Changing climate and water infrastructure affect Mekong water regimes: MRC joint study

The two factors interact and influence the amount, timing and water distribution within the Basin, said the Mekong River Commission (MRC)

The MRC has released the latest findings during its recent Regional Stakeholders Forum, which show that two key factors contribute to hydrological changes in the Lower Mekong Basin; natural factors, which include precipitation patterns, evaporation rates, soil properties and topography, and human activities, such as infrastructure development, water management, land cover and land-use changes. The organisation said these two factors interact and influence the amount, timing and water distribution within the Basin.

While climate-caused drought has adversely affected the mighty Mekong River in recent years, from the historic low flows of 2019–2021 to the rare “reverse flow” that has shrunk Cambodia’s vital Tonle Sap Lake, water infrastructure development is also a contributing factor, impacting the natural flow regime with increased dry season flow and reduced flood season flow.

The findings are part of the Joint Study on the Changing Pattern of Hydrological Conditions of the Lancang-Mekong River Basin and Adaptation Strategies in its Phase 1.

The joint study is jointly conducted by the MRC and Lancang-Mekong Water Resources Cooperation Center (LMC Water Center). They agreed to conduct this study in late 2019, as they expanded their previous collaboration. As this Phase 1 report notes; “In both 2016 and 2019, joint studies conveyed objective information about the severe droughts to the public and made scientific evaluations of the effects of water supplement from the Lancang reach to alleviate the drought conditions on the Mekong reach.”

Under the study, the two parties split their research into two time periods; when water storage dramatically increased from one period to the other between 2000 to 2009 when the LMB accumulated 20% of its storage; and then between 2010 to 2020 when 80% of it was collected at a time of growing irrigation demands, declining rainfall, and generally drier, drought-induced conditions. 

While storage increased over time even today, the regional water governance organisation noted that it amounts to some 27% of the Mean Annual Runoff (MAR) at Stung Treng in Cambodia, which is low compared with river basins in other drought-prone regions of the world. For instance, the Colorado River basin typically holds storage of more than 200% of the MAR. The MRC advocates for more Mekong storage to address future climate change, as well as for the coordinated operation of current storage, it further noted.

The recommendations

The joint study offers key recommendations, particularly a short-term recommendation that urges the riverine neighbours to further jointly study the different impacts of development and climate change along key parts of their common river as well as to share critical data including “real-time sharing of storage levels and hydropower operations”. Among the most significant passages within this report, it recommends that the Mekong partners enhance notifications of any sudden change in the ways water storage operates. 

“As global climate change and the associated droughts and floods will play an increasingly important role in driving the basin’s hydrological conditions, it is critical for basin countries to share more information on meteorological flow conditions, extending to tributaries,” the joint study recommended.

The study continues that real-time data on storage levels and hydropower operations is crucial for operational models and adaptive management. Long-term data on tidal changes, water and land use, and Mekong Delta groundwater levels support basin-wide research. The information-sharing platform proposed under the LMC cooperation framework provides an unprecedented opportunity, the study pointed out.

It also includes a call to action, beyond increased data sharing, with multiple medium-term recommendations that should be driven by “sound science and common understanding.” They include coordinated management of water resources, a comprehensive drought and flood management strategy, more joint studies, and a capacity-building plan for water policymakers, managers, engineers, and scientists, addressing knowledge gaps through formal and informal training.

The joint study in Phase 2 will embrace the recommendations, predict future trends in the evolving hydrology, and propose strategies for the riparian States to adapt to climate and demographic changes,  and continue their support for the Basin’s sustainable management and development.

Dr. Anoulak Kittikhoun, CEO of the MRC Secretariat, says this joint study symbolizes a deepening relationship and trust between the two sides. 

“It’s the result of an unprecedented level of effort that the MRC and LMC have invested in our existing cooperation,” Kittikhoun said. “Indeed, while we’ve conducted some joint research and studies before, this current effort sets a high bar. It truly shows a great commitment towards future cooperation between our two organizations.”