THE POWER OF A RECORD RAIN EVENT 
AUGUST 18-19, 2007, POOLS 6-11, UPPER MISSISSIPPI RIVER 

Shawn Giblin1, Terry Dukerschein1, and Heidi Langrehr1
1WI Department of Natural Resources Mississippi River Monitoring Field 
Station, 2630 Fanta Reed Road, La Crosse, WI 54603

Record rainfalls August 18-20 caused extreme flooding and damage in Pools 6 
through 11 of the upper Mississippi River as well as in associated 
tributaries in Wisconsin, Minnesota, and Iowa. Seven lives were lost in 
flood-related events; washouts and mudslides caused millions of dollars worth 
of damage.  Long Term Resource Monitoring Program (LTRMP) data collected at 
fixed water quality sites in Navigation Pool 8 indicated Dissolved Oxygen 
levels below the standard of 5.0 mg/L were common even in the main channel.  
Eight of the seventeen fixed LTRMP water quality sites sampled in Navigation 
Pool 8 produced the highest turbidity values recorded in the history of the 
Long Term Resource Monitoring program with periods of record at sites dating 
back as far as 1988.  Additionally, new records were set at 8 of 10 non-
tributary sites regularly sampled. Records were established despite sampling 
2-4 days following the record precipitation.  New records for low Secchi 
depth readings and total suspended solids, 2 other parameters relating to 
water clarity, were also set. EMAP-GRE vegetation data collected by Wisconsin 
DNR crews documented storm effects from Pools 6-11 in continuous random 
sampling of main channel borders and large major side channels from late July 
through early September, 2007.  Turbidity tube readings taken before the 
August 18-20 rains were significantly clearer than those taken during the 
week following the events.  Turbidity tube data also demonstrated how the 
turbid water moved downstream into areas previously unaffected by the rains. 
This “cloud” of muddy water moving downstream was detected by LTRMP field 
station crews as far south as Alton, IL.  The degree to which this event 
persisted as well as the magnitude to which previous records were broken at a 
number of sites illustrates the severity of this event. Adequate sampling 
frequency (biweekly monitoring) will be important to increase the probability 
of capturing these system changing events in the future, particularly with 
concerns about the cumulative effects of climate change-related phenomena on 
the horizon.  











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Key Words:  Mississippi River, water qualtiy, flood event, turbidity