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New York Water Science Center 

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Developing and Implementing Predictive Models for Estimating Recreational Water Quality at Great Lakes Beaches

By Brett Hayhurst, Donna Francy


summary pdf

The Great Lakes Restoration initiative (GLRI) template #77 (Beach Recreation Water Quality) in cooperation with 23 local and state agencies expanded the use of predictive modeling at 45 beaches throughout the Great Lakes (fig 1). Local agencies measure fecal-indicator bacteria such as Escherichia coli (E. coli.) along with easily obtained environmental variables used as surrogates to estimate concentrations of fecal-indicator bacteria through a predictive modeling approach. The predictive modeling is being developed by the use of linear regression and/or partial least-squares techniques. The models use software developed by the U.S. Environmental Protection Agency known as “Virtual Beach”. Each beach model is based on a combination of explanatory variables, most commonly, turbidity, day-of-year, change in lake level over 24 hours, rainfall, wave height, and wind direction and speed. Forty-two predictive models were validated in this study where overall correct responses are greater or equal to 80 percent of the percentage of exceedance of the EPA bathing-water standard of 235 colony forming units per 100 milliliters.

First posted September 2013

For additional information contact:
U.S. Geological Survey
Ithaca Program Office
New York Water Science Center
30 Brown Road
Ithaca, NY 14850

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