In a state where programs from welfare to sewage treatment are suffering heavy cutbacks, one agency alone is getting fatter, presumably in case of trouble: the Iowa National Guard is looking forward to a multimillion-dollar increase, mostly for raises and bonuses for the troops.

Under the new federal austerity, families with students in plain old state universities may not be eligible for guaranteed loans but families with higher income and children in exclusive private colleges will be.

As Reaganomics hits Main Street, the folks along the sidewalks are rediscovering the quirkiness that occurs when programs meet people. There are ironies, contradictions, odd winners amid the sea of losers. A policy thrust in one direction sets up currents in another.

In states from Hawaii to Vermont, for instance, officials say much of the savings in welfare cuts could be offset as victims of those reductions become eligible for food stamps as a result.

In Hennepin County, Minn., three-fifths of the mothers who now both work and receive welfare are planning to quit their jobs and rely entirely on public assistance, since under the new rules they will get almost the same income, a study shows.

In states such as Mississippi and Kentucky, whose populations are heavily dependent on public help, officials fear the cutbacks in social programs will jeopardize not just those on the dole but, in a kind of "trickle up" of pain, also some small businesses, such as Mom and Pop grocery stores, whose customers are mostly poor folks.

In Hawaii, state legislators learned the folly of being among the more forward-looking in the nation in trying to plan for the onset of Reaganomics. They convened a special session this summer, designed in part to deal with the threatened loss of nearly $14 million in federal impact aid (compensation to the state for non-taxpayers at military bases on Oahu) and the resulting layoff of more than 500 teachers. Just as they got a plan worked out, Congress eliminated most of the cut.

A certain hardness of heart has surfaced in some quarters in tandem with the general belt-tightening. In a poll taken by the St. Paul Pioneer Press in that solidly Democratic Minnesota city, the bleeding heart quotient was stunningly low. Only 16 percent approved increases in state and local taxes to continue welfare programs axed by the administration. In Dade County, Fla., citizens at a meeting jeered a blind man complaining of cutbacks in the schedules of the van that had transported him to work.

Among those who will be hurt by the changes are farmers. Orson Swindle, director of the Georgia Farmers Home Administration, expects to foreclose on some farms, even though "farming is the lifeblood of Georgia," as the FHA shifts gears to an emphasis on servicing and collecting debts instead of lending.

On a brighter side, controversial cutbacks in the school lunch program already have produced some interesting innovations in several states. In South Carolina, a group of black ministers, the Greater Columbia Chamber of Ministers, is organizing to raise money to help any families who can't afford to feed their children under the new program. In Delaware, schools in populous New Castle County, which includes Wilmington, have started "satelliteing," that is, preparing school food for elementary schools in high school kitchens, in order to cut costs.

And in Georgia's Worth County, food service director Peggy Harris shaved off a penny per serving on the 2,500 lunches she serves per day by buying up fresh corn and peaches in bulk from local farmers and freezing the produce to be served later.

Perhaps the most consistently observed irony in the Reagan program is its negative effect on the work ethic--so basic to the Reagan philosophy--among poor people.

"There is an obvious gap in public policy," said John von Schlegell, a Massachusetts welfare official. "We are trying to encourage people to work and yet most of the cost savings are directed at working people."

Among the women in the Minnesota study, for instance, it was found that working would gain them less than than $50 a month over what they'd get if they just stayed home and collected Aid to Families With Dependent Children.

Only about 15 percent of those receiving AFDC nationwide work full or part time, notes the University of Chicago Center for the Study of Welfare Policy, and yet virtually all of the savings are slated for this small segment, with the probable result a "severe disincentive to work."

Under a revised student loan program, the imposition of income ceilings coupled with state "standards of need" gives higher income families an apparent edge.

In Tennessee, for instance, assuming $3,000 in books, board and other non-tuition expenses, a student attending Vanderbilt, a private university, is eligible for a full $2,500 loan if his family of four has an income of up to $44,650, officials said. That's because Vanderbilt's tuition is relatively high, $5,545 annually.

A student with the same non-tuition expenses attending the University of Tennessee, where tuition is only $741, would be eligible for no financial assistance if his family of four had a yearly income of as much as $30,000.

One purpose of the changes was to cut costs by preventing people from borrowing when they didn't need to, one Washington education specialist said. "I don't see any inequity in that."

If you look at the math, said an official of the Tennessee Student Assistance Corp., it's obvious that the family sending a child to Vanderbilt "will have a higher need."

In Iowa, a state that expects to lose a grand total of $343 million in federal funds, National Guard officials see their ship coming in at last.

The $2.5 million increase in federal money is merely a sign that the pendulum is swinging in the opposite direction from the past, when social programs were stressed at the expense of the military, said state Adjutant General Roger Gilbert.

"We're still damn tight," he said. "Without a guilty conscience I will ask the governor for $300,000 more for maintenance and $300,000 more for educational benefits."