11 October 2021
Surrounded by lush native bush and shimmering every hue of blue and green imaginable, Rotorua’s lakes are the heart and soul of the Te Arawa region.
For centuries they have drawn people to the Bay of Plenty to swim, fish, boat, waterski, kayak, picnic and explore. The waters of some are considered tapu (sacred) while others are enjoyed by thousands of people on a hot day.
But they are also troubled waters – plagued by invasive weeds, pest species, high nutrient levels and toxic algal blooms. The community has come together – particularly in the last 25 years – to address these issues through the Lakes Water Quality Society (LWQS).
The organisation was formed 50 years ago to originally tackle lake weeds. LWQS Chairman John Gifford says large swathes of weeds used to wash up on the beaches, decaying and creating an unpleasant odour. “People got up in arms about it so the society was formed to lobby the government. Now weed management is a major activity of the BOP Regional Council as a result.”
By the late 1990s the focus shifted to water quality as a number of Rotorua’s lakes started to experience algal blooms, releasing toxins that are harmful to human health and the wider ecosystem.
“Several lakes were deteriorating quite rapidly,” John explains. “Nutrient levels such as nitrogen and phosphorus from fertiliser run-off were too high and local residents started to become really concerned about the long-term water quality and how it was impacting their use of the lake. It also started to impact quite significantly on residential property values.”
The LWQS stepped up the pressure and bought residents, regulators and the scientific community together to form an action plan. An academic ‘chair’ was jointly established by the regional council and Waikato University, and Professor David Hamilton was appointed to the position to spearhead research and guide restoration efforts.
“As a result, a whole new crop of science graduates have now filtered through into the freshwater research community. The ‘chair’ really created a vibrancy and a better understanding of the lakes but also a pool of expertise, interest and information that is relevant to the long-term management, conservation and preservation of the lakes.”
Over the past 20 years, John says about $250m has been invested in lakes restoration projects, including the construction of a diversion wall in the Ohau channel to prevent water from Lake Rotorua entering the main body of Lake Rotoiti.
An incentive scheme was set up to encourage landowners to convert from dairying to low nitrogen activities such as forestry, and streams that lead to Lake Rotorua continue to be dosed with alum to help minimise phosphorus concentrations. “There’s also been substantial investment in sewerage reticulation to take effluent from residential septic tanks around the lakes back to the Rotorua effluent treatment plant.”
While the concerted effort has improved the health of many lakes, there is still work to be done, John says. “We have definitely made progress, but you wouldn’t say that it was problem solved.”
In March 2022 the LWQS will host its 12th symposium – a two-day event for the public, research scientists, local authorities, and iwi to come together to examine the current state of the lakes and what challenges lie ahead.
BayTrust has granted $10,000 to the symposium which will feature over 30 speakers including key scientists and researchers from GNS, Te Arawa Lakes Trust, Griffiths University, Te Uru Rakau/NZ Forest Service, NIWA, Scion and the University of Waikato. The Minister for the Environment, Hon David Parker, has also been invited to give an address.
They will collectively discuss the lakes’ current health and what more can be done to reduce nutrients loads, and examine what impact forestry, urban development and climate change will have in future.
“There’s a big issue around climate change,” John says. “As the climate warms, there’s a greater propensity for higher water flows into the lakes. And as the waters warm in the lakes it makes them more susceptible to algal blooms. There’s a whole range of physical and biological phenomena which potentially could make the lakes worse or more difficult to manage as climate change impacts take effect.”
Symposiums cost a lot of money to run and John is grateful for BayTrust’s support. “We want to keep the high level of advocacy going and for people to keep caring about the quality of the lakes. It is wonderful to have support from community funders such as BayTrust.”