IDENTIFICATION OF SOIL CONSERVATION PRIORITY AREA IN JEDEB RIVER WATERSHED, EAST GOJJAM ZONE, AMHARA REGION, ETHIOPIA

Abstract

Soil erosion is the physical movement of soil particles from a given area and a cause for land degradation. The objective of this study was to identify the most erosion vulnerable sub-watersheds for planning appropriate conservation intervention and restoration measures in Jedeb watershed. This is because it is difficult to launch soil and water conservation and other environmental protection projects in all sub-watersheds at the same time. In this study Revised Universal Soil Loss Equation (RUSLE) integrated with satellite remote sensing (RS) and geographical information system (GIS) was applied to calculate potential soil loss at sub-watershed level. Mean annual precipitation, soil map, a 30-m digital elevation model, land-cover map produced from supervised classification of a Land Sat image, and land use types and slope steepness and slope length were used to determine the RUSLE factor values. The RUSLE was calibrated and validated by using ten years sediment data. Before calibration and validation, sensitivity analysis of the parameters was done. The model was found to be most sensitive in crop cover and management practice(C) than others. The result of the study revealed that the potential average annual soil loss of the sub-watersheds ranged from 29.275 to 72.529 ton/ha/year with a mean annual soil loss of 46t/ha/year. Based on the predicted sediment yield rates, the watershed was divided into three priority categories for conservation intervention where as 16 sub-watersheds were identified that would be used as planning units. Four sub-watersheds had shown very high sediment yield rate and covering 27.75% from the total area which was found in the midstream part of the watershed. Under high sediment yield category there were six sub-watersheds which cover 43.46% of the study area. About 28.79% of the watersheds were found in the moderate sediment yield classes. In prioritizing for conservation intervention, four sub-watersheds (SW-15, SW-1, SW 10 and SW-14) should be considered in the first priority areas, six sub-watersheds (SW-3, SW-8, SW-9, SW-11, SW-12 and SW-16) should be considered as the second priority areas and six sub-watersheds (SW-2, SW-4, SW-5, SW-6, SW-7 and SW-13) should be considered in the third priority for soil and water conservation intervention.