Western Cape water supply and demand – the situation | Infrastructure news

The Western Cape Province, which is in the South West corner of South Africa, falls predominantly within two water management areas (WMAs), the Breede-Gouritz and the Berg-Olifants.

By GreenCape

While South Africa is one of the most water stressed countries in the world with a medium to high baseline water stress (20% – 40% average annual withdrawal of available water supply), the majority of the Western Cape falls within the two highest water stress categories (40% – 80% and >80%).

Water supply system

The Western Cape Water Supply System (WCWSS) is a complex, interlinked system of dams, pipelines, and distribution networks that supplies water to the City of Cape Town (CCT), West Coast District Municipality (which supplies water to Swartland, Saldanha Bay, and Bergrivier local municipalities), Stellenbosch, Drakenstein, and Witzenberg local municipalities, and certain agricultural users.

Total water allocation for the system is 590 million m3 per year, which is allocated to various end users. Approximately two-thirds of the allocation is for urban use (including residential, commercial, and industrial use), and the remainder is allocated for agriculture, which is predominantly used in the summer months. Irrigation to support agriculture constitutes the main water use in these two WMAs, followed by urban water use.

<Insert Green Cape Figure 1 on page 31 of 104 of PDF> Overview of Western Cape Water Supply System allocations by type

Effective demand side management

By the end of the 2020 hydrological year (31October 2021), the WCWSS dam levels had recovered to approximately 101%. Water restrictions for the City of Cape Town (CCT) were lifted at the end of the 2020 hydrological year, and demand has remained well below 800 Mℓ/day since 2017.

The ongoing effective demand side management, and resultant lower water use, was a key enabler in the recovery of dam levels. At the end of October 2020, the CCT’s average water consumption was 30% less than its allocation of 358 million m3 per year (981 MℓD) from the WCWSS. This highlights the importance and effectiveness of water conservation and water demand management (WCWDM), and water efficiency interventions, and the key role it has in managing the use of water resources.

However, non-revenue water (NRW) for Nonrevenue for some municipalities in the WC remains high at above the global best practice level (15%).

<insert GreenCape Figure 2 on page 32 of 104 of PDF> Non-revenue water levels for Western Cape municipalities for 2020 (Source: DWS Dashboard, 2020)

MunicipalityNon-Revenue %Water Tariff (R/K)Potential loss in revenue (R/kℓ)
Beaufort West48R19.89R9.55
Breede Valley22R12.80R2.82
Cape Agulhas18R9.92R1.79
Saldanha Bay3R11.59R0.35
Lower than average rainfall necessitates ongoing demand-side reduction to avoid dam levels approaching the critical levels.

The climate projections for the Western Cape indicate a warming trend as well as drying in many areas, with longer periods between increasingly intense rainfall events. Additionally, population and economic growth is placing an additional burden on water supply and sanitation systems, which in turn will have a negative impact on the province and consequently the country’s economy.

Augmentation schemes

In order to address future water constraints, various augmentation schemes have been introduced or planned. Augmentation schemes include potable water reuse (from WWTWs), groundwater development (new resources and artificial recharge), and large-scale permanent seawater desalination.

To date, the CCT augments its surface water with  7 Mℓ per day from groundwater and springs. This is likely to rise by 40 Mℓ per day from the recently commissioned Table Mountain Group (TMG) aquifer when it is fully operational. Other phased augmentation schemes will contribute a total of 240 Mℓ per day by 2026.

InterventionFirst WaterCapacity (MℓD)Total CAPEX (R million)Unit CAPEX (R million)Operating Cost (R/kℓ)
Table Mountain Group Aquifer – SteenbrasJuly 20202546818.75.5
Table Mountain Group Aquifer – NuwebergJuly 20231552334.95.5
Table Mountain Group Aquifer – GroenlandbergNovember 2023 1237631.32.2
Cape Flats Aquifer – StrandfonteinJuly 2021537875.66.5
Cape Flats Aquifer – Hannover ParkMay 2022415839.48.5
Cape Flats Aquifer – Strandfontein North and EastDecember 20221577251.56.5
Cape Flats Aquifer- PhillippiDecember 2024643472.38.5
Cape Flats Aquifer – Mitchells PlainJuly 20252067333.78.5
Atlantis Aquifer Rehabilitation and ExpansionJuly 20221631419.68.5
Berg Voëlvlei River Augmentation SchemeJuly 202340  4.62
Water Reuse – Faure New Water SchemeJuly 202570188226.95.7
DesalinationDecember 202650188033 – 409.0
Alien Vegetation Clearance  372  

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