Streamflow and sediment yield estimation, and area prioritization for better conservation planning in the Dawe River watershed of the Wabi Shebelle River Basin, Ethiopia

Abstract

Estimating sediment yield and streamflow, as well as identifying soil erosion processes, are necessary for properly designing superior management techniques, monitoring and evaluating various management scenarios, and prioritizing better conservation planning. Therefore, this study estimates streamflow and sediment yield and prioritizes the catchment sub-watersheds for conservation planning in the Dawe River watershed. In the continuous-time step, sediment load data is generated by developing a sediment rating curve. Statistical measures were used to weigh the SWAT's performance in estimating streamflow and sediment output over the calibration (2000–2008) and validation (2009–2013) periods. The model's performance in estimating the monthly streamflow was 0.73, 0.55, and 0.79 for NSE, R-factor, and R2, respectively, according to the calibration results. For sediment yield, the Nash Sutcliffe efficiency (NSE), R-factor, and R2 were 0.77, 0.47, and 0.82, respectively. Estimated sediment output rates were higher in agricultural lands with eutric and rendzic leptosols soil types and gradients in the study watershed. For the indicated sub-watersheds in the catchment, the three best sediment management scenarios (BMPs) were considered: S1 (filter strip), S2 (terrace/bund), and S3 (reforestation). With the implementation of S1, S2, and S3, the sediment yield was reduced by 15.7 percent, 21.3 percent, and 24.9 percent, respectively, based on the chosen BMPs. As a result, adopting S3 for the Dawe River watershed for productive sediment reductions should be encouraged. As a result, our findings point to the best strategy for negotiating a stronger conservation plan.