An urgent flood warning was issued to communities downstream of the Orange River, in Upington in the Northern Cape, by the department of water affairs today.
It was predicted that with a water flow of 5 100 cubic metres a second, the Lower Orange River, it would reach a height of 7.7 metres in that area at midday today, spokesperson Linda Page said.
She said this level was about 0.1 metres lower than the peak that caused widespread flooding in January.
The department was still monitoring the situation at the four largest dams in the Vaal and Orange River catchments.
The Vaal Dam was at 106% full, with six floodgates open and an outflow of 770 cubic metres a second.
At the Bloemhof Dam, a capacity of 100% had been reached with outflow of 1400 cubic metres a second and it was expected to remain stable until next week, Page said.
She said the Gariep Dam was 115% full and decreasing steadily.
Its outflow was 2000 cubic metres a second. The capacity of the Vanderkloof Dam was 114% with an outflow of 2500 cubic metres a second.
In the Lower Orange River, the department recorded the flow at Katlani, which is the Orange-Vaal River confluence, at 4600 cubic metres a second.
About 4910 cubic metres a second was recorded at Prieska, which peaked at 5050 cubic metres a second yesterday.
The predicted high flow in Upington was 5100 cubic metres a second today.
The predicted high flow at Brand Karos, near Alexander Bay, for Saturday was 4900 cubic metres a second.
Page said the SA Weather Service was predicting a 30% chance of showers and thundershowers in the next 24-hours in the Upper Vaal River catchment and a 60% chance in the Middle Vaal River.
She said a 60% chance of showers and thundershowers in the next 24 hours was also predicted in the Orange River catchment upstream of Douglas.