Despite widespread drought in the Potomac river basin, the river is bringing an ample supply of water to the Washington area, its biggest user.

Even with traditionally high summer, the river, which begins in the mountains of Virginia and West Virginia, is providing a comfortably safe margin of surplus water for the more than 2 million people of metropolitan Washington who depend on it.

Some area water officials were fearful two months ago that by mid-summer the Potomac's flows might decline to the historic flows of the drought-stricken mid-1960s, creating the possibility that the river could not supply all the demands placed on it. That has not happened.

Instead "it look a lot better than it did a month ago," said Harry C. Ways, director of the Washington Aqueduct, which supplies the District and a small part of Northern Virginia.

"Things are not too bad now, agreed Jerry LaRue, meteorologist in charge of the National Weather Service's Washington forecasting office.

"At the moment, we don't have a critical situation," said Arthur P. Brigham, public infromation officer for the Washington Surbaban Sanitary Commission.

On July 11, the commission, which depends on the Potomac for about two-thirds of the water it supplies to suburban Maryland, installed an emergency weir, or dam, near its water intake pipes to raise trhe level of the water. On that day, the Potomac's flows was only 1.1 billion gallons daily, just a little more than half of its present flow, about 1.9 billion gallons daily.

The seeming paradox - plenty of water in the middle of a drought - has an explanation. While drought in the Shenandoah Valley and elsewhere on the Virginia side of the Potomac basin has starved the river's headwaters, close-to-normal rainfall on the Maryland side has acted as a counter balance.

Thus while the Potomac's flow during July has been only 61 per cent of the normal, right now, because of those "good, healthy thunderstorms," as one official called them, the river is beginning to flow much faster. The river may be flowing at or close to the normal August rate when the month begins next Monday officials say.

Water officials emphasized that 30 or 45 continuous days of dry, hot weather could create the crisis atmosphere of June and early July. "But," as Wayne Solley, a hydrologist at the U.S. Geological Survey's Townson, Md., water office said, "the normal pattern is you do have showers."

Officials start to get edgy when the potomac's flow drops to 1 billion gallons daily during July or August, the periods of heavy water usage. When the level drops to about 800 million gallons daily - half of the recorded maximum daily use - officials would, under an agreement now being negotiated, declare an alert, which is essentially an announcement to the public involving no restrictions. Further drops in the river's level would lead to an allocation formula, which would divide the available water among the users.

How water would be allocated between the District of Columbia, suburban Maryland and a prospective new user, Fairfax County, has engendered a bitter controversy.

Maryland and Virginia have reached agreement on a low-flow allocation formula, but the Army Corps of Engineers, which operates the District's water-supply system, says the proposed formula is unfair to D. C.

Col. G. K. Whiters, the corps' district engineer, claims that the District's share during any future emergencies automatically would decrease as suburban maryland and Northern Virginia's population grew.

Resolution to the dispute is crucial to both suburban areas.Until agreement is reached, the corps will not permit suburban Maryland to built a long-sought permanent weir, which would solve its intake problems. The corps also is holding back on approving construction of a new intake by the Fairfax County Water Authority to augment its supply from the Occoquan River.

Over the summer, Maryland and Virginia officials have wrangled with Withers at a series of meetings, most of them labeled "working sessions" and closed to the public.

At a session Monday in Annapolis Warren Rich, Maryland assistant attorney general for water resources, said, "We're getting blackamiled by the Corps of Engineers," Col. J Lao Bourassa, chairman of the Virginia State Water Control Board, accused the corps of "playing a carrot and jackass game."

As abuse was heaped on him by officials from both states, Whithers maintained calm, Bourassa pounded the table and demanded a decision "today," but Withers said the corps would make up its mind on the proposed agreement in September after a series of public hearings.

While Bourassa, in a press release last week, said Monday's meetings would be a "last attempt to move the corps to break the deadlock," he and Maryland officials agreed they could wait until September.

In June when officials feared a sharp drop in the Potomac's flow was impending, an agreement was more urgent. The unexpected current surplus has brought time.