Water-Resources 

Reconnaissance of Hoopa 

Valley, Humboldt County 

California

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1576-C

Prepared in cooperation with

the U.S. Bureau of Indian Affairs
AN 2 9196^

Water-Resources 

Reconnaissance of Hoopa 

Valley, Humboldt County 

California

By J. L. POOLE

WATER SUPPLY OF INDIAN RESERVATIONS

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1576-C

Prepared in cooperation with

the U.S. Bureau of Indian Affairs

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

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D.C.
CONTENTS

	Page 

Abstract___ _____________________________________________________ C-l

Introduction._____________________________________________________ 2

Purpose and scope_____________________________________________ 2

Location and extent of the area__ _______________________________ 2

Well-numbering system._______________________________________ 4

Geographic features______________________________________________ 4

Topography and drainage._____________________________________ 4

Climate ___---_-_-_-_--___-___-__-__-________-_________--_____ 6

Water resources__-----_---_-__-__-___________-_____________-___--_ 6

Surface water _________________________________________________ 6

Ground water_________________________________________________ 8

Geologic units and their water-bearing properties._____________ 8

Consolidated rocks___________________________________ 8

Unconsolidated alluvial deposits.-_______________________ 10

Source, movement, and discharge____________________________ 13

Adequacy and permanence of the ground-water supply_________ 13

Existing water-supply facilities._____________________________________ 15

Development of a ground-water supply_____________________________ 16

Adequacy of the alluvial deposits as a storage reservoir___________ 16

Methods of developing a ground-water supply_____________________ 18

References.-______________________________________________________ 18

ILLUSTRATIONS

FIGURE 1. Index map showing location of Hoopa Valley______________ C-3

2. Well-numbering system___________________________________ 4

3. Geologic map of the Hoopa Valley area___________________ 9

4. Geologic section along line A-A' through Hoopa Valley._____ 11

5. Geologic sections along lines B-B' and C-C' across Hoopa

Valley______________________________________________ 12

in

WATER SUPPLY OF INDIAN RESERVATIONS

WATER-RESOURCES RECONNAISSANCE OF HOOPA 

VALLEY, HUMBOLDT COUNTY, CALIFORNIA

By J. L. POOLB

ABSTRACT

The Hoopa Valley area is underlain generally by consolidated rocks of preTertiary age, including quartz-mica schist, slate, and slaty sandstone and shale. 

These rocks crop out in the channel of the Trinity River and lie at depths 

ranging from exposures at land surface to about 50 feet beneath the valley 

floor. In Hoopa Valley the consolidated rocks are overlain by alluvial deposits 

of sand, gravel, and boulders which reach a maximum thickness of about 50 

feet beneath the terraces bordering the Trinity River.

The consolidated rocks are relatively impermeable and are not considered to be 

a reliable source of ground water in Hoopa Valley. They serve, instead, as 

a barrier to the downward movement of ground water and form a relatively 

impermeable surface over which ground water moves toward discharge areas 

along the Trinity River. The alluvial deposits are moderately to highly permeable and are capable of transmitting water rapidly from areas of recharge along 

streams and mountain fronts to areas of discharge along the Trinity River. 

Under these conditions there is little opportunity for natural ground-water 

storage through the late summer and fall dry period. Development of moderate 

Quantities of ground water from wells, therefore, is feasible only in small areas 

adjacent to the perennial tributaries of the Trinity River where a substantial 

thickness of saturated alluvium is maintained by infiltration of streamflow 

through the highly permeable stream-channel deposits.

An abundant supply of surface water is perennially available from the Trinity 

River and its four principal tributaries in Hoopa Valley. The perennial flow 

of Mill, Supply, Hostler, and Soctish Creeks is partly utilized for domestic and 

irrigation use and for industrial use by several lumber mills in the area. Supply 

Creek furnishes an ample water supply for U.S. Government installations at 

Hoopa, for small-scale irrigation, for the public school, and for about 50 private 

homes and business establishments in the vicinity of Hoopa.

The present water supply for the U.S. Bureau of Indian Affairs Hoopa Indian Agency and for the U.S. Public Health Service Hospital is obtained by 

pipeline from Supply Creek. Recurring flood damage to the pipeline in the 

section buried in the channel of Supply Creek requires the development of a 

ground-water supply in the vicinity of the Hoopa Indian Agency or the rerouting 

of the pipeline to avoid possible future flood damage. On the basis of observations

C-l
C-2 WATER SUPPLY OF INDIAN RESERVATIONS

of the hydrologic conditions adjacent to Supply Creek and the relative adequacy 

of ground-water and surface-water supplies, it is concluded that either alternative offers a satisfactory solution to the existing water-supply problem.

INTRODUCTION 

PUEPOSE AND SCOPE

The present water supply for the installations of the U.S. Bureau 

of Indian Affairs and U.S. Public Health Service at the Hoopa Indian 

Agency is obtained by pipeline from Supply Creek at an intake about 

half a mile west of the agency headquarters. During periods of emergency when the pipeline from Supply Creek is subject to damage by 

floods and heavy sediment loads, the supply is supplemented by water 

from Hospital Creek.

Owing to the recurring flood damage to the pipeline, the U.S. 

Bureau of Indian Affairs desires an alternate source of supply that 

will be less subject to damage. Accordingly, the Agency requested 

the U.S. Geological Survey to make a reconnaissance hydrologic study 

of the Hoopa Valley area, with special reference to the availability of 

an adequate ground-water supply in the vicinity of the Indian Agency 

headquarters. As a result of this request the author, during the period 

April 4-7,1960, made a field reconnaissance to obtain information on 

the geologic and hydrologic features of the area.

Because the availability and adequacy of a ground-water supply is 

determined largely by geologic conditions, the area was mapped to 

show the thickness, areal extent, and continuity of the water-bearing 

deposits and to show their relation to the underlying, relatively impermeable consolidated rocks. Hydrologic data were collected to serve 

as a basis for determining the source, direction of movement, and 

points of discharge of ground water and to determine the permeability 

and saturated thickness of the water-bearing deposits in the vicinity 

of the Hoopa Indian Agency. The fieldwork and the preparation of 

a report describing the results of the investigation were under the 

supervision of Harry D. Wilson, Jr., district engineer in charge of 

ground-water studies by the U.S. Geological Survey in California.

LOCATION AND EXTENT OF THE AREA

Hoopa Valley is in the northeastern part of Humboldt County, 

about 30 miles by airline and 50 miles by highway northeast of Eureka 

(fig. 1). It is accessible from Eureka and Redding via U.S. Highway 

299 and by a paved county highway that joins U.S. 299 at Willow 

Creek. From the north the area is reached by a paved county highway 

that parallels the Trinity and Klamath Rivers and, at its northern 

terminus, joins U.S. 99 a few miles north of Yreka, Siskiyou County.
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFOBNIA C-3

124°

41

40'

0

L i

10 I

20 MILES 

_I

FIGCEB 1. Index map of Humboldt County, California, snowing location of Hoopa

Valley.
C-4 WATER SUPPLY OF INDIAN RESERVATIONS

The valley floor, with which the present study is primarily concerned, 

is about 5 square miles in area and has a length of about 7 miles and 

an average width of about three-fourths of a mile. The area is shown 

on the Geological Survey topographic map of the Hoopa quadrangle 

at a scale of approximately 1 inch to 1 mile (1: 62,500).

WELL-NUMBERING SYSTEM

Wells in Hoopa Valley are numbered according to their location in 

the township, range, and section, a system in standard use by the 

Geological Survey and the California Department of Water Resources. Under this system each section is divided into 40-acre plots 

that are lettered as shown in figure 2.

D

E

M

N

C

F 

 2

L

P

B

G

K

Q

A

H

J

R

FIGURE 2. Well-numbering system.

Wells are numbered within each of these 40-acre plots according 

to the order in which they are located. For example, the well having 

the number 8/4-25E1 is in sec. 25, T. 8 N., R. 4 E., Humboldt base 

line and meridian. It is further identified as the first well located in 

the 40-acre plot lettered E, which is the SW%NW}4 sec. 25.

GEOGRAPHIC FEATURES 

TOPOGRAPHY AND DRAINAGE

Hoopa Valley is a narrow northwest-trending trough along the 

Trinity River, about 7 to 14 miles upstream from its confluence with 

the Klamath River. Except for the narrow gorge of the Trinity
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFORNIA C-5

Kiver, the valley is enclosed by rugged peaks and ridges of the Klamath Mountains on the east and the South Fork Mountains on the 

west. The maximum relief within the mapped area (fig. 3) is about 

3,900 feet; the highest point, 4,137 feet above sea level, is Telescope 

Peak in the southwestern part of the area.

The floor of Hoopa Valley averages about three-fourths of a mile in 

width a distinct contrast to the gorgelike character of the narrow 

valley of the Trinity River throughout most of its course. The altitude of the valley floor along the river channel ranges from about 250 

feet above sea level at the northern end to about 350 feet at the 

southern end. Prominent terraces, formed by entrenchment of the 

river, flank the present channel and locally stand 100 feet or more 

above the river level. The altitude of the surfaces of these terraces 

generally ranges from about 350 feet to about 400 feet above sea level 

near the central part of the valley and from about 300 to 450 feet 

from north to south, respectively, along the length of the valley. 

The northward slope of the flatter part of the valley floor thus is about 

20 feet per mile and the gradient of the Trinity Eiver about 10 feet 

per river mile.

About 110 square miles of rugged, heavily timbered mountains 

surrounding Hoopa Valley is drained by the Trinity Eiver and its 

tributaries between Campbell Creek (NE% sec. 6, T. 7 N., E. 5 E.) 

and Beaver Creek (SW% sec. 3, T. 8 N., E. 4 E.). The principal 

streams, Mill, Supply, Hostler, and Soctish Creeks, flow throughout 

the year and furnish water for many domestic, irrigation, and industrial requirements in Hoopa Valley. Most of the smaller streams 

drain relatively smaller areas and are either dry during the low-flow 

period of summer and fall or are incapable of furnishing dependable 

water supplies throughout the year.

Flooding of areas immediately adjacent to the mountain streams 

commonly occurs during the high runoff period from winter to early 

spring. Over a long period of recurring winter floods, however, the 

major streams have cut deeply into the alluvial deposits of the valley 

floor, and thus flooding is generally confined to the narrow flood 

plain of the river. Only infrequently does a stream overflow its 

banks and cause significant damage to homes or other installations. 

During the reported record high flow of January I960, for example, 

the waters of Supply Creek did not leave the stream channel. The 

principal damage during this flood was the rupture of the Indian 

Agency's main water-distribution line which is buried in the channel 

of Supply Creek northwest of the Indian Agency headquarters.

603289 61 2
C-6 WATER SUPPLY OF INDIAN RESERVATIONS

CLIMATE

Long-term averages of precipitation and temperature in the Hoopa 

Valley area have not been established owing to the short period of 

complete record at the, Hoopa U.S. Weather Bureau Station. During 

1959 the total precipitation was 42.97 inches, of which 38.58 inches, 

or about 90 percent, fell in the period December through March, and 

0.01 inch fell during June, July, and August.

Compared with records at other stations in the area with similar 

geographic settings and at comparable altitudes, the 1959 precipitation recorded at Hoopa was somewhat less than the long-term average 

for the general area. The indicated seasonal distribution at Hoopa 

also differs from that indicated by the long-term records at Orleans, 

18 miles to the northeast, and at Salyer Eanger Station, 12 miles to 

the southeast. Records at these stations show that 64 percent and 

67 percent of the rainfall, respectively, falls during the period December through March. The comparison also indicates that the 

1959 rainfall deficiency at Hoopa may not be representative because 

records for April through November for the period 1931-52 for 

Orleans and Salyer Ranger Station show that 36 percent and 33 percent of the precipitation, respectively, fell during this period, as 

compared with about only 10 percent at Hoopa in 1959.

Moderate temperatures were characteristic of the Hoopa Valley 

area in 1959, with a monthly average high of 74.8 in July, an average 

of 40.6 in December, and an annual average of 56.7. These averages 

are closely comparable with the mean temperature at the Orleans 

Weather Bureau Station, which has a 21-year period of record (1939- 

59). The 21-year mean temperature at Orleans was 76.1 in July and 

40.3 in December, and the mean annual temperature was 57.1.

WATER RESOURCES

SURFACE WATER

The surface-water resources of Hoopa Valley consist of the perennial flow of the Trinity Eiver and its four principal tributaries 

between the north end of the valley and the Trinity River gaging 

station 1% miles southeast of Hoopa. Flow from streams entering 

the valley from the bordering mountains at points upstream is included in the discharge recorded at the gaging station.

The discharge of the Trinity River, based on 28 years of record 

(1911-13, 1931-57) at the Hoopa gaging station, has averaged 5,613 

cubic feet per second (cfs), or more than 4 million acre-feet per year. 

During this period the maximum discharge of 190,000 cfs occurred on 

December 22, 1955, and the minimum of 162 cfs occurred on October
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFORNIA C-7

4, 1931 (Wells, 1959, p. 595). A flow-duration summary for the 

Hoopa gaging station, adjusted to the base period 1927-52, shows 

that the Trinity Kiver discharge equals or exceeds 160 cfs for 99.9 

percent of the time, and 32,000 cfs for 1 percent of the time. For 

the 2,846 square mile drainage area of the Trinity Kiver above the 

Hoopa gaging station this summary shows the streamflow contribution per square mile of drainage area to be 0.97 cfs for 50 percent of 

the time and 0.20 cfs for 80 percent of the time (Kantz, 1956, p. 71).

There are no continuous records of streamflow for the principal 

tributaries of Trinity Kiver in the Hoopa Valley drainage area. 

These streams, Mill, Supply, Hostler, and Soctish Creeks, drain areas 

of about 50, 18, 12, and 10 square miles, respectively a total area 

of about 90 square miles. Current-meter measurements of discharge 

have been made on occasion, however, at all four of these perennial 

streams. The discharge of Supply Creek was measured nine times 

during the period 1911 to 1918 and twice in 1960. Each of the other 

three streams was measured twice in 1960.

Correlation of concurrent discharge of Supply Creek and Trinity 

River near Hoopa indicates a curvilinear discharge relationship at 

t£ie lower flows. The few concurrent measurements available for the 

other streams indicate the following approximate discharge relationships :

Hostler Creek=0.30 X Supply Creek 

Soctish Creek=0.30 X Supply Creek 

Mill Creek=3.9 X Supply Creek

On the basis of these relationships and the flow-duration data for 

Trinity Kiver, a flow-duration summary for each of the four tributary 

streams has been synthesized. This summary, shown in the following 

table, is limited to durations ranging from 60 to 99 percent of time, 

because the discharge relationships for the several streams are too 

poorly denned to warrant extrapolation beyond this range. The discharges shown in the table are far from precise, but they are useful 

in evaluating the potential of these tributary streams to provide continuous and dependable water supplies in Hoopa Valley.

The discharges summarized above appear to be valid, at least in 

their order of magnitude, as indicated by reports of the adequacy and 

permanence of these streams. Supply Creek is a perennial stream 

that has furnished an adequate water supply for many years for the 

Hoopa Indian Agency, the U.S. Public Health Service Hospital, the 

public school, and about 50 private homes and business establishments. 

Even during relatively dry years and periods of low flow during wet 

years the discharge from Supply Creek reportedly has exceeded the 

local water requirements and has furnished, in addition, sufficient
C-8 WATER SUPPLY OF INDIAN RESERVATIONS

water to irrigate a small parcel of Indian land in the vicinity of the 

Indian Agency headquarters. Mill, Hostler, and Soctish Creeks also 

flow throughout the year and provide sufficient water for local domestic, irrigation, and industrial uses.

Estimated flow duration summary for the principal tributaries of the Trinity

River in Hoopa Valley

Stream

Mill Creek. .

Total---- 

Drainage 

area 

(sq mi)

50 

18 

12 

10

90

Discharge (cfs) expected to be equaled or exceeded during 

percent of time indicated

99

10.0 

2.6 

.8 

.8

14.2

95

13.0 

3.4 

1.0 

1.0

18.4

90

16.0 

4.0 

1.2 

1.2

22.4

80

20.0 

5.2 

1.6 

1.6

28.4

70

28.0 

7.1 

2.1 

2.1

39.3

60

51.0 

13.0 

3.9 

3.9

71.8

GROUND WATER 

GEOLOGIC TTNITS AND THEIR WATER-BEARING PROPERTIES

For the purposes of this report the geologic formations in the 

Hoopa Valley area are divided into two distinct types, on the basis 

of their lithology and water-bearing properties. These are consolidated rocks of pre-Tertiary age and unconsolidated alluvial deposits 

of Quaternary age. The areal distribution of these formations is 

shown on the geologic map (fig. 3) and their stratigraphic and physiographic relations are shown on the geologic sections (figs. 4 and 5).

CONSOLIDATED ROCKS

Consolidated rocks form the mountains surrounding Hoopa Valley 

and underlie, at shallow depth, the unconsolidated alluvial deposits on 

the valley floor. These consolidated rocks consist principally of 

quartz-mica schist, slate, and slaty sandstone and shale of pre-Tertiary 

age. The quartz-mica schist is similar in most respects to the Abrams 

schist, described by Hershey (1901, p. 225-245), and the Kerr Ranch 

schist, described by Manning and Ogle (1950, p. 13-18). Manning 

and Ogle (1950, p. 15) recognized the similarity between the Abrams 

schist and the schist in the Bluke Lake quadrangle; however, they 

proposed the new geologic name, Kerr Ranch schist, principally 

because of differences in the degree of metamorphism. The slate and 

slaty sandstone and shale appear to be a southward extension of the 

Galice formation in Del Norte and northern Humboldt Counties as 

described by Hershey (1911, p. 468), and by Irwin and Tatlock (1955, 

pi. 1).
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFORNIA O-9

As the scope of this report precluded detailed geologic studies and 

correlations, the consolidated rocks in the Hoopa Valley area are 

included in previously recognized geologic units. On the basis of its 

lithologic character, the quartz-mica schist is thus considered equivalent to the Abrams schist of Hershey (1901, p. 225-245) and the 

slate and slaty sandstone and shale to the Galice formation of Hershey 

(1911, p. 468).

Alluvial deposits of Quaternary age. 

Boulders and cobbles in a matrix 

of sand and gravel

Consolidated rocks of pre-Tertiary 

age. Includes quartz-mica schist, 

slate, and slaty sandstone and shale

Contact between consolidated rocks 

and alluvial deposits

A A'

Line of geologic section

OQ2 

Well 

 2 

Favorable test-drilling site

Outcrop of consolidated rocks shown 

 in geologic sections

Base from U. S. Geological Survey 

Hoopa quadrangle, 1952

L_

Geology by J. L. Poole

2MILES 

J

CONTOUR INTERVAL 100 FEET 

DATUM IS MEAN" SEA LEVEL

FIGURE 3. Geologic map of the Hoopa Valley area, Humboldt County, Calif., showing locations of wells and favorable sites for test drilling.
C-10 WATER SUPPLY OF INDIAN RESERVATIONS

Dark-gray to black slate and slaty sandstone and shale are the 

predominant consolidated rock types in the Hoopa Valley area. They 

are exposed in the banks of the Trinity Kiver throughout the length of 

the valley about 30 to 50 feet below the general level of the bordering 

terraces. The Trinity Kiver has entrenched itself to a depth of 20 to 

30 feet in the consolidated rocks and now flows on these rocks except 

along reaches where the river bed is partly filled with coarse channel 

deposits.

The least common of the consolidated rock types is the quartz-mica 

schist observed in roadcuts at the south end of Hoopa Valley and in 

the channel of Supply Creek southwest of the Hoopa highway bridge. 

The schist, ranging from gray to green in color, probably is the "blue 

shale" or "blue clay" reported in drillers' logs of wells in the valley.

The consolidated rocks are of little significance with respect to the 

development of ground water, because they are relatively impermeable 

and can transmit water only very slowly along bedding planes and 

through zones of jointing and faulting. For this reason they are not 

differentiated and are shown on the geologic map and sections as a 

single consolidated rock unit. Owing to the small scale of the geologic 

map (fig. 3), it was not possible to show the small areas of consolidated 

rock outcrop along the Trinity Kiver and its larger tributaries.

UNCONSOLIDATED ALLUVIAL DEPOSITS

The floor of Hoopa Valley is underlain by unconsolidated alluvial 

deposits that range in thickness from a few feet along the valley 

margins to a maximum of about 50 feet along the terraces bordering 

the Trinity River (figs. 4 and 5). The unconsolidated deposits consist of alluvial-fan deposits at the mouths of the principal streams 

that enter the valley, talus-slope deposits along the steep mountain 

fronts, channel deposits of the Trinity River, and terrace deposits 

flanking the Trinity Kiver along its course through the valley. The 

alluvial-fan and talus-slope deposits are composed of poorly sorted 

sand, gravel, and angular to subangular cobbles and boulders derived 

from weathering and erosion of the consolidated rocks in the surrounding mountains. River-channel and terrace deposits are generally well sorted, consist mostly of subrounded gravel, cobbles, and 

boulders, and contain relatively little fine-grained material.

The alluvial deposits are exposed in their maximum known thickness along the banks of the Trinity Kiver, where they range in thickness from about 40 feet at the south end of Hoopa Valley to about 50 

feet at the north end (fig. 4). The alluvial deposits are nowhere 

continuous across the valley, because the Trinity River has trenched 

through them and into the underlying bedrock all along its course
300'-

200'-

DATUM IS MEAN SEA LEVEL

Alluvial deposits Consolidate

FIGUEB 4. Generalized northwest-southeast geologic section along line A-A' through Ho
500'

4001-

DATUM IS MEAN SEA LEVEL

FIGURE 5. Generalized east-west geologic sections along lines B-B' and C-

of sections shown on figure 3.
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFORNIA C-13

(fig. 4). The geologic sections (figs. 4 and 5) indicate that the thickness of the alluvial deposits does not exceed that observed in the banks 

of the river.

The alluvial deposits are moderately to highly permeable and therefore are capable of transmitting water rapidly from areas of recharge 

to areas of discharge. A high permeability is shown by reports of 

rapid infiltration of water applied for watering lawns and for other irrigation in the valley. According to reports, large volumes of water 

allowed to flow from pipelines seep into the ground with little or no 

ponding at the point of discharge.

SOURCE, MOVEMENT, ANI> DISCHARGE

The source of all ground water in Hoopa Valley is the precipitation 

that falls on the valley floor and in the surrounding mountains. Part 

of this precipitation percolates directly into the soil and part 

flows into the mountain streams and upon reaching the valley floor 

percolates into the ground-water body through the highly permeable 

 channel-fill deposits. The remainder either becomes surface runoff or 

5s lost to the atmosphere by evaporation.

Part of the water that percolates into the soil moves slowly down 

the mountain slopes as ground water and seeps into streams or directly 

into the alluvium underlying the floor of Hoopa Valley. The soil 

cover on the slopes provides the storage and slow transmission of 

water essential to the maintenance of perennial flow in the streams 

that drain the area. After reaching the valley floor, ground water 

moves downgradient through the alluvium to points or areas of discharge, the rate of movement depending on the slope of the groundwater surface and the permeability of the alluvial deposits. Highly 

permeable material, such as the terrace deposits covering much of 

the floor of Hoopa Valley, permits rapid movement toward the central part of the valley. Owing to the low permeability of the consolidated rocks in contrast to the higher permeability of the alluvial 

deposits, most of the water that reaches the ground-water body moves 

rapidly through the alluvium just above the surface of the underlying 

consolidated rocks and discharges into the Trinity Eiver. Consequently there is little opportunity for sufficient accumulation of 

ground water in storage in the valley to sustain heavy withdrawals 

during dry seasons of the year when it is needed the most.

ADEQUACY AND PERMANENCE OF THE GROUND-WATER SUPPLY

The water table, or upper surface of the zone of saturation in the 

unconsolidated alluvium, averages about 20 to 30 feet below the land 

surface throughout most of the Hoopa Valley area and is at or near
C-14 WATER SUPPLY OF INDIAN RESERVATIONS

the land surface along the principal streams flowing into the Trinity 

Eiver. It conforms generally with the surface topography; it slopes 

toward the central part of the valley and the discharge area along the 

Trinity Eiver and thus indicates the direction of ground-water 

movement.

The water table fluctuates from season to season; it rises during 

rainy periods in response to recharge through permeable soils and 

stream-channel deposits and declines during dry periods when recharge is at a minimum and is exceeded by ground-water discharge. 

The water level therefore is highest and the saturated thickness of the 

alluvial deposits is greatest during the December to April period of 

heavy precipitation. During the dry season of July through September the water table is lowest and in prolonged dry periods may decline 

sufficiently to leave the lowermost alluvial deposits locally 

unsaturated.

Water levels observed in April 1960 were at or near their maximum 

height and were highest along the principal streams where they enter 

the valley floor. Along these perennial streams, water percolates 

through the permeable channel deposits and builds up ground-water 

mounds beneath the stream course where it is underlain by alluvium. 

These mounds vary in height and areal extent and depend on the 

amount and duration of streamflow; they are persistent along the 

perennial streams near the margins of the valley.

The saturated thickness of the alluvial deposits decreases toward 

the interstream areas of the tributary streams and locally may be 

less than 5 feet even during periods of high water levels. Waterlevel measurements made in April 1960 showed that the saturated 

thickness ranged from about 5 to 19 feet and averaged about 12 feet 

(figs. 3 and 4). It was least along the Trinity River where groundwater discharge was occurring at the bedrock outcrop, and greatest 

at the valley margins near the principal tributaries. Records of 

water levels during dry periods are not available, but the water table 

probably declines so much during late summer and fall that the 

alluvial deposits probably are virtually dewatered. Reports of inadequate yields from wells drilled to bedrock confirm the contention that 

a minimum saturated thickness of the alluvium exists during late 

summer and fall. The following table contains water-level data and 

other information for representative wells in Hoopa Valley that summarize the hydrologic conditions as observed in April 1960. The 

wells indicated are identified according to the previously-described 

well-numbering system and are shown on figure 2.

The adequacy and permanence of a ground-water supply in Hoopa 

Valley depend on how much water a well will yield when the thick-
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFORNIA C-15

ness of the saturated section is least, usually in the autumn. This dependence on the thickness of the saturated section becomes even more 

critical when it is considered that a pumped well must lower the water 

level in the vicinity to establish a cone of depression that will cause 

ground water to move into the well from all directions. The amount 

the water level is lowered depends on the specific capacity of the well, 

or the yield in gallons per minute (gpm) per foot of water-level 

decline. Thus, in order to pump 100 gpm from a well with a specific 

capacity of 10 gpm per foot, the water level must be lowered 10 

feet in the well. Yields of wells in Hoopa Valley, therefore, are 

limited by the relatively thin saturated alluvial section at the times 

when water levels are lowest. As the saturated thickness of the 

alluvium probably ranges from 1 to 10 feet and may average less 

than 5 feet in most of the valley during late summer and fall, only 

small to moderate yields could be obtained from wells, except locally 

along the perennial streams.

Data for selected wells showing general hydrologic conditions in Hoopa Valley

Well

8/4-10G1.. ..............................

10H1__ ..... _ ......................

IINI.. . .............................

14P1 ................................

14Q1............ ......................

14Q2 _ ...............................

23K1............................ .......

23K2-... ....................... ...

25E1...... .............................

8/5-31M1. .................................

31Q1 .............._........ . ..

Depth 

(feet)

37

28

78

50

58

91

25

82

37

1 97

Depth to 

bedrock 

(feet)

»40

37

28

44

25

9fi

40

Water level 

(feet below 

land 

surface)

31.4

27.6

22.3

24.7

OA f\

32.0

10 Q

20.3

18.0

Date of 

water-level 

measurement

4-&-60

4-5-60

4-5-60

4-&-60

4-5-60

4-&-60

4-&-60

4-5-60

4-6-60

Saturated 

thickness 

of alluvium 

(feet, 

rounded)

9

9

6

17

16±

12

5

19±

1 Estimated from outcrop nearby.

EXISTING WATER-SUPPLY FACILITIES

The greatest concentration of population in Hoopa Valley is In 

the vicinity of Hoopa (fig. 3) where most of the water for domestic 

use is furnished by pipeline from Supply Creek. About 200 residents, in addition to the Hoopa Indian Agency, the U.S. Public 

Health Service Hospital, and the public school, obtain water from 

this source. There is no ground-water development at the agency; 

moreover, little ground-water development has been attempted elsewhere in Hoopa Valley owing to the ready availability of surfacewater supplies and the difficulty of developing adequate supplies from 

wells. Most residents of the valley obtain their domestic supplies 

from streams or springs, which are reported to be more dependable 

than existing wells and, in addition, are capable of furnishing suffi-
C-16 WATER SUPPLY OF INDIAN RESERVATIONS

cient water for small-scale irrigation and the industrial requirements 

of several lumber mills.

The present Hoopa Indian Agency water system is dependent on 

the perennial surface flow in Supply Creek, which supplies more 

than 600 gpm continuously through an 8-inch pipeline. This quantity is usually in excess of actual needs, however, and much of the 

flow is diverted back into Supply Creek except during periods of 

peak demand.

With few exceptions, existing wells throughout Hoopa Valley are 

capable of yielding only small quantities of water for domestic use. 

Most of these wells tap the unconsolidated alluvium, but many were 

drilled a few feet into the underlying consolidated rocks, generally 

in unsuccessful attempts to obtain additional and more permanent 

water supplies. Yields of domestic wells, as limited by the small 

capacities of presently used pumping equipment, are generally less 

than 10 gpm. Wells of greater capacity can be developed, however, 

in favorable areas where the water table remains 10 feet or more above 

the top of the consolidated rocks. The largest reported yield is 75 

gpm from the Sugar Pine Lumber Co. well 8/5-31M1, at the south 

end of Hoopa Valley.

DEVELOPMENT OF A GROUND-WATER SUPPLY

ADEQUACY OF THE ALLUVIAL DEPOSITS AS A STORAGE RESERVOIR

Development of wells capable of producing moderate quantities 

of ground water from the alluvial deposits would require the selection 

of well sites having the maximum possible saturated thickness of 

alluvium. The vicinity of Hoopa is considered to be typical of potential ground-water development sites in Hoopa Valley. In this area 

the maximum thickness of the alluvial deposits is about 30 feet, as 

shown by geologic section C-C' (fig. 5). This estimate is based on 

outcrops of the consolidated rocks in the channel of Supply Creek 

and a reported depth to bedrock of 26 feet at well 8/4-25E1. The 

thickness is somewhat less along Supply Creek west of the Hoopa 

Highway, because the stream channel is entrenched from 5 to 15 feet 

below the general level of the terrace. The maximum thickness of 

the alluvium along Supply Creek thus is estimated to be about 20 to 

25 feet in the vicinity of the bridge in the NE*4 sec. 26, T. 8 N., E. 4 E. 

(fig. 3).

The continuing infiltration of water through the permeable deposits 

in the stream channel presumably maintains the water table at a 

high level along Supply Creek. During the rainy season, ground 

water is forced to the surface and is discharged into Supply Creek
HOOPA VALLEY, HUMBOLDT COUNTY, CALIFORNIA C-17

along the bedrock outcrop at the Hoopa Highway bridge. In April 

1960, ground water was ponded in a depression at the base of the 

terrace bordering Supply Creek and, although no surface inflow to 

the pond was observed, water was discharging into the creek through 

a small channel cut into the consolidated rock surface. As the flow 

of Supply Creek decreases, the rate of infiltration in the upstream 

segment also declines and causes a lowering of the water table and 

a decrease in the rate of ground-water discharge into the stream east 

of Hoopa Highway.

Similar geologic and hydrologic conditions exist along Mill, Hostler, 

and Soctish Creeks where they cross the valley floor. The most favorable sites for development of ground-water supplies are along these 

perennial streams, which are the principal sources of recharge to the 

ground-water body. Because of this recharge the water levels are 

expected to be highest and the thickness of saturated alluvium greatest 

in these areas.

Few wells have been drilled in Hoopa Valley in which groundwater levels can be observed. The depth to the water level and the 

thickness of saturated alluvium therefore are estimated on the basis 

of the projected profile of the consolidated rocks (figs. 4 and 5) and 

the predicted effects on the ground-water body of recharge from the 

mountain streams and from ground-water movement along the buried 

bedrock surface to discharge areas. During periods of maximum 

streamflow, the alluvium along the streams is almost fully saturated 

and the water level is within a few feet of the land surface. Because 

of the high permeability of the alluvium and the proximity of discharge areas, however, ground water drains out rapidly and the water 

table declines as streamflow and streambed infiltration decrease. It 

is estimated, therefore, that along Mill, Supply, Hostler, and Soctish 

Creeks the maximum saturated thickness of alluvium during the 

normally dry months of July through September is perhaps less than 

10 feet, and at short distances from these streams may be less than 

5 feet. Elsewhere in Hoopa Valley adequate supplies may be available, but only during part of the year, because the water table declines 

to near the bedrock surface during the late summer and fall. A 

minimum thickness of less than 1 foot is indicated by the driller's 

log of well 8/4-25E1, in which the ground-water level coincides approximately with the level of the bedrock surface at a depth of 26 

feet. This well was drilled near the Indian Agency headquarters, 

in the interstream area between Supply and Hospital Creeks, in an 

attempt to develop a ground-water supply for the public school.
C-18 WATER SUPPLY OF INDIAN RESERVATIONS

METHODS OF DEVELOPING A GBOUND-WATEB SUPPLY

As shown previously, the maximum saturated thickness of alluvium 

along the principal tributary streams during the period July through 

September may be 5 to 10 feet. Assuming a maximum drawdown 

of about 5 feet and a specific capacity of 10 gpm per foot of drawdown in wells completed in the alluvium, a maximum yield of 50 

gpm could be pumped from a single large-diameter well. Larger 

quantities could be obtained readily by the use of large-diameter 

collectors that penetrate the entire thickness of the alluvium and 

have perforated collector pipes extending horizontally along the bedrock surface from the collector well. This method pumps water 

from a larger area with less resultant drawdown and affords the 

maximum yield from the available thickness of saturated alluvium. 

Should the water table decline to near the bedrock surface, the system, of horizontal collector pipes would provide a margin of safety 

that cannot be achieved by standard vertical wells.

Before supply wells or collectors are installed, however^ test wells 

should be drilled to determine the thickness of the alluvium and the 

depth to water adjacent to the streams. Water-level measurements 

also should be made during the period of low streamflow to determine the approximate lowest water level and thus the minimum 

thickness of saturated alluvium during the dry season.

Sites for such test and observation wells should be selected near 

enough to the streams to take full advantage of the maximum thickness of saturated alluvium, yet far enough away to eliminate the 

effect on the ground-water body of pollutants which may be carried 

by streams. Additional wells should be drilled at greater distances 

from the streams to provide information on the slope of the groundwater surface and thus show the effect of recharge from the streams.

REFERENCES

Hershey, O. H., 1901, Metamorphic formations of northwestern California: Am. 

Geol., v. 27, p. 225-245.

 1911, Del Norte County geology: Mining and Sci. Press, v. 102, p. 468.

Irwin, W. P., and Tatlock, D. B., 1955, Geologic map of northwestern California, 

in Geology, mineral resources, and mineral industry, App. to Natural resources of northwestern California: Pacific Southwest Field Committee, 

U.S. GeoL Survey and U.S. Bur. Mines, pi. 1,1:782,000.

Manning, G. A., and Ogle, B. A., 1950, Geology of the Blue Lake quadrangle, 

California: California Div. Mines Bull. 148, 30 p.

Eantz, S. E., 1956, Surface-water hydrology of coastal basins of northwestern 

California, in Water resources, App. to Natural resources of northwestern 

California: Pacific Southwest Field Committee, U.S. Geol. Survey, p. 1-76.

Wells, J. V. B., 1959, Surface-water supply of the United States, p. 11, Pacific 

slope basins in California: U.S. Geol. Survey Water-Supply Paper 1515.

U.S. GOVERNMENT PRINTING OFFICE: 1961