How dirty is that waterway?

Two-year-old Aurora is strung through an inflatable blue tube in the water at Ottawa's Britannia Beach, kicking and splashing along the shore, while her four-year-old brother, Finnegan, wades nearby on a sunny fall afternoon.

Their family actually lives closer to Westboro Beach, but their mother, Bridgette Mallon, moved their regular beach outings further upstream due to concerns about water quality.

Even now, the family takes precautions.

"We're just careful to check the E. coli count before we ever jump in the water ourselves," Mallon said. "And then we make sure we go home and have a good shower and wash off anything that might be a concern."

The Ottawa River is the source of drinking water for more than a million people in Ontario and Quebec who live along its 1,271-kilometre length.

But a recent survey of 800 Ottawa-Gatineau residents found that 49 per cent of respondents thought the river is either highly or quite polluted, and 42 per cent think it is somewhat polluted. Well over half think swimming in the river or eating fish caught in its waters pose a health risk, according to the Segma/Unimarketing survey, commissioned by CBC/Radio-Canada.

Brian Adams, manager of the Ottawa Rowing Club, said he's noticed more and more dead fish and dead birds along the river this year, and the water is particularly dirty after a heavy rainstorm.

"You'll basically see a big water slick of paper and garbage, and I mean maybe a hundred feet by a hundred feet, floating down the river from the storm basins."

The survey found that, like Adams, 44 per cent of Ottawa-Gatineau respondents who believe the river is at least somewhat polluted blame the municipal sewage system, more than double the number who blame it on industrial waste.

But despite their worries about water pollution, 75 per cent of survey respondents said they think the municipal water from the Ottawa River is either very good or good for the health of the people who drink it.

Frances Pick, a University of Ottawa biologist who studies aquatic microbes, said that the quality of the water in the river is, in fact, quite good compared with the water in other rivers of its type and that it is "remarkably clean" upstream from Ottawa.

"It's a beautiful river, and it's certainly a river that you can swim in," she said, adding that that's unusual for an urban watercourse. Many people assume the river's brown colour means it's polluted, Pick said.

"That's completely wrong. It is naturally a brown-water river," she said, adding that the true source of the colour is organic material from the 14,630,000 hectares of soil and wetlands that drain into the river. "It's like a tannin, basically — it's what you have in tea."

According to the Ontario Ministry of the Environment, the river is also clean enough that it's safe for most people to consume crappie, rock bass, brown bullhead, white sucker, channel catfish and sturgeon caught from its waters four to eight times a month, depending on the species (the limits are lower for children under 15 and women of childbearing age.)

Cleaner than it used to be

It appears that things were much worse in the past, Pick said, when there was a lot more industry — including lumber and pulp and paper — along the river and standards of hygiene were poor. She pointed to cholera epidemics in the 19th century and beginning of the 20th century.

To be sure, there isn't a lot of direct data from that era, Pick said. However, the amount of oxygen consumed by microorganisms in the water at Hawkesbury, Ont., was measured between 1970 and 2000, and the data show the amount of organic matter was higher in the past, when there was a lot of lumber processing there. That means the water is cleaner now.

Other data show that in the 1960s, nutrient levels were higher in the water than they are now, Pick added. The drop stems from efforts to remove nutrient-rich pollutants such as phosphorus from sewage in the '70s and '80s.

Down at the rowing club, Adams said there is an old gentleman who has been sculling through the water for half a century and who agrees the river was once much worse.

"He tells about how they used to hit logs and all the pollution that was down here then," Adams said. "He says … he's never seen it so clean, basically."

Dixon Weir, director of water and wastewater services at the City of Ottawa, said the municipality started doing some water testing in the river in 2005. Based on the results, it seems that a mere 1.3 kilometres downstream from the city, dilution is strong enough that water quality no longer registers Ottawa's impact, he said. However, Dixon agreed that testing downstream from Ottawa is still in its very early stages.

Richard Lalonde, mayor of Rockland, an Ontario community 30 kilometres downstream, said his community recently boosted its water testing from once a month to almost daily. In the process, the community has found that there are large variations in the level of bacterial contamination, suggesting a strong effect from upstream communities.

Rockland has had to invest in a an expensive electronic system to adjust its water treatment based on the quality of the water coming in.

"We wouldn't have to do that if everybody wouldn't be throwing their sewage into the Ottawa River," Lalonde said.

Bacteria from sewage aren't the only source of pollution in the river, and nor is keeping microbes out of the water the only solution that needs to be considered, Pick said.

Pharmaceuticals, agriculture have impact

Flushed pharmaceuticals have been shown to change the sex ratios of fish in other waterways, but little study has been done of natural fish populations in the Ottawa River, Pick said.

Meanwhile, agriculture contributes pollution such as fertilizers, pesticides and animal manure

Because the Ottawa River is fast-flowing, communities have traditionally relied on dilution to minimize the impact of their pollution, Pick said.

"And we've gotten away with it to a certain extent, but as the city grows … it's not a solution," she said. "As the city grows, the pressures will increase, and if we want to preserve the quality of life that we're used to having here in Ottawa … then we have to make that effort."