In cooperation with the University of Wisconsin-Green Bay

Hydrology, Phosphorus, and Suspended Solids in Five 

Agricultural Streams in the Lower Fox River and Green Bay 

Watersheds, Wisconsin, Water Years 2004–06

Scientific Investigations Report 2011–5111

U.S. Department of the Interior

U.S. Geological Survey
Cover photo. Runoff from a field in the Ashwaubenon Creek watershed.
Hydrology, Phosphorus, and Suspended 

Solids in Five Agricultural Streams in the 

Lower Fox River and Green Bay Watersheds, 

Wisconsin, Water Years 2004–06

By David J. Graczyk, Dale M. Robertson, Paul D. Baumgart, and Kevin J. Fermanich

In cooperation with the University of Wisconsin-Green Bay

Scientific Investigations Report 2011–5111

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Grayczyk, D.J., Robertson, D.M., Baumgart, P.D., and Fermanich, K.J., 2012, Hydrology, phosphorus, and suspended 

solids in five agricultural streams in the Lower Fox River and Green Bay Watersheds, Wisconsin, Water Years 2004–06: 

U.S. Geological Survey Scientific Investigations Report 2011–5111, 28 p.
iii

Contents

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

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

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

Study Sites .....................................................................................................................................................3

Land Use.................................................................................................................................................3

Watershed and Channel Lengths and Slopes..................................................................................4

Soil Characterization............................................................................................................................4

Methods of Data Collection and Analysis .................................................................................................5

Precipitation Monitoring......................................................................................................................5

Streamflow and Water-Quality Data Collection...............................................................................5

Flow Separation ....................................................................................................................................5

Load Computation.................................................................................................................................6

Statistical Analyses..............................................................................................................................6

Hydrology and Water Quality.......................................................................................................................8

Hydrologic Conditions..........................................................................................................................8

Precipitation..................................................................................................................................8

Streamflow..................................................................................................................................10

Water Quality.......................................................................................................................................12

Water Quality During Base Flow and 

Runoff Events ................................................................................................................12

Suspended Solids and Phosphorus Loads ............................................................................16

Annual Loads and Yields...........................................................................................................16

Seasonality in Loads ........................................................................................................20

Distribution of Daily Flows and Loads ...........................................................................20

Volumetrically Weighted Concentration................................................................................20

Comparison Among Streams ............................................................................................................26

Use of Data for Modeling Studies.............................................................................................................26

Summary........................................................................................................................................................26

References Cited..........................................................................................................................................27

Figures

1. Location of study sites in the Lower Fox River Watershed,

 in northeastern Wisconsin.........................................................................................................2

2. Ratio of dissolved phosphorus to total phosphorus (DP/TP), with breakpoints 

in daily mean discharge for the five sites in the study ...........................................................7

3. Monthly and annual precipitation at four sites in the study area for water years

2004–06, and monthly, annual, and long-term precipitation at the NOAA 

weather station at Austin Straubel Airport, Green Bay, Wisconsin................................................. 8

4. Streamflow characteristics for Apple, Ashwaubenon, Baird, and Duck Creeks 

and the East River.......................................................................................................................10
iv 

5. Total suspended solids concentrations in Apple, Ashwaubenon, Baird, 

Tables

1. Land use and land cover in the watersheds of the five sites in the study..........................4

2. Mean overland slopes by major land use and land-cover class in the 

watersheds of the five sites in the study ..................................................................................4

3. Main stream channel length, mean stream slope, and mean slope 

of the watersheds of the five sites in the study.......................................................................4

4. Soil characteristics and hydrological groups in the watersheds of the 

five sites in the study, based on data in the Soil Survey Geographic Database................4

5. Discharge breakpoints in the dissolved phosphorus to total phosphorus 

(DP/TP) ratio relation and median values of the ratio less than and greater 

than the breakpoints for the at the five sites in the study......................................................6

6. Monthly and annual precipitation at rain gages in the study area and the

National Oceanographic and Atmospheric Administration rain gage............................................ 9

7. Summary of streamflow characteristics for the five sites in the study.............................11

8. Summary of total suspended solids data collected at five sites in in the study ............................13

9. Summary of total phosphorus data collected at five sites in in the study ........................14

10. Summary of dissolved phosphorus data collected at five sites in in the study ...............15

11. Suspended solids, total phosphorus, and dissolved phosphorus loads 

and yields for five sites in the study ........................................................................................17

12. Monthly loads and percentage of the total load at the five sites in the study .................21

13. Percentage of total annual discharge, suspended sediment load, 

and total phosphorus load transported over a specified number of days 

for the five sites in the study.....................................................................................................24

14. Volumetically weighted concentrations of suspended solids, 

total phosphorus, and dissolved phosphorus for the five sites in the study.....................25
v

Conversion Factors

Multiply By To obtain

Length

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.004047 square kilometer (km2

)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3

) 0.02832 cubic meter (m3) 

Flow rate

cubic foot per second (ft3

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

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

ton, short (2,000 lb) 0.9072 metric ton per year

ton per year (ton/yr) 907.2 kilogram per year (kg/yr)

ton per year (ton/yr) 0.9072 metric ton per year

Yield rate

cubic foot per second per square

mile (ft3

/s/mi2)

0.010953 cubic meter per second per square

kilometer (m3/s/km2)

pound per square mile (lb/mi2

) 0.017514 kilogram per square kilometer 

(kg/km2

)

ton per square mile (ton/mi2

) 350.27 kilogram per square kilometer 

(kg/km2

)

Slope

feet per mile (ft/mi) 0.1894 meter per kilometer (m/km)

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

°F=(1.8×°C)+32

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

micrograms per liter (μg/L).
vi

Abbreviations

ADCP Acoustic Doppler current profiler

BMP Best-management practices

DEM Digital Elevation Model

DP Dissolved phosphorus

GCLAS Graphical Constituent Loading Analysis System

GBMSD Green Bay Metropolitan Sewerage District

LFR Lower Fox River

LFRWMP Lower Fox River Watershed Monitoring Program

NOAA National Oceanographic and Atmospheric Administration

NRCS National Resources Conservation Service

RAP Remedial Action Plan

SSURGO Soil Survey Geographic

SWAT Soil and Water Assessment Tool

SWTP Southeastern Wisconsin Till Plains

TMDL Total Maximum Daily Load

TP Total phosphorus

TSS Total suspended solids

USGS U.S. Geological Survey

UWGB University of Wisconsin-Green Bay

UWM University of Wisconsin-Milwaukee

VWC Volumetrically weighted concentration

WDNR Wisconsin Department of Natural Resources

WY Water year
Hydrology, Phosphorus, and Suspended Solids in 

Five Agricultural Streams in the Lower Fox River and 

Green Bay Watersheds, Wisconsin, Water Years 2004–06

By David J. Graczyk1, Dale M. Robertson1, Paul D. Baumgart2, and Kevin J. Fermanich2

Abstract 

A 3-year study was conducted by the U.S. Geological 

Survey and the University of Wisconsin-Green Bay to characterize water quality in agricultural streams in the Fox/Wolf 

watershed in northeastern Wisconsin and provide information to assist in the calibration of a watershed model for the 

area. Streamflow, phosphorus, and suspended solids data were 

collected between October 1, 2003 and September 30, 2006 

in five streams, including Apple Creek, Ashwaubenon Creek, 

Baird Creek, Duck Creek, and the East River. During this 

study, total annual precipitation was close to the 30-year normal of 29.12 inches. The 3-year mean streamflow was highest 

in the East River (113 ft3

/s), followed by Duck Creek 

(58.2 ft3/s), Apple Creek (26.9 ft3/s), Baird Creek (12.8 ft3/s), 

and Ashwaubenon Creek (9.11 ft3/s). On a yield basis, during these three years, the East River had the highest flow 

(0.78 ft3/s/mi2), followed by Baird Creek (0.61 ft3/s/mi2), 

Apple Creek (0.59 ft3/s/mi2), Duck Creek (0.54 ft3/s/mi2), 

and Ashwaubenon Creek (0.46 ft3/s/mi2). 

The overall median total suspended solids (TSS) concentration was highest in Baird Creek (73.5 mg/L), followed 

by Apple and Ashwaubenon Creeks (65 mg/L), East River 

(40 mg/L), and Duck Creek (30 mg/L). The median total phosphorus (TP) concentration was highest in Ashwaubenon Creek 

(0.60 mg/L), followed by Baird Creek (0.47 mg/L), Apple 

Creek (0.37 mg/L), East River (0.26 mg/L), and Duck Creek 

(0.22 mg/L). 

The average annual TSS yields ranged from 111 tons/mi2

in Apple Creek to 45 tons/mi2 in Duck Creek. All five watersheds yielded more TSS than the median value (32.4 tons/mi2

) 

from previous studies in the Southeastern Wisconsin Till 

Plains (SWTP) ecoregion. The average annual TP yields 

ranged from 663 lbs/mi2 in Baird Creek to 382 lbs/mi2 in Duck 

Creek. All five watersheds yielded more TP than the median 

value from previous studies in the SWTP ecoregion, and the 

Baird Creek watershed yielded more TP than the statewide 

median of 650 lbs/mi2

 from previous studies.

Overall, Duck Creek had the lowest median and volumetric weighted concentrations and mean yield of TSS and 

TP. The same pattern was true for dissolved phosphorus (DP), 

except the volumetrically weighted concentration was lowest in the East River. In contrast, Ashwaubenon, Baird, and 

Apple Creeks had greater median and volumetrically weighted 

concentrations and mean yields of TSS, TP, DP than Duck 

Creek and the East River. Water quality in Duck Creek and 

East River were distinctly different from Ashwaubenon, Baird, 

and Apple Creeks.

Loads from individual runoff events for all of these 

streams were important to the total annual mass transport of 

the constituents. On average, about 20 percent of the annual 

TSS loads and about 17 percent of the TP loads were transported in 1-day events in each stream. 

Introduction

Phosphorus and sediment are the primary stressors to 

the Green Bay ecosystem in northeastern Wisconsin, and they 

impair more beneficial uses than any other stressors (Harris 

and others, 1994). In addition to impairing the Green Bay 

ecosystem, phosphorus is exported from Green Bay to Lake 

Michigan and increases its productivity. Excessive algae and 

suspended sediment (often measured as suspended solids) in 

lower Green Bay and Lake Winnebago, upstream of Green 

Bay (fig.1), reduce their water clarity and impair major water 

uses (Millard and Sager, 1994; Wisconsin Department of Natural Resources, 1993). To reach the goals for water clarity and 

water chemistry, total phosphorus (TP) and total suspended 

solids (TSS), in lower Green Bay, the Science and Technical Advisory Committee recommended that external loads of 

TP and TSS be reduced by 50 percent (Green Bay Remedial 

Action Plan, 2000).

Approximately 70 percent of the annual TP load to Green 

Bay and 25 percent of the annual TP load to Lake Michigan 

is from the Fox River (approximately 558,000 kg, Robertson, 

1997; Klump and others, 1997; Pauer and others, 2005). About 

half of this load originates in watersheds that are within the 

610-mi2

 Lower Fox River (LFR) watershed (fig. 1; Wisconsin 

1

 U.S. Geological Survey

2

 University of Wisconsin-Green Bay.
2 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Lower Fox River

study area

Land use/land cover based on composite of 2000–2001 land use from Brown 

County Planning Department, 2000 land use from East Central Wisconsin 

Regional Planning Commission, and 1992 WISCLAND land-cover image from 

the Wisconsin Department of Natural Resources

Lower Fox sub-basin boundary

Study watershed boundary

Main channel of study stream

County boundary

Streamflow-gaging station

Land use and land cover

Urban

Golf course

Agriculture

Grassland

Forest

Open water

Wetland

Barren

EXPLANATION

BROWN COUNTY

BROWN COUNTY

OUTAGAMIE COUNTY

WINNEBAGO

COUNTY

CALUMET COUNTY

G r e e n

B a y

L a k

e

W i n

n e b a g o East River USGS 

streamflow-gaging 

station #040851378

Baird Creek USGS 

streamflow-gaging 

station #040851325

Duck Creek USGS 

streamflow-gaging 

station #04072150

Ashwaubenon Creek 

USGS streamflow-gaging 

station #04085068

Apple Creek 

USGS streamflow-gaging 

station #04085046

0 5 10 MILES

0 5 10 KILOMETERS

Fox River

Apple Creek

East River

Baird Creek

Fox River

Duck Creek

Ashwaubenon Creek

Green

Bay

Appleton

Austin Straubel

International

Airport

Figure 1. Location of study sites in the Lower Fox River Watershed, in northeastern Wisconsin.
Study Sites 3

Department of Natural Resources, 1993), which is within 

the Southeastern Wisconsin Till Plains (SWTP) ecoregion. 

The LFR watershed is the most downstream watershed of the 

6,330-mi2 Fox-Wolf Basin, which drains a large part of Northeastern Wisconsin and represents about 15 percent of the Lake 

Michigan drainage basin. The LFR watershed is dominated by 

agricultural land use, which primarily consists of dairy farm 

operations, but there are relatively large urban centers near the 

outlet of Lake Winnebago and along the Fox River. Because of 

impairment from nonpoint-source pollution, nearly all of the 

subwatersheds and streams in the LFR watershed have been 

classified as priority watersheds or listed as impaired waters 

under Section 303(d) of the Clean Water Act (U.S. Environmental Protection Agency, 2009) by the Wisconsin Department of Natural Resources (WDNR). Therefore, substantial 

reductions in the export of TP and TSS from the LFR watersheds are needed to achieve the desired water-quality goals. 

In reviews of historical water-quality and biological monitoring of streams within the LFR watershed by the 

University of Wisconsin-Green Bay (UWGB) and in the 

Green Bay Remedial Action Plan (RAP), it was concluded 

that more data were needed to provide adequate baseline 

data to: 1) better characterize TP and TSS export from this 

area; 2) support the establishment of Total Maximum Daily 

Loads (TMDLs) to reduce TP and TSS export; 3) support 

water-quality modeling that will be used as a tool in assessing alternative pollutant-reduction schemes to achieve 

water-quality targets; and 4) track water-quality and habitat trends. As a result, UWGB obtained a grant from Arjo 

Wiggins Appleton, Inc., with additional funding from the 

U.S. Geological Survey (USGS), the Oneida Nation, and the 

Green Bay Metropolitan Sewerage District (GBMSD), to 

establish a habitat and water-quality monitoring network. The 

network consisted of five key agricultural watersheds in the 

LFR watershed that were identified as significant contributors 

of nutrients and TSS to the LFR and Green Bay, which represent the range in land use and environmental conditions in the 

area. The Lower Fox River Watershed Monitoring Program 

(LFRWMP) was established to support these monitoring 

efforts. The LFRWMP is a multiyear education, monitoring, and assessment program in and around the LFR watershed. The program was administered by UWGB, with major 

cooperators that include the USGS, University of WisconsinMilwaukee (UWM), GBMSD, Oneida Nation, and six local 

high schools. The overall goal of the LFRWMP program was 

to establish a long-term monitoring network that engages 

watershed stakeholders in the collection of high quality data. 

These data can be used to: educate the community on how 

agricultural watersheds affect water quality, aid in water-quality modeling, and predict impacts of management decisions 

on the ecosystem. The long-term goal of this project was to 

develop cost-effective approaches to reduce the delivery of TP 

and TSS to the Lower Green Bay of Lake Michigan by using 

water-quality models to scale up the methodology and results 

from LFRWMP studies to encompass the entire Fox-Wolf 

River drainage basin.

Purpose and Scope

The purpose of this report is to describe the watersheds of 

the five LFR streams and summarize streamflow, precipitation, 

and water-quality data that were collected by the USGS and 

UWGB for these streams for three water years, from October 

1, 2003 to September 30, 2006. A water year (WY) is defined 

as the 12-month period from October 1 for any given year 

through September 30 of the following year, and is designated 

by the year in which the period ends. Additional data, collected as part of the LFRWMP but not discussed in this report, 

include: 1) habitat, macroinvertebrate, and fish-survey data, 

and real-time sonde data collected by UWM; 2) water-quality, 

habitat, macroinvertebrate, amphibian and bird surveys data 

collected by local high schools; 3) additional monitoring at 

Baird and Duck Creeks by USGS and UWGB after 2006; 

and 4) studies conducted by students from UWGB, including 

those examining the effects of urbanization in the Baird Creek 

watershed (Fink, 2005), the forms of phosphorus at different 

spatial scales in the LFR watershed (Reckinger, 2007), and the 

changes in land management, water quality and biotic conditions in Duck Creek over a 20-year period (Cibulka, 2009).

Study Sites 

As part of this project, five sites were examined in 

the LFR watershed (fig. 1). Monitoring stations at four of 

these sites were installed as part of this study. Streamflowgaging stations equipped with continuous data recorders 

were installed in October 2003 on Apple Creek at Sniderville 

(USGS station number–04085046; 45.8 mi2 drainage area), 

Ashwaubenon Creek near Little Rapids (04085068; 19.9 mi2), 

and Baird Creek at Green Bay (040851325; 20.8 mi2); and one 

station was installed in December 2003, on the East River at 

Green Bay (040851378; 145 mi2). A streamflow-gaging station 

had previously been installed in May 1988 at the fifth site on 

Duck Creek near Howard (04072150; 108 mi2). 

Land Use

The land use/land cover in the watersheds of the 

five study sites is summarized in table 1 and displayed in 

figure 1. Agriculture is the dominant land use and ranges from 

58 percent in the East River watershed to 78 percent in the 

Ashwaubenon Creek watershed. The proportion of wetlands 

ranges from less than 1 percent in the Ashwaubenon Creek 

watershed to 10 percent in Baird Creek watershed. Forested 

areas range from 6 percent in the Apple Creek watershed to 

14 percent in the East River watershed. Urban areas range 

from 7 percent in the Baird Creek watershed to 27 percent in 

the Apple Creek watershed.
4 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Table 1. Land use and land cover in the watersheds of the five sites in the study. 

[Drainage area in square miles, land use and land cover in percent of watershed] 

Watershed Drainage 

area

Land use/land cover

Urban Recreation Cropland Grassland Forest Water Wetland Barren

Apple Creek

Ashwaubenon Creek

45.8

19.9

27

11

1

0

62

78

1

2

6

9

1

0

1

0

1

0

Baird Creek 20.8 7 1 66 3 13 0 10 0

Duck Creek 108 8 0 67 2 12 1 8 1

East River 145 20 1 58 2 14 0 4 1

Watershed and Channel Lengths and Slopes

Mean overland slopes, derived from the WDNR 30-m 

Digital Elevation Model (DEM), are summarized in table 2 by 

major land use/land cover classes for each watershed. Slopes 

in urban and cropland areas are relatively gentle. Cropland and 

urban slopes range from 1 percent in the Ashwaubenon Creek 

watershed to about 2 percent in the East River watershed. 

Forested areas have slopes that are often 2–3 times those of 

cropland and urban areas.

Table 2. Mean overland slopes by major land use and 

land-cover class in the watersheds of the five sites in the study. 

[Drainage area in square miles, land use and land cover in percent of watershed]

Watershed Urban Cropland Forest All

Apple Creek

Ashwaubenon Creek

1.2

1.0

1.3

1.0

3.0

1.7

1.4

1.0

Baird Creek 1.1 1.1 2.8 1.1

Duck Creek 1.8 1.6 2.3 1.7

East River 1.7 2.0 5.7 2.2

The main channel lengths and mean stream slopes of 

each of the monitored streams are summarized in table 3. 

The Wisconsin Department of Natural Resources 24k 

Version 6 hydrography shapefile was used to determine the 

spatial extent of the designated named main channel for each 

stream; however, the south branch of Ashwaubenon Creek 

was merged with the main channel of Ashwaubenon Creek 

for purposes of calculating the combined channel length and 

slope. Stream slopes range from 6.5 ft/mi in Duck Creek to 

18.3 ft/mi in Baird Creek.

Table 3. Main stream channel length, mean stream slope, and 

mean slope of the watersheds of the five sites in the study. 

[ Length in miles, and slopes in feet per mile]

Watershed Length Overall mean 

stream slope

Mean slope of 

watersheds

Apple Creek 19.9 9.3 8.8

Ashwaubenon Creek 11.8 14.3 10.6

Baird Creek 9.6 18.3 22.4

Duck Creek 35.9 6.5 11.1

East River 42.3 7.3 25.8

Soil Characterization

Soil characteristics for each watershed (table 4) were 

estimated from the Soil Survey Geographic (SSURGO) 

Database (U.S. Department of Agriculture, National Resources 

Conservation Service, 2007a). Only the surface soils, from the 

surface to a depth of 5 ft, were quantified. Soils in the LFR 

area are relatively impermeable silt and clay loams, and result 

in high relative runoff rates and low base flow. Soil types are 

mostly silt loam to silty clay loam. Silt loam soils represent 

about 50 percent of soils in each of the five watersheds. The 

percent clay in surface soils ranged from 15 percent in the 

Duck Creek watershed to 26 percent in the Ashwaubenon and 

Apple Creek watersheds. The Duck Creek watershed has the 

highest proportion of sand in the surface soil (35 percent), and 

generally has the most permeable soils. Therefore, its flow is 

expected to have the lowest proportion of surface runoff and 

highest proportion of base flow. 

Table 4. Soil characteristics and hydrological groups in the 

watersheds of the five sites in the study, based on data in the 

Natural Resources Conservation Service’s (NRCSs) Soil Survey 

Database.

[All values are in percent ]

Apple 

Creek

Ashwaubenon 

Creek

Baird 

Creek

Duck 

Creek

East 

River

Soil texture components

Sand 26 25 27 35 30

Silt 48 49 52 50 50

Clay 26 26 21 15 20

NRCS hydrologic group*

A 4 4 1 5 2

A/D 1 0 7 5 2

B 7 5 2 9 12

B/D 1 1 0 6 1

C 84 87 75 72 77

D 5 5 14 3 6

*

When thoroughly wet, runoff potential is A: low, B: moderately low, 

C: moderately high, and D: high.
Methods of Data Collection and Analysis 5

The proportions of soils of specific hydrologic groups are 

summarized in table 4 for each watershed. The U.S. Department of Agriculture, National Resources Conservation Service 

(NRCS) National Soil Survey Handbook (2007b) defines a 

hydrologic group as a group of soils having similar runoff 

potential under similar storm and cover conditions. When 

thoroughly wet, runoff potential is defined as either A: low, 

B: moderately low, C: moderately high, and D: high. In addition, soils designated as dual soil hydrologic groups (A/D and 

B/D) are wetland soils and exhibit properties of a D soil when 

undrained. The combined proportion of soils in hydrologic 

groups C and D soils ranged from 75 percent at Duck Creek to 

92 percent at Ashwaubenon Creek. These groups have a layer 

that impedes the downward movement of water, which results 

in slow to very slow infiltration rates and moderately high to 

high runoff potential. Therefore, most of the soils in the five 

LFRWMP watersheds are expected to have high runoff potential under saturated conditions.

Methods of Data Collection and 

Analysis

Precipitation Monitoring

To describe precipitation throughout the LFR watershed, 

precipitation gages were installed near the stream gages on 

Apple, Ashwaubenon, Baird, and Duck Creeks in October 

2003. Precipitation was collected in 8-in. diameter tipping 

bucket rain gages. Rainfall was summed and recorded every 

5 minutes during non-freezing periods. During winter months 

(November through March), daily precipitation was obtained 

from the long-term National Oceanographic and Atmospheric 

Administration (NOAA) precipitation station at the Green Bay 

Airport (Austin Straubel Airport; fig. 1). 

Streamflow and Water-Quality Data Collection

Streamflow-gaging stations equipped with data recorders 

were installed at each site (fig. 1). At all stations except the 

one at the East River site, stages were measured with a gaspurge-pressure system and recorded in a Campbell Scientific 

data logger. Discharge measurements were made according to 

standard USGS methods every 4 to 6 weeks and more frequently during high flow to define a stage-discharge relation 

for each site (Rantz and others, 1982). An acoustic Doppler 

current profiler (ADCP) was installed at the East River site 

to measure water velocities because this site is affected by 

backwater and seiche effects from Green Bay. Water velocities 

and the cross-sectional areas were then used to determine the 

discharge at this site (Laenen, 1985; Oberg and others, 2005; 

Ruhl and Simpson, 2005). Streamflow data were published 

each year in “Water Resources Data, Wisconsin” for water 

years 2004 through 2006 (Waschbusch and others, 2005–07). 

Each station was equipped with a stage-activated, refrigerated sampler for automated collection of water samples that 

are representative of different flow conditions (increasing and 

decreasing flow). A data logger was programmed to collect 

a sample with each 0.2-ft increase in stage once the stage 

reached an initial sampling threshold. The initial sampling 

threshold was variable and changed seasonally. After the stage 

peaked, samples were collected with each 0.4-ft decrease in 

stage. This sampling strategy was designed to collect most 

samples during increasing stage, when constituent concentrations were expected to be changing most rapidly. Samples 

were only collected at the East River during positive flows to 

Green Bay. To minimize the possibility of collecting water 

from Green Bay, the data logger would send a signal to the 

sampler to collect a sample after a set volume of water passed 

the gage in a positive direction. During events, a daily sample 

was analyzed which was a composite of positive flow subsamples. After the samples were collected, they were chilled 

to 4°C and then analyzed for TSS and TP. A subset of the 

samples was selected and vacuum filtered through 0.45 μm 

mixed cellulose ester membranes, and then analyzed for dissolved phosphorus (DP).

In addition to the automated samples, manual samples 

were collected at each station at a fixed interval − approximately every two weeks in spring, summer, and fall, and once 

a month in winter. These samples were integrated over the 

depth and width of the stream by use of a hand-held sampler 

(Edwards and Glysson, 1999). The fixed-interval samples 

were analyzed for TSS, TP, and DP. Paired manual-automated 

samples were collected to test for any potential bias in the 

autosampler; corrections were applied if needed.

All water samples were analyzed by the GBMSD according to standard methods. TSS was analyzed using Standard 

Method 2540 D (Clesceri and others, 1998). TP and DP 

were analyzed using colorimetric methods using Automated 

Block Digester Method 365.4 from the U.S. EPA Methods for 

Chemical Analysis of Water and Wastes (U.S. Environmental 

Protection Agency, 1983). In this study, DP samples were fully 

digested, so they represent the total dissolved P in the water 

samples.

Flow Separation

Daily mean flows were separated into either base flow or 

overland runoff by use of the Base Flow Index (BFI) automated hydrograph separation program (Institute of Hydrology, 

1980 a,b), and the results were used to classify samples into 

either base-flow samples or runoff samples. The BFI program divides the water year into N-day increments and the 

minimum flow for each N-day period is identified, where 

N is a user-specified duration in days. The application was 

run using standard Institute of Hydrology methods with a 

5-day interval. Overland runoff—the difference between the 

daily mean discharge and base flow—is water that flows over 

the land surface and enters the stream. Base flow primarily 
6 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

represents groundwater discharge to the stream. Each day 

was classified as either dominated by overland runoff or 

base flow. If less than 80 percent of the daily mean flow was 

classified as base flow, then that day was considered a runoff 

event and the samples collected on that day were classified as 

runoff samples. In addition, samples collected within a few 

days following runoff events were also classified as being 

runoff samples. The number of affected days were computed 

from the drainage area of the watersheds (in square miles) 

raised to the 0.20 power and rounded up to the next whole 

value (Viessman and others, 1977). The number of extra days 

affected by runoff was 2 days for Apple, Ashwaubenon, and 

Baird Creeks, and 3 days for Duck Creek and the East River.

Load Computation

TSS and TP loads were computed for the entire monitoring period using the Graphical Constituent Loading Analysis 

System (GCLAS; Koltun and others, 2006). GCLAS is a 

program developed by the USGS to estimate loads of waterquality constituents from instantaneous measurements of 

streamflow and constituent concentration, which collectively 

can be used to compute instantaneous loads. Generally, concentrations are linearly extrapolated between measurements 

except at the beginning and end of each event. Prior to the 

extrapolations, additional concentrations are often added to 

the time series to better describe concentrations just prior to an 

event and just following an event, or to describe events with 

no measured concentrations. Concentrations at the beginning 

of an event were estimated from concentrations measured 

during previous base-flow periods. Concentrations at the end 

of the events were estimated from concentrations measured 

shortly after the end of an event. For the East River site, the 

monthly and annual loads were adjusted for reverse flows and 

negative daily loads. Data collection at the East River was 

started in December of 2003; therefore, for WY 2004, loads 

were only estimated from December 16 to September 30.

Samples were analyzed for DP to describe general 

changes during different flow conditions and different seasons. Loads for DP were not calculated directly from GCLAS 

because too few samples were analyzed to adequately characterize the variability during runoff events required for 

accurate daily load estimation. Therefore, to estimate loads, a 

ratio of DP to TP concentrations (DP/TP) was first computed 

based on all available coinciding samples. Time series plots 

of the DP/TP ratio were constructed for each site to determine 

if there was seasonality in this ratio; however, no seasonality was found. Scatterplots between DP/TP ratios and daily 

mean discharge demonstrated a nonlinear response (fig. 2). 

Therefore, breakpoints were computed such that streamflow 

partitioned the ratios into two groups that minimized the intragroup variance and maximized the intergroup variance. The 

breakpoints were determined by use of regression-tree analysis 

in the statistical package SPLUS (Lam, 2001). The flow breakpoint was different for each stream (table 5). The median DP/

TP ratios below and above the flow breakpoints are also listed 

in table 5. The DP/TP ratio below the breakpoint (low flows) 

ranged from 0.50 for the East River to about 0.7–0.8 for the 

other four sites. The DP/TP ratios above the breakpoint (high 

flows) were all about 0.4–0.5. Each day was assigned a DP/TP 

ratio based on daily mean discharge, and then daily DP loads 

were computed by multiplying the TP load by the DP/TP ratio.

Statistical Analyses

To determine if median concentrations for each constituent for a specified flow condition were statistically different 

among sites, a nonparametric Kruskal-Wallis test was first 

performed to determine if there were differences among the 

groups. If the Kruskal-Wallis test indicated there were differences, then the data were ranked, and a Tukey multiple-comparison procedure was used to determine which groups were 

statistically different from one another (SAS Institute, Inc., 

2004). All statistical differences were significant at p < 0.05, 

unless otherwise stated.

Table 5. Discharge breakpoints in the dissolved phosphorus to total phosphorus (DP/TP) ratio relation and 

median values of the ratio less than and greater than the breakpoints for the at the five sites in the study.

[ft3/s, cubic feet per second]

Stream Breakpoint, in ft3/s Median ratio - dissolved phosphorus/total phosphorus

Ratio less than breakpoint Ratio greater than breakpoint

Apple Creek 106 0.71 0.37

Ashwaubenon Creek 33.6 0.78 0.45

Baird Creek 16.8 0.67 0.47

Duck Creek 533 0.74 0.38

East River 755 0.50 0.40
Methods of Data Collection and Analysis 7

0.0

0.2

0.4

0.6

0.8

1.0

0 100 200 300 400 500 600 700 800 900 1000 1100

0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

1.0

0 100 200 300 400 500 600 700 800 900

0.0

0.2

0.4

0.6

0.8

1.0

0

Mean daily discharge, in cubic feet per second (f3/s)

200 400 600 800 1000 1200 1400 1600 1800

1000

East River

Breakpoint at 755 ft 3

/s

Duck Creek

Breakpoint at 533 ft 3

/s

Baird Creek

Breakpoint at 16.8 ft 3

/s

Ashwaubenon Creek

Breakpoint at 33.6 ft 3

/s

Apple Creek

Breakpoint at 106 ft 3

/s

Ratio DP/TP Ratio DP/TP Ratio DP/TP Ratio DP/TP Ratio DP/TP

Figure 2. Ratio of dissolved phosphorus to total phosphorus (DP/TP), with breakpoints in daily mean discharge for the five sites 

in the study.
8 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Hydrology and Water Quality

Hydrologic Conditions

Precipitation, stream discharge, and runoff data were 

collected at the five monitoring stations during WYs 2004–06, 

and are described in the following sections.

Precipitation

The 30-year normal (1971–2000) total annual precipitation for the study area was 29.12 in., based on data collected at 

the weather station at the Green Bay Airport (fig. 1; National 

Oceanic and Atmospheric Administration, 2006). Total annual 

precipitation for each of the three monitoring years was close 

to the long-term normal precipitation.

In WY 2004, total annual precipitation was slightly above 

normal at all sites, ranging from 30.13 in. (0.94 in. above normal, 3 percent) at Apple Creek to 32.40 in. (3.21 in. above normal, 11 percent) at Ashwaubenon Creek (table 6 and fig. 3). The 

highest monthly precipitation was 9.12 in. at Baird Creek in May 

2004, which was 6.37 in. (232 percent) above normal. Minimum 

monthly precipitation was 0.24 in. at Ashwaubenon Creek in 

October 2003, which was 1.93 in. below normal (-89 percent). 

In WY 2005, total annual precipitation was slightly below 

normal at Duck Creek (29.05 in, -0.14 in., -1 percent), Apple 

Creek (28.45 in., -0.74 in., -3 percent), and Baird Creek (28.76 

in, -0.43 in., -1 percent; table 6 and fig. 3), but above normal at 

Ashwaubenon Creek (31.48 in., 2.29 in., 8 percent). The highest 

monthly precipitation was 5.57 in. in August at Ashwaubenon 

Creek, which was 2.00 in. above normal (53 percent). Minimum 

monthly precipitation was 1.33 in. in February and March 2005, 

estimated from the Green Bay airport when most precipitation 

occurred as snow.

0

5

10

15

20

25

30

35

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Total

Precipitation, in inches

Water year 2004

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

NOAA Green Bay airport

Long-term average

0

5

10

15

20

25

30

35

Water year 2005

0

5

10

15

20

25

30

35

Water year 2006

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Total

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Total

Precipitation, in inches Precipitation, in inches

EXPLANATION

Figure 3. Monthly and annual precipitation at four sites in the study area for water years 2004–06, and monthly, annual, and long-term precipitation 

at the National Oceanographic and Atmospheric Administration (NOAA) weather station at Austin Straubel Airport, Green Bay, Wisconsin.
Hydrology and Water Quality 9

Table 6. Monthly and annual precipitation at rain gages in the study area and the National Oceanographic and 

Atmospheric Administration (NOAA) rain gage, for water years 2004–06.

[all values are in inches]

Month

Watershed NOAA

Apple Creek Ashwaubenon 

Creek Baird Creek Duck Creek Green Bay airport

Water year 2004

October 1.051 0.24 0.65 1.051 1.05

November 4.58 5.02 4.07 3.96 3.83

December 1.681 1.681 1.681 1.681 1.68

January 1.241 1.241 1.241 1.241 1.24

February 1.621 1.621 1.621 1.621 1.62

March 3.581 3.581 3.581 3.581 3.58

April 1.04 1.26 1.31 1.56 1.56

May 7.57 8.21 9.12 8.33 8.31

June 4.10 4.84 4.03 3.79 4.87

July 1.82 1.81 1.42 1.28 1.78

August 1.57 2.38 1.21 1.81 2.00

September 0.28 0.52 1.23 0.56 0.47

Total 30.13 32.40 31.16 30.46 31.99

Water year 2005

October 3.84 3.95 3.40 4.56 3.70

November 1.801 1.93 1.98 2.01 1.80

December 2.261 2.261 2.261 2.261 2.26

January 1.601 1.601 1.601 1.601 1.60

February 1.331 1.331 1.331 1.331 1.33

March 1.331 1.331 1.331 1.331 1.33

April 1.67 1.49 1.55 1.531 1.53

May 2.20 2.34 2.00 2.20 2.52

June 3.13 4.23 3.24 2.62 3.44

July 2.61 1.97 1.70 1.70 1.46

August 3.94 5.77 5.57 4.231 4.23

September 2.74 3.28 2.80 3.68 3.08

Total 28.45 31.48 28.76 29.05 28.28

Water year 2006

October 1.31 1.27 0.95 1.67 1.59

November 2.86 3.09 3.41 3.25 3.07

December 1.041 1.041 1.041 1.041 1.04

January 1.641 1.641 1.641 1.641 1.64

February 1.341 1.341 1.341 1.341 1.34

March 1.161 1.161 1.161 1.161 1.16

April 1.86 2.06 2.20 2.07 1.97

May 4.12 5.04 6.88 5.90 5.90

June 1.44 1.15 2.74 2.84 2.83

July 3.92 2.86 4.72 3.141 3.14

August 1.17 1.40 1.98 1.93 2.11

September 2.19 3.41 3.09 3.82 3.33

Total 24.05 25.46 31.15 29.80 29.12

1

 Monthly total from NOAA Green Bay airport precipitation station.
10 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

In WY 2006, total annual precipitation was slightly above 

normal at Duck Creek (29.80 in., 0.61 in., 2 percent) and Baird 

Creek (31.15 in., 1.96 in., 7 percent), but below normal at 

Apple Creek (24.05 in., -5.14 in., -18 percent) and Ashwaubenon Creek (25.46 in., -3.73 in., -13 percent; table 6 and fig. 3). 

The highest monthly precipitation was 6.88 in. in May at 

Baird Creek, which was 4.13 in. (150 percent) above normal. 

Minimum monthly precipitation was 0.95 in. in October at 

Baird Creek, which was 56 percent below normal.

Streamflow

Annual mean streamflow was the highest in WY 2004 

at all sites. In WY2004, the highest mean flow of 178 ft3/s 

occurred in the East River and lowest mean flow of 14.6 ft3/s 

occurred in Ashwaubenon Creek (table 7 and fig. 4). In WY 

2005, the highest mean flow was 72.6 ft3/s in the East River and 

the lowest mean flow was 6.4 ft3/s in Baird Creek. In WY2006, 

the highest mean flow was 87.4 ft3/s in the East River and the 

lowest mean flow was 5.4 ft3/s in Ashwaubenon Creek.

The average of the three annual mean streamflows was the 

highest in the East River (113 ft3/s), followed by Duck Creek 

(58.2 ft3/s), Apple Creek (26.9 ft3/s), Baird Creek (12.8 ft3s), 

and Ashwaubenon Creek (9.1 ft3/s) (table 7 and fig. 4). On a 

yield basis, the East River had the highest average streamflow (0.78 ft3

/s/mi2), followed by Baird (0.61 ft3/s/mi2), Apple 

(0.59 ft3/s/mi2), Duck (0.54 ft3/s/mi2), and Ashwaubenon 

(0.46 ft3/s/mi2) Creeks.

The annual yield of water was the highest in the 

East River in WY 2004 (1.23 ft3/s/mi2) and WY 2006 

(0.60 ft3/s/mi2), and in WY 2005 the highest was in Apple 

Creek (0.55 ft3/s/mi2) (table 7 and fig. 4). The annual yield 

of water was lowest in all years in Ashwaubenon Creek and 

ranged from 0.27 to 0.73 ft3/s/mi2.

The majority of flow (83–91 percent of total flow over 

the 3 years) at all sites came from overland runoff: 91 percent 

for Ashwaubenon Creek and about 85 percent for the other 

sites. Estimates of base flow were not made at the East River 

site because the flows often reverse and the daily mean 

discharge was occasionally negative. Base flow represented 

16 to 22 percent of the total annual flow. For Baird Creek, 

base flow represented 21 percent of the total flow in WY 

2004, 12 percent in WY 2005, 16 percent in WY 2006, and 

17 percent for the 3 years. In comparison, on average, base 

flow accounted for 14 percent of the flow in Apple Creek, 

15 percent in Duck Creek, and 9 percent in Ashwaubenon 

Creek. 

Lowest daily flows occurred in the East River because 

of negative flows associated with flow reversals caused by 

seiches in Green Bay. Duck Creek had the next lowest daily 

mean flows, and had no flow for seven consecutive days. The 

highest of the minimum daily flows occurred in Baird Creek 

(0.23 ft3/s), followed by Ashwaubenon and Apple Creeks, both 

with 0.02 ft3/s.

0

50

100

150

200

WY 2004 WY 2005 WY 2006 Average

0

0.1

0.2

0.3

0.4

WY 2004 WY 2005 WY 2006 Average

Annual mean base flow yield,

in cubic feet per second per square mile

0

0.3

0.6

0.9

1.2

1.5

WY 2004 WY 2005 WY 2006 Average

0

5

10

15

20

WY 2004 WY 2005 WY 2006 Average

Annual mean streamflow yield,

in cubic feet per second per square mile

Annual mean base flow,in cubic feet per second

Annual mean streamflow,

in cubic feet per second

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

EXPLANATION

Figure 4. Streamflow characteristics for Apple, Ashwaubenon, Baird, and Duck Creeks and the East River, for water 

years 2004–06.
Hydrology and Water Quality 11

Table 7. Summary of streamflow characteristics for the five sites in the study, for water years 2004–06.

[ft3/s, cubic feet per second; ft3/s/mi2, cubic feet per second per square mile; NA, not available; NC, not computed]

Streamflow characteristics WY 2004 WY 2005 WY 2006 3-year average

Apple Creek

 Annual mean streamflow, ft3/s 42.1 25.0 13.5 26.9

 Annual mean runoff , inches 12.5 7.4 4.0 8.0

 Annual streamflow yield, ft3/s/mi2 0.92 0.55 0.29 0.59

 Annual mean base flow, ft3/s 4.4 2.0 3.0 3.1

 Annual mean base flow yield, ft3/s/mi2 0.28 0.13 0.19 0.20

 Percent base flow 10% 8% 22% 14%

 Lowest daily mean, ft3/s 0.05 0.02 0.08 NA

 Annual 7-day-minimum 0.09 0.04 0.34 NA

Ashwaubenon Creek

 Annual mean streamflow, ft3/s 14.6 7.4 5.4 9.1

 Annual mean runoff , inches 10.0 5.0 3.7 6.2

 Annual streamflow yield, ft3/s/mi2 0.73 0.37 0.27 0.46

 Annual mean base flow, ft3/s 1.1 0.5 0.6 0.7

 Annual mean base flow yield, ft3/s/mi2 0.06 0.03 0.03 0.04

 Percent base flow 8% 7% 11% 9%

 Lowest daily mean, ft3/s 0.04 0.02 0.03 NA

 Annual 7-day-minimum 0.06 0.02 0.04 NA

Baird Creek

 Annual mean streamflow, ft3/s 21.9 6.4 9.9 12.8

 Annual mean runoff , inches 14.3 4.2 6.5 8.3

 Annual streamflow yield, ft3/s/mi2 1.05 0.31 0.48 0.61

 Annual mean base flow, ft3/s 4.6 0.8 1.6 2.3

 Annual mean base flow yield, ft3/s/mi2 0.22 0.04 0.08 0.11

 Percent base flow 21% 12% 16% 17%

 Lowest daily mean, ft3/s 0.23 0.23 0.26 NA

 Annual 7-day-minimum 0.26 0.26 0.36 NA

Duck Creek

 Annual mean streamflow, ft3/s 97.5 47.0 30.2 58.2

 Annual mean runoff , inches 12.3 5.9 3.8 7.3

 Annual streamflow yield, ft3/s/mi2 0.90 0.44 0.28 0.54

 Annual mean base flow, ft3/s 17.6 4.6 5.3 9.2

 Annual mean base flow yield, ft3/s/mi2 0.16 0.04 0.05 0.08

 Percent base flow 18% 10% 18% 15%

 Lowest daily mean, ft3/s 0.00 0.00 0.00 NA

 Annual 7-day-minimum 0.02 0.00 0.00 NA

East River

 Annual mean streamflow, ft3/s 178 72.6 87.4 113

 Annual mean runoff , inches 13.3 6.8 8.2 9.4

 Annual streamflow yield, ft3/s/mi2 1.23 0.50 0.60 0.78

 Annual mean base flow, ft3/s NC NC NC NC

 Annual mean base flow yield, ft3/s/mi2 NC NC NC NC

 Percent base flow NC NC NC NC

 Lowest daily mean, ft3/s -401 -551 -431 NA

 Annual 7-day-minimum 7.50 2.0 1.7 NA

1

 Negative daily mean flow result of reverse flow
12 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Water Quality

Water quality in the five monitored streams varied as a 

function of flow. Therefore, in addition to describing overall 

water quality, water quality is described during periods classified as base-flow or overland-runoff dominated. 

 The overall median TSS concentration was highest in 

Baird Creek (73.5 mg/L; table 8 and fig. 5), slightly lower in 

Apple and Ashwaubenon Creeks (about 65 mg/L), moderate in the East River (40 mg/L), and lowest in Duck Creek 

(30 mg/L). Median TSS concentrations in Baird, Ashwaubenon, and Apple Creeks were not statistically different from 

each other, and median TSS concentrations of Duck Creek and 

East River were not statistically different from each other; the 

TSS concentrations were significantly different between the 

two groups (table 8). The highest maximum TSS concentration 

was measured in Ashwaubenon Creek (6,180 mg/L), followed 

by Baird Creek (2,810 mg/L), Apple Creek (2,460 mg/L), 

East River (1,040 mg/L), and Duck Creek (956 mg/L).

The overall median TP concentration was highest in 

Ashwaubenon Creek (0.60 mg/L; table 9 and fig. 6), followed 

by Baird Creek (0.47 mg/L), Apple Creek (0.37 mg/L), East 

River (0.26 mg/L), and Duck Creek (0.22 mg/L). The median 

TP concentrations in Ashwaubenon Creek, Baird Creek and 

Apple Creek were statistically different from each other. 

TP concentrations in Duck Creek and East River were not 

statistically different from each other, but were different from 

the other three sites. The highest maximum TP concentration 

was measured in Ashwaubenon Creek (9.46 mg/L), followed 

by the East River (5.64 mg/L), Apple Creek (4.96 mg/L), 

Baird Creek (3.22 mg/L), and Duck Creek (2.79 mg/L). 

Median total phosphorus concentrations at the five study 

sites were above both the reference or background concentration of 0.03-0.04 mg/L determined for streams in this area of 

Wisconsin (Robertson and others, 2006a) and the 0.075-mg/L 

phosphorus criteria for wadeable streams in Wisconsin 

(J. Baumann, Wisconsin Department of Natural Resources, 

written commun., 2010).

The overall median DP concentration was highest in 

Ashwaubenon Creek (0.33 mg/L; table 10 and fig. 7), followed by Baird Creek (0.20 mg/L), Apple Creek (0.18 mg/L), 

East River (0.15 mg/L), and Duck Creek (0.13 mg/L). Median 

DP concentration for Ashwaubenon Creek was statistically 

different from those at the other four sites. Median DP concentrations for Baird and Apple Creeks were not statistically 

different from each other, but different from the other three 

sites. Median DP concentrations for East River and Duck 

Creek were not statistically different, but different from the 

other three sites. The highest maximum DP concentration was 

measured in the East River (3.25 mg/L), followed by Ashwaubenon (1.23 mg/L), Apple (1.00 mg/L), Baird (0.69 mg/L), 

and Duck (0.44 mg/L) Creeks.

Water Quality During Base Flow and 

Runoff Events

Median TSS concentrations during base flow ranged from 

34 mg/L in the East River to 4 mg/L in Duck Creek (table 8 and 

fig. 5). The median TSS concentration during base flow in East 

River was much higher (statistically different) than the other 

sites. The high concentrations in the East River may be due to 

greater algal productivity in this large stream. Concentrations in 

Ashwaubenon Creek were second highest and statistically different from all other sites. The median TSS base-flow concentrations in Apple and Baird Creeks were next highest and not 

statistically different from each other. Apple and Baird Creeks 

were statistically different from all other sites except Duck 

Creek. The median base-flow concentration in Duck Creek was 

lowest and statistically different from all sites except Apple 

Creek.

Median TSS concentrations during runoff events ranged 

from 119 mg/L in Baird Creek to 43 mg/L in the East River 

(table 8 and fig. 5). The median TSS concentrations during 

runoff events were not statistically different in Baird, Ashwaubenon, and Apple Creeks. Median TSS concentrations 

during runoff events were also not statistically different in Duck 

Creek and the East River, but these sites were statistically different from the other three sites. Median TSS concentrations 

during base flow and runoff events in the East River were fairly 

similar (34 and 43 mg/L, respectively). For all of the other sites, 

concentrations of TSS were much higher during runoff events 

than during base flow. Higher concentrations during runoff 

events than during base flow indicate that overland flow may be 

suspending sediments from the land surface, stream banks, and 

from the bottom of channels.

Median TP concentrations during base flow ranged from 

0.26 mg/L in Ashwaubenon Creek to 0.12 mg/L in Baird and 

Duck Creeks (table 9 and fig. 6). The median TP concentration in Ashwaubenon Creek and the East River during base 

flow were not statistically different from one another. Median 

concentrations in Apple and Baird Creeks were slightly lower 

(statistically significant) than these two but not statistically 

different from one another. Median TP concentration in Duck 

Creek was the lowest, but not statistically different from Baird 

Creek. The highest median TP concentration during runoff 

events was highest in Ashwaubenon Creek (0.64 mg/L), followed by Baird Creek (0.57 mg/L), Apple Creek (0.44 mg/L), 

East River (0.27 mg/L), and Duck Creek (0.26 mg/L). Only 

the median concentrations in the East River and Duck Creek 

were not statistically different from each other. These runoff 

concentrations were higher than during base flow by a factor 

of about 2–3. All median TP concentrations were above both 

the reference concentration of 0.03–0.04 mg/L determined for 

streams in this area of Wisconsin (Robertson and others, 2006a), 

and the 0.075-mg/L phosphorus criteria for wadeable streams 

in Wisconsin (J. Baumann, Wisconsin Department of Natural 

Resources, written commun., 2010).
Hydrology and Water Quality 13

Figure 5. Total suspended 

solids concentrations in Apple, 

Ashwaubenon, Baird, and Duck 

Creeks and the East River, during 

different flow conditions, for 

water years 2004–06.

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

255 270 266 187 158 224 209 227 160 134 31 43 39 27 24

30 Number of

values

EXPLANATION

Schematic boxplot

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper detached

Upper outside

Suspended solids concentration, in milligrams per liter

10,000

1,000

100

 10

 1

ALL SAMPLES OVERLAND-RUNOFF SAMPLES BASE-FLOW SAMPLES

Table 8. Summary of total suspended solids data collected at five sites in in the study, for water years 2004–06.

[Median values with the same letters are not statistically different from one another at p<0.05; median values with two 

letters are similar with either letter. Concentrations are in milligrams per liter]

Apple Creek Ashwaubenon Creek Baird Creek Duck Creek East River

All data (both base-flow and overland-runoff samples)

Minimum

25th percentile

Mean

Median

75th percentile

Maximum

Number of samples

2.00

20.0

184

65a

202

2,460

255

2.00

25.2

236

65.5a

184

6,180

252

2.00

16.0

305

73.5a

279

2,810

266

2.00

8.85

92.6

30b

112

956

187

2.50

22.0

71.6

40b

85.5

1,040

158

Base-flow samples

Minimum

25th percentile

Mean

Median

75th percentile

Maximum

Number of samples

2.00

3.05

8.50

5cd

8.00

51.0

31

2.00

4.65

15.9

9b

23.0

64.0

43

2.00

3.55

7.31

5c

8.85

52.0

39

2.00

2.10

5.08

4d

5.00

18.0

27

3.00

20.8

36.7

34a

43.8

96.0

24

Runoff samples

Minimum

25th percentile

Mean

Median

75th percentile

Maximum

Number of samples

2.00

33.8

209

90.5a

245

2,460

224

5.00

38.0

286

99a

251

6,180

209

3.00

33.5

356

119a

377

2,810

227

2.50

13.0

107

51.5b

128

956

160

2.50

24.0

77.8

43b

91.5

1,040

134
14 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Figure 6. Total phosphorus 

concentrations in Apple, 

Ashwaubenon, Baird, and 

Duck Creeks and the East 

River, during different flow 

conditions, for water years 

2004–06.

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

255 270 266 188 158 224 227 227 159 134 31 43 39 27 24

30 Number of

values

EXPLANATION

Schematic boxplot

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper detached

Upper outside

Total phosphorus concentration, in milligrams per liter

10.00

1.00

0.10

 0.01

ALL SAMPLES OVERLAND-RUNOFF SAMPLES BASE-FLOW SAMPLES

Table 9. Summary of total phosphorus data collected at five sites in in the study, for water years 2004–06.

[Median values with the same letters are not statistically different from one another at p<0.05; median values with two 

letters are similar with either letter. Concentrations are in milligrams per liter]

Apple Creek Ashwaubenon Creek Baird Creek Duck Creek East River

All data (both base-flow and overland-runoff samples)

Minimum

25th percentile

Mean

Median

75th percentile

Maximum

Number of samples

0.074

0.230

0.520

0.37c

0.610

4.96

257

0.070

0.410

0.770

0.60a

0.840

9.46

270

0.040

0.250

0.670

0.47b

0.860

3.22

266

0.050

0.140

0.350

0.22d

0.440

2.79

186

0.010

0.180

0.480

0.26d

0.390

5.64

158

Base-flow samples

Minimum

25th percentile

Mean

Median

75th percentile

Maximum

Number of samples

0.070

0.110

0.190

0.16b

0.215

0.500

31

0.070

0.150

0.329

0.26a

0.420

1.32

43

0.040

0.090

0.225

0.12bc

0.230

2.700

39

0.060

0.070

0.118

0.12c

0.145

0.210

27

0.010

0.160

0.410

0.205a

0.308

2.68

24

Runoff samples

Minimum

25th percentile

Mean

Median

75th percentile

Maximum

Number of samples

0.080

0.280

0.560

0.44c

0.640

4.96

224

0.180

0.470

0.859

0.64a

0.905

9.46

227

0.060

0.325

0.747

0.57b

0.925

3.22

227

0.050

0.170

0.396

0.26d

0.490

2.79

159

0.040

0.190

0.502

0.27d

0.428

5.64

134
Hydrology and Water Quality 15

Figure 7. Dissolved 

phosphorus concentrations in 

Apple, Ashwaubenon, Baird, and 

Duck Creeks and the East River 

during different flow conditions, 

for water years 2004–06.

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

103 97 102 71 47 87 73 81 56 37 16 24 21 14 8

30 Number of

values

EXPLANATION 

Schematic boxplot

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper detached

Upper outside

Dissolved phosphorus, in milligrams per liter

10.00

5.00

1.00

0.50

 0.10

 0.05

 0.01

ALL SAMPLES OVERLAND-RUNOFF SAMPLES BASE-FLOW SAMPLES

Table 10. Summary of dissolved phosphorus data collected at five sites in in the study, for water years 2004–06.

[Median values with the same letters are not statistically different from one another at p<0.05; median values with two 

letters are similar with either letter. Concentrations are in milligrams per liter]

Apple Creek Ashwaubenon Creek Baird Creek Duck Creek East River

All data (both base-flow and overland-runoff samples)

Minimum 0.040 0.050 0.020 0.040 0.040

25th percentile 0.140 0.230 0.110 0.090 0.090

Mean 0.210 0.368 0.228 0.150 0.289

Median 0.18b 0.33a 0.20b 0.13c 0.15c

75th percentile 0.250 0.460 0.330 0.180 0.210

Maximum 1.00 1.23 0.690 0.440 3.25

Number of samples 103 97 102 70 45

Base-flow samples

Minimum 0.040 0.050 0.040 0.040 0.045

25th percentile 0.070 0.120 0.080 0.050 0.060

Mean 0.127 0.286 0.122 0.089 0.103

Median 0.105b 0.165a 0.094b 0.065b 0.085b

75th percentile 0.175 0.318 0.160 0.118 0.148

Maximum 0.420 1.14 0.280 0.220 0.180

Number of samples 16 24 21 14 8

Runoff samples

Minimum 0.060 0.090 0.020 0.040 0.040

25th percentile 0.160 0.260 0.130 0.110 0.100

Mean 0.228 0.396 0.255 0.166 0.170

Median 0.19bc 0.34a 0.22b 0.14d 0.16cd

75th percentile 0.260 0.470 0.350 0.235 0.220

Maximum 1.00 1.23 0.690 0.440 0.420

Number of samples 87 73 81 56 37
16 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Median DP concentrations during base flow ranged from 

0.165 mg/L in Ashwaubenon Creek to 0.065 mg/L in Duck 

Creek (table 10 and fig. 7). The median DP concentration during base flow in Ashwaubenon Creek was statistically different 

than those at the other four sites, which were not statistically 

different from one another. Median DP concentrations during 

runoff events ranged from 0.34 mg/L in Ashwaubenon Creek 

to 0.14 mg/L in Duck Creek. The median DP concentration in 

Ashwaubenon Creek was again the highest and statistically 

different from the other four sites. Median concentrations in 

Baird and Apple Creeks were next highest and not statistically 

different from one another. Median concentrations in Duck 

Creek and East River were the lowest and not statistically 

different from one another, but statistically different from the 

other sites. DP concentrations were about twice as high during 

runoff events than during base flow.

Suspended Solids and Phosphorus Loads

TSS, TP, and DP concentration data alone may not reflect 

the true impact of nutrients because the amount of sediment 

and phosphorus transported downstream (load) to receiving 

waters, such as Green Bay, can impair the waters’ beneficial 

uses. Therefore, daily, monthly, and annual loads and yields 

were computed for TSS, TP, and DP.

Annual Loads and Yields

Average annual TSS loads ranged from 10,300 tons in 

the East River to 1,720 tons in Ashwaubenon Creek (table 11 

and fig. 8). Loads in the East River were highest because it has 

the largest drainage area and highest flows. To better enable 

comparisons among the river and creeks, annual yields (loads 

per unit area of the watershed) were examined. The average 

annual TSS yield was highest in the Apple Creek watershed 

(111 tons/mi2), followed by Baird Creek (95 tons/mi2), Ashwaubenon Creek (87 tons/mi2

), East River (71 tons/mi2), and 

Duck Creek (45 tons/mi2) watersheds (table 11 and fig. 9). 

The yields varied by a factor of about 2.5. All five streams had 

higher yields than the median value of 32.4 tons/mi2 based on 

previously monitored streams in the SWTP ecoregion, but the 

yields were similar to or a little less than the statewide median 

value of 111 tons/mi2 based on previously monitored streams 

(Corsi and others, 1997).

Annual TSS loads and yields were highest in each 

stream in WY 2004 (table 11, and figs. 8 and 9). TSS loads in 

WY 2004 were highest in the East River (22,700 tons, even 

though this value only represented a partial year: December 16 to September 30), followed by Apple (12,000 tons), 

Duck (10,200 tons), Baird (4,350 tons), and Ashwaubenon 

(3,680 tons) Creeks. The lowest annual loads were transported 

in WY 2006, with the exception of Baird Creek and the East 

River, which had their lowest loads in WY 2005. 

Average annual TP loads ranged from 77,400 lbs in the 

East River to 12,400 lbs in Ashwaubenon Creek (table 11 

and fig. 8). The greatest amount of TP was transported in 

WY 2004, similar to TSS. The East River transported the most 

TP (138,000 lbs, even though this value only represents a partial year), followed by Duck (68,100 lbs), Apple (48,900 lbs), 

Baird (27,800 lbs), and Ashwaubenon (21,100 lbs) Creeks. 

The lowest amount of TP was transported in WY 2006 for 

all of the sites except Baird Creek and the East River, which 

had their lowest loads in 2005. The average annual TP yields 

were highest from Baird Creek (648 lbs/mi2), followed by 

Ashwaubenon Creek (625 lbs/mi2), Apple Creek (576 lbs/mi2), 

East River (533 lbs/mi2), and Duck Creek (382 lbs/mi2). 

The yields varied by a factor of about 1.7. All five watersheds 

had higher yields than the median value of 283 lbs/mi2, based 

on previously monitored streams in the SWTP ecoregion 

(283 lbs/mi2; Corsi and others, 1997). Only Baird Creek 

yielded more TP than the median value in previously monitored watersheds throughout the state of 650 lbs/mi2

 (fig. 9).

Average annual DP loads ranged from 35,200 lbs in 

the East River to 6,470 lbs in Ashwaubenon Creek (table 

11 and fig. 8). The average annual DP yields were highest 

from Ashwaubenon Creek (325 lbs/mi2), followed by Baird 

Creek (322 lbs/mi2), Apple Creek (252 lbs/mi2), East River 

(243 lbs/mi2), and Duck Creek (200 lbs/mi2). The yields varied 

by a factor of about 1.6. Over 50 percent of the phosphorus 

in Ashwaubenon and Duck Creeks was transported in the 

dissolved form. The greatest amount of DP was transported in 

WY 2004. East River transported the most DP (59,900 lbs), 

followed by Duck (34,200 lbs), Apple (20,300 lbs), Baird 

(13,300 lbs), and Ashwaubenon (10,600 lbs) Creeks. The 

lowest amount of DP was transported in WY 2006 in all of the 

streams except for Baird Creek and the East River, which had 

the lowest transport in WY 2005. The percentage of phosphorus transported in the dissolved form was highest in Ashwaubenon and Duck Creeks (52 percent), followed by Baird 

Creek (49 percent), East River (45 percent), and Apple Creek 

(44 percent).
Hydrology and Water Quality 17

Table 11. Suspended solids, total phosphorus, and dissolved phosphorus loads and yields for five sites in the study, water years 2004–06.

[NC, not computed; tons/mi2, tons per square mile; lbs/mi2, pounds per square mile]

Water year

Suspended solids Total phosphorus Dissolved phosphorus

Load 

(tons)

Annual yield

(tons/mi2)

Load

(pounds)

Annual yield

 (lbs/mi2)

Load

 (pounds)

Annual yield

(lbs/mi2)

Apple Creek

2004 12,000 262 48,900 1,070 20,300 443

2005 1,850 40 20,800 454 9,600 210

2006 1,420 31 9,270 202 4,760 104

Total 15,300 NC 79,000 NC 34,600 NC

Average 5,100 111 26,300 576 11,500 252

Ashwaubenon Creek

2004 3,680 185 21,100 1,060 10,600 533

2005 1,150 58 10,700 538 5,660 284

2006 340 17 5,500 276 3,120 157

Total 5,170 NC 37,300 NC 19,400 NC

Average 1,720 87 12,400 625 6,470 325

Baird Creek

2004 4,350 209 27,800 1,340 13,300 639

2005 565 27 4,350 209 2,690 129

2006 1,040 50 8,240 396 4,100 197

Total 5,960 NC 41,400 NC 20,100 NC

Average 2,000 95 13,800 648 6,700 322

Duck Creek

2004 10,200 94 68,100 631 34,200 317

2005 3,500 32 39,200 363 18,800 174

2006 845 8 16,600 154 11,800 109

Total 14,500 NC 124,000 NC 64,800 NC

Average 4,840 45 41,300 382 21,600 200

East River

2004a 22,700 157 138,000 952 59,900 413

2005 2,670 18 38,100 263 19,400 134

2006 5,550 38 56,000 386 26,200 181

Totala 30,900 NC 232,000 NC 105,000 NC

Averagea 10,300 71 77,400 533 35,200 243

a

 Partial year for 2004: December 16-September 30.
18 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

0

5,000

10,000

15,000

20,000

25,000

2004 2005 2006 2007

Suspended solids load, in tons

0

40,000

80,000

120,000

160,000

2004 2005 2006 2007

Total phosphorus load, in pounds

Average

0

10,000

20,000

30,000

40,000

50,000

60,000

2004 2005 2006 2007

Water year

Average

Dissolved phosphorus load,

in pounds

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

EXPLANATION

Figure 8. Suspended solids, total phosphorus, and dissolved phosphorus loads in Apple, Ashwaubenon, Baird, and Duck 

Creeks and the East River, for water years 2004–06.
Hydrology and Water Quality 19

0

50

100

150

200

250

300

2004 2005 2006 2007

0

200

400

600

800

1000

1200

1400

1600

2004 2005 2006 2007

Statewide median

Southeastern Wisconsin Till 

Plains ecoregion (SWTP) median

Average

0

100

200

300

400

500

600

700

2004 2005 2006 2007

Water year

Average

Suspended solids yields,

in tons per square mile

Total phosphorus yields,

in pounds per square mile

Dissolved phosphorus yields,

in pounds per square mile

Statewide median

Southeastern Wisconsin Till 

Plains ecoregion (SWTP) median

Apple Creek

Ashwaubenon Creek

Baird Creek

Duck Creek

East River

EXPLANATION

Figure 9. Suspended solids, total phosphorus, and dissolved phosphorus yields for Apple, Ashwaubenon, Baird, and 

Duck Creeks and the East River, for water years 2004–06.
20 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Seasonality in Loads

To determine the seasonality in the loads in these 

streams, daily loads were summed by month and the percentages of the total annual loads were computed for each month; 

the average monthly loads from WY 2005 and WY2006 

were used for October and November in WY 2004 for the 

East River (table 12). Highest TSS loads occurred between 

March and June at each site: highest TSS loads were in 

March in Apple and Baird Creeks, whereas highest loads 

were in June in Ashwaubenon Creek, Duck Creek and the 

East River (fig. 10). Most of the TSS load occurred during 

the four months with the highest flows (March, November, 

May, and June): Ashwaubenon Creek (97 percent), Baird and 

Duck Creeks (96 percent), Apple Creek (95 percent) and the 

East River (87 percent). In Apple, Ashwaubenon, Baird, and 

Duck Creeks, the lowest transport occurred in September and 

October. These months typically had the lowest flows and contributed less than 1 percent of the TSS load. In the East River, 

the minimum loads were transported in January and February, 

although loads in September and October were also very low.

The seasonality in TP loads was similar to that for 

TSS loads and discharge. Highest TP loads were delivered 

in March (table 12 and fig. 10), followed by May, and June 

or November. Most of the TP loads occurred during these 

four months: Baird Creek (88 percent), Ashwaubenon 

Creek (82 percent), Apple Creek (84 percent), Duck Creek 

(86 percent), and East River (80 percent). These four months 

had the highest discharge and the highest TP concentrations. 

Lowest transport typically occurred in September and October, similar to TSS, at all five sites. During September and 

October, less than 1 percent of the TP load was transported.

Distribution of Daily Flows and Loads

The distribution of flows and constituent loads was 

highly nonlinear. Most of the flow and load of various constituents occurred over a small number of days. On average, 

about 50 percent of the annual streamflow occurred in 

14 days at all sites except for the larger East River, for which 

50 percent of the flow occurred in about 30 days (table 13 and 

fig. 11). For these five sites, about 17–27 percent of the total 

annual flow occurred in 4 days. 

Individual runoff events can be very important to the 

total mass transport of most constituents. TSS and TP concentrations were found to be higher during runoff events than 

during base-flow and average conditions; therefore, more 

TSS and TP would be expected to be transported in a shorter 

period of time than the water itself. About 20 percent of the 

annual TSS load was transported in the most extreme 1-day 

event at each site (table 13 and fig. 11). About 48–55 percent 

of the TSS load was transported in 4 days, and 73–85 percent 

was transported in 14 days. A similar pattern was found for TP 

loads, for which about 12–23 percent was transported in 1 day, 

40–60 percent in 7 days, and 68–85 percent in 30 days.

The high percentage of annual load being transported in 

just a few days indicates that only a few storms each year can 

dominate the total annual loading for both TSS and TP 

(table 13). This nonlinearity has implications to the installation 

and types of best-management practices (BMPs) that need to be 

installed in a watershed to reduce nutrient and sediment export. 

To reduce mass transport to the streams, BMPs must be sized 

appropriately to handle the very high single-day runoff events. 

If BMP’s are sized too small, they may be overwhelmed and 

may not be effective in reducing loads to the stream. Constituents transported with sediment are most affected by runoff 

events. About one-half of the annual TSS load is transported 

in 4 days, and 90 percent is transported in 30 days. Constituents that are transported with sediment, such as TP, are also 

strongly affected by rainfall and runoff. Excluding the East 

River watershed, about one-half of the annual TP load was 

transported in 7 days, as compared to 4 days for TSS; and about 

90 percent of the annual TP load was transported in 60 days, as 

compared to 30 days for TSS (table 13). Annual TSS and TP 

loads were separated into that transported during baseflow and 

that transported during runoff events. Over 80 percent of the 

TSS, TP, and DP loads were transported during runoff events in 

streams except Baird Creek. In Baird Creek, a higher percentage of streamflow occurred during base flow and a subsequent 

smaller part of the annual load (60 to 66 percent, 3-year average) occurred during overland runoff periods.

Volumetrically Weighted Concentration

Volumetrically weighted concentrations (VWC) for 

each constituent were calculated for each stream and each 

year (table 14) by dividing the total annual load by the total 

annual flow (with the appropriate conversion factor for unit 

transformation). Highest VWCs of TSS for the entire 3-year 

period were in Apple Creek (193 mg/L), followed by Ashwaubenon Creek (192 mg/L), Baird Creek (158 mg/L), East 

River (104 mg/L), and Duck Creek (84 mg/L). The VWCs of 

TSS were highest in WY 2004 at each site: highest in Apple 

Creek (289 mg/L), followed by Ashwaubenon (256 mg/L), 

Baird Creek (202 mg/L), East River (163 mg/L), and Duck 

Creek (106 mg/L). The lowest annual VWCs for TSS were 

in WY 2005 for Apple Creek, Baird Creek, and East River; 

the lowest VWCs in Ashwaubenon and Duck Creeks were in 

WY 2006. These values agree with estimated median annual 

VWC of TSS in this area found by Robertson and others 

(2006b; 87 to 161 mg/L), and are above their estimated reference or background median concentrations of 29 to 59 mg/L.

The highest VWCs of TP for the entire study period were 

in Ashwaubenon Creek (0.69 mg/L), followed by Baird Creek 

(0.55 mg/L), Apple Creek (0.50 mg/L), East River (0.39 mg/L), 

and Duck Creek (0.36 mg/L) (table 14). The highest annual 

VWC of TP occurred in Ashwaubenon Creek (0.74 mg/L) in 

WY 2005. Ashwaubenon Creek also had the highest VWC of 

DP for the entire study period (0.36 mg/L) and highest average 

annual value (0.39 mg/L measured in WY 2005). Variability in 

the VWCs of DP for the entire study period was the same as for 

TP, with highest concentrations in Ashwaubenon Creek 

(0.36 mg/L), followed by Baird Creek (0.27 mg/L), Apple 

Creek (0.22 mg/L), Duck Creek (0.19 mg/L), and the East 

River (0.18 mg/L).
Hydrology and Water Quality 21

Table 12. Monthly loads and percentage of the total load at the five sites in the study, for water years 2004–06.—Continued

[ft3/s, cubic feet per second]

Month Discharge Suspended solids Total phosphorus

Total (ft3/s) Percent Load (tons) Percent Load (pounds) Percent

Apple Creek

Oct. 361 1.2 21 0.1 635 0.8

Nov. 2,060 7.0 3,900 25.5 14,200 17.9

Dec. 1,190 4.0 154 1.0 2,200 2.8

Jan. 1,130 3.8 81 0.5 1,580 2.0

Feb. 2,810 9.5 203 1.3 5,680 7.2

Mar. 11,200 38.0 5,340 34.9 32,600 41.3

Apr. 1,540 5.2 75 0.5 1,310 1.7

May 5,130 17.4 3,390 22.1 10,900 13.7

June 3,370 11.4 2,060 13.5 8,810 11.2

July 263 0.9 26 0.2 543 0.7

Aug. 284 1.0 42 0.3 466 0.6

Sept. 154 0.5 10 0.1 164 0.2

Ashwaubenon Creek

Oct. 46 0.5 2 0.0 121 0.3

Nov. 429 4.3 200 3.9 1,980 5.3

Dec. 359 3.6 51 1.0 1,510 4.0

Jan. 466 4.7 35 0.7 1,810 4.8

Feb. 888 8.9 67 1.3 2,370 6.3

Mar. 3,750 37.5 1,220 23.7 13,300 35.7

Apr. 420 4.2 20 0.4 643 1.7

May 2,020 20.3 1,520 29.4 7,610 20.4

June 1,480 14.9 2,000 38.6 7,570 20.3

July 35 0.4 4 0.1 79 0.2

Aug. 72 0.7 47 0.9 284 0.8

Sept. 14 0.1 1 0.0 23 0.1

Baird Creek

Oct. 76 0.5 2 0.0 47 0.1

Nov. 538 3.8 474 7.9 2,230 5.3

Dec. 416 3.0 54 0.9 1,070 2.6

Jan. 490 3.5 22 0.4 696 1.7

Feb. 575 4.1 33 0.5 1,110 2.6

Mar. 5,050 36.1 2,960 49.6 19,900 47.5

Apr. 1,060 7.6 54 0.9 1,440 3.4

May 3,050 21.8 1,280 21.4 7,450 17.8

June 2,480 17.7 882 14.8 7,390 17.6

July 111 0.8 51 0.9 217 0.5

Aug. 93 0.7 150 2.5 361 0.9

Sept. 42 0.3 4 0.1 28 0.1
22 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Table 12. Monthly loads and percentage of the total load at the five sites in the study, for water years 2004–06.—Continued

[ft3/s, cubic feet per second]

Month Discharge Suspended solids Total phosphorus

Total (ft3/s) Percent Load (tons) Percent Load (pounds) Percent

Duck Creek

Oct. 283 0.4 8 0.1 300 0.2

Nov. 3,100 4.9 270 1.9 4,740 3.8

Dec. 1,990 3.1 57 0.4 2,080 1.7

Jan. 2,010 3.2 51 0.3 1,890 1.5

Feb. 3,640 5.7 146 1.0 7,140 5.8

Mar. 21,300 33.4 5,360 36.9 62,000 50.1

Apr. 6,740 10.5 265 1.8 5,130 4.1

May 12,000 18.8 1,960 13.5 12,000 9.7

June 12,400 19.4 6,400 44.1 28,000 22.6

July 331 0.5 9 0.1 412 0.3

Aug. 53 0.1 1 0.0 51 0.0

Sept. 42 0.1 1 0.0 20 0.0

East River

Oct. 2,50 1.9 481 1.5 4,090 1.7

Nov. 2,490 2.3 359 1.2 5,560 2.4

Dec. 3,870 3.5 184 0.6 4,380 1.9

Jan. 5,580 5.1 139 0.4 6,280 2.7

Feb. 6,910 6.3 155 0.5 7,680 3.3

Mar. 31,300 28.4 10,100 32.4 93,700 39.8

Apr. 8,670 7.9 884 2.8 8,990 3.8

May 22,900 20.8 6,550 21.0 43,700 18.5

June 14,900 13.5 10,500 33.8 44,300 18.8

July 4,500 4.1 578 1.9 6,700 2.8

Aug. 3,830 3.5 735 2.4 6,790 2.9

Sept. 3,120 2.8 500 1.6 3,440 1.5

a

The average monthly loads from WY 2005 and WY2006 were used for October and November in WY 2004 for the East River.
Hydrology and Water Quality 23

Figure 10. Percentage of annual 

discharge, and total suspended solids 

and total phosphorus load by month for 

Apple, Ashwaubenon, Baird, and Duck 

Creeks and the East River, for water 

years 2004–06.

0

10

20

30

40

50

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Percentage of total load

Apple Creek

0

10

20

30

40

50

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Ashwaubenon Creek

0

10

20

30

40

50

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Baird Creek

0

10

20

30

40

50

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Duck Creek

0

10

20

30

40

50

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

MONTH

East River

Percentage of total load Percentage of total load Percentage of total load Percentage of total load

Suspended solids

Total phosphorus

Discharge

EXPLANATION
24 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Table 13. Percentage of total annual discharge, suspended sediment load, and total phosphorus load transported over a specified 

number of days for the five sites in the study.

Number of days Apple Creek Ashwaubenon 

Creek Baird Creek Duck Creek East River Five site average

Stream discharge

1 6.6 7.8 5.7 6.3 5.5 6.4

2 12.4 15.0 10.9 12.0 10.0 12.1

3 17.7 21.0 15.7 16.5 13.3 16.9

4 22.1 26.6 20.0 20.7 16.6 21.2

5 25.8 31.4 23.8 24.7 19.7 25.1

6 29.0 35.9 27.4 28.4 22.7 28.7

7 32.1 39.5 30.6 31.5 25.4 31.8

14 47.3 57.6 47.5 47.5 34.7 46.9

30 64.8 76.4 66.5 66.0 46.1 63.9

60 79.9 88.8 82.3 81.7 59.5 78.4

90 86.6 93.3 89.5 89.5 69.3 85.6

120 90.7 94.8 93.3 93.4 76.8 89.8

180 95.4 98.1 97.0 97.6 88.5 95.3

270 98.8 99.6 99.0 99.8 98.7 99.2

365 100.0 100.0 100.0 100.0 100.0 100.0

Suspended solids

1 21.4 22.3 21.1 22.6 19.5 21.4

2 31.5 33.7 31.6 33.8 31.7 32.4

3 41.0 42.9 41.0 44.5 40.6 42.0

4 50.3 52.0 50.3 55.2 47.8 51.1

5 57.8 59.1 57.6 62.5 53.5 58.1

6 63.8 64.6 63.3 67.6 58.0 63.5

7 68.6 69.0 67.7 71.7 61.4 67.7

14 83.1 82.9 82.6 84.6 72.7 81.2

30 94.3 94.5 94.4 94.8 83.7 92.4

60 98.4 98.6 98.5 98.6 90.5 96.9

90 99.3 99.5 99.4 99.4 93.9 98.3

120 99.7 99.8 99.8 99.7 96.2 99.0

180 99.8 99.9 99.9 99.8 96.3 99.2

270 100.0 100.0 100.0 100.0 100.0 100.0

365 100.0 100.0 100.0 100.0 100.0 100.0

Total phosphorus

1 16.3 16.4 16.4 22.7 11.5 16.7

2 25.2 24.7 24.3 33.2 19.3 25.3

3 32.4 32.3 31.6 40.6 25.2 32.4

4 39.2 39.6 38.7 47.3 30.1 39.0

5 45.0 45.9 44.8 53.5 34.6 44.7

6 48.4 49.7 48.2 57.1 37.6 48.2

7 51.7 52.9 51.5 60.4 40.3 51.4

14 68.0 69.6 68.3 74.7 54.2 67.0

30 82.9 84.6 83.8 86.3 67.9 81.1

60 92.3 93.7 93.1 93.7 78.6 90.3

90 95.5 96.6 96.3 96.6 84.9 94.0

120 97.0 97.9 97.8 97.9 89.2 95.9

180 98.6 97.2 98.0 99.1 95.2 97.6

270 99.7 99.8 99.8 99.9 100.3 99.9

365 100.0 100.0 100.0 100.0 100.0 100.0
Hydrology and Water Quality 25

0

20

40

60

80

100

0 50 100 150 200 250 300 350

Percentage of annual suspended solids and

total phosphorus load and discharge

Number of accumulated days

Five site average suspended solids

Five site average total phosphorus

Five site average discharge

Figure 11. Percentage of annual discharge, suspended solids loads, and total phosphorus load delivered over a specified number of 

days for Apple, Ashwaubenon, Baird, and Duck Creeks and the East River (five site average).

Table 14. Volumetically weighted concentrations of suspended solids, total phosphorus, and 

dissolved phosphorus for the five sites in the study, for water years 2004–06.

[All values are in milligrams per liter]

Water year Suspended solids Total phosphorus Dissolved phosphorus

Apple Creek

2004

2005

2006

2004–06

289

75

107

193

0.59

0.42

0.35

0.50

0.24

0.19

0.18

0.22

Ashwaubenon Creek

2004

2005

2006

2004–06

256

158

65

192

0.73

0.74

0.52

0.69

0.37

0.39

0.30

0.36

Baird Creek

2004

2005

2006

2004–06

202

89

107

158

0.64

0.42

0.42

0.55

0.31

0.21

0.21

0.27

Duck Creek

2004

2005

2006

2004–06

106

76

28

84

0.35

0.42

0.28

0.36

0.18

0.20

0.20

0.19

East River

2004a

2005

2006

2004–06a

163

37

65

104

0.50

0.27

0.33

0.39

0.21

0.14

0.15

0.18

a

Based on data for a partial year for 2004: December 16–September 30
26 Hydrology, Phosphorus, and Suspended Solids in Five Agricultural Streams in the Lower Fox River and Green Bay Watersheds, WY 2004–06

Comparison Among Streams

The highest TSS concentrations and yields were from 

Baird, Apple, and Ashwaubenon Creeks, and lowest concentrations and yields were from Duck Creek and the East 

River (tables 8 and 11). TP and DP concentrations followed 

relatively similar patterns among sites: highest concentrations were found in Ashwaubenon Creek, followed by Baird 

Creek, Apple Creek, East River, and Duck Creek (tables 9 and 

10). Average TP and DP yields had similar patterns to those 

for concentrations except yields from Baird Creek were the 

highest, and yields from Ashwaubenon Creek were the second 

highest (table 11). These differences may be caused by the 

differences in soil and slopes of the watersheds, and the size 

of their watersheds. Land uses in Apple, Ashwaubenon, and 

Baird Creek watersheds are similar to those in the Duck Creek 

and East River watersheds (table 1); however, Apple, Ashwaubenon, and Baird Creek watersheds have soils with less 

sand and more clays than the soils in the Duck Creek and East 

River watersheds (table 4). Apple, Ashwaubenon, and Baird 

Creek watersheds also have steeper main channel slopes than 

those in the Duck Creek and East River (table 3). In addition, 

East River and Duck Creek have much larger watershed sizes, 

which may result in more storage and a lower proportion of 

sediment delivery. These differences in the watersheds collectively may account for the differences in TSS, TP, and DP 

concentrations and yields. Urban development may explain 

some of the differences observed. It might be expected that 

Baird Creek would have lower concentrations and yields than 

in Apple or Ashwaubenon Creeks, given the relatively high 

proportion of wetlands in its watershed (10%, table 1) and 

higher base flow (table 7); however, rapid urbanization within 

the Baird Creek watershed may have contributed a disproportionate amount of sediment from upland erosion. Development in the Baird Creek watershed may also have caused 

a change in the hydrologic regime that may have created 

unstable stream banks and an indirect sediment source to the 

stream (Fink, 2005). 

It is likely that spatial variability in precipitation 

affected the distribution in annual yields among streams. 

For example, in April through September in 2006, precipitation near Baird Creek was 21.6 in., compared to 14.7, 15.9 

and 16.6 in. near Apple, Ashwaubenon, and Duck Creeks, 

respectively (table 6). The fact that Baird Creek and the East 

River had the highest TSS, TP and DP yields in 2006 (table 

11) was likely related to this large disparity in precipitation. 

The precipitation estimates reported in this document were 

based on a single rain gage in or near each watershed, rather 

than a network of gages within each watershed; however, the 

same pattern in precipitation was observed in a more detailed 

network of rain-gage data assembled by UWGB for each of 

the five watersheds.

Use of Data for Modeling Studies

The Soil and Water Assessment Tool (SWAT) is a distributed parameter, daily time-step watershed model developed 

by the U.S. Department of Agriculture–Agricultural Research 

Service that can simulate hydrologic, climatic, and related 

processes to predict the impact of land management on water, 

sediment, and nutrient export from rural and mixed-use basins 

(Arnold and others, 1996; Neitsch and others, 2002). The 

SWAT model was originally applied to the LFR after being 

calibrated primarily based on TSS and TP data from a single 

stream; however, it was more successfully calibrated and validated by UWGB (Baumgart, 2005) using some of the data for 

the five sites described in this report. After successful validation of the model, the SWAT model was applied by the UWGB 

to the entire LFR basin to allocate loads from various sources 

and to simulate the impact of a variety of agricultural practices 

on water quality in LFR streams (Blake, 2007).

Summary

A 3-year study from October 1, 2003 to September 30, 

2006 was conducted by the U.S. Geological Survey and the 

University of Wisconsin Green Bay to characterize the hydrology and phosphorus and suspended solids in five agricultural 

streams in the Fox/Wolf watershed in northeastern Wisconsin and provide information to assist in the calibration of a 

watershed model for the area. During this study, total annual 

precipitation was close to the 30-year normal of 29.12 inches.

Study results were as follows: 

Average streamflow was highest in the East River, followed by Duck Creek, Apple Creek, Baird Creek, and Ashwaubenon Creek; however on a yield basis, East River had the 

highest flow and Ashwaubenon Creek had the lowest flow. The 

median TSS concentration was highest in Baird Creek, and 

lowest in Duck Creek. The median TP concentration was highest in Ashwaubenon Creek and lowest in Duck Creek. Average 

annual TSS yields were highest in Apple Creek and lowest in 

Duck Creek, whereas average annual TP yields were highest 

in Baird Creek and lowest in Duck Creek. 

Overall, Ashwaubenon, Baird, and Apple Creeks had 

higher TP and TSS concentrations and yields than Duck Creek 

and the East River. These differences may be caused by the 

differences in soil and slopes of the watersheds, and the size 

of their watersheds. Apple, Ashwaubenon, and Baird Creek 

watersheds are smaller, have soils with less sand and more 

clays, and steeper main channel slopes than the Duck Creek 

and East River watersheds.
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— Graczyk, Robertson, Baumgart, Fermanich Lower Fox River Hydrology, Phosphorus, and and Green Bay Watersheds Wisconsin, Water Years 2004–06 — Suspended Solids in Five Agricultural Streams in the Scientific Investigations Report 2011–5111