Convection‐Permitting Regional Climate Simulations Reveal Stronger Drying and Snow Loss in Semi‐Arid Mountainous Basins of Morocco

ABSTRACT Mountainous basins in semi‐arid regions are among the most climate‐sensitive environments, yet their hydro‐climatic processes remain poorly represented by regional climate models. This study provides the first hydrological evaluation of a convection‐permitting regional climate model (WRF3) with a spatial resolution of 3 km in mountainous basins of Morocco in North Africa, using a multi‐model hydrological framework (HYPE and GR4J‐CemaNeige). Results show that hydrological simulations forced by the convection‐permitting WRF3 model provide a better agreement with observed streamflow and a set of different hydrological signatures than those forced by the coarser, convection‐parameterized WRF20 model (20 km). Under the SSP5–8.5 scenario, the projections indicate precipitation decreases of 31%–62%, increases in potential evapotranspiration of 16%–27%, and streamflow reductions ranging from 64%–87%, depending on the climate forcing (WRF3 versus WRF20). There is a systematically stronger reduction in water resources in WRF3 projections than in WRF20 that is consistent across different basins. Snow contributions decline more strongly in simulations forced by the convection‐permitting regional climate model (WFR3), leading to a shift from a snow‐dominated to a predominantly rain‐dominated hydrological regime. These results highlight the added value of high‐resolution climate modelling in capturing fine‐scale mountain processes, strengthening the confidence in climate‐impact assessments, and also reveal the severe vulnerability of semi‐arid mountainous water resources to future warming. The more pessimistic scenarios obtained with the convection‐permitting regional climate model call for a reassessment of currently available scenarios for future water resources in semi‐arid mountainous regions obtained with coarse resolution climate models.