Bacteria forecasting could help swimmers
Sunday, July 21, 2002
BLOOMINGTON, Ind. -- Scientists have developed a rapid method to predict when bacteria levels in Lake Michigan are too high, a finding that could prevent the unnecessary closing of beaches that park managers fear are tainted.
The new approach using a computerized forecasting model takes into account recent rainfall, wind, lake levels, air and water temperatures and sunshine to accurately forecast E. coli bacteria levels within just three hours.
Health officials currently test water samples individually to determine bacteria levels, a process that can take up to 48 hours and lead to beach closings based on information that is days old.
"Now we're making decisions based on what's going on now," said Greg Olyphant, a professor of geological sciences at Indiana University who developed the new approach. "We're not basing decisions on what happened yesterday."
Olyphant has already received requests for more information about the method from officials in Boston, Santa Monica, Calif., and New Zealand.
"There's beaches all over the country that are suffering from the same problem," he said. "All these places are in a terrible situation where they really don't know whether to keep the beaches open."
The findings will be published later this year in the international journal Environmental Monitoring and Assessment.
Federal agencies and groups from Indiana, Illinois, Wisconsin and Michigan have been working together for years to determine the sources of E. coli bacteria in Lake Michigan, as well as faster ways to predict and test for it.
E. coli is a bacteria found in the intestines and feces of warm-blooded mammals. When swallowed, it can cause diarrhea and other health problems.
The Centers for Disease Control and Prevention estimates 73,000 cases of infection and 61 deaths occur each year in the United States from E. coli exposure. Most illnesses have been associated with ingesting food and water but can also occur after swimming in contaminated water.
Dr. Jay Varma, a medical epidemiologist with the CDC in Atlanta, noted that E. coli outbreaks in recreational waters also point to other problems.
"We're not just worried about E. coli," Varma said. "E. coli serves as a marker for other problems in the water, so anything they can use to predict when water is contaminated is obviously a good idea."
The cities of Chicago and Milwaukee hired Olyphant to develop individual models to forecast bacteria levels at their beaches on Lake Michigan. He implemented the models for the 90-day summer season in both cities last summer and compared the findings to water samples taken daily in Milwaukee and about three times a week in Chicago.
The models successfully predicted when bacteria levels would be above an acceptable level 80 percent of the time in Milwaukee and 75 percent of the time in Chicago, Olyphant said.
Milwaukee has since implemented the new testing approach at two beaches and releases an up-to-date forecast of bacteria levels on a Web site and telephone hot line, available in English and Spanish.
The city expects to eventually conduct real-time forecasting at 11 beaches that span a five-county area on Lake Michigan's western shore.
"These are fairly significant advances for a community like Milwaukee, given that we rely primarily on primitive methods of determining bacteria levels," said Paul Biedrzycki, the city's manager of disease control and prevention. "The potential for this method to be used is much more widespread."
Even when the forecast is wrong, health officials aren't losing any ground, Biedrzycki said.
"Our mission is to post the information and let the consumer make an informed decision," he said about closing beaches. "Before it was kind of a flip of the coin. Now it's a little more improved."
Richard Whitman, chief of the U.S. Geological Survey's Lake Michigan Ecological Research Station, said accurate forecasting would have to tide beachgoers over until real-time testing was available.
"You have to accept that you're only going to be right a certain percentage of the time," he said. "Some beach managers are willing to accept that risk and some are not."
At the Indiana Dunes State Park, beaches were closed for five straight days leading up to the July 4 holiday because of high bacteria levels. The state park has not yet implemented real-time forecasting or testing.
"Two weeks ago, we had eight beaches closed, but we now know those beaches were OK," Whitman said. "There's heavy damage now -- we had to turn people away because there was a cost of quality of life, and economic loss and reputation to northern Indiana."