Origin of mineralization and deterioration of ground water quality of the shallow quaternary aquifer in the Rheris basin (Errachidia, Morocco).

摘要

Hydrochemical investigations were carried out in the Rheris area, south-eastern Morocco, to assess the quality of the shallow aquifer. This area is situated in an arid type of climate with annual precipitation less than 120 mm. The quaternary aquifer constitutes the main water resource for water supply and agricultural activities. A total of 21 representative water points were sampled to monitor the water chemistry for various ions. Positive correlations were established between the following pairs of ions: (Cl-, Na++K++Mg2+), (SO42-, Ca2+) and (HCO3-+SO42-, Ca2++Mg2+). Water presented a spatial variability of chemical facies (Na+-Cl, Ca2+-Cl- and Ca2+-HCO3-), which was in relation to their interaction with the geological formation of the basin. The study indicated that the salinization of the aquifer was controlled by the dissolution of evaporate (halite and gypsum), dolomite and calcite, as well as by irrigation water return and water precipitation. The nitric pollution of water was the result of intensive use of fertilizers and a generalized practice of sceptic soilabsorption systems of waste water disposal in the region.