The Colorado River is one of the most extensively managed bodies of water in the United States. Serving an estimated 30 million people and an area with roughly 3.5 million acres of farmland, most of it irrigated, the use of water in the River is controlled by a complex collection of laws, court decisions, interstate compacts and regulations. This body of documents is known collectively as the “Law of the River.”

Major elements of the Law of the River include:

●      The Colorado River Compact of 1922, the interstate agreement, ratified by the federal government, that divided the rights to water in the river between the Upper Basin states of Wyoming, Colorado, Utah and New Mexico and the Lower Basin states of Arizona, Nevada and California.

●      The Boulder Canyon Project Act of 1928, which not only authorized the construction of Hoover Dam, but also apportioned the water available to the Lower Basin among the three states involved.

●      The Arizona v. California US Supreme Court Decision of 1964, which finally settled a 25-year dispute between the two states over their competing claims to the River. The decision also perfected the legal rights of five Colorado River tribes to their share of the water.

●      The Colorado River Basin Project Act of 1968, which authorized the construction of the Central Arizona Project.

●      Treaty agreements between the United States and Mexico providing for Mexico’s rights to a share of the water in the River.