Impact of Reagan Cabinet switch

The face has changed at the Department of the Interior, but will the song remain the same? William P. Clark, President Reagan's new nominee for the Cabinet seat, at least represents a switch in styles. Judge Clark is genial and low-key; his predecessor, James Watt, at times didn't seem happy unless breakfast came with a side order of controversy.

But Clark's appointment is not a clear sign that the administration is softening on environmental issues, as was the installation of William D. Ruckelshaus to head the Environmental Protection Agency, most analysts here explain. It's unlikely, they say, that Clark will substantially alter Watt's policies.

''I don't think a lot is going to change (at Interior), though things will be much quieter over there,'' says an aide to a Senate Republican who serves on the Energy and Natural Resources Committee.

Judge Clark's prime qualification for his new post appears to be the fact that he is one of Ronald Reagan's most trusted aides. He has little experience with environmental or energy issues.

As a stalwart Western conservative, however, Judge Clark likely shares Mr. Watt's pro-development view of natural resources, say Republican sources. During his 1973-81 stint on the California Supreme Court, Clark was the least ''preservation-oriented'' justice, according to a UCLA Law Review survey.

And in any case, Watt's influence will linger at Interior even after the new secretary takes his post. A skilled bureaucrat, Watt during his tenure stocked dozens of key lower-level posts with loyal followers. ''They're the ones running the department,'' claims Tim Mahoney, a Sierra Club public-lands specialist.

Though Clark's calm nature could help ease the now-strained relations between Interior and Congress, it may take more than a change in style to mollify Capitol Hill. Irritated with Jim Watt, and with one eye on the '84 elections, Congress is increasingly taking natural-resource policy into its own hands.

The Interior Department appropriations bill, now awaiting final approval by both chambers, ties the agency's hands in some areas and forces action in others.

Sale of federal coal leases would be banned for some six months. Large chunks of United States coastal waters would be protected from oil and gas drilling. Funds for purchasing new park land would total $225 million, almost four times the level requested by the administration. Administration officials now say it's unlikely the bill will be vetoed.

But there will be other opportunities for pitched battles over what Interior should and shouldn't do. Specifically, congressional aides and environmentalists say these natural resource issues (among others) are likely to be argued about in coming months:

Coal leasing. Watt, in his desire to lease as much US land for coal mining as possible, ran afoul of both Congress and the federal courts. A special Watt-appointed commission is now studying coal-leasing policy, and is expected to issue recommendations in January.

Development in wildlife refuges. Under Watt, Interior was moving to open 1 million acres of refuge land (areas less pristine than national parks) to oil and gas drilling. Environmentalists have sued to stop the action; House Democrats are attempting to pass a restraining order.

Budget. Interior's budget for 1985 will reflect Watt's priorities, since it is already largely completed. Congressional aides predict Congress will try major alterations.

Designation of wilderness areas. Interior's recommendations on how much of some 24 million acres of federal land should be labeled wilderness has constantly irritated many in Congress.