Visitors to some of Indiana’s Lake Michigan beaches will have a new method to rely on for determining E. coli concentration in the water. Project SAFE (Swimming Advisory Forecast Estimate) is being implemented as a pilot study by the US Geological Survey, and it relies on real-time information to assess E. coli count and subsequently public health risk associated with fecal contamination.
Project SAFE is a predictive model that will be used for the five beaches in Lake and Porter Counties that extend to the west of the Burns Ditch outfall: Ogden Dunes, West, Wells Street, Lake Street, and Marquette Beaches. These beaches are directly affected by contaminants in the Burns Ditch outfall, particularly during prevailing north winds.
Current monitoring practices rely on culturing E. coli from water samples collected at the beach. Results are available up to 24 hours after sampling, and beach advisories or closures are implemented. Unfortunately, E. coli counts have typically changed by the time management decisions are made, and too often, beaches are closed too late to protect visitors health, or unnecessarily, which keeps visitors out of clean water. Analysis of data from these five beaches for 2004 indicates that only 3% of the variation is explained using the model of monitoring currently used.
Predictive models are typically developed for a single beach, which can be time-consuming and costly given the number of beaches many managers have to oversee. Because of the similar impact of Burns Ditch, wind direction, and rainfall on E. coli counts at these beaches, they were grouped together for model development, although characteristics of individual beaches are taken into account; therefore a prediction is made for each beach using the overall model.
Using weather and water data collected at several locations, the likelihood is calculated of an E. coli count that exceeds the US EPA recommended standard. Depending on the prevailing wind direction, different weather and water variables are used. E. coli counts can be predicted more successfully during north winds, and the model incorporates parameters from the lake, chlorophyll and turbidity, and also Burns Ditch gage height and rainfall in the previous 48 hours. Separate models can be used for individual beaches.
Compared to current models, Project SAFE models provide a far better real time estimate of E. coli counts and it can be applied to five beaches simultaneously. Similar applications are being developed for other Great Lakes beaches in the hopes that health risk can be determined more accurately and the public can feel confident swimming in Lake Michigan.