Prepared in cooperation with the City of Cold Spring, Minnesota

Effect of Ground-Water Withdrawals on Floe 

in the Sauk River Valley Aquifer and on 

Streamflow in the Cold Spring Area, 

Minnesota

Water-Resources Investigations Report 01–4111

U.S. Department of the Interior

U.S. Geological Survey
Effects of Ground-Water Withdrawals on Flow 

in the Sauk River Valley Aquifer and on 

Streamflow in the Cold Spring Area, 

Minnesota

By R. J. Lindgren

Water-Resources Investigations Report 01-4111

Prepared in cooperation with the City of Cold Spring, Minnesota
U.S. DEPARTMENT OF THE INTERIOR

Gale A. Norton, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Use of brand names in this report is for identification purposes only and does not 

constitute endorsement by the U.S. Geological Survey.

Mound View, Minnesota, 2001

For additional information write to:

U.S. Geological Survey

District Chief

2280 Woodale Drive

Mounds View, MN 55112

Copies of this report can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286, MS 517

Federal Center

Denver, CO 80225

Information regarding the USGS is available on the Internet via the World Wide Web. 

You may connect to the USGS Home Page using the Universal Resource Locator (URL) at 

http://wwwrvares.er.usgs.gov. 

You may also connect to the Minnesota District Home Page at 

http://mn.water.usgs.gov/.

For more information on all USGS reports and 

products (including maps, images, and computerized data), call 1-888-ASK-USGS

Water-Resources Investigations Report 01-4111
v

CONTENTS

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

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

Description of study area................................................................................................................................................3

Methods of investigation................................................................................................................................................3

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

Hydrogeologic setting...........................................................................................................................................................6

Geologic deposits ...........................................................................................................................................................6

Hydrogeologic units .......................................................................................................................................................6

Hydraulic properties.....................................................................................................................................................10

Ground-water flow, sources, and discharge .................................................................................................................10

Ground-water withdrawals ....................................................................................................................................13

Stream-aquifer leakage ..........................................................................................................................................14

Simulation of ground-water flow........................................................................................................................................16

Numerical model description..............................................................................................................................................16

Numerical model calibration and results......................................................................................................................25

Hydraulic heads .....................................................................................................................................................26

Stream-aquifer leakage ..........................................................................................................................................26

Ground-water budget.............................................................................................................................................26

Ground-water flow to wells..........................................................................................................................................28

Effects of increased ground-water withdrawals ...........................................................................................................31

Numerical model limitations and accuracy of results ..................................................................................................32

Summary.............................................................................................................................................................................34

References cited..................................................................................................................................................................36

ILLUSTRATIONS

Figures 1-9a. Maps showing:

1. Location of study area, wells, and streamflow and stream-stage measurement sites, Cold Spring area, 

Minnesota...........................................................................................................................................................4

 1a. Location of wells, and streamflow and stream-stage measurement sites near Cold Spring and 

Gold’n Plump Poultry Processing Plant, Cold Spring area, Minnesota ............................................................5

2. Surficial geology in Cold Spring area, Minnesota ...............................................................................................7

3. Quaternary geology in Cold Spring area, Minnesota...........................................................................................8

4. Measured and simulated potentiometric surface of the upland surficial aquifer, December 1998, 

Cold Spring area, Minnesota..............................................................................................................................9

5. Measured and simulated potentiometric surface of the Sauk River Valley aquifer, December 1998, 

Cold Spring area, Minnesota........................................................................................................................... 11

5a. Measured and simulated potentiometric surface of the Sauk River Valley aquifer, near Cold Spring 

and Gold’n Plump Poultry Processing Plant, December 1998, Cold Spring area, Minnesota ........................12

6. Grid for finite-difference ground-water-flow model, Cold Spring area, Minnesota..........................................17

7. Extent, boundary conditions, and calibrated horizontal hydraulic conductivity zones for ground-waterflow model layer 1, Cold Spring area, Minnesota ...........................................................................................18

8. Extent, boundary conditions, and calibrated vertical hydraulic conductivity zones for ground-water-flow 

model layer 2, Cold Spring area, Minnesota....................................................................................................19

9. Extent, boundary conditions, and calibrated horizontal hydraulic conductivity zones for ground-waterflow model layer 3, Cold Spring area, Minnesota .......................................................................................... 20
vi

ILLUSTRATIONS--CONTINUED

9a. Boundary conditions and calibrated horizontal hydraulic conductivity zones for ground-waterflow model layer 3 near Cold Spring and Gold’n Plump Poultry Processing Plant, Cold Spring 

area, Minnesota ................................................................................................................................................21

10. Extent, boundary conditions, and calibrated horizontal hydraulic conductivity zones for ground-waterflow model layer 4, Cold Spring area, Minnesota ...........................................................................................22

11. Simulated altitude of potentiometric surface of Sauk River Valley aquifer and contributing areas of 

ground-water flow to water-supply wells, 1998 pumpage, Cold Spring area, Minnesota...............................29

11a. Simulated altitude of potentiometric surface of Sauk River Valley aquifer and contributing areas 

of ground-water flow to water-supply wells near Cold Spring, and Gold’n Plump Poultry Processing 

Plant, 1998 pumpage, Cold Spring area, Minnesota .......................................................................................30

12. Simulated altitude of potentiometric surface of Sauk River Valley aquifer, contributing areas, and 

20-year time-of-travel zones of ground-water flow to water-supply wells, projected pumpage, Cold 

Spring area, Minnesota ....................................................................................................................................32

 12a. Simulated altitude of potentiometric surface of Sauk River Valley aquifer, contributing areas, and 

20-year time-of-travel zones of ground-water flow to water-supply wells near Cold Spring and 

Gold’n Plump Poultry Processing Plant, projected pumpage, Cold Spring area, Minnesota..........................33

TABLES

1. Stream discharge and measured and simulated stream-aquifer leakage under low-flow conditions during 

1998-99, Cold Spring area, Minnesota ................................................................................................................15

2. Initial and final calibrated values of hydraulic properties used in ground-water-flow model of aquifer 

system, Cold Spring area, Minnesota ..................................................................................................................24

3. Simulated water budgets from ground-water-flow model of aquifer system with 1998 and projected

 pumpage conditions, Cold Spring area, Minnesota ............................................................................................27

4. Simulated leakage between model layers from ground-water-flow model of aquifer system with 1998 and 

projected pumpage conditions, Cold Spring area, Minnesota .............................................................................28

CONVERSION FACTORS, ABBREVIATED WATER-QUALITY UNITS AND SEA LEVEL DATUM

Multiply By To obtain

inch (in.) 2.54 centimeter

inch per year (in./yr) 2.54 centimeter per year

foot (ft) .3048 meter

foot squared per day (ft2

/d) .09290 meter squared per day

cubic foot per second (ft3

/s) .02832 cubic meter per second

gal (gal) 3.785 liter

gallon per minute (gal/min) 3.785 liter per minute

mile (mi) 1.609 kilometer

square mi (mi2

) 2.590 square kilometer

Chemical concentrations of substances are given in metric units of milligrams per liter (mg/L) and micrograms per liter (μg/L). Milligrams and micrograms per liter express the concentration of the chemical constituent as a mass (mg or μg) per unit volume (L). One 

thousand micrograms per liter is equivalent to 1 milligram per liter.

Sea level: In this report “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic datum derived 

from a general adjustment of the first-order nets of both the United States and Canada, formerly called Sea Level Datum of 1929.
1

Effects of Ground-Water Withdrawals on Flow 

in the Sauk River Valley Aquifer and on 

Streamflow in the Cold Spring Area, 

Minnesota

By Richard J. Lindgren

ABSTRACT

The U. S. Geological Survey, in cooperation with the 

city of Cold Spring, Minnesota conducted a study during 

1998-99 to: (1) determine the contributing areas of groundwater flow to high-capacity wells, (2) delineate the 10-, 

20-, and 30-year time-of-travel zones to high-capacity 

wells, and (3) determine changes in streamflow in the Sauk 

River due to ground-water withdrawals. Surficial aquifers 

underlie a portion of the uplands in the north-central part of 

the study area and the Sauk River Valley. The upland surficial aquifer is unconfined, with saturated thicknesses ranging from 6 to 37 feet. The Sauk River Valley aquifer 

consists of hydraulically connected sand and gravel units: 

(1) the generally continuous surficial unconfined unit 

underlying the Sauk River Valley and (2) buried confined 

units that are overlain by till or lake clays in the upland 

areas. Maximum saturated thickness of the Sauk River Valley aquifer is about 50 feet. Thicknesses of the buried units 

are generally 10 to 20 feet.

Ground-water flow in the upland surficial aquifer is (1) 

to the south and southeast toward the margins of the aquifer 

and (2) toward an unnamed creek valley in the northwestern part of the study area. Ground-water flow in the Sauk 

River Valley aquifer is from upland areas toward the Sauk 

River and the connected chain of lakes. Based on 

hydrograph analysis, ground-water recharge rates to the 

aquifers during 1999 ranged from 5.3 to 8.6 inches per 

year, with an average value of 7.0 inches per year. 

Streamflow measurements indicated net gains of 44.8 

and 25.8 cubic feet per second for the Sauk River from 

Cold Spring to Rockville during October 1998 and August 

1999, respectively. In general, the Sauk River probably is a 

gaining stream in all reaches, except for the reach adjacent 

to the Gold’n Plump Poultry Processing Plant well field. 

Ground-water withdrawals from the well field induce infiltration of water from the Sauk River to the underlying aquifer. The measured gains in streamflow for Brewery Creek 

were 2.75 and 2.25 cubic feet per second during October 

1998 and August 1999, respectively. 

A numerical ground-water-flow model was constructed 

and calibrated for steady-state conditions. Based on the calibrated model, areal recharge accounts for 51.5 percent of 

the sources of water to the aquifers in the Cold Spring area 

and inflow through constant-head boundaries contributes 

45.8 percent. The largest discharges from the aquifers are 

leakage from the Sauk River Valley aquifer to the Sauk 

River and Brewery Creek (53.7 percent) and outflow 

through constant-head boundaries (33.1 percent). 

The simulated contributing areas for selected watersupply wells in the Cold Spring area generally extend to 

and possibly beyond the model boundaries to the north and 

to the southeast. The contributing areas for the Gold’n 

Plump Poultry Processing Plant supply wells extend: (1) to 

the Sauk River, (2) to the north to and possibly beyond to 

the northern model boundary, and (3) to the southeast to 

and possibly beyond the southeastern model boundary. The 

primary effects of projected increased ground-water withdrawals of 0.23 cubic feet per second (7.5 percent increase) 

were to: (1) decrease outflow from the Sauk River Valley 

aquifer through constant-head boundaries and (2) decrease 

leakage from the valley unit of the Sauk River Valley aquifer to the streams. No appreciable differences were discernible between the simulated steady-state contributing areas 

to wells with 1998 pumpage and those with the projected 

pumpage. 
2

INTRODUCTION

Increased demand for ground 

water in the Cold Spring area in central Minnesota has resulted in the 

increased development of glaciallydeposited aquifers, hereinafter termed 

glacial aquifers. These aquifers, composed of surficial and buried sand and 

gravel, underlie the Sauk River Valley 

in the Cold Spring area and are utilized as sources of water supply. The 

Minnesota Department of Health 

(MDH) and public and private water 

suppliers are concerned about the 

effects of ground-water withdrawals 

from high-capacity wells on water 

levels in the aquifers, streamflow in 

the Sauk River, and potential sources 

of contamination to water-supply 

wells. Potential sources of contaminated water to high-capacity watersupply wells in the Cold Spring area, 

some of which are located near the 

Sauk River, include both contaminated ground water and the Sauk 

River. Areas contributing groundwater to high-capacity wells need to 

be delineated so that land use within 

the contributing areas can be managed 

to reduce the risk of water-quality 

degradation. Of particular concern to 

the MDH and water managers is the 

extent and sources of nitrate contamination in the aquifers and the Sauk 

River. A better understanding of 

ground-water flowpaths and groundwater travel times in the Cold Spring 

area and the extent of contributing 

areas to public supply wells is needed 

to manage the water supplies and prevent contamination of public watersupply wells. Changes in contributing 

areas and time-of-travel zones as a 

result of anticipated development also 

need to be assessed. 

During August 1996, nitrate concentrations exceeded the maximum 

contaminant level of 10 milligrams 

per liter as nitrogen (mg/L as N) set 

by the U.S. Environmental Protection 

Agency (USEPA) (1996) in water 

sampled from Cold Spring municipal 

well CS1 (Minnesota Department of 

Health, 1999). Cold Spring municipal 

well CS2 also has shown elevated 

concentrations of nitrate, ranging 

from 7 to 8 mg/L as N (Minnesota 

Department of Health, 1999). These 

two wells make up the city’s primary 

well field. In addition, sampling of 

other public and private wells by local 

well drillers, Stearns County Environmental Services Department, and the 

Minnesota Department of Agriculture 

(MDA) points to a number of other 

areas around the community where 

local ground water has nitrate concentrations approaching or exceeding the 

maximum contaminant level of 

10 mg/L as N. During October 1996, 

monitoring of eight private wells 

located in the vicinity of the proposed 

new well site for Cold Spring municipal well CS4 indicated nitrate concentrations ranging from <1.0 to 

6.2 mg/L as N. Pesticide monitoring 

indicated low concentrations of atrazine in the Cold Spring water system. 

During 1991, MDH monitoring indicated low concentrations of volatile 

organic compounds in two private 

water supply systems (Gold’n Plump 

Poultry Processing Plant and Cold 

Spring Granite Company).

The Wellhead Protection (WHP) 

Program is a provision in the 1986 

Amendments to the Safe Drinking 

Water Act designed to assist State 

agencies in protecting areas surrounding wells against infiltration, percolation, and transport of contaminants 

that may have adverse effects on 

human health. The USEPA prepared a 

guidebook (U.S. Environmental Protection Agency, 1987) to provide 

technical guidance on the hydrologic 

aspects of WHP in the United States. 

For the purposes of WHP, three types 

of recharge areas have been defined: 

the zone of transport, the zone of contribution, and the zone of influence 

(U.S. Environmental Protection 

Agency, 1987). The time required for 

a contaminant to travel between 

points in an aquifer can be identified 

using maps showing lines of equal 

advective travel time. A zone of transport (time-of-travel zone), therefore, 

is defined by the area around a 

pumped well bounded by lines of 

equal travel time. The zone of contribution (contributing area) for a highcapacity well (greater than 

200 gal/min (0.44 ft3

/s)) is defined as 

that part of a ground-water-flow system supplying water to a well. The 

contributing area could be thought of 

as a time-of-travel zone for infinite 

travel time. The zone of influence is 

the area of declines in hydraulic head 

resulting from the withdrawal of 

water from a well. 

To address these needs and concerns, and to further the understanding of stream-aquifer systems, the 

U.S. Geological Survey (USGS), in 

cooperation with the City of Cold 

Spring, conducted a study during 

1998-99. The objectives of this study 

were to: (1) determine the contributing area of ground-water flow to highcapacity wells under current and projected development conditions, (2) 

delineate the 20-year time-of-travel 

zones to high-capacity wells under 

current and projected development 

conditions, and (3) aid in understanding the interaction between the Sauk 

River Valley aquifer and the Sauk 

River and Brewery Creek. This report 

describes the results of field data collection during 1998-99, the sources 

and types of data used in constructing 

a steady-state numerical groundwater-flow model, the model calibration process, and the results of model 

simulations. 
3

Description of Study Area

 The study area covers about 

55 mi2 in southeastern Stearns County 

in central Minnesota (fig. 1). The city 

of Cold Spring, with a population of 

approximately 4,000, is located near 

the center of the study area. The study 

area is drained by the Sauk River, 

which flows from west to east across 

the study area and whose confluence 

with the Mississippi River is about 

15 mi northeast of the study area. 

Average annual precipitation in the 

study area is 27 in. (Baker and Kuehnast, 1978). Of this amount, about 

4.5 in. leaves the Sauk River Basin as 

runoff (Baker and others, 1979). The 

nearest USGS streamflow-gaging station on the Sauk River (station number 05270500) is located about 8 mi 

downstream of Cold Spring. The 

average annual flow in the Sauk River 

at this point is 305 ft3

/s (Mitton and 

others, 1999). The minimum recorded 

discharge is 0.3 ft3/s and the maximum discharge is 9,100 ft3

/s. Brewery 

Creek, a tributary to the Sauk River, 

flows to the southeast through Cold 

Spring. A chain of lakes extending 

from Knaus Lake on the east to 

Horseshoe Lake on the west is located 

in the southwestern part of the study 

area. The Sauk River flows into the 

chain of lakes near the western boundary of the study area and flows out of 

Knaus Lake south of Cold Spring 

(fig. 1). 

Topography is rolling to undulating in upland areas and steep near 

streams and drainageways. The 

topography is relatively flat along the 

Sauk River Valley. In the study area, 

the valley is much wider on the northwest side of the river than on the 

southeast side. Relatively steep bluffs 

(an escarpment with about 70 ft 

change in altitude) dip down to the 

Sauk River Valley about 1 mile northwest of the downtown area of Cold 

Spring and along the southeast side of 

the Sauk River. There is a lower river 

terrace (about 20 ft above river level) 

immediately north of Cold Spring. 

Land use in the Cold Spring area is 

evenly divided between developed 

and undeveloped land. About 25 percent of the area is used for agriculture. 

Undeveloped land other than agriculture includes forest, wetlands, and 

surface-water bodies. 

Methods of Investigation

Existing data on the hydrogeology and hydraulic properties of the 

ground-water system in the study area 

were compiled from a variety of 

sources including test-hole and waterwell logs, geologic maps, State and 

Federal data bases, and published 

reports. New data collected for this 

study includes test drilling and well 

installation, water levels, and stream 

discharge. A numerical ground-waterflow model was constructed using 

information from test-hole logs, 

water-well logs, and geologic maps.

Test-hole and water-well logs 

were obtained from the Minnesota 

Geological Survey’s County Well 

Index for Stearns County, the USGS 

Ground Water Site Inventory data 

base, consulting reports, and the 

MDH. Twenty-one 2-inch-diameter 

observation wells were installed for 

this study. All but one of the observation wells were screened in surficial 

sand and gravel deposits. A pair of 

nested wells was installed near the 

Sauk River at the Gold’n Plump Poultry Processing Plant site and a set of 

three nested wells was installed near 

Cold Spring municipal wells CS1 and 

CS2 (fig. 1a). The deeper well of the 

pair of nested wells at the Gold’n 

Plump Poultry Processing Plant site 

was screened in a lower-permeability 

deposit underlying the surficial sand 

and gravel deposits and overlying granitic bedrock. 

Water levels were measured 

monthly during November 1998 

through October 1999 in the 21 observation wells installed for this study 

and in 7 observation wells screened in 

surficial sand and gravel deposits that 

had been installed prior to this study 

(fig. 1). Water levels were measured 

twice during October 1998 through 

February 1999 in 31 domestic and 

commercial wells (fig. 1). Eight of the 

31 domestic and commercial wells are 

screened in surficial sand and gravel 

deposits in the north-central part of 

the study area, 19 are screened in surficial sand and gravel deposits in the 

Sauk River Valley and buried sand 

and gravel deposits in the adjacent 

uplands, and 4 are open to the granitic 

bedrock. Water levels measured in the 

28 observation wells and 24 of the 

domestic and commercial wells were 

used to calibrate the numerical 

ground-water-flow model. 

Stream- or lake-stage measurements were made monthly during 

November 1998 through October 

1999 (if open-water conditions 

existed) at 5 sites on the Sauk River, 3 

sites on the chain of lakes, and 2 sites 

on Brewery Creek (fig. 1). One of the 

sites on the Sauk River was at Rockville, located about 1 mi east of the 

study area. 

The altitudes of all water-level 

measurement points were determined 

by surveying from nearby benchmarks by the USGS (Greg Payne, 

written commun., 1999). Altitudes of 

measuring points were measured with 

a precision of 0.1 ft. 

Synoptic sets of low-flow measurements were made to quantify 

streamflow gains and losses for 

reaches of the Sauk River and Brewery Creek. Streamflow measurements 

were made at nine sites on the Sauk 
4

p

1

1 1

6 1

6 6

6

36 31 36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

B

B

B

B

2 3

2

2

3

SW1

SW8

SW9

I

G

G

G

2

2

2

2

2

CS#4

CSG

CSG

SEE

FIGURE 1a

0 1 2 3 MILES

0123 KILOMETERS

Location of study area, wells, and streamflow and stream-stage measurement sites, Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Location Map

MINNESOTA

Study

Area

Figure 1.

Area where valley unit of Sauk river Valley aquifer is present

Domestic or commercial well (B indicates well open

to Precambrian bedrock)

Observation well (number indicates nested wells)

WHP partnership water-supply well (Number indicates multiple

wells at a site. CSG indicates Cold Spring Granite Company

supply well. CS indicates Cold Spring municipal well)

Irrigation well

Golf course or landscape well

Industrial well

Streamflow measurement site (with site identifier)

Stream- or lake-stage measurement site

Both streamflow and stream-stage measurement site

(with site identifier)

2

I

2

G

SW8

SW1

EXPLANATION

CS
5

23

14

22

15

24

13

T

123

N

R 30 W

Sauk

River

Brewery

Creek

23

50

2

2

Cold Spring

Knaus Lake

45°27'

45°28'

94°26' 94°25' 94°24'

0 1 MILE

0 1 KILOMETER

Location of wells, and streamflow and stream-stage measurement sites near Cold Spring and Gold'n Plump Poultry

Processing Plant, Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Gold'n Plump

Poultry

Processing

Plant

SW2

CSD

SW4

Domestic or commercial well (B indicates well open

to precambrian bedrock)

Observation well (number indicates nested wells)

WHP partnership water-supply well

GL indicates Gluek Brewing Company supply well

CS indicates Cold Spring municipal well

TE indicates Town's Edge Mobile Home Park supply well

GPP indicates Gold'n Plump Poultry supply well

CSA indicates Cold Spring Alano Society supply well

Irrigation well

Golf course or landscape well

2

I

G

EXPLANATION

Industrial well

Streamflow measurement site

(with site identifier)

Stream- or lake-stage measurement site

Both streamflow and stream-stage measurement site

(with site identifier)

Discharge site

CSD indicates Cold Spring Wastewater Plant discharge site

GPD indicates Gold'n Plump Poultry Plant discharge site

BB

CS

Figure 1a.

CSD

GPD

B

B

B

2

3

SW2

SW3

SW4

SW5

SW6

SW7

SW10

SW11

SW12

I

G

G

G

CS#3

CS#1 CS#2

GL GL

CSA

CSA

GPP

GPP

TE TE
6

River and at three sites on Brewery 

Creek during October 1998 and 

August 1999 (fig. 1). The estimated 

accuracy of individual current-meter 

streamflow measurements was 5 percent for measurements rated good and 

8 percent for measurements rated fair 

(Pelletier, 1988). The measured 

streamflow gains and losses were 

used in the calibration of the numerical ground-water-flow model. 

A numerical ground-water-flow 

model was constructed and calibrated 

for steady-state conditions to achieve 

project objectives. The numerical 

model used was the USGS modular 

three-dimensional, finite-difference 

ground-water-flow model (MODFLOW) developed by McDonald and 

Harbaugh (1988). The model was calibrated using water levels and stream 

stages measured in 52 observation, 

domestic, and commercial wells and 

at 12 stream sites, respectively. Two 

synoptic sets of low-flow streamflow 

measurements made on the Sauk 

River and Brewery Creek at 11 sites 

were also used to calibrate the model. 

VISUAL MODFLOW was used as a 

pre-processor to input the data, to run 

the MODFLOW simulations, and as a 

post-processor to visualize and analyze the results of the simulations 

(Guiguer and Franz, 1999). 

The particle-tracking post-processing package MODPATH (Pollock, 

1989) was used to compute groundwater flow path lines based on output 

from the calibrated steady-state simulation obtained with MODFLOW. In 

addition to three-dimensional path 

lines, MODPATH computes the position of particles at specified points in 

time and the total time-of-travel for 

each particle. Particle tracking was 

used to determine the contributing 

area of ground-water flow to watersupply wells and to delineate the 10-, 

20-, and 30-year time-of-travel zones 

to the wells. 

Acknowledgments

The author is grateful to landowners who allowed the installation of 

observation wells on their property 

and to well owners who permitted 

measurement of water levels in their 

wells. The author is also grateful to 

Gail Haglund of the Minnesota 

Department of Health, Chuck Regan 

of the Minnesota Pollution Control 

Agency, Verena Weber and Ray 

Koppy of the City of Cold Spring, and 

Benjamin Bertsch of the University of 

Minnesota, Duluth for providing 

information and assistance during the 

study. Thanks also are given to 

employees of the U.S. Geological 

Survey in Minnesota for their assistance with this study, particularly 

Michael Menheer, Christopher 

Sanocki, and Robert Borgstede. 

HYDROGEOLOGIC SETTING

Geologic Deposits

Precambrian igneous and metamorphic rocks underlie the glacial 

deposits in the study area (Helgesen 

and others, 1975). Sedimentary rocks 

of Late Cretaceous age once extended 

across most of the area (Meyer and 

Swanson, 1996). Today remnants of 

these strata less than 25 ft thick, consisting chiefly of soft shale, claystone, 

and silty fine sandstone, overlie the 

Precambrian rocks in some areas 

(fig. 2). 

Surficial deposits in the Cold 

Spring area (fig. 2) consist mainly of 

late-Wisconsin glacial till and outwash sands and gravels associated 

with the Des Moines and Superior 

lobes (Meyer and Knaeble, 1995; 

Meyer and Swanson, 1996). Outwash 

sands and gravels from the Des 

Moines lobe fill most of the Sauk 

River Valley. Outcrops of igneous and 

metamorphic rocks, marl, peat, till, 

and alluvium also are present in the 

Sauk River Valley. 

The distribution of Quaternary 

deposits is represented in figure 3. 

The glacial deposits in the uplands are 

composed of impermeable till, but 

have randomly distributed buried sand 

and gravel lenses throughout. Where 

the deposits are thinner in the bedrock 

valley of the Sauk River, continuous 

surficial alluvial deposits of highly 

permeable sand and gravel are 

present. The glacial deposits here 

were eroded by the Sauk River, with 

subsequent deposition of alluvium.

The Quaternary deposits in the 

study area include: (1) till with few, if 

any, buried sand and gravel lenses 

(fig. 3, zone A), (2) complex till and 

ice-contact stratified deposits that 

may include surficial or buried sand, 

sand and gravel lenses, or both (fig. 3, 

zones B and C), and (3) thick surficial 

sand and gravel outwash deposits (fig. 

3, zones D and E). The glacial deposits become thicker with distance from 

the Sauk River (Setterholm, 1995), 

which is incised into the glacial 

deposits and down to the Precambrian 

bedrock in some reaches. Glacial 

deposits with thicknesses of as much 

as 50 ft are present along the river, 

whereas thicknesses of as much as 

250 ft occur in the uplands northwest 

and southwest of Cold Spring. 

Hydrogeologic Units

The areal extent of the surficial 

aquifer underlying the uplands in the 

north-central part of the study area is 

hereinafter termed the upland surficial 

aquifer (fig. 4). The eastern part of 

upland surficial aquifer includes the 

areas of Superior lobe ice contact ice 

contact deposits, which comprise the 

sand and gravel area of the aquifer. 

The western part of the aquifer consists of predominantly sandy Superior 

lobe till, with isolated surficial sand 
7

sl

dsc

dsc

dsc

r

r

r

wt r stt

stt

stp

stp

stp

stp

sc

sc

sc

m

m

m

dc

dc

dc

st st

st

st

st

st

st

si

si

so

so

so

so

dst

dst

dst

dt

dt

dt dt

dt

dt

do

do

do

do

do

do

do

do

do

a

a

a

p

p

p p

p p

p

p

p

p

p

p

p

p

p

p

p

p p

p

p

p p

p

p

Sauk

River

Brewery Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

Geology from G. N. Meyer

and A. R. Knaeble, 1995.

Base from U.S. Geological Survey

Digital data 1:100,000, 1993

US Albers Projection

Marl

Water-washed till

Peat

Alluvium

Outwash deposits

Complex of till, sand and gravel

Till

Till over Superior lobe deposits

Complex of till and Superior lobe ice-contact

or outwash deposits

Outwash deposits

Ice-contact stratified deposits

Complex of till, sand and gravel

Pitted supraglacial till

Till

Thrust complex

Igneous and metamorphic rocks

Lake sand

POSTGLACIAL DEPOSITS

MISSISSIPPI RIVER TERRACE DEPOSITS

DEPOSITS ASSOCIATED WITH THE SUPERIOR LOBE

PRECAMBRIAN ROCKS

m

p

a

do

dc

dt

dst

dsc

sl

so

si

sc

stp

st

stt

r

EXPLANATION

Surficial geology in Cold Spring area, Minnesota.

0 1 2 3 MILES

0123 KILOMETERS

Figure 2.

st

st

st

st

dt dt

dst
8

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

Quaternary geology in Cold Spring area, Minnesota.

0 1 2 3 MILES

0123 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Mostly till of the Des Moines or Superior lobes. Sand beds thicker

than 10 feet may be present at depth, especially where depth to

bedrock exceeds 100 feet. Sand beds are discontinuous and

absent in many areas.

Complex deposits include till and ice-contract stratified deposits

of either or both the Des Moines lobe and Superior or Rainy lobes.

Includes areas of thick surficial sand, thick sand below thin or thick

till(s), and, especially in areas where depth to bedrock is less than

150 feet, thick till(s) with thin or no sand beds.

Less than 50 feet of sand or gravel over one or more beds of till or

clayey lake sediment. One or more sand beds exceeding 10 feet in

thickness may underlie beds of till or clayey lake sediment.

Primarily sand and gravel of the Des Moines lobe outwash over

till or over bedrock; sand and gravel of Superior lobe outwash may

be present in places at depth. Bedrock is near the surface in a few

places. The underlying till, where present, commonly is of the Des

Moines lobe in the western part of the study area and of the

Superior lobe in the eastern part. In some areas the sand is

seperated from bedrock by clayey lake sediment.

Greater than 50 feet of sand or gravel over mostly Superior lobe or

older till, or lake sediment. Beds of sand generally less than 10

feet thick are present between the till and bedrock in places; till

is very thin or absent in some areas.

EXPLANATION

A

B

C

D

E

A

A

A

A

A

A

A

A

A

B

C

C

C

D

D

D

D

E

E

E

Geology from G. N. Meyer

and A. R. Knaeble, 1995.

Figure 3.
9

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

1175

1169.0

1185.1

1182.5

1189.4

1190.1

1194.5

0 1 2 3 MILES

0123 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Measured and simulated potentiometric surface of the upland surficial aquifer, December 1998,

Cold Spring area, Minnesota.

EXPLANATION

U and and gravel

U andy till

Upland surficial aquifer absent

Simulated potentiometric contour. Interval 5 feet. Datum is sea level

Measured potentiometric contour. Interval 5 feet. Datum is sea level

Domestic or commercial well. Number indicates water-level altitude,

in feet above sea level

pland surficial aquifer area of s

pland surficial aquifer area of s

1185.1

Figure 4.
10

and gravel deposits. The upland surficial aquifer is unconfined with saturated thicknesses ranging from 6 to 

37 ft. 

The Sauk River Valley aquifer 

consists of hydraulically connected 

sand and gravel units in different 

hydrogeologic settings: (1) the generally continuous surficial unconfined 

unit underlying the Sauk River Valley 

(valley unit) and (2) buried, confined 

units that are overlain by till or lake 

clays in the upland areas. The areal 

extent of the aquifer (figs. 5 and 5a) 

includes zones B, C, D, and E shown 

in figure 3. The valley unit is composed of outwash deposits of sand, 

gravelly sand, and cobbly gravel 

interbedded with layers of till and glacial lake sediments in some areas. 

South of the Sauk River in the eastern 

part of the study area the aquifer 

extends to bluffs to the south where it 

thins to less than 20 ft thick. Wells 

dug into the side of the bluff reveal a 

more stratified character with layers 

of impermeable clay or till between 

the thinning sand and gravel layers. 

Back from the edges of the bluff away 

from the valley, well logs show the 

continuous, thick till deposit with isolated sand and gravel lenses. These 

lenses are probably not continuous 

and probably do not extend directly 

down into the sand and gravel in the 

Sauk River Valley. However, the Sauk 

River Valley may, to some extent, act 

as a drain for the uplands and receive 

some amount of ground-water flow 

from the uplands. Maximum saturated 

thickness of the valley unit is about 

50 ft and well yields are greater than 

1,000 gal/min (2.22 ft3/s) where sufficient saturated thickness is penetrated. 

Buried units of the aquifer that are in 

hydraulic connection with the valley 

unit are present in the north-central 

and northwestern parts of the study 

area. The continuity of these buried 

units and the degree of hydraulic connection between them is uncertain. 

Thicknesses of the buried units are 

generally 10 to 20 ft in these areas. 

Hydraulic Properties 

Hydraulic properties of the glacial 

deposits are variable. Consequently, 

glacial deposits can be either an aquifer or a confining unit. Movement of 

water in the deposits is primarily 

intergranular. Hydraulic conductivity 

is the capacity of porous material to 

transmit water under pressure. Horizontal hydraulic conductivities for 

glacial aquifers typically range from 

101

 to 104 ft/d (Freeze and Cherry, 

1979, p. 29). Lindholm (1980) 

reported that hydraulic conductivities 

of glacial deposits in central Minnesota, including Stearns County, range 

from 10 ft/d for clay or silt to 700 ft/d 

for gravel. Delin (1988) reported horizontal hydraulic conductivities ranging from 10 to 750 ft/d, with average 

values of 125 to 180 ft/d, for confined 

glacial sand and gravel aquifers in 

west-central Minnesota. A mean horizontal hydraulic conductivity value of 

1.4x10-1 ft/d was calculated for till in 

west-central Minnesota, based on the 

results from eight slug tests (Delin, 

1988). The vertical hydraulic conductivity of till typically ranges from 10-6

to 1 ft/d (Freeze and Cherry, 1979, 

p. 29). Delin (1988) reported that the 

vertical hydraulic conductivity of till 

in west-central Minnesota, based on 

analysis of four aquifer tests, ranged 

from 8.6x10-6 to 1.8 ft/d, with a mean 

value of 4.0x10-1 ft/d. Miller (1982) 

reported a value of 1.8x10-2 ft/d for 

the vertical hydraulic conductivity of 

till in western Minnesota. 

Prior to this study, aquifer tests 

were conducted for the Sauk River 

Valley aquifer in the Cold Spring area 

at two sites. During November 1993, 

a 24-hour aquifer test was conducted 

at the Gold’n Plump Poultry Processing Plant site. A transmissivity (the 

product of horizontal hydraulic conductivity and saturated thickness) of 

11,000 ft2/d was estimated for the 

aquifer from the aquifer-test results, 

with a corresponding horizontal 

hydraulic conductivity of 250 ft/d 

(HDR Engineering, Inc., 1995). In 

October 1997, a 24-hour pumping and 

recovery aquifer test was conducted at 

the site of Cold Spring municipal 

wells CS1 and CS2. A transmissivity 

of 23,000 ft2

/d was estimated for the 

aquifer from the aquifer-test results, 

with a corresponding horizontal 

hydraulic conductivity of 350 ft/d 

(Gail Haglund, Minnesota Department of Health, written commun., 

1999). 

Ground-water flow, sources, 

and discharge

Ground water flows from areas of 

high hydraulic head toward areas of 

low hydraulic head (perpendicular to 

potentiometric contours). The direction of movement is related to locations of recharge to and discharge 

from the ground-water system. The 

rate of movement is related to the 

hydraulic conductivity of aquifer 

material and to the hydraulic gradient. 

Aquifers are less resistant to the horizontal flow of ground water than confining units because the hydraulic 

conductivity of aquifers is much 

greater than that of confining units. 

Flow in aquifers is predominantly 

horizontal, whereas flow in confining 

units is predominantly vertical. 

Ground-water flow in the upland 

surficial aquifer is (1) to the south and 

southeast toward the margins of the 

aquifer, and (2) from the uplands 

toward an unnamed creek valley in 

the central part of the aquifer (fig. 4). 

The water table is the surface in an 

unconfined aquifer at which the water 

pressure is atmospheric and generally 

coincides with the potentiometric surface (fig. 4). A broad, poorly defined 
11

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

36 31

0 1 2 3 MILES

0123 KILOMETERS

Measured and simulated potentiometric surface of the Sauk River Valley aquifer, December 1998,

Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

EXPLANATION

(3)

Sauk River Valley aquifer

Sauk River Valley aquifer absent

Simulated potentiometric contour for ground-water-flow model layer 3,

representing Sauk River Valley aquifer. Interval 10 feet. Datum is sea level

Measured potentiometric contour for the Sauk River Valley aquifer deviates

from simulated potentiometric contour for ground-water-flow model layer 3.

Interval 10 feet. Datum is sea level

Domestic or commercial well. Number indicates water-level altitude,

in feet above sea level

Observation well. Number in parentheses indicates nested wells.

Number indicates water-level altitude, in feet above sea level

1126.8

1128.8

Figure 5.

B

(2)

(2)

(3)

1116.4

1105.5

1131.3

1099.1

1149.0 1131.6

1131.9

1130.3

1122.1 1125.2

1126.8

1128.8

1176.2

1117.6 1112.5

1114.4

1103.8 1118.1

1077.5

SEE

FIGURE 5a
12

23

14

22

15

24

13

T

123

N

R 30 W

Sauk

River

Brewery

Creek

23

50

2

2

Knaus Lake

45°27'

45°28'

94°26' 94°25' 94°24'

0 1 MILE

0 1 KILOMETER

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Measured and simulated potentiometric surface of the Sauk River Valley aquifer, near Cold Spring and

Gold'n Plump Poultry Processing Plant, December 1998, Cold Spring area, Minnesota.

Gold'n Plump

Poultry

Processing

Plant

Figure 5a.

EXPLANATION

(3) 1072.5

1101.5

1100.3

Domestic or commercial well. Number

indicates water-level altitude, in feet above

sea level

Observation well. Number in parentheses

indicates nested wells. Number indicates

water-level altitude, in feet above sea level

Stream-stage measurement site. Number

indicates water-level altitude, in feet above

sea level

Sauk River Valley aquifer

Sauk River Valley aquifer absent

Simulated potentiometric contour for

ground-water-flow model layer 3,

representing Sauk River Valley aquifer.

Interval variable. Datum is sea level

Measured potentiometric contour for the

Sauk River Valley aquifer deviates from

simulated potentiometric contour for

ground-water-flow model layer 3. Dashed

where inferred. Interval variable. Datum is

sea level

1100

Cold Spring

(2)

(3)

1124.9

1087.6

1087.0

1084.8

1084.9

1073.8

1076.9

1072.5

1089.6

1101.5 1103.7

1076.6

1094.2

1100.2

1101.3

1100.3

1110.7

1099.3

1100.1
13

regional potentiometric high occurs in 

the water-table surface in the vicinity 

of Big Fish Lake located about 1 mile 

north of the study area. Ground water 

flows to the south, east, and west 

away from this high (fig. 4). Sources 

of water to the upland surficial aquifer 

are (1) infiltration of precipitation to 

the saturated zone (areal recharge) 

and (2) some ground-water flow 

through the northern boundary due to 

the potentiometric high located north 

of the study area. Discharge from the 

aquifer is by (1) withdrawals from 

domestic and irrigation wells, (2) 

ground-water evapotranspiration in 

areas where the water table is within 

about 5 ft of land surface (approximate depth of root zones), and (3) 

leakage downward through a till and 

clay confining unit to the buried units 

of the Sauk River Valley aquifer. 

Hydraulic heads in the upland surficial aquifer are about 30 to 40 ft 

higher than in the underlying Sauk 

River Valley aquifer. Locally, ground 

water also discharges to small streams 

and lakes. 

Ground-water flow in the Sauk 

River Valley aquifer is from upland 

areas toward the Sauk River and the 

connected chain of lakes (fig. 5). Near 

the west-central boundary of the study 

area, ground-water flow is from east 

to west toward the Sauk River, located 

just west of the boundary. The flow of 

ground water is restricted and altered 

in some areas due to the presence of 

bedrock and low permeability till. The 

aquifer is under unconfined conditions throughout most of its areal 

extent, but is under confined conditions where it is buried by till and clay 

in the northwestern part of the study 

area. The mound in the potentiometric 

surface of the aquifer west of Cold 

Spring (fig. 5) is due to the presence 

of thick till and clay overlying the 

buried aquifer and the transition from 

confined to unconfined conditions. 

The aquifer includes surficial sand 

and gravel deposits in the north-central part of the study area that are in 

hydraulic connection with the sand 

and gravel deposits at lower altitudes 

closer to the Sauk River. These 

higher-altitude sand and gravel deposits continue to the north and allow 

ground-water flow to enter the study 

area from the north. As for the watertable surface, a broad, poorly defined 

regional potentiometric high occurs in 

the vicinity of Big Fish Lake located 

about 1 mile north of the study area. 

In general, the depth to the water table 

in the Sauk River Valley increases 

with increasing distance from the 

Sauk River. The water table near the 

river is about 5 ft below land surface 

and north of Cold Spring near municipal well CS4 is about 40 ft below land 

surface. 

Sources of water to the Sauk 

River Valley aquifer in the study area 

are (1) infiltration of precipitation to 

the saturated zone (areal recharge) in 

areas where the aquifer is unconfined, 

(2) ground-water flow through the 

northern boundary, (3) leakage of 

water through overlying till and clay 

for buried units of the aquifer, and (4) 

probably ground-water flow from the 

undifferentiated glacial deposits in the 

southeastern part of the study area. 

Discharge from the aquifer is (1) by 

withdrawals from wells, (2) by 

ground-water evapotranspiration in 

areas where the water table is within 

about 5–10 ft of land surface (approximate depth of root zones), and (3) to 

the Sauk River, the chain of lakes, and 

Brewery Creek. Locally, ground water 

also discharges to smaller streams and 

lakes. Ground-water withdrawals and 

stream-aquifer leakage are discussed 

further in the following sections.

Water levels in the Sauk River 

Valley aquifer fluctuate in response to 

seasonal variations in recharge and 

discharge. Ground-water levels commonly rise in spring, when areal 

recharge is generally greatest because 

of snowmelt, spring rain, and minimal 

evapotranspiration losses. Conversely, 

ground-water levels generally decline 

in summer because discharge by 

evapotranspiration, ground-water 

withdrawals by wells, and discharge 

to streams and lakes exceed recharge. 

Net recharge to the aquifer also occurs 

in the fall most years, due to rainfall 

and low evapotranspiration losses. 

Ground-water recharge rates to the 

aquifer for 1999 were estimated from 

monthly water-level measurements 

for the 21 observation wells installed 

for this study and the 7 existing observation wells. Recharge rates were 

estimated using the method of 

hydrograph analysis described by 

Rasmussen and Andreasen (1959). 

The method assumes that all waterlevel rises in a well result from areal 

recharge. The estimated ground-water 

recharge rates to the aquifer ranged 

from 5.3 to 8.6 in./yr, with an average 

value of 7.0 in./yr. 

Ground-Water Withdrawals

Ground water provides the primary source of drinking water for the 

Cold Spring area. There are about 25 

public water-supply wells and 200–

300 private water-supply wells in the 

study area (Minnesota Department of 

Health, 1999). All of the public supply wells are screened in the valley 

unit of the Sauk River Valley aquifer. 

Many of the private water-supply 

wells in the northwestern part of the 

study area are screened in buried units 

of the aquifer. A few private watersupply wells are open to Precambrian 

bedrock in areas where glacial aquifers are lacking and the bedrock is 

within about 100 ft of land surface. 

Ground water is also the primary 

source of water for irrigation, golf 

course, and landscape wells in the 

study area. The total pumpage in the 

study area during 1998 from 15 irriga-
14

tion wells was 204.8 million gallons 

(27.37 million ft3). An additional 56.9 

million gallons (7.60 million ft3

) was 

withdrawn during 1998 from five golf 

course and landscape wells. 

During June 1995, the city of 

Cold Spring initiated the development 

of a WHP plan. During September 

1997, the city invited local water suppliers to form a partnership to develop 

a joint WHP management plan. The 

resulting public-private partnership, 

consisting of six public and private 

water suppliers, began to develop a 

single WHP management plan to 

address and manage land-use activities for the combined areas. A total of 

18 wells, screened in the Sauk River 

Valley aquifer comprise the well 

fields of the six water suppliers.

The City of Cold Spring currently 

has four municipal wells and is planning to install a fifth well near municipal well CS4 (Ray Koppy, City of 

Cold Spring, oral commun., 1999). 

Three of the wells are located within 

the city limits (Cold Spring municipal 

wells CS1, CS2, and CS3) and the 

fourth is located in T123N,R30W, 

section 11 about 1 mile north of the 

City (Cold Spring municipal well 

CS4) (figs. 1 and 1a). The wells are 

screened at depths ranging from 51 to 

100 ft. During August 1996, nitrate 

levels exceeded 10 mg/L as N in 

water sampled from Cold Spring 

municipal well CS1 (Minnesota 

Department of Health, 1999). The 

well has not been used for public supply since that time. Withdrawals of 

water from Cold Spring municipal 

well CS4 began during November 

1999. The total pumpage for the Cold 

Spring municipal wells during 1998 

was 140.8 million gallons (18.82 million ft3) (Verena Weber, City of Cold 

Spring, written commun., 1999). 

The Gold’n Plump Poultry Processing Plant is located about 1 mile 

east of Cold Spring (fig. 1a) and currently operates six production wells 

within their property. The well field is 

almost parallel to the Sauk River at an 

average distance of 300 ft from the 

river. The upland bluffs south of the 

plant site are about 2,000 ft away 

from the well field. The wells are 

screened at depths ranging from 37 to 

47 ft. The total pumpage for the 

Gold’n Plump Poultry Processing 

Plant wells during 1998 was 281.6 

million gallons (37.64 million ft3) 

(Clay Watson, Gold ‘n Plump Poultry, 

written commun., 1999). 

The Gluek Brewing Company 

(fig.1a) and Cold Spring Granite 

Company (fig. 1) utilize ground water 

in their product processing operations. 

The Gluek Brewery has two wells 

located within 500 ft of Cold Spring 

municipal wells CS1 and CS2. The 

wells pumped 10.0 million gallons 

(1.33 million ft3) of water during 

1998 (Mike Kneip, Gluek Brewing 

Company, written commun., 1999). 

Cold Spring Granite Company also 

has two wells within their property 

located about 1.5 miles west of Cold 

Spring. The wells pumped an estimated 1.0 million gallons (0.13 million ft3

) of water during 1998 

(reported pumpage amounts were not 

available) (Gail Haglund, Minnesota 

Department of Health, written commun., 1999). The two remaining 

members of the partnership are 

Town’s Edge Mobile Home Park, 

located about 0.5 mile southeast of 

Cold Spring, and Cold Spring Alano 

Society, located about 1 mile northeast of the city (fig.1a). Town’s Edge 

Mobile Home Park withdrew 8.7 million gallons (1.16 million ft3

) of water 

during 1998 from two wells screened 

at depths of 60 and 97 ft (Gene Hesse, 

Town’s Edge Homes Incorporated, 

written commun., 1999). The Cold 

Spring Alano Society withdrew an 

estimated 1.0 million gallons (0.13 

million ft3

) of water during 1998 from 

two wells (reported pumpage amounts 

were not available) (Gail Haglund, 

Minnesota Department of Health, 

written commun., 1999). 

Stream-Aquifer Leakage

Stream-aquifer leakage refers to 

the movement of water between a 

stream and the underlying aquifer. 

Leakage may occur from the aquifer 

to the stream, resulting in an increase 

in streamflow (gaining stream or 

reach), or leakage may occur from the 

stream to the aquifer, resulting in a 

decrease in streamflow (losing stream 

or reach). Streams may be gaining 

water in some reaches and losing 

water in others. The rate of streamaquifer leakage depends on the: (1) 

thickness of the streambed material, 

(2) vertical hydraulic conductivity of 

the streambed material, (3) hydraulic 

conductivity of the aquifer near the 

stream, and (4) hydraulic-head differences between the aquifer and the 

stream. Ground water generally represents most of streamflow during periods of low flow rates. Ground-water 

leakage to streams in the Cold Spring 

area is generally greater than leakage 

from streams to the underlying aquifer, and the streams are therefore gaining streams overall.

Synoptic sets of low-flow measurements were made to determine 

gaining and losing reaches of the 

Sauk River and Brewery Creek and to 

quantify streamflow gains and losses. 

Streamflow measurements were made 

at nine sites on the Sauk River and at 

three sites on Brewery Creek during 

October 1998 and August 1999 (table 

1; figs. 1a and 1). The measurements 

indicated net gains of 44.8 (SW5–

SW9) and 25.8 (SW4 –SW9) ft3/s for 

the Sauk River from Cold Spring to 

Rockville, located about 1 mile east of 

the study area, during October 1998 

and August 1999, respectively. The 

net gains were 15 and 13 percent of 
15

Table 1. Stream discharge and measured and simulated stream-aquifer leakage under low-flow conditions during 1998-99, Cold 

 [--, no discharge measurement or stream reach gain or loss calculation; ft3/s, cubic feet per second; >, greater than. Number in parentheses is for August measurement

measurements. UN indicates that a stream reach gain or loss was not calculated due to unreliable discharge measurements. NC indicates that no comparison was possib

reach gain or loss]

Site location Site identifier (shown in figure 1) Discharge October 1998 (ft3/s) Discharge August 1999 (ft3/s) Discharge measurement uncertainty (percent) Stream reach Stream reach o

loss (-) Octobe

1998 (ft3/s) 

Sauk River

T123N, R30W, section27BBBA SW1 1229 1222 >8

SW1 - SW2 UN 

T123N, R30W, section22DABA SW2 1248 1140 >8

SW2 - SW3 UN 

T123N, R 30W, section23BBBA SW3 1274 -- 5

SW2 - SW4 -- 

T123N, R 30W, section14CCDC Brewery Creek (SW12) 2.9 2.3 5T123N, R 30W, section14CDCC SW4 -- 169 5 SW3 - SW5 UN 

SW4 - SW5 -- 

T123N, R30W, section14CBDD SW5 242 178 5T123N, R30W, section14CDBB Cold Spring Wastewater Plant 0.7 0.7 -- SW5 - SW6 1.3 T123N, R30W, section14ADBD SW6 244 190 5 (8)

SW6 - SW7 -4.0 

T123N, R30W, section13CBBB SW7 240 174 5T123N, R30W, section13CBBA Gold’n Plump Poultry Plant 1.5 1.5 -- SW7 - SW8 -2.5 T123N, R29W, section18CBBB SW8 239 185 5

SW8 - SW9 50 

T123N, R29W, section09CCCC SW9 289 197 5 (8)

SW5 - SW9 44.8 SW4 - SW9 -- 

Brewery Creek

T123, N30W15, section15DCBD SW10 0.15 0.04 8

SW10 - SW11 1.75 

T123N, R30W, section15DDBD SW11 1.9 1.54 5

SW11 - SW12 1.0 

T123N, R30W, section14CCDC SW12 2.9 2.3 5

SW10 - SW12 2.75 

1Discharge measurements are not reliable due to channel structure and flow conditions 
16

the streamflow at Rockville during 

October 1998 and August 1999, 

respectively. In general, the Sauk 

River probably is a gaining stream in 

all reaches, except for the reach adjacent to the Gold’n Plump Poultry Processing Plant well field. Groundwater withdrawals from the well field 

result in declines in the potentiometric 

surface of the aquifer near the supply 

wells (fig. 5a), thereby inducing infiltration of water from the Sauk River 

to the underlying aquifer. Groundwater withdrawals from the well field 

also result in intercepted subsurface 

flow, ground-water flow en route to 

the stream channel that would have 

eventually discharged into the stream, 

but is intercepted by pumped wells. 

The measured streamflow losses 

(SW6–SW7; 4.0 and 16.0 ft3/s) (table 

1) were appreciably greater than the 

volume of water being pumped by the 

Gold’n Plump Poultry Processing 

Plant supply wells (1.2 ft3/s). The differences may be attributed to measurement error in the low-flow 

measurements. Streamflow losses of 

similar magnitude to the pumping 

rates would have been less than the 5 

to 8 percent uncertainty in the streamflow measurements. 

Streamflow gains and losses for 

the Sauk River were less than the 

accuracy of streamflow measurements 

(5–8 percent) in many of the reaches 

during the low-flow measurements 

(table 1). Gaining and losing reaches 

were somewhat inconsistent between 

low-flow measurement periods as a 

result of gains and losses being near 

or below the measurement accuracy 

and due to variations in flow conditions. The measurements during October 1998 indicated a large loss in 

streamflow for the reach between 

SW3 and SW5. However, during the 

August 1999 measurements with 

lower streamflows and stream stages, 

stream channel conditions at SW3 

were such that an accurate streamflow 

measurement was not possible. 

Assuming that stream channel conditions in 1998 were the same as they 

were in 1999, the anomalous large 

loss for the reach indicated by the 

October 1998 measurements is probably incorrect, especially because there 

are no known surface-water diversions in the reach or other explanation 

for a large loss in streamflow to occur. 

The streamflow measurements for 

SW1 and SW2 are also not considered 

to be reliable because of the comparatively large estimated measurement 

errors of greater than 8 percent due to 

very low flow velocities. SW1 and 

SW2 are in the reach of the Sauk 

River between the chain of lakes and 

a natural waterfall with a drop in river 

stage of about 8 ft. The river is wider 

and has much slower flow velocities 

upstream of the waterfall than downstream. The streamflow gains in the 

river reaches downstream from SW4, 

other than the reach adjacent to the 

Gold’n Plump Poultry Processing 

Plant well field (SW6–SW7), during 

August 1999 ranged from 9.0 to 

12 ft3/s (table 1). The measured 

streamflow gain from SW5 to SW9 

during August 1999 (16.8 ft3

/s) was 

much less than in October 1998 

(44.8 ft3/s) and is probably more representative of low-flow conditions.

 Brewery Creek is a gaining 

stream from SW10 to its confluence 

with the Sauk River (table 1; figs. 1a 

and 1). The creek flows through a 

wetland area upstream from SW10 

and the creek channel is poorly 

defined, precluding accurate streamflow measurements. The measured 

gains in streamflow between SW10 

and SW12, located about 100 yards 

above the creek’s confluence with the 

Sauk River, were 2.75 and 2.25 ft3/s 

during October 1998 and August 

1999, respectively.

SIMULATION OF GROUNDWATER FLOW

A conceptual model, a qualitative 

description of the known characteristics and functioning of the groundwater system, was formulated from 

knowledge of the hydrogeologic setting, aquifer characteristics, distribution and amount of recharge and 

discharge, and aquifer boundaries. A 

numerical model of ground-water 

flow was constructed based on the 

conceptual model of the system. The 

model was calibrated for steady-state 

conditions. Steady-state represents 

equilibrium, or average conditions 

whereby hydraulic heads and the volume of water in storage do not change 

substantially with time. Average conditions were used for WHP planning 

purposes.

Numerical Model Description

The study area was subdivided 

into rectangular finite-difference grid 

cells within which the properties of 

the hydrogeologic unit represented are 

assumed to be uniform. The center of 

a grid cell is referred to as a node and 

represents the location for which the 

hydraulic head is computed by the 

model. The variably-spaced finite-difference grid used to spatially discretize the model area has 229 rows 

and 257 columns (fig. 6). Notation of 

the form (11,24), where the first number in parentheses indicates the row 

and the second number indicates the 

column, is used to refer to the location 

of an individual cell within the grid. 

The dimensions of the grid cells range 

from 50 to 400 ft along rows and columns. One criterion used to determine 

the minimum size of grid cells was to 

have only one water-supply well per 

grid cell where possible. The smallest 

cells (50 ft by 50 ft) are in the vicinity 

of the Gold’n Plump Poultry Processing Plant site, where the supply wells 
17

are closest together. Small cells actually extend across the model grid, 

although they are shown only along 

the edges of the grid in figure 6, for 

clarity. Hydraulic properties assigned 

to the cells towards the model area 

boundaries are averaged over larger 

areas than for cells near the well 

fields. The area modeled was 

extended away from the supply wells 

sufficient distances to be located 

beyond the cones of depression 

caused by current or projected 

ground-water withdrawal rates. 

 The ground-water system in 

the model area was subdivided vertically into four layers, corresponding 

to generally horizontal hydrogeologic 

units. The altitudes of the layer tops 

and layer bottoms were specified for 

each model cell for the four layers. 

The thickness associated with a cell 

representing a hydrogeologic unit is 

incorporated in the transmissivity 

term for the cell. Simulation of leakage of water between model layers is 

dependent on the thicknesses and vertical hydraulic conductivities between 

adjacent layers. A more detailed discussion of leakage of water between 

model layers can be found in 

McDonald and Harbaugh (1988). 

The hydrogeologic units represented in the ground-water-flow 

model are, in descending order (figs. 

7–10): (1) the upland surficial aquifer 

(layer 1), (2) the confining unit underlying the upland surficial aquifer 

(layer 2), (3) the valley and buried 

units of the Sauk River Valley aquifer 

and laterally adjacent clay and till 

above an altitude of 1,035 ft (layer 3), 

and (4) the deeply buried part of the 

Sauk River Valley aquifer below an 

altitude of 1,035 ft (deeply buried 

unit) (layer 4). In the upland areas in 

the northwestern part of the study area 

where the buried units of the Sauk 

River Valley aquifer are present, cells 

in model layers 3 and 4 were assigned 

the hydraulic properties of the aquifer. 

36 31

Figure 6. Grid for finite-difference ground-water-flow model, Cold Spring area, Minnesota. Figure 6. Grid for finite-difference ground-water-flow model, Cold Spring area, Minnesota.

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

1 20 40 60 80 120 140 160 180 200 220 229

ROW

1 20 40 60 80 100 120 140 160 180 200 220 240 257

COLUMN

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

Grid for finite-difference ground-water-flow model, Cold Spring area, Minnesota.

0 1 2 3 MILES

0123 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Figure 6.
18

Where the buried units are absent, 

cells in model layers 3 and 4 were 

assigned the hydraulic properties of 

clay and till. 

The transmissivities associated 

with the model cells representing the 

upland surficial aquifer (layer 1) vary 

as the saturated thicknesses vary. The 

transmissivities assigned to the model 

cells representing the confining unit 

underlying the upland surficial aquifer 

(layer 2) and the deeply buried unit of 

Sauk River Valley aquifer (layer 4) 

are constant in time. The Sauk River 

Valley aquifer (layer 3) is unconfined 

and confined in different parts of the 

modeled area. The transmissivities of 

cells representing the aquifer, therefore, vary where the aquifer is under 

unconfined conditions and are constant in time where it is under confined conditions. The aquifer is under 

unconfined conditions in the Sauk 

River Valley and is under confined 

conditions in the upland areas in the 

northwestern part of the study area 

Ideally, all model boundaries 

should be located at the physical limits of the aquifer system or at other 

hydrologic boundaries, such as a 

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

36 31

0 1 2 3 MILES

0123 KILOMETERS

Inactive cells

Active cells assigned a horizontal hydraulic conductivity of 50 feet per day

Active cells assigned a horizontal hydraulic conductivity of 100 feet per day

Active cells assigned a horizontal hydraulic conductivity of 300 feet per day

Constant head boundary

EXPLANATION

Extent, boundary conditions, and calibrated horizontal hydraulic conductivity zones for ground-water-flow model layer 1,

Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Figure 7.
19

major river. Practical considerations, 

such as limitations concerning the size 

of the area modeled may necessitate 

the use of arbitrarily imposed model 

boundaries where the natural hydrologic boundaries lie outside the model 

area. The northern boundaries for layers 1 and 3, and the northwestern 

boundary for layer 4, are arbitrarily 

imposed boundaries placed at the 

northern and northwestern township 

line of Wakefield Township (T123N, 

R30W), respectively.

The southern and eastern boundaries for layer 1 (upland surficial aquifer), the southeastern and parts of the 

south-central boundary for layer 3 

(Sauk River Valley aquifer), and all 

but the northwestern and western 

boundaries for layer 4 (deeply buried 

unit of the Sauk River Valley aquifer) 

are located at the physical limits of 

the hydrogeologic units; therefore, 

no-flow boundaries were used. The 

northwestern and eastern boundaries 

for layer 3 and the western boundary 

for layer 4 are no-flow boundaries 

because the potentiometric surfaces 

for the aquifers indicate that groundwater flow near these boundaries is 

predominantly north to south (parallel 

to the boundaries) toward the Sauk 

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

0123 MILES

0123 KILOMETERS

Inactive cells

Active cells assigned a vertical hydraulic conductivity of 0.00005 of a foot per day

Active cells assigned a vertical hydraulic conductivity of 0.005 of a foot per day

Active cells assigned a vertical hydraulic conductivity of 0.01 of a foot per day

EXPLANATION

Extent, boundary conditions, and calibrated vertical hydraulic conductivity zones for ground-water-flow model layer 2,

Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Figure 8.
20

River and the chain of lakes. The 

potentiometric surface of surficial 

aquifers near the south-central boundary for layer 3 indicates that groundwater flow near this boundary is also 

predominantly parallel to the boundary (east-west, from potentiometric 

surface highs toward an unnamed 

creek) and a no-flow boundary was 

used. The boundaries for layer 2, representing the confining unit, were 

imposed to coincide with the boundaries for layer 1. Because groundwater flow in confining units is predominantly vertical, no-flow boundary conditions were used for all 

boundaries for layer 2. The western 

boundary for layer 1, portions of the 

northern boundaries for layers 1 and 

3, portions of the southeastern and 

south-central boundaries for layer 3, 

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

36 31

0 1 2 3 MILES

0123 KILOMETERS

Inactive cells

Active cells assigned a horizontal hydraulic

conductivity of 1 foot per day

Active cells assigned a horizontal hydraulic

conductivity of 10 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 25 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 100 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 200 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 300 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 350 feet per day

Constant head boundary

EXPLANATION

Extent, boundary conditions, and calibrated horizontal hydraulic conductivity zones for ground-water-flow model layer 3,

Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Figure 9.

SEE

FIGURE 9a
21

23

14

22

15

24

13

T

123

N

R 30 W

Sauk

River

Brewery

Creek

23

50

2

2

Cold Spring

Knaus Lake

45°27'

45°28'

94°26' 94°25' 94°24'

0 1 MILE

0 1 KILOMETER

Inactive cells

Active cells assigned a horizontal hydraulic

conductivity of 1 foot per day

Active cells assigned a horizontal hydraulic

conductivity of 10 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 25 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 200 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 300 feet per day

Active cells assigned a horizontal hydraulic

conductivity of 350 feet per day

Constant head boundary

EXPLANATION

Boundary conditions and calibrated horizontal hydraulic conductivity zones for ground-water-flow model layer 3 near

Cold Spring and Gold'n Plump Poultry Processing Plant, Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Gold'n Plump

Poultry

Processing

Plant

Figure 9a.
22

and the northwestern and western 

boundaries for layer 4 are no-flow 

boundaries. The hydrogeologic units 

in these areas consist of clay and till, 

with predominantly vertical groundwater flow. 

Constant-head cells were used for 

portions of the northern boundaries 

for layers 1 (upland surficial aquifer) 

and 3 (Sauk River Valley aquifer) and 

for the southwestern and a portion of 

the southeastern boundary for layer 3 

(figs. 7 and 9). Constant heads were 

used for the southwestern boundary of 

layer 3 because it coincides with the 

chain of lakes. The stage altitudes for 

the lakes are relatively constant in 

time, with minimal seasonal and 

annual changes. The northern and 

southeastern constant-head boundaries are downgradient from broad, 

poorly-defined highs in the potentiometric surfaces of the aquifers. These 

constant-head boundaries simulate 

inflow of ground water to the study 

area from sources of water beyond the 

study-area boundaries. 

A specified-flux boundary was 

used to represent areal recharge to the 

upland surficial aquifer (layer 1) and 

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

36 31

0 1 2 3 MILES

0123 KILOMETERS

Inactive cells

Active cells assigned a horizontal hydraulic conductivity of 1 foot per day

Active cells assigned a horizontal hydraulic conductivity of 25 feet per day

Active cells assigned a horizontal hydraulic conductivity of 50 feet per day

Active cells assigned a horizontal hydraulic conductivity of 300 feet per day

EXPLANATION

Extent, boundary conditions, and calibrated horizontal hydraulic conductivity zones for ground-water-flow model layer 4,

Cold Spring area, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Figure 10.
23

to the valley unit of the Sauk River 

Valley aquifer (layer 3) where it is the 

uppermost active model layer. Areal 

recharge to the aquifer represents the 

net difference between precipitation 

and evapotranspiration losses occurring above the water table. Areal 

recharge was applied to the highest 

active layer in each model cell. 

Stream-aquifer leakage between 

the Sauk River and Brewery Creek 

and the valley unit of the Sauk River 

Valley aquifer (model layer 3) was 

simulated with head-dependent flux 

nodes (McDonald and Harbaugh, 

1988, chapter 6). The streams were 

divided into reaches, each of which is 

completely contained in a single cell. 

Stream-aquifer leakage through reach 

of streambed is approximated by 

Darcy’s Law as

QRIV = (KLW/M) (HRIV-HAQ)

where

QRIV = stream-aquifer leakage 

through the reach of the streambed 

(L3/T), 

K = vertical hydraulic conductivity of the streambed (L/T), 

L = length of the reach (L), 

W = width of the stream (L), 

M = thickness of the streambed 

(L), 

HRIV = head in the stream (L), 

and

HAQ = head in the aquifer (L). 

The length of the streambed in 

each river cell was measured from 

USGS 7.5-minute-quadrangle topographic maps. The average width of 

the Sauk River streambed, estimated 

at stream stage and discharge measurement sites within the model area, 

is about 100 ft. Average streambed 

width for Brewery Creek is about 

10 ft. The average streambed widths 

were used for every reach of the Sauk 

River and Brewery Creek. The thickness of the Sauk River and Brewery 

Creek streambeds was assumed to be 

1 ft for the model, as for other studies 

with numerical ground-water-flow 

models that simulated stream-aquifer 

leakage (Yager, 1993; Lindgren, 

1990). The lower limit of the streambeds is poorly defined and not easily 

measurable. The initial value for vertical hydraulic conductivity of the 

streambed for the Sauk River and 

Brewey Creek was 1.0 ft/d. Published 

values for vertical hydraulic conductivity of riverbed material for streams 

in glacial terrain commonly range 

from 0.1 to 10 ft/d (Norris and Fidler, 

1969; Jorgensen and Ackroyd, 1973, 

Prince and others, 1987; Delin, 1990; 

Lindgren and Landon, 2000). Stream 

stage for each river cell was linearly 

interpolated between measured stream 

stage sites.

Discharge by ground-water 

evapotranspiration may occur from 

the shallow, unconfined portions of 

the aquifers (layers 1 and 3). The 

model simulates evapotranspiration 

from the saturated zone only. The initial maximum ground-water evapotranspiration rate specified in the 

model was 29 in./yr, which corresponds to the estimated average 

annual lake-evaporation rate in the 

model area (Baker and others, 1979). 

The ground-water evapotranspiration 

rate in the model decreases linearly 

with depth below land surface and 

becomes zero at the extinction depth. 

The extinction depth corresponds to a 

depth below land surface minimally 

greater than the rooting depth of the 

plants present. The plausible range for 

evapotranspiration extinction depth 

was assumed to be from 5 to 10 ft, 

with an initial uniform average value 

of 7 ft specified in the model. The altitude of the land surface for each cell 

was determined from USGS 7.5-

minute-quadrangle topographic maps. 

Ground water is withdrawn by 

high-capacity water-supply wells 

from the upland surficial aquifer 

(layer 1) and valley unit of the Sauk 

River Valley aquifer (layer 3). 

Ground-water withdrawal rates for 

1998 were obtained from the records 

of the Minnesota Department of 

Health and local water suppliers. 

Total annual ground-water withdrawal 

rates from the upland surficial aquifer 

were 0.23 ft3

/s and from the valley 

unit of the Sauk River Valley aquifer 

were 2.83 ft3

/s. 

The initial and final calibrated 

values of hydraulic properties represented in the model are listed in table 

2. Initial values for hydraulic conductivity for each hydrogeologic unit 

were based on the results of aquifer 

tests conducted in the study area and 

published values for similar hydrogeologic materials in the literature. 

Porosity values were derived from 

published values for similar hydrogeologic materials in the literature. 

The initial value for areal recharge 

was 7.0 in./yr, the average rate for 

1999 estimated from hydrograph analysis. The ground-water evapotranspiration rate and extinction depth were 

assigned as explained above. 

Different hydraulic conductivity 

values were assigned to each model 

layer within zones of differing geologic materials. Initially, layer 1, representing the upland surficial aquifer, 

included two hydraulic conductivity 

zones (table 2), based predominantly 

on the surficial geology shown in figure 3. Layer 2, representing the confining unit, was assigned uniform 

horizontal and vertical hydraulic conductivity values. The hydraulic conductivity zones for layers 3 and 4, 

representing the Sauk River Valley 

aquifer and its deeply buried unit, 
24

Table 2. Initial and final calibrated values of hydraulic properties used in ground-water flow model of aquifer system, Cold Sp

 [ft/d, feet per day]

Hydrogeologic unit Model layer

Horizontal hydraulic conductivity

3,4(ft/d)

Vertical hydraulic 

3,4(ft/d

Initial Calibrated Initial 

Upland surficial aquifer 1

 Sand and gravel area1 200 100, 300 20 10 Sandy till area1 1.0 50 0.0005 

Confining unit 2 1.0 1.0 0.00005 Sauk River Valley aquifer 3

 Zone A2 1.0 1.0 - 100 0.0005  Zone B2 100 100 10  Zone C2 6300 100 - 350 30 20  Zone D2 7200 200 - 300 20 20  Zone E2 200 200 - 300 20 20 

Deeply buried unit of Sauk River Valley aquifer 4

 Zone A2 1.0 25 - 50 0.0005  Zone B2 100 50 10  Zone C2 100 1.0, 50 10  Zone D2 200 300 20  Zone E2 100 50 10 

1See figure 42See figure 23Freeze and Cherry (1979)4Delin (1991)5Morris and Johnson (1967) 6Aquifer test at Cold Spring municipal well CS47Aquifer test at Gold’n Plump Poultry water-supply wells
25

respectively, were based predominantly on the five zones of geologic 

deposits shown in figure 3. In addition 

to the five zones shown in figure 3, a 

zone was delineated for layer 3 and 

assigned the hydraulic conductivity 

values of zone A in the area west and 

northwest of Cold Spring. The geologic materials in this area within the 

altitude interval of the Sauk River 

Valley aquifer (from land surface 

down to an altitude of 1,035 ft) are till 

and clay. This sixth zone includes the 

small area of mostly till (A) west of 

Cold Spring shown on figure 3, but 

was expanded based on an analysis of 

well logs in the area. An additional 

zone was also delineated for layer 3 in 

the vicinity of Cold Spring municipal 

well CS4. Well logs in this area indicated that the valley unit of the Sauk 

River Valley aquifer is composed of 

very coarse sand and gravel in this 

area. Therefore, a comparatively high 

horizontal hydraulic conductivity of 

350 ft/d was assigned. The initial 

hydraulic conductivity zones for layer 

4 are based on the composition of the 

geologic materials present below an 

altitude of 1,035 ft, and are derived 

from the zones shown in figure 3 and 

available well logs. In the zone of 

highest assigned horizontal hydraulic 

conductivity for layer 4 (300 ft/d), 

sand and gravel are present from land 

surface down to bedrock and the Sauk 

River Valley aquifer and its deeply 

buried unit are essentially one aquifer. 

Numerical Model Calibration 

and Results

Model calibration is the process 

in which initial estimates of hydraulic 

properties and boundary conditions 

are adjusted until simulated hydraulic 

heads and flows acceptably match 

measured water levels and flows. For 

this study, hydraulic properties and 

areal recharge were adjusted within 

reasonable limits to produce an 

acceptable match between: (1) simulated hydraulic heads and measured 

water levels in wells during December 

1998 and (2) simulated stream-aquifer 

leakage between the Sauk River and 

Brewery Creek and the valley unit of 

the Sauk River Valley aquifer and that 

estimated from measured streamflow 

during October 1998 and August 

1999. Calibration and evaluation of 

the ground-water-flow model were 

conducted for steady-state (equilibrium) conditions. Long-term waterlevel data in many parts of Minnesota 

indicate that winter water levels 

approach and probably attain steadystate (equilibrium) in the groundwater system (Delin, 1990; Lindgren, 

1990; Lindgren and Landon, 2000). 

Therefore, changes in recharge to and 

discharge from the aquifer during 

winter are close to zero, and recharge 

and discharge can be considered to be 

in equilibrium. 

The match between measured and 

simulated hydraulic heads and streamaquifer leakage was improved by: (1) 

subdividing the sand and gravel area 

of the upland surficial aquifer (layer 

1) into two horizontal hydraulic conductivity zones (100 and 300 ft/d), (2) 

increasing the horizontal and vertical 

hydraulic conductivities for the sandy 

till area of the upland surficial aquifer 

(layer 1), (3) increasing the vertical 

hydraulic conductivities of the confining unit (layer 2) near the eastern and 

southeastern margins of the confining 

unit and in the area of the valley of an 

unnamed stream that approximately 

bisects the upland surficial aquifer in 

the study area, (4) increasing the horizontal and vertical hydraulic conductivities for parts of geologic deposit 

zones A, C, D, and E for the Sauk 

River Valley aquifer (layer 3), (5) 

increasing the horizontal and vertical 

hydraulic conductivities for parts of 

geologic deposit zones A and D for 

the deeply buried unit of the Sauk 

River Valley aquifer (layer 4), and (6) 

decreasing the horizontal and vertical 

hydraulic conductivities for parts of 

geologic deposit zones B, C, and E for 

the deeply buried unit of the Sauk 

River Valley aquifer (layer 4). The 

final calibrated values of hydraulic 

properties are given in table 2 and figures 7–10. The effect of increasing the 

vertical hydraulic conductivities of 

the confining unit was to increase 

leakage through the confining unit, 

thereby lowering hydraulic heads in 

the upland surficial aquifer and raising hydraulic heads in the Sauk River 

Valley aquifer. Changing the hydraulic conductivities of the hydrogeologic units in the model reflects the 

complexity of the glacial drift deposits, particularly in the upland areas. 

The changes are all within ranges of 

values reported by previous studies 

and aquifer test results in the Cold 

Spring area. 

In addition to the changes in 

hydraulic conductivity values, additional zones of low hydraulic conductivity were necessary to improve the 

match between measured and simulated hydraulic heads. Low-conductivity zones of comparatively small 

areal extent, with horizontal hydraulic 

conductivities of 1.0 and 10 ft/d, were 

simulated for the Sauk River Valley 

aquifer (layer 3) east of the Sauk 

River southeast of Cold Spring to 

maintain higher hydraulic heads for 

higher terrace-level saturated sand 

and gravel deposits in this area (figs. 9 

and 9a). The degree of hydraulic connection between these terrace deposits 

and the sand and gravel deposits at a 

lower altitude in the river valley is 

uncertain due to a lack of geologic 

logs. Low-conductivity zones of comparatively small areal extent were also 

simulated in the southeastern part of 

Cold Spring near the Sauk River 

(25 ft/d, figs. 9 and 9a) and north of 

the Sauk River in T123N, R29W, sec-
26

tion 18, and T123N, R30W, section 13 

(10 ft/d, fig. 9). Geologic descriptions 

of these deposits in well logs supported these changes. 

 The match between measured 

and simulated hydraulic heads and 

stream-aquifer leakage was improved 

by increasing areal recharge to 

8.0 in./yr (initial value was 7.0 in./yr). 

The final rate (8.0 in./yr) is within the 

range of reported areal recharge rates 

of 6.5 to 9.0 in./yr to surficial unconfined aquifers in Minnesota (Delin, 

1988; Lindgren, 2000). The maximum 

ground-water evapotranspiration rate 

was not changed as a result of model 

calibration, but the extinction depth 

was reduced from 7 ft to 5 ft. 

Hydraulic Heads

The potentiometric surfaces computed by the model for the upland 

surficial and Sauk River Valley aquifers are similar to the contoured surfaces based on measured water levels 

and are considered to acceptably simulate directions of ground-water flow 

in the aquifers (figs. 4 and 5, respectively). The final simulated hydraulic 

heads were within 5 ft of measured 

water levels in all but 5 of the 45 

wells used to calibrate the model. The 

largest difference between measured 

and simulated hydraulic heads was 

7.9 ft. The difference was 2.0 ft or less 

at 24 of the wells. The mean absolute 

difference between measured and 

simulated hydraulic heads, computed 

as the sum of the absolute values of 

the differences divided by the number 

of wells (45) was 2.4 ft. The mean 

algebraic difference between measured and simulated hydraulic heads, 

computed as the algebraic sum of the 

differences divided by the number of 

wells, was -0.9 ft, indicating a possible negative bias in the simulation of 

the hydraulic heads. However, the 

negative mean algebraic difference is 

caused by comparatively high negative differences for a few wells, and 

with the exclusion of these few wells 

the negative differences between measured and simulated hydraulic heads 

were approximately balanced by the 

positive differences. 

Stream-Aquifer Leakage 

Comparison of measured and 

simulated stream-aquifer leakage was 

also used to evaluate how well the 

model simulates the stream-aquifer 

system. Accuracy of the stream-discharge measurements conducted for 

this study was generally plus or minus 

5–8 percent. Estimates of streamaquifer leakage are likely less than the 

measurement error for many of the 

Sauk River reaches. The August 1999 

measurements downstream from SW4 

were most representative of low-flow 

conditions and were used to evaluate 

the model calibration. The model generally duplicated the correct magnitude and direction of stream-aquifer 

leakage for the Sauk River and Brewery Creek, but the simulated streamaquifer leakage for the Sauk River 

was consistently less than the measured stream-aquifer leakage (table 

1). The simulated gains in streamflow 

for the Sauk River reaches were 

within 8 ft3/s of the measured gains, 

except for the reach between SW6 and 

SW7. The comparatively poor agreement between the measured and simulated loss in streamflow for the reach 

between SW6 and SW7 is probably 

due to measurement error, as indicated by the comparison between the 

measured streamflow losses and the 

volume of water pumped by nearby 

wells, discussed previously. The simulated gains in streamflow for the 

Brewery Creek reaches (SW10–

SW11 and SW11–SW12) were within 

0.30 ft3/s of the measured gains 

(table 1). 

Ground-Water Budget

A water budget is an accounting 

of inflow to, outflow from, and storage change in the aquifers. For 

steady-state conditions, inflow 

(sources) to the aquifers equals outflow (discharges) from the aquifers 

(table 3), so that storage changes are 

zero. Areal recharge accounts for 51.5 

percent of the sources of water to the 

aquifers in the Cold Spring area and 

inflow through constant-head boundaries contributes 45.8 percent (table 

3). The remaining 2.7 percent comes 

from leakage from the streams to the 

valley unit of the Sauk River Valley 

aquifer. Most of the areal recharge 

occurs to the valley unit of the Sauk 

River Valley aquifer (74 percent) 

because this aquifer underlies most of 

the Cold Spring area. Eighty-six percent of the inflow through constanthead boundaries occurs to the Sauk 

River Valley aquifer. Ninety-three 

percent of the inflow through constant-head boundaries to the Sauk 

River Valley aquifer occurs through 

the northern model boundary, with 88 

percent of the inflow through the 

northern model boundary occurring 

through the north-central part of the 

boundary. Only 6 percent of the 

inflow through constant-head boundaries to the Sauk River Valley aquifer 

occurs through the southeastern 

model boundary. 

The largest discharges from the 

aquifers in the Cold Spring area are 

leakage from the valley unit of the 

Sauk River Valley aquifer to the Sauk 

River and Brewery Creek (53.7 percent) and outflow through constanthead boundaries (33.1 percent) (table 

3). All but a minor amount of the outflow through constant-head boundaries occurs from the Sauk River 

Valley aquifer (94 percent). Most of 

the outflow through constant-head 

boundaries from the Sauk River Valley aquifer occurs in the southwestern 

part of the model area where the 

direction of ground-water flow is predominantly from east to west toward 
27

Table 3. Simulated water budgets from ground-water-flow model of aquifer system with 1998 and projected pumpage conditions, 

Cold Spring area, Minnesota

 [Percent is percentage of total sources or of total discharges; ft3/s, cubic feet per second]

Source 

1998 pumpage conditions Projected pumpage conditions

Budget component and model layer Rate (ft3/s) Percent Rate (ft3/s) Percent

Areal recharge

 Layer 1 (Upland surficial aquifer) 5.57 13.3 5.57 13.2

 Layer 3 (Valley unit of Sauk River Valley aquifer) 16.04 38.2 16.04 38.1

 Subtotal 21.61 51.5 21.61 51.3

Stream-aquifer leakage

 Layer 3 (Valley unit of Sauk River Valley aquifer) 1.13 2.7 1.09 2.6

 Subtotal 1.13 2.7 1.09 2.6

Inflow through constant-head boundary

 Layer 1 (Upland surficial aquifer) 2.59 6.2 2.60 6.2

 Layer 3 (Sauk River Valley aquifer) 16.63 39.6 16.65 39.9

 Subtotal 19.22 45.8 19.25 46.1

Total 41.96 100.0 41.95 100.0

Discharge

1998 pumpage conditions Projected pumpage conditions 

Budget component and model layer Rate (ft3/s) Percent Rate (ft3/s) Percent

Pumpage

 Layer 1 (Upland surficial aquifer) 0.23 0.6 0.23 0.5

 Layer 3 (Sauk River Valley aquifer) 2.83 6.7 3.06 7.3

 Subtotal 3.06 7.3 3.29 7.8

Stream-aquifer leakage

 Layer 3 (Valley unit of Sauk River Valley aquifer) 22.55 53.7 22.42 53.3

 Subtotal 22.55 53.7 22.42 53.3

Outflow through constant-head boundary

 Layer 1 (Upland surficial aquifer) 0.80 1.9 0.81 1.9

 Layer 3 (Sauk River Valley aquifer) 13.08 31.2 12.96 30.8

 Subtotal 13.88 33.1 13.77 32.7

Ground-water evapotranspiration

 Layer 1 (Upland surficial aquifer) 2.47 5.9 2.47 6.2

 Subtotal 2.47 5.9 2.47 6.2

Total 41.96 100.0 41.95 100.0

the Sauk River (72 percent). Twentyeight percent of the outflow is to the 

chain of lakes. The other discharges 

from the aquifers are withdrawals by 

wells (7.3 percent) and ground-water 

evapotranspiration (5.9 percent). Most 

of the withdrawals by wells are from 

the valley unit of the Sauk River Valley aquifer (92 percent). Ground-
28

water evapotranspiration is a minor 

component of the water budget for the 

model area because ground-water levels are greater than 5 ft below land 

surface, except for near the streams 

and some wetlands in the northwestern part of the study area. 

The net stream-aquifer leakage is 

21.42 ft3

/s from the valley unit of the 

Sauk River Valley aquifer to the Sauk 

River and Brewery Creek (table 3), 

indicating that the streams are gaining 

streams overall in the model area. 

This net discharge from the aquifer to 

the streams represents 52 percent of 

the sources of water to the aquifers 

other than the small amount of leakage from streams to the aquifers (areal 

recharge and inflow through constanthead boundaries). Ground-water withdrawals by supply wells represent 

only 7 percent of the sources of water 

to the aquifers. 

Simulated leakage between model 

layers is in both downward and 

upward directions (table 4). However, other than for model layer 4, 

representing the deeply buried unit of 

the Sauk River Valley aquifer, upward 

movement of water is negligible. The 

large upward component of flow from 

model layer 4 to model layer 3, representing the Sauk River Valley aquifer, 

occurs predominantly near the Sauk 

River and chain of lakes, where 

ground water discharges to these surface-water bodies.

Ground-Water Flow to Wells 

(1998 Conditions)

The simulated steady-state contributing areas (time-of-travel zones 

for infinite travel time) for the WHP 

partnership water supply wells in the 

Cold Spring area, which are all 

screened the Sauk River Valley aquifer, may extend beyond the model 

boundaries to the north and to the 

southeast near the broad, poorly 

defined highs in the potentiometric 

surfaces of the aquifers (fig. 11). The 

contributing areas for the two Cold 

Spring Granite Company private 

water-supply wells and for Cold 

Spring municipal well CS3 extend 

into the area west and northwest of 

Cold Spring where the geologic materials within the altitude interval of the 

Sauk River Valley aquifer (from land 

surface down to an altitude of 

1,035 ft) are till and clay. The contributing areas for these wells generally 

are terminated at highs in the potentiometric surface of the Sauk River Valley aquifer in this area of low 

hydraulic conductivities. The contributing area for one of the Cold Spring 

Granite Company wells, however, 

extends to the north due to leakage 

downward from the upland surficial 

aquifer to the Sauk River Valley aquifer near the southern boundary of the 

upland surficial aquifer. The contributing areas for the Gold’n Plump 

Poultry Processing Plant supply wells 

extend: (1) to the Sauk River, (2) to 

the north to and possibly beyond the 

northern model boundary, and (3) to 

the southeast to and possibly beyond 

the southeastern model boundary. The 

contributing area extends to the north 

past the Sauk River where the 

pumped supply wells create a cone of 

depression that lowers ground-water 

levels at the river below the altitude of 

river stage (figs. 5a and 11a).

The simulated time required for 

water particles from the model boundaries to reach the WHP partnership 

water-supply wells varied. The simulated time-of-travel for water to reach 

Table 4. Simulated leakage between model layers from ground-water-flow model of aquifer system with 1998 and projected pumpage 

conditions, Cold Spring area, Minnesota

[ ft3/s; cubic feet per second] 

1998 pumpage conditions Projected pumpage conditions

Source Discharge Source Discharge

Leakage between model layers (ft3/s) (ft3/s) (ft3/s) (ft3/s)

Layer 1 (Upland surficial aquifer)

 Through lower boundary 0.0008 4.4312 0.0007 4.4625

Layer 2 (Confining unit)

 Through upper boundary 4.4312 0.0008 4.4625 0.0007

 Through lower boundary 0.0005 4.5501 0.0004 4.5848

Layer 3 (Sauk River Valley aquifer)

 Through upper boundary 4.5501 0.0005 4.5848 0.0004

 Through lower boundary 3.5067 3.5946 3.4864 3.5755

Layer 4 (Deeply buried unit of Sauk River Valley aquifer)

 Through upper boundary 3.5946 3.5067 3.5755 3.4864

Total 16.0839 16.0839 16.1103 16.1103
29

the Cold Spring Alano Society and 

Gluek Brewing Company supply 

wells and Cold Spring municipal 

wells CS1 and CS2 from the northern 

model boundary is about 15 years. 

The simulated time-of-travel for water 

to reach the Town’s Edge Mobile 

Home Park and Gold’n Plump Poultry 

Processing Plant supply wells from 

the southeastern model boundary is 

about 75 years. The time-of-travel for 

water to reach the Town’s Edge 

Mobile Home Park and Gold’n Plump 

Poultry Processing Plant supply wells 

is much greater over a shorter distance 

than for the Cold Spring Alano Society wells, Gluek Brewing Company 

wells, and Cold Spring municipal 

wells CS1 and CS2 because their 

time-of-travel zones include areas of 

low hydraulic conductivities (1 and 

25 ft/d) (figs. 8-9a). The simulated 

time-of-travel for water to reach the 

two Cold Spring Granite Company 

supply wells and Cold Spring municipal well CS3 from highs in the potentiometric surface of the Sauk River 

Valley aquifer (layer 3) in the area of 

low hydraulic conductivities to the 

north and northwest of the wells is 

also 50 to 75 years. Water from the 

northern model boundary reaches the 

Gold’n Plump Poultry Processing 

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

36 31

0 1 2 3 MILES

0123 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Simulated altitude of potentiometric surface of Sauk River Valley aquifer and contributing areas of ground-water flow to

water-supply wells, 1998 pumpage, Cold Spring area, Minnesota.

Inactive cells

Simulated potentiometric contour. Interval

10 feet. Datum is sea level

Contributing area

WHP partnership water-supply well (with identifier)

CSG-Cold Spring Granite Company

CSG

EXPLANATION

Figure 11.

1080

CSG CSG

SEE

FIGURE 11a
30

23

14

22

15

24

13

T

123

N

R 30 W

Sauk

River

Brewery

Creek

23

50

2

2

Cold Spring

Knaus Lake

45°27'

45°28'

94°26' 94°25' 94°24'

1100

CS3 GL

GL

CS1, CS2

CSA

GPP 1-6

TE

0 1 MILE

0 1 KILOMETER

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Simulated altitude of potentiometric surface of Sauk River Valley aquifer and contributing areas of ground-water flow

to water-supply wells near Cold Spring and Gold'n Plump Poultry Processing Plant, 1998 pumpage, Cold Spring area, Minnesota.

Gold'n Plump

Poultry

Processing

Plant

Figure 11a.

Inactive cells

Simulated potentiometric contour. Interval

2 feet. Datum is sea level

Contributing area

WHP partnership water-supply well (with identifier)

CS-Cold Spring municipal

GPP-Gold'n Plump Poultry

GL-Gluek Brewing Company

CSA-Cold Spring Alano Society

TE-Town's Edge Mobile Home Park

CS

EXPLANATION
31

Plant supply wells in about 10 years. 

The simulated travel time is much 

shorter than for water from the southeastern model boundary because the 

hydraulic conductivity of the geologic 

material in the contributing area 

extending to the north is greater than 

that in the contributing area extending 

to the southeast. The simulated timeof-travel for water to reach the Gold’n 

Plump Poultry Processing Plant supply wells from the Sauk River ranges 

from less than 1 year for the river 

reach near the supply wells where 

induced infiltration of river water 

occurs to about 5 years for the reaches 

to the northwest and west of the wells.

It is important in the analysis and 

application of the simulated contributing areas to recognize that the model 

results are for steady-state conditions. 

Therefore, all stresses on the aquifer 

system, including pumping rates, 

stream-aquifer leakage, and areal 

recharge, are simulated as constant in 

time. Real pumping rates and aquifer 

recharge and discharge vary seasonally, however, thus altering the timeof-travel zones for a well. Also the 

simulated time-of-travel zones may 

differ under steady-state conditions 

with different pumping rates and precipitation regimes. 

Effects of Increased GroundWater Withdrawals

A model simulation was done to 

evaluate the response of the streamaquifer system in the model area to 

projected increases in ground-water 

withdrawals and to delineate 10, 20, 

and 30-year time-of-travel zones for 

the WHP partnership water-supply 

wells under these conditions. At the 

cooperators request only the 20 year 

time-of-travel zone were included in 

this report. The 20 and 30-year timeof-travel zones were similar. The total 

projected increase in ground-water 

withdrawals estimated by the WHP 

partnership well owners was 

0.23 ft3

/s, an increase of 7.5 percent. 

The projected increases were 10 percent for the Gluek Brewing Company 

and Town’s Edge Mobile Home Park 

supply wells, 12 percent for the 

Gold’n Plump Poultry Processing 

Plant supply wells, and 28 percent for 

the Cold Spring municipal wells. For 

the Cold Spring municipal wells, the 

increased withdrawals would be from 

well CS4, which began pumping in 

November 1999, and well CS5, which 

has not yet been installed. The projected annual withdrawals from 

municipal wells CS2 and CS3 are 

68.8 million gallons (0.29 ft3

/s) less 

than during 1998, a decrease in these 

two wells of 51 percent. No increase 

in ground-water withdrawals from the 

Cold Spring Granite Company and 

Cold Spring Alano Society supply 

wells was projected. The 1998 

reported withdrawal rates for irrigation wells were used in the simulation 

with projected increased groundwater withdrawals from the WHP 

partnership water-supply wells. Withdrawal rates for irrigation have been 

relatively stable during recent years 

and no appreciable increase is foreseen, other than that due to lowerthan-normal precipitation. The final 

calibrated values for all model parameters, including an areal recharge rate 

of 8.0 in./yr, were used in the simulation with projected increased groundwater withdrawals. 

The primary effects of the projected increased ground-water withdrawals were to: (1) decrease outflow 

from the Sauk River Valley aquifer 

through constant-head boundaries and 

(2) decrease leakage from the valley 

unit of the Sauk River Valley aquifer 

to the streams (table 3). The additional water pumped by wells 

(0.23 ft3

/s) was derived from a net 

increase of 0.14 ft3

/s in the flow of 

water to the study area through constant-head boundaries and a net 

decrease of 0.09 ft3

/s in leakage of 

water from the aquifer to the streams. 

The net increase in the flow of water 

to the study area through constanthead boundaries was due primarily to 

a decrease of 0.12 ft3

/s in outflow 

from the Sauk River Valley aquifer 

(table 3). The projected increased 

ground-water withdrawals also 

resulted in: (1) increased leakage 

downward from the upland surficial 

aquifer (layer 1) through the confining 

unit (layer 2) to the Sauk River Valley 

aquifer (layer 3) and (2) decreased 

leakage downward from the Sauk 

River Valley aquifer to the deeply buried unit of the Sauk River Valley aquifer (layer 4) (table 4). 

No appreciable differences are 

discernible between the simulated 

steady-state potentiometric surfaces 

and contributing areas to wells with 

1998 pumpage and those with the projected pumpage (compare figs. 11-

12a), due to the relatively small projected increase in ground-water withdrawals (0.23 ft3/s). The 20-year 

time-of-travel zones for the WHP 

partnership water-supply wells reach 

either the model-area boundaries or 

predominantly clay and till areas for 

the Sauk River Valley aquifer (fig. 

12). Water from the northern boundary of the model area reaches the Cold 

Spring municipal wells CS4 and CS5 

in about 7 years. For wells with 20-

year time-of-travel zones limited to 

the unconfined, surficial sand and 

gravel areas of the Sauk River Valley 

aquifer, the 20-year time-of-travel 

zones and contributing areas coincide. 

For wells with contributing areas that 

include lower hydraulic conductivity 

(25 ft/d or less) geologic materials, 

the 20-year time-of-travel zones are 

smaller than the contributing areas 

due to the much slower travel times 

through the lower hydraulic conductivity materials. 
32

Numerical Model Limitations 

and Accuracy of Results

A numerical ground-water-flow 

model is a practical tool for simulating response of the stream-aquifer 

system to anticipated changes in areal 

recharge and ground-water withdrawals imposed on the system. A model is 

a simplification of a complex flow 

system. The accuracy of the simulations is limited by the accuracy of the 

data used to describe the properties of 

the aquifers and the confining units, 

areal recharge rates, ground-water 

withdrawal rates, streambed hydraulic 

conductivities, and boundary conditions. In addition, a combination of 

these inputs to the model different 

from that used in a simulation could 

produce the same result. 

Use of the calibrated model as a 

predictive tool is based on the premise 

that if historical conditions in the 

aquifer can be simulated, then future 

similar hydrologic conditions can also 

be simulated. The variation in areal 

recharge and discharge occurring during the simulation of hypothetical 

conditions should be similar to that 

for the calibration simulation. The 

accuracy of simulation results for 

hypothetical conditions becomes 

more uncertain if the variation in areal 

1

1 1

6 1

6 6

6

36 31

T

123

N

R 31 W R 30 W R 29 W

Sauk

River

Brewery

Creek

23

23

22

50

50

2

2

71

49

Jacobs Prairie

Cold Spring

Richmond

Lake Schneiders Thein

Lake

Byer Lake

Northern Great

Lake

Krays

Lake

East Lake

Knaus

Lake

Koetter Lake

Lake

Zumwalles

Lake

Horseshoe

Park Lake

Bolfing Lake

Cedar Island Lake

Mud Lake

Fink

Lake

45°25'

45°27'30"

45°30'

94°30' 94°27'30" 94°25' 94°22'30"

1080

36 31

0 1 2 3 MILES

0123 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Simulated altitude of potentiometric surface of Sauk River Valley aquifer, contributing areas, and 20-year time-of-travel

zones of ground-water flow to water-supply wells, projected pumpage, Cold Spring area, Minnesota.

Inactive cells

Simulated potentiometric contour. Interval

10 feet. Datum is sea level

Contributing area

20-year time-of-travel zone

WHP partnership water-supply well (with identifier)

CSG-Cold Spring Granite Company

CS-Cold Spring municipal

CSG

EXPLANATION

Figure 12.

SEE

FIGURE 12a

CSG

CSG

CS4,

CS5
33

23

14

22

15

24

13

T

123

N

R 30 W

Sauk

River

Brewery

Creek

23

50

2

2

Cold Spring

Knaus Lake

45°27'

45°28'

94°26' 94°25' 94°24'

1100

CS3 GL

GL

CS1, CS2

CSA

GPP 1-6

TE

0 1 MILE

0 1 KILOMETER

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Simulated altitude of potentiometric surface of Sauk River Valley aquifer, contributing areas, and 20-year time-of-travel

zones of ground-water flow to water-supply wells near Cold Spring and Gold'n Plump Poultry Processing Plant, projected pumpage,

Cold Spring area, Minnesota.

Gold'n Plump

Poultry

Processing

Plant

Inactive cells

Simulated potentiometric contour. Interval

2 feet. Datum is sea level

Contributing area

20-year time-of-travel zone

CSG

EXPLANATION

WHP partnership water-supply well (with identifier)

CS-Cold Spring municipal

GPP-Gold'n Plump Poultry

GL-Gluek Brewing Company

CSA-Cold Spring Alano Society

TE-Town's Edge Mobile Home Park

Figure 12a.
34

recharge and discharge exceeds the 

range used in calibration. 

The accuracy of simulations of 

hypothetical conditions varies 

depending on the particular conditions 

being simulated. Factors affecting the 

accuracy of the simulations include: 

(1) the duration of the simulation 

period compared to the duration of the 

calibration period, and (2) the rate of 

simulated areal recharge or discharge 

compared to those used in calibration. 

Assuming the model calibration is 

accurate, the most accurate simulations are possible when the duration 

and hypothetical ground-water withdrawal rate for the simulation are less 

than, or comparable to, the duration 

and ground-water withdrawal rate for 

the calibration simulation. Long simulation periods and high ground-water 

withdrawal rates can produce large 

errors, and special care should be 

taken in using the results of such simulations. 

The rate of simulated groundwater withdrawals for the simulation 

with projected ground-water withdrawals done for this study is similar 

to the rate of ground-water withdrawals used in the calibration simulation. 

The total annual ground-water withdrawal rate used in the simulation 

with projected ground-water withdrawals is only 7.5 percent greater 

than the rate used in the calibration 

simulation. The simulated areal 

recharge rate is the same in the calibration and projected ground-water 

withdrawals simulations. 

SUMMARY

Increased demand for ground water in the Cold Spring 

area in central Minnesota has resulted in the increased 

development of glacially-deposited aquifers. Surficial and 

buried sand and gravel aquifers underlie the Sauk River 

Valley in the Cold Spring area and are utilized as sources of 

water supply. Areas contributing ground-water to highcapacity wells need to be delineated so that land use within 

the contributing areas can be managed to reduce the risk of 

water-quality degradation. To address these needs and concerns, and to further the understanding of stream-aquifer 

systems, the U. S. Geological Survey, in cooperation with 

the city of Cold Spring, conducted a study during 1998-99. 

Surficial deposits in the Cold Spring area consist 

mainly of late-Wisconsin glacial till and outwash sands and 

gravels associated with the Des Moines and Superior lobes. 

Outwash sands and gravels from the Des Moines lobe fill 

most of the Sauk River Valley. The Quaternary deposits in 

the study area include: (1) thick surficial sand and gravel 

outwash deposits, (2) complex till and ice-contact stratified 

deposits that may include surficial or buried sand, sand and 

gravel lenses, or both, and (3) till with few, if any, buried 

sand and gravel lenses. Glacial deposits with thicknesses of 

as much as 50 ft are present along the river, whereas thicknesses of as much as 250 ft are present in the uplands northwest and southwest of Cold Spring. Precambrian igneous 

and metamorphic rocks underlie the glacial deposits in the 

Cold Spring area. 

Surficial aquifers underlie a portion of the uplands in 

the north-central part of the study area and the Sauk River 

Valley. The upland surficial aquifer, underlying the uplands 

in the north-central part of the study area, includes areas of: 

(1) Superior lobe ice-contact and outwash deposits and (2) 

predominantly sandy Superior lobe till, with isolated surficial sand and gravel deposits. The aquifer is unconfined, 

with saturated thicknesses ranging from 6 to 37 ft. 

The Sauk River Valley aquifer consists of hydraulically 

connected sand and gravel units with two different hydrogeologic settings: (1) the generally continuous surficial 

unconfined unit underlying the Sauk River Valley (valley 

unit) and (2) buried confined units that are overlain by till 

or lake clays in the upland areas. Maximum saturated thickness of the valley unit of the aquifer is about 50 ft. Buried 

units of the aquifer that are in hydraulic connection with the 

valley unit of the aquifer are present in the north-central 

and northwestern parts of the study area. Thicknesses of the 

buried units are generally 10 to 20 ft. 

Ground-water flow in the upland surficial aquifer is (1) 

to the south and southeast toward the margins of the aquifer 

and (2) from the uplands toward an unnamed creek valley 

in the central part of the aquifer. Ground-water flow in the 

Sauk River Valley aquifer is from upland areas toward the 

Sauk River and the connected chain of lakes. The aquifer is 

under unconfined conditions throughout most of its areal 

extent, but is under confined conditions where it is buried 

by till and clay in the northwestern part of the study area. 

 The primary sources of water to the aquifers are (1) 

areal recharge and (2) ground-water flow through the northern boundary. Based on hydrograph analysis, ground-water 

recharge rates to the aquifers during 1999 ranged from 5.3 

to 8.6 in./yr, with an average value of 7.0 in./yr. Sources of 

water to the Sauk River Valley aquifer also include: (1) 

leakage of water through overlying till and clay for buried 

units of the aquifer and (2) probably ground-water flow 

from undifferentiated glacial deposits in the southeastern 

part of the study area. 

Discharge from the aquifers is by (1) withdrawals from 

wells, (2) leakage to streams, and (3) ground-water evapo-
35

transpiration in areas where the water table is within 5–

10 ft of land surface. Discharge from the upland surficial 

aquifer is also by leakage downward through a till and clay 

confining unit to the buried units of the Sauk River Valley 

aquifer. Discharge from the Sauk River Valley aquifer to 

surface water is to the Sauk River, chain of lakes, and 

Brewery Creek. 

 Streamflow measurements indicated net gains of 44.8 

and 25.8 ft3/s for the Sauk River from Cold Spring to Rockville, located about one mile east of the study area, during 

October 1998 and August 1999, respectively. In general, 

the Sauk River probably is a gaining stream in all reaches, 

except for the reach adjacent to the Gold’n Plump Poultry 

Processing Plant well field. Ground-water withdrawals 

from the well field result in declines in the potentiometric 

surface of the aquifer near the supply wells, thereby inducing infiltration of water from the Sauk River to the underlying aquifer. The streamflow gains in the river reaches 

downstream from Brewey Creek, other than the reach adjacent to the Gold’n Plump Poultry Processing Plant well 

field, during August 1999 ranged from 9.0 to 12 ft3

/s. The 

measured gains in streamflow for Brewery Creek were 2.75 

and 2.25 ft3/s during October 1998 and August 1999, 

respectively. 

A numerical ground-water-flow model was constructed 

and calibrated for steady-state conditions. The match 

between measured and simulated hydraulic heads and 

stream-aquifer leakage was improved by increasing areal 

recharge from 7.0 in./yr, the initial value based on 

hydrograph analysis, to 8.0 in./yr. Areal recharge accounts 

for 51.5 percent of the sources of water to the aquifers in 

the Cold Spring area and inflow through constant-head 

boundaries contributes 45.8 percent. The remaining 2.7 

percent comes from leakage from the streams to the valley 

unit of the Sauk River Valley aquifer. Most of the areal 

recharge occurs to the valley unit of the Sauk River Valley 

aquifer (74 percent). Eighty-six percent of the inflow 

through constant-head boundaries occurs to the Sauk River 

Valley aquifer. Ninety-three percent of the inflow through 

constant-head boundaries to the Sauk River Valley aquifer 

occurs through the northern model boundary. 

The largest discharges from the aquifers in the Cold 

Spring area are leakage from the valley unit of the Sauk 

River Valley aquifer to the Sauk River and Brewery Creek 

(53.7 percent) and outflow through constant-head boundaries (33.1 percent). All but a minor amount of the outflow 

through constant-head boundaries occurs from the Sauk 

River Valley aquifer (94 percent). The other discharges 

from the aquifers are withdrawals by wells (7.3 percent) 

and ground-water evapotranspiration (5.9 percent). The net 

stream-aquifer leakage is 21.42 ft3/s from the valley unit of 

the Sauk River Valley aquifer to the Sauk River and Brewery Creek. This net discharge from the aquifer to the 

streams represents 52 percent of the sources of water to the 

aquifers (areal recharge and inflow through constant-head 

boundaries). 

The simulated steady-state contributing areas (time-oftravel zones for infinite travel time) for the WHP partnership water-supply wells in the Cold Spring area may extend 

beyond the model boundaries to the north and to the southeast near the broad, poorly defined highs in the potentiometric surfaces of the aquifers. The contributing areas for 

the Gold’n Plump Poultry Processing Plant supply wells 

extend: (1) to the Sauk River, (2) to the north to and possibly beyond the northern model boundary, and (3) to the 

southeast to and possibly beyond the southeastern model 

boundary. The contributing area extends to the north past 

the Sauk River where the pumped supply wells create a 

cone of depression that lowers ground-water levels at the 

river below the altitude of river stage. The simulated timeof-travel for water to reach the Cold Spring Alano Society, 

Gluek Brewing Company, and Gold’n Plump Poultry Processing Plant supply wells and Cold Spring municipal wells 

CS1 and CS2 from the northern model boundary is about 

10 to 15 years. The simulated time-of-travel for water to 

reach the Town’s Edge Mobile Home Park and Gold’n 

Plump Poultry Processing Plant supply wells from the 

southeastern model boundary is about 75 years. The simulated time-of-travel for water to reach the Gold’n Plump 

Poultry Processing Plant supply wells from the Sauk River 

ranges from less than 1 year for the river reach near the 

supply wells where induced infiltration of river water 

occurs to about 5 years for the reaches to the northwest and 

west of the wells. 

The response of the stream-aquifer system in the model 

area to projected increases in ground-water withdrawals of 

0.23 ft3

/s, an increase of 7.5 percent, was evaluated. The 

primary effects of the projected increased ground-water 

withdrawals were to: (1) decrease outflow from the Sauk 

River Valley aquifer through constant-head boundaries and 

(2) decrease leakage from the valley unit of the Sauk River 

Valley aquifer to the streams. No appreciable differences 

are discernible between the simulated steady-state potentiometric surfaces and contributing areas to wells with 1998 

pumpage and those with the projected pumpage. The 20-

year time-of-travel zones reach either the model-area 

boundaries or predominantly clay and till areas for the Sauk 

River Valley aquifer.
36

REFERENCES CITED

Baker, D.G., and Kuehnast, E.A., 

1978, Climate of Minnesota 

Part X, Precipitation normals 

for 1941–70: Minnesota Agricultural Experiment Station 

Technical Bulletin 314, 15 p. 

Baker, D.G., Nelson, W.W., and Kuehnast, E.A., 1979, Climate of 

Minnesota, Part XII, The hydrologic cycle and soil and water: 

Minnesota Agricultural Experiment Station Technical Bulletin 322, 23 p.

Delin, G.N., 1988, Geohydrology and 

water quality of confined-drift 

aquifers in the Brooten-Belgrade area, west-central Minnesota: U.S. Geological Survey 

Water-Resources Investigations Report 88–4124, 138 p. 

_____ 1990, Hydrogeology and simulation of ground-water flow in 

the Rochester area, southeastern 

Minnesota, 1987-88: U.S. Geological Survey WaterResources Investigations 

Report 90–4081, 102 p.

_____ 1991, Simulation of effects of 

ground-water development on 

water levels in glacial-drift 

aquifers in the Brooten-Belgrade area, west-central Minnesota: U.S. Geological Survey 

Water-Resources Investigations Report 88–4193, 66 p. 

Freeze, R.A., and Cherry, J.A., 1979, 

Groundwater: Englewood 

Cliffs, New Jersey, PrenticeHall, Inc., 604 p.

Guiguer, N., and Franz, T., 1999, 

Visual MODFLOW user's manual, ver. 2.8: Waterloo, Ontario, 

Canada, Waterloo Hydrogeologic Inc., 282 p. 

Helgesen, J.O., Ericson, D.W., and 

Lindholm, G.F., 1975, Water 

resources of the Mississippi and 

Sauk Rivers watershed, central 

Minnesota: U.S. Geological 

Survey Hydrologic Investigations Atlas HA–534, 3 plates.

HDR Engineering, Inc., 1995, 

Ground-water resources evaluation—Well head protection area 

(WHPA) delineation: Report 

prepared for Gold’n Plump 

Poultry, 120 p.

Jorgensen, D.G., and Ackroyd, E.A., 

1973, Water resources of the 

Big Sioux River valley near 

Sioux Falls, South Dakota: U.S. 

Geological Survey Water-Supply Paper 2024, 50 p. 

Lindgren, R.J., 1990, Simulation of 

ground-water flow in the Prairie 

du Chien-Jordan and overlying 

aquifers near the Mississippi 

River, Fridley, Minnesota: U.S. 

Geological Survey WaterResources Investigations 

Report 90–4165, 152 p.

Lindgren, R.J., and Landon, M.K., 

2000, Effects of ground-water 

withdrawals on the Rock River 

and associated valley aquifer, 

eastern Rock County, Minnesota: U.S. Geological Survey 

Water-Resources Investigations Report 98–4157, 103 p. 

Lindholm, G.F., 1980, Ground-water 

appraisal of sand plains in Benton, Sherburne, Stearns, and 

Wright Counties, central Minnesota: U.S. Geological Survey 

Water-Resources Investigations Report 80-1285, 103 p. 

McDonald, M.G., and Harbaugh, 

A.W., 1988, A modular threedimensional finite-difference 

ground-water flow model: U.S. 

Geological Survey Techniques 

of Water-Resources Investigations, book 6, chap. A1, 586 p.

Meyer, G.N., and Knaeble, A.R., 

1995, Surficial geology: Minnesota Geological Survey County 

Atlas Series Atlas C–10, Part A, 

Stearns County, Minnesota, 

Plate 3. 

Meyer, G.N., and Swanson, Lynn, 

1996, Text supplement to the 

geologic atlas, Stearns County, 

Minnesota: Minnesota Geological Survey County Atlas Series 

Atlas C–10, part C, 63 p.

Miller, R.T., 1982, Appraisal of the 

Pelican River sandplain aquifer, 

western Minnesota: U.S. Geological Survey Open-File 

Report 82–347, 40 p.

Minnesota Department of Health, 

1999, Workplan for the Cold 

Spring Clean Water Partnership project: Report prepared 

for City of Cold Spring, 70 p. 

Mitton, G.B., Guttormson, K.G., 

Stratton, G.W., and Wakeman, 

E.S., 1999, Water-resources 

data, Minnesota, water year 

1998: U.S. Geological Survey 

Water-Data Report MN–98–1, 

410 p. 

Morris, D.A., and Johnson, A.I., 1967, 

Summary of hydrologic and 

physical properties of rock and 

soil materials, as analyzed by 

the hydrologic laboratory of the 

U.S. Geological Survey 1948–

60: U.S. Geological Survey 

Water-Supply Paper 1839–D, 

42 p.

Norris, S.E., and Fidler, R.E., 1969, 

Hydrogeology of the Scioto 

River Valley near Piketon, 

south-central Ohio: U.S. Geological Survey Water-Supply 

Paper 1872, 70 p. 

Pelletier, P.M., 1988, Uncertainties in 

the single determination of river 

discharge—A literature review: 

Canadian Journal of Civil Engineering, v. 15, no. 5.

Pollock, D.W., 1989, Documentation 

of computer programs to compute and display pathlines using 

results from the U.S. Geological 

Survey modular three-dimensional finite-difference groundwater flow model: U.S. Geological Survey Open-File Report 

89–381, 188 p.

Prince, K.R., Franke, O.L., and Reilly, 

T.E., 1987, Quantitative assessment of the shallow groundwater flow-system associated 
37

with Connetquot Brook, Long 

Island, New York: U.S. Geological Survey Water-Supply 

Paper 2309, 28 p. 

Rasmussen, W.C., and Andreasen, 

G.G., 1959, Hydrologic budget 

of the Beaver Dam Creek 

Basin, Maryland: U.S. Geological Survey Water-Supply Paper 

1472, 106 p.

Setterholm, D.R., 1995, Depth to bedrock and thickness of Cretaceous strata: Minnesota 

Geological Survey County 

Atlas Series Atlas C–10, Part A, 

Stearns County, Minnesota, 

Plate 5. 

U.S. Environmental Protection 

Agency, 1987, Guidelines for 

delineation of wellhead protection areas: U.S. Environmental 

Protection Agency Office of 

Ground-Water Protection, 

Washington, D.C., EPA 440/6–

87–010, 189 p.

____, 1996, Drinking water regulations and health advisories: 

U.S. Environmental Protection 

Agency, February, 11 p.

Yager, R.M., 1993, Estimation of 

hydraulic conductivity of a 

riverbed and aquifer system on 

the Susquehanna River in 

Broome County, New York: 

U.S. Geological Survey WaterSupply Paper 2387, 49 p.