5,756 acres (2,329 ha)
28 km (11 sq mi)
The Imperial Reservoir is an artificial lake formed by the construction of the Imperial Diversion Dam across the Colorado River in the Lower Colorado River Valley of Imperial County, California, and Yuma County, Arizona. A component of the Imperial National Wildlife Refuge, the reservoir is 16 miles (26 km) northeast of Yuma, Arizona.
Imperial Reservoir Wikipedia
Dry washes are the major watershed feed systems to Imperial Reservoir. The next upstream major watershed feeder is the Bill Williams River from western Arizona. Upstream on the Colorado River, the basic feeder watershed to Imperial Reservoir is the Havasu-Mojave Lakes Watershed, of Lake Havasu.
Two dry wash watershed attempt to enter the Imperial Reservoir from western Arizona, south of the Bill Williams River: the Bouse and Tyson Washes. Both washes end on the eastern perimeter of the Colorado River Indian Reservation along the Colorado River. Neither enters the river proper, except in extreme flood stage.
No "lengthy" watersheds flow eastwards from California; all are short distance, in the extreme aridity of this desert region.