Loudoun supervisors said yesterday that the county will become the first in the region to approve mandatory restrictions on water use because of the drought, but the agencies that supply water to most of the Washington area said such measures are not yet needed elsewhere.

The hot, rainless weather is expected to continue through this week, though there is a slight possibility of isolated showers today--not nearly enough rain to make up for the area's shortfall, said Andy Woodcock, a National Weather Service meteorologist.

Forecasters said temperatures will remain in the 90s with high humidity for the rest of the week. The high yesterday at Reagan National Airport was 97, five degrees shy of the record.

During the last 12 months, Reagan National has received nearly 14 inches less precipitation than the normal 39 inches. In only two months of the past year has precipitation been normal or above normal.

While saying that mandatory restrictions should prove unnecessary in most areas, the three agencies that supply most of the region's water did urge people to conserve water by avoiding excessive watering, repairing leaks and running dishwashers and washing machines at full capacity.

This month, Poolesville imposed mandatory water restrictions that remain in effect. And Montgomery County Executive Douglas M. Duncan (D) has asked county residents to begin voluntary water conservation.

A majority of the nine-member Loudoun Board of Supervisors said yesterday that they would impose the mandatory restrictions during their regular Wednesday meeting. The restrictions--including limits on washing cars, operating ornamental fountains, watering lawns and serving water in restaurants--would affect 30,000 homes and businesses in eastern Loudoun served by the Loudoun County Sanitation Authority.

"It's really dry. It's really bad," said Loudoun Supervisor Eleanore C. Towe (D-Blue Ridge). "You can just look around you. The streams are down to nothing. Obviously there's a problem."

The proposed restrictions on watering lawns and landscaping would affect houses every other day, depending on whether they have odd- or even-numbered addresses. When the restrictions are in place, residents could be fined as much as $500 for violations.

"We aren't asking for customers to allow their shrubbery to die," said Dale C. Hammes, general manager of the Loudoun Sanitation Authority. "We're simply asking them to water on different days so that the demand will be lowered and the demand will be stabilized."

The county had been under voluntary restrictions. But Loudoun water officials said they have proved insufficient.

The problems stem from reduced water levels at the Goose Creek Water Treatment Plant, which is in Loudoun but is operated by Fairfax City. Loudoun pays the city for treated water from the creek.

The Loudoun Sanitation Authority said that if restrictions are not imposed and there's not much rain, water levels in Goose Creek could reach dangerously low levels. Fairfax City has instituted voluntary water restrictions because of concerns about the creek.

Loudoun and Fairfax City also obtain water from the Potomac and Occoquan rivers via Fairfax County's water authority. But Loudoun does not have the capacity to pump enough water from Fairfax to make up for the reduced levels at Goose Creek. Loudoun's sanitation authority is building a new pipeline to do that.

The three other water suppliers--Fairfax County Water Authority, the Army Corps of Engineers and the Washington Suburban Sanitary Commission--said they had enough capacity to withstand the drought. They have released water from reservoirs into the Potomac to make up for reduced water levels there.

"We don't need water restrictions," said James A. Warfield Jr., executive officer of the Fairfax County water authority, which supplies about 1.2 million people in Northern Virginia. "We've done a lot of planning over the last couple decades, planning water storage. But at the same time, we encourage people always to be prudent and not wasteful."

Staff writer D'Vera Cohn contributed to this report.

SOME ADVICE ON CONSERVING WATER

The average person uses 70 gallons of water a day. Local governments and utilities suggest these ways of cutting back.

* Repair leaks in toilets and faucets. Check hose connections to make sure they are tight. Replace worn-out washers.

* Fill dishwashers and washing machines to full capacity. Avoid using extra cycles. When washing dishes by hand, fill the sink, rather than letting the water run.

* Avoid excessive outdoor watering. Most lawns need an inch of water per week to stay healthy. Reduce evaporation by watering in the evening or early morning. Avoid using the water hose to clean areas that could be swept with a broom. When washing your vehicle, run the water only to wet it and to rinse it off.

* Don't let water run in the sink. When shaving or washing hands, fill the sink. When brushing teeth, fill a cup with water. Instead of cooling water by running the faucet, keep a container of cold water in the refrigerator.

* Install water-saving devices. A faucet aerator can reduce the amount of water used. A plastic jug filled with water can displace water in a toilet tank. A low-flow shower head cuts down on the seven to 10 gallons a minute that are used in a shower.

SOURCE: Public utilities