Loudoun County supervisors yesterday approved mandatory water usage restrictions as a result of the prolonged drought, including limits on washing cars, watering lawns and serving water in restaurants.

By an 8 to 1 vote, Loudoun became the first Washington area county to impose restrictions, saying they were necessary to avoid depleting Goose Creek, a key source of drinking water.

The water regulations will begin Aug. 1. They will affect residents who receive their water from the Loudoun County Sanitation Authority, which serves about 30,000 households and businesses in eastern Loudoun.

Most of western Loudoun relies on wells, and Leesburg has a separate water supply system. Round Hill, which has its own water system, has lifted mandatory restrictions that were in place previously.

The drought has had a pronounced effect on Loudoun, yellowing lawns and fields and drying ponds and streams. During the last 12 months, Reagan National Airport has received nearly 14 inches less precipitation than the typical 39 inches. In only two months of the last year has precipitation been normal or above.

"There is a water crisis in this county," said Supervisor Helen A. Marcum (R-Catoctin). "And I only think we're starting at the tip of the iceberg."

Also yesterday, Loudoun supervisors asked Gov. James S. Gilmore III (R) to petition the U.S. Department of Agriculture to declare Loudoun a drought disaster area and make emergency assistance programs available to county farmers.

Supervisors said it was necessary to limit watering lawns and landscaping with a hose or underground sprinkler system to every other day. They also banned washing cars--except by using three-gallon containers or going to facilities that recycle water--and prohibited the operation of ornamental fountains. Supervisors also said that restaurants should not serve water unless patrons request it. County Administrator Kirby M. Bowers said that he had ordered a halt to watering at county facilities.

Supervisors said they would consider imposing even tougher measures in September if the new restrictions do not significantly cut water use and if the drought continues.

In addition, supervisors said they would send a letter to Fairfax City, which also uses Goose Creek for drinking water, and to other Loudoun towns, asking that they impose mandatory water restrictions. Fairfax City is under voluntary restrictions.

The Loudoun County Sanitation Authority has been directed to notify its customers of the water restrictions by July 30. The Sheriff's Office will enforce the restrictions, issuing warnings to first-time offenders. Repeat violators will be charged with misdemeanors, punishable by a fine of as much as $500.

The restrictions came at the request of the sanitation authority, which has grown increasingly concerned as water levels in Goose Creek have dropped and demand has increased--despite voluntary restrictions being in place.

"It's a fairly serious situation," said Dale C. Hammes, general manager of the Loudoun Sanitation Authority. "Customers are trying to make up for what Mother Nature is not doing."

Goose Creek is a source of drinking water for part of Loudoun and for Fairfax City, which treats the Goose Creek water and sells it to Loudoun. Loudoun also buys water from the Fairfax County Water Authority, which gets its water from the Potomac River. Fairfax County water officials have urged their customers to be prudent in their water use but have not recommended any restrictions.

The Loudoun Sanitation Authority does not have enough pipeline capacity to rely on water from the Potomac. Additional capacity is under construction and is expected to be completed by the end of the year.

Some supervisors raised concerns that heavy development is straining the water supply.

"The real problem I have with this is I don't think it goes far enough," Supervisor Scott K. York (R-Sterling) said of the restrictions. "Our building permits are stacking up. . . .We have to make sure we have the adequate resources."

Supervisor Steven D. Whitener (R-Sugarland Run), the only one to vote against imposing the restrictions, said that instead of such measures, officials should have increased water bills as an incentive to use less.

"It's a big hammer when you're going to fine people $500 for watering their lawn on the wrong day," Whitener said.

Meanwhile, some residents of Ashburn Farm are complaining about discolored and smelly water from their taps, something that could be related to low water levels or to refilling a storage tank, officials said.

Authority officials said that the water was safe to drink and that the problems were temporary. But that did not satisfy residents.

"It's an ongoing problem," said resident Debbie Walls, 42, who started using bottled water when she discovered the discoloration last week. "Most of us, when we get the dirty water, we don't drink it.

Slowing the Flow

Under water restrictions effective Aug. 1, the 30,000 households and businesses served by the Loudoun County Sanitation Authority may not:

* Water lawns or landscaping daily except using three-gallon containers. (Customers with addresses ending in odd numbers may water with a hose or sprinkler system on odd-numbered days of the month, those with even-numbered addresses on even-numbered days.)

* Wash automobiles, trucks and trailers except using three-gallon containers. This does not apply to commercial wash facilities that use a recycling system.

* Fill swimming or wading pools unless they are already more than three-quarters full.

* Serve drinking water in restaurants unless it is specifically requested.

* Operate ornamental fountains.

The first violation may bring an oral warning from the Sheriff's Office. Additional violations are misdemeanors carrying a fine of as much as $500.

These restrictions do not apply in Leesburg, which has a separate water supply, or in western Loudoun, where residents are served by town water systems or private wells.

CAPTION: Beaver Dam Creek Reservoir near Ashburn is about half-full as a result of prolonged regional drought.

CAPTION: Drought has drained Beaver Dam Creek Reservoir, above, and Goose Creek, which supplies eastern Loudoun.