After a fifth sluice gate of the Vaal Dam was opened on Sunday morning, there might be a possible overflowing at the riverbanks downstream of the Vaal and the Bloemhof Dam, affecting infrastructure built in lower-lying areas within the 100-year floodline. This flooding alert has been issued to warn residents.
Due to the rapid increase of inflows into the Vaal Dam, the fifth sluice gate had to be opened at 10:00 on Sunday, 6 April, to manage water levels that had increased overnight due to the ongoing rainfall in the Vaal River catchment, impacting the flooding.
The consequent alert is primarily due to the additional sluice gate opening.
This is 24 hours after the Department of Water and Sanitation (DWS) opened the fourth sluice gate at the Vaal Dam, the department states on Sunday. Another flooding alert was circulated after the sluice gate opened.
The department advises that people living in the high flooding area of the Vaal River downstream of the Vaal Dam and the Bloemhof Dam should evacuate and move to a safe area and remove valuable equipment, movable infrastructure, and livestock.
The warning follows the alert issued due to another sluice gate opening.
The increased outflows from the Vaal Dam are expected to reach the Vaal Barrage in about six hours and the Bloemhof Dam in three to four days and will result in water levels rising in both the dam and the river, overtopping the riverbanks and reaching the floodline.
Outflow at dams increased
The water storage levels at the Vaal Dam stood at 108% on Saturday, but as of this morning the levels have risen to 109%. The outflows at the dam will increase from 550 cubic metre per second (mᵌ/s) to just under 700 mᵌ/s. The inflows into the dam have increased since Sunday morning from 1 000 mᵌ/s to 1 200 mᵌ/s by midday. This includes the flooding alert after Vaal Dam opened another sluice gate and issued a warning.
Storage levels at the Bloemhof Dam have also risen from yesterday’s 103% to 107% this morning, and water releases will be staggered incrementally from the current 1 000 mᵌ/s to 1 100 m³/s at 10:00; 1 200 m³/s at 12:00; 1 300 m³/s at 14:00 and the last increase at 16:00 to 1 400 mᵌ/s thus impacting the areas near the floodline.
At the Grootdraai Dam located in Mpumalanga in the Upper Vaal River Catchment, upstream of the Vaal Dam, one sluice gate remains open to enable water releases. The department has issued multiple alerts, including the recent alert after the Vaal Dam sluice gate opening.
The dam is currently sitting at 102%, still considering its flood line impact.
The department says it is implementing these necessary controlled water releases at the dams as part of dam safety precautions to safeguard the infrastructure.
Wisane Mavasa, spokesperson for the DWS, says the department is continuously monitoring the water levels in the Vaal River System.
“Through various platforms, the department shares hydrology reports and provides regular updates regarding the water levels in the dams, with recommendations in order to provide early warnings in case of flooding,” the department states, ensuring vigilance near the flood line.
The recent alert on flooding was issued after the Vaal Dam opened another sluice gate.
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