Dominant and compounding drivers of monthly-to-multi-year streamflow droughts in Central Europe

Streamflow droughts originate from the interplay of dominant atmospheric processes (i.e., deficits in rain or snow) and compounding conditions at the land surface, specifically evapotranspiration (E) and sub-surface storage. Furthermore, these events can last from a few weeks to multiple years. The dominant drivers of streamflow droughts depend on event type and catchment characteristics. Yet, how dominant and compounding drivers of streamflow droughts vary from monthly to multi-year events and across the landscape remains unclear. To address this knowledge gap, we use a large sample of near-natural catchments in Central Europe. For this case study, we quantify the relative contribution of (i) deficits in rain and snow and (ii) anomalies in E and S to streamflow droughts of varying duration (from monthly to multi-year). To do so, we blend data from ground-based observations, reanalysis datasets, and hydrological modelling covering the last four decades. We show that the contribution of different hydro-climatological processes to streamflow droughts varies with drought duration, onset time, and catchment characteristics. By providing a synthesis of the hydro-climatological drivers of streamflow droughts for a variety of time scales and catchment types, this study can assist regional drought monitoring and management.