Sensitivities of mean and extreme streamflow to climate variability across Europe

Abstract. Floods, droughts and changes in water availability are related to temporal variations in streamflow. Understanding how streamflow responds to variability in climate is an important aspect of regions’ hydrological resilience, particularly under climate change. Streamflow elasticities (ε) (or sensitivities) to climate describe observed percentage changes in river flow conditions per percentage change (or unit change) of a climate driver. Drawing on data from over 8,000 catchments, this study provides a pan-European quantification of elasticities of annual mean and extreme streamflow to annual and seasonal precipitation, and streamflow sensitivities to temperature. Results indicate that elasticities exhibit distinct regional patterns across Europe. As expected, annual mean, maximum, and minimum flows generally increase with higher and decrease with lower annual mean precipitation. A 1 % change in precipitation typically leads to an amplified flow response of >1 % in mean flows (ε~ = 1.2), an even stronger amplification in maximum flows (ε~ = 1.3), and a dampened response of <1 % in minimum flows (ε~ = 0.9). Temperature has a limited influence on annual streamflow, and its effects vary in sign (illustrated by both positive and negative sensitivities), but are relatively similar for mean, maximum and minimum flows. To reveal the underlying physical processes shaping regional differences in elasticities to precipitation, we use a random forest model with 20 climate and catchment factors. Results indicate that elasticities are not modulated by a single dominating factor but arise through complex combinations of catchment properties, likely including influences that are not well captured with the existing metrics, such as anthropogenic influences. This research advances understanding of hydrological resilience of mean and extreme flows to climate change. The regional and continental patterns of amplified and dampened streamflow response to climate can support water management and disaster risk mitigation across Europe.