Geochemical modeling, evaluation of contaminants and impacts of land use, land cover patterns on groundwater quality in Khushab, Pakistan

Abstract

Urbanization and land use/land cover (LULC) transitions exert significant pressure on groundwater resources, particularly in semi-arid regions where reliance on groundwater is high. This study assessed the effects of LULC on groundwater hydrochemistry in Khushab district, Pakistan, by analyzing 155 groundwater samples alongside geospatial mapping and statistical modeling. Hydrochemical distribution patterns revealed elevated sodium (Na⁺), chloride (Cl⁻), sulfate (SO₄²⁻), fluoride (F⁻), and magnesium (Mg²⁺) concentrations in agricultural and urban zones, reflecting inputs from fertilizers, wastewater infiltration, and industrial activities. The Curved Streamline Searchlight Model (CS-SLM) identified distinct LULC and ion linkages: Na⁺, Cl⁻ and F⁻ associations in agricultural land, SO₄²⁻, Mg²⁺ and Na⁺ relationships in built-up areas, and Na⁺, Mg²⁺ and Cl⁻ correlations in rangelands. To assess future risks, LULC dynamics were simulated using a Multilayer Perceptron and Markov Chain Analysis (MLP-MCA) model, projecting substantial increases in agriculture (+14.7 %), built-up land (+25.4 %), and forest (+23.5 %) by 2030, accompanied by declines in rangeland (−24.3 %) and water bodies (−15.8 %). These changes are expected to further elevate Na⁺, Cl⁻, SO₄²⁻, and Mg²⁺ levels in agricultural and urban aquifers, posing risks to groundwater quality and sustainability. The findings provide new evidence that rapid LULC change directly shapes groundwater chemistry, highlighting the urgent need for integrated land and water management practices. Sustainable agricultural inputs, improved wastewater management, and protective policies for rangelands and water bodies are essential to mitigate future degradation of groundwater resources.