Estimation of Runoff and Sediment Yield Using SWAT Model: The Case of Katar Watershed, Rift Valley Lake Basin of Ethiopia

Dulo Husen,Brook Abate

doi:10.11648/j.ijmea.20200806.11

Abstract

Estimating runoff and sediment yield at watershed level is important for better understanding of hydrologic processes and identifying hotspot area by using Soil and Water Assessment Tool (SWAT) model for intervention strategies. From the result of Global sensitivity analysis, 12 highly sensitive parameters identified. The obtained results were satisfactory for the gauging station (coefficient of determination (R2)=0.8, Nash-Sutcliffe Efficiency (NSE)=0.6 and percent difference or percent bias (PBIAS)=0) from 1990 to 2005(16) years used calibration and (R2=0.6, ENS=0.55and PBIAS=1.2) from 2006 to 2013(8 year) were used for validation period respectively. Among all sub-watersheds, nine sub watersheds were more vulnerable to soil loss and potentially prone to erosion risk, which was out of range of tolerable soil loss rate (18 tha-1yr-1). In conclusion, the SWAT model could be effectively used to estimate runoff and sediment yield; and identified hotspot area. In addition, the result could help different stakeholders to plan and implement appropriate interventions strategies in the Katar watershed.

Highlights

Out of 60 million hectares estimated to be agriculturally productive lands, about 27 million hectares are significantly eroded, 14 million hectares are seriously eroded and 2 million hectares have reached the point of no return [6]
Another report by the Soil Conservation Research Project [31] of Ethiopia indicated that the rate of soil loss in extreme cases ranges from 0 to 300 t ha-1yr-1 with an average loss of 70 t ha-1yr-1, which is beyond the concept of any tolerable soil loss
Katar watershed is under heavy pressures [17], climate change [34] and the intensification of agricultural development activities were increasing from time to time [32] as a result huge amount of soil losses from the study area, and some areas under high and sever soil erosion

Summary

Introduction

Out of 60 million hectares estimated to be agriculturally productive lands, about 27 million hectares are significantly eroded, 14 million hectares are seriously eroded and 2 million hectares have reached the point of no return [6]. Land cover change is massively and rapidly taking place, as elsewhere in the Ethiopian Central Rift Valley (CRV) [7] and CRV is one of the environmental vulnerable areas in the country. Katar watershed is under heavy pressures [17], climate change [34] and the intensification of agricultural development activities were increasing from time to time [32] as a result huge amount of soil losses from the study area, and some areas under high and sever soil erosion. Large area of Katar watershed covered by Haplic Luvisols (high clay content) and agriculture is the dominant activities in area. Soil in some parts of sub watershed is highly eroded, due to fragile ecosystem and inherent erodible nature of the soils and some parts of this watershed is already taken out of cultivation due to land dissected by gully

Methods

Results

Conclusion