South Africa’s Largest Water Reservoir Opens In Benoni

The 210 million-litre reservoir is the largest circular post-tensioned reservoir in the world.

By Chriselle Moraes on
10th March 2023

South Africa’s Department of Water and Sanitation Minister, Senzo Mchunu, launched the Vlakfontein reservoir, the country’s largest drinking water storage facility. It has a capacity of 210,000 cubic metres (210 million litres).

The facility is located in Vlakfontein, a town in Ekurhuleni, Gauteng Province. Construction works on the US$25.4 million reservoir project began in May 2020.

The new Vlakfontein reservoir is part of the Mapleton System, which receives water from the Zuikerbosch purification and pumping station via two pipes that are 2,100 millimetres in diameter each and then distributes the water to municipalities in the area.

The reservoir structure consists of a post-tensioned outer concrete wall that is 11.8 metres high, similar to a three-storey building. The wall is tapered from a thickness of 1,100 millimetres at the base to 300 millimetres at the top. The reservoir is covered by a flat slab roof supported by 272 columns spaced at 8.4 metres. It has an internal diameter of 154 metres – equivalent to the length of one and half football fields - with 256 round reinforced concrete columns, 600 millimetres diameter each, to support the roof slab. 

According to a twitter post by Rand Water, the brief for the project was for a unique and innovative design for the reservoir. This led to the reservoir being cylindrical, unlike the majority of Rand Water reservoirs of this size. Rand Water has traditionally preferred rectangular shaped reservoirs for the size required for Vlakfontein.

The reservoir facility was constructed by a joint venture comprising WBHO Construction, ANZI Plant and Mining Services and the Motheo Construction Group. Construction supervision was undertaken by Rand Water in collaboration with the Bosch Projects team.

The project is part of measures by the National Department of Water and Sanitation to refurbish and augment water infrastructure in the country.

The new reservoir will help supplement water reserves and supply in areas east of Tshwane and the Ekurhuleni Metropolitan Municipality until 2035. It will also help maintain a strategic storage capacity equivalent to 24 hours of water on demand should there be any pumping challenges or power outages, especially in view of the current power supply challenges experienced across the country.

The Vlakfontein reservoir is the largest post-tensioned water storage reservoir in South Africa. It is also the largest circular post-tensioned reservoir in the world.

“Currently, the other largest post-tensioned cylindrical reservoirs are in Jeddah, Saudi Arabia, where there is a network of 11 circular post-tensioned reservoirs with a capacity of 187,500 cubic metres each,” says Rand Water.

Because of the dam’s various safety issues, it is registered as a dam with high safety risks and strict safety regulations were required to be adhered to during its design.

Addressing fears of an impending water crisis in the country, Mchunu said, “I accept that the country is facing challenges of power supply, and I do understand the impact of this on water supply. But I do think that it is misleading to say that the water sector is heading in that direction and is in shambles. That is incorrect.”

Mchunu spoke of work by Rand Water in Gauteng and other parts of the country, including the implementation of the Infrastructure Development Planning. This includes the refurbishment and augmentation of infrastructure, and the implementation. 

“The augmentation I am referring to includes expansion of potable production capacity at the river stations, as well as infrastructure that radiates away from river stations, that is, pipework, pumps, reservoirs or associated automation and electrical infrastructure. When pipelines, pump stations, and additional potable capacity at river stations are upgraded, outright additional capacity can be delivered to customers,” Mchunu said.

Top Photo: 210 megalitre Vlakfontein Reservoir (@DWS_RSA Twitter Handle | National Department of Water and Sanitation RSA)

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