Thousands of disabled, unemployed and elderly residents of Washington would see their city aid reduced sharply under Mayor Marion Barry's new budget proposal.

The deepest cut would come in the general public assistance program--aid to those who cannot work because of temporary disabilities--which would end in its current form. Some assistance provided under that program would be combined with other emergency assistance measures, and the new program would be funded at a level of $6.6 million, less than half the amount budgeted for general public assistance this year.

At the same time, the budget would impose new limits or cutbacks on a wide range of programs from Medicaid to shelter for the homeless to unemployment and disability pay for city employes.

District residents also would have to pay part of the cost of services such as drug treatment, routine health services, long-term emergency shelter, day care, and transportation for schoolchildren.

The 5,500 recipients of general public assistance now receive $189.50 a month for an average of 22 3/4 months, according to Department of Human Services figures.

Under the new program, the aid would last for a maximum of six months or it might come in the form of a one-time payment for certified emergencies, such as back rent needed to avoid eviction or payment for overdue utility bills, said Audrey Rowe, D.C. commissioner of social services.

The upper limit on one-time emergency payments generally has been $1,000, she said, compared to a total of $4,000 a recipient would get in 22 months under the old program.

City officials said they want to transfer some individuals receiving general public assistance to federal programs or to other city programs, although funding for most of those is being maintained at previous levels or cut back, as well. The federal government, facing its own severe budget problems, at the same time is tightening its own assistance programs and trying to persuade local governments to take over more of the burden.

The mayor's budget message indicated that some of the unemployed might be switched to job training programs. The funds in the budget of the Department of Employment Services, which runs job training programs, are estimated to decline by about $2.5 million. City officials declined to estimate how many people might lose all city benefits.

"We are not going to say how many are going to be dropped from various social programs , if they are going to be dropped," said Alphonse G. Hill, deputy mayor for financial management. "They may be eligible for other programs. We will have to look at what else we can do."

With an end to general public assistance, the budget states that the permanently disabled will be encouraged to apply for the federal Supplemental Security Income program, which would give them higher benefits if they are accepted.

Spokesmen for some charity groups in the city said the switch could mean that those who are permanently, but not completely, disabled would fall through the cracks because SSI only goes to the totally disabled.

Some nonprofit organizations also said the budget cuts would put more pressures on them to provide services for the needy at a time when they expect to receive less city funding for service contracts.

Human support services is by far the largest category in the city budget, about 26 percent of the total. Appropriated city funds in this category would increase by 3 percent in the mayor's budget, to $481 million. Almost all of the increase is taken up with an estimated $12.4 million in Medicaid costs just to keep up with inflation in the health care field.

Other effects of the mayor's proposed budget on social services, according to city officials, include:

*New Medicaid restrictions would end city payments for hospital stays of more than one day before elective surgery or for nonemergency weekend admissions, and patients would be encouraged to get care in nursing homes rather than hospitals when possible.

*The city will stop covering some optional services under Medicaid, possibly optometry or podiatry.

*A fee would be charged for immunizations, health screening, and drug addiction treatments. Some people would pay less for treatments at clinics, however, under another proposal to charge according to a sliding scale based on income rather than a flat payment for everyone.

*Any family could get free emergency shelter for up to 30 days. After that all families would have to pay part, perhaps 10 or 20 percent, of the $45 a night it costs the city to shelter them.

*The men's Pierce and Blair emergency shelters would be closed from April 1 through Sept. 30.

All families will have to pay something for day-care services on a sliding scale according to income, from $1 to perhaps $20 a week for a family of four. DHS also plans to start contracting at day-care centers for the number of children served rather than for the center's capacity.

*Some 300 wards 19 and older will be eliminated from the foster care program.