The level of Lake Rotoiti is set to be lowered today in the Bay of Plenty Regional Council's annual drawdown.
The council lowers it by 100mm each year to make way for the flushing of the Ohau Channel, which links the lake to Lake Rotorua.
This year's drawdown has been delayed since June because of heavy rain.
The council's principal engineering surveyor, Graeme O'Rourke, said fine weather was forecast until next week so the lake would be lowered from 5pm and held at or near that level for a few weeks.
The public were warned to be watchful of high flows on the Kaituna River.