PHOENIX — This was going to be the year the engineers turned back the clock on the Colorado River.
For a week, a stretch of the world's most regulated river was supposed to roar with a spring flood like those that swept the Grand Canyon in the days when Maj. John Wesley Powell led the first party of whites in wooden boats through the canyon in 1869.
The torrent, 10 feet deep and more, would be artificial, released through the turbines and jet tubes of Glen Canyon Dam on the Arizona-Utah line, 16 miles above Grand Canyon National Park.
The purpose: to lift sand from the river bottom and partly restore a chain of sandy beaches along the river a mile below the tourist lookouts on the canyon rim. The restoration could also help preserve the remains along the river of stone dwellings, hunting camps, and roasting pits used by the Anasazi Indians.
But the nation's dam-building agency announced last week it had postponed the experiment indefinitely. Bureau of Reclamation officials said they need time to determine how the experiment would affect the environment and the dam.
Noting that a new date hasn't been set for the experiment originally planned for April, Sierra Club Southwest director Rob Smith said environmentalists are worried the flood will never happen.
They suspect the bureau is caving in to its traditional constituents: water and power interests that oppose the notion that dams on Western rivers should be operated to benefit wildlife and recreation, as well as farms and industry.
``The people who want to use the Grand Canyon as a cash register don't give up easily,'' says Gail Peters, an environmental activist.
The plan was challenged by the Upper Colorado River Commission, a group of water officials representing Utah, New Mexico, Colorado, and Wyoming.
Barry Wirth, a Bureau of Reclamation spokesman, says the bureau remains committed to the project. ``We don't regard this as dead forever,'' he said. ``We just haven't set the time.''