Dam levels rise as above-average rainfall persists, but what does this mean for water supply?

While the Vaal Dam's levels have increased due to recent persistent rainfall across the country, experts believe water management and security are not only about water in dams. 

“It is about getting water from the dam through purification and to the people. 

“Though the Vaal Dam is filling, we still, specially in Joburg, have challenges with regard to water delivery infrastructure. The rain is making the challenges worse,” said water resources scientist Carin Bosman, who specialises in environmental, water and waste management and governance.

Andrew Kruger, deputy commander at the National Sea Rescue Institute station 22, said rain in catchment areas during mid-December was enough to flatten the decline of the Vaal Dam. The low level was about 24%.

He said around January 5, the level increased sharply due to heavy and persistent rain.

“The dam peaked at around 60% and maintained that level until January 30 due to on and off rain during that time.”

He said there was a slow increase until February 15 to about 62%. The level rose to 71% on Thursday due to the steady rains over the past week.

“If rain continued for a few more days it would've filled. However, weather reports predict rain will stop [on Thursday].”

Kruger said the dam will continue filling [over a couple days yet] until the remaining water stops flowing from catchment areas.

Bosman said: “The Vaal Dam level will probably reach about 80% at the end of the [summer] rainy season. And at the end of March, the Lesotho Highlands water project will come back online.”

A lack of maintenance on stormwater drainage and stormwater tunnels cause the flooding being seen on some roads and residential areas, she said.

“We have road closures mostly caused by stormwater drainage that is not properly done or maintained.”

Mike Muller, engineer, adjunct professor at the Wits School of Governance and former director-general of water and sanitation who advises organisations about water matters, said: “The 14 dams in the [integrated Vaal] system are 85% full so it is looking good.”

After a recent alert from Rand Water that consumption is extremely high in Gauteng, many have asked why the entity doesn't pump more. 

Muller said Rand Water is told by the department of water and sanitation how much water it can take from the dam system. 

“The limit is set by national government to ensure there is enough in storage to survive a three year drought, which has happened in the past,” he said. 

“The department of water and sanitation calculates how much water can safely be supplied from the system and tells Rand Water how much it can take. During summer Gauteng's cities have taken more than is safe and must reduce consumption as we head into winter.

“The safe amount available on a yearly basis will not increase until Polihali Dam (Lesotho Highlands phase 2) is complete.

“Cities must fix leaks and manage users. If they don't, it may be necessary to impose formal restrictions as we would do during a drought,” he said. 

Bosman said South Africa depends on rain but “we get less than the annual average in the rest of the world. We need to start using water sparingly.

“You can’t say 'I need more' when leaking pipes are not fixed.” She said about 42% of water supplied by Rand Water to municipalities is lost through leaking infrastructure.

On Thursday the department of water and sanitation said this week's hydrology report on the status of water reservoirs shows the country’s dam levels have increased from 80.6% to 81.2%.

The department attributed elevated surface water storage levels in most parts of the country, including Gauteng, Limpopo, KwaZulu-Natal, Mpumalanga, the Northern Cape, the North West and the Free State, to persistent rainfall. 

Department spokesperson Wisane Mavasa said most of Gauteng's supply systems exceeded 80%.

Mpumalanga rose from 95.2% to 95.7% this week, and KwaZulu-Natal shot up from 88.9% to 90.4%. Limpopo moved from 84.1% to 86.8% this week, the Northern Cape from  62.6%, to 73.8%, the North West  from 71.1% to 72.4% and the Free State from 75.4% to 75.8%.

Western Cape water levels are on the decline due to insufficient rain [this is a winter rainfall region]. Levels have dropped from last week’s 72.3% to 69.9% this week.

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