River flows on the Kaituna are back to raftable levels after 72 days of high flows following heavy rain in March/April.
Rotoiti lake levels and flows are recovering and are now back inside the usual operating range for the lake, says Bay of Plenty Regional Council principal engineering surveyor Graeme O'Rourke.
This means that the Okere Gates can be lowered, reducing Kaituna River flows to the raftable level of around 26-27cumecs.
“It has been a long haul since we opened the Okere Gates fully on 27 March when we were facing heavy rains and rising lake levels,” says Graeme.
“You can imagine Rotoiti as a large bathtub and the Gates as a small plughole at the end. Nature has turned the taps on full and it has taken a long time to let the water out of a small plughole.
“During April we saw unprecedented lake levels across in the Rotorua district and we needed to keep the Gates fully open to keep up with the rainwater flowing into Rotoiti. It has taken until well into June to finally see lake levels return to normal.”
It won't just be rafting companies celebrating on the Kaituna. The previously high lake levels caused some erosion issues on properties with lake frontages and the high flows in the Ohau Channel saw some inundation of surrounding properties.
Not all lakes in the Rotorua district are returning to normal levels. Lakes Rerewhakaaitu and Okareka are still extremely high, and there are still significant issues with lake edge erosion. The Regional Council is aware of the issue but there is little that can to speed up natural lake lowering.
“Our latest two-week weather outlook is promising, with little rain forecast keeping Kaituna flows and lake levels down for longer,” says Graeme. “We'll continue to monitor lake levels and keep river users updated.”
The Okere Gates and Ohau Weir are man-made structures to help control water levels in the Rotorua lakes. The gates were constructed in 1982 to regulate the flow of water from Lake Rotoiti into the Kaituna River. The Ohau Weir was constructed in 1989 to control water level fluctuations in Lake Rotorua.