The federal government stepped up release of tons of water through Hoover Dam today in an effort to avoid catastrophic flooding of the Colorado River, as continuing rain and hot weather accelerated the melting of snow on western mountains.

Bureau of Reclamation officials said they expect to be releasing 40,000 cubic feet of water every second from Hoover Dam by Thursday--more than twice the normal runoff--in an urgent attempt to prevent even worse flooding from the record mountain snow melt.

A brief bureaucratic war between Colorado River communities led a federal judge here to delay the increased water release Monday, but attorneys for two communities and an Indian tribe concerned about the intentional flooding agreed today to lift their demand that it be stopped.

All along the sunny banks of the Colorado on the border between California and Arizona, residents and National Guard troops piled more sandbags today for the inevitable rise of the river's silt-laden waters. Local officials estimate damage so far at about $1 million and see a potential loss of $5 million or more.

The Coast Guard ordered the river closed to boat traffic in most of Arizona south to the Mexican border. Only law-enforcement and emergency craft will be allowed in the restricted areas because of the "safety hazards posed by riverbank erosion, debris and high currents," a spokesman said.

Local sheriffs' departments will be responsible for enforcing the ban, the spokesman said.

Resort owners had banned power-boating and water skiing Monday after vacationers on jet skis blithely sent waves over neatly stacked sandbags and touched off angry incidents.

Brian Jackson, co-owner of the Echo Lodge near Parker Dam, Calif., angrily questioned the judgment of the Bureau of Reclamation in keeping runoff from upstream dams at a low level until the last minute.

The northernmost point at which the bureau is releasing water is at Hoover Dam about 20 miles southeast of Las Vegas. Davis Dam is 55 miles farther downstream, and Parker Dam is another 45 miles downstream.

"Everybody was passing the buck," Jackson said. "Nobody had the guts to say, 'We've got a real problem here.' "

Dennis Kidd rushed from Los Angeles to help his grandmother, Bernice Kidd, 71, prepare for possible flooding of her home in Parker, Ariz., just 100 feet up a grassy slope from the river.

"We have no damage right now, but our neighbors are much closer to the water," Kidd said.

The weather crisis, coming at the end of a freakish, wet winter that has left the waterlogged West vulnerable to massive floods, has turned town against town as snow banks twice as thick as usual begin to melt down the Sierra Nevada and Rocky Mountains.

Needles, Calif., along with Arizona's Mohave County and Quechan Indian tribe, sued Monday to cut back the Bureau of Reclamation's effort to empty mountainside reservoirs.

Normal flows from the Hoover Dam usually run less than 20,000 cubic feet per second, but by Monday the bureau had gone to about 31,000 cubic feet per second.

U.S. District Court Judge Manuel Real issued a temporary restraining order holding the runoff from Hoover Dam at 31,000 cubic feet per second. But bureau officials and residents of the most affected communities, such as Parker, objected strongly that this would only increase peak flooding as the summer wore on.

Nita Claypoole, wife of a Needles businessman who helped institute the suit, said Needles and the other communities agreed to ask the judge to lift his order after the bureau said "if there is extensive damage, it will all be all Needles' fault."

But she said she still expected the bureau to appear in federal court here Friday to explain what it is doing and to justify what she and others see as unnecessary delay in beginning the increased runoff.

Raymond C. Simpson, an attorney representing Needles and the other communities, said the bureau had increased the runoff from 7,000 to 19,000 cubic feet per second in January, then scaled back to 7,000 again "even though fully aware that a problem was still occurring."

Bill Plummer, the bureau's lower Colorado regional director, said federal meteorologists could not anticipate unusually heavy snows and rain in the late spring and a sudden heat wave that accelerated the snow melt far beyond what had been prepared for.

As late as June 1, he said, experts predicted only 117 percent of the usual summer runoff. By yesterday that estimate had increased to 193 percent.

To save downstream communities from even more serious flooding, Plummer said, Hoover Dam will have to continue a 40,000 cubic feet-per-second release "well into July."