Three major drainages of the Colorado River enter in the Parker Valley region. The Bill Williams River and Bouse Wash have confluences with the Colorado in the northern valley area, from watersheds on the east. Tyson Wash crosses the La Posa Plain and enters downstream, with its watershed east of the river in the Colorado River Indian Reservation.
The long Parker Valley (green) along the Colorado River in southwestern Arizona and southeastern California, shown running north–south on left side of Arizona topographic map.
View of entire region: the larger valley just south, is the Yuma Valley area containing Yuma, Arizona. The Yuma Valley is shown merging into the El Centro, California region at the south of the Salton Sea