Hamilton residents are being asked to urgently conserve water after damage to one of the city's water mains, but the supply is expected to return to normal later this evening.
The city council has implemented alert level four, which means no outdoor water use is permitted.
It wants residents to reduce water use in their homes and businesses.
The Eastern Bulk Main - which supplies about 27,000 homes and runs under the Waikato River - started leaking after a section of the riverbank collapsed.
The council said that until the pipe could be repaired, water would be supplied to the eastern side of the city through the Western Bulk Main and from water in reservoirs.
Hamilton City Council spokesperson Maire Porter said the quality of the water was not an issue, but conservation measures were necessary to maintain supply.
"It is simply that the city needs to make the available water go further.
"Until we complete this repair we need everyone to play their part."
Ms Porter said it was a time the city could come together to help each other out.
"We can get through this situation as smoothly as possible," she said.
"We have a team of expert staff who are working to resolve this situation as quickly and efficiently as possible."
The council said it would provide regular updates on its Facebook page and through the media.