Governor Katie Hobbs officially signed the Northeastern Arizona Indian Water Rights Settlement Agreement Wednesday.
It guarantees the rights of the Navajo Nation, Hopi Tribe and the San Juan Southern Paiute Tribe to the Colorado River.
Both Navajo Nation President Buu Nygren and Hopi Chairman Timothy Nuvangyaoma praised the milestone.
The legislation now needs to secure the support of the other six basin states and be passed by Congress.
Nuvangyaoma emphasized the importance of getting the settlement as "failure is simply not an option."
The agreement could end a decades-long fight for water access as thousands of tribal members throughout Arizona and the Southwest live without a reliable drinking water source.