Phreatophytes

By T. W. ROBINSON

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1423

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1958
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY

Thomas B. Nolan, Director

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

Washington 25, D. C. Price 40 cents (paper cover)
CONTENTS

Page

Abstract ................................................... 1

Introduction ................................................ 2

Acknowledgments ......................................... 2

Use of ground water by phreatophytes ..................... 3

Evidence ............................................... 3

Effect .................................................. 3

Future considerations ..................................... 7

Definitions ................................................. 9

The hydrologic cycle ........................................ 10

Plants classified as phreatophytes ............................ 12

Scientific and common names .............................. 13

Factors affecting occurrence of phreatophytes ................ 13

Climate .................................................. 14

Depth to water ........................................... 14

Quality of ground water .................................. 15

Factors affecting the use of ground water by phreatophytes...... 16

Climatic conditions ....................................... 17

Depth to water ........................................... 22

Density of growth ........................................ 22

Quality of ground water .................................. 23

Salvage of ground water .................................... 24

Status of information concerning phreatophytes .............. 26

Relation of phreatophytes to floods and sedimentation .......... 28

Phreatophytes in Western United States ...................... 30

Summary of information concerning eight common phreatophytes 49

Allenrolfea occidentalis Pickleweed ...................... 49

Chrysothamnus Rabbitbrush ............................ 53

Distichlis Saltgrass .................................... 56

Medicago Alfalfa ...................................... 59

Populus Cottonwood .................................... 61

Salix Willow .......................................... 64

Sarcobatus Greasewood ................................. 66

Tamarix Saltcedar ..................................... 70

Finding index for common names ............................. 76

References ................................................. 78

Index ...................................................... 83

ILLUSTRATIONS

FRONTISPIECE. Saltcedar growth above McMillan Reservoir on the

Pecos River, N. Mex. ............................ VI

FIGURE 1. Comparison of fluctuations of the water table in an 

area of saltcedar growth before, during, and near 

the end of the growing season.................... 4

III
IV CONTENTS

Page

FIGURE 2. Variation and depletion of streamflow resulting from

transpiration by saltcedar........................ 5

3. Effect of transpiration on streamflow in a humid

region ......................................... 7

4. Distinction between phreatophytes and xerophytes 

shown by their occurrence in relation to the water 

table ........................................... 10

5. The hydrologic cycle for an undeveloped closed basin

in an arid region ................................ 11

6. Relation of water-table fluctuations due to transpiration by saltcedar to fluctuations of relative humidity 

and temperature ................................ 17

7. Relation of evapotranspiration of saltgrass grown in 

tanks to depth to water table, and to the average 

temperature during the growing season .......... 18

8. Effect of rainfall on water-table fluctuations due to

transpiration by saltcedar ....................... 20

9. Camelthorn and saltcedar in the flood plain of the

Little Colorado River ............................ 31

10. A typical dense growth of batamote (Baccharis glutinosa) .......................................... 31

11. Vanadium bush and sweet vetch, which are guides in 

the search for uranium-vanadium ore deposits of 

the Colorado Plateau ............................ 41

12. Smoketrees (Dalea spinosa) in a gravel-filled wash

north of Needles, Calif. .......................... 42

13. Giant wildrye (Elymus condensatus) near Rye Patch

Reservoir on the Humboldt River, Nev. ........... 43

14. Blue palo verde (Cercidium floridum) growing in Centennial Wash, Ariz. ............................. 43

15. Giant reedgrass (Phragmites communis), or carrizo, 

growing in association with arrowweed, and closeup 

of the leaves and stem. .......................... 44

16. A luxuriant stand of arrowweed (Pluchea sericea) near

Blythe, Calif. ................................... 45

17. A grove of aspen (Populus tremuloides) marks a spring

and seep area near Carson City, Nev. ............ 46

18. The "devil's corn field" near Stovepipe Wells in Death 

Valley National Monument, Calif. Clumps of arrowweed in a sanddune area. ........................ 46

19. A mesquite tree growing along the Gila River. ...... 47

20. Desertrush (Juncus cooperi) in association with saltgrass (Distichlis stricta) ........................ 48

21. Fourwing saltbush (Atriplex canescens) growing in

clumps along the channel of Salt Creek ............ 48

22. Pickleweed (Allenrolfea occidentalis) associated with

saltgrass on the margin of Great Salt Lake ...... 50

23. Rabbitbrush forming the predominant growth in a

large area of low-lying land near Carson City, Nev. 54

24. Saltgrass associated with greasewood growing near

Battle Mountain, Nev. ........................... 54
CONTENTS Y

Page

FIGURE 25. Cottonwood trees planted long ago meet overhead to 

provide shade along a road east of Carson City, 

Nev. .......................................... 63

26. An unusually luxuriant and tall growth of willows

in Death Valley National Monument, Calif. ...... 65

27. A clump of greasewood growing along Highway 50

west of Grand Junction, Colo. .................. 67

28. Willows and cottonwood in Carson Valley, Nev. .... 67

29. This handsome specimen of the athel tree (Tamarix

aphylla) is about 40 feet high .................. 71

30. A dense growth of saltcedar (Tamarix gallica) along

the dry (April 1954) bed of the Gila River ...... 72

31. An illustration of saltcedar encroachment along a

stream channel ................................ 73

32. Saltcedar along the banks of the Little Colorado River

near Holbrook, Ariz. ........................... 73

TABLES

TABLE 1. Phreatophytes in Western United States ............ 32

2. Annual or seasonal evapotranspiration of water by

saltgrass grown in tanks ........................ 58
FRONTISPIECE. Saltcedar growth on the delta above McMillan Reservoir on the Pecos River, N. Mex. Downstream view of part 

of a 10,000-acre infestation. Photograph courtesy Peeos River Commission
PHREATOPHYTES

By T. W. ROBINSON

ABSTRACT

Phreatophytes are plants that depend for their water supply upon ground 

water that lies within reach of their roots. Although not confined to the 

arid regions of the Western United States, their occurrence there is more 

common, more spectacular, and, because of their effect on water supply, 

more important than it is in humid and subhumid regions. Most phreatophytes have low economic value, and consequently, the water they use and 

return to the atmosphere without substantial benefit to man is defined as 

consumptive waste.

Some phreatophytes are widespread throughout the entire West, and 

others, such as saltcedar, are confined to the river valleys of the Southwest. 

In all, they waste tremendous quantities of ground water each year. It is 

estimated that phreatophytes (excluding beneficial species such as alfalfa) 

cover about 16 million acres in the 17 Western States and discharge as much 

as 25 million acre-feet of water into the atmosphere annually. Although 

little has been done so far to prevent this waste, much of the water undoubtedly can be salvaged by converting consumptive waste to consumptive use. 

There are two basic methods: reducing of consumptive waste by diverting 

water from the plants to other uses, and increasing the efficiency of water 

use by substituting beneficial for nonbeneficial plant species. These methods, 

to be successful, require an understanding of the factors that affect the 

occurrence and amount of water used by phreatophytes: climate, depth to, 

and quality of ground water and soil.

More than seventy plant species have been classified as phreatophytes; 

this report lists information concerning them according to their scientific 

names. The available information about the phreatophytic characteristics 

of most of the species is meager, but for eight, pickleweed, rabbitbrush, saltgrass, alfalfa, cottonwood, willow, greasewood, and saltcedar, there are 

sufficient data to warrant separate discussions. The annual use of water by 

phreatophytes ranges from a few tenths of an acre-foot per acre to more 

than 7 acre-feet per acre.

In the Southwest, saltcedar, an exotic plant that develops a junglelike 

growth, has invaded and choked the normal overflow channels of streams, so 

as to produce a flood hazard that must be reckoned with. In addition, the 

ponding effect of the dense growth results in above-normal sediment deposition in the area of growth, and reduced deposition downstream, as was 

observed at the McMillan Reservoir on the Pecos River in New Mexico.

In the interest of conserving water to meet an ever-growing demand and 

to reduce flood hazards in the Southwest, more and more attention must 

be given to the phreatophyte problem.

1
2 PHREATOPHYTES

INTRODUCTION

Since 1927, when 0. E. Meinzer's paper "Plants as indicators 

of ground water" was published as Geological Survey WaterSupply Paper 577, many reports and papers relating entirely or 

in part to phreatophytes have been released in various forms by 

the Geological Survey and other agencies. As more data on these 

plants have become available, a need has developed for a supplement to Meinzer's original list and description of the plants. The 

need was recognized by the Phreaitophyte Subcommittee of the 

Pacific Southwest Federal Inter-Agency Technical Committee, 

which proposed the preparation of such a paper. This paper is 

an attempt to fulfill that need by assembling and discussing the 

information that is available on phreatophytes. It includes a list 

of all plants in the desert areas of the Western United States that 

have been identified as phreatophytes or which there is good 

reason to class as phreatophytes, together with the available data 

concerning their occurrence, habits, and annual consumption of 

ground water. The information was obtained by a comprehensive 

review of the literature, by consultation with fellow workers, and 

by field study and observation.

Nearly all the available information and data on phreatophytes 

are the result of studies and observations that have been made 

on these plants in the arid areas of the western United States. 

The reason is twofold; first, it was in the desert areas of the West 

that Meinzer first observed the plants that he defined and classified as phreatophytes; second, the West by and large is a waterpoor region, and attention naturally is focused on water problems 

including the role of phreatophytes as they affect the water 

supply. Water-supply problems have increased particularly since 

World War II, partly because of the increased demand for water, 

partly because of a decrease in supply as the result of a prolonged drought in the Southwest, and partly because of the spread 

of one species, saltcedar, a heavy water user, through the stream 

valleys of the Southwest. (See frontispiece.) It has become increasingly common, when referring to factors affecting water 

supply, to include the "phreatophyte problem". In fact, it was 

pointed out by Douglas (1954, p. 8-12) that the word "phreatophyte" is becoming a term that the laymen find convenient for 

designating a group of destructive enemies that formerly were 

regarded merely as nuisances.

ACKNOWLEDGMENTS

The author is grateful to many in the fields of hydrology and 

botany, including the members of the Phreatophyte Subcommittee
INTRODUCTION 3

of the Pacific Southwest Federal Inter-Agency Technical Committee, and its successor, the Pacific Southwest Inter-Agency Committee, for their helpful criticisms, suggestion's, and contributions. 

He is particularly indebted to two former colleagues in the Geological Survey, Walter N. White and Samuel F. Turner. Mr. 

White, who did pioneer work in determining the use of ground 

water by phreatophytes, reviewed the manuscript and made many 

valuable comments and criticisms. Mr. Turner, as the first chairman of the Phreatophyte Subcommittee, was instrumental in 

focusing attention on the phreatophyte problem in the Southwest 

and in preserving data concerning phreatophytes in the minutes 

of the subcommittee. He was one of the first to study the problem 

of saltcedars and to obtain data on their use of ground water. 

His draft of a list of plants that occur as phreatophytes or as 

hydrophytes formed the nucleus for the list of phreatophytes 

given in table 1. The author takes this opportunity to express 

his sincere thanks to these men and also to his associates for the 

data, information, and assistance they so generously contributed.

USE OF GROUND WATER BY PHYREATOPHYTES

EVIDENCE

Evidence that phreatophytes utilize ground water is provided 

by diurnal fluctuations of the water level in shallow wells that 

penetrate below the water table in areas of growth. The water 

level declines during the day when transpiration is greatest and 

rises during the night when transpiration is least, the rise or 

decline beginning at almost the same hour each day. That the 

daily decline of the water table was due to the withdrawal of 

ground water from the zone of saturation by phreatophytes was 

demonstrated by G. E. P. Smith through a series of observations 

in wells located in phreatophyte areas. Although the observations 

began in 1916, Smith first described the phenomenon in 1922 

(White, 1932, p. 4) in an unpublished paper given before the 

Geological Society of Washington on November 22.

The depletion of the flow of streams that pass through areas 

of phreatophytes is further evidence of the use of ground water 

by phreatophytes.

EFFECT

The effect on the water table of transpiration by saltcedar in 

the Safford Valley, Ariz., is clearly shown in figure 1. In March, 

before the saltcedar begins to grow, there is little fluctuation of 

the water table, but 3 months later, when the growing season is 

well under way, the daily fluctuations are regular and large. The
4 PHREATOPHYTES

lowering on June 9, 1944, for instance, was 0.19 foot. In late 

October, when the growing season draws to a close, the daily 

fluctuations gradually diminish in amplitude, and finally they disappear altogether.

g 7.4 

1

25

FIGURE 1. Comparison of fluctuations of the water table as shown in well T-6 in an area 

of saltcedar growth before, during, and near the end of the growing season in 

the Safford Valley, Ariz.

During the growing season transpiration also affects the flow 

of streams that pass through areas of phreatophyte growth, for 

the plants transpire large quantitues of water, a part of which, 

if not thus consumed, would reach the streams (White, 1932, p.
INTRODUCTION 5

95-96). An example is provided by the record of flow of the Gila 

River near Geronimo in the Safford Valley, Ariz., as shown in 

figure 2. The period selected, June 6-13, 1944, is the same as for 

well T-6, shown in figure 1. Well T-6 is about one-eighth of a 

mile south of the river channel, and the gaging station near Geronimo, where the river was measured, is about 20 miles downstream from the well. The flood plain in this reach of the stream, 

as well as above and below, is thickly covered with saltcedar. A 

comparison of the river and well records shows that the diurnal 

fluctuations in the river are quite similar to those in the well. 

The transpiration discharge by the saltcedar resulted not only in 

a marked variation in the daily flow of the stream, but also in a 

depletion of the streamflow. This depletion was estimated by assuming that the maximum observed rate of discharge is the same 

as the daily mean rate of discharge under conditions of no depletion. That is to say, if there were no transpiration loss, then the 

curve obtained by connecting the points of maximum discharge 

would approximate the probable flow of the stream. Actually, as 

suggested by Troxell (1936) and demonstrated by Dunford and 

Fletcher (1947), this method gives results that are too low because it shows only a part of the loss. The drain on the groundwater reservoir adjacent to the stream, lowers the ground-water 

level below the stage at which it would normally stand if there 

were no transpiration discharge. Because of the lower groundwater level, the stream picks up less water (or loses more water) 

in a given stretch than it would if the water table were higher;

MAXIMUM 6.0

MINIMUM 4.7

MEAN 5.4

6.1

5.0

5.4

59

4,6

5.2

5.4

4.3

4.7

5.2

3.9

4.5

4.7

3.8

4.3

4.7

3.8

4.3

4.5

3.7

4.0

RATE OF DISCHARGE, IN CUBIC FEET PER SECOND

TRANSPIRATION 1.2 1.4 1.4 1.4 1.4 0.8 0.8 1.0

LOSS THROUGH TRANSPIRATION, IN ACRE-FEET PER DAY COMPUTED AS DIFFERENCE 

BETWEEN MAXIMUM AND DAILY MEAN RATES OF DISCHARGE

FIGURE 2. Variation and depletion of streamflow resulting from transpiration by saJtcedar, 

as shown in stage of the Gila River near Geronimo in the Safford Valley, Ariz.
6 PHREATOPHYTES

thus, even the high points on the stream graph indicate a flow 

less than would occur if transpiration had not lowered the water 

table.

The Green River in its 437-mile course through Colorado and 

Utah passes through several valleys where the stream is bordered 

by a total of 40,000 acres of flood plain, much of which is covered with phreatophytes. The average daily depletion in flow for 

a 21-day period in September 1948, resulting from evapotranspiration on the flood plain area (transpiration by plants and evaporation from the soil) was, according to Thomas (1952, p. 28), 552.4 

acre-feet, or 278 cfs. In the 320-mile reach from Linwood, near 

the Wyoming border, to Greenriver gaging station evapotranspiration losses accounted for 20 percent reduction in flow past 

the Greenriver gage and a 32 percent reduction in pickup between the two stations.

At the Ouray, Utah, gaging station near the center of the Uinta 

Basin, where the Green River is bordered by broad flood plains 

covered with dense vegetation, diurnal fluctuation in stage was 

clearly shown. Thomas (1952, p. 18-20) computed the reduction 

in flow on the basis of the differences between the actual stage 

and a line connecting the points of successive daily maxima, and 

found it to be about 18 cfs. Similar computation at the Linwood, 

Utah, gaging station upstream from Ouray, where the river is 

lined with phreatophytes, indicated a reduction in flow of about 

12 cfs.

Phreatophytes occur in the humid Eastern States also, but by 

1956 they had not received much attention as such. In those States 

the line between phreatophytic and nonphreatophytic vegetation 

is not so sharp, nor is the phreatophyte problem so spectacular 

or acute as it is in the arid Western States. Nevertheless, the 

effect on ground water and streamflow is much the same as in 

the arid States, though proportionately less serious, because of 

the greater rainfall. Ferris (in Wisler and Brater, 1949) described a record from a shallow well near Roscommon, Mich., 

which shows diurnal fluctuations that are the result of transpiration. 

At the Bigwoods Experimental Forest in North Carolina, Trousdell 

and Hoover (1955) found that the water level in shallow observation wells located in uncut stands of loblolly pine declined during 

the growing season and rose during the nongrowing season. Even 

more significant was the reversal of the downward trend of the 

water level that followed cutting of the timber in the 200-foot strip 

in which one well was located. The water level had declined about 

9.5 feet from the beginning of the growing season in early May
INTRODUCTION 7

until the timber was cut on July 21. After cutting, the downward 

trend halted, and by the end of August, during which 5.66 inches 

of rain fell, the water level had risen 8.8 feet. During this same 

period the water level in a well in the uncut stand of timber nearby 

rose only 0.4 foot. It was found also from a profile of the ground 

water across the cleancut and uncut strips that the water level was 

highest in the cleancut strip, lower at the stand edges, and lowest 

within the stands.

The effect on streamflow in the humid States was demonstrated 

by experiments in the Coweeta Experimental Forest in the Appalachian Mountains of western North Carolina (Dunford and 

Fletcher, 1947). The effect of transpiration on streamflow in 

Maryland is illustrated in figure 3, by the hydrograph of the North 

River near Annapolis. With the exception that the peaks and 

troughs occur from 2 to 3 hours later, the diurnal fluctuations are 

similar to those for the Gila River shown in figure 2. The lag is 

believed due to differences in the time of the daily variations of 

temperature and humidity that directly affect the rate of transpiration (fig. 6).

MAXIMUM

MINIMUM

MEAN

3.28

2.65

3.01

3.28

2.81

3.01

3.35

2.74

3.05

3.28

2.74

2.99

RATE OF DISCHARGE, IN CUBIC FEET PER SECOND

TRANSPIRATION 0.53 0.53 0.60 0(58

LOSS THROUGH TRANSPIRATION, IN ACRE-FEET PER DAY COMPUTED AS DIFFERENCE 

BETWEEN MAXIMUM AND DAILY MEAN RATES OF DISCHARGE

FIGURE 3. Effect of transpiration on streamflow in a humid region as shown in stage of 

the North River near Annapolis, Md.

FUTURE CONSIDERATIONS

With the increasing demand for water, it seems certain that 

more and more attention will be given to a study of transpira-
8 PHREATOPHYTES

tion by both phreatophytic and nonphreatophytic plants in the 

Eastern States, and its effect on water supply. In the humid and 

subhumid regions, the distinction between these two groups of 

plants is not so sharp as in the arid regions, and under certain 

conditions it is difficult to determine whether a plant obtains its 

water supply from soil moisture or from ground water. The 

nonphreatophytic plants indirectly affect the water supply of a, 

region by utilizing water in the soil column that might otherwise 

reach the water table as recharge. Phreatophytic plants, on the 

other hand, directly affect the available water supply by drawing 

from the ground-water reservoir as described earlier, thus reducing 

ground-water storage and related streamflow.

In the Pontiac area of Michigan, for example, planners are 

considering the practicability of salvaging a part of the evapotranspirative discharge. The annual precipitation in this 9-township area is about 30 inches a year, or 450,000,000 gallons per 

day (gpd). Of this amount, about one-third leaves the area as 

streamflow. The remaining 300,000,000 gpd, including 50,000,000 

gpd used by man, is discharged by evapotranspiration. An indeterminate but probably substantial part of this is discharged 

from ground-water reservoirs; the rest is discharged from the 

soil before it has a chance to descend to the water table (Robinson, 

1954).

As explained by Meinzer (1927, p. 82-88), information on the 

occurrence and habits of phreatophytes and their annnal consumption of ground water is a basic requisite in dealing with 

water-supply problems in any area where these plants grow on 

a substantial scale, particularly in the arid regions of the Western 

United States. In many parts of the regions where phreatophytes 

are important, man's increasing demand for water already has 

exceeded, or soon will exceed, the available supply. The supply 

can be made more nearly adequate by reducing consumptive waste 

by phreatophytes, insofar as to do so is practical.

The water consumed by phreatophytes is largely wasted, for 

most of the plants have a low or negligible economic value. As 

some of the plants have a high annual water consumption and 

occupy extensive areas, the amount of water they consume in a 

given locality may be large. Although the water consumed by 

phreatophytes is available for salvage, it may not be economically 

feasible to salvage all the water. In any program involving salvage, however, it is essential to have as much information as 

possible concerning the occurrence and water requirements of the 

plants in the area under consideration.
DEFINITIONS 9

DEFINITIONS

In desert regions in general the flora are sharply divided into 

two classes depending upon their relationship to the water tables. 

Such a distinction, although it exists, is less noticeable in regions 

of greater precipitation, and it may be lost sight of entirely in 

humid regons. The close association of certain species of desert 

plants with the water table and the lack of such association in 

others have been known for many years. The distinction was 

early recognized by 0. E. Meinzer in his work in desert areas, 

beginning about 1910. Later he gave the name " phreatophytes" 

to the plants using ground water. The term appeared first in a 

preliminary mimeographed release of his report entitled "Outline of ground-water hydrology, with definitions," which was 

issued in revised form as U. S. Geological Survey Water-Supply 

Paper 494 in 1923. He defined a phreatophyte as "a plant that 

habitually obtains its water supply from the zone of saturation, 

either directly or through the capillary fringe." The word is derived from two Greek roots, "phreatos" (a well) and "phyte" 

(a combining form denoting a plant having a particular characteristic or habitat), and thus means "well plant." The name is 

apt, for the plants grow where they can send their roots down 

to the water table, or to the capillary fringe immediately overlying the water table, from which the plant pumps its supply of 

water, as illustrated in figure 4. In his introduction to WaterSupply Paper 577, Meinzer (p. 1) compares the phreatophytes, 

with their perennial and secure supply of ground water, with the 

xerophytes, which occur in desert areas where the water table is 

out of reach and the vegetation is forced to depend upon the rains 

for a scanty and extremely irregular water supply. The occurrence of phreatophytes and xerophytes in relation to the water 

table is shown by figure 4. The name "xerophyte," Meinzer explained, also was derived from Greek roots; it means "dry plant.''

In a footnote at the bottom of page 1 of his introduction to 

Water-Supply Paper 577, Meinzer says:

The principal ecologic groups of plants that have been recognized by 

botanists are hydrophytes, which grow in water or at least with their roots 

in water; the halophytes, which can endure large amounts of salt or alkali 

in the soil water on which they live; the xerophytes, which are able to survive on very small and irregular supplies of water; and the mesophytes, 

which are not adapted to endure any of these exti ernes. In proposing the 

name phreatophyte, the writer did not imply that this group should find a 

separate place in the old classification, but rather believed that it would 

overlap some of the other groups. The term "halophyte" has been used for 

marsh plants which are more or less intermediate between hydrophytes and
10 PHREATOPHYTES

FIGURE 4. Distinction between phreatophytes (A) and xerophytes (B) shown by their 

occurrence in relation to the water table.

mesophytes, but this term could not be used to designate the phreatophytes, 

without violating its past usage and introducing much confusion.

By definition a phreatophyte gets its water from the water 

table, and it does under natural conditions. It should be noted, 

however, that phreatophytes will grow and thrive if water is supplied artificially. Thus phreatophytes may be observed growing 

along ditches and canals and in irrigated fields, in areas where 

their roots do not reach the water table but tap irrigation or 

drainage water. One phreatophyte, alfalfa, an important agricultural plant, is grown extensively by irrigation without regard 

to the depth to the water table, and there is little doubt that 

other phreatophytes could be grown in a similar way if it were 

desirable.

THE HYDROLOGIC CYCLE

The roles that the two principal classes of plants, phreatophytes 

and xerophytes, play in the hydrology of arid regions can be
THE HYDROLOGIC CYCLE 11

WATER PRECIPITATED FROM ATMOSPHERIC VAPOR

1

||SNOW AND ICE "X|

Ove and

1 

Interce 

brush a

Dtion by 

nd trees

Eva

WATER VAPOR RETURNED TO ATMOSPHERE

L_J__l__f__t__t___r__L__1__L

FIGURE 6. The hydrologic cycle in an undeveloped closed basin in an arid region. (Shaded 

areas represent water in storage; solid lines, movement as liquid; broken lines, 

vapor.)

readily understood through consideration of the hydrologic cycle. 

Figure 5 depicts a simple hydrologic cycle for an undeveloped 

closed basin in an arid region. Among other things, the diagram 

illustrates: (1) the distnction between the soil water for xerophytes and ground water for phreatophytes; (2) the relative 

positions of the soil-water and ground-water reservoirs in the 

cycle; and (3) the paths of the movement of water to and from 

them.

The water in the soil-water reservoir is not directly available 

to man, for he cannot extract it from the soil in usuable form. It 

may be available to him indirectly in the products of plant life; 

as such, however, it does not quench thirst or supply his other 

everyday needs. Soil water that is excess to the capacity of the 

soil reservoir eventually becomes available to man by downward 

percolation as recharge to the ground-water reservoir. In arid 

regions the excess is generally quite small. Xerophytes, by their draft 

on soil water during the growing season, reduce the amount of 

excess that would otherwise percolate to the water table, and so 

indirectly reduce the amount available to man.

Water in the ground-water reservoir is directly available to 

man through spring discharge and seepage to streams, or it may
12 PHREATOPHYTES

be withdrawn by means of wells, tunnels, or ditches. In some 

localities it is the only available water. This water also is available to phreatophytes which, through their draft on ground water, 

deplete the ground-water reservoir and correspondingly reduce 

the amount of water available to man. The transpirative draft 

by phreatophytes is represented in the diagram as part of consumptive waste. The effect of phreatophytes on the hydrology of 

arid regions becomes apparent when it is realized that most 

phreatophytes have a low economic value, are heavy users of 

water, and occur for the most part on the floors of valleys and 

the flood plains of streams, where ground water is readily available and where it can be utilized most effectively. Unlike the 

soil water transpired by xerophytes, the ground water consumptively wasted by phreatophytes is available for recovery and use 

(p. 25). Man, by reducing the consumptive waste in the area of 

discharge, may salvage for his use an amount of water equal 

to the reduction in waste.

P:LANTS CLASSIFIED AS PHREATOPHYTES

Meinzer (1927) lists the common names of about 50 phreatophytes of the desert regions of the country, together with the 

scientific names of the species to which most of them belong. 

This paper lists, in table 1 and in the discussion that follows, the 

scientific names of 74 species or subspecies and about 100 common names that are applied to plants that are known to occur 

as phreatophytes or which there is good evidence to class as 

phreatophytes. The list is composed of perennial plants that grow 

in the arid and semiarid regions of the Western United States. 

No attempt was made to include plants of the Eastern United 

States or of foreign countries, except as they may occur as phreatophytes in the Western United States also.

The list in table 1 represents our present-day knowledge of 

phreatophytes, but as the plants listed by Meinzer (1927) have 

been added to in this paper, so the list here may well be expanded 

by future work. Additions may come from the group of grass 

and grasslike plants, for the source of water used by some of the 

plants in this group is not certain. Additions may come also from 

exotic plants, as was the case with saltcedar (Tamarix gallica), 

which up to 1927 apparently had not been recognized as a phreatophyte. This plant, imported from the Mediterranean region of 

western Europe, was not mentioned by Meinzer in 1927, although 

today it is widespread and presents a serious problem in the 

river valleys of the Southwest.
FACTORS AFFECTING OCCURRENCE 13

The plants have been listed in table 1 as phreatophytes on the 

basis of observation and field work over a period of years by the 

author in the Western United States. The list was supplemented 

by examination of the literature on the subject and by suggestions from workers in the fields of botany and hydrology.

The phreatophytes given in table 1 are listed alphabetically 

by scientific name. Phreatophytes do not belong to any one family 

of plants, but consist of many species belonging to different plant 

families. As a group they do not have much similarity in occurrence, water use, environment, or habits. Their only common 

characteristic under natural conditions is their typical dependence 

on ground water.

SCIENTIFIC AND COMMON NAMES

In dealing with phreatophytes, as with any other group of 

plants, the problem of names is always a vexing one. Scientific 

names are necessary in order to be exact, and common names are 

desirable in order to be understood by the layman. For the sake 

of exactness and clarity, the scientific name and the common 

name, when it is known, are given in table 1. A scientific name 

applies to one species of plant and to no other. Unfortunately, 

this is not true of common names. However, the use of common 

names is widespread, and more people are familiar with them 

than with scientific names. In fact, to those who do not have a 

working knowledge of botany, scientific names mean little. Generally, too, common names are descriptive of the plant to which 

they apply.

The common names used in this paper are those that have been 

established through use and are generally accepted, although a 

common name may refer to several species, or more than one 

common name may be applied to the same species. Where more 

than one common name is given, the first is the most generally 

accepted. Others listed are not so generally used, or perhaps are 

used only locally. For the convenience of the reader, a finding 

index of the common names, as used in this paper, is provided 

on page 76. The index gives the scientific name to which the 

common name refers.

FACTORS AFFECTING OCCURRENCE 

OF PHREATOPHYTES

Some phreatophytes are widespread; others are restricted to 

certain regions or may occur only in small areas. Not all the 

reasons for the differences in distribution are known, but, on 

the basis of field observations, there appear to be three important
14 PHREATOPHYTES

factors that exert a controlling influence on the occurrence and 

growth of phreatophytes. They are: climate, depth to the water 

table (or capillary fringe), and quality of the ground water. The 

character of the soil may be a fourth important factor in some 

localities.

CLIMATE

Climatic factors, particularly temperature, effectively control 

the occurrence of some species, whereas others are relatively unaffected by them. Some phreatophytes, such as saltcedar (Tamarix 

gallica), mesquite (Prosopis), and baccharis (Baccharis) , thrive 

best in a warm climate; others, such as greasewood (Sarcobatiis 

vermicukitus), prefer the cold desert areas. In general, saltcedar, 

mesquite, and baccharis thrive best south of the 37th parallel 

and below an altitude of about 5,000 feet; greasewood is seldom 

found south of the 37th parallel except at high altitudes. Willow 

(Salix), cottonwood (Populus), and saltgrass (Distichlis stricta), 

on the other hand, have a wide range of climatic tolerance. They 

grow from Canada to Mexico and at altitudes ranging from sea 

level to about 8,000 feet.

The effect of climate on saltcedar is striking when the growth 

and occurrence of the plant in Arizona or New Mexico is compared with that in northern Nevada. Saltcedar plants several 

years old, growing on the shores of Walker and Pyramid Lakes 

in the Carson Sink, and in the vicinity of Carson City and Fallon, 

Nev., (latitude 39° N. and altitude a little above 4,000 feet), are 

not so aggressive nor do they exhibit the vigorous junglelike 

growth that is so typical of the plant in the warm river valleys 

of southern Arizona and New Mexico.

DEPTH TO WATER

As the root systems of some phreatophytes are capable of penetrating to a depth of several tens of feet, whereas those of others 

are relatvely shallow, the depth to water is a controlling factor in 

their occurrence. For example, desert saltgrass (Distichlis stricta) 

generally grows where the depth to the water table is less than 

8 feet, although it has been observed growing where the depth 

was as much as 12 feet (Blaney, Taylor, Nickle, and Young, 

1933, p. 50). Alfalfa (Medicago sativa), however, is a deeprooted plant whose roots have been traced to a depth of 66 feet, 

and observed at a depth of 129 feet below the land surface 

(Meinzer, 1927, p. 55). Mesquite and saltcedar also are deep 

rooted. Plants capable of developing a deep-root system may grow 

also where the water table is close to the surface. Typically shal-
FACTORS AFFECTING OCCURRENCE 15

low-rooted plants, however, occur only in areas where the water 

table is close to the surface.

Extensive studies have been made of the root systems of many 

cultivated plants, but relatively little is known about the root 

systems of phreatophytes. A general idea as to depth of root 

penetration may be inferred from the depth to the water table 

in the area where the plant is growing. However, this information may not always be reliable, for it is possible that, where 

the water table lies at great depth below the land surface, plants 

having a deep and extensive root system may obtain their needed 

water supply from moisture present in the huge volume of soil 

and subsoil enveloped by the root system. It is thought that in 

some localities mesquite with its deep root system may be growing under such conditions. On the other hand, the relation between the occurrence of cottonwood, greasewood, saltgrass, and 

willow, and the depth to ground water is quite sensitive, and the 

boundary between areas of growth and of no growth is generally sharp and distinct. An example of this condition occurs in 

Paradise Valley and Meadow Valley Wash in Nevada (Loeltz, 

Phoenix, and Robinson, 1949, p. 40 and pi. I; Phoenix, Hardeman, Fox, and Miller, 1948, pi. 2).

QUALITY OF GROUND WATER

The quality of the ground water is a third controlling factor 

in the occurrence of phreatophytes. Some phreatophytes grow 

only where the dissolved solids content of the water is low, others 

will grow only where it is high, and still others have a wide 

range of salt tolerance. These last may grow where the salt content of the ground water is very low but are more commonly 

observed growing in areas where it is moderate to high. This 

apparent preference may be due entirely to the degree of competition offered by other plants.

Willow and cottonwood are good examples of phreatophytes 

that have a low salt tolerance. Generally, these plants occur in 

headwater areas, along stream banks, and on the flood plains of 

rivers (see fig. 28). Greasewood and saltcedar are examples of 

plants having a wide range of salt tolerance. These plants may 

be found associated with plants having a low salt tolerance but 

more frequently they occur where the ground water has a moderate to high salt content. They are also examples of plants that 

have a high tolerance for certain mineral constituents in the 

ground water. Greasewood, for example, grows well in areas 

where the ground water is high in sodium carbonate, which forms 

the so-called black alkali. In such areas, other phreatophytes gen-
16 PHREATOPHYTES

erally are not present or occur only sparsely. Saltcedar and saltgrass grow well where the ground water is high in common salt 

(sodium chloride).

Greasewood is widespread in the Great Basin. It commonly 

occupies the lower parts of desert valleys and is nearly always 

present in the vegetation surrounding playas. Saltcedar grows 

in profusion on the flood plains in the lower reaches of rivers in 

the Southwest. Relatively few phreatophytes grow only in areas 

where the ground water is highly saline. Perhaps the best example of a phreatophyte having a high salt tolerance is pickleweed (Allenrolfia occidentalis). This plant (fig. 22) is common 

in the Great Basin, where it fringes barren playas of very alkaline 

or saline soil.

In table 1, the salt tolerance of the various phreatophytes is 

indicated in a general way by a numeral, 1, 2, or 3, denoting a 

qualitative classfication of the type of the ground water used by 

the plant. This classification is based on the correlation of chemical analyses of water from shallow wells and test holes in areas 

occupied by different types of phreatophytes with observations 

of the soil and occurrence and associations of vegetation in the 

field. The water classes referred to by the numerals are those 

used by Magistad and Christiansen (1944, p. 9) in classification 

of standards for irrigation water, namely: (1) excellent to good, 

suitable for most plants under most conditions; (2) good to injurious, probably harmful to the most sensitive crops; (3) injurious to unsatisfactory, probably harmful to most crops, and 

unsatisfactory for all but the most tolerant. The classification is 

not intended to apply to water used for domestic and industrial 

purposes.

FACTORS AFFECTING THE USE OF GROUND WATER 

BY PHREATOPHYTES

As described earlier, an individual phreatophytic plant may 

be considered a pumping plant that obtains its supply of water 

from the zone of saturation. Depending on the species and density of growth, there may be literally thousands of such pumping plants on an acre of land. Throughout the growing season 

these plants transpire ground water into the atmosphere. The 

amount transpired varies with the species. Some species use large 

amounts of ground water, whereas others use relatively small 

amounts. The annual use for any given species varies with climatic conditions, depth to water, density of growth, quality of the 

ground water, and other factors dictated by local conditions.
USE OF GROUND WATER BY PHREATOPHYTES 17

CLIMATIC CONDITIONS

Most of the elements of climate affect the use of ground water 

by phreatophytes. Sunlight is, of course, necessary in the process 

of photosynthesis, essential for plant growth. In addition to sunlight, the elements of temperature, humidity, wind movement, 

rainfall, length of growing season, daytime hours (which are a 

measure of sunlight), and altitude influence the use of ground 

water.

The element that exerts the greatest effect is temperature. 

It not only controls the length of the growing season, but also 

the rate of water use during the growing season. For example, 

it was found in the lower Safford Valley, Ariz. (Gatewood and 

others, 1950, p. 115) that transpiration by saltcedar practically 

ceased in the fall when the monthly mean of daily maximum air 

temperature became less than 73 °F and began again in the spring 

when the mean rose above 73°. Use of water by the saltcedar 

paralleled closely the seasonal changes in temperature, increasing as the maximum air temperature increased, and decreasing 

as the maximum air temperature decreased. As shown in figure

WATER LEVEL IN WELL T-6

r\ r\

TEMPERATURE AT GLENBAR EXPERIMENT STATION

FIGURE 6. Relation of water-table fluctuations due to transpiration by saltcedar to fluctuation 

of relative humidity and temperature, in the Safford Valley, Ariz. The groundwater level falls as transpiration increases and rises as it decreases. (After 

Gatewood and others, 1950, fig. 41.)
EXPLAN

123 

EVAPOTRANSPIRATION DURING GROWING PERIOD, IN FEET

AVERAGE TEMPERATURE DURING THEGROWING SEASON, 

IN DEGREES FAHRENHEIT

OI 2! (Tl >4

S

01 o

Evapotranspiration at 

water-table depths 

of 3 ft, 2 ft, and 1 ft 

A A

/

/ *7

ff:

// / 

/ s

/^

*7

h

/

324

EVAPOTRANSPI RATION 

DURING GROWING P

LOCATION AND PERIOD 

Owens Valley, Calif........April to October 1911

Santa Ana, Calif........... May to April 1929-30, 1931-32

Escalante Valley, Utah... .May to October 1926-27

Los Griegos, N. Me*..... . .March to October 1926-27, 1927-28

San Luis Valley, Colo..... .April to October 1928, 1931

Carlsbad, N. Mex. ........ March to October 1940

Mesilla Dam, N. Mex...... March to October 1936-37

Isleta, N. Mex............ .March to October 1936-37

FIGURE 7. Relation of evapotranspiration of saltgrass grown in tanks to depth to water table and to the av
USE OF GROUND WATER BY PHREATOPHYTES 19

6, it also paralleled the daily changes in temperature in much the 

same manner.

The effect of temperature on the seasonal use of water by 

saltgrass is shown on the right-hand side of figure 7. This illustration, 

based on experimental data at five locations in the western United 

States where the average temperature during the growing season 

ranged from 54° F in the San Luis Valley, Colo. to 70° F at Carlsbad, 

N. Mex., shows a rapid increase in use with temperature.

The three curves show that for this 16° F rise in temperature 

there was about a 100 percent increase in use. In other words, the 

water requirement for saltgrass at 70° F is about twice that at 54° F.

It seems logical to assume that this general relation of increased 

use of water to increase in temperature holds true for all phreatophytes. The temperature at which appreciable transpiration begins 

and ceases probably varies with the species, and the ratio for the 

increase in use with temperature also may not be the same for all 

species.

The effect of humidity on the use of ground water is in reverse 

order to that of temperature. The rate of use decreases as the relative 

humidity increases, and increases as the relative humidity decreases 

(fig. 6). Thus, other things being equal, the rate of use by a 

species may be expected to be greater in arid regions than in semiarid or humid regions. A low relative humidity combined with a 

high air temperature is conducive to a high rate of transpiration and, 

hence, a high rate of use of ground water. As this combination is 

usually found only in arid regions, it explains the higher rates of 

ground-water use observed for phreatophytes growing in desert areas.

Wind movement is effective in increasing water use by keeping the 

relative humidity low next to the plant leaves. This is accomplished 

largely by a replacement of the air made humid by transpiration with 

drier air from the adjacent desert areas. As a rule, in the Western 

States, phreatophyte areas are surrounded by desert areas having 

air of very low humidity.

The effect of rainfall in the growing season is to reduce the use of 

ground water by phreatophytes. This effect was observed in tank 

experiments with saltcedar in the Safford Valley, Ariz., and also 

with alfalfa (White, 1932, p. 48-52, figs. 20-22) in the Escalante 

Valley, Utah. In discussing the effect of rainfall White makes the 

following statement:

It was found that rains at this [the growing] season have little or no 

effect on the water table in plowed fields, in cleared lands, or in fields of 

sagebrush, but usually are followed by an almost immediate rise of the water 

table in saltgrass and marshgrass meadows, in willow thickets, and in fields 

of alfalfa, greasewood, and rabbitbrush.
CHARACTER OF DAY 

Partly cloudy Partly cloudy

TEMPERATURE RANGE, IN DEGREES1 FAHRENHEIT 

105-67 105-70 105-68

WIND MOVEMENTJN MILES PER DAY

EVAPORATION FROM STANDARD WEATHER BUREAU PAN, IN INCHES 

0.304 0.442 I 0.317 0.456

RELATIVE HUMldlTY, IN PERCENT 

44 I 40

n, 0.26 inch\ /--Rain, 0.66 inch

6.6

19 ' 20 

JULY 1944

FIGURE 8. Effect of rainfall on water-table fluctuations due to transpiration by saltcedar. Meteorological dat

distant.
USE OF GROUND WATER BY PHREATOPHYTES 21

In the Safford Valley experiments, it was observed that after light 

to moderate rains which penetrated the soil only a few inches and 

did not recharge the ground-water reservoir in the tanks, the draft 

in the tanks was materially reduced for short periods. The reduction 

in ground-water draft occurred also in the thickets of saltcedar, as 

shown in figure 8.

It will be noted in figure 8 that before the 0.26 inch of rain on 

July 17, the water level had been declining at the rate of about 0.01 

to 0.02 foot per day. As a result of the rain the trend was reversed 

and the water level rose slightly, as shown by the peak and the trough 

for July 18. The substantial rain of 0.66 inch on July 18 and the 

light shower of 0.09 inch on July 20 resulted in a rise in water level 

of about 0.1 foot. That this rise was due to a reduction in draft by 

the saltcedar from the ground water, rather than recharge from rainfall is indicated by observations of the depth of rainfall penetration 

at the Glenbar, Ariz., Experiment Station, that follow. On July 18, 

about 14 hours after the 0.26-inch rain, the depth of rainfall penetration ranged from 0.08 to 0.20 foot and averaged 0.13 foot. On 

July L9, about 16 hours after the 0.66-inch rain on July 18, the 

depth of rainfall penetration ranged from 0.26 to 0.55 foot and averaged 0.38 foot. It is apparent from the rainfall-penetration observations that there was no recharge to the water table, even after a 

total of 0.92 inch of rain had fallen. In most places the line between 

the rain-wetted soil and the dry soil beneath was sharp and distinct. 

Although no observations of rainfall or rainfall penetration were 

made at the site of well T-4, the indications are that they were almost 

the same as at the Glenbar Experiment Station.

One explanation for the reduced draft of ground water may be 

that the plant temporarily obtains part of its supply from the increased soil moisture in the top few inches of soil wetted by the rain. 

Another explanation may simply be a reduced rate of transpiration 

resulting from the increase in humidity and decrease in temperature 

that generally follow summer rains. The meteorological conditions on 

July 19 tend to support this explanation. Very probably, both explanations apply.

Other factors being equal, the use of ground water varies directly 

with the length of the growing season and daytime hours (sunrise 

to sunset). It is greatest when they are long and least when they are 

short. Blaney (1952, p. 61-66) recognizes the effect of daytime hours 

and adjusts for it in his formula for transferring consumptive-use 

data from one area to another.

The effect of altitude on use of ground water is largely the result 

of its effect on temperature and length of growing season. Both de-
22 PHREATOPHYTES

crease as the altitude increases, and hence use of water decreases with 

altitude.

DEPTH TO WATER

The few data on the use of ground water by phreatophytes indicate 

that at shallow depths the rate of use decreases as the depth to the 

water table increases. The left side of figure 7 shows this conclusively 

in the case of saltgrass for depths to 5 feet. In the case of saltcedar, 

it has been demonstrated for depths to 7 feet (Gatewood, Robinson, 

Colby, and others, 1950, p. 137). For depths greater than about 7 

feet, the data are meager and not so conclusive. Nevertheless, this 

relation is inferred to hold true at greater depths. This inference is 

based largely on the field observation that as the depth to the water 

increases, the plants become scattered and less vigorous, and gradually diminish in size until they cease to exist altogether. It seems 

logical to attribute this decrease in vigor and size to a reduction in 

the ability of the plant to obtain the water necessary for normal 

growth.

In areas where the capillary fringe extends to the land surface, 

ground water is discharged by evaporation from the soil and is also 

transpired by phreatophytes. The two processes, evaporation and 

transpiration, are closely associated, and it is difficult to determine 

the quantity of water discharged by each. For this reason, the two 

are commonly referred to as a single process, evapotranspiration. 

According to Lee (1942, p. 290), the maximum rate of evaporation 

occurs with a very shallow water table, decreases as the water table 

declines, and becomes in effect zero after the water table drops to 

such a depth that the capillary fringe does not reach the land surface. 

As many of the data on water used by phreatophytes are actually 

data on evapotranspiration, it is well to recognize that if the capillary 

fringe extends to the land surface, the record of use represents both 

evaporative and transpirative discharge, and if the capillary fringe 

does not extend to the land surface, the data represents only transpirative discharge. This explains the large difference in annual rate 

of use reported for a species growing in an area where the water 

table is shallow and the same species growing in an area where the 

water table is deep. It illustrates also the unfeasibility of attempting 

to apply water-use or evapotranspiration data for a shallow' water 

table to an area having a deep water table, or vice-versa.

DENSITY OF GROWTH

The density of growth of phreatophytes, like that of other plants, 

is not uniform. The number of plants per unit area may from place 

to place vary from a few scattered plants to a dense junglelike forest.
USE OF GROUND WATER BY PHREATOPHYTES 23

The height of the plant and the vertical depth of foliage also may 

differ. These differences in areal and vertical density affect the quantity of ground water transpired. In order to evaluate and compare 

these differences of plant growth, the volume-density method was developed by the author during an investigation of the use of ground 

water by phreatophytes in the Safford Valley, Ariz. (Gatewood and 

others, 1950, p. 23-27). Volume-density is the product of areal density and vertical density, and the computation of it affords a method 

of comparing on a standard basis one area of growth with another. 

It affords also a means of applying to field conditions the data obtained from tank experiments.

Density is measured against a growth so thick that any new growth 

would cause an equivalent amount of old growth to become choked 

out and die; this is maximum possible density, or 100 percent density. 

Areal density is the number of plants in relation to the maximum 

number possible, and vertical density relates the vertical depth of 

foliage to the maximum possible. It was found in the Safford Valley 

(Gatewood and others, 1950, p. 27) that the use of water by saltcedar, cottonwood, and baccharis varied directly with the volume 

density. Thus, it is not sufficient to say that the annual use of water 

by a certain species is a certain amount; conditions of growth must 

also be specified. This may be done by describing the foliage in terms 

of volume density expressed as a percentage.

QUALITY OF GROUND WATER

There is much evidence to indicate that the quality of water affects 

plant growth and, hence, use of water. In general, plants grow less 

and use less water as the dissolved-solids concentration of the water 

increases. The explanation for this is found in the fact that a plant 

in order to absorb soil water must have a tissue fluid of higher osmotic 

pressure, and therefore of higher salt content, than the soil water. 

Thus, plant growth is a function of the ratio of the osmotic pressure 

of tissue fluid to that of soil water. This relation explains why water 

of high salt concentration may be unavailable to a particular plant, 

even though the soil is saturated and the plant needs moisture because 

that plant is unable, without injury, to build up the salt content of its 

fluid to the required density.. Also plants may be injured or their 

growth retarded as a result of the toxic effect of salts in the solution 

(U. S. Dept. of Agriculture, U. S. Salinity Laboratory, 1954, p. 61). 

According to the Salinity Laboratory,

The influence of excessive concentrations of specific salts on plant growth 

is an extremely complex subject involving many fundamental principles of 

plant nutrition.
24 PHREATOPHYTES

Toxicity of water to plants may be a matter of total concentration 

of large concentrations of common salts, or of small concentrations 

of particular substances such as boron.

Data obtained in the Safford Valley, Ariz. (Gatewood and others, 

1950, p. 77) indicate that the quality of the ground water affected 

the rate of transpiration of baccharis (Baccharis glutinosa). In general it was found that plants were smaller and used less water as 

the dissolved-solids concentration of the water increased. This observation is substantiated by experimental determinations on the influence of salts on cultivated crops at the U. S. Salinity Laboratory, 

Riverside, Calif. (U. S. Dept. of Agriculture, 1946, p. 1-25). It was 

found that some species had a greater tolerance for salt than others. 

Although specific data are lacking, there is every reason to believe 

that these experiments and observations apply to phreatophytes in 

general.

SALVAGE OF GROUND WATER

The ground water used by most phreatophytes has a low beneficial 

use so far as man is concerned. Although some phreatophytes have 

ornamental value, furnish cover for game, or are useful to agriculture by providing erosion control, furnishing a limited amount of 

browse, or serving as windbreaks, most of them have a low economic 

value. Of the common phreatophytes, only alfalfa is an important 

agricultural crop.

In referring to the water used by plants, the term "consumptive 

use" has come into general acceptance to denote the quantity of water 

evaporated or transpired from an area. It is considered synonymous 

with the term "total evapotranspiration." The term "consumptive 

use" makes no distinction as to the nature of the use but includes 

the water used for the growing of cultivated crops as well as by the 

uncultivated and native vegetation of forest and rangeland. Some 

vegetation is essential for man's existence, but some other may benefit him very little or not at all. In order to distinguish between these 

conditions of use, the term "consumptive use" has been qualified by 

the addition of the adjectives "beneficial" and "nonbeneficial." As a 

result, the water used in the growing of cultivated crops and other 

vegetation of high economic value is referred to as beneficial consumptive use, and that used by weeds or noxious plants is designated 

nonbeneficial consumptive use.

H. E. Thomas (1951, p. 217) has suggested the general term 

"consumptive waste" to denote '"the water that returns to the atmosphere without benefiting man." When this term is restricted so that 

it applies only to the water used by plant life, "consumptive waste"
SALVAGE OF GROUND WATER 25

may then be applied to the water transpired by plants that have 

very little utility for man. Used in this manner, the term becomes 

the opposite of beneficial consumptive use and synonymous with nonbeneficial consumptive use. Under these conditions, consumptive 

waste is that part of consumptive use that is without substantial 

benefit to man, and it will be used to mean that in this paper. It is a 

part of, rather than a complement to, "consumptive use" as that 

term is broadly defined as synonymous with total evapotranspiration. 

In describing the water used by phreatophytes, the term is very apt, 

conveying a concept that is readily grasped by layman and scientist 

alike.

Ground water that is consumptively wasted by phreatophytes is 

available for salvage. Salvage, as applied to phreatophytes, is converting consumptive waste of water to beneficial consumptive use. 

The extent to which consumptively wasted ground water can be salvaged will vary. In some localities it may be possible to effect 100- 

percent salvage, but in others only a part of the water can be salvaged, 

and under adverse conditions, none at all. The degree of salvage 

undertaken or effected probably will depend largely on economics, for 

in the final analysis salvage is an economic problem.

The water available for salvage in any area is equal to the total 

water requirements of the nonbeneficial phreatophytes in the area. 

In the arid western part of the United States, the amount of water 

consumptively wasted by phreatophytes is very large. Estimates 

based on incomplete data indicate that the area occupied by these 

plants in the 17 Western States, the Dakotas, Nebraska, Kansas, 

Oklahoma, Texas, and States to their west, is nearly 16 million acres, 

from which phreatophytes may discharge as much as 25 million 

acre-feet of water into the atmosphere annually (Eobinson, 1952a, 

p. 60). This amount of water is equivalent to about twice the average 

annual flow of the Colorado Eiver at Lees Ferry, Ariz., or to about 

75 percent of the total storage capacity of Lake Mead. The consumptive waste of this quantity of water in the arid and semiarid regions 

of the West, where the demand for water is on the increase, emphasizes the importance of salvage.

The idea of salvage as applied to phreatophytes is relatively new, 

and methods are largely in the experimental stage. The data available on methods of salvage are probably fewer than those on any 

other phase of the phreatophyte problem. Much study is needed to 

develop methods by which salvage can be accomplished economically.

Salvage may be effected in two ways: lowering the water table 

beyond reach of phreatophytes by pumping or drainage and subsequently using this water economically; and by substituting plants
26 PHREATOPHYTES

of high economic value for nonbeneficial phreatophytes. Either operation requires a knowledge of the occurrence and habits of phreatophytes and their annual consumption of ground water.

To be effective, reducing consumptive waste by lowering the water 

level should be rapid; otherwise, the roots and especially those of 

the deep-rooted plants may keep pace with the declining water level 

and keep the plants alive until the water table again becomes relatively stable. Reduction of consumptive waste may be accomplished also 

by intercepting ground water upgradient from the area of plant 

discharge and diverting it to beneficial consumptive use. Conveying 

the water of streams, especially the short mountain streams of the 

West, through areas of riparian phreatophytes by means of pipes 

or lined ditches also will reduce consumptive waste.

The method of increasing the efficiency of use through substitute 

vegetation has tremendous possibilities. Developments ,in this field 

have not been great, although some advances have been made. The 

outstanding example is in the Escalante Valley, Utah, where alfalfa 

was successfully substituted;, for an association of greasewood, rabbitbrush, and saltgrass (White, 1932). Before replacement vegetation can be planted, it is necessary to rid the area of existing vegetation. This is not always an easy task, especially where aggressive 

and tenacious plants such as saltcedar grow. Two methods of clearing have received considerable attention: cutting down or uprooting 

the plants by mechanical means, and destroying the plants through 

the use of chemical sprays. Considerably more information is needed 

concerning the relative cost and effectiveness of these methods.

It may be possible to turn consumptive waste into beneficial consumption by finding a use for wasteful phreatophytes. Such a method would be of particular value in areas where the dissolved-solids 

content of the ground water is so high as to restrict its usefulness 

for purposes other than growing the plants already present. A 

possibility is the use of rabbitbrush as a source of rubber. (See 

discussion, p. 55.) Also, saltcedar is known to contain tannins, 

and mesquite is noted for the high quality of the charcoal that it 

produces. These are some possibilities that could be studied, and 

there are doubtless many others.

STATUS OF INFORMATION ON PHREATOPHYTES

The considerable amount of information concerning phreatophytes that has become available since Meinzer first introduced 

the subject in 1927 is still not adequate for intelligent handling 

of the problem. Little attention was focused on the effect of phreatophytes on the water supply in the Southwestern United States until
STATUS OF INFORMATION ON PHREATOPHYTES 27

the early 1940's when increased supplies of water were needed to 

meet the demands of World War II. Half of the references listed 

on pages 78-82 were published after 1945.

The greatest advance has been made in determining the annual 

use of water by different species. Information about common 

phreatophytes such as saltcedar, greasewood, cottonwood, baccharis, 

and willow are available for one or two areas, and about saltgrass 

for several areas in the West. There are few data on the phreatophytes of the Eastern United States. Much more information is 

needed even for the common phreatophytes, to say nothing of three 

score others for which there are virtually no data on use of water.

Information on the relation of phreatophyte species to the depth 

to the water table is scanty, and the available information frequently is conflicting. It is known that some phreatophytes such as 

saltcedar, mesquite, and alfalfa are deep rooted and that saltgrass 

is shallow rooted, but there are few data on the limit to which 

the roots will go in search of water. It has been inferred from 

observation that the use of ground water by most species decreases 

substantially beyond a depth of 7 feet, but there is little information to sustain the inference.

Very little is known about the quality of water preferred by 

most species of phreatophytes or the amount of dissolved solids they 

can tolerate. It is known that certain plants, such as pickleweed, 

have a high salt tolerance; others, like greasewood and saltgrass, 

are less tolerant; and some, such as willow, grow only where the 

ground water is low in dissolved solids. Also, very little is known 

of the effect of mineralized ground water on plant growth or the 

tolerance of any species for any particular mineral in the water.

With the exception of that of alfalfa, the known economic or 

cultural value of most phreatophytes is low. In fact, many of them 

aie considered harmful and so may be classified as weeds. It 

should be pointed out, however, that little has. been done to determine whether phreatophytes have an economic value. Additional 

information is needed regarding the value of the plants for food, 

forage,1 browse,2 lumber, erosion control, windbreaks, and other 

uses.

1 Vegetable food of any kind consumed by animals.

2 The tender shoots, twigs, and leaves of trees and shrubs often used and regarded as food 

for cattle and other animals.
28 PHREATOPHYTES

RELATION OF PHREATOPHYTES TO FLOODS 

AND SEDIMENTATION

Not all the problems concerning phreatophytes relate to water 

supply; some relate to flood hazards. This is especially true of 

saltcedar, and to a lesser extent of willow, baccharis, and other 

densely growing riparian vegetation.

Saltcedar, an exotic plant introduced from western Europe, found 

the southwestern part of the United States very much to its liking, growing prolifically and spreading rapidly throughout the 

stream valleys. It is an aggressive and tenacious plant, which in 

the stream valleys of the Southwest invades and chokes the normal overflow channels, greatly reducing their water-carrying capacity. As a result, in times of flood the water spreads over large 

areas that normally would not be flooded, endangering lives and 

damaging property.

The dense river-bottom growth of saltcedar, mesquite, and arrowweed in the 77-mile reach of the Gila and Salt Rivers between 

Granite Reef and Gillespie Dam in Arizona is an example of a major 

flood hazard posed by phreatophytes. The Corps of Engineers has 

recommended the clearing and maintenance of a 2,000-foot-wide 

channel along the entire distance. In addition to reducing the 

flood hazard, this clearing would save an estimated 16,600 acre-feet 

of ground water a year (Turner and Skibitske, 1952, p. 66).

Besides increasing the flood hazard, the damming or ponding 

effect as a result of the dense growth reduces the velocity of the 

floodwater. When, as is quite common, the sediment load of the 

floodwater is high, there is deposition of sediment in the area of 

phreatophyte infestation as a result of the lower velocity. Such 

conditions exist along nearly all streams where there is saltcedar 

infestation,^ but are particularly prevalent along the Gila and Salt 

Rivers in Arizona and the Rio Grande and Pecos River in New 

Mexico. In the Gila River Valley above the San Carlos reservoir, 

the accentuated valley sedimentation resulting from a dense growth 

of vegetation on the flood plain was noted by Eakin and Brown 

(1939, p. 108). The phreatophytes responsible were largely saltcedar and baccharis. In 1954 the writer observed a deposit of silt 4 

to 5 feet thick on the flood plain of the Gila River in an area 

of dense saltcedar growth. This deposit, so far as could be determined, was formed by a single flood a few years earlier.

In the delta above Lake McMillan on the Pecos River, several 

feet of silt may have been deposited as the result of saltcedar 

growth. Eakin and Brown (1939, p. 17-18) have attributed the 

marked decrease in the rate of silting of the reservoir since 1915
RELATION TO FLOODS AND SEDIMENTATION 29

to the dense growth of saltcedar in this area. Before 1912, the 

vegetation in the valley of the Pecos River above Lake McMillan 

was largely low-growing saltgrass. In the fall of 1912, a few seedlings of saltcedar were observed on the mud flats at the head of 

the reservoir. By 1915, these seedlings had grown to heights of 3 

to 5 feet and, according to the National Resources Planning Board 

(1942, p. 57), covered an area of 600 acres. The plants continued 

to spread; by 1939 they were growing on 9,800 acres and by 1950 

on 10,160 acres in the delta at the head of Lake McMillan (Pecos 

River Commission, 1955, p. 10).

The general effect of this saltcedar growth on sediment deposition in the reservoir is shown by the following tabulation prepared 

by Eakin and Brown (1939, p. 17).

Length of Total sediment Deposits per

Period period deposited year

(years) (acre-feet) (acre-feet)

1894-1904... ......... 10.42 18,000 1,730

1904-1910. ........... 6.42 10,000 1,560

1910-1915............ 4.58 13,400 2,920

1915-1925............ 10.00 3,500 350

1925-1932............ 7.00 1,500 215

The average rate of silting in the 21.42 years of record before 

1915 was 1,933 acre-feet per year, as contrasted with 294 acrefeet per year in the 17-year period after 1915. The increasing 

effectiveness of the saltcedar in desilting the flood water is shown 

by a decrease in the average yearly rate of silting from 350 acrefeet in the 10-year period 1915-25 to 215 acre-feet in the 7-year 

period 1925-32.

The desilting effect produced by the screen of saltcedar growth 

suggests the possibility of using such a method of desilting to prolong the effective life of reservoirs. It must be pointed out, however, that such a method would have a high water cost. The 

average streamflow depletion by saltcedar above Lake McMillan 

in the 6-year period May 1934 to July 1940 has been computed 

as 54,300 acre-feet per year (National Resources Planning Board, 

1942, p. 56). This is nearly three times the average annual rate 

of evaporation (19,100 acre-feet) from Lake McMillan and its 

auxiliary diversion reservoir, Lake Avalon. The use of saltcedar 

for desilting, then, evolves into a question of economics, that of 

balancing the additional effective life of the reservoir against the 

annual water use by the plants. A further consideration is the 

question of whether the higher flood levels caused by the phreatophyte growth and the sedimentation can be tolerated.
30 PHREATOPHYTES

In order to reduce water losses resulting from inundation and 

ponding caused by the sedimentation in the area of phreatophyte 

growth, it has been found necessary to construct conveyance channels at the head of McMillan reservoir on the Pecos and Elephant 

Butte reservoir on the Rio Grande.

PHREATOPHYTES IN WESTERN UNITED STATES

Those plants of the Western United States that are known to 

occur as phreatophytes, or which, from available information, can 

with good reason be classified as phreatophytes, are listed in 

table 1. Some of the plants may not occur everywhere and at 

all times as phreatophytes. For example, wirerush (Junius balticus) 

may be found in some areas growing as a hydrophyte, with its 

roots in water. Juniperus scopulorum, or Rocky Mountain juniper, 

generally occurs in the mountains, where, if there is a water table, 

it lies at great depth. However, the plant grows as a phreatophyte 

in two areas of shallow water table in Nevada. The line between hydrophytes and phreatophytes, and phreatophytes and xerophytes, is 

not sharp but appears rather to be a gradual transition. Thus, there 

are some plants that may occur as both hydrophytes and phreatophytes, a large group that occur as true phreatophytes, and then a 

group that may occur as both phreatophytes and xerophytes. The 

fact that a phreatophyte may occur also as a hydrophyte or as a xerophyte is noted in the table, when this information is known.

The list of plants, including the available data on them as phreatophytes, is given alphabetically, by scientific name, in table 1. For 

eight common phreatophytes, alfalfa, cottonwood, greasewood, pickleweed, rabbitbrush, saltcedar, saltgrass, and willows, there is 

considerably more information than could be included in the table. 

Discussions of these plants are given under separate headings, according to genus, after table 1.
PHREATOPHYTES IN WESTERN UNITED STATES 31

 S g o .S

< « « Pk

 u a) a) .

o S5-S

^ ° a

s -2

a e ' S be

co A!
TABLE 1. Phreatophytes in Western United States

[The quality of the ground water with respect to its suitability for crop growth is indicated by numerals as follows: 1, excellent to good; 2, good 

to poor; 3, poor to unsatisfactory. The use of ground water, including precipitation, unless otherwise stated is presumed to be for a plant growth 

of 100-percent volume density (Gatewood and others, 1950, p. 23-27)]

Relation to ground water

Depth to 

water below 

land 

Occurrence as a surface 

Scientific name Common name phreatophyte (feet)

Use (acre 

feet per 

Quality acre) Remarks

Acacia greggii ................................. Catclaw, devilsclaw, Southern California to

A. Gray. una de gato. western Texas.

Acer negundo .................................... Boxelder .....

Linnaeus.

Canada to Oklahoma and 

Arizona.

Alhagi camelorum ....................... Camelthorn ........................ Arizona

Fischer.

Allenrolfea occidentalis ............ Pickleweed, iodine-

(S. Watson) Kuntze. bush.

Alnus ............................................................ AJder .........................................

California to western Texas. 1-20

................... Uses more water than mesquite (McGinnies and Arnold, 1939, p. 236). Forms 

thickets along streams and washes.

.................... Occurs in moist places and along streams,

chiefly in mountains. Observed in the flood plain of the North Canadian River 

near Oklahoma City, Okla. Widely used as a shade tree.

.................... Introduced into Southwestern United States

from Asia Minor. Poor browse plant. 

Observed growing as a phreatophyte 

along Little Colorado River between Hoibrook and Winslow, Ariz., in localities where the depth to water ranged from 

4 to 6 ft. Aggressive and thicket forming, root system deep and extensive 

(Van Dersal, 1938, p. 45). (Fig. 9.)

................... For additional information see page 49 and

figure 22.

5.3 Occurs along streams, river bottom land, 

and other wet sites. The use of 5.3 ft. 

(Blaney and others 1933, p. 112) was 

for the period May to October 1932 in 

Coldwater Canyon, altitude 2,400 ft., San 

Bernardino Mountains, Calif., where alder constituted 82 percent of the vegetation.

COto
Anemopsis californica .......

(Nuttall) Hooker and

Arnott. 

Aster spinosus

Bentham.

Atriplex canescens 

(Pursh) Nuttall.

Yerba mansa

Spiny aster

..... Southern California, southern Nevada to Utah and 

Texas.

............ Arizona .....................................................

Shallow

hastata .... 

Linnaeus.

Fourwing saltbush, South Dakota to Oregon, 

chamiso, chamiza. south to Mexico

Oregon and California to 

Kansas and New Mexico.

'8-62 1-2

lentiformis .................

(Torrey) Watson.

Baccharis emoryi 

A. Gray.

glutinosa ......

Persoon.

sarothroides 

A. Gray.

sergiloides . 

A. Gray.

viminea - 

Crandolle.

Quailbrush, lenscale, Nevada 

saltbush.

Emory baccharis ...

Batamote, seepwillow, watermotie, 

waterwillow.

Broom baccharis, 

desertbroom, 

rosinbrush.

Squaw baccharis, 

waterweed.

Mulefat ............. . ..

Southern Utah and Nevada 

to California and Sonora, 

Mexico.

Texas to southern California and southern Utah.

Colorado and Texas to 

California and Mexico.

Southern California, Arizona, southwestern New 

Mexico.

Arizona, southern California, southern Nevada, 

southwestern Utah.

Southwestern Utah, southern California, Nevada, 

Arizona.

6-15

2-15 H
TABLE 1. Phreatophytes in Western United States Co

Relation to ground water

Scientific name

Bigelovia harttvegii, ..............

probably Aplopappus 

heterophyllus 

A. Gray.

Celtis reticulata ... ....................

Torrey. 

Cercidium floridum ................

Bentham.

Sweet. 

Chrysothamnus pumilus ....

Occurrence as a 

Common name phreatophyte

kom.

southeastern California.

Nevada, Arizona, southern California. 

.... Rabbitbrush .................... Mud Lake. Idaho ..... .... .. ..... .

Depth to 

water below 

land 

surface 

(feet)

To 50

Use 

feet 

Quality ac

......................... ..........

...................... ..........

(Nuttall).

nauseosus consimilis ...

( Greene). 

nauseosus graveolens .

(Nuttall). 

nauseosus mohavensis .

( Greene).

nauseosus oreophilus 

(A. Nelson).

nauseosus viridulus .....

Rubber rabbitbrush. Nevada, Utah, Idaho, Wyoming.

.......................... do ........................ Montana, Idaho, Utah, Nevada, New Mexico.

.......................... do ....................... Northern California,

Nevada.

.......................... do ....................... Wyoming, Colorado, Utah.....

. do ....................... Colorado to Oregon; Nevada, New Mexico.

2.5-15

2-3 ..........

2-3 ...........

2-3 
Cowanin stansburiana 

(Torrey).

Vanadium bush Arizona, Idaho, Utah ...

(Linnaeus) Persoon.

Dalea spinosa ................................. 

Gray.

Linnaeus.

(Linnaeus) Greene.

(Torrey) Rydberg.

Presl. 

triticoides ................. ...

Buckley. 

Eragrostis obtusiflora . ..

(Fournier) Scribner.

.... Smoketree, smokethorn.

cinquefoil.

saltgrass.

Mexican saltgrass,

alkali lovegrass.

nia.

Southeastern California, ................................... ............................... .........

southwestern Arizona.

spread in Oregon, Washington, Utah, Nevada 

and Arizona.

All Western States 2-14 1-3 .......

(Hitchcock, 1951 p. 178).

New Mexico (Dayton, 

1940, p. G52). 

Western United States ............ .................................... 1-2 .........

southwestern New Mex-

4 2.8
TABLE 1. Phreatophytes in Western United States Co

Relation to ground water

Scientific name

Fraxinus velutina ... ..... 

Torrey.

Occurrence as a 

Common name phreatophyte

. Velvet ash, Arizona Southwestern Utah, southash, ern Nevada, California, 

Arizona, New Mexico, 

and western Texas.

Depth to 

water below 

land 

surface 

(feet)

Use 

feet 

Quality ac

Hedysarum boreale ................. . Sweet vetch .................. Colorado, Utah ......................

Nuttall.

Heliotropium curassavicum. Heliotrope, Chinese Southwestern Utah to 

Linnaeus. pusley. southern California.

Hymenoclea monogyra 

Torrey and Gray.

aalsola ...................................

Torrey and Gray. 

Juglans microcarpa ...........

Berlandier.

Burrobush ........................ Western Texas to southern California.

White burrobush .......... Utah to Arizona and

California.

Walnut, nogal, Arizona, New Mexico ... 

butternut.

Shallow

Shallow

2

0 o

1-2

2-20

Juncus balticus ................................. Wirerush, wiregrass... Western United States

Willdenow

57
Juncus cooperi 

Engelmann.

Juniperus scopulorum?

Leptochloa fascicularis 

(Lamarck) A. Gray.

Medicago sativa ..........

Linnaeus. 

Phragmites communis

Trinius.

Picea engelmanni ..........

Parry.

Platanus wrightii 

Watson.

Pluchea sericea 

Coville.

Desertrush ....................... Southern Utah to California.

Rocky Mountain ju- Nevada ..............................

niper; locally 

"swampcedar."

2-3

10 1-2

Sprangletop

Alfalfa

Western United States ............... .................................. 1-3

Western United States

Reed, giant reed- Western United States ...........

grass, carrizo.

Engelmann spruce ... Mountain areas of western United States.

Arizona sycamore ...... Southern Arizona, southeastern and southwestern 

California, New Mexico.

Arrowweed ........................ Texas to southern Utah

and southern California.

4+ 1-2 

1-2

'0-10± 1-2
TABLE 1. Phreatophytes in Western United States Co

Relation to ground water

Occurrence as a 

Scientific name Common name phreatophyte

Depth to 

 water below 

land 

surface 

(feet)

Use 

feet 

Quality acr

Populus ....................................

tremuloides aurea 

Tidestrom.

Prosopis juliflora 

(Swartz.)

velutina ........

Wooton.

pubescens ... 

Bentham.

Quercus agrifoUa .....

Nee. 

lobata . ...................

Nee.

Salicornia europaea 

Linnaeus

Cottonwood ....................... Western United States .......

Quaking aspen ............. Motintainous areas of

Western United States.

Mesquite, honey Southern Kansas to southmesquite. eastern California and

Mexico. 

Velvet mesquite ....... Southern Arizona ....................

Screwbean Western Texas to southern 

mesquite, tornillo. Nevada and southern 

California.

California live oak . California 

Roble oak ................ ...... California

10+

35±

10-20

1-2 ....... ..

1 ........ 

1-2 ...........

1-2 G3

Glasswort

rubra .........

Linnaeus.

utahensis .... 

Tidestrom.

.......... do

do

Colorado, New Mexico, 

Nevada, Utah.

Utah
PHREATOPHYTES IN WESTERN UNITED STATES 39

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soils, alkaline highly Will noton grow is when oter forage rowsed scarce. soils saline-alkali salineOccurs orn

much firstoo with saltincotent as

Agriculture, S. (U.Dept 3.2percent 

58). 1954, p.

M

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TABLE 1. Phreatophytes in Western United States Co

Relation to ground water

Scientific name

Suaeda suffrutescens ..... 

Wntson.

Occurrence as a 

Common name phreatophyte

ico. Arizona .................................

Depth to 

water below 

land 

surface 

(feet)

Use 

feet 

Quality acr

torreyana . Watson.

Tamarix aphytta ..........

Linnaeus.

gallica ...................

Linnaeus.

Washingtonia filifera 

Wendland.

Torrey seepweed, 

iodineweed, inkweed.

Athel tree ........................ 

Eastern 

Southwest

Oregon to New 

Mexico and California.

i4-15

..do.. Saltcedar, French 

tamarisk .......................

Fan palm, Califor- Southern Arizona, California palm .......... .. ..... nia, southeastern New

Mexico.

1-3 ...........

1-3 .............

1-3 .............

1 Meinzer, 1927.

2 Average in Safford Valley, Ariz. (Gatewood and others, 1950). 

8 Considerable for full development.

4 2.85 with 2-ft water level and 2.35 with 3-ft water level in tanks at San Bernardino, Calif. (Young a

5 7.8 with water level at 2 ft, Santa Ana, Calif. (Idem, p. 43-45).

6 Average in the Safford Valley, Ariz. (Gatewood and others, 1950, p. 195).

T 4.01 with 2.0 ft water level; 3.45 with 4.0 ft water level, Carlsbad, N. Mex. (Blaney and others, 19
PHREATOPHYTES IN WESTERN UNITED STATES 41

FIGURE 11. "Vanadium bush" (A) and sweet vetch (B), which have a high tolerance for mineralized ground, are valuable as guides in the search for uraniumvanadium ore deposits on the Colorado Plateau. The "vanadium bush" is able 

to absorb large amounts of uranium. Photographs by Helen L. Cannon.
42 PHREATOPHYTES

FIGURE 12. Smoketrees (Dalea spinosa) in a gravel-filled wash north of Needles, Calif. 

A typical occurrence of this ashy gray leafless shrub, whose branches all end in spines.
PHREATOPHYTES IN WESTERN UNITED STATES 43

FIGURE 13. Giant wildrye (Elymus condensatus) near Rye Patch 

Reservoir on the Humboldt River, Nev. The plant had reached 

a height of 2.5 feet when the photograph was taken in mid-June.

FIGURE 14. Blue palo verde growing in Centennial Wash, Ariz. Two different species of 

palo verde are native to Arizona: blue palo verde (Cercidium floridum) which is a 

phreatophyte, and the foothill palo verde, (C. microphyllum) which is not. Photograph 

by D. G. Metzger.
44 PHREATOPHYTES

FIGURE 15. Giant reedgrass (Phragmites communis), or carrizo as it is known in the 

Southwest, growing in association with arrow-weed (left) along a ditch bank on the 

flood plain of the Colorado River near Yuma, Ariz. Below, detail of giant reedgrass.
PHREATOPHYTES IN WESTERN UNITED STATES 45
46 PHREATOPHYTES

FIGURE 17. A grove of aspen (Populus tremvloides) marks 

a spring and seep area in Clear Creek canyon, near Carson 

City, Nev.

FIGURE 18. The "devil's corn field" near Stovepipe Wells in Death Valley National Monument, Calif., shows clumps of arrowweed in a sand dune area, the roots having been 

partially exposed by wind erosion. The capillary fringe is at the land surface here.
PHREATOPHYTES IN WESTERN UNITED STATES 47

~ ^SwUS^^;?1

°J

1 6?

« s

8 *

.5 ^

v .^

as g

"I

O
48 PHREATOPHYTES

FIGURE 20. Desertrush (Juncus cooperi) in association with saltgrass (Distichlis stricta) 

on edge of the playa about 5 miles north of Furnace Creek ranch, Death Valley, Calif.

21. Fourwing salt-bush (Atriplex canescens) growing in clumps along the channel 

of Salt Creek about 3 miles west of Beatty Junction, Death Valley, Calif.
EIGHT COMMON PHREATOPHYTES 49

SUMMARY OF INFORMATION CONCERNING 

EIGHT COMMON PHREATOPHYTES

The information available for eight of the phreatophytes listed 

in table 1 is more than could be included in the table. This information is presented and discussed, by species, in the following pages.

ALLENROLFEA OCCIDENTALIS PICKLEWEED

Pickleweed, as mentioned earlier, is one of the most salt-tolerant 

phreatophytes, actually appearing to thrive on soil of high salt 

content. It is a succulent, almost leafless shrub (fig. 22) that occurs 

along the fringes of salt lakes, flats, and playas and in moist 

saline and alkaline areas. It occurs closely associated with saltgrass and to a lesser extent with greasewood. However, at the inner 

edge of saline areas, where the salt content of the soil may be too 

great for saltgrass, pickleweed may be the only plant growing. 

A typical occurrence of pickleweed associated with saltgrass growing on strongly saline land is shown on the margin of Great Salt 

Lake in Utah in figure 22. Pickleweed is unpalatable to livestock 

and is eaten only when other forage is lacking. The upper 3 feet 

of soil in a pickleweed area generally has a salt content of more 

than 1 percent frequently as high as 2.5 percent (Shantz and 

Piemeisel, 1940, p. 39). In the Tularosa Basin, N. Mex., Meinzer 

(1927, p. 81) found that, in 10 samples of soil from areas of 

pickleweed, taken at depths of 1 to 6 feet, the total soluble solids 

expressed as a percentage of the total dry soil by weight ranged 

from a minimum of 1.75 to a maximum of 4.20, the sodium chloride 

or common-salt content being 0.401 to 1.55. Assuming that the soil 

has a specific gravity of 1.6, a porosity of 40 percent, and is saturated, and that all the salts pass into solution, the soil moisture 

will range in soluble solids from 70,000 to 170,000 parts per million 

(ppm) and in common salt from 16,000 to 62,000 ppm.

During April 1953 the author collected a sample of soil in the 

Malad Valley, Idaho, from a saline flat in which a sparse growth 

of pickleweed was the 'only plant, and numerous crystals of common salt were observed on the surface of the soil. At the same 

time, a soil sample was collected from an area of greasewood growth 

about a hundred feet distant on the fringe of the saline flat. A comparison of the chemical analyses of the two samples given below 

shows that the soil from the pickleweed area had a soluble-salt 

content 55 times greater than that of the greasewood area, and the 

chloride content was nearly 700 times greater.
50 PHREATOPHYTES

FIGURE 22. Pickleweed (AUenrolfea occidentalis) associated with saltgrass growing 

on strongly saline soil on the margin of Great Salt Lake, near Hooper Hot Springs, 

Utah. Fremont Island in the distance. Photograph by E. J. Brown. Below, detail 

of its much-branched, fleshy, almost leafless stems.
EIGHT COMMON PHREATOPHYTES 51

Chemical analyses of soil samples from a pickleweed and a greasewood 

area, sec. 21, T. 15 S., R. 36 E., Malad Valley, Idaho

[Analyses by the U. S. Bureau of Reclamation]

Pickleweed area

Depth of sample inches__________________________ 0-4

Kind of soil______________________________ ___________________ Silty loam

pH (1:5 dilution) ___________

Percent salt ___ _______ ___ _ __ _ _ ____.

Saturation extract, in parts per 

million except as indicated:

Conductivity micromhos ______

Total dissolved solids . 

Calcium - _ _____ _ _____

S odium __ _ 

Pota ssium __ 

Bicarbonate_ 

Carbonate____

Chloride 

Boron

8.4 

>3.0

95,600

7.5

75,400

288

1,700

23,000

1,340

71

0

149

41,600

.59

Greasewood area

1-3

Sandy loam 

9.7 

.04

1,200

8.9

1,350

8.4

6.3

279

48

685

0

62

60

1.7

Samples of plant tissue also were collected at the same time and 

place from the leaf, branch, and root of the pickleweed and a 

greasewood plant. The analytical results for the pickleweed plant 

and soil sample are given below, and those for greasewood under 

the discussion of that plant on page 69.

Chemical analysis of soil from pickleweed area and plant tissue 

of pickleweed, Malad Valley, Idaho

[Analyses, by U. S. Bureau of Reclamation, in milligrams

per gram of soil or plant tissue]

Plant tissue

Constituents Soil

Calcium .................. 0.138

Magnesium ............... .816

Sodium ................... 11.027

Potassium ................ .641

Chloride ................. 19.987

Sulfate .................. .072

Boron .0003

Leaf

12.47

7.94

20.42

3.11

9.94

11.15

.055

Branch

6.84

6.64

30.36

7.14

37.75

5.90

none

Boot

3.75

6.39

25.93

6.80

26.64

5.11

tr

Although pickleweed has a high alkaline and saline tolerance, it 

is not necessarily confined to areas where the ground water has a 

high content of these constituents. Meinzer (1927, p. 80) reports 

that in the Tularosa Basin, N. Mex., the dissolved solids in four 

samples of ground water from areas where pickleweed was growing ranged from 1,670 to 5,500 ppm, and the chloride from 244
52 PHREATOPHYTES

to 1,130 ppm. One sample of ground water from the Big Smoky 

Valley, Nev., had 4,040 parts ppm of dissolved solids and 1,360 ppm 

of chloride. A chemical analysis of a sample of ground water collected in July 1953 from an uncased well 22 feet deep in an area 

of pickleweed growth, on the bed of China Lake (sec. 34 T.24 S., 

R.40 E.) in the desert area of southern California, had a conductance of 3,330 micromhos and dissolved solids of about 2,000 ppm.

The water level in the well stood 5.8 feet below the land surface. A pure stand of pickleweed grew abundantly around the well. 

Unfortunately, no sample of ground water was collected in the area 

of pickleweed growth in Malad Valley nor samples of soil from the 

area of pickleweed growth in China Lake, Calif., to provide a basis 

for comparison of the quality of the soil and the ground water 

at the two localities.

Some idea of the concentration of ground water in which pickleweed can grow is furnished by the following chemical analysis of 

a sample of water collected in April 1957 at Badwater in Death 

Valley, Calif.

Chemical analysis of ground water from a shallow pit in a seep area 

of pickleweed growth at Badwater, Death Valley, Calif.

[Tarts per million except as indicated]

Conductivity micromhos ...................................... 33,600

Dissolved solids ................................................ 25,600

Calcium ...................................................... 946

Magnesium .................................................... 93

Sodium and potassium .......................................... "8,570

Carbonate .................................................... 0

Bicarbonate ................................................... 156

Sulfate ....................................................... 3,070

Chloride ................................................... .. 12,803

Percent sodium ................................................ 87

Density gram per milliliter .................................... 1.015

1 Calculated.

The concentration of this water, which is about two-thirds that 

of sea water, shows that pickleweed has an extremely high tolerance 

for alkaline and saline ground water. Pickleweed's wide range of 

tolerance is indicated by the conductance of the water from Badwater which has ten times the concentration of that from China 

Lake. In general, the presence of pickleweed in an area is an indication of ground water that is at shallow depth, that contains moderate to high amounts of dissolved solids, especially common salt, 

and that is probably unsuited for irrigation or domestic use.
EIGHT COMMON PHREATOPHYTES 53 

CHRYSOTHAMNTJS RABBITBRUSH

According to Dayton (1940, p. B.54), there are about 70 species 

of the genus Chrysothamnus in western North America, to which 

the name rabbitbrush is commonly applied. The shrub is very widespread, extending from Canada to Mexico and from North Dakota 

and western Nebraska to California, but is most abundant in the 

Great Basin. The botanical name Chrysothamnus is derived from 

two Greek roots, chrysos "golden" and tkamnos "a shrub." During 

the flowering season, from late July to September, the plant is 

rendered very conspicuous by the profusion of small golden yellow 

flowers. Because of the similarity of color and size of its flowers, 

rabbitbrush is often confused with goldenrod.

The genus is both phreatophytic and xerophytic, some species 

occurring in the lowlands where they draw on the ground water, 

but others on dry hillsides and slopes where it is apparent that 

they have no association with the water table. So far as the writer 

is aware, there has been no attempt to classify the various species 

with respect to their association with the water table, but a study 

of this is needed. Generally, a close association with the water table 

is indicated where the growth of rabbitbrush is vigorous, luxurious, 

and abundant (fig. 23). In the Great Basin, the phreatophytic species are frequently found associated with greasewood and saltgrass, 

particularly around playas and on the floors of desert valleys.

Only two species have been identified as phreatophytes. These 

are Chrysothamnus nauseosus and C. pumilus. C. nauseosus has more 

than 40 subspecies, or varieties (Hall, 1919, p. 181), but there is 

evidence to classify only 5 of them as phreatophytes. These are 

C. nauseosus consimilis (Greene), C. nauseosus graveolens (Nuttall), 

C. nauseosus mohavensis (Greene), C. nauseosus oreophilus (A. 

Nelson), and C. nauseosus viridulus. These forms, however are very 

common and widespread, covering extensive areas in the Great 

Basin. C. pumilus is reported as a phreatophyte from only one locality, Mud Lake, Idaho (Stearns and others, 1939, p. 68).

The phreatophytic forms of Chrysothamnus nauseosus occur in 

soil that ranges from lightly to moderately alkaline. From this it 

is inferred that the quality of the ground water used by the plant 

ranges from good to poor.

Data on the use of ground water by rabbitbrush are meager. 

White (1932, p. 84) makes the following comment, based on his 

work in the Escalante Valley, Utah:

Rabbitbrush is known to consume water. Wells put down during the investigation in fields of rabbitbrush invariably developed a daily water-table 

fluctuation of considerable amplitude, and although no actual determination 

was made of the amount of ground water used by rabbitbrush, the assump-
en

FIGURE 23. Kabbitbrush, forming the predominant growth in a 

large area of low-lying "land near Carson City, Nev. Average 

height about 3 feet.

FIGURE 24. Saltgrass associated with greasewood growing near 

Battle Mountain, Nev. The light-colored materials on the ground 

and plant stems are incrustations of white alkali.
EIGHT COMMON PHREATOPHYTES 55

tion that it ordinarily consumes at least as much ground water as greasewood is believed to be safe.

The known uses of rabbitbrush are rather unimportant. According to Dayton (1940, p. B54), "Most species of Chrysothamnus 

have little or no forage value . . . but a few rank as fair to good 

forage for sheep and cattle." By virtue of their deep and extensive root systems, they serve as impediments to wind and water 

erosion. Indians obtained a yellow dye from the flowers and a green 

dye from the inner bark.

During World War I, a rubber-plant survey of western North 

America (Hall and Goodspeed, 1919) revealed that certain species 

of Chrysathamnus nauseosus were a potential source of rubber. 

The rubber, known as chrysil, is present within the individual cells 

of the plant, and it is not a latex rubber. The highest rubber content in individual plants was found in two forms occurring as 

phreatophytes. One, C. nauseosus consimilis, from near Gerlach, 

Nev., contained 6.57 percent rubber and the other, C. nauseosus viridulus, from Benton, Calif., contained 5.56 percent rubber. On the 

basis of field studies and sampling it was estimated that the total 

amount of rubber in rabbitbrush in all of the Western States was not 

less than 300,000,000 pounds. The description of the plants and their 

occurrence given in the estimate show that most of the rubber is 

present in the forms that occur as phreatophytes in the alkaline 

valley bottoms of the Great Basin and in the San Luis Valley of 

Colorado. It is worthy of note also that, in general, the highest 

rubber content was found in plants growing in alkaline soil, too 

strong for the standard agricultural crops, and that the rubberproducing kinds of rabbitbrush all have deep taproots with but few 

main laterals.

In view of the high rubber content of the forms occurring as 

phreatophytes, their preference for alkaline soils, and the extensive areas occupied by them, it is apparent that they present a 

unique opportunity for the salvage of ground water. Should the 

production of chrysil become economically feasible, then much of 

the ground water now considered wasted by phreatophytic rabbitbrush would become of beneficial consumptive use in view of the 

value of these plants for their rubber content. Furthermore, for 

highest rubber content the plants would be grown on wasteland 

land where the ground water is too alkaline for growing agricultural crops. Irrigation and the attendant leveling of land and construction of ditches would not be a problem, for the plants would 

draw on ground water for their supply.
56 PHREATOPHYTES

DISTICHLIS SAI/TGRASS

The two principal species of the genus Distichlis in western 

United States are spicata and stricta. D. spicata, known as seashore 

saltgrass, is confined to low-lying lands adjacent to the ocean. It 

is quite common in the saline soils of the lowlands of the San 

Francisco Bay area. D. stricta, on the other hand, is widespread, 

growing in all Western States. It is the saltgrass of the desert, and 

is referred to as desert saltgrass or, usually, just saltgrass. There 

has been much confusion concerning the two species, for in nearly 

all the early reports and many of the more recent ones on desert 

saltgrass cited in this paper, the plant has been referred to as 

D. spicata. However, the description of the habitat and occurrence 

of desert saltgrass by Chase (Hitchcock, 1951, p. 177-78) leaves 

little doubt that in most cases the plants referred to as D. spicata 

were in reality D. stricta.

Desert saltgrass is quite common in the Great Basin. Shantz and 

Piemeisel (1940, p. 37) describe it as forming meadows in the lowest parts of valleys between the greasewood-shadscale belt and the 

pickleweed areas. It does not push out into the salt-encrusted flats 

so far as pickleweed does. It is commonly associated with rabbitbrush or greasewood (fig. 24), and also alkali sacaton. Saltgrass 

is a shallow-rooted plant that is generally found where the depth 

to the water table is less than 8 feet. However, as mentioned 

earlier, it has been observed growing where the water table was 

about 12 feet below the land surface (Blaney and others 1933, 

p. 50).

In much of the area of saltgrass growth, the capillary fringe 

extends to the land surface so that ground water evaporates directly from the soil. As a result, there is a concentration of alkali 

salts at and near the surface. Depending upon the quality of the 

ground water, the concentration of salts in some areas may be 

small, but in others it may be sufficient to form a crust or an 

efflorescence as shown in figure 24. According to the U. S. Department of Agriculture (1954, p. 57), the soluble-salt content of 

the 4-foot soil profile in a saltgrass area is usually high (0.8 to 

2.0 percent), the highest content being found in the first foot. 

Although saltgrass has a high tolerance for salt, it is not confined 

to saline areas. It will grow where only small amounts of salt are 

present.

Saltgrass makes fair forage, particularly when the leaves and 

stems are green. At other times, the leaves are harsh and not 

relished by livestock.
EIGHT COMMON PHREATOPHYTES 57

More work has been done in determining the use of water by 

saltgrass than has been done for any other phreatophyte. The 

pioneer experiments were by Lee (1912) in the Owens Valley, Calif. 

As the result of tank experiments, he found that the evapotranspiration discharge from 54.59 square miles of (salt) grass and 

alkali lands where the depth to water did not exceed 8 feet was 

equivalent to a continuous flow of 109 cfs or 2 cfs per square mile. 

Experiments to determine the evapotranspirative discharge of saltgrass grown in tanks have been conducted by different workers 

under a wide range of conditions at nine localities in the western 

United States. The depth to the water table in these experiments 

has ranged from about 1/3 foot to nearly 5 feet; the altitude from 

near sea level at Santa Ana, Calif., to more than 7,500 feet at 

Garnett in the San Luis Valley, Colo.; and the temperature (see 

fig. 7) from 54°F to 70°F. The location, period of record, depth 

to water table, and evapotranspiration discharge for these experiments are given in table 2.

The results shown in the tabulation are not always comparable, 

for the periods of record differed considerably. Some of the periods 

are for the year, some are for a full growing season, and some 

are for a part of a growing season. In order to compare the results on as nearly a common basis as possible, the approximate 

growing season for each locality was determined, and the records 

that most nearly fit this period were selected. Using these records, 

curves were drawn to show graphically (fig. 7) the relation of 

evapotranspiration to depth to the water table, and to the average 

temperature during the growing season. Considering1 that the data 

were obtained by different workers in widely separated areas, and 

under a variety of conditions, the relations are remarkably consistent. Several relations are readily apparent from figure 7. Within 

the limits of the curve on the left side of the figure, it may be seen 

that the evapotranspiration decreases as the depth to the water 

table increases. It may be seen also that, with the exception of the 

San Luis Valley, the rate of decrease for the different locations 

is fairly uniform. The much smaller rate of discharge in the San 

Luis Valley appears to be due largely to the lower average temperature during the growing season.

The relation of evapotranspiration and of evaporation to temperature is shown on the right-hand side of the figure. The increase 

of evapotranspiration with an increase in the average temperature 

during the growing season is evident. The apparent lack of agreement of the results from Los Griegos, N. Mex., may have been 

the result of a poorly operating water-supply system. Blaney and 

others, (1942, p. 117) note that difficulty was experienced in main-
58 PHREATOPHYTES

TABLE 2. Annual or seasonal evapotranspiration of water 

by saltgrass grown in tanks

Locality Period of record

Depth to 

water Use 

(feet) (feet)

CALIFORNIA

Owens Valley ............................ Jan. Dec. 1911

Do

Do ...............................

Do ................................

Do ................................

Santa Ana ..........................

Do ........................... ....

Do ................................

Do ................................

San Luis Valley .

Do ...............................

Do ...............................

Do ...............................

Do ..

Do ...............................

Do .........................

Do ............................

Do ......

Do ....................... ... ...

Do .

Do ...

Do

.......... .............................Do ........................

Do ... ... .. .. ......

......................................... Do .......................

......................................Do .......................

May 1929 Apr. 1932

........... .............................Do ........................

Do

..........................................Do ......................

COLORADO

.June Oct. 1927

...........April Oct. 1928

........... ..May Oct. 1930

........... April Nov. 16, 1931

............ June Oct. 1927

........... April Oct. 1928

............ May Oct. 1930

............. April Nov. 16, 1931

.............June Oct. 1927

........... April Oct. 1928

..... ......May Oct. 1930

............ April Nov. 16, 1931

April Nov. 16, 1931

1.83

2.92

3.83

4.92

1.00

2.00

3.00

4.00

.50

.38

.33

.28

1.25

1.17

.79

.98

2.08

2.00

1.92

2.12

3.12

NEW MEXICO

Carlsbad .

Isleta .. . ...... . ...... ... .. . .

Los Griegos ......................

Do ...............................

Do ...............................

Do ........................ ......

Do ..............................

Do .................... .......

Do ............ .............

Mesilla Dam ....................

.Jan. Dec. 1940

June 1936 May 1937

Oct. 1926 Sept. 1927

........... Oct. 1927 Sept. 1928

............. Oct. 1926 Sept. 1927

........ . .. Oct. 1927 Sept. 1928

......... . Oct. 1926 Sept. 1927

.......... . Oct. 1927 Sept. 1928

.........................................Do ........................

. ..... July 1936 June 1937

2.00

.65

.42

.50

1.17

1.33

2.08

1.17

3.08

2.17

1.50 4.07

3.74

3.35

2.05

1.12

3.56

2.94

1.98

1.11

UTAH

Escalante Valley .....................May Oct. 1926 2.58

Do ................ ..................... May Oct. 1927 1.94

Do .......................................................................Do ....................... 2.17

Vernal .............. ...................................April 14 Oct. 28, 1950 2.00

Remarks

(Young and Blaney, 1942, 

p. 126.)

Do.

Do.

Do.

Do.

(Young and Blaney, 1942, 

p. 44.)

Do.

Do.

Do.

.50

.38

.33

.28

1.25

1.17

.79

.98

2.08

2.00

1.92

2.12

3.12

1.42

2.26

2.26

2.31

1.49

1.98

1.75

2.40

1.11

1.69

1.57

1.83

1.69

(Blaney and others, 1938,

p. 335, 336.)

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

4.52 (Blaney and others, 1942,

p. 210.) 

2.63 (Young and Blaney, 1942,

p. 93.) 

4.03 (Young and Blaney, 1942,

p. 126.)

3.87 Do. 

2.77 Do. 

2.93 Do. 

1.51 Do. 

3.32 Do. 

.84 Do. 

1.89 (Young and Blaney, 1942,

p. 99.)

1.60 (White, 1932, p. 100.)

2.26 Do.

1.86 Do.

1.98 (Barrett and Milligan,

1953, p. 11.) Amount 

does not represent a full 

year of normal growth.
EIGHT COMMON PHREATOPHYTES 59

taining a constant water level in the tanks. The effect of temperature is more fully realized when it is recognized that the evapotranspiration in Owens Valley, average temperature 68°F, for the 

7-month period April through October is about 0.6 foot greater 

than at Santa Ana, average temperature 61 °F, for the 12-month 

period May to April. The longer growing period at Santa Ana was 

not sufficient to compensate for the higher temperature in Owens 

Valley.

Comparison of rate of evaporation from a Weather Bureau pan 

with rate of evapotranspiration in figure 7 shows that evaporation 

was always greater. For a depth of 1 foot the evapotranspiration 

ranged from 68 to 75 percent of the pan evaporation, and for depths 

greater than 1 foot the ratio decreased correspondingly. This fact 

is of value in estimating evapotranspiration discharge in saltgrass 

areas, for, if the pan evaporation is known, at least an upper limit 

can then be placed on the amount of the evapotranspiration, but 

this tentative ratio needs much more study.

Saltgrass appears to be a phreatophyte that is well suited for 

such a study, particularly in tank experiments. Because of this 

and the pioneer work that has been done, saltgrass would be an 

excellent plant for research on many phases of evapotranspiration.

MEDICAGO ALFALFA

The genus Medicago comprises about 50 species of herbs and 

small shrubs and is a native of the Old World, probably the Mediterranean, Asia Minor, and the Caucasus Mountains (McKee, 1948, 

p. 714). Medicago sativa, commonly called alfalfa, is by far the 

most important species. Its first recorded introduction into the 

United States was in 1739 in what is now Georgia, and its establishment as a crop began about 1850 along the Pacific Coast. It 

soon became one of the most important hay and forage crops of 

the Southwest, and later of all the Western States. Today alfalfa 

is one of the most important forage crops in the United States 

and is grown in every State.

In the arid Western States alfalfa is quite commonly, though 

not always, grown as an irrigated crop, but in the humid Eastern 

States irrigation generally is not necessary. The yield of alfalfa, 

ranging from about li/2 to 5 tons per acre, is almost directly 

proportional to the available moisture. The many varieties of alfalfa 

combine to give it a wide range of climatic tolerance, so that it is 

successfully grown in both the northern and southern parts of 

the country, and in the high valleys of the mountains as well as 

in the lowlands. It grows on a wide range of soils but prefers deep 

loams; as a rule it does not thrive on acid soils (McKee, 1948,
60 PHREATOPHYTES

p. 715). Experiments at the United States Salinity Laboratory at 

Riverside, Calif., show that alfalfa has a good to strong tolerance 

for salt (U. S. Dept. Agriculture, 1946, p. 21). Magistad and 

Christiansen (1944, p. 14) report that it will grow in soil containing as much as 4,000 ppm of white alkali, but will tolerate only 

a little sodium carbonate (black alkali). It does not thrive on poorly 

drained soils or where the water table is less than about 4 feet 

below the land surface.

Alfalfa is a deep-rooted plant and will send its roots to great 

depth in search of ground water. Meinzer (1927, p. 54) cites three 

reports of the roots of older plants being traced or reported at 

depths of 65, 66, and 129 feet. The latter was in a mine tunnel 

in Nevada, beneath an alfalfa field, where the roots came through 

crevices in "rotten porphyry."

The available data on the use of water by alfalfa are largely 

from tank experiments. White (1932, p. 99) found that at Milford, Utah, the use in the 1927 growing season, April through 

October, was 2.58 feet, the depth to water in the tanks averaging 

about 3 feet. At the Los Poblanos ranch near Albuquerque, N. Mex., 

the use of water was 3.7 feet with the water level in tanks at an 

average depth of 4.5 feet, for the period April 15 to October 31, 

1936 (Blaney and others, 1938, p. 373).

During 1948, in the course of consumptive-use studies in the 

Colorado River area of Utah, two alfalfa tanks were installed at 

the Vernal, Utah, airport. The tanks were operated during the 

growing periods of 1948, 1949, and 1950. The soil column, 3.67 

feet in length, was held in an inner tank, whose bottom and sides 

were perforated. This tank was placed in an outer tank, about 

3 inches greater in depth and in diameter. The soil column was 

not saturated at its lower end through contact with a water table. 

Instead, the soil column was saturated on the first of each month 

and irrigated on the fifteenth of each month with enough water to 

simulate irrigation conditions in the area. The use under these 

conditions was probably less than it would have been with a water 

table at a depth of 3.67 feet, that is, at the bottom of the soil 

columns, for the reason that the plants did not necessarily have a 

constant and unlimited supply of water at all times. The averages 

of the two tanks for the 3 years were: for the growing period May 

17 to October 6, 1948, 3.6 feet, for the growing period May 31 to 

November 5, 1949, 2.5 feet, and for the growing period April 14 

to October 27, 1950, 3.3 feet (Barrett and Milligan, 1953, p. 11).

A review of the characteristics, habits, and tolerances of alfalfa 

indicate that it has great salvage potentialities through conversion 

of consumptive waste of ground water to beneficial consumptive use.
EIGHT COMMON PHREATOPHYTES 61

Its economic importance as a forage crop, its growth under a wide 

range of climatic conditions, its tolerance to salts, and its deep 

root system are factors that make it an ideal plant to substitute 

for uneconomic phreatophytes. The successful substitution of alfalfa 

for an association of "greasewood and weeds" in the Escalante 

Valley, Utah, described by W. N. White (in Meinzer, 1927, p. 

89-91) is evidence of its value as a salvage plant.

POPTJLUS COTTONWOOD

The genus Populus includes aspens, poplars, and cottonwoods. 

According to Dayton (1940, p. Bill), approximately 15 species 

and several varieties of Populus are native to the Western United 

States. This discussion, however, is concerned primarily with cottonwoods, although one species of poplar is included.

Cottonwood trees are widespread throughout the West, being represented in every Western State by one or more of Populus species; 

it is the State tree of Kansas, Nebraska, and South Dakota. The 

names, both scientific and common, and descriptions of the following list of cottonwoods, including poplars, were taken largely from 

Sudworth's excellent descriptive material (1934) for these trees in 

the Rocky Mountain region.

Scientific name Common name 

Populus acuminata Rydberg .......... Lance-leaf or smoothbark cottonwood

angustifolia James .............. Narrowleaf cottonwood

balsamifera Linneus ..... ........ Balsam poplar

deltoides Marsh ................. Eastern cottonwood

fremontii Watson ...... ......... Fremont cottonwood

sargentii Dode .................. Plains cottonwood

texana Sargent ................. Texas cottonwood

trichocarpa Torrey and Gray ..... Black cottonwood

weslizeni S. Watson ............. Valley cottonwood, Rio Grande

poplar, alamo

Even though specific data on the relation of the above-listed 

species to the water table are lacking, it is believed that all of them 

may be classified as phreatophytes. This belief is substantiated by 

the available literature on the occurrence and habits of the trees. 

All the species listed have one characteristic in common; they grow 

along streams or on river bottom lands where ground water is 

generally at shallow depth and readily available. At least two of 

the species, Populus fremontii and P. weslizeni, are known to be 

true phreatophytes (Meinzer, 1927, p. 58). Present-day information indicates that, as phreatophytes, cottonwoods are much alike. 

However, future work may show that there are differences in their
62 PHREATOPHYTES

annual water use, range in depth to water, or chemical quality of 

the ground water or soil they prefer.

Some of the species listed are widespread in their occurrence; 

others are quite local. There is also overlapping of species, so that 

more than one species may be present in a locality. Populus deltoides is a large tree of the Eastern United States that extends 

west into the Plains States. In those States it occupies a belt extending from eastern North Dakota south to eastern Texas. Three cottonwoods, P. angustifolia, P. sargentii, and P. acumenata, occur 

in the Rocky Mountain region from Canada almost to Mexico, 

P. angustifolia being the most widespread. P. sargentii extends eastward from the mountains into the plains of western Oklahoma, 

Kansas, Nebraska, and South Dakota. P. iveslizeni also occurs in the 

Rocky Mountain region, from central Colorado to Mexico. The 

poplar P. balsamifera prefers the colder part of the Rocky Mountain region from Colorado and Wyoming north to Canada. P. trichocarpa grows largely along the Pacific coast in Oregon, Washington and California. P. texana is limited to the Panhandle and 

central' part of Texas. P. fremontii occurs from western Texas to 

Nevada, Arizona, and California. It is intolerant of shade, as are 

most cottonwoods.

Measurements of consumptive use of water by cottonwoods and 

willows growing in tanks along the San Luis Rey River, Calif., were 

made by Muckel and Blaney in 1939-44 (1945, p. 54). The average annual use was 5.2 feet with the water table at 4 feet, and 8.1 

feet with the water table at 3 feet. Density was 100 percent. 

Although the trees were dormant during most of the winter months, 

grass and weeds grew vigorously throughout the year.

As part of the detailed studies of the use of water by bottomland vegetation in the lower Safford Valley, Ariz., cottonwood 

plants (P. fremontii) were grown in tanks. The use of water by 

the plants during the period October 1, 1943, to September 22, 

1944 (Gatewood and others, 1950, p. 138), at 100-percent density was 7.64 feet with the water table at 7.0 feet. In applying 

the tank data to the areas of cottonwoods in the valley, it was 

estimated that the annual use for 100-percent volume density was 

6.0 feet, including 0.57 foot of precipitation. The water table in 

the valley ranged in depth from 4 to 30 feet below the land surface.

Information as to the depth that cottonwood will send its roots 

to the water table is scanty. Meinzer (1927, p. 58) quotes reports 

of cottonwoods growing where the depth to water was 20 feet. 

The writer has observed cottonwoods growing in areas where there 

was reason to believe that the depth to the water table was between 25 and 30 feet. Thirty feet is believed to be near the limit.
EIGHT COMMON PHREATOPHYTES 63
64 PHREATOPHYTES

Cottonwoods prefer a water of good quality, although they tolerate a water of moderate salinity.

The principal use for cotton woods has been as shade trees (see 

fig. 25). They furnish browse for livestock when the leaves are 

within reach. The tree supplies lumber and veneer that is used 

principally for boxes and crates and as a source for excelsior and 

pulpwood.

SALIX WILLOW

There are about 250 species of willows, practically all native to 

the North Temperate and Arctic Zones. According to Dayton (1931, 

p. 15), at least 80 (perhaps considerably more) species occur 

natively in the Far Western States. Willows are familiar to nearly 

everyone, for they compose one of the most prominent groups of 

woody plants that line the banks and flood plains of streams (fig. 

28). They grow also in dense stands over moist bottom lands and 

in mountain meadows. The willow growth on the flood plain of the 

Humboldt River in Nevada is particularly outstanding. Because of 

the many species of Salix and the difficulty of distinguishing among 

them, generic reference will be made here except in the few instances when specific data are available.

Most species of willows are believed to be phreatophytes, for they 

are nearly always associated with moist situations. Sometimes they 

grow "with their feet in the water," but this is not a normal condition. General observations indicate that most of the willow growth 

occurs where the depth to the water table is less than 15 feet. Most 

willows prefer water of good quality and deep fertile soils. They 

have a low tolerance for alkaline or saline conditions.

Although willows are widespread, there is a dearth of data on 

the use of water by these plants. In the course of his investigations in the Escalante Valley, Utah, White (1932, p. 41) demonstrated conclusively that willows were using ground water in that 

area, but he made no determinations of the annual use. Daily waterlevel fluctuations averaging about 0.3 foot were observed in August 

1926 in a water-table well in a thicket of willows. The willows 

(species not given) were "from 8 to 12 feet high and close together and apparently were putting on an abundance of woody 

growth as well as foliage." The water table was between 5 and 6 

feet below the land surface.

Data on use are available for two localities, Santa Ana, Calif., 

and Isleta, N. Mex. At Santa Ana, Calif., a single plant of red 

willow (Salix laevigata) consisting of about 20 stems was transplanted to an isolated 6-foot-diameter tank 3 feet deep. The water 

level was maintained at a depth of 2.0 feet. The total use of water
EIGHT COMMON PHREATOPHYTES 65

«^^_ - ^ :; ' ~ ^t _y .. , _ j

FIGURE 26. An unusually luxuriant and tall growth of willows line the banks of Grapevine 

Creek at Scotty's Castle (background) in Death Valley National Monument, Calif., amidst 

nearly barren hills. Below, typical willow branch and leaves.
66 PHREATOPHYTES

in 11 of the 12 months from May 1930 through April 1931 was 

4.4 feet (Blaney and others, 1933, p. 65). There were no observations of use during January 1931. The amount used probably is 

high, because generally the use by an isolated plant is greater 

than that in a thicket. In an isolated growth the effect of sunlight, 

temperature, and wind movement on water use is greater than in 

thicket growth where the conditions are such as to reduce the 

effect of these factors.

At Isleta, N. Mex., a clump of willows 6 to 8 feet high was 

transplanted to a 6-foot-diameter tank located in a thicket of the 

same growth. The water level averaged about 13 inches below the 

surface. The use of water in the 12 months from June 1936 through 

May 1937 was 2.54 feet in depth for the area of the tank (Young 

and Blaney, 1942, p. 93).

Young and Blaney (1942, p. 144) summarize the use of water 

by willows as follows: "Willows usually grow where the roots extend into the ground-water region, and they appear to use the 

approximate equivalent of evaporation from a free water surface. 

Investigations with willows are limited, and this relation may vary 

for different localities."

Willows are important in erosion control, through stabilizing the 

soil on the banks of streams and gullies. They also form an important browse plant on the western ranges. In commerce their 

chief use is in the manufacture of wicker baskets and furniture.

SARCOBATTJS GREASEWOOD

Grease wood (figs. 24 and 27) is probably more widespread and 

covers more area than any other phreatophyte in the Western United 

States. It occurs from Canada south to northern Arizona, and it 

is the dominant phreatophyte of the Great Basin. It is primarily 

a plant of the cold desert, and so does not thrive in the southern 

deserts, except at altitudes above 5,000 feet. On the basis of Shantz 

and Zon's natural vegetation map of the United States, Dayton 

(1931, p. 2) reports that greasewood covers "19,551 square miles" or 

about 12.5 million acres in the West. It may occur as pure stands, or, 

as is quite common where the water table is shallow, in association 

with two other phreatophytes, rabbitbrush and saltgrass. On higher 

lands where the water table is at depths of about 10 to 50 feet, it 

may be found in association with shadscale, rabbitbrush, or sagebrush.

Greasewood is a deep-rooted plant. According to Meinzer (1927, 

p. 41), greasewood was found growing in the Big Smoky Valley, 

Nev., where the depth to water was as much as 33 feet; near Grand 

View, Idaho, H. T. Stearns observed roots of greasewood pene-
EIGHT COMMON PHREATOPHYTES 67
68 PHREATOPHYTEb'

trating the roof of a tunnel 57 feet below the surface. Shantz and 

Piemeisel (1940, p. 32) report that near Moab, Utah, along a creek 

bank where the roots were exposed

.... a greasewood 6 feet tall had roots down 18 feet, a taproot 3 inches 

in diameter down 6 feet and abundant feeding roots, some 10 feet long, at a 

depth of 10 to 12 feet.

Although greasewood is a very salt- and alkali-tolerant plant, 

it is not confined to saline or alkali soils. The range in soil salinity 

is wide, from 0.05 to 1.6 percent or 500 to 16,000 ppm (U. S. Dept. 

of Agriculture, 1954, p. 57).

Greasewood also has a wide range in tolerance to alkali, and, 

although alkali is not necessary for its growth (Shantz and Piemeisel, 

1940, p. 33), the plant is characteristic of black-alkali sites. The 

physical properties of the soil occupied by greasewood have a considerable range. Although it generally grows on fine-textured soils 

of low permeability, it also inhabits light, sandy soils. It may be 

seen in sand-dune areas where the ground water is at shallow depth.

Evidence for the wide range of tolerance of greasewood to the 

soluble solids in both soil and ground water has been shown by 

Meinzer (1927, p. 81, 82). Ten samples of ground water from 

areas of greasewood growth in the Big Smoky Valley, Nev., had a 

range in dissolved solids of 137 to 2,400 ppm, and in chloride of 

4 to 501 ppm. The total soluble salts in 11 samples of soil from 

the same valley, collected at depths of 1 to 6 feet, ranged from 0.81 

to 2.19 percent of the total dry soil by weight. If the specific gravity 

of the soil is about 1.6 and the porosity about 40 percent, the soil 

extract would range from about 30,000 to about 90,000 ppm in 

dissolved salts.

A sample of soil from an area of greasewood growing on the 

fringe of a saline flat in which there was a sparse growth of pickleweed was collected in April 1953 in the Malad Valley, Idaho. For 

comparative purposes a sample of soil from the area of pickleweed 

growth was collected at the same time. The chemical analyses of 

these two samples of soil are given on page 51. On the basis of the 

analysis, the soil of the greasewood area may be considered a 

"black-alkali" soil, and that of the pickleweed area a "saline" soil.

Samples of plant tissue for chemical analysis were collected from 

both the greasewood and the pickleweed (p. 51) plants at the same 

time and place as the soil samples. The analytical results for the 

greasewood plant tissue and for the soil sample on a comparative 

basis are given below.
EIGHT COMMON PHREATOPHYTES 69

Chemical analysis of soil from greasewood area and plant 

tissue of greasewood, Malad Valley, Idaho

[Analysis, by U. S. Bureau of Reclamation, in milligrams per gram of soil or plant tissue]

Plant tissue

Constituent Soil Leaf Stem Branch Root

Calcium ___.________ 0.0034 9.21 8.06 4.74 8.81

Magnesium _._ ____ .0026 3.16 1.03 .69 .58

Sodium .___________ .1120 69.54 5.29 1.46 1.89

Potassium _ ___...__.._ .0192 29.15 8.21 2.54 3.24

Chloride _._.________ .0238 20.53 2.05 .10 1.16

Sulfate ____________ .0250 10.49 4.22 4.53 8.52

Boron _ _ ____ _______- .0007 .005 none .02 .005

Data on the use of ground water by greasewood are meager. The 

only tank experiments of record were made by W. N. White (1932) 

in the Escalante Valley, Utah. One tank was operated from June 

to October 1926 and May to October 1927. The record for 1926 was 

not considered representative, owing to the shock of transplanting 

to the tank in April and to the fact that the record covered only a 

part of the growing season. In the 1927 growing season, the evapotranspiration discharge including rainfall was 2.47 feet and excluding rainfall was 2.10 feet (White, 1932, p. 100) with a water 

table between 1.25 and 2.5 feet below the surface of the tank. As 

this tank was isolated (White, 1932, pi. 8B), the use likely was 

higher than if the tank had been in a natural environment of greasewood. The seasonal use of ground water computed from the diurnal 

fluctuations of water levels in greasewood and greasewood shadscale 

tracts where the water table stood 5 to 10 feet below the land surface 

ranged from 0.08 to 0.38 foot. It is difficult to make comparisons 

between the results of the tank experiment and the results based 

on diurnal fluctuations. The higher values for the tank experiment 

may be due in part to the isolation of the tank and in part to the 

shallower depth to the water table. A difference in the density and 

vigor of the growth in the tank and around the wells also would 

affect the use of water, for, as shown by Gatewood and others 

(1950), the use varies directly with the growth density.

Dayton (1931, p. 39) rates greasewood as an important range 

browse, although cautioning that, if stock eat too much of it, poisoning may result from the large concentration of oxalate in the edible 

parts of the plant. Greasewood is of value in erosion control, for 

in some places on the desert it is the only plant that will grow. 

In sand dune areas where the water table is near the surface, greasewood, usually growing in clumps, has a stabilizing effect.
70 PHREATOPHYTES

TAMARIX SAI/TCEDAR

Tamarix gallica, tamarisk, or saltcedar, is a plant native to western Europe, the Mediterranean region, and western Asia, and was 

introduced into this country before the turn of the century. According to Bowser (1957, p. 3-5) introduction of the plants into North 

America is not of firm record. He reports that,

The first reliable herbarium record indicates that a collection of Tamarix 

was made by J. F. Joor in 1884 on the San Jacinto River, Harris County, 

Texas, and at that time the species was naturalized completely in that area. 

In 1877 a specimen identified as Tamarix gallica was collected in Fairmont 

Park, Philadelphia. Heller and Hapeman collected specimens of this species 

along the ocean near Corpus Christi and Galveston, Texas in 1894, but other 

collections of the species were made only infrequently until 1915. After that 

widespread collections of tamarisk were made in the tributaries to most drainage channels throughout southwestern United States indicating that the 

plants were then established widely in the plant communities. Complete invasion of these nonende^ic plants now is evidenced along many natural water 

courses.

According to Dodge (1951, p. 71), eight species of the genus were 

introduced by the Department of Agriculture between 1899 and 

1915. There is other evidence to indicate that other plants of the 

genus, species unknown, found their way into this country at a 

much earlier date. For example, in the historical novel "Death 

Comes for the Archbishop," the author, Willa Gather, notes on 

page 228 "old, old tamarisks, with twisted trunks," in the Bishop's 

garden in Sante Fe. The time of the observations is placed about 

May 1859. There are between 60 and 75 species throughout the 

world, of which it is estimated that 40 may occur in the United 

States. Of these, only two species, T. aphylla and T. gallica (the 

latter also referred to as T. pentandra), appear to be important as 

phreatophytes. Both appear to thrive best in the arid regions south 

of the 37th parallel and below an altitude of 5,000 feet in the 

southwestern United States.

Tamarix aphylla, commonly known as the athel tree, is the less 

aggressive of the two. It is a rapid grower and makes a fine shade 

tree in areas where other trees cannot exist because of saline conditions, and also is much used for hedges and windbreaks in the 

Southwest. It has been observed to reach heights of more than 40 

feet (fig. 29). The species is not known to reproduce by seed 

(Bowser, 1957, p. 4) and, consequently, the plant does not create 

the problem of spreading into areas where it is not desired. It differs 

from T. gallica also in that it is not deciduous but retains its leaves 

and remains green throughout the year. In other respects, it is 

much like T. gallica, for it appears to thrive best under arid or 

semiarid conditions, has a high tolerance to saline or alkali soil
EIGHT COMMON PHREATOPHYTES 71

" r

e H
72 PHREATOPHYTES

FIGURE 30. A dense and vigorous growth of saltcedar (Tamaria gaUica) lines the banks 

along the dry (April 1954) bed of the Gila River in the Safford Valley, Ariz. This 

phreatophyte, which infests most stream valleys of the Southwest, is the heaviest known 

user of ground water. Below, the small delicate fronds that are shed in autumn.
EIGHT COMMON FHREATOPHYTES 73

FIGURE 31. Saltcedar encroachment along the Pecos River about 35 miles upstream from Koswell, N. Mex. In 1953, saltcedar was growing on about 41,000 

acres along the Pecos River in New Mexico. Photograph courtesy of Pecos 

River Commission, 1954.

FIGURE 32. A vigorous growth of saltcedar along the bank of the Little Colorado River 

near Holbrook, Ariz. Reports indicate that this growth has taken place since about 1940.
74 PHREATOPHYTES

and water, and, when growing under natural conditions, sends its 

roots to the water table. No data are available on the use of ground 

water by T. aphylla, although it has generally been regarded as 

about the same as that by T. gallica.

Tamarix gallica (figs. 30-32), sometimes called French tamarisk 

but more commonly known as saltcedar, is an aggressive, naturalizing, and spreading shrub that is native from western Europe to 

the Himalaya Mountains. Since its introduction into this country, 

it has spread rapidly and has infested large areas of river bottom 

and low-lying ground in Arizona, southern California, New Mexico, 

and Texas. It is a prolific seeder. One small plant has been estimated 

to bear over 600,000 seeds (Bowser, 1957, p. 6), and the seeds, 

being light, are readily disseminated by the wind. The seeds germinate rapidly, and, once established, the plant grows rapidly, usually 

at the expense of other vegetation. An example of the speed and 

aggressiveness with which the plant spreads is furnished by the 

record of its infestation along the Pecos River between Santa Rosa, 

N. Mex., and the Texas State line. Records indicate that before 1912 

there were no saltcedars in the Pecos River basin. The first reports 

of a few seedlings were in 1912 in the McMillan Delta (Eakin and 

Brown, 1939, p. 11-18). These spread until, in 1915, they covered 

about 600 acres (National Resources Planning Board, 1942, p. 57). 

The plants continued to spread, not only in the delta but also up 

and down stream (fig. 31), so that in 1925 they covered 12,300 

acres and in 1939, 13,000 acres. In 1950, the Pecos River Commission, from an aerial survey, found that between the Alamogordo 

Reservoir and the New Mexico-Texas State line saltcedar covered 

a total of 31,820 acres, and by 1953, an estimated 36,270 acres 

(Pecos River Commission, 1955, p. 9-10). Nearly 5,000 acres at 

the head of Alamogordo Reservoir was not included in the 1953 

estimate, so that the total for the Pecos River Valley in New Mexico 

is about 41,000 acres. The average rate of spread, from 1912, when 

the first seedlings were observed, to 1953 was about 1,000 acres 

per year, but for the period 1950-53, excluding the area at the head 

of Alamogordo Reservoir, the average rate was about 1,500 acres 

per year. This is an increase of 50 percent in the rate of spread 

over the 41-year average. Such a rate of spread cannot continue 

indefinitely, for eventually a saturation point will be reached. It 

does, however, serve to show the aggressive nature of the plant. 

Perhaps even more significant is the increase in the area of dense 

saltcedar growth. In 1939, the area of dense growth was only 490 

acres, but in 1950 it amounted to more than 7,715 acres (Pecos 

River Commission, 1955, p. 10), an average increase of nearly 660 

acres per year.
EIGHT COMMON PHREATOPHYTES 75

Tamarix gallica* is without doubt the outstanding problem phreatophyte of the Southwest because of its aggressive nature and thirst 

for water. Use of ground water by this plant, at optimum volumedensity, is among the highest, if not the highest, of any of the 

phreatophytes. Data on the use of ground water are available from 

studies on the Pecos River in New Mexico and the Gila River in 

Arizona. At Carlsbad, N. Mex., the average use of water during the 

period January to December 1940 by saltcedar grown in tanks with 

a 2-foot water level was 5.48 feet, and with a 4-foot water level, 

4.68 feet (Blaney and others, 1942, p. 202).

The estimate of average annual use of water by saltcedar in the 

Carlsbad area of the Pecos River Valley, N. Mex., was 6.0 feet, 

including an average annual precipitation of 1.0 foot (Natl. Res. 

Plan. Board, 1942, p. 55).

Intensive studies on the use of water by saltcedar in the Safford 

Valley of the Gila River, Ariz., during 1943 and 1944 gave the 

following results:

From tank experiments at 100-percent volume-density, not including precipitation (Gatewood and others, 1950, p. 137) :

Average depth

Use, to water level, 

in feet in feet

9.17 __________________ 4.0

8.42 _____________ 5.0

7.75 _._________-__- 6.0

7.33 ___________ 7.0

7(?) ..__.__._...........__.._.._ 8.0

Calculated from the diurnal fluctuations of water levels in wells 

located in thickets of saltcedar, the use of water was 6.03 feet at 

100 percent volume density, not including precipitation, based on the 

average of 8 wells whose water level ranged from 3.8 feet to 8.5 

feet below the land surface and averaged about 6.3 feet (Gatewood 

and others, 1950, p. 152-53).

Saltcedar is capable of sending its roots to considerable depth in 

search of water. Tamarisk roots (species unknown) penetrating to 

a depth of 30 meters (nearly 100 feet) were observed in excavations 

for the Suez Canal (Renner, 1915).

The uses of Tamarix gallica appear to be few. The wood is reported to make good fenceposts and the flowers are a source of 

honey. The plant is also high in tannins.

3 Early references to the widespread deciduous species of saltcedar list it as Tamarix 

gallica. Recently a question has arisen as to whether it is T. gallica or T. pentandra. Except 

for minute floral differences the two plants are similar. The original name T. gallica, is 

retained here.
76 PHREATOPHYTES

FINDING INDEX FOR COMMON NAMES

COMMON NAME SCIENTIFIC NAME

Alder _..........__.....-..._......................_... ................................... Alnus

Alfalfa ............................................................................................ Medicago sativa Linnaeus

Arrowweed ....._...._..............._............................................... Pluchea sericea Coville

Ash, Arizona .................................................._....._........ Fraxinus velutina Torrey

Ash, velvet ................................................................................. Fraxinus velutina Torrey

Aspen, quaking ......................_._....................._....... Populus tremuloides aurea Tidestrom

Aster, spiny ........................................................................... Aster spinosus Bentham

Athel tree .................................................................................. Tamarix aphylla Linnaeus

Baccharis, broom ................._........................................ Baccharis sarothroides A. Gray

Baccharis, emory .............................. ............................. Baccharis emoryi A. Gray

Baccharis, squaw ....................................................._........ Baccharis sergiloides A. Gray

Batamote .......................................................... .................... Baccharis glwtinosa Persoon

Bermuda grass _................................_................_....... Cynodon dactylon (Linnaeus) Persoon

Boxelder .............................. ..................................... .......... Acer negundo Linnaeus

Buffaloberry ........................................................................ Shepherdia

Burrobush .................................................................... . HymenocJea monogyra Torrey and Gray

Burrobush, white .............._..._...._..........._.__..._.._.... Hymenoclea salsola Torrey and Gray

Butternut ....................... ......................................... .......... Juglans micorcarpa Berlandier

Carrizo ... ............. .......... ......................................... Phragmites communis Trinius

Catclaw ........................................................................................ Acacia greggii A. Gray

Camelthorn . .... ............ ............... ...... ..................... Alhagi camelorum Fischer

Chamiso ....._................................................................................ Atriplex canescens (Pursh) Nuttall

Chamiza ................................................................................... Atriplex canescens (Pursh) Nuttall

Cinquefoil, bush or shrubby ................................... Dasiphora fruticosa Linnaeus

Cottonwood ....__............................_...................................... Populus

Cumaru ...................................................................................... Celtis reticulata Torrey

Desertbroom ................. ................._._._._.___........... Baccharis sarothroides A. Gray

Desertrush ................................................................................. Juncus cooperi Engelmann

Desertwillow ............................................................................. Chilopsis linearis Sweet

Devilsclaw ...................._._...._...._......................................... Acacia greggii A. Gray

Elder .................................................................................................. Sambucus

Elderberry ........................................._..................................... Sambucus

Glasswort ................................................................................... Salicornia europaea Linnaeus

Do. ............................................. ........................................ rubra Linnaeus

Do. ............................................................................................ utahensis Tidestrom

Goldenrod, rayless ................... .................................. Aplopappus heterophyllus A. Gray

Greasewood, big ................................... ........................ Sarcobatus vermiculatus (Hook) Torrey

Hackberry ........................................................................... Celtis reticulata Torrey

Heliotrope ............................................................................... Heliotropium curassavicum Linnaeus

Inkweed __.._.........._......................................................... Suaeda torreyuna Watson

lodinebush .................... .............. ................................. Allenrolfea occide-ntalis (Watson) Kuntze

lodineweed ........................................................................... Suaeda torreyana Watson

Juniper, Rocky Mountain ....................................... Juniperus scopulorum

(locally "swampcedar")

Kom ................................................................................................ Celtis reticulata Torrey

Lenscale ..... ..............................................................._.............. Atriplex lentiformis (Torrey) Watson

Lovegrass, alkali ............................................................... Eragrostis obtusiflora (Fournier) Scribner

Mesquite _..._...._..._..........._................................................ Prosopis juliflora (Swartz)

Mesquite, honey ............... ........ .................................. Prosopis juliflora (Swartz)

Mesquite, screwbean ..._........_...._................................ Prosopis pubescens Bentham

Mesquite, velvet ............... .............................................._ Prosopis velutina Wooton

Mulefat ................................... .................................................... Baccharis viminea Crandolle

Nogal ................................................................................................ Juglans microcarpa Berlandier

Oak, California live ............................................_........ Quercus agrifolia Nee

Oak, Roble ................................................................................. Quercus lobata Nee

Palo verde, blue ___................_..........____ Cercidium floridum Bentham

Palm, California .........................................._......__ Washingtonia filifera Wendland

Palm, fan _...___________________ Wttshingtonia fUifera Wendland
FINDING INDEX FOR COMMON NAMES 77

COMMON NAME SCIENTIFIC NAME

Pickleweed ................................................................................ Allenrolfea occidentalis (S. Watson) Kuntze

Purslane, lowland ........ ................................................... Sesuvium portulocostrum

Pusley, Chinese .............................................._.................... Heliotropium curvassavicum Linnaeus

Quailbrush ....................................................................... Atriplex lentiformis (Torrey) Watson

Rabbitbrush .................. . . .................................................. Chrysothamnus pumilus (Nuttall)

Rabbitbrush, rubber ...._........................____.. Chrysothamnus nauseosus

Do. .......................................................................................... nauseosua var. consimilis (G'reene)

Do. ........................................................... .......................... var. graveolens (Nuttall)

Do. ............................................................................................. var. mohavensis (Greene)

Do. .............................................................. ......................... var. oreophttus (A. Nelson)

Do. ............................................................................................ var. viridulus

Reed .................................................................................................. Phragmites communis Trinius

Reedgrass, giant ....._.......................................................... Phragmites communis Trinius

Rosinbrush ................................................................................ Baccharis sarothroides A. Gray

Sacaton .......................................................................__....... Sporobolus wrightii Munro

Sacaton, alkali ....................................................................... Sporobolus airoides Torrey

Saltbush, four-wing ................... ............................ Atriplex canescens (Pursh) Nuttall

Saltbush, Nevada .................................................................. Atriplex lentiformis (Torrey) Watson

Saltcedar ................... ..................................................... Tamarix gallica Linnaeus

Saltgrass ..................................................................................... Distichlis stricta (Torrey) Rydberg

Saltgrass, Mexican ......................................................... Eragrostis obtusiflora (Fournier) Scribner

Saltgrass, desert .............. ....................................... Distichlis stricta (Torrey) Rydberg

Saltgrass, seashore .......................................................... Distichlis spicata (Linnaeus) Greene

Saltwort ......................................................................................... Suaeda depressa Watson

Sea-purslane .............................................................................. Sesuvium verrucosum Rafinesque

Seepweed ....................................................................................... Suaeda depressa Watson

Seepweed, desert ..._.... ......_...._...__..... .....___..... Suaeda suffrutescens Watson

Seepweed, torrey ............................................................ Swaeda torreyana Watson

Seep willow ............................................................................. Baccharis glutinosa Persoon

Sequoia, giant or big tree .................................... Sequoia gigantea (Lindley)

Sesuvium, warty ................................................................. Sesuvium verrucosum Rafinesque

Smoketree ......_____..._................_.................................. Dalea spinosa A. Gray

Smokethorn ....__............................................................... Dalea spinosa A. Gray

Sprangletop ...................................................................... Leptochloa fascicularis (Lamarck) A. Gray

Spruce, Engelmann ..................................................... Picea engelmanni Parry

Swampcedar ....................................... .................................. See Juniper, Rocky Mountain

Sycamore, Arizona ..................................._....._._...... Platanus wrightii Watson

Tamarisk, French ............................................................... Tamarix gallica Linnaeus

Tornillo ___............................................................................. Prosopis pubescens Bentham

Una de gato ........................._.............................................. Acacia greggii A. Gray

Vanadium bush .......................................................... Cowania stansburiana Torrey

Vetch, sweet .......................................................................... Hedysarum boreale Nuttall

Walnut ...................................................................................... Juglans microcarpa Berlandier

Watermotie .............................. ........... .................. Baccharis glutinosa Persoon

Waterwillow ......................._.................................................. Baccharis glutinosa Persoon

Waterweed .................................................................. ... Baccharis sergiloides A. Gray

Wildrye, creeping ............................................................. Elymus triticoides Buckley

Wildrye, giant ..................... . ....................... .. ......... Elymus condensatus Presl

Willow ......____.................................................... ....... .... Salix

Wiregrass ..................................... .................................... Juncus balticus Willdenow

Wirerush ............................................................ . .................. Juncus balticus Willdenow

Yerba mansa ...................... .......................... Anemopsis californica (Nuttall) Hooker and Arnott
78 PHREATOPHYTES

REFERENCES

Barrett, W. C., and Milligan, C. H., 1953, Consumptive water use and requirements in the Colorado Kiver area of Utah: Agri. Expt. Sta., Utah 

State Agri. College, Special Eep. 8, 28 p.

Benson, L., and Barrow, R. A., 1954, The trees and shrubs of the southwestern deserts: Ariz. Univ. Press and N. Mex. Univ. Press, 437 p.

Bidwell, G. L., and Wooton, E. O., 1925, Saltbushes and their allies in the 

United States: U. S. Dept. Agriculture Bull. 1345, 40 p.

Blaney, H. F., 1952, Determining evapotranspiration by phreatophytes from 

climatological data: Am. Geophys. Union Trans. v. 33, no. 1, p. 61-68.

Blaney, H. F., and Criddle, W. D., 1949, Consumptive use of water in the 

irrigated areas of the Upper Colorado River Basin (Provisional): U. S. 

Dept. Agriculture, Soil Conserv. Service, 49 p.

Blaney, H. F., and Ewing, P. A., 1946, Irrigation practices and consumptive 

use of water in Salinas Valley, Calif.: U. S. Dept. Agriculture, Soil 

Conserv. Service, Div. Irrig. and Water Conserv., 80 p.

Blaney, H. F., Ewing, P. A., Israelsen, O. W., and others; 1938; Part III 

water utilization, in Natl. Res. Comm., Regional Plan., Pt. VI Upper 

Rio Grande, p. 293-427.

Blaney, H. F., Morin, K. V., and Criddle, W. D., 1942; Consumptive water 

use and requirements the Pecos River joint investigation reports of the 

participating agencies: Nat. Res. Plan. Board, p. 170-230.

Blaney, H. F. and Stockwell, Homer, 1941, Irrigation investigations, San 

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80 PHREATOPHYTES

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REFERENCES 81

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82 PHREATOPHYTES

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INDEX

Page 

Acknowledgments ........................................ 2

Alfalfa, summary of information ............ 59-61

Allenrolfea occidentalis pickleweed ........ 49-52

Bigwoods Experimental Forest, N. C. .... 6 

Bowser, C. W., quoted ....................... ...... 70

Carlsbad, N. Mex. ................................ 18, 19, 58

Chrysothamnus rabbitbrush .................... 53-55

Climate, as factor affecting

phreatophytes .................... 14, 17-22

Common names, phreatophytes,

finding index ........................ 76-77

Cottonwood, scientific names .................... 61

summary of information .................... 61-64

Coweeta Experimental Forest, N. C. .... 7

Death Valley, Calif........................................ 52

Density of growth, as factor affecting

use of ground water.............. 22-23

Distichlis saltgrass .................................... 56-59

Economic use, alfalfa ................................ 59

cottonwood ..........................................;. 64

greasewood .............................................. 69

rabbitbrush ............................................ 55

saltcedar .................................................. 75

saltgrass .................................................. 56

willow ...................................................... 66

Escalante Valley, Utah ................ 18, 19, 26, 53,

58, 61, 64, 69

Evapotranspiration, relation to

temperature ............................ 18, 19

relation to water table ........................ 18

Floods, relation of phreatophytes ............ 28-30

Gila River, flow, Safford Valley, Ariz.... 5

Gila River Valley ................................ 28, 72, 75

Glenbar, Ariz., Experiment Station ........ 20-21

Greasewood, analysis of plant tissue.... 69

area, analysis of soil ........................ 69

in Great Basin . .............. 66

summary of information .................... 66-69

Great Basin ...................................... 16, 53, 55, 56

Green River, evapotranspiration losses.... 6

Ground water, chemical analysis in

area of pickleweed growth 52 

consumptive use ................................... 24

consumptive waste .............................. 24-25

depth, as factor affecting

phyreatophytes .............. 14-15,

22, 32-40

Ground water Continued

fluctuations in level, Safford

Valley, Ariz .................... 4

quality, as factor affecting

phreatophytes ................ 15-16

23-24, 32-40 

salvage ................ .... . . 24-26

use by phreatophytes ..........3-7, 12, 32-40,

57-59, 60, 62, 64, 66, 69, 75

Humidity, effect on use of ground water 17, 19 

Hydrologic cycle ............................................ 10-12

Information on phreatophytes, status .... 26-27 

Isleta, N. Mex.....-.-....--....-.--.---- 18, 58, 64

Lake McMillan, N. Mex. ..................... 28, 29

Linwood, Utah, gaging station.. 6 

Los Griegos, N. Mex............................ 18, 57, 58

Malad Valley, Idaho ....................... 49, 51, 68

Medicago alfalfa ........................................ 59-61

Meinzer, O. E. quoted ................................ 9

Mesilla Dam, N. Mex ................................ 18, 58

North River, Md., effect of transpiration 7

Ouray, Utah, gaging station ...................... 6

Owens Valley, Calif ............................ 18, 57-59

Phreatophytes, common names,

finding index 76-77

definition . 9

economic value .............. 8, 27, 55, 56, 64,

66, 69, 75 

effect on stream flow . .... 4-7

factors affecting occurrence ............ 13-16

factor affecting use of

ground water ................ 16-24

in Western United States ................ 30-40

occurrence 32-40

plants classified ............................. . 12-13

relation to ground water ........ 14-15, 32-40,

56, 62, 68

root system 14-15, 55, 56, 60, 66, 68 

salt tolerance .................... 15-16, 32-40

49, 56, 60, 68, 70 

use of ground water ............ 3-7, 12, 18, 19,

22, 32-40, 57-59,

60, 62, 64, 66, 69, 75

Pickleweed, analysis of plant tissue ........ 51

area, analysis of ground water ........ 52

analyses of soil samples ............ 51

summary of information .................... 49-52

83
84 INDEX

Page 

Piemeisel, R. L., quoted .... ~~ ............. 68

Pontiac area, Michigan ............................ 8

Populus cottonwood ............. .................. 61-64

Rabbitbrush, summary of information.... 53-55

Rainfall, effect on use of ground

water by phreatophytes ....... 19- 21

References ...................................................... 78-82

Safford Valley, Ariz., fluctuations of

water table ............................ 4, 17

variation of streamflow .................... 5

Salix willow ................................................ 64-66

Saltcedar, rapid spread ............................ 74

relation to floods .................................. 28

relation to sedimentation .................. 28, 29

summary of information .................... 70-75

transpiration ........................................ 5

Saltgrass, grown in tanks,

evapotranspiration .......... 18, 57, 58

summary of information .................... 56-59

Page 

Salt tolerance, alfalfa ................................ 60

greasewood .............................................. 68

pickleweed .............................................. 49

saltgrass ................................ . . .... 56

San Luis Valley, Colo .................... 18, 19, 55, 5f

Santa Ana, Calif ............................18, 58, 59, 64

Sarcobatus greasewood .............................. 66-69

Sedimentation, relation of phreatophytea 28-30 

Shantz, H. L., quoted ................................ 6?

Tamarix saltcedar .................................... 70-75

Temperature, effect on use of

ground water ........................ 17-lf

Tularosa Basin, N. Mex ............................ 49, 51

Vernal, Utah ................................................ 58, 6C

White, W. N., quoted ................................ 19, 58-

Willow, summary of information ............ 64-66

Xerophyte, definition .................................. S

 &U. S. GOVERNMENT PRINTING OFFICE: 1958 428383