Discharge-based classifications of spatio-temporal patterns of potentially gaining and losing subcatchments in the Bode River catchment, Central Germany

Study Region: Bode River catchment in Central Germany Study Focus: Streamflow shortages driven by low runoff yield and water losses from streams to groundwater are gaining attention amid rising water demand and climate change, which threaten ecosystems and water security. To identify the former phenomena at the subcatchment scale, we present a transferable conceptual approach that classifies subcatchments as high-yield (potentially gaining hotspots) or low-yield (potentially losing hotspots) based on whether their specific discharge exceeds or falls below the catchment average. The method is tested on 18 gauged subcatchments of the Bode River catchment in Central Germany across long-term, annual, and monthly timescales. New Hydrological Insights for the Region: Lowland agricultural subcatchments are predominantly low-yield at the long-term scale, whereas mountainous forested/seminatural subcatchments are mainly high-yield. Comparison with a well-established water balance approach confirms the method’s ability to identify potentially gaining and losing hotspots while reducing uncertainty, as it relies solely on observed discharge rather than precipitation and evapotranspiration data, which are often uncertain. Seasonal analysis reveals dynamic transitions between yield states that the water balance method cannot capture: high-yield subcatchments tend to shift to low-yield in summer, while low-yield subcatchments show higher relative discharge during the same period. Annual analyses also indicate that high-yield mountainous subcatchments are more resilient to prolonged dry conditions. This study provides a proof-of-concept for a simple and transferable approach, which relies on discharge observations only to obtain spatially and temporally differentiated insights into water yield and potentially gaining and losing conditions across gauged catchments.