The trouble facing Canadian rivers

he seasonal waxing and waning of rivers is one of nature's most crucial cycles, influencing everything from the success of salmon runs to having enough water during parched summers to irrigate crops.

But by this measure, many of Canada's major rivers are in trouble, contends a new report that says many of the best known rivers have suffered major alterations in their natural flows due to hydro dams, irrigation schemes and withdrawals by industry, and could be further compromised by the effects of global warming.

The report, by WWF-Canada, one of the country's major environmental organizations, says the rivers that have been most altered from their natural state include the St. Lawrence and the South Saskatchewan, whose “ecosystems are in serious trouble” as a result. But it warned that if safeguards aren't put in place soon, some of North America's last free-flowing rivers, including the Skeena in B.C., the Athabasca in Alberta, and the Mackenzie in the Northwest Territories “could soon be in trouble as well.”

The report, titled Canada's Rivers at Risk, is believed to be the first evaluation of rivers in Canada based on how much human activity has changed their natural flows. Previous studies of rivers by government or environmentalists have focused on such traditional threats as pollution from industries or sewage treatment plants.

“The concept of environmental flows is really emerging globally as a fundamental indicator of how to look at river health,” said Tony Maas, director of freshwater programs at WWF-Canada.

The report assessed 10 major rivers based on more than 300 scientific papers, and is being released Thursday.

Most rivers have a distinct annual flow pattern on which wildlife depend, with amounts peaking in spring when melting snow augments flows. Low levels occur during winter freeze-ups or summer droughts. But dams and other human interferences smooth out these natural fluctuations.

It highlighted the fact that responsibility for most large rivers in Canada is shared by several governments, making efforts to regulate their flows more difficult.

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