A simple approach to estimating channel transmission losses in large South African river basins

Abstract

Study region: South Africa, Lesotho and Swaziland. Study focus: The focus of this study is on the development of simple transmission loss functions that can account for channel evaporation and alluvial storage losses from upstream flows in the downstream sub-basins of large river systems. New hydrological insights for this region: The importance of channel evaporation (and hence the relevance of the proposed model) is quite variable depending on the climate variations within the basins. While the model is validated using a site in the USA, it is difficult to fully assess the importance of alluvial losses in the southern Africa region, as there are almost no appropriate observed data, and few studies that quantify alluvial material extent or properties. Where existing information on transmission losses is available for South Africa, the model generated results that are in broad agreement. Keywords: Transmission losses, Large basins, Hydrological modelling, Uncertainty, Data scarcity