The federal government will release enough extra water into drought-stricken Lake Mead in the coming months to avoid shortages on the lower Colorado River for as long as five years.

The U.S. Bureau of Reclamation said Friday that runoff from snow in the mountains of Wyoming and Colorado is expected to increase storage on the river enough to adjust water levels at two key reservoirs and avert drought restrictions.

The decision comes just six months after Lake Mead dropped to within 7 feet of a level that would have triggered drought restrictions. Under those restrictions, Arizona would have lost about 11 percent of its allocation for at least one year.

Arizona officials had prepared contingency plans that included forfeiting a small amount of the state's allocation as a hedge against larger losses. Those plans are no longer necessary.

"We still want to be somewhat cautious," said Tom McCann, assistant general manager of the Central Arizona Project, which delivers Colorado River water to Phoenix and Tucson. "We've been in drought for 11 years. We've had a good year, and that's very helpful. It pushes us further away from shortages, but it doesn't mean the drought is over."

Still, Friday's action will give the CAP and other water users more time to plan for future shortages.

The extra water should postpone the potential for shortages until about 2016, even if conditions turn dry again, McCann said.

The bureau's decision is based on a 2007 drought plan adopted by the seven states that use the Colorado River.

Those states - Arizona, California, Nevada, Utah, Wyoming, Colorado and New Mexico - agreed to manage water supplies based on storage levels at Lake Powell and Lake Mead, the river's two largest reservoirs.

When Lake Powell is below a designated level, a minimum amount of water - 8.23 million acre-feet - is released downstream into Lake Mead.

If Lake Powell rises above that designated level, additional water can be released to better equalize the two reservoirs' contents.

An acre-foot is 325,851 gallons, enough to serve two households for a year.

The bureau determined this week that Powell would rise above that designated level this year, which meant more water, a projected 11.56 million acre-feet, could be released into Mead.

That determination was based on estimated runoff from mountain snowpack, projected to reach about 120 percent of the 30-year average.

With the extra water, Mead is expected to rise to elevation 1,112.52 feet above sea level by the end of the year. The lake fell to about 1,082 feet above sea level last fall, just 7 feet above the first drought-restriction trigger of 1,075 feet above sea level.

Under the first set of drought restrictions, Arizona would have lost 320,000 acre-feet of its 2.8 million-acre-foot allocation.

That amount would not have affected homes or businesses, McCann said.