It's more than a mere nuisance for those who step in it. Or smell it. Or find it in their gardens.
Dog leavings on streets and sidewalks can contribute to water-quality problems in streams.
"You wouldn't let your dog poop in your pool," said Joanne Dahme, spokeswoman for the Water Department, which is holding the contest. "But if you don't pick up after your dog, after the next rain it could wind up in the river."
Especially in Roxborough, Manayunk, and East Falls, the neighborhoods in the "spokesdog" pilot project.
These are steeply graded communities, offering plenty of opportunity for poop to plummet to the Schuylkill.
Plus, unlike most of the rest of the city, sewer pipes there are separated. Household waste goes to the sewage-treatment plant. Storm water - and all it carries - flows directly into the river.
Not far from drinking-water intakes, it must be noted.
Officials estimate that 5,000 dogs live in the three neighborhoods.
The project grew out of community greening efforts that involved landscaping yards and curbs.
All too often, however, someone would finish a nice project only to find that it also made a nice rest stop for a dog, said Gina Snyder, executive director of the nonprofit East Falls Development Corp.
So, instead of planting, some people started cementing.
"We were horrified to realize it was all about dog waste," Dahme said. "It was becoming an obstacle to us making these communities greener communities."
Dahme has a dog, a rescued greyhound named Terminator - he came with the name - and can vouch for how often a dog goes.
According to statistics cited by the Water Department, dogs in the U.S. produce 3.6 billion pounds of waste a year. And it can take upward of a year to degrade.
Some - probably those who don't pick up after their dogs - regard it as a sort of harmless fertilizer. It's not.
Although the Water Department has chemicals and procedures to deal with fecal coliform bacteria and other contaminants, people who boat on or fish in or walk along the river do not.
The department posts daily updates of the Schuylkill's water quality in the city at www.phillyrivercast.org
It's intended as a guide for recreational users, designating water quality as green, yellow, or red.
The city has no handle on how much of the contamination is due to dog doody, but others do.
About a decade ago, scientists in Virginia were able to use genetic mapping techniques to see whether samples of E. coli came from humans, cattle, poultry, horses, cats, geese, ducks, raccoons, or deer. Or dogs.
In Fairfax County's Accotink Creek, an urban stream, the single biggest source of the bacteria - nearly 25 percent - was, not surprisingly, geese. Humans were also at fault, their failing septic systems and leaking sewer pipes contributing slightly more than 20 percent.
Almost 15 percent of the fecal coliform came from dogs.
Many cities prohibit dumping dog waste on streets. In Philadelphia, the fine is $500.
But more creative methods of dealing with it have emerged.
In one Ithaca, N.Y., park, dog owners who cringed at the idea of all those plastic bags of poop winding up in the local landfill began a composting project.
In Cambridge, Mass., a Harvard art student got a $4,000 grant to create a temporary installation that used methane from decomposing dog waste to power a gaslight in a park.
In Philadelphia, Water Department officials settled on the spokesdog contest.
Residents of Roxborough, Manayunk, and East Falls have until Sunday to enter. Rules, photos of the contenders, and online entry forms are available at www.phillywatersheds.org/spokesdog/
A public vote will determine finalists. Judges will select the two winners - Roxborough and Manayunk will share a spokesdog, East Falls will get its own - based on "friendly nature, best canine smile, charm, and natural spokesdog abilities."
And then, the city says, the spokesdogs will be required to attend at least three community events in 2011, at which information will be distributed on "living the eco-friendly dog life."
Sharon Jaffe said her East Falls cocker spaniels are certain they have a crack at the acclaim.
"Contessa is just a lover of the garden, so she believes in being out in nature, and she also thinks she is the daintiest and perhaps the most attractive dog," her two-legged companion related.
Then again, "Zoe believes she is better suited because Contessa hates the rain, and she doesn't believe anyone who doesn't want to get their feet wet should be a spokesdog for the Water Department," Jaffe said.
"There is a fierce rivalry going on."
In Manayunk, Garrett Elwood has hopes for his rescued dog, Vegas, a mixed breed with a "sweet personality."
She has been on the job already, encouraging waste cleanup in the dog play area at Manayunk's Pretzel Park.
There, dogs and humans rely on peer pressure to get the message across, Elwood said.
"We've established that it's OK to say, 'Excuse me, sir, you probably didn't notice, but your dog just pooped up there. We have bags.' "
Contact staff writer Sandy Bauers at 215-854-5147 or firstname.lastname@example.org. Visit her blog at http://go.philly.com/greenspace