Imperial Reservoir Imperial Reservoir 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 northeast of Yuma, Arizona. 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
Imperial Gift Army). The Imperial Gift enabled the formation of the Royal Australian Air Force on 31 March 1921. An Air Board, answering to the Minister for Defence, would administer the new service. Imperial Gift aircraft were shipped to Australia in 1919, assembled upon delivery in 1920 and served for up to 10 years. The Airco/de Haviland DH-9a (A1-17/F2779) was the longest serving Imperial Gift aircraft, being written off on 4 February 1930. The only original surviving Imperial Gift aircraft in Australia are an Avro 504K (A3-4/H2174), stored at the Treloar Technology Centre (Canberra) and an S.E.5a (A2-4/C1916), in the collection of