Chicago Versus Lake MichiganBreaking News
tags: climate change, Chicago, urban history, Great Lakes, Civil Engineering, Flood Control, Hydrology
IN THE SEARCH FOR A BIG-CITY REFUGE from climate change, Chicago looks like an excellent option. At least, it does on a map.
It stands a half-continent away from the threat of surging ocean levels. Its northern locale has protected it, to some extent, from southern heat waves. And droughts that threaten crops, forests and water supplies in so many places? Chicago hugs the shore of one of the grandest expanses of freshwater in the world.
Water is, in fact, why Chicago exists. The nation’s third-largest city grew from a remarkable geographical quirk, a small, swampy dip in a continental divide that separates two vast watersheds: the Great Lakes and the Mississippi River Basin. In the 19th century, Chicagoans dug a canal linking those two watersheds, transforming their muddy town into a metropolis of commerce by making the riches of the American Midwest accessible to the world.
The mule-drawn barges that worked its canals long ago gave way to trains, planes and eighteen-wheelers.
But the same waters that gave life to the city threaten it today, because Chicago is built on a shaky prospect — the idea that the swamp that was drained will stay tamed and that Lake Michigan’s shoreline will remain in essentially the same place it’s been for the past 300 years.
The lake may have other plans.
Climate change has started pushing Lake Michigan’s water levels toward uncharted territory as patterns of rain, snowfall and evaporation are transformed by the warming world. The lake’s high-water cycles are threatening to get higher; the lows lower. Already, the swings between the two show signs of happening faster than any time in recorded history.
WHILE JACKING UP CHICAGO to make room for sewers may have solved one predicament — the filthy, impassable streets — it caused another. All the sewage still flowed into the Chicago River. And the river still flowed into the lake, the city’s drinking-water source.
Desperate to protect residents from waterborne scourges like cholera, city leaders at the end of the 19th century hatched another audacious plan: Reverse the direction of the river so it flowed away from Lake Michigan instead of into it.
They achieved this by dynamiting a 28-mile-long canal connecting the Chicago River to the Des Plaines River, which flows toward the Mississippi. It was a project typical of a city that, as one author described in 1898, “stands as a stupendous piece of blasphemy against nature.”
The Chicago Sanitary and Ship Canal opened in 1900, a feat of engineering 160 feet wide and 25 feet deep and, importantly, lower than Lake Michigan. So gravity dictated that the Chicago River would henceforth flow in the opposite direction.
Today, on the Chicago waterfront stands the Harbor Lock, a set of mammoth steel gates separating lake water from river water. It marks the spot where boats pass between the Great Lakes Basin and the Mississippi Basin. Chicago has, essentially, fashioned for itself a manmade continental divide, with hinges.
It is Joliet’s dream, realized on a scale he never could have fathomed.
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