SEASONAL VARIATION OF THE RELATIONSHIP BETWEEN SUSPENDED SEDIMENT AND RIVER DISCHARGE

Information on measured sediment load is important in calibrating hydrologic models used in sediment yield prediction. The purpose of this study was to relate sediment load to discharge at a river section. An appropriate section was selected at the Lotanyanda river, Limpopo, South Africa. Depth integrated sediment samples were collected on various dates at an appropriate interval once a day and analyzed to determine the sediment concentration and turbidity. The water level and temperature readings were also taken at the time of sediment sampling. Information on sediment concentration and discharge was used to determine the sediment load on the dates when sampling commenced autumn through winter in 2016. Based on the values of measures of performance that included R2, NSE, RMSE, PBIAS and RSR, performance of predicted sediment concentration based on sediment rating curves was very good and could beused for predicting sediment load. The measures of performance, however varied from season to season. The relationship between sediment load and discharge varied from one season to another and the quality of fit (R2) based on regression analysis differed from one season to another. Knowledge of sediment load discharge relationship can be used in sediment load prediction based on discharge information.