Behind the wall

Lake Rotoiti has suffered from poor water quality for years. A $14 million diversion wall to be erected within the next year could be the saving of the Rotorua lake. KRISTIN MACFARLANE reports.

Sally Brock has been pushing for something to be done about Lake Rotoiti's degrading water quality for years.

Now with news a diversion wall will be built in the lake she's happy things are moving ahead.

Mrs Brock has lived in the Okere Falls area on Lake Rotoiti for the last five years, but has holidayed in the area for 20 years.

She was one of the many people who played a key role in bringing nationwide attention to the state of the lake.

Lake Rotoiti, a long, skinny lake connected to Lake Rotorua by the Ohau Channel, is plagued by nutrient-laden water. Its quality has been a concern for 20 years.

The wall will divert nutrients from the channel down the Kaituna River.

Algal blooms in Lake Rotoiti are fed by nutrients from a range of sources, including lake sediments, farm run-off, septic tanks and groundwater.

In the 2002/2003 summer, the lake was closed for swimming. Since then Mrs Brock has been working passionately towards trying to fix it.

"It's really been four years of following that progress very closely," Mrs Brock said.

She and Rotoiti residents were so concerned about the problem, they urged action to be taken.

This challenge was taken on by Environment Bay of Plenty, the Rotorua District Council and the Te Arawa Maori Trust Board.

These organisations, along with members of the public, joined forces for a project called the Rotorua Lakes Protection and Restoration Action Programme, to protect, and in some cases improve, the water quality of the Rotorua lakes.

Mrs Brock said these organisations, along with other key players like scientist David Hamilton, former LakesWater Quality Society chairman Ian McLean and project co-ordinator Paul Dell, had worked hard on the problem.

"I may have been one of the most vocal [but] it's not just about one person," she said.

She is part of the LakesWater Quality Association, the Lake Rotoiti Residents and Ratepayers Association and the Lake Rotoiti Care Group, which has carried out a number of plantings and clearing work on the lake edge.

Since Lake Rotoiti made its cry for help in the summer of 2002/2003, moves to improve the lake have continued.

A joint action plan for lakes Rotoiti and Rotorua is now in progress and is expected to be completed by the end of the year.

Other actions planned for Lake Rotoiti include:

* Reticulating sewage in Okawa Bay and Mourea (work near completion)

* Reticulation of other Rotoiti settlements within five years

* New rules for hi-tech septic tanks

* Rules to keep stock out of waterways (in progress)

* Large subsidies for fencing and planting water margins

* Possible treatment of Okawa Bay once the sewage is reticulated

However, the biggest news so far is that the diversion wall has been given the go-ahead.

This is the first major project for the Rotorua Lakes Protection and Restoration Action Programme.

Some parties appealed against it but the Environment Court ruled in favour of the wall this month.

One of the groups that appealed the decision was Nga tangata ahi kaa roa o Maketu, which was worried about the effects the diversion would have on the Maketu Estuary. Environment Bay of Plenty will monitor the effects.

The structure will stand on the lake floor and rise to just above water level, from below the Ohau Channel outlet to Te Akau Point, 75m offshore from State Highway 33.

Environment Bay of Plenty has been given consent for the wall, which will mainly be made from solid sheet-pile material, for the next 12 years.



Results are expected in about five years with fewer algal booms and scientists say it will have little impact on Kaituna River quality. This is good news to many who can't wait until Lake Rotoiti's water quality problems are sorted.

Mrs Brock is one of the advocates for the diversion.

"The sooner we can get this started the sooner we can start seeing results."

Bay of Plenty and Lakes medical officer of health Dr Phil Shoemack is excited about the benefits of the diversion wall but knows it won't be a quick fix. "The sooner we put these things in place, the sooner things will flow," Dr Shoemack said.

Lake Rotoiti has been monitored every summer since 1999 when there were major water quality problems in Okawa Bay.



At Lake Rotoehu, blooms, which prompt health warnings, will start in summer and will stick around for about five or six months.

At Lake Rotoiti however, Dr Shoemack said health warnings can extend for the whole lake and be lifted within a week. The blooms can also cause a health warning to be issued weeks later.

Weather plays a big part in the forming of algal blooms. Dr Shoemack said blooms are more likely in sunny, warm, calm weather. He also said the wind could cause a bloom to spread to the whole lake or other lakes.

Rotorua Lakes Protection and Restoration Action Programme project co-ordinator Paul Dell said these blooms were likely to be less frequent with the wall in place.

He said "Rotoiti is a nationally important lake" and said the wall was just the first step in making sure the lake was saved.

Cleaning up Lake Rotoiti and Lake Rotorua was the main focus of the Rotorua Lakes Protection and Restoration Action Programme but Mr Dell assured the public they will look into all other lakes with water quality problems.

"We've got to realise there's only so many hours in a day. We'll get to all of them."

He said action plans were in place for lakes Okareka and Okaro.

Action plans for lakes Rotorua, Rotoehu, Tarawera and Rotoma were also under way.

Once these were complete, Mr Dell said they would look at implementing action plans for lakes Okataina and Tikitapu.

"We're actually making really great progress, things are really moving."