In this context, the Eastern Cape (3 860 702 ha) is the most severely affected province, followed by the Free State (2 153 343 ha), Northern Cape (1 974 854 ha), Limpopo (1 943 376 ha), KwaZulu-Natal (1 284 975 ha), Mpumalanga (1 222 727 ha), Western Cape (1 030 530 ha), North West Province (379 879 ha) and Gauteng (347 149 ha). The results emphasise sheet and rill erosion and illustrate that areas with high erosion risk occur mostly in the eastern parts of South Africa (see Figure 2). The model has sufficient simplicity for application on a national scale with incorporation of the main factors causing soil erosion including rainfall erosivity, soil erodibility, topography and vegetation cover (and management). Prior to above-mentioned study, a soil erosion model, known as the Universal Soil Loss Equation, was used by Dr Le Roux and his colleagues to estimate rainfall erosion in South Africa. The Northern Cape (160 885 ha) and Eastern Cape (151 759 ha) are the most severely affected, followed by KwaZulu-Natal (87 522 ha), the Free State (64 674 ha), Limpopo (58 669 ha), Western Cape (25 403 ha), Mpumalanga (17 420 ha), North West Province The map shows that all provinces are affected by gully erosion (see Figure 1). As a result, the study successfully mapped over 100 000 gully erosion features ranging from just a few cubic metres to several hectares each. SPOT 5 satellite imagery was utilised because it provides high resolution air, photo-like quality for erosion mapping and was acquired from government agencies for the whole of South Africa. The most recent erosion map includes a gully erosion map for South Africa created by Dr Jay le Roux (previously at the Agricultural Research Council, but currently at the University of the Free State) and Mr Ndifelani Mararakanye (Department of Agriculture, Forestry and Fisheries) using satellite imagery. Recent erosion assessments sketch a gloomy picture Given the increasing threat of the sedimentation/siltation of reservoirs, it is important to identify source areas and key processes of sediment transport from field to stream. The soil erosion/sedimentation problem may get worse in the future due to population growth and potential climatic changes. For example, due to siltation, the storage capacity of the Welbedacht Dam near Dewetsdorp in the Free State reduced rapidly from the original 115 million cubic metres to approximately 16 million cubic metres within 20 years since completion in 1973.Īs a result, the Mangaung Municipality in Bloemfontein recently received water from the more distant Katse Dam in Lesotho at a tariff of R2,20 per kilolitre instead of the normal 18,7 cents from the Welbedacht Dam (as reported by Marietjie Gericke in the Volksblad on Friday, 29 August 2014). One of the main concerns of the Department of Water Affairs of South Africa is the mobilisation of eroded soil and its delivery to rivers and dams. Water scarce countries, such as South Africa, are increasingly threatened by pollution and sedimentation of water bodies due to suspended sediment concentrations in streams. Soil erosion not only involves the loss of fertile topsoil and reduction of soil productivity, but is also coupled with serious off-site impacts related to increased mobilisation of sediment and delivery to rivers, causing siltation and pollution of South Africa’s water resource. Several scientists agree that the cost of food production is increasing in many parts of the world due to erosion and loss of nutrients. filtering, infiltration and water holding capacity) of soil.
biomass production) and hydrological functions (e.g.
Prolonged erosion causes irreversible soil loss over time, reducing the ecological (e.g. Soil formation is a relatively slow process and therefore soil is essentially a non-renewable and a limited resource. Poor farming practices as well as the trend toward agricultural intensification have been considered to be major causes of erosion. Although soil erosion is a natural process, it is often accelerated by human activities, for example by the clearing of vegetation, soil tillage or overgrazing. Soil erosion is a major environmental problem confronting land and water resources in South Africa. JAY LE ROUX, lecturer: Department of Geography, University of the Free State and HENDRIK SMITH, conservation agriculture facilitator, Grain SA Soil erosion in South Africa - its nature and distribution
0 kommentar(er)
