Application of GIS for Watershed Prioritization and Management: A Case Study

Abstract

The present investigation is an effort to prioritize the subwatersheds of the Ret watershed using morphometric parameter to identify the suitable sites for soil and water conservation measures. The Ret watershed was delineated into 26 subwatershed and morphometric parameters namely bifurcation ratio, form factor, circularity ratio, elongation ratio, drainage density, stream frequency, drainage texture were derived independently for each of the subwatersheds. Based on the Morphometric parameters watershed prioritization was carried out and water resource management plan were derived by integrating land use/cover, soil and slope information with morphological parameter. The highest value of bifurcation ratio, drainage density, stream frequency, drainage texture among 26 subwatersheds was assigned a rating of 1, the next highest values was given rating of 2, and so on. For the shape parameters i.e. form factor, circularity ratio, elongation ratio, the lowest value was given a rating of 1, the next lowest value was given a rating of 2, and so on. Integration of the above seven parameters was done using simple summation of ratings. Based on the average value of these parameters, the subwatershed having the least rating value was assigned the highest priority number of 1, the next highest value was assigned a priority number 2, and so on. Based on the average value of these parameters, the subwatershed having the least rating value was assigned the highest priority and vice versa. The subwatersheds were classified into the five scales of priority, namely: very high, high, medium, low and very low. Among the identified subwatersheds in the Ret watershed, six subwatersheds covering an area of 66.5 km2 falls under very high category. The count of subwatersheds which fall under high, medium, low and very low priority class are five each and covering an area of 61.7, 58.27, 39.62 and 31.84 km2 respectively. Based on the morphometric parameter, stream order, slope category, land use/land cover, soil type of the subwatersheds, suitable sites for check dams were identified and marked in the map for very high, high, medium, low and very low priority areas of the Ret watershed. In view of the requirement of soil and water conservation measures, it has been proposed to construct 11 numbers of check dams in subwatershed numbers 1, 4, 5, 6, 7, 8, 9, 10, 12, 22, and 24.