Aridity and man;

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Material Information

Title:
Aridity and man; the challenge of the arid lands in the United States
Series Title:
American Association for the Advancement of Science Publication
Physical Description:
xx, 584 p. : illus., maps ; 24 cm.
Language:
English
Creator:
American Association for the Advancement of Science -- Committee on Desert and Arid Zones Research
Hodge, Carle
Publisher:
American Association for the Advancement of Science
Place of Publication:
Washington
Publication Date:

Subjects

Subjects / Keywords:
Arid regions -- Congresses -- United States   ( lcsh )
Desert Climate   ( mesh )
Ecology   ( mesh )
Water Supply   ( mesh )
Régions arides -- Congrès   ( rvm )
Genre:
bibliography   ( marcgt )
conference publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographies.
Statement of Responsibility:
Carle Hodge, editor; Peter C. Duisberg, associate editor.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
oclc - 00490237
lccn - 63022003
ocm00490237
sobekcm - AA00004326_00001
Classification:
lcc - GB614 .A5 1963
ddc - 333.73
nlm - GB 614 A512a 1963
System ID:
AA00004326:00001

Full Text






ARID REGIONS of the UNITED STATES


0 100 200 ?:*** les
200 400 KoI Ie
0 200 400 Kilometers


I-] Extremely arid

Arid

S| Semiarid

SHumid or subhumid


PUERTO RICO
S 50 Km.
I I


























V 4-

S .. -S a .
r- .,, .i ._ ., .- .r- .-


-. -. .
,--'-"


i ...


Tumbling Russian thistles (Salsola hali) have piled up against this lonely barbed-
wire fence near Winslow in northern Arizona. Behind the fence, the once rich
rangeland now is overgrazed and badly wind eroded. The annual mean precipitation
at Winslow, elevation 4850 feet (1478 meters) is a fraction more than 8 inches (200
millimeters). The Hopi Indians, whose reservation is nearby, call the troublesome
Salsola, "the white man's plant." (Courtesy Robert R. Humphrey, University of
Arizona)







Compiled by the Committee on
Desert and Arid Zones Research of the
American Association for the Advancement of Science


Cartography by ALBERT W. SMITH














CARLE HODGE, Editor
PETER C. DUISBERG, Associate Editor




ARIDITY and MAN


The Challenge of the Arid Lands in the United States


Publication No. 74
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE
WASHINGTON, D.C. 1963


































Copyright @ 1963, by the

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE



Second printing, 1965



Library of Congress Catalog Card Number 63-22003



























Printed in the United States of America
The Horn-Shafer Company
Baltimore, Maryland














Foreword


A seed was planted in the arid southwestern soil at El Paso, Texas,
in 1951: a symposium on the "Potentialities of Desert and Arid
Lands," which was held during the annual meeting of the South-
western and Rocky Mountain Division of the American Association
for the Advancement of Science, in session that year at Texas
Western College. At that time, renewed interest in arid-lands re-
search was spreading around the world, and particularly in the
places where water, always a limiting factor, has become a resource
that is especially imperiled by the burgeoning of population. Less
than a year earlier, the United Nations Educational, Scientific, and
Cultural Organization (UNESCO) had formed its Advisory Com-
mittee on Arid Zone Research.
The El Paso program was a direct response to this interest,
and from the symposium grew the division's Committee on Desert
and Arid Zones Research (CODAZR). As Terah L. Smiley, the
present committee chairman, has pointed out, the group was "for-
tunate in having been created prior to the last 10 years, which have
seen unprecedented population growth in the Southwest. It is
probably the only group to have had such an opportunity to ob-
serve closely the beginnings of the arid-lands technologic develop-
ment from the point of view of actual residents as well as scientists."
With the cooperation of the national AAAS, UNESCO, and other
organizations, the committee conceived and helped to carry through
the historic interdisciplinary international meetings on the future
of arid lands, held in 1955 in Albuquerque and Socorro, New
Mexico. Six regional and two national symposiums also have been
arranged since then by the committee. When UNESCO began to
plan the first conference devoted to research on the Latin American
arid lands, in Buenos Aires in September 1963, CODAZR was asked
to serve as the conference coordinating unit in the United States and
was expanded into a national committee for this purpose.







FOREWORD


One contribution that CODAZR chose to make to the conference
in Argentina was a book that, hopefully, would sum up the United
States experience in the arid lands. Aridity and Man is the result.
The aim was to produce an interdisciplinary volume that would
be of value, not only to researchers, but also to scientific administra-
tors and governmental leaders. It was impossible, therefore, to con-
sider any single subject as thoroughly as we would have liked to do.
Both the English system and the metric system of weights and meas-
ures have been used in an effort to facilitate translation and, at the
same time, make the publication widely comprehensible. For the
same reasons, the scientific names of many plants and animals have
been inserted in parentheses after the common names.
In order to have the Spanish copies available for the Buenos Aires
meeting, it was necessary that the volume be planned, written,
edited, translated, and printed in Spanish within a year. This was
made possible by financial support from the Agency for Interna-
tional Development and a grant (NSF-G25199) from the National
Science Foundation.
Obviously, this could not have been accomplished without the
tremendous team effort that made the project unusual. Aridity and
Man is the product of 74 scientists in 14 states and the District
of Columbia, most of them writing under the handicap of a severe
deadline. In one way or another, the assistance of many other people
was needed. Regrettably, not all of them can be singled out for
proper credit.
However, CODAZR is especially indebted to President Richard A.
Harvill, of the University of Arizona, for making editorial office
space and other facilities available at his institution. I wish to ex-
press my personal gratitude to William R. Mathews, editor and pub-
lisher of The Arizona Daily Star, for granting the leave of absence
that allowed me to devote full time to this book.
Although their names do not appear in the table of contents,
the contributions of several other persons were essential. At least
once a day for more than a year, Smiley found himself heavily in-
volved in the problems of the publication. The efforts on its behalf
by Dael Wolfle, executive officer of the AAAS, were considerably
beyond the call of duty.
In the Department of Geography at the University of Colorado,








FOREWORD Vii

a team of cartographers directed by Albert W. Smith worked tire-
lessly to complete the maps and charts on schedule.
Finally, there were two workers without whose wise and skilled
assistance Aridity and Man probably would not have met its dead-
line. They were Charlotte Meeting Phillips, general editor of the
AAAS symposium volumes, and Eileen B. Ferguson, whose value
to the project strongly belied her modest title of editorial secretary.

CARLE HODGE
Tucson, Arizona
July 1963


















Preface


Lands of Little Water




"The soil is very fertile for maize, cotton, and for everything sown
in it, as it is a temperate land. The natives cultivate sandy places
without difficulty because they carefully guard the moisture from
the snow.
"At this place this river is surrounded by an abundance of grape-
vines, many walnut and other trees All this land is rather
warm than cold We saw plants of natural flax similar to that
of Spain and numerous prickly pears."*
These are words that could have been written any place, any time
in an arid land. They are, in fact, the words of Diego Perez de
LuxAn in his journal concerning the expedition into New Mexico
led by Antonio de Espejo in 1582. There is nothing very remarkable
about what Luxin wrote except perhaps the timelessness of the prob-
lem he recognized.
Again and again in the writings of explorers visiting for the first
time peoples who have accommodated themselves to aridity, there
appears the key idea that they have used with care the limited water
supply. We in the machine age, so proud of what we call progress,
either have yet to learn this lesson or, step by step and mistake by
mistake, have to relearn what our ancient forebears once knew.
The distinguished naturalist, Joseph Wood Krutch, in his percep-


D. Perez de Luxan, Expedition into New Mexico Made by Antonio de Espejo,
1582-1583, as Revealed in the Journal of Diego Perez de Luxdn, a Member of the Party,
G. P. Hammond and A. Rey, Translators (The Quivira Society, Los Angeles, Calif.,
1929), pp. 100 and 106.







PREFACE


tive book, The Voice of the Desert, said that the biota of an arid
land has three principal ways of meeting the water problem: by
economizing, by storing, and by lying low. As he points out, the
kangaroo rat (Dipodomys spp.) has even one more: it makes its own.
With all these teachers before us, including the kangaroo rat, modern
man is not yet studying the lessons with diligence. Indeed, the primi-
tive cultures are teachers. In very practical terms, early man learned
through eons of evolution. The native biota of an arid country can
teach, for those who will learn to read, by what it has written on the
landscape. With the tools of the ecologic and physiologic sciences
available to us now, we should be able to read far more easily those
lessons of the native biota than did our primitive forebears, but still
we will not read.
Of the possibilities that Krutch learned from the plants and ani-
mals, modern civilization appears to know only storage. Storage to
us has come to mean only surface storage in reservoirs, the engineer-
ing aspects of which we have developed to a high degree. But the
more subtle ways of handling the water problem seem, for the most
part, to be beyond us.
The second little sermon that is implied in Luxan's journal of
1582 is contained in the words, "similar to that of Spain." In addi-
tion to the arid lands of the southwestern United States, I have seen
the arid plains of Mancha in New Castile, the Golodnaya Steppe of
Uzbekistan, the dry hills of Peloponnesus, and the rocky crags of
Baluchistan. I know, therefore, that I have seen in principle Chile,
Libya, the Fertile Crescent, and many others. The characteristics
displayed in one will be found, with minor variation, in the other
arid lands of the world. This means, then, that the peoples in the
arid zones, all over the world, have learned to make the kinds of
adjustments that we in the United States at least are still trying to
make, compatible with our particular type of civilization.
That some progress is being made, however, might be inferred
from the fact that a group of studious and dedicated men, who know
a variety of things about the problems of aridity, asked themselves
what they could bring from the United States as a useful contribu-
tion to the UNESCO symposium on arid-zones research in Latin
America in the fall of 1963. This book grew from their answer. In-
terestingly, the scientists judge that their best contribution might be
to analyze the American experience in developing the arid portion








LANDS OF LITTLE WATER


of this country, with particular emphasis on places where the United
States appears to have failed. There are, of course, successes to be
reported also, but these scientists put particular emphasis on the
places where we have failed to read well enough the lessons of our
native biota and of our progenitors. The fact that this group of ob-
servant men can see the failures of our society in itself means
progress.
This spirit of self-analysis and constructive criticism may not shine
clearly through a book that, perforce, had to be written by a group
of individuals rather than by a single author, but it certainly was the
spirit in which this volume first was conceived and planned. It is
the hope of the authors and of their interested colleagues that, being
a review of our experience in the United States in developing and
using our arid lands, others elsewhere in the world can profit by our
example.
There is one further idea that will not, because of the nature of
this volume, shine through as clearly as many of us would like to see
it. Perhaps in the present context this idea would not appropriately
be emphasized, but, being acquainted with most of the authors of
these separate chapters, I know that it is important in the thinking
of each one of them. Deserts, like all other natural habitats, have a
variety of unique living and inanimate forms. Their very unique-
ness makes them valuable. But the interrelationship between these
forms and their environments is, because of the nature of aridity,
poised in an even more delicate balance than that which character-
izes other physiographic and climatic types. Many of these unique
forms are as delicate as the equilibrium they maintain with the rest
of the physical world. They can easily be lost, destroyed, or over-
looked.
The unique parts of the physical world generally tend also to be
scarce, and, partly because they are scarce, they are both valueless
and invaluable. The development of resources that have potential
monetary value needs no urging and will generally proceed in keep-
ing with changes in the economic controls of supply and demand. But
the features of any land that are monetarily valueless and are es-
thetically invaluable will soon enough be pushed over by the bull-
dozer of civilization, unless prior steps have been taken to recog-
nize their worth and to protect them from either exploitation or
ruination.








xii PREFACE

In the many lands where people still must fight for the very neces-
sities of life, there is little room for protection of purely esthetic
values. But the time comes soon enough, with population expan-
sion, when some at least will look back and wish that thought had
been given to the protection of rare species, unique history, and
exceptional scenery. This lesson, particularly, is one that is mani-
festly applicable to the arid zones.
LUNA B. LEOPOLD














Contributors


ARDEN A. BALTENSPERGER, Professor of Agronomy and Agronomist
in the Agricultural Experiment Station, University of Arizona,
Tucson [cultivated crops]
GORDON L. BENDER, Professor of Zoology, Arizona State University,
Tempe [Chapter 11]
IVEN BENNETT, Chief, Desert and Tropical Section, Regional En-
vironments Branch, Earth Sciences Division, Quartermaster Re-
search and Engineering Center, U.S. Army, Natick, Massachusetts
insolationn]
ROSHAN B. BHAPPU, Metallurgist, New Mexico Bureau of Mines and
Mineral Resources, New Mexico Institute of Mining and Tech-
nology, Socorro [wet processing]
MILTON I. BLANC, Southwest Area Climatologist, Weather Bureau,
U.S. Department of Commerce, Tempe, Arizona [aridity causes]
THADIS W. Box, Associate Professor of Range Management, Texas
Technological College, Lubbock [range management]
MARX BROOK, Professor of Physics and Senior Physicist, New Mexico
Institute of Mining and Technology, Socorro [thunderstorms]
KAY R. BROWER, Associate Professor of Chemistry, New Mexico In-
stitute of Mining and Technology, Socorro [solar energy]
RUSSELL H. BROWN, Hydraulic Engineer (Research), Water Re-
sources Division, Geological Survey, U.S. Department of the In-
terior, Phoenix, Arizona [Chapter 6]
HELEN L. CANNON, Geochemist, Branch of Geochemical Census,
Geological Survey, U.S. Department of the Interior, Denver,
Colorado [botanical prospecting]
IRA G. CLARK, Professor of History, New Mexico State University,
University Park [Chapter 4]


The subject of each person's contribution is given in square brackets at the end of
the entry.







XIV CONTRIBUTORS

MARION CLAWSON, Director, Land Use and Management Program,
Resources for the Future, Inc., Washington, D.C. [Chapter 15]
BRUCE F. CURTIS, Professor of Geology and Chairman of the Depart-
ment, University of Colorado, Boulder [petroleum; wind energy]
ARTHUR V. DODD, Meteorologist, Earth Sciences Division, Quarter-
master Research and Engineering Center, U.S. Army, Natick,
Massachusetts [Yuma microclimates]
EDWARD J. DORTIGNAC, Chief, Branch of Water Resource Manage-
ment, Division of Watershed Management, Forest Service, U.S.
Department of Agriculture, Washington, D.C. [Rio Puerco]
HAROLD E. DREGNE, Professor of Soils, New Mexico State University,
University Park [Chapter 8]
PETER C. DUISBERG, Arid Lands Consultant, El Paso, Texas [asso-
ciate editor; Chapter 16]
PAUL C. EKERN, Soil Physicist, Pineapple Research Institute of Ha-
waii, Honolulu [dew; fog drip; microclimate modification]
ALLEN F. FLANDERS, Hydrologic Services Division, Weather Bureau,
U.S. Department of Commerce, Washington, D.C. [flash-flood
warning]
JOEL E. FLETCHER, Research Investigations Leader, Watershed En-
gineering, Soil and Water Conservation Research Division, Agri-
cultural Research Service, U.S. Department of Agriculture, Boise,
Idaho [Chapter 10]
MAURICE C. FUERSTENAU, Associate Metallurgist, New Mexico Bu-
reau of Mines and Mineral Resources, New Mexico Institute of
Mining and Technology, Socorro [wet processing]
J. L. GARDNER, Botanist, Agricultural Research Service, U.S. De-
partment of Agriculture, Tucson, Arizona [Chapter 9]
MORRIS E. GARNSEY, Professor of Economics and Chairman of the
Department, University of Colorado, Boulder [Chapter 13]
HOWARD S. GENTRY, Botanist, New Crops Research Branch, Agri-
cultural Research Service, U.S. Department of Agriculture, Belts-
ville, Maryland [new plant uses]
NORRIS W. GILBERT, Research Agronomist, Crops Research Division,
Agricultural Research Service, U.S. Department of Agriculture,
Mesa, Arizona [canaigre]
WARREN A. HALL, Associate Professor of Engineering and Director
of the Water Resources Center (Statewide), University of Cali-
fornia, Los Angeles [Los Angeles]







CONTRIBUTORS


STAFFORD C. HAPP, Chief, Production Services Branch, Production
Evaluation Division, U.S. Atomic Energy Commission, Grand
Junction, Colorado [uranium]
JOHN W. HARSHBARGER, Professor of Geology and Head of the De-
partment, University of Arizona, Tucson [Chapter 6]
JOHN HAY, Retired Water Engineer, Tucson, Arizona [upper Rio
Grande]
DAVID M. HERSHFIELD, Research Meteorologist, Hydrograph Labora-
tory, Soil and Water Conservation Research Division, Agricultural
Research Service, U.S. Department of Agriculture, Beltsville,
Maryland [precipitation]
LESLIE HEWES, Professor of Geography and Chairman of the Depart-
ment, University of Nebraska, Lincoln [short-grass Plains]
CARLE HODGE, Editor, Arid Lands Research Newsletter (CODAZR);
and Science Editor, The Arizona Daily Star [editor; Chapter 1]
HAROLD A. HOFFMEISTER, Professor of Geography, University of
Colorado, Boulder [Rocky Mountain and Sacramento Mountain
region]
FRANK E. HOUGHTON, State Climatologist, Weather Bureau, U.S.
Department of Commerce, Albuquerque, New Mexico [Weather
Bureau records and research]
LYMAN C. HUFF, Geochemist, Branch of Geochemical Exploration,
Geological Survey, U.S. Department of the Interior, Denver Colo-
rado geochemicall exploration]
EDGAR A. IMHOFF, Resources Planner, State Planning Office, State
of New Mexico, Santa Fe [Embudo]
QUENTIN A. JONES, Botanist, New Crops Research Branch, Crops
Research Division, Agricultural Research Service, U.S. Depart-
ment of Agriculture, Beltsville, Maryland [new plant uses]
PAUL R. JULIAN, High Altitude Observatory, Boulder, Colorado
[long-range prediction]
HAROLD M. KAUTZ, Head, Engineering and Watershed Planning
Unit, Soil Conservation Service, U.S. Department of Agriculture,
Upper Darby, Pennsylvania [Sandstone Creek]
FRANK E. KOTTLOWSKI, Economic Geologist, New Mexico Bureau of
Mines and Mineral Resources, New Mexico Institute of Mining
and Technology, Socorro [coal; saline deposits]
CARL F. KRAENZEL, Professor of Rural Sociology, Montana State
College, Bozeman [Great Plains]







CONTRIBUTORS


FRITZ L. KRAMER, Associate Professor of Geography and Director of
the College Museum, Colorado College, Colorado Springs [sage-
brush zone]
C. W. LAURITZEN, Project Supervisor, Agricultural Research Service,
U.S. Department of Agriculture, Logan, Utah [irrigation]
DOUGLAS H. K. LEE, Chief, Occupational Health Research and
Training Facility, Public Health Service, U.S. Department of
Health, Education and Welfare, Cincinnati, Ohio [Chapter 12]
LUNA B. LEOPOLD, Chief Hydraulic Engineer, Geological Survey,
U.S. Department of the Interior, Washington, D.C. [Preface]
RICHARD F. LOGAN, Professor of Geography, University of California,
Los Angeles [Pacific valleys; creosotebush zone]
JAMES A. MCCLEARY, Professor of Botany, Orange State College,
Fullerton, California [native plants]
ANDREW L. MCCOMB, Professor of Watershed Management, Head of
the Department, and Watershed Specialist in the Agricultural Ex-
periment Station, University of Arizona, Tucson [Chapter 10]
RALPH M. MCGEHEE, Associate Professor of Mathematics and Re-
search Mathematician, Research and Development Division, New
Mexico Institute of Mining and Technology, Socorro [Chapter 5]
WILLIAM G. MCGINNIES, Professor of Dendrochronology and Direc-
tor of the Laboratory of Tree-Ring Research, University of Ari-
zona, Tucson [Chapter 10; dendrochronology]
JAMES R. MCNITT, Assistant Mining Geologist, Division of Mines
and Geology, The Resources Agency of California, Department of
Conservation, San Francisco [geothermal energy]
DONALD D. MACPHAIL, Associate Professor of Geography and Chair-
man of the Department, University of Colorado, Boulder [Chap-
ter 2]
DEAN E. MANN, Senior Staff, The Brookings Institution, Washington,
D.C. [Chapter 14]
PAUL S. MARTIN, Associate Professor of Geochronology, University
of Arizona, Tucson [palynology]
PEVERIL MEIGS, Chiet, Earth Sciences Division, Quartermaster Re-
search and Engineering Center, U.S. Army, Natick, Massachusetts
[arid United States climates]
DAVID MITCHELL, Professor of Metallurgical and Mining Engineer-
ing, New Mexico Institute of Mining and Technology, Socorro
[dry processing]







CONTRIBUTORS


J. MURRAY MITCHELL, JR., Investigations Branch, Climatology,
Weather Bureau, U.S. Department of Commerce, Washington,
D.C. [microclimatology; prediction techniques]
GALE MONSON, Assistant Chief, Section of Public Use, Branch of
Wildlife Refuges, Bureau of Sport Fisheries and Wildlife, U.S.
Department of the Interior, Washington, D.C. [game research]
JEROME NAMIAS, Chief, Extended Forecast Branch, Weather Bu-
reau, U.S. Department of Commerce, Washington, D.C. [long-
range prediction]
TOR J. NORDENSON, Hydrologic Services Division, Weather Bureau,
U.S. Department of Commerce, Washington, D.C. [flash-flood
warning]
JOHN R. RITER, Chief Development Engineer, Bureau of Reclama-
tion, U.S. Department of the Interior, Denver, Colorado [water
power]
CARL B. ROUBICEK, Professor of Animal Science and Animal Scien-
tist in the Agricultural Experiment Station, University of Arizona,
Tucson [acclimatization of livestock]
JOSEPH A. SCHUFLE, Professor of Chemistry, New Mexico Institute
of Mining and Technology, Socorro [Chapter 7]
WILLIAM D. SELLERS, Professor of Meteorology and Associate Meteor-
ologist, Institute of Atmospheric Physics, University of Arizona,
Tucson [Arizona climatology]
HERBERT E. SKIBITZKE, Research Mathematician, Water Resources
Division, Geological Survey, U.S. Department of the Interior, and
Lecturer in Hydrology, University of Arizona, Tucson [Chap-
ter 6]
TERAH L. SMILEY, Professor of Geochronology and Director of the
Geochronology Laboratories, University of Arizona, Tucson
[chairman of editorial board]
ALBERT W. SMITH, Associate Professor of Geography, University of
Colorado, Boulder [cartography]
EDWARD C. STONE, Associate Professor of Forestry, University of
California, Berkeley [dew]
JOHN M. STREET, Assistant Professor of Geography, University of
Hawaii, Honolulu [tropical arid lands]
HAROLD E. THOMAS, Geologist, Ground Water Branch, Geological
Survey, U.S. Department of the Interior, Menlo Park, California
[Central Valley]








Xviii CONTRIBUTORS

ROBERT H. WEBER, Economic Geologist, New Mexico Bureau of
Mines and Mineral Resources, New Mexico Institute of Mining
and Technology, Socorro [miscellaneous minerals]
ANDREW W. WILSON, Professor of Geography and Area Development,
University of Arizona, Tucson [Tucson]
NATHANIEL WOLLMAN, Professor of Economics and Chairman of the
Department, University of New Mexico, Albuquerque [Chap-
ter 13]
RICHARD B. WOODBURY, Associate Professor of Anthropology, Uni-
versity of Arizona, Tucson [Chapter 3]












Contents


FOREWORD V

PREFACE: Lands of Little Water, by Luna B. Leopold ix

CONTRIBUTORS xiii

CHAPTER
1 Aridity and Man: An Interpretive Summary, by Carle
Hodge 1
2 Regional Setting, by Donald D. MacPhail 21
3 Indian Adaptations to Arid Environments, by Richard
B. Woodbury 55
4 Historical Framework, by Ira G. Clark 87
5 Weather: Complex Causes of Aridity, by Ralph M.
McGehee 117
6 Water and Its Use, by Herbert E. Skibitzke, Russell H.
Brown, and John W. Harshbarger 145
7 Minerals and Energy Sources in the Arid West, by
Joseph A. Schufle 173
8 Soils of the Arid West, by Harold E. Dregne 215
9 Aridity and Agriculture, by J. L. Gardner 239
10 Role of Watersheds and Forests in the Arid West, by
William G. McGinnies, Andrew L. McComb,
and Joel E. Fletcher 277
11 Native Animals and Plants as Resources, by Gordon
L. Bender 309








XX CONTENTS

CHAPTER

12 Human Factors in Desert Development, by Douglas
H. K. Lee 339

13 Economic Development of Arid Regions, by Morris E.
Garnsey and Nathaniel Wollman 369

14 Political and Social Institutions in Arid Regions, by
Dean E. Mann 397

15 Critical Review of Man's History in Arid Regions, by
Marion Clawson 429

16 Challenge of the Future, by Peter C. Duisberg 461

CASE HISTORY

1 Tucson: A Problem in Uses of Water, by Andrew W.
Wilson 483

2 Upper Rio Grande: Embattled River, by John Hay 491

3 Embudo: Rise and Decline of a Program, by Edgar A.
Imhoff 499

4 Rio Puerco: Abused Basin, by Edward J. Dortignac 507

5 Los Angeles: Growing Pains of a Metropolis, by
Warren A. Hall 517

6 Central Valley: Water Use at Its Maximum, by Harold
E. Thomas 529

7 Great Plains: A Region Basically Vulnerable, by Carl
F. Kraenzel 539

8 Sandstone Creek: How a Watershed Was Saved, by
Harold M. Kautz 549

SELECTED BIBLIOGRAPHY 555

INDEX 561








1




Aridity and Man: An

Interpretive Summary



CARLE HODGE


During the 1950's, a research team visited an Arizona ranch
through which an intermittent river runs. The streambed, which is
dry except during summer seasons of rain, was densely thicketed
with saltcedar (Tamarix pentandra), a water-wasting plant con-
sidered by many range managers to be useless at best. The re-
searchers wanted to determine the extent to which water yield might
be enhanced by removing the growth, but the rancher was adamant.
"Those are the only trees within miles," he told the surprised
scientists. "Leave them alone."
The incident illustrates at least three social attitudes that are im-
portant to an understanding of the present-day civilization of the
arid and semiarid West of the United States. These attitudes are
toward resources, toward research findings, and toward the blind
transfer of customs acquired in a humid environment. The attitudes
toward resources are conditioned by time, place, and culture. For
example, mesquite trees (Prosopis spp.) are being systematically
eliminated from many rangelands, because they compete with grass.
Once, however, the mesquite represented a real resource to the pre-
historic Piman-speaking Indians, who relied on its beans for food, its
bark for basketry, and its wood for fires and housing.
For all his prescience, John Wesley Powell, one of the first ex-
plorers of the western United States, could not have foreseen eight
decades ago the potential of some western rivers as energy sources
for hydroelectric power, just as the possibilities of power from nu-
clear energy are not fully understood at present. But Powell still
personifies what man might have done in adapting to the dry lands.
He insisted, first in 1878, that the political institutions and farm-








ARIDITY AND MAN


ing methods of the humid regions-from which the nation grew on
the east coast-would have to be modified west of the 100th meridian.
He devoted much of his life to campaigning for this principle,
largely in vain.
It is only a little less true today that the scientists who are active
in the field have a perspective of arid-lands problems that goes be-
yond what the politicians and the populace in general are willing to
accept. This is the second factor symbolized by the Arizona rancher
and his precious saltcedars (Tamarix pentandra), and it explains,
in part, the third, and perhaps the most paradoxical, factor. In no
other segment of the United States was the population multiplying
more rapidly in the mid-20th century than in the semiarid and arid
areas, nor did the economic future appear more promising; yet, no-
where else in the nation were the realities of a harsh physical en-
vironment so little comprehended.
The main cause of this lack of comprehension was, and continues
to be, what Powell foresaw: the transfer westward of the customs
and attitudes of the humid East. Had the United States first been
colonized in California, and the pattern of settlement moved to the
east, such an outlook might not have evolved. As it was, the settlers
brought with them what Wallace Stegner has called "the agricultural
expectations of people reared in a country of adequate rainfall" (1) .

Duststorms and Droughts

The people simply refused to believe that periods of little or no
rainfall could last so long; but persist the droughts did. Some dra-
matic agricultural failures were a consequence. The most memo-
rable, partly because they took place at a time of economic crisis
everywhere, were those of the early 1930's on the semiarid Great
Plains. Winds stripped the topsoil from vast areas and carried it half-
way across the continent. In Pennsylvania, a professor of geology at
Bryn Mawr College was able to calculate the western dustfall on his
neighborhood by collecting the dust off his car, which, he reported,
"fortunately had just previously been thoroughly cleaned" (2).
Although major reforms in farming methods followed the great
duststorms on the Plains, human attitudes are not easily changed.
Twenty years later, Harvard University anthropologists studied a
group of Texas farmers who, forced from their homeland by the








AN INTERPRETIVE SUMMARY


drought of the 1930's, settled in New Mexico (3). The migrants be-
gan to raise there the same crop they had grown in Texas-beans-
and with equally disastrous results. A local joke defined a bean
farmer as "a man who is crazy enough to think he is going to make
it next year."
None of this is to say that man, by and large, has failed in the
West. He has irrigated the land, and he harvests rich products from
what once was raw desert, and nearby he erects sprawling, prosperous
cities. Much of his success, though, has been achieved at the expense
of irreplaceable resources. To some extent, the expectations of the
farmer have been transplanted to the city, where they are epitomized
by that mark of the tidy North American homeowner, the well-
watered lawn.
Bearing the brunt of the westward exodus of population are the
arid regions that are afflicted by a combination of water problems-
scarcity, sedimentation, and others (Fig. 1). A large number of the
most explosively growing western cities depend on underground
sources for municipal water, and many of these aquifers are being
pumped out more rapidly than they can be recharged naturally (4).
In 1959, an examination of the Tucson, Arizona, area led scien-







SCHEMIC
DISTRIBUTION SUPPLY and SEDIMENT








POLLUTION FLOODS VARIABILITY
Fig. 1. The maps delineate the regions where six major water problems
are the most likely to be found. Of the six, distribution of water is the
most widespread worry in the West, but water is the scarcest in areas,
such as the Southwest, where several of the problems overlap. (Courtesy
U.S. Geological Survey)







ARIDITY AND MAN


tists of the University of Arizona and the U.S. Geological Survey
to warn that the "local ground-water supplies will become depleted
unless measures are taken to replenish the storage" (5). Although
the study specifically suggested such measures, the city government
refused to contribute financially to further investigations.
The citizens of some western cities where the water future is pre-
carious pay no more for water than do those who live in humid re-
gions and, therefore, are not encouraged to use any less. The irony
of this "undervaluation of [an important] commodity" has been
pointed out by geographer Gilbert F. White, who explains that, "in
Chicago, with annual rainfall of 37 inches [940 millimeters] and a
tremendous source [of water] within a mile [1.61 kilometers] of
the shoreline, a middle-class family pays as much for its water as does
a similar family in Boulder, Colorado, with an annual rainfall of 17
inches [432 millimeters] and a glacier source 20 miles [32 kilo-
meters] away" (6, pp. 9-10).
White also refers to the irony of lawns in the oasis towns of the
West: "Generally, the owner applies much more water than a water-
budget analysis would show it [the lawn] needs. When in doubt
he applies a little more. This is because the owner either doesn't
know about or care about water-budgeting. He tends to use as
much water as he is entitled to, and, indeed, the local water depart-
ment hopes he will, so long as he doesn't exceed restrictions at times
of peak demands. He resents any increase in rates as an infringe-
ment upon his inherited rights, and he thinks the more he uses, the
less he should pay per gallon [liter]. An alternative would be to
have no lawn at all and to cultivate a patio and border vegetation
which gave him cooling relief with less water. He is slow to con-
sider this or any other way of dealing with his arid climate. The
house is unsuited to such a change because it was designed as
though for a Connecticut seacoast village. His midwestern tradition
tells him a neat lawn is a mark of respectable status. Moreover,
watering, in either the homely tug-of-war methods of yesteryear or
the missile-control-board method of tomorrow, has therapeutic value
after a trying day. Here is the water user who thinks more water is
the sure solution for a dry environment, consistently undervalues
his commodity, and is reluctant to consider any alternatives to his
heavy usage" (6, pp. 13-14) .
This anomaly of inexpensive, often wasted water in the arid areas







AN INTIRI'RETIVE SUM MARY


This Resettlement Administration photograph, now considered a classic
of the Dust Bowl days of the 1930's, shows an Oklahoma farmer and
his sons as they walked against a dust-laden wind on their once productive
cropland. (Courtesy Library of Congress)


can be carried a step further. As Table I indicates, westerners in
general also use more water, relatively, than do easterners. The
per-capita consumption of municipal water is twice as great in Ari-
zona, and 3 times as great in Nevada, as it is in Arkansas or Vermont.
Terah L. Smiley, a geochronologist, has summed up the over-all
problem: "We have learned that we can make the desert 'bloom,'
changing it from an unproductive wasteland to a subtropic paradise
by the application of water; but only now are we beginning to see
the extreme price that we must pay for this activity in regard to our
shrinking water supply.
"Few of us have actually learned to live in the desert; rather, we
have brought with us our practices, ideas, economy, even our total
lives from our former humid or subhumid climatic environments,
and we have attempted to adapt the area to these ideas and prac-
tices. We are living in 'air-conditioned' oases environments, and this
is costing us plenty in terms of resources" (7) .








ARIDITY AND MAN


Table I. Daily per-capita water use (in gallons) from municipal water
systems in 1954, by selected states.

State Water used State Water used

Western United States Eastern United States
Nevada 270 Michigan 213
Utah 223 New York 138
Arizona 170 Connecticut 137
New Mexico 150 Alabama 105
California 147 Arkansas 81

Total United States 147
a One gallon (U.S.) equals 3.785 liters; 2.64 gallons equals 1 dekaliter.
Source: U.S. Senate Select Committee on National Water Resources, Future Water
Requirements for Muincipal Use, Comm. Print 7 (Washington, D.C., 1960), p. 8.

Geography of the West

If one knew the West only from fiction, one might visualize it as
a treeless, limitless land of sand dunes and the bleached bones of
cattle. In reality, very little of the country fits this picture. About
one-third of the 48 contiguous states is either arid or semiarid; this
third reaches west from the 100th meridian, or toward the Pacific
Ocean from western Texas and the Great Plains states. But in ter-
rain, vegetation, and even in climate, it varies tremendously (see
Chapter 2) .
Westward from the Plains, the domain of the dry farmer and his
wheatfields, the tall grasses give way to shorter grasses and, eventually,
to desert. There are badlands laid bare by erosion and valleys turned
green by irrigation, and the relatively sparse population tends to
cluster in centers where water is available.
Big sagebrush (Artemisia tridentata) is the dominant vegetation
in the intermontane basins and plateaus, where winters can be cold
and the mean annual precipitation is likely to be between 6 and 20
inches (152 and 508 millimeters) In the hot lowlands of south-
eastern California, by contrast, creosotebush (Larrea divaricata) is
a prevalent plant, and several seasons may pass without rainfall.
High, humid "islands" of forested mountains are scattered over
much of the West, giving rise to its rivers, providing the region with
recreation and timber, and greatly affecting its weather.








AN INTERPRETIVE SUMMARY


Despite these subregional differences, the semiarid and arid areas
share at least one obvious environmental factor: a deficiency of mois-
ture. Precipitation on the prairies and deserts not only is scarce but
also, as Table II shows, is highly variable. "Average" years of rain-
fall mean little. According to a U.S. Geological Survey scientist,
Harold E. Thomas, precipitation in every part of the Southwest was
less than 85 percent of the record mean in at least 3 of the years
from 1942 to 1956, "and in some areas as much as 13 of those years."
He explains that "it is a general rule that dry years-when precipi-
tation is less than average-are more frequent than wet years. In
other words, the median rainfall-the amount that is exceeded in 50
percent of the years-is significantly less than the mean, or long-
term average" (8). Statistics, then, certainly do not bolster the stub-
born hope of homesteaders that "next year" may be better. The
chances are that next year, or any one year, will be dry.
Moreover, the rate of evapotranspiration (which varies little from
year to year) is great and exceeds precipitation in most of the West
in 9 out of 10 years (9) Average annual evaporation from experi-
mental pans at Las Cruces, New Mexico, where precipitation aver-
ages 8.5 inches (216 millimeters) yearly, was found to be more than
92 inches (2337 millimeters) (10), and geologist John W. Harsh-
barger has said that, of the precipitation that falls in Arizona, "less
than 10 percent runs off as streamflow," and about half of that is
lost to vapor (11) .
The problems of adapting to such an environment were, of course,

Table II. Variation in precipitation in the western United States in
inches.

Record Observed Observed Standard
Station Median mean maximum minimum deviation

Indio, Calif. 3.07 3.56 12.47 0.36 1.92
El Paso, Tex. 8.26 8.67 17.46 2.40 3.43
St. George, Utah 8.29 8.45 20.11 3.01 2.81
San Diego, Calif. 9.63 10.05 26.09 3.63 3.48
Tucson, Ariz. 10.80 11.19 20.90 4.73 3.26
Santa Fe, N. Mex. 13.73 14.18 26.75 7.31 4.25
a One inch equals 25.4 millimeters.
Source: H. E. Thomas, "The meteorologic phenomenon of drought in the South-
west," U.S. Geol. Surv. Profess. Paper 372-A (1962), p. A-15.








ARIDITY AND MAN


faced, even though on a comparatively limited scale, long before the
arrival of Europeans in the New World. Archeologic evidence sug-
gests that man had started to spread across North America as early
as 10,000 years ago. The earliest inhabitants (Chapter 3) were hunt-
ers, however, and the climate probably was cooler and moister than
it is now. Wildlife, including large animals now extinct, was abun-
dant. The Indians gradually learned to utilize native plants and,
as the continent became warmer and drier, there were the crude be-
ginnings of agriculture.
Partly because the hunting and gathering people were widely dis-
persed, the diffusion of agricultural knowledge was not rapid. Maize,
beans, and squash, which were first cultivated farther to the south,
were introduced slowly into the present-day United States, perhaps
over several millenniums. But, by at least about 3500 B.c., some corn
was grown in western New Mexico, and, by around A.D. 800, the
prehistoric farmers had devised terraces to hold the soil in their
fields; those in southern Arizona irrigated their crops through an
elaborate network of canals and ditches.
Agriculture, nonetheless, provided an uncertain life in a region
where precipitation was so unpredictable. Whether or not changes
in climate, the most widely accepted theory, were to blame, a great
constriction occurred in the aboriginal agricultural areas, starting in
the 13th century. Three centuries later, the areas were only about
one-tenth as widespread as they once were.
If there is a lesson that modern men might learn from the suc-
cesses and failures of the Indians, probably it is the need for balance
between social institutions and technology. The prehistoric popu-
lations simply were not large enough to afford any real comparison
between their adaptation to the land and the adaptations that are
required today; as advanced as Indian agricultural developments
were for their time, they were far too small in scale to affect the
environment materially. Thus, when Coronado marched into the
Southwest in 1540, the landscape was largely the product of nature
and had scarcely been disturbed by man.

Exploration and Settlement

The Spaniards and then the Mexicans who first colonized the
present western United States came from lands that also were arid







AN INTERPRETIVE SUMMARY


When W. H. Emory, of the Army Corps of Topographical Engineers,
saw this part of central New Mexico near the Rio Grande in 1846, he
found grass "in great abundance." Today, the same scene is dominated
by creosotebush (Larrea divaricata) and tarbush (Flourensia cernua)
and is all but bereft of grass. (Courtesy J. L. Gardner)

or semiarid, and they adjusted much more readily than the other
Europeans who followed them. Although the northernmost settle-
ments of New Spain were never, in present-day terms, extensive
(Chapter 4), the political remnants of the Spanish empire, neverthe-
less, persisted in the West for 250 years.
Army explorers were the first United States citizens who pene-
trated and seriously studied the region. Their reports, which were
less than encouraging, kindled the forbidding concept of the "great
American desert." It was not until the California gold rush of 1849
that a westward migration of consequence took place, and not until
1853 that the United States acquired the last of its western terri-
tories. Then, after the Civil War, came the boom in railroad build-
ing (supported by government aid to the builders) ; the Homestead
Act and other land acts, which made western ranges and farmlands
available; and the growth of the industrial East, which created a
market for the products of those lands.







ARIDITY AND MAN


A thread that is woven through Aridity and Man is the fact that
the arid West would have developed in a very different manner,
and certainly more slowly, had it not been an inseparable segment
of a large, rich nation. This truth was especially apparent during
and after World War II, when the region prospered more than ever
before, chiefly because defense industries and military bases were
established within it and tourists and retired people came to it in
large numbers.
Owing in part to this economic infusion from the outside, the
western United States is beginning, through industrialization, to
shake off the shackles of the extractivee" economy-the exportation
only of raw products-which has been one of its handicaps (12).
The potentialities of this continuing expansion may be virtually
limitless. On the other hand, there remains the enigma of water
supply.
Certainly water is available somewhere within reach, if the citi-
zenry is willing to pay for diverting it. The key question is, On how
grand a scale can the economy support the transportation of water
at any given time? A proposed project, which would carry Colorado
River water to central and southern Arizona, where three-fourths of
the state's population lives, would cost $1.1 billion. Westerners al-
ways have held an abiding faith in science and engineering to solve
their problems; usually their belief has been justified. But the
average, uninformed westerner seems to be convinced today that,
all else failing, scientists are on the verge of releasing rainfall from
the clouds almost at will and of desalinizing unending quantities of
sea water. Unfortunately, neither the attainment of the first of these
accomplishments nor the practical application of the second is within
the realm of immediate reality.

Weather, Water, and Energy

Indeed, recent research has shown not only that present-day tech-
niques fail to increase precipitation appreciably-at least, on the arid
flat lands-but also that a premise on which cloud seeding was based
(the freezing of nuclei in clouds) may have been wrong (Chapter 5).
As a result, meteorologists have taken a renewed interest in the basic
physics and chemistry of clouds. Radar, which has been greatly im-
proved since World War II, has become an important tool in this







AN INTERPRETIVE SI'\IARY


work. Other investigations have concentrated on the very small and
the very large-on microclimatology and on global, large-scale at-
mospheric motions. The latter studies, particularly, are being
furthered through the use of high-speed electronic computers.
Analog computers also have been programed, with considerable
promise, to help hydrologists in understanding the complexities of
ground water. Ground-water problems have been compounded by
the expansion of population, by the cessation of surface streamflow
in many places, and by the introduction of the centrifugal pump, a
device that has profoundly affected the West (Chapter 6).
The centrifugal pump and modern drilling equipment have made
possible deeper and deeper wells during the past half-century. As
a result, irrigation has increased enormously. Ground water has
been further depleted, and the challenge to water scientists has
increased. One eventual answer may be the desalinization and de-
mineralization of sea and brackish waters, and a number of pilot
plants are already in operation. The costs at which they can produce
potable water are approaching those paid by some municipalities
but are too high, thus far, for agricultural use.
Water seldom is scarce, axiomatically, where there is enough
energy to pump it from great depths. Therefore, it is ironic that
the West, where the availability of water can be so crucial, is a major
source of the raw materials of energy, particularly of petroleum,
coal, and uranium (Chapter 7). Larger quantities of these are ex-
ported than are used within the region.
All of the nation's helium and most of its uranium are found in
west Texas and the Mountain States. Indicator-plants-certain spe-
cies that are affected by mineralization-have helped prospectors to
discover deposits of uranium and other minerals. The region is also
an important producer of metallic minerals, especially copper, and
in some places dry processing of ores has been perfected as a means
of saving water.
Although prospectors entered the then largely uncharted West
long before farmers, and mining remains a potent economic and
political force, mining has long been rivaled by agriculture as a
producer of income. Agriculture, of course, had to abandon, im-
measurably more so than mining, old methods and seek new ones
in order to adapt to the aridity.
The necessity for managing the soils of the dry lands in ways








ARIDITY AND MAN


different from those of the humid regions (Chapter 8) was a lesson
that had to be learned slowly, and often painfully, by the pioneer-
ing farmers. Soil salinity, erosion, and waterlogging were severe
and still are. The soils tend to be alkaline and calcareous. But by
experience and experiments, farmers have found how to reclaim
saline soils by leaching and have learned the ways in which water
may be applied to do less harm and more good. They conserve soil
moisture on the Great Plains by fallowing.
Apparently there is no reason why either dry farming or irriga-
tion agriculture cannot continue and, possibly, because of research,
with even greater future yields. Studies of soil-plant-water relation-
ships and of soil classifications, among others, have been intensified.
In another promising line of investigation, scientists in the U.S. Soil
Conservation Service in southern New Mexico are analyzing the
influence of landform and geologic conditions on soil development.
The most spectacular successes in western agriculture have taken
place where there is irrigation: in Utah, on the high plains of west
Texas, in the Salt and Colorado river valleys of Arizona, and, most
of all, in California. As Table III illustrates, the trend toward addi-
tional areas of irrigation continues unabated. This, again, is most
notably true in California (13). In that state's Imperial Valley-a
great green patch against a backdrop of brown desert-vegetables
are grown the year round with water diverted by gravitational flow

Table III. Irrigation development in 17 western states, by acres.

Nonfederal Federal Cumulative
land land Total total
(1000's) (1000's) (1000's) (1000's)

Before 1900 6,700 450 7,150 7,150
1900-1909 3,650 850 4,500 11,650
1910-1919 2,800 1,000 3,800 15,450
1920-1929 950 500 1,450 16,900
1930-1939 900 600 1,500 18,400
1940-1949 3,000 1,450 4,450 22,850
1950-1958 5,950 1,700 7,650 30,500

Total 23,950 6,550 30,500 30,500
a One acre equals 0.4047 hectare.
Source: U.S. Senate Select Committee on National Water Resources, Future Needs
for Reclamation in the Western States, Comm. Print 14 (Washington, D.C., 1961), p. 5.








AN INTERPRETIVE SUMMARY


,--IK '-'''*1 g B ~ -










irrigated fears of the Imperial Valley. Six years were required for con-
*4, ..-










struction of the canal, which was completed in 1940. (Courtesy Imperial
Irrigation District)

from the Colorado River. Sixty years ago, the valley was as parched
and desolate as any to be found in the United States.
Problems are inherent in irrigation, of course, just as they are in
the adaptation of plants and animals to an arid environment (Chap-
ter 9) There are endless efforts to improve dams, ditches, and other
structures, to reduce silting and evaporation, and to remove excess
water from farmlands. Ditches are lined with concrete, and various
chemicals are applied to the surface of reservoirs, in the hope of
significantly reducing seepage and evaporation. The adaptation of
animals and plants is more a matter of basic research.
Precisely how extreme heat affects livestock is not fully under-
stood, but western ranges are extensively stocked with beef cattle
that have been crossbred with the heat-tolerant Brahman zebuu)
cattle of India. Range managers are seeking fuller use of their lands
by removing brush, and low-value plants, such as the pricklypear
cactus (Opuntia spp.), sometimes are utilized as emergency livestock
feed.







ARIDITY AND MAN


In cultivated fields, plastic coverings and petroleum mulch have
been applied to conserve moisture and raise the soil temperature
around germinating seeds. Much research has been focused on the
possibilities of drought-tolerant plants-those that require less mois-
ture-or hybrids that might bring increased yields under the same
climatic conditions. The development of an improved extra-long-
staple cotton (Gossypium barbadense) brought considerably larger
yields in the Southwest, where it must be irrigated. Irrigation, in
fact, still is by far the largest user of water in the region (Fig. 2),
despite the mushrooming of industry and urban population.

Watershed Problems

Almost always any discussion of the future of the West must begin
with two questions. Where does the water come from? Can the sup-
ply be increased or even sustained? Irrigation, at least, often depends
on surface flow. In the truly arid lands at low elevation, where this
type of agriculture is concentrated, local runoff is undependable, if
not all but nonexistent. The lifelines are the rivers that bring water
down from the high, humid mountain chains.
So, oddly as it may strike persons who are oriented to humid en-
vironments, one cannot consider the fate of the North American
deserts without considering snowfall. The maximizing of snowdrifts
and the manipulation of higher-elevation watersheds are tasks to
which numerous investigators have addressed themselves (Chapter
10). Among other approaches, they have set up snow fences to
deepen drifts and have erased water-wasting plants from streambeds.
In an effort to suppress transpiration, they have thinned watershed
vegetation or replaced it with low moisture-using species. One diffi-
culty is that not enough is known about the transpiration by certain
plants; basic research along this line is being undertaken.
Although the forest products of the western mountains are not as
vital as the water yielded, they are important assets to the arid areas
below. Foresters and research scientists are especially concerned with
forest regeneration and management and the control of insects and
fires.
Native plants other than trees (Chapter 11) have proved so far
to be of considerably less commercial worth. Wild stands of canaigre
(Rumex hymenosepalus) have been harvested for their tannin con-








AN INTERPRETIVE SUMMARY


tent, and, to name another, the common creosotebush (Larrea divari-
cata) has been turned into livestock feed. Laboratory screening has
indicated that many other arid-lands plants are potentially valuable
because they are rich in oil and protein. But, among other factors,
the competition of synthetics and the lack of a real need for new
crops have prevented extensive commercial development.
Lately, however, interest has risen in native plants and animals


I
- I


.1 /
r 'x.

/ V


20000
m.g.d.


Irrigation


/1


0 300 Miles

S400 Kilometers
0 400 Kilometers


Fig. 2. Irrigation agriculture uses more water in the West than is taken
by public supplies and industry combined. The reverse is true, of course,
in the humid East, where farming makes use of only a comparatively
small portion of the available water. The graphs represent water use in
millions of gallons (liters) per day (m.g.d.) (Courtesy U.S. Geological
Survey)







ARIDITY AND MAN


simply for their esthetic value. Evidence of this belated appreciation
is indicated by the interdisciplinary research in Arizona on the giant
saguaro cactus (Carnegiea gigantea) and by the management by
wildlife officials in the same state of the collared peccary, or javelina
(Pecari angulatus sonoriensis) an animal once viewed as nothing
more than a pest.
For the most part, man's admiration of the stark natural beauty,
the generally mild climate, and the spaciousness of the arid lands is
a quite recent phenomenon. Whether this attitude has developed
too late to preserve much of the regional uniqueness against the en-
croachment of population is a matter that the present generation
must decide.

Human Adaptation

Man himself, of course, lacks many of the endogenous adaptations
that are naturally provided for the desert-dwelling plants and ani-
mals. But it is as true under arid conditions as elsewhere that man
is among the most adaptive of creatures. Very little research has
been done on the physiologic problems of man in the arid regions
since the intense interest during World War II (Chapter 12). But
enough had been performed previously to establish the fact that
normal, healthy human beings should be scarcely limited by an arid
environment, as long as they respect its extremes. However, much
more work should be done toward practical application of the exist-
ing knowledge of how man should dress in such an environment and
the sort of housing he should build.
Instead of designing buildings with the local climate in mind,
people tend too often to rely entirely on air-conditioning machines
to protect them from the heat of the summers in the arid lands. The
air-conditioner has had a beneficial impact in the Southwest es-
pecially. Just as the windmill and the barbed-wire fence, in their
time, helped to open the West to orderly occupation, the centrifugal
pump and the air-conditioner have transformed the region into the
sort of place it is today. Nevertheless, it is possible for planners and
designers to take the environment into account without rejecting the
amenities offered by technology.
Economically, the arid West poses a riddle (Chapter 13). It is








AN INTERPRETIVE SUMMARY


poor in water, and yet it is rapidly growing in population, employ-
ment, and income. The answer appears to be that the lack of water
has not been a barrier to this expansion, is not considered likely to
be within the near future, but ultimately may become a serious de-
terrent, unless new sources of water are found or wiser use is made
of existing supplies.
One possible alternative was proposed by a team of social scien-
tists. It emerged from what well may have been the most significant
arid-lands research in years. The researchers found in New Mexico
(Chapter 13) that agriculture, traditionally one of the highest-
priority users of water in the West, actually returns less to the total
economy for the water it utilizes than do industry, cities, recrea-
tionists, and other users.
Presumably, the same ratio would apply in other arid states.
Whether it would in other countries, with vastly different economies,
is another matter, of course. But the diversion of more water to non-
farm uses is likely to receive increasingly serious consideration in
the western United States.
Such a change will not come easily. Although the political
processes and the social values of the West were, in the main, super-
imposed from the East (Chapter 14), a number of institutions on
the frontier were tailored to suit the exigencies of the period.
Among them were western water laws. Although these laws became
a bewildering, conflicting complex of statutes, compacts, and dis-
putes, they were a step forward in that they recognized the priority
of use. At the time this system of water rights took shape, though,
the West was predominantly agricultural.
The durability in the West of certain other humid-regions at-
titudes becomes all the more remarkable when one considers them
in context. For instance, the penchant for private ownership is
as deeply ingrained here as anywhere else in the nation, in spite
of the fact that much of the West is owned to this day by the federal
government. But the attitude has asserted itself at various times:
it was strongly felt during the early disposals of the public lands.
Like almost every other event or factor involved in the settlement
of the West, the disposal of public lands was haphazard and often
fraught with fraud and greed; yet, the action at least freed for farm-
ing vast areas that otherwise would have remained raw prairies.







ARIDITY AND MAN


This is the kind of paradox that makes difficult the judging of man's
activities in the region (Chapter 15). Man has actuated the erosion
of land, has denuded the forests, has reduced the grasslands to desert,
and has polluted even the air he breathes. At the same time, he has
brought huge areas under cultivation, constructed cities, and also
built not only a materially rich region but a sound social structure.
Where is the line to be drawn between plunder and progress? An
answer is not easy but must be based on awareness that the dwin-
dling natural resources must be husbanded more carefully in the
West during the next century than they were during the century
past.

Hope for the Future

If water that now evaporates or is otherwise lost could somehow
be saved, a much larger population could be supported in the west-
ern United States; if even a portion of the water now used by agri-
culture could be diverted to industry, regional income could be in-
creased manyfold. Before these things can be accomplished (Chap-
ter 16), there must be planning and cooperation on a regionwide
basis, rising above local and state jealousies and ambitions.
In other words, the over-all problem is largely a social one. The
future of the arid West still hinges to an awesome extent on the
answers that can be supplied by scientific research but, even more,
it depends on public understanding of these answers and the public's
willingness to act on this new knowledge in place of its old prej-
udices and traditions.
That the public may be ready for a better understanding of its
arid environment was illustrated, with an ironic twist, in 1962 with
the publication of a booklet in Phoenix, Arizona. The booklet,
Desert Survival (14), was issued by local civil defense authorities
and was designed for the obvious emergency. The citizens, most of
them presumably city-dwellers, were cautioned by the publication
that, to survive, they should walk in the desert only at night and
that, if they are really hungry, rattlesnake (Crotalus spp.) meat
provides a perfectly palatable meal. The present inhabitants of the
arid lands, comfortable in their air-conditioned oases, may not be
as far removed from their environment as most of them think they
are.








AN INTERPRETIVE SUMMARY


Acknowledgments: Although all the authors in Aridity and Man con-
tributed indirectly to this synthesis of the book, I wish to single out Peter
C. Duisberg, J. L. Gardner, Terah L. Smiley, and Richard B. Woodbury
for their specific suggestions.

REFERENCES

1. W. Stegner, "Editor's introduction" to J. W. Powell, Report on the
Lands of the Arid Regions of the United States (Harvard Univ.
Press, Belknap Div., Cambridge, Mass., 1962), p. x.
2. E. H. Watson, "Note on the duststorm of November 13, 1933,"
Science 79, 320 (1934).
3. E. Z. Vogt, Modern Homesteaders (Harvard Univ. Press, Belknap
Div., Cambridge, Mass., 1955), p. 201.
4. R. Z. Brown, "United States water supply versus population growth,"
Population Bull. 17, 6 (1961).
5. University of Arizona Rillito Creek Hydrologic Commission and
U.S. Geological Survey, Capturing Additional Water in the Tucson
Area (U.S. Geological Survey, Dept. of the Interior, Tucson, Ari-
zona, 1959), p. 1.
6. G. F. White, The Changing Role of Water in Arid Lands, Riecker
lecture 6, November 1960 (Univ. of Arizona Press, Tucson, 1962).
7. T. L. Smiley, "Arid lands: the problem and a reply," unpublished
paper presented before Am. Assoc. for the Advancement of Science,
Philadelphia, Pa., 1962.
8. H. E. Thomas, "The meteorologic phenomenon of drought in the
Southwest," U.S. Geol. Surv. Profess. Paper 372-A (1962), p. A-15.
9. G. Michel et al., "Survey of methods for evaporation control," J. Am.
Water Works Assoc. 55, 157-168 (1963) .
10. E. L. Hardy, J. C. Overpeck, and C. P. Wilson, Precipitation and
Evaporation in New Mexico (New Mexico State Univ., University
Park, 1939).
11. J. W. Harshbarger, "Capturing additional water for the increase of
supplies," in Land and Water Use, W. Thorne, Ed. (Am. Assoc. for
the Advancement of Science, Washington, D.C., 1963), p. 213.
12. A. W. Wilson, "The impact of an exploding population on a semi-
developed state: the case of Arizona," Arizona Rev. 2 (5), 5-9 (1962).
13. H. F. Gregor, "Push to the desert," Science 129, 1329-1339 (1959).
14. Maricopa County-City of Phoenix Civil Defense Joint Council,
Desert Survival (Phoenix, Ariz., 1962) .

















Regional Setting


DONALD D. MACPHAIL


Aridity is seasonal and annual; it accompanies heat and cold
alike, and it varies in intensity. To understand this, one must know
the attributes of the many regions that are called arid or semiarid
and cover about one-third of the land area of the United States. But
aridity is a term that cannot be described to everyone's satisfaction.
"The arid zone," said the late Homer L. Shantz, "has not been
precisely defined. Probably in no zone on the earth are there greater
swings in precipitation, temperature, and aridity" (1, p. 3). To
define such a zone properly would probably not be possible, for if
done, the definition would be bound largely to a single factor of
the environment. A definition based on climatic data would not be
the same as one based on soils, on vegetation, on animal distribution,
or on land use. Since none of these aspects of the landscape is, by
itself, satisfactory for delineating the exact boundary of the arid
zone, it is necessary to consider each one in order to understand the
many broad regional patterns of the physical landscape and the in-
terrelationships of the arid environment.
The climatic expression of aridity is more difficult to ascertain
than one might suppose. A statement of the amount of rainfall
received by a given locality says nothing about the distribution of
rainfall throughout the year or its over-all effectiveness. Aridity is
an expression of water deficiency; and water deficiency is induced
not only by lack of precipitation but also by conditions of soil mois-
ture and permeability, evaporation, transpiration by plants, and the
intensity and duration of sunlight, heat, humidity, and wind.
Many investigators have attempted to express the effects of these
factors as quantitative indexes. Widely used in the United States is

Contributors to this chapter were LESLIE HEWES, HAROLD A. HOFFMEISTER, FRITZ L
KRAMER, RICHARD F. LOGAN, and JOHN M. STREET.
21







ARIDITY AND MAN


C. W. Thornthwaite's index, which, stated simply, establishes a
ratio between water deficiency (or surplus) and water need ex-
pressed as potential evaporation and transpiration (2). Thorn-
thwaite saw that potential evapotranspiration was a useful idea, and
he established moisture regions on the basis of water surplus or de-
ficiency. A modified version of these regions was published in 1960
by Peveril Meigs and is adapted in generalized form as an end paper
of this book (3).

Characteristics of Aridity

Three stages of dry climate emerge-semiarid, arid, and extremely
arid. Semiarid lands occupy one-fourth of the United States, and
arid lands another 10 percent (4) Extremely arid conditions, where
there has been at least 1 year without rain, are confined to relatively
small areas in the Death and Imperial valleys of California.
Most of the semiarid and arid regions lie roughly between the
100th meridian and the Sierra Nevada and Cascade ranges. Offshore,
there are scattered arid and semiarid areas on the Hawaiian Islands
and Puerto Rico; these tropical dry zones follow narrow belts along
leeward coasts and generally are more semiarid than arid.
What is a semarid climate? If Thornthwaite's moisture index is
applied, a pronounced water deficit prevails in the coastal valleys of
southern California, the Colorado Plateau (s) most of the Wyoming
basins, in many intermontane basins of the Rocky Mountains, and
the entire extent of the short-grass Plains. The eastern margin of
these Plains is the conventional boundary between the dry and the
humid United States. In reality, however, this is a dynamic and
fluctuating border.
In a given year, semiaridity may extend as far east as western
Wisconsin, northwestern Iowa, and western Louisiana. What the
eastern boundary of the short-grass Plains does indicate is the prev-
alence of drought. West of this limit, semiarid conditions have oc-
curred from one-half to three-fourths of the years of record. These
characteristics also are manifest in observable landscape conditions.
To the west, the natural grasses change from tall to short varieties,
and the percentage of land in crops drops significantly. Grazing is
the dominant land use, except where irrigation is possible or where
the land is too steep and rocky.







REGIONAL SETTING


Arid conditions, where the moisture deficiency is severe, apply to
parts of the Columbia Basin of Washington State, the San Joaquin
Valley (which is the southern half of the Central Valley of Cali-
fornia) parts of the Wyoming basins, and almost all of the Mohave,
Sonoran, and Chihuahuan deserts.
In most of the West, there is moisture deficiency throughout the
year. The western portions of the northern Rocky Mountains, the
Blue Mountains of northeastern Oregon, the northern Willamette
Valley of Oregon, and the most mountainous areas of California ex-
perience serious periods of moisture deficiency during the summer.
There, the uneven seasonal distribution of precipitation accen-
tuates the problem of dryness. Summer deficits of water are more
moderate along the margins of the Puget Sound Lowland in Wash-
ington, in the middle Rockies of Wyoming and Utah, and along the
high plateau border in Arizona. There is, in fact, along the entire
length of the Rocky Mountains, a sharp east-west break in the sea-
sonal pattern of precipitation. Where cold, dry Canadian air domi-
nates the winters east of the Rockies, summer rainfall maximums are
the rule.
Conversely, across the entire intermontane regions to the Pacific
valleys, winter rainfall and summer drought are usual, since the mid-
latitude, west-coast rainfall regime makes itself felt to a greater or
lesser degree as far east as the continental divide.

Effects of Rainfall

In a land that lacks water, it is curious that running water is the
most important sculptor of the landscape. When the rain comes,
the scant vegetative cover does little to spare weak shale or clay out-
crops from savage bombardment by the raindrops. Torrents of water
rush outward and downward instead of soaking into the compacted
earth. The shale, eroded deeply, becomes a dense barren mass of
oversteepened valleys and razor-sharp ridges known as badlands,
creating the desolate character of the Big Badlands of South Dakota
and the Borrego Badlands of California.
Water works sporadically in the arid zones. Brief storms send
rampaging waters down steep-walled drywashes, or arroyos. Debris
and mud, carried along in the currents, soon drop on the floor of
the arroyo or on the gentle slope of the adjacent basin, or bolson, as







ARIDITY AND MAN


the force of the stream dissipates. Sediment-choked streams disgorge
alluvial fans, which often coalesce into continuous, smooth slopes
called bajadas.
Iarge quantities of alluvium frequently block the existing stream
courses, then new channels cross the fans in different directions.
The upper parts of the fans frequently are scarred by many of these
dry, shallow watercourses that radiate from the mountain canyons.
Farther downslope, the sandy or clayey flat, or playa, of the bolson
usually is covered by encrusted salt, remnant of an ephemeral lake.
Water, which usually is present just below the playa surface, often
is saturated with brine and is high in mineral content. As the basins
gradually fill with alluvium, salts, interbedded occasionally with clay,
accumulate in layers hundreds of feet (meters) thick.
The short-run nature of desert streams confines most of the drain-
age to interior basins, such as those of western Wyoming or the Black
Rock Desert in northwest Nevada. Only the main rivers, which have
their sources in the high, humid "islands" of the Rocky Mountains,
traverse the driest parts of the region to reach the sea. These are the
Colorado, the Columbia, and the Rio Grande. Across the plains east
of the Rockies, tributaries of the Missouri, Arkansas, and Red rivers
flow into the humid basin of the Mississippi and ultimately to the
Gulf of Mexico.
Other landscapes result from resistance to erosion by water. These
possess either precipitous slopes or very low relief, with few examples
between the extremes. Tough sandstones or basalts cap the surface
of the Colorado and Columbia plateaus. Frequently, these are in-
cised by steep-walled canyons a half-mile (approximately 1 kilo-
meter) deep. The Black Canyon of the Gunnison River, and Grand,
Marble, and Glen canyons of the Colorado River are examples. Flat-
topped mesas, inclined cuestas, or solitary pinnacles and buttes often
stand above the surrounding plain, stubbornly and slowly succumb-
ing to the ravages of weathering.
Because of the great fluctuation of daily temperature, rapid ex-
pansion and contraction of the exposed rock surfaces help to crack
and disintegrate them; large amounts of the detached debris accumu-
late and are gradually washed away.
Most of the arid United States has a classic type of desert land-
scape. Mountain ranges occur in echelon, fringed by smooth-sloping
bedrock pediments. These massive fault-blocks, most of which are







REGIONAL SETTING


r ; '-' ..y -.'
,.. .- ^.' : .
*A^^^-".eg**

L:^"tJI -~


Colorado River waters have cut 700 feet (213.4 meters) into the plateau
surface on the Arizona-Utah border. Glen Canyon Dam, photographed
in 1962 as it neared completion, was designed to provide electricity,
stream control, and recreation. (Courtesy U.S. Bureau of Reclamation)

alined north and south, form the crests of ranges. Broad bolsons in-
tervene between them. This "basin-and-range country" typifies the
Great Basin and the entire region of creosotebush (Larrea divari-
cata) .
Contrary to popular belief, winds have rather limited erosive
effects in the truly arid parts of the mountain West. Some sand and
dust, blown away from playas and lower alluvial fans, redeposit
either as miniature dunes in the lee of bushes or as a veneer on the
upper alluvial fans at the windward sides of bolsons, below the
mountain rims.
Several large accumulations of sand (the Algodones Dunes west
of Yuma, Arizona; the Devil's Playground near Baker, California;
and the dunes in Death Valley) are associated with Pleistocene
streams or lakes and apparently are not growing appreciably today.
Other notable sand areas include the glistening, transverse dunes of







ARIDITY AND MAN


white gypsum crystals in New Mexico's Tularosa Basin near Alamo-
gordo, the Great Sand Dunes of Colorado's San Luis Valley, and the
widespread Sand Hills of Nebraska, which occur on the eastward
margin of the semiarid plains. Such areas, however, compose only a
small fragment of the western United States.
Wind has a more vital role on the short-grass portions of the Great
Plains and similar areas of low relief. During years of drought,
when the Plains are denuded of protective vegetative cover, the wind
has whipped clouds of fine, powdery, orange-yellow dust several
thousand feet (meters) into the air. Some of the most severe dust-
storms have deposited more than 30 tons of dust per square mile (12
metric tons per square kilometer) (5).

Zonal Soils

In general terms, the soils of the West have in common the soil-
forming process of calcification and thus are called Pedocals. Their
distribution is shown in Fig. 1. The dryness of climate permits the
accumulation of lime in these soils; this is not the case in humid
regions. The major groups of the Pedocals have a definite regional
basis that consists of many local soils with similarities of profile.
Over a long period of time, the effect of climatic and biotic factors
on a great variety of geologic materials has brought about the de-
velopment of the distinctive characters of the zonal soils.
In the semiarid short-grass Plains, the Chestnut, Reddish Chest-
nut, Brown, and Reddish Brown soils predominate (6). The zonal
soils become shallower with greater aridity. In the cooler parts of
the intermountain regions, Sierozem or Gray Desert soils prevail.
Many Sierozems are underlain with a hardpan layer. These desert
soils are notably deficient in organic matter but have an abundance
of soluble salts and minerals, which can make them highly produc-
tive when they are irrigated. In some cases, however, excessive
salinity or alkalinity makes this impossible.
Red Desert soils abound in the warm deserts of the Southwest and
the Tropics. These reddish-brown and pinkish-gray crumbly soils
overlie a heavier dull-red substratum, which, in turn, grades into the
ever-present layer of lime carbonate. Like the Sierozems, these soils
are quite productive when they are cultivated under irrigation. The









REGIONAL SE11 ING 27




GREAT SOIL GROUPS
ARID UNITED STATES





StL CL
'L
















BROWNS SOL ,
S.
L.. CHERNOM S' L


IC S I L
L L



















SR d








| T LATERITIG SOILS ,a- L
\ ALLUVIAL SOILS
Red i i p k p ra






SHER Z SOILS --






















Fi. 1. The gReat soil groups in the western United States, Hawaii, and
eo R (Adaed
R sR


LT ITIC BSI L









] HES U A ONALS O iLS L '
ITRAZE SOILS
pR iRe d R





B- Bg a rosn r
R-Red ped Y r 1ow
CHESTNUT SOILS

C OHERNONEM SOILS
PRAIRIE SOILS

3 SHANTUNG BROWN SOILS
F l PODZOLIC SOILS Hawa
R Red fap











Puerto Rico. (Adapted from UT_.S. Dep~artmnent ol AgriCL11ture ma~p)







ARIDITY AND MAN


Red Desert soils are bordered in many places by the nonlimy Shan-
tung Brown soils that developed under a forested grassland and the
wet and dry subhumid climate.
In the humid mountain ranges of the West, a Gray-Brown Pod-
zolic soil appears frequently; elsewhere in the mountains, thin, shal-
low, rocky soils, called lithosols, have evolved on the steepest slopes.
Sand dunes, river-bottom soils, bogs, swamps, and alkali flats, all are
of recent origin and develop from local, rather than regional, condi-
tions.
Generally speaking, the Pedocals, with their variable horizons of
surface moisture and dry subsoil, extend beyond the geographic
limits that would satisfy arid conditions of climate and vegetation.
As Shantz points out, the estimated area of arid land in the world
is 43 percent, if the estimate is based on Pedocals; 36 percent, based
on climate; 35 percent, based on interior drainage; and 35 percent,
based on natural vegetation (1).

Western Vegetation

Vegetative cover can be one of the most effective indications of
aridity, because there is close correlation of plants with soil, climate,
and land use. Successful interpretation depends on recognition of
the regional vegetative patterns that result from plant associations,
not of single species. Some principal indicator-species are adjusted
to long periods of rest brought on by perennial or seasonal drought.
Creosotebush (Larrea divaricata) and sagebrush (Artemisia spp.)
are remarkably accurate in delineation of the arid intermountain re-
gions. Creosotebush grows exclusively in the southern part of this
region, and sagebrush appears at higher elevations and farther north.
Where the low, monotonous silvery-brown cover of sagebrush spreads
across the landscape, winters are cold and Sierozem soils predomi-
nate. The distribution of sagebrush from the Columbia and Wy-
oming basins in the north to the southern limits of the Great Basin
and Colorado Plateau outlines a major subregion of the West.
In like manner, the olive-green hue of the creosotebush stretches
over the entire border with Mexico from California to the mouth
of the Rio Grande; its presence is evidence of a warm desert climate
with mild winters and a region of Red Desert soils. Although the
range of creosotebush has probably not been extended within his-








REGIONAL SETTING


Creosotebush (Larrea divaricata) covers a desert slope in southern New
Mexico. In the background, the dark-toned line is mesquite (Prosopis
juliflora), originally seeded there as pack animals followed the historic
Jornada del Muerto between Chihuahua in Mexico and Santa Fe. (Cour-
tesy J. L. Gardner)


toric times, this plant has increased in prominence in some areas.
Descriptions of the tablelands along the Rio Grande of 100 years
ago indicate excellent stands of grass in places that are now com-
pletely dominated by creosotebush (Larrea) or mesquite (Prosopis
spp.) (7).
Using physical landscape, vegetation, and landform, it is possible
to recognize several phytogeomorphic, or natural, regions. Each re-
gion has its own characteristics and, thus, has its own potential for
economic development.
But, transcending regional differences, the pressing problem of
water availability is evident everywhere in the pattern of settlement.
In contrast with the eastern United States, the population of the
arid and semiarid regions is highly concentrated in nodes. A rather
sparse rural population may be found everywhere, except where irri-
gation is well developed, in close proximity to rapidly growing cities.


..,'
L







ARIDITY AND MAN


The geographic outline of the Rocky Mountains and the Colorado
Plateau can be readily discerned on a population map (see Fig. 1,
Chapter 13). Where the mountains meet the eastern plains, there
is a continuous north-to-south string of cities-Great Falls, Billings,
Casper, Cheyenne, Denver, Pueblo, Santa Fe, Albuquerque, and El
Paso.
The oases of Tucson, Phoenix, Provo, Salt Lake City, Boise, and
Spokane line the western fringe of the mountainous moisture belt.
Other clusters of population are found on the Staked Plains of the
Texas Panhandle and in the valleys of the Pacific Coast. These are
some of the fastest-growing areas in the United States.
It is significant that these densely populated areas reflect only in
part the land-use patterns around them (see Fig. 2). Many of the
largest cities now are important manufacturing centers, in addition
to their normal regional service functions in commerce, finance, and
government. Activities such as food processing and meatpacking
reflect long-established practices in the various regions, and the com-
monest uses of the arid and semiarid lands still are sheep and cattle
grazing. Extensive grazing is common to all but the extremely arid
parts of the intermountain regions.
The main irrigated crops of the West are sugar beets, potatoes,
vegetables, cotton, alfalfa, apples, grapes, and citrus fruits. The crops
under cultivation without irrigation are drought-resistant grains-
winter and spring wheat and sorghum-found on the subhumid mar-
gins of the short-grass Plains, the Columbia Basin, and the Central
Valley of California.
When the available facts are analyzed, the physical and cultural
landscapes are easily grouped into several regions, as may be seen
in Fig. 3. The intrinsic character and potential of each are discussed
here.

Pacific Valleys

In the geologic past, deformation of the earth's crust in the ex-
treme western United States formed a broken line of north-to-south
flat-bottomed valleys between the Sierra Nevada and Cascade ranges
and the Pacific Coast. In this structural chain, the coastal lowlands
of southern California and the Central Valley of California are sig-
nificantly arid or semiarid.










REGIONAL SETTING


ARID UNITED STATES


o 100 200 300 Mile*

O 200 400 KIlom Ier


SCropland and pasture land

i 1 Cropland, woodland and grazing land

4 Irrigated land
Forest and woodland grazed

SForest and woodland mostly ungrazed

SSubhumid grassland and semiand grazing land

Open woodland grazed

Desert shrubland grazed

Desert mostly ungrazed


PUER ,



u vu su ou anorneelrs


Fig. 2. Major land uses by area in the arid West include dry farming
and forestry; the irrigated lands also are of great importance. (Courtesv
U.S. Department of Agriculture)







ARIDITY AND MAN


In coastal southern California, the climate, generally semiarid,
changes markedly with the extremes in relief. Temperatures are
moderate along the coast at all seasons, but inland areas are hot in
summer and cool in winter, and the adjacent mountains are warm
in summer and cold in winter (see Table I) Precipitation varies
greatly with the local orographic situation. Rainless summers, gen-
erally speaking, persist in all of the Pacific valleys, although the ex-
tent and intensity of the summer drought diminish progressively
northward.
Adapted to survive the long, dry summer, the vegetation of the
southern California coast has most of its physiologic development
during late winter and spring. Chaparral is the natural cover, ex-
cept along the streams, where grass-carpeted valleys are dotted with
oak (Quercus spp.) .
Not all of the agriculture is irrigated, despite the rainless sum-
mer. Grain, planted early in the winter, matures in late spring and
early summer; walnuts, almonds, apricots, and other tree crops fare
well on winter rain with mulching to conserve water. Lima beans,
tomatoes, and geraniums are cultivated in the foggy, frost-free
coastal belt without supplemental water. The more lucrative crops
of coastal southern California, however, are irrigated, chiefly with
water from wells drilled into the alluvial fill of local basins. Some
water also is available from supplies imported by the Los Angeles
area. Frost-sensitive crops, such as lemons, oranges, and avocados,
grow on upper alluvial fans and lower hill slopes, where the cold air
freely drains away.
The San Joaquin-Sacramento valleys, generally referred to as the
Central Valley, form a gigantic mountain-girt trough. The great
width of the smooth valley floor gives the illusion of a flat, endless
plain rather than an enclosed depression. Streams issuing from the
Sierra Nevada (see end-paper map), and to a lesser degree from the
Coast Range, have carried into the valley a great volume of allu-
vium, much of which is deposited as huge fans. In the southernmost
third of the Central Valley, these have formed an area of interior
drainage without a natural surface outlet to the sea.
The climate of the valley varies from dry, subhumid in the Sacra-
mento Valley to arid in most of the San Joaquin. Summer rainfall
is virtually nonexistent, just as it is along the southern coast, and












REGIONAL SETTING


NATURAL REGIONS

ARID UNITED STATES


'-Ii


r- N'-
\h


! I
"''* ^ -' I ---- .
.: -.X, A


PACIFIC VALLEYS AND irT.i..
I CALIFORNIA
o central Valley
2 PACIFIC NORTHWEST COAST
b W allmetle -Puget Trough
I INTERMOUNTAIN REGION
SSAGEBRUSH (Artemisia) REGION
Columbia Basin, sagebrush
b Coumbi Basin, short gross
Blue Mounta- Region
d Snake Rier Plain
a Great Basin
f Wyoming Borasins
Colorado P oleaus
Ploteau Border
2 CREOSOTE BUSH (Lorrea) REGION
I Mohave and Sonoran Deserts
Chihu hua Desert
k Rio Grande Border
ROCKY AND SACRAMENTO MOU
NORTHERN ROCKIES
2 MIDDLE ROCKIES
3 SOUTHERN ROCKIES
4 SACRAMENTO MOUNTAINS
E SHORT GRASS PLAINS
MISSOURI PLATEAU
2 BLACK HILLS
3 SAND HILLS
4 SOUTHERN PLAINS


j|] TROPICAL ARID ZONES
I LEEWARD HAWAII
2 LEEWARD PUERTO RICO


NTAINS


160


a


HAWAII
Hnw

-^


Fig. 3. The natural (phytogeomorphic) regions in the continental

western United States can be divided into four major groups.


PUERTO RICO

67 6













Table I. Climatic records.


Mean annual Summer precipita-
precipitation tion, Apr.-Sept.


Winter precipitation,
Oct.-Mar.


Mean maximum
temperature, July


Mean minimum
temperature, Jan.


Southern California
Santa Monica
(coast)
Riverside
(interior)
Big Bear Lake
(mountains)

Central Valley, Calif.
Buttonwillow
(southern valley)
Red Bluff
(northern valley)

Larrea region
Phoenix, Ariz.
(Sonoran Desert)
El Paso, Tex.
(Chihuahuan Desert)


Source: U.S. Weather Bureau.


Station


14.90 in.
(378.5 mm)
11.53 in.
(292.9 mm)
36.35 in.
(923.3 mm)


5.5 in.
(139.7 mm)
23.1 in.
(586.7 mm)


7.20 in.
(182.9 mm)
7.89 in.
(200.4 mm)


1.04 in.
(26.4 mm)
1.71 in.
(43.4 mm)
5.38 in.
(136.7 mm)


0.97 in.
(24.6 mrm)
3.6 in.
(91.4 mm)


3.16 in.
(80.3 mnm)
5.00 in.
(127.0 mm)


13.86 in.
(352.0 mm)
9.82 in.
(249.4 mm)
30.97 in.
(786.6 mm)


4.53 in.
(115.1 mm)
19.5 in.
(495.3 mm)


4.04 in.
(102.6 mm)
2.89 in.
(73.4 mm)


75F
(23.90 C)
94F
(34.4 C)
77F
(25 C)


101F
(38.3 C)
98F
(36.7 C)


104.6F
(40.3C)
93.9F
(34.4 C)


46F
(7.8C)
38F
(3.3C)
15F
(-9.4 C)


33F
(0.6-C)
36.9F
(2.7"C)


37.3F
(2.90C)
31.5F
(--0.3 oC)







REGIONAL SETTING


extreme heat and low relative humidity combine with low precipi-
tation to raise evapotranspiration to very high rates.
Fhe original vegetation was adjusted to this arduous climate.
Now, however, weedy annuals replace the perennial grasses where
the land remains in pasture. These annuals sprout after winter
rains, carpeting the land with herbage and colorful flowers; matur-
ing in late spring, the plants die in early summer, and the land turns
a lifeless brown until winter.
Today, much of the valley is irrigated, and many different crops
are grown. East of the San Joaquin River, farming is intensive; in
size, the farms usually are not more than 20 to 40 acres (8 to 16
hectares). In contrast, on the drier, unirrigated western valley floor,
a single field may be 320 acres (129.5 hectares), and the spacious,
mechanized farms produce mainly dry-field barley and wheat (8) .

Sagebrush Zone

In the intermountain regions, one is almost never out of sight
of mountains but is in them only rarely. Because of the persistently
clear air that is common to high elevations, the mountains are al-
ways visible. Great variations in climate follow the extremes of ele-
vation from 282 feet (86 meters) below sea level in Death Valley to
more than 14,000 feet (4267 meters) above sea level in the White
Mountains nearby. The creosotebush zone (warm desert) and the
sagebrush zone (cool desert) divide the regions into two main sec-
tors. Within each, smaller and distinct subregions emerge.
Sagebrush (Artemisia spp.) carpets all of the basins of Wyoming
west of the Bighorn and Rocky mountains, reaching southward over
the lower parts of the Colorado Plateau and westward over the en-
tire Great Basin and Snake River Plain. This ubiquitous shrub also
covers the driest section of the Columbia Basin in the lee of the
Cascade Mountains. Although these areas give the impression of
flatness, they are high country. Few are less than 2000 feet (600
meters), and most of them exceed 5000 feet (1500 meters) above
the sea. Elevation, in part, explains why the temperature ranges
some 10 degrees cooler on the Fahrenheit scale (5 degrees cooler
on the Celsius scale) than in the southern deserts of the creosotebush.
Mean January temperatures fall below freezing, except in the
southernmost edge of the zone. The bright sun glares over the en-







ARIDITY AND MAN


tire sagebrush area 70 to 90 percent of the time during the summer.
During winter, the average sunshine drops to about 60 percent.
Daily extremes of temperatures, owing to elevation and to scant pro-
tective cloud cover, are great, particularly during the summer.
The dry northern subregion, the Columbia Basin, carries a mighty
river that skirts around its northern and western margin. On its
journey from the Canadian Rockies to the Pacific, the Columbia
River occupies a steep-walled canyon 2000 to 3000 feet (600 to 900
meters) below the flat lava surface of the basin. Despite the depth
of the canyon, the river and its tributaries have exposed only a small
portion of the massive basalt flows that blanket the entire area.
Because the river lies so far below the plateau surface, little of
the great volume of flowing water is readily available for agriculture.
Water diverted from the Columbia at Grand Coulee Dam into the
abandoned river channels and man-made canals now irrigates hun-
dreds of thousands of acres (hectares). Skirting the arid core of the
Columbia Basin is a semiarid belt that has been largely plowed up
and planted to winter wheat.
The Blue Mountains, which form a spur of the Rocky Mountains
south of the Columbia Basin, are clothed in ponderosa pine (Pinus
ponderosa) and rise to 4000 feet (1219 meters) to become a mois-
ture reservoir for their semiarid fringes. Man has made these high-
lands an area of seasonal grazing and forestry.
The Snake River Plain spreads in a crescent across 16,000 square
miles (41,440 square kilometers) of southern Idaho. This monoto-
nously rolling surface is deceptive, in both name and appearance; it
is structural, not river-built. Occupying only a small portion of the
plain, the river itself slips along, often hidden from view in a box
canyon deeply entrenched in the lava surface. The gentle surface
of the plain belies its hostile nature. It is built on the horizontal
flows of lava, and cinder cones rise frequently from the plain.
Much of the basaltic surface is broken and rocky and is insuffi-
ciently weathered to form good, workable soil. Where soil has col-
lected in pockets of the lava sheets or where wind-driven loess has
piled up on upland benches and tablelands, man has settled. Suffi-
cient to permit dry farming of grain, the annual precipitation aver-
ages 14 to 16 inches (356 to 406 millimeters) on the tablelands in
the eastern Snake River Plain (8). Agriculture cannot succeed
farther west on the plain without irrigation. Irrigation is centered








REGIONAL SETTING


Potatoes are harvested in an irrigated field at the foot of the Wasatch
Range near Ogden, Utah. Water here in the Weber Basin project is
stored by a dam for use during the dry summer of the sagebrush (Arte-
misia spp.) zone. (Courtesy U.S. Bureau of Reclamation)


on Pocatello, Twin Falls, and Boise, which hold most of Idaho's
population. The principal output includes the world-famous Idaho
potato, sugar beets, and dairy products.
The easternmost extent of sagebrush (Artemisia spp.) lies in the
Wyoming basins, which separate the southern and middle Rocky
Mountains. These sparsely populated, level plateaus rise to eleva-
tions between 6500 and 7500 feet (1981 and 2286 meters). Aside
from mining for fossil fuels, the sagebrush landscape is used sea-
sonally for sheep grazing, with some cattle.
On the Colorado Plateau, which joins the Wyoming basins on the
south and the southern Rockies on the west, a brilliant spectrum of
colors is exposed in the flat-lying sedimentary beds. The colors and
the deep and weirdly eroded canyons cut by the Colorado River and
its tributaries combine to produce one of the most magnificently
scenic regions on earth. The plateau, which comprises several sep-


A-f

It "'W \ $
?** *
1 1 -







ARIDITY AND MAN


arately named plateaus, covers an area of about 130,000 square miles
(336,700 square kilometers) (9). The spectacular canyons are best
developed in the heart of the plateau, where the change from the
surface to canyon is abrupt and precipitous.
The forested, dissected plateau border has two precipitation maxi-
mums-summer and winter (see Table II). A supremely important
water-catchment area is the belt of ponderosa pine (Pinus pon-
derosa) forest, 300 miles (approximately 485 kilometers) long, along
the rim of the Mogollon Plateau in central Arizona and southwestern
New Mexico.
Deeply entrenched canyons discourage irrigation farming, which
is possible only in a few favored localities. In western Colorado, a
lush, green oasis of small farms has developed in the Grand Valley
along the Colorado River. In a few small valleys in eastern Utah,
alfalfa is irrigated to supplement livestock feed. Yearlong grazing is
widespread over all of the Colorado Plateau.
The Great Basin, which is centered on the state of Nevada, is
classic "basin-and-range" country. Its ranges are uplifted and tilted
blocks. Both flora and fauna may be entirely lacking in the lower
sections of the bolsons, but in most of the lower elevations, sage-
brush and other shrubs prevail.
The forested ranges serve as important local moisture reserves,
especially during the dry season; some of the higher eastern ranges
receive more than 15 inches (381 millimeters) of precipitation an-
nually. The western Great Basin in the lee of the Sierra Nevada gets
the least amount, on the average usually 5 inches (127 millimeters),
or even less, each year. A small-scale repetition of this phenomenon
occurs on the lee side of numerous pine-clad individual ranges,
where less moisture occurs than on the windward side. Summer
showers fall more frequently with increasing distance from the coast.
The rainiest month shifts from winter to spring toward the east
(January in Reno, Nevada; March in Salt Lake City, Utah) in this
land of cold winters and warm summers. Settlement in the Great
Basin, "the undisputed domain of cattle, sheep, and coyotes" (8,
p. 189), is extremely sparse, and extensive seasonal grazing is the
only land use. The carrying capacity of the range is so low that the
land is not suited for individual homesteads. Rather, large ranching
operations graze stock with permits on substantial tracts of public
land.








Table II. Climatic records.


Mean annual Summer precipita-
precipitation tion, Apr.-Sept.


Winter precipitation,
Oct.-Mar.


Mean maximum
temperature, July


Mean minimum
temperature, Jan.


Colorado Plateau (s)
Green River, Utah
(northern plateau)
Crown Point, N. Mex.
(central plateau)
Prescott, Ariz.
(plateau border)

Great Basin
Reno, Nev.
(western basin)
Salt Lake City, Utah
(eastern basin)

Short-grass Plains
Great Falls, Mont.
(northern plains)
Denver, Colo.
(central plains)
Lubbock, Tex.
(southern plains)


Source: U.S. Weather Bureau.


Station


6.13 in.
(155.7 mm)
11.28 in.
(286.5 mm)
20.71 in.
(526.0 mm)


7.15 in.
(181.6 mm)
13.90 in.
(353.1 mm)


14.1 in.
(358.1 mm)
14.8 in.
(375.9 mm)
18.8 in.
(477.5 mm)


3.42 in.
(86.9 mm)
7.64 in.
(194.1 mm)
9.99 in.
(253.7 mm)


2.10 in.
(53.3 mm)
6.12 in.
(155.4 mm)


4.35 in.
(110.5 mm)
4.62 in.
(117.4 mm)
5.58 in.
(141.7 mm)


2.71 in.
(68.6 mm)
3.65 in.
(92.7 mm)
10.72 in.
(272.3 mm)


5.05 in.
(128.3 mm)
7.78 in.
(197.6 mm)


9.72 in.
(246.9 mm)
10.19 in.
(258.8 mm)
13.24 in.
(336.3 mm)


100.4F
(38.0C)
84.8F
(29.3 C)
90.4F
(32.4 C)



90.4F
(32.4C)
92.1 F
(33.4 C)


83.7F
(28.7 C)
87.4 F
(30.8C)
93.9F
(34.4 C)


8.1 F
(-13.3C)
19.6F
(-6.9-C)
19.1F
(-7.2 C)


17.2F
(-8.2 C)
19.5F
(-6.9 C)


13.5F
(-10.3C)
16.8F
(-8.4 C)
26.4F
(-3.1C)







ARIDITY AND MAN


Apart from occasional ranch and mining camps, the population is
concentrated in the oases on the periphery of the region. Salt Lake
City and several other towns populate the Great Salt Lake oasis (10) .
At the western extreme of the Great Basin, at the foot of the Sierra
Nevada, is the Reno-Carson City oasis. Farther east, irrigated lands
border the Carson and Truckee rivers and stretch like a beaded
string along the Humboldt before it disappears in the desert.

Creosotebush Zone
Creosotebush (Larrea divaricata) dominates the region that ex-
tends southward into Mexico (see Fig. 3). In southern Nevada, the
plant gives way to its northern neighbor, the sagebrush (Artemisia
spp.). Although there is disagreement on boundaries and even on
names, the Larrea zone can conveniently be divided into four units.
The moderately high Mohave Desert between 2000 and 5000 feet
(600 and 1500 meters) lies west of the Colorado River and north
of the 34th parallel, stretching northward into Death Valley and
southern Nevada. The Sonoran Desert, reaching into southeastern
California and southern Arizona from coastal Mexico, is relatively
low, from sea level or below to somewhat above 2000 feet (600
meters). The higher Chihuahuan Desert includes a small portion
of southeastern Arizona, much of the Rio Grande Valley and Tula-
rosa Basin of New Mexico, and a small section of Texas west of the
Guadalupe and Davis mountains. A change to the east in the flora
and general landscape suggests the fourth unit, the Rio Grande
border, which follows the Pecos River and lower Rio Grande to the
Gulf of Mexico.
Like the Great Basin, this region is mostly built by large-scale
block-faulting. Greatly elongated upthrust and downdropped masses
are alined roughly north and south. Nearly the entire region is arid
or extremely arid, yet a few mountains rise high enough to have
semiarid or humid climates on their upper slopes.
The western Mohave Desert was once probably large mountain
masses but now is worn low to almost undistinguishable relief. In
some places, this virtually achieves the perfection of the pediment
dome, the end-product of erosion under desert conditions. Occa-
sional knobby or mountainous remnants remain, but in no way do
they resemble the typical block-fault mountain of the basin-and-
range type.







REGIONAL SETTING


.. a



Water from the lower Colorado River flows through the Coachella Canal,
foreground, to irrigate the Imperial Valley of California. This scene is
a basin-and-range landscape of the Sonoran Desert. (Courtesy U.S. Bu-
reau of Reclamation)


It is across basin-and-range landscape that the Rio Grande, after
emerging from the southern Rocky Mountains, "picks its way across
the disordered surface [of New Mexico] from basin to basin" until
it reaches El Paso (11). In like manner, the Colorado, Salt, and
Gila rivers find their courses across the drab Larrea-covered bolsons
of Arizona and California.
The Colorado River, with a giant fan-shaped delta, has dammed
completely the structural extension of the Gulf of California, deny-
ing entry to floodwaters from the gulf into the below-sea-level (235
feet or 71.6 meters) Salton trough. When it was first viewed by
white men, the trough was dry, but in 1905 the river surged in
through a canal that had been dug to irrigate the Imperial Valley.
For 2 years the water flowed, creating a large shallow lake now called
the Salton Sea. When the river was forced back into its previous
course, the lake receded through evaporation. It would have dried
up completely if it had not been renewed by large amounts of irri-







ARIDITY AND MAN


gation tail water from the Colorado River, brought to the farms of
the Imperial Valley by the All-American and Coachella canals.
Very little rain and hot summers characterize all of the Larrea
region. The amounts and seasonal distribution of precipitation, hu-
midity, and winter temperatures differ in the several subregions.
Soaking winter rains are characteristic of the western Mohave Desert.
Winter brings snow regularly to the high Chihuahuan Desert and
where altitudes exceed 3000 feet (900 meters) Summer rains pelt
down in torrents from towering thunderheads, sometimes causing
disastrous local floods. From New Mexico eastward, these convective
thunderstorms are from tropical airmasses that originate over the
Gulf of Mexico. At El Paso, 65 percent of the yearly precipitation
occurs in the summer. However, not all of these showers there and
elsewhere reach the ground, for some are only tantalizing phantoms
evaporating in the hot, dry air.
Because prolonged drought is frequent and geographic distribu-
tion is variable, annual precipitation figures are misleading. Calcu-
lated averages represent a nonexisting midpoint between flood and
drought. Bagdad, California, had no rain between 3 October 1912
and 8 November 1914, but in 1905, 9.9 inches (251.5 millimeters)
fell. Nearby Death Valley, the driest place in the United States, re-
ceived 0.15 inch (3.8 millimeters) in 1932, but in 1941, 4.62 inches
(117.3 millimeters). The entire zone suffers from low humidity, ex-
cept the part that is close to the Gulfs of California and Mexico.
The high summer temperatures diminish only with altitude.
Death Valley holds one of the world's highest temperature records,
1340 Fahrenheit (56.7 Celsius) on 10 July 1913. The mean daily
maximum for July there is 116 Fahrenheit (46.7' Celsius). For
comparative maximum daily temperatures in July, see Fig. 4.
The creosotebush, which emits a pungent, tarry aroma after a
desert rain, is associated everywhere with a number of distinct plant
communities. Each community is disposed to special conditions of
climate, soil, drainage, and slope. The geography of these plants be-
comes a study in subtle environmental change. Like the domesti-
cated orange trees, frost-sensitive desert plants could not survive sub-
freezing temperatures without warm "thermal belts." Strong air
drainage on alluvial fans and low hills makes a "warm" environment
for a broad belt of cactuses, yuccas, and agaves interspersed with a
variety of low shrubs. On the other hand, the weirdly branched








REGIONAL SETTING


Joshua tree (Yucca brevifolia) needs a period of dormancy in the
comparative winter cold of the high western Mohave to survive.
Low, gray-domed bur-sage (Franseria dumosa in California; F.
deltoidea in Arizona) and cactuses mix with creosotebush on the
lower bajada slopes of the desert basins. Cactus reaches its most
superb development in the Sonoran Desert of Arizona, especially on


0 400 200 300 Miles
I 2I I 4 I Ki
0 200 400 KI ometers


Fig. 4. Mean daily maximum temperatures for July hit their highest
marks in the low desert valleys of southeastern California. Except where
specifically identified as Celsius (C), all readings are Fahrenheit (F).
(Adapted from a U.S. Weather Bureau map)








ARII)TY AND MAN


the coarser soils of the bajadas. The grasslands of the Chihuahuan
Desert are adjusted to the summer rains from the east.
The mild winters and long, hot summers of the Sonoran Desert
and the Rio Grande border give them a special advantage commer-
cially. Frost-free seasons of not less than 300 days permit the growth
of "off-season" winter food crops, frost-sensitive fruits, and a variety
of subtropic industrial crops. Thus, the oases of the Imperial Val-
ley, on the Gila and Colorado rivers at Phoenix and Yuma, and of
the lower Rio Grande on the Gulf Coast are important to the na-
tional economy.

Rocky and Sacramento Mountain Regions

The Rocky Mountains play a powerful role in the life of the arid
West. No discussion of aridity would be complete without due con-
sideration of the contradictions and extremes that the mountains
represent. The Rockies are responsible, to a large extent, for the
aridity. They screen the adjacent plains and plateaus from rain-
bearing airmasses. On the other hand, they serve as a huge rain-
catcher and are the source of the streams whose waters are basic to
much of the economy of the dry lands that spread out, apron-like,
from their flanks. Latitude, altitude, and topography combine to
create much diversity in local climate. In favored localities, the
mountains provide rich resources that support thriving economic(
communities, but permanent settlement is sparse over large broken
expanses.
The Rocky Mountain system, together with the Sacramento Moun-
tain region (the Sacramento, Guadalupe, Davis, and Santiago moun-
tains of southern New Mexico and west Texas), forms a long ram-
part from the Canadian border to the Rio Grande. The system is
about 200 miles (322 kilometers) wide and trends along a sinuous
axis from northwest to southeast for approximately 1500 miles (2414
kilometers) The Rockies, rising up between the plateaus, basins
and ranges, and plains, have been carved out of a great structural
arch. The Sacramento region, although it is geographically con-
tinuous, is not part of the Rockies geologically but is actually the
easternmost part of the block-faulted ranges of the intermountain
regions.







REGIONAL SETTING


Variety and complexity typify the structure and landforms. Un-
counted numbers of peaks rise 6000 to 8000 feet (1829 to 2438
meters) above the surrounding country. Some of the most ruggedly
beautiful of the mountain masses result from deep erosion in ex-
trusive and intrusive volcanics, such as the San Juan Mountains of
Colorado and the Absaroka peaks of Yellowstone National Park.
Many areas of subdued topography are scattered in the mountain
complex, however. Extensive, elevated erosion surfaces, intermon-
tane basins, parks, and broad valleys are dispersed widely throughout
the region.
The Rocky Mountains are the birthplace of countless small
streams, which combine and create the great rivers that support
much of the agricultural, municipal, and industrial life of the dry
plains. Fed by water from rains and melting snow and ice, these
streams have eroded a maze of canyons and broad valleys through
the uplands. The demand for their water exceeds the supply in
many areas, as lowland populations continue to increase at an ac-
celerated rate. A series of reservoirs on both slopes of the Rocky
Mountains, in addition to transmountain diversion tunnels, control
the flow of the water to areas of greatest need.
Even the dominant controls of climate-the mountain barrier, ele-
vation, local relief, and latitude-are quite variable. Although the
Rockies stand as a great climatic screen, their windward- and leeward-
slope relationships are not fixed. As a result, the western slopes be-
come the windward, wet slopes only when they are under the in-
fluence of Pacific airmasses and the passage of cyclonic cold fronts.
The eastern slopes become the windward, wet slopes when gulf air-
masses are dominant, and the western slopes then lie in the rain
shadow of the mountains. However, more of the total precipitation
occurs in winter, as snow, on the western side than on the eastern
side of the barrier, and the snowpack remains longer on the ground
on the western side. In contrast, many protected basins and valleys
receive little moisture and remain as deserts.
The mountains also serve as uncluttered playgrounds for people
seeking recreation. They are also the source of many valuable wood
products. Except in the northern Rockies, the abrupt topographic
break between plains and mountains is accompanied by an equally
sharp change from grassland to narrow-leaved coniferous forests. At







ARIDITY AND MAN


high altitudes, the timberline is boldly developed and marks the
transition between the forest and the Alpine-tundra formations. The
mountain forests occur in distinct zones; their character and ecology
are discussed in detail in Chapter 10. Timberline, which decreases
in altitude from about 12,000 feet (3658 meters) in southern New
Mexico to 10,600 feet (3231 meters) in Montana, marks the lower
limit of the Alpine tundra.
Transhumance, the movement of grazing livestock to high moun-
tain pastures in summer and back to lower valleys and plains in
winter, is almost universal throughout the region. The range for
cattle is largely confined to the lower slopes of the forested zones and
the grassy parklands. Sheep generally are grazed on drier ranges or
on the rich, nutritive grasses and sedges in the Alpine tundra and
subalpine Engelmann spruce-fir (Picea engelmannii-Abies spp.)
zones.
Agriculture in the mountains, which is dependent on the markets
in tourist and commercial centers, is widely dispersed. The occa-
sional level or more gently sloping areas that will support either irri-
gation or dry farming are essentially the home base or center for
the more important pastoral activities. Thin, lithosolic soils cover
most of the mountains; but, in many of the dry basins, parks, and
broad valleys, immature soils have developed in the alluvium and
are quite productive when rain or irrigation water is available.
Tourism and recreation activities probably support more people
in the Rocky Mountains than all other industries, and without tour-
ism many of the populated areas would disappear. Tourism, which
formerly was confined mainly to the summer season, now continues
throughout the year, as more and more people are attracted by the
opportunities to engage in winter sports.

Short-Grass Plains

The short-grass Plains form the nation's largest grassland in a
long swath east of the Rocky Mountains. They extend across the
Canadian border and south to the Pecos River. The eastern margin
follows the limits of short grasses mapped by Homer Shantz (12).
The wind-formed Sand Hills of Nebraska lie astride the semiarid
climatic boundary and are included because the grassland economy
that characterizes these hills is typical of the western Great Plains.







REGIONAL SETTING


B `S* -.



_H H ii I .,, ..o
' "7, ,d .. .- ,. "t It -
.. /,: .^ ^ *--.- .." .., -, -.. ,
..a .*



a_ ,-^. A ...-.. b,


A sparse cover of Yucca, creosotebush (Larrea divaricata), and Joshua
trees (Yucca brevifolia) typifies an arid, gravel slope in southern Ne-
vada. In the distance, shales are being eroded into badlands. (Courtesy
Robert R. Humphrey, University of Arizona)


Cultivation has been a precarious, marginal enterprise where it
has been pushed westward into the short-grass country. Now, the
already sparse rural population is declining, although numbers are
increasing in the major cities. Crop failure and losses of livestock
on a gigantic scale started the migration out of the Plains. However,
dry farming continues to move into the still drier areas.
The broad, unifying expanses of grassland and plain are in part
illusory, for the Black Hills, the Missouri Plateau, the Nebraska
Sand Hills, the southern short-grass, or High, Plains, each has its
unique character. The usual concept of the Great Plains as a flat,
featureless expanse is realized only in the Staked Plains of the Texas
Panhandle and eastern New Mexico. There, in every direction, flat-
ness extends beyond the range of the eye. Other areas are, of course,
broad and smooth, but not as extensive as in the Staked Plains. Flat-
ness is indeed broken in the high, rough, lava-capped mesas of
northern New Mexico and in the Sand Hills of Nebraska.








ARIDITY AND MAN


The dry climate, coupled with the short grass and a shortage of
wood and water, usually is strange and unattractive to people who
are accustomed to the humid woodlands of the East. In general,
precipitation is the greatest along the eastern margin of the southern
Plains. Except for a narrow belt that hugs the Rocky Mountains,
precipitation in the region decreases westward and northward from
the Gulf of Mexico, the primary source of moisture. Most of it falls
as rain during the summer. During the winter, icy blasts of polar
or Canadian air roll down the Plains unimpeded from the north.
The summers are warm and somewhat more humid than the winters,
when the sky is clear and the air is subfreezing for long periods (see
Table II).
High wind and long hours of sunshine contribute to high rates of
evaporation, making the effectiveness of precipitation low (10).
Windbreaks are often required to reduce the force of destructive
winds. Although unusually torrential and destructive rains do occur,
typically, the rain comes to the Plains as showers. The amount of
precipitation in a single shower and the time of year when it falls
are of utmost importance to the plainsman. Light rains are of little
value during hot weather, although they are beneficial at other
times (13). Showers may fall too early or too late in a growing sea-
son to help the small grain in its early stage of development.
Retention of moisture is of basic importance to dry farming and
stock raising in the drier sections of the short-grass Plains. The de-
gree of slope and the texture of the soil at the surface can be critical.
Excessive runoff is a problem, particularly on the thin, heavy, fine-
textured soils that cover large areas of central and southeastern Mon-
tana, western South Dakota, and northeastern Wyoming. On the
other hand, very sandy lands, such as those in the Nebraska Sand
Hills and along many rivers in the central and southern Plains, are
especially receptive to moisture. Unfortunately, they are limited in
fertility and very susceptible to wind erosion, making them of little
use except for pasture or hay. Rough lands of shale and sand can be
used only for light, scattered grazing and rank high as demerit, or
problem, areas (see Fig. 5) ; stock raising is decreasing. In contrast,
soils of considerable fertility, fine, windblown dust or loess, are
found widely in the central and southern Plains and along the
northern glacial margin, which roughly parallels the Missouri River.
In these fertile areas, the plainsmen practice dry farming.









REGIONAL SETTING


PLEISTOCENE
AEOLIAN DEPOSITS






--- -'- --'.





r. r





















S67-100% Loess Cover
Sj 33-67%
Cover of Glacil Drft
Partial Cover of Glac al Drift


DEMERIT LANDS


I -

.^1:


--'i ^ ^ -








Roughl-nd d Badronds
Mountanos '


i Cly Shales
E Sond


Fig. 5. Demerit, or problem, lands are those that are too mountainous,
rough, sandy, or clayey for full agricultural use. The loessal and glacial
drift areas of the Plains tend to be fertile.

Wheat is planted in the northern Plains in great strips perpendicu-
lar to the direction of the prevailing wind; the alternating strips of
cultivated and fallow land are set in rectangular blocks. To the drier








ARIDITY AND MAN


west, this landscape is replaced by rolling range, whose monotonous
expanse is broken only by the river valleys with their groves of
cottonwoods (Populus sargentii).
The characteristic vegetation of the western Great Plains is short,
native grass. Common species include the purple-spiked blue grama
(Bouteloua gracilis), which does not grow during drought and oc-
curs on loamy-clay uplands; buffalograss (Buchloe dactyloides),
whose gray-green foliage also may be seen in the uplands; and the
western wheatgrass (Agropyron). These short grasses may be in-
vaded by taller species from the subhumid eastern prairies during
wetter years; then the invaders retreat again in the face of prolonged
drought.
Although grazing appears to dominate the area because of the
broad expanse of land it occupies, the direct gross return per acre
(hectare) from crops in much of the region exceeds that from pas-
ture by more than 10 to 1. Even in the Sand Hills, for example, 80
percent of the area of most of the counties was devoted to pasture in
1935, 18 percent to permanent hay, and only 2 percent to crops. Yet
the crops were more valuable than pasture (14).
Recurrent drought on the Plains has started the quest for water
beneath the surface. From southwest Kansas to the Texas Pan-
handle, land under irrigation from well water has developed con-
siderably. West Texas now outranks the South Platte Basin in irri-
gated area. The Llano Estacado around Lubbock, Texas, is the
fastest-growing irrigated area in the United States and the largest
outside of California (15). Here cotton is the primary crop, but,
in the irrigated districts in Montana, alfalfa for winter livestock feed
predominates. On the Colorado piedmont, alfalfa and sugar beets
rule supreme. The highly mechanized dry-farm regions, which are
stricken periodically by drought and crop failure, specialize in spring
and winter wheat in the central part and grain sorghum and cotton
in the south. In all these areas, much land is allowed to lie fallow
to conserve moisture for the crop that follows, particularly wheat.
The towns and cities of the Plains grew in the oases where irriga-
tion developed, where the transportation routes have by easy choice
followed the valleys, and where there are attractive opportunities
for business, service, processing, and manufacturing. The Denver
metropolitan area (population 929,383 in 1960), with its sprawling,
expanding suburbs, is the largest urban center of the region.








REGIONAL SETTING


Wheat is alternated with fallow strips on the dry farms of Cascade
County, near Great Falls, Montana. Shelterbelts and strips "across the
wind" are characteristics of the Great Plains; they provide protection
from high winds. (Courtesy U.S. Department of Agriculture, Soil Con-
servation Service)

Tropical Arid Zones

The environments of Hawaii and Puerto Rico deserve special con-
sideration. These islands, separated by 5600 miles (9010 kilometers),
have many common aspects: latitude, economic development,
and dry coastal lowlands. Northeast trade winds prevail in both
areas. They ascend mountainous slopes and bring copious amounts
of rainfall as they cool. The air continues around the rugged back-
bones of the islands and, as it descends to the leeward slopes, warms
under compression. In Hawaii, these zones occur on the western
and southern margins of the large islands of Hawaii, Maui, Molokai,
Oahu, and Kauai. The small islands of Kahoolawe and Niihau,
which are completely arid, nestle in the lee of huge volcanoes. On
Maui, Oahu, and Molokai, the dry areas push inland along pro-







ARIDITY AND MAN


tected saddle-shaped valleys (16). In the Commonwealth of Puerto
Rico, an east-west semiarid belt along the southern coast parallels
the main Cordillera Central.
Because of high rates of evaporation, high temperature, low rela-
tive humidity, and constant wind, precipitation effectiveness is rough-
ly half that of the mid-latitudes of the mainland United States (17).
Tropical stations that receive more or less than 40 inches (approxi-
mately 1000 millimeters) on the average each year could be con-
sidered as subhumid (or humid) and semiarid (or arid), respectively
(6). But excessively drained, steep slopes and porous soils can pro-
duce drought well beyond this climatic limit. In fact, it is common
to see cultivated crops under irrigation in localities that receive as
much as 50 inches (1270 millimeters) of precipitation annually.
The need for irrigating is heightened by well-defined dry seasons.
Scarcity of water for agricultural, industrial, and residential de-
velopment mars the attractiveness of the leeward localities for settle-
ment. Water is ample on the larger islands of Hawaii and on Puerto
Rico. Problems exist, however, in collecting and transporting it
from areas of surplus to areas of deficit. Farmers of southern Puerto
Rico get supplemental water from wells, tapping in alluvial deposits
along the coast.
Ground-water supplies in Hawaii are vital, since there is no chance
to construct reservoirs where rock is usually porous and where
streams plunge down steep gradients. Some Hawaiian ground water
is perched at high levels above impermeable layers of rock or con-
fined between lava dikes. Such water becomes available when tun-
nels are driven into the mountains. Trapped ground water is some-
times subject to artesian pressure near sea level and is tapped by
skimming tunnels or drilling ordinary wells.
About half of the cultivated lands of the Hawaiian Islands are in
semiarid or arid settings (18). The major land use of the arid low-
lands is the grazing of beef cattle. Grazing forage is abundant in the
winter rainy season, and mesquite (Prosopis chilensis) pods abound
during the dry summer. Sugarcane predominates on irrigated land.
Irrigated canefields occupy portions of the isthmus of Maui and the
dry zones of Oahu and Kaui.
Acknowledgments: The cooperation and assistance of Peveril Meigs
is gratefully acknowledged. Mary H. MacPhail and Genevieve A. Cald-
well helped in compiling and preparing the manuscript.







REGIONAL SETTING


REFERENCES

1. H. L. Shantz, "History and problems of arid lands development,"
in The Future of Arid Lands, G. F. White, Ed. (Am. Assoc. for
the Advancement of Science, Washington, D.C., 1956), pp. 3-25.
2. C. W. Thornthwaite, "An approach toward a rational classification
of climate," Geograph. Rev. 38, 55-94 (1948).
3. P. Meigs, "World distribution of arid and semiarid homoclimes,"
Rev. Res. Arid Zone Hydrol. (UNESCO), Map 393, Rev. 1 (1953).
4. "Arid and semiarid climatic types of the world," Proc.
Intern. Geograph. Union, 17th Congr., Wlashington, D.C. (1957).
5. P. G. Worcester, A Textbook of Geomorphology (Van Nostrand,
Princeton, N.J., 1948), p. 220.
6. U.S. Dept. of Agriculture, Soils and Man, Yearbook Agr., U.S. Dept.
Agr. 1938 (1938).
7. J. L. Gardner, "Vegetation of the creosotebush area of the Rio
Grande Valley in New Mexico," Ecol. Monographs 21, 381-383
(1951).
8. F. J. Marschner, "Land use and its patterns in the United States,"
U.S. Dept. Agr., Agr. Handbook 153 (1958).
9. W. W. Atwood, The Physiographic Provinces of North America
(Ginn, Boston, 1940).
10. C. L. White and E. J. Foscue, Regional Geography of Anglo-
America (Prentice-Hall, Englewood Cliffs, N.J., ed. 2, 1954), pp.
283, 347.
11. N. M. Fenneman, Physiography of Western United States (McGraw-
Hill, New York, 1931), pp. 1-91, 390-392.
12. H. L. Shantz and R. Zon, "Natural vegetation," in Atlas of Ameri-
can Agriculture (U.S. Dept. of Agriculture, Washington, D.C., 1924).
13. J. B. Brandon and 0. R. Mathews, "Dry land rotation and tillage
experiments of the Akron (Colorado) field station," U.S. Dept.
Agr. Circ. 700 (1944), p. 8.
14. U.S. Congress, The Western Range, S. Doc. 199, 74th Congr., 2nd
sess. (Washington, D.C., 1936), p. 299.
15. U.S. Bureau of the Census, "A graphic summary of land utilization,"
U.S. Census of Agriculture, 1959 (1962), vol. 5, Spec. Repts., pt. 6,
chap. 1, pp. 21-22.
16. M. G. Cline et al., Soil Survey of the Territory of Hawaii (U.S. Dept.
of Agriculture, Washington, D.C., 1955).
17. R. C. Roberts, Soil Survey of Puerto Rico (U.S. Dept. of Agriculture,
Washington, D.C., 1942).
18. H. Bartholomew and Associates, An Inventory of Available Informa-
tion on Land Use in Hawaii (Economic Planning and Coordination
Authority, Honolulu, 1957).

















Indian Adaptations to

Arid Environments


RICHARD B. WOODBURY


Before the white man came to the New World, the areas we now
classify as arid and semiarid were the scene of both simple and
complex cultural developments. Such great advances as the domes-
tication of plants, the development of skilled metallurgy, and the
rise of urban centers took place in the arid regions of Central and
South America. Within what is now the United States, no native
culture reached the civilized stage that marked the cultures of the
Mexican Plateau and the Andes. Yet for America north of Mexico
the peaks in population density, which is one rough criterion of
human success in exploitation of the environment, were on the Colo-
rado Plateau and on the Pacific Coast just north of San Francisco
Bay.
The aboriginal occupations of the arid western United States were
varied, ranging from scattered hunters and gatherers with an ex-
tremely simple technology and social organization, in the Great
Basin, to villages of skilled irrigators whose fields covered thousands
of acres (hectares) along the Rio Grande, the Gila, and the Salt
rivers. None of these groups depended on others outside their own
arid homeland for consumption goods. Some produced agricultural
surpluses that supported sizable numbers of craftsmen and priests,
but the scarce and uncertain water supplies placed some limitations
on population.
The Indian was not independent of his arid environment or ob-
livious of it. Instead, he used it with great skill, overcame many of
its limitations, and worked out a great variety of adaptations to it.
These were, of course, cultural, and not instinctive, behavior; they
were learned by each individual from other members of the group,







ARIIITY AND MAN


rather than by his own trials and errors. Through language, com-
plex behavior systems are transmitted from one generation to an-
other; and because cultural behavior can be learned quickly, new
adaptations sometimes can be made with great rapidity. Yet cul-
tures also change slowly at times, each person continuing the patterns
of activity learned from early childhood, with no reexamination or
readjustment of them in the light of changed external conditions.

Arrival of Man in the New World

There is good evidence that man had entered and spread widely
throughout the New World by about 10,000 years ago (1). The
route of entry was through northeastern Siberia to Alaska; hence,
the first arrivals in what is now the western United States probably
moved in slowly from the north in small groups and gradually
learned to make use of the new food resources they encountered.
The climate and vegetation of the Pleistocene epoch were, at
times, markedly different from the present, even far beyond the
glacial borders. With cooler and moister conditions, areas now in
grassland had coniferous forests. Some of the present-day deserts
had heavy grass with tree-bordered streams. For example, pollen
studies in southeastern Arizona indicate that what is now the upper
part of the Sonoran Desert supported woodland in the past, with
pine, oak, juniper, and sagebrush (2). Sites on the Llano Estacado
of New Mexico and Texas, where mammoth and bison once were
killed and butchered, show evidence of former ponds and marshes,
although today there is no permanent surface water in the region.
The earliest arrivals in the New World, then, did not necessarily
face, and have to adjust to, an arid environment. If they came dur-
ing or late in the Wisconsin glaciation, when sea levels were low
enough to permit passage from Siberia to Alaska, they would have
had many centuries of cool, moist conditions.

Food Gatherers

Two main kinds of subsistence economy were developed by the
early inhabitants of North America: one was based on the collection
of wild plant foods supplemented with the hunting of small game;
the other was based primarily on the hunting of large game, includ-








INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


ing some of the now extinct large grazing animals. The utilization
of plant resources was a new development, since the necessary plants
would have been absent to the many generations of hunters who
made the slow expansion eastward across Bering Strait and then
southward. Essential to the collection and preparation of plant seeds
by the food gatherers were baskets, tumplines for carrying them,
sieves, grinding slabs or mortars, and many other artifacts (3). It
is important to realize that the development of techniques and equip-
ment represents a skilled specialization, and not a crude or casual
exploitation of the environment. Intimate knowledge of the area
and its plants (and of the small animals trapped, shot, or clubbed)
was necessary. Many of the small seeds are indigestible by human
beings unless the hard husks are broken by heat (parched with hot
coals in basket trays) or crushed.
Once the potentialities of these abundant, widespread, but unspec-
tacular resources were fully understood by the families or bands
roaming the West, this way of life could continue as long as the nat-
ural resources were available. Indeed, the Shoshonean-speakers of
Utah and Nevada were still living by these same techniques in the
19th century and were forced to change only when the invading white
man introduced changes (cattle, fencing, dams, weeds, and so forth).
If duration is an indication of the success of a pattern of existence,
then these gathering people of the grasslands and deserts achieved
an outstandingly successful subsistence adjustment.

Big-Game Hunters

A different type of skill and probably a considerable degree of
cooperative effort within the small, frequently moving bands were
needed for success in hunting the large grazing animals that were
present in the West until 7000 or 8000 years ago. Much of the hunt-
ing was done at waterholes and streams, where bison, camels, horses,
mammoths, and mastodons, as well as smaller animals, could be am-
bushed and killed at short range. Hunting was with spears or darts,
propelled with a short throwing stick, or thrust, or hurled by hand.
The distinctive lanceolate points with a thin, flaked channel on each
side (Clovis and Folsom types) have proved to be helpful in cor-
relating sites of these hunters, since only a few sites have radiocarbon
dates.







ARIDITY AND MAN


The disappearance of most of the large grazing animals brought an
end to this subsistence pattern, whereas the gathering pattern con-
tinued into times of greater aridity. The relative roles played by
man and climate in the extinction of these late Pleistocene animals
is still disputed, but if waterholes dwindled and herds were forced
into more constricted ranges, even a few scattered bands of hunters
eventually might have killed off one herd after another. The human
population dependent on these animals did not, I believe, die with
them but gradually increased its dependence on plant foods and
small game. If the recent work of Paul S. Martin, palynologist at the
University of Arizona, proves to be correct, no significant climatic
change occurred to contribute to extinction of the animals. Man
may deserve the entire credit or blame.

Introduction of Agriculture

The next major change in the ways in which the aborigines used
the arid western portions of North America was extremely slow to
come. The gathering and small-scale hunting pattern persisted with
little change for many millenniums. But it provided a valuable basis
for the eventual use of domestic plants, since the relationships of
plants to moisture, temperature, and other conditions were already
clearly understood, and the equipment used in gathering and pre-
paring wild seeds was equally appropriate for domestic plant foods.
Thus, the stage was set for the introduction of agriculture long be-
fore the event actually occurred. Initially, the only change required
in basic subsistence patterns was a somewhat less mobile life, with
at least part of the group staying with the crops from planting to
harvesting.
The beginnings of New World agriculture were far to the south
of the area considered here, and as in so many aspects of aboriginal
culture, the peoples north of the Rio Grande were peripheral, the
receivers, rather than the donors, of new ideas. Maize was the major
domestic plant of the North American Indians, with beans and
squash the most important supplemental crops. All three of these
species seem to have been domesticated in Mexico beginning before
5000 B.c., with the changes from wild plant to cultigen proceeding
over several thousand years. Recently Paul C. Mangelsdorf, Harvard
University botanist, and his associates have crossed varieties of corn








INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


containing early, primitive characteristics, as is seen by dissection
of archeologic specimens (4). They have demonstrated that the
primitive cultivated maize was a pod-popcorn, having the valuable
characteristic that, with no special preparation, the kernels could
be heated and would "pop" into an edible starchy mass. The yield
of these early corn plants was slight; only the remarkable later muta-
tions and hybridizations resulted in a crop that could be depended
on for the basis of Indian economy.
For the area that is now the southwestern United States, maize
agriculture did not begin until about 3500 B.c., the radiocarbon
date of tiny ears of corn from Bat Cave in west-central New Mexico.
This suggests a 1000- to 2000-year interval during which knowledge
and use of maize spread along the upland zone of the Sierra Madre
and its Arizona-New Mexico continuation, a distance of some 1700
miles (2700 kilometers) Diffusion took this long because of the
slowness with which maize became a high-yielding plant and the
sparseness of the population through which it spread. Plant gath-
erers and small-animal hunters live in small groups, each roaming a
sizable territory. Thus the opportunities for the transmission of new
culture traits, such as maize cultivation, are reduced to a minimum.
A band might add maize to its diet and grow small patches at suit-
able locations, and yet the seeds and the necessary knowledge of
their use would not be acquired by another band 12 or 18 miles (20
or 30 kilometers) away. Contributing to this slowness of diffusion
was probably the conservatism of groups who had worked out an
effective scheme of exploiting wild food resources, a conservatism
reflected in the persistence of the pattern for some 10 millenniums.

Village-Farming Life

Advantageous as the aboriginal pattern of agriculture may seem,
based on maize and supplemented by squash, beans, and a few other
plants, it nevertheless took millenniums to become established. It
was a profound, though gradual, break with the past, since the se-
quence of preparing the ground, planting, cultivating, and harvest-
ing precluded much of the former seasonal movement. Farming had
the great advantage that stored food supplies usually could support
the group through the winter. Although population density for most
of the arid West probably did not increase markedly with the adop-







ARIDITY AND MAN


tion of agriculture, concentrations in favored locations were possible
on a scale that food collecting had never permitted.
Religious and artisan groups within the larger whole could de-
velop, focusing their energies on many special activities that ulti-
mately benefited the entire village. Individual specialization could
develop advantageously; hence, the expert weaver, potter, house-
builder, jeweler, wood-carver, or other craftsman achieved and
passed on skills far beyond what the "jack-of-all-trades" in a nomadic
band ever could achieve. This pattern of village life is associated
with farming, not only in parts of North America, but throughout
the world.

Villages and Water Sources

Archeologic evidence indicates that the first farms in the South-
west were on the Colorado Plateau or the plateau border, where rain-
fall probably was ample for dry farming. The highest elevations
would not have been suitable, because of the too-short growing sea-
son, even though water was abundant. Much of the terrain was
rough and steep, and some of the soils were unproductive. At much
lower elevations summer rainfall would have been scanty for success-
ful germination and growth of crops. The oldest villages for which
evidence of agriculture reasonably can be dated fall within the 4th
to the 8th centuries A.D., and lie at elevations of 3500 to 6800 feet
(1100 to 2100 meters) (5). The only exception is on the Gila River
in Arizona at about 1200 feet (365 meters), where annual precipita-
tion is about 10 inches (254 millimeters). Since this is insufficient
for dry farming, the Indians simply may have planted in the wet
margins of the river after the spring floods.
This, then, may indicate the beginning of a type of farming that
was not wholly dependent on direct precipitation. But even with
the development of this and more elaborate techniques to use sur-
face water, farming was restricted. The spread of aboriginal farm-
ing was limited severely by environmental shortcomings that were
beyond the technologic skills of the Indians to compensate for, with
the partial exception of the water supply. The water supply was the
"major variable" subject to human manipulation and, thus, became
a major focus of effort.
The maximum spread of Indian agriculture, as is shown in Fig. 1,









INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


was achieved prior to the droughts of the 12th and 13th centuries.
Farming spread to Texas, New Mexico, Colorado, Utah, Nevada,
and Arizona, with its furthest reaches near Great Salt Lake in the
north and along the Canadian River toward the east. On the Great
Plains, agriculture spread westward from the Mississippi Valley and
eastern woodlands, where it had reached from Mexico in an expan-
sion separate from, but related to, that into the Southwest. Farming
advanced along the major rivers, such as the Platte and the Missouri,
avoiding the intervening grasslands.


GREAT BA ? I A
SHOSH 0O
[ f r .


Approximate


o zoo 4oo koo miler
oo 2 4'oo kilometers


Fig. 1. Maximum extent of prehistoric agriculture in the western
United States. All of this area was not farmed simultaneously, and by
the 16th century agriculturists had abandoned much of it. Tribal names
show the location in historical times of the Indian groups discussed in
this chapter.


z


I








ARIDITY AND MAN


It is impossible to show the hundreds of small areas that never
supported farming. The map should, ideally, show a myriad of tiny
oases, each based on a fairly dependable water supply, separated by
larger areas used for the hunting and collection of wild plant foods.
But wherever Indians did establish farming villages, the pattern of
subsistence seems to have been the optimum use of the environment,
within the limitations posed by a simple technology. Fields could be
prepared for planting with the digging stick or the stone or the
buffalo scapula hoe. Planting was with a simple dibble. Women and
children, as well as men, guarded ripening crops from birds, deer,
and rodents, and the harvest was carried on human backs to carefully
built storehouses, where each family hoped to have reserves to carry
it through at least one or two poor years. Only in the manipulation
of the water supply did Indian farmers effectively modify the en-
vironmental situation in order to improve significantly the acreage
and yield of their farms.

Water-Control Techniques

Small terraces on steep, intermittent streams, ditches fed by springs
and creeks, and the large-scale irrigation of the Gila-Salt and the Rio
Grande drainages have long been recognized by archeologists and
recently have received intensive study. Man's entire relationship
with his environment currently is receiving new attention by an-
thropologists. Although the technology of the Indians was simple
and their engineering knowledge elementary, in comparison with
ours, they were more successful than has been realized in managing
the water available for farming.
One of the most widely employed techniques was the building
of small terraces of dry stone masonry across steep, intermittent
streams. Soil rapidly accumulated behind each wall, and, during
periods of streamflow, moisture was held in sufficient quantity to
produce better crops than those in the surrounding area. At Mesa
Verde National Park in southwestern Colorado, recent work by
Arthur H. Rohn disclosed 40 series of terraces containing more than
900 individual terraces on the slopes of Chapin Mesa. In the Point
of Pines area of east-central Arizona similar terraces have been care-
fully mapped and analyzed (6) The area that such locations added
to farmland was probably not as important as the insurance they








INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


Prehistoric stone terraces at Mesa Verde, Colorado, held back soil and ac-
cumulated moisture for the watering of crops. (Courtesy R. B. Wood-
bury)


provided for a crop in all but the most extreme droughts and the
higher yields that they gave. These terraced fields are known,
in most of the area of prehistoric farming and undoubtedly con-
tributed significantly to the success of many farming settlements.
Judged by the age of some nearby archeologically dated ruins,
the terraces at Point of Pines probably were built from the 11th cen-
tury onward. Those of Mesa Verde are of about the same age. All
of these simple but efficient structures increased the agricultural
potentiality of rugged, uncertainly watered land, using moisture that
naturally concentrated in these locations but would otherwise have
been lost.
On gentler slopes without well-defined drainage channels, and on
some quite steep, rocky slopes, low walls or lines of boulders often







ARIDITY AND MAN


were built along the contour to serve a function similar to that of
the terraces. On nearly level ground, these lines of boulders were
sometimes laid out in irregular grids and probably had the addi-
tional purpose of protecting the soil from wind erosion and eliminat-
ing stones from the land to be farmed.
Another widely used farming technique is water spreading, the
planting of crops at the mouths of small canyons or arroyos, where
the gradient abruptly decreases and water tends to soak into the
ground. A little careful ditching and banking around plants at the
moment of runoff assures the optimum use of each small flow. As
with terraces, the area involved may be small, but it is far better
watered than the adjacent land. This type of farming has continued
in use by the Papagos and Hopis of southern and northeastern Ari-
zona, respectively. It has been determined (7) that Hopi fields from
14 to 247 acres (6 to 100 hectares) in size each received runoff from
a watershed with 15 to 30 times its area. In arid areas with infre-
quent, intense local summer rains, this is excellent assurance of water
for a particular field location, resulting from the Indian farmers'
careful observation of natural conditions.
In contrast to these methods for making better use of water where
it occurred naturally, the Indian farmers of the Southwest also
brought water to their fields by means of ditches. These ranged in
size from 1.5 feet (0.5 meter) wide (as at Montezuma Castle Na-
tional Monument in the Verde Valley of Arizona, where ditches are
preserved by a natural mineral deposit) to 33 feet (10 meters) or
more in width for the larger canals along the Gila and Salt rivers
in southern Arizona (8, 9). The large canals were as much as 10
to 12 miles (16 to 20 kilometers) long, and, although built without
engineering instruments, they followed a regular gradient success-
fully, allowing water to move from a place where it could not be
used or was overabundant to a place where it could irrigate crops.
The large canals of southern Arizona are of special interest because
of their number and size. Conservative estimates suggest more than
185 miles (300 kilometers) of main canals, and the total may have
been twice this. Canals irrigated areas as far as 7 or 7.5 miles (11 or
12 kilometers) from live water and watered many thousands of acres
(hectares) of intensively cultivated land. The oldest dated trace of
a major canal was built about A.D. 800. A long, slow development is
probable, starting from simple floodwater farming along the banks








INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


of large rivers, with planting taking place as soon as spring floods
subsided.

Decline of Village-Farming Life

The widely established farming villages of the Southwest and the
considerable penetration of horticulture into the northern short-
grass Plains rested on a highly successful exploitative pattern-maize,
beans, and squash raised in sufficient quantities to provide reserves
against occasional poor years, with villages, sometimes of several
hundred people, maintaining themselves on the same farmlands for
many generations. Nevertheless, this farming life was precarious,
always threatened by the many aspects of the environment over
which the Indians had little or no control. In both the Plains and
the Southwest, it failed at innumerable locations. Beginning in the
13th century, one settlement after another was abandoned, and by
the 16th century the area of village-farming life was about one-
tenth of what it had been earlier. Among explanations for this
eclipse, disease and raiding nomads can be dismissed for lack of con-
vincing evidence. Climatic change of some sort is repeatedly in-
voked as an explanation and is almost certainly correct. But both
the nature of the change and details of its effect on aboriginal farm-
ing are still far from clear.
There is evidence from tree-ring studies of a long and severe
drought in the 13th century, undoubtedly sufficient to have resulted
in crop failures year after year in some places. It may have set off
a cycle of erosion, through the reduction of vegetative cover. An-
other climatic fluctuation, a shift toward lower temperatures and,
therefore, a shorter growing season, also may have contributed im-
portantly to the withdrawal of aboriginal farmers from many areas at
higher elevations.
By the 16th century, in the Southwest, there were villages of farm-
ers only on the Rio Grande in New Mexico and at a few locations
westward to the Hopi villages of northeastern Arizona, along a short
stretch of the Gila River, and in scattered locations in Chihuahua
and Sonora in Mexico. On the short-grass Plains there were still
farmers along the middle Missouri River, but nowhere to the south.
Many of these villages remained during white settlement as enclaves
where traditional Indian farming methods were practiced, and where








ARIDITY AND MAN


New World crops long adapted to arid conditions survived until
white plant breeders and farmers became interested in them. Small,
widely dispersed populations, relying on a large assortment of wild
species, gave up their collecting economy only when the inroads of
white hunters, ranchers, and farmers destroyed the plants and ani-
mals on which they had depended. One such group in the South-
west, the immigrant Navahos, had adopted a senidependence on
agriculture from contact with native farmers they found in the Rio
Grande drainage, before the coming of the whites.

Intrusion by Adaptable Athabascans

Although the Navahos and Apaches, speakers of closely related
Athabascan languages, now are among the largest groups of Indians
in the nation, they are recent arrivals from the Far North. Archeo-
logic evidence is lacking to trace the movement of their ancestors
southward, but small bands probably moved down the eastern side
of the Rocky Mountains, occasionally wandering east as far as the
outlying farming villages of the Plains; other bands may have moved
south through the intermontane region onto tle Colorado Plateau.
By about the beginning of the 16th century, they had reached north-
western New Mexico. Extensive recent research has failed to support
the long-held belief in a much earlier Athabascan arrival.
Although they came to the Southwest as hunters and plant collec-
tors, they quickly acquired the farming skills of the Pueblo Indian
villagers whose ancestral lands they were infiltrating. The rapidity
of this fundamental economic change is evidence of a remarkable
ability in cultural adaptation that marks the Navahos. "The Nava-
hos show, on the one hand, a general lack of emotional resistance to
learning new techniques and using foreign tools, and, on the other,
a capacity for making alien techniques fit in with their preexistent
design for living" (10, p. 28).
With the acquisition of farming, the Navaho population probably
expanded, as did the area they occupied. They only partially adopted,
however, the village pattern of life, most families preferring to live
scattered along the valleys where their fields were. The source of
their agricultural techniques and crops and also of their architec-
ture, weaving, and pottery-making in the 16th and 17th centuries







INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


rnmS*;1
Present-day Hopis in Arizona terrace their hillside gardens in much the
same manner as their forefathers did. (Courtesy U.S. Department of
Agriculture, Soil Conservation Service)

is, nevertheless, clearly Puebloan. But the Navahos maintained their
linguistic and political independence; and their basic outlook on
the world-their value system-altered hardly at all.
By the beginning of the 18th century, however, two other con-
spicuous elements in Navaho life were being adopted: sheepherding
and the use of horses. Although the Puebloans and possibly the
Navahos acquired a few sheep, cattle, and horses as early as 1540
from the Coronado expedition, the farming pattern really was not
changed. Sheepherding, when the Navahos later took it up, provided
a means of using large tracts of sparse grassland and replaced hunting
as a source of meat. Weaving was greatly stimulated by the increased
wool supply, and by the time that Arizona and New Mexico were
wrested from Mexico and added to the United States, herding and
weaving were well established as basic parts of Navaho life. When
the Navahos were released by the U.S. Army in 1868, after 4 years
of captivity (11), they were given 15,000 sheep and goats as a start







ARIDITY AND MAN


toward renewed self-sufficiency. An increase in numbers led to seri-
ous overgrazing of the range in later years and to the bitterly op-
posed stock-reduction program that was carried through by the Bu-
reau of Indian Affairs in the 1930's.
In only about four centuries the Navahos transformed themselves
from a handful of hunters and collectors into a settled, numerous
folk, who depended on corn farming and on large flocks of sheep
and goats for subsistence and on horses for transportation and wealth.
Not only their economy was transformed, but also their dress and
architecture, their handicrafts, and their religious rituals. Never-
theless, their adjustment to the arid lands they had made theirs was
precarious. From their first arrival in the Southwest until the mid-
19th century their numbers probably increased about tenfold; in
1864 the captives totaled 8354. In the last 100 years the population
has increased tenfold again, and the total is now approximately
100,000 (12) Population increase has brought critical problems. In
spite of its 16 million acres (6.5 million hectares), the reservation's
resources have proved to be hopelessly inadequate for a farming
and herding life.

Shift to Wagework

The next great economic change for the Navahos was learning to
work for wages. This required new habits and points of view,
the shift to a money economy instead of a subsistence economy.
Decades of experience at stores in the Navaho country (Fig. 1) had
only partly familiarized the tribe with money as a medium of ex-
change, since much of the business was for credit, and a Navaho's
wool, rugs, silver jewelry, or other goods were credited against his
account on the trader's books. It was not until after 1930 that wage-
work and cash became a crucial part of the income, at a time when
erosion, overgrazing, and drought were causing extreme hardship.
By 1940 about one-third of all Navaho income was from wages,
mostly on the reservation and for the government (10). Off-
reservation work has increased steadily as the Navahos have learned
better the kinds of skills needed by white employers and the kind of
life that depends on cash instead of subsistence from fields and flocks.
This has been slow, however, compared with surrounding non-Indian
areas. By 1960 about 70 percent of Navaho income came from wages,







INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


but per-capita income was about one-third of that of the nation as a
whole.
Undoubtedly the least expected means that the Navahos have
found for taking advantage of their resources, and their increasing
skills, is in their capable management of the mineral wealth dis-
covered on their land. Since the United States government holds
title to reservation lands in trust for the tribe, any leases and royal-
ties go to the tribal treasury. Not until 1947 did the tribe employ
an attorney to assist in protecting its interests, and only in the last
three decades has the tribal organization become truly effective (a
tribal council with a popularly elected chairman; full-time expert
employees in charge of such matters as public welfare, resources,
and law enforcement; and a tribal judiciary) The result has been
close scrutiny by the Navahos of the terms of mineral and other
leases, and also substantial expenditures by the tribe for long-term
developments to supplement the extensive federal program of range
management, irrigation, public health, industrial development, re-
sources appraisal, and so on.
Making this development possible has been the substantial income
from helium, oil, natural gas, coal, vanadium, and uranium, all
found on the reservation in significant quantities. For example, in
1960 there were 860 producing oil wells there with an annual out-
put of 34 million barrels (5.5 million cubic meters). Tribal in-
come on oil and gas leases has been about $110 million since 1935,
and other minerals have added some $7 million more (12).
Through the efforts of the tribal council, royalty rates have been
increased substantially over those originally specified by federal au-
thorities. Oil companies have been forced to shut down wells until
installations permitted the marketing of natural gas that was being
wasted; employment of reasonable numbers of Navahos has been
required in oil and other mineral activities; and several small in-
dustries have been attracted to the reservation.
The financial opportunities afforded the tribe by this flow of
wealth have been important. In a 3-year period, 40 new chapter
houses were built at a cost of $50,000 to $60,000 each, providing
community centers and meeting places for the "chapters," which
form the local means of partial self-government. An off-reservation
ranch was purchased on which to maintain the tribal herd of breed-
ing rams. A tribal public works program, to alleviate economic dis-







ARIDITY AND MAN


tress in selected areas, was begun in 1957, with tribal appropriations
totaling $5 million for this purpose in 1960. In 1954 a tribal scholar-
ship program was started, supported by a trust fund that now has
an annual income of S 1111i 000: by 1961 there were 130 Navahos with
college degrees, a highly promising advance for a tribe determined
to manage well its complex affairs.
The record is unique among Indian tribes, both in growth in
numbers and wealth and in the Navalios' ability to remain self-
respecting and forward-looking in spite of the hardships they have
undergone and the forces that have tended to change every aspect
of their culture. They are almost unique, too, in the unforeseen
wealth that their reservation has brought them, although oil and
timber have proved to be substantial assets to a few other Indian
groups. The Navahos, then, are not an example of what any tribe
might do, but they suggest the latent talents that may be brought
to light by a special sequence of events. The current trend among
the Navahos toward technologically complex uses of their reserva-
tion resources parallels the suggestion made repeatedly that arid
areas, in general, hold more promise of supporting substantial popu-
lations through mining and manufacturing than through the tradi-
tional herding and farming economies.
Although each Indian group has gone through a somewhat differ-
ent sequence of adjustments to white contact, a common pattern
has been initial intermittent contacts with white explorers; then a
sudden rush of liners, ranchers, or farmers whose efforts to pre-
empt land and water for their own uses led to violence and raids
by the Indians, eventual subjugation by military force and the con-
finement of the remnants of the Indian group on a reservation: un-
successful efforts by government agents to convert the Indians to
herding and farming: and finally partial adjustment of the Indians
as marginal farmers, unskilled laborers, and relief recipients.
The Navahos conform in part to this generalized sequence but to
a lesser degree than some other groups. The next few pages contain
a brief discussion of three other "tribes," which followed somewhat
different paths of adaptation to the new circumstances they found
forced on them. They differed from the Navahos and from one an-
other in their precontact cultures. The means by which white cul-
ture reached them also differed; hence, the diversity of their re-
sponses and acculturation is expectable (3) .








INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


Collapse of Great Basin Culture

At the time of the first white explorations and settlement of the
Great Basin (or intermontane region) the aboriginal population
consisted of small, scattered groups of Shoshonean-speakers, the Utes,
Shoshones, and Paiutes. Their culture in most details was a contin-
nation of the millenniums-old pattern of dependence on wild plants
with supplementary hunting. Because of the sparseness of natural
resources, population density was low. Indian groups larger than a
family were never more than temporary, seasonal gatherings, usually
brought together by a rich crop of pine nuts (Pinus monophylla and
P. edulis) These nuts were collected in great quantities and fur-
nished the main food through the winter. Most of the year each
family moved systematically over a poorly defined "territory" extend-
ing 22 miles (35 kilometers) or more in all directions from the win-
ter camp. On the average, a family of five needed the natural prod-
ucts of 115 to 150 square miles (300 to 400 square kilometers) for
subsistence (14).
Except for occasional multifamily rabbit drives and antelope
hunts, families dug roots, collected seeds and insects, and hunted
rodents independently. Since an area would support only a few
people, families preferred to scatter widely. For this meager but
usually sufficient existence, the traditional skills, equipment, and
knowledge developed through the centuries had proved to be ade-
quate. But the culture of these Indians of Utah and Nevada was
not capable of easy adjustment to new circumstances; the balance
was too delicate, and their adaptation to the Great Basin environ-
ment was too little suited for any other conditions.
Sporadic contacts by explorers and trappers from 1776 onward
produced no serious ecologic or cultural disturbances, but in the
1840's large numbers of immigrants traveling with horses, cattle, and
wagons, began to cross the area and occasionally clashed with the
Indians, who were viewed with suspicion and hostility. Indians
often raided the wagon trains for any animals that could be killed
and eaten. This second phase of contact began to disturb the In-
dian way of living through the destruction of grass and game. With
the discovery of gold in California in 1848 and in Nevada in 1849,
miners and immigrants swarmed westward, and the depletion of
plant, animal, and water resources increased rapidly. Although in








ARIDITY AND MAN


1850 the Shoshones of northern Nevada were still stealing horses
only for food, 10 years later they, like other Great Basin groups, had
formed mounted predatory bands, which raided white travelers and
settlers with frequent success. This phase was brief, for white settlers
with Army assistance quickly broke the strength of the raiders. In
spite of serious efforts to settle Indians in agricultural communities,
there was little success, partly because of the Indians' inexperience,
and partly because the white settlers repeatedly dispossessed the In-
dians from fertile land (15) More and more, the Indians were
reduced to living as hangers-on, beggars, scavengers, and pilferers
in the growing white communities.
When reservations were established in the Great Basin, they were
on lands less attractive to white settlers and often remote from the
Indians' former homes. With meager funds from the federal govern-
ment, Indian agents attempted to provide issues of rations that would
prevent outright starvation, but Indian life continued to deteriorate;
only a few Indians learned to farm successfully on the poor land
with inadequate water supplies to which they were confined. They
lacked tools, seed, and knowledge; also, they were unprepared, so-
cially and psychologically, for a settled life with the rigorous sched-
uling of work that irrigation farming demanded.
One of the most catastrophic congressional acts, in terms of long-
term effects on the Indians, was the Allotment Act of 1887, which
permitted small parcels of reservation lands to be given to individual
Indians. With no tradition of individual landholding, and under
strong pressure from both Indian Service officials and the land-
hungry public, much of the best land was leased or sold-not only
from Utah and Nevada reservations, but throughout the West. As
an Indian agent's report of 1905 pointed out, the Utes seemed
to attach value only to money and not to land; they were selling land
and horses, virtually their only valuables, for small sums that were
spent quickly.
Today there are still Utes, Shoshones, and Paiutes in the Great
Basin area, many on reservations and others scattered throughout
the white man's settlements. They have preserved fragments of their
traditional culture but rarely as an effectively functioning pattern
of behavior. In spite of some increase in self-respect and conscious-
ness of their own identity in the last few decades, the trend toward
absorption, both physically and culturally, into the surrounding non-







INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


Indian population continues. Economically the Indians now live by
the same techniques as their white neighbors, perhaps with less re-
current hardship than in prehistoric days, but precariously and on
an impoverished scale compared with the surrounding population.

Rise and Fall of the Sioux

For at least a century the "typical Indian" of popular imagination
in both the Old World and the New has been the mounted warrior
and buffalo hunter of the Plains. This figure is a product of the
Europeanization of the New World, however, since his horse and
gun both were foreign additions to his aboriginal cultural heritage.
Moreover, some "Plains" tribes, such as the Teton-Dakota (the
western Sioux) were not even occupants of the Plains until historic
times (16).
The Dakotas began to move westward in the latter part of the 18th
century as a result of pressure from other Indian groups to the east.
By the time their movement had reached the Black Hills of western
South Dakota, they had large herds of horses. Although the buffalo
had been hunted on foot on the Plains for millenniums, groups on
horseback could increase greatly their hunting effectiveness, in both
the search for buffalo herds and the sudden attack.
The Dakotas successfully ousted one tribe after another from
the fine buffalo lands of Nebraska, North and South Dakota, Wy-
oming, and Montana, and on this vast "sea of grass" they prospered
and grew wealthy. Through the Chippewas and the French trappers
and traders, they obtained guns, beads, knives, and other goods that
they valued. But this Indian adaptation to life on the dry, windswept
northern Plains was only a short-lived phase in a series of changes,
a result of the welding of two important innovations, the horse and
the gun, to an already existent mobile hunting culture. As buffalo
hides succeeded beaver pelts in the fur trade, the slaughter of
buffaloes began to reduce seriously the once "numberless herds."
But a greater threat to the Dakotas appeared before the decimation
of the buffalo became a problem.
Large-scale overland migration by settlers began in 1841, and the
Dakotas and other Plains tribes sensed at once the threat to their
lands and livelihood. There were countless attacks on wagon trains,
and atrocities on both sides, but westward migration continued. In







ARIDITY AND MAN


1854 large-scale military campaigns began against the Sioux, with
the inevitable result that they finally capitulated and were confined
to reservations. By 1877 their power was broken, the buffalo as a
natural resource was wiped out. and an era of peaceful, settled, and
impoverished existence began (17).
The Dakotas' adaptation to Plains life had required vast, sparsely
occupied tracts of land and was based on the buffalo, which provided
not only food but clothing, shelter (the poles of the tipi were covered
with hide), essential equipment (sinew for sewing, bones for scrap-
ers, leather for containers), and finally fuel (sun-dried buffalo drop-
pings, which made a hot and nearly smokeless fire) With confine-
ment on reservations and the buffalo gone, the reaction of the In-
dians was at first complete apathy or bitter despair. The erratic and
often ill-planned efforts of Indian agents and missionaries to turn
them into settled farmers and to educate them in the white man's
ways too often brought only opposition and failure. Most of their
land was unsuited for farming, even if they had had the necessary
skills and equipment. Gradually the Sioux have accepted the ma-
terial culture of the white man, insofar as it has been available to
them. But many traditional beliefs and attitudes persist and make
their way of life a hybrid that is neither satisfying to them nor
successful in providing the necessities of existence.

Adjustment to Reservation Life

For briefly tracing the Indians' adjustment to their new circum-
stances and the development of the new patterns by which their semi-
arid Plains environment might be used, the Pine Ridge Reservation
of the Sioux in southwestern South Dakota can serve as an example
(18) Several features marked the early years of reservation life.
Schooling for children was enforced by every means the agent could
employ, including jailing of truants and their parents. Military dis-
cipline was employed in the boarding schools, and the use of the
Dakota language and the wearing of native clothing or Indian hair
styles were forbidden. Although methods today are less harsh, many
teachers in Indian schools still see as their main goal the creation of
individuals with the white man's attitudes and ambitions.
An equally profound influence in the changing of Dakota life was
the complete breakdown of the power and influence of the chiefs.








INDIAN ADAPTATIONS TO ARID ENVIRONMENTS


The chiefs could not now relieve the poverty and hunger of their
people as could the Indian agents, who controlled the issuing of
government rations. Thus the Sioux lapsed into a paternalism that
made "Washington" the final source of authority and material as-
sistance. Although some farming was practiced in early reservation
days, monthly issues of rations were needed to alleviate even partly
the acute hardships that most families faced. Nevertheless, a start
was made toward self-sufficiency, but not through the farming that
was initially seen as the essential concomitant of reservation life.
As early as the 1870's some Sioux began to raise cattle, the first
stock being some of the animals regularly issued by the Army. By
1885 there were 10,000 head on the Pine Ridge Reservation, for
example, and by 1912 about 40,000. This was, in many respects,
ideal grazing land, and the growth of a cattle economy was hampered
chiefly by the government policy of allotting reservation land to In-
dians individually, a perpetuation of the American myth of the self-
sufficient farmer. Unfortunately, when beef prices were high in























Lines of stones mark the boundaries of farm plots that overlook the Gila
River in Arizona. The fields probably were abandoned by A.D. 1400.
(Courtesy R. B. Woodbury)







ARIDITY AND MAN


World War I, the Indians were encouraged to sell off their herds,
partly by pressure from whites who wanted to lease the rangeland.
By 1917 the Indian herds were gone and the range was in the hands
of non-Indian lessees.
Briefly, the Indians enjoyed a splurge of spending from their new
wealth. Then in 1921, the postwar depression resulted in defaulting
on the leases, and the Indians' income ceased. The Bureau of Indian
Affairs began to encourage the Indians to sell their allotments of
farmland to the swarms of land speculators and wheat farmers who
came into the northern Plains. Again, the Indians' profits were
quickly gone, and the combination of severe drought beginning in
1924 and the great depression in 1929 left the entire area desperately
eroded and poverty-stricken. In 1937 the government again began
to encourage the growth of the cattle business, recognizing that the
rangeland is the only major resource of the Indians. But even with
supplementary wagework and federal aid in establishing a herd,
few families have become self-sufficient.
There have been several scientific studies of the plight and pros-
pects of the Sioux in the last three decades. The most recent of these
(19) focused on the Lower Bruld Reservation of South Dakota,
which lies along the Missouri River. Although originally it was
nearly 247,000 acres (100,000 hectares) in extent, about 40 percent
of the land has been sold to non-Indians by the Indians to whom it
was allotted. The remainder is rangeland, except for about 6200
acres (2500 hectares) of cropland and woodland, and most of this is
now flooded by the waters behind Fort Randall Dam.
Although the tribe has been compensated by money voted by
Congress, and part of this sum has been used for tribal land acquisi-
tion, the Lower Bruld are still seriously lacking in land on which
they can hope to become self-sufficient. Like many Indian groups,
their economic condition reached a low point in the 1930's; in 1935
only 7 out of 102 families in the Lower Bruld community were self-
supporting. Fifteen years later, the sale of livestock reached $166,000
a year, providing about half of the group's entire income (but much
of it went to a few fairly prosperous Indian ranchers) By 1958
livestock sales had declined; welfare assistance made up one-fourth
of the community's income; selling and leasing some of their allotted
land, another one-fourth; and wages, one-fifth of the total income.
Most of the Lower Bruld land is suited only for cattle raising,








INDIAN ADAPiIA II ONS 1() ARI) I NVIRONII N'i N 77

which (can support adequately lbut a fraction (o the group. Tlhcin
human resources are limited by lack of skills, poor health, mndl in-
familiarity with the planning anl mianagelenttt sthat mall indepeld-
ent businesses would recqire. The acciimutlation ol capitall ()r \een
material wealth Ieyond the level of the community is hampered by
the Sioux tradition o() hospitality and sharing and tlie persistence
o)' strong kinship ties, which make every individual leel both the
need and the desire to share widely and generously.
Many non-Indians il the United States have expected that tile
Indian population gradually would be absorbed as Indians left reser-
vations tor work in towns and cities, and that those remaining would
become self-supplorting: thus the nation's "Indiami Iprblem"' wmold
disappear. O()nl the Iragmentation and dispersal into the \cry bot-
tomn ()o the white (co((n ic (c-lommunity of such grups as the Great
Basin Shoshonean-spcakcrs support, this prediction. Recent Sioux
history shows how unrealistic it is, even for economically depressed
tribes. The 1,ower Brultl', for example, are slowly becoming more
effective as a group, working through their tribal council on long-
range conilomic and sc( ial plans, with vigorous help from tile Bureau
of Indian affairs lThy retain certain Indian ways, even though they
have adopted many while c customs, and can look forward to continua-
tion as ll Indian ,mgrup with an increasing degree of sell-governnment,
econmiic sell:-sufficicncy. and sell-rc spect.

Papago Struggles in the Desert

When the Spanish missionaries and explorers pushed north into
Sonora and what is no1w southern Ariz/ona, they found the Papagos
living in small. widely scattered \illalges in the desert region that
today includes their reservation. The Papagos had worked out a life
that took tlie best possible (advan tage (o their extremely limited water
suppllis. They spent the winter months in "well villages" in the
canyons ()o the manuy llmo(untain ranges, where there were springs and
small wells, and the summer tmoiths near their (confields, located
where intermittent streams fromll the mountaills spread out on the
desert, or in the broad valleys where water ()could be impounded
by simple earth dnals. But farming was precarious and gave only a
part of their diet: wild plant foods. such as tile mcesquite (Pros/)is
ju}liIloii) hean. the fruit of tile esaguar t actuis ((,'(< ii',icai gigantc'a)








ARIDITY AND MAN


and many small seeds and greens, were indispensable. Hunting con-
tributed a small but important part of their food supply.
Contacts with the Spaniards, mainly through missions, changed
Papago life only slightly, although systematic attempts were made to
introduce domestic animals and new crops. When the Papago coun-
try became part of the United States in 1854, as a result of the Gads-
den Purchase, the aboriginal way of life had changed relatively little
(20).
With the invasion of their lands by white miners and ranchers
from 1870 onward, changes came rapidly. Mining towns flourished
briefly and collapsed, but some of their wells remained as permanent
assets of the Papagos. The expanding cattle industry of the white
settlers soon resulted in serious depletion of the natural vegetation;
and, with the growth of Papago stock raising, competition for grass
and water was strong. The Papago Reservation was not created until
1916, and by then much of its sparse natural vegetation was de-
stroyed; erosion had made many farming areas unusable. It was im-
possible for the old life to continue. The Papagos managed to con-
tinue some farming, but on a decreasing scale, and their herds of
cattle deteriorated, even though many new wells were drilled by the
government.
By the 1920's and 1930's, the Papagos were close to destitution,
with disease and malnutrition taking a serious toll. When the Pa-
pago development program was prepared by the tribe and the Bu-
reau of Indian Affairs in 1949, it was determined that 56 percent of
Papago income came from wagework, 27 percent from cattle, and
only 7 percent from farming. This reflected a rapid change toward
a cash economy, but average family income was only S1500 a year,
about one-third of the average for Arizona farm families.
No substantial mineral resources have been found on the Papago
Reservation, and the cattle business, in the hands of only a few
families in each district, supports but a small proportion of the
people, in spite of substantial efforts to upgrade stock, reduce erosion,
improve water supplies, and introduce better marketing practices.
To a greater degree than on most Indian reservations, the people
themselves are the only major resource on which hopes for a better
future can be based. Fortunately, the Papagos have a tradition of
hard, steady, hand-labor-essential for either their precarious and