BOB MELVILLE guides his raft down the Colorado River as it carves its way toward the Grand Canyon. In the midst of an explanation of the geology of the 300-million-year-old cliffs that shoot up from the river, the 20-year veteran of rafting the canyon points to a more recent development in the landscape. ``We've lost two-thirds of that beach,'' he says, nodding his battered straw hat toward a steep, narrow ledge of sand on the shore. ``We used to play volleyball there; now we all huddle against the cliff and there's barely enough room for a walkway.''
Thirty miles upstream lies Glen Canyon Dam, which is widely considered the cause of loss of beaches and fish habitat in the canyon.
Built and operated by the United States Bureau of Reclamation, the 27-year-old dam created Lake Powell and provides water and hydroelectric power for much of the West. It also traps sediment that used to replenish beaches in the 292-mile stretch of river that winds through the Glen Canyon Recreation Area and Grand Canyon National Park.
The water released from 200 feet below the surface of Lake Powell emerges cold and clear, a far cry from the seasonally warm, brick-colored water that gave the river its name: Colorado is Spanish for ``colored'' or ``reddish.''
Some of the dam's effects are considered positive: The control of seasonal floods has allowed the lavender-plumed tamarisk, willows, and grasses to take root on the banks, which have become home to one of the most diverse riverside bird populations in the Southwest. Increasing numbers of trout nose through the cool, glassy pools and currents of the river, attracting fishing enthusiasts as well as migrating bald and golden eagles, who feed on spawning trout during winter.
The water released from the bottom of Lake Powell is a shockingly cold andidote to the desert heat. Many also enjoy its clarity: ``I wouldn't take a trip on a river if I knew it was going to be muddy,'' says a lawyer from Washington, D.C., as she makes camp on the river bank after a day on Melville's raft.
But studies initiated by the Department of the Interior in 1982 found that the fluctuating level of the postcard-perfect, blue-green water - which rises and falls as much as 13 feet daily with electrical demand - can strand both fish and rafters and accelerates the erosion of sand.
Particularly hard hit are native fish that proliferated in the murky, seasonally warm Colorado before the dam. Two fish species have disappeared from the stretch of river below Glen Canyon Dam and above Lake Mead, downstream from the Grand Canyon. A third, the endangered humpback chub, now has a stable population in only a few miles of the river where its waters are warmed by tributaries.
``When it dawns on people that not just some company, but the government of the United States, is knowingly destroying the resource of the Grand Canyon by the way it runs the dam, people just freak out,'' says Jim Ruch, the executive vice president of the Grand Canyon Trust. The environmental group, based in Flagstaff, Ariz., is one of many agitating for a change in the way the dam is operated.
In the face of public outcry and political pressure over the degradation of the canyon, Secretary of the Interior Manuel Lujan directed the Bureau of Reclamation to prepare an Environmental Impact Statement (EIS) last July. Because the dam was constructed before the National Environmental Policy Act was passed, no EIS was done before it was built.
The EIS process - which includes dozens of scientific studies and thousands of public comments - could lead to operational changes at the dam or to other ways of protecting the downstream environment.
But conservation and recreation advocates, impatient with what they consider the government's historic stalling on addressing the environmental problems caused by the dam, are backing recently introduced congressional legislation that calls for emergency measures to protect the canyon.
Charging that the Bureau of Reclamation ``might as well be running hundreds of bulldozers down the canyon floor daily,'' Rep. George Miller (D) of California filed a bill in Congress that would minimize fluctuations in the dam's releases and limit both high and low volume releases until the completion of the EIS - currently scheduled for the end of 1992. Arizona senators John McCain (R) and Dennis DeConcini (D) also introduced a bill to protect the canyon last month.
``[Miller's bill] presumes correctly that the Department of the Interior will not, of its own volition, take emergency corrective action,'' testified Rob Elliott, vice president of the Western River Guides Association at a House subcommittee hearing on the bill. ``We've had eight years of studies, and during this time the river has not been managed for environmental mitigation.''
And a scientist currently gathering information for the EIS, who asked not to be named, says that serious environmental damage would be done if the current operation of the dam continues until the EIS is completed.
``You'd lose beaches, that's a known fact,'' he says. ``Does that mean recreation in the Grand Canyon would end? Probably not. But from a scientific point of view, any time you lose sediment it's irreplaceable. We're finding that a lot of cultural resources are being lost. Is it irreparable to have a native American pot or a wall fall into the river? From a scientific perspective, probably yes. From a management point of view, it's debatable.''
Many power interests dispute the existence of an environmental emergency. They say that changing the flows of the river before the EIS is complete is premature:
Robert Lynch, a Phoenix attorney representing the Colorado River Energy Distributors Association, a group of nonprofit utilities that buy power generated at Glen Canyon Dam, says ``[T]his is a long-term problem'' for which he and others favor the exploration of structural changes such as dredging up sediment and re-landscaping beaches to make them more erosion resistant.
``We support the gathering of scientific data to make good management decisions,'' says Kenneth Maxey, deputy area manager for the Western Area Power Administration (WAPA), a federal agency that markets the power generated at Glen Canyon Dam. ``What we object to is going off and making decisions and changing conditions without that firm scientific data. Let's get the science done before we go off and make changes and constrain a valuable resource down there.''
And valuable it is: WAPA's revenues from the sale of Glen Canyon Dam power are projected to reach $60 million this fiscal year, Mr. Maxey says.
WAPA sells power from a system of dams on the Colorado River - 80 percent of which is generated at Glen Canyon Dam - to public utilities for an average price of slightly under a penny per kilowatt-hour.
If constant flows were mandated to protect the canyon it would spur a rate increase of an estimated two-thirds of a cent per kilowatt-hour, Maxey says.
``We recognize that changes may be made in the operations and that rates may go up,'' he says. ``We're interested in seeing the canyon preserved; we're not anti-environmental by any stretch of the imagination.''
Likewise, environmentalists emphasize they aren't advocating that the dam stop storing water or generating power. ``That would be ludicrous,'' says Mr. Ruch of the Grand Canyon Trust. ``Our goal is to change the daily operation of the dam so it's not as totally destructive of the environment as it is today.''
For Melville, who has guided people down the canyon for two decades because ``it's good for people, and it's healthy for me,'' the canyon is a sanctuary.
``This experience is more than recreational, it's spiritual,'' he says, sitting on a beach one evening, the sand still warm from a day of desert sun. ``The preservation of this place as a healthy ecosystem takes primacy over everything,'' he adds. ``In the long run, we may not even be registered as a strata here.''