Prioritization of subwatersheds of a river basin using geographic information system

Abstract

A sub watershed prioritization exercise has been carried out on Kunthipuzha sub basin of Bharathapuzha river basin, one of the major rivers in Kerala. Total catchment area of the Kunthipuzha basin comprises 940 sq.km. ILWIS and SWAT have been used for the study to make the sub watershed delineation and erosion estimation much easier than conventional procedures. Soil erosion has been evaluated from each of the 108 sub watersheds of Kunthipuzha catchment. Erosion rates in different sub watersheds of the river basin are ranging from 2 tons/ha /year to 335.6 tons/ha/year. Out of 108 sub watershed 3 sub watersheds have low erosion rate (<5 tons/ha) and hence included in low priority class. 5 sub watersheds have resulted in medium rate of erosion (5-15 tons/ha) and are put under medium priority class. 51 sub watersheds have high rate of erosion (15-50 tons/ha).and is categorized into high priority class. 49 sub watersheds have very high rate of erosion (> 50 tons/ha), hence very high priority has given to them. From the study, it is concluded that 61% of total catchment of Kunthipuzha has very high priority,47% of area high priority,3.9% of area moderate priority and 0.036% low priority.