A Review of the Integrated Effects of Changing Climate, Land Use, and Dams on Mekong River Hydrology

Abstract

Abstract:The ongoing and proposed construction of large-scale hydropower dams in the Mekong river basin is a subject of intense debate and growing international concern due to the unprecedented and potentially irreversible impacts these dams are likely to have on the hydrological, agricultural, and ecological systems across the basin. Studies have shown that some of the dams built in the tributaries and the main stem of the upper Mekong have already caused basin-wide impacts by altering the magnitude and seasonality of flows, blocking sediment transport, affecting fisheries and livelihoods of downstream inhabitants, and changing the flood pulse to the Tonle Sap Lake. There are hundreds of additional dams planned for the near future that would result in further changes, potentially causing permanent damage to the highly productive agricultural systems and fisheries, as well as the riverine and floodplain ecosystems. Several studies have examined the potential impacts of existing and planned dams but the integrated effects of the dams when combined with the adverse hydrologic consequences of climate change remain largely unknown. Here, we provide a detailed review of the existing literature on the changes in climate, land use, and dam construction and the resulting impacts on hydrological, agricultural, and ecological systems across the Mekong. The review provides a basis to better understand the effects of climate change and accelerating human water management activities on the coupled hydrological-agricultural-ecological systems, and identifies existing challenges to study the region's Water, Energy, and Food (WEF) nexus with emphasis on the influence of future dams and projected climate change. In the last section, we synthesize the results and highlight the urgent need to develop integrated models to holistically study the coupled natural-human systems across the basin that account for the impacts of climate change and water infrastructure development. This review provides a framework for future research in the Mekong, including studies that integrate hydrological, agricultural, and ecological modeling systems.

A Review of SWAT Studies in Southeast Asia: Applications, Challenges and Future Directions

“…Despite the problems caused by dams for fisheries and other riparian uses, pressure to create more sources of hydropower are resulting in construction of additional dams. This is an especially acute issue for the Mekong River system, where existing and planned dams have huge transnational implications that could result in severe degradation of available water resources [14][15][16]. Conversion of SEA tropical forested areas, due to land use shifts such as extensive logging or expansion of oil palm or rubber tree plantations pose additional environmental threats, including potential degradation of water resources, reduction of biodiversity and reduced total carbon biomass [17][18][19][20].…”

Hydropower’s hidden transformation of rivers in the Mekong

“…Unless in situ temperature monitoring efforts dramatically increase, the only way to monitor these changes towards sustainable water resources development will be through the use of satellite remote sensing data, like those used here. Even in the face of overwhelming evidence of the negative environmental impacts that dam development has caused and will cause, there are no signs of slowing dam development in the MRB (Dugan et al 2010, Grumbine and Xu, 2011, Orr et al 2012, Hecht et al 2018, Pokhrel et al 2018.…”

Evaluation of Available Global Runoff Datasets Through a River Model in Support of Transboundary Water Management in South and Southeast Asia

“…While the Mekong River Basin is also characterized by the intensity of its wet season (Hoang et al, 2019), the most critical ongoing hydrologic challenge is the expected increase of large hydropower dams on the main stem of the Lower Mekong River (Kummu and Sarkkula, 2008;Bonnema and Hossain, 2017). The proposed construction of 11 hydropower dams on the now freeflowing river (Orr et al, 2012) is anticipated to have a significant impact on the region's ecohydrology (Pokhrel et al, 2018) and aquaculture-the Mekong contains the world's largest inland fisheries (Hecht et al, 2019). These degradations are expected to continue to grow in the future with a total of 90 and 136 dams to be built within the Lower Mekong basin by the year 2030 and 2060, respectively (Räsänen et al, 2012).…”

“…Hoang et al (2019) used a hydrological model to study the impact of climate change, construction of dams and flow diversion on the future flow of the Mekong river. Similar efforts by Johnston and Kummu (2012) and Pokhrel et al (2018) have studied the expected evolution of the Mekong water resources in in the context of a changing climate.…”