Southbound waters

The Colorado River runs below Glen Canyon Dam in Arizona, slicing through rock walls on its way to the Grand Canyon. (Susan Spano / LAT / August 10, 2012)

From Glen Canyon Bridge on U.S. Highway 89, you can see both sides of an argument. To the north is placid Lake Powell, a big, blue tropical cocktail in the arid no man's land of southeastern Utah. It's Exhibit A in the case for letting 42-year-old Glen Canyon Dam stand. To the south is the Colorado River, testily emerging from impoundment, cutting through sheer rock walls on its way to the Grand Canyon, wild and free, the way nature made it.

I stood there with my brother, John, in early February, thinking about Seldom Seen Smith, the fictional mastermind of a plot to blow up the Glen Canyon Dam in Edward Abbey's 1975 novel, "The Monkey Wrench Gang."

Smith, Abbey wrote, "remembered the golden river flowing to the sea … canyons called Hidden Passage and Salvation and Last Chance … strange great amphitheaters called Music Temple and Cathedral in the Desert. All these things now lay beneath the dead water of the reservoir, slowly disappearing under layers of descending silt."

The book has achieved cult status among lovers of Utah's slick-rock plateau and canyon country. But Abbey's book never expected that nature, in the form of a blistering six-year drought, would toy with the fate of Lake Powell.

The last time the reservoir was full — at 3,700 feet above sea level — was in July 1999. Since then the drought has lowered the water level 144 feet, leaving the reservoir at about 33% capacity, shrinking the length of the lake from 186 miles to 145 miles and gradually re-exposing something remarkable underneath: the arches and spires of Glen Canyon. People travel halfway around the world to see the canyon of China's Yangtze River, doomed by construction of Three Gorges Dam. So was it any wonder that John and I felt compelled to go backpacking in little side canyons on the fringes of Lake Powell, where the water is rapidly receding? It was a chance in a lifetime to see something that couldn't be seen five years ago and may not be seen five years from now.

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Boat trip to Davis Gulch

February isn't prime time on Lake Powell, and just getting to the place where we planned to start backpacking required us to take a motorboat 90 miles up the reservoir to its confluence with the Escalante River. Then, among a maze of unmarked tributaries, we had to find Davis Gulch — a stream that enters the Escalante on the west side — take the boat as far into the channel as possible, tie up and make our way across the quicksand that tends to accumulate at the mouths of such creeks.

There, we were supposed to meet Bill Wolverton, Glen Canyon National Recreation Area's backcountry ranger, who would hike in from the west to show us around for two days.

He had responded to a request from John for information about backpacking in Davis Gulch and Fiftymile Canyon, two deeply embedded Escalante River tributaries where a red Navajo sandstone sculpture gallery similar to the one that once lined the whole of Glen Canyon is gradually being re-exposed.

Wolverton has spent the last 17 springs and autumns prowling around the Lower 48 for the National Park Service and can scale sheer canyon walls without working up a sweat. He almost single-handedly launched an effort to eradicate invasive, nonnative plants from the Escalante River canyons he loves.

Just don't call the big body of water at his doorstep Lake Powell. "It's not a lake," he insists. "Lakes are natural features."

Before I could formulate reservations — How cold would it be in southeastern Utah in February? What if it snowed? How far would we have to hike and how many nights would we camp? — Wolverton and John had started planning the trip.

After taking in the view from the bridge, John and I stopped at the nearby recreation area's Carl Hayden Visitor Center. To enter, we had to pass through a security system tighter than any I've seen at airports, instituted a few years ago to deter terrorist attacks on the dam. We apprehensively noted the posted weather forecast — temperatures between 35 and 49 degrees, with rain or snow in the offing. We studied a 1990 topographical model of Lake Powell, now hopelessly anachronistic because of shrinking water levels, and took a short tour of the 710-foot-high dam, completed in 1963.

It was led by a sandy-haired young man who told us the concrete of Glen Canyon Dam was good for two millenniums but sediment buildup could render the dam inoperable in 700 years.

Environmentalists are less conservative. They say silt coming in from the reservoir's tributaries could clog it up in a few centuries, never mind that the dam has already damaged habitats and geology at the Grand Canyon 100 miles downstream.

Partly for this reason, environmentalists with cooler heads than Seldom Seen Smith have advocated decommissioning the dam and draining the reservoir — a drastic measure that, nevertheless, has been carried out in the last few decades at about 100 dams across America.

For the thirsty dwellers of the dry Southwest, the specter of losing a water and energy source may be upsetting. The dam's power plant produces $90 million of electricity a year, and Lake Powell serves as a holding tank for Lake Mead downriver, a big water supplier to Southern California. Beyond that, the reservoir has undeniable recreational value. But since the onset of the drought, visitation to million-acre Glen Canyon National Recreation Area has decreased from 2.6 million in 1999 to 1.8 million in 2004.

Meanwhile, the National Park Service, which manages the recreation area, is extolling the virtues of newly reclaimed sights while busily extending boat launch ramps at northerly marinas, such as Bullfrog.