The water level of Lake Rotoiti will be reduced this month in the first annual draw-down.
The level will be reduced by as much as 100mm from its usual operating level, and Bay of Plenty Regional Council principal engineering surveyor Graeme O’Rourke says the level will remain lower than usual for anywhere between a few days to a month.
The first annual draw-down of Lake Rotoiti is scheduled for this week. Image: Google Earth.
“If the weather forecast is fine, we’ll start the gradual draw-down in the coming week and the water level will remain low until the lake is replenished by winter rains.
“We will be monitoring the effect of the water reduction throughout the process, but we expect it will expose some rocks and reefs, and may render some boat sheds and launch ramps unusable.”
Graeme says regular users of the lake will most likely notice the changes and vessel operators are warned to take extra care.
He says the draw-down, or ‘flush’, through the Ohau Channel is a condition of the resource consent for the Okere Gates.
“Trials were conducted during the consent renewal process in 2011, whereby the lake was reduced by 60mm from usual operating range, so the reduction planned for this month of 100mm from usual operating levels will be closely monitored.
“The draw-down of Lake Rotoiti will increase water velocity in the Ohau Channel and is predicted to flush out sediment.”
Graeme says in time, the process may help to reduce the effects of flooding from high lake levels, particularly around Mourea.
Regional Council will work with local iwi, the Lake Rotoiti Community Association and Fish and Game throughout the process.