A chasm has opened between the Interior Department and the Department of Energy over the future of Glen Canyon Dam.

Nobody's going to tear down the dam. But if the Interior Department has its way, the dam's operations may be changed to lessen environmental harm to the Grand Canyon.A five-year investigation of damage to the Grand Canyon caused by Glen Canyon Dam was completed in February. It concluded that fluctuations in water released from the dam permanently damaged Grand Canyon National Park, and that the damage is continuing.

Flood releases rip out beaches and riverside plants, the report says. But the beach sand isn't replaced because silt backs up behind the dam.

Flood releases double the risk of boating accidents, as the river level can quickly change by 13 feet, and flow variations harm some fish by stranding them or changing the type of habitat they need.

A federal Executive Review Committee has now analyzed the 350-page Glen Canyon Environmental Studies and released recommendations. The committee had representatives of three Interior agencies - the Fish and Wildlife Service, National Park Service, and Bureau of Reclamation - and the Western Area Power Administration, part of the Energy Department.

The departments agreed that the dam affects the natural resources and recreation downstream.

According to the report, all parties agreed additional studies are immediately needed on the impact of fluctuating flows. They also called for conservation efforts to protect the endangered humpback chub.

They eventually concurred "after extended discussion" that such studies should be paid for as part of the dam's normal operating costs.

All members of the review committee agreed that for the time, no more than 31,500 cubic feet per second should be sent through the dam; exceeded only for emergencies or to reduce dumping.

The committee disagreed on two crucial issues about operating the dam between now and the time the new studies are completed:

- Establishing a minimum flow.

- Setting limits on water fluctuations.

The committee's Interior Department members said an interim minimum flow should be established. For the period April 15-Oct. 30, it would have 5,000 cubic feet per second during weekends, a weekday minimum of 3,000 cfs, a daily average of at least 8,000 cfs, and a requirement to match natural fluctuations. For the rest of the year, a minimum 5,000 cfs would be maintained.

Flows could be cut during an unexpectedly low runoff, probably about once a decade.

The committee could not agree whether an environmental impact statement, with its "full public involvement," is needed if changes are made.

The report points out that the mandate of the Western Area Power Administration, which markets electricity generated by the dam, involves using "as much water as possible for power generation, and minimizing releases that exceed the capacity of the powerplant."

WAPA must try to get the maximum value of the power generated, by producing it at times of peak demand.

So WAPA filed a "minority opinion" in which it strongly objects to changing the dam's rules of operation and to setting new minimum flows.

"The proposed new minimum flow levels violate the provisions of the Colorado River Storage Project (CRSP) Act," says the minority report.

The National Park Service has a different view. Its statement says, "NPS believes that Glen Canyon Dam has significant adverse effects on resources below the dam." It wants an environmental impact statement, as well as changes in dam operations.

To solidify Interior's position, Assistant Secretaries J.W. Zigler and William P. Horn signed a directive June 16,. It authorized studies of low and fluctuating releases, focusing on endangered fish, trout and beach problems; and a detailed economic analysis of various options of running the dam.

Money for the new studies will come out of power revenues, the directive says.

According to Dave Wegner, the expert with the Bureau of Reclamation in Salt Lake City who managed the Glen Canyon Environmental Studies, the new studies are supposed to be worked in with the dam's flows. WAPA and Interior will try to agree on it. But in case of an unresolvable conflict, Interior will make the decisions, not WAPA.

Interior Department Regional Solicitor Lynn R. Collins, Salt Lake City, studied the WAPA legal objections. Collins concluded that the department does have authority to change the dam operations if there are well-supported reasons "such as resource considerations."

With so much controversy swirling, most likely an environmental impact statement will be written on the operation of the dam. Then anyone - even the private citizen - will be able get to get his oar in the water.