Assessment of Surface Water Quality for Drinking and Irrigation in the Coastal Zone of South Vellar Watershed, Tamil Nadu

IJEP 46(5): 459-466 : Vol. 46 Issue. 5 (May 2026)

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M. Lakshmi1 and R.S. SujaRose2*

1. Lady Doak College, Centre for Environmental Studies, Madurai – 625 002, Tamil Nadu, India
2. Madurai Kamaraj University, Department of Environmental Remote Sensing and Cartography (ERAC), School of Earth and Atmospheric Sciences, Madurai – 625 021, Tamil Nadu, India

Abstract

Water is an essential natural resource vital for both human sustenance and ecological balance. Surface water, in particular, plays a crucial role in providing drinking and irrigation water. This study focuses on the coastal region of the south Vellar watershed in Pudukkottai district, Tamil Nadu, which contains 703 surface waterbodies, predominantly tanks. The research aims to evaluate the suitability of these surface water resources for drinking and irrigation. A total of 21 tanks were randomly selected for sampling and water samples were collected during the post-monsoon season of 2023-24. Various physico-chemical parameters, including pH, total alkalinity, total hardness, calcium, chloride, sulphate, magnesium, sodium and potassium, were analyzed to assess water quality for agricultural, domestic and industrial uses. According to the Wilcox diagram, sodium levels were low in all 21 samples; however, 11 samples fell within high salinity categories (C3 and C4). Box and Whisker plots confirmed that sodium concentrations were lower than those of calcium and chloride. The calculated water quality index (WQI) values ranged from 12.21-78.96. Excellent water quality was observed in samples from Karakathikkottai, Kodikulam and Manjakkudi. In contrast, poor water quality was noted in tanks from Karamangalam, Talanur, Thattani and Ammapattinam. Tanks located in built-up areas showed relatively higher WQI values. Villages, such as Mumpalai, Subramanyapuram, Seyyanam, Nilaiyur, Vellur Siruvarai and Kannakkur exhibited low water quality. Despite the proximity to the coast, the study found minimal evidence of seawater intrusion.

Keywords

Surface water quality, Water quality index, Coastal watershed, Physico-chemical parameters, Wilcox classification

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