Only three days worth of water is left for Gisborne if residents do not further reduce their usage, the Gisborne District Council says.
The main water supply was damaged by a landslide on Monday, and could take up to 10 days to be restored.
Every person in the area needed to reduce their water usage by at least a third, the council's deputy chief executive Peter Higgs said.
"Water consumption reduced marginally yesterday but nowhere near enough," he said.
"Gisborne does not have enough water to meet the current demand."
On Sunday and Monday, the area used 23,000 cubic metres a day, but needed to reduce to 14,000 cubic metres a day to avoid turning the taps off, Higgs said.
Gisborne has a standby treatment plant at Waipaoa supplying water, which is being topped up by water from the Te Arai stream feeding through the Waingake treatment plant, he said.
"Together they are providing a small supply of water," Higgs said.
"With careful use this should ensure the city has enough water for essential use only."
If demand for water was not drastically reduced, there would be periods of water stoppages, he said.
The council has taken several measures to reduce water consumption, including a ban on the use of hoses, so people could not wash cars, water gardens, or fill up swimming pools.
Water should be used only for drinking and hygiene reasons, Higgs said.
A fire ban has also been put in place.
The main water supply was damaged by a landslide on Monday. The main water pipe from the Mangapoike Dam into the Gisborne District Council water treatment plant was knocked out.
Engineers and geotechnical experts have a plan to fix the pipe, a process which is expected to take eight to 10 days.
The pipe from the city's Mangapoike Dam burst on Monday afternoon when the hillside slipped around it.
Today the council were doing earthworks to stabilise the work site, and examine the pipe which is still under the slip to determine whether there was still damage.
Workers would also assess whether the existing pipe network could be re-used as a temporary measure to restore water.
Food suppliers have voiced concerns the crisis would pose major issues for their staff, growers, and contractors, Higgs said.