Specific-Yield an 

Particle-Size Relations 

of Quaternary Alluvium 

Humboldt River Valley 

Nevada

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1669-M

Prepared in cooperation with the 

Nevada Department of Conservation 

and Natural Resources

^lSpecific-Yield and 

Particle-Size Relations 

of Quaternary Alluvium 

Humboldt River Valley 

Nevada

By PHILIP COHEN

CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1669-M

Prepared in cooperation with the 

Nevada Department of Conservation 

and Natural Resources

I MTED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963
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__..________________________________ Ml

Introduction..---.-_----_--___-_---__-__-__--_______-___-_-------_ 1

Hydrogeologic features.____________________________________________ 3

Field and laboratory methods__---_____-__-_----________-_--___-__ 3

Laboratory data_________________________________________________ 5

Porosity__________________________________________________ 5

Specific retention-_____________________________________________ 10

Specific yield______________________________________________ 10

Summary of relations between specific yield, porosity, specific retention, sorting coefficient, and median particle-size diameter,_______ 20

Comparison of specific-yield values of the deposits of the Humboldt River 

valley with data published by others_____-_________-___-_-__-____-_ 21

Conclusions__--__--___-_-______-_____________-__-___-_________ 23

References cited.-_________________________________________________ 24

ILLUSTRATIONS

Page 

FIGURE 1. Map of Nevada showing location of Humboldt River Research

Project area___________-___________________-_______-__ M2

2-4. Relation between porosity and sorting-coefficient values 

2. Silt- and very fine sand-size ranges.__________ _____ 6

3. Fine-and medium-sand-size ranges._______ _________ 7

4. Coarse- and very coarse sand- and gravel-size ranges 8 

5. Relation between median particle-size-diameter and porosity

values_____________________________________ 9

6-8. Relation between sorting-coefficient and specific-retention 

values 

6. Silt- and very fine sand-size ranges,___________________ 11

7. Fine- and medium-sand-size ranges.__________________ 12

8. Coarse- and very coarse sand- and gravel-size ranges 13

9. Relation between median particle-size-diameter and specificretention values_.______________________________ 14

10. Histogram showing frequency distribution of specific-yield

values______ _______ _________ _. _ 15

11-13. Relation between sorting-coefficient and specific-yield values 

11. Silt-and very fine sand-size ranges_._________ _ 16

12. Fine-and medium-sand-size ranges ____________ 17

13. Coarse- and very coarse sand- and gravel-size ranges 18

m
IV CONTENTS

TABLES

Page

TABLE 1. Summary of specific-yield values of samples from the Humboldt River valley, Humboldt County, Nev_______________ M19

2. Estimated specific yield, in percent, of sediments in the South

Coastal Basin, southern California _______________________ 21

3. Average specific yield, in percent, of sediments in the Mokelumne area, California._________________________________ 22

4. Specific yields used to estimate ground-water storage capacity

in the San Joaquin Valley, Calif__.-___________.__________ 22

5. Specific yield used to estimate total ground-water storage capacity in the Putah area, California____-_____________-______ 22
CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

SPECIFIC-YIELD AND PARTICLE-SIZE RELATIONS OF 

QUATERNARY ALLUVIUM, HUMBOLDT RIVER VALLEY,

NEVADA

By PHILIP COHEN

ABSTRACT

As part of a study to determine changes of ground water in storage, 323 

samples of unconsolidated alluvium from the Humboldt River valley, Humboldt 

County, Nev., were analyzed for specific yield and particle-size distribution. 

Specific-yield values of the fine-grained deposits are considerably higher than 

previously reported by other writers. These high specific-yield values are partly 

related to the high primary and secondary porosity of the fine-grained deposits, 

and may be due partly to compaction of the samples in the centrifuge.

There are complex interrelations between porosity, specific retention, sorting 

coefficient, and median particle-size diameter in the deposits of the study area. 

Because of these interrelations, specific yield cannot readily be estimated from 

any one or a combination of the aforementioned parameters.

INTRODUCTION

The U.S. Geological Survey, in cooperation with the Nevada Department of Conservation and Natural Eesources and other State and 

Federal agencies, is participating in a comprehensive interagency 

hydrologic study known as the Humboldt River Eesearch Project. 

The study area is shown in figure 1. One of the major objectives of 

this study is to determine a hydrologic budget for the study area. To 

help meet this objective, the U.S. Geological Survey is studying 

changes of ground water in storage in the shallow aquifers. As part of 

this study, 323 sediment samples were collected from the Humboldt 

Eiver valley in the fall of 1959 and the summer of 1960; and these 

samples were analyzed for specific yield and particle-size distribution 

in the Hydrologic Laboratory, U.S. Geological Survey, Denver, Colo. 

The purpose of this report is to analyze these data and describe the 

interrelations between them.

Ml
M2 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

119° 118° 117" 116° 115°

37°

FIODBB 1. Map of Nevada showing the location of the Humboldt River Research Project

area.
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M3

This study was under the immediate supervision of O. J. Loeltz, district engineer in charge of ground-water investigations in Nevada. 

The writer is indebted to the personnel of the Nevada Department of 

Conservation and Natural Resources, who were valuable coworkers in 

the field.

HYDROGEOLOGIC FEATURES

The mountain ranges in the study area are composed of dense sedimentary, igneous, and metamorphic rocks that range in age from 

Paleozoic to Quaternary. These rocks generally have low interstitial 

porosity and do not transmit appreciable amounts of water except, 

perhaps, through fractured zones.

Significant changes of ground water in storage occur only in Quaternary alluvium. The alluvium includes lacustrine deposits of Pleistocene Lake Lahontan age and fluviatile and subaerial flood-plain 

deposits of Recent age. The Lake Lahontan deposits include three 

stratigraphic units: the so-called lower silt and clay, medial gravel, 

and upper silt and clay; the lower two units are recognized only in the 

subsurface. The lower silt and clay unit, whose thickness has not been 

determined, and the upper silt and clay unit, which is about 55 feet 

thick, consist largely of dense relatively impermeable silt, clayey silt, 

and clay. The medial gravel, whose maximum thickness is about 

100 feet, consists of well-sorted highly permeable sand and gravel. 

The flood-plain deposits range from highly permeable stringers 

of sand and gravel to relatively impermeable lenses of silty clay 

and clay. Locally, the porosity of the silty and clayey deposits has 

been increased by plants and burrowing invertebrate animals. Also, 

most of the fine-grained flood-plain deposits are moderately porous, 

because they have been subjected to little or no compaction.

The flow of the Humboldt River tends to increase markedly in the 

spring and to diminish in midsummer. Ground-water levels respond 

to the increased stage and flow of the river and tend to reach their 

maximum altitudes in May. Levels decline in the summer in response 

to the decrease in flow of the river, evapotranspiration, and, to a 

lesser extent, pumpage for irrigation. Ground-water levels recover 

somewhat in the winter because of the virtual cessation of 

evapotranspiration.

FIELD AND LABORATORY METHODS

Test holes were augered with a power auger at approximately 175 

sites on and adjacent to the flood plain of the Humboldt River in a 

40-mile reach centered about the city of Winnemucca in north-central 

Nevada. The usual procedure was to auger two holes at each site. 

The first hole commonly was augered to a depth of about 5 to 10 feet
M4 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

below the water table. Casing was installed upon completion of the 

augering, and after about 30 minutes the water level in the well was 

measured. A second hole then was augered with the power auger to a 

depth of about 1 foot above the interval to be sampled. A hand auger 

was used to complete the augering to the desired sampling depth. 

Undisturbed samples were collected by means of a core barrel that 

consists of a 2-inch-diameter by 4-inch-long core barrel containing two 

brass liners. The barrel was driven into the sediments with the aid of 

a 25-pound slip hammer. The core in the upper brass liner was discarded to eliminate the possibility of contamination that may have 

resulted from material falling into the hole prior to and during the 

insertion of the core barrel. This procedure was repeated until all 

desired samples were collected at each augering site. As a general 

rule, an attempt was made to sample all the representative lithologic 

units within the zone of anticipated water-level fluctuations.

It was not possible to collect undisturbed core samples at some of 

the augering sites, especially where the sediments were coarse or very 

moist. Disturbed samples collected under these conditions were repacked in the laboratory in an attempt to reestablish as nearly as 

possible their original porosity.

Laboratory studies consisted of determining the particle-size 

distribution and the specific yield of 323 sediment samples. The particle-size distribution of each sample was obtained by the hydrometerand-sieve method.

The size classification of sedimentary particles used by the Ground 

Water Branch, U.S. Geological Survey, is used in this report and is 

as follows:

Description Diameter (mm) 

Gravel ____________________________. >2.0 

Very coarse sand_____________________ 1.0-2.0 

Coarse sand_________________________ .5-1.0 

Medium sand_________________________ .25-0.5 

Fine sand _________________________ .125-0.25 

Very fine sand________________________ .0625-0.125 

Silt _______________________________ .004-0.0625 

Clay ____________________________ <.004

It was necessary to determine porosity and specific retention to calculate specific yield. Porosity was determined by the standard pycnometer method. The centrifuge-moisture-equivalent method was 

used to determine the specific-retention values of the sediment 

samples. Meinzer (1923, p. 28) defined the specific retention of a 

rock or sediment sample as "* * * the ratio of (1) the volume of 

water which, after being saturated, it will retain against the pull of 

gravity to (2) its own volume." Multiplying this ratio by 100 ex-
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M5

presses specific retention as a percentage. Specific retention was not 

determined directly. Rather, centrifuge moisture equivalent, or the 

amount of water, expressed as a percentage of the total volume of a 

saturated sample, retained by the sample after having been subjected 

to a force equal to 1,000 times the force of gravity for 1 hour, was 

determined. The specific-retention data were derived from the centrifuge-moisture-equivalent data by a method based upon the work 

of Piper and others (1939, p. 118-119) in which specific retention obtained by drainage in the field was related to the centrifuge moisture 

equivalent of the same materials.

The specific yield of a rock or sediment sample was defined by 

Meinzer (1923, p. 28) as "* * * the ratio of (1) the volume of water 

which, after being saturated, it will yield by gravity to (2) its own 

volume." This ratio multiplied by 100 expresses specific yield as a 

percentage. Specific yield is equal to porosity (the percentage of 

the total volume of the rock or sediment sample occupied by interstices) minus specific retention. Thus, specific yield was calculated 

by subtracting specific retention from porosity.

LABORATORY DATA

Because specific yield is related to specific retention and porosity, 

porosity and specific-retention data are discussed before specific-yield 

data.

POROSITY

It is convenient to relate porosity to the sorting-coefficient and 

median particle-size-diameter values of the samples. Sorting coefficient and the median particle-size diameter are derived from a cumulative curve of the size distribution of the particles that constitute the 

sample. (See Pettijohn, 1949, p. 22, for method of constructing a 

cumulative curve.) Sorting coefficient may be expressed by the 

formula

where So is the sorting coefficient, Q3 is the 75-percent quartile, and 

Q! is the 25-percent quartile. The quartiles are derived from the 

cumulative curve and are the diameters of the particles associated 

with the intersection of the 75- and 25-percent values with the cumulative curve. The median particle-size diameter is the size value associated with the 50-percent quartile.

Figures 2-4 show six graphs illustrating the relation between porosity and sorting-coefficient values of samples from the Humboldt 

Eiver valley. If all the points were plotted on one graph, there would

675128 63 2
M6 CONTKIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

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POROSITY, IN PERCENT

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Median particle-size diameter in very fine sand-size range

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POROSITY, IN PERCENT

FIGCHB 2. Relation between porosity and sorting-coefficient values of samples from the 

Humboldt River valley, silt- and very fine sand-size ranges.

be little or no apparent relation between these parameters. There 

does seem to be a slight tendency for porosity to increase as sorting 

coefficient decreases for samples whose median particle-size diameters 

are in the sand-size ranges. The graphs also suggest that samples 

having coarser median partiele-size diameters tend to have lower 

porosity values than samples having finer median particle-size 

diameters.
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M7

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POROSITY, IN PERCENT

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FIGURE 3. Relation between porosity and sorting-coefficient values of samples from the 

Humboldt River valley, fine- and medium-sand-size ranges.
M8 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

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FIGURE 4. Relation between porosity and sorting-coefficient values of samples from the 

Humboldt River valley, coarse- and very coarse sand- and gravel-size ranges.

Figure 5, a graph with median particle-size diameter as the abscissa 

and porosity as the ordinate, show more conclusively that porosity 

values tend to decrease as median particle-size-diameter values increase, at least for samples whose median particle-size diameters fall 

within the silt-through medium-sand-size ranges.
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M9

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M10 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES 

SPECIFIC RETENTION

The six graphs of figures 6-8 show the relation between sortingcoefficient and specific-retention values of the samples from the Humboldt River valley. Although specific retention tends to decrease as 

sorting coefficient decreases for samples whose median particle-size 

diameters are in the sand-size ranges, for most samples there is no 

exact relation between these parameters.

Figure 9 shows the relation between median particle-size diameter 

and specific retention. The points on the graph tend to define an 

elongate "S" curve. Specific-retention values tend to approach an 

upper limit of about 40 percent for samples whose median particlesize diameters are in the silt-size range, and tend to approach a lower 

limit of about 8 percent for samples whose median particle-size 

diameters are in the medium- and eoarse-sand-size ranges.

SPECIFIC YIELD

Figure 10 is a histogram showing the frequency distribution of 

specific-yield values for 323 samples as determined in the laboratory. 

From the diagram one can see that the modal class of specific-yield 

values, the class of values that occur most frequently, is between 20 

and 22 percent, and that the range of specific-yield values is large.

Table 1, which is a summary of the laboratory specific-yield data, 

shows that the mean specific-yield value and median specific-yield 

value of all samples is about 21 percent. The mean and median 

specific-yield values of the various classes increase from about 19 percent for samples whose median particle-size diameters are in the 

silt-size range to a high of about 29 percent for samples whose median 

particle-size diameters are in the fine-sand-size range, and then decrease to about 19 percent for samples whose median particle-size 

diameters are in the gravel-size range. The data thus further suggest 

that, as is to be expected, there is very little direct relation between 

specific yield and median particle-size diameters alone.

Figures 11-13 show six graphs illustrating the relation between 

sorting coefficient and specific yield. If all the data were plotted on 

one graph, there would be no apparent relation between specific yield 

and median particle-size diameter. The graphs show that there is no 

apparent relationship between these parameters for samples whose 

median particle-size diameters fall within the silt- and gravel-size 

classes. However, in the intervening classes, specific-yield values 

tend to increase as sorting-coefficient values decrease.
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. Mil

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Median particle-size diameter in very fine sand-size range

10 20 30 40 50 

SPECIFIC RETENTION, IN PERCENT

FIGURE 6. Relation between sorting-coefficient and specific-retention values of 

samples from the Humboldt River valley, silt- and very fine sand-size ranges.
CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

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SPECIFIC RETENTION, IN PERCENT

FIGURE 7. Relation between sorttng-coefflcient and specific-retention values of 

samples from the Humboldt River valley, fine- and medium- sand-size ranges.
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NBV. M13

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SPECIFIC RETENTION, IN PERCENT

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Median particle-size diameter in gravel-size range

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SPECIFIC RETENTION, IN PERCENT

PIGOEB 8. Relation between sorting-coefficient and specific-retention values of 

samples from the Hamboldt River valley, coarse- and very coarse sand- and gravelsize ranges.
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MEDIAN PARTICLE-SIZE DIAMETER, IN M

FIGURE 9. Relation between median particle-size-diameter and specific-retention valu
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M15

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FIGURE 10. Histogram showing the frequency distribution of the specific-yield values of 

samples from the Humboldt Elver valley.
M16 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

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PIODRB 11. Relation between sorting-coefficient and specific-yield values of samples 

from the Humboldt River valley, silt- and very fine sand-size ranges.
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M17

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FIGDEB 12. Relation between sorting-coefficient and specific-yield values of samples 

from the Humboldt River valley, fine- and medium-sand-size ranges.
M18 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

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SPECIFIC YIELD, IN PERCENT

FIGOBB 13. Relation between sorting-coefficient and specific-yield values of samples 

from the Humboldt River valley, coarse- and very coarse sand- and gravel-size 

ranges.
TABLE 1. Summary of specific-yield values of samples from the Humboldt R

Number of samples whose median-particlesize-diameter values fall within the size

Particle-size diame

Clay

<0.004

1 

0. 5

Silt

0.004- 

0.0625

174

19. 1 

19. 1 

1. 0- 

34. 1

Sand

Very 

fine 

0.0625- 

0.125

22 

20. 2 

20. 3 

0. 3- 

39. 2

Fine 

0.125- 

0.25

33

26. 0 

29. 2 

4. 3- 

40. 9

Medium 

0.25- 

0.5

38 

28. 3 

28. 4 

7. 2- 

40. 6

Coa

0.6

2

29

10. 

3
M20 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

SUMMARY OF RELATIONS BETWEEN SPECIFIC YIELD, POROSITY, 

SPECIFIC RETENTION, SORTING COEFFICIENT, AND MEDIAN 

PARTICLE-SIZE DIAMETER

The data and graphs presented thus far show the relations, or lack 

of relations, that seem to exist between specific-yield, porosity, specificretention, sorting-coefficient, and median particle-size-diameter values 

of 323 samples from the Humboldt River valley. In summary, these 

apparent relations are:

1. For most samples, porosity values are virtually independent of 

softing-coefficient values alone.

2. Porosity values tend to increase as median particle-size-diameter 

values decrease.

3. For most samples, specific-retention values do not correlate with 

sorting-coefficient values alone.

4. Specific-retention values tend to increase as median particle-sizediameter values decrease.

5. Specific-yield values do not correlate with sorting-coefficient values 

of samples whose median particle-size-diameter values fall within 

the silt- and gravel-size ranges but tend to increase as sorting 

coefficient values decrease in the intervening ranges.

6. There is a poor correlation between specific-yield values and median 

particle-size diameter values.

Theoretically, all other factors being equal, porosity should be a 

function of the degree of assortment and should be independent of 

particle size. Thus, relations 1 and 2 seem to be contrary to theoretical 

considerations. These apparently anomalous relationships probably 

can best be explained as being related to the fact that other factors 

such as shape of the particles, compaction, cementation, and primary 

and secondary sedimentary structures are not equal.

Relation 3 is not entirely contrary to expected theoretical relationships because specific retention also is related to median particle-size 

diameter, especially in the clay- and silt-size ranges. There is very 

little literature describing the relation between specific retention and 

sorting coefficient, but it seems reasonable to assume that if all other 

factors are equal, specific-retention values should increase as the 

sorting-coefficient values increase for samples having the same median 

particle-size diameters. The poor relation between sorting coefficient 

and specific retention undoubtedly is due to the fact that all the other 

factors are not equal. This is especially true for the samples whose 

median particle-size diameters are in the silt-size range. The degree 

of compaction and secondary porosity of these samples is extremely 

variable.

Relation 5 and figures 11-13 show that specific-yield values tend to 

be independent of sorting-coefficient values alone for most of the sam-
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M21

pies. Relation 5 is a consequence of relations 1 and 3. If porosity and 

specific-retention values tend to be independent of sorting-coefficient 

values alone, then it is reasonable to assume that the difference between 

porosity and specific retention, or specific yield, also will tend to be 

independent of sorting-coefficient values alone.

Relation 6 is a consequence of relations 2 and 4. The approximate 

curves of best fit in the graphs of figures 5 and 9 have roughly about the 

same negative slope. Therefore, the difference between porosity and 

specific retention, or specific yield, tends to remain about constant for 

most of the size ranges shown in table 1; and this results in the poor 

correlation between the specific-yield values and median particle-size 

diameters of the samples.

COMPARISON OF SPECIFIC-YIELD VALUES OF THE DEPOSITS OF THE HUMBOLDT RIVER VALLEY WITH 

DATA PUBLISHED BY OTHERS

The laboratory specific-yield values of the deposits of the Humboldt 

River valley differ considerably from specific-yield values determined 

in other areas. Eckis and Gross (1934) studied the water-holding capacity of sedimentary deposits in the South Coastal Basin of the Los 

Angeles area, and the results of their study are summarized in table 2.

TABLE 2. Estimated specific yield, in percent, of sediments in the South Coastal 

Basin, southern California

[After Eckis and Gross, 1934, p. 109, table 5]

Degree of alteration

Unweathered: 

Surface alluvium. _. _ .

Subsurface alluvium___. 

Weathered subsurface alluvial: 

Tight L__ _____________

cn Q VPV 2

Residual clay 8 _ --__-_ -

Gravel

Boulders 

>256 

mm

13. 6 

13

9 

4 

1

Coarse 

64-256 

mm

14.2 

14

9 

5 

1

Medium 

16-64 

mm

20.5 

20

13

7 

1

Fine 

8-16 

mm

26.5 

25

17 

8 

1

Sand

Coarse 

1/2-8 

mm

30.9

28

1

(

Fine 

1/8-1/2 

mm

21.2 

16

>

.

Clay

Sandy

10 

5

1

Clay

1 

1

1 Lime-cemented gravels are included in tight gravels. 

s Lime-cemented sands are included in clayey sand.

3 The specific yield of 1 percent makes allowance for small sandy or gravelly streaks; pure clay would 

have a specific yield near zero.

Piper and others (1939) studied the specific yield of sedimentary 

deposits in the Mokelumne area, California. They used two methods 

to determine the specific yield of 13 and 16 samples, respectively. By 

the first method, the volumes of undisturbed samples, saturated or 

unsaturated in response to the addition or withdrawal of known volumes of water, were determined. This is a direct method of determin-
M22 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

ing specific yield and is referred to as the volumetric method. By the 

second method, referred to as the drainage method, they determined 

the difference between porosity and specific retention of undisturbed 

samples for periods of drainage ranging from 96 to 390 days. The 

results of the studies by the two methods are summarized in table 3.

TABLE 3. Average specific yield, in percent, of sediments in the Mokelumne area,

California

[From Piper and others (1939, p. 121)]

Material

Gravel and coarse sand. __ _________ _________

Medium and fine sand _____________________ _

Very fine sand, silt, and clay.. _______________

Volumetric 

method

34.5

22.6

5.0

Drainage 

method

35

26

3.5

Average

34.8

24.2

4.2

Davis, Green, Olmsted, and Brown (1959); Thomasson, Olmsted, 

and LeEoux (1960); and Olmsted and Davis (1961) estimated the 

specific yield of sedimentary deposits in parts of the San Joaquin and 

Sacramento Valleys. Their estimates, based in large part upon the 

specific-yield investigations summarized in tables 2 and 3, are shown 

in tables 4 and 5.

TABLE 4. Specific yields used to estimate ground-water storage capacity in the San

Joaquin Valley, Calif.

[From Davis, Green, Olmsted, and Brown (1959, p. 209)]

Group

G

S

F

c*

C

X

Material

Gravel; sand and gravel; and related coarse gravelly deposits. _

Sand, medium- to coarse-grained, loose, and well-sorted. _____

Fine sand; tight sand; tight gravel; and related deposits____ _

Silt; gravelly clay; sandy clay; sandstone; conglomerate; and

related deposits __ _____ _. ________ _____ _____ _____

Crystalline bedrock (fresh) __ ____________ __ ___________

Assigned

specific

yield

(percent)

25

25

10

5

3

0

TABLE 5. Specific yield used to estimate total ground-water storage capacity in the

Putah area, Calif. 

[From Thomasson, Olmsted, and LeRoux (1960, p. 286) and Olmsted and Davis (1961, p. 150)]

Material

Specific

yield

(percent)

Gravel_______________________________________________

Sand, including sand and gravel, and gravel and sand____ _________

Tight sand, hard sand, fine sand, sandstone, and related deposits____ 

Clay and gravel, gravel and clay, cemented gravel, and related deposits __ 

"Clay," silt, sandy clay, lava, and related fine-grained deposits. ______

25

20

10

5

3
SPECIFIC YIELD, HUMBOLDT RIVER VALLEY, NEV. M23

A summary of the specific-yield values of the samples from the 

Humboldt River valley is shown in table 1 (p. 19). The samples are 

arranged according to the range of their medium particle-size diameters. Admittedly, size ranges based on the median particle-size 

diameter of the samples are not precisely comparable to the textural 

classifications used by the writers cited on pages 21 and 22. 

However, the classification used by any one of these writers also is not 

precisely comparable to the classification used by any of the others. 

In spite of the somewhat different classifications, it might be expected 

that the specific-yield values should be comparable. The specific-yield 

values shown by the other writers are roughly comparable for most of 

the textural ranges; however, the specific-yield values of the samples 

from the Humboldt River valley differ markedly from those shown 

by the other writers. The most striking difference is the tendency for 

samples from the Humboldt River valley to have considerably higher 

mean specific-yield values for samples whose median particle-size diameters fall within the silt-size range.

The relatively high specific-yield values of the samples whose 

median diameters are in the silt-size range probably partly is a result 

of the relatively high porosity of this material (p. 3). In addition, 

the specific-yield values of these samples in part may be high because 

of compaction of the material in the centrifuge (Terzaghi, 1949, p. 

353). Smith (1961, p. A-ll) showed that specific-yield values obtained from centrifuge-moisture-equivalent data, especially for finegrained material, may be too high because the centrifuge tends to 

expel more water than would drain by gravity.

CONCLUSIONS

The relations between specific yield, based upon centrifuge-moisture-equivalent data, and median diameters and sorting coefficients of 

samples from the Humboldt River valley are complex. Partly because of these complexities, the specific-yield data can be used to 

obtain only a rough approximation of the total ground water avialable from storage, and they have little practical value for computing 

short-term changes of ground water in storage. Also, it seems that it 

would be extremely difficult, if not impossible, to estimate the specific 

yield of the alluvium of the Humboldt River valley by determining 

or estimating such parameters as sorting coefficient and medium 

particle-size diameter.
M24 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

REFERENCES CITED

Davis, G. H., Green, J. H., Olmsted, F. H., and Brown, D. W., 1959, Groundwater conditions and storage capacity in the San Joaquin Valley, Calif.:

U.S. Geol. Survey Water-Supply Paper 1469. 

Eckis, Rollin, and Gross, P. L. K., 1934, South Coastal Basin investigation;

geology and ground-water storage capacity of valley fill: California Div.

Water Resources Bull. 45,279 p. 

Meinzer, O. E., 1923, Outline of ground-water hydrology, with definitions: U.S.

Geol. Survey Water-Supply Paper 494. 

Olmsted, F. H., and Davis, G. H., 1961, Geologic features and ground-water

storage capacity of the Sacramento Valley, Calif.: U.S. Geol. Survey WaterSupply Paper 1497. 

Pettijohn, F. J., 1949, Sedimentary rocks: New York, Harper and Brothers,

526 p. 

Piper, A. M., Gale, H. S., Thomas, H. E., and Robinson, T. W., 1939, Geology

and ground-water hydrology of the Mokelumne area, California: U.S.

Geol. Survey Water-Supply Paper 780. 

Smith, W. O., 1961, Mechanism of gravity drainage and its relation to specific

yield: U.S. Geol. Prof. Paper 402-A. 

Terzaghi, K. V., 1949, Soil moisture, in Hydrology: New York, McGraw-Hill

Book Co., Inc., p. 331-363. 

Thomasson, H. G., Jr., Olmsted, F. H., and LeRoux, E. F., 1960, Geology, water

resources and usable ground-water storage capacity of part of Solano

County, Calif.: U.S. Geol. Survey Water-Supply Paper 1464.

O