APPRAISAL OF WATER FROM SDRFTCIAL-OOTWASH 

AQUIFERS IN TOED COUNTY AND PARTS OF CASS 

AND MDRRISON COUNTIES, CENTRAL MINNESOTA

By C. F. Myette

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 83-4156

Prepared in cooperation with

TOED, CASS, AND MDRRISON OuuNl'usS STEERING COMMITTEE 

and the 

MINNESOTA DEPARTMENT OF NATURAL RESOURCES

Dept, 

Seal

St. Paulr Minnesota 

1984
UNITED STATES DEPARTMENT OF THE INTERIOR

WILLIAM P. CLARKf Secretary 

GEOLOGICAL SURVEY

Dallas L. Peck f Director

For additional information 

write to:

District Chief 

U.S. Geological Survey 

702 Post Office Building 

St. Paul, Minnesota 55101 

Telephone: 725-7 841

Copies of this report can 

be purchased from:

Open-File Services Section 

Western Distribution Branch 

U.S. Geological Survey 

Box 25425 , Federal Center 

Denver, Colorado 80225 

Telephone: (303) 234-5888
CONTENTS

Page

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

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

Purpose and scope.................................................... 2

Location and description of the study area........................... 2

Previous investigations.............................................. 5

Methods of investigation............................................. 5

Test-hole and well-numbering system.................................. 6

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

Hydrology................................................................. 6

Hydrogeology......................................................... 6

Aquifer distribution................................................. 8

Aquifer characteristics.............................................. 8

Ground-water flow.................................................... 12

Water-level fluctuations............................................. 12

Aquifer recharge..................................................... 12

Ground-water discharge to streams.................................... 14

Evapotranspiration................................................... 17

Ground-water use..................................................... 17

Potential yield of wells.................................................. 17

Individual wells..................................................... 17

Mutually interfering wells........................................... 18

Water quality............................................................. 23

Digital model............................................................. 31

Location of the modeled area......................................... 31

Description of the model............................................. 31

Simulation of model boundaries and streams........................... 33

Calibration of the model............................................. 33

Model experiments.................................................... 37

Summary................................................................... 40

References................................................................ 41

ILLUSTRATIONS

Plate 1. Maps showing saturated thickness of the surficial-outwash

aquifers.................................................In back

2. Map showing transmissivity of the surficial-outwash

aquifers.................................................In back

3. Map showing configuration of the water table in the

surficial-outwash aquifers...............................In back

4. Map showing estimated potential yield of wells completed

in the surficial-outwash aquifers........................In back

5. Map showing model grid with boundary conditions (A) and

numerical analysis of experiment 2 (B)...................In back

6. Map showing numerical analysis of experiment 3 (A) and

experiment 4 (B).........................................In back

iii
Rage

Figure 1. Map showing location of study area............................ 3

2. Map showing areal extent of surficial deposits................ 4

3. Graph showing test-hole and well-numbering system............. 7

4. Graph showing particle-size distribution of outwash

deposits at representative wells............................ 10

5. Hydrographs of three representative observation wells

in Todd County, 1979........................................ 13

6. Representative hydrograph illustrating method used to

determine net effective areal ground-^water recharge and 

net change in amount of water in storage in the surficialoutwash aquifer during 1979 at indicated site............... 15

7. Graph showing flow-duration curve for the Long Prairie

River at Long Prairie (1972-79)............................. 16

8. Generalized hydrologic section illustrating effects of 

hydrogeologic boundaries and nearby wells on cones of 

influence................................................... 19

9. Graph showing theoretical relationship of drawdown to

distance from a pumped well................................. 20

10. Graph showing theoretical curves for adjustment of drawdown,

computed by the Tfteis equation as modified by Jacob (1944).. 21

11. Map showing concentration of dissolved solids................. 27

12. Map showing concentration of dissolved nitrogen (N02 + KDj

as nitrogen)................................................ 29

13. Map showing location of modeled area.......................... 32

TABLES

Table 1. Hydraulic conductivity of surficial-outwash materials......... 9

2. Hydraulic properties of the surficial outwash determined

by aquifer tests............................................ 11

3. Chemical analyses of ground water and surface water........... 24

4. Pesticide analyses of water from the surficial aquifer........ 30

5. Comparison of computed and observed water levels for

the calibrated steady-state model........................... 34

6. Difference between computed and observed (Oct. 1979) water

levels for different recharge rates......................... 36

7. Comparison of observed and model-computed ground-water

discharge to the Long Prairie River......................... 37

8. Summary of experiments used to simulate changes in pumpage

and recharge................................................ 39

iv
FACTORS

For readers who prefer to use metric units, conversion factors for terms 

used in this report are listed below:

Multiply inch pound unit By

acre 0.4047

foot (ft) 0.3048

foot per day (ft/d) 0.3048

foot squared per day (ft2/d) 0.09290

cubic foot per second (ft3/s) 0.02832

gallon per minute (gal/min) 0.06309 

million gallons per day (Mgal/d) 0.04382

inch (in) 25.4

mile (mi) 1.609

square mile (mi2) 2.59

To obtain SI unit

hectare (ha)

meter (m)

meter per day (m/d)

meter squared per day (m2/d)

cubic meter per second (mVs)

liter per second (L/s)

cubic meter per second

millimeter (ran)

kilometer (km)

square kilometer (km2)
APPRAISAL OF WATER FROM SURFIOAL-OOTWASH 

AQOIFEKS IN TOED (BOOTY AND PARIS OP CASS 

AND MORRISON UJUNT1KS, CENTRAL MDUESOOA

By C. F. Myette

ABSTRACT

Outwash deposits consisting of medium to very coarse sand constitute a 

major aquifer in Todd County and in parts of Cass and Morrison Counties. The 

outwash ranges in thickness from 0 to 150 feet. Depth to water is generally 

less than 15 feet, and annual water-level fluctuations are less than 5 feet. 

Aquifer-test results indicate that transmissivities range from 4,600 to 18,500 

feet squared per day and storage coefficients range from 0.10 to 0.25. Yields 

of more than 2,000 gallons per minute can be obtained locally from properly 

constructed wells.

Average annual precipitation is 25.93 inches, and average annual recharge 

to the aquifer is estimated to be 8 inches. Base-flow measurements of the Long 

Prairie River between Long Prairie and Motley during October 1978 and October 

1979 indicate average net gains of 0.85 and 1.3 cubic feet per second per river 

mile.

The water is a calcium bicarbonate type and is generally suitable for most 

uses. However, elevated concentrations of selected chemicals in local areas 

may require treatment of the water for specialized uses. The water is hard to 

very hard with dissolved-solids concentrations ranging from about 200 to 400 

milligrams per liter. Locally, nitrate concentrations are as much as 6.4 

milligrams per liter. Residuals of pesticides are present but do not exceed 

recommended limits as established by the U.S. Environmental Protection Agency 

for domestic consumption.

Results from numerical modeling experiments indicate that, with proper 

development, the ground-water system can accommodate additional withdrawals. 

One experiment indicated that reduction in recharge from 8 to 4 inches annually 

over 4 years, and anticipated increases in pumping from 2.1 million gallons per 

day (1978 pumpage) to 7.7 million gallons per day, would cause water levels to 

decline regionally only about 9 feet and ground-water discharge to streams to 

decline only about 20 percent.
Irrigated acreage in Minnesota increased from 4,400 acres in 1970 to 

almost 400,000 acres in 1977 (University of Minnesota, 1978). During the same 

period, irrigated acreage in the study area increased from 2,500 acres to more 

than 8,000 acres. After the drought of 1976, irrigated acreage increased to 

more than 11,000 acres by 1978.

Because of the projected increase in demand for ground water, the U.S. 

Geological Survey, in cooperation with the Minnesota Department of Natural 

Resources and the Todd, Cassr and Morrison Counties Steering Committee, studied 

the surficial aquifers in Todd County and parts of Cass and Morrison Counties 

from July 1977 to June 1980.

and Scope

The purpose of this study was to provide geohydrologic data on the major 

surficial aquifers in Todd and parts of Morrison and Cass Counties. Specifically, the objectives of the study were to (1) map the areal extent of the 

aquifer, (2) determine its hydraulic properties, (3) estimate annual recharge 

to the aquifer, (4) develop a digital computer model of parts of the aquifer to 

simulate its response to various levels of large-scale pumping, (5) determine 

the quality of ground water and its suitability for various uses, and (6) 

install wells for observing changes in water levels and water quality.

This report presents the results of this study and addresses each of the 

study objectives. This report will provide managers with data to guide orderly 

development of ground-water resources for irrigation and for domestic, municipal, and industrial water supplies. Because of present ground-water development practices, the study is limited to an appraisal of the surficial-outwash 

aquifer system.

and D^ribio of i-lv*

The study area is located in central Minnesota, approximately 25 miles 

west-southwest of Brainerd, the geographical center of the State (fig. 1). The 

area lies in the Crow Wing, Mississippi, and Sauk watersheds. Most of the area 

is drained by the Long Prairie River, which joins the Crow Wing River near 

Motley.

Outwash deposits cover approximately 250 mi2 of Todd and parts of Cass and 

Morrison Counties. The major deposit, referred to as the Long Prairie sand 

plain, is long and narrow with its axis alined north-south (fig. 2). The 

Swanville spillway sand-plain area, 40 mi2, also trends generally north-south. 

This area is nearly divided by the Todd-Morrison County line and is limited by 

the extent of its sandy soils (fig. 2).

Sand and gravel aquifers are known to be buried in the drift, but little 

is known about the areal distribution or hydraulic characteristics. Study of 

the buried outwash is beyond the scope of this investigation.
46*15

 - t ."?? : Shamineau * 1 "" 05 -

- "jTU-ittle Falls

[_

Base from U.S. Geological Survey 

State base map. 1:500,000

10 MILES

1O KILOMETERS

Figure 1."Location of study area
94«30'

95'00'

!v:-'.v^c.-'i^\ ' :7-*> u. ^"-- - ---^ i:*^: 'fe^^^

'^^?>.^-'--;«:' ^^ ^',T^ b'-.--->K^tTf^':-V°-4--' : s»

I. .'. f-. i «i .i . -f,^'. -:,c'''-.i^

^^^fe^.

PfifrirfAtS1 -Vli"^ 5:^->-.^-,t

46° 15

^M;*^9^^

fc^X* _, " O * . t" i v - - . Lv*?ir?t'3@tt

tfSSfex

^Little Falls

EXPLANATION

S Outwash CH "Red* drift 

23 "Grey" drift Geologic contact

Boundary Locations From 

Schneider (1961)

10 MILES 

i t

10 KILOMETERS

Figure 2.~Areal extent of surficial deposits
Investiations

The earliest hydrogeologic investigation in the area was done by Winchell 

and Upham (1888) who described the surficial geology, hydrology, and vegetation. A more comprehensive study by Allison (1932) discusses the geology, 

water quality, and potential yields of wells in the surficial drift and bedrock. Studies of the glaciation were made by Leverett (1932), Schneider 

(1961), Wright (1962), Wright and Frey (1965), and Sims and Morey (1972).

Hydrologic atlases by Lindholm and others (1972) and Helgesen and others 

(1975) present geologic, hydrologic, and climatologic data, regional hydrologic 

budgets, general water-quality analyses, and estimated water use. Ground water 

was appraised in adjacent sand plains by Jones and others (1963), Lindholm 

(1970; 1980), Helgesen (1973; 1977), and McBride (1975).

At present (1982) , the MPCA (Minnesota Pollution Control" Agency) is sampling wells in Todd County that are part of a statewide network for observing 

ground-water quality (Hult, 1979).

of Tnvest:igati.on

Data for this report were collected from July 1977 to June 1980. Geologic 

and hydrologic maps were prepared from local soil maps, drillers' logs, aerial 

photographs, and lithologic records from more than 500 augered test holes. 

Twenty-nine test holes were finished with steel casings and sandpoints for use 

as observation wells. Auger samples of several test-hole sites were sent to a 

private testing facility for grain-size analysis. Hydraulic conductivities 

were estimated for each test hole based on visual observations of grain size. 

Transmissivity and storage coefficient were calculated based on results of 

aquifer tests.

Water-table maps were constructed from water-level data from the augered 

holes, observation wells, and irrigation wells. Hydrographs were developed for 

each of the observation wells based on monthly measurements. The hydrographs 

were used to estimate annual ground-water recharge by analysis of water-level 

fluctuations.

Streamflow data were collected daily at three sites on the Long Prairie 

River. Stage was measured daily at two sites, whereas the other site was 

equipped with a continuous recording system. Discharges were measured every 5 

weeks at all three sites. Base flow was measured twice at 35 sites along the 

Long Prairie River and its tributaries. Streamflow data were analyzed, and 

flow-duration curves were constructed.

Water samples were collected several times at sites selected to represent 

areal variations in water quality. The sampling provides data on seasonal and 

annual variations in water quality.

A model (Trescott and others, 1976) of the Long Prairie outwash aquifer 

was constructed to simulate the ground-water-flow system and provide estimates 

of water-level changes in response to variations in climatic and pumping 

conditions.
Test: Hol.fi gpd jfell HmnhgHng System

system of numbering wells and test holes in Minnesota is based on the 

U.S. Bureau of Land Management's system of subdivision of public lands. The 

Todd County area is located in the fifth principal meridian and base-line 

system. Hie first segment of a well or test-hole number indicates the township 

north of the base line, the second indicates the range west of the principal 

meridian, and the third indicates the section in which the well or test hole is 

located. Hie uppercase letters, A, B, C, and D, following the section number, 

locate the well within the section. The first letter denotes the 160-acre 

tract; the second, the 40-acre tract; and the third, the 10-acre tract, as 

shown in figure 3. The letters are assigned in a counterclockwise direction, 

beginning with the northeast quarter. Within a given 10-acre tract successive 

well numbers beginning with 01 are added as suffixes. For example, the number 

131N34W20ABD01 indicates the first well or test hole in the SEW^EH sec. 20, 

T. 131 N., R. 34 W. Wells used in the study are plotted on plate 1.

The author would like to thank the personnel of the U.S. Soil Conservation 

Service for supplying data on land use and on the projected development of 

irrigable lands. Thanks are also extended to the local property owners and 

well drillers who provided information and especially to land owners and irrigators who allowed observation wells to be placed on their property and aquifer 

tests to be made with their equipment. Special thanks are also given to the 

Minnesota Department of Natural Resources, Division of Waters, for water-use 

information and support and to the Steering Committee of Todd, Cass, and 

Morrison Counties without whose support the project would not have been 

possible.

BXEROLOGY

gydrogeology

The predominant geologic formations in the Todd County area are 

Precambrian crystalline rocks and metasedimentary rocks, remnants of Cretaceous 

sedimentary rocks, and Pleistocene drift.

Crystalline rocks generally occur from 100 to 300 feet below land surface. 

The upper 40 to 80 feet of the rocks is weathered to a soft, mostly white, 

kaolinitic clay, although shades of red, brown, and green have been observed 

(Allison, 1932). Two outcrops are known; a "granitic" knoll near Long Prairie 

and a "gabbro" near Philbrook (Allison, 1932). Precambrian metasedimentary 

rocks crop out in several areas of Todd County. Graywacke slate, with little 

surface weathering, crops out in several areas near Staples. Biotite and 

sericite schist with white-quartz veinlets were identified from well cuttings 

near Grey Eagle (Allison, 1932). See figure 1 for locations of the abovementioned towns.

The bedrock generally is a poor aquifer because it is hard and .dense. 

Yields to individual wells are greatest where the upper surface is weathered 

and fractured, but rarely exceed 10 gal/min.
R.37W. 36 35 34 33 32 2 R.1W.

z

o

LU

Q.

u

Z

at

Q.

T.

132 

N.

131 

130

2

T. 

1

N.

Well 131N34W20ABD1

R.34W. Section 20

Figure 3. Test-hole and well-numbering system
Allison (1932) suggests that sedimentary rocks of Cretaceous age underlie 

parts of western Todd County, but the rocks were not identified in the study 

area. Cretaceous rocks r where present, consist mostly of blue shale with 

traces of pyrite and lignite and are commonly thin and of low porosity. Well 

yields vary spatially, but large yields are uncommon.

Glacial deposits cover virtually the entire area (fig. 2). The deposits 

range in thickness from 100 to 300 feet, and consist mainly of till, stratified 

sand and gravel, outwash, and ice-contact deposits. The drift was deposited in 

a complex series of events. The western half of Todd County is covered by 

young "gray" drift deposited by the Wadena Lobe of Wisconsin age, which originated in southern Manitoba (Wright, 1962). The eastern part of the county is 

covered by young "red" drift deposited by the Superior Lobe. The north-south 

trending St. Croix Moraine, which nearly bisects Todd and Morrison Counties, 

separates the gray and red drifts. The glacial sequences have been described 

in detail by Schneider (1961).

The greatest potential for ground-water development is from outwash form 

ing the sand plains and stream valleys. The outwash in these areas generally 

has a high hydraulic conductivity and good hydraulic connection to major 

streams. Yields to wells range from 10 to more than 2,000 gal/min.

The best areas for ground-water development are generally in the 

surficial-outwash plains. The major outwash, the Long Prairie valley outwash 

aquifer, ranges in width from 1 mile near Long Prairie to 3 miles at 

Browerville to 6 miles near the confluence of the Long Prairie and Crow Wing 

Rivers. The thickest deposits are in a trough about 1-mile wide near the Long 

Prairie River. From Round Prairie to north of Browerville, the sand is as 

thick as 150 feet, and has an average thickness of 40 feet. The deposits thin 

to less than 40 feet near Motley. Other areas in which deposits of sand and 

gravel are thick include Scandia valley, Swanville, southwest of Grey Eagle, 

and west of Sauk Lake. See figure 1 for location of outwash area.

Data from nearly 500 augered test holes, several hundred wells (domestic, 

irrigation, and industrial) , 60 observation wells, and 3 aquifer tests were 

analyzed to determine hydraulic properties of the outwash. Its saturated 

thickness was determined by subtracting the altitude of the bottom of the 

aquifer from the altitude of the water table at each test hole and well location. Saturated thickness ranges from 0 to about 140 feet. Average saturated 

thickness is about 35 feet. Plate 1 shows the distribution of saturated thickness based on data collected from test holes and from irrigation and observation wells. Most of the data were collected during fall 1978 and spring 1979.

Hydraulic conductivity is the volume of water that will move in unit time 

under a unit hydraulic gradient through a unit area of an aquifer measured at 

right angles to the direction of flow. It can be expressed in gallons per day 

per square foot, but the units are usually reduced to feet per day. Hydraulic 

conductivity was determined by aquifer-test results, laboratory grain-size
analyses, comparison of augered material with known grain-size analyses, and on 

degree of sorting. Table 1 shows the relation between grain size and estimated 

hydraulic conductivity. The relationship is one used by Helgesen (1977) and 

Lindholm (1980) in areas of outwash adjacent to Todd County. Lower hydraulic

Table 1. Hydraulic conductivity of surficial-outwash materials

Estimated

Predominant grain size hydraulic conductivity 

(Wentworth scale) (ft/d)

Sand, very fine (0.0625-0.125 mm) 10-50

Sand, fine (0.125-0.250 mm) 50-100

Sand, medium (0.250-0.5 mm) 100-300

Sand, medium with gravel (0.250-0.5 mm, >2 mm) 200-400 

Sand, coarse to very coarse (0.5-2.0 mm) 300-500

Sand, coarse to very coarse with gravel (0.5->2 mm) 400-600

Gravel O2.0 mm) 500-700

conductivity was assigned to poorly sorted materials and higher to well-sorted 

material. Figure 4 shows particle-size distribution of sand samples at three 

aquifer-test sites. The grain sizes range from very fine sand to medium gravel 

with most of the material ranging from medium to very coarse sand.

Transmissivity of the outwash aquifer was calculated at each test hole and 

well by summing the products of the saturated thickness of each lithologic unit 

below the water table and the hydraulic conductivity of the unit. Plate 2 

shows the distribution of transmissivity, which ranges from 0 to 20,000 ft2/d. 

Transmissivity is generally between 5,000 and 10,000 ft2/d. Most water supplies 

for irrigation are obtained in areas where transmissivity is greater than 

10,000 ft2/d.

Aquifer tests at three sites in Todd County (table 2) provided information 

from which transmissivity and storage coefficient (which is virtually equal to 

the specific yield of a well in an unconfined aquifer) were calculated. The 

tests varied in duration from 29 to 72 hours. Transmissivity and storage 

coefficient ranged from 4,600 to 18,500 ft2/d and 0.10 to 0.25, respectively. 

Methods used to calculate transmissivity and storage coefficient are from 

Boulton (19 as described by Lohman (1972). The tests are site specific and
OT

<Q

C

I 

I

 o

WEIGHT BY FINER, PERCENT 

I 

«

a

oc

o

 H

O

c

 o 

o

WEIGHT BY COARSER, PERCENT 
Table 2. Hydrologic properties of the surficial outwash determined by aquifer t

Length Average 

Saturated Pumping of Transmis- hydraulic 

Location Lithology thickness rate test sivity conductivity %

(feet) (gal/min) (hours) (ft2/d) (ft/d)

129N33W06ADD Sand, fine to very 51 300 48 4600 90 

coarse; and gravel.

130N33W04DBA Sand, medium to 43 850 72 14,500 337 

very coarse; and 

clean gravel.

131N32W18CBD Sand, fine to very 65 600 29 18,500 285 

coarse; trace of 

gravel.

* Ratio of horizontal to vertical hydraulic conductivity.
represent values at the test locations. At site 129N33W06ADD, for example, a 

nearby lateral boundary (sand-till interface) reduces the potential yield 

compared with that from a well in similar deposits farther away from such a 

boundary. However, the values can be used to estimate hydraulic properties in 

areas where the lithology is similar to that of the test site.

The ratio of horizontal to vertical hydraulic conductivity was also calculated at each test site based on curves showing nondimensional response to 

pumping a fully penetrating well in an unconfined aquifer (Lohman, 1972). The 

ratios (K^/Kg) in table 2 indicate that ground-water flow is largely 

horizontal.

To document fluctuations of the water table, 29 wells were installed and 

observed monthly. On completion of the project, the network will be turned 

over to the Todd County Soil Conservation Service for continued observation of 

water levels and water quality.

Ground-Water Flow

The configuration of the water table, based on water-level data from 

observation wells, irrigation wells, and augered test holes is shown on plate 

3. Ground water moves from areas of high head to areas of low head along lines 

perpendicular to the water-table contours. Regionally, in the Long Prairie 

valley, the direction of ground-water flow is much the same as regional streamflow. North of Little Sauk,.flow is northeast toward the Crow Wing River. 

South of Little Sauk, flow is south toward the Sauk River.

Ground-water flow in the northern part of the Swanville Spillway outwash 

is toward the South Branch Little Elk River. Flow in the southern part of the 

outwash is toward the Swan River.

The water table fluctuates as part of a dynamic flow system in response to 

stresses of recharge to and discharge from the aquifer. Fluctuations are not 

uniform throughout the aquifer because of areal variations in precipitation, 

soil properties, aquifer properties, and proximity of lakes and streams.

. Figure 5 shows water-level fluctuations in three representative observation wells in Todd County in 1979. Climatic records indicate that temperature 

was below normal in 1979 and precipitation was above normal in parts of the 

area in midsummer. The range of annual fluctuations for all the observation 

wells was generally less than 5 feet in 1979.

Recharge

The primary source of recharge in the outwash is precipitation and snowmelt. Recharge does not always correlate well with precipitation and is, 

therefore, difficult to predict. Generally, when precipitation is above 

normal, recharge is greater than when it is below normal. The average annual

12
 T

FEET IN SURFACE, LAND BELOW WATER TO DEPTH 

«Q

c

<D

Ol

I 

I

X

a 

o

«Q

o 

o

O

 »

o

o o-

 >

o t 

^ 

ft

p» 

«».

o

o 

a 

a

o

o 

c

CO

N

CO
precipitation at Long Prairief based on 65 years of record at the U.S. Weather 

Bureau stationf is 25.93 inches. Precipitation for 1978 and 1979 was 24.17 and 

28.63 inches, respectively.

If the physical properties of the aquifer are known, the net recharge can 

be estimated. The volume of water associated with a rise or decline in water 

levels can be estimated by multiplying the change in water level by the 

specific yield. Figure 6 is a hydrograph illustrating the method used to 

estimate annual spring recharge and net change in amount of water in storage in 

the aquifer in 1979 at site 131N32W08BCC. The average recharge based on 

analyses of 20 hydrographs for 1979, a year of above normal precipitation, was 

10.2 inches. Recharge estimates ranged from 5.9 to 13.3 inches. Average 

annual recharge is estimated at 8 inches, which compares favorably with estimates of recharge in adjacent areas (Lindholm, 1970; 1980; Helgesen, 1977).

The configuration of the water table (pi. 3) indicates that water from 

adjacent drift flows into the outwash along the margins of the aquifer. However, because the saturated thickness and hydraulic conductivity of material 

near the aquifer boundary are low, leakage across the boundary is not a significant percentage of the aquifer's water budget.

Some of the water applied for irrigation returns to the aquifer. The 

quantity depends on the rate of application and evapotranspi ration at the time 

of application. However, the return flow is also probably not a significant 

part of the aquifer's water budget.

Discharge* to

The importance of ground-water discharge in sustaining base flow of 

streams can be shown by flow-duration curves, the shape and slope of which 

reflect the hydrogeologic characteristics of the drainage area. Figure 7 shows 

the flow-duration curve of the Long Prairie River based on records collected at 

Long Prairie from 1972 to 1979. The curve was prepared by the total-period 

method, a statistical method based on daily discharge (Searcy, 1959). The 

curve relates stream discharge to the percentage of time during which that 

discharge is equaled or exceeded; for example, discharge of the Long Prairie 

River at Long Prairie equals or exceeds 75 ft^/s during 50 percent of the time.

Searcy (1959) suggests that a flow-duration curve with a steep slope 

denotes highly variable streamflow derived largely from direct runoff; whereas, 

a curve with a flat slope denotes fairly constant streamflow as a result of 

surface-water or ground-water storage. The curve shown in figure 7 of the Long 

Prairie River has a moderate slope, suggesting that streamflow is influenced by 

ground-water storage as well as by runoff from precipitation. The flat slope of 

the lower part of the curve indicates that water released from storage in the 

aquifer sustains streamflow during periods of dry weather.

Measurements of base flow were made to estimate ground-water discharge to 

the Long Prairie River. Thirty-five sites along the river and its tributaries 

from Long Prairie to the Crow Wing River at Motley (fig. 1) were measured 

during October 25-26, 1978, and October 29-30, 1979. For several days prior to

14
tn

O

Q.

O

Z

E

CO

UJ

9.5

10.0

10.5

11.0

O UJ 11.5

-I U.

mz

E 12.0

OIX

IQ. 

UJ 

O

12.5

13.0

13.5

JAN.

T

Hydrograph for ob

131N32W18BCC

Observed water level

Projected water-level trend

FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. O

Recharge (largely from snowmelt and early spring rain) = (water-level rise) x (estim

= (43.92 inches) x (0.25) 

= 10.98 inches

Figure 6. "Representative hydrograph Illustrating method used to determine net eff

water recharge and net change In amount of water In storage In the sur

aquifer during 1979 at Indicated site
§ 1000

o 

o uj

CO

DC UJ

0.

100

UJ 

UJ

u. 

o 

ffi

o

UJ

o

DC

O

1 10

i n i i r i i i r

October 29, 1979 

(base-flow measurement)!

October 26, 1973 

(base-flow measurement)

i i i i i i i i i ii i i i i i i i

0.01 0.1 1 10 30 50 70 90 99 99.9 99.99 

PERCENTAGE OF TIME INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

Figure 7. Flow-duration curve for the Long Prairie River at 

Long Prairie (1972-79)

16
the collection of base-flow measurements, climatic conditions had been cool, 

dry, and above freezing, therefore, reducing direct streamflow losses by evaporation or as storage due to ice buildup and also reducing gains of streamflow 

because of direct precipitation and overland flow. Results of the base-flow 

measurements show net streamflow gains (total minus tributary gains), attributed to ground-water discharge, between Long Prairie and Motley of 38 and 65 

ftVs in 1978 and 1979, respectively. Figure 7 shows dates and stream discharge 

at Long Prairie at the time that measurements were made. The gain in streamflow contributed by ground-water discharge represents a net gain of 0.85 and 

1.3 ftVs per river mile in 1978 and 1979, respectively.

Evapotranspiration

Lindholm and others (1972) estimated that 85 percent of the precipitation 

in the Crow Wing River watershed evaporates or is transpired by plants. Evapotranspiration includes both, direct evaporation from land surfaces and transpiration of water by plants. The rate of evapotranspi ration from the groundwater system depends on length of root system and depth to water in the 

aquifer; it decreases with depth to the water table. In this study, the 

potential evapotranspiration rate is assumed to be a uniform 22.5 inches per 

year as calculated by Lindholm and others (1972) by the method of Thornthwaite 

and Mather (1957). Locally, evapotranspiration is assumed to be maximum (22.5 

inches) when water levels are at land surface and to decrease with depth.

Depth to water in the outwash areas varies with location, altitude, and 

season. Water levels generally range from 0 to 30 feet below land surface, but 

most levels are less than 15 feet deep. Depth to water is greater in upland 

areas, whereas, the water table is at or near land surface in much of the 

valley areas.

use

Data on ground-water use in 1978 were obtained from the Minnesota 

Department of Natural Resources. Reported pumpage was 770 million gallons. 

This total does not include pumpage by the cities of Browerville and Long 

Prairie that obtain water mostly from semiconfined sand and gravel aquifers.

POTENTIAL YTRT.D OF WELLS

Potential yield to wells tapping the surficial-outwash aquifer was 

estimated from known aquifer characteristics (saturated thickness and transmissivity), assumed well characteristics, and pumping effects. In this analysis, 

the following assumptions were made:

1. Wells tapping the surficial-outwash aquifer are open to the full 

saturated thickness of the aquifer, are 100 percent efficient, 

and are of large diameter (16 inches) ;

2. drawdown after 30 days of pumping is equal to two-thirds the 

original saturated thickness;

17
3. interference from other wells and the effects of hydrologic 

boundaries are negligible;

4. storage coefficient of the aquifer is 0.20.

Plate 4 shows the estimated potential yield of wells completed in the 

surficial outwash. The yields were estimated from Tfteis' equation (1935), as 

described by Lohman (1972) and modified by Jacob (1944), to account for 

dewatering and reduction of transmissivity of an unconf ined aquifer near the 

well in response to vertical-flow components. Although some of the assumptions 

may not be fully satisfied, the method produces a quantitative estimate of the 

aquifer's water-yielding potential. The potential yields shown on plate 4 are 

intended to be relative and should not be used to predict production for 

individual wells. Additional test holes need to be drilled for site-specific 

information. Locally, aquifers are capable of supplying more than 2,000 gal/ 

min, but yields of 500 to 1,000 gal/min are more common. Wells in about half 

of the area underlain by the Long Prairie valley and Fawn Lake outwash are 

capable of yielding more than 100 gal/min. Outwash in most of the Scandia 

valley is capable of supplying about 100 gal/min, whereas only about 20 percent 

of the outwash in the Swanville area is capable of supplying more than 100 

gal/min.

Individual well yields may also differ from estimates on plate 4 because 

of proximity to hydrogeologic boundaries such as the outwash-till contact or 

lakes and streams. Yields in marginal areas may be increased by use of infiltration ponds or by connecting several wells to supply one system.

Figure 8 is a generalized hydrogeologic section illustrating four possible 

effects on water levels of hydrologic boundaries and pumping of nearby wells. 

The amount of interference depends on the proximity of the boundary to the well 

and the rate of ground-water flow to the pumped well. The first scheme shows 

the effects of a well pumping near an impermeable boundary. Drawdown is 

greater between the well and the boundary because of a lack of ground-water 

flow toward the well. The second scheme illustrates the effects of a stream 

boundary. Drawdown is not as great because the stream supplies additional flow 

toward the well. The third scheme is similar to the second with water induced 

from a lake instead of a stream. A lake or stream, however, will act as a 

recharge boundary only as long as the withdrawals are less than the storage or 

rate of replenishment. The fourth scheme represents interference from another 

pumping well. Drawdown between the two wells is increased and is equal to the 

sum of the drawdowns that would result at that point caused by pumping each 

well. Well interference is a normal consequence of full development of an 

aquifer. Real drawdowns may be greater than those shown in figures 9 and 10 

because wells are not 100 percent efficient, that is, drawdowns within wells 

are generally greater than drawdowns immediately adjacent to the wells because 

of inefficiencies of the wells. This condition can be caused by improper well 

design, improper well development, or screen-related problems such as clogging 

or corrosion.

18
Well Land surface Wat,er table Water level 

/ Well Stream Lake Well "' "

Impermeable

boundary causes

increased drawdown

Surficial aquifer

^~r*~ 

IF-'. T

NS

 :::,- \

r ' "',-'

tafa??w-^M

': . _i.i- . ^jf ~.i:.^'^

' . .....'. .. .-. ' : 

-i vviiiic puinpiiiy pp^f'-1 r--r-:"

x . r . / ..... :; " ' . ^

.l......i,i.. ,' n " ' ' ; ;' 

UJ i ii . i

y y y

Induced infiltration Well interference 

from stream and lake causes 

causes decreased increased 

drawdown drawdown

NOT TO SCALE

Figure 8. Generalized hydrologic section Illustrating effects of hydrogeologlc boundaries 

and nearby wells on cones of Influence
ro 

o

I I I I I II 

T=3Q

Distance-drawdown curves based on 

nonequilibrium equation of Theis (1935)

Transmissivity (T) = 2500 to 30,000 feet

squared per day

Storage coefficient=0.20

Pumping rate«300 gallons per minute

Period of pumping«30 days

Drawdowns (s') are not adjusted for 

dewatering of the aquifer

10 50 100 500 1000 

DISTANCE FROM PUMPED WELL, IN FEET

5000 10,000

Figure 9."Theoretical relationship of drawdown to distance from a pumped well
IZ

FEET IN f (s') DRAWDOWN UNADJUSTED 

<Q

C

(D O 

Co 3 

* 3 

OQ,

Q)

2o

(0

*

*.

<D

Q,
Analytical methods for determining the cone of influence or drawdown in 

the vicinity of a pumping well are available for a variety of aquifer characteristics and boundary conditions. The method used in this report is the Theis 

nonequilibrium equation as outlined in Lohman (1972). Figure 9 shows theoretical relations of drawdown caused by vertical-flow components near the well 

(unadjusted for dewatering), to distance from a pumped well for various values 

of transmissivity. Drawdown can be calculated for distances from 1 to 10,000 

feet from the pumping well. Although the pumping rate used to construct the 

graph is 300 gal/min, the curves are applicable to other rates because unadjusted drawdown is almost directly proportional to the pumping rate. For 

example, if the pumping rate is doubled to 600 gal/min, drawdowns at a given 

distance and time would be about twice those shown in figure 9. For unconfined 

aquifers, such as in this study, the Theis equation is not directly applicable 

because it does not account for dewatering of the aquifer. Therefore, drawdowns must be adjusted by using the Jacob equation (1944). This factor becomes 

especially important in the immediate vicinity of the pumped well. Figure 10 

illustrates the theoretical curves for adjustment of drawdown for dewatering by 

Jacob's (1944) method. In this analysis, the same assumptions were made as for 

calculating potential yields of individual wells.

If drawdown due to interference between two pumping wells is to be calculated at a specific site, the drawdown at the site caused by pumping each of 

the wells must be calculated by use of figure 9; the results are then summed. 

If water-table conditions exist, the combined drawdowns must be adjusted for 

dewatering by using figure 10. This analytical method for calculating interference is an approximation of drawdown and should be used with caution when 

drawdowns exceed 25 percent of the original saturated thickness.

Hypothetical examples on the use of figures 9 and 10 are given below.

Example 1. A well is pumping 900 gal/min from an unconf ined (water table) 

aquifer where the saturated thickness is 40 feet, the average hydraulic 

conductivity is 500 ft/d (based on table 1) and the storage coefficient is 0.2. 

The well is open to the full saturated thickness and is 100 percent efficient.

A. Find the drawdown 1 foot from the center of the well after 30 days of 

pumping.

1. Transmissivity is 20,000 ft2/d (40 ft x 500 ft/d).

2. From figure 9, unadjusted drawdown for a well pumping 300 gal/min 

is about 3.6 feet, or 10.8 feet (3.6 ft x 3) when pumped at a rate 

of 900 gal/min.

3. From figure 10, an unadjusted drawdown of 10.8 feet in an aquifer 

having an initial saturated thickness of 40 feet gives an adjusted 

drawdown of about 12 feet.

Example 2. Two wells, 200 feet apart, are pumping 900 gal/min from an unconfined aquifer where the saturated thickness is 40 feet, the average hyciraulic 

conductivity is 500 ft/d, and the storage coefficient is 0.2. The wells are 

open to the full saturated thickness and are 100 percent efficient.

22
A. Find the drawdown midway between the two wells after 30 days continuous 

pumping.

1. Transmissivity is 20,000 ft2/d (40 ft x 500 f t/d) .

2. From figure 9, unadjusted drawdown at the midpoint between the 

wells with only one well pumping 300 gal/min is 1.5 feetf or 

4.5 feet when pumped at 900 gal/min.

3. The unadjusted drawdown midway between the interfering wells 

with both wells pumping 900 gal/min would be equal to the sum 

of the drawdown at 100 feet from each well f or about 9.0 feet.

4. From figure 10 , adjusted drawdown for dewatering is about 10.2 feet.

B. Find the drawdown 1 foot from the center of each well after 30 days 

pumping.

1. Transmissivity is 20 , 000 ft2/d (40 ft x 500 ft/d) .

2. From figure 9f unadjusted drawdown 1 foot from a well pumping 300 

gal/min is 3.6 feet f or 10.8 feet when pumped at 900 gal/min. Unadjusted drawdown 200 feet from a well pumping 300 gal/min is 1.2 

feet f or 3.6 feet when pumped at 900 gal/min.

3. Drawdown at one well influenced by the other pumping well will equal 

the sum of the drawdowns; therefore, the drawdown at either well 1 

foot from the center of the well is about 14.4 feet.

4. From figure 10 f adjusted drawdown for dewatering is about 19 feet.

WATER

The naturally occurring concentration of minerals in ground water is 

influenced largely by the soil and rock material through which the water moves. 

The degree of influence largely depends on ion exchange, residence time, 

chemical reactions with the materials, and solubility of the minerals. Chemical or petroleum spills, fertilizers, pesticides, trace organics, and sewage 

can alter the natural quality of ground water if such contaminants seep into 

the aquifer.

Water use primarily determines the acceptability of the water. Limits for 

major chemical constituents in water used for domestic consumption are shown at 

the bottom of table 3 as established by the Minnesota Pollution Control Agency 

(1978). Standards for other water uses, such as for fisheries, recreation, and 

agriculture, are available from the Minnesota Pollution Control Agency.

Water from wells in the outwash is generally suitable chemically for 

domestic consumption and most other uses. However, results indicate that in 

localized areas concentrations of selected constituents exceed Minnesota 

Pollution Control Agency (1978) recommendations for fisheries and recreation

23
Table 3. Chemical analyses of

[Analyses by U.S. Geological Survey. Results

Sampling site 

locations

Ground water 

128N33W17CCB 

128N33W17CCB 

128N33W05CAC 

129N33W05CCB 

129N33W05CCB 

129N33W21BBD 

129N33W21BBD 

130N33W04DBD 

130N33W04BD 

130N33W08BDD 

130N33W08BDD 

130N33W17DBB 

130N33W17DBB 

131N32W18BBC 

131N32W18BCC 

131N32W18BCC 

131N34W27ABB 

131N34W27ABB 

132N33W26DCC 

132N33W26DCC 

133N32W14CCD 

133N32W14CCD 

133N32W14CCD 

Surface wate] 

129N33W20BAA 

129N33W20BAA 

129N33W20BAA 

132N32W05CCB 

132N32W05CCB 

132N32W05CCB 

133N3ML7BCA 

133N31WT7BCA 

133N3ML7BCA

Recommended '. 

consumption 

Control Aqen<

(feet) of well Dpth 

collection of Eate 

62 4-30-79

62 9-18-79 

58 3- 8-79 

27 4-30-79 

27 9-18-79 

83 3- 8-67 

83 11-28-79 

46 4-30-79 

46 9-18-79 

60 6-22-64 

60 11-28-79

27 4-30-79 

27 9-18-79 

27 3- 7-79 

27 5- 1-79 27 9-11 79 M f ^ j.*j* , ^

40 3- 8-67 

40 11-28-79 

31 5- 1-79 

31 9-18-79 

24 5- 1-79 

24 3- 6-79 

24 9-18-79 

c (Long Prairie 

 3- 5-79 

 4-30-79 

 9-18-79 

 3- 6-79 

 5- 1-79 

__ 9-18-79 

 3- 7-79

__ 5- i_79 

 9-18-79

Limits for domes 

(Minnesota Polli 

sy. 1978) .

(CaCC> )Alkalinity 3

250 

220 

320 

180 

150 

290 

310 

200 

220 

290 

330 

290 

290 

310 

220 

250 

270 

290 

200 

220 

180 

180 

260 

Rivei 

250 

190 

230 

280 

160 

230 

270 

160 

240

stic 

ition

dissolved Boron3 

Uvg/L)

i

<10

20

10 

:)

30 

20

20

dissolved Calcium, 

71 

66 

73 

56 

35 

93 

93 

65 

66 

92 

96 

91 

92 

69 

64 

67 

92 

97 

80 

70 

53 

52 

79

50 

53 

44 

64 

47 

51 

68 

48 

52

Organic carbon, 

dissolved

1.6

2.9 

6.4

6.9

2.7

4.7 

4.6

1.4

8.4 

7.1

9.6 

16

10

dissolved Chloride, 

2.1 

9.6 

1.7 

22 

9.4 

5.8 

15 

23 

9.6 

2.0 

12 

8.7 

7.7 

1.1 

1.5 

1.0 

9.4 

92 

32 

5.8 

1.2 

1.3 

2.1

31 

9.3 

12 

13 

6.3 

13 

13 

6.8 

15

250

dissolved Pluorlde, 

0.2 

.1 

.2 

.2 

.1 

.1 

.2 

.1 

.1 

.2 

.2 

.1 

.1 

.2 

.1 

.2

.1 

.1 

.1 

.1 

.1 

.1

0.1 

.1 

.1 

.1 

.1 

.1 

.1 

.1 

.1

1.5

Hardness 

(noncarbonate)

18 

0 

0 

46 

14 

50 

33 

20 

0 

2 

25 

44 

47 

0 

35 

0 

50 

59 

78 

21 

0 

0 

0

0 

16 

0 

0 

15 

4 

0 

20 

0

(total) Hardness 

270 

220 

230 

226 

164 

340 

343 

220 

220 

292 

355 

334 

337 

310 

255 

250 

320 

349 

278 

241 

180 

170 

250

250 

210 

230 

270 

180 

230 

280 

180 

240

dissolved Iron, 

Ufg/L)

20 

5,100 

1,400 

1,400 

570 

1,200 

1,400 

9,800 

5,100 

3,900 

2,100 

60 

60 

2,000 

5,800 

5,500 

110 

10 

1,500 

860 

2,900 

2,700 

3,800

1,300 

110 

30 

1,300 

180

2,800 

150 

300

300

Bicarbonate

205 

180 

262 

148 

123 

238 

254 

164 

180 

238 

271 

238 

238 

254 

180 

205 

221 

238 

164 

180 

148 

148 

213

205 

156 

189 

230 

131 

189 

221 

131 

197

Limit for N03 as N; N02 is assumed to be negligible

24
ground water and surface water

in milligrams per liter, except as noted]

dissolved agneslum, 

s

22

13

24

21

21

26

27

14

13

22

28

26

23

23

23

19

22

25

19

16

9.6

9.6

13

30

18

28

26

14

26

26

14

26

dissolved anganese, 

US/13

s->

20

490

80

210

110

70

160

440

490

180

180

10

8

170

200

250

20

1

160

120

260

260

430

60

80

50

1,700

40

20

2,100

40

20

50

COcd

O CD

H 

+ 0 

CO 

OJ CO

& £

6.4

.09

<.01

<.01

.24

 

.21

.01

.09

 

.03

4.5

5.3

<.01

.03

.01

 

4.5

.02

.01

.01

<.01

.01

.08

.04

.10

.01

.17

.22

<.01

.11

.13

410

ffi

a

7.8

7.4

7.6

7.8

7.8

7.1

7.7

7.3

7.4

7.7

8.0

7.3

7.5

7.7

7.6

7.5

7.4

7.3

7.5

7.6

7.4

7.6

7.5

7.6

7.8

8.0

7.4

7.7

8.1

7.4

7.8

8.4

dissolved hosphorus, 

DH

0.01

<.01

.04

.01

.01

 

.05

.01

<.01

 

.06

.03

<.01

.09

.01

<.01

 

.05

.01

.01

.18

.19

.20

.05

.03

.02

.02

.03

.02

.13

.03

.02

dissolved otassium, 

PH

1.2

1.4

2.6

1.9

1.2

1.2

2.4

1.2

1.4

1.8

2.0

2.1

1.9

1.4

1.4

1.2

1.2

3.7

1.4

1.3

.8

.9

.9

5.2

4.0

3.8

3.9

3.4

3.0

3.8

3.3

3.2

Issolved solidssum) calculated 

Q "* '

315

265

320

273

179

 

403

265

265

 

411

386

381

315

256

276

 

 

319

268

204

202

280

333

231

258

326

198

265

334

198

273

issolved solids)tons/acre-foot solids Issolved residue evapo- on 180 C) atlont odium-adsorption 

atlo

Q * ' (

0.43

.35

.43

.28

.26

 

.54

.38

.35

 

.44

.53

.48

.43

.30

.37

 

.68

.47

.38

.29

.28

.40

.46

.34

.37

.46

.30

.39

.47

.30

.39

 * ^-^ "

316

358

317

206

189

420

3%

377

258

399

324

393

353

314

223

275

460

503

343

279

210

205

291

337

247

269

340

221

285

344

223

285

500

CO ^

0.1

.1

.2

.2

.1

.2

.3

.1

.1

.1

 

.1

.1

.2

.2

.1

.2

 

.1

.1

.1

.1

.1

0.6

.2

.3

.3

.1

.3

.3

.2

.3

ilica, dissolved

CO

20

19

14

5.2

5.3

 

21

13

19

23

23

20

11

22

17

21

 

13

16

15

20

20

20

19

9.7

14

20

5.4

13

22

5.9

12

dissolved odium, 

CO

4.0

3.4

8.2

7.0

3.8

6.4

11

3.6

3.4

5.7

11

4.4

6.4

6.0

6.3

5.1

8.0

3.6

3.5

3.1

3.9

4.1

45

23

5.3

9.9

12

4.2

11

12

4.8

12

peclflc conductance 

C) t/mho/cm 25at dissolved ulfate, 

CO ^> CO

510 14

440 14

475 2.9

390 37

340 5.4

635 43

568 45

465 15

440 14

665 12

580 32

595 39

650 33

535 3.2

520 3.9

470 4.9

650 38

570 25

500 45

480 23

350 3.8

340 2.6

480 .1

582 16

440 17

510 1.0

590 16

325 20

515 2.1

600 9.4

340 18

480 7.9

250

temperature ater 

ac)

^ * ^

7.2

10

6.5

7.2

11.5

 

8.0

8.2

10

9.4

8.0

8.0

9.0

6.0

9.0

10

 

8.0

7.5

9.0

6.0

6.0

7.0

6.1

16

 

6.9

17.5

 

6.5

17

25
and for industrial consumption. The water is predominantly a calcium bicarbonate type, and is hard to very hard. Concentrations of hardness ranged from 

164 to 355 mg/L.

Twenty-three water samples were collected from wells in the outwash and 

nine from the Long Prairie River (table 3). Most sites were sampled once in 

spring, when water levels and streamflow are relatively highr and again in 

fall, when levels and flow are relatively low. Three of the ground-water sites 

(two municipal and one creamery, 129N33W21BBD, 130N33W8BDD, and 131N34W27ABB, 

respectively) were sampled because they provide historical data for comparison 

with current data. The remainder of the sites are observation wells drilled 

specifically for the study. Each of the wells was pumped until pH and specific 

conductance stabilized. All samples were filtered and preserved for shipment 

to the U.S. Geological Survey Central Laboratory in Atlanta, Ga.

As indicated by the results in table 3, the quality of surface water and 

ground water is similar, indicating that ground water is the major contributor 

to streamf low. Generally, the ground water is suitable for most uses. Although data in table 3 suggest slight seasonal variations in most constituents, 

data are insufficient to establish trends.

Dissolved chlorides are essential to plants and animals, but excess concentrations may become toxic. High concentrations generally can be attributed 

to excess amounts of fertilizers, road deicing salts, and (or) sewage effluents. The recommended limits for chloride concentrations in water for 

domestic consumption as established by the Minnesota Pollution Control Agency 

(1978) is 250 mg/L. Chloride concentrations within the study area ranged from 

1.0 to 92 mg/L.

The dissolved solids (listed as "residue on evaporation at 180°C") consist 

primarily of calcium, magnesium, and bicarbonate. High concentrations of these 

constituents may cause well-screen incrustation. Chemical reactions with 

manganese may produce staining and odor. Hie distribution of dissolved solids 

in ground water is shown on figure 11. The Minnesota Pollution Control Agency 

(1978) recommended limit for domestic consumption of dissolved solids is 500 

mg/L. Concentrations within the study area ranged from 189 to 503 mg/L.

Iron is an essential element to both plant and animal metabolism, but can 

make water unsuitable for some uses in excessive amounts. Dissolved iron 

concentrations in ground water generally exceed the limit of 300 jug/L recommended by the Minnesota Pollution Control Agency for domestic consumption. For 

some uses, treatment may be necessary to reduce staining of fixtures and chemical reactions. Lindholm and others (1972) and Helgesen and others (1975) found 

that iron concentrations were generally high in the Pleistocene deposits. Its 

origin may be the "iron range" formation to the north. Slight increases in 

concentrations may also be from the dissolution of the black steel well 

casings.

Some chemical constituents, such as nitrate, may be desirable in certain 

concentrations for plant growth. However, in excessive concentrations, nitrate 

may produce extreme health hazards, especially to infants. High nitrate concentrations, such as those found near Clarissa, are usually indicative of a

26
46° 15

46° 00'-*

"- r")/^Littie Falls

[___

10 KILOMETERS

270

EXPLANATION

282 Ground-water sampling site A Surface-water sampling site 

Number is dissolved-solids Number is dissolved-solids

concentration in milligrams concentration in milligrams

per liter per liter

Figure 11. Concentration of dissolved soiids

27
pollution source attributable to barnyards and sewage. Another source of 

nitrate is fertilizers. As irrigation becomes more intense, nitrate may 

accumulate in water bodies. One localized area in which nitrate concentrations 

in ground water are higher than normal is south of Long Prairie near Round 

Prairie. Figure 12 shows areal distribution of NO? + N03 as nitrogen. Although the laboratory determinations of NC^-N includes N(>2 part of these 

analyses is assumed to be negligible compared to the NO^. The Minnesota 

Pollution Control Agency (1978) recommends a N03 as N limit of 10 mg/L for 

domestic consumption. Concentrations in the study area ranged from less than 

0.01 to 6.4 mg/L.

Manganese is an essential trace element for both plants and animals. In 

lower concentrations, manganese may react with other elements to produce objectionable taste, stains, and odors (U.S. Environmental Protection Agency, 1976, 

p. 179). Accumulation of manganese in ground water may occur with long-term 

application of fertilizers (Gough and others, 1979). The limit recommended by 

the Minnesota Pollution Control Agency (1976) for domestic consumption is 50

Boron, sodium, and salinity can be detrimental to crops if concentrations 

become too great. Small concentrations of boron are essential to plant growth, 

but high concentrations become toxic. The limit recommended by the Minnesota 

Pollution Control Agency for boron for agricultural use is 500-i/g/L. The range 

of concentrations observed in ground water and surface water were relatively 

low «10 to 30^g/L).

The sodium-adsorption ratio (SAR), a computed ratio of sodium, calcium, 

and magnesium was developed by the U.S. Salinity Laboratory (1954) and is used 

as an indicator of the suitability of water for irrigation. The ground-water 

samples all show low sodium-adsorption ratios, ranging from 0.1 to 0.3.

Salinity or salt concentrations in the soil can also be extremely hazardous to crop growth. A method developed by the U.S. Salinity Laboratory (1954) 

rates salinity hazard based on the sodium-adsorption ratio and specific conductance. Water in the study area is in the medium salinity-hazard range, with 

specific conductance ranging from 325 to 665 Jt/mhos/L (table 3). Salinity 

probably will not become a serious problem because of good leaching and 

drainage characteristics of the sandy soils.

Four wells were sampled for pesticide residuals. No trace was found of 

most pesticides, but residuals of atrazine were found at two sites and residuals of simetryne and 2,4-D were found at one site. Table 4 lists pesticides 

analyzed and the concentrations observed. None of these concentrations are at 

levels known to be a health risk to persons drinking the water. The 2,4-D 

limit for domestic water supplies is 100 jjg/L (U.S. Environmental Protection 

Agency, 1976, p. 250). There are no set limits for atrazine and simetryne, and 

the concentrations found in these samples are not considered to be a health 

hazard.

Although the water generally is suitable for most uses, higher than normal 

concentrations of chemicals related to agricultural practices were found 

locally.

28
46° 15

ie Falls

[___

EXPLANATION

 Ground-water sampling site °- 13A 

Number is dissolved nitrogen 

(NO2 + NO3 as N) in milligrams 

per liter

u 10 MILES

I I I I i i

I Til T I 1 

0 10 KILOMETERS

Surface-water sampling site 

Number is dissolved nitrogen 

(NO2 + NO3 as N) in milligrams 

per liter

Figure 12.-Concentration of dissolved nitrogen (NO2 +NO3 as nitrogen)

29
Table 4. Pesticide analyses of water from the surficial aquifer

Values in micrograms per liter; 0.0 indicates concentration is below 

laboratory detection level of 0.1; 0.00 indicates concentration is 

below laboratory detection level of 0.01 _

Physical and ______________Well number_______________

chemical 128N33W17OB 129N33W05CDB 129N33W05CDB 130N33W04DBD 

characteristics

Depth of well

(in feet)........... 40 20 20 25

Date of collection.... 9-18-79 3- 8-79 9-18-79 9-18-79

Ametryne.............. 0.0 0.0 0.0 0.0

Atratone.............. 0.0 0.0 0.0 0.0

Atrazine.............. 2.3 0.0 0.1 0.0

Cyanazine............. 0.0 0.0 0.0 0.0

Cyprazine............. 0.0 0.0 0.0 0.0

Prometone............. 0.0 0.0 0.0 0.0

Prometryne............ 0.0 0.0 0.0 0.0

Propazine............. 0.0 0.0 0.0 0.0

Silvex................ 0.00 0.00 0.00 0.00

Simazine.............. 0.0 0.0 0.0 0.0

Sirnetone.............. 0.0 0.0 0.0 0.0

Simetryne............. 1.0 0.0 0.0 0.0

2,4-0................. 0.01 0.00 0.00 0.00

2,4-DP................ 0.00 0.00 0.00 0.00

2,4,5-T............... 0.00 0.00 0.00 0.00

30
DIGITAL M3DEL

The two-dimensional digital model of Trescott and others (1976) was used 

to simulate the ground-water-flow system and its response to stresses in part 

of the study area. The basic equationf whose solution is approximated by the 

model for an unconf ined aquiferf may be expressed as:

where :

+ W(x f yf t) 

3x x ay y 3t

Kxx f Kyy = the principal components of the hydraulic conductivity 

tensor (Lt"1) ,

Sy = the specific yield of the aquifer (dimensionless) , 

b = the saturated thickness of the aquifer (L) , 

h = the hydraulic head (L) , and

W(x f yft) = the volumetric flux of input or withdrawal per unit 

surface area of the aquifer (Lt-1) .

A two-dimensional model was selected because flow in the aquifer is virtually horizontal. The modeled area is a single layer of relatively uniform 

glacial sand and gravel underlain and generally bordered by till of relatively 

low hydraulic conductivity. The strongly implicit procedure was used in the 

model to solve the simultaneous finite-difference equations representing the 

aquifer system.

Location of the Modeled Area

The modeled area, shown in figure 13, centers on the Long Prairie valley 

outwash. The modeled area is bordered by glacial outwash-till contacts, 

ground-water divides, and small outwash stringers that join the main aquifer. 

Areas not modeled were smaller outwash sands detached from the Long Prairie 

valley outwash; such as (1) the Scandia valley, (2) Swanville, (3) near Grey 

Eagle, and (4) near Sauk Lake where pumpage rates are insignificant.

Description of tll 

In order to simulate the aquifer's irregular boundaries, the model was 

subdivided into blocks by a variable grid containing 25 rows and 30 columns. 

Grid blocks ranged in size from 0.25 to 3 mi 2 (160 to 1,920 acres). The 

smallest blocks were assigned to an area near Browerville where ground-water 

development for irrigation is greatest. A variable grid was necessary to represent the boundaries accurately and provide greater detail in the highly developed areas. The model uses a block-centered scheme, which means calculations are made at the center of each block. This central point is referred to 

as a node. At each node, aquifer properties and hydraulic stresses are assigned 

average block values. The finite-difference grid is shown in plate 5A.

31
94° 30' i

46° 15

jHj_ittle Falls

[___

Outwash 

Till

EXPLANATION

10 MILES I ii i I I I

10 KILOMETERS

E3 Area of grid not modeled 

Geologic contact

Modeled area Grid boundary

Figure 13. Location of modeled area

32
of l mnvl r'

Selection and treatment of model boundaries is critical. The model must 

either simulate the boundary effects explicitly-'- placed far enough away from 

present or anticipated stresses so that model calculations are not significantly affected by the boundary. Boundaries may be treated as (1) constant 

head, (2) constant flux, or (3) head -dependent flux. A constant-head boundary 

allows as much flux across the model boundary as necessary to maintain initial 

water levels at the boundary regardless of stress imposed on the model. A lack 

of water-level declines in the stress area will result if this boundary is not 

placed far enough away from stress areas. A constant-flux boundary allows a 

predetermined and fixed amount of water across the boundary that does not 

change in response to simulated stress. The constant flux may be zero (impermeable boundary) or have a finite value. A head-dependent flux allows the 

model to simulate variable flux into or out of the aquifer in relation to the 

transmissivity and the difference between a model-computed head and a fixed 

head specified in the model.

Constant heads were assigned to nodes at the aquifer boundaries where 

significant amounts of water enter or leave the system as streamflow or groundwater flow. The remainder of the lateral boundary nodes were modeled as noflow boundaries, which allow no inflow to the aquifer from the adjacent till. 

Nodes representing the location of major streams within the modeled area were 

modeled as head-dependent flux boundaries to simulate flow into or out of the 

aquifer as streambed leakage. Assignment of boundary types is shown in plate 

5A.

nalihraHon of the Bfodel

Before the model was used to simulate aquifer response to projected 

stresses, it was calibrated at steady state to assure that it represented 

average annual hydrologic conditions in the aquifer. Steady-state calibration 

was done by successively adjusting input parameters until calculated water 

levels and ground-water discharge to streams acceptably matched those 

observed in the field. Computed ground-water levels were accepted if they were 

within plus or minus 5 feet of water levels measured in observation and irrigation wells in October 1979. At that time, water levels and ground-water 

discharge to streams were approximately equal to average annual conditions. 

Computed ground-water discharge to streams was accepted if it was within plus 

or minus 30 percent of the streamflow gain measured in October 1979. The 

solution obtained by the steady-state model is not unique and similar results 

may be obtained by several combinations of parameter values. However, input 

parameters were adjusted within reasonable limits consistent with the conceptual model of the aquifer system. Table 5 shows a comparison of observed water 

levels with water levels computed by the calibrated model.

Boundary must be simulated so that model responses mimic natural responses,

33
Table 5. Ccn^arison of computed and observed water levels 

for the calibrated steady-state model

Observed

Block Computed water level , Difference 

number water level October 1979 (Computed 

(row, column) (altitude in feet (altitude in feet minus observed

above sea level) above sea level) in feet)

5,

6,

7,

7,

8,

8,

10,

10,

11,

15,

17,

18,

18,

21,

23,

12

8

13

15

14

18

8

25

2

15

27

19

25

28

27

1,268

1,286

1,266

1,262

1,264

1,258

1,279

1,249

1,305

1,277

1,251

1,263

1,239

1,231

1,246

1,267

1,284

1,267

1,262

1,261

1,259

1,282

1,249

1,307

1,276

1,254

1,260

1,240

1,233

1,244

+1

+2

-1

0

+3

-1

-3

0

-2

+1

-3

+3

-1

-2

+2

The approximate water budget for the calibrated steady-state model is:

Inflow

Cubic feet 

per second

Recharge from precipitation................. 68.2

Leakage from streams........................ 2.8

Total.......... 70.0

Outflow

Leakage to streams.......................... 46.4

Pumpage..................................... 3.2

Evapotranspiration.......................... 20.4

Total........... 70.0

34
For model calibration, certain hydrologic characteristics of the groundwater system were fixed based on available data. An evapotranspiration rate 

equivalent to 22.5 inches per year (Lindholm and others, 1972) was used in the 

model. The evapotranspiration rate was assumed to be at full potential when 

water levels are at land surface and to decrease linearly to zero when water 

levels fall below 5 feet.

Pumpage for the calibrated model was based on 1978 records of the 

Minnesota Department of Natural Resources. A total pumpage of 2.1 Mgal/d was 

divided among 30 pumping centers that coincided with the field locations of the 

wells. Locations of these pumping centers are shown in plate 5B.

During model calibration, the values of several hydrologic properties were 

varied to determine the sensitivity of the model to changes in these 

parameters. Factors that caused the greatest differences between computed and 

observed water levels were variations in areal recharge, flow across lateral 

boundaries, and leakage coefficients of the streambed. The following schemes 

were used to determine sensitivity of each of the major factors.

Average annual areal recharge, based on several years of record, was 

estimated to be 8 inches. However, annual recharge rates of 4, 8, and 12 

inches were applied at steady state to determine model response. Table 6 shows 

the difference between computed and observed water levels at representative 

blocks for annual areal recharge rates of 4, 8, and 12 inches. Specific blocks 

listed contain observation wells. An annual recharge rate of 8 inches provides 

the best overall match of water levels and compares favorably with estimates of 

recharge in adjacent outwash areas (Lindholm, 1970; 1980; Helgesen, 1977).

The lateral boundaries were modeled as no-flow, which do not allow the 

model to simulate any ground-water flow across the boundaries into or out of 

the aquifer. Model sensitivity was tested by simulating various amounts of 

leakage across the boundaries based on the local hydraulic gradient and comparing the calculated water levels with the observed water levels. The addition of leakage at lateral boundaries greatly dampened model response to 

changes in other model parameters at nodes adjacent to the boundaries. Simulation of no-flow boundaries produced the best overall results and they were used 

for model calibration and subsequent model experiments.

The sensitivity of the model to stream leakage was tested by varying the 

leakage coefficients in several model simulations. Table 7 shows the difference between computed ground-water discharge to streams and the observed 

discharge upstream from the Philbrook and Motley gaging stations. Ground-water 

discharge rates computed by the model for streambed leakage coefficients of 0.1 

and 1.0 (ft/d) are similar and both match observed discharge in October 1978 

and October 1979 quite well. However, a leakage coefficient 0.1 (ft/d)/ft was 

accepted for model calibration and used in subsequent simulations because it 

represents a more restrictive hydraulic connection between the aquifer and the 

stream. This value also compares favorably with stream-leakage coefficients in 

nearby outwash areas of similar geologic setting (Larson, 1976; Lindholm, 

1980). Use of the leakage coefficient of 0.1 (ft/d)/ft also produced the best 

match of computed to observed water levels at nodes adjacent to stream nodes.

35
Table 6. Difference between computed and observed (October 1979) 

water levels for different recharge rates

uo

ON

Block

(row,

5,

6,

7,

7,

8,

8,

10,

10,

11,

15,

17,

18,

18,

21,

23,

column)

12

8

13

15

14

18

8

25

2

15

27

19

25

28

27

Computed

water level

(feet)

1,267

1,283

1,265

1,261

1,263

1,257

1,278

1,247

1,303

1,274

1,248

1,261

1,237

1,228

1,244

Annual areal recharae (inches)

4

Computed

minus

observed

water level

(feet)

0

-1

-2

-1

+2

-2

-4

-2

-4

-2

-6

+1

-3

-5

0

Computed

water level

(feet)

1,268

1,286

1,266

1,262

1,264

1,258

1,279

1,249

1,305

1,277

1,251

1,263

1,239

1,231

1,246

8

Computed

minus

observed

water level

(feet)

+1

+2

-1

0

+3

-1

-3

0

-2

+1

-3

+3

-1

-2

+2

wa

Total -29 -1 
Table 7. Comparison of observed and model-computed ground-water 

discharge to the Long Prairie River

[All values are expressed in cubic feet per second]

Stream Observed ground-water discharge Computed ground-water discharge 

reach______________________ _______________________

Date Leakage coefficient f(ft/d)/ft]

Oct. 26, 1978 Oct. 29, 1979 1.0 0.1 0.01 0.001

Long Prairie to

Fhilbrook. 36 43 37 35 24 9

Long Prairie to

Motley. 38 65 53 50 36 19

After calibration of the model at current steady-state conditions in the 

aquifer, the model was used to estimate response of the aquifer to several 

possible combinations of water-supply development and climatic conditions. Ihe 

model provides managers with a tool for estimating regional trends in aquifer 

response to drought and ground-water development. However, because the model 

was calibrated to current steady-state hydrologic conditions rather than to 

long-term data, the model results must be used with caution. The accuracy and 

validity of the results can be determined only by collecting additional waterlevel data as development occurs and using that data to recalibrate the model 

and demonstrate its ability to simulate aquifer responses through time. Drawdowns computed by the model are based on simplified assumptions and actual 

drawdowns in the field will probably differ. In addition, computed drawdowns 

are averaged over the entire grid block; therefore, computed values will not be 

as great as actual drawdowns at specific wells.

Experiment 1 simulates aquifer response to increased pumping at existing 

pumping centers with an average recharge rate of 8 inches per year and pumpage 

of 5.2 million gallons per day (1978 pumpage multiplied by 2.5). Computed 

results suggest that at steady state (1) water-level declines may be less than 

1.5 feet regionally and (2) reduction of aquifer discharge to streams would be 

less than 2 percent.

Experiment 2 simulates aquifer response to decreased recharge with present 

pumping rates. A drought of 4 years was simulated, during which the aquifer 

storage coefficient was assumed to be 0.2 and recharge was reduced by half.

37
Recharge was assumed to be 4 inches annually and pumpage was 2.1 million 

gallons per day. Model results indicate that (1) water levels by the end of 

the 4-year cycle may decline locally by as much as 4 feet and (2) aquifer 

discharge to streams may be reduced 5 percent. The distribution of drawdowns 

for experiment 2 is shown in plate 5B.

Experiment 3 simulates aquifer response to a drought of 1 year combined 

with increased pumpage. Aquifer storage coefficient was assumed to be 0.2, 

recharge was assumed to be 4 inches, and pumpage was simulated at 5.2 million 

gallons per day (1978 pumpage multiplied by 2.5) to simulate the additional 

pumpage necessary for adequate moisture to crops. Pumping was timed to simulate seasonal agricultural ground-water withdrawals, whereby 120 days of 

pumping is followed by 245 days of nonpumping. Model results suggest that, 

after 120 days of pumping, water levels could decline locally by as much as 6 

feet. The distribution of drawdown for experiment 3, after 120 days of pumping, is shown in plate 6A. Model results also suggest that 245 days after 

pumping stopped drawdowns may locally still be as much as 1.5 feet. The 

residual drawdown suggests that the system would not fully recover from the 

combined effects of drought and increased pumpage by the end of the cycle. 

Computed ground-water discharge to the streams after 120 days of pumping was 

reduced by 10 percent, but the discharge virtually recovers after the 245-day 

period.

Experiment 4 simulates the aquifer's response to additional ground-water 

development and below-normal precipitation. Placement of additional pumping 

centers was based on areas of maximum transmissivity and saturated thickness 

and areas of expected development, as projected by the Todd County Soil 

Conservation District. Twenty-three pumping centers were added to the model, 

as shown in plate 5A. A drought of 4 years was simulated during which recharge 

was reduced to 4 inches annually. Because of the drought, 1978 rates for 

individual pumping centers were multiplied by 2.5 to simulate the additional 

pumpage necessary for adequate moisture to crops. This same increased rate of 

pumping was also applied to the 23 hypothetical pumping centers (pi. 5B), 

bringing total pumpage simulated in experiment 4 to 7.7 million gallons per 

year. Computed results indicate that (1) water levels at the end of the 4-year 

cycle may decline by as much as 9 feet locally and (2) aquifer discharge to 

streams may be reduced by 20 percent. This distribution of drawdown for experiment 4 is shown in plate 6B.

Table 8 is a summary of the results of the four experiments simulated by 

the model. Although the results indicate that each of the modeled experiments 

would result in water-level declines and reductions in streamflow, with proper 

development and management the aquifer is capable of accommodating additional 

withdrawals.

38
Table 8. Summary of experiments used to simulate 

changes in pumpage and recharge

Experiment Conditions of experiment Aquifer response to experiment

a. 8 inches recharge, 

b. 5.2 million gallons per day 

pumpage.

Water levels decline less than 

1.5 feet regionally, and reduction of ground-water discharge 

to streams is less than 2 percent.

a. 4 inches recharge, 

b. Simulated drought of 4 years, 

c. 2.1 million gallons per day 

pumpage.

a. 4 inches recharge.

b. Simulated drought of 1 year.

c. 1.9 billion gallons pumped

in 120 days followed by

245 days recovery.

a. 4 inches recharge, 

b. Simulated drought of 4 years, 

c. 7.7 million gallons per day 

pumpage.

Water levels decline by as much 

as 4 feet locally, and reduction of ground-water discharge 

to streams is 5 percent.

After 120 days of pumping, water 

levels decline by as much as 

6 feet locally, and reduction 

of ground-water discharge to 

streams is 10 percent. After 

245 days of recovery, water 

levels recover to 1.5 feet of 

drawdown regionally and reduction of aquifer discharge to 

streams is less than 2 percent.

Water levels decline by as much 

as 9 feet locally, and reduction of ground-water discharge 

to streams is 20 percent.

39
SUMMARY

Ihe surficial-outwash aquifers are the largest source of ground water in 

Todd County and parts of Cass and Morrison Counties. The aquifers cover 250 

mi^ and extend from Round Prairie to Motley, where they converge with outwash 

of the Wadena sand plain. Outwash thickness ranges from 0 to 150 feet and 

averages about 40 feet. Depth to water varies with topography, but water 

levels are generally less than 30 feet below land surface. Saturated thickness 

ranges from 0 to 140 feet. Annual water-level fluctuations average less than 5 

feet. Well yields range from 10 to 2,000 gal/min.

Aquifer material ranges from very fine sand to medium gravel, but consists 

mostly of medium to very coarse sand. Aquifer tests indicate that transmissivity ranges from 4,600 to 18,500 ftvd and storage coefficient ranges from 

0.10 to 0.25. Locally the aquifer is capable of supplying as much as 2,000 

gal/min to a properly constructed well.

Average annual precipitation based on 65 years of record at Long Prairie 

Weather Station is 25.93 inches. Annual precipitation during 1978 and 1979 was 

24.17 and 28.63 inches, respectively. Average annual recharge to the aquifer 

was estimated to be 8 inches. Annual recharge for 1979 was estimated to be 

10.2 inches.

A flow-duration curve based on 8 years of record at the Long Prairie 

station indicates that streamflow equals or exceeds 75 ftvs 50 percent of the 

time. Base-flow measurements made on October 26, 1978, and October 29. 1979, 

indicate that the Long Prairie River was gaining 0.85 ft3 /s and 1.3 ft^/s per 

river mile* respectively, due to ground-water inflow.

Both ground water and surface water are generally chemically suitable for 

domestic consumption and most other uses. However, results indicate that in 

localized areas concentrations of selected constituents exceed Minnesota 

Pollution Control Agency recommendations for fisheries and recreation, and for 

industrial consumption. Ihe water is a hard to very hard calcium bicarbonate 

type. Dissolved solids consist primarily of calcium, magnesium, and bicarbonate ions, and concentrations ranged from about 200 to 400 mg/L. Locally, 

dissolved iron concentrations exceed acceptable limits. Nitrate and chloride 

concentrations are generally low; however, concentrations in local areas are 

higher than baseline data indicate. Several samples analyzed for pesticides 

indicate local contamination of ground water by residues of atrazine, 

simetryne, and 2,4-D.

Ihe observation-well network created to meet the objectives of the project 

was used to establish baseline water quality and water-level elevations. The 

network can also be used for continuation of the monitoring program .for documentation of long-term trends.

Results of the digital model experiments suggest that, with proper 

development, the aquifer system probably is capable of accommodating additional 

withdrawals. Results of one experiment, in which average annual recharge was 

reduced from 8 to 4 inches for 4 years and pumping was increased from 2.1

40
million gallons per day to 7.7 billion gallons per day, suggest that water 

levels would locally decline only about 9 feet and that discharge to streams 

would only be reduced by about 20 percent. Validity of these results, however, 

can not be verified. Because of the lack of long-term historical data, the 

model could not be verified through time. The model can only be verified by 

collecting additional water-level data as development occurs and comparing it 

with model results. Ultimately the model could be recalibrated with the new 

field data and validity and accuracy of simulations could be verified.

REFERENCES

Allison, I. S., 1932, The geology and water resources of northwestern 

Minnesota: Minnesota Geological Survey Bulletin 22, 245 p.

Boulton, N. W., 1963, Analysis of data from nonequilibrium pumping tests 

allowing for delayed yield from storage: Institution Civil Engineers 

Proceedings [London], v. 26, p. 469-482.

Gough, L. P., Shacklette, H. T., and Case, A. A., 1979, Element concentrations 

toxic to plants, animals, and man: U.S. Geological Survey Bulletin 1466, 

80 p.

Helgesen, J. 0., 1973, Appraisal of ground water for irrigation in the Little 

Falls area, Morrison County, Minnesota: U.S. Geological Survey Water-supply 

Paper 2009-D, 40 p.

___ 1977, Ground-water appraisal of the Pineland Sands area, central 

Minnesota: U.S. Geological Survey Water-Resources Investigations 77-102, 

49 p.

Helgesen, J. 0., Ericson, D. W., and Lindholm, G. F., 1975, Water resources of 

the Mississippi and Sauk Rivers watershed, central Minnesota: U.S. 

Geological Survey Hydrologic Investigations Atlas HA-534.

Hult, M. F., 1979, Design of a network for monitoring ground-water quality in 

Minnesota: U.S. Geological Survey Open-File Report 79-1164, 44 p.

Jacob, C. E., 1944, Notes on determining permeability by pumping tests under 

water-table conditions: U.S. Geological Survey Bulletin 41, 193 p.

Jones, J. R., Akin, P. D., and Schneider, R., 1963, Geology and ground-water 

conditions in the southern part of the Camp Ripley Military Reservation, 

Morrison County, Minnesota: U.S. Geological Survey Water-Supply Paper 1669- 

A, 32 p.

Larson, S. P., 1976, An appraisal of ground water for irrigation in the 

Appleton area, west-central Minnesota: U.S. Geological Survey Water-Supply 

Paper 2039-B, 34 p.

Leverett, Frank, 1932, Quaternary geology of Minnesota and parts of adjacent 

states: U.S. Geological Survey Professional Paper 161, 149 p.

41
Lindholm, G. F. f 1970, An appraisal of ground water for irrigation in the 

Wadena area, central Minnesota: U.S. Geological Survey Water-Supply Paper 

1983, 56 p.

__ 1980, Ground-water appraisal of sand plains in Benton, Sherburne, Stearns, 

and Wright Counties, central Minnesota: U.S. Geological Survey WaterResources Investigations 80-1285.

Lindholm, G. P., Oakes, E. L., Ericson, D. W., and Helgesen, J. 0., 1972, Water 

resources of the Crow Wing River watershed, central Minnesota: U.S. 

Geological Survey Hydrologic Investigations Atlas HA-380.

Lohman, S. W., 1972, Ground-water hydraulics: U.S. Geological Survey 

Professional Paper 708, 70 p.

McBride, M. S., 1975, Ground-water for irrigation in the Viking Basin, westcental Minnesota: U.S. Geological Survey Water-Resources Investigations 23- 

75, 48 p.

Minnesota Pollution Control Agency, 1978, Minnesota state regulations; rules, 

regulations, classification, and water standards: Minnesota Pollution 

Control Agency Division of Water Quality, 150 p.

National Academy of Sciences, National Academy of Engineering, 1974, Water 

quality criteria 1972: U.S. Government Printing Office, Washington, D.C., 

594 p.

Schneider, A. P., 1961, Pleistocene geology of the Randall region, central 

Minnesota: Minnesota Geological Survey Bulletin 40, 151 p.

Searcy, J. K., 1959, Flow-duration curves: U.S. Geological Survey Water-Supply 

Paper 1542-A, 33 p.

Sims, P. K., and Morey, G. B., 1972, Geology of Minnesota, A Centennial Volume: 

Minnesota Geological Survey, 632 p.

Stallman, R. W., 1965, Effects of water-table conditions on water-level changes 

near pumping wells: Water Resources Research, v. 1, no. 2, p. 295-312.

Theis, C. V., 1935, The relation between the lowering of the piezometric 

surface and the rate and duration of discharge of a well using ground-water 

storage: American Geophysical Union Transactions, v. 16, pt. 2, p.519-524.

Thornthwaite, C. W. and Mather, J. R., 1957, Instructions and tables for computing potential evapotranspiration and the water balance: Drexel Institute 

of Technology, Publications in Climatology, v. 10, no. 3, 311 p.

Trescott, P. C., Pinder, G. P., and Larson, S. P., 1976, Finite-difference 

model for aquifer simulation in two dimensions with results of numerical 

experiments: U.S. Geological Survey Techniques Water-Resources 

Investigations, Book 7, Chapter Cl, 116 p.

42
U.S. Environmental Protection Agency, 1976, Quality criteria for water: U.S. 

Environmental Protection Agency EPA-44Q/9-76-023, Washington, D. C, 501 p.

U.S. Salinity Laboratory, 1954, Diagnosis and improvement of saline and alkali 

soils: U.S. Department of Agriculture Handbook 60, 160 p.

University of Minnesota, 1978, Sprinkler irrigated acreage in Minnesota: 

Extension Agriculture Engineering, 4 p.

Winchell, N. H., and Upham, Warren, 1888, The geology of Minnesota: Minnesota 

Geological Natural History Survey final report, v. 2, 695 p.

Wright, H. E., Jr., 1962, Role of the Wadena lobe in the Wisconsin Glaciation 

of Minnesota: Geological Society of America Bulletin, v. 73, p. 73-100.

Wright, H. E., Jr, and Prey, D. G., 1965, The Quaternary of the United States, 

A review volume for the VII Congress of the International Association for 

Quaternary Research: Prince ton University Press, 922 p.

U.S. Government Printing Office: 1984 765-681/5151 Region No. 6

43