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2012 EPA Research Progress Report

Real-time Beach Monitoring

Aerial view of the Great Lakes showing beaches currently under Nowcast or other water quality monitoring programs.

The principal cause for beach closings and advisories is water pollution caused by elevated levels of bacteria, primarily E. coli, which indicates human or animal waste contamination. However, by conventional methods, measurements of E. coli levels can take up to 24 hours. By the time results are compiled, water-quality conditions may have already changed.

To improve beach water monitoring, EPA scientists developed the Virtual Beach modeling software. This tool, updated in March 2012, is designed to predict pathogen indicator levels at recreational beaches, giving water-quality information in real-time or even before the contamination occurs.

Using the Virtual Beach software, managers can easily map their beach using an intuitive graphical interface. By looking at data on the local watershed, Virtual Beach’s models can find correlations between certain weather and water conditions and bacterial outbreaks, giving beach managers advanced warning of the kinds of contamination events that lead to swim advisories and beach closures.

The Wisconsin Department of Natural Resources partnered with EPA and the U.S. Geological Survey to tap EPA’s Virtual Beach software for real-time water monitoring at Wisconsin beaches. The impact of that effort was the creation of the Nowcast Program, which works with local public health departments along Wisconsin’s Great Lakes coast to improve the timeliness, accuracy, and cost-effectiveness of water-quality monitoring at high-priority recreational beaches. The program creates and implements early-warning models that can predict the level of E. coli bacteria and the probability of exceeding water-quality guidelines in real time.

In 2011, two beaches piloting Nowcast models reduced the number of missed advisories by 20 percent and reduced the number of incorrectly-posted advisories by 50 percent. As of June 2012, Nowcasts were being used to make management decisions at seven high-priority beaches on Lake Michigan. Models have been developed for an additional 21 beaches on Lake Michigan and Lake Superior by the State of Wisconsin and the U.S. Geological Survey.

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