GEOLOGICAL SURVEY CIRCULAR 399

WATER RESOURCES SUMMARY FOR 

SOUTHERN CALIFORNIA, 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Fred A. Seaton, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

GEOLOGICAL SURVEY CIRCULAR 399

WATER RESOURCES SUMMARY FOR 

SOUTHERN CALIFORNIA, 1956

By Walter Hofmann and William C. Peterson

Washington, D. .C., 1957

Free on application to the Geological Survey, Washington 25, D. C.

CONTENTS

Page

Abstract. ..................................... 1 San Bernardino Valley.................... 11

Introduction. .................................. 1 San Gabriel Valley ....................... 11

Water resources for the water year 1955-56. ..... 3 Coastal Plain. ........................... 11

Precipitation ............................... 3 Oxnard Plain ............................ 12

Runoff..................................... 3 Santa Maria Valley. ...................... 12

Annual runoff for the water year 1955-56 ... 5 Antelope Valley. ......................... 12

Current dry period. ...................... 8 Artificial recharge of ground-water storage. . 12

Surface storage. ............................ 8 Imported water. ............................ 12

Ground water. .............................. 9 Annual runoff for the water year 1954-55 ........ 12

Western San Diego County. ................ 9 Areal distribution .......................... 13

Riverside County. ........................ 11 Unit runoff. ................................ 1 3

ILLUSTRATIONS

Page 

Figure 1. Location of selected gaging stations and observation wells. ....................................... 2

2. Progressive 10-year mean annual precipitation ................................................. 4

3. Annual runoff distribution 1896-1956 ........................................................... 6

4. Mean annual runoff for different periods... ...................................................'... 7

5. Water level fluctuations at selected observation wells. ........................................... 10

6. Water imported into southern California. ....................................................... 13

7. Areal distribution of annual runoff for the water year 1954-55 .................................... 14

TABLES

Page 

Table 1. Annual precipitation. ......................................................................... 5

2. Annual runoff for the water year 1955-56 and the average annual runoff for the dry period 1944-56 at

selected gaging stations.................................................................... 8

3. Storage in selected surface reservoirs ......................................................... 9

4. Annual runoff for the water year 1954-55. ...................................................... 15

III

WATER RESOURCES SUMMARY FOR 

SOUTHERN CALIFORNIA, 1956

By Walter Hofinann and William C. Peterson

ABSTRACT

Current water requirements for southern California 

are more than 2, 000, 000 acre-feet per year. These 

requirements are being satisfied by supplementing 

limited local water reserves with imported water.

The average annual precipitation ranges from about 

2 inches in parts of the desert to about 50 inches in the 

higher mountains. Also, there is a great variation in 

annual precipitation at any one place.

The annual variation is not entirely random in that 

the annual precipitation tends to occur in sequences of 

wet and dry years. Records of the 1955-56 climatological year indicate that the dry period which began 

in 1944 continues unabated.

Runoff follows the same cyclic pattern of wet and dry 

periods established by precipitation, but with even 

greater variability. Annual runoff for the 1955-56 

water year at 15 selected gaging stations ranged from 

0. 02 to 7. 6 inches with departures from the average 

annual runoff for the 30-year "base mean" period, 

1920-50, ranging from minus 100 to plus 12 percent. 

The average annual runoff for the 1955-56 water year 

was 1. 77 inches, a departure of minus 59 percent from 

the base mean. The average annual runoff for the 12- 

year dry period, 1944-56, ranged from 0. 27 to 7. 2 

inches with an average departure of minus 50 percent.

As a result of these continuing dry years, most of the 

reservoirs storing natural runoff were practically dry. 

The combined contents of 12 selected reservoirs in 

September 1956 was only 9. 2 percent of total capacity.

The trend in ground-water depletion that began in 

1944 continued during the year. Although the increased use of imported water for recharge of ground-water 

basins reduced the rate of decline in some areas, water 

levels in most observation wells were the lowest of the 

period of record. In areas entirely dependent on local 

ground-water reserves for their supply, the problem of 

obtaining sufficient water became more critical.

The rapid increase in requirements of water stepped 

up the importation of water from the Colorado River 

from 20, 000 acre-feet in 1944 to 430, 000 acre-feet in 

1956. During the same period importations from Owens 

Valley were running close to aqueduct capacity; 

336, 000 acre-feet was imported from this source during 1956.

Annual runoff data for the 1954-55 water year from 

all currently published gaging-station records establish 

that year as one of the driest in recent years.

INTRODUCTION

This water resources summary is the 14th in a 

series issued annually since June 1944. Its main purpose is to present a brief analysis of those phases of 

local water supply associated with the work of the 

Geological Survey in southern California.

The first part of this summary deals with water 

resources for the water year ending September 30, 

1956. It contains a brief analysis of annual precipitation, annual runoff (provisional) at selected gaging 

stations, water reserves in both surface and underground reservoirs, and supplemental imported water.

The second part of this summary gives, in detail, 

annual runoff for the preceding water year ending 

September 30, 1955. About 1 year of effort after the 

conclusion of a water year is usually required to complete computations of daily discharge for all the gaging 

stations. An additional 6 months to a year is required 

to process and present the data in published form in 

the annual Geological Survey Water-Supply Papers. 

Consequently this report on the water resources summary represents the first opportunity to release data 

on magnitude of runoff for all stations now operated in 

southern California for the water year 1954-55.

Some of the information presented in this summary 

was included in previous issues. The repetition is 

made so that each water resources summary will be 

complete and entirely independent of previous issues.

For the purpose of this summary, southern California is that part of the State extending southward 

along the coast from the Arroyo Grande basin to the 

international boundary and inland to include all the 

area to the Colorado River and Nevada State line south 

of the Tehachapi Mountains and Inyo County. The inland part of this 47, 000-square-mile area is predominantly an arid desert. Consequently most of the 

region's population centers and agricultural areas are 

concentrated in the long narrow band of coastal land. 

The chief exceptions are Antelope Valley in the Mojave 

Desert and Coachella and Imperial Valleys in the Colorado Desert. The area covered in this summary is 

shown in figure 1.

Because of many desirable climatic and economic 

factors, the population growth of southern California 

has been phenomenal, probably the greatest in the 

Nation. A population of about 300, 000 at the turn of 

the century increased to 5, 715, 000 by the time the 

1950 census was taken. About 80 percent of this population increase occurred in the three decades since 

1920. Since 1950 the population growth has continued

1
SAN LUIS OBISPOJ

Luis Obispo

SAN 

EXPLANATION

IS/IO-IB

OBSERVATION STREAM-GAfilNG 

WELL STATION

Figure 1. --Location of selected gaging stations and observation wells.
WATER RESOURCES FOR THE WATER YEAR 1955-56

and it is estimated that the present population of southern California is about 8, 000, 000.

Such a vast increase in population greatly intensifies 

the water problems in these arid and semiarid regions 

of limited water reserves. It has been estimated that 

the water requirements for urban and agricultural purposes in the coastal areas amounted to about 1,800,000 

acre-feet in 1950 and have been steadily increasing at 

a rate of about 40,000 acre-feet per year. As a result 

the water situation has changed from good to extremely critical in many areas. Just how critical the situation is depends largely upon the magnitude of the local 

ground-water reserves and the community's ability to 

import water from outside the basin.

Because of limited local water reserves, southern 

California has been forced to go greater distances for 

its water supply, and has paid more for it than any 

other area of comparable size in the Nation.

WATER RESOURCES FOR THE WATER YEAR 1955-56 

Precipitation

Very few areas in the United States experience the 

wide range in the average annual precipitation as that 

observed in southern California. Because of modifications in the atmospheric-moisture circulation by 

local physiographic features, the observed average 

annual precipitation ranges from 2.24 inches at Bagdad 

in the Mojave Desert to 51.53 inches at Morse'in the 

San Bernardino Mountains.

On an areal basis, the average annual precipitation 

of southern California is about 9.5 inches, or only 

about 32 percent of the national average of 30 inches. 

Not more than 2 percent of southern California has an 

average annual precipitation equal to or larger than 

that of the United States. More than 50 percent of 

southern California is arid, with an average annual 

precipitation of 5 inches or less.

In addition to the great range in average annual 

precipitation from place to place, there is often an 

even greater annual variation in the precipitation at the 

same place. For instance, the annual precipitation at 

Los Angeles for the climatological year, July 1 to 

June 30,has ranged from 5. 59 inches in 1898-99 to 

38.18 inches in 1883-84,and averaged 15.06 inches for 

the 79-year period of record. At Indio, in the desert 

area of southern California, the annual precipitation 

has ranged from 0.40 inch in 1879-80 to 11.50 inches 

in-1939-40, and averaged 3.18 inches for the 78-year 

period of record.

The annual variation in precipitation is not entirely 

of a random nature, as the annual precipitation occurs 

in sequences of wet and dry years. The sequences 

represent a time distribution in which the wet years 

are predominant, alternating with other periods in 

which dry "y'e&rs are predominant--resulting in an 

irregular eve lie pattern. This time distribution is 

most pronounced--on the coastal side of the mountains 

and least defined in the arid desert regions.

Possibly the longest existing record of these wet 

and dry sequences is to be found in the growth of annual 

tree rings in certain types of trees growing in the

mountains of southern California. Schulman I/ has 

been able to measure the annual tree-ring growth in 

big-cone spruce for the 559-year period of 1385 to 1944. 

These records indicate a definite cyclic pattern, with 

the average length of dry periods amounting to 14.5 

years and wet periods amounting to 12.5 years, giving 

an average cyclic period of 27 years. Not all the individual years within a wit period are wet, but the wet 

years predominate; likewise, not all the individual years 

within a dry period are dry, but the dry years predominate.

A diagram showing the progressive 10-year means 

(fig. 2) is frequently used to show the existence of the 

alternating wet and dry periods. Points used to define 

these three curves represent the departures of the 10- 

year mean annual precipitation from the average annual 

precipitation for the period of record at Los Angeles, 

Santa Barbara, and San Diego for successive 10-year 

periods. The three pronounced peaks in this diagram 

represent wet periods; the valleys represent dry periods. 

Final points on these curves, in the incomplete valley, 

represent the mean annual precipitation for the last 10- 

year period ending on June 30, 1956.

The observed 1955-56 annual precipitation at these 

three typical southern California stations is given in 

table 1. During this year, the 12th in an extended dry 

period, the annual precipitation exceeded the mean 

annualforthe period of record at Los Angeles and Santa 

Barbara for the first time since the wet year of 1952. 

However, precipitation at San Diego was the lowest 

since 1934, and fifth lowest during the 106 years of 

record. The influence of this year's precipitation on 

the last 10-year period (fig. 2) is such as to continue 

the downward trend at San Diego, and to improve the 

upward trend at Los Angeles and Santa Barbara. However, this upward trend in the incomplete valley (fig. 2) 

does not in itself furnish evidence of the end of the current drought because the variation may be due only to 

the influence of a relatively wet year or years within a 

dry period.

Runoff

The precipitation, after first satisfying the soilmoisture deficiencies in the root zone of the native 

vegetation in mountain and foothill areas and of the agricultural crops in the valley-floor areas, recharges 

the regional ground-water storage or drains into the 

stream channels as runoff. That part of the precipitation appearing as runoff follows the same cyclic tendency shown in figure 2. However, this cyclic tendency 

is often more pronounced because the annual runoff may 

represent only a very small part of annual basin-wide 

precipitation. For example, the annual runoff for San 

Gabriel River near Azusa has ranged from as little as 

0.86 inch throughout the basin during the water year 

ending September 30, 1899, to a maximum of 36.4 

inches in the water year ending September 30, 1922, 

with an average of 9.8 inches during the 61-year period 

of record.

This range in annual runoff, together with its time 

sequence, is shown in figure 3 for the gaging station

I/ Schulman, Edmund, 1947, Tree-ring hydrology 

in southern California: Univ. Ariz., Laboratory of 

Tree-ring Research, Bull. 4.
WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

09-0661

0691

8-8 2 o 2 

4ueaiad ui 'eoojeAD UKUJ uoijpudjaaid lonuuo uoeiu joeX-oi ^
WATER RESOURCES FOR THE WATER YEAR 1955-56 

Table 1.--Annual precipitation

Station

San Diego 

Los Angeles 

Santa Barbara

Period of record

Length 

(years)

106 

79 

89

Mean annual 

precipitation 

(inches)

9.95 

15.06 

17.96

1955-56 annual 

precipitation

Inches

4.52 

16.00 

19.84

Departure 

from mean 

(percent)

-54.5 

+6.2 

+10.5

10-year period 

1946-56 mean annual 

precipitation

Inches

8.36 

12.23 

15.48

Departure 

from mean 

(percent)

-16.0 

-18.8 

-13.8

on San Gabriel River near Azusa and the gaging station 

on Santa Ana River near Mentone. Both stations reflect the runoff from rugged mountain basins within the 

San Bernardino and the Angeles National Forests, 

where efforts are made to protect and to maintain a 

native vegetative cover. The records for these two 

stations are assumed to be typical of the mountain runoff in those areas where the basin-wide average annual 

precipitation ranges from 30 to 40 inches. Both 

records display the same cycliclike tendencies shown 

by the annual precipitation. To accentuate this distribution the records have been segregated into the generally accepted wet and dry periods of the region, with 

the average annual runoff for each of these periods 

shown by the crosshatched area.

A measure of the relative dryness of the dry periods 

is afforded by numbering the 10 driest years for each 

station (fig. 3) in their order of dryness. Of these 20 

years at both stations, 10 occurred in the very dry 9- 

year period ending September 30, 1904. The current 

dry period is next in order with 7 years, and the 14- 

year period ending on September 30, 1936, was the 

least dry, containing only 3 of the 20 years.

One of the methods used for determining wet and 

dry periods is that of cumulative departures as shown 

in figure 4. The diagrams show cumulative departures 

of annual runoff from the mean annual runoff, in percent, 

for the period of record (as of 1954) for both the San 

Gabriel River and Santa Ana River stations. A continuously downward trend represents a dry period; a 

continuously upward trend represents a wet period.

It is evident from an inspection of figure 4 that both 

records contain 3 dry and 2 wet periods and consequently the means for the periods of record tend to be 

biased because of the greater number of dry years.

On the basis of the records for San Gabriel River near 

Azusa, the 49-year period of 1895-1944 and the 50- 

year period of 1904-54 represent the least biased records because each contains 2 wet and 2 dry periods. 

For Santa Ana River near Mentone, the least biased 

records are those for the 47-year period 1896-1943, 

and for the 49-year period 1925-54. There are but few 

gaging stations in southern California where records 

are of sufficient length to contain these optimum time 

periods.

Lack of sufficiently long records necessitates the 

use of shorter periods, each containing a single wet 

and dry sequence. The beginning and ending of each oi 

these sequences, together with the mean annual runoff 

for each sequence, is included in figure 4.

Because of areal differences in the beginning and 

ending dates of the sequence of wet and dry groups of 

years and lack of definition of the sequences in drainage areas of meager precipitation, any time period 

selected for a "base mean" will be quite arbitrary; yet, 

when properly interpreted, it will have considerable 

hydrologic significance in many parts of southern California.

Consequently, the 30-year period beginning in October 1920 and ending in September 1950 has been selected for use as a base mean in the water-resources 

summary. The beginning date was selected to conform 

more nearly with the standard period of October 1920 

to September 1945 for which median monthly discharge 

is computed and used for national coverage by the 

Water Resources Review of the U. S. Geological Survey and the Canadian Water Resources Division of the 

Department of Northern Affairs and National Resources.

One of the purposes of figures 3 and 4--and the 

water resources summary--is to show the weaknesses 

and shortcomings of the mean or median values in reference to most southern California water problems. 

The data suggest that it is doubtful whether the 30-year 

or the long-time mean annual runoff can be used as a 

direct measure of dependable runoff. Consequently the 

mean annual runoff becomes merely a measure of the 

relative runoff among basins rather than a measure of 

usable or available water during extended critical periods.

Annual runoff for the water year 1955-56

Annual runoff for the water year 1955-56 at the 15 

gaging stations shown on figure 1 is briefly summarized 

in table 2 and compared to the aver age-annual runoff 

for the 30-year base period of 1920-50.

The intent of table 2 is to provide a general index of 

the surface runoff throughout southern California during 

each water year. The wide range of the 1955-56 runoff, 0.02 to 7.6 inches, is typical of the region and is 

due largely to the areal distribution of precipitation. 

In its relation to time distribution the departures of 

the 1955-56 runoff from the 30-year base mean were 

about the same as those of the preceding 1954-55 water 

year with the exception of the Huasna River in the 

Santa Maria basin, and Arroyo Grande in the Arroyo 

Grande basin. Runoff in these excepted basins at the 

extreme north end of coastal southern California was 

within relatively few percent of the base mean.
400,000

300,000

200,000

100,000

San Gabriel River near Azusa 

300,000

| Santa Ana River near Mentone

i

. 200,000

100,000

Median

Mean

ent

/0n

on<

m

\

7/m

|-

o 

a> 

oo

o

o

O)

o 

o>

o

CM

o>

o

10

o>

o

<fr 

o>

Figure 3. --Annual runoff distribution 1896-1956.
WATER RESOURCES FOR THE WATER YEAR 1955-56

400

200

~ -200

-400

 S -600

400

' £ 200

-200

-400

San Gabriel River near Me-OnjnMgLrynofLm.90g^cre-feet I

?^-b«««.ni«on.oniHiol runoff

Period-of-record mean annual runoff 112.7OO ocre - feet

Santa Ana River near Mentone

Figure 4. --Mean annual runoff for different periods.
WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

Table 2. Annual runoff for the water year 1955-56 and the average annual runoff for the dry period

1944-56 at selected gaging stations

No. 

on 

fig.

799 

304

721 

102 

616 

765

41 

377

182 

845 

638 

821

666 

499 

647

Station

Pacific Slope Basins: 

Cottonwood Creek at Morena

Santa Ysabel Creek at

Santa Ana River near Mentone 

Cucamonga Creek near Upland 

East Pork San Gabriel River

Santa Anita Creek near Sierra

Huasna River near Santa Maria 

Arroyo Grande at Arroyo GrandeThe Great Basin:

Palm Canyon Creek near Palm

Drainage 

area 

( square 

miles)

120

58 

220 

202 

10.1

88.2 

16.4

10.5 

254 

5.54 

119 

106

137 

23.0

94.0

1920-50 

base mean 

annual 

runoff 

(acrefeet)

12,720

13,400 

9,930 

59,020 

6,080

51,610 

6,720

4,580 

75,290

12,810 

toO.5,400

47,150 

12,890

4,480

1955-56 runoff

Acrefeet

136

856 

610 

26,890 

2,100

22,200 

2,160

2,230 

29,600 

2,230 

10,430 

17,320

16,9dO 

4,800

.2

Inches!

0.02

.28 

.05 

2.5 

3.9

4.8 

2.5

4.0 

2.2 

7.6 

1.6 

3.1

2.3

3.9

0

Departure 

from 

base mean 

annual 

runoff 

(percent)

- 99

- 94 

- 94 

- 54 

- 65

- 57 

- 68

- 51 

- 61

- 19 

+ 12

- 64 

- 63

-100

Average annual runoff 

for 1944-56 dry period

Acrefeet

3,190

4,690 

3,590 

37,810 

3,880

32,040 

3,390

2,660 

37,800 

840 

6,580 

9,150

26,460 

7,890

1,360

Inches

0.50

1.5 

.31 

3.5 

7.2

6.8 

3.9

4.8 

2.8 

2.8 

1.0 

1.6

3.6 

6.4

.27

Departure 

from 

base mean 

annual 

runoff 

(percent)

-75

-65 

-64 

-36 

-32

-38 

-50

-42

-50

-49 

-41

-44 

-39

-72

oRunoff for the period prior to 1940 obtained from State Water Resources Board Bull.

The derivation of an over-all average figure for runoff more or less obscures the purpose of table 2, that 

is, the emphasis of table 2 is on the range and areal 

distribution of runoff; however, an over-all average 

has the merit of simplicity and it is offered on that 

basis. The average annual runoff for the 1955-56 

water year was 1.77 inches over the 1,463 square miles 

of mountain drainage listed in table 2, or about 41 percent of the 30-year base. During the preceding water 

year the average annual runoff for this group of basins 

was 1.44 inches, or about 0.8 as much as 1955-56.

Current dry period

The typical southern California runoff distribution 

shown on figure 3 indicates that the water year ending 

September 30, 1956, was among the driest during the 

observational period. Furthermore, this dry year was 

the 12th in a predominately dry period that has persisted 

since October 1944--and may not be ended for some time. 

The tree growth studies by Schulman suggest that southern California may have experienced dry periods of 

more than 40 years' duration.

The average runoff for this 12-year dry period and 

its relation to the base mean is included in table 2. At 

most of the stations the average runoff for the period 

1944-56 was less than that for the period 1944-55. The 

average departure of the runoff from the 30-year base 

mean during the 12-year dry period for the basins listed was minus 50 percent, whereas that for the 11-year 

dry period was minus 45 percent.

Surface storage

Currently there exists about 1,500,000 acre-feet of 

surface storage in southern California for municipal, 

domestic, and irrigational purposes. Most of this 

storage has been obtained by building dams across 

mountain stream channels. However, because of the 

many adverse topographic features, such as steepness 

of the stream channels and narrowness of the canyons, 

construction costs are high and reservoir capacities 

small. Only 5 reservoirs of 115 built have a capacity 

in excess of 100,000 acre-feet. Because of these relatively small reservoir capacities, it is impossible in 

many instances to carry over the excessive flood runoff occurring during wet periods for use in the following 

dry periods. Furthermore, many of these reservoirs 

were not built for the purpose of storing local flood 

runoff, but were intended for the storing and distribution of imported waters from Owens Valley and the 

Colorado River.

Because of the necessity for flood control in the 

valley-floor areas, additional storage of more than 

400,000 acre-feet has been developed. Even though 

these flood-control reservoirs are primarily for the 

purpose of retarding the flood runoff, there is generally 

a certain amount of water conservation involved in that, 

when possible, releases are controlled to increase 

ground-water recharge.

Data regarding the behavior of 12 reservoirs during the current dry period are given in table 3. All of 

these reservoirs were built for the purpose of supply-
WATER RESOURCES FOR THE WATER YEAR 1955-56

Table 3. Storage in selected surface reservoirs

Reservoir

Morena and

Barret t

El Capitan

Lake Hodges

Lake Henshaw

Vail Lake

Big Bear Lake

Santiago

Matilija

James on Lake

Gibraltar

Caohuma

Total

Average

annual

1920-50

inflow 

(acre-feet)

!»27,100

o35,100

37,310

27,090

10,650

11,670

22,400

4,010

31,360

63,070

<J280,000

Present

spilling

capacity 

(acre-feet)

94,970

112,810

33,550

194,300

49,370

72,200

25,000

7,020

6,760

14,780

210,000

820,760

Ratio

of

storage

to 

inflow

3,5

3.2

.90

7.2

4.6

2.1

.31

1.7

.47

3.3

2.9

Storage

Sept. 30, 1955

Acre-feet

3,550

12,300

'113,680

2,070

1,360

11,700

2,820

4,580

3,940

5,330

19,600

70,930

Percent

of 

capacity

4.0

11

11

1.1

2.8

16

11

65

58

33

9.3

8.7

Sept. 30, 1956

Acre-feet

1,410

6,690

b2,640

»1,800

810

2,830

2,830

5,560

3,030

11,660

36,600

75,860

Percent

of 

capacity

1.5

5.9

7.9

0

1.6

3.9

11

79

45

79

17

9.2

Change

in

storage 

(acre-feet)

- 2,140

- 5,610

- 1,040

- 2,070

550

- 8,870

+ 10

+ 980

910

+ 6,330

+17,000

+ 4,930

Storage on

Sept. 30, 1944

Acre-feet

89,900

79,700

31,100

144,000

-

47,600

20,400

-

6,050

6,120

-

424,870

Percent

of

capacity

86

68

93

74

-

66

82

-

89

38

-

78

1944-56

Change in

storage 

(acre-feet)

- 87,760

- 73,010

-142,200

-

- 44,770

- 17,570

- 3,020

+ 5,540

~

-391,250

4 From State Water Resources Board Bull. 1

>T1ostly Colorado River water.

^Approximately.

<fAverage annual inflow to Big Bear Lake estimated

ing domestic, municipal, or irrigational water. Except for Lake Hodges, the only source of inflow to each 

reservoir during 1956 was from local runoff. The combined capacity of these 12 reservoirs is about 55 percent of the total capacities thus far developed for these 

purposes.

Of this group the Morena and Barrett reservoirs are 

the most southerly in the Tia Juana River basin. At the 

end of the preceding dry year on September 30, 1955 

--these reservoirs were almost empty. At the end of 

the equally dry 1956 water year the reservoirs were 

still almost empty. This is typical of the larger reservoirs where the holdover storage from the preceding 

wet'period has long been exhausted.

Farther north at the Matilija reservoir, the storage 

at the end of the 1955 water year amounted to 65 percent of capacity. At the end of the 1956 water year this 

storage increased to 79 percent of capacity. This relatively large retention is typical of those reservoirs 

in which the average annual inflow is large in terms of 

the reservoir's capacity.

Ground water

Over a large part of southern California, the most 

readily available and best distributed water reserve is 

the water stored in the deep alluvial deposits of the 

valley-floor area. A major part of the region's water 

requirements has been and is being satisfied by pumping from this source. The magnitude of these water 

reserves is difficult to measure; however, they have 

been estimated to be about 7,500,000 acre-feet in the 

alluvial deposits in the basins of the Los Angeles, San 

Gabriel, and Santa Ana Rivers in a zone 100 feet thick 

extending from 50 feet above to 50 feet below the January 1933 water levels. Eckis 2j.

The rapid growth of the industrial and urban developments has overtaxed these reserves. As a consequence 

the current rate of extraction often exceeds the average 

rate of recharge, creating an overdraft. Currently,

2_j Eckis, Rollin, 1934, Geology and ground-water 

storage capacity of valley fill (South Coastal Basin 

Investigation): Calif. Dept. Public Works, Div. Water 

Resources. Bull. 45.

large sections of southern California now have, or are

threatened by, overdrafts.

The usefulness of a ground-water reservoir, like a 

surface-water reservoir, is dependent upon its size,- 

the magnitude of the annual increments of recharge, 

and the annual rate of withdrawal. Also, like a surface 

reservoir, the ground-water reservoir must capture its 

water in the wet periods and retain it in storage to satisfy the needs of the following dry periods.

The valleys of southern California contain a large 

number of ground-water basins, many of which have 

complex geologic and hydrologic features. Changes in 

water levels differ considerably from basin to basin, depending upon the relationship between natural recharge 

and pumping draft. Consequently it has been necessary 

to confine the detailed analysis of the changes in water 

levels to the few observation wells indicated on figure 1.

The records of change in water level at six selected 

observation wells for their period of record are shown 

on figure 5. The division of wet and dry periods arbitrarily is based on figure 4. A light dashed line serves 

to indicate the rate of decline during each dry period, 

and is based chiefly on the group of years having the 

least precipitation during the period. Assuming that 

ground-water recharge during all dry periods is small 

and of about the same magnitude, an increase in the 

rate of decline becomes a measure of the increase in 

ground-water extractions.

At the end of-the 1956 water year almost all water 

levels were the lowest for the period of record a 

reflection of the great increase in regional water requirements and the excess of withdrawals over the 

small increments of recharge during the current 12- 

year dry period.

Western San Diego County

Ground-water levels in the coastal alluvial valleys 

of western San Diego County, including the basins of 

the Tia Juana, Otay, Sweetwater, San Diego, San 

Dieguito, and San Luis Rey Rivers, declined during 

the 1956 water year, continuing a downward trend which 

began about 12 years ago. By September 30, 1956, the 

levels in many wells were the lowest during the entire
10 WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

Figure 5. --Water level fluctuations at selected observation wells.
WATER RESOURCES FOR THE WATER YEAR 1955-56 11

period of record. The water levels were below sea 

level during all or part of the year n«ar the coast in 

the San Luis Rey and Otay River basins. At the present time areas of known or threatened sea-water intrusion exist in the basins of the Tia Juana, Otay, San 

Diego, and San Luis Rey Rivers.

Riverside County

The ground-water levels in the arid and semiarid 

San Jacinto basin have declined steadily since the first 

observations of 1904. The Riverside County Flood 

Control and Water Conservation District reports that 

the water level in the key well 4S/1W35-R1, near the 

city of San Jacinto, which was flowing in 1917, was 

about 180 feet below land surface in September 1956. 

Similarly the water level in a second well 4S/3W33-R1, 

near the city of Perris, was about 189 feet below the 

land surface during September 1956 in an area where 

the water level was about 20 feet below the land surface during March 1904. Both areas now are using a 

limited amount of Colorado River water at double the 

cost of locally pumped water in an effort to supplement the declining water reserves.

Rapidly dropping ground-water levels in the Elsinore, Beaumont, Yacaipa, and Whitewater basins have 

indicated the need for supplemental supplies. The 

Murrieta and Temecula basins have not provided sufficient water for irrigation for some time, and the 

area is largely dry farmed as a result.

which went dry in July 1956 and was still dry in January 1957. The estimated part of the record showr on 

figure 5 is based on the levels in nearby wells.

Deepening of wells, lowering of pumps, and increased pumping costs are imposing serious economic hardships on water users, particularly in the fringe areas 

of the valley.

San Gabriel Valley

The San Gabriel Valley is a deep alluvial valley in 

the San Gabriel River basin along the toe of the San 

Gabriel Mountains. The ground-water-storage capacity 

of these deposits is believed to be about 1,200,000 acrefeet in a zone 100 feet thick, ranging from 50 feet above 

to 50 feet below the January 1933 water level. Eckis £/. 

The once extensive agricultural acreage in this valley 

is rapidly being converted to an urban area. Most of 

the valley's water requirements are satisfied from local 

ground-water reserves.

The record obtained at the Baldwin Park observation 

well IS/10-18, shown on figure 5, is assumed to represent ground-water conditions throughout the valley. 

During the dry period 1922-36 the average rate of decline amounted to about 3.9 feet per year increasing to 

8.8 feet per year during the current dry period. During 

the last few years this rate of decline has moderated, 

owing in part to the wet year 1951-52 and in part to the 

increased use of imported Colorado River water in the 

area.

San Bernardino Valley

The San Bernardino Valley is a relatively deep alluvial valley in the upper Santa Ana River basin east of 

metropolitan Los Angeles. The water needs of the 

valley's prominent agricultural and urban developments 

are satisfied from both local surface and ground-water 

reserves.

The longest available record of changes in the 

valley's ground-water levels is that for the Williams 

well 1S/3W-17C1. This record, started in 1892, and 

Siiown on figure 5, represents a continuous cumulative 

balance between the annuel recharge during the winter 

rainfall period and the annual depletion caused by pumping during the summer months. These cumulative 

differences give the water-level fluctuations a general 

cyclic time distribution that coincides closely with the 

wet and dry periods of figure 4.

The rate of decline during the first and second dry 

periods amounted to about 4.2 feet per year. However, 

during the current dry period the rate of decline increased to about 10 feet per year. This increase in 

rate of decline reflects an increase in ground-water 

use, which, together with substantial prolongation of 

the current dry period, forecasts a condition of overdraft in the near future.

The San Bernardino Valley Water Conservation 

District reports that the valley's ground-water levels 

at the end of the 1956 water year averaged about 98 

feet below the levels at the beginning of the current 

dry period. Many wells have gone dry, or the yields 

have diminished to the point where the wells have become unusable. Among these was the Williams well,

Coastal Plain

The coastal plain is the broad, flat area extending 

along the coast from Santa Monica to Newport Beach 

and inland to the Santa Monica and Santa Ana Mountains, 

the Puente and San Jose Hills, and lesser foothills. The 

three major streams of the Los Angeles area--the Santa 

Ana, San Gabriel, and Los Angeles Rivers cross this 

plain to discharge into the ocean. The plain's rich 

agricultural lands have been converted gradually into 

extensive urban and suburban developments. Currently 

the coastal plain is the most densely populated and industrialized section of southern California.

The fresh-water-bearing deposits underlying the 

plain are composed of marine and alluvial deposits 

which locally attain a thickness of 2,500 feet or more. 

Less than 20 years ago the water stored in these deposits was the principal source of water for the area. 

Because of the rapid increase in water needs during 

recent years, it has been necessary to import a substantial portion of the water requirements from Owens 

Valley and the Colorado River. Even with these imported waters, the ground-water reserves have been so 

depleted that sea water has intruded many sections of 

the coast.

Systematic observations of change in ground-water 

level in the coastal plain have been noted at the Neff 

well 4S/10-22L2 and its companion wells near Anaheim 

since 1898. These records, shown on figure 5, have 

been used as an index of changes in the water level of 

the coastal plain. During the 58-year period of record 

at this site, a net decline of 130 feet, from 112 feet

2/ See footnote p. 9.
12 WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

above sea level to 18 feet below sea level was observed. This decline, which has not been uniform, was 

concentrated largely in the three dry periods. A rate 

of decline of 3.9 feet per year in the first dry period 

increased to 4.6 feet per year during the second dry 

period and to 7.6 feet per year in the current dry period. During the last few years, this rate of decline 

has moderated owing in part to the wet year of 1952 

and in part to greater use of imported waters.

The Orange County Flood Control District reports 

an average decline in ground-water level of about 3 to 

4 feet throughout the eastern part of the coastal plain 

during 1956. About 13,000 acre-feet of Colorado River 

water was purchased by the district for recharging the 

ground-water reserves. In 1955 the average drop in 

water level was about 1 foot during a year in which 

about 52,000 acre-feet of Colorado River water was 

spread in order to replenish the under-ground basin.

Oxnard Plain

The Oxnard Plain is one of the most important agricultural and urban areas in Ventura County. Waterlevel observations made by Ventura County Department 

of Public Works, Division of Water Resources, at well 

9-U-9 in the city of Oxnard, are shown on figure 5, and 

are assumed to represent changes in the ground-water 

reserves of this broad coastal plain. Since 1943 the 

water level at this site has declined almost continuously. Between 1943 and 1951 the rate of decline was 

about 7.4 feet per year. This trend was reversed temporarily by recharge in the wet year 1951-52. However, since 1953, the decline in water level has resumed at a rate somewhat less than that before 1952.

The Ventura County Division of Water Resources 

reports that the ground-water levels of the Oxnard 

Plain were generally about 20 feet below sea level in 

the fall of 1956. At this same time the water levels 

were about 50 feet below sea level in Pleasant Valley, 

an eastward extension of the Oxnard Plain. There is 

evidence of sea-water intrusion in wells near the ocean.

Santa Maria Valley

Changes in water level at well 10/34-14E2 (fig. 5) 

near the center of the Santa Maria Valley, generally 

reflect the status of ground water in storage for a 

large part of the valley. The records from this well 

show a continuous and almost uniform decline in water 

level at a rate of 4.0 feet per year during the dry years 

1917-36. This decline was arrested by the large 

ground-water recharge during the wet period extending 

through 1944. With the advent of the current dry period 

the water level declined more sharply at the rate of 

7.4 feet per year to the lowest level on record, indicating a substantial increased draft on the ground-water 

reserves.

Antelope Valley

Antelope Valley is in the extreme west end of the 

Mojave Desert in Los Angeles and Kern Counties. 

Parts of this arid valley have been farmed successfully 

for more than 60 years. However, the steadily increasing water needs for agricultural and other uses have 

created a critical overdraft in the valley.

In figure 5 are shown the changes in water level at 

a well near Lancaster; they are assumed to be an index 

of changes in the large, heavily pumped part of the 

valley. During the last 25-year period the water level 

in this or nearby wells has declined 143 feet. This decline, which persisted even during the wet years, clearly indicates that extractions exceeded the recharge. A 

rate of decline of about 3.4 feet per year during the 

1922-36 dry period has increased to 8.1 feet per year 

during the current dry period.

Artificial recharge of ground-water storage

The Metropolitan Water District of Southern California reported that it sold about 81,000 acre-feet of 

Colorado River water at a cost of about $800 000 to the 

people of Los Angeles and Orange counties during the 

1956 water year for the major purpose of retarding the 

rapid rate of decline in ground-water levels. This water 

was either permitted to infiltrate into the stream channel 

deposits or spread into highly permeable specially prepared basins overlying the main ground-water bodies.

About 3,000 acre-feet of this Colorado River water 

was put into injection wells along the coast in the vicinity of Manhattan Beach for the purpose of determining 

the feasibility of maintaining a fresh-water barrier 

against sea-water intrusion.

An additional 8,000 acre-feet of local storm runoff 

from the mountain and foothill areas during the 1956 

water year was diverted from natural stream channels 

into specially prepared basins for the purpose of recharging the ground-water storage in Los Angeles 

County.

Imported water

Southern California extends over \ predominately 

arid region which has less than 2 percent of the State's 

natural water supplies. Consequently, to satisfy the 

ever-increasing water requirements of the area, water 

must be imported from distant sources.

Since 1913 the city of Los Angeles has diverted water 

from the Owens Valley east of the Sierra Nevada for 

use in the city some 250 miles to the south. During 

the 1956 water year the Owens River aqueduct, operating at full capacity as in previous years, delivered 

336,000 acre-feet to the Los Angeles area.

By means of a 1,617-foot pumping lift and a 242- 

mile aqueduct from the Colorado River, the Metropolitan Water District of Southern California delivered 

430,000 acre-feet to the greater Los Angeles and San 

Diego areas during the 1956 water year.

As indicated on figure 6, these annual imports have 

increased from 310,000 acre-feet in 1944 to 766,000 

acre-feet in 1956--an increase of 148 percent. About 

37 percent of the annual water requirements in the 

coastal areas now are satisfied by imported water.

ANNUAL RUNOFF FOR THE WATER YEAR 1954-55

Annual runoff data for the water year ending September 30, 1955, for all gaging-station records currently 

published by the Geological Survey, are presented in 

table 4. The mean and median values of the annual
ANNUAL RUNOFF FOR THE WATER YEAR 1954-55 13

1,000,000

800,000

600,000

o 

<

400,000

200,000

General climatic distribution

Annual diversion from the Colorado River by the 

Metropolitan Water District of Southern California

Figure 6. --Water imported into southern California.

runoff for the period of record and the relation of the 

annual runoff to the base mean are included for the 

stations with sufficient length of record.

Areal distribution

The normal storm tracks moving over southern 

California are such that the precipitation along the 

coast generally decreases from north to south. The 

eastward movement of these storms is blocked by the 

high mountain barriers which cause the greatest precipitation on the windward side of these barriers. 

Across the barriers the precipitation decreases rapidly 

to near zerjo in the desert areas.

A generalized areal distribution of the annual runoff 

for the water year ending on September 30, 1955,is 

shown on the map of figure 7. The runoff quantities 

used to define this distribution were obtained from 

table 4; the quantities are relative in that they express 

the departure, in percent, of the runoff for the 1955 

water year from the mean of the 30-year period 

1920-50.

The 1955 water year was a very dry year the llth 

year in a series of dry years. The annual runoff in

many valley streams in the agricultural areas was 

zero, or nearly zero, representing departures as 

much as 100 percent below the 30-year base mean. 

However, this was not the case in many highly urbanized valley-floor areas in or near metropolitan Los 

Angeles. During 1955 the precipitation on the paved 

streets and the roofs of buildings in these urban areas 

tributary to the Los Angeles River resulted in a runoff 

of 60,130 acre-feet into the ocean at Long Beach. 

Annual runoff of this magnitude is only 32 percent below the average runoff of the base period at this site.

Unit runoff

Unit rates of runoff generally decrease rapidly as the 

streams cross the valley-floor areas and discharge into the ocean. In the predominantly agricultural areas, 

the 1955 runoff into the ocean was zero from the basins 

of the Tia Juana, San Luis Rey, and Santa Margarita 

Rivers. In contrast the highly urbanized areas tributary to the Los Angeles River discharged into the ocean 

the equivalent of 73.2 acre-feet per square mile, or 

1.4 inches, over the basin. The street drainage in the 

Beverly Hills and Hollywood areas produced a 1955 

runoff of 244 acre-feet per square mile, or 4.6 inches, 

over the Ballona Creek basin.
14 WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

X .'f ^\{o:jf\::\t.-\\:-\*i'l\il* ,y/LiiimKima.

I i C'' ^iTiilill^H

K"^._^- :.=5g^0:^
ANNUAL RUNOFF FOR THE WATER YEAR 1954-55 15

Table 4.--Annual runoff for the water year 1954-55

[Basic data furnished by: a city of San Diego; 6 California Water and Telephone Co.; cLa Mesa, 

Lemon Grove, and Spring Valley Irrigation District; d Vista Irrigation District; iMontecito 

County Water District; i city of Santa Barbara.

Plow: e regulated by Vail Reservoir (capacity, 49,370 acre-ft) since November 1948.

Records furnished by: /Orange County Flood Control District; g Los Angeles County Flood Control 

District; h Ventura County Water Resources Division.]

Basin and stream

PACIFIC SLOPE BASINS 

Tia Juana River basin:

Cottonwood Creek above Tecate Creek,

Otay River basin:

Sweetwater River basin: 

Sweetwater River at Loveland Dam, near

Sweetwater River at Sweetwater Dam .6 -- 

San Diego River basin:, 

B'oulder Creek at Cuyamaca Reservoir,

San Dieguito River basin: 

Santa Ysabel Creek at Sutherland Dam----

San Luis Rey River basin: 

San Luis Rey River at Lake Henshaw, near

San Luis Rey River at Monserate Narrows,

Santa Margarita River basin: 

Temecula Creek at. Vail Dam, near

Santa Margarita River near Temecula « - 

Santa Margarita River near Fallbrook e --

San Juan Creek basin:

San Juan Creek near San Juan CapistranoTrabuco Creek near San Juan Capistro / 

Aliso Creek basin: 

Aliso Creek at El Toro / 

Drainage 

area 

( square 

miles)

120

316 

84 

478 

1,668

72

100 

181

12.0 

190 

380

58 

110 

24 

28 

58 

303

209

383 

514

557

319 

220 

592 

645 

740

110 

36.5

8.5

L954-55 annual runoff

Acrefeet

506

10 

70 

80 

0

26

906 

1,639

573 

2,519 

325

713 

158 

159 

0 

33 

**-55

1,599

670 

.2 

0

1,820 

970 

4,750 

3,420 

0

2,170 

76

6.1

' 

Acrefeet 

per 

square 

mile

4.22

.03 

.83 

.17 

0

.36

9.06 

9.06

47.8 

13.3 

.86

12.3 

1.44 

6.62 

0 

.57 

-.18

7.65

1.75 

0 

0

5.71 

4.41 

8.02 

5.30 

0

19.7 

2.08

.72

Departure 

from 

base 

mean 

(percent)

-96

-88 

-99

-95 

-100

-94 

-100

-83 

-90 

-77 

-86 

-100

-78 

-98

-99

Period of record (Base mean

Length 

years)

19

19 

19 

19 

19

15

11 

68

34

19 

40

34 

22 

8 

10 

16 

39

44

12 

28 

23

32 

25 

32 

30 

31

27 

25

25

Mean 

annual 

runoff 

(acrefeet)

11,480

8,140 

2,420 

13,160 

35,880

4,660

*2,240 

30,420 

20,870

15,980 

21,220

572 

4,240 

31,800

27,700

9,050 

22,620 

16,650

9,140 

8,030 

1,790 

22,840 

26,210

9,820 

3,830

552

Median 

annual 

runoff 

(acrefeet)

7,400

2,000 

1,800 

4,800 

10,100

2,300

*1,300 

17,400 

3,800

8,900 

8,600 

750 

140 

800 

15,400

15,600

3,300 

8,200 

1,400

5,100 

2,300 

7,400 

9,000 

10,400

2,200 

430

220

Mean 

annual 

runoff

1920-50 (acrefeet)

12,720

4,640

23,200 

13,400

37,310 

27,090

25,440

10,650 

9,930 

20,420 

24,790 

30,140

9,960 

3,840

547

* 11 years (1944-55). 

** Adjusted for 9,202 acre-ft of Colorado River water.

INT.-DUP. SBC.. WASH., B.C.
16 WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

Table 4. Annual runoff for the water year 1954-55 Continued

Basin and stream

Peters Canyon Wash basin:

Santa Ana River basin:

Little San Gorgonio Creek near BeaumontEast Twin Creek near Arrowhead Springs 

Waterman Canyon Creek near Arrowhead

City Creek near Highland 

Devil Canyon Creek near San Bernardino 

Lytle Creek (east channel) at San

Santa Ana River at Riverside Narrows,

Santa Ana River at county line, below

Santiago Creek at Santiago Dam, near

Villa Pnr>lr--------------- - ___ __

Qoy-»+-4Qrr*~i P yoolr nooT* \T "5 T ~\ Q ^o ~r*\f _

San Gabriel River basin: 

East Fork San Gabriel River near Camp

West Fork San Gabriel River at Camp

San Gabriel River below Santa Fe .Dam,

San Gabriel River at Spring Street, near

Brea Creek below Brea Dam, near

Fullerton Creek below Fullerton Dam,

Drainage 

area 

( square 

miles)

202 

39.9

16.9

2.61 

123

8.6

4.55 

19.8 

6.16 

46.9 

40.9 

15.0

4.8 

10.1 

140 

39.4 

717

16.9

63 

83.8

>,418

88.2

102 

211 

6.4 

6.5

231 

18.3 

7.5 

2.7 

85.2

584

23.4 

26.2

3.05 

6.2 

110 

?n A

1954-55 annual runoff

Acrefeet

328

27,860 

13,510 

292 

2,120 

1,330 

73 

123 

569 

2,020

958 

2,830 

1,540 

14,800 

2,730 

257

343 

20,400

f22,470 

1,420 

2,270 

5,900 

297 

56 

23 

t8,510 

43,950

t44,220

3,168 

51 

528 

178

26,090

12,850 

40,070 

311 

567

0 

603 

20 

45 

1,170 

9,250

820

53 

114

49

165 

1,210

1 1

Acrefeet 

per 

square 

mile

13.8 

339

125

28.0 

1.00

235

211 

143 

250 

316 

6.67 

17.1

296 

225 

42.1 

7.54 

.08

504

50.3 

.61

.07

296

126 

190 

48.6 

87.2

0 

33.0 

2.67 

16.7 

13.7

1.40

2.26 

4.35

16.1 

26.6 

11.0 

ft 1*;

Departure 

from 

base 

mean 

(per 

cent)

-53 

-49

 

-92

-43

-52 

-64 

-37 

-53 

-62 

-80

-52

-61 

-66 

-63 

-78

-100

-50

-56

-73 

-99 

-90 

-99

-49

-76 

-64 

-87 

-82

-83 

-98 

-93 

-80 

-75

-78

Period of record (Base mean

t Length 

[years]

6

59 

27 

16 

36 

10 

7 

29 

1 

35

37 

36 

36 

51 

35 

24

26 

35

25 

26 

26 

35 

8 

39 

26 

38 

15

36

24 

35 

26 

32

22

28 

60 

38 

38

13 

38 

35 

26 

26 

27

28

13 

25

14 

20 

26

R

Mean 

annual 

runoff 

(acrefeet)

62,170 

24,490 

2,085

6,780

1,120

3,420

2,000 

7,580 

2,350 

31,920 

6,720 

989

43,510

41,220 

4,020 

5,680 

24,550

10,660 

2,910 

15,900

95,630

13,190 

6,210 

4,080 

15,103

52,850

48,200 

111,500 

2,170 

2,930

3,200 

801 

569 

6,090 

33,260

19,360

502 

861

131 

513 

5,790

Median 

annual 

runoff 

(acrefeet)

52,300 

17,400 

580

830

430

2,500

1,400 

5,700 

1,700 

26,200 

4,300 

430

40,500

30,400 

3,100 

4,300 

14,800

230 

43 

12,300

81,200

7,500 

1,000 

510 

2,000

37,600

27,500 

81,100 

1,200 

1,900

2,000 

220 

350 

3,600 

15,900

1,800

140 

330

22 

220 

3,200

Mean 

annual 

runoff 

1920-50 

(acrefeet)

59,020 

26,270

1,410

3,560

2,000 

7,920 

2,450 

31,640 

7,150 

1,280

42,830

57,790 

4,220 

6,080 

26,400

12,610

17,090

100,500

11,670 

6,070 

5,310 

21,880

51,610

53,040 

111,020 

2,380 

3,210

3,540 

845 

602 

5,980 

37,460

5,500

t Adjusted for 52,430 acre-ft of Colorado River water released by Metropolitan Water District into 

Santa Ana River above Riverside Narrows.
ANNUAL RUNOFF FOR THE WATER YEAR 1954-55 17

Table 4. Annual runoff for the water year 1954-55 Continued

Basin and stream

Los Angeles River basin:

Tujunga dreek below Mill dreek, near

Little Tujunga Creek near San Fernando g

Little Santa Anita Creek near Sierra

Ballona Creek basin:

Topanga Creek basin:

Malibu Creek basin: 

Malibu Creek at Crater Camp, near

Santa Clara River basin:

Qo <ai^o P "poo lr nossT* T5M1T m^T»o _ «_ _«__..__ _ _

Ventura River basin: 

Matilija Creek above Reservoir, near

Matilija Hot Springs 

Matilija Creek at Matilija Hot Springs 

North Pork Matilija Creek at Matilija Hot

Carpinteria Creek basin:

Atascadero Creek basin:

San Jose Creek basin:

Santa Ynez River basin: 

Santa Ynez River at Jameson Lake, near

Santa Ynez River above Gibralter Dam,

]

Drainage 

area 

( square 

miles)

155 

28.2

64.9 

106 

1.2 

21.0 

148 

510 

16.4 

614 

5.3 

10.5

1.9 

6.5

822 

88.6 

17.9

103

410 

432 

23.0 

50 

254 

39.8

51 

55

15.5 

41.1 

187

13.8 

18.3 

5.54

16.0

9~\ Q

L954-55 annual runoff

Acrefeet

16,080 

736

1,910 

3,580 

45 

47 

20 

18,270 

1,280 

39,310 

686 

1,440

178 

700 

11,350 

3,100 

8,010 

60,130

21,600 

354

758

612 

11,880 

740 

1,110 

17,060 

3,010

3,820 

4,630

1,350 

750 

4,910

16 

387 

475

312

 ^ Q7fl

Acrefeet 

per 

square 

mile

104 

26.1

29.4 

33.8 

37.5 

2.24 

.14 

35.8 

78.0 

64.0 

129 

137

93.7 

108

73.2 

244 

19.8

7.36

1.49 

27.5 

32.2 

22.2 

67.2 

75.6

74.9 

84.2

87.1 

18.2 

26.3

1.16 

21.1 

85.7

19.5 

1ft ?

Departure 

from 

base 

mean 

(per 

cent)

-90

-84 

-98

-56 

-81

-66 

-69

-75 

-80 

-73

-32

-90

-94

-94 

-73

-77 

-79

-79

-78 

-92 

-90

-92 

-ft?

Period of record

Length 

years)

12 

38

7 

38 

38 

27 

15 

26 

41 

27 

38 

39

38 

37 

27 

25 

27 

26

27 

24

24

26 

28 

23 

7 

34 

28

7 

28

26 

27 

28

14 

14 

14

24 

 vs

Mean 

annual 

runoff 

(acrefeet)

15,000 

6,780

20,690

1,920 

16,020 

42,070 

6,770 

70,000 

1,840 

4,200

644 

2,740 

38,770 

11,920 

19,720 

1.03,300

4,050

14,410

10,360 

41,050 

3,550

69,490 

13,670

21,420

6,290 

9,090 

48,630

1,130 

1,450 

904

4,470 

SO . .S4.O

Median 

annual 

runoff 

(acrefeet)

11,600 

3,300

11,600

510 

3,700 

24,600 

3,800 

43,400 

1,400 

2,700

360 

1,800 

27,500 

11,600 

8,000 

67,300

1,400

4,900

2,500 

20,300 

1,600

38,100 

8,000

10,900

3,200 

3,600 

24,900

290 

510 

580

2,200 

i ? . i on

Base mean

Mean 

annual 

runoff 

1920-50 

(acrefeet)

7,360

22,680

2,160

41,800 

6,720

2,000 

4,580

710 

3,420 

42,670

88,580

3,640

12,660

10,440 

43,280

75,290 

14,040

22,380

6,110 

8,820 

48,900

4,010 

31 . SfiO
18 WATER RESOURCES SUMMARY FOR SOUTHERN CALIFORNIA, 1956

Table 4.--Annual runoff for the water year 1954-55 Continued

Basin end stream

Santa Ynez River basin Continued 

Santa Ynez River below Gibralter Dam,

Santa Ynez River below Los Laureles

Santa Ynez River at Grand Avenue near

Santa Ynez River at Santa Rosa Damsite,

Santa Ynez River at Cooper's Reef, near

Santa Ynez River below Santa Rita Creek,

Salsipuedes Creek near Lompoc 

Santa Ynez River at narrows, near

Santa Ynez River near Lompoc 

Santa Ynez River at H Street, near

Santa Ynez River at 13th Street, near

San Antonio Creek basin:

Santa Maria River basin:

Arroyo Grande basin:

THE GREAT BASIN 

Salton Sea basin:

Palm Canyon Creek near Borrego Springs 

Mojave River basin:

West Fork Mojave River near Hesperia 

Mojave River at lower narrows, near 

VIctorville 

Antelope Valley:

Little Rock Creek near Little Rock a -- 

Drainage 

area 

{ square 

miles)

219

77.2

435 

56.4

585

38.7

46.6

790

101

90

912 

87.7 

119 

290 

86.7 

28.9 

442 

,763

106 

57.4

94.0 

8.78

21.7

137 

74.8

530

23.0 

49.0

1954-55 annual runoff

Acrefeet

84

930 

1,890 

485 

2,610 

150 

1,360

3,090 

4,200 

1,860 

7.4 

2,640

2,020 

1,670

1,480 

1,320

2,060 

1,650

209

47 

413

65

2,130 

1,230 

1,240 

1,420 

5,260 

572 

539 

609 

0

4,320

9,562 

1,530 

245 

1,350 

1,690 

312

L6,260 

4,800

22,520 

0 

913

5,940 

7,310

Acrefeet 

per 

square 

mile

.38

24.5

6.00 

2.66

7.18

.19

28.3

2.09

.64

23.7 

1.35 

14.1 

11.9 

18.1 

6.60 

18.7 

1.38 

0

40.8 

167

2.61 

154

144

119 

64.2

42.5 

0

258 

149

Departure 

from 

base 

mean ( percent )

 

 

-96

 

 

 

-98

-91 

-89

-72

-95

-66 

-82

-64 

-100

-54 

-49

Period of record

Length 

[years]

35

8 

13 

5 

25 

14 

1

1 

17 

1 

14 

3

1 

1

1 

14

3 

30

8

1 

8

14

10 

25 

12 

25 

12 

12 

12 

14 

14

15

7 

8 

20 

7 

5 

5

42 

43

30 

25 

5

32 

23

Mean 

annual 

runoff 

(acrefeet)

26,560

7,230

65,860 

1,710

32,340

195

4,579

87,850

844

3,980 

15,230 

3,210 

14,010 

17,450 

2,880 

730 

17,010 

14,840

16,050

3,670

56,020 

32,330

57,740 

22,300

11,300 

13,010

Median 

annual 

runoff 

(acrefeet)

8,700

5,100

16,200 

720

1.2,400

22

2,000

31,800

250

2,700 

8,000 

1,300 

5,400 

9,400 

360 

360 

7,000 

1,800

8,800

1,000

42,100 

21,000

34,000 

190

7,100 

7,500

Base mean

Mean 

annual 

runoff 

1920-50 

(acrefeet)

63,070

86,420

14,400

12,810

15,400

4,840

47,150 

26,330

62,550 

29,550

12,890 

14,340