California, I read, is now in the fifth year of its worst drought ever. By now it's an old story on the West Coast: Rain and snow are nowhere to be seen, and this has dismayed a lot of people, especially the big-time farmers who need a great deal of water to irrigate their crops of lettuce and so on.

What happens in California is usually California's own business, at least for those of us who live on the opposite coast, but this time it's harder to shake the feeling that this drought will be widely felt. Water shortages are starting to pinch California severely, and since the state grows half of all the fruits and vegetables sold in America, the shortage of water could boost produce prices in supermarkets across the country.This impact, however, could prove trivial compared with the long-term impact on California's own future.

If the drought should be heralding a permanent shift in the California climate, as some speculation suggests, and if consumption patterns did not dramatically change, the state's water-dependent agriculture might have to contract. The spectacular growth that has boosted California's population to 30 million would be sharply curtailed, with severe impacts on the state's economy.

California depends heavily for its water on runoff from melting snow, but the snow has been scarce. This month the Sierra Nevada snowpack stands at a mere 13 percent of normal, and the state's reservoirs are said to be down to barely a third of their capcity.

A few days ago, in a controversial move to conserve supplies, the state ordered a halt in sending water to farmers from the sprawling California Central Water Project. Major cities appeared certain to tighten up on water rationing, which is already widespread. The state is already exploring ways to cut back water demand, and the new governor, Pete Wilson, may have to invoke a state of emergency.

Like the rest of the American West, California has experienced droughts before, always managing to bounce back more vigorous than ever. It has been able to count on its vast size, its immense mountain snowpacks and its buoyant, diverse economy to help it keep nature at bay. Its cities, like other metropolises of the West such as Phoenix and Denver, have been able to grow at a phenomenal pace, largely because they relentlessly tapped available water sources and could spend huge sums to transport water across vast distances.

One result for California has been an exploding population - with its subdivisions, airports, malls, golf courses and other amenities - that has sent water demand soaring. In normal times, with at least an average water flow from the mountains, the booming population might pose no great threat. Yet five drought years have heavily taxed supplies, and have shown that long-term water planning, even by outsized California standards, has not been adequate.

California's drought should stand as a clear, early warning to the rest of the arid West, where the expansion of metropolitan areas has rolled on almost unchecked. Even if the water shortage in California should ease, the state's supply of fresh water is finite. Absent revolutionary techniques for desalination of sea water on a large scale, this imposes limits on how much the state can grow.

Like much of the West, California has managed to do rather nicely for itself by flouting these limits and manipulating nature to serve its burgeoning population; but this cannot go on forever. The metropolises of the West have boomed in spite of, and not because of, their modest water supplies. With California's drought as a possible foretaste of worse to come, those states need to give more attention to limiting water consumption and stretching their limited water resources.

The water outlook for the West is hardly all bleak, of course. As with any other resource, dwindling supplies and rising prices have a wonderful way of encouraging farmers and governments to do what they should have done all along, and that's conserve. But neither should the signals from California be ignored. If its people have to accommodate themselves to a semi-desert way of life, the rest of the West may have to adjust, as well.