Movement of Moisture 

in the Unsaturated Zone 

in a Loess-Mantled Area, 

Southwestern Kansas

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1021

Prepared in cooperation with the 

Kansas Geological Survey

Movement of Moisture 

in the Unsaturated Zone 

in a Loess-Mantled Area, 

Southwestern Kansas

By ROBERT C. PRILL

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1021

Prepared in cooperation with the 

Kansas Geological Survey

UNITED STATES GOVERNMENT PRINTING OFFICE, WASH INGTON : 1977
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Prill, R. C.

Movement of moisture in the unsaturated zone in a loess-mantled area, southwestern Kansas

(Geological Survey Professional Paper 1021) 

Bibliography: p. 21. 

Supt. of Docs. No.: I 19.16:1021

1. Groundwater flow-Kansas. 2. Loess-Kansas. 3. Soil moisture. 4. Water, UndergroundArtificial recharge. I. Kansas State Geological Survey. II. Title. III. Series: United 

States Geological Survey Professional Paper 1021 

GB1197.7.P74 551.4'9 76-608403

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

Washington, D.C. 20402

Stock Number 024-001-02973-1
CONTENTS

Page Page

Glossary —————————————————————————————————— IV Test results— Continued

Abstract —— ______ — _______________ ——— ______ —— _______ 1 Redistribution of moisture after ponding __ _____________ 10

Introduction ————————————————————————————————— 1 Ponding test 2 __________________________ 11

Acknowledgments ——————————————————————————— 2 Ponding test 3 ________________________ 11

Geohydrology of the study area __ ___ _ _____ _ ______ 2 Perching beds __________ ________________ 12

Test procedures ________ __ ____ ___ _____________________ 4 Soil zone____ ___ _____ ___ ___ _ __ _ _______ ___ 12

Test results ——————————————————————————————— 6 Clay and silt stratum at 42-49 feet (13-15 m) ____ 14

Infiltration —— __________ — _ —— _________ — ______ —— _ 6 Additions to the saturated zone ______ __ _ _____ __ ___ 14

Movement of moisture during ponding _ _ __ __ _ _ ___ 8 Water-level fluctuations _ ____ _ __________ __ ___ 15

Moisture buildup near the center of the pond____ _ __ 8 Water-table mound _ ___________ ___ _____________ 16

Moisture buildup outside the pond______ __ _________ 9 Changes in water quality __ _________ _ __ __ _____ 18

Wetting-front patterns ______________ __ ________ _ 9 Summary __ ___ _ _ __ ___ _____ __ _______ ___ ______ _ 20

	References cited __ __ __ _____ __ __ ____ __ ____ ___ 21

ILLUSTRATIONS

Page

FIGURE 1. Map of southwestern Kansas showing location of study area and distribution of loess deposits _ _ __ _ __ —— — ___- 2

2. Location map showing study area and facilities pertinent to ponding tests _____ _ _ ____ _ ___ _________ — — — _ 3

3. Cross section of ponding site showing neutron-probe access holes and lithologic units in the 0-25-ft (0-7. 5-m) zone 4

4. Cross section of southeast radial of ponding site showing observation wells and lithologic units of the 25-90-ft

(7.5-27-m) zone __ ______________________________________________________ --- 5

5. Map showing location of facilities installed at ponding site ____ ___ ________________ — —— __________ —— ______ 5

6. Graph showing recorded depth of water in pond during test 2 ____ __ _ _ _ ___ _ _________ __ _ _ _ _ __ — —— __ 7

7. Graph showing relation between time and infiltration rate during ponding tests ___- _ __ _ __ ________ — — — _ _ _ _ 7

8. Logs at access hole 1 showing moisture content before ponding and at selected times during ponding in test 2 compared

with porosity of upper loess_---_- _ _____ ___ __ _ __ __ ___ _ __ __ ____ _ _______ _ _____________ — ___ 8

9. Logs at access hole 5 showing buildup of moisture content with time during test 2 _ _ ________ ——— _________ —— 9

10. Cross section of ponding site showing location of wetting front with time after start of ponding during test 2 ______ 10

11. Logs at access hole 1 showing moisture content at end of ponding and at selected times after ponding ceased in

test 2 _________________________________________________________________ 11

12. Graph showing reduction of total moisture content in 0.5-12.0-ft (0.15-3.6-m) zone with time after end of ponding in

test 2 __________________________ _ ___ __________ _______________________ 11

13. Logs at access hole 1 showing moisture content before ponding, at end of ponding, and 6 days after end of ponding in

test 3 _________________________________________________________________ 12

14. Graph showing reduction of total moisture content in the 0.5-6-ft (0.15-1.8-m) zone with time after end of ponding in

test 3 _________________________________________________________________ 12

15. Comparison of saturation percentages in the upper loess at access holes 1, 2, and 3 after 2 days of ponding in test 2 13

16. Hydrograph for observation well O4 showing mounding above a perching bed during test 4 __ _ _ _____ — — ___ 15

17. Hydrographs showing water table in the unconfined aquifer and potentiometric surface of the semi-confined aquifer in

1968 - __ _________ _ ___ ___ ______ __ ____ _ _______ ___ _________________ ___ ________ __ _____ _ 16

18. Moisture-content logs at access hole 16 showing resaturation of materials associated with a rising water table —— 17

19. Hydrographs showing effects of ground-water mounding at southeast radial of pond during test 4 ____ —— ________ 18

20. Graph showing changes in specific conductance of water samples at selected observation wells on southeast radial of

pond during test 4 __ ___ _______________ ___ _______________ __ ________ ___ ________ _ __________ —— _ 19

TABLES

Page

TABLE 1. Physical properties of strata in the 0-20.5-ft (0-6.2-m) zone _______________ _____ ——— —— —————— 5

2. Information concerning application of water and collection of data for ponding tests _ — ___ ——— ______ ————— — 6

3. Comparison of moisture buildup in the 0-22-ft (0-6. 6-m) zone at access hole 1 and cumulative infiltration (test 2)__ 8

4. Chemical analyses of water samples __ ______ ___ __ _ _ _ ___ __ __ __ _ _ _ ___ ___ __________ — —— ____ 19

in
IV CONTENTS

CONVERSION FACTORS

Multiply English units

inches (in.) 

feet (ft) 

miles (mi)

feet per day (ft/d) 

feet per hour (ft/hr) 

feet per minute (ft/min)

square feet (ft2 )

square feet per day (ft2/d)

cubic feet (ft3)

By 

Length

2.54

.3048

1.6093

Flow

0.3048

.3048

.3048

Area

0.09290

.09290

Volume 

0.02832

To obtain SI units

centimeters (cm) 

meters (m) 

kilometers (km)

meters per day (m/d) 

meters per hour (m/hr) 

meters per minute (m/min)

square meters (m2 )

square meters per day (m2/d)

cubic meters (m3 )

GLOSSARY

Aquifer. A formation, group of formations, or part of a formation 

that contains sufficient saturated permeable material to yield 

significant quantities of water to wells and springs.

Confined aquifer. A water-yielding zone in which ground water is 

confined under pressure by impervious or semipervious strata.

Confining bed. A body of impermeable material stratigraphically 

adjacent to one or more aquifers.

Dry unit weight. The ratio of the mass to the bulk or macroscopic 

volume of soil particles plus pore spaces in a sample.

Effective hydraulic conductivity. The rate of flow of water 

through a porous medium that contains more than one fluid, such 

as water and air, in the unsaturated zone.

Flux. The rate at which water of the prevailing kinematic velocity 

is transmitted through a cross section of unit area.

Hydraulic conductivity. The rate at which water of the prevailing kinematic velocity is transmitted through a cross section of 

unit area that is at right angles to the direction for flow, under a 

hydraulic gradient of unit change in head over unit length of flow 

path.

Hydraulic gradiant. The change in static head per unit of 

distance in a given direction.

Infiltration. The downward entry of water into the soil, expressed 

as a rate.

Moisture content. A ratio, expressed in percent, of the volume of 

water to the total volume of the porous material.

Perched ground water. Unconfined ground water separated from 

an underlying body of ground water by an unsaturated zone.

Perching bed. A bed that supports a body of perched ground 

water.

Percolation. Movement of water through soil.

Porosity. The property of containing intergranular space or voids.

It is expressed as a ratio, in percent, of the total volume of

intergranular space to total volume of the medium. 

Potentiometric surface. A surface that represents the static

head. As related to an aquifer, it is defined by the levels to which

water will rise in tightly cased wells. 

Pressure head. The height of a column of static water that can be

supported by the static pressure at that point. The pressure head is

positive when the height of water is above the point and is

negative when the height of water is below the point. 

Saturation percentage. A ratio, expressed in percent, of the

volume of water to the total volume of intergranular space. 

Saturated zone. A zone in which all spaces, large and small, are

filled with water. The water table is the upper limit of this zone,

and the water in it is under greater than atmospheric pressure. 

Soil water. See term "Moisture content." 

Static head. The height of a column of water above a standard

datum that can be supported by the static pressure at a given

point. 

Storage coefficient. The volume of water an aquifer releases from

or takes into storage per unit surface area of the aquifer per unit

change in head. 

Unconfined ground water. Water in an aquifer that has a water

table. 

Unsaturated zone. The zone between land surface and the water

table. 

Water table. That surface in an unconfined water body at which

the pressure is atmospheric. 

Wetting front. The leading edge of moisture buildup resulting

from natural or artificial application of water at the land surface.
MOVEMENT OF MOISTURE IN THE UNSATURATED ZONE 

IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

By ROBERT C. PRILL

ABSTRACT

A study of moisture movement associated with four ponding tests 

in a loess-mantled area near Garden City, Kans., provides significant 

information on the potential of using the area for artificial recharge 

by water spreading.

Infiltration during the four ponding tests stabilized at rates 

ranging from 0.7 to 2.2 feet (0.2 to 0.7 meter) per day. The large 

differences in infiltration rates reflect changes in the hydraulic 

conductivity of the soil horizons developed in loess materials. The 

underlying loess has an appreciably greater hydraulic conductivity 

than the soil. Removing the soil zone should increase infiltration 

rates, provided that the underlying loess is not severely compacted 

during excavation or during subsequent recharge operations.

When the wetting front of infiltrated water is in the loess, the 

moisture-buildup pattern shows the characteristic wetting and 

transmission zones observed for infiltration in homogeneous 

materials. When the wetting front penetrates the underlying 

alluvium, the wetting front becomes indistinct.

The loess has the capacity to take large quantities of water into 

temporary storage. If adequate time is allowed between water 

applications for the loess to drain, the amount may be as much as 1 

cubic foot (0.03 cubic meter) of water for each 6 cubic feet (0.17 cubic 

meter) of the material.

At the ponding site, several fine-grained strata are in the 

unsaturated alluvium underlying the loess. Because these strata 

have relatively high hydraulic conductivities, they did not act as 

effective perching beds during the ponding tests. Strata of this type 

probably would not cause sufficient mounding to impede infiltration 

significantly or cause water-logged conditions during water 

spreading.

The ground-water mound that developed after application of 21 

feet (6 meters) of water has a maximum thickness of 2 feet (0.6 

meter) at the edge of the pond. The boundary of the mound moved 

laterally a distance of 50 feet (15 meters) from the edge of the pond in 

2 days. The mound, which dissipated very slowly because of 

additional drainage from the unsaturated zone, was discernible 3 

months after ponding. Although the mound on the saturated zone 

spread rapidly as a result of pressure transmission, the recharged 

water actually spread slowly by lateral displacement.

Because accumulated salts are leached from the unsaturated zone, 

the specific conductance of water arriving at the water table is higher 

than that of the applied water. The amount of increase is dependent 

on the extent of leaching from previous applications of water and on 

dilution by infiltrated water.

A general appraisal of the ponding-test data indicates that the 

study area has an excellent potential for artificial recharge by water 

spreading. Infiltration rates in the loess-mantled area would be 

favorable for water spreading, and fine-grained strata in the 

unsaturated zone would not significantly impede downward 

percolation. Water that is put into underground storage by utilizing

the dewatered part of the reservoir would help to sustain the 

productivity of the aquifer system.

INTRODUCTION

The extensive use of ground water for irrigation has 

caused appreciable declines in the water table in 

several loess-mantled areas in southwestern Kansas 

because the rate of withdrawal greatly exceeds the rate 

of replenishment. The life of the alluvial aquifer 

underlying the loess could be extended by more 

efficient irrigation practices and by artificial recharge 

to supplement natural replenishment.

Ponding tests in a loess-mantled area have yielded 

significant information on the potential of these 

deposits for artificial recharge by water spreading as 

well as information basic to the development of more 

efficient irrigation practices. This report describes 

infiltration rates under various test conditions, buildup 

of moisture during ponding and the subsequent 

redistribution after ponding, mounding on perching 

beds, and effects of ponding on the water table in terms 

of mounding and water-quality changes. Owing to the 

homogeneity of the loess materials, the data provide a 

classic field demonstration of water movement in the 

unsaturated zone according to theoretical projections. 

Green, Dabiri, Weinaug, and Prill (1970) have used a 

computer to simulate moisture changes with depth, as 

monitored by neutron moisture logs from this study. 

Excellent agreement between the calculated and the 

observed data was obtained.

Figure 1 shows the study area, 9 mi (14.5 km) 

northwest of Garden City in Finney County, southwestern Kansas, and the distribution of loess deposits 

that mantle about 60 percent of the 11-county area 

that forms southwestern Kansas. Much of the irrigation in southwestern Kansas takes place in the areas 

mantled by loess. Because soil surveys show the loess 

deposits of the 11 counties to be similar in physical and 

chemical properties, the results of this study have 

application throughout this area.

Details of the ponding site and pertinent facilities of 

the study area are shown in figure 2. The test pond is
MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

38°—

Loess deposits

O IIMORTON COUNTYiytlP

37 C

0 10 20 30 KILOMETERS 

FIGURE 1.—Map of southwestern Kansas showing location of study area and distribution of loess deposits.

located on the Irrigation Rresearch Project Farm of the 

Garden City Branch, Kansas Agricultural Experiment 

Station. The land within the study area is irrigated 

mostly by ground water obtained from 11 wells (fig. 2). 

Some supplemental supplies are obtained from ditches 

that convey water diverted from the Arkansas River.

ACKNOWLEDGMENTS

The writer is indebted to A. B. Erhart, superintendent, and to Paul Penas, Jay Swensen, and Kenneth 

Snelling, staff members of the Experiment Station, for 

their cooperation and assistance in conducting these 

experiments.

Special recognition is extended to W. A. Long, U.S. 

Geological Survey, for assistance in the installation of 

test facilities and in the collection and interpretation of 

neutron-moisture data. Appreciation is expressed for 

the cooperation of personnel of the Kansas Geological

Survey, the Division of Environment of the Kansas 

Department of Health and Environment, and the 

Division of Water Resources of the Kansas State Board 

of Agriculture.

GEOHYDROLOGY OF THE STUDY AREA1

Consolidated rock (defined as bedrock) underlying 

the study area is a calcareous shale within the 

Greenhorn Limestone of Late Cretaceous age (Meyer 

and others, 1970). The Greenhorn is relatively impervious and yields little or no water to wells.

Unconsolidated alluvial deposits of Pliocene and 

Pleistocene age, which overlie the bedrock, are the 

principal source of ground water in the study area. 

These deposits, consisting of interbedded clay, silt,

'The classification and nomenclature of the rock units used in this report are those of the 

U.S. Geological Survey and differ somewhat from those used by the Kansas Geological

Survey.
GEOHYDROLOGY OF THE STUDY AREA

R. 34 W.

0 400 METERS 

EXPLANATION

g Irrigation well and 

• identification letter

•—••• Conveyance ditch 

N>^| Research farm

FIGURE 2.—Study area and facilities pertinent to ponding tests.

sand, and gravel, extend to a depth of about 340 ft (104 

m). During the study, depth to water near the ponding 

site flucturated with seasonal pumping from 72 to 82 ft 

(22 to 25 m) below land surface.

The saturated part of the alluvial deposits consists of 

a lower sand and gravel aquifer that is semiconfined 

(semiartesian), a semiconfining layer of silt and clay 

that retards the vertical movement of water, and an 

upper sand and gravel aquifer where the water is 

unconfined. Irrigation wells in the study area pump 

water from the lower aquifer at a depth of 190-280 ft 

(58-85 m)

The unsaturated part of the alluvial deposits, which 

extends from about 16 to 80 ft (5 to 24 m) below land 

surface, consists of sand and gravel layers interbedded 

with clay, silty clay, and loam layers.

The loess, which is generally correlated by Frye and 

Leonard (1952) with Peoria Loess of late Pleistocene 

age, underlies the land surface to depths ranging from 

5 to 30 ft (1.5 to 9 m). In the study area, the loess is 

subdivided into an upper loess (0-12.5-ft or 0-3.8-m 

zone) and a lower loess (12.5-16.5-ft or 3.8-5.0-m zone).

The association of molluscan fauna in the upper loess, 

which was identified by E. D. Gutentag (oral commun., 

1969), is indicative of the lower molluscan zone of the 

Peoria Loess of early Wisconsin age (Leonard, 1952). 

The lower loess is considered to be equivalent to the 

basal zone of the Peoria Loess (Leonard, 1952). A 

reddish hue in the clay loam of the lower loess clearly 

distinguishes this stratum from the yellowish-brown 

silt loam of the upper loess in field sampling.

Surveys by the U.S. Department of Agriculture in 

cooperation with the Kansas Agricultural Experiment 

Station show that Richfield, Spearville, and Ulysses 

soils are the predominant loess-derived soils in 

southwestern Kansas. The ponding experiments were 

run in an area of Richfield soil. (A detailed description 

of the soil at the ponding site is given in the following 

paragraph.) Reports of the soil survey show that the 

texture of the A horizon of the Richfield ranges from 

silt loam to clay loam, and the texture of the B horizon 

ranges from silty clay loam to clay loam. These surveys 

show the profile characteristics of the Ulysses and 

Spearville soils to be very similar to those of the 

Richfield soils. The profiles differ primarily in the 

amount of clay in the B horizon. In the B horizon, the 

clay content of the Richfield soils is several percent 

greater than that of the Ulysses soils and is several 

percent less than that of the Spearville soils.

The following description of the Richfield soil was 

obtained from a pit dug in the pond area after completion of the tests. The description is according to soil 

survey nomenclature (Soil Survey Staff, 1951).

Ap —0-0.4 foot, very dark grayish brown (10YR 3.5/2); 

medium silty clay loam, weak, fine, subangular block structure, friable when moist, 

slightly calcareous.

Bl —0.4-0.9 foot, very dark grayish-brown (10YR 

3.5/2); heavy silty clay loam, weak, fine to 

medium, subangular block structure, firm 

when moist, slightly calcareous.

B2 —0.2-1.2 feet, very dark grayish brown (10YR 

3.5/2) with many dark-brown mottles (10YR 

4/3); heavy silty clay loam, weak, fine to 

medium, subangular block structure, firm 

when moist, slightly calcareous.

B3 —1.2-1.7 feet, dark brown (10YR 4/3) with many 

dark grayish-brown mottles (10YR 3.5-2); 

medium silty clay loam, weak, fine, subangular block structure, friable to firm, slightly 

calcareous.

Cca—1.7-2.9 feet, brown (10YR 5.5/3) with many dark 

grayish-brown mottles (10YR 4/2); light silty 

clay loam, massive, friable to firm, very calcareous.

Cca—2.9-4.0 feet, brown (10YR 5/3) with many
MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

grayish-brown mottles (10YR 5/2); silt loam, 

massive, friable, very calcareous.

The materials in the upper part of the unsaturated 

zone (0-25-ft or 0-8-m-depth interval) are shown in 

figure 3. The classification of the materials is based on 

samples collected during the installation of neutronprobe access holes. Physical properties of the materials 

are presented in table 1.

The materials in the lower part of the unsaturated 

zone and the upper part of the saturated zone (25-90-ft 

or 8-28-m zone) are shown in figure 4. The classification is based on samples from rotary drill cuttings and 

natural gamma-ray logs of observation wells.

TEST PROCEDURES

Four ponding tests were made at the study site. The 

location of facilities installed for these tests is shown in 

figure 5. Information concerning the application of 

water and the types of data collected during the four 

tests are summarized in table 2.

A circular pond 50 ft (15 m) in diameter was formed 

by constructing a 1-ft (O.S-m)-high earthen berm with a 

1:1 inside slope. The soil of the pond area, which had 

been used for growing sorghum the previous year, was 

not appreciably altered. During three of the tests, a 

black polyethylene sheet covered the pond to reduce 

the effects of evaporation and precipitation.

Water for the test was pumped from irrigation well A 

(fig. 2) at the southwest corner of the Research Farm.

An underground pipeline from the well supplied water 

to a riser pipe equipped with an alfalfa-valve hydrant 

to control discharge. Water was conveyed from the 

hydrant to the pond by 120 ft (37 m) of 8-in. (20-cm) 

pipe. A flow meter was installed in the pipeline to 

measure the quantity of water applied. In all four tests, 

the temperature of the applied water was about 59°F 

(15°C). The temperature of the water in the pond 

differed only slightly from that of the applied water.

The depth of the water in the pond was maintained 

between 0.1 and 0.6 ft (0.03 and 0.2 m) in three of the 

tests and between 0.1 and 0.9 ft (0.03 and 0.3 m) in the 

last test. During test 1, water levels were measured 

with a steel tape. A continuous water-level recorder 

was used during subsequent tests. The manner in 

which the depth of water fluctuated during ponding is 

illustrated by the data for test 2, shown in figure 6. 

Infiltration rates were determined from the water-level 

records when the depth of water in the pond was 0.40 ft 

(0.12 m). The rate was based on the slope of the 

water-level decline curve at the 0.40-ft (0.12-m) depth.

Sixteen access holes were installed (fig. 5) for 

measurement of moisture content by a nuclear meter. 

Thin-wall aluminum tubing with welded joints was 

used for casing. Holes 1-15 were installed by driving 

tubing behind a percussion barrel. The depths of holes 

1-9 are shown in figure 3; holes 10-15 are 8.0 ft (2.4 m) 

deep, and hole 16 was augered to a depth of 105 ft 

(32 m).

DISTANCE FROM CENTER OF POND, IN METERS 

202468 10 12

Berm,

SURFACE, DEPTH BLOW LAND INFEET

N> SO -» 

OCJ1 

yoerm

\

Upper loess

Lower loess

Alluvium 

———— i — t i i

:

Richfield soil

Silt loam 

Clay loam

Loam

Clay

Stratifie

———— i ____ i ———— L_

i ;

d deposits 

___ i ___

1

s'

__l

t £

K

** — 

i _

> (

• *•

—— i

3 •M

— -•

; £

i

j

-

- —

C/5 

CC 

LU

LU

LL 

CC.

C/3

25 20 15 10 5 05 10 15 20

DISTANCE FROM CENTER OF POND, IN FEET

25 30 35 40

6 g

I 

t

LU 

Q

FIGURE 3.—Cross section of ponding site showing neutron-probe access holes and lithologic units of the 0-25-ft (0-7.5-m) zone.
TEST PROCEDURES 

TABLE 1.—Physical properties of strata in the 0-20.5-ft (0-8.2 m) zone

Depth interval 

(ft)

0.1- 0.4 _____________________

.5- .8 ____________________

.9- 1.2 _________________ ____________________

1.3- 1.4 _________________________________________

1.7 1.9 ______________________________

2.0- 2.4 _________________________________________

3.0- 3.4 _______ _ _____________ _

3.5- 3.9 _________________________________________

4.0- 4.4 ___________________ __ ____________ _ _ _

4.5- 4.9 ______ __________ _ _ __ _

5.5- 5.9 _________________________________________

6.0- 6.2 ____________________ __ _ _ __ .

6.5- 8.5 ___ _ ________________________________

8.6-10.5 __________________________

19.5-20.5 __________________________________________

Distribution (percent) for indicated 

particle size (mm) 1

Clay 

(0.002)

___________ 38.7

___________ 38.3

_ __ _____ 34.6

___________ 34.2

___________ 28.5

._-_______ 25.4

___________ 31.4

___________ 44.2

Fine silt 

(0.002-0.02)

16.7 

17.3 

16.5 

19.4

22.6

24.1

18.1 

11.8

Coarse silt Sand 

(0.02-0.05) (0.05)

24.2 20.4 

24.4 20.0 

28.7 20.2 

28.5 17.9

——

—— ——

30.6 18.3

28.4 22.1

22.1 28.4 

8.3 35.7

Dry unit Specific 

weight2 gravity3 

(g/cm3 ) (g/cm3 !

1.27 -__ — 

1.39 ______ 

1.42 ______

1.40 ______ 

1.44

1.38

1.40 ______

1.41 ______ 

1.38 ___---

1.32

1.30 ______ 

1.28 ______

1.22

1.26 2.66 

1.20 ____

1.24 ______ 

1.29 ______

Porosity2 

(percent) Type of clay4

52.3 

47.7 

46.6 

47.4 

45.9

48.1 

47.4

47.0 

48.1 

50.4 

51.1 

51.9 

54.1

52.6 

54.9 

53.4 

51.4

Mixed layered clay: 

montmorillonite and illite.

Mixed layered clay: 

montmorillonite and illite.

Mixed layered clay: 

montmorillonite and illite.

'Analysis by Garden City Branch, Kansas Agricultural Experiment Station.

2Analysis by Garden City Subdistrict Office, U.S. Geological Survey.

3Analysis by Hydrologic Laboratory, U.S. Geological Survey, Denver, Colo.

•"Analysis by Hydrologic Laboratory, U.S. Geological Survey, Denver Colo. Differential thermal analysis.

DISTANCE FROM CENTER OF POND, IN METERS 

4 8 12 16 20

0401 0 2

40

80

Mixed clay 

to gravel

Sand and 

gravel

Clay and silt

Mixed clay 

to gravel

Sand and 

gravel

Clay

_ ——————————

—————————— --

!_ ———— t.J_1_J

-

:

10 20 30 40 50 60 70 

DISTANCE FROM CENTER OF POND, IN FEET

80

0 4

EXPLANATION

Observation well and identification number. Pattern shows 

screened or slotted interval

Limits of water-table fluctuation

FIGURE 4.—Cross section of southeast radial of ponding site showing observation wells and lithologic units of the 25-90-ft (7.5- 

27-m) zone.

Moisture was measured with a continuous-logging 

nuclear meter (Prill and Meyer, 1968) at a logging 

speed of 2.5 ft/min (0.8 m/min). Because it is difficult to 

relate nuclear-meter readings to moisture content near 

land surface, moisture contents from the land surface 

to a depth of 0.5 ft (0.15 m) were estimated.

Five observation wells were drilled (fig. 5). Wells

56789

Trace of section 

shown in figure 3

EXPLANATION

1 Neutron-probe access 

• hole and number

Observation well 

and number

Intake pipe and stilling 

well with automatic 

recorder

20 FEET

6 METERS

Trace of section 

shown in figure 4

P2

-8 - inch 

aluminum pipe

Flow meter

OB

ri^ Alfalfa valve

Underground pipeline 

FIGURE 5.—Location of facilities installed at ponding site.
MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

TABLE 2.—Information concerning application of water and collection 

of data for ponding tests

Test 1 Test 2 Test 3 Test 4

Covering on polyethylene polyethylene polyethylene none 

pond ____ sheet sheet sheet

Date tests were 

started ____ 4-26-66 10-20-66 4-4-67 11-6-67

Time from start 

to end of ponding, in days _. 5.3 2.5 0.2 11.7

Quantity of 

water applied, 

in feet _____. 3.25 7.00 1.00 21.50

Depth of water 

in pond, 

in feet _____ 0.1-0.6 0.1-0.6 0.1-0.6 0.1-0.9

Neutron-probe 

access holes 

monitored for 

moisture 

movement ___- 1, 5, 6, 

8-15

1-16 1-9 none

Wells monitored 

for water 

levels ______ none Oi-Os

Wells sampled 

for measurements of 

predominant 

chemical constituents and 

specific conductance ____- none Oi-O4

Oi-Os were screened in the sand and gravel stratum in 

which the water table fluctuated (the 72-84-ft or 

22-26-m zone). Well C>4 was screened just above a clay 

and silt stratum that occurs at the 42-49-ft (13-15-m) 

zone. Well Qs was screened in the confined aquifer, 

which is at the 190-280-ft (58-85-m) zone. Water 

samples from these wells were analyzed for specific 

conductance and predominant chemical constituents.

TEST RESULTS

Test results are discussed in the order of water 

movement: infiltration into the soil, percolation 

through the unsaturated zone, and addition to the 

saturated zone.

INFILTRATION

Marked variations in infiltration rates were observed during the four tests, as shown in figure 7. The 

initial rate was high in all tests but decreased at a 

decreasing rate during the first day of testing. After

about 1 day, the rate stabilized. The infiltration rate in 

test 1 stabilized at 0.7 ft/d (0.2 m/d), whereas the rate 

in test 2 stabilized at 2.2 ft/d (0.7 m/d). Test 3 was not 

run long enough for the rate to become stable, and in 

test 4 the infiltration rate stabilized after the first day 

at 1.2 ft/d (0.4 m/d). As ponding continued, however, 

the rate in the fourth test gradually increased until the 

end of 7 days. Thereafter, the infiltration rate remained at 2.1 ft/d (0.6 m/d) until the end of ponding 

(about 12 days).

In general, the variations in infiltration rates after 

the first day of ponding can be related to changes in the 

hydraulic conductivity of the soil horizons. Although 

an analysis of the causes of these changes is beyond the 

scope of this study, some possible reasons for the 

changes in infiltration rates are listed. (1) The protection afforded by the polyethylene covering on the pond 

probably increased biological activity in the soil zone. 

This increased biological activity could have created a 

soil structure more favorable for conducting water and 

caused part of the large increase in infiltration rates 

from test 1 to test 2. (2) The effect of compaction would 

have been greatest during test 1 because the land was 

tilled during the previous season but not prior to the 

subsequent tests. Compaction by the tillage implements could reduce hydraulic conductivity and cause 

the infiltration rates to be lowest during test 1. (3) 

Because of the abnormally large applications of water, 

the accumulated soluble salts would be leached from 

the soil horizons. A change in chemical composition of 

the soil owing to the loss of salts would likely modify 

the soil structure and increase its water-transmitting 

capability.

The decrease in infiltration rates during the first day 

of ponding in all tests is related to a number of factors. 

The most significant of these probably are a change in 

hydraulic gradient in the soil zone as the wetting front 

moves to greater depth and swelling of montmorillonite and illite clays in the soil zone. Both factors 

probably have a significant effect on the infiltration 

rate during the first few hours of ponding.

After several hours, the hydraulic gradient becomes 

stable; thereafter, the principal cause for reduction in 

the infiltration rate is the swelling of clay colloids. This 

suggestion is supported by the data from ponding test 

1. The application of water during this test was 

temporarily discontinued after 12 hours because of 

wind damage to the polyethylene cover. The cover was 

repaired, and the application of water was resumed 42 

hours after the start of the test. During the first 12 

hours, as shown in figure 7, the infiltration rate 

followed the characteristic pattern of decreasing at a 

decreasing rate with time. At the end of the initial 

application, the rate was 1.3 ft/d (0.4 m/d). When
TEST RESULTS

Start of test

at 1000 hours

10-20-66

End of test

at 2130 hours

10-22-66

0300 0600 0900 1200 1500 

TIME, IN HOURS

1800 2100 2400

FIGURE 6.—Recorded depth of water in pond during test 2.

O

>- 7

Q

cc _ uj 6

Q. hLJJ 

LJJ C 

U. °

z

LJJ" 4

h- q

CC

O 3

h-

£ 2

_l

iZ

- 1

n

i i < i i i i i i i i i i i i i i i i i i g i

EXPLANATION

—— Test 1

t — - Test 2

; ----- Test3

T

i

i

I — — Test 4

'\

\ \

\ 

\

\

\

A\ "—

V^._ __ ^— - — — -

__,^^-^

_ — -• — — "

v _

i i i i i i i i i i i i i i i i . i . i > i >

>

Q

-2.0 „.

LJJ 

Q.

CO

CC

LJJ

-1.5 uj ^

z

LJJ"

h-

-1.0 J

z

O

hQC

-0.5 Hj

u_

Z

- n

3456789 

TIME AFTER START OF PONDING, IN DAYS

10 11 12

FIGURE 7.—Relation between time and infiltration rate during ponding tests.

application of water was resumed at 41 hours, the 

infiltration rate was again high but decreased rapidly, 

and within 2 hours it had essentially stabilized at 0.8 

ft/d (0.2 m/d), which is 0.5 ft/d (0.2 m/d) less than the

rate at 12 hours. During the nonapplication period, the 

hydraulic conductivity apparently continued to decrease as though the water application had been 

continuous. The decrease was probably caused by the
MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

swelling clay colloids. The resumption of a high 

infiltration rate at 42 hours probably reflected a 

moisture buildup and a high hydraulic gradient in the 

soil horizon. The effects of these factors apparently 

were short lived, however, for the infiltration rate 

stabilized after 2 hours.

MOVEMENT OF MOISTURE DURING 

PONDING

The movement of moisture below the ponding area 

was analyzed by comparing logs of moisture content 

run during ponding with logs run before the start of 

ponding. The most complete record of moisture movement was obtained from ponding test 2; therefore, the 

data reported in this section pertain to that test. 

Although emphasis is placed on moisture movement in 

the loess, data that describe moisture movement in the 

upper part of the underlying alluvial deposits also are 

given.

MOISTURE BUILDUP NEAR THE CENTER 

OF THE POND

The nature of moisture movement at the center of 

the pond is illustrated by the logs for access hole 1 in 

figure 8, which shows the moisture content in the 

0.5-22.0-ft (0.15-6.7-m) zone at selected times after the 

start of ponding.

The logs are assumed to reflect the pattern of flow 

below the center of the pond. As shown in table 3, the 

values for moisture buildup at 6.8, 9.3, and 15.3 hours 

after ponding are markedly similar to values for 

cumulative infiltration for the same periods of time. 

Because flow in the center of the pond is essentially 

vertical (see section "Wetting-Front Patterns"), the 

similarity of values indicates that the infiltration rate 

near access hole 1 is about the same as the average 

infiltration rate for the pond. Green, Dabiri, Weinaug, 

and Prill (1970), using a mathematical model based on 

the theory of unsaturated flow, have successfully 

reproduced the moisture curve for 9.3 hours. Their 

work has demonstrated the effectiveness of modeling 

techniques for predicting water movement in unsaturated materials.

When all the moisture buildup is contained in the 

upper loess, as it was 6.8 hours after the start of

TABLE 3.—Comparison of moisture buildup in the 0-22-ft (9-6.6-m) 

zone at access hole 1 and cumulative infiltration (test 2)

Hours after 

start of ponding

6.8———— _ _____ _ _

9.3— ________________

15.3-_- _____ _____ _

Moisture buildup at 

access hole 1 (ft)

_—____— 1.5

— _ ______ 2.0

._ _ _______ 2.8

Cumulative 

infiltration (ft)

1.7

2.1

2.8

0

LITHOLOGY

ILJJ 

LJJ

± 6

LJJ 

CO

_C

Q.

LJJ 

Q

10

12

14

16

18

20

22

Porosity_

Soil 

zone

Silt 

loam

Clay 

loam

Loam

Clay

§ 8 

o o

- 1

-2 _._

-3

Porosity

GO

CC

LJJ 

O

___ 

CC

GO

Q

-4 -J

-5

LJJ 

CO

I 

Q_

20 30 40 50 60 20 30 40

MOISTURE CONTENT AND POROSITY, IN PERCENT BY VOLUME

50 60

FIGURE 8.—Logs at access hole 1 showing moisture content before ponding and at selected times during ponding in test 2 compared

with porosity of upper loess.
TEST RESULTS

ponding, the moisture-distribution curve shows the 

characteristic wetting and transmission zones observed for infiltration in homogeneous materials 

(Bodman and Coleman, 1944). The wetting zone, which 

extends from a depth of 10.5-12.5 ft (3.2-3.8 m), is a 

zone of rapid change in moisture content. The transmission zone, which extends from the base of the soil 

zone (4.0 ft or 1.2 m) to the wetting zone (10.5 ft or 3.2 

m), is characterized by an essentially constant moisture content. The transmission zone increases in 

length as infiltration proceeds. When the wetting front 

penetrates the alluvium, as shown on the log at 15.3 

hours after the start of ponding (fig. 8), wide variations 

in moisture content occur in the wetting and transmission zones because of large differences in the hydraulic 

properties of individual strata. Thus, the wetting and 

transmission zones tend to lose their identity.

The amount of entrapped air is apparently reduced 

as infiltration proceeds. This reduction is indicated by 

a general increase in moisture content of about 2 

percent in the upper loess during the 6.8-15.3-hour 

period of ponding. It is significant that the infiltration 

rate during this period decreased from 4.1 to 2.6 ft/d or 

1.2 to 0.8 m/d (fig. 7). Thus, the moisture content was 

increasing as the rate of water moving through the 

upper loess was decreasing. This inverse relationship 

probably reflects a changing hydraulic conductivity of 

the loess materials caused by swelling of clay colloids, 

as discussed in the section "Infiltration."

An appreciable quantity of water will be taken in 

temporary storage in the loess during ponding regardless of the restriction that the underlying deposits have 

on the downward movement of water. During test 2, 

when the underlying alluvial deposits did not affect 

flow through the loess, moisture buildup in the silt 

loam loess was about 15 percent. If adequate time 

intervals were provided between water applications to 

allow the loess to drain to antecedent conditions, as 

was done before the start of test 2, then as much as 1 ft3 

(0.03m3 ) of water could be put into temporary storage 

for each 6 ft3 (0.16 m3) of the material.

MOISTURE BUILDUP OUTSIDE THE POND

The nature of moisture buildup associated with 

lateral movement outside the ponded area is illustrated in figure 9 by logs for access hole 5, which is 2.5 

ft (0.8 m) outside the center of the berm.

At 16 hours after the start of ponding, the lateral 

movement of moisture extended only slightly beyond 

access hole 5. A moisture increase occurred only in the 

materials above a depth of about 6 ft (1.8 m). This 

increase represents a moisture buildup of only a few 

percent, which suggests that the wetting front is 

nearby.

LITHOLOGY

12

O 14

LU 

CO

I 16 

t

LU

Q 18 

20 

22

Start of ponding 55 hours

Soil

zone

Silt

loam

Clay 

loam

Loam

Clay

Stratified

_o

Q. 

Q.

D

_J O —O

Alluvium

0 10 20 30 40 50 

MOISTURE CONTENT, IN PERCENT BY VOLUME

FIGURE 9.—Logs at access hole 5 showing buildup of moisture 

content with time during test 2.

At 55 hours after the start of ponding, the buildup of 

moisture content extended throughout the 0.5-22-ft 

(0.15-6.7-m) zone. However, the values of moisture 

content are noticeably less than values for comparable 

materials below the center of the pond (fig. 8). The 

apparent lower saturation percentages for the materials at access hole 5 are evidence that none of the 

materials at this location were acting as perching beds. 

It is significant that the clay stratum at the 19.0-20.5- 

ft (5.8-6.2-m) zone did not appear to be acting as a 

perching bed even though the infiltration rate at 55 

hours was 2.2 ft/h (0.7 m/h). Apparently, this finegrained stratum either has a high hydraulic conductivity or is discontinuous.

WETTING-FRONT PATTERNS

The wetting-front patterns shown in figure 10, which 

are based on moisture-content measurements for the 

access holes on the east radial during test 2, illustrate 

how applied water moved vertically and laterally 

below the ponded area. Moisture measurements at the 

access holes on the northwest, southwest, and east 

radials (fig. 5) all showed similar patterns of lateral 

movement, which indicates that flow below the ponded 

area had radial symmetry. Therefore, measurements 

along the east radial shown in figure 10 should provide 

a representative projection of the wetting-front pattern 

associated with ponding.

The wetting-front patterns indicate that the major 

part of the water applied during ponding test 2 

(estimated to be about 90 percent) moved downward 

below the pond. Lateral movement was very slow and
10 MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS 

DISTANCE FROM CENTER OF POND, IN METERS

8 10

NEUTRON-PROBE ACCESS HOLES

0 -

5-

LLJ

o

LL

oc

C/) 

Q

15-

20-

oo

I

Q_

30-

35-

1 2 C

5 hours __ ___— — """

_ _ — — — — — •"""

10 hours _____ — --

15 hours ____—'"

— — — — — — """" ~~ ~"

20 hours __---"'

^ - "

__ --— "

/

^^''

/

/

/

/ .'

.'' /

x /

X 

X

X /

X''' /

/''

! /l

X

^_>

/'

/

/'

/

t

/

/

' ,

/

/

/ '

1 1

1

1

K 5 (

nr i >

'/

// /

/ /

/ '

/ /

/ /

/

/ /

^ /

/ /

7 ///x

// ^ /

/

/

/

/

/

1 40 

/ hours

x- /

^^^ /

25 hours _______ — -" "" '

Mil ! 1 

II I'.i "

' 

II 1 

Hi 1

HI 1

'II '

/ '

i

1

' ' 1 i

/i i

'(I 1

1

// '

/ /

y

,

/

/

/ 1

/ i

i /

/ /

/;/ 1 1 1

/ 1

/ ' 100 / 50 . ^^ . hours ^^ hours

30 hours __ _- — -~ ""

I I I I

•*

i

i

i

i

i

i

— —-

CO

CO

0)

—

CD

a 

a

D

t.

Q) M 

^ M

o 5

— -

E

"^

2.

5

- 0

- 2

C/3 

CC

LU

1- 

LU

^

LU"

O

LL

cc

w

Q

_?*

-6 <

O

_l

LU 

00

I 

Q_

LU

- 8 Q

-10

5 10 15 20 25 30 

DISTANCE FROM CENTER OF POND, IN FEET

FIGURE 10.—Location of wetting front with time after start of ponding during test 2.

35

was restricted to a short distance. By the end of the 

ponding period (59 hours), the wetting front in the 

loess was not evident at access hole 6, located about 5 ft 

(1.5 m) outside the center of the berm. Although 

moisture content was measured several months after 

ponding had ceased, no moisture buildup was discernible at access hole 7, located 7 ft (2 m) from the center of 

the berm. Lateral movement of the wetting front after 

ponding apparently was restricted to a few feet.

The progressive downward movement of the wetting 

front (fig. 10) indicates that none of the strata between

the soil zone and the 25-ft (8-m) zone acted as perching 

beds; also, the wetting-front patterns are not distorted 

enough to suggest appreciable lateral movement above 

any particular stratum.

The relatively slow rate at which the water moved 

the short distance outside the pond indicates that the 

size of the pond could be increased appreciably without 

markedly reducing the soil's ability to accept water.

REDISTRIBUTION OF MOISTURE AFTER PONDING

The redistribution of moisture after the cessation of
TEST RESULTS 11

ponding was analyzed by comparing the soil-moisture 

contents at various depths at selected times. Observed 

data from access hole 1 (center of the pond) during tests 

2 and 3 were used to illustrate the subsequent movement of moisture within the 0-22-ft (0-7-m) zone.

PONDING TEST 2

Logs of moisture content at selected times after the 

cessation of ponding in test 2 were compared to show 

the reduction of moisture content with time. Because 

the redistribution period was from late fall to early 

spring (October 22,1966, to April 3,1967) and the pond 

was covered with a polyethylene sheet, little water 

evaporated. Most of the moisture reduction was by 

gravity drainage or by deep percolation.

A typical pattern of moisture reduction with time 

after water application is a very rapid initial rate that 

decreases with time (Van Bavel and others, 1968). The 

series of logs in figure 11 shows how moisture content 

decreased with time after ponding in the 0.5-22-ft 

(0.15-6.7-m) zone; figure 12 shows the total moisture 

content calculated for the 0.5-12.0-ft (0.15-2.6-m) zone 

(upper loess) versus the number of days after cessation 

of ponding. The curve in figure 12 shows that total 

moisture content in the 0.5-12.0-ft (0.15-3.6-m) zone 

had decreased 22 percent at 10 days, 29 percent at 30 

days, and 35 percent at 100 days. Although the amount 

of reduction after the 100-day period is very small, the 

nature of the curve indicates that reduction would 

continue at an ever-decreasing rate for several months.

Because the infiltrated water applied during test 2 

reached the water table just prior to the cessation of 

ponding, there was a buildup of moisture content

o

2

I- 4

LU

LL

z 6

in"

2 8

u_

(T

D 10 to

Q

112

O 14 _i

LUm 

I 16

Q_

S 18 

20 

22

LITHOLOGY

163 days

Soil

zone

Silt

loam

Clay

loam

_oam

Clay

Upper loess

«8

o _o

E

>

3 

<

0 10 20 30 40 50 

MOISTURE CONTENT, IN PERCENT BY VOLUME

FIGURE 11.—Logs at access hole 1 showing moisture content at 

end of ponding and at selected times after end of ponding in test 2.

throughout the unsaturated zone at the end of the test. 

Addition of infiltrated water to the water table would 

be expected to continue at a decreasing rate for several 

months after the cessation of ponding. The decrease in 

moisture content at a selected time after cessation of 

ponding depends on the depth of material below the 

ponded area. The general relationship is this: the 

greater the depth of material below the ponded area, 

the smaller the decrease in moisture content. Although 

data concerning moisture reduction with time after 

ponding were not available for the entire unsaturated 

zone (approximately the 0-75-ft or 0-23-m zone), it is 

probable that the reduction of moisture content in this 

zone after ponding would be much more gradual than 

the reduction in the 0.5-12.0-ft (0.15-3.6-m) zone. 

Thus, appreciable additions to the saturated zone 

would be anticipated for an extended period after 

ponding—probably several months.

PONDING TEST 3

One ft (0.3 m) of water was applied to the pond in a 

4-hour period during test 3. Logs at access hole 1, as 

shown in figure 13, illustrate moisture content before 

ponding, at the end of ponding, and about 6 days after 

the end of ponding. At the end of the ponding period, 

the depth of the wetting front was 9 ft (2.7 m), and the 

buildup in moisture content was calculated to be 1.0 ft 

(0.3 m). Six days after the end of ponding, the depth of 

the wetting front was 17 ft (5.2 m), and the buildup of 

moisture content was calculated to be 1.1 ft (0.33 m). 

The similarity of moisture-content buildup at the two 

measurement times indicates that moisture movement 

after ponding was essentially downward.

Because the zone of evapotranspiration extends to a 

depth of about 6 ft (2 m) for predominant row crops of 

southwestern Kansas, such as sorghum (Musick and 

Grimes, 1961) and sugar beets (Herron and others, 

1964), most of the buildup in moisture content below

5.5

40 60 80 100 120 140 

TIME AFTER END OF PONDING, IN DAYS

160

FIGURE 12.—Reduction in total moisture content in the 0.5-12.0- 

ft (0.15-3.6-m) zone with time after end of ponding in test 2.
12 MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

O 14

Q 18 

20 

22

LITHOLOGY

Start of ponding

Soil

zone

Silt

loam

Clay

loam

Loam

Clay

o

a 

a

| 8

.3 —

Alluvium

10 20 30 40 

MOISTURE CONTENT, IN PERCENT BY VOLUME

50

FIGURE 13. — Logs at access hole 1 showing moisture content before 

ponding, at end of ponding, and 6 days after end of ponding 

in test 3.

this zone will move as deep percolation. The decrease 

in calculated moisture content in the 0.5-6-ft (0.15- 

1.8-m) zone in relation to time after cessation of 

ponding in test 3 is plotted in figure 14 to illustrate 

how deep percolation may occur if irrigation water is 

applied when soil-moisture content is high and evapotranspiration losses from the soil zone are low. The 

total moisture content in the 0.5-6-ft (0.15-1.8-m) zone 

was reduced about 0.2 ft or 0.06 m (8 percent) within 2 

days after the end of ponding; reduction after 13 days 

was about 0.4 ft (0.12 m). The test results indicate that 

a measurable reduction will continue for several 

weeks, but at an ever-decreasing rate.

The manner in which soil moisture is reduced by 

vertical percolation after infiltration is an important 

factor in determining appropriate water-management 

practices. Deep percolation can be very rapid when 

water is applied prior to or at the time of planting. The 

moisture in the loess will be especially high when the 

moisture content has not been diminished appreciably 

by evapotranspiration by the previous crop. During the 

long period required for seed germination and establishment of a crop's root system, a large part of the 

water applied may move below the root zone. For 

maximum irrigation efficiency, water should be 

applied at the proper time and in the proper quantity to 

meet plant requirements and to allow sufficient deep 

percolation to maintain an appropriate salt balance in 

the soil by leaching.

PERCHING BEDS

During the ponding tests, mound development was 

observed on two perching beds — the soil zone and a

^ 2.5

2.0

- 0.8

- 0.7

— 0.6

- 0.5

4 6 8 10 12 

TIME AFTER END OF PONDING, IN DAYS

14

FIGURE 14.—Reduction in total moisture content in the 0.5-6-ft 

(0.15-1.8 m) zone with time after end of ponding, test 3.

clay and silt stratum 42-49 ft (13-15 m) below land 

surface.

SOIL ZONE

Ground water held by a perching bed is unconfined 

and is separated by an unsaturated zone from an 

underlying body of ground water. During ponding, the 

water level in the pond represents a perched water 

table. The underlying perching bed may not be 

completely saturated because of entrapped air, but 

most of the intergranular space will be filled with 

water.

The nearly saturated zone immediately below the 

pond and the underlying unsaturated zone are depicted 

in figure 15 by saturation percentages for the upper 

loess during ponding test 2. Percentages are plotted for 

access holes 1, 2, and 3, which are all within the 

ponding area (fig. 5). The percentages for the B and Cca 

horizons (0.5-4-ft or 0.15-1.2-m zone) are almost all 

greater than 90 percent, which indicates a nearly 

saturated condition. The saturation percentages in the 

C horizon are mostly between 80 and 87 percent, which 

indicates an unsaturated condition. The perching bed 

controlling infiltration rates during test 2 evidently 

extended to about the 4-ft (1.2-m) depth, which 

includes the entire soil zone (the A, B, and Cca 

horizons).

The pattern of saturation percentages in figure 15 

suggests that infiltration rates would be increased if 

the soil zone were removed. The saturation percentages of the soil zone exceeded 90, while the percentages of the C horizon averaged about 84. Because the 

effective hydraulic conductivity of a material increases 

as the saturation percentage decreases, the hydraulic 

conductivity of the nearly saturated C horizon must be
TEST RESULTS 13

I- 4

LII

LU

~ 5

LU 

O

CC R D 6 

CO

Q 

5 7

LU

GQ 8

Q.

LU

Q 9

10

11

12

13

50

HoleS

O

N 

CC 

O

I

-0.5

C Ca

-1.0

M.5

-2.0

I- 2.5

CO 

CC 

LII

LU

o

<

LU 

CC

o

_l

LU

Q. 

LU 

Q

-3.0

-3.5

60 70 80 

SATURATION PERCENTAGE

90 100

FIGURE 15.—Comparison of saturation percentages in the upper loess at access holes 1, 2, and 3 after 2 days of ponding in test 2.

appreciably higher than that of the soil zone. The 

excavation of tail water and recharge pits in southwestern Kansas indicates, however, that the friable 

silt loam of the C horizon is easily compacted. Thus, 

caution would be required in excavating the soil zone 

to prevent compaction of the underlying material.

One objective in many water-spreading operations is 

to apply the available water over the smallest possible 

area in order to reduce land requirements. Thus, it is 

important to know how changes in the height of water

in the spreading area will affect the infiltration rate. 

The following discussion shows how the data for 

ponding-test 2 can be used to define the relationship 

between the height of water in a pond and infiltration 

rates.

When water moves through a perching bed, flow 

resulting from head gradients across the bed should 

follow Darcy's law. At the center of the pond, where 

flow is essentially vertical, this relationship can be 

stated as
14 MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

q 

K

where

= flux or infiltration rate, 

= hydraulic conductivity,

AA = change in pressure head across the perching bed, and

AZ = thickness of the perching bed. 

By the use of data from ponding test 2, the hydraulic 

conductivity of the perching bed can then be determined. The perching bed is the 0-4-ft (0-1. 2-m) zone. 

The infiltration rate is 2.2 ft (0.7 m) per day (fig. 7). The 

pressure head at the upper boundary is 0.4 ft or 0.12 m 

(the average height of water in the pond), and the 

pressure head at the lower boundary of the perching 

bed is considered to be -2.5 ft or -0.76 m (based on 

tensiometer readings made during subsequent tests 

when infiltration rates were near 2.2 ft/d or 0.7 m/d). 

The hydraulic conductivity is determined to be

K =

2.2 ft/day

2.9 ft 

4.0 ft

= 1.28 ft/day (0.39 m/d).

By using 1.28 ft/d (0.39 m/d) as the hydraulic 

conductivity and assuming the pressure head at the 

lower boundary of the perching bed to be -2.5 ft (—0.76 

m), we can compute the infiltration rates when the 

water levels in the pond are at 0.1 and 0.6 ft (0.03 and 

0.18 m) above the land surface as follows: 

When hi is 0.1 ft (0.03 m),

, = 1.28 ft/day [ ^ ft " ( ~TM ft) + l] =

4.0 ft

2.11 ft/day (0.64 m/d); 

when hi is 0.6 ft (0.18 m),

1 OQ ft/j r 0.6 ft -(-2.5 ft) , q = 1.28 ft/day ——————————— + 1 = 

L 4.0ft J

2.27 ft/day (0.69 m/d).

These computations show only a 7-percent decrease 

in the infiltration rate with a change in depth of water 

in the pond from 0.6 to 0.1 ft (0.18 to 0.03 m). Although 

the pressure head at the lower boundary of the 

perching bed in these examples is shown as a constant, 

a change in flux would cause a slight change in 

pressure head at the lower boundary. Because this 

change is directly related to flux, an increase in depth 

of water in the pond would result in an increase in the 

pressure head at the lower boundary of the perching

bed. Consequently, the range in the infiltration rates 

would be slightly less than the 7 percent shown here. 

That infiltration rate is not greatly affected by the 

depth of water in the pond is also indicated by the 

nature of the curves showing water-level decline for 

test 2. In general, the slope of the curve decreased 

gradually as the height of the water in the pond 

decreased. For instance, the height of water in the pond 

between 1200 and 1500 hours on November 22, 1966, 

decreased from 0.52 to 0.25 ft (0.15 to 0.07 m), whereas 

the slope of the decline curve decreased from 2.22 to 

2.15 ft/d (0.67 to 0.65 m/d). This change represents only 

a 3-percent decrease in the infiltration rate.

CLAY AND SILT STRATUM AT 42-49 FT (13-15 M)

A thin mound of water was observed during test 4 

above a clay and silt stratum at a depth of 42-49 ft 

(13-15 m), which showed that this stratum was acting 

as a perching bed. During test 4, a total of 21 ft (6.4 m) 

of water was applied to the pond over a period of 12 

days. The water-level hydrograph for observation well 

O4, shown in figure 16, shows that mounding occurred 

in the overlying sand and gravel after 7 days of 

ponding. The mound, which obtained a maximum 

height of 1 ft (0.3 m), dissipated rapidly after the 

cessation of ponding and disappeared in 1 day.

The nature of the growth and decline of the perched 

ground-water mound indicates that the clay and silt 

stratum acts as a perching bed only when infiltration 

rates are high. The first evidence of a water-table 

mound in the saturated zone was noted after 7 days of 

ponding (see section "Water-Table Mound"), which is 

the same time that mounding was first observed above 

the perching bed. Because the water table of the 

saturated zone is about 40 ft (12 m) below the perching 

bed, water probably had been moving through the 

perching bed for several days before mounding commenced. The apparent delay in the development of 

mounding may be related to the gradual increase in 

the infiltration rate from the 2d to 7th day. As shown in 

figure 7, the infiltration rate for test 4 initially 

stabilized at 1.2 ft/d (0.4 m/d), then gradually increased 

until it stabilized again at 2.1 ft/d (0.6 m/d) after 7 

days. Because the clay and silt stratum apparently 

functions as a perching bed only at the higher infiltration rates, the hydraulic conductivity of this finegrained stratum must be quite high.

ADDITIONS TO THE SATURATED ZONE

Additions to the saturated zone from water applied 

at land surface are difficult to measure. Observed 

water levels during the test period also reflect the 

fluctuations associated with ground-water pumping
TEST RESULTS 15

40

41

tLU 

LU

LU 

O

cc

D 

CO

Q 42

LU 

CO

CL 

LU

Q

43

44

Base of observation well

I I

• '6

\ 'o

°.'-°:

' .0

p.'

%

o' •

?EE

~~ ~~

~!

1EE

-12.25

CO

cc

LU

-12.50 t

z

LU 

0

-12.75 DC

CO

Q

z

-13.00 g

LU 

CO

I 

tCL 

LU 

Q

-13.25

6 8 10 12 14 

TIME AFTER START OF PONDING, IN DAYS

EXPLANATION 

r.'-:«rl Sand and gravel

Imj Clay and silt

FIGURE 16.—Hydrograph for observation well O4 showing 

mounding above a perching bed during test 4.

from a confined aquifer and return flow from applied 

irrigation water. Although a sharp rise in the water 

table measured in an observation well at the edge of 

the pond indicates that initial mounding was easily 

detected, the configuration of the mound became less 

evident with time and distance from the pond. In the 

following section, data describing water-level changes 

in the study area are used to show fluctuations in water 

levels that result from pumping for irrigation. Data 

from ponding test 4 are used to estimate the relative 

thickness and radial extent of mounding caused by 

ponding alone. Both water-level measurements and 

changes in chemical quality of water are analyzed to 

evaluate lateral spreading.

WATER-LEVEL FLUCTUATIONS

Water levels in the study area fluctuate during the

year as a result of ground-water pumping for irrigation. The observed magnitude of the fluctuations 

depends on the zone in which the observation well is 

screened. Because these seasonal changes mask the 

water-table mounding that occurs during the ponding 

tests, the following information is basic to the evaluation of mounding directly associated with ponding.

The saturated zone at the study site contains an 

unconfined aquifer from 72 to 84 ft (22 to 26 m), a 

confining bed from 84 to 190 ft (26 to 58 m), and a 

semiconfined aquifer from 190 to 280 ft (58 to 85 m) 

below land surface. Aquifer-test data from the study 

area show that the transmissivity of the semiconfined 

aquifer is l.OxlO4 ft2/d (9.3xl02 m/d) and the hydraulic conductivity of the confining bed is 3.2xlO~2 

ft/d (9.7X10-3 m/d).

The water-level hydrographs in figure 17 show the 

fluctuations of the water table of the unconfined 

aquifer (observation well 62) and fluctuations of the 

potentiometric surface of the semiconfined aquifer 

(observation well Os) in 1968. The water level in well 

O2 fluctuated between 73 and 82 ft (22 and 25 m) below 

land surface in this period. A change in water level in 

this well reflects a corresponding change in the volume 

of water in storage. The water level in well Os 

fluctuated between 73 and 95 ft (22 and 29 m) below 

land surface in the observed period. A change in the 

potentiometric surface measured in this well reflects a 

response to changes in pressure.

During the irrigation season, the change in the 

water table of the unconfined aquifer was markedly 

different from the change in the potentiometric surface 

of the semiconfined aquifer, as shown by the hydrographs from March through October 1968. The water 

level declined gradually during the season; the 

maximum rate of decline was 0.07 ft/d (0.02 m/d), and 

the maximum decline was 9 ft (2.7 m). In the same 

period, the potentiometric surface fluctuated erratically in response to pumping for irrigation. The 

maximum decline during the season measured in well 

Os was about 18 ft (5 m).

The water levels in both observation wells declined 

during the irrigation season and rose during the 

nonirrigation season. The potentiometric surface was 

much lower than the water table in the pumping 

season but rose 1-2 ft (0.3-0.6 m) above the water table 

in the nonpumping season. Because very little ground 

water pumped for irrigation is withdrawn directly from 

the unconfined aquifer, it is evident that some water 

leaks through the confining zone in response to a 

pressure gradient. In general, the lag is about 3 weeks 

between pressure changes in the semi-confined aquifer 

and water-table changes in the unconfined aquifer.

The resaturation of materials resulting from a rise in
16 MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

LLJ 

LU

LU 

o 

<

LL 

QC 

D 

CO

0

LU 

CD

X

Q_ 

LU

Q

68

73

? 78

83

88

93

98

Water table of unconfined aquifer 

Observation well 02

Potentiometric surface of 

semiconfined aquifer 

Observation well h24

-25

-26

- 27

- 28

- 29

cc.

LU

01

UO

D 

CO

O

_i

LU

X

Q. 

LU 

Q

M M J J 

1968

O N

FIGURE 17.—Hydrographs showing water table in the unconfined aquifer and potentiometric surface of the semiconfined

aquifer in 1968.

the water table is illustrated by the moisture-content 

logs on figure 18. During the period from October 23, 

1966, to April 5, 1967, a 7.7-ft (2.3-m) rise in the water 

table was measured in access hole 16. On the basis of 

moisture-content values in the formation from figure 

18, the total moisture buildup was determined to be 1.7 

ft (0.5 m). This represents a ratio of a 1-ft (0.3-m) rise in 

the water table for each 0.22 ft (0.07 m) of water added 

to the upper aquifer.

WATER-TABLE MOUND

The water-table mound associated with ponding test 

4 is shown in figure 19 by hydro graphs of observation 

wells 25 ft or 8 m (Oi), 50 ft or 15 m (O2 ), and 75 ft or 23 

m (Os) from the center of the pond. The period of 

observation began November 6, 1967 (date of initial 

application of water for test 4), and ended February 10, 

1968. The water table was rising during this period in

response to the general cessation of irrigation pumping. Thus, the water-level hydrographs in figure 19 

reflect both the seasonal rise and the addition of water 

from ponding.

A projected water-table rise due to recovery when 

the wells are shut off, without additions from ponding, 

was drawn to estimate the thickness of the groundwater mound. The rate of the projected rise was based 

on the measured rise prior to mounding and on the 

effect of pumpage from nearby irrigation wells during 

the following year. The rate of rise measured in the 

observation wells for a 7-day period prior to mounding 

was 0.04 ft/d (0.012 m/d). Because several irrigation 

wells were pumped for short intervals throughout the 

0-40-day period, the rate of 0.04 ft/d (0.012 m/d) is 

considered to be applicable for the rise projected to 40 

days after the start of ponding. During the 40-100-day 

period, the regional rate of rise probably increased
TEST RESULTS 17

64

66

68

70

ILU

ff 72

LLJ

LiCC

D c/3

Q 76

O 78

LU 

CO

fc 80

82

84

86

88

o

/ '*.

-20

-21

-22

-23

c/i 

cr

LUho 

<

LL

§

c/3

Q

2

LU 

DO

I

Q.

LU

Q

-25

-26

10 20 30 40 

MOISTURE CONTENT, IN PERCENT BY VOLUME

50

EXPLANATION

Sand

Sand and gravel ~ Clay

FIGURE 18.—Moisture-content logs at access hole 16 showing the resaturation of materials associated with a rising water table.

slightly because all irrigation pumping had ceased. 

The rise at observation well Cte for a comparable period 

in the winter of 1968-69 indicates a rate of 0.06 ft/d 

(0.018 m/d). The rate for the latter period, which 

reflects no additions of water from ponding and no

irrigation-well pumping, is considered applicable for 

the rise projected from 40 to 100 days after the start of 

ponding.

Only a small part of the water-table rise, as shown 

by the hydrographs on figure 19, appears to be related
18 MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

72

73

hLU

u! 74

LU

< 75

LICC

Q 76

O 77

LU 

DQ

I

fc

LLJ 

Q

78

79

80

Observation well O-j 

Observation well 62 

Observation well 63

—— • • —— Projected water table 

without mounding

-22.0

-22.5

-23.0

-23.5

-24.0

C/5

OC 

LLJ

LU 

O

LL 

OC

D

Q

Z 

<

DQ

I 

IQ. 

LU 

Q

0 10 20 30 40 50 60 70 80 90 100

TIME AFTER START OF PONDING, IN DAYS

FIGURE 19.—Hydrographs showing effects of ground-water mounding at southeast radial of pond during test 4.

to mounding during ponding test 4. Most of the rise is 

in response to the recovery of the water table in a well 

field during the nonirrigation season.

Because the water-table changes result from a 

complex hydrologic interaction, only a few general 

features of the mound are discernible from the test 

data. The significant features of the observed mounding are the initial rate of spreading during development, the relative thickness, and the manner of 

dissipation after the ponding ceases.

The mound spread rapidly during its early development (fig. 19). The first occurrence of mounding, which 

was indicated by a sharp increase in the rate of 

water-table rise, was observed after 7.5 days at well Oi 

and 10.5 days at well Os; thus, the mound spread 

laterally from well Oi to well Os—a distance of 50 ft (15 

m) from the edge of the pond—in only 3 days. This 

spreading represented a severalfold increase in the 

areal extent of the mound.

When the hydrographs are compared with the 

projected rate of seasonal rise, the ground-water 

mound resulting from ponding appears to be very thin. 

The estimated maximum thickness of mounding 

during ponding test 4 was 2.0 ft (0.6 m) at well Oi, 1.2 

ft (0.4 m) at well O2 and 0.8 ft (0.2 m) at well Os. The

mound attained maximum thickness at each observation well in a relatively short time; for example, it 

reached maximum thickness at well Oi in 12.5 days, or 

5 days the first indication of mounding. Thereafter, the 

thickness gradually diminished to about 0.7 ft (0.2 m) 

at 100 days.

The ground-water mound is shown to dissipate very 

slowly with time. At 100 days after the start of 

ponding, there is still distinct evidence of a mound. The 

persistence of the mound is related to the slow 

drainage of the unsaturated zone. As discussed in the 

section "Ponding Test 2," appreciable additions to the 

saturated zone from drainage can be anticipated for 

several months after ponding.

CHANGES IN WATER QUALITY

As water moves through the unsaturated zone, an 

increase in the concentration of dissolved solids and a 

corresponding increase in specific conductance are 

caused by the leaching of soluble salts from the soil. 

The increases caused by percolation during test 4 are 

reflected by changes in ground-water quality below the 

ponding site. Figure 20 shows the fluctuations in 

specific conductance of water samples collected at the
TEST RESULTS 19

5000

o

cc

LU

t 40°°

3000

£ 2000

LU*

o

z 

<

o

D 

Q

1000

Applied water from irrigation well A

20 40 60 80 100

TIME AFTER START OF PONDING, IN DAYS

120 140 160

FIGURE 20.—Changes in specific conductance of water samples at selected observation wells on southeast radial of pond during test 4.

water table from three wells on the southeast radial of 

the pond. These wells are 25 ft or 8 m (Oi), 50 ft or 15 m 

(62), and 75 ft or 23 m (Os) from the center of the pond. 

The measurements shown for a 157-day period represent the conditions during ponding as well as during 

subsequent drainage. The relationship of specific 

conductance to dissolved constituents for selected 

water samples is shown by the chemical analyses in 

table 4.

Appreciably higher specific conductances at the 

water table than that of the applied water apparently 

reflect additions of leachate to the water table. The 

initial occurrence of mounding was at 7.5 days at well

Oi, 9 days at well O2 , and 10.5 days at well Os (fig. 19), 

whereas the initial specific conductance readings for 

the three wells were from samples collected at 9 days. 

The specific conductance values at well Oi, which is at 

the edge of the pond, averaged about 3,000 micromhos 

at 25°C, which is assumed to be representative of the 

average dissolved-solids content of water moving 

directly below the pond. The specific conductance of 

samples collected at wells Cte and Os after 9 days were 

similar to that of the applied water, but appreciably 

higher values were recorded after 12 days at well O2 

and after 106 days at well Os. These values, which 

range from 3,500 to 4,600 micromhos at 25°C, probably

TABLE 4.—Chemical analyses of water samples

[Analyses by Kansas Department of Health and Environment. Dissolved constitutents given in milligrams per liter]

Specific 

conductance 

(micromhos

Well No.

Irrigation well A _ _ _ _ ___

Observation well Oi .

Observation well Oi

Observation well Oa

Observation well Oa

Observation well Oa _

Observation well Oa

Depth

(ft)

_ _ ______ 309

_________ __ 89

____ ______ 89

_ __. _____ 89

___________ 89

.__ ________ 89

_____ ______ 89

Date of

collection

11-20-67

11-20-67

04-11-68

11-20-67

04-11-68

11-20-67

04-09-68

Dissolved

solids

1,643

2,230

2,490

3,010

3,430

1,660

3.960

per centimeter at

25°C)

2,130

2,910

3,170

3,540

3,930

2,200

4.630

pH Silica

(SiOa)

7.8 20

8.0 24

7.3 14

7.7 14

7.4 16

7.5 7.9

8.0 22

Calcium

(Ca+ +

250

152

251

368

432

222

482

Magnesium

) (Mg+ + )

94

141

169

232

256

107

348

Sodium

(Na-H

123

345

305

228

260

146

240

Potassium

(K+)

11

17

16

17

18

12

20

Carbon- Bicarate

(COa0

0

0

0

0

0

0

bonate

-MHCOs-.

181

278

459

273

410

154

185

Sulfate

(SO4 — )

932

1,260

1,360

1,810

2,060

920

2,320

Chloride

(C1-)

113

129

125

176

165

167

417

Nitrate

(NQj-l

10

28

18

30

24

.9

24

Fluoride IF-)

0.9

1.2

1.1

1.1

1.1

1.2

1.1
20 MOVEMENT OF MOISTURE IN A LOESS-MANTLED AREA, SOUTHWESTERN KANSAS

reflect the dissolved-solids content of both the water 

moving directly below the pond and the water moving 

laterally outside the pond. Water moving directly 

below the pond would tend to have a lower dissolvedsolids content than water moving laterally beyond the 

edge of the pond before percolating downward because 

the leaching of salts by 11 ft (3.6 m) of water applied 

during the earlier ponding tests would be more intense 

in the materials immediately below the pond, and thus 

smaller quantities of salt would be present during 

subsequent percolation through those materials. Also, 

movement of water outward from the pond edge 

generally will occur at a lower saturation percentage 

than that moving downward below the pond, and water 

moving through a material at a low saturation percentage is more effective in leaching salts than at a high 

saturation percentage (Biggar and Nielsen, 1967).

Although the ground-water mound associated with 

additions of leachate to the saturated zone during 

ponding test 4 spread rapidly, the rate of lateral 

spreading of the leachate is apparently very slow. The 

first indication of mounding at well Oa was at 10.5 days 

after the start of ponding, whereas a high specific 

conductance was first measured at 106 days. A gradual 

increase in specific conductance from 2,100 to 2,800 

micromhos at 25°C that occurred from 10 to 80 days 

after the start of ponding may have been caused by 

factors unassociated with pond recharge, whereas the 

high specific conductances after 106 days probably 

were related to the lateral movement of pond leachate 

in the aquifer. Part of the leachate added to the 

saturated zone would be taken into storage as the 

water table rose, and part would move by displacing 

water in the saturated zone. Because the water 

generally moved upward through the confining bed 

during most of the period of observation (fig. 19), the 

displacement of water would mostly have occured in 

the unconfined aquifer (the saturated sand and gravel 

above 84 ft or 26 m).

A comparison of the volume of saturated materials in 

the upper aquifer within a radius of 75 ft (23 m) from 

the center of the pond with the volume of water applied 

during test 4 indicates that a long time lapse between 

mounding and the arrival of leachate at well Oa is 

possible. The bulk volume of saturated materials was 

computed to be 17.7xl04 ft3 (5.0 xlO3 m3), whereas the 

quantity of water applied during test 4 was 4.3x 104 ft3 

(1.2xl03 m3 ). Assuming that the quantity of water 

displaced per unit volume of saturated sand and gravel 

is 0.22, then the volume of displaceable water is 

3.9x 104 ft3 (1.1 x 103 m3), which is almost the volume of 

water applied.

SUMMARY

The study area, which is in a loess-mantled area 

underlain by thick unconsolidated alluvial deposits, 

has excellent potential for artificial recharge by water 

spreading. Infiltration rates observed during a series of 

ponding tests would be favorable for most waterspreading operations. Fine-grained strata in the 

unsaturated alluvium, which have high hydraulic 

conductivities, are not likely to cause sufficient 

mounding of water to impede infiltration. Water could 

be put into underground storage by using the volume of 

material that has been dewatered by pumping. The 

added water could sustain the productivity of the 

existing well field.

A primary factor in water-spreading operations in 

loess would be the development and maintenance of 

high hydraulic conductivities in the soil horizons. 

Infiltration rates, which ranged from 0.7 to 2.2 ft/d (0.2 

to 0.7 m/d) during the ponding tests, indicate high 

hydraulic conductivities for the soil horizons at the 

study site. The lowest measured infiltration rate of 0.7 

ft/d (0.2 m/d) probably would be considered favorable 

for many recharge operations. That the rate increased 

appreciably in subsequent tests illustrates that much 

can be done by appropriate management practices to 

increase the hydraulic conductivity of the soil horizons. 

If extensive water-spreading operations are considered, additional data should be obtained on the effects 

of different management practices and on the chemical 

compatability of water from other sources.

The silt loam loess underlying the soil zone has an 

appreciably higher conductivity than the soil zone. 

Thus, stripping the soil zone could be a procedure for 

obtaining higher recharge rates. As the silt loam loess 

is very susceptible to compaction, caution would be 

required to prevent compaction during the stripping 

operation and subsequent recharge operations.

The silt loam loess deposits have the capacity to take 

large quantities of water into temporary storage. If 

adequate time is allowed between water applications, 

the amount of water that can be taken into storage is 

about 1 ft3 (0.03 m3) of water for each 6 ft3 (0.17 m3 ) of 

material. In areas where the loess deposits are thick, 

considerable quantities of water can be applied by 

surface spreading regardless of the hydro logic characteristics of the underlying alluvium.

Several fine-grained strata are in the unsaturated 

alluvium underlying the loess at the study area. Owing 

to their relatively high hydraulic conductivities, they 

did not act as effective perching beds during the 

ponding tests. Strata of this type probably would not
REFERENCES CITED 21

cause sufficient mounding to impede infiltratio significantly during water-spreading operations.

Most of the water applied during ponding moved 

directly downward below the pond. Lateral spreading 

in the loess was restricted to only a few feet. This small 

lateral movement indicates that the size of the pond 

could be increased appreicably without markedly 

reducing its effectiveness.

Moisture content of the loess decreased at a gradually decreasing rate for a 5-month period after the 

cessation of ponding. This pattern of moisture reduction shows that deep percolation from irrigation could 

be large when water is applied during periods when 

moisture content is high and evapotranspiration losses 

from the soil zone are low.

As the applied water moves from land surface 

through the unsaturated zone, an increase in the 

concentration of dissolved solids can be anticipated. 

The increase in dissolved-solids content, which is 

caused by the leaching of soluble salts, depends on the 

quality of the water applied, the extent of previous 

leaching, and the saturation percentage of the materials through which the water is moving. The amount 

of dissolved solids leached from the unsaturated zone 

can be expected to decrease with continued application 

by water spreading.

The manner in which water is redistributed in the 

unsaturated materials after ponding shows that, 

although drainage of the materials in the unsaturated 

zone continues for many months after the application 

of water, most of the applied water can be expected to 

reach the saturated zone in a few months. Once the 

water reaches the water table, it becomes part of the 

ground-water supply available for irrigation. In the 

study area, water-table levels fluctuated markedly 

during the year as a result of ground-water pumping 

for irrigation. During the 1968 irrigation season, the 

maximum decline of the water table was 9.0 ft (2.7 m). 

On the basis of moisture-content values, the watertable rise of 7.7 ft (2.3 m) during the following 

nonirrigation season represented a total moisture 

buildup of 1.7 ft (0.05 m). Thus, a 1-ft (0.3-m) rise in the 

water table represents an addition of 0.22 ft (0.07 m) of

water to the upper aquifer. The nature of these 

water-table fluctuations suggests that there is considerable flow between the upper aquifer, where the 

depletion and accretion in storage occurs, and the 

lower aquifer, from which most of the ground water is 

withdrawn. Thus, for areas of similar lithologic and 

hydrologic conditions, additions from water spreading 

would become an integral part of the whole aquifer 

system contributing to the available ground-water 

supply. The actual applied water may not be immediately available for irrigation, but the resulting 

addition to pressure heads in the saturated zone would 

aid in maintaining the production of wells.

REFERENCES CITED

Biggar, J. W., and Nielsen, P. R., 1967, Miscible displacement and 

leaching phenomenon, in Hagen and others, eds., Irrigation of 

agricultural lands: Advances in Agronomy, no. 11, p. 254-274.

Bodman, G. B., and Coleman, E. A., 1944, Moisture and energy 

conditions during downward entry of water into soils: Soil Sci. 

Soc. America Proc.,v. 8, p. 116-122.

Frye, J. C., and Leonard, A. B., 1952, Pleistocene geology of Kansas: 

Kansas Geol. Survey Bull. 99, 230 p.

Green, D. W., Dabiri, Hassan, Weinaug, C. F., and Prill, R. C., 1970, 

Numerical modeling of unsaturated groundwater flow and 

comparison of the model to a field experiment: Water Resources 

Research, v. 6, no. 2, p. 862-874.

Herron, G. M., Grimes, D. W., andFinker, R. E., 1964, Effect of plant 

spacing and fertilizer on yield, purity, chemical constituents and 

evapotranspiration of sugar beets in Kansas: Am. Soc. Sugar 

Beet Technol, Jour., v. 12, p. 686-698.

Leonard, A. B., 1952, Illinoisan and Wisconsinan molluscan faunas 

in Kansas: Kansas Univ. Paleont. Contr., Mollusca, art. 4, 38 p.

Meyer, W. R., Gutentag, E. D., and Lobmeyer, D. H., 1970, 

Geohydrology of Finney County, Kansas: U.S. Geol. Survey 

Water-Supply Paper 1891, 117 p.

Musick, J. T., and Grimes, D. W., 1961, Water management and 

consumptive use by irrigated grain sorghum in western Kansas: 

Kansas Agr. Exp. Sta. Tech. Bull. 133, 20 p.

Prill, R. C., and Meyer, W. R., 1968, Neutron moisture measurements by continuous- and point-logging procedures, in 

Geological Survey research 1968: U.S. Geol. Survey Prof. Paper 

600-B, p. B226-B230.

Soil Survey Staff, 1951, Soil survey manual: U.S. Dept. Agriculture 

Handb. 18, 501 p.

Van Bavel, C. H., Brust, K. J., and Stirk, G. B., 1968, Hydraulic 

properties of a clay loam soil and the field management of water 

uptake by roots: Soil Sci. Soc. America Proc., v. 32, p. 317-321.

.S. GOVERNMENT PRINTING OFFICE: 1977 - 789-025/72