Groundwater and surface water quality under urbanization pressure: A water quality index assessment in Siliguri Planning Area, India

Abstract

Safe drinking water and sustainable water resource management require routine evaluations of groundwater and surface water quality. Rapidly expanding urban areas depend heavily upon these crucial assessments. Consequently, the spatial distribution of water quality parameters within the Siliguri Planning Area of West Bengal, India, was evaluated in this work. The Water Quality Index (WQI) was also calculated for both groundwater and surface water resources. The Weighted Arithmetic Water Quality Index method categorized the overall condition of these hydrological resources. A spectrum ranging from good to very poor conditions (WQI ranging from 34.02 to 182.30) defines the current groundwater quality. Elevated nitrate (up to 118 mg/L), iron (0.55 mg/L), and potassium concentrations heavily contaminate the central and southeastern urban zones. Strong positive relationships among nitrate, sodium, and sulphate (r > 0.90) were identified through correlation analysis. Human-driven pollution from agricultural runoff and domestic sewage is clearly indicated by these substantial linkages. Notable spatial variation characterized the surface water quality, with SWQI scores fluctuating between 12 and 76.97. Elevated BOD, TDS, and chloride concentrations drove a progressive deterioration along the urban corridors of the Mahananda River. Conversely, relatively healthy conditions were maintained throughout the Balason River. Agricultural activities, improper waste disposal, and intense urbanization severely impact these vital reserves. Immediate intervention is absolutely necessary to halt this widespread degradation. Ultimately, policymakers and civic authorities can construct targeted water quality management strategies using these empirical results. The design of vital treatment infrastructure throughout the region can be supported by the scientific foundation presented in this study.