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Accueil du site → Master → Afrique du Sud → 2014 → Integrated catchment modelling of sedimentation processes of reservoirs : a case study of the Welbedacht Reservoir, South Africa

Tshwane University of Technology (2014)

Integrated catchment modelling of sedimentation processes of reservoirs : a case study of the Welbedacht Reservoir, South Africa

Chabalala, Dunisani Thomas

Titre : Integrated catchment modelling of sedimentation processes of reservoirs : a case study of the Welbedacht Reservoir, South Africa.

Auteur : Chabalala, Dunisani Thomas.

Université de soutenance : Tshwane University of Technology

Grade : MAGISTER TECHNOLOGIAE : CIVIL ENGINEERING 2014

Résumé _Sedimentation is one of the major problems affecting reservoir storage capacities in South Africa. For example, the Welbedacht reservoir capacity has been reduced rapidly from the original 114 x 106 m3 to approximately 16 x 106 m3 in a period of 20 years since its completion. This has been brought about by land use changes within the catchment associated with land clearing for agricultural and housing development, and road construction. These activities have resulted in widespread soil erosion of the land surface leading to sedimentation of the reservoir.
The aim of this research was to investigate and develop a model for an integrated catchment modelling of sedimentation processes and management for the Welbedacht reservoir. The methodology involved reviewing and analysing current erosion prediction models of sediment yield . The Revised Universal Soil Loss Equation (RUSLE) was chosen after subjection to several criteria and subsequently used to predict annual soil loss in different land uses in the catchment. Data such as rainfall, soil type, topography, cover management and support practice were utilised for soil modelling using RUSLE. The results revealed that the main sources of sediment in the watershed are cultivated land (273 t/ha/yr), built-up land (103.3 t/ha/yr), forest and forest plantation contribute 6.2 and 16.6 t/ha/yr, respectively. Grassland, degraded land, mining and quarry which contributed 3.9, 9.8 and 5.3 t/ha/yr, respectively.
The RUSLE model was then used to examine the impact of soil conservation practices, the results revealed that the total aver age annual soil loss in the catchment decreased by 72 % and the sediment yield from cultivated land decreased by 75 %, while built-up land and thicket bush decreased by 42 % and 99%, respectively. Thus, the proposed remedy is to implement the control at source strategy, based on modifications to the current land use practices, so as to encourage soil conservation and minimise soil loss from the contributing catchments, thus reducing sediment loads into the streams and reservoir.

Sujets  : Sedimentation and deposition — South Africa — Bloemfontein. Reservoirs

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