Increases in Water Balance‐Derived Catchment Evapotranspiration in Germany During 1970s–2000s Turning Into Decreases Over the Last Two Decades, Despite Uncertainties

Abstract

AbstractUnderstanding variations in catchment evapotranspiration (EC) is critical as it directly affects water availability for humans and ecosystems. Previous studies found increases in EC in Central Europe over recent decades, but fixed study periods may not fully reveal inter‐decadal hydroclimatological variability. We performed a multi‐temporal trend analysis of water balance‐derived EC for 461 German catchments and the period 1964–2019. We accounted for previously often neglected changes in storage and uncertainties in precipitation. EC generally increased throughout Germany during 1970s–2000s (>2 mm year−2), while it showed milder changes and decreases afterward. These variations were robust to uncertainties in precipitation (median relative uncertainty of 26%) and broadly coherent with sparse plot‐scale data. Variations in EC were related with variations in precipitation and radiation, with a potentially increasing influence of precipitation after 2000s. These findings provide a reference for synthesizing current knowledge on variations in EC and their uncertainties.