Ground Water for Irrigation Near 

Lake Emily, Pope County, 

West-Central Minnesota

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1899-J

Prepared in cooperation with the 

West-Central Minnesota Resource 

Conservation and Development 

Committee and the Minnesota 

Department of Conservation, 

Division of Waters, Soils, and 

Minerals
Ground Water for Irrigation Near 

Lake Emily, Pope County, 

West-Central Minnesota

By WAYNE A. VAN VOAST

CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1899-J

Prepared in cooperation with the 

West-Central Minnesota Resource 

Conservation and Development 

Committee and the Minnesota 

Department of Conservation, 

Division of Waters, Soils, and 

Minerals

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1971
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY

William T. Pecora, Director

Library of Congress catalog-card No. 71-608833

For sale by the Superintendent of Documents, U.S. Government Printirf* Office 

Washington, D.C. 20402 - Price 25 cents (paper cover)
CONTENTS

Page

Abstract _ ____ ________________________________________________ ___________________________________ Jl

Introduction __ __ _ _ __ _ __ ___ _ ________ .__ ___ __________________________ 1

Previous investigations ___ _ ____ _ _ 2

Methods of investigation __________________________________________________________________________ 2

Test-hole numbering system __________ _ ___ ____________ 4

Acknowledgments - _ ___ ___________ _____________ ________ __.._______.__ 4

Geology _ ____ _._.____ _______________..__________ ____________________ ____________________ ________ 4

Bedrock __ ..........._________________________________________________________________ 4

Glacial drift . _ . .___________________________________________________ 5

Ground-water hydrology _______________________________________________________ __ _____ 7

Principles of occurrence __________________________________ ___ __ ____ 7

Buried aquifers __ __ __ _ 9

Surficial aquifer __ __ ____. ___. __.___....._....__._________________________________ 9

Physical and hydrologic properties _ _ ______ __ - 9

Water movement _ .__________ _____________________ ______ __._____ _______.___.____ ___ 14

Water budget _____ _______ ___ ______ __________________ ____._ __ 14

Theoretical maximum yields ____ __ __ _ _ 14

Well interference .._ ____ __ ___ ______.. _..... ..__ ...____ .._. __- 19

Water quality ____________ _._____.__. ____ . _ _ 23

Suitability of water for irrigation ____________________.._____-_ __ _ __. 23

Conclusions ___ ___ _ _ _ ______ _________________________ _ _ 27

References _ _ _. __ _________ ___...._____._....-_ ______ ___ .____ _ . 27

ILLUSTRATIONS

Page

FIGURE 1. Map of area of this report _______ _______________ __ ____________________ J3

2. Diagrams showing well and test-hole numbering system________._ 5

3-10. Maps showing:

3. Generalized surficial geology and thickness of glacial

drift -_____--__--_-_--_-_--_-____-___-___ _ _______________ 6

4. The configuration of the till surface underlying the

surficial outwash west of Lake Emily ___.. _._ _ 8

5. Depth to the water table in surficial acquifer __ ___________ 11

6. Saturated thickness of the surficial aquifer _______ ________ 12

7. Transmissivity of the surficial aquifer _________.__ ____ 13

8. Configuration of water table and direction of groundwater flow in the surficial acquifer ________.. ___ 15

III
IV CONTENTS 

FIGURES 3-10. Maps showing Continued

Page

9. Approximate base flow (September 1968) in Hi Chippewa River and tributaries ______ __. _..__-.. .._..._-. _ ._ J16

10. Theoretical maximum possible yields for individual

wells finished in the surficial aquifer ._. . __ . _ 18

11. Profile showing example of well interference .-.___.__. ___.__._ 20

12. Distance-drawdown curves - . _____.._._. __________ -_______-__._____ _______ 21

13. Curves for adjusting drawdown for dewatering of

the aquifer _, .. ______ _._ ________._________________ _________ _. 22

14. Map showing specific conductivity for ground water in the

surficial aquifer and for base flow ___________________ .__________________.__ 26

TABLES

Page

TABLE 1. Values of hydraulic conductivity used in the estimation of transmissivity of the surficial aquifer west of Lake Emily ________________ JIO

2. Approximate hydrologic budget for 1968 for the surficial aquifer west of Lake Emily __________________ __.____._-_____._-____._-_______ - _- 17

3. Chemical analyses of ground water near Lake Emily ________ 29
CONTRIBUTIONS TO THE HYDROLOGY OF THE 

UNITED STATES

GROUND WATER FOR IRRIGATION

NEAR LAKE EMILY, POPE COUNTY,

WEST-CENTRAL MINNESOTA

By WAYNE A. VAN VOAST

ABSTRACT

In the Lake Emily area, thickness of the glacial drift ranges from about 

200 feet to more than 400 feet. Within the drift are sand and gravel aquifers, 

some of which can yield adequate water supplies for irrigation. Outwash, as 

much as 60 feet thick, lies at the surface. The outwash has saturated thicknesses of more than 40 feet and transmissivities of more than 50,001 gallons 

per day per foot locally in the northern and western parts of the area. In the 

places of large saturated thickness and high hydraulic conductivity, the 

aquifer should yield more than 600 gallons per minute to wells. Theoretical 

maximum yields to wells in most of the area are more than 100 gallons per 

minute.

Chemically, water in the buried and surficial aquifers is mainly of a calcium 

magnesium bicarbonate type and is suitable for irrigation. Calculated and 

estimated sodium adsorption ratios and salinity and boron concentrations are 

below the limits recommended by the U.S. Department of Agriculture.

INTRODUCTION

This investigation of the availability of ground water for 

irrigation near Lake Emily is one of several investigations conducted in sandy-soil areas in Minnesota where development of 

irrigation supplies from ground water in surficial aquifers might 

be feasible to supplement precipitation. Because of low waterholding capacity in these sandy soils and insufficient rainfall 

during the growing season, crop yields generally are poor. The 

purpose of the study is to investigate the adequacy of groundwater quantity and quality for irrigation. Results of this study

Jl
J2 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITFD STATES

should provide guidelines to local planners and irrigators in the 

proper development of the area's water resources. The study 

was made by the U.S. Geological Survey in cooperation with the 

West-Central Resource Conservation and Development Committee and the Division of Waters, Soils and Minerals, Minnesota 

Department of Conservation.

The report area is in west-central Minnesota (fig. 1), about 

130 miles west of Minneapolis and St. Paul. The area occupies 

about 35 square miles in T.124 N., R.40 W. (Walden Township) 

and T.123 N., R.40 W. (Hoff Township) in the southwestern corner of Pope County. There are no towns in the report area. 

Nearby towns include Hancock, about 1 mile west of the area; 

Morris, about 10 miles northwest; and Benson, about 10 miles 

south.

The report area is in the central part of the Chippewa River 

watershed unit as outlined in the Minnesota Division of Waters 

Bulletin 10, "Hydrologic Atlas of Minnesota." The Chippewa 

River is the main watercourse draining the area in addition to 

several unnamed tributaries, most of which are ephemeral.

Farming is the principal occupation; corn, soybeans, and hay 

are the principal crops. The soils are sandy and are subject to 

droughtiness and wind erosion. Mean annual precipitation is 

about 24 inches, of which about 18 inches fall during the growing season (May through September). Average daily maximum 

temperatures during the growing season vary from at out 56°F 

(13°C) in April to about 86°F (30°C) in July.

PREVIOUS INVESTIGATIONS

The earliest investigation which included the Lake Emily area 

was a cursory survey of the general geology of Minnesota (Upham, 1888). A report on the geology and water resources of 

northwestern Minnesota by Allison (1932) and a report on the 

glacial geology of Minnesota and adjacent states by Leverett 

(1932) gave brief mention of the project area. A cartographic 

presentation of the hydrology of the Chippewa River watershed 

by Cotter, Bidwell, Van Voast, and Novitzki (1968) included a 

general description of the geology and water resources of the 

western third of the report area.

METHODS OF INVESTIGATION

Fieldwork began in the summer of 1966. Selected domestic 

wells in the area were inventoried, and water samples were collected for chemical analysis. More than 50 power-auger test
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY

95°40'

J3

4 MILES

FIGURE 1. Area of this report.
J4 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

holes were drilled to determine the extent and geologic characteristics of the water-table aquifer. Altitudes were obtained from 

topographic maps or by altimeter.

Continuous records of water-level fluctuations were collected 

at two observation wells from December 1966 to December 1968. 

Precipitation during the growing season of 1967 was recorded at 

three points for comparison with water levels in observation 

wells. Base flow in all streams in the area was measured in 

September 1968.

TEST-HOLE NUMBERING SYSTEM

The system of numbering test holes and wells is based on the 

U.S. Bureau of Land Management's system of subdivision of the 

public lands. The Lake Emily area is in the fifth-principal-meridian and base-line system. The first segment of a well or test-hole 

number indicates the township north of the base line; the second, 

the range west of the principal meridian; and the third, the 

section in which the test hole is situated. The lowercase 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. The letters 

are assigned in a counter-clockwise direction, beginning in the 

northeast quarter. Within one 10-acre tract, consecutive numbers beginning with one are added as suffixes.

Figure 2 illustrates the method of numbering a test hole. Thus, 

the number 124.40.8ddbl identifies the first well or test hole located 

in the NWi/^SE^SE^ sec.8, T.124 N., R.40 W.

ACKNOWLEDGMENTS

The author thanks the many residents and well drillers who 

provided information and assistance. A special debt is owed to

residents who recorded precipitation data during the study. (

GEOLOGY

BEDROCK

Crystalline rocks of Precambrian age form the basement complex. Where reached by wells in west-central Minnesota, the Precambrian rocks are granitic, and locally their upper surface is 

weathered to a soft kaolinitic clay. According to Cotter, Bidwell, 

Van Voast, and Novitzki (1968), basement rocfcs lie about 200 

feet below land surface in the northern part of the area and 

more than 400 feet below land surface in the south.
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY

R. 42 W.41 40 39 38 37 3 2 R. 1 W.

Base line

co 1 

-Jo 

0)

15 

'og 

T.

125

N.

124

123

J5

Well 124.40. Sddbl

R 40 W.

T. 

124 

N.

6

7

18

19

30

31

5

8

 c

17

20

29

32

4 

/

/9

---_

16

21

28

33

X

10

15

22

27

34

2

11

~~14^

23

26

35

1

12

13

24

25

36

Sec. 8

- b a----

-__ |_ ___L__J ___

FIGURE 2. Well and test-hole numbering system.

Sedimentary rocks of Cretaceous age commonly overlie the 

basement complex in west-central Minnesota, but according to 

Cotter, Bidwell, Van Voast, and Novitzki (1968), are not present 

in the report area.

GLACIAL DRIFT

Glacial drift representing the Wisconsin Glaciation forrrs the 

land surface in the project area (fig. 3). Pre-Wisconsin drift may 

be present in the subsurface. The glacial deposits are about 200 

feet thick north of Lake Emily and are more than 400 feet thick 

in the southwestern part of the project area (fig. 3). The drift is 

of two main types: till, an unstratified, unsorted mixture of clay, 

silt, sand, and gravel deposited directly by glacial ice; anc1 outwash, stratified beds of sand and gravel deposited by glacial 

meltwaters.
J6 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

95°40'

Glacir 1 till

Nonsorted, nonstratified clay, 

silt, sand, c.nd gravel

Contact

 3OO 

Line of equal thickness of 

glacial drift (from Cotter and 

others, 1968). Interval is 100 

feet

U.S. Geological Survey auger 

test hole from which geologic 

and hydrologic data were obtained

4 MILES

FIGURE 3. Generalized surficial geology and thickness of glacial drift.
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J7

The drift in the project area was deposited by the Des Moines 

lobe of glacial ice (Leverett, 1932), which advanced southeastward 

across western Minnesota. Outwash was deposited by meltwaters 

from the ice sheet as it receded to the north and west. The meltwaters flowed southward into the Lake Emily area by way of two 

main channels, the eastern one of which is now occupied by the 

Chippewa River. The streams of meltwater flowed into a broad, 

shallow lake which covered most of the project area (R. Diedrick, 

written commun., 1967), and was centered southwest of Lake 

Emily. Most of the outwash near Lake Emily was deposited as a 

delta in this temporary glacial lake. Figure 4 shows the corfiguration of the till surface beneath the deltaic deposits. Along the 

southern and western boundaries of the project area, where the 

lowest depressions in the till surface occur, the outwash is as much 

as 60 feet thick; here it is composed of fine to coarse sand. In the 

northern part of the area, closer to the ancient meltwater channels, 

thickness of the outwash is mainly less than 40 feet, and grain sizes 

are mostly medium to very coarse. Narrow gravel bars are common 

within both channels.

GROUND-WATER HYDROLOGY

PRINCIPLES OF OCCURRENCE

Ground water occurs within the basement rocks and glacial deposits in the project area. The uppermost surface below which the 

geologic materials are saturated under hydrostatic pressure is 

termed the "water table." Water is stored within spaces between 

grains which make up geologic materials; the ratio of voHme of 

pore space to total volume of material, expressed as a percentage, 

is known as porosity. All geologic materials are porous to some degree. The ability to transmit water is termed "hydraulic conductivity" and depends upon the size of the pore spaces and their degree 

of interconnection. Hydraulic conductivity, as used in this report, 

is defined as the flow of water in gallons per day through a crosssectional area of geologic material 1 foot high and 1 foot wide under 

a hydraulic gradient of 1 foot per foot. In the project area, geologic materials of significant hydraulic conductivity include sand 

and gravel, and where saturated with water will be referred to 

herein as aquifers. Less permeable materials in the area are 

granitic rock, till, silt, and clay. Transmissivity is used to indicate 

the ability of an aquifer to transmit water and is equivalent to the 

hydraulic conductivity multiplied by the aquifer thickness in feet. 

Transmissivity is defined as the flow of water in gallons per day 

through a strip of aquifer 1 foot wide under a hydraulic gradient
J8 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

95°45'

EXPLANA~ION

 1040 

Structure contour

Shows altitude of top of till surface underlying the surficial 

outwash. Contcur interval 

20 feet. Datum is mean sea 

level

Glacial outvash

Glacial t; ll

Contact

SWIFT CO R 40 W. 

1 4 MILES 

I

FIGURE 4. Configuration of the till surface underlying the surficial outwash

west of Lake Emily.
GROUND WATER FOR IRRIGATION NEAR LAKE EMII/7 J9

of 1 foot per foot. The volume of water that geologic materials can 

release from or take into storage per unit of aquifer surface per 

unit of change in head is known as the storage coefficient. Storage 

coefficient and transmissivity are the main characteristics which 

determine the worth of an aquifer as a source of water.

Aquifers described in this report are sand and gravel deposits 

which occur buried beneath less permeable deposits of clay, silt, 

and till, and sand and gravel deposits which occur at the land surface. Buried and surficial aquifers will be discussed separately, 

with major emphasis on the surficial aquifer.

BURIED AQUIFERS

Sand and gravel deposits, which occur at various depths in the 

glacial drift, are common in and near the Lake Emily area. The 

individual aquifers generally do not have wide areal extent and 

may be highly variable in thickness and hydraulic conductivity. 

Most wells which penetrate buried aquifers in the area are less 

than 150 feet deep and probably tap the uppermost sand and gravel 

deposits. Other aquifers probably occur at greater depths. That 

nonpumping (static) water levels in the deep wells are lower than 

the water level in the surficial sand and gravel deposits by as 

much as 50 feet indicates that the deeper aquifers may be recharged at least partly by water from the surficial aquifer. Little 

information on well performance is available. Most domestic and 

stock wells are pumped at less than 10 gpm (gallons per minute) 

but are probably capable of greater yields. Municipal wells in the 

town of Hancock, about 1 mile west of the project area, reportedly 

yield as much as 500 gpm and have specific capacities of as much 

as 50 gpm per foot of drawdown after 6 hours of pumpirg. Data 

presented by Cotter, Bidwell, Van Voast, and Novitzki (1968), 

indicates that the wells at Hancock yield greater volumes of water 

than most wells in the Chippewa River watershed. It is not known 

whether the aquifer at Hancock is also in the project ar?a. Test 

drilling will be necessary to locate buried aquifers that c^n yield 

water in sufficient quantity for irrigation.

SURFICIAL AQUIFER

PHYSICAL AND HYDROLOGIC PROPERTIES

A surficial aquifer in glacial outwash covers most of t\e project area (fig. 3). The aquifer's upper limit is the water table, and 

its base is the top of the glacial till. It is bounded by poorly permeable till to the north and east and extends beyond the southern and 

western limits of the project area.
J10 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

The water level is within 10 feet of the land surface in most of 

the project area (fig. 5); however, in the northern part of the area, 

the depth to water is locally somewhat greater but is generally less 

than 20 feet.

Saturated thickness of the outwash varies from less than 10 feet 

along the eastern edge of the aquifer to more than 50 feet in the 

western part of Walden Township (fig. 6). Saturated thicknesses 

are more than 40 feet in the meltwater channel in sec. 6, Walden 

Township and more than 30 feet in the southwest corner of Hoff 

Township.

An interpretation of the transmissivity of the aquifer, based on 

aquifer thickness and grain-size data, is shown in figure 7. Hydraulic conductivities of materials were estimated by correlating 

grain-size information and using the hydraulic conductivity values shown in table 1. Validity of these values for the Lake Emily 

area could not be verified because of the absence of aquifer performance data. The values were used in this study because they 

were found to be compatible with hydraulic conductivities determined from controlled pumping tests and from specific capacity 

information in similar materials in the Brooten-Belgrade area, 

about 25 miles east of Lake Emily (Van Voast, 1968).

The highest transmissivities occur along the western edge of the 

project area and in the narrow channels in northern Walden Township, (See fig. 7.) In these areas the aquifer is relatively thick and 

consists of relatively coarse materials. Transmissivity values are 

low in the southeastern part of Hoff Township because the aquifer 

is relatively thin and is composed mainly of fine to medium sand.

TABLE 1. Values of hydraulic conductivity used in the estimation of transmissivity of the surficial aquifer west of Lake Emily

[Values are taken from a more detailed study of similar material near 

Brooten, Minnesota (Van Voast, 1968)]

Hydraul'a conductivity

Material (gpd 

(based on Wentworth size scale) per «</ ft)

Clay and silt ................................................................................... 0- 100

Sand, very fine, silty .................................................................. 100- 300

Sand, fine to medium ................................................................... 300- 400

Sand, medium ................................................................................. 400- 600

Sand, medium to coarse ............................................................... 6?0- 800

Sand, coarse ................................................................................... 8^0- 900

Sand, very coarse ......................................................................... 9?0-1,000

Sand and gravel ............................................................................ 1,070-2,000

Storage coefficient or specific yield for the water-table aquifer 

is estimated to be about 0.2, a reasonable value for unconfined
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY JH

95°40'

Generalized depth to water 

table in the surficial aquifer 

(glacial outwash), in feet

FIGURE 5. Depth to water table in surficial aquifer.
J12 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

95°45'

Line of equal thickness of

surficial aquifer

Interval is 20 feet. Supplementary dashed lines are 10 foot 

intervals

4 MILES

FIGURE 6. Saturated thickness of the surficial aquifer.
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J13

95°40'

Line of equal tranemissivity

of the surficial aquifer 

Interval 20,000 gallons per day 

per foot. Supplemental 

dashed lines are 10,000 gallons 

per day per foot intervals

4 MILES

FIGURE 7. Transmissivity of the surficial aquifer.
J14 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

aquifers. On the basis of this value, it is estimated that about 

115,000 acre-feet of water is contained in storage in the surficial 

aquifer within the project area.

WATER MOVEMENT

The general direction of ground-water movement is shown in 

figure 8. Ground water enters the aquifer as underflow near Lake 

Emily and through narrow channels of sand and gravel in the 

northern part of Walden Township. Ground water leaves the 

area as underflow along the southern boundary of Hoff township. Ground-water flow to the Chippewa River occurs along its 

entire reach in the project area (fig. 9), but the tributaries have 

relatively little base flow.

WATER BUDGET

Under natural conditions, the ground-water system is in a 

state of dynamic equilibrium, continually recharging in some 

places and discharging in others, but always tending toward a 

balance between input and output. Sources of recharge to the 

surficial aquifer include precipitation, overland flow from topographically higher adjacent areas, surface runoff, and groundwater underflow. Most recharge occurs during the spring because of snowmelt and heavy rainfall. Ground water leaves the 

area as underflow, seepage to streams (base flow), ard as evaporation and transpiration. Underflow is continuous; base flow 

occurs during most of the year; and evapotranspiration occurs 

mainly during the growing season.

No long-term depletion of storage in the aquifer is assumed, 

and the ground-water system is considered to be in a state of 

equilibrium in which inflow is equal to outflow. A general water 

budget for 1968 (table 2) shows the relative magnitudes of recharge and discharge components for the surficial aquifer.

The estimated water budget indicates that spring recharge is 

much greater than recharge by underflow. The budget also indicates that ground-water discharge to the Chippewa River is 

much greater than ground-water losses as underflow and evapotranspiration. Most water pumped for irrigation will originate 

as spring recharge and will be intercepted before discharging to 

the Chippewa River.

THEORETICAL MAXIMUM YIELDS

To quantify hydraulic properties of the surficial aquifer, potential well discharges were determined (fig. 10). The values
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J15

95°40'

Lake Ermly

EXPLANATION

 1080 

Water-table contour 

Shows altitude of water table 

Contour interval 10 feet 

Datum is mean sea level

General direction of 

ground-water flow

4 MILES

FIGURE 8. Configuration of water table and direction of ground-water flow 

in the surficial aquifer.
J16 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

I/

95°40'

EXPLANATION

Width of pattern along stream 

indicates approximate base 

flow (September 1968), in 

cubic feet per second

Discharge less than 0.1 cubic 

foot pe- second

45° 

25

FIGURE 9. Approximate base flow (September 1968) in the CHppewa River

and tributaries.
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J17

TABLE 2. Approximate hydrologic budget for 1968 for the surficial aquifer

west of Lake Emily

Budget components Volume of water 

for the surficial aquifer (acre-feet per year)

Spring recharge, estimated from

observation-well hydrographs ......................................... 4,900

Underflow, calculated by

Darcy's law ...................................................-.........-.---... --. 400

Total inflow ........................ ............................................. 5,300

Baseflow, measured in the

Chippewa River .............................. ........ ........................... 4,800

Underflow, calculated by the

Darcy equation ....... ............................................................... 300

Evapotranspiration, estimated

to balance annual budget .......................................................... 200

Total outflow ..................................................... ............... 5,300

were calculated using the nonequilibrium equation of Theis 

(1935), and they represent the theoretical possible yields, disregarding well interference, for 30 days of continuous puirping 

with drawdowns limited to about two-thirds of the aquifer thickness. When drawdown equals two-thirds of the aquifer thicl'ness, 

about 90 percent of maximum yield is being obtained and the 

well is being pumped at maximum efficiency (Edward E. Johnson, Inc., 1966, p. 107, 108). In calculation of values for figure 10, 

interference between wells was assumed to be negligible, and 

drawdowns at the wells were corrected for decreasing transmissivity caused by dewatering of the aquifer (Jacob, 1944). It must 

be noted that 30 days of continuous pumping is a stringent condition when applied to present irrigation practices in western 

Minnesota, and probably would be necessary only in abnomally 

dry years. Further, local exceptions to the yield values shown 

will be common because of local variations in transmissivity. 

The map is intended only to show relative differences in wateryielding capacity for general areas.

The areas of highest maximum yields correspond generally 

with areas of highest hydraulic conductivity and greatest saturated thicknesses. Yields of more than 600 gpm (gallonr per 

minute), under the time and drawdown conditions described 

above, should be available to individual wells in the outwash 

channel in northwestern Walden Township and near the project 

area boundary directly west of Lake Emily. Yields of more than 

300 gpm, but probably less than 600 gpm, should be available to 

wells in southwestern Hoff Township. In most of the outwash in 

Walden Township, yields of between 100 and 300 gpm should be 

obtainable. In a large part of Hoff Township, directly south of
J18 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

95°40r

Lake Emily

EXPLANATION

Surficial aqrifer (glacial

outwash)

Theoretical maximum yields, in 

gallons per minute, possible 

for 30 days continuous pumping with drawdowns less than 

or equal to two-thirds aquifer 

thickness. Values are based 

on aquifer data collected for 

this study and nonequilibrium equations by Theis 

(1935). Valuec apply to single 

wells, assuming no interference, and hav} been adjusted 

for dewateriny of the aquifer

Less than 100 More than 600

FIGURE 10. Theoretical maximum possible yields for individual wells finished

in the surficial aquifer.
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J19

Lake Emily, yields to individual wells will probably be limited to 

less than 100 gpm because of small aquifer thickness and low 

hydraulic conductivity.

It is likely that in most areas where maximum yields of less 

than 300 gpm are indicated in figure 10, prospective irrigators 

will have to rely upon multiple well systems or pits dug- in the 

surficial aquifer, or must try to get additional water from deeper 

aquifers buried in or beneath the glacial drift.

WELL INTERFERENCE

In an area where high well yield and high pumping efficiency 

are needed, a common problem can be the interference of the 

cones of depression of wells. Some well interference will be necessary for optimum development; however, a decrease in yield or 

in pumping efficiency can occur should interference cause drawdown at a well to exceed two-thirds of the aquifer thickness. 

Drawdown at any particular point in an area of influence of one 

or more wells will be the sum of drawdowns caused by the individual wells (fig. 11). Figures 12 and 13 can be used to estimate approximate drawdowns in the water-table aquifer between 1 and 800 

feet from a pumping well. Because drawdown decreases the 

aquifer's saturated thickness, theoretical drawdowns (fig. 12) 

calculated by the nonequilibrium formula (Theis, 1935) must be 

adjusted for the decreased transmissivity. Adjustment of drawdown for dewatering of the aquifer can be made with an equation 

derived by Jacob (1944), presented graphically in figure 13. 

To best explain use of figures 12 and 13 for estimating or 

predicting well interference, a hypothetical problem correrponding to figure 11 is presented and solved below. 

Example: Two wells, 200 feet apart, are each pumping 300 gpm

from a water-table aquifer which is 40 feet thick and has a

transmissivity of 40,000 gpd per ft. Storage coefficient is 0.2.

Each well fully penetrates the aquifer and is 100 percent

efficient.

Find the drawdown midway between the two wells after 30

days of continuous pumping.

1. The curve for 40,000 gpd per ft (fig. 12) shows that the 

unadjusted drawdown 100 feet from one well would be about 

4.4 feet (A'}. The 40-foot curve (fig. 13) shows that the adjusted drawdown would be about 4.8 feet (A).

2. The drawdown midway between the interfering wells 

would be the sum of the drawdowns 100 feet from each well, 

or about 9.6 ft.
LU

LU 

LJ_

Z

LU

LJ.

^3

a

o 20 -

a.

O

S

§30-

LJ.

I

t '

LU

Q 

40 -

Well discharge

300 gpm-^

 -^^\x

^""- v. \

^x. \

\.

\

Land surface

Nonp

1 4.8 ft

Pumping level without _ _ r=-~ ~ _ _ _ _

well interference^^-- ~~ 

^.*--~ /Total drawdown 

s^ - ~~ "X 

/ ^^----"""'^ Pumping level with 

/ -^^^^ two interfering wells 

/ /'^ 

.s 

/ 

Example showing interfering cones of de

of two wells, 200 feet apart, after 30 d

w .. each well pumping 300 gallons per min

.-wen screen a water-table aquifer which is 40 feet 

has a transmissivity of 40,000 gallons pe

foot. Storage coefficient is 0.2. Eff

ameter of each well is 2 feet

Base of aquifer

0 50 

III 

VERTICAL EXAGGERATION X 2V2

FIGURE 11. Interfering cones of depression caused by hypothetical wells 
30

Distance-drawdown curves for t

gpd per ft to 50,000 gpd per 

equilibrium method (Theis, 193

downs are not adjusted for de

Discharge = 300 gpm Pumping period 

5 10 

DISTANCE FROM CENTER OF 

FIGURE 12.- -Theoretical distance-drawdown curve

at the end of 30 days of c
40

30

Plotted from 5' =5 , derived by Jacob (1944)

2/77

s' =unadjusted theoretical drawdown (found from figu

m = thickness of water-table aquifer 

 5 = adjusted drawdown (theoretical drawdown in the w

10 20 30 

ADJUSTED DRAWDOW

FIGURE 13. Theoretical curves for adjustment of dr

for dewatering of the wa
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J23

Find the drawdown 1 foot from the center of each well after 

30 days.

1. The curve for 40,000 gpd per ft (fig. 12) shows that the 

unadjusted drawdown at one well would be about 12.4 feet (B\) . 

The 40-foot curve (fig. 13) shows that the adjusted drawdown 

would be about 15.3 feet (#1).

2. The curve for 40,000 gpd per ft (fig. 12) shows that the 

unadjusted drawdown 200 feet from the other well would be 

about 3.2 feet (5'2 ). The 40-foot curve (fig. 13) shows that the 

adjusted drawdown would be about 3.7 feet (B2 ).

3. The drawdo\vn at either well when influenced by the other 

would be the sum of the drawdowns found in steps 1 and 2, or 

about 19 feet.

Although the curves in figure 11 and the example problem are 

for a well discharge of 300 gpm, they are also applicable to different discharges. Drawdown varies directly with discharge; for 

example, if 600 gpm is the anticipated or obtained yield, drawdowns could be found by doubling those indicated by figure 12 

before adjustment for dewatering.

WATER QUALITY

Ground water in the surficial aquifer near Lake Emily is of 

the calcium magnesium bicarbonate type (table 3). Water in the 

buried aquifers is chemically similar to that in the surficial 

aquifer but commonly contains higher concentrations of sulfate. 

Because water-table aquifers receive much of their recharge 

directly from the land surface, they are highly susceptible to pollution. However, sulfate, chloride, and nitrate concentrations in 

water from the surficial aquifer are relatively low and do not 

indicate any present pollution problems. A major concern resulting from irrigation in the area will be the possibility of pollution 

in the surficial aquifer through the increased use of fertilizers. 

Chemical analyses of samples obtained periodically would provide the necessary data to warn of any incipient pollution problem.

SUITABILITY OF WATER FOR IRRIGATION

The chemical suitability of water for irrigation depends upon 

the concentrations of dissolved mineral constituents in the 

water. In western Minnesota, chemical factors in ground vrater 

which can be harmful to plant growth include sodium concentration, salinity, and boron concentration. The chemical factors are 

most critical in arid regions where dissolved constituents are
J24 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES 

TABLE 3. Chemical analyses of water in and near the Lake Emily area

Well No. 

or surfacewater location

122.39.8.dcd .........

124.38.6.cbb . . .... 

124.41. IS.add 

122.41. SS.cdd ...... 

124.39. 17.bdc ... 

123.40.10.bbb. . 

123.40. 20.daa ....... 

124.40.29.aca . 

West End, 

Lake Emily . ...

Depth Date of 

of collection 

well of 

(ft) sample

147 

H43 

1183 

1113 

1208

216 

210 

215

30

8-25-65 

8-30-65 

8-30-65 

8-25-65 

8-30-65 

9- 5-67 

9- 5-67 

9- 5-67

9- 5-67

Calcium 

(Ca)

210

82 

87 

84 

90

50

Constituents in milligrams per liter (r>g/l)

Mag- So- Potas- Bicar- Car- Sul- Chlonesium dium sium bonate bonate fate ride 

(Mg) (Na) (K) (HCOs) (CO3 ) (SO4 ) (CD

15

5.2 

14 

74 141 

109 25 

47 

32 

45

60

3.9 510 0 

3.6 450 0 

4.0 427 0 

8.8 415 0 

5.4 418 6 

341 

318 

378

358

32 

55 

240 

735 

325 

72 

50 

69

68

1.6 

.5 

1.2 

2.5 

2.0 

2.5 

9.0 

2,.5

11

Fluoride 

(F)

0.2 

.2 

.2 

.2 

.2

Constituents in milligrams 

per liter (mg/1)

Well No. 

or surfacewater location

122.39.8.dcd ...... 

124.38.6.cbb .........

124.41. IS.add 

122. 41. SS.cdd. 

124.39.17.bdc-, 

123.40.10.bbb. 

123.40.20.daa 

124.40.29.aca ..... 

West End, 

Lake Emily.....

Depth Date of 

of collection 

well of 

(ft) sample

147 

1143 

1183 

1113 

1208

216

210 

215

30

8-25-65 

8-30-65 

8-30-65 

8-25-65 

8-30-65 

9- 5-67 

9- 5-67 

9- 5-67

9- 5-67

Nitrate

(NOS )

4.4 

4.4 

4.4 

5.4 

20 

22 

8.0 

2.0

1.0

Dissolved 

Boron solids

470 

490 

470 

0.72 1520 

.18 831

Hardness as 

CaCO3 (mg/1)

Calcium, Nonmagne- carsium bonate

390 0 

420 50 

800 450 

828 488 

653 300 

382, 102 

320 60 

380 70

332 44

Sodiumadsorptionratio

0.2 

.0 

.1 

2.1 

.4

Specific 

conductance 

(micromhos 

at 

25°C)

720 

780 

750 

1810 

1170 

680 

580 

680

630

pH

7.5 

7.5 

7.7 

7.9 

8.3

1 Wells finished in buried aquifers.

2 Wells finished in the surficial aquifer.

3 Surface water.

allowed to accumulate in the root zone because of inadequate 

leaching. In western Minnesota the amount and distribution of 

rainfall and snowmelt are such that leaching of the root zone 

probably occurs annually, particularly in areas of highly permeable soil such as near Lake Emily.

Dangers from excessive concentrations of sodium in irrigation 

water include possible breakdown of soil structure and possible 

nutritional disturbance in crops. A parameter used to evaluate 

sodium hazard for irrigation water is the sodium adsorption 

ratio (SAR) recommended by the Salinity Laboratory of the 

U.S. Department of Agriculture (1954). The SAR is defined by 

the equation:

SAR =-

NaCa Mg H

where the concentrations of the constituents are expressed in 

milliequivalents per liter. Rating of SAR values of water for
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J25

irrigation depends upon factors which include type of crop, 

soil texture, soil chemistry, and dissolved solids content of the 

irrigation water. A generalized rating based upon these and 

other factors (Bernstein, 1967) indicates that waters having 

SAR values less than about 8 should not cause breakdown of soil 

structure and that waters having SAR values less than about 4 

should not cause nutritional disturbance to crops.

SAR values for water in the buried aquifers (table 3) are 

mostly less than 1. One analysis for well 122.41.33cdd indicated 

an SAR value of 2.1. SAR values for water in the rurficial 

aquifer could not be calculated because sodium concentrations 

were not analyzed. Approximations of sodium content, based 

upon a balancing of the relative concentrations of other common cations and anions, are less than 1 milliequivalent p^r liter 

and indicate that SAR values would be less than about 0.5. According to Bernstein's criteria, waters in the Lake Emily area 

are suitable for irrigation, with little danger of the development 

of harmful amounts of .exchangeable sodium in the soil or toxic 

accumulations of sodium in plants.

Salinity or dissolved-solids concentrations can be critical to 

the growth of certain plants. Of the crops likely to be irrigated 

in the project area, green beans have the least tolerance to salinity. Crops which have a moderate tolerance for salinity and 

which could be grown in the Lake Emily area include peas, sweet 

corn, potatoes, and alfalfa.

The common test for salinity hazard in irrigation water is the 

measurement of specific conductivity of the water. Waters having specific conductivities less than about 2,250 micromhos per 

centimeter are probably satisfactory for irrigation where annual 

leaching of the root zone occurs (Wilcox, 1955, p. 15, 16). Values 

of specific conductivity for water in buried aquifers (table 3) are 

less than 2,000 micromhos per centimeter. Specific conductivity 

values for water in the surficial aquifer and for base flow in the 

Chippewa River (fig. 14) are less than 750 micromhos pe^ centimeter. The salinity or dissolved-solids concentrations in all waters in the area, as indicated by specific conductivities, are suitably low for irrigation.

Relatively low concentrations of boron in irrigation waters 

can be toxic to certain crops. According to a classification of the 

tolerance of plants for boron by Wilcox (1955), crops grown in 

the project area may be sensitive to concentrations greater than 

about 1 mg/1 (milligram per liter). Values of boron content are 

not available for most chemical analyses of water in th« Lake
J26 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

V Lake Emily

630 EXPLANATION

680

"^ Specific conductivity of water 

in micromhos at 25° Celsius

A

Surface-water source 

(Sept. 19f8)

Ground-water source in 

surficial aquifer

Salinity or dissolved solids (milligrams per liter)=0.7± 0.1 

times specific conductivity 

(micromhos)

Glacial till

Contac4

4 MILES 

I

FIGURE 14. Specific conductivity for ground water in the surficial aquifer 

and for base flow.
GROUND WATER FOR IRRIGATION NEAR LAKE EMILY J27

Emily area. Boron concentrations in ground water throughout 

western Minnesota commonly are highest in the deepest aquifers, particularly those in the Cretaceous sedimentary rocks. In 

waters from glacial drift aquifers less than about 100 feet below 

land surface, boron concentrations are rarely more than 0.5 

mg/1. It is likely that most ground water in the Lake Emily area, 

particularly that in the surficial aquifer, does not contain dangerous boron concentrations, even for sensitive crops.

CONCLUSIONS

Glacial drift in the report area is more than 200 feet thick and 

probably contains significant aquifers buried at various depths. 

Extensive test drilling may be necessary to locate buried aquifers capable of yielding sufficient quantities of water for irrigation.

Outwash, deposited by meltwaters from the Des Moines lobe of 

glacial ice, covers the report area and is as much as 60 feet 

thick. The outwash contains a water-table aquifer having a saturated thickness of generally more than 20 feet and locally more 

than 40 feet. Thickness and hydraulic conductivity of the aquifer 

are greatest in the northern and western parts of the report 

area. The surficial aquifer holds an estimated 115,000 acre-feet 

of water in storage. Estimated maximum yields for wells, based 

upon 30-day pumping periods with drawdowns limited to less 

than two-thirds of the aquifer thickness, are more than 600 

gpm in the northern and western parts of the report area. In the 

southeastern part of the area, potential yields from the surficial 

aquifer are less than 100 gpm, and prospective irrigators will 

have to rely upon groups of wells, infiltration pits, or wells in 

buried aquifers to obtain adequate water supplies.

Water in the buried and surficial aquifers is mainly of tl^ calcium magnesium bicarbonate type and probably is chemically 

suitable for irrigation. Sodium-adsorption-ratios, calculated for 

water in buried aquifers and estimated for water in the surficial 

aquifer, are below recommended limits. Salinity hazards for all 

water in the area are below recommended limits. Boron concentrations are estimated to be below critical levels, even for sensitive crops.

REFERENCES

Allison, I. S., 1932, The geology and water resources of northwestern Minnesota: Minnesota Geol. Survey Bull. 22, 245 p.
J28 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

Bernstein, Leon, 1967, Quantitative assessment of irrigation water quality, in 

Water quality criteria: Am. Soc. Testing Materials STP-416, p. 51-65.

Cotter, R. D., Bidwell, L. E., Van Voast, W. A., and Novitzki, R. P., 1968, 

Water resources of the Chippewa River watershed, west-central Minnesota: U.S. Geol. Survey Hydrol. Inv. Atlas HA-286.

Edward E. Johnson, Inc., 1966, Ground water and wells: St. Paul, 440, p.

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

water-table conditions: U.S. Geol. Survey open-file report.

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

states: U.S. Geol. Survey Prof. Paper 161, 149 p.

Minnesota Division of Waters, 1959, Hydrologic atlas of Minnesota: Minnesota Div. Waters Bull. 10, 182 p.

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: Trans. Am. Geophys. Union, 16th Ann. Mtg., pt. 2, p. 519-524.

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

and alkali soils: U.S. Dept. Agriculture Handbook 60, 160 p.

Upham, Warren, 1888, The geology of Douglas and Pope Counties, in Winchell, N. H., Geology of Minnesota: Geol. and Nat. History Survey 

Minnesota Final Rept., v. 2, p. 471-498.

Van Voast, W. A., 1968, Ground water for irrigation in the Broofen-Belgrade 

area, west-central Minnesota: U.S. Geol. Survey open-file report.

Wenzel, L. K., 1942, Methods for determining permeability of water bearing 

materials, with special reference to discharging-well method's: U.S. Geol. 

Survey Water-Supply Paper 887, 192 p.

Wilcox, L. V., 1955, Classification and use of irrigation waters: U.S. Dept. 

Agriculture Circ. 969, 19 p.

 &U.S. GOVERNMENT PRINTING OFFICE: I97O O 4O1-I39