Ecological Reservoir Operation And Transboundary Cooperation In Lancang-mekong River Basin

The Lancang-Mekong River Basin is one of the most important transboundary basins in the world.Reservoir operations are increasingly being asked to consider environmental flow,which is necessary to sustain a healthy river ecosystem.Rapid economic development and population growth in this region make it imperative that water resources be used fairly and efficiently among all interested parties.In this paper,the effects of two large reservoirs on downstream flow regime are discussed,and the impacts of climate change and human activities on flow regime of the Mekong River are identified.A two-objective reservoir operation model that includes explicit IHA constraints is proposed.On this basis,an integrated hydrology-operation-cooperation model is developed.The effects of reservoir construction and operation on tranboundary cooperation in the Mekong River countries are analyzed.Streamflow data from 1960 to 2014 obtained from five gauging stations located along the Mekong mainstream are divided into three periods,i.e.,the pre-impact period(1960–1991),the transition period(1992–2009),and the post-impact period(2010–2014).The flow regimes were investigated using eco-flow metrics and indicators of hydrologic alteration(IHA).The results show that the construction and initial filling of the upstream dams reduced the annual streamflow in the upstream Chiang Saen gauging station,whereas no clear effect was observed in the downstream Stung Treng station.The construction and operation of dams clearly have significant impacts on low pulse duration.It is observed that climate change dictated the changes in the annual streamflow during the transition period 1992–2009(82.28%),whereas human activities contributed more in the post-impact period 2010–2014(61.88%).A series of formulae is developed to calculate IHA parameters without using a loop or conditional statement,which allows operators to manage environmental flow directly.An experimental operation of the Jinghong reservoir in the upstream portion of the Mekong Basin is conducted to apply the method.The economic objective is defined by hydropower production(HP),while the environmental flow objective is represented by a weighted aggregate eco-index(EI)based on IHA parameters.Five scenarios with different objective functions and constraints are compared,and the results show that the scenario with “HP–EI” as its objective achieved optimal benefits for both indices.Hard EI and explicit IHA constraints led to significant loss of HP that can be attributed to variations of inflow.To make this model more convenient for practical use,operation rule curves are regressed from the optimized results of the model.The implications of different strategies for dam construction by the river's five stakeholders(China,Thailand,Laos,Cambodia,and Vietnam)are accessed.Water benefits allocation is more sensitive in dry years when water resources are limited.Three cooperative game theoretical methods,namely,the Shapley value,the Gately point,and the Nash-Harsanyi solution,are employed to find the possible benefit allocation solutions.China will always obtain compensation from downstream countries in coalitions no matter which method is used,because China needs to operate its reservoirs for downstream countries' beneficial uses,while downstream countries' willingness to cooperate are rising with the increase of their reservoir storage capacities,especially in dry year.The ecological environment in the 3S(i.e.,Sesan,Srepok,and Sekong rivers)basin may be destroyed considerably.Results show that damming in the 3S basin may cause larger effects than damming in the upper Lancang-Mekong River Basin in the far future senario.