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 units of 1858 transferred to The Crown the right to publish the official pharmacopoeia and to regulate apothecaries' weights and measures. Metric equivalents in this article usually assume the latest official definition. Before this date, the most precise measurement of the imperial Standard Yard was metres. In 1824, the various different gallons in use in the British Empire were replaced by the imperial gallon, a unit close in volume to the ale gallon. It was originally defined as the volume of of distilled water weighed in air with brass weights with the barometer standing at at a temperature of . In