Warming-Induced Changes in Potential Surface Water Availability across Indian Dams

Abstract Dams in India collectively store around 400 BCM of freshwater and play a crucial role in national water security. However, the water available to these reservoirs is increasingly vulnerable to climate change and poorly understood at the dam-catchment scale in a warming climate. In this study, we evaluate changes in potential surface water availability across 5687 Indian dam catchments during the observed period (1951–2022) and the future periods (2031–2065: mid-period; 2066–2100: end-period) using VIC-simulated total runoff. During the observed period, our analysis shows a significant increase (by more than 20%) in potential surface water availability across the majority of dam catchments in Western and Southern India, while a decline of more than 15% in the dams located in the Southern Gangetic Plains and Eastern India. These changes in potential surface water across the majority of dam catchments are associated with systematic shifts in monsoon-season rainfall and rainy days during the recent period (1987–2022), which result in frequent consecutive surplus/deficit years and changes in precipitation partitioned into runoff during recent warming. Consistent with the observations, we find a similar shift in potential surface water availability in the future climate, indicating further increases (decreases) in dam catchments in the Western and Southern (Eastern) regions of India under all four SSP scenarios during the mid- and end of the century. Based on these changes in potential surface, effective water sustainability strategies can be prepared at the dam-catchment scale (such as capacity augmentation of existing dams, inter-basin water transfer) to provide an evidence based prioritize future investments in dam infrastructure in India.