An assessment of soil erosion risk by water and conservation practices in Dilla watershed of Blue Nile basin

Abstract

The main objective of the study was to assess the susceptibility of different parts of Dilla watershed to soil erosion by water and to explore the conservation interventions being practiced The Dilla watershed is part of the Dabus catchment in the Eastern Blue Nile basin located in mid-west region of Ethiopia. The soil erosion risk was assessed using the Revised Universal Soil Loss Equation (RUSLE) and the micro-watersheds were prioritized for SWC interventions accordingly. Geo-spatial datasets such as Digital Elevation Models, temporal satellite imageries, topographic maps were entered into the model for obtaining spatial erosion risk values. Conservation interventions were explored by field visits, interviews, focused group discussions and ancillary data. The model revealed that the total and mean annual soil loss in the watershed is 17,688 and 95 t/ha-1/y-1 respectively. Based on the estimated soil erosion rates, the micro- watershed was prioritized for conservation intervention and nine micro-watersheds with severe erosion risk were identified that may be used as planning units. The results from interviews and group discussions have shown that both the farmers and the local experts considered soil erosion as a major problem constraining land productivity. The local experts in the study area were delineating micro-watersheds for soil and water conservation through field observation by examining the topography and drainage of each locality in the watershed. Prioritization for conservation measures is done based on trend analysis, visual observation, and reports from Development agents (DAs) working in the study watershed. The research concludes that under the conditions of the present situation in the study area, priority should be given to those watersheds, which have been severely affected by soil erosion, and the traditional way of delineating micro-watersheds and means of identifying erosion-prone areas should be augmented by empirical geo-spatial methods. These methods provide reliable estimation of soil erosion rates and prioritization of micro-watersheds for treatment.