Joseph S. Wholey, Arlington County Board member and Metro Board chairman, is returning to the Department of Health, Education and Welfare this week - an agency he left 10 years ago - as a consultant to Henry Aaron, assistant secretary for Planning and Evaluation.

The $43,000-a-year position is temporary, pending a departmental reorganization, which is likely to result in the creation of a new high-level post for Wholey, an HEW spokesman said. Since 1968 when he resigned from HEW to run unsuccessfully for the Arlington Board, Wholey has been a senior staff member at the Urban Institute.

Wholey, 43, said his federal job would not affect his position on either the Arlington or Metro boards because state and federal law allows a federal employe to serve on a local governing body. However, the Hatch Act bars federal employes from participating in partisan political campaigns.

"I mentioned throughout my discussions with HEW that I intend to complete my terms on both boards," Wholey said. "I've followed a very cautious track. We've explored the issue very carefully and I've gotten written assurances from lawyers" that dual service is permitted.

In 1968, Wholey resigned from his job as director of program analysis at HEW to run for the County Board. Later that year Virginia repealed a law that banned federal employes from running for local office as nonpartisans. Although Wholey was unsuccessful in 1968, he was elected to the County Board the following year.

Last January, a month before he announced that he would not run for a third four-year term on the Arlington County Board, Wholey, 43, said he was "holding himself open . . . to see what comes along." Among the possible options he mentioned was a high-level federal or academic appointment.

Some political observers say that they were surprised a year ago when Wholey, an expert in zero-based budgeting and federal program evaluation, did not receive a high-level job with the Carter Administration. His book on zero-based budgeting has recently been published and he is finishing another on program evaluation.

"At the Urban Institute I evaluated 10 different (government) agenceis and had a staff of 25 professionals," Wholey said. "I've been a kind of adviser to an adviser. I'm liking the idea of getting back one step closer to the process. I'd be an adviser to a person who can do something.