| They were able to come up with an equation where they can plug in all the variables in current time and predict E. coli concentrations. |
When coastal resource managers have to wait 24 hours for the results of water quality tests that show unsafe levels of E. (Escherichia) coli bacteria, their subsequent decision to close beaches can be a day late in protecting swimmers. Managers in Lake County, Illinois, have developed a high-tech E. coli prediction system, which during trials last summer dramatically increased the speed and accuracy of beach closure decisions.
The system, called SwimCast, uses meteorological equipment to monitor a beach's environment, such as air temperature, wind speed and direction, water temperature and clarity, sunlight, and wave heights—all factors that can hinder or encourage the growth of E. coli.
"Right now, SwimCast is being shown to have been 86 to 87 percent accurate" at the two beaches where it was tested, says Mark Pfister, aquatic biologist for the Lakes Management Unit of the Lake County Health Department. "That's far superior to what we've seen in past years when we were 67 to 100 percent wrong in calling swim bans just on testing alone."
Pfister cautions that SwimCast is not meant to replace government-mandated water sampling but to augment it.
E. coli contamination of coastal waters comes from human and animal fecal matter, and is used as an indicator of other harmful human pathogens that can potentially cause gastrointestinal illness in swimmers.
Pfister says that there is a public perception that Illinois has a lot of beach closures when compared to other Lake Michigan beaches. He says the comparisons are "apples to oranges" because monitoring for E. coli is done daily at Illinois beaches, which is far more frequent than that of neighboring states.
"The more you monitor, the greater the probability that you are going to find changes in the E. coli concentrations," he says. "One day, you can have a high count and the next day it can drop dramatically."
The state's coastal managers are often frustrated by an 18 to 24 hour delay in getting monitoring test results back from laboratories, which means that swimmers can be in the water during peak times and may be kept out of the water when it is safe.
Because of this, Lake County managers began looking at all the independent variables that might affect E. coli concentrations. They were able to come up with an equation where they can plug in all the variables in current time and predict E. coli concentrations.
The data for the equation comes from $30,000 worth of monitoring equipment on the beach that is continually sending readings to a data logger. "The beauty is you can log in any time of day to look at the readings," he says.
The initial cost of purchasing the monitoring equipment was paid for by a grant from the U.S. Environmental Protection Agency.
Pfister says the system could be used in other coastal areas, but because it is not "off the shelf" and the cause of elevated E. coli at each beach may be different, a new equation would need to be developed for each site.
More testing of the model also is needed, he adds. "It's been very effective to date. We want to continue making sure we maintain the same level of accuracy next year."
For more information about SwimCast, contact Mark Pfister at (847) 377-8028, or mpfister@co.lake.il.us.
