Rainy spell helps to increase Vaal Dam levels

Recent rain in the right catchment areas has resulted in an increase in Vaal Dam levels.

The Vaal Dam is currently at 60.6%. Sterkfontein Dam is at 95.8% and the Grootdraai and Bloemhof dams are at over 100%.

The flow of water into the Vaal Barrage Dam by yesterday morning was 89.718m³/sec, just short of the maximum flow of water recorded on Wednesday, at 90.087m³/sec, according to Rand Water.

About 24.5mm of rain fell on Wednesday, with an evaporation rate of 11.5mm of water.

It is incredibly difficult to fi ll the dam, which has a storage capacity of 2.57 billion m³. This is because the dam’s shoreline stretches 880km through three provinces – Gauteng, the Free State and Mpumalanga.

The last time the dam reached 100% capacity was in January 2011, when 14 sluice gates had to be opened to release the water, which was flowing at 1 800m³/sec.

This equates to more than two billion Olympic-sized swimming pools passing through the sluice gates in two weeks.

The latest spell of rain this week is significant because the difference made to its fullness means rain lasted long enough to produce runoff to the dam.

Good rain could be partly attributed to the effects of the current La Nina phenomenon, where cool waters build up in the eastern Pacific.

For some regions in the world, this means extended dry spells, but in southern Africa, it means cooler temperatures and more regular rainy spells.

Last year, Storm Report SA predicted a moderate-to-strong La Nina, which was expected to peak between November and this month.