Hydrological regime change and water scarcity in a semi-arid lacustrine ecosystem: A case study of lake Abkhan (Middle Atlas Mountains of Morocco) using remote sensing and drought indices

This study examines the determinants of hydrological degradation of Lake Abkhan, an endorheic wetland in the Middle Atlas Mountains of Morocco, over four decades (1984-2024). The methodological approach combines the analysis of drought indices (SPI, SPEI), remote sensing (Sentinel-2) from 2015 to 2023 to assess lake dynamics and land cover, as well as statistical methods (Pettitt test, correlations). The results reveal a major hydrological disruption in September 2019, marking the beginning of a chronic structural drought. From 2015 to 2023, the lake's surface area shrank by 94.67%, from 25.91 to 1.38 hectares. Simultaneously, human impact on the watershed accelerated, with irrigated agriculture expanding by 181%. Statistically, temperature is the strongest predictor of this contraction (r = -0.576, p < 0.001). The increase in evapotranspiration demand, exacerbated by massive agricultural withdrawals, has now exceeded rainfall. In conclusion, the collapse of Lake Abkhan is the result of a destructive synergy between climate change and human pressures. The long-term viability of this hydrosystem requires an urgent overhaul of water management and strict regulation of irrigation in the face of these new arid conditions.