Nonprofit and volunteer agencies in the Washington area may lose nearly one-third of their yearly revenue by 1985 under proposed Reagan administration budget cuts, according to a new study by the Washington Council of Agencies.

"The impact is going to be substantial," said James Kalish, executive director of the council, which includes more than 140 nonprofit agencies in the Washington area with revenues totaling $35 million.

Kalish said many of the several hundred nonprofit social service agencies in the Washington area will be forced to lay off workers, and some agencies will close.

He said the WCA agencies, which represent about one-quarter of the region's nonprofit groups, may lose as much as $6 million to $7 million next year, and $9.5 million a year by 1985 unless Congress alters planned cuts in social service, community development, education, health and other programs.

"We will be severely squeezed," he said, because the local agencies will lose substantial revenue at the same time numbers of needy clients are expected to increase.

The nonprofit and volunteer groups provide a wide range of charitable and social services, including day care, foster care, alcohol and drug abuse counseling, and referral services for people needing assistance from government or private sources.

The nonprofit agencies, traditionally low key in providing community services, are beginning what Kalish called a "crash program" of trying to publicize the potential loss in crucial services.

"If the mayor saw retail clothing stores were reducing employment, he would look hard at it and study it, but nobody seems to care about this sector," he said.

The Washington study was based in part on nationwide projections by the Urban Institute, a Washington-based research group which Wednesday released results of a nationwide study showing that nonprofit agencies will lose $33 billion over the next three years.

In what it called the first detailed study of the country's nonprofit groups, the Urban Institute concluded that because of the financial loss, the agencies will fall far short in their effort to help clients cope with a cumulative total of $115 billion in federal program cuts by 1985.

In addition to the study, the Urban Institute plans detailed looks at the situation of nonprofit agencies in 12 major cities.

In the first of those city studies, the institute gathered data from 78 Washington area nonprofit agencies, and WCA used that information to estimate the local impact of budget cuts, Kalish said.

Kalish said that WCA agencies currently depend on the government for $14.5 million yearly, but as much as 65 percent of that amount will be lost through planned cuts.

To cope with inflation and budget cuts, Kalish said the nonprofit agencies would be forced to seek more money from the D.C. government and charitable donors.

However, Kalish said D.C. government has been reducing the amount of funding for nonprofit agencies, and charitable giving would offset only part of the difference.

Kalish said the council plans meetings this month to discuss strategies for coping with the budget problems.

"Maybe we'll end up getting 10,000 people together and march," he said. "But I am not sure where we will march."