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The New York Nowcast predicts water quality conditions at select beach swimming areas in New York State. The Nowcast estimates conditions similar to a weather forecast, by merging environment and climate data with variables measured at a beach by 8 AM each morning and entering them into a computer program. The program provides a probability from 1 to 100 as to whether or not the beach has exceeded the bathing-water standard of 235 colony forming units of E. coli.
As a part of the Great Lakes Beach Health Initiative, the U.S. Geological Survey (USGS), and other federal, state, and local agencies and universities have developed and implemented the use of predictive modeling at over 50 beaches across the Great Lakes to provide advisories for water-quality. Water quality (specifically, high levels of E. coli bacteria typically indicate fecal contamination of water) is an important topic at swimming locations along the Great Lakes, coastal regions and inland lakes. The U.S. Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory (Athens, GA) provided the Virtual Beach software that is used extensively to develop predictive models. The models rely heavily on USGS research and national monitoring programs, and are considered essential to any beach-management program working toward real-time beach advisory systems. Please visit the publications linked below for more information.
Developing and Implementing Predictive Models for Estimating Recreational Water Quality at Great Lakes Beaches:
U.S. Geological Survey Scientific Investigations Report 2013-5166
by Donna S. Francy, Amie M.G. Brady, Rebecca B. Carvin, Steven R. Corsi, Lori M. Fuller, John H. Harrison, Brett A. Hayhurst, Jeremiah Lant, Meredith B. Nevers, Paul J. Terrio, and Tammy M. Zimmerman
Available at: https://pubs.usgs.gov/sir/2013/
Tools for Beach Health Data Management, Data Processing, and Predictive Model Implementation:
U.S. Geological Survey Fact Sheet 2013–3068
by U.S. Geological Survey
Available at: https://pubs.usgs.gov/fs/2013/
Real-Time Assessments of Water Quality—Expanding Nowcasting Throughout the Great Lakes:
U.S. Geological Survey Fact Sheet 2013–3069
by U.S. Geological Survey
Available at: https://pubs.usgs.gov/fs/2013/
Coastal Processes Influencing Water Quality at Great Lakes Beaches:
U.S. Geological Survey Fact Sheet 2013–3070
by U.S. Geological Survey
Available at: https:/pubs.usgs.gov/fs/2013/
Research on Pathogens at Great Lakes Beaches—Sampling, Influential Factors, and Potential Sources:
U.S. Geological Survey Fact Sheet 2013–3071
by U.S. Geological Survey
Available at: https:/pubs.usgs.gov/fs/2013/
Understanding Beach Health Throughout the Great Lakes—Continuing Research:
U.S. Geological Fact Sheet 2012–3113
by U.S. Geological Survey
Available at: https:/pubs.usgs.gov/fs/2012/
Understanding Beach Health Throughout the Great Lakes—Entering a New Era of Investigations:
U.S. Geological Survey Fact Sheet 2010–3093
by U.S. Geological Survey
Available at: https:/pubs.usgs.gov/fs/2010/
What are pathogens, and why is E. coli used to indicate their presence in water?
The E. coli bacterium, which is present in the feces of warm-blooded animals, is commonly associated with and is an indicator of several different disease-causing organisms, called pathogens.
Because of its association with pathogens and because it is comparatively easy to grow in the laboratory, E. coli is the basis for New York, Pennsylvania, and Ohio recreational water-quality standards. There are several varieties of pathogenic E. coli and hundreds of varieties of harmless E. coli. One variety of E. coli that is pathogenic has been associated with undercooked ground beef.
How are E. coli levels measured?
Daily water samples are collected from the beach each morning in sterile bottles. The samples are brought to the laboratory where they are processed for E. coli within 6 hours of collection. The method used to determine levels of E. coli is called membrane filtration. During membrane filtration, a measured amount of water is poured through a filter to trap bacteria onto the filter. The filter is placed on an agar plate and allowed to incubate at a warm temperature overnight. Colonies are counted the next day and recorded as colonies per 100 milliliters. A milliliter is a very small quantity of water—about 0.03 fluid ounces or one-fifth of a teaspoon.
What is a water quality advisory?
A Water Quality Advisory is a public notification, typically in the form of a sign posted at the beach, to advise the public that current water quality standards are not acceptable for swimming due to elevated bacteria levels. A Water Quality Advisory remains in effect until another measurement is made that shows that E. coli levels are within acceptable limits.
How do beach managers determine when to issue a water quality advisory?
There are state standards for E. coli in recreational waters. The state standards are based on those recommended by USEPA and determined by earlier USEPA studies. In USEPA studies, investigators determined that when E. coli levels went up, the number of swimming-associated gastrointestinal illnesses also increased. The New York, Pennsylvania and Ohio bathing-water standard for E. coli is a single-sample value of 235 colonies per 100 milliliters. If the count for E. coli is equal to or above 235, the beach manager will issue a water-quality advisory.
What are the problems with the current method used for issuing beach advisories (based on the previous day’s E. coli level)?
Current methods to assess concentrations of E. coli using membrane filtration or other cultural methods 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. Alternatively, a bright sunny day may cause E. coli levels to fall. So, the beach may be erroneously posted based on measured E. coli levels from the previous day.
What is being done to improve the accuracy of the beach advisory system?
Scientists are developing and testing tools that can provide beach managers with quick, reliable indicators of recreational water-quality conditions. Predictive models are one means to provide these rapid assessments. Predictive models use easily and quickly measured water-quality surrogates, such as rainfall and wave height, to estimate levels of E. coli or the probability that the bathing-water standard will be exceeded.
Is the water safe for swimming?
The beach water may appear to be clear and clean, but it doesn’t mean it is safe for swimming. Bacteria cannot be seen in the water; it is therefore important to remember the following guidelines:
What illnesses may result from swimming in the water?
There is a potential for illness to occur when bacteria levels are unsafe. Gastrointestinal upset, including nausea, vomiting, abdominal cramps, and diarrhea may occur as a result of swallowing contaminated water. There is also a potential for developing upper respiratory infections, in addition to ear and eye infections. Skin infections may also occur if an exposed wound is in contact with contaminated water.
Who is most at risk for becoming ill?
Children, the elderly, and individuals with weakened immune systems are most at risk for developing illnesses from swimming when bacteria levels are unsafe.
What should I do if I became ill after swimming at the beach?
If you should become ill, or suspect you became ill, after swimming at the beach, you should notify your doctor and your local health department. Your local health department is interested in tracking illnesses that may have resulted from water-contact activities and will conduct follow-up investigations where necessary.
Where does beach pollution come from?
Pollution in beach water can be attributed to several factors, the most common of which are sanitary and storm-sewer overflows. In older, urban areas, sanitary and storm-sewer systems were often combined and designed to overflow during heavy rains to prevent basement flooding. It is therefore important not to swim near storm drains or other discharge pipes.
Other sources of pollution include sewage-treatment-plant overflows, runoff from lawns and streets, animal wastes (especially waterfowl wastes), malfunctioning home and commercial sewage systems, and boating wastes.
How can I help to keep the beach clean?
Everyone has a role in keeping the beaches clean, safe, and enjoyable places to visit. The following practices will help to maintain one of our greatest natural resources—fresh water lakes.
Is there a “pathogen problem” at beaches? Are people getting sick?
There is no true measure of the magnitude of disease associated with recreational water exposures (USEPA, 1999), in New York, Pennsylvania, Ohio or elsewhere. That is because when people get sick after a weekend at the beach, the cause of illness is unknown. In addition, the illness is not reported unless there was an outbreak among a specific population, like a group of athletes participating in a triathlon.
Swimming in polluted water can make you sick (Natural Resources Defense Council, 1998). Epidemiological studies in the United States have consistently found an association between gastrointestinal illness and exposure to contaminated recreational waters; the potential for other types of infections is not completely understood (USEPA, 1999).
How would use of the nowcasting system and predictive models differ from the current way of assessing swimming safety?
Current methods to assess recreational water quality rely on collecting a sample of water from the beach area, transporting it to a laboratory, and determining numbers of indicator organisms, such as E. coli. It takes as least 18 hours to grow E. coli in the laboratory. Therefore, by the time E. coli results are compiled, beach water-quality conditions may have already changed. By contrast, it takes less than an hour to estimate recreational water quality using the predictive model and transmit results through the nowcasting system.
How well do the predictive models work?
The nowcast has been operating in Ohio at Huntington since 2006, at Edgewater since 2008, at Maumee Bay State Park since 2011, and at Villa Angela since 2012. Performances of the models in the nowcast were monitored for those years. If one were to examine the data in hindsight and assume the culture results for E. coli were the correct results, we can compare the performance of predictive models to that of using the previous day’s E. coli concentration to predict the current day’s E. coli concentration, the later being the old method used by many beach managers. Overall, the nowcast provided more correct responses than the previous day’s E. coli concentration at the four Ohio nowcast beaches.
Why was the USGS involved in this research?
Water quality and quantity are critical topics in which the USGS has developed expertise over many years. The relatively recent addition of biological science to the agency’s core program creates opportunities to apply science in a variety of new ways.
The USGS did not do this research alone. State, county, and local agencies cooperated with USGS on data collection and model development or provided funding.
Are models being developed for other beaches?
Yes, models are being developed by research institutions and public agencies for other coastal and inland beaches in the United States.
As part of a Great Lakes Beach Health initiative, a USGS Midwest area team worked with local agencies to develop and implement the use of predictive models at 49 beaches across the Great Lakes.
New York, Pennsylvania, and Ohio continue to work with agencies to develop and implement the use of predictive models along the shores of Lake Erie and Lake Ontario and at inland recreation beaches.
Is anyone else doing the same kind of research? Are other predictive models being used at beaches?
Yes, the USGS and other researchers are working on developing and testing predictive models at coastal beaches. Operational models (those used daily to issue swim advisories or closings) that rely on several explanatory variables (rainfall, wave height, wind direction, etc.) are being used in other communities in the United States, mainly in the Great Lakes. These include beaches in Wisconsin and in Chicago, Illinois. The USGS Georgia Water Science Center has initiated a bacteria alert program for a recreational river that provides the same type of output as the Lake Erie models—the probability that the standard will be exceeded (Lawrence, 2005).
Is it acceptable to use a model to assess recreational water quality?
USEPA states that a monitoring program is essential to any beach-management program and recommends that the current E. coli laboratory method be used for assessing ambient waters and for making decisions concerning the protection of human health (USEPA 2002, p. 4-17). However, USEPA also states that modeling tools may be used to supplement, not replace, monitoring. Modeling tools can provide conservative estimates when there is a lag time between sampling the water quality and obtaining results. If models are properly developed and applied, they can be used in making beach advisory or closing decisions (USEPA 2002, p. 4-22).
Centers for Disease Control, 2003, Infectious disease information: Atlanta, GA, accessed April 2010 at https://www.cdc.gov/ncidod/diseases/index.htm.
Lawrence, S., 2005, Chattahoochee Riverway Project—BacteriALERT Project: Atlanta, GA, accessed April 2010 at https://ga2.er.usgs.gov/bacteria/
Natural Resources Defense Council, 1998, Testing the Waters VIII: New York, 145 p.
U.S. Environmental Protection Agency, 2002, National beach guidance and required performance criteria for grants: Washington, D.C., EPA-823-B-02-004.
U.S. Environmental Protection Agency, 1999, EPA action plan for beaches and recreational waters: Washington, D.C., Office of Water, EPA-600-R-98-079.
These definitions of water-related terms might help you understand our Web site better. They are not universal definitions, so other definitions may be valid. This list was compiled from a number of sources and should not be considered an official U.S. Geological Survey glossary.
Bacterium (bacteria, plural). A small one-celled microorganism that can either be free living or parasitic. Some bacteria are disease causing.
Combined sewer. A sewer that carries both sanitary (sewage) and storm water in the same pipe, often in older, urban areas.
Combined sewer overflow (CSO). An event that takes place, often with the aid of a control device, that allows for a combined sewer to overflow into area waterways in order to prevent flooding. A CSO event is most likely to occur during a heavy rain event.
Escherichia coli (E. coli). A rod shaped, gram-negative bacterium, commonly found in the gastrointestinal tract and feces of warm-blooded animals. It is one species within the fecal-coliform group of bacteria and is distinguished from other fecal coliforms by biochemical tests. Although most strains of E. coli are harmless, some strains cause illness. E. coli is an “indicator” of fecal contamination and the possible presence of disease-causing organisms. E. coli is the preferred indicator for freshwater recreational waters.
Explanatory variable. A quantity of something that varies and can be used to explain increases and decreases in another variable. Explanatory variables for recreational waters include rainfall, wave height, and turbidity, and are used to explain increases and decreases in E. coli concentrations.
Fecal coliforms. A group of bacteria that were used in past to establish standards for fecal contamination in recreational waters. Fecal coliforms are still used to establish standards for shellfish-harvesting waters and for some permitting applications. Although they are used to assess fecal contamination of water, some fecal coliforms actually come from nonfecal sources. Fecal coliforms are defined by the methodology used for detection (lactose fermentation at 44.5°C).
Foreshore head. Water level data from a piezometer (shallow ground-water well) installed 20 ft inland from the edge of water. The foreshore head measured in this manner can best be characterized as a combination of the pressure changes due to the local water table, fluctuations in barometric pressure, the water level in the lake, and the pressure variance due to wave action (Francy and others, 2009).
Indicator bacteria. A type or group of bacteria that indicate the possible presence of disease causing (pathogenic) microorganisms. Indicator bacteria are not usually pathogenic themselves, but they are often associated with pathogens because they are present in large quantities in the feces of warm-blooded animals.
Membrane filtration. A technique used for the detection and enumeration of bacteria from water. This method provides a direct count of bacteria based on the growth of colonies on the surface of a membrane filter through which sample was passed. To assess the sanitary quality of water using bacterial indicators such as E. coli, the number is expressed as colonies per 100 milliliters (col/100 mL).
Milliliter. A milliliter is a metric unit of volume equivalent to one-millionth of a cubic meter. 100 milliliters is equivalent to about 3.5 fluid ounces or slightly less than ½ cup.
Multiple linear regression (MLR). A standard statistical technique that uses several explanatory variables to predict the outcome of another variable (response variable). The goal of MLR is to select a group of explanatory variables that explain as much as possible of the variation observed in the response variable, leaving as little variation as possible to unexplained “noise.” In the case of predictive models for beaches, rainfall and wave height are examples of explanatory variables and E. coli is the response variable.
Nephelometric turbidity unit (NTU). A unit of measure for the turbidity (cloudiness) of water.
Nowcasting. A “nowcast” of recreational water quality is similar to a weather forecast except it provides an estimate of current conditions instead of future conditions. A nowcast gives the probability that the bathing-water standard will be exceeded and swimming would result in an excessive health risk.
Pathogen. An organism that causes disease.
Photosynthetically-active radiation (PAR). Radiation in the 400-700 nanometer range measured by use of sensor at the beach. PAR from the previous day is negatively related to the concentration of E. coli in water at some beaches.
Predictive models. Mathematical models that use easily measured environmental and water-quality variables (“explanatory variables”), such as wave height and rainfall, to estimate the E. coli concentration or the probability of exceeding the bathing-water standard of 235 col/100 mL E. coli.
qPCR. Quantitative polymerase-chain reaction. qPCR is a rapid analytical method that can be performed in about 2 hours. It is a molecular method that targets the DNA of a specific organism – for recreational water-quality, qPCR methods were designed to target genes specific for E. coli or enterococci.
Recreational water-quality standards. Standards established by the state and based on recommendations and epidemiological studies from the U.S. Environmental Protection Agency, they are used to decide when to issue a water-quality advisory. In New York, Pennsylvania, and Ohio, the single-sample bathing-water standard for E. coli is 235 colonies per 100 milliliters (col/100 mL). This means that when the E. coli concentration is equal to or greater than 235 col/100 mL, swimming in the water would pose a high risk of illness.
Sanitary sewer overflow (SSO). An event that takes place in which sewage from a sanitary sewer system overflows, or spills, often from a sanitary manhole. A SSO can occur if a blockage is present within a sanitary sewer system and/or there is too much flow.
Threshold probability. To decided whether or not there’s too great a risk to go swimming on any particular day, beach managers establish a beach-specific threshold probability based on historical data. Probabilities equal to or above the threshold would indicate to the beach manager that E. coli concentrations are most likely above the standard, and an advisory would be issued. Probabilities below the threshold indicate that E. coli concentrations are most likely below the standard.
Turbidity. A quantitative value for the clarity of water sample—the higher the turbidity the more cloudy the water. Turbidity is measured with a turbidimeter, which measures the scattering effect that suspended particles have on light.
Virus. A submicroscopic particle (are too small to be seen by regular light microscopes) that is only able to replicate by taking over the machinery of a living cell. Many viruses cause disease.
Water quality. A term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose.
Water-quality advisory. A public notification, typically in the form of a sign posted at the beach and (or) on the Internet, to advise the public that current recreational water-quality standards are not acceptable for swimming because of elevated E. coli levels.
For information on swimming advisories, health issues, and general inquiries about the website, please contact (click logo):
Swimming Advisories and Health Issues:
Chautauqua County Department of Health
Erie County Department of Health
Monroe County Health Department
New York State Department of Health
New York State Office of Parks, Recreation and Historic Preservation
U.S. Geological Survey
New York Water Science Center, 30 Brown Road, Ithaca, NY 14850
Phone: (607) 266-0217 x3003