Sediment Yield Modelling Considering Future Land use Change: Case Study of the Usuthu River Catchment in South Africa and Swaziland
- Twenty-Sixth International Congress on Large Dams / Vingt-Sixième Congrès International des Grands Barrages. : 508-527
Résumé
In order to develop an integrated water resources development plan, accurate prediction of sediment yields in a catchment is important. The physically based and distributed hydrological model SHETRAN was applied to a sub-catchment of the Usuthu River, which has a total area of 3577 km2 , located in South Africa and Swaziland. The aim of the modelling was to predict the long term future sediment yields in the catchment due to the expected land use change (deforestation and increase in arable land). The model simulates the rainfall-runoff-sediment transport processes by using daily data. The main input data for this model includes spatial data, physical property data and meteorological data of the catchment. The model was first calibrated against observed flow data and then the sediment transport calibration was conducted for the same period. After obtaining satisfactory calibration results the long-term sediment loads simulation was carried out for a 32 year period. The maximum sediment yield for the current development scenario was found in the central catchment and was simulated as 905 t/km2.a, while a relatively low yield (74 t/km2.a) was found in the upper catchment. The mean sediment yield at the outlet of the catchment is 304 t/km2.a.
Mots-clés
Basin, Erosion, Numerical model, Runoff, Sedimentation, Jericho Dam, Heyshope Dam, Morgenstond Dam.