Nearly one-fifth of Washington's families now receiving food stamps will have their stamps either reduced or cut off because their incomes are too high under federal guidelines that went into effect March 1, Department of Human Resources officials said yesterday.

The families to be affected, many of them AFDC (Aid to Families with Dependent Children) recipients, will be notified of the changes by letter on May 16. The letter will explain the reason for the changes and the family's options for appeal.

The cutbacks were announced following food stamp workers' review of the 25,128 welfare families currently receiving the stamps.

Of these families, 16 percent, or more than 10,000 people, will have their benefits reduced by up to 90 percent. Three percent, or more than 2,000 people, will be cut off from the program completely, said Muriel Yager, the city's food stamp outreach officer.

The affected families may appeal the changes by requesting a conference with food stamp workers or a hearing at the city's Fair Hearing Division office, located at 500 First St. NW, Room 8000, Yager said.

Current benefits will continue until the hearing process is completed, she said. However, if the final finding is in the city's favor the family will be required to repay the city for the extra food stamp benefits received.

The recently announced cutbacks are just a preview of what is to come, DHR officials said. The review of approximately 11,000 nonwelfare food stamps families is expected to be completed by June 30. Undoubtedly some of these recipients will lose food stamp benefits as well, Yager said.

In all, 37,000 District families (70,000 people) currently receive food stamps. The figure represents only half the District residents eligible to receive the stamps, Yager said.

Yager said many of the poorest families have avoided food stamps in the past because they were required to purchase them with cash that was not always available.

A mother of two with a monthly income of $450, for example, might have been eligible for stamps with grocery purchasing power equivalent to $150. For these, however, she would have had to pay around $75.

Under current guidelines, the same woman would simply qualify for $75 in food stamps free, with no cash payment required.

While dropping, the purchasing requirement, however, the government also eliminated other provisions of the program through which the higher income poor often qualified for food stamps.

Chief among these were regulations permitting families with incomes too high to qualify for the program to reduce their incomes on paper by deducting such items as medical bills and child-care costs.

For an individual, the maximum monthly income allowed is $277. The figure is $542 for a family of four.