ORC HEAD OF LAKE WHAKATIPU - JULY 2024 UPDATE

Jul 5, 2024

CaptureHEAD AKE WAKATIPU

Kia ora koutou,

In this edition we provide a programme update and share plans for an upgraded lake level recorder at the Glenorchy boat ramp.

In August, we’ll be presenting a general programme update to Councillors at the ORC Safety and Resilience Committee meeting.

This is a chance for us to share how different parts of the work programme are progressing, and we will include a link to this meeting in the next newsletter.

Programme updates

The following assessments are progressing well:

The flood and erosion mitigation and nature-based solutions feasibility assessment studies potential engineered flood and erosion management and a ‘nature-based solutions’ approach for the Rees and Dart floodplain areas and the Glenorchy township.

The Glenorchy and Kinloch natural hazard risk assessment studies flooding from the Rees and Dart rivers, Lake Whakatipu and the Buckler Burn, and liquefaction and lateral spreading at Glenorchy.

The consultants are working hard to finalise these studies, and they will be completed in the coming weeks. We know some of you may be eager to see the findings of these studies, and we plan to share the results with the community within the next few months.

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Image: Current water level recorder at the Glenorchy boat ramp

Upgrade of Lake Whakatipu water level recorder planned at Glenorchy boat ramp

An upgrade of monitoring equipment at the Glenorchy boat ramp will improve the reliability of the information we collect about Lake Whakatipu level changes.

Over the next few months, the solar-powered water level recorder will be upgraded and raised to ensure it keeps monitoring, even at very high lake levels.

The boat ramp recorder was installed three years ago as a trial to complement the Glenorchy Lagoon water level recorder installed in December 2020 and the Rees River flow recorder installed in December 2021.

The data has been so valuable that we are futureproofing this monitoring site and making it a permanent part of the monitoring network.

Capturejetty Image: Proposed water level recorder at the Glenorchy boat ramp (mockup)

How is lake and river level information used?

The near real-time information we receive from these recorders enhances our monitoring and response during heavy rainfall events and provides a longer-term dataset of baseline information we can use to analyse flooding hazards.

For example, during a heavy rain event that caused elevated river and lake levels across Otago in September 2023, we could see:

the Rees River reach its highest flow (235 cumecs) since the installation of the flow recording station in December 2021.
the Glenorchy Lagoon also reach its highest level (312.49 m) since monitoring of its levels began in October 2020.
Lake Whakatipu reach a level of 310.83 m.

The water level recorder also helps us compare lake levels between the head of the lake and the NIWA monitoring station at Frankton.

Data from environmental monitoring (e.g. rainfall, river flow and lake levels) is used to alert Emergency Management Otago of potential flooding to inform a response.

It also complements our other flood response tools, such as flood forecasting models which can be used to forecast water levels for Lake Whakatipu and the Glenorchy Lagoon.

Near real-time data from the Glenorchy boat ramp water level recorder is available on the ORC’s Environmental Data Portal.

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Image: Example of water level data for Glenorchy on ORC’s Environmental Data Portal

As always, we value your feedback

This adaptation programme was initiated because complex, increasing natural hazards in the Head of Lake Whakatipu require a comprehensive management response that takes a long-term view and encompasses all types of natural hazards.

This is your community, and we want to work with you to develop understanding and resilience. Check here to learn more about the whole programme.

If you have questions or need information, visit our website to see the reports and get answers.

You can also speak to a member of the ORC Natural Hazards team on 0800 474 082 or email us for more information at headofthelake@orc.govt.nz.

We will provide responses to any emailed questions and facilitate answers from our consultants if needed.