Hydrological response to climate change across semi-arid sub-basins of the Tensift watershed, Morocco

The hydrological systems of watersheds are increasingly affected by climate change, resulting in altered rainfall patterns, more intense droughts, and disrupted runoff. This study analyzes the impacts of these changes on streamflow across eight sub-basins of the Tensift Basin. To achieve this objective, the GR2M hydrological model was applied using bias-corrected climate data from five RCM–GCM modelling chains (CNRM, CMCC, IPSL, GUF, and ICTP) from the Med-CORDEX initiative. Monthly streamflow was projected for the period 2019–2050 and compared with the reference period (1989–2019) under RCP4.5 and RCP8.5 scenarios. Eight sub-basins were analyzed. Precipitation data, provided by the Tensift Hydraulic Basin Agency (ABHT), were spatially distributed using the IDW method, while ERA5-Land temperatures were used to estimate potential evapotranspiration via the Hargreaves formula. The model showed variable performance across the eight sub-basins (KGE: 0.33–0.66 in calibration and 0.20–0.67 in validation; NSE: 0.23–0.54 and 0.17–0.62; PBIAS: -18.31 to 24.56). The results indicate mean temperature increases of + 1.50 °C under RCP4.5 and + 2.56 °C under RCP8.5 and mean precipitation of -29.37% and − 39.25%, respectively, over the future period (2019–2050) relative to the reference period (1989–2019). These changes are accompanied by mean projected streamflow reductions of 44.63% under RCP4.5 and 54.30% under RCP8.5, averaged across the five climate-model chains and eight sub-basins. These results highlight spatially differentiated hydrological sensitivity across the Tensift sub-basins and the relevance of considering these differences when evaluating adaptation options for water resources management.