ASSESSMENT OF LONG TERM WATER QUALITY VALUES (WQV) AND INDEX (WQI): ENVIRONMENTAL PERSPECTIVESR. Subramanian, R. Vidhya and V. E. Nethaji Mariappan
The temporal variation water quality of Tiruvallur district was assessed using intermittent historical data (1975-80; 85-90; 95-2000; 05-10) for 24 years. Groundwater data includes both pre monsoon (June) and post monsoon (December/January) data evenly distributed. Spatially data were collected from about 45 villages within the ambit of Tiruvallur district. Nine physio-chemical parameters viz., pH, E.C. TDS, Total Hardness, Calcium, Magnesium, Bi Carbonate, Sodium and Chlorides were utilized for water quality assessment. In order to understand the water quality in accordance to drinking purpose the same has been verified with WHO and BIS standards. Water Quality Index was arrived for year wise data (pre monsoon and post monsoon) for minimum, maximum and mean values. The results reveal that WQI derived for pre and post monsoon minimum values exhibited excellent water suitable for drinking purpose, upon pre and post monsoon maximum values deems unsuitable for drinking. WQI of mean of pre and post monsoon values significantly showed poor water quality. Results of the analysis of historical mean value water quality index, majority of the samples fall under poor water quality and not suitable drinking water purpose. There need to be a change in water quality standards exclusively for coastal regions with higher ground water extraction, sea water intrusion and at industrial zones.
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