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 and US customary measurement systems of any direction by Congress, the United States Treasury chose the second smallest gallon, the "Queen Anne gallon" of 231 cubic inches (3.785 litres) to be the official gallon in the United States for fiscal purposes. Sixteen US fluid ounces make a US pint (8 pints equals 1 gallon in both customary and imperial systems). During the reform of Weights and measures legislation in the United Kingdom in 1824, old gallons were replaced by the new imperial gallon which was defined to be the volume to 10 pounds of water at 62 °F (17 °C) and determined experimentally to be