How do droughts influence catchment response and flood dynamics?

Droughts can substantially alter catchment hydrological behaviour by modifying  vegetation productivity and composition, soil hydraulic properties, surface water-groundwater interactions, and water storage. These changes can persist beyond the drought period, shaping catchment response to precipitation and subsequent flood dynamics. Yet, the influence of drought characteristics on catchment response remains unclear.

Here, we present a global-scale analysis of drought influence on catchment response to precipitation, using long-term satellite and in-situ observations from thousands of catchments worldwide. By employing multivariate statistical analysis, our analysis shows that drought events generally lead to significantly lower streamflow than expected from the historical norm. While arid and semi-arid regions show lower resilience to drought-induced changes in the streamflow-precipitation relationship, wet catchments, such as those in snow-influenced climates, show greater resilience due to their water-buffering mechanisms. In catchments with non-stationary streamflow-precipitation relationships, severe and prolonged droughts can lead to both positive and negative shifts in catchment response. These shifts can have implications for subsequent flood severity and flood timing.

Overall, our findings highlight the importance of accounting for drought characteristics and regional hydroclimatic differences when assessing catchment responses to precipitation and flood risk under and following drought conditions.