Tackling South Africa's Day Zero crisis

The Western Cape Water Supply System (WCWSS) serves the City of Cape Town and smaller surrounding cities and irrigators. In 2018, the Western Cape region suffered three drought years in a row, and the bulk water supply system which supplies 95% of the city’s water was critically low.

The water consumption of the region was constant for a decade, at around 800 million litres per day (MLD). This led the City of Cape Town to institute water consumption restrictions. The restrictions led to a consumption reduction of approximately 520 MLD. The target, however, to meet national restrictions is 450 MLD.

Other water resources needed in the supply

The city’s primary water resource was – and still is – surface water. Only about 2% of water is supplied from groundwater. But reservoir water storage decreased in previous years due to drought. Therefore, other water resources are needed. The City of Cape Town plans to make a more robust water supply system by integrating groundwater, desalinising seawater, and reusing wastewater.

Besides the municipality’s groundwater abstraction, many private landowner’s abstract groundwater from their own borehole or wells. Both in crisis, but also on a more permanent basis, getting access to this groundwater would help make water supply more resilient in the future.

Feasibility study

Ramboll made a feasibility study for the City of Cape Town and Western Cape to augment bulk water supply with private boreholes in times of drought or other instances where water security is tested.

The study includes a technical baseline study, where existing groundwater data is collected and analysed. Based on analyses, potentially high yielding groundwater areas and areas with an expected good water quality were delineated. Moreover, nearly 10,000 addresses of private boreholes and well points were converted to coordinates. Out of the 10,000 boreholes, five clusters were identified that lay within potential high yielding groundwater areas and near the distribution grid. The business cases for implementing three of the clusters were conducted.

Parallel with the technical approach, Ramboll led an investigation of legislation relating to potential public water supply access to boreholes on private lands. These investigations showed several options are available, but consent from private landowners is crucial.

Relevant roadmaps

Based on both the technical and legislative investigations, several roadmaps were developed on to apply groundwater from private boreholes into the public water supply. These roadmaps are generic, so they can be used for all municipalities interested in implementing groundwater.