Bibliography: pages 239-249. / The littoral aquatic plant community of Swartvlei declined after 1978, apparently as a result of increased lake water turbidity. To investigate the causes of this, land use and land management of the Swartvlei catchment area have been studied. Possible causes and the extent of accelerated runoff and sediment loss in different rainfall conditions were determined. Rainfall, water flow, Secchi disc and sediment load data are reviewed and the apparent relationship between them noted. Water samples were collected at 32 different sample sites to determine sediment loads. Samples were vacuum filtered through coarse and fine glass fibre filters and the results recorded in milligrams of sediment per litre of water. The quantity and duration of rainfall in the immediate pre-sampling period were recorded. Secchi disc transparency of Swartvlei water was recorded. Catchment land use and land management are described in four areas based on land use and geographical location. The naturally vegetated montane upper catchment area, the foothill plantation area, the agricultural areas on the tertiary plateau and the road reconstruction and recreation areas are considered separately. Land use and land management information was obtained from a literature review and study of topographical maps, orthophotographs, geological survey maps and aerial photographs. Flights over the area enabled confirmation of observations. Informal interviews with persons involved in catchment management, property-owners and roads authorities were conducted. Areas of accelerated sediment loss were determined and the magnitude of the problem noted. Results show that rainfall duration, intensity, quantity and distribution determine the effect of sediment-laden runoff on river and vlei water quality. Small storm events (< 50 mm) influence the water quality of tributaries particularly in the lower catchment areas. Storm events of > 50 mm influence the main catchment rivers and light penetration in Swartvlei at the river inflow points. Long-duration flood rainfalls bring about massive soil loss in the catchment and cause reduced light penetration over the entire surface area of Swartvlei. Most sediment originates from the lower sections of the catchment area where human activities are most intense. Natural vegetation acts as a protective barrier against soil loss and its removal and the lack of suitable runoff channels leads to greater sediment loss. Recommendations to reduce sediment loss are made. The topographical and soil characteristics of the area make it sensitive to soil loss, the significance of which has only been recognised recently. The socio-economic circumstances in the region and the present economic recession are limiting amelioration of the situation in this beautiful natural area.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/15793 |
| Date | January 1985 |
| Creators | Barker, Janet Alexandra |
| Publisher | University of Cape Town, Faculty of Science, Department of Environmental and Geographical Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MA |
| Format | application/pdf |
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