Sensitivities of mean and extreme streamflow to climate variability across Europe

Abstract

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 7000 catchments, this study provides the first panEuropean 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. Annual mean, maximum, and minimum flows generally increase with higher annual mean precipitation. A 1 % change in precipitation typically leads to an amplified flow response of > 1 % in mean flows (median elasticity: ε̃=1.2), an even stronger amplification in maximum flows (ε̃=1.3), and a dampened response of < 1 % in minimum flows (ε̃=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 assess regional differences in elasticities to precipitation, we use a random forest model that considers catchment characteristics beyond commonly studied climate factors. Results indicate that elasticities are not modulated by a single dominant characteristic but emerge with complex combinations of catchment characteristics, likely including influences not well captured by typically available characteristics (e.g., anthropogenic influences). By revealing regional and continental patterns of amplified and dampened streamflow response across Europe, this research provides valuable insights into the hydrological resilience of mean and extreme flows to climate variability and climate change, and offers support for targeted water management and disaster risk mitigation.