Soil Erosion Modeling Using GIS Based RUSEL Model in Gilgel Gibe-1 Catchment, South West Ethiopia

Abstract

This study was aimed to estimate soil loss in Gilgel Gibe-1 catchment by GIS-based RUSLE model and prioritize sub-watersheds for soil conservation planning. Both primary and secondary data from different sources were used in this study. The amount of soil loss from the catchment is estimated with GIS-based RUSLE model which uses the rainfall-runoff erosivity, soil erodibility, topographic effect, soil/surface coverage and land management practice of the catchment as an input. The result of the study shows the mean annual soil loss of the catchment is 62.98 t ha-1year-1 which is about 26.56x106 ton year-1. Erosion ‘hotspot’ areas are identified and prioritized on the bases of soil loss. Accordingly, SW4, SW3, SW5, SW6, SW9, SW8, SW7, SW2, and SW1 got 1 to 9 priority level respectively. 35.2% of the catchment area is covered by soil loss class ranging 0-5 t ha-1year-1 and about 56 % of the catchment have soil loss greater than a tolerable level which is 11 t ha-1year-1. The result of this study indicates the catchment and reservoir were under a problem of soil loss and siltation. Therefore, this study recommends immediate action, soil and water conservation measures, should be taken in the catchment according to the priority of sub-watershed and, also a detailed study is appreciated, especially on experimental test plots.