James G. Watt's influence will not vanish from the Interior Department when he does. In his wake, he leaves not only massive policy changes and considerable controversy but also a cadre of loyal aides determined to perpetuate his programs long after he is gone.

"Secretary Watt was a great interpreter of Ronald Reagan," said Assistant Interior Secretary Garrey E. Carruthers, who directs Watt's program to speed up the leasing of federal coal reserves to mining companies. "We'll just continue to carry on. We have the management system in place. The team is in place and continuing to operate."

Interior was far from a one-man show under Watt. While he consumed much of the media attention for the last 2 1/2 years, he also stocked the agency with dozens of second- and third-tier appointees who labored daily, in obscurity, to translate his philosophy into policies. They will continue to try to do so.

Through these people, Watt planned to institutionalize his approach to the management of national parks, offshore oil leasing, coal development, strip-mining regulations, grazing, wildlife management and more. In the last year he directed extensive personnel transfers "to make sure that the right type of people are there to carry out" what he set in motion, he told an interviewer.

Watt relied heavily on Interior Solicitor William H. Coldiron, former legal counsel and executive officer of Montana Power Co., which conducts extensive oil, natural gas and mining operations on Interior lands. Coldiron, as Watt's lawyer, supervised the drafting of legal opinions authorizing each of Interior's new policies and regulations.

Watt and his aides invoked Coldiron's opinions to relax regulations governing strip-mining reclamation, reduce protections on 800,000 acres of wild western lands being considered for inclusion in the federal wilderness preservation system, authorize development of an airport on a wilderness island off the coast of Alaska, open 1 million acres of national wildlife refuges to potential oil and gas leasing and allow oil and gas companies to seek leases in wilderness areas, a position Watt later repudiated.

"Coldiron was the secretary's alter ego," said a senior Interior official. "Watt basically worked through Coldiron. His goal was not to change the laws, but to find ways to exercise his discretion within the old laws. That required help from the solicitor's office. If Coldiron hadn't been here things would have been different."

Just as Watt transformed Interior, Coldiron, 67, transformed its legal shop. Past and present officials said they were regularly assigned to produce legal opinions justifying Interior programs, not to examine them objectively.

Last February, after the California regional solicitor wrote an opinion saying there may have been no legal basis for relaxing protections on certain of the 800,000 acres of wild western lands, she was transferred to Washington, and Interior officials were ordered in a memorandum to "destroy or return" all copies of her opinion.

There was an exodus of lawyers, draining what officials called the "institutional memory" of certain quarters of the solicitor's office. In the surface-mining division, which was mobilized early in the Reagan administration to help relax 90 percent of existing federal reclamation rules, 15 of 20 attorneys on the staff in 1981 have left.

"After spending the Carter administration trying to figure out how much a federal statute allows the secretary to regulate, it was pretty demoralizing to be told to go back and figure out how little it allows you to regulate," said one attorney who left the division.

Other aides still in place are David C. Russell and William P. Pendley, considered Watt's ideological twins within Interior. In staff meetings, the two fervently supported Watt's programs to accelerate the leasing of government-owned minerals despite growing opposition from Congress.

They designed the controversial 1982 sale of leases to 1.1 billion tons of coal along the Wyoming-Montana border in which, according to congressional auditors, Interior sold the leases for $100 million less than they were worth.

Controversy over that lease sale, which drew virtually no competition and low bids, turned Watt's coal program into a political powder keg, leading ultimately to last month's Senate vote imposing a moratorium on the program until it is investigated by an independent commission.

Administration officials said there is no indication that the White House plans to move Coldiron, Pendley, Russell or others of Watt's top aides from their posts. Russell heads the Minerals Management Service, responsible for managing billions of dollars in royalties from government oil, gas, coal and other minerals. Pendley is acting assistant secretary in charge of Energy and Minerals, which includes offshore and oil drilling.

Russell, co-author of the Heritage Foundation's 1980 conservative critique of the Carter administration's Interior policies, shares Watt's penchant for fiery rhetoric as well as for conservative politics.

Earlier this year, he startled some Canadian officials who complained in a diplomatic message that Interior, in a Federal Register notice, had claimed mineral rights to some Canadian reserves.

In a memo to Pendley, which was obtained by the Canadians, Russell wrote: "Our response to Canada's terse diplomatic note should be 'Dear Canada: "Our F.R. Federal Register notice obviously pertained to our offshore areas, not yours. Therefore, up yours! Love America.' "

Watt also moved a new team of managers into the National Park Service, which for years had been run by career Park Service employes. Although director Russell E. Dickenson was not replaced, only one of his top 11 assistants is now a career Park Service employe.

With the help of his aides, Watt brought about a major shift in conservation policy, swinging the pendulum toward more development and less restrictive protection of the nation's natural resources.

But because most of the changes were contained in new regulations and policy directives--not in legislation--they could be reversed by a new administration with different objectives, officials said yesterday. In addition, many of the changes could be struck down by the courts.

It is also unclear how Watt's tenure has changed the composition of Interior's civil service. Many career bureaucrats supported his policies, and many who opposed him managed to wait him out. Others became "moles" for environmentalists and reporters, working late into the night copying confidential documents and sharing this information with people on the outside.

"Everybody in town had a mole in Interior, whether they wanted one or not," said Jack Lorenz, executive director of the Izaak Walton League, a conservation group. "I had a guy who called me almost every night. He identified himself as 'Deep Trout.' "

"I leave behind people and programs--a legacy that will aid America in the decades ahead," Watt wrote in his letter of resignation. "Our people and their dedication will keep America moving in the right direction."