The area in question is centred around the mouth of the Waiteti Stream, just past the Ngongotaha township.
"Our river is choking, it's suffocating, it's dying... I've lived here for more than 50 years and when we were children we used to swim in this lake, eat the koura (freshwater crayfish) - you could pretty much drink the water," Mr Ngatai said.
"Now there's no way anybody would swim in this and the koura are gone. They were taken over by layers and layers of silt.
"We are ready to take action if it's not immediately cleaned up, we've had enough, this has gone on too long, it's time we breathe some life back into our lake."
Mr Ngatai said he was aware there were measures in place to improve the quality of the lake, but in his opinion a more comprehensive plan was needed.
"This ... problem has created pockets in our lake that are infested, diseased and unhealthy.'
"We want the management of the lake back so we can begin to try reverse the damage and restore our lake to something we can have pride in, it's our taonga and we want it back."
Bay of Plenty Regional Council general manager for integrated catchments Chris Ingle said the regional council was not aware of the hapu's concerns until approached by the Rotorua Daily Post.
"Ngati Ngararanui is a hapu of Te Arawa and part of Te Arawa Lakes Trust who we work closely with along with Rotorua Lakes Council to protect and restore water quality under the Rotorua Te Arawa Lakes Programme.
"The measure used to indicate the health of lakes in New Zealand is Trophic Level Index (TLI) and in the last four years the TLI for Lake Rotorua has either met or is only slightly above its target set by the community of 4.2.
"Our weekly water testing and monitoring of the lakes has not detected any algal blooms in Lake Rotorua throughout the summer period."
He said a land management officer visited the site recently to assess the western banks of the lake.
"It appears as though the lack of rainfall over summer has resulted in low lake levels but not exceptionally low for this time of the year. Areas of mud are now exposed that may not normally be exposed and we can expect it to return to normal when we have had decent rainfall."
He said there were measures in place to stop run-off reaching the lake.
"This includes retirement of steep areas and along stream sides. In the Waiteti catchment, there are currently 61 individual environmental plans resulting in the retirement of about 165 hectares of land alongside Waiteti Stream and its tributaries. The entire stream length has been fenced and stock proofed.
"Regional council has also co-funded two detainment bunds in the upper catchment. These structures assist in catching sediment by capturing water during storm events and releasing it slowly over several days. This allows sediment to settle and remain on the property rather than entering the lake.
"The western side of the lake is more sheltered than normal. Any stench being released may be a result of vegetation that is breaking down in the sediment and a prolonged period of westerly winds may exacerbate any odour."
Rotorua Lakes Council is responsible for many lakeside reserves, including at the mouth of the Waiteti Stream, sport and recreation manager Rob Pitkethley said.
"In recent times we have done a lot of work at the Reeme Street Reserve, which borders part of the Waiteti Stream mouth, to increase public usability of the area and a stormwater discharge area is being tidied up and planted.
"Where erosion prevention is required on a reserve, the council undertakes planting or constructs rock walls but that's not been a problem at the Reeme Street Reserve.
"We have not been contacted by the hapu but would be more than happy to speak with them to discuss their concerns," Mr Pitkethley said.
Mr Ngatai said the hapu had not contacted Te Arawa Lakes Trust about its concerns, which was confirmed by the trust's chairman Sir Toby Curtis.
"I am not aware of the problem," Sir Toby said.
"But I would encourage them to come and meet with us to discuss the issue."
