The Crown has failed to pay tribes to use Lake Waikaremoana for hydro-electric generation and caused damage to a significant taonga in Tuhoe territory.
The findings are in the fifth Waitangi Tribunal report on Te Urewera, released this morning.
Claims were lodged by Tuhoe, Ngati Ruapani, Ngati Kahungunu, Ngai Tamaterangi, and other collectives and people.
The Tribunal today said the claimant groups were still the owners of Lake Waikaremoana and its kaitiaki, but their authority was a pale shadow of what it once was.
It has found the Crown breached the Treaty of Waitangi when it refused to pay for use of the water to generate power.
The report also said when the lake was lowered for the power stations in 1946, tribes were neither consulted nor compensated.
The Tribunal said under the Treaty guarantee of Maori property rights, they were entitled to full, exclusive, and undisturbed possession of their taonga.
It writes that claimants were prejudiced economically by the Crown, and their mana and tino rangatiratanga were infringed.
The 378-page report gives a detailed historical account of Lake Waikaremoana, and contains a series of other findings.