WATERSHED PRIORITIZATION FOR SOIL AND WATER CONSERVTION PRACTICE USING InVEST SDR MODEL: THE CASE OF AWADI WATERSHED, NORTH SHOWA ZONE, ETHIOPIA

ABSTRACT Watershed resource degradation is one of the major challenges in agricultural production in many parts of the world, especially in developing nations. Among the various forms of watershed degradation, soil erosion is the most serious problem challenging the sustainability of agriculture. This study was aimed at prioritizing sub watersheds for soil and water conservation practices by using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Sediment Delivery Ratio (SDR) model with estimates of soil loss and sediment export in data-scarce regions of the Awadi watershed in the northern highlands of Ethiopia. The most important InVEST SDR model parameters are land use land cover type (LULC), digital elevation model (DEM), soil erodibility (K factor), rainfall erosivity (R factor), biophysical table mapping each LULC code to biophysical properties of that LULC class, sub watershed boundary, Borselli k parameter, Borselli IC0 parameter, and the Maximum SDR Value. This study revealed that the mean annual soil loss was 51 t ha-1 yr-1 and the average annual sediment export that reached the stream was 5 t ha -1 yr -1 for the Awadi watershed. The result of this study indicated that the current mean soil loss rate in this watershed (51 t ha -1yr -1) is higher than the tolerable soil limit loss of 2–18 t ha-1yr-1 estimated for Ethiopia's highlands. Sub-watersheds were prioritized based on soil erosion risk. Sub watershed 2 (SW 2) has the highest soil loss rate (73.1 t ha-1yr-1), while sub-watershed 7 (SW 7) has the lowest soil loss rate (31.3 t ha-1 yr-1). As a result, Sub-watershed (SW 2) and sub-watershed (SW-1) in the Awadi watershed were the most severely affected watersheds by soil erosion and sediment export, respectively. A sub-watershed presenting a high soil erosion risk needs to be given first priority in soil conservation planning.