Chemical Tracers and Stable Isotopes Mixing Models for Groundwater Quality and Recharge Study in the Moroccan High Atlas Mountains

Abstract

A common global practice in the High Atlas Mountains is upstream water storage in dammed reservoirs that captures mountainous snowmelt, and downstream agriculture irrigation. However, the intensive use of water for irrigation, coupled with the effects of climate change, makes the region subject to high water stress. This implies the establishment of an integrated management system adapted to such water resources. Effective management of groundwater requires good control upstream of the different sources of supply and their contribution. Thus, we conducted a study on the contribution of the components snow and rain recharge of surface water and groundwater in the High Atlas, using chemical and isotope investigations. The isotopic results from the 2 sites upstream catchments (Souss and Tensift) compared to those obtained in the Draa basin highlight the importance of spatial and temporal variabilities of isotopic signal, which may impact quantifying the contributions of snowmelt to stream flow and groundwater. Using the stable isotope mixing model, the contribution of runoff derived from snowmelt (SN) ranges between 42 and 75% in the headwaters of the studied catchments, while the component of rainfall is 25–58%. The low mineralized waters from the High Atlas induce a dilution of the water salinity in the neighboring plains (Souss, Tensift and Draa). The results could be used to help refining hydrological conceptual models at various scales.