The Crown and Waikato-Tainui have signed a revised deed of settlement over the Waikato River.
An earlier settlement signed last year provided a $210 million cleanup fund and co-governance arrangements for the river.
The revised deed establishes a single body to oversee the river, the Waikato River Authority, which will be made up of an equal number of members appointed by iwi and the Crown.
Waikato-Tainui negotiator Tukuroirangi Morgan says the signing ensures the integrity of last year's settlement is protected and enhanced.
Treaty Negotiations Minister Chris Finlayson says the agreement is vital for the economic, environmental and recreational goals of the region and the country.