Drought risk and hydrological changes in the Ganga River Basin, India

Droughts pose significant threats to water resources, agriculture, and livelihoods in the Ganga River Basin, a region highly dependent on monsoon rainfall and home to over 500 million people. Despite increasing climate variability, comprehensive assessments integrating multiple drought indicators remain limited. This study aims to address this gap by analyzing long-term trends in precipitation, temperature, and evapotranspiration (ET) from 1980 to 2020, and evaluating drought conditions using the Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI) at 3, 6, and 12-month time scales, and Evaporative Stress Index (ESI) at multiple time scales. Results reveal significant declining trends in seasonal precipitation and rainy days, coupled with rising ET, particularly during the monsoon and pre-monsoon periods. Minimum temperatures show consistent increases across seasons, while maximum temperatures exhibit moderate changes. Drought indicators demonstrate increasing frequency and severity of hydrological and meteorological droughts in central and southern regions of the basin. The findings highlight the urgent need for region-specific adaptive water management strategies to mitigate the increasing drought risks and ensure sustainable water availability in the Ganga River Basin. • Significant decreasing trends in monsoon, post-monsoon, and winter precipitation identified using Modified Mann-Kendall test and Sen's slope analysis. • Increasing evapotranspiration trends observed during pre-monsoon and monsoon seasons, indicating higher atmospheric moisture demand. • Spatial variability in extreme precipitation events (R99, R95 indices) with increasing trends in eastern regions and decreasing trends in central and western regions. • Frequency of long-term droughts (SPI-6, SPI-12) intensifying in central and southern Ganga River Basin. • Minimum temperatures show statistically significant increasing trends across all seasons; maximum temperatures exhibit mild seasonal variability. • Analysis emphasizes growing hydrological stress and the need for region-specific adaptive water management strategies.