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Testing Bacteria Levels at Six Ohio Lakes for Future Nowcasts
Released: 6/10/2010 6:10:00 AM

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Donna Francy, USGS 1-click interview
Phone: 614-430-7769

Scott Fletcher, Ohio Department of Natural Resources
Phone: 419-424-7121



You may see someone taking measurements and collecting water samples four days a week at some of Ohio’s inland lake beaches this summer.

These employees are in the water as part of a project coordinated by the U.S. Geological Survey (USGS).   Employees will collect data and make water quality and weather measurements that will be used to test a system to quickly estimate bacteria levels and provide advisories to swimmers headed to selected inland lake beaches in Ohio. This type of system has been used at Lake Erie beaches as part of the Ohio Nowcast but has not been tested on inland lakes before.

Included in the studies are Ohio State Park beaches at Alum Creek, Buck Creek, Buckeye Lake, and Grand Lake St. Mary’s and Muskingum Watershed beaches at Atwood Lake and Tappan Lake (map). 

“The Nowcast system is similar to a weather forecast except that current water-quality conditions instead of future conditions are estimated,” said Donna Francy, USGS research hydrologist for the study.  “Current bacteria levels are estimated with a computer model especially calibrated for each beach, which takes into account current weather and environmental conditions.” 

“The USGS will collect data for two years, develop mathematical models, and test a Nowcast system in 2012.  If the Nowcast is successful at any of the study beaches, the system will be available to the public in 2013,” said Francy. “In the future, before you head to some inland beaches in Ohio, you may be able to check the predicted bacteria levels by 9:30 in the morning.”

Beach advisories or closings in the United States are issued when levels of bacterial indicators, such as Escherichia coli (E. coli), exceed safety standards.  E. coli is found in the intestines and feces of warm-blooded animals.  Indicator organisms do not necessarily cause disease, but they are present in sewage and waste and indicate the possible presence of disease-causing organisms.  If the concentration of E. coli exceeds state standards, officials will advise visitors not to swim because of the risk of illness.

Current methods to determine levels of E. coli take at least 18 hours to complete.  During this period, E. coli levels may increase or decrease substantially.  A heavy rainfall may cause an increase in E. coli levels overnight.  A bright sunny day may cause E. coli levels to fall.  So, the beach may be erroneously posted with an advisory based on measured E. coli levels from the previous day.

“During the first year of our study, we will increase daily monitoring at twenty beaches from every other week to four days each week.  At the same time, we will collect weather and environmental data to develop mathematical models to predict E. coli concentrations at the beaches.  If E. coli concentrations are found to increase as rainfall or others factors increase, we will continue to collect data a second year and then develop mathematical models,” said Francy.  “Instead of waiting 18 hours for E. coli to grow in the laboratory, we’ll be able to use quickly measured factors that explain changes in E. coli concentrations, enter them into a computer modeling program, and obtain a Nowcast of recreational water quality in less than 15 minutes.”

For Lake Erie beaches, USGS scientists found that wave height, rainfall in the past 48 hours, turbidity (water clarity), and day of the year were the best factors to estimate E. coli levels.  These factors may or not be used to estimate E. coli levels at inland lakes.  USGS scientists discovered that the determining factors vary by beach and no two beaches are the same.

The models predict the probability of exceeding the Ohio single-sample maximum bathing-water standard for E. coli (235 colonies per 100 milliliters). If the system works for any of the inland beaches, water-resource managers will establish a threshold probability.  Probabilities equal to or more than the threshold indicate that the water quality is probably unacceptable and a water-quality advisory will be issued.  This “threshold probability” is unique to each beach.

“We are very pleased to be working with the USGS to establish Nowcast systems at these inland lakes,” said Scott Fletcher, Operations Section Manager for the Ohio State Parks.  “The increased monitoring this year will provide the public with more information on the potential exposure to waterborne pathogens.  The tools developed over the next two years will allow us to base water-quality advisories on today’s conditions rather than yesterday’s.  And they help officials protect and inform the public in a timely manner.  We are proud to offer these increased services to the public.”

Agencies cooperating with USGS on the project include Ohio Water Development Authority, Ohio Department of Natural Resources, Muskingum Watershed Conservancy District, the Clark County Combined Health District, and the City of Celina. 

The Nowcast Web site and more information about USGS beach research can be viewed online.


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