Chicago's Drought

Last week, I looked at the extremes of flow in the Mississippi River by using HydroDesktop to download and examine discharge data from three sites along the river. For this post, I've decided to look at the effect of drought a bit further North.

Prior to European settlement, the Chicago River flowed into Lake Michigan. The flow was reversed in 1900 to improve sanitary conditions. Presently, however, drought conditions have caused the water level of Lake Michigan to drop to such an extent that the flow of the Chicago River may reverse to its natural (post-glacial) course. Such a reversal would have significant implications for the Chicago Metropolitan Area's infrastructure and, as such, this topic has been covered by multiple media outlets that include:

• CBS Chicago
• The Huffington Post
• The Smithsonian

I was hoping to examine data from two angles to see the impact of drought on water bodies in the region. First, I wanted to find a time series of the water level of Lake Michigan, and second, I wanted to find discharge data of the Chicago River. Unfortunately, I did not find data I was satisfied with for the changing water level in the lake over the past few years, but I was able to find a solid source for the observed discharge of the river's North Branch (NWIS Daily Values) at a location near Albany Avenue.

Data for this post were downloaded from a site on the North Branch of the Chicago River...

...near Albany Avenue.

The data set from this site shows the impact that the drought has had on flow in this section of the river.

The graph above shows that the discharge during Spring of 2012 never reached the levels of the previous two years. While both 2010 and 2011 experienced flows of over 1,500 cubic feet per second, 2012's peak discharge did not even reach 1,000 cubic feet per second. If we take a look at precipitation data for the past three years, we can also see the drought signature in precipitation data. A quick look at the below graphs - precipitation observed near the Chicago Harbor Lock - reveals the fact that rainy days were less frequent in 2012 than in either of the previous two years.

2010 Precipitation near Chicago Harbor Lock

2011 Precipitation near Chicago Harbor Lock

2012 Precipitation near Chicago Harbor Lock