Northern Virginia's water emergency appears to be driving neighboring jurisdictions farther apart rather than bringing them closer to either.

Although Fairfax and Prince William Counties and Alexandria all depend on the steadily receding Occoquan Reservoir for water only Fairfax County has served notice that mandatory conservation will be imposed starting this week.

Alexandria has yet to pass an ordinance that would permit restrictions to be imposed, and only reluctantly have the city council and the Prince William Board of Supervisors agreed to put the issue on their Tuesday meeting agendas. Leaders of the two jurisdictions think Fairfax County, acting on its own is ignoring crisis guidelines that everyone presumably would follow.

A meeting called by business leaders on Friday encourage a single regional solution to water supply problems was chilied by Prince William water authority representative Lawrence Randall, who said:

"Prince William has zero interest in a regional system. We feel we have been abused by the system that exists. If we're taken into such a system it will be kicking and screaming."

Most of the squabbing involves the triangle of Fairfax and Prince William Counties and the Fairfax County Water Authority, which supplies water to most of those two counties as well as Alexandria.

"Prince William has been put in the position of being a political pawn," said that county's board chairman Alice Humphries. "We're in the middle of a fight between the water authority and the Fairfax County Board of Supervisors."

Disenchanted with its minority role in water authority affairs (commissioner Randall has no vote on the board). Prince William has taken steps to set up its own water agency and create its own reservoir.

Though Fairfax officials publicly preach cooperation, the supervisors' vote to go ahead with mandatory restrictions (barring heavy rainfall by Monday) annoyed Alexandria and Prince William officials, who felt the action was premature and unilateral.

Water authority officials are also angry at Fairfax. Its engineer-director, James J. Corbalis, has tried to stay in the background of the controversy, but after Fairfax County Executive Leonard Whorton announced a voluntary conservation drive in early August, he said, "I was not consulted at any time."

Fairfax officials, unhappy with the authority's technical analysis of current supply problems, has mobilized its own in-house team to assess the mase of figures on fluctuating reservoir elevation, demand, stream flow, evaporation and voter tables.

In the midst of the emergency, the supervisors found time to attack the authority for its plans to buy new furniture for its new headquarters instead of using old desks and chairs.

When the authority hired WTOP weatherman Gordon Barnes to provide long-range weather forecasts, at the cost of $1,700, one dismayed supervisors cracked, "At least they didn't hire a rainmaker."

Disagreements among the jurisdictions served by the authority are as basic as whether there actually is a serious problem of water supply.

Fairfax County environmental planner John H. Thillmann, on whom County Executive Whorton relies heavily, says the Occoquan could be so low on Dec. 1 that with a cold winter producing little runoff, the reservoir could run out of water in February.

"Ridiculous," says Prince William's Randall, "We shouldn't believe we're going to run out of water soon," he says. "We're not about to . . . The technical people at the water authority aren't worried about running out of water at all."

Until last year, the Occoquan had always had an ample supply of water for the authority's customers, who now number more than 600,000. In fact, for six and seven months of the year, the agency has routinely released water stored behind the dam to generate electricity.

This year, however, the comfortable pattern of plentiful supply was broken. In mid-May, the reservoir began an almost straight-line decline that has continued into September.

By Dec. 1, the reservoir usually is stocked with 8 1/2 billion gallons. But by that date this year, according to Fairfax's Thillmann, the reservoir will probably have less than half that amount, even with a 1 1/2-billion-gallon purchase from Manassas' nearby reservoir.

While the low level of the Occoquan is blamed on drought within its watershed, precipation this year has not been abnormally lower than last years. At the Manassas slation, for example, precipation in the first eight months of 1976 totaled 20.43 inches. In 1977, the total has been 17.34 inches.

"Where has the water gone?" asks Fairfax Supervisor Audrey Moore, who abstained from her colleagues' vote for mandatory restrictions because she felt not enough facts had been developed to justify the move.

The answer, Mrs. Moore feels, may lie in the depleted water table. When the level of water in the ground is down, as it is this year, there is less run-off into the tributaries that replenish the Occoquan.

Mrs. Moore, a long-time critic of Fairfax County growth, thinks urban development has been the main factor in lowering the water table. She sees disturbing long-term implications for the reservoir.

Mrs. Moore's colleagues on the County board feel she exploits environmental concerns to try to stop any growth at all and are likely to interpret her warnings about the water table as more politics.

"The question of water is too important to become a political football. Prince William board chairman Humphries says of the overall wrangling among the jurisdictions and the water authority.