Washington — Interior Secretary William Clark has friends in Congress. Friends who are Democrats, no less. There's Mo Udall, for instance. Representative Udall, chairman of the House Interior Committee, is a champion of environmental groups. He and James Watt used to go at each other like two squalling cats.
But Mr. Udall and Secretary Clark, Mr. Watt's successor, are pals. ''Mo finds Secretary Clark simpatico,'' says an aide to the congressman. ''They had lunch once, I think. Clark's been up to the office a few times.''
The relationship is symptomatic of the changes Clark has wrought since taking over Interior. Watt had a stormy ''Ride of the Valkyries'' approach to management; Clark has made gestures of conciliation to Congress and environmental groups.
So far actual changes in policy have been more symbol than substance. But Clark, if nothing else, appears to have made the environment a somewhat less contentious political issue.
''Between now and November, Clark obviously wants to avoid confrontation,'' says Brooks Yaeger, a Sierra Club energy specialist.
It has been two months since Clark took over as top man at Interior's barracks of a headquarters on C Street. During that time, he has not had to make any decisions on such major questions as ''How much government land should we lease to coal mining companies?''
Still, there have been some interesting developments at the Interior building. They include:
* An exodus of Watt lieutenants. When Watt was forced from office, environmentalists complained that his spirit would linger on, because he had left hard-line aides in many key positions. These aides are now starting to fall. Minerals officials William Pendley and David Russell, who helped design Watt's controversial coal and oil leasing programs, have been dumped; William Coldiron, the department's top lawyer and a master at devising pro-development rule interpretations, has announced he will soon leave.
On the other hand, another key Watt associate - Garrey Carruthers, now assistant secretary for land and minerals - was actually promoted by Clark.
* Softer words on offshore oil leasing. Last week, the Supreme Court ruled Interior did not have to consider coastal states' concerns when selling offshore oil and gas leases. Clark quickly announced that he was renovating the offshore lease program to give states and the public more say in the proceedings.
''That could be a significant step toward toning down the controversy over (offshore leasing),'' admits Mr. Yaeger of the Sierra Club.
Clark has stressed, however, that Watt's ''basic approach'' to continental shelf energy development will be retained.
* A request for money to buy new parklands. James Watt placed a moratorium on the purchase of new parkland, saying scarce funds were needed for park maintenance. But Clark has promised to request $157 million in 1985 for park acquisition, with most of the money to be used for ''rounding out'' existing parks.
Environmentalists complain the request is a publicity stunt. Congress routinely forced park purchase funds on a reluctant Watt, they point out - $240 million last year, for instance.
The key question in all this is whether the rumblings at Interior are portents of change or random noise.
If nothing else, they do seem to indicate an un-Wattlike concern for public relations. It is probably no accident that the new nominee for Interior's No. 2 spot - Ann McLaughlin - was assistant secretary of public affairs for the Treasury.
And Clark, by all accounts, listens to differing opinions more than did Watt.
''He likes a lot of information,'' says a midlevel Interior official who remains critical of Clark's policies. ''That's good.''
But critics insist Clark's changes are so much smoke, and that policies remain unchanged.
''Yes, the initial PR effort is having some effect,'' says William Turnage, director of the Wilderness Society. ''But after Watt it's impossible not to look reasonable. All you have to do is smile and once in a while take an environmentalist to lunch.''