The Department of Water and Sanitation (DWS) must stick to the amounts of water it is allocating to farmers in the Western Cape to protect the available dam water for Cape Town, Democratic Alliance leader Mmusi Maimane warned on Wednesday.
"It is important that the national department sticks to these allocations, and does not exceed them, which would impinge on the remaining dam water available to the city," Maimane said at a Defeat Day Zero briefing.
Maimane has started giving water briefings after Mayor Patricia De Lille was side-lined during party political turmoil within the Cape Town council.
Maimane noted, in a statement released after the briefing, that the agricultural sector's steady decline in water use helped push Day Zero back to May 11, giving Capetonians some relief.
That is the date that a large percentage of municipal supply systems could be turned off and water ration queues at 200 points of distribution will start, if consumption is not reduced to 450Ml (megalitres) a day.
The last consumption figure, released on Monday, was 547Ml a day and the last average dam level was 25.5%.
"It is important for residents to understand that the allocation of water to agricultural users is determined solely by national government," said Maimane.
Because the City of Cape Town has no legal powers to supply water, farmers will have to apply to the national government for permission to get more.
He said that the agricultural sector had used about 90% of its allocation and so the demand on the Western Cape Water Supply System (WCWSS) "will drop significantly, if not altogether".
In addition to declining use, on Wednesday farmers in the Groenland Water Users Association (GWUA) released water stored in their private dams in the Elgin and Grabouw fruit growing region so that it could flow via the Palmiet River to the Steenbras Dam which forms part off the city's water supply.
GWUA chief executive Johan Groenewald said the release was not without risk, as they are depending on good rains when winter sets in.
DWS spokesperson Sputnik Ratau told News24 the transfer of water formed part of an agreement that was reached between the DWS and GWUA during November 2017.
It will benefit not only the city, but irrigators and surrounding towns within the WCWSS.
"The GWUA accepts the risks of managing the remainder of their private storage until the onset of the winter rainfall season," said Ratau.
He said water for the City of Cape Town, surrounding urban towns, as well as the irrigators along the Berg, Eerste and Sonderend Rivers is drawn from the WCWSS, which is a system with a series of dams that serves 3.2 million residents of the area.
The WCWSS infrastructure is owned and jointly operated by the DWS and the City of Cape Town.
The system comprises six major dams, being Voëlvlei, Wemmershoek, Theewaterskloof, Berg River and Steenbras Dams at the headwaters of the major rivers and their tributaries.
According to the City of Cape Town's "water dashboard", farmers exceeded their allocations slightly in 2017, but the national department has now shut off supply to two irrigation boards that utilised their full allocation by the end of January 2018.
In the meantime, plans continue to bring more water into the city's system through a combination of temporary desalination plants and aquifers, with people in the city restricted to 50l of water per person per day.