Estimating Socioeconomic Impact of Building Dams on the Mekong River Using an Integrated System Dynamics

Abstract

Dam construction is one typical way to utilize river, which retains water resources for drinking and irrigation, mitigates the effects of climate change, and yields electricity. The Mekong, which has been the only river running to the sea without dam through five of six riparian countries, is undergoing hydropower development nowadays amid rapid economic growth of Mekong riparian countries. The purpose of this study is to estimate sediment flux change and corresponding socioeconomic impacts of cascade dam construction on the Mekong River. For this purpose, statistical analysis and integrated system dynamics were employed as methodologies. In order to understand past effects of dams on the Mekong River and create variable for model validation, t-test, ANOVA test and multiple regression analysis are used. Season, Chinese cascade dam construction, and stations are all significant as to put in the model. By multiple regression analysis, it is shown that Chinese dam construction has a significant effect on suspended sediment concentration in the Lower Mekong Basin with other variables controlled. With the equation from multiple regression, estimated suspended sediment concentration data for each station is produced. Possible impacts of existing Chinese dams on the Mekong mainstream are modelled using system dynamics approach. The model shows same trend with actual sediment load data. Sediment load shows decreasing trend after Chinese dam construction, but the rate of decrease is 10%, which is smaller than that of previous studies. It can be because this study reflects dynamic feature of trapping capacity of dam reservoirs. The impacts of future dam constructions are modelled and discussed. Four scenarios with different number of dams in the Lower Mekong Basin are built. According to the results of the model, additional six dams in scenario B trap 140 million tons of sediments more, three more dams in scenario C trap 150 million tons of sediments more, and Sambor dam in scenario D traps 270 million tons of sediments more. The effects of dam constructions in the Upper Mekong Basin seem larger than the effects of dams in the Lower Mekong Basin, but the effects of Chinese dams mitigated by the distance. The net present value of costs of cascade dam construction is estimated from 1.57 to 4.72 billion US dollars. This study is an attempt to account for not only environmental impact but also agro-economic impact related to dam constructions. Integrated system dynamics can act as an effective tool to integrate various knowledge so that make stakeholders understand and take into account transnational impact of dam construction.