ENGINEERING: Cape Town's Work On A Master Plan
Recent Western Cape Business News
THE City of Cape Town has laid the groundwork for a far-reaching master plan to explore all viable water supply alternatives for the Cape metropole.
“Cape Town, its neighbouring municipalities and the agricultural sector in the region are supplied with water from the Western Cape Water System (WCWS), a system of dams and pipelines owned and operated by the city and the Department of Water Affairs (DWA),” says Phil Mashoko, the city’s director: Water and Sanitation.
“The city and DWA operate the WCWS co-operatively to ensure that the volume of water in the system is maximised during the hydrological year, to the benefit of all water users.”
“Dam levels are currently lower than previous years due to a lower than average rainfall over the past year. However, with the recent completion of the Berg River Dam and Supplement Scheme, volumetrically there should be sufficient water in the short to medium term for all water users in the region,” he says.
According to long term rainfall records, the city’s main catchment dams are not yet reflecting any change in long term rainfall trends, however, the potential impact of climate change has been factored into strategic water resource planning.
“Cape Town is a growing city, with a burgeoning economy and population. Thanks to the implementation of a long term Water Conservation and Demand Management (WC&DM) strategy, Cape Town’s water demand is now 27% less than what it would have been if demand had grown at an unconstrained rate from 2000 onwards.”
“Our key focus is to reduce per capita demand in order to ensure that existing resources and infrastructure are used as cost-effectively as possible. This could also significantly delay the need for expensive new water supply schemes,” says Mashoko.
The city’s WC&DM initiatives include pressure reduction in the reticulation system, leakage management, pipe replacement, wastage reduction by consumers through education and awareness programmes and substituting the use of potable water for sports field and garden irrigation with treated effluent.
“The city is laying the groundwork to ensure that feasible resource schemes can be implemented when required. The Water & Sanitation Department is currently investigating a suite of potential resource schemes, which include greater water re-use, desalination of sea water and a much greater use of groundwater. At the same time, the Department of Water Affairs is considering a number of surface water options from rivers to supplement the inflow to the Voëlvlei Dam.”
“The re-use of water for industrial use and irrigation is being expanded, as well as the re-use of water for potable purposes, as these are significant water resources that are currently underutilised,” he says.
The future implementation of a 100 – 200 Ml/day sea water desalination plant on Cape Town’s West Coast is also being considered, as this is one of the fastest growing areas where additional water supply will be required. Although the costs of desalination have decreased significantly over the last few years, the process remains energy intensive and also carries a significant environmental impact.
The feasibility study into the use of groundwater from the Table Mountain Group Aquifer is well advanced. Not to be confused with the mountain itself, this is a vast deep aquifer in a highly fractured geological group of rock strata between 300 to 900 m underground, extending from Vanrhynsdorp through the Western Cape all the way to Port Elizabeth. The city is exploring drilling sites within the Western Cape in close proximity to established bulk water infrastructure of the WCWS. Due to the potential environmental impacts of large scale groundwater abstraction, the city has decided to adopt a precautionary approach. A decision will be made soon on progressing from the exploratory phase to a pilot phase during which the environmental impact will be fully assessed.
“With Cape Town’s current demand growth, it is anticipated that the current WCWS supply will be sufficient until between 2017 and 2019, after which a new resource or supply scheme will be required. While six to eight years is a fairly tight timeframe for the implementation of a large water supply scheme, the groundwork is being laid now to ensure that this can be achieved when needed,” says Mashoko.
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