Assessment of quality and geochemical properties of groundwater for multipurpose utility in the northeastern district of Tamil Nadu state

Abstract

Groundwater quality in coastal aquifers is increasingly threatened by salinization and anthropogenic pressures, necessitating integrated assessment approaches. This study evaluates the hydrogeochemical characteristics and groundwater suitability in the Cuddalore district, Tamil Nadu, India, using a multi-index process-based framework. The study region is geologically, geomorphologically, and hydro-geologically more interesting; a total of 69 groundwater samples were collected and analysed for major hydrochemical parameters. Water quality index (WQI) classifies the groundwater samples into five categories, and around 58% of samples are in the excellent to good category, 26% of samples are in the poor to very poor category, and 16% of samples are unsuitable for drinking. Hydrochemical facies results indicate that Na–Cl and mixed Ca–Mg–Cl are predominant water types, and this reflects the influence of the reverse ion exchange, mineral weathering, and saline conditions. Moreover, cation–anion relation and electrical conductivity ranges in the coastal regions authorize the presence of a saline nature. Irrigation suitability assessments demonstrate that 54% of the samples belong to the C3S1 class, indicating moderate suitability, while approximately 10% of the samples are under high salinity hazard classifications. Elevated sodium and salinity levels in localised areas may adversely affect soil permeability and crop productivity. Ultimately, the results demonstrate that groundwater chemistry in this region is governed by the combined effects of rock–water interaction in the hard rock region, agricultural inputs, and coastal salinization. The integrated approach adopted in this study provides a reliable framework for groundwater quality assessment and management in coastal aquifers, offering applicability to similar hydrogeological settings worldwide.