[Great Lakes region: Lake effect snow operates in alternating bands of rising warm air and clear bands of falling cold air. Taken December 5, 2000 image using NASA's SeaWiFS satellite.]

In a recent drive back from Syracuse to Toronto, I was struck by the inevitable presence of snow in Buffalo. No snow before Buffalo, or after Buffalo, but in Buffalo it was full-on large fluffy precipitation. This micro-weather is a little gift from the surface of Lake Erie to the region of Buffalo. It is known as lake effect snow; something the Great Lakes region specializes in. With winter winds prevailing from the northwest, there is a significant difference in the snowfall on the southern and eastern shores versus the northern and western shores of the Great Lakes. Cold air picks up lake surface water in the form of water vapor, then it freezes and is dumped on the leeward side of the lake shores.

[Compostite image of precipitation showing lake effect snow bands, National Weather Service, 20:18 UTC, February 10, 2008. Obviously data is not coordinated with the Canadian equivalent.]

[Lake Effect in full effect.]

With hundreds of thousands of years knowledge embedded in that geography and ecology, there is an inherent intelligence in the localized weather phenomenon. But what about when a body of water unexpectedly accumulates in a region, providing surface water for just such a micro-weather effect? And this is exactly what many hydrologists have found to be the case in many reservoirs. Call it reservoir effect.

[Lake Volta, created in 1965 in Ghana, is the largest surface area of reservoir in the world.]

Wired recently picked up on the influences that dams have been recorded to have on local weather patterns. And in some cases this has caused concern, as very large reservoirs are known to increase rainfall. All of this means that the dam that was built for one condition may soon have to contend with another enhanced condition by the nature of its very presence. The possibility for micro-weather is created as more standing water means more evaporation which means more precipitation.

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