Another sluice gate opened at the Vaal Dam

The department of water and sanitation has taken decisive action to control rising water levels across the Vaal River system, opening sluice gates at both the Grootdraai and Vaal dams.

A sluice gate is a hydraulic structure, or movable barrier, used to control or regulate the flow of water in open channels, rivers and canals.

It is primarily for managing water levels, preventing floods and ensuring a consistent water supply.

The department’s flood monitoring and forecasting office on Friday issued recommendations for dam management, advising that all valves at the Vaal Dam be closed and an additional sluice gate be opened from 10 am.

With the opening of a sluice gate at the Grootdraai Dam, large amounts of water is expected to reach the Vaal Dam, with efforts needed to relieve some of the inflow.

To manage the rising water levels caused by continuous rainfall, the department previously opened six Vaal Dam valves at 12 pm on Monday.

This action followed the earlier opening of a single sluice gate the previous week. The goal was to gradually increase water outflows by approximately 200 cubic metres per second.

“At Bloemhof Dam, water releases have also been increased by 50 cubic metres per second from yesterday’s 350.97mᵌ/s to 400mᵌ/s to allow for the extra flows that are expected from the Vaal Dam,” the department earlier said.

The recent opening of another sluice gate is expected to increase the outflow to approximately 240 cubic meters per second, helping to manage increasing upstream water volumes.

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Grootdraai Dam’s strategic response

On Friday, The Reservoir, a water resource information centre, reported that the Grootdraai Dam water levels had reached a critical point of 104.90%, compelling authorities to open one gate at 9am.

The gate was raised to a height of one metre, ensuring a controlled downstream water release.

Current dam measurements reveal a water level of 27.30 metres, with an inflow of 179.95 cubic metres per second and an outflow of 40.80 cubic metres per second.

Recent rainfall of 14.8 millimeters has further contributed to the rising water levels, prompting continuous monitoring by water resource management teams.

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Vaal Dam’s water levels

The Vaal Dam is experiencing even more significant water accumulation, currently standing at 106.52% of its full storage capacity.

According to the Reservoir, the dam is receiving an inflow of 239.9 cubic metres per second, with an outflow of 192.0 cubic metres per second.

Two sluice gates have been opened, with all the valves opened on Monday now closed.

Downstream, the Vaal Barrage presents additional challenges, with water levels at 7.4 metres and an outflow of 266.5 cubic metres per second.

The water temperature is 22 degrees Celsius.

ALSO READ: ‘Loads of water, not a drop to drink’: Here’s why a full Vaal Dam doesn’t mean less water outages

Public safety advisory

Water management officials continue to closely monitor the situation to manage dam capacities and prevent potential flooding in low-lying areas.

Residents along the Vaal River have been urged to remain vigilant and take necessary precautions.

“Officials continue to monitor the situation closely to manage the dam’s capacity and prevent potential flooding in low-lying areas,” the department said.

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