Te Waihora/Lake Ellesmere opened to the sea

Te Waihora/Lake Ellesmere was reopened to the sea on Sunday (15 June), following a week-long earthworks operation that saw a dedicated team working to ready the site.

After a successful opening in early May, the lake closed naturally due to sea swells depositing shingle and seawater at the opening site.

“Two south-westerly weather events created sea swells of up to 5 metres over the past few weeks, depositing significant amounts of shingle and seawater at the opening site,” said Leigh Griffiths, general manager hazards.

Crews tackled the task over the last week, bracing sub-zero temperatures and dark mornings, using heavy machinery to:

• rebuild protective gravel bunds
• reestablish deepwater at the lake edge
• carve a pilot channel through the shingle at Kaitorete, near Taumutu.

Their efforts were timed precisely with the tides to maximise the chances of a successful opening.

“Our team has worked diligently to restore the site and make this opening possible,” said Leigh.

Opening Te Waihora is no simple task. Working under a suite of consents and the National Water Conservation Order, strict environmental and legal requirements must be met.

Once a joint decision to open has been made by us and Te Rūnanga o Ngāi Tahu, the operation itself can take between seven to ten days, with costs ranging from $50,000 to $200,000 depending on the complexity of the job.

Council Chair Craig Pauling stressed the importance of balancing environmental needs, cultural values, and safety:

“The lake opening process takes account of habitat protection, lake levels, and flood risks. While consultation can move quickly, it’s the on-the-ground work that takes time and skill.”

A lake opening is declared successful only if it remains open for at least four days – something the team is now monitoring closely.