Prepared in cooperation with the City of Wichita, Kansas

Effects of Aquifer Storage and Recovery Activities on Water 

Quality in the Little Arkansas River and Equus Beds Aquifer, 

South-Central Kansas, 2011–14

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2016–5042
Cover. Photograph showing the Little Arkansas River near Sedgwick, Kansas, May 2012, by

Mandy Stone, U.S. Geological Survey.
Effects of Aquifer Storage and Recovery 

Activities on Water Quality in the Little 

Arkansas River and Equus Beds Aquifer, 

South-Central Kansas, 2011–14

By Mandy L. Stone, Jessica D. Garrett, Barry C. Poulton, and Andrew C. Ziegler

Prepared in cooperation with the City of Wichita, Kansas

Scientific Investigations Report 2016–5042

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Suggested citation:

Stone, M.L., Garrett, J.D., Poulton, B.C., and Ziegler, A.C., 2016, Effects of aquifer storage and recovery activities on 

water quality in the Little Arkansas River and Equus Beds aquifer, south-central Kansas, 2011–14: U.S. Geological 

Survey Report 2016–5024, 88 p., http://dx.doi.org/10.3133/sir20165042.

ISSN 2328-0328 (online)
iii

Contents

Acknowledgments.......................................................................................................................................xii

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

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

Overview of the Equus Beds Aquifer Storage and Recovery Project..........................................3

Purpose and Scope ..............................................................................................................................4

Description of Study Area and Background Information...............................................................4

Recent Investigations ..........................................................................................................................6

Methods...........................................................................................................................................................6

Data Collection......................................................................................................................................7

Continuous Water-Quality Monitoring......................................................................................7

Discrete Water-Quality Samples...............................................................................................8

Streambed-Sediment Samples..................................................................................................8

Habitat Assessment ....................................................................................................................9

Macroinvertebrates ....................................................................................................................9

Fish .................................................................................................................................................9

Data Analysis.......................................................................................................................................10

Water Chemistry Data...............................................................................................................10

Macroinvertebrate Data...........................................................................................................11

Fish Data......................................................................................................................................11

Geochemical Modeling.............................................................................................................12

Quality Assurance and Quality Control ...........................................................................................12

Water Chemistry Data...............................................................................................................12

Streambed Sediment Data .......................................................................................................18

Macroinvertebrate Data...........................................................................................................18

Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas 

River and Equus Beds Aquifer .....................................................................................................18

Surface Water Physicochemical and Biological Conditions of the Little Arkansas River

Upstream and Downstream from the Aquifer Storage and Recovery Facility............18

Streamflow..................................................................................................................................19

Water Quality of Stream Water and Releases......................................................................19

Continuous Water-Quality of Stream Water and Releases .......................................19

Discrete Water-Quality of Stream Water and Releases ............................................25

Dissolved and Suspended Solids, Major Ions, and Suspended Sediment ....25

Nutrients....................................................................................................................28

Trace Elements and Associated Compounds......................................................30

Coliform Bacteria and Viral Indicators.................................................................32

Biological Activity Reaction Tests ........................................................................34

Organic Compounds................................................................................................34

Streambed-Sediment Chemistry .............................................................................................35

Habitat Assessment ..................................................................................................................38

Macroinvertebrates ..................................................................................................................40

Macroinvertebrate Community Composition ...............................................................41
iv

Macroinvertebrate Metrics ............................................................................................41

Fish Community Composition and Metrics ............................................................................48

Groundwater Environmental Conditions ........................................................................................51

Groundwater Quality .................................................................................................................51

Continuous Groundwater Quality...................................................................................51

Discrete Groundwater Quality........................................................................................58

Solids and Primary Ions..........................................................................................58

Nutrients and Organic Carbon...............................................................................58

Indicator Bacteria....................................................................................................58

Trace Elements.........................................................................................................62

Pesticides..................................................................................................................62

Brominated and Chlorinated Organic Compounds ............................................62

Radioactive Chemistry ............................................................................................62

Geochemical Effects ................................................................................................................62

Summary and Conclusions.........................................................................................................................70

References Cited..........................................................................................................................................73

Appendix 1. Water-Quality Data of the Little Arkansas River and Equus Beds Aquifer, 

Aquifer Storage and Recovery Project, South-Central Kansas, 2011–14 .............................84

Appendix 2. S+® Output of Regression Model Development and Graphs from Simple 

Linear Regression Analysis ..........................................................................................................85

Figures

1. Maps showing study area and locations of monitoring wells for the city of Wichita,

Kansas, Equus Beds aquifer storage and recovery project..................................................3

2. Graph showing duration curve for hourly measured streamflow for the Little

Arkansas River near Sedgwick, Kansas, January 2011 through December 2014 ...........19

3. Graphs showing duration curves for hourly measured constituents for the Little

Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, and the Little Arkansas River near Sedgwick, Kansas, March

2011 through December 2014....................................................................................................20

4. Graph showing relations between sensor and laboratory measured nitrate plus

nitrite for the Little Arkansas River near Sedgwick, Kansas, March 2012 through

December 2014............................................................................................................................22

5. Graphs showing duration curves for hourly measured or computed constituents 

for the Little Arkansas River near Sedgwick, Kansas, January 2011 through 

December 2014............................................................................................................................23

6. Graphs showing relations between discrete and computed constituents using

regression models for the Little Arkansas River near Sedgwick, Kansas, March

2012 through December 2014....................................................................................................24

7. Graphs showing relation between discrete and computed constituents using

models developed in Rasmussen and others (2016) for the Little Arkansas River 

near Sedgwick, Kansas, January 2011 through December 2014........................................25

8. Diagrams showing mean relative abundances of macroinvertebrate functional

feeding groups for the Little Arkansas River upstream from the aquifer storage 

and recovery facility near Sedgwick, Kansas, and the Little Arkansas River near 

Sedgwick, Kansas, May 2011 through August 2014..............................................................42
v

9. Diagrams showing mean relative abundances of macroinvertebrate behavioral 

groups for the Little Arkansas River upstream from the aquifer storage and

recovery facility near Sedgwick, Kansas, and the Little Arkansas River near

Sedgwick, Kansas, May 2011 through August 2014. ...........................................................43

10. Diagrams showing mean relative abundances of macroinvertebrate tolerance

groups for the Little Arkansas River upstream from the aquifer storage and

recovery facility near Sedgwick, Kansas, and the Little Arkansas River near

Sedgwick, Kansas, May 2011 through August 2014. ............................................................44

11. Graphs showing mean macroinvertebrate aquatic life-support metrics for the

Little Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, and the Little Arkansas River near Sedgwick, Kansas, April 2011

through August 2014...................................................................................................................49

12. Diagrams showing mean fish feeding group percentage of total abundance for the

Little Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, and the Little Arkansas River near Sedgwick, Kansas, 

September 2011 and 2012 and September 2013 and August 2014......................................52

13. Diagrams showing mean fish tolerance group percentage of total abundance for the

Little Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, and the Little Arkansas River near Sedgwick, Kansas,

September 2011 and 2012 and September 2013 and August 2014. ....................................53

14. Graphs showing groundwater conditions continuously monitored or measured in

wells near infiltration basin, 2011 through 2014.....................................................................55

15. Graphs showing saturation indices of minerals calculated for stream water and

groundwater samples collected from monitoring wells near the infiltration basin,

2011 through 2014 .......................................................................................................................68

16. Graphs showing pH of minerals calculated for groundwater samples collected

from monitoring wells near the infiltration basin, 2011 through 2014 ................................69

Appendix Figures

2–1. S+® output of regression model development using chromophoric dissolved

organic matter as the explanatory variable for dissolved organic carbon from the

Little Arkansas River near Sedgwick, Kansas, 2009 through 2012 .....................................85

2–2. S+® output graphs from simple linear regression analysis from the Little Arkansas

River near Sedgwick, Kansas, 2012 through 2014.................................................................86

2–3. S+® output of regression model development using chromophoric dissolved

organic matter and turbidity as explanatory variables for total organic carbon from

the Little Arkansas River near Sedgwick, Kansas, 2009 through 2012 ..............................87

2–4. S+® output graphs from simple linear regression analysis using turbidity and

log-transformed chromophoric dissolved organic matter as explanatory variables

for total organic carbon concentrations from the Little Arkansas River near

Sedgwick, Kansas, 2012 through 2014 ....................................................................................88
vi

Tables

1. Volumes of discharge from the Little Arkansas River aquifer storage and recovery

facility and streamflow volumes from the Little Arkansas River near Sedgwick,

Kansas, May 2013 through September 2014 ............................................................................5

2. Total and mean annual precipitation during 2011 through 2014, and mean annual

precipitation during 1900 through 2014 at the “Newton 2 SW” station...............................5

3. Summary statistics for continuously measured physicochemical properties and

computed water-quality constituents of interest for the Little Arkansas River

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas, 

Little Arkansas River near Sedgwick, Kansas, and discharge from the Little 

Arkansas River aquifer storage and recovery facility near Sedgwick, Kansas, 

March 2011 through December 2014.......................................................................................13

4. Discretely collected dissolved and suspended solids, primary ions, and suspended

sediment summary statistics for the Little Arkansas River upstream from the

aquifer storage and recovery facility near Sedgwick, Kansas, Little Arkansas River

near Sedgwick, Kansas, and discharge from the Little Arkansas River aquifer

storage and recovery facility near Sedgwick, Kansas, March 2011 through

September 2014...........................................................................................................................27

5. Discretely collected nutrient and carbon summary statistics for the Little Arkansas

River upstream from the aquifer storage and recovery facility near Sedgwick,

Kansas, Little Arkansas River near Sedgwick, Kansas, and discharge from the Little

Arkansas River aquifer storage and recovery facility near Sedgwick, Kansas,

March 2011 through September 2014......................................................................................29

6. Discretely collected trace element and associated compound summary statistics

for the Little Arkansas River upstream from the aquifer storage and recovery

facility near Sedgwick, Kansas, Little Arkansas River near Sedgwick, Kansas, and

discharge from the Little Arkansas River aquifer storage and recovery facility near

Sedgwick, Kansas, March 2011 through September 2014...................................................31

7. Discretely collected viral and bacteria summary statistics for the Little Arkansas

River upstream from the aquifer storage and recovery facility near Sedgwick,

Kansas, Little Arkansas River near Sedgwick, Kansas, and discharge from the Little

Arkansas River aquifer storage and recovery facility near Sedgwick, Kansas,

March 2011 through September 2014......................................................................................33

8. Discretely collected pesticide summary statistics for the Little Arkansas River

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas,

Little Arkansas River near Sedgwick, Kansas, and discharge from the Little

Arkansas River aquifer storage and recovery facility near Sedgwick, Kansas,

March 2011 through September 2014......................................................................................36

9. Streambed-sediment nutrients, carbon, and trace element summary statistics for

the Little Arkansas River upstream from the aquifer storage and recovery facility

near Sedgwick, Kansas, Little Arkansas River near Sedgwick, Kansas, and

discharge from the Little Arkansas River Aquifer Storage and Recovery facility

near Sedgwick, Kansas, April 2011 through April 2013 and July through September

2014 ...............................................................................................................................................37

10. Streambed-sediment organic wastewater indicator compound summary statistics

for the Little Arkansas River upstream from the aquifer storage and recovery

facility near Sedgwick, Kansas, Little Arkansas River near Sedgwick, Kansas, and

discharge from the Little Arkansas River aquifer storage and recovery facility near

Sedgwick, Kansas, April 2011 through April 2013 and July through September 2014 ....39
vii

11. Habitat assessment scores for the Little Arkansas River upstream from the aquifer

storage and recovery facility near Sedgwick, Kansas, and Little Arkansas River

near Sedgwick, Kansas, during August 2011 and September 2014 ...................................40

12. List of five most dominant macroinvertebrate taxa for the Little Arkansas River

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas, 

and Little Arkansas River near Sedgwick, Kansas, April 2011 through April 2013 and 

September 2013 through August 2014.....................................................................................41

13. Mean selected macroinvertebrate metric values and Kansas Department of Health

and Environment aquatic-life-support status for the Little Arkansas River upstream

from the aquifer storage and recovery facility near Sedgwick, Kansas, and Little

Arkansas River near Sedgwick, Kansas, April 2011 through April 2013 and

September 2013 through August 2014.....................................................................................45

14. Criteria for four macroinvertebrate metrics used in Kansas to evaluate

aquatic-life-support status of streams....................................................................................48

15. Mean fish community summary statistics for the Little Arkansas River upstream

from the aquifer storage and recovery facility near Sedgwick, Kansas, and Little

Arkansas River near Sedgwick, Kansas, September 2011 and 2012 and September

2013 and August 2014.................................................................................................................50

16. Mean selected fish community metrics for the Little Arkansas River upstream from

the aquifer storage and recovery facility and the Little Arkansas River near

Sedgwick, Kansas, during September 2011 and 2012 and September 2013 and

August 2014..................................................................................................................................51

17. Physicochemical properties for sites near the recharge basin near Sedgwick,

Kansas before, during, and after artificial recharge and at the Little Arkansas River

near Sedgwick, Kansas, summary of daily statistics from continuously measured

data ...............................................................................................................................................54

18. Discretely collected solids and primary ions summary statistics for groundwater

samples at sites near the recharge basin near Sedgwick, Kansas, before and after

artificial recharge .......................................................................................................................59

19. Discretely collected nutrient and carbon summary statistics for groundwater

samples at sites near the recharge basin near Sedgwick, Kansas, before and 

after artificial recharge..............................................................................................................60

20. Discretely collected bacteria summary statistics for groundwater samples at sites

near the recharge basin near Sedgwick, Kansas, before and after artificial 

recharge.......................................................................................................................................61

21. Discretely collected trace element summary statistics for groundwater samples

at sites near the recharge basin near Sedgwick, Kansas, before and after artificial

recharge.......................................................................................................................................63

22. Discretely collected pesticides summary statistics for groundwater samples at

sites near the recharge basin near Sedgwick, Kansas, before and after artificial

recharge.......................................................................................................................................64

23. Discretely collected brominated and chlorinated organic compounds and

radioactivity summary statistics for groundwater samples at sites near the

recharge basin near Sedgwick, Kansas, before and after artificial recharge.................65

24. Saturation indices for select minerals for groundwater samples collected at sites

near the recharge basin near Sedgwick, Kansas, before and after artificial 

recharge.......................................................................................................................................67
viii

Appendix Tables

1–1. Discretely collected constituents from the residual basin aquifer storage and

recovery treatment plant near Sedgwick, Kansas, diverted water at the Sedgwick

recharge site, Kansas, and treated source water at the high service pump station, 

July 2012 through September 2014 ..........................................................................................84

1–2. Sample collection dates and streamflow conditions for discrete water-quality

samples collected at surface-water sites, the residuals return line site, and

groundwater well sites, March 2011 through September 2014 ..........................................84

1–3. High flow summary statistics for continuously measured physicochemical

properties and computed water-quality constituents of interest for the Little

Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, the Little Arkansas River near Sedgwick, Kansas, discharge

from the Little Arkansas River aquifer storage and recovery facility near Sedgwick,

Kansas, January 2011 through December 2014.....................................................................84

1–4. Regression models and summary statistics for continuous dissolved and total

organic carbon concentration computations for the Little Arkansas River near

Sedgwick, Kansas, March 2012 through September 2014...................................................84

1–5. Dissolved and total organic carbon datasets using chromophoric dissolved organic

matter and turbidity as explanatory variables for the Little Arkansas River near

Sedgwick, Kansas, 2012 through 2014 ....................................................................................84

1–6. Discretely collected during high flow condition water-quality constituent summary

statistics for the Little Arkansas River upstream from the aquifer storage and

recovery facility near Sedgwick, Kansas, the Little Arkansas River near Sedgwick,

Kansas, and discharge from the Little Arkansas River aquifer storage and recovery

facility near Sedgwick, Kansas, March 2011 through September 2014 ............................84

1–7. Discrete organic material characterization data for samples collected at the Little

Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, the Little Arkansas River near Sedgwick, Kansas, and

discharge from the Little Arkansas River aquifer storage and recovery facility near

Sedgwick, Kansas, March 2011 through September 2014...................................................84

1–8. Macroinvertebrate taxa abundances identified for the Little Arkansas River

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas,

and the Little Arkansas River near Sedgwick, Kansas, April 2011 through August

2014 ...............................................................................................................................................84

1–9. Seasonal and annual mean selected macroinvertebrate metric values and Kansas

Department of Health and Environment aquatic life-support status for the Little

Arkansas River upstream from the aquifer storage and recovery facility near

Sedgwick, Kansas, and the Little Arkansas River near Sedgwick, Kansas, April 2011

through August 2014...................................................................................................................84

1–10. Constituents analyzed but not detected in groundwater samples for sites near the

recharge basin near Sedgwick, Kansas, January 2011 to December 2014......................84
ix

Conversion Factors

[International System of Units to U.S. customary units]

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

micrometer (μm) 0.001 millimeter (mm)

meter (m) 1.094 yard (yd) 

Area

square kilometer (km2

) 0.3861 square mile (mi2)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

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

 °F = (1.8 × °C) + 32.

Supplemental Information

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

25 °C).

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

or micrograms per liter (μg/L).

Concentrations of water-quality constituents are given in colony forming units per 100 milliliters 

(cfu/100 mL), colonies per 100 milliliters (col/100 mL), most probable number per 100 milliliters 

(mpn/100 mL), or plaque forming units per 100 milliliters (pfu/100 mL).

Concentrations of streambed-sediment constituents are given in milligrams per kilogram 

(mg/kg).

Activities for radioactive constituents in water are given in picocuries per liter (pCi/L).

Flow rate is given in cubic feet per second (ft3

/s) or million gallons per day (Mgal/d).

Volume is given in million gallons (Mgal).

Aquifer storage volume is given in billion gallons (Bgal).

Turbidity is given in formazin nephelometric units (FNU).

Precipitation is given in inches (in.).
x

Abbreviations

1Q first quartile

3Q third quartile

ASR aquifer storage and recovery

BART Biological Activity Reaction Test

CDOM chromophoric (colored) dissolved organic matter

Df degrees of freedom

DOC dissolved organic carbon

CIAT 2-Chloro-4-isopropylamino-6-amino-s-triazine

CV coefficient of variation

E. coli Escherichia coli

EPA U.S. Environmental Protection Agency

EPT Ephemeroptera, Plecoptera, and Trichoptera

F Value explained variance divided by unexplained variance

FID floating intercedent device

GIS geographic information system

h hour

HBMP hydrobiological monitoring program

IBI Index of Biotic Integrity

ILWS Integrated Local Water Supply

KDHE Kansas Department of Health and Environment

LOG10 log10

Max maximum

MCL maximum contaminant level

MCLG maximum contaminant level goal

Min minimum

NPDES National Pollutant Discharge Elimination System

NWQL National Water Quality Laboratory

ORP oxidation-reduction potential

OWC organic wastewater-indicator compound

PEC probable effect concentration

Post-ASR May 2013 through December 2014

Pre-ASR January 2011 through April 2013

Pr(F) probability value of an F-test
xi

Pr(>|t|) probability of observing a test statistic that follows a Student’s t 

 distribution if the null hypothesis is supported

p-value probability of observing a test statistic that is as extreme or more 

extreme than currently observed assuming that the null hypothesis is true

QA/QC quality assurance and quality control

R2 coefficient of determination

Residual standard error square root of residual sum of squares divided by degrees of 

 freedom

RMSE root mean square error

ROS regression on order statistics

RPD relative percentage difference

SI saturation index

SMCL secondary maximum contaminant level

Sum of Sq sum of squares

t value coefficient divided by its standard error

TBY turbidity

THM trihalomethane

TMDL total maximum daily load

TOC total organic carbon

USGS U.S. Geological Survey
xii

Acknowledgments

The authors thank Mike Jacobs, Deb Ary, and Scott Macey of the city of Wichita; and Tim Boese 

and the Groundwater Management District 2 staff for technical assistance and providing data 

and information about the Equus Beds aquifer storage and recovery project. The authors also 

thank Terryl Pajor, Vernon Strasser, and the laboratory staff at the city of Wichita Municipal 

Water and Wastewater Laboratory for laboratory analyses. The authors greatly appreciate the 

efforts of Jeff Conley, Aaron Austin, Ryan Waters, Jessica Mounts, Mark Van Scoyoc, and other 

personnel from the Kansas Department of Wildlife, Parks and Tourism who helped with fish 

sampling.

The authors thank the U.S. Geological Survey staff that assisted with data collection, analysis, 

and interpretation, including Billy Justus, Trudy Bennett, Carlen Collins, Beatrice Richie, Barb 

Dague, John Rosendale, and Chelsea Paxson. Brian Kelly of the Missouri Water Science Center 

and Teresa Rasmussen of the Kansas Water Science Center provided helpful reviews that contributed to technical and editorial clarity of the report.
Effects of Aquifer Storage and Recovery Activities on 

Water Quality in the Little Arkansas River and Equus Beds 

Aquifer, South-Central Kansas, 2011–14

By Mandy L. Stone, Jessica D. Garrett, Barry C. Poulton, and Andrew C. Ziegler

Abstract

The Equus Beds aquifer in south-central Kansas is a 

primary water source for the city of Wichita. The Equus Beds 

aquifer storage and recovery (ASR) project was developed to 

help the city of Wichita meet increasing current (2016) and 

future water demands. The Equus Beds ASR project pumps 

water out of the Little Arkansas River during above-base flow 

conditions, treats it using drinking-water quality standards as 

a guideline, and recharges it into the Equus Beds aquifer for 

later use. Phase II of the Equus Beds ASR project currently 

(2016) includes a river intake facility and a surface-water 

treatment facility with a 30 million gallon per day capacity. 

Water diverted from the Little Arkansas River is delivered to 

an adjacent presedimentation basin for solids removal. Subsequently, waste from the surface-water treatment facility and 

the presedimentation basin is returned to the Little Arkansas 

River through a residuals return line. The U.S. Geological 

Survey, in cooperation with the city of Wichita, developed and 

implemented a hydrobiological monitoring program as part 

of the ASR project to characterize and quantify the effects of 

aquifer storage and recovery activities on the Little Arkansas 

River and Equus Beds aquifer water quality. 

Data were collected from 2 surface-water sites (one 

upstream and one downstream from the residuals return 

line), 1 residuals return line site, and 2 groundwater well 

sites (each having a shallow and deep part): the Little Arkansas River upstream from the ASR facility near Sedgwick, 

Kansas (upstream surface-water site 375350097262800), 

about 0.03 mile (mi) upstream from the residuals return 

line site; the Little Arkansas River near Sedgwick, Kans. 

(downstream surface-water site 07144100), about 1.68 mi 

downstream from the residuals return line site; discharge 

from the Little Arkansas River ASR facility near Sedgwick, 

Kansas (residuals return line site 375348097262800); 25S 

01 W 07BCCC01 SMW–S11 near CW36 (MW–7 shallow groundwater well site 375327097285401); 25S01 W 

07BCCC02 DMW–S10 near CW36 (MW–7 deep groundwater well site 375327097285402); 25S 01W 07BCCA01 

SMW–S13 near CW36 (MW–8 shallow groundwater 

well site 375332097284801); and 25S 01W 07BCCA02 

DMW–S14 near CW36 (MW–8 deep groundwater well site 

375332097284802). The U.S. Geological Survey, in cooperation with the city of Wichita, assessed the effects of the ASR 

Phase II facility residuals return line discharges on stream 

quality of the Little Arkansas River by measuring continuous 

physicochemical properties and collecting discrete waterquality and sediment samples for about 2 years pre- (January 

2011 through April 2013) and post-ASR (May 2013 through 

December 2014) Phase II facility operation upstream and 

downstream from the ASR Phase II facility. Additionally, habitat variables were quantified and macroinvertebrate and fish 

communities were sampled upstream and downstream from 

the ASR Phase II facility during the study period. To assess 

the effects of aquifer recharge on Equus Beds groundwater 

quality, continuous physicochemical properties were measured 

and discrete water-quality samples were collected before and 

during the onset of Phase II aquifer recharge in two (shallow 

and deep) groundwater wells.

Little Arkansas River streamflow was about 10 times 

larger after the facility began operating because of greater 

rainfall. Residuals return line release volumes were a very 

minimal proportion (0.06 percent) of downstream streamflow 

volume during the months the ASR facility was operating. 

Upstream and downstream continuously measured water 

temperature and dissolved oxygen median differences were 

smaller post-ASR than pre-ASR. Turbidity generally was 

smaller at the downstream site throughout the study period and 

decreased at both sites after the ASR Phase II facility began 

discharging despite a median residuals return line turbidity 

that was about an order of magnitude larger than the median 

turbidity at the downstream site. Upstream and downstream 

continuously measured turbidity median differences were 

larger post-ASR than pre-ASR. Median post-ASR continuously measured nitrite plus nitrate and continuously computed 

total suspended solids and suspended-sediment concentrations 

were smaller than pre-ASR likely because of higher streamflows and dilution; whereas, median continuously computed 

dissolved and total organic carbon concentrations were larger 

likely because of higher streamflows and runoff conditions.
2 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

None of the discretely measured water-quality constituents (dissolved and suspended solids, primary ions, suspended 

sediment, nutrients, carbon, trace elements, viral and bacterial 

indicators, and pesticides) in surface water were significantly 

different between the upstream and downstream sites after the 

ASR Phase II facility began discharging; however, pre-ASR 

calcium, sodium, hardness, manganese, and arsenate concentrations were significantly larger at the upstream site, which 

indicates that some water-quality conditions at the upstream 

and downstream sites were more similar post-ASR. Most of the 

primary constituents that make up dissolved solids decreased 

at both sites after the ASR Phase II facility began operation. 

Discretely collected total suspended solids concentrations were 

similar between the upstream and downstream sites before the 

facility began operating but were about 27 percent smaller at 

the downstream site after the facility began operating, despite 

the total suspended solids concentrations in the residuals return 

line being 15 times larger than the downstream site.

Overall habitat scores were indicative of suboptimal 

conditions upstream and downstream from the ASR Phase 

II facility throughout the study period. Substrate fouling and 

sediment deposition mean scores indicated marginal conditions at the upstream and downstream sites during the study 

period, demonstrating that sediment deposition was evident 

pre- and post-ASR and no substantial changes in these habitat characteristics were noted after the ASR Phase II facility 

began discharging. Macroinvertebrate community composition 

(evaluated using functional feeding, behavioral, and tolerance 

metrics) generally was similar between sites during the study 

period. Fewer macroinvertebrate metrics were significant 

between the upstream and downstream sites post-ASR (6) than 

pre-ASR (14), which suggests that macroinvertebate communities were more similar after the ASR facility began discharging. Upstream-downstream comparisons in macroinvertebrate 

aquatic-life-support metrics had no significant differences for 

the post-ASR time period and neither site was fully supporting 

for any of the Kansas Department of Health and Environment 

aquatic-life-support metrics (Macroinvertebrate Biotic Index; 

Kansas Biotic Index with tolerances for nutrients and oxygendemanding substances; Ephemeroptera, Plecoptera, and 

Trichoptera [EPT] richness; and percentage of EPT species). 

Overall, using macroinvertebrate aquatic life-support criteria 

from the Kansas Department of Health and Environment, 

upstream and downstream sites were classified as partially supporting before and after the onset of ASR facility operations. 

Fish community trophic status and tolerance groups generally 

were similar among sites during the study period. Fish community Little Arkansas River Basin Index of Biotic Integrity 

scores at the upstream and downstream sites were indicative of 

fair-to-good conditions before the facility began operating and 

decreased to fair conditions after the facility began operating.

Groundwater physicochemical changes concurrent with 

the beginning of recharge operations at the Sedgwick basin 

were more pronounced in shallow groundwater. No constituent concentrations in the pre-recharge period in comparison to 

the post-recharge period increased to concentrations exceeding 

drinking water regulations; however, nitrate decreased significantly from a pre-recharge exceedance of the U.S. Environmental Protection Agency maximum contaminant level to a 

post recharge nonexceedance. Shallow groundwater chemical 

concentrations or rates of detection increased after artificial 

recharge began for the ions potassium, chloride, and fluoride; 

phosphorus and organic carbon species; trace elements barium, 

manganese, nickel, arsenate, arsenic, and boron; agricultural 

pesticides atrazine, metolachlor, metribuzin, and simazine; 

organic disinfection byproducts bromodichloromethane and 

trichloromethane; and gross beta levels. Additionally, water 

temperature, and pH were larger after recharge began; and total 

solids and slime-forming bacteria concentrations and densities were smaller. Total solids, nitrate, and selenium significantly decreased; and potassium, chloride, nickel, arsenic, 

fluoride, phosphorus and carbon species, and gross beta levels 

significantly increased in shallow groundwater after artificial 

recharge. Results of biological activity reaction tests indicated 

that water quality microbiology was different before and after 

artificial recharge began; at times, these differences may lead 

to changes in dominant bacterial populations that, in turn, 

may lead to formation and expansion in populations that may 

cause bioplugging and other unwanted effects. Calcite, iron 

(II) hydroxide, hydroxyapatite, and similar minerals, had shifts 

in saturation indices that generally were from undersaturation 

toward equilibrium and, in some cases, toward oversaturation. 

These shifts toward neutral saturation indices might suggest 

reduced weathering of the minerals present in the Equus Beds 

aquifer. Chemical weathering in the shallow parts of the aquifer 

may be accelerated because of the increased water temperatures 

and the system is more vulnerable to clogged pores and mineral 

dissolution as the equilibrium state is affected by recharge and 

withdrawal. When oversaturation is indicated for iron minerals, 

plugging of aquifer materials may happen.

Introduction

The city of Wichita’s water supply currently (2016) 

comes from two primary sources: (1) Cheney Reservoir and 

(2) the Wichita Equus Beds aquifer (fig. 1) well field, which 

was first constructed in the 1950s (Ziegler and others, 2001). 

The city of Wichita’s Water Utilities Department developed 

an Integrated Local Water Supply (ILWS) Plan because future 

water demands are expected to exceed current supply (City of 

Wichita, 1993). A primary component of the ILWS Plan is to 

increase the city of Wichita’s available water supply for their 

future water demands through 2050 by artificial recharge of 

the Equus Beds aquifer (City of Wichita, 1993). The Equus

Beds aquifer storage and recovery (ASR) project, as part of the 

ILWS Plan, pumps water out of the Little Arkansas River during above-base flow conditions, treats it according to National 

Primary Drinking Water Regulations (U.S. Environmental 

Protection Agency, 2009), and injects it into the Equus Beds 

aquifer. The U.S. Geological Survey (USGS), in cooperation 
Introduction 3

with the city of Wichita, developed and implemented a hydrobiological monitoring program (HBMP) as part of the mitigation described in City of Wichita, Department of Water and 

Sewer (2003) for the ILWS Plan (now part of the ASR project). 

The USGS, in cooperation with the city of Wichita, completed a study to assess the effects of ASR project activities on 

the Little Arkansas River and the Equus Beds aquifer (fig.1). 

The primary objective of this study was to establish baseline conditions before expanded implementation for aquifer 

recharge and to evaluate changes that may be related to the 

recharge program. To complete this objective, physical, chemical, and biological data were collected from the Little Arkansas River and the Equus Beds aquifer before and after the ASR 

Phase II facility began operation to quantify and characterize 

water-quality relative to before recharge conditions and to 

compare to water-quality and biological criteria. 

Overview of the Equus Beds Aquifer Storage 

and Recovery Project

The city of Wichita, Kansas, uses the Equus Beds aquifer 

as a primary municipal water supply source. The volume of 

water that has been pumped out of parts of the Equus beds 

aquifer has exceeded its natural recharge rate; as such, water 

levels in the aquifer have decreased substantially (Whisnant 

KANSAS

Map area

Approximate 

boundary of the 

Equus Beds aquifer

North BranchKisawa Cree k

375350097262800

97°26’32” 97°26’30” 97°26’28” 97°26’26”

37°53’50”

37°53’48”

37°53’46”

375348097262800

Little Arkansas RiverLittle Arkansas River

0 50 100 150 FEET

0 20 40 60 METERS

Base from U.S. Department of Agriculture, Farm Service Agency, 

Aerial Photography Field Office, digital ortho mosaic, 2014

97°40’

38°05’

38°00’

37°55’

37°50’

37°45’

97°30’

EXPLANATION

07143375

Study area

Approximate extent of High Plains 

aquifer (modified from Juracek 

and Hansen, 1995; Stullken and 

others, 1985)

Dune sand (modified from Kansas 

Geological Survey, 1992) Approximate boundary of the Equus Beds aquifer 

(modified from Juracek and Hansen, 1995; 

Stullken and others 1985; Stramel, 1967) 

U.S. Geological Survey (USGS) streamgage and identifier

Phase II USGS monitoring well

Aquifer storage and recovery (ASR) facility location

0 2 4 6 MILES

Base from U.S. Geological Survey digital data, 2015, 1:24,000 0 2 4 6 KILOMETERS

Universal Transverse Mercator projection, zone 14 North

Wichita

Burrton

Halstead

Hesston

Newton

Sedgwick

Buhler

Haven

Andale

Bentley

Colwich

Maize

Mount

Hope

HARVEY

SEDGWICK

07143330

07143375

07143665

07143672

07144100

07144200

LOW-HEAD DAM 

AT HALSTEAD, 

KANSAS

LOW-HEAD DAM AT 

 HARVEY COUNTY 

 PARK, KANSAS

HARVEY

RENO

Little A rkansas River SEDGWICK RENO

Chloride concentrations from wells where well 

depth is greater than 80 feet below the land 

surface in this approximate area exceed the 

Environmental Protection Agency's National 

secondary drinking-water regulation of 

250 milligrams per liter (modified from Tappa 

and others, 2015)

Kisawa Creek

Little Arkansas River

135

50

K96

Cheney

Reservoir

Gar Creek

West Em

ma Creek

Dry Creek

Middle Emma Creek

Mud Creek

Sand Creek

Cowskin Creek

Arkansas River

MW–7 deep and shallow

MW–8 deep and shallow

Figure 1. Study area and locations of monitoring wells for the city of Wichita, Kansas, Equus Beds aquifer storage and recovery

(ASR) project.
4 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

and others, 2015; Hansen and others, 2014). The aquifer is 

susceptible to saltwater contamination from the Arkansas River 

(fig. 1) and saltwater intrusion from existing upgradient contamination plumes caused by oil field evaporation pits remaining from the 1930s (Whittemore, 2007; Klager and others, 

2014). The Equus Beds ASR project, along with increased reliance on Cheney Reservoir, will help the city of Wichita meet 

increasing future water demands. The ASR project will also 

inhibit saltwater encroachment into the Wichita well field (not 

shown) (Ziegler and others, 2010; Klager and others, 2014).

The Equus Beds ASR project consists of four phases of 

construction. Phase I construction was completed in 2006, 

with a designed capacity to capture 10 million gallons per day 

(Mgal/d) of above-base flow water diverted directly from the 

Little Arkansas River and indirectly through streambank diversion wells for recharge. Phase I recharge activity began in 2007 

with water injection in four wells and two recharge basins; 

Phase I recharge activity is currently (2016) ongoing with 

intermittent pauses as a result of low flows on the Little Arkansas River. Directly diverted stream water is treated to reduce 

sediment and remove organic materials before being recharged 

to the aquifer through the two recharge basins; water pumped 

from streambank diversion wells does not receive additional 

treatment before being recharged to the aquifer through the 

Phase I injection wells or recharge basins (Garinger, 2011).

Phase II activity began in 2009 with construction of a 

30 Mgal/d surface-water treatment facility and a 60 Mgal/d 

river intake facility currently (2016) equipped to divert 

30 Mgal/d and treat 15 Mgal/d, drilling of seven new recharge 

injection wells, and creation of a third recharge basin. The 

Phase II ASR facility began operating in May 2013 and is 

currently (2016) ongoing. The city of Wichita has a National 

Pollutant Discharge Elimination System (NPDES) permit to 

discharge waste from the ASR Phase II surface water treatment facility to the Little Arkansas River. The city of Wichita 

was appropriated a 60 Mgal/d diversion when permit requirements are met (Kansas Department of Agriculture and Kansas 

Geological Survey, 2015). The Phase II ASR facility diversion 

permit requires that 30 cubic feet per second (ft3

/s) or greater 

is maintained in the Little Arkansas River at the streamgage 

at Valley Center, Kans. (site 07144200; fig. 1). The current Phase II ASR facility capacity of 30 Mgal/d (46.4 ft3

/s) 

requires a streamflow of about 100 ft3

/s or greater at the USGS 

streamgage near Sedgwick, Kansas (site 07144100; fig. 1); 

Phase II water is directly diverted from the Little Arkansas 

River at the intake structure when streamflow exceeds about 

100 ft3

/s at this site. The ASR facilities have an operational 

period of April 15 through October 15 because of climatological restrictions related to the potential for freezing conditions. 

Intake structure pumps deliver water to an adjacent 

presedimentation basin for solids removal. Water from the 

presedimentation basin is subsequently treated (the main processes are membrane ultrafiltration and advanced oxidation) at 

the surface-water treatment facility and then recharged directly 

into infiltration basins and wells. A summary table of gallons 

of water recharged for each month during Phase II is available 

at http://ks.water.usgs.gov/water-recharge#phase2. A residuals 

return line conveys residuals from the surface water treatment 

facility and from the presedimentation basin back to the Little 

Arkansas River; delays between river water withdrawal and 

releases to the river may last as much as 5 hours. The city of 

Wichita’s original NPDES permit to discharge waste from the 

ASR Phase II surface water treatment facility through the residuals return line to the Little Arkansas River was effective during January 1, 2010, through December 31, 2014, and the city 

of Wichita currently has a NPDES permit dated May 1, 2015, 

through December 31, 2015. The ASR total residuals return 

line volume during 2013 through 2014 was about 600 million 

gallons (table 1). More information about the city of Wichita 

ASR project is available at http://www.wichita.gov/Government/Departments/PWU/Pages/PublicWaterSupply.aspx.

Purpose and Scope

The purpose of this report is to document baseline and 

postoperational conditions upstream and downstream from 

the Phase II surface-water diversion, treatment, and infiltration facilities on the Little Arkansas River before and after 

facility operations began in May 2013 and describe effects of 

aquifer recharge on river water quality (including biology) and 

groundwater quality in comparison to relevant drinking water 

and biological criteria. The data in this report will be used to 

establish baseline conditions before expanded implementation 

of artificial aquifer recharge and to evaluate changes that may 

be related to the recharge program. In addition, data from this 

report will be used to document stream and groundwater quality, evaluate changing conditions, identify environmental factors affecting streams and groundwater, provide science-based 

information for decision-making, and help meet regulatory 

monitoring requirements. Physical, chemical, and biological 

conditions during March 2011 through December 2014, using 

sample data collected from two primary sites, upstream and 

downstream from the ASR facility, and geochemical modeling are described in this report. Streamflow, continuously and 

discretely collected water-quality, streambed-sediment, macroinvertebrate, fish, and habitat data were collected to quantify and characterize conditions in the Little Arkansas River. 

Water-quality data collected from two groundwater sites are 

also summarized in this report. Results presented in this report 

also contribute to the understanding of potential effects related 

to ASR activities throughout the Nation. 

Description of Study Area and Background 

Information

The study area is in south-central Kansas (fig. 1). The 

Little Arkansas River drainage basin is about 3,107 square 

kilometers of primarily agricultural (corn, sorghum, soybeans, 

and wheat) land. Fertilizers (such as nitrogen and phosphorus) and herbicides (such as alachlor and atrazine) are commonly applied in the drainage basin (Kansas Department of 
Introduction 5

Agriculture, 2015). Cattle and hogs are the primary livestock 

raised in the area (Kansas Department of Agriculture, 2015). 

Long-term mean annual precipitation (1900 through 2014) in 

the study area, based on data recorded near Newton, Kans., 

was 31.1 inches (in.) (table 2). During the study period (2011 

through 2014) mean annual precipitation was 29.4 in. (table 2).

The study area is underlain by the Equus Beds aquifer, 

which is part of the easternmost extent of the larger High Plains 

aquifer (fig. 1). The Equus Beds aquifer is named for Pleistocene horse fossils in its sediments. The Equus Beds aquifer 

is about 300 feet (ft) thick and consists of alluvial deposits 

of sand and gravel interbedded with clay or silt and is an 

important source of groundwater because of its water quality, 

shallow depth to the water table, and large saturated thickness 

(Williams and Lohman, 1949). Groundwater in the study area 

generally moves to the east except where the hydraulic gradient 

is altered by pumping wells and near a low-head dam on the 

Little Arkansas River at Halstead, Kansas (fig. 1; Whisnant 

and others, 2015). The city of Wichita well field is one of the 

primary sources of water for the city and surrounding area, and 

numerous irrigation wells also withdraw aquifer water within 

the boundaries (not shown) of Equus Beds Groundwater Management District Number 2 (GMD2; Equus Beds Groundwater 

Management District No. 2, 1990), which contain the study 

area boundary. Water withdrawals exceeding natural recharge 

of the Equus Beds aquifer have resulted in water-level declines 

of as much as 50 ft and exacerbated the threat of saltwater 

contamination (Hansen and Aucott, 2003, 2010; Hansen, 2007; 

Klager and others, 2014).

Consequently, the city of Wichita’s Water Utilities Department developed an ILWS Plan that was implemented in 1993. 

The goal of the ASR project, as part of the ILWS Plan, is to 

increase the city of Wichita’s available water supply for their 

future water demands through 2050 by artificial recharge of the 

Equus Beds aquifer using water from the Little Arkansas River 

above minimum flow requirements (City of Wichita, 1993; 

Warren and others, 1995). Phase I recharge of the ASR project 

began in 2007, and Phase II expansion became operational in 

2013. Phase II of the ASR project includes a water intake structure along the Little Arkansas River, a presedimentation basin, 

a surface water treatment facility, and a residuals return line. 

The facility operational period is April 15 through October 15 

when streamflow exceeds 100 ft3

/s.

Table 1. Volumes of discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 

375348097262800) and streamflow volumes from the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), May 2013 through September 2014.

[See figure 1 for site locations. Data were provided by the city of Wichita.]

Time period

Volume (gallon) Downstream surface-water 

site volume from the residuals 

return line site 

(percent)

Residuals return line site Downstream surface-water site

May 2013 4,376,517 2,203,809,235 0.20

June 2013 12,681,174 2,813,025,142 0.45

July 2013 3,160,602 19,279,500,570 0.02

August 2013 23,500,358 100,659,358,070 0.02

September 2013 9,879,790 1,409,797,575 0.70

May 2014 5,577,225 1,326,622,586 0.42

June 2014 15,138,362 20,160,222,942 0.08

July 2014 12,816,712 3,285,525,627 0.39

August 2014 45,129 630,685,853 0.01

September 2014 12,350,376 10,065,903,335 0.12

Total 2013‒2014 99,526,247 161,834,450,935 0.06

Table 2. Total and mean annual precipitation during 2011 through 

2014, and mean annual precipitation during 1900 through 2014 at 

the “Newton 2 SW” station (Global Historical Climatology Network 

USC00145744).

[Data from Global Historical Climatology Network, 2015. Values for years 

in ranges are mean annual precipitation, whereas values for 1 year are total 

annual precipitation]

Year or time period Total or mean annual precipitation 

(inch)

2011 19.9

2012 25.4

2013 41.0

2014 31.5

2011 through 2014 29.4

2011 through 2012 22.6

2013 through 2014 36.2

1900 through 2014 31.1
6 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

The Kansas Department of Health and Environment 

(KDHE) has listed several streams in the Little Arkansas 

River drainage basin as impaired waterways under section 

303(d) of the 1972 Clean Water Act (Kansas Department of 

Health and Environment, 2014a). Impairments for streams in 

or near the study area include arsenic and chloride for water 

supply; dissolved oxygen, selenium, total suspended solids, 

atrazine, copper, total phosphorus, biology, and biology/sediment for aquatic life; and Escherichia coli (E. coli) bacteria 

for recreation (Kansas Department of Health and Environment, 2014a, 2014b). Main pollutants of concern listed in the 

Little Arkansas River Watershed Restoration and Protection 

Strategy (WRAPS) were atrazine, sediment, nutrients, and 

fecal coliform bacteria (Kansas State University Research and 

Extension: Kansas Center for Agricultural Resources and the 

Environment, 2011). The Little Arkansas River has total maximum daily loads (TMDLs) for atrazine; effect on aquatic life 

by nutrients, sediment, and low dissolved oxygen; chloride; 

fecal coliform bacteria; and total suspended solids (Kansas 

Department of Health and Environment, 2000b, 2000c, 2000d, 

2006, 2008b, and 2014b).

Recent Investigations

Kelly and others (2013) and Klager and others (2014) 

developed Wichita well field numerical groundwater models. 

Kelly and others (2013) characterized groundwater flow and 

quantified artificial recharge in the Equus Beds aquifer. The 

Kelly and others (2013) model can be used for the following: 

quantify artificial and natural recharge, well pumping, and 

streamflow change effects on groundwater; simulate changes 

in water withdrawals, water levels caused by drought or pumping, and natural and artificial aquifer recharge; and simulate 

chloride movement throughout the aquifer and evaluate the 

effects of withdrawal and injection scenarios on chloride transport. Klager and others (2014) simulated chloride transport 

scenarios in the Equus Beds aquifer between the Arkansas and 

Little Arkansas Rivers (fig. 1) near the Wichita Equus Beds 

aquifer well field. Simulated scenario results indicated that the 

chloride plume near Burrton, Kans., originating from previous 

oil and gas activities will continue moving eastward toward 

the well field regardless of pumping in that area. Eastward 

movement of the Burrton chloride plume could be slowed by 

additional recharge at Phase I sites. Decreasing pumping along 

the Arkansas River or increasing water levels in the aquifer 

may slow chloride movement and prevent further encroachment into the southern part of the well field area.

Hansen and others (2014) and Whisnant and others 

(2015) documented water levels and storage volumes in the 

Equus Beds aquifer. Water levels in the aquifer during 1993 

through 2015 increased in the central part of the Equus Beds 

aquifer study area as a result of the city of Wichita decreasing water use by 40 percent since an all-time low in water 

levels happened in 1993. Storage volumes in the aquifer were 

determined to be about 95 percent of the total aquifer storage 

(Hansen and others, 2014; Whisnant and others, 2015); and 

the 1993 to 1995 recovery of storage volume previously lostfrom predevelopment to 1993 was about 46 percent (Whisnant 

and others, 2015).

Tappa and others (2015) summarized Little Arkansas 

River and Equus Beds aquifer (fig. 1) water quality before 

(1995 through 2006) and concurrent with (2007 through 2012) 

ASR Phase I recharge by defining water quality using measured and regression-computed data. Computed chloride concentrations in the Little Arkansas River exceeded the Federal 

secondary maximum contaminant level (SMCL) of 250 milligrams per liter (mg/L) about 20 percent of the time, primarily during minimal flow conditions. Groundwater chloride 

concentrations exceeded the SMCL between 6 and 7 percent 

of shallow and deep samples, primarily near Burrton, Kans., 

and along the Arkansas River. Few surface-water nitrate 

concentrations exceeded the Federal maximum contaminant 

level (MCL) of 10 mg/L. Groundwater nitrate concentrations 

exceeded the MCL in 16 percent of shallow samples and rarely 

in deep samples. Several trace elements including arsenic, 

iron, and manganese often exceeded drinking-water criteria.

Phase I recharge activities did not result in substantial 

effects on groundwater quality in the Equus Beds aquifer 

study area, likely because the total amount of recharged water 

is small (1 billion gallons) compared to aquifer storage volume 

(greater than [>] 990 billion gallons in winter 2012; Tappa and 

others, 2015). Artificial recharge at Phase I recharge locations 

likely slowed eastward movement of the Burrton chloride 

plume. Water-quality constituents of concern (primary ions, 

nutrients, trace elements, triazine herbicides, and indicator 

bacteria) did not increase substantially and were likely more 

affected by climatological (for example, natural recharge by 

precipitation) and natural processes (for example, geochemical reactions and metabolic and decay rates) than artificial 

recharge. Arsenic remained a constituent of concern because 

of natural, persistent concentrations exceeding the Federal 

MCL of 10 micrograms per liter (μg/L), particularly in the 

deeper aquifer.

Methods

Data collection efforts followed protocols (Stone and 

others, 2012) developed for the HBMP project. A total of 2 

surface-water sites along the Little Arkansas River, 1 site 

inside the residuals return line, and 2 groundwater wells 

(each having a shallow and deep part) were established 

to quantify and characterize environmental and biological responses to Phase II residuals return line discharge 

and groundwater recharge activities: the Little Arkansas 

River upstream from the ASR facility near Sedgwick, 

Kansas (upstream surface-water site 375350097262800), 

about 0.03 mile (mi) upstream from the residuals return 

line site; the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), about 
Methods 7

1.68 mi downstream from the residuals return line site; 

discharge from the Little Arkansas River ASR facility (residuals return line site 375348097262800); 25S 

01 W 07BCCC01 SMW–S11 near CW36 (MW–7 shallow groundwater well site 375327097285401); 25S01 W 

07BCCC02 DMW–S10 near CW36 (MW–7 deep groundwater well site 375327097285402); 25S 01W 07BCCA01 

SMW–S13 near CW36 (MW–8 shallow groundwater 

well site 375332097284801); and 25S 01W 07BCCA02 

DMW–S14 near CW36 (MW–8 deep groundwater well site 

375332097284802). Although the upstream surface-water 

site is near the residuals return line site discharge, water 

quality should be minimally affected at this site because of 

residuals returns being discharged during higher streamflow 

conditions; residuals returns discharged are assumed to move 

downstream under these conditions. Three sites (not shown) 

were established to provide data for ASR Phase II facility operations: the residual basin ASR treatment plant near 

Sedgwick, Kansas (site 375330097290200); diverted water at 

the Sedgwick recharge site, Kansas (site 375331097285301); 

and treated source water at the high service pump station, 

Kansas (site 375338097290800), which is part of the ASR 

treatment facility. Data collected by the USGS are stored in 

the USGS National Water Information System (NWIS) database (U.S. Geological Survey, 2016).

Data Collection

Continuous and discrete water-quality data were collected 

at surface-water sites upstream and downstream from the ASR 

Phase II facility, inside the ASR Phase II residuals return line, 

and in the shallow and deep parts of two groundwater wells 

associated with ASR Phase II recharge activities. Discrete 

water-quality data also were collected from the ASR treatment 

facility residual basin, diverted water at the Sedgwick recharge 

site, and treated source water at the ASR treatment facility high service pump station to aid in ASR Phase II facility 

operations; these data are presented in appendix table 1–1 and 

are not otherwise discussed in this report. Streambed sediment samples were collected at surface-water sites upstream 

and downstream from the ASR Phase II facility and inside the 

ASR Phase II residuals return line. Habitat, macroinvertebrate, 

and fish data were collected upstream and downstream from 

the ASR Phase II facility. Data collected by the USGS anytime 

during January 2011 through April 2013 (hereafter referred to 

as pre-ASR) and May 2013 through December 2014 (hereafter 

referred to as post-ASR) were used to evaluate the environmental and biological conditions upstream and downstream 

from the ASR Phase II residuals return line site discharges to 

the Little Arkansas River before and after the onset of facility 

operations.

Continuous Water-Quality Monitoring

Detailed method descriptions for continuous waterquality monitoring for the USGS Kansas Water Science 

Center (KSWSC) are presented in Bennett and others (2014) 

and Putnam and Hansen (2014). Continuous streamflow 

data were measured at the downstream surface-water site 

(07144100, fig. 1). Continuous water-quality data were 

collected from the upstream (375350097262800) and 

downstream surface-water sites and the shallow and deep 

parts of the aquifer from groundwater well sites MW–7 

(375327097285401 and 375327097285402, respectively) and 

MW–8 (375332097284801 and 375332097284802, respectively) (fig. 1). A streamgage and continuous monitoring site 

was established and has been operational at the downstream 

site since 1998 (fig. 1). Streamflow was measured using standard USGS methods (Sauer and Turnipseed, 2010; Turnipseed 

and Sauer, 2010). Continuous water-quality monitors were 

installed at the upstream surface-water site in April 2011 and 

in the residuals return line in August 2011; although no continuous data were collected from the residuals return line until 

the ASR facility began operating in 2013, the monitor was 

installed in August 2011 for operational testing given the novel 

installation location. An additional continuous monitor was 

installed at the downstream surface-water site in March 2012 

to quantify stream cross-sectional differences (for example, 

mixing). All continuously monitored sites were equipped with 

YSI 6600EDS water-quality monitors that measured specific 

conductance, pH, water temperature, dissolved oxygen (YSI 

optical dissolved oxygen sensor), and turbidity (YSI 6136 

optical turbidity sensor). A nitrate sensor (HACH® Nitratax 

plus sc) and a Turner Designs Cyclops-7TM chromophoric 

(or colored) dissolved organic matter (CDOM) sensor were 

installed at the downstream surface-water site in March 2012. 

The nitrate sensor does not differentiate between nitrate and 

nitrite (Pellerin and others, 2013); therefore, all nitrate sensor 

data include nitrite and are reported as nitrate plus nitrite concentrations in this report.

Some equipment was upgraded throughout the life of the 

project. YSI 600OMS water-quality monitors were installed 

in the shallow parts of groundwater wells MW–7 (on the 

southwest corner of the surface recharge basin) and MW–8 

(on the northeast corner of the surface recharge basin, about 

180 meters [m] away from MW–7) during July 2011 through 

June 2014 and the deep parts during October 2012 through 

June 2014. YSI 600OMS monitors were equipped with specific conductance, pH/oxidation-reduction potential (ORP), 

temperature, and dissolved oxygen (YSI optical dissolved 

oxygen sensor) sensors. Xylem EXO1 water-quality monitors 

were installed in the shallow parts of both groundwater wells 

in June through December 2014. Xylem EXO1 monitors were 

equipped with specific conductance, pH/ORP, water temperature, and dissolved oxygen sensors. Continuously collected 

ORP data were not evaluated in this report.

Surface-water monitors were installed near the centroid 

of the stream cross section to best represent conditions across 
8 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

the width of the stream and were maintained in accordance 

with standard USGS procedures (Wagner and others, 2006; 

Rasmussen and others, 2008; Pellerin and others, 2013; Bennett and others, 2014). Groundwater monitors were in the 

well screen and were maintained in accordance with standard 

USGS procedures (Wagner and others, 2006; Bennett and 

others, 2014). Continuous streamflow, water level, and waterquality data were recorded at hourly intervals. Continuous data 

are available at http://waterdata.usgs.gov/ks/nwis.

Discrete Water-Quality Samples

About eight surface-water discrete water-quality samples 

were collected annually at each site during a range of Little 

Arkansas River (fig. 1) streamflows during 2011 through 2014 

(appendix table 1–2) following USGS equal width increment 

(EWI) methods (U.S. Geological Survey, 2006; Rasmussen 

and others, 2014; Putnam and Hansen, 2014). Surface-water 

samples were analyzed for dissolved and suspended solids, 

primary ions, suspended sediment, nutrients (nitrogen and 

phosphorus species), organic carbon, trace elements, arsenic 

speciation, fecal and viral indicator bacteria, volatile organic 

compounds, and pesticides. Groundwater samples were collected about biannually at each site during 2011 through 2014 

(appendix table 1–2) and were analyzed for the same constituents as surface-water samples except for suspended sediment. 

Analyses for physicochemical properties and concentrations of dissolved and suspended solids, primary ions, 

nutrients, organic carbon, trace elements, coliform bacteria, 

volatile organic compounds, and pesticides used methods 

described by Ziegler and Combs (1997), Ziegler and others (1999), Ziegler and others (2010), and Tappa and others 

(2015). Arsenic speciation data were collected and analyzed 

using methods described in Garbarino and others (2002). Fecal 

and viral indicator bacteria analyses were done using methods 

described by Myers and others (2014), Bushon (2003), and the 

U.S. Environmental Protection Agency (2000a, 2001b, 2006a, 

2006b, 2006c, and 2006d). Reported values may be denoted as 

estimated (E) for some constituents when values are reported 

outside of instrument calibration range, performance of the 

analyte does not meet acceptable method-specific criteria, or 

if there were matrix interferences. Values reported with the E 

qualifier are considered firm detections, although the precision 

of the value is frequently less than that of values without this 

qualifier (Childress and others, 1999).

Methods used to analyze biological activity reaction tests 

(BART) are described by Droycon Bioconcepts, Inc. (2004). 

The BART for iron-related and sulfate-reducing bacteria were 

used to evaluate the potential for aquifer material plugging and 

well fouling. The BART is a semiquantitative assessment of 

the select bacterial community in the sample using a bacteriaspecific nutrient medium and a floating intercedent device 

(FID) that acts as a barrier to oxygen diffusion into the sample 

thereby creating at least three distinct environments for bacterial growth. Aerobic bacteria grow in the oxygen-rich environment above the FID, and anaerobic bacteria grow in the anoxic 

environment beneath the FID; facultative anaerobes grow at 

the oxidation-reduction (redox) front at the interface of the 

two environments. The iron-related bacteria BART (IRB–

BART) uses a ferric-iron nutrient media for select growth of 

iron-related bacteria, and the sulfate-reducing bacteria BART 

(SRB–BART) uses a short-chain fatty-acid culture medium 

for the growth of sulfate-reducing bacteria. Distinct reactions 

defined by color and other visual properties indicate the bacteria type present in the water sample. The order in which these 

reactions happen (reaction pattern signature) and the time to 

the first reaction indicate which bacteria are dominant and provide an estimate of the number of bacteria in the water sample.

Samples were analyzed by the city of Wichita Municipal Water and Wastewater Laboratory (Wichita, Kansas), the 

USGS National Water Quality Laboratory (Denver, Colorado), 

and the USGS Organic Geochemistry Research Laboratory (Lawrence, Kans.). Suspended-sediment concentration 

was analyzed at the USGS Iowa Sediment Laboratory, Iowa 

City, Iowa, according to methods described in Guy (1969). 

Samples were analyzed by ALS Environmental Laboratories 

in Fort Collins, Colo., for alpha and gross beta radioactivity 

(U.S. Environmental Protection Agency and Environmental 

Monitoring and Support Laboratory, 1980). Further information regarding data-collection methods, preservation, sample 

holding times, analytical methods, and reporting levels are 

presented in Ziegler and Combs (1997) and Stone and others 

(2012). Discrete water-quality data are available at http://

waterdata.usgs.gov/ks/nwis.

Streambed-Sediment Samples

Streambed-sediment samples were collected once annually during 2011 through 2014 at the upstream and downstream surface-water sites (375350097262800 and 07144100, 

respectively [fig. 1]) after at least 1 week without any 

substantial streamflow events and in 2014 from the residuals 

return line. Samples were collected into a large glass container, homogenized, passed through a 63 micrometer (μm) 

sieve, split into aliquots for different laboratories, and either 

shipped chilled (Shelton and Capel, 1994; Radtke, 2005) for 

nitrogen and wastewater compound analysis or allowed to air 

dry as required by the laboratory for about 2 weeks before 

shipping for analysis. Analysis was done only on the fraction 

of the sediment sample with particles less than (<) 63 μm 

in diameter (silt and clay size) to minimize sediment-size 

effects on chemical concentrations. A detailed description of 

streambed sediment sampling is presented in Stone and others 

(2012).

Sediment carbon, nutrient, and trace element analyses 

were completed at the USGS Sediment Chemistry Laboratory, Atlanta, Georgia, using digestion (Horowitz and others, 

2001) on samples collected in 2011. Test America Laboratories (Denver, Colo.) analyzed sediment nitrogen (nitrate 

plus nitrite and total Kjeldahl nitrogen) in 2012 and 2013 and 

RTI Laboratories Incorporated (Livonia, Michigan) analyzed 

sediment nitrogen in 2014 according to methods presented in 
Methods 9

O’Dell (1993a and 1993b) and U.S. Environmental Protection 

Agency (1983). Sediment trace elements and total phosphorus were analyzed using Inductively Coupled Plasma Mass 

Spectrometry (ICP–MS) 4-acid digestion by the USGS Crustal 

Geophysics and Geochemistry Science Center (Denver, Colo.) 

in 2012, 2013, and 2014 following methods by Taggart (2002). 

Sediment carbon, sulfur, and selenium were analyzed by the 

USGS Central Mineral and Environmental Resources Science 

Center (Denver, Colo.) in 2012, 2013, and 2014 following 

methods detailed in Brown and Curry (2002a and 2002b), 

Brown and others (2002), and Hageman and others (2002). 

Organic wastewater-indicator compounds were analyzed at 

the USGS National Water Quality Laboratory (NWQL) using 

methods described by Burkhardt and others (2006). These 

methods are sensitive to submicrogram per kilogram (μg/kg) 

levels. 

Habitat Assessment

Habitat assessments were completed in August 2011 

and September 2014 at the surface-water sites upstream 

(375350097262800) and downstream (07144100; fig. 1) from 

the ASR Phase II facility. A total of 14 habitat assessment 

variables, described in detail in Stone and others (2012), were 

used in this study to integrate data for three general habitat 

categories: channel, streambank/riparian, and instream aquatic. 

Variables measured in the channel category include indicators of overall channel morphology such as channel slope and 

sinuosity. Variables included in the streambank/riparian category provide information on organic material sources, bank 

conditions, and the degree of disturbance in the riparian zone. 

Variables in the instream aquatic category provide information on the availability of cover and substrate materials and 

the stream’s capacity for meeting basic physical requirements 

for support of a diverse and well-balanced aquatic community. 

Each habitat variable was scored on a scale of 1 (poor conditions) to 12 (optimal conditions). 

Habitat data were evaluated at two hierarchical scales 

(stream segment and stream reach) using a classification system proposed by Frissell and others (1986) and slightly modified by the National Water-Quality Assessment (NAWQA) 

program (Fitzpatrick and others, 1998). Segment-scale data 

also were obtained from geographic information system 

(GIS) coverages, topographic maps, and aerial photographs. 

A stream segment was defined as a section of stream that is 

relatively homogeneous with respect to physical, chemical, 

and biological properties and generally bounded by tributary 

junctions, point-source discharges, or other features that might 

be expected to change stream properties (Fitzpatrick and 

others, 1998). The upstream boundaries of stream segments 

were defined by a change in stream order and the downstream 

boundaries of stream segments were defined as 50 m downstream from the downgradient boundary of the reach. Stream 

reaches were defined as the section of the stream where a 

streamgage was located and where biological sampling happened. The reaches included at least two riffle-pool sequences 

or at least two runs where current velocity was greater than in 

pools to capture habitat diversity that is representative of the 

segment. The same geographical stream segments and reaches 

were assessed in 2011 and 2014. 

Macroinvertebrates

Macroinvertebrate sampling events were completed during spring to late summer and were determined to some extent 

by hydrologic stability. Macroinvertebrates were collected 

at the upstream and downstream sites (375350097262800 

and 07144100 [fig. 1], respectively) within the same 24-hour 

period in April, July, and August 2011; May, June, and September 2012; April and September 2013; and June and August 

2014 after 1 week without substantial streamflow events. Triplicate samples were collected from three continuous reaches at 

each site in April and August 2011, May and September 2012, 

September 2013, and June 2014 to more accurately compare 

differences among sites while accounting for within-site variability. Macroinvertebrate sampling reaches were selected 

to maximize diversity of available habitat types and similarity of habitat types between sites. Sampling reaches were 

approximately 50 to 100 m upstream from the upstream and 

downstream surface-water sites. Individual sampling reaches 

were about 120 m in length. Macroinvertebrate samples were 

collected following semiquantitative protocols described in 

detail in Stone and others (2012) that were developed based on 

KDHE’s protocols (Kansas Department of Health and Environment, 2000a), which have been used for stream evaluations 

in water-quality monitoring studies within the state (Poulton 

and others, 2007; Rasmussen, T.J., and others, 2009, 2012; 

Graham and others, 2010, 2014). Two independent 100-organism subsamples were collected at each sampling site with a 

rectangular framed aquatic kick net (23 centimeters [cm] by 

46 cm, 530 μm mesh netting) from multiple habitat types. 

Organisms were picked and counted onsite by two scientists 

simultaneously for 1 hour and later pooled into one 200-organism sample. Samples were preserved in 80 percent ethanol 

and shipped to the USGS NWQL for taxonomic identification 

and enumeration following methods described by Moulton 

and others (2000). Macroinvertebrate data are available in the 

USGS BioData Database at https://aquatic.biodata.usgs.gov.

Fish

Fish communities were sampled yearly at the upstream 

and downstream sites (375350097262800 and 07144100 

[fig. 1], respectively) within the same 24-hour period in September 2011, 2012, and 2013 and August 2014. Fish sampling 

protocols were adapted from U.S. Environmental Protection 

Agency (EPA) and USGS protocols (Barbour and others, 

1999; Moulton and others, 2002). Two complementary methods were used for fish sampling: electrofishing and seining. 

Electrofishing was done in two separate passes of the stream 

reach using a backpack electrofisher. Electrofishing crews 
10 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

consisted of a minimum of three people: the person electrofishing and at least two crew members to collect stunned fish 

with dip nets. Fish collected from the first pass were identified and processed before the second electrofishing pass was 

made and were released outside of the sampling reach. After 

electrofishing, five to seven seine hauls were made with a 

15-ft, 3/16-in. mesh size minnow seine. The first 30 individuals of each species were weighed to the nearest gram (g) with 

an electronic portable scale and measured (total length) to the 

nearest millimeter (mm) with a fish measuring board. Stone 

and others (2012) provide additional fish sampling protocol 

detail. Fish data are available in the USGS BioData Database 

at https://aquatic.biodata.usgs.gov.

Data Analysis

Water chemistry, macroinvertebrate, and fish data were 

analyzed to quantify and compare stream water and groundwater quality pre- and post-ASR Phase II facility operation. 

Pre- and post-ASR surface water, groundwater, and macroinvertebrate data were compared using nonparametric statistical 

methods. Macroinvertebrate and fish community metrics were 

computed. Stream and groundwater data were geochemically 

modeled.

Water Chemistry Data

Water-quality conditions at the upstream and downstream 

surface-water sites (375350097262800 and 07144100 [fig. 1], 

respectively) pre-and post-ASR Phase II facility operation 

were compared during all streamflow conditions, including 

during streamflow conditions under which the facility could 

have been (pre-ASR) or could be (post-ASR) operating (for 

example, flow conditions of 100 ft3

/s or greater). Comparison 

of upstream and downstream continuous and discrete waterquality data pre- and post-ASR during these higher streamflow 

conditions were included to allow comparisons between sites 

and time periods under similar streamflows and addresses 

limitations of upstream and downstream comparisons under 

different streamflow conditions. Water chemistry data comparisons to specifically assess ASR facility discharge effects 

between time periods with substantially different streamflows may be complicated because of streamflow influences 

on water quality. Sample pairs at similar pre- and post-ASR 

streamflows were compared; however, there were too few 

sample pairs for a robust statistical analysis; therefore, comparisons between overall pre- and post-ASR water chemistry 

data sets include limitations because of streamflow effects; 

higher streamflow conditions can dilute some water-quality 

constituent concentrations or have larger sediment-associated 

constituent concentrations from runoff. These streamflowrelated dilution or runoff conditions may not allow detection 

of ASR discharge effects on stream water chemistry.

Duration curves were used to compare continuously 

collected surface-water data during all flow conditions. 

Duration curves are cumulative distribution functions and 

were constructed using hourly values to evaluate and compare 

frequency and magnitude characteristics upstream and downstream from the ASR Phase II facility before and after facility 

operation began (Rasmussen and Ziegler, 2003; Rasmussen and others, 2005). Duration curves are indicative of the 

percentage of time that specified conditions were equaled or 

exceeded, or the frequency of exceedance (Maidment, 1993). 

The Weibull formula (Helsel and Hirsch, 2002) was used for 

plotting position. Streamflow and water-quality condition 

duration curves are available for the upstream and downstream 

surface-water sites for the period of record at http://nrtwq.

usgs.gov/ks/.

Statistical differences in water-quality constituent pairs 

for the upstream and downstream surface-water sites pre- and 

post-ASR were determined. Paired samples were considered 

to be samples collected during the same 24-hour period from 

both sites during similar flow conditions. To avoid false-positive quantification of a constituent, low concentrations are leftcensored and reported as “less than” values by the laboratory 

(Childress and others, 1999). Several water-quality constituents had left-censored values. Summary statistics (means and 

medians) for constituents that had left-censored values were 

calculated using regression on order statistics (ROS; Helsel 

and Cohn, 1988). The ROS is recommended for datasets with 

sample sizes <50 and having as much as 80 percent censored 

data (Helsel, 2005). Summary statistics were not computed 

when >80 percent of data were left-censored. For constituent pairs that did not contain left-censored data, a two-sided 

nonparametric Wilcoxon signed-rank test (Helsel and Hirsch, 

2002; Sokal and Rohlf, 2012) was used to statistically compare paired values from the upstream and downstream surfacewater sites. For constituent pairs that contained left-censored 

data, a two-sided paired Prentice generalized Wilcoxon test 

(Kalbfleisch and Prentice, 2002) was used to statistically compare values among sites. Upstream and downstream constituent pairs with severe (>50 percent; Helsel and Hirsch, 2002) 

censoring were not statistically compared because the selected 

comparison test would have little power to detect differences 

in central values with datasets that have severe censoring 

(near 50 percent or greater; Helsel, 1990). The Wilcoxon tests 

determine if the median difference between paired values is 

significantly different than zero. Statistical significance for 

both analyses was set at a p-value of <0.05 and was completed 

using R 3.0.1 (R Core Team, 2013).

Similarly, summary statistics for groundwater samples 

were calculated using ROS (means) and maximum likelihood 

estimation (MLE, for medians) for handling datasets with 

values reported above maximum detection (right censored), 

below lower detection limit or laboratory reporting level (leftcensored), and for multiple levels of detection. A generalized 

Wilcoxon test of unpaired samples was used for a two-sided 

test of differences between samples before and after the beginning of artificial recharge in May 2013. Statistical summaries 

of groundwater samples were computed using R 3.2.0 (R Core 

Team, 2015) and the smwrQW package (Lorenz, 2015).
Methods 11

Continuous (hourly) total suspended solids and suspended sediment concentration data were computed for the 

upstream and downstream surface-water sites before and after 

the onset of Phase II ASR facility operation using regression 

models developed in Rasmussen and others (in press). New 

regression models were developed as part of this report using 

simple linear (ordinary least squares) regression analyses to 

establish relations between discretely sampled dissolved and 

total organic carbon and concurrent continuously measured 

physicochemical properties (Helsel and Hirsch, 2002; Rasmussen and others, 2008; Rasmussen, P.P., and others, 2009). 

Untransformed and log10 transformations (log-transformed) 

were used for discrete dissolved and total organic carbon concentrations and continuously measured water-quality properties. The methods used for the development of models and 

quantifying uncertainty are described in detail in Rasmussen, 

P.P., and others (2009) and Stone and Graham (2014). Data 

were analyzed using TIBCO Spotfire S+® 8.1 for Windows®

statistical software (TIBCO Software, Inc., 2008).

Continuous data corresponding to each discrete sample 

were determined from time-series datasets by using timeweighted averages of continuous data values recorded immediately before, during, and after sample collection. Concurrent 

instream continuous measurements were used to correspond 

with discrete dissolved and total organic carbon measurements 

as described in Rasmussen, P.P., and others (2009). All continuously measured physical properties and seasonal components (sine and cosine variables) were tested for significance 

for each response variable. Outliers in discrete samples were 

identified and removed as described in Rasmussen, P.P., and 

others (2009). Five outliers were removed from dissolved and 

total organic carbon datasets because of large heterogeneity in 

corresponding turbidity measurements of cross-sectional data 

recorded during discrete sampling.

Regression models were evaluated based on diagnostic 

statistics (coefficient of determination [R2

]; Mallow’s Cp; root 

mean square error [RMSE]; prediction error sum of squares 

[PRESS]), patterns in residual plots, and the range and distribution of discrete and continuous data (Helsel and Hirsch, 

2002). Models were selected that maximized the amount of 

variance in the response variable that was explained by the 

model (multiple R2

 for models with one explanatory variable 

and adjusted R2

 for models with more than one explanatory 

variable), maximized fit to the data (Mallow’s Cp

), and minimized heteroscedasticity (irregular scatter) in the residual plots 

and uncertainty associated with computed values (RMSE and 

PRESS). Variance inflation factor (VIF) was used to measure 

collinearity (the exact or approximate linear relation between 

variables; Marquardt, 1970). Model simplicity was additionally considered for selection because, as more variables are 

included in a model, the likelihood that the variability of 

the system is not being described by the sampling dataset 

increases. Variables were included if p-values were significant 

(<0.05). Significant (p-value<0.05) additional explanatory 

variables were included in models if their retention increased 

the amount of variance explained by 10 percent or more, 

decreased Mallow’s Cp

, and minimized heteroscedasticity in 

residual plots. 

Mean square error (MSE) and RMSE were calculated 

for each model to assess the variance between predicted and 

observed values (Helsel and Hirsch, 2002). Model standard 

percentage error (MSPE) was calculated as a percentage of 

the RMSE (Hardison, 1969). A bias correction factor (BCF) 

was calculated for models with logarithmically transformed 

response variables (Duan, 1983) because transformation of 

estimated values back into original units results in a lowbiased estimate (Helsel and Hirsch, 2002).

Macroinvertebrate Data

Macroinvertebrate community metrics were calculated 

using the Invertebrate Data Analysis System v. 5.0.28 (IDAS) 

developed for NAWQA (Cuffney, 2003). Among the large 

number of indicator metrics this program calculates (>100), 

metrics were selected that have been used for evaluating 

aquatic life in Kansas streams as part of previous studies (Rasmussen and others, 2008; Rasmussen and others, 2012; Graham and others, 2014; Graham and others, 2010; Huggins and 

Moffet, 1988) and are recommended by the EPA Rapid Bioassessment Protocols (RBPs; Barbour and others, 1999). During 

analysis with IDAS, rare taxa were not deleted, lowest practical 

taxonomic levels were used, and taxonomic ambiguities were 

resolved by retaining ambiguous taxa. Four KDHE aquatic lifesupport metrics (Macroinvertebrate Biotic Index, Davenport 

and Kelly, 1983; Kansas Biotic Index, Huggins and Moffet, 

1988; Ephemeroptera, Plecoptera, and Trichoptera [EPT] taxa 

richness, Lenat and Penrose, 1996; and relative abundance of 

EPT taxa, Lenat and Penrose, 1996) were used to calculate 

multimetric aquatic life-support scores for each site. Statistical differences in each of the macroinvertebrate community 

composition metrics between the upstream and downstream 

surface-water sites (375350097262800 and 07144100 [fig. 1], 

respectively) before and after the onset of ASR Phase II facility 

operation were determined with the two-sided nonparametric 

Wilcoxon signed-rank test as described in the “Water Chemistry Data” section for discrete water-quality constituents.

Fish Data

Fish metrics were selected that represent those used in 

several State evaluation programs and those known to be sensitive and reliable for quantifying stream degradation. Average 

fish metrics were calculated for the upstream and downstream 

surface-water sites (375350097262800 and 07144100 [fig.1], 

respectively) pre- and post-ASR. Fish species were classified 

into feeding and tolerance groups as described in Barbour and 

others (1999). Shannon’s diversity index was calculated by 

quantifying the proportion of an individual species relative 

to the total number of species in the sample and multiplying 

that proportion by its natural log, then summing these values 

across species and multiplying by -1 (Brower and others, 
12 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

1998). Index of Biotic Integrity (IBI) scores that were specific 

to the Little Arkansas River Basin (not shown) were calculated 

as described in Lydy and others (2000). Little Arkansas River 

Basin IBI scores were calculated using 12 metrics that represent the structure and function of fish assemblages in the Little 

Arkansas River basin (Lydy and others, 2000).

Geochemical Modeling

Changes in groundwater chemistry and microbiological dominance and growth as a result of artificial recharge 

and water withdrawals may result in precipitation or dissolution of minerals causing physical plugging or changes in the 

aquifer properties as can changes in microbiology that may 

cause bioplugging. Mineral precipitation could adversely 

affect water yield by clogging aquifer pores, and dissolution of certain minerals may release harmful constituents 

like arsenic into the aquifer. To describe the potential for 

precipitation and dissolution of various minerals, PHREEQC 

(Parkhurst and Appelo, 2013) geochemical modeling software, 

executed in R (R Core Team, 2015; Charlton and Parkhurst, 

2011) with the wateq4f.dat database file derived from Ball 

and Nordstrom (1991) and distributed with the PHREEQC 

software (Parkhurst and Appelo, 2013), was used to calculate 

ion speciation and saturation indices for discrete groundwater 

and stream water samples. Input for PHREEQC computations included discrete sample data for water temperature, pH, 

alkalinity, water level, and dissolved concentrations of oxygen, 

calcium, magnesium, sodium, potassium, chloride, sulfate, 

nitrite, nitrate, orthophosphate, fluoride, silica, arsenic, iron, 

and manganese.

For a solution near equilibrium, indicated as a saturation 

index (SI) value near zero, the given mineral may precipitate 

and dissolve to maintain balance. Positive SI values indicate 

oversaturation and the potential for the mineral to precipitate. 

Conversely, negative SI values indicate the potential for mineral dissolution. In addition to the equilibrium state, described 

by the SI, additional factors affect precipitation and dissolution 

reactions, including kinetics and the presence of the mineral at 

available reaction sites. A mineral SI is calculated as the log of 

the ion-activity product of a solution (water sample), divided 

by the solubility product (Ksp) for the mineral, such as for 

calcite (CaCO3):

SI Log

Ca CO

Ksp calcite

=

+ − [ ][ ]

( )

2

3

2

(1)

Where

[Ca2+] is the activity of the calcium ion;

[CO3

2+] is the activity of the carbonate ion; and

Ksp(calcite) is the solubility product of calcite.

Quality Assurance and Quality Control

Quality assurance and quality control (QA/QC) samples 

routinely were collected to identify, quantify, and document 

bias and variability in data that resulted from collecting, 

processing, handling, and analyzing samples (U.S. Geological Survey, 2006). The QA/QC samples included replicate, 

blank, and standard reference samples for discretely collected 

water-quality and streambed-sediment constituents. Triplicate 

QA/QC samples were collected for macroinvertebrates. Relative percentage difference (RPD) was used to evaluate differences in analyte concentrations detected in replicate water 

and streambed-sediment samples. The RPD was calculated by 

dividing the difference between replicate pairs by the mean 

and multiplying that value by 100, creating a value that represents the percent difference between replicate samples (Zar, 

1999). The coefficient of variation (CV) was used to evaluate 

differences in macroinvertebrate community metrics because 

more than two samples can be included in the calculations. 

The CV was calculated by dividing the standard deviation by 

the mean and multiplying that value by 100, creating a value 

that represents the percent variation between replicate samples 

(Zar, 1999).

Water Chemistry Data

The specific conductance, pH, water temperature, and 

dissolved oxygen sensors have wide ranges of operation (for 

example, pH sensors measure from 0 to 14 units; Wagner and 

others, 2000 and 2006) that were not exceeded in this study. 

The manufacturer specifications for the YSI 6136 optical 

turbidity sensor indicate the maximum is 1,000 formazin 

nephelometric units (FNU). Individual turbidity sensors differ 

in actual maximum readings. The maximum turbidity reading 

recorded at all sites was 1,410 FNU at the residuals return line 

site (table 3; 375348097262800, fig. 1). The maximum turbidity readings for the upstream and downstream surface-water 

sites (375350097262800 and 07144100 [fig. 1], respectively) 

were 1,280 FNU and 1,250 FNU, respectively (table 3). Less 

than 0.01 percent of turbidity data at the upstream and downstream surface-water sites exceeded 1,000 FNU and about 

7 percent of residuals return line site turbidity data exceeded 

1,000 FNU. Data that exceeded the maximum operation value 

were retained in datasets and classified as poor.

Comparison of field cross-sectional measurements 

collected during high and low flow conditions at the surfacewater sites, the additional continuous monitor data at the 

downstream surface-water site, and field measurements at 

the residuals return line site provided verification that bias 

in continuous data because of monitor location within the 

stream cross-section or residuals return line was minimal. The 

RPDs between continuous and field monitors were <3 percent 

except turbidity. Turbidity had median RPDs of <8 percent at 

all study sites compared to cross-sectional field data. Larger 

differences between continuous and field monitor values 

commonly happened when conditions were changing rapidly. 
Methods 13

Table 3. Summary statistics for continuously (hourly) measured physicochemical properties and computed water-quality constituents 

of interest for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream 

surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), 

and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near 

Sedgwick, Kansas, March 2011 through December 2014.

[Continuous real-time water-quality data are available on the U.S. Geological Survey National Real-Time Water Quality Web site at http://nrtwq.usgs.gov. Data 

collected hourly. n, number of measurements; ft3/s, cubic foot per second; <, less than; pre, March 2011 through April 2013; ASR, aquifer storage and recovery; 

post, May 2013 through December 2014; μS/cm at 25 °C, microsiemen per centimeter at 25 degrees Celsius; —, not applicable; °C, degrees Celsius; mg/L, 

milligram per liter; FNU, formazin nephelometric units; NO3+NO2, nitrate plus nitrite; N, nitrogen; CDOM, chromophoric (colored) dissolved organic material; 

ppb, part per billion; QSE, quinine sulfate equivalent]

Continuous variable Data collection 

period n Minimum Maximum Mean Median

Missing or 

deleted data 

(percent)

Streamflow (ft3

/s)

All data

Downstream surface-water site January 2011 though 

December 2014

35,064 <1 16,735 206 31 <1

Pre-ASR data

Downstream surface-water site January 2011 through 

April 2013

20,424 <1 2,094 44 14 <1

Post-ASR

Downstream surface-water site May 2013 through 

December 2014

14,640 1.0 16,735 431 39 <1

Specific conductance (μS/cm at 25 °C)

All data

Upstream surface-water site April 2011 through 

December 2014

27,824 107 1,910 776 801 15

Downstream surface-water site January 2011 though 

December 2014

31,349 83 1,910 777 798 11

Pre-ASR data

Upstream surface-water site April 2011 through 

April 2013

13,750 153 1,910 759 773 24

Downstream surface-water site January 2011 through 

April 2013

17,695 148 1,910 769 775 13

Post-ASR data

Upstream surface-water site May 2013 through 

December 2014

14,074 107 1,830 792 848 4

Downstream surface-water site May 2013 through 

December 2014

13,654 86 1,630 787 838 7

Residuals return line site1 May 2013 through 

December 2014

1,727 46 1,890 348 268 —

pH (standard units)

All data

Upstream surface-water site April 2011 through 

December 2014

28,260 6.7 9.3 8.0 8.0 14

Downstream surface-water site January 2011 though 

December 2014

33,053 6.6 9.1 8.0 8.0 6

Pre-ASR data

Upstream surface-water site April 2011 through 

April 2013

14,352 6.7 9.3 8.1 8.0 21

Downstream surface-water site January 2011 through 

April 2013

18,413 7.1 9.1 8.0 8.0 10
14 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Table 3. Summary statistics for continuously (hourly) measured physicochemical properties and computed water-quality constituents 

of interest for the Little Arkansas River upstream surface-water site from the aquifer storage and recovery facility near Sedgwick, 

Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) 

near Sedgwick, Kansas, March 2011 through December 2014.—Continued

[Continuous real-time water-quality data are available on the U.S. Geological Survey National Real-Time Water Quality Web site at http://nrtwq.usgs.gov. Data 

collected hourly. n, number of measurements; ft3/s, cubic foot per second; pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 

2013 through December 2014; μS/cm at 25 °C, microsiemen per centimeter at 25 degrees Celsius; —, not applicable; °C, degrees Celsius; mg/L, milligram per 

liter; FNU, formazin nephelometric units; NO3+NO2, nitrate plus nitrite; N, nitrogen; CDOM, chromophoric (colored) dissolved organic material; ppb, part per 

billion; QSE, quinine sulfate equivalent]

Continuous variable Data collection 

period n Minimum Maximum Mean Median

Missing or 

deleted data 

(percent)

pH (standard units)—Continued

Post-ASR data

Upstream surface-water site May 2013 through 

December 2014

13,908 6.7 9.0 7.9 7.9 5

Downstream surface-water site May 2013 through 

December 2014

14,640 6.6 8.9 7.9 8.0 <1

Residuals return line site1 May 2013 through 

December 2014

1,803 6.6 8.4 7.4 7.4 —

Water temperature (°C)

All data

Upstream surface-water site April 2011 through 

December 2014

28,427 <1 36.6 15.9 16.8 13

Downstream surface-water site January 2011 through 

December 2014

33,053 <1 35.5 14.8 14.9 6

Pre-ASR data

Upstream surface-water site April 2011 through 

April 2013

14,353 <1 36.6 15.4 15.4 21

Downstream surface-water site January 2011 through 

April 2013

18,413 <1 35.5 13.6 12.4 10

Post-ASR data

Upstream surface-water site May 2013 through 

December 2014

14,074 <1 35.3 16.4 19.0 4

Downstream surface-water site May 2013 through 

December 2014

14,640 <1 34.4 16.2 18.4 <1

Residuals return line site1 May 2013 through 

December 2014

1,809 9.8 27.1 21.9 22.6 —

Dissolved oxygen (mg/L)

All data

Upstream surface-water site April 2011 through 

December 2014

28,425 1.4 21.4 9.4 9.1 13

Downstream surface-water site January 2011 through 

December 2014

33,055 1.6 24.3 10.2 10.2 6

Pre-ASR data

Upstream surface-water site April 2011 through 

April 2013

14,351 1.6 21.4 9.5 9.3 21

Downstream surface-water site January 2011 through 

April 2013

18,415 2.5 24.3 10.7 10.8 10
Methods 15

Table 3. Summary statistics for continuously (hourly) measured physicochemical properties and computed water-quality constituents 

of interest for the Little Arkansas River upstream surface-water site from the aquifer storage and recovery facility near Sedgwick, 

Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) 

near Sedgwick, Kansas, March 2011 through December 2014.—Continued

[Continuous real-time water-quality data are available on the U.S. Geological Survey National Real-Time Water Quality Web site at http://nrtwq.usgs.gov. Data 

collected hourly. n, number of measurements; ft3/s, cubic foot per second; pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 

2013 through December 2014; μS/cm at 25 °C, microsiemen per centimeter at 25 degrees Celsius; —, not applicable; °C, degrees Celsius; mg/L, milligram per 

liter; FNU, formazin nephelometric units; NO3+NO2, nitrate plus nitrite; N, nitrogen; CDOM, chromophoric (colored) dissolved organic material; ppb, part per 

billion; QSE, quinine sulfate equivalent]

Continuous variable Data collection 

period n Minimum Maximum Mean Median

Missing or 

deleted data 

(percent)

Dissolved oxygen (mg/L)—Continued

Post-ASR data

Upstream surface-water site May 2013 through 

December 2014

14,074 1.4 19.4 9.2 8.9 4

Downstream surface-water site May 2013 through 

December 2014

14,640 1.6 24.0 9.6 9.4 <1

Residuals return line site1 May 2013 through 

December 2014

1,758 2.5 10.8 7.6 7.8 —

Turbidity (FNU)

All data

Upstream surface-water site April 2011 through 

December 2014

27,578 2.1 1,280 54 30 16

Downstream surface-water site January 2011 through 

December 2014

32,670 1.1 1,250 47 26 7

Pre-ASR data

Upstream surface-water site April 2011 through 

April 2013

14,113 5.4 1,170 60 33 22

Downstream surface-water site January 2011 through 

April 2013

18,348 2.9 880 50 29 10

Post-ASR data

Upstream surface-water site May 2013 through 

December 2014

13,465 2.1 1,280 47 24 8

Downstream surface-water site May 2013 through 

December 2014

14,322 1.1 1,250 43 19 2

Residuals return line site1 May 2013 through 

December 2014

1,776 11 1,410 561 380 —

NO3

+NO2 (mg/L) as N

All data

Downstream surface-water site March 2012 through 

December 2014

21,959 <0.01 11.50 1.17 0.90 12

Pre-ASR data

Downstream surface-water site March 2012 through 

April 2013

7,419 <0.01 11.50 1.59 1.42 27

Post-ASR data

Downstream surface-water site May 2013 through 

December 2014

14,540 <0.01 7.66 0.95 0.80 <1
16 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Table 3. Summary statistics for continuously (hourly) measured physicochemical properties and computed water-quality constituents 

of interest for the Little Arkansas River upstream surface-water site from the aquifer storage and recovery facility near Sedgwick, 

Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) 

near Sedgwick, Kansas, March 2011 through December 2014.—Continued

[Continuous real-time water-quality data are available on the U.S. Geological Survey National Real-Time Water Quality Web site at http://nrtwq.usgs.gov. Data 

collected hourly. n, number of measurements; ft3/s, cubic foot per second; pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 

2013 through December 2014; μS/cm at 25 °C, microsiemen per centimeter at 25 degrees Celsius; —, not applicable; °C, degrees Celsius; mg/L, milligram per 

liter; FNU, formazin nephelometric units; NO3+NO2, nitrate plus nitrite; N, nitrogen; CDOM, chromophoric (colored) dissolved organic material; ppb, part per 

billion; QSE, quinine sulfate equivalent]

Continuous variable Data collection 

period n Minimum Maximum Mean Median

Missing or 

deleted data 

(percent)

CDOM (ppb QSE)

All data

Downstream surface-water site2 March 2012 through 

December 2014

11,059 15 338 104 104 55

Pre-ASR data

Downstream surface-water site2 March 2012 through 

April 2013

4,782 15 199 72 59 51

Post-ASR data

Downstream surface-water site2 May 2013 through 

December 2014

6,277 55 338 129 129 57

Computed dissolved organic carbon (mg/L)

All data

Downstream surface-water site3 March 2012 through 

December 2014

11,059 1.42 17.2 6.61 6.72 55

Pre-ASR data

Downstream surface-water site3 March 2012 through 

April 2013

4,782 1.42 11.3 4.89 4.26 51

Post-ASR data

Downstream surface-water site3 May 2013 through 

December 2014

6,277 4.02 17.2 7.93 7.95 57

Computed total organic carbon (mg/L)

All data

Downstream surface-water site4 March 2012 through 

December 2014

11,059 0.13 50.0 8.95 7.93 55

Pre-ASR data

Downstream surface-water site4 March 2012 through 

April 2013

4,782 0.13 39.7 6.93 6.05 51

Post-ASR data

Downstream surface-water site4 May 2013 through 

December 2014

6,277 4.21 50.0 10.48 9.52 57

Computed total suspended solids (mg/L)

All data

Downstream surface-water site5 January 2011 through 

December 2014

32,670 2 1,646 63 36 7

Pre-ASR data

Downstream surface-water site5 January 2011 through 

April 2013

18,348 4 1,212 67 39 10
Methods 17

Table 3. Summary statistics for continuously (hourly) measured physicochemical properties and computed water-quality constituents 

of interest for the Little Arkansas River upstream surface-water site from the aquifer storage and recovery facility near Sedgwick, 

Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) 

near Sedgwick, Kansas, March 2011 through December 2014.—Continued

[Continuous real-time water-quality data are available on the U.S. Geological Survey National Real-Time Water Quality Web site at http://nrtwq.usgs.gov. Data 

collected hourly. n, number of measurements; ft3/s, cubic foot per second; pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 

2013 through December 2014; μS/cm at 25 °C, microsiemen per centimeter at 25 degrees Celsius; —, not applicable; °C, degrees Celsius; mg/L, milligram per 

liter; FNU, formazin nephelometric units; NO3+NO2, nitrate plus nitrite; N, nitrogen; CDOM, chromophoric (colored) dissolved organic material; ppb, part per 

billion; QSE, quinine sulfate equivalent]

Continuous variable Data collection 

period n Minimum Maximum Mean Median

Missing or 

deleted data 

(percent)

Computed total suspended solids (mg/L)—Continued

Post-ASR data

Downstream surface-water site5 May 2013 through 

December 2014

14,322 1 1,727 57 25 2

Computed suspended-sediment concentration (mg/L)

All data

Downstream surface-water site6 January 2011 through 

December 2014

32,670 2 1,876 78 44 7

Pre-ASR data

Downstream surface-water site6 January 2011 through 

April 2013

18,348 6 1,416 81 48 10

Post-ASR data

Downstream surface-water site6 May 2013 through 

December 2014

14,322 2 1,876 75 34 2

1

Intermittent hourly data during May 2013 through December 2014.

2

Data temperature- and turbidity-corrected following Downing and others (2012).

3

Computed using regression model and hourly CDOM data.

4

Computed using regression model and hourly CDOM and turbidity data.

5

Computed using regression model in Rasmussen and others (2016) and hourly turbidity and temperature data.

6

Computed using regression model in Rasmussen and others (2016) and hourly turbidity data.

Median RPDs between the two in-place continuous monitors 

at the downstream surface-water site for specific conductance, 

pH, water temperature, and dissolved oxygen were <3 percent 

except for turbidity, which was 6 percent. Continuous data 

during the study period generally required corrections (such 

as computations to account for instrument fouling or calibration drift) of <10 percent, which classifies the data-quality 

rating as good according to established guidelines (Wagner 

and others, 2006). During the study period, <1 percent of 

the streamflow record and 16 percent or less of the specific 

conductance, water temperature, dissolved oxygen, turbidity, and nitrate plus nitrite records were missing or deleted 

(table 3) because of equipment malfunction, excessive sensor 

fouling, and low-flow conditions. A total of 55 percent of the 

CDOM record was missing or deleted, primarily because of 

equipment malfunction and subsequent lengthy repair times 

as well as low-flow conditions (table 3). The CDOM data 

were temperature- and turbidity-corrected following protocols 

described by Downing and others (2012).

About 10 percent of discrete water-quality samples were 

QA/QC samples. Sequential, split, and concurrent replicate 

water-quality samples were collected during the study period 

among the sampling sites over a range of streamflow conditions. Replicate pairs with a RPD within 10 percent were 

considered acceptable for inorganic constituents (Ziegler and 

Combs, 1997). Replicate pairs with a RPD within 20 percent 

were considered acceptable for nutrient and organic constituents and RPDs within 50 percent were considered acceptable 

for bacterial analysis. All inorganic constituent replicate pairs 

had median RPDs that were <10 percent except for arsenite 

(12 percent). All nutrient and organic constituent replicate 

pairs had median RPDs that were less than or equal to (≤) 

10 percent. All bacteria constituent replicate pairs had median 

RPDs that were <20 percent except for E. coli (21 percent).
18 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Blank samples were collected to measure the magnitude 

of contaminant concentration that might have been introduced 

into samples as a result of sampling, processing, and analytical procedures (U.S. Geological Survey, 2006). Blank samples 

consisted of deionized water, inorganic blank water, or pesticide-grade blank water depending on analyses. During 2011 

through 2014, 16 blank samples were collected. Filtered and 

unfiltered organic carbon samples had the largest number of 

detections, however, nearly all carbon detections were near the 

laboratory reporting level. Detections for ammonia and E. coli

coliphage were also at, or near, the laboratory reporting level or 

method detection limit. Fluoride had two detections and beryllium and thallium each had one detection out of eight samples.

Standard reference samples were analyzed by the Wichita 

Municipal Water and Wastewater laboratory and submitted to 

the USGS Branch of Quality Systems at least annually and 

oftentimes biannually for laboratory performance evaluation. 

Standard reference sample data is available at https://bqs.usgs.

gov/srs/. Reported values usually were within 10 percent of 

the most probable value during 2011 through 2014. Median 

percent differences between laboratory results and most 

probable values indicated that laboratory data generally were 

consistent and unbiased.

Streambed Sediment Data

Approximately 30 percent of streambed-sediment 

samples were QA/QC samples and included split and concurrent replicates. Median replicate pairs for nutrients, carbon, 

and trace elements had RPDs that were <10 percent except 

for antimony (13 percent). Most organic wastewater-indicator 

compound data were below either the laboratory reporting 

level or reported as estimated concentrations. Where concentrations were measured or estimated, the RPD ranged from 0 

to 40 percent for the upstream and downstream surface-water 

and residuals return line sites (37535009726280, 07144100, 

and 375348097262800 [fig. 1], respectively) (median=12 percent). Poor replication and large RPD values are likely 

because of the low detection levels for these compounds and 

matrix interference conditions.

Macroinvertebrate Data

Concurrent replicate macroinvertebrate samples were 

collected in triplicate at the upstream and downstream 

surface-water sites (375350097262800 and 07144100 [fig. 1], 

respectively) during April and August 2011, May and September 2012, September 2013, and June 2014. The CVs for 

macroinvertebrate metrics ranged from 0 percent to 173 percent (median=26 percent; n=780); however, 67 percent of 

metric comparisons had CVs <40 percent. Metric comparisons 

with CVs >100 percent (8 percent of metric comparisons) 

were caused by rare taxa (consisting of <10 percent of the 

overall community) present in some of the replicate samples 

but not others. Metrics affected by rare taxa included percent 

abundance of Trichoptera, percent abundance and richness of 

Orthocladinae Chironomidae, percent abundance and richness 

of Tanytarsini Chironomidae, percent abundance of non-Chironomidae Diptera, percent abundance of Mollusca and Crustacea, percent abundance and richness of Bivalvia, and percent 

abundance and richness of Oligochaeta. Additional variability 

sources likely were habitat differences among the sampling 

locations at each site. Large variances in some macroinvertebrate community metrics are often observed because of natural 

spatial variation, which can preclude statistical detection of 

minimal differences among sites (Miller and others, 2008).

Effects of Aquifer Storage and 

Recovery Activities on Water Quality 

in the Little Arkansas River and Equus

Beds Aquifer

The city of Wichita’s HBMP presented the opportunity to 

quantify and characterize Little Arkansas River stream quality 

above and below the ASR facility as well as Equus Beds aquifer (fig. 1) groundwater quality in response to ASR activities. 

Continuous measurement and computation of physicochemical 

properties in real time allowed characterization during conditions and time scales that would not have been possible otherwise and served as a complement to discrete water-quality 

sampling as well as biological monitoring. Similar future data 

collection efforts will provide data during different conditions, 

identify new and changing trends, and allow more powerful 

statistical analyses.

Surface Water Physicochemical and Biological 

Conditions of the Little Arkansas River Upstream 

and Downstream from the Aquifer Storage and 

Recovery Facility

Evaluated physicochemical conditions included streamflow, stream-water chemistry, and streambed-sediment 

chemistry. Conditions were evaluated at three sites: upstream 

and downstream from the ASR Phase II facility (surface-water 

sites 375350097262800 and 07144100 [fig. 1], respectively) 

and the residuals return line site (375348097262800, fig. 1). 

Evaluated physical and biological conditions included habitat 

and macroinvertebrate and fish communities upstream and 

downstream from the ASR Phase II facility. Data collected 

during January 2011 through December 2014 were used to 

evaluate differences upstream and downstream from the ASR 

Phase II facility pre- and post-ASR. The facility operated 

intermittently May through September 2013 and May through 

September (except August) 2014.
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 19

Streamflow

Stream ecosystem structure and function are largely 

affected by streamflow (Allan and Castillo, 2007). Annual 

differences in streamflow can be attributed to differences in 

precipitation. There was a large difference in precipitation during pre-ASR compared to post-ASR: mean annual precipitation was 22.6 in. during 2011 through 2012 and 36.2 in. during 

2013 through 2014 (table 2). Duration curves, which graphically represent the relation between streamflow magnitude and 

frequency during a period, were computed for the downstream 

surface-water site (fig. 1). Hourly streamflow ranged from 

<1 ft3/s to 2,094 ft3/s pre-ASR and 1.0 ft3/s to 16,735 ft3/s postASR (table 3; fig. 2). Streamflow was about 10 times larger 

post-ASR than pre-ASR because of larger post-ASR precipitation (table 3, fig. 2). During May 2013 through December 

2014, streamflow exceeded 100 ft3

/s about 20 percent of the 

time (fig. 2). During the facility operational period (April 15 

through October 15) in 2013 and 2014, streamflow exceeded 

100 ft3

/s about 30 percent of the time. Residuals return line 

site (375348097262800, fig. 1) release volumes included a 

very minimal proportion (0.06 percent) of downstream streamflow volume during the months the ASR facility was operating 

during 2013 and 2014.

Water Quality of Stream Water and Releases

Continuous and discrete water-quality data were collected at the upstream and downstream surface-water sites 

(375350097262800 and 07144100 [fig. 1], respectively) and 

in the residuals return line site (375348097262800, fig. 1) and 

were used to evaluate stream-water chemistry pre- and postASR. The following sections describe continuously measured 

and discretely collected water-quality constituents of stream 

water and ASR residuals return line site (375348097262800, 

fig. 1) releases. 

Continuous Water-Quality of Stream Water and Releases

Data from continuously measured and computed physicochemical properties were used to describe water-quality 

conditions at the upstream and downstream surface-water 

sites (375350097262800 and 07144100 [fig. 1], respectively) 

pre- and post-ASR. Continuously measured physicochemical 

properties in the residuals return line site (375348097262800, 

fig. 1) were also used to quantify residuals return line site 

water quality. Continuously measured water-quality data 

included specific conductance, pH, water temperature, dissolved oxygen, turbidity, and nitrate plus nitrite. Continuously 

computed water-quality data included total and dissolved 

organic carbon, total suspended solids, and suspended-sediment concentration. Continuous physicochemical property 

data during higher flow conditions (>100 ft3

/s) under which 

the ASR facility could have been (pre-ASR) or could be (postASR) operating are presented in appendix table 1–3. Continuous physicochemical property data collected under higher flow 

conditions were not substantially different between sites and 

are not discussed further in this report.

Specific conductance is an indirect measure of dissolved 

solids in water (Hem, 1992). Specific conductance was similar 

Frequency of exceedance, in percent

0 20 40 60 80 100

Streamflow, in cubic feet per second

0.1

1

10

100

1,000

10,000

100,000

January 2011–December 2014

January 2011–April 2013 [pre-aquifer 

storage and recovery (ASR)]

May 2013–December 2014 (post-ASR)

Streamflow required for ASR Phase II 

operation—100 cubic feet per second

EXPLANATION

Figure 2. Duration curve for 

hourly measured streamflow 

for the Little Arkansas River 

near Sedgwick, Kansas

(downstream surface-water 

site 07144100), January 2011 

through December 2014.
20 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

EXPLANATION

Upstream surface-water site April 2011–December 2014

Upstream surface-water site April 2011–April 2013 [pre-aquifer 

storage and recovery (ASR)]

Upstream surface-water site May 2013–December 2014 (post-ASR)

Downstream surface-water site January 2011–December 2014

Downstream surface-water site January 2011–April 2013 (pre-ASR)

Downstream surface-water site May 2013–December 2014 (post-ASR)

Frequency of exceedance, in percent

0 20 40 60 80 100

Dissolved oxygen, in milligrams per liter

0

5

10

15

20

25

Specific conductance, in microsiemens per centimeter

at 25 degrees Celsius

0

500

1,000

1,500

2,000

Water temperature, in degrees Celsius

0

10

20

30

40

A

C

pH, in standard units

6.5

7

7.5

8

8.5

9

9.5

B

Kansas Department of Health and Environment

aquatic life support criterion—6.5–8.5

D

Kansas Department of Health and 

Environment aquatic-life-support 

criterion—5.0 milligrams per liter

Turbidity, in formazin nephelometric units

1

10

100

1,000

U.S. Environmental 

Protection Agency Level III 

Ecoregion 27 guideline—

22.13 formazin turbidity units

E

Frequency of exceedance, in percent

0 20 40 60 80 100

Figure 3. Duration curves for hourly measured constituents for the Little Arkansas River upstream from the aquifer storage and 

recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and the Little Arkansas River near Sedgwick, 

Kansas (downstream surface-water site 07144100), March 2011 through December 2014. A, specific conductance; B, pH; C, water 

temperature; D, dissolved oxygen; and, E, turbidity.
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer 21 Equus Beds Aquifer

upstream and downstream from the ASR Phase II facility during the study period. Median pre-ASR hourly specific conductance was 773 microsiemens per centimeter at 25 degrees 

Celsius (μS/cm at 25 °C) at the upstream surface-water site 

and 775 μS/cm at 25 °C at the downstream surface-water site 

(table 3). Median post-ASR hourly specific conductance was 

848 μS/cm at 25 °C at the upstream surface-water site and 838 

μS/cm at 25 °C at the downstream surface-water site (table 3). 

Upstream and downstream surface-water site median specific 

conductance was similar pre- and post-ASR: median values 

at the upstream and downstream surface-water sites varied 

by <1 percent pre-ASR and 1.2 percent post-ASR (fig. 3A; 

table 3). Median residuals return line site specific conductance (268 μS/cm at 25 °C) was about 68 percent less than the 

downstream surface-water site (table 3).

pH is a measure of the effective hydrogen ion concentration and 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, 2005). The 2010 through 2014 and current 

(2015 through 2019) NPDES permits for the ASR Phase II 

treatment facility state that the effluent (residuals return line 

site) limits for pH are 6.0 to 9.0. Median pre-ASR hourly 

pH at the upstream and downstream surface-water sites was 

8.0 (table 3). Median post-ASR pH was 7.9 at the upstream 

surface-water site and 8.0 at the downstream surface-water 

site (table 3). Upstream and downstream surface-water site 

median pH was similar pre- and post-ASR: median values 

above and below the ASR Phase II facility varied by less 

than 1 percent pre-ASR and 1.3 percent post-ASR (fig. 3B; 

table 3). Upstream and downstream surface-water site pH was 

never smaller than 6.6; however, upstream and downstream 

pre-ASR pH exceeded 8.5 about 8 percent and 4 percent of the 

time, respectively. Upstream and downstream surface-water 

site post-ASR pH exceeded 8.5 about 3 percent and 4 percent 

of the time, respectively (fig. 3B). Residuals return line site 

pH had a median of 7.4 and never exceeded Kansas aquatic 

life-support criteria or the ASR Phase II NPDES permit limits 

during the study period (table 3).

Water temperature affects the solubility of chemicals in 

water and biological activity. Kansas water-quality criteria 

require that discharges to streams not change water temperature more than 3 degrees Celsius (oC) above or below natural 

conditions or raise the water temperature above 32 oC (Kansas 

Department of Health and Environment, 2005). Median water 

temperature generally was lower at the downstream surfacewater site (fig. 3C; table 3) throughout the study period. 

Median pre-ASR hourly water temperature was 15.4 oC at the 

upstream surface-water site and 12.4 oC at the downstream 

surface-water site (table 3). Median post-ASR water temperature was 19.0 oC at the upstream surface-water site and 18.4 oC 

at the downstream surface-water site (table 3). Upstream 

and downstream surface-water site water temperature differences were smaller post-ASR (RPD=3 percent) than pre-ASR 

(RPD=22 percent); however, the difference in median water 

temperature upstream and downstream from the facility was 

3 oC or less pre- and post-ASR and did not exceed the KDHE 

criterion (table 3). Median residuals return line site water 

temperature was about 23 percent higher than the downstream 

surface-water site and had a median of 22.6 oC (table 3). 

Residuals return line site water temperature never reached 

32 oC during the study period; as such, ASR Phase II facility 

discharges did not exceed this criterion (table 3). 

Dissolved oxygen is important for aquatic organisms 

and concentrations in surface water primarily are related 

to photosynthesis, respiration, atmospheric reaeration, and 

water temperature (Rounds and others, 2013). Kansas aquatic 

life-support criteria require that dissolved oxygen concentrations are not less than 5.0 mg/L (Kansas Department of Health 

and Environment, 2005). Dissolved oxygen was somewhat 

larger at the downstream surface-water site compared to the 

upstream surface-water site during the study and decreased 

slightly at both sites post-ASR (fig. 3D; table 3). Hourly 

median pre-ASR dissolved oxygen concentrations were 

9.3 mg/L at the upstream surface-water site and 10.8 mg/L at 

the downstream surface-water site. Median post-ASR dissolved oxygen concentrations were 8.9 mg/L at the upstream 

surface-water site and 9.4 mg/L at the downstream surfacewater site (table 3). Upstream and downstream surface-water 

site dissolved oxygen differences were smaller post-ASR 

(RPD=5 percent) than pre-ASR (RPD=15 percent). Dissolved oxygen was less than the Kansas aquatic life-support 

criterion (5.0 mg/L) about 6 percent and 3 percent of the time 

pre-ASR at the upstream and downstream surface-water sites, 

respectively, and about 7 percent of the time post-ASR at both 

sites (fig. 3D). Median residuals return line site dissolved 

oxygen was about 17 percent smaller than the downstream 

surface-water site. Residuals return line site dissolved oxygen 

ranged from 2.5 mg/L to 10.8 mg/L and had a median value of 

7.8 mg/L (table 3).

The EPA guidelines for turbidity (based on reference 

conditions that are determined as the 25th percentiles of all 

compiled nutrient data for that ecoregion) list 22.13 nephelometric turbidity units (NTU; a reporting unit equivalent to 

FNU [Anderson, 2005]) as the criterion for level III ecoregion 27 (central Great Plains) streams, which includes the 

Little Arkansas River (U.S. Environmental Protection Agency, 

2001a). The guidelines are nonenforceable criteria developed 

for the protection of water quality, aquatic life, and human 

health. Turbidity generally was smaller at the downstream 

surface-water site throughout the study period and decreased 

at both sites post-ASR (fig. 3E, table 3). Median turbidities throughout the study period varied by no more than 4 to 

5 FNU (table 3). Median pre-ASR hourly turbidities were 

33 FNU at the upstream surface-water site and 29 FNU at the 

downstream surface-water site (table 3). Median post-ASR 

hourly turbidities were 24 FNU and 19 FNU at the upstream 

and downstream surface-water sites, respectively (table 3). 

Upstream and downstream surface-water site continuously measured turbidity differences were larger post-ASR 

(RPD=23 percent) than pre-ASR (RPD=13 percent). Pre-ASR 
22 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

turbidities exceeded the EPA guideline about 72 percent of 

the time at the upstream surface-water site and 62 percent of 

the time at the downstream surface-water site and post-ASR 

turbidities exceeded the guideline about 52 percent of the time 

at the upstream surface-water site and 46 percent of the time at 

the downstream surface-water site (fig. 3E). Median residuals return line site turbidity (380 FNU) was about an order 

of magnitude (20 times) larger than the downstream surfacewater site and ranged from 11 FNU to 1,410 FNU (table 3).

Large concentrations of inorganic nitrogen compounds, 

such as nitrate plus nitrite, may be toxic to aquatic organisms. 

Large nitrate concentrations in drinking water can impair the 

oxygen-carrying capacity of hemoglobin in humans (Camargo 

and Álonso, 2006). The EPA guidelines for nitrate plus nitrite 

list 0.19 mg/L as the criterion for level III ecoregion 27 

streams (U.S. Environmental Protection Agency, 2001a). The 

EPA Federal maximum contaminant level (MCL) for nitrate in 

drinking water is 10 mg/L as nitrogen, which is the concentration above which methemoglobinemia, or blue baby syndrome, may happen in infants (U.S. Environmental Protection 

Agency, 2009). Sensor- and laboratory-measured nitrate plus 

nitrite concentrations were strongly correlated (R2

=0.98) and 

the nitrate sensor tended to overestimate nitrate concentrations 

by about 6 percent (fig. 4). Median pre-ASR hourly nitrate 

plus nitrite concentration was 1.42 mg/L and post-ASR was 

0.80 mg/L (about 44 percent smaller; table 3), likely because 

of larger post-ASR streamflow and dilution. Nitrate plus 

nitrite concentrations exceeded the EPA level III ecoregion 27 

guideline of 0.19 mg/L about 89 percent of the time pre-ASR 

and 90 percent of the time post-ASR (fig. 5A). Nitrate plus 

nitrite concentrations exceeded the EPA nitrate Federal MCL 

of 10 mg/L <1 and 0 percent of the time pre- and post-ASR, 

respectively (fig. 5A).

Organic carbon is of interest for ASR operation because 

of its role in trihalomethane (THM) formation during the 

water-treatment process. The THMs are disinfection byproducts (DBPs) that are formed when naturally existing inorganic 

and organic materials in water react with the disinfectants 

chlorine and chloramine. The THMs can cause liver, kidney, 

and central nervous system problems and are cancer-causing 

agents (U.S. Environmental Protection Agency, 2005; Pyne 

and others, 1996). An additional concern regarding organic 

carbon concentrations for ASR operations is the potential for 

decreased oxygen leading to increased arsenic concentrations 

in groundwater. Organic carbon from surface-water sources 

has impeded ASR operations in Florida (Mirecki and others, 

2013). 

Continuous (hourly) dissolved and total organic carbon 

concentrations were computed based on developed regression models for the downstream surface-water site (appendix 

tables 1–4 and 1–5 and figs. 2–1 through 2–4). Both carbon 

models used CDOM sensor data as an explanatory variable 

and the total organic carbon model also used turbidity as an 

explanatory variable (figs. 6A and 6B; appendix tables 1–4 

and 1–5 and figs. 2–1 through 2–4). The dissolved carbon 

model explained 81 percent of the variance in dissolved 

carbon concentrations and the total carbon model explained 

94 percent of the variance in total carbon concentrations 

(figs. 6A and 6B; appendix table 1–4 and figs. 2–1 and 2–3). 

Computed dissolved and total organic carbon concentrations 

were about 87 percent and 57 percent larger, respectively, 

post-ASR (figs. 5B and 5C; table 3), likely because of runoff 

during larger streamflows during this period. Median computed dissolved organic carbon was 4.26 mg/L pre-ASR and 

7.95 mg/L post-ASR (table 3). Median computed total organic 

carbon pre-ASR was 6.05 mg/L and was 9.52 mg/L post-ASR 

(table 3).

Total suspended solids and suspended-sediment concentration are two analytes typically used to describe concentrations of suspended solid-phase material in surface water. 

Studies have shown that total suspended solids is a poorer 

measure for natural water compared to suspended-sediment 

concentration (Gray and others, 2000); total suspended solids 

was measured for this study because it is required for TMDLs. 

Although the terms often are used interchangeably, the laboratory analytical methods differ. Total suspended solids represent suspended solids material and may consist of organic or 

inorganic materials. Total suspended solids originate from 

sources such as algae, decaying vegetation, agricultural and 

urban runoff, municipal and industrial discharges, and physical degradation of geologic formations. The amount of total 

suspended solids in a medium is equal to the dry weight of 

organic and inorganic solids filtered from a subsample of the 

original. Suspended-sediment concentration is the measure 

of the dry weight of the organic and inorganic sediment in a 

Sensor measured nitrate plus nitrite (SNO3+NO2), 

in milligrams per liter as nitrogen

0 2 4 6 8 10 12

Laboratory measured nitrate plus nitrite (LNO3+NO2), 

in milligrams per liter as nitrogen

0

2

4

6

8

10

12

1:1 line

LNO3+NO2=0.94(SNO3+NO2)

Coefficient of determination (R 2)=0.98

number=64

Figure 4. Relations between sensor and laboratory measured 

nitrate plus nitrite for the Little Arkansas River near Sedgwick, 

Kansas (downstream surface-water site 07144100), March 2012 

through December 2014.
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 23

Frequency of exceedance, in percent

Total suspended solids, in milligrams per liter

0

10

100

1,000

10,000

Frequency of exceedance, in percent

Suspended-sediment concentration, 

in milligrams per liter

0

10

100

1,000

10,000

0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100

Nitrate plus nitrite, in milligrams per liter as nitrogen

0.01

0.1

1

10

100

Downstream surface-water site January 2011–December 2014

Downstream surface-water site January 2011–April 2013 

(pre-aquifer storage and recovery [ASR])

Downstream surface-water site May 2013–December 2014 (post-ASR)

Dissolved organic carbon, in milligrams per liter

0

5

10

15

20

Total organic carbon, in milligrams per liter

0

10

20

30

40

50

EXPLANATION

B

C D

E

A

U.S. Environmental Protection Agency 

Level III Ecoregion 27 guideline—0.19 mg/L

U.S. Environmental Protection Agency Federal 

maximum contaminant level (nitrate)—

10 milligrams per liter (mg/L)

Figure 5. Duration curves for hourly measured or computed 

constituents for the Little Arkansas River near Sedgwick, 

Kansas (downstream surface-water site 07144100), January 

2011 through December 2014. A, measured nitrate plus nitrite; 

B, computed dissolved organic carbon; C, computed total 

organic carbon; D, computed total suspended solids; and E, 

computed suspended sediment concentration.
24 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Figure 6. Relations between discrete and computed constituents using regression models for the Little Arkansas River near Sedgwick, 

Kansas (downstream surface-water site 07144100), March 2012 through December 2014. A, dissolved organic carbon; and, B, total 

organic carbon.

Discrete dissolved organic carbon, in milligrams per liter

0 2 64 8 10 12 14

Computed dissolved organic carbon, in milligrams per liter

0

2

4

6

8

10

12

14

1:1 line

Discrete total organic carbon, in milligrams per liter

0 5 10 15 20

Computed total organic carbon, in milligrams per liter

0

5

10

15

20

1:1 line

TOC=0.063(TBY)+8.84log(CDOM)−12.4

R 2=0.94

n=17

A B

log(DOC)=0.797log(CDOM)−0.789

R 2=0.81

n=39

Dissolved organic carbon, in milligrams per liter

Colored dissolved organic matter

Total organic carbon, in milligrams per liter

Coefficient of detemination

Turbidity, in formazin nephelometric units

Number of samples

DOC

CDOM

TOC

R 2

TBY

n

EXPLANATION

full sample volume of a water-sediment mixture (Guy, 1969). 

Suspended sediment may consist of clay, silt, sand, or organic 

material. Suspended solids and sediment in stream water typically are from erosion and subsequent transport of surface and 

channel bank soils. Increased suspended sediment in streams 

reduces light penetration and photosynthesis, smothers benthic 

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

Additionally, suspended particulates provide attachment sites 

for nutrients, organic compounds, and other potential contaminants. Sediment is a pollutant of concern in the Little Arkansas 

River drainage basin (Kansas State University Research and 

Extension: Kansas Center for Agricultural Resources and the 

Environment, 2011). Sediment is an impairment for aquatic 

life for streams in or near the study area and the Little Arkansas River drainage basin has a TMDL for total suspended solids (Kansas Department of Health and Environment, 2014a,b). 

The ASR Phase II treatment facility’s 2010 through 2014 and 

current (2015 through 2019) NPDES permits state that total 

suspended solids should be monitored monthly while the facility is operating.

Regression-computed total suspended solids concentrations tended to overestimate total suspended solids concentrations by about 6 percent and regression-computed suspended 

sediment concentrations tended to overestimate suspended 

sediment concentrations by about 19 percent during the study 

period (fig. 7). Median continuously computed total suspended 

solids and suspended-sediment concentrations were 36 percent 

and 29 percent smaller, respectively, post-ASR (figs. 5 D and 

5E; table 3), likely because of larger post-ASR streamflow 

and dilution. Median total suspended solids concentration was 

39 mg/L pre-ASR and 25 mg/L post-ASR (table 3). Median 

suspended-sediment concentration was 48 mg/L pre-ASR and 

34 mg/L post-ASR (table 3).

Because facility operations are limited to high flow 

conditions, water-quality concentrations and physical properties of stream water and residuals return line releases are more 

indicative of event conditions than the distribution of all continuously collected water-quality data. During events, stream 

specific conductance, pH, and dissolved oxygen are smaller 

than during base-flow conditions, and turbidity is larger. 

Though stream dissolved oxygen tends to be smaller, even 

below 5 mg/L, residuals return line releases are turbulent and 

would entrain air, resulting in dissolved oxygen concentrations 

near saturation. The short delay (as much as 5 hours) between 

water withdrawals and residual releases could prolong event 

conditions for specific conductance, pH, and turbidity; 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 25

however, effects would likely be localized near the residuals 

return line outflow.

Discrete Water-Quality of Stream Water and Releases

Data from discrete stream-water samples also were used 

to describe water-quality conditions at the upstream and downstream surface-water sites (375350097262800 and 07144100 

[fig. 1], respectively) pre- and post-ASR. Discrete data from 

residuals return line site (375348097262800, fig. 1) water 

samples also were used to quantify residuals return line site 

water quality. Discrete water-quality data collected included 

dissolved solids and primary ions, nutrients, trace elements, 

indicator bacteria, and organic compounds. Upstream and 

downstream surface-water site water-quality variables were 

statistically compared pre- and post-ASR to determine differences between sites. Discrete water-quality data collected during higher flow conditions (>100 ft3

/s) under which the ASR 

facility could have been (pre-ASR) or could be (post-ASR) 

operating are presented in appendix table 1–6. No statistical 

comparisons for discrete water-quality data collected under 

higher flow conditions were significant and these data are not 

discussed further in this report.

Dissolved and Suspended Solids, Major Ions, and Suspended 

Sediment

The primary constituents of dissolved solids generally 

are calcium, magnesium, sodium, potassium, bicarbonate, 

carbonate, chloride, and sulfate ions. These ions come from 

decomposing rocks and soils. Concentrations of dissolved 

solids in stream water may increase because of atmospheric 

deposition, sewage inputs, industrial effluents, agricultural 

runoff, and urban runoff (Hem, 1992; Wetzel, 2001). Dissolved solids often are used as a general indicator of salinity 

or water quality. Large concentrations of dissolved solids are 

undesirable in drinking water because of possible physiological effects, strong mineral tastes, increased treatment costs, 

and corrosion in plumbing. The EPA has established National 

Secondary Drinking Water Regulations that set nonmandatory water-quality standards. The EPA does not enforce these 

SMCLs; they were established as guidelines to assist public 

water-supply systems in managing their drinking water for 

aesthetic considerations such as taste, color, and odor (U.S. 

Environmental Protection Agency, 2009). The EPA has established a SMCL for dissolved solids in drinking water of 500 

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

Figure 7. Relation between discrete and computed constituents using models developed in Rasmussen and others (2016) for the 

Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), January 2011 through December 2014. A, total 

suspended solids; and, B, suspended-sediment concentration.

Discrete total suspended solids, in milligrams per liter

0 200 400 600 800 1,000

Computed total suspended solids, in milligrams per liter

0

200

400

600

800

1,000

Discrete suspended-sediment concentration, 

in milligrams per liter

0 200 400 600 800 1,000 1,200 1,400

Computed suspended-sediment concentration, 

in milligrams per liter

0

200

400

600

800

1,000

1,200

1,400

1:1 line

A B

Rasmussen and others (2016) model data—

log(TSS)=1.01log(TBY)+0.076

R 2=0.92

Rasmussen and others (2016) model data—

log(SSC)=0.933log(TBY)+0.0431log(Q)+0.262

R 2=0.98

1:1 line

Total suspended solids, in milligrams per liter

Turbidity, in formazin nephelometric units

Suspended-sediment concentration, in milligrams per liter

Streamflow, in cubic feet per second

Coefficient of detemination

TSS

TBY

SSC

Q

R 2

EXPLANATION
26 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Dissolved solids at the upstream and downstream 

surface-water sites (375350097262800 and 07144100 [fig. 1], 

respectively) were 18 percent to 27 percent smaller postASR (table 4). Pre-ASR dissolved solids medians at the 

upstream and downstream surface-water sites were 473 mg/L 

and 438 mg/L, respectively; post-ASR upstream and downstream surface-water site dissolved solids medians were 

345 mg/L and 359 mg/L, respectively (table 4). Upstream 

and downstream surface-water site dissolved solids differences were smaller post-ASR (RPD=4 percent) than preASR (RPD=8 percent). The median residuals return line site 

(375348097262800, fig. 1) dissolved solids concentration was 

281 mg/L and was about 20 percent smaller than median dissolved solids concentrations at the upstream and downstream 

surface-water sites post-ASR (table 4). Median dissolved solids concentrations at all sites did not exceed the EPA SMCL; 

individual samples from all sites, except for the downstream 

surface-water site post-ASR, occasionally exceeded the EPA 

SMCL during the study period (table 4). 

All the primary constituents of dissolved solids, with the 

exception of potassium, were smaller at both sites post-ASR 

compared to pre-ASR (table 4). With the exception of potassium, primary dissolved solids constituents were smaller at the 

downstream site pre-ASR; with the exception of magnesium, 

chloride, and sulfate, primary dissolved solids constituents 

were smaller at the downstream site post-ASR (table 4). 

Median primary dissolved solids constituent concentrations in 

the residuals return line, with the exception of potassium, were 

always at least about 10 percent smaller than median primary 

dissolved solids constituent concentrations at the upstream and 

downstream surface-water sites post-ASR (table 4). Median 

calcium concentrations at the upstream and downstream surface-water sites were 87.0 mg/L and 80.9 mg/L, respectively, 

pre-ASR and 57.9 mg/L and 56.5 mg/L, respectively, postASR (table 4). Median pre-ASR sodium concentrations were 

62.0 mg/L at the upstream surface-water site and 52.0 at the 

downstream surface-water site; median post-ASR sodium concentrations were 43.0 mg/L at the upstream surface-water site 

and 42.0 mg/L at the downstream surface-water site (table 4). 

Median calcium and sodium concentrations were significantly larger (p-value=0.04 and p-value=0.03, respectively) 

at the upstream surface-water site pre-ASR and were not 

significantly different post-ASR (table 4). Carbonate hardness 

was significantly (p-value<0.05) smaller at the downstream 

surface-water site (255 mg/L) compared to the upstream 

surface-water site (285 mg/L) pre-ASR and was not significantly different post-ASR (table 4). Pre-ASR calcium, sodium, 

and carbonate hardness concentrations that were significantly 

different between the upstream and downstream surface-water 

sites and not significantly different post-ASR indicates that 

water-quality conditions were more similar between sites after 

the facility began discharging; however, this result could be 

because of the higher post-ASR streamflow conditions compared to pre-ASR streamflow conditions.

The EPA SMCL for chloride is 250 mg/L (U.S. Environmental Protection Agency, 2009) and KDHE has established 

an aquatic-life-support criterion for chloride of 860 mg/L 

(Kansas Department of Health and Environment, 2011). Chloride was lower at both surface-water sites post-ASR. Median 

pre-ASR chloride was 79 mg/L at the upstream surface-water 

site and 58 mg/L at the downstream surface-water site; median 

post-ASR chloride was 51 mg/L at the upstream surfacewater site and 54 mg/L at the downstream surface-water 

site (table 4). Median residuals return line site chloride was 

44 mg/L (table 4). No chloride samples collected during the 

study exceeded the EPA SMCL or the KDHE aquatic-lifesupport criterion (table 4). The EPA has a SMCL for fluoride 

of 2.0 mg/L (U.S. Environmental Protection Agency, 2009); 

no fluoride samples collected during the study exceeded the 

SMCL (table 4). The EPA has a SMCL for sulfate of 250 mg/L 

(U.S. Environmental Protection Agency, 2009); no sulfate 

samples collected during the study exceeded this SMCL 

(table 4).

Discretely collected total suspended solids concentration medians were similar at the upstream and downstream 

surface-water sites (70 mg/L and 74 mg/L, respectively) 

pre-ASR and about 27 percent smaller at the downstream 

surface-water site (upstream median=78 mg/L; downstream 

median=57 mg/L) post-ASR, despite a median residuals return 

line total suspended solids concentration (858 mg/L) that 

was about 15 times larger than the downstream surface-water 

site (table 4), likely because of dilution. Discretely collected 

pre-ASR suspended-sediment concentration medians were 

similar at the upstream (79 mg/L) and downstream (74 mg/L) 

surface-water sites. Discretely collected post-ASR suspendedsediment concentration medians were larger than pre-ASR 

concentrations at both sites (upstream median=112 mg/L; 

downstream median=154 mg/L; table 4), which is contradictory to the continuously computed suspended-sediment concentration medians at the downstream surface-water site that 

decreased post-ASR (table 3). These differences in suspendedsediment concentration medians highlight the utility of continuous monitoring by capturing temporal variability and the 

need to continue continuous monitoring as a complement to 

discrete water-quality sampling. The median residuals return 

line site suspended-sediment concentration was 1,175 mg/L 

and was about 10 times greater than the upstream surfacewater site and 8 times greater than the downstream surfacewater site post-ASR (table 4).

Sodium hypochlorite is used in ASR facility operations 

to clean filtration membranes and is subsequently dechlorinated. The 2010 through 2014 NPDES permit for the residuals 

return line requires monthly total residual chlorine monitoring when the facility is operating. The current (2015 through 

2019) NPDES permit for the residuals return line limits total 

residual chlorine (because of aquatic organism sensitivity) 

to 100 μg/L. Total residual chlorine was not detected in at 

least 50 percent of upstream surface-water site, downstream 

surface-water site, or residuals return line site samples during 

the study period (table 4). Median pre-ASR total residual 

chlorine was 12 μg/L at the upstream surface-water site and 

19 μg/L at the downstream surface-water site (table 4). Two 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer 27

Table 4. Discretely collected dissolved and suspended solids, primary ions, and suspended sediment summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas 

River near Sedgwick, Kansas (downstream surface-water site 07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through September 2014.

[See figure 1 for site locations. Medians in bold indicate statistically significant differences (p-value less than 0.05) between the upstream and downstream surface-water sites; the upstream and downstream surface-water sites were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014; n, number of measurements; mg/L, milligram per liter; μg/L, microgram per liter; <, less than; --, not applicable; SiO2

, silicon dioxide; CaCO3, calcium carbonate]

Water-quality constituent 

(unit of measure)

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site Upstream surface-water site Downstream surface-water site Residuals return line site

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Dissolved solids (mg/L) 0 20 141 735 475 473 0 20 153 666 444 438 0 7 86 517 294 345 0 7 78 497 294 359 0 7 96 817 344 281

Total solids (mg/L) 0 20 342 862 589 560 0 20 376 1,520 615 531 0 6 242 596 468 499 0 6 230 590 460 474 0 7 726 6,750 2,179 1,580

Calcium (mg/L) 0 20 21.6 111 80.0 87.0 0 20 23.1 103 73.7 80.9 0 7 12.7 96.3 48.8 57.9 0 7 10.5 98.3 49.7 56.5 0 7 11.7 79.1 42.3 43.1

Magnesium (mg/L) 0 20 3.4 18.3 14.1 15.5 0 20 3.6 18.7 12.9 14.2 0 7 2.4 17.8 9.6 12.3 0 7 1.9 17.8 9.8 12.7 0 7 2.1 13.1 7.9 7.8

Potassium (mg/L) 0 20 5.0 14.0 7.2 6.5 0 20 4.0 14.0 7.2 7.0 0 7 6.0 10.0 8.0 8.0 0 7 6.0 10.0 7.9 7.0 0 7 6.0 10.0 8.3 9.0

Sodium (mg/L) 0 20 11.9 134 68.8 62.0 0 20 14.1 123 62.5 52.0 0 7 2.5 57.3 30.1 43.0 0 7 2.1 56.2 30.0 42.0 0 7 2.29 191 53.1 34.7

Bromide (mg/L) 0 19 0.1 1 0.2 0.2 0 19 0.1 0.5 0.2 0.2 29 7 <0.04 0.2 0.2 0.2 29 7 <0.04 0.3 0.1 0.1 0 6 0.0 0.3 0.1 0.1

Chloride (mg/L) 0 20 15 240 95 79 0 20 19 226 86 58 0 7 6.6 69 39 51 0 7 5.8 76 41 54 0 7 5.7 210 62 44

Total residual chlorine 

(μg/L)

80 15 <50 240 42 12 80 15 <50 210 44 19 83 6 <50 80 -- -- 50 6 <50 80 54 48 50 6 <50 310 120 50

Flouride (mg/L) 0 20 0.2 0.5 0.4 0.4 0 20 0.2 0.5 0.3 0.4 0 7 0.3 0.6 0.4 0.4 0 7 0.2 0.5 0.3 0.3 0 7 0.1 0.4 0.3 0.3

Silica (mg/L as SiO2

) 0 20 7.0 23.6 14.4 14.9 0 20 6.5 21.8 14.2 15.3 0 7 9.1 20.1 15.4 16.1 0 7 9.6 20.1 15.0 14.6 0 7 11.3 16.6 13.5 12.7

Sulfate (mg/L) 0 20 11 88 53 59 0 20 12 88 52 55 14 7 <5 57 31 44 14 7 <5 67 36 49 14 7 <5 210 63 40

Carbonate hardness 

(mg/L as CaCO3

)

0 20 68 350 258 285 0 20 73 330 237 255 0 7 42 310 162 200 0 7 34 320 164 190 0 7 38 250 137 140

Alkalinity (mg/L as CaCO3

) 0 20 60 286 210 222 0 20 58 276 197 212 0 7 42 278 146 160 0 7 39 273 145 154 0 7 44 198 106 112

Bicarbonate (mg/L) 0 20 73 350 257 270 0 20 71 340 240 260 0 7 51 340 178 200 0 7 48 330 177 190 0 7 54 240 131 140

Total suspended solids 

(mg/L)

0 20 14 162 72 70 0 20 11 740 110 74 0 7 48 528 154 78 0 7 48 552 153 57 0 7 259 5,220 1,405 858

Suspended-sediment 

concentration (mg/L)

0 20 18 241 100 79 0 20 13 1,270 151 74 0 7 45 724 270 112 0 7 58 660 249 154 0 6 286 5,314 1,643 1,175
28 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

pre-ASR total residual chlorine samples at each upstream (190 

μg/L and 240 μg/L) and downstream (210 μg/L and 170 μg/L) 

surface-water site exceeded the level established in the 2015 

permit during June 2011. Median post-ASR chlorine was 48 

μg/L at the downstream surface-water site (table 4). Median 

residuals return line site total residual chlorine was 50 μg/L, 

ranged from <50 μg/L to 310 μg/L, and was above the level 

established in the 2015 draft permit in two samples collected 

in May 2013 (270 μg/L) and May 2014 (310 μg/L). Total 

residual chlorine may be present upstream and downstream 

from the ASR facility because of water treatment discharges 

to streams in the drainage basin at locations upstream from the 

study sites. Samples that exceeded the current (2015 through 

2019) NPDES permit total residual chlorine limit may be 

due to interferences during sample analysis (Harp, 2002), or 

municipal wastewater discharges from upstream sources, or 

ASR facility treatment.

Nutrients

Nutrient sources for streams include upstream sources, 

terrestrial runoff, groundwater, and the atmosphere. Nutrients, 

including species of nitrogen and phosphorus, are necessary 

for plant and animal growth but can lead to eutrophication, 

algal blooms, low dissolved oxygen, fish kills, and taste-andodor problems when present in excess amounts. Nutrients, 

particularly nitrogen and phosphorus, have been identified as a 

primary source of water-quality degradation in Kansas and the 

Nation (Kansas Department of Health and the Environment, 

2004a; U.S. Environmental Protection Agency, 2000c, 2006e).

Nitrogen is present as ammonia, nitrate, nitrite, and as 

part of organic compounds. Most algae use dissolved forms of 

inorganic nitrogen (Hem, 1992). Nitrate is the form of nitrogen 

most easily used by plants and algae and is the most common 

ion in many oxygen-rich waters because the nitrite ion is easily oxidized. The large increase in use of nitrogen fertilizers 

on agricultural land in recent decades prompted concern about 

nitrate concentration increases in surface and groundwater 

(Hem, 1992). Large nitrate concentrations in drinking water 

can pose adverse health effects on humans, such as methemoglobinemia, a condition also known as blue baby syndrome. 

This condition restricts the oxygen-carrying capacity of the 

blood in infants and may be fatal (Walton, 1951).

There were no substantial differences in discretely 

collected nitrogen species concentration medians between 

the upstream and downstream surface-water sites 

(375350097262800 and 07144100 [fig. 1], respectively) 

throughout the study period. Median pre-ASR total Kjeldahl 

nitrogen (ammonia plus organic nitrogen) was 1.25 mg/L at 

the upstream surface-water site and 1.20 mg/L at the downstream site; median post-ASR total Kjeldahl nitrogen was 

1.80 mg/L at the upstream site and 1.85 at the downstream 

surface-water site (table 5). Median residuals return line 

site (375348097262800, fig. 1) total Kjeldahl nitrogen was 

7.30 mg/L and about 4 times larger than either surface-water 

site post-ASR (table 5). The EPA guidelines for total Kjeldahl 

nitrogen list 0.52 mg/L as the criterion for level III ecoregion 

27 streams (U.S. Environmental Protection Agency, 2001a); 

all samples from all sites exceeded this guideline (table 5).

Median nitrate plus nitrite and nitrate concentrations 

were smaller at the upstream surface-water site during both 

pre- and post-ASR and were smaller at both surface-water 

sites post-ASR likely because of larger post-ASR streamflow 

and dilution. There was no change in nitrite medians. Median 

pre-ASR nitrate plus nitrite was 0.74 mg/L at the upstream 

surface-water site and 0.95 at the downstream surface-water 

site; median post-ASR nitrate plus nitrite was 0.50 mg/L at 

the upstream surface-water site and 0.79 at the downstream 

surface-water site (table 5). The EPA guidelines for nitrate plus 

nitrite list 0.19 mg/L as the criterion for level III ecoregion 

27 streams (U.S. Environmental Protection Agency, 2001a); 

nitrate plus nitrite samples collected from all sites throughout this study frequently exceeded this guideline. Residuals 

return line site median nitrate plus nitrite was 1.57 mg/L and 

was about 3.1 times larger than the upstream surface-water 

site median and about 2 times larger than the downstream 

surface-water site median post-ASR (table 5). Pre-ASR nitrate 

medians were 0.69 mg/L at the upstream surface-water site 

and 0.88 mg/L at the downstream surface-water site; postASR nitrate medians were 0.43 mg/L at the upstream surfacewater site and 0.72 mg/L at the downstream surface-water 

site (table 5). Median residuals return line site nitrate was 

1.45 mg/L, never exceeded the Federal MCL of 10 mg/L, 

and was about 3.4 times than the upstream surface-water site 

nitrate median and about 100 percent larger than the downstream surface-water site nitrate median (table 5). 

Median pre-ASR total nitrogen was similar at both 

surface-water sites (upstream=2.17 mg/L; downstream=2.15 mg/L), whereas the post-ASR total nitrogen 

median was about 26 percent larger at the downstream surface-water site (upstream=2.00 mg/L; downstream=2.51 mg/L; 

table 5). Median residuals return line site total nitrogen was 

8.89 mg/L and was about 4.4 times larger than the upstream 

surface-water site median and about 3.5 times larger than the 

downstream surface-water site median post-ASR (table 5). 

The EPA guidelines for total nitrogen list 0.71 mg/L as the criterion for level III ecoregion 27 streams (U.S. Environmental 

Protection Agency, 2001a); all total nitrogen samples collected 

throughout this study exceeded this guideline (table 5).

Phosphorus is introduced into the environment by soil 

and rock mineral breakdown. Most phosphorus in surface 

water is organically bound and much of the organic phosphorus fraction is in the particulate phase of living cells, primarily algae (Wetzel, 2001). Sources of phosphorus in the Little 

Arkansas River drainage basin include inorganic phosphates 

from fertilizer, manure from animal production, and runoff. 

There were no substantial differences in phosphorus species 

concentration medians between the upstream and downstream 

surface-water sites pre- or post-ASR. Phosphorus species 

were generally smaller at the downstream surface-water site 

compared to the upstream surface-water site and were larger 

at both sites post-ASR. Median pre-ASR orthophosphate was 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 29

Table 5. Discretely collected nutrient and carbon summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surfacewater site 07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through September 2014.

[See figure 1 for site locations. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014; n, number of measurements; mg/L, milligram per liter; N, nitrogen; <, less than; P, phosphorus]

Water-quality 

constituent 

(unit of measure)

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site Upstream surface-water site Downstream surface-water site Residuals return line site

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Total Kjeldahl nitrogen 

(mg/L as N)

0 20 0.69 1.90 1.28 1.25 0 20 0.79 5.20 1.51 1.20 0 8 0.89 3.40 1.85 1.80 0 8 0.96 3.10 1.87 1.85 0 7 2.60 18.0 8.14 7.30

Ammonia (mg/L as N) 45 20 <0.03 0.36 0.09 0.04 25 20 <0.03 0.38 0.12 0.04 29 7 <0.03 0.34 0.13 0.09 29 7 <0.03 0.37 0.14 0.09 0 7 0.17 1.03 0.46 0.35

Nitrate plus nitrite 

(mg/L as N)

5 22 <0.02 4.79 1.16 0.74 9 22 <0.02 5.24 1.19 0.95 0 7 0.04 1.80 0.75 0.50 14 7 <0.02 1.74 0.77 0.79 0 7 0.08 2.42 1.52 1.57

Nitrate (mg/L as N) 5 20 <0.01 3.16 0.96 0.69 10 20 <0.01 5.04 1.10 0.88 0 7 0.04 1.76 0.70 0.43 14 7 <0.01 1.70 0.71 0.72 0 7 0.08 2.38 1.44 1.45

Nitrite (mg/L as N) 35 20 <0.01 0.14 0.05 0.04 30 20 <0.01 0.20 0.06 0.04 43 7 <0.01 0.12 0.06 0.04 43 7 <0.01 0.16 0.07 0.04 14 7 <0.01 0.16 0.09 0.10

Total nitrogen 

(mg/L as N)1

0 20 0.87 4.37 2.28 2.17 0 20 0.96 6.59 2.66 2.15 0 7 0.97 4.40 2.37 2.00 0 7 0.97 4.24 2.46 2.51 0 7 3.28 19.96 9.66 8.89

Orthophosphate 

(mg/L as P)

0 20 0.22 0.94 0.52 0.47 0 20 0.19 1.24 0.44 0.36 0 7 0.37 0.71 0.54 0.55 0 7 0.35 0.80 0.56 0.52 0 7 0.34 0.88 0.56 0.56

Dissolved phosphorus 

(mg/L as P)

0 20 0.32 1.10 0.55 0.54 0 20 0.23 1.07 0.46 0.41 0 7 0.37 0.72 0.59 0.59 0 7 0.35 1.94 0.73 0.54 0 7 0.35 0.98 0.60 0.56

Total phosphorus 

(mg/L as P)

0 20 0.49 1.16 0.80 0.77 0 20 0.45 1.58 0.76 0.70 0 8 0.69 1.46 0.94 0.89 0 8 0.69 1.36 0.92 0.89 0 7 0.96 6.76 3.03 2.67

Dissolved organic 

carbon (mg/L)

0 20 3.7 12.5 6.2 5.4 0 20 2.3 13.7 6.4 5.2 0 8 4.4 13.3 9.2 9.2 0 8 4.2 13.0 9.3 9.7 0 7 6.5 19.4 13.3 14.8

Total organic carbon 

(mg/L)

0 20 5.1 15.6 8.2 7.1 0 20 4.4 32.4 9.3 7.3 0 8 5.1 22.6 12.3 13.1 0 8 5.1 29.4 13.0 12.3 0 7 8.8 71.6 31.0 23.6

1

Calculated as the sum of total Kjeldahl nitrogen plus nitrate plus nitrite.
30 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

0.47 mg/L at the upstream surface-water site and 0.36 mg/L at 

the downstream surface-water site (table 5). Median post-ASR 

orthophosphate was 0.55 mg/L at the upstream surface-water 

site and 0.52 mg/L at the downstream surface-water site 

(table 5). Median residuals return line site orthophosphate was 

0.56 mg/L and was about 2 and 8 percent larger than median 

orthophosphate at the upstream and downstream surface-water 

sites post-ASR, respectively (table 5). Median pre-ASR total 

phosphorus was 0.77 mg/L at the upstream surface-water site 

and 0.70 mg/L at the downstream surface-water site; median 

post-ASR total phosphorus was 0.89 mg/L at both surfacewater sites (table 5). Residuals return line site total phosphorus ranged from 0.96 mg/L to 6.76 mg/L and the median 

was about three times larger (median=2.67 mg/L) than the 

upstream and downstream surface-water site median phosphorus concentrations post-ASR (table 5). The EPA guidelines for 

total phosphorus list 0.09 mg/L as the criterion for level III 

ecoregion 27 streams (U.S. Environmental Protection Agency, 

2001a); all samples collected from all sites throughout the 

study period exceeded this guideline (table 5).

Organic material in natural waters is composed of living 

and senescent organisms, cellular exudates, and degraded 

detrital material (Aiken, 2002). An important artificial 

recharge concern is the introduction of potentially reactive 

organic material into an aquifer (Aiken, 2002). Organic carbon 

is a constituent of interest for ASR operation because of its 

role in THM formation during the water treatment process. 

Data related to organic material characterization is presented 

in appendix table 1–7. There were no substantial differences 

in dissolved or total organic carbon medians between the 

upstream and downstream surface-water sites pre- or postASR. Dissolved and total organic carbon was larger post-ASR 

likely because of runoff during larger streamflows during 

this period. Median pre-ASR dissolved organic carbon was 

5.4 mg/L at the upstream surface-water site and 5.2 mg/L at 

the downstream surface-water site; median post-ASR dissolved organic carbon was 9.2 mg/L at the upstream surfacewater site and 9.7 mg/L at the downstream surface-water site 

(table 5). Median residuals return line site dissolved organic 

carbon was 14.8 mg/L and was about 61 and 53 percent larger 

than the upstream and downstream surface-water sites postASR, respectively (table 5). Pre-ASR total organic carbon 

was 7.1 mg/L at the upstream surface-water site and 7.3 mg/L 

at the downstream surface-water site; median post-ASR total 

organic carbon was 13.1 mg/L at the upstream surface-water 

site and 12.3 mg/L at the downstream surface-water site 

(table 5). Median residuals return line site total organic carbon 

was 23.6 mg/L and was about 80 and 92 percent larger than 

the upstream and downstream surface-water sites post-ASR, 

respectively (table 5).

Trace Elements and Associated Compounds

Dissolved concentrations of trace elements of particular 

interest in this report include copper, iron, manganese, and 

arsenic and associated arsenic species. The 2010 through 2014 

NPDES permit for the ASR Phase II treatment facility stated 

that total recoverable copper should be monitored monthly 

while the facility was operating; however, total recoverable 

copper is not listed in the current (2015 through 2019) NPDES 

permit. Exposure to copper may cause health problems that 

include stomach distress and liver or kidney damage (U.S. 

Environmental Protection Agency, 2009). Arsenic is a carcinogen and iron and manganese can give water an undesirable 

taste and color and can plug groundwater wells. Infiltration 

of stream water or treated water into the Equus Beds aquifer 

(fig. 1) by artificial recharge operations could affect dissolved 

arsenic mobility or could stimulate microbial activity and 

cause iron and manganese precipitation of groundwater. 

Sources of copper include corrosion of plumbing systems 

and erosion of natural deposits (U.S. Environmental Protection Agency, 2009). The EPA Federal SMCL for copper is 

1.0 mg/L (1,000 μg/L). At least 80 percent of total copper 

samples were below the laboratory reporting level in surfacewater samples collected during the study period (table 6). 

Median residuals return line site (375348097262800, fig. 1) 

total copper was 39 μg/L and ranged from 18 μg/L to 48 μg/L 

(table 6). No samples collected during the study exceeded the 

EPA Federal SMCL for copper.

Iron in water is derived from rocks and soils (Hem, 

1992). Water having excessive concentrations of iron is unpalatable because of odor, a metallic taste, and rusty color. The 

EPA Federal SMCL for iron is 300 μg/L (U.S. Environmental 

Protection Agency, 2009). Iron was not detected in at least 

75 percent of pre-ASR surface-water samples and 57 percent 

of post-ASR surface-water samples (table 6). Pre-ASR iron 

concentrations ranged from <100 to 200 μg/L at the upstream 

surface-water site (375350097262800, fig. 1) and <100 to 

350 μg/L at the downstream surface-water site (07144100, 

fig. 1) (table 6). Median post-ASR iron concentrations were 

102 μg/L at the upstream surface-water site and 115 μg/L 

at the downstream surface-water site (table 6). Iron was 

not detected in about 30 percent of residuals return line site 

samples; median residuals return line site iron concentration 

was 140 μg/L and ranged from <100 to 920 μg/L (table 6). 

Iron concentrations exceeded the EPA SMCL in one pre-ASR 

sample from the downstream surface-water site and one postASR sample from each surface-water site. Iron concentrations 

exceeded the EPA SMCL in two residuals return line samples.

Manganese originates from rocks and soil (Hem, 1992). 

The EPA SMCL for manganese is 50 μg/L (U.S. Environmental Protection Agency, 2009). Drinking water consumers may 

notice a bitter metallic taste, a black to brown color, and black 

staining on plumbing fixtures at concentrations larger than 

the SMCL (U.S. Environmental Protection Agency, 2009). 

Median manganese concentrations were larger at both surfacewater sites pre-ASR. Manganese was significantly larger 

(p-value=0.02) at the upstream surface-water site (252 μg/L) 

compared to the downstream surface-water site (170 μg/L) 

pre-ASR but not post-ASR (table 6). Median post-ASR manganese concentrations were 51 μg/L at the upstream surfacewater site, 94 μg/L at the downstream surface-water site, and 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer 31

Table 6. Discretely collected trace element and associated compound summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas

(downstream surface-water site 07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through September 2014.

[See figure 1 for site locations. Medians in bold indicate statistically significant differences (p-value less than 0.05) between the upstream and downstream surface-water sites; the upstream and downstream surface-water sites were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014; n, number of measurements; μg/L, microgram per liter; <, less than; --, not applicable; As, arsenic]

Water-quality 

constituent 

(unit of measure)

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site Upstream surface-water site Downstream surface-water site Residuals return line site

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n Minimum MaximumMean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Total copper (μg/L) 81 16 <5 10.0 -- -- 94 16 <5 10.0 -- -- 100 1 <10 <10 -- -- 100 1 <10 <10 -- -- 0 4 18 48 36 39

Iron (μg/L) 85 20 <100 200 -- -- 75 20 <100 350 59 17 57 7 <100 330 143 102 57 7 <100 310 148 115 29 7 <100 920 281 140

Lead (μg/L) 25 20 <0.1 0.36 0.15 0.13 25 20 <0.1 0.35 0.16 0.13 29 7 <1 0.44 0.15 0.10 71 7 <0.1 0.35 0.12 0.05 0 7 0.12 6.67 1.16 0.22

Manganese (μg/L) 0 20 26 1,480 377 252 0 20 15 708 239 170 0 7 6 187 75 51 0 7 5 168 78 94 0 7 7 445 141 56

Nickel (μg/L) 0 20 1.3 5.4 2.8 2.4 0 20 0.7 5.8 2.7 2.5 0 7 2.6 4.5 3.6 3.8 0 7 2.5 4.5 3.5 3.6 0 7 3.1 6.4 4.2 4.0

Strontium (μg/L) 0 20 132 811 551 575 0 20 142 690 520 605 0 7 76 660 353 483 0 7 57 657 358 474 0 7 65 574 318 298

Arsenic (μg/L) 0 20 5.0 27.3 12.3 10.5 0 20 3.0 15.9 8.5 8.8 0 7 3.1 12.4 8.0 8.5 0 7 3.0 11.3 7.4 8.2 0 7 3.4 6.7 5.1 5.1

Arsenate (μg/L as As) 0 20 3.4 20.1 8.7 7.6 15 20 <1.6 11.5 5.6 5.7 0 8 1.8 11.3 5.3 3.8 0 8 2.2 10.2 5.7 5.2 0 7 2.2 5.4 3.8 3.8

Arsenite (μg/L as As) 85 20 <0.4 1.0 -- -- 80 20 <0.4 1.0 0.4 0.3 38 8 <0.2 12.4 1.9 0.5 25 8 <0.2 0.6 0.3 0.3 86 7 <0.2 0.5 -- --

Dimethylarsinate 

(μg/L as As)

100 20 <0.6 <2 -- -- 100 20 <0.6 <2 -- -- 100 8 <0.3 <0.6 -- -- 88 8 <0.3 0.3 -- -- 100 7 <0.3 <0.6 -- --

Monomethylarsonate 

(μg/L as As)

100 20 <0.8 <3.2 -- -- 100 20 <0.8 <3.2 -- -- 100 8 <0.8 <3.2 -- -- 95 13 <0.8 1.6 -- -- 100 7 <3.2 <3.2 -- --

Selenium (μg/L) 0 20 1.0 4.5 2.2 2.0 0 20 0.5 5.3 2.1 1.8 14 7 <0.5 2.9 1.6 1.5 14 7 <0.5 2.7 1.4 1.4 29 7 <0.5 15.1 4.7 1.0
32 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

56 μg/L at the residuals return line site (table 6). Manganese 

concentrations exceeded the SMCL at the upstream and downstream surface-water sites in about 80 percent of pre-ASR 

samples and 60 percent of post-ASR samples; the residuals 

return line site exceeded the SMCL in about 40 percent of 

samples.

Arsenic is present naturally in clay layers associated with 

iron sulfide minerals (Hem, 1992) and is a health concern 

in drinking water because it causes skin damage, affects the 

circulatory system, and increases the risk of cancer (U.S. 

Environmental Protection Agency, 2009). Arsenic mobility is 

generally controlled by adsorption and desorption reactions 

as well as solid-phase precipitation and dissolution reactions 

(Hem, 1992; Hinkle and Polette, 1999; Smedley and Kinniburgh, 2002; McMahon and Chapelle, 2008). These processes 

are affected by pH, oxidation/reduction reactions, and competing anion presence, all of which could be altered as a result of 

artificial recharge activities. The EPA Federal MCL for arsenic 

is 10 μg/L (U.S. Environmental Protection Agency, 2009). 

Median arsenic concentrations were 7 to 19 percent larger 

before the ASR Phase II facility began operating and were 

similar upstream and downstream after the facility began operating. Median pre-ASR arsenic concentrations were 10.5 μg/L 

and 8.8 μg/L at the upstream and downstream surface-water 

sites, respectively (table 6). Median post-ASR arsenic concentrations were 8.5 μg/L and 8.2 μg/L at the upstream and 

downstream surface-water sites, respectively (table 6). Median 

residuals return line site arsenic was about 38 percent smaller 

than the downstream surface-water site. Median arsenic concentration in the residuals return line was 5.1 μg/L and ranged 

from 3.4 μg/L to 6.7 μg/L (table 6). Arsenic concentrations 

exceeded the MCL in about 55 and 30 percent of pre-ASR 

samples for the upstream and downstream surface-water sites, 

respectively; post-ASR arsenic concentrations exceeded the 

MCL in about 43 percent of samples for both the upstream and 

downstream surface-water sites. Arsenic concentrations never 

exceeded the MCL in the residuals return line site samples 

during the study.

Arsenic in natural waters is mostly found in the inorganic forms arsenate and arsenite (Smedley and Kinniburgh, 

2002). Median pre-ASR arsenate concentrations were larger 

at both surface-water sites. Pre-ASR arsenate was significantly (p-value<0.05) larger at the upstream surface-water 

site (7.6 μg/L) compared to the downstream surface-water 

site (5.7 μg/L; table 6). Median post-ASR arsenate concentrations were not significantly different between the two 

surface-water sites (upstream median=3.8 μg/L; downstream 

median=5.2 μg/L; table 6). Median residuals return line site 

arsenate was 3.8 μg/L (table 6). Greater than 80 percent of 

pre-ASR arsenite samples were below the laboratory reporting level at both surface-water sites as well as the residuals 

return line site (table 6). Median pre- and post-ASR arsenite 

concentrations were 0.3 μg/L at the downstream surface-water 

site (table 6). All dimethylarsinate and monomethylarsonate 

samples were less than the laboratory reporting level at the 

upstream surface-water site, the downstream surface-water 

site pre-ASR, and the residuals return line site (table 6). One 

dimethylarsinate sample and one monomethylarsonate sample 

at the downstream surface-water site were at or near the laboratory reporting level post-ASR. 

Coliform Bacteria and Viral Indicators

E. coli and fecal coliform bacteria are types of coliform 

bacteria that are generally specific to fecal material from 

humans and other homeotherms and are common types of bacteria used as indicators of pathogens. E. coli and fecal coliform 

presence indicate that water may be contaminated with human 

or animal wastes, and may indicate that other harmful bacteria or viruses are present (Dufour and others, 1981; Dufour, 

1984). These bacteria indicate potential for pathogens that may 

cause diarrhea, nausea, headaches, and abdominal cramps, and 

may pose a particular health risk for infants, young children, 

and people with compromised immune systems (U.S. Environmental Protection Agency, 2009). All indicator bacterial 

and viral densities were generally larger after the ASR Phase II 

facility began operating, likely because of runoff during larger 

streamflows during this period.

The State of Kansas established surface water recreational-use criteria in 2004 for E. coli. The criteria for publicly 

accessible (Class B) Kansas streams with flows of at least 

1 ft3/s require that the geometric mean of at least five samples 

collected during separate 24-hour periods within a 30-day 

period not exceed 262 colony forming units per 100 milliliters 

(cfu/100 mL) for primary contact during April 1 through October 31 of each year and 2,358 cfu/100 mL at any time of year 

(Kansas Department of Health and Environment, 2004b and 

2011). For the purposes of this report, cfu/100 mL are considered equivalent to colonies per 100 milliliters (col/100 mL). 

Median pre-ASR E. coli bacteria densities were 96 col/100 mL 

at the upstream surface-water site (375350097262800, 

fig. 1) and 83 col/100 mL at the downstream surface-water 

site (07144100, fig. 1); median post-ASR E. coli densities 

were 855 col/100 mL at the upstream surface-water site and 

995 col/100 mL at the downstream surface-water site (table 7). 

Residuals return line site (375348097262800, fig. 1) median 

E. coli density was 9,300 col/100 mL (table 7). The upstream 

surface-water site E. coli densities exceeded 262 col/100 mL 

in about 33 percent of pre-ASR samples and 75 percent of 

post-ASR samples; the downstream surface-water site E. coli

densities exceeded 262 col/100 mL in about 28 percent of 

pre-ASR samples and about 63 percent of post-ASR samples. All residuals return line site E. coli samples exceeded 

262 col/100 mL. The upstream and downstream surface-water 

site E. coli densities exceeded 2,358 col/100 mL in about 

6 percent of pre-ASR samples and 25 percent of post-ASR 

samples after facility operation onset. The residuals return line 

site E. coli sample densities exceeded 2,358 col/100 mL in 

about 71 percent of samples.

The State of Kansas’ recreational-use guidelines for Kansas stream water fecal coliform densities are 200 col/100 mL 

for primary contact (swimming) during April 1 through 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer 33

Table 7. Discretely collected viral and bacteria summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surfacewater site 07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through September 2014.

[See figure 1 for site locations. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014; n, number of measurements; E. coli, Eschericihia coli; col/100 mL, colony per 100 milliliters; mpn/100 mL, most probably number per 100 milliliters; pfu/100 mL, plaque forming unit per 100 milliliters; 

<, less than; cfu/mL, colony forming unit per milliliter]

Water-quality 

constituent 

(unit of measure)

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site Upstream surface-water site Downstream surface-water site Residuals return line site

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

E. coli bacteria 

(col/100 mL)

0 18 8 19,000 1,240 96 0 18 11 4,100 462 83 0 8 110 8,100 2,185 855 0 8 45 8,000 2,078 995 0 7 700 30,000 14,086 9,300

Fecal coliform 

bacteria 

(col/100 mL)

0 20 18 18,000 1,295 200 0 20 12 5,600 681 89 0 8 140 7,000 2,781 1,000 0 8 93 100,000 14,298 1,750 0 7 850 160,000 30,611 4,500

Total coliform 

bacteria 

(mpn/100 mL)

0 17 900 150,000 24,641 16,000 0 17 820 77,000 22,789 10,000 0 7 21,000 290,000 110,429 46,000 0 7 19,000 200,000 68,857 37,000 0 5 16,000 240,000 152,000 240,000

E. coli coliphage 

(pfu/100 mL)

6 18 <1 1,400 155 50 6 18 <1 660 105 45 0 8 3 2,700 577 320 0 8 1 2,500 494 114 0 7 130 17,000 5,773 2,100

Iron-related 

bacteria 

(cfu/mL)

0 20 9,000 140,000 32,450 35,000 0 20 9,000 140,000 38,300 35,000 0 8 9,000 35,000 22,000 22,000 0 8 9,000 35,000 22,000 22,000 0 7 9,000 140,000 42,571 35,000

Slime-forming 

bacteria 

(cfu/mL)

0 20 66,500 1,800,000 742,475 350,000 0 20 12,500 1,800,000 709,850 350,000 0 8 350,000 1,800,000 712,500 350,000 0 8 350,000 1,800,000 712,500 350,000 0 7 350,000 1,800,000 764,286 350,000

Sulfate-reducing 

bacteria 

(cfu/mL)

0 20 1,200 6,800,000 1,155,060 700,000 0 20 5,000 700,000 545,250 700,000 0 8 500 700,000 364,963 400,000 0 8 500 700,000 354,713 359,000 0 7 5,000 700,000 331,857 100,000
34 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

October 31 of each year and 2,000 col/100 mL for primary 

contact during the rest of the year and for secondary contact (boating or wading; Kansas Department of Health and 

Environment, 2001). Median pre-ASR fecal coliform bacteria 

densities were 200 col/100 mL at the upstream surface-water 

site and 89 col/100 mL at the downstream surface-water 

site, and median post-ASR densities were 1,000 col/100 mL 

at the upstream surface-water site and 1,750 col/100 mL at 

the downstream surface-water site (table 7). Median residuals return line site fecal coliform density was 4,500 col/100 

mL (table 7). The upstream surface-water site fecal coliform 

densities exceeded 200 col/100 mL in about 61 percent of 

pre-ASR samples and 88 percent of post-ASR samples. 

The downstream surface-water site fecal coliform densities 

exceeded 200 col/100 mL in about 44 percent of pre-ASR 

samples and about 63 percent of post-ASR samples. All residuals return line site fecal coliform sample densities exceeded 

200 col/100 mL.

The EPA Federal MCL for total coliform bacteria in 

drinking water is that no greater than 5 percent of samples 

test positive during 1 month for water systems that collect 

at least 40 routine samples per month (U.S. Environmental 

Protection Agency, 2009). If fewer than 40 samples are collected per month, no greater than 1 sample can test positive 

for total coliform bacteria (U.S. Environmental Protection 

agency, 2009). The EPA Federal maximum contaminant level 

goal (MCLG) for total coliform bacteria in drinking water is 

0 col/100 mL. For the purposes of this report, col/100 mL are 

considered equivalent to most probable number per 100 milliliters (mpn/100 mL). Median pre- and post-ASR total 

coliform bacteria densities were smaller at the downstream 

surface-water site. Median pre-ASR total coliform densities 

were 16,000 mpn/100 mL at the upstream surface-water site 

and 10,000 mpn/100 mL at the downstream surface-water 

site (table 7). Median post-ASR total coliform densities were 

46,000 mpn/100 mL at the upstream surface-water site and 

37,000 mpn/100 mL at the downstream surface-water site 

(table 7). Median residuals return line site total coliform bacteria density was 240,000 mpn/100 mL (table 7). All samples 

at all sites tested positive for total coliform bacteria during the 

study and the minimum pre-ASR density (820 mpn/100 mL) 

was at the downstream surface-water site.

E. coli coliphage virus is an indicator of possible fecal 

contamination because it infects coliform bacteria. Pre- and 

post-ASR E. coli coliphage densities were generally smaller 

at the downstream surface-water site. Median pre-ASR E. 

coli coliphage densities were 50 plaque forming units per 

100 milliliters (pfu/100 mL) at the upstream surface-water 

site and 45 pfu/100 mL at the downstream surface-water 

site (table 7). Median post-ASR E. coli coliphage densities 

were 320 pfu/100 mL at the upstream surface-water site and 

114 pfu/100 mL at the downstream surface-water site (table 

7). Median residuals return line site E. coli coliphage density 

was 2,100 pfu/100 mL (table 7).

Biological Activity Reaction Tests 

Iron-related, slime-forming, and sulfate-reducing bacteria 

are a natural part of the environment and multiply in conditions suitable to growth. These bacteria are of interest because 

they may enter an aquifer through wells or other interaction 

with the surface. Iron-related bacteria use iron in their metabolism and grow optimally in water with large iron content. 

Iron-related bacteria tend to colonize on well and pump 

surfaces, can cause slime and unpleasant odors and tastes, and 

may deposit iron oxide on surfaces or produce corrosive acids. 

Many iron-related bacteria can grow in aerobic or anaerobic environments by substituting nitrates for oxygen during 

metabolism. Slime-forming bacteria can produce extracellular 

polysaccharide polymers that act as a foundation for biofilm, 

or slime, formation. The slime supports the growth of ironrelated and sulfate-reducing bacteria. Sulfate-reducing bacteria 

reduce sulfates to obtain energy, primarily in anaerobic and 

reducing conditions. Hydrogen sulfide is a byproduct of 

sulfate-reducing bacteria metabolism (Cullimore, 2007).

Median pre-ASR iron-related bacteria densities were 

35,000 colony forming units per 100 milliliters (cfu/100 mL) 

at the upstream and downstream surface-water sites 

(375350097262800 and 07144100 [fig. 1], respectively) 

(table 7). Median post-ASR iron-related densities were 

22,000 cfu/100 mL at the upstream and downstream surface-water sites (table 7). Median residuals return line site 

(375348097262800, fig. 1) iron-related bacteria density was 

35,000 cfu/100 mL. Median slime-forming bacteria densities 

were 350,000 cfu/100 mL for all sites and all time periods 

during the study (table 7). Median sulfate-reducing bacteria 

was 700,000 cfu/100 mL at the upstream and downstream 

surface-water sites pre-ASR, and 400,000 cfu/100 mL at the 

upstream surface-water site and 359,000 cfu/100 mL at the 

downstream surface-water site post-ASR (table 7). Median 

residuals return line site sulfate-reducing bacteria density was 

100,000 cfu/100 mL (table 7). 

Organic Compounds

Many of the organic compounds detected in surface 

water and groundwater in the study area are pesticides (Tappa 

and others, 2015). These organic compounds enter streams or 

slowly infiltrate into the aquifer from the application on fields 

or through irrigation return flow and surface runoff. Atrazine 

is a primary constituent of concern in the study area (Ziegler 

and others, 1999). Atrazine is an herbicide commonly used 

on corn and sorghum, which are crops commonly grown in 

the study area. Atrazine can cause cardiovascular system 

or reproductive problems in humans (U.S. Environmental 

Protection Agency, 2009). The EPA MCL in drinking water for 

atrazine is 3.0 μg/L as an annual average (U.S. Environmental 

Protection Agency, 2009). The 2010 through 2014 and current 

(2015 through 2019) NPDES permits for the ASR Phase II 

treatment facility require that atrazine be monitored monthly 

while the facility is operating. Atrazine was generally larger 

at the upstream surface-water site (375350097262800, fig. 1) 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 35

and post-ASR. Median atrazine concentrations increased 

by 361 percent to 393 percent post-ASR, likely because of 

runoff during larger streamflows during that time period. 

Median pre-ASR atrazine concentrations were 0.69 μg/L at the 

upstream surface-water site and 0.58 μg/L at the downstream 

surface-water site (07144100, fig. 1) (table 8). Median postASR atrazine concentrations were 3.18 μg/L at the upstream 

surface-water site and 2.86 μg/L at the downstream surfacewater site (table 8). Median residuals return line atrazine 

concentration was 2.95 μg/L (table 8). Atrazine concentrations 

at the upstream surface-water site exceeded the EPA MCL 

of 3.0 μg/L in about 20 percent of pre-ASR samples and 50 

percent of post-ASR samples. Atrazine concentrations at the 

downstream surface-water site exceeded 3.0 μg/L in about 25 

percent and 38 percent of samples pre- and post-ASR, respectively. Residuals return line site (375348097262800, fig. 1) 

atrazine concentrations exceeded 3.0 μg/L in about 43 percent 

of samples.

Alachlor is an herbicide used to control weeds in soybeans and was frequently detected in study samples. Alachlor 

potentially can cause eye, liver, kidney, or spleen problems, 

anemia, and an increased risk of cancer (U.S. Environmental 

Protection Agency, 2009). The EPA Federal drinking-water 

criterion for alachlor is 2 μg/L (U.S. Environmental Protection 

Agency, 2009). Alachlor was detected less frequently and concentrations were generally smaller at the surface-water sites 

post-ASR (table 8). Alachlor concentrations never exceeded 

the EPA drinking-water criterion at any sites during the study 

period (table 8).

Chlordane is an insecticide that was sold in the United 

States until 1983. Chlordane can potentially cause liver or 

nervous system problems and increase the risk of cancer (U.S. 

Environmental Protection Agency, 2009). The EPA Federal 

drinking-water criterion for chlordane is 2 μg/L (U.S. Environmental Protection Agency, 2009). Among all sites and samples 

during the study period, including the residuals return line 

site, chlordane was only detected at the downstream surfacewater site post-ASR in about 50 percent of samples (table 8). 

Chlordane never exceeded the EPA drinking-water criterion 

(table 8). Chlordane is no longer required for monitoring in the 

current (2015 through 2019) NPDES permit.

Glyphosate is an herbicide that can cause kidney problems and reproductive difficulties (U.S. Environmental Protection Agency, 2009). The EPA Federal drinking-water criterion 

for glyphosate is 700 μg/L (U.S. Environmental Protection 

Agency, 2009). Glyphosate was not analyzed pre-ASR. 

Glyphosate was detected in all post-ASR samples. Median 

post-ASR glyphosate concentrations were 1.600 μg/L at the 

upstream surface-water site, 1.800 μg/L at the downstream 

surface-water site, and 0.790 μg/L at the residuals return line 

site (table 8). Glyphosate never exceeded the EPA drinkingwater criterion (table 8).

Simazine is an herbicide that can cause weight loss and 

changes in blood (U.S. Environmental Protection Agency, 

2009). The EPA Federal drinking-water criterion for simazine 

is 4 μg/L (U.S. Environmental Protection Agency, 2009). 

Simazine concentrations were below the laboratory reporting 

level for about 40 percent of pre-ASR surface-water samples 

and about 60 percent of post-ASR surface-water samples 

(table 8). Median pre-ASR simazine concentrations were 

0.006 μg/L at the upstream surface-water site and 0.008 μg/L 

at the downstream surface-water site (table 8). Median postASR simazine concentrations were 0.012 μg/L at the upstream 

surface-water site and 0.009 μg/L at the downstream surfacewater site (table 8). Median residuals return line site simazine 

concentration was 0.010 μg/L (table 8).

Streambed-Sediment Chemistry

Some compounds are hydrophobic and are associated 

with sediment; therefore, concentrations of these compounds 

are larger in sediment than in the overlying water column 

(Horowitz, 1991). Contaminated sediment can be toxic to benthic organisms, including periphyton and macroinvertebrates, 

and contaminants may bioaccumulate in fish and mammals 

(U.S. Environmental Protection Agency, 2000b). Streambedsediment samples were collected annually at the upstream 

and downstream surface-water sites (375350097262800 and 

07144100 [fig. 1], respectively) during 2011 through 2014 (a 

total of three pre-ASR samples), and one sediment sample was 

collected from the residuals return line site in September 2014. 

All samples were analyzed for nutrients, carbon, trace elements, and organic wastewater-indicator compounds (OWCs). 

Because there are no set criteria for trace elements or OWCs 

in sediments, probable effect concentrations (PECs) have been 

established for some compounds (MacDonald and others, 

2000). The PEC represents the concentration of a contaminant 

in streambed sediment that is expected to adversely affect 

benthic biota. 

Streambed sediment nutrients generally were larger at 

the downstream surface-water site during the study period 

and smaller at both surface-water sites post-ASR. Median 

pre-ASR total nitrogen was 1,500 mg/kg at the upstream 

surface-water site and 3,003 mg/kg at the downstream surfacewater site (table 9). Post-ASR total nitrogen was 1,002 mg/kg 

at the upstream surface-water site and 1,601 mg/kg at the 

downstream surface-water site after facility operation 

onset (table 9). Residuals return line site total nitrogen was 

3,203 mg/kg and two times (50 percent) larger than the downstream site (table 9). Median pre-ASR total phosphorus was 

1,200 mg/kg at the upstream and downstream surface-water 

sites and exceeded mean background levels for the conterminous United States (1,000 mg/kg; table 9; Horowitz and Stephens, 2008). Post-ASR total phosphorus concentrations were 

910 and 980 mg/kg at the upstream and downstream surfacewater sites, respectively (table 9). Residuals return line site 

total phosphorus was 850 mg/kg and was about 7 to 13 percent 

smaller than the post-ASR upstream and downstream surfacewater site concentrations, respectively (table 9). 

Organic and total carbon generally was larger at the 

downstream surface-water site during the entire study period 

and larger at both surface-water sites pre-ASR (table 9). 
36 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Table 8. Discretely collected pesticide summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through September 2014.

[See figure 1 for site locations. The upstream and downstream surface-water sites were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 

2013 through December 2014; n, number of measurements; μg/L, microgram per liter; <, less than; --, not applicable; EPA, U.S. Environmental Protection Agency; MCL, maximum contaminant level]

Water-quality constituent 

(unit of measure)

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site Upstream surface-water site Downstream surface-water site Residuals return line site

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Leftcensored 

data 

(percent)

n

MinimumMaximum

Mean Median

Acetochlor (μg/L) 20 20 <0.01 4.36 0.41 0.02 15 20 <0.01 5.67 0.58 0.03 0 8 0.14 3.42 0.75 0.27 0 8 0.14 2.98 0.70 0.30 0 7 0.03 1.16 0.47 0.20

Atrazine (μg/L)1 0 20 0.04 19.10 2.94 0.69 0 20 0.02 21.30 3.03 0.58 0 8 0.20 8.56 3.51 3.18 0 8 0.18 7.56 3.44 2.86 0 7 0.19 11.00 3.35 2.95

Alachlor (μg/L)2 55 20 <0.008 0.063 0.012 0.007 45 20 <0.008 0.125 0.018 0.009 88 8 <0.009 0.008 -- -- 75 8 <0.008 0.008 0.005 0.004 27 7 0.004 0.031 0.009 0.004

Chlordane (μg/L)2 100 18 <0.1 <0.1 -- -- 100 18 <0.1 <0.1 -- -- 100 2 <0.1 <0.1 -- -- 50 2 <0.1 0.05 0.05 0.05 100 4 <0.1 <0.1 -- --

Desulfinylfipronil (μg/L) 0 20 0.003 0.010 0.006 0.006 0 20 0.003 0.010 0.006 0.005 38 8 <0.012 0.005 0.004 0.004 38 8 <0.012 0.006 0.005 0.004 43 7 <0.012 0.006 0.005 0.005

Fipronil sulfide (μg/L) 25 20 <0.012 0.012 0.004 0.004 40 20 <0.012 0.012 0.004 0.004 38 8 <0.012 0.012 0.003 0.004 38 8 <0.012 0.012 0.003 0.004 71 7 <0.012 0.006 0.005 0.006

Glyphosate (μg/L) -- -- -- -- -- -- -- -- -- -- -- -- 0 6 0.590 3.500 1.763 1.600 0 6 0.650 3.500 1.942 1.800 0 3 0.640 3.300 1.577 0.790

Metolachlor (μg/L) 0 20 0.019 3.340 0.622 0.113 0 20 0.014 3.630 0.860 0.101 0 8 0.202 6.820 1.680 0.467 0 8 0.212 6.830 2.098 0.486 0 7 0.105 11.20 2.170 0.297

Prometon (μg/L) 5 20 <0.12 0.030 0.012 0.011 25 20 <0.12 0.031 0.012 0.010 25 8 <0.12 0.105 0.024 0.012 13 8 <0.12 0.132 0.028 0.012 0 7 0.002 0.272 0.063 0.016

Simazine (μg/L)3 40 20 <0.006 0.067 0.013 0.006 45 20 <0.006 0.043 0.013 0.008 63 8 <0.006 0.038 0.014 0.012 63 8 <0.006 0.038 0.013 0.009 29 7 <0.006 0.047 0.016 0.010

Triazines (μg/L as atrazine) 15 20 <0.1 19.00 2.29 0.46 5 20 <0.1 12.00 2.37 0.63 0 8 0.28 10.00 3.86 3.35 0 8 0.16 8.30 3.69 3.15 0 7 0.26 12.00 3.56 2.40

1

EPA MCL of 0.003 μg/L (U.S. Environmental Protection Agency, 2009).

2

EPA MCL of 0.002 μg/L (U.S. Environmental Protection Agency, 2009).

3

EPA MCL of 0.004 μg/L (U.S. Environmental Protection Agency, 2009).
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 37

Table 9. Streambed-sediment nutrients, carbon, and trace element summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas

(downstream surface-water site 07144100), and discharge from the Little Arkansas River Aquifer Storage and Recovery facility (residual return line site 375348097262800) near Sedgwick, Kansas, April 2011 through April 2013 and July through September 2014.

[See figure 1 for site locations. Means and medians were not computed when greater than 80 percent of data were left-censored. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014; n, number of measurements; mg/kg, milligram per kilogram; --, not applicable; <, less than]

Constituent 

(unit of measure)

Probable effect 

concentration1

Background 

concentration2

Pre-ASR Pre-ASR

Post-ASR

Upstream surface-water site Downstream surface-water site

Left-censored 

data 

(percent)

n Minimum Maximum Mean Median

Left-censored 

data 

(percent)

n Minimum Maximum Mean Median

Upstream 

surface-water 

site

Downstream 

surface-water 

site

Residuals 

return line site

Nutrients and carbon Nutrients and carbon

Total Kjeldahl nitrogen (mg/kg) -- -- 0 1 590 590 -- -- 0 1 3,000 3,000 -- -- 1,000 1,600 3,200

Nitrate plus nitrite (mg/kg) -- -- 100 1 <1.6 <1.6 -- -- 100 1 <5.2 <5.2 -- -- 2 1 3

Total nitrogen (mg/kg) -- 0 3 591 2,900 1,664 1,500 0 3 2,400 3,900 3,101 3,003 1,002 1,601 3,203

Total phosphorus (mg/kg) -- 1,000 0 3 820 1,600 1,207 1,200 0 3 1,000 1,600 1,267 1,200 910 980 850

Organic carbon (mg/kg) -- 24,000 0 3 14,000 20,000 16,000 14,000 0 3 18,000 24,000 20,000 18,000 14,000 17,000 23,200

Total carbon (mg/kg) -- 33,000 0 3 14,000 25,000 18,333 16,000 0 3 20,000 32,000 24,000 20,000 15,000 17,000 23,200

Total sulfur (mg/kg) -- 800 0 3 500 1,400 833 600 0 3 600 1,300 867 700 2,900 2,700 900

Trace elements Trace elements

Aluminum (mg/kg) -- 59,000 0 3 59,000 61,000 59,667 59,000 0 3 60,000 64,000 62,667 64,000 64,000 64,000 80,200

Antimony (mg/kg) -- 0.7 0 3 0.7 0.8 0.7 0.7 0 3 0.7 0.9 0.8 0.7 0.8 0.8 1.2

Arsenic (mg/kg) 33 6.6 0 3 6.0 8.8 7.2 6.8 0 3 6.4 7.8 7.3 7.7 8.3 8.5 11

Barium (mg/kg) -- 490 0 3 670 800 720 690 0 3 650 740 700 710 660 650 568

Beryllium (mg/kg) -- 1.8 0 3 1.4 2.0 1.7 1.8 0 3 1.6 2.0 1.8 1.9 1.9 1.9 2.5

Calcium (mg/kg) -- 18,000 0 3 10,000 22,000 14,667 12,000 0 3 11,000 24,000 16,333 14,000 10,000 10,000 10,300

Chromium (mg/kg) 111 58 0 3 40 52 47 50 0 3 40 60 52 55 45 10 76

Cobalt (mg/kg) -- 12 0 3 9.0 10 9.3 9.0 0 3 10 11 10 10 10 10 13

Copper (mg/kg) 149 20 0 3 16 21 19 19 0 3 19 21 20 21 21 22 32

Iron (mg/kg) -- 29,000 0 3 24,000 28,000 25,333 24,000 0 3 25,000 29,000 27,333 28,000 27,000 28,000 46,000

Lead (mg/kg) 128 20 0 3 20 37 26 21 0 3 23 36 28 24 22 23 32

Lithium (mg/kg) -- 30 0 3 22 29 26 27 0 3 24 32 29 31 28 28 39

Magnesium (mg/kg) -- 9,000 0 3 5,000 7,000 6,067 6,200 0 3 6,000 7,000 6,533 6,600 7,000 7,400 9,390

Manganese (mg/kg) -- 840 0 3 620 940 827 920 0 3 770 1,200 1,057 1,200 1,000 1,200 701

Nickel (mg/kg) 48.6 23 0 3 16 19 18 18 0 3 19 22 20 19 21 22 36

Potassium (mg/kg) -- 15,000 0 3 18,000 19,000 18,333 18,000 0 3 17,000 20,000 18,333 18,000 18,000 17,000 19,800

Selenium (mg/kg) -- 0.7 0 3 0.5 0.6 0.6 0.6 0 3 0.7 0.9 0.8 0.7 0.6 0.7 0.6

Silver (mg/kg) -- 0.2 66 3 <0.25 0.30 0.27 0.25 0 3 <0.25 0.60 0.38 0.30 <0.02 <0.02 <0.5

Sodium (mg/kg) -- 6,000 0 3 7,500 8,000 7,833 8,000 0 3 7,000 7,000 7,000 7,000 6,900 6,500 2,330

Strontium (mg/kg) -- 150 0 3 150 200 170 160 0 3 160 210 177 160 150 140 127

Vanadium (mg/kg) -- 83 0 3 65 78 72 72 0 3 73 83 77 76 78 78 122

Zinc (mg/kg) 459 91 0 3 73 91 83 86 0 3 87 97 91 88 94 96 131

1

From MacDonald and others (2000).

2

Background concentrations for the conterminous United States from Horowitz and Stephens (2008).
38 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Organic and total carbon did not exceed mean background 

levels (24,000 mg/kg and 33,000 mg/kg, respectively) for 

the conterminous United States at any site during the study 

(table 9). Pre- and post-ASR organic carbon at the upstream 

surface-water site was 14,000 mg/kg (table 9). Organic carbon 

at the downstream surface-water site was 18,000 mg/kg preASR and 17,000 mg/kg post-ASR (table 9). Residuals return 

line site organic carbon concentration was 23,200 mg/kg 

(table 9). Median pre-ASR total carbon concentrations 

were 16,000 mg/kg at the upstream surface-water site and 

20,000 mg/kg at the downstream surface-water site (table 9). 

Post-ASR total carbon was 15,000 mg/kg at the upstream 

surface-water site, 17,000 mg/kg at the downstream surfacewater site, and 23,200 mg/kg at the residuals return line site 

(table 9). Residuals return line site organic and total carbon 

were about 27 percent larger than the downstream surfacewater site.

Streambed sediment trace element concentrations at the 

surface-water sites generally were similar among sites pre- and 

post-ASR. Residuals return line site trace element concentrations generally were larger than the downstream surface-water 

site concentrations, with the exception of barium, manganese, 

selenium, sodium, and strontium (table 9). No trace element 

samples from any site exceeded their respective PEC (table 9). 

Median arsenic, barium, lead, and potassium concentrations 

from all sites exceeded their respective mean background 

levels for the conterminous United States during the study 

period (table 9). Concentrations of streambed trace elements 

above median background levels may be due to natural variability, local geology, or agricultural land use. Streambed 

trace element concentrations at the surface-water sites were 

within the range of previously collected data in the drainage 

basin (Juracek and Rasmussen, 2008). Most residuals return 

line site trace element concentrations were within the range 

of previously collected data in the drainage basin, with the 

exception of exceedances in aluminum, antimony, iron, nickel, 

and vanadium (Juracek and Rasmussen, 2008). Median preASR arsenic concentrations were 6.8 mg/kg at the upstream 

surface-water site and 7.7 mg/kg at the downstream surfacewater site (table 9). Post-ASR arsenic concentrations were 

8.3 mg/kg at the upstream surface-water site, 8.5 mg/kg at the 

downstream surface-water site, and 11 mg/kg at the residuals 

return line site (table 9). Median pre-ASR copper concentrations were 19 and 21 mg/kg at the upstream and downstream 

surface-water sites, respectively (table 9). Post-ASR copper 

concentrations were 21 and 22 mg/kg at the upstream and 

downstream surface-water sites, respectively (table 9). The 

residual return line site copper concentration was 32 mg/kg 

(table 9). Median pre-ASR manganese concentrations were 

920 mg/kg at the upstream surface-water site and 1,200 mg/

kg at the downstream surface-water site (table 9). Post-ASR 

manganese concentrations were 1,000 mg/kg at the upstream 

surface-water site, 1,200 mg/kg at the downstream surfacewater site, and 701 mg/kg at the residuals return line site 

(table 9).

 Streambed and residuals return line site sediment samples were analyzed for 57 OWCs, 21 of which were detected 

(table 10). Detected compounds included pesticides, natural 

organics, polycyclic aromatic hydrocarbons (PAHs), sterols 

or stanols, flavorings or fragrances, detergents, components of 

coal tar and asphalt, solvents, disinfectants, and fire retardants. 

The most frequently detected compounds at all sites during the 

study period were pesticides, which are used in agricultural 

activities in the drainage basin. There were no clear patterns in 

OWC concentrations before and after the ASR Phase II facility began operating, although the downstream surface-water 

site tended to have larger OWC concentrations compared to 

the upstream surface-water site throughout the study period 

(table 10). Of the data that were above the laboratory reporting 

level, residuals return line OWC concentrations generally were 

smaller than the downstream surface-water site (table 10).

Habitat Assessment

Habitat-quality evaluations are a critical part of assessing 

ecological integrity and integrate several factors that directly 

or indirectly affect stream water quality and biota (Barbour 

and others, 1996; Barbour and others, 1999). Habitat degradation is one of the principal stressors affecting diversity 

and abundance of stream organisms (Karr and others, 1986). 

Channel, bank, riparian, and aquatic habitat conditions were 

evaluated before the ASR Phase II facility began operating 

during August 2011 and after the facility began operating during September 2014.

Mean total habitat scores were indicative of suboptimal 

conditions at the upstream and downstream surface-water sites 

(375350097262800 and 07144100 [fig. 1], respectively) during the study period (table 11). Mean channel conditions and 

characteristics scores were indicative of marginal conditions 

at the upstream surface-water site pre- and post-ASR and the 

downstream surface-water site pre-ASR (table 11). The postASR mean channel conditions and characteristics score for the 

downstream surface-water site was indicative of suboptimal 

conditions (table 11).

Mean bank and riparian conditions scores were indicative of suboptimal conditions at the upstream surface-water 

site and optimal conditions at the downstream surface-water 

site during the study period (table 11). Within the bank and 

riparian category, both surface-water sites generally scored 

suboptimally for bank stability, canopy cover, and bank/riparian protection and optimally for length and extent of buffers, 

mean buffer width, and percent altered banks (table 11). 

Mean aquatic habitat availability scores were indicative of marginal conditions at the upstream and downstream 

surface-water sites during the study period (table 11). Within 

the aquatic habitat availability category, substrate fouling and 

sediment deposition mean scores indicated marginal conditions at the upstream and downstream surface-water sites 

during the entire study period (table 11), demonstrating that 

sediment deposition was evident pre- and post-ASR and no 

substantial changes were noted after the ASR facility began 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer 39

Table 10. Streambed-sediment organic wastewater indicator compound summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), Little Arkansas River near Sedgwick, Kansas

(downstream surface-water site 07144100), and discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, April 2011 through April 2013 and July through September 2014.

[See figure 1 for site locations. Means and medians were not computed when greater than 80 percent of data were left-censored. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014; n, number of measurements; μg/kg, microgram per kilogram; --, not applicable; <, less than; E, estimated; 

PAH, polycyclic aromatic hydrocarbon; β, beta]

Constituent

(unit of measure) General use1

Probable 

effect 

concentration2

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site

Upstream 

surfacewater site

Downstream 

surfacewater site

Residual 

return line 

site

Leftcensored 

data 

(percent)

n Minimum Maximum Mean Median

Leftcensored 

data 

(percent)

n Minimum Maximum Mean Median

Carbazole (μg/kg) Insecticide, manufacturing dyes, explosives, and lubricants -- 33 3 <60 E14 17 14 100 3 <63 <112 -- -- 12 14 10

Metolachlor (μg/kg) Herbicide -- 67 3 <60 4 30 30 67 3 <72 6 33 36 11 12 <76

p-Cresol (μg/kg) PAH or combustion by-product, wood preservative -- 0 3 E20 320 190 230 0 3 80 E4,900 2,830 3,510 250 190 93

2,6-Dimethylnaphthalene 

(μg/kg)

PAH or combustion by-product, present in diesel and kerosene -- 0 3 34 E150 82 62 0 3 70 E189 115 86 50 87 13

3-β-Coprostanol (μg/kg) Sterol or stanol, carnivor fecal indicator -- 67 3 <540 E370 313 300 67 3 <630 E360 345 360 <1,360 E530 E248

3-Methyl-1H-indole (Skatole) 

(μg/kg)

Flavoring or fragrance, stench in feces, coal tar -- 0 3 5 12 10 12 0 3 20 E563 206 34 68 83 36

4-tert-Octylphenol diethoxylate 

(μg/kg)

Nonionic detergent metabolite -- 100 3 <54 <114 -- -- 67 3 <63 E25 38 32 <136 <138 <76

9,10-Anthraquinone (μg/kg) Pesticide, manufacturing dye and textiles, seed treatment, 

bird repellant

-- 33 3 <94 E27 29 27 67 3 <112 E33 49 56 27 E31 <76

Acetophenone (μg/kg) Fragrance or flavor -- 100 3 <160 <340 -- -- 100 3 <190 <340 -- -- <410 <410 E39

Benzo[a]pyrene (μg/kg) PAH or combustion by-product, used in cancer research 1,450 0 3 7 E26 15 11 33 3 <63 E15 19 15 12 17 <76

β-Sitosterol (μg/kg) Plant sterol -- 0 3 E5,730 E7,200 6,417 6,320 0 3 E5,050 E7,420 5,873 5,150 E2,760 E3,200 E5,210

β-Stigmastanol (μg/kg) Plant sterol -- 0 3 E760 E990 890 920 0 3 E620 E900 743 710 <1,360 E850 E938

Cholesterol (μg/kg) Fecal indicator, plant sterol -- 0 3 E2,420 E4,580 3,417 3,250 0 3 E3,790 E6,210 5,140 5,420 E2,840 E4,110 E2,840

d-Limonene (μg/kg) Fungicide, antimicrobial, antiviral, fragrance in aerosols -- 100 3 <54 <114 -- -- 67 3 <63 E30 39 32 <136 <138 E30

Fluoranthene (μg/kg) Component of coal tar and asphalt 2,230 0 3 27 79 48 38 0 3 26 E48 34 27 33 43 20

Indole (μg/kg) Pesticide inert ingredient, fragrance in coffee -- 0 3 E140 260 183 150 0 3 240 E480 353 340 850 810 350

Isophorone (μg/kg) Solvent for lacquer, plastic, oil, silicon, resin -- 100 3 <54 <114 -- -- 67 3 <72 E3 32 36 <136 <138 <76

Phenanthrene (μg/kg) Manufacturing explosives, component of tar, diesel fuel, or 

crude oil, combustion product

1,170 33 3 <54 E41 28 27 33 3 <63 E27 24 27 20 24 <76

Phenol (μg/kg) Disinfectant, manufacturing of several products -- 67 3 <54 E80 55 57 33 3 <263 E459 228 132 <415 <451 <190

Pyrene (μg/kg) Component of coal tar and asphalt 1,520 0 3 21 64 39 33 0 3 20 E40 27 21 23 32 14

Tris(2-butoxyethyl) phosphate 

(μg/kg)

Fire retardant -- 67 3 <180 E30 97 90 100 3 <190 <340 -- -- <410 <410 <226

1

Compound uses and sources from Zaugg and others (2006), Lee and others (2005), and Wilkison and others (2006).

2

From MacDonald and others (2000).
40 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

discharging, although this could be related to higher postASR streamflow conditions. Substrate fouling is a measure 

of periphyton growth and accumulation of fine materials 

covering substrates. Excessive amounts of accumulation can 

clog interstitial substrate spaces and lead to a decline in living 

space for macroinvertebrates and fish. Sediment deposition is 

a measure of the amount of accumulated sediment as a result 

of deposition. Large amounts of sediment deposition may 

indicate a continually changing environment that is unsuitable for organisms. Pool variability scores were indicative 

of marginal conditions for both surface-water sites during 

the study period and pool substrate composition scores were 

indicative of suboptimal conditions for both surface-water 

sites during the study period (table 11). Diversity of epifaunal 

substrate and cover types scores were indicative of suboptimal 

conditions at the upstream surface-water site for the study 

period and the downstream surface-water site pre-ASR; the 

post-ASR diversity of epifaunal substrate and cover types 

score for the downstream surface-water site was indicative of 

marginal conditions (table 11). Diversity of epifaunal substrate 

and cover is a measure of the number and variety of instream 

habitat and cover types. A wide variety and abundance of good 

habitat increases overall biotic diversity within the stream 

reach.

Macroinvertebrates

Macroinvertebrate community-level responses are commonly used for evaluation of biological conditions, diagnosis 

of stream impairment sources and causes, restoration activity success measurement, and development of biological 

criteria in support of water-quality compliance and regulation (Rosenberg and Resh, 1993; Southerland and Stribling, 

1995). Macroinvertebrate communities have also been widely 

used as an indicator of stream quality in agricultural drainage basins (Allan, 2004). Macroinvertebrate community 

assessments include evaluation of changes in abundance or 

dominance of ecologically important taxa and sensitive taxa 

Table 11. Habitat assessment scores for the Little Arkansas River upstream from the aquifer storage and recovery facility near 

Sedgwick, Kansas (upstream surface-water site 375350097262800), and Little Arkansas River near Sedgwick, Kansas (downstream 

surface-water site 07144100), during August 2011 and September 2014.

[See figure 1 for site locations. Habitat assessment scores of 10–12 indicate optimal conditions, 7–9 indicate suboptimal conditions, 4–6 indicate marginal conditions, and 1–3 indicate poor conditions. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, May 2013 through December 2014]

Habitat variable

Pre-ASR Post-ASR

Upstream 

surface-water site

Downstream 

surface-water site

Upstream 

surface-water site

Downstream 

surface-water site

Channel conditions and characteristics

Flow status 4 5 5 6

Channel slope and morphological status 8 7 7 8

Sinuosity 6 5 5 8

Mean channel conditions and characteristics score 6 6 6 7

Bank and riparian conditions

Bank stability 7 9 6 9

Canopy cover 8 7 7 6

Bank/riparian protection 6 8 7 8

Length and extent of buffers 12 12 12 12

Mean buffer width 10 11 11 11

Percentage of altered banks 12 12 12 12

Mean bank and riparian conditions score 9 10 9 10

Aquatic habitat availability

Substrate fouling 6 5 5 6

Pool variability 5 5 5 5

Pool substrate composition 8 9 7 8

Sediment deposition 5 6 5 5

Diversity of epifaunal substrate and cover types 8 7 8 6

Mean aquatic habitat availability score 6 6 6 6

Mean total habitat score 8 8 7 8
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 41

that have been eliminated or decreased as a result of stream 

condition changes. More specifically, abundance and diversity 

values can be used to calculate specific metrics for ecologically important and sensitive taxa that respond to changes in 

stream condition. These metrics provide diagnostic information related to stressor responses and effects on community 

function.

Macroinvertebrate Community Composition

A total of 229 macroinvertebrate taxa were identified 

from samples collected at all sites during 2011 through 2014: 

193 taxa were present at the upstream surface-water site 

(375350097262800, fig. 1) and 192 taxa were present at the 

downstream surface-water site (07144100, fig. 1) (appendix 

table 1–8). Overall, 193 taxa of insect macroinvertebrates and 

36 taxa of non-insect macroinvertebrates were included in 

the samples. Both surface-water sites contained 41 EPT taxa 

and 44 midge (Diptera: Chironomidae) taxa. Water boatmen 

(Hemiptera: Corixidae), including the genus Trichocorixa sp., 

the caddisfly Nectopsyche candida (Trichoptera: Leptoceridae), and midges (including Polypedilum sp., Glyptotendipes

sp., Chironomus sp., and Cricotopus/Orthocladius sp.) were 

among the most dominant taxa collected at the two Little 

Arkansas River surface-water sites (table 12). Across sampling 

dates, there were minor seasonal differences in total richness 

at the sites, with 151 taxa in April/May, 145 taxa in June/July, 

and 172 taxa in August/September (appendix tables 1–8 and 

1–9). 

Macroinvertebrate community composition, including 

functional feeding, behavioral, and tolerance groups, generally was similar among sites during the study period. Among 

functional feeding groups, predators and collector-gatherers 

were the two most abundant groups, collectively made up over 

50 percent of the macroinvertebrates at both surface-water 

sites for pre- and post-ASR (fig. 8). Among macroinvertebrate behavioral groups, most organisms were swimmers and 

sprawlers, which collectively made up more than 50 percent 

of the organisms pre-ASR and more than 75 percent postASR (fig. 9). Intolerant macroinvertebrates had the lowest 

abundance among tolerance groups at both surface-water sites 

during the duration of the study (fig. 10).

Macroinvertebrate Metrics

Overall, there were 16 indicator metrics for which 

significant differences existed between the upstream and 

downstream surface-water sites (375350097262800 and 

07144100 [fig. 1], respectively) (table 13; figs. 8–10). Four 

relative abundance metrics, three taxa richness metrics, four 

functional feeding and behavioral group metrics, four tolerance metrics, and one other metric were significant (table 13). 

There were 14 significantly different macroinvertebrate 

metrics between the upstream and downstream surface-water 

sites pre-ASR and 6 significantly different metrics between 

the two surface-water sites post-ASR, indicating that the two 

sites are more similar post-ASR, which is likely related to 

higher post-ASR streamflow conditions. No diversity and 

evenness indices were significantly different between the 

upstream and downstream surface-water sites during the study 

period (table 13). Four indicator metrics were significantly 

different between upstream and downstream surface-water 

sites for both pre-ASR and post-ASR time periods and these 

included percent filterer-collectors (upstream<downstream) 

and three of the Kansas Biotic Indices (AP, HM, and SA, all 

upstream>downstream; table 13).

As compared to macroinvertebrates at the upstream 

surface-water site, the downstream surface-water site pre-ASR 

had a significantly greater relative abundance of Tanytarsini (a 

tribe of midges belonging to Chironomidae), Bivalvia, filterercollectors, and climbers and greater richness of Trichoptera 

and Tanytarsini (table 13). In contrast, the upstream surfacewater site pre-ASR had significantly greater relative abundance of Gastropoda and predators (table 13). As compared to 

the upstream surface-water site, the downstream surface-water 

site post-ASR had a significantly greater mean relative abundance of caddisflies (Trichoptera) that was nearly twice that 

of the upstream surface-water site; however, the downstream 

surface-water site had significantly greater caddisfly richness than the upstream surface-water site pre-ASR (table 13). 

Table 12. List of five most dominant macroinvertebrate taxa for the Little Arkansas River upstream from the aquifer storage and 

recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and Little Arkansas River near Sedgwick, 

Kansas (downstream surface-water site 07144100), April 2011 through April 2013 and September 2013 through August 2014.

[See figure 1 for site locations. Values in parentheses are percentage of total abundance. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; 

post, May 2013 through December 2014]

Pre-ASR Post-ASR

Upstream surface-water site Downstream surface-water site Upstream surface-water site Downstream surface-water site

Physa sp. (5.1) Simulium sp. (4.2) Corixidae (8.3) Polypedilum sp. (7.1)

Corixidae (4.9) Cricotopus/Orthocladius sp. (4.2) Polypedilum sp. (8.2) Nectopsyche candida (6.7)

Nectopsyche candida (4.6) Trichochrixa sp. (3.9) Chironomus sp. (6.8) Glyptotendipes sp. (6.4)

Polypedilum sp. (4.1) Paracloeodes minutus (3.9) Argia sp. (5.3) Argia sp. (5.3)

Trichocorixa sp. (3.7) Polypedilum sp. (3.8) Nectopsyche candida (4.9) Corixidae (4.6)
42 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Figure 8. Mean relative abundances of macroinvertebrate functional feeding groups for the Little Arkansas River 

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 

375350097262800), and the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), 

May 2011 through August 2014.

Predator

Omnivore

Collector-gatherer

Filterer-collector

Scraper

Shredder

EXPLANATION

Upstream surface-water site Downstream surface-water site

Pre-ASR

Post-ASR

36.39

24.54

24

7.72

10.91

11.43

9.01

32.20

5.16

15.49 13.14

10.51

37.19

27.97

7.44

8.02

9.32

10.06

34.14

10.10

16.64

22.35

5.62

11.15

Mean relative abundance, in percent—

Underlined percentages indicate 

statistically significant differences 

(p less than 0.05) in median values

between sites

ASR Aquifer storage and recovery
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 43

Figure 9. Mean relative abundances of macroinvertebrate behavioral groups for the Little Arkansas River upstream from 

the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and the 

Little Arkansas River near Sedgwick, Kansas(downstream surface-water site 07144100), May 2011 through August 2014. 

Clinger

Climber

Sprawler

Burrower

Swimmer

EXPLANATION

Mean relative abundance, in percent—

Underlined percentages indicate 

statistically significant differences 

(p less than 0.05) in median values

between sites

ASR Aquifer storage and recovery

Upstream surface-water site Downstream surface-water site

Pre-ASR

Post-ASR

29.11

9.78

6.59

17.89

36.63

24.96

10.47

13.77

30.88

19.92

7.84

29.72

7.38

5.64

49.41

30.54

8.09

47.04

12.59

1.74
44 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Figure 10. Mean relative abundances of macroinvertebrate tolerance groups for the Little Arkansas River 

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water 

site 375350097262800), and the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), May 2011 through August 2014. 

Intolerant

Moderately tolerant

Tolerant

EXPLANATION

Mean relative abundance, in percent

ASR Aquifer storage and recovery

Upstream surface-water site Downstream surface-water site

Pre-ASR

Post-ASR

58.09

32.87

9.04 64.26

26.69

9.05

51.51 10.16

38.33

54.98

34.01

11.01
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 45

Table 13. Mean selected macroinvertebrate metric values and Kansas Department of Health and Environment aquatic-life-support 

status for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surfacewater site 375350097262800), and Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), April 2011 

through April 2013 and September 2013 through August 2014.

[See figure 1 for site locations. Medians in bold indicate statistically significant differences (p-value less than 0.05) between the upstream and downstream 

surface-water sites. Values in parentheses are plus or minus 1 standard deviation. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, 

May 2013 through December 2014; EPT, Ephemeroptera, Plecoptera, and Trichoptera; NO, tolerances for nutrients and oxygen-demanding substances; AP, tolerances for agricultural pesticides; HM, tolerances for heavy metals; POC, tolerances for persistent organic compounds; SA, tolerances for salinity; SSS, tolerances for suspended solids and sediments; KBI, Kansas Biotic Index; <, less than]

Metric 

(unit of measure)

Pre-ASR Post-ASR

Upstream 

surface-water site

Downstream 

surface-water site

Upstream 

surface-water site

Downstream 

surface-water site

Relative abundance metrics

Most abundant taxon (percent) 11.90 (3.77) 12.09 (4.85) 13.78 (4.19) 12.77 (3.22)

Five most abundant taxa (percent) 38.27 (5.65) 39.07 (6.95) 41.00 (5.29) 43.54 (8.23)

EPT (percent)1 18.21 (9.53) 21.92 (10.31) 23.92 (7.62) 29.68 (13.7)

Ephemeroptera (percent) 10.76 (6.28) 13.40 (5.90) 15.92 (7.05) 15.19 (10.38)

Trichoptera (percent) 7.11 (5.25) 8.32 (5.90) 8.00 (5.03) 14.48 (10.30)

Odonata (percent) 7.57 (4.95) 10.11 (7.71) 10.36 (3.90) 10.22 (4.17)

Coleoptera (percent) 10.27 (5.73) 12.46 (5.66) 5.46 (2.19) 5.87 (1.64)

Diptera (percent) 33.95 (9.99) 31.89 (15.82) 29.64 (6.51) 28.80 (8.81)

Chironomidae (percent) 28.48 (7.42) 27.74 (11.73) 28.48 (6.53) 27.41 (8.50)

Orthocladinae Chironomidae (percent) 4.58 (7.90) 5.72 (9.66) 0.85 (1.03) 1.78 (2.34)

Tanytarsini Chironomidae (percent) 1.29 (1.47) 2.79 (2.07) 1.28 (2.08) 2.20 (3.90)

Non-Chironomidae Diptera (percent) 5.46 (4.74) 4.15 (5.42) 1.16 (0.56) 1.38 (0.67)

Noninsects (percent) 12.96 (7.28) 11.55 (5.35) 12.86 (8.30) 12.05 (3.67)

Non-Chironomidae Diptera and 

noninsects (percent)

18.42 (8.02) 15.70 (4.32) 14.02 (8.80) 13.43 (4.21)

Mollusca and crustacea (percent) 9.74 (6.02) 8.99 (5.85) 9.66 (6.30) 9.54 (3.31)

Gastropoda (percent) 6.00 (3.96) 3.92 (2.78) 3.53 (3.14) 3.22 (0.84)

Bivalvia (percent) 2.36 (1.87) 3.90 (4.07) 1.15 (1.25) 0.88 (0.97)

Oligochaeta (percent) 2.78 (2.37) 1.43 (1.64) 1.83 (2.68) 0.59 (1.27)

Taxa richness metrics

Taxa richness 44.38 (7.51) 46.06 (7.84) 41.57 (6.70) 40.14 (3.67)

EPT richness1 6.88 (3.50) 7.88 (3.81) 9.14 (3.08) 8.86 (4.14)

Ephemeroptera richness 4.50 (2.56) 4.94 (2.67) 6.86 (2.48) 6.14 (2.79)

Trichoptera richness 2.06 (1.00) 2.69 (1.54) 2.29 (1.11) 2.71 (1.38)

Odonata richness 3.50 (1.21) 4.25 (1.98) 3.86 (1.07) 3.14 (1.07)

Coleoptera richness 7.38 (2.94) 8.31 (2.87) 4.29 (1.38) 4.14 (1.07)

Diptera richness 14.50 (3.67) 14.69 (5.22) 11.57 (3.55) 11.43 (1.40)

Chironomidae richness 12.06 (3.64) 13.50 (4.76) 10.29 (3.15) 10.00 (0.82)

Orthocladinae Chironomidae richness 0.94 (1.18) 1.44 (1.36) 0.86 (0.90) 1.29 (0.95)

Tanytarsini Chironomidae richness 0.81 (0.66) 1.69 (0.95) 0.71 (0.95) 1.14 (1.21)

Non-Chironomidae Diptera richness 2.44 (1.63) 1.19 (0.91) 1.29 (0.49) 1.43 (0.79)

Noninsect richness 5.25 (2.32) 5.38 (2.42) 6.57 (3.21) 6.29 (1.25)

Non-Chironomidae Diptera and 

noninsect richness

7.69 (3.42) 6.56 (2.76) 7.86 (3.63) 7.71 (1.38)

Mollusca and crustacea richness 3.19 (1.42) 3.31 (1.89) 4.43 (1.62) 3.86 (1.35)
46 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Table 13. Mean selected macroinvertebrate metric values and Kansas Department of Health and Environment aquatic-life-support 

status for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surfacewater site 375350097262800), and Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), April 2011 

through April 2013 and September 2013 through August 2014.—Continued

[See figure 1 for site locations. Medians in bold indicate statistically significant differences (p-value less than 0.05) between the upstream and downstream 

surface-water sites. Values in parentheses are plus or minus 1 standard deviation. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, 

May 2013 through December 2014; EPT, Ephemeroptera, Plecoptera, and Trichoptera; NO, tolerances for nutrients and oxygen-demanding substances; AP, tolerances for agricultural pesticides; HM, tolerances for heavy metals; POC, tolerances for persistent organic compounds; SA, tolerances for salinity; SSS, tolerances for suspended solids and sediments; KBI, Kansas Biotic Index; <, less than]

Metric 

(unit of measure)

Pre-ASR Post-ASR

Upstream 

surface-water site

Downstream 

surface-water site

Upstream 

surface-water site

Downstream 

surface-water site

Taxa richness metrics—Continued

Gastropoda richness 1.38 (0.81) 1.00 (0.63) 1.43 (0.53) 1.43 (0.79)

Bivalvia richness 1.25 (0.93) 1.44 (0.73) 0.86 (0.69) 0.57 (0.53)

Oligochaeta richness 1.44 (1.03) 0.94 (0.85) 0.86 (0.69) 0.43 (0.79)

Diversity and evenness indices

Margalef’s diversity index 19.86 (2.73) 20.18 (2.67) 18.80 (2.76) 18.36 (1.80)

Manhinick’s diversity index 3.60 (0.32) 3.53 (0.32) 3.47 (0.42) 3.45 (0.40)

Simpson’s diversity index 0.96 (0.01) 0.95 (0.01) 0.95 (0.01) 0.95 (0.02)

Shannon’s diversity index 1.46 (0.07) 1.46 (0.08) 1.43 (0.06 1.40 (0.08)

Brillouin’s diversity index 1.30 (0.07) 1.31 (0.08) 1.27 (0.05) 1.24 (0.06)

Simpson’s evenness index 0.97 (0.01) 0.97 (0.01) 0.97 (0.01) 0.97 (0.01)

Brillouin’s evenness index 0.90 (0.02) 0.89 (0.03) 0.89 (0.03) 0.88 (0.04)

Shannon’s evenness index 0.89 (0.02) 0.88 (0.03) 0.89 (0.02) 0.88 (0.04)

Functional feeding and behavioral groups

Predators (percent) 36.39 (10.56) 32.20 (15.13) 37.19 (6.10) 34.14 (10.24)

Omnivores (percent) 7.72 (5.43) 5.16 (4.87) 7.44 (5.23) 10.10 (4.69)

Collector-gatherers (percent) 24.54 (10.81) 23.50 (10.31) 27.97 (4.17) 22.35 (8.00)

Filterer-collectors (percent) 10.91 (5.31) 15.49 (6.46) 8.02 (2.47) 16.64 (10.53)

Scrapers (percent) 11.43 (5.91) 13.14 (5.24) 9.32 (4.34) 5.62 (1.62)

Shredders (percent) 9.01 (4.43) 10.51 (7.97) 10.06 (3.99) 11.15 (1.79)

Clingers (percent) 9.78 (11.42) 10.47 (11.53) 7.84 (7.46) 1.74 (1.65)

Climbers (percent) 6.59 (6.34) 13.77 (10.74) 5.64 (4.93) 8.09 (6.37)

Sprawlers (percent) 29.11 (12.23) 24.96 (16.87) 29.72 (14.44) 30.54 (14.31)

Burrowers (percent) 17.89 (9.43) 19.92 (11.81) 7.38 (10.09) 12.59 (15.01)

Swimmers (percent) 36.63 (14.54) 30.88 (20.36) 49.41 (19.98) 47.04 (14.08)

Tolerance metrics

Intolerant (percent) 9.04 (3.97) 9.05 (5.98) 10.16 (5.56) 11.01 (9.43)

Moderately tolerant (percent) 58.09 (10.05) 64.26 (11.70) 51.51 (7.29) 54.98 (11.04)

Tolerant (percent) 32.87 (11.30) 26.69 (14.20) 38.33 (9.74) 34.01 (13.88)

Kansas Biotic Index (NO)1 3.07 (0.14) 3.00 (0.14) 3.09 (0.17) 3.08 (0.16)

Kansas Biotic Index (AP) 3.09 (0.23) 2.95 (0.22) 3.01 (0.24) 2.84 (0.33)

Kansas Biotic Index (HM) 2.29 (0.25) 2.17 (0.20) 2.39 (0.19) 2.22 (0.14)

Kansas Biotic Index (POC) 2.59 (0.16) 2.53 (0.21) 2.43 (0.17) 2.31 (0.35)

Kansas Biotic Index (SA) 3.19 (0.14) 3.12 (0.11) 3.31 (0.11) 3.22 (0.15)

Kansas Biotic Index (SSS) 3.28 (0.12) 3.21 (0.14) 3.29 (0.20) 3.19 (0.22)
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 47

Table 13. Mean selected macroinvertebrate metric values and Kansas Department of Health and Environment aquatic-life-support 

status for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surfacewater site 375350097262800), and Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), April 2011 

through April 2013 and September 2013 through August 2014.—Continued

[See figure 1 for site locations. Medians in bold indicate statistically significant differences (p-value less than 0.05) between the upstream and downstream 

surface-water sites. Values in parentheses are plus or minus 1 standard deviation. pre, March 2011 through April 2013; ASR, aquifer storage and recovery; post, 

May 2013 through December 2014; EPT, Ephemeroptera, Plecoptera, and Trichoptera; NO, tolerances for nutrients and oxygen-demanding substances; AP, tolerances for agricultural pesticides; HM, tolerances for heavy metals; POC, tolerances for persistent organic compounds; SA, tolerances for salinity; SSS, tolerances for suspended solids and sediments; KBI, Kansas Biotic Index; <, less than]

Metric 

(unit of measure)

Pre-ASR Post-ASR

Upstream 

surface-water site

Downstream 

surface-water site

Upstream 

surface-water site

Downstream 

surface-water site

Tolerance metrics—Continued

Intolerant taxa (percent) 

(KBI–NO <3.0)

18.05 (5.83) 19.93 (3.87) 16.12 (7.14) 12.49 (4.73)

Macroinvertebrate Biotic Index1 5.90 (0.76) 5.37 (0.37) 5.73 (0.82) 5.44 (0.50)

Other metrics

EPT/Chironomidae ratio 0.69 (0.45) 0.96 (0.55) 0.87 (0.34) 1.27 (0.77)

Orthocladinae Chironomidae/Chironomidae ratio0.13 (0.22) 0.14 (0.21) 0.03 (0.04) 0.06 (0.06)

Tanytarsini Chironomidae/Chironomidae 

ratio

0.05 (0.07) 0.11 (0.08) 0.04 (0.06) 0.08 (0.12)

Scraper/filtering collector ratio 1.31 (0.99) 1.12 (0.89) 1.26 (0.68) 0.80 (1.20)

EPT richness/Chironomidae richness 

ratio

0.57 (0.24) 0.57 (0.19) 0.96 (0.40) 0.89 (0.41)

Orthocladinae Chironomidae richness/

Chironomidae richness ratio

0.07 (0.09) 0.09 (0.09) 0.07 (0.07) 0.13 (0.10)

Tanytarsini Chironomidae richness/Chironomidae richness ratio0.07 (0.06) 0.13 (0.06) 0.06 (0.09) 0.11 (0.12)

1

Kansas Department of Health and Environment aquatic life-support metrics.

Scrapers were also significantly greater at the upstream 

surface-water site, but this difference was only observed during the post-ASR time period (table 13). Filterer-collectors 

were significantly greater at the downstream surface-water site 

pre- and post-ASR (table 13).

Several macroinvertebrate indicators for which significant differences existed between upstream and downstream 

surface-water sites suggest an effect of overall greater flow 

velocities in the study reach downstream of the ASR facility. 

Even though flow velocities were not measured throughout 

the reach at either surface-water site and differences in habitat 

properties between the sites were of small magnitude (scores 

for pool substrate composition and flow status slightly larger 

downstream; table 11), there were more run and glide locations and fewer distinct pools within the reach at the downstream surface-water site. This may partially explain the 

larger abundance and mean richness of Trichoptera, larger 

mean Tanytarsini Chironomidae richness, and overall larger 

abundances of filterer-collectors at the downstream surfacewater site (table 13, fig. 8). Similarly, the larger abundances 

of Gastropods (for example, Physa sp.) and water boatmen 

(Corixidae; table 12) at the upstream site (tables 12, 13) may 

reflect a greater predominance of distinct pools at that site 

because these taxa are more commonly associated with pool 

margins (Merritt and others, 2008; Thorp and Covich, 2010).

Upstream-downstream surface-water site comparisons 

of macroinvertebrate aquatic-life-support metrics (table 14) 

did not reveal any significant differences for either pre- or 

post-ASR time periods, and neither surface-water site was 

fully-supporting for any of the four metrics (figs. 11A–11D); 

however, pre-ASR EPT richness was non-supporting at 

both surface-water sites, and post-ASR EPT richness was 

partially-supporting at both surface-water sites (fig. 11C). 

Pre- and post-ASR values were slightly greater at the upstream 

surface-water site for the Macroinvertebrate Biotic Index and 

slightly greater at the downstream surface-water site for the 

percent EPT metric (figs. 11A and 11D; table 13). Overall, 

using macroinvertebrate aquatic life-support criteria from the 

Kansas Department of Health and Environment (2008a), both 

upstream and downstream surface-water sites were classified 

as partially supporting pre- and post-ASR (fig. 11E).
48 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Table 14. Criteria for four macroinvertebrate metrics used in Kansas to evaluate aquatic-life-support status of streams (Kansas 

Department of Health and Environment, 2008a).

[KDHE, Kansas Department of Health and Environment; MBI, Microinvertebrate Biotic Index; KBI, Kansas Biotic Index; NO, tolerances for nutrients and 

oxygen-demanding substances; EPT, Ephemeroptera, Plecoptera, and Trichoptera; <, less than; >, greater than]

KDHE aquatic lifesupport statusKDHE aquatic lifesupport score MBI KBI–NO EPT richness EPT 

(percent)

Mean KDHE 

aquatic lifesupport score

Fully supporting 3 <4.51 <2.61 >12 >48 >2.49

Partially supporting 2 4.51–5.39 2.61–2.99 8–12 31–47 1.5–2.49

Nonsupporting 1 >5.39 >2.99 <8 <31 1.0–1.49

Fish Community Composition and Metrics

Fish communities can be good indicators of long-term 

effects and broad habitat conditions because fish can live many 

years and are mobile (Karr and others, 1986). Fish assemblages include species that comprise a variety of trophic levels 

and integrate effects of lower trophic levels; therefore, fish 

community structure is reflective of integrated environmental 

health (Barbour and others, 1999). Fish metrics calculated 

with abundance, richness, and diversity data can provide diagnostic information related to ecological condition.

A total of 23 fish taxa were identified from samples collected at all sites during 2011 through 2014 (table 15). Nine 

taxa belonged to the order Cypriniformes (minnows and carp) 

and four of the five dominant taxa were shiners (for example, 

Cyprinidae family) belonging to this order. Nine taxa belonged 

to the order Perciformes (perch-like fishes) and fish in this 

order were less common. The red shiner (Cyprinella lutrensis) 

was the dominant species at both surface-water sites (upstream 

surface-water site 375350097262800 and downstream surfacewater site 07144100 [fig. 1]) during the study period, followed 

by sand shiners (Notropis stramineus), western mosquitofish 

(Gambusia affinis), bullhead minnows (Pimephales vigilax), 

and suckermouth minnows (Phenacobius mirabilis). Shiners were the most dominant group at both surface-water sites 

during the entire study period (table 15). The red shiner was 

the dominant taxon at the upstream surface-water site during the study period (pre-ASR mean=42.38 percent of total 

abundance; post-ASR mean=80.35 percent of total abundance) and at the downstream surface-water site post-ASR 

(mean=62.04 percent of total abundance) as well as the second 

most dominant taxon at the downstream surface-water site 

pre-ASR (mean=30.86 percent of total abundance; table 15). 

The sand shiner was the dominant taxon at the downstream 

surface-water site pre-ASR (mean=33.42 percent of total 

abundance) as well as the second most dominant taxon at the 

upstream surface-water site pre-ASR (mean=13.49 percent 

of total abundance) and at the downstream surface-water site 

post-ASR (mean=15.18 percent of total abundance; table 15). 

The bullhead minnow was the second most dominant taxon at 

the upstream surface-water site post-ASR (mean=5.03 percent 

of total abundance; table 15). 

Pre-ASR mean taxa richness was 14.50 at the upstream 

surface-water site and 20.00 at the downstream surfacewater site and post-ASR mean taxa richness was 16.50 at 

the upstream surface-water site and 15.00 at the downstream 

surface-water site (table 16). Fish community trophic status generally was similar among sites during the study 

period. Omnivores increased and insectivores and piscivores 

decreased at the upstream and downstream surface-water sites 

post-ASR. Omnivores were the most dominant feeding group 

at the upstream site surface-water pre-ASR (mean=58.69 percent of total abundance) and at the upstream and downstream 

surface-water sites post-ASR (mean=87.42 and 65.16 percent 

of total abundance, respectively; table 16, fig. 12). Insectivores were dominant at the downstream surface-water site 

pre-ASR (mean=53.26 percent of total abundance) as well 

as second most dominant post-ASR (mean=34.06 percent of 

total abundance). At the upstream surface-water site, insectivores were second most dominant during the study period 

(pre-ASR mean=38.08 percent of total abundance, post-ASR 

mean=12.14 percent of total abundance; table 16, fig. 13). 

Piscivore abundance was minimal (ranged from 0.44 to 

5.57 percent of total abundance) at both surface-water sites 

during the study period (table 16, fig. 12).

Tolerant species increased and intermediately tolerant 

and intolerant species decreased at both the upstream and 

downstream surface-water sites post-ASR. Tolerant species 

made up the greatest percentage of fish communities at the 

upstream surface-water site pre-ASR (mean=50.72 percent 

of total abundance; table 16, fig. 13) and at both upstream 

and downstream surface-water sites post-ASR (mean=85.42 

and 65.49 percent of total abundance, respectively; table 16, 

fig. 13). The downstream surface-water site was dominated by 

intermediately tolerant species pre-ASR (mean=63.70 percent; 

table 16, fig. 13). Intermediately tolerant species were second 

most dominant at the upstream surface-water site pre-ASR 

(mean=47.83 percent of total abundance) and at the upstream 

and downstream surface-water sites post-ASR (mean=13.76 

and 32.28 percent of total abundance, respectively; table 16, 

fig. 13). Intolerant species were minimal at both surface-water 

sites during the study period and means ranged from 0.82 percent of total abundance at the upstream surface-water site 

post-ASR and 2.69 percent of total abundance at the downstream surface-water site pre-ASR (table 16, fig. 13).
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 49

Figure 11. Mean macroinvertebrate aquatic life-support metrics 

for the Little Arkansas River upstream from the aquifer storage 

and recovery facility near Sedgwick, Kansas (upstream surfacewater site 375350097262800) and the Little Arkansas River near 

Sedgwick, Kansas (downstream surface-water site 07144100), 

April 2011 through August 2014. A, Macroinvertebrate Biotic Index; 

B, Kansas Biotic Index; C, EPT Richness; D, Percent of EPT; and E, 

KDHE aquatic life-support score.

Macroinvertebrate Biotic Index

0

1

2

3

4

5

6

7

Kansas Biotic Index

0

1

2

3

4

EPT richness

0

2

4

6

8

10

12

14

Pre-ASR Post-ASR

Percent of EPT

0

10

20

30

40

50

60

Pre-ASR Post-ASR

KDHE aquatic life support score

0

0.5

1.0

1.5

2.0

2.5

3.0

Fully

supporting

Partially

supporting

Nonsupporting A B

C

E

D

Fully

supporting

Partially

supporting

Nonsupporting

Fully

supporting

Partially

supporting

Nonsupporting

Fully

supporting

Partially

supporting

Nonsupporting

Fully

supporting

Partially

supporting

Nonsupporting

EXPLANATION

Upstream surface-water site

Downstream surface-water site

Standard deviation

Median

Ephemeroptera, Plecoptera, and Trichoptera

Kansas Department of Health and Environment

Aquifer storage and recovery

EPT

KDHE

ASR
50 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Table 15. Mean fish community summary statistics for the Little Arkansas River upstream from the aquifer storage and recovery 

facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and Little Arkansas River near Sedgwick, Kansas

(downstream surface-water site 07144100), September 2011 and 2012 and September 2013 and August 2014.

[See figure 1 for site locations. Values in parentheses are plus or minus 1 standard deviation. pre, March 2011 through April 2013; ASR, aquifer storage and 

recovery; post, May 2013 through December 2014]

Species 

(unit of measure)

Pre-ASR Post-ASR

Upstream 

surface-water site

Downstream 

surface-water site

Upstream 

surface-water site

Downstream 

surface-water site

Gizzard shad (Dorosoma cepedianum) (percent) 0.65 (0.91) 0.57 (0.32) 0.02 (0.03) 0.10 (0.14)

Goldfish (Carassius auratus) (percent) 0.08 (0.11) 0.13 (0.06) 0.03 (0.04) 0

Red shiner (Cyprinella lutrensis) (percent) 42.38 (17.97) 30.86 (9.18) 80.35 (12.13) 62.04 (13.77)

Common carp (Cyprinus carpio) (percent) 1.16 (0.87) 1.15 (0.81) 0.46 (0.07) 2.09 (2.95)

Sand shiner (Notropis stramineus) (percent) 13.49 (2.43) 33.42 (9.07) 3.12 (1.88) 15.18 (11.06)

Suckermouth minnow (Phenacobius mirabilis) 

(percent)

8.18 (6.90) 10.18 (6.59) 0.78 (0.61) 1.57 (1.52)

Fathead minnow (Pimephales promelas) (percent) 1.91 (0.49) 0.85 (0.50) 0.18 (0.15) 0.33 (0.11)

Bullhead minnow (Pimephales vigilax) (percent) 10.56 (8.33) 7.20 (0.79) 5.03 (5.57) 2.88 (3.89)

River carpsucker (Carpiodes carpio) (percent) 0.65 (0.91) 0.82 (0.43) 0.32 (0.29) 0.03 (0.05)

Quillback (Carpiodes cyprinus) (percent) 0 0.11 (0.09) 0.03 (0.04) 0.03 (0.05)

Black bullhead (Ameiurus melas) (percent) 0 0 0.02 (0.03) 0.03 (0.05)

Channel catfish (Ictalurus punctatus) (percent) 3.17 (3.05) 4.05 (2.55) 0.37 (0.13) 0.43 (0.44)

Flathead catfish (Pylodictus olivaris) (percent) 0.56 (0.80) 0.30 (0.07) 0 0.10 (0.04)

Western mosquitofish (Gambusia affinis) (percent) 10.58 (4.48) 3.30 (2.72) 4.86 (0.99) 7.78 (3.05)

Green sunfish (Lepomis cyanellus) (percent) 1.98 (0.85) 0.91 (0.55) 2.85 (2.60) 4.18 (0.16)

Orangespotted sunfish (Lepomis humilis) (percent) 2.57 (0.01) 3.41 (2.98) 0.40 (0.34) 1.29 (0.09)

Bluegill (Lepomis macrochius) (percent) 0.89 (1.25) 0.69 (0.74) 0.30 (0.31) 0.78 (1.10)

Longear sunfish (Lepomis megalotis) (percent) 0.70 (0.31) 1.59 (0.06) 0.55 (0.78) 0.95 (1.34)

Largemouth bass (Micropterus salmoides) (percent) 0.40 (0.57) 0.08 (0.12) 0.03 (0.04) 0.14 (0.19)

White crappie (Pomoxis annularis) (percent) 0 0.15 (0.03) 0 0

Black crappie (Pomoxis nigromaculatus) (percent) 0 0.06 (0.09) 0.09 (0.12) 0

Slenderhead darter (Percina phoxocephala) 

(percent)

0.08 (0.11) 0.08 (0.12) 0.20 (0.29) 0.06 (0.09)

Freshwater drum (Aplodinotus grunniens) (percent) 0 0.08 (0.12) 0.03 (0.04) 0

Mean percent abundance of the five most abundant 

species was larger at the upstream surface-water site during 

the study period and increased at both surface-water sites 

post-ASR (table 16). Fish community diversity decreased 

post-ASR at the upstream and downstream surface-water sites. 

Shannon’s diversity index was 1.83 at both sites pre-ASR and 

decreased to 0.85 at the upstream surface-water site and 1.38 

at the downstream surface-water site post-ASR (table 16). 

The region-specific Little Arkansas River Basin IBI was 

developed for fish communities in the Little Arkansas drainage 

basin by Lydy and others (2000) by regionally modifying an 

index of biotic integrity that was first used to assess the biotic 

integrity of Midwestern streams (Karr, 1981; Karr and others, 1986) using reference conditions from the Central Great 

Plains ecoregion. The Little Arkansas River Basin IBI encompasses taxa richness and composition, tolerance, trophic guild, 

abundance, reproductive guild, and individual health and 

condition (Lydy and others, 2000). The Little Arkansas River 

Basin IBI was similar among surface-water sites pre-ASR 

(upstream=46, downstream=47) and post-ASR (upstream=44, 

downstream=42). The Little Arkansas River Basin IBI integrity class was the same among sites pre- and post-ASR. The 

pre-ASR Little Arkansas River Basin IBI integrity classes 

were indicative of fair-to-good conditions and post-ASR 

decreased to fair conditions at the upstream and downstream 

surface-water sites (table 16). Although the Little Arkansas River Basin IBI integrity class decreased post-ASR, the 

decrease could be related to different streamflow conditions 

post-ASR compared to pre-ASR. These results were within the 

Little Arkansas River Basin IBI integrity class range for fish 

assemblages from agricultural streams in the Little Arkansas 

River drainage basin reported by Eaton and Lydy (2000).
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 51

Table 16. Mean selected fish community metrics for the Little Arkansas River upstream from the aquifer storage and recovery facility 

(upstream surface-water site 375350097262800) and the Little Arkansas River (downstream surface-water site 07144100) near Sedgwick, 

Kansas, during September 2011 and 2012 and September 2013 and August 2014.

[See figure 1 for site locations. Values in parentheses are plus or minus 1 standard deviation. pre, March 2011 through April 2013; ASR, aquifer storage and 

recovery; post, May 2013 through December 2014]

Metric 

(unit of measure)

Pre-ASR Post-ASR

Upstream surfacewater siteDownstream surfacewater siteUpstream surfacewater siteDownstream surfacewater site

Taxa richness metrics

Taxa richness 14.50 (4.95) 20.00 (2.83) 16.50 (3.54) 15.00 (4.24)

Trophic status metrics

Omnivores (percent) 58.69 (6.22) 41.17 (1.50) 87.42 (6.19) 65.16 (12.71)

Insectivores (percent) 38.08 (1.78) 53.26 (0.18) 12.14 (4.73) 34.06 (9.38)

Piscivores (percent) 3.23 (4.44) 5.57 (2.90) 0.44 (0.13) 0.78 (0.40)

Tolerance metrics

Intolerant (percent) 1.45 (1.07) 2.69 (0.91) 0.82 (0.31) 2.23 (0.09)

Intermediately tolerant (percent) 47.83 (14.49) 63.70 (0.09) 13.76 (7.53) 32.28 (13.92)

Tolerant (percent) 50.72 (15.56) 33.61 (0.82) 85.42 (9.45) 65.49 (16.76)

Little Arkansas River Basin Index of 

Biotic Integrity1

46 (2.83) 47 (4.24) 44 (0.00) 42 (2.83)

Little Arkansas River Basin Index of 

Biotic Integrity class1

Fair-to-good Fair-to-good Fair Fair

Abundance and diversity metrics

Five most abundant species (percent) 87.18 (9.21) 84.77 (2.46) 94.97 (3.06) 89.39 (4.89)

Shannon’s diversity index 1.83 (0.50) 1.83 (0.17) 0.85 (0.45) 1.38 (0.46)

1

Index of Biotic Integrity scores were calculated as described in Lydy and others (2000).

Groundwater Environmental Conditions 

Baseline and postoperational groundwater conditions 

were assessed with continuous and discrete groundwater-quality data and by modeling the geochemical equilibrium state of 

the aquifer with respect to select minerals.

Groundwater Quality

Continuous and discrete water-quality data collected in 

four wells near the surface recharge basin near Sedgwick, 

Kansas (fig. 1) was used to describe conditions before (January 2011 to April 2013), during (May to September 2013 and 

May to July 2014), and after (October 2013 to April 2014 and 

August to December 2014) recharge periods. Continuously 

collected groundwater data included specific conductance, pH, 

water temperature, and dissolved oxygen. Discretely collected 

groundwater data included solids and primary ions, nutrients, 

indicator bacteria, trace elements, pesticides, chlorinated and 

brominated organic compounds, and radioactive chemistry. 

The total amount of water recharged at the Sedgwick basin 

was 356 million gallons during 2013 and 2014.

Continuous Groundwater Quality

Summary statistics of daily water quality (as daily 

means for dissolved oxygen, specific conductance, and water 

temperature; median for pH) are listed below. Additionally, 

water level was monitored October 10, 2012 through 2014, 

and aquifer withdrawal periods were determined by response 

in water level to account for multiple pumping sources 

(table 17, fig. 14A). During 2011 through 2012, the preartificial recharge shallow groundwater altitudes varied from 

about 1,344 to 1,358 ft in a few discrete measurements that 

were made associated with sample collection. Shallow and 

deep groundwater levels were within about 1 ft with the shallow water levels higher indicating a downward movement of 

water. In the post-recharge period during 2013 through 2014, 

water levels varied from altitudes of about 1,343 to 1,363 ft in 

response to a nearby pumping well and in response to recharge 

activities that caused increased elevation (fig. 14A).

Although stream and deep groundwater dissolved oxygen were similar before and after recharge periods, shallow 

groundwater dissolved oxygen during recharge were more 

variable in response to artificial and natural recharge. Dissolved oxygen in the MW–7 shallow groundwater well (site 

375327097285401) recovered to values similar to before 
52 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Figure 12. Mean fish feeding group percentage of total abundance for the Little Arkansas River upstream from the aquifer 

storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and the Little Arkansas 

River near Sedgwick, Kansas (downstream surface-water site 07144100), September 2011 and 2012 and September 2013 and 

August 2014.

Omnivore

Insectivore

Piscivore

EXPLANATION

Mean fish feeding group total

 abundance, in percent

ASR Aquifer storage and recovery

Upstream surface-water site Downstream surface-water site

Pre-ASR

Post-ASR

58.69

38.08

3.23

41.17

53.26

5.57

87.42

12.14

65.16

34.06

0.44 0.78
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 53

Figure 13. Mean fish tolerance group percentage of total abundance for the Little Arkansas River upstream from the aquifer 

storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and the Little Arkansas 

River near Sedgwick, Kansas (downstream surface-water site 07144100), September 2011 and 2012 and September 2013 and 

August 2014. 

Intolerant

Intermediately tolerant

Tolerant

EXPLANATION

Mean fish tolerance group total

 abundance, in percent

ASR Aquifer storage and recovery

Upstream surface-water site Downstream surface-water site

Pre-ASR

Post-ASR 2.23

0.82

1.45

2.69

47.83

50.72

63.70

85.42

13.76

32.28

65.49

33.61
54 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Table 17. Physicochemical properties for sites near the recharge basin near Sedgwick, Kansas before (January 2011 to April 2013), during (May to September 2013 and May to July 2014), and after (October 2013 to April 2014 and August to December 2014) artificial recharge and at the Little Arkansas River near Sedgwick, Kansas (downstream surface- water site 07144100), summary of daily statistics from continuously measured data. [See figure 1 for site locations. Continuous real-time water-quality data are available on the U.S. Geological Survey National Real-Time Water Quality Web site at http://nrtwq.usgs.gov. mg/L, milligram per liter; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; <, less than] Description Dissolved oxygen (mg/L) pH (standard units) Specific conductance (μS/cm at 25 °C) Water temperature (°C) Minimum Median Maximum Minimum Median Maximum Minimum Median Maximum Minimum Median Maximum Stream Overall 2.0 10.0 17.4 6.6 8.0 8.9 98 799 1,620 0.1 14.6 30.5 During recharge 2.0 7.7 16.1 6.6 7.9 8.6 98 638 1,520 11.6 24.5 30.3 MW–7 shallow well Overall 0.2 3.4 9.9 6.6 6.8 7.5 165 663 902 14.3 16.1 28.3 Before recharge 1.9 3.6 4.6 6.7 6.8 6.9 532 701 767 14.5 15.6 16.2 During recharge 0.2 3.5 9.9 6.7 6.9 7.5 165 470 902 14.3 22.6 28.3 After recharge 1.1 2.4 4.7 6.6 6.8 7.2 333 440 842 19.8 23.2 26.5 During and after recharge 0.2 2.6 9.9 6.6 6.9 7.5 165 444 902 14.3 22.9 28.3 MW–8 shallow well Overall <0.1 4.6 7.9 6.0 6.7 7.6 139 512 924 14.3 21.9 27.6 Before recharge 3.6 5.5 7.6 6.0 6.5 6.7 380 504 569 14.3 15.6 16.6 During recharge <0.1 5.2 7.9 6.8 7.0 7.6 139 465 914 19.3 23.0 27.6 After recharge 0.1 0.7 6.0 6.6 6.9 7.4 408 832 924 21.7 22.7 24.1 During and after recharge <0.1 1.2 7.9 6.6 7.0 7.6 139 580 924 19.3 22.7 27.6 MW–7 and MW–8 deep wells MW–7 Deep <0.1 0.1 0.2 7.0 7.3 7.5 737 760 804 15.2 15.3 15.3 MW–8 Deep <0.1 0.1 0.2 7.1 7.2 7.4 689 729 752 15.6 15.7 15.8
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer 55

Figure 14. Groundwater conditions continuously monitored or measured in wells near infiltration basin, 2011 through 2014. A, water 

level and streamflow; B, dissolved oxygen; C, pH; D, specific conductance; and E, water temperature.

1,340

1,345

1,350

1,355

1,360

1,365

1,370

Water level, in feet above mean sea level

A. Water level and streamflow

B. Dissolved oxygen

0.1

1

10

100

1,000

10,000

100,000

Streamflow, in cubic feet per second

−1

 0

 2

 4

 6

 8

10

12

14

16

18

Dissolved oxygen, in milligrams per liter

2011 2012 2013 2014

Calendar year

2011 2012 2013 2014

Calendar year

B

Little Arkansas River near 

Sedgwick, Kansas

MW−7 shallow

MW−7 deep

MW−8 shallow

MW−8 deep

Artificial recharge

Aquifer withdrawals, 

after 10/10/2012 only

Site

EXPLANATION

Lines represent continuously-monitored 

data. Squares represent measured data.

Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer
56 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer pH, in standard units

C. pH

D. Specific conductance

Specific conductance, in microsiemens per centimeter

2011 2012 2013 2014

Calendar year

2011 2012 2013 2014

Calendar year

B

5.8

6.0

6.5

7.0

7.5

8.0

8.5

9.0

50

200

400

600

800

1,000

1,200

1,400

1,600

1,800

Little Arkansas River near 

Sedgwick, Kansas

MW−7 shallow

MW−7 deep

MW−8 shallow

MW−8 deep

Artificial recharge

Aquifer withdrawals, 

after 10/10/2012 only

Site

EXPLANATION

Lines represent continuously-monitored 

data. Squares represent measured data.

Figure 14. Groundwater conditions continuously monitored or measured in wells near infiltration basin, 2011 through 2014. A, water 

level and streamflow; B, dissolved oxygen; C, pH; D, specific conductance; and E, water temperature.—Continued
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 57 Water temperature, in degrees Celsius

E. Temperature

2011 2012 2013 2014

Calendar year

Little Arkansas River near 

Sedgwick, Kansas

MW−7 shallow

MW−7 deep

MW−8 shallow

MW−8 deep

Artificial recharge

Aquifer withdrawals, 

after 10/10/2012 only

Site

EXPLANATION

Lines represent continuously-monitored 

data. Squares represent measured data.

 0

 5

10

15

20

25

30

32

Figure 14. Groundwater conditions continuously monitored or measured in wells near infiltration basin, 2011 through 2014. A, water 

level and streamflow; B, dissolved oxygen; C, pH; D, specific conductance; and E, water temperature.—Continued

recharge, but the MW–8 shallow groundwater well (site 

375332097284801) dissolved oxygen was reduced after 

recharge periods. Stream daily mean dissolved oxygen varied 

seasonally, peaking in winter and smallest in the summer, 

around an overall median daily mean of 10.0 mg/L (table 17, 

fig. 14B). Summer low stream dissolved oxygen is coincident 

with the period of water withdrawals and aquifer recharge. 

In the MW–7 shallow groundwater well, median dissolved 

oxygen before, during, and after recharge were 3.6, 3.5, and 

2.4 mg/L, respectively. Median daily mean dissolved oxygen 

in the MW–8 shallow groundwater well was 5.5 mg/L before 

recharge, 5.2 mg/L during recharge periods, and 0.7 mg/L 

after each recharge period. Though shallow well median daily 

mean dissolved oxygen was little changed during recharge 

periods, the range was higher during recharge than before for 

both groundwater wells. The MW–7 shallow groundwater 

well mean dissolved oxygen ranged from 1.9 to 4.6 mg/L, 

0.2 to 9.9 mg/L, and 1.1 to 4.7 mg/L before, during, and after 

recharge, respectively; and the MW–8 shallow groundwater 

well mean dissolved oxygen ranged from 3.6 to 7.6 mg/L, 

<0.1 to 7.9 mg/L, and 0.1 to 6.0 mg/L before, during, and after 

recharge, respectively. Deep groundwater dissolved oxygen 

was monitored from March 29, 2013, to May 31, 2014, was 

consistently anoxic, and had a maximum daily mean in both 

wells of 0.2 mg/L.

Continuously monitored pH in groundwater well sites 

generally was smaller than stream pH (table 17; fig. 14C). 

Median daily stream pH was 8.0 during 2011 through 2014. 

Shallow well pH was monitored from July 21, 2011 through 

2014 and the first recharge period began in May 2013. 

Median pH was 6.8 in the MW–7 shallow groundwater 

well and differed minimally before the first recharge period 

(median=6.8) compared to during and after the first recharge 

period (median=6.9). Median pH was 6.7 in the MW–8 shallow groundwater well and was slightly smaller before the 

first recharge period (median=6.5) compared to during and 

after the first recharge period (median=7.0). Deep wells were 

monitored for continuous pH from March 21, 2013 through 

May 31, 2014, from just before the first artificial recharge 

event and into the second artificial recharge period. Median 

daily pH was 7.3 in the MW–7 deep groundwater well (site 

375327097285402, fig. 1) and 7.2 in the MW–8 deep groundwater well (site 375332097284802, fig. 1). 

Specific conductance in shallow groundwater wells 

tended to reflect stream water conditions during recharge 

periods (table 17, fig. 14D). Stream median daily mean 

specific conductance was 799 μS/cm at 25 °C. Median daily 

mean specific conductance was 663 μS/cm at 25 °C in the 

MW–7 shallow groundwater well and 512 μS/cm at 25 °C in 

the MW–8 shallow groundwater well. Specific conductance 

in deep wells varied little from the median daily mean of 

760 μS/cm at 25 °C and 729 μS/cm at 25 °C for MW–7 and 

MW–8 deep groundwater wells, respectively.

Stream water and deep groundwater temperatures were 

similar before and after recharge periods but shallow groundwater temperature increased during the first recharge period 
58 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

and remained higher. Stream withdrawals and aquifer recharge 

periods were coincident with seasonal high stream daily mean 

temperatures. Before recharge, the median daily mean temperature in the MW–7 and MW–8 shallow groundwater wells 

was 15.6 oC. Temperatures in shallow wells increased substantially during the first recharge period and remained higher 

through the study period, with median daily mean temperatures during and after recharge of 22.9 oC (range=14.3 oC to 

28.3 oC) in the MW–7 shallow groundwater well and 22.7 oC 

in the MW–8 shallow groundwater well. Water temperatures 

in deep groundwater wells were consistent around median 

daily means of 15.3 oC and 15.7 oC for the MW–7 and MW–8 

deep groundwater wells, respectively (table 17). 

Discrete Groundwater Quality

Data from discrete groundwater well samples were used 

to describe water-quality conditions in shallow and deep wells 

before and after recharge periods. Discrete water-quality data 

collected included dissolved solids and primary ions, nutrients, 

indicator bacteria, trace elements, pesticides, chlorinated and 

brominated organic compounds, and radioactive chemistry. 

Samples from before and after the beginning of artificial 

recharge were compared for shallow wells and deep wells 

using a generalized two-sided Wilcoxon test of unpaired samples. Sample counts and censoring levels (laboratory reporting 

levels) for additional constituents analyzed but not detected 

are presented in appendix table 1–10.

Solids and Primary Ions

Solids and the individual ions calcium, magnesium, 

potassium, sodium, alkalinity, bicarbonate, carbonate, bromide, 

chloride, fluoride, silica, and sulfate are summarized in table 

18. Median total solids significantly decreased, potassium 

significantly tripled, chloride significantly doubled, and fluoride 

significantly increased in shallow groundwater after artificial 

recharge (p-values <0.05); all other measures of solids and individual ion concentrations were not significantly different before 

and after recharge began. These significant changes in shallow 

groundwater concentrations were likely caused by the artificially recharged treated surface water and natural infiltration of 

precipitation. Deep groundwater samples were not significantly 

different for any solids or ion concentrations. No solids and primary ion constituent concentrations in the pre-recharge period 

in comparison to the post-recharge period increased to concentrations exceeding drinking water regulations.

Nutrients and Organic Carbon

Nitrogen species, except ammonia and nitrite, significantly decreased in shallow groundwater, whereas phosphorus and carbon species significantly increased after artificial 

recharge (table 19). Ammonia and nitrite datasets had high percentages of left-censored data and were not statistically compared. Median shallow groundwater nitrate before recharge was 

10.3 mg/L and exceeded the Federal MCL of 10 mg/L; during 

and after recharge median nitrate was 1.06 mg/L. Four of six 

shallow groundwater samples before recharge began exceeded 

the MCL of 10 mg/L for nitrate. None of the post-recharge onset 

nitrate samples exceeded the MCL. Median shallow groundwater orthophosphate and dissolved phosphorus concentrations 

were similar and increased after recharge began from 0.04 and 

0.06 mg/L to 0.17 and 0.18 mg/L, respectively. Total carbon was 

predominantly in dissolved forms and median shallow groundwater total carbon and dissolved carbon increased after recharge 

began from 0.5 to 1.3 mg/L, respectively. Of all deep groundwater nutrients and carbon constituents, only dissolved carbon was 

statistically (p-value <0.05) different before and after recharge 

in deep groundwater but increased minimally from 0.4 to 0.6 

mg/L after recharge began. These statistical increases following recharge remain within the range of concentrations for total 

organic carbon throughout the aquifer (Tappa and others, 2015).

Indicator Bacteria

Bacteria and indicators had datasets with severe leftcensoring and some also contained right-censored data. All 

E. coli and fecal coliform bacteria densities were below the 

method detection limits (<1 mpn/100 mL and <1 col/100 mL, 

respectively), except for one deep well E. coli sample that 

was at the method detection limit after the onset of recharge 

(table 20). The EPA Federal MCL in drinking water for total 

coliform bacteria is that no more than 5 percent of samples test 

positive during 1 month for water systems that collect at least 

40 routine samples per month (U.S. Environmental Protection Agency, 2009). If fewer than 40 samples are collected 

per month, only 1 sample can test positive for total coliform 

bacteria (U.S. Environmental Protection Agency, 2009). The 

EPA Federal MCLG in drinking water for total coliform bacteria is 0 col/100 mL. For the purposes of this report, col/100 

mL are considered equivalent to mpn/100 mL. Total coliform 

bacteria densities were within the range of densities throughout 

the aquifer (Tappa and others, 2015). Total coliform bacteria 

detections were smaller after recharge onset. Total coliform 

bacteria densities exceeded the EPA MCLG in 83 percent of 

shallow groundwater samples before recharge and 50 percent after recharge began. Total coliform bacteria densities 

exceeded the EPA MCLG in 50 percent of deep groundwater 

samples prior to recharge and 38 percent after recharge onset. 

Median shallow groundwater slime-forming bacteria before 

recharge was 1,080,000 cfu/100 mL and was significantly 

smaller (p-value=0.03) after the onset of artificial recharge 

(median=208,000 cfu/100 mL; table 20). Deep groundwater 

sulfate-reducing bacteria increased from a median of <1 to 

1,200 cfu/100 mL after artificial recharge began, although the 

pre-recharge sample dataset was severely censored. Results of 

biological activity reaction tests indicated that water quality 

microbiology was different before and after artificial recharge 

began; at times, these differences may lead to changes in dominant bacterial populations that, in turn, may lead to formation 

and expansion in populations that may cause bioplugging and 

other unwanted effects.
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 59

Table 18. Discretely collected solids and primary ions summary statistics for groundwater samples at sites near the recharge basin near Sedgwick, Kansas, before (January 

2011 to April 2013) and after (May 2013 to December 2014) artificial recharge.

[Medians in bold indicate significant differences (p-value less than 0.05) between before and after recharge. Censoring levels are for all samples. The before and after groundwater samples were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. n, number of measurements; mg/L, milligram per liter; CaCO3, calcium carbonate; --, not applicable; <, less than; SiO2, silicon dioxide]

Water-quality constituent 

(unit of measure)

Before recharge After recharge

Left-censored 

data (percent) n Minimum Maximum Mean Median Left-censored data (percent) n Minimum Maximum Mean Median

Shallow groundwater

Dissolved solids (mg/L) 0 6 329 413 369 364 0 14 205 522 340 298

Hardness (mg/L as CaCO3

) 0 6 171 251 219 216 0 14 114 316 194 176

Suspended solids (mg/L) 83 6 <4 5 -- -- 100 14 <4 <4 -- --

Total solids (mg/L) 0 4 340 424 383 384 0 4 216 298 267 276

Calcium (mg/L) 0 6 53.5 79.5 68.7 67.8 0 14 35.1 96.9 60.7 54.9

Magnesium (mg/L) 0 6 9.05 12.8 11.3 11.3 0 14 6.16 17.8 10.3 9.3

Potassium (mg/L) 0 6 2 3 3 3 0 14 5 12 9 9

Sodium (mg/L) 0 6 29.7 47.6 36.7 34.2 0 14 15.3 64.4 38.6 34.2

Alkalinity (mg/L as CaCO3

) 0 6 142 192 166 165 0 14 88.0 228 149 136

Bicarbonate (mg/L) 0 6 170 230 200 200 0 14 110 280 182 165

Bromide (mg/L) 0 4 0.1 0.1 0.1 0.1 0 14 0.1 0.3 0.2 0.1

Chloride (mg/L) 0 6 23 32 27 26 0 14 23 110 62 55

Fluoride (mg/L) 0 6 0.3 0.5 0.4 0.4 0 14 0.2 0.8 0.6 0.6

Silica (mg/L as SiO2

) 0 6 16.5 20.6 18.5 18.5 0 14 15.0 19.6 17.3 17.1

Sulfate (mg/L) 0 6 54 64 58 58 0 14 19 72 45 43

Deep groundwater

Dissolved solids (mg/L) 0 6 442 477 456 448 0 8 427 492 453 450

Hardness (mg/L as CaCO3

) 0 6 191 251 223 217 0 8 211 253 228 227

Suspended solids (mg/L) 100 6 <4 <4 -- -- 100 8 <4 <4 -- --

Total solids (mg/L) 0 4 460 486 474 474 0 2 464 490 477 477

Calcium (mg/L) 0 6 57.2 75.9 67.1 65.0 0 8 63.3 76.6 68.6 68.2

Magnesium (mg/L) 0 6 11.5 15.0 13.3 13.2 0 8 12.6 14.8 13.5 13.5

Potassium (mg/L) 0 6 3 3 3 3 0 8 3 3 3 3

Sodium (mg/L) 0 6 67 92 82 85 0 8 75 82 78 78

Alkalinity (mg/L as CaCO3

) 0 6 248 262 257 260 0 8 258 268 262 262

Bicarbonate (mg/L) 0 6 300 320 315 320 0 8 320 330 321.25 320

Bromide (mg/L) 33 6 <0.02 0.1 0.1 0.1 0 8 0.1 0.1 0.1 0.1

Chloride (mg/L) 0 6 44 63 54 55 0 8 40 67 52 52

Fluoride (mg/L) 0 6 0.4 0.5 0.5 0.5 0 8 0.4 1.0 0.6 0.5

Silica (mg/L as SiO2

) 0 6 21.6 27.2 24.9 25.0 0 8.0 23.8 27.4 25.4 25.3

Sulfate (mg/L) 0 6 57 64 61 61 0 8 56 66 60 61
60 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Table 19. Discretely collected nutrient and carbon summary statistics for groundwater samples at sites near the recharge basin near Sedgwick, Kansas, before (January 2011 to April 2013) and after (May 2013 to December 2014) artificial recharge. [Medians in bold indicate significant differences (p-value less than 0.05) between before and after recharge. Censoring levels are for all samples. The before and after groundwater samples were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. n, number of measurements; mg/L, mil- ligram per liter; N, nitrogen; <, less than; --, not applicable; P, phosphorus] Water-quality constituent (unit of measure) Before recharge After recharge Left-censored data (percent) n Minimum Maximum Mean Median Left-censored data (percent) n Minimum Maximum Mean Median Shallow groundwater Ammonia (mg/L as N) 83 6 <0.03 0.04 -- -- 71 14 <0.01 0.04 0.03 0.02 Nitrate plus nitrite (mg/L as N) 0 6 3.64 11.6 8.73 10.3 0 14 0.41 3.94 1.36 1.06 Nitrate (mg/L as N) 0 6 3.64 11.6 8.73 10.3 0 14 0.41 3.94 1.36 1.06 Nitrite (mg/L as N) 100 6 <0.01 <0.01 -- -- 93 14 <0.001 0.02 -- -- Orthophosphate (mg/L as P) 0 6 0.03 0.05 0.04 0.04 0 14 0.06 0.33 0.18 0.17 Dissolved phosphorus (as above for shallow groundwater)

0 6 0.05 0.07 0.06 0.06 0 14 0.06 0.30 0.17 0.18

Dissolved organic carbon (mg/L) 0 4 0.4 0.6 0.5 0.5 0 14 0.6 3.2 1.6 1.3

Total organic carbon (mg/L) 0 4 0.41 0.54 0.49 0.50 0 14 0.62 3.14 1.64 1.30

Deep groundwater

Ammonia (mg/L as N) 67 6 <0.03 0.03 0.02 0.02 88 8 <0.03 0.03 -- --

Nitrate plus nitrite (mg/L as N) 0 6 0.04 2.44 1.22 1.10 0 8 0.07 2.11 1.07 1.09

Nitrate (mg/L as N) 0 6 0.04 2.41 1.20 1.06 0 8 0.07 2.05 1.04 1.06

Nitrite (mg/L as N) 67 6 <0.01 0.07 0.02 0.01 50 8 <0.01 0.07 0.06 0.04

Orthophosphate (mg/L as P) 67 6 <0.02 0.02 0.01 0.01 75 8 <0.02 0.04 0.02 0.02

Dissolved phosphorus (as above 

for shallow groundwater)

33 6 <0.03 0.05 0.03 0.04 75 8 <0.03 0.03 0.02 0.02

Dissolved organic carbon (mg/L) 0 4 0.4 0.5 0.4 0.4 0 8 0.5 0.9 0.6 0.6

Total organic carbon (mg/L) 0 4 0.37 0.63 0.46 0.43 0 8 0.49 0.63 0.57 0.56
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 61

Table 20. Discretely collected bacteria summary statistics for groundwater samples at sites near the recharge basin near Sedgwick, Kansas, before (January 2011 to April 

2013) and after (May 2013 to December 2014) artificial recharge.

[Medians in bold indicate significant differences (p-value less than 0.5) between before and after recharge. All bacteria are left-censored at one unit. The before and after groundwater samples were not statistically compared when greater than 50 percent of data were left- or right-censored. Means and medians were not computed when greater than 80 percent of data were left- or right-censored. n, number of measurements; E. coli, Escherichia coli; mpn/100 mL, most probable number per 100 milliliters; <, less than; --, not applicable; col/100 mL, colony per 100 milliliters; >, greater than; pfu/100 mL, plaque forming unit per 100 milliliters; 

cfu/mL, colony forming unit per milliliter]

Water-quality constituent 

(unit of measure)

Before recharge After recharge

Left-censored 

data (percent) n Minimum Maximum Mean Median Left-censored data (percent) n Minimum Maximum Mean Median

Shallow groundwater

E. coli bacteria (mpn/100 mL) 100 6 <1 <1 -- -- 100 14 <1 <1 -- --

Fecal coliform bacteria 

(col/100 mL)

100 6 <1 <1 -- -- 100 14 <1 <1 -- --

Total coliform bacteria 

(mpn/100 mL)

17 6 <1 >200 109 41 50 14 <1 >200 40 10

E. coli coliphage (pfu/100 mL) 75 4 <1 1 1 1 100 14 <1 <1 -- --

Iron-related bacteria (cfu/mL) 0 4 9,000 9,000 9,000 9,000 0 14 150 35,000 15,600 9,000

Slime-forming bacteria 

(cfu/mL)

0 4 350,000 1,800,000 1,080,000 1,080,000 7.1 14 <1 1,800,000 299,000 208,000

Sulfate-reducing bacteria 

(cfu/mL)

50 4 <1 5,000 1,650 600 57 14 <1 18,000 1,830 <1

Deep groundwater

E. coli bacteria (mpn/100 mL) 100 6 <1 <1 -- -- 88 8 <1 1 -- --

Fecal coliform bacteria 

(col/100 mL)

100 6 <1 <1 -- -- 100 8 <1 <1 -- --

Total coliform bacteria 

(mpn/100 mL)

50 6 <1 18 4 <1 63 8 <1 34 8 <1

E. coli coliphage (pfu/100 mL) 100 4 <1 <1 -- -- 100 8 <1 <1 -- --

Iron-related bacteria (cfu/mL) 50 4 <1 9,000 9,000 4,500 0 8 150 35,000 11,400 5,650

Slime-forming bacteria 

(cfu/mL)

0 4 12,500 1,800,000 544,000 181,000 13 8 <1 1,800,000 359,000 181,000

Sulfate-reducing bacteria 

(cfu/mL)

75 4 <1 200 200 <1 0 8 500 100,000 14,200 1,200
62 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Trace Elements

Metals and other trace elements detected include aluminum, barium, cadmium, lead, manganese, nickel, strontium, 

thallium, vanadium, zinc, arsenate, arsenic, boron, and selenium. Arsenite, beryllium, chromium, copper, cyanide, iron, 

mercury, and silver were not detected in groundwater samples 

during the study (appendix table 1–10). Shallow groundwater barium, manganese, nickel, arsenate, arsenic, and boron 

concentrations increased, whereas strontium and selenium 

decreased after recharge onset (table 21). Shallow groundwater nickel and arsenic significantly increased after the beginning of the first recharge period (table 21). Shallow groundwater median arsenic concentrations increased from 0.9 μg/L 

before recharge to 1.7 μg/L after recharge onset (table 21). 

The increase in arsenic concentrations is likely because of the 

recharged surface water, but arsenic remained about 6 times 

smaller than the EPA MCL of 10 μg/L. None of the shallow 

or deep groundwater sample arsenic concentrations exceeded 

the MCL during the study. Shallow groundwater selenium 

medians decreased significantly from 11 to 1.9 μg/L (table 21). 

Deep groundwater manganese, nickel, arsenate, and selenium 

increased, whereas strontium, arsenic, and boron decreased 

after recharge onset (table 21). Pre- and post-recharge deep 

groundwater manganese medians exceeded the EPA SMCL 

of 50 μg/L and significantly increased from 88 μg/L before 

recharge to 216 μg/L after recharge onset (table 21). Deep 

groundwater nickel medians significantly doubled after 

recharge onset (table 21). Significant manganese and nickel 

increases in deep groundwater are unlikely related to recharge 

activities.

Pesticides

Pesticides detected in shallow groundwater samples 

included acetochlor, atrazine, metolachlor, metribuzin, and 

simazine. These pesticides, along with detected degradation 

compounds and total triazines, are summarized in table 22. 

Undetected analytes included many additional pesticides and 

degradation compounds that are summarized in appendix 

table 1–10. Atrazine and the triazine degradate 2-Chloro4-isopropylamino-6-amino-s-triazine (CIAT) were the only 

pesticides detected before recharge. Atrazine was detected 

prior to recharge in one shallow well sample at the laboratory 

reporting level. Shallow groundwater atrazine concentrations 

increased after recharge began to a median of 0.035 μg/L. 

Comparison summary statistics were not computed for most 

pesticides because of datasets with severe censoring. With 

the exception of CIAT, no pesticides were detected in deep 

groundwater during the study period. The CIAT was present 

in all but one of the samples from the deep groundwater wells 

(MW–7 deep, site 375327097285402), but concentrations 

were not significantly different before and after recharge. All 

concentrations of pesticides were less than drinking water 

regulatory criteria before and after artificial recharge.

Brominated and Chlorinated Organic Compounds

Though residual chlorine from the water treatment 

process was not detected in groundwater samples, brominated 

and chlorinated organic compounds, such as trihalomethanes 

(THM), are summarized in table 23 for compounds detected 

in groundwater or appendix table 1–10 for compounds analyzed but not detected. Most statistical comparisons for these 

compounds having datasets with severe censoring were not 

computed. Detection frequencies increased after recharge in 

shallow groundwater samples for bromodichloromethane and 

trichloromethane, but detection frequencies decreased in deep 

groundwater for bromodichloromethane, dibromochloromethane, tribromomethane, trichloromethane, and THM.

Radioactive Chemistry

Alpha radioactivity and gross beta radioactivity are 

summarized in table 23. Alpha radioactivity (Th-230 curve) 

was detected but not different before compared with after the 

beginning of recharge, and the maximum level in all samples 

tested (5.7 picocuries per liter [pCi/L]; table 23) was below 

the EPA MCL of 15 pCi/L (U.S. Environmental Protection 

Agency, 2005). Gross beta radioactivity (Cs-137 curve) significantly increased in shallow and deep groundwater samples; 

median shallow groundwater well values increased from 3.1 to 

13.2 pCi/L and median deep well values increased from 3.1 to 

5.8 pCi/L (table 23). The maximum sample gross beta radioactivity was 18 pCi/L, which was below a screening level of the 

50 pCi/L, above which EPA may require testing for individual 

beta-emitting species (U.S. Environmental Protection Agency, 

2005).

Geochemical Effects 

To determine if changes in groundwater quality might 

affect mineral precipitation and dissolution, discrete samples 

were assessed for a change in saturation index (SI), particularly near or across the equilibrium threshold of SI near zero. 

A mineral SI is calculated as the log of the ion-activity product 

of a water sample, divided by the solubility product (Ksp) 

for the mineral and indicates the extent of disequilibrium 

with respect to the mineral (Parkhurst and Appelo, 2013). 

Equilibrium state only describes the potential for precipitation (positive SI) and dissolution (negative SI), but reaction 

kinetics and interaction among other constituents also affect 

whether minerals precipitate or dissolve. Therefore, a mineral 

is of particular interest if it has relatively short reaction times 

(fast kinetics) and if the SI changes across equilibrium during 

the study period, as did calcite, chalcedony, dolomite, aqueous 

iron (III) hydroxide, hydroxyapatite, and rhodochrosite. Saturation equilibrium for many minerals is closely and positively 

related to pH across the range of sample conditions. 

In assessing changes in the aquifer during recharge, SI 

values that were strongly and consistently negative (such as 

gypsum) or positive (such as quartz) for groundwater samples 

before and after artificial recharge indicate no change in 
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 63

Table 21. Discretely collected trace element summary statistics for groundwater samples at sites near the recharge basin near Sedgwick, Kansas, before (January 2011 to 

April 2013) and after (May 2013 to December 2014) artificial recharge.

[Medians in bold indicate significant differences (p-value less than 0.05) between before and after recharge; the before and after groundwater samples were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. n, number of measurements; μg/L, microgram per liter; <, less than; --, not applicable]

Water-quality constituent 

(unit of measure)

Before recharge After recharge

Left-censored 

data (percent) n Minimum Maximum Mean Median Left-censored data (percent) n Minimum Maximum Mean Median

Shallow groundwater

Aluminum (μg/L) 100 4 <20 <20 -- -- 100 14 <20 <20 -- --

Barium (μg/L) 0 4 93 164 112 96 0 14 74 274 156 150

Cadmium (μg/L) 100 4 <0.05 <0.05 -- -- 57 14 <0.05 0.11 0.06 0.05Lead (μg/L) 50 4 <0.1 0.1 -- -- 93 14 <0.1 0.1 -- --Manganese (μg/L) 100 4 <5 <5 -- -- 71 14 <5 15 2.2 3.0Nickel (μg/L) 0 4 0.4 1.8 1.1 1.2 0 14 0.8 3.8 2.2 2.0

Strontium (μg/L) 0 4 445 501 482 491 0 14 283 618 424 379

Thallium (μg/L) 52 4 <0.05 0.2 0.1 0.1 86 14 <0.05 0 -- --Vanadium (μg/L) 100 4 <5 <5 -- -- 100 14 <5 <5 -- --

Zinc (μg/L) 25 4 <5 6.0 5.1 6.0 29 14 <5 11.0 5.7 5.0

Arsenate (μg/L) as arsenic 100 4 <0.3 <1.6 -- -- 0 14 0.6 2.1 1.3 1.2

Arsenic (μg/L) 0 6 0.7 1.3 1.0 0.9 0 14 0.8 3.5 1.7 1.7

Boron (μg/L) 0 4 33 41 38 38 0 14 22 69 50 51

Selenium (μg/L) 0 4 6.7 13 10 11 0 14 0.7 3.5 1.9 1.9

Deep groundwater

Aluminum (μg/L) 75 4 <20 32 16 10 100 8 <20 <20 -- --Barium (μg/L) 0 4 26 56 41 41 0 8 24 57 40 41

Cadmium (μg/L) 100 4 <0.05 <0.05 -- -- 100 8 <0.05 <0.05 -- --Lead (μg/L) 50 4 <0.1 0.2 0.2 0.1 100 8 <0.1 <0.1 -- --Manganese (μg/L) 0 4 43 198 112 88 0 8 171 311 224 216

Nickel (μg/L) 0 4 0.2 1.4 0.9 0.9 0 8 1.4 2.1 1.7 1.7

Strontium (μg/L) 0 4 761 800 781 781 0 8 735 851 782 775

Thallium (μg/L) 50 4 <0.05 0.1 0.1 0.1 100 8 <0.05 <0.05 -- --Vanadium (μg/L) 25 4 <5 9.0 6.6 7.5 38 8 <5 10.0 6.4 7.5Zinc (μg/L) 50 4 <5 6.0 4.3 4.3 38 8 <5 8.0 4.9 5.0Arsenate (μg/L) as arsenic 0 4 2.2 3.1 2.7 2.7 0 8 2.4 4.3 3.3 3.2

Arsenic (μg/L) 0 6 2.5 5.5 4.1 4.2 0 8 3.1 5.1 4.0 4.0

Boron (μg/L) 0 4 37 41 39 39 0 8 31 39 36 36

Selenium (μg/L) 0 4 1.3 5.9 3.3 2.9 0 8 1.4 10 5.7 6.5
64 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Table 22. Discretely collected pesticides summary statistics for groundwater samples at sites near the recharge basin near Sedgwick, Kansas, before (January 2011 to April 2013) and after (May 2013 to December 2014) artificial recharge. [Censoring levels are for all samples. The before and after groundwater samples were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. n, number of measurements; CIAT, 2-Chloro-4-isopropylamino-6-amino-s-triazine; μg/L, microgram per liter; CEAT, 2-Chloro-6-ethylamino-4-amino-s- triazine; <, less than; --, not applicable; OIET, 2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine] Water-quality constituent (unit of measure) Before recharge After recharge Left-censored data (percent) n Minimum Maximum Mean Median Left-censored data (percent) n Minimum Maximum Mean Median Shallow groundwater CIAT (μg/L) 0 4 0.024 0.148 0.071 0.056 0 14 0.027 1.79 0.361 0.056 CEAT (μg/L) 100 4 <0.02 <0.02 -- -- 0 1 0.86 0.86 -- -- OIET (μg/L) 100 4 <0.02 <0.02 -- -- 0 1 0.03 0.03 -- -- Acetochlor (μg/L) 100 4 <0.01 <0.01 -- -- 79 14 <0.01 0.049 0.017 0.003 Atrazine (μg/L) 25 4 <0.02 0.02 0.008 0.008 0 14 0.015 1.39 0.344 0.035 Metolachlor (μg/L) 100 4 <0.02 <0.02 -- -- 29 14 <0.02 0.138 0.047 0.029 Metribuzin (μg/L) 100 4 <0.012 <0.012 -- -- 93 14 <0.012 0.017 -- -- Simazine (μg/L) 100 4 <0.006 <0.006 -- -- 79 14 <0.006 0.02 0.413 0.036 Triazines (μg/L as atrazine) 100 6 <0.1 <0.1 -- -- 57 14 <0.1 1.8 0.5 0.1 Deep groundwater CIAT (μg/L) 50 4 <0.006 0.016 0.013 0.010 50 8 <0.006 0.040 0.015 0.011 CEAT (μg/L) 100 4 <0.06 <0.06 -- -- 100 1 <0.02 <0.02 -- -- OIET (μg/L) 100 4 <0.06 <0.06 -- -- 100 1 <0.02 <0.02 -- -- Acetochlor (μg/L) 100 4 <0.01 <0.01 -- -- 100 8 <0.01 <0.01 -- -- Atrazine (μg/L) 100 4 <0.008 <0.008 -- -- 100 8 <0.008 <0.008 -- -- Metolachlor (μg/L) 100 4 <0.02 <0.02 -- -- 100 8 <0.02 <0.02 -- -- Metribuzin (μg/L) 100 4 <0.012 <0.012 -- -- 100 8 <0.012 <0.012 -- -- Simazine (μg/L) 100 4 <0.006 <0.006 -- -- 100 8 <0.006 <0.006 -- -- Triazines (μg/L as atrazine) 100 6 <0.1 <0.1 -- -- 100 8 <0.1 <0.1 -- --
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 65

Table 23. Discretely collected brominated and chlorinated organic compounds and radioactivity summary statistics for groundwater samples at sites near the recharge basin near Sedgwick, Kansas, before (January 2011 to April 2013) and after (May 2013 to December 2014) artificial recharge.[Medians in bold indicate significant differences (p-value less than 0.05) between before and after recharge. Censoring levels are for all samples. The before and after groundwater samples were not statistically compared when greater than 50 percent of data were left-censored. Means and medians were not computed when greater than 80 percent of data were left-censored. n, number of measurements; μg/L, microgram per liter; <, less than; --, not applicable; α, alpha; pCi/L, picocurie per liter; β, beta]

Water-quality constituent 

(unit of measure)

Before recharge After recharge

Left-censored 

data (percent) n Minimum Maximum Mean Median Left-censored data (percent) n Minimum Maximum Mean Median

Shallow groundwater

Bromodichloromethane (μg/L) 100 4 <0.1 <0.1 -- -- 21 14 <0.1 0.5 0.2 0.2

Dibromochloromethane (μg/L) 100 4 <0.2 <0.2 -- -- 100 14 <0.2 <0.2 -- --

Tribromomethane (μg/L) 100 4 <0.2 <0.2 -- -- 100 14 <0.2 <0.2 -- --Trichloromethane (μg/L) 75 4 <0.1 4.7 4.7 0.0 0 14 1.3 5.2 2.3 1.8

Trihalomethanes, maximum 

summation (μg/L)

100 4 <0.6 <0.6 -- -- 100 14 <1.9 <1.9 -- --

Trihalomethanes, minimum 

summation (μg/L)

0 1 4.7 -- -- -- 0 14 1.4 5.5 2.5 2.05

α radioactivity (pCi/L) 0 4 0.6 1.1 0.9 1.0 0 14 0.1 5.7 2.4 2.0Gross β radioactivity (pCi/L) 0 4 2.5 4.4 3.3 3.1 0 14 5.3 18.0 12.7 13.2

Deep groundwater

Bromodichloromethane (μg/L) 50 4 <0.1 0.8 0.4 0.2 100 8 <0.1 <0.1 -- --

Dibromochloromethane (μg/L) 50 4 <0.2 0.8 0.5 0.3 100 8 <0.2 <0.2 -- --

Tribromomethane (μg/L) 50 4 <0.2 0.3 0.3 0.2 100 8 <0.2 <0.2 -- --

Trichloromethane (μg/L) 25 4 <0.1 3.2 1.5 1.4 100 8 <0.1 <0.1 -- --

Trihalomethanes, maximum 

summation (μg/L)

50 4 <0.6 5.0 3.5 2.2 100 8 <0.6 <0.6 -- --

Trihalomethanes, minimum 

summation (μg/L)

0 3 0.3 5.0 3.0 3.8 -- 0 -- -- -- --

α radioactivity (pCi/L) 0 4 1.6 3.0 2.3 2.2 0 8 1.0 5.4 2.9 2.3

Gross β radioactivity (pCi/L) 0 4 2.9 3.8 3.2 3.1 0 8 3.6 9.4 5.9 5.8
66 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

overall equilibrium status with regard to those specific minerals. Undersaturation (negative SI) of metal-bearing minerals, either consistent across the study period or as a result of 

changes in the aquifer, can indicate potential for release of 

metals such as manganese and arsenic, which are harmful in 

drinking water. Similar to previous analyses describing artificial recharge in another location in the Equus Beds aquifer 

(fig. 1) (Schmidt and others, 2007; Ziegler and others, 2010; 

Garinger and others, 2011), for this study near the recharge 

basin near Sedgwick, Kans., SI values for manganite (manganese bearing) and scorodite (arsenic bearing) were consistently 

negative throughout the study (table 24). The absence or very 

low concentrations of manganese or arsenic in groundwater 

samples near the Sedgwick recharge basin, however, suggests that these minerals are either not present in this part 

of the aquifer or that kinetic factors were not conducive to 

dissolution. Additional select minerals near or ranging across 

equilibrium for discrete groundwater samples are summarized 

in table 24.

Several carbonate minerals varied near or across equilibrium state, such as calcite (table 24, fig. 15A). Stream 

sample CaCO3

 SI (median=0.5), ranged more broadly (-1.8 to 

1.2) than groundwater. Before recharge periods, CaCO3

 was 

slightly under-saturated in shallow groundwater wells (MW–7 

site 375327097285401 and MW–8 site 375332097284801), 

with little change after the onset of recharge. Before recharge, 

median SI with respect to CaCO3

 in shallow groundwater well 

samples was -0.8; after recharge the median SI with respect 

to CaCO3

 was -0.6. Median deep groundwater well (MW–7 

site 375327097285402 and MW–8 site 375332097284802) 

CaCO3

 SI values were similar before (median=-0.1) and after 

(median=-0.1) recharge. The near-equilibrium of CaCO3

 in 

shallow groundwater and the broad range of stream-water 

saturation states indicate a vulnerability to a shift toward 

over-saturation of CaCO3

, potentially resulting in formation of 

CaCO3

 mineral deposits.

Phosphate minerals, such as hydroxyapatite, before 

recharge periods were under-saturated in groundwater, but 

samples after recharge began were closer to equilibrium for 

shallow groundwater well samples (table 24, fig. 15B). Stream 

water was generally oversaturated with respect to hydroxyapatite, with a median SI of 3.8. Shallow groundwater median 

hydroxyapatite before recharge was -5.7 and was -1.7 after 

recharge began. Deep groundwater was similar before and 

after recharge. 

Similar to carbonates, oxyhydroxides, such as the iron 

bearing mineral iron (II) hydroxide, were under-saturated in 

shallow groundwater well samples before recharge with a shift 

toward equilibrium (table 24, fig. 15C). Median SI for iron 

(II) hydroxide in streams was 2.0 and ranged from -1.3 to 6.6 

with seasonal minima in summer and peaks in winter. Median 

SI for shallow groundwater well samples was -3.8 before 

and -1.3 after recharge. Deep groundwater was consistently 

near equilibrium with respect to iron (II) hydroxide and had a 

median of 0.5 before and 0.2 after recharge.

Shifts in saturation indices of the minerals calcite, iron 

hydroxide, hydroxyapatite, and similar carbonates, oxyhydroxides, and phosphate minerals were generally from undersaturation toward equilibrium and, in some cases, toward 

over-saturation. Saturation indices for these minerals are 

closely related to pH, and the recharge source water tended to 

have higher pH values and positive (oversaturated) SI values, 

relative to groundwater (fig. 16). The shift toward neutral SI 

may indicate decreased weathering of the minerals present in 

the aquifer. Even at equilibrium, however, these minerals may 

react and move in and out of solution, with the reaction rates 

governed by kinetic factors such as accessible reaction sites on 

particle surfaces and temperature.

Because of positive shifts in SI closely related to pH, 

conditions are more favorable to precipitate iron during and 

after recharge periods. Though dissolved iron was not detected 

in the groundwater wells studied near the recharge basin, iron 

is present in other wells in the well field and was measured in 

stream samples. Ongoing continuous monitoring of shallow 

groundwater for changes in pH, specifically an increase above 

7.0, may highlight periods when the conditions are favorable to precipitate iron. Additionally, recharge source water 

samples can be used to determine if dissolved iron may have 

been introduced into the aquifer system through the recharge 

basin.

Precipitation and dilution reaction rates increase with 

water temperature at disequilibrium, with SI as an indication 

of the net direction of the reaction. Even for SI near zero, however, a mineral still will dissolve and precipitate to maintain 

local equilibrium at a faster rate with increased water temperature. This exchange includes the potential release of key 

ions, such as arsenic, iron, and manganese. Observed water 

temperatures in shallow groundwater wells after recharge have 

remained about 4 to 11 °C warmer than median temperatures 

before the first recharge period. Thus, chemical weathering 

in the shallow parts of the aquifer will be accelerated because 

of the increased water temperatures, and the system is more 

vulnerable to clogged pores and mineral dissolution as the 

equilibrium state is affected by recharge and withdrawal.
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 67

Table 24. Saturation indices for select minerals for groundwater samples collected at sites near the recharge basin near Sedgwick, Kansas, before (January 2011 to April 2013)

and after (May 2013 to December 2014) artificial recharge.

[n, number of measurements]

Mineral 

(unitless)

Stream 

(n=47)

Shallow groundwater Deep groundwater

Before recharge 

(n=6)

After recharge 

(n=14)

Before recharge 

(n=6)

After recharge 

(n=8)

Minimum Median Maximum Minimum Median Maximum Minimum Median Maximum Minimum Median Maximum Minimum Median Maximum

Aragonite -2.0 0.4 1.0 -1.2 -1.0 -0.6 -1.2 -0.8 -0.2 -0.3 -0.2 -0.2 -0.5 -0.3 -0.2

Calcite -1.8 0.5 1.2 -1.1 -0.8 -0.5 -1.0 -0.6 -0.0 -0.2 -0.1 -0.0 -0.4 -0.1 -0.0

Chalcedony -0.3 -0.0 0.3 0.1 0.1 0.2 -0.0 0.0 0.1 0.2 0.3 0.3 0.2 0.3 0.3

Cristobalite -2.9 0.0 0.3 0.1 0.2 0.2 -0.0 0.1 0.1 0.3 0.3 0.4 0.3 0.3 0.4

Dolomite -4.0 0.6 1.9 -2.7 -2.2 -1.5 -2.5 -1.7 -0.4 -0.8 -0.6 -0.5 -1.2 -0.8 -0.5

Iron (III) 

hydroxide (Fe(OH)3

)

0.6 2.1 3.5 -0.6 -0.3 0.6 -0.2 0.7 1.2 1.1 1.4 1.6 0.5 1.2 1.6

Iron (II) 

hydroxide (Fe3(OH)2

)

-1.3 2.0 6.6 -4.7 -3.8 -1.5 -3.5 -1.3 -0.1 -0.2 0.5 1.2 -1.7 0.2 1.2

Fluorapatite -1.3 5.4 7.4 -4.0 -2.6 -1.1 -1.7 1.0 3.2 -1.3 -1.0 -0.6 -1.2 -0.3 0.5

Gypsum -3.5 -1.9 -1.2 -1.9 -1.8 -1.7 -2.5 -2.0 -1.7 -1.9 -1.8 -1.8 -1.9 -1.9 -1.8

Hydroxyapatite -4.1 3.8 6.2 -7.2 -5.7 -4.2 -4.8 -1.7 0.7 -3.9 -3.6 -3.2 -4.2 -3.3 -2.3

Manganite -8.1 -4.0 -2.1 -9.1 -8.8 -8.0 -8.8 -7.9 -7.4 -6.2 -5.9 -5.2 -6.3 -5.6 -5.3

Rhodochrosite -2.7 -0.0 1.0 -2.7 -2.5 -2.2 -2.5 -2.1 -1.9 -0.8 -0.6 -0.1 -0.5 -0.2 -0.0

Scorodite -8.8 -7.3 -6.5 -9.0 -8.8 -8.1 -8.6 -7.8 -7.3 -7.6 -7.3 -7.1 -7.8 -7.4 -7.1

Strengite -1.5 0.1 1.5 -1.6 -1.4 -1.0 -0.7 -0.1 0.4 -1.0 -0.9 -0.9 -1.0 -0.8 -0.5

Quartz 0.1 0.4 0.7 0.5 0.6 0.6 0.4 0.5 0.5 0.7 0.7 0.8 0.7 0.7 0.8
68 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

−2.0

−1.5

−1.0

−0.5

 0.0

 0.5

 1.0

 1.5

Calcite (CaCO3) saturation index

2011 2012 2013 2014

Calendar year

A. Calcite

−6

−4

−2

 0

 2

 4

 6

 8

Iron (II) hydroxide (Fe(OH)2 saturation index

2011 2012 2013 2014

Calendar year

C. Iron (II) hydroxide

−8

−6

−4

−2

 0

 2

 4

 6

 8

Hydroxyapatite (Ca5(PO4

)

3OH) saturation index

2011 2012 2013 2014

Calendar year

B. Hydroxyapatite

Little Arkansas River near 

Sedgwick, Kansas

MW−7 shallow

MW−7 deep

MW−8 shallow

MW−8 deep

EXPLANATION

Artificial recharge

Aquifer withdrawals, 

after 10/10/2012 only

Saturation equilibrium

Site

Figure 15. Saturation indices of minerals calculated for stream water and groundwater samples collected from monitoring wells near 

the infiltration basin, 2011 through 2014. A, calcite; B, hydroxyapatite; and C, iron (II) hydroxide.
Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer Equus Beds Aquifer 69

−2.0

−1.5

−1.0

−0.5

 0.0

 0.5

 1.0

 1.5

Calcite (CaCO3) saturation index

A. Calcite

−6

−4

−2

 0

 2

 4

 6

 8

Iron (II) hydroxide (Fe(OH)2 saturation index

pH, in standard units

C. Iron (II) hydroxide

−8

−6

−4

−2

 0

 2

 4

 6

 8

Hydroxyapatite (Ca5(PO4

)

3OH) saturation index

B. Hydroxyapatite

Little Arkansas River near 

Sedgwick, Kansas

MW−7 shallow

MW−7 deep

MW−8 shallow

MW−8 deep

EXPLANATION

Saturation equilibrium

Site

6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8

pH, in standard units

6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8

pH, in standard units

6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8

Figure 16. pH of minerals calculated for groundwater samples collected from monitoring wells near the infiltration basin, 2011 

through 2014. A, calcite; B, hydroxyapatite; and C, iron (II) hydroxide.
70 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Summary and Conclusions

The city of Wichita, Kansas, uses the Equus Beds aquifer 

as a primary municipal water supply source. The Equus Beds 

aquifer storage and recovery (ASR) project was developed to 

help the city of Wichita meet increasing future water demands. 

The Equus Beds ASR project pumps water out of the Little 

Arkansas River during above-base flow conditions, treats it 

using drinking-water quality standards as a guideline, and 

recharges it into the Equus Beds aquifer for later use. Phase II 

of the Equus Beds ASR project includes a river intake facility currently (2016) equipped to divert 30 million gallons per 

day (Mgal/d) and a 30 Mgal/d surface-water treatment facility. 

Water diverted from the Little Arkansas River is delivered to an 

adjacent presedimentation basin for solids removal. Waste from 

the surface-water treatment facility and the presedimentation 

basin is returned directly to the Little Arkansas River through 

a residuals return line. The U.S. Geological Survey, in cooperation with the city of Wichita, developed and implemented 

a hydrobiological monitoring program (HBMP) as part of the 

ASR project to characterize and quantify the effects of aquifer 

storage and recovery activities on the Little Arkansas River and 

Equus Beds aquifer water quality. 

For this study, data were collected from two surfacewater sites, one upstream and one downstream from the 

residuals return line; one residuals return line site; and two 

groundwater well sites (each having a shallow and deep 

part) to characterize and quantify the effects of aquifer 

storage and recovery activities on Little Arkansas River 

and Equus Beds aquifer water quality: the Little Arkansas 

River stream from the ASR facility near Sedgwick, Kansas 

(upstream surface-water site 375350097262800), about 0.03 

miles (mi) upstream from the residuals return line site; the 

Little Arkansas River near Sedgwick, Kansas (downstream 

surface-water site 07144100), about 1.68 mi downstream 

from the residuals return line site; discharge from the Little 

Arkansas River ASR facility near Sedgwick, Kansas (residuals return line site 375348097262800); 25S 01 W 07BCC01 

SMW–S11 near CW36 (MW–7 shallow groundwater well site 

375327097285401); 25S01 W 07BCCC02 DMW–S10 near 

CW36 (MW–7 deep groundwater well site 375327097285402); 

25S 01W 07BCCA01 SMW–S13 near CW36 (MW–8 shallow groundwater well site 375332097284801); and 25S 01W 

07BCCA02 DMW–S14 near CW36 (MW–8 deep groundwater 

well site 375332097284802). The U.S. Geological Survey, in 

cooperation with the city of Wichita, assessed the effects of the 

ASR Phase II facility residuals return line discharges on stream 

quality of the Little Arkansas River by measuring or computing 

continuous physicochemical properties and collecting discrete 

water-quality and sediment samples for about 2 years pre- 

(January 2011 through April 2013) and post-ASR (May 2013 

through December 2014) Phase II facility operation upstream 

and downstream from the ASR Phase II facility discharges as 

well as in the residuals return line. Additionally, habitat variables were quantified and macroinvertebrate and fish communities were sampled upstream and downstream from the ASR 

Phase II facility during the study period. To assess the effects 

of aquifer recharge on Equus Beds groundwater quality, continuous physicochemical properties were measured and discrete 

water-quality samples were collected before and during the 

onset of Phase II aquifer recharge in four groundwater wells 

(two well clusters having a shallow and deep well).

The city of Wichita’s HBMP presented the opportunity to 

quantify and characterize Little Arkansas River stream quality upstream and downstream from the ASR facility as well 

as Equus Beds aquifer groundwater quality in response to 

ASR activities. Continuous measurement and computation of 

physicochemical properties in real time allowed characterization during conditions and time scales that would not have 

been possible otherwise and served as a complement to discrete 

water-quality sampling as well as biological monitoring. Similar future data collection efforts will provide data under different conditions, identify new and changing trends, and allow 

more powerful statistical analyses.

Little Arkansas River post-ASR streamflow was about 

10 times larger than pre-ASR streamflow because of larger 

post-ASR precipitation. Residuals return line release volumes 

included a very minimal proportion (0.06 percent) of downstream streamflow volume during the months the ASR facility 

was operating during 2013 and 2014. Specific conductance was 

similar upstream and downstream from the ASR facility during 

the study period. Residuals return line specific conductance 

was about 68 percent smaller than the specific conductance 

downstream from the facility. Upstream and downstream water 

temperature differences were smaller post-ASR than pre-ASR; 

however, median water temperature upstream and downstream 

from the facility was within 3 degrees Celsius (oC) or less 

before and after facility operation onset and did not exceed 

the Kansas Department of Health and Environment (KDHE) 

criterion of 32 oC during the study. Median residuals return line 

temperature was about 23 percent larger than the downstream 

site and never exceeded the KDHE temperature criterion during the study. Median pH upstream and downstream from the 

facility varied by less than 2 percent before and after the facility began operating. Upstream and downstream pH exceeded 

the Kansas aquatic life-support criterion of 8.5 about 8 and 4 

percent of the time before facility operation onset and 3 and 

4 percent of the time after facility operation onset, respectively. Residuals return line pH never exceeded Kansas aquatic 

life-support criteria or the ASR Phase II National Pollutant 

Discharge Elimination System (NPDES) permit limits (6.0 to 

9.0) during the study period. Dissolved oxygen was somewhat 

larger at the downstream site compared to the upstream site 

during the study and decreased slightly at both sites after the 

ASR Phase II facility began operating. Upstream and downstream dissolved oxygen differences were smaller post-ASR 

than pre-ASR. Dissolved oxygen exceeded the Kansas aquatic 

life-support criterion about 6 percent and 3 percent of the 

time before facility operation at the upstream and downstream 

sites, respectively, and about 7 percent of the time after facility 

operation began at both sites. Residuals return line dissolved 

oxygen was about 17 percent smaller than the downstream site. 
Summary and Conclusions 71

Turbidity generally was smaller at the downstream site 

compared to the upstream site throughout the study period and 

decreased at both sites after the ASR Phase II facility began 

discharging despite a median residuals return line turbidity that 

was about an order of magnitude larger than the downstream 

site. Upstream and downstream continuously measured turbidity median differences were larger post-ASR than pre-ASR. 

Turbidity exceeded the U.S. Environmental Protection Agency 

(EPA) level III ecoregion 27 guideline of 22.13 formazin 

turbidity units about 72 percent of the time at the upstream 

site and 62 percent of the time at the downstream site before 

facility operation onset, and about 52 percent of the time at 

the upstream site and 46 percent of the time at the downstream 

site after facility operation onset. Regression-computed total 

suspended solids and suspended-sediment concentrations at the 

downstream site were generally smaller after the onset of facility operation, likely because of larger post-ASR streamflow 

and dilution. Because the ASR facility operates only during 

high-flow conditions, physicochemical properties and waterquality concentrations of stream water and residual return line 

releases are more indicative of higher flow event conditions 

than the distribution of all continuously collected water-quality 

data. During events, stream specific conductance, pH, and dissolved oxygen are smaller than during base-flow conditions, 

and turbidity is larger. The small delay (as much as 5 hours) 

between water withdrawal and residual releases could prolong 

event conditions for pH, specific conductance, and turbidity; 

however, effects would likely be localized near the residuals 

return line outflow.

None of the discretely measured water-quality constituents (dissolved and suspended solids, primary ions, suspended 

sediment, nutrients, carbon, trace element, viral and bacterial 

indicator, and pesticides) in surface water were significantly 

different between the upstream and downstream sites after the 

ASR Phase II facility began discharging; however, pre-ASR 

calcium, sodium, hardness, manganese, and arsenate concentrations were substantially larger at the upstream site, indicating 

that some water-quality conditions at the upstream and downstream sites were more similar post-ASR. Dissolved solids 

at both surface-water sites upstream and downstream from 

the ASR Phase II facility were about 18 percent to 27 percent 

smaller after the facility began operating. Median dissolved 

solids concentrations at all sites during the study period did 

not exceed the Federal Secondary Maximum Contaminant 

Level (SMCL) although occasionally individual samples from 

all sites did. Most of the primary dissolved solids constituents decreased at both sites after the facility began operation; 

however, dilution during higher post-ASR streamflow conditions compared to pre-ASR streamflow conditions complicate 

comparisons. Median primary dissolved solids constituent 

concentrations in the residuals return line, with the exception of 

potassium, were always at least about 10 percent smaller than 

median primary dissolved solids constituent concentrations at 

the upstream and downstream sites after the facility began discharging. Discretely collected total suspended solids concentrations were similar among the upstream and downstream sites 

before the facility began operating but were about 27 percent 

smaller at the downstream site after the facility began operating, despite the residuals return line total suspended solids 

concentration being 15 times larger than the downstream site. 

Discretely collected post-ASR suspended-sediment concentration medians were larger than pre-ASR concentrations at both 

sites, which is contradictory to the continuously computed 

suspended-sediment concentration medians at the downstream 

site that decreased post-ASR. These differences in suspendedsediment concentration medians highlight the utility of continuous monitoring by capturing temporal variability and the need 

to continue continuous monitoring as a complement to discrete 

water-quality sampling.

Nitrate concentrations were smaller at the upstream site 

during the entire study period and decreased about 38 and 

18 percent at the upstream and downstream sites, respectively, 

after the facility began operating despite the residuals return 

line nitrate being about 100 percent larger than the downstream 

site. Median total nitrogen was similar upstream and downstream from the facility before operation and about 26 percent 

larger downstream from the facility after operation began. 

Residuals return line total nitrogen was about 250 percent 

larger than the downstream site. All upstream, downstream, and 

residuals return line total nitrogen samples collected during the 

study period exceeded the EPA guideline of 0.71 milligrams 

per liter (mg/L) for level III ecoregion streams. Phosphorus 

species generally were smaller downstream from the ASR 

facility and were larger upstream and downstream from the 

facility after the facility began operating. Total phosphorus 

was similar upstream and downstream from the ASR facility 

despite the residuals return line total phosphorus being about 

200 percent larger than the downstream site. All upstream, 

downstream, and residuals return line total phosphorus samples 

collected during the study period exceeded the EPA guideline 

of 0.09 mg/L for level III ecoregion streams.

Median arsenic concentrations in surface water were 7 

to 19 percent larger before the ASR Phase II facility began 

operating and were similar upstream and downstream from 

the facility after operation onset, likely because of larger 

post-ASR streamflow and dilution. Median residuals return 

line arsenic concentration was about 38 percent smaller than 

downstream from the facility. Surface water arsenic concentrations exceeded the EPA Maximum Contaminant Level (MCL) 

of 10 micrograms per liter (μg/L) in about 30 to 55 percent of 

samples before the facility began operating and about 43 percent of samples after the facility began operating. Arsenic 

concentrations never exceeded the MCL in the residuals return 

line during the study period.

All indicator bacterial and viral densities upstream and 

downstream from the ASR Phase II facility generally were 

larger after the facility began operating, likely because of runoff during larger streamflows during this period. The upstream 

site’s Escherichia coli (E. coli) densities exceeded the State 

of Kansas’ primary contact criterion of 262 colonies per 100 

milliliters (col/100 mL) in about 33 percent of samples before 

the facility began operating and 75 percent of samples after the 
72 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

facility began operating; the downstream site’s E. coli densities exceeded 262 col/100 mL in about 28 percent of samples 

before facility operation onset and about 63 percent of samples 

after facility operation onset. All residuals return line E. coli

samples exceeded 262 col/100 mL. The upstream site’s fecal 

coliform densities exceeded the State of Kansas’ primary 

contact criterion of 200 col/100 mL in about 61 percent of 

samples before the facility began operating and 88 percent of 

samples after the facility began operating; the downstream 

site’s fecal coliform densities exceeded 200 col/100 mL in 

about 44 percent of samples before facility operation onset and 

about 63 percent of samples after facility operation onset. All 

residuals return line fecal coliform sample densities exceeded 

200 col/100 mL.

Pesticide concentrations generally were similar upstream 

and downstream from the ASR Phase II facility and larger after 

facility operation onset. Residuals return line pesticide concentrations generally were similar to surface-water concentrations. 

Atrazine concentrations were larger at the site upstream from 

the ASR Phase II facility and at both sites after the facility 

began operating, likely because of runoff during larger streamflows during this period. Atrazine concentrations at the site 

upstream from the facility exceeded the EPA MCL of 3.0 μg/L 

in about 20 percent of samples before the facility began operating and 50 percent of samples after the facility began operating. 

Atrazine concentrations downstream from the facility exceeded 

the MCL in about 25 and 38 percent of samples before and 

after facility operation onset, respectively. Residuals return line 

atrazine concentrations exceeded the MCL in about 43 percent 

of samples.

Nutrients (nitrogen and phosphorus species) and carbon 

(total and organic) in streambed sediment generally were larger 

downstream from the ASR Phase II facility during the study 

period and smaller at both surface-water sites after the facility began operating. Residuals return line total nitrogen, total 

phosphorus, and total and organic carbon was 50 percent larger, 

13 percent smaller, and 27 percent larger than the downstream 

site, respectively. Streambed-sediment trace element concentrations at the surface-water sites generally were similar among 

sites before and after the facility began operating. Residuals 

return line sediment trace element concentrations were larger 

than those downstream from the facility with the exception of 

barium, calcium, manganese, selenium, silver, sodium, and 

strontium. No trace element samples from any site exceeded 

their respective probable effect concentration (PEC). Pesticides were the most frequently detected organic wastewater 

compound (OWC) at all sites during the study period and there 

were no clear patterns in OWC concentrations before and after 

the ASR Phase II facility began operating.

Overall habitat scores were indicative of suboptimal 

conditions upstream and downstream from the ASR Phase II 

facility throughout the study period. Channel conditions and 

characteristics scores were indicative of marginal conditions 

at the upstream site before and after the ASR Phase II facility began operating and the downstream site before facility 

operation onset. Channel conditions and characteristics at 

the downstream site after the facility began discharging were 

indicative of suboptimal conditions. Bank and riparian conditions were suboptimal at the upstream site and optimal at the 

downstream site during the entire study period. Aquatic habitat 

availability was marginal at the upstream and downstream sites 

during the study period. Substrate fouling and sediment deposition mean scores indicated marginal conditions at the upstream 

and downstream sites during the study period, demonstrating 

that sediment deposition was evident pre- and post-ASR and no 

substantial changes in these habitat characteristics were noted 

after the ASR facility began discharging.

Macroinvertebrate community composition, including 

functional feeding, behavioral, and tolerance groups, generally 

was similar among sites during the study period. Predators and 

collector-gatherers were the two most common macroinvertebrate functional feeding groups throughout the study. Among 

macroinvertebrate behavioral groups, most organisms were 

swimmers and sprawlers during the study period. Intolerant 

macroinvertebrates had the lowest abundance among tolerance groups at both sites for the duration of the study. Several 

indicator metrics were significantly different between the 

upstream and downstream sites. These included 14 metrics 

before the ASR Phase II facility began operating and 6 metrics 

after the facility began operating, indicating that the upstream 

and downstream sites were more similar post-ASR; however, 

higher post-ASR streamflow conditions compared to pre-ASR 

streamflow conditions complicate comparisons. Upstreamdownstream comparisons in macroinvertebrate aquatic-lifesupport metrics did not reveal any significant differences for 

post-ASR time periods and neither site was fully-supporting 

for any of the four metrics. Overall, using macroinvertebrate 

aquatic life-support criteria from the Kansas Department of 

Health and Environment, both upstream and downstream sites 

were classified as partially-supporting both before and after the 

onset of ASR facility operations. 

Shiners were the most dominant fish group at the 

upstream and downstream sites during the study period. Fish 

community trophic status generally was similar among sites 

during the study period. Omnivores increased and insectivores 

and piscivores decreased at both the upstream and downstream 

sites after the ASR Phase II facility began operating. Fish 

community tolerance groups generally were similar among 

sites during the study period. Tolerant species increased and 

intermediately tolerant and intolerant species decreased at both 

sites after the ASR Phase II facility began operating. Fish community Little Arkansas River Basin Index of Biotic Integrity 

scores at the upstream and downstream sites were indicative of 

fair-to-good conditions before the facility began operating and 

decreased to fair conditions after the facility began operating at 

both sites.

Groundwater physicochemical changes concurrent with 

the beginning of recharge operations at the Sedgwick basin 

were more pronounced in shallow groundwater. No constituent concentrations in the pre-recharge period in comparison to 

the post-recharge period increased to concentrations exceeding 

drinking-water regulations; however, nitrate concentrations 
References Cited 73

decreased significantly by 90 percent from a 3 percent prerecharge EPA MCL (10 mg/L) exceedance to nonexceedance 

after recharge onset. Shallow groundwater chemical concentrations or rates of detection increased after artificial recharge 

began for the ions potassium, chloride, and fluoride; phosphorus and organic carbon species; trace elements barium, 

manganese, nickel, arsenate, arsenic, and boron; agricultural 

pesticides atrazine, metolachlor, metribuzin, and simazine; 

organic disinfection byproducts bromodichloromethane and 

trichloromethane; and gross beta levels. Additionally, water 

temperature and pH were larger after recharge began; and total 

solids and slime-forming bacteria concentrations and densities were smaller. Total solids, nitrate, slime-forming bacteria, 

and selenium significantly decreased; and potassium, chloride, 

nickel, arsenic, fluoride, phosphorus, carbon species, and gross 

beta levels significantly increased in shallow groundwater 

after artificial recharge. These significant changes in shallow 

groundwater concentrations were likely caused by the artificially recharged treated surface water and natural infiltration 

of precipitation. 

Changes in deep groundwater chemistry were less 

pronounced than changes in shallow wells before and after 

recharge activities. Although increased concentrations were 

statistically significant for dissolved organic carbon, absolute 

changes in the mean and median concentrations were minimal. 

Bacteria detection frequencies increased for iron-related bacteria and sulfate-reducing bacteria. Results of biological activity 

reaction tests indicated that water quality microbiology was 

different before and after artificial recharge began; at times, 

these differences may lead to changes in dominant bacterial 

populations that, in turn, may lead to formation and expansion in populations that may cause bioplugging and other 

unwanted effects. Manganese and nickel concentrations were 

significantly larger after recharge and frequency of detections 

increased for arsenate. Frequency of detections increased for 

several brominated and chlorinated organic compounds. Similar to shallow groundwater, gross beta levels were significantly 

larger in deep groundwater after recharge began.

Changes in groundwater chemistry can affect mineral 

saturation, resulting in precipitation and dissolution of the 

minerals. Calcite, iron (II) hydroxide, hydroxyapatite, and 

similar minerals, had shifts in saturation indices (SI) that 

generally were from under-saturation toward equilibrium and, 

in some cases, toward over-saturation. These shifts toward 

neutral SI might suggest reduced weathering of these minerals, if present in the aquifer. Even for minerals at equilibrium, 

these minerals may react to move in and out of solution with 

reaction rates governed by kinetic factors such as accessible 

reaction sites on particle surfaces and temperature, which was 

notably warmer after recharge. Chemical weathering in the 

shallow parts of the aquifer may be accelerated because of the 

increased water temperatures, and the system is more vulnerable to clogged pores and mineral dissolution as the equilibrium 

state is affected by recharge and withdrawal. When oversaturation is indicated for iron minerals, plugging of the aquifer 

materials may happen.

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Appendixes
84 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

Appendix 1. Water-Quality Data of the Little Arkansas River and Equus Beds 

Aquifer, Aquifer Storage and Recovery Project, South-Central Kansas, 2011–14

Appendix tables 1–1 through 1–10 are available for download at http://dx.doi.org/10.3133/sir20165042. See the Abbreviations list in the front of this report for definitions of variables in the appendixes.

Table 1–1. Discretely collected constituents from the residual basin aquifer storage and recovery treatment plant near Sedgwick, 

Kansas (site 375330097290200), diverted water at the Sedgwick recharge site, Kansas (site 375331097285301), and treated source water 

at the high service pump station (site 375338097290800; part of Aquifer Storage and Recovery treatment facility), July 2012 through 

September 2014.

Table 1–2. Sample collection dates and streamflow conditions for discrete water-quality samples collected at surface-water sites

(upstream and downstream sites 375350097262800 and 0714100, respectively), the residuals return line site (375348097262800), and 

groundwater well sites (MW–7 shallow, 375327097285401; MW–7 deep, 375327097285402; MW–8 shallow, 375332097284801; and MW–8 

deep, 375332097284802), March 2011 through September 2014.

Table 1–3. High flow summary statistics for continuously (hourly) measured physicochemical properties and computed water-quality 

constituents of interest for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas

(upstream surface-water site 375350097262800), the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), discharge from the Little Arkansas River aquifer storage and recovery facility (residuals return line site 375348097262800)

near Sedgwick, Kansas, January 2011 through December 2014.

Table 1–4. Regression models and summary statistics for continuous dissolved and total organic carbon concentration computations 

for the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), March 2012 through September 2014.

Table 1–5. Dissolved and total organic carbon datasets using chromophoric (colored) dissolved organic matter and turbidity as 

explanatory variables for the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), 2012 through 

2014.

Table 1–6. Discretely collected during high flow condition water-quality constituent summary statistics for the Little Arkansas River 

upstream from the aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), 

the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), and discharge from the Little Arkansas 

River aquifer storage and recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through 

September 2014.

Table 1–7. Discrete organic material characterization data for samples collected at the Little Arkansas River upstream from the 

aquifer storage and recovery facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), the Little Arkansas River 

near Sedgwick, Kansas (downstream surface-water site 07144100), and discharge from the Little Arkansas River aquifer storage and 

recovery facility (residuals return line site 375348097262800) near Sedgwick, Kansas, March 2011 through September 2014.

Table 1–8. Macroinvertebrate taxa abundances identified for the Little Arkansas River upstream from the aquifer storage and recovery 

facility near Sedgwick, Kansas (upstream surface-water site 375350097262800), and the Little Arkansas River near Sedgwick, Kansas

(downstream surface-water site 07144100), April 2011 through August 2014.

Table 1–9. Seasonal and annual mean selected macroinvertebrate metric values and Kansas Department of Health and Environment 

aquatic life-support status for the Little Arkansas River upstream from the aquifer storage and recovery facility near Sedgwick, Kansas

(upstream surface-water site 375350097262800), and the Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 

07144100), April 2011 through August 2014.

Table 1–10. Constituents analyzed but not detected in groundwater samples for sites near the recharge basin near Sedgwick, Kansas, 

January 2011 to December 2014.
Appendix 2. S+® Output of Regression Model Development and Graphs from Simple Linear Regression Analysis 85

Appendix 2. S+® Output of Regression Model Development and Graphs from

Simple Linear Regression Analysis

 *** Linear Model *** 

Call: lm(formula = LOG10DOC ~ LOG10CDOM, data = SEDG.DOC.ALL.PTS.REM, na.action = 

 na.exclude) 

Residuals: 

 Min 1Q Median 3Q Max 

 -0.1558 -0.06308 -0.002884 0.06727 0.1295 

Coefficients: 

 Value Std. Error t value Pr(>|t|) 

(Intercept) -0.7888 0.1284 -6.1420 0.0000 

 LOG10CDOM 0.7973 0.0636 12.5298 0.0000 

Residual standard error: 0.08401 on 37 degrees of freedom 

Multiple R-Squared: 0.8093 Adjusted R-squared: 0.8041 

F-statistic: 157 on 1 and 37 degrees of freedom, the p-value is 6.994e-015 

58 observations deleted due to missing values 

Correlation of Coefficients: 

 (Intercept) 

LOG10CDOM -0.9945 

Analysis of Variance Table 

Response: LOG10DOC 

Terms added sequentially (first to last) 

 Df Sum of Sq Mean Sq F Value Pr(F) 

LOG10CDOM 1 1.108087 1.108087 156.9954 6.994405e-015 

Residuals 37 0.261149 0.007058 

Figure 2–1. S+® output of regression model development using chromophoric (colored) dissolved organic matter

(CDOM) as the explanatory variable for dissolved organic carbon (DOC) from the Little Arkansas River near Sedgwick, 

Kansas (downstream surface-water site 07144100), 2009 through 2012.
86 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

1.4 1.6 1.8 2.0 2.2

Log10CDOM

0.2

0.4

0.6

0.8

1.0

1.2

Log10DOC

2 4 6 8 10 12 14

Measured DOC

Fitted log10CDOM Quantiles of standard normal

1

3

5

7

9

11

Predicted DOC

0.4 0.5 0.6 0.7 0.8 0.9 1.0

Residuals

-2.5 -2.0 -1.5 -1.0 -0.5

0.05

0.0

-0.05

-0.10

-0.15

0.10

Residuals

0.05

0.0

-0.05

-0.10

-0.15

0.10

A B

C D

Line of best fit

Dissolved organic carbon, in milligrams per liter

Chromophoric (colored) dissolved organic material

DOC

CDOM

EXPLANATION

Figure 2–2. S+® output graphs from simple linear regression analysis from the Little Arkansas River near Sedgwick, Kansas

(downstream surface-water site 07144100), 2012 through 2014. A, log-transformed chromophoric (colored) dissolved organic matter 

(CDOM) versus log-transformed dissolved organic carbon (DOC) concentrations; B, measured versus predicted DOC concentrations; 

C, computed log-transformed DOC concentrations versus regression residuals; and, D, standard normal quantiles versus regression 

residuals.
Appendix 2. S+® Output of Regression Model Development and Graphs from Simple Linear Regression Analysis 87

*** Linear Model *** 

Call: lm(formula = TOC ~ TBY + LOG10CDOM, data = SEDG.TOC.ALL.PTS.REM, na.action = 

 na.exclude) 

Residuals: 

 Min 1Q Median 3Q Max 

 -1.684 -0.6288 -0.3303 0.4346 2.525 

Coefficients: 

 Value Std. Error t value Pr(>|t|) 

(Intercept) -12.3672 2.8405 -4.3538 0.0007 

 TBY 0.0630 0.0081 7.8043 0.0000 

 LOG10CDOM 8.8422 1.5540 5.6899 0.0001 

Residual standard error: 1.26 on 14 degrees of freedom 

Multiple R-Squared: 0.9382 Adjusted R-squared: 0.9294 

F-statistic: 106.3 on 2 and 14 degrees of freedom, the p-value is 3.431e-009 

112 observations deleted due to missing values 

Correlation of Coefficients: 

 (Intercept) TBY 

 TBY 0.4269 

LOG10CDOM -0.9813 -0.5690 

Analysis of Variance Table 

Response: TOC 

Terms added sequentially (first to last) 

 Df Sum of Sq Mean Sq F Value Pr(F) 

 TBY 1 286.2619 286.2619 180.2776 0.00000000218 

LOG10CDOM 1 51.4072 51.4072 32.3744 0.00005584709 

Residuals 14 22.2305 1.5879

Figure 2–3. S+® output of regression model development using chromophoric (colored) dissolved organic matter

(CDOM) and turbidity (TBY) as explanatory variables for total organic carbon (TOC) from the Little Arkansas River near 

Sedgwick, Kansas (downstream surface-water site 07144100), 2009 through 2012.
88 Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer

2.5 5.0 7.5 10.0 12.5 15.0 17.5

Measured TOC

5

0

10

15

1.2

Predicted TOC

5 10 15

Fitted TBY+log10CDOM

Quantiles of standard normal

-1

0

1

2

Residuals

Residuals

2

1

0

-1

A B

C

-25 -20 -15

Line of best fit

Dissolved organic carbon, in milligrams per liter

Chromophoric (colored) dissolved organic material

DOC

CDOM

EXPLANATION

Figure 2–4. S+® output graphs from simple linear regression analysis using turbidity (TBY) and log-transformed chromophoric 

(colored) dissolved organic matter (CDOM) as explanatory variables for total organic carbon (TOC) concentrations from the 

Little Arkansas River near Sedgwick, Kansas (downstream surface-water site 07144100), 2012 through 2014. A, measured versus 

predicted TOC concentrations; B, computed TOC concentrations versus regression residuals; and, C, standard normal quantiles 

versus regression residuals. 
Publishing support provided by: 

Rolla Publishing Service Center

For additional information concerning this publication, 

contact:

Director, USGS Kansas Water Science Center 

4821 Quail Crest Place

Lawrence, KS 66049

(785) 842–9909

Or visit the Kansas Water Science Center Web site at:

http://ks.water.usgs.gov
Stone and others—Effects of Aquifer Storage and Recovery Activities on Water Quality in the Little Arkansas River and Equus Beds Aquifer—SIR 2016–5042

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20165042