Lower Colorado River Water Delivery Contracts
In Nevada, Arizona, and California, the use and distribution of Colorado River water is subject to laws, judicial rulings and decrees, contracts, interstate compacts, operating criteria, and an international treaty. These documents and decisions, collectively known as the "Law of the River," apportion available water between the states and establish certain priorities in use.
Part of this law, the Boulder Canyon Project Act of 1928, authorizes the Secretary of the Interior to operate as the sole contracting authority for water from the lower Colorado River. It also provides for specific irrigation and domestic water contracts on a permanent basis. The Act requires any user of Colorado River water in the Lower Basin to have a water delivery contract with the Bureau of Reclamation. This requirement, which was confirmed by the U.S. Supreme Court in its Consolidated Decree in Arizona v California, applies to all diversions made from the River, including those made through wells that draw water from the Colorado River aquifer.
Here are several questions and answers to help you understand Colorado River water distribution and contracts in the Lower Basin. (Note: This information refers ONLY to Colorado River water use in Arizona, California, and Nevada, and not to diversions and use in the Upper Basin). The Lower Basin includes parts of five states: Arizona, California, Nevada, New Mexico, and Utah. The Upper Basin also includes parts of five states: Arizona, Colorado, New Mexico, Utah, and Wyoming. The states of Arizona, New Mexico, and Utah are included in both the Upper and the Lower Basins.
The four Upper Basin States of Colorado, New Mexico, Utah, and Wyoming are referred to as the Upper Division States. The three Lower Basin States of Arizona, California, and Nevada are referred to as the Lower Division States. This distinction between "Basin" and "Division" is important because of how Colorado River water is allocated among the states.
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What is the source of Colorado River water?