Prepared in cooperation with the Kansas Water Office, the City of Lawrence, the City of Olathe, 

the City of Topeka, and Johnson County WaterOne

Water-Quality Conditions with an Emphasis on 

Cyanobacteria and Associated Toxins and Tasteand-Odor Compounds in the Kansas River, Kansas, 

July 2012 through September 2016

Scientific Investigations Report 2018–5089

U.S. Department of the Interior

U.S. Geological Survey
Cover (front). Photographs showing the Kansas River at De Soto (left; by T. Williams, U.S. Geological 

Survey [USGS], May 28, 2016); the Kansas River at De Soto (right, upper; by J. Graham, USGS, May 

30, 2014); and the Kansas River at Wamego (right, lower; by J. Graham, USGS, September 22, 2014).

Cover (back). Photographs showing a USGS hydrologist inspecting the gage house at Kansas 

River at De Soto (upper; by J. Graham, USGS, May 30, 2014); a USGS hydrologist taking a sample 

through the ice at Kansas River at De Soto (middle, by G. Foster, USGS, February 10, 2014); and USGS 

hydrologists returning from sampling on the Kansas River at De Soto (lower, by J. Graham, USGS, 

June 2, 2014).
Water-Quality Conditions with an 

Emphasis on Cyanobacteria and 

Associated Toxins and Taste-andOdor Compounds in the Kansas 

River, Kansas, July 2012 through 

September 2016

By Jennifer L. Graham, Guy M. Foster, Thomas J. Williams, Matthew D. Mahoney, 

Madison R. May, and Keith A. Loftin

Prepared in cooperation with the Kansas Water Office, the City of Lawrence, the 

City of Olathe, the City of Topeka, and Johnson County WaterOne

Scientific Investigations Report 2018–5089

U.S. Department of the Interior

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

RYAN K. ZINKE, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2018

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Graham, J.L., Foster, G.M., Williams, T.J., Mahoney, M.D., May, M.R., and Loftin, K.A., 2018, Water-quality conditions 

with an emphasis on cyanobacteria and associated toxins and taste-and-odor compounds in the Kansas River, Kansas, 

July 2012 through September 2016: U.S. Geological Survey Scientific Investigations Report 2018–5089, 55 p., https://

doi.org/10.3133/sir20185089.

ISSN 2328-031X (print)

ISSN 2328-0328 (online)
iii

Contents

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

Introduction.....................................................................................................................................................2

Purpose and Scope .......................................................................................................................................3

Description of Study Area ............................................................................................................................3

Methods...........................................................................................................................................................3

Continuous Water-Quality Monitoring...............................................................................................5

Discrete Water-Quality Sampling.......................................................................................................6

Data Analysis.........................................................................................................................................8

Streamflow Conditions..................................................................................................................................9

Select Water-Quality Conditions...............................................................................................................14

Water Temperature, pH, and Dissolved Oxygen............................................................................14

Turbidity and Suspended Sediment.................................................................................................14

Dissolved Solids and Major Ions......................................................................................................16

Nutrients...............................................................................................................................................17

Trace Elements....................................................................................................................................18

Indicator and Actinomycetes Bacteria...........................................................................................18

Cyanobacteria, Cyanotoxins, and Taste-and-Odor Compounds ..........................................................18

Algal Biomass and Community Composition..................................................................................19

Cyanotoxins..........................................................................................................................................21

Cyanotoxins in Kansas River Tributaries................................................................................21

Cyanotoxins in the Kansas River Main Stem ........................................................................21

Taste-and-Odor Compounds .............................................................................................................23

Geosmin and 2-Methylisoborneol in Kansas River Tributaries ..........................................23

Geosmin and 2-Methylisoborneol in the Kansas River Main Stem...................................24

Co-Occurrence of Cyanotoxins and Taste-and-Odor Compounds.............................................25

Environmental Factors Associated with Occurrence of Cyanotoxins and Taste-and-Odor

Compounds......................................................................................................................................25

Microcystin..........................................................................................................................................26

Taste-and-Odor Compounds .............................................................................................................26

Logistic Regression Model Evaluation.....................................................................................................29

Cyanobacteria Models.......................................................................................................................30

Microcystin Models............................................................................................................................30

Geosmin Models .................................................................................................................................30

Model Refinement...............................................................................................................................33

Summary........................................................................................................................................................35

References Cited..........................................................................................................................................38

Appendixes 1–6............................................................................................................................................55
iv

Figures

1. Map showing location of reservoirs, U.S. Geological Survey streamgages, and

discrete water-quality sampling sites in the lower Kansas River Basin.............................4

2. Graph showing duration curves for discrete water-quality sample collection with

respect to streamflow at the Kansas River at Wamego, Kansas, and Kansas River

at De Soto, Kansas, streamgages..............................................................................................7

3. Graphs showing duration curves for overall and annual streamflows during

January 2012 through December 2016....................................................................................11

4. Graphs showing contribution of upstream reservoirs and other sources to

streamflow in the Kansas River during January 2012 through December 2016...............12

5. Graphs showing duration curves for continuously measured water-quality

constituents at the Kansas River at Wamego, Kansas, and Kansas River at De Soto,

Kansas, streamgages during July 2012 through September 2016......................................15

6. Graph showing monthly patterns in cyanobacterial abundance at the Kansas River

at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages during

July 2012 through September 2016 ..........................................................................................20

7. Graphs showing occurrence of toxins and taste-and-odor compounds at the

Kansas River at Wamego, Kansas; Kansas River at De Soto, Kansas; Republican

River at Junction City, Kansas; Big Blue River near Manhattan, Kansas; and

Delaware River at Perry, Kansas, streamgages during July 2012 through 

September 2016...........................................................................................................................22

8. Graphs showing co-occurrence of microcystin and taste-and-odor compounds in

samples at the Kansas River at Wamego, Kansas; Kansas River at De Soto, Kansas;

Republican River at Junction City, Kansas; Big Blue River near Manhattan, Kansas;

and Delaware River at Perry, Kansas, streamgages collected during July 2012

through September 2016............................................................................................................25

9. Graphs showing performance of logistic regression models estimating the

probability of cyanobacterial occurrence above thresholds of concern at sites on

the Kansas River during July 2012 through September 2016 ..............................................31

10. Graphs showing performance of logistic regression models estimating the

probability of microcystin occurrence above a threshold of concern at sites on the

Kansas River during July 2012 through September 2016 .....................................................32

11. Graphs showing performance of logistic regression models estimating the

probability of geosmin occurrence above a threshold of concern at sites on the

Kansas River during July 2012 through September 2016 .....................................................34

Tables

1. Streamflow summary statistics for the Kansas River at Wamego, Kansas, and

Kansas River at De Soto, Kansas, streamgages during January 2012 through

December 2016............................................................................................................................10

2. Seasonal and annual means for discretely collected and continuously measured

water-quality constituents at the Kansas River at Wamego, Kansas, and Kansas

River at De Soto, Kansas, streamgages during July 2012 through September 2016.......44 

3. Potential cyanotoxin and taste-and-odor producing cyanobacteria in the Kansas

River during July 2012 through September 2016 ..................................................................20
v

4. Summary statistics for cyanobacterial toxins and taste-and-odor compounds at 

the Kansas River at Wamego, Kansas, and Kansas River at De Soto, Kansas,

streamgages during July 2012 through September 2016 .....................................................23

5. Selected differences in environmental conditions during microcystin, geosmin, 

and 2-methylisoborneol events at the Kansas River at Wamego, Kansas, and 

Kansas River at De Soto, Kansas, streamgages during July 2012 through 

September 2016...........................................................................................................................27

Conversion Factors

International System of Units to U.S. customary units

Multiply By To obtain

Length

micrometer (m) 0.0001 centimeter (cm)

Area

hectare (ha) 0.003861 square mile (mi2

)

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 33.81402 ounce, fluid (fl. oz)

milliliter (mL) 0.0338 ounce, fluid (fl. oz)

cubic meter (m3

) 0.0008107 acre-foot (acre-ft)

Flow rate

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

Mass

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

microgram (μg) 0.00000003527 ounce, avoirdupois (oz)

nanogram (ng) 0.00000000003527 ounce, avoirdupois (oz)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit 

 (°F) as °F = (1.8 × °C) + 32.

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
vi

Supplemental Information

Concentrations of chemical constituents in water are given in either milligrams per liter (mg/L), 

micrograms per liter (μg/L), or nanograms per liter (ng/L).

Phytoplankton abundances are given in cells per milliliter (cells/mL)

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 C).

Abbreviations

ANCOVA analysis of covariance

AVLD absolute value logarithmic difference

CFU colony forming unit

Chl laboratory-measured chlorophyll

E. coli Escherichia coli

EPA U.S. Environmental Protection Agency

fChl sensor-measured chlorophyll fluorescence

FNU formazin nephelometric units

KDHE Kansas Department of Health and Environment

MIB 2-methylisoborneol

NWIS National Water Information System

PDWR primary drinking-water regulations

ppm parts per million

p-value probability value

QA quality assurance

QC quality control

R2 coefficient of determination

Rs Spearman rank-correlation coefficient

RPD relative percentage difference

SDWR secondary drinking-water regulations

SSC suspended-sediment concentration

TN total nitrogen

TP total phosphorus

TPPC threshold probability for positive classification

USGS U.S. Geological Survey
Water-Quality Conditions with an Emphasis 

on Cyanobacteria and Associated Toxins and 

Taste-and-Odor Compounds in the Kansas River, 

Kansas, July 2012 through September 2016

By Jennifer L. Graham, Guy M. Foster, Thomas J. Williams, Matthew D. Mahoney, Madison R. May, and Keith 

A. Loftin

Abstract

Cyanobacteria cause a multitude of water-quality concerns, including the potential to produce toxins and taste-andodor compounds that may cause substantial economic and 

public health concerns, and are of particular interest in lakes, 

reservoirs, and rivers that are used for drinking-water supply. 

Extensive cyanobacterial blooms typically do not develop in 

the Kansas River; however, reservoirs in the lower Kansas 

River Basin occasionally develop blooms that may affect 

downstream water quality. During July 2012 through September 2016, continuous and (or) discrete water-quality data were 

collected at several sites (Wamego, De Soto, and three main 

reservoir-fed tributaries) on the Kansas River to characterize the sources, frequency and magnitude of occurrence, and 

causes of cyanobacteria, cyanobacterial toxins, and taste-andodor compounds and to develop a real-time notification system 

of changing water-quality conditions that may affect drinkingwater treatment. 

Algal biomass, as estimated by chlorophyll, was consistently higher at the downstream De Soto site than the upstream 

Wamego site. Higher algal biomass at the De Soto site likely 

was caused by algal growth during downstream transport 

without major losses due to grazing by aquatic organisms or 

other processes. Algal biomass at the Wamego and De Soto 

sites was negatively correlated with streamflow and total and 

bioavailable nutrient concentrations. The negative association 

between algal biomass and nutrients in the Kansas River likely 

reflects the relatively strong positive association between 

nutrient concentrations and streamflows.

Cyanobacteria were relatively common in the Kansas 

River but rarely dominated the algal community. Like overall algal biomass, cyanobacterial abundances typically were 

higher at the De Soto site than the Wamego site. Cyanobacterial abundances generally peaked in late summer or early 

fall (July through October), with smaller peaks occasionally 

observed in spring (April through May). Cyanobacteria in the 

Kansas River rarely exceeded 20,000 cells per milliliter, the 

abundance at which cyanobacteria may become a concern 

for drinking-water treatment. Relations between cyanobacterial abundance and streamflow, turbidity, and nutrients in the 

Kansas River were similar to those between chlorophyll and 

total phytoplankton abundance, indicating the same processes 

that influence overall algal biomass and dynamics also are 

influencing cyanobacteria.

The cyanotoxin microcystin was detected in about 27 

percent of the samples collected from Kansas River tributary 

and main-stem sites. Cylindrospermopsin was detected in one 

sample from the De Soto site. Microcystin occurrence and 

concentration were similar between the Wamego and De Soto 

sites. Concentrations exceeded the U.S. Environmental Protection Agency health advisory guidance values for finished 

drinking water of 0.3 (for bottle-fed infants and pre-school 

children) and 1.6 micrograms per liter (μg/L; for school-age 

children and adults) in 6 percent or less of samples collected. 

These guidance values are for finished drinking water and are 

not directly applicable to observed environmental concentrations but do provide a benchmark for comparison. Microcystin 

was detected most often and had the highest concentrations 

during summer. Though seasonal patterns in microcystin 

occurrence were generally consistent, seasonal maxima varied 

by an order of magnitude across years.

The taste-and-odor compounds geosmin and 2-methylisoborneol (MIB) were detected in about 78 and 43 percent 

of samples, respectively, collected across all sites (main stem 

and tributaries). Geosmin and MIB occurrence and concentration varied considerably between the Wamego and De Soto 

sites. Geosmin was detected in about 67 percent of Wamego 

samples and 81 percent of De Soto samples. The human detection threshold of 5 nanograms per liter (ng/L) was exceeded 

for geosmin in about 11 and 17 percent of the samples collected at the Wamego and De Soto sites, respectively. Geosmin 
2 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

was detected during all months of the year at both sites, and 

there were no clear seasonal patterns. MIB was detected less 

frequently in the Kansas River than geosmin and was observed 

in about 42 percent of Wamego samples and 33 percent of 

De Soto samples. Concentrations exceeded 5 ng/L in about 7 

and 5 percent of samples from the Wamego and De Soto sites, 

respectively. As observed for geosmin, there were no clear 

seasonal patterns in MIB occurrence or concentration.

There seems to be a connection between microcystin 

detections in the Kansas River and occurrence of microcystin 

in upstream reservoirs (and tributary streams). Microcystin 

concentrations greater than 0.3 μg/L may be likely during the 

summer when streamflow is less than 3,000 cubic feet per second (ft3

/s) and contributions from Milford Lake exceed about 

30 percent of total flow in the Kansas River. Observed microcystin concentrations typically were higher at the De Soto site 

than the Wamego or tributary sites during 2012 through 2016, 

indicating cyanobacteria may continue to grow and produce 

microcystin once introduced to the Kansas River.

The spatial and temporal patterns in geosmin and MIB 

occurrence and concentration were more complex than microcystin. There were no clear connections between geosmin and 

MIB occurrence in the Kansas River and potential upstream 

reservoir (or tributary stream) sources. Likewise, there was 

not a clear relation between algal biomass, cyanobacteria, 

or actinomycetes bacteria and taste-and-odor events in the 

Kansas River. Geosmin and MIB were not strongly correlated 

with any measured environmental variable at either Kansas 

River site. 

Continuous water-quality data may be used independently or in combination with regression models to provide 

information on changing water-quality conditions that may 

affect drinking-water treatment processes or recreational 

activities on the Kansas River. For example, logistic regression model outputs and continuous water-quality data may 

both be indicative of the potential for microcystin events. 

Logistic regression models that are estimating a high probability of microcystin occurrence at concentrations above 0.1 μg/L 

can be used as one indicator. Streamflows less than 3,000 ft3/s 

during upstream reservoir releases during periods with low 

turbidity and increased chlorophyll fluorescence, specific conductance, and pH values may also be indicative of microcystin 

events. Advanced or near-real-time notification may inform 

proactive, rather than reactive, management strategies when 

water-quality conditions are changing rapidly or are likely to 

cause cyanobacteria-related events.

Introduction

Cyanobacteria (also called blue-green algae) cause a 

multitude of water-quality concerns, including the potential 

to produce toxins and taste-and-odor compounds. Toxins and 

taste-and-odor compounds may cause substantial economic 

and public health concerns and are of particular interest in 

lakes, reservoirs, and rivers that are used for drinking-water 

supply (Graham and others, 2016). Cyanobacterial toxins 

(hereafter referred to as “cyanotoxins”) have been implicated 

in human and animal illness and death in at least 43 States 

in the United States, including Kansas (Graham and others, 

2016; Trevino-Garrison and others, 2015). In 2015, the U.S. 

Environmental Protection Agency (EPA) established health 

advisory values for the cyanotoxins microcystin and cylindrospermopsin in finished drinking water. The 10-day health 

advisory values for microcystin in finished drinking water are 

0.3 microgram per liter (μg/L) for young children (less than 

[<] 6 years old) and 1.6 μg/L for all other ages. The 10-day 

health advisory values for cylindrospermopsin are 0.7 μg/L for 

young children and 3.0 μg/L for all other ages (U.S. Environmental Protection Agency, 2015). Unlike cyanotoxins, tasteand-odor compounds have no known effects on human health, 

and there are no regulations or advisory values for these 

compounds. Aesthetic issues are associated with taste-andodor compounds at low concentrations (5 to 10 nanograms per 

liter [ng/L]), and remedial actions commonly are implemented 

as soon as taste or odor is detected in a drinking-water supply 

(Taylor and others, 2005).

The Kansas River and its associated alluvial aquifer are 

primary sources of drinking water for about 800,000 people 

in northeastern Kansas (Graham and others, 2012). In addition to serving as a drinking-water supply, designated uses of 

the Kansas River include recreation, aquatic life support, food 

procurement, groundwater recharge, irrigation, and livestock 

watering (Kansas Department of Health and Environment, 

2011). All of these designated uses potentially may be affected 

by cyanobacteria (Chorus and Bartram, 1999; Hudnell, 2008). 

Extensive cyanobacterial blooms typically do not develop in 

the Kansas River; however, reservoirs in the lower Kansas 

River Basin occasionally develop blooms that may affect 

downstream water quality (Graham and others, 2012).

Water releases from Milford Lake during a toxic cyanobacterial bloom in late August 2011 prompted concerns about 

potential for downstream transport. Water samples were collected weekly by the U.S. Geological Survey (USGS) during 

September and October 2011 to characterize the transport of 

cyanotoxins and taste-and-odor compounds from upstream 

reservoirs to the Kansas River (Graham and Others, 2012). 

Within a week after initial reservoir releases in late August 

2011, the cyanotoxin microcystin and the taste-and-odor 

compounds geosmin and 2-methylisoborneol (MIB) were 

detected throughout a 174-mile reach of the Kansas River 

from Junction City, Kansas (Kans.), to Kansas City, Kans., and 

these compounds remained detectable throughout the reach 

until mid-October. Patterns in microcystin occurrence and concentration at the Kansas River tributary and main-stem sites 

indicated that Milford Lake was the source of microcystin in 

the Kansas River. The source of taste-and-odor compounds 

was not as evident, possibly because multiple tributaries contributed taste-and-odor compounds to the Kansas River. Using 

simple dilution models, measured concentrations of cyanobacteria and associated compounds were substantially higher 
Methods 3

than expected concentrations at some sites and substantially 

lower at others, with unique spatial and temporal patterns for 

individual compounds. Thus, simple dilution models were not 

sufficient to describe the downstream transport of cyanobacteria, cyanotoxins, and taste-and-odor compounds in the Kansas 

River (Graham and others, 2012). The September through 

October 2011 study (Graham and others, 2012) was one of the 

first to quantitatively document the transport of cyanobacteria 

and associated compounds during reservoir releases and the 

improved understanding of cyanotoxin and taste-and-odor 

compound fate and transport downstream from reservoirs in 

Kansas. Since July 2012, the USGS, in cooperation with the 

Kansas Water Office, the City of Lawrence, the City of Olathe, 

the City of Topeka, and Johnson County WaterOne, has collected discrete and continuously measured water-quality data 

at two sites on the Kansas River to better characterize the 

sources, frequency and magnitude of occurrence, and causes 

of cyanobacteria, cyanotoxins, and taste-and-odor compounds 

and to develop a real-time notification system of changing water-quality conditions that may affect drinking-water 

treatment.

Purpose and Scope

The purpose of this report is to (1) describe water-quality 

conditions, with an emphasis on cyanobacteria and associated 

toxins (microcystin) and taste-and-odor compounds (geosmin and MIB), in the Kansas River during July 2012 through 

September 2016; (2) describe the environmental factors 

associated with the occurrence of cyanobacteria and associated toxins and taste-and-odor compounds in the Kansas River 

during July 2012 through September 2016; and (3) evaluate 

previously published logistic regression models that used 

continuous water-quality data to estimate the probability of 

cyanobacteria, microcystin, and geosmin occurrence above 

relevant thresholds in the Kansas River (Foster and Graham, 

2016). Detailed analyses of all regression models published by 

Foster and Graham (2016) and all water-quality data collected 

from the Kansas River during July 2012 through September 

2016 are beyond the scope of this report. Quantification of 

cyanobacteria, cyanotoxins, and taste-and-odor compounds, 

and the conditions under which they are most likely to occur 

in the Kansas River will provide drinking-water suppliers 

and the State of Kansas a better understanding of associated 

water-quality concerns in the river. The logistic regression 

models evaluated in this report may provide useful indicators 

of cyanobacteria, microcystin, and geosmin occurrence in the 

Kansas River. In addition, the methods used in this study could 

be applied to other sites regionally, nationally, and globally. 

This study was cooperatively funded in part by the Kansas 

Water Office through the State Water Plan, the City of Lawrence, the City of Olathe, the City of Topeka, Johnson County 

WaterOne, and the USGS cooperative matching funds through 

the National Water Quality Program.

Description of Study Area

The Kansas River Basin has an area of 60,097 square 

miles (mi2) and includes most of the northern one-half of 

Kansas and parts of Nebraska and Colorado. The Kansas River 

is formed by the confluence of the Smoky Hill and Republican 

Rivers, near Junction City, Kans., and flows about 174 miles 

east into the Missouri River (not shown), at Kansas City, 

Kans. (fig. 1). The area downstream from the Smoky Hill and 

Republican Rivers confluence commonly is called the lower 

Kansas River Basin, which has an area of 5,448 mi2 and forms 

the study area. Streamflow in the study area is regulated by 

four large reservoirs (Milford Lake, Tuttle Creek Lake, Perry 

Lake, and Clinton Lake; fig. 1). All four are bottom-release 

reservoirs constructed in the 1960s and 1970s for flood control 

but also are used for other purposes including recreation and 

drinking-water supply (either directly or through releases 

for downstream use; U.S. Army Corps of Engineers, 2017). 

Although urban development represents a small part of total 

land use in the study area (about 9 percent of land use; Fry 

and others, 2011), major urban and industrial areas are located 

along the Kansas River at Manhattan, Topeka, Lawrence, and 

Kansas City, Kans. (fig. 1). These cities, in addition to many 

smaller communities, withdraw water from the Kansas River 

and associated alluvial aquifer for municipal water supply. More detailed descriptions of the character of the lower 

Kansas River Basin have been published elsewhere (Rasmussen and others, 2005; Rasmussen and Christensen, 2005; and 

Graham and others, 2012).

Two main-stem sites were sampled to describe 

water-quality conditions in the Kansas River during July 

2012 through September 2016 (fig. 1). The Kansas River 

at Wamego, Kans., streamgage (USGS station number 

06887500; hereafter referred to as the “Wamego site”) has a 

drainage area of 55,280 mi2 and is located downstream from 

Milford and Tuttle Creek reservoirs (fig. 1). The Kansas 

River at De Soto, Kans., streamgage (USGS station number 

06892350; hereafter referred to as the “De Soto site”) has 

a drainage area of 59,756 mi2. The De Soto site is located 

about 98 river miles downstream from the Wamego site and 

is downstream from all four large reservoirs (fig. 1). Samples 

also were collected on the tributary Republican, Big Blue, and 

Delaware Rivers between 2.3 and 4.9 miles downstream from 

the dams forming Milford, Tuttle Creek, and Perry Lakes, 

respectively. The Wakarusa River downstream from Clinton 

Lake was not sampled because it did not contribute substantively to streamflow in the Kansas River during the study 

period.

Methods

Continuous real-time and discrete water-quality data 

have been collected at the Wamego and De Soto sites since 

July 2012. Additionally, event-based discrete water-quality 
4 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Leavenworth

Kansas City

Lenexa

Olathe

Overland Park

Shawnee

Lawrence

Topeka

Manhattan

Big Blue

Wamego

Delaware

De Soto Republican Republican

R

Delaware

W

R

olf R

mi T eb Cr r

Stranger

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Cr

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Wakarusa R

Missouri R

West Fancy Cr

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Cr

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Soldier Cr

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Little Soldier Cr

Cr

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Little Blue R

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Cr noyL Cr

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Blue

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KANSAS

COLORADO

NEBRASKA

Kansas River

Basin

Studyarea

Base from U.S. Geological Survey digital data, 1994, 1:2,000,000Albers Equal-area Conic projectionStandard parallels 29°30’ and 45°30’, central meridian 96°

95° 95°30’ 96° 96°30’ 97° 97°30’

40°

39°30’

39°

EXPLANATION

Boundary of lower 

Kansas River Basin in Kansas

U.S. Geological Survey 

streamgage, continuousand discrete water-quality sample site and identifier

U.S. Geological Survey

streamgage, discrete water-quality sample site and identifier

De Soto

Big Blue

0 10 20 30 MILES0 10 20 30 KILOMETERS

KANSAS

MISSOURI

Figure 1. Location of reservoirs, U.S. Geological Survey streamgages, and discrete water-quality sampling sites in the lower Kansas River Basin.
Methods 5

samples have been collected at three reservoir outflow sites 

that are tributaries to the Kansas River: Republican River at 

Junction City, Kans., streamgage (downstream from Milford 

Lake; USGS station number 06857100), Big Blue River near 

Manhattan, Kans., streamgage (downstream from Tuttle Creek 

Lake; USGS station number 06887000), and Delaware River 

at Perry, Kans., streamgage (downstream from Perry Lake; 

USGS station number 06890900). Continuous and discrete 

water-quality data collected by the USGS at these sites during 

July 2012 through September 2016 were used to characterize 

water-quality conditions in the lower Kansas River Basin and 

to evaluate previously published (Foster and Graham, 2016) 

logistic regression models developed to estimate the probability of cyanobacteria, microcystin, and geosmin occurrence 

above relevant thresholds at the Wamego and De Soto sites. 

Because of the emphasis on cyanobacteria and associated 

toxins and taste-and-odor compounds, other regression models 

published by Foster and Graham (2016) are not evaluated in 

this report.

Continuous Water-Quality Monitoring

Continuous (15-minute intervals) streamflow and waterquality data were collected from the Wamego and De Soto 

sites. Streamgages have been operating at the Wamego and 

De Soto sites since January 1919 and July 1917, respectively 

(U.S. Geological Survey, 2018). Streamflow at both sites was 

measured using standard USGS methods (Sauer and Turnipseed, 2010; Turnipseed and Sauer, 2010). Streamflow data 

are available through the USGS National Water Information 

System (NWIS) database (U.S. Geological Survey, 2018).

Continuous water-quality data were collected at the 

Wamego and De Soto sites during July 1999 through September 2004 (Rasmussen and others, 2005). Continuous waterquality monitors were reinstalled at the Wamego and De Soto 

sites in August and July 2012, respectively. Monitors were 

installed near the centroid of the stream cross-section to best 

represent conditions across the width of the stream and were 

maintained in accordance with standard USGS procedures 

(Wagner and others, 2006; Bennett and others, 2014). All 

continuous water-quality data are available through the NWIS 

database (U.S. Geological Survey, 2018).

During July 2012 through June 2014, sites were equipped 

with YSI 6600 V2 water-quality monitors to measure water 

temperature, pH, dissolved oxygen (YSI 6150 optical dissolved oxygen sensor), turbidity (YSI 6136 sensor), specific 

conductance, and chlorophyll fluorescence (fChl; YSI model 

6025 sensor). In June 2014, Xylem YSI EXO water-quality 

monitors were installed and measured the same parameters as 

the YSI 6600 V2. All data are considered comparable during 

the period of record despite changes in the water-quality monitors during the study, with the exception of fChl.

Relative percentage difference (RPD) was used to estimate differences in fChl sensor readings between sensor types. 

RPD was calculated using the following equation:

RPD A B A B = −  +



 



 



 



 100

2

/

,

(1)

where 

A and B are concentrations in each replicate pair (Zar, 

1999).

Based on data collected from both sites, the median RPD 

between fChl (reported as micrograms per liter) measured by 

the YSI 6025 and EXO sensors was 37 percent (n=26), and the 

median difference in values was 11.5 μg/L. In general, fChl 

values measured by the EXO sensors were higher than those 

measured by the YSI 6025 (median ratio of EXO:YSI 6025 

values=1.4). Though there was a linear association between 

YSI 6025 and EXO measured fChl (coefficient of determination [R2

]=0.98, n=26), available data were not considered sufficient to develop a relation to convert values between the two 

sensors. Therefore, sensor-measured fChl data were corrected 

to laboratory-measured chlorophyll (Chl) samples for the YSI 

6025 and EXO sensors at the Wamego and De Soto sites (see 

appendixes 1 through 4). Corrected sensor-based fChl data are 

used to describe among-site and seasonal patterns in chlorophyll concentrations.

There are documented differences in the YSI 6136 and 

EXO turbidity sensors (Yellow Springs Instruments, 2012). 

Based on data collected from both sites, the median difference in turbidity values measured by the YSI 6136 and EXO 

sensors was 2.5 formazin nephelometric units (FNU) (n=29; 

range=0.26 to 17.1; mean=4.1), and the median RPD was 

11 percent (n=29; range=1.3 to 83 percent; mean=15 percent) (appendix figs. 5.1 to 5.3). The relations between Hach 

2100AN turbidity values and turbidity values measured by the 

YSI 6136 and EXO sensors also were evaluated to determine differences between sensors. Analysis of covariance 

(ANCOVA) was used to determine if the relation between 

Hach 2100AN turbidity values and turbidity values measured 

by the YSI 6136 and EXO sensors were different (appendix 

fig. 5.4). The ANCOVA test is used to determine if the slopes 

and intercepts of two or more regression lines are statistically significant (Helsel and Hirsch, 2002). The F-value, also 

called the sample variance ratio, is calculated as a nested 

F-statistic comparing the variance between regression models. 

Significance for these analyses was set at a probability value 

(p-value) of <0.05. The slopes of the two relations were not 

statistically different (YSI 6136 slope=0.82; EXO slope=0.76; 

p-value=0.38); however, though the difference between intercepts was small (YSI 6136=6.52; EXO=8.14) it was statistically significant (p-value=0.04). Given the documented differences between the two sensors (Yellow Springs Instruments, 

2012), this difference is expected. The median difference in 

values between turbidity measured by the HACH 2100AN 

and the YSI 6136 and EXO sensors were 2.6 and 5.5 FNU, 

respectively (YSI 6136: n=55, range=0.02 to 202, mean=12.6; 

EXO: n=85, range=0.10 to 164, mean=20). At turbidities <200 

FNU, the difference between most measured turbidity values 

was <20 FNU, regardless of sensor type (appendix fig. 5.5). 
6 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

About 90 percent of the turbidity data collected at the Wamego 

(n=135,068) and De Soto (n=138,287) sites were <200 FNU 

during July 2012 through September 2016. The median RPDs 

between turbidity measured by the HACH 2100AN and the 

YSI 6136 and EXO sensors were 21 and 15 percent, respectively (YSI 6136: n=55, range=1.6 to 200 percent, mean=32 

percent; EXO: n=85, range=0.24 to 200 percent, mean=20 percent) (appendix fig. 5.6). For the purposes of this report, turbidity data from the two sensors were considered comparable 

because differences between the YSI 6136 and EXO turbidity 

sensors were small at turbidities <200 FNU and the relations 

between each sensor and the HACH 2100AN were similar. 

However, future analyses focused specifically on spatial and 

temporal patterns in turbidity and suspended sediment may 

want to consider the potential for differences between the two 

sensors, particularly at turbidities greater than (>) 200 FNU.

Sensor maxima were not exceeded for any of the physicochemical properties measured except for the YSI 6136 

turbidity sensor (operable range 0–1,000 FNU) during runoff 

events in July 2013, April 2014, and June 2014 at the Wamego 

site (maximum turbidity=1,180 FNU). At the De Soto site, the 

same sensor model also exceeded sensor maxima during runoff events in April–May 2013, August 2013, and April 2014 

(maximum turbidity=1,330 FNU). During July 2012 through 

September 2016, approximately 90 percent of the continuous 

data at the Wamego and De Soto sites were rated as excellent 

(requiring corrections of less than plus or minus [±] 5 percent), 

6 percent were rated as good (requiring corrections of <±10 

percent), 2 percent were rated as fair (requiring corrections 

of <±15 percent), and 2 percent were rated as poor (requiring corrections of >±15 percent) according to the established 

guidelines (Wagner and others, 2006).

Time-series measurements occasionally were missing 

or deleted from the dataset during the data quality-assurance/

quality-control (QA/QC) process because of equipment 

malfunction, excessive fouling caused by environmental 

conditions, or temporary removal of the sensors due to icy 

conditions in the river. For the Wamego site, during July 2012 

through September 2016, approximately 6 percent of the 

water temperature and dissolved oxygen records, 8 percent of 

the specific conductance record, 7 percent of the pH record, 

16 percent of the turbidity record, and 13 percent of the fChl 

record were missing or deleted. For the De Soto site, during 

the same time period, approximately 6 percent of the water 

temperature record, 12 percent of the specific conductance 

record, 5 percent of the pH record, 8 percent of the dissolved 

oxygen record, 19 percent of the turbidity record, and 17 percent of the fChl record were missing or deleted. Missing and 

deleted data at both sites were primarily due to sensor removal 

during ice cover and (or) sensor malfunction. Missing waterquality data cannot be estimated and data gaps were not filled. 

Therefore, duration curves developed using these data are 

based solely on sensor-measured values.

Discrete Water-Quality Sampling

During July 2012 through September 2016, discrete 

water-quality samples at the Wamego and De Soto sites were 

collected on a biweekly basis during May through October 

and a monthly basis during November through April. Using 

this long-term, fixed-schedule sampling approach, discrete 

water-quality data were collected over a range of streamflow 

conditions at the Wamego and De Soto sites during July 2012 

through September 2016 (fig. 2). Discrete water-quality samples were collected following USGS equal-width-increment 

methods (U.S. Geological Survey, 2006), unless precluded 

by ice or extreme cold conditions. During ice or extreme cold 

conditions, weighted basket or grab samples were collected 

from the centroid of flow or at the safest possible nearshore 

location (U.S. Geological Survey, 2006). Samples for bacterial analyses were always collected at the centroid of flow 

using a weighted basket or grab approach. All water-quality 

samples were analyzed for suspended-sediment concentration 

(SSC), dissolved solids and major ions, nutrients (nitrogen and 

phosphorus species), trace elements, indicator and actinomycetes bacteria, algal biomass, phytoplankton abundance and 

community composition, the cyanotoxin microcystin, and the 

taste-and-odor compounds geosmin and MIB. The cyanotoxin cylindrospermopsin also was analyzed during July 2015 

through September 2016.

Event-based discrete water-quality samples also were 

collected during July 2012 through September 2016 at the 

Wamego and De Soto sites and the three reservoir outflow 

sites from Milford Lake (Republican River), Tuttle Creek 

Lake (Big Blue River), and Perry Lake (Delaware River). 

At least four and as many as six event-based samples were 

collected per year at each site during scheduled increases in 

reservoir release, cyanobacterial blooms in the reservoirs, or 

taste-and-odor or microcystin detections in routine samples 

collected from the Kansas River at Wamego and De Soto sites. 

Event-based samples were collected using depth-integrated 

sampling techniques at the centroid of flow, except during 

icy or extreme cold conditions when weighted basket or grab 

samples were collected from the centroid of flow or at the 

safest possible nearshore location (U.S. Geological Survey, 

2006). These samples were analyzed for the cyanotoxin microcystin and the taste-and-odor compounds geosmin and MIB. 

The cyanotoxin cylindrospermopsin was analyzed during July 

2015 through September 2016. All discrete water-quality data 

(except phytoplankton abundance and community composition), are available through NWIS (U.S. Geological Survey, 

2018) and as a USGS data release in Williams and others 

(2018). Phytoplankton community composition and abundance data are available as a USGS data release in Kramer and 

others (2018).

Suspended sediment was analyzed as described in Guy 

(1969) at the USGS Iowa Sediment Laboratory, Iowa City, 

Iowa. Dissolved solids, major ions, nutrients, and trace 

elements were analyzed by the USGS National Water Quality Laboratory, Lakewood, Colorado. Analytical methods 
Methods 7

Kansas River streamflow July 2012–September 2016

Frequency of exceedance, in percent

100

1,000

10,000

100,000

Kansas River at Wamego, Kansas

Kansas River at De Soto, Kansas

Kansas River at Wamego discrete samples

Kansas River at De Soto discrete samples

0 10 20 30 40 50 60 70 80 90 100

Streamflow, in cubic feet per second

EXPLANATION

Figure 2. Duration curves for discrete water-quality sample collection with respect to streamflow at the Kansas River at Wamego, 

Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, respectively).

for these constituents are described by Fishman and Friedman (1989). Escherichia coli (E. coli), fecal coliform, and 

enterococci indicator bacteria were analyzed using membrane 

filtration methods described by Myers and others (2014) at 

the USGS Kansas Water Science Center, Lawrence, Kans. 

Actinomycetes bacteria were analyzed using the standard plate 

counts method (Rice and others, 2012) at the USGS Ohio 

Water Microbiology Laboratory, Columbus, Ohio.

Chlorophyll (uncorrected for degradation products) was 

analyzed fluorometrically at the USGS Kansas Water Science 

Center, Lawrence, Kans., using EPA Method 445.0 (Arar and 

Collins, 1997) modified for heated ethanol extraction (Sartory and Grobbelaar, 1984) and a fluorometer equipped with a 

flow-through cell (Knowlton, 1984). Quality-control procedures using this modified method for chlorophyll analysis are 

described by Foster and others (2017). Phytoplankton samples 

were preserved with a 9:1 Lugol’s iodine:acetic acid solution 

and analyzed for taxonomic identification and enumeration 

by BSA Environmental Service, Inc., Beachwood, Ohio, as 

described by Graham and others (2017). The cyanotoxins 

microcystin and cylindrospermopsin were analyzed by the 

USGS Organic Geochemistry Research Laboratory, Lawrence, 

Kans. These samples were lysed sequentially by three freezethaw cycles. Following the freeze-thaw cycle, samples were 

filtered using 0.7-micrometer glass-fiber syringe filters (Loftin 

and others, 2008) before analysis. Abraxis® enzyme-linked 

immunosorbent assays were used to measure microcystin and 

cylindrospermopsin (-adda specific; Fischer and others, 2001). 

The taste-and-odor compounds geosmin and MIB were analyzed using solid phase microextraction gas chromatography/

mass spectrometry (Zimmerman and others, 2002) by Engineering Performance Solutions, LLC, Jacksonville, Florida.

Cyanotoxins and taste-and-odor compounds may exist in 

particulate (intracellular) and dissolved (extracellular) forms 

(Graham and others, 2008). Total concentrations (includes 

both particulate and dissolved forms) of microcystin, cylindrospermopsin, geosmin, and MIB were measured in all samples. 

Dissolved concentrations of microcystin and cylindrospermopsin were analyzed when total concentrations were >0.1 μg/L. 

Similarly, dissolved concentrations of geosmin and MIB were 

analyzed when total concentrations were >5 ng/L.

QA/QC samples were collected to evaluate variability 

in sample collection and processing techniques (Bennett and 

others, 2014; Mueller and others, 2015). Concurrent replicate 

samples were collected to estimate variability caused by sample collection and processing methodology. RPD was used to 

estimate differences in analyte concentrations between concurrent replicate pairs and could not be calculated if one or both 

of the replicate water-quality samples had a censored value 

reported (less than the laboratory reporting level). Generally, 

median RPDs for all constituents met data QA/QC objectives 

(RPDs<20 percent). Three constituents had median RPDs >20 

percent: dissolved ammonia (median=25.2 percent; n=5), fecal 

coliform (median=28.6 percent; n=13), and dissolved iron 
8 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

(median=33.5 percent; n=16). RPDs >20 percent generally 

were due to low concentrations near the laboratory reporting 

level. Data for all analytes met the QA/QC objectives for this 

report.

Absolute value logarithmic difference (AVLD) was used 

to estimate differences in phytoplankton and cyanobacterial 

abundance, in cells per milliliter, between concurrent replicate 

pairs (Graham and others, 2017). AVLD was used because 

RPD is sensitive to rare taxa found in one of the samples 

and not the other. AVLD was calculated using the following 

equation:

AVLD l = − og10A log10B (2)

where 

A and B are abundance (cells per milliliter) in each 

replicate pair (Francy and others, 2015).

Replicate pairs with AVLDs<1 differed by less than an 

order of magnitude; replicate pairs with AVLDs >1 varied by 

an order of magnitude or more.

The AVLDs for phytoplankton at the Wamego and De 

Soto sites ranged from 0 to 0.26 (median=0.12; n=15). The 

AVLDs for cyanobacterial abundance ranged from 0 to 3.1 

(median=0.82; n=15). Fifty-three percent of the replicate pairs 

of cyanobacterial abundance had AVLDs of <1. Replicate 

pairs of cyanobacterial abundance with AVLDs >1 occurred 

when cyanobacteria were rare and accounted for <7 percent of 

the total phytoplankton abundance. Variability among replicate 

pairs of cyanobacterial abundance was less when cyanobacteria accounted for a larger portion of the total phytoplankton 

abundance. Phytoplankton and cyanobacteria data met QA/

QC objectives when the influence of rare taxa was taken into 

consideration.

Data Analysis

Reservoir contributions to Kansas River streamflow were 

estimated using the USGS streamgage network in the lower 

Kansas River Basin. The percentages of flow at the Wamego 

and De Soto sites contributed by reservoir outflows from Milford Lake, Tuttle Creek Lake, Perry Lake, and Clinton Lake 

were calculated as described in Graham and others (2012). 

The estimated contribution from each reservoir was calculated 

for each day during January 2012 through December 2016. 

Dynamic streamflow conditions complicate calculations of 

the percentage of flow contributed by reservoir outflows and 

estimated contributions are most accurate when streamflow 

conditions are stable. Streamflows were only stable for 393 

days during January 2012 through December 2016. Although 

streamflow conditions were not stable on most dates, estimated reservoir contributions to streamflow were calculated 

for the entire study period to characterize relative patterns 

across seasons, years, and streamflow conditions. Reservoir 

contributions to streamflow in this analysis should be considered general estimates.

Ordinary least-squares analysis (Helsel and Hirsch, 2002) 

was used to develop regression models between sensormeasured fChl and laboratory-measured Chl concentrations. 

Because the relation between fChl and Chl is sensor and site 

dependent, separate models were developed for the YSI 6025 

and EXO fChl sensors at the Wamego and De Soto sites. All 

sensors and sites had strong linear associations between fChl 

and Chl, and fChl explained between 74 and 88 percent of the 

variance in Chl, as indicated by the adjusted R2 (appendixes 1 

through 4). Kansas River chlorophyll concentrations at the 

Wamego and De Soto sites during July 2012 through September 2016 were estimated by using the fChl data collected 

by continuous monitors and the regression models developed 

using fChl and laboratory-measured Chl concentrations. 

Details of the regression models used to estimate chlorophyll 

concentrations are presented in appendixes 1 through 4. 

Regression-estimated chlorophyll concentrations were used 

to describe spatial and temporal patterns in the Kansas River 

during the study period.

Water-quality conditions in the Kansas River were 

described by site and season using discretely collected and 

continuously measured water-quality data. Seasons were 

defined as winter (January–March), spring (April–June), summer (July–September), and fall (October–December). Nondetections, or censored values reported as less than the laboratory reporting limit, were substituted with a value one-half of 

the minimum reporting limit for all analyses. Small sample 

sizes (<50 observations) prevented the use of the commonly 

accepted maximum likelihood estimation approach when 

calculating means of constituents that contained censored 

values during a given season of a given year (n=2–8 in most 

cases). Additionally, the maximum likelihood estimation 

approach does not return estimations for individual censored 

values that could then be used to describe data on a seasonal 

or annual basis, but instead returns an estimation of the mean 

value using an assumed distribution based on the censored and 

noncensored data (Helsel, 2005).

Nonparametric Spearman rank-correlation analysis 

(Helsel and Hirsch, 2002) was used to determine monotonic 

relations between streamflow, water-quality conditions, and 

algal indicators (chlorophyll, algal abundance, cyanotoxins, 

and taste-and-odor compounds). Spearman rank-correlation 

coefficients (rho values; Rs) were considered significant when 

p-values were <0.01. Mann-Whitney rank sum tests (Helsel and Hirsch, 2002) were used to determine differences in 

environmental conditions when microcystin, geosmin, or MIB 

occurred above concentrations of 0.3 μg/L, 5 ng/L, or 2 ng/L, 

respectively. These concentrations were selected based on 

values relevant to drinking-water treatment and were exceeded 

frequently enough to allow the development of statistically 

valid models (Helsel and Hirsch, 2002; Taylor and others, 

2005; U.S. Environmental Protection Agency, 2015). MannWhitney rank sum test statistics were considered significant 

when p-values were <0.05.

Previously published models were used to estimate 

the probability of cyanobacteria, microcystin, and geosmin 
Streamflow Conditions 9

occurrence above relevant thresholds on the basis of continuous water-quality data at the Wamego and De Soto sites (Foster and Graham, 2016). The models developed by Foster and 

Graham (2016) were considered suitable for estimating the 

probability of occurrence if they accurately classified at least 

65 percent of the sample data, including the highest measured 

concentrations for a given constituent (Foster and Graham, 

2016). After the best models were selected, the threshold 

probability for positive classification (TPPC) for each individual model was adjusted to maximize the number of samples 

classified as positive to make the model more conservative 

(more likely to give a false positive than a false negative) 

by guarding more strongly against false negatives (Foster 

and Graham, 2016). Models were developed using discrete 

water-quality and continuous-sensor data collected during July 

2012 through June 2015 (Foster and Graham, 2016) and then 

evaluated using data collected during July 2015 through September 2016. Model performance was evaluated by comparing 

continuously estimated probability of occurrence to measured 

concentrations and placing data into one of four categories: 

positive response predicted as positive (true positive; model 

sensitivity), reference response predicted as reference (true 

negative; model specificity), positive response predicted as 

reference (false negative), and reference response predicted as 

positive (false positive). Model performance was considered 

good if at least 65 percent of the sample data were accurately 

classified, including the highest measured concentrations for a 

given constituent.

Streamflow Conditions

The structure and function of riverine ecosystems are 

largely affected by streamflow (Poff and others, 1997; Poff 

and Zimmerman, 2010; Archfield and others, 2014). Reservoirs in the Kansas River Basin control streamflow in about 

85 percent of the drainage area and are operated for flood 

control and to maintain streamflows during low-flow conditions (Perry, 1994). Typically, reservoirs change downstream 

streamflow regimes by reducing the magnitude of peak flows 

and increasing the magnitude of low flows (Williams and Wolman, 1984). Reservoirs also affect downstream water quality 

by acting as sinks and sources for nutrients, sediments, and 

other compounds (Thornton and others, 1990).

Mean streamflow at the upstream Wamego site was 

about 34 percent lower than streamflow at the downstream De 

Soto site across all years and seasons during the study period. 

During 2012 through 2016, mean streamflows at both sites 

were highest during spring, and lowest during winter (table 1). 

Kansas was generally in a drought status during 2012 through 

2014 (The National Drought Mitigation Center, 2018), and 

streamflow data reflected these conditions. Mean annual 

streamflows during 2012 through 2014 at the Wamego and 

De Soto sites were 55 to 69 percent lower than mean annual 

streamflows during 2015 and 2016 (table 1). Summer 2012 

through winter 2013 had the lowest mean seasonal streamflows 

during the study period. Flows during 2015 and 2016 had a 

marked increase compared to previous years and included the 

largest flows observed during the study period.

During 2012 and 2013, streamflows at both sites in the 

Kansas River were below the study period average (figs. 3A, B). 

Streamflows during 2014 also were below average, except at a 

probability of exceedance of 70 percent and higher. At <50 percent probability of exceedance, 2015 and 2016 had higher 

streamflows than the study period average, likely due to storm 

events delivering episodic flows, rather than extended reservoir 

releases. In both analyses (summary statistics and duration 

curves), streamflows during 2012 through 2014 follow patterns 

expected during a period of drought, and patterns in 2015 and 

2016 are indicative of nondrought streamflows.

Reservoirs contributed more than one-half of daily streamflow 49 percent or more of the time annually at the Wamego 

site during 2012 through 2016 (annual average=71 percent) 

(fig. 4A). At the De Soto site, reservoirs contributed more than 

one-half of daily streamflow between 36 and 62 percent of 

the time annually during 2012 through 2016 (annual average=45 percent) (fig. 4B). The Wamego site typically had a 

greater percentage of flow from upstream reservoirs than the 

De Soto site, despite De Soto having more contributing reservoirs (figs. 4A, B).

Seasonally, fall and winter had the greatest number of days 

where reservoirs contributed more than one-half of the total 

flow at the Wamego and De Soto sites, and spring and summer 

had the least number of days (figs. 4A, B). Seasonal reservoir 

contribution to total streamflow follows precipitation patterns 

typically experienced in the study area, with wet springs and 

early summers, and dry late summers into winters. During the 

fall season, reservoir elevations are sometimes lowered for the 

creation of wetland habitats for migratory birds and to reduce 

potential ice impacts on dams, which results in increased 

reservoir outflows. The percentage of days with more than 

50 percent reservoir contributions to total streamflow at the 

Wamego and De Soto sites seasonally was 86 and 43 percent, 

respectively, during winter; 67 and 33 percent during spring; 58 

and 40 percent during summer; and 75 and 65 percent during 

fall.

The highest annual streamflow contributions from 

reservoirs in the Kansas River were observed in 2012, when 

reservoirs contributed more than 50 percent to total streamflow 

87 percent and 62 percent of the time at the Wamego and De 

Soto sites, respectively. The lowest annual reservoir contributions were observed in 2016, when 49 percent and 36 percent 

of the time reservoirs contributed more than 50 percent of total 

streamflow at the Wamego and De Soto sites, respectively. 

In 2016, Tuttle Creek Lake contributed more than one-half 

of the total streamflow at least 27 percent of the time at the 

Wamego site and 5 percent of the time at the De Soto site. No 

other reservoir annually contributed more than one-half of total 

streamflow at either site more than 3 percent of the time (for 

example, Milford Lake at the Wamego site during 2012 and 

2015) (figs. 4A, B).
10 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 1. Streamflow summary statistics for the Kansas River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages

(U.S. Geological Survey stations 06887500 and 06892350, respectively) during January 2012 through December 2016.

[min, minimum; max, maximum]

Period Summary 

statistic 2012 2013 2014 2015 2016 2012–16

Wamego

Entire year Min 195 456 701 646 1,086 195

Max 12,247 24,430 24,643 31,987 35,142 35,142

Mean 2,008 2,359 2,192 5,468 5,297 3,463

Winter Min 1,466 481 779 749 1,086 481

Max 4,165 1,189 3,930 3,178 9,009 9,009

Mean 2,464 678 1,699 1,391 3,039 1,861

Spring Min 1,076 456 819 944 1,086 456

Max 12,247 12,759 24,643 31,987 35,142 35,142

Mean 3,403 3,174 3,176 11,410 10,774 6,307

Summer Min 851 901 701 1,137 1,898 701

Max 3,092 24,430 10,204 30,197 13,967 31,749

Mean 1,481 3,831 2,223 5,838 4,270 3,603

Fall Min 195 839 730 646 1,487 195

Max 1,143 4,443 4,735 20,742 7,853 20,742

Mean 703 1,737 1,668 3,230 3,118 2,084

De Soto

Entire year Min 526 545 819 769 1,270 526

Max 12,988 24,816 38,593 90,874 103,973 103,973

Mean 2,689 2,951 3,198 8,613 8,640 5,219

Winter Min 1,578 545 853 769 1,303 545

Max 12,988 2,992 7,528 4,300 15,309 15,309

Mean 3,907 829 2,119 1,947 4,263 2,623

Spring Min 1,135 640 1,157 1,235 1,270 640

Max 12,705 19,787 38,593 90,874 103,973 103,973

Mean 4,320 4,791 5,057 19,328 18,505 10,295

Summer Min 926 1,022 1,052 1,504 2,570 926

Max 3,596 24,816 8,877 50,367 54,865 54,865

Mean 1,727 4,407 2,851 8,548 7,270 5,063

Fall Min 526 753 819 879 2,057 526

Max 2,919 5,272 11,193 21,080 15,255 21,080

Mean 836 1,759 2,768 4,630 4,582 2,905
Streamflow Conditions 11

100

1,000

10,000

100,000

1,000,000

B. Kansas River at De Soto, Kansas

2012

2013

2014

2015

2016

2012–16 average

EXPLANATION

Streamflow, in cubic feet per second

100

1,000

10,000

100,000

0 10 20 30 40 50 60 70 80 90 100

Frequency of exceedance, in percent

A. Kansas River at Wamego, Kansas

Figure 3. Duration curves for overall and annual streamflows during January 2012 through December 2016. A, Kansas River at the 

Kansas River at Wamego, Kansas (U.S. Geological Survey station 06887500). B, Kansas River at De Soto, Kansas (U.S. Geological Survey 

station 06892350).
12 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

0

102030405060708090

100

t necr ep ni , noit ubirt noc wolf maert S

Milford Lake Tuttle Creek Lake Other sources

EXPLANATION

01/01/2012

04/01/2012

07/01/2012

10/01/2012

01/01/2013

04/01/2013

07/01/2013

10/01/2013

01/01/2014

04/01/2014

07/01/2014

10/01/2014

01/01/2015

04/01/2015

07/01/2015

10/01/2015

01/01/2016

04/01/2016

07/01/2016

10/01/2016

A. Kansas River at Wamego, Kansas

Estimated contribution

DATE

Figure 4. Contribution of upstream reservoirs and other sources to streamflow in the Kansas River during January 2012 through December 2016. A, Kansas River at the Kansas River at Wamego, Kansas (U.S. Geological Survey station 06887500). 

B, Kansas River at De Soto, Kansas (U.S. Geological Survey station 06892350).
Streamflow Conditions 13

tnecrepni,noitubirtnocwolfmaertS

102030405060708090

100

0 01/01/2012 04/01/2012 07/01/2012 10/01/2012 01/01/2013 04/01/2013 07/01/2013 10/01/2013 01/01/2014 04/01/2014 07/01/2014 10/01/2014 01/01/2015 04/01/2015 07/01/201510/01/2015 01/01/2016 04/01/2016 07/01/2016 10/01/2016

Milford Lake Tuttle Creek Lake Perry Lake Clinton Lake Other sources

EXPLANATION

Estimated contribution

DATE

B. Kansas River at De Soto, Kansas

Figure 4. Contribution of upstream reservoirs and other sources to streamflow in the Kansas River during January 2012 through December 2016. A, Kansas River at the Kansas River at Wamego, Kansas (U.S. Geological Survey station 06887500). B, Kansas River at De Soto, Kansas (U.S. Geological Survey station 06892350)—Continued.
14 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Select Water-Quality Conditions

The USGS has collected continuous (15-minute intervals) 

and discrete water-quality data at two sites (Wamego and De 

Soto, fig. 1) on the Kansas River since July 2012. Continuous 

water-quality data collected at the upstream Wamego site during August 2012 through September 2016 and the downstream 

De Soto site during July 2012 through September 2016 were 

used to describe water-quality conditions in the Kansas River. 

Continuous water-quality data included water temperature, 

pH, dissolved oxygen, turbidity, specific conductance, and 

fChl. Discrete water-quality samples were collected at both 

sites during July 2012 through September 2016. Samples were 

collected approximately bimonthly during May through October and monthly during November through April. Discrete 

samples were analyzed for SSC, dissolved solids and major 

ions, nutrients (nitrogen and phosphorus species), trace elements, and indicator and actinomycetes bacteria.

Water Temperature, pH, and Dissolved Oxygen

Water temperature affects the solubility of chemicals in 

water and biological activity. Water temperatures in the Kansas River ranged from −0.8 to 34 degrees Celsius (°C). Overall 

differences in water temperature between the Wamego and De 

Soto sites were relatively small (about 2 percent on average; 

table 2 at the back of this report; fig. 5A). Summer 2012 average water temperatures seem to be 2 to 4 °C lower than other 

summers, possibly because only a partial season of data was 

collected during the first year of the study. Water temperatures 

were warmest in summer during low streamflows and coldest 

during winter. Spring, summer, and fall seasonal mean water 

temperatures were generally similar across years and typically 

varied by about 2 °C or less. Mean winter water temperature 

in 2016 was notably warmer than other years, with mean water 

temperatures about 3 to 4 °C higher than observed in 2014 

(table 2).

pH is a measure of the effective hydrogen ion concentration and is often used to evaluate chemical and biological 

reactions in water (Hem, 1992). Kansas aquatic life support 

criteria require that pH in streams not measure less than 6.5 or 

more than 8.5 standard units (Kansas Department of Health 

and Environment, 2015). Measured pH was never lower 

than 6.5 at the Wamego and De Soto sites but exceeded the 

maximum criterion of 8.5 about 33 percent of the time at the 

Wamego site and 39 percent of the time at the De Soto site 

(fig. 5B). Exceedances were observed across all seasons and 

years but occurred more often during low-flow conditions in 

2012 through 2014. At the Wamego site, 76 percent of pH values higher than 8.5 were observed during 2012 through 2014, 

and at the De Soto site, 64 percent were observed during 2012 

through 2014. Exceedances often extended for periods of days 

or weeks and likely were caused by increased algal photosynthesis during low-flow conditions when biological processes 

may have a substantial influence on water chemistry (Wetzel, 

2001). Patterns in exceedance of the maximum pH criterion 

during 2012 through 2016 were similar to those observed in 

the Kansas River during 2000 through 2003 (Rasmussen and 

others, 2005).

Dissolved oxygen is an important factor for the survival 

of aquatic organisms, and concentrations in surface water are 

related primarily to photosynthesis, respiration, atmospheric 

reaeration, and water temperature (Wilde, 2008). Kansas 

aquatic life support criteria require that dissolved oxygen concentrations are not <5.0 milligrams per liter (mg/L) (Kansas 

Department of Health and Environment, 2015). Dissolved 

oxygen concentrations were lowest in summer, concurrent 

with seasonal lows in streamflow and highs in water temperature, and highest in winter during seasonal lows in water 

temperature (table 2, fig. 5C). Less than 1 percent of dissolved 

oxygen values during the study period were <5.0 mg/L (0.22 

and 0.03 percent at the Wamego and De Soto sites, respectively). At the Wamego site, low dissolved oxygen concentrations were observed over a 5-day period during a summer 

2013 runoff event and at night over a 4-day period during 

low-flow conditions (<1,000 cubic feet per second [ft3/s]) in 

summer 2014. At the De Soto site, low dissolved oxygen concentrations were observed for a 3-hour period during a spring 

2013 runoff event and once overnight in summer 2014 during 

low-flow conditions (about 1,100 ft3/s).

Turbidity and Suspended Sediment

Suspended sediments in streams typically are from erosion and subsequent transport of land-surface soils and channel banks. Increased suspended sediment in streams decreases 

light penetration and photosynthesis, smothers benthic 

habitats, and interferes with feeding activities (Wetzel, 2001). 

In addition, suspended particulates promote sorption of nutrients, organic compounds, and other potential contaminants. 

Turbidity often is used as a surrogate measure for suspended 

sediment, and in the Kansas River there is a strong positive 

association between turbidity and SSC (Rasmussen and others, 

2005; Foster and Graham, 2016).

Although turbidities tended to be higher at the De Soto 

site than the Wamego site, overall differences between the 

sites were small and occurred at the lower and upper ends 

of the observed range (table 2, fig. 5D). On average, turbidity was about 10 percent higher at the De Soto site than the 

Wamego site. The EPA guidelines for turbidity (based on 

reference conditions) list 19.5 FNU for level III ecoregion 

28 (Flint Hills) streams, which includes the Kansas River at 

Wamego, Kans. streamgage (U.S. Environmental Protection 

Agency, 2001). The EPA guidelines for turbidity (based on 

reference conditions) list 15.5 FNU for level III ecoregion 40 

(central irregular plains) streams, which includes the Kansas 

River at De Soto, Kans., streamgage (U.S. Environmental 

Protection Agency, 2000). Guidelines are nonenforceable 

criteria developed for the protection of water quality, aquatic 

life, and human health. Turbidities exceeded 19.5 FNU about 
Select Water-Quality Conditions 15

A. Water temperature

Water temperature, in degrees Celsius

-10

0

10

20

30

40

B. pH

pH, in standard units

7

7.5

8

8.5

9

9.5

10

Maximum criterion for aquatic life support

C. Dissolved oxygen

Dissolved oxygen, in milligrams per liter

2

4

6

8

10

12

14

16

18

20

22

Aquatic life support criterion

D. Turbidity

Turbidity, in formazin nephelometric units

10

100

1,000

10,000

U.S. Environmental Protection Agency

level III ecoregion 28 (Flint Hills) turbidity 

guideline for the Kansas River at De Soto

U.S. Environmental Protection Agency 

level III ecoregion 40 (central irregular 

plains) turbidity guideline for the 

Kansas River at Wamego 

E. Specific conductance

Specific conductance, 

in microsiemens per centimeter at 25 degrees Celsius 

10

100

1,000

10,000

F. Chlorophyll fluorescence

Regression-estimated chlorophyll, 

in micrograms per liter

1

10

100

1,000

Kansas River at Wamego, Kansas

Kansas River at De Soto, Kansas

EXPLANATION

Frequency of exceedance, in percent

0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100

Figure 5. Duration curves for continuously measured water-quality constituents at the Kansas River at Wamego, Kansas, and Kansas 

River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, respectively) during July 2012 through 

September 2016. A, water temperature; B, pH; C, dissolved oxygen; D, turbidity; E, specific conductance; and F, chlorophyll fluorescence.
16 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

63 percent of the time at the Wamego site and 70 percent of 

the time at De Soto site. The 15.5 FNU criterion was exceeded 

about 72 and 80 percent of the time at the Wamego and De 

Soto sites, respectively (fig. 5D).

At both sites, seasonal mean turbidity values were lowest 

in winter and highest in spring and summer (table 2). Winter 

mean turbidity was 83 to 89 percent lower than spring and 

summer mean turbidity values. Seasonal mean turbidities at 

both sites generally increased throughout the study period 

(table 2). For example, spring mean turbidities in 2015 and 

2016 were 17 to 133 percent higher than mean spring turbidities in 2013 and 2014. Transport of suspended sediments 

generally increases with increased streamflows. The observed 

seasonal and interannual patterns in turbidity values were 

associated with seasonal and annual changes in streamflows. 

Seasonal minima in streamflow and turbidity occur during 

winter, and streamflows and turbidities increased between 

2012 and 2016 (tables 1, 2).

Patterns in SSC based on discrete samples collected 

during 2012 through 2016 match patterns in turbidity. On 

average, SSCs were about 15 percent higher at the De Soto 

site (331 mg/L) than the Wamego site (288 mg/L) (table 2). 

Seasonal mean SSCs were highest in spring and lowest in 

winter. Spring mean SSCs were about 57 to 579 percent higher 

than any other season. Patterns in seasonal mean SSCs were 

not as evident as observed for turbidity, but spring mean SSCs 

in 2016 were 165 to 341 percent higher than mean spring 

SSCs in 2013 (table 2).

Dissolved Solids and Major Ions

Specific conductance is a measure of water’s ability to 

conduct an electrical current and is related to the concentration 

of ionized materials in water (Hem, 1992). Major constituents 

of dissolved solids generally are calcium, magnesium, sodium, 

potassium, bicarbonate, carbonate, sulfate, and chloride ions 

(Hem, 1992). Because specific conductance is a measure of 

ionized materials in water, there is a strong positive association between specific conductance, dissolved solids, and major 

ions in the Kansas River (Rasmussen and others, 2005; Foster 

and Graham, 2016). Specific conductance, dissolved solids, 

and major ions in surface water are influenced by watershed 

geology and soils and are typically higher during low streamflows. In addition, road salt may substantially increase specific 

conductance and associated ions, particularly chloride, in 

streams during winter months (Corsi and others, 2010). Precipitation and runoff events often decrease specific conductance and concentrations of dissolved solids and major ions in 

surface waters.

Specific conductance was consistently higher at the 

Wamego site than the De Soto site, but overall differences 

between sites were relatively small (table 2, fig. 5E). On 

average, specific conductance was about 10 percent higher at 

the Wamego site than the De Soto site. At both sites, seasonal 

mean specific conductance values were 12 to 50 percent 

higher during winter than any other season, likely because of 

the combined influence of seasonal lows in streamflow and 

road salt applications. Mean annual specific conductance values at both sites decreased each year between 2012 and 2016 

(table 2). The decrease across years likely can be attributed to 

the increase in streamflows between 2012 and 2016 (table 1).

Spatial and temporal patterns in dissolved solids and 

major ion concentrations from discrete samples matched 

patterns in continuous specific conductance. On average, 

constituent concentrations were about 6 to 25 percent higher 

at the Wamego site than De Soto site (table 2). Differences 

in calcium, magnesium, and bicarbonate were lowest (6 to 

7 percent difference) between the two sites and differences 

in sodium and chloride were highest (20 to 25 percent difference). With the exception of potassium, seasonal mean values 

of all measured constituents were 5 to 105 percent higher 

during winter than any other season. Potassium concentrations 

varied by <2 mg/L (1 to 26 percent difference) across seasons 

(table 2). Sodium and chloride had the highest differences in 

seasonal mean concentrations. As observed for specific conductance, mean annual concentrations of dissolved solids and 

major ions at both sites generally decreased between 2012 and 

2016 (table 2).

The EPA has established nonenforceable secondary 

drinking-water regulations (SDWR) for dissolved solids 

(500 mg/L), sulfate (250 mg/L), and chloride (250 mg/L, with 

an advisory level of 20 mg/L for people on low sodium diets; 

U.S. Environmental Protection Agency, 2009). These regulations and the advisory level are for finished drinking water 

and are not directly applicable to observed environmental 

concentrations but do provide a benchmark for comparison. 

Discrete sample data were compared to the regulations and 

advisory level. Dissolved solids concentrations exceeded 

500 mg/L in 46 and 34 percent of discrete samples collected at the Wamego and De Soto sites, respectively, during 

2012 through 2016 (Williams and others, 2018). In addition, 

continuous estimates of dissolved solids, sulfate, chloride, 

and sodium were calculated from regression models that used 

specific conductance as an explanatory variable (Foster and 

Graham, 2016). Continuous estimates for all constituents with 

regression models developed by Foster and Graham (2016) 

are available on the USGS National Real-Time Water Quality website (https://nrtwq.usgs.gov/). Based on continuous 

estimates, dissolved solids concentrations during 2012 through 

2016 exceeded 500 mg/L about 52 percent of the time at the 

Wamego site and 36 percent of the time at the De Soto site. 

Exceedances for dissolved solids were observed across all 

seasons and years but were observed most frequently during fall and winter. Sulfate concentrations based on discrete 

samples and continuous estimates never exceeded 250 mg/L 

at either site during 2012 through 2016 (Williams and others, 

2018) (table 2). Sodium concentrations exceeded 20 mg/L in 

most discrete samples collected at the Wamego (96 percent) 

and De Soto (87 percent) sites during 2012 through 2016 

(Williams and others, 2018) (table 2). Based on continuous 

estimates, sodium concentrations almost always exceeded 
Select Water-Quality Conditions 17

20 mg/L at both sites (96 and 94 percent at the Wamego and 

De Soto sites, respectively) (Williams and others, 2018).

Chloride has an established SDWR as well as criteria 

for protection of aquatic life (U.S. Environmental Protection 

Agency, 1986, 2009). The EPA SDWR is 250 mg/L, the acute 

exposure criterion is 860 mg/L, and the chronic exposure 

criterion is 230 mg/L. Based on discrete samples, chloride 

concentrations never exceeded 230 mg/L at either site during 

2012 through 2016. Continuous estimates of chloride concentrations indicated that concentrations never exceeded the acute 

exposure criterion at either site, but the SDWR and chronic 

exposure criterion were exceeded at the Wamego site, though 

only rarely (<1 percent of the time). Most exceedances at the 

Wamego site occurred during low flows (<2,300 ft3/s) in the 

spring.

Nutrients

Nutrients, particularly nitrogen and phosphorus, are considered leading causes of water-quality impairment in Kansas 

and throughout the Nation (Kansas Department of Health and 

Environment, 2004; U.S. Environmental Protection Agency, 

2009). Nutrients are essential for the growth of all organisms; 

however, excessive concentrations in aquatic environments 

may cause adverse human health and ecological effects. 

Excess nutrients are associated with eutrophication and can 

result in algal blooms, decreased dissolved oxygen, taste-andodor issues, increased turbidity, and depletion of flora and 

fauna (Wetzel, 2001).

In 2000, the EPA recommended ecoregion-based nutrient criteria for streams. Reference conditions for total nitrogen (TN) and total phosphorus (TP) in level III ecoregion 

28 (Flint Hills) streams, which includes the Kansas River at 

Wamego, Kans., streamgage, are defined as 0.58 and 0.06 

mg/L, respectively (U.S. Environmental Protection Agency, 

2001). Reference conditions for TN and TP in level III ecoregion 40 (central irregular plains) streams, which includes the 

Kansas River at De Soto, Kans., streamgage, are defined as 

0.855 and 0.0925 mg/L, respectively (U.S. Environmental 

Protection Agency, 2001). These criteria were intended as a 

preliminary attempt to describe the nutrient concentrations 

that would protect designated uses and mitigate the effects of 

nutrient enrichment and are not used for regulatory purposes. 

The Kansas Department of Health and Environment (KDHE) 

uses a median TP concentration of 0.201 mg/L to determine if 

a stream site should be on the Clean Water Act Section 303(d) 

list of impaired waters for phosphorus (Kansas Department 

of Health and Environment, 2004). All TN and TP sample 

concentrations at the Wamego and De Soto sites exceeded 

ecoregion criteria for reference conditions. During a 2000 

through 2003 study, Rasmussen and others (2005) also determined that all TN and TP sample concentrations exceeded 

ecoregion criteria in the Kansas River. TP sample concentrations at both sites almost always exceeded the KDHE value 

for 303(d) listing (table 2). About 95 percent of TP samples 

collected at the Wamego (n=79) and De Soto (n=89) sites had 

concentrations higher than 0.201 mg/L (Williams and others, 

2018). TP concentrations <0.201 mg/L were observed during 

low streamflows (<800 and 1,400 ft3/s at the Wamego and De 

Soto sites, respectively) and low turbidities (<23 and 14 at the 

Wamego and De Soto sites, respectively) in December through 

April.

Inorganic nitrogen compounds, such as nitrate and 

ammonia, may be toxic to aquatic organisms at high concentrations. In addition, high nitrate concentrations in drinking 

water can impair the oxygen-carrying capacity of hemoglobin 

in humans (Camago and Álonso, 2006).

The EPA has established enforceable primary drinkingwater regulations (PDWR) for nitrate (10 mg/L) and nitrite 

(1 mg/L) (U.S. Environmental Protection Agency, 2009). 

These regulations are for finished drinking water and are not 

directly applicable to observed environmental concentrations 

but do provide a benchmark for comparison. Nitrate and nitrite 

concentrations in discrete samples never exceeded 3.0 and 

0.24 mg/L, respectively, at the Wamego and De Soto sites 

(Williams and others, 2018).

The EPA has established acute and chronic ammonia 

criteria for the protection of aquatic life (U.S. Environmental 

Protection Agency, 2013). The toxicity of ammonia is dependent on pH and water temperature; therefore, criteria vary 

with conditions of these water-quality parameters. At a pH of 

7.0 and a water temperature of 20 °C, the acute criterion for 

total ammonia nitrogen is 17 mg/L and the chronic criterion is 

1.9 mg/L. Ammonia was above the laboratory reporting level 

(0.01 mg/L) in 42 percent of samples collected at each site. 

Concentrations never exceeded 0.25 mg/L in samples at either 

site on the Kansas River during 2012 through 2016 (Williams 

and others, 2018).

Overall differences in TN and TP concentrations between 

the Wamego and De Soto sites were small (table 2). Mean TN 

and TP concentrations were 4 and 7 percent higher at the De 

Soto site than the Wamego site, respectively. Seasonal mean 

nutrient concentrations were highest in spring and lowest 

during fall and winter. Spring mean TN and TP concentrations 

were 3 to 114 percent higher than any other season. Mean 

annual total nutrient concentrations at both sites generally 

increased each year between 2012 and 2016 (table 2). Transport of nutrients increased with increased streamflows, and 

TN and TP concentrations in the Kansas River were positively 

correlated with streamflow (all Rs>0.67, all p<0.01). The 

observed seasonal and interannual patterns in total nutrient concentrations were associated with seasonal and annual 

changes in streamflows. Seasonal maxima in streamflow occur 

during spring, and streamflow increased between 2012 and 

2016 (tables 1, 2).

Inorganic nutrient concentrations were positively correlated with streamflow, though correlations were not as strong 

as for total nutrients. Nitrate plus nitrite was more strongly 

correlated with streamflow (all Rs>0.58, all p<0.01) than 

orthophosphorus (all Rs<0.43, all p<0.01). On average, nitrate 

plus nitrite and orthophosphorus concentrations were about 
18 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

36 to 41 percent higher at the Wamego site than the De Soto 

site. Seasonal mean nitrate plus nitrite concentrations at both 

sites were highest in spring (table 2). In contrast, orthophosphorus concentrations were 36 to 41 percent lower in spring 

than other seasons at the De Soto site and about 20 percent 

lower in spring and winter than other seasons at the Wamego 

site. As observed for total nutrients, mean annual inorganic 

nutrient concentrations at both sites generally increased each 

year between 2012 and 2016 (table 2).

Trace Elements

Trace elements are typically present in low concentrations in stream water and are influenced by watershed geology 

(Hem, 1992). Of the trace elements measured as part of this 

study, three (arsenic, fluoride, and selenium) have enforceable PDWR. These regulations are for finished drinking water 

and are not directly applicable to observed environmental 

concentrations but do provide a benchmark for comparison. 

The PDWR for arsenic, fluoride, and selenium are 0.010, 4.0, 

and 0.05 mg/L, respectively (U.S. Environmental Protection 

Agency, 2009). Sampled arsenic (maximum 0.007 mg/L), fluoride (maximum 0.38 mg/L), and selenium (maximum 0.002 

mg/L) concentrations never exceeded the regulatory criteria in 

the Kansas River during 2012 through 2016.

Indicator and Actinomycetes Bacteria

Fecal coliform, E. coli, and enterococci are the three most 

common types of bacteria used as indicators of pathogens 

in surface water. Indicator bacteria are used to evaluate the 

sanitary quality of water and its use as a public water supply 

and for recreational activities (Eaton and others, 2005). KDHE 

uses seasonal criteria for E. coli bacteria to protect public 

health during primary (swimming) and secondary (wading, 

boating, and fishing) contact recreation (Kansas Department 

of Health and Environment, 2015). Because the Kansas River 

is publicly accessible, it supports both types of recreation. 

Criteria for primary contact recreation are defined as geometric means for two seasons: April through October (spring/summer) and November through March (fall/winter). The criterion 

for primary contact recreation is a geometric mean of 262 colony forming units per 100 mL (CFUs/100 mL) during spring/

summer. About 20 percent of samples collected at the Wamego 

and De Soto sites during July 2012 through September 2016 

exceeded 262 CFUs/100 mL. The criterion for primary contact 

recreation during fall/winter and secondary contact recreation 

is a geometric mean of 2,358 CFUs/100 mL. About 2 and 6 

percent of samples collected at the Wamego and De Soto sites 

exceeded 2,358 CFUs/mL, respectively. With the exception 

of sample exceedances (>20,000 CFUs/100 mL) at both sites 

during one event in December 2015, all exceedances occurred 

during spring/summer. Exceedances typically were associated 

with rainfall and runoff events.

Mean concentrations of indicator bacteria in the Kansas 

River were about 55 to 159 percent higher at the De Soto site 

than the Wamego site during 2012 through 2016 (table 2). Seasonal mean concentrations of E. coli and enterococci bacteria 

were substantially higher in spring than any other season (18 

to 12,372 percent overall). Fecal coliform bacteria concentrations had similar variability during spring through fall, but 

were typically an order of magnitude or two lower in winter 

than in any other season (table 2). Mean annual indicator bacteria concentrations at both sites generally increased each year 

between 2012 and 2016 (table 2).

Bacteria in the actinomycetes group may produce the 

taste-and-odor compounds geosmin and MIB (Taylor and others, 2005). The actinomycetes bacteria typically are terrestrial 

organisms associated with soils and are washed into aquatic 

ecosystems during rainfall and runoff events (Zaitlin and others, 2003; Zaitlin and Watson, 2006). The highest observed 

actinomycetes concentration at the Wamego site (21,000 colonies per milliliter) was about 130 percent higher than the next 

highest concentration observed at the Wamego site (9,000 colonies per milliliter) and 50 percent higher than the highest 

concentration observed at the De Soto site (14,000 colonies 

per milliliter) (Williams and others, 2018) (table 2). The one 

high value at the Wamego site had a substantial influence 

on mean site, seasonal, and annual concentrations and was 

excluded from calculations of descriptive summary statistics. 

When the unusually high value was excluded from the dataset, 

patterns in actinomycetes bacteria were similar to indicator 

bacteria. Mean actinomycetes concentration was about 42 percent higher at the De Soto site than Wamego site (table 2). 

Seasonal mean actinomycetes concentrations were 55 to 

87 percent lower during winter than any other season. Seasonal mean actinomycetes concentrations were highest during 

spring at the Wamego and De Soto sites, though this pattern 

was inconsistent across years. Mean annual actinomycetes 

concentrations varied across years and did not display clear 

patterns (table 2). Transport of actinomycetes bacteria typically increases with increased streamflows, and concentrations 

in the Kansas river were positively correlated with streamflow 

(all Rs>0.58, all p<0.01). Other factors, such as time since last 

rainfall and runoff event, soil temperatures, and temporal variability of actinomycetes communities in soils, likely also influence transport of actinomycetes bacteria in the Kansas River.

Cyanobacteria, Cyanotoxins, and 

Taste-and-Odor Compounds

In addition to commonly measured water-quality constituents, discrete water-quality samples collected at both sites 

during July 2012 through September 2016 were analyzed 

for cyanobacteria and associated compounds. Algal biomass, 

phytoplankton abundance and community composition, 

the cyanotoxins microcystin and cylindrospermopsin (July 

2015 through September 2016 only), and the taste-and-odor 
Cyanobacteria, Cyanotoxins, and Taste-and-Odor Compounds 19

compounds geosmin and MIB were analyzed in all routinely 

collected samples.

Algal Biomass and Community Composition

Chlorophyll is commonly used as an estimate of algal 

biomass because analysis is simpler and less time consuming 

than identifying, counting, and measuring algal cells (Hambrook Berkman and Canova, 2007). The sensor-measured 

fChl data at the Wamego and De Soto sites were corrected 

to laboratory-measured chlorophyll samples (appendixes 1 

through 4) and used to describe spatial and temporal patterns 

in algal biomass in the Kansas River during July 2012 through 

September 2016. Sensor-measured chlorophyll concentrations 

were consistently higher at the De Soto site than the Wamego 

site during the study period (fig. 5F). Mean sensor-measured 

chlorophyll concentration was 74 percent higher at the De 

Soto site than the Wamego site (table 2). Seasonal mean 

sensor-measured chlorophyll concentrations were highest in 

spring and summer (the growing season) and lowest during 

winter. Winter sensor-measured chlorophyll concentrations 

were 26 to 72 percent lower than any other season. Mean 

annual sensor-measured chlorophyll concentrations varied less 

across years (6 to 24 percent during years with data collection 

across all seasons) than seasons, likely reflecting the influence 

of temperature on algal growth (Reynolds, 1984).

Dodds and others (1998) proposed a trophic classification 

system for rivers based on chlorophyll concentrations. Chlorophyll concentrations <10 μg/L are indicative of oligotrophic 

(nutrient poor, low productivity) systems; concentrations 

between 10 and 30 μg/L are indicative of mesotrophic (moderate nutrient levels, intermediate productivity) systems; and 

concentrations >30 μg/L are indicative of eutrophic (nutrient 

rich, high productivity) systems. Sensor-measured chlorophyll 

concentrations in the Kansas River were indicative of mesotrophic to eutrophic conditions (fig. 5F, table 2). Sensor-measured chlorophyll concentrations exceeded 10 μg/L 97 percent 

of the time at the Wamego site and 100 percent of the time at 

the De Soto site. The 30 μg/L threshold was exceeded 45 percent of the time at the Wamego site and 68 percent of the time 

at the De Soto site.

Typically, algal biomass in aquatic ecosystems is highest 

during low streamflows when light and nutrients are abundant, though relations may be more complex in rivers because 

streamflow may far exceed algal growth rates and preclude 

accumulation of biomass (Søballe and Kimmel, 1987; Wetzel, 

2001; Allan and Castillo, 2007). Based on discretely collected 

data, chlorophyll concentrations at the Wamego and De Soto 

sites were negatively correlated with streamflow (all Rs

<−0.44, 

all p<0.01) and total and bioavailable (orthophorphorus and 

nitrate plus nitrite) nutrient concentrations (all Rs

<−0.36, all 

p<0.01). Chlorophyll concentrations also were negatively, but 

weakly, correlated with turbidity (an indicator of underwater light conditions) at the De Soto site (Rs

=−0.30, p<0.01), 

but there was no significant correlation at the Wamego site 

(Rs

=−0.17, p=0.14). The negative association between chlorophyll and nutrients in the Kansas River likely is caused by 

the relatively strong positive association between nutrient 

concentrations and streamflows. Algal biomass at the De Soto 

site was always higher than at the Wamego site, despite the 

higher streamflows and lower bioavailable nutrient concentrations observed at the De Soto site. Higher algal biomass 

at the De Soto site likely was caused by algal growth during 

downstream transport without major losses due to grazing by 

aquatic organisms or other processes. Although nutrients are 

of importance for algal growth, downstream transport often 

makes the influence of nutrients and other processes on algal 

biomass difficult to discern (Allan and Castillo, 2007).

Total phytoplankton abundance in the Kansas River was 

strongly, and positively, correlated with chlorophyll concentrations (all Rs

>0.85, all p<0.01). Spatial and temporal patterns 

in total phytoplankton abundance generally matched patterns 

in chlorophyll. Abundances were consistently higher at the 

De Soto site than the Wamego site and seasonal mean abundances were highest during summer and lowest in winter 

(table 2). Like chlorophyll, total phytoplankton abundances at 

the Wamego and De Soto sites were negatively, and relatively 

weakly, correlated with streamflow (all Rs

< −0.39, all p<0.01) 

and nutrients (all Rs

<−0.27, all p<0.01). Total phytoplankton 

abundance was negatively correlated with turbidity at the De 

Soto site (Rs

=−0.24, p=0.03), but the relation between total 

abundance and turbidity was not statistically significant at the 

Wamego site.

Reservoirs can substantially impact the phytoplankton 

community composition in rivers, and cyanobacteria and 

diatoms tend to persist farther downstream than other algal 

groups, perhaps due to differential trapping and settling 

(Reynolds, 1984; Allan and Castillo, 2007; Wehr and Sheath, 

2003; Graham and others, 2012). Generally, diatoms dominate 

riverine phytoplankton communities, though cyanobacteria 

can also commonly be present (Allan and Castillo, 2007; Wehr 

and Sheath, 2003). Algal communities in the Kansas River 

typically were dominated (>50 percent of total phytoplankton 

abundance) by diatoms (about 81 percent of samples overall, 

n=165). In this study, cyanobacteria were of particular interest 

because of their potential for production of cyanotoxins and 

taste-and-odor compounds. Cyanobacteria were relatively 

common in the Kansas River, present in about 66 and 69 percent of samples collected at the Wamego (n=82) and De Soto 

(n=83) sites, respectively, during July 2012 through September 

2016; however, cyanobacteria rarely dominated the algal community (4 and 7 percent of samples collected at the Wamego 

and De Soto sites, respectively).

Fourteen cyanobacterial genera that have the potential 

to produce cyanotoxins and taste-and-odor compounds were 

observed in the Kansas River during July 2012 through September 2016 (Graham and others, 2008; Meriluoto and others, 

2017) (table 3). Most of these genera were rare, occurring 

in <20 percent of samples; however, Aphanizomenon, Dolichospermum (formerly Anabaena), and Raphidiopsis were 

present in 30, 27, and 21 percent of samples collected from the 
20 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 3. Potential cyanotoxin and taste-and-odor producing cyanobacteria in the Kansas River during July 2012 through 

September 2016.

[MIB, 2-methylisoborneol; X, present; --, not applicable]

Cyanobacterial genera Cyanotoxins Taste and odors

Microcystins Cylindrospermopsins Geosmin MIB

Anabaenopsis X -- -- --

Aphanizomenon -- X X --

Aphanocapsa X -- -- --

Cylindrospermopsis -- X -- --

Dolichospermum (formerly Anabaena) X X X --

Limnothrix X -- X X

Merismopedia X -- -- --

Microcystis X -- -- --

Oscillatoria (Planktothrix) X X X X

Phormidium X -- X X

Planktolyngbya -- -- X X

Pseudanabaena X -- X X

Raphidiopsis -- X -- --

Wamego site, respectively. At the De Soto site, Aphanizomenon, Dolichospermum, and Microcystis were present in 26, 

23, and 23 percent of samples, respectively. Though potential 

cyanotoxin and taste-and-odor producers were present, genetic 

analyses are required to definitively determine which genera 

produce these compounds in the Kansas River (Graham and 

others, 2008; Otten and others, 2015; Otten and others, 2016; 

Graham and others, 2017).

Like chlorophyll and total phytoplankton abundance, 

cyanobacterial abundances typically were higher at the De 

Soto site than the Wamego site (table 2, fig. 6). On average, 

cyanobacterial abundance was 282 percent higher at the De 

Soto site than the Wamego site. Cyanobacterial abundances 

generally peaked in late summer or early fall (July through 

October), with smaller peaks occasionally observed in spring 

(April through May) (fig. 6). Cyanobacteria may be a concern 

for drinking-water treatment at abundances of 20,000 cells per 

milliliter (cells/mL) or higher (Taylor and other, 2005). Cyanobacterial abundance exceeded 20,000 cells/mL in about 7 and 

16 percent of the samples collected from the Wamego and De 

Soto sites, respectively, during July 2012 through September 

2016. Exceedances typically occurred during summer months, 

though occasional exceedances were observed during spring 

and fall. Cyanobacterial dominance of the phytoplankton 

community typically occurred during summer or early fall. 

The most extended period of cyanobacterial dominance during 

the study period was observed during 2012, when cyanobacteria dominated the phytoplankton community for most of the 

summer.

Cyanobacterial abundance

Jan.

Feb.

Mar.

Apr.

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.

Monthly mean cyanobacterial abundance, 

in cells per milliliter

0

100

1,000

10,000

100,000

Drinking-water treatment concern of 

20,000 cells per milliliter 

Month

Kansas River at Wamego, Kansas

Kansas River at De Soto, Kansas

EXPLANATION

Figure 6. Monthly patterns in cyanobacterial abundance at the 

Kansas River at Wamego, Kansas, and Kansas River at De Soto, 

Kansas, streamgages (U.S. Geological Survey stations 06887500 

and 06892350, respectively) during July 2012 through September 

2016.
Cyanobacteria, Cyanotoxins, and Taste-and-Odor Compounds 21

Relations between cyanobacterial abundance and streamflow, turbidity, and nutrients in the Kansas River were similar 

to those for chlorophyll and total phytoplankton abundance, 

indicating the same processes that influence overall algal 

biomass and dynamics also are influencing cyanobacteria. 

Cyanobacterial abundances at the Wamego and De Soto 

sites were negatively, and relatively weakly, correlated with 

streamflow (all Rs

<−0.23, all p<0.05). With the exception of 

orthophosphorus, there were negative, but relatively weak, 

relations between nutrients and cyanobacterial abundance (all 

Rs

<−0.23, all p<0.04). The relation between orthophosphorus 

and cyanobacterial abundance was not statistically significant 

at the Wamego or De Soto sites. Cyanobacterial abundance 

was negatively correlated with turbidity at the De Soto site 

(Rs

=−0.24, p=0.03), but the relation between cyanobacterial 

abundance and turbidity was not statistically significant at the 

Wamego site.

Cyanotoxins

There are three main groups of cyanotoxins: hepatotoxins (affect the liver), neurotoxins (affect the central nervous 

system), and dermatoxins (affect the skin and mucous membranes) (Chorus and Bartram, 1999). The hepatotoxin microcystin was the only cyanotoxin detected in the Kansas River 

during 2011 (Graham and others, 2012); therefore, this study 

focused on microcystin. Cylindrospermopsin analysis was 

added in July 2015 after the EPA published guidance values 

for cylindrospermopsin in finished drinking water (U.S. Environmental Protection Agency, 2015). Microcystin is the most 

commonly detected cyanotoxin worldwide and occurs in lakes 

and reservoirs throughout the United States (Loftin and others, 

2016). Overall, microcystin was detected in about 27 percent 

(n=257) of the samples collected across all sites (main stem 

and tributaries). Total microcystin concentrations ranged from 

<0.1 to 2.41 μg/L (median=<0.1 μg/L) at the main-stem and 

tributary sites (fig. 7A). Cylindrospermopsin was detected in 

one sample across all sites (main-stem and tributaries), with 

a concentration of 0.05 μg/L at the De Soto site (laboratory 

reporting level: 0.05 μg/L) during July 2015 through September 2016.

Cyanotoxins in Kansas River Tributaries

During July 2012 through September 2016, microcystin 

was detected most often and concentrations were highest in 

the Republican River downstream from Milford Lake (fig. 1). 

Microcystin was detected in about 64 percent of the samples 

(n=28) collected from the Republican River, with concentrations ranging from <0.1 to 2.1 μg/L (median=0.12 μg/L). The 

EPA health advisory guidance values for finished drinking 

water of 0.3 and 1.6 μg/L (U.S. Environmental Protection 

Agency, 2015) were exceeded during the study period in 

14 percent and 4 percent of the Republican River samples, 

respectively. These guidance values are for finished drinking 

water and are not directly applicable to observed environmental concentrations but do provide a benchmark for comparison. 

The highest microcystin concentrations in the Republican 

River were observed in August 2012 (1.25 μg/L) and July 

2014 (2.1 μg/L). Microcystin concentrations in the Republican 

River during July 2012 through September 2016 were lower 

than observed during September through October 2011, when 

microcystin concentrations ranged from <0.1 to 7.4 μg/L 

(median=0.26 μg/L) and exceeded 0.3 and 1.6 μg/L in about 

43 and 21 percent of the samples, respectively (Graham and 

others, 2012).

Microcystin was detected less frequently in the Big 

Blue River (downstream from Tuttle Creek Lake) and the 

Delaware River (downstream from Perry Lake). Microcystin was detected in about 10 percent of the samples (n=21) 

collected from the Big Blue River (range=<0.1 to 0.22 μg/L; 

median=<0.1 μg/L). Microcystin was detected in about 44 percent of the samples (n=25) collected from the Delaware River 

(range=<0.1 to 0.71 μg/L; median=<0.1 μg/L). Concentrations 

exceeded 0.3 μg/L in 12 percent of Delaware River samples. 

The highest microcystin concentrations in the Delaware River 

were observed in August 2012 (0.63 μg/L), September 2014 

(0.4 μg/L), and October 2015 (0.71 μg/L). Maximum microcystin concentrations observed in the Big Blue and Delaware 

Rivers during July 2012 through September 2015 were about 2 

times higher than those observed in 2011 (Graham and others, 

2012).

Cyanotoxins in the Kansas River Main Stem

Microcystin occurrence and concentration were similar 

between the Wamego and De Soto sites during July 2012 

through September 2016. Microcystin was detected in about 

20 and 23 percent of the samples collected from the Wamego 

(n=90) and De Soto (n=93) sites, respectively (table 4). Microcystin concentrations ranged from <0.1 to 1.7 μg/L at the 

Wamego site and <0.1 to 2.41 μg/L at the De Soto site (both 

site medians <0.1 μg/L, table 4). At the Wamego site, microcystin concentration exceeded the EPA health advisory guidance values for finished drinking water of 0.3 and 1.6 μg/L in 

about 6 and 1 percent of the samples, respectively. Similarly, 

at the De Soto site, microcystin concentrations exceeded 

0.3 and 1.6 μg/L in about 5 and 1 percent of the samples, 

respectively. The EPA health advisory guidance values are 

for finished drinking water and are not directly applicable 

to observed environmental concentrations but do provide a 

benchmark for comparison.

Seasonal patterns in microcystin occurrence were consistent between sites and among years. Microcystin was detected 

most often and had the highest concentrations during summer 

(fig. 7A). Overall, microcystin was detected in 39 percent 

of summer samples (n=75). Microcystin was typically first 

detected (greater than or equal to [≥] 0.1 μg/L) in June or July, 

increased to the annual maxima during July through September, and then decreased. This seasonal pattern is similar to the 

overall pattern for cyanobacterial abundance (fig. 6). Though 
22 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Kansas River at Wamego, Kansas

Kansas River at De Soto, Kansas

EXPLANATION

Republican River at Junction City, Kansas

Big Blue River near Manhattan, Kansas

Delaware River at Perry, Kansas 

0.1

1

10

A. Microcystin

Total microcystin, in micrograms per liter

Analytical detection threshold

Human detection threshold

Analytical detection threshold

Human detection threshold

0.1

Analytical detection threshold

07/12 10/12 01/13 04/13 07/13 

10/13 01/14 04/14 07/14 10/14 01/15 

04/15 

07/15 10/15 01/16 04/16 07/16 10/16 

1

10

100

Month/year

Total MIB, in nanograms per liter

0.1

1

10

100

1,000

Total geosmin, in nanograms per liter

B. Geosmin

C. 2-methylisoborneol (MIB)

Figure 7. Occurrence of toxins and taste-and-odor compounds at the Kansas River at Wamego, Kansas; Kansas River at De Soto, 

Kansas; Republican River at Junction City, Kansas; Big Blue River near Manhattan, Kansas; and Delaware River at Perry, Kansas, 

streamgages (U.S. Geological Survey stations 06887500, 06892350, 06857100, 06887000, and 06890900, respectively) during July 2012 

through September 2016. A, microcystin. B, geosmin. C, 2-methylisoborneol (MIB).
Cyanobacteria, Cyanotoxins, and Taste-and-Odor Compounds 23

Table 4. Summary statistics for cyanobacterial toxins and taste-and-odor compounds at the Kansas River at Wamego, Kansas, and 

Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, respectively) during July 2012 

through September 2016.

[MIB, 2-methylisoborneol; n, number of samples; <, less than]

Microcystins, 

in micrograms per liter

Cylindrospermopsins, 

in micrograms per liter

Geosmin, 

in nanograms per liter

MIB, 

in nanograms per liter

Wamego De Soto Wamego De Soto Wamego De Soto Wamego De Soto

n 90 93 29 29 90 94 90 94

Minimum <0.1 <0.1 <0.05 <0.05 <1 <1 <1 <1

Median <0.1 <0.1 <0.05 <0.05 1.90 2.05 <1 <1

Maximum 1.70 2.41 <0.05 0.05 16.2 41.6 10.7 25.9

Detection limit 0.10 0.10 0.05 0.05 1.0 1.0 1.0 1.0

Nondetects 72 72 29 28 30 18 52 63

Percent detection 20 23 0 3 67 81 42 33

seasonal patterns in microcystin occurrence were generally 

consistent, seasonal maxima varied by an order of magnitude 

across years (fig. 7A).

The highest microcystin concentrations were observed 

in August 2012 (Wamego site maximum=0.82 μg/L; De Soto 

site maximum=2.41 μg/L) and July 2014 (Wamego site 

maximum=1.7 μg/L; De Soto site maximum=0.78, fig. 7A). 

Cyanobacteria dominated the algal community during these 

time periods. Microcystin concentrations observed in the 

Kansas River during July 2012 through September 2016 (<0.1 

to 2.41 μg/L) were similar to those observed during September 

through October 2011 (<0.1 to 2.7 μg/L); however, the maximum microcystin concentration observed at the De Soto site 

in the current study (2.41 μg/L) was about 3 times higher than 

observed in 2011 (0.80 μg/L) (Graham and others, 2012).

Dissolved-phase cyanotoxins may persist for several days 

to weeks after the decline of a cyanobacterial population and 

may be more difficult to remove than particulate-bound cyanotoxins during drinking-water treatment processes (Jones and 

Orr, 1994; Heresztyn and Nicholson, 1997; Chiswell and others, 1999; Chorus and Bartram, 1999). Dissolved microcystin 

was measured in most samples where total microcystin concentrations were >0.1 μg/L. About 8 percent of Kansas River 

main-stem samples (n=183) collected during the study period 

were analyzed for dissolved microcystin concentrations (Williams and others, 2018). Dissolved microcystin represented 

between 6 and 100 percent of total microcystin concentrations 

(median=43 percent, n=15). When total concentrations were 

>0.3 μg/L and dissolved concentrations were measured (n=6), 

dissolved microcystin represented between 6 and 21 percent of 

total concentrations (median=13 percent). These data indicated 

that the dissolved phase infrequently dominated the microcystin pool in the Kansas River when total microcystin was above 

detectable levels.

Taste-and-Odor Compounds

The taste-and-odor causing compounds geosmin and MIB 

can create earthy and (or) musty tastes and odors in finished 

drinking water when present at concentrations >5 to 10 ng/L. 

Geosmin and MIB are produced by several microorganisms, 

including actinomycetes bacteria; however, cyanobacteria are 

typically the cause of geosmin- and MIB-related taste-andodor episodes in source water supplies (Taylor and others, 

2005). Overall, geosmin and MIB were detected in about 78 

and 43 percent of samples (n=258), respectively, collected 

across all sites (main stem and tributaries) during July 2012 

through September 2016. Total geosmin and MIB concentrations ranged from <1 to 133 ng/L (median=2.2 ng/L) and 

<1 to 29 ng/L (median=<1 ng/L), respectively (figs. 7B, C). 

The human detection threshold of 5 ng/L was exceeded in 

about 18 percent of geosmin samples and 10 percent of MIB 

samples.

Geosmin and 2-Methylisoborneol in Kansas River 

Tributaries

During July 2012 through September 2016, both geosmin 

and MIB were frequently detected in all tributary streams, 

though patterns in occurrence and concentration varied 

among sites. Geosmin and MIB were detected in about 93 and 

50 percent (n=28) of samples, respectively, collected from the 

Republican River. Concentrations ranged from <1 to 133 ng/L 

(median=3.85 ng/L) and <1 to 9.1 ng/L (median <1.45 ng/L), 

respectively. Geosmin and MIB exceeded the human detection threshold of 5 ng/L in about 36 and 14 percent of samples, 

respectively. The highest geosmin concentrations in the 

Republican River were observed during April through June of 

2013 (maxima=45.8 to 133.1 ng/L; fig. 7B). The highest MIB 
24 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

concentration (9.1 ng/L) occurred during September 2014 

(fig. 7C) (Williams and others, 2018).

In the Big Blue River, geosmin and MIB were detected 

in about 62 percent of samples (n=21). Geosmin and MIB 

concentrations ranged from <1 to 13 ng/L (median=<1.5 ng/L) 

and <1 to 29 ng/L (median=1.9 ng/L), respectively. Geosmin 

exceeded 5 ng/L in about 5 percent of samples, and MIB in 

about 24 percent. The highest geosmin concentration occurred 

in December 2015 (maximum=13 ng/L; the only sample that 

exceeded the human detection threshold). The highest MIB 

concentrations occurred during April through May 2013 

(maxima=18.7 to 29 ng/L) (Williams and others, 2018).

In the Delaware River, geosmin and MIB were detected 

in about 96 and 60 percent of samples (n=25), respectively. 

Geosmin and MIB concentrations ranged from <1 to 26.6 ng/L 

(median=3.5 ng/L) and <1 to 10.6 ng/L (median=2.1 ng/L), 

respectively. Geosmin and MIB exceeded 5 ng/L in 36 and 

20 percent of samples, respectively. The highest geosmin concentrations were observed during July through August 2012 

(maxima=13.1 to 26.6 ng/L) and December 2013 (maxima=17.9 to 21.2 ng/L). The highest MIB concentration was 

observed in September 2014 (maximum=10.6 ng/L) (Williams 

and others, 2018).

Geosmin and MIB concentrations in the Kansas River 

tributary streams during July 2012 through September 2016 

were substantially higher than September through October 

2011. With one exception, maximum geosmin and MIB 

concentrations at all sites were about 3 to 6 times higher from 

July 2012 through September 2016 than in September through 

October 2011 (Graham and others, 2012), most likely because 

the longer study duration captured a wider range of conditions. 

The exception was MIB at the Delaware River site, downstream from Perry Reservoir where maximum MIB concentrations in 2011 were about 3 times higher than the maximum 

concentration observed from July 2012 through September 

2016.

Geosmin and 2-Methylisoborneol in the Kansas 

River Main Stem

Unlike microcystin, geosmin and MIB occurrence and 

concentration varied considerably between the Wamego and 

De Soto sites during July 2012 through September 2016. 

Detection frequency of geosmin was higher at the De Soto 

site than the Wamego site, reflecting overall patterns in algal 

biomass and actinomycetes abundance (tables 2, 4). Geosmin 

was detected in about 67 percent of Wamego samples (n=90) 

and 81 percent of De Soto samples (n=94; table 4). Geosmin concentrations at the Wamego and De Soto sites ranged 

from <1 to 16.2 ng/L (median=1.9 ng/L) and <1 to 41.6 ng/L 

(median=2.05 ng/L), respectively (table 4). The human detection threshold of 5 ng/L was exceeded for geosmin in about 

11 and 17 percent of the samples collected at the Wamego and 

De Soto sites, respectively. Geosmin concentrations ≥5 ng/L 

were detected in all years, except for 2012 at the Wamego 

site. Although percent detection and range of concentrations of geosmin differed among the Wamego and De Soto 

sites, overall patterns in occurrence were quite consistent 

throughout the study period (fig. 7B). The highest geosmin 

concentrations occurred at both sites in April 2013 (Wamego 

site maximum=16.2 ng/L; De Soto site maximum=41.6 ng/L). 

Cyanobacteria did not dominate the phytoplankton community 

during April 2013. Geosmin was detected during all months of 

the year at both sites, and there were no clear seasonal patterns 

(fig. 7B); however, 80 percent of concentrations ≥5 ng/L at the 

Wamego site (n=10) and 62 percent of such concentrations 

at the De Soto site (n=16) were observed during December 

through April.

MIB was detected less frequently in the Kansas River 

than geosmin and was observed in about 42 percent of 

Wamego samples (n=90) and 33 percent of De Soto samples 

(n=94; table 4). MIB concentrations also were lower than 

geosmin concentrations, ranging from <1 to 10.7 ng/L at the 

Wamego site and <1 to 25.9 ng/L at the De Soto site (both site 

medians=<1 ng/L; table 4). Concentrations exceeded 5 ng/L 

in about 7 and 5 percent of samples from the Wamego and 

De Soto sites, respectively. MIB concentrations ≥5 ng/L were 

detected in all years, except for 2012 at the Wamego site and 

2012 and 2015 at the De Soto site. At the Wamego site, the 

highest MIB concentrations were observed in August 2013 

(10.7 ng/L), June 2014 (10.1), and August 2015 (8.9 ng/L). 

Cyanobacteria did not dominate the phytoplankton community in August 2013. At the De Soto site, the highest MIB 

concentrations were observed during May through June 2014 

(maxima=21.8 to 25.9 ng/L); cyanobacteria did not dominate 

the phytoplankton community during this time period. As 

observed for geosmin, there were no clear seasonal patterns in 

MIB occurrence or concentration (fig. 7C).

Similar to the tributary streams, geosmin and MIB concentrations in the Kansas River were higher during July 2012 

through September 2016 than September through October 

2011, though differences were not as pronounced. Maximum 

geosmin and MIB concentrations were about 1.2 to 2 times 

higher during July 2012 through September 2016 than during September through October 2011 (Graham and others, 

2012). Higher concentrations likely were observed in this 

study because the longer duration captured a wider range of 

conditions.

Like the cyanotoxins, dissolved-phase taste-and-odor 

compounds may be more difficult to remove than particulatebound taste-and-odor compounds during drinking-water 

treatment processes. Dissolved geosmin and MIB were 

measured in samples where total concentrations of one or both 

compounds were >5 ng/L. About 28 percent of Kansas River 

main-stem samples (n=184) collected during the study period 

were analyzed for dissolved geosmin and MIB concentrations. 

Overall, dissolved geosmin and MIB represented between 

0 and 100 percent of total concentrations (both medians=0 

percent; both n=52). When total concentrations were ≥5 ng/L, 

dissolved geosmin represented a larger portion of the total 

concentration (median=65 percent; n=20). Dissolved MIB still 
Environmental Factors Associated with Occurrence of Cyanotoxins and Taste-and-Odor Compounds 25

represented a small portion of the total concentration when 

concentrations were ≥5 ng/L (median=0; n=6), but the small 

number of samples may influence this result. These data indicate that the dissolved phase may dominate the geosmin pool 

in the Kansas River when concentrations are high, potentially 

creating additional challenges for drinking-water treatment.

Co-Occurrence of Cyanotoxins and Taste-andOdor Compounds

Optimal drinking-water treatment processes can be complicated by the presence of cyanotoxins, taste-and-odor compounds, or mixtures of the two (Westrick and others, 2010). 

Both share multiple common potential producers (Graham and 

others, 2008), and co-occurrence of cyanotoxins and taste-andodor compounds can be expected (Graham and others, 2010). 

The cyanotoxin microcystin and the taste-and-odor compounds geosmin and MIB co-occurred in 91 percent of cyanobacterial blooms (n=23) sampled in Midwestern United States 

lakes (Graham and others, 2010). By comparison, microcystin 

co-occurred with geosmin and MIB in 22 percent of routinely 

collected integrated photic zone samples (n=213) from Cheney 

Reservoir, Kans. (Graham and others, 2017).

During July 2012 through September 2016, geosmin was 

detected more frequently in the Kansas River tributary and 

main-stem sites (78 percent of samples; n=258) than MIB 

(43 percent of samples; n=258) or microcystin (27 percent of 

samples; n=257). Overall, only 10 percent of samples analyzed 

for microcystin, geosmin, and MIB did not have detectable 

concentrations of at least one of these compounds (n=257; 

fig. 8). Microcystin and taste-and-odor compounds (either 

geosmin, MIB, or both) co-occurred in 22 percent of samples, 

similar to co-occurrence in routinely collected samples from 

Cheney Reservoir (Graham and others, 2017). Co-occurrence 

in the Kansas River and Cheney Reservoir may be similar 

because both studies focused on routinely collected samples, 

rather than samples collected during bloom events such as the 

Graham and others (2010, 2012) studies. Therefore, though 

microcystin and taste-and-odor compounds can occasionally 

occur together, presence of one may not be indicative of presence of the other. Furthermore, sufficient warning for human 

health protection cannot be provided by the presence of odor 

alone (Graham and others, 2017).

Environmental Factors Associated with 

Occurrence of Cyanotoxins and Tasteand-Odor Compounds

Streamflow, reservoir contributions to flow, and all waterquality variables were included in an analysis of potential factors associated with occurrence of microcystin, geosmin, and 

MIB in the Kansas River during July 2012 through September 

No detections—10 percent of samples (n=257)

2-methylisoborneol (MIB)—6 percent

Geosmin—31 percent

Geosmin and MIB—26 percent

Microcystin—5 percent

Microcystin and taste-and-odor compounds 

(either geosmin, MIB, or both)—22 percent 

EXPLANATION

Figure 8. Co-occurrence of microcystin and taste-and-odor 

compounds in samples at the Kansas River at Wamego, Kansas; 

Kansas River at De Soto, Kansas; Republican River at Junction 

City, Kansas; Big Blue River near Manhattan, Kansas; and 

Delaware River at Perry, Kansas, streamgages (U.S. Geological 

Survey stations 06887500, 06892350, 06857100, 06887000, and 

06890900, respectively) collected during July 2012 through 

September 2016.

2016. The nonparametric Mann-Whitney rank sum test and 

Spearman rank-correlation analysis were used to characterize 

environmental conditions when microcystin, geosmin, and 

MIB occurred above concentrations of 0.3 μg/L, 5 ng/L, or 

2 ng/L, respectively. These concentrations were selected based 

on values relevant to drinking-water treatment and the distribution of the data (U.S. Environmental Protection Agency, 

2015; Taylor and others, 2005) and were used as thresholds to 

define microcystin, geosmin, and MIB events.
26 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Microcystin

Microcystin was detected in about 20 percent of Kansas 

River main-stem samples collected during the study period, 

though concentrations were typically <0.3 μg/L. Microcystin 

was always detected during the summer months when cyanobacterial abundances were highest in the Kansas River; 

however, microcystin concentrations >0.3 μg/L were only 

observed during the summers of 2012 and 2014 (fig. 7A). 

Because of the low detection frequency and high microcystin 

concentrations associated with two events during the study 

period, correlation analysis was not a valid method for determining environmental factors that were associated with microcystin occurrence and concentration; however, environmental 

conditions during the entire 2012 and 2014 summers (July 

through September) in which microcystin events occurred 

were compared with conditions during other summers.

Median streamflows during summers 2012 and 2014 

were about 2.5 times less than streamflows during nonevent 

summers at the Wamego and De Soto sites (table 5). When 

microcystin concentrations were >0.3 μg/L, total streamflow 

was always <3,000 ft3

/s. In addition, reservoir contribution to 

total streamflow was nearly 1.5 times greater during the summer 2012 and 2014 microcystin events relative to nonevent 

summers. In particular, streamflow contributions from Milford 

Lake when microcystin concentrations were >0.3 μg/L ranged 

from 36 to 57 and 11 to 34 percent of total streamflow at 

the Wamego and De Soto sites, respectively. Milford Lake 

contributions to total streamflow during the 2012 and 2014 

microcystin event summers (July through September) were 

about 3 to 4.5 times greater than contributions during nonevent 

summers (table 5, fig. 4).

In addition to streamflow and reservoir contributions to 

flow, algal biomass, cyanobacterial abundance, and several 

continuously measured water-quality variables were significantly different during microcystin event summers (2012 and 

2014) relative to nonevent summers at the Wamego and De 

Soto sites. Median regression estimated-chlorophyll concentrations were about 1.5 to 2 times greater during microcystin 

event summers at the Wamego and De Soto sites, respectively. 

Turbidity was significantly lower and specific conductance and 

pH were significantly higher during 2012 and 2014 than other 

summers (tables 2, 5). Less material suspended throughout the 

water column and more light penetration may create favorable 

conditions for cyanobacterial growth and microcystin production in the Kansas River (Reynolds, 1984; Chorus and Bartram, 1999; Wetzel, 2001). Higher specific conductance values 

during the summer 2012 and 2014 microcystin events may be 

an artifact of low-flow conditions rather than a potential influence on microcystin occurrence (Hem, 1992). Algal biomass 

and cyanobacterial abundance were significantly higher during event summers (tables 2, 5) and likely resulted in higher 

Kansas River pH values caused by increased photosynthesis 

(Wetzel, 2001).

During September through October 2011 (not shown) 

and July 2012 through September 2016, peak microcystin 

concentrations in the Kansas River main stem coincided with 

peak concentrations in the Republican River (fig. 7A; Graham 

and others, 2012). In addition, during July 2012 through September 2016 peak microcystin concentrations at the Delaware 

River usually coincided with elevated concentrations at the 

downstream De Soto site (fig. 7A). Streamflow, reservoir 

contributions to total streamflow, and contributions from 

Milford Lake in particular were significantly different between 

summers with and without microcystin events (table 5). During the 2012 and 2014 microcystin events, streamflows were 

low (<3,000 ft3

/s) and Milford Lake contributions to total 

streamflows were relatively high (36 percent or more of total 

streamflow at the Wamego site and 11 percent or more at the 

De Soto site; table 5, fig. 4) when microcystin concentrations were >0.3 μg/L. By comparison, when microcystin was 

detected in the Kansas River during the September through 

October 2011 microcystin event, Milford contributed 40 percent or more to total streamflows at the Wamego site and 30 

percent or more at the De Soto site (Graham and others, 2012). 

Streamflows at the beginning of the 2011 event were similar 

to streamflows during the summer 2012 and 2014 events but 

were substantially higher throughout the 2011 event (maxima 

of about 14,600 to 15,800 ft3

/s at the Wamego and De Soto 

sites, respectively) because of ongoing reservoir releases. 

Even though maximum streamflows were higher during the 

2011 event, the highest measured microcystin concentrations 

were observed at streamflows around 3,000 ft3

/s or less (Graham and others, 2012).

There seems to be a connection between microcystin 

detections in the Kansas River and occurrence of microcystin 

in upstream reservoirs (and tributary streams). Microcystin 

concentrations >0.3 μg/L may be likely during the summer 

when streamflow is <3,000 ft3

/s and contributions from Milford Lake exceed about 30 percent of total flow in the Kansas 

River. Observed microcystin concentrations typically were 

higher at the De Soto site than the Wamego or tributary sites 

during 2012 through 2016, indicating cyanobacteria may continue to grow and produce microcystin once introduced to the 

Kansas River. Downstream increases in microcystin concentration have been previously reported in the Kansas River by 

Graham and others (2012). Similar downstream transport and 

growth of microcystin-producing cyanobacteria from upstream 

reservoir sources have been observed in the Klamath River 

in Oregon and California (Kann and others, 2010; Otten and 

others, 2015) and the Tualatin River in Oregon (Rounds and 

others, 2015).

Taste-and-Odor Compounds

Geosmin and MIB were detected in about 74 (Wamego 

site) and 38 (De Soto site) percent of the Kansas River 

main-stem samples collected during the study period, though 

concentrations were typically less than the human detection 

threshold of 5 ng/L. As observed in 2011 (Graham and others, 2012), the spatial and temporal patterns in geosmin and 
Environmental Factors Associated with Occurrence of Cyanotoxins and Taste-and-Odor Compounds 27

Table 5. Selected differences in environmental conditions during microcystin, geosmin, and 2-methylisoborneol events at the Kansas River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, respectively) during July 2012 through September 2016.[Wamego event number of samples: microcystin=14, geosmin=18, MIB=24; Wamego nonevent number of samples: microcystin=23, geosmin=72, MIB=65; De Soto event number of samples: microcystin=14, geosmin=20, MIB=16; De Soto nonevent number of samples: microcystin=24, geosmin=74, MIB=77; microcystin event summers (July through September) were defined as summers where concentrations exceeded 0.3 microgram per liter and were in 2012 and 2014; nonevent summers were in 2013, 2015, and 2016; geosmin events were defined as time periods with persistent concentrations greater than 5 nanograms per liter and were during December 2012 through May 2013 and November 2015 through May 2016 at the 

Wamego and De Soto sites and October 2013 through January 2014 at just the De Soto site; 2-methylisoborneol events were defined as times when concentrations exceeded 2 nanograms per liter; 

p-values highlighted in yellow indicate statistically significant 

differences; reservoir contribution represents the percentage of overall reservoir contribution to total streamflow; p = probability value; ft3/s, cubic foot per second; %, percent; °C, degrees Celsius; 

FNU, formazin nephelometric unit; μS/cm, microsiemen per centimeter at 25 °Celsius; mL, milliliter; μg/L, microgram per liter; MIB, 2-methylisoborneol]

Environmental condition

Event 

median

Nonevent 

median

Mann-Whitney 

U statistic

p

Event 

median

Nonevent 

median

Mann-Whitney 

U statistic

p

Wamego De Soto

Microcystin

Streamflow (ft3/s) 1,161 2,971 55 0.001 1,983 4,014 59 0.001

Reservoir contribution 73% 49% 66 0.003 57% 40% 87.5 0.015

Milford contribution 36% 12% 91 0.029 25% 6% 94.5 0.027

Water temperature (°C) 25.3 24.5 136 0.657 26.4 26.4 162 0.868

pH (standard units) 8.37 8.16 89 0.048 8.6 8.26 52 <0.001

Turbidity (FNU) 33.4 78 82 0.027 26.1 69.5 74 0.007

Specific conductance (μS/cm at 25 °C) 881 701 75 0.015 754 573 73 0.004

Actinomycetes bacteria (colonies/mL) 155 320 56 0.044 88 380 40 0.006

Regression-estimated chlorophyll (μg/L) 43.8 30.2 98 0.093 90.2 41.3 60 0.002

Cyanobacterial abundance (cells/mL) 7,236 290 61 0.009 23,137 990 74 0.021

Geosmin

Streamflow (ft3/s) 1,690 1,827 522 0.236 2,039 2,619 562 0.101

Reservoir contribution 62.5% 61.5% 601 0.639 52.5% 49% 730 0.934

Milford contribution 14% 9% 634 0.92 6.5% 5.5% 738 0.993

Water temperature (°C) 5.16 21.9 110 <0.001 6.96 23.2 104 <0.001

pH (standard units) 8.25 8.21 558 0.408 8.29 8.4 648 0.398

Turbidity (FNU) 22.9 50.4 383 0.009 20.4 43.4 419 0.004

Specific conductance (μS/cm at 25 °C) 974 782 418 0.024 887 655 420 0.007

Actinomycetes bacteria (colonies/mL) 60 230 252 0.011 130 230 384 0.258

Regression-estimated chlorophyll (μg/L) 25.2 28.4 454 0.114 25.5 49.7 492 0.101

Cyanobacterial abundance (cells/mL) 24 267 456 0.26 309 699 475 0.327
28 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas Table 5. Table 5. Selected differences in environmental conditions during microcystin, geosmin, and 2-methylisoborneol events at the Kansas River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, respectively) during July 2012 through September 2016. — Continued

[Wamego event number of samples: microcystin=14, geosmin=18, MIB=24; Wamego nonevent number of samples: microcystin=23, geosmin=72, MIB=65; De Soto event number of samples: microcystin=14, geosmin=20, MIB=16; De Soto nonevent number of samples: microcystin=24, geosmin=74, MIB=77; microcystin event summers (July through September) were defined as summers where concentrations exceeded 0.3 microgram per liter and were in 2012 and 2014; nonevent summers were in 2013, 2015, and 2016; geosmin events were defined as time periods with persistent concentrations greater than 5 nanograms per liter and were during December 2012 through May 2013 and November 2015 through May 2016 at the 

Wamego and De Soto sites and October 2013 through January 

2014 at just the De Soto site; 2-methylisoborneol events were defined as times when concentrations exceeded 2 nanograms per liter; p-values highlighted in yellow indicate statistically significant differences; reservoir contribution represents the percentage of overall reservoir contribution to total streamflow; p = probability value; ft3/s, cubic foot per second; %, percent; °C, degrees Celsius; FNU, formazin nephelometric unit; μS/cm, microsiemen per centimeter at 25 °Celsius; mL, milliliter; μg/L, microgram per liter; MIB, 2-methylisoborneol]

Environmental condition

Event 

median

Nonevent 

median

Mann-Whitney 

U statistic

p

Event 

median

Nonevent 

median

Mann-Whitney 

U statistic

p

Wamego De Soto

MIB

Streamflow (ft3/s) 1,827 1,865 796 0.975 2,833 2,381 547 0.442

Reservoir contribution 55% 65% 500 0.005 30.50% 54.00% 249 <0.001

Milford contribution 4% 14% 499 0.005 3.50% 6.00% 535 0.372

Water temperature (°C) 19.7 19.4 773 0.809 21.07 20.9 532 0.36

pH (standard units) 8.23 8.22 797 0.982 8.36 8.36 608 0.88

Turbidity (FNU) 73.1 34.6 624 0.109 65.8 32.2 380 0.019

Specific conductance (μS/cm at 25 °C) 780 824 757 0.698 606 707 520 0.328

Actinomycetes bacteria (colonies/mL) 400 160 469 0.391 390 180 204 0.027

Regression-estimated chlorophyll (μg/L) 31.03 24.1 520 0.02 58.07 44.9 492 0.262

Cyanobacterial abundance (cells/mL) 227 279 577 0.378 772 538 394 0.679
Logistic Regression Model Evaluation 29

MIB occurrence and concentration were more complex than 

microcystin. Detections occurred throughout the year and were 

not necessarily concurrent at the Wamego and De Soto sites 

(figs. 7B, C). There were two geosmin events (time periods 

with persistent detections and maxima >5 ng/L) that affected 

the Wamego and De Soto sites (December 2012 through May 

2013 and November 2015 through May 2016) and one event 

that affected just the De Soto site (October 2013 through January 2014) (fig. 7B). Sixty-five percent of geosmin concentrations >5 ng/L (n=26) were observed during these three events; 

other exceedances had short durations (<2 weeks). Therefore, 

environmental conditions during the three longer-duration 

geosmin events were compared with nonevent environmental 

conditions. Although MIB detections did occasionally exceed 

the human detection threshold of 5 ng/L during the study 

period, long duration events did not occur (fig. 7C), precluding 

an event-based analysis similar to microcystin and geosmin. Instead, environmental conditions when concentrations 

exceeded 2 ng/L were compared to environmental conditions 

when concentrations were <2 ng/L.

In contrast to microcystin, streamflow and reservoir 

contributions to streamflow were not significantly different 

during geosmin events and nonevent periods. Geosmin events 

occurred across the range of streamflow conditions and flow 

contributions from Milford, Tuttle Creek, and Perry Lakes 

(table 5; figs. 4 and 7B). Although the highest geosmin concentrations were observed during the lowest streamflows at the 

Wamego and De Soto sites, concentrations >5 ng/L also were 

observed across the entire range of flow conditions at both 

sites; however, runoff events may have been an important factor associated with MIB occurrence. Reservoir contributions 

to total streamflow were nearly 10 to 24 percent less when 

MIB concentrations were >2 ng/L than when concentrations 

were <2 ng/L. These results, combined with an overall lack of 

concurrent, relatively high concentrations, at main-stem and 

tributary sites (figs. 7B, C) indicate there are no clear connections between geosmin and MIB occurrence in the Kansas 

River and potential upstream reservoir (or tributary stream) 

sources.

There was not a clear relation between algal biomass or 

cyanobacteria and taste-and-odor events in the Kansas River. 

With the exception of MIB and chlorophyll at the Wamego 

site, regression-estimated chlorophyll concentrations and 

cyanobacterial abundance were not significantly different during geosmin events or when MIB concentrations were >2 ng/L 

(table 5), and correlations were not statistically significant. 

Actinomycetes bacteria typically are associated with runoff 

events and also may produce geosmin and MIB. The abundance of actinomycetes bacteria was significantly lower during 

geosmin events at the Wamego site and significantly higher 

during MIB events at the De Soto site (table 5). Similarly, 

geosmin was significantly, but negatively, correlated with 

actinomycetes bacteria (Rs=−0.28, p=0.02) at the Wamego 

site, and MIB was significantly and positively correlated with 

actinomycetes bacteria at the De Soto site (Rs=0.353, p<0.01). 

The lack of clear associations with potential producers may be 

indicative of multiple geosmin and MIB sources in the Kansas 

River.

Geosmin and MIB were not strongly correlated (all 

Rs<0.55) with any continuously measured environmental variable at either Kansas River site. Water temperature, turbidity, 

and specific conductance were the only environmental variables that were significantly different during geosmin events 

at the Wamego and De Soto sites. Median water temperatures 

and turbidities were about 17 °C and 25 FNU lower, respectively, and specific conductance was about 200 microsiemens 

per centimeter at 25 °C higher during geosmin events than 

other time periods (table 5). When MIB concentrations were 

>2 ng/L, turbidity was significantly higher than when concentrations were <2 ng/L at the De Soto site but not the Wamego 

site. MIB was significantly correlated with actinomycetes 

bacteria at the De Soto site, and higher turbidities when MIB 

was >2 ng/L may be indicative of taste-and-odor events caused 

by runoff rather than cyanobacteria. Additional data collection 

during cyanobacteria- and runoff-driven taste-and-odor events 

is necessary for a better characterization of environmental 

factors associated with geosmin and MIB occurrence on the 

Kansas River.

Logistic Regression Model Evaluation

Continuous and discrete data collected at the Wamego 

and De Soto sites during July 2015 through September 2016 

were used to evaluate previously developed logistic regression 

models that continuously estimate the probability of occurrence above selected thresholds for cyanobacteria, microcystin, and geosmin at the Wamego and De Soto sites (Foster 

and Graham, 2016). Ordinary least squares regression was 

not an appropriate approach for these constituents owing to a 

high percentage (10 to 70 percent depending on constituent; 

Foster and Graham, 2016) of discrete sample concentrations 

below the analytical detection limit (Helsel and Hirsch, 2002). 

The models were developed using discrete water-quality and 

continuous-sensor data collected during July 2012 through 

June 2015 (Foster and Graham, 2016). Models were considered suitable for estimating probability of occurrence if they 

accurately classified at least 65 percent of the sample data, 

including the highest measured concentrations for a given constituent (Foster and Graham, 2016). All models were developed to be conservative by guarding against false negatives 

when estimating the probability of exceeding a given threshold 

(Foster and Graham, 2016). Conservative models minimize 

the risk of missing a potential cyanobacterial, microcystin, 

or geosmin event in the Kansas River. Collection of model 

validation data, including discrete cyanobacteria, microcystin, 

and geosmin samples, was continued during July 2015 through 

September 2016.
30 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Cyanobacteria Models

The best fit multiple logistic regression models for 

cyanobacteria occurrence at concentrations >2,000 cells/mL 

(Wamego site) and 10,000 cells/mL (De Soto site) included 

a seasonal component and turbidity as explanatory variables 

and accurately classified 80 and 91 percent of the samples 

used for model development at the Wamego (n=56) and De 

Soto (n=57) sites, respectively (Foster and Graham, 2016). 

As defined by Foster and Graham (2016), the TPPC used to 

classify samples during the validation period was 0.31 at the 

Wamego site and 0.48 at the De Soto site. During July 2015 

through September 2016 these models accurately classified 

71 and 79 percent of the validation samples at the Wamego 

(n=24) and De Soto (n=24) sites, respectively (figs. 9A, 

B). The lack of detections above selected thresholds likely 

influenced overall model performance during the validation 

period. Although most validation samples were accurately 

classified, few detections exceeded the selected thresholds 

of interest for cyanobacteria at either site during the validation period (Wamego site: 5 of 24; De Soto site: 3 of 24). At 

the Wamego site, one of the detections above the threshold 

was incorrectly classified and at the De Soto site all three of 

the detections above the threshold were incorrectly classified (false negatives). Therefore, although the models 

accurately classified more than 65 percent of the validation 

samples at both sites, the De Soto model did not fulfill the 

model suitability criteria of classifying the highest measured 

concentrations.

Because turbidity is an explanatory variable in the 

cyanobacteria models at both sites, the change from the YSI 

6136 turbidity sensor to the EXO turbidity sensor may have 

an influence on model performance. Overall influence of the 

change in turbidity sensor on performance likely is minimal 

because the models were developed using data from the YSI 

6136 and EXO turbidity sensors and the difference between 

the two sensors was relatively small at <200 FNU (appendix 

figs. 5.1 to 5.6). About 90 percent of the sensor-measured 

turbidity data collected during July 2012 through September 2016 was <200 FNU (fig. 5D). An evaluation of model 

performance over a range of turbidity conditions at both sites 

indicated that turbidity has the most substantial influence 

on the models at turbidities between about 30 and 75 FNU 

(appendix figs. 6.1 and 6.2). About 60 percent of improperly 

classified validation samples at each site had turbidities within 

the 30 to 75 FNU range. Improper classification within this 

range likely was caused by how rapidly the estimated probability of exceedance changed rather than differences caused 

by the change in turbidity sensors.

Microcystin Models

The best fit multiple logistic regression models for 

microcystin occurrence at concentrations greater than the 

0.1-μg/L detection threshold included a seasonal component, 

streamflow, and turbidity (Wamego site only) as explanatory 

variables and accurately classified 85 and 78 percent of the 

samples used for model development at the Wamego (n=59) 

and De Soto (n=60) sites, respectively (Foster and Graham, 

2016). As defined by Foster and Graham (2016), the TPPC 

used to classify samples during the validation period was 

0.40 at the Wamego site and 0.36 at the De Soto site. During 

July 2015 through September 2016 these models accurately 

classified 53 and 58 percent of the validation samples at 

the Wamego (n=30) and De Soto (n=31) sites, respectively 

(figs. 10A, B). The multiple logistic regression models for 

microcystin did not fulfill the model suitability criteria 

outlined in Foster and Graham (2016) during the validation 

period. However, there were few microcystin detections at 

either site in the validation dataset; 13 percent of samples 

had concentrations ≥0.1 μg/L during the validation period 

(Wamego site: 4 of 30; De Soto site: 4 of 31). In addition, the 

intended conservative nature of these models caused most of 

the inaccurate classifications to be false positives.

Because turbidity is an explanatory variable in the microcystin model at the Wamego site, the change from the YSI 

6136 turbidity sensor to the EXO turbidity sensor may have 

an influence on model performance. Overall influence of the 

change in turbidity sensor on performance likely is minimal 

because the model was developed using data from the YSI 

6136 and EXO turbidity sensors and the difference between 

the two sensors was relatively small at <200 FNU (appendix 

figs. 5.1 to 5.6). About 90 percent of the sensor-measured 

turbidity data collected during July 2012 through September 

2016 was <200 FNU (fig. 5D). An evaluation of model performance over a range of turbidity conditions indicated that turbidity has the most substantial influence on the model during 

May through December at turbidities between 30 and 75 FNU 

(appendix fig. 6.3). About 38 percent of improperly classified 

validation samples had turbidities within the 30 to 75 FNU 

range, and all improper classifications occurred during May 

through December. Even though the microcystin model for the 

De Soto site did not have turbidity as an explanatory variable, 

model performance at the two sites was similar. Most (82 percent) improper classifications at the De Soto site also occurred 

during May through December. Improper classification likely 

was caused by the conservative nature of the model rather than 

differences caused by the change in turbidity sensors.

Geosmin Models

The best fit multiple logistic regression models for 

geosmin occurrence at concentrations >2.0 ng/L included 

a seasonal component, chlorophyll fluorescence (Wamego 

site), and streamflow (De Soto site) as explanatory variables 

and accurately classified 73 and 75 percent of the samples 

used for model development at the Wamego (n=59) and De 

Soto (n=61) sites, respectively (Foster and Graham, 2016). 

As defined by Foster and Graham (2016), the TPPC used to 

classify samples during the validation period was 0.53 at the 
Logistic Regression Model Evaluation 31

B. Kansas River at De Soto, Kansas

Probability of exceeding 10,000 cells per milliliter

1

10

100

1,000

10,000

100,000

1,000,000

A. Kansas River at Wamego, Kansas

Probability of exceeding 2,000 cells per milliliter

0 0.2 0.4 0.6 0.8 1.0

0 0.2 0.4 0.6 0.8 1.0

Cyanobacteria, in cells per milliliter

1

10

100

1,000

10,000

100,000

Model calibration data 

Model validation data

Threshold probability for positiveclassification (Foster and Graham, 2016) 

Threshold probability for positive

classification (Foster and Graham, 2016) 

Selected threshold of exceedance

(2,000 cells per milliliter) 

Selected threshold of exceedance

(10,000 cells per milliliter) 

Reference response

predicted as positive

(false positive) 

Reference response

predicted as reference

(true negative) 

Positive response

predicted as reference

(false negative) 

Positive response

predicted as positive

(true positive) 

Reference response

predicted as positive

(false positive) 

Reference response

predicted as reference

(true negative) 

Positive response

predicted as reference

(false negative) 

Positive response

predicted as positive

(true positive) 

 July 2015–September 2016

July 2012–June 2015

EXPLANATION

Figure 9. Performance of logistic regression models estimating the probability of cyanobacterial occurrence above thresholds of 

concern at sites on the Kansas River during July 2012 through September 2016. A, Kansas River at the Kansas River at Wamego, Kansas 

(U.S. Geological Survey station 06887500). B, Kansas River at De Soto, Kansas (U.S. Geological Survey station 06892350).
32 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Reference response

predicted as positive

(false positive) 

Reference response

predicted as reference

(true negative) 

Positive response

predicted as reference

(false negative) 

Positive response

predicted as positive

(true positive) 

B. Kansas River at De Soto Kansas River at De Soto, Kansas

A. Kansas River at Wamego

Probability of exceeding 0.1 microgram per liter

0 0.2 0.4 0.6 0.8 1.0

0 0.2 0.4 0.6 0.8 1.0

Microcystin, in micrograms per liter

0.01

0.1

1

10

0.01

0.1

1

10

Analytical detection threshold

and selected threshold of

exceedance (0.1 microgram per liter) 

Analytical detection threshold

and selected threshold of

exceedance (0.1 microgram per liter) 

Threshold probability for positiveclassification (Foster and Graham, 2016) 

Threshold probability for positiveclassification (Foster and Graham, 2016) 

Reference response

predicted as positive

(false positive) 

Reference response

predicted as reference

(true negative) 

Positive response

predicted as reference

(false negative) 

Positive response

predicted as positive

(true positive) 

Model calibration data 

Model validation data

 July 2015–September 2016

July 2012–June 2015

EXPLANATION

A. Kansas River at Wamego, Kansas

Figure 10. Performance of logistic regression models estimating the probability of microcystin occurrence above a threshold of 

concern at sites on the Kansas River during July 2012 through September 2016. A, Kansas River at the Kansas River at Wamego, Kansas 

(U.S. Geological Survey station 06887500). B, Kansas River at De Soto, Kansas (U.S. Geological Survey station 06892350).
Logistic Regression Model Evaluation 33

Wamego site and 0.50 at the De Soto site. During July 2015 

through September 2016 these models accurately classified 80 

and 84 percent of the validation samples at the Wamego (n=30) 

and De Soto (n=31) sites, respectively, including the highest 

measured concentrations (figs. 11A, B). Overall, the multiple 

logistic regression models for geosmin at the Wamego and De 

Soto sites continued to fulfill the model suitability criteria outlined in Foster and Graham (2016) during the validation period. 

Consistency in model performance may be due to the high 

number of detections during both time periods at both sites. In 

addition, several concentrations exceeded the selected threshold 

of interest of 2 ng/L at both sites during the validation period 

(Wamego site: 11 of 30; De Soto site: 13 of 31).

Because fChl is an explanatory variable in the geosmin 

model at the Wamego site, the change from the YSI 6025 fChl 

sensor to the EXO fChl sensor may have an influence on model 

performance (appendixes 1 through 4). Given that the geosmin model at the Wamego site accurately classified more than 

70 percent of validation samples, including the highest measured concentrations, the change in fChl sensors seems to have 

had a minimal influence on model performance. The change in 

sensors may have had minimal influence because the model was 

developed using data from the YSI 6025 and EXO fChl sensors. An evaluation of model performance over a range of fChl 

conditions indicated that fChl had the most substantial influence 

on the model performance during May through November and 

at concentrations between 11 and 22 μg/L (appendix fig. 6.4). 

About 17 percent of improperly classified validation samples 

had fChl values within the 11 to 22 μg/L range, and all occurred 

during May through November. Even though the geosmin 

model for the De Soto site did not have fChl as an explanatory 

variable, model performance at the two sites was similar. Most 

(67 percent) improper classifications at the De Soto site also 

occurred during May through November. Improper classifications during May through November likely occurred because 

of the seasonal influence on the models (for example, appendix 

fig. 6.4) rather than differences caused by the change in fChl 

sensors.

Model Refinement

Continued monitoring of underlying environmental conditions is essential for further model refinement and ongoing 

model evaluation. Erosional events, shifting stream channels, 

changes in reservoir management strategies, algal community 

composition, or other underlying factors that affect ecosystem 

structure and function could potentially affect model performance. For example, Cheney Reservoir, a primary drinkingwater supply in south-central Kansas, had a large inflow event 

during August 2013 that resulted in the reservoir gaining about 

89,000 acre-feet in 10 days (Graham and others, 2017). Following this event, a previously published logistic model for 

geosmin occurrence above the selected threshold of 5 ng/L 

performed poorly, likely because of shifts in algal community 

composition. Continued data collection allowed identification 

of the model performance issue and the development of a new 

model (Graham and others, 2017).

Further refinement of the Kansas River models estimating 

the probability of occurrence of cyanobacteria, microcystin, 

and geosmin above relevant thresholds likely will increase 

model performance. However, additional data collected during cyanobacteria, microcystin, and taste-and-odor events are 

required. Few detections above selected thresholds of interest 

during the model validation period prevented refinement of 

models as part of this report.

Overall and individual reservoir contributions to total 

streamflow were significantly different during microcystin 

and geosmin events during July 2012 through September 

2016. However, this methodology is currently (2018) limited 

to discrete time applications; it cannot be implemented on a 

continuous basis. Therefore, considering reservoir contribution 

as a potential explanatory variable in the logistic regression 

models that continuously estimate the probability of occurrence 

above selected thresholds for cyanobacteria, microcystin, and 

geosmin at the Wamego and De Soto sites is not currently feasible. Implementation of the methods used to determine overall 

and individual reservoir contributions to total streamflow on a 

continuous basis should be explored and would likely enhance 

model performance.

Model functionality could be enhanced by raising the 

thresholds of interest from 0.1 to 0.3 μg/L for microcystin and 

from 2 to 5 ng/L for geosmin. The higher microcystin threshold 

of 0.3 μg/L may be more relevant to water treatment owing to 

its importance as an EPA health advisory guidance threshold 

for finished drinking water (U.S. Environmental Protection 

Agency, 2015). Additionally, the higher geosmin threshold of 

interest of 5 ng/L may be more practical to water treatment 

because it is the concentration at which humans can begin to 

detect the taste-and-odor compound. Changing the thresholds of concern in the models would provide a more practical estimation of the probability of microcystin and geosmin 

occurrence in real-time to water-treatment managers that use 

the Kansas River as a source water supply; however, for the 

thresholds of interest to be changed, additional data need to be 

collected during microcystin and taste-and-odor events.

Continuous water-quality data may be used independently, 

or in combination with regression models, to provide information on changing water-quality conditions that may affect 

drinking-water treatment processes or recreational activities 

on the Kansas River. For example, logistic regression model 

outputs and continuous water-quality data may both be indicative of the potential for microcystin events. Logistic regression 

models that are estimating a high probability of microcystin 

occurrence at concentrations above 0.1 μg/L can be used as one 

indicator. Streamflows <3,000 ft3/s during upstream reservoir 

releases during periods with low turbidity and increased fChl, 

specific conductance, and pH values may also be indicative of 

microcystin events. Advanced or near-real-time notification 

may inform proactive, rather than reactive, management strategies when water-quality conditions are changing rapidly or are 

likely to cause cyanobacteria-related events.
34 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Probability of exceeding 2 nanograms per liter

Geosmin, in nanograms per liter

Selected threshold 

of exceedance 

(2 nanograms per liter) 

Threshold probability for positiveclassification (Foster and Graham, 2016) 

Selected threshold 

of exceedance 

(2 nanograms per liter) 

B. Kansas River at De Soto, Kansas

0 0.2 0.4 0.6 0.8 1.0

0 0.2 0.4 0.6 0.8 1.0

0.1

1

1

10

100

0.1

10

100

Reference response

predicted as positive

(false positive) 

Reference response

predicted as positive

(false positive) 

Reference response

predicted as reference

(true negative) 

Reference response

predicted as reference

(true negative) 

Positive response

predicted as reference

(false negative) 

Positive response

predicted as reference

(false negative) 

Positive response

predicted as positive

(true positive) 

Positive response

predicted as positive

(true positive) 

Threshold probability for positiveclassification (Foster and Graham, 2016) 

Model calibration data 

Model validation data

 July 2015–September 2016

July 2012–June 2015

EXPLANATION

A. Kansas River at Wamego, Kansas

Figure 11. Performance of logistic regression models estimating the probability of geosmin occurrence above a threshold of concern 

at sites on the Kansas River during July 2012 through September 2016. A, Kansas River at the Kansas River at Wamego, Kansas (U.S. 

Geological Survey station 06887500). B, Kansas River at De Soto, Kansas (U.S. Geological Survey station 06892350).
Summary 35

Summary

Cyanobacteria cause a multitude of water-quality concerns, including the potential to produce toxins and taste-andodor compounds. Toxins and taste-and-odor compounds may 

cause substantial economic and public health concerns and are 

of particular interest in lakes, reservoirs, and rivers that are 

used for drinking-water supply. The Kansas River and its associated alluvial aquifer are primary sources of drinking water 

for about 800,000 people in northeastern Kansas. Extensive 

cyanobacterial blooms typically do not develop in the Kansas 

River; however, reservoirs in the lower Kansas River Basin 

occasionally develop blooms that may affect downstream 

water quality. Since July 2012, the U.S. Geological Survey, in 

cooperation with the Kansas Water Office, the City of Lawrence, the City of Olathe, the City of Topeka, and Johnson 

County WaterOne, has collected discrete and continuously 

measured water-quality data at two sites on the Kansas River 

to better characterize the sources, frequency and magnitude 

of occurrence, and causes of cyanobacteria, cyanotoxins, and 

taste-and-odor compounds and to develop a real-time notification system of changing water-quality conditions that may 

affect drinking-water treatment. The purpose of this report 

is to (1) describe water-quality conditions, with an emphasis 

on cyanobacteria and associated toxins (microcystin) and 

taste-and-odor compounds (geosmin and 2-methylisoborneol 

[MIB]), in the Kansas River during July 2012 through September 2016; (2) describe the environmental factors associated 

with the occurrence of cyanobacteria and associated toxins and 

taste-and-odor compounds in the Kansas River during July 

2012 through September 2016; and (3) evaluate previously 

published logistic regression models that used continuous 

water-quality data to estimate the probability of cyanobacteria, 

microcystin, and geosmin occurrence above relevant thresholds in the Kansas River. Quantification of cyanobacteria, 

cyanotoxins, and taste-and-odor compounds, and the conditions under which they are most likely to occur in the Kansas 

River will provide drinking-water suppliers and the State of 

Kansas a better understanding of associated water-quality 

concerns in the river. The logistic regression models evaluated 

in this report may provide useful indicators of cyanobacteria, 

microcystin, and geosmin occurrence in the Kansas River.

The U.S. Geological Survey collected continuous 

and discrete streamflow and water-quality data at two sites 

(Wamego and De Soto) on the Kansas River during July 

2012 through September 2016. Continuous water-quality 

data included water temperature, pH, dissolved oxygen, 

turbidity, specific conductance, and chlorophyll fluorescence. 

Discrete water-quality samples were collected approximately 

bimonthly during May through October and monthly during 

November through April. Discrete samples were analyzed 

for suspended-sediment concentration, dissolved solids and 

major ions, nutrients (nitrogen and phosphorus species), trace 

elements, indicator and actinomycetes bacteria, algal biomass, 

phytoplankton abundance and community composition, the 

cyanotoxins microcystin and cylindrospermopsin (July 2015 

through September 2016 only), and the taste-and-odor compounds geosmin and MIB. Additionally, event-based discrete 

water-quality samples were collected at three reservoir outflow 

sites that are tributaries to the Kansas River: the Republican 

River (downstream from Milford Lake), the Big Blue River 

(downstream from Tuttle Creek Lake), and the Delaware 

River (downstream from Perry Lake). Event-based samples 

were analyzed for the cyanotoxins microcystin and cylindrospermopsin (July 2015 through September 2016 only) and the 

taste-and-odor compounds geosmin and MIB.

Streamflow at the upstream Wamego site was lower than 

streamflow at the downstream De Soto site across all years 

and seasons during the study period. Mean annual streamflows 

during 2012 through 2014 at the Wamego and De Soto sites 

were lower than mean annual streamflows during 2015 and 

2016. Streamflows during 2012 through 2014 follow patterns 

expected during a period of drought, and patterns in 2015 and 

2016 are indicative of nondrought streamflows. The Wamego 

site typically had a greater percentage of flow from upstream 

reservoirs than the De Soto site, despite De Soto having more 

contributing reservoirs. The highest annual streamflow contributions from reservoirs in the Kansas River were observed in 

2012.

In general, differences in water temperature, pH, dissolved oxygen, specific conductance, turbidity, and most 

discretely measured water-quality variables between the two 

Kansas River study sites were small. Observed seasonal and 

interannual patterns were typical and associated with characteristic changes in water temperature, streamflow, and biological processes. Differences in total nitrogen and phosphorus 

concentrations between the Wamego and De Soto sites were 

small. Seasonal mean nutrient concentrations were highest in 

spring and lowest during fall and winter. Mean annual total 

nutrient concentrations at both sites generally increased each 

year between 2012 and 2016. The observed seasonal and interannual patterns in total nutrient concentrations were associated 

with seasonal and annual increases in streamflows. Seasonal 

mean nitrate plus nitrite concentrations at the Wamego and De 

Soto sites were highest in spring. In contrast, orthophosphorus 

concentrations were lower in spring than other seasons at both 

sites. As observed for total nutrients, mean annual inorganic 

nutrient concentrations at both sites generally increased each 

year between 2012 and 2016.

Bacteria in the actinomycetes group may produce the 

taste-and-odor compounds geosmin and MIB. Mean actinomycetes concentration was higher at the De Soto site than the 

Wamego site. Seasonal mean actinomycetes concentrations 

were lower during winter than any other season. Actinomycetes concentrations were highest during spring at the Wamego 

and De Soto sites, though this pattern was inconsistent across 

years. Mean annual actinomycetes concentrations varied 

across years and did not display clear patterns. Transport of 

actinomycetes bacteria typically increases with increased 

streamflows, and concentrations in the Kansas river were 

positively correlated with streamflow. Other factors, such as 

time since last rainfall and runoff event, soil temperatures, and 
36 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

temporal variability of actinomycetes communities in soils, 

likely also influence transport of actinomycetes bacteria in the 

Kansas River.

Chlorophyll is commonly used as an estimate of algal 

biomass. Sensor-measured chlorophyll concentrations were 

consistently higher at the De Soto site than the Wamego site 

during the study period. Seasonal mean sensor-measured 

chlorophyll concentrations were highest in spring and summer (the growing season) and lowest during winter. Mean 

annual sensor-measured chlorophyll concentrations varied 

less across years than seasons, likely reflecting the influence 

of temperature on algal growth. Chlorophyll concentrations 

at the Wamego and De Soto sites were negatively correlated 

with streamflow and total and bioavailable (orthophosphorus 

and nitrate plus nitrite) nutrient concentrations. The negative 

association between chlorophyll and nutrients in the Kansas 

River likely is caused by the relatively strong positive association between nutrient concentrations and streamflows. Algal 

biomass at the De Soto site was always higher than at the 

Wamego site. Higher algal biomass at the De Soto site likely 

was caused by algal growth during downstream transport 

without major losses due to grazing by aquatic organisms 

or other processes. Although nutrients are of importance for 

algal growth, downstream transport often makes the influence 

of nutrients and other processes on algal biomass difficult to 

discern.

Algal communities in the Kansas River typically were 

dominated by diatoms. Cyanobacteria were relatively common 

in the Kansas River but rarely dominated the algal community. 

Cyanobacterial abundances typically were higher at the De 

Soto site than the Wamego site. Cyanobacterial abundances 

generally peaked in late summer or early fall (July through 

October), with smaller peaks occasionally observed in spring 

(April through May). Cyanobacteria may be a concern for 

drinking-water treatment at abundances of 20,000 cells per 

milliliter (cells/mL) or higher. Cyanobacterial abundance 

exceeded 20,000 cells/mL in about 7 and 16 percent of the 

samples collected from the Wamego and De Soto sites, 

respectively. Exceedances typically occurred during summer 

months, though occasional exceedances were observed during 

spring and fall. Relations between cyanobacterial abundance 

and streamflow, turbidity, and nutrients in the Kansas River 

were similar to those for chlorophyll and total phytoplankton abundance, indicating the same processes that influence 

overall algal biomass and dynamics also are influencing 

cyanobacteria.

The cyanotoxin microcystin was detected in about 

27 percent of the samples collected across all sites (main-stem 

and tributaries) during July 2012 through September 2016. 

Cylindrospermopsin was detected in one sample across all 

sites (main stem and tributaries) during July 2015 through 

September 2016. Microcystin occurrence and concentration 

were similar between the Wamego and De Soto sites during July 2012 through September 2016. Microcystin was 

detected in about 20 and 23 percent of the samples collected from the Wamego and De Soto sites, respectively. 

Microcystin concentrations ranged from less than (<) 0.1 to 

1.7 micrograms per liter (μg/L) at the Wamego site and <0.1 

to 2.41 μg/L at the De Soto site (both site medians <0.1 μg/L). 

At the Wamego site, microcystin concentration exceeded the 

U.S. Environmental Protection Agency health advisory guidance values for finished drinking water of 0.3 and 1.6 μg/L in 

about 6 and 1 percent of the samples, respectively. Similarly, 

at the De Soto site, microcystin concentrations exceeded 0.3 

and 1.6 μg/L in about 5 and 1 percent of the samples, respectively. These guidance values are for finished drinking water 

and are not directly applicable to observed environmental 

concentrations but do provide a benchmark for comparison. 

Seasonal patterns in microcystin occurrence were consistent 

between sites and among years. Microcystin was detected 

most often and had the highest concentrations during summer. Though seasonal patterns in microcystin occurrence were 

generally consistent, seasonal maxima varied by an order of 

magnitude across years.

Dissolved-phase cyanotoxins may persist for several 

days to weeks after the decline of a cyanobacterial population 

and may be more difficult to remove than particulate-bound 

cyanotoxins during drinking-water treatment processes. Dissolved microcystin represented between 6 and 100 percent of 

total microcystin concentrations. When total concentrations 

were greater than (>) 0.3 μg/L and dissolved concentrations 

were measured, dissolved microcystin represented between 6 

and 21 percent of total concentrations. These data indicated 

that the dissolved phase infrequently dominated the microcystin pool in the Kansas River when total microcystin was above 

detectable levels.

The taste-and-odor compounds geosmin and MIB were 

detected in about 78 and 43 percent of samples, respectively, 

collected across all sites (main-stem and tributaries) during July 2012 through September 2016. Geosmin and MIB 

occurrence and concentration varied considerably between the 

Wamego and De Soto sites. Detection frequency of geosmin 

was higher at the De Soto site than the Wamego site, reflecting 

overall patterns in algal biomass and actinomycetes abundance. Geosmin was detected in about 67 percent of Wamego 

samples and 81 percent of De Soto samples. Geosmin concentrations at the Wamego and De Soto sites ranged from <1 to 

16.2 nanograms per liter (ng/L) (median=1.9 ng/L) and <1 to 

41.6 ng/L (median=2.05 ng/L), respectively. The human detection threshold of 5 ng/L was exceeded for geosmin in about 

11 and 17 percent of the samples collected at the Wamego and 

De Soto sites, respectively. Geosmin was detected during all 

months of the year at both sites, and there were no clear seasonal patterns. MIB was detected less frequently in the Kansas 

River than geosmin and was observed in about 42 percent of 

Wamego samples and 33 percent of De Soto samples. MIB 

concentrations also were lower than geosmin concentrations, 

ranging from <1 to 10.7 ng/L at the Wamego site and <1 to 

25.9 ng/L at the De Soto site (both site medians=<1 ng/L). 

Concentrations exceeded 5 ng/L in about 7 and 5 percent of 

samples from the Wamego and De Soto sites, respectively. As 
Summary 37

observed for geosmin, there were no clear seasonal patterns in 

MIB occurrence or concentration.

Like the cyanotoxins, dissolved-phase taste-and-odor 

compounds may be more difficult to remove than particulatebound taste-and-odor compounds during drinking-water 

treatment processes. Overall, dissolved geosmin and MIB 

represented between 0 and 100 percent of total concentrations 

(median=0 percent). When total concentrations were greater 

than or equal to 5 ng/L, dissolved geosmin represented a 

larger portion of the total concentration (median=65 percent). 

Dissolved MIB still represented a small portion of the total 

concentration when concentrations were greater than or equal 

to 5 ng/L. These data indicate that the dissolved phase may 

dominate the geosmin pool in the Kansas River when concentrations are high, potentially creating additional challenges for 

drinking-water treatment.

During July 2012 through September 2016, geosmin 

was detected more frequently in the Kansas River tributary 

and main-stem sites (78 percent of samples) than MIB (43 

percent of samples) or microcystin (27 percent of samples). 

Overall, only 10 percent of samples analyzed for microcystin, 

geosmin, and MIB did not have detectable concentrations of 

at least one of these compounds. Microcystin and taste-andodor compounds (either geosmin, MIB, or both) co-occurred 

in 22 percent of samples. Therefore, though microcystin and 

taste-and-odor compounds can occasionally occur together, 

presence of one may not be indicative of presence of the other. 

Furthermore, sufficient warning for human health protection 

cannot be provided by the presence of odor alone.

There seems to be a connection between microcystin 

detections in the Kansas River and occurrence of microcystin 

in upstream reservoirs (and tributary streams). Microcystin 

concentrations >0.3 μg/L may be likely during the summer when streamflow is <3,000 ft3

/s and contributions from 

Milford Lake exceed about 30 percent of total flow in the 

Kansas River. Observed microcystin concentrations typically 

were higher at the De Soto site than the Wamego or tributary 

sites during 2012 through 2016, indicating cyanobacteria may 

continue to grow and produce microcystin once introduced to 

the Kansas River.

The spatial and temporal patterns in geosmin and MIB 

occurrence and concentration were more complex than microcystin. There were no clear connections between geosmin and 

MIB occurrence in the Kansas River and potential upstream 

reservoir (or tributary stream) sources. Likewise, there was 

not a clear relation between algal biomass, cyanobacteria, or 

actinomycetes bacteria and taste-and-odor events in the Kansas River. Geosmin and MIB were not strongly correlated with 

any continuously measured environmental variable at either 

Kansas River site. Additional data collection during cyanobacteria- and runoff-driven taste-and-odor events is necessary for 

a better characterization of environmental factors associated 

with geosmin and MIB occurrence on the Kansas River.

Continuous and discrete data collected at the Wamego 

and De Soto sites during July 2015 through September 2016 

were used to evaluate previously developed logistic regression 

models that continuously estimate the probability of occurrence above selected thresholds for cyanobacteria, microcystin, and geosmin at the Wamego and De Soto sites. Models 

were considered suitable for estimating probability of occurrence if they accurately classified at least 65 percent of the 

sample data, including the highest measured concentrations 

for a given constituent. The best fit multiple logistic regression models for cyanobacteria occurrence at concentrations 

>2,000 cells/mL (Wamego site) and 10,000 cells/mL (De Soto 

site) included a seasonal component and turbidity as explanatory variables. Although the cyanobacteria occurrence models 

accurately classified more than 65 percent of the validation 

samples at both sites, the De Soto model did not fulfill the 

model suitability criteria of classifying the highest measured 

concentrations. The best fit multiple logistic regression models 

for microcystin occurrence at concentrations greater than the 

0.1-μg/L detection threshold included a seasonal component, 

streamflow, and turbidity (Wamego site only) as explanatory 

variables. The best fit multiple logistic regression models 

for microcystin did not fulfill the model suitability criteria 

the validation period. However, there were few microcystin 

detections at either site in the validation dataset; 13 percent of 

samples had concentrations greater than or equal to 0.1 μg/L 

during the validation period. In addition, the intended conservative nature of these models caused most of the inaccurate classifications to be false positives. The best fit multiple 

logistic regression models for geosmin occurrence at concentrations >2.0 ng/L included a seasonal component, chlorophyll 

fluorescence (Wamego site), and streamflow (De Soto site) as 

explanatory variables. The models for geosmin continued to 

fulfill the model suitability criteria during the validation period.

Continued monitoring of underlying environmental 

conditions is essential for further model refinement and ongoing model evaluation. Further refinement of the Kansas River 

models estimating the probability of occurrence of cyanobacteria, microcystin, and geosmin above relevant thresholds likely 

will increase model performance. However, additional data 

collected during cyanobacteria, microcystin and taste-and-odor 

events are required. Few detections above selected thresholds 

of interest during the model validation period prevented refinement of models as part of this report. Overall and individual 

reservoir contributions to total streamflow were significantly 

different during microcystin and geosmin events during July 

2012 through September 2016. Implementation of the methods 

used to determine overall and individual reservoir contributions 

to total streamflow on a continuous basis should be explored 

and would likely enhance model performance. Model functionality could be enhanced by raising the thresholds of interest 

from 0.1 to 0.3 μg/L for microcystin and from 2 to 5 ng/L for 

geosmin. Changing the thresholds of concern in the models 

would provide a more practical estimation of the probability 

of microcystin and geosmin occurrence in real-time to watertreatment managers that use the Kansas River as a source water 

supply; however, for the thresholds of interest to be changed, 

additional data need to be collected during microcystin and 

taste-and-odor events.
38 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Continuous water-quality data may be used independently, 

or in combination with regression models, to provide information on changing water-quality conditions that may affect 

drinking-water treatment processes or recreational activities 

on the Kansas River. For example, logistic regression model 

outputs and continuous water-quality data may both be indicative of the potential for microcystin events. Logistic regression 

models that are estimating a high probability of microcystin 

occurrence at concentrations above 0.1 μg/L can be used as one 

indicator. Streamflows <3,000 ft3/s during upstream reservoir releases during periods with low turbidity and increased 

chlorophyll fluorescence, specific conductance, and pH values 

may also be indicative of microcystin events. Advanced or 

near-real-time notification may inform proactive, rather than 

reactive, management strategies when water-quality conditions are changing rapidly or are likely to cause cyanobacteriarelated events.

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Table 2
44 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Water temperature (°C)—Continuous water-quality monitor

Wamego 2012 -- -- 22.5 9.37 12.8

2013 4.27 18.2 25.6 8.15 14.2

2014 3.26 19.9 26.0 9.20 14.9

2015 5.81 19.3 26.0 11.1 16.7

2016 6.17 19.4 26.3 -- 17.5

2012–16 4.80 19.2 25.7 9.46 15.4

De Soto 2012 -- -- 24.7 8.91 15.6

2013 3.67 19.1 26.4 8.10 14.4

2014 2.77 20.8 26.3 8.95 14.7

2015 3.58 19.9 26.5 11.2 16.6

2016 6.55 20.3 27.0 -- 18.0

2012–16 4.22 20.0 26.3 9.29 15.7

pH (standard units—seasonal/annual/total median)—Continuous water-quality monitor

Wamego 2012 -- -- 8.6 8.7 8.7

2013 8.6 8.3 8.4 8.4 8.5

2014 8.4 8.5 8.5 8.4 8.4

2015 8.2 7.8 8.4 8.5 8.3

2016 8.4 8.2 8.2 -- 8.3

2012–16 8.4 8.4 8.4 8.4 8.4

De Soto 2012 -- -- 9.0 8.5 8.7

2013 8.3 8.3 8.3 8.1 8.2

2014 8.6 8.6 8.7 8.4 8.6

2015 8.0 8.0 8.5 8.6 8.4

2016 8.2 8.2 8.2 -- 8.3

2012–16 8.4 8.4 8.4 8.4 8.4

Dissolved oxygen (mg/L)—Continuous water-quality monitor

Wamego 2012 -- -- 9.43 11.8 11.2

2013 13.2 9.40 8.04 11.7 10.6

2014 13.0 9.70 8.67 11.8 10.7

2015 12.9 9.13 8.66 11.4 10.2

2016 12.5 9.26 7.67 -- 9.77

2012–16 12.9 9.37 8.35 11.7 10.4

De Soto 2012 -- -- 10.1 13.0 11.8

2013 14.0 9.72 8.40 11.9 11.0

2014 13.1 9.51 9.27 11.9 10.9

2015 13.4 8.69 8.51 11.8 10.4

2016 13.4 9.51 8.00 -- 10.3

2012–16 13.5 9.38 8.79 12.1 10.8
Table 2 45

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Turbidity (FNU)—Continuous water-quality monitor

Wamego 2012 -- -- 32.0 11.4 16.1

2013 7.30 99.3 111 22.6 60.6

2014 13.2 81.6 89.8 51.9 60.9

2015 11.4 190 75.9 50.1 88.9

2016 19.3 120 188 -- 111

2012–16 13.0 122 111 34.6 73.3

De Soto 2012 -- -- 27.8 16.5 20.7

2013 9.66 145 126 29.6 75.1

2014 19.6 120 71.9 48.7 64.5

2015 12.3 206 91.1 66.9 96.6

2016 24.8 170 168 -- 121

2012–16 17.0 159 103 40.7 80.6

Suspended-sediment concentration (mg/L)—Discretely collected

Wamego 2012 -- -- 158 55.3 117

2013 31.7 303 445 149 286

2014 59.7 258 185 218 195

2015 17.0 299 214 484 266

2016 459 804 349 -- 567

2012–16 142 421 267 237 288

De Soto 2012 -- -- 85.0 79.2 82.4

2013 82.3 210 434 148 253

2014 115 855 206 87.3 333

2015 28.5 721 159 282 362

2016 179 928 181 -- 532

2012–16 102 694 214 145 331

Specific conductance (μs/cm)—Continuous water-quality monitor

Wamego 2012 -- -- 823 992 948

2013 1,111 712 668 917 851

2014 1,043 843 597 735 794

2015 927 575 628 873 729

2016 835 655 680 -- 723

2012–16 985 693 658 879 794

De Soto 2012 -- -- 778 908 856

2013 1,032 609 597 852 775

2014 987 696 654 648 746

2015 842 560 562 728 660

2016 730 567 591 -- 631

2012–16 903 609 624 779 723
46 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Dissolved solids (mg/L)—Discretely collected

Wamego 2012 -- -- 524 576 545

2013 720 442 403 519 491

2014 658 459 430 532 497

2015 652 329 405 524 445

2016 458 396 440 -- 428

2012–16 622 405 440 539 477

De Soto 2012 -- -- 462 571 511

2013 629 405 335 512 437

2014 583 396 387 376 425

2015 529 317 358 489 398

2016 466 373 319 -- 380

2012–16 547 369 374 491 424

Calcium (mg/L)—Discretely collected

Wamego 2012 -- -- 71.1 78.8 74.1

2013 86.3 61.6 59.4 73.7 67.3

2014 94.2 68.3 64.3 72.0 71.9

2015 87.8 52.8 66.0 73.1 66.8

2016 77.8 67.1 71.8 -- 71.4

2012–16 86.5 62.3 66.5 74.4 69.9

De Soto 2012 -- -- 59.0 79.1 68.2

2013 81.0 57.0 53.0 72.5 62.2

2014 86.6 59.9 60.3 59.1 64.9

2015 78.0 52.0 64.7 75.3 64.4

2016 82.5 65.0 58.0 -- 67.3

2012–16 82.1 58.0 59.0 71.9 65.1

Magnesium (mg/L)—Discretely collected

Wamego 2012 -- -- 17.5 19.7 18.4

2013 23.9 16.7 13.4 17.2 16.9

2014 21.6 17.2 14.5 15.9 16.8

2015 21.2 12.3 14.6 17.4 15.5

2016 18.5 16.0 14.5 -- 15.9

2012–16 21.3 15.5 14.9 17.6 16.5

De Soto 2012 -- -- 16.8 19.7 18.1

2013 20.8 14.7 12.0 17.0 15.2

2014 19.9 15.5 13.7 13.1 15.4

2015 18.4 11.9 13.5 16.9 14.5

2016 19.3 15.6 11.6 -- 15.3

2012–16 19.5 14.3 13.6 16.8 15.4
Table 2 47

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Bicarbonate (mg/L)—Discretely collected

Wamego 2012 -- -- -- 260 260

2013 261 194 171 225 202

2014 267 241 -- 176 228

2015 240 119 130 245 184

2016 212 194 176 -- 194

2012–16 250 190 166 238 208

De Soto 2012 -- -- -- 237 237

2013 241 174 153 200 183

2014 208 200 176 172 194

2015 236 174 176 211 197

2016 217 194 165 -- 197

2012–16 224 185 164 211 195

Sodium (mg/L)—Discretely collected

Wamego 2012 -- -- 83.5 93.6 87.6

2013 127 62.3 54.0 81.9 74.2

2014 102 66.5 62.5 79.5 73.6

2015 111 40.1 49.7 77.2 62.2

2016 51.1 43.4 55.9 -- 50.4

2012–16 97.7 53.1 61.1 83.1 68.6

De Soto 2012 -- -- 74.6 93.5 83.2

2013 108 52.0 40.7 75.8 61.6

2014 81.5 53.9 53.1 44.3 57.1

2015 75.5 38.7 37.4 68.5 50.4

2016 54.3 42.0 32.7 -- 42.2

2012–16 78.0 46.3 48.2 71.6 57.1

Chloride (mg/L)—Discretely collected

Wamego 2012 -- -- 99.3 117 106

2013 168 72.4 70.9 108 94.9

2014 136 79.1 79.1 107 94.0

2015 136 44.5 58.9 99.9 75.2

2016 55.6 45.4 71.0 -- 58.6

2012–16 124 60.5 75.8 108 85.0

De Soto 2012 -- -- 82.4 115 97.0

2013 141 59.5 51.0 99.8 77.0

2014 103 62.3 62.0 52.8 68.1

2015 88.6 43.3 41.5 85.6 58.8

2016 64.4 46.0 37.1 -- 47.9

2012–16 96.4 52.4 55.4 89.1 67.8
48 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Potassium (mg/L)—Discretely collected

Wamego 2012 -- -- 10.5 9.51 10.1

2013 8.37 8.06 8.70 9.38 8.57

2014 8.44 8.16 10.1 10.7 9.36

2015 9.77 9.01 9.66 9.10 9.35

2016 8.41 8.16 10.0 -- 9.02

2012–16 8.75 8.37 9.82 9.70 9.23

De Soto 2012 -- -- 9.83 9.41 9.64

2013 8.18 6.88 8.02 8.96 7.82

2014 8.53 7.26 10.1 8.38 8.52

2015 9.39 7.35 8.63 8.48 8.28

2016 7.23 6.91 8.23 -- 7.44

2012–16 8.34 7.13 8.98 8.84 8.27

Sulfate (mg/L)—Discretely collected

Wamego 2012 -- -- 99.6 106 102

2013 156 96.2 83.9 101 103

2014 140 93.9 81.7 108 100

2015 139 64.8 80.4 101 89.1

2016 97.8 84.4 92.3 -- 90.6

2012–16 133 84.3 87.6 104 96.7

De Soto 2012 -- -- 95.9 115 105

2013 140 82.6 71.3 107 92.5

2014 127 87.5 79.7 62.6 88.1

2015 110 60.0 67.5 97.2 77.9

2016 101 77.6 60.7 -- 78.1

2012–16 118 76.1 75.5 96.0 86.8

Total nitrogen1 (mg/L)—Discretely collected

Wamego 2012 -- -- 1.63 1.18 1.45

2013 0.854 2.59* 1.81* 1.40 1.80*

2014 1.51 1.92 1.60 1.91 1.75

2015 1.41 2.45 1.63 1.86 1.91

2016 2.28 3.03 2.19 -- 2.51

2012–16 1.51 2.47* 1.77* 1.60 1.89*

De Soto 2012 -- -- 1.37* 1.33 1.35*

2013 1.38 2.34* 2.13* 1.42* 1.96*

2014 1.73* 2.68* 1.80* 1.66 2.05*

2015 1.55 2.71* 1.54* 1.49* 1.96*

2016 1.65* 2.64* 2.18* -- 2.24*

2012–16 1.59* 2.61* 1.81* 1.47* 1.96*
Table 2 49

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Total phosphorus (mg/L)—Discretely collected

Wamego 2012 -- -- 0.386 0.237 0.326

2013 0.142 0.440 0.505 0.324 0.390

2014 0.247 0.420 0.445 0.517 0.421

2015 0.359 0.568 0.468 0.610 0.512

2016 0.368 0.547 0.592 -- 0.528

2012–16 0.279 0.494 0.479 0.428 0.443

De Soto 2012 -- -- 0.318 0.281 0.301

2013 0.213 0.388 0.596 0.321 0.417

2014 0.276 0.687 0.497 0.414 0.502

2015 0.361 0.730 0.440 0.447 0.532

2016 0.280 0.605 0.631 -- 0.537

2012–16 0.287 0.615 0.496 0.363 0.474

Nitrate (mg/L)—Discretely collected

Wamego 2012 -- -- 0.620 0.549 0.592

2013 0.211 0.957* 0.583* 0.716 0.651*

2014 0.920 0.561* 0.534 1.02 0.705*

2015 0.727 1.17* 0.704* 0.447 0.801*

2016 1.39 1.67* 0.894* -- 1.28*

2012–16 0.811 1.07* 0.667* 0.680 0.803*

De Soto 2012 -- -- 0.0185* 0.342 0.166*

2013 0.611 0.798* 0.518* 0.527* 0.628*

2014 0.844* 0.418* 0.447* 0.886 0.597*

2015 0.820 0.741* 0.489* 0.236* 0.595*

2016 0.715* 1.05* 0.675* -- 0.840*

2012–16 0.757* 0.751* 0.430* 0.486* 0.596*

Nitrite (mg/L)—Discretely collected

Wamego 2012 -- -- 0.00834 0.00793 0.00817

2013 0.0120 0.0496* 0.00661* 0.00381 0.0197*

2014 0.0229 0.0162* 0.00559 0.00396 0.0113*

2015 0.00772 0.0242* 0.00457* 0.00490 0.0113*

2016 0.0180 0.0429* 0.00294* -- 0.0205*

2012–16 0.0151 0.0321* 0.00561* 0.00524 0.0144*

De Soto 2012 -- -- 0.00149* 0.0102 0.00546*

2013 0.0121 0.0138* 0.00917* 0.00353* 0.0103*

2014 0.0884 0.0165* 0.00415* 0.00556* 0.0246*

2015 0.0120 0.0140* 0.00335* 0.00361* 0.00885*

2016 0.00665* 0.0104* 0.00579* -- 0.00791*

2012–16 0.0310* 0.0137* 0.00479* 0.00615* 0.0123*
50 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Nitrate plus nitrite (mg/L)—Discretely collected

Wamego 2012 -- -- 0.629 0.557 0.600

2013 0.223 1.01* 0.708* 0.720 0.713*

2014 0.943 0.577 0.539 1.02 0.716

2015 0.735 1.19 0.709 0.452 0.812

2016 1.40 1.71 0.897 -- 1.30

2012–16 0.826 1.10* 0.696* 0.685 0.828*

De Soto 2012 -- -- 0.02* 0.353 0.171*

2013 0.623 0.812* 0.528* 0.531* 0.639*

2014 0.932* 0.435* 0.452* 0.890 0.621*

2015 0.832 0.755* 0.493* 0.239* 0.604*

2016 0.722* 1.06* 0.681* -- 0.848*

2012–16 0.788* 0.764* 0.435* 0.492* 0.608*

Orthophosphorus (mg/L)—Discretely collected

Wamego 2012 -- -- 0.250 0.190 0.226

2013 0.088 0.126 0.232 0.245 0.178

2014 0.207 0.158 0.262 0.369 0.243

2015 0.300 0.306 0.342 0.282 0.311

2016 0.279 0.256 0.269 -- 0.266

2012–16 0.219 0.213 0.271 0.273 0.247

De Soto 2012 -- -- 0.107 0.154 0.128

2013 0.119 0.111 0.208 0.192 0.158

2014 0.203 0.084 0.231 0.301 0.190

2015 0.282 0.157 0.269 0.151 0.209

2016 0.140 0.131 0.212 -- 0.162

2012–16 0.191 0.122 0.206 0.197 0.175

Ammonia (mg/L)—Discretely collected

Wamego 2012 -- -- 0.013* 0.007* 0.011*

2013 0.028* 0.054* 0.013* 0.013* 0.028*

2014 0.042* 0.008* 0.005* 0.013* 0.013*

2015 0.036* 0.053* 0.009* 0.024* 0.030*

2016 0.102* 0.024* 0.006* -- 0.033*

2012–16 0.052* 0.034* 0.009* 0.014* 0.024*

De Soto 2012 -- -- 0.010* 0.005* 0.008*

2013 0.042* 0.015* 0.016* 0.013* 0.019*

2014 0.064* 0.037* 0.005* 0.030 0.032*

2015 0.036* 0.022* 0.008 0.021* 0.020*

2016 0.046* 0.017* 0.024* -- 0.026*

2012–16 0.047* 0.023* 0.012* 0.017* 0.022*
Table 2 51

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Arsenic (mg/L)—Discretely collected

Wamego 2012 -- -- -- 0.00599 0.00599

2013 0.00407 0.00408 0.00562 0.00517 0.00481

2014 0.00401 0.00427 0.00664 0.00549 0.00523

2015 0.00475 0.00473 0.00647 0.00577 0.00550

2016 0.00422 0.00409 0.00594 -- 0.00491

2012–16 0.00426 0.00431 0.00617 0.00563 0.00518

De Soto 2012 -- -- -- 0.00528 0.00528

2013 0.00347 0.00349 0.00537 0.00464 0.00431

2014 0.00391 0.00322 0.00646 0.00473 0.00456

2015 0.00447 0.00374 0.00578 0.00444 0.00456

2016 0.00333 0.00327 0.00496 -- 0.00385

2012–16 0.00381 0.00345 0.00567 0.00481 0.00442

Fluoride (mg/L)—Discretely collected

Wamego 2012 -- -- 0.316 0.313 0.315

2013 0.287 0.281 0.300 0.319 0.296

2014 0.307 0.301 0.340 0.313 0.317

2015 0.319 0.271 0.292 0.291 0.289

2016 0.272 0.266 0.275 -- 0.271

2012–16 0.296 0.280 0.304 0.308 0.297

De Soto 2012 -- -- 0.317 0.321 0.319

2013 0.299 0.293 0.292 0.326 0.299

2014 0.333 0.300 0.338 0.290 0.315

2015 0.298 0.260 0.283 0.278 0.276

2016 0.276 0.258 0.261 -- 0.264

2012–16 0.302 0.277 0.299 0.304 0.293

Selenium (mg/L)—Discretely collected

Wamego 2012 -- -- -- 0.00117 0.00117

2013 0.00134 0.00121 0.00104 0.00106 0.00115

2014 0.00145 0.00110 0.00105 0.00107 0.00113

2015 0.00129 0.00103 0.00103 0.000916 0.00105

2016 0.00139 0.00117 0.00109 -- 0.00118

2012–16 0.00137 0.00112 0.00105 0.00105 0.00113

De Soto 2012 -- -- -- 0.000897 0.000897

2013 0.000984 0.000929 0.000806 0.000895 0.000891

2014 0.00112 0.000847 0.000887 0.000713 0.000885

2015 0.00104 0.000824 0.000776 0.000673 0.000822

2016 0.000996 0.000924 0.000759 -- 0.000888

2012–16 0.00104 0.000876 0.000809 0.000795 0.000871
52 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Fecal coliform (CFUs/100 mL)—Discretely collected

Wamego 2012 -- -- 725 86.7 470

2013 21.8 1,607 740 38.3 744

2014 34.7 538 354 58.8 286

2015 16.7 242 442 2,617 770

2016 17.0 903 1,778 -- 1,088

2012–16 22.5 795 810 744 670

De Soto 2012 -- -- 591 54.5 377

2013 17.7 684 1,875 59.3 743

2014 9.00 1,539 676 76.3 671

2015 4.50 1,452 409 2,249 1,062

2016 37.0 2,148 3,766 -- 2,389

2012–16 17.0 1,456 1,462 647 1,066

Escherichia coli (CFUs/100 mL)—Discretely collected

Wamego 2012 -- -- 207 66.1 150

2013 14.9 1,331 329 30.7 516

2014 20.3 593 153 44.0 229

2015 15.7 162 155 2010 526

2016 9.00 714 888 -- 638

2012–16 15.0 674 346 571 427

De Soto 2012 -- -- 44.3 40.2 42.7

2013 16.3 545 526 62.3 350

2014 10.0 1,520 67.4 226 522

2015 5.67 3,382 307 2,050 1,687

2016 37.7 2,759 3,765 -- 2,607

2012–16 17.4 2,173 988 630 1,105

Enterococci (CFUs/100 mL)—Discretely collected

Wamego 2012 -- -- 88.0 83.9 86.4

2013 214 965 496 53.3 506

2014 79.7 2,023 188 108 662

2015 117 330 445 142 301

2016 67.0 1,531 2,341 -- 1,565

2012–16 119 1,170 712 97 633

De Soto 2012 -- -- 296 17.7 184

2013 156 789 685 44.7 498

2014 50.7 2,478 214 133 798

2015 40.0 3,065 311 17.3 1,135

2016 173 2,461 2,834 -- 2,130

2012–16 105 2,239 874 56.3 979
Table 2 53

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Actinomycetes (colonies/mL)—Discretely collected

Wamego 2012 -- -- 344 63.3 232

2013 27.0 1,220 2,282 103 1,187

2014 101 1,291 252 1,243 765

2015 80.0 1,536 196 177 623

2016 447 980 2,127 -- 1,386

2012–16 171 1,273 1,069 433 870

De Soto 2012 -- -- 29.5 34.5 31.5

2013 146 1,554 2,270 120 1,305

2014 76.0 2,058 387 280 843

2015 570 2,735 242 3,150 1,789

2016 953 713 3,341 -- 1,981

2012–16 424 1,832 1,289 948 1,239

Regression-estimated chlorophyll (μg/L)—Continuous water-quality monitor

Wamego 2012 -- -- 64.3 29.9 38.9

2013 29.7 65.0 48.1 31.1 43.6

2014 19.2 98.0 55.7 25.6 46.2

2015 17.3 34.2 59.3 38.2 39.8

2016 19.7 28.6 21.1 -- 23.2

2012–16 22.1 79.4 47.5 31.2 39.0

De Soto 2012 -- -- 133 73.5 100

2013 51.5 90.0 56.3 73.8 68.2

2014 42.4 121 93.0 51.2 72.8

2015 33.7 59.5 59.4 72.7 58.5

2016 66.5 53.8 41.6 -- 54.0

2012–16 50.0 104 73.5 67.6 67.8

Phytoplankton (cells/mL)—Discretely collected

Wamego 2012 -- -- 83,955 19,498 60,516

2013 13,545 58,531 40,044 23,526 38,010

2014 2,204 50,210 59,510 10,316 38,285

2015 1,176 10,863 57,812 45,626 31,478

2016 25,382 11,734 15,586 -- 16,309

2012–16 10,577 32,625 52,271 24,823 35,878

De Soto 2012 -- -- 290,411 106,589 223,566

2013 20,859 80,703 133,050 67,972 91,284

2014 3,899 86,443 91,163 10,704 60,565

2015 4,417 54,501 107,735 102,225 73,451

2016 30,980 36,499 28,464 -- 31,873

2012–16 15,039 65,076 133,900 72,132 87,310
54 Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas

Table 2. Seasonal and annual means for discretely collected and continuously measured water-quality constituents at the Kansas 

River at Wamego, Kansas, and Kansas River at De Soto, Kansas, streamgages (U.S. Geological Survey stations 06887500 and 06892350, 

respectively) during July 2012 through September 2016.—Continued

[winter, January through March; spring, April through June; summer, July through September; fall, October through December; °C, degrees Celsius; --, no data; 

mg/L, milligram per liter; FNU, formazin nephelometric unit; μs/cm, microsiemen per centimeter at 25 °C; *, indicates that the mean value was calculated using 

one or more censored values (less than the minimum reporting limit), and censored values were substituted with a value one-half of the minimum reporting 

limit; CFU/100 mL, colony forming unit per 100 milliliters; colonies/mL, colonies per milliliter; μg/L, microgram per liter]

Site Year

Mean

Winter Spring Summer Fall Annual

Cyanobacteria (cells/mL)—Discretely collected

Wamego 2012 -- -- 32,418 2,365 21,490

2013 1,504 2,057 3,737 102 2,292

2014 207 1,094 12,299 90.8 4,682

2015 103 68.2 3,877 2,162 1,717

2016 12.3 1,002 194 -- 444

2012–16 456 1,012 11,018 1,252 5,002

De Soto 2012 -- -- 103,257 3,285 66,903

2013 954 4,764 36,934 106 16,972

2014 179 3,045 19,942 747 8,070

2015 369 306 36,719 31,718 18,428

2016 923 1,790 735 -- 1,152

2012–16 606 2,404 40,664 9,555 19,109

1

Calculated as the sum of ammonia plus organic nitrogen and nitrite plus nitrate nitrogen.
Appendixes 1–6

Appendixes 1–6 are available at https://doi.org/10.3133/sir20185089.
For more information about this publication, contact

Director, USGS Kansas Water Science Center 

1217 Biltmore Drive

Lawrence, KS 66049

(785) 842–9909

For additional information visit https://www.usgs.gov/centers/kswsc

Publishing support provided by the

Rolla Publishing Service Center

Graham and others—Cyanobacteria and Associated Toxins and Taste-and-Odor Compounds in the Kansas River, Kansas —Scientific Investigations Report 2018–5089

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20185089