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Detailed measurements were taken on Thursday with the Vaal Dam operating with three open sluice gates and no river valves in use.
Vaal Dam. Picture: Supplied.
The water level at the Vaal Dam has fallen slightly, according to officials monitoring the water resource that supplies Gauteng.
Midvaal councillor Pieter Swart reported on Thursday that the dam’s level had declined to 106.65% capacity, following Wednesday’s measurement of 107.04%.
“This comes after the opening of a third sluice yesterday [Wednesday], which increased the outflow to just over 400m³/s (cubic metres per second),” said Swart.
The councillor noted that the water inflow was about 380m³/s, necessitating the adjustment in outflow volumes to manage the dam’s levels.
Swart emphasised the importance of the dam’s primary purpose: “It should be noted that the primary purpose of the Vaal Dam is to supply water to Gauteng. The entire water management strategy revolves around maintaining the dam’s level as high as possible for as long as possible to ensure this supply.”
The department of water and sanitation in its weekly report of dam levels confirmed that the Vaal Dam capacity, which flows into the Vaal River and has a full storage capacity of 2.5 billion cubic metres, was at 107.3% this week.
This represents a slight decrease from 107.4% reported last week, but a significant improvement compared to the 62.5% recorded in the same period last year.
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According to reports from The Reservoir, detailed measurements on Thursday showed the Vaal Dam operating with three open sluice gates and no river valves in use.
The outflow had been increased to 414m³/s while the inflow measured 381.6m³/s.
Downstream at the Vaal Barrage, the water level stood at 7.6 metres with an outflow of 544.5m³/s and a water temperature of 20.5°C.
These figures reflect changes from Wednesday, when the dam level was at 107.04% with inflow at 375.8m³/s and outflow at 390m³/s.
The Vaal Barrage on Wednesday measured 7.5 metres with an outflow of 519.8m³/s and a slightly higher water temperature of 21.2°C.
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The Reservoir issued recommendations on Friday morning for the broader Vaal River system.
It focused on the Bloemhof Dam, which is located downstream from the Vaal Dam.
“We recommend increasing the outflow from Bloemhof Dam to 600m³/s, effective 10am today. This adjustment is in response to continued inflows and rising dam levels,” The Reservoir said.
The centre also said that: “The current outflows from Vaal Dam can continue today [Friday],” suggesting that water management officials believe the current release strategy at the Vaal Dam is appropriate.
Water management authorities continue to closely monitor the situation across the integrated water system as they balance flood prevention with water storage priorities.
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