Dry wash in southwest Arizona
Tyson Wash is one of the larger eastern-bank dry washes that enter the Colorado River in western Arizona. It drains the La Posa Plain south-to-north and is also coincident with the Plain's southern two thirds.
It is also the southwest drainage of a pair of drainages, the other being the Bouse Wash drainage. They are in the Lower Colorado River Valley, south of Parker, Arizona and both enter the region east of the Colorado River, with no Colorado River confluence; they both end at regions on the eastern border of the Colorado River Indian Reservation located along the Colorado River in the Parker Valley.
The two drainages, the Tyson and the Bouse, enter upper regions of the Imperial Reservoir Drainage.
Description
La Posa Plain
While northeasterly, the Bouse Wash drainage borders the Bill Williams River Drainage, (almost a de facto separation line of the Mojave Desert northwest and the Sonoran Desert south and east), the Tyson Wash drains the extensive 75-mile (120 km) long north-south La Posa Plain. Quartzsite, Arizona and four mountain ranges to the south, including western regions of the Kofa National Wildlife Refuge, all drain north into Tyson Wash. The Tyson Wash forms a water divide on the south as the Castle Dome Wash and Plain drain to the south and southwest.
Tyson Wash drains northward on the western perimeter of the La Posa Plain; the Trigo Mountains are southwest, and in the north the wash turns west around the north end of the Dome Rock Mountains-(see Table). As proof of the aridity of this stretch of the western Sonoran Desert, the main transportation route north-south on the La Posa Plain is a stretch of U.S. Route 95-State Route 95 which makes no turns, even minor, for 75 miles (121 km).
The La Posa Plain turns northwest to meet the Colorado River, and the south of the Parker Valley; Tyson Wash remains to the left (southwest) of the plain's direction and enters land abutting the southeast of the Colorado River Indian Reservation.
Communities
The community of Quartzsite is located on the central-north section of the wash and east-central Dome Rock Mountains; Granite Mountain south of Interstate 10 and part of southwest Quartzsite, has drainage washes feeding into Quartzsite proper. The entire Quatzsite region is a winter visitor region noted for its winter population of recreational vehicles and for its rockhounding activities because of old mines, mineralized mountains, and mild winter temperatures. An annual bazaar is held focussed partially on Rocks and Minerals. Numerous access routes to the wash and mountain areas surround Quartzsite.
Access from north
The northern region of the wash is accessed by dirt road west of AZ Route 95; the route is about 25 miles (40 km) long and ends at the southern area of the Colorado River Indian Reservation, 35 miles (56 km) north of Ehrenberg, Arizona. This access route off AZ Route 95 is 2.5 miles (4 km) south of an intersection to a paved route northeasterly to Bouse through the Plomosa Mountains; that paved route is called Plomosa Road-(Bouse-Quartzsite Road), and ends at Bouse, the Bouse Wash, and the north end of the Ranegras Plain.
