The Army Corps of Engineers is not worried about supplying the Washington area with water now, recently melted snow and high water tables combine to give the Engineers confidence. But next summer there could be trouble, they say.
In 1974 there were 13 days during June, July and August when the extraction of water from the Potomac River exceeded the lowest flow of record in 1966.
"If the low flow of the Potomac River is under 400 million gallons per day this summer, then there's trouble," said Harry Ways, the Army Corps of Engineers chief of the Washington Aqueduct Division.
Ways cautioned on making any predictions, but also said the Metropolitan Washington Council of Governments predicts a 3 to 4 per cent rise in population per year for the area which means a 3 to 4 per cent rise in water demand per year.
In 1975 - the latest year for which figures are available - more then 74 per cent of the area's water came from the Potomac. The daily withdrawals from the river averaged 315 million gallons.
Sightly more than 13 per cent of the area's water was withdrawn from the Occoquan Creek, a tributary of the Potomac. The daily withdrawals from the creek averaged 56 million gallons.
The northern suburbs of Washington, which got just over 10 per cent of the area's water, drew their supplies from the Patuxent River. The daily withdrawals averaged 45 million gallons.
Goose Creek in Loudoun County supplied almost 2 per cent or 7.5 million gallons on daily average.
Smaller quantities, less than 1 per cent or 3.7 million gallons per day, came from wells and reservoirs in outlying areas.
The 1975 total average withdrawals from the Potomac River, Occoquan Creek, Patuxent River, Goose Creek and various well and reservoir systems in 1975 was just over 427 million gallons.
Under a complex plan, known as the Potomac Low Flow Allocation Agreement, the Washington Suburban Sanitary Commission, the State of Maryland and the Commonwealth of Virginia have agreed to limit the amount of water they withdraw during period when the Potomac is too low to fill the demand. The other major water agency, the Corps of Engineers, has not yet signed the agreement.
The Corps needs congressional authorization to sign and that has not yet been forthcoming. The authorization was part of a large Senate water resources bill last year.
Chairman of the Senate Water Resources Subcommittee, Sen. Mike Gravel (D-Alaska) said last May that he was aware the area needed the Corps' cooperation but said he did not want to separate the authorization from the water resources bill because "the House is extremely reluctant to deal with the individual bills on Corps of Engineers projects."
Other plans to ease the area's water shortage are proceeding, but slowly.
For example, a plan for the town of Leesburg, Va., to withdraw up to 3 million gallons per day from the Potomac has been postponed for at least a year.
A Potomac estuary piolot water treatment plant is not expected to be built until 1983 or 1984, according to a Council of Governments official.
The Potomac estuary pumping station, which was included in the District of Columbia's fiscal year 1976 budget, is expected to be delayed at least a year.
Whitey Secor, the Council of Government's liaison to the U.S. Soil Conservation Service, commented that right now "with the ground water supply so good and a good stream flow, we wouldn't have any shortages."