Groundwater quality and its suitability for domestic and agricultural use in Tondiar river basin, Tamil Nadu, India K. Ramesh & L. Elango Received: 18 October 2010 /Accepted: 15 July 2011 # Springer Science+Business Media B.V . 2011 Abstract Assessment of suitability of groundwater for domestic and agricultural purposes was carried out in Tondiar river basin, Tamil Nadu, India. The study area covers an area of 315 km 2 and lies in a semiarid region. Groundwater is the major source for domestic and agricultural activity in this area. Groundwater samples were collected from 45 wells during pre- monsoon and post-monsoon period in the year 2006. The water samples were analysed for physical and chemical characteristics. Suitability of groundwater for irrigation was evaluated based on salinity hazard, sodium percent, sodium adsorption ratio, residual sodium carbonate, US salinity diagram, Wilcox’ s diagram, Kelly’ s ratio and permeability index. Ca- HCO 3 , mixed Ca–Mg–Cl and Na–Cl were the dominant groundwater types. High hardness and electrical conductivity in this area makes the ground- water unsuitable for drinking and agricultural pur- poses. Concentration of trace elements (Mn, Cu, Zn, Pb and Ni) did not exceed the permissible limit for drinking and agricultural purposes. Majority of the groundwater samples were unsuitable for domestic and agricultural purposes except for 31% and 36%, which were suitable for drinking and irrigation purposes, respectively. Keywords Water quality . Drinking purpose . Major ions . Nitrate . Sodium absorption ratio . Residual sodium chloride . Permeability index . Magnesium hazard . Kelly’ s ratio Introduction Groundwater is the major source of water for domestic, agricultural and industrial purposes in many countries. India accounts for 2.2% of the global land and 4% of the world water resources and has 16% of the world’ s population. It is estimated that approxi- mately one third of the world’ s population use groundwater for drinking (Nickson et al. 2005). Therefore, water quality issues and its management options need to be given greater attention in devel- oping countries. Intensive agricultural activities have increased the demand on groundwater resources in India. Water quality is influenced by natural and anthropogenic effects including local climate, geology and irrigation practices. Once undesirable constituents enter the ground, it is difficult to control their dissolution. The chemical characteristics of ground- water play an important role in classifying and assessing water quality. Geochemical studies of groundwater provide a better understanding of possi- ble changes in quality. Many naturally occurring major, minor and trace elements in drinking water Environ Monit Assess DOI 10.1007/s10661-011-2231-3 K. Ramesh Centre for Water Resources, Anna University, Chennai 600 025, India L. Elango (*) Department of Geology, Anna University, Chennai 600 025, India e-mail: elango@annauniv.edu