Hydrochemical and Isotopic Investigation of the Groundwater from Wajid Aquifer in Wadi Al-Dawasir, Southern Saudi Arabia

The Wajid aquifer is considered the main source of water for drinking and irrigation in Wadi Al-Dawasir Najran, southern region Saudi Arabia. This has been used since 1960s, due to expansion agricultural activities, overexploited. study aims understand origin, hydrochemical processes groundwater shallow unconfined, deep confined parts area. In-situ parameters (pH, temperature, EC, TDS) were measured field, samples collected major ions stable isotopes (2H 18O) measurements laboratory. results show that aquifers are two types; Cl.SO4-Ca. Na Cl.SO4-Na. Ca; however, deep, unconfined characterized as HCO3-Ca. Na, Cl. Na; types groundwater. isotopic analysis reveal all have values δ18Oand δ2Hclose local global meteoric lines, indicating origin Three processes, including rock weathering, ion exchange, evaporation, identified key controls on chemical composition studied aquifer. evaporation exchange more influence aquifers. On contrary, weathering carbonate minerals affected chemistry a section shows reverse pattern salinity with higher recharge area, which most probably related return leaching salty soil. open fractures upper part sandstone likely act conduits percolated saline