Hydrochemical characteristics and groundwater quality assessment for irrigation and drinking purposes: a case of Enfidha aquifer system, Tunisia

The Enfidha aquifer in Northeastern of Sousse city Tunisia, is the main water supply for agricultural and drinking. The aquifer overexploitation due to the agriculture activity growth led to a decrease in the piezometric level and groundwater quality degradation. This study implemented graphical representation and statistical methods to assess the groundwater quality suitability for agricultural and drinking purposes. Analyzed groundwater samples present two hydrochemical facies, the NaCl and the CaMgClSO4. The main mineralization process is related to the dissolution of reservoir minerals such as anhydrite, gypsum, and halite. The comparison of the groundwater quality parameters with the World Health Organization and the Tunisian standards indicated that the majority of groundwater samples are unsuitable for drinking. The drinking water quality index (DWQI) indicates that 30% of the groundwater samples in the Enfidha region represent a good quality for drinking and 70% are unsuitable for drinking purposes. The calculated Sodium adsorption ratio (SAR), Sodium ratio (Na%), Kelley’s ratio (KR), Magnesium ratio (MR) and Permeability Index (PI) indicate that almost 60% of samples are suitable for irrigation. While according to Wilcox classification, only 15% of groundwater samples are suitable for irrigation. And according to the US Salinity Classification, 65% of the groundwater samples are unsuitable for irrigation in ordinary conditions. Nevertheless, it may be used occasionally under special situations. Hence, appropriate groundwater development and management based on water quality indexes are necessary to ensure a safe and healthy use of groundwater without damage to humans, soils and plants.