Hydrogeology of the Ribat El-Kheir Plateau and Its Relationship with Tectonics, Middle Atlas, Morocco

The limestone plateau of Ribat El-Kheir is situated within Tabular Middle Atlas of Morocco, NW of the North Middle Atlas Fault. It is a limestone plateau bordered to the East and Southeast by anticlinal ridges that act as a watershed divide for surface waters. The geological formations that compose it mainly consist of Lias limestones and dolomitic limestones resting on the red saline clays of the Triassic. These fractured and karstified limestones form a significant aquifer, whose waters are used for supplying drinking water to the local population and irrigating apple and cherry orchards. Excessive groundwater exploitation and consecutive drought periods have significantly affected both the quantity and quality of these waters. Geological surveys and the piezometric investigation carried out have shown that groundwater flow initially occurs from SW to NE along major faults such as the NMAF, later faults oriented NW-SE redirect the flow in the NW-SE direction, the presence of Triassic red saline clays as an impermeable substratum of the Lias aquifer favors the emergence of several water springs along the edges of the limestone plateau, which are drained by faults, abnormally high conductivity and pH values observed in some boreholes and springs are associated with the red clays that release sulfates and sodium chlorides through dissolution. The ongoing hydro-geophysical study would be of great value in managing water resources for the sustainable development of the region.