U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Geohydrology and Water Chemistry of

the Alexander Valley, Sonoma County, California

Scientific Investigations Report 2006-5115

In cooperation with the

SONOMA COUNTY WATER AGENCY
Cover. Photograph of Alexander Valley, 

 Sonoma County, California, 

 by GAMA program staff, U.S. Geological Survey
Geohydrology and Water Chemistry of 

the Alexander Valley, Sonoma County, 

California

By Loren F. Metzger, Christopher D. Farrar, Kathryn M. Koczot, and 

Eric G. Reichard

In cooperation with the Sonoma County Water Agency

Scientific Investigations Report 2006–5115

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Dirk Kempthorne, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Metzger, L.F., Farrar, C.D., Koczot, K.M., and Reichard, E.G., 2006, Geohydrology and Water Chemistry of the Alexander 

Valley, Sonoma County, California: U.S. Geological Survey Scientific Investigations Report 2006-5115, 83 p..
iii

Contents

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

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

Purpose and Scope .............................................................................................................................2

Location of the Study Area..................................................................................................................2

Land and Water Use.............................................................................................................................2

Climate ...................................................................................................................................................8

Previous Investigations and Data Bases........................................................................................13

Acknowledgments..............................................................................................................................14

Physiography and Geologic Setting .........................................................................................................14

Geology..........................................................................................................................................................16

Basement Rocks ................................................................................................................................16

Basin Fill ...............................................................................................................................................17

Sonoma Volcanics .............................................................................................................................17

Glen Ellen Formation ..........................................................................................................................17

Quaternary Alluvial Units ..................................................................................................................21

Quaternary Landslides.......................................................................................................................21

Geologic Structures............................................................................................................................21

Hydrology .....................................................................................................................................................21

Surface-Water Hydrology .................................................................................................................21

Geohydrology.......................................................................................................................................23

Water Budget ......................................................................................................................................28

Ground-Water Levels and Movement.............................................................................................28

Long-Term Changes in Ground-Water Levels................................................................................30

Ground-Water and Surface-Water Quality ............................................................................................37

Methods of Water Sampling and Analysis .....................................................................................37

Ground-Water and Surface-Water Chemistry ..............................................................................42

Water-Quality Monitoring.........................................................................................................42

General Chemical Composition of Ground and Surface Water .........................................42

Summary and Conclusions ........................................................................................................................49

References Cited..........................................................................................................................................50

Appendix........................................................................................................................................................53
iv

Figures

Figure 1. Map showing location of study area .......................................................................................3

Figure 2. Map showing location of Alexander Valley watershed, topographic and 

 hydrologic features, in Sonoma County, California...............................................................4

Figure 3. Maps showing land use in the Alexander Valley study area, 

 Sonoma County, California: 1974 and 1999..............................................................................5

Figure 4. Graph showing annual precipitation, and cumulative departure from the 

 mean of precipitation, at Healdsburg, Sonoma County, California, 

 1932–2004 ....................................................................................................................................13

Figure 5. Geologic map of the Alexander Valley watershed, Sonoma 

 County, California.......................................................................................................................15

Figure 6. Geologic cross sections of the Alexander Valley watershed, 

 Sonoma County, California ......................................................................................................18

Figure 7. Map showing drainage areas for USGS streamflow-gaging stations 

 11463000 and 11464000 in Alexander Valley, Sonoma County, 

 California .....................................................................................................................................22

Figure 8. Graphs showing discharge of Russian River, Sonoma County, 

 California: mean daily discharge for water years 1990–2000 near Cloverdale; 

 mean daily discharge for water years 1990–2000 near Healdsburg; difference

 in discharge in the Russian River between Cloverdale and Healdsburg for 

 water year 1977; difference in discharge in the Russian River between 

 Cloverdale and Healdsburg for water year 1995, and difference in discharge

 in the Russian River between Cloverdale and Healdsburg for water year 2000.............24

Figure 9. Map showing locations of wells in the California Department of Water 

 Resources ground-water-level monitoring network in Alexander Valley, 

 Sonoma County, California ......................................................................................................29

Figure 10. Maps showing generalized hydraulic head in Alexander Valley, Sonoma 

 County, California: autumn 1980 and autumn 2002...............................................................32

Figure 11. Map showing drilled wells per section in Alexander Valley, Sonoma County, 

 California, 1950–2004.................................................................................................................34

Figure 12. Water level hydrographs for selected wells in Alexander Valley, 

 Sonoma, County, California: Cloverdale area; Geyserville area; Jimtown 

 area; and southern area ...........................................................................................................35

Figure 13. Map showing location of ground- and surface-water quality sampling 

 sites, Alexander Valley, Sonoma County, California ..........................................................38

Figure 14. Trilinear diagram showing chemical composition of water from selected 

 ground- and surface-water sampling sites in the Alexander Valley, Sonoma 

 County, California, 1951–2001: all sites; wells in sections 9N/8W and 9N/9W; 

 wells in section 10N/9W; and wells in sections 10N/10W and 11N/10W.........................43

Figure 15. Trilinear diagram showing chemical composition of water from selected 

 ground-water sampling sites in the Alexander Valley, Sonoma County, 

 California, 2002–2004.................................................................................................................45

Figure 16. Stiff diagrams showing chemical composition of samples from selected wells

 in the Alexander Valley, Sonoma County, 2002–04...............................................................47

Figure 17. Time-series plots of electrical conductance for selected ground-water wells

 in the Alexander Valley, Sonoma County, California, 1969–2004........................................48
v

Tables

Table 1. Land use in Alexander Valley, Sonoma County California, 1974 and 1999...........................7

Table 2. Estimates of irrigated acreage by crop type, unit applied water, estimated 

annual applied water, and irrigation efficiency, Alexander Valley, Sonoma 

County, California, 1974 and 1999 ...............................................................................................9

Table 3. Precipitation at Healdsburg, Sonoma County, California, water years 1932–2004 ..........10

Table 4. Well construction information and water-level change in wells in the California 

Department of Water Resources ground-water level monitoring network in 

Alexander Valley, Sonoma County, California .......................................................................31

Table 5. Construction data for selected wells used for water-chemistry sampling in the

Alexander Valley, Sonoma County, California........................................................................39

Table 6. Summary of laboratory conductivity measurements for samples from selected 

ground-water wells, Alexander Valley, Sonoma County, California, 1969–2004 ..............40

Appendix

Appendix A. Field measurements and laboratory analyses of samples from streamflow- 

 measurement stations and ground-water wells, Alexander Valley, 

 Sonoma County, California, 1951–2004.............................................................................54
vi

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3) 0.02832 cubic meter (m3)

acre-foot (acre-ft) 1,233 cubic meter (m3

)

Flow rate

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic feet per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Conversion Factors, Datum, Abbreviations, and 

Acronyms

Inch/Pound to SI

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the North American Vertical Datum of 

1988 (NAVD 88), unless otherwise noted. Horizontal coordinate information is referenced to 

the North American Datum of 1983 (NAD 83).

Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot 

times foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, 

foot squared per day (ft2/d), is used for convenience.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/

cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter 

(mg/L) or micrograms per liter (μg/L).

NOTE TO USGS USERS: Use of hectare (ha) as an alternative name for square hectometer (hm2

) is restricted to the measurement of small land or water areas. Use of liter (L) as a 

special name for cubic decimeter (dm3) is restricted to the measurement of liquids and gases. 

No prefix other than milli should be used with liter. Metric ton (t) as a name for megagram 

(Mg) should be restricted to commercial usage, and no prefixes should be used with it.
vii

Abbreviations and Acronyms

bls below land surface

EC electrical conductance

ET evapotranspiration

ETa actual evopotranspiration

ETo potential evapotranspiration

GAMA Ground-Water Ambient Monitoring and Assessment program

GIS geographical information system

ma millions of years before present

meq/L milliequivalent per liter

mg/L milligrams per liter

NGVD 29 National Geodetic Vertical Datum of 1929

PRISM Parameter-Elevation Regressions on Independent Slopes Model

R2 correlation coefficient

ROE residue on evaporation

SMD soil moisture deficit

μg/L micrograms per liter

μS/cm microsiemens per centimeter

WY water year

Organizations

CADWR California Department of Water Resources

SCWA Sonoma County Water Agency

SWRCB California State Water Resources Control Board

USGS U.S. Geological Survey
viii

Well-Numbering System

Wells are identified and numbered according to their location in the rectangular system for the subdivision of 

public lands. Identification consists of the township number, north or south; the range number, east or west; and the 

section number. Each section is divided into sixteen 40-acre tracts lettered consecutively (except I and O), beginning with “A” in the northeast corner of the section and progressing in a sinusoidal manner to “R” in the southeast 

corner. Within the 40-acre tract, wells are sequentially numbered in the order they are inventoried. The final letter 

refers to the base line and meridian. In California, there are three base lines and meridians; Humboldt (H), Mount 

Diablo (M), and San Bernardino (S). All wells in the study area are referenced to the Humboldt base line and 

meridian (H). Well numbers consist of 15 characters and follow the format 010N009W-026L002. In this report, 

well numbers are abbreviated and written 10N/9W-26L2. Wells in the same township and range are referred to 

only by their section designation, -26L2. The following diagram shows how the number for well 10N/9W-26L2 is 

derived.

10N/9W-26L2

C B A

F G H

L K J

P Q R

6 5 4 3 2 1

7 8 9 10 11 12

18 17 16 15 14 13

19 20 21 22 23 24

30 29 28 26 25

31 32 33 34 35 36

27

R7W R6W

T9N

T10N

T11N

R8W

RANGE

TOWNSHIP

R10W R9W

T8N

T7N

R9W

Well-numbering diagram

SECTION 26

T10N

D

E

M

N
Abstract

This study of the geohydrology and water chemistry 

of the Alexander Valley, California, was done to provide an 

improved scientific basis for addressing emerging water-management issues, including potential increases in water demand 

and changes in flows in the Russian River. The study tasks 

included (1) evaluation of existing geohydrological, geophysical, and geochemical data; (2) collection and analysis of new 

geohydrologic data, including subsurface lithologic data, 

ground-water levels, and streamflow records; and (3) collection and analysis of new water-chemistry data.

 The estimated total water use for the Alexander Valley 

for 1999 was approximately 15,800 acre-feet. About 13,500 

acre-feet of this amount was for agricultural use, primarily 

vineyards, and about 2,300 acre-feet was for municipal/industrial use. Ground water is the main source of water supply for 

this area.

The main sources of ground water in the Alexander Valley are the Quaternary alluvial deposits, the Glen Ellen Formation, and the Sonoma Volcanics. The alluvial units, where 

sufficiently thick and saturated, comprise the best aquifer in 

the study area.

Average recharge to the Alexander Valley is estimated 

from a simple, basinwide water budget. On the basis of an 

estimated annual average of 298,000 acre-feet of precipitation, 

160,000 acre-feet of runoff, and 113,000 to 133,000 acre-feet 

of evapotranspiration, about 5,000 to 25,000 acre-feet per year 

is available for ground-water recharge. Because this estimate 

is based on differences between large numbers, there is significant uncertainty in this recharge estimate.

Long-term changes in ground-water levels are evident in 

parts of the study area, but because of the sparse network and 

lack of data on well construction and lithology, it is uncertain 

if any significant changes have occurred in the northern part 

of the study area since 1980. In the southern half of the study 

area, ground-water levels generally were lower at the end of 

the 2002 irrigation season than at the end of the 1980 season, 

which suggests that a greater amount of ground water is being 

pumped in the southern half of the study area in recent years 

compared with that pumped in the early 1980s.

Water-chemistry data for samples collected from 11 wells 

during 2002–04 indicate that water quality in the study area 

generally is acceptable for potable use. Two wells, however, 

each contained one constituent (241 μg/L of manganese and 

1,350 μg/L of boron) in excess of the recommended standards 

for drinking water (50 μg/L and 1,000 μg/L, respectively). 

The chemical composition of water from most of the 

wells sampled for major ions plot as a mixed cation-bicarbonate, magnesium-bicarbonate, or calcium-bicarbonate type 

water. The ionic composition of the historical and recent 

samples from wells in the Alexander Valley is similar to that 

of the historical surface-water samples collected from the 

Russian River near Healdsburg. This suggests a similar source 

of water, particularly for wells that are less than 200 feet total 

depth and perforated in Quaternary alluvial deposits. Water 

from deeper, non-alluvial wells may contain slightly higher 

concentrations of sodium as a result of cation exchange. 

Water samples collected from several wells over an 

approximately 30–year period suggest a progressive change 

in water chemistry over time. Samples from the southern part 

of the valley show a trend towards higher ionic concentrations 

and increasing concentrations of particular constituents such 

as sulfate. 

Geohydrology and Water Chemistry of the Alexander 

Valley, Sonoma County, California

By Loren F. Metzger, Christopher D. Farrar, Kathryn M. Koczot, and Eric G. Reichard
Introduction

The Alexander Valley is a topographically defined 

ground-water basin in northern Sonoma County, California. 

Sonoma County is in the northern part of the greater San 

Francisco Bay region, an area of northern California that has 

experienced rapid population growth and accelerated urbanization during the past 30 to 40 years. The Alexander Valley has 

undergone significant changes in land use, mostly involving 

the conversion from native vegetation to irrigated vineyards. 

The ground-water system in the Alexander Valley is closely 

linked to the Russian River. Increased pumpage has affected 

some ground-water levels in the valley; future changes in 

pumpage will likely affect recharge and discharge rates from 

the river. Conversely, possible future changes in the flow 

regime of the Russian River could affect the ground-water 

levels in the Alexander Valley. Changes in land use and in the 

ground-water flow system in the Alexander Valley may affect 

the sources and transport of potential contaminants to ground 

water and the Russian River.

The U.S. Geological Survey (USGS) began a study to 

improve the understanding of the geohydrology and geochemisty of the Alexander Valley in order to gain knowledge 

regarding potential future changes in the ground-water/surface 

water system. The project is part of a multi-phase USGS study 

of the ground-water resources of Sonoma County being conducted in cooperation with the Sonoma County Water Agency 

(SCWA). In addition, wells in the area have been sampled as 

part of the statewide California Ground-Water Ambient Monitoring and Assessment (GAMA) program, which is being done 

by the USGS in conjunction with the California State Water 

Resources Control Board (SWRCB). 

Purpose and Scope 

The USGS, in cooperation with SCWA, undertook this 

study to evaluate the ground-water resources of Alexander 

Valley. The goals of the study were to update the geohydrologic characterization of the study area and to provide a 

current assessment of hydrologic conditions, including an 

evaluation of ground-water level and water-quality changes 

during the past 25 to 50 years. 

To meet the objectives of this study, three principal tasks 

were undertaken: (1) evaluation of existing geohydrological, 

geophysical, and geochemical data; (2) collection and analysis 

of new geohydrologic data, including subsurface lithologic 

data, ground-water levels, and streamflow records; and (3) 

collection and analysis of new water-chemistry data (note that 

water-chemistry data were collected as part of the GAMA 

program, funded by the SWRCB).

The purpose of this report is to present a geologic and 

hydrologic description of the study area, present selected 

hydrologic data collected from the 1950s to 2004, quantify 

changes in the ground-water system that have occurred in the 

past 50 years, and quantify changes in water use. This information is essential for future management of the ground-water 

system, which is the primary water supply for this area of 

Sonoma County.

Location of the Study Area

The Alexander Valley study area is located approximately 

50 miles (mi) north of San Francisco in northern Sonoma 

County, California. A small part of the Valley extends into 

southern Mendocino County (figs. 1, 2). The study area comprises 127 square miles (mi2

) that includes the valley floor and 

the hills immediately adjacent where most of the agricultural 

development is located. Alexander Valley is drained by the 

Russian River, which discharges to the Pacific Ocean to the 

west of the study area. This part of the Russian River drainage 

basin commonly is referred to as the Middle Russian River 

(California Department of Water Resources, 1980). In this 

report, Alexander Valley refers to Alexander Valley proper and 

its northwestward extension, Cloverdale Valley. This designation conforms to the most recent ground-water basin delineation given by California Department of Water Resources 

(2004). In some reports a distinction is made between the two 

valleys; however, these valleys are hydraulically connected 

through thin deposits of alluvial materials beneath the Russian River. A series of low hills, part of the Mendocino Range, 

form the western boundary of the watershed, and the Mayacmas Mountains form the eastern boundary (fig. 2).

Land and Water Use

Land use in study area is predominantly native vegetation and agriculture (fig. 3, table 1) (California Department of 

Water Resources, 1974, 1999). From the 1950s to the present, 

the primary crop has been vineyards, followed by orchards 

(table 2) (California Department of Water Resources, 1974, 

1999). Lands designated as urban, residential, commercial, 

and industrial purposes make up less than 5 percent of the 

study area. The major urban/residential areas include the communities of Preston, Cloverdale, Asti, and Geyserville, several 

unincorporated communities, and areas of rural and semi-rural 

residential development. According to the population census 

of 2000, about 12,000 people lived in the part of the study area 

located in Sonoma County (Association of Bay Area Governments, accessed November 11, 2004). Sonoma County makes 

up a total of 96 percent of the study area, with the remaining 4 

percent located in Mendocino County.

2 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Lake

Mendocino

Lake

Sonoma

Clear

Lake

R i v e r

R

u s s i a

n

Napa

River

128

12

29

29

20

175

1

1

116 128

37 101

101

San

Pablo

Bay

Bay

San

Francisco

Mendocino

Co

Sonoma

Co

Marin Co

Napa Co

Lake Co

Solano Co

Contra

Costa

Co

N

o

r

t

h

C

o

a

s

t

R

a

n

g

e

s

Sonoma

Santa Rosa

Healdsburg

Geyserville

Cloverdale

San

Francisco

Ukiah

Base from U.S. Geological Survey digital data, 1:1,000,000,

downloaded 2003 State Plane Projection, FIP zone 402.

Shaded relief base from 1:250,000 scale Digital Elevation Model:

sun illumination from northwest at 30 degrees above horizon

0 25 50 Miles

0 25 50 Kilometers

Alexander

Valley

M a y a

c m

a

s

M

o

u

n t a i n

s

M e

n d o

c i

n

o

R

a

n

g

e

S o

n

o

m

a

M ts Sonoma

Valley

Napa Valley

Area of

C

map

a l i f o r n i a

Pacific Ocean

Pa c i f i c

O c e a n

Figure 1. Location of study area.

Introduction 3
R i v e

Lake r

Sonoma

Warm

Springs

Dam

R

u ssi a n

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston M

a

y a

c

m

a

s

M

o

u

n

t

a i

n

s

M e n d o c i n o

R a n g e

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402.

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

D r y C r e e k

A

l

e

x

a

n d

e

r

V

a

l

l

e

y

EXPLANATION

USGS stream gage and

identifier 11464000

Figure 2. Location of Alexander Valley watershed, topographic and hydrologic features, in Sonoma County, 

California.

4 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
R i v e r

Lake

Sonoma

Warm

Springs

Dam

R

u ssi a n

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

D r y C r e e k

Irrigated agriculture

Non-irrigated agriculture

Urban/residential

Native vegetation

Water

EXPLANATION

Land-use type (1974)—Single use

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Alexander

Valley

A

Figure 3. Land use in the Alexander Valley study area, Sonoma County, California. A, 1974; B, 1999. [Modified from 

land-use surveys of the California Department of Water Resources (1974, 1979)]. 

Introduction 5
R i v

e r

Lake

Sonoma

Warm

Springs

Dam

R

u ss i a n

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

D r y C r e e k

Irrigated agriculture

Non-irrigated agriculture

Urban/residential

Urban/non-irrigated

agriculture

Urban/residential/

native vegetation

Native vegetation

Riparian

Barren land

Barren land/water

Water

EXPLANATION

Land-use type (1999)—Single use

Land-use type (1999)—Multiple use

Alexander

Valley

B

Figure 3.—Continued.

6 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Land-use type

Land-use surveys1

1974 1999

Acres mi2 Acres mi2

Single use

 Irrigated agriculture (Including lawns) 8,618 13 14,465 23

 Non-irrigated agriculture 3,616 6 1,114 2

 Urban/residential (including commerical and industrial) 1,624 3 3,245 5

 Native vegetation 67,497 105 59,227 92

 Riparian NA NA 755 1

 Barren NA NA 231 0

 Barren/water NA NA 1,276 2

 Water surface 87 0 327 0

Mixed use

 Urban/residential/non-irrigated agriculture NA NA 5 0

 Urban/residential/native vegatation NA NA 654 1

Unknown designation NA NA 66 0

Total area 81,442 127 81,366 127

1974 1999

Percent of total area Percent of total area

Single use

 Native vegetation 83 73

 Riparian NA 1

 Barren and barren/water NA 2

 Urban/residential (including commerical and industrial) 2 4

 Total agriculture 15 19

 Irrigated agriculture 11 18

Mixed use

 Urban/residential/non-irrigated agriculture NA 0

 Urban/residential/native vegatation NA 1

 1Modified from land-use surveys by the California Department of Water Resources, 1974, 1999.

Table 1. Land use in Alexander Valley, Sonoma County California, 1974 and 1999.

[Because of rounding, all values may not add to totals; mi2, square miles; NA, not applicable]

Introduction 7
Changes in land use between 1974 and 1999 were evaluated in this study (fig. 3, table 1; California Department of 

Water Resources, 1974 and 1999). In 1974, 83 percent of the 

land in the study area consisted of native vegetation; of the 

remaining 17 percent, 15 percent was for agri­cultural use and 

2 percent was for urban and residential use. Agriculture was 

irrigated in 11 per­cent of the study area (table 1). By 1999, 

native vegetation in the study area declined to 73 percent. This 

was primarily due to the conversion of native lands to irrigated 

agriculture and urban and residential use. In 1999, mixed-use 

lands amounted to about 1 percent of the study area.

For the current study, the demand for irrigation water 

was estimated by multiplying crop acreages derived from 

California Department of Water Resources (CADWR) landuse surveys times the estimates, obtained from CADWR, of 

unit applied water (table 2; Scott Matyac, California Department of Water Resources, unpub. data, 2005). For this study, 

only one growing season per year was assumed for truck and 

field crops. Unit applied water is the total amount of water, 

in feet/year, estimated by CADWR to be delivered to a crop. 

Estimates of evapotranspiration of applied water were also 

obtained from CADWR (Scott Matyac, California Department 

of Water Resources, unpub. data, 2005). Irrigation efficiency is 

the ratio of evapotranspiration of applied water to unit applied 

water. In Alexander Valley, vineyards are the predominant 

crop type and are typically underwatered to stress plants to 

produce better grapes for wine production. Therefore, in Alexander Valley, the estimated irrigation efficiency for vineyards 

is about 89 percent; the other crops combined averaged about 

72 percent irrigation efficiency (table 2).

In Alexander Valley, water demand for irrigation was 

estimated in this study to increase 43 percent from 9,400 acrefeet per year (acre-ft/yr) in 1974 to 13,500 acre-ft/yr in 1999, 

and irrigated agri­cultural fields increased by 68 percent, from 

8,618 acres in 1974 to 14,465 acres in 1999 (table 2). The peracre agricultural demand of water declined from 1974 to 1999 

because farmers converted from higher water-consuming crops 

(pasture) to lower water-consuming crops (vineyards).

Water-use estimates (table 2) were evaluated against 

irrigation sources noted in parcels of the 1999 land-use survey 

(California Department of Water Resources, 1999). Of the 

estimated 13,500 acre-feet (acre-ft) of water used for irrigation in 1999, about 78 percent was met solely by ground water, 

about 6 percent was met solely by surface water, and about 

1 percent was met by a combi­nation of ground and surface 

water. About 15 percent of the estimated irrigation water had 

an unknown source of water. The areas irrigated solely by 

surface water were located primarily on the eastern bank of 

the Russian River at Cloverdale and in a limited area south 

of Jimtown. Areas of unknown water source adjacent to the 

Russian River south of Jimtown and east of Healdsburg likely 

used surface water diverted from the Russian River. Fields 

with unknown origin of irriga­tion water located on hillsides 

away from the Russian River were likely irrigated with ground 

water. It was assumed to be unlikely that water from the Russian River is being diverted signifi­cant distances.

By 2000, domestic water demand was estimated to be 

about 2,300 acre-ft/yr, based on an estimated population of 

12,313 and an estimated domestic consumption of 0.19 acreft/yr per person (California Department of Water Resources, 

1994). Most water for domestic use can be considered to be 

from ground water. However, many wells are located in proximity to the Russian River.

In summary, the estimated total water use for the Alexander Valley for 1999 was about 15,800 acre-ft (about 13,500 

acre-ft for agriculture and about 2,300 acre-ft for domestic 

use), most of which was drawn from ground water. If one 

assumes that approximately 80 percent of agricultural use and 

100 percent of domestic use is from ground water, then this 

equates to about 13,000 acre-ft of pumpage in 1999. This can 

be contrasted with Cardwell’s (1965) estimate of 4,500 acreft/yr of pumpage in 1954. 

From a water-rights perspective, water pumped from 

some wells near the river in the Alexander Valley may be 

legally considered as surface water drawn from the Russian 

River. However, this report does not consider water-rights 

definitions, only whether water is known to be pumped from a 

well.

Climate 

The climate of the study area is Mediterranean, with 

moderate temperatures and distinct wet and dry seasons. 

Mean annual air temperature at Healdsburg is about 14.7°C 

and about 15.4°C at Cloverdale. Freezing temperatures on the 

valley floor are rare but do occur on the higher slopes of the 

bordering mountains. About 90 percent of the area’s yearly 

precipitation falls from November through April. Nearly all 

the precipitation falls as rain. Mean annual precipitation at 

Healdsburg averaged about 42 inches (in.) for water years 

1932 through 2004 (table 3) (National Oceanic and Atmospheric Administration, accessed December 19, 2005). As 

shown in figure 4 and table 3, annual precipitation in any 

given year can deviate greatly from the 74-year average. 

8 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Crop class

Year

Irrigation 

efficiency Acres irrigated1 Unit applied water2 Estimated applied water3 (acre-ft/yr)

1974 1999 (ft/yr) 1974 1999 (percent)

Citrus, deciduous,

and field

703 188 2.0 1,406 376 75

Pasture and lawn 373 113 3.3 1,231 373 64Grain 0 68 0.4 0 27 75Truck 29 41 1.7 49 70 76Vineyard 7,513 14,055 0.9 6,762 12,650 89Totals 8,618 14,465 9,448 13,496

1Estimated from California Department of Water Resources Crop surveys, California Department of Public Works (1974 and 1999).2California Department of Water Resources (Scott Matyac, unpub. data, 2005).3Applied water was estimated to be acreages multiplied by unit applied water.

Table 2. Estimates of irrigated acreage by crop type, unit applied water, estimated annual applied water, and irrigation efficiency, Alexander Valley, Sonoma County, California, 1974 and 1999.[ft/yr, feet per year; acre-ft/yr, acre-feet per year]

Introduction 9
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Water year total

1932 1.89 3.19 15.59 3.05 1.91 1.14 1.71 1.83 0.03 0 0 0 30.341933 0.05 2.6 4.81 9.37 1.39 5.65 0.16 2.43 0 0 0 0.21 26.671934 2.07 0 14.67 1.42 8.14 1.2 0.92 1.57 1.12 0 0 0.08 31.191935 4.07 7.17 3.71 12.07 4.8 8.23 5.28 0.03 0 0 0.03 0.17 45.561936 1.44 1.83 5.19 8.59 13.54 1.76 2.58 1.05 1.34 0.12 0 0 37.441937 0.27 0.03 4.48 5.19 11.86 8.45 1.73 0.15 1.77 0 0 0 33.931938 1.34 9.74 9.49 8.14 13.47 10.67 2.79 0.03 0 0.01 0 0.41 56.091939 2.74 2.55 1.85 5.2 1.87 3 0.22 1.79 0 0 0 0.05 19.271940 0.23 0.72 7.07 17.12 20.68 7.07 1.88 1.84 0 0.02 0 0.42 57.051941 2.85 3.15 21.35 15.15 12.7 6.89 7.6 1.82 0.6 0 0.04 0.04 72.191942 2.54 5.14 12.38 10.42 10.11 4.01 7.05 3.12 0 0 0 0.1 54.871943 1.2 5.49 7.52 13.29 3.54 3.75 3.67 0 0.01 0 0 0 38.471944 1.43 1.68 3.43 7.56 8.9 2.87 2.9 2.83 0.21 0 0 0.02 31.831945 3.19 7.48 4.97 3.82 6.05 7.02 0.53 1.53 0 0 0 0 34.591946 6.71 6.7 14.84 2.49 4.06 1.89 0.1 0.5 0 0.18 0 0.07 37.541947 0.14 5.23 3.29 0.96 5.54 7.94 0.12 0.68 1.92 0 0 0 25.821948 6.54 1.06 2.11 3.75 1.55 6.43 12.93 1.23 0.42 0 0 0.09 36.111949 1.03 1.69 4.93 1.81 4.61 13.38 0.04 0.37 0 0.18 0** 0 28.041950 0.07 2.48 2.87 10.49 8.49 2.98 1.75 0.69 0.28 0 0 0 30.101951 6.04 8.13 10.73 6.2 3.86 1.23 1.33 2.55 0 0 0 0.01 40.081952 2.76 8.82 13.69 13.41 3.92 6.17 1.69 0.39 1.97 0 0 0 52.821953 0.07 3.7 19.93 10.97 0.1 4.23 4.77 1.25 0.66 0 0.45 0 46.131954 1.54 6.85 1 12.28 5.13 6.88 4.61 0.05 0.42 0.07 3.17 0 42.001955 1.45 8.44 7.61 3.84 1.33 0.62 5.76 0 0.01 0 0 0.33 29.39

Table 3. Precipitation at Healdsburg, Sonoma County, California, water years 1932–2004.[Precipitation in inches. Data from National Oceanic & Atmospheric Administration website http://www1.ncdc.noaa.gov/pub/orders/110904743047dat.txt, Dec 19, 2005. *, missing values taken from reported values for alternate station: Russian River Near Healdsburg (HEA). Station data may be retrieved from the California Department of Water Resources, division of Flood Management, 2006, California Data Exchange Center (CDEC)—access point to the Department of Water Resources Operational Hydrologic Data: http: cdec.water.ca.gov/ (accessed January 2, 2006); **, estimated valued based on median rainfall for August for period of record]

10 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Water year total

1956 0.47 4.58 22.34 16.62 9.05 0.31 2.9 0.84 0.05 0 0 0.12 57.281957 2.86 0.31 0.57 6.96 8.55 3 3.32 4.36 0.4 0 0 4.09 34.421958 8.77 1.17 5.28 10.04 23.34 9.64 6.5 0.3 0.85 0.09 0 0 65.981959 0.09 0.27 2.12 15.66 9.15 1.44 0.42 0.13 0 0 0 4.52 33.801960 0 0 2.04 9.27 10.45 5.95 1.49 1.12 0 0 0 0 30.321961 1.21 6.72 7.64 7.64 4.17 5.79 1.64 0.41 0.08 0 0.21 0.56 36.071962 0.29 6.8 3.79 1.88 16.91 7.13 0.4 0.14 0 0 0.3 0.26 37.901963 10.83 2.06 6.4 10.75 3.99 7.74 6.85 1.14 0 0 0 0.01 49.771964 3.14 12.09 1.26 5.74 0.22 2.68 0.26 0.62 0.46 0.03 0 0 26.501965 3.5 9.14 15.07 10.46 1.94 1.58 5.75 0 0 0.04 0.49 0 47.971966 0.11 12.42 6.61 11.33 6.29 1.34 1.25 0.13 0.05 0 0.11 0.11 39.751967 0 13.2 10.12 16.37 0.41 8.6 6.49 0.17 2.17 0 0 0.02 57.551968 1.14 3.47 5.89 10.96 6.59 4.89 1.44 0.23 0 0 0.86 0.03 35.501969 2.79 4.07 13.47 20.38 15.5 2.02 3.13 0.03 0 0 0 0.01 61.401970 2.71 1.56 18.58 25.24 5.2 2.63 0.12 0.02 0.45 0 0 0 56.511971 3.08 11.46 12.23 4.95 0.16 6 1.68 0.28 0 0 0.01 0.29 40.141972 0.43 3 7.77 2.02 2.92 1.23 3.12 0.13 0.06 0 0 0.67 21.351973 4.17 9.89 5.32 18.39 9.54 3.83 0.15 0.03 0 0 0 0.75 52.071974 4.79 21.2 6.65 10.67 5.21 12.17 2.07 0.15 0 1.71 0 0 64.621975 1.77 1.96 7.5 2.72 13.86 11.33 1.73 0 0.01 0.21 0.04 0 41.131976 5.62 1.43 1.92 0.41 2.93 1.01 3.24 0 0 0.03 1.12 0.56 18.271977 0.42 2.78 1.17 2.53 2.74 2.38 0.35 1.77 0 0 0 2.78 16.921978 1.1 8.48 9 19.14 9.79 7.45 4.44 0.15 0 0 0 2.21 61.761979 0 1.49 0.49 10.99 11.71 3.25 2.39 0.92 0 0 0 0.11 31.351980 4.98 7.08 10.75 8.82 14.61 1.79 3.06 0.36 0.27 0.04 0 0 51.761981 0.57 0.62 11.23 10.78 3.92 4.62 0.36 0.62 0 0.07 0 0.46 33.25

Table 3. Precipitation at Healdsburg, Sonoma County, California, water years 1932–2004—Continued.[Precipitation in inches. Data from National Oceanic & Atmospheric Administration website http://www1.ncdc.noaa.gov/pub/orders/110904743047dat.txt, Dec 19, 2005. *, missing values taken from reported values for alternate station: Russian River Near Healdsburg (HEA). Station data may be retrieved from the California Department of Water Resources, division of Flood Management, 2006, California Data Exchange Center (CDEC)—access point to the Department of Water Resources Operational Hydrologic Data: http: cdec.water.ca.gov/ (accessed January 2, 2006); **, estimated valued based on median rainfall for August for period of record]

Introduction 11
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Water year total

1982 4.66 13.34 13.06 9.03 6.51 9.41 7.2 0 0.04 0 0 0.87 64.121983 5.05 9.47 8.58 15.7 14.84 20.34 6.31 0.86 0 0 1.52 0.59 83.261984 1.15 17.57 17.37 0.86 3.07 3.97 1.58 0.2 0.22 0 0.2 0.06 46.251985 2.37 15.44 2.43 1.35 3.4 7.31 0.28 0 0 0.05 0 1.37 34.001986 1.65 4.92 4.98 9.89 21.95 9.24 0.98 0.46 0 0 0 1.95 56.021987 0.64 0.15 2.95 6.25 6.47 8.53 0.2 0.1 0 0 0 0 25.291988 2.65 4.92 11.54 9.16 0.65 0.07 2.58 0.75 0.25 0 0 0 32.571989 0.41 5.92 4.53 1.5 1.21 12.01 1.75 0.19 0.45 0 0 2.98 30.951990 4.47 1.97 0 7.08 4 1.81 0.21 6.44 0 0 0 0.2 26.181991 0.77 0.38 1.33 1.1 5.26 18.35 0.47 0.25 0.63 0 0.02 0 28.561992 0.82 2.03 4.43 2.83 12.86 5.89 1.84 0 0.8 0 0 0 31.501993 3.64 0.43 12.25 15.23 9.43 3.29 2.58 2.31 0.97 0 0 0 50.131994 0.97 3.42 6.62 4.39 7.58 0.68 2.43 0.98 0 0 0 0 27.071995 0.98 9.54 5.36 29.9 0.36 20.01 3.31 1.54 0.38 0 0 0 71.381996 0.03 0.4 12.63 9.97 14.14 3.23 3.34 3.12 0 0 0 0.02 46.881997 2.29 4.68 17.21 14.43 0.43 2.46 1.01 0.8 0.59 0 1.05 0.4 45.351998 1.26 11.59 4.09 15.38 25.41 4.61 3.21 7.52 0.03 0 0 0.09 73.191999 1.37 8.88 1.62 5.06* 12.88 6.62 2.31 0.04 0.06 0 0 0.07 33.852000 1.19 6.98 0.99 9.61 14.58 3.15 3.09 1.83 0.26 0 0** 0.13 41.812001 3.44 1.25 1.12 7.97 9.77 2.94 1.4 0 0.04 0 0 0.21 28.142002 3.03 10.44 12.83 3.08 1.8 3.46 0.51 1.58 0 0 0 0 36.732003 0 5.16 25.21 6.5 2.8 4.84 6.55 1.19 0 0.04 0 0.01 52.302004 0* 4.06 18.81 5.75 12.82 1.79 1.55 0.08 0 0 0 0.05 44.91

Max. 10.83 21.20 25.21 29.90 25.41 20.34 12.93 7.52 2.17 1.71 3.17 4.52 83.26Min. 0.00 0.00 0.00 0.41 0.10 0.07 0.04 0.00 0.00 0.00 0.00 0.00 16.92Mean 2.18 5.40 7.98 8.89 7.52 5.44 2.62 0.99 0.28 0.04 0.14 0.39 41.87

Table 3. Precipitation at Healdsburg, Sonoma County, California, water years 1932–2004—Continued.[Precipitation in inches. Data from National Oceanic & Atmospheric Administration website http://www1.ncdc.noaa.gov/pub/orders/110904743047dat.txt, Dec 19, 2005. *, missing values taken from reported values for alternate station: Russian River Near Healdsburg (HEA). Station data may be retrieved from the California Department of Water Resources, division of Flood Management, 2006, California Data Exchange Center (CDEC)—access point to the Department of Water Resources Operational Hydrologic Data: http: cdec.water.ca.gov/ (accessed January 2, 2006); **, estimated valued based on median rainfall for August for period of record]

12 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
The average precipitation for the study area was computed for water years 1952–2004 using the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) of 

Daly and others (1994) and monthly precipitation data from 

the Oregon State University Spatial Climate Analysis Service (accessed January 13, 2006). PRISM is designed to map 

climate in complex environmental regimes, including high 

mountainous terrain and rain shadows (Daly and others, 1994). 

PRISM uses point measurements, digital elevation models, 

and other spatial data to generate gridded estimates of monthly 

and yearly precipitation. PRISM fits separate precipitation/altitude relations to neighboring stations with the same 

topographic aspect to generate interpolated values. This is a 

departure from simply applying a single altitude-dependent 

precipitation measurement to similar altitudes within the basin. 

Thus, PRISM is automated to adjust its frame of reference 

to accommodate local and regional climatic differences, rain 

shadows and coastal effects to create a pattern of precipitation 

(Daly and others, 1994). Average precipitation for the study 

area for water years 1952–2004 is 44 in.

Previous Investigations and Data Bases

Weaver (1949) carried out one of the earliest comprehensive geologic investigations that included the study area. 

His work defined the basic geology of the area in terms of 

stratigraphy and structure. A more detailed description of the 

geology of the southern part of the study area is given by Fox 

and others (1985). 

The geographic area of the current study was included in 

a comprehensive hydrogeologic investigation of the Russian 

River Valley by the U.S. Geological Survey (Cardwell, 1965). 

Cardwell’s data and interpretation have provided a foundation for later hydrologic studies. The ground-water resources 

of Sonoma County, including Alexander Valley, are described 

in a report by the California Department of Water Resources 

(1975). In the early 1980s, the California Department of Water 

Resources carried out a more detailed study focused solely on 

Alexander Valley and the Healdsburg area (California Department of Water Resources, 1983). The CADWR study estimated storage capacities for the area of the valley underlain by 

alluvial units, showed changes in ground-water levels between 

the 1960s and 1980, and described the quality of ground water.

Figure 4. Annual precipitation, and cumulative departure from the mean of precipitation, at Healdsburg, Sonoma County, 

California, 1932–2004.

Introduction 13

1932 1937 1942 1947 1952 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002

WATER YEAR (OCT. 1 TO SEPT. 30)

PRECIPITATION, IN INCHES

CUM

MULATIVE DEPARTURE, IN PERCENT

Mean = 41.87

-200

-150

-100

-50

0

50

100

0

10

20

30

40

50

60

70

80

90

Annual

precipitation

Cumulative

departure from

the mean
The SCWA developed a geographic information system 

(GIS) for Alexander Valley. The USGS has built on this database. The current working database includes: geology; soils; 

surface hydrology; digital elevation information describing 

slope, aspect, and altitudes; climate data; water-well location 

and construction data; surface-water gaging station information; public water supply service areas; septic, wastewater 

treatment, and reclaimed-water delivery systems; landfills; 

historical land use; roads; pipelines; a census population map; 

public land survey system delineations; and land ownership 

parcel information. The GIS was used to manage spatial data, 

to compute supporting data for this study, and to characterize 

the study area in terms of land-use water-demand categories, 

ground- and surface-water quality, ground-water levels, topography, altitudes, geology, and the distribution of precipitation 

and runoff.

Acknowledgments

The authors acknowledge the assistance of the staffs 

of the Sonoma County Water Agency, the Central District 

of the California Department of Water Resources, the California Department of Conservation, the Farmland Mapping 

and Monitoring Program, and the Sonoma Ecology Center. 

Water-quality sampling, conducted by the USGS as part of 

the GAMA program done in cooperation with the SWRCB, 

provided essential data to this study. Our gratitude is extended 

to David Wagner, California Geological Survey, and Robert 

McLaughlin, USGS, for their helpful discussions on the local 

geology. Special thanks are extended to the private property 

owners for allowing access to wells to collect water samples.

Physiography and Geologic Setting

The Alexander Valley study area is located in the North 

Coast Ranges geomorphic province of California. This province is characterized by a strong northwest-trending topography (Page, 1966). The mountain ranges are underlain by thick, 

highly deformed Mesozoic sedimentary strata that in places 

are covered by younger volcanic and sedimentary rocks. The 

mountains commonly have a hummocky, irregular topography 

produced in part by deep-seated landslides and shallow debrisand earth-flows (McLaughlin and others, 2005). The core of 

the North Coast Ranges consists of three major pre-Tertiary 

rock groups: the Franciscan Complex, the Coast Range Ophiolite, and the Great Valley Sequence (Blake and others, 2000) 

(fig. 5). In the eastern and northern parts of the Alexander 

Valley watershed, exposed basement rocks are predominantly 

Franciscan Complex but include a few minor outcrops of 

Coast Range Ophiolite. The Great Valley Sequence crops out 

in the hills along the western side of the watershed (Blake and 

others, 2002). All three pre-Tertiary rock groups, which overlap in age, were tectonically transported from a marine basin 

in the Pacific Ocean and accreted to the continental margin 

of California during Cretaceous to early Tertiary time (Blake 

and others, 2000). During and after accretion the rocks were 

folded and faulted into mountain ranges and intervening valleys. Within the study area, several northwest trending faults 

have been mapped in the Mayacmas Mountains and in the 

hills along the southwestern part of the area (fig. 5). The faults 

in the Mayacmas Mountains are part of the Maacama Fault 

Zone and the faults along the western side of the study area are 

part of the Rodgers Creek–Healdsburg Fault zone (Blake and 

others, 2002). These faults are related regionally to the San 

Andreas Fault system. 

Within the study area, the mountains are of moderate 

relief, sloping gently toward the valley from mountain crests; 

altitudes are mostly between 400 and 1,000 feet (ft). The 

mountainsides commonly exhibit a subdued topography of 

rolling grass- and oak-covered slopes and swales. Parts of 

the Franciscan Complex have eroded to form resistant blocks 

ranging from a few feet to miles in the long dimension embedded in a soft matrix that forms intervening slopes of moderate 

relief (McLaughlin and others, 2005).

The northwest-trending elongate depression of Alexander 

Valley extends roughly 20 mi from near Healdsburg to the 

county line north of Cloverdale (fig. 2). The valley floor has 

a maximum width of about 4 mi and averages about 1.5 mi 

wide. The valley can be subdivided into two parts on the basis 

of topography. The northern part of the valley, which includes 

Cloverdale, extends about 6 mi southeastward from the county 

line to about 1 mi southeast of Asti, and is sometimes referred 

to as Cloverdale Valley. The flood plain is less than 2 mi wide 

and bordered by low terraces near Cloverdale. The valley 

narrows to less than 0.5 mi near Asti. The southern part of the 

valley extends for about 14 mi southeastward from the narrows 

near Asti. Near the southern end, the valley floor widens to 

about 4 mi. The Russian River leaves the southern end of the 

valley through a narrow and sinuous canyon. The course of the 

Russian River is probably controlled, in part, by the northwest 

trending Maacama Fault Zone. Over the full length of the valley, altitudes along the Russian River drop from 400 ft at the 

north end to about 100 ft at the south end.

14 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Figure 5. Geologic map of the Alexander Valley watershed, Sonoma County, California.

Physiography and Geologic Setting 15

R i v e r

Lake

Sonoma

R

u ss i a n

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

M

a

y a

c

m

a

s

M

o

u

n

t

a i

n

s

Maacama Fault Zone

Healdsburg Fault Zone

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

C

B

A

C'

B'

A'

4E1

13H1

7C1

7J1

8N1

17L1

20H1

18B1

17D1

17C1

34F1

26L1

26H1

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402 Geology modified from Blake and others, 2002.

Qal

Qal

Qal

Qal

Qls Qls Qls

Qls

Qls

Qt

Qt

Tsvu

Tsvu

Tsvu

QTge

QTge

QTge

QTget

QTget

TKJf

TKJf

TKJf

TKJf

TKJf

KJgv

KJgv

KJgv

D r y C r e e k

Alexander

Valley
Geology

The stratigraphy of the study area described here is 

based on the recent compilation of the regional geology by 

Blake and others (2002). The geologic units shown for the 

study area conform to the most recent stratigraphic nomenclature. The geology of Blake and others (2002) is similar to 

that shown in Cardwell (1965) and California Department of 

Water Resources (1983). The main differences are that the 

recent mapping subdivides the Franciscan Complex into a 

greater number of lithologic units, the Coast Range Ophiolite 

is delineated, and the Glen Ellen Formation is subdivided to 

show the outcrops of the tuffaceous member. The entire watershed is underlain by basement rocks comprised of Franciscan 

Complex, Coast Range Ophiolite, and Great Valley Sequence, 

which are overlain by younger volcanic and sedimentary rocks 

and unconsolidated sediments (fig. 5). 

Basement Rocks 

The Franciscan Complex, as the name implies, includes 

rocks of several different lithologies; they include sandstone, 

graywacke, shale, mélange, conglomerate, chert, greenstone, 

and serpentinite (Bailey and others, 1964). These rocks, originally deposited in marine basins during Jurassic to Cretaceous 

time, have become highly indurated through the processes of 

compaction and secondary mineralization (Blake and Jones, 

1981). Most of the rocks are weakly to strongly metamorphosed, having been deeply buried and subjected to elevated 

temperatures during a period of millions of years. 

Rocks of the Franciscan Complex are exposed over much 

of the northern and eastern parts of the watershed and probably underlie much of the valley floor (fig. 5). The thickness 

is unknown but undoubtedly is a few tens of thousands of feet 

(Blake and others, 2000). Porosity and permeability are very 

low in Franciscan rocks because most of the original pore 

spaces are filled by minerals that cement the individual grains 

together. Most of the modern permeability resulted from 

fractures that developed in response to the deformation of the 

various rock packages as they were transported from the sea 

floor to the continent. Because of the low permeability and 

specific storage capacity, Franciscan rocks commonly are considered to be non-water bearing and to form the boundaries of 

ground-water basins throughout the Coast Ranges (California 

Department of Water Resources, 1958). 

Exposures of Coast Range Ophiolite in the Mayacmas 

Mountains have been mapped as small outcrops within larger 

masses of Franciscan Complex (Blake and others, 2002). The 

Ophiolite consists of serpentinized peridotite, gabbro, and 

basalt that has been faulted and tectonically interleaved with 

the Franciscan Complex (McLaughlin and others, 2005).

The Great Valley Sequence is exposed in the hills along 

the western side of the study area and probably extends 

beneath parts of the adjacent valley floor. Great Valley 

Sequence rocks are mostly sandstone, shale, and conglomerate units. A distinctive unit, informally named the Dry Creek 

Conglomerate, was mapped by Blake and others (2002) along 

a 10-mi-long outcrop area that extends northwestward from 

near Lytton. This unit consists of well-rounded cobbles and 

boulders, mostly derived from the Franciscan Complex, in a 

sand matrix. The total thickness of the Dry Creek Conglomerate was estimated to be about 5,000 ft (Gealey, 1951). Most of 

the Great Valley Sequence rocks are typically well-cemented 

and indurated. Wells drilled in these rocks generally yield little 

or no water (Kunkel and Upson, 1960; Page, 1986).

Holocene

to

Pleistocene

Early Pleistocene

to

Pliocene

Early Creataecous

to

Late Jurassic

Late Eocene

to

Jurassic

Quaternary alluvial units—Stream

channel deposits, stream terrace

deposits, alluvial fan deposits,

and flood plain deposits

Sonoma Volcanics—Undifferentiated

Unconformity

Tsvu

Glen Ellen Formation—Fluvial

deposits of gravels, sand, and clay

Glen Ellen Formation—Tuffaceous

member

QTge

QTget

Qal

Q Quaternary landslide deposits ls

Qt Alluvial terrace deposits

Pliocene

to

Miocene

EXPLANATION

Geologic unit Age

Franciscan Complex—

Undifferentiated

TKJf

Great Valley Sequence—

Undifferentiated

KJgv

Fault—Dashed where approximately located; small

dashes where inferred; dotted where concealed;

queried where location is uncertain; magenta

denotes Quaternary active fault

Line of geologic section—Shown in figure 6

B

B'

Figure 5.—Continued.

16 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Basin Fill

The basin is filled with younger rocks and sediments 

deposited unconformably upon basement rocks. The basin fill 

material includes the Sonoma Volcanics, the Glen Ellen Formation, and Quaternary alluvial units (fig. 6A–C). Landslide 

deposits have been mapped in the hills adjacent to the valley 

floor (fig. 3).

Sonoma Volcanics 

The Sonoma Volcanics are of Miocene to Pliocene age 

and are widely distributed throughout Napa and Sonoma 

Counties (Weaver, 1949). The Sonoma Volcanics are exposed 

in a few small outcrops in the southern part of the study area 

where they lie unconformably on rocks of the Franciscan 

Complex or of the Great Valley Sequence (fig. 5). The Sonoma 

Volcanics were first described by Osmont (1905). The geologic unit is a thick, highly variable sequence of continental 

volcanic and volcaniclastic rocks including basalt, andesite, 

and rhyolite lavas interbedded with tuffs, lahar deposits, 

avalanche deposits, mudflow units, hyaloclastites, reworked 

tuffs, sedimentary deposits derived from volcanic rocks, and 

lacustrine deposits. 

Although exposures of the Sonoma Volcanics are quite 

limited in the study area, a great deal is known about its 

lithologic characteristics from observations made in nearby 

locations. The Sonoma Volcanics were produced by a complex 

eruptive history of the many vents in the study area; the vents, 

which varied in chemical composition, produced lava flows, 

dikes, plugs, breccias, pumice beds, welded tuff layers, and 

debris flows (McLaughlin and others, 2005). Many individual 

units show lenticular form in cross section. Most lava flows 

are from a few feet to a few tens of feet thick. In places these 

rocks are strongly folded or broken by faults. Kunkel and 

Upson (1960) divided the unit into three members: a basal 

member of mostly basalt and andesite lavas interbedded with 

tuff units; a diatomite member; and an upper member consisting mostly of rhyolite lavas and tuffs, often welded. The 

Sonoma Volcanics are overlain by the Glen Ellen Formation; 

however, in places the upper part of the Sonoma Volcanics 

may interfinger with the Glen Ellen Formation (Cardwell, 

1965; Blake and others, 2002). In locations around the valley 

margin, where the Glen Ellen Formation has eroded away, the 

Sonoma Volcanics are overlain unconformably by Quaternary 

alluvial units (fig. 5). 

Glen Ellen Formation 

The Glen Ellen Formation was first described by Weaver 

(1949) for continental deposits that crop out near Glen Ellen in 

Sonoma Valley. The assignment of sedimentary strata in Alexander Valley to the Glen Ellen Formation is based on chronostratigraphic relations to the Sonoma Volcanics (McLaughlin and others, 2005). The sedimentary rocks making up the 

Glen Ellen Formation were probably originally deposited as 

alluvial fans and piedmont. The formation is widely exposed 

in the southern part of the study area and is estimated to be 

about 1,500 ft thick in outcrops along the east side of the valley (Cardwell, 1965). The formation underlies much of the 

valley floor south of Geyserville and may underlie the valley 

floor in places between Geyserville and Asti. The formation 

is largely of fluvial origin and consists of clay-rich stratified 

deposits of poorly sorted sand, silt, and gravel interbedded 

with minor beds of matrix-supported conglomerate and silicic 

tuffs (Cardwell, 1965). Beds grade from coarse- to finegrained laterally and vertically, commonly over distances of a 

few tens to a few hundreds of feet. Bedding is thick to massive 

and often lenticular in form. Most of the clasts and probably 

much of the matrix were derived from the Sonoma Volcanics. Cobbles in the conglomerates are mostly subangular to 

rounded and, for the most part, range between 3 and 6 in. in 

diameter. The cobbles are mostly of andesitic or basaltic composition and include obsidian clasts that are characteristic of 

this formation (Cardwell, 1965). In some areas, the Glen Ellen 

Formation consists primarily of tuffaceous material (QTget) 

reworked by streams. This differentiated material occurs in the 

southern part of the study area (fig. 5). 

Stratigraphic relations indicate that the Glen Ellen 

Formation is of late Pliocene to early Pleistocene age (Blake 

and others, 2002). The formation overlies tuff in the Sonoma 

Volcanics dated at 3.1 million years before present (ma) ; the 

upper part of the formation contains tephra dated at 1.2 to 0.8 

ma (McLaughlin and others, 2005). Within parts of the study 

area, the Glen Ellen Formation is in fault contact with, or rests 

unconformably upon, rocks of the Franciscan Complex but in 

other parts of the area laps onto the Sonoma Volcanics (fig. 5). 

Along the valley floor, the Glen Ellen Formation is overlain by 

alluvial units of Quaternary age. 

Geology 17
Figure 6. Geologic cross sections of the Alexander Valley watershed, Sonoma County, California. 

See figure 5 for location of sections.

A

NW

A' SE

400300200100

NAVD

88

revi RnaissuR

1 C7- W01/ N11

1J7- W01/ N11

1 N8- W01/ N11

1L71- W01/ N11

1 H02- W01/ N11

Land surface

FEET

Holocene

to

Pleistocene

Late Eocene

to

Jurassic

Quaternary alluvial units—Stream

channel deposits, stream terracedeposits, alluvial fan deposits,and flood plain deposits

Unconformity

Trace of section shown on figure 5

VERTICAL EXAGGERATION X5

Qal

Qal

Qal

E

X

P

L

A

N

ATIO

N

Geologic unit Age

Franciscan Complex—

Undifferentiated T

KJf

T

KJf

T

KJf

Contact—

Depositional or intrusive contact or large

mélange block edge; dashed where approximatelylocated

Well and identifier—

Used to construct cross section

1J7- W01/ N11

0 1 Mile0 1 Kilometer

A

18 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
?

? ?

B

West

B' East

200

300

400

100

0 1 Mile

0 1 Kilometer

-100

-200

NAVD

88

Russian River

10N/10W-13H1

10N/9W-18B1

10N/9W-17D1

10N/9W-17C1

FEET

Land surface

348

Holocene

to

Pleistocene

Late Eocene

to

Jurassic

Quaternary alluvial units—Stream

channel deposits, stream terrace

deposits, alluvial fan deposits,

and flood plain deposits

Unconformity

Qal

Qal

Qal

EXPLANATION

Geologic unit Age

Franciscan Complex—

Undifferentiated

TKJf

TKJf

TKJf

Well and identifier—Used to construct cross section.

Number, if shown, is depth of well

10N/9W-18B1

Contact—Depositional or intrusive contact or large

mélange block edge; dashed where approximately

located; queried where location is uncertain

?

Trace of section shown on figure 5

VERTICAL EXAGGERATION X5

B

Figure 6.—Continued.

Geology 19
Figure 6.—Continued.

20 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California

C

SW

C'

NE

200300400100

-100-200

NAVD

88

revi RnaissuR

1E4- W9/ N9

1F43- W9/ N01

1L62- W9/ N01

1 H62- W9/ N01

821 ya whgi H

FEET

Land surface

? ? ? ?

?

?

Holocene

to

Pleistocene

Early Pleistocene

to

Pliocene

Early Creataecous

to

Late Jurassic

Quaternary alluvial units—Stream

channel deposits, stream terracedeposits, alluvial fan deposits,and flood plain deposits

Unconformity

Trace of section shown on figure 5

Glen Ellen Formation—Fluvial

deposits of gravels, sand, and clay Q

Tge

Q

Tge

Q

Tge

Qal

Qal Qal Qal

E

X

P

L

A

N

ATIO

N

Geologic unit Age

Contact—

Depositional or intrusive contact or large

mélange block edge; dashed where approximatelylocated; queried where location is uncertain

Well and identifier—

Used to construct cross section

Great Valley Sequence—

Undifferentiated KJgv

Sonoma Volcanics—

Undifferentiated Tsvu

Tsvu

Pliocene

to

Miocene

1E4- W9/ N9

?

KJgv

VERTICAL EXAGGERATION X5

0 1 Mile0 1 Kilometer

C
Quaternary Alluvial Units 

The alluvial sediments of Quaternary age have been 

mapped by various investigators (Cardwell, 1965) as river 

channel deposits, alluvium, and terrace deposits, on the basis 

of the degree of consolidation, cementation, clast size and 

sorting, and geomorphic expression. In this report the alluvial 

units are not differentiated. The alluvial units cover about 24 

mi2 of the watershed and form a band covering the main part 

of the valley floor from north of Cloverdale to south of Jimtown (fig. 5) The alluvial units consist of poorly consolidated 

to unconsolidated clastic materials ranging from clay size 

to boulders. The deposits, depending on mode of origin, are 

wedge-shaped, lens-shaped, or channel-shaped. Sorting within 

a particular unit depends on the distance from source materials, the type of source materials, and the hydraulic energy of 

the transporting medium. Data from drillers’ logs indicate that 

the alluvial materials nearest the valley axis generally contain 

the greatest proportions of course clasts and generally are 

better sorted than deposits closer to the mountain flanks. The 

logs also show that the greatest thicknesses of coarse-grained 

materials are beneath the central axis of the valley and in the 

southern part of the valley where thicknesses are as much as 

80 ft. Near the present-day course of the Russian River and 

near some of the larger tributaries, stream channel deposits 

consisting of boulders, cobbles, gravel, and sand form thin 

sinuous bodies within more poorly sorted, finer grained sediments deposited on flood plains. The channel deposits tend to 

be thin and discontinuous owing to shifting channel locations 

over time. 

Quaternary Landslides

Landslides have been mapped in the hills adjacent to the 

eastside of the valley (Blake and others, 2002). The landslides 

are composed mostly of material derived from the Franciscan 

Complex. The material consists of poorly sorted boulders and 

smaller clasts embedded in a matrix of finer grained particles. 

Some of the vegetation that had been growing in the slide 

area before sliding began was incorporated into the slide mass 

as it moved down slope. Most of the landslides are probably 

relatively thin, on the order of 100 ft or less. The slide areas 

often have a hummocky topography and may include areas of 

poor drainage.

Geologic Structures

Alexander Valley is a fault-controlled structure that lies 

between the Maacama Fault Zone and the Healdsburg Fault 

Zone (Blake and others, 2002), two major northwest-striking 

faults in the northern Coast Ranges (fig. 5). Both faults have 

had large components of right-lateral strike-slip movement 

but also have had compressional slip normal to the strike. 

The fault geometry and strike-slip movement results in the 

formation of depressions along zones of oblique pull-apart 

extension between the faults (McLaughlin and others, 2005). 

Ukiah Valley and Little Lake Valley to the north of the study 

area are recognized as sediment-filled pull-apart basins 

(McLaughlin and Nilsen, 1982); Alexander Valley likely has a 

similar origin. The later compressional component of slip on 

the faults has caused folding in the Sonoma Volcanics and the 

Glen Ellen Formation. The folding is especially evident in the 

southern part of the study area where beds of the tuffaceous 

member of the Glen Ellen Formation dip away from outcrops 

of the Franciscan Complex. Dips are generally 30 degrees 

or less but, in places are more than 50 degrees and appear to 

define an anticlinal structure.

Hydrology 

Surface-Water Hydrology

The headwaters of the Russian River are in Mendocino 

County where the east fork of the Russian River has been 

dammed to create Lake Mendocino, a reservoir for public 

water supply and recreation (fig. 1). The Russian River enters 

the study area through a bedrock narrow near the MendocinoSonoma County line and continues its course of about 36 mi 

to where it exits the study area on the southwestern side. The 

river surface drops with a fairly constant gradient of about 

9 feet per mile (ft/mi) from the county line to Healdsburg.

Since 1959, discharge in the Russian River has been 

strongly affected by the controlled releases of water from 

Coyote Valley Dam, which created Lake Mendocino 

(fig. 7), located north of the study area in Mendocino County. 

The reservoir is operated by the U.S. Army Corps of Engineers to provide flood control and water-supply storage of 

118,000 acre-ft. The Sonoma County Water Agency and the 

Mendocino County Russian River Flood Control and Water 

Conservation Improvement District share appropriative water 

rights to store and use water in the reservoir. The Sonoma 

County Water Agency has sole rights to determine the releases 

from the water-supply pool. 

Discharge in the Russian River is gaged by the USGS at 

a point about 5.5 mi northwest of Cloverdale (USGS Station 

11463000), upstream of the study area boundary, and at a 

second location about 2 mi east of Healdsburg (USGS Station 

11464000), near the southern end of the study area (fig. 7). 

The approximate drainage area between the two gages is 290 

mi2, which includes about 163 mi2 outside of the study area 

(fig. 7). The maximum daily discharge measured at the gage 

near Healdsburg (period of record: 1939 to 2004) was 69,300 

cubic feet per second (ft3/s) on January 9, 1995, and the 

minimum was 12 ft3/s on June 14, 1988 (Webster and others, 

2005). 

Hydrology 21
Lake

Mendocino

Lake

Sonoma

Clear

Lake

R i v e r

R

u s s i a

n

Mendocino

Co

Sonoma

Co Napa

Co

Lake Co

N

o

r

t

h

C

o

a

s

t

R

a

n

g

e

s

12

116

1

128

128

175

29

20

101

101

Ukiah

Cloverdale

Geyserville

Healdsburg

Santa Rosa

11463000

11464000

Alexander

Valley

M e

n d

o

c i

n

o

R

a

n

g

e

M a y a

c

m a

s

M

o

u

n

t

a

i

n

s

0 5 10 20 Miles

0 5 10 20 Kilometers

EXPLANATION

USGS stream gage and

identifier 11464000

Estimated drainage area

(503 mi2), 11463000

Estimated drainage area

(793 mi2), 11464000

Base from U.S. Geological Survey digital data, 1:24,000, 2003. State Plane Projection, Fipzone 402.

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

Figure 7. Drainage areas for USGS streamflow-gaging stations 11463000 and 11464000 in Alexander Valley, 

Sonoma County, California.

22 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
In most water years, discharge to the Russian River in 

response to the normal annual cycle of precipitation does 

not increase markedly until November or December; it then 

decreases rapidly in April or May (figs. 8A and 8B). A period 

of 10 years is shown in figures 8A and 8B, rather than the full 

period of record to allow the annual cycles of discharge to be 

seen more clearly. Discharge from the Russian River remains 

relatively constant through late summer and early autumn 

and does not increase significantly until about 10 to 12 in. of 

precipitation has fallen at Healdsburg. This amount of precipitation represents the soil-moisture deficit that develops from 

evapotranspiration during the dry season, which runs from 

late spring to late autumn in most years. Streamflow does not 

increase significantly until the soil moisture increases to near 

field capacity. Similar soil-moisture deficits have been estimated for Sonoma Valley and parts of Napa Valley (Johnson, 

1977; Farrar and others, 2006).

The difference in discharge between the gage near Cloverdale (11463000) and the gage near Healdsburg (11464000) 

(figs. 8C–E) offers insights into ground-water/surface-water 

interaction. The difference in discharge is dependent on the 

amount of additional water entering the Russian River from 

tributaries between the two gages, the amount of water used 

by evapotranspiration in the riparian zone, diversions, and 

ground-water recharge. Graphs showing the difference in discharge between the two gages are shown for 3 selected water 

years: 1977, 1995, and 2000. The 3 years represent a drought 

year, a wet year, and a near-normal year, respectively, in terms 

of annual total precipitation. As shown in figure 4, precipitation varies greatly from year to year; there is virtually no year 

that has exactly the mean preciptation. These comparisons of 

daily discharge values do not account for travel times between 

the gages. This is not considered significant for the analysis of 

seasonal trends. 

Discharge at the downstream gage (near Healdsburg) generally first decreases in June or July to below that discharged 

at the upstream gage (near Cloverdale). A decrease in discharge tends to occur later following very wet winter seasons 

and earlier in years of below average precipitation. Following winters having above average precipitation (for example 

1995), tributaries contribute water to the Russian River later 

into the dry season than during years with below average 

precipitation. Also, soil-moisture remains higher later into the 

dry season and therefore less irrigation for crops is required, 

which reduces the amount of river water diverted. These factors account for the greater discharge at the downstream gage 

than at the upstream gage. As the summer progresses, greater 

amounts of water are diverted from the Russian River, pumping from wells near the river increases, and riparian vegetation 

consumes greater amounts of underflow and shallow ground 

water through evaptranspriation. This causes a decrease in 

discharge between the two gages. In dry years (for example, 

1977), soil moisture may not be completely replenished before 

the rains stop. Consequently, irrigation will begin earlier in the 

spring or summer, which will result in a depletion of discharge 

in the Russian River between the two gages earlier in the year.

Water year 2000 represents a near normal year in terms of 

precipitation; with 41.57 in. measured at Healdsburg compared 

with an average precipitation of 41.87 in. for 1932–2004. 

Discharge at the Healdsburg gage was greater than that at 

the Cloverdale gage between February and June 17, 2000, 

(except for 1 day) primarily because of inflow from tributaries 

downstream of the Cloverdale gage. After June 17, discharge 

decreased between Cloverdale and Healdsburg on most days; 

this pattern persisted until October 25, when discharge began 

to increase consistently between the two gages. The decrease 

in discharge is a measure of evapotranspiration along the riparian corridor, direct diversions from the river, indirect diversions from ground-water pumping near the river, and seepage 

from the river into the alluvial aquifer. The total difference in 

discharge between the two gages from June 17 to October 25, 

2000 was about 2,776 acre-ft. This represents the minimum 

amount of water consumed between the two gages; additional 

water may have entered the river from tributaries or from irrigation return. However, these quantities were not gaged. 

Geohydrology

Ground water in the Alexander Valley watershed is 

contained in all the geologic formations and alluvial deposits 

present (figs. 5 and 6). However, the water-bearing properties 

of the various geologic units vary considerably and largely 

determine how much water can be obtained from a well in 

different parts of the watershed. Most wells in the study area 

are drilled to depths of less than 200 ft. On the basis of data on 

350 wells provided by the CADWR, the median well depth is 

102 ft. The main sources of ground-water recharge in the study 

area are direct infiltration of local precipitation that falls on 

the mountains and valley floor and infiltration of surface water 

from the Russian River and its tributaries. Excess irrigation 

water, originally derived from streams or ground water, probably provides additional ground-water recharge. 

The primary sources of ground water in the study area 

are the Quaternary alluvial deposits, the Glen Ellen Formation, and the Sonoma Volcanics. All these geologic units have 

a wide distribution and zones of high porosity (greater than 20 

percent) and high permeability. 

Hydrology 23
WATER YEAR (OCT. 1 TO SEPT. 30)

DISCHARGE, IN CUBIC FEET PER SECOND

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

10

100

1,000

10,000

100,000

10

100

1,000

10,000

100,000

Russian River near Cloverdale

11463000

Russian River near Healdsburg

11464000

A

B

Figure 8. Discharge of Russian River, Sonoma County, California. A, Mean daily discharge for water years 1990–2000 near 

Cloverdale. B, Mean daily discharge for water years 1990–2000 near Healdsburg. C, Difference in discharge in the Russian 

River between Cloverdale and Healdsburg for water year 1977. D, Difference in discharge in the Russian River between 

Cloverdale and Healdsburg for water year 1995. E, Difference in discharge in the Russian River between Cloverdale and 

Healdsburg for water year 2000.

24 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Quaternary alluvial units, as discussed in this report, 

include alluvial fans, stream terraces, flood-plain deposits, and 

channel alluvium. All these deposits contain variable amounts 

of poorly consolidated, uncemented to weakly cemented 

sand, gravel, cobbles, and boulders, in a matrix of silt- and 

clay-sized material. The alluvial units have high porosity and, 

where they consist mostly of coarse-grained material, have 

high permeability. Where the units contain large fractions of 

silt and clay, permeability is greatly reduced. Cardwell (1965) 

estimated that the specific yield of the alluvial units averages 

about 20 percent in the depth range between 10 and 50 ft 

below land surface (bls). 

Most wells with a high yield are completed in alluvial 

units that have a saturated thickness that exceeds 50 ft. The 

high–yielding wells generally are located near the Russian 

River, which flows along the axis of the valley. Wells that are 

completed in alluvial units range in yield from a few gallons 

per minute (gal/min) to more than 1,000 gal/min. Well yields 

generally increase as saturated thickness, grain size, and sorting increase. Yields of 1,000 gal/min tend to occur in wells 

that tap alluvial units that are predominantly composed of 

cobbles, gravel, and sand (Cardwell, 1965). 

The Glen Ellen Formation mostly consists of consolidated, weakly- to moderately-cemented silt, and clay with 

minor sand beds. The large amount of clay-sized material 

in this formation, although high in porosity, greatly limits 

permeability. The estimated specific yield of the Glen Ellen 

in Sonoma Valley (fig. 1) is 3 to 7 percent (California Department of Water Resources, 1982); a similar range is likely for 

Alexander Valley. Well yields from the Glen Ellen generally 

are lower than those from the alluvial units. However, some 

wells that tap a few hundred ft of the formation intersect 

enough thin beds of coarse-grained materials to provide up to 

400 gal/min (Cardwell, 1965). The Glen Ellen Formation is an 

important source of water to wells in the southern part of the 

study area because its thickness exceeds 400 ft and the overlying alluvial units are thin. 

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

DIFFERENCE IN DISCHARGE, IN CUBIC FEET PER SECOND

WATER YEAR 1977

-1,000

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

700

800

900

1,000

C

Figure 8.—Continued.

Hydrology 25
The Sonoma Volcanics have the greatest variability in 

lithology, and also in water-bearing properties. Within the 

Sonoma Volcanics, fractured lavas, interflow zones, scoria, 

and unwelded tuffs provide the best aquifers. Exposures of 

the Sonoma Volcanics in the study area are limited to andesite 

and basalt lavas; however, other lithologies may be present 

in the subsurface. The primary permeability of the lavas is 

insignificant, except where they are strongly jointed owing 

to the cooling fractures. The secondary permeability of the 

lavas is mostly due to fracturing related to folding or faulting, 

and this can result in rocks with high permeability. Separations between cooling units are commonly seen in outcrops 

in the study area, and although thin (less than 1 ft), they can 

be laterally extensive and provide significant transmissivity to 

the entire lava flow. The interflow zones between lavas often 

consist of rubbly material and scoria that can have very high 

porosity and permeability. Unwelded tuffs are composed of 

ash, lapilli, and larger sized pumice fragments and other lithic 

clasts. Such units have hydraulic characteristics similar to 

those of alluvial materials with high porosity and high permeability. The debris-flow deposits and lahars are poorly sorted 

and contain large fractions of fine-grained materials which, 

although high in porosity, are low in permeability. An accurate distribution of lithologies within the Sonoma Volcanics at 

depth throughout the study area is not known, which precludes 

predicting well productivity. In Sonoma Valley, the combined 

lithologies of the Sonoma Volcanics have a variable specific 

yield ranging between 0 and 15 percent (California Department of Water Resources, 1982). A similar range probably 

applies to Alexander Valley. 

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

DIFFERENCE IN DISCHARGE, IN CUBIC FEET PER SECOND

WATER YEAR 1995

-1,000

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

700

800

900

1,000

D

Figure 8.—Continued.

26 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
The basement rocks, which include the Great Valley 

Sequence, the Coast Range Ophiolite, and the Franciscan 

Complex, generally are considered non-water-bearing because, 

compared with the overlying formations, these rocks yield 

much less water to wells. However, in many locations the 

basement rocks can provide 1 to 5 gal/min of water to wells, 

which may be enough for an individual domestic supply (California Department of Water Resources, 1958). The basement 

rocks consist of several different lithologies that have different 

hydraulic properties. Many wells drilled in the basement rocks 

result in dry holes. The most indurated lithologies have very 

low primary porosity and permeability, but where fractured 

can have significant secondary permeability. The mélange 

of the Franciscan Complex consists of a fine-grained matrix 

with embedded clasts and large rock bodies. The fine-grained 

matrix has high porosity but very low permeability. Wells 

completed in the mélange typically yield less than 1 gal/min 

to a few gal/min (California Department of Water Resources, 

1982). 

Within the study area, ground water occurs under both 

confined and unconfined conditions. Generally unconfined 

conditions prevail at shallow depths (less than 200 ft); however, where wells are drilled through thick sections of impermeable rocks (for example, clay or unfractured lavas), confined or semi-confined conditions can exist. Ground water in 

the alluvial units generally is unconfined because the alluvial 

units consist of primarily coarse-grained material and generally are less than 100 ft thick. Ground water can occur under 

confined conditions in the Glen Ellen, the Sonoma Volcanics, 

and the basement rocks because all these units contain some 

fine-grained materials and all extend to depths of a few hundred feet or more in places. 

The quantity of ground-water storage has been estimated 

during previous studies. Cardwell (1965) estimated that about 

65,000 acre-ft of ground water is stored in the alluvial units, 

which range between 10 and 50 ft in thickness beneath an 

area of about 10,500 acres of the valley floor. The California 

Department of Water Resources (1983) estimated that there 

is about 602,000 acre-ft of ground-water storage throughout 

the entire thickness of the basin-fill deposits. This estimate 

is based on ground-water levels in 1980. However, the total 

amount of ground water in storage in the watershed has little 

value in determining the amount of ground water that might 

be available or the rates at which it can be withdrawn on a 

sustained basis (Bredehoeft and others, 1982). The amount 

by which annual ground-water recharge can be increased or 

discharge decreased generally are more important factors in 

determining the long-term sustainable yield from a basin.

Figure 8.—Continued.

Hydrology 27

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

DIFFERENCE IN DISCHARGE, IN CUBIC FEET PER SECOND

WATER YEAR 2000

-1,000

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

700

800

900

1,000

E

June 17
Water Budget

The study area receives abundant precipitation in most 

years. The mean annual precipitation for water years 1952 

through 2004 is estimated to be about 298,000 acre-ft/yr based 

on PRISM (Daly and others, 1994; Oregon State University 

Spatial Climate Analysis Service, accessed January 13, 2006). 

Part of this amount is absorbed by soils in the study area; the 

amount absorbed varies from season to season and interannually depending on climatic variables and antecedent conditions 

in the watershed. The mean annual amount of precipitation 

absorbed by soils is the soil-moisture deficit replenishment, 

which is estimated to be about 75,000 acre-ft/yr (equivalent 

to 11 in. over the study area). This estimate was based on the 

quantity of precipitation received before stream discharge 

increased significantly. The soil-moisture deficit is caused 

by evapotranspiration during the dry months (generally 

May–September). Evapotranspiration includes the transfer of 

water from surface-water bodies, soils, and vegetation to the 

atmosphere. Total annual evapotranspiration is greater than the 

soil-moisture deficit because plants continue to transpire water 

and water evaporates from water surfaces even during the 

cooler months of October to April. The mean annual potential evapotranspiration (Eto

) at Healdsburg between 1986 and 

1994, calculated from hourly meteorological measurements, 

was 50.5 in. (California Department of Water Resources, 

accessed March 21, 2005). Actual evapotranspiration (Eta) is 

much less than Eto because most of the time soil moisture is 

below field capacity and many plants have periods of dormancy during part of the year, during which water consumption is greatly reduced. For this study, Eta was estimated by 

comparing the soil moisture deficit (SMD) with the calculated 

Eto for the months May through September. The ratio of SMD 

to Eto for those months is 0.33. Eta for the entire year was 

estimated to be 16.7 in. by multiplying annual Eto (50.5 in.) 

by 0.33. This estimate is similar to estimates of Eta reported 

by the California Department of Water Resources (1980) for 

various crops. The estimate of Eta for orchards was about 

19.7 inches per year (in/yr). Most of the study area is covered 

by native vegetation, which, with the exception of riparian 

vegetation, consumes less water than crops. So the mean Eta

for the study area is probably less than 19.7 in. Total annual 

Eta for the study area can be calculated assuming an areally 

constant Eta. For the 81,280-acre study area, with an Eta ranging between 16.7 and 19.7 in., total Et is calculated to range 

between 113,000 and 133,000 acre-feet per year (acre-ft/yr). 

Part of the precipitation falling within the study area 

finds its way to streams and ultimately leaves the watershed 

as runoff by way of the Russian River. The mean annual 

amount of runoff generated within the study area is about 

160,000 acre-ft/yr (equivalent to 23.6 in.); this estimate was 

made using records of discharge for 1952−2004 for the gages 

near Cloverdale and Healdsburg and using the size of drainage areas within the study area (127 mi2

) compared with the 

size of the drainage area of the Healdsburg gage (290 mi2). 

This estimate is consistent with the estimated mean annual 

unit-runoff of 21.4 in. for the Russian River drainage between 

the Cloverdale and Healdsburg gages (stations 11463000 and 

11464000) for 1931–63 based on data given by Rantz and 

Thompson (1967). When the sum of evapotranspiration (using 

a range of 113,000 to 133,000 acre-ft/yr) and runoff (160,000 

acre-ft/yr) is subtracted from the total amount of precipitation 

(298,000 are-ft/yr) received in the study area, the remainder 

is the potential amount of ground-water recharge (water that 

infiltrates to the water table), which is estimated to be about 5 

to 25,000 acre-ft/yr. There is considerable uncertainty associated with this estimate because it was computed as residual 

from other, much larger water-budget components that have 

considerable uncertainties. 

Ground water includes all subsurface water below the 

water table but does not include moisture held in soils. Ground 

water is discharged from the watershed directly by springs 

and seepage into streams. Baseflow in streams is sustained by 

ground-water discharge. Ground water is used by riparian vegetation that has roots extending below the water table. Plants 

growing outside the riparian zones can have roots that extend 

deep enough to extract ground water (Lewis and Burgy, 1964). 

Ground water can be evaporated directly to the atmosphere in 

locations where the water table is at, or very near, land surface. 

Ground water is also pumped from wells to provide supplies 

for irrigation, municipal, industrial, and domestic uses. 

Ground-Water Levels and Movement

Ground-water levels have been measured by California 

Department of Water Resources in a network of wells on the 

floor of Alexander Valley (fig. 9). Most of the network was 

developed between the mid-1960s and 1981. Measurements 

at some wells were discontinued because of difficult access, 

well-bore obstructions, or other reasons. Other wells were 

added either to replace wells removed from the network or to 

improve areal coverage of the initial network. However, the 

network is still sparse with only three wells in the northern 

part of the valley, two wells near the middle of the valley, and 

six wells in the southern part of the valley. Measurements 

generally were made at these wells in April and October, the 

beginning and ending of the dry season, respectively. 

Despite the effort to avoid making water-level measurements while wells were pumping or recovering from recent 

pumping, some measurements may have been made during 

non-static conditions. Measurements suspected of having been 

affected by recent or nearby pumping were excluded from the 

analysis of water-level conditions in this report. 

In addition to the water levels monitored as part of the 

DWR network, some earlier water-level measurements were 

made in a smaller number of wells (Cardwell, 1965).

28 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Figure 9. Locations of wells in the California Department of Water Resources ground-water-level monitoring 

network in Alexander Valley, Sonoma County, California. 

Hydrology 29

R i v e r

Lake

Sonoma

Warm

Springs

Dam

R

u ssi a n

D r y C r e e k

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

8P1

19F2 17P2

18B1

33D1 26L2

1K2

1D1 6L1

7Q1

20L1

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

Well less than 200 feet deep 18B1

Well greater than 200 feet deep 19F2

EXPLANATION

California Department of Water Resources

well and identifier—-

Alexander

Valley
Ground-water-level measurements do not necessarily 

represent the water table because hydraulic head can vary with 

depth in an aquifer. Therefore, the water levels in wells open 

to a large span of depth intervals represent composite heads 

for the respective depth intervals. The correct interpretation 

of ground-water-level data is, in part, dependent on complete 

well-construction information, including total depth, perforation intervals, seals, and gravel-pack depth. Complete construction information, however, was not available for several 

of the wells in the water-level monitoring network, which 

limited analysis and interpretation of the data.

The map of hydraulic head previously published by 

California Department of Water Resources (1983) is reproduced in this report (fig. 10A) to show the general distribution 

of heads beneath the valley floor. The map shows hydraulic 

gradients from which the approximate directions of groundwater movement can be determined and changes in hydraulic 

heads between autumn 1980 and more recent periods can be 

compared. The general direction of ground-water movement 

is from recharge areas in the mountains around the perimeter 

of the study area toward the valley axis and from the northwest end of the valley southeastward toward the narrows east 

of Healdsburg. The ground-water-level gradient has a strong 

component transverse to the valley axis in the area east of 

Lytton where a large number of wells have been drilled

(fig. 11). 

Ground-water-level altitudes for autumn 2002 are shown 

in figure 10B. Data from 2002 were chosen for comparison 

because water levels had been measured at about the same 

time of the year as levels measured in 1980, making comparisons of change simpler. The contour lines are based on only 

eight measurements and therefore are considered approximations of the true water-level altitude. The individual contour 

lines for the 2002 data were constructed using the 1980 

contour lines as a guide of their general configuration and 

adjusted in accordance with the change in water-level altitude 

between 1980 and 2002. In general, the changes in water 

levels between 1980 and 2002 were less than 10 ft. The largest differences were in the area from Geyserville to Jimtown 

where water levels declined by as much as 26 ft between 

autumn 1980 and autumn 2002. 

Long-Term Changes in Ground-Water Levels

Graphs showing long-term changes in ground-water 

levels were made using data for wells in the CADWR monitoring network (fig. 12A–D). The graphs show data for groups of 

wells, based primarily on geographic location, to allow comparison of water-level changes in various parts of the study 

area. Table 4 provides selected well-construction information 

for these monitoring wells and changes in ground-water levels. 

Water-level monitoring has been done at three wells near 

Cloverdale (fig. 12A); however, monitoring at one well tapping alluvium was discontinued in 1999. Data for 1966–2004 

are available for the other two wells One of the active wells 

(11N/10W-8P1) is 28 ft deep and completed in alluvium; 

water levels declined about 5 ft at this well between spring 

1967 and spring 2004. The other active monitoring well 

(11N/10W-19F2) is 334 ft deep and completed in the Franciscan Complex; the difference in water levels in this well was 

less than 1 ft between spring 1967 and spring 2004 

(fig. 12A, table 4). Between 1996 and 2004, seasonal waterlevel differences were mostly less than 1 ft, and smaller than 

earlier years. This smaller difference may be caused by a shift 

in the timing of measurements from March or April to May or 

June, and from October to November or December.

Two wells in the network are within about 1 mi of Geyserville (fig. 10B). One well (10N/9W-33D1) is 98 ft deep and 

completed in the Glen Ellen Formation, and the other well 

(10N/9W-18B1) is 178 ft deep and completed in the Sonoma 

Volcanics (table 4). Both wells show water-level declines of 

about 4 ft (comparing measurements made in spring of each 

year) over periods of 23 to 37 years (fig. 12B). For well 33D1, 

the annual low (autumn) water levels have shown slightly 

greater declines, probably caused by increased pumping 

locally. 

Four wells in the network are located near Jimtown 

(fig. 10B). Three of the wells (9N/9W-1D1, 9N/9W-1K2, and 

9N/8W-6L1) are completed in the Glen Ellen Formation and 

one well (10N/9W-26L2) is completed in alluvium. The periods of record for these wells range between 23 and 37 years. 

Over the period of record, all four wells have had water-level 

declines of 1 to 8 ft (fig. 12C, table 4). Water levels in well 

-1D1 have shown increased seasonal variation since about 

2000. The recent amplitude of water level variation (difference 

between spring and autumn water levels) at this well exceeds 

30 ft. This is probably caused by increased local pumping.

Two wells in the network (9N/8W-7Q1 and 9N/8W20L1) are in the southern area (fig. 10B). Both are drilled 

into the Glen Ellen Formation, however, well -7Q1 also taps 

alluvium (table 4). Well -7Q1 is 490 ft deep and had a 2-ft rise 

in water level between 1974 and 2004. Note that water levels 

at well -7Q1 declined significantly through the early 1980s 

(fig. 12D). This well has not been used for supply since some 

time between April and October 1985. The lack of pumping at 

this well is clearly reflected by the smaller annual water-level 

fluctuations that begin in 1985 (fig. 12D), which could explain 

the modest rise in water levels since 1985. Well -20L1 is 204 

ft deep and had a 41-ft decline between spring 1974 and spring 

2003; most of this change has occurred since 2000. This 

decline in water level probably is due to the pumping of larger 

quantities of ground water in recent years.

30 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
State

 well

No.

Area Well 

depth 

Depth of 

perforated 

interval 

Geologic

unit

Period of 

record1

Number

 of years2

Water-level change (ft)

Period of 

record

Fall 

1980– Fall 

2002

Spring 

1981– 

Spring 

2003

11N/10W-8P1 Cloverdale 28 8–28 Qal 1967–2004 37 –5 –4 –3

11N/10W-17P2 32 28–32 Qal 1967–1999 32 –5 — —

11N/10W-19F2 334 90–320 KJf 1967–2004 37 0 +6 0

10N/9W-18B1 Geyserville 178 — Tsv 1967–2004 37 –4 –4 –2

10N/9W-33D1 98 83–98 QTge 1981–2004 23 –4 –9 –5

10N/9W-26L2 Jimtown 40 — Qal 1967–2004 37 –7 –8 –4

9N/9W-1D1 108 388–108 QTge 1981–2004 23 –1 –26 –2

9N/9W-1K2 403 350–264 QTge 1981–2004 23 –6 — –6

9N/8W-6L1 240 160–240 QTge 1981–2004 23 –8 +8 –8

9N/8W-7Q1 Southern 490 — Qal+QTge 1973–2004 31 +2 — +6

9N/8W-20L1 204 130–204 QTge 1974–2003 29 –41 — –40

1

Period of record between first and last spring measurement.

2

Number of years between the first and last spring measurements.

3

Depth information uncertain.

Table 4. Well construction information and water-level change in wells in the California Department of Water Resources ground-water 

level monitoring network in Alexander Valley, Sonoma County, California. 

[See figure 5 for explanation of geologic units. Depths in feet (ft) below land-surface datum; —, missing data]

Hydrology 31
Figure 10. Generalized hydraulic head in Alexander Valley, Sonoma County, California. A, Autumn 

1980. B, Autumn 2002.

32 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California

R i v e r

Lake

Sonoma

Warm

Springs

Dam

R

u ssi a n

Dry Creek

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

300

300

320

280

260

240

220

200

200

180

160

140

180

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

EXPLANATION

Line of equal ground-water-level altitude—

Contour interval is 20 feet. Data from

California Department of Water

Resources Bulletin, Autumn 1980.

Datum is NGVD 29

180

Alexander

Valley

A
Figure 10.—Continued.

Hydrology 33

R i v e r

Lake

Sonoma

Warm

Springs

Dam

R

u ssi a n

Dry Creek

175 29

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

300

300

320

340

280

260

240

220

200

200

180

180

160

160

140

140

287

205

158

185

139

164

146

342

8P1

19F2 17P2

18B1

33D1

26L2

1K2

1D1

6L1

7Q1

20L1

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

EXPLANATION

Line of equal ground-water-level altitude—

20

Contour interval is 20 feet. Autumn 2002 0

Well less than 200 feet deep

18B1

Well greater than 200 feet deep 19F2

California Department of Water Resources

well and identifier—- Number, if shown,

indicates water-level altitude (2002).

Datum is NGVD 29

205

342

Alexander

Valley

B
R i v e r

Lake

Sonoma

Warm

Springs

Dam

R

u ssi a n

D r y C r e e k

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

11463000

11464000

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

EXPLANATION

1–10

11–20

21–30

31-40

Unknown

Well density—Known wells drilled per

section, 1950-2004

Greater than 40

Alexander

Valley

Figure 11. Drilled wells per section in Alexander Valley, Sonoma County, California, 1950–2004.

34 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
GROUND-WATER-LEVEL ALTITUDE, IN FEET

1960 1965 1970 1975 1980

YEAR

1985 1990 1995 2000 2005

Cloverdale area

250

260

270

280

290

300

310

320

330

340

350

EXPLANATION

Well—

11N/10W-19F2

11N/10W-8P1

11N/10W-17P2

10N/9W-18B1

10N/9W-33D1

Geyserville area

150

160

170

180

190

200

210

220

230

240

250

EXPLANATION

Well—

A

B

Figure 12. Water level hydrographs for selected wells in Alexander Valley, Sonoma, County, California. A, Cloverdale area. 

B, Geyserville area. C, Jimtown area. D, southern area. Data points are connected by lines only for consecutive seasonal 

high or low water levels or where the data are less than six months apart. Datum is NGVD29.

Hydrology 35
GROUND-WATER-LEVEL ALTITUDE, IN FEET

120

130

140

150

160

170

180

190

200

210

220

1960 1965 1970 1975 1980

YEAR

1985 1990 1995 2000 2005

Jimtown area

EXPLANATION

Well—

10N/9W-26L2

9N/8W-6L1

9N/9W-1D1

9N/9W-1K2

60

70

80

90

100

110

120

130

140

150

160

Southern area

EXPLANATION

Well—

C

D

9N/8W-7Q1

9N/8W-20L1

Figure 12.—Continued..

36 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
In summary, 9 of the 11 monitoring wells in the network 

had slight water-level declines over their varying periods of 

record (table 4). Comparing water-level changes for these 

wells for the same time period provided a consistent basis to 

compare water-level changes in different parts of the study 

area. First, water levels were compared for the period between 

spring 1981 and spring 2003. This allowed an assessment of 

the balance between ground-water use in the previous irrigation season and ground-water recharge during the rainfall 

season. Eight of 10 wells had ground-water-level declines 

between spring 1981 and spring 2003, one well had a 6-ft rise 

(9N/8W-7Q1), and one well had no change (11N/10W-19F2). 

The declines were 8 ft or less for all but one well (9N/8W20L1), in the southern part of the area, which had a 41 ft 

water-level decline. The geneal condition of slightly lower 

ground-water levels at the end of the rainfall season in recent 

years suggests a small imbalance in which ground-water 

use slightly exceeds annual recharge. Water levels also were 

compared for the period between autumn 1980 and autumn 

2002. Ground-water levels generally were lower in 2002 (by 

4 to 26 ft) in the Jimtown and Geyserville areas at the end of 

the irrigation season. However, the water level in one well near 

Jimtown (9N/8W-6L1) was higher by 8 ft in 2002 (table 4). 

Data were too sparse to make a determination of water-level 

changes in other parts of the valley. 

Ground-Water and Surface-Water 

Quality 

Water-chemistry data compiled by the USGS and 

California Department of Water Resources were used to help 

characterize the spatial variations in surface- and groundwater quality, and to help identify the source and movement 

of ground water in the Alexander Valley. Ground-water and 

surface-water data from sites located in and adjacent to the 

Alexander Valley were used for this study (fig. 13; table 5 and 

Appendix A). Field constituent data (water temperature, pH, 

specific conductance, and alkalinity), and major ion, trace 

element, silica, and nutrient data collected during 2002–2004 

from 1 site along the Russian River (Russian River at Digger Bend near Healdsburg, station id 11463980) and from 13 

wells are summarized in Appendix A. Specific conductance 

measurements at eight wells sampled from 1969 through 2004 

are summarized in table 6. Historical water-chemistry data 

(1951–2001) for 1 additional surface-water site on the Russian 

River (Russian River near Healdsburg, 11464000) and for 

23 wells in the Alexander Valley were compared with recent 

(2002–04) data. USGS water-chemistry data presented in this 

report include field measurements from 1 surface-water site 

monitored as part of a separate USGS study of the lower Russian River (Marisa Cox, U.S. Geological Survey, Menlo Park, 

written commun., 2005) and data from 5 wells sampled in 

2004 for the Ground-water Ambient Monitoring and Assessment program (GAMA), a comprehensive statewide effort 

designed to understand and identify water-quality risks to 

ground-water resources (Kulongoski and others, 2006). 

In general, water chemistry can vary with depth in 

ground-water systems. In the study area, ground-water wells 

have a fairly narrow range of completed depths and perforated 

intervals. Among 28 wells with historical (1951–2001) and 

recent (2002–2004) major ion and specific conductance data 

used for this study, 19 wells (68 percent) are drilled or completed (cased) at a depth of less than 200 ft bls, 6 wells

(21 percent) are completed at a depth greater than 200 ft, and 

the remaining 3 wells have no depth information (table 5). 

For wells with water-chemistry and perforation information, 

the average perforation depth for each depth category is 57 ft 

(completed well depth less than 200 ft) and 220 ft (completed 

well depth greater than 200 ft). Less than half (43 percent) 

of the wells sampled have available perforation information; 

thus, to make a statistically meaningful comparison of water 

chemistry between depths, the wells were divided into the two 

depth categories indicated for illustration and discussion in 

this report. 

Methods of Water Sampling and Analysis

Surface-water samples for the measurement of selected 

field constituents including dissolved oxygen, pH, specific 

conductance, and water temperature were collected using 

a DH-81 sampler according to methods given in Wilde and 

others (1999). USGS ground-water samples from wells 

were collected from faucets either at or near the well head to 

minimize potential chemical alteration of the water between 

the well and the sampling point. Prior to the collection of the 

ground-water samples, the wells were purged a minimum 

of three casing volumes of water. Sequential measurements 

of specific conductance, pH, and temperature were made at 

5-minute intervals until readings had stabilized to ensure they 

were representative of the ground water. All USGS samples 

collected for the analysis of major ions, trace elements, silica, 

and nutrients were collected, treated, and preserved following procedures outlined by U.S. Geological Survey (1997 to 

present). These samples were analyzed at the USGS National 

Water Quality Laboratory at Arvada, Colorado, using standard analytical methods described by Fishman and Friedman 

(1989), Fishman (1993), and Struzeski and others (1996). All 

California Department of Water Resources samples were analyzed at the California Department of Water Resources Bryte 

Analytical Lab in West Sacramento, California (Bruce Agee, 

California Department of Water Resources, written commun., 

2005). CADWR laboratory analyses and field measurements 

were done according to the referenced methods of the American Public Health Association (1999), and the U.S. Environmental Protection Agency (1993, 1994). 

Ground-Water and Surface-Water Quality 37
R i v e r

Lake

Sonoma

R

u ss i a n

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402.

Well less than 200 feet deep

Surface-water sampling site and identifier

18N1

Well greater than 200 feet deep 6M2

29H3 Well with unknown depth

For explanation of geology, see figure 5.

EXPLANATION

Geology modified from Blake and others, 2002.

11463980

Well and identifier—- Slash ‘ \ ’ through well symbol

indicates inactive monitoring well.

Alexander

Valley

D r y C r e e k

6M2

7Q1

18C1

1K2

1P1

4G1

17D1

18B1

18N1

18P118R1

19C1 19B1

26L1

26L2

32R3

33D1

12G1

13K5

8P1

28M1

28N1

29H3 33A1

33G1 33__

34D1

34D2

Figure 13. Location of ground- and surface-water quality sampling sites, Alexander Valley, Sonoma County, 

California. 

38 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
State 

well

No.

USGS site

identification

No.

Depth

drilled

Depth

cased

Depth of 

perforated 

interval

Landsurface

 altitude

Period of 

waterchemistry data 

used in report

Data 

source

9N/8W-6M2 383916122473501 600 600 125–600 190 2004 USGS

9N/8W-7Q1 — 490 490 — 160 1957–80 CADWR

9N/8W-18C1 383758122471901 — — — — 2004 USGS

9N/9W-1K1 — — — — 170 1975–2002 CADWR

9N/9W-1P1 — — 90 — 160 1957–2002 CADWR

9N/9W-4G1 — 320 320 220–320 220 1951–57 CADWR

10N/9W-17D1 384309122531301 315 315 20–315 233 2004 USGS

10N/9W-18B1 384320122534201 180 178 — 230 1972–2002 CADWR

10N/9W-18N1 — 66 66 4–56 215 1976–2003 CADWR

10N/9W-18P1 384238122541201 120 120 62–120 207 2004 USGS

10N/9W-18R1 — — 114 — — 1957–64 CADWR

10N/9W-19B1 — 43 — — 200 1951 CADWR

10N/9W-19C1 — 25 — — — 1951 CADWR

10N/9W-26L1 — 1320 1320 143–244 208 1957–86 CADWR

10N/9W-26L2 — — 40 — 205 1973–2003 CADWR

10N/9W-32R3 — 245 — — 175 1952–60 CADWR

10N/9W-33D1 — 198 98 83–98 178 1972–2003 CADWR

10N/10W-12G1 — 33.5 33.5 12–33.5 228 1975–1985 CADWR

10N/10W-13K5 — 172 172 75–172 — 1974 CADWR

11N/10W-8P1 384831122594701 32 32 8–28 305 1972–2003 CADWR

11N/10W-28M1 — — 21 — 260 1951–52 CADWR

11N/10W-28N1 — — 19 — — 1957–2002 CADWR

11N/10W-29H3 2 384628122592701 — — — 415 2004 USGS

11N/10W-33A1 — 20 — — 255 1951–63 CADWR

11N/10W-33__ 3 — 40 30 110–30 — 1956 CADWR

11N/10W-33G1 — 20 18 — 290 1951–64 CADWR

11N/10W-34D1 — — 5 — — 1951 CADWR

11N/10W-34D2 — — 4 — — 1951 CADWR

1 Depth information uncertain.

2 Projected State well number, verification pending.

3 Location uncertain.

Table 5. Construction data for selected wells used for water-chemistry sampling in the Alexander Valley, Sonoma County, California.

[State well No.: See well-numbering diagram in text; see figure 13 for site locations; USGS (U.S. Geological Survey) identification number: the unique number 

for each site in USGS NWIS (National Water Information System) database; depths in feet below land surface; land-surface altitude in feet above sea level; 

—, no data; data sources: USGS, U.S. Geological Survey; CADWR, California Department of Water Resources]

Ground-Water and Surface-Water Quality 39
Date

(mm/dd/yyyy)

Electrical 

conductance

(μS/cm)

Date

(mm/dd/yyyy)

Electrical

 conductance

 (μS/cm)

Date

(mm/dd/yyyy)

Electrical 

conductance

 (μS/cm)

9N/9W-1K1

06/12/1975 347 08/17/1984 311 09/18/2002 438

08/03/1977 298 08/28/1986 348

07/29/1980 300 08/27/1998 374

9N/9W-1P1

07/08/1969 333 08/06/1981 433 09/01/1993 431

07/16/1970 360 08/10/1983 349 08/27/1998 398

07/26/1973 388 08/18/1987 389 09/18/2002 357

06/23/1976 362 08/31/1989 418

08/09/1978 351 09/19/1991 434

10N/9W-18B1

08/10/1972 306 09/17/1986 322 09/18/2002 400

08/08/1974 288 08/25/1992 410 09/12/2004 372

08/03/1977 431 08/29/1995 365

07/16/1980 304 08/27/1998 374

10N/9W-18N1

06/23/1976 345 08/18/1987 336 08/24/1999 350

08/09/1978 373 09/10/1990 413 09/17/2001 362

07/09/1981 369 08/25/1992 378 09/24/2003 377

08/10/1983 294 08/29/1995 335

08/28/1985 359 09/16/1997 354

Table 6. Summary of laboratory conductivity measurements for samples from selected ground-water wells, Alexander Valley, Sonoma 

County, California, 1969–2004.

[Samples were collected and analyzed by the California Department of Water Resources. See figure 13 for locations of wells; °C, degrees Celsius; μS/cm, 

microsiemens per centimeter at 25°C; mm/dd/yyyy, month/day/year]

40 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Table 6. Summary of laboratory conductivity measurements for samples from selected ground-water wells, Alexander Valley, Sonoma 

County, California, 1969–2004—Continued.

[Samples were collected and analyzed by the California Department of Water Resources. See figure 13 for locations of wells; °C, degrees Celsius; μS/cm, 

microsiemens per centimeter at 25°C; mm/dd/yyyy, month/day/year]

Date

(mm/dd/yyyy)

Electrical 

conductance 

(μS/cm)

Date

(mm/dd/yyyy)

Electrical 

conductance

 (μS/cm)

Date

(mm/dd/yyyy)

Electrical 

conductance 

(μS/cm)

10N/9W-26L2

07/25/1973 535 08/17/1984 496 08/29/1995 692

06/12/1975 538 08/28/1986 583 09/16/1997 614

08/03/1977 454 08/30/1988 605 08/24/1999 615

07/16/1980 544 09/10/1990 740 09/17/2001 697

09/22/1982 529 08/25/1992 744 09/24/2003 805

10N/9W-33D1

08/09/1972 288 08/10/1983 325 09/01/1993 373

08/08/1974 304 08/28/1985 349 09/16/1997 457

06/23/1976 310 08/19/1987 442 08/24/1999 392

07/12/1979 324 08/31/1989 342 09/17/2001 441

07/09/1981 325 09/19/1991 384 09/24/2003 438

11N/10W-8P1

08/09/1972 419 09/22/1982 357 08/25/1992 425

08/08/1974 359 08/17/1984 352 09/16/1997 402

06/23/1976 384 08/28/1986 356 08/24/1999 396

08/09/1978 421 08/30/1988 388 09/17/2001 426

07/16/1980 353 09/10/1990 419 09/24/2003 442

11N/10W-28N1

09/08/1969 318 07/09/1981 278 09/19/1991 357

07/15/1970 388 09/10/1983 362 09/01/1993 392

08/08/1974 440 08/28/1985 377 08/29/1995 425

06/23/1976 454 08/19/1987 340 08/27/1998 237

07/12/1979 386 08/31/1989 370 09/18/2002 252

Ground-Water and Surface-Water Quality 41
Ground-Water and Surface-Water Chemistry 

Water-Quality Monitoring

Ground-water quality in the Alexander Valley has been 

monitored since 1950. Most sampling efforts represented a 

one-time analysis for short-term studies or individual wellspecific assessments. Data shown in this report are available 

for 28 wells (fig. 13, table 5), but only 11 wells have sufficient 

data for determining the recent (2002–04) ionic composition 

of ground water. A few select wells have been repeatedly 

sampled every 2 to 3 years for more than 10 years. The longest 

sustained water-quality monitoring effort in the Alexander 

Valley has been done by the CADWR. Since the late 1950s, 

the CADWR has sampled and analyzed ground water for 

major ions (calcium, magnesium, potassium, sodium, chloride and sulfate), boron, nitrate, total dissolved solids, total 

alkalinity, electrical conductance, pH, and water temperature. 

Water-chemistry data covering a minimum of 10 years and 

maximum of 45 years is available for 13 wells that have been 

monitored by CADWR, including 8 wells that are currently 

(2004) monitored. Samples from these wells are collected on 

average every 2 to 3 years between the months of July and 

September. Water-quality monitoring of surface water in the 

Alexander Valley has occurred sporadically since 1951. Eight 

sites on the Russian River between Cloverdale and Healdsburg 

have been sampled by the USGS, primarily for nutrients and 

microbiological constituents. The Russian River near Healdsburg (station id 11464000) is the only surface-water site for 

which multiple analyses for major ions, trace elements, and 

nutrients for multiple, consecutive years (1951–66 and 1980) 

are available. 

General Chemical Composition of Ground and 

Surface Water

Selected samples collected by the USGS from wells and 

from the Russian River in 2002–04 were measured on site for 

dissolved oxygen, pH, specific conductance, water temperature, and alkalinity following procedures outlined by the U.S. 

Geological Survey (1997 to present). Dissolved oxygen concentrations ranged from 0.1 to 11.4 milligrams per liter 

(mg/L); the highest concentrations were measured in samples 

from the Russian River at Digger Bend near Healdsburg 

(Appendix A). The maximum concentration of dissolved 

oxygen in ground water was 5.7 mg/L in a sample from 

well 10N/9W-18P1, which is perforated from 62 to 120 ft. 

bls. The pH of all samples collected by both the USGS and 

the CADWR during 2002–04 ranged between 6.8 and 8.5 

(Appendix A). Specific electrical conductance (conductivity), 

a measurement of the ability of water to conduct an electrical 

charge and an indicator of ionic concentration, ranged from 

240 microsiemens per centimeter (μS/cm) (November 2003 

sample from Russian River near Healdsburg) to 799 μS/cm 

(September 2003 sample from well 10N/9W-26L2, which has 

a depth of 42 ft bls). Although recent seasonal data representing the full range of conductivity values are unavailable, 

conductivity can be expected to vary depending on the location and the time of year. For example, the highest conductivity values for surface water can be expected to occur in the 

late summer and autumn months corresponding to the lowest 

surface-water flows of the season. Conversely, the lowest 

conductivity values can be expected to occur in the late winter 

and spring corresponding with the highest surface-water flows. 

Conductivity and discharge for the Russian River near Healdsburg (11464000) for the period 1951–66 are strongly correlated [conductivity = 603.41 (discharge)-0.1461; R2

= 0.71]. 

Water-chemistry data for samples collected from 11 

wells during 2002–04 indicate that water quality in the study 

area generally is acceptable for potable use (Appendix A). The 

water from two wells, however, each contained one constituent 

in excess of the recommended standards for drinking water. 

Water in a sample from well 9N/8W-6M2 had a concentration 

of manganese (241 μg/L) that exceeded the secondary drinking-water standard of 50 μg/L (U.S. Environmental Protection 

Agency, 2002; California Department of Health Services, 

accessed April 15, 2005). Oxygen and nitrate concentrations 

in the same sample were reported at detection limits, suggesting that dissolution of manganese could be caused by low 

oxidation/reduction (redox) conditions. Boron, a constituent 

of particular concern because of its potential effects on crops, 

exceeded the 1,000 μg/L California Department of Health Services notification level in a sample from well 11N/10W-29H3 

(1,350 μg/L).

The ionic composition of historical surface- and groundwater samples (1951–2001) and of recent ground-water 

samples (2002–04) are plotted on trilinear diagrams (figs. 14

and 15, respectively). A trilinear diagram shows the proportions of common cations and anions for comparison and 

classification of water samples independent of total analyte 

concentrations (Hem, 1985). Trilinear diagrams can be used 

to identify groups of samples that have similar relative ionic 

concentrations (Freeze and Cherry, 1979). Historical surfacewater data plotted on figure 14A include 32 samples with 

complete major-ion analyses collected by the USGS between 

1951 and 1966 from one surface-water site on the Russian 

River (station id 11464000). Although these samples represent 

spring and late summer conditions for 15 consecutive years, it 

is uncertain if they are representative of surface-water quality 

throughout the Alexander Valley because of the lack of comparable data from other locations. Historical ground-water data 

plotted on figure 14 are for 96 samples collected by California 

Department of Water Resources from 23 wells. Recent data, 

plotted on figure 15, are for 11 samples (5 collected by the 

USGS and 6 collected by the California Department of Water 

Resources) from 11 wells. Well 10N/9W-18B1, which was 

sampled twice during 2002–04, is represented in figure 15 by 

the latest (2004) analyses listed in Appendix A.

42 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
80

60

40

20

80

60

40

20

80 60 40 20 20 40 60 80

Magnesium

Sulfate

Sodium

+ Potassium

Carbonate

+

Bicarbonate

Sulfate

+

Chloride

Calcium Chloride

C A T I O N S A N I O N S

Calcium

+ Magnesium

80

60

20

40

80

20

60

40

20

80

40

60

20

60

80

40

20

60

80

40

20

80

40

60

Percentage of total milliequivalents per liter

Well greater than 200 feet deep

Example of how to read a trilinear diagram

EXPLANATION

Surface-water sample from Russian River at Healdsburg (11464000)

Well less than 200 feet deep

Well-—

A

Figure 14. Chemical composition of water from selected ground- and surface-water sampling sites in 

the Alexander Valley, Sonoma County, California, 1951–2001. A, All sites. B, Wells in sections 9N/8W and 

9N/9W. C, Wells in section 10N/9W. D, Wells in sections 10N/10W and 11N/10W. 

Ground-Water and Surface-Water Quality 43
Figure 14.—Continued.

44 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California

33G1

33__ 34D1

34D2 33A1

Sodium

+ Potassium

Carbonate

+

Bicarbonate

Sulfate

+

Chloride

Calcium

+ Magnesium

80

60

20

40

80

20

60

40

20

60

80

40

20

80

40

60

28M1

13K5

8P1

28N1

12G1

28M1

D

18R1

26L1

26L2

19B1

19C1

18B1

18N1

Sodium

+ Potassium

Carbonate

+

Bicarbonate

Sulfate

+

Chloride

Calcium

+ Magnesium

80

60

20

40

80

20

60

40

20

60

80

40

20

80

40

60

C

33D1

32R3 4G1

1K1

1P1

7Q1

Sodium

+ Potassium

Carbonate

+

Bicarbonate

Sulfate

+

Chloride

Calcium

+ Magnesium

80

60

20

40

80

20

60

40

20

60

80

40

20

80

40

60

B

Well greater than 200 feet deep

EXPLANATION

18N1 Well less than 200 feet deep

4G1

Well and identifier—- Shaded areas show

multiple samples from the same well
1K1

1P1

18B1

18N1

18P1

26L2

33D1

8P1

28N1

29H3

6M2

80

60

40

20

80

60

40

20

80 60 40 20 20 40 60 80

Magnesium

Sulfate

Sodium

+ Potassium

Carbonate

+

Bicarbonate

Sulfate

+

Chloride

Calcium Chloride

C A T I O N S A N I O N S

Calcium

+ Magnesium

80

60

20

40

80

20

60

40

20

80

40

60

20

60

80

40

20

60

80

40

20

80

40

60

Percentage of total milliequivalents per liter

EXPLANATION

Well less than 200 feet deep

18N1

Well greater than 200 feet deep 6M2

29H3 Well with unknown depth

Example of how to read a trilinear diagram

Well and identifier—-

Figure 15. Chemical composition of water from selected ground-water sampling sites in the Alexander 

Valley, Sonoma County, California, 2002–2004.

Ground-Water and Surface-Water Quality 45
The composition of most of the historical surface-water 

samples can be characterized as a mixed cation-bicarbonate 

type water. Twenty-nine of the 32 samples from the Russian River (station id 11464000) with complete analyses for 

the period 1951–66 were a mixed-cation-bicarbonate type 

water (fig. 14A). Calcium was the predominant cation in these 

samples, but in terms of a chemical equivalence basis (milliequivalents per liter, meq/L) calcium constituted less than 

50 percent of all cations in each sample. The remaining three 

samples from the Russian River were a calcium-bicarbonate 

type water. 

The composition of most ground-water samples collected 

from wells in the Alexander Valley is similar to the composition of the historical surface-water samples from the Russian 

River near Healdsburg. Thirty-five of 96 historical groundwater samples (fig. 14A) and six of 11 recent (2002–2004) 

ground-water samples (fig. 15) were a mixed cation-bicarbonate type water. Magnesium was the predominant cation 

in about three-fourths of these mixed-bicarbonate samples. 

Among the other ground-water samples, 33 historical samples 

from 10 wells (9N/9W-1K1, -1P1; 10N/9W-26L1, -26L2, 

-33D1; 10N/10W-12G1; 11N/10W-8P1, -28N1, -34D1, and 

-34D2) (fig. 14B–D) and three recent samples from three wells 

(9N/9W-1K1, 10N/9W-33D1, and 11N/10W-8P1) (fig. 15) 

had a magnesium-bicarbonate composition; a recent sample 

from one well (10N/9W-26L2) had a magnesium-mixed anion 

composition (fig. 15); 10 historical samples from five wells 

(9N/9W-1P1; 10N/9W-18R1, -19B1; 11N/10W-28M1 and 

-28N1) (figs. 14B–D) had a calcium-bicarbonate composition; 

2 historical samples from one well (11N/10W-33G1) 

(fig. 14D) had a mixed cation-mixed anion composition; 15 

historical samples from four wells (9N/8W-7Q1, 10N/9W32R3, 11N/10W-28M1 and -33A1) (figs. 14B–D) and a 

recent sample from one well (9N/8W-6M2) had a sodiumbicarbonate composition; and a historical sample from one 

well (11N/10W-33G1) (fig. 14D) had a sodium-chloride 

composition. In summary, nearly three-fourths (72 percent) 

of historical and recent ground-water samples collected from 

wells in the Alexander Valley can be characterized as magnesium-bicarbonate or mixed-cation bicarbonate type water with 

magnesium as the predominant cation.

The spatial distribution of different water types in the 

Alexander Valley for 2002–04 is illustrated using Stiff diagrams (fig. 16). Stiff diagrams plot in an identical sequence the 

concentration [in milliequivalents per liter (meq/L)] of major 

cations to the left of zero and major anions to the right of zero 

(Stiff, 1951). The width of the diagram is an approximate indication of the total ionic content (Hem, 1985). Well 10N/9W18B1, which was sampled twice during 2002–04 for major 

ions, is represented by the latest (2004) analyses listed in 

Appendix A. Dissolved-solids concentrations (ROE, residue on 

evaporation) for ground-water samples collected from 11 wells 

during 2002–04 ranged from 151 mg/L (11N/10W-28N1) 

to 551 mg/L (10N/9W-26L2). Stiff diagrams for samples 

from eight wells (9N/9W-1K1, -1P1; 10N/9W-18B1, -18N1, 

-18P1, -33D1; 11N/10W-8P1 and -29H3) located from near 

Cloverdale to south of Jimtown are similar. The similar ionic 

composition of these water samples suggests a similar source 

of recharge to these wells, probably a combination of infiltrated precipitation and seepage from the Russian River and 

its tributaries. The relatively narrow Stiff diagram representing the sample from well 11N/10W-28N1 indicates a total 

ionic content that is lower than any other sample represented 

in figure 16. The ROE concentration of the sample from well 

11N/10W-28N1 was identical to the mean ROE concentration (151 mg/L) of the historical samples collected from the 

Russian River near Healdsburg (station id 11464000) during 

1951–64, suggesting that recharge from the Russian River 

constitutes the primary source of recharge to this well. Wider 

Stiff diagrams representing the samples from wells 9N/8W6M2 and 10N/9W-26L2 are indicative of higher total ionic 

content. The ROE concentrations of samples from these wells 

were 381 mg/L and 551 mg/L, respectively, compared with the 

median value of 254 mg/L for samples from all 11 wells. The 

higher ionic content of ground water from these wells may be 

attributed to lithology, well depth, or land use. 

 Geologic setting and well depth may explain why the 

water samples from some wells, which plot beyond the main 

cluster of sample points on the trilinear diagrams (figs. 14 and 

15), have a distinct ionic composition. Samples from wells 

9N/8W-6M2, 9N/8W-7Q1, 9N/9W-4G1, 10N/9W-32R3, 

11N/10W-33A1, 11N/10W-33G1, and 11N/10W-33__ have 

significant proportions of sodium (at least 35 percent, on an 

equivalent basis, of the total cation balance). These wells are 

located either in or near geologic units other than Quaternary 

alluvial deposits, which form the most productive water-bearing unit in the Alexander Valley. Well 11N/10W-33A1 and 

11N/10W-33__, located near Asti, were completed in alluvium 

and alluvial terrace deposits (fig. 13) and are less than 200 ft 

deep. The amount of chloride as a proportion of the total anion 

balance for samples from well 11N/10W-33A1 ranged from 

24 to 57 percent, significantly higher than the mean percentage of chloride (10 percent) in all samples plotted on figures 

14 and 15. Wells 9N/8W-6M2, 9N/8W-7Q1, 9N/9W-4G1, 

and 10N/9W-32R3 are located in the vicinity of Lytton and 

Jimtown in the southern part of the Alexander Valley and are 

greater than 200 ft deep. Drillers’ logs for these wells indicate the presence of blue clay and conglomerates of clay and 

gravel, particularly at greater depths. The ionic composition 

of samples from these wells suggest that ground water in deep 

wells in the southern part of the Alexander Valley may have 

higher proportions of sodium and potassium concentrations 

than water in shallow wells completed in alluvium. Ground 

water that interacts with clay-bearing aquifer deposits may 

be modified by cation exchange; for example, sodium cations 

on the clay minerals are replaced by calcium and magnesium 

cations, releasing the sodium cations to water (Drever, 1982). 

46 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
R i v e r

Lake

Sonoma

Warm

Springs

Dam

R

u ssi a n

D r y C r e e k

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

9N/9W-1K1

10N/9W-26L2

10N/9W-18B1

11N/10W-8P1

11N/10W-29H3

11N/10W-28N1

10N/9W-18N1

10N/9W-18P1

10N/9W-33D1

9N/9W-1P1

9N/8W-6M2

8P1

28N1

29H3

18B1 18N1

18P1

33D1

26L2

6M2 1K1

1P1

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

HCO3+CO3

SO4

SO4

SO4

SO4

SO4

SO4

SO4

SO4

SO4

SO4

SO4

Mg

Mg

Mg

Mg

Mg

Mg

Mg

Mg

Mg

Mg

Mg

Ca

Ca

Ca

Ca

Ca

Ca

Ca

Ca

Ca

Ca

Ca

Na+K

Na+K

Na+K

Na+K

Na+K

Na+K

Na+K

Na+K

Na+K

Na+K

Na+K

CATIONS Milliequivalent per liter ANIONS

10 5 5 10

Stiff Diagram Scale

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

Well less than 200 feet deep 18N1

Well greater than 200 feet deep 6M2

29H3 Well with unknown depth

EXPLANATION

Well and identifier—-

Figure 16. Stiff diagrams showing chemical composition of samples from selected wells in the Alexander 

Valley, Sonoma County, 2002–04.

Ground-Water and Surface-Water Quality 47
R i v e r

Warm

Springs

Dam

R

u ssi a n

D r y C r e e k

Lake

Sonoma

29

175

128

128

101

101

Mendocino Co

Lake Co

Sonoma Co

Asti

Lytton

Jimtown

Healdsburg

Geyserville

Cloverdale

Preston

11463000

11464000

11463980

T10N

T9N

T8N

T11N

T12N

R11W R10W R9W R8W

YEAR

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

1969 1974 1979 1984 1989 1994 1999 2004

YEAR

200

300

400

500

600

700

800

900

1,000

11N/10W-8P1 11N/10W-28N1

10N/9W-18B1

10N/9W-26L2

9N/9W-1K1

9N/9W-1P1

10N/9W-33D1

10N/9W-18N1

8P1

28N1

18B1

18N1

33D1

26L2

1K1

1P1

123°5' 123°0' 122°55' 122°50' 122°45'

38°

55'

38°

50'

38°

45'

38°

40'

38°

35'

0 5 10 Miles

0 5 10 Kilometers

Base from U.S. Geological Survey digital data, 1:250,000, 2003. State Plane Projection, Fipzone 402

Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from northwest at 30 degrees above horizon

Well less than 200 feet deep

Specific conductance, in microsiemens

per centimeter

18N1

Well greater than 200 feet deep 1K1

EXPLANATION

Graphs

Well and identifier—-

Figure 17. Time-series plots of electrical conductance for selected ground-water wells in the Alexander Valley, 

Sonoma County, California, 1969–2004.

48 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
As illustrated by figure 14, the composition of water 

from several wells has varied over time. Individual samples 

collected from shallow (less than 200 ft deep) wells 11N/10W28M1, -33A1, and -33G1 (fig. 14D) had ionic compositions in 

autumn 1951 (wells -28M1 and -33G1) and spring 1952 (well 

-33A1) that were markedly different from most of the samples 

collected from the same wells during 1951–52, 1952–63, and 

1951–64, respectively. Cardwell (1965) suggested that the 

anomalous sodium-bicarbonate (samples from wells -28M1 

and -33A1) and sodium-chloride (sample from well -33G1) 

compositions could be attributed to seasonal variations in 

the source of water to these wells. Cardwell postulated that 

underflow from bedrock replaced recharge from precipitation or water from shallow alluvial or colluvial deposits as the 

source of water to wells 11N/10-28M1 and -33G1. For well 

11N/10W-33A1, Cardwell attributed the one-time increase in 

sodium to recharge from a nearby creek fed by discharge of 

poor-quality ground water from bedrock. 

Water samples from other wells suggest a progressive 

change in water quality over time that may reflect long-term as 

opposed to seasonal variations. The ionic composition of samples collected from wells 10N/9W-26L1 (1957–86; fig. 14C), 

-26L2 (1973–2003; figs. 14C and 15), and -33D1 (1972–2003; 

figs. 14C and 15) show a trend towards higher ionic concentrations and an increasing proportion of sulfate in particular. 

This long-term trend is also reflected by time-series plots of 

conductivity. The temporal variation of conductivity in water 

from eight wells used as long-term monitoring sites by the 

CADWR is shown on figure 17. Time-series plots of conductivity suggest that the most significant changes in water chemistry during 1969–2004 have occurred in the southern part of 

the Alexander Valley from Geyserville to Lytton and Jimtown. 

The conductivity at well 10N/9W-26L2 increased 27 percent 

during the late 1980s and early 1990s, from 583 μS/cm in 

1986 to 744 μS/cm in 1992, coinciding with a period of below 

normal rainfall (1987–92). Conductivity has increased 59 percent at well 10N/9W-33D1, from 288 μS/cm in 1972 to a peak 

reading of 457 μS/cm in 1997. It cannot be determined on the 

basis of the limited water-chemistry data whether the increases 

in conductivity and in concentrations of particular constituents 

such as sulfate are limited to these particular wells. The reason 

for the slow degradation of water quality is also unknown, but 

could be related to localized changes in land use or changes in 

irrigation practices, including leaching from irrigation. Alternatively, increasing conductivity may reflect an underlying 

trend toward lesser contribution of lower conductivity water 

from shallower depths as water levels decline. 

Summary and Conclusions 

This study was undertaken to update the geohydrologic 

and geochemical characterization of the Alexander Valley in 

order to better address surface-water/ground-water-management issues.

The most important sources of ground water in the study 

area are the Quaternary alluvial deposits, the Glen Ellen Formation, and the Sonoma Volcanics. The alluvial units, where 

sufficiently thick and saturated, comprise the most productive 

aquifer in the study area. On most of the valley floor, except 

immediately adjacent to the bounding hills, the alluvial aquifer 

generally provides sufficient quantities of water to wells, 

negating the need to drill into deeper formations. Near the low 

hills on the valley floor or near the valley sides, the alluvium 

generally is thinner, and deeper formations are relied upon to 

provide a part of the total well yield. 

Average recharge to the ground-water system for the 

period 1952–2004 is derived from an estimated average 

298,000 acre-ft of precipitation falling within the watershed 

and from infiltration of part of the water in the Russian River 

that originates outside of the watershed. Runoff and evapotranspiration from the study area are estimated to be about 

160,000 and 113,000 to 133,000 acre-ft/yr, respectively. On 

the basis of these values, about 5,000 to 25,000 acre-ft/yr is 

available for ground-water recharge. The estimate of recharge 

is an order of magnitude smaller than any of the other three 

main components of the water budget. Because of the relative 

magnitudes of the values, even a small percentage change in 

the estimates of precipitation, runoff, or evapotranspiration 

could result in a large change in the estimate for recharge.

The estimated total water use for the Alexander Valley 

for 1999 was about 15,800 acre-ft. About 13,500 acre-ft of 

this amount is agricultural use, predominantly vineyards, and 

about 2,300 acre-ft is municipal/industrial use. Ground water 

is the main source of water supply. Some wells are located 

very close to the Russian River. A better quantification of surface-water diversions and pumpage would be needed to more 

accurately assess the balance between water use and water 

supply.

Summary and Conclusions 49
Ground-water-level monitoring in the study area is 

sparse, with only nine active wells in the California Department of Water Resources network. Long-term changes in 

ground-water levels are evident in parts of the study area, but 

because of the sparse network and the lack of data on well 

construction and lithology, it is uncertain if any significant 

changes have occurred in the northern part of the study area 

since 1980. In the southern half of the study area, groundwater levels were generally lower at the end of the irrigation 

season in 2002 than in 1980, which suggests that a greater 

amount of ground water is being pumped in the southern 

half of the study area in recent years compared with that in 

the early 1980s. The slightly lower water levels measured in 

spring during recent years compared with those measured in 

the early 1980s suggests that ground-water use in the southern 

half of the study area in recent years has been greater than the 

annual recharge. To more rigorously monitor future changes in 

the ground-water flow system, a denser water-level monitoring 

network would be needed. 

Water-chemistry data for samples collected from 11 wells 

during 2002–04 indicate that water quality in the study area 

generally is acceptable for potable use. The water from two 

wells, however, each contained one constituent in excess of the 

recommended standards for drinking water (manganese and 

boron). 

Ground-water composition is a reflection of the source 

waters and water-rock interactions of the system in which 

water moves and resides. The chemical composition of water 

from most of the wells sampled for major ions is a mixed 

cation-bicarbonate, magnesium-bicarbonate, or calcium-bicarbonate type water. The ionic composition of most historical 

and recent samples from many wells in the Alexander Valley 

is similar to that of the historical surface-water samples collected from the Russian River near Healdsburg. This similarity in ionic composition suggests that recharge to most wells, 

particularly wells that are less than 200 ft total depth and perforated in Quaternary alluvial deposits, may be a combination 

of infiltration from precipitation and seepage from the Russian 

River and its tributaries. Recharge to wells that are greater than 

200 ft total depth and (or) perforated in geologic units, including continental terrace deposits and clay and gravel conglomerates, consist of slightly more mineralized water as a result of 

reactions such as cation exchange. These waters generally are 

characterized by higher concentrations of total dissolved solids 

and of particular constituents such as sodium. 

Water samples collected from several wells over a number of years suggest a progressive change in water chemistry 

over time. Samples spanning more than 30 years from two 

wells in the Lytton and Jimtown area show a trend towards 

higher ionic concentrations and increasing concentrations of 

particular constituents such as sulfate. These water-quality 

changes may be attributed to natural processes, such as cation 

exchange, or to anthropogenic impacts, such as changes in 

land use or irrigation practices. Water-quality changes in a 

well also may result from declining water levels, which can 

reduce the amount of water drawn from shallower depths. 

Ascertaining the areal extent of these possible water-quality 

trends and their possible causes will require more comprehensive surface- and ground-water sampling in the Alexander 

Valley. 

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52 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Appendix

Appendix 53
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

USGS 

identification 

No.

Sample

 date

(mm/dd/yyyy)

Collecting 

and analyzing 

agency

Oxygen, 

dissolved

(mg/L)

[00300]

pH,

field

 (standard 

units)

[00400]

Specific

 conductance, 

field 

(μS/cm)

 [00095]

Streamflow-measurement stations

Russian River at Digger Bend 

near Healdsburg 11463980 11/05/2003 USGS 111.4 18.5 1240

08/19/2004 USGS 19.0 18.4 1256

Russian River near Healdsburg 11464000 05/08/1951 USGS — 8.1 243

09/09/1951 USGS — 8.1 281

05/19/1952 USGS — 8.2 241

10/06/1952 USGS — 7.9 252

05/04/1953 USGS — 7.8 235

09/14/1953 USGS — 7.8 238

05/03/1954 USGS — 8.2 249

09/13/1954 USGS — 7.9 273

05/02/1955 USGS — 7.5 234

09/12/1955 USGS — 8.2 305

05/07/1956 USGS — 7.9 252

09/11/1956 USGS — 7.5 287

05/06/1957 USGS — 7.8 243

09/10/1957 USGS — 8.1 258

05/09/1958 USGS — 8.0 273

09/12/1958 USGS — 7.8 262

05/11/1959 USGS — 8.0 282

09/04/1959 USGS — 7.8 234

05/09/1960 USGS — 8.1 233

09/14/1960 USGS — 8.2 248

05/03/1961 USGS — 8.3 237

09/06/1961 USGS — 8.0 215

05/08/1962 USGS — 7.8 281

09/11/1962 USGS — 8.3 243

05/06/1963 USGS — 7.9 235

09/11/1963 USGS — 8.2 245

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

54 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

USGS 

identification 

No.

Sample

 date

(mm/dd/yyyy)

Collecting 

and analyzing 

agency

Oxygen, 

dissolved

(mg/L)

[00300]

pH,

field

 (standard 

units)

[00400]

Specific

 conductance, 

field 

(μS/cm)

 [00095]

05/12/1964 USGS — 7.9 309

09/02/1964 USGS — 7.9 257

05/12/1965 USGS — 8.2 252

09/14/1965 USGS — 8.0 251

05/03/1966 USGS — 8.1 262

09/23/1966 USGS — 8.0 249

Wells

9N/8W-6M2 383916122473501 09/27/2004 USGS 0.1 7.4 640

9N/8W-7Q1 — 01/15/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/__/1960 2 CADWR — — —

08/21/1961 2 CADWR — — —

09/19/1963 2 CADWR — — —

09/23/1964 2 CADWR — — —

07/08/1969 2 CADWR — 8.1 590

07/16/1980 2 CADWR — 8.1 585

9N/8W-18C1 383758122471901 09/15/2004 USGS — — 310

9N/9W-1K1 — 06/12/1975 2 CADWR — — 345

08/28/1986 2 CADWR — 7.1 336

08/27/1998 2 CADWR — 7.0 377

09/18/2002 2 CADWR — 7.1 430

9N/9W-1P1 — 01/08/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/__/1960 2 CADWR — — —

09/__/1961 2 CADWR — — —

09/19/1963 2 CADWR — — —

07/08/1969 2 CADWR — 7.1 345

07/26/1973 2 CADWR — 7.1 380

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 55
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

USGS 

identification 

No.

Sample

 date

(mm/dd/yyyy)

Collecting 

and analyzing 

agency

Oxygen, 

dissolved

(mg/L)

[00300]

pH,

field

 (standard 

units)

[00400]

Specific

 conductance, 

field 

(μS/cm)

 [00095]

08/10/1983 2 CADWR — 6.9 330

09/01/1993 2 CADWR — 6.4 428

09/18/2002 2 CADWR — 7.2 351

9N/9W-4G1 — 10/23/1951 2 CADWR — — —

01/08/1957 2 CADWR — — —

10N/9W-17D1 384309122531301 09/30/2004 USGS — — 488

10N/9W-18B1 — 08/10/1972 2 CADWR — 6.7 325

09/17/1986 2 CADWR — 6.3 312

08/27/1998 2 CADWR — 6.6 377

09/18/2002 2 CADWR — 6.8 397

09/12/2004 2 CADWR — 7.7 (L) 382

10N/9W-18N1 — 06/23/1976 2 CADWR — 6.7 333

08/18/1987 2 CADWR — 6.8 351

08/24/1999 2 CADWR — 5.7 347

09/17/2001 2 CADWR — — —

09/24/2003 2 CADWR — 7.0 375

10N/9W-18P1 384238122541201 09/28/2004 USGS 5.7 6.8 362

10N/9W-18R1 — 01/10/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/19/1963 2 CADWR — — —

09/23/1964 2 CADWR — — —

10N/9W-19B1 — 09/27/1951 2 CADWR — — —

10N/9W-19C1 — 09/27/1951 2 CADWR — — —

10N/9W-26L1 — 01/15/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

12/__/1962 2 CADWR — — —

09/23/1964 2 CADWR — — —

07/08/1969 2 CADWR — 7.5 600

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

56 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

USGS 

identification 

No.

Sample

 date

(mm/dd/yyyy)

Collecting 

and analyzing 

agency

Oxygen, 

dissolved

(mg/L)

[00300]

pH,

field

 (standard 

units)

[00400]

Specific

 conductance, 

field 

(μS/cm)

 [00095]

09/05/1986 2 CADWR — 7.2 587

10N/9W-26L2 — 07/25/1973 2 CADWR — 6.9 510

08/17/1984 2 CADWR — 6.6 438

09/17/2001 2 CADWR — — —

09/24/2003 2 CADWR — 7.2 799

10N/9W-32R3 — 04/02/1952 2 CADWR — — —

01/15/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/__/1960 2 CADWR — — —

10N/9W-33D1 — 08/09/1972 2 CADWR — 7.3 300

08/10/1983 2 CADWR — 7.1 312

09/01/1993 2 CADWR — 6.9 377

09/17/2001 2 CADWR — — —

09/24/2003 2 CADWR — 7.0 437

10N/10W-12G1 — 06/12/1975 2 CADWR — 7.0 390

08/28/1985 2 CADWR — 6.9 339

10N/10W-13K5 — 08/08/1974 2 CADWR — 7.3 530

11N/10W-8P1 — 08/09/1972 2 CADWR — 7.0 410

09/22/1982 2 CADWR — 6.8 365

08/25/1992 2 CADWR — 7.2 416

09/17/2001 2 CADWR — — —

09/24/2003 2 CADWR — 7.0 437

11N/10W-28M1 — 10/19/1951 2 CADWR — — —

03/20/1952 2 CADWR — — —

04/16/1952 2 CADWR — — —

11N/10W-28N1 — 01/09/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/__/1961 2 CADWR — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 57
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

USGS 

identification 

No.

Sample

 date

(mm/dd/yyyy)

Collecting 

and analyzing 

agency

Oxygen, 

dissolved

(mg/L)

[00300]

pH,

field

 (standard 

units)

[00400]

Specific

 conductance, 

field 

(μS/cm)

 [00095]

09/19/1963 2 CADWR — — —

09/23/1964 2 CADWR — — —

09/08/1969 2 CADWR — 7.3 365

07/12/1979 2 CADWR — 7.1 388

08/31/1989 2 CADWR — 7.0 401

09/18/2002 2 CADWR — 6.9 (L) 252 (L)

11N/10W-29H3 384628122592701 09/29/2004 USGS 0.6 7.2 440

11N/10W-33A1 — 10/19/1951 2 CADWR — — —

03/20/1952 2 CADWR — — —

04/16/1952 2 CADWR — — —

01/09/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/__/1961 2 CADWR — — —

09/19/1963 2 CADWR — — —

11N/10W-33__ — 01/16/1956 2 CADWR — — —

11N/10W-33G1 — 10/19/1951 2 CADWR — — —

03/20/1952 2 CADWR — — —

04/17/1952 2 CADWR — — —

01/10/1957 2 CADWR — — —

07/__/1958 2 CADWR — — —

09/__/1959 2 CADWR — — —

09/__/1961 2 CADWR — — —

09/19/1963 2 CADWR — — —

09/23/1964 2 CADWR — — —

11N/10W-34D1 — 10/18/1951 2 CADWR — — —

11N/10W-34D2 — 10/18/1951 2 CADWR — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

58 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

Sample 

date

(mm/dd/yyyy)

Temperature, 

water

°C

 [00010]

Hardness, 

total 

(mg/L as 

CaCO3)

[00900]

Calcium, 

dissolved 

(mg/L)

 [00915]

Magnesium, 

dissolved 

(mg/L)

[00925]

Potassium, 

dissolved 

(mg/L)

 [00935]

Sodium,

dissolved 

 (mg/L)

 [00930]

Streamflow-measurement stations

Russian River at Digger Bend 

near Healdsburg 11/05/2003 114.5 — — — — —

08/19/2004 125.5 — — — — —

Russian River near Healdsburg 05/08/1951 — 110 24 13 0.9 6.4

09/09/1951 — 130 28 15 1 11

05/19/1952 — 110 22 13 0.9 8.1

10/06/1952 — 110 26 11 1.1 13

05/04/1953 — 110 23 12 1.1 8.7

09/14/1953 — 110 23 12 1 9.2

05/03/1954 — 110 25 12 0.8 7.8

09/13/1954 — 110 25 12 1.3 14

05/02/1955 — 110 25 11 0.9 8.7

09/12/1955 — 120 28 12 1.2 18

05/07/1956 — 110 28 9.8 1.2 11

09/11/1956 — 120 27 14 1.4 14

05/06/1957 — 120 25 13 0.8 7.8

09/10/1957 — 120 24 15 1.4 8.7

05/09/1958 — 130 28 14 1.7 8.6

09/12/1958 — 120 26 14 1.2 7.4

05/11/1959 — 130 25 16 1.4 8.4

09/04/1959 — 110 23 12 1.5 8.5

05/09/1960 — 110 23 13 1.3 7.3

09/14/1960 — 110 23 13 1 9.8

05/03/1961 — 110 23 12 1.4 9.5

09/06/1961 — 98 24 9.2 1 7

05/08/1962 — 130 28 15 1.2 9.8

09/11/1962 — 110 26 12 0.8 8.1

05/06/1963 — 110 22 14 1.2 6.8

09/11/1963 — 110 25 13 1 7.4

05/12/1964 — 140 33 15 1 9.2

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 59
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

Sample 

date

(mm/dd/yyyy)

Temperature, 

water

°C

 [00010]

Hardness, 

total 

(mg/L as 

CaCO3)

[00900]

Calcium, 

dissolved 

(mg/L)

 [00915]

Magnesium, 

dissolved 

(mg/L)

[00925]

Potassium, 

dissolved 

(mg/L)

 [00935]

Sodium,

dissolved 

 (mg/L)

 [00930]

09/02/1964 — 120 27 13 1 8.8

05/12/1965 — 120 28 11 1.3 7.4

09/14/1965 — 120 26 12 1.3 8.3

05/03/1966 — 120 26 13 1.1 8.8

09/23/1966 — 120 25 13 1.2 8

Wells

9N/8W-6M2 09/27/2004 22.0 170 34.5 19.2 1.3 76.7

9N/8W-7Q1 01/15/1957 16 24 3.8 3.5 5.1 75

07/15/1958 — 16 1 3 4.9 131

09/15/1959 — 17 4.8 1.2 6.2 134

09/15/1960 — 15 4 1 4 138

08/21/1961 — 18 3.7 2.2 5.0 118

09/19/1963 — 13 3.6 1.0 4.0 132

09/23/1964 — 12 2.6 1.3 5.4 132

07/08/1969 27 13 4.1 0.7 5.8 130

07/16/1980 27 13 2 2 5.3 132

9N/8W-18C1 09/15/2004 18.0 — — — — —

9N/9W-1K1 06/12/1975 17 162 26 23 0.7 12

08/28/1986 19 168 26 25 0.8 12

08/27/1998 19.0 175 29 25 0 13

09/18/2002 16.5 185 31 26 0.6 9

9N/9W-1P1 01/08/1957 9 203 48 20 1.0 13

07/__/1958 — 169 28 24 0.3 11

09/__/1959 — 141 25 19 0.8 12

09/__/1960 — 148 21 23 1 13

09/__/1961 — 144 19 23 0.7 10

09/19/1963 — 122 17 19 0.8 13

07/08/1969 16 167 28 24 0.5 8.0

07/26/1973 14 184 30 26 0.6 9.2

08/10/1983 16 165 28 23 0.6 9

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

60 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

Sample 

date

(mm/dd/yyyy)

Temperature, 

water

°C

 [00010]

Hardness, 

total 

(mg/L as 

CaCO3)

[00900]

Calcium, 

dissolved 

(mg/L)

 [00915]

Magnesium, 

dissolved 

(mg/L)

[00925]

Potassium, 

dissolved 

(mg/L)

 [00935]

Sodium,

dissolved 

 (mg/L)

 [00930]

09/01/1993 15.6 206 33 30 0.6 10

09/18/2002 18.5 149 25 21 0.8 13

9N/9W-4G1 10/23/1951 — 110 28 9.8 2.3 34

01/08/1957 11 114 28 11 1.7 32

10N/9W-17D1 09/30/2004 19.5 — — — — —

10N/9W-18B1 08/10/1972 17 118 20 16 0.3 17

09/17/1986 17 129 25 16 0.5 16

08/27/1998 19.0 151 26 21 0.9 15

09/18/2002 18.5 156 26 22 0.8 15

09/12/2004 19.0 151 26 21 0.8 15

10N/9W-18N1 06/23/1976 16 147 26 20 0.6 16

08/18/1987 17 145 25 20 0.5 16

08/24/1999 18.1 143 26 19 1 14

09/17/2001 — 154 27 21 1 13

09/24/2003 18.5 168 31 22 0.9 14

10N/9W-18P1 09/28/2004 16.5 190 35.7 24.8 0.90 9.06

10N/9W-18R1 01/10/1957 — 153 31 18 1.1 8.5

07/__/1958 — 169 32 22 0.7 9

09/__/1959 — 146 29 18 0.9 8.4

09/19/1963 — 170 31 22 0.7 8.5

09/23/1964 — 141 34 14 1.2 8.5

10N/9W-19B1 09/27/1951 — 151 44 10 0.4 10

10N/9W-19C1 09/27/1951 — 116 20 16 0.6 11

10N/9W-26L1 01/15/1957 17 242 25 44 0.2 10

07/__/1958 — 256 28 45 0.3 13

09/__/1959 — 263 28 47 0.3 12

12/__/1962 — 265 29 47 0.4 12

09/23/1964 — 274 22 53 0.4 11

07/08/1969 18 309 30 57 0.5 11

09/05/1986 18 325 31 60 0.3 11

10N/9W-26L2 07/25/1973 19 258 30 44 0.1 11

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 61
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

Sample 

date

(mm/dd/yyyy)

Temperature, 

water

°C

 [00010]

Hardness, 

total 

(mg/L as 

CaCO3)

[00900]

Calcium, 

dissolved 

(mg/L)

 [00915]

Magnesium, 

dissolved 

(mg/L)

[00925]

Potassium, 

dissolved 

(mg/L)

 [00935]

Sodium,

dissolved 

 (mg/L)

 [00930]

08/17/1984 18 246 29 42 0.1 11

09/17/2001 — 347 40 60 < 0.5 14

09/24/2003 19.5 406 47 70 <0.5 15

10N/9W-32R3 04/02/1952 17 74 21 5.3 0.8 77

01/15/1957 19 287 78 22 0.7 72

07/__/1958 — 130 36 10 0.7 69

09/__/1959 — 125 37 7.9 3.4 70

09/__/1960 — 89 20 10 1 71

10N/9W-33D1 08/09/1972 18 128 18 20 0.3 11

08/10/1983 18 139 21 21 0.9 12

09/01/1993 18.8 171 24 27 0.8 12

09/17/2001 — 193 26 31 0.8 12

09/24/2003 19.5 193 26 31 0.8 13

10N/10W-12G1 06/12/1975 — 193 33 27 0.8 8.8

08/28/1985 18 160 31 20 0.9 9

10N/10W-13K5 08/08/1974 — 220 44 27 0.7 25

11N/10W-8P1 08/09/1972 — 192 28 30 0.2 10

09/22/1982 18 166 27 24 0.7 9

08/25/1992 17.6 208 32 31 0.9 10

09/17/2001 — 191 32 27 0.7 9

09/24/2003 18.0 203 32 30 0.9 10

11N/10W-28M1 10/19/1951 — 36 6.8 4.6 0.6 140

03/20/1952 — 195 42 22 0.7 8.9

04/16/1952 14 195 45 20 1.1 7.6

11N/10W-28N1 01/09/1957 17 187 30 27 0.6 10

07/__/1958 — 189 47 17 0.7 12

09/__/1959 — 199 47 20 1.0 11

09/__/1961 — 178 43 17 1.0 9.4

09/19/1963 — 183 44 18 1.0 9.8

09/23/1964 — 144 28 18 0.9 8.5

09/08/1969 17 148 32 16 1.3 9.2

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

62 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or State well No.

 (abbreviated 

or local identifier)

Sample 

date

(mm/dd/yyyy)

Temperature, 

water

°C

 [00010]

Hardness, 

total 

(mg/L as 

CaCO3)

[00900]

Calcium, 

dissolved 

(mg/L)

 [00915]

Magnesium, 

dissolved 

(mg/L)

[00925]

Potassium, 

dissolved 

(mg/L)

 [00935]

Sodium,

dissolved 

 (mg/L)

 [00930]

07/12/1979 18 184 44 18 1.0 11

08/31/1989 17 181 43 18 1.0 9

09/18/2002 — 99 23 10 0.9 9

11N/10W-29H3 09/29/2004 18.0 200 38.4 24.5 0.99 13.3

11N/10W-33A1 10/19/1951 — 135 26 17 0.6 12

03/20/1952 — 103 20 13 0.7 16

04/16/1952 — 230 21 43 3.7 145

01/09/1957 14 153 32 18 0.8 14

07/__/1958 — 115 23 14 1.0 12

09/__/1959 — 111 24 12 1.4 11

09/__/1961 — 103 22 12 1.2 9.2

09/19/1963 — 165 31 21 1.5 24

11N/10W-33__ 01/16/1956 — 103 17 15 0.7 27

11N/10W-33G1 10/19/1951 — 14 4.0 1.0 9.2 112

03/20/1952 — 55 11 6.7 0.7 15

04/17/1952 13 61 12 7.5 1.4 17

01/10/1957 9 54 10 7.1 0.8 15

07/__/1958 — 65 13 8 1.0 18

09/__/1959 — 49 9.2 6.3 0.6 16

09/__/1961 — 59 10 8.3 0.9 15

09/19/1963 — 50 9.6 6.3 1.6 15

09/23/1964 — 52 11 6.0 0.7 14

11N/10W-34D1 10/18/1951 — 400 43 71 25 39

11N/10W-34D2 10/18/1951 — 820 139 115 28 41

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 63
Stream site identifier

 or state well No.

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Alkalinity, 

field

 (mg/L as 

CaCO3)

 [29802]

Bicarbonate

(mg/L)

 [00440]

Bromide,

 dissolved

(mg/L)

 [71870]

Chloride, 

dissolved

(mg/L)

 [00940]

Fluoride,

 dissolved 

mg/L)

 [00950]

Iodide,

 dissolved

 (mg/L)

 [71865]

Streamflow-measurement stations

Russian River at Digger 

Bend near Healdsburg 11/05/2003 — — — — — —

08/19/2004 — — — — — —

Russian River near 

Healdsburg 05/08/1951 — 133 — 4.2 — —

09/09/1951 — 162 — 5.5 0 —

05/19/1952 — 133 — 5.5 0.2 —

10/06/1952 — 143 — 5.8 0 —

05/04/1953 — 126 — 5.5 0.2 —

09/14/1953 — 133 — 5 0 —

05/03/1954 — 135 — 3.6 0.1 —

09/13/1954 — 145 — 9.8 0.1 —

05/02/1955 — 129 — 7.5 0.1 —

09/12/1955 — 164 — 12 0.1 —

05/07/1956 — 140 — 4.6 0.3 —

09/11/1956 — 165 — 9.1 0 —

05/06/1957 — 138 — 5 0.2 —

09/10/1957 — 156 — 5.5 0.2 —

05/09/1958 — 154 — 5 0 —

09/12/1958 — 148 — 7 0 —

05/11/1959 — 159 — 7 0.1 —

09/04/1959 — 136 — 4.2 0 —

05/09/1960 — 135 — 5 0 —

09/14/1960 — 143 — 4.8 0.1 —

05/03/1961 — 130 — 3.8 0.2 —

09/06/1961 — 120 — 2.2 0.1 —

05/08/1962 — 153 — 4.5 0 —

09/11/1962 — 133 — 4 0 —

05/06/1963 — 137 — 3.8 0.2 —

09/11/1963 — 141 — 5.8 0.1 —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

64 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
See footnotes at end of table.

Stream site identifier

 or state well No.

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Alkalinity, 

field

 (mg/L as 

CaCO3)

 [29802]

Bicarbonate

(mg/L)

 [00440]

Bromide,

 dissolved

(mg/L)

 [71870]

Chloride, 

dissolved

(mg/L)

 [00940]

Fluoride,

 dissolved 

mg/L)

 [00950]

Iodide,

 dissolved

 (mg/L)

 [71865]

05/12/1964 — 171 — 8.5 0.2 —

09/02/1964 — 145 — 4.8 — —

05/12/1965 — 137 — 4.2 — —

09/14/1965 — 140 — 4 — —

05/03/1966 — 145 — 5.2 — —

09/23/1966 — 140 — 3.2 — —

Wells

9N/8W-6M2 09/27/2004 298 3365 0.11 13.2 0.3 0.069

9N/8W-7Q1 01/15/1957 — 218 — 9.9 0.4 —

07/15/1958 — 308 — 41 0.8 —

09/15/1959 — 292 — 38 0.9 —

09/15/1960 — 243 — 42 0.72 —

08/21/1961 — 287 — 33 0.8 —

09/19/1963 257 270 — 38 1.0 —

09/23/1964 251 306 — 36 — —

07/08/1969 — 299 — 18 — —

07/16/1980 252 3307 — 37 — —

9N/8W-18C1 09/15/2004 — — — — — —

9N/9W-1K1 06/12/1975 — 193 — 6 — —

08/28/1986 167 3204 — 6 — —

08/27/1998 162 3198 — 6 — —

09/18/2002 192 3234 — 8 — —

9N/9W-1P1 01/08/1957 — 255 — 8.5 0 —

07/__/1958 — 191 — 11 0 —

09/__/1959 — 172 — 4.8 0.2 —

09/__/1960 — 170 — 14 0.11 —

09/__/1961 — 175 — 6.2 0.2 —

09/19/1963 126 154 — 9.0 0.1 —

07/08/1969 — 194 — 4.3 — —

07/26/1973 — 192 — 6.2 — —

08/10/1983 160 3195 — 5 — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

Appendix A 65
See footnotes at end of table.

Stream site identifier

 or state well No.

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Alkalinity, 

field

 (mg/L as 

CaCO3)

 [29802]

Bicarbonate

(mg/L)

 [00440]

Bromide,

 dissolved

(mg/L)

 [71870]

Chloride, 

dissolved

(mg/L)

 [00940]

Fluoride,

 dissolved 

mg/L)

 [00950]

Iodide,

 dissolved

 (mg/L)

 [71865]

09/01/1993 174 3212 — 9 — —

09/18/2002 162 3198 — 6 — —

9N/9W-4G1 10/23/1951 — 208 — 10 0 —

01/08/1957 — 206 — 15 0 —

10N/9W-17D1 09/30/2004 — — — — — —

10N/9W-18B1 08/10/1972 — 125 — 12 — —

09/17/1986 91 3111 — 17 — —

08/27/1998 139 3 170 — 13 — —

09/18/2002 148 3180 — 15 — —

09/12/2004 126 3154 — 14 — —

10N/9W-18N1 06/23/1976 — 151 — 7.6 — —

08/18/1987 122 3149 — 6 — —

08/24/1999 125 3152 — 6 — —

09/17/2001 135 3165 — 8 — —

09/24/2003 144 3176 — 8 — —

10N/9W-18P1 09/28/2004 167 3204 0.17 5.94 <0.2 E0.001

10N/9W-18R1 01/10/1957 — 184 — 8.4 0 —

07/__/1958 — 204 — 5 0 —

09/__/1959 — 170 — 4.8 0.1 —

09/19/1963 156 170 — 6.5 0.1 —

09/23/1964 136 150 — 4.5 — —

10N/9W-19B1 09/27/1951 — 170 — 6.0 0.1 —

10N/9W-19C1 09/27/1951 — 122 — 8.0 0.1 —

10N/9W-26L1 01/15/1957 — 282 — 7.2 0.1 —

07/__/1958 — 281 — 14 0.2 —

09/__/1959 — 278 — 5.8 0 —

12/__/1962 — 300 — 8.3 0.2 —

09/23/1964 252 275 — 7.0 — —

07/08/1969 — 310 — 8.0 — —

09/05/1986 276 3337 — 11 — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

66 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
See footnotes at end of table.

Stream site identifier

 or state well No.

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Alkalinity, 

field

 (mg/L as 

CaCO3)

 [29802]

Bicarbonate

(mg/L)

 [00440]

Bromide,

 dissolved

(mg/L)

 [71870]

Chloride, 

dissolved

(mg/L)

 [00940]

Fluoride,

 dissolved 

mg/L)

 [00950]

Iodide,

 dissolved

 (mg/L)

 [71865]

10N/9W-26L2 07/25/1973 — 193 — 10 — —

08/17/1984 208 3254 — 7 — —

09/17/2001 202 3246 — 23 — —

09/24/2003 196 3239 — 22 — —

10N/9W-32R3 04/02/1952 — 247 — 8.2 0.8 —

01/15/1957 — 488 — 12 0.5 —

07/__/1958 — 294 — 15 0.5 —

09/__/1959 — 289 — 12 0.4 —

09/__/1960 — 234 — 13 0.90 —

10N/9W-33D1 08/09/1972 — 150 — 8.3 — —

08/10/1983 131 3160 — 8 — —

09/01/1993 137 3167 — 10 — —

09/17/2001 145 3177 — 14 — —

09/24/2003 146 3178 — 15 — —

10N/10W-12G1 06/12/1975 — 236 — 0.0 — —

08/28/1985 162 3198 — 4 — —

10N/10W-13K5 08/08/1974 — 309 — 3.8 — —

11N/10W-8P1 08/09/1972 — 177 — 8.8 — —

09/22/1982 139 3170 — 5 — —

08/25/1992 148 3180 — 12 — —

09/17/2001 159 3194 — 11 — —

09/24/2003 168 3205 — 12 — —

11N/10W-28M1 10/19/1951 — 384 — 20 0.1 —

03/20/1952 — 218 — 5.8 0 —

04/16/1952 — 237 — 3.0 0 —

11N/10W-28N1 01/09/1957 — 226 — 5.7 0.0 —

07/__/1958 — 235 — 12 0.2 —

09/__/1959 — 246 — 8.4 0.0 —

09/__/1961 — 222 — 4.6 0.0 —

09/19/1963 185 222 — 7.5 0.1 —

09/23/1964 148 180 — 4.2 — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

Appendix A 67
See footnotes at end of table.

Stream site identifier

 or state well No.

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Alkalinity, 

field

 (mg/L as 

CaCO3)

 [29802]

Bicarbonate

(mg/L)

 [00440]

Bromide,

 dissolved

(mg/L)

 [71870]

Chloride, 

dissolved

(mg/L)

 [00940]

Fluoride,

 dissolved 

mg/L)

 [00950]

Iodide,

 dissolved

 (mg/L)

 [71865]

09/08/1969 — 181 — 4.9 — —

07/12/1979 167 3204 — 9 — —

08/31/1989 182 3222 — 5 — —

09/18/2002 110 3134 — 7 — —

11N/10W-29H3 09/29/2004 189 3232 0.07 9.82 <0.2 0.007

11N/10W-33A1 10/19/1951 — 157 — 14 0 —

03/20/1952 — 142 — 7.5 0 —

04/16/1952 — 546 — 78 0.0 —

01/09/1957 — 195 — 10 0.0 —

07/__/1958 — 147 — 13 0.2 —

09/__/1959 — 144 — 7.5 0.2 —

09/__/1961 — 134 — 4.6 0.1 —

09/19/1963 177 206 — 18 0.1 —

11N/10W-33__ 01/16/1956 — 159 — 13 0 —

11N/10W-33G1 10/19/1951 — 133 — 110 0.8 —

03/20/1952 — 53 — 13 0 —

04/17/1952 — 57 — 20 0.0 —

01/10/1957 — 61 — 21 0.0 —

07/__/1958 — 63 — 30 0 —

09/__/1959 — 40 — 24 0.0 —

09/__/1961 — 55 — 21 0.1 —

09/19/1963 39 47 — 18 0.1 —

09/23/1964 45 55 — 17 — —

11N/10W-34D1 10/18/1951 — 572 — 20 0.1 —

11N/10W-34D2 10/18/1951 — 1,090 — 29 0 —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

68 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or state well No. 

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Silica, 

dissolved

(mg/L)

 [00955]

Sulfate, 

dissolved 

(mg/L)

 [00945]

Solids, 

sum of 

constituents,

 dissolved

 (mg/L)

 [70301]

Solids, residue 

on evaporation

 at 180°C 

(mg/L)

 [70300]

Nitrogen, 

ammonia, 

dissolved 

(mg/L)

 [00608]

Nitrite plus 

nitrate as N, 

dissolved 

(mg/L)

 [00631]

Streamflow-measurement stations

Russian River at 

Digger Bend near 

Healdsburg 11/05/2003 — — — — — —

08/19/2004 — — — — — —

Russian River near 

Healdsburg 05/08/1951 16 14 145 — — —

09/09/1951 14 12 166 — — —

05/19/1952 23 11 150 — — —

10/06/1952 9.8 8.3 146 — — —

05/04/1953 16 12 142 — — —

09/14/1953 14 9.6 140 — — —

05/03/1954 14 11 141 — — —

09/13/1954 13 9.3 159 — — —

05/02/1955 5.6 13 137 — — —

09/12/1955 12 7.8 176 — — —

05/07/1956 16 12 154 — — —

09/11/1956 17 8.1 174 — — —

05/06/1957 18 12 151 — — —

09/10/1957 18 2.9 153 — — —

05/09/1958 19 12 165 — — —

09/12/1958 13 7.7 151 — — —

05/11/1959 13 8.6 160 — — —

09/04/1959 11 7.2 135 — — —

05/09/1960 15 11 144 — — —

09/14/1960 17 9 148 — — —

05/03/1961 13 11 140 — — —

09/06/1961 12 7 123 — — —

05/08/1962 15 15 166 — — —

09/11/1962 12 10 141 — — —

05/06/1963 21 11 149 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 69
Stream site identifier 

or state well No. 

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Silica, 

dissolved

(mg/L)

 [00955]

Sulfate, 

dissolved 

(mg/L)

 [00945]

Solids, 

sum of 

constituents,

 dissolved

 (mg/L)

 [70301]

Solids, residue 

on evaporation

 at 180°C 

(mg/L)

 [70300]

Nitrogen, 

ammonia, 

dissolved 

(mg/L)

 [00608]

Nitrite plus 

nitrate as N, 

dissolved 

(mg/L)

 [00631]

09/11/1963 15 9 146 — — —

05/12/1964 12 15 179 — — —

09/02/1964 12 11 150 — — —

05/12/1965 14 14 148 153 — —

09/14/1965 13 10 144 148 — —

05/03/1966 13 14 153 154 — —

09/23/1966 13 11 144 146 — —

Wells

9N/8W-6M2 09/27/2004 38.1 21.7 385 381 0.16 E0.04

9N/8W-7Q1 01/15/1957 72 2.1 279 — — —

07/15/1958 41 0 — 444 — —

09/15/1959 74 1.0 — — — —

09/15/1960 55 1 401 — — —

08/21/1961 95 0.0 400 — — —

09/19/1963 83 1.0 — 416 — —

09/23/1964 — 1.0 — 425 — —

07/08/1969 — 0.5 — 402 — —

07/16/1980 — 0 — 436 — —

9N/8W-18C1 09/15/2004 — — — — — —

9N/9W-1K1 06/12/1975 — 18 — 209 — —

08/28/1986 — 15 — 201 — —

08/27/1998 — 26 — 214 — —

09/18/2002 — 28 — 262 — —

9N/9W-1P1 01/08/1957 18 5.8 242 — — —

07/__/1958 24 14 — 274 — —

09/__/1959 28 11 195 — — —

09/__/1960 19 13 190 — — —

09/__/1961 16 12 175 — — —

09/19/1963 36 5 — 179 — —

07/08/1969 — 18 — 150 — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

70 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or state well No. 

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Silica, 

dissolved

(mg/L)

 [00955]

Sulfate, 

dissolved 

(mg/L)

 [00945]

Solids, 

sum of 

constituents,

 dissolved

 (mg/L)

 [70301]

Solids, residue 

on evaporation

 at 180°C 

(mg/L)

 [70300]

Nitrogen, 

ammonia, 

dissolved 

(mg/L)

 [00608]

Nitrite plus 

nitrate as N, 

dissolved 

(mg/L)

 [00631]

07/26/1973 — 28 — 215 — —

08/10/1983 — 18 — 204 — —

09/01/1993 — 34 — 244 — —

09/18/2002 — 17 — 215 — —

9N/9W-4G1 10/23/1951 30 3.0 220 — — —

01/08/1957 31 1.0 222 — — —

10N/9W-17D1 09/30/2004 — — — — — —

10N/9W-18B1 08/10/1972 — 18 — 187 — —

09/17/1986 — 31 — 212 — —

08/27/1998 — 29 — — — —

09/18/2002 — 27 — 240 — —

09/12/2004 — 32 — 215 — —

10N/9W-18N1 06/23/1976 25 38 — 228 — —

08/18/1987 — 35 — 211 — —

08/24/1999 — 33 — 210 — —

09/17/2001 — 33 — 224 — —

09/24/2003 — 35 — 226 — —

10N/9W-18P1 09/28/2004 24.9 26.2 237 231 <0.04 1.89

10N/9W-18R1 01/10/1957 19 9.6 189 — — —

07/__/1958 7 6 — 254 — —

09/__/1959 21 13 — — — —

09/19/1963 25 13 — 202 — —

09/23/1964 — 13 — 154 — —

10N/9W-19B1 09/27/1951 18 18 198 — — —

10N/9W-19C1 09/27/1951 25 23 173 — — —

10N/9W-26L1 01/15/1957 36 13 288 — — —

07/__/1958 35 11 — 384 — —

09/__/1959 39 11 — 307 — —

12/__/1962 38 12 313 — — —

09/23/1964 — 16 — 325 — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 71
Stream site identifier 

or state well No. 

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Silica, 

dissolved

(mg/L)

 [00955]

Sulfate, 

dissolved 

(mg/L)

 [00945]

Solids, 

sum of 

constituents,

 dissolved

 (mg/L)

 [70301]

Solids, residue 

on evaporation

 at 180°C 

(mg/L)

 [70300]

Nitrogen, 

ammonia, 

dissolved 

(mg/L)

 [00608]

Nitrite plus 

nitrate as N, 

dissolved 

(mg/L)

 [00631]

07/08/1969 — 32 — 307 — —

09/05/1986 — 43 — 378 — —

10N/9W-26L2 07/25/1973 — 73 — 322 — —

08/17/1984 — 51 — 305 — —

09/17/2001 — 135 — 464 — —

09/24/2003 — 196 — 551 — —

10N/9W-32R3 04/02/1952 52 8.1 306 — — —

01/15/1957 43 23 492 — — —

07/__/1958 38 16 — 364 — —

09/__/1959 51 24 350 — — —

09/__/1960 34 25 292 — — —

10N/9W-33D1 08/09/1972 — 13 — 162 — —

08/10/1983 — 21 — 190 — —

09/01/1993 — 33 — 215 — —

09/17/2001 — 45 — 274 — —

09/24/2003 — 44 — 258 — —

10N/10W-12G1 06/12/1975 — 12 — 219 — —

08/28/1985 — 15 — 189 — —

10N/10W-13K5 08/08/1974 — 15 — 313 — —

11N/10W-8P1 08/09/1972 — 40 — 254 — —

09/22/1982 — 30 — 217 — —

08/25/1992 — 37 — 246 — —

09/17/2001 — 39 — 262 — —

09/24/2003 — 39 — 257 — —

11N/10W-28M1 10/19/1951 30 14 409 — — —

03/20/1952 15 13 231 — — —

04/16/1952 16 13 224 — — —

11N/10W-28N1 01/09/1957 25 14 229 — — —

07/__/1958 14 9 — 304 — —

09/__/1959 19 12 240 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

72 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or state well No. 

(abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Silica, 

dissolved

(mg/L)

 [00955]

Sulfate, 

dissolved 

(mg/L)

 [00945]

Solids, 

sum of 

constituents,

 dissolved

 (mg/L)

 [70301]

Solids, residue 

on evaporation

 at 180°C 

(mg/L)

 [70300]

Nitrogen, 

ammonia, 

dissolved 

(mg/L)

 [00608]

Nitrite plus 

nitrate as N, 

dissolved 

(mg/L)

 [00631]

09/__/1961 21 9.4 215 — — —

09/19/1963 20 12 — 229 — —

09/23/1964 — 1.0 — 194 — —

09/08/1969 — 17 — 161 — —

07/12/1979 — 23 — 228 — —

08/31/1989 — 15 — 216 — —

09/18/2002 — 11 — 151 — —

11N/10W-29H3 09/29/2004 24.8 19.1 249 254 <0.04 0.62

11N/10W-33A1 10/19/1951 65 8.8 224 — — —

03/20/1952 16 9.4 156 — — —

04/16/1952 46 7.2 613 — — —

01/09/1957 11 8.6 193 — — —

07/__/1958 27 5 — 204 — —

09/__/1959 19 9.0 156 — — —

09/__/1961 17 5.1 139 — — —

09/19/1963 82 9.0 — 298 — —

11N/10W-33__ 01/16/1956 24 7.8 — — — —

11N/10W-33G1 10/19/1951 76 9.3 391 — — —

03/20/1952 31 14 — 132 — —

04/17/1952 33 13 — 144 — —

01/10/1957 35 1.0 — 127 — —

07/__/1958 19 7 — 164 — —

09/__/1959 35 4.0 129 — — —

09/__/1961 36 4.4 143 — — —

09/19/1963 38 3.0 — 138 — —

09/23/1964 — 1.0 — 130 — —

11N/10W-34D1 10/18/1951 31 1.3 518 — — —

11N/10W-34D2 10/18/1951 24 3.3 934 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 73
Stream site identifier

 or state well No. 

(abbreviated or 

local identifier)

Sample

date

(mm/dd/yyyy)

Nitrate as NO3, 

dissolved

 (mg/L) 

Nitrogen,

nitrite,

dissolved 

(mg/L)

 [00613]

Phosphorus, 

orthophosphate, 

dissolved

(mg/L)

 [00671]

Arsenic,

 dissolved

 (μg/L)

 [01000]

Barium,

dissolved 

(μg/L)

 [01005]

Streamflow-measurement stations

Russian River at Digger 

Bend near Healdsburg 11/05/2003 — — — — —

08/19/2004 — — — — —

Russian River near 

Healdsburg 05/08/1951 — — — — —

09/09/1951 — — — — —

05/19/1952 — — — — —

10/06/1952 — — — — —

05/04/1953 — — — — —

09/14/1953 — — — — —

05/03/1954 — — — — —

09/13/1954 — — — — —

05/02/1955 — — — — —

09/12/1955 — — — — —

05/07/1956 — — — — —

09/11/1956 — — — — —

05/06/1957 — — — — —

09/10/1957 — — — — —

05/09/1958 — — — — —

09/12/1958 — — — — —

05/11/1959 — — — — —

09/04/1959 — — — — —

05/09/1960 — — — — —

09/14/1960 — — — — —

05/03/1961 — — — — —

09/06/1961 — — — — —

05/08/1962 — — — — —

09/11/1962 — — — — —

05/06/1963 — — — — —

09/11/1963 — — — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

74 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier

 or state well No. 

(abbreviated or 

local identifier)

Sample

date

(mm/dd/yyyy)

Nitrate as NO3, 

dissolved

 (mg/L) 

Nitrogen,

nitrite,

dissolved 

(mg/L)

 [00613]

Phosphorus, 

orthophosphate, 

dissolved

(mg/L)

 [00671]

Arsenic,

 dissolved

 (μg/L)

 [01000]

Barium,

dissolved 

(μg/L)

 [01005]

05/12/1964 — — — — —

09/02/1964 — — — — —

05/12/1965 — — — — —

09/14/1965 — — — — —

05/03/1966 — — — — —

09/23/1966 — — — — —

Wells

9N/8W-6M2 09/27/2004 4 E0.2 <0.008 0.09 1.5 247

9N/8W-7Q1 01/15/1957 0.2 — — — —

07/15/1958 0 — — — —

09/15/1959 0.2 — — — —

09/15/1960 0 — — — —

08/21/1961 0.5 — — — —

09/19/1963 1.0 — — — —

09/23/1964 0.3 — — — —

07/08/1969 1.2 — — — —

07/16/1980 0.0 — — — —

9N/8W/-18C1 09/15/2004 — — — — —

9N/9W-1K1 06/12/1975 2.4 — — 0 —

08/28/1986 0.6 — — — —

08/27/1998 3 — — — —

09/18/2002 2.1 — — — —

9N/9W-1P1 01/08/1957 0.1 — — — —

07/__/1958 10 — — — —

09/__/1959 4.8 — — — —

09/__/1960 1 — — — —

09/__/1961 2.1 — — — —

09/19/1963 5 — — — —

07/08/1969 4.2 — — — —

07/26/1973 9.8 — — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 75
Stream site identifier

 or state well No. 

(abbreviated or 

local identifier)

Sample

date

(mm/dd/yyyy)

Nitrate as NO3, 

dissolved

 (mg/L) 

Nitrogen,

nitrite,

dissolved 

(mg/L)

 [00613]

Phosphorus, 

orthophosphate, 

dissolved

(mg/L)

 [00671]

Arsenic,

 dissolved

 (μg/L)

 [01000]

Barium,

dissolved 

(μg/L)

 [01005]

08/10/1983 2.3 — — — —

09/01/1993 9.1 — — — —

09/18/2002 2 — — — —

9N/9W-4G1 10/23/1951 0.0 — — — —

01/08/1957 0.8 — — — —

10N/9W-17D1 09/30/2004 — — — — —

10N/9W-18B1 08/10/1972 22 — — — —

09/17/1986 14 — — — —

08/27/1998 9.5 — — — —

09/18/2002 10.1 — — — —

09/12/2004 10.8 — — — —

10N/9W-18N1 06/23/1976 9.0 — — — —

08/18/1987 6.9 — — — —

08/24/1999 8.6 — — — —

09/17/2001 9.7 — — — —

09/24/2003 10.9 — — — —

10N/9W-18P1 09/28/2004 4 8.5 <0.008 0.01 E0.1 172

10N/9W-18R1 01/10/1957 0.8 — — — —

07/__/1958 2 — — — —

09/__/1959 5.3 — — — —

09/19/1963 5.6 — — — —

09/23/1964 0.2 — — — —

10N/9W-19B1 09/27/1951 8.3 — — — —

10N/9W-19C1 09/27/1951 9.1 — — — —

10N/9W-26L1 01/15/1957 13 — — — —

07/__/1958 14 — — — —

09/__/1959 13 — — — —

12/__/1962 13 — — — —

09/23/1964 13 — — — —

07/08/1969 19 — — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

76 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier

 or state well No. 

(abbreviated or 

local identifier)

Sample

date

(mm/dd/yyyy)

Nitrate as NO3, 

dissolved

 (mg/L) 

Nitrogen,

nitrite,

dissolved 

(mg/L)

 [00613]

Phosphorus, 

orthophosphate, 

dissolved

(mg/L)

 [00671]

Arsenic,

 dissolved

 (μg/L)

 [01000]

Barium,

dissolved 

(μg/L)

 [01005]

09/05/1986 8.8 — — — —

10N/9W-26L2 07/25/1973 37 — — — —

08/17/1984 4.9 — — — —

09/17/2001 12.1 — — — —

09/24/2003 13.6 — — — —

10N/9W-32R3 04/02/1952 0 — — — —

01/15/1957 0.3 — — — —

07/__/1958 0 — — — —

09/__/1959 1.6 — — — —

09/__/1960 0 — — — —

10N/9W-33D1 08/09/1972 7.7 — — — —

08/10/1983 8.8 — — — —

09/01/1993 14 — — — —

09/17/2001 20.7 — — — —

09/24/2003 21.8 — — — —

10N/10W-12G1 06/12/1975 1.1 — — — —

08/28/1985 1.0 — — — —

10N/10W-13K5 08/08/1974 1.6 — — 0 —

11N/10W-8P1 08/09/1972 18 — — — —

09/22/1982 14 — — — —

08/25/1992 22 — — — —

09/17/2001 13.7 — — — —

09/24/2003 15.4 — — — —

11N/10W-28M1 10/19/1951 0.4 — — — —

03/20/1952 16 — — — —

04/16/1952 1.5 — — — —

11N/10W-28N1 01/09/1957 5.9 — — — —

07/__/1958 0 — — — —

09/__/1959 0.2 — — — —

09/__/1961 0.6 — — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 77
Stream site identifier

 or state well No. 

(abbreviated or 

local identifier)

Sample

date

(mm/dd/yyyy)

Nitrate as NO3, 

dissolved

 (mg/L) 

Nitrogen,

nitrite,

dissolved 

(mg/L)

 [00613]

Phosphorus, 

orthophosphate, 

dissolved

(mg/L)

 [00671]

Arsenic,

 dissolved

 (μg/L)

 [01000]

Barium,

dissolved 

(μg/L)

 [01005]

09/19/1963 1.4 — — — —

09/23/1964 0.3 — — — —

09/08/1969 0.5 — — — —

07/12/1979 4.0 — — — —

08/31/1989 0.3 — — — —

09/18/2002 0.8 — — — —

11N/10W-29H3 09/29/2004 42.8 <0.008 0.03 0.5 203

11N/10W-33A1 10/19/1951 0.4 — — — —

03/20/1952 1.3 — — — —

04/16/1952 0.1 — — — —

01/09/1957 0.7 — — — —

07/__/1958 0 — — — —

09/__/1959 0.6 — — — —

09/__/1961 0.8 — — — —

09/19/1963 0.9 — — — —

11N/10W-33__ 01/16/1956 0 — — — —

11N/10W-33G1 10/19/1951 0.3 — — — —

03/20/1952 14 — — — —

04/17/1952 12 — — — —

01/10/1957 6.6 — — — —

07/__/1958 11 — — — —

09/__/1959 14 — — — —

09/__/1961 20 — — — —

09/19/1963 25 — — — —

09/23/1964 14 — — — —

11N/10W-34D1 10/18/1951 4.2 — — — —

11N/10W-34D2 10/18/1951 14 — — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

78 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or state well No.

 (abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Boron,

dissolved 

(μg/L)

 [01020]

Iron, 

dissolved 

(μg/L)

 [01046]

Lithium,

 dissolved

 (μg/L)

 [01130]

Manganese, 

dissolved

 (μg/L)

 [01056]

Streamflow-measurement stations

Russian River at 

Digger Bend near 

Healdsburg 11/05/2003 — — — —

08/19/2004 — — — —

Russian River near 

Healdsburg 05/08/1951 590 — — —

09/09/1951 670 — — —

05/19/1952 650 0 — —

10/06/1952 860 0 — —

05/04/1953 340 0 — —

09/14/1953 930 20 — —

05/03/1954 380 10 — —

09/13/1954 52,900 10 — —

05/02/1955 160 — — —

09/12/1955 53,500 20 — —

05/07/1956 51,200 20 — —

09/11/1956 52,100 0 — —

05/06/1957 280 10 — —

09/10/1957 540 0 — —

05/09/1958 170 0 — —

09/12/1958 800 0 — —

05/11/1959 500 20 — —

09/04/1959 400 30 — —

05/09/1960 300 20 — —

09/14/1960 500 0 — —

05/03/1961 300 20 — —

09/06/1961 400 — — —

05/08/1962 300 — — —

09/11/1962 400 — — —

05/06/1963 200 — — —

09/11/1963 300 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 79
Stream site identifier 

or state well No.

 (abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Boron,

dissolved 

(μg/L)

 [01020]

Iron, 

dissolved 

(μg/L)

 [01046]

Lithium,

 dissolved

 (μg/L)

 [01130]

Manganese, 

dissolved

 (μg/L)

 [01056]

05/12/1964 500 — — —

09/02/1964 500 — — —

05/12/1965 300 — — —

09/14/1965 200 — — —

05/03/1966 300 — — —

09/23/1966 400 — — —

Wells

9N/8W-6M2 09/27/2004 120 21 14.6 6241

9N/8W-7Q1 01/15/1957 170 — — —

07/15/1958 340 20 — —

09/15/1959 400 — — —

09/15/1960 420 — — —

08/21/1961 320 7120 — —

09/19/1963 400 — — —

09/23/1964 300 20 — —

07/08/1969 500 — — —

07/16/1980 500 — — —

9N/8W-18C1 09/15/2004 — — — —

9N/9W-1K1 06/12/1975 0 720 — 80

08/28/1986 100 — — —

08/27/1998 100 — — —

09/18/2002 <100 — — —

9N/9W-1P1 01/08/1957 51,300 — — —

07/__/1958 100 30 — —

09/__/1959 0 — — —

09/__/1960 0 — — —

09/__/1961 90 6,73,600 — —

09/19/1963 0 — — —

07/08/1969 100 — — —

07/26/1973 0 — — —

08/10/1983 100 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

80 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or state well No.

 (abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Boron,

dissolved 

(μg/L)

 [01020]

Iron, 

dissolved 

(μg/L)

 [01046]

Lithium,

 dissolved

 (μg/L)

 [01130]

Manganese, 

dissolved

 (μg/L)

 [01056]

09/01/1993 <100 — — —

09/18/2002 100 — — —

9N/9W-4G1 10/23/1951 50 — — —

01/08/1957 120 — — —

10N/9W-17D1 09/30/2004 — — — —

10N/9W-18B1 08/10/1972 0 — — —

09/17/1986 100 — — —

08/27/1998 100 — — —

09/18/2002 100 — — —

09/12/2004 100 — — —

10N/9W-18N1 06/23/1976 100 — — —

08/18/1987 100 — — —

08/24/1999 100 — — —

09/17/2001 100 — — —

09/24/2003 200 — — —

10N/9W-18P1 09/28/2004 260 <6.0 6.5 E0.1

10N/9W-18R1 01/10/1957 51,800 — — —

07/__/1958 700 0 — —

09/__/1959 500 — — —

09/19/1963 400 — — —

09/23/1964 400 20 — —

10N/9W-19B1 09/27/1951 180 — — —

10N/9W-19C1 09/27/1951 150 — — —

10N/9W-26L1 01/15/1957 130 — — —

07/__/1958 10 10 — —

09/__/1959 0 — — —

12/__/1962 170 720 — —

09/23/1964 500 10 — —

07/08/1969 100 — — —

09/05/1986 100 — — —

10N/9W-26L2 07/25/1973 100 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System (NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

Appendix A 81
Stream site identifier 

or state well No.

 (abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Boron,

dissolved 

(μg/L)

 [01020]

Iron, 

dissolved 

(μg/L)

 [01046]

Lithium,

 dissolved

 (μg/L)

 [01130]

Manganese, 

dissolved

 (μg/L)

 [01056]

08/17/1984 100 — — —

09/17/2001 100 — — —

09/24/2003 100 — — —

10N/9W-32R3 04/02/1952 590 — — —

01/15/1957 280 — — —

07/__/1958 620 10 — —

09/__/1959 400 — — —

09/__/1960 0 — — —

10N/9W-33D1 08/09/1972 0 — — —

08/10/1983 200 — — —

09/01/1993 <100 — — —

09/17/2001 <100 — — —

09/24/2003 <100 — — —

10N/10W-12G1 06/12/1975 200 — — —

08/28/1985 500 — — —

10N/10W-13K5 08/08/1974 100 71,300 — 8190

11N/10W-8P1 08/09/1972 400 — — —

09/22/1982 400 — — —

08/25/1992 300 — — —

09/17/2001 300 — — —

09/24/2003 300 — — —

11N/10W-28M1 10/19/1951 52,900 — — —

03/20/1952 480 — — —

04/16/1952 240 — — —

11N/10W-28N1 01/09/1957 120 — — —

07/__/1958 350 10 — —

09/__/1959 200 — — —

09/__/1961 290 720 — —

09/19/1963 300 — — —

09/23/1964 400 20 — —

09/08/1969 300 — — —

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

See footnotes at end of table.

82 Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California
Stream site identifier 

or state well No.

 (abbreviated or 

local identifier)

Sample 

date

(mm/dd/yyyy)

Boron,

dissolved 

(μg/L)

 [01020]

Iron, 

dissolved 

(μg/L)

 [01046]

Lithium,

 dissolved

 (μg/L)

 [01130]

Manganese, 

dissolved

 (μg/L)

 [01056]

07/12/1979 800 — — —

08/31/1989 200 — — —

09/18/2002 300 — — —

11N/10W-29H3 09/29/2004 51,350 13 18.8 37

11N/10W-33A1 10/19/1951 30 — — —

03/20/1952 51,800 — — —

04/16/1952 130 — — —

01/09/1957 51,800 — — —

07/__/1958 51,150 30 — —

09/__/1959 600 — — —

09/__/1961 670 740 — —

09/19/1963 54,200 — — —

11N/10W-33__ 01/16/1956 54,200 — — —

11N/10W-33G1 10/19/1951 52,900 — — —

03/20/1952 170 — — —

04/17/1952 320 — — —

01/10/1957 60 — — —

07/__/1958 800 10 — —

09/__/1959 0 — — —

09/__/1961 70 710 — —

09/19/1963 100 — — —

09/23/1964 100 10 — —

11N/10W-34D1 10/18/1951 52,000 — — —

11N/10W-34D2 10/18/1951 54,000 — — —

1

Approximate mid-point of river cross-section on date sampled.

2

Data collected and analyzed by CADWR not in USGS NWIS (National Water Information System) database; parameter codes are not applicable.

3

Bicarbonate value calculated from alkalinity.

4

Nitrate as NO3 value calculated from nitrite plus nitrate as N.

5

Value equals or exceeds the State notification level (California Department of Health Services, 2005).

6

Value equals or exceeds the maximum contaminant level (MCL) or is outside of the acceptable range for primary or secondary Federal and State drinkingwater standards (California Department of Health Services, 2003; U.S. Environmental Protection Agency, 2002).

7

Total recoverable iron.

8

Total recoverable manganese.

Appendix A. Field measurements and laboratory analyses of samples from streamflow-measurement stations and ground-water wells, 

Alexander Valley, Sonoma County, California, 1951–2004—Continued.

[See figure 13 for location of streamflow/measurement stations, and wells. USGS (U.S. Geological Survey) identification number: the unique number for each 

site in USGS NWIS (National Water Information System) database. Collecting and analyzing agency: USGS, U.S. Geological Survey; CADWR, California 

Department of Water Resources. Parameter code, in brackets, is a five-digit number in the USGS computerized data system, National Water Information System 

(NWIS), used to uniquely identify a specific constituent or property. CADWR conductance measurements are referred to as electrical conductance (EC). 

CADWR alkalinities are laboratory values. CaCO3, calcium carbonate; °C, degree Celsius; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per 

liter; μg/L, micrograms per liter; E, value estimated by the USGS National Water Quality Laboratory, Denver Colorado; (L), measured in laboratory; mm/dd/

yyyy, month/day/year; <, actual value is less than value shown; —, no data]

Appendix A 83


METZGER AND OTHERS—Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California—SIR 2006-5115