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Title: Application of SWAT to assess the effects of land use change in the Murchison Bay catchment in Uganda

Author
item ANABA, LISTOWEL - Makerere University
item BANADDA, NOBLE - Makerere University
item KIGGUNDU, NICHOLAS - Makerere University
item WANYAMA, JOSHUA - Makerere University
item ENGEL, BERNIE - Purdue University
item Moriasi, Daniel

Submitted to: Grazinglands Research Laboratory Miscellaneous Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2016
Publication Date: 12/20/2016
Citation: Anaba, L.A., Banadda, N., Kiggundu, N., Wanyama, J., Engel, B., Moriasi, D.N. 2016. Application of SWAT to assess the effects of land use change in the Murchison Bay catchment in Uganda. Computation Water, Energy, and Environmental Engineering. 6:24-40.

Interpretive Summary: In this study, the Soil and Water Assessment Tool (SWAT) model was used to simulate the impact of land use changes on streamflow and sediment loss from the Murchison Bay catchment, Uganda. The SWAT model was calibrated and validated for streamflow and used to estimate sediment and nutrient losses as a result of landuse changes between 1995 and 2003. The model was satisfactorily calibrated for streamflow. Simulated surface runoff increased from 101 mm yr-1 to 128 mm yr-1 between 1995 and 2003. Within the same period, upland sediment transport to stream network increased from 5.2 tons ha-1 yr-1 to 6.3 tons ha-1 yr-1. The increased surface runoff rate and sediment loss can lead to severe and frequent flooding, lower water quality, and reduce crop yield in the catchment. Therefore, comprehensive water management steps should be taken to reduce surface runoff and the subsequent sediment losses in the catchment. These results showed that if the SWAT model is properly calibrated, it can be used to characterize local east African conditions to support land management decisions related to land use changes.

Technical Abstract: The Soil and Water Assessment Tool (SWAT) is a versatile model presently used worldwide to evaluate water quality and hydrological concerns under varying land use and environmental conditions. In this study, SWAT was used to simulate streamflow and to estimate sediment yield and nutrients loss from the Murchison Bay catchment as a result of land use changes. The SWAT model was calibrated and validated for streamflow for extended periods. The Sequential Uncertainty Fitting (SUFI-2) global sensitivity method within SWAT Calibration and Uncertainty Procedures (SWAT-CUP) was used to identify the most sensitive streamflow parameters. The model satisfactorily simulated stream discharge from the catch-mint. The model performance was determined with different statistical methods. The results showed a satisfactory model streamflow simulation performance. The results of runoff and average upland sediment yield estimated from the catchment showed that, both have increased over the period of study. The increasing rate of runoff can lead to severe and frequent flooding, lower water quality and reduce crop yield in the catchment. Therefore, comprehensive water management steps should be taken to reduce surface runoff in the catchment. This is the first time the SWAT model is used in the Murchison Bay catchment. The results showed that, if all uncertainties are minimized, a well calibrated SWAT model can generate reasonable hydrologic simulation results in relation to land use that are useful to water and environmental resources managers and policy and decision makers.