Poughkeepsie, N.Y., now losses an estimated half of its water supply each year through leaky mains, some so old they are made of wood.

In Massachusetts, a proposals to divert water from the Connecticut River to Boston has enflamed rivalry between the eastern and western parts of the state, each of which regards water as crucial to future jobs and growth.

While most big federal water projects traditionally have gone to the West, New York City is now petitioning the Army Corps of Engineers for a king-size projects of its own, including a $2 billion water tunnel from Westchester County to New York City.

"Water-rich" - that's what western states call the rainy East. But the Wast today is facing growing water supply problems much like those of the West - short supplies, waste, competition.

The situation, which has approached crisis proportions in a number of communities, has prompted eastern governors, led by Massachusetts' Michael S. Dukakis and New York's Hugh L. Carey, to call on President Carter to include their concerns in national water policy changes under review in the White House.

For the past century, billions of dollars in public works have flowed westward to irigate the desert, store water and promote the economic well-being of dry western cities.

"We've got to get some of the pork-barrel back East," says Theodore Hullar, an aide to Carey. "We lack equitability. New York State gets less than 2 percent of federal water resources dollars and we have 9 percent of the people."

In a recent letter to presidential assistant Stuart Eizenstat, Dikakis complained that "water concerns have historically been associated with the western more rural state." But rapidly deteriorating water systems in the urban East "will require the infusion of hassive financial assistance if cities are to accommodate sustained economic rejuvenation," he wrote.

These rumblings have not yet broken into regional warfare - indeed eastern and western governors are currently cooperating on water policy recommendations in a you-scratch-my back - I'll scratch-yours fashion. But they have unmistakably altered the politics of water.

"The East has the votes in COngress," says Joseph Nagel, an Interior Department official. "They can say. 'If you don't support my eastern water rehabilitation. I won't support your western dam.'"

Eastern states are only beginning to acknowledge they must plan for droughts. In Northern Virginia last year, 600,000 suburbanites were forbidden to wash cars or water lawns during a three-month dry spell. Unless new supplies are developed soon, officials predic Washington will face severe shortages in a few decades.

Boston's water supply system. Dukakis said, "dates back to the 1980s and still relies, to some extention, on hollowed-out logs to carry its water. Last year, approximately 90 million gallons per day (almost a third of the supply) were totally unaccounted for, either lost through leakage, poor metering or some other reason."

A March 1977 study found that 35 Massachusetts communities, or about half the state, will face water shortages by 1990 because of leaking pipes, ground-water pollution and poor management. Yet "growth, jobs, housing and economic stability depend in large measure on a sufficient quantity of high-quality, low-cost water," Dukakis said.

Massachusetts officials estimate the cost of repairing corroded pipes in Boston alone at $300 million to $500 million. Such figures, applied to New York and other cities, could amount to "many times what we spend now on western projects," Nagel said. "Think what it cost Washington to tear up its streets to build Metro."

But the tightfisted Carter aides who have tried to cut funding for western dams have no intention of funding any massive new programs for the East. In fact, the very idea makes the Office of Management and Budget "cringe," according to one water policy official.

Instead, the draft water policy proposes money - possibly $40 million - for states to develop water resource plans. Thus the East could find out how bad its problems are, and how much it would cost to correct them. Technical assistance could be offered through such agencies as the U.S. Geological Survey.

But such measures may stave off eastern demands for short time only. "That train's coming down the track," Nagel said. Already, New York State is pressing Congress to fund a $2 billion water tunnel from Westchester County to New York City and a $4 billion program to tap the Upper Hudson River for city supplies.

The Army Corps of Engineers, which has been running out of dam and navigation projects in recent years, relishes the thought of getting into the eastern water supply business. New York City has an "immediate need" for the Hudson River project, a corps report said last year, or it will face a deficit of 390 million gallons a day by the year 2000.

The problems are not confined to big cities. Lynnfield Center, Mass., placed a moratorium on the building of homes not equipped with private wells, in New Castle, Del., the sewer capacity exceeds the water supply, thus encouraging development that will want to tap nonexistent supplies.

Hamilton Township, a Trenton, N.J., suburb, is one of many communities to realize that water, like energy, should be conserved. The town has distributed $200,000 worth of control-flow showerheads to its 26,000 homes, thus saving citizens $2.6 million in water and fuel to heat it - as well as freezing up sewage capacity.

Water conservation - whether through metering, installing water-saving devices, changing irrigation techniques, increasing the price of water, or repairing leaky pipes - was to be a central part of Carter's policy. But protest from westerners have led the administration to back off any strict conservative measures.

Eastern officials seem more willing to support federal role in conservation. "Urban development has proceeds as though water resources were unlimited," says Evelyn Murphy, Massachusetts secretary of environmental affairs. 'The implicit assumption has been: there will always be enough water.

'That assumption has led us to build beyond existing water supplies . . . (and) to assume that past development of water systems requires no special attention."

In a recent speech to the Georgia Conservancy, an enviromental group. Murphy said Atlanta, which used 204 millions gallons of water a day in 1970, will use 500 million in the year 2000 - an amount the Chattahoochee River cannot sustain.

Lik New York, which wants to divert the Hudson, Massachusetts, which is eyeing the Connecticut River, or Denver and Los Angeles, which draw water across mountain ranges from the Colorodo River, Atlanta is considering dams and reservoirs on various Georgia rivers.

"But the engineering solution - another dam, another pipeline, another reservoir" - should be replaced by conservation, Murphy argued.

New York's Hullar also argues for "a dramatic increase in attention to nonstructural solutions," suggesting that the Corps of Engineers require lead-detection programs before funding watersupply programs.

However, there is little indication that the eastern constituency has made enough of an impact on the drafting of the water policy to turn the current focus from massive western dams and engineering works to conservation.

"Eastern governors are getting snookered" if they think they've had any influence, said one water policy officials. The policy may "extract slight conservation improvements from western states in exchange for a truckload of carrots. And where are those carrots coming from? Eastern gardens."