Wairoa residents are being asked to conserve water while the town's water supply reservoir refills.
The water supply reached crisis levels on Monday, causing water to be cut to the town's largest employer, Affco.
The weekend's heavy rain caused high levels of sediment to enter the river, meaning the water treatment plant, which takes its water supply from the river, was unable to operate.
Wairoa District Council operations manager Bill Lewis said the plant began processing at 7am yesterday, but it would take a few days for water storage levels to build up again. Reservoirs had dropped to 10 per cent of capacity, but were now a third full.
"At this stage we just need people to conserve as much as they can, just to make sure we can get back up," Mr Lewis said.
Temperatures were on the rise, which normally brought a spike in water use.
Mr Lewis said the sediment problem was compounded because the previous dry spell had left the river low and water storage already down.
The Affco plant's water had to be cut to preserve town supply, engineering manager Neil Cook said.
"This rain went on for quite a long time and kept flow rates in the river elevated. A high level of sediment came with that.
"When that happens, one of the first things to go is the Affco water supply. There's just not enough water to keep the town and Affco going.
"That's not ideal but that's effectively the policy we follow to protect the health and wellbeing of the town, which comes first," Mr Cook said.
One Affco worker said water was vital to the plant, especially with washing and sterilising while processing. The meatworks is the town's largest single water-user and its water was cut off at 6pm Monday night, causing the night shift to finish early.