Increased Drought Synchronicity in Indian Rivers Under Anthropogenic Warming

Synchronous streamflow droughts across multiple river basins can lead to large-scale water scarcity and disruptions in food and water security. However, the drivers and changes in drought synchronicity across Indian rivers remain unexplored due to the limited length of instrumental records. Using streamflow observations and paleohydrological records, we reconstructed streamflow for 45 gauge stations on major Indian rivers, spanning 1200–2012 C.E., to examine the changes and drivers of streamflow drought synchronicity. Our reconstructed streamflow record for the past ∼800 years shows that streamflow drought frequency and synchronicity have increased during the recent period (1850–2012). While past major synchronous droughts in Indian rivers were associated with El Niño and positive Indian Ocean Dipole (IOD) conditions, the recent increase in streamflow drought synchronicity is linked with anthropogenic climate warming. Simulations of the Paleo Model Intercomparison Project Phase 4 (PMIP4-CMIP6) that include both natural and anthropogenic forcings confirm the role of anthropogenic warming in enhancing drought synchronicity. Our findings provide critical insights into the long-term variability of droughts in Indian rivers and underscore the growing risk of large-scale water scarcity.