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The authority overseeing the South Nation watershed has some good news and bad news about long-term contamination trends in the water.
Over the last four decades, there has been an increase in nitrates, which are associated with fertilizers and fecal contamination from septic systems, sewage treatment plants and manure spreading, South Nation Conservation said.
Ian Ockenden, water resources specialist with the conservation authority, said nitrate levels in the South Nation River and its tributaries are generally two to three milligrams per litre. He said it averaged 0.2 milligrams per litre in the 1960s.
However, Ockenden said nitrate levels are not considered a health concern by provincial standards until they reach about 10 milligrams per litre.
The increase in nitrate levels is thought to result from population growth and increased farming activities, according the conservation authority.
“You can kind of see a gradual increase in the ‘70s, the ‘80s and the ‘90s,” Ockenden said.
“As the population pressures increase, you get a combination of greater densities of septic systems in rural but not yet fully urban areas. ... And as urban areas grow, you either get larger treatment plants or there’s just more pressure on the current ones they have.”
However, there are some positive trends detected in the South Nation watershed as well.
Bacteria associated with fecal matter, such as E. coli, has been on the decline since the 1970s, the conservation authority said. This is thought to be the result of more sewage-treatment plants along the watershed replacing private septic systems.
On the apparent contradiction of nitrates being up but bacteria decreasing, Ockenden said, “It’s kind of different aspects of the same thing.”
He said provincial standards for modern sewage-treatment plants emphasize the elimination of bacteria more than nitrates, since the former is more of a concern.
Nonetheless, people are warned they swim at their own risk in the South Nation River system.
Seventy-six per cent of the time, the level of bacteria in the system is lower than the provincial limit of 200 E. coli per 100 millilitres, which is considered safe for swimming, he said.
He added that levels tend to increase after rain and on hot days.
Another positive finding cited by South Nation Conservation is that phosphorus, associated with algae growth that can kill fish, is on the decline. However, it is still 300 to 500 per cent above provincial objectives.
Ockenden said phosphorus often comes from fertilizers, soaps and detergents. Waste-water treatment plants were credited somewhat for the decrease in this contaminant, as well as better farming practices.
He added that standards for the amount of phosphorus that can be included in soap and detergent are more stringent than before.
Daniel Green, a scientific adviser for the Sierra Club of Canada, said contamination trends with the South Nation are better than what’s seen with a lot of other water systems in eastern Ontario and western Quebec, where bacteria and phosphorus levels are increasing.
“What we’re seeing, in the rivers of Quebec for instance, is this advantage of sewage treatment is cancelled by spreading manure in the fields,” he said.
“Evidently, in the South Nation watershed, there seems to be some better practices to deal with this issue of coliform and phosphorous flowing from the field,” Green said.
Geri Kamenz, vice-president of the Ontario Federation of Agriculture and a farmer on the South Nation watershed, said the farmers in this area have worked in close partnership with the conservation authority to maintain the health of the water system.
He said farmers increasingly ensure there are physical barriers between fields and waterways and avoid spreading manure when the ground is not ideal for absorbing it, such as when the ground is frozen.
Kamenz said it’s more efficient for farmers to find ways to keep their nutrients and fertilizers from flowing into the river, because the materials are staying on the fields and doing what they’re supposed to do.
“But also … we don’t want denigrate the environment,” he added.
As for safety precautions that should be taken by the public, Ockenden said drinking untreated water from any body of water is not recommended.
As for eating fish caught in the South Nation, Ockenden said bigger fish are more likely to have absorbed more contaminants.
He said the provincial government’s Ministry of the Environment’s Guide to Eating Ontario Sport Fish gives guidelines about what fish are less safe to eat, and gives limits on how often certain fish should be eaten out of different bodies of water.
The guide can be downloaded at www.ene.gov.on.ca/envision/guide.
The South Nation River stretches about 175 kilometres from Elizabethtown-Kitley east to the Ottawa River.