Cape Town draws its water from the Western Cape Water Supply System: six large dams in the mountains east of the city with a combined capacity of about 889 million cubic metres. Theewaterskloof alone holds more than half. The system also supplies neighbouring towns and irrigation for agriculture.
Storage follows the winter rains. Dams normally peak in September or October and fall through summer as the city uses roughly 850–950 million litres a day. In the drought of 2015–2018 three dry winters in a row pushed the system to 19% in June 2017; the City rationed to 50 litres per person per day and prepared for “Day Zero”, when taps would have been turned off. Good rains in 2018 refilled the dams and the crisis passed, but it changed how the city thinks about water.
Sources. Current levels: the Department of Water and Sanitation’s weekly State of Dams report (Mondays, published Tuesday/Wednesday). History: the City of Cape Town Open Data Portal, daily readings January 2012 – April 2026, reduced here to weekly points. Percentages are of full storage capacity; values above 100% mean a dam is spilling.