Debra Upchurch won't be at her desk at the U.S. Census Bureau in Suitland this morning. She'll be home "on furlough," helping the government solve its budget shortages.

Starting this week and hard on the heels of reductions-in-force (RIFs) ordered by President Reagan, the first wave of approximately 10,000 federal workers here and a total of 42,000 nationwide face payless days off that will mean cuts of up to 10 percent in their paychecks over the next several months.

Census is furloughing its 5,900 workers for 10 days over the next 20 weeks--one day each pay period--and there is a possibility that the furloughs will extend to 22 days. Several other agencies, most notably the Federal Aviation Administration, which proposes furloughing 30,000 of its 50,000 workers beginning next month, also are drawing up furlough schedules.

Federal managers say they have resorted to furloughs because of budget cuts and Congress' failure to approve budgets for the fiscal year that began last October. It is the first time in federal history that furloughs have been used on such a wide scale, and the unprecedented disruptions are taking their toll on employe morale as well as on government productivity.

A few workers are planning to use their furlough time to take vacations, but most say they live from paycheck to paycheck and will need to economize all the more to make up the lost income. And the prospect of three-day weekends is only a slight comfort when compared with the financial loss.

For Upchurch, a 28-year-old forms designer who earns about $20,000 a year, the order to take every other Monday off for the next 20 weeks poses only a moderate financial problem. Her husband works--"not for the federal government, thankfully"--and they'll get by despite her reduced salary.

"We're just going to have to cut back some, pay the bills that are necessary and do away with luxury items," said Upchurch, who has worked for the agency for nearly five years and is being furloughed along with all 3,500 other employes at Census' Suitland complex.

But Debbie Flippin, 22, said she has recently taken a part-time job so she can make up the money she will lose because of the furlough. She works from 7 a.m. to 3:30 p.m. as an $11,800-a-year clerk-typist at Census, then shows up for the 5 p.m. to 10 p.m. shift behind the counter at Church's Fried Chicken.

"I don't like taking the pay cut but I'm thankful I still have my job," Flippin said.

Census spokesman Jim Gorman said the use of furloughs will prevent further RIFs at the bureau, where about 430 received final dismissal notices last week. Another 700 workers will be downgraded or reassigned in addition to being furloughed.

Gorman said the need to RIF and furlough has been exacerbated because budget cuts in other agencies have meant a corresponding 15 percent cut in what Census calls its "reimbursable work"--the surveys and statistical studies it does for other departments. Also, completion of the 1980 census has lessened the workload in some offices.

Census workers, like other federal employes, say they would rather have furloughs than RIFs, according to a survey conducted by Local 2782 of the American Federation of Government Employees, the union that represents the vast majority of Census workers here.

"We don't like pay cuts or furloughs but our position is that it's better than being fired," said Russ Davis, president of the AFGE local. He testified on the Hill against the RIFs and helped negotiate a flexible furlough policy with Census management that allows workers, if they choose, to take all their furlough days at once, almost like an unpaid vacation.

But whichever way the furloughs are taken, the impact on productivity and programs is expected to be detrimental, according to John Trimble, chief of the bureau's wholesale trade census branch. He said his four-person office has been hit by both RIFs and furloughs at a time when it is busier than ever gathering data for the 1982 Census trade report.

"With everyone shifted around and taking days off, I don't see how we're going to stay on schedule," said Trimble, who will soon be "bumped" from his $40,000-a-year job by a RIF and moved into the agency's Demographics Survey Division, although he will keep his same salary. His assistant is being moved out of the office also "and someone who doesn't have any census experience is coming in." In addition, Trimble, his assistant and his replacement will be furloughed.

The 10,000 furloughs in the Washington area include the 3,500 employes at Census and from 2,500 to 3,500 at the FAA. Additionally, the Office of Personnel Management is planning to furlough 5,000 of its 5,700 employes, most of whom are based here, early next month, according to a spokesman. The OPM workers will lose one day's salary per pay period for at least 20 weeks. A smaller furlough affecting 200 employes here and 200 in the regions is also set for the Commerce Department's Economic Development Administration, on a schedule similar to what OPM is doing.

The furloughs and RIFs have led many federal employes to hunt for jobs outside the government, but only clerical workers or those in specialized fields are finding any demand for their services in a tight job market, according to employes and personnel officials.

Most employes, like the Census Bureau's Upchurch, say they have reconciled themselves to sitting at home when they would prefer to work. But this doesn't mean they have stopped looking.

"I enjoy my job very much, but this constant pressure and waiting for what will happen next is hard to work under," she said. "Of course my morale's going to go down and probably my work--I'd like to find some place where I'd be more appreciated."