Prof. A. Avent-Oldewage

The relationship between Man and Nature can be divided into three ‘eras.’ The first era refers to a time when Man was dominated by Nature, governed by her fluctuating seasons and at the mercy of her erratic moods. Man’s advancement brought into being the Machine, which enabled Man to move into a second era. This era brought about a brief state of equilibrium between Nature and Man, before Man advanced even further and faster into a third era in which Man and Machine dominated Nature. Man’s appropriation of Nature’s resources is his most intimate experience of the Natural world. However, in this third phase of development, Man has negated the ‘natural’ source of Nature’s resources and has thus disconnected himself from her. As a result of this disconnection, the third era is characterised by an imbalance which is leading towards the possibility of Man tipping off the scales entirely. This thesis explores the possibility of a fourth era in which Man and Nature once again achieve an equilibrium of mutually beneficial symbiosis. A fourth era would be the setting of a mend in the severed Man-Nature relationship. A ‘reconnection’ could be achieved through a renewed understanding of the systems, both natural and technological, that supply Man with Nature’s resources. The ‘Machine’ that is the Vaal Dam Wall and its surrounds was chosen as a locus for the theoretical application of a form of inhabited resource infrastructure that takes steps towards a fused Man-Nature entity. The dam wall is a significant piece of existing infrastructure that plays a major role in the capture, storage, and distribution of water to people in Gauteng, South Africa’s economic powerhouse. A legible, multi-use intervention sensitively placed on this site could reconnect the water-users to the natural water resource that is so vital to their livelihoods. The intervention is in the form of a visitor centre which incorporates water purification and hydroelectric power generation as well as a management facility for the Department of Water Affairs, the entity with jurisdiction over the Vaal water system and dam wall site. The Vaal Dam Visitor Centre could provide much-needed infrastructure to the chosen site in its un-realised capacity as a locus for tourism, education, research and management. In doing so, the Centre could be the ‘Machine’ that reconnects Man to Nature through responsible use and understanding of her resources.

M.Sc. / The Vaal River is the main source of water supply to the central industrial, mining and metropolitan regions of South Africa, and is, therefore, strictly regulated by small dams and weirs. The Vaal Dam is the main regulator of water to the Vaal River and is of great importance as it supplies water for human consumption and also to the industrial powerhouse of South Africa. Situated at the confluence of its major tributaries, namely the Vaal and Wilge Rivers, and straddling the convergence of the borders of Gauteng, Free State and Mpumalanga provinces, the Vaal Dam is approximately 77 km south of Johannesburg. It is South Africa’s second-largest dam in terms of area, and third-largest in terms of volume, and is a key component in South Africa’s water supply infrastructure. Gauteng, as well as the surrounding provinces are reliant on it for their water supply. Water flow fluctuations are deemed to be important as they could negatively impact upon the water quality. Knowledge of the relationship between fluctuating water flows and water quality is important as strategies can then be devised on this basis to improve the freshwater situation of the country, the associated management systems, and treatment technologies. By establishing the nature of the respective relationships between high water flow and the selected water quality parameters, ways could be found of reducing the costs of water quality problems, such as eutrophication. The various relationships between high water flow and the selected water quality parameters of the Vaal Dam that were established during the course of this study are as follows: In terms of pH, the study found that in the event of a decline in the water flow, the pH value increased and the water body became more alkaline. A decrease in water flow was also found to be associated with an increase in EC. An increase in water flow was found to be associated with a decrease in pH, EC and Chlorophyll-a. An increase in water flow up to a certain level was found to be associated with an increase in nitrates, sulphates and COD.

The main purpose of this study is to determine the difference in water quality of the rivers between the Katse and Vaal Dams (Wilge River and Vaal Dam reservoir sub-catchments) after the construction of the Lesotho Highlands Water Project. These rivers include the Ash, Liebenbergsvlei and Wilge Rivers. The temporal changes in water constituents, namely: electrical conductivity, chemical oxygen demand, pH, turbidity, ammonia, calcium, manganese and chlorophyll a, at selected water sampling points were analysed to clarify if Katse Dam water has had any impact on the water quality of the Ash, Liebenbergsvlei and Wilge Rivers and the Vaal Dam. The water quality was studied over an eleven-year period from November 1994 until December 2005. This includes a five-year period prior to, and a six-year period following the completion of the Katse Dam. The Ash, Liebenbergsvlei and Wilge Rivers fall within the Wilge sub-catchment, and the Vaal Dam falls within the Vaal Dam reservoir sub-catchment. Both the aforementioned sub-catchments form part of the Vaal River catchment. Physical, chemical and microbiological sampling results were obtained from Rand Water. The results were compared with the in-stream water quality guidelines as set by the Vaal Barrage Catchment Executive Committee. The results of the selected constituents were depicted visually in the form of graphs. Trends in the constituents over the period were then determined. The graphs were divided into two sections namely, pre-Katse Dam (before 1999) and post-Katse Dam (1999 to 2005). Differences in water quality before and after the construction of the Katse Dam were determined from sampling and chemical analysis at six locations, and hence evaluations were made whether the release of Katse Dam water has had a significant effect on the water quality results in the Vaal River System. The water quality results with respect to the different water constituents illustrated a distinct change in water quality over the period. Northwards, towards the Vaal Dam, the difference in water quality became less apparent. Sampling points throughout the study area experienced decreases in: electrical conductivity, chemical oxygen demand, turbidity, ammonia, and manganese. Hence, the release of Katse Dam water into the Vaal River system has had a ii positive influence on the water quality and thus changed the riverine environments in the Vaal River system. The high quality water from the Katse Dam that enters the Vaal River system thus initially increases the quality of the water in the recipient system with a lesser effect downstream. The result is an improvement of water quality in the upper reaches of the Vaal River system and no significant influence on the Vaal Dam itself. However, the change in water quality may have a detrimental effect on the river environment as a result of the increased volume of water entering the system and the resultant soil erosion, which serves for further studies. Consequently, the advantageous high quality water from the Lesotho Highlands is not being optimally utilised, hence the proposed recommendation by Rand Water to alternatively transfer Katse Dam water via a gravity-fed pipeline to the Vaal Dam thereby receiving the full benefit of high quality water, leaving river environments unaltered and possibly lowering purification costs. / Prof. J. T. Harmse Prof. H. J. Annegarn