Katse Dam in Lesotho is the largest of the Lesotho Highlands Water Project's reservoirs, with a storage capacity of approximately 2 billion cubic meters. (Walter Dhladlhla/Getty Images)
Late at night on September 30, large gates were closed at two locations along the Lesotho Highlands Water Project (LHWP), beginning a six-month maintenance outage, the longest in its 20-year history.
The outage comes amid ongoing water supply problems in South Africa's urban highlands, which draw water from LHWP via the Vaal Dam. Johannesburg's water supply problems have been linked to poor management of water infrastructure by the municipality, but some analysts warned ahead of the LHWP closure that the outages could exacerbate these problems. was.
But water management expert Karin Bosman disagrees.
“Many more people, including some who should know better, seem to believe that the planned outage of LHWP is contributing to Johannesburg's water supply problems, when in fact these The aspects are irrelevant,” Bosman said.
The fact that the water level in the Vaal Dam was only 41% of its capacity last week, compared to 80% this time last year, “helps dispel the idea that we are facing a water shortage. No,” said Bosman, who worked at Dum Dum. Water authorities before and after the advent of democracy.
she says: “It is not unusual for water levels in the Vaal dam to be around 40% at the end of the dry season. There is a difference between a meteorological drought, which occurs due to lack of rain during the rainy season, and an institutional drought, which occurs as a result of water management failure. Yes, Johannesburg suffers from the latter.
Department of Water and Sanitation (DWS) spokesperson Mandla Mathebula said the Sterkfontein Dam, located on the edge of the Drakensberg Escarpment, was acting as a backup dam for the Vaal Dam. Although the Sterkfontein dam has a similar water storage capacity as the Vaal dam, Mathebula says, “The dam is deeper and the environment is cooler, so there is not as much water loss through evaporation.” That's it.
“Standard operating rules are that when the level of the Vaal dam drops below 18%, water is released from the Sterkfontein dam to the Vaal dam. The Sterkfontein dam is currently full [98%] It will then be used to replenish the Vaal dam should the need arise,” Mr Mathebula said.
Water and sanitation expert Richard Holden puts it in more stark terms: “Sterkfontein has over 2.6 billion cubic meters of capacity, which alone is enough to meet the needs of Johannesburg and the surrounding region for almost two years,” he said. .
But Johannesburg uses more water than is wise. Rand Water, which supplies large amounts of water to Gauteng, has exceeded the amount of water it is licensed to supply to municipalities in Gauteng each year for the past six years. The power company is licensed to supply the state with 1.6 billion cubic meters per year, but will exceed this by 193 million cubic meters in 2023/2024.
Speaking at the Strategic Water Partners Network in June, DWS Executive Director Sean Phillips warned: [Rand Water] To make it more abstract. If a drought occurs, Day Zero conditions could occur in Gauteng. ”
The term “Day Zero” refers to the day when most municipal water supplies are cut off due to supply shortages, and was used in the Western Cape during the 2015-2020 water crisis to encourage people to use water sparingly. used by authorities. Although there is no official Day Zero campaign in Johannesburg, the term is used by some.
“Some unscrupulous extortionists are using the word to sell water tanks and the word is increasingly appearing in media headlines. This is unfortunate as Johannesburg is not facing Day Zero. That's true,” Bosman said.
“It's important that people become smarter about water, and the department is trying to find a way to balance between, on the one hand, putting pressure on citizens and local water authorities to change their ways and, on the other hand, not giving the impression that water doesn't exist.” There is not enough water around to meet their needs. ”
And then there's the big problem: almost half of Johannesburg's water is lost to leaks. I will write more about this in a future article.
How to get water in Johannesburg
Mr Mathebula explained that Johannesburg receives water from the Integrated Vaal River System (IVRS). The IVRS is a network of 14 dams, interconnected by a system of rivers, canals, tunnels, pipelines and pumping stations, that collectively store more than 9.3 billion units of water. meter3 of water.
“The Vaal Dam is the most important reservoir in the system because it is from here that Rand Water pumps water for treatment, but it is only one part of a much larger system that DWS manages. We can transfer water from one part of the system to another if needed,” he said.
Johan Tempelhoff, a professor of history at North West University, said the complexity of the IVRS was a result of the fact that Johannesburg was built on a watershed.
“Several rivers flow into the area, and there are also some good springs, but their ability to meet the needs of a rapidly growing city had already been exceeded by the time of the drought of 1895. ” he said.
To solve this problem, the government turned its attention to the distant waters of the Vaal River, completing a reservoir called the Vaal Weir in 1923, and an even larger Vaal Dam in 1938. Currently, all of Johannesburg's treated water comes from the Vaal Dam.
“It was not long before the natural flow of water into the Vaal Dam was insufficient to meet the demands of the increasingly industrialized highlands. Two major 'inter-basin' water transfer schemes have been developed that can supply water to the river,” Tempelhoff said.
The first interbasin plan, completed in 1974, was the Thukela Vaal Transfer Plan, fed by the Mont Haut Source above the Drakensberg Escarpment.
Holden said: “Water from the Tukela River enters Woodstock Dam and some of it is ultimately pumped across the Drakensberg River to Dreikloof Dam for use in the Drakensberg Pumped Storage Scheme. ”When the Drykloof is full, the excess water flows into the Sterkfontein dam and is stored here until it is needed in the Vaal river system,” he said. DWS does not release water from Sterkfontein until absolutely necessary.
“Pumped water means expensive water, so it is only stored for emergencies,” he said.
The other plan is LHWP, which would store water from several catchments in Lesotho in two large reservoirs called Mohale and Katse.
Water released from these reservoirs is drawn through a series of pipes and tunnels to South Africa's Ash River, which flows into the Liebenbergsvlei, where it joins the Vilge River and flows into the Vaal Dam.
When asked if LHWP is the largest water supplier to the Vaal Dam, Holden chuckles.
“We don’t operate the system that way,” he said. “One part of the system always supplements the other. That's just the nature of the water cycle.”
He cited the example of 2015, during the Lesotho drought, when “water flows from Lesotho were significantly reduced without affecting security of supply”.
However, Mr Holden said LHWP provided the most consistent water supply to Vaal Dam.
“On the Lesotho side, we have a hydroelectric power plant that needs a consistent flow of water to that power plant to keep the turbines running. So no matter how high or low the water level in the Vaal River is, the water is consistent. “The dam just happened to be that way,” he said.
Mathebula said the governments of South Africa and Lesotho agree annually on the amount of water to be transferred.
“This year's agreement was to supply 780 million cubic meters while producing 72 megawatts of hydropower through Lesotho's Muela power station,” he said.
The suspension of LHWP will result in a shortfall of 80 million cubic meters, which Mathebula said will be covered when LHWP restarts in April 2025.
The second phase of the LHWP, currently scheduled for completion in 2028, will store water from the Senku and Kuber rivers in a dam called Polihari, adding approximately 2.325 billion cubic meters to the LHWP's storage capacity. Mr Holden said LHWP would be the largest supplier of water to the Vaal River system.
“That's why maintenance outages are so important. If they're not done, there could be longer outages in the future, and if this happens in a drought year, it could cause problems. If people could focus on that instead of the false idea that Johannesburg doesn't have enough water, we'd all be better off,” Mr Holden said.
This article was first published ground up