Science et changements planétaires / Sécheresse


Origin of mineralization and deterioration of ground water quality of the shallow quaternary aquifer in the Rheris basin (Errachidia, Morocco) Volume 19, issue 1, janvier-février-mars 2008


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Laboratoire radiochimie, Département de chimie, Faculté des sciences, Université Med V, BP 1014, Rabat, Maroc, Laboratoire des formations superficielles : sciences du climat, de l’eau, de l’environnement et du patrimoine (LFS/SCEEP), BP 509, Boutalamine, Faculté des siences et techniques, Université My Ismail, BP 509, Boutalamine, 52 000 Errachidia, Maroc

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 + + Mg 2+), (SO 4 2-, Ca 2+) and (HCO 3 - + SO 4 2-, Ca 2+ + Mg 2+). Water presents a spatial variability of chemical facies (Na +-Cl, Ca 2+-Cl - and Ca 2+- HCO 3 -) which is in relation to their interaction with the geological formation of the basin. The study indicates that the salinization of the aquifer is 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 is the result of intensive use of fertilisers and a generalised practice of sceptic soil-absorption systems of wastewater disposal in the region.