At Monterey Bay, commercial salmon fishermen return disconsolately with empty nets. A hundred miles south on the California coast, the freshwater table has sunk so far below sea level that town wells have been invaded by salt water. On a Los Angeles patio, a swarm of voracious ants envelop a scrap of bone discarded by the family dog. On the Great Plains, the thin soil cover is ripped away by swirling windspouts reminiscent of the Dust Bowl.

"The heart of the West is a desert, unqualified and absolute," the late Walter Prescott Webb wrote two decades ago in an article that was decided by Westerners who thought they had conquered their environment.

Now the supposedly vanquished forces of nature have arisen and the desert is closing in. Even Californians, long the most favored of Westerners, are beginning to suspect that the good life may be going, going, gone. It is a suspicion which does not prevent 3 of 4 Californians surveyed by pollster Mervin Field from saying that California remains "one of the best" places to live. But a popular gas company billboard in southern California conveys another message. Across the picture of a man showering, the billboard urges: "Sing shorter songs."

For a returning Westerner who spent 7 years in what he used to think of as the effete East, this billboard is a disquieting sign of diminished expectations.

Westerners, even more than other Americans, always thought of themselves as a people who could do anything. The example favored in Western textbooks and in Western schools was of the Mormons, who literally made the desert bloom in the arid flatlands around the Great Salt Lake. Those who did not make the desert bloom, like the Indians who tried to live with it, were always suspect in the West. "Develop and conquer" might well have been the motto of the region.

Both the development impulse and the optimism about the good life were strongest in California where, in the words of Carey McWilliams, "the lights went on all at once, in a blaze, and they have never been dimmed." Now the optimism has been diminished by reality and the development slowed down by events. Along the California coastline, building has been brought to a near-standstill by the California Coastal Commissions created by vote of the people in 1972.

A real estate saleswoman, explaining the location of various homesites to a prospective buyer in a California coastal town, says matter-of-factly, "I assume you don't want to build before 1980 at the earliest." The would be buyer stares in disbelief and walks out of the office. As a true Californian, he wants to build immediately.

There are other harbingers for the returning Westerner, other signs the land may have reached its limit.

California's most important industry is agriculture. Last year the state's farmers planted 6.6 million acres of crops with a total value of $2.6 billion. This is less than a 1 per cent increase in two years, but pesticides used on this land to maintain this high standard of production have increased 75 per cent during the same period, to a total of 83 million pounds of pesticides in 1976.

The small towns and cities throughout the mountain West are steadily losing population, even their chambers of commerce now concede. But billboards en route to the Grand Canyon still advertise "Desert Land Cheap." Recently, all the national forests in Arizona and New Mexico were closed because of extreme fire danger that could last to the end of the year or beyond.

In Las Vegas, a weary driver arrived without a reservation at a hotel on the Strip usually booked full at this time of year. "Do you have any rooms?" he asked. "All the rooms you want," replied the desk clerk. "I don't know what's happened to the people."

Lake Shasta, largest reservoir in California and the most important source of water for the agricultural economy, is less than one-quarter full. The lake has dropped 172 feet and no longer possesses sufficient cold water to save the salmon's spawning run this fall. Oroville Reservoir, the state's second largest, is one-third full and has dropped by 200 feet. Unless the drought cycle ends this winter, Oroville may go dry next spring.

LATE IN THE 19th Century an Irishman by the name of Tiffin Patrick Cannon left Sacramento because of the floods that then recurred regularly there. He settled on a farm 40 miles away, above a bend in the American River known as Salmon Falls. Three-quarters of a century later. Salmon Falls was flooded deliberately to create Folsom Lake and help prevent flooding in the Sacramento area. Tiffin Patrick Cannon was my grandfather. Today, several acres of his one-time farm are out of water again as Folsom Lake steadily retreats from what used to be its shoreline.

What has happened in California is more than a drought. It is a change in the fundamental mind-set of a people who acted as if they believed that the supply of water, energy, shoreline, fish, wildlife, crops and forests was inexhaustible. In past years, Californians always talked about when something would happen -- when we get this development going, when we build this dam, when this freeway goes through. Now, the word is "if," not "when." And the big "if" concerns the water supply and the energy and fuel supply after 1977.

Of course, there are those who say that there is nothing to worry about, who point out that the state recovered from a severe drought in the 1930s. The comparison does not stand up. California's present population of 21.5 million is four times the state's population in the mid-'30s, and Californians suffered from the ravages of the Dust Bowl migration and the Depression until World War II. This time the damages to the land, and to the economy, could prove beyond repair.

Even a winter's long rainfall would not restore the expectations of ever-expanding progress that used to prevail. That expectation was a sort of guns-and-butter attitude that the West could have all the development it wanted, set aside all the beach and parkland it needed, use all the water it desired.

In the late 1960s, for instance, conservationists within the administration of Gov. Ronald Reagan were able to persuade Reagan to support and sign legislation preserving California's remaining wild rivers. Now, a bill that would remove many of the protections is moving with bipartisan support through the California legislature.

IN ONE SENSE, the environmentalists should be the heroes of the hour. After all, it was they who warned about future scarcities and about the costly waste of endless freeways and urban sprawl. Mostly, it was conservationists who talked about the foolishness of building recreational communities in second-growth forests around artificial lakes where the water supply could not be sustained.

Instead, the environmentalists are the villains. Partly, this is because of a lingering Western conviction that development is the solution as well as the problem. Partly, it is because the environmental movement crested early in California, and environmentalists hold important positions in state and local administrations here. Some Californians hold them responsible simply because they are in office but are as powerless as anyone else to stave off natural disaster.

At the same time, the scapegoating of conservationists has been enhanced by their growing alienation from one-time allies in the labor movement. John Henning, president of the California Labor Federation, says that many environmentalists are "cultists" who will bring "absolute death and destruction to the economic growth and future of this state." The AFL-CIO lobbyists in Sacramento have worked with industry to kill legislative attempts to emulate Oregon's law banning throwaway containers. A group called the Council on Economic and Environmental Balance has united big labor and big business in a mutual push for development.

Many Californians simply seem confused about the possible solutions to their problems, as does their government. As a recent article in the conservationist magazine Cry California puts it:

The governor's office, at the moment, is working on energy and resource-conserving appropriate technologies and simultaneously figuring out how to bring energy and resource-wasting heavy industry to California. The legislature is considering agricultural lands preservation bills and, at the same time, perpetuating the transportation policies that encourage urban sprawl."

This schizophrenia is even more pronounced in water policy. Recently, a number of northern California communities ended or curtailed water rationing because water users had cut back so much that the water districts were losing revenue. In Los Angeles, the experts anticipate that a mandatory 10 per cent water cutback now in effect won't save anything because city residents already have made a 20 per cent voluntary water use reduction.

While everyone sings shorter shower songs, southern Californians otherwise are responding to the crisis with a burst of hedonism reminiscent of a sailor's last fling ashore. Big cars are selling briskly in Los Angeles, even with the strict gas consuming air pollution controls required in California, and the 55-mile-an-hour speed limit is a bad joke. On the Los Angeles freeways, the speeding motorists are aided by radio traffic tie-up reports from helicopter pilot Gary Francis Powers of U-2 fame.

The big fad in California now is vans, campers, jeeps and an indescribable variety of front-drive and off-road vehicles. Carwashes are closed through much of the West (a sign on a car wash in Boulder City, Nev., near Lake Mead, says "No Water, No Wash"), but they are doing a lively business in Los Angeles. One prominent car wash, open until 9 p.m. every night, closes on Wednesday, which it proclaims as "C-day," announcing, "We're doing out bit for conservation."

IT WOULD BE WRONG to say that the returning Westerner finds everything changed for the worse Lake Tahoe is no longer the crystal pool of boyhood memory, but it is less polluted than it was in the late 1960s, before rudimentary interstate pollution controls were enforced. There are fewer Western rivers that have water in them, but many of these flow clearer than they once did. Rainbow trout are fished out of the Truckee River by the creel-full in downtown Reno. The sewage-caused stench which once permeated the eastern shore of San Francisco Bay has been cleaned up. These are welcome signs of environmental progress in a time of drought and scarcity.

They are welcome signs, but they are not enough. In Los Angeles, a radio station now offers the prize of a weekend in Detroit. The fishing boats return empty to Monterey Bay. In the land where Tiffin Patrick Cannon lies buried, an hour's drive from Sacramento, only the cemetery is green.

"The overriding influence that shapes the West is the desert," Walter Prescott Webb wrote prophetically in 1957. "That is its one unifying force. It permeates the plains, climbs to all but the highest mountain peaks dwells continually in the valleys. The desert is the guest that came to dinner, never to go away."