Temporal drought dynamics in Germany: climate and catchment controls

Hydrological droughts result from the propagation of meteorological drought through the terrestrial hydrological system. Their temporal dynamics, including onset, development, intermittency, and recovery, show pronounced spatial variability reflecting different climatic and catchment controls. These characteristics are critical for drought risk management because they control the timing, magnitude, and persistence of water deficits, with implications for water supply, agricultural water demand, aquatic ecosystems, and energy production. Despite their importance, these temporal characteristics are seldom examined, and their controlling factors remain insufficiently quantified.

Here, we investigate the climatic and catchment controls on the temporal dynamics of hydrological drought using observations of precipitation, streamflow, and groundwater levels from 132 German catchments for the period 1951 to 2020. Using the Variable Threshold Method, we identify 1,574 hydrological drought events and characterize their onset, development, intermittency, and recovery times. We examine the spatial variability of these characteristics across the study catchments and identify the controls underlying their similarity, including the synchronization between precipitation and evapotranspiration seasonality, catchment storage capacity, and groundwater-surface water interactions (gaining-losing conditions). Within catchments exhibiting similar drought dynamics, we then examine how temporal variations in gaining-losing conditions affect drought onset, development, intermittency, and recovery.

Our findings advance mechanistic understanding of drought dynamics and support improved water resources management under increasing climate variability.