Altered Hydrological Response and Water Availability of Indian Dams under Observed and Changing Climate

The Indian Subcontinent comprises approximately 5,700 dams, many of which are decades old, to fulfill the water demands of the agricultural, domestic, and industrial sectors. However, hydrological response and water availability in these dam catchments have either significantly changed or are expected to change under global warming. To effectively manage the water resources storage and water supply in the densely populated and agriculturally driven region, here, we assessed the changes in hydrological components and water availability in 5700 dams over India during the observed (1951-2022) and future warming climate (2031-2065: mid period; 2066-2100; end period). Using the Variable Infiltration Capacity (VIC) model, we simulated water budget components across the Indian Subcontinent during both the observed period and the future period to evaluate alterations in hydrological response and water availability. Our results showed that runoff-induced water availability has increased significantly in the Sabarmati, Pennar, Cauvery, and South Coast River basins, and decreased in the Ganga and Brahmaputra River basins, during the observed period. Moreover, we found that the majority of Indian dam catchments (except those in the Ganga and Brahmaputra River Basins) experienced a significant increase in monsoon precipitation and total runoff over the past three decades (1986-2022). Based on future analysis, we also found that nearly half of the dam catchments in the end period under SSP5-8.5 experienced around a 25% increase in monsoon precipitation and total runoff, which affects the reservoir operation and dam functionality in a future warming climate.