Why the Vaal Dam is not filling up after the recent rains

Some have wondered why the Vaal Dam levels have not increased despite the recent heavy rains across Gauteng. 

The Department of Water and Sanitation released on Tuesday (10 December) that the current dam levels in the Vaal were still very low at 39.05 per cent.

Many surrounding dams such as the Hartbeespoort Dam are nearly at full capacity, with Grootdraai Dam from 53 per cent to 77 per cent on Monday. Rand Water said in a post on Twitter that there are numerous factors that influence the rise and fall of dam levels, such as where it rained, how much it rained and the level of runoff that occurs.

Depending on how much it rained, Rand Water wrote the first rainfall soaks into the ground and fills depression such as farm dams before it runs off to our rivers and dams, in order there to be an increase in dam levels there has to be continuous rain for a long period of time.

“It takes up to three days for the runoff to reach the Vaal Dam, so there is no immediate change in dam levels after rains.”

Where it has rained matters, “None of the rain we have had in Gauteng goes to the Vaal Dam so there will be no immediate change, the water flows either towards the Crocodile and Jukseki Rivers or it joins the Vaal River downstream of the Vaal Dam to go towards Bloemhof Dam.”

The statement continued to explain that, “The Vaal Dam catchment includes the western parts of Mpumalanga (Standerfontein, Ermelo and Secunda) and the eastern parts of the Eastern Cape (Villers, Harrismith, Bethlehem, Frankfort). The Grootdraai Dam at Standerfontein also needs to fill, currently, 77 per cent as it upstreams in Vaal River.”

Water consumption plays a part too Rand Water concluded water supply has been reduced to parts of Johannesburg as demands have exceeded supply.

Related articles:

https://midrandreporter.co.za/231757/heavy-rains-little-impact-vaal-dam/

https://midrandreporter.co.za/226691/vaal-dam-drops-50-per-cent/