Alternative proposals on a major environmental controversy - how to manage Glen Canyon Dam - were presented Monday to dozens of environmentalists and electricity industry representatives.

Federal studies showed fluctuating levels of the Colorado River - resulting from the dam's power generation - destroyed Grand Canyon beaches and stranded fish.More than 15,000 written comments submitted to the U.S. Bureau of Reclamation and years of analysis at the dam near Page, Ariz., generated the alternatives.

Officials at the meeting emphasized now is not the time to choose which of the options is best.

"The natural tendency is to rush the process and begin debating the merits of particular alternatives," Bureau of Reclamation assistant regional director Rick Gold said. "We're making this list public to assure that a full range of alternatives is being considered - not to choose among alternatives."

The 10 alternatives are based in three strategies:

- Managing water releases in a way that mimics how the river flowed before the dam was built.

- Allowing water to flow from the dam in a moderated and relatively constant stream.

- Allowing amounts of fluctuation or relatively high amounts of monthly fluctuation in water levels - considered a more flexible operation.

Currently, releases from the dam have caused as much as a 5-foot fluctuation in the river's level during one day.

The alternatives were developed as part of an environmental-impact statement that will be written by the Bureau of Reclamation and nine other government agencies.

The statement "will consider the impacts of current operations of Glen Canyon Dam on downstream environmental and ecological resources in Glen Canyon National Recreation Area and Grand Canyon National Park," said Barry Wirth, spokesman for the Bureau of Reclamation in Salt Lake City.

A draft environmental impact statement is scheduled for release in July 1992. The final statement is due out in September 1993.

The alternative designed to mimic pre-dam conditions includes a plan to pump sand onto Grand Canyon beaches that have been eroded by the fluctuating water level. Equipment would be rafted down the river and sand from nearby channels pumped onto the beaches.

The pumping would take place during January and February - months when recreation use is the lowest.

A written-comment period concerning which proposals should be studied will last through April. Meanwhile, those wanting information about the studies can contact the bureau's Colorado River Studies Office in Salt Lake City at 524-4099.