Some iwi are worried the government's proposed water reforms could undermine - and possibly unravel - their Treaty of Waitangi settlements.
Iwi with water-based settlements, like Waikato-Tainui and Te Arawa, fear they could be sidelined by large entities with little representation.
Waikato-Tainui fought for years for its river settlement, an arduous process that finally concluded in 2010 with enshrined recognition of mana whenua and its role in making decisions that affect the awa.
A decade later, Waikato-Tainui chair Linda Te Aho fears the proposed water reforms could see all that effort go to waste.
"We are anxious that the settlement mechanisms that we fought for in our river settlement could be undermined or unravelled," she said.
The government is planning wholesale change to how water services are managed.
Some iwi with settlements that embed some kind of water management are worried these new entities could see them cast aside.
Te Arawa is one them. A 2006 settlement created a three-way body for the Rotorua lakes, with the Rotorua Lakes Council, the Bay of Plenty Regional Council and Te Arawa Lakes Trust.
Te Arawa Lakes Trust chief executive Karen Vercoe said it had not been made clear to them how the new bodies would affect such agreements, and whether it would see their representation watered down.
She worried the government could be sleepwalking into a situation where settlements like that with Te Arawa are undermined.
"It would be unfair for us to, you know, have one or two representatives that would have to speak to all of the collective issues across our different iwi," she said.
"But for us as a Tiriti settlement partner the impact on us is that we're no longer sitting at the decision-making table."
There is enough concern over this that a hui was recently called, bringing together iwi from the proposed 'Entity B' in the Water Services Bill: Waikato down to Taranaki, Tūwharetoa across to Whānau-ā-Apanui at the East Cape.
Te Aho said it was also a major topic at a recent bilateral between the government and the Kiingitanga, and at last week Iwi Chairs Forum.
But Local Government Minister Nanaia Mahuta, who is leading the reform, said she was hearing the concerns and would not allow settlements to be undermined.
She said there could be opportunity for iwi, too.
"I've been really clear that one of the ways that we can ensure that settlements are taken account of is at the legislative level," she said.
"But ... it's at the operational end of service delivery that the real opportunities will emerge."
Linda Te Aho, of Waikato-Tainui, said her concern was that there was no specific provision to protect and uphold the settlements.
She said there had been a lack of consultation with iwi which was ironic considering the settlements were meant to enshrine partnerships with the Crown.
"The way that the legislation is rolling out, the information we're getting is making us nervous," she said.
Mahuta said conversations were ongoing.
Karen Vercoe, from the Te Arawa Lakes Trust, said the intention of the reforms - to fix failing infrastructure and improve health - had wholesale support. But she wants partnership.
"You know we're not just sitting there trying to protect our settlements, we too care about our community," she said. "I think to leave us out of that picture given our intergenerational perspective would be short-sighted."