WBEZ's 848 devoted a program today to the future of Chicago's water supply. You can listen online on the WBEZ website.
A part of the program was the mini-documentary The End of the Pipe, which summarizes how Chicago's water supply and water treatment are connected to the reversal of the Chicago River and limits to growth of the western suburbs.
The documentary is a bit sensationalized and fails to explain a number of key facts about how the city water system works, such as how the level of the Chicago River is managed. In fact the river level is controlled by simply opening the gates of the Lockport dam which is the downstream outlet of the river. When a heavy storm threatens, engineers open the gates, allowing more of the river to run out downstream, in preparation for rainwater to run off city streets.
During a storm, run-off enters the sewer system through street drains, which can be diverted into the Deep Tunnel so that the sewer system is not overloaded, and sewage mixed with stormwater can be stored until treated when time allows. During last August's perfect week of storms, stormwater filled both the Deep Tunnel and the river. Engineers chose to dump sewage-contaminated water from the system into the river, and open the locks into Lake Michigan, sending mixed sewage and stormwater into the Lake, where the city gets its drinking water. This just happened to be the week we floated downstream on our boat!
As the documentary mentions, the current battleground over the use of Great Lakes water is not from the thirsty sunbelt, but from suburbs that straddle the continental divide between the Lakes and the Mississippi River, which at the southern end of Lake Michigan lies only a 10-20 miles from the lake.
If groundwater wells become contaminated by pesticides or underground pollutants, many smaller cities are tempted to get fresh water from nearby cities which draw from the lake. But the Great Lakes Compact, which was finally passed by the Senate last Friday, allows only those cities which are within the Lakes watershed to use and treat water from the Great Lakes, so that these waters ultimately are returned to the lakes after use. Even if a suburb might be close to Lake Michigan, it may not be legally allowed to use Lake Michigan water.