Federal authorities yesterday sent extra water gushing from three dams on the swollen Colorado River in what one official called a "controlled disaster" in flooding communities.

The widening of the floodgates at Hoover Dam near Las Vegas and two others downstream was necessary to keep water from overflowing the dams, Bureau of Reclamation officials said. They said water was within a foot of the top of one.

The Colorado, which winds 1,450 miles from its source in the Rocky Mountains to Mexico, where it empties into the Gulf of California, was running 5 feet above normal levels and rising in most locations.

"It's like living with a time bomb," said Colorado Gov. Richard D. Lamm.

In the Southwest, where the Colorado River forms a boundary between a corner of Arizona and Nevada and Arizona and California, residents shored up sandbag and dirt barriers against the water. Officials said the release at the dams would increase today and continue for the next several weeks.

"It's a controlled disaster on a day-to-day basis," said Don Denton, chairman of the La Paz County Board of Supervisors. He estimated that 300 to 500 people were sandbagging in the Parker Strip, a 15-mile-long recreational area of lodges, bars, restaurants and houses between Parker Dam and the community of Parker.