Contribution Of Hydrogeochemical And Isotopic Tools To The Management Of Upper And Middle Cheliff Aquifers

Résumé: In the alluvial aquifers of Upper and Middle Cheliff (North-West Algeria), the groundwater quality is deteriorating. The objective of this study was to characterize the physical and chemical properties of these aquifers; and to evaluate the groundwater quality and its appropriateness for drinking and agricultural use. An investigation was carried out by estimating of the physiochemical parameters (Ca2+, Mg2+, Na+, K+, Cl−, SO2− 4, HCO− 3, NO− 3, Br− and TDS) to identify the chemical characteristics of groundwater. Morever, the isotopic composition was examined to identify the sources of recharge of these aquifers. The groundwater geochemistry for the high water level (May, 2012 and June, 2017) and low water level (November, 2012 and October, 2017) was studied. Accordingly, water samples from 39 water sampling points were collected (October, 2017 and June, 2018), for the purpose of analyzing stable isotopes (18O, 2H). The results show that the groundwater is mainly characterized by Ca-Cl and Na-Cl type. The chemical quality of the water is from fair to poor with the presence of nitrates used in agricultural and urban discharge. Also, the Br/Cl ratio gives indications on the origin of the salinity. This salinity is due to the leaching of chlorinated fertilizers, the dissolution of evaporite deposits and the rise of deep salty water by the fault of Chellif. While, the diagram of δ2h=f (δ18O) indicates that the origin of the recharge of these aquifers is the Atlantic and Mediterranean oceanic meteoric rainwater.

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