U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 03-4130

In cooperation with the Bayfield County Land and Water Conservation Department and 

the U.S. Fish and Wildlife Service

Simulation of Ground-Water Flow and Rainfall 

Runoff with Emphasis on the Effects of Land Cover, 

Whittlesey Creek, Bayfield County, Wisconsin, 

1999–2001

North Fork

Whittlesey Creek

North Fork

Whittlesey Creek

Lake Superior

12 13

19a

19

6

5

18 17

4 30 3 2 1

14 1a 15 16

10

9

11

8

22 21

20

7

29

23

2

2a

5a

13a

7a

11a

20a
Simulation of Ground-Water Flow and 

Rainfall Runoff with Emphasis on the 

Effects of Land Cover, Whittlesey Creek, 

Bayfield County, Wisconsin, 1999–2001

By Bernard N. Lenz, David A. Saad, and Faith A. Fitzpatrick

In cooperation with the Bayfield County Land and Water Conservation Department 

and the U.S. Fish and Wildlife Service

Water-Resources Investigations Report 03–4130

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2003

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.
iii

Contents

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

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

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

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

Climate ........................................................................................................................................... 5

Study Design................................................................................................................................. 6

Acknowledgments....................................................................................................................... 6

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

Field Investigations...................................................................................................................... 7

Simulation of Ground-Water Flow ............................................................................................ 8

Estimates of Hydraulic Conductivity and Recharge.................................................... 10

Parameter Sensitivity and Model Calibration .............................................................. 13

Pathline Analysis and Delineation of Ground-Water-Contributing Area................. 13

Simulation of Rainfall Runoff.................................................................................................... 13

SWAT Model Calibration ................................................................................................. 17

Rainfall-Runoff Model Simulations ................................................................................ 18

Field Data ............................................................................................................................................. 19

Ground-Water-Flow Simulations...................................................................................................... 30

Preliminary Ground-Water-Flow Models............................................................................... 30

GFLOW Model ................................................................................................................... 30

MODFLOW Model............................................................................................................. 30

Updated Models, Sensitivity, and Calibration ....................................................................... 31

Ground-Water-Contributing Area ........................................................................................... 32

Land-Cover Effects on Recharge and Base Flow................................................................. 33

Rainfall-Runoff Simulations............................................................................................................... 36

Land-Cover Effects on Annual Runoff and Flood Peaks...................................................... 37

Land-Cover Effects on Water Budget..................................................................................... 41

Land-Cover Effects on Sources of Flow ................................................................................ 42

Land-Cover Effects on Soil Infiltration Rates ........................................................................ 42

Summary and Conclusions................................................................................................................ 43

References Cited ................................................................................................................................ 45
iv

Figures

 1-2. Maps showing:

 1. Whittlesey Creek, Wis., study area and sampling and monitoring sites, 

 1999-2001........................................................................................................................ 2

 2. Land-cover data and subbasins used in the Whittlesey Creek, Wis., 

 Soil and Water Assessment Tool (SWAT) model, 1992-93 ..................................... 3

 3-4. Cross sections showing:

 3. Generalized geology and conceptual model of the deep ground-water

 flow system of the Bayfield Peninsula, Wis............................................................. 4

 4. Geology of the southern part of the Whittlesey Creek, Wis., study area............ 5

 5-6. Maps showing:

 5. Hydrologic features simulated with analytic elements for the GFLOW 

 model of the Whittlesey Creek, Wis., study area and vicinity............................... 9

 6. Boundary conditions and location of calibration targets used in 

 the MODFLOW model of the Whittlesey Creek, Wis., study area ...................... 11

 7. Block diagram showing the MODFLOW model hydraulic conductivity/

recharge zonation, river nodes, and layer configuration............................................ 12

 8-9. Maps showing:

 8. Digital Elevation Model of land surface for the Whittlesey Creek, Wis., 

 surface-water-contributing basin............................................................................ 15

 9. Soils in the Whittlesey Creek, Wis., surface-water-contributing basin 

 from STATSGO data.................................................................................................... 17

 10. Graph showing measured hourly stage data used in timing peak stages 

through Whittlesey Creek, Wis., for calibration of channel characteristics

in the Soil and Water Assessment Tool (SWAT) model, May 9-10, 2001 .................. 18

11-15. Maps showing:

 11. Land cover in the Whittlesey Creek, Wis., surface-water-contributing 

 basin, from the 1928 Land Economic Survey ......................................................... 20

 12. Land cover in the Whittlesey Creek , Wis., surface-water-contributing 

 basin used in the modeled reforested simulation................................................. 20

 13. Base flows for Whittlesey Creek and tributaries, Wis., August 2000 ................ 27

 14. Streambed heads for Whittlesey Creek and tributaries, Wis., 

 August 2000 ................................................................................................................. 29

 15. Streambed temperatures for Whittlesey Creek and tributaries, Wis., 

 August 2000 ................................................................................................................. 29

 16-17. Graphs showing:

 16. MODLFOW ground-water-flow model parameter sensitivities from 

 UCODE for the Whittlesey Creek, Wis., study area............................................... 32

 17. Relation of measured and modeled head and stream flux for the 

 calibrated MODFLOW model for the Whittlesey Creek, Wis., study area ........ 33

 18-19. Maps showing:

 18. Whittlesey Creek, Wis., ground-water-contributing area based on 

 results from the calibrated MODFLOW model....................................................... 34

 19. Particle pathlines tracked backwards from Whittlesey Creek, Wis., 

 to the water table in the ground-water-contributing area ................................. 35
v

 20-22. Graphs showing:

 20. Hydrographs of daily mean flow from the Whittlesey Creek, Wis., 

 streamflow-gaging station 040263205 and Soil and Water Assessment 

 Tool (SWAT) model for 1992-93 land cover............................................................. 38

 21. Flood hydrographs of measured daily mean and instantaneous (15-minute)

 flow from the Whittlesey Creek, Wis., streamflow-gaging station 040263205

 and simulated daily mean flow from the Soil and Water Assessment Tool 

 (SWAT) model for 1992-93 land cover, July 1999 and April 2001......................... 39

 22. Flood hydrographs of daily mean flow from the Whittlesey Creek, Wis., 

 Soil and Water Assessment Tool (SWAT) models of all land-cover 

 simulations................................................................................................................... 40
vi

Tables

 1. Streamflow statistics for U.S. Geological Survey streamflow-gaging 

station 040263205, Whittlesey Creek near Ashland, Wis., for April 1, 1999, 

to September 30, 2001 ......................................................................................................... 8

 2. Estimated range or value of aquifer properties, recharge, and stream 

characteristics in the study area .................................................................................... 10

 3. Physical characteristics of subbasins used in Whittlesey Creek, Wis., 

Soil and Water Assessment Tool (SWAT) model.......................................................... 14

 4. Soil and Water Assessment Tool (SWAT) model input parameter values 

for Whittlesey Creek, Wis., for five model simulations................................................ 16

 5. Percentages of land-cover types used in Whittlesey Creek, Wis., Soil 

and Water Assessment Tool (SWAT) model simulations ............................................ 19

 6. Results of field investigations of base flow and physical characteristics 

of Whittlesey Creek and adjacent streams, Wis. ......................................................... 21

 7. Comparison of base flow and drainage area for Whittlesey Creek and 

adjacent streams, Wis. ..................................................................................................... 28

 8. Preliminary estimate and UCODE-optimized parameter values used 

in the MODFLOW model ................................................................................................... 30

 9. Head statistics and simulated base flows at selected locations for 

preliminary, updated, and calibrated ground-water-flow models............................. 31

 10. Simulated changes in base flow for Whittlesey Creek, Wis., as a result 

of changes in recharge in the ground-water-contributing area ............................... 35

 11. Daily mean and instantaneous peak flows for U.S. Geological Survey 

streamflow-gaging station on Whittlesey Creek, Wis., and the calibrated 

SWAT model output using 1992-93 WISCLAND land-cover data .............................. 36

 12. Average annual runoff and flood peaks from the Whittlesey Creek, Wis., 

streamflow-gaging station 040263205 and the Soil and Water Assessment 

Tool (SWAT) model simulations....................................................................................... 37

 13. Percentage of total precipitation that becomes evapotranspiration, 

surface-water runoff, and ground water in the Whittlesey Creek, Wis., 

Soil and Water Assessment Tool (SWAT) model simulations .................................... 41

 14. Percentage of streamflow at the Whittlesey Creek, Wis., U.S. Geological 

Survey streamflow-gaging station from surface runoff, soil-profile 

drainage, and regional ground water based on Whittlesey Creek Soil 

and Water Assessment Tool (SWAT) model simulations ............................................ 42

 15. Average ground-water infiltration rates by soil type in the Whittlesey 

Creek, Wis., Soil and Water Assessment Tool (SWAT) model simulations.............. 43
vii

Conversion Factors, Vertical Datum, and Abbreviated 

Units of Measurement

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

cubic inch (in3

) 16.39 cubic centimeter (cm3) 

cubic foot (ft3

) 0.02832 cubic meter (m3) 

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

cubic foot per second (ft3

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

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

inch per hour (in/h) 0.0254 meter per hour (m/h)

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

follows:

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 

1929 (NGVD 29).

Abbreviated units of measurement used in this report: Specifi c conductance is given in 

microsiemens per centimeter at 25°C (μS/cm). Permeability rate is given in inches per hour 

(in/h). Average annual runoff and recharge are given in inches per year (in/yr). 
viii
Simulation of Ground-Water Flow and Rainfall Runoff 

with Emphasis on the Effects of Land Cover, Whittlesey 

Creek, Bayfield County, Wisconsin, 1999-2001

By Bernard N. Lenz, David A. Saad, and Faith A. Fitzpatrick

Abstract 

The effects of land cover on flooding and base-flow 

characteristics of Whittlesey Creek, Bayfield County, Wis., 

were examined in a study that involved ground-water-flow 

and rainfall-runoff modeling. Field data were collected 

during 1999-2001 for synoptic base flow, streambed head 

and temperature, precipitation, continuous streamflow 

and stream stage, and other physical characteristics. Well 

logs provided data for potentiometric-surface altitudes and 

stratigraphic descriptions. Geologic, soil, hydrography, 

altitude, and historical land-cover data were compiled 

into a geographic information system and used in two 

ground-water-flow models (GFLOW and MODFLOW) 

and a rainfall-runoff model (SWAT). A deep ground-water 

system intersects Whittlesey Creek near the confluence 

with the North Fork, producing a steady base flow of 17–

18 cubic feet per second. Upstream from the confluence, 

the creek has little or no base flow; flow is from surface 

runoff and a small amount of perched ground water. Most 

of the base flow to Whittlesey Creek originates as recharge 

through the permeable sands in the center of the Bayfield 

Peninsula to the northwest of the surface-water-contributing basin. Based on simulations, model-wide changes in 

recharge caused a proportional change in simulated base 

flow for Whittlesey Creek. Changing the simulated amount 

of recharge by 25 to 50 percent in only the ground-watercontributing area results in relatively small changes in base 

flow to Whittlesey Creek (about 2–11 percent). Simulated 

changes in land cover within the Whittlesey Creek surfacewater-contributing basin would have minimal effects on 

base flow and average annual runoff, but flood peaks (based 

on daily mean flows on peak-flow days) could be affected. 

Based on the simulations, changing the basin land cover 

to a reforested condition results in a reduction in flood 

peaks of about 12 to 14 percent for up to a 100-yr flood. 

Changing the basin land cover to 25 percent urban land 

or returning basin land cover to the intensive row-crop agriculture of the 1920s results in flood peaks increasing by as 

much as 18 percent. The SWAT model is limited to a daily 

time step, which is adequate for describing the surfacewater/ground-water interaction and percentage changes. 

It may not, however, be adequate in describing peak flow 

because the instantaneous peak flow in Whittlesey Creek 

during a flood can be more than twice the magnitude of the 

daily mean flow during that same flood. In addition, the 

storage and infiltration capacities of wetlands in the basin 

are not fully understood and need further study.

Introduction

Whittlesey Creek (fig. 1) is considered a regionally 

important stream for fish spawning and rearing (Gardner, 

1994; Wisconsin Department of Natural Resources, 1996). 

The U.S. Fish and Wildlife Service established the Whittlesey Creek National Wildlife Refuge in 1999 and acquired 

97 of the 570 acres proposed for the refuge that surrounds 

the mouth of Whittlesey Creek. The main objectives for the 

refuge are to protect and restore habitat in Whittlesey Creek 

and surrounding creeks for migration, spawning, and rearing of trout and salmon from Lake Superior and to protect 

important bird nesting areas. However, as in many Wisconsin tributaries to Lake Superior, aquatic habitat in Whittlesey Creek is possibly degraded because of accelerated 

runoff and associated sedimentation problems that have 

potentially resulted from agriculture, forestry practices, 

and development of roads (Red Clay Interagency Committee, 1967). In addition, the sources for abundant base flow 

in Whittlesey Creek are not well understood. This study 

was done in cooperation with the Bayfield County Land 

and Water Conservation Department and the U.S. Fish and 

Wildlife Service to identify land-cover effects on the flow 

characteristics of the creek.
2 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Boyd Creek

WISCONSIN

Washburn

Ashland

Lake

Superior

Chequamegon

Bay

Chequamegon National

Forest

North Fish Creek

National Forest

Urban

BAYFIELD CO.

ASHLAND CO.

Surface-waternoncontributing basin

Whittlesey Creek

Wildlife Refuge

Sioux River

12

27 28

31

24

Ashland 

Experimental 

Farm

90 ̊57'

46 ̊40'

46 ̊32'

North Fork

Whittlesey Creek

0 1 2 KILOMETERS

0 1 2 MILES

1

31b

31a

26

25

Whittlesey Creek

North Fork

12 13

19a

19

6

5

18 17

4 30 3 2 1

14 1a 15 16

10

9

11

8

22 21

20

7

29

23

2

2a

5a

13a

7a

11a

20a

A'

A

0

0

1 2 MILES

1 2 KILOMETERS

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

EXPLANATION

Surface-watercontributing basin 

boundary

Stream

Stage recorder

Base flow and/or 

physical characteristics 

site and field number 

Coring site and number

Gaging station

040263205

A A'

Road

Line of section for

geologic profile (fig. 4)

Base from Wisconsin Department of Natural 

Resources hydrography and U.S. Environmental Protection

Agency RF3 stream coverages, 1:100,000 digital data

Wisconsin Transverse Mercator Projection, NAD83. 1

Bayfield

Highlands

Bayfield

Study area

9191'08'  ̊08'

Figure 1. Location map of Whittlesey Creek, Wis., study area and sampling and monitoring sites, 1999-2001.
Purpose and Scope

The purpose of this report is to present results of 

ground-water-flow and rainfall-runoff simulations as they 

related to historical, present, and potential future landcover effects on flooding and base-flow characteristics of 

Whittlesey Creek. The objectives of the report include the 

following:

 1. Quantify current streamflow characteristics—base 

flow, floods, and seasonal fluctuations,

 2. quantify contribution of runoff and ground water to 

streamflow,

 3. identify the ground-water contributing area1 and 

gaining and losing reaches of Whittlesey Creek,

 4. estimate presettlement hydrologic conditions

 5. quantify the relation between present land-cover 

characteristics and base flows and floods in Whittlesey Creek, and 

 6. identify areas (if any) within the Whittlesey Creek 

surface-water contributing basin that have the greatest effect on runoff.

1

 In this report, “ground-water-contributing area” refers to the twodimensional land-surface area projected from the three-dimensional 

subsurface volume of water discharging to the streambed of Whittlesey 

Creek.

The scope of work included conducting base-flow, 

streambed-head, and streambed-temperature surveys, 

monitoring stream stage and flow of Whittlesey Creek, 

and development of ground-water-flow and rainfall-runoff 

models for Whittlesey Creek. The field surveys were done 

in August 1999 and April and August 2000.

Description of Study Area

The Whittlesey Creek drainage basin, as delineated 

from topographic divides, covers an area of about 38 mi2

(fig. 1). This basin includes surface-water-noncontributing 

and contributing areas (fig. 1). The noncontributing basin 

of Whittlesey Creek is in the Bayfield Highlands and is 

composed of sandy deposits with no surface-drainage features. The surface-water-contributing basin is only about 

7.4 mi2

. Hydrologic features in the contributing basin 

include the main stem of Whittlesey Creek, the North Fork 

Whittlesey Creek, and numerous unnamed tributaries. 

Streamflow near the mouth of Whittlesey Creek is a consistent 17 to 18 ft3

/s at base flow, with flood peaks of over 

500 ft3/s. Just upstream from the confluence of the main 

stem and North Fork, the main stem becomes ephemeral 

or has base flow of less than 1 ft3/s. 

North Fork

Whittlesey Creek

North Fork

Whittlesey Creek

Nonforested wetland

Forested wetland

Water

Rangeland

Grassland/pasture

Forest

Agriculture (other)

Row-crop agriculture

Hay

Land use/land cover

Subbasin boundary 

and identifier

Stream

EXPLANATION

Surface-water-contributing 

basin boundary

4

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10

11

12

13

14

MILE

0 KILOMETER

0 0.5

0.5 1

1

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

Figure 2. Land-cover data and subbasins used in the Whittlesey Creek, Wis., Soil and Water Assessment Tool (SWAT) model, 

1992-93. Land cover from WISCLAND data from 1992-93 from Reese and others (2002). Drainage divides for subbasins were 

derived from 10-meter Digital Elevation Model data (Benchmark GIS, 2001).

Introduction 3
4 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

The surface-water-contributing basin of Whittlesey 

Creek is 65.5 percent forested, 29.1 percent pasture/

grassland/hay, 3.4 percent brushy rangeland, and 2 percent 

wetland based on 1992-93 land-cover data (fig. 2) (Reese 

and others, 2002). The basin generally has sloping plains 

in the uplands and deeply incised valleys. Surface water 

generally moves as sheet flow in the contributing basin 

until reaching a ditch or gully leading to the channel 

network. The gullies and the stream channels are generally steeply sloped, so water passes rapidly through the 

basin after reaching a ditch or gully. Near the mouth at 

Lake Superior, the channel slope flattens considerably. For 

example, the North Fork Whittlesey Creek has an average 

slope of 0.02, whereas the average slope of Whittlesey 

Creek below the confluence with the North Fork Whittlesey Creek is 0.005.

Bedrock in the study area includes the Precambrian 

Bayfield Group, which consists dominantly of sandstone 

and siltsone and locally abundant shale and conglomerate 

(Morey and Ojakangas, 1982; Mudrey and others, 1982; 

Cannon and others, 1996). The Bayfield Group is estimated to be up to 6,900 feet thick (Morey and Ojakangas, 

1982) and crops out at several sites along the Lake Superior shoreline near the study area. The Bayfield Group is 

overlain by glacial, glaciolacustrine, and fluvial deposits, 

including sandy till of the Copper Falls Formation in the 

Bayfield Highlands and the clayey Miller Creek Formation 

at lower altitudes towards Lake Superior (Clayton, 1984) 

(fig. 3). Unconsolidated deposits are several hundred feet 

thick in the Bayfield Highlands and generally thin toward 

Lake Superior. Where present, the Miller Creek Formation 

overlies the Bayfield Group and the Copper Falls Formation up to an altitude of about 1,100 ft. Locally, coarsegrained beach deposits overlie the Miller Creek Formation 

along relict early Holocene shorelines of ancient Lake 

Superior. Well logs commonly indicate alternating layers 

of sand and clay in the area underlain by the Miller Creek 

Formation (fig. 4).

There are two ground-water flow systems in the study 

area: a deep flow system and a shallow flow system. In the 

Lake Superior

Lake Superior

ALTITUDE, IN FEET ABOVE SEA LEVEL

Land surface

? ? ?

Vertical scale greatly exaggerated

Primary recharge area for deep groundwater-flow system 

1,600

600

400

200

0

-200

800

1,000

1,200

1,400

B B'

Potentiometric surface of the deep ground-water-flow system (dashed where inferred)

General direction of ground-water flow

Miller Creek Formation - glaciolacustrine clay or glaciofluvial deposits

Copper Falls Formation - sandy till

Bayfield Group - sandstone and siltstone, locally abundant shale and conglomerate (”?“ indicates 

area where location of geologic contact is inferred)

Turning point of section

EXPLANATION

0

0

4

4

8

8

MILES

KILOMETERS

B

B' Bayfield Peninsula

WEST EAST

WISCONSIN

Figure 3. Cross section showing generalized geology and conceptual model of the deep ground-water flow system of the 

Bayfield Peninsula, Wis.
deep system, which underlies the entire study area, ground 

water moves primarily through the Copper Falls Formation and the upper part of the Bayfield Group (fig. 3). The 

deep system receives a relatively large amount of recharge 

through the Copper Falls Formation in the Bayfield Highlands. The deep system is unconfined in the higher altitudes and confined at lower altitudes near Lake Superior, 

where the Miller Creek Formation overlies it. The deep 

system discharges to Lake Superior and deeply incised 

streams, such as Whittlesey Creek. The extent of the shallow system is difficult to delineate but probably includes 

much of the area underlain by the Miller Creek Formation. 

The alternating layers of clay and sand in this area result 

in isolated areas of perched water that may be separated 

from the deep system by 100 ft or more near the headwaters of Whittlesey Creek. The shallow system receives 

less recharge than the deep system because the Miller 

Creek Formation is less permeable than the Copper Falls 

Formation. Some ground water from the shallow system 

discharges to Whittlesey Creek, and some likely recharges 

the deep system. The two systems merge where the deep 

system intersects the stream channel near the confluence 

of the main stem and North Fork (fig. 4). The deep system 

and the nonperched part of the shallow system are included 

in simulations of ground-water flow, whereas perched flow 

is included in simulations of surface-water flow. 

Climate

The regional climate is dominated by three air 

masses: the cold, dry polar continental air mass from the 

arctic and northwestern Canada; the warm, moist maritime tropical air masses from the Gulf of Mexico; and the 

mild, temperate maritime polar air mass from the Pacific 

(Eichenlaub, 1979). In addition, the moderating effects of 

Lake Superior influence the local climate. Average annual 

precipitation is 32 in. (Gebert, 1986), including an average 

annual snowfall of about 70 in. (Eichenlaub, 1979). 

Average annual evapotranspiration is estimated to be 

17.7 in. (Young and Skinner, 1974). Daily mean July 

MILES INLAND OF LAKE SUPERIOR

7 6 5 4 3 2 10

Surface-waternoncontributing basinSurface-watercontributing basin

Main Stem Whittlesey Creek confluence with 

North Fork Whittlesey Creek

WEST EAST

1,300

1,200

1,100

1,000

900

800

700

600

500

400

Sand and gravel

Sand

Clay

Hardpan/sandy clay

Potentiometric surface based on 

well information

Main stem Whittlesey Creek

Estimated boundary between geologic units

Well (geologic information 

projected from locations 

adjacent to the stream)

A A'

VERTICAL SCALE GREATLY EXAGGERATED

Data not available

EXPLANATION

Bayfield Group

ALTITUDE, IN FEET ABOVE SEA LEVEL

Figure 4. Cross section showing the geology of the southern part of the Whittlesey Creek, Wis., study area. Location of section is 

shown on figure 1.

Introduction 5
6 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

maximum temperature is 25.5°C, and daily mean January temperature is –4.5°C. There are an average of 120 

frost-free days annually (Phillips and McCulloch, 1972). 

Because of the cool temperatures and short growing season, the ratio of precipitation to evapotranspiration is high 

compared to that in the southern part of Wisconsin.

Study Design

Ground-water and surface-water contributions to 

streamflow in Whittlesey Creek were simulated by use of 

separate models. Ground-water-flow models were used to 

understand the base-flow characteristics and delineate the 

ground-water-contributing area for the stream. A rainfallrunoff model was used to understand the surface-water 

characteristics of the basin and predict how land-cover 

changes would affect annual runoff and flood peaks.

Development of the ground-water flow models for 

the Whittlesey Creek study area followed the stepwise 

modeling approach described by Haitjema (1995). 

Stepwise modeling starts with a preliminary model 

(constructed from available data) that is used to guide 

additional data collection. Based on results of the preliminary model, additional data needs are identified, field data 

are collected, and the model is updated and improved. 

These steps are repeated until reasonable model results 

are achieved. Field data collected for the model included 

multiple measurements of base flow, streambed head and 

temperature, and other physical characteristics of Whittlesey Creek and adjacent streams.

A continuous rainfall-runoff model, called Soil 

and Water Assessment Tool (SWAT) (Neitsch and others, 2001), was used to simulate annual runoff and flood 

peaks in Whittlesey Creek. The model was calibrated to 

data collected at a USGS streamflow-gaging station near 

the mouth and to stage data collected at various upstream 

locations in the basin (fig. 1). After calibration, the SWAT 

model was run for five simulations of varied land cover: 

(1) present (1992-93), (2) land cover from 1928, representing the peak of agricultural land cover, (3) a forested basin, 

representing pre-European settlement prior to about 1870, 

(4) a reforested basin where forest is substituted for grassland and agriculture land, and (5) and a developed basin 

in which 25 percent of the basin is developed into urban 

residential land.

Acknowledgments

The project was made possible through the collaborative efforts of Maureen Gallagher, formerly with the 

U.S. Fish and Wildlife Service, Ashland, Wis., and Sandra 

Schultz, formerly with Bayfield County Land and Water 

Conservation Department. Ulf Gafvert, formerly with the 

Natural Resources Conservation Service, provided digital 

elevation model data for the rainfall-runoff model, assisted 

with field data collection, and provided much insight into 

the local soil and hydrologic characteristics of the basin. 

This study could not have happened without the cooperation of riparian landowners who provided access for baseflow surveys and for checking and downloading data from 

stage recorders.

In addition, the authors of this report acknowledge the 

late Jeff Carlson (trout conservationist and active member of Trout Unlimited) for his great efforts at preserving 

current fish habitat and his dedication toward reestablishing brook trout in the Whittlesey Creek National Wildlife 

Refuge. Jeff and other volunteers built the gage house for 

the streamflow-gaging station on Whittlesey Creek that 

shelters the stream monitoring equipment. 

Methods

Field investigations included measurements of base 

flow, pH, specific conductance, water temperature, streambed head, and streambed temperature from 1999 through 

2000 in Whittlesey Creek, Boyd Creek, Sioux River, and 

North Fish Creek (fig. 1). Surficial deposits were probed 

and core samples were collected at two locations in the 

study area by use of a hydraulically powered coring 

device. Continuous streamflow was monitored on Whittlesey Creek at one streamflow-gaging station. Stream stages 

were monitored at five remote sites on Whittlesey Creek 

from 2000 through 2001.

Ground-water flow for the study area was simulated 

using an analytic-element model (GFLOW) and a finitedifference model (MODFLOW). GFLOW (Haitjema, 

1995) was used to construct a simplified one-layer screening model; MODFLOW (McDonald and Harbaugh, 1988) 

was used to construct a more detailed three-dimensional 

ground-water-flow model. The GFLOW model was used 

for hypothesis testing, estimating recharge, and improving 

the MODFLOW model. The analytic-element methodology is not as widely utilized for numerical modeling as 

finite-difference techniques (Hunt and Krohelski, 1996; 

Hunt and others, 2000). A complete description of analytic 
elements is beyond the scope of this report; a brief description is given below. Strack (1989) and Haitjema (1995) 

provide detailed discussions of this method.

An infinite aquifer is assumed in analytic element 

modeling. The problem domain does not require a grid or 

involve interpolation between cells. To construct an analytic-element model, features that affect ground-water flow 

(such as wells and surface-water bodies) are entered as 

mathematical elements or strings of elements. The amount 

of detail specified for the features depends on distance 

from the area of interest. Each element is represented 

by an analytic solution. The effects of these individual 

solutions are added together to arrive at a solution for the 

ground-water-flow system. Because the solution is not 

confined to a grid, heads and flows can be computed anywhere in the model domain without nodal averaging. In the 

GFLOW model, the analytic elements are two-dimensional 

and are used to simulate only steady-state conditions. 

A continuous rainfall-runoff model, based on 

meteorological data, altitude, land cover, and soils, was 

created for the surface-water-contributing basin of Whittlesey Creek by use of SWAT (Neitsch and others, 2001). 

SWAT uses a geographic information system (GIS)-based 

interface and GIS coverages of digital elevation models to 

divide a drainage basin into similar-sized subbasins that 

are further divided, on the basis of soil type and land cover, 

into areas of like hydrologic characteristics. Meteorological data were used as inputs if available; if measured 

values were not available, then the model’s estimating 

routines for nonexistent or missing periods of data were 

used. The SWAT model incorporates many commonly 

applied, widely accepted empirical formulas in its calculations of continuous runoff and flow routing. The model 

also accounts for antecedent conditions by tracking soilmoisture changes with continuous and seasonally adjusted 

mathematical routines representing soil and plants. The 

calibrated rainfall-runoff model was used to simulate the 

effects of five land-cover simulations and their effects on 

annual runoff and flood peaks in Whittlesey Creek.

Field Investigations

Streamflow measurements were made in Whittlesey 

Creek and surrounding streams during low-flow (baseflow) conditions by use of standard USGS techniques 

(Buchanan and Somers, 1984). Base-flow measurements 

were made in August 1999, April 2000, and August 2000. 

Stream-water temperature was measured near the center 

of flow with a hand-held thermometer or water-quality 

multimeter. In August 2000, pH and specific conductance 

also were measured with a water-quality multimeter 

(fig. 1). 

Streambed head and temperature data were collected 

during August 2000 from a subset of the base-flow sites. 

Streambed head was measured by installing a minipiezometer to a depth of 3 ft below the stream bottom near 

the center of flow in the stream. The minipiezometers 

were constructed of a high-density polyethylene tubing 

attached to a 6-in. stainless steel mesh screen. The head 

in the minipiezometer was allowed to equilibrate and was 

then measured relative to the stream surface. Streambed 

temperature data were collected by use of a hand-held 

thermometer inserted 6-12 in. below the stream bottom. 

Temperature measurements were made near the center of 

flow and in shaded locations where possible. 

Estimates of streambed leakance (the vertical 

hydraulic conductivity of the streambed sediments divided 

by its thickness) were calculated for three sites on Whittlesey Creek and one site on North Fish Creek. Estimates 

of vertical hydraulic conductivity (Kv

) were based on 

Darcy’s Law (Freeze and Cherry, 1979) and measurements 

of gradient between the surface-water and ground-water 

systems (minipiezometer head data) and unit groundwater discharge to the creek. Unit discharge to the creek 

was determined from the measured change in discharge 

(August, 2000 base-flow measurements) over a known 

stream area. The stream area was determined from streamwidth measurements made in the field and stream-length 

measurements between base-flow sites made with a GIS. A 

streambed thickness of 3 ft was used to calculate leakance 

and was based on the depth of minipiezometer penetration. 

Streambed leakance was used as ground-water-flow model 

input to quantify the interaction between ground-water and 

surface-water features of the model. 

Surficial deposits were probed and core samples collected at one location underlain by the Copper Falls Formation and another location underlain by the Miller Creek 

Formation during July 2000 (fig. 1). The Copper Falls site 

was approximately 1 mi west of the headwaters of Whittlesey Creek in the Chequamegon National Forest. The Miller 

Creek site was approximately 800 ft south of Whittlesey 

Creek near the confluence with the North Fork. Cores were 

collected to verify the texture of surficial deposits. Probing 

was done with a wire-wound stainless steel screen to determine the depth to the water table and determine whether 

there were perched ground-water conditions. 

Continuous stream stage was recorded at 15-minute 

intervals at the streamflow-gaging station (fig. 1). Data 

collection started April 1, 1999, and continues to the 

present (2003); however, several periods of record are 

Methods 7
8 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

missing from times when the equipment was vandalized 

before a more secure structure was built. Periods of missing record are April 1-21, 1999; May 30-June 2, 1999; 

October 31, 1999-February 29, 2000; March 9-10, 2000; 

and April 19-August 28, 2000. During periods of missing 

data, stage at the monitoring site was measured weekly 

by a local observer, and peak stage was recorded by use 

of a crest-stage recorder (Buchanan and Somers, 1984). 

Flow measurements were made at varying stream stages 

throughout the year by use of standard USGS methods 

(Buchanan and Somers, 1984). Relations between stage 

and flow were determined from these data, and a rating 

table was developed to convert stage data into flow data. 

Flow was calculated for each 15-minute interval (when 

data were available) and used to determine the daily mean 

streamflow at the station (Kennedy, 1983). During periods 

of missing stage data, estimated flows were based on daily 

measurements of stage at the station and by comparison of 

recorded flow in the nearby North Fish Creek. Streamflow 

statistics for the station (USGS station number 040263205) 

for the period April 1, 1999, to September 30, 2001, are 

listed in table 1.

Table 1. Streamflow statistics for U.S. Geological Survey 

streamflow-gaging station 040263205, Whittlesey Creek 

near Ashland, Wis., for April 1, 1999, to September 30, 2001

[ft3/s, cubic feet per second]

Annual mean flow 22 ft3/s

Maximum daily mean flow 370 ft3

/s (on April 23, 2001)

Maximum instantaneous flow 777 ft3

/s (on April 23, 2001)

Minimum daily mean flow 16 ft3

/s

Minimum instantaneous flow 16 ft3

/s

Remote stage recorders were placed in the basin 

upstream from the streamflow-gaging station and used 

to determine the timing of peak flows through the channel network (fig. 1). The remote recorders collected stage 

data at 1-hour or 15-minute increments. Data from these 

recorders were used to determine the time of concentration 

(the amount of time it takes a drop of water falling at the 

hydraulically farthest point from the drainage basin outlet 

to reach the outlet used for peak runoff calculation) and to 

help determine the channel routing variables to use during 

model calibration. Damage from vandalism and the debris 

carried by floods resulted in a significant amount of lost 

data from these stage recorders and required moving the 

stage recorders between floods to get sufficient data for the 

SWAT model.

Simulation of Ground-Water Flow 

The GFLOW model domain includes all major 

drainage basins in the vicinity of the Bayfield Peninsula, 

ranging from the Bois Brule River in the west to the Bad 

River in the east (fig. 5). Other surface-water features 

include Lake Superior to the north and several lakes and 

streams to the south. The geometry of the model layer 

includes a stepped bottom altitude ranging from 500 ft 

near Lake Superior to 750 ft beneath the Bayfield Highlands. The single layer represents all of the unconsolidated 

deposits and the shallow part of the Bayfield Group. Zones 

of horizontal hydraulic conductivity (Kh) and recharge to 

the ground-water system are represented in the GLFOW 

model as inhomogeneities and represent the sandy deposits 

of the Copper Falls Formation and the clayey Miller Creek 

Formation. The GFLOW model includes “far-field” and 

“near-field” linesinks. The far field surrounds the near field 

area of interest. In the far field, streams and lakes are simulated with coarse linesinks having little or no resistance 

between the surface-water feature and the ground-water 

system. The purpose of simulating the far field is to have 

the model explicitly define the regional ground-water-flow 

field in the vicinity of the area of interest. The near field 

represents the area of interest and includes several of the 

streams adjacent to and including Whittlesey Creek 

(fig. 5). Near-field streams are simulated using slightly 

more detailed linesinks with streambed resistance to control 

ground-water/surface-water interaction. In GFLOW, resistance is calculated by dividing streambed sediment thickness by the Kv

 of the sediments. Near-field streams are used 

for flux calibration; far-field streams are not. The linesinks 

representing streams and lakes were assigned altitudes 

based on USGS 7.5-minute quadrangle maps. Near-field 

linesinks were assigned stream widths (ranging from 2 to 

75 ft) based on field measurements and stream order.

Fifty-nine head targets and eight flux targets were 

used for the GFLOW model calibration. Head targets were 

compiled using depth to water information from drillers’ 

logs. Depth to water was converted to water-level altitude 

based on site location and land-surface altitudes on USGS 

7.5-minute quadrangle maps. Flux targets included four 

sites on Whittlesey Creek, three sites on North Fish Creek, 

and one site on an unnamed tributary north of Whittlesey 

Creek (fig. 6). Recharge and hydraulic-conductivity values 

were adjusted until simulated heads and base flows were 

similar to measured values. 
0 10 20 KILOMETERS

0 10 20 MILES

EXPLANATION

Approximate extent of near-field area

MODFLOW boundary

Area of high recharge and high hydraulic conductivity (inhomogeneity analytic element)

Area of low recharge and low hydraulic conductivity (inhomogeneity analytic element)

Rivers and lakes (linesink analytic element)

DOUGLAS COUNTY BAYFIELD COUNTY

ASHLAND COUNTY IRON COUNTY

WASHBURN COUNTY SAWYER COUNTY PRICE COUNTY Bois Brule River

Chequamegon Bay

Bad River

Whittlesey Creek

L A K E S U P E R I O R

Figure 5. Hydrologic features simulated with analytic elements for the GFLOW model of the Whittlesey Creek, Wis., study area 

and vicinity. (The locations of flux and head targets are shown in figure 7.)

Methods 9
10 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

The MODFLOW model (figs. 6 and 7) includes all of 

the delineated surface-water drainages of Whittlesey Creek 

and much of North Fish Creek and the Sioux River, and 

part of Lake Superior. The MODFLOW model consists 

of two layers with layer 1 representing unconsolidated 

deposits and layer 2 representing the Bayfield Group. The 

model grid contains 200 rows and 200 columns per layer 

(40,000 model cells per layer). Each model cell is 462 ft 

on a side. Model-layer top and bottom altitudes were based 

on various data sources. Layer 1 top altitudes were based 

on 500-m (1,640-ft) and 30-m (98-ft) Digital Elevation 

Model (DEM) data (U.S. Geological Survey, 2001). Layer 

1 bottom altitudes were determined from geologic and 

drillers’ logs obtained from the Wisconsin Geological and 

Natural History Survey and from published bedrock altitudes (Wold, 1979) and unconsolidated deposit thickness 

maps of the area (Young and Skinner, 1974). Because of 

the extreme thickness of the Bayfield Group (as much as 

6,900 ft), it was assumed the altitude of the base of the 

ground-water-flow system (bottom of layer 2) was much 

shallower than the bottom of the sandstone. It is possible 

that the ground-water-flow system may be bounded at 

depth by a fresh-water/saline-water interface. Information 

about the possible location of this interface is unavailable; 

therefore, the bottom of the ground-water flow system 

was arbitrarily set at an altitude of zero. Sensitivity of 

the model simulations to changes in bottom altitude was 

tested. Lateral boundaries for this model are represented 

by constant flux (MODFLOW well package), which was 

extracted from the corresponding area of the GFLOW 

model following the method described by Hunt and others 

(1998). This extraction feature is particularly important 

for this study area because the extent of the surface-water 

noncontributing basin is difficult to delineate, and surfacewater topographic divides may not coincide with groundwater divides. The extent of the MODFLOW model 

includes several major hydrologic boundaries for Whittlesey Creek and therefore should have minimal impact 

on simulation of ground-water flow in the vicinity of the 

creek. The major boundaries include Lake Superior to the 

east, Sioux River to the north, North Fish Creek to the 

south, and a regional ground-water divide in the Bayfield 

Highlands to the west. No high-capacity wells are within 

the MODFLOW model area; therefore, the only wells 

included in the model are those that represent the constant 

flux boundaries. 

The MODFLOW model was divided into three zones 

of hydraulic conductivity and two zones of recharge (fig. 

7). Model layer 1 includes two K zones and corresponding 

recharge zones representing areas underlain by the Copper 

Falls and Miller Creek Formations. Layer 2 has a third K 

zone that represents the Bayfield Group. Initial estimates 

of many of the hydrogeologic parameters used in the 

model are listed in table 2. Gaining reaches of streams and 

Lake Superior were simulated using the MODFLOW river 

package (McDonald and Harbaugh, 1988). Streambed 

leakance for most of the simulated streams was based on 

field measurements. Streambed leakance for Lake Superior 

was initially estimated and then adjusted during model 

calibration. 

Table 2. Estimated range or value of aquifer properties, 

recharge, and stream characteristics in the study area

[Kh, horizontal hydraulic conductivity; Kv, vertical hydraulic 

conductivity; Fm, formation; ft, feet; d, day; in/yr, inches per year]

Characteristic Estimated range 

or value

Kh

 Miller Creek Fm 30 ft/d

Kh

 Bayfield Group 0.13 to 10 ft/d

Kh

 Copper Falls Fm 0.48 to 230 ft/d

Kv

 Miller Creek Fm 0.03 ft/d

Kv

 Bayfield Group 0.14 ft/d

Kv

 Copper Falls Fm 0.48 to 230 ft/d

Effective bottom elevation 

of layer 2

 0 ft

Recharge through Miller Creek Fm 1 to 3 in/yr

Recharge through Copper Falls Fm 8 to 18 in/yr

Stream width 1 to 75 ft

Streambed leakance 0.01 to 96 ft/d/ft

Streambed thickness 3 ft

The same head and flux targets used in the GFLOW 

model were also used for calibration of the MODFLOW 

model (fig. 6). Of the 59 head targets, 53 are in unconsolidated deposits (model layer 1) and 6 are in bedrock (model 

layer 2). 

Estimates of Hydraulic Conductivity and 

Recharge

Estimates of horizontal hydraulic conductivity (Kh) 

for the Bayfield Group and sandy Copper Falls Formation 

were calculated by use of the computer program TGUESS 

(Bradbury and Rothschild, 1985), which uses data collected during pumping tests conducted when a well is 

drilled. Data were available for 53 wells completed in the 
EXPLANATION

Constant flux boundary

Head-dependent flux boundary (river-node)

Surface-water-contributing and noncontributing basin

Road

Flux target

Head target, layer 1

Head target, layer 2

0 1 2 MILES

0 1 2 KILOMETERS

Boyd Creek

North Fish Creek

Sioux River

Whittlesey Creek

1

200

1 200

Row

Column

Figure 6. Boundary conditions and location of calibration targets used in the MODFLOW model of the Whittlesey Creek, Wis., 

study area.

Methods 11
12 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Copper Falls Formation and 6 wells completed in the Bayfield Group. The average value of Kh

 for wells in the Copper Falls Formation was 38 ft/d (values ranged from 0.48 

to 230 ft/d) and 1.4 ft/d (ranging from 0.13 to 4.6 ft/d) for 

in wells in the Bayfield Group. Kh

 values calculated from 

a nearby pumping test, conducted by the USGS on 

Precambrian bedrock similar to the Bayfield Group, 

range from about 2 to 10 ft/d (Charles Dunning, USGS, 

oral commun., April 2000). No pumping-test data were 

available for the Miller Creek Formation. The Miller 

Creek Formation and underlying deposits were typically 

described as alternating layers of sand and clay in drillers’ 

logs, and for this reason, Kh in this part of the study area 

was assumed to be lower than Kh of the Copper Falls Formation (a Kh

 of 30 ft/d was used in the preliminary models). Hydraulic conductivities for unconsolidated deposits 

underlying Lake Superior were assigned values similar 

to those used for the Miller Creek Formation (table 2). 

Because of the relatively homogeneous nature of the Copper Falls Formation, vertical hydraulic conductivity (Kv

) 

North

Model layer 2

Model layer 1

B a y f i e l d H i g h l a n d s

Copper Falls Formation

Miller Creek Formation

North Fish Creek

Whittlesey Creek

Lake Superior

Bayfield Group

B a y f i e l d H i g h l a n d s

Copper Falls Formation

Miller Creek Formation

North Fish Creek

Whittlesey Creek

Lake Superior

Bayfield Group

WISCONSIN

Study area

Geology from Clayton, 1984 

and Mudrey and others, 1982.

NOT TO SCALE

EXPLANATION

Hydraulic conductivity/recharge zone 1

Hydraulic conductivity/recharge zone 2 

Hydraulic conductivity zone 3 

MODFLOW river node

Figure 7. Block diagram showing the MODFLOW model hydraulic conductivity/recharge zonation, river nodes, and layer 

configuration. (Area shown is the same as MODFLOW model extent in figure 6.)
was set equal to Kh

. Because the Bayfield Group includes 

layers of sandstone, siltstone, and shale and the Miller 

Creek Formation includes layers of sand and clay, Kv was 

assumed to be lower than Kh for the Bayfield Group and 

Miller Creek Formation. Kv values of 0.14 and 0.03 ft/d for 

the Bayfield Group and Miller Creek Formations, respectively, were used in the preliminary model.

Ground-water recharge in the study area was estimated to be between 8 and 18 in/yr in the areas directly 

underlain by the Copper Falls Formation (mostly sand) and 

1 to 3 in/yr in areas underlain by the Miller Creek Formation (mostly clay) (table 2). Initial estimates of recharge 

were based on base-flow estimates from streamflow data 

from nearby stations on North Fish Creek, and the Bois 

Brule, White, and Bad Rivers. Recharge was estimated 

from these stations by means of the computer program 

HYSEP (Sloto and Crouse, 1996) and ranged from 8.2 

to 17.4 in/yr. Most of these rivers have ground-watercontributing areas directly underlain by both the Copper 

Falls and Miller Creek Formations. Therefore, the resulting estimates of recharge are a combination of higher 

recharge in areas underlain by sand and lower recharge in 

areas underlain by clay. Since there are no surface-drainage features in the Bayfield Highlands, another estimate 

of recharge through the Copper Falls Formation can be 

calculated as average annual precipitation (32 in.) minus 

average annual evapotranspiration (17.7 in.). The resulting estimate of 14.3 in/yr of recharge assumes negligible 

underflow and change in storage. An additional streamflow 

site on North Fish Creek near the headwaters has base flow 

that represents about 2 to 3 in/yr of ground-water recharge 

and is in an area mostly underlain by clay (Rose and 

Graczyk, 1996). The underlying assumptions in estimating recharge from streamflow records are that base flow 

represents ground water discharging to the stream and that 

the surface-water-contributing basin and the ground-watercontributing area are coincident. Although the second 

assumption is not necessarily true in the study area, it does 

provide a starting point for estimating recharge, which can 

be reevaluated during model calibration. 

Parameter Sensitivity and Model Calibration

The computer program UCODE (Poeter and Hill, 

1998) was used for parameter sensitivity testing and automatic calibration of the MODFLOW model. Observations 

used for sensitivity testing and model calibration include 

the 59 head targets and 8 flux targets. Observation weights 

were assigned as follows: all heads, standard deviation = 5 

ft; all streamflow stations or sites measured during 

low-flow conditions, coefficient of variation = 0.1; and 

sites where streamflow was estimated from staff gages, 

coefficient of variation = 0.15. Parameters tested for 

sensitivity were: Kh and Kv of the Copper Falls and Miller 

Creek Formations and the Bayfield Group, recharge (two 

zones), Lake Superior streambed leakance, and the altitude 

of the bottom of layer 2. Parameters used in model calibration were: Kh

 of the Miller Creek and Copper Falls Formations, Kv

 of the Miller Creek Formation and the Bayfield 

Group, and streambed leakance for Lake Superior.

Pathline Analysis and Delineation of GroundWater-Contributing Area

The ground-water-contributing area (from the deep 

flow system and nonperched part of the shallow system) 

for Whittlesey Creek was delineated using the computer 

program MODPATH (Pollock, 1994) and output from the 

calibrated MODFLOW model. Ten hypothetical particles 

of water were placed in each river cell that represents the 

gaining part of Whittlesey Creek. The particles were then 

tracked backward to the water table, and the corresponding pathlines were exported into a GIS coverage. The areal 

extent of the pathlines was manually digitized and represents the ground-water-contributing area. Values of porosity used in this analysis were 14 percent for the Bayfield 

Group (Ojakangas, 1986), 25 percent for the Copper Falls 

Formation, and 35 percent for the Miller Creek Formation. 

The porosities used for the unconsolidated deposits were 

based on ranges of values published by Freeze and Cherry 

(1979). 

Simulation of Rainfall Runoff

For the SWAT model, the Whittlesey Creek surfacewater-contributing basin was divided into 19 subbasins 

based on tributary junctions and similarities in soils, land 

cover, and slopes (table 3). Each subbasin was further 

divided into Hydrologic Response Units (HRUs) based on 

the significant land cover and soil type. In this study, land 

cover was considered significant if it made up 10 percent 

or more of the subbasin area and a soil type significant if it 

made up 15 percent or more of the subbasin area. An HRU 

was created for every combination of soil and land cover 

greater than those thresholds. Areas of land cover and soil 

type less than those thresholds were considered insignificant and were divided among the significant HRUs based 

on the ratio of HRU area to total area. Thus, if 60 percent 

of the basin was HRU1, then 60 percent of the insignificant area was treated the same as HRU1.

Methods 13
14 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis. Table 3. Physical characteristics of subbasins used in Whittlesey Creek, Wis., Soil and Water Assesment Tool (SWAT) model [mi, miles; mi2, square miles; ft, feet; in/hr, inches per hour] Subbasin Area (mi2

)

Average basin 

slope length 

(ft)

Average basin 

slope 

Average width 

of channel at 

top of bank

(ft)

Average 

depth of main 

channel; top of bank to bottom 

(ft)

Main channel 

slope 

Main channel 

length

(mi)

Effective 

hydraulic 

conductivity in 

main channel 

(in/hr)

Channel width 

to depth ratio 

1 1.12 200 0.054 8.20 0.656 0.015 1.3041 3.94 12.32 .490 200 .063 10.2 .755 .024 .19 3.94 13.23 .108 60 .181 10.5 .787 .017 .50 3.94 13.44 1.64 300 .047 10.2 .755 .017 2.5 3.94 13.25 .281 120 .102 15.4 1.02 .012 .62 3.94 15.36 .278 120 .112 16.4 1.05 .012 .56 3.94 15.57 .0618 120 .117 17.7 1.12 .010 .24 .00 16.08 .131 80 .127 11.8 .853 .012 .68 .00 14.09 .355 200 .071 3.94 .427 .024 1.4 3.94 9.810 .127 200 .055 24.0 1.35 .007 .31 .00 17.711 .0579 200 .061 24.3 1.38 .002 .31 .00 17.712 .0541 300 .021 24.3 1.38 .004 .43 .00 17.813 .0541 400 .018 24.3 1.38 .004 .56 .00 17.814 .0309 400 .015 24.6 1.38 .003 .25 .00 17.815 .772 80 .127 13.1 .919 .029 .87 3.94 14.416 .587 120 .110 5.58 .492 .031 1.5 3.94 10.817 .390 80 .145 11.5 .820 .020 1.6 3.94 13.818 .479 200 .071 4.92 .459 .032 1.4 3.94 10.419 .166 200 .089 23.0 1.31 .009 .50 .00 17.5
The Whittlesey Creek SWAT model used the Soil 

Conservation Service (SCS) Curve Number Method for 

runoff estimation. (Soil Conservation Service, 1972). This 

method uses soil and land-cover information to determine 

curve numbers, which in turn are used by the model to 

predict annual runoff. Time of concentration and the peak 

rain intensity are used to calculate the peak flood flows. 

SCS curve numbers used in the Whittlesey Creek SWAT 

model for the five land-cover simulations are listed in 

table 4. The SWAT model adjusts the SCS curve numbers 

(and thus the amount of runoff) between runoff events on 

the basis of antecedent soil moisture conditions. SWAT 

uses Manning’s equation and channel roughness coefficients to define the rate and velocity of flow (Chow, 1959). 

Water is routed through the channel network by use of the 

Muskingum Method, which is a modification of the kinematic wave flood-routing model described by Chow and 

others (1988). The SWAT model uses a procedure developed by Lane (1983) for estimating transmission losses; 

that is, the loss of water through the bottom and sides of 

the channel. 

Evapotranspiration was calculated in the model by the 

Priestly-Taylor Method (Priestly and Taylor, 1972) using 

solar radiation, air temperature, and relative humidity 

from the National Oceanic and Atmospheric Administration station in Gordon, Wis., about 50 mi southwest of the 

Whittlesey Creek Basin. Snowmelt was modeled by use of 

snowfall and temperature records and was based on equations developed by Anderson (1976). Hourly rainfall data 

at the streamflow-gaging station were limited because of 

repeated vandalizing of equipment at the site (no data from 

rain events greater than 1 in. were available); thus, precipitation data available from the Ashland Experimental Farm 

Weather Station of the National Weather Service were used 

in the model. Only daily data were available at the Ashland 

Experimental Farm; thus, a skewed normal distribution 

of daily rainfall was used in the model (Fiering, 1967, 

Nicks, 1974). Daily temperature means, maximums, and 

minimums used in the model also came from the Ashland 

Experimental Farm Weather Station.

DEM data were produced by use of softcopy photogrammetric software solutions as part of the Whittlesey 

Creek Orthophoto Production Project (fig. 8) (Benchmark 

GIS, 2001). GIS programs were used to develop highresolution othophotography and spatially accurate terrain 

models. The DEM has 10-meter cell spacing and was 

derived by interpolation of vector contour lines from 1:

24,000-scale USGS topographic maps (Benchmark GIS, 

2001). The surface-water-contributing basin derived from 

DEM data and used in the SWAT model had an area of 

7.2 mi2

, which is slightly smaller than the basin derived 

from USGS 7.5-minute topographic maps (7.4 mi2).

Subbasin boundary 

and identifier

Stream

EXPLANATION

Surface-water-contributing 

basin boundary

4

4 1

2

16

3

15 6

18

5

17

9

8

7 19

10

11

12

13

14

MILE

0 KILOMETER

0 0.5

0.5 1

1

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

Altitude, in feet

600–689

690–782

783–874

875–966

967–1,054

1,055–1,146

1,147–1,237

Figure 8. Digital Elevation Model of land surface for the Whittlesey Creek, Wis., surface-water-contributing basin. Drainage 

divides were derived from 10-meter Digital Elevation Model data (Benchmark GIS, 2001).

Methods 15
16 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Table 4. Soil and Water Assesment Tool (SWAT) model input parameter values for Whittlesey Creek, Wis., for five model simulations

[SCS, Soil Conservation Service (1972); oC, degrees Celsius.]

Land cover Soil 1992-93 Presettlement

(before 1870)

Peak 

agriculture

(1928)

Reforested Developed

SCS curve number

Forest Sand 28 28 28 28 381

Forest Clay 69 69 69 69 731

Grassland Sand 39 -- -- -- 461

Grassland Clay 74 -- -- -- 771

Brushland Clay 70 -- -- -- 701

Forested wetland Sand 76 76 76 76 76

Nonforested wetland Clay 76 -- -- 76 76

Agriculture Sand -- -- 67 -- --

Agriculture Clay -- -- 85 -- --

Overland flow number

Forest Sand 0.25 0.8 0.8 0.8 0.25

Forest Clay 0.25 0.8 0.8 0.8 0.25

Grassland Sand 0.15 -- -- -- 0.15

Grassland Clay 1.15 -- -- -- 1.15

Brushland Clay 0.6 -- -- -- 0.6

Forested wetland Sand 0.25 0.8 0.8 0.8 0.25

Nonforested wetland Clay 0.3 -- -- 0.7 0.3

Agriculture Sand -- -- 0.06 -- --

Agriculture Clay -- -- 0.06 -- --

Channel roughness coefficient

All All 0.06 0.15 0.06 0.15 0.014

Other SWAT model input parameters

Ground-water delay time 31 days

Base-fl ow alpha factor 0.098 days

Ground-water revaporation coeffi cient 0.07

Deep aquifer percolation factor 1

Snowmelt base temperature 2.0 o

C

Snow pack temperature lag factor 0.4 o

C

Soil evaporation compensation factor 0.01

1Represent a 25-percent increase in urban residential land having curve numbers of 68 for sand and 85 for clay.
The WISCLAND (Wisconsin Initiative for Statewide 

Cooperation on Landscape Analysis and Data) land-cover 

data used in the model were derived from LANDSAT 

Thematic Mapper (TM) satellite imagery acquired from 

flyovers in August 1991; May, July, September, and October 1992; and May 1993 (Reese and others, 2002).

Copies of township-based maps of land cover in 

1928 were obtained from the Wisconsin Historical Society 

Library (Wisconsin Department of Agriculture and Wisconsin Geological and Natural History Survey, 1928). The 

maps were digitized and spatially rectified by use of a GIS.

Soil-characteristic information for the study area was 

compiled from USSOILS, a national digital coverage of 

the State Soil Geographic Database (STATSGO) (Schwarz 

and Alexander, 1995). Soil characteristics examined in 

this study included clay content (percentage of soil with 

particles less than 2 μm in size), organic-matter content 

(percentage by weight), soil erodibility (K factor), permeability rates (in/hr), and slope (percent). The USSOILS 

coverage was intersected with the drainage subbasin outlines (fig. 9), and each of the soil characteristics of interest 

was calculated as an area-weighted average. The scale of 

the soils coverage is coarse (1:250,000) given the size of 

the Whittlesey Creek surface-water-contributing area, but 

it was the best source of digital soils data when the SWAT 

model was run.

SWAT Model Calibration

Whittlesey Creek had a consistent measured base 

flow of 17 to 18 ft3/s at the USGS streamflow-gaging station during the study. The consistency of this base flow 

and the results of the ground-water-flow modeling done 

as part of this study indicate that most of this base flow 

originates outside the surface-water-contributing basin for 

Whittlesey Creek, mostly from ground water in the deep 

regional flow system. The amount of base flow originating inside the surface-water-contributing basin is minimal. 

Without a regional source of base flow, all of Whittlesey 

Creek would likely be ephemeral. 

The SWAT model is able to track water that falls 

within the surface-water-contributing basin. The model 

does not have the ability to account for water that crosses 

surface-water drainage divides, such as regional ground 

water. Because of this, the model was calibrated to the 

flow at the streamflow-gaging station (field number 2, 

fig. 1). This flow was first adjusted for the regional 

ground-water component by subtracting a constant 

16.75 ft3

/s from the station flow record. The value of 

16.75 ft3/s was used because it was the lowest base flow 

recorded at the station during water year 1999 and the 

uncalibrated SWAT model indicated no base flow originated from the surface-water-contributing basin during 

Subbasin boundary 

and identifier

Stream

EXPLANATION

Surface-water-contributing 

basin boundary

Sand

Clay

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10

4

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10

11

12

13

14

MILE

0 KILOMETER

0 0.5

0.5 1

1

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

Figure 9. Soils in the Whittlesey Creek, Wis., surface-water-contributing basin from STATSGO data (Schwartz and Alexander, 

1995). Drainage divides were derived from 10-meter Digital Elevation Model data (Benchmark GIS, 2001).

Methods 17
18 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

extended periods of minimal precipitation. The lowest flow 

ever recorded at the streamflow-gaging station is 16 ft3

/s, 

whereas the ground-water-flow model estimated regional 

base flow at the station to be 15 ft3/s. 

In addition to data from the streamflow-gaging 

station, data for the timing of peak stage in the channel 

upstream of the station were gathered from continuous 

stage-recorder sites (fig. 1) and used to calculate the time 

of concentration for model calibration. Hourly stage data 

showing the shape and timing of a peak from the main 

stem of Whittlesey Creek above the confluence, the North 

Fork of Whittlesey Creek, and at the USGS streamflowgaging station are shown in figure 10 for a runoff event 

that occurred on May 9-10, 2001.

The period of record used in the SWAT model 

calibration was April 1, 1999, to October 15, 2001. The 

calibration targets were annual runoff for the period of 

calibration, the peak daily mean flows for three of the 

largest floods during the period of calibration, peak timing, 

base flow, snowmelt timing, and the regression rate of both 

peaks and base flow. Modeled annual runoff and flood 

peaks were calibrated by adjusting water-budget variables 

such as SCS curve numbers, evapotranspiration rates, overland-flow rates, and ground-water interaction parameters. 

It was determined during calibration that the USSOILS 

coverage, which lumps similar soil types in groups, was 

not adequate by itself for this scale model. Therefore, 

soil-profile parameters were adjusted for several subbasins 

on the basis of county-level soil survey maps (unpublished 

data, Ulf Gafvert, Natural Resources Conservation Service, 

written comm., 2002) that more accurately detail the 

complexity in the soils within the Whittlesey Creek Basin. 

Peak timing was calibrated by adjusting channel-routing 

characteristics and snowmelt parameters until peak timing 

matched the values calculated from actual stage data. 

Use of a continuous model like SWAT can help 

account for varying antecedent conditions such as moisture 

content, seasonal variations in land cover, and even factors 

as detailed as the amount of detritus on the land surface. 

The inherent problems in modeling remain, however, in 

that empirical formulas incorporate a finite number of variables to represent a complex real system. Because of this, 

the model was calibrated with a best-fit approach. During 

model calibration, input parameters were adjusted until 

the modeled results best fit all calibration targets, though 

emphasis was placed on the average annual runoff for the 

period of calibration, the size and timing of the three largest peak flows, and base-flow recession rates. 

Rainfall-Runoff Model Simulations

Using the calibrated SWAT model, conditions for 

1992-93 land cover and four alternative land-covers were 

simulated (table 5). The first simulation (presettlement) 

represented conditions before European settlement (pre1870), and the second (peak agriculture) represents historical conditions in the 1920s and 1930s, when row-crop 

agriculture in the area was at its peak. Both simulations 

-4

-2

0

2

4

6

8

10

12

14

12:00 AM

3:00 AM6:00 AM9:00 AM

12:00 PM

3:00 PM6:00 PM9:00 PM

12:00 AM

3:00 AM6:00 AM9:00 AM

12:00 PM

ARBITARY STAGE, IN INCHES

Whittlesey Creek at

gaging station (site 2)

Whittlesey Creek above

confluence (site 6)

North Fork Whittlesey Creek

above confluence (site 19)

Figure 10. Measured hourly stage data used in timing peak stages through Whittlesey Creek, Wis., for calibration of channel 

characteristics in the Soil and Water Assessment Tool (SWAT) model, May 9-10, 2001.
use land-cover data from the 1928 Land Economic Inventory (Wisconsin Department of Agriculture and Wisconsin 

Geological and Natural History Survey, 1928) (fig. 11). 

The peak agriculture scenario uses the data as is, whereas 

all land cover other than wetland is converted to forest in 

the presettlement scenario because it is assumed that the 

forest was clear cut from about 1870 to 1900. 

All land-cover categories for 1992-93 (other than wetland) were changed to forest in the third model simulation 

(reforested) (table 5). Additionally, overland and channel 

roughness coefficients in the model were increased to the 

maximum published values for forest to simulate the greatest amount of debris in the forest floors in the upland and 

the greatest amount of woody debris in the stream channel 

itself that would be reasonable (fig. 12). It should be noted 

that the reforested simulation has about 10 percent less 

wetland than the presettlement simulation.

A fourth simulation (developed) was made by adjusting all curve numbers for each HRU in the calibrated 

model to represent a new mix of land cover, including 

25 percent more urban residential land in each subbasin 

(table 5). Curve numbers from the 1992-93 land-cover 

categories HRU’s were multiplied by 0.75; representing 

that 75 percent of the HRU stayed the same. The theoretical curve numbers for HRU’s with urban-residential land 

use (1/4- to 1/8-acre lots and the same soil) were determined and multiplied by 0.25; representing development 

of 25 percent of the basin. These curve numbers were then 

added together to get the new HRU’s curve numbers that 

represent 75 percent of the 1992-93 land cover and 

25 percent developed land cover. 

Field Data

Results of field measurements of streamflow, water 

temperature, pH, and specific conductance are shown in 

table 6. Base-flow data indicated ephemeral and/or losing 

reaches in the upper parts of the main stem and North 

Fork of Whittlesey Creek, where flows were typically 

zero to less than 0.10 ft3

/s (fig. 13). Base flows increased 

substantially near the confluence of the main stem and 

North Fork. Specific conductance was highest and water 

temperatures lowest near the confluence, indicating that 

regional ground water was discharging to the stream near 

the confluence. Ratios of base flow to drainage areas are 

given in table 7 for Whittlesey Creek and several adjacent 

streams. The ratios in Whittlesey Creek increased significantly below the confluence and were greater than those in 

adjacent streams, including North Fish Creek, Sioux River, 

Boyd Creek, and a Lake Superior tributary to the south 

of Whittlesey Creek. Base flows were generally slightly 

higher in April than in August.

Table 5. Percentages of land-cover types used in the Whittlesey Creek, Wis., Soil and Water Assessment Tool (SWAT) model simulations

[All data are percentages. 1992-93 land cover from WISCLAND land cover (Reese and others, 2002). Peak agriculture data from 1928 Land Economic 

Inventory (Wisconsin Department of Agriculture and Wisconsin Geological and Natural History Survey, 1928)]

1992-93 Presettlement

(before 1870)

Peak agriculture

(1928) Reforested Developed

Row crop agriculture 0.04 0 28.2 0 0.03

Forest-deciduous 50.2 0 0 0 37.6

Forest-evergreen 2.3 0 0 0 1.7

Forest-mixed 13 88.4 60.2 98 9.8

Hay .6 0 0 0 .4

Rangeland 3.4 0 0 0 2.6

Grassland/pasture 28.5 0 0 0 21.4

Wetland-forested 1.6 11.6 11.6 1.6 1.2

Wetland-nonforested .4 0 0 .4 .3

Urban 0 0 0 0 25

Methods 19
20 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Forest

Forested wetland

Nonforested wetland

Agriculture

Subbasin boundary 

and identifier

Stream

EXPLANATION

Land use/land cover

Surface-water-contributing 

basin boundary

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10

4

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10

11

12

13

14

MILE

0 KILOMETER

0 0.5

0.5 1

1

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

Figure 11. Land cover in the Whittlesey Creek, Wis., surface-water-contributing basin, from the 1928 Land Economic Survey 

(Wisconsin Department of Agriculture and Wisconsin Geologic and Natural History Survey, 1928). Drainage divides were 

derived from 10-meter Digital Elevation Model data (Benchmark GIS, 2001).

Forest

Forested wetland

Nonforested wetland

Subbasin boundary 

and identifier

Stream

Water

EXPLANATION

Land use/land cover

Surface-water-contributing 

basin boundary

4

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10 11

12

13

14

4

4

1

2

16

3

15 6

18

5

17

9

8

7 19

10

11

12

13

14

MILE

0 KILOMETER

0 0.5

0.5 1

1

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

Figure 12. Land cover in the Whittlesey Creek, Wis., surface-water-contributing basin used in the modeled reforested simulation. 

Drainage divides were derived from 10-meter Digital Elevation Model data (Benchmark GIS, 2001).
Table 6. Results of field investigations of base flow and physical characteristics of Whittlesey Creek and adjacent streams, Wis.

[USGS, U.S. Geological Survey; mi2, square miles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; in., inches; ns, not sampled; —, no USGS station number 

established; e, estimated. Drainage area reflects surface-water-contributing basin only.]

Field 

number

USGS station 

number Name

Drainage

area

(mi2)

Date

sampled

Discharge 

(ft3/s) pH

Specific

conductance 

(μS/cm)

Water

temperature 

(oC)

Streambed

head,

relative to

stream

surface (in.)

Temperature 

below stream 

bottom

(oC)

August 1999

1 04026321 Whittlesey Creek at State Hwy. 13 

near Ashland, Wis.

 7.5 8/31/1999 18.7 ns ns ns ns ns

2 040263205 Whittlesey Creek near Ashland, Wis. 7.4 8/31/1999 19.0 ns ns ns ns ns4 040263199 Whittlesey Creek near Ondassagon Rd. 

near Ashland, Wis.

 7.2 8/30/1999 14.3 ns ns ns ns ns

5 040263197 Whittlesey Creek near Town Rd. 23 

near Ashland, Wis.

 6.75 8/30/1999 10.1 ns ns ns ns ns

6 040263192 Whittlesey Creek near Cherryville Rd. 

near Ashland, Wis.

 4.28 8/30/1999 4.67 ns ns ns ns ns

7 040263189 Whittlesey Creek near Galligan Rd. 

near Moquah, Wis.

 3.48 8/31/1999 .0261 ns ns ns ns ns

8 040263187 Whittlesey Creek near Buvala Rd. 

near Moquah, Wis.

 1.79 8/31/1999 0 ns ns ns ns ns

11 040263185 Whittlesey Creek near Range Rd. 

near Moquah, Wis.

 1.2 8/31/1999 .101 ns ns ns ns ns

12 040263191 Whittlesey Creek tributary near 

Galligan Rd. near Ashland, Wis.

 1.51 8/31/1999 .104 ns ns ns ns ns

13 04026319 Whittlesey Creek near Galligan Rd. 

near Ashland, Wis.

 3.7 8/31/1999 1.17 ns ns ns ns ns

14 04026324 Whittlesey Creek tributuary at State 

Hwy. 13 near Ashland, Wis.

 1.29 8/31/1999 .730 ns ns ns ns ns

15 04026323 Whittlesey Creek tributuary near Ondassagon Rd. near Ashland, Wis. .93 8/31/1999 .691 ns ns ns ns ns17

 —

Whittlesey Creek tributuary #2 near 

Town Rd. 23 near Ashland, Wis.

 .05e 8/30/1999 .0695 ns ns ns ns ns

Field Data 21
22 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis. Table 6. Results of field investigations of base flow and physical characteristics of Whittlesey Creek and adjacent streams, Wis. [USGS, U.S. Geological Survey; mi2, square miles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; in., inches; ns, not sampled; —, no USGS station number established; e, estimated. Drainage area reflects surface-water-contributing basin only.] Field number USGS station number Name Drainage area (mi2

)

Date

sampled

Discharge

(ft3/s) pH

Specific

conductance 

(μS/cm)

Water

temperature 

(

oC)

Streambed

head,

relative to

stream

surface (in.)

Temperature 

below stream 

bottom

(

oC)

19 040263196 North Fork Whittlesey Creek near 

Cherryville Rd. near Ashland, Wis.

 2.31 8/30/1999 3.47 ns ns ns ns ns

20 040263195 North Fork Whittlesey Creek near Cozy 

Corner Rd. near Moquah, Wis.

 2.07 8/31/1999 .243 ns ns ns ns ns

22 040263194 North Fork Whittlesey Creek at Cozy 

Corner Rd. near Moquah, Wis.

 1.82 8/31/1999 .241 ns ns ns ns ns

23 — North Fork Whittlesey Creek .1e 8/31/1999 <.05 ns ns ns ns ns24 04026318 Boyd Creek at Ondassagon Rd. 

near Ashland, Wis.

 3.12 8/31/1999 .00248 ns ns ns ns ns

25 040263182 Boyd Creek at State Hwy. 13 

near Ashland, Wis.

 3.85 8/31/1999 .289 ns ns ns ns ns

26 040263515 Lake Superior tributary at Terwillger 

Rd. near Ashland, Wis.

 2 8/31/1999 .0841 ns ns ns ns ns

27 04026350 North Fish Creek near Ashland, Wis. 47.4 8/31/1999 77.1 ns ns ns ns ns28 040263494 North Fish Creek tributary near County 

Trunk G near Moquah, Wis.

 1.77 8/31/1999 0 ns ns ns ns ns

30

 —

Whittlesey Creek tributuary #3 near 

Town Rd. 23 near Ashland, Wis.

 .075e 8/30/1999 .131 ns ns ns ns ns

31 04026290 Sioux River near Washburn, Wis. 2.51 8/31/1999 .0377 ns ns ns ns ns

April 2000

1 04026321 Whittlesey Creek at State Hwy. 13 

near Ashland, Wis.

 7.5 4/5/2000 19.8 ns ns 5.6 ns ns

2 040263205 Whittlesey Creek near Ashland, Wis. 7.4 4/5/2000 20.2 ns ns 6.0 ns ns3 04026320 Whittlesey Creek at Ondassagon Rd. 

near Ashland, Wis.

 7.3 4/5/2000 19.7 ns ns 6.8 ns ns
Table 6. Results of field investigations of base flow and physical characteristics of Whittlesey Creek and adjacent streams, Wis.

[USGS, U.S. Geological Survey; mi2, square miles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; in., inches; ns, not sampled; —, no USGS station number 

established; e, estimated. Drainage area reflects surface-water-contributing basin only.]

Field 

number

USGS station 

number Name

Drainage

area

(mi2)

Date

sampled

Discharge

(ft3/s) pH

Specific

conductance 

(μS/cm)

Water

temperature 

(oC)

Streambed

head,

relative to

stream

surface (in.)

Temperature 

below stream 

bottom

(oC)

4 040263199 Whittlesey Creek near Ondassagon Rd. 

near Ashland, Wis.

 7.2 4/5/2000 18.4 ns ns ns ns ns

5 040263197 Whittlesey Creek near Town Rd. 23 

near Ashland, Wis.

 6.75 4/5/2000 11.2 ns ns ns ns ns

6 040263192 Whittlesey Creek near Cherryville Rd. 

near Ashland, Wis.

 4.28 4/5/2000 5.03 ns ns 7.2 ns ns

9 040263186 Whittlesey Creek #2 near Range Rd. 

near Moquah, Wis.

 1.68 4/5/2000 .749 ns ns ns ns ns

12 040263191 Whittlesey Creek tributary near 

Galligan Rd. near Ashland, Wis.

 1.51 4/5/2000 .107 ns ns 7.0 ns ns

13 04026319 Whittlesey Creek near Galligan Rd. 

near Ashland, Wis.

 3.7 4/5/2000 2.16 ns ns 7.0 ns ns

14 04026324 Whittlesey Creek tributuary at State 

Hwy. 13 near Ashland, Wis.

 1.29 4/5/2000 1.08 ns ns 4.5 ns ns

15 04026323 Whittlesey Creek tributuary near 

Ondassagon Rd. near Ashland, Wis.

 .93 4/5/2000 .888 ns ns 6.2 ns ns

18 040263198 Whittlesey Creek tributuary near Town 

Rd. 23 near Ashland, Wis.

 .33 4/5/2000 .595 ns ns ns ns

19 040263196 North Fork Whittlesey Creek near 

Cherryville Rd. near Ashland, Wis.

 2.31 4/5/2000 3.62 ns ns 7.0 ns ns

22 040263194 North Fork Whittlesey Creek at Cozy 

Corner Rd. near Moquah, Wis.

 1.82 4/5/2000 .682 ns ns 3.2 ns ns

24 04026318 Boyd Creek at Ondassagon Rd. 

near Ashland, Wis.

 3.12 4/5/2000 1.08 ns ns 3.0 ns ns

25 040263182 Boyd Creek at State Hwy. 13 

near Ashland, Wis.

 3.85 4/5/2000 1.94 ns ns 6.2 ns ns

Field Data 23
24 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis. Table 6. Results of field investigations of base flow and physical characteristics of Whittlesey Creek and adjacent streams, Wis. [USGS, U.S. Geological Survey; mi2, square miles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; in., inches; ns, not sampled; —, no USGS station number established; e, estimated. Drainage area reflects surface-water-contributing basin only.] Field number USGS station number Name Drainage area (mi2

)

Date

sampled

Discharge

(ft3/s) pH

Specific

conductance 

(μS/cm)

Water

temperature 

(

oC)

Streambed

head,

relative to

stream

surface (in.)

Temperature 

below stream 

bottom

(

oC)

26 040263515 Lake Superior tributary at Terwillger 

Rd. near Ashland, Wis.

 2 4/5/2000 .428 ns ns 4.0 ns ns

27 04026350 North Fish Creek near Ashland, Wis. 47.4 4/5/2000 94.1 ns ns 5.5 ns ns28 040263494 North Fish Creek tributary near County 

Trunk G near Moquah, Wis.

 1.77 4/5/2000 .0609 ns ns 6.0 ns ns

31 04026290 Sioux River near Washburn, Wis. 2.51 4/5/2000 1.34 ns ns 5.0 ns ns

August 2000

1 04026321 Whittlesey Creek at State Hwy. 13 

near Ashland, Wis.

 7.5 8/2/2000 18.4 7.8 145 10.0 0 10.0

1a — Whittlesey Creek at Lake Superior ns 8/2/2000 ns ns ns ns 0 11.0

2 040263205 Whittlesey Creek near Ashland, Wis. 7.4 8/2/2000 18.3 7.9 144 9.5 .20 9.2

2a — Whittlesey Creek between sites 2 and 3 ns 8/2/2000 ns ns ns ns .59 9.2

3 04026320 Whittlesey Creek at Ondassagon Rd. 

near Ashland, Wis.

 7.3 8/2/2000 18.3 7.9 144 9.8 .28 9.0

4 040263199 Whittlesey Creek near Ondassagon Rd. 

near Ashland, Wis.

 7.2 8/2/2000 16.6 8.1 143 9.8 ns ns

5 040263197 Whittlesey Creek near Town Rd. 23 

near Ashland, Wis.

 6.75 8/2/2000 10.3 8.2 151 10.3 1.06 8.5

5a — Whittlesey Creek, upstream from site 5 ns 8/2/2000 ns ns ns ns 1.38 7.5

6 040263192 Whittlesey Creek near Cherryville Rd. 

near Ashland, Wis.

 4.28 8/2/2000 4.52 8.2 158 10.7 5.12 8.5

7 040263189 Whittlesey Creek near Galligan Rd. 

near Moquah, Wis.

 3.48 8/2/2000 .0233 7.8 221 11.1 0 17.0

7a — Whittlesey Creek, upstream from site 7 ns 8/2/2000 ns ns ns ns .08 18.0
Table 6. Results of field investigations of base flow and physical characteristics of Whittlesey Creek and adjacent streams, Wis.

[USGS, U.S. Geological Survey; mi2, square miles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; in., inches; ns, not sampled; —, no USGS station number 

established; e, estimated. Drainage area reflects surface-water-contributing basin only.]

Field 

number

USGS station 

number Name

Drainage

area

(mi2)

Date

sampled

Discharge

(ft3/s) pH

Specific

conductance 

(μS/cm)

Water

temperature 

(oC)

Streambed

head,

relative to

stream

surface (in.)

Temperature 

below stream 

bottom

(oC)

8 040263187 Whittlesey Creek near Buvala Rd. near Moquah, Wis. 1.79 8/2/2000 0.0 ns ns ns ns ns

9 040263186 Whittlesey Creek #2 near Range Rd. 

near Moquah, Wis.

 1.68 8/3/2000 .0957 7.5 66 15.5 ns ns

10

 —

Whittlesey Creek at Range Rd. 

near Moquah, Wis.

 .2e 8/3/2000 .0262 ns ns ns ns 17.0

11 040263185 Whittlesey Creek near Range Rd. 

near Moquah, Wis.

 1.2 8/3/2000 .0687 7.5 64 15.8 -.20 17.0

11a

 —

Whittlesey Creek, upstream from 

site 11

ns 8/3/2000 ns ns ns ns ns 17.0

12 040263191 Whittlesey Creek tributary near 

Galligan Rd. near Ashland, Wis.

 1.51 8/2/2000 .0995 7.9 280 11.2 ns ns

13 04026319 Whittlesey Creek near Galligan Rd. 

near Ashland, Wis.

 3.7 8/2/2000 1.09 8.0 173 11.0 6.89 8.5

13a

 —

Whittlesey Creek, upstream from 

site 13 ns

8/2/2000 ns ns ns ns ns 12.0

14 04026324 Whittlesey Creek tributuary at State 

Hwy. 13 near Ashland, Wis.

 1.29 8/3/2000 .776 7.9 230 13.1 ns 13.5

15 04026323 Whittlesey Creek tributuary near 

Ondassagon Rd. near Ashland, Wis.

 .93 8/3/2000 .542 7.9 237 10.2 ns ns

18 040263198 Whittlesey Creek tributuary near 

Town Rd. 23 near Ashland, Wis.

 .33 8/2/2000 .607 8.1 143 8.8 ns ns

19 040263196 North Fork Whittlesey Creek near 

Cherryville Rd. near Ashland, Wis.

 2.31 8/2/2000 2.85 8.1 132 10.0 1.97 8.1

19a

 —

North Fork Whittlesey Creek #2 near 

Cherryville Rd. near Ashland, Wis.

 2.2e 8/2/2000 .677 7.8 221 11.1 1.61 9.0

Field Data 25
26 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis. Table 6. Results of field investigations of base flow and physical characteristics of Whittlesey Creek and adjacent streams, Wis. [USGS, U.S. Geological Survey; mi2, square miles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; in., inches; ns, not sampled; —, no USGS station number established; e, estimated. Drainage area reflects surface-water-contributing basin only.] Field number USGS station number Name Drainage area (mi2

)

Date

sampled

Discharge

(ft3/s) pH

Specific

conductance 

(μS/cm)

Water

temperature 

(

oC)

Streambed

head,

relative to

stream

surface (in.)

Temperature 

below stream 

bottom

(

oC)

20 040263195 North Fork Whittlesey Creek near 

Cozy Corner Rd. near Moquah, Wis.

 2.07 8/2/2000 .0279 7.5 116 19.7 -.04 19.0

20a

 —

North Fork Whittlesey Creek, 

downstream from site 20

ns 8/2/2000 ns ns ns ns ns 11.0

21

 —

North Fork Whittlesey Creek #2 near 

Cozy Corner Rd. near Moquah, Wis.

 1.9e 8/3/2000 .0746 7.6 69 17.4 -.31 16.8

22 040263194 North Fork Whittlesey Creek at Cozy 

Corner Rd. near Moquah, Wis.

 1.82 8/3/2000 .0626 7.5 69 17.9 .31 19.5

24 04026318 Boyd Creek at Ondassagon Rd. 

near Ashland, Wis.

 3.12 8/3/2000 .00188 ns ns 19.0 ns 19.0

25 040263182 Boyd Creek at State Hwy. 13 

near Ashland, Wis.

 3.85 8/3/2000 .138 8.0 468 20.9 0 18.5

26 040263515 Lake Superior tributary at Terwillger 

Rd. near Ashland, Wis.

 2 8/3/2000 .0512 7.5 278 17.0 ns ns

27 04026350 North Fish Creek near Ashland, Wis. 47.4 8/2/2000 75.9 8.0 161 16.6 .12 14.528 040263494 North Fish Creek tributary near 

County Trunk G near Moquah, Wis.

 1.77 8/3/2000 0 ns ns ns ns ns

31 04026290 Sioux River near Washburn, Wis. 2.51 8/3/2000 .0123 ns ns 17.0 ns 17.0

31a — Sioux River near site 31 ns 8/3/2000 ns ns ns ns ns 16.8

31b — Sioux River near site 31 ns 8/3/2000 ns ns ns ns ns 15.5
Streambed-head measurements ranged from – 0.35 

to 6.9 in. in Whittlesey Creek (fig. 14). Negative heads, 

mostly found near the headwaters, indicate losing reaches, 

whereas positive heads indicate gaining reaches. The highest measured heads were near the confluence. Streambed 

temperatures ranged from 7.5 to 19.5 oC (fig. 15). Similar 

to water temperature, the highest streambed temperatures 

were measured in the headwater reaches, and the lowest 

were measured near the confluence. Slightly increasing 

streambed temperatures downstream from the confluence 

may indicate a larger proportion of contributions from 

warmer water of the shallow system or seasonal warming 

of the streambed sediments where the hydraulic gradient 

is more horizontal. Calculated streambed-leakance values, 

based on stream-channel area, discharge, and streambed 

head, ranged from 45 to 96 ft/d/ft for Whittlesey and North 

Fish Creeks. A leakance value of 45 ft/d/ft was used for 

the Sioux River. Leakance values for Boyd Creek and the 

other small tributaries in the area were not measured, but 

were assumed to be much lower than those for deeply 

incised, steep-gradient streams like Whittlesey Creek. A 

streambed leakance of 0.1 ft/d/ft for the unnamed tributary 

north of Whittlesey Creek resulted in simulated base flows 

that were close to measured values. For this reason, 

0.1 ft/d/ft was used as the leakance value for Boyd Creek 

and the other small tributaries. Leakance values for Lake 

Superior sediments were assumed to be even lower than 

those of the small creeks and tributaries in the area because 

of greater thickness and lower permeability in the relatively undisturbed offshore depositional environment. A 

leakance value of 0.01 ft/d/ft was used for Lake Superior.

Core samples were collected to identify the soil types 

and determine the depth to the water table at two sites in 

the basin (fig. 1). The Copper Falls site (coring site 1) was 

probed to a depth of 46 ft, and core samples were collected 

from land surface to a depth of 12 ft. The surficial deposits 

associated with the Copper Falls Formation were easy to 

probe and consisted of loose, reddish-brown, mediumgrained sand. The water table was deeper than 46 ft below 

land surface at this location. The Miller Creek site (coring 

site 2) was probed to a depth of 21 ft. Core samples were 

collected from land surface to a depth of 16 ft. The surficial deposits, consisting of layers of red sandy clay, red 

sand, and red clay, were very tight at this location, making 

probing difficult. At 21 ft below land surface, the surficial 

deposits were unsaturated; however, a perched water table 

was present at 11 ft below land surface.

No flow

Greater than 0.00 to 0.10

Greater than 0.10 to 5.0

Greater than 5.0

Base flow, August 2000,

in cubic feet per second

EXPLANATION

Surface-waternoncontributing basin

Surface-water-contributing 

basin boundary

Stream North Fork

Whittlesey Creek

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

0

0

1 MILE

1 KILOMETER

0.06 0.07

0.10 0.00

0.03

0.02

0.03

0.68

0.10 4.5

2.9

10

17

18 18

18

1.1

0.61

Figure 13. Base flows for Whittlesey Creek and tributaries, Wis., August 2000.

Field Data 27
28 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis. Table 7. Comparison of base flow and drainage area for Whittlesey Creek and adjacent streams, Wis. [USGS, U.S. Geological Survey; e, estimated; mi2, square miles; ft3/s, cubic feet per second; –, no USGS station number established. Average discharge reflects average of August 1999 and August 2000 discharge measurements. Drainage area reflects surface-water-contributing basin only.] Field number USGS station number Name Drainage area (mi2

)

Average 

discharge 

(ft3/s)

Ratio of

discharge to 

drainage area

1 04026321 Whittlesey Creek at State Hwy. 13 near Ashland, Wis. 7.5 18.55 2.472 040263205 Whittlesey Creek near Ashland, Wis. 7.4 18.7 2.523 04026320 Whittlesey Creek at Ondassagon Rd. near Ashland, Wis. 7.3 18.3 2.514 040263199 Whittlesey Creek near Ondassagon Rd. near Ashland, Wis. 7.2 15.45 2.155 040263197 Whittlesey Creek near Town Rd. 23 near Ashland, Wis. 6.75 10.2 1.516 040263192 Whittlesey Creek near Cherryville Rd. near Ashland, Wis. 4.28 4.6 1.077 040263189 Whittlesey Creek near Galligan Rd. near Moquah, Wis. 3.48 .0247 .018 040263187 Whittlesey Creek near Buvala Rd. near Moquah, Wis. 1.79 0 .009 040263186 Whittlesey Creek #2 near Range Rd. near Moquah, Wis. 1.68 .0957 .0611 040263185 Whittlesey Creek near Range Rd. near Moquah, Wis. 1.2 .0849 .0712 040263191 Whittlesey Creek tributary near Galligan Rd. near Ashland, Wis. 1.51 .102 .0713 04026319 Whittlesey Creek near Galligan Rd. near Ashland, Wis. 3.7 1.13 .3114 04026324 Whittlesey Creek tributuary at State Hwy. 13 near Ashland, Wis. 1.29 .753 .5815 04026323 Whittlesey Creek tributuary near Ondassagon Rd. near Ashland, Wis. .93 .617 .6617 – Whittlesey Creek tributuary #2 near Town Rd. 23 near Ashland, Wis. .05e .0695 1.3918 040263198 Whittlesey Creek tributuary near Town Rd. 23 near Ashland, Wis. .33 .607 1.8419 040263196 North Fork Whittlesey Creek near Cherryville Rd. near Ashland, Wis. 2.31 3.16 1.3719A – North Fork Whittlesey Creek #2 near Cherryville Rd. near Ashland, Wis. 2.2e .677 .3120 040263195 North Fork Whittlesey Creek near Cozy Corner Rd. near Moquah, Wis. 2.07 .135 .0721 – North Fork Whittlesey Creek #2 near Cozy Corner Rd. near Moquah, Wis. 1.9e .0746 .0422 040263194 North Fork Whittlesey Creek at Cozy Corner Rd. near Moquah, Wis. 1.82 .152 .0824 04026318 Boyd Creek at Ondassagon Rd. near Ashland, Wis. 3.12 .00218 .0025 040263182 Boyd Creek at State Hwy. 13 near Ashland, Wis. 3.85 .214 .0626 040263515 Lake Superior tributary at Terwillger Rd. near Ashland, Wis. 2 .0677 .0327 04026350 North Fish Creek near Ashland, Wis. 47.4 76.5 1.6128 040263494 North Fish Creek tributary near County Trunk G near Moquah, Wis. 1.77 0 .0030 – Whittlesey Creek tributuary #3 near Town Rd. 23 near Ashland, Wis. .075e .131 1.7431 04026290 Sioux River near Washburn, Wis. 2.51 .025 .01
EXPLANATION

Surface-waternoncontributing basin

Surface-water-contributing 

basin boundary

Stream North Fork

Whittlesey Creek

91 ̊02' 90 ̊57'

46 ̊38'

46 ̊35'

0

0

1 MILE

1 KILOMETER

0.01 to 0.59

0.6 to 1.59

1.6 to 6.9

0.0

-0.35 to -0.01

Head below stream bottom

(relative to stream surface,

in inches)

Figure 14. Streambed heads for Whittlesey Creek and tributaries, Wis., August 2000.

Streambed temperature,

in degrees Celsius

EXPLANATION

Surface-waternoncontributing basin

Surface-water-contributing 

basin boundary

Stream

7.5 – 9

9.1 – 10.9

11 – 13.9

14 – 19.5

North Fork

Whittlesey Creek

91 02' 90 ̊57'

46 38'

46 35'

0

0

1 MILE

1 KILOMETER

Figure 15. Streambed temperatures for Whittlesey Creek and tributaries, Wis., August 2000.

Field Data 29
30 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Ground-Water-Flow Simulations

As a result of the stepwise modeling approach used in 

this study, several iterations of ground-water-flow models 

were developed for the study area. Each iteration included 

a GFLOW model simulation and a MODFLOW model 

simulation. Initially, preliminary models were constructed 

from available data and were used to help understand the 

ground-water-flow system, test hypotheses, and guide 

field-data collection. The second set of models incorporated updates to the preliminary models and included 

results of data and insights from field observations. The 

updated MODFLOW model was then calibrated by use 

of the computer program UCODE. The hydraulic conductivities from the calibrated MODFLOW model were 

incorporated into a final GFLOW model. The calibrated 

MODFLOW model was used to delineate the groundwater-contributing area to Whittlesey Creek.

A summary of the model results is given below. 

Optimized model parameters are listed in table 8. For each 

simulation, head statistics and simulated base flows at 

selected locations are listed in table 9. 

Preliminary Ground-Water-Flow Models

GFLOW Model

The preliminary GFLOW model includes the Bayfield Peninsula and vicinity (fig. 5) and was used as a 

screening tool to test hypotheses about the ground-waterflow system in the study area, estimate recharge, and to 

help improve the subsequent MODFLOW model. One 

question addressed with the GFLOW model was whether 

the expected distribution and range of recharge values 

could simulate sufficient base flow in Whittlesey Creek. 

Hydraulic conductivities of 30 and 100 ft/d and recharge 

rates of 2 and 17 in/yr (for the area underlain by the Miller 

Creek Formations and Copper Falls Formation, respectively) gave reasonable preliminary results and were within 

the expected range for those parameters. These values 

produced slightly low base flows in Whittlesey Creek and 

slightly high base flows for North Fish Creek (table 9). 

The absolute residual mean head error for this model was 

22.3 ft. 

MODFLOW Model

The preliminary MODFLOW model includes all of 

the Whittlesey and North Fish Creek drainages and much 

of the Sioux River drainage. The lateral boundaries of this 

model are represented by constant flux cells (simulated 

using the MODFLOW well package) that were extracted 

from the corresponding area of the preliminary GFLOW 

model. This extraction feature is particularly important 

for this study area because the extent of the surface-water 

drainage is difficult to delineate and, on the basis of 

GFLOW model, does not coincide with the ground-water 

divides. Horizontal hydraulic conductivities (Kh

) of 100, 

30 and 1.4 ft/d, for the Copper Falls and Miller Creek 

Formations and the Bayfield Group, respectively, and 

recharge values of 17 and 2 in/yr, for the area underlain 

by the Copper Falls and Miller Creek Formations, respectively, gave reasonable preliminary results (table 9). Again, 

the simulated base flows were slightly low for Whittlesey 

Creek and slightly high for North Fish Creek. The absolute 

residual mean head error for this model was 21.0 ft. 

Table 8. Preliminary estimate and UCODE-optimized parameter 

values used in the MODFLOW model

[Kh, horizontal hydraulic conductivity; Kv, vertical hydraulic conductivity; 

ft, feet; d, day; in/yr, inches per year]

Parameter Preliminary 

estimate

UCODEoptimized 

value

Kh

 Miller Creek Formation 30 ft/d 34.4 ft/d

Kh

 Bayfield Group1 1.4 ft/d 1.4 ft/d

Kh

 Copper Falls Formation 100 ft/d 69.8 ft/d

Kv Miller Creek Formation 0.03 ft/d 0.04 ft/d

Kv

 Bayfield Group 0.14 ft/d 0.88 ft/d

Kv

 Copper Falls Formation2 100 ft/d 69.8 ft/d

Recharge through Miller 

Creek Formation3

2 in/yr 2 in/yr

Recharge through Copper 

Falls Formation3

17 in/yr 17 in/yr

Lake Superior streambed 

leakance

0.01ft/d/ft 0.001ft/d/ft

Effective layer 2 bottom 

elevation2

0 ft 0 ft

1Bayfield Group Kh

 was highly correlated with Miller Creek Kh; 

therefore, both could not be estimated effectively with UCODE. More 

data were available for estimating Bayfield Group Kh, so this parameter 

was excluded from optimization.

2Parameter not optimized because of model insensitivity. For Copper 

Falls Formation, Kv

 was set equal to optimized Kh.

3 Parameter not optimized. Preliminary estimate from GFLOW model.
Modeled heads and fluxes for the preliminary 

GFLOW and MODFLOW models were reasonably close 

to measured values, with slightly better modeled head 

results from the MODFLOW model. Results of both 

ground-water-flow models indicate that much of the 

headwaters of Whittlesey Creek receive no ground-water 

contributions from the deep system. Both models also 

indicated that the deep ground-water-flow system intersected Whittlesey Creek just upstream from the confluence 

of the main stem and North Fork. In addition, both models 

indicated that the ground-water-contributing area to the 

stream was not coincident with the delineated surfacewater-contributing basin. Because the preliminary models 

gave reasonable results, subsequent field investigations 

focused mainly on verifying preliminary model results 

and collecting additional base-flow data. In addition, field 

determination of streambed leakance was expected to 

improve modeled base-flow values. 

Field measurements of base flow, streambed head, 

and streambed and water temperature indicated that the 

deep flow system intersected Whittlesey Creek near the 

confluence of the main stem and North Fork (table 6). 

Small streamflows, negative minipiezometer heads, and 

warmer streambed temperatures in headwater reaches indicated that those areas were receiving only a small amount 

of ground water from perched parts of the shallow system 

upstream from the confluence. Losing reaches and negative heads also indicated that some streamflow, derived 

from the perched part of the shallow system, recharged the 

deep system by percolating through the stream bottom. 

Updated Models, Sensitivity, and Calibration

The GFLOW and MODFLOW models were updated 

with field-measured streambed leakance. In addition, the 

distribution of recharge in both models was altered to 

improve simulated base flows in North Fish Creek. The 

distribution of the high-recharge zone corresponding to 

the area underlain by the Copper Falls Formation was 

limited to the thick, permeable deposits of the Bayfield 

Highlands. Areas underlain by relatively thin deposits 

of the Copper Falls Formation, mainly south and west 

of the upper reaches of North Fish Creek, were assigned 

recharge rates similar to those used for areas underlain by 

the Miller Creek Formation. The updated models resulted 

in improved simulated heads and base flows for North 

Fish Creek. Simulated base flows for Whittlesey Creek 

were relatively unchanged. A range of recharge values was 

simulated in the GFLOW model—from 10 to 21 in/yr in 

the area underlain by the Copper Falls Formation and from 

1 to 3 in/yr in the area underlain by the Miller Creek Formation. Values of 17 and 2 in/yr for the Copper Falls and 

Miller Creek areas, respectively, provided the best overall 

fit for heads and base flows simulated using GFLOW. In 

the MODFLOW model, the GFLOW-extracted boundary 

flux was based on the recharge values used in the GFLOW 

Table 9. Head statistics and simulated base flows at selected locations for preliminary, updated, and calibrated ground-waterflow models

[ft, feet; ft3/s, cubic feet per second]

Simulation 

description

Absolute residual 

mean, head (ft)

RMS error, 

head (ft)

Error range, 

head (ft)

Simulated base 

flow for Whittlesey 

Creek1

 (ft3/s)

Simulated base 

flow for North Fish 

Creek2

 (ft3/s)

GFLOW, preliminary 22.3 29.6 -46.1 to 86.6 15.9 162

MODFLOW, preliminary 21 24.3 -62.4 to 37.5 15.2 178

GFLOW, updated 21.6 28.1 -62.3 to 67.8 15.2 104

MODFLOW, updated 17.7 22.2 -54.8 to 54.2 14.6 115

MODFLOW, UCODE 

calibration

 17 21.8 -53.7 to 52.2 14.8 112

GFLOW, updated with 

UCODE estimated 

parameters

 20.1 24.7 -63.4 to 57.3 14.9 106

1

Measured base flow target for Whittlesey Creek (field number 1) is 17 ft3/s.

2

Measured base flow target for North Fish Creek (field number 27) is 86 ft3/s.

Ground-Water Flow Simulations 31
32 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

model. Because the boundary flux was fixed to the values 

used in the GFLOW model, aerial recharge in the MODFLOW model could not be properly estimated using 

UCODE. As a result, recharge values from the updated 

GFLOW model were used in the MODFLOW model 

instead of being estimated with UCODE. 

Input parameters for the MODFLOW model were 

evaluated for model sensitivity by means of UCODE 

(fig. 16). The model is most sensitive to recharge and Kh

of the Miller Creek and Copper Falls Formations. The 

model is least sensitive to Kv of the Copper Falls Formation and the bottom altitude of layer 2. The least sensitive 

parameters were excluded from UCODE estimation. 

The MODFLOW model was calibrated using 

UCODE. The preliminary estimates and optimized 

values for model parameters are listed in table 8. The 

model parameters representing Kh

 of the Bayfield Group 

and Miller Creek Formations were highly correlated 

(r2

 = -0.99). Estimating highly correlated parameters with 

UCODE can result in nonunique results (Hill, 1998, p. 39); 

therefore, one of the highly correlated parameters should 

be excluded from estimation. Information on the Kh of the 

Bayfield Group was available, and the model was much 

less sensitive to this parameter; therefore, it was excluded 

from UCODE estimations. Most of the UCODE-estimated 

parameter values fell within the expected range or close to 

the estimated values listed in table 2. Using the parameter 

values from UCODE, the absolute residual mean head 

error for the calibrated MODFLOW model was 17.0 ft 

(table 9). Simulated base flows were improved, though 

still slightly low for Whittlesey Creek and slightly high 

for North Fish Creek. The relation of measured and modeled heads and stream flux for the calibrated MODFLOW 

model is shown in figure 17. Optimized parameter values 

for hydraulic conductivity from the calibrated MODFLOW model were then added to a final GFLOW model. 

The simulated base flows from the final updated GFLOW 

model were nearly unchanged; however, simulated heads 

improved slightly (table 9). 

Simulated base flows in Whittlesey Creek were still 

lower than measured flows for several possible reasons. 

First, measured base flows included flow from the perched 

part of the shallow flow system. Simulations included only 

flow from the nonperched system. Second, measured base 

flows may have been slightly lower than 17 ft3

/s under 

drier conditions, resulting in values closer to those modeled. Finally, the model is only an approximation of the 

real system. The model may require more detail and complexity (better geologic information, 

more layers, more recharge zones, 

more zones of hydraulic conductivity, 

accounting of perched flow, etc,) to 

provide a more accurate simulation 

of the system. With additional data, 

the model could be refined to address 

future issues or areas of interest.

Ground-Water-Contributing 

Area

Results from the final calibrated 

MODFLOW model were used to 

delineate the ground-water-contributing area to Whittlesey Creek 

from the deep flow system and the 

nonperched part of the shallow flow 

system. Ground-water pathlines were 

simulated with the computer program 

MODPATH. In all, 480 particles of 

water were tracked backwards, from 

the parts of Whittlesey Creek that 

received ground water from the deep 

flow system, to the water table. 

11

25

1.0 0.50 1.3

0.03

15

19

0.003

1.1

0

5

10

15

20

25

30

COMPOSITE SCALED SENSITIVITY 

(DIMENSIONLESS) *Kh Miller Ck Fm 

Kh Bayfield Group

*Kh Copper Falls Fm

*Kv Miller Ck Fm

*Kv Bayfield Group

Kv Copper Falls Fm

Recharge (Miller Ck)

Recharge (Copper Falls)

*Lake Superior streambed leakance

Layer 2 bottom (Bayfield Group)

Figure 16. MODFLOW ground-water-flow model parameter sensitivities from UCODE 

for the Whittlesey Creek, Wis., study area. [Red asterisk (*) indicates parameters 

estimated with UCODE. Kh

; horizontal hydraulic conductivity, Kv; vertical hydraulic 

conductivity.]
The 22-mi2

 land-surface area projected from the volume 

of aquifer encompassing those pathlines is the contributing area shown in figure 18. The average traveltime from 

the stream back to the water table was about 215 years; 

the median traveltime was about 94 years. Particle-tracking results indicated that the ground-water-contributing 

area did not coincide with the delineated surface-watercontributing basin. The Miller Creek Formation underlies 

approximately half of the ground-water-contributing area, 

and half is underlain by the Copper Falls Formation (fig. 

19). Based on modeled recharge rates, about 90 percent of 

the base flow to Whittlesey Creek originated as recharge 

through the permeable deposits of the Copper Falls Formation in the Bayfield Highlands. On the basis 

of these results, concerns about land-cover effects on, 

and changes to, base flow in Whittlesey Creek should 

focus on this heavily forested part of the ground-watercontributing area.

Land-Cover Effects on Recharge and 

Base Flow

The relations among land-cover changes, recharge 

rates, and base flow in the vicinity of Whittlesey Creek 

are unclear. Changes in land cover could have an effect on 

ground-water recharge rates. Additionally, changing the 

recharge rate in an area can result in changes in base flow 

of nearby streams. Logging might increase ground-water 

recharge by reducing interception and evapotranspiration. 

Development on forested or agricultural land could reduce 

ground-water recharge by creating large impermeable 

areas (roofs, parking lots, roads, etc.). Tiling of agricultural land could reduce recharge by capturing and diverting 

water moving through the unsaturated zone. Land-cover 

changes and recharge effects on base flow in Whittlesey 

Creek were simulated using the calibrated MODFLOW 

model. Land-cover changes were represented by increasing 

recharge by 25 and 50 percent (a deforestation simulation) 

and decreasing it by 25 and 50 percent (an urbanization 

or tiling simulation). It is unknown exactly how much 

recharge in the vicinity of Whittlesey Creek would be 

affected by land-cover changes; however, the rates listed 

above should represent extreme cases. 

Model-wide changes in recharge caused a proportional change in simulated base flow for Whittlesey Creek. 

Changes in base flows resulting from changes in recharge 

in only the ground-water-contributing area of Whittlesey 

Creek also were simulated (table 10). These localized 

changes in recharge were simulated for the entire groundwater-contributing area or for individual recharge zones 

(clayey zone or sandy zone) in the contributing area. Simulated changes in base flow are for Whittlesey Creek near 

USGS Station 040263205 (fig. 1). 

MEASURED FLUX, IN 

CUBIC FEET PER SECOND

MODELED FLUX, IN 

CUBIC FEET PER SECOND

0 20 40 60 80 100 120

A B

0

20

40

60

80

100

120

600 700 800 900 1,000

MEASURED HEAD, 

IN FEET ABOVE SEA LEVEL

MODELED HEAD, 

IN FEET ABOVE SEA LEVEL

600

700

800

900

1,000

Model layer 2 

Model layer 1

Figure 17. Relation of measured and modeled (A) head and (B) stream flux (base flow) for the calibrated MODFLOW model for 

the Whittlesey Creek, Wis., study area.

Ground-Water Flow Simulations 33
34 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Sioux River

Boyd Creek

North Fish Creek

850

800

750

700

650

650

700

750

800

900

900

1000

950

900

1050

1000

950

850

800

750

700

650

650

700

750

800

900

900

1000

950

900

1050

1000

950

850

EXPLANATION

Potentiometric-surface contour, MODFLOW model layer 1 (based on calibrated model, 50-ft interval)

Ground-water-contributing area (arrow indicates general direction of ground-water flow in this area)

Constant flux boundary

Head-dependent flux boundary (river node)

Dry cell (layer 1, based on calibrated model)

Surface-water-contributing and noncontributing basin boundary

Lake

Superior

Road

0

0

4 MILES

4 KILOMETERS

2

2

1

200

1 200

Row

Column

Whittlesey Creek

Figure 18. Whittlesey Creek, Wis., ground-water-contributing area based on results from the calibrated MODFLOW model.
Lake Superior

Whittlesey Creek surface-water-contributing and noncontributing basins

EXPLANATION

Particle pathline

Approximate contact of Copper Falls Formation and Miller Creek Formation

Bayfield Highlands

North

Figure 19. Particle pathlines tracked backwards from Whittlesey Creek, Wis., to the water table in the ground-watercontributing area.

Table 10. Simulated changes in base flow for Whittlesey Creek, Wis., as a result of changes in recharge in the groundwater-contributing area

[ft3/s, cubic feet per second; in/hr, inches per hour; %, percent]

Zone where change in recharge occurs

Percent change in base flow1

 for given change in recharge2

Increase 

recharge by 

25%

Increase 

recharge by 

50%

Decrease 

recharge by 

25%

Decrease 

recharge by 

50%

Both zones +5.6 +11.1 -5.6 -10.2

Clayey zone only +1.6 +3.1 -1.6 -3.1

Sandy zone only +4.1 +8 -4.1 -7.1

1

 Simulated base flow for Whittlesey Creek at State Hwy. 13 is 14.8 ft3/s using the calibrated MODFLOW model

2

 Recharge rates used in the calibrated MODFLOW model are 17 and 2 in/hr for the sandy and clayey zones, respectively.

Ground-Water Flow Simulations 35
36 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

Changing total recharge in the entire ground-watercontributing area by 25 percent resulted in an increase 

or decrease of about 6 percent in base flow (table 10). A 

50-percent increase or decrease in recharge in the groundwater-contributing area resulted in about a 10 to 11 percent 

increase or decrease in base flow. Base flow did not change 

at the same rate as recharge because changes in recharge 

were applied only to the ground-water-contributing area of 

Whittlesey Creek. One outcome of the localized changes 

in recharge was that the size of the resulting contributing 

area to Whittlesey Creek changed. For example, increasing recharge by 50 percent in the original contributing area 

caused some mounding of the potentiometric surface there; 

the mounding changed the direction of ground-water flow 

and actually reduced the size of the resulting contributing 

area. Even though more recharge was applied, some of that 

recharge was lost to adjacent streams. Reducing recharge 

in the contributing area caused a depression in the potentiometric surface that resulted in a larger contributing area; 

when recharge was reduced, the larger contributing area 

made up for some of the decrease in recharge. If recharge 

was increased or decreased throughout the model area 

(not just the ground-water-contributing area), then localized mounding or depression of the potentiometric surface 

did not occur and the size of the contributing area hardly 

changed; the resulting percentage changes in base flow to 

Whittlesey Creek were, in this case, closely correlated with 

the percentage change in recharge.

The two recharge zones within the ground-watercontributing area to Whittlesey Creek were about the same 

size; however, on the basis of the calibrated model, about 

90 percent of base flow originated as recharge through the 

sandy Copper Falls Formation. Only about 10 percent of 

base flow was from recharge through the clayey Miller 

Creek Formation. Changing recharge in a single zone 

(sand or clay) would represent land-cover changes in part 

of the contributing area. A 25-percent change in recharge 

in the clayey zone resulted in about a 2-percent change in 

base flow (table 10). A 50-percent change in recharge in 

this zone resulted in about a 3-percent change in base flow. 

A likely land-cover change would be logging of forests 

in the sandy zone and a increase in recharge of possibly 

25 percent, which would cause an increase in base flow of 

about 4 percent. A 50-percent change in recharge in the 

sandy zone would result in about a 7- to 8-percent change 

in base flow.

Rainfall-Runoff Simulations

Hydrographs of measured and simulated daily mean 

flows at the Whittlesey Creek streamflow station (field 

number 2) for the period of calibration are shown in figures 20 and 21. Daily mean flows were used in the simulation because of the lack of hourly rain data and because the 

SWAT model used was unable to calculate runoff in hourly 

time steps. Instantaneous peaks at the streamflow station 

from recorded 15-minute data were more than twice the 

simulated daily mean flows. Hydrographs of simulated 

daily mean flows for 1992-93 land cover, measured daily 

flow, and 15-minute data for the three largest peak flows 

during the period of model calibration are shown in figure 

21. Daily mean and instantaneous peak flows and the 

calibrated model output are listed in table 11. Instantaneous peak flows were twice as high as daily peak flows 

during floods. Though modeling with a daily time step is 

adequate to determine average annual runoff 

and differentiate between surface runoff, 

evapotranspiration, and infiltration, it is not 

adequate to determine the absolute change in 

instantaneous peak flow. An hourly time step 

would improve the model results, especially 

for peak flows.

For the modeled period, the average 

annual runoff from the surface-watercontributing area (excluding regional base 

flow) for the streamflow-gaging station was 

10.9 in/yr (table 12). The SWAT model simulated the same value for 1992-93 conditions. 

The calibrated model underestimated the first 

large rainfall-derived daily mean flow for the 

flood peak on July 5, 1999, but it overestimated the daily mean flow for the peak that 

Table 11. Daily mean and intantaneous peak flows for U.S. Geological 

Survey streamflow-gaging station on Whittlesey Creek, Wis. and the 

calibrated SWAT model output using 1992-93 WISCLAND land-cover 

data (Reese and others, 2002)

[ft3/s; cubic feet per second]

Date

Daily mean flow (ft3

/s) Instantaneous 

peak flow 

at gaging 

station (ft3

/s)

Streamflow 

station

Calibrated 

model

July 5, 1999 286 203 710

July 9, 1999 127 166 585

April 23, 2001 370 349 777

Average of three dates 261 239 691
followed four days later (fig. 21). These runoff events 

were caused by thunderstorms, likely with rainfall intensity and amounts varying throughout the basin. The 

designed storm used in the simulation may not accurately 

represent this type of rain event. Hourly precipitation data 

from locations within the basin would have improved the 

model. The simulated daily mean flow for the April 23, 

2001, rainfall- and snowmelt-derived peak closely matched 

actual values (fig. 21). The event on April 23, 2001, was 

the largest flood on record (3 years) at the streamflowgaging station on Whittlesey Creek and data from nearby 

long-term streamflow-gaging stations indicate that it was 

an 80- to 100-year event.

Land-Cover Effects on Annual Runoff and 

Flood Peaks

Land-cover effects on average annual runoff in various model simulations for 1999 to 2001 were between 

1 and 11 percent (table 12). The largest difference was 

between presettlement or reforested and peak agriculture. 

Flood peaks (based on daily mean flows on peak-flow 

days) increased in the developed and peak-agriculture 

simulations and decreased in the presettlement and 

reforested simulations (table 12). The increase in forest in 

the presettlement and reforested simulations resulted in 

smaller and broader flood peaks, whereas the developed 

and peak-agriculture simulations produced larger and 

steeper flood peaks compared to those peaks simulated 

with 1992-93 land use (fig. 22). 

On the basis of data from North Fish Creek, an adjacent basin to the south of Whittlesey Creek, sediment loads 

were related to flow by a power function, indicating that 

decreasing peak flow, even without decreasing total runoff, 

can reduce erosion and resulting sediment loads (Fitzpatrick and others, 1999). It is assumed that Whittlesey 

Creek, which drains similar geologic deposits, would have 

a similar relation between sediment load and flow, and that 

small decreases in flood peaks could result in decreases in 

sediment loading.

Effects of the various land-cover simulations on flood 

peaks were affected by antecedent soil moisture; effects 

were less for subbasins with high runoff rates under nearly 

all conditions, such as urban development, intensive agriculture, and clay soils. Increased soil moisture has little 

effect on a land cover that can only absorb 10 percent of 

rainfall when dry, while a land cover that normally absorbs 

50 percent of rainfall when dry will have much larger 

increases in runoff when saturated. 

The storm of July 5, 1999, that occurred during 

dry conditions resulted in a greater difference in peaks 

between simulations than the storms of July 9, 1999, and 

April 23, 2001, which fell on nearly saturated soils (fig. 

22). Simulations of developed and agricultural land cover 

resulted in larger increases in flood peaks during dry 

antecedent conditions (12 and 18 percent) than during wet 

conditions (0 and 7 percent). The entire basin, regardless 

of land cover, had nearly saturated soils during the storm 

of July 9, 1999, so the entire basin had high runoff for that 

storm in the calibrated model regardless of land cover. 

Table 12. Average annual runoff and flood peaks (based on daily mean flows on peak-flow days) from the Whittlesey Creek, 

Wis., streamflow-gaging station 040263205 and the Soil and Water Assessment Tool (SWAT) model simulations

[in/yr, inches per year; ft3/s, cubic feet per second. Average annual runoff (April 4, 1999, through October 15, 2001) does not include the regional 

ground-water flow of 16.75 ft3/s and reflects the modeled surface-water-contributing basin of 7.2 square miles.]

Characteristic Streamflow

station data

Model simulations

1992-93 Presettlement

(before 1870)

Peak agriculture

(1928) Reforested Developed

Average annual runoff (in/yr) 10.8 10.4 10.3 11.4 10.3 10.9

July 5, 1999 daily mean flow 

(ft3

/s)

 286 203 201 240 174 228

July 9, 1999 daily mean flow 

(ft3

/s)

 127 166 163 177 143 166

April 23, 2001 daily mean 

flow (ft3

/s)

 370 349 335 354 308 352

Average of three daily mean 

flows (ft3

/s)

 261 239 233 257 208 249

Rainfall-Runoff Simulations 37
38 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

A

M J J A S O N D J F M

A

M J J A S O O N D J F M

A

M J J A S

1999 2000 2001

DISCHARGE, IN CUBIC FEET PER SECOND

Measured daily mean flow from Whittlesey Creek streamflow-gaging stationSimulated daily mean flow from SWAT model of 1992–93 land cover

0

400

755025

375350325300275250225200175150125100

Figure 20. Hydrographs of daily mean flow from the Whittlesey Creek, Wis., streamflow-gaging station 040263205 and Soil and Water Assessment Tool (SWAT) model 

for 1992-93 land cover.
3 4 5 6 7 8 9 10 11

July 1999

DISCHARGE, IN CUBIC FEET PER SECOND

Measured 15-minute flow from Whittlesey Creek streamflow-gaging stationMeasured daily mean flow from Whittlesey Creek streamflow-gaging stationSimulated daily mean flow from SWAT model of 1992–93 land-cover

19 20 21 22 23 24 25 26

April 2001

0

800700600500400300200100

0

800700600500400300200100

Figure 21. Flood hydrographs of measured daily mean and instantaneous (15-minute) flow from the Whittlesey Creek, Wis., streamflow-gaging station 040263205 and simulated daily mean flow from the Soil and Water Asessment Tool (SWAT) model for 1992-93 land cover, July 1999 and April 2001.

Rainfall-Runoff Simulations 39
40 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

3 4 5 6 7 8 9 10

July 1999

DISCHARGE, IN CUBIC FEET PER SECOND

EXPLANATION

1992–93Presettlement (before 1870)Peak agriculture (1928)ReforestedDeveloped

19 20 21 22 23 24 25 26 27

April 2001

Land-cover simulation

0

400

50

350300250200150100

0

400

50

350300250200150100

Figure 22. Flood hydrographs of daily mean flow from the Whittlesey Creek, Wis., Soil and Water Assessment Tool (SWAT) models of all land-cover simulations.
Differences in land cover between the simulations thus had 

a limited effect on the modeled results for that storm. 

Flood peaks from the developed land-cover simulation were slightly smaller than those from the peak-agriculture simulation (fig. 22) because of the conversion 

of agriculture from predominately row crops in 1928 

to predominately hay and grasslands in the developed 

simulation. SCS curve numbers for 25-percent developed 

grassland and forest are lower than those for row crops 

(table 4) and the area of urban land (25 percent) in the 

developed simulation is slightly smaller than the area of 

row crop agriculture (28.2 percent) in the peak-agriculture 

simulation (table 5).

 Increases in forest in the reforested and presettlement 

simulations resulted in reduced daily mean flows on peakflow days (12-14 percent and 1-4 percent, respectively) 

compared to 1992-93. It was assumed that the presettlement Whittlesey Creek Basin was 11.6 percent wetland 

as in the 1928 land economic survey (mostly in the upper 

basin), whereas 1.6 percent of the basin is wetland in the 

WISCLAND data used for the 1992-93 and reforested 

simulation. However, because of how the SWAT model 

simulates runoff from wetlands, modeled daily mean 

flows for peak-flow days in the presettlement simulation 

were higher than those for the reforested simulation. In 

the SWAT model, wetlands are assumed to be consistently 

wet or saturated, resulting in little storage and substantial 

runoff from the wetlands during storms. However, field 

observation of the wetlands in the Whittlesey Creek Basin 

show they likely do provide some degree of storage capacity, which would reduce rather than increase runoff peaks. 

It is also likely that more than 11.6 percent of the actual 

presettlement basin land cover was wetland. Even by 1928, 

some wetlands would have been drained. More research 

is needed to determine the extent and function of presettlement and 1992-93 wetlands in the Whittlesey Creek 

Basin before wetland storage can be accurately modeled. 

Because wetland storage could be an important part of the 

model that is missing, presettlement-simulation runoff and 

peak flows may be overestimated. 

Land-Cover Effects on Water Budget

In all of the land-cover simulations, most of the 

precipitation falling in the Whittlesey Creek Basin (which 

averaged 37.3 in/yr for the modeled period) left the basin 

as evapotranspiration (greater than 65 percent; table 13). 

The remainder of the precipitation either ran off the land 

surface to become streamflow or percolated past the root 

zone of the soil profile to become ground water, which 

either reappeared as flow in the creek or became recharge 

to the deep aquifer system. Percentages of total precipitation that became evaporation, runoff, or ground water 

for the modeled simulations are listed in table 13. The 

percentages in table 13 do not add to 100 percent because 

of changes in soil-moisture storage in the basin during the 

1999-2001 modeling period. Precipitation sources were 

20.4 percent snowmelt and 79.6 percent rainfall for the 

1999-2001 period.

Evapotranspiration rates were slightly lower in the 

peak-agriculture simulation than in the other simulations. The peak-agriculture simulation also had the lowest 

percentage of forest. Forests have higher transpiration rates 

because the foliage of the trees has more surface area than 

that of crops and grasses and foliage has higher evaporation because it intercepts precipitation that then evaporates. 

Table 13. Percentage of total precipitation that becomes evapotranspiration, surface-water runoff, and ground water in the 

Whittlesey Creek, Wis., Soil and Water Assessment Tool (SWAT) model simulations 

[Average annual precipitation for April 4, 1999, through October 15, 2001 was 37.3 inches per year. The percentages in this table do not add up 

to 100 percent because of changes in soil-moisture storage in the basin during the 1999-2001 modeling period.]

Water-budget

component

Model simulations

1992-93 Presettlement

(before 1870)

Peak agriculture

(1928) Reforested Developed

Evapotranspiration 

(percent)

 67 66.7 65.5 67.3 67

Surface-water 

runoff (percent)

 18.4 17.6 19.9 17.3 19.7

Ground water 

(percent)

 9.8 10.6 8.3 10.1 8.4

Rainfall-Runoff Simulations 41
42 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

In the peak-agriculture and the developed simulations, 

much of the land cover had high runoff rates, so proportionately more precipitation became surface runoff and less 

water infiltrated past the root zone. In the presettlement 

and reforested simulations, land cover had lower runoff 

rates, so proportionately less of the precipitation became 

runoff. 

Land-Cover Effects on Sources of Flow 

Regional base flow, simulated with a constant 

16.75 ft3/s, constituted nearly 75 percent of the flow 

in Whittlesey Creek in all land-cover simulations. The 

remaining flow to Whittlesey Creek simulated in the 

SWAT model came from either surface runoff or perched 

ground-water discharge. Simulated sources of all flow in 

Whittlesey Creek for the modeled period 1999-2001 are 

listed in table 14. The percentages of flow by source simulated with the SWAT model, excluding the regional base 

flow, are shown in parentheses in table 14.

The peak-agriculture and the developed simulations indicated that increased agriculture or development increased the percentage of Whittlesey Creek flow 

from surface runoff by 2.2 percent and 0.9 percent and 

decreased the percentage of the flow from perched 

ground water by 0.7 percent and 0.2 percent, respectively 

(table 14). In contrast, the presettlement and reforested 

simulations indicated that a more fully forested basin 

increased the percentage of shallow ground-water flow 

by 0.2 percent and 4.1 percent, respectively, and reduced 

surface runoff by 0.5 percent and 4.2 percent, respectively, 

compared to 1992-93 land-cover conditions. 

Land-Cover Effects on Soil Infiltration Rates

Infiltration rates determined by the SWAT model 

varied by soil type and varied slightly between land-cover 

simulations within each soil type (table 15). Infiltration 

rates for sand were two to three times that for clay. Infiltration rates were lower for the peak-agriculture and developed simulations, whereas rates were highest for 

the presettlement simulation. 

Infiltration rates for clay soils in the SWAT model 

were similar to recharge rates used for the area underlain 

by the Miller Creek Formation in the ground-waterflow model (about 2 in/yr). Sandy-soil infiltration rates 

(4 to 5 in/yr) were much lower in the SWAT model than 

those used in the ground-water-flow model (17 in/yr) 

because the rates represented sands from two different 

areas. The SWAT model included only the surface-watercontributing basin of Whittlesey Creek, so infiltration rates 

for sand in the SWAT model represented mainly the sandy 

parts of the Miller Creek Formation, containing interbedded silts and clays. In contrast, the recharge rates for sand 

in the ground-water-flow model primarily represented the 

thick, sandy deposits of the Copper Falls Formation in the 

Bayfield Highlands, which have no surface-water drainage. 

Infiltration rates in the developed and peak-agriculture simulations were lower than the other simulations for 

both sand and clay. Increased agriculture and increased 

development both caused a reduction in infiltration rates 

of soils and a decrease in the amount of time the water was 

on the land surface before reaching the stream; this in turn, 

resulted in more of the precipitation running off and reductions in ground-water recharge rates.

Table 14. Percentage of streamflow at the Whittlesey Creek, Wis., U.S. Geological Survey streamflow-gaging station from surface 

runoff, soil-profile drainage, and regional ground water based on Whittlesey Creek Soil and Water Assessment Tool (SWAT) 

model simulations

[ft3/s, cubic feet per second. Numbers in parentheses are the percentages from just the SWAT model, excluding regional flow.]

Sources of streamflow

Model simulations

1992-93 Presettlement

(before 1870)

Peak

agriculture

(1928)

Reforested Developed

Percentage of surface runoff 15.7 (61.5) 15.2 (60.0) 17.9 (66.1) 11.5 (45.0) 16.6 (63.2)

Percentage of soil-profile 

drainage/perched ground water

 9.9 (38.5) 10.1 (40.0) 9.2 (33.9) 14.0 (55.0) 9.7 (36.8)

Percentage of regional ground 

water at a constant 16.75 ft3

/s

 74.4 74.7 72.9 74.5 73.7
The reduction of infiltration due to changing land 

cover from forest to agriculture was more dramatic in the 

clay soils than sand because of the differing infiltration 

properties of the soils. Pure clay is relatively impervious, 

whereas sand is relatively permeable. Clay soils require 

additional structure in the soil profile (such as plant roots, 

organic matter, and such) to promote porosity; therefore, 

the infiltration rates of clay soils are susceptible to landcover factors. Sand remains relatively porous regardless 

of soil structure, barring the overlayment of impervious 

surfaces (such as buildings or paving) or intense compaction. On the basis of generalized soil maps used in the 

SWAT model, subbasins 5, 6, 7, 8, 9, 10, 16, 17, 18, 19, and 

parts of subbasins 2, 4, and 15 are mostly clay (fig. 9) and 

therefore most dependent on land cover and soil structure 

for infiltration capacity. More detailed soils data would be 

needed to characterize the effects of localized land-cover 

changes.

The reforested and presettlement simulations both 

showed an increase in ground-water recharge rates from 

the 1992-93 simulation. Forests increase soil structure and 

the amount of time the runoff remains on the land surface 

because overland flow must pass around and through 

the forest floor, which is littered with detritus. Increased 

structure and runoff residence time on land surface 

resulted in increased infiltration and lower peaks. Forest 

cover increased the evapotranspiration rates, meaning less 

water is available for infiltration; however, the increase in 

infiltration on clay soils that change from grass to forest is 

greater than the effect of the increased evapotranspiration 

from the forest. Therefore, clay soils showed increases in 

local ground-water contributions to Whittlesey Creek in 

the forested simulations. The reforested simulation showed 

a slight drop in recharge rates on sand soils, a result of the 

increased evapotranspiration from the trees being greater 

than the increased infiltration caused by the changes in 

the soil structure from reforestation. The relation between 

increased infiltration and increased evapotranspiration 

when changing from grassland to a forest is not linear for 

all climates (Priestly and Taylor, 1972) and can be quite 

different and more dramatic in areas with different 

climate and vegetation than those in the Whittlesey Creek 

Basin. The increased presence of wetlands in the presettlement simulation resulted in increased infiltration on both 

soil types.

Summary and Conclusions

The U.S. Geological Survey studied the effects of 

land cover on flooding and base-flow characteristics 

of Whittlesey Creek, Bayfield County, Wis., by use of 

ground-water and rainfall-runoff models. The study was 

done in cooperation with the Bayfield County Land and 

Water Conservation Department and the U.S. Fish and 

Wildlife Service. These cooperators are interested in the 

protection and restoration of habitat in Whittlesey Creek 

and surrounding creeks for migration, spawning, and rearing of trout and salmon from Lake Superior and to protect 

important bird nesting areas. 

The approach for the study involved collection of 

field data during 1999-2001 for base-flow, streambed head 

and temperature, meteorological data, continuous streamflow and stage, and other physical characteristics. Drillers’ 

well logs provided data for potentiometric-surface altitudes 

and geologic descriptions. Geologic, soil, hydrographic, 

altitude, and historical land-cover data were compiled into 

a geographic information system. Streamflow characteristics for Whittlesey Creek—floods, base flow, seasonal 

fluctuations, relative contributions of runoff and ground 

water, and the relation between 1992-93 land-cover 

characteristics and base flows and flooding in Whittlesey 

Creek—were quantified. These data were used in two 

ground-water-flow models (GFLOW and MODFLOW) 

and a rainfall-runoff model (SWAT).

The synoptic surveys of base flow and streambed 

head and temperature for Whittlesey Creek and adjacent 

streams revealed that ground water from the deep flow 

system intersected Whittlesey Creek near the confluence 

of the main stem and North Fork. Small base flows, 

Table 15. Average ground-water infiltration rates by soil type in the Whittlesey Creek, Wis., Soil and Water Assessment 

Tool (SWAT) model simulations

Soil Type

Ground-water infiltration rate (inches per year)

1992-93 Presettlement

(before 1870)

Peak agriculture

(1928) Reforested Developed

Sand 4.48 4.88 4.13 4.45 4.34

Clay 1.94 2.35 1.45 2.03 1.13

Rainfall-Runoff Simulations 43
44 Simulation of Ground-Water Flow and Rainfall Runoff with Effects of Land Cover, Whittlesey Creek, Bayfield County, Wis.

negative streambed heads, and warm streambed temperatures in headwater reaches of Whittlesey Creek indicated 

that those areas were receiving only a small amount of 

ground water from perched parts of the shallow groundwater-flow system upstream from the confluence. Losing 

reaches and negative heads above the confluence of the 

North Fork and main stem of Whittlesey Creek also indicated that some streamflow, derived from the perched part 

of the shallow system, recharged the deep system through 

the streambed. 

Results from the MODFLOW and GFLOW groundwater-flow models were consistent with field data. Both 

models indicate that much of the headwaters of Whittlesey 

Creek do not receive ground-water contributions from the 

deep system. Results from both models also indicate that 

the deep ground-water-flow system intersected Whittlesey 

Creek just upstream from the confluence of the main stem 

and the North Fork and that the ground-water-contributing 

area did not coincide with the topographically delineated 

surface-water-contributing basin. Instead, about 90 percent 

of the base flow to Whittlesey Creek originated as recharge 

through the permeable sands of the Bayfield Highlands in 

the center of the Bayfield Peninsula, to the northwest of 

the topographically delineated Whittlesey Creek drainage basin. The land cover in the recharge area is heavily 

forested. Presently, base flow is 17-18 ft3

/s at the streamflow-gaging station on Whittlesey Creek and through the 

Wildlife Refuge. Regional ground-water flow (baseflow) 

(74.4 percent), runoff from rainfall and snowmelt (15.7 

percent), and perched ground-water flow 

(9.9 percent) constitute the annual mean streamflow 

in Whittlesey Creek (22 ft3/s) near the mouth.

The effects of changing land cover on ground-water 

recharge and base flow were simulated by changing 

recharge rates in the MODFLOW model. Deforestation 

could cause an increase in recharge due to decreased 

evapotranspiration, whereas decreased recharge could 

occur from development and resulting loss of pervious surfaces. Model-wide changes in recharge caused a proportional change in base flow to Whittlesey Creek. 

To test the sensitivity of base flow to more localized 

changes in recharge, recharge rates were increased by 25 

and 50 percent and decreased by 25 and 50 percent within 

the ground-water-contributing area for Whittlesey Creek. 

These changes resulted in relatively small changes in base 

flow to Whittlesey Creek (about 2-11 percent, respectively) because the change in recharge also caused changes 

in the size of the resulting ground-water-contributing area. 

The most likely land-cover change for the ground-watercontributing area is logging of forests in the sandy zone. 

If this resulted in a 25 percent increase in recharge, the 

base flow of Whittlesey Creek would be expected to 

increase by about 4 percent. 

The SWAT model simulated the effects of land-cover 

change on average annual runoff and flood peaks (daily 

mean flow on peak flow days) for Whittlesey Creek. The 

model was calibrated with data from continuous streamflow 

and stage data from Whittlesey Creek for the period April 

1999 through October 2001. Conditions from 1992-93 

WISCLAND satellite-derived land cover and four landcover simulations were modeled. Simulations were: 

(1) presettlement (mainly forested before European settlement in the late 1800s); (2) peak agriculture, based on 

land-cover data from 1928; (3) reforested; and (4) developed (based on a hypothetical increase of 25-percent urban 

residential land). Presettlement and reforested simulations 

involved two different simulations because the 1928 landcover map indicated 11.6 percent of the basin was wetland 

compared to 1.6 percent in 1992-93. In 1928, 28 percent 

of the basin was in row crop agriculture, compared to less 

than 1 percent in 1992-93. The amount of forested land was 

similar in 1928 and 1992-93.

 Results from the SWAT model indicate that changes 

in land cover would have minimal effects on average 

annual runoff for Whittlesey Creek, but would affect flood 

peaks. An increase in forested land cover would result 

in a reduction of flood peaks by about 12-14 percent for 

floods with a recurrence interval of up to 100 years. The 

flood hydrographs from the more forested simulations had 

wider and broader peaks than the hydrographs for conditions in 1992-93. If land cover in 1992-93 were converted 

to forest, the daily mean flow for the day of the largest 

flood on record (370 ft3

/s on April 23, 2001) would be 

reduced by about 12 percent. The data from nearby longterm USGS streamflow-gaging stations indicated that the 

event on April 23, 2001, was an 80- to 100-year event. 

The reduction of flood peaks under more forested conditions could potentially cause a reduction in sedimentation 

near the mouth of the creek, through the National Wildlife Refuge. If the basin were developed into 25-percent 

urban or returned to the intensive row-crop agriculture of 

the 1920s, daily mean flow on peak-flow days would be 

expected to increase up to 12 and 18 percent, respectively. 

These increases would be greatest for floods with dry 

antecedent conditions. The April 23, 2001, flood occurred 

under nearly saturated conditions, and the model showed 

an increase of only 1 percent for flood peaks for the 

developed and peak-agriculture simulations. The SWAT 

model is limited to a daily time step, which is adequate for 

describing the surface-water/ground-water interaction and 
percentage changes. It may not however, be adequate in 

describing instantaneous peak flow because the instantaneous peak flow in Whittlesey Creek during a flood can be 

more than twice the magnitude of the daily mean flow.

The models used in this study are inherently a simplistic approximation of a complex system. However, they 

adequately describe the effects of changing land cover 

on flood peaks, average annual runoff, and base flow in 

Whittlesey Creek. During the course of this study, several 

factors were identified that might improve models used 

in future studies. The SWAT model could be improved by 

the following: (1) use of a hourly time step (if this features 

became available in the model code), (2) a longer period of 

streamflow record for calibration, (3) use of more detailed 

county-level soil survey data, (4) increased understanding of the storage capacity of the large wetland in the 

upper basin, and (5) hourly precipitation data from within 

the drainage basin. The MODFLOW ground-water-flow 

model for the study could be improved by adding more 

detail and complexity such as additional layers, recharge 

zones, and zones of hydraulic conductivity. Flow from the 

perched part of the shallow flow system could also 

be incorporated into a future model. 

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