Fairfax County police will begin enforcing mandatory water conservation regulations at noon today. Similar restrictions on outdoor water use are expected to be enacted this morning in Alexandria and will likely go into effect at noon in the city as well.

The restrictions prohibit:

Watering lawns and other greenery, except with a three-gallon or smaller container. Plant nurseries, commercial agricultural operations and golf course greens, however are not covered by this rule.

Washing automobiles, trucks and other vechicles, except from a three-gallon or smaller container or, in the case of vehicle-washing facilities, unless there is recycling equipment. However, any business is exempt if therestrictions would require the layoff of any personnel.

Washington streets, driveways, parking lots and other residential and commercial surfaces, except from a three-gallon or smaller container. The restrictions do not apply if washing is required to eliminate a hazard.

Filling or adding water to any swimming or wading pool, except for residential ones not requiring more than five gallons. In addition, pools may be filled to a leveel two feet below normal or water may be added up to the point necessary to avoid hydrostatic damage.

Any other use of the water supply for outdoor recreation.

Operating air conditioning . . . rooms below 78 degrees, except in closed systems with recirculating water.

Operation of any ornamental fountain or similar structure, unless it is part of an air-conditioning system.

Serving of drinking water in restaurants, except on request.

In addition, the Fairfax restrictions require operators of commerical and insutrial installations, apartments and condominiums to inspect their water systems by noon Thyrsday, correct any leaks and post a notice of compliance.

Appeals of any of the restrictions can be made to a board consisting of representatives from the Fairfax County Leauge of Women Voters, the fairfax County Federation of Citizens Associations and Fairfax County Chamber of Commerce. If an appeal is denied, it can be taken to the Board of Supervisors.

There are no published guidelines saying when the restrictions would be lifted. They were voted when the Occoquan Reservoir fell to a third of its capacity.

The restrictions cover all residences and businesses served by the Fairfax County Water Authority, which owns and operates the reservoir, except those in Prince William County, which has refused to impose mandatory conservation but will continue promoting voluntary efforts.

The rules, if formally adopted by Alexandria today, will cover virtually all 110,000 city residents. Fairfax's restrictrions cover nearly 400,000 county residents served by the water authority. But they do not affect the 106,000 people served by the Falls Church public utilites department, 5 department about 100 homes contnected to the Arlington County system and all those residents who have a private well supply.

Violation of the Fairfax restrictions is a misdemeanor and could result in a fine of up to $500.