The implication of the hydrogeochemical processes for groundwater chemistry in a semi-arid region: A case study of the Bokoya massif (Central Rif, Morocco)

Abstract

Natural and anthropogenic factors control groundwater chemistry in the semi-arid area in northern Morocco called Bokoya massif. The main goal of this study was to evaluate the geochemical processes that affected groundwater mineralization in the Bokoya massif. As a result, In April 2016, sixty-one (61) water samples were collected from various locations, including wells and springs throughout the Bokoya massif, and analyzed for physicochemical parameters using standard methods. The descriptive study of the physicochemical parameters revealed that the waters were neutral to slightly basic (pH values range between 7,16 and 8,5) and moderately to strongly mineralized (TDS values range between 555,20 and 7980,10 mg/l). Sodium chloride was the dominant hydrochemical facies in the groundwater of the study area, with a percentage reaching (80%) noting the minority of magnesium bicarbonate facies and the absence of sodium bicarbonate and chlorinated calcium type. The tests of the ionic ratio (Cl- /Na+, Cl-/HCO3- versus Cl-, Ca2+/Mg2+, Ca2+/SO4-, Ca2+/Mg2+ versus Cl-, (Ca2+ Mg2+)/ HCO3-), indicate that the order of the dominant cations is Na+ >Ca2+>Mg2+>K+ and of the dominant anions is Cl- >HCO3->SO42-. It suggests that the dominant factors controlling water chemistry are rock dissolution and evaporation, silicate weathering, and ion exchange. Gibbs diagram defines the relationship between water chemistry and the lithology of the aquifer. It showed that most of the groundwater composition in this area is linked to the geochemical processes of evaporation and crystallization, and carbonates and silicate alteration control the minority.