A meeting called by Rep. Herbert E. Harris (D-Va.) in an effort to resolve Northern Virginia's water crisis ended yesterday with most of the principals headed on different courses.

"It's absolutely essential that we try to cut through the red tape . . . and come up with an immediate solution to the immediate problem," Harris told the group. But even before the 1 1/2-hour meeting broke up, it was clear there was no consensus on who should do what to enable the Fairfax County Water Authority to move ahead with plans to tap the Potomac River.

With its Occoquan Reservoir continuing to decline and its 616,000 customers in Fairfax and Prince William counties and Alexandria under restrictions on outdoor water use, the authority wants to use Potomac water as a supplement to the reservoir.

But the Army Corps of Engineers will not grant a permit until Virginia - along with Maryland, which already uses the Potomac - agrees to preserve the District of Columbia's share of river water into the future.

Harris earlier had proposed a conditional permit that would permit the water authority to build the Potomac tap, but not use river water during low flow, when demand might exceed supply.

Water authority chairman Fred C. Morin said at the meeting the agency "would be amenable" to such a solution. But State Water Control Board officials said they would oppose any concessions, and insisted that Virginia was entitled to Potomac water at low as well high flow.

"I'm going to recommend that the State Water Control Board ask Virginia to sue the Army Corps of Engineers," board vice chairman Leo J. Bourassa declared.

"A law suit would be totally counter-productive," claimed John F. Herrity, chairman of the Fairfax County Board of Supervisors.

Herrity called instead for a metting of the governors of Virginia and Maryland, District of Columbia Mayor Walter E. Washington and the Secretary of the Army - in hope they could expedite approval of a permit.

"What's that going to accomplish?" Harris asked after the meeting was over. The congressman, who represents southern Fairfax, Price William County and Alexandria, said more could be accomplished by him dealing directly with Secretary of the Army Clifford L. Alexander Jr.

"Let's see how long it takes for a congressman to get through to the Secretary of the Army," he said at the meeting's conclusion.

Prince William's representative at the session. Supervisor Kathleen K. Seefeldt said, "If the Fairfax County Water Authority wants to expand its service area, that's fine. We're going it alone."

She said Prince William's top priority is not the same as Fairfax's or Alexandria's. "Prince William," she said, "is interested in going ahead with its dam" on Cedar Run upstream from the badly depleted Occoquan Reservoir.

Half of Prince William now depends on the Fairfax water authority, but if the Cedar Run dam is built, Mrs. Seefeldt said, it will be able to supply all the county's needs to the year 2000.

Rep. Ray Roberts (D-Tex.), chairman of the House water resources subcommittee and a resident of Fairfax, proposed a regional solution that has been abandoned by virtually all local leaders."I think we ought to start building some dams," Roberts, who was the invited guest of Harris, told the group.

As for the Potomac pipe that Northern Virginia leaders are trying to get the Corps of Engineers to expendite, Roberts said, "I would say you're not going to get it." He recalled that a dam first approved in 1955 still has not yet been built because the environmental impace statement is tied up in court.

Under repeated questioning by Harris the corps' district engineer, Col. G.K. Withers, said he could not promise a definite date for the impact statement on the Potomac pipe. He said the draft was unacceptable and was sent back to the contractor for revision.

After the statement comes back, he said, there will have to be more review, public hearings, and then more review before the document, assuming it is approved, can be sent to the Council on Environmental Quality, where it must remain for 30 days before the corps can act on the permit application.

Unless construction begins by January, the Potomac facility will not be ready by the summer of 1980, when the water authority says it may not be able to meet all demand through the Occoquan.

The Occoquan already has been strained by an extended drought, and despite restrictions on outdoor water use, in effect for more than a month, the reservoir has continued to decline. It now contains less than a quarter of its usable storage.