Colorado River Compact

The 1922 agreement allocated Colorado River water between the basin’s Upper and Lower Basins, setting legal rules that still shape water disputes across the American Southwest.

Colorado River Basin: The watershed drained by the Colorado River and its tributaries across the southwestern United States and northwestern Mexico. The compact divides this watershed into Upper and Lower Basins.
Colorado River Commission: An interstate commission formed in 1922 to negotiate an allocation agreement for the Colorado River’s seven basin states. Its negotiations produced the compact.
Boulder Canyon Project Act: A 1928 U.S. law authorizing Hoover Dam and allocating Lower Basin Colorado River water among states. It implemented the compact’s Lower Basin framework.
Colorado River Compact over-allocation: The mismatch between Colorado River water commitments and the river’s long-term dependable supply. The compact allocated water using flow estimates that proved too high.
Rio Grande Compact: A 1938 agreement allocating Rio Grande water among Colorado, New Mexico, and Texas. It addresses a different river basin through a separate interstate compact.
Upper Colorado River Basin: The part of the Colorado River Basin above Lee Ferry, encompassing portions of seven U.S. states. The compact assigns this basin a duty not to deplete specified flows at Lee Ferry.
Herbert Hoover: The 31st U.S. president, who chaired the Colorado River Commission before entering national politics. As commission chair, he helped broker the agreement.
Arizona v. California: A series of U.S. Supreme Court cases that resolved disputes over Colorado River water allocations among Lower Basin parties. The cases clarified how compact-era allocations applied to Arizona and California.
Colorado River Compact curtailment: A proposed reduction in Upper Basin water use to meet obligations under the Colorado River Compact. States dispute when compact duties require the Upper Basin to curtail use.
Republican River Compact: An interstate agreement allocating Republican River water among Colorado, Kansas, and Nebraska. It offers a smaller-basin comparison to the Colorado River settlement.

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