Quantifying and predicting hydrological responses of water quality associated with land cover changes within the upper Vaal River, South Africa

Ph.D. (Geography)South Africa is characterised by limited natural water resources and is water-stressed. The Upper Vaal Water Management Area (WMA) is part of the Vaal River system, which is deemed to be the ‘workhorse’ of South Africa as it is located in the economic heart of the country. The WMA supplies water to all of the major economic entities in the economic hub of the country and is fully exploited in terms of the water that it makes available. Owing to its prime importance in terms of the economic development of the country, the quality of the water in the Upper Vaal WMA is an important factor which needs to be investigated and monitored intensively. The degradation in the quality of the water in this region will in its turn reduce the availability of water in the Upper Vaal WMA and have widespread environmental, social, as well as economic consequences and impacts. The aim of this study is thus to quantify and predict future hydrological responses, in terms of water quality, towards land cover changes in the case of the Upper Vaal WMA for the period, July 2000 to June 2012. In so doing, model equations can be formulated and predictions can be made for future hydrological changes in terms of future concentrations of the selected water quality parameters linked to specific land cover change scenarios. The quality of the water in the Upper Vaal WMA varies significantly across all of the secondary and tertiary catchments and could, therefore, be described as being of a heterogeneous nature. Its quality as a whole is below average and in some cases, poor. The quality of the water in the secondary catchment of the Wilge River, on the other hand, is for the most part of an ideal to acceptable standard. However it has been degraded to a certain extent as it displays tolerable concentrations of phosphate, COD and Chlorophyll a and unacceptably high concentrations of nitrate. The Vaal River, Vaal River Barrage and the Mooi River catchments are significantly degraded owing to the mainly tolerable to unacceptably high concentrations of most of the selected water quality parameters that they contain....