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Kansas Water Science Center

U.S. Geological Survey
Water-Resources Investigations Report 03-4056

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Comparison and Continuous Estimates of Fecal Coliform and 
Escherichia Coli Bacteria in Selected Kansas Streams, 
May 1999 Through April 2002

By Patrick P. Rasmussen and Andrew C. Ziegler


The sanitary quality of water and its use as a public-water supply and for recreational activities, such as swimming, wading, boating, and fishing, can be evaluated on the basis of fecal 
coliform and Escherichia coli (E. coli) bacteria densities. This report describes the overall sanitary quality of surface water in selected Kansas streams, the relation between fecal coliform and 
E. coli, the relation between turbidity and bacteria densities, and how continuous bacteria estimates can be used to evaluate the water-quality conditions in selected Kansas streams.

Samples for fecal coliform and E. coli were collected at 28 surface-water sites in Kansas. Of the 318 samples collected, 18 percent exceeded the current Kansas Department of Health and 
Environment (KDHE) secondary contact recreational, single-sample criterion for fecal coliform (2,000 colonies per 100 milliliters of water). Of the 219 samples collected during the recreation months (April 1 through October 31), 21 percent exceeded the current (2003) KDHE single-sample fecal coliform criterion for secondary contact rec-reation (2,000 colonies per 100 milliliters of water) and 36 percent exceeded the U.S. Environmental Protection Agency (USEPA) recommended single-sample primary contact recreational criterion for E. coli (576 colonies per 100 milliliters of water). Comparisons of fecal coliform and E. coli criteria indicated that more than one-half of the streams sampled could exceed USEPA recommended E. coli criteria more frequently than the current KDHE fecal coliform criteria. In addition, the ratios of E. coli to fecal coliform (EC/FC) were smallest for sites with slightly saline water (specific conductance greater than 1,000 microsiemens per centimeter at 25 degrees Celsius), indicating that E. coli may not be a good indicator of sanitary quality for those streams. Enterococci bacteria may provide a more accurate assessment of the potential for swimming-related illnesses in these streams. 

Ratios of EC/FC and linear regression models were developed for estimating E. coli densities on the basis of measured fecal coliform densities for six individual and six groups of surface-water sites. Regression models developed for the six individual surface-water sites and six groups of sites explain at least 89 percent of the variability in E. coli densities. The EC/FC ratios and regression models are site specific and make it possible to convert historic fecal coliform bacteria data to estimated E. coli densities for the selected sites. The EC/FC ratios can be used to estimate E. coli for any range of historical fecal coliform densities, and in some cases with less error than the regression models. The basin- and statewide regression models explained at least 93 percent of the variance and best represent the sites where a majority of the data used to develop the models were collected (Kansas and Little Arkansas Basins).

Comparison of the current (2003) KDHE geometric-mean primary contact criterion for fecal coliform bacteria of 200 col/100 mL to the 2002 USEPA recommended geometric-mean criterion of 126 col/100 mL for E. coli results in an EC/FC ratio of 0.63. The geometric-mean EC/FC ratio for all sites except Rattlesnake Creek (site 21) is 0.77, indicating that considerably more than 63 percent of the fecal coliform is E. coli. This potentially could lead to more exceedances of the recommended E. coli criterion, where the water now meets the current (2003) 200-col/100 mL fecal coliform criterion. 

In this report, turbidity was found to be a reliable estimator of bacteria densities. Regression models are provided for estimating fecal coliform and E. coli bacteria densities using continuous 
turbidity measurements. Prediction intervals also are provided to show the uncertainty associated with using the regression models. Eighty percent of all measured sample densities and individual turbidity-based estimates from the regression models were in agreement as exceeding or being less than the primary and secondary contact recreational criteria. The continuous turbidity measurements and regression models were used to construct probability curves that can be used to estimate bacteria concentrations on the basis of measured turbidity values. Duration curves developed for six sites using the hourly estimates of bacteria density indicate that the current KDHE (fecal coliform bacteria) and USEPA recommended (E. coli bacteria) primary contact recreational criteria were exceeded for 21 to 94 and 31 to 97 percent of the spring and summer, respectively. Estimated bacteria densities most commonly exceeded the current and recommended criteria in the spring (April through June). Hourly estimates provided in real time (available on the World Wide Web at allow the public and water-management agencies to make decisions in regard to whether planned water activities are appropriate by considering current stream conditions relative to water-quality criteria.

Annual and seasonal loads and yields were calculated using hourly estimated fecal coliform and E. coli bacteria densities and streamflow at six surface-water sites for the calendar years 2000 
and 2001. Estimated bacteria loads in 2001 were about 2 to 8 times larger than the bacteria loads in 2000 for the Kansas and Little Arkansas Rivers. Data from major point sources upstream from the surface-water sites in these basins indicate that nonpoint sources accounted for more than 97 percent of the annual loads. Mean daily bacteria loads in 2000 were largest in the winter for five sites and in the spring for one site. In 2001, mean daily bacteria loads were largest in the spring for four sites and in the winter for two sites. Annual load differences are caused by varying hydrologic conditions and higher streamflow caused by over-land runoff. Surface-water sites in the Little Arkansas River Basin had the largest bacteria yield per acre of watershed.



  • Abstract
  • Introduction
  • Purpose and Scope
  • Methods
    • Bacteria Sample Collection and Analysis
    • Turbidity Measurements
    • Development of Regression Models to Estimate Bacteria Densities
  • Measured Bacteria Densities
  • Comparison of Fecal Coliform and Escherichia Coli Densities
  • Continuously Estimated Bacteria Densities
    • Relation Between Turbidity and Fecal Coliform Density
    • Probability and Duration of Estimated Fecal Coliform Densities
    • Relation Between Turbidity and Escherichia Coli Density
    • Probability and Duration of Estimated Escherichia Coli Densities
  • Estimated Bacteria Loads and Yields
  • Summary
  • References

Rasmussen, Patrick 2003, Comparison and Continuous Estimates of Fecal Coliform and Escherichia Coli Bacteria in Selected Kansas Streams, May 1999 Through April 2002 03-4056, 87 p.

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For additional information contact:

Patrick Rasmussen
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, KS 66049-3839
Telephone: (785) 832-3542
Fax: (785) 832-3500