Can the levels and flows of the Great Lakes be controlled?
Over the last century the Great Lakes have experienced years of extremely high water levels and years of very low levels. To a certain degree, the Control Boards are able to affect the levels and flows. However, numerous studies have shown that the effects of artificial controls are dwarfed by the influence of climate. The major factors that decide the amount of water in the Great Lakes are natural – evaporation, precipitation and runoff. This is known as the hydrological cycle. Water evaporates from the surface of the lakes as it comes into contact with dry warm air and forms water vapour. Water vapour falls into the Great Lakes Basin as rain or snow, either directly onto the surface of the lakes or as runoff from the drainage basin. These factors caused high water levels in the early 1950s and mid-1980s, and low levels in the 1930s and mid-1960s. More recently in 1998 and 1999 low precipitation in the Lake Superior region in winter resulted in less runoff to the lake and reduced flow
