Impacts of climate change and reservoir operation on droughts: a case study in the Upper Part of Dong Nai River Basin, Vietnam

ABSTRACT This study aims to investigate the impacts of climate change and reservoir operation on drought in the Upper Part of Dong Nai (UPDN) River Basin. Climate change scenarios for the UPDN River Basin were portrayed according to the Coupled Model Intercomparison Project Phase 6 (CMIP6) based on an ensemble of five general circulation models (GCMs), namely, EC-Earth3-Veg, CanESM5, EC-Earth3, HadGEM3-GC31-LL, and CNRM-CM6-1-HR for two Shared Socioeconomic Pathway scenarios, SSP2-4.5 and SSP5-8.5. The historical climate monitoring data at five weather stations and three hydrological gauges related to upstream reservoirs in the period 1990–2020 were collected. The streamflow for the period 2021–2099 was simulated by applying the Soil and Water Assessment Tool (SWAT) model. Two meteorological and hydrological drought indices of the 6-month time scale, namely, standardized precipitation index (SPI6) and streamflow drought index (SDI6), were calculated through designed modules integrated in the Drought Index Calculator (DrinC) software. The results show that climate change coupled with reservoir operation has seasonally changed the runoff, which has changed the drought situation in the entire basin. The lag time variations of hydrological drought in response to meteorological drought were significant in the main basin of the UPDN River Basin. These findings provide useful information for managers and policymakers in sustainable water resources management and development adapting to climate change.