A proposed action plan has been announced to help improve the water quality at Lake Okataina.
The plan has been drawn up by the Bay of Plenty Regional Council because Lake Okataina's water quality does not meet the water quality standard set by the community.
Nitrogen and phosphorus nutrients are said to be entering the lake from a range of natural sources and human activities.
These nutrients contribute to the growth of toxic algal blooms and aquatic weeds in the lake.
Bay of Plenty Regional Council general manager natural resource operations Warwick Murray said the council had discussions and workshops with the Lake Okataina community, iwi and other groups to develop the draft action plan.
"What was clear from these discussions was that the Lake Okataina community wants to retain the lake's unique and tranquil environment for everyone to enjoy," he said.
"Water quality in the lake is not as good as it should be so we've taken a look at why and we've talked to the community about what we can do about it. It is not obvious what the problem is. We suspect that nitrogen is under control but phosphorous is going up and we're not sure why."
Mr Murray said the key action was to do some more work to understand where the phosphorous was coming from and what could be done about it.
He said the regional council was keen to hear views of the community on what should be done.
Mr Murray said Lake Okataina was unique in that the majority of the nutrients entering the lake were from native bush, rather than from surrounding farmland.
"Science is telling us that the nitrogen levels entering the lake will reduce over time. What we don't know is why the phosphorus levels are increasing. One of the key actions in the draft action plan is to investigate where the phosphorus is coming from and what we can do to reduce this," he said.
"We want the community to tell us what they think of the draft action plan. Do they agree with our proposed actions and is there anything else that we should consider?"
Mr Murray said actions to improve Lake Okataina's water quality such as changing land uses and management and managing animal pests and aquatic weeds, had been under way for some time.
The draft action plan is part of the Rotorua Lakes Protection and Restoration Programme, a partnership between Bay of Plenty Regional Council, Rotorua District Council and Te Arawa Lakes Trust.
The $200 million programme's goal is to improve water quality in all 12 Rotorua Te Arawa Lakes.
"The Rotorua Te Arawa Lakes are an important part of our community. We all need to work together to improve water quality in our lakes," Mr Murray said.
Copies of the draft action plan and a feedback form are available on the Regional Council's website www.boprc.govt.nz, or from Regional Council Rotorua District Council and Te Arawa Lakes Trust offices.
Feedback closes on October 31.