A conserve water notice has been issued for parts of Queenstown after a slip affected the Two Mile Water Treatment Plant on Thursday.

The Queenstown Lakes District Council said it was asking residents in Fernhill and Sunshine Bay, the Queenstown CBD (including Gorge Rd) and Frankton Rd to reduce water use where possible while crews work to restore normal service.

"Crews are working hard to restore normal service as quickly as possible, however challenging site conditions mean repairs may take some time,” the council said.

“While the Two Mile Water Treatment Plant remains offline, water supply to the affected areas will rely on existing reservoir storage. Crews are also working to further supplement the supply from the Frankton network.”

The council said there was no need to boil water.

QLDC infrastructure operations manager Simon Mason said residents in the affected areas should reduce water use where possible until normal operations can be resumed.

“We'd like to thank residents and businesses for their patience and support while our crews respond to this issue. Every little bit helps, so we're asking people to be mindful of their water use until the network is operating normally again.”

An update was expected on Friday morning.

The Two Mile Water Treatment Plant is on the Glenorchy-Queenstown road, which has been closed by the slip.

A wintry blast has affected roads across the South Island for much of Thursday, and police have urged motorists to avoid or delay travel in some areas.

— Allied Media