Understanding E.coli Contamination in Lake Michigan: A Meteorological Perspective

The Great Lakes are the largest surface freshwater system on Earth, with a basin that is home to around 30 million people (USEPA, 2015). Lake Michigan is the only one of the Great Lakes that lies entirely within the United States, with a maximum length of 307 miles and maximum width of 118 miles. The Lake Michigan shoreline, composed mainly of sand and pebble beaches, stretches 1,640 miles along the coasts of Illinois, Indiana, Michigan, and Wisconsin, as well as some islands (NOAA, 2015a). The Illinois portion of the Lake Michigan watershed (Figure 1) is only 100 square miles (0.22% of the lake’s total area) and the state’s coastline borders the lake for a short 63 miles (IEPA, 2014). However, despite this relatively small area of Lake Michigan, half of the state’s population lives within the watershed. Recreational water activities are popular throughout the Great Lakes and along Illinois’ Lake Michigan coastline. Lake Michigan is Illinois’ biggest recreational resource, as well as the state’s largest supply of drinking water and a major economic boon (IEPA, 2014). With so many people engaging in water activities, and both affecting and being affected by the lake in turn, it is important to frequently monitor the lake for potential health hazards.

Major efforts have been taken to protect the health of humans from contaminated water during recreation, especially swimming. For many years, waters have been tested for certain types of fecal indicator bacteria (FIB) – bacteria commonly found in human and animal feces. While FIB generally do not cause human disease, FIB in the water may indicate the presence of feces and associated pathogenic bacteria, viruses, and protozoans – organisms and agents which have also been found ...

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...s in Cook County and Lake County may be similarly affected, as the EPA determined that the entire Lake Michigan coastline in Illinois is without any CSO communities (USEPA, 2007).

Numerous studies have examined various meteorological variables and environmental conditions, and found some that are associated with higher or lower densities of E. coli and other bacteria in water. There are 10 major meteorological variables included for investigation in this study that provide a detailed description of the climate and lake conditions in which E. coli were sampled. These 10 variables are atmospheric pressure, air temperature, dew point, precipitation, relative humidity, solar radiation (insolation), water temperature, wave height, wind speed, and wind direction. From a meteorological standpoint, a number of these variables are closely related and influence each other.