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

Extremes on the Mississippi River

Over the last two years, the flow in the Mississippi River has been marked by extremes. In Spring 2011, record water levels forced evacuations while, more recently, drought has threatened shipping routes. After seeing another NYT article covering the impacts that the drought is having on shipping routes last Friday, I decided to take a look at the data in HIS. 

Ideally, I wanted to find a few different sites along the Mississippi and download and compare discharge data over the past couple years. I knew that the USGS NWIS Daily Values, readily accessible in HIS, has national coverage measuring discharge levels daily. So, I went about scrolling down the Mississippi in HydroDesktop looking for NWIS sites to compare. 

HydroDesktop Tip: Use the Select Data Sources tool to limit searches to specific data sources.

I found three such sites where I could compare the discharge values since 2011: St. Louis (MO), Vicksburg (MS), and Belle Chasse (LA). The location of these sites can be seen in Google Earth below...

I found that the discharge time series of all three of these sites displayed a signature of these recent extreme events, but the typical flow, and amplitude of these events, differed by site...

While the St. Louis site is characterized by consistently lower rates of discharge (a maximum of ~600,000 cubic feet per second since January 2010) and less fluctuation, the other two sites have both crossed the 1,000,000 cubic feet per second seasonally. A dramatic increase in flow can definitively be observed in 2011 at the Vicksburg site (corresponding to the aforementioned Spring 2011 record water levels). And, while the flow rate at the Belle Chasse site is more similar to Vicksburg than that of St. Louis, the signal of the extreme events does not display as dramatic fluctuations.

Individual graphs of each of the time series can be seen below...

Observed Discharge of the Mississippi River at St. Louis, MO since January 2011. Note the decrease in 2012 when compared to the previous two years.

Observed Discharge of the Mississippi River at Vicksburg, MS since January 2011. Note the dramatic peak flow in Spring 2011.

Observed Discharge of the Mississippi River at Belle Chasse, LA since January 2011.

A HydroDesktop Progress Report

Dan Ames, who leads the HydroDesktop development team at BYU, recently delivered a HydroDesktop Progress Report on a CUAHSI Community Informatics Teleconference. Dr. Ames highlighted the new features in the current version of HydroDesktop as well as discussed the development strategy that has been employed.

Check out Dr. Ames' slides below: