The river drains an arid region of 1,026 square miles (2,660 km2), situated mostly within the San Carlos Indian Reservation.

[2] The river originates as the confluence of Ash Creek (30 miles (48 km) long) and Kidde Creek in the Natanes Mountains, a subrange of the Gila Mountains, at 4,300 feet (1,300 m) above sea level.

Flowing west, it enters a deep canyon along the Gila–Graham County line.

Below the lake the valley widens and the river turns south, passing San Carlos and Peridot, before emptying into the northern arm of San Carlos Lake, a reservoir on the Gila River.

Most of the flow in the river originates from springs in the canyons above Takalai Lake.