Reclamation and Arizona
Supreme Court Clears the Way for the Central Arizona Project
The Colorado River Basin States, Bureau of ReclamationThe Colorado River Basin States, Bureau of Reclamation

The Arizona v. California Supreme Court case settled a longstanding dispute over claims to Colorado River waters in the river's Lower Basin. In this landmark decision, the Court issued an opinion in 1963 and a decree in 1964.

Arizona filed its original suit against California in the Supreme Court in 1952. Nevada, New Mexico, Utah, and the United States were subsequently added as parties to the proceedings. The controversy was related to how much water each State had a legal right to use out of the waters of the Colorado River and its tributaries.

The Court appointed a Special Master to gather evidence, find facts, state conclusions of law, and recommend a decree. Appointed in 1955, Special Master Simon H. Rifkin held more than 2 years of formal hearings. In 1960, he submitted a 433-page report to the Supreme Court containing his findings, conclusions, and recommendations, most of which the Court adopted in its majority opinion and decree.

The decision in Arizona v. California established several important elements of the Law of the River:

  • The Court determined that Congress – through the Boulder Canyon Project Act of 1928 –had created a comprehensive plan for apportionment of the Lower Basin's share of the Colorado River.
  • It reserved to Arizona, California, and Nevada exclusive use of the waters of each state's own tributaries. This was of special importance to Arizona which refused to ratify the Colorado River Compact in the 1920s based, in part, on Arizona's questionable rights to the Gila River.
  • It reflected a decision that "fair division" of the first 7.5 million acre-feet of the Colorado's mainstream waters "would give 4,400,000 acre-feet to California, 2,800,000 to Arizona, and 300,000 to Nevada," and that "Arizona and California would each get one-half of any surplus."
  • It determined that Congress also gave the Secretary of the Interior authority to make these divisions through the Secretary's "... power to make contracts for the delivery of water and by providing that no person could have water without a contract." And through these contracts, the Secretary could not only allocate water among the lower basin states, but could also decide which users within each state would get water.

Breaking new ground in federal water law, the Supreme Court also found the Secretary of the Interior had sweeping powers over Colorado River management, especially in the lower basin:

  • It determined that the Secretary was not bound by the law of prior appropriation in allocating water among – or within – the states.
  • Recognizing that the massive network of projects on the lower river needed a management entity able to develop and administer a coordinated plan that could take into account the diverse, often conflicting interests of the people and communities of the lower basin States, Congress put the Secretary of the Interior in charge of these works with "... sufficient power … to direct, manage, and coordinate their operation."

Finally, the Court upheld claims of the United States to water in the Colorado River mainstem and in some of its tributaries for use on Indian reservations, recreational areas, wildlife refuges, and other federal government lands.

Archive documents (copies of originals),4402 – Progress report: news of Arizona's water fight, Central Arizona Project Association, August 1, 1949.,3294 – Let the Supreme Court Decide, Colorado River Association (California) fact sheet on Arizona v. California, 1947(?),2333 – Special Master's Simon H. Rifkin Report to the U.S. Supreme Court, December 5, 1960,2114 – Supreme Court Decree in Arizona v. California, March 9, 1964,4270 – Colorado River: The Paramount Issue in Arizona, Arizona Governor Hunt campaign literature, May (?) 1926


acre-foot – equal to 325,900 gallons, or the amount of water needed to cover an acre of land 1 foot deep

beneficial consumptive use – the consumption of water brought about by human endeavors including use of water for municipal, industrial, agricultural, power generation, export, recreation, fish and wildlife, and other purposes, along with the associated losses incidental to these uses (i.e. evaporation).

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