Users on the Kaituna River, particularly rafting companies, will be pleased to see river flows back to raftable levels last week after 72 days of high flows.
Bay of Plenty Regional Council principal engineering surveyor Graeme O’Rourke said that Rotoiti lake levels and flows are recovering and are now back inside the usual operating range for the lake. This means that the Okere Gates can be lowered, reducing Kaituna River flows to around 26-27cumecs, a raftable level.
“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.
“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,” Mr O’Rourke said.
On the Kaituna, it won’t just be rafting companies celebrating. 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. Some lakes are still extremely high including Rerewhakaaitu and Ōkāreka, and there are still significant issues with lake edge erosion. 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. We’ll continue to monitor lake levels and keep river users updated,” Mr O’Rourke said.
The Okere Gates and Ohau Weir are man-made structures to help control water levels in 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.
There is more information on the website on the structure and how it works.