Vaal Dam Reopens Third Sluice Gate as Heavy Inflows Surge; More Rainfall Expected

At midday on Wednesday, water inflows into the Vaal Dam were measured at a staggering 943 m³/s, while the water level stood at an alarming 108.4% of full capacity.

In response to unrelenting rainfall in the Upper Vaal Catchment, the Department of Water and Sanitation (DWS) has intensified flood management operations across key infrastructure within the Integrated Vaal River System (IVRS). As part of its continued response to increased hydrological stress on major dams, the third sluice gate at the Vaal Dam was officially reopened at 4 p.m. on Wednesday, 23 April 2025.

This move comes after the dam operated with two open sluice gates since 16 April, a decision taken to manage unusually high inflow volumes safely. The reopening of the third gate raises the dam’s water release from 299.59 cubic metres per second (m³/s) to an estimated 400 m³/s. The DWS emphasized that the action is a precautionary measure to maintain dam safety and reduce the risk of structural stress on the infrastructure.

Rising Inflows and Dam Levels

At midday on Wednesday, water inflows into the Vaal Dam were measured at a staggering 943 m³/s, while the water level stood at an alarming 108.4% of full capacity. The situation remains dynamic, and further escalation in inflows could prompt the department to open additional sluice gates as early as Thursday.

In a statement, the department warned, “There is a possibility that another sluice gate will be opened tomorrow [Thursday] should the inflows continue to increase.” This measure, they noted, is part of a larger strategy to protect the dam structure and minimize flood risks in surrounding regions.

Bloemhof Dam Increases Outflows

Simultaneously, Bloemhof Dam is also experiencing surging inflows, prompting increased water releases to accommodate the rising levels. The DWS reported that outflows were increased from 500 m³/s to 650 m³/s at 10 a.m. and further up to 800 m³/s by midday on Wednesday. The dam is currently operating at 106.71% capacity, with continued monitoring in place to ensure safe water regulation.

Inflows into Bloemhof were recorded at approximately 640 m³/s by Wednesday afternoon, and this figure is projected to climb further over the next 24 hours. Authorities are prepared to scale up outflows once more on Thursday if the forecasted rainfall materializes and upstream inflows intensify.

Monitoring at Grootdraai Dam

Meanwhile, at Grootdraai Dam, all sluice gates remain closed. The dam is at 104.92% of capacity, with inflows measured at 32.44 m³/s. Although current levels are not as severe as those at Vaal and Bloemhof, the DWS continues to closely monitor the dam given the saturated condition of the entire catchment area.

Downstream Impact and Community Safety

The combined effect of controlled releases from both Vaal and Bloemhof Dams has led to overtopping of riverbanks downstream. Settlements situated within the 1-in-100-year floodline along the Vaal River have already been affected. Emergency evacuations are underway in low-lying areas, and the department has reiterated warnings for residents not to return to flooded zones.

“People living within the floodline of the Vaal River downstream of the Vaal and Bloemhof Dams, and have evacuated, should continue to avoid the flooded areas as the river catchment remains oversaturated,” the DWS advised.

Ongoing Hydrological Monitoring

With more rainfall predicted in the region, the department has assured the public that real-time monitoring systems are being used to track changes in water levels across the IVRS. Data collected supports informed decision-making to ensure infrastructure integrity, flood attenuation, and the safety of human lives.

“Opening sluice gates is a necessary precaution,” the department stated. “These actions are implemented to prevent dams from breaching their full supply capacity, which could otherwise result in infrastructure failure and potential disasters of unimaginable scale.”

The department is working in coordination with disaster management teams, local municipalities, and hydrological experts to update emergency protocols and mitigate risks as rainfall continues to drench the upper catchments.