Urban groundwater development and management: basement water use
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South Africa is a water-scarce country and is among the 30 driest countries in the world. Urban areas have a high water demand due to population growth and increased urbanisation. Most of the urban areas of metropolitan municipalities use surface water, which is essentially fully allocated. There was an urgent need to investigate for alternative water sources to meet the rapid water demand in urban areas. It was, therefore, necessary to address the indirect use of groundwater and the lack of active management of groundwater because urban areas in South Africa have not currently been utilising groundwater to its full potential. The study identified high-level technical solutions, strategies, and tools as a decentralised approach that could address groundwater use and lack of management. This included water sensible designs, basement water use, the agency managing groundwater management and issuing licenses, and using numerical groundwater models in decision-making. The main aim of this study was to determine the current groundwater use and groundwater protection measures in urban areas and compare the status quo of groundwater use and management with the international best practices and adopt the best practices that are suitable for South Africa. Furthermore, the aim of the case study was to promote the beneficial use of basement water and encourage more buildings to use the basement water rather than to discharge it with no beneficial use. The overall results from the analysis of the status quo of metropolitan municipalities were that groundwater use and management were poorly integrated into the key statutory planning processes at metropolitan municipalities. No coherent plan for groundwater development and management was evident from metropolitan municipalities. Five case studies investigated the feasibility of the use of basement water for five buildings and the results revealed that each building has significant volumes of basement water ranging from 4.3 kl/d to 155 kl/d. The basement water is discharged into stormwater systems and none of the buildings are using the basement water beneficially. At the State Theatre building in the City of Tshwane, up to 75% of the water demand is used for the air conditioning system, and the feasibility of replacing this demand with basement water was investigated. The capital cost to implement the use of basement water for the cooling system was estimated to be around R1.5 million, which would be recovered over a three-year period. The results showed that the use of the basement water would be feasible and efficient for the South African Reserve Bank and Tshwane House. The investment would require R2.7 million and be recovered over a two-year period. Furthermore, Tshwane House would only require R500 000 to develop the basement water use system over a period of two years. A hydrocensus of the other buildings in the central business district of the City of Tshwane was conducted, leading to an estimated total basement water yield of 1.1 –2.3 Ml/d. The study recommended that the basement water use innovation should be implemented across the City of Tshwane (on a regional scale) to alleviate some of the city’s water demands in a sustainable manner and reduce reliance on limited surface water resources. The study further recommended that all metropolitan municipalities should amend their by-laws to discourage the discharge of basement water to ensure beneficial use.