Prepared in cooperation with the Arkansas Department of Environmental Quality and the 

U.S. Environmental Protection Agency

Determination of Organic and Inorganic Percentages and 

Mass of Suspended Material at Four Sites in the Illinois 

River in Northwestern Arkansas and Northeastern 

Oklahoma, 2005–07

Scientific Investigations Report 2008–5136

U.S. Department of the Interior

U.S. Geological Survey

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008–5136

Prepared in cooperation with the Arkansas Department of Environmental Quality and the 

U.S. Environmental Protection Agency

Determination of Organic and Inorganic Percentages and 

Mass of Suspended Material at Four Sites in the Illinois 

River in Northwestern Arkansas and Northeastern 

Oklahoma, 2005–07
Cover photographs: Illinois River downstream of bridge at County Road 631, May 2008 (photograph by Brian Haggard, University of 

Arkansas). Inset: Scanning electron microscope image of a diatom from a sample collected on the Illinois River at Savoy, Arkansas, 

August 2006.
Determination of Organic and Inorganic 

Percentages and Mass of Suspended 

Material at Four Sites in the Illinois River in 

Northwestern Arkansas and Northeastern 

Oklahoma, 2005-07

By Joel M. Galloway

In cooperation with the Arkansas Department of Environmental Quality and the 

U.S. Environmental Protection Agency

Scientific Investigations Report 2008-5136

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Galloway, J.M., 2008, Determination of organic and inorganic percentages and mass of suspended material at four 

sites in the Illinois River in northwestern Arkansas and northeastern Oklahoma, 2005-07: U.S. Geological Survey Scientific Investigations Report 2008-5136, 31 p.
iii

Contents

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

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

Study Area Description........................................................................................................................2

Purpose and Scope ..............................................................................................................................2

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

Data Collection......................................................................................................................................3

Laboratory Analysis..............................................................................................................................4

Quality Control and Quality Assurance .............................................................................................4

Data Analysis.........................................................................................................................................4

Hydrologic and Water-Quality Conditions .................................................................................................5

Comparison of Suspended Material Method Results..............................................................................8

Organic and Inorganic Percentages of Suspended Material ..............................................................13

Spatial Variability ................................................................................................................................14

Hydrologic Variability .........................................................................................................................14

Seasonal Variability............................................................................................................................17

Implications...................................................................................................................................................17

Summary........................................................................................................................................................20

References Cited..........................................................................................................................................21

Appendix Water-quality data from August 2005 to July 2007 for the Illinois River sites near

Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas;

and near Tahlequah, Oklahoma ...................................................................................................24

Figures

1. Map showing the Illinois River Basin study area....................................................................3

2. Graph showing daily base flow and total daily mean streamflow and water-quality 

sample times from August 2005 to July 2007 for the Illinois River sites at Savoy,

Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma ...............6

4-6. Boxplots showing:

 3. Distribution of turbidity in water samples collected from August 2005

to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, 

Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma........7

 4. Distribution of suspended-sediment concentrations and total suspended solids

in water samples collected from August 2005 to July 2007 for the Illinois River 

sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, 

Arkansas; and near Tahlequah, Oklahoma .......................................................................9

 5. Distribution of volatile suspended solids and ash-free dry mass in water samples 

collected from August 2005 to July 2007 for the Illinois River sites near Viney 

Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and 

near Tahlequah, Oklahoma ................................................................................................10

 6. Distribution of chlorophyll a in water samples collected from August 2005

to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, 

Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma......11
iv

7-9. Graphs showing:

 7. Comparison of volatile suspended solids and ash-free dry mass in water samples

collected from August 2005 to July 2007 for the Illinois River sites near Viney Grove, 

Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near 

Tahlequah, Oklahoma..........................................................................................................12

 8. Comparison of suspended-sediment concentrations and total suspended solids 

 in water samples collected from August 2005 to July 2007 for the Illinois River 

sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, 

Arkansas; and near Tahlequah, Oklahoma......................................................................12

 9. Comparison of the percentages of inorganic material in water samples collected

 from August 2005 to July 2007 for the Illinois River sites near Viney Grove, 

Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near 

Tahlequah, Oklahoma using two different methods ......................................................13

10. Boxplot showing distribution of organic material in water samples collected from

August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; 

at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah,

Oklahoma .....................................................................................................................................15

11. Images of suspended material from a scanning electron microscopy analysis of a

sample collected during high-flow conditions on August 23, 2006, from the Illinois

River at Savoy, Arkansas...........................................................................................................18

12. Graphs showing seasonal concentrations and percentages of organic material in

water samples collected from August 2005 to July 2007 for the Illinois River sites near

Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and 

near Tahlequah, Oklahoma .......................................................................................................19

Tables

1. Comparison of results of three methods for determining the organic and inorganic

composition of suspended material in samples collected at the Illinois River sites

near Viney, Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs,

Arkansas; and near Tahlequah, Oklahoma.............................................................................13

2. Results of scanning electron microscopy analysis of samples collected at the

Illinois River sites near Viney, Grove, Arkansas; at Savoy, Arkansas; south of Siloam 

Springs, Arkansas; and near Tahlequah, Oklahoma.............................................................16
v

Conversion Factors and Datums

Multiply By To obtain

Length

inch (in.) 25.40 millimeter (mm)

inch (in.) 2.54 × 107 nanometer (nm)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2)

Flow rate

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

Temperature in degrees Celsius (  ̊C) may be converted to degrees Fahrenheit ( ̊F) as follows:  ̊F = (1.8 x  ̊C) + 32

Temperature in degrees Fahrenheit (  ̊F) may be converted to degrees Celsius ( ̊C) as follows:  ̊C =( ̊F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD of 88).

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

Altitude, as used in this report, refers to distance above the vertical datum.
Determination of Organic and Inorganic Percentages 

and Mass of Suspended Material at Four Sites in the 

Illinois River in Northwestern Arkansas and Northeastern 

Oklahoma, 2005-07

By Joel M. Galloway

Abstract

The Illinois River located in northwestern Arkansas and 

northeastern Oklahoma is influenced by point and nonpoint 

sources of nutrient enrichment. This has led to increased algal 

growth within the stream, reducing water clarity. Also, sediment runoff from fields, pastures, construction sites, and other 

disturbed areas, in addition to frequent streambank failure, has 

increased sedimentation within the stream and decreased water 

clarity. A study was conducted by the U.S. Geological Survey 

in cooperation with the Arkansas Department of Environmental Quality and the U.S. Environmental Protection Agency to 

characterize the increased turbidity by determining the organic 

and inorganic composition and mass of suspended material in 

the Illinois River from August 2005 through July 2007. Waterquality samples were collected at four sites on the Illinois 

River (listed in downstream order): near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; 

and near Tahlequah, Oklahoma. 

In general, turbidity, total suspended solids, suspendedsediment concentration, organic material concentration (measured as volatile suspended solids and ash-free dry mass), and 

chlorophyll a concentration were the greatest in samples collected from the Illinois River at Savoy and the least in samples 

from the most upstream Illinois River site (near Viney Grove) 

and the most downstream site (near Tahlequah) from August 

2005 through July 2007. For example, the suspended-sediment 

concentration at the Illinois River at Savoy had a median of 

15 milligrams per liter, and the total suspended solids had a 

median of 12 milligrams per liter. The Illinois River near Tahlequah had the least suspended-sediment concentration with a 

median of 10 milligrams per liter and the least total suspended 

solids with a median of 6 milligrams per liter. 

The turbidity, total suspended solids, suspended-sediment 

concentration, organic material concentration, and chlorophyll 

a concentration in samples collected during high-flow events 

were greater than in samples collected during base-flow conditions at the Illinois River at Savoy, south of Siloam Springs, 

and near Tahlequah. For example, the median turbidity for 

the Illinois River at Savoy was 3 nephelometric turbidity ratio 

units during base-flow conditions and 52 nephelometric turbidity ratio units during high-flow conditions. 

Organic material in the Illinois River generally composed between 13 and 47 percent of the total suspended 

material in samples collected from August 2005 through July 

2007. Therefore, most of the suspended material in samples 

collected from the sites was inorganic material. Overall, 

the highest percentage of organic material was found at the 

Illinois River near Viney Grove and at the Illinois River near 

Tahlequah. The Illinois River south of Siloam Springs had the 

lowest percentage of organic material among the four sites. 

In general, the percentage of organic material was greater in 

samples collected during base-flow conditions compared to 

samples collected during high-flow conditions. 

The mean seasonal concentrations and percentages of 

organic material were the least in the fall (September through 

November) in samples collected from August 2005 to July 

2007 from the four Illinois River sites, while the greatest 

concentrations and percentages of organic material occurred 

at various times of the year depending on the site. The 

greatest concentrations of organic material occurred in the 

summer (June through August) in samples from sites on the 

Illinois River near Viney Grove, at Savoy and south of Siloam 

Springs, but in the spring (March through May) in samples 

from the Illinois River near Tahlequah. The greatest percentages of organic material (least percentages of inorganic 

material) occurred in the summer in samples from the site near 

Viney Grove, the winter and summer at the site at Savoy, in 

the spring, fall, and winter (December through February) at 

the site south of Siloam Springs, and in the winter at the site 

near Tahlequah. 

Although a wide range of variability is evident in the 

data, several observations can be made about the suspendedmaterial data collected from the four sites on the Illinois River 

from August 2005 through July 2007. Samples from the 

Illinois River near Savoy had the greatest turbidity, suspendedsediment concentration, total suspended solids, chlorophyll 
2 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

a, and organic material concentrations among the four sites, 

indicating that it may be the most affected by activities in the 

basin upstream from the site, causing increased suspended 

inorganic and organic material. Downstream from the Illinois 

River at Savoy, the data indicate that although a similar concentration of suspended material is being transported downstream, less organic material is being entrained, transported, 

or being added to the stream near the site south of Siloam 

Springs compared to the site upstream at Savoy. Even farther 

downstream at the Illinois River near Tahlequah, the data indicate that less of the suspended material, which was observed 

in samples from the two upstream sites, is being transported 

past the site near Tahlequah and the concentration of inorganic 

particles is less because of deposition upstream from the site, 

or the channel morphology may be more conducive for algal 

growth, increasing the effects of sources of organic material on 

the total mass of suspended material.

Introduction

The Illinois River located in northwestern Arkansas and 

northeastern Oklahoma is influenced by point and nonpoint 

sources of nutrient enrichment. This has led to increased algal 

growth within the stream, reducing water clarity. Also, sediment runoff from fields, pastures, construction sites, and other 

disturbed areas, in addition to frequent streambank failure, 

has increased sedimentation within the stream and decreased 

water clarity (Arkansas Department of Environmental Quality, 

2008). 

Water clarity in streams is often determined by measurements of turbidity. Turbidity is an expression of the optical 

properties of a sample that causes light rays to be scattered 

and absorbed (Gray and Glysson, 2003). Turbidity of water is 

caused by the presence of dissolved and suspended inorganic 

matter such as clay and silt; dissolved and suspended organic 

matter such as plankton, microscopic organisms, and small 

terrestrial organic material; organic acids; and water color. A 

study was conducted by the U.S. Geological Survey (USGS), 

in cooperation with the Arkansas Department of Environmental Quality (ADEQ) and the U.S. Environmental Protection 

Agency (USEPA), to determine the organic and inorganic percentages and mass of suspended material in the Illinois River 

from August 2005 through July 2007 to characterize the main 

causes of turbidity. Such data will provide water-resource 

managers with information that will be beneficial in the evaluation and refinement of current (2008) turbidity standards; in 

the development of nutrient criteria for rivers; and in the development of a total maximum daily load (TMDL), watershed 

plan, or any other instrument the States deem appropriate to 

protect the resource.

Study Area Description

The Illinois River Basin has a drainage area of 1,641 mi2

at its confluence with the Arkansas River and is about equally 

divided between northwestern Arkansas and northeastern 

Oklahoma (fig. 1). The basin is dominated by about equal 

proportions of agricultural (pasture and cropland) and forest 

land uses and is interspersed with minor amounts of commercial and residential land uses. Livestock production on pasture is the primary form of agriculture in the basin; about 48 

percent of agricultural land use is pasture for cattle and horses. 

Numerous large-scale poultry and swine production facilities 

are in the basin and poultry and swine manures are used to 

fertilize pastures (Sims and Wolf, 1994). The upper basin is 

also one of the fastest-growing metropolitan statistical areas in 

the United States (Fayetteville-Springdale-Rogers, Arkansas) 

(U.S. Census Bureau, 2007).

Water-quality data collected at four sites in the Illinois 

River Basin are described in this report: the Illinois River near 

Viney Grove, Arkansas (USGS station number 07194760); 

Illinois River at Savoy, Arkansas (USGS station number 

07194800); Illinois River south of Siloam Springs (USGS 

station number 07195430); and Illinois River near Tahlequah, 

Oklahoma (USGS station number 07196500) (fig. 1). The 

Illinois River near Viney Grove is the most upstream site with 

a drainage area of 80.7 mi2. The drainage area contributing 

to the site does not contain any large point sources and the 

land use is about equally proportioned with agricultural (56 

percent, mainly pasture) and forested (42 percent) land use. 

The Illinois River at Savoy has a drainage area of 167 mi2 

and is downstream from several wastewater-treatment plant 

discharges in its drainage area. Land use is mainly composed of agricultural land (approximately 60 percent, mainly 

pasture), and forest (approximately 30 percent). The Illinois 

River south of Siloam Springs, located near the Arkansas 

and Oklahoma State line, has a drainage area of 575 mi2. The 

land use is also mainly pasture and forest and the site receives 

discharge from numerous wastewater-treatment plants in the 

drainage area. The Illinois River near Tahlequah, Oklahoma, 

is the most downstream site and has a drainage area of 959 

mi2, which is also mostly pasture (48 percent) and forested (37 

percent) land uses. 

Purpose and Scope

The primary purpose of this report is to describe the 

spatial and temporal variability of the organic and inorganic 

percentages and mass of suspended material at four sites in 

the Illinois River from August 2005 through July 2007. A 

secondary purpose of this report is to describe differences 

between methods used in the determination of the organic 

and inorganic percentages of suspended material. Waterquality samples were collected every 2 months and during 

four high-flow events at three sites on the Illinois River: at 

Savoy, Arkansas; south of Siloam Springs, Arkansas, near 

the Arkansas and Oklahoma State line; and near Tahlequah, 

Oklahoma (fig. 1). Water-quality samples also were collected 

every 2 months for the 2-year period at the Illinois River near 
Methods 3

BENTON

WASHINGTON

CHEROKEE ADAIR

OKLAHOM

A

ARKANSAS

# #

#

07194800

07195430

07194760

07196500

I-540

412

62

59

Springdale

Siloam 

Springs

Tahlequah

Savoy

Viney

Grove

Fayetteville

#

Illinois

River

Flint

Creek

Osage Creek

Creek

Clear

Fork

Muddy

Illinois River

Study area

OKLAHOMA

ARKANSAS

Location Map

0 100 200 MILES

0 100 200 KILOMETERS

EXPLANATION

Streamflow and water-quality station

 and identifier

Water-quality station and identifier

07196500

07194760

36°12'

35°48'

95°06' 94°12'

#

#

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection

Zone 15

Figure 1. The Illinois River Basin study area.

Viney Grove, Arkansas, located upstream from all wastewatertreatment plant discharges in the Illinois River Basin.

Methods

Streamflow and water-quality data were collected at 

four sites on the Illinois River from August 2005 through 

July 2007. The following sections describe methods used for 

measurement of streamflow and the collection and analysis of 

water-quality samples and other water-quality data. 

Data Collection

Stream stage was measured continuously at the Illinois 

River at Savoy, Arkansas (USGS station number 07194800), 

south of Siloam Springs, Arkansas (USGS station number 

07195430) and near Tahlequah, Oklahoma (USGS station 

number 07196500) (fig. 1). Stage and instantaneous discharge were measured to compute the continuous streamflow 

from stage-discharge rating curves using methods described 

in Rantz and others (1982). At the Illinois River near Viney 

Grove, Arkansas (USGS station number 07194760) only 

instantaneous discharge was measured when water-quality 

samples were collected.

Water-quality samples were collected every 2 months and 

during four high-flow events at three sites on the Illinois River: 

at Savoy, south of Siloam Springs, and near Tahlequah (fig. 1) 

from August 2005 through July 2007. Water-quality samples 

also were collected every 2 months for the 2-year period at the 

Illinois River near Viney Grove. Samples were collected following equal-width increment methods using depth-integrated 

samplers and processed using protocols described in U.S. 

Geological Survey (variously dated). Samples were analyzed 

for suspended-sediment concentration (SSC), turbidity, chlorophyll a, ash-free dry mass, total suspended solids (TSS), and 

volatile suspended solids (VSS). Samples also were analyzed 

for nutrients (total ammonia plus organic nitrogen, dissolved 

nitrite plus nitrate, dissolved ammonia, total nitrogen, dis-
4 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

solved orthophosphorus, and total phosphorus) and total 

dissolved solids (TDS), although the nutrient and TDS data 

are not described in this report. All water-quality data are 

presented in the appendix of the report. One sample collected 

during high-flow conditions and one sample collected during 

base-flow conditions also were analyzed for organic and inorganic composition using scanning electron microscopy (SEM). 

Field measurements, including water temperature, dissolvedoxygen concentration, pH, and specific conductance also were 

collected with each sample (Appendix) following protocols 

described in Wilde and Radke (1998).

Laboratory Analysis

Water-quality samples were analyzed for nutrients, TDS, 

SSC, turbidity, chlorophyll a, ash-free dry mass, TSS, and 

VSS. Nutrients, TDS, turbidity, chlorophyll a, and ash-free dry 

mass analyses were conducted by the USGS National Water 

Quality Laboratory in Lakewood, Colorado using methods 

described in Arar and Collins (1997), Fishman (1993), and 

the American Public Health Association and others (1995). 

SSC analyses were conducted by the USGS Missouri Water 

Science Center in Rolla, Missouri, following procedures 

described in Guy (1969). Analyses for TSS and VSS were 

conducted by the USGS Arkansas Water Science Center in 

Little Rock, Arkansas, following procedures in American 

Public Health Association and others (1995).

One sample collected at high-flow conditions and one 

sample collected at base-flow conditions at each site also were 

analyzed for the visual determination of organic and inorganic 

composition of the suspended material using scanning electron 

microscopy (SEM). Analysis by SEM was completed by 

the USGS Microbeam Laboratory in Denver, Colorado. For 

sample preparation, the samples were shaken vigorously for 2 

minutes, and then 20 milliliters of water were filtered through 

0.2-micron polycarbonate filters using a Millipore apparatus. 

Water was withdrawn from the sample bottles in 5-milliliter 

aliquots from four levels in the bottle (bottom, lower middle, 

upper middle, and top) to obtain a representative sampling 

in case of particle settling. The samples then were coated in 

a carbon evaporator with approximately 40 nanometers of 

carbon for conductivity. Carbon-coated filters were analyzed 

using a JEOL 5800LV scanning electron microscope operated 

at 15 kilovolts using a 0.5-3.0 nanoamp beam current. Energy 

dispersive x-ray spectroscopy (EDS) data were processed with 

the OXFORD ISIS standardless analysis software package 

(Isabelle Brownfield, U.S. Geological Survey, written commun., 2007). The low concentration of organic material in 

the sample collected during high-flow conditions required a 

different analysis procedure than was performed on the sample 

collected at base-flow conditions. The aliquots were filtered 

through a 0.4-micrometer pore filter using a Millipore apparatus. Afterwards, the filter was coated with gold. Gold-coated 

filters were analyzed using a JEOL 5800LV SEM operated at 

10 kilovolts using a 0.5-3.0 nanoamp beam current. The samples were mapped at 1,000 times magnification for gold (to 

get total particulate coverage), carbon (organic fraction), and 

silicon (inorganic fraction) (Heather A. Lowers and Gregory P. 

Meeker, U.S. Geological Survey, written commun., 2007). The 

occurrence of diatoms was determined manually because they 

were identified as silicon by the SEM and was added to the 

organic fraction. 

Quality Control and Quality Assurance

To maintain proper quality assurance and control (QA/

QC) of water-quality data, protocols for instrument calibration 

(Wilde and Radke, 1998) and equipment cleaning (Wilde and 

others, 1998) were followed. Associated blank and replicate 

water-quality samples also were collected periodically by 

USGS personnel. Thirty-six blank samples and 57 replicate 

samples were collected at sites that were part of the USGS 

water-quality monitoring program in Arkansas from August 

2005 through July 2007. Results indicated that cleaning 

procedures were adequate in preventing cross-contamination 

of samples and that the laboratory results were reproducible. 

QA/QC sample data were stored in the USGS National Water 

Information System (NWIS) database (http://waterdata.usgs.

gov/nwis).

Laboratory QA/QC of water-quality sample analyses also 

were conducted by the respective laboratories. QA/QC procedures followed by the USGS National Water Quality Laboratory in Lakewood, Colorado, are presented in Maloney (2005). 

The USGS Arkansas Water Science Center laboratory in Little 

Rock, Arkansas, followed similar procedures. Analytical balances were used for accurate weighing of samples, reagents, 

and calibration standards. Prior to each use, balances were 

checked with Class I weights in the expected-use range that 

were certified by a National Institute of Standards and Technology (NIST) or a NIST-certified entity. The balances were 

cleaned and certified once a year by a contract service technician. The calibration, maintenance, and use were documented 

in a log book. Balances that failed calibration checks were not 

used until repaired and recertified by a contract service technician. A laboratory blank sample analysis also was conducted 

for each set of samples that was processed.

Data Analysis 

Streamflow recorded at the Illinois River at Savoy, south 

of Siloam Springs, and near Tahlequah was separated using 

the Base-Flow Index (BFI) hydrograph separation computer 

program to identify the base-flow and surface-runoff components of streamflow (Wahl and Wahl, 1995). The BFI program 

uses the Institute of Hydrology method of base-flow separation, which divides the water year into increments and identifies the minimum flow for each increment. Minimums are 

compared to adjacent minimums to determine turning points 

on the base-flow hydrograph. If 90 percent of a given minimum is less than both adjacent minimums, then that minimum 
Hydrologic and Water-Quality Conditions 5

is a turning point. Straight lines are drawn between the turning 

points to define the base-flow hydrograph (Wahl and Wahl, 

1995). The area beneath the hydrograph is the estimate of the 

volume of base flow for the period. The ratio of the base-flow 

volume to total-flow volume is the base-flow index.

Water-quality samples collected from the Illinois River 

sites near Savoy, south of Siloam Springs, and near Tahlequah 

were separated into those collected under base-flow or highflow conditions. Base-flow water-quality samples were collected on days when the estimated base flow was greater than 

or equal to 70 percent of the total daily mean flow. High-flow 

samples were defined as water-quality samples collected on 

days when the surface-runoff component was greater than 30 

percent of total daily mean flow.

The resulting streamflow and water-quality data were 

analyzed or summarized using several statistical and graphical 

techniques. Boxplots were used to compare concentrations of 

selected water-quality constituents. Concentrations reported as 

less than a laboratory reporting level were converted to onehalf the laboratory reporting level for preparation of boxplots 

and statistical analyses. 

The percentages of organic and inorganic material in 

water-quality samples were determined using three different 

methods. The VSS, or the matter that is removed when the 

dried material from a sample is ignited at 550°C (American 

Public Health Association and others, 1995), provides an estimate of the mass of the total suspended solids that is organic. 

The inorganic suspended solids (ISS) were determined by 

substracting the VSS from the TSS (referred to as the TSS 

method in this report). Another method used to determine the 

organic and inorganic material in each sample used the analyses for ash-free dry mass and for SSC. The ash-free dry mass 

represents the organic fraction and the SSC represents the total 

suspended material in the sample. Therefore, the inorganic 

suspended solids were determined by substracting the ash-free 

dry mass from the SSC (referred to as the SSC method in this 

report). SEM analysis also was used to visually determine the 

percentages of organic and inorganic material by counting the 

different particle types from an aliquot of the sample. This 

analysis was conducted on only two samples from each site 

(one collected at base-flow conditions and one collected at 

high-flow conditions) and is referred to as the SEM method.

Hydrologic and Water-Quality 

Conditions

Streamflow increased substantially from the most 

upstream site (with continuous streamflow data) on the Illinois 

River (at Savoy) to the most downstream site (near Tahlequah) 

from August 2005 through July 2007 (fig. 2). Also, the mean 

annual streamflow was considerably less from August 2005 

through July 2007 compared to the long-term mean annual 

streamflow recorded at each site. The streamflow for the Illinois River near Viney Grove was collected only when samples 

were collected and was not recorded continuously as it was 

at the other three sites. Measured streamflow for the site near 

Viney Grove ranged from 4.0 to 199 ft3/s. The daily mean 

streamflow at the Illinois River at Savoy ranged from 5.3 to 

5,690 ft3/s with mean of 105 ft3/s for the period (August 2005 

through July 2007). The mean annual streamflow for the entire 

period of record (July 1979 to October 2007) was 147 ft3/s 

(U.S. Geological Survey, 2008). The Illinois River south of 

Siloam Springs had daily mean streamflows ranging from 50.0 

to 8,620 ft3/s with a mean daily streamflow of 338 ft3/s for 

the period. The mean annual streamflow for the Illinois River 

south of Siloam Springs for the entire period of record (August 

1995 through October 2007) was 540 ft3/s. The daily mean 

streamflow for the Illinois River near Tahlequah ranged from 

86.0 to 11,300 ft3/s from August 2005 through July 2007. The 

mean daily streamflow was 530 ft3/s compared to the annual 

mean of 930 ft3/s for the entire period of record (October 1935 

to October 2007).

In general, turbidity was greatest in samples collected 

from the Illinois River at Savoy and least in samples from the 

most upstream Illinois River site (near Viney Grove) and the 

most downstream site (near Tahlequah) from August 2005 

through July 2007 (fig. 3). Samples from the Illinois River 

at Savoy had a median turbidity of 6 nephelometric turbidity 

ratio units (NTRU) and a maximum turbidity of 930 NTRU. In 

comparison, the median and maximum turbidities for samples 

from the Illinois River near Tahlequah were 5 and 79 NTRU, 

respectively. Samples from the Illinois River south of Siloam 

Springs had a median turbidity of 6 NTRU and a maximum 

turbidity of 180 NTRU. The Illinois River near Viney Grove, 

that did not have any high-flow event samples collected, had a 

median turbidity of 5 NTRU, and a maximum turbidity of 13 

NTRU.

The turbidity in samples collected during high-flow 

events was considerably greater than in samples collected 

during base-flow conditions at the Illinois River sites at Savoy, 

south of Siloam Springs, and near Tahlequah from August 

2005 through July 2007 (fig. 3). The median turbidity for 

samples from the Illinois River at Savoy was 3 NTRU during 

base-flow conditions and 52 NTRU during high-flow conditions. Similarly, samples from the Illinois River sites south of 

Siloam Springs and near Tahlequah had median turbidities of 

1 and 3 NTRU, respectively, in samples collected during baseflow conditions, and 17 and 6 NTRU, respectively, in samples 

collected during high-flow conditions.

TSS and SSC commonly are used to quantify concentrations of suspended solid-phase material in surface water. 

However, the analytical methods differ and the two may not 

be equivalent when solid-phase material, especially sand, 

becomes more concentrated (Gray and others, 2000). SSC 

analytical methods measure all the sediment and the mass of 

the entire water-sediment mixture of the original sample; TSS 

methods only use an aliquot of the original sample for subsequent analysis.

Samples from the Illinois River at Savoy had the greatest TSS and SSC among the four sampling sites in the Illinois 
6 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

07194800 Illinois River at Savoy, Arkansas

1

10

100

1,000

10,000

100,000

07195430 Illinois River South of Siloam Springs, Arkansas

STREAMFLOW, IN CUBIC FEET PER SECOND

1

10

100

1,000

10,000

100,000

07196500 Illinois River near Tahlequah, Oklahoma

8/1/05 11/1/05 2/1/06 5/1/06 8/1/06 11/1/06 2/1/07 5/1/07 8/1/07 

1

10

100

1,000

10,000

100,000

Total daily streamflow

Daily base flow

Sample associated with base flow

Sample associated with high flow

EXPLANATION

Mean annual streamflow 

 for period of record

Figure 2. Daily base flow and total daily mean streamflow and water-quality sample times from August 2005 to July 2007 for the Illinois 

River sites at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.
Hydrologic and Water-Quality Conditions 7

All samples

0.1

1

10

100

1,000

Base-flow samples

TURBIDITY, IN NEPHELOMETRIC TURBIDITY RATIO UNITS

0.1

1

10

100

1,000

High-flow samples

0.1

1

10

100

1,000

EXPLANATION

90th percentile

75th percentile

25th percentile

Median (50th percentile)

10th percentile

Data value greater than

 or less than 90th

 or 10th percentile

16 Number of samples

12

16

16

14

12

8 8 6

8

8

8

SITE, IN DOWNSTREAM ORDER

Illinois River 

near

Tahlequah

Illinois River 

at Savoy

Illinois River 

near

Viney Grove

Illinois River 

south of 

Siloam Springs

No high-flow

samples

collected 

Figure 3. Distribution of turbidity in water samples collected from August 2005 to July 2007 for the Illinois River sites near Viney Grove, 

Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.
8 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

River from August 2005 through July 2007 (fig. 4). The TSS 

in samples from the Illinois River at Savoy ranged from less 

than 1 to 1,240 mg/L with a median of 12 mg/L and the SSC 

ranged from 6 to 1,480 milligrams per liter (mg/L) with a 

median of 15 mg/L. Samples from the Illinois River near Tahlequah had the least TSS, ranging from less than 1 to 124 mg/L 

with a median of 6 mg/L and the least SSC, ranging from 2 to 

140 mg/L with a median of 10 mg/L. Although no high-flow 

samples were collected at the Illinois River near Viney Grove, 

samples had similar values of TSS (ranging from 2 to 13 

mg/L, with a median of 8 mg/L) and SSC (ranging from 4 to 

123 mg/L, with a median of 15 mg/L) as measured at the Illinois River near Tahlequah. Similar to turbidity, TSS and SSC 

were greatest in samples collected during high-flow conditions 

compared to samples collected at base-flow conditions.

Organic matter in stream ecosystems can originate from 

many sources within the stream (autochthonous) and from 

outside the stream channel (allochthonous). Autochthonous 

sources of organic matter include primary production by periphyton, macrophytes, and phytoplankton, while allochthonous 

sources can include terrestrial plant litter and soil particulates 

(Allen, 1995). 

Concentrations of suspended organic material (measured 

as VSS and ash-free dry mass) measured in samples from 

the Illinois River at Savoy were greater than in samples from 

the three other sites in the Illinois River from August 2005 

through July 2007 (fig. 5). The VSS and ash-free dry mass in 

samples from the Illinois River at Savoy had median values 

of 3.1 and 4.3 mg/L, respectively. The VSS ranged from less 

than 1.0 to 130.0 mg/L and the ash-free dry mass ranged from 

less than 2.0 to 143.8 mg/L. Samples from the Illinois River 

south of Siloam Springs had similar median values of VSS 

(2.2 mg/L) and ash-free dry mass (3.4 mg/L) but did not have 

as great a range of values of VSS (less than 1.0 to 30.0 mg/L) 

and ash-free dry mass (less than 3.2 to 41.4 mg/L) as the site 

at Savoy. Samples from the Illinois River sites near Viney 

Grove and near Tahlequah had median VSS values of 2.0 and 

1.8 mg/L, respectively, and had median ash-free dry mass 

values of 3.2 and 1.9 mg/L, respectively. 

Organic material concentrations in samples collected during high-flow conditions generally were greater than concentrations in samples collected during base-flow conditions (fig. 

5). For example, samples from the Illinois River at Savoy had 

median VSS and ash-free dry mass concentrations of 1.0 and 

2.5 mg/L, respectively, during base-flow conditions, compared 

to median VSS and ash-free dry mass concentrations of 10.0 

and 12.7 mg/L, respectively, during high-flow conditions. The 

greater concentrations of organic material during high-flow 

conditions may reflect an increase in allochthonous sources 

such as plant litter and soil that are washed into the stream 

channel or scouring of the periphyton (benthic algae) from the 

streambed as velocities in the stream increased.

Chlorophyll a is a photosynthetic pigment found in algae 

and other green plants. The concentration of chlorophyll a, 

from samples collected in open water, commonly is used as a 

measure of the density of the algae. 

Chlorophyll a concentrations were greatest in samples 

from the Illinois River at Savoy compared to the other three 

sites in samples collected from August 2005 through July 

2007 (fig. 6). Chlorophyll a concentrations in samples from 

the Illinois River at Savoy ranged from 0.7 to 29.1 micrograms 

per liter (μg/L) with a median of 3.2 μg/L. In comparison, 

samples from the Illinois River south of Siloam Springs had 

the least median concentration (1.6 μg/L). Chlorophyll a

concentrations ranged from 0.3 to 14.1μg/L in samples from 

the Illinois River south of Siloam Springs. Samples from the 

Illinois River near Tahlequah had chlorophyll a concentrations 

ranging from 0.8 to 12.3 μg/L with a median of 2.5 μg/L.

Chlorophyll a concentrations in samples collected during 

high-flow conditions generally were greater than concentrations in samples collected during base-flow conditions at most 

of the sites (fig. 6). The median chlorophyll a concentration 

increased from 1.4 μg/L in samples collected during base-flow 

conditions to 5.5 μg/L in samples collected during high-flow 

conditions at the Illinois River at Savoy and from 1.6 μg/L 

during base-flow conditions to 3.2 μg/L during high-flow 

conditions in samples from the Illinois River south of Siloam 

Springs. However, the median concentration in samples from 

the Illinois River near Tahlequah was slightly less during 

high-flow conditions (2.5 μg/L) than during base-flow conditions (2.7 μg/L). The greater concentrations during high-flow 

conditions at the Illinois River sites at Savoy and south of 

Siloam Spring may be the result of scouring of the periphyton 

(benthic algae) from the streambed as velocities in the stream 

increased. The concentrations in samples from the Illinois 

River near Tahlequah during high-flow conditions possibly did 

not increase because of greater dilution effects (greater volume 

of streamflow than the upstream sites) or because habitat in 

the stream channel and water chemistry upstream from the 

site was not as conducive for algal growth as at the other sites. 

There are other factors that may have had an influence on the 

measured chlorophyll a concentrations, such as the time of 

the year the sample was collected and whether the sample was 

collected on the rise, peak, or fall of the streamflow hydrograph during high-flow conditions. 

Comparison of Suspended Material 

Method Results

To determine the organic and inorganic composition of 

the suspended material at the four sites in the Illinois River, 

three different methods were used (TSS method, SSC method, 

and SEM method) for comparison. The mass of the suspended 

organic material was determined by analysis of ash-free dry 

mass and an analysis of VSS from the samples collected at the 

four sites. Likewise, the mass of the total suspended material 

was determined by two different analyses, including SSC and 

TSS analyses from the samples collected at the four sites. 
Comparison of Suspended Material Method Results 9

All samples

CONCENTRATION, IN MILLIGRAMS PER LITER

0.1

1

10

100

1,000

10,000

TSS SSC TSS SSC TSS SSC TSS SSC

Base-flow samples

0.1

1

10

100

1,000

10,000

High-flow samples

1

10

100

1,000

10,000

 Total suspended solids

 Suspended sediment concentraton

EXPLANATION

90th percentile

75th percentile

25th percentile

Median (50th percentile)

10th percentile

Data value greater than

 or less than 90th

 or 10th percentile

16 Number of samples

11

12

16 16

16 16

13 12

11

12

8

8

8

8

5

5

8

8

8

8

8 7

Illinois River 

near

Tahlequah

Illinois River 

at Savoy

Illinois River 

near

Viney Grove

Illinois River 

south of 

Siloam Springs

TSS 

SSC

SITE, IN DOWNSTREAM ORDER

No high-flow

samples

collected 

Figure 4. Distribution of suspended-sediment concentrations and total suspended solids in water samples collected from August 2005 

to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near 

Tahlequah, Oklahoma.
10 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

ALL SAMPLES

0.1

1

10

100

1,000

BASE-FLOW SAMPLES

CONCENTRATION, IN MILLIGRAMS PER LITER

0.1

1

10

100

1,000

HIGH-FLOW SAMPLES

0.1

1

10

100

1,000

No high-flow

samples

collected 

10

12

16 16

16

16

13

14

10 9

12

9

8 8 5

7

7

7 8

8

8

7

EXPLANATION

90th percentile

75th percentile

25th percentile

Median (50th percentile)

10th percentile

Data value greater than

 or less than 90th

 or 10th percentile

16 Number of samples

Volatile

suspended

solids

Ash-free

dry mass

Volatile

suspended

solids

Ash-free

dry mass

Volatile

suspended

solids

Ash-free

dry mass

Volatile

suspended

solids

Ash-free

dry mass

SITE, IN DOWNSTREAM ORDER

Illinois River 

near

Tahlequah

Illinois River 

at Savoy

Illinois River 

near

Viney Grove

Illinois River 

south of 

Siloam Springs

Figure 5. Distribution of volatile suspended solids and ash-free dry mass in water samples collected from August 2005 to July 2007 

for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, 

Oklahoma.
Comparison of Suspended Material Method Results 11

ALL SAMPLES

0.1

1

10

100

BASE-FLOW SAMPLES

CHLOROPHYLL a , IN MICROGRAMS PER LITER

0.1

1

10

100

HIGH-FLOW SAMPLES

0.1

1

10

100

11

16

16 13

11

8 8

6

8

8

7 No high-flow

samples

collected 

EXPLANATION

90th percentile

75th percentile

25th percentile

Median (50th percentile)

10th percentile

Data value greater than 

 or less than 90th 

 or 10th percentile

16 Number of samples

SITE, IN DOWNSTREAM ORDER

Illinois River 

near

Tahlequah

Illinois River 

at Savoy

Illinois River 

near

Viney Grove

Illinois River 

south of 

Siloam Springs

Figure 6. Distribution of chlorophyll a in water samples collected from August 2005 to July 2007 for the Illinois River sites near Viney 

Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.
12 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

VSS and ash-free dry mass data compared relatively well 

at VSS concentrations greater than 3.0 mg/L (fig. 7). At lower 

concentrations, ash-free dry mass was consistently greater 

than VSS. Some of the differences in the values at the lower 

concentrations may be explained by measurement errors in 

the laboratory analysis. As the mass of material decreases, 

the measurement of mass is more affected by accuracy of the 

laboratory balances, thus increasing the uncertainty in the 

measurement.

VOLATILE SUSPENDED SOLIDS, IN MILLIGRAMS PER LITER

0.1 1 10 100 1,000

ASH-FREE DRY MASS, IN MILLIGRAMS PER LITER

0.1

1

10

100

1,000

Line of

equal value 

Illinois River near Viney Grove

Illinois River at Savoy

Illinois River south of Siloam Springs

Illinois River near Tahlequah

Figure 7. Comparison of volatile suspended solids and ash-free 

dry mass in water samples collected from August 2005 to July 

2007 for the Illinois River sites near Viney Grove, Arkansas; at 

Savoy, Arkansas; south of Siloam Springs, Arkansas; and near 

Tahlequah, Oklahoma.

Similar to the comparison of VSS and ash-free dry 

mass, the TSS and SSC data compared relatively well at TSS 

concentrations greater than 3 mg/L, although the differences 

between values were more variable at most concentrations 

(fig. 8). Some of the differences in the values at the lower 

concentrations also may be explained by measurement errors 

in the laboratory analysis. In addition, as mentioned earlier, 

the analytical methods differ and the two methods may not 

be equivalent when solid-phase material, especially sand, 

becomes more concentrated (Gray and others, 2000).

The results of the three methods used to determine the 

organic and inorganic portions of the suspended material were 

widely variable among the different methods. Comparisons 

between the TSS method and the SSC method showed that differences between percentages calculated using the two methods generally increased as the percentage of organic material 

increased (fig. 9). Much of the differences between the results 

of the TSS and SSC methods may be attributed to the sample 

processing methods. In the analysis of TSS and VSS, the two 

constituents were determined from the same volume of water 

from the same sample container (American Public Health 

Association and others, 1995). However, the ash-free dry mass 

was analyzed by a separate laboratory and from a different 

sample container than the SSC analysis. Although the samples 

in each container should have the same composition among 

the containers because they were split from the composite 

sample collected from the stream, differences in results could 

arise from different instrument and measurement accuracies 

among the laboratories and particle distributions can change 

within the different containers because of adhesion to the container walls and from settling. 

The SEM method also showed variable results from the 

TSS and SSC methods (table 1). In general, the SEM method 

yielded greater percentages of organic material than the other 

methods in samples collected during base-flow conditions 

when concentrations of TSS were relatively small, except for 

the sample collected at the Illinois River near Tahlequah where 

the SEM value was similar to the SSC method value and 

less than the TSS method value. In samples collected during 

high-flow conditions when TSS concentrations were usually 

greater, the SEM results were similar to results from the other 

two methods, except in the sample from the Illinois River near 

Tahlequah, where the SEM yielded a much smaller percentage 

of organic material than the other two methods. The greatest difference between the SEM method and the two other 

methods is that the SEM method determines the percentage of 

organic material from the area that the inorganic and organic 

particles occupy on the sample and the other two methods 

determine the percentages from the mass of the particles in 

the sample. The SEM method may show a higher percentage 

Figure 8. Comparison of suspended-sediment concentrations 

and total suspended solids in water samples collected from 

August 2005 to July 2007 for the Illinois River sites near Viney 

Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, 

Arkansas; and near Tahlequah, Oklahoma.

TOTAL SUSPENDED SOLIDS, IN MILLIGRAMS PER LITER

0.1 1 10 100 1,000 10,000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER 

0.1

1

10

100

1,000

10,000

Illinois River near Viney Grove

Illinois River at Savoy

Illinois River south of Siloam Springs

Illinois River near Tahlequah

Line of

equal value 
Organic and Inorganic Percentages of Suspended Material 13

SUSPENDED ORGANIC MATERIAL, IN PERCENT OF TOTAL SUSPENDED MATERIAL,

DETERMINED FROM VOLATILE SUSPENDED SOLIDS AND TOTAL SUSPENDED-SOLIDS DATA

0 20 40 60 80 100

SUSPENDED ORGANIC MATERIAL, IN PERCENT OF

TOTAL SUSPENDED MATERIAL, DETERMINED FROM

ASH-FREE DRY MASS AND SUSPENDED-SEDIMENT DATA 

0

20

40

60

80

100

Illinois River near Viney Grove

Illinois River at Savoy

Illinois River south of Siloam Springs

Illinois River near Tahlequah

Line of

equal value 

Figure 9. Comparison of the percentages of inorganic material 

in water samples collected from August 2005 to July 2007 for 

the Illinois River sites near Viney Grove, Arkansas; at Savoy, 

Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, 

Oklahoma using two different methods.

Table 1. Comparison of results of three methods for determining the organic and inorganic compositon of suspended material in 

samples collected at the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and 

near Tahlequah, Oklahoma.

[mg/L, milligrams per liter; <, less than]

Percent of total suspended material that is 

organic

Site

number

 (fig. 1) Site name Sample date

Flow 

condition

Total

 suspended 

solids

 concentration

 (mg/L)

Total 

suspended 

solids

 method

Suspended 

sediment 

concentration 

method

Scanning 

electron 

microscope 

method

07194760 Illinois River near Viney Grove 10/26/2005 Base flow 7 20 27 63

07194800 Illinois River at Savoy 10/26/2005 Base flow 3 33 6 67

07195430 Ilinois River south of Siloam 

Springs

10/26/2005 Base flow 2 44 38 56

07196500 Illinois River near Tahlequah 12/7/2005 Base flow <1 80 60 57

07194800 Illinois River at Savoy 8/23/2006 High flow 1,240 10 9 9

07195430 Ilinois River south of Siloam 

Springs

8/23/2006 High flow 230 13 13 6

07196500 Illinois River near Tahlequah 8/24/2006 High flow 12 17 22 1

of organic particles than the other two methods when flow 

conditions are lower and TSS concentrations are less because 

stream velocities also would be less, so inorganic particles 

entrained in the water column would probably have less mass 

(silt and clay-sized particles). Likewise, when flow conditions 

are higher (greater stream velocities), inorganic particles with 

greater mass (sand-size particles), but not necessarily occupying greater space, would be entrained in the water column, 

resulting in lower or similar percentages of organic material 

from the SEM method compared to the other two methods that 

use mass to measure the amount of material. 

Organic and Inorganic Percentages of 

Suspended Material 

The percentage of organic material in the Illinois River 

varied spatially, with flow conditions, and seasonally in 

samples collected at four sites from August 2005 through July 

2007. Organic material in the Illinois River generally composed between 13 and 47 percent (based on 25th and 75th percentiles of samples collected at all of the sites using both TSS 

and SSC methods for determining percentages) of the total 
14 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

suspended material in samples collected from August 2005 

through July 2007. Therefore, most of the suspended material 

in samples collected from the sites was inorganic material. In 

general, the percentage of organic material in samples collected during base-flow conditions was greater than in samples 

collected during high-flow conditions. Organic material composed the greatest percentage of the total suspended material 

in samples from the Illinois River in the winter (December 

through February) and summer (June through August) at 

Savoy; in the spring (March through May), fall (September 

through November), and winter south of Siloam Springs; in 

the winter near Tahlequah; and in the summer near Viney 

Grove. 

Spatial Variability

Overall, the greatest percentage of organic material 

determined from the TSS method was found in samples from 

the Illinois River near Viney Grove compared to the other 

three sites from August 2005 through July 2007 (fig. 10). The 

percentage of organic suspended material in samples from the 

Illinois River near Viney Grove ranged from 7 to 38 percent of 

the suspended material with a median of 28 percent. Because 

high-flow events were not sampled at the Illinois River near 

Viney Grove, the concentrations of inorganic material were 

probably low and effects of biological processes such as algal 

growth would be more prevalent, increasing the percentage of 

organic material in samples. Samples from the Illinois River 

south of Siloam Springs had the least median percentage of 

organic material (16 percent) compared to the other three sites 

and had percentages ranging from 10 to 75 percent of the total 

suspended material. The Illinois River near Tahlequah had 

the greatest range of percentages of organic material, ranging 

from 10 to 81 percent of the total suspended material. The 

Illinois River at Savoy had organic material that composed 10 

to 50 percent of the total suspended material with a median of 

26 percent organic material. 

Using the SSC method for determining the percentage 

of organic material, the greatest median percentage of organic 

material was found in samples from the Illinois River near 

Tahlequah from August 2005 through July 2007 (fig. 10). The 

median percentage of organic material in samples from the 

Illinois River near Tahlequah was 35 percent and the range 

was 12 to 60 percent of the total suspended material. The 

median percentage of organic material using the SSC method 

in samples from Illinois River sites near Viney Grove and at 

Savoy were 24 and 23 percent, respectively, slightly less than 

was determined using the TSS method. Similar to the results 

from the TSS method, the lowest median percentages of 

organic material were found in samples from the Illinois River 

south of Siloam Springs. 

The SEM method showed different results than the other 

two methods, with the greatest percentage of organic material among the four sites in samples from the Illinois River 

at Savoy and the least in samples from the Illinois River near 

Tahlequah (table 2). However, only two samples (one collected 

during base-flow conditions and one collected during highflow conditions) were analyzed for each site except for the 

Illinois River near Viney Grove that had only one sample collected during base-flow conditions. One reason that the SEM 

may show a difference from the TSS and SSC methods may 

be related to the size and mass of the organic and inorganic 

particles in samples collected from the sites. The particlesize distribution in samples from the Illinois River at Savoy 

was mostly silt and clay-sized (90 percent of the particles in 

the base-flow sample and 93 percent in the high-flow sample 

had diameters less than 0.063 millimeters, see appendix) 

compared to the particle size distribution in samples from the 

Illinois River near Tahlequah (56 percent of the particles in the 

base-flow sample and 71 percent in the high-flow sample had 

diameters less than 0.063 millimeters, see appendix).

Hydrologic Variability

In general, organic material (determined from the TSS 

method) composed a smaller percentage of the suspended 

material in samples collected during high-flow conditions 

compared to samples collected during base-flow conditions 

(fig. 10). For example, the organic material composed 23 

percent of the total suspended material (median value) in 

samples collected during base-flow conditions and 13 percent 

in samples collected during high-flow conditions at the Illinois 

River south of Siloam Springs. Samples from the Illinois River 

near Tahlequah had the greatest median percentage of organic 

material (36 percent) during base-flow conditions compared 

to the median percentages in samples from sites on the Illinois 

River near Viney Grove (28 percent), at Savoy (29 percent) 

and south of Siloam Springs (23 percent). However, during 

high-flow conditions, the organic material composed the greatest median percentage of suspended material in samples collected from the Illinois River at Savoy (17 percent) compared 

to the sites on the Illinois River south of Siloam Springs (13 

percent) and near Tahlequah (15 percent) (fig. 10). Samples 

were not collected during high-flow conditions at the Illinois 

River near Viney Grove. The Illinois River south of Siloam 

Springs had the least percentage of organic material during 

high-flow conditions, or conversely, the greatest percentage of 

inorganic material. The greater percentage of inorganic material during high-flow conditions can result from streambank 

failure, streambed scouring, and terrestrial sources, including 

activities that may increase the erosion of soil material such 

as row-crop agriculture, animal grazing, timber harvesting, 

mining, road construction and maintenance, and urbanization 

(Guy, 1970). 

Similar to the results of the TSS method, the results from 

the SSC method also showed the least median percentages 

of organic material in samples collected during high-flow 

conditions (highest percentage of inorganic material) and the 

greatest median percentages of organic material in samples 

collected during base-flow conditions (fig. 10). However, the 
Organic and Inorganic Percentages of Suspended Material 15

SUSPENDED ORGANIC MATERIAL, IN PERCENT OF TOTAL SUSPENDED MATERIAL

0

10

20

30

40

50

60

70

80

90

0

10

20

30

40

50

60

70

80

90

0

10

20

30

40

50

60

70

80

90

ALL SAMPLES

HIGH-FLOW SAMPLES

BASE-FLOW SAMPLES

TSS METHOD SSC METHOD

10

14

13

11

12

16

16 11

10

12

6

8

5

8

3

6

8

8

8

8

8

5

No high-flow

samples

collected 

No high-flow

samples

collected 

SITE, IN DOWNSTREAM ORDER

Illinois River 

near

Tahlequah

Illinois River 

at Savoy

Illinois River 

near

Viney Grove

Illinois River 

south of 

Siloam

Springs

Illinois River 

near

Tahlequah

Illinois River 

at Savoy

Illinois River 

near

Viney Grove

Illinois River 

south of 

Siloam

Springs

 Total suspended solids

 Suspended sediment concentraton

EXPLANATION

90th percentile

75th percentile

25th percentile

Median (50th percentile)

10th percentile

Data value greater than

 or less than 90th

 or 10th percentile

16 Number of samples

TSS 

SSC

Figure 10. Distribution of organic material in water samples collected from August 2005 to July 2007 for the Illinois River sites near 

Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.
16 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River Table 2. Results of scanning electron microscopy analysis of samples collected at the Illinois River sites near Viney Grove, Arkansas; at Savoy Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma. Site number (fig. 1) Site name Sample date Flow condition Common minerals identified, in decreasing abundance Organic material identified Organic material (percent of total suspended material) 07194760 Illinois River near Viney Grove 10/26/2005 Base flow Quartz, kaolinite, potassium feldspar, plagioclase Diatoms and small carbon particulate 63 07194800 Illinois River at Savoy 10/26/2005 Base flow Kaolinite, quartz, potassium feldspar Long filament algae (coated with clay minerals and manganese), diatoms, and small carbon particulate 67 07195430 Ilinois River south of Siloam Springs 10/26/2005 Base flow Quartz, kaolinite, potassium feldspar, plagioclase, titanium oxide, iron oxide Diatoms and small carbon particulate 56 07196500 Illinois River near Tahlequah 12/07/2005 Base flow Quartz, kaolinite, potassium feldspar, plagioclase, apatite Diatoms and small carbon particulate 57 07194800 Illinois River at Savoy 8/23/2006 High flow Quartz, kaolinite, potassium feldspar Diatoms and small carbon particulate

9

07195430 Ilinois River south of Siloam Springs 8/23/2006 High flow Quartz, kaolinite, potassium 

feldspar, albite

Diatoms and small carbon 

particulate

6

07196500 Illinois River near Tahlequah 8/24/2006 High flow Quartz, kaolinite, potassium 

feldspar, calcite, iron oxide

Diatoms and small carbon 

particulate

1
Implications 17

distribution of percentages of organic material in samples collected at high-flow and base-flow conditions at individual sites 

was more variable when values were calculated using the SSC 

method for sites on the Illinois River. For example, in samples 

collected during base-flow conditions at the Illinois River 

south of Siloam Springs, the percentage of organic material 

ranged from 4 to 59 percent of the total suspended material 

compared to percentages determined by the TSS methods, 

which ranged from 12 to 23 percent of the total suspended 

material. 

The results from the SEM method showed that in the 

samples collected during base-flow conditions (one sample 

at each site), organic material particles composed 56 to 67 

percent of the total suspended material particles and in the 

samples collected at high-flow conditions (one sample at 

each sites except for the Illinois River near Viney Grove), the 

material was mostly (more than 90 percent) inorganic particles 

(table 2). Most of the organic material identified during highflow and base-flow conditions was composed of diatoms and 

small carbon particulate matter (table 2 and fig. 11). However, some filamentous algae also were identified in samples 

collected from the Illinois River at Savoy during base-flow 

conditions. Most of the inorganic material at the four sites 

was composed of quartz, kaolinite (a clay-forming mineral), 

and potassium feldspar (table 2 and fig. 11).

Seasonal Variability

The mean seasonal concentrations and percentages of 

organic material (determined from the TSS method) were 

the least in samples collected in the fall from August 2005 to 

July 2007 from the four Illinois River sites, while the greatest 

concentrations and percentages of organic material occurred 

at various times of the year depending on the site (fig. 12). 

The greatest concentrations of organic material occurred in 

the summer (June through August) in samples from sites on 

the Illinois River near Viney Grove, at Savoy, and south of 

Siloam Springs, but in the spring (March through May) in 

samples from the Illinois River near Tahlequah. The greatest percentages of organic material (least percentages of 

inorganic material) occurred in the summer in samples from 

the site near Viney Grove, the winter and summer at the site 

at Savoy, in the spring, fall (September through November), 

and winter (December through February) at the site south of 

Siloam Springs, and in the winter at the site near Tahlequah. 

In samples collected during high-flow conditions, the greatest 

concentrations and percentages of organic material occurred 

in the summer at the Illinois River sites at Savoy and south 

of Siloam Springs and in the winter at the site near Tahlequah. No high-flow samples were collected at the Illinois 

River near Viney Grove for comparison. In samples collected 

during base-flow conditions, the greatest concentrations also 

occurred in the summer at the sites at Savoy, south of Siloam 

Springs, and near Viney Grove, and during the spring at the 

site near Tahlequah. However, the greatest percentage of 

organic material (least percentage of inorganic material) in 

samples collected during base-flow conditions occurred in 

the winter at the Illinois River sites at Savoy, south of Siloam 

Springs, and near Tahlequah, and in the summer at the site 

near Viney Grove. Variability in organic material during different seasons at the four sites could reflect different sources 

of inorganic and organic material. Greater organic mass can 

occur in the spring and summer when water temperatures are 

greater, more sunlight occurs, and base-flow conditions are 

more dominant (lower stream velocities); conditions more 

conducive for increased algal growth in the stream. However, 

some algal groups, such as diatoms, can grow at lower water 

temperatures, such as in the late winter and spring, and also 

can increase the biomass in the stream (Stevenson and others, 

1996). Greater percentages of organic material in the winter 

also may be because the concentration of total suspended 

solids is the least, and even small amounts of organic material could compose a large percentage of the total material. 

The winter months also are dominated by greater base-flow 

conditions with greater streamflow rates than the other seasons 

(fig. 2) with larger inputs of ground water that generally has 

little inorganic suspended material. In the spring and summer 

months, the suspended material also could be more dominated 

by allochthonous sources of organic and inorganic material 

because of the greater occurrence of storm-runoff events and 

more activities in the watershed, such as agriculture and urban 

construction. 

Implications

In addition to variability among the different methods 

used to determine the amount of organic material, sources of 

variability in organic material concentrations and percentages 

among sites during different flow conditions and seasons can 

be difficult to quantify because of the complexities of algal 

dynamics in the streams and the processes that occur in the 

basin that affect the terrestrial sources of organic material. 

Algal biomass can be affected by many factors including nutrient concentrations, stream substrate, light availability (stream 

channel shading), flow velocities, channel structure (pools, 

riffles, runs), and other aquatic fauna (Stevenson and others, 

1996). Terrestrial sources of organic material can be affected 

by season (for example, greater amounts of leaf litter in the 

fall), the location and timing of activities that may increase the 

erosion of soil material (row-crop agriculture, animal grazing, 

timber harvesting, mining, road construction and maintenance, 

and urbanization), and differences in organic material content 

in disturbed soils (Guy, 1970).

Although a wide range of variability is evident in the 

data, several observations can be made about the suspended 

material data collected from the four sites on the Illinois River 

from August 2005 through July 2007. Samples from the 

Illinois River near Savoy had the greatest turbidity, TSS, SSC, 

chlorophyll a, and organic material concentrations among the 
18 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

Explanation

C

Q

K

A

D

50 micrometers

10 micrometers 50 micrometers

Diatom Diatom

Carbon

Quartz

Potassium feldspar

Albite

Diatom

Figure 11. Images of suspended material from a scanning electron microscopy analysis of a sample collected during high-flow 

conditions on August 23, 2006, from the Illinois River at Savoy, Arkansas.
Implications 19

SEASON

Winter Spring Summer Fall

0

1

2

3

4

5

6

SEASON

MEAN SEASONAL SUSPENDED ORGANIC MATERIAL, IN PERCENT OF TOTAL SUSPENDED MATERIAL,

DETERMINED FROM VOLATILE SUSPENDED SOLIDS AND TOTAL SUSPENDED SOLIDS DATA 

0

10

20

30

40

50

60

Base-flow samples

High-flow samples

All samples

MEAN SEASONAL VOLATILE SUSPENDED SOLIDS CONCENTRATIONS, IN MILLIGRAMS PER LITER

0

2

4

6

8

10

12

14

16

18

EXPLANATION

0

1

2

3

4

5

No data

No data

No data

No data

0

10

20

30

40

50

No data

No data

No data

No data

0

10

20

30

40

50

60

No data

0

10

20

30

40

50

No data

Winter Spring Summer Fall

0

20

40

60

80

100

No data

ILLINOIS RIVER NEAR TAHLEQUAH ILLINOIS RIVER NEAR TAHLEQUAH 

 ILLINOIS RIVER NEAR VINEY GROVE ILLINOIS RIVER NEAR VINEY GROVE

ILLINOIS RIVER SOUTH 

OF SILOAM SPRINGS 

ILLINOIS RIVER SOUTH OF SILOAM SPRINGS 

ILLINOIS RIVER AT SAVOY ILLINOIS RIVER AT SAVOY

Figure 12. Seasonal concentrations and percentages of organic material in water samples collected from August 2005 to July 2007 

for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, 

Oklahoma.
20 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

four sites, indicating that it may be the most affected by activities in the basin upstream from the site, causing increased 

suspended inorganic and organic material. Sources of organic 

material can include primary production by periphyton, macrophytes, and phytoplankton; terrestrial plant litter; and soil 

particulates. The greater chlorophyll a concentrations indicate 

the stream habitat and nutrient concentrations (appendix) 

are more conducive for algal growth than at the other sites. 

Downstream from the Illinois River at Savoy, at the site south 

of Siloam Springs, samples had the least chlorophyll a concentrations, the least percentage of organic material (greatest 

percentage of inorganic material), and similar concentrations 

of TSS and SSC as the site at Savoy. This would indicate 

that although a similar concentration of suspended material is 

being transported downstream, less organic material is being 

entrained, transported, or being added to the stream near the 

site south of Siloam Springs compared to the site upstream 

at Savoy. The lesser chlorophyll a concentrations in samples 

from the Illinois River south of Siloam Springs would indicate 

that the stream habitat or chemistry might not be as favorable 

for algal growth (a source of organic material) as observed 

upstream at the site at Savoy. Even farther downstream at the 

Illinois River near Tahlequah, samples had the least turbidity, 

TSS and SSC, and organic material concentrations among the 

four sites, yet had the greatest percentage of organic material 

(determined from the SSC method). The lesser concentrations 

of TSS and SSC and lesser turbidity values would indicate that 

less of the suspended material that was observed in samples 

from the two upstream sites is being transported past the site 

near Tahlequah. The greater percentage of organic material 

in samples from the Illinois River near Tahlequah may be 

because the concentration of inorganic particles is less because 

of deposition upstream from the site, increasing the effects 

of sources of organic material on the total mass of suspended 

material. Also, the channel morphology may be more conducive for algal growth, such as the presence of longer, wider 

pools with less stream velocities. 

Summary

The Illinois River located in northwestern Arkansas and 

northeastern Oklahoma is influenced by point and nonpoint 

sources of nutrient enrichment. This has led to increased algal 

growth within the stream, reducing water clarity. Also, sediment runoff from fields, pastures, construction sites, and other 

disturbed areas, in addition to frequent streambank failure, has 

increased sedimentation within the stream and decreased water 

clarity. A study was conducted by the U.S. Geological Survey, 

in cooperation with the Arkansas Department of Environmental Quality and the U.S. Environmental Protection Agency, to 

characterize the increased turbidity by determining the organic 

and inorganic percentages and mass of suspended material in 

the Illinois River from August 2005 through July 2007. Waterquality samples were collected every 2 months and during four 

high-flow events at three sites on the Illinois River: at Savoy, 

Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma. Water-quality samples also were collected 

every 2 months for the 2-year period at the Illinois River near 

Viney Grove, Arkansas, located upstream from all wastewatertreatment plant discharges in the Illinois River.

Streamflow increased substantially from the most 

upstream site on the Illinois River (with continuous streamflow data) at Savoy to the most downstream site near Tahlequah from August 2005 through July 2007. Also, the mean 

annual streamflow was considerably less from August 2005 

through July 2007 compared to the long-term mean annual 

streamflow recorded at each site.

In general, turbidity, total suspended solids (TSS), suspended-sediment concentration (SSC), organic material concentration (measured as volatile suspended solids and ash-free 

dry mass), and chlorophyll a concentration were the greatest in 

samples collected from the Illinois River at Savoy and the least 

in samples from the most upstream Illinois River site (near 

Viney Grove) and the most downstream site (near Tahlequah) 

from August 2005 through July 2007. For example, the TSS 

at the Illinois River at Savoy had a median of 12 milligrams 

per liter (mg/L), and the SSC had a median of 15 mg/L. The 

Illinois River near Tahlequah had the least TSS with a median 

of 6 mg/L and the least SSC with a median of 10 mg/L. 

The turbidity, TSS, SSC, organic material concentration, 

and chlorophyll a concentration in samples collected during 

high-flow events were greater than in samples collected during 

base-flow conditions at the Illinois River at Savoy, south of 

Siloam Springs, and near Tahlequah. For example, the median 

turbidity for the Illinois River at Savoy was 3 nephelometric 

turbidity ratio units (NTRU) during base-flow conditions 

and 52 NTRU during high-flow conditions. The median VSS 

and ash-free dry mass concentrations were 1.0 and 2.5 mg/L, 

respectively during base-flow conditions, compared to median 

VSS and ash-free dry mass concentrations of 10.0 and 12.7 

mg/L, respectively, during high-flow conditions. 

The results of the three methods used to determine the 

organic and inorganic percentages of the suspended material 

were widely variable among the different methods. Comparisons between the TSS method and the SSC method showed 

that differences between percentages calculated using the 

two methods generally increased as the percentage of organic 

material increased. Much of the differences between the 

results of the TSS and SSC methods may be attributed to the 

sample processing methods. In general, the SEM method 

yielded greater percentages of organic material than the other 

methods in samples collected during base-flow conditions 

when concentrations of TSS were relatively small, except for 

the sample collected at the Illinois River near Tahlequah where 

the SEM value was similar to the SSC method value and less 

than the TSS method value.

Organic material in the Illinois River generally composed between 13 and 47 percent of the total suspended 

material in samples collected from August 2005 through July 

2007. Therefore, most of the suspended material in samples 
References Cited 21

collected from the sites was inorganic material. Overall, 

the highest percentage of organic material was found at the 

Illinois River near Viney Grove using the TSS method and at 

the Illinois River near Tahlequah using the SSC method. The 

Illinois River south of Siloam Springs had the lowest percentage of organic material among the four sites for both methods. 

In general, the percentage of organic material was greater in 

samples collected during base-flow conditions compared to 

samples collected during high-flow conditions. For example, 

organic material at the Illinois River at Savoy composed 29 

percent of the suspended material (median value) during 

base-flow conditions and 17 percent of the suspended material 

(median value) during high-flow conditions (TSS method). 

The mean seasonal concentrations and percentages of 

organic material (from the TSS method) were the least in samples collected in the fall from August 2005 to July 2007 from 

the four Illinois River sites, while the greatest concentrations 

and percentages of organic material occurred at various times 

of the year depending on the site. The greatest concentrations 

of organic material occurred in the summer (June through 

August) in samples from sites on the Illinois River near Viney 

Grove, at Savoy, and south of Siloam Springs, but in the spring 

(March through May) in samples from the Illinois River near 

Tahlequah. The greatest percentages of organic material (least 

percentages of inorganic material) occurred in the summer in 

samples from the site near Viney Grove, the winter and summer at the site at Savoy, in the spring, fall, and winter (December through February) at the site south of Siloam Springs, and 

in the winter at the site near Tahlequah. 

Although a wide range of variability is evident in the 

data, several observations can be made about the suspended 

material data collected from the four sites on the Illinois River 

from August 2005 through July 2007. Samples from the 

Illinois River near Savoy had the greatest turbidity, TSS, SSC, 

chlorophyll a, and organic material concentrations among the 

four sites, indicating that it may be the most affected by activities in the basin upstream from the site, causing increased 

suspended inorganic and organic material. Downstream 

from the Illinois River at Savoy, at the site south of Siloam 

Springs, samples had the least chlorophyll a concentrations, 

the least percentage of organic material (greatest percentage 

of inorganic material), and similar concentrations of TSS and 

SSC as the site at Savoy. This would indicate that although 

a similar concentration of suspended material is being transported downstream, less organic material is being entrained, 

transported, or being added to the stream near the site south 

of Siloam Springs compared to the site upstream at Savoy. 

Even farther downstream at the Illinois River near Tahlequah, 

samples had the least turbidity, SSC and TSS, and organic 

material concentrations among the four sites, yet had the 

greatest percentage of organic material (determined from the 

SSC method). This would suggest that less of the suspended 

material that was observed in samples from the two upstream 

sites is being transported past the site near Tahlequah and the 

concentration of inorganic particles is less because of deposition upstream from the site, or the channel morphology may 

be more conducive for algal growth, increasing the effects of 

sources of organic material on the total mass of suspended 

material.

References Cited

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running waters: London, Chapman and Hall, 388 p.

American Public Health Association, American Water Works 

Association, and Water Pollution Control Federation, 1995, 

Standard methods for the examination of water and wastewater (19th ed.): Washington D.C., American Public Health 

Association, variously paginated.

Arar, E.J., and Collins G.B., 1997, U. S. Environmental 

Protection Agency Method 445.0, In vitro determination 

of chlorophyll a and pheophytin a in marine and freshwater algae by fluorescence, Revision 1.2: Cincinnati, Ohio, 

U.S. Environmental Protection Agency, National Exposure 

Research Laboratory, Office of Research and Development, 

22 p.

Arkansas Department of Environmental Quality, 2008, 

Integrated water-quality assessment report, accessed April 

5, 2008 at URL http://www.adeq.state.ar.us/water/branch_

planning/pdfs/WQ08-04-01.pdf.

Fishman, M.J., ed., 1993, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water 

and fluvial sediments: U.S. Geological Survey Open-File 

Report 93-125, 217 p.

Gray, J.R. and Glysson, G.D., eds., 2003, Proceedings of the 

Federal interagency workshop on turbidity and other sediment surrogates, April 30-May 2, 2002, Reno, Nevada: U.S. 

Geological Survey Circular 1250, 56 p.

Gray, J.R., Glysson, G.D., Turcios, L.M., and Schwarz, G.E., 

2000, Comparability of suspended-sediment concentration 

and total suspended solids data: U.S. Geological WaterResources Investigations Report 00-4191, 14 p.

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of Water-Resources Investigations Reports, book 5, chap. C1, 58 p. 

Guy, H.P., 1970, Fluvial sediment concepts: U.S. Geological Survey Techniques of Water-Resources Investigations 

Reports, book 3, chap. C1, 55 p.
22 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

Maloney, T.J., ed., 2005, Quality management system, U.S. 

Geological Survey National Water Quality Laboratory: U.S. 

Geological Survey Open-File Report 2005-1263, version 

1.3, 9 November 2005, chapters and appendixes variously 

paged.

Rantz, S.E, and others, 1982, Measurement and computation of streamflow: Volume 1. Measurement of stage and 

discharge and Volume 2. Computation of discharge: U.S. 

Geological Survey Water-Supply Paper 2175, 631 p.

Sims, J.T. and Wolf, D.C., 1994, Poultry waste management—

Agricultural and environmental issues: Advances in 

Agronomy, v. 52, p. 1-83.

Stevenson, R.J, Bothwell, M.L., and Lowe, R.L., 1996, Algal 

ecology, freshwater benthic ecosystems: San Diego, Academic Press, Inc., 753 p.

U.S. Census Bureau, 2007, Current Lists of Metropolitan and 

Micropolitan Statistical Areas and Definitions, accessed 

February 26, 2008 at URL http://www.census.gov/population/www/estimates/metrodef.html

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chaps. A1-A9, available online at http://pubs.water.usgs.

gov/twri9A.

U.S. Geological Survey, 2008, Water-resources data for the 

United States water year 2007, accessed May 27, 2008 at 

URL http://wdr.water.usgs.gov/wy2006/search.jsp

Wahl, K.L., and Wahl, T.L., 1995, Determining the flow of 

Comal Springs at New Braunsfel, Texas: Conference of 

Water Resources Engineering, August 16-17, 1995, San 

Antonio, Texas, American Society of Civil Engineers, p. 

77-86.

Wilde, F.D., and Radke, D.B., 1998, Field measurements: U.S. 

Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6, variously paginated.

Wilde, F.D., Radke, D.B., Gibs, J., Iwatsubo, R.T., 1998, 

Cleaning of equipment for water sampling: U.S. Geological 

Survey Techniques of Water-Resources Investigations, Book 

9, chap. A3, variously paginated.
APPENDIX
24 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma. [ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters] Sample date Sample time Dis- charge, instan- taneous (ft3/s) (00061) Flow condition Turbidity, unfiltered, broad band light source (400-680 nm), detectors at multiple angles including 90 and 30 degrees, ratiometric correcion (NTRU) (63676) Dissolved oxygen (mg/L) (00300) pH (standard units) (00400) Specific conduc- tance (μs/cm at 25°C) (00095) Water temper- ature (°C) (00010) Total dissolved solids (mg/L) (70300) Residue, fixed non- filterable (mg/L) (00540) Total sus- pended solids (mg/L) (00530) Volatile sus- pended solids (mg/L) (00535) Ammonia plus organic nitrogen, unfiltered (mg/L as N) (00625) Ammonia, filtered (mg/L as N) (00608) Illinois River near Viney Grove, Arkansas (07194760) 08/31/05 1430 -- Base flow 3.9 6.3 7.8 358 23.6 207 69 -- -- 0.21 <0.04 10/26/05 1300 -- Base flow E2.5 6.8 8.0 380 11.0 215 8 10 2.0 0.20 <0.04 12/13/05 1300 -- Base flow <2.0 11.5 7.7 385 4.6 183 2 2 <1.0 0.21 <0.04 03/07/06 0850 4 Base flow 5.1 7.9 7.7 351 10.6 204 5 7 2.0 0.32 E0.02 05/03/06 0900 40 Base flow 13.0 6.0 7.2 254 19.5 151 9 11 3.0 0.42 E0.04 06/22/06 0930 -- Base flow 12.0 4.5 7.6 366 24.0 207 8 12 4.0 0.32 0.06 08/16/06 0900 -- Base flow 8.1 3.3 7.5 353 24.5 201 8 12 4.0 0.69 0.22 10/04/06 1000 -- Base flow 4.7 6.1 7.6 347 19.7 214 5 6 1.0 0.24 E0.02 01/17/07 1145 199 Base flow 8.3 11.8 7.4 207 3.7 139 5 8 3.0 0.21 E0.01 03/07/07 1405 38 Base flow <2.0 15.6 8.5 269 12.3 167 3 5 1.5 0.22 <0.02 04/10/07 1045 14.4 Base flow <2.0 8.6 7.9 336 10.5 185 2 4 1.0 0.20 <0.02 07/19/07 0700 19.8 Base flow 9.9 5.2 8.1 315 24.2 179 10 13 3.7 0.29 0.02
Appendix 25

Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued

[ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; 

μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters]

Sample 

date

 Sample 

time

Discharge, 

instantaneous 

(ft3/s) 

(00061)

Flow 

condition

Turbidity, 

unfiltered, 

broad band 

light source 

(400-680 nm), 

detectors at 

multiple angles 

including 

90 and 30 

degrees, 

ratiometric 

correcion 

(NTRU) 

(63676)

 Dissolved 

oxygen 

(mg/L) 

(00300)

 pH 

(standard 

units) 

(00400)

Specific 

conductance 

(μs/cm 

at 25°C) 

(00095) 

Water 

temperature

 (°C) 

(00010)

Total 

dissolved 

solids 

(mg/L) 

(70300)

Residue, 

fixed nonfilterable 

(mg/L) 

(00540)

Total 

suspended 

solids 

(mg/L) 

(00530)

Volatile 

suspended 

solids 

(mg/L) 

(00535)

Ammonia

 plus 

organic 

nitrogen, 

unfiltered 

(mg/L as N)

 (00625)

Ammonia, 

filtered 

(mg/L as N) 

(00608)

Illinois River at Savoy, Arkansas (07194800)

08/31/05 1245 7 Base flow 3.2 5.4 7.8 305 25.0 184 8 14 6.0 0.26 <0.04

10/26/05 1400 7 Base flow E2.4 7.8 8.1 334 12.5 191 2 3 1.0 0.24 <0.0412/13/05 1215 11 Base flow 2.7 13 8.0 350 3.1 201 <1 2 <1.0 0.24 <0.04

03/07/06 0950 10 Base flow 3.1 8.6 7.7 303 10.2 178 <1 <1 <1.0 0.42 0.0705/03/06 0715 88 Base flow 12.0 6.6 7.5 249 19.8 149 10 14 3.0 0.54 0.0505/05/06 0715 1,190 High flow 79.0 7.3 7.8 141 16.8 104 91 106 15.0 1.10 0.0406/22/06 0840 7 High flow 4.5 5.7 7.6 329 24.4 189 5 7 2.0 0.38 0.0308/16/06 0800 15 High flow 6.1 3.9 7.5 306 25.4 182 7 11 4.0 0.54 0.0408/23/06 1610 1,840 High flow 930.0 4.2 7.7 202 23.8 122 1,110 1,240 130.0 4.70 0.1110/04/06 0910 37 Base flow 5.6 5.9 7.6 332 20.7 195 6 7 1.0 0.30 0.0201/17/07 0930 549 High flow 15.0 11.3 7.2 212 4.3 131 16 20 4.0 0.42 0.0302/13/07 1600 1,320 High flow 52.0 11.7 7.4 151 5.4 105 59 71 12.0 0.84 0.0503/07/07 1245 84 Base flow 2.8 14.3 8.3 277 11.4 161 5 6 1.5 0.21 <0.02

04/10/07 1145 22 Base flow <2.0 10.2 8.0 322 11.2 186 2 3 <1.0 0.30 E0.02

04/25/07 1230 426 High flow 60.0 9.2 7.7 238 18.5 195 70 80 10.0 1.20 E0.0207/19/07 0815 41 Base flow 6.4 6.2 7.9 297 25.4 171 8 12 3.2 0.33 0.02
26 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued [ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters] Sample date Sample time Dis- charge, instan- taneous (ft3/s) (00061) Flow condition Turbidity, unfiltered, broad band light source (400-680 nm), detectors at multiple angles including 90 and 30 degrees, ratiometric correcion (NTRU) (63676) Dissolved oxygen (mg/L) (00300) pH (standard units) (00400) Specific conduc- tance (μs/cm at 25°C) (00095) Water temper- ature (°C) (00010) Total dissolved solids (mg/L) (70300) Residue, fixed non- filterable (mg/L) (00540) Total sus- pended solids (mg/L) (00530) Volatile sus- pended solids (mg/L) (00535) Ammonia plus organic nitrogen, unfiltered (mg/L as N) (00625) Ammonia, filtered (mg/L as N) (00608) Illinois River south of Siloam Springs, Arkansas (07195430) 08/31/05 0820 107 Base flow 4 6.3 7.9 400 24.5 239 14 17 2.0 0.20 <0.04 10/26/05 0900 100 Base flow E1.0 8.0 8.2 444 11.8 253 <1 2 <1.0 0.19 <0.04 12/13/05 0915 108 Base flow <2.0 12.5 8.3 450 3.7 258 <1 <1 <1.0 0.26 <0.04 03/07/06 1115 106 Base flow <2.0 12.3 7.9 428 11.9 246 <1 <1 <1.0 0.33 <0.04 05/03/06 1115 309 High flow 14.0 7.2 7.5 324 20.0 193 16 19 3.0 0.40 <0.04 05/05/06 0730 3,660 High flow 180.0 6.6 7.0 192 17.4 134 145 167 22.0 1.50 E0.03 06/22/06 0740 67 High flow 5.7 5.8 7.6 420 25.2 242 8 10 2.0 0.28 0.01 08/16/06 0710 54 Base flow 6.0 4.3 7.8 429 26.8 254 10 13 3.0 0.31 0.02 08/23/06 1655 1,670 High flow 170.0 5.5 7.5 240 24.7 144 200 230 30.0 1.30 0.02 10/04/06 0810 221 High flow 6.4 7.2 7.6 370 20.7 218 8 10 1.0 0.20 E0.01 01/17/07 1430 1,490 High flow 12.0 10.4 7.3 245 5.5 147 15 18 3.0 0.36 E0.02 02/13/07 1700 3,770 High flow 120.0 10.1 7.6 211 6.6 130 149 166 18.0 1.20 0.06 03/07/07 1045 338 Base flow <2.0 12.9 8.1 334 9.7 190 4 5 1.2 0.20 <0.02

04/10/07 0920 202 Base flow <2.0 9.3 7.9 368 10.8 202 1 2 <1.0 0.25 <0.02

04/25/07 1500 1,120 High flow 19.0 12.7 7.6 354 19.5 216 52 57 5.6 0.73 E0.0107/18/07 1000 409 Base flow 6.3 7.4 8.1 342 25.2 193 12 14 2.3 0.28 <0.02
Appendix 27

Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued

[ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; 

μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters]

Sample 

date

 Sample 

time

Discharge, 

instantaneous 

(ft3/s) 

(00061)

Flow 

condition

Turbidity, 

unfiltered, 

broad band 

light source 

(400-680 nm), 

detectors at 

multiple angles 

including 

90 and 30 

degrees, 

ratiometric 

correcion 

(NTRU) 

(63676)

 Dissolved 

oxygen 

(mg/L) 

(00300)

 pH 

(standard 

units) 

(00400)

Specific 

conductance 

(μs/cm 

at 25°C) 

(00095) 

Water 

temperature

 (°C) 

(00010)

Total 

dissolved 

solids 

(mg/L) 

(70300)

Residue, 

fixed nonfilterable 

(mg/L) 

(00540)

Total 

suspended 

solids 

(mg/L) 

(00530)

Volatile 

suspended 

solids 

(mg/L) 

(00535)

Ammonia

 plus 

organic 

nitrogen, 

unfiltered 

(mg/L as N)

 (00625)

Ammonia, 

filtered 

(mg/L as N) 

(00608)

Illinois River near Tahlequah, Oklahoma (07196500)

12/07/05 1100 159 Base flow <2.0 14.1 8.1 341 6.4 195 <1 <1 <1.0 E0.08 E0.01

02/02/06 1400 247 High flow <2.0 15.2 8.5 360 11.6 208 1 2 1.0 0.19 0.0204/13/06 1245 240 High flow <2.0 12.5 8.4 321 20.3 184 1 2 1.0 0.26 <0.0505/06/06 1100 3,260 High flow 68.0 7.4 7.2 244 18.3 156 85 96 11.7 0.88 0.0306/13/06 1215 208 Base flow 4.7 9.6 8.0 299 25.7 181 3 3 -- 0.16 0.0208/08/06 1145 116 Base flow 5.6 12.1 7.9 335 29.1 188 8 10 2.0 0.17 0.0108/24/06 1015 565 High flow 6.0 5.0 8.0 355 27.1 210 10 12 2.0 0.35 <0.0110/03/06 1215 344 High flow 5.0 8.5 7.8 323 22.6 185 3 3 <1.0 0.11 <0.02

12/05/06 1030 1,850 High flow 10.0 11.0 7.8 261 7.6 158 16 18 1.8 0.26 <0.0202/12/07 1215 487 Base flow <2.0 12.7 7.8 279 6.5 157 -- -- -- 0.10 <0.0202/14/07 1115 3,740 High flow 79.0 11.1 7.5 286 4.7 163 112 124 12 0.89 0.0304/03/07 1030 236 Base flow 2.2 9.0 8.0 297 19.2 167 4 6 2.0 0.20 <0.0204/26/07 0930 460 High flow 2.1 9.1 7.6 297 17.1 185 9 11 1.5 0.26 <0.0206/07/07 0945 363 Base flow 4.3 6.6 7.9 290 23.5 174 -- -- -- 0.19 <0.0207/18/07 0800 615 Base flow 4.5 6.4 8.1 291 24.6 164 4 6 2.8 0.19 E0.01
28 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued [ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters] Sample date Sample time Nitrite plus nitrate, filtered (mg/L as N) (00631) Total nitrogen, unfiltered (mg/L as N) (00600) Ortho- phos- phorus, filtered (mg/L as P) (00671) Phos- phorus, filtered (mg/L as P) (00666) Phos- phorus, unfiltered (mg/L as P) (00665) Biomass, phytoplan- kton, ash-free dry mass (mg/L) (49953) Biomass, plank- ton, ash weight (mg/L) (81533) Biomass, plankton, dry weight (mg/L) (81354) Chloro- phyll a, phyto- plankton, chromato- graphic- fluoro- metric method (μg/L) (70953) Pheo- phytin a, phyto- plankton (μg/L) (62360) Sus- pended sediment, sieve diameter (percent smaller than 0.063 mm) (70331) Sus- pended sediment concen- tration (mg/L) (80154) Illinois River near Viney Grove, Arkansas (07194760) 08/31/05 1430 2.14 2.4 E0.010 E0.03 0.05 6.6 329 336 -- -- 75 13 10/26/05 1300 2.48 2.7 0.020 E0.03 E0.04 3.4 151 155 0.2 0.5 50 123 12/13/05 1300 2.46 2.7 E0.010 <0.04 E0.03 2.2 89.3 91.5 2.7 1.1 73 60 03/07/06 0850 1.71 2.0 <0.020 <0.04 E0.03 4.5 180 185 8.5 4.6 75 20 05/03/06 0900 1.16 1.6 0.020 E0.03 0.05 5.1 176 182 1.5 4.4 90 19 06/22/06 0930 1.66 2.0 0.031 E0.04 0.07 5.2 236 241 E1.9 E2.3 80 29 08/16/06 0900 1.30 2.0 0.028 E0.02 0.08 5.7 266 271 2.2 3.7 84 12 10/04/06 1000 3.85 4.1 0.035 E0.03 0.06 3.1 146 150 0.7 1.3 87 5 01/17/07 1145 3.42 3.6 0.036 E0.02 0.07 <4.3 194 198 0.4 0.4 84 14 03/07/07 1405 2.49 2.7 E0.004 <0.04 <0.04 <3.0 136 139 3.1 2.2 80 4 04/10/07 1045 2.74 2.9 0.010 <0.04 E0.03 <4.3 191 195 2.0 1.8 73 5 07/19/07 0700 2.02 2.3 0.036 0.04 0.07 <5.0 231 236 1.0 2.3 96 16
Appendix 29

Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued

[ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; 

μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters]

Sample 

date

 Sample 

time

Nitrite 

plus 

nitrate, 

filtered 

(mg/L as 

N) (00631)

Total 

nitrogen, 

unfiltered 

(mg/L as 

N) (00600)

Orthophosphorus, 

filtered 

(mg/L as P) 

(00671)

Phosphorus, 

filtered 

(mg/L as P) 

(00666)

Phosphorus, 

unfiltered 

(mg/L as P) 

(00665)

Biomass, 

phytoplankton, 

ash-free 

dry mass 

(mg/L) 

(49953)

Biomass, 

plankton, ash 

weight 

(mg/L) 

(81533)

Biomass, 

plankton, 

dry weight 

(mg/L) 

(81354)

Chlorohyll a, 

phytoplankton, 

chromatographicfluorometric 

method

 (μg/L) 

(70953)

Pheophytin a, 

phytoplankton 

(μg/L) 

(62360)

Suspended 

sediment, 

sieve 

diameter 

(percent 

smaller 

than 

0.063 mm) 

(70331)

Suspended 

sediment 

concentration 

(mg/L) 

(80154)

Illinois River at Savoy, Arkansas (07194800)

08/31/05 1245 0.41 0.7 0.020 0.04 0.06 <3.8 164 168 1.2 -- 92 610/26/05 1400 0.59 0.8 E0.010 E0.03 0.05 <3.2 138 140 0.7 0.7 90 5512/13/05 1215 1.23 1.5 <0.020 <0.04 E0.03 <2.0 88 90 0.8 0.9 86 5903/07/06 0950 0.52 0.9 E0.010 E0.03 0.05 2.5 95 97 3.0 3.4 82 605/03/06 0715 1.27 1.8 0.070 0.09 0.14 4.8 172 177 1.8 4.6 80 1905/05/06 0715 0.90 2.0 0.100 0.13 0.31 22.5 733 755 5.5 9 85 11806/22/06 0840 0.71 1.1 0.059 0.07 0.10 3.7 168 172 E3.8 E5.6 76 708/16/06 0800 0.14 0.7 0.051 0.05 0.11 6.5 267 273 16.0 7.5 70 908/23/06 1610 0.95 5.7 0.051 0.08 1.61 143.8 3,920 4,070 29.1 56.8 93 1,48010/04/06 0910 3.00 3.3 0.053 0.07 0.09 3.2 145 148 1.7 1.3 87 1001/17/07 0930 3.19 3.6 0.077 0.07 0.14 7.0 222 229 1.2 1.0 88 2602/13/07 1600 1.16 2.0 0.165 0.19 0.28 12.7 511 524 5.5 3.7 82 8303/07/07 1245 2.29 2.5 0.009 <0.04 E0.02 <5.0 225 230 3.7 2.8 74 704/10/07 1145 1.97 2.3 0.017 E0.03 0.05 <4.3 190 193 1.1 1.1 80 604/25/07 1230 1.57 2.8 0.066 0.08 0.25 15.3 484 499 10.3 16.4 94 8607/19/07 0815 1.56 1.9 0.057 0.05 0.09 5.0 230 234 3.3 2.5 96 11
30 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued [ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters] Sample date Sample time Nitrite plus nitrate, filtered (mg/L as N) (00631) Total nitrogen, unfiltered (mg/L as N) (00600) Ortho- phos- phorus, filtered (mg/L as P) (00671) Phos- phorus, filtered (mg/L as P) (00666) Phos- phorus, unfiltered (mg/L as P) (00665) Biomass, phytoplan- kton, ash-free dry mass (mg/L) (49953) Biomass, plank- ton, ash weight (mg/L) (81533) Biomass, plank- ton, dry weight (mg/L) (81354) Chlorophyll a, phyto- plankton, chromato- graphic- fluorometric method (μg/L) (70953) Pheo- phytin a, phyto- plankton (μg/L) (62360) Sus- pended sediment, sieve diameter (percent smaller than 0.063 mm) (70331) Sus- pended sediment concen- tration (mg/L) (80154) Illinois River south of Siloam Springs, Arkansas (07195430) 08/31/05 0820 1.32 1.5 0.120 0.12 0.14 <3.3 144 148 0.4 -- 87 7 10/26/05 0900 2.03 2.2 0.090 0.10 0.11 <3.2 143 145 0.3 0.6 99 80 12/13/05 0915 2.32 2.6 0.140 0.14 0.14 2.2 89 91 1.5 0.9 94 49 03/07/06 1115 1.59 1.9 0.070 0.08 0.08 1.7 73 75 2.2 3.0 67 3 05/03/06 1115 1.79 2.2 0.090 0.11 0.14 6.6 274 281 1.6 4.1 97 13 05/05/06 0730 1.06 2.5 0.130 0.15 0.48 41.4 1,550 1,590 8.6 18.3 92 276 06/22/06 0740 1.38 1.7 0.110 0.12 0.13 6.5 301 308 E1.4 E3.5 72 12 08/16/06 0710 0.79 1.1 0.138 0.14 0.15 3.8 172 176 1.6 3.6 66 18 08/23/06 1655 1.49 2.8 0.250 0.29 0.54 37.7 1,520 1,560 4.8 11.0 94 256 10/04/06 0810 2.75 3.0 0.094 0.11 0.22 3.0 143 146 0.8 0.9 92 12 01/17/07 1430 3.87 4.2 0.081 0.07 0.13 5.4 196 202 1.1 0.8 91 22 02/13/07 1700 1.67 2.8 0.145 0.16 0.34 22.5 834 856 14.1 9.1 92 201 03/07/07 1045 3.14 3.3 0.018 <0.04 0.04 <3.8 168 171 6.2 2.9 79 3 04/10/07 0920 2.53 2.8 0.042 0.05 0.06 <4.3 190 193 1.4 1.3 82 3 04/25/07 1500 2.14 2.9 0.059 0.07 0.16 9.2 323 332 13.2 19.1 91 61 07/18/07 1000 2.11 2.4 0.080 0.09 0.10 <5.0 233 238 1.9 2.0 79 15
Appendix 31

Appendix - Water-quality data from August 2005 to July 2007 for the Illinois River sites near Viney Grove, Arkansas; at Savoy, Arkansas; south of Siloam Springs, Arkansas; and near Tahlequah, Oklahoma.—Continued

[ft3/s, cubic feet per second; nm, nanometers; NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; °C, degrees Celsius; μs/cm, microsiemens per centimeter; N, nitrogen; P, phosphorus; 

μg/L, micrograms per liter; <, less than; E, estimated; nm, nanometers; mm, millimeters]

Sample 

date

 Sample 

time

Nitrite 

plus 

nitrate, 

filtered 

(mg/L as 

N) (00631)

Total 

nitrogen, 

unfiltered 

(mg/L as 

N) (00600)

Orthophosphorus, 

filtered 

(mg/L as P) 

(00671)

Phosphorus, 

filtered 

(mg/L as P) 

(00666)

Phosphorus, 

unfiltered 

(mg/L as P) 

(00665)

Biomass, 

phytoplankton, 

ash-free 

dry mass 

(mg/L) 

(49953)

Biomass, 

plankton, ash 

weight 

(mg/L) 

(81533)

Biomass, 

plankton, 

dry weight 

(mg/L) 

(81354)

Chlorophyll a, 

phytoplankton, 

chromatographicfluorometric 

method

 (μg/L) 

(70953)

Pheophytin a, 

phytoplankton 

(μg/L) 

(62360)

Suspended 

sediment, 

sieve 

diameter 

(percent 

smaller 

than 

0.063 mm) 

(70331)

Suspended 

sediment 

concentration 

(mg/L) 

(80154)

Illinois River near Tahlequah, Oklahoma (07196500)

12/07/05 1100 0.55 0.63 0.014 0.03 0.03 <3.0 127 129 0.8 0.9 56 202/02/06 1400 1.20 1.39 0.023 0.04 0.04 <3.4 149 152 2.5 2.7 58 304/13/06 1245 0.24 0.50 E0.028 0.03 0.04 <3.2 138 140 3.1 3.0 48 605/06/06 1100 1.45 2.33 0.104 0.12 0.23 -- -- -- -- -- 93 9106/13/06 1215 0.70 0.86 0.060 0.07 0.08 <3.3 153 155 2.4 3.2 73 1208/08/06 1145 0.09 0.26 0.069 0.07 0.09 3.8 163 167 3.0 2.5 86 1208/24/06 1015 0.69 1.04 0.091 0.11 0.14 4.8 185 190 2.5 3.0 71 1710/03/06 1215 1.81 1.92 0.078 0.09 0.09 <3.0 136 139 1.2 0.8 -- --12/05/06 1030 3.23 3.49 0.085 0.10 0.12 <5.0 233 237 1.1 1.0 84 2002/12/07 1215 3.17 3.27 0.034 0.04 0.05 <3.2 141 144 1.5 0.4 87 402/14/07 1115 2.55 3.44 0.088 0.10 0.22 18.5 746 764 12.3 7.4 84 14004/03/07 1030 1.80 2.00 0.038 0.05 0.06 <3.6 159 162 6.5 4.0 -- --04/26/07 0930 1.50 1.76 0.046 0.05 0.07 <7.5 338 343 2.8 5.5 77 806/07/07 0945 0.98 1.17 0.056 0.06 0.07 <3.8 165 168 3.4 3.5 -- --07/18/07 0800 1.03 1.22 0.062 0.07 0.07 <5.0 226 230 3.2 2.6 84 8
32 Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River

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Galloway—Organic and Inorganic Percentages and Mass of Suspended Material at Four Sites in the Illinois River—Scientific Investigations Report 2008–5136

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