agricultural production and can be considered as a combination of both meteorological and hydrological droughts due to its dependency on meteorological and hydrological parameters (NDMC 2012; UNDP 2011; UN-ISDR 2009; Wilhite and Svoboda 2000). Also a socio-economic drought has been defined reflecting the relationship between the supply and demand for some commodity or economic good that is dependent on precipitation (UNDP 2011; UN-ISDR 2009). In the following table, these most common drought categories are listed: Table 13: Drought types and their characteristics Drought categories Meteorological drought Agricultural drought Hydrological drought Socio-economical drought Characteristics Decreased rainfall and changes in seasonal pattern, increased temperature and evaporation reduced crop yields, reduced land carrying capacity, sales of livestock at poor prices, increased credit risk, increased debt reduced surface water availability, reservoir drawdown, lower groundwater levels, increased evapotranspiration food and energy shortage, price increases, increased imports, reduced incomes, rural unemployment, socio-political pressure Hence, drought events need to be assessed from each of these perspectives: meteorological, hydrological and agricultural drought risks. Historical and actual meteorological and hydrological time series, salinity values in surface and groundwater, water storage reservoir data and soil moisture need to be analyzed regarding their relationship to droughts and suitability for effective drought risk indicators. Unlike floods, droughts evolve slowly and depending on the regional features they have a duration of several weeks to several years and their structure and impacts vary significantly 32

42 from one region to another (Hannaford et al. 2011; Mc Kee et al. 1993; Wilhite and Svoboda 2000). Thus, drought risks need to be assessed by considering both anthropogenic impacts and bio-physical factors (Vogt et al. 2011; Wilhite and Svoboda 2000). Adamson and Bird (2010) stated that the severity of a drought and its impact is dependent not only on its duration, intensity and spatial extent, but also on the specific environment and the economic activities carried out within it as well as the capacity of the prevailing institutional and social system to cope with it. From the meteorological perspective, also large scale climate patterns can serve as valuable sources for drought assessment and prediction. The El Niño-Southern Oscillation phenomenon (ENSO) for example leads to irregularly occurring episodes of changed ocean temperature and weather patterns, often coherent with extreme weather events in South East Asia and worldwide (Boucharel et al. 2011; NDMC 2012; UN-ISRD 2009). Furthermore, drought events not only evolve due to low rainfall rates but also due to shifts in precipitation patterns (Adamson & Bird 2010; MRC 2010a; MRC 2005). Therefore the drought risk of some regions under climate change forces might increase (ICEM, 2010). In Chapter 5, different simulations for the drought risk distribution in the riparian countries are presented. In general, a lot of investigation has been carried out on drought risk assessment and drought hazard monitoring has been widely applied especially for arid and semiarid regions of the developed world (NDMC 2012; UCL 2011; Wilhite and Svoboda 2000). Droughts in South East Asia, however, so far have been neglected in scientific literature and in international strategies (UNDP 2011) Drought risk assessment in the Mekong Basin A common method how to assess the hydrological drought risk in the Lower Mekong Basin is to measure and observe the flow in the Mekong mainstream and the degree to which they fall below some average runoff (MRC 2005). Adamson et al. (1999), states that the dry season hydrology can serve as a key indicator for classifying drought incidence and severity from year to year. During the dry season, the competition for water resources is high for irrigation, domestic and industrial uses, for navigation of ships and sufficient water supply to the Mekong Delta to minimize the risk of salt water intrusion. 33

43 The recent annual frequency of droughts in each riparian state of the MRB is summarized in Table 14. The table represents the ratio of the number of severe drought years (one or more droughts in different regions of the country) relative to the total number of years in the period (MRC 2010a; Pandey et al., 2007). According to this data, Lao PDR and Thailand are more likely to be affected by meteorological droughts, whereas Cambodia and Vietnam show the lowest drought probabilities. Table 14: Frequency of Droughts in the Mekong Region Country Drought Probability Additional Information China 0.48 Occurrence of drought events in the MRB in the last Myanmar 0.20 decade: 1992, 1993, 1998 and Most severe drought events started in 2003 and generally Lao PDR 0.42 lasted to Thailand 0.45 In some regions, water levels and flows were below the average level until Cambodia 0.34 Vietnam 0.30 Source: MRC 2010a; Navuth 2007; Pandey et al To detect the different susceptibilities to drought events of the region, Terink et al. (2011) developed a Drought Management and Assessment Toolbox. The toolbox includes a framework for drought monitoring and impact assessment with a number of technical drought-, hazard- and vulnerability indicators. Meteorological drought was assessed using the Standardized Precipitation Index (SPI) together with the Moisture Availability Index (MAI). Furthermore, agricultural drought was analyzed using the Normalized Differenced Vegetation Index (NDVI) and a Soil Moisture Deficit Index. Satellite information from the ENVISAT Satellite Imagery or flow rate observations provided data to analyze hydrological drought. 4.2 Drought Vulnerability and socioeconomic impacts The agricultural sector in the Mekong region is highly sensitive to water shortages as a result of below average flow during both the dry and rainy season. A decrease in water supply during dry season can lead to a reduced crop yield due to reduced soil moisture availability and irrigation possibilities. During rainy season, water shortages can diminish the volume and extent of essential floodwaters for controlled field inundation and can lead to salt water intrusion in the delta region (MRC 2010a; Navuth 2007). Drought events in the Mekong River Basin pose serious socio-economic threats to those dependent on secure water availability and supplies. The devastating drought of 2004, for example, affected millions of farmers and the low-income population and caused substantial agricultural deficits in Northeast Thailand and Cambodia, a considerable reduction in the second rice crop in Lao PDR and very critical levels of saline intrusions in the Mekong Delta (Navuth 2007). The potential socio-economic impacts of droughts for each riparian state of the MRB are summarized in table

44 Table 15: Some of the Potential Impacts of Droughts in the Mekong Region Livelihoods: 1. Lack of fodder; lack of drinking water for cattle, for irrigation purposes, and industries 2. Reduced crop yield and reduced quality 3. Impaired productivity of forest land 4. Land degradation 5. Damage to fish farming Food security: 1. Loss of availability of food 2. Loss of availability of nutritious food Health: 1. Dependence on unsafe drinking-water sources 2. Insufficient water for hygiene purposes 3. Stress due to loss of livelihoods and income Economic impacts: 1. Loss of income from agriculture and fishery 2. Loss of employment 3. Increased prices of food and fodder Social impacts: 1. Migration and related impact on families/communities and on social structure 2. Loss of human life 3. Increased inequity among social groups 4. Increased conflicts 5. Increased mental and physical stress 6. Increase in crime rate 7. Reduction in school attendance 8. Increased burden on women and children 9. Increased burden on government and non-government organizations Environmental impacts: 1. Increase in deforestation, partially due to forest fires 2. Water quality and quantity deterioration/environmental pollution 3. Extinction of endangered species and loss of bio-diversity Source: OXFAM 2008a; Oxfam 2008b The following section describes the impacts of droughts and estimated economic costs for each riparian country. The regional information on droughts is often incomplete and therefore does not reflect the real extent of the total costs. Except for Cambodia, the impact of hydrological droughts on yields of fisheries, for instance, has not been assessed in riparian countries of the Mekong. The same can be applied to the significance of droughts on animal husbandry which also has not been evaluated sufficiently. However, as mentioned in the introduction to this chapter, the severity of a drought depends on its type, its intensity (e.g. water deficit, yield deficit), its point of time and duration, as well as on 35

45 its resultant socio-economic impacts (e.g. effects on agriculture and society). In addition, the major economic costs of droughts in the MRB are caused by a limited agricultural production potential (e.g. reduced yields), a total loss of crops and/or reduced livestock and fishery yields (MRC 2010a) China (Yunnan): Meteorological droughts can be considered as the most severe hazards in Yunnan province. Due to low precipitation and high temperatures, Yunnan has experienced drought events almost every year, with severe socio-economic and environmental impacts (Liu et al. 2007; Pandey et al. 2007). From a long term meteorological drought has significantly affected Yunnan s water availability and drinking water supply. Over 273 rivers and 413 small reservoirs have been dried up or dropped to record low levels. As a result of a reduction in reservoir capacity, around 6 million people had to suffer from water shortages and agricultural losses which were estimated to be more than US$ 2.5 billion. Moreover, about ha of forest and ha of croplands and livestock grazing ground were seriously affected. The scarcity of water resources further increased the probability of social conflicts, especially among desperate farmers. In this connection, there were over cases of disputes reported, where officials had to intervene. The potential in hydropower generation also has been dramatically slowed down by the sustained drought. In this relation, it was reported that in some regions the electricity generation from hydropower facilities has been 50% lower than the normal production (NASA 2013; Thupgon 2012) Myanmar: There is a substantial lack of information on drought issues in the Mekong region of Myanmar. However, the hazard profile of Myanmar, which has been published by the Government of Myanmar in 2009, outlines that Shan, the only province, which is located next to the Mekong, so far is not considered as a drought-prone region (Government of Myanmar 2009) Lao PDR: Lao PDR is vulnerable to droughts, but has only been seriously affected by five droughts in the last 40 years. The most severe drought occurred in 1977 and had significant impacts on 3.5 million people. The drought of 1998, in contrast, affected people (GFDRR 2011b). Comparatively to the other riparian countries of the MRB, Lao PDR has been less impacted by the drought of , but resulting from reduced rainfall and low stream flows, the country still experienced a 25% reduction in dry season s plantings (MRC, 2010a). Furthermore, the Laotian Department of Meteorology indicated that the drought conditions between 1995 and 2005 were characterized by a higher and an irregular increase in temperature. It is also noteworthy, that Lao PDR frequently faced localized droughts, which have the potential to considerably impact rice production and the associated household food security. In this connection, it is estimated that around households are currently at risk of food security because of droughts. The Laotian provinces which have been identified to be highly vulnerable to drought events are: Khammuane, Savannakhet, Saravane, Champasack, Xayaburi, Vientiane and Bolikhamxai (GFDRR 2011b; Phommachanh 2003) Thailand: Thailand is one of the countries with a high drought probability index. The north-eastern regions along the western part of the Khorat Plateau are the most affected areas due to rain shadow effects from the Phang Hoei Range. The mountains block the passage of rain-producing 36

46 weather systems, creating a "shadow" of dryness on the lee back side of a mountainous area (MRC 2012; Terink et al. 2011). For the agricultural production of Thailand, droughts have become an important factor to be considered because they adversely affect many of the country s agricultural, as well as economic activities (especially rice cultivation) (Pandey et al. 2007). In the north-eastern parts of Thailand, for example, the average annual costs of droughts were amounted to be US$ 10 million (MRC 2010a). In addition, Thailand had to face several droughts in the last decade, but one of the most severe droughts occurred between the years of , where the total damage and loss in farm income was amounted to be US$ 290 million. The drought of also had significant impacts on the country`s socio-economic conditions. Serious water shortages in storage facilities resulted in significant consequences for the agricultural production sector because water for irrigation was restricted in order to safe water for domestic purposes. As a consequence, 8 to 9 million people, 63 out of 76 provinces (92%) and about 2 million ha of agricultural land in Thailand were affected. Moreover, production losses from major crops were assessed to be US$ 320 million, an equivalent to 2.2% of the agricultural GDP. The drought-induced scarcity of water for agricultural purposes continued into 2005 and decreased the production of major crops by 16.7% and dropped the agricultural GDP by 8,2% in the first 3 month of 2005 (Pandey et al. 2007). The far-reaching consequences of droughts for the economic conditions of Thailand are also illustrated in the following Table. Table 16: Economic Impacts of Droughts in Thailand Major drought years Number of provinces affected (% of total (no.) provinces) Cropped area affected (million ha) Economic losses (% of (million US$) agricultural GDP) Source: Pandey et al Cambodia: Southeastern Cambodia belongs to the most meteorological drought prone areas within the Mekong Basin. Due to the rain shadow effect of the Cardamom and Elephant Mountains in the southwest of Cambodia, the southeastern parts of the country show limited monsoon rainfall and thus a high susceptibility to drought events (MRC, 2012). The past drought periods showed the impact such events have on the Cambodian socio-economy. The average fishery catch in the basin area in Cambodia has been estimated to be tons per year. In the drought years , , however, annual fish catches fell to about tons and increase costs of about US$ 14.5 million (MRC, 2010a). Between , a 20% the loss of the total rice production was attributed to droughts and Svay Rieng, the most drought-prone province of Cambodia, was hardly affected. Damage to seeding was the consequence and about hectares of planted rice was affected in 2002 (GFDRR 2011a). The most 37

47 significant socio-economic impacts resulted from the drought of In addition, Cambodian rice production has been extremely reduced in large parts of the country (14 out of 24 provinces were affected) and people had to face food shortages (MRC 2010a) Vietnam: Agricultural drought in the Mekong River Delta in Vietnam is a recurring phenomenon. Especially the highly agriculturally productive South-Eastern part of the Mekong Delta is frequently affected by the summer drought called Madame Chang which is considered as more severe than the winter-spring drought and before 2000 occurred in 1988, 1990 and During each crop season 700 ha to ha of farmland were affected by drought, and 300 to 760 ha were entirely destroyed. The winter- spring droughts from October to December in 1958, 1983, 1992 and 1998 affected 691,000 households by water shortage. Especially the winter- spring and summer- autumn drought in 1998 cut the drinking water supply of more than 1,100,000 people in the Mekong Delta and affected nearly ha of summer- autumn crop area and entirely destroyed over ha (UNDP, 2000). Within the last 10 years, at least four water shortage events have been reported as drought in the years of 2004, 2009, 2010 and more recently Information on estimates about losses and damage vary slightly but however, the different local sources agree on certain particular districts/areas within the provinces that are heavily affected. The drought events together with areas which have been directly affected taken from local news sources are listed in Table 17. This is used as a tool to identify the various drought hotspots within the region. Table 17- Identifying Drought Hotspots in Vietnam Year Province Districts Source 2004 An Giang Tri Ton town (Vnexpress 2004a) 2004 Dong Thap Cao Lanh (Vnexpress 2004a) 2004 Ben Tre Chau Thanh (Vnexpress 2004b) 2004 Soc Trang My Xuyen (Vnexpress 2004b) 2004 Soc Trang Thanh Tri (Vnexpress 2004b) 2004 Soc Trang My Tu (Vnexpress 2004b) 2009 Long An Thanh Hoa (MARD 2013) 2009 Ben Tre Chau Thanh (MARD 2013) 2009 Tra Vinh Tieu Can (MARD 2013) 2009 Vinh Long Vung Liem (MARD 2013) 2010 Soc Trang Nga Nam (Soc Trang PPC 2010) 2010 Soc Trang Tran De (Soc Trang PPC 2010) 2010 Soc Trang Soc Trang city (Soc Trang PPC 2010) 2010 Soc Trang Long Phu (Soc Trang PPC 2010) 2010 Soc Trang My Xuyen (Soc Trang PPC 2010) 2010 Ben Tre Binh Dai (BaoMoi 2010) 2010 Ben Tre Ba Tri (BaoMoi 2010) 38

48 2010 Ben Tre Thanh Phu (BaoMoi 2010) 2010 Kien Giang Kien Hai (SGGP, 2010) 2010 Bac Lieu Hong Dan (SGGP, 2010) 2010 Bac Lieu Hoa Binh (SGGP, 2010) 2010 Bac Lieu Phuoc Long (SGGP, 2010) 2010 Bac Lieu Vinh Loi (SGGP, 2010) 2010 Hau Giang Long My (SGGP, 2010) 2010 Hau Giang Vi Thanh township (SGGP, 2010) 2013 Ben Tre Binh Dai (VnTimes 2013) 2013 Ben Tre Ba Tri (VnTimes 2013) 2013 Ben Tre Thanh Phu (VnTimes 2013) 2013 Soc Trang Tran De (BaoMoi 2013) 2013 Tien Giang Go Cong Dong (BaoMoi 2013) 2013 Tien Giang Tan Phu (BaoMoi 2013) 2013 Tien Giang Tan Phu Dong (BaoMoi 2013) In particular, it can be seen that for the four most recent drought events, the districts of Chau Thanh, Binh Dai, Ba Tri, Thanh Phu (Ben Tre province) and My Xuyen (Soc Trang province) are those which are listed as severely affected more than once. In the more widely covered drought of , more than ha of rice were reported damaged. In Ben Tre, for instance, which was one of the worst affected province, ha of rice and ha of fruit orchards were destroyed. The total costs were estimated to be US$ 33 million and families required the purchase of water for domestic use (MRC 2010a). 4.3 Conclusion Based on national study reports, the technical support division of the Mekong River Commission Secretariat has identified four major problems that can be particularly attributed to droughts and to the increasing vulnerability of people and the environmental conditions of the Mekong region. These problems are briefly highlighted below: 1) Lack of detailed information concerning the extreme variability of climatic and hydrological conditions in drought prone regions of the Mekong River Basin. 2) Lack of capacity in the fields of improved and tested drought preparedness, management and mitigation strategies. 3) Imbalance between water supply and demand in drought prone parts of the Mekong River Basin. 4) Inadequate or unfinished institutional and legal framework for an enabling environment regarding an effective drought management (Navuth, 2007) The problem of imbalance between water supply and demand in drought prone parts of the Mekong River Basin should be considered as the most critical. This is because it directly affects the local economy in terms of irrigation, drinking water supply, power and industrial production. 39

49 In the drought-prone areas of Cambodia and the north-eastern parts of Thailand, for instance, the insufficient water storage capacity is the most pressing problem. Source: own concept based on Navuth (2007) Figure 8: Main Effects of Increased Drought-related Vulnerability in the MRB 40

50 Figure 8 shows three identified major effects of increased vulnerability that have the potential to create severe consequences for social, economic and environmental status quo of the Mekong region. In addition, the following assumptions can be made: Poverty and vulnerability to droughts are closely connected to each other. Poor people, especially in rural areas, are generally more susceptible to diseases and are much more threatened by natural disaster than other groups. Most of them also do not have the resources to easily recover from any kind of material and economics losses. For most of the Mekong riparian countries, the agricultural sector still contributes substantially to the country s GDP. Drought, therefore, have the potential to significantly affect the socioeconomic conditions, especially of those who are highly vulnerable. An increasing drought probability will further lead to the situation that an increasing number of people falling below the poverty line because their incomes and food supply is decreased as a result of reduced agricultural, livestock and fish production. This situation also impacts the processing industry because their facilities may not be utilized sufficiently. The same holds true for hydropower stations and navigation because it can be expected that the increased vulnerability of water resource systems will cause a substantial loss of revenues. The loss of sustainability and productivity of water and natural resources also can be attributed to the increased regional vulnerability to drought-stresses. These losses can emerge in many different ways (e.g. increasing land degradation processes, deterioration of water quality and quantity, etc.) In order to save water for individual purposes an increased extraction of groundwater resources can be found in the drought-prone regions of the Mekong. This situation can particularly have a severe negative effect, if the groundwater resources are characterized by high salinity. A loss of productivity and fertility, as well as soil salinity would be the consequence. Therefore, the Mekong Delta is particularly threatened by droughts because saline intrusion is already significantly impacting the vulnerable soils of this region. Resulting from the socio-economic impacts of droughts, a decline in social and institutional stability of the riparian population can be expected, especially in those regions that are characterized by a high drought hazard potential and where people, but also water resource systems are extremely vulnerable to droughts. Increasing migration processes from rural to urban areas and inequality in water utilization, especially in regions that do not have mainstream access, could be the consequence (Navuth, 2007). The different above mentioned aspects show the requirement of an effective drought management for the Mekong region. In 2006, the MRC Secretariat together with the MRC member states developed the Drought Management Program (DMP). Ever since they are working stronger in the fields of drought forecasting, drought impact assessment, drought management policy and drought preparedness and mitigation measures (Navuth, 2007). But like other authors depict (Adamson and Bird, 2010; Oxfam, 2008; Terink, 2011) there is still a lot of work to be done and drought management in the Mekong River Basin has to be put high up on the agenda of all MRC member states. 41

51 Figure 9 visualizes the areas impacted by significant droughts observed in the past decades. Source: various (compare tables and text in this chapter) Figure 9: Regional distribution of major observed droughts 42

52 5 Key Drivers and Pressures 1: Climate change 5.1 Introduction and overview of literature The Tibetan plateau has been identified as a tipping point for climate change impacts as accelerated glacier and snow melt causes a positive feedback accelerating the melting process by the enlarged dark rocky ground attracting more heat. During the low flow season in April and May, 75-95% of the Mekong runoff in Vientiane originates in Tibet and during the peak flow months from July to September over 50%. Changes in snow melt driven hydrology in Tibet will hence significantly impact downstream hydrology and especially the dry season flow (Adamson2006). This strong vulnerability of the Mekong hydrology towards climate change impacts requires profound research on the climate-hydrology interactions under different scenarios. The following literature review summarizes the State of the Art on the following topics: 1. The general findings on the role of the ENSO phenomenon on climate variability in South East Asia: AchutaRao and Sperber 2006; Cruz el al. 2007; Giorgi and Mearns 2002; Mc Avaney et al. 2001; Mc Phaden et al. 2006; Montecinos & Aceituno 2003; Räsänen & Kummu 2013; Tudhope et al The State of the Art regarding General Circulation Models : AchutaRao and Sperber 2006 ; Collins et al ; Flato et al. 2000; IPCC: SREX report 2012; Johns et al ; Randall et al ; Roeckner et al Climate related research and downscaling focusing on the Mekong region by: Hoanh et al. 2003; ; Johnston et al. 2010; Lacombe et al. 2012; Mac Sweeney et al. 2008; TKK & SEA START RC Impact of climate change on river discharge predictions and lake water levels: Eastham et al. 2008; Ishidaira 2008; Keksinen et al. 2010; Kiem et al 2008; Laurie et al. 2012;TKK and SEA START RC Current Situation and Tendencies The ENSO phenomenon and its impact on climate variability in the Mekong region The El Niño Southern Oscillation (ENSO) is a well-known phenomenon. In South East Asia it is leading to low rainfall rates during el Niño years and higher precipitation in la Niña years (AchutaRao and Sperber, 2002; Räsänen & Kummu, 2012). Räsänen and Kummu (2012) analysed the correlation of the ENSO phenomenon with recent climate variations in the Mekong Basin for rainfall data (149 precipitation stations, ) and discharge (six Mekong gauging stations, ) using spatial GIS analyses and statistical methods, such as linear correlations, spectral analysis and stochastic regression models. They detected that the hydrological dynamics of the Mekong River were significantly influenced by ENSO events, especially in the southern and central part of the basin. The precipitation and discharge data correlated particularly in the years of ENSO events, decreasing during El Niño years with shorter annual flood periods and increasing during La Niña years with longer flood periods. Furthermore, they found out that the correlation between ENSO and the hydrological processes of the Mekong changed significantly in the period From 1910 to 1940 and from 1975 to 2008 a strong correlation in the data could be observed, whereas between 1940 and 1975 low correlations were recorded (Räsänen & Kummu, 2013). 43

53 The irregular (every 2-7 years) El Niño and La Niña years originate in the tropical Pacific and are accompanied by interactions between the ocean and the atmosphere of the tropical Indian and Pacific Oceans. They have clear signals in sea surface temperature (SST), atmospheric pressure patterns and a varying strength of the Pacific trade winds. While El Niño years account for higher sea surface temperatures and lower air pressure in the Eastern Pacific, La Niña conditions are generated by cold sea surface temperatures originating in the tropical Pacific (Mc Phaden et al. 2006; Tudhope et al. 2001). Higher El Niño SSTs lead to higher evaporation rates and hence to above-average rainfall in the eastern Pacific and South America during winter and late spring. At the same time, it causes droughts in eastern Australia, South East Asia and storms along the equator. Measuring sea surface temperature and atmospheric pressure is considered as a suitable tool to predict El Niño and la Niña events and hence precipitation more than several months ahead (Montecinos & Aceituno, 2003). For the Mekong Basin, it is suggested to have a high potential for prediction of ENSO induced hydro-meteorological extremes. ENSO index values from December-February explained approximately 50% of the 562 inter-inter-annual variation of the Mekong s following year discharge (Räsänen & Kummu, 2013) General Circulation Models and regional downscaling General Circulation Models (GCMs) are based on mathematical equations that are solved using a three-dimensional grid covering the globe. The major components of the climate system are represented in sub-models for e.g. atmosphere, ocean, land surface, cryosphere and biosphere (Randall et al. 2007). Climate numerical modeling with GCMs is applied for weather forecasting, climate analyses and projecting climate change. While the first generations of GCMs only addressed the atmospheric dimension of the climate and were called Atmosphere General Circulation Models (AGCMs), now both atmosphere and ocean circulations can be involved through Atmosphere-Ocean General Circulation Models (AOGCMs). Although still of coarse spatial resolution, most AOGCMs are able to simulate large scale climate events. Many global climate models (GCMs) were developed since the early 1990s, including ECHAM4 (Roeckner et al., 1996), HADCM3 (Johns et al. 2003) and CSIRO-MK3, CGCM3.1 (Flato et al., 2000). However, climate models try to display the real climate system which so far is not completely understood and hence cannot be projected by models (Collins et al., 2012). AOGCMs are not able to capture detailed effects at higher resolution sub-grid scales. This is especially problematic in mountainous areas with strong microclimatic variations (AchutaRao and Sperber, 2006). The simulation and projection of the climate in a specific region is only possible at a much finer resolution via regional dynamical and statistical downscaling of GCMs. Extreme temperatures are better simulated than extreme precipitation events (Mc Avaney et al., 2001; Randall et al., 2007). For temperature scenarios the different models often yield similar results. However, for annual precipitation amounts or even more for the distribution of precipitation over the year and the precipitation intensity (IPCC, 2012) the results vary from model to model. The recent SREX report (IPCC, 2012) presents the state of the art regarding research on linkages between Climate Change and Extreme Events. Significant trends in the increase of minimum and maximum temperature as well as heat waves can be detected in the past decades and are very likely to increase due to climate change in the decades to come. Nevertheless there are only very few regions in the world where either drought or flood hazards were significantly increasing over the past decades. The obvious global trend of increasing intensity of damages related to climate extremes can mostly be attributed to increasing vulnerability. 44

54 Regarding the likelihood of future trends of precipitation, flood and drought hazard, IPCC (2012) concludes that at a global level significant changes cannot be stated with a high level of certainty. In order to make future estimates on the regional level covering the Mekong Basin, downscaling of GCMs is necessary. Here it is important to note that downscaling requires tremendous effort and time. Depending on the chosen GCMs, global socioeconomic scenarios (A or B scenarios) and the large variety of available hydrological models calculating runoff etc. the resultant outcomes are related to high levels of uncertainties. This leads to the fact that so far it has not been possible to come up with a reliable analysis or even predictions regarding future climate elements and hydrology. Each study can rather be interpreted as one possible future scenario Climate trend analysis and regional downscaling for the Mekong region The following authors have carried out downscaling exercises for the Mekong region: Hoanh et al. (2003) used the HADCM3 GCM under A2 and B2 SRES scenarios to compare temperature and precipitation projections for the periods and with the baseline in the Mekong Basin. Results indicate that mean temperature in the Mekong basin will increase by 1.0 C between the baseline and for both scenarios. Between the baseline and temperatures will increase by 4 C and 2.9 C, for scenarios A2 and B2 respectively. For both scenarios, relative changes in annual precipitation between the baseline and 2010 to 2039 varie between -6% and +6%, depending on the sub-basins. This range increases to -12% and +32% for the period (Hoanh et al., 2003). Mac Sweeney et al. (2008) analyzed the climate trends and carried out downscaling of GCMs for 52 countries using historical climate data and 15 GCMs from IPCC (2007). Within the Mekong Basin, they addressed Vietnam and Cambodia. They simulated climate projections for the period , based on grid-based temperature and precipitation time series under A2, A1B and B1 SRES scenarios. For both countries, the results suggest that temperature is expected to increase from 0.7 to 2.7 C by the 2060s, and from 1.4 to 4.3 C by the 2090s. Precipitation is expected to increase, leading to wetter wet seasons -11% to +31% and -1% to +33% by 2090s in Cambodia and Vietnam respectively and by drier dry seasons with a decrease of precipitation of -54% to +35% and -62% to +23% by 2090s in Cambodia and Vietnam respectively. The proportion of total rain that falls in high intensity events is projected, by all models, to increase by up to 14% in the 2090s (Mac Sweeney et al., 2008). Lacombe et al. (2012) characterizes projected fine-scale changes in precipitation and temperature in Southeast Asia over the period He uses grid-based daily precipitation and temperature time series produced by the PRECIS regional climate model under A2 and B2 scenarios. Trend analysis and detection was carried out by applying the modified Mann-Kendall test. The results indicate that temperature increases over the whole region with steeper trends in higher latitudes (Lacombe et al. 2012). Changes in precipitation rates are minor over continental areas in contrast to other climate studies that suggested significant precipitation changes over Southeast Asia. TKK & SEA START RC (2009) carried out dynamical downscaling of the PRECIS regional climate model based on ECHAM4 GCM data. In their study they considered two climate scenarios based on two different CO2 rising schemes, SRES A2 and B2 (IPCC, 2000). The regional climate scenarios were simulated at high resolution of approximately 25km x 25km, and rescaled to resolution of 20x20km. Their results from both GCMs for maximum and minimum temperatures also indicate that the region will become slightly warmer in the future. Concerning precipitation, model simulations indicate that precipitation will fluctuate in the first 45

55 half of the century, but show an increasing trend during the latter half of the century. The simulations according to the B2 scenario show fewer changes in precipitation than the A1 scenario. No detailed analyses of these downscaling results were included in the cited publication (Keksinen et al., 2010; TKK & SEA START RC, 2009). Johnston et al. (2010) at IWMI carried out a climate change analysis for the Mekong region. They used observed ( ) and projected ( , using PRECIS climate model) rainfall and temperature data in the region, to identify climate trends. Based on the results of this study and others, Johnston et al. (2010) summarized the projected climate changes in the GMS to 2050 as follows: - Increase in temperature of C per year across the entire region in both warm and cold seasons, with higher rates of warming at higher latitudes - Higher temperatures will increase evapotranspiration and hence irrigation demand - No significant change in annual rainfall across most of the region (projected changes in rainfall vary from decreases of a few millimeters per year to increases of up to 30 mm, with a high degree of uncertainty). - Some (small) seasonal shift in rainfall, with drier dry seasons, and in some studies shorter, more intense wet seasons. This means that even if total annual rainfall does not change significantly, it is possible that the availability of water for agriculture may change, with increases in the incidence of both droughts and floods. - Increase in temperature of sea surface may increase the intensity and incidence of typhoons during El Niño years (MRC 2009b) Climate Change and runoff projections for the Mekong Basin Several studies have been undertaken in Southeast Asia with the objective to predict future river discharge and lake water levels. Ishidaira et al. (2008) combined GCM predictions with land use change scenarios and modeled (YHyM-Model) future discharge for the 2020s, 50s and 80s. While annual discharge is supposed to increase the overall pattern/seasonality of discharge will largely be maintained. Model runs for the 2080s simulate that the flood season has a tendency to start around 1-2 weeks earlier (Ishidaira et al. 2008). Kiem et al. (2008), estimated that annual mean rainfall would increase 4.2% during , compared to for the entire MRB (using JMA AGCM, A1B scenario and the YHyM hydrological model). Main contribution to these changes is related to the upper Mekong Basin. Annual mean temperature over the basin is estimated to increase by 2.6 C (averaged over the entire basin). Applying hydrological modeling they calculated discharge and estimate that Q10 would increase at average by 9.8 % while Q90 would increase at average by 9.6 %. This indicates that the probability of hydrological drought to occur is decreasing while the flood hazard is likely to increase. Eastham et al. (2008) selected 11 GCMs for the Mekong Basin using scenario A1B, to construct scenarios of future (2030) rainfall in the MRB. They identified that the most likely projected response in annual rainfall averaged across the basin is a 13.5% increase. Their model results show that runoff will increase in most sub-basins during the wet and dry season with the highest increase in the late flood season. However, Eastham et al. (2008) depict that their projections still adhere significant uncertainties. They range from a mean annual runoff decrease of ~ 8% to an increase of 90%. Their best estimate for future runoff responses is a 21% increase of the median runoff. According to the spatial distribution of runoff increase their model results show a 46

56 larger increase for the Upper Mekong catchment with up to 111% compared to historical values. For the lower catchments and especially the delta region the projected changes in runoff values are the lowest (10-20%) or even unmodified. The contributions of glacier melt to stream flow are supposed to be small, as glacier melt only contributes 0.1% of the mean annual discharge. Snow cover on the contrary contributes 8% to the annual runoff and could account for a bigger part of the projected increase of river discharge in the Upper River catchment (Eastham et al. 2008). TKK and SEA START RC (2009) analyzed the hydrological impacts of climate change on the Tonle Sap basin and the Mekong Delta. The RCM PRECIS forced by the GCM ECHAM4 was used as input to 1.) the basin-wide hydrological Variable Infiltration Capacity (VIC) model to simulate future river runoff, and 2.) the Princeton Ocean Model (POM) to simulate future sea level change at the mouth of the Mekong River. Output from VIC, POM and PRECIS were used as input for the EIA 3D model simulating the hydrological behavior of the Mekong River floodplain system. Simulations were run for a baseline period ( ) and four decades (2010s, 2020s, 2030s and 2040s). The results indicate that the Mekong River discharge will increase (decrease) in the wet (dry) season by about 5.14% (2.18%), equivalent to an annual 4.3% increase between the baseline and the period (TKK and SEA START RC 2009). Lauri et al (2012) combined downscaling of five GCMs with distributed hydrological modeling (VMod with a grid resolution of 5x5m) to estimate future temperatures, precipitation and runoff (scenarios for compared with baseline ). The VMod model also simulated the operation of multiple hydropower reservoirs including existing and planned dams. Discharge simulation results strongly varied depending on the GCM used as input. The projected discharge at Kratie, Cambodia for the time period ranges from 11% to +15% for the wet season and from 10% to +13% for the dry season. It is also remarkable that results show a much larger impact on discharges due to planned reservoirs than those simulated due to climate change: the model simulated % higher dry season flows and 5 24% lower flood peaks in Kratie (Lauri et al., 2012) Expected impacts of increasing temperature and changes in precipitation patterns in the MB: The high degree of uncertainty makes it challenging to precisely predict the impacts of climate change in the Mekong region, as these might vary by location and time. It is projected that by 2050 the impacts of climate change on the MRB will comprise decreasing overall water availability, increasing temperatures, as well as an increasing flood and drought likelihood. Other effects include a decreasing food production capacity and a rising sea level, especially in the Mekong Delta region (Cruz et al., 2007; Grumbine et al., 2012). Studies on vulnerability and adaption to climate change have been published by Anshory-Yusuf and Francisco, 2009; Eastham et al., 2008; TKK and SEA START RC, Some researchers suggest that the regional rice cultivation will potentially experience a significant reduction in its production (Mainuddin et al., 2011, Rerkasem, 2011). Others outline the possibility of sea-level rise, which could cover 19-38% of the Vietnam`s Mekong Delta landmasses. This would strongly affect the socio-economic development of Vietnam, as this particular region currently produces 25% of the country`s GDP (Tuan 2011). 47

57 5.3 Current and potential CC hotspots Considering the significant uncertainties related to emission scenarios, GCMs and hydrological modeling exercises we can conclude that no reliable statement can be made regarding future hydrological processes in the basin as a result of climate change. Nonetheless, in the following sections, the expected changes in the riparian countries will be listed Yunnan, China, Lancang Basin. Hoahn et al. (2010) predict a rise in mean annual temperatures of 1.4 C for Yunnan province during the period for IPCC emission scenario A2. This represents the highest value in the whole Mekong Basin. Eastham et al. (2008) for 2030 also simulate highest temperature increases in the Northern part of the basin, with the strongest increase (>1.0 C) in Yunnan. Furthermore they project an increase in wet season as well as in dry season precipitation by up to 130 mm. Due to glacier melting and increased snowmelt they predict an increased annual runoff as well as an increased runoff during dry season resulting in a higher potential for flooding. According to Snidvongs et al. 2003, however, Yunnan is expected to face decreasing overall water availability and an increasing drought likelihood as rainfall during the rainy season could be reduced by about 20% (Snidvongs et al. 2003). Chinvanno (2003) predicts that Yunnan province will be the only part of the Mekong Basin where the annual rainfall will be significantly reduced; from 109 billion m³ (bcm) per year to 87 bcm per year, or about 20% reduction. He expects remaining season patterns on the one hand but less rainfall throughout the year on the other hand. Rainfall rates during the dry season months (September- April) might remain the same but over the wet season (May-August) rainfall will be significantly lower Myanmar Similarly as for the Chinese portion of the Mekong basin, Eastham et al. (2008) predict increasing temperatures and annual precipitation for Myanmar. Dry season precipitation and a rise of annual flows into Lower Mekong Basin are likely to increase by 30% (Eastham et al., 2008) Lao PDR Snidvongs et al. (2003) simulate an increase in precipitation during the early wet season, especially June and July for Central and Southern Lao PDR. The Southern provinces Attapeu, Champassak and Sekong and the Central province Borikhamxay show particular signals for higher precipitations in June and July. Also the late season rain peaks are expected to be longer, especially in September (Snidvongs et al., 2003). Eastham et al. (2008) state that dry season rainfall is projected to decrease by around 0.13 m in catchments in central Laos as Nakhon Phanom, Mukdahan, Ban Keng Done. Annual precipitation is expected to rise as well as temperature which might lead to higher agricultural productivity. Due to an expected higher annual runoff during the rainy season, flood probability might increase. For Northern Laos as Moung Nouy and Luang Prabang as well as for Tha Ngon in Central Laos annual precipitation is expected to increase with higher dry season precipitation rates. Hence dry season and annual runoff would rise with 30% higher inflows into the Lower Mekong Basin. This might lead to floods and losses in agricultural productivity as well as to increased food scarcity. On the other hand increasing rainfall might increase agricultural activities and food production in areas like Vientiane. 48

58 In Southern Laos as Pakse as well as Sesan, however, projections show a decrease of precipitation rates by around 130 mm during dry season. Annual precipitation is expected to rise as well as temperature which might lead to higher agricultural productivity. Due to an expected higher annual runoff during the rainy season, flood probability might increase. For Southern Laos they calculate an increased flood probability from 5% to 76% with higher peak flows, flood duration and larger flooded area (Eastham et al., 2008) Thailand Eastham et al. (2008) predict that in 2030 the catchments of northeast Thailand Nakhon Phanom, Mukdahan, Yasothon and Ubon Ratchathani will continue to face high levels of waterstress during the dry seasons, despite higher annual precipitations. Driving forces are rising temperatures and decreased dry season precipitation as well as higher water withdrawals than availability. The Khorat Plateau area may also experience significant shift in season. Rainfall during the early months of the wet season will increase especially in July. The dry spell between the early season rain peak and late season rain peak will be reduced from 3 months (July-September) to 2 months (July-August). The areas which will be particularly wetter in June and July will be the southern provinces (Attapue, Champassak and Sekong) and central provinces (Borikhamxay) of Lao PDR. The late season rain peak will be longer and wetter, especially in September when the monthly rainfall will be increased from 15 bcm per month to 26 bcm per month. The overall rainfall in the area of the Khorat Plateau will be increased from 124 bcm per year to 137 bcm per year, i.e. a 10 % increase Cambodia For Kratie in Central Cambodia, Eastham et al. (2008) calculate an increased flood probability from 5% to 76% with higher peak flows, longer flood duration and larger flooded area. Arias et al. (2012) also project an increased flood probability affecting an additional area of up to 1,000 km 2. For the dry season, their climate simulations predict that in 2030 the Tonle Sap will face high levels of water-stress during dry season as dry season rainfall is projected to decrease by around 130 mm. Chinvanno (2003) came to the conclusion that the provinces Pusat, Kampong Chhang, Banteay Meanchey and Kandal are expected to be more adversely impacted by droughts than in the past. Snidvongs et al. (2003) also projected a longer and dryer dry season by about two months as well as a shorter and wetter rainy season with an 80% increased rainfall in September. The total precipitation per year would remain the same Vietnam Annual discharge and flood hazards in the Mekong Delta are expected to significantly increase according to several authors (Dinh et al., 2011; Hoanh et al., 2010; Huong & Pathirana, 2013; ICEM, 2010). Simulations by Dinh at al. (2010), predict that almost 75% of the area would be subject to medium to very high risk of flood hazard by This is caused mainly by sea level rise and a projected increased average annual discharge of the Mekong of 4%, also affecting large urban centers as Can Tho City (Dingh et al., 2010; Huong & Pathirana, 2013). ICEM (2010) predict an 15-21% increase in annual runoff by 2050 and 22% increase in flood duration in the delta region, based on a 13.5% increase in annual rainfall. Floods will start earlier, end later and peak flood would happen later on average years. (Hoanh et al., 2010; ICEM, 2010). 49

59 The Mekong Delta is expected to be extremely at risk due to climate change driven sea level rise (Eastham et al. 2008; Doyle et al. 2010; Vastila et al., 2010). Vastila et al. (2010) state that according to the POM and DIVA simulation, sea level rises at a rate of 7 8cm per decade which would affect the sea level being 31cm higher in 2045 than in According to the study of the US Geological Survey (Doyle et al., 2010), sea level will rise at rates of 4.3 mm/year under IPCC s emission scenario B1 (best case) to 5.5 mm/year under scenario A1FI (worst case) for the period They calculate that the land, currently at 0.5 meters above sea level, would expect to be flooded by 2035 and to be completely submersed by The locations of the most affected areas are pointed out in the official climate change scenarios and sea level rise report from the Ministry of Natural Resources and Environment in Three different scenarios were chosen including emission scheme B1, B2 and A1FI. Corresponding to each emissions scenario, inundation maps were created for the year In more detail, the locations of areas at risk of inundation are described in Figures The areas in red (and encircled by a dotted line) represent inundated area. Source: IMHEN 2009 Figure 10- Inundation map of the Mekong Delta in 2100 at 65cm of sea level rise under B1 emissions scheme 50

60 Source: IMHEN 2009 Figure 11- Inundation map of the Mekong Delta in 2100 at 75 cm of sea level rise under B2 emissions scheme Source: IMHEN 2009 Figure 12- Inundation map of the Mekong Delta in 2100 at 100cm of sea level rise under A1FI emissions scheme Within the same report, it is estimated that 12.8%, 19% and 37.8% of the Mekong Delta area in the year 2100 will be inundated according to emissions scenario B1, B2 and A1FI respectively. 51

61 In an update of the official climate change and sea level rise report in Vietnam in 2012, other impacts as a result of climate change are included. In particular, the areas under risk of inundation due to different sea level rise scenarios, the percentage of inundated national and provincial route length and the percentage of population that could be adversely affected. The results in the report are listed in the following table: Table 18- Percentage of area at risk of inundation according to the different sea level rise scenarios Sea level rise (m) Area (%) National Route (%) Provincial route (%) Population (%) Conclusion and recommendations As the above described chapter shows, a clear prediction of future climate change impacts for the Mekong region is a difficult task. Data from global climate models such as GCMs or AOGCMs do not have the appropriate spatial resolution for detailed information on regional or local scale. Methods like statistical or dynamical downscaling are dealing with this problem but still have to be handled carefully as their results are performed with high levels of uncertainty. Therefore it is not surprising that the results from several scientific studies on future climate change scenarios for the Mekong Basin, which are based on downscaling techniques, vary significantly. Despite the uncertainty concerning precipitation events all cited studies clearly project increasing temperatures for the entire Mekong catchment, in warm as well as in cold seasons. Like described above this could lead to increasing evaporation rates as well as to increasing irrigation demand in especially dry areas, putting a secure and constant water supply at risk. Rainfall rates could only be projected with high uncertainties and no clear statement can be made yet according to changes in future rainfall rates. Due to this high uncertainty about future precipitation dynamics, the prediction of future river discharge and possible high or low flow events according to climate change is likewise challenging. Again no reliable statement can be made regarding future runoff projections for the Mekong River. However in general an increase in river discharge seems to be likely, especially in the upper basin part. Coming along with increasing runoff flows, flood events are predicted to increase significantly. Hence, changes in the hydrodynamics are of crucial importance and therefore need to be studied carefully. Concluding, it can be stated that further studies on climate change impacts for the Mekong Region are necessary to be able to make detailed statements on future climate conditions on the Mekong River Basin and the risks they cause for the environment and the socio-economy of the basin member states. 52

62 Figure 13 localizes areas with a high likelihood of climate change to occur. It should be emphasized once more that all climate change scenario results are associated with high to very high levels of uncertainty. Figure 13: Possible climate change hotspots as identified in the reviewed literature 53

63 6 Key Drivers and Pressures 2: Socio-economic developments 6.1 Introduction and overview of literature After it has been outlined that the impacts of hydro-meteorological extremes in the Mekong River Basin repeatedly caused substantial socio-economic damages in this region and constitute a complex problem for health and security, it is now necessary to shed more light on the background to these events. Are the frequency and severity of extreme weather events a reflection of climate-induced increases in the variability of rainfall and temperature? Or are they simply caused by population growth, which led to the situation that more inhabitants of the Mekong region are increasingly vulnerable and affected by floods and droughts? How much do socio-economic patterns and human-induced activities affect the risk probability of hydro-meteorological extremes in this particular region? In order to consider this, this chapter is focused on economic and societal changes and their interaction with poverty and urbanization processes. The following literature review summarizes the State of the Art on the following: 1. Discussion about factors influencing the impact of hydro-meteorological extremes: Adamson 2006; Chinvanno 2003; Snidvongs et al Population dynamics and increasing exposure to hydro-meteorological events: Eastham et al. 2008; Grumbine et al. 2012; Hook et al.2003; Keskinen 2009; Menniken 2008; MRC 2003; MRC 2010a; Pech and Sunada, 2008; 3. Risk for socio-economic factors such as water supply, human settlements and agriculture: Chinvanno 2003; Eastham et al. 2008; Hoanh et al. 2003; ICEM 2010; IPCC 2007; Johnston et al. 2010; MRC 2010a; Snidvongs et al.2003; Wassmann et al Current situation and tendencies One of the numerous changes taking place in the MRB is a dynamic population growth. Even if estimates are varying within the scientific discussion, the approximately 70 million people that currently inhabit the MRB will grow up to million by 2025 (MRC 2003; Menniken 2008; Pech and Sunada 2008; Eastham et al. 2008). This trend is due primarily to high fertility rates, though there are distinct differences between countries as well as between urban and rural areas. In Thailand and Vietnam previously high fertility rates dropped below or near the replacement level of 2.1 births per woman (Hook et al. 2003). In contrast, Lao PDR and Cambodia still maintain high average annual population growth rates of 2.2% and 1.5% respectively, even though they too are slowly declining (ADB 2012; ICEM 2010). The average annual population growth rates in the other countries are: Vietnam 1.1%, Myanmar 1.0%, China, (Yunnan Province) 0.7% and Thailand 0.6% (ADB 2012). Figure 14 shows the current (2011) distribution of population density with population hotspots Vientiane, Phnom Penh and the Mekong Delta region. 54

64 Figure 14: Population density in provinces within the LMB As a result, all countries but Thailand have a very young and predominantly rural population. In Cambodia the percentage of rural population is highest with 80.5%, but even in Thailand, which ranks lowest, still two thirds of the population are classified as rural. The rural population comprises 69.8% in Vietnam, 69.2% in Myanmar, 67% in Lao PDR, 65.2% in Yunnan Province PCR (ADB 2012).These huge parts of the population are faced with severe limitations as the rural areas offer few job opportunities and health and education services are weak or nonexistent. The constraints link rural livelihoods with poverty: In several rural provinces more than 40% of the population lives below the poverty line, in extreme cases like in rural Lao PDR poverty levels can exceed 60% (Kristensen 2004, Hook et al. 2003; JICA 2010). Defined by limited access to assets, poverty often manifests in people practicing traditional, low-efficiency 55

65 agriculture, as their limited means do not allow for more and risks like market price changes can thus be avoided (UNISDR 2009). Also strongly interrelated with poverty is the depletion of natural resources, malnutrition and weakened resilience against illnesses (MRC 2010g). Floods and droughts are also thought to have led to an increase in water-related disease outbreaks such as, malaria, diarrhoea, dysentery, dengue fever and pneumonia. A striking example for this is Cambodia, which registers the highest rates of fatalities from malaria in Asia (GFDRR 2011). Even though there have been great successes in poverty reduction, many people are still on the brink to poverty and therefore vulnerable to hazards, as they only have a very low resilience (MRC 2010g; Voelker et al. 2011). The disasters mainly strike unprivileged populations, who reside in high-risk areas, such as along the banks of rivers or in non- protected coastal zones. As an example, water treatment facilities are often destroyed by floods, which bring drinking water contamination by bacteria, viruses, parasites and toxic substances. Both population growth and rural lack of prospects contribute to the rural-urban migration that is occurring in the countries of the MRB: As people seek employment and better opportunities to make a living, urbanization has taken on remarkable speed. In 2010, over 30% of the population in Thailand, Vietnam, Lao PDR and Myanmar lived in urban areas; by 2050 each of these countries expects that over 50% of their population lives in urban areas (UN-DESA 2012). Cambodia, which has only 19.5% of urban population nowadays, also exhibits a positive annual growth rate and is estimated to have an urban population of 37.6% by 2050 (ADB 2012; UN- DESA 2012). These population dynamics will consequently affect the environmental and hydrological conditions of this region and therefore will play an important role when it comes to the severity and socio-economic impacts of floods and droughts (MRC 2003; MRC 2010a). The demographic trends therefore are important factors to be considered as they are highly influencing the vulnerability levels that relate to hydro-meteorological extremes in the MRB. Another process, which was only made possible by the decades of peace after the regional conflicts of the 1960s and 1970s, was international integration and economic progress. As Thailand looks back on a longer history of economic growth it leads this development with a nearly steady growth of GDP over the last decades to its momentary $345.7 billion in With exception of China, this is more than the GDP of the other countries in the MRB combined (GDP in Vietnam: $123.6 billion, Myanmar $51.4 billion, Cambodia $12.8 billion, Lao PDR $8.3 billion) (World Bank 2013). Regarding only the four downstream riparian states, the economy of Thailand accounted thus for 70% of the GDP in 2011, followed by Vietnam with 25%, Cambodia with 2.6% and Lao PDR with 1.7%. Yet these ratios are not set in stone: Small economies like Lao PDR can experience fast changes by large-scale investments, e.g. in natural resources. Such foreign direct investments (FDI) are in planning for hydropower development as well as mining (ICEM 2010; Gunawardana 2008). Developments as these are visible in high growth rates of GDP, which were in % in Lao PDR, 7.1% in Cambodia, 5.9% in Vietnam, 5.5% in Myanmar and 0.1% in Thailand (World Bank 2013). The region as a whole is expected to grow 240% from 2005 levels to 2030 (ICEM ). These positive trends were only made possible by market liberalization. International economic integration, trade and investments paved the way for a growing importance of industry and services, which are mainly situated in urban areas. Already over 60% of GDP are generated by the sectors of industry and services in each country, Thailand leading once more with 88.4% of GDP (ADB 2012). Yet despite the increase of industry and services, the importance of 56

66 agriculture has not diminished in the LMB, as an estimated 75% of the population still earn their livelihood from it (Rowcroft 2005). Again, this is not evenly distributed over the countries: Employment in agriculture is highest in Lao PDR, where 75.1% (2010) of total employment concentrate on it. In Cambodia, employment in agriculture accounts for 57.6% (2009), in Vietnam for 48% (2011), in Thailand for 40.7% (2011) of total employment (CIA 2013). Yet, change is also occurring in agriculture itself: Partly induced by the LMB governments in order to increase incomes and create employment, farmers shift from traditional agricultural practices to cash crop agriculture and from subsistence and to more diversified economies (Nesbitt et al. 2003; Rowcroft 2005). This industrialization of agriculture does sometimes spark social unrest as it reduces land availability in poor rural areas. In countries like Cambodia, where up to 40% of farmers lack legal documents for the land they cultivate, land insecurity is rather high, which makes them vulnerable to displacement by land concessions and forced evictions (Devichand 2011; WFP 2008). This competition for resources also takes place on the international level in the MRB, as all riparian countries draft their own projects to develop the Mekong and its tributaries, be it for food security by irrigation, energy production for their evolving industries or the export of electricity to neighbouring countries to generate national income as in Lao (Lire 2010, Varis et al. 2008). The MRC as institutionalized form of cooperation, which was established in 1995 by the four downstream riparian countries, is thus an important actor in the MRB, as national water resource management policies gain an international governance angle (MRC 2011b, Schulze and Schmeier 2012). 6.3 Current and potential hotspots Socio-economic change in South East Asia does modify spatial patterns of hazard risk, with the highest dynamics both in remote rural areas and the fast growing cities of the region. As the populations of the MRB countries still continue to grow, rural livelihoods are put under great strain. In rural, often remote areas people mainly depend on agriculture and natural resources, which support only a limited output. Typical characteristics for remote rural areas like missing infrastructure, little economic diversion and imperfect markets further limit the economic opportunities of the population. Faced with constrained access to productive assets like arable land, fertilizer or irrigation, the rural population mostly keeps to traditional, low efficiency agriculture and is thus highly dependent on the main harvest. These processes lead to widespread poverty, which is exacerbated by the population pressure and leaves rural households with only a very low resilience. In combination with the absence of safe housing and supporting public services these constraints of development consign people living in rural and remote areas to high exposure as well as high vulnerability to hazard impacts (ESCAP 2012; UNISDR 2009). Urban areas face a different set of difficulties, even though these can be ascribed to the initial dynamic of population growth as well, resulting in massive rural-urban migration and thus urbanization. As housing is not affordable for most, those migrants start to settle on marginal land in or around the cities. These informal settlements often consist of structurally weak housing and lack sufficient living area and access to improved water or sanitation facilities (World Bank 2011). Even though the existing infrastructure is put under extreme stress, investments in infrastructure like a waste management system or drainage systems fall short of the rapidly expanding needs. While those developments expose ever larger parts of the population to already existing risks and thereby increase the vulnerability particularly of poor urban dwellers, they sometimes also magnify the hazards themselves: Because of an increase 57

67 in built area and missing drainage possibilities, heavy rainfall events lead to increased run-off, and flood impacts get exacerbated by the location of informal settlements on previous floodplains (Gerrard 2004; UNISDR 2009). Flooding is associated with an increased risk of infection, especially if the drinking-water facilities get contaminated China In its upper reaches, the Mekong crosses the Chinese province Yunnan from North to South. This mostly mountainous area is just sparsely populated, though this region is experiencing demographic growth as well (Huijun et al. 2002). Yunnan is among the PRC s least developed provinces, 73 of its 129 counties are categorized as poor (ADB 2012; Yunlai and Fengying 2009). Many of these are situated in the Mekong River catchment near the western border: In the county Lancang (Pu'er prefecture) poverty levels are estimated to exceed 30%, other counties with high poverty incidences are situated in the neighboring prefectures Xishuangbanna and Lincang (Ahmad and Goh 2007). These counties feature low accessibility and are dominated by small-scale agriculture, owing to the high poverty rates large parts of the population are considered food insecure (Gupta et al. 2012; Yunlai and Fengying 2009) Myanmar There are large difficulties connected with obtaining data for Myanmar, particularly for remote border regions as the eastern part of Shan State which belongs to the MRB (FAO 2007). As vulnerability research concerning Myanmar mainly focuses on the coastal parts and the Dry Zone, it is difficult to ascertain particular problems of the mountainous region. However, Myanmar as a whole is confronted with the same trends of population and economic development as the other riparian states. Hence, it can be assumed that the poverty levels of the rural population are rather high, which enhances their vulnerability to changes in the ecosystem Lao PDR Despite its impressive growth rates, Lao PDR is still a relatively poor country, ranking last in comparisons of the regions GDP. The poverty rates are highest in the remote rural areas in the North and South region of Lao PDR: In the North, more than 50% of households in every province with exception of Xayaburi were categorized as poor. In all the South provinces, with exception of Champassak, more than 60% of households were poor (2004) (JICA 2010). Both regions are characterized by their large portions of young populations and high dependency ratios, leaving households very vulnerable to hazards as many persons depend on a single income (MRC 2010g; GFDRR 2011). While the northern region is for the most parts mountainous and hence rather remote and inaccessible, the southern region is mainly remote because of limited transport infrastructure and the large distance to the urban centers further north. In both North and South of Lao PDR, people depend on traditional agricultural systems for their livelihoods and are very vulnerable to changes in the ecosystem (Hook et al. 2003). In the North of Lao PDR, the province Bokeo (bordering Myanmar and Thailand) can be identified as a hotspot due to socio-economic reasons. Three of its five districts are categorized as poor (2004) (JICA 2010) and over 32% of households are categorized as food insecure (WFP 2007). Additionally, more than 50% of the population is not within a 10 km radius of a Health Center (2007/08), which is exacerbated by the lack of transport infrastructure (JICA 2010). The province Xiangkhouang (at the border to Vietnam) is another hotspot, as five of eight districts classify as poor (2004) and food insecurity burdens over 20% of the population (JICA 2010; WFP 2007). 58

68 In the South, there is a clear pattern of poverty affecting the eastern, upland districts. Especially the provinces Saravane and Sekong count as hotspots: There, over 22% of households are considered food insecure, and over 40% of the population of Saravane are at risk of becoming food insecure because of droughts (WFP 2007). A Health Center within a distance of 10km is only available to less than 50% of the population of Sekong, and for less than 60% of the people of Saravane (2007/08) (JICA 2010). This inadequately developed health system combined with the lack of transport infrastructure maximizes the hazard risk posed by floods, as illnesses related to stagnant water can be expected to increase (GFDRR 2011; Government of Lao PDR 2009). Vientiane, which is situated on an alluvial plain of the Mekong, is with 740,000 inhabitants by far the largest city of Lao PDR (2010) (MRC 2010g). As the capital, Vientiane is in the epicenter of the countries fast changing dynamics. Its population has been growing rapidly at nearly 5% annually, which can mainly be attributed to migration influx from rural areas (ADB Atlas 2012). This gives cause for concern as infrastructure cannot be adapted this fast. The facilities for sewage treatment are e.g. only rudimentary as of yet, to which the cities underground, characterized by a high water table and low soil permeability, only adds complication (Gerrard 2004, ADB Atlas 2012). With economic development and rising income levels there is also an increase in consumption, leading on the downside to an increased production of solid waste, which is simply disposed of at a waste dumb on the outskirts of town (ADB Atlas 2012) Thailand The Northeastern region, which coincides with the part of Thailand belonging to the MRB, consists mainly of the Korat plateau, a flat region which by poor soils and a dry climate supports only limited agricultural productivity. Other factors that limit/restrict agriculture are small farm sizes, the lack of fertilizers as well as low market power of farmers, which is why traditional forms of agriculture prevail (Hook et al. 2003, NESDB 2005). The Northeast registers as the poorest region of Thailand. It comprises over half of the country s poor. However, it did experience the same rapid drop of poverty over the last decades, as poverty was reduced from 48% (1988) to 17% (2002) (NESDB 2005). This positive development is mainly driven by the cities of the region, but as over four in five families live in rural areas, this change did not reach all inhabitants. Thus, the provinces Sakon Nakhon and Phetchabun list a poverty rate of over 30% and the provinces Nakhon Phanom, Kalasin and Buriram even exceed 40% (World Bank 2012). This is in stark contrast to the average poverty headcount of 1.87% in Thailand Cambodia In Cambodia, vulnerability to hazards takes on various forms. One region that should be taken into account is the area of the Tonle Sap Lake. This is a densely populated region, and most people rely directly on the lake and its natural resources and are well adapted to its regular water level variations (Nuorteva et al. 2010). However, their adaptive capacity to unexpected change like higher floods and droughts is weak (Keskinen et al. 2010). This can be attributed to the high percentage of poverty prevailing in the region. In relation to this, the province Kampong Chhnang stands out with 37% of poor households, but rates of about 30% are the norm in the Tonle Sap floodplain (WFP 2012). Therefore it is not surprising that 17% of households in this area are food insecure (WFP 2008). In addition to this, inequality increases with environmental change, as fishing villages closest to the lake and the poorer population on the floodplain exhibit the lowest levels of resilience (Nuorteva et al. 2010). Another hotspot can be seen in Phnom Penh, a city caught in a rapid urbanization process. With the population growth pressures on municipal services and infrastructure increase and so 59

69 does environmental deterioration: As in Vientiane, the treatment of solid waste and water drainage pose serious problems. In 2011 only 67% of the urban population of Cambodia had access to save water and as domestic and industrial sewage are discharged into rivers without treatment, this problem will prevail (UNSTATS 2013, ADB Atlas 2012) Vietnam Vietnam has made remarkable progress in poverty reduction over the last decades to reach a rate of 20.7% in However, this has led to an increasing spatial concentration of poverty in remote, rural areas that are inhabited by large proportions of ethnic minorities: While poverty is most extreme in the Northern Mountains, the Central Highlands also record a poverty rate above average with 32.8%, especially the Kon Tum Province with a poverty rate of 47.58% (World Bank 2012a). The completely different environment is located at the Mekong River delta that takes up the whole southern Vietnam headland. As in Cambodia, the rhythm of the river dictates everyday life of the population. However, cities in the delta like Cao Lanh and Long Xuyen have serious flooding problems. Even though adapted to floods, their marginal elevation over sea-level in combination with higher water levels and tidal changes lead to the entry of water into the houses (Few and Tran 2007). Can Tho, a city with a population of 1.2 million, is situated even further downstream and has an average height of just 1 to 1.5 meters over sea level. As this city is growing fast due to migration, the flooding that already takes up larger parts of the city will affect more people in the future, while at the same time the inundation depth is predicted to increase (Huong and Pathirana, 2011). 6.4 Conclusion and recommendation Just as climate variability and change constantly alter the spatial distribution of hazard risk in South East Asia, so do socio-economic processes. Undiminished demographic dynamics and poverty greatly influence the exposure and vulnerability of different population groups to environmental and climatic hazards. Urban areas of the MRB are faced with manifold growth: On the one hand the rapidly increasing GDP of the countries is in large parts generated in cities and linked to new employment opportunities and rising incomes (ADB 2012). However, the benefits of economic growth are not distributed equally, the revenues for the poor limited. At the same time, cities like Phnom Penh and Vientiane have annual population growth rates as high as 5% (2001), which have the effect that over 60% of the urban population live in informal settlements (2005) (UN Habitat 2013). As the geographic location of these hubs of growth are the floodplains of the Mekong, the concentration of economic wealth and population increases the potential impact of annual flood events as well as flash floods following extreme events and other hazards. Especially the inhabitants of informal settlement areas suffer a high risk to their lives and homes by disasters, as they lack the means necessary for precautions (ADB 2012; World Bank 2011). Thus, the ongoing rapid urbanization is a strong risk driver as growing numbers of people are exposed to risk. This vulnerability should be addressed by urban governance, which can influence future level of risk strongly, e.g. by infrastructure planning (ESCAP 2012; UNISDR 2009). The fast pace of developments in the cities of the MRB result in increasing inequality between their population and those living in rural areas: These are largely not included in the process of economic growth, a fact made clearly visible in the high poverty rates. The reduction of poverty rates on national scale did not reach every district, instead poverty is nowadays concentrated on remote rural areas: The poor are predominately dependent on agriculture, and regions with a 60

70 high percentage of ethnic minorities are particularly affected (JICA 2010; World Bank 2012a). Furthermore, while people in rural areas often do not gain from the advancing development of their countries, it still interferes with their livelihoods, be it by the expansion of agribusiness and mining or by governmental policies like the creation of forest reserves or bans of agricultural practices, e.g. shifting cultivation in Lao PDR (WFP 2007). In combination with land degradation, the precarious situation of the poor in remote rural areas becomes apparent. Their high vulnerability is founded in limited access to productive assets and a high dependency on their yearly harvest. Hence poverty is a main risk driver in Southeast Asia, as the impact of natural disasters hits the poor parts of the population the hardest and they lack the adaptive capacity to absorb economic shocks brought on by floods and droughts or even minor changes in the regional climate that affect harvests (World Bank 2012a; UNISDR 2009). Figure 15 Regional distribution of socio-economic vulnerability 61

71 7 Key Drivers and Pressures 3: Land use change 7.1 Introduction and overview of literature Land use is, according to Ty et al. (2012), permanently changing, as it is influenced by different factors. Population dynamics, economic reforms and anthropogenic activities belong to these factors which led to significant land use changes in the Mekong basin. Major alterations, which were taking place in the last decades, are the reduction of forest cover and the replacement by agricultural land, extension and intensification of irrigation areas and the construction of large dams for hydropower development and irrigation purposes (Costa-Cabral et al., 2008; Adamson, 2006). To explore the possible impacts of land use changes on hydro-meteorological extremes, a sound understanding of land use and its changes is needed. Thus, all recent documents dealing with this topic will be summarized to understand the situation in the study area. The following literature review summarizes the state of the art on the following topics: 1. Studies dealing with local and regional land use changes: Müller 2004 (Viet Nam); MRC s Planning Atlas 2011b; Stibig, 1999 (South-east Asia); Thongmanivong and Fujita, 2006 (Lao PDR) 2. Modeling of land use changes and their impacts on Mekong s hydrology: Adamson 2006; Adamson et al. 2009; Chapell and Tynch 2012; Costa-Cabral et al. 2008; Hoanh et al.2012; Ishidaira et al. 2008; Mango 2011; Price 2011; Ty et al. 2012; Wohl Current and potential hotspots for land use changes: Adamson 2006; Kawasaki 2010; Lefroy et al. 2011; Storch and Downs 2011; Ty et al Current Situation and tendencies of land use changes in the MRB The major land uses according to MRC s land use data base (accessed in August 2013) are shown in Figure 16. Among the agricultural uses in all Mekong riparian countries paddy rice is the number one crop. Regarding plantations rubber is the leading crop (except in the Vietnamese Central Highland where coffee is the most significant crop). How these land use types underwent changes in the past decades or how the current dynamics may form future land use is not comprehensively studied for the Mekong river basin. Even regional or local studies on land use dynamics are quite rare. A detailed study of available publications on this topic shows that there is very little primary data available from investigations on land use change detection and on expected future land use trends. 62

72 Source: MRC data base Figure 16: Major Land uses in the lower Mekong River Basin 63

73 Several studies exist on the modeling of future CC and land use change impacts on Mekong s hydrology (Adamson 2006 etc,; Chapell and Tynch 2012; Costa-Cabral et al. 2008; Hoanh et al. 2012; Ishidaira et al. 2008; Ty et al. 2012). But even these studies give little information on how the primary data for the modeling process was obtained. Studies which explicitly deal with land use changes could only be found regarding summary data at national or supra-national level (Müller in 2004 for Viet Nam, Thongmanivong and Fujita in 2006 for Lao PDR and Stibig in 2004 for South-east Asia). Clear predictions on future trends of land use changes on the scale of the Mekong River Basin could not be found. Regarding deforestation rates this impression is shared by Costa-Cabral et al. (2008): With the exception of data obtained from Stibig (1999), no reliable estimates of deforestation rates are available for the basin. However, looking at the economic development in this region, the probability that the construction of dams and the extension of agricultural areas, especially irrigation areas will be extended is high, like the MRC Strategic Plan (2011d) and studies on hydropower development (see next chapter) confirm. Thus, the impact for future water resources should be of high concern and deserves further studies. Development trends in the hydropower field as well as in the agricultural sector threaten to alter hydrological processes such as water storage, water extraction, water availability etc. To analyze the possible impacts of these land and water use changes many studies have been undertaken (see references cited above). Following conceptual models regarding the impact of deforestation on hydrology, it could be assumed (but no evidence is found so far for the Mekong basin) that areas with high deforestation rates would lead to lower dry season flows and higher flood season flows. Many reports from other regions indicate a reduction of water storage, increased runoff in the wet season, decreased runoff in dry season (less base flow) after deforestation (see e.g. Mango 2011). In addition, most studies agree that large scale deforestation leads to higher mean annual runoff due to reduced evapo-transpiration. Even though large deforestation occurred in parts of the Mekong basin, Adamson et al (2009) and Adamson (2006) found no significant trend in the discharge of key stations in the lower Mekong basin (based on data from ). Also Ty et al. (2012) and Ishidaira et al. (2008) conclude that land and vegetation cover changes may only produce a minor increase in runoff in the near future. Nevertheless, they conclude for the Srepok basin that expected land use changes in this area produce a stronger increase in water demand and in sum will have a higher impact on future water stress than climate change. In general, scientific literature is not very specific regarding the impacts of land deforestation on hydrology in the Mekong. Price (2011) points out that some studies show increased base flow (due to reduced evapotranspiration) and others show decreased base flow (less infiltration without forest) after deforestation. Wohl et al. (2012), in a recent review article about hydrology of the humid tropics, emphasizes the huge deficits regarding scientific understanding of relations between hydrologic impacts of land use changes. 7.3 Current and potential hotspots Resulting from increased population and commercial pressures, large forest areas have been lost due to resettlement policies; migration and forestland development for agricultural purposes (see Table 19). Nevertheless, not all Mekong countries behaved the same in this regards which is visible in the increasing cover of Vietnamese forest since According to McElwee (2009) this was due to the Vietnamese reforestation program. They furthermore point out, that the increasing population led to a fragmented landscape due to the continuation of shifting cultivation. Apart from this, Adamson et al. (2009) state that both the logging ban of Thailand, in 64

74 1990, and the fast growth in China caused higher logging rates in Lao and Cambodia, which can also be seen in the forest cover changes (Table 19). Table 19: Percentage of Forest Cover of the Mekong countries Country Period 1960s-1970s circa 1980 circa 1990 circa 2000 Cambodia > 70% > 70% 67% 53% Lao PDR 60% - 47% 41% Thailand 53% 34% 28% 29% Viet Nam 42% - 28% 30% Myanmar 58% % China (Yunnan) Source: Stibig % % Though, there is a lack of reliable deforestation estimates, some land use changes, mainly on the sub-basin/district level, can be described (see next sub-chapters) China Most research data of land use for the Chinese part of the Mekong basin is available for the most southern prefecture, Xishuangbanna in the province of Yunnan. Historically the region with an elevation between 475m and 2430m would have been completely covered with forest. As Li et al report, the total forest cover amounted to 70% in 1976 and was further reduced to 50% until Most of this area was transformed to shrubland for shifting cultivation and rubber plantations, to cover the Chinese industry s growing demand for rubber. Mostly affected by the deforestation is the seasonal rain forest, whose environmental requirements suits best for growing rubber trees. The two possible future scenarios presented either assume a decrease of total forest cover to 24% in case of rubber expansion or, in contrary an increase to 72% forest cover in case of the forest recovery scenario. According to Qiu (2009), the total area of the highly profitable rubber plantations already amount to hectares and hence cover 20% of Xishuangbanna prefecture. Consequences of intensive rubber monocultures are local farmers dependence on rubber price and the risk of pest introduction (Langenberger et al. 2008). Qiu (2009) also assesses changes in microclimate respectively increasing temperatures since 1960 and less occurrence of fog caused by the rubber plantations which work as water pumps and hence reduce soil moisture. Rainforests converted to rubber plantations reveal a 3- fold higher surface water runoff which leads to a multiplication of soil erosion with the factor of 45. Finally there are already effects on some villages water supply due to streams that ran dry (Mann 2009). Moving upwards the Mekong and gaining elevation, rubber loses importance due to low profitability on elevations higher 1000m (Li et al. 2007). Even further North, agriculture gets less intensive. The study of Zhang et al. (2012) dealt with the land cover change of two regions on the Mekong watershed, one of them in the Hegduan mountain range in Northern Yunnan. The surveyed area has an elevation between 1500m and 4500m. Since 1970 many conifer areas have been logged and are now covered with deciduous species. In the study period between 65

75 1990 and 2003, they assessed a decrease in forest cover and an increase in low density forest and shrubland due to logging, in particular right before the logging ban was established for this region in Moreover on lower altitudes more area is used for agriculture and cash crop production as tea and medicinal plants, which was promoted by dam and road construction. Fox et al. (2009) simulated the land cover change for the entire Montane Mainland Southeast Asia from 2001 to 2025 and 2050 and discussed Yunnan province as an own region. They predict a decline in mixed forests, forest/field mosaic, tall grass and growth in Urban/built-up, evergreen shrubs, deciduous broadleaf trees and evergreen broadleaf trees area. Jiang et al. (2011) describe in their study the land use changes which have occurred in the Xishuangbanna region in the Yunnan province, China, from 1986 to Their research states that the land use forestland had the biggest change with a decrease of 57.62% in 1986 to 42.86% in Areas which have increased during the research period are shrub land, increased from 12.40% in 1986 to 23.87% in 2008, and plantations which increased from 4.77% in 1986 to 15.10% in Other than the land use types mentioned above, the land use type crop land did not show a certain trend, it was rather constant (see Figure 17 and Table 20) (Jiang et al. 2011). Source: Jiang et al Figure 17: Areal changes in land use types in Xishuangbanna region from Table 20: Changes in land use types in Xishuangbanna region from Source: Jiang et al

76 Similar changes in the Xishuangbanna region have been described by Hu et al. (2008) whose study is concerned with the impact of land use/cover changes on ecosystem services in the township Menglun. Three land use types showed the largest changes: forests (1986: ha; 2006: ha), swidden fields (1986: ha; 2006: ha) and rubber plantations (1986: ha; 2006: ha) (see Table 21 and Figure 18 (Hu et al., 2008). A shift from ecologically important tropical forest (by 21.16% of total land area) and swidden field (by 12.68% of total land area) and a concomitant increase in economic production due to rubber plantation (by 33.53% of total land area) has occurred (Hu et al., 2008). According to this research, rubber plantations tend to impact the water balance. This assumption is shared with Wahren et al. (2010) who state that rubber plantations affect the climate by affecting the water balance. They describe the reduction of cloudy days in Jinghong City, Xishuangbanna, in the time period 1950 to 1980 from 166 days to 91 days. A similar effect has been seen in Jinghong County, were the foggy days were also reduced (Li et al. 2007). Source: Hu et al Figure 18: Change in land use from in Menglun township, SW China 67

77 Table 21: Changes in land use/cover from in Menglun township, SW China Source: Hu et al Lao PDR Lefroy et al. (2010) describe the land use changes and its drivers going on in Lao PDR. Their research states that the whole country had a reduction in forest cover of 2.35% and one of its provinces, the Xayabouri province, had a vegetation decline of 14.59% (Table 22). Their results show furthermore those areas in Lao PDR which are decreasing in vegetation and the magnitude (see Figure 17). Highlighted in red are those areas which can be described as being stressed by, for instance, deforestation, logging, hydropower and infrastructure development and mining activities. Areas which are characterized by heavy vegetation decline are: Luang Prabang, Huaphanh and Xayabouri province. Still, also other areas, like Attapeu and Luang Namtha, show a vegetation decline. In Attapeu it is mainly due to the better accessibility from the roads, timber extraction and cropping activities. Whereas the reason for the vegetation decline, in Luang Namtha, was population growth, infrastructure development and increasing rubber plantations. In the upper western part of Luang Prabang (Nambak District) it is mainly due to the fact that cash crops expand. In Xayabouri province land use change is extremely strong, especially in the southern parts. Reasons for this are: upgrade of roads, road construction, timber extraction and expansion of maize cultivation (Kenethao and Paklai district). Nevertheless, there are also areas which show a vegetation increase, namely areas at an higher altitude and which are not easily accessible from roads. Those areas are highlighted in the next figure in a more greeinish colour. 68

78 Source: Lefoy et al Figure 19: Vegetation Cover Changes in Lao PDR Table 22: Change in NDVI for whole Lao PDR PDR and the Sayabouri Province Source: Lefoy et al In addition to the overall vegetation changes, Lefroy et al. (2010) also describe the changes in selected crops from 2000 to According to them, the changes (increase/decrease in crops) in Table 23 nearly totally explain the increase in the land use type arable land for the whole country. 69

79 Table 23: Changes in area harvested of selected crops (ha) in Lao PDR PDR ( ) Source: Lefroy et al Thailand According to Trisurat et al. (2010), Thailand s annual forest loss, in 1995, was ranked the highest from all countries belonging to the Greater Mekong region over the past 50 years. The reduction of forest cover by approximately 28%, during the time period , (Cropper et al. 1999) in combination with disastrous floods in southern Thailand, led to a logging ban in 1989 (Rowcroft 2005). On the Khorat Plateau, which includes the Mun and Chi tributary systems, forest cover was reduced from 42 per cent in 1961 to 13 per cent in 1993 (MRC 2005). The land use changes which have occurred after this logging ban are analyzed in the report written by Cassidy et al. (2010). This report focuses on the land use changes which have occurred in the Sisatek province in Thailand and the Ordar Mean Chey province in Cambodia in the years 1989, 1994, 2000 and According to the study, rice is dominating the landscape and is at some points traversed by the river course (see Figure 20). Comparing the different land use maps it becomes apparent that both the forest in the south close to the Cambodian border and the rice fields have undergone minor changes. Nevertheless, at a more local level, changes in land use have occurred which are highlighted by rectangles. Close to the Cambodian border land use/cover changes occurred at the forest foothills, three mountainous areas in the southeast and northeast. These areas have transitioned between woodland, upland crops, and increasingly, rubber plantations (Cassidy et al. 2010). 70

80 Source: Cassidy et al Figure 20: Land use/land cover for Sisaket, Thailand and Ordar Mean Chey, Cambodia Cassidy et al. (2010) state furthermore that land tends to be more diverse the closer it is to roads. Table 24 indicates this phenomenon. Nevertheless, road density hardly changed during the period under discussion. Apart from this, they point out that land use/cover change has been influenced by the uneven market distribution which has changed to a more evenly distributed one. The last factor they mention is elevation. The three mountainous areas at intermediate elevation are compared to the forest foothills at higher elevation and it is pinpointed that those at lower elevation are often easier to access and have better soils. Table 24: LULC diversity as response to road distance, at different scales and different time-steps at Sisatek province in Thailand (1989, 1994, 2000 and 2005) Source: Cassidy et al

81 The study of Walsh et al. (2001) assessed the land use/land cover variation in Nang Rong district, northeast Thailand and obtained basically similar results compared with Cassidy et al. (2010). According to this study, rice is the main land use class in the study area (70%). The second biggest class, accounting for 15% of the study area, is forest, followed by cash crops (13%) and finally other land uses (2%). Additionally, the study emphasizes the impact of roads and elevation. They state that land which is closer to roads or lower in elevation are often easier to access and, thus tend to have important impacts on land use practices, flooding potential, and soil suitabilities which in turn may influence NDVI (Normalize Differenced Vegetation Index) (Walsh et al. 2001) Cambodia Ty et al. (2012) assess in their report the land use change for the Srepok River basin, a transboundary sub-basin of the Mekong which lies between Vietnam and Cambodia. For them it is obvious that agricultural land will expand, as a higher population will mean a higher demand for agricultural commodities. Urban areas are predicted to expand, whereas forests are projected to decline. The land use prediction is similar to the predicted land use change of Kawasaki et al. (2010), but the values differ slightly as a consequence of the different methods used. Source: Ty et al.2012 Figure 21: a) Land Use in 1997; b) Predicted Land Use in 2050 for the Srepok River basin Senevirathene et al. (2011) investigated land use/land cover changes of the Tonle Sap watershed for the period of 1990 to 2009 using Landsat TM and ALOS AVNIR 2 data. The most prominent land use/land cover changes were growing agricultural areas, as well as deforestation due to the demand of land for agriculture and illegal logging. The deforestation led to increased erosion in the upper watershed, as a consequence sediments accumulated in the river mouth which caused downstream floods. If the deforestation will continue with the analyzed rate of 2.26% per year, the overall forest cover will be destroyed in 25 years. Table 25: Results of Land Use/Land Cover change detection analysis (edited by Author) (Senevirathene et al.2011) Land Use/Land Cover Class Area in 1990 (km 2 ) Area in 2009 (km 2 ) Changes Compared to the Initial State Agriculture % Forest % Shrubs % 72

82 Water Bodies % Wetland % Other Vegetation % Built Up Areas % Bare Soil % Vietnam Vietnam has and will experience profound changes in its land use. In the Srepok River basin, a sub-basin of the Mekong, which is shared by Vietnam and Cambodia, the majority of the areas that are vulnerable to changes are in the upstream part of Vietnam. According to this study, forestland is projected to decline, whereas urban and agricultural land is projected to expand (Ty et al. 2012). Thu and Populus' research (2007) focuses on the Tra Vinh province in the Mekong Delta. The past and current status of mangrove forests is assessed in this study. The authors claim that mangrove forests underwent considerable changes (Figure 22). Table 26 shows that the results underline the fact that mangrove forests were reduced in the study area from ha in 1965 to ha in 2001 and for the northeastern part, forest cover reduced from 7877 ha in 1965 to 3122 ha in The reduction of mangrove forestland (MF) is associated with the expansion of shrimp farms as shown in Figure 22 Table 26: Changes in mangrove forest in Tra Vinh (-: reduction; +: increase) Source: Thu and Populus

83 Source: Thu and Populus 2007 Figure 22: Relationship shrimp farm and mangrove forest in Tra Vinh Similar observations have been made at the southernmost part of the Mekong Delta, the Ca Mau Peninsula. Gowing et al. (2006) observed a rapid expansion of brackish-water shrimp farming in the study area indicated farmers' preference for this production over rice : Source: Gowing et al.2006 Figure 23: Land use change at the Ca Mau Peninsula, Vietnamese Mekong Delta 74

84 A study focusing on the future land use change projected to take place in Can Tho, Vietnam delta, has been carried out by Huong and Pathirana (2011). Their research focused on urbanization and climate change affecting the future flood risk of the city. Comparing the land use map for the year 2005 with the three projected maps (2035, 2050 and 2100) it becomes apparent that the land use will change. Grasslands and shrublands will be converted to urban land which will mean a grassland/shrublands decrease of 12% by 2035 and 17% by The urbanization will be first in a medium intensity by the end of the 21 st century and a high increase in intensity by Urban land will increase by 41% by 2025 and by 55% by Furthermore, urban areas will densify close to the city core and rivers (see Figure 24; Source: Huong and Pathirana, 2011). Source: Huong and Pathirana 2011 Figure 24: Projected land use in Can Tho, Vietnam delta According to the research results, such a land use change will lead to a higher flood risk, as the conditions have been altered and, thus, the vulnerability increased. Huong and Pathirana (2011) state that the effects of urbanization can be seen in the whole study area and they furthermore say that the developments described above would mean a 21% increase in inundation depth in the study area, as a result of the land-use change driven hydrological and hydro-meteorological effects. Very seriously impacted areas are, based on the study, the intersections Mau Than Streets and Nguyen Van Cu. 7.4 Conclusion and recommendations Changes in land use and land cover can be considered, as the last major non-climatic factor. By altering ecosystem system services and the hydrological cycle, land-use change and patterns are able to affect the water quality and quantity of the Mekong and its tributaries. This might be particularly the case in the North-eastern parts of Thailand and in the Vietnamese Mekong Delta region, where the areas that are suitable for agricultural production are almost used to its full 75

85 extent (Pech/Sunada 2008). In this connection, it has been outlined, that the drivers of land-use change can be generally related to the increasing demands for natural resources and agricultural outputs that emerged as a result of population growth, economic developments, technical progress, market liberalization and trade etc. Changes in land-uses within the Mekong region, are thus an extremely complex phenomenon, which can take many forms and cause various consequences. However, human-induced land-use and land cover changes, which could influence the frequency, magnitude and socio-economic costs of floods and droughts are: 1) Transformation from forestland to agricultural land; 2) Forest decline due to logging and overexploitation of natural resources; 3) Land degradation as a consequence of agricultural intensification; 4) Land-cover change that can be associated with large-scale infrastructure projects (hydropower facilities) and urbanization (Rowcroft, 2005). In this connection, it is very important to consider that these potential land-use changes so far did not considerably impact the hydrological conditions of the Mekong region. Adamson (2006), for instance, concludes: the significant deforestation that has taken place since the 1960s has not, as is often claimed, generated any detectable change in the flow regime (Adamson 2006: 23). Thus, with current knowledge no clear statements can be made on possible impacts of land use changes on hydrological floods or drought hazards. Source: own concept Figure 25: summary of hotspots regarding land use changes 76

86 8 Key Drivers and Pressures 4: Hydropower development 8.1 Introduction and overview of literature A detailed and sound understanding on the effects of hydropower development is crucial for objective considerations how to design the future of the Upper and Lower Mekong Basin (Keskinen and Kummu, 2010). The following chapter gives an overview of current research activities in this field. The following literature review summarizes the State of the Art on the following topics: 1. Overall state of hydropower development: Baird, 2009; Beechham and Cross, 2005; Chenaphun, 2011; Gao et al., 2012; Grumbine et al. 2012; Halls et al., 2009; Herbertson, 2012; Joy, 2012; Keskinen and Kummu, 2010; Laurie et al., 2012; McCartan, 2010; MRC, 2010 b; MRC, 2011c; MRC Data Base 2013; Pearse-Smith, 2012; Stone, 2011 Suu, 2011; Vrieze and Chansy, 2011Ziv et al., Impacts on hydro-meteorological extreme events: Arias et al. 2012; Baran et al. 2007; Costanza et al. 2011; Hoanh et al. 2010; ICEM 2010a; ICEM 2010b; Keskinen et al. 2009; and Sarkkula 2008; Laurie et al. 2012; MRC 2010a; MRC 2010b; MRC 2011a; Västilä et al. 2010; Zhao et al Hydropower hotspots, impacts on sediment load and discharge: Baran et al. 2007; Chu at al. 2009; Fu at al. 2008; Grimsditch 2012; Hoanh et al. 2010; ICEM 2010 b; International River Network 2002; Keskinen et al. 2009; Keskinen et al. 2012; Kummu et al. 2010; Laurie et al. 2012; Lu and Siew 2006; MRC, 2011a; MRC 2011d; Räsänen et al. 2012; Zhao et al Hydropower development: current situation and planning Due to increasing energy demands that result from population growth, as well as human and economic developments, it has been shown (see section 2.1), that any or all of the hydropower facilities, which are either in operation, under construction or under consideration might have profound and wide-ranging environmental and socio-economic effects for the riparian countries of the MRB, especially for those which are located furthest downstream. For this reasons, several authors have described the increasing number of current and upcoming hydropower development projects as one of the major factors why the water flows of the Mekong and its tributaries are going to experience a considerable change within the near future (Grumbine et al. 2012; King et al. 2007; ICEM 2010). In addition, it can be expected that large water storage projects, like the cascade of hydropower dams in Yunnan, may increasingly be considered as the major driver of environmental change in this region. Published hydrological impacts projections of the Mekong region, point to the fact that climate-induced fluctuations in the mean annual flow range from 5% to 20% (Johnston et al. 2010; also see Hoanh et al. 2003, Eastham et al. 2008). Hydropower development projects, in contrast, are estimated to increase dry seasons flows by 10-50% and wet season flows are expected to decrease by 6-16% (Johnston et al. 2010; also see Hang/Lennaerts 2008). Thus, hydropower facilities can be regarded as one of the major factors, which will influence (positively and negatively) the magnitude, as well as the socio-economic impacts of floods and droughts in the MRB. In the 1990s the Chinese Government started a project containing the setup of eight dams and reservoirs for hydropower production in the upper Mekong. The first dam put into use was the Manwan Dam in 1993 followed by the Dachaoshan Dam in 2003, the Jinghong Dam in 2008 and the Xiaowan Dam which started filling in 2009 (MRC 2010b). 77

87 Hydropower development increased rapidly in the Lower Mekong Basin in the recent years, 110 mainstream and tributary projects are under planning or under construction in 2011 (MRC 2011c). Currently there are no dams on the Mekong mainstream but 11 mainstream dams are planned, while the construction on Xayaburi Dam (Lao PDR) has officially begun in November 2012 (Chenaphun 2011, Suu 2011). Other sources report on twelve mainstream dams planned in the LMB e.g. Grumbine et al.2012; Stone 2011; Pearse-Smith 2012; taking into account the Thakho hydropower project between Don Sahong and Stung Treng. As this scheme involves no dam construction, it will be neglected in this study. Predictions on the number of hydropower dams vary due to the ongoing progress in development. This study refers to the Mekong River Commission, which is expected to hold most reliable data. There are 26 dams existing on the tributaries in the LMB, 14 are under construction and 85 are planned, 71 of them are located in Lao PDR. Several of the 71 planned tributary projects by Lao PDR will be operated as a cascade. The overall state of hydropower development in the upper and lower Mekong Basin, on the mainstream and its tributaries is as shown in the following tables: Table 27: Number of existing, planned and under construction hydropower projects in the Lower Mekong Basin on the Mekong mainstream and its tributaries per country and in total Mekong Tributary Existing or Country Under Tributary Total under Planned Existing Planned construction total construction China Cambodia Lao PDR 1 8* Thailand Viet Nam Total *Two of the planned mainstream dams share the border of Lao PDR and Thailand. Source: MRC 2011c 78

88 Figure 26 below shows all planned Mekong mainstream projects and 125 existing, planned and under construction tributary hydropower projects for the Lower Mekong Basin. 79

89 Source: Mekong River Commission Database 2013 Figure 26: Hydropower projects on the Mekong mainstream and tributaries in the LMB Size of hydropower projects In compliance with organizations like the Mekong River Commission or the Asian Development Bank we will use the term live storage to describe the total reservoir capacity minus the inactive storage capacity, also referred to as active storage capacity. The live storage is the amount of water which can be used for power production in a reservoir, but also for flood controlling or irrigation. The purpose of the reservoir and the corresponding management of the live storage is decisive for the impact of the reservoir on the hydraulic system. The storage capacity planned on the mainstream LMB projects is relatively small compared to several tributary projects, with a capacity of virtually 0 to m 3, except the Sambor dam in Cambodia with an expected live storage of about m 3. The possible impact of the mainstream reservoirs in the LMB is considerably small compared to the UMB with a planned live storage of 23, m 3 (see also Table 29). Some of the LMB tributary hydropower projects have a huge live storage due to their geographical environment and position. Nam Ngum 1 and Nam Thuen 2 have a live storage capacity of about and m 3, three of the planned dams in the 3S system will have a live storage of > m 3. According to Laurie et al. (2012) the overall live storage considering 126 Hydropower projects adds up to m 3 Hence, the largest impact may be expected by the reservoirs in the area creating the runoff in the LMB. According to MRC (2010b) about 10% of the estimated hydroelectric potential of ca. 30,000 MW on the Lower Mekong has been developed until now. The basin wide total installed capacity is slightly above 2,600 MW, but is supposed to increase more than tenfold if all planned projects will be implemented. About half of the planned capacity will be generated at the eleven Mekong mainstream projects, since eight of them will have a capacity >1,000 MW. The largest will be the Sambor hydropower project with a proposed capacity of 3,300 MW, and a mean annual energy output of 14,780 gigawatt hour (GWh) (MRC 2011c). Table 28: Installed capacity of existing, under construction and planned hydropower projects (in MW) in the Lower Mekong basin on the Mekong mainstream and its tributaries per country and in total Mekong Tributaries Country Under Tributary Total Planned Existing Planned construction total Cambodia 4, ,309 1,310 5,590 Lao PDR 10,417 (a) 738 2,764 6,847 10,350 20,767 Thailand Viet Nam - 1,204 1, ,583 2,583 Total 14,697 2,688 3,780 8,519 14,987 29,684 (a)two of the planned mainstream dams (altogether 11) share the border of Lao PDR and Thailand. Source: MRC 2011c 80

90 Table 29: Proposed capacity on mainstream hydropower projects in the Greater Mekong Basin Project Country Mean Installed Live Storage Start of Reservoir Area (km 2 Capacity (MW) (10 6 m 3 ) Operation ) Gongguoqiao China Xiaowan China 4,200 9, Manwan China 1, Dachaoshan China 1, Nuozhadu China 5,850 12, Jinghong China 1, Ganlanba China Mengsong China total 15,900 23,200 Pak Beng Lao PDR 88 1, Luang Prabang Lao PDR 73 1, Xayaburi Lao PDR 45 1, Pak Lay Lao PDR 77 1, Sanakham Lao PDR 21 1, Pak Chom Ban Koum Lao PDR- Thailand Lao PDR- Thailand 72 1, , Lat Sua Lao PDR Don Sahong Lao PDR Stung Treng Cambodia Sambor Cambodia 1,000 3,300 2, Total 1,618 14,697 5,226 Source: Information Service; MRC Data; Räsänen et al Hydropower development: Impacts on hydro-meteorological extreme events / hotspots While maritime and rainfall caused floods are driven naturally, anthropogenic interferences alter the effect of those events. Hydraulic infrastructure interacts with natural events in several ways and can therefore intensify or mitigate those effects, hence, the level of impact need to be identified to assess and manage anthropogenic impacts on the environment. Not only the infrastructure will affect the extent of floods, but also other human encroachments on land use and land management, which often arise consequently. This development leads to additional pressures on the system like pollution, exploitation and extraction of resources (Costanza et al. 2011) Hydropower projects are, however, a high-impact form of disturbance, causing chain reactions and affecting land use dynamics. To understand how this development affects the environment, it is mandatory to issue guidelines and management strategies (Zhao et al. 2012). Hydrological future predictions must always take into account the regional development; therefore assumptions of a future without hydropower development are unrealistic. Hence, both drivers, 81

91 possible climate change and reservoir operation impacts must be considered basin wide (Hoanh et al. 2010; Keskinen et al. 2009; Lauri et al. 2012; MRC 2009d; Västilä et al ). According to Beecham and Cross (2005) and Adamson (2007) the hydropower development in the UMB has a high potential to reduce the flood peak in the upper parts of the LMB. In combination with the hydropower development in the LMB (expected live storage >100, m 3 ) a reduction of 4 to 5 dm on annual flood peaks can be achieved downstream. In the Mekong Delta the reduction would be limited to 1 to 2 dm. However, flood mitigation by reservoirs is theoretical, since it is found that dam construction just have a little impact even on minor floods. In general the management of a reservoir for power production leaves just a small available volume for flood storage, compared to the volume of flood generating runoff (Joy 2012) The following country specific paragraphs show examples of existing and arising impacts described by recent studies and first experiences. As a result of the advanced development in the UMB, China provides the most detailed examples and results by this time. A major subject discussed in several studies is the sedimentation in reservoirs, the affected sediment transport and the subsequent downstream impacts. For instance, International Rivers Network (2002) predicted that about 35 % of the suspended sediment load will be trapped in the Xiowan Dam in future. Shaojuan and Daming (2008) reported on flow regulations by existing dams in the UMB. Downstream effects on the water level are limited on annual mean and wet season mean levels, but relatively significant on daily and hourly timescales China The hydropower development on the upper Mekong (Lancang) in China comprises eight dams of which four are already under operation. Four dams are in operation, Manwan, Dachaoshan Dam, Jinghong Dam and Xiaowan Dam, the other projects are under construction or at the planning stage. The largest projects are the Xiaowan Dam (9, m 3 live storage) and Nuozhadu (12, m 3 live storage), total or live storage information for the Ganlanba and Mengsong Project are not available yet. The overall regulation capacity of the UMB would be more than 23, m 3 and the installed capacity would be about 15,900 MW, which is ca.50% of the total installed capacity in the LMB (see also Table 29) (MRC Data and Information Service; Räsänen et al. 2012). Impacts on sediment load Soil erosion is possibly affected by climate change in terms of higher erosion rates due to an expected increase of the number of extreme events and higher amount and intensity of rainfall per event. Especially with progressing deforestation not only the runoff will increase in future but also the sediment load due to more areas prone to soil erosion. (Gao et al. 2012) Lu and Siew (2006) analyzed the sediment situation of the post-dam period of the Manwan Dam and figured out that a decrease only occurred on the reach above Vientiane while the suspended sediment load downstream of Vientiane have increased. Whereas Kummu and Varis (2007) analyzed the dam impacts on environmental and ecological system of the UMB and stated that 94 % of the suspended sediment load will be held back from the transport to the LMB, moreover, the effects will be recognized in Cambodia. Fu et al. (2008) reported in their study that the mean sediment trapped in the Manwan Dam on the upper Mekong Mainstream in China is estimated at *10 6 t/a since 1993, when the operation started. According to the sedimentation the reservoir lose about *10 6 m 3 of its storage capacity per annum; this equals about % loss of its overall storage in 82

92 eleven years. The sedimentation in the Manwan reservoir not only affects the reservoir body itself but also the base level of the tributaries to the reservoir was raised and erosion has stopped, while sedimentation extended further upstream. Kummu et al. (2010) stated that ca Mt of the sediment load will be trapped in the Upper Mekong Basin if the cascade system of eight dams is finished. About 65 % of the basin sediment load originates from that stretch and since the trapping efficiency will increase to about 80 %, more than 50 % of the total sediment load (ca. 140 Mt) will be trapped. Subsequent downstream impacts are a limited delivery of nutrients, increased inundation and erosion (Baran et al., 2007). Impacts on discharge Chu et al. (2009) quantified the extreme impact of the filling of the Three Gorges Reservoir on downstream discharge which could even be detected 1,800 km downstream at the tidal limit of the river mouth. Similar effects are already measureable in the MRB, as shown below in Figure 27. Hence, first effects of the Hydropower development in the UMB on discharge already reach Chiang Saen gauging station. In 2009 the discharge pattern appears to be inconsistent with the general hydrological response to the run-off generation, showing high frequency day to day fluctuations in the dry and the wet season (MRC 2011a). Since average discharge rates usually are blurry compared to single values, these statements must be considered carefully and need a further investigation with post-dam average discharge rates. Figure 27: Daily hydrograph of Chiang Saen gauging station during filling of Xiowan Dam in 2009 (left) and in 2010 (right) showing a considerable noise due to operation of Chinas mainstream hydropower projects. Source: MRC 2011a The future hydrological changes by the Lancang-Jiang cascade in the Upper Mekong Basin have been assessed by considering three scenarios (Baseline, 3 Dams, 6 Dams) by Räsänen et al. (2012) using the hydrological VMod model. The general outcome shows a decrease for the average wet season flow as well as an increase for the average dry season flow. As the total active storage for the three dam cascade scenario were m 3 and m 3 for the six dam cascade scenario, the 6 dam scenario shows a more substantial change. The following table shows the changes in discharge and the range of hydrological variability of the 6 dam cascade scenario. 83

93 Table 30: Monthly discharge anomalies and the range of hydrological variability of the 6 dam cascade scenario compared to the baseline scenario Month Average discharge anomaly under 6 dam scenario [m 3 /s] Range of hydrological variability under 6 dam scenario [m 3 /s] Range of hydrological variability under baseline scenario [m 3 /s] Change in rate Jan , % Feb 1, , % Mar 1, , % Apr 1, , % May , , % Jun , % Jul -1, ,213 1, % Aug -2, ,745-1,959 2, % Sep -2, ,057-1,551 1, % Oct , , % Nov ,424-1,162 1, % Dec % Source: Räsänen et al Consequently, the flood pulse characteristics changed by a decrease of the duration, the amplitude and the maximum water level, while the timing of the flood starts and the peaks are delayed. These results correlate with findings by other studies, e.g. Baran et al. 2007; Hoanh et al. 2010; MRC 2011d; Lauri et al Accordingly the hydropower development leads to a new hydrological regime of the UMB, highlighting the fact that hydropower impacts are closely linked to climate variations (Räsänen et al. 2012). Table 31: Average flood pulse parameters of Baseline, 3 Dam and 6 Dam scenarios at Chiang Saen. Scenario Flood start [date] Flood end [date] Flood duration [days] Flood maximum [day] Amplitude [m] Max. Water level [m] Baseline 26. May 25. Dec Aug Dam 25. Jun. 27. Nov Sep Dam 06. Jul. 15. Nov Oct Source: Räsänen et al., 2012 Vastila et al. (2010) modeled the climate change impacts on the flood pulse in the lower Mekong floodplains and discovered that the projected impacts were mostly opposite to those resulting from the hydropower development. Although they are of similar order of magnitude, these impacts take place at different time scale. A cumulative impact assessment is required to obtain information on the combined effects of infrastructure development and climate change. According to MIZZIMA (2010) China refused to release water from their upstream dams in March 2010 as lower Mekong countries suffered from water shortage. Due to the shallow water level, commercial boats could not navigate on the Mekong mainstream. Moreover local residents complained about fluctuating water levels and unexpected flooding, which might be related to the dam operation in the UMB. The Asia Times published an article by McCartan 84

94 (2010), saying that China rejects reports blaming chinese dams for the state of the river. Although there is no evidence for false statements by the Chinese government, however, the unwillingness to release detailed information caused an absence of transparency which raised diplomatic tensions Myanmar The Mekong forms the border between Myanmar and Lao PDR for about 234 km and is also called Lancang by the Lahu, one of the main ethnic groups in this region (Burma Rivers Network 2013). The Mekong mainstream also forms the border of the Upper and Lower Mekong Basin according to the MRC (2011c). Most of its catchment area in Myanmar belongs to the UMB and the smaller area counts to the LMB, particularly to the catchments Nam Mae Kok and Nam Mae Kanh. Due to minor data available from Myanmar, the MRC is trying to strengthen the cooperation for an improved basin-wide development (MRC 2011e). According to the Lahu National Development Organization (2009), unseasonal flooding damaged rice paddy fields along both banks of the Mae Sai River. It is believed that the flooding as well as unprecedented fluctuations in the water level are the result of Chinese upstream dams. MRC (2009d) reported that the proposed Nam Kok hydropower project will have a huge potential to control the flow in the Nam Mae Kok Basin, since the overall storage has about m 3, which is approximately 50% of the annual river flow Lao PDR Lao PDR plans the largest development on hydropower projects compared to the other riparian countries with 100 dams in total (9 mainstream dams and 91 tributary dams). This rapid development includes several hydropower cascades on tributaries. Sub catchments with a huge number of (planned) reservoirs are Nam Ou, Nam Cadinh, Nam Ngum and Se Kong (part of the 3S system). Table 32: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects on the Mekong mainstream and its tributaries in Lao PDR Hydropower Project Mean Reservoir Area (km 2 ) Live Storage (10 9 m 3 ) Installed capacity (MW) Mainstream total* 1, ,305 Tributary total 2, ,545 Hydropower total 4, ,850 *Two of the planned mainstream dams (altogether 11) share the border of Lao PDR and Thailand. Source: MRC Data and Information Service Mainstream Nine of eleven mainstream hydropower projects in the LMB will be located in Lao PDR, two of the nine projects (Pak Chom and Ban Koum) will share the border with Thailand (MRC, 2011c). Six dams are located north of Vientiane forming a cascade of which five dams create a linked stepped reservoir of 800 km. The other three dams located in Lao PDR are located in the southern part of Lao PDR, from the confluence of Mun/Chi River to the Cambodian border. The Don Sahong project would not be a full mainstream dam. (ICEM, 2010b) 85

95 Tributaries The tributary system of the LMB in Lao PDR will be transformed to a partly artificial hydraulic system, managed according to the reservoir operation rules. Most projects are still in planning state or under construction, thus repercussions are not clearly evident yet. International Rivers (2008) considered several case studies in their report on impacts of rapid dam development in Lao PDR emphasizing the fact, that most of the generated power will be exported to Thailand, Vietnam and China, while tens of thousands of Laotians will lose their livelihoods. In general they remark that there is an underestimation of scales and magnitude of expected impacts by the conducted environmental and social impact assessments. The following table gives an overview on dams considered in this case studies. Table 33: Summary of impacts for dams featured in power surge cases studies Project Don Sahong Houay Ho Nam Kong 1 Nam Leuk Nam Ngum 2 Nam Ngum 3 Nam Ngum 5 Nam Song Nam Tha 1 Nam Theun 1 Nam Theun 2 Sekong 4 Sekong 5 Theun Hinboun Exp. Theun Hinboun Xekaman 1 Xekaman 3 Xekatam Xepian Xenamnoi Main Issues First dam proposed on the LMB Block main fish migration channel, severe impacts expected Resettling about 2,500 ethinc minorities causal affecting land use Impacting about 1,600 ethnic minorities Affecting about 9,500 people downstream in terms of fishery and clean water losses Resettling about 6,000 ethnic minorities Impact on fishery as food and income source for about 9,000 people Resttling about 500 people, affecting about 2,500 people Affecting paddy land of about 50 households About 1,000 families affected by loss of fishery and flooding/erosion impacts Resettling about 8,000 ethnic minorities Affecting more than 4,600 people downstream Resettling about 3,700 ethnic minorities Significant impacts on fisheries affecting about 32,000 people Downstream impacts for about 120,000 people Resettling more than 5,000 ethnic minorities Affecting fisheries for about 190,000 people Resettling unknown number of ethnic minorities Exacerbating fishery losses and water quality problems caused by Sekong 4 Resettling about 4,400 ethnic minorities Affecting about 50,000 people downstream Exacerbating flooding and erosion About 30,000 people lost fisheries and agriculture land Resettling about 800 ethnic minorities Affecting about 10,000 people downstream through water quality changes, fishery losses and erosion Affecting about 47 villages Resettling about 300 ethnic minorities Resettling four and affecting eight villages 86

96 Source: International Rivers 2008 Tha main issues in the table above describe mainly the number of affected and resettled people which will cause causal effects on land use changes and illegal logging. (International Rivers 2012) As the Theun Hinboun hydropower project is in operation since 1998, data are available showing that erosion and flooding in the Hai and Hinboun River is caused, leading to destruction of rice paddy fields and fatalities due to fluctuating water levels. Moreover it is a trans-basin diversion project, relocating water from the Theun-Cadinh River to the Hai and Hinboun River. Hence, downstream areas of the Theun-Cadinh River suffer from decreased dry season water supply. According to International Rivers (2008) The Theun-Hinboun Expansion Project, which is under construction, is likely to significantly increase the frequency and duration of flooding and also cause greater erosion along the riverbanks. Also FIVAS (2007) reported on fluctuating water levels and stronger flows causing severe erosion as well as losses of fertile agricultural land downstream of the Theun-Hinboun Hydropower Project. Increased flooding and fluctuating water levels caused several deaths and the Theun-Hinboun Expansion Project is likely to cause extra erosion, sedimentation and aggravated flooding to be disastrous. Despite the huge number of planned hydropower projects all over the Mekong catchment in Lao PDR, there are several sub-catchments who will face intense changes in the hydrological regime due to the vast amount of water to be managed in future. According to MRC (2009d) the hydropower development has a significant potential to mitigate flood events, especially in Lao PDR as large storage volumes will be created. The hydrology can be considerably controlled, depending on the operation rules of the reservoir. However, flood mitigation was not the subject of most feasibility studies for hydropower development projects (see also Size of Hydropower Projects). The following table shows all sub-catchments in Lao PDR with a total live storage greater than m 3. Table 34: Sub-catchments with a total live storage greater than m 3 in Lao PDR Sub-Catchment Number of reservoirs Live Storage (10 6 m 3 ) Se Kong 20 11,068 Nam Ngum 10 10,385 Nam Cadinh 6 8,437 Nam Ou 13 3,556 Nam Pho 1 2,738 Nam Khan 2 2,193 Nam Suong 2 2,102 Nam Sane 3 2,079 Se Done 5 1,757 Se Bang Nouan 1 1,477 Se Bang Hieng 4 1,464 Nam Hinboun 2 1,249 Nam Mang Nam Tha Se Bang Fai Nam Phoul

97 Nam Nhiam Nam Beng 1 98 Nam Nhiep 5 77 Nam Phuong 4 40 Huai Bang Lieng 1 35 Source: MRC Data and Information Service ADB (2007) stated that the Nam Ngum Basin already faced significant changes due to the existence of Nam Ngum 1 Reservoir and the development of additional hydropower projects will lead to cumulative impacts. The water flow and sediment load of the river will be further regulated and reduced. Dry season flows will be higher, and wet season flows will be below than pre-construction averages in the downstream sites of hydropower reservoirs. Rapid fluctuations in water levels below dam sites on a daily basis could have safety implications, and may affect river bank stability (ADB 2007, p. 69) Thailand Thailand s contingent on hydropower projects in the LMB is relatively small compared to other riparian countries. There are seven hydropower dams in three sub-basins, Nam Chi, Nam Mun and Nam Kam. The Pak Mun Dam, located about 5 km West of the confluence of Mun River and the Mekong mainstream, plays an important role as it regulates the flow of the Mun Chi River System into the Mekong. Although the overall catchment area of about 120,000 km 2 equals 22% of the Mekong drainage area at Pakse, the Mun-Chi River System contributes just 10% of the average flood volume at that point, but it is nevertheless a key tributary system regarding the flood hydrology of the Mekong (MRC 2008). According to MRC (2009d) projects in the Nam Chi and Nam Mun Basin are multipurpose, irrigation and hydropower. The mitigating capacity of the dams is considered to be limited, since the area is controlled by reservoirs with a small storage capacity. Table 35: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects in Thailand Hydropower Project Mean Reservoir Area (km 2 ) Live Storage (10 9 m 3 ) Installed capacity (MW) Tributary total Source: MRC Data and Information Service Cambodia Cambodia is up to develop their hydropower sector in future, but in a smaller extend than Lao PDR. According to the MRC Data and Information Service thirteen hydropower projects are under planning, two of them in the Mekong Mainstream (Stung Treng and Sambor). The Sambor dam will be the largest LMB mainstream dam with an installed capacity of MW, a live storage of m 3 and an estimated max. reservoir area of more than km 2. Altogether Cambodia plans to develop an installed capacity of MW. 88

98 Table 36: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects on the Mekong mainstream and its tributaries in Cambodia Hydropower Project Mean Reservoir Area (km 2 ) Live Storage (10 9 m 3 ) Installed capacity (MW) Mainstream total 1, ,280 Tributary total 3, ,310 Hydropower total 4, ,590 Source: MRC Data and Information Service Cambodia not only plans to set up the largest LMB Mekong mainstream dam, but also an intensive development of the Cambodian parts of the 3S River System. However, most studies on changing hydrology focus on the Tonle Sap System, which is highly important for Cambodia and has a perfectly adapted ecosystem to the exceptionally high natural variability of the lake (Baran et al. 2007). Tonle Sap In his synthesis report of eleven scientific studies under the Technical Assistance to the Kingdom of Cambodia for the Study of the Influence of Built Structures on the Fisheries of the Tonle Sap-report, Baran et al. (2007) stated that the largest impact of upstream development on the Tonle Sap system will be felt in dry years. According to hydrological modeling results, the lake inflow will decline between m 3 (4 % in a dry year, 10 % in a wet year) and m 3 (10 % in a wet year, 25 % in a dry year) under different scenarios. Moreover, upstream development will delay the onset of the annual flood by about 12 days and shorten the duration for about one week. An abrupt modification of the flood pattern is one of the biggest threats to the ecology of a floodplain; also costs for both, rehabilitation or balancing financial losses are very high. (Baran et al., 2007) A recent study on the Tonle Sap system by Arias et al. (2012) focused on changes in flooding and habitats due to the development of the water infrastructure and climate change. Water level data from 1986 to 2010 have been used to quantify the recent flood history and the impact of five future infrastructure development and climate change model scenarios have been analyzed for dry, wet and average years. The least expected changes are for wet years and the biggest changes are expected to occur in dry years where the water level remain the same for April and May but increase by 0.2 to 0.75 m the rest of the year as a result of climate change. The changes in dry years due to infrastructure development predict an increase of 0.2 to 0.4 m from April to June and a decrease up to 0.5 m from August to January. Kummu and Sarkkula (2008) stated in 2008 that an increase in dry season water levels of m would threaten the present ecosystem of the Tonle Sap lake. A more detailed prognosis from Arias et al. (2012) reported that shifts in habitat cover are expected in terms of an increase of open water area and a net reduction of the optimum area for gallery forests, leading to major implications on the Tonle Sap affecting livelihoods, sedimentation patterns, nutrient cycling and the fisheries. These outcomes matches the predictions by Baran et al. (2007) who stated that the consequences of negative impacts on the floodplain environment are far reaching and exceed the recipients of primary impacts like fisheries and agriculture, by affecting the sediment flow, hence the fertility of soils will decrease and the nutrient content deteriorates, causing secondary impacts downstream down to the delta region. 89

99 Future prospects of Tonle Sap By downscaling high resolution future climate projection data for the 21 st Century by PRECIS regional climate model, using input data sets of ECHAM4 Global Circulation Model under two different scenarios (A2, B2), Keskinen et al. (2009) stated that the future flood pulse in the Tonle Sap system is likely to be wetter. Higher water levels, more extensive flooded area as well as longer flood durations are expected to occur; moreover, the average water level during dry season is likely to increase as well. Additionally to climate change factors the hydropower development can be seen as the most important change factor and for a sound understanding, a cumulative impact assessment should be carried out. Lauri et al. (2012) used the VMod model in their study on future changes in the Mekong hydrology, particularly computing the possible change in discharge at Kratie, Cambodia between the baseline ( ) and the projected time period ( ). 126 hydropower reservoirs have been taken into account according to the MRC database, with a total volume of active storage of m 3. The predicted climate change impact bases on two different scenarios used (A1b and B1). The daily average temperature increased by C (A1b) and C (B1), the precipitation increased by % (A1b) and % (B1), the modeled runoff increased in six model runs but decreased in four runs. The modeled impacts of reservoir operations on the mainstream discharge without climate change parameters show correlating results as mentioned above. Compared to the baseline data, reservoir operations cause an increase in the monthly average discharge in the dry season ( % in Kratie, % in Chiang Saen), and a decrease of the wet season discharge (5-24 % in Kratie, 3-53 % in Chiang Saen). The cumulative impact of climate change and reservoir operations on the mainstream discharge show that the dry and early wet season discharge is mostly defined by reservoir operations. The impact of climate change and reservoir operations on the selected flood pulse parameters is shown in Table 37. Most changes in flood volume are significant by testing the statistical significance using the paired two-sided t-test (Lauri et al., 2012). Table 37: Flood parameters in Kratie as an average of 10 year discharge data ( ) Scenario Flood peak discharge Climate change Flood volume Climate change Flood peak discharge Climate change and reservoirs Flood volume Climate change and reservoirs A1b 2 to 20 % -17 to 7 % -15 to 7 % 2 to 25 % B1 0 to 13 % -13 to 1 % 0 to -15 % 7 to 22 % Source: Lauri et al S River System A significant and rapid hydropower development is planned for the transboundary Se San, Se Kong and Sre Pok River System (3S System). The catchment shares parts of Lao PDR, Cambodia and Vietnam, its confluence with the Mekong River is at Stung Treng Town and about 10 km downstream of the future Stung Treng Hydropower Project. The 3S System covers an area of about 78,347 km 2 and contributes approximately 18 to 20% of the overall annual flow of the Mekong (Adamson et al. 2009, Piman et al. 2012). The development in the Se Kong catchment is situated in Lao PDR comprising 20 dams with a total live storage of m 3. The Se San catchment covers parts of Cambodia and Vietnam, both countries plan to develop eleven dams in the catchment with a total live storage of m 3. As the Se San catchment, the Sre Pok basin covers downstream parts of Cambodia 90

100 and the upstream area belongs to Vietnam. Altogether ten hydropower projects will be set up with a live storage of m 3 (MRC Data and Information Service). Table 38: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects in the 3S River System Hydropower Project Number of Hydropower Projects Live Storage (10 6 m 3 ) Installed capacity (MW) Se Kong total 20 11,068 2,471 Se San total 11 5,539 2,090 Sre Pok total 10 9,416 1,575 3S System total 41 26,023 6,136 Source: MRC Data and Information Service 19 of the overall 41 dams are currently running or under construction, 22 more dams are in planning stage. The completion and the operation with the purpose of maximum power generation of 41 proposed dams in the 3S System would result in an average 98% increase in dry season flows and a decrease of 29% of the wet season flows. Operation rules can reduce daily and seasonal flow changes but would also result in an average reduction of 50% on energy output (Piman et al. 2012). Nevertheless, MRC (2009d) predicts that the development will affect the regime of the 3S System and due to its enormous storage it could be beneficial for flood mitigation. Grimsditch (2012) reported on the hydropower development of the tributary system and pointed out new threats and challenges to biodiversity and community rights by 20 hydropower projects existing or are under construction and 26 more dams in planning stage. Due to the upper Kon Tum hydropower project in Viet Nam, water has been diverted to the Dac Sngeh River, creating an increased area s drought in the lower areas of the Se San River. The lower Se San 2 project is believed to have large scale negative impacts on the whole 3S basin. It is located at the confluence between the Sesan and the Srepok rivers and will be operational by 2017, producing 400 MW. The size of the reservoir will be 340 km 2 or larger (Grimsditch 2012). Approximately ha of forest and ha will be flooded and about villagers need to be resettled. The International Center of Environmental Management assumes that the dam will block about 50% of the sediment flow from the 3S basin. This might reduce the overall sediment load of the Mekong by an average of 6 to 8%. The consequences would be reduced stability of river channels downstream and the Mekong Delta Coastline increasing erosion and diminishing aquatic and agricultural productivity (Vrieze and Chansy 2011). Ziv et al stated that the development in the LMB would cause a drop in fish productivity by 51% and endanger 100 fish species. Individually, the Lower Se San 2 project will cause a basin-wide drop in fish biomass of 9.3%. A study commissioned by the Rivers Coalition in Cambodia stated that about people will lose access to migratory fish, including including more than 160 villages on the Sesan and Srepok rivers and its tributaries. It is suggested that the negative impacts may be felt as far away as the Tonle Sap Lake, the Mekong Delta and the middle Mekong River in Lao PDR (Baird 2009). 91

101 8.3.6 Viet Nam The first relation of Vietnam and the Mekong River is of course the Mekong Delta, receiving the overall annual discharge of the Mekong River and the consequences of upstream river management. But Vietnam also covers some parts in the 3S transboundary river basins. Nine dams exist or are under construction, six more dams are proposed for development of the Vietnamese parts of the 3S System. Altogether Vietnam will run fifteen hydropower projects with a total live storage of m 3. Table 39: Mean reservoir area, installed capacity and live storage of existing, under construction and planned hydropower projects in Vietnam Hydropower Project Mean Reservoir Area (km 2 ) Live Storage (10 9 m 3 ) Installed capacity (MW) Tributary total 224 3,2 2,583 Source: MRC Data and Information Service Figure 28 shows the location and size of existing and planned reservoirs in the MRB. It also illustrates the cumulative storage volume per sub-basin. Figure 29 differentiates the reservoirs according to their status (operational, under construction, planned). 92

102 Figure 28: location and size of reservoirs in the MRB 93

103 Figure 29: status of reservoir construction in the MRB 8.4 Conclusion and recommendations Future hotspots regarding hydro-meteorological extreme events in the MRB are generally around new hydropower projects. The first dam of the LMB mainstream will be the Xayaburi dam in Lao PDR, the constructions started already in late 2012 and is expected to be finished in According to the Mekong River Commission Secretariat (2011, p. iii) The construction of the proposed Xayaburi dam will not materially affect the quantity or timing of river flows in the Tonle Sap or the Mekong Delta. Cumulative impacts of other projects in the LMB and the Xayaburi project would progressively increase the magnitude of these impacts on regional scale. This underscores the assumption to consider each hydropower dam as a new hotspot. Small-scale effects on hydrology depend on the regional geo-morphology, land cover and microclimate. In terms of hydro-meteorological extremes, the impact of a single dam may be limited on regional scale but impacts on the hydrology by several hydropower dams may also reach or create spots further downstream. Effects of changed discharge pattern, variations in the suspended sediment load can be expected to be primary impacts by each hydropower dam in the MRB. Secondary impacts may be changes in land cover and soil erosion caused by changed land use in consequence of the reservoir impoundment with influences on the surface 94

104 run-off as a causal effect. Flood peak and maximum discharge, as well as the flood timing in downstream areas depend on the operation rules of the hydropower dam. Especially confluence areas from high-developed catchments and the Mekong mainstream might evolve to future hotspots. Small or no buffers in the reservoir may cause severe flooding at unexpected points of time causing severe damages, threatening life and infrastructure. Dams always involve the risk of mass of water to be released in a very short time, this on one hand can happen due to dam releases via the spillway in the case of emergency or on the other hand if the dam breaks. However, in both cases vast amounts of water will deluge the downstream area with a fast and high flood peak, offering nearly no time for an early warning. Especially in the mountainous area of the tributaries, flash floods may occur if vast masses of water are released to the small and steep riverbeds and though hydropower reservoirs involve the risk being the reason for flash floods, threatening human life. But dams also have the potential to reduce the hazardous potential of climatic extremes like flash floods, depending on the management of reservoirs (see also 8.3 Hydropower development: Impacts on hydro-meteorological extreme events / hotspots). Joy (2012) showed that the greatest reduction in flood levels due to dam development in China occurs in Luang Prabang, further downstream the flood mitigation effect declines and additional tributary runoff enters the Mekong. The construction of dams in the LMB increase the likelihood of dam release and dam break flooding and moreover it will affect the hydraulic behavior of the Tonle Sap system. 95

105 9 Summary: comparative evaluation and hotspot analysis With currently available data on future climate change scenarios, no scientifically sound statement can be made neither on the future water balance, nor on the possible impact on hydro-meteorological extremes. Each modeling step (emission scenarios, GCMs, downscaling, hydrological models) entails high levels of uncertainties which add up and make predictions of the future rather impossible. Past time series of any relevant hydro-meteorological indicator, except temperature, does not show any significant trend. While the overall precipitation trends or its spatial patterns in the future are associated with high level of uncertainties, trends in future temperature are very likely to increase. As a consequence, the potential and real evapotranspiration in large parts of the basin are likely to increase leading potentially to higher risk of drought. These findings are in accordance with findings of IPCC (2012) at the global level. There is no study proving that land use changes in the past did significantly alter the hydrograph of the Mekong system (mainstream or tributary). Impacts of future land use change on hydrology lacks any scientific basis to make predictions for the Mekong. The currently available predictions only show minor possible impacts on hydrology while being associated with a high degree of uncertainties. Cumulative effects of climate change, reservoir construction and land use change have a potential to impact with significant increase or decrease the flood pulse of the river Mekong. However, quantitative statements on the future behavior on the combined effects are virtually impossible. Several authors warn that the changing flood pulse will alter the ecosystems of floodplains and in particular the Tonle Sap System. However, there is currently no clear evidence on the possible impact of flood pulse changes on the ecosystem productivity or biodiversity. Further studies are needed. Hydro-meteorological extremes could be impacted by climate change, and reservoir operation. However, at the basin scale there is very little evidence of trends in extremes in the past or studies available on how extremes may be altered in the future. Currently, scenarios suggest that future developments of climate change and hydropower rather even out discharge extremes. Impacts of hydro-meteorological extremes will increase if either the level of hazards or the vulnerability with respect to these hazards increases. Studies suggest that impacts of floods and droughts increased due to higher levels of exposure and vulnerability (IPCC 2012). However, any reliable predictions on the hazard level of floods or drought cannot be made due to the above mentioned uncertainties. 9.1 Floods in combination with key drivers Predictions of climate change impacts on the hydrograph are diverse and most simulations do not come to the same conclusion concerning the majority of the climatic regions in the Mekong basin. Uncertainties of studies stemming from various GCMs multiplied by uncertainties in hydrological modeling are significant thus no scientifically sound conclusion can be made on impacts of climate change on flood risk (compare chapter 5). However, there are similar climate simulation results for increasing precipitations and hence discharge in Eastern Central Cambodia and the Mekong Delta (Arias et al. 2012; Delgado et al. 2010; Eastham et al. 2008; compare to chapter 5 and chapter 3). Therefore it is likely that flood frequency in the Mekong 96

106 Delta and South eastern Cambodia will increase and hence flood risk assessment and management in those regions should be addressed with more emphasis. Furthermore, increasing flood related damages indicate that the vulnerability component of the flood risk is more dynamic compared to the hazard component. Socio-economic, infrastructural, demographic changes and especially agricultural intensification can be attributed very clearly to flood risks. Cities like Vientiane, CanTho and Phnom Penh with growth rates of 5 % p.a. and up to 60 % of the population living in informal settlements expanding in flood prone areas pose a significant contribution to flood risk. The expansion of agricultural activities as irrigated rice cultivation and the number of people living in flood prone areas is thus a major driver to increase flood risk in the near and mid-term future (ADB 2011; Huong and Pathirana 2011; Künzer et al. 2013; MRC 2008a; MRC 2008b; compare with chapter 3). There are almost no studies analyzing in depth the impact of land use change on flood peak. Even though some studies describe the likelihood of hydrograph changes due to land use change, they are typically based on conceptual models rather than on scientific evidence. Hydropower development can have negative impacts on floods when during strong rainfall events water is released from the reservoirs (ICEM 2010). However, the majority of authors have found out that it increases the storage volume in the basin even out the peak hydrograph (Johnston et al. 2010; Räsänen et al. 2012). A further significant risk connected to floods in combination with hydropower is the risk of a catastrophic failure and dam breakage especially in river stretches with reservoir cascades (ICEM 2010). 9.2 Droughts in combination with key drivers Concerning meteorological droughts, uncertainties of RCMs apply as much as they apply to floods and predictions of regional precipitation patterns are contradictory for most regions in the Mekong (Eastham et al. 2008; IPCC 2012, TKK&SEA START RC 2009; compare chapter 5). Droughts are frequent events in many parts of the basin as depicted in chapter 4. However, it is very likely that in most regions especially in Yunnan and Myanmar temperature will rise and hence evapotranspiration which would lead to a higher frequency of drought situations in rainfed agriculture. As the linkage between climate change and hydrology due to model uncertainty cascading is less clear, no predictions can be made on future hotspots regarding the likelihood of hydrological droughts which are crucial for irrigation performance (Ishidaira et al. 2008; Keksinen et al. 2010; Kiem et al. 2008; Laurie et al. 2012). As for floods, socio-economic changes will lead to an expansion of (irrigated) agriculture and in consequence will increase the drought vulnerability and hence the drought risk in absolute terms. Increasing competition between agricultural, urban and industrial demands in urban areas will increase the drought risk during dry season (see chapter 4). Strongly developing drought prone areas are exposed to an especially high drought risk. Ty et al. (2012) and Adamson et al. (2010) depict that no stream flow changes can be detected by major land use changes. However, the increase of water demanding land uses, in particular of irrigated agriculture, will lead to a reduced discharge in some sub-basins. Hydropower reservoirs increase the overall storage volume in the basin which does not necessarily lead to an aggravation of droughts. During the filling period of the newly built reservoirs and drought periods, however, downstream discharge can be significantly reduced and lead to severe water shortage in the downstream part (ICEM 2010). 97

107 9.3 Current and future hotspots regarding floods and droughts Yunnan, China Severe droughts since 2009 have affected up to 6 million people repeatedly cutting their drinking water supply. Highest temperature increases in the Mekong basin are expected for this region which could lead to more frequent drought hazards. However, some authors suggest that increasing temperatures will accelerate the regional water cycle and have simulated higher precipitation rates (compare chapters and 5.3.1) Myanmar Only a small portion of Myanmar forms part of the Mekong and besides rising temperatures and consequent impacts no larger flood and drought problems have been recorded or are expected Lao PDR Climate and flow projections for Lao PDR strongly vary depending on the GCMs used. Either higher or lower precipitation rates have been simulated for 2030, 2050 and 2100 respectively for both the wet and dry season. However, as almost the entire rural population depends on rain-fed rice cultivation, the country and its food economy is extremely vulnerable to drought and unusual flood events. Besides the poor countryside (more than 50% are considered as poor countrywide) also Vientiane with 5% of yearly population growth and 66% of urban population in Lao PDR living in informal settlements can be considered as a hotspot for drought and flood vulnerability and risk (compare chapters 4.2.3, 5.3.3, 6.3.3). Most significant hydropower development in the Mekong basin with 9 mainstream dams and 91 tributary dams is planned in Lao PDR and will lead to significant changes fostering development of rural areas on the one hand (ICEM 2010) and impacting environment, especially river discharge and ecology on the other. Positive and negative impacts on floods and droughts are expected but require further observation Cambodia Although climate and flow predictions also vary significantly for Cambodia, for the Tonle Sap region and Kratie an increased precipitation and flood probability has been simulated more often (compare to chapter 5). On the other hand, the South eastern part is expected to be more drought affected due to decreasing precipitation. Hydropower development in the 3S system (the Se Kong, Se San and Srepok river basins) and on the Mekong`s main tributaries will affect stream flow in the upstream areas and require further impact studies. The area of the Tonle Sap Lake as a densely populated region, Phnom Penh and the poorest provinces prone to floods and droughts should be considered as hotspots Vietnam There is a broad consensus in literature that the entire Mekong Delta is and will be affected by all the mentioned drivers and risks as climate change, more frequent droughts and unusual floods as well as upstream hydropower development. Sea level rise as well as increased precipitation and river discharge are projected which will affect especially coastal and Mekong River riparian areas. Furthermore, fast socioeconomic development, demographic change as well as the increase in agricultural productivity and coastal fish farming will increase the socioeconomic vulnerability to the region (compare chapters 3-5). 98

108 99

109 9.4 Hotspot overview The following map roughly illustrates all the different identified hotspots in one figure: Figure 30: Combination of all the identified hotspots 100

110 10 Conclusion and recommendations for further studies and projects The extensive literature review related with this study revealed huge knowledge gaps regarding the cause and effect relationships on floods and droughts issues. While floods in the Lower Mekong basin have recently been well documented in the annual Mekong Flood Reports by MRC, a similar comprehensive database is not available for droughts. Thus we strongly recommend to strengthen the systematic drought risk assessment process for the Mekong River Basin. Drought risk assessment should go along with a comprehensive drought monitoring process involving ground and space based measurements. Conclusions drawn from GCM models regarding future climate or extreme events for the region vary widely depending on the choice of GCM, scenario family, downscaling method or subsequently employed hydrological model. The resulting uncertainties involved in past studies on future impacts of climate change were so drastic that a clear conclusion of this study is that no reliable information can be drawn from any study which would serve as a sound basis for decision making processes. In this regard it is extremely important to keep up and intensify ground monitoring of climate and hydrological parameters in order to eventually be able to detect trends and improve model validation with the goal to identify reliable models on future climate change scenarios. Regarding GCM and past trend analysis the only parameter which can be modeled reliably is temperature. As increasing evapotranspiration (next to reduced precipitation) is a key factor to determine drought hazard it is likely that those areas suffering from drought today are likely to be future drought risk hotspots. This is in particular true for the drought prone areas in Cambodia and north-eastern parts of Thailand. As these areas are also characterized by insufficient water storage capacities, these regions have a relatively low adaptation capacity to drought risks. Here drought impacts are likely to negatively impact local economy in terms of irrigation, drinking water supply, power and industrial production. An often quoted risk associated with the dry season is salt water intrusion. While an increasing sea level is likely to pose growing inundation and salt water intrusion risk to the Mekong Delta, the contribution of a potential lower dry season flow is not clear. In fact there is no trend yet indicating lower flows in the dry season nor any clear relationship between hydropower development or land use changes causing lower dry season flows. If major hydropower developments impact the low flow discharge they are more likely to increase them. While individual studies on impact of hydropower development on downstream hydrology do exist, there is a vast uncertainty regarding the cumulative effects of reservoir construction in the mainstream and in tributaries on the downstream hydrograph. While in theory the available storage capacity associated with the hydropower project could have a positive impact on floods by reducing peak discharge, the ultimate effects will depend on the way these reservoirs are being operated. We recommend a comprehensive study on the cumulative effect of planned hydropower projects considering different operational rules and the associated implications on hydrograph, energy production and irrigation security. Independent of the future magnitude of hydro-meteorological extremes and the high uncertainties involved as discussed in the previous chapter, it is certain that the Mekong system will remain to be characterized by a high level of seasonal and inter-annual variability of factors which determine or cause these extremes. Thus, analyzing in detail levels of vulnerability and 101

111 adaptive capacity of various sectors and societal strata in response to different types of hazards should be a focal task of future projects. To date, little is known about current levels of vulnerabilities in the different parts of the Mekong Basin. This is partially due to a lack of basic concepts to evaluate vulnerability. More fundamentally, there is a great demand to develop systematic approaches to understand and quantify vulnerabilities to climate extremes. In particular the growing urban centers posed the highest number of victims to flood events in the past and are likely hotspots of future risks. Thus we suggest analyzing in depth the urbanization processes in particular urban sprawl dynamics of fast growing cities like Vientiane, Phnom Penh and centers in the Mekong Delta like Can Tho. The study of published data and reports reveals an overall huge knowledge gap regarding meteorology, hydrology, land use maps and land cover change as well as local flood and drought risks. In order to tackle this fundamental deficit we recommend establishing systematic sub-basin inventories in close cooperation with the local stakeholders. This should lead to creating data bases at sub-basin level with a long term perspective to create reliable and significant time series. These data or basin inventories can serve to develop baseline data and allow tracking changes over longer time periods. They can serve as a common basis to discuss and develop basin development plans or early warning systems. Furthermore they can serve as a basis for feasibility studies and impact assessment of large infrastructure projects which will be accepted and supported by the local stakeholders as they will be involved from the beginning and develop a sense of ownership and acceptance for the data included in the inventory and resultant state of sub-basin reports. Additionally, such sub-basin inventories will support an informed and participatory decision making process on questions of future development, for example if a dam will be build or how it should be build and operated. For those hydropower projects where decision is already taken, particular emphasis should be placed on the immediate impacts during and after dam construction. Local impacts on land use, hydrograph changes but also opportunities (electricity, irrigation) for local people are very high. Projects should be designed to accompany reservoir construction and to support local people in better understanding the local environment and options to adapt and to benefit from the new situation. The fact that in many sub-basins as in the Mekong mainstream as well - reservoirs are constructed in a cascade or as multiple, interacting reservoirs in the same basin it is of utmost importance to develop approaches towards coordinated reservoir management. So far no clear rules, regulations, models exist to tackle this problem. This activity could also be addressed by the aforementioned basin inventories and data bases integrated in local approaches to river basin management. The huge data and knowledge gaps identified through this study should serve as an affirmation of the demand to create a sound knowledge base as the precondition for a thorough problem analysis and for subsequent decision making processes. In the MRB there seems to be a demand to develop in particular information and knowledge at the sub-basin level involving all relevant stakeholders of a basin community. Furthermore it still seems to be difficult to have access to information from the riparian countries. Mechanisms to share data i) between the Mekong river riparian countries ii) with the scientific community and iii) between the central and local level should be encouraged. 102

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127 Imprint Published by Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH Mekong River Commission - GIZ Cooperation Programme P.O. Box 9233 Vientiane, Lao PDR T ext 3061 mrc@giz.de Programme: Providing support to measures for adaptation to climate change in the Mekong region Responsible Dr. Philipp Magiera (philipp.magiera@giz.de) Editor Anja Waldraff (anja.waldraff@giz.de) Authors Lars Ribbe, Alexandra Nauditt, Dominic Meinardi, Matthias Morbach, Rike Becker Institute for Technology and Resources Management in the Tropics and Subtropics (ITT) Cologne University of Applied Sciences Cologne, Germany Design and layout GIZ Photo credits GIZ/Lucas Wahl, Disclaimer The analysis, results and recommendations in this paper represent the opinion of the author and are not necessarily representative of the position of GIZ Reproduction The manual may be reproduced in whole or in part in any form for educational purposes with prior permission from the copyright holder. Date of publication November 2013

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