Correlation of GroundWater Levels and Air 

Temperatures in the 

Winter and Spring in 

Minnesota

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1539-D

Prepared in cooperation with the Division of Waters, Minnesota Department 

of Conservation, and the Minnesota Iron 

Range Resources and Rehabilitation 

Commission

Correlation of GroundWater Levels and Air 

Temperatures in the 

Winter and Spring in 

Minnesota

By ROBERT SCHNEIDER

CONTRIBUTIONS TO HYDROLOGY

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1539-D

Prepared in cooperation with the Division of ff^aters, Minnesota Department 

of Conservation, and the Minnesota Iron 

Range Resources and Rehabilitation 

Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D,C.
CONTENTS

	Page 

Abstract _______________________________________________________ D-1

Introduction...___________________________________________________ D-1

 General pattern of water-level fluctuations in water-table wells._________ D-2

Water levels and air temperatures in the winter and spring.____________ D-2

Relation between ground-water levels and air temperature____________ D-7

Melting of the frost layer from the bottom____________________ D-10

Capillary movement of water to the frost zone ____________________ D-11

Effect of the frost layer on recharge and runoff________________________ D-12

Conclusions_____________________________________________________ D-13

Heferenees______________________________________________________ D-14

ILLUSTKATIONS

Page 

FIGTJEE 1. Hydrograph of observation well 108.30.9add, Brown County,

and air temperature at New Ulm, Minn., 1946.___________ D-3

2. Hydrograph of observation well 108.30.9add, Brown County,

and air temperature at New Ulm, Minn., 1948____________ D-5

3. Hydrograph of observation well 108.30.9add, Brown County,

and air temperature at New Ulm, Minn., 1951 ____________ D-6

4. Hydrograph of observation well B58.20.16dbel, Chisholm, and

air temperature at Mahoning Mine, Hibbing, Minn., 1954__ D-8

5. Hydrograph of observation well B58.20.16dbcl, Chisholm, and

air temperature at Mahoning Mine, Hibbing, Minn., 1955__ D-9

<6. Sketch illustrating thermal conditions, the trend of the water

table, and the occurrence of frost in the winter and spring. _ D-12

m

CONTRIBUTIONS TO HYDROLOGY

CORRELATION OF GROUND-WATER LEVELS AND AIR

TEMPERATURES IN THE WINTER AND SPRING

IN MINNESOTA

BY ROBERT SCHNEIDBR

ABSTRACT

In a study of natural ground-water recharge in Minnesota a close relationship was observed between air temperatures and ground-water levels in the 

winter and spring. Hydrographs of two wells, one in the south-central part 

of the State, the other in the northeast, indicate that the water table declines 

 during the winter when the mean daily air temperature remains below 32°F. 

Within a few days after the air temperature has risen above freezing, groundwater recharge begins. If below-freezing temperatures return for some time, 

the water table again declines.

It has been shown in the laboratory that capillary water and water vapor 

move in the direction of the thermal gradient. The winter decline of the water 

table probably is caused in part by the upward movement of moisture below 

the frozen soil by capillarity, resulting in accretion to the frost layer from below. 

When the air temperature rises above freezing, the water table begins to rise 

as a result of downward percolation of melt water from the bottom of the frost 

layer.

The largest increment of ground-water recharge in Minnesota occurs in the 

spring. Because of the comparatively great depth of frost penetration and the 

relative impermeability of frost, the initial source of spring recharge is largely 

frostmelt. The frozen soil impedes or prevents the downward movement of 

snowmelt and rain. Once the frost layer is dissipated, recharge from infiltrating surface water begins. In addition, the reversal of the temperature 

gradient results in the downward movement of moisture from the warming soil 

zone to the water table.

INTRODUCTION

The largest increments to ground-water storage in Minnesota commonly occur in the spring. In a study of this recharge phenomenon, 

a, close relationship was noted between air temperatures and water 

levels in the winter and spring. This paper describes the relationship and discusses its significance in the hydrologic cycle.

The study was made as part of a statewide ground-water investigation by the U.S. Geological Survey in cooperation with the Division of Waters, Minnesota Department of Conservation, and the

D-l
D-2 CONTRIBUTIONS TO HYDROLOGY

Minnesota Iron Eange Eesources and Eehabilitation Commission. 

This statewide investigation was supervised by the author, as district 

geologist for Minnesota.

The water-level data used herein have been published or are in the 

process of being published as water-supply papers of the Geological 

Survey. Air temperatures were obtained from records of the U.S. 

Weather Bureau.

GENERAL PATTERN OP WATER-LEVEL FLUCTUATIONS IN WATER-TABLE WELLS

The water table in Minnesota is usually at a relatively low level during the winter. In the spring it rises abruptly and generally reaches 

the highest level of the year. The spring peak is followed by a declining trend during the summer, caused by the large evapotranspirative draft of vegetation and the lateral movement of water toward lakes and streams. Summer and fall rains recharge the soil and 

ground-water reservoirs, occasionally reversing the downward trend 

of the water table.

The low water levels in winter have been attributed to the fact 

that the ground remains frozen, and precipitation, which is largely 

in the form of snow, cannot infiltrate to recharge the ground-water 

reservoirs. It is inferred that the decline results from continued 

natural ground-water discharge, which contributes to the base flow of 

streams. The spring recharge has been ascribed to the downward 

percolation of snowmelt and rain.

The present study of water levels and air temperatures suggests 

that the phenomena of spring recharge and declining winter water 

levels may involve factors other than those mentioned above.

WATER LEVELS AND AIR TEMPERATURES IN THE 

WINTER AND SPRING

The hydrograph of well 108.30.9add, SE^SE^NE^ sec. 9, T. 108 

N., E. 30 W., in south-central Minnesota, was the first used in the 

study. This water-table well, completed in glacial drift at a depth 

of 32 feet, has been measured about once a week since 1942, and daily 

maximum and minimum air temperatures have been recorded at the 

U.S. Weather Bureau station at New Ulm, Minn., about 10 miles 

north of the well. Several portions of the hydrograph, which best 

illustrate the subject of the paper, have been selected for the following discussion.

The water-level record for 1946 (fig. 1) indicates a gradual winter 

decline interrupted by one reversal early in February. This isolated
 *

a 2

MEAN DAILY TEMPERATURE, 

IN DEGREES FAHRENHEIT

WATE

L

OJ

ro

GO 

O
JD-4 CONTRIBUTIONS TO HYDROLOGY

 winter reversal can be correlated with a rise of the mean daily air 

temperature at about the same time (February 5). Significantly, the 

mean daily temperature rose slightly above 32° F. Prior to this date, 

and for almost 2 weeks afterward, the mean temperatures were generally much lower. The spring rise of the water table began during 

the last half of February, and, although the mean daily temperature 

did not rise to 32'° F. at New TJlm until the end of the month, it may 

have exceeded 32°F. at the well about mid-February.

In 1948 the hydrograph (fig. 2) indicates a downward trend of the 

water table through January and most of February, during which 

period the mean daily temperature was well below freezing. The 

first reversal in the trend of the water level in February can be correlated closely with the time when the mean daily temperature first 

exceeded 32°F. From the end of February until the middle of March, 

the mean daily temperature again dropped below 32°F, and this is 

reflected in the "plateau" in the hydrograph for most of the first half 

of March. During the rest of March and April, the water table and 

temperature continued to rise.

The slight rise of the water table from the beginning of January 

to the early part of February 1951 (fig. 3) has no obvious relation to 

the temperature record. The decline during most of February is typical of the trend of the water table in the winter. A significant 

feature of the hydrograph is the abrupt rise that started in the latter 

part of February. A few days earlier the mean daily temperature 

exceeded 32°F for the first time that year. The pronounced flattening and slight decline of the hydrograph during March can be correlated with the period of mean daily subf reezing temperatures that 

started at the end of February.

A correlation between the water level in well 108.30.9add and the 

air temperature at New Ulm is apparent. Minor discrepancies probably can be attributed in part to the long distance between the observation well and the weather station or to the fact that water-level 

measurements were made at intervals of 1 week or longer.

In an attempt to study this phenomenon in greater detail in another 

area, a well in northeastern Minnesota was selected for observation. 

Well B58.20.16dbcl, SW^NW^SE^ sec. 16, T. 58 N., R. 20 W., 

Chisholm, St. Louis County, is equipped with a recording gage, is 

40 feet deep, and taps glacial sand and gravel. The water is under 

a small artesian pressure but the static water level is slightly lower 

than the water table. The water level is affected by the pumping of 

two nearby wells, although the pumping regimen is fairly regular. 

The nearest weather station is about 5 miles southwest, at the Mahoning Mine in Hibbing.
GROUND-WATER LEVELS AND AIR TEMPERATURES

80

60

40

32

20

 20

JANUARY FEBRUARY MARCH APRIL

FIGUBB 2. Hydrograph of observation well 108.80.9add, Brown County, and air 

temperature at New Ulm, Mlnn., 1948.

581729 61-
CONTRIBUTIONS TO HYDROLOGY

I- ^ 

UJ* UJ O

u. uj

a: z

UJ UJ

a. o:

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-20

FIGURE 3.-

JANUARY FEBRUARY MARCH APRIL

-Hydrograph of observation well 108.30.9add, Brown County, and air 

temperature at New Ulm, Minn., 1951.
GROUND-WATER LEVELS AND AIR TEMPERATURES D-7

Although no record was obtained of the precise date of the initial 

spring rise of the water table in 1954 (fig. 4), the start of the rising 

trend appears to correlate with the date when the mean daily temperature rose to 32° F for the first time that year. Part of the waterlevel rise in March resulted from the gradual reduction in discharge 

from one of the nearby pumped wells. The drop in temperature 

to 1°F early in March can be correlated with the relatively flat portion 

of the hydrograph for about the same period. On April 2 the mean 

temperature was 6°F, which is the bottom of a "trough" in the 

thermograph coinciding with a decrease in slope of the rising hydrograph for about the same time interval. The almost vertical portion 

of the graph, starting early in April, coincides with the time when 

the mean daily temperature rose well above 32 °F and remained above 

this temperature. During part of February and March, when the 

water level was rising at a lesser rate, the mean temperature fluctuated considerably but was close to 32°F most of the time.

In 1955 the water level dropped steadily from January through 

March (fig. 5), while the mean daily temperature remained well below 

freezing most of the time. The brief above-freezing period, March 

9-10, coincides with a flat portion of the hydrograph. At the end of 

March, the mean daily temperature exceeded and remained above 

32°F, and the period of spring recharge started a few days later. 

The distinct increase in the slope of the rising curve early in the 

second week of April should be noted. This break in slope is similar 

to the one that occurred early in April 1954 (fig. 4).

Despite the long distance between the observation well and the 

weather station, the relationship between water levels and air temperatures appears to be well exhibited by the hydrograph of well 

B58.20.16dbcl and the temperature data at the Mahoning Mine at 

Hibbing.

RELATION BETWEEN GROUND-WATER LEVELS AND 

AIR TEMPERATURE

As a prelude to an explanation of the relationship discussed above, 

it is necessary to describe the physical characteristics of frozen soil. 

The form of the frost layer is influenced by several factors, among 

which are the type of soil or rock and the availability and state of 

the moisture.

Storey (1955) describes four types of frozen soil: concrete, granular, honeycomb, and stalactite. Concrete frost structure consists of 

thin ice lenses and crystals; it is dense and usually associated with 

freezing to great depths. Granular frost is a loose, porous arrange-
D-8 CONTRIBUTIONS TO HYDROLOGY

JANUARY FEBRUARY MARCH APRIL

FlGOBB 4. iHydrograph of obsenratlon well B68.20.16dbcl, Chlsholm, and air 

temperature at Mahonlng Mine, Bibbing, Mlnn., 1954.
MEAN DAILY TEMPERATURE, 

IN DEGREES FAHRENHEIT

DAILY LOWEST 

SURFACE 

o> 
D-10 CONTRIBUTIONS TO HYDROLOGY

ment of small grains or crystals of ice scattered through the soil; 

it occurs as a result of shallow freezing. Honeycomb frost is loose 

and porous; it also is associated with shallow freezing. Stalactite 

frost consists of many small icicles partly fused into sheets or loosely 

bound blocks; it is formed during a refreeze of partly thawed honeycomb frost. ;

Storey states that concrete frost is relatively impermeable. Although the other frost structures described probably have little significance so far as percolation of water is concerned, as little as 1 

inch of concrete frost prevents infiltration of rain or melting snow. 

The freezing of heavy-textured soils prevents percolation of precipitation more effectively than frost in light-textured soils.

MELTING OP THE FROST LAYER FROM THE BOTTOM

The rise of the water table in the spring generally has been attributed to the downward percolation of snowmelt and rain. In 

Minnesota the available data indicate that spring recharge starts 

within a few days after the mean daily air temperature rises to 32° F. 

If downward-percolating snowmelt from the land surface were responsible for the initial rise of the water table in the spring, it would 

be necessary for the relatively impermeable frozen soil to thaw within 

a few days after the air temperature rose to 32°F. Unfortunately, 

no quantitative data are available on the depth of the frozen soil in 

the areas under consideration. However, according to a study made 

at Madison, Wis., by Bay, Wunnecke, and Hays (1952), frost penetration reached depths of 30 to 35 inches under various field conditions 

in the winter of 1949-50. They indicate also that it took at least 

2 to 3 weeks from the time thawing started for the frozen layer to 

dissipate. The climate at Madison is similar to that in the vicinity 

of well 108.30.9add in south-central Minnesota. Winter temperatures 

are considerably lower in northeastern Minnesota, where well B58.- 

20.16dbcl is located, and the general depth of penetration of frost 

in the soil probably is greater than it is at Madison.

Because of the denseness of the soil at both well sites it is probable 

that impermeable (concrete) frost is present. Consequently a source 

other than snowmelt must be responsible for the start of spring recharge within a few days after the air temperature rises above freezing, The author believes that, under these conditions, melt water 

from the bottom of the layer of frozen soil produces the initial rise 

of the water table in the spring. Also, when the mean daily air 

temperature rises above freezing periodically during the winter, when 

the general water-level trend is downward, some melt water from the
GROUND-WATER LEVELS AND AIR TEMPERATURES D-ll

bottom of the frozen soil percolates to the water table. In a study; 

by the Portland, Me., Water District (Public Works, 1940), it was 

observed that thawing of the frozen soil, which was 45 inches thick, 

began at the bottom; a few days later, thawing started at the top^ 

The frost layer disappeared at a depth of 15 inches below the sur-i 

face, after having melted both upward and downward to this depth. 

In the investigation by Bay, Wunnecke, and Hays (1952) of fouif 

sites at Madison, Wis., the frozen layer (30 to 35 inches thick)' 

started to thaw from the bottom first. At each site the frozen layeir 

disappeared at a depth equal to about one-half to one-third the orig-r 

inal thickness of the layer. i

CAPILLARY MOVEMENT OF WATER TO THE FROST ZONE |

Bouyoucos (1915) showed by laboratory experiments that soil 

moisture moves from a warm to a cold column of soil. He attribute4 

the movement to the increase in cohesion between water particles and 

in adhesion between water and soil particles that occurs with a decrease in temperature.

Smith (1943) stated that capillary water and water vapor move 

in the direction of the thermal gradient, and that condensation of 

vapor, by the forming of capillary bodies, triggers the capillary 

movement.

According to Jumikis (1956), Ruckli derived an equation for the 

depth of frost penetration and stated as one of his assumptions that, 

under the proper thermal gradient, there is upward movement of 

capillary moisture derived from ground water toward the growing 

and downward-advancing ice lenses or crystals (frozen soil).

The sketch in figure 6 illustrates hypothetical thermal conditions, 

the trend of the water table, and the occurrence of frost in the winter 

and spring. In the winter, heat moves upward from the zone of 

saturation to the atmosphere. The thermal gradient induces the upward movement of moisture, which freezes to form the frost layer 

as heat is continually removed. When the air temperature rises above 

32°F in the spring, heat continues to move upward from the zone of 

saturation; however, instead of moving through the frozen layer, it 

starts thawing the bottom of the layer because an opposing thermal 

gradient now causes heat to move downward from the atmosphere 

to the frozen soil.

It is concluded, on the basis of the preceding paragraphs, that 

part of the water-level decline during periods when the air temperatures are below freezing results from upward movement of moisture from the water table with the thermal gradient. In Minnesota,
D-12 CONTRIBUTIONS TO HYDROLOGY

LAND SURFACE

Mean daily temperature < 32* f i Mean daily temperature > 32* F

UNSATURATED

ZONE OF SATURATION

JANUARY FEBRUARY MARCH APRIL

FIGURE 6. Sketch Illustrating thermal conditions, the trend of the water table, and the 

occurrence of frost in the winter and spring.

where the depth of frost penetration is greater than it is in most of 

the rest of the United States, such upward movement probably accounts for a significant part of the winter decline of ground-water 

levels and accumulation of frost.

EFFECT OF THE FROST LAYER ON RECHARGE AND

RUNOFF

Recharge occurs when the mean daily air temperature rises above 

32°F for some time and the bottom of the frost layer starts to melt. 

Where concrete frost is present, the frozen layer is relatively impermeable and impedes or prevents recharge from snowmelt and rain. 

The steepening of the hydrographs of well B58.20.16dbcl early in 

April 1954 and April 1955 (figs. 4: and 5) probably represents the 

final disappearing of the frost layer, when more rapid recharge by 

snowmelt and rain, as well as by the f rostmelt that had been accumulating above the last of the remaining frost, became possible.

Drescher (1955, p. 12) presents the hydrograph of a shallow well 

near Hancock, Wis., which was completed in sand and gravel of a 

glacial-outwash plain. The rise of the water level was greatest and 

most rapid at the end of March and the beginning of April 1952, 

before all the snow melted. In a written communication (1957), 

Drescher states that it is doubtful that the frost was completely gone, 

but much of the melting snow probably percolated to the water table
GROUND-WATER LEVELS AND AIR TEMPERATURES IM.3

through the frost zone. This interpretation apparently corroborates 

Storey's statement (1955) that frost in light-textured (sandy) soils 

is relatively ineffective in preventing percolation of precipitation. 

The areas under consideration in the present study are underlain 

largely by dense silty or clayey soils, in which concrete frost is likely 

to form.

The frost layer affects surface runoff to a considerable degree. 

In view of the fact that much of the winter streamflow represents 

discharge from ground-water storage, thickening of the frost layer 

as described above, as well as a declining water table, is a factor 

contributing to the progressive diminution of streamflow during the 

winter. Also, because the frost layer retards or prevents infiltration, 

it affects surface runoff in another way it leads to flooding when 

heavy winter rains are unable to infiltrate the soil.

CONCLUSIONS

A significant part of the winter water-table decline in Minnesota 

probably results from the upward movement of capillary moisture 

to the frost layer, which is thickened by accretion from below. The 

movement is in response to the thermal gradient, and it begins when 

the mean daily air temperature declines in the late fall or early winter. 

Within a few days after the air temperature has risen above 32°F, 

the water table begins to rise as a result of downward percolation 

of frostmelt from the bottom of the frost layer.

In the spring, the initial source of recharge to aquifers in areas of 

dense soil and concrete-type frost is frostmelt because the frost impedes or prevents the downward movement of snowmelt and rain. 

After the frost layer disappears, the main source of recharge is infiltrating surface water. Because of the reversal of the temperature 

relations, downward movement of moisture will be accelerated by 

a downward temperature gradient.
D-14 CONTRIBUTIONS TO HYDROLOGY

REFERENCES

Bay, C. E., Wunnecke, G. W., and Hays, O. E., 1952, Frost penetration into 

soils as influenced by depth of snow, vegetative cover, and air temperatures: 

Am. Geophys. Union Trans., v. 33, no. 4, p. 541-546.

Bouyoucos, G. J., 1915, Effect of temperature on movement of water vapor and 

capillary moisture in soils: Agr. Research Jour., v. 5, no. 4, p. 141-172.

Drescher, W. J., 1955, Some effects of precipitation on ground water in Wisconsin: Wisconsin Geol. Survey Inf. Circ. 1, 17 p.

Jumikis, A. R., 1956, The method of solution of Ruckli's frost-penetration equation : Am. Geophys. Union Trans., v. 37, no. 2, p. 181-184.

Paulsen, C. G., and others, 1949, Water levels and artesian pressure in observation wells in the United States in 1946; Part 3, North-Central States: 

U.S. Geol. Survey Water-Supply Paper 1073.

 1951, Water levels and artesian pressure in observation wells in the 

United States in 1948; Part 3, North-Central States: U.S. Geol. Survey 

Water-Supply Paper 1128.

Public Works, 1940, Buried thermometers register depth of frost in clay and 

gravel soils: Public Works, v. 71, no. 8, p. 40.

Sayre, A. N., and others, 1954, Water levels and artesian pressures in observation wells in the United States in 1951; Part 3, North-Central States: 

U.S. Geol. Survey Water-Supply Paper 1193.

 1956, Water levels and artesian pressures in observation wells in the 

United States in 1954; Part 3, North-Central States: U.S. Geol. Survey 

Water-Supply Paper 1323.

 1957, Water levels and artesian pressures in observation wells in the

United States in 1955; Part 3, North-Central States: U.S. Geol. Survey

Water-Supply Paper 1406. 

Smith, W. O-, 1943, Thermal transfer of moisture in soils: Am. Geophys. Union

Trans., v. 24, pt. 2, p. 511-524. 

Storey, H. C., 1955, Frozen soil and spring and winter floods, in Water, The

Yearbook of Agriculture: U.S. Dept. Agriculture, p. 179-184. 

U.S. Weather Bureau, 1946, 1948, 1951, 1954, and 1955, Climatological data.

Minnesota.

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