Colorado River too much of the lower basin allotment; in 1944 a compromise was reached in which Arizona would get a firm allocation of , but only if California's allocation was prioritized during drought years. These and nine other decisions, compacts, federal acts and agreements made between 1922 and 1973 form what is now known as the Law of the River. On September 30, 1935, the United States Bureau of Reclamation (USBR) completed Hoover Dam in the Black Canyon of the Colorado River. Behind the dam rose Lake Mead, the largest artificial lake in the U.S., capable of holding more than two
Agriculture in the Southwestern United States any other region of the United States, so it is warmer on average. There are two main physiographic regions which Arizona is a part of. North and east Arizona is part of the Colorado Plateau, and the Basin and Range is in southern and western Arizona. The Colorado Plateau is a flat, elevated land of soft sedimentary rock about 5,000 to 9,000 feet above sea level. Rivers cut deep canyons and gorges into the plateau, the largest of which is the Grand Canyon of the Colorado River, which is in the northwest corner of Arizona. There are also scattered mountains