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The relationship between dam levels and municipal supply is often misunderstood.
Vaal Dam. Picture: Department of Water and Sanitation
Despite the Vaal Dam being at more than 100% capacity, Johannesburg and broader Gauteng residents should not expect an end to water disruptions, according to the Department of Water and Sanitation.
Recently, the Vaal Dam exceeded its full capacity. As of Friday, the dam stood at 102.4%, prompting water authorities to implement measured releases to maintain safe water levels.
Current Vaal Dam status
According to The Reservoir, a water resource information centre for the catchment management forums of the Upper Vaal water management area, measurements taken on Friday showed the dam recording an inflow of 139.2m³/s while maintaining an outflow of 21.6m³/s.
At the Vaal Barrage downstream, Friday’s readings indicated a water level of 7.5m with an outflow of 59.7m³/s.
The dam, an essential part of the Integrated Vaal River system (IVRS), boasts a full storage capacity (FSC) of 2.5 billion cubic metres.
According to the Department of Water and Sanitation’s (DWS) latest weekly report, around this time last year, the Vaal Dam, which supplies water to Gauteng, stood at a much lower capacity of 65.9%.
ALSO READ: Vaal Dam reaches 100% capacity for first time since 2023
No direct connection between Vaal Dam levels and supply to residents
Though the Vaal Dam is currently exceeding capacity, it doesn’t automatically translate to increased water availability for Johannesburg or other Rand Water customers, the Department of Water and Sanitation spokesperson Wisane Mavasa clarified.
“The only benefit from the recent rains is that water required for irrigation may decrease since water users are not using water from Rand Water for their irrigation purposes,” Mavasa told The Citizen.
The relationship between dam levels and municipal supply is widely misunderstood.
There is often confusion between raw water availability and treated water distribution capacity.
Speaking to The Citizen, water expert Carin Bosman said the Vaal Dam would likely fill higher over the weekend, but that things are still under control.
“The excess is going out on the normal outflow release channel. It is not yet necessary to open sluices,” Bosman added.
ALSO READ: The Vaal Dam is full, now what?
Tight supply-demand relationship
The fundamental issue facing Gauteng’s water system is that demand frequently approaches or exceeds supply capacity.
This weak balance makes the entire system vulnerable to disruptions.
“This is largely because demand for water has risen due to rapid population growth and leaks in the municipal water infrastructure, increasing the risk of water supply disruptions.”
According to Mavasa, the primary cause of water shortages in Johannesburg stems from this delicate balance.
“The main underlying cause of the water supply disruptions in Johannesburg is therefore that the peak demand for water is close to, and occasionally exceeds, the available supply from Rand Water.”
“The demand-supply relationship for treated water in Johannesburg is very tight and the system is vulnerable to disturbances caused by electro-mechanical breakdowns or spikes in demand caused by heatwaves.”
Bosman emphasises that the issue is compounded by misappropriated funds.
“The water supply situation in Joburg can only be improved by better procurement management and more severe consequences for municipal officials who misspend funds, or who fail to appropriately allocate budgets for water infrastructure maintenance,” she said.
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Rand Water’s Vaal Dam extraction licence limitations
Even with the dam at full capacity, Rand Water’s extraction remains strictly regulated.
“The volume of water that Rand Water can abstract from Vaal is still limited to the water use licence issued by the department of water and sanitation, which is 5 200 million litres per day,” Mavasa said.
“Rand Water cannot abstract more than what they are licensed.”
This water serves Johannesburg and other municipalities in Gauteng, industries and parts of Free State, North West and Mpumalanga provinces.
These licence limitations are necessary for sustainable water management.
They highlight why the department cannot simply increase extraction when dams are full. The department also says water security requires long-term planning, not reactive measures.
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Complex water distribution system
The water supply chain involves multiple entities.
Johannesburg Water, a city entity, purchases treated water from Rand Water, which in turn buys raw water from the department.
Meanwhile, Rand Water draws from the IVRS, consisting of 14 interconnected dams, including the Vaal Dam, Sterkfontein Dam and the Lesotho dams of Katse and Mohale.
“Rand Water treats the raw water so that it meets drinking water quality standards, stores it in bulk storage reservoirs and pumps it into the municipality’s reservoirs,” Mavasa said.
“From the municipal storage reservoirs, the water either flows under the force of gravity or is pumped through various distribution pipelines to households and industries across the city.”
What causes water shortages?
Despite sufficient water in the Vaal Dam, several factors contribute to ongoing shortages in parts of Johannesburg.
“Water losses through leaks and illegal connections, reservoir leaks, poor infrastructure maintenance and poor investment in the city’s water supply systems,” are the main culprits, according to Mavasa.
Bosman points to systemic issues in municipal management.
She characterised Johannesburg’s situation as a “socio-economic drought”, which she described as “loads of water everywhere, not a drop to drink”.
She placed the blame squarely on institutional failures.
“The causes of this socio-economic drought is 100% institutional failure on the part of the City of Johannesburg, which allocates millions of rands for ‘mayoral functions’ and other ‘events’, but which fails to allocate sufficient resources for the maintenance of water supply infrastructure,” Bosman said.
“It is actually appalling that the city has money to buy liquor for their parties, but not money to pay to fix pipes.”
The situation worsens during planned maintenance or major breakdowns.
“Because the demand is close to, or occasionally exceeds the available supply of water, after repairs and maintenance are completed, the water levels in the reservoirs rise very slowly, taking time for their systems to recover,” Mavasa explained.
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Water shortages: solutions and strategies
Municipalities across Gauteng need to implement several key measures to address these ongoing challenges.
“There is agreement that all the municipalities in Gauteng including the City of Johannesburg need to focus on fixing the leaks in their water distribution systems and removing illegal connections, putting in place water-use restrictions and enforcing them as well as implementing punitive tariffs for customers that use water in a wasteful manner,” said Mavasa.
She added that specific measures include implementing and enforcing water restrictions, ensuring prompt repairs of leaks, removing illegal connections, improving system performance through valve refurbishment, expediting infrastructure projects and engaging in public education on water conservation.
Bosman suggested that, “like the City of Cape Town and other large cities all over the world, the City of Joburg can look at various water reuse strategies”.
“The best and latest technologies in the world won’t be able to improve water management if there is no political will to ensure proper planning and management,” Bosman said when asked about innovative technologies that could improve water management.
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Lesotho Highlands Water Project
The South African government is working on expanding the water supply through the Lesotho Highlands Water Project Phase 2, which includes building the Polihali Dam “to augment water into the IVRS from the Katse and Mohale dams built in the mountains in Lesotho as part of Phase 1”.
“The completion of Phase 2, which is anticipated to be in 2028-9, will bring an additional 490 million cubic metres per year from the current 780 million m³/year to make it 1260 million m³/year into the IVRS,” Mavasa said.
However, Mavasa emphasised that infrastructure improvements alone won’t solve the water crisis problem.
“Over and above the measures the municipality is expected to implement, Gauteng citizens are urged to play their part in reducing demand by using water sparingly, complying with restrictions and municipal bylaws, addressing leaks at home and reporting municipal leaks and pipe bursts to relevant municipalities.”
ALSO READ: Full Vaal Dam to the rescue as Lesotho Highlands Water Project takes bad turn
Vaal Dam flood management
Current flood management protocols for the Vaal Dam do not affect the supply to Rand Water.
“The flood management is to ensure that the inflows in the dam do not put the infrastructure at risk and also to ensure that the dam remains at full capacity,” explained Mavasa.
Bosman said the current Vaal Dam flood management system was sufficient.
“The releases are done per the operational management plan for the Vaal Dam, which has been in place for a long time and has worked well in the past.
“As long as the plan is being followed, the releases are in accordance with the system’s needs.”
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