Evaluation of groundwater quality using Water-Quality Index and Geographical Information System for human consumption and irrigation in Kanyakumari District, South India

Groundwater is a vital source of freshwater in both urban and rural regions of the world, supporting drinking water supply, agriculture, industry, and ecosystem sustainability. Its role becomes especially critical in areas where surface water resources are limited or seasonal. Geographical Information System (GIS)-based groundwater quality evaluation using the Water Quality Index (WQI) has emerged as a cost-effective and reliable approach for assessing groundwater quality and its spatial variability over large regions. This integrated method not only simplifies the interpretation of complex water quality datasets but also provides a visual representation of groundwater status, thereby supporting effective water resource management and policy planning. A GIS-based Water Quality Index (WQI) approach was adopted to assess the suitability of groundwater in Kanyakumari district for domestic, irrigation, and industrial purposes. A total of 118 groundwater samples were collected from the study area in the year 2024. The primary physico-chemical parameters, including potential of Hydrogen (pH), Total Dissolved Solids (TDS), Total Hardness (TH), calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), potassium (K⁺), bicarbonate (HCO₃⁻), carbonate (CO₃²⁻), chloride (Cl⁻), sulphate (SO₄²⁻), nitrate (NO₃⁻), and fluoride (F⁻), were analysed to compute the Drinking Water Quality Index (DWQI). In addition, secondary irrigation water quality indices such as Sodium Adsorption Ratio (SAR), Sodium Soluble Percentage (SSP), Residual Sodium Carbonate (RSC), Permeability Index (PI), Corrosivity Ratio (CR), Magnesium Adsorption Ratio (MAR), and Kelley’s Ratio (KR) were derived from the primary parameters to evaluate the irrigation water quality. The Drinking Water Quality Index (DWQI) and irrigation indices were classified into categories ranging from excellent to unfit conditions of groundwater quality.