Assessment of climate change impacts on the streamflow for the Mun River in the Mekong Basin, Southeast Asia: Using SWAT model

Abstract The typical warm and wet regions of Southeast Asia have significant water resource issues. Deep insight of the future streamflow in the region is therefore necessary for effective water resource management and prediction. We coupled the Soil and Water Assessment Tool (SWAT) with a downscaling method (Delta) and global circulation models (GCMs) in the Mun River Basin (MRB), in Thailand under three Representative Concentration Pathways (RCPs). The results show that the calibrated SWAT model can accurately characterize the hydrological process on the daily, monthly, and yearly terms. The future monthly minimum temperature would rise by >1.5 °C, >2 °C, and >3 °C in the 2030s, 2060s, and 2080s respectively, under all RCPs (2.6, 4.5, and 8.5), which would also occur at the maximum temperature. The temperature increase in dry season was more significant than that of the wet season. The average annual precipitation decreased in the 2030s, and increased by 8.9%, 12.8%, and 13.9% in the 2060s under the three climate scenarios, respectively. Moreover, precipitation from June to September in wet season markedly increased. The streamflow was projected to increase by 10.5%, 20.1%, and 23.2% during 2020–2093 under three climate scenarios, respectively. Monthly average streamflow increased from June to September and decreased from February to May, and the dry seasonal streamflow decreased by 1.1%-37.2%. These changes in flow were closely related to climate change. Monthly flow changes were negatively related to temperature (p