WASHINGTON - President Clinton helped clear a flood-damaged canal, while House Speaker Newt Gingrich served as a tour guide for schoolchildren at a zoo.

Bob Dole, Senate majority leader and certain GOP presidential nominee, said the nation's environmental heritage ''was forged under Republican stewardship'' by such presidents as Ulysses Grant, Theodore Roosevelt and Richard Nixon.

Interior Secretary Bruce Babbitt said Americans' ''love affair'' with nature is putting a strain on national parks, while the Sierra Club accused the government of dumping toxic chemicals into the Anacostia River.

This was the 26th anniversary celebration of Earth Day. And some of yesterday's events seemed to mix concern for the environment with a little election-year politicking.

The president announced a series of actions he intends to take to boost the national parks system, which has been under severe strain because of an increased number of visitors. The package, National Parks for Tomorrow, would expand or obtain two prized properties in states that are pivotal to Clinton's re-election bid.