2 minute read
WESTERN CAPE water supply and demand – the situation
South Africa’s Western Cape province 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 (CoCT),
West Coast District Municipality (which supplies water to the 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
Augmentation schemes for the City of Cape Town
water use in these two WMAs, followed by urban water use.
Effective demand-side management
By the end of the 2020 hydrological year (31 October 2021), the WCWSS dam levels had recovered to approximately 101%. Water restrictions for the CoCT 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 CoCT’s average water consumption was 30% less than its allocation of
URBAN: CITY OF CAPE TOWN
AGRICULTURAL (CAPPED)
URBAN: WEST COAST DISTRICT
URBAN: STELLENBOSCH
URBAN: CITY OF CAPE TOWN
AGRICULTURAL (CAPPED)
URBAN: OVERBERG WATER
URBAN: WEST COAST DISTRICT
URBAN: DRAKENSTEIN
URBAN: STELLENBOSCH
URBAN: PIKETBERG
URBAN: OVERBERG WATER
URBAN: DRAKENSTEIN
URBAN: OTHER
URBAN: PIKETBERG
URBAN: OTHER 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
Source: DWS 2018
Source: DWS 2018
358 million m3 per year (981 Mℓ/day) from the WCWSS. This highlights the importance and effectiveness of water conservation and water demand management (WC/WDM), as well as water efficiency interventions, and the key role it has in managing the use of water resources.
However, non-revenue water (NRW) for some municipalities in the Western Cape remains high and above the global best practice level (15%).
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
Non-revenue water levels for Western Cape municipalities for 2020 (Source: DWS Dashboard, 2020)
