Summary Appraisals of the 

Nation's Ground-Water ResourcesPacific Northwest Region 

G E 0 L 0 G I C A L S U R V E Y P R 0 FE S S I 0 N A L P A P E R 813-S 

OREGON IDAH 0 

SUMMARY APPRAISALS OF THE NATION'S 

GROUND-WATER RESOURCESPACIFIC NORTHWEST REGION 
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HAWAII 

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CARIBBEAN 

PR VI, 

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Water Resources 

Regions 

s 

Letters indicate chapter 

designations 

Chapters are published or in press in U.S.G.S. 

Professional Paper 813 

series 

Geographic lndex to the Series, U.S. Geological Survey Professional Paper 813, Summary Appraisals of the Nations Ground-Water Resources. 

Boundaries shown are those established by the United States Water-Resources Council for Water-Resources Regions in the United States. 
Summary Appraisals of the 

Nation's Ground-Water ResourcesPacific Northwest Region 

By BRUCE L. FOXWORTHY 

G E 0 L 0 G I C A L S U R V E Y P R 0 F E S S I 0 N A L P A P E R 813-S 

Opportunities and problems prese,nted 

by the region's ground-water resource 

UNITED STATES PRINTING OFFICE, WASHINGTON: 1979 
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary 

GEOLOGICAL SURVEY 

H. William Menard, Director 

Library of Congress Catalog-card Number 79-600032 

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

Washington, D.C. 20402 

Stock Number 024-001-03189-2 
CONTENTS 

Page 

)lbstract -------------------------------------------------- 1 

Introduction________________________________________________ 1 

The challenge of meeting future water requirements __________ 2 

Projections of water needs ------------------------------ 2 

Significance of ground water in the regional water supply 6 

Geographic factors affecting the ground-water resources ______ 8 

Landforms and drainage -------------------------------- 8 

Precipitation and replenishment patterns ________________ 8 

Geologic sources and distribution of ground water ____________ 13 

The productive aquifers -------------------------------- 13 

Description of the ground-water reservoirs ________________ 16 

Major ground-water problems ________________________________ 16 

Progressively declining water levels ______________________ 16 

Water-quality problems -------------------------------- 22 

Problems of natural origin __________________________ 22 

Dissolved iron---------------------------------- 22 

Salinity---------------------------------------- 22 

Other dissolved constituents -------------------- 22 

Problems related to man's activities __________________ 23 

Contamination from the land surface ____________ 23 

Household septic systems ________________________ 23 

Saltwater intrusion ---------------------------- 24 

Problems related to artifical recharge and 

disposal wells -------------------------------- 24 

Waterlogging ------------------------------------------ 24 

Inadequate information -------------------------------- 25 

Page 

Major ground-water problems-Continued 

Competition for available supplies ---------------------- 25 

Anticipated or potential problems ________________________ 26 

Management opportunities and constraints ------------------ 27 

Development of additional supplies ---------------------- 27 

Deeper aquifers of known potential ------------------ 28 

New sources of supply ------------------------------ 28 

Contamination abatement and avoidance ---------------- 29 

Improved design and construction of wells---------------- 30 

Reduction of waterlogging ------------------------------ 30 

Subsurfacestorage ______________________________________ 31 

)lrtificial recharge ---------------------------------- 31 

Wastes -------------------------------------------- 32 

Natural gas---------------------------------------- 32 

Improved management and conservation ---------------- 33 

Conjunctive use of ground water and surface water -- 33 

Efficiencies in conveyance and use ------------------ 33 

Management using predictive models ---------------- 34 

Energy-related opportunities and constraints ------------ 34 

Geothermal energy -------------------------------- 34 

Hydropower generation with ground water ---------- 35 

Ground water and coal ______________________________ 35 

Subsurface storage of heat -------------------------- 35 

Summary of needs for additional information ---------------- 36 

Selected references __________________________________________ 37 

ILLUSTRATIONS 

Page 

FRONTISPIECE Index map to chapters in Professional Paper 813. 

FIGURE 1. Map showing the Pacific Northwest Region and other regions of similar ground-water appraisals----------------------- 3 

2. Bar graphs comparing Pacific Northwest water withdrawals--------------------------------------------------------- 4 

3. Generalized water budget and volume~ of ground water in storage for the region-------------------------------------- 7 

4. Major land and water features of the region_________________________________________________________________________ 9 

5. Generalized distribution of annual precipitation in the region-------------------------------------------------------- 10 

6. Seasonal distribution of precipitation at selected weather stations in the region __ ~------------------------------------- 12 

7. Generalized distribution and types of major aquifers _________________________________________________________________ 14 

8. Areas designated as major ground-water reservoirs, water in available storage, and 1970 pumpage ______________________ 17 

9. Areas of significant declines in ground-water levels __________________________________________________________________ 20 

TABLES 

Page 

TABLE 1. Summary of conditions in major ground-water reservoirs ------------------------------------------------------------ 18 

2. Summary of information about water-level declines------------------------------------------------------------------ 21 

v 
VI CONTENTS 

CONVERSION TABLE 

Factors for conversion from units used in this report to metric units 

From Unit Abbreviation Multiply by 1b obtain Unit Abbreviation 

acre 4,047 square meter m2 

0.4047 hectare 

cubic foot ft3 .02832 cubic meter m3 

cubic feet per second ft3/s 28.32 liter per second L/s 

.02832 cubic meters per second m3/s 

cubic mile mi3 4.166 cubic kilometer km3 

foot ft .3048 meter m 

gallon gal .003785 cubic meter m3 

3.785 liter L 

gallons per minute gal/min .06309 liters per second L/s 

inch in 2.540 centimeter em 

mile mi 1.609 kilometer km 

million gallons per day Mgal!d .003785 cubic meters per day m3/d 

square mile mF 2.59 square kilometer km2 

ton, short (2,000 pound) .9072 ton, metric t 

907.1848 kilograms kg 
SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER 

RESOURCES-PACIFIC NORTHWEST REGION 

By BRUCE L. FOXWORTHY 

ABSTRACT 

The Pacific Northwest Region's ground-water reservoirs are capable of providing large additional fresh-water supplies; these reservoirs become more important as undeveloped surface-storage sites 

and unapportioned surface-water supplies dwindle. Withdrawals of 

fresh water from all surface and underground sources are increasing; 

they may rise from the rate of 30 billion gallons per day in 1970 to 

about 60 billion gallons per day in 2020. By 1975 the withdrawal of 

ground water had increased 70 percent over the 1970 rate and accounted for 22 percent of total fresh-water withdrawal. Substantial 

increases in ground-water withdrawal must continue if projected 

water demands are to be met in the future. 

Large variations exist in the availability of and needs for ground 

water in the region, largely because of the great variety oflandforms, 

climate, and earth materials. More than one-half the region is underlain by rock materials capable of yielding ground water to wells at 

moderate to large rates; six extensive areas are identified as major 

ground-water reservoirs. The most significant current problems pertaining to one or more ofthese ground-water reservoirs are: (1) Progressively declining water levels; (2) water-quality problems; (3 l 

waterlogging; (4) inadequate information; and (5) competition for 

available supplies. In the future these same problems are expected to 

persist and generally worsen (especially water-quality deterioration) 

in most of the major reservoir areas. 

Management opportunities in the region include: (1) Development 

of new supplies and additional uses of ground water; (2) protection 

and enhancement of water quality; (3) reduction of waterlogging; (4) 

energy development from some ground-water reservoirs; (5) improving access to the ground water; (6) increased use of underground 

space for storage and disposal; and (7) greater use of advanced management and conservation techniques. Conjunctive use of surface 

and ground water to provide greater available supplies probably is 

the most promising water-management opportunity. However, if the 

full potential of the ground-water resources is to be realized, important constraints, including present water-right structures and serious deficiencies in information, must be overcome. 

INTRODUCTION 

The Pacific Northwest, a region largely drained by 

The Columbia River, the second biggest river in the 

Nation, has the reputation for having abundant water. 

The long-term average discharge of stream water from 

the region has been estimated at 384,000 cubic feet per 

second-much greater than from most other U.S. regions of comparable area (Columbia-North Pacific 

Technical Staff, 1970b, p. 18). In spite of the apparent 

large total supply, however, water is not always available where and when it is needed. The distribution of 

runoff throughout the region is extremely uneven, and 

large variations in streamflow occur on a monthly, 

yearly, and long-term basis. Serious competition exists 

between irrigation diversions and important instream 

uses of surface water, and thousands of square miles of 

irrigated farmland are subject to water shortages. Although additional supplies of surface water can be developed at many places, problems associated with 

surface-water supplies are likely to worsen in the future as demands for water increase. 

The Pacific Northwest Region's ground-water reservoirs, on the other hand, are capable of providing large 

additional fresh-water supplies, represent huge 

amounts of storage space for surplus runoff, and have 

the potential for greatly alleviating present and 

foreseeable water-supply problems. As undeveloped 

surface-storage sites and unapportioned surface-water 

supplies dwindle, the ground-water reservoirs of the 

region should become the focus of water-management 

schemes. Traditionally, however, the ground-water resources have been accorded a subordinate role in regional resource planning, owing partly to the major 

importance of surface water in the region and partly, no 

doubt, to a general lack of understanding of the potential value of the ground-water resource and of the underground space containing it. 

The purpose of this report is to summarize the general status and significance of the region's groundwater resources, some of the likely demands upon them 

in the future, and major problems and constraints associated with their use, and to evaluate some of the 

ways in which the ground-water reservoirs can be 

further utilized. The intended audience includes, but is 

not restricted to, officials responsible for resource development and administration, and experienced in 

water-resource planning and management, but with 

1 
2 SUMJ\IARY APPRAISALS OF THE NATIO:'\'S GROUND-WATER RESOURCES 

somewhat limited familiarity with the ground-water 

resource. The report is intended to focus attention on 

the importance of, and opportunities for, ground-water 

management and conjunctive use of ground waters and 

surface waters to meet water needs under the changing 

conditions that seem likely within the next several 

decades. 

The data on which this report is based were gleaned 

mainly from reports of many earlier studies. The U.S. 

Geological Survey has made water-resource studies in 

the region since about 1900, largely in cooperation with 

State, local, and other Federal agencies. Many of the 

reports of those studies are listed in the section on 

((Selected References," along with several reports of 

studies by other agencies or individuals on subjects 

that are especially pertinent to this report. Information 

derived from these earlier reports was augmented by 

the writer's experience on several hydrologic studies in 

this region and by contributions from ground-water 

hydrologists currently working in the individual 

States of the region. Contributors included E. G. Crosthwaite and A. M. La Sala, Jr., Boise, Idaho; A. R. 

Leonard and J. H. Robison, Portland, Oreg.; R. G. 

McMurtrey and J. A. Moreland, Montana; and K. L. 

Walters, Tacoma, Wash. 

Especially helpful to the present study were two 

earlier reports containing water-resources data and interpretations of regional and subregional scope, compiled mostly by colleagues in the U.S. Geological Survey. Those reports are: ((The role of water in shaping 

the economy of the Pacific Northwest" (Bodhaine and 

others, 1965); and the ((Water Resources" appendix 

(app. 5) of the ((Columbia-North Pacific Region comprehensive framework study of water and related 

lands" (Columbia-North Pacific Technical Staff, 1970b), 

compiled largely by G. L. Bodhaine and M. J. Mundorff. 

The reader is referred to the latter report, especially, 

for subregional summaries of ground-water resources 

and conditions, includ"ing the types and productivity of 

water-bearing rock materials in the different parts of 

the region. 

The present report is designed to be a regional part of 

a broad-perspective analysis by the U.S. Geological 

Survey of the ground-water resources of the nation. 

This part, previously designated the Columbia-North 

Pacific Region and now designated the Pacific Northwest Region, is shown in figure 1. This region includes 

all the Columbia River drainage basin in the United 

States, the drainage areas of coastal streams in Oregon 

and Washington, and the closed basins in south-central 

Oregon. This region of about 274,400 square miles 

(271,430 mi2 of land and 2,980 mi2 of water) comprises 

all of Washington, most of Idaho and Oregon, parts of 

Montana, Nevada and Wyoming, and a very small part 

of Utah. It is bounded on the east by the Rocky 

Mountains, on the north by the Canadian border, on 

the west by the Pacific Ocean, and on the south mainly 

by the California and Nevada state lines and the Snake 

River drainage divide. (See also fig. 4.) 

THE CHALLENGE OF MEETING FUTURE WATER 

REQUIREMENTS 

The requirements for water in the Pacific Northwest 

Region are increasing, and will become a progressively 

greater challenge to water-management skills and 

regulatory innovation. For a variety of reasons, the 

ground-water resources seem destined to play an increasing role in meeting the future water requirements. 

PROJECTIONS OF WATER NEEDS 

Projections of future water needs in various parts of 

the region are available from the report of the 

((Columbia-North Pacific Region Comprehensive 

Framework Study of Water and Related Land;' by the 

Columbia-North Pacific Technical Staff-hereafter 

shortened to CNPTS (1972). Those projections are 

summarized in figure 2, along with compilations of 

water use during 1970 and 1975 obtained by canvass of 

water managers and others (Murray and Reeves, 1972, 

1977). As shown in the figure, total water diversions 

and withdrawals are strongly dominated by irrigation 

requirements, and these requirements are expected to 

dominate in the future, also. The water withdrawn for 

irrigation in 1970 was about eight times greater than 

the combined withdrawals for industrial, municipal, 

and rural-domestic uses. As projected, water for irrigation would still represent the dominant need by 2020, 

amounting to about 85 percent of the total diversions 

within the region (fig. 2). The projected irrigation requirements by 2020 would represent a nearly 90-

percent increase over the 1970 diversions for that use 

and would be equivalent to about 20 percent of the 

total stream discharge from the region (fig. 3). 

The projections of irrigation water needs in figure 2 

include not only diversions to irrigate cropland and 

pasture, but also water for nonfarm irrigation (such as 

parks, golf courses, and cemeteries), and a predicted 

need for irrigation of forest crops. Expected irrigation 

of forest lands will constitute an essentially new type of 

irrigation need, based on predictions of an increased 

wood-fiber demand and downward trend in future 

amounts of natural forest land. Irrigation to assure 

tree survival during the early years and to establish 

forests on dry or marginal lands is seen as one way to 

maintain or even increase wood-fiber yields from the 

region (CNPTS, 1971c, p. 28). Estimates in the 
PACIFIC :"JORTHWEST REGION 3 

0 400MILES I 

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OahuC:> Malokai c:> . o c::ap 

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0 0 80MILES 0._. .,__..........,. 4_,90 Ml LES ....__....__....._ .... t I I 

FIGURE 1.-Map showing the Pacific-Northwest Region and other regions of similar ground-water appraisals. 

uframework" study indicate that roughly 5 million 

acres of forest land in the region might respond favorably if water were available. 

Industrial and municipal water requirements, which 

constituted 6 and 4 percent respectively of the total 

withdrawals in 1970, were projected (fig. 2) to increase 

at rates much greater than the irrigation requirements. By the year 2020, needs for industry were expected to increase nearly 170 percent, and those for 

municipal supplies by more than 160 percent over the 

1970 amounts. Even after those sizeable increases, 

however, the industrial and municipal water needs 

would amount to only 8 and 6 percent respectively of 

the projected total by 2020. Future needs for industrial 

and municipal water supplies are expected to be 

greatest in areas where these uses are already 

concentrated-namely, the Willamette-Puget Sound 

Trough and the vicinities of metropolitan centers 

throughout the rest of the region. 

Rural-domestic water requirements were expected to 

grow generally apace with the projected total increases, remaining at less than 1 percent of the totals. 

Sizeable demands for water that were not foreseen in 

the ((framework" study may develop in the region, such 

as water for processing and transport of coal or other 

new uses associated with energy production. However, 

the needs for such' purposes are expected to be restricted to only a few parts of the region, and the total 

of such unforeseen demands is expected to be relatively 

small. 

The projections of water requirements (fig. 2), like all 

projections, are based on certain assumptions. Some of 
60,000 

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EXPLANATION 

Type of use, all water sources 

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Ground water, total withdrawal [Q 

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FIGURE 2.-Pacific Northwest water withdrawals compiled by U.S. Geological Survey for 1970 and 1975 and those projected by Columbia-North Pacific Technical Staff for 

1980, 2000, and 2020. Sources: For 1970, Murray and Reeves (1972); for 1975, Murray and Reeves (1977); for 1980-2020, CNPTS (1972). Possible differences in reporting for the categories shown here as "municipal" and "rural" have no significant effect on the indicated relationships. Withdrawals for power generation are not 

included. 

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PACIFIC NORTHWEST REGION 5 

these are discussed in appendix 6 of the !!framework" 

study report (CNPTS, 1971a, p. 5, 6). Most of the assumptions involved extension of socioeconomic conditions that prevailed prior to about 1965. The assumptions do not take into account certain shifts away from 

some earlier trends during the decade 1966--75, especially in the last half of the decade. Also, significant 

international events and shifts in national policies 

have occurred which, along with changes in socioeconomic trends, probably will affect future water requirements in the region. 

Although a detailed analysis of the earlier assumptions and subsequent departures from them is beyond 

the scope of this report, certain near-term probabilities 

seem fairly obvious. These include a general slowdown 

in population growth, domestic commerce, and industry below the assumed trends for the region, with attendant slowing of related water needs. 

Future energy sources and the fate of industries dependent upon them seem uncertain. The major industries are agriculture and food processing, lumbering 

and forest products, services (including tourism), minerals, metals, chemicals, and manufacturing. Some industries doubtless will be affected adversely, but deployment of industry (for environmental, energy, or 

other reasons) may create unexpected demands for 

water supplies at various places. 

In judging the continued usefulness of the waterneed projections from the !!framework" study (fig. 2), 

requirements for irrigation are the key factor. In 1970 

about 7.5 million acres were irrigated-roughly onethird of the total crop land at that time. The Snake 

River Plain accounted for more than half the total irrigated acreage, and the Columbia Plateau accounted for 

the second greatest fraction. Sizeable acreages are irrigated in all major parts of the region; even the farms in 

the more humid parts west of the Cascade Range can 

produce more and better crops with timely irrigation. 

About one-fourth of the land irrigated in 1970 reportedly had late-season water shortages. The dry 

lands that were classed as potentially irrigable totaled 

some 33 million acres, more than 40 percent of which 

were judged capable of producing high yields of climatically adapted crops (CNPTS, 1972, p. 85). Irrigated 

land was forecast to increase by 6 million acres, reaching a total of 13.5 million acres by 2020-still only 

one-third of the total irrigable land in the region. 

The projected growth trend in irrigated farming also 

seems likely to be affected by counteracting influences. 

The depressing effects of economic slowdown, reduced 

population growth, and sharply higher farming expenses may be largely offset, or even dominated, by the 

spurring effect of strong export markets for farm products. Conversely, rising energy costs seem likely to constrain large-scale water withdrawals that involve high 

pumping lifts. 

A comparison of water withdrawals in 1970 and 1975 

(fig. 2) provides some insight into the durability of the 

projections for later years, although the extrapolations 

of a trend based on withdrawals for only those two 

years is tenuous, at best. A linear projection of the 

increase in withdrawals between 1970 and 1975 (upper 

dashed line in fig. 2) suggests that the total withdrawals by 1980 will fall far short of the projection for that 

year. This is not surprising, inasmuch as that 

forecasted growth in withdrawals would have required 

!!a decade of unprecedented irrigation development 

during the 1970's" (CNPTS, 197la, p. 45). Beyond 1980, 

however, the 1970--75 trend line is aimed generally toward the tops of the bars representing total withdrawals for 2000 and 2020; this trend line therefore suggests that the earlier forecasts of total withdrawals 

(largely irrigation withdrawals) for those years are 

still reasonable. 

There are other reasons to expect that the projected 

needs for irrigation water by the years 2000 and 2020 

may still be reasonable even though the needs for 1980 

were overestimated in the earlier analysis: 

1. The strong advantages that irrigation provides 

in the farming of the Pacific Northwest Region; 

2. exports apparently will need to be maintained 

at high levels to offset U.S. purchases of 

foreign petroleum and other products; 

3. worldwide needs for food and fiber resources 

continue to grow; 

4. increased opportunities for international commerce with Communist-bloc nations including broadened markets for food and fiber 

products from the region. 

Although irrigation use by 1980 apparently will fall 

far short of the projected amount, the withdrawals for 

nonirrigation uses in 1975 (fig. 2) had already exceeded 

the projections for 1980, owing largely to a 90-percent 

increase in withdrawal by industries. 

In the aggregate, the water-need projections from the 

!!framework" study seem to provide adequate guidance 

for the present study with regard to the general magnitude of future additional water requirements. Because of the aforementioned changing conditions that 

were not foreseen at the time the projections were 

made, the estimates of region-wide requirements by 

2020 may be somewhat less reliable for the industrial 

and municipal categories than for the irrigation and 

rural-domestic categories. 
6 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

SIGNIFICANCE OF GROUND WATER IN THE REGIONAL 

WATER SUPPLY 

The Pacific Northwest Region's ground-water system 

may be thought of as a series of separate reservoirs, the 

upper parts of which are intersected by the surfacewater system. The upper few hundred feet of the 

ground-water reservoirs serve the essential functions 

of moderating streamflow and sustaining the dryweather flow of streams, feeding springs, and supplying water for most wells. Water in the deeper parts of 

the ground-water system is less available for use at 

present; however, the deeper zones may become very 

important in the future for subsurface disposal of 

wastes or as more water is required. 

Ground water is by far the largest part of the region's 

freshwater resource, although most of it is hidden. 

Ground water fills the pore spaces and crevices in rock 

materials beneath all parts of the region down to 

depths of many thousands of feet. Very deep lying 

ground water, however, is commonly salty and is costly 

to extract because the rock materials at depth tend to 

have low permeability, or hydraulic conductivity. Furthermore, the renewability of the deep ground water is 

generally very limited; because of the low conductivity, 

water moves very slowly underground and commonly 

must move considerable distances from sources of replenishment at or near the land surface. Even discounting the very deepest water, however, the amount 

of fresh ground water in storage in the upper 1,000 feet 

of saturated rock materials is estimated to be about 

160,000 billion ft3 (cubic feet) or more than 13 times the 

average yearly outflow from the region through 

streams, which is about 12,100 billion ft3 • For a variety 

of reasons, not all this fresh ground water can be considered available for man's uses; the estimated amount 

of fresh ground water in ((recoverable" storage at any 

time probably is on the order of 24,000 billion ft3 

(CNPTS, 1970b, p. 85), or about double the average 

yearly stream discharge from the region. The ground 

water receives an estimated 100 million acre-feet 

(CNPTS, 1970b, p. 89), or about 4,000 billion fP, of 

annual recharge, most of which ultimately discharges 

to streams and becomes part of the stream discharge. 

The estimated amounts of inflow to, and outflow from, 

the region are shown in relation to ground-water storage in figure 3. 

The ground water and surface water are inseparable 

parts of the region's hydrologic system, with good hydraulic interconnection in many areas. This continuity 

between the ground water and surface water provides 

opportunities for greater beneficial use of the water 

resources but, at the same time, makes efficient management of the resources a difficult task under prevailing water laws, which tend to treat each of these two 

phases of water occurrence separately. Although 

greater utilization of the ground-water reservoirs cannot add to the total water supply (the inflow amounts 

in fig. 3), it can increase the dependability and the 

proportion of the total supply that is available for 

man's use. The improvement in dependability accrues 

through greater use of the reservoir function of the 

ground-water system. The increase in available supply 

results from the salvage of water that otherwise would 

evaporate or discharge naturally without being put to 

beneficial use. In contrast to these benefits, greater use 

of the ground water depletes the total water supply 

only to the extent that additional water from underground evaporates or is transported outside the region 

or area of management. 

The available ground water is not evenly distributed 

throughout the region, as is shown schematically in 

figure 3, but varies greatly in availability from place to 

place. Ground water can be obtained nearly every place 

in the region, but at some places the quantities obtainable from a well are small. Also, in some areas a 

well must be more than 1,000 feet deep to obtain a 

dependable water supply. As stated by Mundorff 

(CNPTS, 1970b, p. 69), 

About 42 percent of the region is underlain by aquifer units with low 

porosity or permeability that generally will yield only small supplies 

of ground water. It is fortunate that these units are confined mainly 

to thinly populated (mostly mountainous) areas where water needs 

are comparatively small and surface-water supplies are plentiful. 

The ground-water reservoirs that are most important 

in resource-management considerations are those capable of yielding water to wells at moderate or large 

rates and, therefore, which are large enough to be of 

public significance. Discussions in later sections of this 

report emphasize the major ground-water reservoirs 

that comprise the more extensive and productive 

aquifers in the region. 

Up to the present time, man's use of the ground-water 

resources in the Pacific Northwest Region has been relatively small in comparison with the total amount available, and use of the ground-water reservoirs must increase 

greatly if the projected water needs (fig. 2) are to be met 

fully (or even largely) in the future. The average regionwide rate of ground-water withdrawal in 1975 was 

estimated to be about 7,300 Mgal/d of which about 4,500 

Mgal/d were for irrigation and 2,800 Mgal/d for municipal, 

industrial, and rural water supplies. The ground-water 

withdrawal during 1975 constituted about 22 percent of 

the 33,000 Mgal/d diverted and withdrawn for all the uses 

listed in figure 2. 

From 1970 to 1975, the withdrawal of ground water 

apparently increased by the largest amount in the history of the region. The estimated increase was 70 percent of the 1970 amount of 3,000 Mgal/d-the same as 
PACIFIC NORTHWEST REGION 7 

WATER-BUDGET SUMMARY 

Billion Million 

·=Z> Inflow ft3jyr galfd 

Precipitation 17,600 361~000 

~ Inflow from Canada 2,300, 41,000 

GROUND WATER IN STORAGE Totals (rounded) 20,000 410,000 

6 Total in upper 

Bi1lion ft3 

~ Outflow 

1,000 feet 160,000 Stream discharge 12,100 248,000 

7 Amount ".rec.overable" 24,000 :;!> Ground-wat~ discharge 300 6,000 to saltwater 

(fraotion of total-not intended :0> to show depth of wells) Evapotranspiration 7,600 156,000 

Totals (rounded) 20,000 410,000 

FIGURE 3.-Generalized water budget and volumes of groundwater in storage for the region (data largely 

from Columbia-North Pacific Technical Staff, 1972, and appendices). 

the increase in total withdrawal from all freshwater 

sources (fig. 2). The difference in indicated withdrawal 

rates apparently represents a legitimate, generally 

progressive increase during the 5-year period rather 

than an anomalous difference caused, for example, by 

drastically different amounts of rainfall during the irrigation seasons in the two years. Most of the increase 

was in ldah.~, including shift of about 1,400 Mgal/d of 

irrigation withdrawals from surface-water to groundwater sources, and an increase of more than 1,500 

Mgal/d in withdrawals by self-supplied industries. 

Further increases in use of the ground-water reser-
8 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

voirs in the region seem inevitable for several reasons: 

1. The dry-season flows of most streams east of the 

Cascade Range are fully appropriated (some 

are overappropriated). 

2. Most cost-effective surface reservoir sites already have been used; therefore, further deliberate storage of water for later utilization 

must be largely in the ground-water reservoirs. 

3. As ground-water information and watermanagement techniques develop further, 

management of the stream systems and 

ground-water reservoirs conjunctively will 

become more practical and effective. 

Even in cases where choices exist, use of ground-water 

reservoirs has important advantages over use of 

surface-water reservoirs. For example, the initial costs 

connected with management of subsurface reservoirs 

commonly are much lower than for surface-water reservoirs. Also, ground-water bodies are less subject to 

evaporation, pollution, and temperature changes, and 

do not present hazards of downstream flooding. 

GEOGRAPHIC FACTORS AFFECTING THE 

GROUND-WATER RESOURCES 

Because the distribution, availability, and abundance of ground water in the Pacific Northwest Region 

are largely controlled by the landforms, climate, and 

earth materials, a general understanding of these features is necessary as a foundation for more specific discussions of the ground-water resources. 

If one word could be used to describe the geography 

of the Pacific Northwest Region, that word probably 

would be !!variety." The region is a composite of contrasts in physical and cultural geography. In population it ranges from dense urban centers, such as Seattle 

and Portland, to large tracts of land with no permanent 

human inhabitants. Its climate is dominated mostly by 

marine air masses but at times is influenced by continental air. It includes the wettest spot in the 48 conterminous states and some of the driest places in the 

Nation. The region contains examples of most of the 

landforms known to man, at altitudes ranging from sea 

level to more than 14,000 feet. Its vegetation assemblages range from rain forest to alpine to desert. It 

is not surprising, therefore, that great variety exists in 

the availability of and needs for the region's water resources, including its large and valuable ground-water 

resources. 

LANDFORMS AND DRAINAGE 

The landforms of the Pacific Northwest Region 

largely control the availability and use of ground water 

as well as the patterns of replenishment from precipitation and of drainage. The features of greatest 

significance to this ground-water appraisal include: 

The mountains, which receive much of the precipitation and divide the region into climatic zones; the flatter lands-valley floors, plains, and plateaus-which 

contain most of the population and account for most of 

the ground-water use; and the streams, which variously recharge or drain the ground-water reservoirs. 

The general physiographic divisions of the region are 

shown in figure 4. Detailed discussion of the physiographic features is beyond the scope of this report but 

can be found in CNPTS (1970b) from which this figure 

was taken. 

One important feature of the landforms that is not 

shown in figure 4 is the altitude of the flatter lands. 

The altitude strongly influences the growing season 

which, along with other factors such as soil productivity and growing-season precipitation, largely controls the demands for irrigation water. In order of increasing altitude, the areas of extensive flatter land 

labeled in figure 4 are: Willamette-Puget Sound 

Trough (most populous part), Columbia Plateau, Snake 

River Plain, and Oregon Closed Basins. At the two extremes, the Willamette-Puget Sound Trough has much 

land below the 500-foot altitude and an average growing season commonly greater than 160 days per year; 

the Oregon Closed Basins area has much land above 

4,000 feet where frost may occur during any clear night 

of the year. The Columbia Plateau and Snake River 

Plain are intermediate in growing season as they are 

in altitude. 

PRECIPITATION AND REPLENISHMENT PATTERNS 

Precipitation over the Pacific Northwest Region (fig. 

5) is the ultimate source of all the water except inflow 

from Canada. The characteristics of the precipitation 

(mainly the rates, seasonal distribution, and amounts 

as rain and snow) control the water that is available to 

recharge (replenish) the ground-water reservoirs, 

either by direct infiltration at the land surface or by 

seepage from streams. The actual recharge from precipitation, of course, is also controlled by other factors, 

principal of which are the character of the soil and of 

the rock materials that constitute the ground-water reservoirs. 

The most abundant annual precipitation in the conterminous 48 States occurs at high altitudes in the 

Olympic Mountains (northern part of Coast Range, fig. 

4), where it exceeds 200 inches. Eastward from the 

crest of the Olympics and the coastal mountains to the 

south, precipitation decreases to about 35 inches along 

the Willamette-Puget Sound Trough, then rises to 120 
0 40 80 120 160 200 KILOMETERS 

f I 1 1 11 'I 11 ) l t I IiI 

0 40 80 1'20 MIL-ES 

FIGURE 4.-Major land and water features of the region (Columbia-North Pacific Technical Staff, 1970b, fig. 2). 

\11'0 1100 

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0 40 80 120 160 200 KILOMETERS ~ I I I I I I I I I J I I I I I I 

0 40 80 120 MILES 

EXPLANATION 

Inches of water per year 

MORE THAN 120 

IZ::l!';liWMi.SM 8-120 

I!! I!! i! i! i!!! i6 48-80 

I ·. · · :: .. : l 24-48 

t/777777771 12-24 

LESS THAN 12 

FIGURE 5.-Generalized distribution of annual precipitation in the region (adapted from Columbia-North Pacific Technical 

Staff, 1970b, fig. 3). 

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PACIFIC NORTHWEST REGION 11 

inches or more toward the crest of the Cascade Range. 

East of the Cascade Range in Washington and Oregon the annual precipitation decreases sharply to 

about 10 inches or less in the valleys and on the 

plateaus, but generally increases again toward the 

east, where it reaches 40-50 inches in mountain areas. 

The Snake River Plain receives from 6 to 15 inches of 

annual precipitation, and mountains surrounding the 

plain receive as much as 40 inches. In northern Idaho 

annual precipitation ranges from about 16 to 70 inches. 

Westem Montana receives about 12 inches per year in 

some intermontane valleys but more than 150 inches at 

places in Glacier National Park (too small to show in 

fig. 5). Relatively dry belts exist in the rain shadows of 

the mountain ranges, and the greatest precipitation 

generally falls on the western, windward slopes. 

Extreme variations occur in the distribution of annual runoff in the region. In the westem part, large 

amounts of precipitation generate an average annual 

runoff that exceeds 100 inches in a substantial area of 

the Coast and Cascade Ranges. In contrast, annual 

runoff averages less than 1 inch in much of eastem 

Washington, eastern Oregon, and southem Idaho. Annual runoff greater than 40 inches is rare east of the 

Cascade Range. Patterns and amounts of runoff in various parts of the region are further described in CNPTS 

(1970b). 

In areas receiving less than 12 inches, much of the 

precipitation water is likely to run off or evaporate 

soon after it falls or, if it infiltrates below land surface, 

to be held in the soil and be used up by vegetation. In 

these areas, the amount of precipitation that percolates 

down to the ground-water system probably is equivalent to less than one inch of rainfall except where the 

infiltration capacity of the soil or rocks at land surface 

is unusually favorable. Where infiltration is poor, and 

in some drier areas, precipitation might recharge the 

ground water only during unusually wet periods. 

In areas shown as receiving less than 12 inches of 

precipitation per year (about 27 percent of the region), 

crops generally cannot be grown without irrigation. 

Exceptions occur in some areas that are subirrigated 

by shallow ground water, and in areas that are too 

small to be differentiated in figure 5 and which have 

slightly greater precipitation. Also, at places where 

soil conditions are especially favorable in depth and 

texture to store the moisture, dry-land farming practices have evolved which allow successful production of 

grain crops in alternate years on land that apparently 

receives only 10-12 inches of precipitation per year. In 

general, where soil and other conditions are favorable 

for farming, these areas potentially would benefit most 

of all areas in the region from the availability of water 

for irrigation. 

The areas receiving 12-24 inches (about 34 percent 

of the region) are intermediate in regard to potential 

recharge for ground water and water needs for farming. The places that receive precipitation amounts in 

the upper part of this range (generally closer to the 

higher-precipitation areas in fig. 5) commonly have a 

few inches potentially available for recharging the 

ground water. Actual recharge is more likely to be limited by land slope and infiltration capacity of soils 

rather than by precipitation amounts. In these places, 

crops that can be grown by dry-land farming methods 

are somewhat more varied and considerably more dependable and productive than in drier areas. 

Areas receiving more than 24 inches of precipitation 

per year may be generally considered to have abundant 

water available at the land surface for recharging the 

ground water. Some of these areas, including lowland 

parts of the Willamette-Puget Sound Trough and the 

floors of many smaller valleys, are underlain by 

permeable rock materials and receive large amounts of 

recharge. However, in some of the areas of abundant 

precipitation, actual recharge may be insignificant. 

Many of these areas, especially east of the Cascade 

Range, consist of mountains where the combination of 

steep slopes and soils of low permeability induces a 

large proportion of surface runoff from the precipitation. (Compare figs. 4 and 5.) Therefore, except in areas 

of permeable rocks in the high Cascades of Oregon and 

southern Washington (the High Cascades groundwater reservoir, table 1 and fig. 8), the local recharge in 

the mountainous areas of abundant precipitation is 

relatively unimportant to the manageable parts of the 

regional ground-water resources. Also, for several 

reasons including rugged terrain, generally poor or absent soils, and available surface water, the higher areas 

of abundant precipitation generally do not require additional ground water for irrigation or other purposes. 

The higher areas of abundant precipitation are 

significant to the management of ground-water mainly 

in that they generate stream runoff which flows to 

lower, generally drier parts of the region and contributes to the recharge of major ground-water reservoirs 

located there. 

The seasonal distribution and type of precipitation 

also affect the availability of water and opportunity for 

recharge of the ground water. Although average yearly 

precipitation ranges widely, the seasonal distribution 

of precipitation is similar throughout most of the region. Except for parts of westem Montana and northcentral and southeastern Idaho, the region has distinctly dry summers and wet winters. About one-third, 

or less, of the annual precipitation generally occurs 

during the 6-month period April-September, and less 

than 15 percent during the latter 3 months of that 
12 SUMMARY APPRAISALS OF THE 1\'ATION'S GROUND-WATER RESOURCES 

period (fig. 6). About two-thirds occurs during 

October-March, when it generally falls as rain at the 

lower altitutdes and as snow at the higher altitutdes. 

Abundant snow on many of the high mountains has 

maintained glaciers and perennial snowfields that are 

important sources and regulators of streamflow. The 

heaviest annual snowfalls-sometimes totaling more 

than 60 feet-are in the higher parts of the Cascade 

Range. In most mountain areas at altitudes above 

6,000 feet, snow cover commonly persists from early 

November until early June. Melting of the abundant 

snow maintains flow at relatively high levels in many 

of the streams throughout the spring; in some places 

the high flow does not end until early July. 

At the stations shown in figure 6, precipitation is 

greatest during the winter but differs significantly in 

amounts. Astoria, Oregon, receives 13 times as much 

precipitation in December as does Yakima, Washington. In some eastern parts of the region, however, the 

seasonal distribution of precipitation is different, and 

1-

<( 

!:: 

:!:: 

z' 6 ~ 

FIGURE 6.-Seasonal distribution of precipitation at selected 

weather stations in the region (Bodhaine and others, 

1965, fig. 8). 

the differences between amounts during the summer 

and winter are generally less distinct. At some lowland 

precipitation stations in western Montana and northcentral and southeastern Idaho more than one-half the 

annual precipitation falls during the period AprilSeptember. 

The coincidence of the wettest period with the cooler, 

nongrowing season is highly favorable for recharge 

to the ground-water reservoirs. During the cooler 

months, the losses of precipitation to evaporation and 

vegetation are minimal, and the opportunity for available water to infiltrate the land surface is greatly enhanced. Conversely, the small percentage of precipitation that arrives during the growing season causes 

greater water needs for irrigation and summertime 

municipal uses than would occur in comparable situations in most other regions of the Nation. The distinctly dry summer period is the reason why even the 

crops grown west of the Cascades benefit greatly from 

irrigation. 

Evaluation of the supplies of water that can be expected in the future, and of future water needs as well, 

must include the possibility of protracted periods of 

drought or above-normal precipitation. Previous 

analyses of long-term variations in precipitation, including determination of prehistoric climatic trends 

based on tree growth rings, have yielded the following 

conclusions (Bodhaine and others, 1965, p. 31): 

1. Periods during which precipitation will be considerably above or below the average for several successive years can be expected occa2. 

3. 

4. 

sionally in any part of the region. 

The cumulative effects of several closely spaced 

periods of deficient or abundant precipitation 

will be greatest in the drier parts of the region. 

During the period 1287-1937, there was no persistent trend toward a wetter or drier climate 

in eastern Oregon. 

Although significant variations of the climate 

(including precipitation) have occurred 

throughout much of eastern Oregon (and 

probably beyond), no rhythmic cycle was evident or could be predicted on the basis of tree 

. rings. 

5. A general drought in eastern Oregon, which 

began in 1918 and lasted until about 1940, 

was the most severe that the area had experienced during the 650 years prior to 1937. 

One of the unstated assumptions related to the projections of future water needs (fig. 2) is that the patterns of precipitation will continue in the future about 

the same as those in the past. 
PACIFIC NORTHWEST REGIO N 13 

GEOWGIC SOURCES AND DISTRIBUTION OF 

GROUND WATER 

THE PRODUCTIVE AQUIFERS 

The main focus of this report is on the more than half 

of the Pacific Northwest Region that is underlain by 

rock materials known, or believed from geologic evidence, to be capable of yielding ground water to wells 

at moderate to large rates. These are the areas where 

proper planning and effective water management, 

based on adequate data and sound hydrologic principles, along with the removal of nonessential constraints, can produce a significant increase in the 

amount of water available for man's use. These are also 

the areas where the ground-water reservoirs are most 

likely to be economic sources of supplies for irrigation, 

industrial, and municipal uses. 

The major ground-water reservoirs can be classified 

mainly in three groups-those made up of (1) predominantly sedimentary rocks (including deposits 

from streams, glaciers, and the wind), (2) predominantly volcanic rocks, and (3) combinations of sedimentary and volcanic rocks. The generalized distribution of 

these types of aquifers where they are capable of yielding 100 gallons per minute or more of water to individual wells (but without regard to depth of well or 

amount of pumping lift) is shown in figure 7. 

Differences in the occurrence and movement of 

ground water in the two main classes of rockssedimentary and volcanic-are significant to the functions and management of these rocks as ground-water 

reservoirs. The sedimentary rocks yield water to wells 

mainly from layers of sand and gravel, which are the 

kinds of sedimentary rocks in this region that are most 

likely to yield water at moderate to high rates. Less 

permeable sedimentary materials, such as clay and 

silt, are more common in the region and, although they 

yield water to wells at lower rates, they serve the extremely valuable function of long-term storage that 

can drain slowly to adjacent permeable aquifers. These 

fine-grained deposits have a relatively high porosity, 

but the pore spaces are so small that considerable force 

(in the form of hydraulic pressure or weight of overlying rocks) is required to dislodge much of the water 

they contain. The saturated space within the permeable sedimentary rocks consists mostly of the primary 

pore space left between the particles of rock materials 

as they were deposited. Those sedimentary rocks in the 

region that have been hardened by such natural processes as compaction or cementation may develop secondary joints and fractures which transmit water, but 

the benefits of such secondary openings commonly do 

not offset the loss of pore space and permeability that 

results from the rock-hardening processes. 

The volcanic rocks yield water mainly from permeable zones that occur at or near the contacts between 

some flow layers; central and lower parts of the flow 

layers are nearly always denser and much less permeable. The abundance, causes, and nature of the permeable zones differs greatly. The zones tend to occur less 

commonly in rocks of the Columbia Plateau (fig. 4) 

than in rocks of the Snake River Plain and younger 

volcanic rocks. (See table 1, "Remarks".) They commonly result from the incomplete filling of openings at 

the top of one flow layer (such as rubble, cinders, or 

scoria) by the lava of a succeeding flow. Other permeable interflow zones have other origins, including deposition of sedimentary materials during the times between lava outpourings. 

The volcanic ground-water reservoirs commonly 

yield water to wells at high rates but generally can 

yield less water from storage than the same volume of 

permeable sedimentary rocks. This is because the total 

volume of openings in the volcanic rocks is nearly always less than that in productive sedimentary rocks; 

moreover, many openings in the volcanic rock are 

likely to be poorly connected. 

Both the sedimentary and the volcanic reservoir 

rocks are layered and, consequently, movement of 

water through the rocks along the beds (mainly horizontal) is less restricted than movement across the 

beds (mainly vertical). In the sedimentary reservoirs, 

vertical movement between the permeable beds 

(mostly sand and gravel) is commonly impeded by intervening layers of silt, clay, or naturally cemented 

materials. In the volcanic rocks, vertical movement is 

impeded by the dense and poorly permeable rock which 

generally constitutes the bulk of each flow layer. Even 

the dense parts of the flow layers, however, generally 

contain enough fracture and joint openings to allow 

some movement of water, although leakage from one 

permeable interflow zone to another may be greatly 

restricted. Cross-bed leakage between permeable zones 

in both the sedimentary and volcanic rocks is "shortcircuited" by many wells that are either unlined (uncased) in the interval between permeable zones, or 

have casing that is open to more than one of the zones. 

Some large bodies of the saturated permeable rocks 

shown in figure 7 are at such great depths, or in such 

high or rugged terrains, that imminent development is 

unlikely. However, at many places, as in the Cascade 

Range in Oregon and southern Washington, these remote aquifers are very valuable because of the large 

quantities of water they supply to streams. Also, some 

of these remote aquifers are likely to be future sources 

of water for increased forest irrigation, (See table 1, 

High Cascades ground-water reservoir.) 
14 SUMMARY APPRAISALS OF THE l\ATION'S Gl<OUND-WATF:l< l<F:SOCRCES 

0 40 80 120 j 160 200 KILOMETERS 

r-~~--~TI~-, --~1,-l--~-L,~1 

40 80 120 MILES 

FIGURE 7.- Generalized distribution and types of major aquifers 
PAC! FIC ;\IQRTHWEST REGION 

EXPLANATION 

Areas underlain by major aquifers 

of the following rock types: 

CJ 

Chief1y sedimentary rocks 

Chiefly volcanic rocks 

Sedimentary and volcanic rocks 

-----------, \ 

(Columbia-North Pacific Technical Staff, 1970b, fig. 20). 

15 
16 SUf\1:\I A RY A PPRA ISALS OF T ilE :\ATIO:\'S GRO UN D-W ATER RESO C RCI::S 

DESCRIPTION OF THE GROUND-WATER RESERVOIRS 

Extensive areas in the region are similar enough in 

climate, topography, water uses, and character of the 

aquifers to be considered as a unit for discussion of 

ground-water problems and management opportunities. Six such areas, referred to in this report as major 

ground-water reservoirs, are shown in figure 8. The 

general characteristics of these major ground-water reservoirs are summarized in table 1, along with associated problems and water-management opportunities. 

The grouping of areas into the major ground-water 

reservoirs is not intended to imply that all parts of the 

designated reservoirs are hydraulically interconnected 

or can be managed as a unit, or that water necessarily 

moves across the state boundaries that cross some of 

the designated reservoirs. Unfortunately, the natural 

extent of these major ground-water reservoirs does not 

fit drainage-basin or other subregional boundaries and, 

therefore, the reservoir areas are difficult to relate to 

the summary values found in earlier regional reports. 

However, a few general statements can be made. For 

example, the major ground-water reservoirs probably 

receive more than one-half the estimated 4,000 billion 

ftJ of annual recharge (p. 6); they contain about twothirds of the region's ground water in recoverable storage (fig. 3), or 16,000 billion ftJ; and the ground-water 

withdrawal from them in 1970 (about 3,600 Mgal/d) 

accounted for more than four-fifths of the total for the 

region that year (fig. 2). More detailed information 

about various parts of designated reservoir areas is 

available in reports listed in "Selected References," especially in the aforementioned Appendix 5 of the 

"framework" study (CPNTS, 1970b). The notes in table 

1 help relate the major ground-water reservoirs to the 

subregions used in that earlier study. 

Besides those areas shown in figure 8, there are 

many smaller ground-water reservoirs in the region 

that are capable of yielding water at rates suitable for 

industrial, irrigation, and public supplies. Some of 

these, including scattered areas along the coastlines of 

the Pacific Ocean and along major streams, are shown 

in figure 7, but others are too small to be shown at the 

scale of that map. The smaller size of these groundwater reservoirs does not reflect their relative importance in the region; their aggregate volume is several hundred cubic miles, and at many places they are 

the only usable sources of fresh ground water. 

Moreover, they include some of the areas most likely to 

benefit from water-management possibilities. Therefore, although they are not listed individually in this 

report, they are included as a category in table 1 and 

are mentioned in the following summary discussions of 

ground-water problems and management opportunities. Some of these smaller reservoir areas were described in greater detail by Mundorff (CPNTS, 1970b). 

MAJOR GROUND-WATER PROBLEMS 

The most significant problems pertaining to ground 

water, which are listed briefly for each of the groundwater reservoirs in table 1, fall into five general 

categories. These are: (1) Progressively declining water 

levels; (2) ground-water quality problems; (3) waterlogging; (4) inadequate information, and (5) competition for available supplies. 

PROGRESSIVELY DECLINING WATER LEVELS 

A decline in ground-water levels is an inevitable consequence of withdrawing water from wells-it does not 

necessarily represent a long-term depletion of the 

ground-water reservoir, otherwise called ground-water 

mining. The long-term significance of water-level declines depends on several interrelated conditions, 

among which are the year-to-year rate and persistence 

of decline, the size of the ground-water reservoir in relation to the area where the decline occurs, and the 

hydrologic and economic consequences of continuing 

decline. Short-term declines in levels can have beneficial water-conservation effects, such as the salvage of 

water otherwise lost as evapotranspiration from waterlogged land, or creation of storage space in the 

ground-water reservoir for subsequent filling by 

surplus stream water. Even if water-level decline can 

be identified as a long-term depletion of a ground-water 

reservoir, the results may not be all bad, especially if 

there is no compelling reason to preserve the ground 

water and if undesirable consequences of the depletion 

(such as reduction of streamflow or ultimate disruption 

of local economy based on irrigation farming) can be 

tolerated. Each declining water level must be judged 

on its own special conditions. 

Persistent declines of ground-water levels have occurred in several areas of the region, and major depletion of the ground-water reservoir has been projected 

for a few areas. The declines are all in areas of sizable 

pumping for irrigation, although pumping for municipal and industrial uses has contributed to the declines 

in some areas. Most ofthe declines involve the volcanic 

aquifers, and most are in the arid and semiarid parts of 

the region. Significant, persistent declines have occurred in the Willamette Valley, the High Desert, the 

Columbia Plateau, and the Southern Idaho major 

ground-water reservoirs shown in figure 8. Locations of 

the areas of decline are shown in figure 9, and information about the declines is summarized in table 2. 
0 40 80 120 160 200 KILOMETERS 1 I I I I ! I I I I 1 

I I I I I 

0 40 80 120 M ILES 

FIGURE 8.-Areas designated as major ground-water reservoirs, estimates of recoverable water in each (billion cubic feet), 

and 1970 pumpage (in parentheses-million gallons per day). 

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18 SU\1'-'IARY APPRAISALS OF THE NATION'S GROU;\D-WATER RESOURCES 

TABLE 1-Summary of conditions in major ground-water 

Designation used 

in this report 

Puget Sound 

ground-water 

reservoir 

Willamette Valley 

ground-water 

reservoir' 

High Cascades 

ground-water 

reservoir4 

High Desert 

ground-water 

reservoir 

Columbia Plateau 

ground-water 

reservoir6 

Southern Idaho 

ground-water 

reservoir7 

Smaller groundwater 

reservoirs 11 

Major aquifer• materials 

and yields w wells 

Sedimentary rocks deposited by 

streams or glaciers; 

moderate to very 

large rates of yield. 

Sedimentary rocks deposited by 

streams and glaciers 

and (in northern part) 

interflow zones in 

basalt; alluvial gravel 

along Columbia River has 

very large rates of 

yield. 

"Young" volcanic 

rocks; very large rates 

of yield. 

Sedimentary rocks deJX)sited from streams 

and lakes; "young" 

volcanic rocks; older 

sedimentary and volcanic 

rocks. Rates of yield are 

moderate to very large. 

Volcanic rocks of the 

Columbia River Group (and 

similar rocks in Oregon); 

alluvial deposits from 

modem streams and from 

Glacial-Age meltwater 

floods; older sedimentary 

basin-fill deposits. 

Rates of yield are 

moderate to very large. 

Young basaltic volcanic 

rocks; young sedimentary 

deJX>Sits; older volcanic 

and sedimentary rocks. 

Rates of yield are 

moderate to very large. 

Mainly young sedimentary 

deposits (alluvial fan, 

floodplain, glacial outwash, and lake deposits; 

dune and b·~ach sand); some 

volcanic rocks. 

Recharge w major aquifers 

Infiltration of precipitation and streamflow; 

generally ample in 

relation to pumpage. 

Mainly by infiltration of 

precipitation water; flood 

waters from m~or streams 

recharge a<ijacent aquifers; 

irrigation augments natural 

recharge, Recharge generally ample, except for 

basalt aquifers. 

Infiltration of precipi· 

tation water; recharge 

rates greatest of all the 

major ground·water reser· 

voirs in the region. 

Infiltration of precipita· 

tion and of runoff from 

mountains within and 

bordering the area. Away 

from the mountains, 

recharge may occur only 

occasionally. 

Infiltration of rain and 

snowmelt water from land 

surface and stream channels; 

infiltration of irrigation 

water. Recharge in non· 

irrigated areas is limited 

by dry climate; recharge 

incidental to irrigation 

can be many times the 

natural recharge. At 

places, recharge probably 

occurs only during 

unusually wet periods. 

Nat ural recharge is mainly 

by seepage from streams 

during their high-flow 

periods (especially streams 

that carry water into the 

area from adjacent uplands), 

and by direct infiltration 

of rain and snowmelt water. 

Water lost from the 

irrigation process is a 

large source of recharge, 

the largest source at 

places. 

Infiltration of precipita· 

tion water; seepage from 

streams during their high· 

flow periods; seepage 

from irrigated soils and 

conveyance ditches. 

Discharge modes 

and withdrawal 

Seepage to streams and 

marine waters; springflow 

along slopes. Pumpage is 

small in relation to 

recharge. 

Seepage w Columbia and 

Willamette Rivers and 

their m~or tributaries. 

Pumpage from sedimentary 

aquifers is small in 

relation to recharge. 

Seepage w streams, which 

have very high dry·season 

flows, and springflow. 

Very little pumpage. 

Evapotranspiration, spring· 

flow, and (in northern 

parts of the area) seepage 

to streams. Pumpage very 

small in relation to ground 

water in storage and average 

recharge. 

Seepage to streams; spring· 

flow and seepage at land 

surface; evaJX)transpiration. 

Pumpage is generally small 

in relation w wtal 

recharge and amount of 

ground·water in storage, 

but tends w be concentrated. 

Springflow and seepage to 

streams; evapotranspiration; 

pumpagc for irrigation is 

very large, but is causing 

water.level declines in 

only a few areas. 

Seepage to streams during 

their low·fiow periods; 

evapotranspiration; 

springfiow; seepage w the 

ocean. In relation to the 

amounts in the individual 

ground·water reservoirs, 

pumpage ranges from very 

small w large. 

Largest existing 

use of the 

ground water 

Public supplies, 

largely supplemental to stream 

supplies. 

Industrial sup--

plies, mostly in 

metropolitan 

area near 

Columbia River, 

Rural domestic and 

stock supplies. 

Irrigation. 

Irrigation. 

Irrigation. 

Generally 

irrigation. 

NOTES: 1. Arbitrarily designated as capable of yielding water to a properly constrUcted w·ell at a rate of 100 gpm or more, from a depth that is reasonable for common drilling methods and 

modem pumping equipment. 

2. Lies entirely within Subregion 11 of the CNPTS study. 

3. Comprises southern part of Subregion 8 and lowland parts of Subregion 9 of the CNPTS study. 

4. Comprises mountainous parts of Subregions 3, 7, 8, 9, and 10 of the CNPTS study. 
PACIFIC i'\ORTHWEST RECIO:\ 

reservoirs (General location and extent shown in fig. 8) 

Major problems pertaining to ground water 

Existing 

Troublesome amounts of 

dissolved iron in some aquifers; 

local deterioration of water 

quality resulting from waste· 

disposal practices; lack of 

adequate information in 

critical near·shore areas; 

seasonal waterlogging. 

Limited distribution of largeyield aquifers; excessive dissolved minerals at places, 

including salty water; deterioration of water quality 

resulting from disposal of 

household wastes and water used 

for air conditioning; declining 

water levels in basalt aquifers, 

local waterlogging. 

Lack of adequate information. 

Water quality, generally not as 

good as in other major groundwater reservoirs; lack of 

adequate information; water· 

logging in some basin·floor 

areas. 

Declining water levels and 

local depletion of 

the ground·water reservoir; 

competition for available 

supplies; waterlogging. 

Conflicts between ground· 

water withdrawals and surface· 

water rights; waterlogging; 

lack of adequate information 

about ground·water availability 

at places. 

Inadequate total supply; 

conflicts between ground· 

water uses and surface-water 

rights; waterlogging; 

unsatisfactory water quality. 

Foreseeable 

Continued local deterioration of 

water quality resulting from 

waste disposal; local saltwater intrusion resulting 

from increased near-shore 

pumping. 

Continued local deterioration of 

water quality resulting from 

waste-disposal practices; continued depletion of water in basalt 

aquifers. 

Some undesirable dissolved minerals may be present locally. 

Major problems unlikely until development increases considerably. Intensive pumping fOr 

irrigation could easily deplete 

aquifers that receive little recharge. More waterlogging is 

likely if some basin-floor areas 

are irrigated. 

Continuing and growing areas of 

water-level decline; some actual 

depletion of water in aquifers of 

limited extent and recharge; increased waterlogging caused by 

increased irrigation. 

Management opportunities 

I 

Reduction of pollution from surface or 

shallow waste disposal; greater use of ground water 

as supplies for near-shore development and for 

irrigation; use of deep, confined salty-water 

aquifers for waste disposal or storage of 

freshwater and natural gas. 

Reduction of pollution from waste disposal; 

promotion of well designs best suited for 

improved yields from marginal sedimentary 

aquifers; additional pumpage from alluvial 

aquifers; possible use of salty-wa ter 

aquifers for subsurface storage or disposal 

of fluids; pumping from waterlogged areas 

as drainage measure. 

Forest irrigation in areas of fa vorable 

topography and soils; drainage, by artificial 

tunnels, for hydropower generation; controlled 

drainage for support of low-level flow or 

quality of streams. 

Greater development of ground water in most areas; 

use of deep aquifers for storage 

or disposal of fluids. Possible development of 

geothennal ground water. 

Additional ground-water withdrawal, especially 

in deeper aquifers and away from areas of 

concentrated pumping; greater use of 

sed imentary aquifers; conjunctive use of surface 

water and ground water; deep .subsurface waste 

disposal; lining of leaking well bores and 

improvement of new-well construction; 

a rtificial recharge using surplus stream water; 

salvage of some evapotranspiration discharge; 

reducing and forestalling waterlogging. 

More areas of water-level decline; Withdrawal of water from untapped parts of the 

continuing waterlogging; increasing conflicts with surfacewater rights; increased occurrences of local pollution of 

ground water 

Increased competition for avai lable water supplies; spread of 

ground-water pollution; saltwater intrusion near the Pacific 

Ocean. 

ground-water reservoir; conjunctive use of 

surface water and ground water; artificial 

recharge with surplus stream water; salvage of 

some evapotranspiration discharge; reducing and 

forestalling waterlogging 

More beneficial use of the total water supply 

through conjunctive use and management of both 

surface water and ground water; reducing and 

forestalling local pollution and waterlogging; 

salvage of some evapotranspiration discharge. 

19 

Remarks 

Very large additional supplies of ground water are 

avai lable; development has been retarded by general 

abundance of good-quality stream waters. 

Withdrawal for public supplies is about equal to 

combined withdrawals for industrial, irrigation, and 

rural-domestic uses. Ground-water resources in 

many island and peninsular areas are extremely 

valuable but inadequately appraised. 

Very large additional supplies are available, chiefly 

from alluvial aquifers, especially those along 

Columbia River. Industrial and irrigation uses constitute about 90 percent of total ground-water use. 

Development will be constrained by limited availability of large-yield aquifers, water-quality problems, and declining levels in basalt aquifers. 

Ground water is of go<XI to excellent quality and 

recharge is adequate to support almost any conceivable withdrawals. Development will be severely restricted by remoteness, short growing season, and 

great depth to water table in many places. May have 

potential for geothermal development at places. 

Young volcanic aquifers are capable of the 

largest yields to wells, but much of the available 

ground water is stored in sedimentary rocks. Availability of ground water is limited by great depth to 

water in many places and meager recharge. Reservoir system is complicated by abundant faulting. 

Development will be constrained by short growing 

season, remoteness, by locally poor water quality, 

and by risks in prospecting for large-yield aquifers 

owing to inadequate information. 

In much of the area the basalt aquifer is the only 

ava ilable source of rural-domestic, stock, and public 

water supplies. Where recharge is small, the bsalt 

aquifer is very susceptible to overpumping and depletion because of the large rate of yield and very 

small storage capacity. The ground-water is generally of good to excel lent quality; hardness and 

dissolved-iron content are greater than desirable 

at places. 

The young volcanic rock aquifer of this area is one of 

the most extensive and productive aquifers in the 

U.S.; it is considerably more permeable and porous 

than most basalt of the Columbia Plateau groundwater reservoir, and its storage capacity may be on 

the order of 20 times greater, volume for volume. 

Water from the younger volcanic and sedimentary 

rocks usually has satisfactory quality for most uses. 

Some of the hottest (90"C) and most mineralized 

ground water in the region is fOund in some of the 

older, less permeable rocks. 

The aggregate volume of the reservoir rock materials 

in areas of this category is several hundred cubic 

miles. In many places these are the only usable 

sources of fresh ground water; examples are deposits 

along the coastli nes of the Pacific Ocean and Puget 

Sound, and stream-valley deposits in 

widely ~.:attered areas 

that otherwise are underlain by impermeable rocks. The locations of these smaller areas 

can be found by comparing figures 7 and 8. They are 

described in greater detail by Mundorff (CNPTS, 

1970bl. 

5. Comprises areas in southwestern part of Subregion 5, southeastern part of Subregion 7, and all of Subregion 12, of the CNPTS study. 

6. Comprises areas in southern part of Subregion 2, eastern part of Subregion 3, western part of Subregion 6, and northern part of Subregion 7, of the CNPI'S study. 

7. Comprises areas in central and southern parts of Subregion 4, eastern part of Subregion 5, and southern part of Subregion 6, of the CNPTS study. 

8. Mainly in Subregions 1, 2, 4, 6, and 10, of the CNPTS study. 
~loho 

, Lalt Ab trt 

0 40 80 120 160 200 KILOMETERS l I I I I I l ! I I 1 I I I I I 1 

0 40 80 120 M ILES 

FIGURE 9.-Location of areas where significant declines in ground-water levels have occurred. Rates and duration of decline are listed in table 2. Circles represent 

areas where extent of decline is indefinite or too small to be shown precisely at this scale. 

0 "" 

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v 

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rr: 

z 

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c 

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PACIFIC NORTHWEST REGION 21 

TABLE 2. Summary of information about water-level declines 

[Areas shown in figure 9. Values represent net differences between yearly high water levels:] 

Area and reference report 

Salem Heights 

(Foxworthy, 1970) 

'fualatin Valley 

(Bartholomew and 

others, 1973) 

Cow Valley 

(Brown and Newcomb, 1962) 

The Dalles 

!Bartholomew and 

others, 1973 

Ordnance-Butter 

Creek (Bartholomew 

and others, 1973) 

Walla Walla 

(MacNish and 

others, 1973) 

Ahtanum Valley 

(Foxworthy, 1962) 

Toppenish Creek 

(U.S. Geol. Survey, 

1975) 

Odessa-Lind 

(Luzier and 

Skrivan, 1975) 

Davenport 

(Luzier and Burt, 

1974) 

Decline 

As much as 8 ft/yr, at 

least 38 ft total by 

1961; thereafter, levels 

have risen gradually. 

As much as 12 ft/yr; more than 40 ft total, 

early 1960's to 197 4; 

thereafter, levels have 

generally risen. 

As much as about 

3 ft/yr by 1959, slower 

by late 1960's. 

As much as about 

6 ft/yr by 1965; levels 

largely stabilized 

since 1970. 

Ranged from less than 

4 to about 40 ft/yr, 

1961-73. 

As much as 15 ft/yr; 

total as much as 150ft 

since the late 1890's. 

As much as 31h ft/yr, 

1953-57. 

As much as 7 ft/yr, 

1960-70 

As much as 40ft total, 

1967-71. 

Began about 1966; 

amounted to about 17 ft 

(3.4 ft/yr) during the 

period 1972-77. 

Cheney-Airway Heights Generally less than 

(Luzier and Burt, 5 ft/yr. 

1974) 

Moscow-Pullman 

(Barker, 1979) 

Raft River Valley 

(Sisco, 197 4) 

Rock Creek and 

Goose Creek 

(Sisco, 1974) 

Castleford 

(Sisco, 197 4) 

Began in 1890's; total more than 100 ft at 

places, but averaged 

only about 1 ft/yr. 

Began by at least the 

early 1950's; has been as much as about 5 ft/yr. 

As much as 22 ft/yr 

(total greater than 200 

ft) 1961-72 in limestone aquifer; as much as 5 ft/yr in other 

aquifers. 

Mostly in the range 

of 2-4 ft/yr; as much as 60 ft total since the 

1960's. 

Aquifer(s) 

Basalt 

(small extent) 

Basalt 

Basalt and 

overlying 

sand and gravel 

Basalt 

(faulted 

and folded) 

Basalt and 

overlying 

gravel 

Basalt 

Basalt 

Basalt 

Basalt 

Basalt 

Basalt 

(relatively 

thin) 

Basalt and 

interbedded 

sand 

Basalt and 

sedimentary 

rocks 

Basalt and 

other volcanic, alluvial, and 

limestone 

rocks 

Volcanic rocks 

Main use(s) of water 

Public supply, industrial 

Irrigation, public supply 

Irrigation 

Irrigation, 

industrial, 

public supply 

Irrigation, 

industrial, 

public supply 

Irrigation, 

industrial, 

public supply 

Irrigation 

Irrigation 

Irrigation 

Irrigation 

Irrigation, public supply 

Public supply, irrigation 

Irrigation 

Irrigation, industrial 

Irrigation 

Remarks 

Alternative public water supply was provided in 1961; aquifer later used 

mainly for artificial recharge and 

supplying peak demands. 

Declared to be a critical ground-water area by Oregon State Engineer in 

1974; that same year, the WolfCreek 

Irrigation Project began supplying 

water from 'fualatin River and 

ground-water use declined. 

Declared to be a critical ground-water area by Oregon State Engineer in 

1959; pumpage restricted thereafter. 

Declared to be a critical ground-water area by Oregon State Engineer in 

1959. Substitute water supply from 

Columbia River was provided by 

The Dalles Irrigation Project 

beginning in 196 7. 

Declared to be a critical ground-water area by Oregon State Engineer 

in 1976. 

Rate of decline is expected to slow 

greatly unless pumpage continues to 

increase substantially. 

Additional large-yield wells tapping 

the basalt have been restricted by 

Washington Department of Ecology. 

Yakima Tribal Council was considering 

(1977) prohibiting additional largeyield wells tapping the basalt, and 

further regulation of pumping. 

Washington Department of Ecology is 

trying to regulate pumping so that 

progressive decline does not exceed 

about 10 ft/yr. 

Declines have been monitored, but no regulation of pumping had been 

imposed by 1977. 

The basalt (only aquifer available) 

is unusually susceptible to total 

depletion. 

Declines are expected to slow unless 

future pumping continues 

to increase. 

Idaho State Reclamation Engineer 

declared the valley to be a critical area in 1963, and restricted the 

drilling of additional wells; declines 

subsequently slowed or stopped. 

Idaho State Reclamation Engineer 

stopped issuing well permits in 1962; 

thereafter, declines slowed or stopped. 

Idaho Department of Water Resources 

closed the area in 197 4 to further 

ground-water development. 
22 SL'.\niARY APPRAISALS OF THE :\ATIO:\'S CROU\'D-\\'ATER RESOCRCES 

WATER-QUALITY PROBLEMS 

Water quality is presently not a significant limiting 

factor to the use of water from the major ground-water 

reservoirs. Although at places some dissolved constituents are found in concentrations greater than desirable for some purposes, most of the ground water is 

considered good to excellent for common use. Saline 

ground water is known to underlie several hundred 

square miles of the major ground-water reservoirs, but 

it is generally at considerable depth in areas where 

other sources of fresh ground water are available. Contamination resulting from man's activities is a growing 

problem, but only in a few areas has it reached proportions that cause serious limitations to continued use 

of the ground water. 

The data that are presently available on groundwater quality pertain mostly to inorganic chemical 

constituents of the water that occur in varying 

amounts under natural conditions. In this respect, the 

data are mostly indicative of ((baseline" conditions. 

Data on occurrences of organic compounds, which include most pesticides and many industrial products, 

are gradually becoming increasingly available, but are 

commonly related only to known or suspected cases of 

ground-water contamination. 

PROBLEMS OF NATURAL ORIGIN 

The most significant problems involving natural 

ground-water quality are: 

DISSOLVED IRON 

Probably the most widely bothersome natural constituent in the ground water of the region is dissolved 

iron, sometimes in combination with manganese. It occurs in undesirable concentrations at places in all the 

major ground-water reservoirs. 

Dissolved iron does not affect the usefulness of 

ground water for irrigation, but causes problems in 

some industrial uses of the water and in household use 

where it may impart undesirable taste and color to 

drinking water and cause staining of plumbing fixtures 

and laundry. Some type of treatment (usually simple) 

to remove or reduce the effects of dissolved iron is a 

common adjunct to the development of ground-water 

supplies for public or individual domestic uses in the 

region. 

SALINITY 

Ground waters containing enough dissolved minerals to be considered ((saline" waters probably underlie 

much of the area of the major groundwater reservoirs 

but are troublesome in only a few places. Well waters 

with dissolved-solids concentrations of1,000 mg/L (milligrams per liter) or more have been found mostly in 

the Puget Sound, Willamette Valley, High Desert, and 

Southern Idaho ground-water reservoirs. Ground waters having dissolved-solids concentrations greater 

than 1,000 mg/L are mainly in older rocks that are not 

permeable enough to be important aquifers, and almost all these areas also have freshwater aquifers capable of larger yields. The saline ground waters are tapped by wells generally deeper than 100 feet, but in a 

few coastal areas of the Puget Sound ground-water reservoir, salty water is pumped from shallow wells. Also, 

saline ground water from older rocks locally migrates 

into shallow aquifers, and even discharges at the land 

surface as mineral springs in the High Desert and 

Southern Idaho ground-water reservoirs. In the latter 

reservoir area most of the springs that yield water with 

dissolved-solids concentrations greater than 1,000 

mg/L are thermal springs. 

Throughout the region, well waters having dissolved 

solids concentrations of 3,000 mg/L or more are rare, 

and generally represent seawater intrusion (Puget 

Sound ground-water reservoir) or thermal ground 

water (High Desert and Southern Idaho ground-water 

reservoirs). 

OTHER DISSOLVED CONSTITUENTS 

In addition to iron, a few other dissolved constituents 

occur naturally in waters of the major ground-water 

reservoirs in undesirably high concentrations. These 

occurrences are generally rather localized, in terms of 

aquifer zones as well as areal extent, and are mostly in 

the arid parts of the region. They tend to be near the 

margins of the major ground-water reservoirs, where 

the important aquifers are close to older rocks which 

generally are the sources of the undesirable constituents. These occurrences include concentrations of 

sodium and boron that are excessive for irrigation waters, mostly at places in the area of the High Desert 

ground-water reservoir, and concentrations of fluoride 

that exceed national drinking water standards, mainly 

at places in the High Desert and the Columbia Plateau 

ground-water reservoirs and a few places in thermal 

waters in the Southern Idaho ground-water reservoir 

(National Academy of Sciences and National Academy 

of Engineering, 1973). 

The only known naturally occurring dissolved constituent in the region posing a health threat to humans 

is arsenic in ground water that was used for domestic 

supplies in the southern part of the Willamette Valley 

ground-water reservoir. However, that threat was recognized (Goldblatt and others, 1963) and alternative 

supplies developed, and the occurrence is now 

significant mainly as a historical reminder. 
PACIFIC :\'ORTHWEST RH~IOi\: 23 

PROBLEMS RELATED TO MAN'S ACTIVITIES 

Degradation of ground-water quality as a result of 

man's activities is a greater problem in this region 

than the naturally occurring water-quality characteristics, but it has not reached the major proportions 

found in some other regions. Degradation of the quality 

is, as would be expected, related largely to population 

distribution, being best known and most varied in 

cause where people and industries are concentrated. 

CONTAMINATION FROM THE LAND SURFACE 

Known and suspected occurrences of ground-water 

contamination from sources at the land surface are 

numerous, but so far no major ground-water supplies 

have been abandoned for this reason. The sources of 

such contamination differ widely, and include such 

things as solid-waste landfills, spilled chemicals and 

petroleum fuels, wastes from mining and milling operations, waste-treatment lagoons, feedlots, large woodwaste disposal sites, and fertilizer and pesticide applications. This type of contamination occurs at places in 

all the major ground-water reservoirs, except possibly 

in the High Cascades, and in many of the smaller 

ground-water reservoirs. 

In the more populous areas west of the Cascade 

Range, solid-waste disposal sites are among the more 

obvious sources of contaminants. In these areas water 

from the abundant precipitation enters and percolates 

through the disposal sites, dissolving and carrying 

material from the wastes and becoming a generally 

noxious liquid called ''leachate." As with other types of 

contamination from the land surface, migration of the 

leachate down to the ground water may take many 

years, and even covered disposal sites remain as pollution sources for years after their operation is stopped 

(Wilson, 1975). 

Considering the incidences of known and suspected 

contamination, the relatively small number of apparent problems seems remarkable. The principal reasons 

seem to be: 

1. Public-health officials and others have been 

alert in recognizing and reacting to some 

cases of contamination. 

2. The soil and shallow rock materials adsorb or 

filter some contaminants. 

3. Dissolved contaminants, moving through the 

unsaturated soil and the ground water, do not 

generally disperse widely but rather tend to 

move along narrow paths that make detection and sampling difficult; thus, some problems have not been recognized or have been 

underestimated. 

4. The contaminants generally enter ground 

water of good quality which is capable of assimilating and diluting the contaminants to 

acceptable concentrations. 

5. Most contaminants enter shallow aquifers and 

may discharge into streams without reaching 

the deeper aquifers that are favored as public 

water supplies. 

6. Rate of movement is so slow that contaminants 

have not been detected, even at fairly short 

distances from the sources. 

HOUSEHOLD SEPTIC SYSTEMS 

Urban and suburban growth, which intensified during the 1940's, 50's, and 60's and which still continues, 

has involved a pattern of waste disposal that is having 

a significant impact on ground-water quality. In the 

developing areas, disposal of household wastes usually 

was initially through individual septic-tank systems or 

cesspools, the effluent from which percolated 

downward toward the ground water. Communal sewer 

systems and treatment plants normally were installed 

only where soil conditions prevented acceptable functioning of the individual disposal systems, or after 

housing densities and attendant waste discharges 

caused public-health hazards too great to ignore. In the 

meantime, contaminants from the household wastes 

have accumulated in the soils and in the upper part of 

the ground-water system. 

Although a proper septic tank system is designed to 

destroy most or all bacteria in the household wastes, 

inorganic and some organic compounds pass through 

the system in the effluent and enter the soil. Where the 

homes and disposal systems are densely spaced, large 

concentrations of these compounds have been added to 

the soil column. Because of the usually slow rates of 

liquid movement underground, years or even decades 

may pass before the effluent from the septic tanks in a 

new housing development shows up as measurable 

contamination in a well or stream fed by the ground 

water. However, in this region those years and decades 

since the most intensive suburban growth are adding 

up, and increasing concentrations of certain dissolved 

solids from household sewage can be found in the shallow ground water beneath such areas. Several lakes in 

the Puget Sound ground-water reservoir area that are 

fed by shallow ground water have deteriorated for this 

reason. Also, contamination of the ground water beneath a suburban area east of Portland, Oregon has 

been reported and attributed to septic-tank effluent 

(Quan and others, 1974). Studies of ground-water quality have been or are being made in several other areas 

in anticipation of the problem, including areas southwest of Tacoma, Washington (Lakewood area), east of 

Spokane, Washington (Spokane Valley), near Boise, 
24 SUJ\11\IAR\' APPRAISALS OF THE 1'\ATION'S GROUND-WATER RESOURCES 

Idaho (Boise Valley), and southeast of Kalispell, 

Montana (Swan-Avon Valley). 

SALTWATER INTRUSION 

In coastal areas of the region, including areas of the 

Puget Sound ground-water reservoir and smaller 

ground-water reservoirs along the coasts of Oregon and 

Washington, the known intrusions of seawater into 

freshwater aquifers are surprisingly few. This is 

largely due to the general abundance of precipitation 

to recharge the coastal aquifers. Also, the pumping 

from the smaller coastal ground-water reservoirs has 

not yet reached major proportions and, in Oregon, few 

productive aquifers are in contact with seawater. 

At present, the aquifers contaminated by modern 

seawater are probably outnumbered by those contaminated by relict seawater contained in extensive deposits of older marine sedimentary rocks. In the 

Willamette Valley ground-water reservoir and some 

smaller ground-water reservoirs west of the Cascade 

Range, intensive pumping of wells that tap younger 

aquifers has locally caused migration of salty water 

from those adjacent older rocks. 

PROBLEMS RELATED TO ARTIFICIAL 

RECHARGE AND DISPOSAL WELLS 

In Portland, Oregon, and a few places in the Puget 

Sound area, ground water, returned underground following its use for heating or cooling, has resulted in 

local water-quality problems. Not only is the water returned to the aquifers at a drastically different temperature, but, in several places, aeration of the recharge water has promoted the growth of nuisance 

bacteria which reduce the permeability of the aquifers 

in the vicinity of the recharge well. 

Related problems result from the use of wells for disposal of surplus irrigation water and waterborne 

wastes from households and other sources. Such disposal is workable only where the aquifer materials are 

extremely permeable, so that they can assimilate the 

waste products without rapidly clogging. Disposal 

wells have been used in the region for many years, 

mainly in the High Desert and especially in the Southern Idaho ground-water reservoirs. In the latter reservoir there are thousands of disposal wells. According to 

Whitehead (1974, p. 1) and Seitz, La Sala, and 

Moreland (1977, p. 2), most of the disposal wells in the 

eastern part of the Southern Idaho ground-water reservoir are for disposal of household wastes, but most of 

the water injected is from irrigation tail water and 

street runoff. The widespread use of disposal wells is 

considered to be clearly a potential threat to the quality of water in the major basalt aquifer which is the 

source of almost all the water used locally for household and community supplies. Experiments reported 

by Graham, Clapp, and Putkey (1977) suggest that 

some bacteria introduced through disposal wells may 

survive for a month or more after disposal stops. There 

is some local concern that the waste water may increase the nutrient content of the ground water that 

discharges into the Snake River and into lakes and 

ponds in canyon-bottom lands and contribute to occasional algal blooms in those waters. 

WATERLOGGING 

Waterlogging, the buildup of ground water to such a 

shallow depth that it hampers the use or productivity 

of agricultural land, occurs in all the major groundwater reservoir areas except the High Cascades, and in 

areas of many of the smaller ground-water reservoirs, 

as well. The region reportedly had about 2.5 million 

acres of "wet cropland" in 1966 (CNPTS, 1971b, p. 17). 

In the more humid parts of the region, especially 

west of the Cascade Range, waterlogging is mainly a 

naturally occurring condition. It is most troublesome 

in low-lying, typically floodplain areas where the water 

table is never far below the land surface. Planting and 

crop production are delayed because the water table 

rises as a result of seasonally abundant precipitation, 

flooding of through-flowing streams, or runoff from adjacent lands, and the soil drains slowly. 

In the drier parts of the region, the problems of 

waterlogging are characteristically found in flat or 

gently sloping areas that are irrigated with diverted 

stream water. In some places, the saturated zone that 

extends to the land surface and waterlogs the soil is 

temporarily perched above the general water table by a 

relatively impermeable material (for example clay, 

cemented gravel, or the top of the basalt). In many 

places, however, the application of irrigation water has 

raised the general water table to near the land surface, 

so that all the soil and underlying rock materials are 

saturated. The areas most susceptible to waterlogging 

by ground water are the localities of natural discharge 

of upwelling ground water-low-lying floodplains and 

the lowermost parts of closed basins or faultbounded 

ground-water "compartments." Some of these areas of 

ground-water discharge were waterlogged under natural, preirrigation conditions, but irrigation extended 

and worsened the waterlogging. Most, if not all, of the 

major irrigation projects have had associated waterlogging problems. In the Columbia Basin Irrigation 

Project of central Washington, for example, the seepage from canals distributing the Columbia River water 

and the application of the water for irrigation have 
PACIFIC NORTHWEST REGION 25 

caused the water table to rise more than 100 feet at 

places, waterlogging a few thousand acres of land. 

INADEQUATE INFORMATION 

Inadequate information about the ground-water reservoirs and their role in the total water resources of 

the region presently restricts the ability to deal effectively with the known and foreseeable problems, and 

hampers future management opportunities. There are 

two main levels of information needs: One is for the 

public officials, consultants, and others having major 

responsibilities in planning for, developing, regulating, 

or conserving the water resources; the second is for the 

direct user of the water resource-the irrigator, plant 

manager, water superintendent, and the general public. The two information levels largely overlap, but not 

entirely. The following discussion pertains mainly to 

the first level, and includes needs for new basic information about aquifers and their potential, needs for 

more quantitative information, and needs for waterquality information. 

Probably no truly unknown additional major freshwater aquifers exist in the region, but the knowledge 

about every aquifer is incomplete, and for some aquifers is very sketchy, particularly in the more arid, 

sparsely inhabited parts of Idaho, Oregon, and Nevada. 

Geologic mapping in many of those areas has been of a 

reconnaissance type; consequently, although the general character of the aquifers is known, their actual 

potential can only be inferred. Because these areas are 

mostly in arid parts of the region, lack of firm water 

supplies is a severe and obvious deterrent to most types 

of development. Occasional private prospecting efforts 

to develop ground-water supplies in these areas during 

the 1960's and 1970's have been farily successful, although often unduly expensive. Much greater and 

more productive use of some of these areas could be 

expected if definitive information about ground-water 

potential were available. Information about potential 

aquifers in the deeper parts of some of the major 

groundwater reservoirs and on ground-water availability in some of the coastal areas of the region is also 

lacking. Until the ground-water conditions, including 

the geologic controls on the occurrence and movement 

of ground water, have been studied in greater detail, 

development of additional supplies of ground water 

will be largely a prospecting venture, with associated 

risks and expense. 

For many of the ground-water reservoir areas, information is available about the general occurrence of the 

ground water and character of the aquifers, but 

water-management needs call for more quantitative 

data. Such data needs are likely to include volumes of a 

ground-water reservoir and of water it contains, 

amounts ofpumpage and resultant water-level change, 

and numerical values for hydraulic characteristics of 

the aquifers. Quantitative data are considerably more 

difficult and expensive to obtain than more general information, commonly requiring the drilling of wells, 

the complex testing of aquifers, and the metering of 

discharges of large-yield wells. However, there is no 

substitute for the quantitative information in some 

types of water-management procedures, such as the use 

of mathematical models to predict future changes in 

the ground-water reservoirs (see section on ((Management using Predictive Models"). 

A type of information that is increasingly needed, 

especially in the developing areas, is information on 

the quality of the ground water. More information is 

needed about the inorganic chemical constituents (the 

kinds of data that now are available for many ground 

waters), especially for previously unexplored aquifers 

and those susceptible to contamination. In addition, 

programs of reliable sampling and analysis for noxious 

organic compounds are needed at many places where 

such compounds present a threat to valuable groundwater sources-for example, in some areas of pesticide 

application, industrial waste disposal, and chemical 

spills. 

COMPETITION FOR AVAILABLE SUPPLIES 

Of the major ground-water reservoirs, the competition for available water supplies is a serious problem 

only with respect to the Columbia Plateau and the 

Southern Idaho ground-water reservoirs. It is also a 

major regional problem because: (1) It also occurs in 

areas of several smaller ground-water reservoirs; (2) it 

involves most, if not all, the States comprising theregion, (3) the amount of water involved in the competition is large, and (4) the problem is critical to prospects for fullest and most effective use of the total 

water resource. 

In the area of Columbia Plateau ground-water reservoir, the competition for available supplies has produced problems of interference between pumping 

wells, conflicts between ground-water and surfacewater rights, and litigation between Indian and nonIndian users of ground water and surface water. The 

early, uncontrolled development of limited groundwater supplies caused rapidly declining ground-water 

levels that led to pumping restrictions in areas listed in 

table 2. 

In the area of the Southern Idaho ground-water reservoir, surface and ground water are closely related at 

many places. Development of large supplies of ground 

water in the eastern part of the area affects to some 

degree return flows to the Snake River farther west; 
26 SUI\LMARY APPRAISALS OF THE NATIOI\"S GROUND-WATER RESOURCES 

this interrelationship is also true in some of the basins 

flanking the Snake River Plain. Therefore, large withdrawals of ground water may have an adverse affect on 

the surface-water supply, and are, or will be, in conflict 

with surface-water rights. 

ANTICIPATED OR POTENTIAL PROBLEMS 

Problems foreseeable in the future for the Puget 

Sound ground-water reservoir include local deterioration of water quality as a result ofwaste-disposal practices, and seawater intrusion associated with additional pumping in near-shore areas. The growth of 

these two problems seems to be an inevitable consequence of present waste-disposal practices and developmental trends in near-shore areas. Some of the better aquifers in this part of the region lie beneath areas 

that have fairly dense spacing ofhousehold septic-tank 

disposal systems. Doubtless the combination of abundant recharge to dilute the wastes and the slow movement of water underground has helped limit the effects 

of potential pollution from these waste-disposal systems. However, pollutants now in the soil and shallow 

rock materials will continue to migrate downward to 

the ground-water and increasing effects of these pollution sources can be expected in the future despite 

whatever near-term management steps are likely to be 

taken. Local problems of seawater intrusion are also a 

likely future consequence of indiscriminate development of ground water in near-shore areas. This problem may be troublesome at places but will be somewhat self-limiting; pumping that induces landward 

movement of the salty water generally decreases as the 

wells ('go salty." 

For the Willamette Valley ground-water reservoir, 

foreseeable problems include further depletion of water 

in the basalt aquifers and water-quality deterioration 

in areas of waste disposal by landfills and by densely 

spaced septic-tank systems. 

No special problems are foreseen in greater development of the ground-water of the High Cascades 

ground-water reservoir. Meager water-quality information indicates that the ground water is of good to 

excellent quality, but experience in similar terranes 

suggests that undesirable dissolved minerals might be 

present locally. The available recharge is adequate to 

support almost any conceivable direct withdrawals of 

ground water with little impact on the low-level flows 

of the streams that drain these aquifers. The short 

growing season and the remoteness of the areas underlain by this reservoir suggest little possibility that 

much of this supply will be needed within the 

mountains in the near future, and most of the reservoir 

probably will remain an untapped reserve for many 

years. 

Future problems in the area of the High Desert 

ground-water reservoir are likely to be largely the 

same as present problems-namely, limitations on 

ground-water supplies imposed by meager recharge, 

locally poor water quality, and waterlogging. In addition, areas of intensive pumping may develop or enlarge, and result in significant water-level declines, 

perhaps to the extent of long-term depletion of the 

ground water in localized areas (table 1). Future major 

ground-water development may tend to be areally concentrated for two reasons: (1) A relatively small 

amount of land in the area is privately owned, and 

(2) successful wells tend to foster prospecting for 

ground water in their immediate vicinity. Management of the ground-water reservoir, however, is not 

likely to be a major problem until development proceeds to a considerably greater extent than at present. 

In the future, problems related to ground water in 

the Columbia Plateau ground-water area are likely to 

be of the same kinds as at present (table 1) but more 

extensive and in new places. Problems of declining 

water levels are expected to become more widespread 

as development of water from the basalt progresses. 

Because the basalt has relatively small storage capacity, any intensive withdrawals from wells tapping 

the basalt can be expected to cause sizable water-level 

declines. Examples of areas now undergoing such development, where the increased pumping from the 

basalt is likely to cause significant water-level declines 

within a few years, are the Moxee Valley and Horse 

Heaven Hills areas (not shown on included maps) both 

in south-central Washington, respectively east and 

southeast of Yakima (fig. 7). In areas of presently declining levels, the declines are likely to continue until 

limited by such factors as excessive pumping lifts, importation of surface-water supplies (as in The Dalles 

area, Oregon, table 2), legal restriction on pumping 

withdrawal, or actual dewatering of the available 

aquifers-a possibility in the Cheney-Airway Heights 

area, eastern Washington (table 2; also Luzier and 

Burt, 1974, p. 47). Where the depleted zones include 

shallow aquifers which supply most of the rural domestic and stock water and the dry-season flow of small 

streams, troublesome reductions may occur in the 

streamflow and in these rural well-water supplies. In 

areas having many wells that penetrate deeply into the 

aquifer system and are open to more than one aquifer 

zone, the continual leakage from one zone to another 

through the well bores may contribute to declines in 

some aquifer zones. 

Future ground-water problems in the Southern 

Idaho ground-water reservoir area probably will be related mainly to further declining water levels (local 

overdrafts on the ground-water reservoir), increasing 
PACIFIC ~ORTHWEST REGION 27 

conflicts with surface-water rights, spreading of waterlogging associated with the growth of irrigated farming, and increasing contamination. If withdrawals for 

irrigation follow the predicted increasing trend, declining ground-water levels can be expected to show up in 

new places and perhaps resume in some of the areas 

already noted (table 2). The decrease of ground water 

in storage, reflected by water-level declines, is likely to 

affect the low flow of streams and, therefore, the availability of surface water for use under existing rights. 

The greatest undesirable impacts on surface-water 

rights likely would result from development of additional large supplies of ground water in the eastern 

and northern parts of the reservoir system. 

Soluble residues and waste products from intensive 

agriculture and processing of agricultural products are 

expected to be sources of increasing ground-water contamination. Most organic compounds tend to be filtered 

out or adsorbed in their passage through the first few 

feet of soil; however, dissolved salts, including the 

major constituents of fertilizers and some pesticides, 

infiltrate the soil and percolate downward readily with 

the rainwater and irrigation water. Some of the best 

evidence for this type of ground-water-quality deterioration is in the extensive Columbia Basin Irrigation 

Project (Columbia Plateau ground-water reservoir; 

Van Denburgh and Santos, 1965 ), but the effects are 

being felt and can be expected to increase also in the 

Southern Idaho ground-water reservoir and elsewhere 

in the more arid parts of the region. 

The major water-related problems that are foreseen 

for the areas of the smaller ground-water reservoirs 

are increasing conflicts in the use of surface water and 

ground water and increasing water-quality problems. 

Some of the smaller ground-water reservoirs, such as 

isolated coastal sand deposits or valley-filling alluvial 

deposits in areas of impermeable bedrock, are extremely valuable as sources of water but, because of 

their relatively small volume, have limited wasteassimilating capability. The preservation of goodquality ground water under conditions of expected 

growth in these reservoir areas will require some difficult (and probably expensive) choices regarding 

waste-disposal practices and land use. An example is in 

the Spokane Valley-Rathdrum Prairie area, 

Washington-Idaho, east and northeast of Spokane (fig. 

7; Drost and Sites, 1978). Because of the importance of 

the ground-water reservoir in that area as a source of 

public water supplies and the lack of suitable alternative supplies, the U.S. Environmental Protection 

Agency, in 1978, designated the reservoir as a "solesource aquifer" (U.S. Environmental Protection 

Agency, 1978). Such a designation restricts future 

waste-disposal practices and land uses that might degrade the ground water in that area. 

By 1977, the intrusion of sea water in the western 

part of the region was not a widespread problem. However, despite strong trends to protect these shorelands 

through State and Federal legislation, the projected 

development in these areas doubtless will lead to intensified local ground-water withdrawal that will be 

accompanied by problems of potential seawater intrusion. Elsewhere in the region, the induced migration of 

saline water into the freshwater aquifers of the small 

ground-water reservoirs is not expected to be 

significant unless pumping is intensive in areas adjacent to older saline-water-bearing rocks. Saline-water 

problems also may accompany future development of 

geothermal energy in the smaller reservoir areas. 

MANAGEMENT OPPORTUNITIES 

AND CONSTRAINTS 

Management opportunities presented by groundwater reservoirs in the region are discussed below, 

along with related constraints and problems. As in 

foregoing discussions, the major ground-water reservoirs are emphasized, but most of these management 

opportunities and constraints apply also to the smaller 

ground-water reservoirs. 

DEVELOPMENT OF ADDITIONAL SUPPLIES 

Additional large supplies of water can be developed 

from each of the major ground-water reservoirs, but 

most of the reservoir areas have their own set of constraints on such further development. Additional 

major supplies, large enough for industrial, irrigation, 

and municipal uses, are available from presently 

utilized aquifers at places in all the major reservoir 

areas, but especially in parts of the Puget Sound and 

Willamette Valley ground-water reservoirs. 

In the Puget Sound area, underutilized glacial and 

alluvial aquifers are capable of meeting much of the 

foreseeable increase in water demand, such as additional supplemental irrigation water and new industrial and community supplies. Some coastal aquifers 

contain a considerable resource of fresh ground water 

that is now flowing to the sea without being used beneficially; however, the optimum use of this resource 

will require improved information about the coastal 

aquifers and adroit management to minimize problems 

of seawater intrusion. 

In the Willamette Valley ground-water reservoir, 

large additional supplies of ground water also are 

available, chiefly from the alluvial deposits. Not only is 

the present withdrawal only a small fraction of the 

natural recharge, but recharge might locally be increased by increasing withdrawals. That is, if more 
28 SLT\IMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

storage space were provided in the aquifer by intensified pumping during the summer months, that space 

would be largely refilled by abundant recharge water 

during winter and spring. Also, for many of the largeyield wells near the Columbia River and other major 

streams, much of the water they produce is induced 

infiltration from the rivers. That induced infiltration 

could be increased-at the expense of river flow, if 

course. Along favorable reaches of the Columbia River, 

for example, yields of about 50-100 million gallons per 

day might be obtained per mile of river length (Mundorff, 1964, p. 93). 

At places near the margins of the Columbia Plateau 

and Southern Idaho ground-water reservoirs, large 

bodies of saturated older sedimentary rock materials 

occur beneath, overlying, or interfingered with basalt 

aquifers. These sedimentary rocks can be used more 

extensively as sources of ground water not only by tapping them directly with effective wells (see section on 

((Improved Design and Construction ofWells"), but also 

by inducing these reservoir rocks to drain into adjacent, more permeable basalt aquifers. Such drainage 

might be accomplished by purposely causing large 

water-level declines in the adjacent basalt aquifers to 

accelerate the migration of water from the sedimentary materials. 

Where ground-water reservoirs are already heavily 

stressed by pumping, greatly increased pumping from 

the same aquifers will tend to increase or create problems of declining water levels and conflicts between 

water users. It can also accelerate the spread of any 

ground-water c0111taminants by increasing rates of 

ground-water flow in the heavily pumped parts of the 

ground-water reservoir. 

In some areas, increased pumping from presently 

utilized aquifers probably will include pumping to reduce waterlogging (see section on ((Reduction of Waterlogging") and to salvage ground water now used by 

vegetation. Common water-loving vegetation, 

phreatophytes and hydrophytes, do not grow extensively in the region, but they are abundant enough in 

the low lands and along stream courses to consume a 

significant part of the summer water supply. In the 

ground-water reservoir areas east of the Cascade 

Range, where evapotranspiration rates are high and 

summertime water supplies are especially valuable, 

some of this water may be economically salvageable. 

Phreatophytes may be removed by uprooting, mowing, 

or spraying with growth-retardant chemicals. An alternative, and generally more effective, method of reducing evapotranspiration is to remove the water supply by draining marshes or pumping wells to lower the 

water table below the root zone. 

Destroying the natural vegetation in order to increase the water yield, however, would eliminate possible benefits of the vegetation and might create other 

problems. For example, the plants may be a valuable 

habitat for wildlife and shelter for livestock. Moreover, 

they may inhibit evaporation losses from surface water 

by shading the water and thereby reducing its temperature. Also, removing all the natural vegetation might 

create problems of increased flood damage and erosion. 

DEEPER AQUIFERS OF KNOWN POTENTIAL 

In some of the major ground-water reservoirs, productive aquifers are known to occur at depths greater 

than the presently utilized aquifers, and thus are in 

the category of proven reserves. This is especially true 

for parts of the Puget Sound, Columbia Plateau, and 

Southern Idaho ground-water reservoirs. Constraints 

on development of these deeper aquifers include high 

costs of drilling the required deep wells, less desirable 

water quality (at places in the Puget Sound and Southern Idaho areas), high pumping lifts, and present 

availability of more accessible alternative water 

supplies. The temperature of the ground water increases with depth, and the higher temperature is generally considered to be a constraint to the use of the 

water for municipal supplies, some industrial purposes 

and, if sufficiently high, for irrigation. 

Three points regarding the future development of 

deep aquifers in the region should be emphasized. 

First, in many of the reservoir areas, the total depth of 

productive aquifer materials, being controlled by the 

geology, is fairly well known. In these areas, hydrologists can say with some assurance that highly 

productive aquifers do not occur at greater depths. Second, the productivity of sedimentary aquifers especially, and volcanic aquifers to a lesser extent, locally 

tends to decrease with greater depth. Third, the withdrawal of water from deeper zones in a presently 

utilized ground-water reservoir does not necessarily 

constitute ((new" water; although it may increase the 

short-term supply, in the long term it must be counted 

as part of the total draft on the reservoir. 

NEW SOURCES OF SUPPLY 

All the major and many of the smaller ground-water 

reservoirs offer opportunities for finding and developing water supplies from presently unknown or unproven aquifer zones. This is especially true of the 

sparsely inhabited areas, including much of the High 

Cascades and High Desert, and parts of the Columbia 

Plateau and Southern Idaho ground-water reservoirs. 

Much of this sparsely populated land has low foreseeable demands for ground water because of high altitude or rugged terrain, short growing season, scarcity 
PACIFIC NORTHWEST REGION 29 

of arable land or privately owned land, and adequacy of 

surface water (at places). A further constraint on 

ground water development in unproven areas will be 

the high cost and financial risk of prospecting for new 

sources of supply. Also, especially in the High Desert 

area and in deeper zones elsewhere, undesirable water 

quality may be a constraint. Demands for ground 

water doubtless will increase somewhat as additional 

information about the potential reservoirs becomes 

available, and as new uses develop such as forest irrigation, fish-hatchery supply, and energy production 

(see section on ~~Geothermal Energy"). Also, in some 

remote areas where streams are contiguous to permeable aquifers with a large storage capacity, groundwater supplies might be economically developed to 

supplement the low flow of the stream during relatively short but intense periods of drought. 

CONTAMINATION ABATEMENT AND AVOIDANCE 

Significant opportunities exist for reducing presently 

occurring contamination of ground water and for 

avoiding future contamination in critical areas of 

ground-water need. These ,opportunities exist mainly 

in the Puget Sound, Willamette Valley, Columbia 

Plateau, and Southern Idaho ground-water reservoirs, 

and several smaller reservoir areas. 

Effective abatement of presently occurring contamination must start with identification of the areas undergoing the contamination and determination of the 

sources and degree of contamination before appropriate regulatory or management steps are formulated 

and undertaken. A number of areas of ground-water 

contamination in the region-mainly areas of solidwaste disposal, concentrated septic-tank systems, disposal wells, and chemical spills-have been or are 

being studied to some degree, and some monitoring of 

ground-water quality in impacted areas has been going 

on for decades. However, few of these studies have 

yielded information that is adequate for such purposes 

as deciding between alternative abatement schemes or 

estimating future die-away rates of contamination following abatement. For such purposes data are needed, 

for example, on: Rates and modes of contaminant 

movement in the ground-water system and the unsaturated zone above the ground water; adsorption of the 

contaminants on the soil and rock materials; and the 

ultimate discharge of the contaminants from the 

ground-water system. Much of this information must 

be obtained through test drilling and detailed subsurface sampling. 

Actual abatement steps might include stopping a 

specific waste-disposal operation, changing the locality 

or method of waste disposal, clean-up of accidental 

spills, pumping or artificial recharge to change flow 

directions of the contaminated ground water, or even 

the direct pumping of the contaminated water for disposal elsewhere. In the humid parts of the region west 

of the Cascade Range, the only practical way to reduce 

contamination from landfill disposal may be to collect 

as much as possible of the leachate and other drainage 

from the disposal sites and treat these waste waters to 

make them acceptable for redisposal by dilution in 

large streams or marine waters. 

Avoidance of future ground-water contamination 

should focus on the parts of the ground-water reservoirs that are most important to protect and retain in a 

high-quality state, such as aquifers that are sources of 

present or anticipated public supplies, aquifers that 

are the only feasible source of water supply, or those 

clearly advantageous economically or otherwise as 

present or future high-quality supplies. For example, 

ground-water resources are extremely important in 

marine island and peninsular areas where sites for surface reservoirs are limited, stream supplies are 

inadequate or subject to pollution, and where great 

costs would be incurred in piping water from dependable mainland sources. 

Because of the importance of considering future 

needs in decisions about protection of the ground water, 

such decisions are best made within the framework of 

comprehensive land-use and water-use plans. After a 

decision that a particular ground-water body should be 

protected, the steps necessary to avoid ground-water 

contamination must be taken by the agency having 

jurisdiction over use of the overlying land or recharge 

areas. Depending on the ownership and jurisdiction of 

the land, the protective measures may include: Land 

zoning to control population density; prohibition of 

waste disposal; open-space designation of identified recharge areas, or ~~watershed" designation with accompanying restriction on entry into recharge areas. Also, 

because withdrawal of ground water can accelerate the 

spread of contaminants, the protective measures might 

include restrictions on pumping wells in areas subject 

to salt-water contamination. 

In many areas where contaminants are being added 

to the subsurface, remedial action apparently will not 

be started before there is obvious evidence that 

significant contamination of valuable ground-water 

supplies has occurred. Future impacts of the contamination might be lessened in those areas if the onset of 

the contamination can be detected as soon as possible. 

This will require identification of such areas (if they 

have not been identified already), studies to determine 

the degree or threat of the contamination and the subsurface conditions in the threatened areas, and 

monitoring programs to detect the onset and trace the 
30 SC:\11\IARY APPRAISALS OF THE NATION'S GROL;:'\JD-WATER RESOURCES 

movement of contamination. In most cases, existing 

wells will not suffice for an effective monitoring 

program-special test-observation wells probably will 

be needed also to provide information not available 

from supply wells. The monitoring programs in such 

areas may be needed for decades into the future. 

Careful monitoring of the underground disposal of 

potentially hazardous contaminants-for example, the 

radioactive wastes in the Hanford, Washington (Columbia Plateau ground-water reservoir) and the Arco, 

Idaho (Southern Idaho ground-water reservoir) 

areas-are required by existing environmental protection laws. 

IMPROVED DESIGN AND CONSTRUCTION OF WELLS 

Well-construction practices in this region can be substantially improved to the advantage of future development and management of the ground-water reservoirs. Many wells that presently yield less than enough 

for irrigation, industrial, or public supplies could be 

brought up to that range through better well construction. In general, the finer the saturated material, the 

more the yield of the well depends on good design and 

construction. 

Techniques that have been used to increase well efficiency and productivity, and that hold promise for 

wider application in the region, include: 

(1). Recently developed rock-drilling methods and 

equipment; 

(2). use of well screens and graded gravel or sand 

((packs" for greatest yields from sedimentary aquifers; 

(3). use of special drilling fluids that reduce clogging of aquifer pores; 

(4). greater use of well-development techniques 

(surging, chemical treatment, water jets, 

and so forth) in completion of wells; use of 

these techniques for wells tapping volcanic, 

as well as sedimentary, aquifers. 

Although some of these techniques are applicable 

mainly to new well construction, several can be used 

beneficially on wells that are being rehabilitated or 

deepened. 

One conspicuous opportunity for improvement is the 

reduction of unwanted vertical ground-water leakage 

because of ((short circuiting" through unlined or leaky 

well bores (see section on ((The Productive Aquifers"). 

The best way to prevent this cross-bed leakage is to 

design and construct wells using well casing cemented 

to the rock materials so as to isolate the different 

aquifer zones; the casing should be open only to the 

zone or zones actually to be developed. Installation of 

casing in existing unlined wells is likely to be much 

more troublesome, but may be necessary at places in 

order to reduce ground-water contamination (Foxworthy, 1970, p. 14) or alleviate the draining of aquifer 

zones tapped for domestic supplies (Luzier and Burt, 

197 4, p. 44). 

The recognition of deficiencies in many of the older 

wells has led the State water-management agencies in 

the region to formulate and recommend, and in some 

cases legally require, minimum standards for waterwell design and construction. Moreover, in some areas 

of intensive ground-water management, such as the 

Odessa-Lind area of Washington, certain well designs 

(specified depths of well casing) are made a condition 

for approval of additional wells. As problems of waterlevel declines and ground-water contamination increase in the region, the imposition of well-design requirements by State and local water-management 

agencies is likely to increase. 

REDUCTION OF WATERWGGING 

Waterlogging might be reduced by greater pumping 

from aquifers in some waterlogged areas, and gravity 

drains within the saturated zone also can be useful; at 

other places, a reduction in the application of irrigation 

water may be the only practical corrective measure. At 

some places a combination of these measures may be 

the most effective. Pumping from wells to reduce 

waterlogging is effective only if: (1) Aquifers of at least 

moderate permeability can be tapped at relatively 

shallow depths, and (2) the pumping can induce substantial downward migration of water from the waterlogged zone or can intercept significant amounts of 

naturally upwelling ground water. Moreover, for such 

remedial pumping to be economically feasible in most 

cases, there must be beneficial uses for the water 

pumped from the shallow aquifers. ((Relief wells" and 

drainage tunnels to reduce waterlogging have been 

used in the area of the Southern Idaho ground-water 

reservoir for several decades, and relief wells, alone or 

combined with drains, have been suggested for a 

waterlogged area south of Yakima, Wash. (fig. 7; Mundorff and others, 1977, p. 81). 

The widespread buildup of ground-water levels and 

occurrences of waterlogging in areas of major irrigation projects strongly suggest that future irrigation 

projects should be designed, if possible, for importation 

of only part of the water supply needed, with the balance of the supply to be obtained from aquifers recharged by the irrigation. This approach would not 

only reduce the amount of surface-water diversion required but would also tend to reduce waterlogging 

problems. 
PACIFIC NORTHWEST REGION 31 

SUBSURFACES~RAGE 

Underground space has been used in the region for 

some common and some uncommon types of waste disposal. It has also been used to store freshwater and 

natural gas. The following are brief discussions of the 

opportunities for and experiences in use of the underground space for these and other types of subsurface 

storage. 

ARTIFICIAL RECHARGE 

Artificial recharge-the addition of water to the 

ground-water reservoir as a result of man's 

activities-is important to the concept of total waterresources management. It offers possibilities of manipulating input to the ground-water reservoirs in addition to the manipulation of withdrawals that is afforded by regulation of pumping. In the broadest sense, 

artificial recharge includes not only planned replenishment but also additions to the ground water 

that are incidental to other activities; it includes not 

only good-quality water but also the waste water that 

is added. 

In this sense, the most significant type of artificial 

recharge in the region is that occurring as a result of 

irrigation. Seepage from irrigated lands and conveyance ditches occurs in all areas where irrigation is 

extensive, but it is most significant in the more arid 

parts of the region. Irrigation is the major form of recharge in parts of the Columbia Plateau and Southern 

Idaho ground-water reservoirs and in some smaller 

ground-water reservoirs. Recharge from this source is 

so great at places that waterlogging has become a problem (see section on ((Waterlogging"). 

A related type of artificial recharge is surface spreading, which consists of diverting water from a stream 

and allowing it to flow over or stand upon permeable 

material so that it may infiltrate to the ground-water 

body. Spreading can be accomplished by simply flooding flat areas in which the water can be retained for 

substantial periods of time, by holding the water in 

artificially constructed basins or in natural ponds, or 

by directing the recharge water into ditches or furrows. 

Surface spreading was used with reasonable success to 

augment natural recharge for an alluvial aquifer 

tapped by municipal wells at Richland, Wash. (Price 

and others, 1965, p. C5-C19), and occurs incidental to 

the operation of storm-water retention basins in the 

area of the Puget Sound ground-water reservoir and 

other urban areas in the region. 

A method of increasing the recharge to aquifers, at 

the expense of flow in contiguous streams, is the deliberate drawdown of ground-water levels in shallow 

aquifers adjacent to streams so as to induce or increase 

infiltration of water from the streams into the aquifers 

(see section on ((Development of Additional Supplies"). 

This practice, called induced infiltration, is fairly 

common, and is used largely to obtain water for municipal and industrial supplies that requires less treatment than if they were taken directly from the 

streams. The gain in well supplies by this method, of 

course, is offset by a corresponding reduction in the 

flow of the affected streams. However, at places where 

the wells can be located sufficiently far from the affected streams, the reduction in streamflow caused by 

the seasonal pumping from wells may be delayed until 

after periods of low streamflow. This method offers important opportunities for increasing the amount of 

water available during periods of low streamflow by 

utilizing even relatively small ground-water reservoirs. Moreover, it is a key to practical conjunctive use 

of surface and ground-water resources (see section on 

((Conjunctive Use of Ground Water and Surface Water). 

In addition to the disposal of storm-runoff and waste 

waters through wells (see section on ((Problems Related 

to Artificial Recharge and Disposal Wells"), which is 

most significant in the areas of highly permeable 

young basalt rocks (Southern Idaho and High Desert 

reservoirs), injection of good-quality water through 

wells for later recovery from the aquifers has been attempted elsewhere in the region. Experiments and 

trial injection through wells, mainly in the Willamette 

Valley and Columbia Plateau ground-water reservoir 

areas, have utilized aquifers of moderate to high permeability, though not as permeable nor nearly as porous as the young basalt. These experiments had limited success. They indicated that the artificial recharge 

through wells generally is technically feasible, but it 

requires sediment-free water of good chemical quality, 

careful injection techniques, and occasional cleaning of 

the injection well for practical long-term success (Foxworthy and Bryant, 1967; Price and others, 1965). Also, 

not all the water recharged artificially was recoverable 

for later use. 

Artificial recharge, to be a feasible watermanagement aid, requires three basic conditions: (1) 

The aquifer must be at least moderately permeable and 

must have adequate storage capacity to receive the water; (2) the supply of recharge water must be of 

adequate quantity and suitable quality; and (3) the 

water must be economically recoverable from the 

ground-water reservoir and of a quality suitable for the 

intended use. Economic considerations may be as complex as the technical aspects in judging the feasibility 

of artificial recharge. They include consideration of the 

economic benefits of sustaining or improving the 

ground water, cost of the artificial recharge operations, 

value of the water added to the aquifers, and relative 
32 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

value of the recharge water if used for other purposes, 

such as hydropower generation. 

Conditions favorable for artificial recharge probably 

can be found in several parts of the region, including 

some of the smaller ground-water reservoirs. In many 

valleys and basins, there are terraces underlain by 

young sedimentary rocks which could be potentially 

productive aquifers except that they are mostly above 

the normal water table. The water-yielding capability 

of these terrace deposits depends not only on the 

character of the rock materials, but also on their saturated thickness. At some places the terrace deposits 

were unsaturated under natural conditions but have 

become partly saturated from irrigation water. At 

other places, the unsaturated deposits await only the 

artificial addition of water to become valuable storage 

reservoirs. 

Artificial recharge seems to be a strong possibility 

for increasing the usable supplies of ground water in 

the Southern Idaho ground-water reservoir. No 

planned artificial recharge is being done in the reservoir area; however, recharge incidental to irrigation is 

a major factor in the hydrologic regimen. Mundorff 

(1962), in his study of the feasibility of artificial recharge of aquifers underlying the Snake River Plain, 

concluded that surplus water for recharging was available and that artificial recharge was hydrologically 

feasible. There are several places where water could be 

diverted to flow by gravity to recharge sites on the 

Snake River Plain. Opportunities also exist for artificial recharge in basins flanking the Snake River Plain. 

In some areas, surplus river water is available locally 

to recharge the aquifers; in other areas no local surplus 

water is available and recharge water would need to be 

diverted from one of the major rivers. 

Several parts of the Columbia Basin ground-water 

reservoir area are included in plans for additional irrigation with surface water. These include the East High 

division of the Columbia Basin Irrigation Project, 

east-central Washington, and lands adjacent to the Columbia River in south-central Washington and northcentral Oregon. These or similar expansions of irrigation using surface water are likely to provide artificial 

recharge to aquifers underlying the irrigated areas, 

thereby improving the productivity and dependability 

of such aquifers. In addition, opportunities may exist 

for more deliberate artificial recharge using irrigation 

canals to convey surplus water to recharge sites during 

the nonirrigation seasons (Garrett and Londquist, 

1972, p. 15, 16). 

WASTES 

Many types of wastes have been committed to subsurface disposal in the region. They range from the 

least troublesome types, such as burials of nondegrading construction materials, to wastes that are toxic or 

otherwise dangerous, including the radioactive wastes 

disposed of at sites near the Hanford nuclear facility, 

Washington and INEL (the Idaho National Engineering Laboratory), Idaho. 

In general, the more hazardous the waste, the 

farther away it should be from the realm of living 

things (biosphere); this often requires disposal deep 

underground. Successful disposal of wastes in underground space with the least undesirable consequences 

requires thorough knowledge of the geologic 

framework and of the path that the ground water-and 

any contaminants derived from the wastes-takes 

through that framework. Obviously, the more hazardous the waste, the more important this knowledge. 

Exhaustive studies and elaborate test drilling have 

been conducted and are being continued in the vicinity 

of the Hanford nuclear facility, to determine the feasibility of storing high-level hazardous wastes deep in 

volcanic rocks. At INEL, also, many observation wells 

have been drilled to monitor the movement of radioactive wastes. 

Some rocks, but not all, are worthy of consideration 

for subsurface disposal of hazardous wastes in areas of 

the major ground-water reservoirs. Included are deeplying, older sedimentary rocks containing salty water 

in the Puget Sound and Willamette Valley groundwater reservoirs, and deep zones of the basalt or underlying rocks in the Columbia Plateau and Southern 

Idaho ground-water reservoirs. In addition, parts of the 

High Desert ground-water reservoir seem to offer possibilities. This ground-water reservoir includes a 

number of closed basins that have no surface outflow 

and probably insignificant ground-water outflow; there 

the discharge of water is nearly all by evapotranspiration or from wells. Owing to the remoteness and lack of 

substantial outflow from much of the area, opportunity 

may exist for storage of wastes in deep saline aquifers, 

but additional subsurface studies are needed for verification. 

NATURAL GAS 

Deep, confined salty-water aquifers in the Puget 

Sound and Willamette Valley ground-water reservoirs 

may offer unusual opportunities for underground storage of natural gas in proximity to major urban centers. 

Confined zones at depths of about 1,800 to 2,100 feet 

have been used for the storage of many billions of cubic 

feet of natural gas in a small area a few miles south of 

the Puget Sound ground-water reservoir. The further 

use of deep confined aquifers for storage of this type 

should be based on greatly increased knowledge about 

subsurface conditions in the areas involved, including 

deep circulation patterns of the ground water. 
PACIFIC NORTHWEST REGION 33 

IMPROVED MANAGEMENT AND CONSERVATION 

Many opportunities exist for improved management 

and conservation of proven, available water resources. 

These include greater conjunctive use of ground water 

and surface water, conservation of existing resources 

through changes in conveyance and use, and management of water resources with the aid of predictive 

models of ground-water flow systems. Of these, greater 

conjunctive use of ground water and surface water 

probably offer the largest benefits, but this management opportunity also has the greatest problems and 

constraints. 

CONJUNCTIVE USE OF GROUND WATER AND SURFACE 

WATER 

The integral relationship between ground water and 

surface water is most apparent in the smaller groundwater reservoirs, where the best aquifers commonly 

are well connected hydraulically to the local stream 

system. Because of this degree of interconnection, and 

because the ground-water reservoirs feed the streams 

through most of the year, any change that has a major 

effect on the ground water, such as intensive pumping 

or changes in recharge, generally has a rapid and obvious effect on the streams. The same interrelationship 

also exists for the larger ground-water reservoirs, 

creating conflicts between use of wells and stream 

water (see section on ~~Deeper Aquifers of Known Potential"), and dooming to failure any attempt to manage effectively either the ground water or surface 

water separately. Water flowing through an area commonly passes back and forth between the aquifers and 

the stream channels. For example, in the area of the 

Southern Idaho ground-water reservoir, all outflow ultimately is through the Snake River; however, 

throughout the reservoir area the river alternately 

gains and loses in several reaches before finally collecting all surface and ground-water discharge near the 

west end of the reservoir area. Some water that is diverted for irrigation cycles back into the aquifer system at least three times as it moves from the upper end 

to the lower end of the Southern Idaho ground-water 

reservoir. 

In this region, largely because of the highly seasonal 

nature of the precipitation and snowmelt (p. 11), some 

runoff commonly escapes from most areas without apparent beneficial use. Management of the streamflow 

and aquifers conjunctively might provide the flexibility 

to salvage and store for later use some of this runoff. 

Such management might include intensive pumping 

for the deliberate drawdown of ground-water levels 

during periods of low stream flow to make space for 

additional recharge water available during periods of 

high runoff, provided this can be accomplished without 

serious reduction of streamflow during critical periods. 

Conjunctive use of ground water and surface water 

probably represents the most widely available opportunity in the region for effectively managing the available water supplies. The benefits possible from this 

management approach are effectively blocked, however, by existing water-rights laws. In many areas efficient management will require flexibility to allow the 

source of water supplies to be shifted from stream to 

underground sources and back again in accordance 

with water availability. It also may require the readjudication of withdrawal periods and rates of withdrawal. 

EFFICIENCIES IN CONVEYANCE AND USE 

For some parts of the region, no matter how much 

emphasis is given to water supplies, the supplydemand equation cannot be balanced without sensible 

and effective conservation of the water. Fortunately, 

opportunities are available for conserving the ground 

water; some of these-reduction of water-loving plants, 

artificial recharge, and repair of leaky wells-were 

discussed previously. 

A conservation opportunity of considerable promise 

is a relatively new method of irrigation-drip irrigation. Great savings of water are possible because much 

soil that is wetted during the conveyance and application of water in other irrigation methods remains dry 

during drip irrigation. Savings are also possible in fertilizer and some pesticides, which can be applied in the 

irrigation water, and in weed control. Other advantages include the virtual elimination of irrigation return flow with its degrading effect on water quality, 

avoidance of waterlogging resulting from excessive 

water application or irrigation return flow and, for 

some crops, a reduced need for levelland. Constraints 

on widespread use of drip irrigation include capital investment required for pipelines and drip nozzles, major 

investments that already have been made in other irrigation systems, possibility of salt build-up in the soil, 

and some problems of clogging of the drip nozzles with 

particles such as weed seeds and with chemical precipitates. 

Ground water not only is suitable for drip irrigation, 

it is a preferred supply. One major reason is that 

ground water usually can be delivered free of weed 

seeds, spores, algae, or other clogging agents. Sand or 

silt in water from some wells however, may be a problem, as in many surface-water supplies. Moreover, the 

smaller demand rate for irrigation water for this 

method favors the decentralizing of supply wells-that 

is, the use of several widely separated, smaller-yield 

wells with short, efficient supply lines instead of one 
34 Sl'~I:\IARY A .. PPRAISALS OF THE NATION'S GROC:"\D-WATER RESOURCES 

large-yield well pumping into long supply lines or 

inefficient distribution ditches .. The decentralizing of 

supply wells may have economic benefits even in areas 

where large-yield aquifers are available .. In addition, 

the smaller water demand for the drip method makes 

irrigation with ground water much more attractive for 

areas where aquifers do not have the proven capability 

for the large yields normally required for irrigation by 

other methods. 

Any other means of increasing efficiency in the use of 

the irrigation water or decreasing need for water application can also help stretch supplies of surface and 

ground water. Such improvements might include 

greater use of efficient sprinkler systems, or techniques 

of fertilizer application and soil treatment to reduce 

the need for excess water to flush the soil. Because of 

the huge amount of the total water withdrawal that is 

dedicated to irrigation (fig. 2), even small individual 

savings of irrigation water could be valuable. For 

example, a saving of only 18 percent in the average 

irrigation-water diversion or withdrawal in 1975 would 

have conserved water in an amount equivalent to all 

other withdrawals combined for that year (5 billion 

gallons per day). 

MANAGEMENT USING PREDICTIVE MODELS 

Research in the field of ground-water hydrology has, 

within the last two decades, developed a set of powerful 

tools for assisting water management-models of 

ground-water flow systems that allow prediction of 

conditions in the ground-water reservoir under different schemes of development. These models were made 

practical by ' recent advances in electronics and highspeed computers. Predictive models have been developed and used for several ground-water reservoirs in 

the region and are possible for other areas as well. 

Ground-water models have been used to predict 

water-level changes likely to result from different rates 

and patterns of pumping withdrawal in the Columbia 

Plateau (about 10 models, some overlapping); the 

Southern Idaho (9 models); the Willamette Valley (1 

model); and a few smaller ground-water reservoirs. 

Some models have been deliberately developed on the 

basis of preliminary or sketchy information in order to 

define sharply the data needed for a more reliable 

model to be used for management guidance. In addition, some models are being developed principally to 

predict the movement of contaminants in the ground 

water. A few of the ground-water models reflect the 

interrelationships of the streams and aquifer systems 

and, therefore, could guide management programs for 

conjunctive use of ground water and surface water (see 

section on ((Conjunctive Use of Ground Water and Surface Water"). 

Constraints on the greater use of ground-water 

models include: The large investments in facilities, 

data handling, and time usually required for development of a reliable, effective model; lack of adequate 

data for modeling many ground-water reservoirs, a 

situation that often can be overcome only by collecting 

field data, which is expensive and time-consuming; a 

shortage of ground-water hydrologists with the skills, 

support, and facilities necessary for successful modeling of complex hydrologic systems; and the lack of assurance that, even with the best expectations, a reliable model can be developed that is suitable for the 

intended use. Despite these constraints, however, predictive ground-water models remain one of the more 

useful water-management tools available for problem 

areas that warrant, and are amenable to, modeling. 

Once calibrated and verified against actual conditions, 

such models can be used indefinitely, with appropriate 

modifications, for study of a large variety of watermanagement problems. 

ENERGY-RELATED OPPORTUNITIES AND CONSTRAINTS 

Events of the past few years have brought into sharp 

focus the dependency of the Pacific Northwest Region 

and the Nation on abundant energy. Accordingly, no 

contemporary analysis of resource-management opportunities and constraints would be complete without 

considering those related to energy. 

Opportunities for energy-related uses of groundwater in the region appear at present to be few but may 

be substantial in the future. They include geothermal 

energy development; use of ground water in mining, 

processing and (or) movement of coal; small amounts of 

additional hydropower generation using ground water; 

and use of the ground water for disposal and (or) storage of heat. Ground-water problems associated with 

these possible uses include depletion of supplies and 

degradation of water quality. 

GEOTHERMAL ENERGY 

Naturally occurring hot ground water has been used 

in this region for several decades for irrigation and 

space heating, and is now being explored for wider applications, including generation of electrical power. 

Warm ground water is used for irrigation in many 

areas east of the Cascade Range, and thermal ground 

water also is used to heat buildings in the Boise and 

Sun Valley areas, Idaho. 1 

The term "geothermal resources" is commonly used 

to mean ground water or rocks hot enough to be of 

1

ln the Klamath Falls area, Oregon, which is adjacent to but outside this region, the use of 

hot ground water for heating home, commercial, and institutional buildings is said to be the 

largest use of thermal ground water for space heating in the United States. 
PACIFIC NORTHWEST REGION 35 

economic value-for example, to produce electrical 

power by releasing steam through drill holes for operation of turbine generators. About 120,000 acres of land 

in the region has been classed as being within KGRA's 

Cknown geothermal resource areas"), that is, areas 

worthy of careful evaluation for geothermal potential 

(Godwin and others, 1971). These KGRA's are mainly in 

the vicinity of the volcanoes of the Cascade Range and 

in the areas of the High Cascades, High Desert, and 

Southern Idaho ground-water reservoirs. To date 

(1977), by far the most intensive drilling and testing 

has been done in the Raft River basin, Idaho (fig. 9). 

There, several dozen holes have been drilled for subsurface samples, heat-flow measurement, and production of hot water or steam. The deepest known geothermal test well in the region (6,543 feet) is in this 

basin. 

None of the geothermal zones tapped has yielded 

water hotter than about 150°C, a temperature generally considered too low for efficient steam-power generation. However, experiments are planned at the Raft 

River basin site to investigate the practical applications of this low-temperature geothermal water for 

both electrical power generation and nonelectrical heat 

uses in industries related to agriculture and food processing. The experimental project is based on an integrated ((energy park" concept, in which heat remaining 

after one use of the hot water would be used in other 

applications requiring successively lower temperatures. If this experimental project is successful, it may 

lead to more nenergy parks" across southern Idaho and 

southeastern Oregon. 

The hot water from the Raft River basin is similar to 

most other thermal waters of the region, in that it is 

saline enough to be a potential contaminant to other 

water resources. The dissolved-solids concentration in 

water from one core hole in that area was 6,650 mg/L 

in September 1974 (U.S. Geological Survey data). 

HYDROPOWER GENERATION WITH GROUND WATER 

One unusual, though small-scale, energy-related use 

of ground water in this region is for the generation of 

electrical power. In the Thousand Springs area of the 

Snake River canyon near Twin Falls, Idaho, the discharge from springs high on the canyon wall is so large 

that the water is collected in flumes and used to drive 

generators located on the canyon floor. The combination of copious spring flow and discharge of the water at 

a relatively high elevation is needed for this use of the 

ground water; the combination exists in few other 

areas of the region. However, opportunities probably 

exist in parts of the High Cascades ground-water reservoir, where very permeable young volcanic rocks 

underlie steep land and receive abundant recharge 

from precipitation. The abundant yield of the young 

volcanic rocks was confirmed in Linn County, Oregon, 

where a tunnel was driven to drain these rocks and 

produce extra water for hydropower generation (R. B. 

Sanderson, U.S. Geol. Survey, written communication). 

GROUND WATER AND COAL 

Coal is the only fossil fuel known to occur in commercial quantities in the Pacific Northwest Region. 

Most of the coal is in and near the area of the Puget 

Sound ground-water reservoir, and in the eastern foothills of the Cascade Range. The estimated reserves in 

Washington are sizable-more than 6 billion (short) 

tons, but the reserves consist largely of subbituminous 

coal and lignite (about 4.3 billion tons; Livingston, 

197 4, p. 41). In addition to the relatively low ranking 

and heat content of most of the coal, the coal beds have 

been contorted by folding and faulting so that they 

commonly are steeply dipping, discontinuous, or 

sheared. In only a few areas are dips of the beds gentle 

enough to permit strip mining. Despite these problems, 

Washington has had some coal production almost continuously since the late 1800's, the largest being a 

strip-mining operation near Centralia, Wash. (south of 

the Puget Sound ground-water reservoir); this operation supplies as much as 2.6 million tons a year to a 

nearby steam-electric generating plant (Livingston, 

197 4, p. 41). 

Washington's coal has two important attributes that 

partly offset the aforementioned problems. One is that 

it is ((low-sulfur" coal and, therefore, it offers some economic advantages in meeting environmentalprotection requirements during mining and use. The 

other is that most of the coal occurs in reasonably close 

proximity to abundant water resources. This affords 

the possibility of using water for some forms of remote 

mining of the deep coal beds (hydraulic fracturing or 

flushing the broken coal to the surface), for conveying 

the coal in slurry pipelines, or for in-place gasification 

of the coal. 

At a few places near the coal beds, ground water 

could be produced at rates that would be useful in such 

processes, but the main impact of future coal development on ground water is likely to be a degradation of 

water quality. Water-quality impacts of coal-mine 

drainage and possible increased production of coal in 

Washington are being assessed by the U.S. Geological 

Survey (Packard and Haushild, 1977). 

SUBSURFACE STORAGE OF HEAT 

Water has a very high specific heat, meaning that a 

comparatively large amount of heat can be added to, or 

taken from, water for a given change in the water's 
36 SCMl\IAR\' APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

temperature. Also, slowly moving ground water and 

the rocks that enclose it conduct heat very slowly. 

These conditions make ground water advantageous for 

the storage of heat for later recovery. Similarly, the 

ground-water can be a sink for waste heat, although 

the cooling or assimilation rates using ground water 

normally cannot equal the rates possible with disposal 

of heat to streams or the atmosphere. Although there 

has been some use in the region of ground water for 

heat storage and disposal, much greater opportunities 

exist for utilizing the subsurface for the deliberate 

storage of heat. 

Ground water has been used for disposal and storage 

of heat mainly in the Puget Sound and Willamette Valley ground-water reservoir areas, mostly in the 

Portland, Oreg. area (Price and others, 1965, p. 20-33). 

Although problems of clogging of the aquifers have 

been a constraint to the continued or more widespread 

use of this type of subsurface storage and disposal, 

these problems can be largely overcome by improved 

methods such as closed-loop transfer of the water, selection of permeable aquifers, and use of the best wellconstruction methods for injection wells. As energy 

costs rise, reverse-cycle heat-pump systems, using 

ground water as the heat reservoir, are likely to become 

more popular for homes and other buildings. 

In addition to the saturated rocks available to 

serve as a heat reservoir, large bodies of permeable but 

unsaturated rocks are available, especially in arid 

parts of the region, that might serve for storage of local 

sources of heat-for example, heat from solarcollection systems or waste heat from power-generation 

facilities. 

SUMMARY OF NEEDS FOR ADDITIONAL 

INFORMATION 

The need for additional information is a recurring 

theme in this appraisal. State officials who were contacted, contributing hydrologists, technical reviewers, 

as well as this writer, generally agree that improved 

management of the ground-water resources in the 

Pacific Northwest Region is seriously hampered by information inadequacies. The scarcity of unappropriated surface water and accelerating uses of ground 

water are increasing the water-related problems and 

intensifying the need for ground-water management. 

Some difficult and far-reaching decisions are being 

made or must be made about the region's ground-water 

resources within the next decade. Without sound technical information, those decisions must be based 

largely on supposition and conjecture. 

Opinions differ as to which kinds of information are 

most needed and in what degree of detail. Judgments of 

this nature will be important because the total amount 

and variety of ground-water-related information that 

could be beneficially used within the next decade seem 

far beyond the present capabilities of hydrologists and 

others to supply. Efficiencies in the use of the limited 

technical manpower can be fostered by anticipating 

problems and maintaining an orderly program of investigations and research to provide information before water problems reach crisis proportions. 

The water managers of the region need ground-water 

information for the following purposes: 

1. To assess the resource-a recurring need that, 

for some parts of the region, has not been met 

even the first time; 

2. to detect changes with time; 

3. to make sound management responses to 

current problems; 

4. to identify developing or future problems, and 

to formulate strategies for forestalling, circumventing, or mitigating the problems; 

5. to gain public understanding of and support for 

the needs to manage the ground water; 

6. to combine scientific knowledge with economic, 

social, and political considerations as a basis 

for formulating water-resources policies. 

The kinds of ground-water data, investigations, and 

research that are needed by the water managers and 

others in the coming decade range widely, in accordance with the varied settings and problems of theregion. Discussion of the full range of information needs 

is beyond the scope of this summary section, but the 

following general statements seem pertinent: 

1. Ground-water-quality data, evaluations, and 

monitoring will be needed increasingly. 

2. More complete and reliable information on 

ground-water withdrawals and resultant 

water-level declines is needed for all the 

major and many smaller ground-water reservoirs. 

3. Although reconnaissance-type data will continue to be adequate for some purposes, more 

quantitative, detailed information will be required, especially in problem areas, areas 

destined for conjunctive use of surface and 

ground water, and areas considered for 

disposal of wastes. 

4. More perspective will be needed of the total 

ground-water reservoir or basin-the 

geologic framework and controls on the 

ground water; places and amounts of recharge and discharge; ground-water flow patterns (including deep parts of the reservoirs); 

hydraulic characteristics of the rock mate-
PACIFIC NORTHWEST REGION 37 

rials; and quality of the ground water 

throughout. 

5. The more detailed, extensive, and quantitative 

information will be more difficult and expensive to obtain, in general. Some information 

about deeper parts of the ground-water reservoirs can be obtained only by the drilling 

and testing of expensive, deep wells. Though 

not substitutes for the deep-well information, 

geologic mapping and geophysical surveys 

likely will be used increasingly to extend the 

information returns from deep testobservation wells. 

6. As the ground-water management problems increase in complexity, they will require reliable interpretations of greater sophistication 

and incisiveness. Mathematical models of 

ground-water flow systems will remain as 

powerful interpretive tools and will maintain 

a high level of demand for quantitative basic 

data. 

7. Presentation and dissemination of the 

ground-water information in a clear and 

understandable form will continue to be 

nearly as important, for some purposes, as 

the information itself. 

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38 SU~n1ARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

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--- 1964, Geology and ground-water conditions of Clark County, 

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