Comparing hourly climate change projections for hydrology in a Mediterranean meso-scale catchment

The 42 km 2 Claduègne catchment in southern France, under Mediterranean climate is subject to long, dry summers with limited water resources and intense, convective storm events leading to flash floods and overland flow (OF). The impact of simulated mid- and end-century climate on hydrology, specifically seasonality, hydrological extremes (high and low flows), and flow processes (OF versus groundwater GW) was investigated, using hourly climate projections and a spatially distributed process-based hydrological model (J2000P). Potential differences between native hourly projections with a convection-permitting regional climate model (CP-RCM) and temporally downscaled projections were evaluated. All projections agreed on a longer and drier summer. Simulated low flows decreased significantly throughout the century, while flood discharge may increase by the end of the century. A higher overland flow and lower GW contribution were projected in the future due to a changed temporal distribution of precipitation. The CP-RCM improved simulated sub-daily extreme precipitation and seasonal distribution of flow generating processes compared to temporally downscaled projections. There were no notable advantages for the simulation of streamflow extremes or other hydrological variables. • Five hourly climate projections + distributed process-based hydrological model. • More overland flow & less groundwater contribution in the future. • Substantially lower low-flow from the mid-century, higher flood peaks in the end. • Implications for water supply, flood management & contaminant transfer. • Evaluation of advantages of convection-permitting models for hydrology.