SOIL LOSSES FROM OLUR MICRO-CATCHMENT IN THE CORUH RIVER BASIN USING GEOWEPP MODEL

Soil is a very important resource for protecting productive agricultural lands and for ensuring their sustainable use. In this context, it is important to take the necessary measures to prevent the losses of soil by erosion and to determine amount of soil losses with relevant models. In this study, by using the Geo-Spatial Interface for Water Erosion Prediction Project (GeoWEEP) model, both surface (hillslope) and channel erosions were estimated to evaluate the total soil loss from the Olur Micro-catchment (37517 ha) within the Coruh River Basin. Additionally, for the conservation purposes, areas with high erosion potential in the micro-catchment were also identified and mapped by the model. The land uses of Olur Micro-catchment, which has a slope of 28.07%, consist of approximately 45% grassland, 19% forest and 14% agriculture. In this study, GeoWEPP model was run with 2 different simulation programs. In the first run, only one-year climate data from the year 2018 was utilized for the soil loss estimation. The total precipitation amount for the 2018 was 561 mm/yr. In the second run, 20-year climate data were utilized and the estimated soil loss values were obtained for 20 years. The recorded average precipitation over 20-year period was 426 mm/yr, which was much lower than in 2018. Based on this information, the total soil loss (sediment yield) in 2018 determined by the GeoWEPP model from the catchment was found to be 89123 tons/yr (2.8 tons/ha/yr). As for the 20-year simulation, a soil loss of 9501 tons/yr (0.27 tons/ha/yr) was estimated by the model. Results revealed that the higher amount of precipitation in 2018 caused soil loss to be 10.4 times higher than the 20 years average soil loss. The surface erosion (136525.2 ton/yr) was found to be almost 7 times higher than the channel erosion (19989.4 ton/yr) indicating the dominant pathway of erosion in the Olur micro-catchment. Additionally, the areas with high erosion risk in the study area were predicted very accurately and showed in the produced soil loss map. In conclusion, an idea with the study was obtained about the amount of soil loss from the Olur Micro-catchment to Ayvalı Dam, and the recommendations were made for soil protection measures to reduce the amount of soil loss in the erosion-sensitive areas that were identified over the the Olur micro-catchment.