Assessment of groundwater mineralization of alluvial coastal aquifer of essaouira basin (Morocco) using the hydrochemical facies evolution diagram (HFE-Diagram)

Abstract

The relation between the hydrochemical variation and the marine intrusion in the coastal alluvial aquifer of Essaouira basin (Morocco) was characterized by the major ionic ratios, the ratio Br−/Cl−, the hydrochemical facies evolution diagram (HFE-Diagram), and by the stable isotopes of oxygen and hydrogen (δ18O and δ2H). The results of major ionic ratios have shown that groundwater mineralization is controlled by the dissolution phenomenon and by the inverse Bases Exchange phenomenon caused by the marine intrusion. Br−/Cl− ratio shows that some water points are contaminated by seawater. The application of HFE-Diagram shows that the samples of the 1990 are grouped in the SW + i4 (52%) and i3 (14%) sub-stages. The samples of 1995 campaign show an evolution from the i1 (3%) sub-stage towards the FW + i4 (38%) sub-stage by reflecting the advancement of seawater in the aquifer. Samples representing the 2009 campaign are characterized by the dominance of the f1 (56%) sub-stage relative to the SW + i4 (38%) sub-stage, suggesting the trend of the aquifer towards the equilibrium phase due to the significant recharge that known this aquifer. While the samples of the 2015 campaign are dominated by the i3 (49%) and SW + i4 (32%) sub-stages reflecting the re-contamination of the aquifer by seawater. However, the groundwater mineralization of the alluvial coastal aquifer of Essaouira basin is controlled by the dissolution phenomenon and by the bases exchange phenomenon caused by the marine intrusion. Exploiting the results of this paper can lead to better management of the aquifer by identifying the areas contaminated by seawater.