WATER QUALITY INDEXING OF RIVER GANGA BETWEEN RISHIKESH AND HARIDWAR

Abstract

To ascertain the pollutional quality level of Ganga, the holy river of the Hindus, in between Rishikesh and Hardwar during the lean period between 27th December 1985 to 4th February 1986, 5 water samples each were collected, from 7 sampling stations at about a week's time interval between two samplings - Water samples were tested to find the levels in which the ten pollution parameters viz. Dissolved Oxygen, Chemical Oxygen demand, pH, total plate count, hardness, alkalinity,total solids, Sp. conductance, turbidity and temperature, are present. Analysis of the results of the individual parameters do not permit any conclusive inference regarding the quality (or pollution) level of the river with respect to time or space. Therefore, a water quality index' (WQI) ;tfr;regating these parameters, has been attempted, as WQI expressed on a numerical scale, is easy to understand and is a better mode of expression. Many water quality indices have been developed since 1965. Out of these, NSF WQI is considered to be better than others as a general water quality index and it is widely used. Here a modified form of NSF WQI with a weighted arithmatic aggregation function has been adopted. The quality level of the river Ganga varies from 85.92 during the lean period, measured on a scale ranging 0 — 100, (10! represents 100 percent polluted and 100 represents unpolluted or purest water). The point of maximum pollution is Satyanarayana sampling station, almost at the middle of the stretch, with a WQI of 85. All other stations, do not show much variation in water quality with a WQI around 90.