A small amount of surplus Colorado River water will be made available for municipal use in 2006, but water managers in Nevada, California and Arizona are not expected to take it, federal officials announced Wednesday.

Interior Secretary Gale Norton on Monday approved the "partial domestic surplus" as part of the 2006 annual operating plan for the Colorado.

Under that designation, 300,000 acre-feet of surplus water could be taken for use in cities and towns in the lower basin states of Nevada, Arizona and California. However, state officials acting in the "spirit of cooperation" are expected to forgo the surplus to help Lake Mead and Lake Powell, said Terry Fulp, area manager for the Bureau of Reclamation in Boulder City.

"We've just seen the worst five-year drought on record," Fulp said. "Prudent water management says if you don't need that water now, leave it in the system."

Lake Mead is filled to 58 percent of capacity, while Lake Powell stands at about 49 percent.

The operating plan essentially maintains the status quo for another year while the seven Colorado River Basin states continue to discuss new operating strategies and criteria for dividing shortages on the river in lean water years.

Norton announced her approval of the operating plan in a letter sent Monday to the governors of Nevada, Arizona, California, Colorado, New Mexico, Utah and Wyoming.

She is scheduled to speak Friday morning at a water conference in Las Vegas, but there were indications Wednesday that she might have to cancel to attend to business in Washington.

Water use on the river is planned on an annual basis, but earlier this year, federal officials held a midyear review to see if operational changes were needed to preserve water deliveries and power generation on the Colorado. No changes were made.

Rather than mandate another midyear review in 2006, Norton has tied her decision to specific reservoir conditions. She announced that she will hold the review in April if the combined storage in lakes Mead and Powell is projected to fall below where it was on Sept. 30, 2004.

At the moment, that is not expected to happen.

By the end of September 2004, the twin reservoirs contained a total of 23.1 million acre-feet of water. The Bureau of Reclamation's latest projection for Sept. 30, 2006, predicts 28.1 million acre-feet of combined storage.

There are 325,851 gallons in an acre-foot, which is almost enough water to supply two Las Vegas Valley households for a year.

At 300,000 acre-feet a year, Nevada has the smallest share of the Colorado River but depends on it more for municipal use than any other state.