JENNIE LAKES WILDERNESS — It is the last weekend in November, and the road and trail have led us from summer through fall and into the realm of winter.

It seemed like summer at the coast, where warm breezes blew, and where my son and I began this quick backpacking trip in the early hours. It was autumn when we drove through the middle elevations of the Sierra's western slope, where the dead leaves of deciduous trees carpeted the ground with yellow and brown. And it is winter here as we hike more than 8,000 feet above sea level. There are no obvious signs of the season save one: It is just past noon, the warmest this day will get, and the air temperature is in the mid-40s.

As we trudge upward along the dusty path, we leave the shade of scattered pines and cross an exposed slope of shattered granite that reflects the glare of sunlight. The open slope grants a view to the north. And what we see there is an image from the restless nightmares of California's water managers.

In the distance stand the peaks of the Monarch Divide, a winding crest of crags and fluted summits rising high above the Kings Canyon drainage. It is one of the most dramatic instances of topographic inequality in North America: From the 12,000-foot peaks of the divide, the land falls away in a series of steep and nearly unbroken slopes to the bed of the South Fork Kings River nearly 8,000 feet below.

And there is not so much as a glimmer of white anywhere to be seen on those slopes. Not a single patch of snow or ice breaks the gray monotony of naked rock.

As our trail leads us higher, eventually depositing us on the shore of gemlike Jennie Lake, we pass through the zone of greatest winter snow accumulation on the western slope. In a normal winter, it is common for the ground here to be blanketed already by Thanksgiving, and in the depths of February and March the snowpack may be 30 feet deep. But now it is all dust and duff. The abundant moisture contained in the snowpack, released slowly as the drifts melt, supports a magnificent forest. When we pitch camp near the lake, our tent is shaded by huge specimens of red fir. As the sun disappears behind a ridge, we build a small fire for warmth using their fallen branches. In a sense, we are turning last year's snow into heat.

The winter snowpack, multiplied along the 400-mile length and 50-mile width of the Sierra, also hold the key to California's vast water storage and distribution system. Sierra snow holds more water than all the state's storage reservoirs combined, and the system of dams and aqueducts is designed to capture and move all that snowmelt as it flows toward the sea. No snow means rapidly emptying reservoirs.

Given that half the Sierra precipitation falls between January and March, it is early yet to conclude that the picture this year is grim. But last year was a dry one in the Sierra; on April 1, the date on which the snow accumulation typically is greatest, the statewide snowpack was only 40 percent of average. It was essentially gone by June 1. And it has yet to begin its slow reconstitution.

A little more than a week before this post-Thanksgiving alpine trek, at a breakfast meeting of the Association of Water Agencies of Ventura County, managers of the county's three biggest water agencies had reiterated their call for a voluntary 10 percent reduction in water use by their customers.

"If we do that now, we won't have to go to rationing," said Don Kendall, general manager of the Calleguas Municipal Water district. Joining him in that warning of potential shortages were Steve Wickstrum, general manager of the Casitas Municipal Water District, and Dana Wisehart, general manager of the United Water Conservation District.

They were motivated in part by low rainfall in their own region, crucial to the supplies of Casitas and United, but also by potential reductions in the amount piped south by the State Water Project — water that originates, for the most part, as snow in the Sierra. Some of those pending cuts are due to endangered-species protections, but drought also is playing a role. And beyond the immediate shortages and disruptions looms the bigger issue: the likelihood that in an era of warming climate, the anemic Sierra Nevada snowpack of 2006-07 will be the norm, not the exception.

We rose shortly after dawn, and quickly built another small campfire to ward off the sub-freezing chill. A coyote barked and howled briefly across the lake, but otherwise the forest was silent. No birds, no squirrels, no sound of anything but the crackle of burning twigs. It's as if everything was waiting — waiting for snow.

— John Krist is a senior editor and Opinion page columnist for The Star. To read previous columns, visit www.johnkrist.com. His e-mail address is jkrist@VenturaCountyStar.com.