A comparative study of Water Quality Index (WQI) of Peruvanthanam and Valiyathodu sub-watersheds of Manimala river basin, Kerala, South India.

Abstract

Water Quality Index (WQI) is the rating that reflects the composite influence of different water quality parameters such as pH, TDS, Hardness, Sulphate, Chloride and Turbidity. WQI has been classified as excellent, good, fair, marginal and poor.Thematic maps for the study area were prepared from SOI toposheets and IRS P6 LISS-III image (P 100 /R 67) using Arc GIS 9.2 software.WQI values were added as attribute data and spatial distribution maps for both sub-watersheds were prepared. Critical analysis and comparison of WQI for both sub-watersheds reveals that, during monsoon period, Peruvanthanam has maximum 'excellent' category ie, 47.06% than Valiyathodu sub-watershed ie, 33.33%. 'excellent' ie, 23.52%,'good' ie, 29.41% and 'fair' ie, 47.06% during pre monsoon, 'good' ie, 35.29% and 'fair' ie,17.65% during monsoon and 'excellent' ie, 17.65% 'good' ie, 23.53% and 'fair' ie, 58.82% during post monsoon season. Valiyathodu sub-watershed has 'excellent' ie, 26.67%, 'good' ie, 33.33% and 'fair' ie, 40.00% during pre monsoon. It shows constant value of 40.00% for good category during monsoon and post monsoon season. WQI having fair value of 6.67% and 33.33% for monsoon and post monsoon seasons respectively. Marginal category for monsoon and post monsoon season is 20.00% and 26.67% respectively. Hence it is explicit that, in general water quality is good in Peruvanthanam sub-watershed, compared to Valiyathodu sub-watershed. Keywords -Arc GIS.9.2, IRS P6 LISS-III image (P 100 /R 67), SOI toposheet, Spatial distribution Water Quality Index (WQI)