KVIG Informative

The Mexican Water Treaty of 1944 forced the United States to build a second dam on the Colorado River just to keep its promise to deliver water south of the border. More than eight decades later, federal officials are still working out exactly how that promise gets kept, under Colorado River operating rules the Interior Department finalized this past August.

The Interior secretary authorized construction of Davis Dam on April 26, 1941, under the Reclamation Project Act of 1939, according to a Historic American Engineering Record prepared for the National Park Service and held by the Library of Congress. Reclamation named the dam for Arthur Powell Davis, who led the Bureau of Reclamation from 1914 to 1932.

The federal government awarded the construction contract to Utah Construction Company on June 25, 1942, and crews began building a railhead near Kingman, Arizona, that same month, the Historic American Engineering Record states. Drilling and blasting started Sept. 12, 1942. The War Production Board revoked the priority ratings the project needed for steel and other materials on Oct. 27, 1942, and no further construction happened for the rest of World War II. Reclamation formally terminated the contract on Feb. 20, 1943.

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Reclamation awarded a new construction contract to Utah Construction Company on Jan. 15, 1946, and work resumed with a formal notice to proceed on March 22, 1946, according to the Historic American Engineering Record. Crews finished excavating the diversion and forebay channels by February 1947 and completed foundation grouting by the end of that year. Concrete placement for the spillway and outlet structure began in January 1948, and the Colorado River was diverted that June. The dam’s earthfill embankment reached its full height in April 1949, and the spillway was finished in October 1950.

The dam, its reservoir and its power plant were transferred to operations and maintenance on Dec. 1, 1951, and Davis Dam was officially dedicated on Dec. 10, 1952, the Historic American Engineering Record states. The reservoir behind it, Lake Mohave, holds 1,818,300 acre-feet of water and stretches 67 miles upstream to the tailrace of the Hoover Powerplant, according to the Bureau of Reclamation’s own project data for Davis Dam.

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The dam exists because of a treaty, not just a water shortage. The Mexican Water Treaty of 1944 required the United States to construct Davis Dam, according to the Historic American Engineering Record. That treaty guaranteed Mexico an annual delivery of 1.5 million acre-feet of Colorado River water, according to the Bureau of Reclamation’s own history of the treaty. Storing water behind Davis Dam, through the coordinated operation of the Hoover and Davis powerplants, is what lets the United States regulate its releases closely enough to meet that guarantee.

That same obligation is still being worked out. The Interior Department issued a Record of Decision for Post-2026 Colorado River Operations on Aug. 21, 2026, setting a 10-year framework that cuts Lower Basin deliveries by 1.25 million acre-feet in 2027, including a 50,000-acre-foot reduction to Nevada’s share, according to the Bureau of Reclamation’s own news release on the decision. The same release states that a separate binational process to determine deliveries to Mexico under the 1944 treaty is nearing completion through the International Boundary and Water Commission, in consultation with the State Department.

Davis Dam settled its own construction questions in 1952, after a war twice put the project on hold. The treaty that justified building it is still unsettled eight decades later, and it is the federal government’s own water agency saying so.