Impact of High-End Climate Change on Floods and Low Flows of the Brahmaputra River

Abstract

The release of high-resolution climatic projections through the Coordinated Regional Climate Downscaling Experiment (CORDEX) initiative provides unique opportunities to assess the risk of hydrological extremes in various world regions. The Brahmaputra is the second largest river in South Asia and is the main freshwater source of Bangladesh. Climate change in the Brahmaputra River Basin is a serious concern for Bangladesh, because of its possible influence on high flows (floods) and low flows (hydrological droughts). This research assesses the impact of climate change on the frequency, magnitude, and timing of extreme discharges and on the mean monthly discharges of the Brahmaputra River. Bias-corrected data from an ensemble of 11 climate projections with the representative concentration pathway (RCP) of RCP8.5 from the CORDEX-South Asia database were used to force the hydrological model Soil and Water Assessment Tool (SWAT). Results show that floods are likely to become more frequent in the future, and their magnitude will also become more severe. Hydrological droughts are projected to become less frequent in the future and their magnitude to become less severe. The average timing of both floods and hydrological droughts is projected to shift earlier compared to the present hydrological regime. Mean monthly discharges are projected to increase in the premonsoon months and decrease in the postmonsoon months.