The Bureau of Reclamation has used data projections of Lake Powell and Lake Mead reservoir elevations that a release of 7.48 million acre-feet (maf) from Lake Powell is required in water year 2014 (Oct. 1, 2013 -- Sept. 30, 2014), per the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations.
The 7.48 maf release is the lowest since the filling of Lake Powell in the 1960s, Reclamation said, and is expected to cause Lake Mead to decrease an additional eight feet during 2014.
The bureau said Lake Mead will operate under normal conditions in calendar year 2014, however, "with water users in the Lower Colorado River Basin and Mexico receiving their full water orders in accordance with the 2007 Interim Guidelines and the 1944 Treaty with Mexico".
"This is the worst 14-year drought period in the last hundred years," Upper Colorado Regional Director Larry Walkoviak said. "Reclamation's collaboration with the seven Colorado River Basin states on the 2007 Interim Guidelines is proving to be invaluable in coordinating the operations of the reservoirs and helping protect future availability of Colorado River water supplies."
The 2007 Interim Guidelines were signed by the Secretary of the Interior after consultations with Colorado River Basin states, Native American tribes, federal agencies, environmental organizations, and other stakeholders and interested parties, Reclamation said.
The guidelines help "coordinate reservoir management strategies and address annual operations of Lake Powell and Lake Mead, particularly under low reservoir conditions."
Decreasing levels are particularly worrisome at Lake Mead, which -- as the largest reservoir by volume in the United States -- provides water not only for the 2,078-MW Hoover Dam, but also for a large portion of Las Vegas' potable supply.
Still, Reclamation officials say a crises could be avoided, assuming snow and rain increases next year.
"With a good winter snowpack next year, the outlook could change significantly as it did in 2011," Lower Colorado Regional Director Terry Fulp said. "But we also need to be prepared for continuing drought."
Fulp said Reclamation's longer-term hydrologic models show a "very small chance" of lower basin delivery shortages in 2015, with the first "significant chance" of reduced water deliveries in the lower basin coming in 2016.
These projections are updated monthly and reflect changes in weather and the resulting hydrology, Fulp said.