Evaluation of Best Watershed Management Practice for Sediment Yield Reduction (The Case Study of Baro Akobo of Upper Gilo Watershed, Ethiopia)

Abstract

This study aimed to estimate the sediment yield, evaluating its distribution, and compare the selected Best Management Practices (BMPs) and identify relatively effective management practices to alleviate soil erosion and sedimentation yield in the Upper Gillo watershed. Soil and Water Assessment Tool (SWAT) model with the interface of Geographical Information System (GIS) were used to simulate, streamflow and sediment yield. Meteorological, hydrological and spatial data were used while modeling the Upper Gillo watershed. After the simulation has executed, the model was calibrated using flow and sediment data from 1990–2004 and validated for 2005–2014. The coefficient of determination (R2) and Nash Sutcliff efficiency (NSE) values for the daily flow calibration using SUFI2 are 0.76 and 0.8 respectively and for validation, it was 0.82 and 0.81. For monthly sediment yield by using the SUFI2 calibration technique the model evaluation coefficients R2 and NSE for calibration were computed as 0.78 and 0.69 respectively, for validation, it was 0.64 and 0.72 respectively after calibration was performed, the simulated average annual sediment yield was estimated to be 57.98 million ton/yr at the outlet. The sediment yield distribution analysis showed that 18 sub-basins showed a relatively high sediment yield rate (> 20 ton/ha/yr) among the 45sub basins. The Scenarios practical in this paper were Base scenario, terraces, contouring and introduce strip cropping. Three watershed management scenarios were simulated to compare their effectiveness of sediment yield reduction from the existing baseline condition. The result shows that the mean annual sediment yield could be reduced by 37.59% by applying filter strips, 20.41% by applying to terrace, and 41.99% by applying to contour. Therefore, applying to the terrace is relatively effective to reduce the mean annual sediment yield from the Upper Gillo watershed. Keywords: Best Management Practice, Scenario, Sediment, SWAT model, Upper Gillo Watershed.