The big clean-up: How central lakes got their groove back

Mac Pacey, Barbara Allen, Chris Sutton, Marcel Schweizer and Bob Parker are keen to keep Lake Rerewhakaaitu clean. Photo / Alan Gibson

How did the state of Rotorua's 12 treasured lakes go from being a national outrage to a model for environmental collaboration? Jamie Morton dives in.

This lake is dying", ran the stark headline above an aerial photograph of a sick Lake Rotoiti.

The picture, which dominated the front page of the Herald, on September 1, 2003, began a week-long series on the ailing state of the region's lakes, amid a climate of division between farmers, authorities and conservationists.

Lake Rotoiti, badly hit by algal blooms and struggling under nutrient loads flowing in from neighbouring Lake Rotorua, had turned the colour of pea soup.

A top government official warned there was a good chance the algal blooms would kill all life in the lake by that summer.

Scientists were worried that even the healthiest of the region's dozen lakes, Lake Okareka, was beginning to deteriorate.

And the state of Lake Rotorua, described at the time as being stable but sick, had not greatly improved even a decade after treated sewage was diverted away.

How the Herald reported on a sick Lake Rotoiti in 2003.

This left farmers taking much of the blame, and at heated public meetings, some angered residents called for an end to all dairy farming around the catchment.

"To some degree, farmers felt that an unjustified stance and there was push-back because of that," recalled long-time farmer Stuart Morrison.

"But right from the get-go, nobody was saying a dirty lake was acceptable. Everyone wanted a clean lake."

The picture has changed remarkably since.

"The indicators back then showed there was a very sad future for our lakes," Rotorua MP Todd McClay said.

"But today you can swim in nearly every one of them."

Some lakes have had their best water-quality results in decades and only two lakes - Lake Tarawera and Lake Rotokakahi - have been found to still be in decline.

Long-standing tensions between conservationists and farmers have given way to a new era of collaboration, with impressive results.

Last year, farmers around Lake Rotorua agreed to major catchment nutrient reduction targets, even though the cost may be more than some can shoulder.

And there is hope that momentum to protect and restore the 12 lakes, driven by a $230 million programme, will mean they are never threatened again.

John Green, chairman of the Lakes Water Quality Society, said the quality of each lake reflected the catchment surrounding it.

"In the beginning, the key issue for our society was to understand what chemicals were affecting the lakes - principally nitrogen and phosphorus - and what sources did they come from."

While natural processes played a part, the majority of issues had been put down to land use.

The intensification of pastoral farming around catchments worsened the problem.

Most nitrogen that entered water bodies around the Rotorua lakes was in nitrate form, and the bulk of it came from livestock urine patches.

Groundwater aquifers had been progressively enriched with nutrients that will still feed into the lakes over coming decades. But farming hasn't been the only problem.

Sewage was flowing in from lakeside communities, and nutrients in the bottom sediments of some lakes could be traced back to historical practices, such as the discharge of treated sewage into Lake Rotorua.

Toxins that were in the water could cause illness in the liver and nervous system as well as skin rashes, hay fever and asthma.

In the late 1990s, the formation of a working group between council leaders and Te Arawa Maori Trust Board helped address a lack of co-ordination between those involved in managing the lakes.

Its original strategy was later formalised and a joint committee, the Rotorua Te Arawa Lakes Strategy Group, was launched.

But as the worsening state of the lakes became apparent, Mr Green's group still couldn't get answers over what was happening to them.

"So we decided, as a society, to use a science-based approach for dealing with the problem."

The society organised symposiums and tracked down scientists from around the world. A list of research needs was drawn up.

After the first symposium in 2001, the Bay of Plenty Regional Council endowed a chair in Lakes Restoration and Management at the University of Waikato, and recruited freshwater scientist Dr David Hamilton as inaugural professor.

In 2007, five "priority lakes" - Rotorua, Rotoehu, Okaro, Rotoiti and Okareka - became the focus of a $144 million funding agreement, the Government paying half the bill.

Water-quality targets and plans were set for each lake.

In 2011, progress took another major step when members of the Lake Rotorua Primary Producers Collective, representing farmers, sat down with the Lakes Water Quality Society.

"I realised they wanted the same things, but weren't talking to each other," said Mr McClay, who got the two parties together.

The resulting Waiora Agreement allowed the two groups to work through a list of sticking points, including stock movement in the catchment, management of erosion and sediment control, and other mitigation strategies such as wintering barns and biogas production.

But farmers could still not accept a regional council regulation requiring the nitrogen load into the lake to be cut by more than 300 tonnes to a sustainable level within a decade.

For some farmers, especially drystock farmers who had been struggling for years, the requirement would have put them out of business.

Mr McClay again intervened, and helped strike a landmark deal.

The deadline would be pushed back to 2032, but 70 per cent must still be achieved within a decade.

After signing the agreement, Federated Farmers dropped an Environment Court challenge against the regional council.

But farmers, a key part of the local economy, still faced uncertainty over the costs of meeting the obligations, collective chair Wendy Roe said.

Over recent years, she said, landowners had made improvements, with increasing help from technology and farm advisers.

Warwick Murray, the regional council's general manager of natural resource operations, said much effort was being made to ensure authorities were working closely with affected farmers.

And they had been given a greater voice through the Lake Rotorua Stakeholder Advisory Group, which was set up in 2012 and also represented iwi, the forestry sector and others with a connection to the lake.

Work by the group meant all representatives were now in agreement on a way forward to set nitrogen limits.

"The group itself is critical," chairman Tanira Kingi said.

"We've now got a mechanism where the different stakeholders can have input into what is going on."

Rules were devised to reduce nutrient loading in the lake and included a publicly funded $45 million incentive for landowners to slash levels.

In the past two years, Lake Rotorua has returned its best water-quality results in decades, thanks to farm changes, favourable climate conditions and short-term interventions such as alum dosing.

But the lake still poses the biggest challenge to the programme - nitrogen inputs still need to be cut by 320 tonnes, and 70 per cent of nutrients are still coming from agriculture.

Rotorua District Council has also moved to stem other sources of nutrients flowing into the lake.

The combined treatment process of the town's wastewater plant and land irrigation now remove 90 per cent of nitrogen from its wastewater, stopping up to 290 tonnes of nitrogen reaching the lake each year.

Methods are being tested to strip geothermally produced nitrogen from the Waiohewa Stream before it gets to the lake, while the Lake Rotorua "P-Project" has been testing detainment bunds to reduce the 12 tonnes of phosphorus that flows in annually after storms.

In March, entries will close for a challenge appealing for new ways to use land in the catchment that will cut nutrient loss, with a $20,000 prize for the best idea.

Elsewhere in the region, community interventions are already showing better water quality.

Lake Rotoiti's latest results showed it was below its water quality target for the first time since the programme began. The best result since the early 1960s was put down to improvement in sewerage schemes and the construction of the Ohau Diversion Wall, which diverts nutrient-laden water from Lake Rotorua to the Kaituna River.

Teamwork by farmers around Lake Rerewhakaaitu also brought the lake's water quality measure to below target within the past year.

The long-term water quality of lakes Rotoehu, Rotoma and Tikitapu are also improving, while quality at Okataina, Okareka and Rotomahana was considered stable.

Levels at Lake Okaro have fluctuated over the past decade, and a prolonged algal bloom and health warning has been in place since July 2012.

Modelling is needed to understand why its water quality has declined since briefly meeting its target in 2010.

At Lake Okataina, where levels are considered stable, a PhD study is underway to investigate how pests have been weakening the understory of native bush surrounding the lake and worsening its water quality.

Mr Murray said science and research had been crucial to the programme.

"Through innovation, science and technology, we are leading the way in lakes water quality management."

Mr Green is keen to see the scientific work consolidated with the establishment in Rotorua of a centre of excellence in lake water quality research.

Stuart Morrison said while modelling in Lake Rotorua was still being finessed, the latest results had astounded many.

Mrs Roe believed the improvement had shown what could be achieved through a collaborative approach, rather than a strictly regulatory one.

Farmers unite to create success story

To the farmers who live around it, picturesque Lake Rerewhakaaitu is more than just somewhere to fish, camp and play.

The small, shallow lake, lying at the base of Mt Tarawera's southern slopes, has been the fabric that binds together its little rural community.

But from the 1970s its water quality began suffering as dairying activity intensified, with nutrient levels rising in streams feeding it.

A decade ago, when a report spelled out a bleak future for the lake if nothing changed, farmers decided to act. They did not want to see their treasured lake become like Lake Rotorua, 30km to the east.

"We talked about this and having work done to look at the causes and potential remedies, and that turned out to be the first action," said horticultural consultant Bob Parker, who met local farmers.

"We gained not only information, but also confidence in each other."

The eventual outcome, dubbed Project Rerewhakaaitu, is believed to be a first for New Zealand - local landowners creating and putting into practice their own catchment plan.

Landowners had already made gradual improvements, including retiring lakeside land as buffer zones, to minimise the effect of their farms on the lake. But they still wanted a clear picture on what processes were affecting the water quality.

The first few years were spent gathering data on how much nitrogen and phosphorous was being applied to farms around the lake and how much was entering waterways.

In 2009 the Bay of Plenty Regional Council invited the farmers to carry on their work.

"We were asked, how would you like to write the catchment plan? And there was a stunned silence," Mr Parker said. "We had a night meeting a week later, and it was a big yes."

The main focus of the plan was to prepare and implement nutrient management plans for each farm, and farmers had committed to undertake all actions by the year. Steps included fencing off streams, wintering cows off the farms or areas where soil is prone to pugging, using low-nitrogen supplements, and changing where, when and how fertiliser is used.

After six years of falling levels of nitrogen in the water, the lake last year met its quality target for the first time - and the farmers want to keep it that way.