Integration of hydrochemical, GIS, and remote-sensing data for assessment of shallow groundwater aquifers in Wadi Nisah, Central Saudi Arabia

Groundwater samples were collected in May 2015 from 23 wells distributed in the western part of Wadi Nisah, mainly used for irrigation. Calculation of saturation indices showed that the samples were generally undersaturated with respect to halite, gypsum, anhydrite, calcite, and aragonite. Groundwater facies analysis showed that most of the collected samples were dominated by Ca–Na–SO₄-type water. This water type indicates rock–water interaction, mainly gypsum dissolution. The second major water type was Na–Ca–SO₄. Evaporation is the major process that controls the groundwater chemistry in the study area. Principal component analysis resulted in the extraction of two principal components. All the elements analyzed showed significant positive factor loading in the first principal component (PC1) except NO₃ and Pb which showed high negative loadings in the second principal component (PC2). R-mode cluster analysis identified two groups of variables. The variables in Group 1 are the result of rock–water interaction and contamination by human and agricultural activities. Variables in Group 2 represent the dissolution of evaporite minerals. The total dissolved solids’ (TDS) results demonstrated that the water samples could be classified as either brackish or freshwater. The high TDS concentration in the brackish samples could be a result of soil–water interaction. Moreover, human activities, especially those producing agricultural and household wastewater, can increase TDS in groundwater. Remote-sensing results demonstrated that the areas of agricultural and urban land use have increased with time and have contributed to groundwater pollution.