Sources of soil erosion in the Hazelmere catchment KwaZulu-Natal, South Africa.

Abstract

Sedimentation of reservoirs is of major concern, particularly in South Africa where water resources are scarce. When a reservoir is filled with sediments, it is not only the water storage capacity which is reduced but the reservoir site could be lost. An investigation into the sources of sediment that pose a threat to the economic life of the Hazelmere Dam, located on the Mdloti River, was undertaken with a view to determining the extent to which siltation problems within the catchment may be attributed to soil characteristics as opposed to being related to other factors such as potential land use practices. The study determined that soils of the catchment are naturally prone to erosion. From particle size analysis, it is evident that these soils are highly erodible, whereas chemical analysis suggest that some of these soils are dispersive. Soil erosion does not necessarily develop as a direct consequence of a single variable such as soil chemistry nor of soil physical properties only, but is multivariate in nature and may be associated with a combination of factors. Using the factors of slope, land use, geological type and rainfall, an erosion risk or hazard map of the Hazelmere catchment has been produced. The actual erodibility of soil as determined by the Eijkelkamp rainfall simulator was then compared to this risk map. It is evident that there is a relationship between soil loss and soil erosion risk. Furthermore, results of soil loss and land use showed that there is a relationship between the two factors, a similar relationship existed between land use and soil erosion risk where soil erosion risk increased with grazing and cultivation land uses. This study has mainly focused on the scientific and technical aspects concerning the sources of sediment. However, it has also shown that some of the contributing factors and barriers to adequate soil conservation are related to socio-economic and socio-political factors.