If you do not need this report after it has served your purpose, please return it to 

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UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Water-Supply Paper 796-E

GROUND WA^ER IN 

AVRA-ALTAR VALLEY, ARIZONA

\

BY

DAVID A. ANDREWS

Contributions to the hydrology of the United States, 1937 

(Pages 163-180)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1937

For sale by the Superintendent of Documents, Washington, D. C. ------ Price 10 cents
CONTENTS

Abstract........................................................... 163

Introduction....................................................... 163

Location and extent........................................... 163

Previous Investigation........................................ 165

Present report................................................ 165

Geography.......................................................... 165

Mountains...................................... % .............. 165

Pediments..................................................... 166

Valley land................................................... 166

Drainage...................................................... 167

Climate....................................................... 167

Vegetation.................................................... 169

Roads and settlements......................................... 169

Industries.................................................... 170

Geology and ground-water conditions................................ 171

Mountain areas................................................ 171

Pediment zone................................................. 172

Alluvial land................................................. 173

Ground-water developments.......................................... 174

Explanation of map showing wells.............................. 174

Wells in the pediment zone.................................... 174

Wells in alluvium............................................. 175

Quality of ground water............................................ 177

ILLUSTRATIONS

Page 

Plate 41. Map of Avra-Altar Valley, Arizona, showing wells and

ground-water conditions............................... 164

42. A, Cerro Colorado, on east side of Altar Valley;

B, Baboqulvari Mountains, on west side of Altar Valley. 168

43. A, Lowland near Brawly Wash and bluffs rising to terrace 

land, looking east to Slerrlta Mountains 5 B, Sparse 

vegetation in Altar Valley west of Slerrlta Mountains. 168

44. A, Sahuaro cactus on upper slope of Avra Valley, west of 

Tucson Mountains; B, Vegetation on upper slope of 

Altar Valley, looking southeast to Slerrlta Mountains. 169 

Figure 28. Index map of Arizona showing area covered by the

present report and by other water-supply papers of

the United States Geological Survey.................. 164

II
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA

By David A. Andrews

Abstract

Avra-Altar Valley Is In Plma County, southeastern Arizona, about 30 

miles west of Tucson and tributary to the Santa Cruz Valley, in which 

Tueson is situated. It heads about 70 miles farther south, near the international boundary, and is 8 to 15 miles wide. The valley is sparsely 

inhabited, chiefly by cattle ranchers. Within recent years several settlers have entered land in its northern portion under the Grazing Homestead Act.

The valley is bordered by several partly detached mountain masses, 

consisting of several kinds of rock. Prom the mountain bases a gently 

sloping bedrock surface partly covered by a thin layer of gravel forms a 

mountain pediment. The pediment surface merges into lower slopes underlain by deep gravelly wash, and these extend to flat lowlands along the 

central part of the valley.

The area is drained by intermittent streams that carry water only 

during and shortly after rainy periods. The average yearly rainfall is 

about 10 inches in the lower part of the valley, increasing to nearly 18 

inches along its upper border. In the lower lands the vegetation is 

sparse and consists chiefly of small mesquite and other thorny bushes. 

Creosote bush and several kinds of cacti grow on the gravelly upper 

slopes. The sahuaro cactus and palo verde and palo fierro trees cover 

part of the pediment zone. In the southern part of the valley, which 

has somewhat more rainfall than the northern part because of its higher 

altitude, are large areas of grassland.

The demands for water are almost wholly for domestic needs and 

stock, but a few acres of wheat has been irrigated with water lifted 160 

feet. Other irrigation has been confined to a few fields of Johnson 

grass, irrigated when flood water is available, and to.some lawns that 

are irrigated with pumped water.

Water in moderate amounts is obtained from wells in the lower 

alluvial lands at depths of about 150 to 350 feet. A few wells on the 

higher alluvial slopes have been drilled to the water table at 550 to 

800 feet. In some parts of the pediment zone small amounts of water are 

obtained at depths of about 20 to 100 feet in disintegrated rock. In 

most places the ground water is of good quality, but in a few places in 

the pediment zone where sandstone and shale of Cretaceous age are penetrated the water is hard and contains undesirable quantities of soluble 

salts.

INTRODUCTION 

Location and extent

Avra-Altar Valley is in Pima County, southeastern Arizona, and is 

tributary to the Santa Cruz River, in whose valley is the city of 

Tucson. It extends northward from a point near the international 

boundary nearly parallel with the Santa Cruz Valley and 20 to 30 miles 

west of it. Its main drainage channel joins the Santa Cruz River about 

30 miles northwest of Tucson. The location of Avra-Altar Valley and of

146874 O 37 2

163
164 CONTRIBUTIONS TO HYDROLOGY, 1937

other areas that have been described in 'water-supply papers of the 

United States Geological Survey is shown in figure 28.

109" 

Figure 28. Index map of Arizona showing area covered by the present 

report and by other water-supply papers of the U. S. Geological Survey.

The southern portion of the area described in this report is a part 

of Altar Valley, which extends southward into Mexico; a broad though 

definite drainage divide about 3 miles north of the International 

boundary separates the two valleys, as shown on plate 41.

In its northern portion Avra Valley expands to a wide flat area 

that extends to open land along the Santa Cruz River. Avra-Altar Valley 

is about 70 miles long and about 8 to 15 miles wide between the bases of 

the bordering mountains. The total area within its drainage basin is 

nearly 1,400 square miles. The valley land ranges in altitude from
U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 796 PLATE 41

R.8E.

R. 12 E. 

FINAL CO. 

_T~PTMA CO"

T. US.

Silver Bel I

T.I2S. -

EXPLANATION

T.I3S.

T. 14 S.

T. 16 S.

T.20S.

T.2IS.

T.225.

(Very little ground water)

Small amounts ofshallowgroundtvater)

Upper alluvial land

ir amounts of ground water,

r/E>4;°y/ Lower alluvial land

(Ground wafer conditions similar to

those beneath upper alluvia} land)

Dug well, depth to water

(Where only one numberisgiven it

represents the depth to water)

T.17S.

T. 18 S.

T.I95.

to MILES

MAP OF AVRA-ALTAR VALLEY, ARIZ., SHOWING WELLS AND GROUND-WATER CONDITIONS

GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 165

about 1,900 feet above sea level near the Santa Cruz River to about 

3,700 feet on the broad divide separating Avra Valley from Altar Valley.

Previous investigation

The geology, geography, and ground-water conditions in Avra-Altar

Valley have been briefly described by Bryan in a report on a large area

I/ in southern Arizona. Little else that treats specifically of the

valley has been published, for it is sparsely settled and has been of 

slight economic interest except for grazing, although for many years 

there have been sporadic prospecting and small gold-mining operations in 

the bordering mountains.

Present report

The present report is the result of field work done in January and 

February 1934. The work was carried on under the supervision of G. A. 

Waring, geologist, of the U. S. Geological Survey, and the general 

direction of 0. E. Meinzer, geologist in charge of the division of 

ground water, with funds allotted by the Public Works Administration to 

the Geological Survey for such studies.

GEOGRAPHY 

Mountains

The mountains that border Avra-Altar Valley consist of several 

partly detached masses. On the northeast side the Tucson Mountains constitute a rugged area about 20 miles long and 3 to 6 miles wide. In the 

northern part the slopes are in some places precipitous. They culminate 

in Amole Peak (Wasson Peak), 4,700 feet above sea level, or about 1,500 

feet above the valley land. The southern part of the mountains has 

lower and smoother slopes and terminates in an outlier known as the 

Black Hills. A few miles farther south the Sierrita Mountains constitute a group of peaks of which Samaniego Peak rises to an altitude of 

5,300 feet. The Cerro Colorado is a smoothly rounded mountain mass, as 

shown in plate 42, A. It is separated from the Sierrita Mountains to

I/ Bryan, Kirk, The Papago country, Ariz., a geographic, geologic, 

and hydrologic reconnaissance with a guide to desert watering places: 

U. S. Geol. Survey Water-Supply Paper 499, pp. 109-110, 169-172, 184- 

188, 243-248, 287-293, 374-377, 1925.
166 CONTRIBUTIONS TO HYDROLOGY, 1937

the north and from the small mass of the Guijas Mountains to the south 

by passes 3 or 4 miles wide. At the southeast end of the valley the San 

Luis and Oro Blanco Mountains form an upland area extending southward 

into Mexico and rising southeastward to the higher mass of the Tumacacori Mountains.

On the west side of the valley the Pozo Verde, Baboquivari, and 

Coyote Mountains form a continuous range with steep slopes rising to 

prominent crests and culminating in Baboquivari Peak, shown on plate 

42, B, at an altitude of 7,740 feet. The Roskruge Mountains are a lower 

range, of which the Waterman Mountains form a northern extension. On 

the northwest the valley is bordered by the Silverbell Mountains, whose 

summits reach altitudes of about 4,000 feet.

Pediments

Prom the steep mountains gentler slopes extend down to lower lands 

at gradients of 50 to 200 feet to the mile. These slopes are in most 

places covered with only a thin layer of gravel and rock debris and form 

essentially a bedrock surface. This bedrock slope, from which the steep

mountains rise abruptly, has been termed a mountain pediment by Bryan,

2/ 

who defined it as follows:

In general the mountains of the Papago country rise from 

plains which are similar in form to the alluvial plains that 

commonly front mountains of an arid region, but large parts of 

the plains are without alluvial cover and are composed of solid 

rock. These plains constitute a land form that is distinct and 

requires a name. "Mountain pediment" has been chosen as the 

name for such a plain of combined erosion and transportation at 

the foot of a desert mountain range.

The character of the pediment surface rising gently to the Gerro 

Colorado on the east side of the valley Is shown in plate 42, A, and the 

pediment at the base of the Baboquivari Mountains, on the west side of 

the valley, is shown in plate 42, B. A few hills rise above the pediment surface, but in general it has been eroded to a nearly even plain.

Valley land

Prom the lower border of the pediment zone the slope continues 

downward toward the axis of the valley at a gradually lessening gradient. 

Although topographically the boundary between the mountain pediments and 

the valley land is not very definite, the character of the surface

2/ Bryan, Kirk, op. cit. (Water-Supply Paper 499), p. 93.
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 167

changes within a short distance from one in which the bedrock is occasionally exposed to land which is deeply underlain by gravelly wash. 

The lower border of the gentle gravelly slope merges into nearly flat 

loamy land along the axis of the valley except where the streams have 

developed inner valleys, as explained in the following paragraph.

Drainage

The main drainage channel of Avra-Altar Valley is Brawly Wash, 

named from the old Brawly ranch, in the central part of the valley. Its 

principal tributary is Arivaca Creek, which drains a mountainous area in 

the southeastern part of the basin. Arivaca Creek flows throughout most 

of the year in its upper portion, but the other streams carry water only 

a small part of the year, during and shortly after rainy periods. 

Numerous washes carry flood water from the mountains and valley sides to 

the main drainage channels. The lower portion of Arivaca Creek and the 

upper portion of Brawly Wash and adjacent parts of several tributaries 

are in a flat-bottomed inner valley a quarter of a mile to lj miles in 

width, bordered by bluffs of sand and gravel from a few feet in height 

to a maximum of about 70 feet near the mouth of Arivaca Creek. Within 

this narrow valley the main stream channels are entrenched 5 to 15 feet 

between nearly vertical banks of alluvium. Some of this trenching has 

taken place within comparatively recent years. Arivaca Creek is entrenched near the village of Arivaca in a channel 15 feet deep and 200 

yards wide. The bluffs bordering the inner valley gradually decrease in 

height downstream, being about 20 feet high near the road bridge across 

Brawly Wash, as shown on plate 43, A, and disappearing northward within 

a distance of about 10 miles. Some of the tributary washes are entrenched 10 to 30 feet deep in the disintegrated rock of the pediment 

zone, but as they approach the lowlands they become less and less distinct, and many of them disappear as definite channels before reaching 

Brawly Wash.

Climate

Avra-Altar Valley, like other parts of southern Arizona, has an 

arid climate, with long periods of slight precipitation. Rain falls 

chiefly during July, August, and September, with a secondary rainy 

season during the winter. In January and February there are occasional 

falls of snow on the higher mountain slopes. The mean annual
168 CONTRIBUTIONS TO HYDROLOGY, 1937

temperature is about 65° P.; the maximum is about 115° during July and 

August, and the minimum about 20° in January and February.

The following statistics of precipitation at Redrock, a few miles 

beyond the north end of the valley, at Silverbell, near its northwest 

border, and at the Santa Margarlta ranch, on its southwest border, are 

taken from the records of the United States Weather Bureau.

Rainfall, in Inches, at stations in or near

Avra-Altar Valley, Arizona 

(From records of the United States Weather Bureau)

Year

1907

1908

1909

1910

1911

1913

1914

1915

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929

1930

1931

1932

1933

Average

Redrock

(altitude

1,885 feet)

....

(a)

9.68

8.00

10.88

(a)

(a)

11.55

8.22

(a)

15.16

(a)

(a)

11.27

12.36

6.29

(a)

14.88

6.96

3.29

8.61

9.29

12.78

8.10

5.93

9.60

Silverbell

(altitude

2,500 feet)

11.43

13.83

(a)

(a)

14.84

11.42

13.76

(a)

(a)

15.01

(a)

13.79

13.44

Santa Margarita

ranch (altitude

4,000 feet)

25.51

15.55

22.78

(a)

17.02

9.19

18.79

25.63

18.83

8.99

15.19

17.14

30.34

17.14

12.82

18.22

a Record incomplete.

These figures show the irregularity of the yearly rainfall during 

the periods covered by the records and indicate that the average is 

about 10 inches In the lower part of the valley and 13 to 18 inches in 

the higher parts.
U. S. GEOLOGICAL StTBVEY WATER-SUPPLY PAPER 796 PLATE 42

A. CERRO COLORADO, ON EAST SIDE OF ALTAR VALLEY.

B. BABOQUIVARI MOUNTAINS, ON WEST SIDE OF ALTAR VALLEY.

U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 796 PLATE 43

A. LOWLAND NEAR BRAWLY WASH AND BLUFFS RISING TO TERRACE 

LAND, LOOKING EAST TO SIERRITA MOUNTAINS.

B. SPARSE VEGETATION IN ALTAR VALLEY WEST OF SIERRITA MOUNTAINS.
U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 796 PLATE 44

A. SAHUARO CACTUS ON UPPER SLOPE OF AVRA VALLEY WEST 

OF TUCSON MOUNTAINS.

B. VEGETATION ON UPPER SLOPE OF ALTAR VALLEY, LOOKING 

SOUTHEAST TO SIERRITA MOUNTAINS.
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 169

3/

Vegetation

In these lower parts of the valley, where the soil Is loamy or 

clayey, the native vegetation Is sparse and consists almost exclusively 

of small mesquite bushes and catclaw, as shown In plate 43, B. On the 

somewhat higher slopes of coarse wash several other bushes, chiefly 

creosote and ocotillo are common. In these areas several varieties of 

cactus, including the blsnaga or barrel cactus and the giant sabuaro, 

abound, as shown in plate 44, A. On these slopes the palo verde and 

Olneya tesota (Ironwood) trees are plentiful in some places, and along 

Arivaca Creek and upper Brawly Wash there are a few cottonwood and hackberry trees. The mountain pediments of thin soil support a scanty 

growth of stunted shrubs consisting chiefly of burro weed and bursage, 

with occasional bushes of mesqulte and catclaw, as shown in plate 44, B. 

On the pediment slopes of the southern part of the valley these low 

shrubs give way to grasses, which form large areas of good grazing land 

where the precipitation due to higher altitude is greater than In the 

main valleys.

On the mountain slopes bordering the southern part of the valley 

the mesquite and palo verde are replaced by live oaks above an altitude 

of 4,000 feet. In the southeast, parts of the San Luls and Oro Blanco 

Mountains support a thin forest of oaks, and this area has been included 

within the Coronado National Forest. The trees are of little value for 

timber, but under their protecting shade there Is a thick growth of 

grasses, and the lands are leased for grazing.

Roads and settlements

Avra-Altar Valley Is crossed about midway of Its length by an improved road that extends from Tucson to the copper-mining town of Ajo, 

180 miles to the west. State Highway 84 extends northwestward from 

Tucson parallel with the Southern Pacific Railroad. Prom this highway a 

road branches westward at Cortaro and leads across the north end of Avra 

Valley to the mining camp of Sllverbell. Secondary roads extend northward to the Irrigated district near Marana and southward, up the valley, 

to join the Tucson-AJo road at the Robles ranch. Thence a main road 

leads southward along the east border of the inner valley for about 17

5/ Most of this information was supplied by G. M. Kerr, of the 

United States Geological Survey.
170 CONTRIBUTIONS TO HYDROLOGY, 1937

miles, then crosses Brawly Wash, and continues southward along the west 

side of the valley to and beyond Sasabe at the international boundary.

On the east side of the valley near its north end a settlement of 

several homesteaders was established in 1925 near Avra, where there was 

a school and nearly a dozen families in 1934. In the fall of 1933 this 

settlement was augmented by a camp of the Civilian Conservation Corps, 

established three-quarters of a mile to the south. Farther north in the 

valley were several other homesteaders and also older ranchers. A small 

area in the east-central part of the valley and another in the west-central part are within the Papago Indian Reservation and are used as grazing lands by the Indians, some of whom reside farther west and others to 

the east in Santa Cruz Valley.

Near the southwest base of the Tucson Mountains several settlers 

have filed claims on homesteads near the main road. The upper part of 

the valley has long been occupied by several cattle ranches. The Palo 

Alto, La Osa, Las Moras, and Las Delicias are important centers of this 

ranching.

On the southwest border of the valley the Santa Margarita ranch has 

been headquarters for the Carlos Ronstadt cattle interests, which also 

have a large area under lease for grazing.

Arivaca, in the southeast, a village of about 50 people in 1934, is 

connected with Tucson by a road extending northeastward across the drainage divide and into Santa Cruz Valley. Oro Blanco in the 1880's was an 

active mining camp near the base of the mountains of the same name. 

After declining it had a revival of prosperity about 1911, but since 

then it has been nearly deserted.

Sasabe, half a mile north of the international boundary, was in 

1934 a village of about 75 people, with stores, post office, school, and 

a United States customs office. The Mexican customs office was about 2 

miles farther south.

Industries

By far the largest industry in the valley is that of cattle raising, 

which has long been carried on by several companies. Within recent 

years many horses have also been raised, especially on the Palo Alto 

ranch.

Although the homesteaders in the .northern part of the valley made 

entry under the Grazing Homestead Act, most of them took up land
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 171

primarily In order to obtain a place to reside for reasons of health; 

for the region around Tucson as well as the city Itself has come to be 

recognized as having a climate favorable to people suffering from throat 

and lung diseases. Little attempt has been made by these settlers 

either to graze or to cultivate the land. On several of the older 

ranches, however, some Johnson grass is grown as stock feed, by irrigation with flood water from Brawly Wash and Its main tributaries. Flood 

water collected in Agulrre Lake, at the head of the valley, is used to 

irrigate Johnson grass for cattle feed, and several acres of beans have 

also been grown by Irrigation from this lake. On the Glover dairy 

ranch, 4 miles northwest of Avra, about 20 acres of wheat was under Irrigation In 1934, with well water pumped from a depth of 160 feet.

Gold placer mining and prospecting for lodes have been carried on 

In the Guijas Mountains near Arivaca since about 1870, but little ore 

has been taken out. Prospects farther north, In the Slerrita Mountains, 

have been described by Ransome, who discussed the nature of the ore deposits. In the mountains along the west side of the valley there has 

also been much prospecting, one small mine having been opened at the 

base of the Baboquivari Mountains. In the northwest, Sllverbell was 

from 1904 to 1910 a copper-mining camp of some importance; It has been 

described by Stewart.

GEOLOGY AND GROUND-WATER CONDITIONS

Mountain areas

Like most of the other mountains In southern Arizona, the detached 

mountains that border the Avra-Altar Valley are composed of various 

kinds of rocks. These rocks are not differentiated on plate 41, as they 

have no especial significance with regard to ground water, but they may 

be briefly described as follows:

On the east side of the valley granite of presumably pre-Cambrian 

age forms the northern part of the Sierrlta Mountains and is also exposed In their southwest parts. On the opposite side of the valley 

granite constitutes the Coyote -and Qulnlan Mountains. At the south end 

of the valley ancient granite forms a large part of the San Luis and

JL/ Ransome, F. L., Ore deposits of the Slerrita Mountains, Plma 

County, Arlz.; U. S. Geol. Survey Bull. 725, pp. 407-440, 1922.

5/ Stewart, C. A., The geology and ore deposits of the Sllverbell 

mining district, Arlz.: Am. Inst. Min. Eng. Trans., vol. 43, pp. 240, 

290, 1913.
172 CONTRIBUTIONS TO HYDROLOGY, 193V

Oro Blanco Mountains, on the east, and the Pozo Verde Mountains, on the 

west. At the northwest border of the valley granite forms the central 

part of the Silverbell Mountains. Small areas of limestone of Paleozoic 

age are exposed In the Waterman Mountains and the southern part of the 

Sllverbell Mountains; and on the opposite side of the valley In the 

Tucson Mountains. At Snyder Hill, an outlier at the south end of these 

mountains, an outlier of an overthrust fault of the limestone has been 

quarried and burned for lime. On the southwest side of the valley sandstone and shale of Cretaceous age cover an area of several square miles 

on the flank of the Baboqulvarl Mountains. To the southeast these sedimentary rocks form a large part of the slopes near Arlvaca between the 

San Luls and Guijas Mountains. Farther north considerable areas of 

Cretaceous rock are also present on the west sides of the Slerrlta and 

Tucson Mountains. In both of these mountain masses there are also considerable areas of Intrusive granite and porphyry, which are considered 

to be of Cretaceous age. Some of these Intrusive rocks are mineralized, 

and In them most of the prospecting of the region has been done. On the 

east side of the valley the Cerro Colorado (pi. 42, A) Is a rounded 

mountain mass composed of lavas of Tertiary age. In the southwest the 

Baboqulvarl Mountains are composed chiefly of lavas of Tertiary age, 

which form rugged slopes culminating in the pluglike Baboquivari Peak 

(pi. 42, B). Most of the mountain areas farther north on this side of 

the valley are also composed of lavas, of Tertiary and Quaternary age.

In the mountains there are a few small perennial springs and 

several minor wet-weather springs. In a few places short tunnels have 

been driven to develop stock water, but available ground water beneath 

the upper slopes is scanty.

Pediment zone

The rocks underlying the pediment zone, which borders the mountains 

as shown on plate 41, are the same as those of the adjacent mountain 

slopes} but as granite and the harder lavas are the most resistant rocks, 

they constitute practically all the gravel that forms the thin cover of 

the pediments. In most places these bedrock slopes merge so gradually 

into the lower alluvial slopes that the boundary between the two is indefinite. It has therefore been indicated on the map by a broken line. 

Within the pediment zone several dug wells have found shallow water in 

small quantities in washes where the rock is sufficiently fractured and
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 173

disintegrated to serve as a storage reservoir for rain or run-off water 

that penetrates below the surface.

Alluvial land

The alluvial land consists of outwash slopes that lie between the 

pediment zone and the flat valley land. It is nearly everywhere underlain by sand, gravel, and cobbles, mainly of granitic and basaltic 

origin, with a few boulders 1 or 2 feet in diameter. Wells generally 

find fairly large supplies of water in this valley fill, but in some 

places the material is cemented with lime and yields little or no water.

The depth to the water table is determined largely by the altitude 

above the axis of the valley, although the water table seems to slope 

from the upper parts of the alluvial lands gently downward toward the 

valley. In the upper part of the alluvial slopes several wells have 

been drilled to depths of 600 to 800 feet before reaching water. In 

addition to showing the great depth to water beneath these upper slopes, 

these wells indicate that the coarse alluvial fill of the valley is deep 

and of fairly uniform character. The bench lands on each side of the 

inner valley along the upper course of Brawly Wash are essentially the 

same in character as the upper parts of the alluvial land in the 

northern part of the valley. They are really parts of the upper alluvial slopes in which narrow valleys have been cut.

The axial part of Avra-Altar Valley, as shown on plate 41, is an 

area of lower alluvial land. This area is nearly flat, as distinguished 

from the sloping upper alluvial lands, and its soil is largely sandy or 

loamy, in contrast to the coarse materials of the higher slopes. The 

decline in the upper part of the valley from the Secundino ranch northward to the Robles ranch is about 800 feet, or 30 feet to the mile. 

Prom the Robles ranch downstream to the valley of the Santa Cruz River 

the gradient gradually flattens, the average for this lower part being 

about 22 feet to the mile. Until Brawly Wash reaches several miles below the Robles ranch it has a channel trenched 5 to 10 feet deep in the 

dark, fine-grained alluvium of its inner valley. The channel then becomes shallow and divides into several branches, which distribute the 

flood* water over the flat lands. Such water is used, whenever available, 

for the irrigation of fields of Johnson grass, which is cut as cattle 

feed.
174 CONTRIBUTIONS TO HYDROLOGY, 1937

There seem to be no perched water tables in the gravelly fill of 

Avra-Altar Valley, and wells must be sunk to the deep water level in the 

valley fill. In the northern part of the valley the depth to water is 

somewhat less than in the southern part. The depth ranges from about 

150 feet near the mouth of Brawly Wash to 200 feet in the central part 

of the valley and about 380 feet at the Secundino ranch, in the southern 

part. Apparently some artesian head is locally developed when the 

gravel of the valley fill becomes fully saturated. The only well that 

was reported to have encountered water under pressure was that of 

H. Alexander, near Brawly Wash, 5 miles northwest of Avra. In this well 

the water was said to have risen temporarily about 15 feet above the 

level at which it was struck.

GROUND-WATER DEVELOPMENTS 

Explanation of map showing wells

On plate 41 are shown all the wells which were visited or concerning which information was obtained in 1934. They are believed to constitute nearly all the wells in use in the valley at that time. Most of 

the figures of depth to water and total depth were obtained from the 

owners or drillers of the wells. Measurements of several wells were 

kindly furnished by Mr. McCash, assistant county agricultural agent of 

Pima County. The data on the various wells show the approximate depth 

to water in most parts of the valley.

Wells in the pediment zone

In the pediment zone on the northwest side of Avra-Altar Valley a 

dug well on the Valenzuela ranch reached water at 85 feet in disintegrated granite. By means of a windmill and small gasoline engine this 

well has furnished water for 500 head of cattle at one time. At the 

Cosio ranch, 6 miles to the south, two shallow wells in decomposed 

andesite have supplied water for 200 cattle. Near the base of an 

eastern outlier of the Roskruge Mountains, J. Burrell obtained water 

at 40 feet in disintegrated lava.

In the pass through which the Tucson-Ajo road extends westward*a 

few wells were dug several years ago by gold prospectors. At Alamo 

mining camp water was obtained at about 40 feet in disintegrated lava.
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 175

The Dobbs well, 2 miles farther west, reached water at 50 feet In the 

lava of a small wash and has long been a watering place for travelers 

and prospectors in the region.

In the pediment zone along the southwest side of the valley two 

wells at the Redondo ranch found fair supplies of water at about 90 feet 

in disintegrated granite. Farther south water has been obtained along 

the base of the Baboquivari Mountains in disintegrated lava on the 

Otero, Fresnal, and Ronstadt ranches, at depths of 35 to 160 feet. 

Along the base of the Pozo Verde Mountains water is found at about 50 

feet on the Santa Margarita ranch and in several other wells. Water is 

also found at comparatively shallow depths on the pediment slopes of the 

opposite side of the valley. In a reentrant of the Sierrita Mountains 

H. C. Keeney obtained a small domestic supply at a depth of 12 feet. 

Several wells near Arivaca obtained small supplies of water from sandstone of Cretaceous age at depths of about 40 to 100 feet. Near the 

town the Boice well was drilled to 160 feet to obtain an ample supply.

A short distance beyond the south limit of Avra Valley two wells 

in disintegrated granite near Sasabe reached water at 78 and 90 feet and 

have supplied most of the needs of the village.

On the southwest flank of the Tucson Mountains several wells have 

been put down by homesteaders for domestic supply. The well of J. C. 

Praps reached water at 117 feet and that of P. Merriman at 105 feet. 

Farther east 0. P. Virch obtained a small supply of water of poor quality at 165 feet.

Wells in alluvium

In sinking wells in the valley alluvium little attempt has been 

made by the drillers or diggers to keep records of the materials penetrated. The material consists almost entirely of gravel, with minor 

layers of sand and silt at irregular intervals, and the water table is 

fairly uniform.

In the north end of the valley two wells drilled on the Aguirre 

ranch struck water at a depth of 150 feet and were equipped with small 

engines and storage tanks to supply water for stock. To the south a 

dug well on the Buena Vista ranch obtained water at 160 feet and was 

pumped by horsepower for domestic use and stock. In much of the 

northern part of the valley the gravel fill is sufficiently cemented by 

lime so that wells can be dug or drilled without curbing or casing,
176 CONTRIBUTIONS TO HYDROLOGY, 1937

although in the course of several years they may cave in. This happened 

to the well on the Maish ranch, dug 165 feet to water, but about 2 miles 

to the east J. A. Wash had dug a well 205 feet deep to water without encountering caving ground. On the Glover dairy ranch a large supply of 

water was struck in coarse sand at 160 feet. To the southwest, near 

Brawly Wash, H. Alexander's well had water at 205 feet. Other wells to 

the southeast toward Avra found water at somewhat greater depths, due to 

the rise of the surface. E. Johanson's well struck water at 225 feet, 

and others near Avra at about 250 to 300 feet, depending on the surface 

altitude. The well of D. H. Newcomer, 5 miles northeast of Avra, although started in alluvium, is said to have struck water at 180 feet at 

the base of a layer of andesite lava resting on hard blue limestone. On 

the ranches of Chico, Luis, and Prank Garcia, near Brawly Wash, southwest of Avra, water was found in dug wells at a little more than 200 

feet. The north well was dug to 240 feet, or about 30 feet below the 

ground-water level, and was drilled to 410 feet, in an unsuccessful attempt to obtain a larger supply. Each well was reported to have a 

capacity of about 10 gallons a minute and was pumped by a windmill for 

domestic and cattle supply.

The Manvel Jones well, near Avra School, struck water at 322 feet 

and was drilled to bedrock at 450 feet. During the winter of 1933-34 it 

furnished 8,000 gallons a day for a camp of the Civilian Conservation 

Corps three-quarters of a mile to the south.

On the San Joaquin ranch, farther up the valley, water was pumped 

by windmill from a depth of 180 feet, and the supply was sufficient for 

about 100 head of cattle. On the Cocoraque ranch, on the higher slopes 

to the southwest, water was found at 310 feet, and on the Phillip ranch, 

3 miles farther south, water was struck at 365 feet. At the Robles 

ranch water for cattle was obtained from two wells at 185 and 168 feet. 

Farther south along the axis of the valley water was obtained at somewhat greater depths. The water table is about 220 feet below the surface at the King ranch, 280 feet at the Palo Alto ranch, 340 feet at the 

Espinosa ranch, 360 feet at the Pozo Nuevo ranch, and 380 feet at the 

Secundino ranch. So far as could be learned, water was found in each 

well in coarse gravel. Some of these wells have yielded 200 gallons a 

minute during the summer. On the upper alluvial slope on the west side 

of the valley two wells on the Gill ranch had water at 195 and 280 feet.
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 177

The well on the Coleman ranch, on higher slopes, reached water at 380 

feet. On the opposite side of the valley the Blacklidge well was 

drilled to 820 feet before encountering water and was continued to bedrock at 900 feet without greatly increasing the supply. About 15 miles 

farther south, an unsuccessful well was drilled by the West Coast Cattle 

Co. to bedrock at 800 feet. This was reported to have found only a very 

small supply of water below 600 feet. On the opposite side of the 

valley the Manning well reached water at 550 feet and was continued to 

710 feet without obtaining a much larger supply than was yielded by the 

upper 50 feet of water-bearing material. The alluvium below the water 

table may in some places be cemented by lime so as to be a poor water 

bearer.

QUALITY OP GROUND WATER

During the course of the field examination samples of water were 

collected from 11 wells in the valley. These were later analyzed by 

E. W. Lohr, of the United States Geological Survey. The analyses of

water from 5 other wells in the valley, collected by Kirk Bryan in 1917,

I/ 

are also available. Analyses of samples from 10 other wells, made by

Robert A. Green, of the University of Arizona, were kindly furnished by 

him. The results of these analyses are given in the table on page 179 

arranged in two groups 15 samples from wells in the valley alluvium 

and 11 samples from wells in bedrock of the pediment zone.

All the waters analyzed from the valley alluvium except that of the 

Blacklidge well (sample 10) are satisfactory for domestic use. They 

contain only 150 to 270 parts per million of total dissolved solids; the 

principal constituents are sodium and bicarbonate, with secondary 

amounts of chloride, and only minor amounts of calcium and magnesium. 

They are therefore fairly soft waters. The unusually small quantities 

of sulphate present are noteworthy. The very small amount of fluoride 

in all the waters is of interest, because in several other valleys of 

southern Arizona, notably the San Pedro and San Simon Valleys, to the 

east, some well waters contain several parts per million of fluoridej 

and this is recognized as the cause of mottled teeth among a considerable portion of the residents who use these waters for domestic supplies.

&/ Bryan, Kirk, The Papago country, Ariz., a geographic, geologic, 

and hydrologic reconnaissance with a guide to desert watering places: 

U. S. Geol. Survey Water-Supply Paper 499, pp. 172, 184, 188, 1925.
178 CONTRIBUTIONS TO HYDROLOGY, 1937

The content of about 2 parts per million of Iron reported In samples 10 and 12, which, are from the deepest two wells, may be derived 

from the well tubing and Is of little significance. Sample 10, from the 

deepest well, contains about twice as much total solids as most of the 

other alluvial waters. Its chief constituents are sodium, bicarbonate, 

and chloride. In Its comparatively Mgh content of chloride, 168 parts 

per million, this water differs markedly from the other alluvial waters. 

The chloride may be derived from sandstone and shale of Cretaceous age, 

for these rocks form part of the adjacent mountain slopes and may have 

been reached In the well, which was drilled to bedrock.

Of the 11 samples of water from wells In the pediment zone, the 

first 5 (samples 16-20) are comparatively high In total solids. Sample 

16 Is from disintegrated lava, and although Its chief dissolved solids 

are sodium and bicarbonate, It contains sufficient calcium and magnesium 

to make It noticeably hard. The high content of nitrate Indicates that 

this shallow dug well receives drainage water which carries the products 

of oxidation of organic matter. Samples 17, 18, and 19 contain the 

highest amounts of dissolved solids. In addition to sodium and bicarbonate, they contain comparatively large amounts of calcium, magnesium, and 

sulphate and are hard waters. Their mineral matter Is very probably 

derived from the Cretaceous sandstone and shale In which the wells are 

sunk. The water of the Vlrch ranch (sample 19), In the road pass on the 

west side of the valley, contains more sodium chloride (common salt) and 

is much harder than most of the other waters analyzed.

Sample 21 came from a shallow dug well on the north flank of the 

Slerrita Mountains. The water contains considerable calcium and magnesium In addition to sodium and bicarbonate and hence Is rather hard. 

The mineral substances probably are derived from Cretaceous rocks, which 

form the adjacent slopes. Sample 22, from the well on the Santa 

Margarlta ranch near the southwest border of the valley, is fairly low 

In mineral content and Is a soft water, as the principal substances are 

sodium and bicarbonate. Sample 23, from the Bolce well near Arivaca, Is 

also a water of fairly low mineral content, although It probably comes 

from Cretaceous rocks. It contains nearly five times as much calcium as 

sodium, however. It is essentially a calcium carbonate water and Is 

therefore rather hard. Samples 24 and 25, from wells In the granite 

pediment near Sasabe, are low In dissolved mineral matter and are 

fairly soft.
GROUND WATER IN AVRA-ALTAR VALLEY, ARIZONA 179

The principal well at Oro Blanco is dug through the alluvium of a 

wash and a few feet Into the underlying bedrock In the upper part of the 

pediment zone. Analysis 26 shows the water to be of fair quality.

Analyses of water from wells In Avra-Altar Valley, Arizona 

Parts per million

.

K

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

SO

SI

22

23

S4

25

26

1

 H a "3

3s

EH

203

241

270

184

151

240

208

214

314

448

249

229

211

192

258

509

1,008

780

3,199

667

452

181

184

146

109

306

1? H

"«

 H

10

__

 _.

__

__

 

34

__

__

3S

36

__

_ .

__

_

62

__

.. 

__

_ .

24

I

g

H

_

_ .

__

__

 

0.93

_

_..

__

2.2

.06

2.1

.08

__

__

MM

....

.3

__

__

_..

.15

5

 H

1

15

30

48

30

22

28

22

7

15

35

38

40

37

49

16

66

105

38

105

73

52

22

47

37

20

46

1

 H

t

o

7

4

14

7.9

4

5

11

4

8

13

7.2

8.3

5.7

11

31

49

41

52

30

22

4

11

7.7

15

O aS "d

1 S'B

35-S

m

57

60

37

32

35

51

45

75

6S

123

46

37

32

12

88

84

190

198

985

143

97

46

10

10

14

31

-p

{?

 Hss

n

183

195

188

184

163

158

179

138

185

186

210

192

166

S12

260

376

407

442

1,281

460

407

163

soo

160

78

214

I

1

I

SO

25

8

10

Trace

29

SO

Trace

Trace

16

19

35

14

4

5

46

300

191

1,200

26

40

20

3

3

4

27

H

S

su

14

S6

63

9.0

10

18

22

60

38

168

11

13

10

9.0

17

66

164

92

226

122

40

10

10

5.0

10

29

S

 a

 H 

F<§&.

-_

 

0.0

.0

_

««

__

.s

_

.6

__

.0

.8

.2

 .

.8

. .

__

__

.2

.0

.0

-

S

-p

a&

- 

7.8

5.0

3.5

 .

 

__

1.5

Trace

.24

8.1

2.4

3.9

31

__

.93

12

__

__

3.8

4.9

16

0

a

is

H

v a

66

91

177

107

71

90

100

34

70

141

124

134

116

168

57

292

465

265

476

506

220

71

165

124

64

176

The analyses were made by E. W. Lohr, A. A. Chambers, and C. H. kidwell, 

United States Geological Surrey; and Robert A. Green, Department of Agricultural 

Engineering, University of Arizona.

The water from wells 1 to 15 is derived from the valley alluvium, that from 

wells 16 to 26 from the rocks underlying the pediment zone.

1 H. Alexander, NWi sec. 26, T. 12 S., R. 10 E. Depth 205 feet. 

Collected Apr. 19, 1932. Analyst, Robert A. Green.

2 E. Johanson, NEi sec. 29, T. 12 S., R. 11 E. Depth 225 feet. 

Collected Apr. 5, 1931. Analyst, Robert A. Green.

3 P. Garcla, SWi sec. 29, T. 13 S., R. 11 E. Depth 240 feet. 

Collected Feb. 5, 1934. Analyst, E. W. Lohr.

4 San Joaquln ranch, SEi sec. 9, T. 14 S., R. 11 E. Depth 180 feet. 

Collected Feb. 5, 1934. Analyst, E. W. Lohr.
180 CONTRIBUTIONS TO HYDROLOGY, 1937

5 Charles J. Phillip, SEi sec. 2, T. 15 S., R. 11 E. Depth 365 feet. 

Collected Oct. 2, 1930. Analyst, Robert A. Green.

6 Warren Bros., SEi sec. 26, T. 15 S., R. 10 E. Depth 200 feet. 

Collected Dec. 2, 1917, Analysts, A. A. Chambers and C. H. 

Kidwell.

7 Robles ranch, NWi sec. 34, T. 15 S., R. 10 E. Depth 185 feet. 

Collected Feb. 20, 1931. Analyst, Robert A. Green.

8 R. A. Dill, NEi sec. 27, T. 16 S., R. 9 E. Depth 195 feet. 

Collected Jan. 7, 1931. Analyst, Robert A. Green.

9 R. H. Coleman, SEi sec. 29, T. 16 S., R. 9 E. Depth 820 feet. 

Collected Feb. 18, 1931. Analyst, Robert A. Green.

10 F. Blacklidge, SEi sec. 3, T. 17 S., R. 10 E. Depth 820 feet. 

Collected Feb. 3, 1934. Analyst, E. W. Lohr.

11 Palo Alto ranch, SEi sec. 2, T. 18 S., R. 9 E. Depth 280 feet. 

Collected Dec. 10, 1917. Analysts, A. A. Chambers and C. H. 

Kidwell.

12 H. L. Manning, SEi sec. 13, T. 19 S., R. 8 E. Depth 550 feet. 

Collected Feb. 15, 1934. Analyst, E. W. Lohr.

13 Pozo Nuevo ranch, NWi sec. 22, T. 19 S., R. 9 E. Depth 360 feet. 

Collected Dec. 10, 1917. Analysts, A. A. Chambers and C. H. 

Kidwell.

14 Secundino ranch, NEi sec. 17, T. 20 S., R. 9 E. Depth 380 feet. 

-Collected Jan. 17, 1934. Analyst, E. W. Lohr.

15 Buenos Aires ranch, NEi sec. 27, T. 21 S., R. 8 E. Depth 140 

feet. Collected Feb. 11, 1934. Analyst, E. W. Lohr.

16 J. Burrell, SWi sec. 10, T. 14 S., R. 10 E. Depth 40 feet. 

Collected Jan. 22, 1934. Analyst, E. W. Lohr.

17 J. C. Fraps, SEi sec.'26, T. 14 S., R. 12 E. Depth 117 feet. 

Collected Feb. 5, 1932. Analyst, Robert A. Green.

18 P. Merriman, NW-J sec. 35, T. 14 S., R. 12 E. Depth 105 feet. 

Collected Feb. 9, 1934. Analyst, E. W. Lohr.

19 0. F. Virch, NWi sec. 31, T. 14 S., R. 13 E. Depth 165 feet. 

Collected Aug. 25, 1929. Analyst, Robert A. Green.

20 Dobbs claim, NEi sec. 15, T. 16 S., R. 8 E. Depth 50 feet.

Collected Nov. 26, 1917. Analysts, A. A. Chambers and C. H. 

Kidwell.

21 H. C. Keeney, SWi sec. 35, T. 17 S., R. 10 E. Depth 12 feet. 

Collected July 5, 1933. Analyst, Robert A. Green.

22 Santa Margarita ranch, NWi sec. 24, T. 20 S., R. 7 E. Depth 55 

feet. Collected Dec. 20, 1931. Analyst, Robert A. Green.

23 C. G. Boice, SWi sec. 28, T. 21 S., R. 10 E. Depth 60 feet. 

Collected Feb. 6, 1934. Analyst, E. W. Lohr.

24 F. Escalante, NWi sec. 29, T. 22 S., R. 8 E. Depth 78 feet. 

Collected Jan. 23, 1934. Analyst, E. W. Lohr.

25 Mrs. A. Hardgrave, NEi se c« 30, T. 22 S., R. 8 E. Depth 90 feet. 

Collected Jan. 23, 1934. Analyst, E. W. Lohr.

26 Oro Blanco village, NWi sec. 24, T. 22 S., R. 10 E. Depth 45 feet. 

Collected Dec. 11, 1917. Analysts, A. A. Chambers and C. H. 

Kidwell.

O