Water restrictions continue in Tauranga because of low flow in the streams that supply the city's drinking water.
Tauranga City Council said the "unprecedented situation" reflects the knock-on effect of three unusually dry summers for the Bay of Plenty.
Stephen Burton, council director of city waters, said despite recent rain the stream flow rates have not improved.
"The situation is a first for Tauranga. Never have city-wide sprinkler restrictions been necessary beyond the first week of April.
"Also, historically, restrictions have been necessary due to water treatment capacity constraints during peak summer periods.
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"What we're looking at now is a potential problem sourcing water due to unprecedented drought in our region and the need to protect stream health.
"We are working to bring additional source water and treatment capacity into service for Tauranga as soon as possible.
"The new Waiāri water supply scheme, due to be completed late 2022, will supplement existing supplies, provide additional resilience in extended periods of drought and cater for future growth."
The Bay of Plenty Regional Council has suggested there may be less rain this winter, the city council said, which will directly affect groundwater, river flow and soil moisture across the region.
Burton emphasised similar problems were being experienced throughout New Zealand.
"Even though the effects of a changing climate show up differently for various regions, it requires us all to look at how water is managed in a new light.
"We are working hard to find alternative solutions for sourcing and supplementing our water, however none of these will be quick fixes."
The city council continues to work closely with the regional council to assess the effect of drought conditions and water levels in the region on source water supplies.