By altering evapotranspiration and influencing how water is routed and stored in a basin, natural and agrarian ecosystems affect river flow. To quantify the impact of ecosystems on streamflow in two large river basins in Asia and Africa, simple statistical relationships were calculated, enabling flow characteristics to be ascertained from basic catchment features. This approach allows the impact of specified land-use change on streamflow to be determined. For example, it shows that extending paddy areas in the Mekong River Basin reduces downstream low flows, while conversion of forests to crops increases the magnitude of downstream floods in the Volta River Basin. The approach could assist river basin planners to better account for flow-related ecosystem services.
This Brief provides a cross-sectional analysis of development-directed investments in the wider Mekong region. The wider Mekong region includes Laos, Cambodia, Thailand, Vietnam, Myanmar, and the Chinese province of Yunnan. Evidence highlights that a few critical dynamics, including human migration, natural resource flows, and financial investments, generate a high level of connectivity between these countries. Such high levels of connectivity increase complexity and the potential for ripple effects of national decisions. The emerging links between countries can unfold in financial investments, migration, or the flow of resources. As these links intensify the regional connectivity increases and over time a highly connected region can emerge, as experienced by the Mekong region. This Brief also contains a chapter at the end of the book featuring numerous charts and diagrams further illustrating the impact of development activities in the area.
The Mekong River Basin: Ecohydrological Complexity from Catchment to Coast, Volume Three presents real facts, data and predictions for quantifying human-induced changes throughout the Mekong watershed, including its estuaries and coasts, and proposes solutions to decrease or mitigate the negative effect and enable sustainable development. This is the first work to link socio–ecological interaction study over the whole Mekong River basin through the lens of ecohydrology. Each chapter is written by a leading expert, with coverage on climate change, groundwater, land use, flooding drought, biodiversity and anthropological issues. Human activities are enormous in the whole watershed and are still increasing throughout the catchment, with severe negative impacts on natural resources are emerging. Among these activities, hydropower dams, especially a series of 11 dams in China, are the most critical as they generate massive changes throughout the system, including in the delta and to the livelihoods of millions of people and they threaten sustainability. Presents an extensive collection of eco-hydrological changes in the river basin driven by both nature and anthropological factors Provides state of the art modeling, data analysis methodologies for complex socio-ecological complexity applied in the Mekong river basin Includes specific cases of ecohydrology in the river basin, especially from the Mekong delta
Water is essential for all living things on the planet, growing the economy and sustaining the world's ecosystems. Human-made water infrastructure regulates about three-quarters of the world's river networks to meet the socio-economic development demand. A common approach applied involves upstream regulation of major rivers. However, this can significantly change river flow regimes and stages downstream. Many studies have assessed the impact of the use of surface water for hydropower development via scenarios and estimation of environmental consequences on river flows, fisheries, aquaculture, and livelihoods. However, little is known of the impact of change in the river flow regimes, as consequences of anthropogenic factors, on surface water-groundwater interactions and groundwater systems. This thesis contributes to reducing this knowledge gap by studying these impacts and effects by comparing the pristine and post-dam conditions of the Nam Ngum River Basin, a major tributary of the Mekong River in Laos. -- This research addresses the impact of human activities and climatic factors from the pre- to post-dam period on river flow regimes and connected groundwater systems. Specifically, the aims of this research are as follows: (1) evaluating the impacts of anthropogenic induced changes in water yield by observing the trends and driving factors; (2) assessing the impact of irrigation water, diverted from the surface water, on different water balance components (i.e., groundwater recharge, actual evapotranspiration, surface runoff, and interception); (3) evaluating the impact of river stages, as a consequence of hydropower reservoir operations, on downstream groundwater systems. The body of the thesis consists of five chapters: Chapter 1 provides a global overview of river regulation and describes the geographical context for the study area with problem statements, research aims and contribution of the PhD research, while the main part of the thesis is Chapter 2 to 4, which are written in the style of potential academic papers. Chapter 5 provides a summary of the main findings and conclusions from the three main chapters of the thesis as well as suggestions for the importance of future research. -- The first part of this research (Chapter 2) examines the historically observed river flow patterns caused by anthropogenic and natural hydroclimatic drivers and investigates factors that significantly affect the river flow regime. This part also estimates how the river flow affects the water yield in a downstream basin (water productivity generated in the basin) from the pre- to post-dam period. Methods used are statistical trend analysis of relevant indicators such as GRACE total water storage, soil moisture, and actual evapotranspiration. The results show that the river flow was highly seasonal under pre-dam conditions, and the river was losing water to the groundwater in the dry season. However, in the post-dam period, the monsoonal peak flow decreased by 39%, while the flow increased by 120% in the dry season. Moreover, the river has become gaining year-round from 2001 onwards. It is concluded that the water infrastructure has a greater impact on the river flow regime than the climate-related factors. The annual and dry season water yield exhibit an increasing trend from the pre- to post-dam period. -- The second part of the research (Chapter 3) evaluates the impact of irrigation water diverted from the river on groundwater recharge and other water balance components. This part aims to assess which portion of the groundwater recharge comes from irrigation schemes and will likely influence water yield in the downstream basin. The recharge and water balance components are quantified for the two different conditions: without irrigation schemes (pre-dam) and with irrigation (post-dam). The methodology is based on the WetSpass-M model. Estimated recharge is compared with assessments of the Water Table Fluctuation (WTF) method, showing an excellent agreement. It is concluded that irrigation has caused a relatively minor increase in groundwater recharge with an average of additional recharge (2012-2014) of 83 mm within the command irrigated areas and 6 mm for the basin-wide increase, resulting in a minimal influence on the water yield in the downstream part of the basin. The annual average recharge with irrigation schemes is assessed to be 444 mm, equivalent to 19% of the average annual rainfall. -- The final part of the research (Chapter 4) investigates the impact of changes in river flow regime and river stages due to upstream reservoirs on surface water-groundwater interactions and groundwater systems in the downstream part of the Lower Nam Ngum River Basin. Elements studied are the river-groundwater budget, water table, and groundwater balance in the pre- and post-dam periods. The study develops an interpretive groundwater conceptual model, which focuses on demonstrating the status of groundwater systems when river stages are changed. The model is simulated for the pre- and post-dam conditions using the recharge estimated in the second part of the thesis, observed river stages, and aquifer properties obtained from well-tests. The result shows the status and change in river interaction. In the pre-dam period, the river and its tributaries were losing in the rainy season and gaining water in the dry season. However, they have become gaining year-round in the post-dam period, except for two tributaries upstream exhibiting slight changes from the pre- to post-dam period. The surface water-groundwater exchange has significantly declined in the post-dam period compared to the pre-dam period; the amount of water lost and gained by the river system has reduced by 53% and 23%, respectively. The total amount of water entering and leaving the groundwater system also declines by 22% compared to the pre-dam period. The increase in river stages in the dry season has raised the groundwater tables in the riparian and downstream areas in the post-dam period. Apart from a number of benefits from damming and regulating large rivers (i.e., energy production, flood and drought mitigation, and irrigation development), these research findings show the impacts of dam development on groundwater systems. The reduced surface water-groundwater interaction in the post-dam condition also has potential consequences for reduced hyporheic exchange and hence increased vulnerability of the surface water-groundwater quality and ecosystems in the lower basin.
The Mekong is the most controversial river in Southeast Asia, and increasingly the focus of international attention. It flows through 6 counties, China, Myanmar, Laos, Thailand, Cambodia and Viet Nam. The 4 downstream countries have formed the Mekong River Commission to promote sustainable development of the river and many of their people depend on it for their subsistence ? it has possible the largest freshwater fishery in the world, and the Mekong waters support rice agriculture in the delta in Viet Nam (which produces about 40% of that country's food) as well as in Cambodia, Laos and Thailand. China is now building the first large mainstream dam on the river, and has proposals for several more. These dams are likely to affect the downstream countries. Several of the downstream countries also have plans for large scale hydropower and irrigation development which could also impact the river. This book will provide a solid overview of the biophysical environment of the Mekong together with a discussion of the possible impacts, biophysical, economic and social, of some possible development scenarios. It is intended to provide a technical basis which can inform the growing political and conservation debate about the future of the Mekong River, and those who depend on it. It is aimed at river ecologists, geographers, environmentalists and development specialists both in the basin and (especially) outside for whom access to this material is most difficult. This book will be the first comprehensive treatment of the Mekong system. The first comprehensive overview of all aspects of the Mekong River system Deals with a regionally critical ecosystem and one under threat The Mekong supports the world's largest freshwater fishery and provides water underpinning a major regional rice paddy system Presents the authoritative findings of the Mekong River Commission's research for a wider audience for the first time outside of limited distribution reports
Water-related infrastructure could contribute significantly to the development of the Mekong region. At the same time, poor water infrastructure could lead to development challenges for the countries in the region. Innovation for Water Infrastructure Development in the Mekong Region discusses the challenges facing the region as well as the possible innovative policy options, including those used in Emerging Asian countries, and with reference to the experiences of OECD member countries.
This book about the Mekong Delta presents a unique collection of state-of-the-art contributions by international experts from different scientific disciplines about the characteristics and pressing water-related challenges of the Mekong Delta in Vietnam. The Mekong Delta belongs to one of the areas, which are to expect the largest challenges concerning environmental change and climate change induced sea level rise . The Delta acts as the “rice bowl” of Southeast Asia and is home to over 17 Million people, who need to cope with ecologic as well as socio-economic changes linked to the rapid economic development of the country. Annual floods, severe droughts, salt water intrusion, degrading water quality, tropical cyclones, hydrologic changes due to hydropower projects in the upstream of the Mekong, coastal erosion, and the loss of biodiversity are some of the problems in the region. Heterogeneous resource management responsibilities, and the fact that the Mekong – and thus also the Delta – is influenced by six countries aggravate the situation. Integrated water resources management and fostered cooperation and information exchange are pressing needs for the sustainable development of the Delta.
Environmental flows (EF) are an important component of Goal 6 (the ‘water goal’) of the Sustainable Development Goals (SDGs). Yet, many countries still do not have well-defined criteria on how to define EF. In this study, we bring together the International Water Management Institute’s (IWMI’s) expertise and previous research in this area to develop a new methodology to quantify EF at a global scale. EF are developed for grids (0.1 degree spatial resolution) for different levels of health (defined as environmental management classes [EMCs]) of river sections. Additionally, EF have been separated into surface water and groundwater components, which also helps in developing sustainable groundwater abstraction (SGWA) limits. An online tool has been developed to calculate EF and SGWA in any area of interest.
Hori, a consulting engineer, describes the ecosystem, flow, and water quality along the Mekong River basin, as well as current conditions and future possibilities for development. He then relates what water management has been done in the Mekong, and why, demonstrating how international thinking and action have evolved since 1958. Over the years, more attention has been given to the social and economic condition of the indigenous people, investigations into the relationships between human activity and the quality of ecosystem processes has changed, and methods of assessing the need for hydroelectric power and the consequences of proposed reservoirs has evolved. c. Book News Inc.
