THE POTOMAC RIVERFEST, the city's celebration of the success in cleaning up the river, is bigger than ever this year.

The festival, which organizers say drew 200,000 people each day last year, kicks off this weekend with two days of free entertainment along the city's Southwest waterfront between Pier 5 and the fishing wharf.

In addition to four stages offering nonstop entertainment Saturday and Sunday, there'll be a parade, hovercraft and sailboard demonstrations, tall ships, crafts, food, fireworks and exhibits on the history and environmental status of the Potomac.

The festival, now in its third year and a favorite project of Mayor Marion Barry, is sponsored by the D.C. government. Here are a few highlights. (For more information, call 673-7660.)

*A major festival deserves a major parade. And at 10 Saturday, Riverfest celebrates its first-ever parade. Among the 87 entries (a thousand people in all) are clowns, kung fu artists and German and Chinese dragon dancers, as well as marching, military, bagpipe, reggae and calypso bands. There'll also be floats, dancers and steel bands from Trinidad and Tobago, Jamaica and St. Kitts. The parade heads west along Constitution Avenue from Seventh Street NW to the Ellipse at 17th Street.

*Always a big draw, the tall ships return, with six American or Canadian sloops and schooners open to the public this weekend. Boarding times will be posted in front of the ships, which will be moored at the Municipal Pier (550 Water Street SW), Gangplank Marina (600 Water Street SW) and the Capital Yacht Club (1000 Water Street SW). Over the course of the summer, a total of 22 tall ships from all over the world will visit Washington.

*The blues grew up along rivers, so it's only natural that the festival serve up a generous portion. The stage to watch is No. 2 on Sunday, when four blues bands featuring harmonica players begin serious wailing at 6:30. Veteran bluesman James Cotton -- who's played with Muddy Waters and is considered one of the best live blues performers -- tops the bill with his band starting at 9.

*Riverfest has always been keen on the phrase, "finishing with a bang." This year is no exception. Saturday and Sunday nights at 10, there'll be 30-minute firework displays on par with the Fourth of July show on the Mall. Recommended areas for viewing are along the Southwest waterfront and Hains Point. Riverfest month even finishes with a bang -- fireworks and lasers on June 28 beginning at 10 at West Potomac Park.