Characterization of Ground-Water Flow 

Between the Canisteo Mine Pit and 

Surrounding Aquifers, Mesabi Iron Range, 

Minnesota

By Perry M. Jones

Water-Resources Investigations Report 02-4198

Prepared in cooperation with the Minnesota Department of Natural Resources
U.S. DEPARTMENT OF THE INTERIOR

Gale A. Norton, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

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

constitute endorsement by the U.S. Geological Survey.

Mound View, Minnesota, 2002

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://www.rvares.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 02-4198
iii

Contents

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

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

Acknowledgments ................................................................................................................................................................................4

Physical setting of Canisteo Mine Pit study area..................................................................................................................................4

Methods of Investigation.............................................................................................................................................................................6

Single-well hydraulic tests....................................................................................................................................................................6

Stream-hydrograph analyses.................................................................................................................................................................6

Ground-water flow model of the Canisteo Mine Pit study area ...........................................................................................................8

Data sets used ...............................................................................................................................................................................8

Discretization of the model...........................................................................................................................................................8

Model calibration, sensitivity analyses, and simulations............................................................................................................ 12

Model limitations and accuracy.................................................................................................................................................. 14

Single-well hydraulic test ................................................................................................................................................................... 17

Stream-hydrograph analyses............................................................................................................................................................... 17

Calibration of the MODFLOW-96 ground-water flow model ........................................................................................................... 17

Model sensitivity to ground-water recharge and hydraulic conductivity ........................................................................................... 19

Simulations characterizing current and potential future ground-water flow conditions near the mine pit ........................................ 20

Summary and conclusions......................................................................................................................................................................... 28

References ................................................................................................................................................................................................ 28

Illustrations

Figure 1. Map showing location of Canisteo Mine Pit study area, mining freatures, and Prairie River near Taconite, Minnesota 

streamflow gaging station, Bovey, Minnesota.............................................................................................................................2

Figure 2. Graph showing water-level altitudes in Canisteo Mine Pit, Bovey, Minnesota, November 1994–June 2001 ............................3

Figures 3–4. Maps showing:

3. Location of monitoring and municipal wells in the Canisteo Mine Pit study area, Bovey, Minnesota.......................................7

4. Model segmentation for MODFLOW simulation of aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota ..............9

Figures 5–6. Graphs showing:

 5. Water-level altitudes in monitoring wells surrounding the Canisteo Mine Pit, Bovey, Minnesota, water-level altitudes 

in the Canisteo Mine Pit, and daily precipitation at North Central School Weather Bureau Station, Grand Rapids, 

Minnesota - Station Number 213303, July 1999–May 2001 ................................................................................................... 13

6. Measured versus simulated water-level altitudes in monitoring wells at a constant pit water-level altitude of 1,300 feet 

above sea level ......................................................................................................................................................................... 19

Figures 7–8. Maps showing:

7. Simulated steady-state altitude of potentiometric surface of ground-water flow and ground-water flow direction in the 

vicinity of the Canisteo Mine Pit, Bovey, Minnesota .............................................................................................................. 23

8. MODPATH flow lines for ground-water outflow from the Canisteo Mine Pit at pit water-level altitudes of 1,300 

and 1,320 feet above mean sea level, Bovey, Minnesota......................................................................................................... 25

Figure 9. Graph showing Simulated total ground-water inflow, total net ground-water inflow, outflow, total ground-water 

outflow rates from the entire pit, ground-water outflow from the pit in the Holman Lake area, the Trout Lake area, 

and the Prairie River area, at various constant pit-lake water-level altitudes for the Canisteo Mine Pit, Bovey, Minnesota ... 27

Tables

 1. Data sources used in the MODFLOW steady-state simulations of aquifers surrounding the Canisteo Mine Pit, Bovey, 

Minnesota............................................................................................................................................................................................. 10

 2. Ground-water recharge and hydraulic conductivity values for the best-fit calibration of the MODFLOW steady-state 

simulations of aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota.................................................................................. 12

 3. Monitoring well data and single-well aquifer hydraulic properties measured during 1999-2000 for aquifers surrounding the 

Canisteo Mine Pit, Bovey, Minnesota ................................................................................................................................................. 15

 4. Quarterly and annual estimates of ground-water recharge from stream-hydrograph analyses of 1968-82 discharge records 

for the Prairie River near Taconite, Minnesota gage using the U.S. Geological Survey’s Programs RORA and PART, and 

annual precipitation data from 1968-82 for the Grand Rapids Forestry Laboratory/North Central School........................................ 16

 5. Measured and simulated water-level altitudes in monitoring wells for the best-fit calibrations of the MODFLOW steady-state 

simulations surrounding the Canisteo Mine Pit, Bovey, Minnesota....................................................................................................18
iv

 Tables—Continued

6. Simulated water-level altitudes in monitoring wells and simulated ground-water flow rates into and out of the Canisteo 

Mine Pit, Bovey, Minnesota for MODFLOW steady-state simulations at various multiples of the calibrated horizontal 

hydraulic conductivity values .............................................................................................................................................................. 20

7. Simulated water-level altitudes in monitoring wells and simulated ground-water flow rates into and out of the Canisteo Mine 

Pit, Bovey, Minnesota for MODFLOW steady-state simulations at various multiples of the calibrated vertical hydraulic 

conductivity values .............................................................................................................................................................................. 21

 8. Simulated water-level altitudes in monitoring wells and simulated ground-water flow rates into and out of the Canisteo Mine Pit, 

Bovey, Minnesota for MODFLOW steady-state simulations at various multiples of the calibrated ground-water recharge rates..... 22

 9. Simulated ground-water flow rates into and out of the Canisteo Mine Pit, Bovey, Minnesota for MODFLOW steady-state 

simulations at various constant pit-lake water levels...........................................................................................................................24

10. Simulated water budgets for steady-state MODFLOW simulations for aquifers surrounding the Canisteo Mine Pit, Bovey, 

Minnesota............................................................................................................................................................................................. 26

Conversion Factors, Abbreviations, and Sea Level Datum, 

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 level nets of both the United States and Canada, formerly called Sea Level Datum 

of 1929.

Water year: The water year is October 1 through September 30 and is named for the calendar year in which it ends. 

Multiply By To obtain

inch (in.) 2.54 centimeter 

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

acre 4,047 square meter

square mile (mi2) 2.590 square kilometer 

square foot per day (ft2/day) 0.09290 square meter per day

cubic foot (ft3) 0.02832 cubic meter

gallon (gal) 0.003785 cubic meter

acre-foot (acre-ft) 1,233 cubic meter

cubic foot per second (ft3

/s) 0.02832 cubic meter per second

degrees Fahrenheit °C = (°F – 32) / 1.8 degrees Celsius
1

	











 
!




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ABSTRACT

The U.S. Geological Survey, in cooperation with the Minnesota Department of Natural Resources, conducted a study to 

characterize ground-water flow conditions between the Canisteo Mine Pit, Bovey, Minnesota, and surrounding aquifers following mine abandonment. The objective of the study was to estimate the amount of steady-state, ground-water flow 

between the Canisteo Mine Pit and surrounding aquifers at pit water-level altitudes below the level at which surface-water 

discharge from the pit may occur. Single-well hydraulic tests and stream-hydrograph analyses were conducted to estimate 

horizontal hydraulic conductivities and ground-water recharge rates, respectively, for glacial aquifers surrounding the mine 

pit. Average hydraulic conductivity values ranged from 0.05 to 5.0 ft/day for sands and clays and from 0.01 to 121 ft/day 

for coarse sands, gravels, and boulders. The 15-year averages for the estimated annual recharge using the winter records 

and the entire years of record for defining baseflow recession rates were 7.07 and 7.58 in., respectively. These recharge estimates accounted for 25 and 27 percent, respectively, of the average annual precipitation for the 1968-82 streamflow monitoring period. Ground-water flow rates into and out of the mine pit were estimated using a calibrated steady-state, groundwater flow model simulating an area of approximately 75 mi2

 surrounding the mine pit. The model residuals, or difference 

between simulated and measured water levels, for 15 monitoring wells adjacent to the mine pit varied between +28.65 and 

–3.78 ft. The best-match simulated water levels were within 4 ft of measured water levels for 9 of the 15 wells, and within 

2 ft for 4 of the wells. The simulated net ground-water flow into the Canisteo Mine Pit was +1.34 ft3

/s, and the net groundwater flow calculated from pit water levels measured between July 5, 1999 and February 25, 2001 was +5.4 ft3

/s. Simulated water levels and ground-water flow to and from the mine pit for the calibrated steady-state simulation were most sensitive to changes in horizontal hydraulic conductivity, suggesting that this characteristic is the predominant parameter 

controlling steady-state water-level and flow conditions. A series of 14 steady-state simulations at constant pit water-level 

altitudes between 1,300 and 1,324 ft was completed with the calibrated model to assess the effect of current and potential 

future pit water-level altitudes on ground-water inflow to and outflow from the mine pit. Total simulated ground-water 

inflow to the mine pit at a constant pit water-level altitude of 1,300 ft was 1.40 ft3

/s, with a total simulated ground-water 

outflow of 0.06 ft3/s discharging from the mine pit to local aquifers. Steady-state simulations indicate that total simulated 

ground-water inflow will decrease from 1.40 to 1.00 ft3

/s and total simulated ground-water outflow will increase from 0.06 

to 0.91 ft3/s as the pit water-level altitude rises from 1,300 to 1,324 ft. When the pit water-level altitude is 1,324 ft3

/s, the 

lowest pit-rim altitude, the simulated net ground-water inflow is 0.09 ft3/s. At pit water-level altitudes between 1,302 and 

1,306 ft, all but a small rate (less than 0.01 ft3

/s) of the total simulated ground-water outflow from the pit occurs in the 

Trout Lake area. At pit water-level altitudes between 1,308 and 1,324 ft, simulated outflow occurs in three outflow locations: the Trout Lake, the Prairie River, and Holman Lake areas.

INTRODUCTION

Rising water level in the Canisteo 

Mine Pit (fig. 1) and other mine pits 

on the Mesabi Iron Range, Minnesota 

is a concern of downgradient communities, land owners, and the Minnesota 

Department of Natural Resources 

(MNDNR). Concern exists that as the 

pit water-level altitude continues to 

rise, mine water may eventually discharge from the pit over land surface, 

resulting in undesirable downgradient 

erosion and localized flooding. Since 

mine adandonment in 1985, water 

level in the Canisteo Mine Pit has 

risen nearly 300 ft. Since November 

1994, the water level has risen at an 
2

T

57

N

T

56

N

T

55

N

T

54

N

R 25 W R 24 W R 23 W

6 1

31 36

6

36 31 36 31

1

36

1 6 1 6

31

31

6

31

6

31 36

6 1

31 36

6 1

31

6

Canisteo Mine Pit Lake

Little

Wabana

Lake

Inky

Lake

Bosely

Lake Clearwater

Lake Big

Sucker

Lake

Lake

Charlotte

Little

Inky Lake

Big Rain

Barrel Lake

Spring

Lake Island

Lake Hay

Lake

Horseshoe

Lake Shamrock

Lake

Reiley

Lake

Island

Lake

Little

Reiley

Lake

Dunning

Lake

Big

Diamond

Lake

Little

Diamond

Lake

Upper

Panaca

Lake

Lakes

Twin Holman

Lake

Prairie

Lake

Lower

Prairie

Lake Lower

Panaca

Lake

Shoal Lake

Bass

Lake

Nagel

Lake

Trout

Lake

Little

Sand

Lake

McKinney

Lake

Crystal

Lake

Hale

Lake

Mud Lake

Bass

Lake

Lily

Lake Round

Lake Horseshoe

Lake

Paper Mill

Reservoir

Clearwater

Lake

Blackberry

Lake

Jaques

Lake

Pokegama Lake

Rice

Lake

River

Mississippi

Creek

Trout

Swan

Swan

Swan

River

River

River

River

Prairie

River

Prairie

2

2

169

169

38

Marble

Taconite

Bovey

Coleraine

Grand

Rapids

Calumet

0 1 2 3 4 5 MILES

012345 KILOMETERS

Location of Canisteo Mine Pit study area, mining features, and Prairie River near Taconite, Minnesota streamflow

gaging station, Bovey, Minnesota.

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Mine features from Minnesota Department

of Natural Resources, 1999

Study area

Crest of Giants Range

(approximate location)

Mine pits

Tailing and settling ponds

Mine stockpiles

(includes in-pits stockpiles)

Streamflow gaging station

EXPLANATION

River

Minnesota

River

Lake Superior

94°

92°

90°

96°

48°

46°

44°

Itasca CountyStudy

Area

Mesabi Iron Range

Location Map

Mississippi

Figure 1.

47°10'

47°15'

47°20'

93°35' 93°30' 93°25' 93°20' 93°15'
3

average rate of 2.5 to 5 ft/yr (fig. 2) 

(John Adams and Joe Maki, Minnesota Department of Natural 

Resources, oral commun., 1999). During May 2001, the water-level altitude 

in the Canisteo Mine Pit was 1,301 ft. 

The lowest pit wall altitude is 1,324 

ft.

The development and abandonment of large, open-pit mines has a 

substantial effect on local water 

resources. Dewatering activities at 

large taconite (iron ore) pits form 

huge hydrologic sinks during mining, 

capturing surface and ground water 

from multiple watersheds. About 12 

billion gallons (36,800 acre-ft) of 

water is currently pumped annually 

from Mesabi Iron Range taconite pits, 

with many pits dewatering several 

thousand gallons of water per minute 

(Adams, 1994). Dewatering ceases 

with mine abandonment, but surface 

and ground waters continue to flow 

into the mine. The pit water level 

rises until a relatively steady-state 

hydrologic condition is achieved. 

Prior to achieving this steady-state 

condition, the pit water level could 

rise above the lowest pit-rim altitude, 

resulting in surface discharge of 

water. The outflow from the mine pits 

may result in flooding and water quality and erosion problems (Adams, 

1994).

In general, components of the 

water balance for an abandoned mine 

pit include direct precipitation to the 

pit, evaporation from the pit, surfacewater flow to and from the pit, and 

ground-water flow to and from the pit. 

For mine pits on the Mesabi Iron 

Range, surface-water flow can 

include overland flow and inflowing 

water from streams and other surface 

conveyances. Ground-water flow to 

and from pits occurs in bedrock aquifers, glacial aquifers, surrounding 

overburden, and tailings piles.

Often the most important and difficult dependent variable to estimate in 

an abandoned mine pit water balance 

prediction is the amount of groundwater inflow and outflow. During the 

initial stage of water-level recovery 

following mine abandonment, 

ground-water inflow is often the main 

water-balance component controlling 

pit water-level rise. Other water-balance components usually become 

important as a steady-state water balance becomes established. Mine pit 

water-level data collected by the 

MNDNR suggest that ground-water 

inflow currently is the largest and 

most significant water-balance component of the Canisteo Mine Pit (John 

Adams, Minnesota Department of 

Natural Resources, oral commun., 

PIT WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

1,330

1,320

1,310

1,300

1,290

1,280

1,270

N JJJJJJJ MMMMMMM MMMMMMM JJJJJJ SSSSSS NNNNNN 1994

1995 1996 1997 1998 1999 2000 2001

Lowest pit rim altitude 1,324 feet above sea level

Figure 2. Water-level altitude in the Canisteo Mine Pit, Bovey, Minnesota, November 1994-June 2001.
4

1998). Prediction of ground-water 

inflow and outflow rates of the Mesabi Iron Range mine pits is often difficult due to a lack of water-level data 

for glacial and bedrock aquifers surrounding the mines, and the complexity of the glacial and fractured 

bedrock aquifers. Also, large surface 

mining operations often crosscut surface- and ground-water divides, further complicating the hydrologic 

balance of the mine setting.

The U.S. Geological Survey 

(USGS), in cooperation with the 

MNDNR, conducted a study to characterize ground-water flow conditions 

between the Canisteo Mine Pit and 

surrounding aquifers following mine 

abandonment. The main objective of 

the study was to estimate the amount 

of ground-water flow between the 

Canisteo Mine Pit and surrounding 

aquifers at pit water-level altitudes 

below the level at which surfacewater discharge from the pit may 

occur. This study was part of a more 

comprehensive water-balance study 

of the Canisteo Mine Pit conducted by 

the MNDNR and supported by the 

State of Minnesota under the recommendation of the Legislative Commission on Minnesota Resources 

(LCMR). Ground-water flow estimates from this study will be used by 

MNDNR to predict the pit’s probable 

steady-state water-level altitude and 

possible surface outflow locations and 

rates (Minnesota Department of Natural Resources, 1999). This report presents results of the study and includes 

descriptions of single-well hydraulic 

tests, stream-hydrograph analyses, 

and ground-water flow simulations of 

aquifers surrounding the Canisteo 

Mine.

ACKNOWLEDGMENTS

The author gratefully thanks the 

Minnesota Department of Natural 

Resources and the Legislative Commission on Minnesota Resources for 

providing assistance needed to complete this study. Mr. Robert T. Leibfried, Mr. John L. Adams, Mr. Joseph 

R. Maki, Mr. Carl F. Rundberg, and 

Mr. John Z. Mackiewicz of the Minnesota Department of Natural 

Resources provided much assistance 

during the course of this study. Mr. 

Dave Lorenz, Mr. Chris Sanocki, and 

Mr. Brian Fischer of the U.S. Geological Survey provided assistance in 

geographic information systems (GIS) 

work needed for conducting flow simulations. Mr. Tim Cowdery, Mr. Geoff 

Delin, and Mr. Brain Chaplin of the 

U.S. Geological Survey provided 

assistance in the development of the 

GMS and MODFLOW files. Mr. Fred 

Baker of Baker Consultants, Inc. provided the code and assistance with the 

PITLAKE Package for the MODFLOW-96 Model. Attempts were 

made to simulate the mine pit using 

the PITLAKE package developed by 

Baker Consultants, Inc. (Baker Consultants, Inc., 2000). However, incompatibility between the PITLAKE code 

and the version of MODFLOW-96 

used with the GMS interface could 

not be overcome.

PHYSICAL SETTING OF 

CANISTEO MINE PIT STUDY 

AREA

The study area is approximately 75 

mi2

 surrounding the Canisteo Mine 

Pit (fig. 1). The Canisteo Mine Pit is 

a complex of abandoned natural ore 

pits located on the Mesabi Iron 

Range, Itasca County, north-central 

Minnesota, north of the cities of Coleraine, Bovey, and Taconite (fig. 1). 

The mine pit is approximately 4.8 

miles in length and has an average 

width of approximately 0.5 miles 

(Bob Leibfried, Minnesota Department of Natural Resources, written 

commun., 2001). At a surface-water 

altitude of 1,301 ft, the pit holds 

approximately 140,000 acre-ft of 

water. Mining of iron and associated 

dewatering from the pit ceased in 

1984. The pit’s watershed is approximately 4,536 acres (7.09 mi2

) and is 

part of the upper Mississippi River 

Basin, hydrologic unit 07010103 

(U.S. Geological Survey, 1974). No 

active iron-ore mining has occurred in 

the study area since 1985.

Climate in the watershed is continental: cold winters and hot summers. 

The mean annual temperature (1961-

90) at Grand Rapids, Minnesota is 

38.6 °F, and the mean annual precipitation is 27.54 in. (Minnesota State 

Climatologist, 2001). January is the 

coldest month and July is the warmest 

month. February is the driest month 

and June is the wettest month. Mean 

January temperature is 3.8 °F, and 

mean July temperature is 67.4 °F. 

Mean February precipitation is 0.54 

in., and mean June precipitation is 

4.11 in.

Land-surface altitude in the study 

area ranges from 1,260 ft along the 

Mississippi River in the southern portion to 1,550 ft along the Giants 

Range. The Giants Range is a linear 

ridge composed of Precambrian granitic and undifferentiated metasedimentary rocks that trend northeast to 

southwest, north of the Canisteo Mine 

Pit (fig. 1). This range is the major 

topographic high, with land-surface 

altitude along its’ crest varying from 

1,400 to 1,550 ft in the study area. 

Local topography and hydrology 

of the Iron Range have been affected 

by previous mining activities. 

Twenty-two percent of the land cover 

of the study area has been directly or 

indirectly affected by mining, with 

most of the open mine pits, tailings, 

and stockpiles present in the central 

mining region of the study area (fig. 

1) (Minnesota Department of Natural 

Resources, 2001b). Tailings and 

stockpiles are as high as 170 ft above 

the land surface and extend over an 

area of several square miles. Since no 

active iron ore mining is present in the 

study area, the heights and extents of 
5

these piles are relatively static. In 

addition to pits and excavations, tailings and settling ponds used previously for the treatment of mine waters 

exist throughout the mining region 

(fig. 1).

Vegetative land cover in the study 

area consists of a mix of northern 

hardwood forest and grasslands. 

Thirty-eight percent of the study area 

consists of forest, with 61 percent of 

the forest cover being deciduous forest, 24 percent being mixed-wood forest, and 15 percent being young forest 

(Minnesota Department of Natural 

Resources, 2001b). Grasslands cover 

11 percent of the study area. 

Twenty-two percent of the land 

cover of the study area is open water 

or wetlands (Minnesota Department 

of Natural Resources, 2001b). Many 

natural lakes and six abandoned mine 

pit lakes, including the Canisteo Mine 

Pit Lake, are present within the study 

area (fig. 1). Lakes in minor excavations and natural ore pits are found 

throughout the central portion of the 

study area. With the exception of the 

Canisteo Mine Pit Lake, relatively 

steady-state water levels exist in all of 

the mine pits. The remaining 7 percent of the land cover consists of 

urban and residential areas. 

Surface drainage and groundwater flow through the study area is 

generally to the north-northwest, 

north of the crest of the Giants Range 

and to the south-southeast, south of 

the Giants Range crest (Oakes, 1970). 

Surface drainage north of the crest 

flows to the Prairie River, which 

enters the study area from the north. 

The Prairie River flows west-southwest along the western edge of the 

study area and into the Prairie LakeLower Prairie Lake System, a system 

formed by the damming of the river 

south of the Lower Prairie Lake (fig. 

1). Downstream of the Lower Prairie 

Lake, the Prairie River flows to the 

Mississippi River. The Mississippi 

River flows from Grand Rapids to the 

southeast out of the study area.

South of the Canisteo Mine Pit, 

drainage is to the south and is divided 

into three watersheds: Trout Lake, 

Holman Lake, and Prairie River (fig. 

1). Trout Lake is one of the largest 

lakes in the study area, with an area of 

3.0 mi2

 (1,890 acres). Discharge 

from the lake is to the east through 

Trout Creek, which flows east-southeast into Swan River. The Swan 

River flows southeast out of the study 

area. Water from Dunning Lake, Big 

Diamond Lake, Little Diamond Lake, 

wetlands, and tributaries north of the 

Holman Lake flows into Holman 

Lake from the northwest during portions of the year. The area of Holman 

Lake is 0.2 mi2

 (146 acres). Water 

entering Holman Lake discharges into 

the Swan River upgradient of the 

Trout Creek/Swan River confluence. 

Glacial drift covers much of the 

study area, with the exception of bedrock outcrops along the Giants 

Range. Three major morainal till 

units and associated glaciofluvial outwash deposits exist, formed during 

the Wisconsin glaciation ice advances 

from the north and west of the study 

area (Winter, 1971). Total drift thicknesses range from zero along portions 

of the Giants Range to more than 300 

ft in the southern part of the study 

area and in bedrock valleys. The 

stratigraphically lowest till unit, the 

basal till, is a dark-greenish and 

brownish-gray till that is sandy, silty, 

clayey, and calcareous (Winter, 

1971). The basal till is found mainly 

in the southern portion of the study 

area. The middle boulder and upper 

surficial till units are found throughout the study area. The boulder till 

ranges widely in color from gray to 

yellow, and consists of sands and 

silts, with abundant cobbles and boulders (Winter, 1971). This till tends to 

be the thickest unit in the study area. 

The surficial till is brown in color; 

sandy, silty, and calcareous; and is 

generally less than 30 ft thick in the 

study area.

Glaciofluvial outwash deposits lie 

stratigraphically between surficial and 

boulder tills, and often lie between the 

boulder and basal till or bedrock (Winter, 1973a). These outwash deposits 

consist largely of sands, gravels, and 

boulders. Glaciofluvial outwash deposits between the surficial and boulder 

tills are the thickest and most continuous outwash deposits in the study area, 

often greater than 50 ft thick and sometimes greater than 100 ft in portions of 

buried valleys (Winter, 1973a). These 

outwash deposits consist of fine–

grained sands throughout much of the 

study area, but are highly transmissive, 

coarse-grained sands, gravels, and 

boulders in buried valleys, and at other 

locations where the bedrock surface is 

low. The glaciofluvial sediments found

below the boulder till are fairly continuous south of the Canisteo Mine Pit. 

These sediments are poorly sorted and 

are generally less than 50 ft thick, but 

are greater than 100 ft thick locally in 

buried bedrock valleys and in the vicinity of Trout Lake (Winter, 1973a).

Clays, silts, and sands reworked and 

redeposited by Glacial Lake Aitkin 

overlie surficial tills near Trout Lake, 

and in the western and southern portion 

of the study area (Winter 1973a).

Iron ore was extracted from the 

Canisteo Mine and other mines from a 

narrow belt of iron-rich bedrock strata 

known as the Biwabik Iron Formation, 

which trends to the northeast for 

approximately 120 miles across northeast Minnesota (Morey, 1972). The 

Biwabik Iron Formation is overlain and 

bounded to the south by the Virginia 

Formation. The Virginia Formation 

consists of argillites, siltstones, and 

graywackes, and is underlain and 

bounded to the north by the Pokegama 

Quartzite. The Precambrian granitic 

rocks that form the Giants Range 

underlie the Pokegama Quartzite. Cretaceous sandstones, iron formation, and 

shales overlie the Precambrian rocks in 
6

portions of the study area. Bedrock 

valleys have been identified in the 

study area (Bruce A. Bloomgren, 

Minnesota Geological Survey, oral 

commun., 2001), but the extent and 

depth of these valleys is poorly 

defined due to the insufficient spacing 

of wells and boreholes. 

Present ground-water withdrawals 

are mainly from glaciofluvial aquifers 

through municipal, small industrial, 

and domestic wells. In 1999, the city 

of Coleraine (population 1,110) (U.S. 

Census Bureau, 2002) withdrew 51.1 

million gallons of water from two 

wells screened in buried glacial sands 

and gravels (Minnesota Department 

of Natural Resources, 2001c) (fig. 3). 

The city of Bovey (population 662) 

(U.S. Census Bureau, 2002) withdrew 

32 million gallons of water from a 

well screened in buried glacial sands 

and gravels (Minnesota Department 

of Natural Resources, 2001c) (fig. 3). 

The city of Taconite (population 315) 

(U.S. Census Bureau, 2002) withdrew 

11.7 million gallons of water from 

two wells completed in the Biwabik 

Iron Formation and other Precambrian 

bedrock (Minnesota Department of 

Natural Resources, 2001c) (fig. 3). 

Domestic wells in the study area 

extract water mostly from glaciofluvial aquifers, with few households 

using the Biwabik Iron Formation for 

a source of water.

METHODS OF 

INVESTIGATION

Ground-water flow rates into and 

out of the Canisteo Mine Pit were estimated by a steady-state, numerical, 

ground-water flow model. Once the 

steady-state model was calibrated to 

water levels measured in 15 monitoring wells, it was used to examine 

ground-water flow rates into and out 

of the mine pit at various potential 

future pit water-level altitudes. Single-well hydraulic tests and streamhydrograph analyses were used to 

estimate hydraulic conductivities and 

ground-water recharge rates, respectively, for glacial aquifers surrounding 

the mine pit. These estimates were 

used as initial input values for the 

model.

SINGLE-WELL HYDRAULIC 

TESTS

Single-well hydraulic tests and 

slug tests were performed during 

1999-2000 in 14 of the 18 monitoring 

wells surrounding the mine pit (fig. 

3). The MNDNR installed 16 of these 

18 monitoring wells to monitor 

ground-water levels, characterize the 

surficial geology, and assess hydraulic 

properties of glacial aquifers surrounding the mine pit. A total of 21 

pumping tests and 20 slug tests were 

performed in the 14 wells. A Grundfos Redi-Flo2 submersible pump with 

a check valve was used to lower water 

levels during the pumping tests, 

whereas a PVC-cased, sand-filled 

slug was placed in the wells to displace water during the slug tests. A 

Druck PDCR 830 (0-10 psi) pressure 

transducer with a Campbell Scientific 

CR-10 data logger and/or a Solinst 

Levelogger pressure transducer/data 

logger system were used to record 

water levels during the pumping and 

slug tests. The length of these tests 

varied from less than one minute to 17 

hours.

Water-level data from the pumping 

and slug tests were analyzed using the 

AQTESOLV for Windows, version 

2.16, program (Duffield, 1995). 

Transmissivity values were obtained 

from analysis of water levels during 

the pumping tests using the Theis 

(1935) and Cooper and Jacob (1946) 

curve-matching methods. The recovery periods during the pumping tests 

were only analyzed if the check valve 

in the pump prevented water in the 

pump’s hose from flushing down into 

the well after the pump was shut off. 

The Bouwer and Rice (1976) method 

was used to determine hydraulic conductivity values from the water-level 

recovery data during both the pumping and slug tests. 

STREAM-HYDROGRAPH 

ANALYSES

Daily stream discharge records 

during 1968-82 for the Prairie River 

near Taconite, Minnesota streamflow 

gaging station were used in streamhydrograph analyses to determine 

ground-water recharge estimates for 

surficial aquifers in the study area 

(fig. 1). This discontinued gage is the 

only stream gage located in or near 

the study area, and therefore offered 

the best opportunity to assess groundwater recharge rates using daily 

streamflow records with streamhydrograph analysis methods.

Discharge records were analyzed 

using the USGS RECESS and RORA 

Programs (Rutledge, 1998). The 

RECESS Program was used to select 

periods of time in the discharge record 

when streamflow was considered to 

be solely from ground-water discharge, and use these portions of the 

record to determine a best-fit equation 

for the rate of recession as a function 

of the logarithm of flow. Because the 

recession rate values can be affected 

by ground-water evapotranspiration 

(Rutledge, 2000), best-fit recession 

equations were determined for winter 

records, when most of the streamflow 

record is considered to be solely from 

ground-water recharge, and for the 

entire annual streamflow record. 

Coefficients of these best-fit equations were used to derive a master 

recession curve of streamflow recession. The RORA Program uses the 

derived master recession curve with 

the recession-curve-displacement 

method to estimate the ground-water 

recharge for each streamflow peak 

(Rutledge, 1998). Annual and quarterly estimates of the mean rates of 

ground-water recharge were calcu-
7

T

56

N

T

55

N

R 25 W R 24 W

36 31

1 6

Little

Diamond

Lake

Buckeye

Lake

Trout Lake

Mud Lake

Holman Lake

Trout

Creek

Swan

Swan

River

River

Canisteo Mine Pit Lake

Taconite

Holman

Bovey

Coleraine

47°14'

47°16'

47°18'

47°20' 93°28' 93°26' 93°24' 93°22'

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Base from U.S. Geological Survey digital data 1:100,000 1972

U.S. Albers Equal Area Projection

standard parallels 29°30' and 45°30', central meridian -93°30'

Location of monitoring and municipal wells in the Canisteo Mine Pit study area, Bovey, Minnesota.

Monitoring well installed in 1999-2000. Number is site identifier

Location of two monitoring wells that existed prior to June 1999. Number is site identifier

Municipal well

EXPLANATION

Figure 3.

3

4

16

5

17

8

9

11

15

14

13

18

12

10

6, 7

2 1
8

lated using both the winter and entire 

annual records in RORA for each year 

of the 1968-82 record.

GROUND-WATER FLOW 

MODEL OF THE CANISTEO 

MINE PIT STUDY AREA

A three-dimensional, numerical 

ground-water flow model was developed, incorporating an area of approximately 75 mi2

 surrounding the 

Canisteo Mine Pit (fig. 4). The USGS 

Modular Ground-Water Flow Model, 

commonly referred to as MODFLOW-96, was used to simulate 

ground-water flow conditions surrounding the mine site. MODFLOW96 is a modular, three-dimensional, 

finite-difference, ground-water-flow 

model that simulates ground-water 

flow in multiple aquifers (Harbaugh 

and McDonald, 1996). The steadystate representation of the study area 

was done using the BASIC, BCF, 

General-Head, River, Well, Drain, 

Recharge, and Preconditioned Conjugate Gradient (PCG2) Solver modules 

of MODFLOW-96. The MODFLOW-96 simulations were developed, run, and analyzed using a 

graphic-user interface called the 

Groundwater Modeling System 

(GMS) (U.S. Department of Defense, 

1998). The USGS MODPATH, Version 3 particle-tracking, post-processing package (Pollock, 1994) was used 

to compute ground-water flow paths 

originating from the pit at pit waterlevel altitudes of 1,300 and 1,320 ft 

based on water-level outputs from the 

MODFLOW simulations at these two 

pit water levels.

Simulation of ground-water flow 

conditions surrounding the Canisteo 

Mine Pit was undertaken using a fivestep approach: (1) compile existing 

hydrologic and geologic data needed 

to construct the model; (2) discretize 

the compiled data; (3) calibrate the 

model through the comparison of simulated and measured ground-water 

levels and flow rates; (4) perform sensitivity analyses on the calibrated 

model, assessing the effect of groundwater recharge and hydraulic conductivity on ground-water levels and flow 

rates; and (5) run predictive simulations of future ground-water levels 

under potential future elevated pit 

water levels. 

Data Sets Used

A variety of data sources were 

used to represent various hydrologic 

features in the model. The properties 

needed in the model to represent these 

features include the extent and thickness of aquifers and confining units; 

the boundaries, water-level altitudes, 

and depths of surface-water bodies 

that affect ground-water flow, and 

well withdrawal rates from aquifers. 

Table 1 is a list of data sources used in 

the construction of the model. This 

data consisted of geologic logs, GIS 

data sets, water-level altitudes, mine 

pit dimensions, and municipal well 

pumping records.

Geologic logs from existing 

municipal, domestic and monitoring 

wells and previously drilled auger 

holes, were used to develop representations of glacial and bedrock units in 

the model. The well logs were 

obtained from water-well records in 

the Minnesota Geological Survey’s 

(MGS) County Well Index (table 1). 

Existing auger-hole data were collected from the USGS Ground-Water 

data base and MNDNR existing 

records. Geologic logs were entered 

into GMS, where the layering of the 

simulated aquifers were constructed 

through interpolation between the 

logs. Interpolation was done referencing geologic maps and publications by 

Oakes (1970), and Winter (1971, 

1973a, and 1973b), and bedrockdepth maps developed by MNDNR 

using collected borehole data and 

results from seismic surveys conducted in the study area (Petersen and 

Berg, 2000). Based on this geologic 

interpolation method, a three-dimensional model representing the geology 

of the study area was created.

A series of GIS data sets were used 

to identify and represent hydrologic 

features and processes occurring in 

the study area (table 1). Data sets for 

perennial wetlands, lakes, and rivers 

were obtained from the National Wetland Inventory data base (U.S. Fish & 

Wildlife Service, 1994). Included 

were natural and man-made lakes, 

such as tailings ponds, settling ponds, 

and mine pits. Water-level altitude 

data for the perennial wetlands, rivers, 

and most of the lakes used in the 

model were obtained directly from 

these data sets. Water-level altitude 

data for 15 lakes, including 4 mine 

pits, were obtained from MNDNR 

hydrologists and the MNDNR LakeLevel data base (Minnesota Department of Natural Resources, 2001a) 

(table 1). Dimensions for the Canisteo 

Mine Pit were obtained from GIS data 

sets developed by the MNDNR from 

altitude data obtained in the Mesabi 

elevation project (Minnesota Department of Natural Resources, 1999). 

Pumping records for municipal wells 

in the study area were obtained from 

the MNDNR Water-AppropriationPermit data base (Minnesota Department of Natural Resources, 2001c). A 

data set representing areal recharge to 

the surficial layer of the model was 

developed using USGS recharge rate 

data obtained from streamhydrograph analysis (table 1).

Discretization of the Model

A three-dimensional, numerical 

ground-water flow model was constructed based on a conceptual model 

of hydrogeology in the study area. 

The conceptual model was created 

based on a knowledge of the hydrogeologic setting, aquifer characteristics, distributions and amounts of 

ground-water recharge and discharge, 

and aquifer boundaries. 
9

T

57

N

T

56

N

T

55

N

T

54

N

R 25 W R 24 W R 23 W

6 1

31 36

6

36 31 36 31

1

36

1 6 1 6

31

31

6

31

6

31 36

6 1

31 36

6 1

31

6

Little

Wabana

Lake

Inky

Lake

Bosely

Lake Clearwater

Lake Big

Sucker

Lake

Lake

Charlotte

Little

Inky Lake

Big Rain

Barrel Lake

Spring

Lake Island

Lake Hay

Lake

Horseshoe

Lake Shamrock

Lake

Reiley

Lake

Island

Lake

Little

Reiley

Lake

Dunning

Lake

Big

Diamond

Lake

Upper

Panaca

Lake

Lakes

Twin Holman

Lake

Prairie

Lake

Lower

Prairie

Lake Lower

Panaca

Lake

Shoal Lake

Bass

Lake

Nagel

Lake

Trout

Lake

Little

Sand

Lake

McKinney

Lake

Crystal

Lake

Hale

Lake

Mud Lake

Bass

Lake

Lily

Lake Round

Lake Horseshoe

Lake

Paper Mill

Reservoir

Clearwater

Lake

Blackberry

Lake

Jaques

Lake

Pokegama Lake

Rice

Lake

River

Mississippi

Creek

Trout

Swan

Swan

River

Swan River

River

Prairie

River

Prairie

Swan

River

River

2

2

169

169

38

Marble

Taconite

Bovey

Coleraine

Grand Rapids

47°10'

47°15'

47°20'

93°35' 93°30' 93°25' 93°20' 93°15'

Canisteo Mine Pit Lake

Model segmentation for MODFLOW simulation of aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota.

EXPLANATION

Model boundary

General head boundary cell representing perennial

wetlands, streams, or lakes

Constant head boundary cell representing water in

the Canisteo mine pit

River segment cell representing rivers (ground-water/

surface-water interaction)

Municipal well

Drain representing surface outlet from Canisteo mine pit

Figure 4.

0 1 2 3 4 5 MILES

012345 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection
10

A “true-layer” approach was 

undertaken to define layering represented by the model, explicitly defining altitudes and aquifer hydraulic 

properties of cells in each layer based 

on the three-dimensional model. The 

study area was discretized into rectangular finite-difference grid cells 

within which the hydrogeologic properties were homogeneous and isotropic. Ground-water flow within the 

aquifers was simulated using a blockcentered approach, where flow was 

calculated between discretized cells 

based on head conditions at the cell’s 

central nodes (McDonald and Harbaugh, 1988). Hydrogeologic properties and stresses were applied to 

model cells assuming that the 

assigned properties and stresses represent average conditions within the 

cells. Starting hydraulic head values 

in the cells were set at 1,324 ft in each 

of the layers, and were later modified 

to reflect head values calculated by 

early iterations of the model.

The three-dimensional, finite-difference grid used in the model representation of the study area was evenly 

spaced, consisting of 222 rows and 

200 columns. The dimensions of the 

grid cells were 328 ft (100 m) along 

rows and along columns. The model 

was divided vertically into seven layers, based generally on the hydrogeologic units and depth of the Canisteo 

Mine Pit. All of the layers were represented as either confined or unconfined, with their transmissivities 

varying with saturated thicknesses. 

Simulation of flow between the cells 

and the layers was dependent on the 

cellular dimensions, thicknesses, and 

hydraulic conductivities between 

adjacent cells and layers. A detailed 

discussion of flow between cells and 

layers in the model can be found in 

McDonald and Harbaugh (1988).

The horizontal boundaries of the 

model were, for the most part, 

imposed along a series of perennial 

rivers, streams, lakes, and wetlands, 

that were located a sufficient distance 

from the Canisteo Mine Pit to have 

minimal effect on ground-water flow 

to and from the mine pit (fig. 4). The 

boundaries were present in each of the 

seven layers in the model, and were 

no-flow boundaries. Cells outside of 

the model boundary were inactive. 

The model area was bounded to the 

north and northwest by the Prairie 

River, and bounded to the west by the 

MacDougal Bay-Prairie Lake-Lower 

Prairie Lake System and the Prairie 

River. The southwestern portion of 

the model was bounded by the Mississippi River. The southeastern boundary of the model consisted of 

perennial wetlands and three lakes; 

Blackberry, Clearwater, and Round 

Lakes. The model was bounded to the 

east by the Swan River, Twin Lakes, 

and a series of lakes and perennial 

wetlands. Sucker Brook was the 

northeast boundary of the model. The 

bottom of the lowest layer in the 

model was simulated as a no-flow, 

vertical boundary. The amount of vertical flow across the bottom of the 

lowest layer in the model was 

assumed to be small relative to the 

amount of horizontal flow. 

The hydrogeology of the study 

area was represented in the model by 

three hydrogeologic units: (1) glaciofluvial sediments (sands, gravels and 

boulders) present in two layers of the 

model; (2) glacial clays and tills (mixture of clays, fine sands, gravels and 

Table 1. Data sources used in the MODFLOW steady-state simulations of aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota

Data Type of data Source of data Type of information Date compiled

Wells and auger holes Geologic logs

(interpolated geology)

Minnesota Geological Survey’s County Well 

Index, U.S. Geological Survey GroundWater data base, Minnesota Department of 

Natural Resources, Divisions of Minerals 

and Waters records

Location, geologic description, stratigraphyNovember 2000

Wetlands GIS data sets U.S. Fish & Wildlife Service, National Wetlands Inventory data baseLocation, area, water-level 

altitude

January 2001

Lakes GIS data sets U.S. Fish & Wildlife Service, National Wetlands Inventory data baseLocation, area, water-level 

altitude

January 2001

Rivers (polygons) GIS data sets U.S. Fish & Wildlife Service, National Wetlands Inventory data baseLocation, area, water-level 

altitude, stage

January 2001

Rivers (Arc and Node) GIS data sets U.S. Fish & Wildlife Service, National Wetlands Inventory data baseLocation, area, water-level 

altitude, stage

January 2001

Lake Water-level altitude Minnesota Department of Natural Resources, 

Division of Waters, Lake Level data base

Altitude for eleven lakes June 1999

Canisteo Mine Pit Dimensions Minnesota Department of Natural Resources, 

Division of Minerals records

Location, area, altitude January 2001

Areal Recharge GIS data sets Developed from U.S. Geological Survey data Location, recharge rate January 2001

Municipal wells of Taconite, 

Bovey, and Coleraine

Pumping records Minnesota Department of Natural Resources, 

Division of Waters, Water-AppropriationsPermit data base

Annual pumping rates January 2001
11

boulders) present in three layers of the 

model; and (3) bedrock, including 

Biwabik Iron Formation, Virginia 

Formation, Pokegama Quartzite, Precambrian granitic, and Cretaceous 

sandstones, iron formation, and shales 

present in two layers of the model. 

Initial hydraulic conductivities were 

specified for each of three hydrogeologic units based on pumping and slug 

test analyses conducted during this 

study, and hydraulic conductivity values published by Winter (1973a). 

All lakes and perennial wetlands 

were represented in the model as general-head boundaries (fig. 4), using 

the general-head module in MODFLOW-96. Lakes and perennial wetlands were segmented to individual 

cells in the finite-difference grid. A 

total of 11,654 general-head boundary 

cells were specified in the model. 

With general-head boundaries, flow 

into and out of a cell is portioned 

based on the hydraulic-head difference between the head in the cell and 

the assigned general head, and on a 

conductance term (McDonald and 

Harbaugh, 1988). In each of the 

model cells specified as a generalhead boundary, the conductance for 

the boundary is defined as the hydraulic conductivity of the bed material 

divided by the vertical thickness of 

the lake or wetland bed material, multiplied by the area of the lake or wetland in the cell. A hydraulic 

conductivity of 0.07 ft/day and a vertical thickness of 3.28 ft were used in 

calculating the conductance term in 

each of the general-head boundary 

cells. Both hydraulic conductivity and 

vertical thickness of lake and wetland 

bed material can be highly variable 

for lakes and wetlands. The selected 

hydraulic conductivity value represents a low value for the range of 

hydraulic conductivity values for glacial tills obtained from single-well 

hydraulic tests in this study and for 

hydraulic conductivity values determined for lake-bed material of Shingobee Lake, Minnesota (Kishel and 

Gerla, 2002). Many of the lakes and 

wetlands in the study area lie above 

glacial till, so a hydraulic conductivity 

value for the glacial till was used for 

the lake-bed material. An assumed 

value of 3.28 ft was used to represent 

an average thickness for the bed material for lakes and wetlands in the area.

Lake and wetland areas and altitudes 

from the National Wetland Inventory 

GIS data sets were used for the areas 

and head values, respectively, for the 

general head boundaries representing 

the lake and perennial wetlands segments. 

Selected streams and rivers not 

simulated as part of wetlands were 

simulated using the river module of 

MODFLOW-96. The river module is 

used to simulate flow between the surface-water features and ground-water 

systems (McDonald and Harbaugh, 

1988). Streams and rivers were segmented into reaches, with each reach 

corresponding to individual cells in 

the finite-difference grid (fig. 4). A 

total of 791 river cells were specified 

in the model. Flow between the river 

reaches and the ground-water flow 

systems was calculated for each cell 

based on a conductance term and the 

head difference between the river altitude and the aquifer (McDonald and 

Harbaugh, 1988). In the river module, 

the conductance term is defined as the 

hydraulic conductivity divided by the 

vertical thickness of the river-bed 

materials, multiplied by the surficial 

area of the river bed in that cell 

(McDonald and Harbaugh, 1988). A 

hydraulic conductivity of 0.07 ft/day 

and a vertical thickness of 3.28 ft 

were used for the river-bed hydraulic 

conductivity and vertical thickness, 

respectively. Many of the streams and 

rivers in the study area lie above glacial till, so a hydraulic conductivity 

value for the glacial till was used. An 

assumed value of 3.28 ft was used to 

represent an average thickness for the 

bed material for streams and rivers in 

the area. Surficial areas and altitudes 

for the river segments were obtained 

from the National Wetland Inventory 

GIS data sets. River stage values 

were assumed to be 6.56 ft above the 

altitude of the riverbed. The stage of 

rivers varies seasonally with precipitation rates, and therefore, the chosen 

river stages were assumed to represent 

average stage values for the rivers. 

A specified-flux boundary was 

used to represent areal recharge to the 

surficial layer of the model using the 

recharge module in MODFLOW-96. 

Areal recharge to the surficial layer 

represents the net difference between 

precipitation and evapotranspiration 

losses occurring above the water 

table. Initial recharge rates were proportioned based on results from 

stream hydrograph analyses and geology in the surficial layer of the model 

(table 2). The largest recharge rates 

were simulated where glaciofluvial 

sediments were present on the land 

surface, and the smallest recharge 

rates were simulated where glacial 

clays and tills and bedrock were 

present at the land surface.

Pumping from the five municipal 

wells in the study area was simulated 

in the model using the well module in 

MODFLOW-96 (fig. 4). Water withdrawals from municipal wells for the 

cities of Taconite, Bovey, and Coleraine were simulated. In the simulation for each well, water was 

withdrawn from the aquifer at a specified rate during the simulation, where 

the rate was independent of the cell 

area and head (McDonald and Harbaugh, 1988). Flow rates for the simulated wells were based on an average 

of annual pumping rates for 1984-99. 

Annual pumping rates for the municipal wells were obtained from the 

MNDNR Water Appropriations Permit data base (Minnesota Department 

of Natural Resources, 2001c). The 

two municipal wells for the city of 

Taconite were simulated as two separate wells pumping 2,190 ft3/day each 
12

from bedrock in the lowest two layers 

in the model. Pumping from the 

Bovey municipal well was simulated 

as a single well pumping a total of 

13,738 ft3/day from sand in two layers 

of the model. The two municipal 

wells for the city of Coleraine were 

simulated as a single well in a single 

model cell, since little is known about 

what proportion of the city’s water is 

being pumped from each well. A total 

pumping rate of 26,839 ft3

/day was 

used for the simulated Coleraine well, 

pumping water from glaciofluvial 

sediments in two layers of the model.

The Canisteo Mine Pit was represented in the model as a series of 

highly conductive, constant-head 

cells. This approach has been used by 

researchers in simulations of several 

other mine pits and has been shown to 

be valid (Chung and Anderson, 1998). 

An initial hydraulic conductivity 

value of 3,280 ft/day was used for the 

pit constant-head cells (table 2). This 

initial value was used because this 

large value allows water levels in the 

pit cells to be relatively consistent and 

to respond similar to a lake. During 

calibration, a constant-head value of 

1,300 ft, representing the pit waterlevel altitude on January 4, 2001, was 

used for each of the pit cells. A rate 

of 0.0014 ft/day was used to represent 

the recharge (amount of precipitation 

minus evaporation) entering the pit 

(table 2).

The drain module of MODFLOW96 was used in two mine pit cells to 

simulate surface outflow from the pit 

above the lowest pit-rim altitude (fig. 

4). Each simulated drain removed 

water from the pit cell at a rate based 

on a specified conductivity value and 

the difference between the head in the 

pit cell and a specified-fixed head. A 

fixed head of 1,324 ft, representing 

the lowest pit-rim altitude, was 

applied to the drains. A hydraulic 

conductivity of 32,800 ft/day was 

used for both of the drains.

Within the model boundaries, 

model cells were allowed to wet and 

rewet, using the following linear 

equation with a wetting factor of 1.0 

and a wetting iteration interval of 1:

h = BOT + WETFCT (hn - BOT)

where 

h is the head at a cell,

BOT is the altitude of the aquifer bottom,

WETFCT is the wetting factor, a factor that is initially established at a cell 

when it is converted from dry to wet, 

and

hn is the head at the neighboring cell 

that causes the cell to wet (McDonald 

and others, 1991).

This equation is a simplification of 

flow through the vadose zone because 

the model does not simulate the 

effects of the capillary fringe. The 

Preconditioned Conjugate Gradient 

(PCG2) solver module was used with 

the modified incomplete Cholesky 

preconditioning option (relaxation 

parameter = 1.0) to solve the matrix 

equations produced by the model 

(Hill, 1990). This module was 

selected because the preconditioned 

conjugate-gradient method has been 

shown to be an efficient iterative 

method for solving difficult modeling 

problems (Meijerink and van der 

Vorst, 1977). 

Model Calibration, Sensitivity 

Analyses, and Simulations

Model calibration involved adjusting initial estimates of aquifer properties and boundary conditions by trialand-error until simulated steady-state 

water levels and flows acceptably 

match measured values. For this 

study, recharge rates and hydraulic 

conductivities were the only inputs 

adjusted during calibration. Storage 

terms were not included in the simulations. Once the model was calibrated, 

a sensitivity analysis was performed 

using the model to determine the 

effects of changes in hydraulic conductivity and ground-water recharge 

on simulated water levels and flows 

and identify important parameters 

governing water levels and flows in 

the system. Finally, a series of 14 

steady-state simulations were run to 

determine ground-water inflow and 

outflow rates from the Canisteo Mine 

Pit to the surrounding aquifers. 

Model calibration was accomplished by visually and statistically 

matching simulated hydraulic heads 

to measured water levels measured on 

January 4, 2001 in 15 monitoring 

wells surrounding the mine pit and 

comparing simulated and calculated 

flow rates to the mine pit. Water levels on January 4, 2001 were chosen 

because they appeared to be the most 

stable. Therefore, they were assumed 

to most accurately represent steadystate conditions. Water levels in the 

monitoring wells were recorded 

between July 1999 and May 2001 

(fig. 5). Water levels in most of the 

wells tended to follow seasonal flucTable 2. Ground-water recharge and hydraulic conductivity values for the best-fit calibration of the MODFLOW steady-state simulations of 

aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota

 [All values are in feet per day]

Type of simulated cell Ground-water recharge Hydraulic conductivity

Initial Final Inital Final

Glaciofluvial sediments 1.6 x 10-3 1.1 x 10-3 6.6 13.1, 32.8

Glacial tills 1.6 x 10-4 3.9 x 10-6 7.0 x 10-2 7.0 x 10-2

Bedrock 1.6 x 10-4 2.3 x 10-4 7.0 x 10-3 7.0 x 10-3

Pit 1.4 x 10-3 1.4 x 10-3 3.28 x 103 3.28 x 104
13

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

PRECIPITATION, IN INCHES

1,386

1,295

1,297

1,304

1,365

1,370

1,302

1,304

1,306

1,384

1,293

1,302

1,360

1,300

2.5

1,382 1,291

1,300

1,355

1,298

2

0.5

1,380

1,289

1,298

1,350

1,296

1.5

1,378

1,287

1,296

1,345

1,294

1

1,376

1,285

1,294 1,340

1,292

1,374

1,283

1,281

1,279

1,292 1,335

1,290

1,288 0

Water-level altitudes in monitoring wells surrounding the Canisteo Mine Pit, Bovey, Minnesota, water-level altitudes

in the Canisteo Mine Pit, and daily precipitation at North Central School Weather Bureau Station, Grand Rapids, Minnesota -

Station Number 213303, July 1999-May 2001 (Well numbers shown in figure 3).

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

1999 2000 2000 2001 1999 2001

Monitoring Well North of Western Portion of Canisteo Mine Pit

A

Monitoring Wells South of Western Portion of Canisteo Mine Pit

B

Monitoring Wells South of Central Portion of Canisteo Mine Pit

C

Monitoring Wells South of Central and East Central Portion of

Canisteo Mine Pit

D

Monitoring Wells South of Northeastern portion of Canisteo Mine Pit

E

Daily Precipitation at North Central School Weather Bureau Station,

Grand Rapids, Minnesota - Station Number 213303

F

Well 8

Well 9

Well 10

Well 11

Well 13

Well 14

Well 1

Well 2

Well 3

Well 4

Well 5

Well 16

Well 17

Well 12

Canisteo Mine Pit

Well 18

Figure 5.
14

tuations in response to precipitation 

and snowmelt, with the level of 

response varying with well depth 

(table 3) and aquifer properties. For 

example, water levels in wells 1 and 2 

declined, whereas water levels in well 

10 rose during the monitoring period 

(fig. 5). The water-level rise in well 

10 seemed to correlate with the waterlevel rise in the mine pit, indicating a 

strong hydraulic connection. In general, water levels in the monitoring 

wells were stable between December 

2000 and February 2001 during the 

1999-2001 monitoring period. 

Prior to installation of the 

MNDNR monitoring wells, little 

other ground-water level data existed 

in the study area. Only two monitoring wells (6 and 7, fig. 3), were 

located in the vicinity of the Canisteo 

Mine Pit prior to the installation of the 

15 monitoring wells. These wells 

were only 20 ft deep (table 3), and little water-level data were available. 

Water levels for domestic wells 

recorded during installation were 

available for water wells in the MGS 

County Well Index data base. However, the data base did not contain 

temporal water-level data. A piezometric contour map published by 

Oakes (1970) was used as a reference 

for generally assessing the simulated 

water-table contours.

During calibration, the simulated 

net ground-water flow rate into the 

Canisteo Mine Pit, at a pit water-level 

altitude of 1,300 ft, was compared to a 

net flow rate determined from waterlevel altitudes measured between July 

5, 1999 and February 25, 2001. 

Water-level altitudes in the mine pit 

rose from 1,295 ft to 1,300 ft for this 

period with a net water-volume 

change of 6,459 acre-ft in the mine 

over a 600-day period (fig. 2). The 

net flow rate for this 600-day period 

was 5.4 ft3

/s. This method of calibration of flow is only an approximate 

calibration because the match is 

between transient flow data and 

steady-state simulated flow data.

Once the model was calibrated, 15 

simulations were performed to assess 

the sensitivity of the model to changes 

in ground-water recharge rates and 

hydraulic conductivity. The purpose 

of these sensitivity analyses is to provide an understanding of the importance of various parameters on 

simulation results and how data limitations related to these parameters 

may affect modeling results. Four of 

the 15 simulations were conducted 

under various ground-water recharge 

rates, varying the recharge rates by 

factors of 0.5, 0.75, 1.25, and 1.5 

times the rates of the calibrated 

model. This range in recharge rates 

approximates the range in annual 

ground-water recharge estimates produced using stream-hydrograph methods (table 4). In the other 11 

simulations, horizontal hydraulic conductivity values were varied by factors of 0.2, 0.5, 2, 5 and 10 times the 

values of the calibrated model, and 

vertical hydraulic conductivity values 

were varied by factors of 0.1, 0.2, 0.5, 

2, 5 and 10 times the values of the calibrated model. Sensitivity analysis 

runs were compared to the calibrated 

model by observing changes in water 

levels in the monitoring wells and 

total ground-water flow rates into and 

out of the Canisteo Mine Pit.

Fourteen steady-state simulations 

were conducted to assess the effect of 

current and potential future pit waterlevel altitudes on ground-water inflow 

to and outflow from the Canisteo 

Mine Pit. Simulations were run at 

various constant values for the mine 

pit water-level altitude. These constant-head values were varied by1 or 

2 ft increments from 1,300 to 1,324 ft. 

Ground-water inflow rates were 

determined for the entire mine pit 

through summation of inflows to 

model pit cells along the simulated 

pit-aquifer boundary. Outflow rates 

were determined for the entire mine 

pit and for three areas along the south 

pit-aquifer boundary: the Holman 

Lake area, the Prairie River area, and 

the Trout Lake area. GMS was used 

to generate the simulated altitude of 

potentiometric surface for the MODFLOW simulation at the pit waterlevel altitude of 1,300 ft. 

The USGS MODPATH package 

was used to compute ground-water 

flow paths originating from the mine 

at pit water-level altitudes of 1,300 

and 1,320 ft for MODFLOW simulations. MODPATH computes the position of water particles at points in 

time and total travel time for each particle. Using MODPATH and pit 

water-level altitudes of 1,300 and 

1,320 ft, starting locations for hypothetical water particles were placed 

along the boundary of the simulated 

mine pit in each of the model layers. 

The particles were then tracked forward in time through the flow field 

until they reached a sink (discharge 

point). Sinks included lakes, pumped 

wells, and wetlands.

Model Limitations and Accuracy

The numerical ground-water flow 

model is a simplification of a complex 

glaciated terrain and flow system 

located in a fractured bedrock, mining 

region. The accuracy of the simulations is limited to the accuracy, 

amount, and distribution of the data 

used to describe the hydrologic 

parameters of the flow system. These 

parameters include the hydraulic 

properties of the aquifers and confining units, areal recharge rates, and 

hydrologic boundary conditions. 

Parameters determined for the model 

during calibration are not unique. 

Due to parameter correlation, different combinations of model input 

could produce similar results.

The hydraulic conductivity, 

ground-water level, and flow data 

used in model calibration were measured in glacial drift in the vicinity of 

the Canisteo Mine Pit. Therefore, the 
15

Table 3. Monitoring well data and single-well aquifer hydraulic properties measured during 1999-2000 for aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota

 [ft2/day, square feet per day; ft/day, feet per day; ---, no value]

Monitoring 

well number 

(figure 3)

Number of 

pumping 

tests

Number of 

slug tests

Well depth 

(feet below 

land surface)

Geology at well screen

Average transmissivity (ft2/day) Average hydraulic conductivity (ft/day)

Single-well 

pumping test 

(Theis,1935)

Single-well 

pumping test 

(Cooper-Jacob, 

1946)

Single-well 

pumping test 

recovery 

(Bouwer & Rice, 

1976)

Slug test, 

recovery 

following slug 

insertion 

(Bouwer & Rice, 

1976)

Slug test, 

recovery 

following slug 

removal 

(Bouwer & Rice, 

1976)

1 6 3 50 Coarse sand and gravel, iron formation 98 107 58 52 512 0 0 69 Clay and coarse sand, iron formation --- --- --- --- ---3 2 1 82 Large boulders, sand, gravel 183 182 40 2.2 124 0 3 82 Coarse sand and gravel, iron formation --- --- --- 2.7 1.65 0 2 46 Coarse sand, gravel, boulders --- --- --- 10.01

1Only partial recovery during slug test.

---

6 0 0 20 Sand --- --- --- --- ---7 0 0 20 Sand --- --- --- --- ---8 1 1 30 Blue clay 21 22 --- 5.0 4.89 2 2 35 Gray sand 8.6 8.5 --- 2.5 1.6

10 4 1 85 Sandy gravel 236 224 50 62 62

11 0 2 80 Gray sandy clay and rocks --- --- --- 0.06 0.08

12 4 2 50 Coarse sand and gravel 258 252 121 120 12113 0 1 62 Sandy clay and boulders, slate --- --- --- 0.05 ---14 0 2 77 Fine to medium gray sandy clay, medium gray sand, boulders --- --- --- 0.23 0.23

15 0 0 28 Granite --- --- --- --- ---16 0 1 70 Gray clay, fine to medium sand --- --- --- 0.23 ---17 1 0 80 Boulders, some iron formation 222 214 21 --- ---18 1 0 70 Coarse sand and gray clay 247 300 68 --- ---
16

Table 4. Quarterly and annual estimates of ground-water recharge from stream-hydrograph analyses of 1968-82 discharge records for the Prairie River near Taconite, Minnesota gage 

using the U.S. Geological Survey’s Programs RORA and PART (Rutledge, 1998), and annual precipitation data from 1968-82 for the Grand Rapids Forestry Laboratory/North Central 

School (1961-1990 )

 [All values are inches, except values in parentheses which are recharge as a percent of annual precipitation; normal, 27.54 inches]

Year

Ground-water recharge estimates (using the best-fit equation obtained 

from winter records for estimating baseflow recession rates)

Ground-water recharge estimates (using the best-fit equation obtained from 

the entire records for estimating baseflow recession rates) Annual precipitation - 

Grand Rapids January- March April-June July - September October - December Annual January- March April-June July - September October - December Annual

1968 0.23 6.12 0.62 0.94 7.91 (27) 0.18 4.36 1.65 1.57 7.76 (26) 29.621969 0.85 5.78 0.29 1.56 8.48 (32) 0.76 6.78 0.74 1.39 9.67 (36) 26.811970 0.55 5.72 -1.43 1.42 6.26 (25) 0.57 4.94 0.04 0.86 6.41 (26) 24.871971 0.64 5.61 -1.00 3.39 8.64 (28) 0.50 5.95 0.09 2.36 8.90 (29) 31.121972 -0.35 4.19 2.05 0.44 6.33 (25) 0.39 4.11 1.96 0.60 7.06 (28) 24.871973 1.79 1.80 0.95 2.19 6.73 (24) 1.10 2.37 0.91 2.99 7.37 (26) 28.331974 0.36 7.83 -0.97 1.10 8.32 (30) 0.20 8.35 0.33 0.86 9.74 (35) 27.631975 1.15 5.32 0.89 0.84 8.20 (28) 0.89 5.04 2.82 0.68 9.43 (33) 29.001976 0.37 1.77 0.26 0.12 2.52 (14) 0.24 2.14 0.58 0.11 3.07 (17) 17.981977 0.49 0.74 3.06 2.22 6.51 (17) 0.32 0.67 1.99 3.27 6.25 (16) 38.001978 0.08 5.32 2.07 0.03 7.50 (25) 0.17 4.78 2.95 0.22 8.12 (27) 30.461979 0.98 7.36 -0.26 1.44 9.52 (39) 0.84 6.02 2.09 0.79 9.74 (40) 24.571980 0.40 1.27 1.78 0.43 3.88 (18) 0.33 1.40 1.43 0.74 3.90 (18) 21.621981 0.32 3.42 0.56 1.48 5.78 (20) 0.23 2.90 1.32 1.61 6.06 (21) 29.421982 0.65 5.54 0.61 2.69 9.49 (28) 0.64 6.25 1.11 2.37 10.37 (31) 33.94

15-year average 0.57 4.52 0.63 1.35 7.07 (25) 0.49 4.40 1.33 1.36 7.58 (27) 27.88
17

accuracy of the simulations could 

decrease farther away from the simulated mine pit. The accuracy of the 

model in the bedrock aquifers is 

unknown because water-level data 

were not available for the bedrock formations. 

The calibrated, steady-state model 

is believed to be a reasonable tool for 

water-resources management based 

on the premise that future hydrologic 

conditions will be similar to historical 

conditions. Furthermore, it is assumed 

that variations in annual recharge and 

discharge for the simulations of 

steady-state conditions will be similar 

to those simulated in the calibrated 

model. The accuracy of the simulations of steady-state conditions 

becomes more uncertain if the variation in annual recharge or discharge 

exceeds the range used in the calibrated model. Because the model was 

calibrated under the assumption of 

steady-state flow conditions, the 

model will most accurately reflect the 

effects of annual or multiple-year 

stresses, and not short-term transient 

stresses, on the flow system.

SINGLE-WELL HYDRAULIC 

TEST

Average transmissivity and 

hydraulic conductivity values 

obtained from the single-well hydraulic tests are listed in table 3. Average 

transmissivity values ranged from 8.5 

to 300 ft2

/day, with little variations 

seen between values obtained from 

Theis and Cooper-Jacob analyses for 

all of the wells, with the exception of 

well 18. The lowest values were 

obtained from tests conducted in wells 

completed in sand or clay, while the 

higher values were obtained from 

tests conducted in wells completed in 

coarse sands, gravels, and boulders 

(table 3). Average hydraulic conductivity values ranged from 0.01 to 121 

ft/day. Hydraulic conductivity values 

for wells completed in sands and 

clays ranged from 0.05 to 5.0 ft/day. 

The lower values of this range were 

the best available values for representing the hydraulic conductivity of glacial tills in the area, and therefore, an 

initial hydraulic conductivity value of 

0.07 ft/day was used in the model 

(table 2). Hydraulic conductivity values for coarse sands, gravels, and 

boulders ranged from 0.01 to 121 

ft/day. The lowest values, ranging 

from 0.01 to 2.7 ft/day, were obtained 

from wells with a completion interval 

of less than 1 ft, and therefore, may 

not accurately represent the actual 

hydraulic conductivity of the geology 

around the well. An average value of 

6.6 ft/day obtained from initial singlewell tests conducted in wells completed in coarse sands and gravels was 

used as an initial value for simulated 

glaciofluvial sediments (table 2). 

Hydraulic conductivity values 

obtained from analyses of pumping 

test recovery, slug insertion, and slug 

removal tests conducted in four individual wells (wells 1, 3, 10, and 12) 

varied little, with the exception of 

well 3 (table 3).

STREAM-HYDROGRAPH 

ANALYSES

Quarterly and annual estimates of 

ground-water recharge based on 

stream-hydrograph analyses of the 

Prairie River and annual precipitation 

values for the Grand Rapids Forestry 

Laboratory/North Central School are 

listed in table 4. Quarterly estimates 

of recharge for the 1968-82 record 

ranged from –1.43 to 7.83 in. using 

the best-fit equation obtained from 

winter streamflow records, and 

ranged from 0.04 to 8.35 in. using the 

best-fit equation obtained from the 

annual streamflow records (table 4). 

During most years, the greater values 

tended to occur in the spring (AprilJune) and the lower values occurred in 

the winter (January-March).

Annual estimates of recharge during 1968-82 ranged from 2.52 to 9.52 

in. using the best-fit equation obtained 

from the winter streamflow records, 

and ranged from 3.07 to 10.37 in. 

using the best-fit equation obtained 

from the annual streamflow records 

(table 4). Annual estimates between 

1962-82 using either solely the winter 

record or the entire record for baseflow recession analysis accounted for 

between 14 to 40 percent of annual 

precipitation. The 15-year average for 

the annual recharge estimate was 7.07 

in. using the winter streamflow 

records and 7.58 in. using annual 

streamflow records, accounting for 25 

and 27 percent, respectively, of the 

average annual precipitation for 1968-

82 (table 4). 

A value of 7 in./yr (1.6 x 10-3 

ft/day), similar to the 15-year average 

for the annual recharge values using 

winter streamflow records, was used 

in the model to represent groundwater recharge to surficial glaciofluvial sediments. An initial value of 0.7 

in./yr (1.6 x 10-4 ft/day) was used in 

the model to represent ground-water 

recharge rates to surficial glacial tills 

and bedrock. Delin (1988) computed 

average recharge rates of 0.61 and 

10.7 in./yr through glacial tills and 

surficial sands, respectively, in the 

Brooten-Belgrade area, west-central 

Minnesota.

CALIBRATION OF THE 

MODFLOW-96 GROUNDWATER FLOW MODEL

The final calibration values for the 

hydraulic conductivity and groundwater recharge rates are listed in table 

2. The match between simulated and 

measured water levels was improved 

by (1) increasing the hydraulic conductivity for the glaciofluvial sediments from 6.6 to 32.8 ft/day 

southwest of the mine pit, (2) increasing the hydraulic conductivity for the 

glaciofluvial sediments from 6.6 to 
18

13.1 ft/day in the rest of the model, 

(3) decreasing ground-water recharge 

rates for glaciofluvial sediments from 

1.6 x 10-3 to 1.1x 10-3 ft/day and for 

glacial tills from 1.6 x 10-4 to 3.9 x 

10-6 ft/day, and (4) increasing groundwater recharge rates for bedrock from 

1.6 x 10-4to 2.3 x 10-4 ft/day. The 

above changes are considered to be 

acceptable because they are all within 

ranges of values calculated or measured in the field for this study or 

reported in previous studies.

Simulated an measured water levels for 15 of the 18 monitoring wells 

and the simulated minus measured 

water-level difference for the 15 wells 

are presented in table 5. The difference between simulated and measured 

water levels varied between +28.65 

and –3.78 ft (table 5). The best-match 

simulated water levels were within 2 

ft of measured water levels for 4 of 

the 15 wells, and within 4 ft for 9 of 

the wells. These 9 wells were located 

north of the Canisteo Mine Pit and 

south of the mine pit in the Trout Lake 

and Holman Lake areas (figure 3 and 

table 5). The mean absolute difference 

between simulated and measured 

water levels, computed as the sum of 

the absolute values of the differences 

divided by the number of wells, for 

the 15 wells is +7.25 ft. The mean 

algebraic difference between simulated and measured water levels, computed as the algebraic sum of the 

differences divided by the number of 

wells, for the 15 wells is +4.25 ft, 

indicating the positive differences 

were not balanced by the negative differences. Positive water-level differences greater than 6.6 ft were found in 

five monitoring wells located southwest of the mine pit and northwest of 

Trout Lake, and for one well (18) 

located near Holman Lake (figure 3 

and table 5). The root mean squared 

error, or the average of the squared 

differences in simulated and measured 

heads, was +10.28 ft.

A plot of measured versus best-fit 

simulated water levels for the monitoring wells is shown in figure 6. 

Most of the measured values lie close 

to the 1:1 linear relation, except for 

water levels for the six monitoring 

wells with a positive water-level difference greater than 6.6 ft. Topographically, these six monitoring 

wells are located at relatively low altitudes near the mine pit. Water-level 

altitudes for five of the six wells are 

less than 1,300 ft (figure 6).

The positive water-level differences found in five monitoring wells 

located southwest of the mine pit may, 

in part, be explained by the presence 

of unidentified zones of greater 

hydraulic conductivity in the glaciofluvial sediments or vertical leakage to 

bedrock aquifers. The lack of monitoring wells completed in bedrock in 

the vicinity of the Canisteo Mine Pit 

makes it impossible to determine 

directly if vertical leakage is occurring to bedrock aquifers.

The simulated net ground-water 

flow into the Canisteo Mine Pit was 

+1.34 ft3/s, and the net ground-water 

flow calculated from pit water-level 

altitudes measured between July 5, 

1999 and February 25, 2001 was +5.4 

ft3

/s. Several reasons can be given for 

explaining why the calculated value is 

higher than the simulated value. 

Greater than normal precipitation in 

Table 5. Measured and simulated water-level altitudes in monitoring wells for the best-fit calibrations of the MODFLOW steady-state 

simulations surrounding the Canisteo Mine Pit, Bovey, Minnesota 

 [ft, feet; ---, no value]

Monitoring well number Water-level altitudes in monitoring wells (ft) Simulated - measured (ft) Simulated Measured on 1/4/01

1 1,372.77 1,375.94 -3.17

2 1,378.12 1,381.90 -3.78

3 1,309.88 1,281.23 +28.65

4 1,300.69 1,294.00 +6.69

5 1,301.02 1,289.21 +11.81

8 1,293.08 1,294.65 -1.57

9 1,298.46 1,299.89 -1.43

10 1,299.15 1,300.41 -1.26

11 1,348.72 1,352.19 -3.47

12 1,302.03 1,301.45 +0.58

13 1,343.93 1,340.93 +3.00

14 1,359.22 1,362.32 -3.10

16 1,304.00 1,287.66 +16.34

17 1,297.18 1,290.46 +6.72

18 1,325.92 1,316.22 +9.70

Mean absolute difference --- --- +7.25

Mean algebraic difference --- --- +4.25

Root mean squared error --- --- +10.28
19

the modeling area during the three 

years prior to January 4, 2001 could 

have resulted in a temporal increase in 

flow rates to the mine pit. Annual precipitation at Grand Rapids, Minnesota 

for 1998, 1999, and 2000 was greater 

than the normal mean-annual precipitation by 1.16, 7.26, and 1.76 in., 

respectively. The use of temporal data 

to determine the calculated value may 

also explain the greater value. The 

calculated value was an average of 

transient, rising water levels, and the 

simulated value was obtained from 

the steady-state model. Head gradients around the mine pit during rising 

pit water-level conditions were 

greater than gradients during the simulated steady-state condition. Since 

flow rates to the mine are directly 

related to the surrounding head gradients, transient flow rates would be 

greater. In all of the model simulations, no flow occurred out of either 

of the drains.

MODEL SENSITIVITY TO 

GROUND-WATER RECHARGE 

AND HYDRAULIC 

CONDUCTIVITY

Simulated water levels and 

ground-water flow to and from the 

Canisteo Mine Pit were most sensitive 

to changes in horizontal hydraulic 

conductivity, suggesting that this 

characteristic is the predominant 

parameter controlling steady-state 

water-level and flow conditions. 

Table 6 lists simulated water levels in 

15 monitoring wells and total groundwater flow into and out of the Canisteo Mine Pit for simulations at various 

multiples of the calibrated horizontal 

hydraulic conductivity. Maximum 

water-level differences from the calibrated model varied between –21.13 

and +59.91 ft for the monitoring wells 

under various multiples (table 6). 

Simulated ground-water inflow to the 

mine pit varied from 0.47 to 6.79 ft3/s 

and simulated ground-water outflow 

from the mine pit varied from 0.01 to 

0.63 ft3

/s under various multiples of 

the calibrated horizontal hydraulic 

conductivity values (table 6).

Water levels and ground-water 

flow rates were less sensitive under 

various multiples of the calibrated 

vertical hydraulic conductivity values 

compared to the horizontal hydraulic 

conductivity values. Maximum 

water-level differences from the calibrated model for each well varied 

between –17.29 and +21.69 ft for the 

SIMULATED WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

MEASURED WATER-LEVEL ALTITUDE, IN FEET ABOVE MEAN SEA LEVEL

1,400

1,380

1,360

1,340

1,320

1,300

1,280

1,280 1,300 1,320 1,340 1,360 1,380 1,400

Measured versus simulated water-level altitude in monitoring wells at a constant pit water-level altitude of 1,300 feet

above sea level (see table 5).

Measured value = Simulated value

Figure 6.
20

monitoring wells (table 7). Simulated 

ground-water inflow to the mine pit 

varied from 1.10 to 1.52 ft3

/s and simulated ground-water outflow from the 

mine pit varied from 0.04 to 0.11 ft3

/s 

under various multiples of the calibrated vertical hydraulic conductivity 

values (table 7).

Water levels and ground-water 

flow rates were the least sensitive 

under various multiples of the calibrated ground-water recharge rates 

compared to the hydraulic conductivity values. Maximum water-level differences from the calibrated model for 

each well varied between –10.93 and 

+9.28 ft for the monitoring wells 

(table 8). Simulated ground-water 

inflow to the mine pit varied from 

1.31 to 1.47 ft3/s and simulated 

ground-water outflow from the mine 

pit varied from 0.06 to 0.07 ft3/s 

under various multiples of the calibrated ground-water recharge rates 

(table 8).

SIMULATIONS 

CHARACTERIZING CURRENT 

AND POTENTIAL FUTURE 

GROUND-WATER FLOW 

CONDITIONS NEAR THE 

MINE PIT

Simulated ground-water flow conditions obtained from the calibrated 

model for January 4, 2001 (constant 

pit water-level altitude of 1,300 ft) 

indicate that estimated total groundwater inflow to the Canisteo Mine Pit 

was 1.40 ft3/s, with only 0.06 ft3/s 

discharging to local aquifers (table 6). 

The potentiometric surface of the simulated ground-water flow indicates 

that ground water was flowing into 

the mine pit along most of the pit 

boundary, with ground-water outflow 

occurring from the pit to the Trout 

Lake area (fig. 7, and table 9). Most 

ground-water inflow originates less 

than one mile from the pit boundary. 

Ground-water inflow occurs along the 

north side of the pit and near Taconite, 

and from the south north of U.S. 

Highway 169 (fig. 7). Steep hydraulic 

gradients in the potentiometric surface 

that exist near the north and southeast 

pit boundaries are in part due to the 

presence of poorly conductive glacial 

Table 6. Simulated water-level altitudes in monitoring wells and simulated ground-water flow rates into and out of the Canisteo Mine Pit, Bovey, 

Minnesota for MODFLOW steady-state simulations at various mulitples of the calibrated horizontal hydraulic conductivity values

 [values in parentheses are water-level or flow differences from calibrated model values; ft, feet above sea level; ft3/s, cubic feet per second]

Monitoring 

wells

Water-level altitudes in monitoring wells (ft)

Calibrated 

model

0.2 times the 

calibrated horizontal 

hydraulic 

conductivity values

0.5 times the 

calibrated horizontal 

hydraulic 

conductivity values

2 times the calibrated 

horizontal hydraulic 

conductivity values

5 times the calibrated 

horizontal hydraulic 

conductivity values

10 times the 

calibrated horizontal 

hydraulic 

conductivity values

1 1,372.77 1,432.68 (59.91) 1,409.71 (36.94) 1,359.12 (-13.65) 1,359.12 (-13.65) 1,359.12 (-13.65)

2 1,378.12 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00)

3 1,309.88 1,310.93 (1.05) 1,310.20 (0.32) 1,309.51 (-0.37) 1,308.43 (1.45) 1,306.92 (2.96)

4 1,300.69 1,300.85 (0.16) 1,300.72 (0.03) 1,300.59 (-0.10) 1,300.49 (-0.20) 1,300.39 (-0.30)

5 1,301.02 1,301.80 (0.78) 1,301.35 (0.33) 1,300.72 (0.30) 1,300.33 (-0.69) 1,300.07 (-0.95)

8 1,293.08 1,289.34 (-3.74) 1,288.58 ( 4.50) 1,295.05 (1.97) 1,296.13 (3.05) 1,296.62 (3.54)

9 1,298.46 1,306.56 (8.10) 1,296.26 (-2.20) 1,299.11 (0.65) 1,299.28 (0.82) 1,299.31 (0.85)

10 1,299.15 1,307.78 (8.63) 1,300.10 (0.95) 1,298.00 (-1.15) 1,297.05 (-2.10) 1,296.69 (-2.46)

11 1,348.72 1,373.26 (24.54) 1,356.14 (7.42) 1,341.04 (-7.68) 1,331.82 (-16.90) 1,327.59 (-21.13)

12 1,302.03 1,302.13 (0.10) 1,302.07 (0.04) 1,302.07 (- 0.04) 1,302.03 (0.00) 1,301.97 (-0.06)

13 1,343.93 1,339.86 (-4.07) 1,344.26 (0.33) 1,342.75 (-1.18) 1,337.57 (-6.36) 1,333.66 (-10.27)

14 1,359.22 1,343.14 (-16.08) 1,356.99 (-2.23) 1,355.97 (-3.25) 1,359.35 (0.13) 1,346.75 (-12.47)

16 1,304.00 1,305.12 (1.12) 1,304.46 (0.46) 1,303.51 (-0.49) 1,304.17 (0.17) 1,302.00 (-2.00)

17 1,297.18 1,297.21 (0.03) 1,297.11 (-0.07) 1,297.4 (0.06) 1,297.21 (0.03) 1,297.57 (0.39)

18 1,325.92 1,320.70 (-5.22) 1,323.95 (-1.97) 1,327.66 (1.74) 1,326.02 (0.10) 1,327.36 (1.44)

Total ground-water flow - Canisteo Mine Pit (ft3/s)

Type of flow Calibrated 

model

0.2 times the 

calibrated horizontal 

hydraulic 

conductivity values

0.5 times the 

calibrated horizontal 

hydraulic 

conductivity values

2 times the calibrated 

horizontal hydraulic 

conductivity values

5 times the calibrated 

horizontal hydraulic 

conductivity values

10 times the 

calibrated horizontal 

hydraulic 

conductivity values

Inflow 1.40 0.47 0.86 2.26 4.36 6.79

Outflow 0.06 0.01 0.03 0.13 0.33 0.63

Net 1.34 0.46 0.83 2.13 4.03 6.16
21

Table 7. Simulated water-level altitudes in monitoring wells and simulated ground-water flow rates into and out of the Canisteo Mine Pit, Bovey, Minnesota for MODFLOW steadystate simulations at various mulitples of the calibrated vertical hydraulic conductivity values 

 [values in parentheses are water-level or flow differences from calibrated model value; ft, feet above sea level; ft3/s, cubic feet per second]

Monitoring 

well numbers

Water-level altitudes in monitoring wells (ft)

Calibrated model

0.1 times the calibrated 

vertical hydraulic 

conductivity values

0.2 times the calibrated 

vertical hydraulic 

conductivity values

0.5 times the calibrated 

vertical hydraulic 

conductivity values

2 times the calibrated 

vertical hydraulic 

conductivity values

5 times the calibrated 

vertical hydraulic 

conductivity values

10 times the calibrated 

vertical hydraulic 

conductivity values

1 1,372.77 1,359.12 (-13.65) 1,359.12 (-13.65) 1,365.12 (-7.65) 1,394.42 (21.65) 1,394.46 (21.69) 1,384.84 (12.07)2 1,378.12 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00) 1,378.12 (0.00)3 1,309.88 1,310.07 (0.19) 1,310.01 (0.13) 1,309.91 (0.03) 1,309.84 (-0.04) 1,309.84 (-0.04) 1,309.84 (-0.04)4 1,300.69 1,300.92 (0.23) 1,300.85 (0.16) 1,300.69 (0.00) 1,300.66 (-0.03) 1,300.66 (-0.03) 1,300.66 (-0.03)5 1,301.02 1,300.95 (-0.07) 1,301.12 (0.10) 1,300.95 (0.07) 1,301.08 (0.06) 1,301.08 (0.06) 1,301.08 (0.06)8 1,293.08 1,291.34 (-1.74) 1,292.91 (-0.17) 1,291.96 (-1.12) 1,293.90 (0.82) 1,294.69 (1.61) 1,294.13 (1.05)9 1,298.46 1,295.51 (-2.95) 1,296.92 (-1.54) 1,297.44 (-1.02) 1,299.34 (0.88) 1,300.26 (1.80) 1,299.54 (1.08)10 1,299.15 1,297.44 (-1.71) 1,297.87 (-1.28) 1,298.39 (-0.76) 1,299.90 (0.75) 1,300.85 (1.70) 1,299.90 (0.75)11 1,348.72 1,338.91 (-9.81) 1,342.06 (-6.66) 1,346.29 (-2.43) 1,350.82 (2.10) 1,353.18 (4.46) 1,351.90 (3.18)12 1,302.03 1,302.07 ( 0.04) 1,302.03 (0.00) 1,302.03 (0.00) 1,302.07 (0.04) 1,302.07 (0.04) 1,302.07 (0.04)13 1,343.93 1,326.64 (-17.29) 1,327.33 (-16.60) 1,342.68 (-1.25) 1,345.05 (1.12) 1,345.51 (1.58) 1,345.80 (1.87)14 1,359.22 1,350.82 (-8.40) 1,355.68 (-3.54) 1,356.76 (-2.46) 1,359.02 (-0.20) 1,363.75 (4.53) 1,363.45 (4.23)16 1,304.00 1,304.13 ( 0.13) 1,304.53 (0.53) 1,303.94 (0.06) 1,304.00 (0.00) 1,304.00 (0.00) 1,304.00 (0.00)17 1,297.18 1,297.41 (0.23) 1,297.47 (0.29) 1,297.08 (-0.10) 1,297.24 (0.06) 1,297.28 (0.10) 1,297.28 (0.10)18 1,325.92 1,328.71 (2.79) 1,327.95 (2.03) 1,326.71 (0.79) 1,325.16 (-0.76) 1,324.44 (-1.48) 1,324.15 (-1.77)

Total ground-water flow - Canisteo Mine Pit (ft3/s)

Type of flow Calibrated model

0.1 times the calibrated 

vertical hydraulic 

conductivity values

0.2 times the calibrated 

vertical hydraulic 

conductivity values

0.5 times the calibrated 

vertical hydraulic 

conductivity values

2 times the calibrated 

vertical hydraulic 

conductivity values

5 times the calibrated 

vertical hydraulic 

conductivity values

10 times the calibrated 

vertical hydraulic 

conductivity values

Inflow 1.40 1.10 1.21 1.35 1.45 1.50 1.52Outflow 0.06 0.11 0.06 0.07 0.05 0.04 0.04Net 1.34 0.99 1.15 1.28 1.40 1.46 1.48
22

tills and mine tailings surrounding the 

mine pit (fig. 7). MODPATH simulations of water flowing from the pit to 

local aquifers at the constant pit 

water-level altitude of 1,300 ft indicate that water from the pit was flowing to Trout Lake or the municipal 

wells of Bovey or Coleraine on January 4, 2001 (figure 8a). 

A water budget is an accounting of 

inflow to, outflow from, and storage 

change in the simulated aquifer. For 

the steady-state model, inflow 

(sources of water) to the aquifer 

equals outflow (discharges) from the 

aquifer. General head-dependent 

boundaries at simulated wetlands and 

lakes accounted for 80.1 percent and 

areal recharge to the aquifers contributed 18.3 percent of the sources of 

water to aquifers in the calibrated 

model for January 4, 2001 (constant 

pit water-level altitude of 1,300 ft) 

(table 10). The remaining 1.6 percent 

comes from rivers and the Canisteo 

Mine Pit. Discharge from general 

head-dependent boundaries accounted 

for 90.6 percent of the total discharge 

from the aquifer (table 10). Discharge 

from rivers, the Canisteo Mine Pit, 

and municipal wells accounted for 9.4 

percent of the total discharge.

Model simulations indicate that as 

water levels continue to rise in the 

Canisteo Mine Pit, total ground-water 

inflow rates will decrease and total 

ground-water outflow rates will 

increase until a steady-state balance is 

reached, or surface outflow occurs. 

Simulations of steady-state conditions 

at various constant pit water levels 

indicate that total ground-water 

inflow will decrease from 1.40 to 1.00 

ft3/s and total ground-water outflow 

will increase from 0.06 to 0.91 ft3

/s as 

the pit water-level altitude rises from 

1,300 to 1,324 ft (table 9). Over the 

same pit water level rise, the net 

ground-water inflow will decrease 

from 1.34 to 0.09 ft3/s. At the highest 

pit water-level altitude (1,324 ft), 

model results indicate a net groundwater inflow rate of 0.09 ft3

/s, which 

will likely result in discharge to land 

surface at the location of the lowest 

pit-rim altitude.

Total ground-water inflow and 

total net ground-water flow decreases 

nearly linear with increasing pit 

water-level altitudes (figs. 9a and 9b), 

while the total ground-water flow out 

of the mine pit (total ground-water 

outflow) increase occurs nearly curvilinear as a power function (figure 9c). 

A Mann-Kendall test (Helsel and Hirsch, 1992) on the total ground-water 

Table 8. Simulated water-level altitudes in monitoring wells and simulated ground-water flow rates into and out of the Canisteo Mine Pit, Bovey, 

Minnesota for MODFLOW steady-state simulations at various mulitples of the calibrated ground-water recharge rates

 [values in parentheses are water-level or flow differences from calibrated model value; ft, feet above sea level; ft3/s, cubic fee per second]

Monitoring well 

numbers

Water-level altitudes in monitoring wells (ft)

Calibrated model

0.5 times the calibrated 

ground-water recharge 

rates

0.75 times the 

calibrated ground-water 

recharge rates

1.25 times the 

calibrated ground-water 

recharge rates

1.5 times the calibrated 

ground-water recharge 

rates

1 1,372.77 1,361.84 (-10.93) 1,365.22 (-7.55) 1,371.98 (-0.79) 1,382.05 ( 9.28)

2 1,378.12 1,378.12 (0.00) 1,378.12 ( 0.00) 1,378.12 ( 0.00) 1,378.12 ( 0.00)

3 1,309.88 1,309.38 (-0.50) 1,309.65 (-0.23) 1,310.14 ( 0.26) 1,310.37 ( 0.49)

4 1,300.69 1,300.62 (-0.07) 1,300.66 (-0.03) 1,300.69 ( 0.00) 1,300.69 ( 0.00)

5 1,301.02 1,300.92 (-0.10) 1,300.98 (-0.04) 1,301.08 ( 0.06) 1,301.12 ( 0.10)

8 1,293.08 1,292.72 (-0.36) 1,292.88 (-0.20) 1,293.24 ( 0.16) 1,293.43 ( 0.35)

9 1,298.46 1,298.03 (-0.43) 1,298.26 (-0.20) 1,298.69 ( 0.23) 1,298.88 (0.42)

10 1,299.15 1,298.62 (-0.53) 1,298.88 (-0.27) 1,299.41 (0.26) 1,299.67 (0.52)

11 1,348.72 1,345.90 (-2.82) 1,347.31 (-1.41) 1,350.10 (1.38) 1,351.41 (2.69)

12 1,302.03 1,302.03 (0.00) 1,302.03 (0.00) 1,302.07 (0.04) 1,302.07 (0.04)

13 1,343.93 1,343.96 (0.03) 1,344.09 (0.16) 1,344.13 (0.20) 1,344.13 (0.20)

14 1,359.22 1,359.02 (-0.20) 1,359.19 (-0.03) 1,359.28 (0.06) 1,359.35 (0.13)

16 1,304.00 1,303.84 (-0.16) 1,303.94 (-0.06) 1,304.07 (0.07) 1,304.17 (0.17)

17 1,297.18 1,297.11 (-0.07) 1,297.15 (-0.03) 1,297.21 (0.03) 1,297.21 (0.03)

18 1,325.92 1,325.79 (-0.13) 1,325.85 (-0.07) 1,325.98 (0.06) 1,326.02 (0.10)

Total ground-water flow - Canisteo Mine Pit (ft3/s)

Type of flow Calibrated model

0.5 times the calibrated 

ground-water recharge 

rates

0.75 times the 

calibrated ground-water 

recharge rates

1.25 times the 

calibrated ground-water 

recharge rates

1.5 times the calibrated 

ground-water recharge 

rates

Inflow 1.40 1.31 1.36 1.43 1.47

Outflow 0.06 0.07 0.06 0.06 0.06

Net 1.34 1.24 1.30 1.37 1.41
23

inflow at the various constant pit 

water levels (fig. 9a) has a median 

slope of -0.02. This slope represents 

the rate of ground-water inflow 

decrease per foot of change in pit 

water-level rise. A Mann-Kendall test 

(Helsel and Hirsch, 1992) on the total 

net ground-water flow at the various 

constant pit water-level altitudes (fig. 

9b) has a median slope of -0.05. This 

slope represents the rate of net 

ground-water flow decrease per foot 

of change in pit water-level rise. 

Model results also indicate that the 

location of ground-water flow from 

the mine pit (ground-water outflow) 

will vary as the pit water level rises. 

At the constant pit water-level altitude 

of 1,300 ft, all ground-water outflow 

occurred in the Trout Lake area. At pit 

water-level altitudes between 1,302 

and 1,306 ft, all but a small rate (less 

than 0.01 ft3

/s) of the total groundwater outflow occurred in the Trout 

River

Swan

Taconite

Bovey Coleraine

169

1300

1320

1320

1320

1340

1340

1340

1360

1360

1360

1360

1360

1380

1380

1380

1380

1400

1400

1400

1420

1380

1400

1320

1300

1380

1340

1380

Big

Diamond

Lake

Holman

Lake

Trout

Lake

Canisteo Mine Pit Lake

47°20'

47°19'

47°18'

47°17'

93°27' 93°25' 93°23' 93°21'

012 3 MILES

0 1 2 3 KILOMETERS

Base from U.S. Geological Survey

Digital data, 1:100,000, 1993

U.S. Albers projection

Simulated steady-state altitude of potentiometric surface of ground-water flow and ground-water flow direction in the

vicinity of the Canisteo Mine Pit, Bovey, Minnesota (Constant pit water-level altitude of 1,300 feet above sea level).

Holman

Lake

Area

Trout Lake

Area

Prairie River

Area

EXPLANATION

1380

Mine stockpiles; tailings and setting ponds

Simulated potentiometric contour. Hachures indicate

depression. Interval 10 feet. Datum is sea level

Crest of Giants Range

Ground-water flow direction

Area of ground-water discharge from the

Canisteo mine pit

Figure 7.
24

Lake area. This small amount of 

ground-water outflow occurs in the 

Holman Lake area (fig. 7, table 9). At 

pit water-level altitudes between 

1,308 and 1,324 ft, model results indicate that ground-water outflow will 

occur in three locations: the Trout 

Lake, Prairie River, and Holman Lake 

areas (fig. 7). Model-computed 

ground-water outflow in the Prairie 

River area increases from 0.01 to 0.31 

ft3

/s between pit water-level altitudes 

of 1,308 and 1,324 ft, accounting for 4 

and 34 percent of the total groundwater outflow, respectively (table 9). 

This water will eventually discharge 

to wetlands southwest of the mine pit 

in the direction of the Prairie River 

(figure 8b). Between pit water-level 

altitudes of 1,308 and 1,324 ft, simulated ground-water outflow in the 

Trout Lake area increases from 0.21 

to 0.54 ft3/s, accounting for 94 and 59 

percent of the total simulated groundwater outflow, respectively. Similar 

to simulated ground-water outflow at 

the pit water-level altitude of 1,300 ft, 

this simulated ground-water outflow 

in the Trout Lake area will either 

eventually end up in Trout Lake or the 

municipal wells of Bovey or Coleraine (fig. 8b). Simulated groundwater outflows are much lower in the 

Holman Lake area, increasing from 

0.01 to 0.06 ft3

/s between pit waterlevel altitudes of 1,308 and 1,324 ft, 

respectively (fig. 9d, table 9). This 

simulated ground-water outflow 

remains within 0.1 mi of the pit wall 

under steady-state conditions (figure 

8b). 

Simulated ground-water outflow 

in the Trout Lake and Prairie River 

areas increases nearly linear with 

increasing pit water levels (figs. 9e 

and 9f), while the simulated groundwater outflow in the Holman Lake 

area increases nearly curvilinear as a 

power function for outflow values 

below 0.01 ft3

/s (figure 9d). MannKendall tests (Helsel and Hirsch, 

1992) on the simulated ground-water 

outflow in the Trout Lake area (fig. 

9e) and in the Prairie River area (fig. 

9f) at the various constant pit water 

levels have median slopes of 0.02. 

The slopes in these relations represent 

the rate of simulated ground-water 

outflow increase in the Trout Lake 

and Prairie River area, per foot of 

change in pit water-level rise.

Water budgets for the model simulations at various pit water levels are 

listed in table 10. Total inflow to 

(sources) and outflow (discharges) 

from the modeled area tend to gradually increase with increasing constant 

pit water levels. Simulated inflows to 

the modeled area increase from 59.85 

to 60.38 ft3/s and simulated outflows 

increase from 59.85 to 60.40 ft3/s 

from the 1,300 ft simulation to the 

1,324 ft simulation, respectively 

(table 10). Inflow from the simulated 

mine pit increases with higher pit 

water levels, and were somewhat offset by decreases in simulated inflow 

from wetlands and streams, represented by general head-dependent 

boundaries. Outflow to the aquifer 

from the simulated mine pit decreases 

with higher pit water levels, and were 

offset by increases in simulated outflow from the wetlands and streams 

(table 10). Simulated recharge and 

inflow from rivers did not vary 

between the various constant pit 

water-level simulations, as did simulated ground-water outflow from rivers and municipal wells.

Table 9. Simulated ground-water flow rates into and out of the Canisteo Mine Pit, Bovey, Minnesota for MODFLOW steady-state simulations 

at various constant pit water levels 

 [ft3/s, cubic feet per second; values in parentheses are percent of total pit ground-water outflow]

Constant pit water levels 

(ft)

Total ground-water 

inflow (ft3

/s)

Ground-water outflow (ft3/s) Net ground-water 

flow (total inflow - 

total outflow) 

(ft3/s)

Total Prairie River area Trout Lake area Holman Lake area

1300 1.40 0.06 0 (0) 0.06 (100) 0 (0) 1.34

1302 1.38 0.10 0 (0) 0.10 (99) < 0.01 (1) 1.28

1304 1.32 0.13 0 (0) 0.13 (99) < 0.01 (1) 1.19

1305 1.30 0.15 0 (0) 0.15 (99) < 0.01 (1) 1.15

1306 1.26 0.17 0 (0) 0.17 (99) < 0.01 (1) 1.09

1308 1.24 0.22 0.01 (4) 0.21 (94) < 0.01 (2) 1.02

1310 1.21 0.29 0.03 (11) 0.25 (86) 0.01 (3) 0.92

1312 1.16 0.36 0.06 (17) 0.29 (80) 0.01 (3) 0.80

1314 1.12 0.44 0.09 (21) 0.34 (77) 0.01 (2) 0.68

1315 1.12 0.47 0.11 (23) 0.35 (75) 0.01 (2) 0.65

1316 1.09 0.52 0.13 (25) 0.38 (73) 0.01 (2) 0.57

1318 1.04 0.60 0.18 (30) 0.41 (68) 0.01 (2) 0.44

1320 1.04 0.70 0.22 (31) 0.46 (65) 0.03 (4) 0.34

1322 1.03 0.80 0.26 (33) 0.50 (62) 0.04 (5) 0.23

1324 1.00 0.91 0.31 (34) 0.54 (59) 0.06 (7) 0.09
25

Little

Diamond

Lake

Little

Diamond

Lake

Buckeye

Lake

Buckeye

Lake

Trout Lake

Trout Lake

Holman Lake Holman Lake

Canisteo Mine Pit Lake

Canisteo Mine Pit Lake

Taconite

Taconite

Holman

Holman

Bovey

Bovey

Coleraine

Coleraine

47°18'

47°18'

47°20'

47°20'

93°28' 93°26' 93°24' 93°22'

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Base from U.S. Geological Survey digital data 1:100,000 1972

U.S. Albers Equal Area Projection

standard parallels 29°30' and 45°30', central meridian -93°30'

MODPATH flow lines for ground-water outflow from Canisteo Mine Pit at pit water-level altitude of: A.) 1,300 and B.) 1,320

feet above mean sea level, Bovey, Minnesota.

Pit-lake water-level altitude at 1,300 feet mean sea level (January 4, 2001)

Pit-lake water-level altitude at 1,320 feet mean sea level

A

B

Municipal well

EXPLANATION

MODPATH flow line

Figure 8.
26

 Table 10. Simulated water budgets for steady-state MODFLOW simulations for aquifers surrounding the Canisteo Mine Pit, Bovey, Minnesota.

 [all values are in cubic feet per second; ft, feet above sea level]

Discharge

Budget component

Pit water-level altitudes (ft)

11,300

1The pit water level of 1,300 ft represents the calibrated steady-state model, which was calibrated to water levels measured on January 4, 2001.

1,302 1,304 1,305 1,306 1,308 1,310 1,312 1,314 1,315 1,316 1,318 1,320 1,322 1,324

In

Constant head - Canisteo Mine Pit 0.06 0.10 0.13 0.15 0.17 0.22 0.29 0.36 0.44 0.47 0.52 0.60 0.70 0.80 0.91Rivers 0.88 0.88 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87 0.87Recharge 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97 10.97Head-dependent Boundaries 47.94 47.92 47.88 47.86 47.85 47.83 47.80 47.82 47.72 47.73 47.71 47.68 47.68 47.67 47.63Total in 59.85 59.87 59.85 59.85 59.86 59.89 59.93 60.02 60.00 60.04 60.07 60.12 60.22 60.31 60.38

Out

Constant head - Canisteo Mine Pit 1.40 1.38 1.32 1.30 1.26 1.24 1.21 1.16 1.12 1.12 1.09 1.04 1.04 1.03 1.00Rivers 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.69 3.70 3.70Head-dependent boundaries 54.22 54.26 54.32 54.35 54.38 54.43 54.50 54.58 54.66 54.70 54.75 54.85 54.95 55.05 55.16Municipal wells 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54Total out 59.85 59.87 59.87 59.88 59.87 59.90 59.94 59.97 60.01 60.05 60.07 60.12 60.22 60.32 60.40Total in - out 0.00 0.00 -0.02 -0.03 -0.01 -0.01 -0.01 0.05 -0.01 -0.01 0.00 0.00 0.00 -0.01 -0.02
27

INFLOW, IN CUBIC FEET PER SECOND

INFLOW-OUTFLOW, IN CUBIC FEET PER SECOND

OUTFLOW, IN CUBIC FEET PER SECOND

OUTFLOW, IN CUBIC FEET PER SECOND

OUTFLOW, IN CUBIC FEET PER SECOND

OUTFLOW, IN CUBIC FEET PER SECOND

1.5

1.2

1.4

1

0.05

0.06

0.07

0.4

0.5

0.6

1.4

1

0.8

0.9

0.35

1.3

0.6

0.7

0.04

0.3

0.3

0.05

0.1

1.2

0.8

0.3

0.4

0.5

0.03

0.02

0.2

0.2

0.25

1.1

0.6

0.2

0.15

1

0.4

0.1

0.01

0.9

0.2

0

0 0

0.1

0 0

Total Ground-Water Inflow To Canisteo Mine Pit

A

Total Net Ground-Water Flow to the Canisteo Mine Pit

B

Total Ground-water Outflow from Canisteo Mine Pit

C

Total Ground-water Outflow in Holman Lake Area

D

Total Ground-water Outflow in the Trout Lake Area

E

Total Ground-water Outflow in Prairie River Area

F

1,295 1,300 1,305 1,310 1,315 1,320 1,325 1,330 1,295 1,300 1,305 1,310 1,315 1,320 1,325 1,330

Simulated total ground-water inflow, net ground-water inflow, outflow (C) total ground-water outflow rates

from the entire pit, ground-water outflow from the pit in the Holman Lake area, the Trout Lake area, and the Prairie River

area at various constant pit-lake water-level altitudes for the Canisteo Mine Pit, Bovey, Minnesota.

(A) (B) total

(D) (E) (F)

WATER-LEVEL ALTITUDE, IN FEET ABOVE MEAN SEA LEVEL WATER-LEVEL ALTITUDE, IN FEET ABOVE MEAN SEA LEVEL

y = 6.0003 (x-1,301)

For the first 10 values

Mann-Kendall Test, median slope=-0.02

Mann-Kendall Test, median slope=0.02 Mann-Kendall Test, median slope=0.02

Mann-Kendall Test, median slope=-0.05

y = 0.00009 (x-1,291.90) 1.99 1.27

Figure 9.
28

REFERENCES

Adams, J.L, 1994, The water balance 

of abandoned mine pits: Minnesota Ground Water Association, v. 

13, no. 1, p. 4-9.

Baker Consultants, Inc., 2000, User’s 

documentation for the PITLAKE 

package for the MODFLOW-96 

model: Version 2.1, 38 p.

Bouwer, H. and Rice, R.C., 1976, A 

slug test method for determining 

hydraulic conductivity of unconfined aquifers with completely or 

partially penetration wells: Water 

Resources Research, v. 12, no. 3, 

p. 423-428.

Chung, K.P. and Anderson, M.P., 

1998, Simulation of lake levels— 

Comparison between MODFLOW's lake package and the use 

of high conductivity zones: Proceedings of MODFLOW98 Conference, v. 1, Golden, Colorado, 

October 4-8, 1998, p. 339-344.

Cooper, H.H. and Jacob, C.E., 1946, 

A generalized graphic method for 

evaluating formation constants and 

summarizing well field history: 

American Geophysical Union 

Transactions, v. 27, p. 526-534.

Delin, G.N., 1988, Geohydrology and 

water quality of confined-drift 

aquifers in the Brooten-Belgrade 

area, west-central Minnesota: U.S. 

Geological Survey WaterResources Investigations Report 

88-4124, 138 p.

Duffield, G.M., 1995, AQTESOLV 

Aquifer Test Solver: Reston, Virginia, Geraghty & Miller, Inc., 132 

p.

Harbaugh, A.W., and McDonald, 

M.G., 1996, User’s documentation 

for MODFLOW-96, an update to 

the U.S. Geological Survey Modular Finite-Difference GroundSUMMARY AND CONCLUSIONS

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

Minnesota Department of Natural Resources, conducted a 

study to characterize ground-water flow conditions 

between the Canisteo Mine Pit, Bovey, Minnesota, and 

surrounding aquifers following mine abandonment. The 

objective of the study was to estimate the amount of 

steady-state, ground-water flow between the mine and surrounding aquifers at pit water-level altitudes below the 

level at which surface-water discharge from the pit may 

occur.

Single-well hydraulic tests and stream-hydrograph 

analyses were conducted to estimate horizontal hydraulic 

conductivities and ground-water recharge rates, respectively, for glacial aquifers around the mine pit. Average 

hydraulic conductivity values ranged from 0.05 to 5.0 

ft/day for sands and clays and from 0.01 to 121 ft/day for 

coarse sands, gravels, and boulders. The 15-year averages 

for the estimated annual recharge using the winter records 

and the entire years of record for defining baseflow recession rates were 7.07 and 7.58 in., respectively. These 

recharge estimates accounted for 25 and 27 percent, 

respectively, of the average annual precipitation for the 

1968-82 streamflow monitoring period. 

Ground-water flow rates into and out of the Canisteo 

Mine Pit were estimated using a calibrated steady-state, 

ground-water flow model. The U.S. Geological Survey's 

MODFLOW-96 code was used to simulate an area of 

approximately 75 mi2

 surrounding the mine pit. The model 

residuals, or difference between simulated and measured 

water levels, for 15 monitoring wells adjacent to the Canisteo Mine Pit varied between +28.65 and –3.78 ft. The 

best-match simulated water levels were within 4 ft of measured water levels for 9 of the 15 wells, and within 2 ft for 

4 of the wells. The simulated net ground-water flow into 

the Canisteo Mine Pit was +1.34 ft3

/s, and the net groundwater flow calculated from pit water-level altitudes measured between July 5, 1999 and February 25, 2001 was 

+5.4 ft3

/s. Simulated water levels and ground-water flow 

to and from the Canisteo Mine Pit for the calibrated 

steady-state simulation were most sensitive to changes in 

horizontal hydraulic conductivity, suggesting that this 

characteristic is the predominant parameter controlling 

steady-state water-level and flow conditions.

A series of 14 steady-state simulations at constant pit 

water-level altitudes between 1,300 and 1,324 ft was completed to assess the effect of current and potential future pit 

water levels on ground-water inflow and outflow from the 

Canisteo Mine Pit. Simulated ground-water flow conditions obtained from the calibrated model indicate that total 

simulated ground-water inflow to the Canisteo Mine Pit 

was 1.40 ft3

/s, with only 0.06 ft3/s discharging to local 

aquifers, at a constant pit water-level altitude of 1,300 ft. 

Simulations of steady-state conditions at various constant 

pit water-level altitudes indicate that total simulated 

ground-water inflow will decrease from 1.40 to 1.00 ft3

/s 

and total simulated ground-water outflow will increase 

from 0.06 to 0.91 ft3

/s as the pit water-level altitude rises 

from 1,300 to 1,324 ft. At the lowest pit-rim altitude of 

1,324 ft, model results indicate a net simulated groundwater flow of 0.09 ft3

/s into the mine pit, and it is likely 

that surface discharge to land surface will occur at the 

location of the lowest pit-rim altitude. At pit water-level 

altitudes between 1,302 and 1,306 ft, all but a small rate 

(less than 0.01 ft3

/s) of the total simulated outflow occurs 

in the Trout Lake area. At pit water-level altitudes between 

1,308 and 1,324 ft, simulated outflow occurs in three locations: the Trout Lake, the Prairie River, and Holman Lake 

areas.
29

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