On August 13, 2014, the United States Bureau of Reclamation (Reclamation) released its latest Operation Plan for Colorado River System Reservoirs 24-Month Study.The study projects operations and water releases for major reservoirs in the Colorado River Basin, including Lake Mead (impounded by Hoover Dam) and Lake Powell (impounded by Glen Canyon Dam). The study is available here.
According to Reclamation, “[t]he Upper Colorado River Basin runoff in 2014 was 94% of average, compared to only 47% in 2013 and 45% in 2012. Despite this near-average runoff, Lake Mead is currently at elevation 1,080 feet, its lowest elevation since the lake filled in the 1930s, due to the 15-year drought that began in 2000.”See 2015 Lake Powell Water Release to Lake Mead Will Increase, available here.
In the 24-month study, Reclamation predicts that the water elevation in Lake Mead will continue to fall over the next year.By August 2015, Reclamation estimates that Lake Mead’s water elevation will be 1,073 feet above sea level.This is below the elevation that would trigger a shortage declaration by the Secretary of the Interior for the Lower Colorado River Basin under the Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead, issued in 2007 (Interim Guidelines).The Interim Guidelines require a shortage declaration if the water elevation in Lake Mead drops below 1,075 feet. As such, if Reclamation’s 24-month study prediction holds true, there will be a shortage declared for the 2016 water year.
The impact of a shortage declaration would be felt most significantly in Arizona – but the overall impacts are likely to reverberate throughout the Colorado River Basin.Under the decree in Arizona v. California, 373 U.S. 546 (1963), most recently revised at 531 U.S. 1 (2000), Arizona is entitled to 2.8 million acre-feet of Colorado River water each year.Nevada is allocated 300,000 acre-feet and California is allocated 4.4 million acre-feet.However, under the Shortage Sharing Criteria set forth in the Interim Guidelines, if a shortage is declared, Arizona’s allocation would be reduced by 320,000 acre-feet and Nevada’s allocation would be reduced by 13,000 acre-feet.In contrast, a shortage declaration in 2016 will not reduce California’s Colorado River supply.California will continue to receive its full allocation of 4.4 million acre-feet per year as specified in the Arizona v. California decree.A reduction to Arizona’s allocation in 2016 would directly affect deliveries of water through the Central Arizona Project (CAP) canal.Reductions would come out of the “non-Indian Agricultural” portion of the CAP water supply.CAP supplies for municipal and industrial users would not be affected by this level of shortage.
Despite the grim forecast and the possibility of a shortage declaration, hydrology predictions are inherently uncertain and subject to change (for better or worse) due to unpredictable variations in the weather.A good winter snowpack in 2014 and 2015 could alter the current projections and delay or avoid a shortage declaration.However, if the snow does not fall, water users should prepare for the potential impacts of the first shortage declaration on the Colorado River.