President Carter formally notified Congress yesterday that he intends to hold the October federal and military pay increase to 5.5 percent despite data indicating a bigger raise is needed by the 3 1/2 million people affected.

Carter said that under normal circumstances he would not hesitate to order the full 8.4 percent increase his advisers say is necessary to allow civil servants to catch up to wage gains in private industry. But he said the government must "set an example" for private industry to holdthe line on wages and prices and to stop the "treadmill" of inflation.

Carter's announcement of the 5.5 percent raise, which will cost $2.9 billion, brought immediate warnings of labor troubles from the government's biggest union and mixed reactions from federal employes. The American Federation of Government Employees said its members will throw up "informational" picket lines around major federal offices and installations. The AFL-CIO group also warned of "job actions" unless Congress overrides the president, and approves the full catch-up-with-industry pay raise, which would cost around $4.4 billion.

Congress has 30 days to veto the president's pay plan or it will go into effect automatically in October. A veto by either the Senate or the House - in the form of a resolution of disapproval - would mean government workers would get the full 8.4 percent raise. Rep. Herbert Harris (D. Va.) and other Washington-area legislators who represent 13 percent of the nation's federal work force are preparing such a resolution for action when Congress returns next week.

The pay raise would go to 1.4 million white collar government workers, from clerks to scientists, in an across-the-board amount. Equivalent raises would be given the 2.1 million uniformed personnel in most ranks.

If Congress goes along with the 5.5 percent pay raise as recommended, the average white collar government worker would get a raise of $18.46 each pay period.

The pay increases, if approved by Congress, would be substantially below some recent wage increases won by unions in private industry. In this year's first major settlement, for example, 180,000 coal miners received wage and benefit increases averaging nearly 40 percent over three years. That settlement increased the pressure on such other unions as the Teamsters, the railroad workers and postal workers for similar raises.

A 5.5 percent raise would pump an [WORD ILLEGIBLE] $35 million mostly into the Washington area's economy. It would increase the annual payroll here for [WORD ILLEGIBLE]white collar civil servants and [WORD ILLEGIBLE]military personnel in this area post the $3 billion mark.

Earlier this year, the president said he would put a 5.5 percent "cap" on [WORD ILLEGIBLE] pay raises for 1979.. He said it is the cornerstoneof his program to persuade labor and business to voluntarily accept wage and price restraints as part of an all-out war on inflation.

Robert S. Strauss, the president's inflation counselor, said this week that the rate for the year would be close to 3 percent. That was a sharp revision upward from an administration prediction in July of a 7.2 percent state and President Carter's own prediction last January in his annual economic message that the rate would be [WORD ILLEGIBLE]percent for the year.

Speaking at a national governor's conference earlier this week, Strauss conceded that the administration has had little success in its efforts to persuade unions to moderate their wage demands. Last month's postal settlement, which called for wage increases more in line with the government's anti-inflation goals, was rejected by the members of the postal unions.

The overall consumer price index, which came out earlier this week, stood at 196.7 percent of its 1967 average. That index, which was unadjusted for seasonal variation, means that a selection of goods and services that cost $10 in 1967 cost $19.67 in July of this year.

The overall consumer price index has been rising at an annual rate of 9.3 percent for the last six months and is 7.7 percent higher than it was in July of last year.

By law, the government makes regular annual surveys of salaries paid for similar jobs in industry. This year's survey, by the bureau of Labor Statistics, showed it would take 3.4 percent to make government wages generally comparable with industry.Carter rejected the "catch-up" amount yesterday, saying "pay comparability must be viewed in the light of the overall economic situation now facing our country."

Members of Congress, who got raises of nearly $13,000 last year are not included in the upcoming adjustment. Earlier, Congress voted to freeze pay raises for anybody in government making $47,500 or more. Nearly 90 percent of those "frozen" executives live and work in the Washington area.

Federal employes interviewed here yesterday had mixed reactions to the president's plan. Some felt it was unreasonably low, others said they did not mind taking the lead in terms of belt-tightening.

"It stinks," Janet Thompson, an administrative aide in the Veteran Administration's Department of Medicine and Surgery, said of the increase. "With the cost of living, it's no good . . . 5.5 is a drop in the bucket. My house (payments are) going up. My health insurance has gone up. It's no good."

On the other hand, Steve Campbell, who works at the Veterans Administration as a management analyst in the medical statistics division, said he is not disappointed with the level of the increase.

"I think it's fine," Campbell, a GS-7, said. "I get upset at other unions refusing to go along with it, like the postal workers. It (cutting back) has got to start somewhere. I just hope other people do it, too."

Sheldon Cheney, a librarian at the Department of Agriculture, said he is not completely satisfied with the 5.5 percent increase. "I would think that was enough if the money supply inflated at 5.5 per cent per year," Cheney said. "I doubt that's going to happen. We're coming out short. We're not even keeping even."

Margaret Evans, a management analyst and GS-11, said she accepts the increase without disappointment. "We've got to stop somewhere. Maybe this is the proper way to do it," Evans said.

Ken King, a computer specialist and GS-13 at the agriculture department, concurred. "I think that inflation's got to be cut," King said. "I'd rather have prices stablized."

The president's action further damages his relations with the unions that represent more than half the total federal work force.

A spokesman for Kenneth Blaylock, president of the 275,000 member AFGE, said the union had mandated him at its recent Chicago convention to take "almost any action" to beat the anticipated pay ceiling. He said such action would take the form of lobbying in Congress and picket lines around federal agencies and could also include slowdowns and "sickouts" by workers in key operations.

Strikes by government workers are illegal, carrying a penalty of dismissle, a fine and a year-and-a-day in jail. But the recent postal service contract talks with unions representing its 550,000 workers have been resumed under the threat of a nationwide mail strike. Rank-and-file members sent negotiators back to the bargaining table, protesting the three-year, 19.5 percent raises.

Postal union officials have been given by their members 15 days to come up with a better contract or to call a strike.

At midday we pulled into a landing. For lunch we had river fish, and Tony said we should try a soft drink called Guarana.

"It's got twice as much caffein as coffee," he read aloud, "And legend says Guarana makes you live longer, have a better sex life, and never get heart trouble."

"It probably causes cancer," I shook my head. "What's it made of?"

"Berries." He smiled as he drained his glass.

Then we got on our next boat with one other passenger, a Frenchman from Sao Paulo. He wanted to study Indian culture, he said, but it wasn't easy. Outsiders had been coming in and cutting down trees, building roads or ranches, and the tribes were upset. In fact, he said, it wasn't really safe to go much farther upstream.

I could understand this, looking up and down the lonely stretch of water we were on. Maybe we should send word to Duca that we wouldn't need him after all.

"And get him upset, too?" Tony demanded. "That's exactly what the outside world has done to these people - break the faith. I won't be a party to it."

Late that afternoon we reached Duca's settlement - some huts built on stilts with extra platforms to hold the chickens and pigs - and we found our lodging, a room in back of the store with no shutters or screens. Mosquitoes weren't the problem; the black waters of the river had a high acid content that kills their larvae, but all through our supper of river fish I thought about scorpions and snakes.

"Do you remember that James Bond movie, the one where the tarantula was crawling all over his chest?" I asked Tony casually that night as we lay sweating on our pallets and listening to the sounds of the vibrant land around us.

At dawn Sunday I had trouble with breakfast, a bowl of uncooked tapioca called manioc. I couldn't get it unstuck from the roof of my mouth, so Tony had to go outside and greet Duca, and load our canvas bags in his canoe.

I looked at the flooded landscape, with its thousands of trees shimmering in the sun. The high water was normal for this time of year, but somehow I hadn't realized there weren't going to be any trails or landmarks. There was only Duca, who was supposed to take us through by recognizing signs and sniffing the air.

"It's really different from the C&O Canal," I said.

Duca started his little outboard and we spun off across a lake behind the settlement, heading for a low line of trees. When we reached them he cut the engine and we drifted in. Thick trunks rose out of dark water, vines hung everywhere, and clouds of butterflies floated before us. We were in the jungle.

Duca paddled, not talking, twisting expertly through the watery avenues under tunnels of green, cool shade, banks of flowers; we struggled to sort out a jumble of impressions as the tiny dugout's prow nosed steadily ahead. He watched as expectantly until we spotted everything he pointed at: a big green iguana melted into a green branch, large blue birds with bright red stomachs, monkeys dancing and leaping through thick branches overhead. There were fields of yellow water plants with marvelous smells. Orchids bloomed on vines and creepers. Pink flowers burst from huge water-lily pads.

We drew together, in love with the silence, the bird calls, the sense of timeless, dreaming distance.We hardly noticed as the heat rose; the air and our bloodstreams melted together and came out in constant cooling water on our skins.

An hour passed. Duca started his outboard again. Another 30 minutes and we came out onto a huge shallow lake, covered with lilies, thick with swaying grasses. Flights of birds, all kinds and sizes, took off around us and swooped ahead as we sped into the open, like escorts into the unknown. The sky stretched limitlessly in every direction, and the shoreline looked forever away. How, I wondered, could Duca possibly know where he was going?

"By the sun," Tony said.

"But the sun's exactly overhead."

The lilies were narrowing the channel. Grass thickened around us, and Duca slowed down. Suddenly he cut the motor and we stopped dead. Frowning, he pointed at the water.

"I think he wants me to get out," Tony said.

"Get out?" I stared at the sharp, pointed stick Duca was waving, and I remembered the Frenchman's words about outsiders. "You mean he's leaving us here, as a lesson to the outside world?"

"No, we're snagged on something. He needs help getting loose, he wants you to pole the boat."

Tony followed Duca overboard. I stood up in the broiling sun. Two large brown herons with yellow wings flew by, very rare, but I barely glanced at them. I was too busy working, and wondering if we would ever see MacArthur Boulevard again. Why hadn't we gone somewhere normal, like Galesville, instead of insisting coming here, where no one we knew would ever find us again?

The dugout was moving. I sat down, heaving, sweat pouring down my arms and neck. Duca scrambled black in, Tony behind him, and started the outboard. In a minute we were speeding across the lake again. Duca pulled some grass from the water and split its seeds, gesturing for us to sniff them.

"Veneno," poison, he said in Portuguese. His chiseled face was calm and his expression was warm and interested. "Never eat these."

"We won't," Tony leaned back and stretched. "We only eat nuts and berries."

Late that afternoon we burst through the last trees onto the Solimoes and put away our binoculars.

"I like it here," Tony said. "We should definitely try and get back sometime."

I rested coming downriver in the launch to Manaus, and I dozed while a taxi took us to the airport for our Sunday-night flight to Bogota. But when we got out I stopped. The terminal doors were 10 feet in front of us. Through them lay the cold, silky air of the jetport, the ramp to the plane, the 55-degree temperatures of the Andes ahead. It would be over. I stood, watching a drop of sweat run down my arm and fall onto the soil.

"So what was it like?" people would be asking us later.

"Fascinating, just like the movies," I, would say. "You know that scene in "The African Queen,' when Humphrey Bogart has to jump overboard, and pull the boat with his bare hands?"

"You mean -"

"That's right," I would say, and I smiled at Tony now as I picked up my bag for home. "It was exactly like that."