Rule-Making Associated with Regulating the Use of Lower Colorado River Water Without an Entitlement

Unlawful Use Regulation Index

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To enable the Bureau of Reclamation to properly account for the use of lower Colorado River water, and to ensure existing and future use of the water is consistent with Federal law, Reclamation is developing a rule that establishes procedures for making determinations of unlawful use of lower Colorado River water.

The proposed rule will:

  • Adopt a "River Aquifer/Accounting Surface" methodology that Reclamation will use to determine which wells are pumping Colorado River water,

  • Provide options for unlawful users to legitimize their lower Colorado River water use,

  • Establish the criteria water users must satisfy to demonstrate that their wells do not pump water that would be replaced by lower Colorado River water,

  • Establish a process for water users to appeal Reclamation determinations that specific wells pump Colorado River water, and

  • Provide for public review and comment on the rule and methodology.


The Boulder Canyon Project Act requires water users who divert water from the lower Colorado River to lands in Nevada, Arizona and California to have an entitlement to that water. All Colorado River water users must enter into a water delivery contract with the Secretary of the Interior, unless they have a water right, perfected under state law, prior to December 21, 1928 (the effective date of the Act).

The Secretary, through the Bureau of Reclamation, is required by the Consolidated Decree of the U.S. Supreme Court in Arizona v California to account for all diversions, returns, and consumptive uses of water from the lower Colorado River mainstem, including water withdrawn by underground pumping.

Reclamation annually delivers 9 million acre-feet of water to Lower Basin states and Mexico. Current data indicates that 9,000 to 15,000 acre-feet per year of lower Colorado River water is being used without an entitlement. The majority of this water is diverted for domestic and agricultural use from wells located in the floodplain. Reclamation has an on-going program to identify the location of these wells and the type of use for the water being pumped.

Rule-Making Process

A notice of the proposed rule-making was published in the Federal Register on August 18, 2006, and a 60-day comment period under this notice ended on October 17, 2006. The comments, which were submitted by 20 entities, generally supported the rule-making process. The draft rule was published in the Federal Register on July 16, 2008, and interested parties were invited to submit comments until September 15, 2008.

The processes related to this action are continuing; for more information on this activity, navigate through the menu options above or contact Margot Selig at or 702-293-8192.

Last Updated: 7/2/15