Drought influences on hydrological regimes

Persistent drought conditions may alter catchment response to precipitation, both during and after the drought period. Drought impacts on vegetation and hydrological dynamics may persist beyond the drought event, challenging accurate streamflow forecasting especially under flooding conditions. Yet, the influence of drought characteristics on the catchment response to precipitation remains unclear. In this study, we use a comprehensive dataset consisting of observations and remote sensing data of streamflow, precipitation, soil moisture, and total water storage for 3957 catchments worldwide. By employing multivariate statistical analysis, we identify significant abrupt shifts in the precipitation-streamflow relationship and examine the role of drought in driving these shifts. Our analysis shows that drought events may generally lead to significantly lower streamflow than expected from the historical norm during and after drought conditions. While warm-temperate and equatorial regions generally experience a slight decrease in streamflow during drought compared to expected values, arid regions predominantly exhibit an unexpected increase during soil moisture drought. In snow-influenced regions both increases and decreases of streamflow compared to expected were found. Notably, soil moisture drought events emerge as main drivers of hydrological regime shifts, particularly in snow-influenced and arid regions.  This study sheds light on the importance of considering regional characteristics in predicting dynamic catchment response to precipitation under and after persistent drought conditions.