Abstract
The significantly high water stress affecting Morocco during the past decades was an impact of drought and overexploitation of water resources. Therefore, assessment of these resources for better water management is a necessity. In our context, the High and Middle Atlas Mountains are the main contributors of downstream feeding within the country. The objective of this study is to assess rainfall and snowmelt runoff supplying groundwater of the aforementioned regions using the stable isotopes approach. Sampling campaigns and chemical and isotopic analyses were carried out in the Ourika and High Oum Er-Rbiaa sub-catchments, belonging to the great Tensift and the Oum Er-Rbiaa basins respectively. The snowmelt sampling in the Ourika basin was effectuated in two ways: the polyvinyl chloride snow cover boring and the passive capillary samples. The isotopic data of the Ourika basin allows estimating a recharge altitude between 2000 and 3000 m, following an altitudinal gradient of 0.27 parts per thousand/100m. The contribution of rainfall and snowmelt in groundwater recharge using the isotopic mass balance model suggests a snowmelt recharge rate of 47% while rainfall supplies about 53%. The isotopic preliminary results from the HOER catchment indicates that all samples are close to global and local water meteoric lines suggesting their common origin from the Atlantic air masses, and recharge altitude varies between 1600 and 2900 m according to a gradient of 0.27 parts per thousand/100 m. Ultimately, this study reveals the usefulness of environmental tracers to assess the endmembers contributions (snow and rain) to groundwater recharge at the catchment scale.