Hamilton residents are urged to conserve water after a collapsed riverbank damaged one of the city's most important water mains.
Hamilton City Council has now put in place the city's highest water alert level.
There are no issues with water quality but supply levels could be reduced significantly due to the damage, the council stated in a media release.
Alert level four means no outdoor water usage is permitted.
But, residents are urged to look at all water usage in their homes and businesses as staff work to repair the Eastern Bulk Main.
The Eastern Bulk Main supplies around 27,000 homes and runs under the Waikato River from the city's water treatment plant opposite Hamilton Gardens.
A substantial section of the riverbank has collapsed around the Bulk Main and there is a significant water leak at the site, the council stated.
City Waters staff have been on site this morning making the area safe to work in, and identifying the extent of the breach and repair options.
Until the pipe can be repaired, water will be supplied to the eastern side of the city through the western bulk main and from water stored in reservoirs.
This means a concerted effort will be required from the whole city to maintain supply.