A Comparative Study Of Water Quality Index (Wqi) Of Vagamon And Peermade Sub-Watersheds Of Meenachil And Pamba River Basins Of Western Ghats, Kerala, South India.

Abstract

Water quality rating methods provide a single number that reflects the combined influence of different water quality parameters and is of much significance in the sustainable development of a watershed. pH, EC, TDS, total alkalinity, total hardness, chloride, nitrate and sulphate were used to calculate WQI in weighted arithmetic index method. Accordingly water quality is classified as excellent, good, poor, very poor and unfit for drinking. Thematic maps for the study area were prepared from SOI toposheets and IRS P6 LISS-III image (P100/R67) using Arc GIS 9.2 software. Spatial distribution maps were prepared for both watersheds by adding WQI index values as attribute data. In both sub-watersheds, percentage of excellent category is higher during Post monsoon season compared to other two seasons. When both sub-watersheds are compared Vagamon has better water quality than Peermade sub-watershed. It is represented by 44.44% excellent, 44.44% good and 11.12% poor category of WQI during Pre monsoon season; 33.33% excellent and 66.67% good category of WQI during Monsoon season; and 77.78% excellent and 22.22% good category WQI during Post monsoon season. The corresponding values for Peermade sub-watershed, for different seasons are 36.36% excellent and good, 18.18% poor and 9.10% very poor WQI during Pre monsoon; 36.36% excellent, 54.55% good and 9.09% poor WQI during Monsoon; and 45.45% excellent and good and 9.10% very poor category WQI during Post monsoon season.