22-Mapping of Surface Water Quality Status using Overall Index of Pollution in Tapi River Sub-Basin in Maharashtra

Abstract

The wholesomeness of water i.e. the water free from visible suspended matter, excessive color, odour, taste, objectionable dissolved matter and bacteria indicative of fecal pollution is the prime requirement for any type of use such as drinking, bathing or domestic use, recreation etc. Therefore, major rivers in India are monitored regularly with the objective of assessment of pollution level and plan for its control. In this context, Water Quality Index can be of immense use as a decision making tool in formulation of action plan for pollution mitigation or control.

In developing Water Quality Index, the indicator parameters which are measured in different units of measurement are brought on commensurate unit and due consideration is given to the water quality standards/criteria. However, the standards specification by different agencies such as WHO, EC etc., differ in terms of terminologies used such as Action Level, Guide Level, Desirable Concentration and so on. Therefore, authors have developed a general classification scheme such as Excellent, Acceptable, Slightly Polluted, Polluted and Heavily Polluted water, wherein the concentration ranges are defined with due consideration to Indian Standards and CPCB criteria. Based on this scheme an Overall Index of Pollution (OIP) can be estimated considering different water quality parameters. The present paper describes the application of OIP to basic water quality data collected for the Tapi River Sub-basin in Maharashtra. Physico-chemical and bacteriological quality of water monitored at 15 stations in different stretches of Tapi river system has been used for mapping surface water quality status. The seasonal variation in surface water quality as described by the OIP is detailed in the paper. The application of OIP to surface water quality data can help in formulating action plan to restore and maintain river water quality at designated best use.