The decline has been managed through progressive gate adjustments throughout the week.
The Vaal Dam is experiencing a steady decline in water levels this week, dropping to 100.25% on Wednesday after beginning the previous week at 103.8%, according to the Department of Water and Sanitation’s weekly report.
The dam is an essential part of the integrated Vaal River system, and has been managing the overflow through controlled gate operations.
According to The Reservoir, a Water Resource Information Centre for the Catchment Management Forums of the Upper Vaal Water Management Area, on 10 December, the dam recorded an inflow of 286.2m³/s.
With one gate open and an outflow of 117.0m³/s, the organisation said the “outflow [was] to be confirmed still”.
Potential milestone as capacity trends downward
If heavy rains do not rapidly increase capacity this week, the dam could drop below 100% for the first time this year, since March, when it reached full capacity.
That March milestone marked the first time the dam had hit 100% since 2023.
The decline has been managed through progressive gate adjustments throughout the week. On Monday, the dam stood at 100.74% with four gates open, discharging 493.9m³/s.
By Tuesday, levels had decreased to 100.37% with two gates operational and an outflow of 236.5m³/s.
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Management recommendations for integrated system
The Reservoir provided specific operational guidance for Wednesday.
It advises that “for Vaal Dam, the recommendation today is to keep one gate open”.
The Vaal Barrage maintained a level of 7.5 metres on Tuesday, with an outflow of 178.4 m³/s and a water temperature of 23.5 °C, indicating stable downstream conditions.
Dramatic year-on-year improvement
The current levels represent a remarkable turnaround from the same period last year.
According to the Department of Water and Sanitation, the dam stood at just 26.8% around the beginning of last week in 2024.
Historical data from The Reservoir show that on 9 December 2024, the dam measured 26.50%, compared with 67.60% in 2023.
Furthermore, the organisation’s records indicate that the last time the Vaal Dam exceeded 100% capacity on this date was in 2022, when it reached 100.30% and operated with one gate open.
The Reservoir’s decade-long tracking reveals fluctuating conditions, with the dam reaching as low as 36.80% in 2020 and 38.47% in 2016, while recording higher levels of 88.30% in 2021 and 79.44% in 2017.
The organisation noted that 2019 saw particularly challenging conditions, with 39.05% representing “the lowest level for 2019”
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