Western Cape dam levels.
The six dams of the Western Cape Water Supply System (WCWSS) hold Cape Town's drinking water. They also supply surrounding municipalities in the Boland and Overberg — Stellenbosch, Paarl, Drakenstein and parts of the Cape Winelands all draw from the same pool. The system is run jointly by the national Department of Water and Sanitation (DWS) and the City of Cape Town.
The combined system is up 2.6 pts on last week and down 14% on the same week a year ago. Theewaterskloof on its own holds roughly half the system, so a single weak winter at one catchment shows up in the combined number quickly.
- Theewaterskloof Dam479 Mm³ at full · Riviersonderend RiverLast week · 47.7% Last year · 59.8% vs last year · -17%50%Full page →
- Voëlvlei Dam159 Mm³ at full · Voëlvlei RiverLast week · 49.9% Last year · 58.3% vs last year · -13%51%Full page →
- Berg River Dam127 Mm³ at full · Berg RiverLast week · 48.7% Last year · 60.5% vs last year · -11%54%Full page →
- Wemmershoek Dam59 Mm³ at full · Wemmers RiverLast week · 49.1% Last year · 50.5% vs last year · +8%54%Full page →
- Steenbras-Lower Dam34 Mm³ at full · Steenbras RiverLast week · 40.0% Last year · 42.0% vs last year · +8%45%Full page →
- Steenbras-Upper Dam32 Mm³ at full · Steenbras RiverLast week · 55.4% Last year · 90.5% vs last year · -39%55%Full page →
Three winters, then everything changed.
Combined storage in the Western Cape sat at 71% in May 2014. Three poor winters in a row took it to 21% by May 2017, where it stayed through 2018 — the Day Zero crisis. The rain came back. The system was at 47% in May 2019, 53% by 2020, and 75% by 2021. It's mostly held near 60% in the years since. The Cape Town drought case study walks through the data year by year.
Run a Day Zero scenario.
The predictor starts from the combined level shown above, runs a thousand simulated winters against a decade of historical rainfall, and shows when storage would cross the 13.5% Day Zero threshold under different rainfall and consumption choices.