U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009–1192

In cooperation with Cuyahoga Valley National Park and the Ohio Lake Erie Commission

Relations Between Environmental and Water-Quality

Variables and Escherichia coli in the Cuyahoga River

With Emphasis on Turbidity as a Predictor of Recreational 

Water Quality, Cuyahoga Valley National Park, Ohio, 2008

Relations Between Environmental and 

Water-Quality Variables and Escherichia coli

in the Cuyahoga River With Emphasis on Turbidity 

as a Predictor of Recreational Water Quality, 

Cuyahoga Valley National Park, Ohio, 2008

By Amie M.G. Brady and Meg B. Plona

In cooperation with Cuyahoga Valley National Park and the Ohio Lake Erie Commission

Open-File Report 2009–1192

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Brady, A.M.G., and Plona, M.B., 2009, Relations between environmental and water-quality variables and Escherichia 

coli in the Cuyahoga River with emphasis on turbidity as a predictor of recreational water quality, Cuyahoga Valley 

National Park, Ohio, 2008: U.S. Geological Survey Open-File Report 2009–1192, 6 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Methods...........................................................................................................................................................2

Sample Analyses and Environmental Data Collection ...................................................................2

Statistical Analyses..............................................................................................................................3

Correlations Between E. coli Concentrations and Environmental Variables ......................................3

Validation of Turbidity-Based Predictive Model.......................................................................................4

Ongoing Work.................................................................................................................................................6

Summary..........................................................................................................................................................6

References Cited............................................................................................................................................6

Figures

1. Cuyahoga Valley National Park, Ohio, and water-quality sampling sites during 

the recreational season (May through August) of 2008.........................................................2

2. Escherichia coli concentrations at four sites along the Cuyahoga River during the 

recreational season (May through August) of 2008................................................................4

3. Escherichia coli concentrations in water samples collected from the 

Cuyahoga River at Jaite (Brecksville), Ohio, compared to predicted concentrations 

from a simple linear regression model based on turbidity.....................................................5

Tables

1. Cuyahoga River water-quality sampling sites during the recreational season 

(May through August) of 2008, Cuyahoga Valley National Park, Ohio.................................3

2. Summary statistics for Escherichia coli concentrations in the 

Cuyahoga River during the recreational season (May through August) of 2008, 

Cuyahoga Valley National Park, Ohio........................................................................................3

3. Relations between log10-transformed Escherichia coli concentrations and 

environmental variables in the Cuyahoga River during the recreational season 

(May through August) of 2008, Cuyahoga Valley National Park, Ohio.................................5
iv

Conversion Factors

Multiply By To obtain

inch (in.) 25.4 millimeter (mm)

liter (L) 0.2642 gallon (gal)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Bacteria concentrations are given in colony-forming units per 100 milliliters (CFU/100 mL).
Relations Between Environmental and Water-Quality 

Variables and Escherichia coli in the Cuyahoga River 

With Emphasis on Turbidity as a Predictor of Recreational 

Water Quality, Cuyahoga Valley National Park, Ohio, 2008

By Amie M.G. Brady1 and Meg B. Plona2

Abstract

During the recreational season of 2008 (May through 

August), a regression model relating turbidity to concentrations of Escherichia coli (E. coli) was used to predict recreational water quality in the Cuyahoga River at the historical 

community of Jaite, within the present city of Brecksville, 

Ohio, a site centrally located within Cuyahoga Valley National 

Park. Samples were collected three days per week at Jaite and 

at three other sites on the river. Concentrations of E. coli were 

determined and compared to environmental and water-quality 

measures and to concentrations predicted with a regression 

model. Linear relations between E. coli concentrations and 

turbidity, gage height, and rainfall were statistically significant 

for Jaite. Relations between E. coli concentrations and turbidity were statistically significant for the three additional sites, 

and relations between E. coli concentrations and gage height 

were significant at the two sites where gage-height data were 

available. The turbidity model correctly predicted concentrations of E. coli above or below Ohio’s single-sample standard 

for primary-contact recreation for 77 percent of samples 

collected at Jaite.

Introduction

Traditional culture-based methods for determining 

recreational water quality with respect to Escherichia coli

(E. coli) concentrations can take 18 hours or longer to obtain 

results. Consequently, information about current recreational 

water quality is based on conditions that may no longer be 

relevant. Decisions based on such information can result in 

either unneeded no-swimming alerts and lost recreational

opportunities or—more unfavorably—unintended exposure for 

recreationists to waters that do not meet recreational standards 

if an alert is warranted but not issued. At Cuyahoga Valley 

National Park (CVNP), which is in northeastern Ohio, park 

managers discourage use of the Cuyahoga River for recreation 

because water-quality conditions can change so quickly. 

The Ohio Environmental Protection Agency assigns minimum water-quality requirements for all state surface waters 

on the basis of use designations. Within CVNP, the Cuyahoga 

River has been assigned a use designation of primary-contact 

recreation, meaning the waters are capable of supporting fullbody-contact recreation activities such as wading, swimming, 

and canoeing (Ohio Environmental Protection Agency, 2008). 

The specific numeric criterion for E. coli for this use designation in a single sample is 298 colony-forming units per 100 

milliliters (CFU/100 mL). This water-quality standard (WQS) 

was used as a benchmark to evaluate recreational water quality 

in this study. 

Regression models used to predict same-day recreational 

water quality have been shown to produce accurate predictions 

for coastal beaches (Francy and Darner, 2007; Francy and 

others, 2003; Nevers and Whitman, 2006; Nevers and others, 2007) and rivers (U.S. Geological Survey BacteriALERT 

Program, http://ga2.er.usgs.gov/bacteria/default.cfm). During 

previous studies within the park, the U.S. Geological Survey 

(USGS), in cooperation with CVNP, collected water-quality 

data to develop a regression model to predict recreational 

water quality of the river at one site centrally located within 

the park: the historical community of Jaite, within the present 

city of Brecksville, Ohio (fig. 1) (Brady and others, 2009). 

The Jaite model correctly predicted exceedances and nonexceedances of the WQS in 77 percent of samples collected at 

this site during the recreational seasons (May through August) 

of 2004–7. 

In 2008, the USGS, in cooperation with CVNP and the 

Ohio Lake Erie Commission, did a study to validate the Jaite 

regression model developed from data collected during 2004 

through 2007 and examine other water-quality variables that 

may be of use for predicting recreational water quality in 

1

U.S. Geological Survey.

2

Cuyahoga Valley National Park.
2 Relations Between Environmental and Water-Quality Variables and Escherichia coli in the Cuyahoga River, Ohio, 2008

the Cuyahoga River. Results of the culture-based method of 

determining E. coli concentrations were compared to environmental and water-quality variables at Jaite and at three other 

sampling sites near or within CVNP. In addition, for the Jaite 

site, results of the culture-based method were compared to the 

predicted E. coli concentrations from the regression model. 

E. coli concentrations measured at the three other sites were 

compared to predicted concentrations at Jaite to determine 

whether the model could also predict E. coli concentrations 

elsewhere in the river. This report summarizes the data 

collected from the 2008 study.

Methods

Water samples were collected from the Cuyahoga River 

at Jaite, the site studied by Brady and others (2009), three days 

per week from June through August 2008. Three other sites 

(table 1, fig. 1) were sampled along with sampling at Jaite 

at various times during the recreational season. Old Portage, 

a site just upstream from the park and from a municipal 

wastewater-treatment facility near Bath, Ohio, was sampled 

from mid-June through mid-July. Sampling at Old Portage was 

abandoned in favor of focusing on a stretch of the river more 

often frequented by recreationists—between Lock 29 and 

Independence (Lisa Petit, Cuyahoga Valley National Park, oral 

commun., 2008). Independence, a site near the downstream 

edge of the park, was sampled from mid-July through August. 

Lock 29 in Peninsula, Ohio, a site several miles downstream 

from the municipal wastewater-treatment facility and upstream 

from Jaite, was sampled from late July through August. Within 

the park, the Cuyahoga River flows north into Lake Erie. 

Further site information can be found in table 1. 

Samples were collected from a bridge by using a 

weighted-bottle sampler fitted with a sterile 1-L bottle at 

one location near the center of flow (U.S Geological Survey, 

2006). The weighted sampler was submerged several inches 

and the bottles were allowed to fill to within 2 in. of the top. 

The bottles were then capped and placed on ice in a cooler 

until analyses were performed. 

Sample Analyses and Environmental Data 

Collection

Determination of E. coli concentrations always began 

within 6 hours of sample collection in accordance with U.S. 

Environmental Protection Agency Method 1603 (U.S. Environmental Protection Agency, 2006). Aliquots of sample were 

filtered through membrane filters, and the filters were transferred to modified mTEC agar and incubated for 2 hours at 

35°C and then 22 hours at 44.5°C. Magenta-colored colonies 

visible after incubation were counted as E. coli and reported as 

colony-forming units per 100 milliliters.

Other environmental parameters/variables were measured 

in addition to E. coli concentrations. These included water 

level at time of sampling (used to estimate streamflow), turbidity, and total rainfall in the 24 hours prior to sample collection. 

Water level was measured by means of a USGS streamgage 

(at Old Portage and Independence) or a manual, steel-tape 

measurement from a known elevation on the bridge to the surface of the water (at Jaite). Gage height was not measured at 

Figure 1. Cuyahoga Valley National Park, Ohio, and 

water-quality sampling sites during the recreational 

season (May through August) of 2008.

I-71

41°20'

41°10'

OHIO

Study area

Cleveland

Akron

I-80

I-271

Cuyahoga

River

EXPLANATION

Approximate area of park

Urban areas

 Sampling site

I-77

Independence

Jaite

(Brecksville)

Lock 29

Old Portage 







81°40' 81°30'

0 5 MILES

0 5 KILOMETERS

Base from Cuyahoga Valley

National Park, digital data

EXPLANATION

Approximate area of park

Urban areas

 Sampling site
Correlations Between E. coli Concentrations and Environmental Variables 3

Lock 29 because this was a new site selected for this project, 

and no historical streamflow information was available. Turbidity was determined in the laboratory with a portable turbidimeter and was reported in nephelometric turbidity ratio units 

(NTRU). Local rainfall totals for the previous 24 hours were 

obtained from the Ohio Emergency Management Agency’s 

Automated Flood Warning System (http://www.afws.net). 

Quality-control checks were performed onsite monthly to 

ensure that sample collection and analyses were done according to protocols. In addition, filter blanks, replicates, and field 

blanks (described in detail by Francy and others, 2008) were 

collected and analyzed daily, weekly, and monthly, respectively, throughout the study. Filter blanks consist of sterile 

buffer water filtered prior to sample processing and then 

analyzed in the same manner as environmental samples to 

ensure sterility of equipment and buffer. A replicate is a second sample collected and processed with the regular sample to 

assess analytical and sampling variability. A field blank is an 

aliquot of sterile buffer water that is transferred into a sterile 

sample bottle in the field and then analyzed in the same manner as environmental samples to evaluate proper handling of 

samples. No quality-control problems were identified during 

quality-control checks. No bacterial growth was observed on 

the filter blanks or on filters plated from the field blanks. Variability, defined as the absolute value of the difference between 

log10-transformed replicate pair concentrations divided by the 

average of the log10-transformed concentrations, ranged from 

1 to 4 percent.

Statistical Analyses

Correlation analysis and scatterplots were used to examine the relations between E. coli concentrations and turbidity, 

total rainfall, and gage height. A linear correlation coefficient 

(Pearson’s r) was used to determine the degree to which E. coli

concentration was linearly related to covariates. The more the 

coefficient differs from 1 or -1, the weaker the relation. Simple 

linear regression analysis was used to estimate E. coli concentrations in the river on the basis of one explanatory variable. 

The level of significance for statistical tests was set at α = 0.05 

for this report.

Correlations Between E. coli

Concentrations and Environmental 

Variables

Site-specific summary statistics for E. coli concentrations are listed in table 2. Higher average concentrations of 

E. coli were observed at the Old Portage and Jaite sites than 

at the Lock 29 and Independence sites. This may be because 

the other two sites were not sampled until later in the summer, after the higher concentrations were observed at Old 

Portage and Jaite (fig. 2). Also, samples were collected during 

three high-streamflow events (daily mean streamflow greater 

Table 1. Cuyahoga River water-quality sampling sites during the recreational season (May through August) of 2008 from the most 

upstream to the most downstream locations, Cuyahoga Valley National Park, Ohio.

[CVNP, Cuyahoga Valley National Park]

Site name USGS station 

identification number Short description of location

Old Portage 04206000 Just upstream from CVNP at North Portage Path, Akron, Ohio.

Lock 29 411433081330000 Just downstream from Peninsula on the Ohio and Erie Canal Towpath Trail near Lock 29 

Trailhead, Peninsula, Ohio.

Jaite 411747081341300 Centrally located within CVNP at Vaughn Road, Brecksville, Ohio

Independence 04208000 At the downstream boundary of CVNP at Old Rockside Road, Independence, Ohio

Table 2. Summary statistics for Escherichia coli concentrations in the Cuyahoga River during the recreational season

(May through August) of 2008, Cuyahoga Valley National Park, Ohio.

[CFU/100 mL, colony-forming units per 100 milliliters]

Site name Number of samples

Escherichia coli, in CFU/100 mL

Minimum Median Maximum Average

Old Portage 12 130 420 10,000 2,000

Lock 29 8 77 330 930 430

Jaite 31 51 390 34,000 2,900

Independence 13 78 200 800 290
4 Relations Between Environmental and Water-Quality Variables and Escherichia coli in the Cuyahoga River, Ohio, 2008

than 450 ft3/s, as observed at Old Portage) prior to the start of 

sampling at Lock 29 and Independence (fig. 2). These events 

were associated with high E. coli concentrations. Although 

sampling at Lock 29 and Independence included one highstreamflow event, concentrations were not as high during this 

event as during previous ones.

At Jaite and Old Portage, correlations between 

log10-transformed concentrations of E. coli and log10-transformed turbidity, rainfall total for the previous 24 hours, and 

gage height at the time of sampling were statistically significant (table 3). The relation between turbidity and E. coli at 

Jaite had a higher Pearson’s r correlation coefficient than the 

other relations examined, suggesting that turbidity is the best 

predictor of recreational water quality than the other variables at this site. At Lock 29 and Independence, correlations 

between concentrations of E. coli and turbidity or gage height 

(Independence only) were significant, but rainfall was not 

significantly related to E. coli concentrations at these sites. 

Validation of Turbidity-Based 

Predictive Model

A turbidity-based model developed from data collected 

during 2004 through 2007 for the Jaite site (Brady and others, 

2009) was validated by using the 2008 data presented in this 

report. Of the 31 samples collected at Jaite, 24 samples, or 

77 percent, were correctly predicted in terms of being above, 

at, or below the WQS (fig. 3) as measured by the culture-based 

method. The model generally underpredicted concentrations 

when measured E. coli concentrations were greater than 1,000 

CFU/100 mL but still correctly predicted these concentrations as exceedances of the WQS. Five samples were “false 

negatives,” meaning the E. coli concentrations in the samples 

exceeded the WQS, but the model predicted these sample 

concentrations below the WQS. The remaining two samples 

were “false positives,” meaning the model predicted E. coli

concentrations above the WQS, but the actual concentrations 

were below the WQS. 

5/26/2008 6/16/2008 7/7/2008 7/28/2008 8/18/2008

Date

101

102

103

104

105

Es

c

h

eric

hia

c

oli, in c

olony-forming

units p

er 10

0

milliliters

Old Portage

Jaite

Lock 29

Independence

0

225

450

675

900

D

aily

m

e

an stre

a

mflo

w,

in cubic fe

et p

er se

c

ond

Figure 2. Escherichia coli concentrations at four sites along the Cuyahoga River during the recreational season (May through 

August) of 2008. Daily mean streamflow measured at one site (Old Portage) also is shown.
Validation of Turbidity-Based Predictive Model 5

101 102 103 104 105

Measured Escherichia coli, in colony-forming units per 100 milliliters

101

102

103

104

105

Pre

dicte

d

Es

c

h

eric

hia

c

oli, in

c

olo

n

y-formin

g

u

nits

p

er 10

0

milliliters

1:1 line

Table 3. Relations between log10-transformed Escherichia coli concentrations and environmental variables in the 

Cuyahoga River during the recreational season (May through August) of 2008, Cuyahoga Valley National Park, Ohio.

[Rainfall, the total rainfall during the previous 24 hours prior to sample collection; --, no data available]

Site name Number of samples

Pearson’s correlation coefficient, r (p-value)

Log10 turbidity Gage height Rainfall

Old Portage 12 0.92 (<0.0001) 0.78 (0.0026) 0.71 (0.0102)

Lock 29 8 .89 (0.0032) -- .18 (0.6666)

Jaite 31 .86 (<0.0001) .67 (<0.0001) .57 (0.0008)

Independence 13 .67 (0.0126) .80 (0.0011) .35 (0.2440)

Figure 3. Escherichia coli concentrations in water samples collected from the Cuyahoga River at Jaite (Brecksville), 

Ohio, compared to predicted concentrations from a simple linear regression model based on turbidity. The red dashed 

lines indicate Ohio’s single-sample standard for primary-contact recreation (298 colony-forming units per 100 milliliters).

The concentrations predicted by the model developed for 

the Jaite site were compared to measured E. coli concentrations at the other three sites sampled. The Jaite model correctly 

predicted exceedances or non-exceedances of the WQS in 75 

percent of the samples collected at Lock 29 and Independence 

and in 83 percent of the samples collected at Old Portage. 

Further testing would need to be completed prior to use of the 

Jaite model for predictions elsewhere along the river.
6 Relations Between Environmental and Water-Quality Variables and Escherichia coli in the Cuyahoga River, Ohio, 2008

Ongoing Work

During the recreational season of 2009, samples were 

collected at Jaite four times per week and predicted concentrations of E. coli for this site were posted on the Ohio Nowcast 

website (www.ohionowcast.info). Samples were also collected 

at Lock 29 and Independence four times per week to further 

examine the relations between the actual concentrations at 

these sites, as determined by the culture-based method, and 

the predicted E. coli concentrations at Jaite. This research is 

planned to continue through the recreational season of 2010.

Summary

The U.S. Geological Survey, in cooperation with 

Cuyahoga Valley National Park and Ohio Lake Erie Commission, completed a study during the recreational season (May 

through August) of 2008 to validate a regression model used 

for predicting recreational water quality in the Cuyahoga River 

within the Cuyahoga Valley National Park. 

Within the Cuyahoga Valley National Park, water-quality 

of the Cuyahoga River was examined during the recreational 

season (May through August) of 2008. Concentrations of 

E. coli were measured three days per week at a site centrally 

located within the park (Jaite) and at three other sites on 

the river. Environmental and water-quality measures were 

compared to E. coli concentrations. At all four sites, relations 

between turbidity and E. coli concentrations were statistically significant. Relations between E. coli concentrations 

and gage height were statistically significant at the three sites 

where gage height data were available. Rainfall amounts were 

significantly correlated to E. coli concentrations at Jaite and 

Old Portage, a site just upstream from the park, but not at the 

other two sites.

A turbidity-based simple linear regression model, 

developed from data collected during the recreational seasons of 2004 through 2007, was validated during 2008. E.coli

concentrations at Jaite were compared to predicted E. coli

concentrations from the model. The model correctly predicted 

exceedances or non-exceedances of Ohio’s single-sample 

standard for primary-contact recreation (WQS) in 77 percent 

of the samples collected at Jaite. Further, predicted concentrations based on turbidity measured at Jaite were compared to 

measured concentrations at the other three sites. The predicted 

concentrations agreed with the measured concentrations 

(above, at, or below the WQS) between 75 and 83 percent for 

the samples collected at the other sites.

Future work at the Cuyahoga Valley National Park is 

expected to include posting predicted concentrations on the 

Ohio Nowcast website and further study of using the turbidity 

model to predict exceedances or non-exceedances of the WQS 

at other sites on the river.

Acknowledgements

Donald J. Doyle III is thanked for his tireless assistance 

with sample collection and analysis.

References Cited

Brady, A.M.G, Bushon, R.N., and Plona, M.B., 2009, Predicting recreational water quality using turbidity in the 

Cuyahoga River, Cuyahoga Valley National Park, Ohio 

2004–7: U.S. Geological Survey Scientific Investigations 

Report 2009-5192, 16 p.

Francy, D.S., Bushon, R.N., Bertke, E.E., Likirdopulos, C.A., 

Brady, A.M.G., Kephart, C.M., Stelzer, E.A., and Stoeckel, 

D.M., 2008, Quality assurance/quality control manual: 

U.S. Geological Survey Ohio Water Microbiology Laboratory, accessed March 13, 2009, at http://oh.water.usgs.gov/

micro_qaqc.htm

Francy, D.S., and Darner, R.A., 2007, Nowcasting beach 

advisories at Ohio Lake Erie beaches: U.S. Geological 

Survey Open-File Report 2007–1427, 13 p.

Francy, D.S., Gifford, A.M., and Darner, R.A., 2003, Escherichia coli at Ohio beaches—Distribution, sources, wastewater indicators, and predictive modeling: U.S. Geological 

Survey Water-Resources Investigations Report 02–4285, 

120 p.

Nevers, M.B., and Whitman, R.L., 2006, Nowcast modeling of 

Escherichia coli concentrations at multiple urban beaches 

of southern Lake Michigan: Water Research, v. 39, no. 20, 

p. 5250–5260.

Nevers, M.B., Whitman, R.L., Frick, W.E., and Ge, Z., 2007, 

Interaction and influence of two creeks on E. coli concentrations of nearby beaches—Exploration of predictability and 

mechanisms: Journal of Environmental Quality, v. 36, no. 5, 

p. 1338–1345.

Ohio Environmental Protection Agency, 2008, Water quality 

standards: Ohio Administrative Code chap. 3745–1, January 

23, 2008, p. 01:1, 07:1–8, 07:23, and 26:6.

U.S. Environmental Protection Agency, 2006, Method 1603—

Escherichia coli in water by membrane filtration using 

modified membrane-thermotolerant Escherichia coli agar: 

Washington, D.C., EPA 821–R–06–011 [variously paged].

U.S. Geological Survey, 2006, Collection of water samples 

(ver. 2.0): U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A4, September, 

accessed August 4, 2009, at http://pubs.water.usgs.gov/

twri9A4/

Brady and Plona—Relations Between Environmental and Water Quality Variables and Escherichia coli in the Cuyahoga River, 2008—Open-File Report 2009–1192

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