Assessment of groundwater quality for irrigation and drinking purposes and identification of hydrogeochemical mechanisms evolution in Northeastern, Tunisia

Oligocene and Mio-Plio-Quaternary siliciclastic deposits constitute the most important deep aquifers of the Kairouanai-Sahel region. Considering the over-exploitation and contamination of the surface groundwater, recourse to use deep groundwater was crucial. These aquifers revealed three major hydrochemical facies: HCO 3 /Mg, HCO 3 /Na and SO 4 /Mg water types. Rock–water interaction showed the main mechanisms are rock weathering and evaporation. Different parameters such as water quality index (WQI), sodium absorption ratio (SAR), percentage of sodium, residual sodium carbonate (RSC), magnesium hazard (MH) and permeability index (PI) were used to evaluate groundwater suitability for drinking and irrigation purposes. Results highlighted that groundwater is unsafe for irrigation based on PI, MH, RSC and salinity diagram. According to the WQI values, 10.25 % of the water samples had good water quality, 69.23 % were considered as poor water, 12.82 % were very poor water and 7.69 % were considered unsuitable for drinking purpose.