Groundwater quality assessment for drinking and irrigation: A case study in the Cauvery River Basin (CRB) of Tiruchirappalli District, Tamil Nadu, India

ABSTRACT The long-term impacts of human activities on groundwater quality in the Cauvery River Basin are not well understood, particularly the combined effects of urbanization, industrialization, and agriculture. Seasonal factors, such as precipitation and water-table fluctuations, also influence groundwater chemistry, affecting its suitability for drinking and irrigation. This research aims to assess the hydrochemical characteristics of groundwater and evaluate its long-term suitability for these purposes, considering both natural and anthropogenic factors. A total of 56 groundwater samples were collected and analyzed for various physicochemical and biochemical parameters. The results showed that the most prevalent ions are bicarbonate (27.3%), chloride (24.1%), and calcium (16.6%), followed by sulfate, magnesium, sodium, and others. The Piper and Gibbs plots indicated that most groundwater samples belong to the mixed calcium chloride facies, and rock–water interaction is the dominant natural mechanism, with some anthropogenic influences, respectively. The GIS-based drinking water quality index (DWQI) map showed that 66% of the samples were of excellent to good quality for drinking without treatment, while the remaining samples were of moderate quality and nearly unsuitable for drinking, requiring further treatment. However, most of the groundwater samples were suitable for irrigation based on irrigation water quality indices.