Denver ? After five years of consistent drought, the vast arid stretches of the American west finally had a winter of heavy precipitation in 2004-2005. As the spring thaws begin, the federal Bureau of Reclamation says, the mountain snow pack that feeds the Colorado River is above average for the first time in years.

Far from celebrating this welcome flood, though, the seven dry states that depend on the Colorado for water supply are engaged in yet another intractable water war.

Despite a year of negotiations, the governors of Wyoming, Colorado, New Mexico, Utah, Arizona, Nevada, and California have been unable to agree on an annual plan for sharing the Colorado’s water, the most precious resource in a region where the rain rarely falls. So, the final decision has been bumped up to the Bush administration.

Water is for fightin’

Today, Interior Secretary Gale Norton is due to tell the seven feuding governors how much water they can draw from the river and its tributaries this year.

The issue Norton must decide seems extremely technical: how many million acre-feet of water federal engineers will shift this summer from Lake Powell to Lake Mead, the two main reservoirs that control flow on the Colorado. That hydrological determination, though, reflects intense competition in a region where, as the saying goes, the whiskey is for drinkin’ and the water is for fightin’.

A seven-state compact created in 1922 governs allocations of Colorado River flow. For most of its life, the agreement was fairly easy to adhere to, because there was more water in the river than the people, factories, and farms in the Southwest could use. But a tidal wave of population growth — coupled with a drought that made a dry region even drier — has aggravated the water wars.

The Colorado River begins as a foot-wide trickle of melting snow in Colorado’s Never Summer mountains, northwest of Denver, and flows 1,500 miles southwest toward Baja California. Fed by major tributaries like the Green, Gunnison, Yampa, and San Juan Rivers, the Colorado cuts through 200 miles of sheer rock to form the Grand Canyon; it once poured billions of gallons each year into the Gulf of California in northern Mexico.

But today, a thick network of dams and diversion canals, built over the past century to hydrate desert development, sucks up all the water before the river reaches its mouth. “It’s a rare year now when the Colorado flows to the Pacific,” says Bill Bates, a resource engineer with the Denver Water Board.

‘Unity of drought’

The pressure to bring water to the driest corner of the country turns politics upside down. Conservative Republicans who routinely denounce “big spending” and “big government” fight hard to bring more big-budget government water projects to their states. Liberal Democrats in the region with otherwise pristine environmental records break with their green backers when it comes to proposals for new dams and concrete-lined canals.

All this is necessary because much of the Western United States — from the 100th meridian, just west of Wichita, Kan., to the coastal strip of California — is desert land, in climatic terms, getting less than 20 inches of rain per year. (The East Coast averages about twice as much.) For all the variety of mountain, prairie, forest and salt flat, the American west is marked by “one overmastering unity — the unity of drought,” as historian Wallace Stegner put it.

Upper vs. lower

Under the 1922 compact, the Colorado’s annual flow is supposed to be split evenly between the “upper basin” states — Wyoming, Colorado, Utah, and New Mexico — and the “lower basin,” comprised of Nevada, Arizona, and California.

This division is engineered by shifting water between two huge federal reservoirs on the Colorado — Lake Powell, behind Glen Canyon Dam on the Utah-Arizona border, and Lake Mead, behind Hoover Dam, in the corner where Arizona, Nevada, and California meet.

This year, the upper-basin governors have balked at the requirement for shipping Lake Powell’s reserves downstream. They want to keep more water in the upper basin than the compact would normally require.

The argument for this is that the lower basin states are currently awash. There was so much precipitation last winter — causing major flooding in Southern California, and record snow depths at Lake Tahoe — that Lake Mead is unusually full this spring.

This is partly because of runoff into Lake Mead from the winter precipitation, notes Kip White, of the federal Bureau of Reclamation, and partly because drenched farmland didn’t take as much irrigation water as usual from Mead.

As of late April, White said, Lake Mead held 60 percent of its total capacity, the highest spring level since the drought began. Lake Powell, in contrast, stood at just 33 percent of capacity, although that figure should go up as mountain snows melt in May and June.

States concede

A year ago, federal officials told the seven states in the compact to work out a mutual agreement for water flows in 2005. With the governors still arguing last December, federal officials gave them a deadline of April 30 to settle on an annual operating plan. At a meeting in Las Vegas last week, the states conceded that they could not agree, and handed the issue to Norton.

While she is required to come up with a solution for 2005 today, the Interior secretary says she wants the states to look beyond the current year and come up with a long-range plan to deal with the possibility of extended drought.

“We had good precipitation this winter, but you can’t count on that,” says White. “The basic rule for water managers is that one wet year does not end a drought.”