Application of the swat model in estimating sediment yield: a case of songwe river basin in Mbeya, tanzania

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University of Dar es Salaam,
Songwe River basin covering about 4214.3 km2, has undergone tremendous changes in land use/land cover in the recent past. These changes are suspected to have impacted negatively on the hydrology and soil conservation of the catchment. In order to make recommendation on catchment management, SWAT model was calibrated using observed stream flow and sediment data, but, sensitivity analysis was carried out before calibration to understand the most sensitive parameters. SWAT model has been chosen as it is an integrated physically based distributed watershed model. Also, its suitability to different parts of the world has also been well established. Data from year 1984-2009 were used to simulate stream flow and sediment yield. Auto-calibration has been performed first followed by manual, with 6 and 3 years’ time series of stream flow were used for calibration and validation respectively. Flow calibration efficiency has been tested by ENS and R2. On calibration the values of R2 and ENS were 0.63 and 0.54 while on validation were 0.62 and 0.51 respectively. On sediment Calibration the model performance was tested using RMSE and relative error. The results of relative error were <20% except two pairs which were 21% and 22% respectively. Sediment calibration gave a RMSE of 29.75. Validation of sediment was done using factors that contribute to sediment detachment, transport and deposition. The factors included rainfall variability, runoff and sub basin elevation/slope. Results showed that sediment yield has close relationship with these factors. The estimated annual average sediment yield was about 377 t/km2/yr. The study recommended further studies; especially on land use/cover change should be carried out to investigate the most causative of sedimentation in Songwe River Basin.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark ( THS EAF GB656.2.H9E84)
Hydrologic models, Sediment yield, Songwe river basin, Mbeya region, Tanzania
Eslan, Ph (2012) Application of the swat model in estimating sediment yield: a case of songwe river basin in Mbeya, Tanzania Master dissertation, University of Dar es Salaam. Dar es Salaam