Development of an overall index of pollution for surface water based on a general classification scheme in Indian context.

Various National and International Agencies involved in water quality assessment and pollution control have defined water quality criteria for different uses of water considering different indicator parameters. Classification schemes for water quality criteria/standards developed by these agencies differ in addition to terminologies used such as Action level, Guide level etc. in defining the concentration values in these classes. In the present article a general classification scheme viz. Excellent, Acceptable, Slightly Polluted, Polluted and Heavily Polluted water is proposed for surface water quality assessment. The concentration ranges in these classes are defined in Indian scenario considering Indian Standards and CPCB criteria. Standards by the European Community (EC), WHO etc. and the reported facts about the pollution effects of important water quality indicator parameters on the surrounding were also taken into account. The mathematical equations to transform the actual concentration values into pollution indices are formulated and corresponding value function curves are plotted. Based on the individual index values, an 'Overall Index of Pollution' (OIP) is estimated. The application of OIP is demonstrated at a few sampling stations on river Yamuna based on observed water quality data. The general classification scheme along with concentration ranges defined in these classes will be of immense use for determining the surface water quality status with reference to specific individual parameter, and the OIP for assessing the overall water quality status in Indian context.