Geology and GroundWater Resources of the 

Ahtanum Valley, Yakima 

County, Washington

By BRUCE L. FOXWORTHY

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1598

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1962
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

The U.S. Geological Survey Library has cataloged this publication as follows:

Foxworthy, Bruce La Verne, 1925-

Geology and ground-water resources of the Ahtanum Valley, Yakima 

County, Washington. Washington, U.S. Govt. Print. Off., 1962.

v, 100 p. maps (1 col.) diagrs., tables. 25 cm. (U.S. Geological 

Survey. Water-supply paper 1598)

Part of illustrative matter in pocket. 

Bibliography: p. 66.

1. Water, Underground Washington (State) Ahtanum Valley. 

2. Water-supply Washington (State) Ahtanum Valley. 3. Borings Washington (State) Ahtanum Valley. I. Title. II. Title: 

Ahtanum Valley, Yakima County, Washington. (Series)

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

Washington 25, D.C.
CONTENTS

Page

Abstract__. _____________________________________________________ 1

Introduction._ ____________________________________________________ 2

Purpose and scope of the investigation_._______.___..__...._______ 2

Location and extent of the area_ ______-______-_-.____-_-_-__._ _ 3

Previous investigations._____-________-__--.__-_____-_--__-____-_ 4

Acknowledgments _____________________________________________ 5

Well-numbering system ____.___.__-_--_____.______________-__-- 5

Geography_. ___________________________ _________________________ 6

Landforms_ _ _______-.._----______-__-_-_-_-___-_-_-___._____- 6

Drainage_________________________________ ____________________ 7

Climate ______________________________________________________ 8

Vegetation._ __________________________________________________ 11

Culture and industry__________________________________________ 12

History of water use_-_-_-_--_-_________________-___-_________- 12

Geology._-____-._-_______-----________-___-___-_____-_-___.____-_ 14

Description of the rock units____ ________________________________ 14

Yakima basalt. ___. __-_---___-_-__.________-.-____________ 14

Ellensburg formation_______________________________________ 16

Cemented basalt gravel. ___________________________________ 19

Rock materials of Recent age_--___--_--_-___-_-_-.__________ 21

Structure.._-_____-_------_-_-_-___-_-___-_______-_________.__ 22

Geologic history.._____________________________________________ 24

Water resources_-__-_-_---------_-_-_-_-___________.____________-- 25

Surface water._______-_-_--___ _______________________________ 26

Surface-water inflow.______________________________________ 27

Surface-water outflow._---____________-_-___________.___. . 28

Utilization of surface water.________________________________ 30

Ground water._-___-----_-_-_-_______---_-_-_-_-.---_____._-_- 31

Aquifer properties.________________________________________ 31

Water table_..--_-----__--.-_------__-_-_-_---_-___-_-_-_- 32

Confined ground water.____.-_____-_-_________-_____.___--_ 33

Recharge to aquifers.______________________________________ 33

Movement of ground water_________________________________ 34

Ground-water discharge_____-__--___-_-____-._-___________. 34

Hydraulics of a well. _____-_______-----__ .__---__________-_ 35

Occurrence of water in the rock units. _______________________ 36

Yakima basalt._______________________________________ 36

Ellensburg formation._______--_--_-_____-_----.________- 39

Cemented basalt gravel. ____-__-__-_-_-__ ______________ 42

Unconsolidated alluvium. _____---_________-_________--- 43

Water-level fluctuations.____.-._______-_____---_--___-_---_ 49

m
IV CONTENTS

Water resources Continued 

Ground water Continued

Development---___-_-____-__-_-_-_--_-__-_-__---_--___-__ 53

Upper valley____-____-___-__----__--___-_-___________- 53

Upland benches_____--_-_____--_-_--_-_____________--- 54

Lower valley__________________________________________ 55

Present development..______-_--___.-___-_-_____-__ 55

Potential development_____________________________ 56

Summary of withdrawals.___-_____-_---_-___________-_- 58

Chemical quality___________ ______________________________ 59

Range in chemical concentration. _______________________ 59

General character______________________________________ 59

Suitability for use_____________________________________ 62

Ground-water discharge to the Yakima River._____________--- 62

Problems of future water supply_____________________________________ 64

Streamflow.__________________________________________________ 64

Ground water.________________________________________________ 65

Water use____________________________________________________ 65

Precipitation. _________________________________________________ 65

References cited.-_________________________________________________ 66

Basic data________________________________________________________ 67

Index.___________________________________________________________ 99

ILLUSTRATIONS

[Plates in pocket]

PLATE 1. Geologic map and sections of Ahtanum Valley, showing location of 

representative wells, Yakima County, Wash.

2. Hydrographs of selected wells.

3. Hydrograph of well 12/17-2R2, for the period June 1951-July 1953.

Page 

FIGURE 1. Map of the Ahtanum-Moxee subbasin showing study area---- 3

2. Diagram showing well-numbering system.__________________ 5

3. Mean monthly precipitation at three stations in and near

Ahtanum Valley_____________________________________ 9

4. Graph showing annual precipitation at Yakima_ _____^_____- 10

5. Diagrammatic cross section showing various occurrences of

ground water.________________________________________ 34

6. Diagrammatic section through a discharging water-table well. 35

7. Hydrograph of well 12/17-2R2, showing diurnal water-level

fluctuations and drawdown from pumping of a nearby well__ 51

8. Graph showing chemical character of water from wells______.. 61
CONTENTS

TABLES

Page 

TABLE 1. Monthly surface-water inflow and outflow, Ahtanum Valley. __ 29

2. Summary of pumping tests, lower Ahtanum Valley___________ 46

3. Estimated ground-water withdrawals in subareas of the Ahtanum Valley__________________________________________ 58

4. Records of representative wells in Ahtanum Valley.__________ 68

5. Materials penetrated by representative wells in the Ahtanum

Valley_-_________-_---__________________--------_----_ 86

6. Chemical analyses of ground water in the Ahtanum Valley.___ 96

7. Field analyses of water from wells in the Ahtanum Valley_____ 97

GEOLOGY AND GROUND-WATER RESOURCES OF THE 

AHTANUM VALLEY, YAKIMA COUNTY, WASHINGTON

By BRTJCE L. FOXWORTHY

ABSTRACT

The Ahtanum Valley covers an area of about 100 square miles in an important 

agricultural district in central Yakima County, Wash. Because the area is 

semiarid, virtually all crops require irrigation. Surface-water supplies are inadequate in most of the area, and ground water is being used increasingly for irrigation. The purpose of this investigation was the collection and interpretation of 

data pertaining to ground water in the area as an aid in the proper development 

and management of the water resources.

The occurrence and movement of ground water in the Ahtanum Valley are 

directly related to the geology. The valley occupies part of a structural trough 

(Ahtanum-Moxee subbasin) that is underlain by strongly folded flow layers of a 

thick sequence of the Yakima basalt. The upper part of the basalt sequence 

interfingers with, and is conformably overlain by, sedimentary rocks of the 

Ellensburg formation which are as much as 1,000 feet thick. These rocks are in 

turn overlain unconformably by cemented basalt gravel as much as 400 feet 

thick. Unconsolidated alluvial sand and gravel, as much as 30 feet thick, form 

the valley floor.

Although ground water occurs in each of the rock units within the area, the 

Yakima basalt and the unconsolidated alluvium yield about three-fourths of the 

ground water currently used. Wells in the area range in depth from a few feet 

to more than 1,200 feet and yield from less than 1 to more than 1,000 gallons 

per minute.

Although water levels in water-table wells usually are shallow often less than 

5 feet below the land surface levels in deeper wells tapping confined water 

range from somewhat above the land surface (in flowing wells) to about 200 

feet below. Wells drilled into aquifers in the Yakima basalt, the Ellensburg 

formation, and the cemented gravel usually tap confined water, and at least 12 

wells in the area flow or have flowed in the past. Ground-water levels fluctuate 

principally in response to changes in stream levels, variations in the flow of 

irrigation ditches and in rates of water application, variations in local precipitation, and seasonal differences in withdrawals from wells. Annual fluctuations of 

levels generally are less than 10 feet except in localities of heavy pumping. 

Periodic measurements of water levels in two observation wells in the area indicate, 

locally at least, a persistent decline in artesian pressures in confined basalt aquifers, 

although the record is too short to show whether withdrawal by pumping has 

reached, or is nearing, an optimum balance with recharge.

The aquifers are recharged by precipitation, by infiltration from streams, and 

by ground-water underflow into the area. Ground water is discharged by seepage 

to streams, by evapotranspiration, by springs and seeps at the land surface, 

and, artificially, by withdrawal from wells. It is estimated that the seepage

1
2 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

discharge to the Yakima River from the area studied may range from about 

20,000 to 25,000 acre-feet per year. The consumptive waste of ground water 

by phreatophytes probably exceeds 4,000 acre-feet per year and may represent a 

large reclaimable source of water in the area. The annual withdrawal of ground 

water from wells in the area for domestic, industrial, irrigation, public, and stock 

supplies is estimated to be 6,300 acre-feet.

The chemical quality of the ground water generally is satisfactory for most 

purposes, although the water from many wells is harder than is desirable for 

domestic use.

INTRODUCTION

PURPOSE AND SCOPE OF THE INVESTIGATION

The surface-water supplies that usually are available for irrigation 

in the Ahtanum Valley during the growing season are inadequate for 

the full development of the agricultural potential of the area. About 

60 percent of the irrigable land in the area is irrigated entirely with 

surface water, but only about 15 percent receives an amount considered adequate throughout the growing season. An additional 10 to 

15 percent of the irrigable land is, or has been, irrigated partly or 

entirely with ground water. Hence, although ground water does not 

now constitute a major part of the total irrigation water used, the 

acreage that has been supplied by ground water is nearly as large as 

that for which adequate supplies of surface water are available. 

Because the surface-water resources of the area are completely apportioned, future agricultural development of the area will depend largely 

upon the availability and proper utilization of ground water, even 

though the efficiency of surface-water utilization might be improved. 

Ground water also provides virtually all the water now used for 

domestic, industrial, and municipal purposes; hence, its availability 

could be a limiting factor in future population growth and industrial 

development within the area.

The purpose of this investigation was the collection and interpretation of data pertaining to ground water in the Ahtanum Valley in 

order to aid in the proper development and management of the water 

resources. Special consideration has been given to the source and 

movement of the ground water, its availability throughout the valley, 

its hydraulic relation to the streams, and its suitability for domestic 

and irrigation use.

The occurrence of underground water in any area is controlled by 

the character, distribution, and structure of the rocks and is influenced 

by the climate and the drainage pattern of the area. Therefore, discussions of the geology, landforms, climate, and drainage in the Ahtanum Valley, and their relation to the occurrence of ground water in the 

area, are included in this report.

The report is based largely upon fieldwork done by the writer 

between April 1951 and July 1952. During that time, wells were can-
INTRODUCTION

vassed and well logs and hydrologic data were gathered. A network 

of observation wells was established, in which water levels were measured periodically. Detailed geologic mapping was done on aerial 

photographs.

In 1953, during the course of this investigation, the writer prepared 

a brief report on ground water in the lower Ahtanum Velley (Foxworthy, 1953), at the request of, and under cooperative financing with, 

the State of Washington's Department of Conservation, Division of 

Water Resources. Many of the data presented in that report are 

included herein, although the area covered and the scope of the present 

report are much broader than those of the earlier report.

This study is part of a continuing program of the U.S. Geological 

Survey for the collection and interpretation of information bearing on 

the Nation's ground-water resources. It was conducted under the 

supervision of M. J. Mundorff, former District Geologist of the Ground 

Water Branch of the Geological Survey for the State of Washington.

LOCATION AND EXTENT OP THE ABBA

The area of this investigation is the Ahtanum Creek valley, in 

central Yakima County (fig. 1). The area extends from the Yakima 

River westward for 21 miles and ranges in width from 6 miles at 

the west end to about 3 miles in the eastern part. It constitutes the 

southwestern part of the Ahtanum-Moxee subbasin. The total area 

mapped is about 100 square miles.

The center of the area is about 11 miles west-southwest of Yakima, 

which is the county seat of Yakima County and the largest commercial center in south-central Washington. The southern side of the 

valley, south of Ahtanum Creek, is part of the Yakima Indian 

Reservation.

FIGURE l. Map of the Ahtanum-Moxee subbasin, Yakima County, Wash., showing location of study area.
4 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

Because there is virtually no farming, and consequently little 

ground-water use in the mountain valleys drained by the upper reaches 

of the North and South Forks of Ahtanum Creek, these areas were not 

included in the investigation.

PREVIOUS INVESTIGATIONS

In 1893, I. C. Russell made a preliminary investigation of the geologic features of central Washington to ascertain whether the region 

was favorable for a supply of artesian water for irrigation. In his 

description of what is called in this report the Ahtanum-Moxee subbasin, Russell presented well logs and descriptions of some of the 

pioneer wells in Yakima County.

A more detailed study of part of Yakima County, including the 

Antanum-Moxee subbasin, was made by G. O. Smith (1901), who 

described the main geologic features, the general conditions affecting 

ground water, and the flowing artesian wells in the subbasin.

Smith (1903) also mapped the geology of the Ellensburg quadrangle, 

which covers an area of 820 square miles and includes the Ahtanum 

Valley. In his description of the quadrangle, Smith treated in detail 

the rock units and geologic structure of the Ahtanum Valley and included a general evaluation of ground-water resources in the Yakima 

area.

In 1943 a short report on the ground water of the Ahtanum Valley 

was completed by S. N. Twiss of the Soil Conservation Service, U.S. 

Department of Agriculture. Twiss differentiated a rock unit that had 

not been recognized as a separate unit by earlier workers, and he 

described the water-yielding potentialities of the various rock materials in the valley.

In 1954, J. E. Sceva completed a report evaluating the streamflow 

records from the Yakima basin, including the Ahtanum Valley, with 

regard to possible subsurface flow of water past stream-gaging stations. The report contains descriptions of the rock units and the 

larger structural features in the Yakima basin, and of their influence 

on the hydrology of the region; discussions of the various subbasins, 

including the Ahtanum-Moxee subbasin, and the utilization of water 

within them; descriptions of the geologic conditions at each gaging 

station; a generalized geologic map and a section along the Yakima 

River; and detailed geologic sections at the sites of gaging stations.

The geology of the Yakima East quadrangle, which includes the 

eastern \% miles of the lower Ahtanum Valley, and of the adjacent 

Moxee Valley was mapped and described in detail by A. C. Waters 

(1955). Although Waters' report is concerned primarily with the 

area east and northeast of the Ahtanum Valley, it provides an excellent 

description of the rock units and geomorphology of the region.
INTRODUCTION

Because all these publications deal with the area herein considered, 

they have been consulted frequently during this investigation.

ACKNOWLEDGMENTS

The fieldwork and preparation of this report were greatly facilitated 

by the assistance of many persons. Well owners, operators, and 

drillers provided many of the well data included in this report. Special acknowledgment is given to the owners who allowed their wells to 

be usad for water-level observations and for aquifer tests. The Rankin Equipment Co., of Yakima, contributed many records of pumping 

tests. Mr. J. L. Dobie furnished information and collaborated in the 

collection of fossils. Vertebrate fossils from the collection of the State 

College of Washington have proved extremely valuable in the assignment of ages for the rock units; appreciation is expressed to Mr. 

Harold E. Culver for the use of his lucid field notes, and to Mr. W. 

Frank Scott for his help in making the fossils available for examination. 

The cooperation of personnel of the State Division of Water Resources 

in supplying well records and comments on this report also is gratefully acknowledged. Assistance given by members of the Geological 

Survey includes the identification of invertebrate fossils by Mr. T. C. 

Yen and identification of vertebrate fossils by Miss Jean Hough.

WELL-NUMBERING SYSTEM

Well numbers used in this report are based on and show locations of 

wells according to the rectangular system for subdivision of public 

land, indicating township, range, section, and 40-acre tract within the 

section. For example, in the well number 12/17-9J1, the part preceding the hyphen indicates successively the township and range

D

E

M

N

C

F

L

P

B

G

K

Q

A

H

o^

J

R

FIGURE 2. Diagram showing well-numbering system.

(T. 12 N., R. 17 E.) north and east of the Willamette base line and 

meridian. The first number following the hyphen indicates the 

section (9), and the letter (J) gives the 40-acre subdivision of the 

section as shown in figure 2. The last number is the serial number of
6 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

the well (1) in that particular 40-acre tract. Thus, the first well recorded in the NEjiSEJi sec. 9, T. 12 N., R. 17 E., would have the 

number 12/17-9J1, and the second well would have the number 

12/17-9J2.

GEOGRAPHY

LANDFOBMS

The Ahtanum Valley descends eastward from the foothills of the 

Cascade Mountains to the Yakima River. It is one of several structurally controlled eastward-trending valleys in the central Yakima 

basin. In general, the valley has steep sides, a relatively flat floor, 

and considerable downvalley slope. Altitudes within the area range 

from about 940 feet at the Yakima River to about 4,100 feet at the 

crest of Cowiche Mountain.

The major landforms of the area are directly related to the geologic structure. The valley itself occupies the southwestern part of 

the Ahtanum-Moxee subbasin, which is a structural trough, or syncline 

(fig. 1). The ridges that border the area on the south, west, and 

northwest are formed by structural upfolds, or anticlines.

The valley is bordered on the south by Ahtanum Ridge, a narrow, 

even-crested anticlinal ridge that rises about 1,000 feet above the 

valley floor and locally exceeds 2 miles in width. It extends eastward from the irregular and deeply eroded Cascades some 40 miles to 

the Yakima River. Its eastward extension, beyond the Yakima 

River, is known as the Rattlesnake Hills. The Yakima River, flowing 

southward across the axis of the ridge, has eroded a narrow, steepwalled gorge called Union Gap, for which the nearby town is named.

Sedge Ridge and Cowiche Mountain are similar to Ahtanum Ridge, 

though somewhat higher. They are the topographic expression of 

the Sedge Ridge-Cowiche Mountain anticline and form the west and 

northwest boundaries of the Ahtanum-Moxee subbasin.

Discussions of ground water in the area may be related effectively 

to the valley's three main physiographic sections, herein termed the 

lower valley, the upper valley, and the upland benches.

The lower valley includes the broad valley floor along the lower, or 

eastern, reach of Ahtanum Creek and the adjacent lower slopes of 

Ahtanum Ridge. For a distance of approximately 6 miles west of 

the Yakima River, the lower valley floor has no marked natural 

boundary on the north. This part of the valley floor is a southern 

continuation of a broad alluvial plain that extends southwestward 

from Yakima. Farther west, however, the lower valley is bordered 

on the north by a moderately dissected terrace remnant that rises, at 

places, more than 100 feet above the valley floor. The lower valley 

floor is about 1 to 2% miles wide and has a relatively flat cross-valley
GEOGRAPHY 7

(north-south) profile. The down valley (easterly) gradient of the 

lower valley floor ranges from about 36 to 75 feet per mile and averages 

52 feet per mile.

Fourteen miles west of the Yakima River, the valley floor is sharply 

constricted by resistant lava rock which forms low bluffs and vertical 

cliffs along both sides of Ahtanum Creek for a distance of 3 or 4 miles. 

In this constriction, locally called the Narrows, the valley floor is less 

than half a mile wide. Upstream from the Narrows, the valley floor 

widens somewhat, although it is less than a mile wide at its widest 

point, in the vicinity of Tampico. The upper valley, as described in 

this report, comprises the Narrows and the valley floors to the west, 

including those of the North and South Forks of Ahtanum Creek for 

distances of about 4 and 3 miles, respectively, upstream from their 

confluence.

The upper valley is sharply delimited by steep banks and bluffs 

that rise to well-defined upland benches on the north and south sides 

of the valley floor and on the west between the North and South Forks 

of Ahtanum Creek. In general, these upland benches are terrace 

remnants formed between bedrock valley Walls and overlying irregularities in the upper surface of the underlying bedrock. The benches 

adjacent to the valley floor slope upward toward the margins of the 

basin, merging with the alluvial fans and pediment slopes along the 

flanks of the anticlinal ridges.

The upland bench on the north side of the valley locally is more 

than 200 feet above the valley floor. It extends eastward beyond the 

Narrows and merges with the terrace remnant that separates the lower 

Ahtanum Valley from Wide Hollow. This terrace gradually diminishes in height toward the east and dies away near the center of the 

lower valley.

The bluffs and slopes on both sides of the valley have been moderately gullied by small, intermittent streams. From the mouths of the 

gullies and ravines, fan-shaped deposits of gravel have been built out 

onto the edges of the valley floor. On the south side of the lower 

valley, these alluvial fans coalesce to form a continuous, undulating 

slope along the base of Ahtanum Ridge.

DRAINAGE

The most important stream in the area is Ahtanum Creek, a perennial stream which flows eastward through the entire length of the 

Ahtanum Valley and enters the Yakima River at Union Gap. Wide 

Hollow Creek, which flows southeastward across the east end of the 

lower valley and enters the Yakima River less than half a mile above 

the mouth of Ahtanum Creek, also is a perennial stream, although its
8 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

flow is largely supported during the summer months by waste water 

from irrigation outside the area.

The Ahtanum Creek drainage area covers about 171 square miles, 

almost half of which lies to the west of the area studied, on the high, 

well-dissected east slope of the Cascades. This headwater region is 

drained by the North Fork and South Fork of Ahtanum Creek, which 

converge near Tampico to form the main stream. Gradients along 

Ahtanum Creek range from 36 feet per mile near Union Gap to more 

than 100 feet per mile along the North and South Forks above Tampico.

The drainage pattern in the area mapped is closely controlled by 

the structure of the underlying rocks. Ahtanum Creek and its South 

Fork follow the axis of the structural trough that forms the Ahtanum 

Valley, whereas the North Fork, after following a course paralleling 

the Sedge. Bidge-Cowiche Mountain anticline, turns directly across 

that upfold. Also, because the geologic structure closely controls 

the topography, most of the intermittent streams in the area flow 

generally in the direction of dip of the underlying rocks.

In the lower valley Ahtanum Creek splits into three main courses 

which converge again into one main stem before leaving the area. At 

some places these natural distributaries have been incorporated into 

a complex system of canals used to irrigate that part of the valley. 

During the summer the water of Ahtanum Creek is diverted for irrigation and returned to the main channels of the creek several times in 

its course between Tampico and the Yakima River.

CLIMATE

The climate of the Ahtanum Valley is of the continental semiarid 

type characteristic of southeastern Washington. Summer days are 

clear, hot, and dry, and the nights usually are cool. Winters are 

comparatively wet and cloudy and have occasional periods of cold.

Precipitation and perhaps other weather conditions in the region 

vary substantially with elevation and with proximity to the Cascade 

Mountains. Because these factors differ considerably from place to 

place within the Ahtanum Valley, observations made at one place may 

not relate directly to weather conditions in other parts of the area. 

For this reason, and to provide supplemental information not available 

from the area itself, climatological data from four weather stations in 

the Yakima basin are included herein. Weather observations made at 

the U.S. Weather Bureau station at the Yakima Airport doubtless 

apply over much of the lower Ahtanum Valley. A weather station 

at Rimrock, about 15 miles northwest of Tampico, is about 1,700 feet 

higher and some 30 miles closer to the crest of the Cascades than the 

Yakima station. Data from the Rimrock station probably are indicative of weather conditions over much of the headwaters area of
GEOGRAPHY 9

Ahtanum Creek, and the climate in the upper Ahtanum Valley probably is intermediate between climatic conditions at the Rimrock and 

Yakima stations. At a weather station at White Swan, 16 miles 

southwest of the Yakima Airport and at about the same elevation, 

only temperature and precipitation data are recorded. These data 

compare very closely with similar data for Yakima. Evaporation 

data, which are not available for the Yakima station, have been 

obtained from a station near Prosser. The Prosser station is about 

45 miles southeast of Yakima, in an area climatologically similar to 

the lower Ahtanum Valle}7 .

Figure 3 shows the mean monthly precipitation at three stations, 

Rimrock, White Swan, and Yakima, all in or near the Ahtanum Valley. 

The records indicate that more than half the precipitation in the 

Yakima region occurs during the 4 months from November through 

February. December is the wettest month of the year and July is 

the driest. There is a tendency (at 2 of the 3 stations) for June to 

be wetter than either April or May, largely because of occasional 

thunderstorms.

Figure 3 also indicates a general relationship between precipitation 

and altitude. For example, at the Yakima station, 1,061 feet above 

sea level, the mean annual precipitation is 7.21 inches, whereas at 

Rimrock, 2,730 feet above sea level, the mean is 26.2 inches. Although 

no climatological data are available for the upper valley, this relationRimrock 

Mean annua 

Altitude, 2

26 2 inches/ 

730feet z-^.

V

White Swan 

Mean annual 7.60 in 

Altitude, I 061 feet 

I

Yakima

Meon annual 7.21 inches

Altitude, I 061 feet

May June July Aug. Sept. Oct Nav Dec.

FIGURE 3. Mean monthly precipitation at three stations in and near the Ahtanum Valley. (From U.S.

Weather Bureau records.)
10 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

ship suggests that at Tampico, at about 2,120 feet, a mean of about 

15-18 inches might be expected.

The annual precipitation at the Yakima station from 1910, the 

first year of record, to 1956 is shown in figure 4. As the figure shows,

15

Ld -

I

o H 

z ~ 10

o -

< ~~

E ~~

UJ 5

a: -J

Q.

Average, 1910-56, 7.25 inches

FIGURE 4. Graph showing annual precipitation at Yakima during the period 1910-56. (Data from U.S.

Weather Bureau records.)

there has been considerable variation in annual precipitation during 

the 47-year period. The least amount, 3.90 inches, fell in 1930; 

the greatest amount, 11.87 inches, in 1948. However, the annual 

precipitation was less than 6 inches in only 12 of the years of record 

(about 1 year in 4), and exceeded 9 inches in only 8 years (about 1 

year in 6). The annual precipitation during 1917-36 averaged about 

1 inch less than the long-term mean, a deficiency of about 14 percent 

per year. During 1937-56, the annual precipitation averaged about 

1 inch more than the long-term mean.

Snowfall data from the Yakima station, not presented herein, 

indicate that about one-fifth of the annual precipitation at that 

station falls as snow.

Temperatures in the Ahtanum Valley are relatively mild, but the 

area occasionally has extremely high and low temperatures. Weather 

Bureau records show that, although the average temperature at 

Yakima during the period of record was 50.2° F, a high of 111° F 

(July 1928) and a low of 25° F (February 1950) have been observed. 

July is the warmest month and January is the coolest. The mean
GEOGRAPHY 11

temperatures at the Yakima station for those months are 71.4° F 

and 26.9° F.

The regional movement of air generally is from the west and 

southwest; however, because of the effect of the topography of the 

Ahtanum Valley, the wind comes from the west or northwest during 

most of the year. Winds are mostly light; wind speed at the Yakima 

station averages 5.6 miles per hour.

The average relative humidity is comparatively high in winter, 

moderate to low during most of the year, and very low in summer 

afternoons and evenings. At the Yakima station the monthly relative humidity is highest, 81 percent, in December. It is lowest, 

41 percent, in July.

Evaporation in the Ahtanum Valley is great during the months of 

low humidity. No evaporation data are available for the Yakima 

station, but those for a class A Weather Bureau land pan at a weather 

station near Prosser, in the lower Yakima Valley about 45 miles 

southeast of Yakima, probably are representative of the Ahtanum 

Valley. Average monthly pan evaporation at the station near Prosser 

during the period 1948-56, in inches, is as follows: March, 2.61; 

April, 4.35; May, 5.64; June, 6.58; July, 7.56; August, 6.29; September, 4.29; October, 2.09; and November, 0.75.

The average growing season at the Yakima station is 193 days. 

The average dates of the last killing frost in spring and the first in 

fall are April 13 and October 23, respectively. This growing season 

and its limits probably apply over most of the lower Ahtanum Valley. 

The growing season in the upper valley is shorter, but its length 

probably is closer to the Yakima average than to the 111-day average 

recorded at Rimrock.

VEGETATION

Vegetation in the area reflects the area! range of climatic conditions. 

In the eastern part, the slopes and ridges are generally treeless, and 

in their native condition they are covered with sagebrush and associated desert shrubs and grasses. Trees are more abundant closer 

to the high Cascades, and extensive thick groves of yellow pine, fir, 

cedar, and mountain hemlock grow in the headwaters area. However, except in the extreme western part of the area, conifers are rare. 

One of the most abundant trees in the upper valley is the scrub white 

oak, which grows in dense thickets along stream courses and in ravines 

west of the Narrows.

Cottonwood, willow, and associated water-loving plants (phreatophytes or "well-plants") grow in belts and clumps along streams and 

in marshy parts of the valley floor. These phreatophytes grow only

603275 O £2 2
12 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

in areas where their roots can be sent down to the water table or to 

some other secure, perennial supply of water. The consumptive use 

of ground water by the phreatophytes is an important factor in the 

study of water resources of the Ahtanum Valley and is discussed in 

a subsequent part of this report.

CULTURE AND INDUSTRY

Union Gap is the only incorporated city in the area; in 1950 it 

had a population of about 1,800. The remainder of the population 

is scattered throughout the valley or centered around the three small 

communities of Ahtanum, Tampico, and Wiley. Probably less than 

one-tenth of the valley's population lives south of Ahtanum Creek, 

on the Yakima Indian Reservation.

Although there is some manufacturing in and near Union Gap, 

the principal industries in the valley are agriculture, animal husbandry, and the processing of agricultural products. Fruit of the 

finest quality is grown and processed within the area. Hops are an 

important crop, and much hay is grown throughout the valley. 

Sheep and beef cattle graze in the uplands during the open seasons 

of the year and are wintered in the valley.

Some grain has been grown on the upland by dry-farming methods, 

but most of the crops in the Ahtanum Valley require irrigation during 

at least part of the growing season. In the valley, most of the water 

supply developed as of 1958 is used for these irrigation needs.

HISTORY OF WATER USE

The first known irrigation in the Ahtanum Valley began about 

1864 (Kinnison, 1952, p. 3). At that time, and for many years 

thereafter, the magnitude of irrigation was small and the surfacewater supplies were more than adequate to irrigate the developed lands 

of both the settlers north of Ahtanum Creek and the Yakima Indians 

south of the creek. However, continued development of irrigable 

land, with the accompanying need for more water, subsequently led 

to a series of legal acts aimed at apportioning the water resources of 

the area and regulating their use for irrigation.

The first of these acts was an agreement in 1908 between the Yakima 

Indian Nation and the non-Indian water users, 1 wherein one-quarter 

of the total surface inflow of Ahtanum Creek was allotted to the lands 

of the Yakima Indian Reservation, south of Ahtanum Creek, and 

three-quarters to the lands north of the Creek.

i Agreement of May 9, 1908, between U.S. Indian Bureau and W. W. Clidden et al., representing users 

of water from Ahtanum Creek. Approved June 30, 1908, by Franklin Pierce, First Assistant Secretary of 

the Interior.
GEOGRAPHY 13

By an adjudication decree in 1925,2 the tracts of land north of 

Ahtanum Creek were assigned water rights according to preexisting 

irrigation usage. These water rights are ranked according to classes 

numbered from 1 to 32, the lower numbers representing the more 

generous allotments. According to Wallace Owen, stream patrolman 

for the Ahtanum Valley, the lands having water right numbers 1 to 4 

are usually assured adequate surface water for irrigation, but lands 

having water rights numbered higher than about 8 receive little or no 

surface water for irrigation after the middle of July. No supervised 

apportionment of the surface water is m,ade until the summer flow of 

Ahtanum Creek no longer supplies all the irrigation demands. As 

the flow of the creek diminishes in early summer, surface irrigation 

water for the higher numbered water rights is decreased gradually, 

class by class, until toward the end of the irrigation season only the 

lower numbered classes receive surface water. Those landowners who 

in the past have planted crops requiring more water than they could 

obtain from their surface-water rights have been obliged to obtain the 

extra water by buying or leasing water rights or by developing groundwater supplies. Mr. Owen reported (oral communication, August 

1951) that the water shortage has been considerably relieved by the 

greater development of ground-water supplies in recent years, even 

though more land has been put under irrigation during that time.

In 1945 the State of Washington established a ground-water code 

(Washington State legislature, 1945) requiring permits for the withdrawal of ground water in excess of 5,000 gpd (gallons per day). 

The regulation of ground-water withdrawals is designed to prevent 

the indiscriminate and wasteful development of this valuable resource.

In 1957 the validity of the aforementioned 1908 agreement was 

challenged by the U.S. Bureau of Indian Affairs. In the resulting 

lawsuit 3 the Bureau of Indian Affairs petitioned for a higher proportion of the surface-water inflow than the 25 percent provided for 

in the original agreement. The decision on this lawsuit was pending 

when this report was written. A judgment for the Bureau of Indian 

Affairs would necessitate the development of additional irrigation 

supplies to replace surface water diverted from the non-Indian lands, 

and probably would result in accelerated development of additional 

ground-water supplies in the area.

2 Stateof Washington v. Annie AchepohletaL, CauseNo. 18279, Superior Court of the State of Washington, 

Yakima County.

' United States v. Ahtanum Irrigation District et al., Civl. cause No. 31?, United States Dist. Court, Eastern 

Dist. of Washington, Southern Div.
14 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

GEOLOGY

DESCRIPTION OF THE BOCK UNITS

YAKIMA BASALT

The oldest and most prominent rock unit exposed in the Ahtanum 

Valley is the Yakima basalt. This formation is composed of a sequence 

of basaltic lava flows several thousand feet thick, interbedded with 

a few minor sedimentary strata. It is the basal rock unit, or bedrock, 

of the Yakima region, and in the lower Ahtanum Valley and many 

other places the top of the formation is hundreds of feet below the 

land surface. The basalt is quite resistant to erosion and weathering 

and is a notable cliff-forming rock. Arched strata of basalt form 

the highest ridges of the region, including Ahtanum Ridge, Sedge 

Ridge, and Cowiche Mountain.

The basalt is a dense rock, having a texture so fine that most of the 

individual crystals cannot be seen by the unaided eye. Fresh, 

unweathered surfaces are black or dark gray; weathered surfaces 

range in color from gray to reddish brown. According to Warren 

(1941, p. 802) the basalt consists principally of small crystals of calcic 

labradorite, pyroxene, and olivine in a dense matrix of sodic labradorite, augite, and volcanic glass. Magnetite and apatite are common 

accessory minerals. Calcite, siderite, zeolites, opal, and chalcedony 

are common in veins and vesicles in the basalt.

Individual flow layers in the Yakima basalt range from less than 

20 to more than 200 feet in thickness, and individual flows may differ 

considerably in thickness from place to place. The thicker flows, 

especially in their basal parts, exhibit a characteristic jointing that 

forms well-developed prismatic columns at right angles to the upper 

and lower surfaces of the flow layers. Subsequent jointing has divided 

many of the columns into closely spaced plates or irregular blocks. 

In the upper parts of the thicker flows, and in the thinner flows, the 

jointing may be predominantly irregular or platy. The abundance 

and configuration of jointing vary greatly from flow to flow and may 

even change abruptly in short distances within the same flow. Usually the joints are most abundant at the top of a flow and decrease in 

number toward the base. However, in areas of strong folding, such 

as along the north side of Ahtanum Ridge, there are zones of extreme 

shattering that apparently extend from base to top across the flow 

layers.

The upper parts of many of the lava flows are characterized by 

zones of abundant gas cavities (vesicles) which give the rock a spongy 

appearance. These vesicles were formed by bubbles of gases that 

issued from the molten lava as it solidified. At places the vesicles 

have been partly or completely filled with secondary minerals deposited by water percolating through the rocks. Generally, however,
GEOLOGY 15

except where the vesicular zones have been fractured or deeply 

weathered, the vesicles are separated from each other by the encasing 

solid rock.

Enough time elapsed between extrusion of some lava flows to 

allow considerable weathering, and thin soil zones developed at places 

on top of the basalt and were buried by subsequent flows. One 

buried soil zone more than a foot thick can be seen in a small basalt 

quarry on the north slope of Ahtanum Ridge, due south of Wiley 

(SEtfNEtf sec. 23, T. 12 N., R. 17 E.). Generally, weathering 

did not affect the basalt deeper than a few feet below the upper 

surfaces of the flows. It is the upper parts of certain flows, rendered 

relatively permeable by weathering, jointing, and (in conjunction 

with these processes) vesicularity that constitute the principal waterbearing zones in the basalt sequence.

The base of many flows is a layer of dense black volcanic glass, 

usually less than half an inch thick, which is the result of a quick 

chilling of the first part of the basalt flow as it came in contact with 

the cooler surface below.

The total thickness on the basalt in the Yakima area has not 

been determined, for no wells have penetrated to the rocks beneath. 

However, it is at least 2,000 feet at Union Gap. An oil test well 

(12/19-17C1) was drilled in that gorge to an approximate depth of 

3,800 feet, almost entirely in basalt (table 5). The well was drilled 

through steeply dipping flow layers; consequently, for most of its 

depth the well penetrates the flow layers diagonally, and it may even 

follow the dip of the flows for a considerable distance at depth. However, the total penetration of the well is almost certainly equivalent 

to more than 1,000 feet stratigraphically that is, across the flow 

layers. As there is also about 1,000 feet of basalt exposed in and 

above the gorge, the basalt sequence must be at least 2,000 feet 

thick at Union Gap and probably is much thicker.

In the western part of the Ahtanum Valley, the upper 2 or 3 lava 

flows (total thickness about 250 feet) are separated from the main 

body of the basalt by a discontinuous member or tongue of the 

overlying Ellensburg formation. The upper, separated group of 

flows is similar in appearance, thickness, and stratigraphic position 

to the Wenas basalt member of the Yakima (previously the Wenas 

basalt of formation rank) which is exposed at Selah Gap. Although 

these 2 basalt units may be equivalent, no method of definite correlation has been found because at other places in the region, 1 layer, 

and possibly 2, of sedimentary rocks similar in appearance and 

lithology to the Ellensburg formation are interbedded with lava 

flows in the upper part of the basalt sequence (Mackin, 1947; Waters, 

1955, p. 670-672).
16 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

The name Yakima basalt is applied locally to the thick sequence 

of basaltic lava flows underlying southeastern Washington and extending into Oregon and Idaho; elsewhere this sequence is known 

as the Columbia River basalt. The name was applied by Smith 

(1901) to that part of the Columbia River basalt that poured out 

in the Yakima region during the Miocene epoch. The age assignment was made on the basis of fossil plants in the Manastash formation (Eocene), which underlies the Yakima basalt in the vicinity of 

Cle Elum, Wash., and fossil plants in the overlying Ellensburg formation, which were first assigned an age of late Miocene (Russell, 1893, 

p. 103). Subsequent workers have assigned an age of Miocene or 

early Pliocene, and Pliocene, to the Ellensburg formation.

In 1952 an assemblage of fossil fresh-water mollusks was collected 

from large blocks of loose debris high on the northwest flank of 

Sedge Ridge, in a locality some 4% miles west of Tampico (NE%SW# 

sec. 16, T. 12 N., R. 15 E.). The enclosing material, once an alluvial 

sand, has been altered to a tan or rusty-brown highly resistant richly 

fossiliferous quartzite. It can be traced for about half a mile in a 

band roughly parallel to the strike of the basalt flows of Sedge Ridge. 

Although the contact of the fossiliferous material with the basalt 

was not seen, apparently being covered by slope wash, the material 

almost certainly is a minor interflow deposit near the top of the 

sequence of basalt flows. Mr. T. C. Yen of the U.S. Geological 

Survey has identified the fossils (Sphaerium, sp. undet.; Viviparus 

cf. V. leiostracta Brusinia; Fluminicola cf. F. williamsi (Hannibal); 

Goniobasis cf. G. kettlemanensis), and he listed their age as probably 

Pliocene. This new evidence indicates that at least the latest flows 

of the Yakima basalt may have poured out during the Pliocene 

epoch.

ELLENSBURG FORMATION

The Yakima basalt is overlain by the Ellensburg formation, which 

consists of several hundred feet of semiconsolidated clay, silt, sand, 

and gravel. In the Ahtanum Valley, rocks of the Ellensburg formation underlie the gravels of the upland benches in the vicinity 

of the Narrows and crop out in bands along the slopes of Ahtanum 

Ridge and Sedge Ridge. In general, the formation is easily eroded, 

and over much of the uplands it has been entirely stripped away 

from the underlying basalt.

A somewhat unusual topography has been developed on the south 

side of the lower valley by differential erosion of the sedimentary 

rocks. Headward erosion by northward-flowing intermittent streams 

has formed a number of steep, narrow canyons in the north flank 

of the anticlinal Ahtanum Ridge, creating well-defined spur ridges 

that extend northward from the main ridge. The bases of these
GEOLOGY 17

spur ridges are formed in the resistant basalt of Ahtanum Ridge, 

the central parts in steeply dipping beds of the Ellensburg formation, 

and the noses in moderately resistant cemented gravel. As a result 

of differential erosion, most of the spur ridges terminate in knobs 

consisting of this resistant cemented gravel. Saddles occur where 

the less resistant Ellensburg formation appears at the land surface 

for example, between the knobs and the basalt of Ahtanum Ridge.

In appearance and lithology, the Ellensburg formation in the 

Ahtanum Valley is identical to exposures of the formation in other 

parts of the Yakima region. It consists of 85 to 95 percent semiconsolidated clay, silt, and sand and only 5 to 15 percent gravel 

and conglomerate. The color is predominantly gray, tan, and buff, 

although there are a few relatively thin rusty-brown sand and gravel 

strata. The clay and silt parts are massive at most places, but 

excellent bedding and shaly parting also are found. Some sand 

and gravel strata are crossbedded. The thickness of the individual 

beds ranges from a few feet to more than 100 feet; strata of clay, 

silt, and fine sand usually are somewhat thicker than strata of the 

coarser materials.

The Ellensburg formation is mostly indurated and tough, but some 

sand and gravel strata are weakly cemented and appear moderately 

permeable. Cementing material is mostly argillaceous.

The silt and sand are composed chiefly of pumice, volcanic ash, 

quartz, and scattered feldspar and hornblende particles, Clay-size 

particles consist mostly of finely divided pumice and ash. The gravel 

of the Ellensburg formation contains large amounts of tuff and a distinctive purple or gray tuffaceous hornblende andesite. Minor 

amounts of diorite, quartzite, and various granitic and metamorphic 

rock types also are found locally in the gravel; basaltic fragments are 

rare.

In the area mapped, most of the gravel of the Ellensburg formation 

is found in the lower valley and is best exposed along the north side 

of Ahtanum Ridge 2 to 3 miles west of Union Gap. In that locality, 

the gravel includes a wide variety of rock types.

Beneath the upper valley and in the adjacent slopes, a discontinuous layer of the Ellensburg is interbedded with lava flows 250 to 300 

feet below the present upper surface of the basalt. This sedimentary 

bed crops out in a discontinuous band on the lower slopes of Sedge 

Ridge and along the north flank of Ahtanum Ridge. The same stratum has been reported in the logs of four wells in the Narrows and the 

upper valley. It is 20 to 30 feet thick in surface exposures and is 

reported to be 77 feet thick at well 12/16-15F1, about. 2% miles east of 

Tampico. The bed could not be found on the north side of the valley,
18 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

and apparently it has been hidden by an overlying body of cemented 

gravel (pi. 1).

The sedimentary bed apparently pinches out a short distance east of 

the Narrows, for it could not be traced farther east by surface mapping 

and has not been reported in the logs of wells east of the Narrows. 

However, probably only a few of the deeper wells in the lower valley 

have been drilled deep enough into the basalt to have reached the 

horizon of the bed.

To show the interbedded Ellensburg material on the geologic map 

(pi. 1), its thickness has been exaggerated somewhat. Its true thickness is shown in the geologic sections.

A section of about 900 feet of the Ellensburg formation is exposed 

in sec. 11, T. 12 N., R. 18 E., and well logs indicate that this unit is 

almost certainly more than 1,000 feet thick beneath the east end of 

the lower valley floor. At least the lower part of the main body of the 

Ellensburg formation apparently is conformable with the underlying 

Yakima basalt. The contact between the Ellensburg formation and 

the overlying cemented gravel generally is sharp where it is exposed 

along the north flank of Ahtanum Ridge, where at several places an angular unconformity exists between the two units. However, logs of 

wells in the lower valley indicate considerable gradation and interbedding of the upper part of the Ellensburg formation and the lower 

part of the overlying cemented gravel in the center of the subbasin.

Most of the material constituting the Ellensburg formation obviously was derived from a region of intense volcanic activity. Its composition shows that the volcanism that produced it was violently 

eruptive, as opposed to the slow, quieter extrusions of the Yakima 

basalt. The source area for the Ellensburg apparently was west of 

the Yakima region, in the area occupied by the present Cascade 

Mountains.

Most of the material making up the Ellensburg formation was deposited by streams or in lakes and ponds. However, scattered thin 

beds of volcanic ash or shards of volcanic glass indicate that at least 

small amounts fell directly from the sky.

The first determination of the age of the Ellensburg formation was 

made by F. H. Knowlton (Russell, 1893, p. 103) on the basis of fossil 

plants, which were classified as belonging to the upper part of the 

Miocene series. Smith (1903) cited an unpublished report by Knowlton confirming this age determination. Subsequently the Ellensburg 

formation has been assigned ages of Miocene or early Pliocene (Merriam and Buwalda, 1917, p. 255-256; Beck, 1940).

In 1936, during construction of a tunnel through Yakima Ridge 

about 6K miles north of the city of Union Gap, fossil bones were found 

in sedimentary rocks mapped by Smith (1903) as the Ellensburg
GEOLOGY 19

formation (NEtfNWtf sec. 5, T. 13 N., R. 19 E.). Elephant remains 

were found 8 to 10 feet stratigraphically above the top of the Wenas 

basalt member, and camel bones were collected from a clay layer about 

15 feet below the base of the Wenas member. These fossils subsequently were borrowed from the collection of the State College of 

Washington and were identified by Miss Jean Hough. In her report 

on the fossils, Miss Hough states her belief that the possible age of 

these vertebrate fossils (Mammut (Miomastodon) merriami Osborn, 

and a large camelid, Pliauchenia merriami Frick?) is not younger than 

late Pliocene and not older than middle Miocene; the balance of evidence being in favor of an early Pliocene age. This age assignment, 

along with the age determination for the fossils from Sedge Ridge, 

strongly indicates that the main body of the Ellensburg formation 

probably was deposited entirely during the Pliocene epoch, and that 

the Wenas basalt member, and perhaps the uppermost flows of the 

main body of the Yakima basalt, probably are of early Pliocene age.

CEMENTED BASALT GRAVEL,

An extensive body of cemented basalt gravel overlies the older 

rocks along both sides and throughout the entire length of the Ahtanum Valley. The cemented gravel is moderately resistant to erosion, and it caps, or forms entirely, the upland-bench deposits in the 

west half of the Ahtanum-Moxee subbasin. It may be wholly or 

partly contemporaneous with similar gravel bodies in other parts of 

the Yakima basin. A typical exposure of the cemented gravel may 

be seen in a small gravel pit at the north base of Ahtanum Ridge, in 

the SWtfNWtf sec. 11, T. 12 N., R. 18 E. Smith (1903) mapped the 

gravel in the Ellensburg formation and did not describe it in detail. 

On the basis of lithology, structure, and hydrologic properties, however, the cemented gravel should be treated as a separate rock unit.

The gravel unit consists of 75 percent or more cemented basaltic 

gravel and 25 percent or less sand, silt, and clay in lenses and discontinuous layers. The color ranges from buff and gray to reddish brown 

and black. The gravel strata usually are massive but may exhibit 

fair to indistinct bedding. Crossbedding is rare in the gravel but is 

not uncommon in layers of sand. Pebbles and larger particles generally constitute about 75 percent of the gravel strata, boulders make 

up only a few percent and the matrix of sand and finer material 

generally is less than 25 percent. Most of the cobbles and pebbles 

are moderately well or well rounded; the finer material commonly is 

more angular.

The cemented gravel differs greatly in lithology from gravel typical 

of the Ellensburg formation, which Smith (1903, p. 3) correctly 

described as containing very little basalt. Most of the pebbles and
20 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

larger particles in the cemented gravel consist of basalt which is 

identical in texture and composition to the Yakima basalt. Tuff and 

hornblende andesite are predominant accessory rock types in some 

parts of the report area; diorite, quartzite, and many granitic and 

metamorphic varieties are less common. The relative amount of each 

rock type varies considerably. For example, at the gravel pit described above, basalt constitutes only about half the pebbles and 

larger particles, whereas in the west half of the valley, and particularly 

on the pediment slopes, all or nearly all the large particles are basalt.

The matrix in the gravel is a heterogeneous mixture of sand, silt, 

and clay similar in composition to the gravel-free interbedded layers. 

Finely pulverized pumice, quartz, volcanic glass, augite, and clay 

minerals predominate. Cementing material commonly is argillaceous 

or ferruginous, or a combination of both. The gravel generally is well 

cemented and, at places, constitutes a true conglomerate. At most 

places the interbedded clay lenses are well indurated and tough, but 

the sandy layers are weakly cemented and friable. Some of these 

sandy layers appear to be moderately permeable and may typify the 

water-bearing zones in the cemented-gravel unit.

In some localities the basaltic cobbles and boulders have undergone 

considerable weathering in place. Weathering of a fragment of basalt 

rock typically forms concentric shells of decayed rock that separate 

from the core, giving an onionlike appearance. Evidently the weathered material has been incorporated to some extent in the matrix, so 

that it is difficult to determine what the size and degree of angularity 

of the gravel fragments were at the time of their deposition.

Exposures of the cemented gravel, and records of wells that have 

penetrated it, indicate that this unit is almost certainly more than 

400 feet thick at some places. Few sand and clay layers within the 

gravel are thicker than about 10 feet. Cemented gravel rests on each 

of the older rock units in, various parts of the area, and many exposures 

show some evidence of unconformity (either angular or erosional). 

Where bedding is evident, that in the upper part of the gravel unit 

appears to be horizontal, or nearly so. However, in the vicinity of 

the type locality described above, the basal part of the unit was somewhat tilted, apparently at the time of the deformation of the underlying Ellensburg formation. Also in the type area, minor thrust 

faults can be found in the cemented-gravel unit. Thus, at some places 

part of the basalt gravel apparently was deposited before or during 

the last deformation. Conversely, the obvious unconformity with 

Tertiary rocks in other parts of the valley, and the nearly horizontal 

attitude of the upper, younger layers of the gravel unit, indicate that 

the upper part of this rock body was deposited since the last period 

of deformation.
GEOLOGY 21

The cemented basalt gravel has the physical characteristics of 

fanglomerate, flood gravel, or glacial outwash, indicating that the 

agent of deposition was abundant fast-moving water. Much of this 

material obviously was deposited in the form of alluvial fans along the 

flanks of upfolds and was derived from the upfolds themselves. The 

terrace remnants along the upper valley and the north side of the 

lower valley indicate that the gravel unit formerly was much more 

extensive than it is at present. Because the gravel probably was 

deposited during the Pleistocene or glacial epoch, outwash from 

alpine glaciation may have contributed to it. The foreign rock types, 

such as quartzite and metamorphic and granitic rocks, that are 

present in the gravel may indicate deposition from melt water; however, they may have been derived by reworking of the Ellensburg 

formation in which these same rock types occur locally.

Smith (1903, p. 4) mapped a large deposit of cemented gravel in 

the small valley of Cowiche Creek, approximately 8 miles north of 

the Ahtanum Valley, and gave it the name Cowiche gravel. Smith 

did not describe the gravel in detail, but he attributed its deposition 

to the damming of Cowiche Creek by flows of the Tieton andesite in 

the Pleistocene epoch. Recent geologic reconnaissance and study of 

logs of wells in that area indicate that gravel apparently identical 

with some of that mapped as the Cowiche gravel is beneath, and 

interbedded with, the andesite flows. Therefore, the deposition of 

the Cowiche gravel was, at least in part, independent of any damming 

by the andesite flows.

In appearance, lithology, and stratigraphic relations with the older 

rocks, the Cowiche gravel of Smith is almost identical with some of 

the cemented gravel in the Ahtanum Valley. Also, the cementedgravel unit in the Ahtanum Valley has been traced northward to within 

3% miles of the Cowiche gravel in an area where the 2 units are separated by the Cowiche Mountain anticline. For these reasons, it is 

concluded that the cemented basalt gravel in the area mapped was 

deposited during virtually the same time, and under the same general 

conditions, as was the Cowiche gravel of Smith and the other gravel 

bodies associated with the Tieton andesite. The interbedded relationship of the gravel and the Tieton andesite (of Pleistocene age) indicates that at least a large part of the deposition took place during the 

Pleistocene epoch.

ROCK MATERIALS OF RECENT AOE

The Ahtanum Valley is floored by a relatively thin mantle of unconsolidated and semiconsolidated stream deposits of Recent age. In the 

upper valley and through the Narrows, this alluvial material consists 

of unsorted to sorted gravel, sand, and silt. Downstream, the allu-
22 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

vium generally is slightly finer and better sorted, and in many places it 

includes discontinuous, semiconsolidated strata of silt and clay, which 

locally are called hardpan. However, even in the lower end of the 

valley near Union Gap, the alluvium contains a considerable proportion of cobbles. The thickness of the alluvium, as determined from 

well logs, ranges from a few feet to about 30 feet.

The material in the alluvial fans on both sides of the valley is generally coarser and less well sorted than that of the flood-plain alluvium. 

Most unconsolidated gravel throughout the Ahtanum Valley is composed of basalt particles; however, the gravel in the alluvial fans was 

derived from the Ellensburg formation or from the less basaltic parts 

of the cemented-gravel unit.

Over much of the upland benches, patches and mounds of windblown silt, or loess, a few feet thick overlie the resistant cemented gravel or the basalt. The patchy cover evidently is a remnant of a mantle 

of loess which covered the Yakima area at one time and which is similar to, and may be correlative with, the Palouse formation of eastern 

Washington. Some of the patches are large enough to be cultivated; 

the mounds generally are 10 to 30 feet long and a few feet high and are 

protected from erosion by grass and shrubs.

The unconsolidated alluvium in the valley floor and in alluvial fans 

is shown without pattern on plate 1. The loess is neither widespread 

nor thick enough to map separately from the underlying units.

STRUCTURE

The Tertiary rocks of the Yakima region have been deformed into a 

series of prominent east- and southeast-trending folds, which closely 

control the main topographic features. The upfolds, or anticlines, 

form the ridges; the downfolds, or synclines, make troughlike basins. 

The Ahtanum Valley occupies part of one such synclinal trough (the 

Ahtanum-Moxee subbasin) and is bordered on the south and west, respectively, by the Ahtanum Ridge and Sedge Ridge-Cowiche Mountain anticlines.

In the area of this investigation, the Ahtanum-Moxee syncline 

slopes, or plunges, east (pi. 1, section A-A'}. The axis of the syncline 

is located definitely only where the depth and configuration of the 

upper basalt flows can be determined from geologic mapping and reliable well logs. Information available at present indicates that smaller 

flexures are superimposed along and across the main folds, but the deep 

burial of the basalt and the scarcity of reliable deep-well logs precludes 

the early delineation of this structural detail.

Ahtanum Ridge, the anticlinal ridge south of the valley, is a tight 

asymmetrical fold the inclination, or dip, being steeper on the north 

side of the ridge. This asymmetry is readily seen at Union Gap, where
GEOLOGY 23

the arched basalt strata that form the ridge are well exposed. The 

flow layers at the north end of the gorge are vertical, but within half a 

mile to the south across the fold, the attitude changes to a moderate 

southerly dip.

From the east end of the Narrows to within 2 miles of Union Gap, 

the north side of Ahtanum Ridge is flanked by the upturned edges of 

Ellensburg strata. As a rule, the Yakima basalt and the Ellensburg 

formation on this flank of the ridge dip moderately or steeply north, 

toward the center of the valley. However, in the southern parts of 

sees. 9-12, T. 12 N., R. 18 E., sandstone and conglomerate strata of the 

Ellensburg formation have been overturned slightly past the vertical 

by strong thrusting from the south, and dip steeply south.

The intensity and complexity of the deformation in this part of the 

valley may be judged from the abrupt changes in the attitudes of the 

rocks. For example, in the SEtfSWtf sec. 11, T. 12 N., R. 18 E., Ellensburg strata dip southward at a high angle; about 500 yards to the 

west,rocks of the same formation dip about 46° N.; half a mile farther 

west-northwest and north, in the SE#NE# sec. 10, the strata dip about 

20° S.

The complexity of the structure at this locality probably is due to 

either a slumping or a wrinkling of a large block of the sedimentary 

rocks during the major diastrophism that produced the Ahtanum 

Ridge anticline, although minor faulting also may have occurred here.

No evidence of major displacement by faulting was found in the 

area, although some minor displacement, which may have been caused 

by several small thrust faults, is present in the cemented-gravel unit in 

the structurally complex locality just described. The tight folding 

exposed at Union Gap shows that the basalt was strongly deformed by 

folding alone.

The Narrows, in sees. 13-15, T. 12 N., R. 16 E., is the result of a 

gentle cross flexure in the Ahtanum-Moxee subbasin. The lava flows 

in the bottom of that syncline were warped upward and were later cut 

through by stream erosion to produce this narrow, steep-walled part 

of the Ahtanum Valley. The Narrows has an important influence on 

the movement of ground water in the area, as the cross flexure partially 

separates the upper Ahtanum Valley from the rest of the AhtanumMoxee subbasin to the east (pi. 1, section A-A], and retards groundwater flow from the upper valley. At the upstream end of the Narrows the nearly horizontal basalt strata emerge from beneath the 

alluvial materials and gradually pass into steep bluffs and vertical 

cliffs, as the valley floor slopes more steeply to the east than does the 

basalt. The flow layers are quite distinct at numerous places, and 

examples of typical columnar jointing may be seen along the highwa}-. 

The attitude of the basalt throughout most of the Narrows is so nearly
24 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

horizontal that no dip is discernible, but in sec. 13 a slight eastward 

plunge becomes apparent. Farther east the plunge gradually increases to about 2.5°, or 225 feet per mile, between the downstream 

end of the Narrows and Wiley. The steepness of the plunge probably 

diminishes somewhat between Wiley and Union Gap, as shown in 

section A-A' (pi. 1), but the top of the basalt probably is at least 1,500 

feet below the land surface, or some 500 feet below sea level, at the 

Yakima River. Well 13/18-29Q1, just north of the lower valley 

(pi. 1), was reported to have penetrated basalt at about 60 feet below 

sea level (table 4).

GEOLOGIC HISTORY

At the end of the Miocene epoch, the area that is now the Ahtanuin 

Valley was part of a vast, monotonous plain of basaltic lava that covered most of eastern Washington and extended eastward into Idaho 

and southward into Oregon. The basaltic lava flows were extruded 

from fissures which probably were centered somewhere southeast of 

the Yakima region. At the west side of the lava plain, approximately 

where the present Cascade Mountains now stand, there was a region 

of more intense volcanic activity at an elevation somewhat higher than 

the lava plain but probably lower than the present Cascades. Those 

ancestral Cascade Mountains were the source for the sedimentary 

materials, constituting the Ellensburg formation, that were transported by eastward-flowing streams and deposited along the west side 

of the lava plain.

The outpourings of basaltic lava probably continued intermittently 

into the Pliocene epoch, covering the discontinuous sedimentary deposits, changing stream courses, and forming new basins of deposition. 

Before the period of lava extrusion ended, there was increased uplift 

and volcanic activity in the ancestral Cascades, furnishing more volcanic debris and resulting in thicker deposits of sedimentary material 

which became interbedded with the upper basalt flows. After the 

flows ceased, and as the Cascades continued to rise, the main body of 

the Ellensburg formation was deposited. Most of the Ellensburg was 

deposited from streams or in lakes, but some ash and pumice fell 

directly from the sky.

The deformation that produced the sharp folds in the older rocks of 

the Yakima region probably began during Pliocene time, while the 

Ellensburg sedimentary material was still accumulating. This deformation undoubtedly was related to the Cascade uplift, but in part it 

may have beon due also to subsidence of the center of the lava body, 

somewhere to the southeast. The folding proceeded slowly so that 

the Yakima River was able to maintain its course at Union Gap by 

eroding its channel as the Ahtanum Ridge anticline rose. The Yakima
WATER RESOURCES 25

River was never dammed to a very great depth by the uplift of Ahtanum Ridge; if it had been deeply ponded, the water would have spilled 

over and established a new course through Donald Pass (fig.l), a 

structural gap about 5 miles east of Union Gap and some 400 feet lower 

than the present crest of Ahtanum Ridge near Union Gap.

As the folding continued, the sedimentary material previously deposited on the parts of the plain that became the anticlinal ridges was 

eroded off and carried down into the centers of the synclinal basins. 

This process accounts in part for the great thickness of the Ellensburg 

formation (1,000-1,500 feet) in the center of the Ahtanum-Moxee subbasin. It is very unlikely that such a tremendous thickness of sedimentary material was continuous throughout the Yakima basin.

After the easily eroded Ellensburg material had been removed from 

the ridges, the underlying lava rock was exposed to erosion, and 

basaltic debris was carried down the flanks of the ridges and out to the 

centers of the valleys, forming a part of the cemented-gravel unit. 

The lower part of the cemented gravel along the ridges has been considerably tilted, indicating that deposition of the gravel began before 

the folding ended. However, probably most of the cemented gravel 

was deposited after the folding and uplift of the anticlinal ridges had 

ceased.

Deformation of the rocks in the Yakima area had ceased by the last 

of the Pliocene or the beginning of the Pleistocene, or glacial, epoch. 

Since then, the major topographic features in the Ahtanum Valley 

probably have not changed. Gravel continued to accumulate during 

Pleistocene time, and, as evidenced by the terrace remnants on either 

side, the valley probably was once filled with a nearly continuous sheet 

of gravel to a level as much as 200 feet above the present valley floor. 

Much of the gravel undoubtedly was deposited as fans, but melt water 

and outwash sediments fiom alpine glaciers in the Cascade Mountains 

may have contributed to the forming of the gravel sheet.

A change in physical conditions, probably related to the recession of 

Pleistocene glaciers, resulted in active erosion of the extensive gravel 

deposit into the form of the present valley floor. Sometime before or 

during this period of downcutting, the uplands in the Ahtanum-Moxee 

subbasin were covered by a nearly continuous mantle of windblown 

silt, or loess, of which there are only remnants today.

WATER RESOURCES

Of the precipitation that falls within the drainage basin of Ahtaiium 

Creek, part evaporates directly or is transpired by vegetation, part 

begins its return to the Pacific Ocean as direct runoff, and the remainder infiltrates into the soil and rocks to the zone of saturation, the 

surface of which is called the water table. This ground water moves
26 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

slowly toward the streams and either is discharged into them, forming 

most of their dry weather (base) flow, or is evaporated and transpired 

as it approaches the land surface.

Ground water in the unconsolidated alluvium in the area is freely 

interconnected with the streams. Water may alternately rise to or 

sink below the land surface several times during its course eastward 

through the valley. During most of the year, the flows of the streams 

are maintained largely by ground-water discharge; conversely, much 

of the recharge to both the shallow and the deep ground-water bodies 

occurs by direct infiltration from stream channels and by infiltration 

of irrigation water derived from streams. Therefore, any quantitative study of the ground-water resources of the area necessarily must 

include an appraisal of the surface-water supplies.

SURFACE WATER

The surface runoff in the Ahtanum Valley varies widely from year 

to year and from season to season. The amount of annual runoff is 

determined mainly by the total yearly precipitation in the drainage 

basin, but other influencing factors are the type and seasonal distribution of precipitation, air temperature, soil conditions, and evaporation. Seasonal distribution of the runoff is determined mostly by 

the amount and melting rate of snow in the headwaters area. About 

one-fifth of the total precipitation falls as snow; consequently, years 

of high total precipitation usually are years of above-normal snowfall.

The runoff is greatest during years in which the snowfall is excessive, 

especially if the melting of accumulated snow is rapid. Conversely, 

the runoff is least during years of scanty snowfall, especially if the 

melting is slow. During years of rapid melting and quick runoff, 

the loss of water through evaporation is considerably less than in 

years of slow melting of the snow and correspondingly slow runoff.

The Geological Survey maintains two stream-gaging stations in 

the area studied. One is on the North Fork and the other is on the 

South Fork of Ahtanum Creek above all major diversions. Three 

other Geological Survey gaging stations have been discontinued at 

the Narrows, at the mouth of Ahtanum Creek near Union Gap, and 

on the South Fork near Tampico. (See pi. 1 for location of gaging 

stations.) Complete streamflow records from these stations have 

been published by the U.S. Geological Survey.4

The U.S. Bureau of Reclamation formerly maintained a gaging 

station on Wide Hollow Creek near its mouth (pi. 1). The records 

from that station have not been published, but they are available for 

inspection at the office of the Bureau of Reclamation in Yakima.

« U.S. Geol. Survey Water-Supply Papers 252, 272, 292, 492, 812, 832, 862, 870, 882, 902, 932, 962, 982, 1012, 

1042, 1062, 1092, 1122, 1152, 1182, 1216, 1246, 1286, 1346, 1396, 1446, 1516.
WATER RESOURCES 27 

SURFACE-WATER INFLOW

More than half the water that supplies the area of the investigation 

enters as streamflow in the North and South Forks of Ahtanum 

Creek. The remainder consists of precipitation falling within the 

area, irrigation water supplied from outside the area, streamflow 

entering the lower valley in the channel of Wide Hollow Creek, and 

probably ground-water inflow from Wide Hollow.

The streamflow entering the valley in the North and South Forks 

of Ahtanum Creek may be at a maximum during any of the months 

from March through June. The runoff in both streams during those 

4 months usually constitutes about two-thirds of the year's total. 

Flows are at a minimum in the fall and winter; yearly minimums 

have been recorded at least once in each of the months from August 

through February. The following table shows that the average 

annual inflow (North Fork plus South Fork Ahtanum Creek) to the 

upper Ahtanum Valley during the periods 1909-14 and 1931-55 was 

about 62,000 acre-feet. It shows also that May was the month of 

greatest average runoff, and September was the month of minimum 

average flow.

January_______ 2,920

February._______ 2, 840

March..._______ 4,930

April_____._____ 9,520

May____________ 15,000

June. ___________ 12,000

July____________ 4,340

August________ 2,010

September. ______ 1, 530

October________. 1,630

November_____ 2, 170

December. ______ 3, 210

Avg annuaL62, 100

A considerable amount of surface water passes through the northeast corner of the lower valley in the channel of Wide Hollow Creek, 

which discharges into the Yakima River about half a mile upstream 

from the mouth of Ahtanum Creek. Wide Hollow Creek is a perennial 

stream that is fed principally by runoff, unused canal water, and 

return flow from irrigation in the area north of the lower valley. The 

flow of Wide Hollow Creek undoubtedly is related to ground water in 

much the same manner as are the flows of other streams of the area, 

in that it supplies some recharge to the shallow ground-water bodies 

during flood stages and in turn is supplied by ground water during 

low stages. However, the role of the creek in the hydrologic regimen 

of the area is not clearly known because of a lack of concurrent streamflow records and water-level data covering a period great enough for 

dependable analysis.

The only continuous record of the flow of Wide Hollow Creek was 

obtained from a gaging station near the mouth of the creek and, therefore, does not indicate the amount of surface water entering the lower 

Ahtanum Valley, but only the outflow from the stream.

Some additional surface water enters the area from the Tieton

603275 O 62 3
28 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

canal, which brings in almost the entire water supply for the terrace 

known as Wiley Heights, north of the lower Ahtanum Valley. Of 

this, perhaps as much as 1,000 acre-feet per year eventually reaches 

the Ahtanum Creek drainage system or recharges the water-bearing 

formations, within the Ahtanum Valley.

Near the east end of the Narrows, the flow of Ahtanum Creek splits 

into three principal channels which rejoin downstream before Ahtanum Creek empties into the Yakima River. The surface water is 

further distributed throughout the valley by a complex system of 

irrigation distributaries. Thus, the surface runoff, and particularly 

the flood-stage runoff, of Ahtanum Creek is spread widely over the 

floor and on the lower slopes of the valley.

Of the total surface-water inflow, part is used beneficially by crops, 

part recharges the ground-water reservoir, part evaporates directly 

from streams and irrigation canals, and part is evaporated and transpired by stream-bank vegetation and other water-loving plants; the 

remainder leaves the valley by surface runoff and underflow to the 

Yakima River.

SURFACE-WATER OUTFLOW

Records of surface-water outflow from the Ahtanum Valley include 

those for Ahtanum Creek near Union Gap and for Wide Hollow Creek 

near its mouth. The records on Ahtanum Creek were collected by the 

Geological Survey during three short periods March-October 1910, 

April 1911-September 1914, and June 1951-March 1953. Records 

of the flow of Wide Hollow Creek were collected by the Bureau of 

Reclamation during the periods April 1911-March 1915 and May 

1922-February 1933.

Records of the outflow of Ahtanum Creek at its mouth (near Union 

Gap) and the inflow to the west end of the valley, in the North and 

South Forks of Ahtanum Creek, are shown together for corresponding 

months of record in table 1. A comparison of the figures in this table 

shows that, during the period of record, Ahtanum Creek lost about 22 

percent of its annual inflow in its course through the area. However, 

downstream loss occurred mainly during the months April through 

November, and a slight to moderate downstream gain occurred during 

the months December through March.

The period of downstream loss coincides approximately with the 

growing season. During this period, large amounts of water are 

diverted from Ahtanum Creek. More water is lost by evapotranspiration and by ground-water outflow from the east part of the valley 

than is gained by the Ahtanum Creek system from irrigation return 

flow, from ground-water discharge, or from other sources such as 

runoff. Seasonal differences in the inflow-outflow relationship are 

due to variations in the relative magnitudes of these losses and gains.
WATER RESOURCES 29

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30 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

Downstream gain occurs during the period of high precipitation and 

low evaporation, and it probably represents chiefly runoff from precipitation within the valley.

The data in table 1 indicate that, for a given inflow into the valley, 

the surface outflow during the months of August, September, October, 

and November in recent years has been appreciably higher than it 

was during the earlier years of record. For example, the inflow dur ng 

September 1951 was about the same as it had been during September 

1910; however, the outflow during September 1951 was 1,640 acre-feet, 

or about 3% times the 476 acre-feet recorded for the same month in 

1910. The same general relationship is shown for each of the autumn 

months during the two periods of measurement. The periods of 

record are too short to allow any definite conclusion regarding the 

validity of this indicated increase in autumn outflow. If the increase 

is truly representative, it could be due to one or more changes in conditions affecting the seasonal gain or distribution of the water supplies 

in the valley, such as (1) increased utilization of Ahtanum Creek water 

for irrigation, resulting in a delay in the down-valley transit of some 

of the water and a correspondingly greater return flow to the stream 

during autumn; (2) an increase in unmeasured surface inflow to the 

area, such as water reaching the area via the Tieton canal; and (3) an 

increase in the amount of irrigation water, pumped from the deep 

ground-water bodies, that ultimately reaches the channel of Ahtanum 

Creek during and after the irrigation season.

The outflow in Wide Hollow Creek was measured by the U.S. 

Bureau of Reclamation during the periods 1911-15 and 1922-33 at a 

gaging station near the mouth of the creek. Unpublished records 

from that station show that the average annual runoff was about 

20,000 acre-feet and that the seasonal variation in flow was much less 

than that in Ahtanum Creek.

Because Wide Hollow Creek was gaged only near its mouth, it is 

not possible to determine the amount of gain or loss in the flow of the 

stream as it passes through the area. However, the relatively small 

range between maximum and minimum flow suggests that the stream 

receives substantial amounts of ground-water effluent throughout 

most of the year.

UTILIZATION OF SURFACE WATER

The most important use of surface water in the Ahtanum Valley 

is for irrigation. Water from Ahtanum Creek is used and reused for 

irrigation a number of times between the creek's entrance into the 

valley above Tampico and its confluence with the Yakima River at 

Union Gap. The lower valley in particular is served by a maze of 

interlacing irrigation canals and stream channels, so complex that
WATER RESOURCES 31

tabulation of the flow in individual channels is impractical for this 

report.

Perhaps 17,000 acres of arable land in the area could be irrigated 

with water from Ahtanum Creek if the supply were sufficient throughout the irrigation season. However, because the available surfacewater supplies are not adequate during late summer, much of the land 

in the valley is not cultivated, is irrigated only during the first 2 or 3 

months of the irrigation season (when the creeks are at high stage), or 

is irrigated partly or completely with ground water. Although no 

quantitative records of surface-water use are available, it is estimated 

that the water of Ahtanum Creek constitutes the entire irrigation 

supply for about 10,000 acres. Kinnison (1952, p. 31) reported, 

however, that only 2,600 acres is irrigated under water rights of a 

priority high enough to assure a supply of surface water throughout 

the irrigation season of an average year.

The above estimates do not include an unknown amount of land 

that is irrigated partly with surface water and partly with ground 

water, nor do they include an undetermined acreage that is irrigated 

with water brought into the area by the Tieton canal.

GROUND WATER

That portion of subsurface water that fills voids or interstices in the 

rocks under hydrostatic pressure is ground water. The water above 

the zone of saturation is under less than atmospheric pressure, whether 

or not it completely fills the interstices in which it occurs, and is not 

considered to be ground water. This water is called vadose, and the 

zone in which it occurs is called the zone of aeration.

AQUIFER PROPERTIES

Because ground water occurs in the interstices in the rock materials that is, in the spaces not occupied by solid material the 

ability of a soil or rock to transmit water is determined by the abundance, character, and degree of interconnection of the interstices. A 

rock material that is capable of transmitting and yielding appreciable 

quantities of water to a well is called an aquifer.

The interstices in the rock materials of the Ahtanum Valley vary 

widely in size, shape, and arrangement. They range in size from the 

minute pore spaces in clay of the Ellensburg formation to the larger 

openings between coarse gravel particles and crevices in the basalt. 

Likewise, the shapes of the interstices range from the simple nearly 

round vesicles in basalt and thin, tabular joints in the consolidated and 

semiconsolidated rocks to the complex interstices in poorly sorted 

granular rocks. In most of the sedimentary rocks the interconnection 

between interstices is good. Conversely, interconnection of interstices, particularly vesicles, in the basalt often is poor or lacking.
32 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

The porosity of a rock or soil is the ratio of the volume of its interstices to its total volume. Thus, it is a measure of the ability of the 

rock to contain water. Natural rock materials differ greatly in porosity. The porosity of some consolidated rocks, such as tightly cemented 

sandstone or massive lava flows, is only a few percent or even a fraction 

of a percent, whereas the porosity of some clays may exceed 50 percent. In unconsolidated rocks, the well-sorted materials, such as 

clay or clean even-textured sand or gravel, have very high porosity. 

Poorly sorted materials, in which the smaller particles fill the openings 

between the larger grains, have low porosity.

Soil or rock may have a high porosity and yet yield little water. 

For example, a clay having a porosity of 50 percent or more might 

yield virtually no water because of the smallness of the pore spaces. 

Also, water may be retained in isolated or poorly interconnected pore 

spaces, such as the vesicles in basalt flows. Saturated vesicular zones 

of most basalt flows will not yield appreciable amounts of water unless 

the walls between adjacent vesicles are broken down by weathering 

or shattering. The ratio of the volume of water a saturated rock will 

yield by gravity to the total volume of the rock is known as the specific 

yield and usually is stated as a percentage. If water moves freely 

through a rock material under ordinary conditions, the material is 

said to be permeable, or pervious. Material described as impermeable, or impervious, allows relatively little movement of water through 

it. Another convenient term, closely related to permeability, is 

transmissibility. It, also, refers to the ability of a rock material to 

transmit water, but of the whole thickness of an aquifer rather than 

a unit thickness such as 1 foot.

WATER TABLE

The upper surface of an unconfined saturated zone is known as the 

water table. The level at which water stands in a well penetrating an 

unconfined zone of saturation represents the water table at that place.

The water table in most places is a sloping surface. It is highest 

in areas of recharge, where water is added to the aquifer, and slopes 

downward to areas of discharge, where water leaves, or is removed 

from, the aquifer. The slope of the water table (hydraulic gradient) 

adjusts automatically to the velocity of the moving water and the 

permeability of the rock. Rocks of low permeability require a steeper 

gradient than more permeable rocks to transmit water at a given rate.

The water table has irregularities that are generally comparable 

with the configuration of the land surface, although more subdued. 

Additional irregularities are caused by local differences in the permeability of the rock materials and by local differences in ground-water 

discharge and recharge. The water table fluctuates chiefly in response
WATER RESOURCES 33

to variations in recharge to, and discharge from, the ground-water 

body.

A saturated zone may be held above an unsaturated zone by a relatively impermeable rock stratum. Such a saturated water zone is 

called perched, and its upper surface is a perched water table.

CONFINED GROUND WATER

Water moving in an unconfined aquifer may pass between relatively 

impermeable beds and become confined there under a pressure due to 

the weight of the water in the unconfined part of the aquifer. Such 

water will rise higher in a well than the bottom of the overlying confining bed and is called confined, or artesian. The imaginary surface 

coinciding with the level to which confined water will rise in wells is 

called the piezometric surface. The piezometric surface is similar to 

the water table of an unconfined aquifer in that it usually is a sloping, 

irregular, fluctuating surface. It is highest in areas of ground-water 

recharge and lowest in areas of discharge. Fluctuations and irregularities in the piezometric surface are caused by variations in recharge 

and discharge and by differences in permeability within the aquifer.

Water which flows naturally from the top of a well, particularly a 

deep well, is commonly called artesian water. However, in the Geological Survey the term is used to mean water that is under pressure 

sufficient to raise it above the top of the confined aquifer. If the top 

of the well is at a lower elevation than the piezometric surface, the 

well is called a flowing artesian well. Of the examples shown in 

figure 5, wells A, C, and D are artesian wells, although only wells A and 

C flow. There are many artesian wells in the Ahtanum Valley, but 

relatively few of them flow.

RECHARGE TO AQUIFERS

Aquifers receive natural replenishment (recharge) chiefly by downward seepage from the surface, either from rain and melting snow or 

from streams and lakes which themselves are supplied by precipitation. Irrigation may be considered a form of artificial recharge, 

inasmuch as part of the water that is spread over the land surface 

commonly seeps downward to a zone of saturation.

Streams that cross permeable zones above the water table contribute to the ground-water reservoirs. On the other hand, streams that 

flow at a level lower than the water table receive contributions from 

the ground-water body. At places within the report area, Ahtanum 

Creek and its principal distributaries recharge the aquifers during 

their flood stage, when stream levels are higher than the adjacent 

water table, but receive virtually their entire flow from ground-water 

discharge during the low-flow periods, when streams are below the 

water table.
34 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

FIGURE 5. Diagrammatic cross section showing various occurrences of ground water. Water in the 

aquifers and wells is indicated by crosshatching. Arrows show the direction of ground-water movement. 

Wells A, C, and D arc artesian wells tapping a basalt aquifer confined by impermeable basalt and clay. 

At wells A and C the land surface is below the piezometric surface of the confined aquifer, and these wells 

flow. Well B taps an unconfined (water-table) gravel aquifer. Well E taps an unconfined aquifer perched 

above the regional water table by impermeable strata within the cemented gravel.

When a! permeable zone is completely saturated, the rate of recharge 

cannot exceed the rate of discharge. Any water available for recharge 

in excess of the amount of discharge will be rejected and will flow 

off as direct runoff. Generally, the ground-water system tends 

toward a state of equilibrium wherein annual recharge equals annual 

discharge.

MOVEMENT OF GROUND WATER

Ground water moves in response primarily to the force of gravity. 

Therefore, areas of discharge from an aquifer are necessarily lower 

than areas of recharge, and ground water moves down the hydraulic 

gradient, even though it may locally move upward toward a point 

of discharge, such as in a confined aquifer or in an unconfined aquifer 

near a stream. The rate of movement varies directly with the hydraulic gradient that is, if all other factors >remain the same, doubling 

the hydraulic gradient doubles the velocity.

GROUND-WATER DISCHARGE

Ground water is discharged naturally through springs and seeps 

(either at the land surface or into streams, lakes, or the sea), by 

evaporation or transpiration, and artificially by withdrawal from wells 

or drains.

Evaporation directly from the zone of saturation can take place 

where the water table is close to the land surface. Discharge by
WATER RESOURCES 35

transpiration takes place where the roots of plants extend to a shallow 

zone of saturation or to the "fringe" water drawn up from it by 

capillarity; the water is drawn up through the plants and is evaporated 

from the leaves.

HYDRAULICS OF A WELL,

As soon as a well begins discharging water, the water table (or 

piezometric surface) around the well is drawn down in a shape similar 

to an inverted cone, which is called the cone of depression. Thus, 

a hydraulic gradient is established, and water moves downgradient 

into the well. As the pumping of the well continues, the cone of 

depression expands, but more and more slowly, and water moves 

toward the weU from greater distances. The drawdown in the well 

also continues at a decreasing rate. Eventually, the cone of depression may become so large that the aquifer receives recharge at the 

rate at which the weU is being pumped. The cone of depression then 

remains virtually stable so long as all conditions remain unchanged. 

Conditions in the vicinity of a discharging water-table well are 

shown in figure 6.

The shape and the rate of expansion of a cone of depression are 

determined almost entirely by the rate of withdrawal, the ability of 

the aquifer to transmit water, and the rate at which water can be

Land surface

FIGURE 6. Diagrammatic section through a discharging water-table well. C-D'-C' is a section through the 

cone of water-table depression. D-D' represents the drawdown from the static (nonpumpingl water level. 

Arrows indicate direction of water movement.
36 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

removed from storage in the rock material during the withdrawal. 

A higher gradient (steeper cone of depression) is required to transmit 

water in material of low permeability at the same rate as in more 

permeable material. Similarly, a cone of depression expands more 

rapidly in material that has a low storage capacity than in material 

that has a high storage capacity. When the rate of pumping from 

a well is increased, the hydraulic gradient at every point on the cone 

of depression must become steeper so that water can move to the well 

at the increased rate.

The area of influence of a well is the land area beneath which the 

water table (or piezometric surface) is perceptibly lowered by withdrawal of water from the well. In the area of influence of a well that 

is being pumped, water levels are lowered in all other wells tapping 

the same aquifers.

The rate at which a well will yield water can be called its capacity. 

The amount of water it will yield with a given drawdown is the specific capacity and usually is expressed in gallons per minute per foot 

of drawdown.

OCCURRENCE OF WATER IN THE ROCK UNITS

Locally within the Ahtanum Valley each of the major rock units 

(the Yakima basalt, the Ellensburg formation, the cemented basalt 

gravel, and the unconsolidated alluvium) yields ground water. At 

most places in the valley, however, only one or two of these units 

will yield supplies adequate for substantial uses.

YAKIMA BASALT

The basalt sequence contains the most productive aquifers in the 

Ahtanum Valley. It supplies ground water to at least 14 irrigation 

wells in the area, some of which yield more than 1,000 gpm (gallons 

per minute) by punming. Of the wells, 6 are in the upper valley or 

in the Narrows, 2 are on the upland bench north of the upper valley, 

and 6 are in the lower valley, between the Narrows and Wiley. Most 

of the ground water in the basalt is under artesian pressure, controlled 

by the troughlike structure of the subbasin and confined by the overlying Ellensburg formation or by adjacent, less permeable layers of 

basalt. About half the wells that penetrate basalt either flow or 

have water levels standing less than 10 feet below the surface.

At least locally near the east end of the Narrows, the uppermost 

basalt flows, the Wenas(?) member of the Yakima basalt, may contain an important aquifer. In that area, well 12/16-13D1 was drilled 

to a depth of 146 feet, reportedly without penetrating the interbedded 

sedimentary layer that overlies the main body of the Yakima basalt. 

(For location of this well and others cited in text or tables, see pi. 1.) 

That well has a reported pumping yield of 850 gpm and is used regu-
WATER RESOURCES 37

larly for irrigation. Farther west, however, the Wenas(?) member 

apparently contains no significant aquifers. Without exception, 

wells in the upper valley that penetrate the Wenas(?) flows have failed 

to yield water from that unit in quantities sufficient for irrigation. 

Most of the wells have been drilled deeper, through the underlying 

sedimentary layer, into the main body of the Yakima basalt in order 

to produce enough water for irrigation.

The basalt aquifers of the Ahtanum Valley are recharged partly 

within the area mapped, partly north of the area along the south side 

of the Cowiche Mountain anticline, and partly just west of the area 

along the valley of the South Fork of Ahtanum Creek between Sedge 

Ridge and Ahtanum Ridge. Sources of recharge to the basalt are 

infiltration from precipitation, influent seepage from the intermittent 

streams on the slopes and upland benches, and influent seepage from 

Ahtanum Creek in 1 or 2 localities where the piezometric surface of 

the basalt aquifers is below stream level. The relative amounts of 

recharge received from each of these sources is not known. Some 

recharge from streamflow probably goes on throughout the year, but 

the infiltration from precipitation is limited to the wetter seasons of 

the year.

Most of the direct infiltration to the basalt from precipitation takes 

place on the slopes bordering the west half of the Ahtanum-Moxee 

subbasin, where the beveled flow layers are exposed at the surface or 

covered only by a thin mantle of slope wash; however, some infiltration 

from precipitation probably occurs at most places where the basalt is 

at or near the land surface. Some of the recharge from precipitation 

that occurs within the subbasin, but outside the area mapped for 

example, in the valley of the South Fork and on the slope of Cowiche 

Mountain reaches the basalt aquifers in the Ahtanum Valley as 

ground-water inflow. Most of the recharge to the basalt from streamflow probably takes place in the Narrows, where Ahtanum Creek 

flows directly on basalt of the Wenas(?) member or through a shallow 

layer of permeable gravel overlying the basalt, and where the piezometric surface of the basalt aquifers is about 30 to 40 feet lower than 

the stream. The streams probably contribute some recharge also in 

the vicinity of Tampico during the irrigation season, when the largeyield irrigation wells in that area draw the artesian levels down below 

the stream levels. The basalt undoubtedly recieve's additional recharge by infiltration from the intermittent streams around the 

margins of the subbasin.

In the lower valley, few wells tapping basalt aquifers have penetrated more than about 200 feet into the basalt. In the western part 

of the lower valley, this upper part of the basalt sequence probably 

corresponds to the Wenas(?) flows exposed in the Narrows. Ground
38 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

water entering the Wenas(?) basalt member as influent seepage from 

Ahtanum Creek in the Narrows may migrate eastward and provide 

part of the supply for wells that penetrate the upper part of the basalt 

sequence.

Movement of ground water in the basalt consists of slow percolation 

across the beds, through joints in the massive parts of the flows, and 

lateral flow through the interflow zones, toward areas of discharge. 

In general, ground water in the basalt moves from the intake areas on 

higher slopes toward the axis of the subbasin and eastward toward 

the Yakima River. Locally, however, the movement may be toward a discharging well, or away from a localized area of recharge 

such as the Narrows. Because of the extremely wide range in permeability of the basalt, the rate of ground-water movement through it 

also ranges widely. Percolation across the flow layers undoubtedly 

is very slow, but the amounts of water removed each year from wells 

indicate that lateral movement through some of the water-bearing 

zones may be comparatively rapid perhaps several feet per day 

under the hydraulic gradients occurring naturally within the area. 

Under conditions of pumping, the movement near wells is still more 

rapid.

Ground water is discharged from the Yakima basalt principally 

by seepage to streams, through seeps and minor springs at the surface, 

and from wells. The basalt loses water also by upward leakage to 

shallower aquifers.

Some ground water from the Yakima basalt undoubtedly discharges 

directly into the Yakima River (or into the unconsolidated alluvium) 

in Union Gap. Also, some ground water undoubtedly is discharged 

from the basalt to streams in the upper valley. As this effluent seepage cannot be seen or measured directly, the actual amount is unknown, but it is believed to be only a few thousand acre-feet per year 

or less.

Small seeps and springs issuing from the basalt are common on the 

lower slopes in the area. Few of these seeps and springs flow perennially, however, and this form of discharge is believed to account for 

only a small percentage of the total ground-water discharge from the 

basalt.

Ground water is withdrawn from about 20 wells tapping basalt 

aquifers in the area mapped. At least 14 of those wells are used for 

irrigation. Possibly as much as 1,500 acres is irrigated partly or 

completely with ground water from the Yakima basalt. The maximum withdrawal from basalt aquifers may be as much as 4,000 

acre-feet per year, but the average withdrawal probably is closer to 

3,000 acre-feet per year. The rate of withdrawal is influenced by
WATER RESOURCES 39

variations in climate and streamflow and by the market demand for 

agricultural products. As much as one-quarter or one-fifth of the 

ground water withdrawn from the Yakima basalt (and also from the 

Ellensburg formation) eventually may reach the shallow aquifer or 

discharge into the small streams as return flow from irrigation.

Perhaps the largest discharge of ground water from the Yakima 

basalt in the Ahtanum-Moxee subbasin is that by interformational 

leakage to the overlying rock units and thence to the Yakima River 

and the smaller streams. Ground water in the basalt beneath the 

lower valley is under pressure sufficient to raise it 50 or more feet 

above the land surface in many places. For example, well 12/17- 

16D3, which is 384 feet deep and penetrates 59 feet of basalt, had a 

shut-in pressure of 25 pounds per square inch in 1952. That pressure 

is sufficient to raise a column of water about 58 feet above the land 

surface. Thus, where the water table is 10 feet below the land 

surface, the differential upward pressure exerted upon the confining 

bed between the artesian and water-table aquifers is about 30 pounds 

per square inch. Even though the confining beds have a very low 

permeability and are several hundred feet thick, it is believed that 

thousands of acre-feet of ground water leaks upward each year from 

the Yakima basalt, through the small pores and joints in the confining 

strata, into the unconsolidated alluvium or into permeable zones in 

the Ellensburg formation or the cemented gravel unit. From these 

more permeable rock bodies, the ground water may then be discharged 

into the streams or through wells.

ELLENSBURG FORMATION

Within the Ahtanum Valley the Ellensburg formation is important 

as an aquifer only in the lower valley and northwest of Wiley on the 

terrace known as Wiley Heights. West of the Narrows that is, 

throughout the upper valley and on the adjacent upland benches the 

Ellensburg formation generally is too impervious, too thin, or too 

discontinuous to yield appreciable amounts of water to wells.

Of the wells tapping the Ellensburg formation, the most productive 

are in the center of the valley east of Wiley. Seven wells in that part 

of the valley are known to obtain water from the Ellensburg formation, 

and only 2 are reported to have yields smaller than 100 gpm. Well 

12/18-1 Ml, at the Yakima Farm Labor Camp, is the most productive 

well tapping this aquifer. It is 620 feet deep and in 1939 was reported 

to flow at a rate of 560 gpm. In contrast, the wells on Wiley Heights 

that tap the Ellensbm-g formation usually yield less than 100 gpm, 

although larger yields might be obtained by deeper penetration into 

the aquifer. Seven wells on the floor of the lower valley between 

Wiley and the Narrows have failed to obtain water from the Ellens-
40 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

burg formation in amounts sufficient for irrigation and were drilled 

deeper, into the underlying Yakima basalt, to obtain economic yields.

The principal aquifers in the Ellensburg formation consist of 

weakly cemented, permeable layers of gravel and well-sorted sand 

which are interbedded with less permeable layers of clay and shale. 

The aquifers are confined by the less permeable strata in the Ellensburg formation and by the underlying basalt. The structure of the 

formation (the rock layers of the sides of the valley dip inward toward 

the center of the valley and eastward toward the Yakima River) 

and the alternation of permeable and impermeable strata produce 

artesian pressure in the confined aquifers, so that several of the wells 

tapping the Ellensburg formation in the center of the lower valley 

are flowing wells.

The water-bearing properties of the Ellensburg formation within the 

valley are not well known, for only a few wells in the area are known 

to obtain all their water from that rock unit, and the information 

derived from these wells is sufficient for only general conclusions. 

It is believed, however, that the water-bearing zones in the Ellensburg 

become generally deeper downvalley (eastward) from the vicinity of 

Wiley. Also, the records indicate that the permeability of the Ellensburg formation, at some places, changes rather abruptly within short 

distances. Records of several of the wells indicate that the basal 

layer of the formation, which is about 10 to 20 feet thick and lies 

directly above the uppermost basalt flow, may be one of the most 

productive of the water-bearing zones in the Ellensburg formation.

The Ellensburg formation is recharged by infiltration from precipitation and irrigation, by influent seepage from streams, and by upward 

leakage from the Yakima basalt. The principal intake areas probably 

are those in which the Ellensburg formation is exposed at the surface, 

as on the upland bench northwest of the Narrows and along the north 

flank of Ahtanum Ridge in the lower valley. In these areas, infiltration from precipitation, from irrigation, and from streams undoubtedly 

contributes much of the recharge. Some recharge to the Ellensburg 

formation probably takes place by downward percolation from the alluvium in a small area of the valley floor near the east end of the Narrows 

(sees. 8, 17, and 18, T. 12 N., R. 17 E.) where the saturated alluvial 

gravels directly overlie the Ellensburg formation (pi. 1,A-A'). At least 

locally in that area, the lower part of the Ellensburg formation is 

somewhat permeable, and water levels in that part of the formation 

apparently are below stream levels. For example, in well 12/17-8K1 

(tables 4 and 5), which reportedly derives its water entirely from a 

20-foot-thick layer of permeable sand directly overlying the basalt, 

the water level is about 20 or 30 feet below local stream level. Here
WATER RESOURCES 41

the ground water in the alluvial gravel is able to percolate downward 

into the Ellensburg formation.

At other places where the Ellensburg formation contains significant 

aquifers, the pressure head in those aquifers generally is above the 

levels of the streams and the local water table; hence, no water moves 

downward to the aquifers. The Ellensburg formation receives additional recharge to the north of the area mapped, where the formation 

is exposed along the south flank of the Cowiche Mountain anticline. 

The amount of recharge that normally migrates from outside the 

area to aquifers beneath the Ahtanum Valley proper is not known, 

but it probably does not constitute a major source of ground water 

for the valley. One reason is that most of the water that is recharged 

to the Ellensburg formation from north of the area probably migrates 

toward Wide Hollow, where a large part of it is intercepted by wells. 

Also, the postulated small buried upfold (see p. 23) in the beds of the 

Ellensburg formation between Wide Hollow and the lower Ahtanum 

Valley (pi. 1, sections E-E' and F-F'} doubtless would retard the 

southward movement of ground water from Wide Hollow. However, 

unless additional information becomes available through future drilling 

of deep wells in the Wiley Heights area, this hypothetical structure 

cannot be affirmed.

Probably one of the most important sources of recharge to the 

Ellensburg formation is upward leakage from the Yakima basalt. 

In parts of the lower valley, ground water in the basalt is under 

pressure sufficient to cause appreciable upward leakage, and it doubtless contributes to the ground water available for withdrawal from 

aquifers of the Ellensburg formation.

Although the overall movement of ground water in the Ellensburg 

formation is toward the center of the subbasin and eastward toward 

the Yakima River, the hydraulic gradient may be modified by pumping 

so that locally the water may be diverted to a discharging well. No 

measurements or estimates have been made of the velocity of groundwater movement in the formation, but the water probably moves very 

slowly in the dense, clayey strata and moderately slowly even in the 

more permeable zones.

In the Ahtanum Valley, ground water from the Ellensburg formation 

probably is discharged mainly by withdrawal from wells and by upward leakage to the cemented gravel and unconsolidated alluvium.

The Ellensburg formation may yield as much as 800 acre-feet of 

ground water each year to wells. More than 95 percent of that total 

comes from irrigation wells, and most is withdrawn between July 1 

and October 1.

Perhaps the largest part of the natural discharge from the Ellensburg 

formation is the upward seepage to the overlying cemented-gravel
42 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

unit and unconsolidated alluvium, from which the water then discharges into the Yakima River. Of course, such upward leakage can 

occur only where the pressure is sufficient to raise the confined water 

in the Ellensburg formation above stream levels or the water table. 

Near the center of the subbasin in the eastern part of the lower valley, 

the relatively high transmissibility of the cemented-gravel unit and 

the high head in the underlying aquifers favor upward leakage.

Although the total amount of ground-water discharge from the 

Ellensburg formation has not been estimated, it is believed to be 

approximately balanced by recharge.

CEMENTED BASALT GRAVEL

The cemented basalt gravel is important as a source of ground water 

only in the eastern part of the lower valley and on the upland bench 

north of the lower valley. Elsewhere in the area, wells generally have 

failed to obtain water from the cemented-gravel unit in amounts 

sufficient for either domestic or irrigation use.

Although at most places part or all of the cemented gravel is saturated, the interstices generally have been so nearly filled with 

cementing material that the unit has low permeability and will yield 

very little water to wells. Even on the upland bench north of the 

lower valley, where supplies of water adequate for domestic use are 

obtained from the cemented gravel, the yields of individual wells are 

small (commonly less than a gallon per minute) and apparently are 

derived from discontinuous sandy or poorly cemented lenses. However, beneath the eastern part of the lower valley, an abrupt change 

in the character of the materials constituting the cemented-gravel 

unit is indicated by the logs of wells. In that part of the area, the 

unit contains more and thicker layers of sand and gravel, some of 

which are only weakly cemented and constitute productive aquifers. 

Well 12/19-5N1, a municipal well of the city of Union Gap, is the most 

productive of several large-yield wells that tap the cemented gravel 

unit in that part of the area. The well is 370 feet deep and produces 

as much as 970 gpm from gravel and sand.

The cemented gravel on the slopes and upland benches is recharged 

entirely by infiltration of precipitation, irrigation water, and water 

from intermittent streams. The more permeable zones beneath the 

eastern part of the lower valley, however, may be recharged mostly 

by upward leakage from the underlying artesian aquifers.

In general, movement of water in the cemented gravel is very slow. 

Even the presence of permeable lenses within the gravel may increase 

its overall permeability only slightly, as most of these sandy or poorly 

cemented lenses are discontinuous or poorly connected hydraulically. 

On the upland benches, the direction of movement generally is toward
WATER RESOURCES 43

the edges of the benches. On the south side of the lower valley, where 

beds of cemented gravel have been tilted along with the underlying 

rock units, some water, recharged from local precipitation and irrigation, probably moves northward toward the center of the valley. 

Beneath the eastern part of the valley floor, ground water in the unit 

moves generally toward the Yakima River.

Ground water is discharged from the cemented gravel on the upland 

benches mainly as seeps along the bluffs and terrace faces and by withdrawal from wells. At the east end of the valley, a considerable 

amount of ground water undoubtedly seeps directly from the unit 

into the Yakima River, but in that area also the withdrawal from 

wells constitutes a major form of discharge. It is estimated that 

about 500 acre-feet of ground water is pumped from the unit each 

year for industrial uses in and around the city of Union Gap, and 

another 300 acre-feet per year supplies the water system of that city.

UNCONSOLIDATED ALLUVIUM

The unconsolidated alluvium is the second most productive aquifer 

in the Ahtanum Valley, being surpassed in total yield only by the 

Yakima basalt. Most of the wells in the area tap the alluvium, and 

even though many of these are small-yield, domestic wells, the alluvium 

produces about a third of the ground water used. The alluvium provides nearly all the domestic water for the entire valley, and in the 

lower valley it is an important source of irrigation water. Yields as 

great as 400 gpm have been reported from shallow dug wells and, at 

most places in the floor of the lower valley, yields of more than 100 

gpm can reasonably be expected from a properly constructed dug well. 

The unconsolidated materials making up the alluvial slope on the south 

side of the lower valley also yield moderate supplies of ground water, 

but the depth to water there is somewhat greater than beneath the 

flood plain of Ahtanum Creek, and the yields of individual wells 

generally are less. The water table in the alluvium of the valley floor 

is generally less than 10 feet below the surface.

Ground water in the alluvium generally is unconfined, although 

at places lenses of silt and clay within the gravel body doubtless retard 

the movement of water and create small bodies of confined water.

The unconsolidated alluvium is recharged by infiltration from 

streams, irrigation canals, and irrigated fields; by precipitation; and 

by upward leakage from underlying artesian aquifers.

During the freshet stage, water from the swollen creeks percolates 

downward to the water table, filling the interstices of the alluvium 

and gradually replenishing the ground-water reservoir. During the 

rest of the year, the streams are at levels so low that ground water

603275 0 62 4
44 GEOLOGY, GROUND WATER, AHTANUM VALLEY, .WASH.

from the alluvium seeps into the stream channels and helps maintain 

the flow of the streams.

Throughout the irrigation season, the slow draining of the valley 

alluvium is partly offset by more or less continuous recharge from 

irrigation ditches and irrigated fields. It should be noted that a considerable part of the ground water withdrawn from both the shallow 

and the deep aquifers eventually recharges the shallow alluvium, and 

some of this flows into the streams.

During the wetter seasons of the year, local precipitation is an 

important form of recharge to the unconsolidated alluvium. Precipitation is greatest when evaporation is low, and much of the rainfall 

or melt water percolates downward to the shallow water table. 

During the summer months, however, the meager precipitation (usually 

less than 1 inch for the period July-August) is largely intercepted by 

vegetation or evaporates directly from the soil without reaching the 

water table.

On much of the gentle alluvial slope south of the lower valley, the 

elevation of the water table is higher than the highest possible stage of 

Ahtanum Creek. Therefore, the alluvium on those slopes cannot 

receive recharge from Ahtanum Creek; instead, ground water from 

the alluvial slopes discharges slowly but continuously into Ahtanum 

Creek. The water table beneath the lower alluvial slope is, in many 

places, maintained at fairly high levels by recharge from local irrigation, by seepage from irrigation canals and drainage courses from 

the higher slopes, and by precipitation that falls directly on the slope.

In the lower valley, and particularly in its eastern part, the alluvium 

that forms the valley floor doubtless is recharged to some extent by 

upward leakage from the underlying artesian aquifers. The difference 

in head between the water table and the piezometric surface of the 

artesian aquifers may be as much as 70 feet at places. Even though 

the rock materials that separate the alluvium from the artesian 

aquifers are relatively impermeable, they do not prevent entirely the 

upward movement of ground water, and it is possible that thousands 

of acre-feet of water per year leaks upward into the alluvium in this 

manner.

Ground water in the valley alluvium moves generally downstream, 

toward the Yakima River, but the movement at any given place may 

be toward or away from a stream or toward a discharging well, 

according to the local gradient of the water table.

It is obvious from the records of the shallow wells in the area 

that at most places the alluvium is at least moderately permeable, 

and that water readily moves through it. However, in order to estimate the velocity of ground-water movement and to make other 

quantitative estimates, it was necessary to make some quantitative
WATER RESOURCES 45

determination of the ability of the alluvium to transmit water. To 

this end, pumping tests were made in September 1951 on four wells 

that tap the valley alluvium. In these tests, the wells were pumped 

at a constant rate, and water-level measurements were made in them 

during and after the periods of pumping. The data were then analyzed by the recovery method developed by Theis (1935, p. 522; 

see also Wenzel, 1942, p. 95). Under certain conditions, this method, 

when applied to data obtained from a pumping test of a well tapping 

an ideal aquifer, affords a satisfactory means of determining the 

coefficient of transmissibility of the aquifer. The coefficient of 

transmissibility may be defined as the number of gallons per day of 

water, at the prevailing water temperatures, that will pass through 

a vertical section of the aquifer 1 mile wide (measured normal to the 

direction of flow) under a hydraulic gradient of 1 foot per mile. The 

coefficient of transmissibility, when divided by the thickness of the 

aquifer in feet, gives the field coefficient of permeability, which is 

the rate of flow of water, in gallons per day, through a section of the 

aquifer 1 foot thick and 1 mile wide under a hydraulic gradient of 1 

foot per mile, at the prevailing water temperature.

The characteristics of the alluvium and the conditions under which 

the aquifer tests in the area were made differ greatly from the ideal 

conditions assumed in the derivation of the recovery method. For 

example, the recovery method assumes a homogeneous artesian 

aquifer, of infinite areal extent, bounded above and below by perfectly impervious confining beds; the well is assumed to penetrate 

the aquifer completely. In contrast, the alluvium in the area is 

typically heterogeneous in character, and the ground water is unconfined. None of the wells completely penetrates the aquifer, and all 

undoubtedly have less than perfect efficiency. Furthermore, the 

wells were pumped for only short periods 2 hours or less in order 

to prevent recirculation of the discharge water; thus, the cone of 

pumping depression of the water table in the vicinity of the well 

could not spread far enough from the well to test a large area. All 

these differences between theoretical and field conditions tend to 

cause inaccuracies in the results of an aquifer test. Their overall 

effect on the tests in the Ahtanum Valley is not known, but the results 

of the tests are considered to represent only the general magnitude 

of transmissibility in the permeable gravels of the alluvium, and they 

are the best basis presently available for quantitative estimates of 

ground-water movement in the alluvium.

The four tests and the results derived therefrom are summarized 

in table 2. As the table shows, the indicated coefficients of transmissibility range from about 30,000 to 90,000 gpd (gallons per day) 

per foot, and the coefficients of permeability from about 5,000 to
46 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

6,000 gpd per square foot. However, each of the wells tested derives 

all or most of its water from coarse gravel, and the values obtained 

from the tests do not apply to the lenses and discontinuous layers 

of the finer grained materials, such as sand and silt. It is concluded, 

therefore, that the average transmissibility and permeability are 

less, but how much less is not known.

TABLE 2. Summary of pumping tests on wells tapping sand and gravel aquifers 

of alluvium, in lower Ahtanum Valley

Well

12/17-2R2... 

12/17-10C1 

12/18-5J1- 

Distance 

(miles) 

from 

WILEY 

In Wiley 

AHTANUM

IV E

Depth 

(feet)

9

8

12 

18

Thickness of 

producing 

zone 

(feet)

1 15 

6

9

Duration 

of test

hr min

2 0 

1 9

52 

1 42

Depth 

to 

water 

level 

before 

pumping 

(feet)

3.66 

1.18

6.45 

7.54

Average 

yield 

(gpm)

69 

64

64 

62

Maximum 

drawdown 

(feet)

0.74 

2.27

1.00 

.85

Specific 

capacity 

(gpm 

per ft)

93

28

64 

73

Coefficient of 

transmissibility 

(gpd 

per ft)

90,000 

30, 000

51,000

Coefficient of 

permeability 

(gpd 

per 

sqft)

6,000 

5,000

5,700

1 Estimated.

2 Data derived from test not suitable for calculation of coefficient of transmissibility.

It is assumed, however, that the average permeability of the least 

permeable body of alluvium of substantial size is 100 gpd per square 

foot. Doubtless there are pods of clay having extremely low permeability, but any such pods are believed to be small and not of consequence in affecting areal movement of ground water. The value of 100 

is believed to be reasonable for bodies of mixed sand and silt.

With these data, the probable range of velocity of water moving in 

the shallow alluvium can be calculated by the use of the following 

formula based on Darcy's law and adapted from Tolman (1937, p. 

215):

Ve= (2.632X10-P,)*

where Ve is the effective velocity of the water, in feet per day,

Pf is the field coefficient of permeability, in gallons per day per

square foot,

h is the hydraulic gradient, in feet per mile, 

p is the porosity.

As stated, the field coefficient of permeability (Pf) of the valley alluvium is estimated to range from about 6,000 to 100 gpd per square 

foot. The hydraulic gradient in the upper valley and through the 

Narrows averages about 85 feet per mile, and in the lower valley the 

gradient between Wiley and Union Gap averages about 40 feet per
WATER RESOURCES 47

mile. The average porosity of the valley alluvium probably is between 

0.15 and 0.25.

Substituting the values above so as to obtain the widest numerical 

spread for the sections of the valley where alluvium is present, the 

results indicate the limits of the downvalley velocity at which ground 

water in the shallow alluvium might be expected to move.

Upper valley:

T7 , , 2.532X10-5 (6,000) (85) _. ,, , Fe (max) = ^ -=86 ft per day 

U.lo

T7 , . , 2.532X10-5 (100) (85) . _ ., , Fe (mm)= ^ ^^=o.9 ft per day

Lower valley, Wiley to Union Gap:

T7 , , 2.532X10-5 (6,000) (40) An .. , Fe (max)= j^ -=4:0 ft per day

U. lo

T7 , . v 2.532X10-5 (100) (40) . . ., , Fe (mm) = Q-^5 ^A ^=0.4 ft per day

Thus, in the upper valley, ground water in the inconsolidated alluvium might be expected to move downstream at a velocity approaching 100 feet per day in the permeable coarse gravels, and less than a 

foot per day in the bodies of mixed sand and silt. The rates in the 

lower valley would be expected to be roughly half as great. Thus, in 

the floor of the lower valley, using the highest calculated velocity, 

several months would elapse while ground water in the very permeable 

gravel of the unconsolidated alluvium moved a mile downstream. 

In the least permeable material a considerable number of years would 

be required for water to move the same distance.

In the lower valley, the profile across the valley floor is much flatter 

than the downvalley gradient, and the gradient at which water moves 

laterally toward the small streams probably is lower also. Therefore, 

the average velocity of ground water moving laterally across the 

lower valley floor probably is considerably less than the downvalley 

movement, on the order of a few feet or less per day. In the upper 

valley, the gradient across the valley is much steeper, and in many 

places the velocity of ground water moving laterally through the 

alluvium may be equal to, or greater than, the downvalley velocity.

Ground water is discharged from the unconsolidated alluvium 

naturally by effluent seepage to the Yakima River and the smaller 

streams, by evapotranspiration, and probably, in the Narrows and the
48 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

upper valley, by seepage to the deeper aquifers. It is also discharged 

artificially by means of wells and drainage systems. Of these modes 

of discharge, effluent seepage is one of the more important.

That part of the seepage discharge from the unconsolidated alluvium which reaches the small streams, including Ahtanum Creek, helps 

to maintain their low-level flow (p. 44). That part which discharges 

directly to the Yakima River results in a contribution of perhaps 

5,000 acre-feet per year to the flow of the river in its course past the 

mouth of Ahtanum Valley. (See p. 63.)

It is not known how much ground water migrates downward from 

the alluvium to the lower aquifers. However, the water table in 

most parts of the area is lower than the piezometric surfaces of deeper 

aquifers, and there could be no downward leakage from the alluvium 

at these places. In a few rather small areas in the upper valley and 

the Narrows, the alluvium is underlain at shallow depth by basalt and 

the Ellensburg formation, in which the piezometric surfaces are lower 

than the water table. In these areas, water from the alluvium moves 

downward probably at rates depending on the transmission capabilities of the underlying materials.

Evapotranspiration from the shallow alluvium includes (a) consumptive waste of shallow ground water by phreatophytes of low 

economic value, (b) consumptive use by crops, and (c) direct evaporation of moisture from the capillary fringe where the water table 

is near the surface.

The group of phreatophytes, or "well plants," that grow within 

the Ahtanum Valley includes cottonwood, willows and associated 

shrubs, and marsh grasses. Alfalfa is an economic plant that acts as 

a phreatophyte in areas where it can send its roots down to the water 

table. Where phreatophytes grow near streams, their roots may 

withdraw water from both the surface- and ground-water bodies.

The amount of water used by a unit area of phreatophytes may be 

as much as, or more than, the evaporation from a free water surface 

covering the same area. In an extensive study made in the Safford 

Valley, Ariz. (Gatewood and others, 1950, p. 203), careful measurements showed that dense stands of cottonwood use as much as 6 acrefeet of water per acre in the year ended September 30, 1944. It 

cannot be stated whether the year of the estimate was typical, but the 

estimate gives at least a good general idea of the magnitude of transpiration by cottonwood.

The amount of stream-bank vegetation growing in medium to 

dense stands in the Ahtanum Valley has been estimated from aerial 

photographs at about 1,200 acres. The average consumptive waste 

by that vegetation is assumed to be half that for cottonwood in the 

Safford Valley, or 3 acre-feet per acre, to allow for both the lower
WATER RESOURCES 49

temperature in the Ahtanum Valley and the fact that not all the 

vegetation grows at maximum density. On the basis of this estimate, 

about 3,600 acre-feet of water is lost each year. No attempt has been 

made to determine the evapotranspiration losses from marshy or 

waterlogged land between the streams. However, the annual nonbeneficial discharge of ground water by evapotranspiration throughout 

the valley probably exceeds 4,000 acre-feet. This consumptive 

waste may represent a large reclaimable source of water in the Ahtanum Valley. Even though not all the wasted water could be salvaged, the possibility of reclaiming a part of it to alleviate the water 

shortage certainly warrants a careful study of the problem.

Withdrawals from wells tapping the alluvium are estimated to 

average about 1,800 acre-feet per year. Of that total, about 1,300 

acre-feet is used for irrigation, about 400 acre-feet for domestic supplies, and less than 100 acre-feet for industrial purposes.

In addition to that withdrawn from wells, some ground water is 

discharged artificially from the unconsolidated alluvium in the lower 

valley by drainage systems. Several large drains were constructed 

beneath the Yakima Airport and at the east end of the lower valley, 

in the vicinity of Union Gap. In addition, experiments were started 

about 1950 on the effectiveness of drainage systems for use on farms 

in some of the waterlogged areas of the lower valley (A. L. Dickinson, 

U.S. Soil Conservation Service, oral communication, September 

1952). The quantity of ground water that is discharged through 

these drains is not known. Apparently, however, the systems are 

effective in lowering the water table only in very localized areas near 

the drains.

WATEK-LEVEL FLUCTUATIONS

During the investigation, levels in 9 wells in the area were measured 

at intervals of 1 or 2 months for periods of a year or more, and levels 

in several other wells, in the lower valley and in Wide Hollow, were 

measured for shorter periods. In addition, during part of the time, 

recording gages were maintained on wells 12/17-2R2 and 12/17-9J3. 

Hydrographs from 11 wells in the Ahtanum Valley are shown on 

plates 2 and 3.

Of these wells, 2 tap the Yakima basalt, 1 the EUensburg formation, 

and 8 the unconsolidated alluvium. The location of the wells are 

shown on plate 1, and descriptions of the wells are given in table 4.

Water-level fluctuations in the alluvium are moderate. In the observation wells tapping the alluvium, the maximum observed change in 

water levels was 6.96 feet in well 12/16-18A1, from 14.02 feet (Oct. 18, 

1951) to 7.06 feet below the land surface (May 19, 1952). The minimum observed change was 1.24 feet in well 12/17-16Q1, from 6.02 feet 

(Aug. 10, 1951) to 4.78 feet below the land surface (Feb. 20, 1952).
50 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

The water-level measurements indicate that fluctuations of ground 

water in the alluvium are related principally to variations in stream 

levels, in irrigation and the flow of canals, and in local precipitation. 

The water level fluctuates less in response to withdrawals from wells 

and differences in evapotranspiration discharge from the shallow 

ground-water body. Of the major fluctuations the largest are those 

related to changes in the level of Ahtanum Creek and its major 

branches. The highest recorded water levels of the shallow wells in the 

valley floor usually are in the spring, coinciding with the high stages of 

Ahtanum Creek. Other important seasonal fluctuations are caused by 

differences in irrigation and in the flow of water through the irrigation 

canals, and by precipitation within the valley. Smaller, more localized fluctuations apparently are caused by different rates of pumping 

from irrigation wells in the shallow alluvium and by sharp decreases in 

the consumptive use of the shallow ground water by vegetation when 

crops are harvested or after the first killing frost of fall. Minor fluctuations of a few hundredths of a foot are caused during the summer 

months by the differences in the nighttime and daytime rates of evapotranspiration of ground water by vegetation. An example of such 

diurnal fluctuations is shown in figure 7, which is a copy of a portion 

of an original chart from the recording gage on well 12/17-2R2, at 

Wiley. Figure 7 also shows the drawdown in well 12/17-2R2 caused 

by pumping of a nearby well.

Because the water table beneath much of the alluvial slope south 

of the lower valley is higher in elevation than the maximum stage of 

Ahtanum Creek, the seasonal variations in the level of Ahtanum Creek 

probably have little effect on its position except in the immediate vicinity of the creek. For example, the hydrograph of well 12/17-16Q1 

(pi. 2) shows no fluctuations that can be correlated with streamflow. 

In fact, the only marked fluctuation was a downward trend that probably was related to evapotranspiration and to pumping from the well 

itself during the summer months. The highest level, during February 

1951, probably was the result of recharge from local precipitation.

Well 12/18-7J1, owned by A. W. Knight, is the only well tapping 

the Ellensburg formation that was measured regularly during the investigation. It is a 362-foot drilled irrigation well that penetrates 22 

feet into the Ellensburg. Fluctuation of the water level in that well 

is shown in plate 2. The measured range in water level was only about 

2 feet, but the actual range is greater by an unknown amount because 

the well flowed during the summer months and the water level was 

not measured. The lowest observed level, 1.56 feet below the land 

surface, was recorded in March 1952, and the highest level probably 

was in July. In 1951 the well was pumped only during August.
WATER RESOURCES 51

from 

pumping of

nearby well

18 19 20 21 22 23 24 25 26 27 28 29 30 31

JULY 1951

FIGURE 7. Hydrograph of well 12/17-2R2, showing diurnal water-level fluctuations and drawdown from

pumping of a nearby well.

The water-level fluctuations in well 12/18-7J1 probably are controlled chiefly by differences in the recharge to the formation. However, in other parts of the lower valley, the water-level fluctuations 

may be controlled mainly by withdrawals from wells tapping the Ellensburg formation.

The two observation wells that tap basalt aquifers are 12/16-13D2, 

at the east end of the Narrows, and 12/17-9J3, 2 miles west-southwest 

of Wiley.

Well 12/16-13D2, owned by Herke Bros., was drilled as a test well. 

It is about 8 feet from a very productive irrigation well that probably
52 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

withdraws water entirely, or mostly, from the Yakima basalt. As its 

hydrograph shows, the water level in well 12/16-13D2 is controlled 

primarily by pumping from the irrigation well. The water levels in 

both wells respond immediately to pumping, which usually is begun in 

July, and continue to decline throughout the period of pumping which 

usually continues steadily for 60 or 70 days at the rate of about 850 

gpm. The maximum drawdown during a season of pumping usually 

is less than 40 feet. After pumping is stopped, the water levels in the 

wells do not recover as rapidly as might be expected from the specific 

capacity of the pumped well. Instead, the aquifer requires about 10 

months, or until the next irrigation season, to be replenished, and in 

some years the water levels do not fully recover before pumping is resumed. It is therefore assumed that, although the transmissibility of 

that particular water-bearing zone in the basalt is rather high, the recharge is limited by adjacent materials of low permeability, so that a 

period of 10 months is required to replenish the ground water that is 

discharged during 2 months of heavy pumping.

Well 12/17-9J3, owned by Walter Mclnnis, is 575 feet deep and also 

taps aquifers in the Yakima basalt. The well originally supplied water 

for a school, but it has been used exclusively for observation since the 

U.S. Geological Survey installed a recording gage in January 1953.

On July 20, 1953, the water level in this well was 66.80 feet below 

the land-surface datum. This level represented the seasonal high for 

that year. On July 19, 1957, the approximate seasonal high was 80.98 

feet below the datum. Hence, the overall decline was 14.18 feet, or 

about 3% feet per year, for the 4-year span. The year-to-year decline 

was not consistent however. In the years 1954, 1955, and 1956 the 

seasonal highs were as much as 10 feet below the 5-year average trend, 

but the reason for these inordinately low levels is not known. Major 

water-level fluctuations in the Mclnnis well probably are caused largely by the pumping of four large-yield irrigation wells, which tap basalt 

aquifers and are located within 1.5 miles of the Mclnnis well. The 

water level doubtless is affected also by other factors, such as seasonal 

variations in recharge and natural discharge.

The hydrographs of wells 12/17-9J3 and 12/16-13D2 suggest that at 

least locally in the western part of the lower valley, there may be a 

declining trend in the artesian pressures in the basalt aquifers. However, the length of record is not adequate to determine whether pumping has reached, or is approaching, an optimum balance with recharge.

In the Pullman area (Foxworthy and Washburn, 1957, p. 56-58), increased pumping withdrawals and the attendant decline in groundwater levels have resulted in an increase hi natural recharge to basalt 

aquifers recharge that otherwise would have been rejected. In the 

Ahtanum Valley, therefore, moderate drawdown of water levels in the
WATER RESOURCES 53

basalt aquifers may not necessarily be detrimental to the hydrologic 

regimen of the area but could result, as in the Pullman area, in increased recharge to the aquifers.

DEVELOPMENT

UPPER VALLEY

The ground-water resources of the upper valley are developed on a 

moderate scale. Virtually all domestic water is derived from wells, 

and the irrigation water from streams is supplemented to a considerable extent by ground water. The Yakima basalt and the unconsolidated alluvium are the principal sources of ground water; the 

Ellensburg formation and the cemented gravel are not important 

aquifers. The estimated withdrawals of ground water from the upper 

valley, and also from other parts of the area, are presented in table 3.

All the large-yield wells in the upper valley derive water from 

basalt aquifers which yield as much as 1,700 acre-feet of water per 

year to 6 irrigation wells. The irrigation wells range in depth from 

146 to 598 feet, and a pumping yield of 1,300 gpm has been reported 

for one of them (12/16-13D1). All 6 wells tap artesian aquifers, and 

4 of the wells either flow or have flowed in the past.

The unconsolidated alluvium is an important aquifer in the upper 

valley, although not a highly productive one at present. It supplies 

nearly all the domestic wells, the total withdrawal from which is about 

15 acre-feet per year. At some places, as in the Narrows, the alluvium 

may be generally thinner than in the lower valley, but its similarity 

in appearance to the unconsolidated gravel in the lower valley suggests 

that it may be capable of yielding much larger quantities of water 

than are presently withdrawn.

Any sizable increases in ground-water withdrawals from the upper 

valley probably would come mostly from wells in the main body of the 

Yakima basalt. Withdrawals from the basalt aquifers probably could 

be increased somewhat without exceeding the long-term yield. However, any additional irrigation wells that tap the basalt should be 

spaced as far as possible from other wells in the same aquifer, in order 

to minimize interference that is overlapping of the cones of depressions of the discharging wells.

Although properly constructed wells tapping the unconsolidated 

alluvium of the upper valley might produce as much as several hundred gallons per minute each, continued pumping of several such 

wells throughout an irrigation season might cause at least slight 

decreases in streamflow. The floor of the upper valley is so narrow 

that on most farms it would be difficult to locate a well more than a 

few hundred yards away from a branch of Ahtanum Creek, and after 

several months of pumping the cone of depression around the dis-
54 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

charging well probably would spread far enough to affect the flow of 

the stream either by inducing direct infiltration from the stream 

channel or by intercepting appreciable amounts of ground water that 

normally would discharge into the stream. The possible effects of 

increased withdrawals from the alluvium are discussed more fully in 

a subsequent part of this report.

UPLAND BENCHES

Ground water on the upland bench north of the upper valley is 

developed by means of three irrigation wells and half a dozen domestic 

wells. All the irrigation wells derive water from the basalt, which 

is the only source available in that part of the area for the development 

of large supplies of ground water. The maximum withdrawal from 

the irrigation wells is estimated to be about 800 acre-feet per year. 

The domestic wells, of which some have barely adequate yields, derive 

water from cemented gravel or from the Ellensburg formation, overlying the basalt.

East of the Narrows the basalt dips below the surface, and the 

upland bench or terrace north of the lower valley is formed mostly 

by cemented gravel, underlain at depths of about 50 to more than 

100 feet by the Ellensburg formation. During the investigation, 

wells were canvassed in the southern part of this terrace. (See pi. 

1.) Most of the wells range in depth from 90 to 200 feet; they completely penetrate the cemented-gravel units and tap aquifers in the 

upper part of the Ellensburg formation. A few deeper wells penetrate 

farther into the Ellensburg formation, and a few shallower wells 

evidently derive small supplies of water from the cemented gravel. 

In general, the wells tapping the cemented gravel are the least productive of those in the southern part of the terrace and have yields 

of not more than a few gallons per minute. Somewhat larger yields, 

up to perhaps 50 gpm, usually are obtained from the wells that penetrate a short distance into the Ellensburg formation, and yields of 

more than 50 gpm have been obtained from the deeper wells. Well 

12/17-3M3, owned by F. T. Tissell, about 2 miles west of Wiley, is 

the most productive well in that part of the area. This drilled well, 

which is 262 feet deep, penetrates more than 100 feet into the Ellensburg formation and reportedly was pumped at a rate of 90 gpm for 

4 hours, with a drawdown of 33 feet. In the southern part of the 

terrace, the estimated ground-water withdrawal is 65 acre-feet per 

year, most of which is derived from the Ellensburg formation (table 4).

No wells have been drilled on the bench south of the Narrows, 

although it probably is potentially as good an area for ground-water 

development as the bench on the north side. The structure of the 

basalt layers that underline the upland benches on both sides of the
WATER RESOURCES 55

upper valley is generally favorable for the occurrence of ground water 

under artesian pressure.

Well records indicate that any additional large-capacity wells that 

are drilled on the upland benches must penetrate a considerable distance into the older rock units that is, the Yakima basalt (adjacent 

to the upper valley) and the Ellensburg formation (on the terrace 

north of the lower valley). Yields of more than 100 gpm probably 

will require wells at least 200 feet deep. Recharge to those deeper 

aquifers probably is sufficiently great that a few additional largecapacity wells located on the upland benches would not withdraw 

ground water in excess of the long-term average intake.

LOWER VALLEY 

PRESENT DEVELOPMENT

In the lower Ahtanum Valley, sizable amounts of ground water are 

withdrawn from all the rock units; however, the degree of development of the various aquifers differs widely from place to place. 

Estimated withdrawals of ground water from the rock units in the 

lower valley are given in table 3.

In the lower valley between the Narrows and Wiley, the unconsolidated alluvium and the Yakima basalt are the only productive sources 

of ground water. Neither the cemented-gravel unit nor the Ellensburg formation is known to yield more than small amounts of water 

to wells. Basalt aquifers yield as much as 1,050 acre-feet per year 

to 5 wells in the lower valley; individual well yields range from 210 

gpm (well 12/17-8R3) to 640 gpm (well 12/17-16D3). The wells 

range in depth from 243 feet (well 12/17-17C1) to 1,078 feet (well 

12/17-16R1).

Farther east the Yakima basalt plunges deeper beneath the valley 

floor; its upper surface may be as much as 1,500 feet below the land 

surface near the city of Union Gap. Its depth in the eastern part of 

the lower valley makes the cost of drilling to the basalt prohibitive, 

and no wells have been drilled deep enough to reach it. Well 13/18- 

29Q1, in Wide Hollow, penetrated basalt at a depth of 1,250 feet, 

but it apparently was not drilled far enough into the basalt to tap a 

productive aquifer (table 4). Fortunately, the Ellensburg formation 

contains productive aquifers east of the Wiley-Ahtanum district, and 

the cemented-gravel unit is a productive source of ground water at 

the mouth of the lower valley. The Ellensburg formation yields 

about 730 acre-feet per year to 10 wells in the lower valley. The 

wells produce up to 1,100 gpm (well 12/18-2E1), and range from less 

than 100 to more than 600 feet in depth. The cemented-gravel unit 

yields about 800 acre-feet per year, mostly to wells in and near the 

town of Union Gap.
56 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

The unconsolidated alluvium yields most of the domestic water 

used in the lower valley and is a productive source of irrigation water 

in most of that area. Most of the wells tapping the alluvium are dug 

or driven and are less than 30 feet deep. Yields as great as 400 gpm 

have been reported for some of the shallow dug wells, and the total 

withdrawal from the alluvium in the lower valley is estimated to be 

about 1,750 acre-feet per year.

POTENTIAL DEVELOPMENT

Recharge to the Ellensburg formation, the cemented-gravel unit, 

and the unconsolidated alluvium probably is sufficient that additional 

withdrawals could be made from those aquifers in the lower valley 

without lowering the water levels excessively. However, in any additional development of the ground-water resources, wells should be 

spaced to minimize interference, and observations of water levels 

should be made regularly to give early warning of any overdraft.

Because of the trend toward declining water levels in wells tapping 

basalt aquifers, any additional development of these aquifers should 

be planned carefully, and the plan should include a program for the 

collection of hydrologic data.

Each of the aquifers in the lower valley, in localities favorable for 

development, is capable of yielding several hundred gallons of water 

per minute to a properly constructed well. The unconsolidated alluvium is, of course, the most easily developed of the aquifers. In 

most parts of the lower valley, a properly constructed dug well can be 

expected to produce more than 100 gpm. However, the probable 

depth, yield, and construction cost of wells in the other aquifers differ 

widely in different parts of the lower valley. In general, the withdrawal of additional ground water from aquifers other than the alluvium will require drilled wells ranging in depth from a few hundred 

feet to 1,000 feet, or even more.

Some of the probable results of increased withdrawal from the 

alluvium would be a lowering of the water table; a decrease, at least 

temporarily, in effluent seepage to streams, with a corresponding 

temporary increase in ground-water recharge; and possibly a slight 

increase in the consumptive use by vegetation if the water is used for 

irrigation. In order to estimate the overall effects of such increased 

withdrawal, it is necessary to consider not only the individual results 

but also the interrelation of all foreseeable results.

Any increase in the withdrawal of ground water from the unconsolidated alluvium of the lower valley would tend to lower the water 

table in the vicinity of the wells. This effect, by itself, would be 

desirable in some waterlogged areas, but along the banks of streams a 

lowering of the water table might be considered undesirable, as it
WATER RESOURCES 57

would decrease the gradient, and therefore the amount, of water 

moving to the streams or, if the water table locally were lowered 

below the stream levels, would induce local infiltration from the 

stream. In either event it would decrease the streamflow. Unless 

the wells were located close to the streams, however, the resulting 

decrease in streamflow would not occur until some time after pumping 

was increased. On the basis of the yields from existing wells and the 

probable rates of ground-water movement in the alluvium, it is 

believed that withdrawals from shallow irrigation wells located more 

than a mile or two west of the town of Union Gap would have no 

direct effect upon the seepage of ground water directly to the Yakima 

River during the same irrigation season, but the cones of depression 

of most irrigation wells in the valley alluvium probably would be 

extensive enough during the latter part of the irrigation season to 

cause at least slight decreases in the flow of the smaller streams 

(Foxworthy, 1953, p. 18).

These effects that is, the decrease in streamflow and the lowering 

of the water table would be partly offset by return flow from the additional irrigation. Under normal conditions, an estimated 25 percent 

of the water applied returns to the streams or to the shallow groundwater body.

Additional cultivation and irrigation in the lower Ahtanum Valley 

would of course increase the consumptive use of water by crops. 

Evaporation losses also would be increased during the period of 

application of irrigation water. On the other hand, the nonbeneficial 

evapotranspiration loss would be virtually eliminated on the tracts 

brought under cultivation. Also, if the water table were lowered 

generally by increased pumping, the consumptive waste by phreatophytes in surrounding areas probably would be decreased somewhat, 

because in general the deeper the water table the smaller the waste 

by phreatophytes. The net effect that increased irrigation would 

have upon the amount of annual evapotranspiration discharge depends 

upon the degree to which these factors would balance each other.

On much of the reclaimable land in the lower Ahtanum Valley, the 

annual nonbeneficial evapotranspiration loss doubtless is as much as 

2 acre-feet per acre, and in localities having rather dense phreatophytic 

growth, it probably reaches or exceeds 3 acre-feet per acre. If reasonably efficient irrigation methods were used, any crop suitable to the 

lower Ahtanum Valley probably would not require the application of 

more than about 3.5 acre-feet of irrigation water per acre, and of this 

amount perhaps 1 acre-foot would return to streams or the groundwater body. If this irrigation water were applied to land that is now 

wasting 2 or 3 acre-feet per acre, little or no additional water would 

be lost by evapotranspiration. Hence, the proper reclamation of a
58 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

considerable area in the lower Ahtanum Valley probably would require 

little, if any, additional water. Any decrease in streamflow resulting 

from the withdrawal of ground water to irrigate the reclaimed land 

would be only temporary, occurring partly during the latter part of 

the irrigation season but mostly later in the year when the demand on 

streams is no longer critical.

SUMMARY OF WITHDRAWALS

The estimated withdrawal of ground water in the subareas of the 

Ahtanum Valley, the amounts withdrawan from the various rock 

units, and the utilization of the ground water in the area are summarized in table 3.

TABLE 3. Estimated ground-water withdrawals, in acre-feet per year, in subareas 

of the Ahtanum Valley, according to use and principal aquifer

(USE)

Stocki 

Total..... ..........- ..............

(AQUIFER)

Total....... _ _.

Upper 

valley

15

0

1,100

0

2<5

1,115

1,100

0

0

15

1,115

Lower 

valley

400

700

3,000

220

10

4,330

1,050

730

800

1,750

4,330

Upland 

benches

45

20

800

0

2<5

865

800

60

5

0

865

Total

460

720

4,900

220

10

6,310

2,950

790

805

1,765

6,310

1 Includes supplies for dairies.

2 Not included in total.

Most of the estimates are based on data gathered during the 

canvass of wells in the area. Estimates of irrigation withdrawals, 

however, were based largely on ground-water certificates issued by 

the Washington State Department of Conservation. The average 

irrigation withdrawal undoubtedly is considerably less than the maximum allowable under the water-right certificates, as some of the 

irrigation wells are not operated during years of above-average streamflow, and many others are not utilized to the extent of their water 

rights. Therefore, to estimate average withdrawals from wells for 

which certificates have been granted, the maximum allowable withdrawals have been arbitrarily reduced by one-third. For irrigation 

wells for which water-right certificates have not been issued, such as 

those south of Ahtanum Creek on the Yakima Indian Reservation, 

the averages were based on reported or estimated irrigated acreages.

Irrigation demands of course vary greatly from year to year, depending on such factors as climate, the availability of surface water, and
WATER RESOURCES 59

market prices for crops. All the ground water used for irrigation is 

withdrawn during the period from May to October, and most of the 

large-scale pumping is done after July 1.

CHEMICAL QUALITY

Comprehensive chemical analyses of samples of water from 7 wells 

in the area were made by the U.S. Geological Survey in 1951 and 

1952. Of these, 3 tap the unconsolidated alluvium, 2 the basalt, 1 

the Ellensburg formation, and 1 the cemented basalt gravel. The 

results of the analyses are given in table 6. In addition, field determinations of hardness and chloride content were made of samples 

from about a tenth of the wells visited. The results of determinations 

of hardness and chloride are given in table 7. These data indicate 

the general character of water from the various aquifers.

RANGE IN CHEMICAL CONCENTRATION

The overall range in chloride concentration was from 0.7 to 26 ppm 

(parts per million), and the range in hardness was from 49 to 265 

ppm. The chloride content and hardness of samples from the various 

aquifers range as follows:

Source of samples

Number of 

samples

6

9

10

19

Chloride 

(ppm)

1.2-8

6 -26

5 -26

.7-14

Hardness as 

CaCO3 

(ppm)

54-95

75-240

120-265

49-148

The range in concentration of all dissolved constituents was not 

determined for the area as a whole because the scope of the investigation did not warrant an extensive geochemical study. In the 

analyses shown in table 6, the dissolved solids ranged from 113 ppm 

(well 12/16-17J1, tapping unconsolidated alluvium) to 235 ppm (well 

12/18-11E1, tapping the Ellensburg formation). Values for pH indicated all samples to be slightly alkaline; the bicarbonate content 

ranged from 74 to 180 ppm.

GENERAL CHARACTER

The analyses show that the concentrations of chemical constituents 

in the ground water are related much more closely to the rock material 

in which the water occurs than to the depth of the aquifer or the 

geographic location of the well. Water from basalt aquifers generally 

has a lower concentration of chloride and lower hardness than water 

from the other aquifers. Water from both the basalt and the alluvium 

is lower in concentration of chloride and hardness than water from

603275 O 62 5
60 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

either the Ellensburg formation or the cemented gravel. Hardness 

of water in the alluvium apparently increases slightly downvalley, 

and shallow ground water in the alluvial slope south of Ahtanum 

Creek generally is harder than water from the alluvium north of the 

creek.

Differences in the chemical character of the ground water from 

different aquifers can be seen more clearly in figure 8, which is a 

graph upon which the seven comprehensive analyses have been plotted. 

In general, the position of each point on the graph is dependent upon 

the chemical character of the water with respect to proportions of 2 

groups of major cations (calcium and magnesium, and sodium and 

potassium) and 2 groups of major anions (bicarbonate and carbonate, 

and sulfate and chloride) (Piper, 1944). Analyses of water samples 

of nearly identical chemical character plot closely together, but 

analyses of samples of different chemical character plot in different 

parts of the graph. The analyses of water from the basalt and the 

alluvium, represented by points 1, 3, 5, 6, and 7, all plot in a fairly 

close group in a part of the graph that indicates they are all of the 

calcium magnesium bicarbonate type. In contrast, the analyses of 

water from the Ellensburg formation and the cemented gravel, points 

2 and 4, are entirely separate from the other group, apparently owing 

largely to a higher proportion of sulfate and chloride in these two 

water samples.

An important chemical characteristic of water for irrigation is the 

proportion of sodium to the principal basic constituents (calcium, 

magnesium, sodium, and potassium) the "percent sodium." The 

U.S. Department of Agriculture (Wilcox, 1948, p. 25-27) commonly 

rates water as to its suitability for irrigation according to the percent 

sodium and the concentration of dissolved solids. By this classification, all samples analyzed rated "excellent to good" for irrigation.

The temperature of water in shallow aquifers is controlled largely 

by the mean annual temperature of the area. Water from deeper 

aquifers usually is warmer, in response to the effect of the geothermal 

gradient. The type of material that yields the water usually has very 

little influence upon the temperature of ground water. In the Ahtanum Valley, the water from the shallow wells, as much as about 40 

feet deep, showed a considerable range of temperatures from 43° to 

55° F. In wells deeper than 50 feet, the temperature increases about 

1° F for every 45 feet of depth, with no apparent relation to the type 

of material from which the water is derived. For example, well 12/17- 

3D1, which is 125 feet deep, yields water at 54° F, whereas well 

12/18-lMl, which is 620 feet deep, yields water about 11° warmer, 

or at 65° F. Measurements of the ground-water temperatures in the 

area are given in table 4.
WATER RESOURCES 61

FIGURE 8. Graph showing chemical character of water from wells in Ahtanum Valley.

Plot Well

I........................................... 12/16-13D1

2--.__. _.-_..--___. -...- __. .-.__ 12/18-11E1

3-.. _.-- .. _._ 12/18-5G2

^........................................... 13/19-31J1

5....._____._.____...__...._.... 12/18-5J1

6. .... ................................. 12/16-17J1

7.... .........._............_........ 12/17-16R1

Depth

(feet)

146

213

10

84

18

11

1,078

Principal

aquifer 

Basalt.

Ellensburg formation. 

Alluvium. 

Cemented gravel. 

Alluvium. 

Alluvium. 

Basalt.
62 GEOLOGY, GROUND "WATER, AHTANUM VALLEY, WASH.

SUITABILITY FOR USE

The analyses, together with information supplied by residents 

during the canvass of wells in the area, show that the chemical quality 

of ground water in the Ahtanum Valley generally is satisfactory for 

most purposes, although water from many wells is harder than 

desirable for domestic use. The water generally is clear and cool 

and has no objectionable taste or odor. A few wells that tap basalt 

aquifers reportedly yield water that has a slight odor of hydrogen 

sulfide, but this odor usually disappears if the water is allowed to 

stand in an open vessel.

GROUND-WATER DISCHARGE TO THE YAKIMA RIVER

Analyses of available streamflow records indicate that the flow of 

the Yakima River increases substantially as it traverses the AhtanumMoxee subbasin. This increase is attributable partly to direct runoff 

from tributary streams and partly to ground-water discharge. It is 

possible to estimate the amount of ground-water discharge to the 

Yakima River within the subbasin provided that concurrent records 

of the flow of the river as it enters and leaves the subbasin and of 

streams tributary to the river within that reach are available for 

study.

Streamflow records have been collected concurrently at stations on 

the Yakima and Naches Rivers at Selah Gap, the Yakima River at 

Union Gap, and Ahtanum and Wide Hollow Creeks near their mouths 

during only two brief periods, July-October 1911 and July-September 

1912. Additional measurements were made at all these stations 

except Wide Hollow Creek during the period May-November 1904.s 

These periods are too short to allow more than a tentative estimate 

of ground-water discharge.

The records show that the flow of the Yakima River nearly doubles 

between Selah Gap, where it enters the Ahtanum-Moxee subbasin, 

and Union Gap, where it leaves the subbasin. Most of the increase 

comes from the Naches River, which discharges into the Yakima just 

below Selah Gap, and from Ahtanum and Wide Hollow Creeks. The 

rest enters the river as ground-water seepage and intermittent surface 

runoff.

On the basis of records for the period cited above (but omitting 

those for May and June 1904, which reflect flood stages that apparently 

mask the effect of ground-water discharge), the average monthly 

ground-water increment to the Yakima River between Selah Gap and 

Union Gap is estimated at 9,000 acre-feet per month.

 Kecords cited above, except those for Wide Hollow Creek, have been published in U.S. Geological 

Survey Water-Supply Paper 1316. The records for the station on Wide Hollow Creek have not been 

published but are available for examination at the office of the U.S. Bureau of Reclamation at Yakima.
WATER RESOURCES 63

Ground-water contributions from specific areas within the subbasin 

also may be estimated from the total discharge, provided that certain 

additional assumptions are made. It is assumed that more than half 

the ground-water increment to the Yakima River, perhaps 5,000 acrefeet per month, came from the west side of the Ahtanum-Moxee subbasin, where precipitation and surface discharge are greater. If it is 

assumed further that the contribution from the west side of the subbasin is evenly distributed throughout the 8-mile reach, the yearly 

total for each mile would amount to about 7,500 acre-feet. Because 

of lack of precise data on elevations of the land surface and on water 

levels in wells and streams, no ground-water drainage divide between 

wide Hollow Creek and the Ahtanum Creek system has been located. 

Hence, the ground-water contribution from the area drained by 

Ahtanum Creek cannot be determined directly. However, for the 

3-mile reach of the Yakima River shown on figure 1 the effluent seepage directly into the Yakima River and to the short intermittent 

streams and drains which empty into the river may be on the order of 

20,000 to 25,000 acre-feet per year. Doubtless a part of that groundwater discharge is from Wide Hollow, but the proportion cannot be 

determined on the basis of available data.

The preceding estimate of ground-water discharge to the Yakima 

River constitutes the total for all the aquifers. The discharge from 

the unconsolidated alluvium may be estimated separately, using the 

transmissibility data derived from aquifer tests and the gradient of the 

water table, according to the following modification of the gradient 

formula:

Q=Thl

where Q is the quantity of water discharged, in gallons per day,

Tis the coefficient of transmissibility, in gallons per day per

foot,

h is the hydraulic gradient, in feet per mile, 

I is the length of the discharging area, in miles. 

The gradient of the water table (h) in the lower valley near the 

Yakima River is about 25 feet per mile, and the length of the discharging area (I) is 3 miles. If the average coefficient of transmissibility ( T) 

is assumed to be 60,000 gpd per foot on the basis of the results of the 

aquifer tests previously described (table 2), the discharge (Q) is on the 

order of 4.5 mgd (million gallons per day), or about 5,000 acre-feet 

per year. Thus it is estimated that the alluvium discharges as much 

as one-fourth of the total ground-water discharge from the area to the 

Yakima River.
64 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

PROBLEMS OF FUTURE WATER SUPPLY

The foregoing discussion outlines the ground-water conditions in the 

Ahtanum Valley during 1951-58, insofar as avaliable data permit. 

This period has been marked by continuing construction of wells for 

irrigation and by a major lawsuit concerning apportionment of the 

inadequate summertime flow of the streams. If the productivity of 

the land and the economy of the population are to reach optimum 

levels, a comprehensive plan must be established for the systematic 

development and management not only of the ground water but also 

of the total water resources of the area.

Efficient management requires a comprehensive inventory of the 

water resources of the area. This report provides estimates for some 

of the factors pertinent to such an inventory; the available data allow 

only tentative conclusions about other critical factors. Also, some 

of the quantitative estimates presented in this report may require 

revision as new data become available or if the use of water changes 

materially. To complete a comprehensive water-resources inventory, 

insofar as possible, to refine and check the conclusions reached during 

the present investigation, and to evaluate the long-term effect of 

water use upon the hydrologic regimen, the investigative studies outlined in the following paragraphs are recommended, to begin as soon 

as possible.

STREAMFLOW

For a continuing evaluation of the inflow-outflow relationship of 

Ahtanum Creek, the records from the existing gaging stations on the 

North and South Forks of the creek need to be supplemented by additional streamflow data at its mouth. Therefore, permanent reestablishment of the former gaging station on Ahtanum Creek near Union 

Gap is recommended. In addition, a station at the Narrows would 

provide data for determining seasonal gains and losses in streamflow 

within the upper or lower parts of the valley.

Additional data are needed also on the flow of Wide Hollow Creek 

to determine gains or losses in the stream as it traverses the lower 

Ahtanum Valley and to establish its relation to the water table in that 

part of the area. A gaging station located near its mouth would be 

required to provide adequate data on the outflow from the creek; 

another gaging station near the Yakima Airport would be required to 

measure the surface inflow to the lower valley.

The present estimate of ground-water discharge from the Ahtanum 

Valley to the Yakima River probably could be refined if additional 

data were available on the gain in flow of the river in the reach adjacent
PROBLEMS OF FUTURE WATER SUPPLY 65

to the valley. This would necessitate at least one additional gaging 

station, on the river upstream from the project area and below the 

confluence with the Naches River, to provide records to supplement 

those from the existing station at Parker. However, much better 

results would be obtained if the downstream record were collected in 

Union Gap (below the mouth of Ahtanum Creek) rather than at 

Parker.

GROUND WATER

Periodic field canvasses should be made of newly constructed wells, 

particularly those of modera/te or large yield, to fill gaps in current 

information on the availability of ground water in various parts of the 

area, on the extent and yield of the aquifers, and on ground-water 

levels.

The network of observation wells used in this investigation 

should be expanded and maintained on a continuing basis to define 

more accurately the seasonal fluctuations of water levels and artesian 

pressures and to give early warning of any possible overdraft from the 

aquifers. The network should include at least a few wells tapping 

each aquifer and as many of the irrigation and other large-yield wells 

as possible. The elevations of the measuring point at each well on the 

network should be established precisely by leveling. In the eastern 

part of the lower valley, relatively close spacing of observation wells 

tapping the unconsolidated alluvium will be necessary to determine 

whether a clearly defined ground-water divide exists between the lower 

Ahtanum Valley and Wide Hollow.

WATER USE

Inasmuch as the amount of water used in the Ahtanum Valley varies 

from year to year, a continuing appraisal of water use for all purposes 

from both surface- and ground-water sources is needed for effective 

management of the water resources. Data on annual withdrawals 

from wells are especially important as a possible means of determining 

optimum yields of some of the aquifers where the withdrawal can be 

related to water-level changes.

PRECIPITATION

In order to determine the total amount of water entering the 

Ahtanum Valley, it will be necessary to refine the estimates, made in 

this report, of the distribution of precipitation throughout the valley. 

Operation of additional precipitation gages on the floor and slopes of 

the upper valley for at least a few years probably would yield the data 

required.
66 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

REFERENCES CITED

Beck, G. F., 1940, Late Tertiary stratigraphy and paleontology of south-central 

Washington and adjacent Oregon [abs].: Geol. Soc. America Bull., v. 51, 

no. 12, pt. 2, p. 2018.

Foxworthy, B. L., 1953, Ground water in the lower Ahtanum Valley, Washington 

and' possible effects of increased withdrawal in that area: U.S. Geol. Survey 

open-file report, 26 p., 1 pi.

Foxworthy, B. L., and Washburn, R. L., 1957, Ground water in the Pullman 

area, Whitman County, Washington: U.S. Geol. Survey open-file report 122 

p., 8 pis., 9 figs.

Gatewood, J. S., Robinson, T. W., Colby, B. R., Hem, J. D., and Halpenny, 

L. C., 1950, Use of water by bottom-land vegetation in lower Safford Valley, 

Arizona: U.S. Geol. Survey Water-Supply Paper 1103, 210 p., 5 pis., 45 figs.

Kinnison, Hallard B., 1952, Evaluation of streamflow records in Yakima River 

basin, Washington: U.S. Geol. Survey Circ. 180, 38 p., 1 pi., 2 figs.

Mackin, J. H., 1947, Diatomite deposits in eastern Washington [abs.]: Northwest Sci., v. 21, p. 33.

Merriam, J. C., and Buwalda, J. P., 1917, Age of strata referred to the Ellensburg 

formation in the White Bluff of the Columbia River: California Univ. Pub., 

Dept. Geology Bull., v. 10, p. 255-266.

Piper, A. M., 1944, A graphic procedure in the geochemical interpretation of 

water analyses: Am. Geophys. Union Trans., v. 25, pt. 6, p. 914-923.

Russell, I. C., 1893, A geological reconnaissance in southeastern Washington: 

U.S. Geol. Survey Bull. 108, 108 p., 12 pis.

Sceva, J. E., 1954, Geohydrologic evaluation of streamflow records in the Yakima 

River basin, Washington: U.S. Geol. Survey open-file report 129 p., 3 pis., 

18 figs.

Smith, G. O., 1901, Geology and water resources of a portion of Yakima County, 

Washington: U.S. Geol. Survey Water-Supply Paper 55, 68 p., 7 pis.

 1903, Description of the Ellensburg quadrangle [Washington]: U.S. Geol. 

Survey Geol. Atlas, Folio 86.

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

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

Am. Geophys. Union Trans., p. 519-524.

Tolman, C. F., 1937, Ground water: New York, McGraw-Hill, 593 p., illus.

Twiss, S. N., 1943, Report on ground water in Ahtanum Valley, Yakima County, 

Washington: U.S. Soil Conserv. Service duplicated rept., 10 p., illus.

Warren, W. C., 1941, Relation of Yakima basalt to the Keechelus andesite series: 

Jour. Geology, v. 49, no. 8, p. 795-814.

Washington State Legislature, 1945, Ground water code relating to the regulation and control of certain ground waters within the State and rights to the 

use thereof, chap. 263 of Session laws, 1945: Washington Dept. Conserv. 

and Devel., Div. Water Resources, 18 p.

Waters, A. C., 1955, Geomorphology of south-central Washington, illustrated by 

the Yakima East quadrangle: Geol. Soc. America Bull., v. 66, p. 663-684.

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

materials, with special reference to discharging-well methods, with a section 

on direct laboratory methods and bibliography on permeability and laminar 

flow, by V. C. Fishel: U.S. Geol. Survey Water-Supply Paper 887, 192 p., 

6 pis.

Wilcox, L. V., 1948, The quality of water for irrigation use: U.S. Dept. Agriculture Tech. Bull. 962, 40 p.
BASIC DATA

67
TABLE 4. Records of representative wells in Ahtanum Val

[Locations of wells are shown on pi. 1]

Topography:

Ap, alluvial plain; As, alluvial slope; S, slope; Ub, Upland bench; V, valley. 

Land-surface datum: Approximate altitude of land-surface datum at well interpolated

from topographic maps.

Type of well: Bd, bored; Dg, dug; Dn, driven; Dr, drilled. 

Depth to water level: Measurements made by the Geological Survey expressed in feet

yp

S, suction; T, tu

Use of water: D, 

irrigation; PS, p

dicates former u

Remarks: C, com

In flowing wells, "+" preceding the water-level measurement indicates static head in table 5; temp

in feet above land-surface datum. "Flows" indicates unmeasured static head.

Well Owner or Tenant Topography

Altitude ofland- surface datum

(feet)

Type of well Depth of well

(feet)

Diameter ofwell

(inches)

Depth of casing 

(feet)

Water-bearing zone(s)

Depth toop

(feet)

Thickness 

(feet) Formation an

Material

T. 12 N., R. 15 E.

13R1... William Monder.. Ap 2,180 Dr..... 329 16 50 53 Yakima basalt. 

T. 12 N., R. 16 E.

4H1.__. 

4J1. .

4R1....

8H1- 

8N1- 

W. H. Shuck ...... 

Anna G. Aumiller.

M. D. Spohn..... 

Vernon Mondor ...

Ub 

Ub

Ub 

Ub

Ub

2,180 

2,180

2,160 

2,250

2,200

Dg 

Dg

Dg 

Dr

Dg

48 

51

19 

380

30

48 

54

2 

10-8

48

4

19 

380

Ellensburg form

tion (clayey 

sand). 

Ellensburg form

tion (clayey 

sand).

Cemented basa

gravel (?).
9H1

9M1

10N1...

1 1 VI

13D1...

13H1...

14F1 .

15D1...

17D1...

17J1. 

1 *7V1

18A1

18B4...

M A Lesh

__ do... _ .. __ .

 ..do...... ...

TTb

TTb

R

V

Ap

Ap

Ap

Ap

Ap

Ap

Ap

Ap

Ap

An

Ap

Ap

Ap

An

An

2,080

2,150

1,990

1,850

1,750

1,690

1,700

1 830

1 960

I'goo

i onn

1,870

2 160

2,050

9 Oftn

2,110

2,120

2,200

2,110

Dg

Dg

Dr

Dr

Dr

Dg

Dg

Dr

Dn

Dr

Dr

Dr

Dg

Dg

Dg

Dr

Dr

Dr

Dr

Dr

16

18

i ift

9

13

160

Q

598

544

43

20

11

19

100

16

196

987

36

6

6

14

8

36

24

1W

12

10-6

12

1J4

60

24

6

6

8

14-7

19

72

27

255

278

42+

0

12

90±

287

40

130

235

411

210

10±

58

gravel(?). 

.. ..do _ . ___ 

 do ... 

.....do ___ . ..

Alluvium (grav

_ ..do. -... 

Yakima basalt. 

 do. . 

 ..do.- _ . __

Alluvium (grav

coarse, unsorted).

Cemented basa

gravel(?).
TABLE 4. Records of representative wells in Ahtanum Valley, Yak

Well Owner or Tenant Topography

Altitude ofland- surface datum 

(feet)

Type of well

a

*3I 

S?

Diameter ofwell

(inches)

Depth of casing 

(feet)

Water-bearing zone(s)

Depth toop

(feet)

Thickness 

(feet) Formation and 

Material

T. 12 N., R. 16 E. Continued 

18K1... 

18LL 

Ap 

Ap

2,110 

2,130

Dr 

Dg

343

18

8-5 

36

315

15± 4 14

Yakima basalt ..

Alluvium (sand 

and gravel).

T. 12 N., R. 17 E. 

1B2. ... 

1DL...

1E3.... 

1G2....

1J4- .

ILL....

1M2 ....

1N1..._ 

1P1 

2AL...

Lane Ferguson .... 

H. C. Wilson. .... 

O. J. Bayle. .....

Lyman Lennington. 

B. E. Snelling .....

Lyman Lennington. 

R. Shaw. ........

Arthur Fulbright.

Springbrook 

Dairy.

S. T. Ray .........

Ub 

Ub

Ub 

Ub

Ub

Ap 

Ap

Ap 

Ap

Ap 

Ub

1,310 

1,350

1,360 

1,360

1,280

1,280 

1,320

1,360 

1,350

1,300 

1,400

Dg 

Dr

S

Dr

Dn 

Dr

Dr 

Dr

17 

180

47 

159

200

15 

33

4

77

79 

198

72 

6

48 

6

6-5

1J4 

6

96 

6

6 

6

6 

180

100± 

200

20

10

197±

29

7

3±

Cemented basal

gravel. 

Ellensburg form

tion.

mation. 

Ellensburg form

tion (coaise 

sand).

Alluvium (sand 

and gravel).

Cemented basal

gravel. 

Alluvium(?)

Ellensburg form

tion.
2J2

2J3

2K1._._

2N1-... 

2P1 -

2P2 - 

2Q1 -

2Q3 -

2R1-.--

2R2..-. 

3A1 -

3B1_._..

301 

3Dl..-_

3E1..... 

3J1

3M2 .

3M3-...

3Nl..-_

4F1._ 

FloydWillard- 

 -do-. - ...

Gilbert Orchards, 

Inc.

Gilbert Orchards, 

Inc. 

Conrad Kuhl

J. A. Richartz, Jr. 

RuthKerl... .....

E. Spohn__-._ ....

FloydWillard---.

Frank Glaspey __ 

Olaf Lawrie .......

Henry Carlson __

M. W. Beecham--

N. S. Kelly- ......

E. H. Lovestrand. 

G. E. Clasen ......

A. V. Anderson. 

F. T. Tissell ___

Carl Nystrom .._..

C. R. Holtzinger 

Ub

Ub

Ub

Ub 

Ap

Ap 

Ap

Ap

Ap

Ap 

Ub

Ub

Ub

Ub

Ub 

Ub

Ub

Ub

Ub

Ub

1,400

1,400

1,460

1,390 

1,380

1,380 

1,390

1,380

1,350

1,325 

1,510

1,540

1,550

1,580

1,580 

1,510

1,560

1,600

1,600

1,630

Dr

Dr

Dr 

Dr

Dg

Dg

Dr

Dg

Dr

Dg

Dr

Dr

Dr

Dr

Dr 

Dr

Dr

Dr

Dr

Dr

92

94

160

11

16

75

16

489

107

92

319

125

90 

160

118

262

100

80

66

6 6466

366

3666

5H6

6 6666

6-4

40

40

42

60

90

40±

60

60

90±

Of) _i_

13

90±

300±

Ellensburg form

tion (black 

sand). 

- _ do-- ___ - 

tion(?) 

Ellensburg form

tion (?). 

Alluvium (grave

. __ do- __ 

gravel(?).

and gravel) . 

Alluvium (?)

(coarse gravel)

tion(?).

tion (sand).

(?).

tion(?). 

- .do. _ . 

tion.

tion.

tion(?) (sand 

and gravel).
TABLE 4. Records of representative wells in Ahtanum Valley, Yak

Well Owner or Tenant Topography

Altitude ofland- surface datum 

(feet)

Type of well

a

o>

"3^

Diameter ofwell

(inches;

Depth of casing 

(feet)

Water-bearing zone(s)

Depth toop

(feet)

Thickness 

(feet) Formation and 

Material

T. 12 N., R. 17 E. Continued 

4H2-...

4P1 __

5B1 ..... 

5E1 .....

6F2 .. 

6J1-... .

J, E. Borton &

Sons.

__ do .............

L. H. Mansperger.

C. E. Kuhnke....

Cohodas, Lancaster, Frank Co.

 do... ..........

E. L. Lenington..

Otis Bailey. ___ .

Peter Pan 

Arendonk.

Gilbert Orchards, 

Inc. 

E. F. Morozzo

George Weaver ....

Ub

Ub 

Ub

Ub 

Ub

Ub 

V

V 

Ub

Ub 

V 

V

1,600

1,590 

1,590

1,630 

1,600

1,600 

1,560

1,620 

1,650

1,740 

1,680 

1,680

Dr

Dr 

Dr

Dr 

Dr

Dg 

Dr

Dr 

Dr

Dr 

Dr 

Dr

360

235 

101

240 

397

39 

170

117 

215

315 

159 

140

6

6 

6

48 

6

6 

6

6 

6 

6

80

235 

0

77

10

294 

44 

140

110

160

204

306 

140

"Few 

feet"

10

10

Ellensburg forma

tion (sand).

- do....... 

Ellensburg forma

tion (?).

Ellensburg forma

tion (sand). 

__ do _ . ..

Cemented gravel

Ellensburg forma

tion (sand).

Ellensburg forma

tion. 

Ellensburg forma

tion (sand and 

gravel). 

Ellensburg forma

tion. 

Ellensburg forma

tion (sand). 

Ellensburg forma

tion.
6J2

7R1

8C1 __

8G1 .....

8J1

8K1....

8R2....

8R3-...

901 .....

9E1 ._

9H1-...

9J1

9J3- 

10A2- 

10B1- 

10C1

1002

10E1 .

10H1 

10J1 

10N1... 

10N3-.

10R1...

11A1 _

 .do 

E. E. Orosno ......

John Austin .......

Volney Eglin 

__ do. - _ ......

Merle Carson... 

A. W. Qrissom ....

James Bowers _____

F. M. Stull &

Son.

Dean Rutherford

R. J. Schmella-- 

Walter Mclnnis _

Walter Mclnnis

(formerly

Marks School).

C. L. Lester..

Claude Ekland- 

 _ _do .... ... ...

 do 

Marian and Irene .

Hall.

Alex Iriarte.. _____

C. R. Holtzinger..

William Hunger _ 

Leland Torson. _

C. R. Karney __

Gilbert Orchards,

Inc.

V

Ap

Ub

Ap

Ap

Ap

Ap

Ap

Ub

Ap

Ap

Ap

Ap

Ap

AP

A rk AP

Ar» AP

Ap

Ap

Ap

AP 

Ap

Ap

Ap

1,680

1,620

1,700

1,560

1,550

1,570

1,530

1,550

1,610

1,520

1,460

1,450

1,470

1,400

1,420

1,420

1,420

1,450

1,380

1,390

1,450

1,440

1,390

1,347

Bd

Dg

Dr

Dg

Dg

Dr

Dr

Dr

Dr

Dr

Dr

Dg

Dr

Dr

Dr

Dg

Dr

Dg

Dg

Dr

Dg

Dg

Dn

Dr

35

12

320

12

14

100

22

410

91

80

157

575

33

358

470

10

13

100

30

11

18

786

6

1*_ 68

168

8 666

36

VA8

36

48

488

36

362

10

0

12

60

245 

68

sn8

330

80

30

11

787

37

 

70

248

5224

805

 

25

159

53

12

do ___

Ellensburg forma

tion. 

Alluvium. __ . _ 

_ __ do .. ___

Ellensburg forma

tion (sand).

Yakima basalt- _ 

Cemented basalt

gravel.

Alluvium.-.-. .

 do 

gravel).

tion (clay and 

shale).

gravel).

gravel(?).

Cemented basalt

gravel, Ellensburg formation
TABLE 4. Records of representative wells in Ahtanum Valley, Yak

Well Owner or Tenant Topography

Altitude ofland- surface datum 

(feet)

Type of well 1 

o

Diameter ofwell

(inches)

Depth of casing 

(feet/

Water-bearing zone(s)

P. o

o

i?

g-g P"

Thickness 

(feet) Formation and 

Material

T. 12 N., R. 17 E. Continued 

11A8-- 

11A9-- 

11B2--

11C1 .... 

11D1...

11D4...

11M1 ... 

11N2...

12C1 . 

12D8--

12H3~~rr 

12K1...

School District 

128. 

 ..do ..... .

W. H. Neumiseter. 

Shirley Ward--. .

Manuel MeCully.

Ernest Bitz.. .....

Shirley Ward ......

Phillip Meyer 

Henry Dinzl __ 

Otis Goode ___ .

H. E. BrownleyAllen Shockley-.-. 

E. S. Shockley. ...

Ap 

Ap 

Ap

Ap 

Ap

Ap

Ap

Ap 

Ap

Ap 

Ap

Ap 

Ap

Ap 

Ap

1,330 

1,330 

1,360

1,370 

1,380

1,370

1,390

1,380 

1,360

1,300 

1,330 

1,320 

1,280

1,290 

1,300

Dr 

Dr 

Dn

Dg 

Dg

Dr

Dr

Dg 

Dr

Dg 

Dg 

Dr 

Dr

Dg 

Dn

30 

101 

11

14 

10

390

30

10 

35

8 

8 

26 

25

12

6 

6-4 

2

36 

96

10

6

30

6

36-6 

36 

6 

8

8 

2

30

35 

4

26

33± 

3

4+

Alluvium. ....._._

Cemented basalt 

gravel.

 do. . __ .

Alluvium (gravel

Ellensburg forma

tion (?).

Cement basalt 

gravel (gravel 

and sand).

Alluvium (gravel

....-do..... ..

Alluvium, ._._...

.... .do ..

___ do ...
iqTi

14H2--.

15N1...

16D1...

16D3-,- 

16Q1---

16R1.-.

17O1

17O*>

17G2

17H1--.

17J1- 

18H1-.-

Bros. 

Adaline Um-Tuch.

Sons. 

Robert F. Wiley_.

Jack Sehreiner.--. 

Kenneth Withers.

B. 8. Borton & 

Sons.

.. do-. . ...

 do..... .....

An

As

Ap 

Ap

As

An

Ap

Ap

As

As 

Ap

An

An

An

An

Ap

An

1,310

1,370

1,350 

1,395

1,510

1,460

1,530

1,510 

1,530

1,550 

1,670

1,570

1,570

1,540

1,540

1,610

1,610

Dr

Dr

Dr 

Dr

Dr

Dg

Dg

Dr 

Dg

Dr 

Dr

Dr

Dr

Dg

Dg

Dg

Dr

31

100±

31 

17

140

12

10

384 

11

1,078

OJQ

56

6

8

15

4

lift

6

6 

6

6

12

1J4

10 

1

12-6^

ft ft

6

82

1J4

60

36

6

22

312

940 

243

30±

15

4

40

 _.

325

1035 

204

16

15

1

 

59

38 

36±

14

Cemented basal

gravel (?). 

__ do .. __

Alluvium. . _____

.....do __ _ 

Cemented basal

 . .do.... ... 

Yakima basalt- 

Yakima basalt. 

__ do _ 

Alluvium and ce

mented basalt 

gravel.

Ellensburg form

tion (sandston

Alluvium (san

and gravel). 

Alluvium (grave

and gravel).
HOO BO § <O W M Q J3td (*} 

i ! i ' ' r i ' i ' i 

|| 1 j" f 1 , o f 5 

f5f Pi |i | ^t I if i 

*?f i 1 B ^ F ~ P' Pi f 

££££££ £ £ £ £ ££ £ 

§ i 

t-- Hill i§ i § I § i i 

000 00 0 0 0 0 0 00 0 

B'lW ^f "" "" B n n "SB B 

ooeoo ooo o to o en co EStj tj 

?

o 

M i-> * ao * 001-' >-> 

tS^ iS-^ ^ ^ 

CO

<Si

Cemented basalt

gravel. Alluvium. __ ..

« S 

r r 

r r 

Cn Oi 

H^ 1-^ 

00 w 

co en 

tO i^ Oi !*.. <! 

WO OO Cn O OS CO H~

g CO 

os o oo o to 

H-

§ X§ X P^B g§ ^§ 

p- B ^ s P.B P. 

>fk to Cn <D <! Ji 

Cn to O) to O 

CO 1 I- tO M 

**j ' i oo os ~i 

en co en en en n 

1 OH- 1 I- IO 1 I- h-* 

co O 2, ^ ^O^ 

O i en ) 

s

o

Alluvium __ (silt) Alluvium (gravel). Alluvium .. ___ do_- _____

os o to 

5< en n 

OJCDtd J3 

»i ! 

000 0^ ^ 0 ^ 3* 0 SO 0 

d w cj H "_ p. 

§ q 

rt- ».rt- 3 HO^SS'O^S w® * i * ** pf 03 CT B* fi t±¥3 SD 

i n n p ^ isiili 

I 1J i| i Hljlj 

§ " S ^ S.? "M oj ° 2. 8= S ' 1?" (2 2 

S, »<S Pco^ °C: S B S »> 5. 

^ ogfi KgS P B »ST 

H

b

CO

K

I

o

I

Topography

land- of Altitude 

datum surface 

(feet)

well of Type 

well of Depth 

(feet)

well of Diameter 

(inches)

casing of Depth 

(feet)

top to Depth 

(feet)

Thickness 

(feet)

and Formation Material

(feet Depth 

land- below 

surface 

datum)

meas- Date 

ured

Type

Horsepower

1

f

I 

<

1

water of Use 

Remarks

h 

> 

tJ

& 

4

K

«

C

Cr

«s

5 

t* «Cr

0

1

^.

1 

1

?*

§

^. 

 

& 

I

i

r 

8r«

<?

a

0

s 

sC"1

s 2

^

s

c

r

t 

o

92,

' aJSUlOHD ' MONVJ,HV ' HSVA1 
2L1-. ...

2N1 . 

2Q1 -.

SOUSES 

3F1 .....

3H1..._

3K4____

3M3 .... 

4F1. 

4R1.-..

6A1 ..

602.- 

603 -

607--.

5D1___-

6E2--. 

6E3-.--

5G1..-- 

6O2 .

5H1___.

5J1...-. 

6J3- 

6M1- 

5M2. ... 

5M3. ... 

5M5_ ...

Riley Kelly. ......

L. C. Moorehead 

Roy Purviance .... 

Harold Armstrong 

D. F. Woerner ....

R. E. Davis ___

Herman Center ...

David Pattison...

R. B. Shoemaker. 

J. H. Rettig... .

Claire Van Eaton, 

-....do .

 . -do... . 

Maurice Renville.

A. J. Mowatt__ _

Mrs. Flora Rush.. 

H. E. Anderson.. .

Joel Richwine._ _

G. E. Stewart __ ...

George Ashbaugh. 

Benjamin Wagner.

Ap

Ap 

An

AP 

Ap

Ap 

Ap

Ap

Ap 

Ap

AP 

A n

Ap 

Ap

Ar>

Ap

Ap

An

Ap 

Ap

Ap

Ap

An

Ap

Ap 

AP

Ap

1,050

1,060 

1,040

1,105 

1,100

1,100 

1,070

1,080

1,100 

1,130

1,100 

1,180

1,190 

1,190

1,190

1,210

1,205 

1,200

1,190 

1,190

1,180

1,170 

1,165

1,210

1,205 

1,210 

1,210

Dg

Dn 

Dr

Dg 

Dn

Dg 

Dn

Dg

Dg 

Dg

Dn 

Dg

Dg 

Dr

DR

Dn

Dg 

Dr

Dn 

Dg

Dn

Dg 

Dr

Dg

Dg 

Dg 

Dg

15

13

41 

11

13g

189

15

12

27

11 

13

285

15

20

17

27

10

20

18

280 

169

15

14

48

1H

8 

16

1J4

on

1J4

48

48±

362

48 

248

14

366

1J4

30

154

308

79

36

72

AQ

15

41

12

27

12

205

18

203

 -

33

17

275 67

 9

12g

5 

10+

15+

Alluvium (silt?).

Allu vium (?)--.. 

 -do 

 -do . .

- do 

and sand).

Alluvium (grave

and sand).

(gravel?)

gravel.

gravel (?).

and gravel). 

_____ do.---. . 

and gravel) .

Ellensburg forma

tion (sand).

. .do------ 

and gravel).
OS O5 OS OS O5O5 

- P3 S^ SS 

J. R.Pittman _____ _ Tyler ,Riy Ernest Ests J. W. _ Mudd... W. GCampbell.. Mrs. Lillian

££££££

to to to to ' to to 

JS* H^ OO Cj« Ol (^ 

d d dd dd 

OTQ QTq P 0q QTq Jq 

O5 O5 

O td 

bO f 

Ol O5 O5 O5 O5 O5 

S ^ ^ bO S ^ 

? ^ 22 - | « 

n 1-3 1 5 P hj^ S<? 5 w 

ill! ! Sp- s * i CD J3 Cfl 

03-;! £T 

| J oj O p 

£ £ 

1 I 

x d > > > > 

1 g i i i § 

dd dd Odd d 

+1+1 rrqorq orq orq OTQ orq 

fcO l fcO-^J COO 

S£OS£ O bO ife 00 S O S£ O 

s « 

* f! 

. O5 COI H-!

 _- do---. __ do---.. _._.._. Alluvium.- __ . Alluvium (gravel, 

loose). Alluvium.- 

 do-.-. 

to >K OS W OS 

Q & 1 I- O5O 

£ S S XS 

i-3 1-3 CQCQ _j{Q 

Oi Ol 

g

oo 

OJ

M

-

§ § 

cS 5 S CD H- nhK 1 I- W 

O5 O5 00 00 O5 

. 8 . - = 

f

CD <I 

+ -1- 

__ ° _ § -^_ > 

2* B 3 B 4| § 3 3^ S" i 

^ & »<5 »<2 5. ^. 5 

^ilp' i^l i 

rjL'S' g o" g m^ 

p. £.' & EL & 1 

tO CO 

bO ~J 00 W O5 

Hi ii r "T* V f 

^ i " f f f f 

CJi *» Cn CJi Ol CJ1 Ol 

gj «H CQ Q CQCQCQ "-.Si CQ 

"I £ ~ *** | " * 1 M £* ~ 

5|§ STST §S ds: ffd o s! s? _» 

d » d " HH 

hjCQ CQCQ "flCQQ hj hj 1 CQC

c; M2i5*'' c: »2 §"2 § B » SI? a w H Ef TO' IT 

p p «!! 

* ?Ii a ^i-8- sgSll r l r 9« Hi_H 11! 

M iwSg ¥» 5 1 ^'coS 1 S "" P 

ct- I P- O >-t CO >-l ^ 

T. 12R ISE. Continued N., 

1

O 

»

S 

I

Topography

land- of Altitude 

datum surface 

(feet)

well of Type 

well of Depth 

(feet)

well of Diameter 

(inches)

casing of Depth 

(feet)

top to Depth 

(feet)

Thickness 

(feet)

Formation andMaterial

(feet Depth 

land- below 

surface 

datum)

meas- Date 

ured

Type

Horsepower

Water-bearing zone(s)

Water level

c

water of Use 

Remarks

h 

> 

6

. 

\f

h 

(

r 

c

<s

c

c o 

c

c 

e

« 

§

I

O 

« 

i

? ?

s»

i<c

h 

«

?

{

C"

NC

<n 

P

' HONVXHV 
6R2. _.

6R3-... 

7A1

7B2- 

7E1_ . 

7J1 

7K1__-

7M1....

7Q2 

8A1 ._

8B1_ .

Q"T\O

8G1---.

8J1- 

8K1....

8N1..._ 

9L1.. 

.....do...... 

Fred X. Savage. 

Gene Woodcock ...

Mrs. Mary 

Rnyder.

A. W. Knight.....

H. B. Fairbanks ..

Mrs. Tony 

Coupal.

Vernon Mondor ... 

Carrel Morton....

.....do.... .....

P. J. Vetsch _

William Adam .... 

Walter R. Ready..

Ap

Ap 

Ap

Ap 

Ap

Ap 

Fp

Ap

Ap

Ap 

Ap

Ap

Ap

Ap

Ap

Ap

Ap

As

1,230

1,225 

1,225

1,240 

1,260

1 260 

1,230

1,240

1,260

1,260 

1,180

1,180

1,210

1,200

1,200

1,210

1,270 

1,210

Dg

Dr

Dg

Dg 

Dg 

Dr

Dr

Dg

Dg

Dg 

Dr

Dr

grg

Dg 

Dr

Dg

Dr

12

21

14

15 

12 

30

362

15

16

20 

100

635

17 

103

38

85

60

49

363

36

37 

30 6

8-6

72

36

60 

10

12

48 6

5 6

366

....do- _--_-- 

Alluvium (grave

Alluvium.... ..

....do... ... ... .

Alluvium (grave

Ellensburg form

tion (sand).

Alluvium (grave

.-.do.... ......

....do ... ... .

Ellensburg form

tion (sand). 

... .do...... .

Alluvium.. __ 

tion (sand). 

Alluvium (?)_-. 

tion (sand).

Cemented basal

gravel (?) (sand 

and gravel).
TABLE 4. Records of representative wells in Ahtanum Valley, Ya

Well Owner or Tenant Topography

Altitude ofland- surface datum 

(feet)

"3 

o

EH

Depth of well

(feet)

Diameter ofwell

(inches)

ho

.s

"3

5?

Is

Water-bearing zone(s)

Depth toop

(feet)

Thickness 

(feet) Formation and 

Material

T. 12 N., R. 18 E. Continued 

10D1__- 

10D2_._

10H1.--

11D1--- 

11E1_ 

11E2 __ 

HJl-___

12C1- 

12E1 _ _ 

12K1_._

Axel Erickson __ 

 __do . _________

Masterson 

Pahosta & 

Parchese 

Wolloack. 

R. L. McDougal, 

Sr. 

S. H. Schreiner __

Fred Westburg __ 

A. W. Sapp_______

Harry Qimmaka- -

Thurman 

Schuttle. 

Wade Langell __

As

As 

As

Ap

As

As 

As

Ap

As 

As

1,150

1,150 

1,200

1,100 

1,170

1,185 

1,190

1,110

1,105 

1,140

Dr

Dg 

Dr

Dg 

Dr

Dr 

Dg, Dr

Dr

Dr 

Dr

300

24 

100

17 

213

183 

127

245

72 

225

8

96 

6

6 

5

6 

6

8

6

5

68

151

165 

80

45

55 

220±

205 

180

245 

60

8 

3+

8+

Ellensburg form

tion (sandy 

clay).

Ellensburg form

tion (sand and 

gravel).

Ellensburg form

tion (sand). 

Cemented basal

gravel(?) .

Ellensburg form

tion (sand).

Ellensburg form

tion (sand). 

Ellensburg 

formation (?).
17C1- 

18D1.--

As 

Ap

1,280 

1,300

Dr 

Dr

60 

28

4 

6

65 60± 5+ Ellensburg form

tion (sandston

Cemented bas

gravel (?).

T. 12 N., R. 19 E.

5E1____.

5E2__ 

5F1_ _ 

5F2_ 

5M1_ _ 

5M2. _

5N1._._ 

6A1 _

La Casa Motel.. __

State of Washington, Dept. 

of Highways. 

__ do.... ...... ...

City of Union 

Gap.

- do- ... .....

City of Union 

Gap.

N. C. Root... __ .

Ap 

Ap

Ap

Ap 

Ap

Ap

Ap 

Ap

980 

980

980

980 

980

980

975 

990

Dg 

Dr

Dr

Dr 

Dr

Dr

Dr 

Dg

8 

68

26

75 

215

217

370

7

36 

6

6

6 

12-10

12-10

12 

3

68

26

75 

215

198

370 

9

187 174

Alluvium 

(sand and 

gravel). 

Alluvium (grave

-..-do........

Cemented bas

gravel(?). 

Cemented basa

gravel.

. do. 

Cemented basa

gravel (sand 

and gravel) .

Alluvium (grave
ii

to

(sandstone) (sandstone)

1

t-

%

£

Congdon 

Orchards.

 o

i

a -j

to

wo

g

g

8

for- Ellensburg 

mation (sand- blue). stone, 

8

T

5

51

At 873ftlowed 13 

at 1220 ftgpm; flowed 112 gpm; ft a1252flowed in 3001912; gpm flowed 50 ingpm 

£J 

O

i

sf

p M 

® * 

5

Ti 

 O

8

O

I

to

Nt-> O 

g

cn

*5

Si

1

££

i

CO

T

S

S5

!

S5

d

for meatpackin plant. Oil testflow well;

intermittently;

"N W £H 

Oi Oi Cl 

H l! s 

wj

HP

1

1 p 

> > > wo o 

§i i 

aa a 

-ip i 

00 CO 

h- oo at 

00 CO 

Cn tO 

0> > 

£" o ? £* 

Ittl § 

^*l fl 

P3 < 

, ^^ CD 

^!- P 

1 i- to 

O5 O 00 

J£ S 

^co 0 

5 M 

W D P 

ft ft 

co hd 

§If-i ill lltsf 

-^P-ft 'rB«D.g (I< |3

g>« °-ao| !'»§" 

^1 8| 5| D ||

^-O ?^ T> K (D 

O3

M

S

o

i

> 

 a

i

a>-j

S

,^

to

o

H-

+

>-

'*"£'

< p 

ftp

T5

w

1-1

r

?w

CO

S

O

Soil t7"hard- ft,

10 toft; pan" 

? B 

Topography

land- of Altitude 

datum surface 

(feet)

well of Type 

well of Depth 

(feet)

well of Diameter 

(inches)

casing of Depth 

top to Depth 

(feet)

Thickness 

(feet)

(feet Depth 

land- below 

surface 

datum)

meas- Date 

ured

Type

Horsepower

water of Use 

w 

g 

!** 

? 

o

8-

 5,

S3

^ 

Ss

I

£

O

§!±

13 

C

'jLQOIOaQ HajLVA\ ( KOKVJLHV 
29Q1 

.

QOTl

QOT>1

32R1-.-

33L3 ....

33L4. ...

33M1 ...

33N1-.-

oq'M'O

34J1- 

34M1 ...

35J1____

35R1...

36J1- 

36J2 .

36K1...

36P2 __

Estate.

G. E. Stewart __

 .do.... 

 .do..... -

School. 

R. H. Crow __ .

E. J. Crawford . 

Edgar A. Pearson.

Service.

ton Fish Hatchery.

R. L. Epperson.-.

AlHort Wpllnpr

Thomas H. Pollock.

Ap

Ap

AP

Ap

Ap

Ap

Ap

Ap

Ap

Ap

Ap

Ap

Ap 

Ap

Ap

Ap

Ap

Ap

Ap 

Ap

Ap

1,190

1,190

1,220

1,190

1,180

1,170

1,170

1,160

1,170

1,180

1,180

1,180

1,100 

1,130

1,070

1 060

1,040

1,030

1,040 

1,050

1,040

Dr

Dr

Dr

Dg

Dg

Dr

Dr

Dg

Dr

Dg

Dg

Dr 

Dg

Dr

Dr

Dr

Dn

Dg 

Dg

Dr

1267

257

 w9

22

17

137

34

on

613

15

17

10 

17

69

65

87

28

16 

15

45

6-3.566

48

72-4

36

10638

30

30

8 

308666

18 

is6

22

20

49.5

35

600

...... .

16

800

1,000

1,050

119533

4±

55

12

18+

30+

17+

17+

ll"8

4+

tion.

tion(?).

.... do..-.. 

Ellensburg forma

tion (sand and 

gravel). 

Alluvium (gravel

and gravel).

tion (sand and 

gravel). 

Alluvium (grave

....do.. 

Alluvium- _ ...

Alluvium (sand 

and gravel).

gravel(?). 

....do..-- 

Alluvium (sand

and gravel). 

Alluvium (grave

Cemented basalt

gravel(?) (sand 

and gravel).
TABLE 4. Records of representative wells in Ahtanum Valley, Yak

Well Owner or Tenant Topography

Altitude ofland- surface datum

(feet)

Type of well Depth of well 

(feet)

Diameter ofwell

(inches)

Depth of casing 

(feet)

Water-bearing zone(s)

Depth top

(feet)

Thickness 

(feet)

Formation and 

Material

T. 13 N., R. 19 E. 

31J1- 

31K2.--

31K3... 

31M1-.

32L1.... 

32M1__.

32M2 

32M3... 

32M4 

Yakima Farmers 

Supply Co.

J. F.Scott.... ...

George Hargraves.

Niagara Chemical 

Corp. 

H. P. McGlothern.

Frederick Mercy 

Yakima Cooperative Association. 

Forney Fruit & 

Produce Co.

Cascade Casting 

Co.

Sears Lumber 

Market.

Ap

Ap 

Ap

Ap 

Ap

Ap 

Ap

Ap

Ap 

Ap

1,015

1,010 

1,015

1,010 

1,025

990 

1,005

1,005

1,005 

1,000

Dr

Dg 

Dg

Dr 

Dr

Dr 

Dr

Dr

Dr 

Dr

84

3 

14

38 

20

36 

40

125

42 

42

6

120X240 

36±

6 

6

6 

6

8

6 

6

84 

3+

38

39 

38

82

42± 

42

31 9+

Cemented basalt 

gravel(?) (sand 

and gravel). 

Alluvium (gravel

 .do.-.. 

 -do--. . 

Alluvium (sand 

and gravel).

Alluvium (gravel

Cemented basalt 

gravel(?) (sand 

and shale) . 

Cemented basalt 

gravel.

 ..do ... 

 do .
qoTVr^

qo"pt

qopo

Court.

& Sons.

Station.

Ap

An

An

1 000

090

090

Dr

Dr

Dr

45

46

47

466

45

46

47

32 114- __ do __ 

-

 . -do ... ... ...

.. _ do 
86 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

TABLE 5. Materials penetrated by representative wells in the Ahtanum Valley

Most of the information in this table was obtained from records made by well drillers at the time the wells 

were constructed, although some information was supplied from memory by drillers and well owners. 

A few of the wells were visited during construction, and samples were examined by the writer. The records were edited for consistency of terminology and presentation and for conformance with the stratigraphic units described in the text but were not changed otherwise. For the purpose of clarity, the 

writer's interpretations have been added in parentheses after some of the drillers'designations.

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/15-13R1

[William Mondor. About 1 mile southwest of Tampico. Altitude about 2,180 ft. Drilled by N. C. Jannsen, 1939. Casing, 16-in to 50 ft]

Alluvium:

Gravel, cemented, and boulBasalt, hard _________

43

30

cq

*9

82

87

140

Ellensburg formation (unamed

Yakima basalt:

38

20

45

9

23

49

178

198

203

248

257

280

329

12/16-8H1

[Vernon Mondor. About 1 mile northeast of Tampico. Altitude about 2,250 ft. Drilled by N. C. Jannsen, 

1926. Casing, 10-in to 200 ft, 8-in to 380 ft; no perforations]

Yakima basalt:

300

20

300

320

Yakima basalt continued

Rac«lt 60 380

12/16-13D1

[HerkeBros. About 6 miles west-southwest of Wiley. Altitude about 1,800 ft. Drilled by Oscar Boehler.

Casing, 14-in to 27 ft]

Alluvium: 

Soil 17 17

1Q

Yakima basalt (Wenas? basalt

Basalt, black, water-bearing- .

Ill

10 

6

130

140 

146

12/16-15F1

[Arthur Hanses. About 2.5 miles east of Tampico. Altitude about 1,900 ft. Drilled by A. A. Durand, 

1945. Casing, 10-in to 71 ft, 6-in to 278 ft]

Soil. 

Basalt, broken, water-bearing.

"Rock" (basalt?) _ . _ ......

Basalt, hard __________

5

18

19

6

21

11

OT

19

77

15

31

5

23

qc

41

62 

70

81

174

270

285

316

"Good water-bearing forma15

25

55

1

14

6

20

8

13

12

49

1

9

331

356

411

412

426

432

452

460

473

485

534

535

544
BASIC DATA 87

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness 

(feet)

Depth 

(feet) Materials

Thickness 

(feet)

Depth

(feet)

12/16-18B4

[Frank Mayfleld. Tamplco. Altitude about 2,116 ft. Drilled by N. C. Jannsen. Casing, 8-in.]

Alluvium:

Cemented basalt gravel:

9 

41

10 

33

9 

50

60 

93

Cemented basalt gravel Con.

Clay and sand ________

21 

41 

11 

30

114 

155 

166 

196

12/16-18C1

[Garrison and Hazen. About 0.5 mile west of Tampico. Altitude about 2,200 i't. Drilled by A. A. 

Durand, 1945. Casing, 14-in to 80 ft, 10-in to 250 ft, 7-in to 287 ft. Perforated from 165 ft to 287 ft]

Alluvium and cemented basalt 

gravel, undlflerentiated:

Rock (cemented basalt

Boulders and cemented baYakima basalt (Wenas? basalt 

member) :

17 

3

3

18

16 

13

7 

20

30

17 

20

23

41

57 

70

77 

97

127

Yakima basalt (Wenas? basalt 

member) Continued

Basalt 

Ellensburg formation (unnamed 

member) : Clay.-... 

Yakima basalt: 

Basalt, broken, water-bearing. 

Basalt, solid ______ .......

Basalt, broken, water-bearing.

10 

23 

29

21

11 

15 

27 

5 

19

137 

160 

189

210

221 

236 

263 

268 

287

12/16-18G1

[Frank A. Mondor. About 0.25 mile south of Tampico. Altitude about 2,107 It. Drilled by N. C. 

Jannsen, 1926. Casing, 12-in to 40 ft, perforated from 20 ft to 40 ft]

Alluvium:

Gravel, cemented, and "hard37

74

20

8

10

54

8

7

8

37

111

131

139

149

203

211

218

226

Cemented basalt gravel Con.

Clay... ....... . .-.. .

Clay.. 

8

3

10

6

14

6

97

7

4

3

234 23'

24"

25C 26"

27S

37( 37"

38]

384
88 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Voile y Continued

Materials

Thickness 

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/16-18K1

[HerkeBros. About 0.5 mile south of Tampico. Altitude about 2,110 ft. Drilled by A. A. Durand, 1946. 

Casing. 8-in to 55 ft, 6^1-in from 59 ft to 208 ft, 5-in from 170 to 315 ft; perforations from 162 ft to 164 ft, 

from 166 ft to 170 ft, from 200 ft to 204 ft, and from 208 ft to 315 ft]

Alluvium and cemented basalt 

gravel (?), undifferentiated:

Sand, brown, and black,

Shale......-.-.-.-...-......

OE

14

17

9

18

16

OO

7

25

14

24

34

OK

49

66

75

93

139

164

202

236

Yakima basalt (Wenas? basalt 

member) : Continued

"Rock," brown (basalt?). __

10

14

23

7

2

25

8

1

9

5

249

263

286

293

295

320

328

329

338

343

12/17-1G2

[B. E. Snelling. About 0.5 mile west of Ahtanum. Altitude about 1,280 it. Drilled by F. Riebe & 

W. G. Ludwig. Casing, 6-in to 60 ft, 5-in to 200 ft]

Cemented basalt gravel and 

Ellensburg(?) formation undifferentiated:

Clay.........................

Sand.... ........... ......

20

80

100

Cemented basalt gravel and 

Ellensburg(?) formation undifferentiated: Continued

3

197

200

12/17-5B1

[E. L. Lenington. About 3.5 miles west-northwest of Wiley, in Cotton wood Canyon. Altitude about 

1,560 ft. Drilled by F. Riebe. Casing, 6-in to 77 ft]

Alluvium and cemented basalt 

gravel, undifferentiated:

38 38

Ellensburg formation: 

Clay, brown, pumiceous, __ . 

Sand.... ...... ......

122 

10

16( 

17(

12/17-6F2

[R. F. Morozzo. About 5 miles west of Wiley, in Cotton wood Canyon. Altitude about 1,680 ft. Drilled 

by Oscar Boehler, 1950. Casing, 6-in to 44 ft]

Ellensburg formation: 

Clay, blue, sandy.----. ...

Sand.......................

30

2

10

9

30

v>

159

Yakima basalt (Wenas? basalt

12/17-8K1

[Merle Carson. About 3.5 miles west of Wiley. Altitude about 1,570 feet. Drilled by N. C. Jamisen.

Casing, 6-in to 60 ft]

Alluvium:

Ellensburg formation:

55

20

OA

75

95

Yakima basalt:

5 100
BASIC DATA 89

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/17-8R3

[James Bowers. About 3.5 miles west-southwest of Wiley. Altitude about 1,550 ft. Drilled by Boehler 

and Huber, 1953. Casing, 8-in to 245 ft, open end, no perforations]

Alluvium: 

Soil............... .........

Cemented basalt gravel: 

Gravel, cemented __ ___ ..

Ellensburg formation:

Clay.....-.. - .

2

9

9

220

2

11

20

240

Yakima basalt:

Basalt, black (lost flow at 400ft).

60

100

7

3

300

400

407

410

12/17-9J3

[Walter Mclnnis, (formerly Marks School). About 2 miles west-southwest of Wiley. Altitude about 1,470 

ft. Drilled by Hughett. Casing, 4.25-in]

Alluvium and cemented basalt

Soil.......... ..............

Ellensburg formation: 

Clay.........................

Clay........... ..............

Gravel...-- __ ___ .. __ ..

Clay.........................

12

8

70

30

10

25

20

25

10

25

12

20

Qn

100

1QA

140

ioc

210

220

245

Ellensburg formation Con.

"Dnealf-

"Rock" (basalt), water-bearClay....... ...... ............

100

60

20

5

23

6

45

18

53

345

405

425

430

453

459

504

522

575

12/17-10C2

[Claude Ekland. About 1.5 miles west of Wiley. Altitude about 1,420 ft. Drilled by F. Reibe, 1952. 

Drilling suspended, yield inadequate. Casing, 8-in to 33 ft]

Soil ... 5

29

5

34

381

55

415

470

12/17-11A1

[Gilbert Orchards, Inc. Wiley. Altitude about 1,347 ft. Drilled by Hughett. Casing, 10-in to 787 ft; 

intermittent perforations from 103 ft to 725 ft]

Alluvium:

Clay....................

Clay................

Ellensburg formation:

Sandstone _____

Gravel, cemented, hard

16

16

10

7

11

Q7

AK

12

6

QQ

4

5

15

16

to

42

AQ

60

97

103

148

160

175

181

220

231

235

240

255

Ellensburg formation Con. 

Clay.........................

Clay. ........................

Clay.. ..................... ..

Clay.........................

Clay.........................

Clay.. ................ .......

Clay.........................

Clav. blue, and sandstone __

56

4

108

8

7

2

20

6

10

61

24

22

62

20

20

8

23

4

21

311

315

423

431

438

440

460

466

476

537

561

583

645

665

685

693

716

720

741
90 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/17-11 Al Continued

Ellensburg formation Con.

Clay and sandstone, water1Q

26

20

12

QQ

8

3

8

710

785

OAK

817

858

869

Yakima basalt Continued

Shale, blue, and "rock,"

90

4

22

6

9

13

6

3

3

959

963

985

991

1,000

1,013

1,019

1,022

1,025

12/17-11D4

[Ernest Bitz. About 1 mile west of Wiley. Altitude about 1,390 ft. Drilled by J. E. White, 1953. 

Casing, 6-in to 30 ft. Perforated with 1 slot per ft for entire depth]

Soil. .................... ....... 4 4

22

4

26

30

12/17-16D3

[Jack Schreiner. About 3 miles west-southwest of Wiley. Altitude about 1,510 ft. Drilled by Ralph 

Cassel, 1952. Casing, 10-in to 312 ft; unperforated]

Alluvium:

Ellensburg formation:

oo

10

58

32

42

100

Ellensburg formation Con. 

Clay-- 

Yakima basalt:

79

75

46

25

42

17

179

254

300

325

367

384

12/17-16R1

[B. S. Borton & Sons. About 3 miles southwest of Wiley. Altitude about 1,550 ft. Drilled by Durand 

& Son, 1944. Casing, 12-in to 183 ft, 8-in from 180 ft to 699 ft, 6W in from 744 ft to 940 ft]

Clay, brown (loess?) and soil.. _ 

Cemented basalt gravel:

Gravel, clay, and boulders _

Boulders and sand ______ .

Sand.... - 

Gravel and sand, cemented.

Gravel, coarse, boulders, and

Clay..... .............

Clay, sand, gravel, and 

boulders.. _____ ..

20

52 

21

7

7

91

4

16

28

16

14

17

68

22

8

20

72 

93

98

105

112

1 3°.

1 37

1 *\3

181

197

201

215

000

3nn

304

OOQ

337

Cemented basalt gravel Con.

Ellensburg formation:

Cl&v stick v brown

Clay-.-- - - -

Clay...- --------

Basalt, black, water-bearing 

Basalt, hard, black . 

16

32

5

30

20

10

30

15

15

38

17

71

3

31

21

11

4

24

23

7

41

5

353

385

390

420

440

450

480

495

510

548

565

636

639

670

691

702

706

730

753

760

801 

806
BASIC DATA 91

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/17-16R1 Continued

Yakima basalt Continued

Basalt, "honeycomb" (vesic9

5

3

4

2

6

4

2

3

11

10

815

820

823

C97

829

836

842

848

851

862

872

Yakima basalt Continued

Basalt, black, water-bearing.

21

8

15

19

19

6

29

21

5

20

5 

16

2

1

5

3

6

2

3

8C«

901

916

935

954

960

989

1,010

1,015

1,035

1,040 

1,056

1,058

1,059

1,064

1,067

1,073

1,075

1,078

12/17-17C1

[Carl Sheneberger. About 3.5 miles west-southwest of Wiley. Altitude about 1,573ft. Drilled by Boehler 

and Huber, 1948. Casing, 8-in to 166 ft, 6-in to 243 ft; perforated below 166 ft]

Alluvium: 

Soil .

v^ucti&e g ctvtn____ ___________

Cemented basalt gravel: 

Gravel, cemented __ _-_. _ _

Ellensburg formation:

Clay. ........................

11

14

92

5

30

122

Ellensburg formation Continued 

Clay, brown and yellow,

sticky..-.. __ - ---. - .-

Yakima basalt:

48

23

1

1

48

170

193

195

243

12/17-17J1 

[.T.R.Rutherford. About 3.5 miles southwest of Wiley. Altitude about 1,540 ft. Casing, 6-in to bottom]

Alluvium: 

Soil....--- ________________

8

Allu viu m C on tinue d 

Clay.-... -_ --- - 5 15

12/18-1M1

[Yakima Farm Labor Camp. About 2 miles west of Union Gap. Altitude about 1,010 ft. Drilled by 

Durand & Son, 1939. Casing, 10-in to 366 ft, 8-in from 366 ft to 555 ft; no perforations]

Alluvium: 

Soil . . 

Gravel and clay, loose and

Gravel and clay, caving------

fift3275 O RV 7

6

1

19

6

9

9

3

15 

12

20

3

6

7

12

31

07

46

55

KO

73

85

105

110

1 ^9

135

Cemented basalt gravel Con.

\ Clay, sandy, and gravel _ _ _

Clay, sandy, more gravel. ....

caving

5

28

5

24

11

12

10

13

10

4 

4

4

3

35

147

175

180

204

215

227

237

250

260

264 

268

272

275

310
92 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/18-1M1 Continued

Ellensburg formation Con.

1S

15

62

11

4

5

13

7

15

19

8

315

333

Q/tQ

410

421

425

430

443

450

455

470

AGO

490

Ellensburg formation Con.

Sand, brown... _ -- ___

5

10

15

5

8

2

5

10

5

5

40

20

495

505

520

525

533

535

540

550

555

560

600

620

12/I8-2E1

[LeRoy Sehreiner. About 3 miles west of Union Gap. Altitude about 1,080 ft. 

Cassel. Casing, 10-in to 86 ft, 8-in to 150 ft, and 6-in to 376 ft]

Drilled by Ralph

Alluvium: 

Soil 

ferentiated:

Sand.-.----..--- _ ----------

10

12

23

80

5

10

10

99

45

125

130

140

Cemented basalt gravel and

Sand, gravel, and rocks, loose.

10

25

80 

40

48

62

150

175

255 

295

343

405

12/18-5J1

[Joel Richwine. About 1.7 miles east of Ahtanum. Altitude about 1,170 ft. Dug by owner, 1932.

Casing, 30-in to 18 ft]

1S 13

17

1 18

12/18-5J3

[Oral Brown. About 5 miles west of Union Gap. Altitude about 1,165 ft. Drilled by Ralph Cassel, 1953.

Casing, 8-in to 203 ft]

Soil 

Clay...... ................

Clay.. 

Clay 

10

76

4

10

12

17

7

10

86

on

100

104

116

133

137

144

Clay...- 

Gravel, cemented .. 

48

5

8

48

5

17

5

192

197

205

253

258

275

280
BASIC DATA 93

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/18-8A1

[Carrel Morton. About 2 miles southeast of Ahtanum. Altitude about 1,170 ft. Drilled by Joe Riebe,

1943. Casing, 10-in to 20 ft]

Soil.... 12

8

78

12

20

98

2 100

12/18-8B1

[Carrel Morton. About 1.7 miles southeast of Ahtanum. Altitude about 1,180 ft. Drilled by Joe Riebe,

1937. Casing, 12-in to 22 ft]

Dirt.. - 

Cemented basalt gravel:

10±

20±

10±

30±

Sand, argillaceous, yellow. ... 605± 63,

12/18-11E1

[S. II. Schreiner. About 3 miles west-southwest of Union Gap. Altitude about 1,170 ft. Drilled by 

Ralph Cassel, 1946, Casing, 5-in to 151 ft; unperforated]

Soil 10

100

45

10

110

15

20

15

8

170

190

205

213

12/18-11E2

[Fred Westburg. About 3 miles west-southwest of Union Gap. Altitude about 1,186 ft. Drilled by 

W. G. Ludwig, 1952. Casing, 6-in to 165 ft; unperforated]

Soil.... ....... ......

Gravel and boulders, poorly

6

60 66

174

Basalt, black (boulders) -.. _

3

3

3

177

180

183

12/19-5M1

[City of Union Gap. Altitude about 930 ft. Drilled by A. A. Durand, 1936. Casing, 12-in to 80 ft, 10-in 

to 208 ft; perforated from 159 ft to 214 ft]

Alluvium:

15

85

5

100

Cemented basalt gravel Con.

70

17

23

175

192

215

12/19-5M2

[City of Union Gap. Altitude about 980 ft. Drilled by A. A. Durand, 1936. Casing, 12-in to 83 ft, 10-in 

to 198 ft; perforated from 142 ft to 197 ft]

Soil 

Clay .

Gravel, cemented, caving __ 

Gravel, cemented, and boul4

. 46

' 13

42 

40

CA

63

68

110

9

31

14

13

159

190

204

217
94 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

12/19-5N1

[City of Union Gap. Altitude about 975 ft. Drilled by N. C. Jannsen, 1949. Casing, 12-in to 370 ft; 

perforated from 130 ft to 138 ft and from 182 ft to 361 ft]

Alluvium:

15

6

28

9

3

91

27

55

64

67

Cemented basalt gravel Con.

Clay...-.- ----------

9

105

20

154

9

76

82

187

207

361

370

12/19-17C1

[Miocene Petroleum Co. About 1 mile south of the City of Union Gap. Altitude about 950 ft. Drilled by 

N. C. Jannsen, 1929. Casing, 12.5-in to 711 ft, 10-in to 1,045 ft; no perforations]

Alluvium:

21 21

Yakima basalt:

3,779 3,800

13/18-28L1

[Congdon Orchard. About 3 miles northeast of Ahtanum. Altitude about 1,160 ft. Drilled by N. C. 

Jannsen, 1912. Casing, 10.5-in to 284 ft, 8.25-in to 769 ft, 6.5-in to 1,026 ft, 5.25-in to 1,227 ft]

Alluvium:

Gravel and boulders, cemented and sandstone _ ..

Sandstone and gravel, soft 

Mud, with boulders on one

9

2

22

25

26

CO

2

28

2

35

12

15

10

20

16

82 

11

24

12

29

15

54

21

6

9

33

58

84

1Q7

10A

210

212

247

324

00 C

350

360

one

409

491

CftO

538

KR7

582

586

eon

600

601

655

676 

682

Ellensburg formation Con.

Clay-.--- ---------

Clay, sticky, stiff _______

to 993 ft.. .. - -- -

Sandstone, hard, coarse, and 

blue shale in alternating 

layers

1,220ft--... - 

Sandstone, with 1 layer of 

white sand, and 1 layer of

12

29

38

2

9

10

5

6

7

5

10

2

10

9

5

14

93

46

8

13

11

69

5

43

50

27

32

694

723

761

763

772

782

787

793

800

805

815

817

827

836

841

855

948

994

1,002

1,015

1,026

1,095

1,100

1,143

1,193

1,220

1,252
BASIC DATA 95

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Voile y Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

13/18-33L2

[Q. E. Stewart. About 2 miles east-northeast of Ahtanum. Altitude about 1,170 ft. Dug, 1945. Casing,

36-in to 20 ft]

Alluvium: 

Dirt-- - . 4

5

4

9

A lluvium Con.

11 21

13/18-33L3

[O. E. Stewart. About 2.5 miles northeast of Ahtanum. Altitude about 1,170 ft. Drilled by Fred 

Riebe, 1948. Casing, 10-in to 49.5 ft, perforated with torch from 10 ft to 49.5 ft]

Soil 4

20

30

15

4

24

54

69

30

20

18

99

119

137

13/18-33M1

[Rainier State School. About 1 mile east-northeast of Ahtanum. Altitude about 1,180 ft. Drilled by 

Hughett. Casing, 8-in to 600 ft; perforated from 500 ft to 600 ft]

Alluvium: 

Soil - . . ...... ....

Clay... ..

Clay-.-. ..... -

Clay...- _ -

23

19

90

19

24

20

23

26

45

loe

154

178

198

Ellensburg formation Con.

Clay... 

Sand. ____ ~

Clay... r - 

Clay...-. - 

47

132

14

61

48

47

63

3

245

377

391

452

500

547

610

613

13/18-34M1

. A. Pearson. About 2.5 miles east-northeast of Ahtanum. Altitude about 1,130ft. Dug, 194S. Casing,

30-in to 18 ft]

Alluvium: 

Silt, fine .... ...... 5 5

7

8

Alluvium Continued

10 18

13/19-31J1

[Yakima Farmers Supply Co. About 1 mile northwest of Union Gap. Altitude about 1,015 ft. Drilled 

by J. E. White, 1951. Casing, 6-in to 84 ft; perforated from 75 ft to 84 ft]

Alluvium:

Cemented basalt gravel (?) and 

Ellensburg formation, undiffer17

2

6

6

17

19

25

31

Cemented basalt gravel(?) and

entiated Continued 

Sand, medium, water-bearing. 15 

19

17

2

46 

65

82

84
96 GEOLOGY, GROUND WATER, AHTANUM VALLEY, WASH.

TABLE 5. Materials penetrated by representative wells in the Ahtanum 

Valley Continued

Materials

Thickness

(feet)

Depth

(feet) Materials

Thickness

(feet)

Depth

(feet)

13/19-32M1

[Yakima Cooperative Association. About 1 mile north of Union Gap. Altitude about 1,010 ft. Drilled 

by J. E. White, 1951. Casing 6-in to 38 ft; unperforated]

Alluvium:

Cemented basalt gravel(?) and

entiated:

2

6

17

19

25

Cemented basalt gravel (?) and

entiated Continued

Sand and shale, water-bear6

9

31

40

13/19-32M5

[Honeymoon Auto Court. About 1 mile north of Union Gap. Alt!tuae about 1,000ft. Drilled by Shookman, 1942. Casing, 4-in to 15 ft]

Soil. 

2

4

OK

31

1

13

32

45

TABLE 6. Chemical analyses, in parts per million, of ground water in the Ahtanum

Valley

[Analyses by U.S. Geological Survey]

Well.- 

Silica (SiOj)______. ________

Iron (Fe) 1 --..-----------.--

Total iron (Fe)______ ______

Manganese (Mn)

Magnesium (Mg) _

Sodium (Na) _

Potassium (K) .

Bicarbonate (HC03)

Sulfate (S04) - - _

Chloride (Cl)______________

Fluoride (F)_'______________

Nitrate (N03) __________ __

Dissolved solids

Noncarbonate hardness. 

Percent sodium.

Specific conductance (micromhos at 25° C) _ _

pH_____ __________________

12/1&- 

13D1

8/30/51

Yakima 

basalt

54 

.02 

.06

.00 

16 

9.7 

10 

1. 8 

116 

4.4 

3.0 

. 2 

1. 6 

158 

80 

0 

21

194

7.7

12/1&- 

17J1

8/30/51

Unconsolidatecl 

alluvium

47 

. 11

.00 

10 

5.8 

5.6 

3.7 

74 

2.4 

. 7 

. 2 

1.0 

113 

49 

0 

19

98 

7.3

12/17- 

16R1

4/18/52

Yakima 

basalt

38 

.24

.27

.00 

12 

6.6 

7.2 

3. 1 

85 

4.4 

1. 2 

. 3 

. 2 

115 

57 

0 

20

136

7. 9

12/18- 

5G2

8/29/51

Un consolidated 

alluvium

52 

.03

.28 

23 

12 

19 

5.3 

160 

8.0 

11 

.2 

1. 5 

211 

107 

0 

27

285

7. 2

12/18- 

5J1

8/29/51

Unconsolidated 

alluvium

51 

.02

.00 

24 

14 

16 

5.6 

180 

5. 1 

2. 5 

.3 

1. 8 

209 

117 

0 

22

284 

7.2

12/18- 

11E1

8/30/51

Ellensburg formation

61

.03

.00 

30 

16 

9.6 

3.2 

133 

29 

18 

.3 

2. 7 

235 

141 

32 

13

315 

7.3

13/19- 

31J1

8/29/51

Cemented 

gravel

39 

.02

.00 

34 

11 

12 

4. 8 

116 

21 

26 

.3 

6.0 

211 

130 

35 

16

320 

7.3

 In solution when soialyzed.
BASIC DATA 97

TABLE 7. Field analyses, in parts per million, of water from wells in the Ahtanum

Valley '

Well

12/15-13R1___

12/16-8N1____

9M1___.

15M1___

17D1___

17K1___

18K1___

12/17-1L1___.

1P1____

2N1____

2Q1____

2R2____

5B1__._

6Jl __

8Jl_-__

8K1___.

9E1____

10J1____

10N3___

10R1___

11M1___

12E1___

12K1___

13H1__.

15N1___

16Q1___

17C1-..

12/18-1M1____

5G1___.

6F4____

6G2_.__

7K1____

8B1____

9L1____

12E1___

18D1._.

12/19-6E1____

13/18-33L1___

13/19-32M2___

Depth 

(feet)

329

30

4320-

12

343

33

7Q

75

9

170

140

14

100

80

100

11

18

10

26

12

31

140

11

243

620

11

15

15

635

49

72

28

50

22

125

Principal aquifer

Basalt

Cemented gray el (?) _ _ ___

_____do__ _____________________________

Basalt

Gravel _____

_____do__ _-_-_-_-_-_-_-___-___________

Basalt

Gravel and sand _ _

Alluvium(?) __________ _ _____________

Ellensburg(?) formation _

_____do___.__ _________________________

_-_-_do_-____________ _________________

Alluvium _

Sand_____- ___________________________

Alluvium. _ _

___ do __ __

__-__do__________________ _____________

_____do_._____________________________

Cemented gravel (?) _ _ _

Alluvium _ _

Basalt _

Sand _ _ _ _ _ _ _

Alluvium ___

_____do__________________ _____________

_____do_______ ________________________

Sand

Gravel and sand _ _

Sand______- __________________________

Cemented gravel(?)

Sand _ __

Chloride

8

4

8

8

10

6

8

24

12

6

10

8

8

20

6

8

6

6

8

6

6

5

6

14

20

8

8

10

10

8

10

6

10

20

26

18

16

14

Hardness (as 

CaCOs)

95

105

180

54

85

55

Q 1!

265

95

85

135

74

135

170

60

75

80

135

90

115

110

100

125

195

120

135

60

82

112

130

120

110

202

266

240

255

235

148

103

Analyses approximate only; not made under laboratory control.

INDEX

Page 

Acknowledgments_...______________ 5

Ahtanum Creek, drainage area...__........ 7,8

inflow of water..____________ 12,27-30 

irrigation use......__..__.__ 12,13,30-31

outflow of water__..._________ 28-30

Ahtanum-Moxee subbasin__________ 3,

4,6,19, 22,23,25,37,39,62,63

Ahtanum Ridge.. 6, 7,14,15,16,17,19,22,23, 25,37,40 

Ahtanum Ridge anticline - .__ 6,16,22,23,24 

Ahtanum Valley, geologic history._........ 24-25

location. ______.,_ _..._....._._____________ 3

physiography___ ______________ __. 6-7

structure_..___________________ 22-24

Alluvium, ground water in.-.._____ 43-49,63 

ground-water withdrawals_______ 56-58 

lithology and occurrence___-_.---_---. 7,21-22 

pumping tests on wells in ___________ 45-47

quality of water in__-..._____________ 59-62

water-level fluctuations_________ 49,50,51 

Aquifers, properties-.----___--.__________ 31-32

recharge___________ ________ 33-34 

Artesian water, denned____.._._____ 33

occurrence..__________ 36,39,40,43,53,55 

Artesian well, flowing, defined,.. ______. 33

Bibliography. 66

Canal system________________ 8, 28,30-31 

Cascade Mountains..________ 6,8,11,18,24,25 

Cemented basalt gravel, age__________ 21

geologic history..______. __......._ 25

ground water in. ___________ 42-43,54,55 

ground-water withdrawals___ 42,43,54,55,58 

lithology and occurrence______________ 19-21

quality of water in__._.__--.__.._ 59-62 

Columbia River basalt.____________ 16 

Cone of depression, defined.-..--_-._.---_ 35 

Cowiche gravel-...-._------------____- 21

Cowiche Mountain..._____________ 6,14,37 

Cowiche Mountain anticline____ 6,8,21,22,37,41

Discharge, defined____________ ____ 34-35

See also Ground water. 

Donald Pass-.__________________ 25

Ellensburg formation, age..________ 16,18-19 

geologic history__-------_-______-- 24-25

ground water in.__._.._______ 39-42,55 

ground-water withdrawals_____ 41,54,55,58 

lithology and occurrence....________._____ 16-19

quality of water in.________ - ____ 59-62 

water-level fluctuations__________ 50-51 

wells in_________________ 39-40,54,55

Evaporation...__.____ 11,25,26,28,34,44,48, 55

Page 

Farming---.-.-_-___--_____--____------------- 12

Fluminicola u'illiamsi.--...... __-____-_ ___ 16

Folding......-..-. -. - 6,22-23,24-25

Gaging stations..__... .... 4,26,27,30,64-65

Ooniobasis kettlemanensis-.............. ____ 16

Ground water, confined.. __ 33,34,36,39,40,42,43 

defined 31

discharge.---.---------------------.--- 26,

32,33,34-35,38,39,41,42,43,44,47-49,62-63

movement__... 23,

26,32,33,34,35,36,38,41,42,43,44,46-47

occurrence. See particular formation.

recharge. 28,32,33-34,37-38,40-41,42, 43,52,53

withdrawals____..__ 35,

38-39,41, 43,49,53,54,56-57, 58-59,65

yield.. --- ___ 32,36,39,41,42,43,53,54,55, 56

Growing season__.________--.-_-____---___- 11

Hardpan. 22

Impermeability, defined . _ ---- 32

Irrigation, available water for 2,

4,12,13,31,53,54,55,56

history. 12-13

ground-water use 38-39,

41,43,49,53,54,56,58-59,65

quality of water for_____... 60,62

surface-water use.. 30-31

Loess. 22,25

Lower valley, development of ground-water

resources... ... _. ------- 55-58

physiography... 6-7,16-17 

wells...___________-- 36,39,42,43,46,55-56

Mammut (Miomastodori) merriami. 

Manastash formation . -_

Narrows 7,23,36,37,40

Palouse formation. .... . - 22 

Permeability, defined....------ .. 32

Phyreatophytes. ..... ..... .... 11-12,48,57

Piezometric surface, defined. 33,34 

Pliauchenia merriami.................... ___.- 19

Porosity, defined-. . ----- 32

Precipitation 8-10,25, 26,37,40,65

Previous investigations -__-_ ___ 4 

Pumping test, wells in alluvium 45-46

Quality of water, chemical concentration. _.. - 59

general character... ---------- .- 59-61

suitability __.-- .. 60,62

99
100 INDEX

Page

Rattlesnake Hills_______________ 6 

Recharge, defined..__.________._. 33-34

See also Ground water. 

Runoff______________________ 25-30,62

Sedge Ridge ............._.. 6,8,14,16,17,22,37

Specific capacity, defined.-.__-..-_______ 36 

Specific yield, defined---.--_............... 32

Sphaeriumsp............. _____._____ 16

Streamflow records............ 26, 27,28,29,30,62,64

Streams.. _________________ 7-8,

26-30,43, 44,47-48,50, 56, 57, 62-63,64-65

Structural features.. ____________ 6, 22-24, 25

Surface water, inflow. ---.-.._---. 27-28,29,30, 64-65

irrigation agreements..................... 12-13

outflow..........._._.____.._....._. 28-30, 64-65

Surface-water use. See Irrigation.

Tampico.--.-----._..........._ 7,8,10,12,26,27

Temperature, atmospheric____---.-___-.. 10-11 

ground water________.__....___ 60

Tieton andesite..___..._____._____.. 21

Transmissibility, defined_..-------.-._... 32

Transpiration, discharge by.____ 34-35,48-49,57

Union Gap. . 6,7, 8,12,15,22, 23,38, 42,55, 62,65 

Upland benches, development of groundwater resources,__.__.. ___.... 54-55 

physiography_____..__.______ 7 

wells.. ................._..._ 36,39,54-55

Page 

Upper valley, development of ground-water

resources-______________ 53-54 

physiography._________.......... 7

wells.....__._.................... 36,37,53

Vadose water, defined... -.__.._.-.._.. 31 

Vegetation___._________ 11-12,35,48,56,57 

Viviparus leiostracta........... ._._ - _. 16

Volcanism_.---..._.__---....__... 24

Water-level fluctuations-. -- 49-53 

Water table..__________________ 25, 

32-33,34,35,36, 43,44,48,49,50, 56,57 

Well capacity, defined __.______.. 36 

Well-numbering system._..-..---__-_.. 5-6 

Wenas basalt member of the Yakima basalt-. 15,

19,36,37,38

Wide Hollow Creek... . 7-8,27,28,29,30,62,63,64 

Wiley-- . 12,39

Yakima-- .. 3,6

Yakima basalt, age _... 16 

geologic history.-... 24-25 

ground water in.......____ 15,36-39,53, 54,55

ground-water withdrawals. 36,38, 52,53,54,55,58 

lithology and occurrence_. -... ...- 14-16 

quality of water in___........._... 59-62

water-level fluctuations_. ._ 52-53 

wells... .. 36,37,38,53,54,55

Yakima River, ground-water discharge to.... 62-63

Zone of aeration, defined.--.-- ..-.-- 31

U.S. GOVERNMENT PRINTING OFFICE; 1962 O 603275