Federal pay raises (typically worth about $20 a week to Washington area employes) would be smaller in the future if Congress buys a new White House "reform" plan of U.S. civilian and military compensation.

In addition to establishing an area wage tie-in between local industry and local federal jobs, President Carter's plan also proposes linking federal salaries and fringe benefits to the typically less generous scales of the nation's 12 million city, state and local government workers.

With very few exceptions federal workers average much higher salaries than their counterparts paid out of Pierre, Jackson, Carson City, Frankfort and other state capitals.

Although some state and local government workers get more holidays and often put in fewer hours a week, pay for federal workers and the U.S. retirement system is generally superior to what states, cities and counties offer their employes.

A recent federal survey of wages paid in key professional, technical and clerical jobs in all 50 states showed that Uncle Sam was consistently among the top three in almost every job category. The comparison could be made because the District of Columbia government - with its link to federal pay - was among the salary leaders among all states and big cities.

The Carter pay reform plan won't go to Congress until Wednesday. But enough of it has leaked out, intentionally and otherwise, to show that it is a mammoth proposal. And it would almost certainly mean millions of dollars less each year for federal workers than under the present "comparability with industry" system.

Federal wages are set now on the basis of annual Bureau of Labor Statistics studies of salaries - and only salaries - paid in 3,000 firms nationwide. That pay data is adjusted here in Washington and offered as a proposed October catch-up-with industry raise for the president's consideration.

By law the president can cut (and several have) the amount of the "comparability" raise. His lower pay figure prevails unless Congress vetoes it. Politically, neither the Senate nor House can be expected to override the president and order a a bigger raise, no matter how justified it may seem to be.

By comparing the value of federal vs. industry fringe benefits (and those in local government), administration planners believe they have a reasonable system that Congress will be forced to accept. And all indications are that those calculations would result in lower annual pay raises in future for U.S. civil servants.

Federal unions can be expected to oppose the Carter plan, and they probably will be joined by state and local government groups that have used federal pay raises in the past in their "catch-up" wage demands.