When the federal money tree is shaken, it rains hundreds of millions of dollars on Washington-area governments.

While all local jurisdictions outside the District of Columbia rely most heavily on real estate taxes, federal aid has become a big help to hard-pressed municipal treasuries.

In the current year alone, the U.S. government is underwriting more than $1.3 billion worth of local government programs in the Washington area, according to budget officials. In addition, the Virginia and Maryland state governments are getting just over $1 billion each, in federal aid in the year ending June 30, some of which also is sent to Washington-area governments in the form of "state" aid.

The District government is by far the largest recipient of federal largesse in the Washington area, receiving $832.9 million toward its overall budget of $1.962 billion, or 42.5 percent from federal funds.

While that percentage is easily higher than in any other jurisdiction here, it is somewhat inflated since the District government acts as a state government in receiving many of the 240 federal grants the D.C. government gets. Included in the $832.9-million figure is the annual federal payment to the city, $238 million this year, which is designed to compensate the District for lost real estate taxes on federal properties and expenses it incurs as the nation's capital.

The Washington-area jurisdictions together will receive $340.9 million this year for Metro subway construction and aid to retire the debt on Metro revenue bonds.

Individual governments surrounding the District support up to 14 percent of their expenditures with a variety of federal grants for specific programs and federal revenue sharing funds that can be used as the local jurisdictions see fit.

The federal government is sending $68.7 million to Prince George's County, $36 million to Fairfax County, $27.4 million to Montgomery County, $16.3 million to Arlington County, $15 million to Alexandria, $9.5 million to Prince William County and $750,000 to Fairfax City, according to officials in those jurisdictions.

While the federal treasury pays for about 14 percent of the Prince George's budget of $493 million, it pays for about 9.8 percent of Arlington's and 5.6 percent of Fairfax County's. The Fairfax figure would jump sharply to 12.8 percent however, if the county receives a projected $53 million sewer grant this year.

Local governments here take differing views of the federal handouts, wanting to get all the financial help they can, yet not wanting to become so hooked on it are unable to cope if the federal money dries up.

The District government uses its federal payment plus $28.3 million in revenue sharing to finance general operating expenses. In Alexandria, however, the annual revenue sharing money, $2.3 million this year, is used to finance one-time expenditures such as buying parkland, improving the city computer operations or improving flood control of Cameron Run.

Much federal aid is earmarked for specific programs, such as giving public jobs and training to the hard-core unemployed, providing assistance to build housing for low-income people and helping Indochinese refugees. A large chunk is in so-called impact aid to jurisdictions with large numbers of schoolchildren whose parents work for the federal government.

Numerous local officials said that if the federal money for some of these specific programs ever ends, the local governments are likely to drop them altogether or curtail them sharply. Particularly hard hit, they said, would be the jobs program financed by the Comprehensive Employment and Training Act (CETA).

"Basically it's money that the feds hope we'll use to get interested in some programs we otherwise wouldn't provide," Jeff Goldman, Prince George's deputy budget director, said of the various federal programs.

Because of the whims of Congress and how it treats various programs from year to year, Arlington does not even budget its federal grants until the county is certain the programs will be financed.

"Some of them we're reasonably assured of funding from year to year, such as housing, welfare and community development grants," said Patrick Hyland Arlington's financial analysis supervisor. "Some are difficult to anticipate. CETA regulations change all the time and revenue sharing is a question mark this year."

In Fairfax County, Deputy County Executive James P. McDonald said that while the overall federal impact on the county's $641-million budget is not great, the federal dollars finance large portions of specific programs, such as sewer construction. If the federal money were not available, he said homeowners who use the county's sewage system would have to pay much higher rates.

But in Fairfax City, with its population of 22,000, city manager George Hubler says that while he hates to admit it, the city wouldn't feel much of a blow if it suddenly lost its $750,000 in federal aid.

"We've been planning for the demise of impact (to education) aid for a long time," Hubler said.