Champagne flowed last night in at least one of Capitol Hill's favorite spas in celebration of the new fiscal year, but today it is somebody else's hangover.

Beyond the Potomac, the impact will be felt mostly in the pocketbook. Welfare recipients will be spending more time scanning the help-wanted ads. Medicaid and Medicare patients will be paying more out of pocket for health care. States will be figuring how to stretch $100 million less in federal education funds under a new block grant program.

American businessmen, including fishermen, meat producers and inventors, will be paying new or increased user fees for government services.

But the effect will be felt inside the Beltway as well, even though departments and agencies, under a continuing resolution, will be operating with the same old budgets they saw in fiscal 1981 and 1982. Fiscal 1983 brings tighter federal procurement regulations and a new U.S. Court of Appeals for the federal circuit.

It also marks the passing of a few government entities. The U.S. Metric Board, set up in 1975 to usher the nation into the metric age, disappeared with barely a millitrace into the bowels of the Commerce Department. The Water Resources Council dried up and blew away at the stroke of midnight.

In a significant symbolic passing, CETA, the Comprehensive Employment and Training Act of 1973, which provided millions of federally subsidized jobs, officially expired at midnight, although funds in the pipeline will continue to be spent. The Labor Department expects some of that money to be used to plan for a new $3.8 billion jobs training program being drawn up by Congress.

For the millions of Americans affected, the fiscal 1983 headache won't be as bad as last year's, when the government embarked on program changes designed to cut federal spending by $35 billion.

Congress has ordered $6.6 billion in savings in entitlement programs for fiscal 1983, and much of that will come from nickel and dime accounting changes.

For people on the Aid to Families with Dependent Children rolls, for example, the fiscal year will eliminate spare change in benefit checks. AFDC checks will be rounded to the nearest dollar. Similarly, the Agriculture Department will round down the family income figure in determining food stamp allotments. The changes are expected to save AFDC $10 million and the food-stamp program $180 million.

Taken together, the changes are a strong indicator that the Reagan administration is on track in its crusade to curb federal spending, particularly in the increasingly expensive entitlement programs.

The most critical of the changes that take effect today are in AFDC, the nation's largest welfare program, which provides aid to 10.4 million people in families with dependent children, at an annual cost of $7.6 billion.

The government expects to save $14 million by asking applicants, as well as those already receiving AFDC, to search for jobs. Those who refuse will be eliminated from the rolls.

Under other AFDC changes, states will be able to tighten eligibility for benefits by limiting a family's deductions for shelter and utilities if that family lives with others who are not on the welfare rolls. That will save $43 million.

The estimated 10,000 families with one parent in the military will not be able to get welfare benefits, saving $16 million, and payments to new recipients will be retroactive to the date of application, not to the beginning of the month, saving $14 million.

Another of President Reagan's block grant programs goes into effect today, providing $437.47 million in educational funds for states to divvy up. That will be about $100 million less than was available in fiscal 1982 under 28 separate grant programs ranging from desegregation assistance to library aid.

James G. Horn, director of the Education Department's state and local programs division, said reducing the programs' funding by one-fifth won't harm educational programs because there will be "less paper work and less overhead and less demand on administrative time to comply with federal regulations. States run education programs, the federal government does not, and it is not this administration's philosophy to run local school districts from Washington."

In the food-stamp program, the average allotment will go up more than 8 percent. A benchmark family of four with no income will receive $253 a month, up from $233.

But the stamps will go to fewer people, partly as a result of tightened eligibility standards.

"The primary focus of our restrictions will impact on areas of waste, fraud and abuse," said Robert E. Leard, assistant administrator of the food and nutrition service.

Other changes include penalizing those states that make the most errors in determining eligibility of recipients while rewarding those that have low error rates, saving $90 million, and bumping from the rolls 7,000 families where one spouse is a student and the other is in the work force.

Medicare, the medical insurance program for the elderly, will limit reimbursements to hospitals. While these costs legally cannot be passed on to beneficiaries, they could prompt hospitals to raise rates. Some advocacy groups fear that the elderly will wind up paying a larger share of their medical bills out of their own pockets.

In the Medicaid program for the poor, individuals may be required to make a small payment for almost all kinds of non-emergency medical care, with the states deciding how much recipients should pay.

Medicaid also will begin paying for the home care for disabled children as long as it does not cost more than institutional care, a change that came about because Reagan complained that Katie Beckett, a disabled Des Moines child, was being kept in a hospital under antiquated federal rules.