Mapping hydrological drought under the CMIP6 climate change scenarios at the sub-basin scale: A case study in the upper part of the Dong Nai river basin

Abstract

Hydrological droughts have become more severe due to the compounded effects of climate change and anthropogenic activities. This study aims to assess how climate change could impact hydrological droughts at the sub-basin scale for the Upper Part of Dong Nai (UPDN) river basin. The study used the Soil and Water Assessment Tool (SWAT) to simulate hydrological conditions based on climate change scenarios of SSP2-4.5 and SSP5-8.5 from the CMIP6 projections for the future period of 2030s (2021-2040) and 2050s (2041-2060). The streamflow drought index (SDI) was applied to evaluate the drought severity and frequency. The findings indicate a clear increasing trend in minimum (Tmin) and maximum temperatures (Tmax) relative to yearly rainfall. Under the SSP2-4.5 scenario, yearly rainfall shows a slight increase. However, under the SSP5-8.5 scenario, annual rainfall has a slight increase in the West-Southwest and a decrease in the East-Southeast regions. Rainfall trends show a decrease in the dry season and an increase in the rainy season. The frequency and severity of hydrological droughts can vary between sub-basins. Da Tam, Don Duong, Da Quyn, Da Dang, Dak Nong, Dong Nai 2 and Dak R‘Keh are the sub-basins that have more extreme drought conditions compared to the rest of the basins. These results emphasize the need for targeted drought management strategies in the UPDN river basin to build resilience against future climate impacts.