Hydrochemical and isotopic characterisation of Eastern Haouz plain groundwater, Morocco

The groundwater of Eastern Haouz of Morocco is an important source for the high-density population and intensive agricultural activity in the area. The water demand here is increasing year by year. Groundwater levels measured in the study area show that the water table is quite deep (40–50 m) and that the groundwater flow is closely following the surface topography. Major ion chemistry was made on 40 groundwater samples, and about 20 samples among them were used for stable isotope measurements. A large variation is found between the minimum and the maximum values of different ions. The dominant cation Na+ concentration varied between 18 and 1,159 mg/L and the anion Cl− varied between 53 and 2,176 mg/L. Samples from Schist and Triassic sediments are relatively more mineralised, thus unsuitable for drinking as well as agricultural purposes. Groundwater within the plains (alluvium) is relatively less mineralised than the other older formations. However, hydrochemical values of many samples collected from alluvium are also not in the potable range owing to the natural and the anthropogenic contamination. Hence, hydrochemical data of the study area show geological control on water quality. Apart from salinity, about 25 % of the samples have higher nitrate content than the drinking water permissible limit. Stable isotope measurements show that groundwater recharge to the phreatic aquifer is controlled by local conditions.