This Tuesday in Los Angeles and on Wednesday in San Francisco, the Department of the Interior will solicit the public's view on whether it should protect one of the world's most revered natural treasures or literally allow it to wash away.

In a three-week series of forums that began this month in Salt Lake City, the department is taking testimony on establishing the scope of a study on the environmental impact of the Glen Canyon Dam on the famed Grand Canyon National Park, just a few miles downstream.

Each day, the federal Bureau of Reclamation releases a wall of water from Lake Powell, the reservoir of Colorado River water backed up by the Glen Canyon Dam. As this water falls through the dam's giant turbines, it generates "peaking" electric power demanded by utilities in the Southwest. Later in the day, as the demand for electricity diminishes, the flows are reduced to a trickle.

These widely fluctuating water releases are washing away the once-pristine beaches along the canyon floor and causing other problems for endangered species and recreational users in Grand Canyon National Park.

The Grand Canyon is clearly a wonder to people the world over. Dramatic canyon walls, reaching a height of more than 7,000 feet, provide unequaled vistas on the American landscape. The United Nations has selected the Grand Canyon as a World Heritage Site, one of only 12 natural areas in the United States to be so honored. The canyon is also an economic magnet for the Southwest. It attracts millions of people from all over the world each year, including thousands who float downriver in rafts, kayaks and wooden dories.

It took the Colorado River 40 million years to carve the canyon. But in just a few years the Bureau of Reclamation tamed the mighty Colorado with huge dams and literally corralled the Grand Canyon between Hoover Dam and Glen Canyon Dam.

Despite the historical and natural attractions of the Grand Canyon, a Department of the Interior study issued last year found that the Bureau of Reclamation's operation of Glen Canyon Dam was having "substantial adverse effects on downstream resources," including the Grand Canyon. It might as well be running hundreds of bulldozers down the canyon floor daily.