Gauteng may not be in the grip of a drought at present, but scientists warn that another multiyear dry spell — similar to the drought in 2015-16 — could severely threaten the water security of SA’s economic hub.
The scientists’ concerns come amid a further delay in completing the Polihali Dam, part of the second phase of the Lesotho Highlands Water Project (LHWP).
Initially scheduled for completion in 2019, the project has faced multiple delays — blamed on incompetent contractors, political interference and corruption — and is now a decade behind schedule.
Gauteng’s water problems are often in the news, with reports highlighting how failing infrastructure, rising demand and inconsistent supply are putting the province under increasing pressure.
The LHWP is considered one of the most significant long-term solutions to the province’s water supply challenges. While the first phase, which includes the Katse and Mohale dams, is operational, the long-overdue Polihali Dam is essential to meet the region’s rising demand.
“Without Polihali, we don’t have the additional capacity we need,” said Chris Herold, a hydrologist and former president of the SA Institution of Civil Engineering (SAICE). SAICE represents more than 15,000 civil engineering professionals in SA.
“If we experience a major drought before it [Polihali Dam] is completed, we’ll have no backup. We’re in for major trouble.”
Herold told Business Day the initial 2019 commissioning date was planned with a 10-year lead time, during which municipalities drawing water from the Vaal river were expected to reduce water losses to no more than 15%.
That didn’t happen.
“[In] 2008 a desperate DWS [department of water & sanitation] senior planner made a presentation to the SAICE water crisis committee showing that after 10 years the municipalities had made no progress and the leakage loss had grown to 30%.”
At that rate, he said, by the Polihali Dam’s initial commissioning date of 2019, losses would have grown so significantly that the deficit would amount to 85% of the dam’s yield.
Even a “big emergency indaba of all municipalities” in 2010 didn’t make the desired difference “and the backlog of old deteriorating pipework has continued to widen, with an inevitable increase in water losses to about 36% that we are now experiencing”, he said.
A drought similar to that of the 1980s would have effectively cut off Rand Water’s supply for about a year — taking with it half of SA’s GDP.
— Hydrologist engineer Chris Herold
Herold said that means cities and industries are now using 22% more water than the system was designed to reliably supply. He warns the situation will deteriorate further should there be a drought for several years.
“This has a profound effect on the assurance of supply [during] a drought of similar magnitude to the 1930s and 1980s droughts,” he said.
Climatologists have been raising concerns for some time. During the drought in 2015-16, the Vaal Dam level dropped to critical lows, exposing the vulnerability of the integrated Vaal river system (IVRS).
“Drought just worsens the [water] scarcity,” said climatologist Prof Tafadzwanashe Mabhaudhi. “Drought is not our only challenge; it’s also getting warmer, and warmer temperatures mean higher rates of evaporation.
“Any further delays [in Polihali's construction] only worsen the situation in terms of Gauteng’s water supply. And with the population growth in Gauteng as well as urbanisation, it means that at the same time we are having increased demand for water, while the water supply is being constrained.”
Francois Engelbrecht, a professor of climatology at the Global Change Institute at Wits University previously told Business Day the possibility of taps running dry in Gauteng drought cannot be predicted with certainty, but he believes Gauteng’s risk of reaching day zero is extremely high if adequate plans are not in place.
He said the issue was one of the biggest climate-related risks facing the country.
“I have been deeply concerned since 2008 when I first heard about all the nonsense that was going on. The more our crisis committee looked into it, the more horrified I became,” Herold said.
He also warned that even if the Polihali Dam were completed by 2029, it would offer little immediate relief if its commissioning coincided with a drought.
“If the Polihali Dam is commissioned during a major multiyear drought, it cannot be relied upon to contribute much to the yield of the system until after the drought is broken. This is because new dams start empty and tend to stay that way until the drought is broken.”
Herold said 2015-16 was a clear warning. “The IVRS operating rule calls for the implementation of level 1 (15%) water restrictions when the system dam storage drops to 60%. This occurred in 2016. However, examination of the records shows that at that time, system storage should have been at 74%.”
“Four percent of the water loss was attributable to multiple Tugela-Vaal and Usutu-Vaal pumps that were found to be inoperable due to a scandalous lack of maintenance. But the much bigger 10% reduction in system storage loss was due to the cumulative effect of excessive municipal water leakages.”
Had the drought continued, he said, the region would have faced level 2 and perhaps even level 3 water restrictions.
“A drought similar to that of the 1980s would have effectively cut off Rand Water’s supply for about a year — taking with it half of SA’s GDP,” he said.
“The reason for the delays [in the Polihali Dam] is that two of the major contracts are behind schedule,” the DWS said in a response.
“An acceleration plan has been put in place by the Lesotho Highlands Development Authority, which is responsible for implementation of the project,” said department spokesperson Wisane Mavasa.
“The IVRS consists of a system of 14 dams. The biggest backup reserve dam in the system is Sterkfontein Dam. The main purpose of Polihali Dam is not to provide a reserve, it is rather to augment the amount of water in the IVRS.
“DWS will continue to use the Sterkfontein Dam as its main reserve dam, both before and after the completion of the Polihali Dam.”
Would you like to comment on this article?
Sign up (it's quick and free) or sign in now.
Please read our Comment Policy before commenting.