Starting from the last half of the nineteenth century, a tremendous flow of immigration entered the West. Two developments both spurred settlement and necessitated a legal doctrine for water allocation: the discovery of gold and silver in the western mountains and the widespread use of irrigation in crop production. To work a claim on ore deposits, miners had to divert water from streams in flumes and pipes. Thus, a body of informal water law grew in the mining camps. The procedures by which gold and silver claims were established and worked were easily transferred from ore to water. The first person to file a mining claim received priority over any later claimants. To keep one’s ownership of a mining claim, one had to stake it, take possession of it, and work the claim productively.

The water law, born in the mining camps, followed the doctrine of prior appropriation. The right to use water was exclusive, absolute, and established by the act of prior diversion. Third parties often suffered from the effects of water use. One user’s return flows were another’s source of supply. Any change in the point of diversion or type of use affected appropriators (third parties) downstream. Legislators attempted to correct these third party effects by adding restrictive clauses to the doctrine such as beneficial and reasonable use requirements and regulations for compensating parties injured by transfers. These corollaries were vague, however and custom dictated the quantity of water considered reasonable.

The history of Glen Canyon Dam reveals how western states developed legal definitions and allocation rules for water rights both within their borders and how major rivers were apportioned among states. The time line below relates important events in the history of Glen Canyon. It tells the story of how the West reached the critical juncture it currently confronts. Water use in cities and industries grows each day. Simultaneously, voices argue for water conservation, ecological restoration and water reallocation. As these conflicting evocations create vibrant debates, they reveal both the complexity and uncertainty the West must deal with as it makes choices about water resources.

Basic time line:

• 1869 John Wesley Powell, the first to navigate the mighty Colorado River through Glen Canyon, begins his journey.

• 1900 Imperial Valley Irrigation District opened. It is the largest irrigation district in the western world, and it uses the Colorado River water. The water was delivered to the Imperial Valley through the Alamo Canal.

• 1902 The Reclamation Act is recognized as the beginning of many decades of Government involvement in constructing and heavily subsidizing water projects in the west. The Bureau of Reclamation was established to construct federally financed dams and to contract water deliveries with the local beneficiaries (usually irrigation districts).

• 1905  A heavy flow in the Colorado caused a break in the banks of the Alamo Canal, and the entire flow of the river was diverted to the Imperial Valley. For two years the Colorado River flowed not to the Gulf of California, but to the Salton Sea.

• 1908 Under The Winters Doctrine, the Supreme Court concluded that the federal law established Indian water rights. Reservations were designed to encourage the "nomadic and uncivilized" Indians to become pastoral. The lands involved were so arid, they could produce virtually nothing without irrigation. Therefore, the court ruled that Indian tribes have the right to hold "reserved rights" to water to fulfill the purposes of their reservations.

• 1922  All seven states in the Colorado River Basin (Utah, New Mexico, Colorado, Arizona, Wyoming, California and Nevada) met in New Mexico and everyone except Arizona signed the Colorado River Compact. This agreement divided the river at a town called Lee Ferry. The states based the division of water on the "virgin flow" at Lee Ferry, that is, the amount of water that would flow through Lee Ferry if there were no irrigation use or reservoir losses above Lee Ferry. The Upper and Lower Basins were each assigned 7.5 maf per year.

• 1928  The Boulder Canyon Project Act authorized the building of Hoover Dam and allocated Lower Basin water. California received 4.4 maf, Arizona received 2.8 maf, and Nevada received 0.3 maf. This division was negotiated in Congress, not between the states.

• 1944  The Mexican Treaty Guaranteed Mexico 1.5 maf annually. This had no provision for the quality water.

• 1948  The Upper Basin States signed the Upper Colorado River Basin Compact which split their part of the river on a percentage basis, plus a token 50,000 af to Arizona. It allocated Colorado 51.75%, Utah 23%, Wyoming 14%, and New Mexico 11.25%.

• 1956 The Upper Colorado River Storage Project Act authorized Flaming Gorge, Glen Canyon, Navajo and Curecanti dams. Glen Canyon was built right above Lee Ferry because at this site every drop of water entering the Colorado in the Upper Basin can be caught. No tributary of the Colorado in the Upper Basin comes in below Glen Canyon Dam. Therefore, the Upper Basin can control releases to meet the terms of the compact.

• 1963  The Glen Canyon Dam is completed and Lake Powell is formed.

• 1963  Arizona vs California: Supreme Court ruled that Arizona had the right to 2.8 maf from the mainstream of the Colorado.

• 1968  Colorado River Basin Project Act authorized the Central Arizona Project, which provides for the aqueduct that carries water form the Colorado to the Phoenix-Tucson area, mainly for irrigation. Under the agreement, California was given the absolute priority of 4.4 maf.

• 1972 Glen Canyon National Recreation Area was set aside by Congress

• 1973  Endangered Species Act requires the determination of endangered species, a Recovery plan for habitat protection, facilitates cooperation among states.

• 1986 The Colorado River Floodway Protection Act resulted from the aftermath of the 1983-1985 flooding along the Lower Colorado River. The Act required the Secretary to identify and establish the "Colorado River Floodway" to provide benefits to river users and minimize the loss of life and property damage.

• 1992  The Grand Canyon Protection Act required the Secretary to implement "interim operating criteria" for the operation of Glen Canyon Dam in order to protect the downstream resources in the Grand Canyon National Park. The Secretary was required to complete an analysis of the operation of Glen Canyon Dam under the National Environmental Policy Act (NEPA).