Water quality indices are mathematical equations that transform water quality data into a particular number which describe the status of water. A number of water quality indices have been developed by various researchers for categorizing the water quality for different uses. These indices are developed based on classification criteria, sub-indices, and aggregation function. In the present study, a generalized Composite Water Quality Index (CWQI) is developed to classify the water into five categories, viz excellent, good, fair, poor, and polluted. For this purpose, the concentration ranges have been categorized on the basis of the Indian Standards (IS) and Central Pollution Control Board (CPCB) standards and considering International standards of World Health Organization (WHO) and European Commission (EC). Twenty-five water quality parameters are selected based on the social and environmental impacts, and weights are computed using the Saaty's Analytic Hierarchy Process (AHP) Multiple Criteria Decision Analysis (MCDA) tool. These parameters are selected such that the same indices can be used to assess the quality of both surface and ground water. The computed weights minimize the subjectivity in assigning the parameter weights. The proposed index improves understanding of water quality issues by integrating complex data and generates a score which describes the status of water quality. The index will be very useful for the water management authorities to maintain good health of surface water resources.
Keywords: CWQI; Gangotri; Indices; Saaty AHP; Sagar lake; Water quality; Yamuna river.