Terence Monmaney had been promised a canoe trip down an ancient river, with steep, wooded banks, coves thick with water lilies and great blue herons overhead. He expected something pristine. He got the Anacostia.

"The Anacostia? I thought that was a Washington sewer," said Monmaney, 27, a descendant of French-Canadian fur trappers who never had seen the river before our canoe trip last week. But he had heard it slandered often enough to believe its unsavory reputation was deserved. "This isn't exactly what I had in mind," he said.

The Anacostia don't get no respect. While the Potomac has been rehabilitated during the last decade, at a cost of a billion dollars, Washington's other river has remained a festering sore. Mention the Anacostia to most folks and noses wrinkle in disgust. The river, which meanders from its headwaters near Bladensburg through Southeast Washington to the Potomac, is the kind of stream that gives running water a bad name.

"Much of the Anacostia is underutilized, unkempt, sediment laden and at times so oxygen depleted that even such pollution-tolerant fish as catfish and carp are the victims of fish kills," says the Potomac Basin Reporter, the Interstate Commission's publication on the Potomac River Basin. "Many look on the river as a regional symbol of neglect, surrounded by a neglected community."

The Anacostia has suffered a long fall from an earlier period of grace. In the 1700s, when Pierre Charles l'Enfant was designing Washington, he wrote that Anacostia's harbor was "in every respect to be preferred to that of the Potomac." In the first half of the 18th century, Bladensburg was Maryland's busiest port town. Ocean-going ships sailed up the Anacostia to load hogsheads of tobacco for European trade.

But it was the tobacco trade that led to the Anacostia's demise. As land in the watershed was cleared of trees for farming, erosion began filling in the river with silt. Today, the Anacostia at Bladensburg is just one-fifth as wide as it was in 1700. And it is shallow enough in places for a canoe to run aground.

The depth of the river, however, is not as serious a problem as its water quality. Because more than a third of the District's sewers carry both raw sewage and storm runoff, heavy rains regularly dump sewage directly into the Anacostia. At times the river appears to be half water and half lighter fluid.

Help, though long overdue, appears to be on the way. Last summer, D.C. Mayor Marion Barry and Maryland Gov. Harry Hughes signed a cooperative agreement to clean up the Anacostia and 153 square miles of watershed. The District has promised to spend $40 million on the project during the next 16 years.

The surprising thing about the Anacostia is that, despite the quality of its water and reputation, it still is essentially scenic. Because approximately 90 percent of the shoreline is publicly owned, most of the obvious eyesores could be healed with a thorough scrubbing.

A canoe trip from Bladensburg to the Potomac is a journey between extremes. Within a few hundred yards of the Bladensburg Marina, the shoreline blossoms with willows, oaks and sycamores. A hundred yards later, a mud flat appears that is so littered with old tires, car parts, cans and bottles it looks as if a trash truck had overturned there.

"You know the American Indian on those television commercials about pollution?" Monmaney asked. "They could use him right here, with a tear rolling down his cheek."

Around another bend we faced a steep, tree-covered hill of the National Arboretum, a park as pretty as any in the city. Directly across the river was the Kenilworth Aquatic Gardens, a 102-year-old floating garden with 50 lagoons that support Egyptian water lilies and East Indian lotus.

Jolting us again was the appearance of a massive Pepco power plant with tall smokestacks. But before that sight could change our mood, a great blue heron swooped out of a nearby tree and flapped its big wings downriver. We would see another heron before the day was over, along with nearly two dozen mallards.

The closer we got to the Potomac, the less lovely became the Anacostia. We paddled under five great bridges carrying cars and subway trains. We passed the Navy Yard and half a dozen small marinas, some with ancient wooden boats sunk beside their docks.

The most appealing of the marinas was the Washington Yacht Club, a white wooden building on top of a cinderblock base with a sign announcing its birth year as 1910. The door to the club was wide open. Inside we found a pool table, a stuffed dolphin and a cola machine that dispensed beer rather than soda. But no one was there to tell us about the club's history. We were glad to invent it for ourselves.

For the rest of the trip we took turns making up verses for our "Ode to the Anacostia." A lot of them ended in words that rhymed with mud and crud. Maybe the next generation of Washington canoeists won't have to sing that kind of song.