International Journal of Advanced Engineering Applications, Vol.2, Iss.3, pp.25-37 (2013) 25 Fragrance Journals A Hydrochemical analysis and Evaluation of groundwater quality index in Thoothukudi district,Tamilnadu, South India S.Selvam 1 , R.Iruthaya Jeba Dhana Mala 2 and V.Muthukakshmi 2 1 Department of Geology, V.O.Chidambaram College, Tuticorin-8, Tamilnadu, India Email: geoselvam10@gmail.com 2 Departments of Civil Engineering, Anna University, Tuticorin-8, Tamilnadu, India Abstract - The present study was carried out to evaluate and hydrochemical characteristics of coastal aquifers in Tuticorin, Tamilnadu. GIS has been applied to visualize the spatial distribution of groundwater quality in the study area. A total of 23 groundwater samples were collected and analyzed for various physicochemical parameters in the years 2010. Very wide ranges and high standard deviations of hydrochemical parameters such as TDS, EC, Cl - , K, SO 4 , Mg suggest the groundwater in the coastal aquifer shows seawater mixing and anthropogenic contamination and most of the water sample exceed the maximum permissible limit of ISO standards. A total of 64% of the groundwater sample of the study area exceeded the permissible limit of TDS. About 84% of the groundwater sample of the study area exceeded the recommended limit of EC as per the Indian drinking water standard. The EC and TDS hydrochemical data clearly showed the consequences of seawater intrusion. Among the major anions, sulphate plays dominant role in PRM, but in the POM period chloride and bicarbonate was dominant. So anion Cl and HCO3 shows a prominent role in the study area. GIS based spatial analysis and Weighted Index Overlay Analysis technique has been proven to be a powerful tool to represent the distribution of major ions in the study area. Weighted Index Overlay Index map was also generated with the same technique to better understand the water potability over space. The categories of water quality evaluated by Weighted Index values based on major part of the study area falls under moderate category in the PRM and POM period. Weighted Index Overlay Analysis of the present study zone shows a higher Weighted Index Overlay Analysis value occur in SW portion during PRM period and SE and SW portion during POM period, indicating the deteriorated water quality. Keywords - hydrochemical parameters, GIS, spatial analysis, weighted index overlay analysis 1 INTRODUCTION Groundwater is widely distributed than surface water and is used for domestic, industrial and agricultural purposes throughout the world. More than 95% of rural population depends on groundwater for all needs. Because of the rapidly increasing population, several environmental problems are created which includes groundwater quality degradation (Selvam et.al 2012a and 2012b). Degradation of groundwater quality in coastal region generally occurs due to natural processes such as saline water intrusion, wind driven sea spray and marine aerosols deposited on the topsoil , evaporation, and interaction of groundwater with brines and sedimentary formations (Magesh N.S and Chandrasekar 2011 and Singaraja et.al 2012). Besides, anthropogenic contamination is another major cause of water quality deterioration, derived from distinguished origins such as industrial effluents, irrigation return flow, agricultural fertilizers, farm manures, municipal waste water, septic tank effluent, animal wastes and landfill. Several studies have quantified anthropogenic contamination effects on groundwater composition using geochemical approaches. The chemical parameters taken into consideration are hydrogen ion concentration (pH), specific conductance (EC), Total Dissolved Solids (TDS), total hardness (TH) and all major cations and anions. Various workers in our country have carried out extensive studies on water quality. (Amer 1995) have studied ground water chemistry of shallow aquifers in the coastal zones of Cochin and concluded that groundwater present in the shallow aquifers of some of the stations were poor in quality and beyond potable limit as per the standard set by WHO. The aim of the study was to assess the spatial distribution of hydrogeochemical parameters for suitability of groundwater resources and geochemical process controlling the water composition based on the major ion chemistry of 23 groundwater samples (Pre-monsoon and Post monsoon) in the coastal aquifer in Tuticorin district. 2 LOCATION OF THE STUDY AREA The study area is located in the coastal tract of southern Tamilnadu. The coastal stretch between Tuticorin and Thiruchendur extends over a distance of about 60 km. Tuticorin is in South Tamilnadu about 540 km south west of Madras (Chennai) and is geographically located in the Gulf of Mannar. The coastal stretch of Tuticorin was extensively studied due to the presence of a major port. Between Tuticorin and Sippikulam, the beach is flat and narrow. The islands of Pandyan Tivu, Van Tivu, Kasuvari Tivu, Vilangu Shuli Tivu and Kariya Shuli Tivu are present within 5 km of the coastline along this segment and offer protection from wave action and erosion. The study area is situated in the southeast coast of Tamil Nadu, India and is located between 8° 19′ to 9° 22′ N latitude and 77° 40′ to 78° 23′ E longitude (Fig. 1) covering an area of about 4,590.54 km2. Tuticorin is a coastal city popularly known as “Pearl city” with a major port and rapidly developing industrial area. The total area of the district is 4621 km². The administrative headquarters is an urban agglomeration and also one of the taluk headquarters within. Tuticorin District was derived from Tirunelveli District in 1986. In 2011, Tuticorin had population of 1,738,376 of which male and female were 858,919 and 879,457 respectively.