Geochemical and isotopic characterization of groundwater and identification of hydrogeochemical processes in the Berrechid aquifer of central Morocco

The hydrogeochemical characteristics and processes affecting the groundwater chemistry of the Berrechid Basin, central Morocco, were determined using chemical and isotopic data from 71 groundwater and six surface water samples. Chemical data shows a wide variation in mineralization, notably exceeding the permissible level of potability. Unlike the northern area, which seems to be separate from the main system, the salinity profile demonstrates a rising trend from the intake area in the south to the downstream area in the east and west, where the groundwater becomes more saline. Three basic hydrogeochemical facies are distinguished: Na–Cl, Na–Mg–Ca–Cl, and Ca–Mg–HCO3–Cl. A trend was also noticed for the last two types toward Na–Cl. Chemical composition of the groundwater is mainly determined by the influence of evaporation, cation exchange, rock weathering, salt dissolution, and anthropogenic activities. The dolomitization process has also been put forward as an explanation for groundwater saturation with respect to the carbonate minerals, particularly in the eastern and western parts. The groundwater is enriched with 2H and 18O, which independently, as well as with Cl− and NO3−, strengthens the findings from the chemical data by affirming the dominant effects of evaporation, the dissolution of minerals, and anthropogenic activities in assessing the geochemical evolution of the groundwater. Furthermore, this allows a twofold identification of recharge sources in the Berrechid aquifer: a lateral flow from the Phosphate Plateau, mainly along the southern part of the basin, and a vertical downward movement of evaporated water from rainfall, rivers, and the return of irrigation flow.