Lake Okareka Discharge Long Term Resource Consent Application

Lake Ōkāreka water levels update, June 2019

In contrast to the autumn 2017, autumn 2019 has been a relatively dry period and lake levels have been maintained within the normal operational range.

However, Bay of Plenty Regional Council staff have not been resting on this matter and it may seem to lake side residents things have quietened down, our staff have continued to take a raft of actions to prepare for possible high lake levels and the need to allow high flows from the lake in the future.

The following is a brief update of current activity: 

1. The emergency consent that was applied for as a result of the 2017 flooding has now been granted. This is a necessary part of the actions that we took at that time including releasing higher lake outlet flows and protection works to look after the bed of the Waitangi Stream to Lake Tarawera. This consent now allows BOPRC to manage higher flows for a period of two years from March 2019, while we apply for a longer term consent and potentially get approval for managing the higher flows permanently.
2. The emergency consent also allows for the installation of the permanent stream protection works down stream of Spencer Road. The first stage of this major project is nearly completed and the second stage will be completed during the next 12 months. This is a significant investment in the protection of the stream and ecological habitat. The works have had to overcome a number of challenges, including avoiding works that affect the trout spawning habitat as well as access via private land. The BOPRC is highly grateful to the local Tarawera residents who have suffered the inconvenience of the protection works during construction.
3. The application for the long term consent has been filed with BOPRC regulatory staff. We are now awaiting feedback on the processing and conditions of consent.
4. Below is a graph of the lake level since February 2017. It can be seen that we finally got the lake back into its normal operating range in February 2019, 2 years after the initial event.
5. Any work required to upgrade the outlet pipe to allow a great gravity flow to be released from the lake is dependent on the outcome of the resource consent application. We will keep you informed of progress.

Ensuring no excessive pressure put on Waitangi Stream

Bay of Plenty Regional Council staff continues to monitor the water levels at Lake Ōkāreka and the quantity of water flowing down the Waitangi Stream.

As of today, the Lake Ōkāreka water level is still sitting within 185mm of the target range maximum.

Council staff have been able to maintain this level since May through discharging 360L/s water under the emergency consent.

Staff have maintained this moderate flow to ensure that no excessive pressure has been put on the Waitangi Stream through this time.

Last month a working party meeting was held with various parties from Lake Ōkāreka, Lake Tarawera and local iwi.

As an outcome of the meeting, a draft resource consent application is being prepared to allow a higher flow to be discharged down the Waitangi Stream while it is expected that the permanent protection works for the Waitangi Stream will be authorised by the emergency consent.

The protection work would involve engineering rock design areas of the stream with the highest risk of erosion.

Geotechnical investigations have revealed risk areas of the stream bank in some locations. The investigations have shown that there was the risk of stream bank failure without additional flows down the stream. The need to discharge increased flows during 2017 initiated the geotechnical investigations that identified this risk.

For more information, please contact Ruth Keber at The Rotorua Te Arawa Lakes Programme on info@rotorualakes.co.nz. 

Emergency works at lower Lake Ōkāreka

Bay of Plenty Regional Council is about to invoke the emergency works provisions of the Resource Management Act to address rising lake levels around the Rotorua region going into winter.

Council is taking this action before the winter months for two reasons.

The Lake Ōkāreka water level is already high and exceeds the target range now by more than 200mm after recent weather events.

Bay of Plenty Regional Council Lakes Operation Manager Andy Bruere said it was difficult to predict what risk to homes and infrastructure there was over winter.

"It is expected that lake levels will keep rising and if Council undertakes to discharge a higher flow rate now, it is likely that we can address the risk of high lake levels while discharging a lower flow in the Waitangi Stream."

This would have the impact of reducing potential damage to the stream through the winter, he said.

The second reason was if lake levels continued to rise, as Council expected during winter, and homes were at risk of flooding then Bay of Plenty Regional Council would have limited ability to respond in a meaningful way.

"Our ability to lower the lake is restricted by the outlet pipeline and the auxiliary pump that we installed last year," Mr Bruere said.

"In effect, a major storm event can raise the lake level up to 250mm in a single day where our ability to lower the lake is limited to less than 10mm per day."

Bay of Plenty Regional Council is required to obtain consent for the ongoing emergency works. Work will begin today.

In addition, Council is working with the communities around Lake Ōkāreka and Lake Tarawera to find a long-term solution to this problem. This work will be ongoing.

Images taken at Acacia Bay Reserve

An image taken of Lake Ōkāreka water levels at Acacia Bay Reserve on 13 November 2017.

Minimising stream bank erosion

Stream-bank erosion protection work has been underway on Waitangi Stream this week.

The aim was to complete work by 25 January so water flow from Lake Okareka could be increased to 500 l/s, which has been done. 

As shown in the graph below, the Lake Okareka water level has been dropping in recent weeks and is almost back within the consented range. 

We will continue to monitor lake level changes and keep you informed.