Deputy mayor Ian Neilson said the City was finalising the latest Water Outlook report which would be available this week.
But a Water Outlook status report as at March 18 says the City is currently contending with the decision of the right volume, location, timing and procurement method of permanent desalination.
“At the current stage of evaluation, this appears to be optimal between 120 to 150 million litres per day at a single plant, with delivery of first water possible in 2021.
“In parallel work is continuing at the pilot site at Koeberg which is planned to produce 20 million litres per day in two years’ time (March 2020),” the report said.
The report also said the introduction of more expensive water such as ground and desalinated water necessitated maximising value by re-use.
“Having assessed all the available capacity at the City’s wastewater treatment plants alongside the Cape Flats aquifer injection requirements, a plant of between 70 to 90 million litres per day is being assessed for injection at Faure water treatment plant at an attractive cost with first water in the second half of 2020.
“The long-term outlook for additional augmented water needs to be balanced with water provision from the department of water and sanitation (such as 60 million litres per day from the Berg River to Voel- vlei surface water augmentation scheme) as well as changing rainfall patterns and risk appetite.
“The above assessment with Cape Town providing in the region of 350 million litres per day thus needs to be considered as provisional and is likely to change,” it said.
Sandra Dickson, founder of the group Stop COCT, said it had become clear that City had no clear plan.
“They are most likely waiting for the national government to step in because on their own they won’t be able to tackle this drought on their own.
“It is disheartening to see that the process is being delayed and we cannot get finality to this.
“The same is happening to budget process at the moment,” she said.
Although the City’s three temporary desalination plants at the V&A Waterfront, Monwabisi and Strandfontein are completed, water quality tests have hampered the delivery of water.
Sources in the City said however that the Strandfontein desalination plant was pumping water.
The report also said the V&A site was to be converted to a permanent yield of 5 million litres a day.
With the use of temporary water re-use, it was hoped that 10 million litres a day would be yielded over two years.
The Zandvliet temporary re-use scheme would be completed in late-2018; the Newlands-Albion spring in operation at 3 million litres a day.
“We aim to add all feasible springs into the reticulation system which will increase the volume in Oranjezicht - routing 1 million litres per day into the system, looking at other springs to enter thesystem where possible to increase volume; also Lourensriver - injection of 3.5 million litres per day into the system,” the report read.
Janine Myburgh, president of the Cape Chamber of Commerce, said desalination was a contentious issue.
“On the one hand it seems the most logical choice as we are surrounded by water, yet the costs seem to be curtailing any initiatives by local government.
“However, our calculations don’t concur with theirs, so we still believe it is costly but affordable - certainly most affordable when you take into account the cost of running out of water.
“Also, like all technology we can expect substantial progress in the field of desalination to bring costs down. The interesting thing is that our members have not waited for the city to act, but Sea Harvest and Tsogo Sun, for example, have built their own small-scale desalination plants.”