With meetings about to begin on how to manage regional water supplies during a future drought, water has joined transportation and growth controls as a flash-point issue between Maryland and Virginia, say observers of water politics in the Washington area.

Three weeks of bickering among politicians about how to deal with current water supplies have exposed deep and stubborn rifts between the two states. Long after enough rain has fallen to wash away current debate over Maryland's mandatory restrictions, the area still will face divisive questions with long-range implications for the environment, recreation, population growth and the quality of life.

For instance, Fairfax County and the state of Maryland are locked in a dispute over whether the county can build a drinking water intake pipe in the Potomac River. And a politically explosive debate is about to begin over whether officials should maintain higher water levels in the river to protect wildlife.

Meanwhile, the region's leaders still face the biggest challenge of all: addressing predictions that the current water supply system with its two reservoirs won't be enough to sustain the area's growing population in 20 or 30 years.

"The bickering clearly isn't a good thing," said Joy Hecht, chairman of a League of Women Voters task force that last winter called for regional action on water issues.

Hecht says she is discouraged by a lack of effort by the two states and the District "to really sit down and come to a consensus . . . to make it a social issue and a values issue and not just a political fight," she said.

Gus Bauman, a Maryland land-use lawyer who has been involved in regional politics for 25 years, agreed. The water debate, he said, is merely the latest issue to spin out of control.

"What drives all of these issues--water, transportation, trash--is the economic competition between Virginia and Maryland," Bauman said. "The bickering is just phase one. . . . In the long run, water is going to move toward the top of the agenda, and we still have no regional solution in sight, because we have a complete disconnect between Maryland and Virginia. The political cultures of the two states could not be more different."

Maryland officials have criticized Virginia for not joining them in imposing mandatory water restrictions during the drought and for its willingness to tap reservoirs without first launching more serious conservation efforts.

Montgomery County Executive Douglas M. Duncan (D) has staked out a hard line, calling Virginia's approach shortsighted and risky.

"To me, this water shortage is showing that our system is broken in the region," Duncan said. "We are hurt when some people say conserve--whether it's voluntary or mandatory--and some people say, 'Don't worry.' " He has even accused water officials of being more interested in making money from ratepayers than in conservation.

Officials in Virginia are just as forthright, arguing that the reservoirs are there to be tapped and citing assessments by water experts that the reserves can meet the region's needs for another year even under a worst-case scenario of continued drought. One member of the Fairfax Water Authority has called the mandatory water restrictions backed by Maryland Governor Parris N. Glendening (D) "unnecessary and harmful."

To avoid a future crisis, politicians in the two states and the District will need to swallow some of those differences and make a series of hard choices to accommodate the demands of population growth, local water planners say. The critical decisions will include whether to build expensive reservoirs, whether to ask residents to live with long-term water restrictions and whether to find the money to buy water from somewhere else.

Next month, when the Metropolitan Washington Council of Governments convenes a panel of area officials to discuss how the next drought will be handled, the panel will address "head-on" the issue of what circumstances should trigger mandatory water restrictions for everyone in the region, according to Stuart Freudberg, the council's director of environmental programs.

"I'm hoping that we can create more harmony and less discord," Freudberg said. "It's a big family, and big families sometimes have differences. But they work them out. We will learn from this and do much better the next time around."

Perhaps as early as next spring, the Interstate Commission for the Potomac River Basin, which attempts to manage how much water is in the Potomac, wants to study the issue of how much water the river needs to remain healthy.

Duncan and some Maryland environmentalists have said the health of the river's ecosystem is threatened by the region's current agreement to use reservoir releases to keep the Potomac's flow from dropping below 100 million gallons a day.

The issue is sensitive, because raising the minimum flow would require tapping the reservoirs more deeply and more frequently than they have been this summer. That, in turn, could exhaust reservoir supplies more quickly and prompt restrictions to save water.

Finally, in an effort to deal with the most contentious issue of all--how to make sure there will be enough water for the area well into the next century--the region's water utilities plan to update their estimates for population growth and water needs.

That study, due out next year, could lead to calls for a third reservoir in the Potomac watershed or an expansion of the Jennings Randolph reservoir, officials say.

Officials with the river basin commission estimate that because of population growth, the region could run out of water during a severe drought by 2035. That date could be moved up if flow levels are raised for river health.

The dispute between Maryland and Fairfax County over the proposed intake pipe seems headed for court, officials say. Maryland, which has jurisdiction over the Potomac, has refused to give the county a permit to construct an intake pipe that Fairfax says is necessary to get cleaner water from the river than it's now getting.

Maryland fears that construction of the $6.6 million concrete intake pipe on the river bottom, which would replace the county's existing intake, will do environmental harm to the Potomac.

This summer, Virginia Attorney General Mark L. Earley threatened on behalf of Fairfax County to file a lawsuit and take the issue to the U.S. Supreme Court.

CAPTION: Montgomery County Executive Douglas M. Duncan has called neighboring Virginia's approach to the region's water problems shortsighted and risky.