Another sluice gate has been opened at the Vaal dam as inflows increased rapidly amid ongoing rainfall in the Vaal river catchment.
With five sluice gates now open to manage the dam’s water levels, there is potential for the riverbanks to overflow, with the Department of Water and Sanitation (DWS) on Sunday urging evacuation for low-lying areas next to the river.
The DWS opened the fourth sluice gate on Saturday and the fifth sluice gate less than 24 hours later, as the Vaal dam’s water levels increased from 107.82% to 109.39% overnight.
According to the department, the current inflows into the dam increased from 1 000 cubic metres per second (mᵌ/s) to 1 200 mᵌ/s during the course of Sunday morning, while the outflows at the dam increased from 550 mᵌ/s to just under 700 mᵌ/s.
Owing to the increased water releases by the five sluice gates, there might be a possible overflowing at the riverbanks downstream and this will affect infrastructure built in lower lying areas within the 100-year floodline, the DWS warned, urging people living within the high floodline of the river downstream of the Vaal dam and the Bloemhof dam to evacuate and move to a safe area, and remove valuable equipment, movable infrastructure and livestock.
“Areas around the Vaal Triangle, Parys low-lying areas next to the river and farmers having pumps and infrastructure next to the river need to evacuate, [as well as] people residing below barrage, next to the river and also in the tributaries close to the Vaal river. Downstream Bloemhof dam, the rising water level will affect all those at the riverbanks downstream at the lower Vaal catchment.”
“Those in the riparian of the Vaal river are urged to start removing valuable equipment, movable infrastructure and livestock and to evacuate to avoid any possible damage or loss of life when the riverbanks overtop.”
The increased outflows from Vaal dam are expected to reach the Bloemhof dam in three to four days, resulting in water levels rising in both the dam and the river, overtopping the riverbanks.
Bloemhof dam storage levels also increased overnight, from 103.23% to 106.91%, and water releases had been staggered incrementally in two-hour blocks, from 1 000 mᵌ/s to 1 400 m3/s by 16:00 on Sunday.
At Grootdraai dam, in the Upper Vaal river catchment upstream of Vaal dam, one sluice gate remains opened at 2.5 m to enable the water releases. The dam is currently sitting at 102.41%.
The opening of the sluice gates forms part of dam safety precautions to safeguard the infrastructure.
“The department, through various platforms, continuously shares hydrology reports and updates on regularly basis on the water levels in the dams, and on daily and hourly basis when there is rainfall and/ or possibility of floods owing to rising water levels upstream the dam, with recommendations in order to send early warning systems and activate evacuation plans in case of flooding.”
Stakeholders include the Disaster Management operations at national, provincial and local municipalities affected, local police services (police water wing), farmers and locals upstream and downstream along the Vaal river system. 