Estimation of Soil Loss Rate Using RUSLE Model Integrated with GIS and Remote Sensing Techniques: The Case of Wama Watershed, Western Ethiopia

Abstract

One of Ethiopia's most problematic issues is soil loss due to degradation and erosion. Estimating the quantity of soil loss at the watershed level is required to solve this problem. However, in many catchments (watersheds) in Ethiopia, specific up-to-date information is still lacking. The goal of this study was to use model estimates and GIS to investigate the nature, extent, and rate of soil loss in the watershed. The Revised Universal Soil Loss Equation (RUSLE) was used in conjunction with satellite remote sensing and geographic information systems(GIS) as a useful tool for conservation planning. Mean annual precipitation, digital soil map, digital elevation model, LULC map, and slope steepness were used to determine the RUSLE parameters. The result showed that the potential annual soil loss of the watershed ranges from 0 to 53200.7t/ha/year and the mean annual soil loss rate is 357ton/ha/year. The study area was classified into five severity classes as, Low (0 – 15 t h^-1 yr^-1), Moderate (15.1 – 35 t h^-1 yr^-1), High ((35.1 – 50 t h^-1 yr^-1), Very High (50.1 – 75 t h^-1 yr^-1) and Severe (>75 t h^-1 yr^-1).  Moreover, the total annual soil loss in the study area was 13400000 tons from 3344.Km². According to the study result, an area that covers 62% (2074.82 sqr. km) of the watershed have low soil loss which indicated more than half of the area has low soil loss while 38% (1269.58 sqr. km) of the watershed has severe to moderate soil loss. As a result, governments, non-governmental organizations, and communities in the watershed should concentrate on implementing soil and water conservation measures that will assist to alleviate the situation. The integration of the  RUSLE model and geographic information systems platforms are also presented in this study as a strong and relevant strategy for estimating and monitoring the geographical rate of soil loss distribution for sustainable soil resource management.