NOW THAT Joseph P. Yeldell is no longer in charge of the city's department of human resources, it is possible to set aside the question of whether he was ever competent or fit to handle the job and to examine the more fundamental question of whether that huge agency is manageable at all. We don't happen to believe that Mr. Yeldell was the right man for DHR in any case. But the fact remains that DHR, as presently constituted, probably could not be run efficiently by even the most skillful and conscientious director. Of course, Mr. Yeldell could have done something about that, and that was not the least of the problems with his stewardship. As staff writer Alice Bonner reported in this newspaper the other day, the major opposition to reorganizing or dismantling DHR came from the former director, who insisted, according to one confidant of Mayor Washington, on keeping his unwiedy domain intact. Even while conceding that the "super-agency" concept created administrative problems, Mr. Yeldell was somehow never able to come forward with proposals for better management that risked any substantive reductions in the agency's scope or influence.

The crucial question now is whether the powers at city hall will seize the opportunity to begin reorganizating DHR. The agency is the city's largest governmental entity, with one-fifth of the population of the Distric of Columbia under its care. It is charged with administering welfare, public health services, narcotics treatment, mental health and other programs such as violational rehabilitation. The goal of such an umbrella organization, which became popular in many cities during the 1960s, was to provide centralized, "one-stop" health and welfare services for citizens. The basic structure more or less followed the lines of the federal Department of Health, Education and Welfare. Now, of course, the incoming Carter administration is apparently reconsidering the whole HEW concept, as part of President-elect Carter's larger program for reorganizing the government. So it might not be a bad idea for the city to have the benefit of the federal government's thinking about HEW before reaching any final conclusions on how to overhaul the local agency.

That should not be a reason, we hasten to emphasize, for the city government not to get started on its over rethinking of the proper shape and structure for DHR. The mayor and city council are apparently disposed to take some needed initiatives. From the start, the council has recognized the need for organizational changes in DHR. Chairman Sterling Tucker and other members have been particularly interested in detaching most if not all of the city's health services. One significant move has already been made; the council has passed a bill that would remove D.C. General Hospital from DHR's control. When this measure is presented to Mayor Washington, he should sign it - for it enjoys not only unanimous council support, but also the strong backing of the medical community.

Beyond that, Mayor Washington, too is said to have begun efforts to trim and reshape DHR. According to news reports, he has ordered a departmental realignment and has assigned the job to Albert P. Russo, the agency's acting director. Officials say Mr. Russo's planning will incorporate a two-year-old reorganization plan designed by Mr. Yeldell but withdrawn after its submission to the city council. It is unclear how much change that plan would have brought. In any case, Mr. Tucker has let it be known that he is determined to reduce DHR's size. He expects to have a task force set to work in about two weeks.

There is always a danger that in the zeal to change, the city might revert to the very fragmentation that the super-agency was intended to eliminate. Certainly the coordination of city services must be preserved and improved. Ideally, the reorganization of DHR ought to be a joint executive-legislative venture. Mr. Russo's long experience in the field should be helpful in developing measures agreeable to the mayor and the council. But if the executive branch does not show a serious intention to cooperate, the council should get on with the job on its own.