New data showing "likely worsening" water quality trends at several Rotorua lakes has prompted a request for a review of the restoration programme.
The Lakes Water Quality Society has raised concerns that work to restore the lakes is "stalling".
Society chairman John Gifford yesterday brought concerns about increasing algal blooms, weed issues and other indicators to a Rotorua Te Arawa Lakes Strategy Group meeting.
The group is responsible for the management of the Rotorua Te Arawa lakes and consists of representatives from the Bay of Plenty Regional Council, Te Arawa Lakes Trust and Rotorua Lakes Council, with support from the Ministry for the Environment.
During his presentation, Gifford said there were indications that restoration work may not be "on course" to achieve expected outcomes.
Indicators included increasing algal blooms in Lake Rotorua and Lake Rotoiti, trophic level index values remaining "stubbornly" above the target and significant weed issues.
He said data showed seven of the lakes' total phosphorous levels were "very likely worsening", while four showed the same for nitrogen.
According to Land Air Water Aotearoa, the trophic level index score for a lake is calculated using four water quality measurements; total nitrogen, total phosphorus, water clarity and chlorophyll-a.
Lake water quality data released by Stats NZ last week showed between 2011 and 2020, the index for sites in five of 12 lakes in Rotorua was very likely worsening, and three were likely worsening.
These included at Lake Rotorua and Rotoiti, while Lake Ōkataina was very likely improving and Lake Ōkāreka was likely improving.
"The issues indicate that we may not know quite what is happening in the lakes and raises the question over whether our current actions alone are sufficient to ensure the long-term sustainable management of the lakes," Gifford said.
He told the meeting that entities such as the society should be included more in its activities.
The society's suggested way forward was for the group to consider recent regulation changes, as well as increased public awareness of freshwater values.
It also called for a technical and scientific review of the whole lakes programme.
He said this did not need to be as detailed as had been proposed for Lake Rotorua.
"This review was more about asking the question 'are we doing enough?' and if not, what needs to be done to meet community needs?"
Group deputy chairperson and Rotorua mayor Steve Chadwick asked if the group had a particular concern or if it wanted to be part of the programme and report at meetings.
Gifford said the society believed it could keep oversight of "all the issues that need to be considered".
Chadwick asked whether the society had a view on Te Arawa Lakes Trust's oversight of the programme, to which Gifford said it had a critical role.
"They are the lakebed owners. We recognise and value that contribution. From the society's point of view, we want to work closer with Te Arawa Lakes Trust."
But he said the society could provide information about broader catchment-related issues.
Group independent chairperson Ta Toby Curtis welcomed the society if it wanted to work alongside the trust in the physical work, such as with weed control.
Chadwick said the request for a review had funding implications and Bay of Plenty regional councillor Kevin Winters said including the society in the group would require a law change.
He moved the report as being received and said the requests would be taken to staff to consider.
Water quality of Rotorua lakes
Trend direction of tropic level index 2011-2020
Very likely worsening
- Lake Rotorua (one of two sites)
- Lake Rotoiti (two of three sites)
- Lake Rotoehu
- Lake Rerewhakaaitu
- The Blue and Green Lakes
- Lake Rotorua (one of two sites)
- Lake Rotoiti (one of three sites)
- Lake Rotoma
- Lake Okareka
Very likely improving
- Lake Okataina
- Lake Rotomahana
- Lake Okaro
Source: Stats NZ, Environment Aotearoa 2022