The national Department of Water and Sanitation has ruled that Cape Town needs to cut water consumption by only 10% for the year starting in December.

This comes just days after the City of Cape Town announced that residents would need to cut consumption by a much bigger 30% for the coming year.

But, in spite of the national department's announcement, the City has said it is not going to change its more conservative decision in the near future in order to avoid getting back to the Day Zero-type crisis Cape Town faced last summer. Instead, it will adopt a wait-and-see approach.

Deputy Mayor Ian Neilson expressed surprise that the national department had set water savings as low as 10% - a big step down from the 45% savings the department had set for the past year.

"We thought they might go down to 20%. I find 10% a bit surprising," Neilson said on Monday.

Neilson added that the City would monitor both dam levels and water consumption, and would reassess the situation early next year.

"We will decide in the new year if we need to make further adjustments. We set savings at 30% because we wanted to have a situation where we made sure we did not relax restrictions by too much, too soon. We did not want a situation where we went too low and then had to bounce back quickly to avoid another crisis," Neilson said.

The City said the more cautious 30% reduction in water use would help with the recovery of the dams and cater for the uncertainty of future rainfall in the face of climate change. This translated into Level 3 water restrictions - less stringent than the former Level 5.

The daily amount of water a person could use increased from 70 litres to 105 litres.

The national department has the mandate to set water restrictions. It decides on the amount of water different sectors can use in certain areas and publishes the figures in the Government Gazette.

The way these restrictions are implemented is left up to municipalities.

The City and other municipalities had meetings with the national department earlier in November about the proposed water cuts for the coming year. The City said the national department had indicated then that the cuts could be between 10% and 20%, but it had not made a final decision.

The City said on Thursday it could not wait any longer for the department's decision, so it decided to make its own percentage cuts of 30%, based on a conservative approach.

Environmentalist Patrick Dowling commended the City for taking a more conservative approach.

"It is encouraging to see the City err on the side of caution, which they have not been doing in other areas, especially not in development approvals."

Dowling said the City now needed to get to grips with how much groundwater was being drawn up by Capetonians who had put down boreholes during the height of the Day Zero predictions.

"The City needs to wise up on the groundwater situation. The full consequence of that is still going to be felt. Everyone is talking about aquifer recharge, but at the moment nothing is happening. The City needs to take a significant sample of all these boreholes and measure the amount of water used," Dowling said.

He said many Capetonians had installed rainwater tanks that would help reduce water consumption from the supply dams, but would not have a negative effect as boreholes did.

The big six dams in the Cape supply system are 70.3% of storage capacity, down from 71.3% from last Monday, but still double the 35.3% it was this time in 2017.

With Level 3 water restrictions, the target for total consumption in the city rose from 500-million litres a day to 650-million litres. Last week, residents used 563-million litres a day - a reduction from the 576-million litres the week before.