You may see someone taking measurements and collecting water samples at Grand Lake St. Mary’s beaches this summer.
An employee with the U.S. Geological Survey (USGS) is in the water to 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 beaches at Grand Lake St. Mary’s State Park. This type of system has been used at some Lake Erie beaches as part of the Ohio Nowcast but has not been tested on inland lakes, such as Grand Lake St. Mary’s, in Ohio.
“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 beaches at the Park, 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 Grand Lake St. Mary’s beaches, the system will be available to the public in 2013.” said Francy, “In the future, before you head to the beach, you may be able to check the predicted bacteria levels by 9:30 in the morning.”
This system will not predict algae levels.
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.
Unfortunately, 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 Grand Lake St. Mary’s 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. As part of this project, scientists will also be examining factors at five other inland lakes in Ohio.
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 Grand Lake St. Mary’s 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 a Nowcast system,” 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.”
The City of Celina is providing laboratory space and equipment for processing samples for E. coli. The Ohio Water Development Authority, Ohio Department of Natural Resources, and Muskingum Watershed Conservancy District are also cooperating on this state-wide study.
Links and contacts within this release are valid at the time of publication.