ANALYSIS OF WATER INFRASTRUCTURE DEVELOPMENT AND CLIMATE CHANGE IMPACT ON THE STREAMFLOW IN THE LOWER MEKONG RIVER BASIN

Abstract

 In the recent decade, many projects of water infrastructure development namely, hydropower development and irrigation expansion have been rapidly increasing and are expected to have more in the Mekong River Basin, thus the substantial influence on the streamflow of the Mekong mainstream are unavoidable. Also, climate change is the dominant driving factor affecting the streamflow regime. For better water resource management for the Mekong River Basin, this study aims to assess the streamflow change driven by these drivers, i.e., hydropower development, irrigation expansion, and global climate change based on the SWAT model simulations. The results show that hydropower and irrigation development have limited impacts on annual flows under 2040 development scenarios compared to the early development period. However, climate change can reduce the streamflow up to 13%-36% and 14%-62% in June between 2040 to 2080 for RCP4.5 and RCP8.5 scenarios, respectively, while the streamflow is projected to increase up to 45%-85% and 65%-130% in October between 2040 to 2080 for RCP4.5 and RCP8.5 scenario, respectively. Furthermore, the streamflow shows significant increases in the long-term period during SeptemberNovember and December-February, but decreases during March-May and June-August. Whilst, hydropower decreases the streamflow in the wet season by 7%, but increases in the dry season by 29%. And, for the irrigation, there is not much impact on the streamflow, but it shows substantial flow reductions during the dry season and up to 18% in the middle part to the lower part of the basin. Furthermore, the combined impacts of all driving factors cause substantial flow reductions during the first half of the wet season (-42%), but increase the flow in the dry season by 40% and 14% compared to the early development and nearly current scenario, respectively. This result can be a reference for water management in the Mekong River Basin, particularly flood and drought management as well as agricultural production planning.