Climate change: Changing the great Lakes

Climate change could reduce water levels in the Great Lakes to lower than they have ever been before – changes that would have an impact on the transport, power generation, and wildlife of Ontario.

That's because, even though most climate scenarios predict increased precipitation for the region around the Great Lakes, higher temperatures will mean greater evaporation of water into the atmosphere. They will also mean less snow in winter, so less spring run-off and snow melt entering the lakes. And that, in a nutshell, means less water in the Great Lakes – so much less that some scientists are predicting that water could become a continental issue in the 21st century in much the same way oil and gas were in the 1970s and 80s.

Areas of Ontario away from the Great Lakes that depend on groundwater for water supplies could face even greater water shortages because of increased evaporation.

Together, the Great Lakes are the largest freshwater body in the world, covering 246,000 square kilometres and storing 20 per cent of the world's freshwater. As part of the Canada Country Study reports examining the impact of climate change on Ontario, Canadian scientists looked at different climate models, and what they reveal about the future status of the Great Lakes. And the models are consistent: they all show decreases in water levels, in some cases of more than one metre, by the latter part of the 21st century.

The Great Lakes, together with the St. Lawrence River, form a transportation network that supports Canada's largest concentration of manufacturing and other industries. Together, they form the busiest waterway in the world, serving the needs of four provinces and 17 states in North America.

Low lake levels can restrict the maximum cargo capacity of vessels, and can increase the operating costs of ports and shipping channels, such as the costs associated with dredging a harbour. In the past, when the variability of climate has caused water levels in the lakes to be lower than usual, millions of dollars were lost because shipping was disrupted. On the other hand, however, reduced ice on the lakes could be expected to lengthen the shipping season.

Using water to generate electricity is one of the "cleanest" ways to produce power, without the environmental harms of burning fossil fuels such as coal. A significant proportion of water from the Great Lakes Basin is used for electricity generation and lower levels would affect power production. In the past, the same low flows that affected transportation also resulted in a 19-26 per cent decrease in hydro power production. Lower water levels in the Great Lakes could have the same effect. This will likely coincide with greater demands for electricity, at least in the summer, as people turn to their air conditioners at home and at work to offset higher temperatures.

And, just as air temperatures are expected to be higher due to climate change, water temperatures are also expected to increase. This will have impacts on the fish and other wildlife in the Great Lakes, with many fish species expected to shift northward, and many southern species expected to "invade" the Great Lakes aquatic ecosystem, with unknown effects on the delicate balance of life. In the past, water temperature changes as small as one degree have caused substantial changes in the home range of species.

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