Influence of intensive human activities on the propagation of meteorological to hydrological drought in the Southern Indian Peninsula

With cascading impacts on agriculture and the livelihoods of millions of people, drought is one of the most severe natural hazards affecting water and food security in India. While meteorological droughts occur due to an initial precipitation deficit, their propagation to streamflow depletion depends fundamentally on the catchment characteristics and natural and man-made water storage, which are increasingly modified by human interventions. Over the southern Indian Peninsula, where human influence on river systems is significant, the impact of large-scale human interventions on streamflow regimes and drought mechanisms remains poorly understood. In this study, we investigate how meteorological droughts propagate into hydrological droughts across 14 major river basins in southern India under natural conditions (i.e., without human influence on streamflow) and anthropogenic conditions (i.e., with human influence). Utilizing daily meteorological data (precipitation and temperature) from IMD and streamflow data (observed and model-simulated), we estimate various drought characteristics and propagation dynamics under natural and anthropogenic conditions for each streamflow station during the period 1986 to 2006.  Our findings indicate that human interventions to river systems notably delay the onset of droughts and reduce recovery periods, especially during severe events. Moreover, we show a significant difference between how natural and managed hydrological systems respond to meteorological droughts in peninsular river basins. Overall, our results highlight the role of human activities in modulating hydrological drought characteristics and emphasize the importance of considering human activities in evaluating drought risk and monitoring.