TN Water Watch

Project Overview

This project currently provides modelled predictions of waterborne harmful microbial densities at river access points around Middle TN, with plans to expand to include other sites and rivers in the region. Conventional water quality sampling can only provide readings from the past couple of days, which is inadequate to forecast human health risk associated with recreational usage. Real-time data are retrieved from US Geological Survey and local weather stations to make predictions based on a model built from past E. coli samples and environmental conditions, and updated on an hourly basis. It is important to note that predictions are inherently uncertain and cannot guarantee risk or safety, and it is still possible to be negatively impacted even when the predictions indicate a safe environment, or remain healthy even if the predictions indicate that caution should be taken.

Model Summary

A predictive E. coli model was created by correlating levels of E. coli with real-time environmental factors (weather, river flow, precipitation, etc.) resulting in a simple predictive equation that forecasts the levels of E. coli for the day (see below).

Refresh Rate?

The predictive model refreshes and reevaluates the public health recommendations each hour - check map for time and date of most recent update.

Graphical representation of the predictive E. coli model.

Model Details

The health of our rivers is integral to environmental sustainability, protection of wildlife, and clean water, and subsequently the health of residents that depend on the use of the water. River health is determined by monitoring various factors of water quality, such as temperature, precipitation, dissolved oxygen and other particles, and concentration of microbial life and contaminants. Water quality data are utilized to identify and quantify contamination/impairments, inform protection and management strategies, and verify and evaluate management efforts.

Among all the factors affecting water quality, harmful microbials such as bacteria threaten our waterways and pose health risks to swimmers, kayakers, and recreational fishers. Waterborne pathogens (bacteria capable of causing disease in humans) have been known to cause Salmonellosis, Legionnaires’ disease, Dysentery, and other stomach, respiratory, skin, and brain effects. Bacteria sources may include sewage, urban runoff, agricultural runoff, or industrial waste. When these bacteria flow into our beaches and rivers they can pose serious health risks.

Recreational waters are threatened by fecal contamination from urban and agricultural drainage that may contain human pathogens associated with gastrointestinal and respiratory illness. Many recreational rivers are monitored for fecal contamination, arousing threat to human health. According to the data from Center for Disease Control, human pathogens are one of the top causes of recreational water illness, which can be indexed with measurements of E. coli level in the water.

Unfortunately, there is very little E. coli sampling work being done, particularly in our highly recreational rivers (i.e. >500,000 visit the Harpeth River State Parks annually) and none of these sampling efforts are paired with predictive modeling, which provides the general public “early warning” notice if waters may be unsafe to swim based on levels of E. coli. Typically, water samples must be processed in a lab environment and take up to a couple of days to acquire E. coli levels, which is inadequate for informing recreational use to people that the water from two days ago was a health hazard.

Fortunately, it is possible to develop a framework model using past sample data in conjunction with live data from environmental monitors such as live water quality and weather data to predict the level of harmful bacteria in the water. 

Why are we concerned about E. coli?

Previous incidents investigated by Tennessee of Department of Environment and Conservation (TDEC)

In 2014, TDEC investigated an uncommon waterborne salmonellosis outbreak.  There was one risk factor in common to many of the cases — having enjoyed water recreation at a splash pad.  The investigation lead to a state survey of water quality and patron behaviors at splash pads. 

In July 2017, TDEC investigated a large outbreak of legionellosis linked to a hotel in Western Tennessee. A total of 92 ill people were identified and ill people were more likely to have spent time in or around the aquatics area (outdoor pool, hot tub). Water testing of the aquatics area identified the Legionella bacteria was present.

In 2018, TDEC investigated a large outbreak involving multiple pathogens was investigated at an outdoor adventure company in Eastern Tennessee. Visitors to the facility had drank water from an untreated well and later become ill. Testing of the water identified E. coli and coliforms, which indicated contamination.