Groundwater quality appraisal and geospatial mapping in Tiruvallur district, Tamil Nadu, India: insights from water quality index evaluation

Abstract Groundwater quality is a critical indicator of water usability for drinking and irrigation. Tiruvallur district, spanning approximately 3,394 square kilometres, is one of the largest districts in Tamil Nadu, India. Due to rapid population growth, urbanization, and industrial activities, overexploitation of groundwater has significantly deteriorated its quality, posing challenges for sustainable living. This study evaluates the groundwater quality in Tiruvallur, where groundwater serves as the primary source of drinking water due to inadequate surface water availability. The study addresses declining groundwater quality in Tiruvallur District using a novel integration of Water Quality Index and GIS-based spatial mapping. Groundwater samples were collected from 10 dug wells across the district. Key physicochemical parameters, including pH, total hardness (TH), total dissolved solids (TDS), and electrical conductivity, were analyzed to calculate the Water Quality Index (WQI). The suitability of groundwater for drinking and irrigation was assessed against the standards set by the Bureau of Indian Standards (BIS) and the World Health Organization (WHO). Geographic Information System (GIS) techniques, particularly QGIS, were employed to create spatial distribution maps of water quality parameters. Box plot analysis highlighted a strong correlation between total dissolved solids and electrical conductivity, further emphasizing the need for sustainable groundwater management. This study provides a comprehensive spatial representation of groundwater quality, aiding stakeholders in implementing effective water resource management strategies.