The morning sun lit the colors of the urban river: a pale blue heron bolting overhead, neon orange lilies piercing the green thicket along the shore, raspberry wildflowers atop leafy water plants.

While the rest of the city cranked up for a dirty, steamy rush hour, the Anacostia River, from the vantage point of a canoe paddling downstream, offered a quiet and cool bit of bliss -- that is, if you didn't look at the water.

The river itself was clotted with polystyrene cups, crumpled potato chip bags, tampon sheaths and tennis balls. The river is a dumping ground for society's fast-food picnic, so cluttered with trash that a paddle cannot dip in without bumping garbage. A sluggish waterway, it does not flush its trash downstream.

The Anacostia is not a river to explore for aesthetic pleasure. People who put into this water do so for a reason -- fishing, duck-hunting or, in Robert Boone's case, missionary work.

Boone is among a corps of believers in the Anacostia, the tainted tributary of the Potomac that is the focus of a cleanup campaign launched three years ago by a coalition of private organizations, regional planning groups and local governments. Boone, a longtime environmentalist, is cofounder and executive director of the Anacostia Watershed Society, a private nonprofit group lobbying on behalf of what is sometimes called the city's "other river."

"We've got the Potomac," Boone says, "and then there's that other one over there that we don't want to talk about because it's so ugly and polluted."

The river's problems of erosion and raw sewage are being addressed by a package of technology-based solutions with names like "stormwater retrofit" or "combined sewer overflow abatement project." But Boone correctly figured that knowing how these things work is not the only way to learn about beautifying a prize of nature, so he invited a reporter to see the worst by paddling a canoe from the Prince George's Marina in Bladensburg to Anacostia River Park, about four miles downstream.

The journey took 2 1/2 hours at a leisurely pace, but was not done with leisure in mind. After a rainstorm, the river's count of fecal coliform -- the bacteria in human waste -- is 500 times higher than is considered safe for swimming.

Brown with mud and tree branches, the river was so starved for oxygen that fish leapt from the water, apparently seeking fresh air. That might be a fisherman's joy, except that local health authorities warn that catfish and carp caught here may contain toxic chlordane and PCBs.

An abandoned Oldsmobile appeared on the left, its nose plunged into the riverbottom and its backside on the bank. Not built as a convertible, it had decayed into one long ago. Downstream, a vinyl couch sat marooned on a sandbar. Unlike these larger items, food wrappers and other trash items were not dumped into the river itself. The little stuff washes in from storm drains or creeks, making its way downstream.

Amid its shame, though, the river asserted a certain loveliness. The land along the journey was owned by the public, so the green fringe was unbroken along shore. We heard voices from the Langston golf course on the other side of the trees. The Japanese garden of the National Arboretum beckoned, the lawn so soft and green it seemed perfect for a picnic.

South of the Benning Road bridge, the scenery turned grittier -- RFK Stadium, a sewer outflow pipe -- and the air got hotter. We slipped under the railroad bridge that crosses the river. Nearby, the Anacostia boat landing was being refurbished by the Park Service for motorboats.

Boone and other Anacostia believers want a canoe landing installed there or nearby, to make the journey from Bladensburg easy for all. First, though, the river has to be clean enough to interest people in the trip.

We hoisted ourselves out of the water onto a crumbling shorewall.

"That," said Boone grimly, "is the dirtiest I ever saw it."