Lake put on life support

TRIAL BEGINS: Te Waiu o Tutira is a partnership between Maungaharuru-Tangitu Trust and Hawke’s Bay Regional Council, aimed at improving water quality and habitats in Waikopiro and Tutira Lakes. Maungaharuru-Tangitu Trust kaumatua Bevan Taylor (centre) gave a karakia before an air curtain was installed at Waikopiro Lake to trial pumping in oxygen to reduce algal blooms. Picture by Helen Shea

A POLLUTED Hawke’s Bay lake will be electronically pumped with oxygen in a bid to improve its mauri (life-supporting capacity).

An air curtain, much like a bubbler in a fish aquarium, is being trialled in Waikopiro Lake at Tutira as part of work to improve water quality in the area.

The system is being piloted in the smaller Waikopiro this summer, and if successful a larger air curtain will be installed in Tutira Lake next summer.

A lack of oxygen and the lake water heating up in hotter months have caused algal blooms, resulting in the death of fish and tuna (eels), posing a risk to human and dog health, and leaving the lakes largely out of bounds to camping, swimming and boating.

Pressurised air will be pumped through a 50m pipe tethered close to the bottom of the deepest part of the lake, creating an air curtain and increasing oxygen levels at all depths throughout the lake by creating a circulation current.

Hawke’s Bay Regional Council (HBRC) water quality scientist Andy Hicks said the air bubbles would keep the oxygen levels high in the lake so nutrients from the bottom of the lake did not fuel algal blooms, causing hostile conditions for fish and other things living in the lake.

Legacy of sediment

“The lake floors contain a legacy load of sediment with nutrients that continues to feed algal blooms.

“There is no way to get rid of it, and options to seal the layer have other potentially damaging environmental outcomes. Oxygenating the water is the safest option.

“The bubbles from the air curtain on the bottom of the lake create circulation and keep the bottom water in continual contact with the air and should stop algal blooms from occurring.”

A similar attempt in the 1970s, using older technology and structures, was unsuccessful.

However, HBRC had sought advice from NIWA lake mitigation specialist Dr Max Gibbs, who confirmed the current approach should be successful.

The same air curtain approach had brought algal blooms under control at several WaterCare reservoirs around Auckland, as well as in Lake Manuwai near Kerikeri.

Bill Hunter, who installed the successful Lake Manuwai system, had been contracted to guide the installation at Waikopiro.

The trial is part of Te Waiu o Tutira project, a partnership between Maungaharuru-Tangitu Trust and Hawke’s Bay Regional Council, aimed at improving water quality and habitats in Waikopiro and Tutira Lakes.

The area is one of six identified in the HBRC’s annual plan as environment hot spots needing attention.

“It is a great second step in building on our initial project to improve the mauri of the lakes, and partnerships are important to our success,” said Shayne Walker of Maungaharuru-Tangitu Trust.

HBRC chairman Rex Graham said having the water clean and clear again would be a boost to the area.

“The lakes are the centrepiece of a spectacular area, with so many outdoor recreation and adventure opportunities.”

A POLLUTED Hawke’s Bay lake will be electronically pumped with oxygen in a bid to improve its mauri (life-supporting capacity).

An air curtain, much like a bubbler in a fish aquarium, is being trialled in Waikopiro Lake at Tutira as part of work to improve water quality in the area.

The system is being piloted in the smaller Waikopiro this summer, and if successful a larger air curtain will be installed in Tutira Lake next summer.

A lack of oxygen and the lake water heating up in hotter months have caused algal blooms, resulting in the death of fish and tuna (eels), posing a risk to human and dog health, and leaving the lakes largely out of bounds to camping, swimming and boating.

Pressurised air will be pumped through a 50m pipe tethered close to the bottom of the deepest part of the lake, creating an air curtain and increasing oxygen levels at all depths throughout the lake by creating a circulation current.

Hawke’s Bay Regional Council (HBRC) water quality scientist Andy Hicks said the air bubbles would keep the oxygen levels high in the lake so nutrients from the bottom of the lake did not fuel algal blooms, causing hostile conditions for fish and other things living in the lake.

Legacy of sediment

“The lake floors contain a legacy load of sediment with nutrients that continues to feed algal blooms.

“There is no way to get rid of it, and options to seal the layer have other potentially damaging environmental outcomes. Oxygenating the water is the safest option.

“The bubbles from the air curtain on the bottom of the lake create circulation and keep the bottom water in continual contact with the air and should stop algal blooms from occurring.”

A similar attempt in the 1970s, using older technology and structures, was unsuccessful.

However, HBRC had sought advice from NIWA lake mitigation specialist Dr Max Gibbs, who confirmed the current approach should be successful.

The same air curtain approach had brought algal blooms under control at several WaterCare reservoirs around Auckland, as well as in Lake Manuwai near Kerikeri.

Bill Hunter, who installed the successful Lake Manuwai system, had been contracted to guide the installation at Waikopiro.

The trial is part of Te Waiu o Tutira project, a partnership between Maungaharuru-Tangitu Trust and Hawke’s Bay Regional Council, aimed at improving water quality and habitats in Waikopiro and Tutira Lakes.

The area is one of six identified in the HBRC’s annual plan as environment hot spots needing attention.

“It is a great second step in building on our initial project to improve the mauri of the lakes, and partnerships are important to our success,” said Shayne Walker of Maungaharuru-Tangitu Trust.

HBRC chairman Rex Graham said having the water clean and clear again would be a boost to the area.

“The lakes are the centrepiece of a spectacular area, with so many outdoor recreation and adventure opportunities.”

Your email address will not be published. Comments will display after being approved by a staff member. Comments may be edited for clarity.

Poll

  • Voting please wait...
    Your vote has been cast. Reloading page...
    Is MMP in its current form the best way for us to elect our government?