WASHINGTON'S WELFARE families -- that's 10 percent of the population, 30

percent of the children -- have been losing precious ground to inflation. Since 1969, according to testimony at a D.C. Council hearing, benefits under Aid to Families with Dependent Children have dropped at least 35 percent behind inflation. That's why the local government decided to raise AFDC payments. But now the council has gone a step beyond what Mayor Barry had been seeking. By a narrow vote Tuesday, members approved automatic annual increases pegged to the Consumer Price Index. Mayor Barry objects to making such raises automatic raises -- and his point is well taken if not universally understood.

It isn't that any family will get rich on these raises, or that the prospect of regular increases will encourage more people either to become or to stay idle. What the city government now considers its standard of need for a family under AFDC is $7,848. That's substantially below the federally established poverty level of $8,850. With two increases approved for this year, the local payment would go to $4,368 a year. There are other factors in this math: besides AFDC, there are Medicaid, food stamps and, for certain recipients, housing subsidies. Still, all of this amounts to minimal standards of living for about 62,000 people -- of which 46,000 are children.

Correlating the benefits and the CPI is sound too. But Mayor Barry's objection is that the automatic-increase measure would bind the council as of fiscal 1987 in ways that could affect other programs. The mayor cautioned the council that the city should "preserve our options to provide programs and services to our needy clients in a variety of ways," particularly in light of federal budget cuts. That is a prudent approach, and council members should consider some softening of the automatic provision in their measure.