Colorado is running out of water. It doesn't act yet as if it knows it, or understands the implications, and most easterners, dreaming of the snow-packed Rockies, night find the idea preposterous.

But it is true. Virtually all of Colorado's surface water is contained in four watersheds of modest size: the Colorado River, the Rio Grande, the Arkansas and the Platte. The Rio Grande, the Arkansas and the Platte are virtually 100 percent allocated. There is hardly a drop left in them for Colorado. The state has already used up about three-quarters of its entitlement to the Colorado River, which it must share with six neighboring states, and several irrigation projects being built or planned on tributaries to the Colorado could use up most of what is left. Then there is groundwater, which is being drawn much faster than it can be replaced in the part of the state which rely on it most. Then nothing.

The West has always been running out of water, just as America has always been running out of oil. As in the case of oil, new technology, capital formation, federal subsidies and sheer ambition managed to save the day. Each time a crisis neared, more water was stored behind bigger and more expensive dams and brought further to where it was needed. But there are limits to everything, and the absolute limits to water in the arid West are steadily being approached. It is nearly certain that they will be reached first in Colorado or Arizona.

Why Colorado? To begin with, it is an arid state. Denver, if it is lucky, gets 15 inches of rainfall a year to Washington's 40. The runoff in Colorado's rivers is only one-fifth as great as the runoff in California's rivers (easterners never seem to understand that runoff is what determines the growth and prosperity of any state in the arid West), and all of Colorado's rivers cross into neighboring states which are largely desert, so the water has to be shared with them. Most of California's rivers, by contrast, never leave the state. The result is that Colorado, second only to California in the arid West in population, industry and irrigated acreage, has available for its use just over one-tenth as much water. i

Now consider: The state's principal agricultural areas are located in what one might as well call desert, so agriculture is largely dependent upon irrigation for its survival. A 2,000-acre irrigated farm in the West uses as much water as a city of 50,000 people; not surprisingly, almost 90 percent of Colorado's water goes to irrigation. The farmers, who hold extraordinary political power in the state, want more water, and they will probably get it. Meanwhile, Denver, the Los Angeles of the Rockies, is metastasizing across the Front Range; it needs more water. A gigantic federally subsidized energy industry is about to settle into the western part of the state, attracted by more oil, locked in shale, than exists in Saudi Arabia. It needs water. Droves of tourists swarm over the Rocky Mountains every year to fish and hike and raft and kayak and swim. They need water. Wildlife needs water.

There isn't enough.

I visited Colorado in the summer. The first sign I saw that the state is running out of water was the general level of hostility amoung the many interests competing for it. Even compared with my home state of California, where people have been at war over water from the moment the first white settlers arrived, it was high. Responsible public officials and political leaders who had been at odds over water policy described each other in the most disparaging terms imaginable. So-and-so was "an idiot," one told me; so-and-so was "a disgrace," said another, all because of positions taken on water. Downstream irrigators cursed upstream irrigators, West Slopers cursed East Slopers, farmers cursed the cities and water lawyers -- who seem to abound in Colorado -- spun conspiracies before my eyes. l

The second sign I saw that Colorado is running out of water was its price.

Shortly after World War II, the Bureau of Reclamation completed the Colorado-Big Thompson Project, which captures the headwaters of the Colorado in the mountains northwest of Denver and pipes the water through a 13-mile tunnel under the Continental Divide to irrigators along the Front Range. It is now the most expensive water in the nation, and irrigators with good water rights are selling them to the burgeoning cities and industries around them and retiring on the profits.

"Ten years ago, Colorado-Bit Thompson water rights were selling for 240 an acre-foot, and I thought that was really high," said Earl Phipps, director of the Northern Colorado Water Conservancy District. "Three years ago, when the water rights were up to $850 per acre-foot, if you had told me the price would hit $2,000 by 1979, I'd have said you were crazy. That's where it is today. I still can't believe it." Six weeks later, the price had gone to $2,250. In 1947, it was $1.50.

(Is it legal or proper for farmers te resell super-subsidized federal water at whatever price the market will bear? "It's discouraging," says Dan Beard, the Interior Department's deputy assistant secretary for land and water, "but I think we're helpless to do anything about it.")

Because water is used more efficiently by cities and industry than by agriculture -- which is to say that the economic return per acre-foot consumed by agriculture is generally the lowest -- the transfer of water rights from agricultural to urban or industrial uses might be viewed as a good thing. It could give Colorado room for considerable economic growth before it literally dries up, and help ensure that growth does not have as its price the damming of every last mountain stream in the state. However, most of the state's political leaders are religiously holding to policies which will leave the last of Colorado's unappropriated surface water in the hands of agriculture.

Years ago, in exchange for supporting the Central Arizona Project, the man who dominated western water resource development in the 1950s and 1960s, former Colorado Rep. Wayne Aspinall, won authorization for a number of irriagation projects in the upper Colorado River watershed. The projects are widely considered among the most wasteful and extravagant in the nation -- most were on President Carter's original water projects hit list -- but they have been defiantly supported by virtually the entire congressional delegation of the state. Even members of the delegation who are usually regarded as environmentalists, such as Sen. Gary Hart and former Sen. Floyd Haskell, were apoplectic when the projects appeared on Carter's hit list. The administration of Gov. Richard Lamm also supports them adamantly, in keeping with a policy of promoting agricultural water development seemingly at any cost. "Even the Bureau of Reclamation knows those projects are dogs," a former state water expert told me. "They're an ambarrassment to the bureau. But the politicians want them built. It's partly because they're afraid that if Colorado doesn't use the water in a hurry, some neighboring state will."

Unlike the Colorado-Big Thompson Project, water from the Aspinall-inspired projects could not easily be transferred to other uses, such as domestic water supply or oil shale development. They are literally, and purposely -- as Wayne Aspinall admitted to me during an interview last summer -- in the middle of nowhere. What they will do is irrigate some marginal high altitude cropland, offer a few hundred farmers federal subsidies of around a million dollars per farm, and hasten the day when Colorado begins to push against the limits of its water supply.

What goes through the minds of Colorado's political leaders? Do they believe, in this inflationary age, that multi-billion-dollar interbasin water projects, taking water from the Missouri River, perhaps, or the Yellowstone, or Canada, rescue them? Are they counting on groundwater? It is still a great resource, but it is replenished very slowly -- and in some cases not at all -- in the arid West. California pumped out much of its huge reserve in a matter of three of four decades and had to be saved by the two largest, water projects ever built in this nation. Moreover, founding a desert economy on the mining of groundwater is often a chimera. In the eastern part of Colorado, where groundwater is already being rapidly exhausted, a prosperous agricultural economy will, according to a Lamm administration water expert, "collapse within 25 to 40 years."

And what does one make of the reverent attitude displayed toward irrigated agriculture -- which is heavily consumptive of water and often deeply subsidized -- in Colorado, and, for that matter, throughout most of the arid West? Is it merely the entrenched power of the agricultural interests? Have the boom and bust periods in the state's past make it cherish, almost to the point of sacrosanctity, the stabilizing influence of an agricultural economy? Is Colorado terrified of becoming the nation's energy colony, and by using up its remaining water in agriculture, trying to prevent such a thing from ever happening? Has the wish to watch the desert bloom become, as one scornful western economist puts it, an "atavistic cultual twitch"?

Whatever the answers, the day of reckoning is drawing near. Denver and the Front Range continue to boom, more of the desert is put into bloom, the energy rush is on, and the amount of available water is steadily going down to a trickle. It is happening in Colorado, but it is a harbinger for the American West.