School of Civil & Environmental Engineering (ETDs)
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Item Groundwater resource exploration within the inner-city of Johannesburg(2020) Tywakadi, Ondela; Taigbenu, Akpofure E.This study examined the hydrogeological characterisation of the Johannesburg inner-city. Residents reported a high water table that has resulted in groundwater seepage into building basements, posing a safety threat and limited functionality of these structures. Although this high groundwater table triggered this investigation, it took a deeper and broader approach by seeking to quantify the amount of groundwater resource that is available to be used to supplement the existing municipal supply. The study also aimed at establishing long-term sustainable abstraction rates and viable fit-for-purpose use of the available groundwater. The study then evaluated the abstraction rates against the water table response in order to achieve a safe water table level at which groundwater seepage into building basements does not occur. The methodology employed included assessing and verifying the number and distribution of buildings affected by groundwater seepage. Information was gathered by circulating a survey in the form of a questionnaire to a network database of property owners and managers. Field work, in the form of drilling and testing boreholes, and subsequent data processing were carried out to characterise the aquifers and establish the quantity of the resource. In order to determine possible uses of the groundwater, water chemistry testing was carried out. The characteristics and recharge dynamics of the aquifers that were established served as inputs into a numerical model which estimated the quantity of groundwater that can be sustainably abstracted for utilisation, while ensuring the water table is sufficiently suppressed. An estimated 2.47 million-m3 (or billion-litres) of groundwater is available as a total yield potential within the Johannesburg inner-city. This water can be sustainably withdrawn from the ground at a safe yield (abstraction rate) of over 56 million-litres per annum (56 902m3/a) from the nine drilled boreholes. The system response corresponding to this abstraction rate is predicted to cause a 2.3m decline in the water table level compared to the current scenario. This desired pumping scenario would suppress the water table level to be at an average of 8.6m below ground. The average basement depth in the Johannesburg inner-city is 8m below ground and hence, most building basements would consequently not be flooded under this scenario. Currently, 60% of building basements are subjected to the risk of flooding, and this would reduce to 30%, which is made up of those deeper than 9m. The current water demand in the Johannesburg inner-city is approximated to be 80Ml/day. Therefore, the estimated groundwater yield to supplement the municipal supply is insignificant (0.2%), and does not justify an investment into retrofitting the groundwater infrastructure into the bulk infrastructure system. Thus, developing a groundwater source infrastructure for bulk water supply purposes is not volumetrically viable in the case of Johannesburg inner-city, but can be beneficial for building strategic reserves and resilience into the system. It is recommended that in future, fine-tuning and continuous calibration of the numerical model should be carried out when the boreholes are in operation. Further research is also required to examine the aquifer geo-mechanics in order to assess the risk of land subsidence with decreasing water table levels, especially in a possible future scenario of over-exploitation of the aquifer.Item Comparative study of five country-specific labour-intensive infrastructure development programmes : implications for South Africa(University of the Witwatersrand, Johannesburg, 2010) Quainoo, Harry Akyen; McCutcheon, R.T.Unemployment and abject poverty in South Africa are widespread, persistent and disproportionately high. These problems are aggravated by inadequate capacity at all tiers of government and huge infrastructure backlogs in rural South Africa. Employment-intensive means of infrastructure delivery have been successfully implemented in several sub-Saharan African countries and elsewhere to generate employment and reduce poverty. It should be possible to replicate similar large-scale national programmes in South Africa. But South Africa has failed. Both prior to and since 1994, several supposedly employment-intensive programmes have been implemented in South Africa with poor results. In an endeavour to contribute to future South African policy and good practices regarding employment, this thesis describes and analyses in detail five major Sub-Saharan programmes and reaches conclusions regarding their achievements and shortcomings. Lessons derived bridge the knowledge gap between the large-scale programmes embarked upon in the sub-Saharan countries in the mid-1980s and the year 2007; these lessons should be applied to future endeavours in South Africa to generate significant employment per unit of expenditure and contribute to poverty alleviation. A major conclusion reached was that the success of employment-intensive infrastructure development programmes depends to a large extent on fundamental factors such as appropriate and implementable policy, government commitment, adequate and sustainable funding, adequate capacity and good preparation. Specifically, the thesis demonstrated that prior to implementation a sufficient timeframe is required for programme preparation in order to make significant contribution towards poverty reduction. Equally, national programme expansion requires a strategic balance between centralisation and decentralisation. In particular, for programme extension and decentralisation, due regard must be given to training and capability building and available resources. Deriving from the thesis’ major conclusions, the author developed three crucially important frameworks for anti-poverty infrastructure development programmes, namely; a four-phased model for evaluating the chances of success of infrastructure programmes, a five-phased result-oriented guidelines for testing the workability of infrastructure development policies, and a practical guideline for monitoring and evaluating employment-creation programmes that maximises the benefits thereof and pre-empts institutional memory loss through systematic knowledge management.