ISOTOPIC TOOLS FOR GROUNDWATER MANAGEMENT IN SEMI-ARID AREA: CASE OF THE WADI OUAZZI BASIN (MOROCCO)

Abstract

Climate aridity and intensive exploitation due to uncontrolled pumping for irrigation have caused a drastic decrease in the piezometric level aquifers of ouazzi basin plain, and have seriously degraded groundwater quality. Overexploitation of coastal aquifers and pollution vulnerability are among the main problems related to groundwater resources assessment and management in arid and semi-arid regions threatened by desertification being the only source for agricultural and public water supply. The overall objective of this study is to identify the possible human impact on groundwater quality, and the elaboration of a conceptual circulation model of Essaouira coastal aquifer (W Morocco). A study was conducted, having as main goal the characterization of the groundwater evolution from the chemical and isotopic point of view from the recharge areas towards the coast line. Groundwater samples from Plio- Quaternary and Turonian aquifers were collected and analysed: i) variable electric conductivity from 900 μs/cm to 3880 μs/cm with similar Cl-Na facies; ii) carbon-14 varies from30 to 60 pMC, with3H levels (Ouazzi Basin) below the detection limit, SW of Essaouira city, tritium content range between 1.5 and 3 TU.