<p class="MDPI12title">Assessing the Impacts of Climate Change on Precipitation and Evapotranspiration in the Guir Watershed: Implications for Water Resources in the Boudenib Oasis (Morocco)

The Boudenib Oasis in southeastern Morocco depends heavily on its limited water resources for domestic use and agriculture. However, climate change is expected to intensify water scarcity through changes in precipitation and evapotranspiration (ET). This study assesses the potential impacts of climate change on precipitation (P) and evapotranspiration in the Guir watershed using the Soil and Water Assessment Tool Plus (SWAT+). Historical (1984–2015) and future (2070–2100) simulations were conducted under the high-emission Representative Concentration Pathway (RCP8.5), driven by five bias-corrected global climate models (GCMs): GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2-HR, MRI-ESM2-0, and UKESM1-0-LL. Model outputs show a projected decline in annual precipitation of approximately 25–30%, from an average of 380 mm during the historical period to about 280 mm by 2100, and a reduction in ET of 15–20%, from roughly 380 mm to 314 mm. Despite uncertainties inherent in climate projections, consistent multi-model agreement increases confidence in these results. This study represents one of the first applications of SWAT+ in southeastern Morocco, providing new insights into hydrological responses to climate change in data-scarce arid environments. The findings highlight the urgent need for adaptive water management, integration of traditional systems such as khettaras, and sustainable land-use planning to strengthen resilience under future climate conditions.