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Accueil du site → Master → Afrique du Sud → 2000 → An assessment of land degradation in the headwater catchment of the Klein Zeekoei River, Great Karoo, South Africa

University of Cape Town (2000)

An assessment of land degradation in the headwater catchment of the Klein Zeekoei River, Great Karoo, South Africa

Holland RM

Titre : An assessment of land degradation in the headwater catchment of the Klein Zeekoei River, Great Karoo, South Africa

Auteur : Holland RM

Université de soutenance : University of Cape Town

Grade : Master of Science (Ms) 2000

Résumé
The headwater catchment of the Klein Zeekoei River is situated in the Sneeuberg uplands of the Great Karoo, and is one of the tributaries to the Orange River system. The region comprises a semi-arid area of extensive stock farming and is an important contributor to the South African economy. The Klein Zeekoei River valley has suffered extensive land degradation in the form of sheetwash, rill, and gully erosion and badland development. This study focussed on the history of land degradation in the upper Klein Zeekoei River catchment, and the relative contributions of inherent soil properties, grazing, cultivation, slope, vegetation, and land management practices to land degradation. The study also assessed the effectiveness of anti-erosion measures that have been implemented since the late 1940’s in the upper Klein Zeekoei River Valley. These objectives were achieved by using a combination of the analysis of textural and chemical properties of soils and sediments, the analysis and mapping of aerial photography, an archival investigation, conducting a number of interviews, and from observations made in the field. The findings indicate that approximately 25% of land in the upper Klein Zeekoei River valley is moderately to severely degraded, and that this figure has remained relatively constant since 1945. This can be attributed partly to the effectiveness of soil erosion measures implemented in the area which have led to limited rehabilitation of some areas. Other areas of degradation have increased in extent since 1945, and many areas of badland erosion are presently actively eroding. Valley floor incision in the area probably started in the latter part of the 19th century. The most likely trigger for the onset of incision is the disturbance of valley floor vegetation caused by grazing and trampling from animals outspanned along this part of the wagon route to the Kimberley diamond fields to the north. The dispersive and erodible nature of soils and sediments in the Klein Zeekoei River valley, in combination with over-grazing (rather than cultivation) of footslope areas in the first half of the 20th century, is the main cause of the extensive badland erosion in the area. An understanding of the mechanisms that control soil erosion in headwater catchments such as the upper Klein Zeekoei River are important for two main reasons. Firstly, there is the issue of reduced stock carrying capacities in these areas. Secondly, there is the strategic issue of water quality and water supply due to the downstream siltation of storage dams within the Orange River system, of which the Klein Zeekoei River is a tributary.

Présentation (NRF)

Page publiée le 19 octobre 2017