President Carter's "hit list" of Corps of Engineers water projects he wants cut from the federal budget is coming face to face with political realities.

Just a few hundred yards from the Red River, which snakes through this north Louisiana city, the state's congressional delegation, led by Sen. Russell B. Long (D-La.), fired the first volley Saturday in what promises to be an all-out drive to save the $954 million Red River Waterway.

Long, chairman of the Senate Finance Committee, arose at a packed public hearing to speak of "honor" and a federal commitment. Fellow Democrat Sen. J. Bennett Johnston followed calling development of a navigable waterway along the Red "our birthright."

Supported by an enthusiastic audience of 600 business and civic leaders, farmers and state and local politicians, Long shook his finger at Col. Early J. Rush, the New Orleans district engineer who chaired the hearing, and assailed Carter's new criteria for evaluating water projects.

Long pounced particularly on Carter's use of a 6.38 per cent interest rate - instead of the congressionally authorized 3.25 per cent rate - in computing cost benefits to justify Corps projects.

If the interest rate on money borrowed for the project is increased from 3.25 per cent to 6.38 per cent, the cost-benefit ratio drops to less than 1 - meaning that the project would cost more than the benefits it would provide.

"The President might win his argument over interest rates before a bunch of environmentalists, but let him try it before a bunch of businessmen," Long, said to a tumult of applause.

While Long didn't personally attack the President, it was clear to everyone attending the hearing that if necessary the senator will fight Carter's attempt to kill the project.

In an interview afterward, Long predicted that the President's list will be "further reduced."

Although "I don't fault the President on this," Long was quick to say, "I think Red River will be funded, even if I'm not right about the economics - and I think I am."

The Red River Waterway was authorized by Congress in 1968 and first funded in 1972. The project, which until Carter put it on the "hit list" was estimated for completion by 1985, consists of a network of five locks and dams, and would provide a 236-mile navigable link between Shreveport and the Mississippi River.

Johnston catalogued unemployment rates, substandard housing and other indicators that the parishes along Louisiana's Red River Valley are economically depressed.

Johnston, who chaired Carter's Louisiana election campaign, said afterward, "If the people in Louisiana thought Carter would cut out the the Red River and some of these other projects the state wouldn't have gone for him."

Rep. Joe. D. Waggonner Jr. (D-La) was applauded when he assailed Carter's willingnes to sharply increase funding to the World Bank - much of which Waggonner said goes to water projects in developing countries - while cutting back on the Red River project.

Of more than 60 who registered with the Corps to speak at the hearing, only one opposed the project. Steve Forsythe, of the Fish and Wildlife Service's Vicksburg office, detailed numerous adverse environmental effects, including reduced habitat for endangered species.

Able Conyous Skannal was typical of many at the hearing who favor the project. Skannal, who has spent all of his 74 years in the Shreveport area, raises cattle and farms on 1,200 acres along the nearby Bayou Bodcau River, and believes "it will bring progress."

Said Skannal, whose sister is married to one of the President's cousins, "If Carter ultimately disapproves the Red River project, the people will be disappointed and will be counting on an override."

The community support for the Red River project is attributable to growing concern about the Shreveport area's economic future. In recent years Louisiana's oil and gas production have declined, and signs of that decline have already hit Shreveport.

Texas Eastern, one of the nation's largest gas transmission companies, recently announced plans to transfer 400 Shreveport-area employees to Houston.

Two years ago Pennzoil, a major domestic oil and gas producer, moved its last employees from Shreveport.

Sinclair B. Kouns, president of the seven-member Caddo Bossier Port Commission, summed it up: "Unless we have some new industry here in the 1980s we could have a serious economic shock." Kouns, who also serves on the Shreveport Policy Jury, parish government body, believes the project will attract business.

William Cockrell, an executive of Atlas Processing Co. in Shreveport, said after the hearings," There are a lot of disgruntled people here." Cockrell also recalled former President Ford's assurance during a 1976 campaign visit to Shreveport that Congress will see to it that the funds are approprated.

One of the major determinants in the future of the Red River project is a plan to develop the massive coal deposits, mostly lignite, along the Red River Valley.

Arnold C. Chauviere, Louisiana's assistant commissioner of conservation, speaking before a nearly empty auditorium late in the afternoon, said there are 1,470 million tons of proven and known lignite reserves, equivalent to 3.6 billion barrels of oil, near the project.

According to state mining officials, Dow Chemical, Shell Oil, Phillips Petroleum, Southwest Electric Power Co. and Olin have obtained permits to explore the area for econmically recoverable lignite deposits.

For the lignite to be competitive with bituminous coal, which has twice the heat content, developers would need access to cheaper water transportation.