Climate change could worsen water contamination by causing heavy rainstorms that overflow sewers, dumping wastewater into lakes and rivers and washing more manure and fertilizer from farmers' fields into nearby bodies of water, one report said. (CBC)

Canada's lakes and rivers are awash in harmful contaminants, but new documents warn the federal government's murky understanding of the problem is putting the country at risk.

Senior bureaucrats reached that conclusion in a pair of internal reports on contaminants and excess nutrients in fresh water.

The officials warned that Ottawa needs to know much more about the contaminants before it can tell how dangerous they are, what happens when they mix together, or where to focus cleanup efforts.

"There are significant gaps in the understanding of contaminants in groundwater in several areas which hinder the advancement of effective risk assessment and management activities," says one of the reports.

Algae blooms a growing problem

The reports were produced by working groups of high-ranking civil servants from several departments that the government formed two years ago to study water issues.

The Canadian Press obtained two of the groups' draft discussion documents under the Access to Information Act. The reports, dated December 2008, were only released last month.

One report looked at contaminants in fresh water. The other was on excess nutrients, such as phosphorus and nitrogen, that cause toxic algae blooms.

Giant floating fields of algae have taken over swaths of the Great Lakes, Lake Winnipeg and many other lakes across the country in recent years. The algae sucks oxygen from the water and produces toxins that are harmful to fish, humans and other living things.

Run-off carrying agricultural fertilizers, wastewater from sewers and industrial pollution are identified as the main sources of nutrients in Canadian freshwater lakes.

The report warns the problem will only get worse.

More human waste will end up in the water as the population grows. More people using more water means there will be less of it to wash away excess nutrients from lakes and rivers, leading to more build-up.

Climate change may worsen problem

The effects of climate change could also exacerbate the problem.

Heavy rainstorms could overflow sewers, dumping wastewater into lakes and rivers and washing more manure and fertilizer from farmers' fields into nearby bodies of water. Heavy rain followed by warmer and sunnier weather are the perfect conditions for algae blooms to grow.

The report suggests a national, publicly available source of information on nutrient levels in fresh water could help the government tackle algae blooms.

"Government response to reports of harmful algal blooms is being hampered due to lack of knowledge," the document says. "Especially about blooms of 'blue-green algae'."

The bureaucrats couldn't put a price tag on the problem.

"The value of these costs has not been quantified for the Canadian context, but is likely considerable," they wrote.

Too many nutrients is only part of the problem in Canada's bodies of water.

Pathogens such as bacteria and viruses, pharmaceuticals and chemicals, pesticides and run-off from mining sites also end up in lakes and rivers, bringing with them a slew of health and environmental risks.

"When groundwater contamination occurs, it has the potential to have serious, negative human health, environmental and economic impacts," the report says.

Groundwater contaminated with a nasty strain of E. coli killed seven people in Walkerton, Ont., 10 years ago and made half the community of 5,000 people sick. The report says Walkerton is a cautionary tale.

"These events highlight the importance of preventing contamination and protecting groundwater as a key source of drinking water."

'Exceedingly complex'

Meanwhile, the question of what happens when all those contaminants mix together confounded the government officials.

"One outstanding issue the working group considered is that of cumulative effects," the report says.

"This refers to the impacts that multiple contaminants have on aquatic ecosystems when they interact. Concerns apply to the majority of contaminants, and the issue is both not well understood and exceedingly complex."

No one from Environment Canada was immediately available to comment on the reports.