GIS-based assessment of groundwater quality index (DWQI and AWQI) in Tiruchendur Coastal City, Southern Tamil Nadu, India

The present study was conducted to evaluate the hydrochemical parameters to improve a water quality index for Tiruchendur, an agricultural area in the Tuticorin district of Tamil Nadu, India. The population growth and intensive agricultural activities in and around the groundwater system in the study area have a direct effect on the quality of this groundwater. A total of 39 samples were collected and analyzed for physicochemical parameters and assessed the suitability of groundwater for drinking and irrigation purposes based on the Water Quality Index (WQI) mapping by the Geographic Information System (GIS). The measured data were used to compute irrigation factors such as sodium percentage (Na%), sodium adsorption ratio (SAR), residual sodium carbonate (RSC) and permeability index (PI) to determine the suitability of water for agricultural activities. The hydro-chemical facies reflect that 57% of Ca²⁺-Mg²⁺-Cl⁻-SO₄²⁻ type of facies with an alkaline (Ca²⁺ and Mg²⁺) nature exceeds the alkalis (Na⁺ and K⁺) and chloride (strong acid) exceed HCO₃⁻ (weak acid) with the sequence of cation Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ and anion Cl⁻ > HCO₃⁻ > SO₄²⁻ > NO₃⁻ respectively. The Drinking Water Quality Index (DWQI) results show that no area is in excellent to good water class for drinking while 41% of samples have poor water quality, 20% of samples have very poor categories and 39% are of inappropriate for drinking utilities. The Agricultural Water Quality Index (AWQI) indicates that the vast majority (41%) areas can be used for agriculture with Moderate Restriction and 5% of estuary areas are classified as having low restriction over agricultural use. This comprehensive research provides a geological database through such spatial surveys as the DWQI and AWQI, which will help to plan and improve the sustainable management of groundwater resource along with the Tiruchendur coastal city.