Evaluating InVEST model for estimating soil loss and sediment export in data scarce regions of the Abbay (Upper Blue Nile) Basin: Implications for land managers

Abstract

This study was aimed to evaluate the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Sediment Delivery Ratio (SDR) model for estimating soil loss and sediment export in data scarce regions of the Abbay (Upper Blue Nile) Basin, Ethiopia with a case study in the Andassa and Koga watersheds. Inputs maps required for InVEST SDR such as rainfall erosivity and soil erodablity factors, Digital Elevation Model (DEM) and land use maps were prepared. Calibration of InVEST SDR was made using the sediment yield data collected at the outlets of the corresponding study watersheds. Model predictions showed different pattern and rates of net soil loss, and sediment export rates in the study watersheds. The result revealed that net soil loss was 58.2 and 27.3 t ha−1 yr−1 for Andassa and Koga watersheds, respectively. The observed sediment yield of Andassa watershed was 19.5 t ha−1 yr−1 while the modeled sediment export with InVEST SDR was 18 t ha−1 yr−1. On the other hand, the observed and simulated sediment yield of Koga watershed was 6 t ha−1 yr−1 and 5.1 t ha−1 yr−1, respectively. The estimated soil loss rates in both watersheds is more than the tolerable soil loss (1–6 t ha−1 yr−1) and soil formation (10–14 t ha−1 yr−1) rates of the study region. The results indicated that InVEST SDR could be used for identifying erosion hotspots and prioritizations of sub-watersheds for soil and water conservation (SWC) planning in data scarce regions of the Upper Blue Nile Basin in particular and the Ethiopian highlands in general.