Hydrological drought and flood extremes across Indian river basins using CAMELS-IND

Global climate change is altering hydrological extremes worldwide, yet how droughts and floods evolve jointly and what drives their changes in India remains poorly understood. Using the Catchment Attributes and Meteorology for Large-sample Studies – India (CAMELS-IND) dataset, we analyze long-term changes in hydrological drought and flood extremes across 55 minimally regulated Indian catchments (reservoir index < 0.25) during 1980–2017. Trends in annual minimum 7-day flows (Q7min) and annual maximum daily flows (Qmax) are quantified using robust non-parametric methods, and their concurrent behavior is classified using a quadrant framework. Results reveal widespread drying, with 38% of catchments exhibiting simultaneous declines in low and high flows, while only 13% show opposing trends indicative of divergence between extremes; remaining basins exhibit weak or mixed changes. Median trend magnitudes reach −3.3% per decade for drought flows and −4.5% per decade for flood flows. Fixed-effects panel regression shows that climate variability dominate streamflow changes, while terrestrial water storage anomalies significantly influence both drought and flood extremes, highlighting groundwater’s critical buffering role. In contrast, land-cover change shows weak or negligible effects. These findings provide the first India-scale, observation-based assessment of joint hydrological extremes and underscore emerging risks to long-term water security.