South Atlantic Water Science Center

Chattahoochee River BacteriAlert: Home

Current Estimated E. coli (based on turbidity)

Station#
(locality)
Estimated
E. coli count
Estimated
Risk Level
Date
Time
Turbidity
(NTU)
02335000
(Medlock Bridge Road)
134 Low 2018-10-23
07:15:00 am
13.1
02336000
(Paces Ferry Road)
56 Low 2018-10-23
07:45:00 am
4.7
Estimated E. coli colony counts per 100mL of water: (Estimated risk level based on NPS and EPA information)
Low risk: E. coli < 177 High risk: E. coli > 235

Most Recent Sampled E. coli data

Station#
(locality)
Date
Time
Sampled
E. coli count
02335000
(Medlock Bridge Road)
2018-10-18
10:05:00 am
44
02335880
(Powers Ferry Road)
2018-10-18
08:16:00 am
90
02336000
(Paces Ferry Road)
2018-10-18
08:40:00 am
113

Background

How safe is it to swim, wade, and boat in the Chattahoochee River today? For a highly urbanized river such as the Chattahoochee, much of the answer depends on bacteria levels in the water. This website provides "real time" turbidity data, the estimated E coli bacteria count, the most recent E. coli bacteria counts (sample collected each Thursday), and National Park Service health advisories for two locations on the Chattahoochee River (view map).

NWIS links (Current Conditions)

Here are the current conditions for the Chattahoochee River sites:

Understanding E coli

Publications

USGS Scientific-Investigations Report 2012-5037
Escherichia coli Bacteria Density in Relation to Turbidity, Streamflow Characteristics, and Season in the Chattahoochee River near Atlanta, Georgia, October 2000 through September 2008—Description, Statistical Analysis, and Predictive Modeling

Estimating E coli

E. coli predictions are based on the current turbidity values. It is important to understand how the bacteria counts are estimated using turbidity. After taking many water samples, the sampled turbidity and actual E coli counts were analyzed statistically, which showed that as turbidity went up so did E coli counts. The statistical "best fit" formula was produced, which is used to estimate E coli counts. But, it is important to realize that the actual (sampled) E coli counts vary a great deal even at the same turbidity. Thus, the water samples taken when turbidity was at, for example, 50 could produce E coli counts of 500, 1000, or 1,500. As all of these results are from actual samples, and each E coli count is accurate.

This just means that there is a lot of variability in the data. In this Website, the estimated E coli count is produced using the average of the samples taken at any specific turbidity. To try to summarize simply, when we show the estimated E coli count, the actual E coli at that moment might be much more or much less than the estimated count, but, using past data, the estimated value is the average of the range of sampled values, for that turbidity. And, most important, E coli counts do go up as turbidity goes up, and the National park Service advisory statements should be considered valid.

Do you want to receive a weekly email of the sampled bacteria counts? Contact rsyoung@usgs.gov.