Geochemical evaluation of groundwater quality and its suitability for drinking and irrigation purposes in arid and semiarid regions: The case of Zeuss-Koutine and a part of Mio-Plio-Quaternary aquifers (SE Tunisia)

Abstract

Water scarcity is a significant issue in the southeastern region of Tunisia, where the sole source of water is from overexploited, salinized, and contaminated aquifers. Despite considerable advancements in studying groundwater hydrochemistry in the study area, Jeffara plain, further investigation is crucial to comprehensively assess groundwater quality in greater depth. The present study investigates the hydrochemistry of the Zeuss-Koutine (ZK) and a part of Mio-Plio-Quaternary (MPQ) groundwater of the Jeffara plain to identify groundwater quality and assess its suitability for drinking and irrigation purposes, as it serves as a vital water source for various sectors. Groundwater samples were collected from 43 exploitation wells and analyzed for temperature, pH, conductivity, major cations (Ca2+, Mg2+, K+ and Na+), major anions (Cl−, HCO3−, NO3−, SO42−), F−, trace elements and NH4+. The findings revealed that the groundwater hydrochemical type in the ZK aquifer is dominated by Na–Ca/SO4–Cl, while the MPQ samples fall under the Na–Ca–Mg/SO4–Cl category. Most of samples show too high concentrations of Na+, Ca2+, Cl−, SO42− and Fluoride. The studied groundwaters are highly affected by gypsum dissolution. The WQI indicate that 86% of samples have poor and very poor water quality and 14% are unsuitable for drinking. These findings are further supported by the TH measurements, which classify all water samples as very hard and unsuitable for drinking purposes. Irrigation water quality index indicate that samples fall in severe and high restriction, so, careful attention should be given to the high sodium and salinity content when used in intensive irrigation. The combination of water quality indices and GIS tools is performed to raise awareness among decision makers about groundwater availability and quality in the study area. Additionally, the need to develop strategies for the treatment and preservation of these valuable resources.