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Sediment Yield Prediction for South Africa: 2010 Edition
Expanded Title:This is a report of the work on the revision of the sediment yield map of Southern Africa. The current sediment yield determination methodology of Southern Africa was developed in 1992 (Rooseboom et al., 1992). Continual revision of sediment yield prediction methods is necessary in the wake of changing environments, more data, advanced analysis tools, increased experience and current technological advancements in the sedimentation field. This report presents the revised methods for the prediction of sediment yields from ungauged catchments for South Africa and Lesotho. The development of the revised methods involved steps that ranged from data collection to the development of sediment yield estimation methods. The proposed Polihali Dam in Lesotho was selected as a case study to illustrate the role and application of mathematical modelling in sediment yield prediction within a catchment. The observed sediment yields were calculated from reservoir sediment deposition data and river sediment sampling. The relationships between sediment yields and the variables that determine sediment yields were investigated. Ten relatively homogeneous sediment yield regions were demarcated across Southern Africa. The sediment yield map of Southern Africa has been revised to incorporate the following sediment yield prediction methods: probabilistic, empirical and mathematical modelling. The probabilistic and empirical methods were validated on all the ten homogeneous regions, and recommendations are made as to which approach will be suitable for which sediment yield regions. It is recommended that estimation of sediment yields in Region 10 (Lesotho Highlands) should be based on direct measurements and locally observed data since no meaningful analysis of sediment yield values was possible due to poor and limited data. Revised sediment yield confidence bands for both the probabilistic and empirical method have been provided to allow for the prediction of sediment yields at varying preset confidence bands. Additionally, an investigation of the application of SHETRAN and ACRU as erosion and sediment yield models has shown that the models can be successfully used to simulate sediment yield in a catchment, but calibration and validation against observed sediment loads are very important. Systematic sediment monitoring in rivers and dams through sediment sampling and reservoir surveys respectively has been proposed.
Date Published:01/08/2010
Document Type:Research Report
Document Subjects:Water Resource Management/IWRM - Catchment Management
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:1765/1/10
ISBN No:978-1-4312-0042-9
Authors:Gibson L; le Roux J; Rooseboom A; Basson GR; Msadala V
Project No:K5/1765
Organizations:ARC; Stellenbosch University
Document Size:8 782 KB
Attachments:Table of Contents for 1765.pdf
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