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Scientists are holding back from suggesting record low levels on Lake Superior are signs of things to come, but they are having an impact throughout the Great Lakes and St. Lawrence River. “We wish we knew,” said David Fay, manager of the Great Lakes St. Lawrence regulatory office for Environment Canada. “We don’t know for sure if this is due to normal climate variation or global warming. We really can’t say, although there is some evidence what we’ve seen is a warming trend in the Great Lakes.”
In recent weeks, levels on Lake Superior have reached lows not seen since the early part of the last century.
Experts have suggested the low levels are due to an 18-month regional drought in the area surrounding Lake Superior, but that recent precipitation levels have caused the levels to rise considerably.
Fay said just one month ago, Lake Superior was about 55 centimetres below average; that level has risen to 35 centimetres below average in the last few weeks.
“We aren’t the best predictors of precipitation levels,” Fay said, suggesting there’s no way scientists can foresee whether water levels on the Great Lakes will continue to increase in the coming months.
“Out beyond three days, it’s difficult to predict.
“In fact, it’s perhaps impossible to do that.”
When water levels are low on the Great Lakes, the effect is felt system-wide.
Levels on Lake St. Lawrence, which is west of Cornwall, may actually be higher than usual because regulators are allowing less water to flow through the power dam at the Robert Moses generating station in order to preserve the highest levels of water possible west of the dyke.
This means less water is flowing through the St. Lawrence River in this area, and ultimately means water levels in the Port of Montreal are below average.
Fay said lower flows from the Great Lakes, combined with drought conditions surrounding the Ottawa River and some of the tributaries which feed the port are to blame for the low levels in that area. Shipping companies are forced to send vessels between ports with decreased cargo loads and some ecological species can be at risk. Jeff Ridal, a scientist at the St. Lawrence River Institute of Environmental Science in Cornwall, said decreasing water levels can have an impact on habitats. “Studies have shown the muskrat is actually one of the species most at risk,” said Ridal. “They build their dens at the water’s shoreline, so low levels will impact that shoreline.” Ridal said scientists will often turn to species when attempting to determine how the system is coping with things such as low water levels. “The muskrat is actually a key indicator species,” said Ridal. “We can learn a lot about what’s happening in the system according to how that species is affected.” Long-term forecasts suggest wetter weather may continue through the end of the year.