How do you say gathering of waters in Navajo?

I'm not exactly sure what you are referring to.

There is a Navajo clan name that means "water flows together clan"

That clan name is : Tó Aheedlínii

It comes from a place in New Mexico called Tó Aheedlį́ in Navajo (Literally: water flows in a circle)

It is Thohedlih in English.

It is at the opening of a deep box canyon. About a mile downstream of where the San Juan and Los Pinos rivers meet.

It is the starting point of the story in the Tł'éé'jí , the Night Chant

That this location, which has important religious meaning was submerged by the building of Navajo Dam (1958-1963) making Navajo Lake is a source of distress to some traditionalists.

After the Hero twins slew all the monsters, they went to the junction of the San Juan and Los Piños rivers. This location has shield petroglyphs representing the twins. These were destroyed by the dam.

It is comparable to flooding Nazareth with a dam and forming a lake over it.

It does provides water for approximately 110,000 acres of farmland on the Navajo Indian Reservation. This is the Navajo Indian Irrigation Project, founded in 1962, the largest irrigated farm in the country.