The cut-off low that tore through the Western Cape this week sent already strained dam levels soaring past capacity, raising serious flooding risks downstream and forcing authorities to monitor rivers and estuaries around the clock.
Dams spill as rivers rise at alarming speed
Several dams across the Garden Route and Central Karoo reached or exceeded full capacity within hours as the storm intensified.
The Haarlem Dam climbed from 104% to 116% capacity, releasing 80 cubic metres per second.
The Oukloof Dam rose from 30% to 107%, while the Buffeljags Dam hit 103% and was spilling.
The Haarlem Dam peaked at 116% before stabilising, while both the Leeugamka Dam at 97% and the Gamkapoort Dam at 98% were being closely watched.
Dr Colin Deiner, head of Western Cape Disaster Management, said the speed of the rise was what most alarmed authorities. “Literally at around about 6am, we started seeing a very, very sharp increase.
“The flow was at 7.7 metres and increased from 7.52 on the latest data in the Keurbooms River,” he said. The Knysna River was simultaneously surging, peaking at 4 metres before beginning to ease slightly.
Dams still climbing included the Gamka Dam, up from 43% to 60% capacity, the Wolwedans Dam at 66%, and the Garden Route Dam at 54.7%.
Cape Town dams also climbing after dry summer
The storm’s broader impact was also reflected in Cape Town’s municipal dam system.
Data from 4 May 2026 showed the city’s six major dams at 48.3%, up from 47.3% the previous week, but still significantly lower than the 59.9% recorded at the same time in 2025.
By 6 May, a separate reading showed overall storage had ticked up further to 49.2%, with Berg River at 50.8%, Theewaterskloof, the system’s largest dam at 480 188 ML capacity, at 48.5%, Voëlvlei at 50.4%, and Wemmershoek at 50.5%.
Estuaries and downstream communities under threat
Beyond the dams themselves, authorities were also monitoring three estuaries – the Great Brak River, Klein Brack, and Hartenbos – where rising water threatened to push flooding further inland.
“Kammanasie and Stompdrift dams are rising quickly; if they do spill, challenges will be experienced downstream between Calitzdorp and Oudtshoorn,” said Deiner.
Diner explained that protocols were in place to breach estuaries when necessary to relieve pressure, adding that all tributaries within key catchment areas remained under continuous observation.
With aircraft set to conduct flyovers across affected regions, and damage assessments still pending, officials cautioned that the full picture of the storm’s water-related impact was yet to emerge.
