Hydrogeochemistry and carbonate saturation model of groundwater, Khanyounis Governorate—Gaza Strip, Palestine

Groundwater is a critical resource in Khanyounis city as it is the main source of water. The aquifer has deteriorated to a high degree, during the last two to three decades, in quality and quantity. More than 90% of the population get their drinking water from brackish water desalination plants. Fifteen domestic wells were sampled in 2002 to probe the hydrogeochemical components that influence the water quality. Na, K, Ca, Mg, Cl, SO₄, NO₃, and HCO₃ were analyzed. The data were statistically treated and plotted on the Piper diagram. A hydrogeochemical numerical model for carbonate minerals was constructed using the PHREEQ package. The results show that the groundwater is polluted with Cl, from seawater, and NO₃, sourced from fertilizers and sewage. The regression analysis shows that there are three groups of elements that are significantly and positively correlated. Na–Cl signature and plot show that seawater intrusion is advancing into the aquifer. The main hydrochemical facies of the aquifer (Na+K–Cl+SO₄), represents 60% of the total wells. Whereas 32.3% of the wells are located in the no pair up and no pair down fields on the Piper diagram. Calcite, dolomite, and aragonite solubility were assessed in terms of the saturation index where they show positive values indicating supersaturation. The hydrogeochemical behavior is rather complicated and is affected by anthropogenic and natural parameters.