The storm last February that sent waves crashing into the condos on Sheridan Road and threatened to relocate the Oak Street beach to the lobby of One Magnificent Mile made lake levels a hot political issue.
The idea seems simple. The Great Lakes are too full of water, so let’s pull the plug and drain some of it out. The machinery is already in place to do this, thanks to the engineering wonders that turned the Chicago River around.
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Before the glaciers reworked the landscape of the midwest, the Mississippi River used to flow through the channel that is now the Illinois River. The Mississippi is a very big river, and the valley it carved is much larger than the modest vale a stream the size of the Illinois would require.
As if diversion were not enough, our wasteful farming methods send a huge amount of sediment to the river every year. The present annual sediment load in the Illinois is over 27 million tons, enough soil to cover Chicago to a depth of one inch. Less than half this is transported by the river’s sluggish current. Over 15 million tons of it is deposited in the river and its backwater lakes. The sediment is too soft to provide a suitable substrate for aquatic plants, or spawning fish, and it is steadily filling the lakes, making them less able to absorb floodwaters.
However, all is not negative. The report does note a positive benefit for increased water flow, concluding that “Highly suitable nesting conditions provided by dead trees would probably result in increased woodpecker populations.”
