Estimation of Annual Soil Erosion from Upper Fincha’aa catchment By Using Rusle

Abstract

Quantifying the amount of the soil loss using GIS and RUSLE helps to substantiate investment in sustainable land management for the benefit it’s to land users. Soil erosion is recognized as one of the world's most serious environmental and economic problems. It deteriorates the soil quality, loss of nutrients ,changes in physical, chemical and biological processes and reducing agriculture productivity resulting in global food insecurity .Like other highland parts of Ethiopia, the soil erosion by water is the major factor for soil loss in the Fincha’a catchment. Hence, the general objective of this research is to Estimate average Annual Soil Erosion from Upper Fincha’a catchment By Using Revised Universal Soil Loss Equation (RUSLE. Geographic Information System (GIS) with (RUSLE) was used to estimate average annual soil loss, sediment yield at the outlet and identify the most vulnerable area of soil erosion in the Fincha’a catchment. Data that are used for this study was gathered from different sources such as National Mapping Agency, National Meteorological service Agency, Ministry of Water, Irrigation and Electricity of Ethiopia. Types of data used was the monthly precipitation of 24 year (1991-2015) for seven stations, soil data, Digital Elevation Models (30 x 30m), Land use and land cover data of the study area. Eventually, each of the RUSLE factors, with associated attribute data were digitally encoded in a GIS database to create five thematic map layers of each factor. By integrating these five map layers in GIS raster calculator, the required spatially distributed annual average soil loss rate was determined. The result showed that the potential annual soil loss rate of the watershed varies from 0 to 375 ton/ha/yr and the mean annual soil loss rate was found to be 31 ton/ha/yr. The total annual soil erosion from the entire watershed area was about 4.08 Million tons annually. The estimated sediment yield at watershed outlet was about 386628.6 ton/yr from 1318 square kilometer by using Sediment Delivery Ratio (SDR) technique. . In present study areas that were highly vulnerable to soil erosion were characterized by steep slopes, very low vegetation cover, and high rainfall. The result shows that, it could be difficult to maintain the sustainability of the soil productivity if the specified much of soil removed annually. It also reveals that most of the watershed erosion severity evaluated under low and moderate soil erosion severity classes covering 46 % of the watershed areas which is due to the effect of Cropland and Sparse forest which shows less vulnerable to soil erosion. In the soil loss rate map of upper Fincha’a watershed, the steep slope lands of northwest and northeast areas which were identified as extensive soil loss. Hence, those areas needs immediate attention and priorities when implementing soil conservation and management activities before the area jumps to recover soil degradations