Professional and technical workers are expected to account for more than half a million jobs in the Washington region by 1990, replacing clerical employes as the area's largest occupational group, according to projections by the D.C. Department of Employment Services.

Total employment in the D.C. area is projected to grow at an annual rate of 2.3 percent, to almost 2 million by 1990. At least 55 percent of those 2 million jobs will be held by professional, technical, management, sales and clerical employes.

The services sector, which currently ranks as the Washington area's largest private-sector industry, is expected to be the growth leader, increasing at a projected annual rate of 4 percent through the 1980s.

"Nationally, you can see that trend, but I think in the District it's happening proportionately greater," said Richard Groner, director of labor market information and research at the DES. "The District has always had a service economy, and it is in the forefront of that nationwide movement toward a service economy," Groner added.

Jobs in sales and other services and in professional and technical areas are expected to grow most quickly because those industries are expanding so rapidly, the DES said. On the other hand, slower-than-average growth is projected for jobs in the finance, insurance and real estate group; transportation, communications and utilities; construction, and government.

Clerical jobs are expected to account for more than 25 percent of all jobs by 1990, but increases may be below average because of technological changes and slow growth in the federal sector. Federal employment, which is the single largest source of jobs in the area, will remain relatively flat, with a predicted annual growth rate of only 0.1 percent.

"Clearly, the underlying trend here is that professional and technical jobs will outnumber clerical jobs, and that's significant," Groner said.

The projections -- not forecasts -- by DES are based on trends, occupational surveys and economic conditions in the Washington Standard Metropolitan Statistical Area (SMSA).

The Washington SMSA includes the cities of Washington, Alexandria, Fairfax, Falls Church, Manassas and Manassas Park; Arlington, Fairfax, Loudoun and Prince William counties in Virginia, and Montgomery, Prince George's and Charles counties in Maryland. The DES compiles labor-market information and produces statistical analyses for the entire Washington region.

The latest projections, which are included in an economic profile titled, "Washington Area Jobs and Occupations in the Year 1990," indicate that more than 97,000 jobs will be created annually in the region in the 1980s.