U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5108

Prepared in cooperation with the Santa Barbara County Water Agency

Geology, Water-Quality, Hydrology, and Geomechanics

of the Cuyama Valley Groundwater Basin, California,

2008–12
Cover. View of the Caliente Range, Cuyama Valley area, Santa Barbara and San Luis Obispo Counties, California. 

(Photography by Joseph Nawikas, U.S. Geological Survey.)
Geology, Water-Quality, Hydrology, and 

Geomechanics of the Cuyama Valley 

Groundwater Basin, California, 2008–12

By Rhett R. Everett, Dennis R. Gibbs, Randall T. Hanson, Donald S. Sweetkind, 

Justin T. Brandt, Sarah E. Falk, and Christopher R. Harich

Prepared in Cooperation with the Santa Barbara County Water Agency

Scientific Investigations Report 2013–5108

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation:

Everett, R.R., Gibbs, D.R., Hanson, R.T., Sweetkind, D.S., Brandt, J.T., Falk, S.E. and Harich, C.R., 2013, Geology, waterquality, hydrology, and geomechanics of the Cuyama Valley groundwater basin, California, 2008–12: 

U.S. Geological Survey Scientific Investigations Report 2013–5108, 62 p. 
iii

Contents

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

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

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

Description of Study Area ................................................................................................................. 2

Geologic Units ............................................................................................................................ 2

Geologic Structure .................................................................................................................... 5

Aquifer System ........................................................................................................................... 5

Accessing Data ................................................................................................................................... 6

Description of the Monitoring Network ................................................................................................... 6

Geology ........................................................................................................................................................ 17

Lithologic Descriptions .................................................................................................................... 17

Geophysical Logs .............................................................................................................................. 17

Temperature Logs ............................................................................................................................. 21

Core Measurements ......................................................................................................................... 22

Geology at the Monitoring Well Sites ............................................................................................ 22

Water-Quality .............................................................................................................................................. 24

Field and Laboratory Methods ........................................................................................................ 24

Comparison Benchmarks ................................................................................................................. 26

Selected Chemical Attributes.......................................................................................................... 26

Major Ions........................................................................................................................................... 27

Nitrate ................................................................................................................................................. 27

Isotope Analyses................................................................................................................................ 27

Age Dating........................................................................................................................................... 29

Arsenic, Iron, and Chromium Species ........................................................................................... 31

Hydrology ..................................................................................................................................................... 32

Rainfall Gaging Stations ................................................................................................................... 32

Streamflow Gaging Stations ............................................................................................................ 32

Cuyama River ............................................................................................................................ 34

Santa Barbara Canyon ............................................................................................................ 35

Groundwater Levels .......................................................................................................................... 35

Manual Measurements ........................................................................................................... 36

Time-Series Water Levels ...................................................................................................... 36

Historic Water Levels .............................................................................................................. 43

Aquifer Tests ...................................................................................................................................... 43

Slug Tests .................................................................................................................................. 43

Pump Tests ................................................................................................................................ 46

Geomechanical Activity ............................................................................................................................ 47

GPS Data ............................................................................................................................................ 47

InSAR Data ......................................................................................................................................... 48

Summary and Conclusions ....................................................................................................................... 56

References Cited ........................................................................................................................................ 59
iv

Figures

1. Map showing the location of Cuyama Valley, including multiple-well monitoring 

sites, selected domestic and supply wells, and hydrologic units, Cuyama Valley, 

Santa Barbara County, California ............................................................................................. 3

2. Map showing geologic formation outcrops, faults, folds, InSAR reference points,

 continuously operating GPS stations, oil wells, and rainfall stations, Cuyama

 Valley, Santa Barbara County, California ............................................................................... 4

3. Geophysical logs, well-construction diagram, and generalized lithologic description 

for multiple-well monitoring site Cuyama Valley Kirschenmann Road, 

Cuyama Valley, Santa Barbara County, California .............................................................. 14

4. Geophysical logs, well-construction diagram, and generalized lithologic 

description for multiple-well monitoring site Cuyama Valley Bell Road, 

Cuyama Valley, Santa Barbara County, California .............................................................. 15

5. Geophysical logs, well-construction diagram, and generalized lithologic 

description for multiple-well monitoring site Cuyama Valley Foothill Road, 

Cuyama Valley, Santa Barbara County, California .............................................................. 16

6. Diagram showing rock-type nomenclature used for lithologic-log descriptions ............... 21

7. Graph showing sonic velocity and bulk density of core CVKR-1C-1 collected from 

the bottom of the Cuyama Valley Kirschenmann Road borehole, Cuyama Valley, 

Santa Barbara County, California ........................................................................................... 23

8. Map showing the location of multiple-well monitoring sites, domestic and supply 

wells, springs, and surface water sites with available water-quality data, 

Cuyama Valley, Santa Barbara County, California .............................................................. 25

9. Piper diagrams depicting major-ion composition for groundwater samples, Cuyama 

Valley, California, collected from A, the selected multiple-well monitoring sites; 

and B, multiple-well monitoring sites, domestic and supply wells grouped by zone .... 28

10. Graphs showing isotopic composition of water samples, Cuyama Valley, California, 

collected from A, selected multiple-well monitoring sites and surface-water sites, 

and B, multiple-well monitoring sites, domestic and supply wells, grouped by 

zone and springs ........................................................................................................................30

11. Historic annual rainfall graphs from four rainfall stations in the study area, Cuyama 

Valley, Santa Barbara County, California .............................................................................. 33

12. Monthly rainfall graphs for three rainfall stations in the study area from June 2008 

to March 2012, Cuyama Valley, Santa Barbara County, California ................................... 33

13. Daily discharge graphs for two streamflow gaging stations on the Cuyama River, 

Cuyama Valley, Santa Barbara County, California .............................................................. 34

14. Daily discharge graphs for streamflow gaging stations in Santa Barbara 

Canyon, Cuyama Valley, Santa Barbara County, California ............................................... 35

15. Map showing the location of multiple-well monitoring sites, domestic, and supply 

wells with available water-level data, Cuyama Valley, Santa Barbara County, 

California .................................................................................................................................... 37

16. Water-level hydrograph from multiple-well monitoring site Cuyama Valley 

Kirschenmann Road from April 8, 2009, to February 20, 2012, Cuyama Valley, 

California .................................................................................................................................... 38

17. Water-level hydrograph from multiple-well monitoring site Cuyama Valley 

Bell Road from September 29, 2009, to March 5, 2012, Cuyama Valley, 

California .................................................................................................................................... 38
v

18. Water-level hydrograph from multiple-well monitoring site Cuyama Valley Foothill 

Road (CVFR) from October 27, 2009, to February 28, 2012, Cuyama Valley, 

California .................................................................................................................................... 39

19. Water-level hydrograph from CUY-02, from January 1, 2008, to March 23, 2012, 

Cuyama Valley, California ........................................................................................................ 40

20. Water-level hydrograph from CUY-05, from January 1, 2008, to February 28, 2012, 

Cuyama Valley, California ........................................................................................................ 41

21. Water-level hydrograph from CUY-07, from January 1, 2008, to February 21, 2012, 

Cuyama Valley, California ........................................................................................................ 41

22. Water-level hydrograph from CUY-12, from January 1, 2008, to March 5, 2012, 

Cuyama Valley, California ........................................................................................................ 42

23. Water-level hydrograph from CUY-35, from January 1, 2008, to March 6, 2012, 

Valley, California ....................................................................................................................... 42

24. Historic water-level hydrographs from 16 selected domestic and supply wells, 

Cuyama Valley, Santa Barbara County, California .............................................................. 44

25. Map showing the location of multiple-well monitoring sites, domestic and supply 

wells with aquifer test data, Cuyama Valley, Santa Barbara County, California ............ 45

26. Graph showing land-surface position, up coordinate, in millimeters, for the GPS 

stations Cuyama High School, Ventucopa Station, McPherson_CS2008, 

Bitter Creek Wildlife Refuge, and OZST_SCGN_CS2000, Cuyama Valley, 

Santa Barbara County, California ........................................................................................... 49

27. Graphs showing daily detrended land-surface position, in millimeters, for the 

GPS station Cuyama High School (CUHS) for the A, north; B, east; and C, up 

direction; and D, water levels in selected wells near CUHS, in feet below land 

surface, Cuyama Valley, Santa Barbara County, California ............................................... 50

28. Graphs showing vertical deformation in Cuyama Valley, Santa Barbara County, 

California, relative to A, first SAR acquisition for the Cuyuma High School 

continuous GPS station; and B, selected reference points ................................................52

29. Conventional InSAR interferogram images for Cuyama Valley, Santa Barbara County, 

California, from A, May 18, 2006, to October 25, 2007; and B, February 7, 2008, to 

April 17, 2008 ...............................................................................................................................53

30. Persistent scatterer InSAR interferogram images for Cuyama Valley, Santa Barbara 

County, California, from A, May 13, 2004, to August 26, 2004; and B, August 31, 

2006, to February 22, 2007 .........................................................................................................54

31. Persistent scatterer InSAR interferogram images for Cuyama Valley, Santa Barbara 

County, California, from March 9, 2006, to November 29, 2007 ..........................................55
vi

Tables

1. Selected characteristics and data availability for wells in the Cuyama Valley 

groundwater basin, Santa Barbara County, California.......................................................... 7

2. Summary of well completion for selected wells, Cuyama Valley, Santa Barbara 

County, California ...................................................................................................................... 10

3. Site identification and data availability for selected springs and surface-water sites 

in the Cuyama Valley groundwater basin, Santa Barbara County, California ................ 13

4. Lithologic log from sieved drill cuttings from multiple-well monitoring site Cuyama 

Valley Kirschenmann Road ..................................................................................................... 18

5. Lithologic log from sieved drill cuttings from multiple-well monitoring site Cuyama 

Valley Bell Road ......................................................................................................................... 19

6. Lithologic log from sieved drill cuttings from multiple-well monitoring site Cuyama 

Valley Foothill Road .................................................................................................................. 20

7. Summary of cores collected from multiple-well monitoring sites, Cuyama Valley 

groundwater basin, Santa Barbara County, California ....................................................... 22

8. Results for analyses of major and minor ions, silica, and total dissolved solids in 

samples collected from selected sites, Cuyama Valley groundwater basin, 

Santa Barbara County, California ........................................................................................... 26

9. Results for analyses of stable isotopes, tritium and carbon-14, estimated age 

since recharge, and nitrate in samples collected from selected sites, Cuyama 

Valley groundwater basin, Santa Barbara County, California ........................................... 27

10. Results for analyses of arsenic, iron, and chromium speciation and dissolved 

oxygen in samples collected from selected well sites, Cuyama Valley, Santa 

Barbara County, California ...................................................................................................... 27

11. Summary of sites with manual water level measurements including period of 

record, number of observation, and minimum and maximum observed water 

levels for selected wells, Cuyama Valley, Santa Barbara County, California ................. 35

12. Summary of slug-test estimates of hydraulic properties for selected multiple-well 

monitoring sites, Cuyama Valley, Santa Barbara County, California ................................ 46

13. Summary of pump-test estimates of hydraulic properties for selected well sites, 

Cuyama Valley, Santa Barbara County, California .............................................................. 46

14. Annual velocities and associated uncertainties for selected GPS monitoring 

stations in the Cuyama study area, reported from the regionally filtered data 

from the U.S. Geological Survey Earthquakes Hazard Program for the period of 

record, Cuyama Valley, Santa Barbara County, California ................................................. 46
vii

Conversion Factors, Datums, and Abbreviated Water-Quality Units

Inch/Pound to SI

Multiply By To obtain

Length

inch (in) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

yard (yd) 0.9144 meter (m)

Area

acre 4,047 square meter (m2

)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

ounce, fluid (fl. oz) 0.02957 liter (L) 

gallon (gal) 3.785 liter (L) 

cubic inch (in3

) 16.39 cubic centimeter (cm3) 

cubic foot (ft3

) 0.02832 cubic meter (m3)

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

) 

Flow rate

acre-foot per day (acre-ft/d) 0.01427 cubic meter per second (m3

/s)

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

/yr)

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per minute (ft/min) 0.3048 meter per minute (m/min)

cubic foot per second (ft3

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

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

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L) 

Specific capacity

gallon per minute per foot [(gal/min)/ft)] 0.2070 liter per second per meter [(L/s)/m]

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Hydraulic gradient

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

Transmissivity*

foot squared per day (ft2

/d) 0.09290 meter squared per day (m2/d) 

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

°F=(1.8×°C)+32

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

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Water-level measurements in this report are given in feet with reference to land-surface datum 

(lsd). Land-surface datum is a datum plane that is approximately at land surface at each well.
viii

*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) which are equivalent to parts per million (ppm) or parts per billion 

(ppb), respectively.

Activities of radiochemical constituents in water are given in picocuries per liter (pCi/L).

Results for stable isotopes in water are reported in delta notation , iE, where the ratio of the 

rarer isotope of an element ( iE) is expressed relative to the more common lighter isotope of that 

element, relative to a standard reference material, and expressed in per mil. 

Abbreviations and Acronyms

bls below land surface

CSU combined standard uncertainty

CUY Cuyama Valley study well

CVBR Cuyama Valley Bell Road

CVFR Cuyama Valley Foothill Road

CVKR Cuyama Valley Kirschenmann Road 

GPS Global Positioning System

MCL maximum contaminant level

MCL-US maximum contaminant level (USEPA)

LSD land surface datum

NWIS National Water Information System (USGS)

OEHHA-PHG Office of Environmental Health Hazard Assessment public health goal

SMCL secondary maximum contaminant level

SMCL-CA California Department of Public Health secondary maximum contaminant level

SMCL-US secondary maximum contaminant level (USEPA)

U.S. United States

USEPA United States Environmental Protection Agency

USGS United States Geological Survey 
ix

Acknowledgements

This study could not have been accomplished without the assistance of personnel from the 

Santa Barbara County Water Agency. In addition, we acknowledge the valuable participation of 

the residents and well owners of the Cuyama Valley who assisted in the study.

Finally, we acknowledge the valuable guidance of U.S. Geological Survey geologists and 

geophysicists of the Earth Surface Processes Group, Earthquake Hazards Group, Coastal 

Marine Geology Group, and Urban Hazards Group and thank them for their efforts supporting 

the selection of sites, collection of data, and subsequent analysis. 
x
Geology, Water-Quality, Hydrology, and Geomechanics of 

the Cuyama Valley Groundwater Basin, California, 2008–12

By Rhett R. Everett, Dennis R. Gibbs, Randall T. Hanson, Donald S. Sweetkind, Justin T. Brandt, Sarah E. Falk, 

and Christopher R. Harich

Differences in the stable-isotopic values of hydrogen and 

oxygen among groundwater samples indicated that water does 

not move freely between different formations or between different zones within the Cuyama Valley. Variations in isotopic 

composition indicated that recharge is derived from several 

different sources. The age of the groundwater, expressed as 

time since recharge, was between 600 and 38,000 years before 

present. Detectable concentrations of tritium indicated that 

younger water, recharged since the early 1950s, is present in 

parts of the groundwater basin.

Hydrologic data were collected from 12 monitoring wells, 

56 domestic and supply wells, 3 surface-water sites, and 4 

rainfall-gaging stations. Rainfall in the valley averaged about 

8 inches annually, whereas the mountains to the south received 

between 12 and 19 inches. Stream discharge records showed 

seasonal variability in surface-water flows ranging from 

no-flow to over 1,500 cubic feet per second. During periods 

when inflow to the valley exceeds outflow, there is potential 

recharge from stream losses to the groundwater system. 

Water-level records included manual quarterly depth-towater measurements collected from 68 wells, time-series data 

collected from 20 of those wells, and historic water levels 

from 16 wells. Hydrographs of the manual measurements 

showed declining water levels in 16 wells, mostly in the 

South-Main zone, and rising water levels in 14 wells, mostly 

in the Southern Ventucopa Uplands. Time-series hydrographs 

showed daily, seasonal, and longer-term effects associated 

with local pumping. Water-level data from the multiple-well 

monitoring sites indicated seasonal fluctuations as great as 

80 feet and water-level differences between aquifers as great 

as 40 feet during peak pumping season. Hydrographs from the 

multiple-well groundwater monitoring sites showed vertical 

hydraulic gradients were upward during the winter months and 

downward during the irrigation season. Historic hydrographs 

showed water-level declines in the Southern-Main, Western 

Basin, Caliente Northern-Main, and Southern Sierra Madre 

zone ranging from 1 to 7 feet per year. Hydrographs of wells 

in the Southern Ventucopa Uplands zone showed several years 

with marked increases in water levels that corresponded to 

increased precipitation in the Cuyama Valley. 

Investigation of hydraulic properties included hydraulic 

conductivity and transmissivity estimated from aquifer tests 

performed on 63 wells. Estimates of horizontal hydraulic 

Abstract 

To assess the water resources of the Cuyama Valley 

groundwater basin in Santa Barbara County, California, a 

series of cooperative studies were undertaken by the U.S. Geological Survey and the Santa Barbara County Water Agency. 

Between 2008 and 2012, geologic, water-quality, hydrologic 

and geomechanical data were collected from selected sites 

throughout the Cuyama Valley groundwater basin. 

Geologic data were collected from three multiple-well 

groundwater monitoring sites and included lithologic descriptions of the drill cuttings, borehole geophysical logs, temperature logs, as well as bulk density and sonic velocity measurements of whole-core samples. 

Generalized lithologic characterization from the monitoring 

sites indicated the water-bearing units in the subsurface consist 

of unconsolidated to partly consolidated sand, gravel, silt, clay, 

and occasional cobbles within alluvial fan and stream deposits. 

Analysis of geophysical logs indicated alternating layers of 

finer- and coarser-grained material that range from less than 

1 foot to more than 20 feet thick. On the basis of the geologic 

data collected, the principal water-bearing units beneath the 

monitoring-well sites were found to be composed of younger 

alluvium of Holocene age, older alluvium of Pleistocene age, 

and the Tertiary-Quaternary Morales Formation. At all three 

sites, the contact between the recent fill and younger alluvium 

is approximately 20 feet below land surface. 

Water-quality samples were collected from 12 monitoring 

wells, 27 domestic and supply wells, 2 springs, and 4 surfacewater sites and were analyzed for a variety of constituents 

that differed by site, but, in general, included trace elements; 

nutrients; dissolved organic carbon; major and minor ions; 

silica; total dissolved solids; alkalinity; total arsenic and iron; 

arsenic, chromium, and iron species; and isotopic tracers, 

including the stable isotopes of hydrogen and oxygen, activities of tritium, and carbon-14 abundance. 

Of the 39 wells sampled, concentrations of total dissolved 

solids and sulfate from 38 and 37 well samples, respectively, 

were greater than the U.S. Environmental Protection Agency’s 

secondary maximum contaminant levels. Concentrations 

greater than the maximum contaminant levels for nitrate were 

observed in five wells and were observed for arsenic in four 

wells. 
2 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

conductivity ranged from about 1.5 to 28 feet per day and 

decreased with depth. The median estimated hydraulic 

conductivity for the older alluvium was about five times 

that estimated for the Morales Formation. Estimates of 

transmissivity ranged from 560 to 163,400 gallons per day 

per foot and decreased with depth. The median estimated 

transmissivity for the younger alluvium was about three times 

that estimated for the older alluvium.

Geomechanical analysis included land-surface elevation 

changes at five continuously operating global positioning 

systems (GPS) and land-subsidence detection at five 

interferometric synthetic aperture radar (InSAR) reference 

points. Analysis of data collected from continuously operating 

GPS stations showed the mountains to the south and west 

moved upward about 1 millimeter (mm) annually, whereas 

the station in the center of the Southern-Main zone moved 

downward more than 7 mm annually, indicating subsidence. 

It is likely that this subsidence is inelastic (permanent) 

deformation and indicates reduced storage capacity in the 

aquifer sediments. Analysis of InSAR data showed local 

and regional changes that appeared to be dependent, in part, 

on the time span of the interferogram, seasonal variations 

in pumping, and tectonic uplift. Long-term InSAR time 

series showed a total maximum detected subsidence rate 

of approximately 12 mm per year at one location and 

approximately 8 mm per year at a second location, while 

short-term InSAR time series showed maximum subsidence of 

about 15 mm at one location and localized maximum uplift of 

about 10 mm at another location.

Introduction 

Currently, groundwater is the sole source of water supply 

in the Cuyama Valley (fig. 1). Groundwater withdrawals, 

mainly for the irrigation of agricultural crops, have resulted 

in water-level declines of as much as 300 ft in some areas 

since the 1940s (California Department of Water Resources, 

1998). The Cuyama Valley groundwater basin was identified 

in 1980 by the California Department of Water Resources 

(CA DWR) to be in the “critical condition of overdraft,” 

which indicates that a “continuation of present water 

management practices would probably result in significant 

adverse overdraft-related environmental, social or economic 

impact” (California Department of Water Resources, 2003). To 

provide for sustained beneficial use, it is necessary to define 

groundwater availability with respect to quantity and quality 

and to establish tools to allow water users and managers to 

efficiently utilize the available groundwater resources. The 

U.S. Geological Survey (USGS), in cooperation with the Santa 

Barbara County Water Agency, began a study in 2008 to assess 

the water resources of the Cuyama Valley groundwater basin. 

The study included a monitoring component (described in 

this report), a modeling component and a geologic framework 

component (presented in Sweetkind and others, 2013). As part 

of this study, the existing monitoring and modeling tools are 

being updated to provide water managers with the data and 

resources necessary to address the water-management issues.

Purpose and Scope

The primary purpose of this report is to present selected 

data that describe current groundwater conditions of the major 

aquifers in the Cuyama Valley groundwater basin. This report 

presents a summary of lithologic, geologic, geophysical, 

water-quality, hydrologic, and land-deformation data collected 

at three new multiple-well monitoring sites, selected domestic 

and supply wells (irrigation-supply and municipal-supply), 

springs, streams and various other sites in the Cuyama Valley 

during 2008–12. In addition to a summary of data collection, this report includes initial interpretations from these 

data. Geologic interpretation includes the depths of formation 

contacts based on lithologic and geophysical data collected at 

the multi-well monitoring sites. Water-quality interpretations 

include age dating and isotopic analysis. Hydrologic interpretations include definition of the depths of increased groundwater flow, determination of sources of recharge, and estimation 

of hydraulic properties. Interpretations of land deformation 

data include estimating the rate and cause of changes in landsurface elevation. 

Description of Study Area

The Cuyama Valley groundwater basin is approximately 

40 miles (mi) west of Bakersfield, California, in the southern 

Coast Ranges physiographic province (fig. 1). The 230 square 

mile (mi2) basin lies near the intersection of San Luis Obispo, 

Santa Barbara, Ventura, and Kern counties. The Coast Ranges 

province lies west of the Great Valley and north of the westtrending Transverse Ranges. Although within the Coast 

Ranges, the Cuyama Valley has many of the climatic features 

of a desert basin, because it is surrounded by relatively high 

mountains. The Cuyama Valley basin is characterized by 

hot, dry summers and cold winters. Rainfall averages from 

7 to 15 inches per year (in/yr) on the valley floor (California 

Department of Water Resources, 2003) to about 24 to 30 in/yr 

in the mountain headwaters of the Cuyama River and along 

the crest of the Sierra Madre Mountains.

Geologic Units

The Cuyama Valley groundwater basin is underlain by 

a sequence of unconsolidated to partly consolidated nonmarine deposits including the Pliocene to Pleistocene Morales 

Formation and Pleistocene to recent alluvial and fluvial 

deposits (Hill and others, 1958; DeLong and others, 2008). 

These deposits unconformably overlie a late Cretaceous to 

middle Cenozoic succession of consolidated marine and nonmarine sedimentary rocks, which in turn overlie crystalline 

granitic and gneissic rocks at depth (Hill and others, 1958; 

Lagoe, 1987). In terms of water-bearing properties, the 
Introduction 3

Figure 1. The location of Cuyama Valley, including multiple-well monitoring sites, selected domestic and supply wells, and hydrologic 

units, Cuyama Valley, Santa Barbara County, California.

166

166

33

33

CVKR 1-4

CVBR 1-4 CVFR 1-4

Cuyama

Ventucopa

New Cuyama

Kern

County

Ventura

County

Santa Barbara

County

San Luis Obispo

County

119°50’ 119°40’ 119°30’ 119°20’

35°

34°

50’

34°

40’

Reyes Creek

Cuyama

Creek

Sierra Madre Mountains

Tehachapi

Cuyama Valley

groundwater

basin

Cuyama River

Caliente Range

Mts

EXPLANATION

0 5 10 Miles

0 5 10 Kilometers

Shaded relief base created from 30-m digital elevation model from USGS National 

Elevation Dataset (NED), North America Vertical Datum 1988 (NAVD88)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009 

Albers Projection, NAD83

Site type

Spring

Surface-water site

U.S. Geological Survey 

monitoring site

Well (domestic or supply)

Cuyama groundwater basin zones

Caliente Northern-Main

Central Sierra Madre Foothills

Northeast Ventucopa Uplands

Northwestern Sierra Madre Foothills

Northern Ventucopa Uplands

Southern Sierra Madre Foothills

Southern Ventucopa Uplands

Southern-Main

Western Basin

Area of

 map

C

a

l

i

f o

r

n i

a

Pacific Ocean

geology of the Cuyama Valley can be generalized into four 

main units: (1) non-water-bearing rocks—the crystalline 

granitic rocks and all consolidated sedimentary rocks older 

than the Morales Formation, (2) the Morales Formation, (3) 

older alluvium of Pleistocene age, and (4) younger alluvium 

of Holocene age (Upson and Worts, 1951; Singer and 

Swarzenski, 1970). The aquifer system that is made up of the 

water-bearing portions of units 2−4 is described in more detail 

in the “Aquifer System” section.

The Morales Formation (QTm, fig. 2) is a PliocenePleistocene fluvial deposit that is up to 5,000 feet thick and 

consists of massive- to thick-bedded, partly consolidated 

deposits of clay, silt, sand, and gravel (Hill and others, 1958; 

Ellis and others, 1993). The Morales Formation is widely 

exposed as badland topography to the east of the Cuyama 

River in the Ventucopa area (Dibblee, 1982; Dibblee and 

Minch, 2006; Kellogg and others, 2008). The geologic 

mapping of Dibblee (Dibblee, 1973; Dibblee and Minch, 

2005 and 2006) included all young, deformed, non-marine 
4 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 2. Geologic formation outcrops, faults, folds, InSAR reference points, continuously operating GPS stations, oil wells, and rainfall

stations, Cuyama Valley, Santa Barbara County, California.

Station 436

Station 402

Station 347

Station 174A

Cuyama

Ventucopa

New Cuyama

Kern

County

Ventura

County

Santa Barbara

County

San Luis Obispo

County

CVKR 1-4

CVBR 1-4

CVFR 1-4

Morales fault

South Cuyama fault

Russell fault

TTRF GRF

Whiterock 

SBCF

VCST

P521

OZST

BCWR

Cuyama

Badlands

CUHS

Ref Pt. 1 Ref Pt. 2 Ref Pt. 3

Ref Pt. 4

Ref Pt. 5

fault

166

166

33

33

Rehoboth Farms fault

M M M

M M M

M M

M

M M M

Cuyama

syncline

(

(

( (

(

( (

119°50’ 119°40’ 119°30’ 119°20’

35°

34°

50’

34°

40’

Reyes Creek

Cuyama

Creek

Sierra Madre Mountains

Tehachapi

Cuyama Valley

groundwater

basin

Cuyama River

Caliente Range

Mts

EXPLANATION

Russel Ranch oil well

Geologic unit (age)

Cuyama continuous-GPS site

USGS-monitoring site

0 5 10 Miles

0 5 10 Kilometers

Shaded relief base created from 30-m digital elevation model from USGS National 

Elevation Dataset (NED); North America Vertical Datum 1988 (NAVD88)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

Geology from: Kellogg and others, 2008,

and Graham and others, 1999

Qc: fluvial channel deposits associated with the 

Cuyama River (Holocene)

Qya: Younger (inactive) alluvium (Holocene and late 

Pleistocene)

Qoa: Older alluvium (late and middle-Pleistocene)

QTm: Morales Formation, undivided (Pleistocene and 

upper Pliocene)

Tq: Quatal Formation, undivided (Pliocene)

BR1: Caliente Formation (upper and middle Miocene)

BR2: Miocene and older consolidated rocks

(

Normal fault

Thrust fault

Thrust fault,

 concealed

M M Syncline

Syncline, concealed

GRF, Graveyard fault

SBCF, Santa Barbara Canyon fault

TTRF, Turkey Trap Ridge fault

Rainfall station

Santa Barbara Canyon

Salisbury Canyon

Apache Canyon

Quatal Canyon
Introduction 5

sediments of the Cuyama area in the Morales Formation; these 

maps portray the piedmont upland area along the south edge 

of the Cuyama Valley as being composed of exposed outcrops 

of Morales Formation. Subsequent workers (Vedder, 1968; 

Vedder and Repenning, 1975; Schwing, 1984; Spitz, 1986) 

classified the upper part of Dibblee’s Morales Formation 

as “deformed older Quaternary alluvium.” Using this 

classification, the Morales Formation is hundreds to greater 

than 1,000 ft below the surface on the south side of Cuyama 

Valley, rather than exposed at the surface. 

Older alluvium (Qoa, fig. 2) consists of unconsolidated 

to partly consolidated sand, gravel, and boulders, with some 

clay (Vedder and Repenning, 1975; DeLong and others, 

2008). The percentage of clay increases in the western part 

of the valley (Singer and Swarzenski, 1970; DeLong and 

others, 2008). Interpretation of geophysical logs from oil 

exploration wells indicated that this unit is typically 400 to 

600 feet thick, but is as thick as 1,000 feet near the axis of 

Cuyama Valley (Schwing, 1984; Spitz, 1986). In the study 

area, older alluvium includes dissected alluvial fans, colluvial 

deposits, and sediments on multiple terraces and alluvial 

surfaces (Hill and others, 1958; DeLong and others, 2008). 

Older alluvial deposits are slightly deformed and are probably 

of late Pleistocene age, although in some places they could 

be Holocene (Vedder, 1968; DeLong and others, 2008). Older 

alluvium is exposed on the piedmont uplands along the south 

side of Cuyama Valley and locally at two fault-bounded ridges 

in the center of the valley (Vedder and Repenning, 1975; 

DeLong and others, 2008).

Younger alluvium (Qya, fig. 2) consists of unconsolidated 

sand, gravel, and boulders, with some clay deposited as 

alluvium in stream channels, floodplains, alluvial fans, and 

stream terraces. The unit is mainly Holocene in age, but 

locally can be late Pleistocene in part. Active stream deposits 

consist of river-bed gravels of the Cuyama River and other 

active channels (Vedder and Repenning, 1975; DeLong and 

others, 2008).

Geologic Structure 

During Miocene and older time, the Cuyama Valley 

groundwater basin was the site of extensional and strike-slip 

deformation; older, inactive faults were buried by the Morales 

Formation and younger units (Yeats and others, 1989; fig. 2). 

During the Pliocene-Pleistocene, structural deformation of the 

Cuyama Valley changed to a predominantly compressional 

mode, resulting in the formation of folds and folding and 

thrust faults (Davis and others, 1988).

As a result of compression, the Cuyama Valley is currently 

a downfolded basin bounded to the north and south by faults. 

Miocene rocks of the Caliente Range to the north of Cuyama 

Valley are being thrust southward over older and younger 

alluvium on the Morales and Whiterock thrusts; similar-aged 

rocks in the Sierra Madre to the south of Cuyama Valley are 

being thrust northward over older alluvium on the South 

Cuyama fault (Vedder and Repenning, 1975; Davis and others, 

1988; fig. 2).

The Morales Formation and older alluvium are deformed 

into tight synclines along the north and south margins of the 

basin near the bounding thrust faults (Spitz, 1986; Kellogg 

and others, 2008). The eastern part of the basin is underlain 

by the Cuyama syncline; its strike is parallel to the valley 

axis and the fold plunges toward the northwest (Ellis, 1994; 

Dibblee and Minch, 2006; Kellogg and others, 2008). The fold 

is exposed in outcrops in the Ventucopa area and the Cuyama 

Badlands to the east; beneath the central part of the valley, it is 

buried but known to be present from subsurface data from oil 

exploration wells (Spitz, 1986; Ellis, 1994). 

Several ridges of older alluvium are mapped in the center 

of the Cuyama Valley, north of Highway 166 (Vedder and 

Repenning, 1975), on the north side on the Turkey Trap Ridge 

and Graveyard faults (fig. 2). These ridges trend slightly northnorthwest and are oriented in a right-stepping, en echelon 

pattern. Upson and Worts (1951) suggested that these ridges 

were fault-related on the basis of their orientation and the 

presence of springs along the ridges. Vedder and Repenning 

(1975) mapped inferred reverse faults associated with these 

ridges; the faults cut alluvium and bring older alluvium to the 

surface. Seismic profiles collected across these ridges indicate 

that these faults cut the Morales Formation (Ellis, 1994), 

although their ultimate downdip projection is unknown.

Other faults, not obviously related to the overall 

compressional tectonics that affect the basin, have been 

inferred in the subsurface, primarily, on the basis of marked 

differences in water levels over short distances. One such 

fault (SBCF on fig. 2) is inferred to trend northeast-southwest 

near the mouth of the Santa Barbara Canyon (Singer and 

Swarzenski, 1970); similarly aligned structures are mapped 

in the piedmont upland to the west of Santa Barbara Canyon 

(Dibblee and Minch, 2007). Another fault (Rehoboth Farms 

fault on fig. 2) inferred to exist on the basis of water-level 

changes is in the west-central part of the valley; the inferred 

fault trends northwest-southeast near the town of New 

Cuyama and projects southeastward beneath the Salisbury 

Canyon drainage (Lane-Western Company, written commun., 

1982).

Aquifer System 

The main water-bearing deposits in the study area are the 

saturated portions of the younger and older alluvium and the 

Morales Formation (fig. 2). All rocks that are older than the 

Morales Formation were considered by previous investigators 

to be non-water-bearing (Upson and Worts, 1951; Singer and 

Swarzenski, 1970). The regional flow pattern of groundwater 

under natural conditions is northwestward, parallel to the 

central axis of the basin, similar to the orientation of the 

overlying Cuyama River, with a substantial component of 

flow northward from the Sierra Madre Mountains (Singer and 

Swarzenski, 1970). Historically, most of the water pumped 

from the study area was from the younger and older alluvium. 

Inspection of available geologic and geophysical logs 

indicated that the hydraulic conductivity, in general, decreases 

with depth.
6 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12

Large-capacity wells perforated in the alluvium yield 

1,000–3,000 gallons per minute (gpm) and have specific 

capacities of that range from 100 to 200 gpm per foot (Singer 

and Swarzenski, 1970). Yield and specific capacities generally 

tend to decrease with depth. Wells perforated in the younger 

alluvium have a median yield of 1,800 gpm and median 

specific capacity of 60 gpm per foot. Wells perforated in 

both the younger and older alluvium have a median yield of 

1,200 gpm and median specific capacity of 40 gpm per foot. 

Wells perforated in the older alluvium have a median yield 

of 620 gpm and median specific capacity of 20 gpm per foot. 

Yield and specific capacities are less on the western half of the 

valley compared to the eastern half, indicating a spatial trend; 

however, a greater percentage of wells in the western part are 

perforated in the older alluvium. 

The water-bearing properties of the Morales Formation are 

not well defined, but available data indicate that the hydraulic 

conductivity of the formation varies greatly both areally and 

with depth. 

Wells perforated in the Morales Formation in the western 

part of the valley have specific capacities of 5–25 gpm per 

foot, whereas those in the north-central part of the valley 

have specific capacities of 25–50 gpm per foot (Singer and 

Swarzenski, 1970). Inspection of available geologic and 

geophysical logs indicated that the hydraulic conductivity of 

the Morales Formation decreases with depth.

Several faults that offset the basin-fill deposits, associated 

with measured water-level offsets, are inferred to impede 

groundwater movement (Upson and Worts, 1951; Singer and 

Swarzenski, 1970; fig. 2). Because the faults do not intersect 

land surface and are not readily apparent in the unconsolidated 

surface sediments, their locations have been inferred from 

well data and topographic features. The Graveyard and Turkey 

Trap Ridges faults on the northern side of the Cuyama Valley 

(fig. 2) are postulated from groundwater data by Upson and 

Worts (1951) and shown on the geologic map of Vedder and 

Repenning (1975). A fault on the south side of the basin, here 

called the Santa Barbara Canyon fault (fig. 2), was suggested 

by Singer and Swarzenski (1970) to be the cause of a steep 

hydraulic gradient in this part of Cuyama Valley, where 

water levels in the vicinity of Ventucopa were observed to be 

100 feet higher than water levels 2 miles to the north. The fault 

is mapped in the uplifted piedmont older alluvium to the west 

of Santa Barbara Canyon (Dibblee and Minch, 2007) and is 

visible in outcrops to the west of the Cuyama River, but is not 

readily projected to the eastern side of the Cuyama River on 

the basis of geologic data. Water-level offsets along the valley 

were used to infer the location of the fault in the sediment 

(Sweetkind, 2013).

Historically, flowing springs were found along the trace of 

faults that parallel Graveyard and Turkey Trap Ridges (Santa 

Barbara County Planning and Development Department, 

1994), and other springs have been reported along the South 

Cuyama and Santa Barbara fault. While many of the springs 

and seeps that flowed in 1946 have since dried up (Singer and 

Swarzenski, 1970), several springs still have seasonal flow. 

Two springs, one in the Southern Sierra Madre Foothills zone 

and another in the Northern Ventucopa Uplands zone (fig. 1), 

were sampled during the study.

This study required a better delineation of the groundwater 

basin than previously available. The basin was divided into 

nine groundwater subregional hydrologic zones (fig. 1). 

These zones separate the aquifers into regions that are fault 

bounded and where the response to the use, movement, 

and consumption of water is similar in specific parts of the 

aquifers, but differs from the other zones. In this context, 

Cuyama Valley can be considered a collection of zones 

that are partially connected, but have different geologic 

boundaries, hydrologic features and hydraulic properties, 

water quality and age of groundwater, and dominant aquifers 

that respond to natural and anthropogenic stresses differently.

Accessing Data

Users of the data presented in this report are encouraged 

to access information through the USGS National Water 

Information System (NWIS) web page (NWIS Web) at 

http://waterdata.usgs.gov/nwis/. NWIS Web serves as an 

interface to a database of site information and groundwater, 

surface-water, and water-quality data collected throughout 

the 50 states and elsewhere. NWIS Web is updated from the 

database on a regularly scheduled basis. Data can be retrieved 

by category and geographic area, and the retrieval can be 

selectively refined by a specific location or parameter field. 

NWIS Web can output water-level and water-quality graphs, 

site maps, and data tables (in HTML and ASCII format) 

and can be used to develop site-selection lists. Updates to 

data presented in this report after publication will be made 

to the NWIS. Additional data could be available on the 

project web site at http://ca.water.usgs.gov/projects/cuyama/. 

Formal requests for specific data may be directed to the U.S. 

Geological Survey California Water Science Center, Public 

Information Officer in Sacramento, California.

Description of the Monitoring Network

Most information presented in this report focuses on three 

multiple-well monitoring sites installed between December 

2008 and October 2009 within the study area (fig. 1). Data 

collected from the monitoring sites provided information on 

vertical differences in hydraulic properties, water levels, and 

water chemistry at the same location; these data can be used 

to characterize the three-dimensional groundwater system. 

Existing wells (domestic and supply) were incorporated into 

the monitoring network to help meet additional needs (fig. 1). 

Table 1 lists all wells referenced in this report, including 

information on the well location by zone, and data collected 

from each well site. Well-identification and well-construction 

information for groundwater wells in the monitoring network 

are presented in table 2. Supporting data were collected 

from four surface-water sites and two springs; related siteidentification information and available data for these sites are 

presented in table 3.
Description of the Monitoring Network 7

Table 1. Selected characteristics and data availability for wells in the Cuyama Valley groundwater basin, Santa Barbara County, 

California. 

[See figures 1, 8, 15, and 25 for well locations. Abbreviations: CVKR, Cuyama Valley Kirschenmann Road; CVBR, Cuyama Valley Bell Road, CVFR, Cuyama Valley Foothill Road; 

CUY, Cuyama Valley study well; PT, Pump test well; x, data are available; —, data not available]

Common well 

name

Site 

identification number

Cuyama 

groundwaterbasin zones

Water-quality 

data

Discrete (manual) 

water-level 

measurements

Time-series (automated) water-level 

measurements

Aquifertest 

data

CVKR-1 345552119354201 Southern-Main x x x x

CVKR-2 345552119354202 Southern-Main x x x x

CVKR-3 345552119354203 Southern-Main x x x x

CVKR-4 345552119354204 Southern-Main x x x x

CVBR-1 345359119392701 Northwestern Sierra Madre Foothills x x x x

CVBR-2 345359119392702 Northwestern Sierra Madre Foothills x x x x

CVBR-3 345359119392703 Northwestern Sierra Madre Foothills x x x x

CVBR-4 345359119392704 Northwestern Sierra Madre Foothills x x x x

CVFR-1 345351119323101 Central Sierra Madre Foothills x x x x

CVFR-2 345351119323102 Central Sierra Madre Foothills x x x x

CVFR-3 345351119323103 Central Sierra Madre Foothills x x x x

CVFR-4 345351119323104 Central Sierra Madre Foothills x x x x

CUY-01 345838119452001 Western Basin x x — —

CUY-02 345603119411901 Northwestern Sierra Madre Foothills x x x —

CUY-03 345100119290001 Southern Ventucopa Uplands x x — —

CUY-04 345602119362401 Southern-Main x x x —

CUY-05 345600119400001 Southern-Main x x x —

CUY-06 345300119310001 Southern-Main x x — —

CUY-07 345538119332201 Southern-Main x x x —

CUY-08 345405119325101 Southern-Main x x — —

CUY-11 344143119193001 Southern Ventucopa Uplands x x — —

CUY-12 345100119290002 Southern Ventucopa Uplands x x x —

CUY-13 344910119270501 Southern Ventucopa Uplands x x — —

CUY-14 345338119324801 Central Sierra Madre Foothills x — — —

CUY-16 345540119410901 Northwestern Sierra Madre Foothills x x — —

CUY-17 344729119233501 Northeast Ventucopa Uplands x x — —

CUY-18 344859119280801 Southern Ventucopa Uplands x x — —

CUY-19 345003119283501 Southern Ventucopa Uplands x x — —

CUY-20 345615119285501 Outside basin boundary x x — —

CUY-21 345359119350201 Central Sierra Madre Foothills x x — —

CUY-22 345552119362901 Southern-Main x x — —

CUY-23 345539119393901 Southern-Main x x — —

CUY-24 345325119365603 Central Sierra Madre Foothills x x — —

CUY-25 345302119380701 Central Sierra Madre Foothills x x — —

CUY-26 345753119421701 Western Basin x x — —

CUY-27 345539119394001 Southern-Main — x — —

CUY-28 344900119332201 Southern Sierra Madre Foothills x — — —

CUY-30 344156119184801 Southern Ventucopa Uplands — x — —

CUY-31 344154119184801 Southern Ventucopa Uplands — x — —

CUY-32 344231119224101 Southern Ventucopa Uplands — x — —

CUY-33 344828119265301 Southern Ventucopa Uplands — x — —

CUY-34 344843119272401 Southern Ventucopa Uplands — x — —

CUY-35 344825119271001 Southern Ventucopa Uplands — x x —
8 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

[See figures 1, 8, 15, and 25 for well locations. Abbreviations: CVKR, Cuyama Valley Kirschenmann Road; CVBR, Cuyama Valley Bell Road, CVFR, Cuyama Valley Foothill Road; 

CUY, Cuyama Valley study well; PT, Pump test well; x, data are available; —, data not available]

Common well 

name

Site 

identification number

Cuyama 

groundwaterbasin zones

Water-quality 

data

Discrete (manual) 

water-level 

measurements

Time-series (automated) water-level 

measurements

Aquifertest 

data

CUY-36 344742119240201 Northeast Ventucopa Uplands — x — —

CUY-38 345040119285101 Southern Ventucopa Uplands — x — —

CUY-39 344944119275701 Southern Ventucopa Uplands — x — —

CUY-40 344939119275901 Southern Ventucopa Uplands — x — —

CUY-42 344904119273101 Southern Ventucopa Uplands — x — —

CUY-43 344904119273401 Southern Ventucopa Uplands — x — —

CUY-44 344915119262001 Northern Ventucopa Uplands — x — —

CUY-45 345209119304901 Southern Sierra Madre Foothills — x — —

CUY-46 345206119294701 Southern Ventucopa Uplands — x — —

CUY-47 344940119330501 Southern Sierra Madre Foothills — x — —

CUY-48 345315119371501 Central Sierra Madre Foothills — x — —

CUY-49 345353119373601 Central Sierra Madre Foothills — x — —

CUY-50 345600119351001 Southern-Main — x — —

CUY-51 345606119310301 Southern-Main — x — —

CUY-52 345511119322801 Southern-Main — x — —

CUY-53 345447119315101 Southern-Main — x — —

CUY-54 345512119354101 Southern-Main — x — —

CUY-55 345631119402901 Southern-Main — x x —

CUY-56 345709119415501 Southern-Main — x — —

CUY-57 345618119393701 Southern-Main — x — —

CUY-58 345540119394301 Southern-Main — x — —

CUY-59 345538119374601 Southern-Main — x — —

CUY-60 345808119433501 Western Basin — x x —

CUY-61 345604119340201 Southern-Main x — — —

CUY-62 345822119391801 Caliente Northern-Main — x — —

CUY-63 345721119383401 Caliente Northern-Main x — — —

CUY-64 345540119384201 Southern-Main x — — —

CUY-73 345014119224901 Northern Ventucopa Uplands — x — —

CUY-74 344749119265301 Southern Ventucopa Uplands — x — —

CUY-75 345637119394701 Southern-Main — x — —

PT-01 — Southern-Main — — — x

PT-02 — Southern-Main — — — x

PT-03 — Caliente Northern-Main — — — x

PT-04 — Caliente Northern-Main — — — x

PT-05 — Caliente Northern-Main — — — x

PT-07 — Southern-Main — — — x

PT-08 — Southern-Main — — — x

PT-09 — Southern-Main — — — x

PT-10 — Southern-Main — — — x

PT-11 — Southern-Main — — — x

PT-12 — Southern-Main — — — x

PT-13 — Southern-Main — — — x

PT-14 — Southern-Main — — — x

PT-15 — Southern-Main — — — x

Table 1. Selected characteristics and data availability for wells in the Cuyama Valley groundwater basin, Santa Barbara County, 

California.—Continued 
Description of the Monitoring Network 9

[See figures 1, 8, 15, and 25 for well locations. Abbreviations: CVKR, Cuyama Valley Kirschenmann Road; CVBR, Cuyama Valley Bell Road, CVFR, Cuyama Valley Foothill Road; 

CUY, Cuyama Valley study well; PT, Pump test well; x, data are available; —, data not available]

Common well 

name

Site 

identification number

Cuyama 

groundwaterbasin zones

Water-quality 

data

Discrete (manual) 

water-level 

measurements

Time-series (automated) water-level 

measurements

Aquifertest 

data

PT-16 — Southern-Main — — — x

PT-17 — Southern-Main — — — x

PT-18 — Southern-Main — — — x

PT-19 — Southern-Main — — — x

PT-20 — Southern-Main — — — x

PT-21 — Southern-Main — — — x

PT-22 — Southern-Main — — — x

PT-23 — Southern-Main — — — x

PT-24 — Southern-Main — — — x

PT-25 — Central Sierra Madre Foothills — — — x

PT-26 — Southern-Main — — — x

PT-27 — Caliente Northern-Main — — — x

PT-28 — Caliente Northern-Main — — — x

PT-30 — Southern-Main — — — x

PT-31 — Southern-Main — — — x

PT-32 — Southern-Main — — — x

PT-34 — Southern-Main — — — x

PT-35 — Southern-Main — — — x

PT-36 — Southern-Main — — — x

PT-37 — Southern-Main — — — x

PT-38 — Southern-Main — — — x

PT-39 — Southern-Main — — — x

PT-40 — Southern-Main — — — x

PT-41 — Southern-Main — — — x

PT-42 — Southern-Main — — — x

PT-43 — Southern-Main — — — x

PT-44 — Southern-Main — — — x

PT-45 — Southern-Main — — — x

PT-46 — Northwestern Sierra Madre Foothills — — — x

PT-47 — Northwestern Sierra Madre Foothills — — — x

PT-48 — Northwestern Sierra Madre Foothills — — — x

PT-49 — Western Basin — — — x

PT-50 — Western Basin — — — x

PT-51 — Western Basin — — — x

PT-52 — Western Basin — — — x

PT-53 — Northwestern Sierra Madre Foothills — — — x

PT-54 — Northwestern Sierra Madre Foothills — — — x

Table 1. Selected characteristics and data availability for wells in the Cuyama Valley groundwater basin, Santa Barbara County, 

California.—Continued 

Each of the multiple-well monitoring sites consists of four 

2-inch diameter wells installed at different depths in the same 

borehole. Individual wells are screened over a specific 20-foot 

interval and isolated from other wells by a low-permeability 

bentonite grout. The construction of these wells enables the 

collection of depth-specific water-quality, water-level, and 

aquifer hydraulic-property data. Well-construction information 

for the three multiple-well monitoring sites is summarized in 

table 2. 

Boreholes at each site were drilled by the USGS Western 

Region Research Drilling Unit using the mud-rotary method. 

Borehole diameter decreased with depth, ranging in diameter 

from 14-3/4 to 4-1/2 inches. After total hole depth was 

attained, geophysical log surveys were completed, and the 
10 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Table 2. Summary of well completion for selected wells, Cuyama Valley, Santa Barbara County, California. 

[See figures 1, 8, 15, and 25 for well locations. Abbreviations: CVKR, Cuyama Valley Kirschenmann Road; CVBR, Cuyama Valley Bell Road, CVFR, Cuyama Valley Foothill Road; 

CUY, Cuyama Valley study well; ft bls, feet below land surface; —, data not available; * denotes data that were reported to the U.S. Geological Survey from various sources and are 

not stored in the National Water Information System database. Qya, Younger alluvium; Qoa, Older alluvium; QTm, Morales]

Common 

well name

Site 

identification number

Depth to bottom 

of well 

(ft bls)

Depth to 

top of perforations 

(ft bls)

Depth to bottom of 

perforations

(ft bls)

Depth to top of 

sand pack

(ft bls)

Depth to bottom 

of sand pack 

(ft bls)

Formation 

at top of 

screen

Formation 

at bottom of 

screen

CVKR-1 345552119354201 980 960 980 944 1,000 Qoa Qoa

CVKR-2 345552119354202 780 760 780 728 800 Qoa Qoa

CVKR-3 345552119354203 620 600 620 575 627 Qoa Qoa

CVKR-4 345552119354204 460 440 460 417 471 Qoa Qoa

CVBR-1 345359119392701 850 830 850 807 858 QTm QTm

CVBR-2 345359119392702 750 730 750 702 767 QTm QTm

CVBR-3 345359119392703 560 540 560 518 581 Qoa Qoa

CVBR-4 345359119392704 380 360 380 303 403 Qoa Qoa

CVFR-1 345351119323101 980 960 980 935 1,000 QTm QTm

CVFR-2 345351119323102 830 810 830 787 839 QTm QTm

CVFR-3 345351119323103 700 680 700 660 720 QTm QTm

CVFR-4 345351119323104 610 590 610 568 625 QTm QTm

CUY-01 345838119452001 188 45 125 — — Qoa Qoa

CUY-02 345603119411901 790 340 790 — — Qoa QTm

CUY-03 345100119290001 — 75* 200* — — Qya Qya

CUY-04 345602119362401 720 420 720 — — Qya Qoa

CUY-05 345600119400001 — 100* 300* — — Qya Qya

CUY-06 345300119310001 800 640 800 — — QTm QTm

CUY-07 345538119332201 750 250 750 — — Qya Qoa

CUY-08 345405119325101 550 100* 400* — — Qya Qoa

CUY-11 344143119193001 357 100* 357* — — Below QTm Below QTm

CUY-12 345100119290002 93 50* 150* — — Qya Qya

CUY-13 344910119270501 233 100* 233* — — Qya QTm

CUY-14 345338119324801 1,100 580 1,100 — — Qya Qoa

CUY-16 345540119410901 880 380 880 — — Qoa QTm

CUY-17 344729119233501 400 300 400 — — Below QTm Below QTm

CUY-18 344859119280801 — 100* 212* — — Undetermined Undetermined

CUY-19 345003119283501 198 87* 198* — — Qya Qya

CUY-20 345615119285501 155 100* 155* — — Undetermined Undetermined

CUY-21 345359119350201 805 620 800 — — QTm QTm

CUY-22 345552119362901 1,000 401 1,000 — — Qya Qoa

CUY-23 345539119393901 2,120 400 2,120 — — Qya Qoa

CUY-24 345325119365603 500 300 500 — — Qoa Qoa

CUY-25 345302119380701 750 325* 400* — — Qoa Qoa

CUY-26 345753119421701 — 100* 215* — — Qya Qoa

CUY-27 345539119394001 993 144 993 — — Qya QTm

CUY-28 344900119332201 — — — — — Undetermined Undetermined

CUY-30 344156119184801 73 100* 500* — — Undetermined Undetermined

CUY-31 344154119184801 140 40 140 — — Undetermined Undetermined

CUY-32 344231119224101 125 65 125* — — Undetermined Undetermined

CUY-33 344828119265301 360 50* 372* — — Qya QTm

CUY-34 344843119272401 284 120 302 — — Qya QTm
Description of the Monitoring Network 11

[See figures 1, 8, 15, and 25 for well locations. Abbreviations: CVKR, Cuyama Valley Kirschenmann Road; CVBR, Cuyama Valley Bell Road, CVFR, Cuyama Valley Foothill Road; 

CUY, Cuyama Valley study well; ft bls, feet below land surface; —, data not available; * denotes data that were reported to the U.S. Geological Survey from various sources and are 

not stored in the National Water Information System database. Qya, Younger alluvium; Qoa, Older alluvium; QTm, Morales]

Common 

well name

Site 

identification number

Depth to bottom 

of well 

(ft bls)

Depth to 

top of perforations 

(ft bls)

Depth to bottom of 

perforations

(ft bls)

Depth to top of 

sand pack

(ft bls)

Depth to bottom 

of sand pack 

(ft bls)

Formation 

at top of 

screen

Formation 

at bottom of 

screen

CUY-35 344825119271001 220 100* 175* — — Qya Qya

CUY-36 344742119240201 435 255 435 — — Undetermined Undetermined

CUY-38 345040119285101 200 120 200 — — Qya Qya

CUY-39 344944119275701 212 100* 212* — — Qya Qya

CUY-40 344939119275901 200 50* 200* — — Qya Qya

CUY-42 344904119273101 160.7 100* 174* — — Qya Qoa

CUY-43 344904119273401 225 125 225 — — Qya Qoa

CUY-44 344915119262001 230 100* 235* — — QTm QTm

CUY-45 345209119304901 230 100* 300* — — Qya Qoa

CUY-46 345206119294701 175 120* 175* — — Qya Qya

CUY-47 344940119330501 151 31 151 — — Undetermined Undetermined

CUY-48 345315119371501 — 425* 500* — — Qoa Qoa

CUY-49 345353119373601 750 425* 500* — — Qoa Qoa

CUY-50 345600119351001 — 50* 300* — — Qya Qya

CUY-51 345606119310301 800 50* 800* — — Qya QTm

CUY-52 345511119322801 1,008 484 1,008 — — Qoa QTm

CUY-53 345447119315101 — 50* 500* — — Qya Qoa

CUY-54 345512119354101 239 124* 370* — — Qya Qoa

CUY-55 345631119402901 425 100* 441* — — Qya Qoa

CUY-56 345709119415501 240 58* 237* — — Qya Qoa

CUY-57 345618119393701 1,004 160 1,004 — — Qya QTm

CUY-58 345540119394301 — 150* 500* — — Qya Qoa

CUY-59 345538119374601 — 306 620 — — Qya Qoa

CUY-60 345808119433501 215 100* 215* — — Qya Qoa

CUY-61 345604119340201 — 50* 745* — — Qya Qoa

CUY-62 345822119391801 238 108 232 — — Qya Qoa

CUY-63 345721119383401 634 200 628 — — Qya Qoa

CUY-64 345540119384201 — 150* 425* — — Qya Qoa

CUY-73 345014119224901 232 100* 232* — — Qoa Qoa

CUY-74 344749119265301 — 100* 290* — — Qya QTm

CUY-75 345637119394701 646 166 640 — — Qya Qoa

PT-01 — 392 50* 392* — — Qya Qoa

PT-02 — 194 97* 319* — — Qya Qya

PT-03 — 346 50* 346* — — Qya Qya

PT-04 — 288 50* 288* — — Qya Qya

PT-05 — 203.5 50* 304* — — Qya Qya

PT-07 — 316 112* 310* — — Qya Qya

PT-08 — — 110* 371* — — Qya Qya

PT-09 — 656 108* 656* — — Qya Qoa

PT-10 — 298.5 50* 337* — — Qya Qya

PT-11 — 623 94* 623* — — Qya Qoa

PT-12 — — 50* 600* — — Qya Qoa

PT-13 — 660 108 660* — — Qya Qoa

Table 2. Summary of well completion for selected wells, Cuyama Valley, Santa Barbara County, California.—Continued
12 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

[See figures 1, 8, 15, and 25 for well locations. Abbreviations: CVKR, Cuyama Valley Kirschenmann Road; CVBR, Cuyama Valley Bell Road, CVFR, Cuyama Valley Foothill Road; 

CUY, Cuyama Valley study well; ft bls, feet below land surface; —, data not available; * denotes data that were reported to the U.S. Geological Survey from various sources and are 

not stored in the National Water Information System database. Qya, Younger alluvium; Qoa, Older alluvium; QTm, Morales]

Common 

well name

Site 

identification number

Depth to bottom 

of well 

(ft bls)

Depth to 

top of perforations 

(ft bls)

Depth to bottom of 

perforations

(ft bls)

Depth to top of 

sand pack

(ft bls)

Depth to bottom 

of sand pack 

(ft bls)

Formation 

at top of 

screen

Formation 

at bottom of 

screen

PT-14 — 810 175 810 — — Qya Qoa

PT-15 — 666 119* 665* — — Qya Qoa

PT-16 — 239 124* 370* — — Qya Qoa

PT-17 — 186 120* 369* — — Qya Qya

PT-18 — 417 50* 417* — — Qya Qya

PT-19 — — 50* 400* — — Qya Qya

PT-20 — — 100* 359* — — Qoa Qoa

PT-21 — 370 100* 370* — — Qya Qoa

PT-22 — 400 100* 400* — — Qya Qya

PT-23 — — 156* 351* — — Qya Qya

PT-24 — 333 100* 204* — — Qya Qya

PT-25 — 390 190* 390* — — Qoa Qoa

PT-26 — 204 100* 204* — — Qya Qoa

PT-27 — 222 42* 218* — — Qoa Qoa

PT-28 — 380 33* 212* — — Qoa Qoa

PT-30 — 508 226 — — — Qya Qoa

PT-31 — 409 108* 308* — — Qya Qya

PT-32 — 240 58* 237* — — Qya Qoa

PT-34 — 465 173 465* — — Qya Qoa

PT-35 — 350 128 350* — — Qya Qoa

PT-36 — 441 100* 441* — — Qya Qoa

PT-37 — 407 133* 407* — — Qya Qya

PT-38 — 514 133* 514* — — Qya Qoa

PT-39 — — 166* 454* — — Qya Qoa

PT-40 — 371 50* 190* — — Qya Qya

PT-41 — — 150* 310* — — Qya Qya

PT-42 — — 130* 322* — — Qya Qya

PT-43 — 278 130* 278* — — Qya Qya

PT-44 — 720 420 720 — — Qya Qoa

PT-45 — 298 53* 275* — — Qya Qya

PT-46 — 1,006 196 1003* — — Qoa QTm

PT-47 — 603 224* 560* — — Qoa Qoa

PT-48 — 404 100 404* — — Qoa QTm

PT-49 — 215 100* 215* — — Qya Qoa

PT-50 — 378 36* 117* — — Qya Qya

PT-51 — 138 40* 138* — — Qya Qya

PT-52 — 294 40* 294* — — Qya Qoa

PT-53 — 110 57* 128* — — Qoa Qoa

PT-54 — 700 125 625* — — Qoa Qoa

Table 2. Summary of well completion for selected wells, Cuyama Valley, Santa Barbara County, California.—Continued 
Description of the Monitoring Network 13

Table 3. Site identification and data availability for selected springs and surface-water sites in the Cuyama Valley groundwater basin, 

Santa Barbara County, California 

[See figure 8 for locations. An “x” denotes data are available. Abbreviations: mm/dd/yyyy, month, day, year; SP, spring site; SW, surface water site; —, data not available]

Common 

site 

name

Site 

type

Site 

identification 

number

Sub-region Site 

description

Waterchemistry 

data

Discharge 

data

Discharge 

data start

(mm/dd/yyyy)

SP-01 Spring 344740119224801 Northeast Ventucopa UplandsQuail Creek Spring x — —

SP-02 Spring 344857119334701 Southern Sierra 

Madre Foothills

Reyes Creek Spring x — —

SW-01 Surface water 344143119191701 Southern Ventucopa UplandsReyes Creek at Lockwood Valley Road 

near Ventucopa

x — —

SW-02 Surface water 344147119191601 Southern Ventucopa UplandsCuyama River at Lockwood Valley 

Road near Ventucopa

x — —

SW-03 Surface water 11136600 Southern Sierra 

Madre Foothills

Santa Barbara Canyon Creek near 

Ventucopa

x x 9/30/2009

SW-04 Surface water 11136500 Outside basin 

boundary

Cuyama River near Ventucopa x x 5/15/2009

SW-05 Surface water 11136800 Outside basin 

boundary

Cuyama River below Buckhorn Canyon 

near Santa Maria

— x 2/10/1962

monitoring wells were installed. The monitoring wells were 

constructed by using flush-threaded, 2-inch-diameter, schedule 

80 polyvinyl chloride (PVC) casing. The screened interval for 

each monitoring well typically consisted of a 20-foot section 

of slotted PVC (slot size is 0.020 inch) at the bottom. Once 

the well was lowered to the desired depth, a filter pack was 

tremied around the screened interval using No. 3 Monterey 

sand. A low-permeability bentonite grout was then tremied in 

place to seal the borehole and effectively isolate the screened 

interval of the monitoring well. The process was repeated for 

each successive well. Well-construction diagrams for each 

multiple-well monitoring site are presented in figures 3–5.

After completion, drilling fluid was evacuated from each 

monitoring well by using compressed air. Extensive airlifting 

and a surging technique with compressed air were employed 

to further develop the filter pack surrounding the well. Specific 

conductance, pH, temperature, apparent color, and turbidity, 

along with the discharge rate and total volume, were recorded 

during this process. Development was continuous until no 

discernible drilling mud was present and field measurements 

had stabilized.
14 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 3. Geophysical logs, well-construction diagram, and generalized lithologic description for multiple-well monitoring site Cuyama 

Valley Kirschenmann Road (CVKR), Cuyama Valley, Santa Barbara County, California.

Well

construction

( is depth-to-water,

August 31, 2010)

Recent Younger Alluvium Older Alluvium

Generalized

lithology

100

0

200

300

400

500

600

700

800

900

1,000

0 2412 0 200100 -40 600 0 200100 1000 200 0 400200 0 4020

Depth, in feet below land surface

NO DATA

SAND

SAND

SAND SAND

GROUT GROUT GROUT GROUT

CVKR-1

CVKR-3

CVKR-2

CVKR-4

Caliper,

in inches

Natural

gamma,

in counts

per second

Sonic

(Delta t), in

microseconds

per foot

Resistivity,

in ohm-meters

(16n-short normal,

64n-long normal)

Electromagnetic

conductivity,

in millimhos

per meter

Spontaneous

potential,

in millivolts

Temperature

gradient, in

degrees Celsius

per kilometer

16N

64N

Fill / Soil

Sand

Sandy silt

Clay

Sandy gravel

Clayey silty sand 

Sandy gravel

Interbedded

sand/silt/clay

Silty sand

Interbedded

sand/silt/clay

Silty sand

Interbedded

cemented

sands/clay 

Sandy silty clay

Interbedded

cemented

sands/clay

Sandy clay

Silty sand, soil horizon

Interbedded

cemented

sands/clay

Slightly sandy clay

Sand

Clay

Interbedded

cemented

sands/clay

Slightly

clayey/silty

sand

Core: Interbedded clay,

sand and sandstone 

Zones of flow
Description of the Monitoring Network 15

Figure 4. Geophysical logs, well-construction diagram, and generalized lithologic description for multiple-well monitoring site Cuyama 

Valley Bell Road (CVBR), Cuyama Valley, Santa Barbara County, California.

Well

construction

( is depth-to-water,

August 31, 2010)

Recent

fill

Older Alluvium Morales Formation

Generalized

lithology

100

0

200

300

400

500

600

700

800

900

1,000

0 2412 0 200100 0 10050 0 5025 1000 200 0 500250

NO DATA SAND SAND

SAND SAND

GROUT GROUT GROUT

GROUT GROUT

Depth, in feet below land surface

CVBR-1

CVBR-3

CVBR-2

CVBR-4

0 8040

Caliper,

in inches

Natural

gamma,

in counts

per second

Sonic

(Delta t), in

microseconds

per foot

Resistivity,

in ohm-meters

(16n-short normal,

64n-long normal)

Electromagnetic

conductivity,

in millimhos

per meter

Spontaneous

potential,

in millivolts

Temperature

gradient, in

degrees Celsius

per kilometer

16N

64N

Sandy gravel

Sandy gravel

Sandy silt

Clayey silt

Gravelly sand

Clayey silt

Gravelly sand

Clayey silt

Sandy silt

Silty sand

Silty sand

Gravelly sand

Clayey silt

Silt/clay

Sandy silt

Clayey sandy silt

Silty clay

Silty sand

Silty sand

Silt/clay

Sandy silt

Silt/clay

Silty sand

Silty sand

Clayey silt

Silty sand

Clayey silt

Sandy silt

Silty clay

Silty sand

Silty clay

Silty sand

Zones of flow
16 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 5. Geophysical logs, well-construction diagram, and generalized lithologic description for multiple-well monitoring site Cuyama 

Valley Foothill Road (CVFR), Cuyama Valley, Santa Barbara County, California.

Generalized

lithology

Well

construction

( is depth-to-water,

August 29, 2010)

Recent

Gravelly sand

Gravelly sand

Gravelly silty sand

Gravelly silty sand

Gravelly silty sand

Gravelly silty sand

Gravelly silty sand

Gravelly silty clay

Sandy gravel

Sandy gravel

Sandy gravel

Sandy gravel

Silty sandy gravel

Silty sandy gravel

Silty sand

Silty sand

Clay

Silty sand

Silty sand

Silty sandy

clayey gravel

Slightly gravelly

silty sand

Clay

YoungerAlluvium

Older Alluvium Morales Formation

100

0

200

300

400

500

600

700

800

900

1,000

0 2412

Caliper,

in inches

0 200100 -40 600

Natural

gamma,

in counts

per second

Sonic

(Delta t), in

microseconds

per foot

0 200100 100

Resistivity,

in ohm-meters

(16n-short normal,

64n-long normal)

0 200 0 400200

Electromagnetic

conductivity,

in millimhos

per meter

Spontaneous

potential,

in millivolts

NO DATA

SAND

SAND

SAND

SAND

GROUT GROUT GROUT GROUT

Depth, in feet below land surface

CVFR-1

CVFR-3

CVFR-2

CVFR-4

0 2010

Temperature

gradient, in

degrees Celsius

per kilometer

16N

64N

Zones of flow
Geology 17

Geology

Geologic information was collected to characterize and 

correlate stratigraphic units and boundaries associated with the 

aquifer system. Geologic information for each multiple-well 

monitoring site included lithologic cutting descriptions and a 

suite of geophysical logs. At two locations, CVKR and CVBR, 

whole core samples were collected.

Lithologic Descriptions

Detailed lithologic logs were compiled from descriptions 

of drill cuttings or whole core samples collected at each 

borehole site and from observations recorded during drilling. 

Cuttings samples (tables 4–6), termed “sieved drill cuttings,” 

were composited from 20-foot depth intervals and sieved at 

the borehole surface by using a No. 120 sieve (0.125-mm 

screen opening). Additional cutting samples, termed “shaker 

cuttings,” were collected at 10-ft depth intervals from a No. 60 

screen (0.250-mm screen opening) mounted on the drill rig’s 

shaker tank. 

Sieve and shaker cuttings were first described in the field. 

Subsequently, samples were examined in greater detail in the 

office by using a microscope and characterized by grain size, 

texture, sorting, rounding, color, and other features.

Texture descriptions followed the National Research 

Council (National Research Council, 1947) grain-size 

classification shown in figure 6. This classification allows 

for correlation of grain-size terms (such as “sand”) to size 

limits in millimeters or inches. For samples containing gravel, 

the terms “silt” and “clay” are used in lieu of “mud.” Color, 

determined on moist samples, followed the numerical color 

designations in Munsell Soil Color Charts (Munsell Color, 

1994). Lithologic logs from the sieved drill cuttings are 

presented in tables 4–6. 

The generalized lithology next to each monitoring site 

diagram (figs. 3–5) was compiled by grouping similar 

lithologic units, as determined from the detailed lithologic 

logs from the sieved and shaker samples. The lithologic units 

were categorized into textural groups, such as gravels or sands 

(fig. 6), on the basis of estimated percentages of gravel and 

sand and the ratios of sand, silt, and clay present following 

the nomenclature of Folk (1954). Information collected from 

borehole geophysical logs also was used to help identify 

contact depths between major lithologic units.

Geophysical Logs

Borehole geophysical surveys provided information about 

the nature of the lithologic units and the water chemistry and 

flow patterns of groundwater. Geophysical log surveys were 

done shortly after attaining total hole depth in the uncased, 

fluid-filled borehole. These surveys included caliper, bulknatural gamma, spontaneous potential, 16- and 64-inch normal 

resistivity, electromagnetic induction, and acoustic logs. Highresolution temperature logs were performed in the deepest 

completed well at each site at a later date. Geophysical logs 

for each multiple-well monitoring site are presented in figures 

3–5. 

Calipers were used to measure the diameter of the borehole. 

The caliper log can be used to identify the depth intervals 

of consolidated layers, washed-out sand, or the presence of 

swelling clay. Caliper logs also are useful in the construction 

of multiple-well sites by providing accurate boreholevolume calculations for placement of sand filter packs and 

environmental sealing materials. 

Bulk natural-gamma logs measure the intensity of gammarays emitted from the natural decay of potassium-40 and of 

the daughter products of uranium and thorium (Schlumberger, 

1972). Gamma logs are used primarily to define lithology 

indicators and for correlation of geologic units among 

boreholes within the same region. Typically, increases in 

gamma-ray emissions are observed in clay, feldspar-rich sand 

and gravel, and granite. 

The spontaneous potential (SP) log measures the difference 

in electrical potentials, as a voltage, that develops at the 

contacts between different formations, such as shale or clay 

beds and a sand aquifer. Spontaneous potential is a function of 

the chemical activities of fluids in the borehole and adjacent 

rocks, the temperature, and the type and quantity of clay 

present; therefore, SP logs are directly influenced by the 

drilling fluid in undeveloped water wells. If the drilling fluid in 

the borehole is fresher than the native interstitial water, there 

is a negative spontaneous potential opposite sand beds—this is 

the so-called standard response. If the salinities are reversed, 

the spontaneous-potential response is reversed also (Keys and 

MacCary, 1983). SP logs are not directly related to porosity or 

permeability.

Resistivity tools measure the apparent resistivity of a 

volume of material surrounding the borehole under the 

direct application of an electric current (Keys and MacCary, 

1983). These logs are used to determine formation and fluid 

resistivity and to estimate formation porosity. In general, 

low resistivity indicates water with higher concentrations 

of dissolved solids or fine-grained deposits such as silt, 

clay, and shale; high resistivity indicates water with lower 

concentrations of dissolved solids or coarser material, such as 

sand or gravel. 

The 16-in. normal resistivity probe measures the apparent 

resistivity of material surrounding the borehole that was most 

likely invaded with drilling fluid. The 64-in. normal resistivity 

probe measures the apparent resistivity at a greater radius, 

which is considered to be representative of material that is 

saturated with formation water beyond the invaded zone. 

Comparison of the two logs is a useful indicator of aquifer 

zones with relatively high total dissolved solids. 

Electromagnetic (EM) induction logs yield detailed 

information about the vertical electrical conductivity of 

the formation and pore water (McNeill, 1986). Electrical 

conductivity is affected by the porosity, permeability, clay and 

silt content of the sand-and-gravel aquifers, and the dissolvedsolids concentration of the groundwater in the aquifer. EM 

induction logs can help identify water-bearing units to 
18 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Depth (ft) Description From To

0 20 Sand (S); fine to coarse sand; well sorted; angular to subangular; very pale brown (10YR 7/4)

20 40 Sand (S); fine to medium sand; well sorted; angular to subangular; yellowish brown (10YR 5/4)

40 60 Clayey sand (cS); fine to coarse sand with clay; well sorted; subangular; yellowish brown (10YR 5/4)

60 80 Slightly gravelly sand ((g)S); medium sand with granules to small pebbles; well sorted; subangular; yellowish brown (10YR 5/4)

80 100 Gravelly sand (gS); fine to coarse sand with granules to medium pebbles; poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

100 120 Gravelly sand (gS); very fine to coarse sand with granules to small pebbles; poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)

120 140 Gravelly sand (gS); fine to coarse sand with granules to medium pebbles; poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

140 160 Slightly gravelly sand ((g)S); very fine to very coarse sand with minor small pebbles; poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4) 

160 180 Slightly gravelly sand ((g)S); fine to coarse sand with minor granules; poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

180 200 Sand (S); medium to very coarse sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

200 220 Slightly gravelly sand ((g)S); fine to very coarse sand with granules to small pebbles; poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)

220 240 Gravelly sand (gS); fine to coarse sand with granules; poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

240 260 Slightly gravelly clayey sand ((g)mS); medium to coarse sand with clay and small pebbles; poorly sorted; subrounded to subangular; yellowish 

brown (10YR 5/4)

260 280 Clayey sand (cS); medium sand with clay; very well sorted; rounded to subrounded; yellowish brown (10YR 5/4)

280 300 Clayey sand (cS); medium sand with clay; very well sorted; rounded to subrounded; yellowish brown (10YR 5/4)

300 320 Sand (S); fine to medium sand; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

320 340 Sand (S); fine to medium sand; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

340 360 Sand (S); fine to medium sand; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

360 380 Slightly gravelly sand ((g)S); medium to coarse sand with minor granules; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

380 400 Sand (S); medium to coarse sand; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

400 420 Sand (S); medium to coarse sand; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

420 440 Sand (S); medium to coarse sand; well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

440 460 Sand (S); medium to very coarse sand; well sorted; rounded to subrounded; yellowish brown (10YR 5/4)

460 480 Sand (S); medium to very coarse sand; well sorted; rounded to subrounded; yellowish brown (10YR 5/4)

480 500 Sand (S); fine to medium sand; well sorted; rounded to subrounded; yellowish brown (10YR 5/4)

500 520 Sand (S); very fine to medium sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

520 540 Sand (S); very fine to medium sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

540 560 Sand (S); very fine to medium sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

560 580 Sand (S); very fine to medium sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

580 600 Sand (S); very fine to medium sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

600 620 Sand (S); fine to medium sand; well sorted; subangular; yellowish brown (10YR 5/4)

620 640 Sand (S); fine to coarse sand; well sorted; subangular; yellowish brown (10YR 5/4)

640 660 Sand (S); fine to coarse sand; well sorted; subangular; yellowish brown (10YR 5/4)

660 680 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4) 

680 700 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

700 720 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

720 740 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

740 760 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

760 780 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

780 800 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

800 820 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

820 840 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

840 860 Sand (S); fine to medium sand; well sorted; subangular; yellowish brown (10YR 5/4)

860 880 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

880 900 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

900 920 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

920 940 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

940 960 Sand (S); fine to coarse sand; moderately sorted; subangular; yellowish brown (10YR 5/4)

960 980 Sand (S); fine to coarse sand; well to moderately sorted; subangular; yellowish brown (10YR 5/4)

980 1,000 Sand (S); fine to coarse sand; well to moderately sorted; subangular; yellowish brown (10YR 5/4)

980 1,000 Sand (S); medium to coarse sand with trace granules; well sorted; angular to subangular; yellowish brown (10YR 5/4)

Table 4. Lithologic log from sieved drill cuttings (0.125-millimeter screen opening) from multiple-well monitoring site Cuyama Valley 

Kirschenmann Road (CVKR). 

Cuyama Valley Kirschenmann Road
Geology 19

Table 5. Lithologic log from sieved drill cuttings (0.125-millimeter screen opening) from multiple-well monitoring site Cuyama Valley 

Bell Road (CVBR).

Depth (ft) Description From To

0 19 Slightly gravelly sand ((g)S); medium to coarse sand with minor small pebbles; well to moderately sorted; subrounded to subangular; 

light yellowish brown (2.5Y 6/4)

19 39 Gravelly sand (gS); medium to very coarse sand with granules to medium pebbles; moderately sorted; subrounded to subangular; light 

yellowish brown (2.5Y 6/4)

39 60 Sand (S); fine to medium sand; well sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

60 80 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

80 100 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

100 120 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

120 140 Sand (S); fine to coarse sand; moderately to poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

140 160 Sand (S); fine to very coarse sand with minor clay; poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

160 180 Sandy clay (sC); clay with very fine to medium sand; moderately sorted; light yellowish brown (2.5Y 6/4)

180 200 Sandy clay (sC); clay with fine to medium sand and trace coarse sand; moderately sorted; light yellowish brown (2.5Y 6/4)

200 220 Sand (S); fine to coarse sand; moderately to poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

220 240 Sand (S); fine to very coarse sand; poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

240 260 Silty sand (zS); medium to coarse sand with silt; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

260 280 Slightly gravelly sand ((g)S); fine to very coarse sand with small amounts of medium pebbles; poorly sorted; subrounded to subangular; 

light yellowish brown (2.5Y 6/4)

280 300 Sand (S); fine to coarse sand; moderately to poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

300 320 Sand (S); fine to coarse sand; moderately sorted; rounded to subrounded; light yellowish brown (2.5Y 6/4)

320 340 Silty sand (zS); fine to coarse sand with silt; moderately to poorly sorted; rounded to subrounded; light yellowish brown (2.5Y 6/4)

340 360 Slightly gravelly silty sand ((g)mS); fine to coarse sand with silt and small pebbles; poorly to very poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

360 380 Sand (S); very fine to coarse sand; moderately to poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

380 400 Silty sand (zS); very fine to coarse sand with silt; moderately to poorly sorted; subrounded to subangular; light yellowish brown 

(2.5Y 6/4)

400 420 Silty sand (zS); very fine to coarse sand with silt; moderately to poorly sorted; subrounded to subangular; light yellowish brown 

(2.5Y 6/4)

420 440 Silty sand (zS); very fine to coarse sand with silt; moderately to poorly sorted; subrounded to subangular; light yellowish brown 

(2.5Y 6/4)

440 460 Silty sand (zS); very fine to coarse sand with silt; moderately to poorly sorted; subrounded to subangular; light yellowish brown 

(2.5Y 6/4)

460 480 Sand (S); fine to coarse sand; moderately sorted; rounded to subrounded; light yellowish brown (2.5Y 6/4)

480 500 Sand (S); fine to medium sand; well sorted; rounded to subrounded; light yellowish brown (2.5Y 6/4)

500 520 Sand (S); fine to coarse sand; well sorted; rounded to subrounded; light yellowish brown (2.5Y 6/4)

520 540 Sand (S); fine to coarse sand; well sorted; rounded to subrounded; light yellowish brown (2.5Y 6/4)

540 560 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

560 580 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

580 600 Sand (S); fine to very coarse sand; moderately to poorly sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

600 620 Sand (S); very fine to medium sand; well to moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

620 640 Sand (S); very fine to medium sand; well to moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

640 660 Sand (S); very fine to medium sand; well to moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

660 680 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

680 700 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

700 720 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

720 740 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

740 760 Sand (S); medium to coarse sand; well sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

760 780 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

780 800 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

800 820 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

820 840 Sand (S); fine to medium sand; well sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

840 860 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)

860 880 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; light yellowish brown (2.5Y 6/4)
20 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Table 6. Lithologic log from sieved drill cuttings (0.125-millimeter screen opening) from multiple-well monitoring site Cuyama Valley 

Foothill Road (CVFR).

Depth (ft) Description From To

0 20 Sand (S); medium to coarse sand; well sorted; angular to subangular; light yellowish brown (2.5Y 6/3)

20 40 Slightly gravelly sand ((g)S); fine to coarse sand with minor amounts of medium pebbles; moderately sorted; angular to subangular; 

light olive brown (2.5Y 5/4)

40 60 Slightly gravelly sand ((g)S); fine to very coarse sand with minor amounts of granules; poorly sorted; subangular; light olive brown 

(2.5Y 5/3)

60 80 Sandy gravel (sG); small to medium pebbles with medium to very coarse sand; poorly sorted; subrounded to subangular; light olive 

brown (2.5Y 5/4)

80 100 Gravelly sand (gS); fine to coarse sand with granules to medium pebbles; poorly sorted; angular to subangular; light olive brown 

(2.5Y 5/4)

100 120 Sandy gravel (sG); small to medium pebbles with very fine to coarse sand; very poorly sorted; angular to subangular; light olive brown 

(2.5Y 5/4) 

120 140 Gravelly sand (gS); very fine to coarse sand with granules to medium pebbles; very poorly sorted; angular to subangular; light olive 

brown (2.5Y 5/4)

140 160 Sandy gravel (sG); small to large pebbles with very fine to coarse sand; very poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)

160 180 Gravelly sand (gS); very fine to coarse sand with small to medium pebbles; poorly sorted; angular to subangular; yellowish brown 

(10YR 5/4)

180 200 Sandy gravel (sG); granules to very large pebbles with very fine to coarse sand; very poorly sorted; angular; yellowish brown 

(10YR 5/4)

200 220 Sandy gravel (sG); granules to medium pebbles with very fine to medium sand; poorly sorted; angular to very angular; yellowish brown 

(10YR 5/4)

220 240 Gravelly silty sand (gmS); fine to coarse sand with silt and small to medium pebbles; poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

240 260 Gravelly silty sand (gmS); fine to coarse sand with silt and small pebbles; poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)

260 280 Gravelly sand (gS); medium to coarse sand with small pebbles; moderately sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)

280 300 Sand (S); fine to medium sand; well sorted; subangular to subrounded; yellowish brown (10YR 5/4)

300 320 Sand (S); very fine to coarse sand; moderately sorted; rounded to subrounded; yellowish brown (10YR 5/4)

320 340 Sand (S); very fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

340 360 Slightly gravelly sand ((g)S); very fine to coarse sand with minor granules to small pebbles; poorly sorted; subrounded to subangular; 

yellowish brown (10YR 5/4)

360 380 Slightly gravelly sand ((g)S); very fine to very coarse sand with minor granules and clay; poorly sorted; angular to subangular; yellowish brown (10YR 5/4)

380 400 Sand (S); very fine to coarse sand; moderately to poorly sorted; subangular to subrounded; yellowish brown (10YR 5/4)

400 420 Gravelly sand (gS); very fine to coarse sand with granules; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

420 440 Gravelly sand (gS); very fine to coarse sand with granules; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

440 460 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

460 480 Slightly gravelly sand ((g)S); fine to coarse sand with small amounts of granules; moderately sorted; angular to subangular; yellowish 

brown (10YR 5/4)

480 500 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

500 520 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

520 540 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

540 560 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

560 580 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

580 600 Sand (S); fine to coarse sand; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

600 620 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

620 640 Sand (S); fine to very coarse sand; moderately to poorly sorted; angular; yellowish brown (10YR 5/4)

640 660 Gravelly sand (gS); fine to very coarse sand with granules; poorly sorted; angular; yellowish brown (10YR 5/4)

660 680 Sand (S); fine to very coarse sand; poorly sorted; angular; yellowish brown (10YR 5/4)

680 700 Gravelly sand (gS); medium to very coarse sand with granules; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

700 720 Gravelly sand (gS); medium to very coarse sand with granules; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

720 740 Gravelly sand (gS); fine to very coarse sand with granules; poorly sorted; angular to subangular; yellowish brown (10YR 5/4)

740 760 Gravelly sand (gS); fine to very coarse sand with granules; poorly sorted; angular to subangular; yellowish brown (10YR 5/4)

760 780 Gravelly sand (gS); medium to very coarse sand with granules; moderately sorted; angular to subangular; yellowish brown (10YR 5/4)

780 800 Sand (S); fine to very coarse sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

800 820 Sand (S); fine to coarse sand; moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

820 840 Gravelly sand (gS); fine to very coarse sand with granules to small pebbles; poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)
Geology 21

Depth (ft) Description From To

840 860 Gravelly sand (gS); fine to coarse sand with granules; moderately to poorly sorted; subrounded to subangular; yellowish brown 

(10YR 5/4)

860 879 Sand (S); fine to very coarse sand; moderately to poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

879 899 Slightly gravelly sand ((g)S); fine to medium sand with minor small pebbles; moderately sorted; subrounded to subangular; yellowish 

brown (10YR 5/4)

899 919 Sand (S); very fine to very coarse sand; poorly sorted; subrounded to subangular; yellowish brown (10YR 5/4)

919 939 Sand (S); very fine to medium sand; well to moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

939 959 Sand (S); very fine to medium sand; well to moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

959 979 Sand (S); fine to coarse sand; well to moderately sorted; subrounded to subangular; yellowish brown (10YR 5/4)

979 1,000 Sand (S); medium sand; very well sorted; subrounded to subangular; yellowish brown (10YR 5/4)

Table 6. Lithologic log from sieved drill cuttings (0.125-millimeter screen opening) from multiple-well monitoring site Cuyama Valley 

Foothill Road (CVFR).—Continued

determine optimum depths for the placement of monitoring 

well screens and can help identify temporal changes in water 

quality through sequential logging (Williams and others, 

1993). 

An acoustic (sonic) log measures the time it takes for a 

pulsed compressional sound wave to travel from a downhole 

source to downhole receivers. The sonic tool used has two 

receivers, near and far, that recorded the arrival time of the 

compressional sound wave. The difference in arrival times 

between the receivers, or delta t, can be related to the physical 

properties of the adjacent material. In unconsolidated material, 

sonic logs principally are used to identify contacts between 

lithologic units that were penetrated by the borehole.

Temperature Logs

High-resolution borehole temperature logs were collected 

in the deepest well at each multiple-well monitoring site 

on June 24, 2010. To ensure that the water temperature was 

characteristic of ambient groundwater conditions, logging was 

performed several months after the site had been constructed, 

developed, and sampled for water-quality to allow sufficient 

time for the water column in the well to equilibrate with the 

surrounding material. Generally, groundwater temperature 

increases with depth, and the global average is about 25 

degrees Celsius (°C) per kilometer. The geothermal gradient 

in sedimentary basins generally exceeds this average because 

of the relatively low thermal conductivity of sedimentary 

Figure 6. Rock-type nomenclature used for lithologic-log descriptions.

M sM

30 

80 

5 

Trace

(0.01%) 

G 

sG 

(g)M (g)S

mG msG

gM gmS

(g)sM (g)mS 

gS 

S 

GRAVEL 

Gravel, in percent (%) 

Samples containing gravel 

(>2 mm) 

Clay + Silt: Sand ratio 

9:1 1:1 1:9

<0.0625 mm) 

Silt + Clay (0.625-2 mm)

MUD SAND 

mS 

50 

90 

10 

S 

Sand, in percent (%) 

SAND 

Clay:Silt ratio 

CLAY 2:1 1:2 SILT

Samples with no gravel present 

cS zS 

sC sZ 

M Z

sM 

mS 

C 

EXPLANATION 

Gravel 

Gravelly 

Slightly gravelly 

G 

g 

(g) 

Silt 

Silty 

Z 

z 

Sand 

Sandy 

S 

s 

Clay 

Clayey 

C 

c 

Mud 

Muddy 

M 

m 

> is greater than; < is less than; mm is millimeters
22 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Table 7. Summary of cores collected from multiple-well monitoring sites, Cuyama Valley groundwater basin, Santa Barbara County, 

California.

[See table 1 for definitions of common well names. Abbreviations: —, data not available; ft bls, feet below land surface; %, percent; F, fine; VF, very fine; M, medium; C, coarse]

Common 

well name

Core ID (sitecore#-section)

Top of 

core interval 

(ft bls)

Bottom of core 

interval 

(ft bls)

Total coreinterval length 

(ft)

Total 

recovery 

(%)

Description

CVKR CVKR-1C-1 1,000.5 1,003.5 3 93 Interbedded clay, sand, and sandstone throughout

CVBR CVBR-1C-1 903 906 3 88 Top: clay with minor sand (F); Bottom: Silty sand (VF-M with trace C)

CVFR — — — — — No core collected

materials (Ingebritsen and Sanford, 1998). Perturbations 

in the geothermal gradient in temperature logs can provide 

information about geologic formations as well as horizontal 

and vertical groundwater-flow patterns. Groundwater 

temperature is related to factors such as lithology (which 

affects thermal conductance), depth, recharge source, and 

residence time within the aquifer. Measured temperature 

logs, when expressed as a measured vertical temperature 

gradient and compared with the geothermal gradient, can be 

used to identify potential zones of groundwater flow. Depth 

intervals where the temperature gradient is concave upward, 

or increases more quickly than the geothermal gradient, are 

consistent with the cooling influence of groundwater flow 

through relatively permeable units. Depth intervals exhibiting 

greater temperature perturbation (relatively large increases in 

temperature gradient with depth) can be interpreted as zones 

of greater flow.

Changes in the temperature gradients were used, in 

conjunction with other logs, to identify discrete flow zones at 

each monitoring site (see figs. 3, 4 and 5). At the CVKR site 

(fig. 3), five flow zones were identified: (1) 513–637 ft, (2) 

655–695 ft, (3) 745–804 ft, (4) 823–850 ft, and (5) 865–880 

ft below land surface. A comparison of the magnitude of the 

vertical change in temperature gradient with depth among flow 

zones indicated a general decrease in flow with increasing 

depth and that the majority of flow at the CVKR site is in the 

shallowest zone. This zone not only is the thickest, but also 

showed the greatest temperature perturbation. At the CVBR 

site (fig. 4), six flow zones were identified: (1) 357–385 ft, (2) 

520–590 ft, (3) 625–670 ft, (4) 690–710 ft, (5) 735–760 ft, and 

(6) 825–840 ft below land surface. A comparison of the flow 

zones indicated a general decrease in flow with increasing 

depth and that a majority of the flow is in zone 2. Similar in 

nature to the zone of greatest flow at CVKR site, zone 2 is the 

thickest at CVBR and also showed the greatest temperature 

perturbation. At the CVFR site (fig. 5), eight flow zones were 

identified: (1) 580–600 ft, (2) 610–630 ft, (3) 667–720 ft, (4) 

730–775 ft, (5) 795–825 ft, (6) 860–870 ft, (7) 885–900 ft, 

and (8) 940–967 ft below land surface. Overall, differences 

in flow among zones at CVFR were less apparent than at the 

other sites, as was indicated by a relatively small perturbation 

in the gradient. The majority of flow at CVFR could be in the 

deepest zones (7 and 8), unlike the CVKR and CVBR sites. 

Although the deeper zones at CVFR are not as thick as some 

of the shallower zones, they exhibited greater fluctuations in 

the temperature gradient.

Core Measurements

Core samples were collected from the bottom of the 

borehole at the CVKR and CVBR sites. The cores were 

collected in 3-inch-diameter thin-walled metal tubes. Each 

coring “push” retrieved a cylinder of sediment as long as 3 

feet. The locations, depths, and the total recovery of these core 

samples are given in table 7. The CVKR core was analyzed 

for bulk density and sonic velocity (fig. 7) by using a multisensor core log scanner (Kayen and others, 1999). The CVKR 

core varied in density from approximately 1.5–2.7 grams per 

cubic centimeter. Density changes indicated seven distinct 

layers within the 2.8 feet of recovered sediment. On the basis 

of a visual inspection of the top and bottom of the core, and 

the density measurements, the core was characterized as 

interbedded clay, sand, and sandstone. The CVBR core was 

not analyzed with a multi-sensor core log scanner. The top of 

the core contained clay and minor fine sands, and the bottom 

of the core contained a silty very fine to medium sand. For 

any future use, the cores were sealed and are stored under 

refrigerated conditions at the USGS core storage facility in 

Menlo Park, California.

Geology at the Monitoring Well Sites

Geologic maps of the Cuyama Valley (Vedder and 

Repenning, 1975; Kellogg and others, 2008) show two units 

of Holocene and Pleistocene-aged alluvial deposits, termed 

younger and older alluvium, underlying the three monitoringwell sites. Interpretive geologic cross sections, which were 

based in part on deep oil and gas exploration wells, showed 

that these alluvial deposits extend to a depth of approximately 

1,000 ft bls beneath the monitoring-well sites (Vedder and 

Repenning, 1975). These alluvial deposits are underlain by the 

weakly to moderately indurated arkosic Morales Formation 

of Pleistocene to upper Pliocene age. The three multiplewell monitoring sites test different sections of the basin-fill 

alluvial stratigraphy relative to their locations within the basin 

(fig. 1). The CVKR site is in the main axis of Cuyama Valley 

in younger alluvium, west of the active alluvial channel of 

the Cuyama River. The CVFR site, 3.8 miles to the southeast 

of CVKR at the northern edge of the Central Sierra Madre 

Foothills zone, is also west of the active alluvial channel of 

the Cuyama River, but is close to the mapped contact between 
Geology 23

younger and older alluvium. The CVBR site is in the alluvial 

uplands that lie to the north of the Sierra Madre Mountains 

and south of Cuyama Valley, next to the Salisbury Canyon 

drainage. The well site is in older alluvium; the site is above 

and to the west of the young alluvial fill in the main part of the 

valley.

Lithologic and borehole geophysical logs aided 

distinguishing among the younger and older alluvium and the 

underlying Morales Formation. Younger alluvium in Cuyama 

Valley tends to be the coarsest-grained deposit, typically 

consisting of unconsolidated sand, gravel, and boulders, with 

some clay. These coarse-grained deposits tended to yield 

the greatest response on borehole resistivity logs and, where 

thin clays were present, indicated large SP-log deflections 

as well. By contrast, the relatively fine-grained, massively 

bedded Morales Formation typically yielded a subdued 

response on SP and resistivity logs. The older alluvium 

produced an intermediate response on borehole geophysical 

logs. Similar to the younger alluvium, the older alluvium 

contains unconsolidated to partly consolidated sand, gravel, 

and boulders, but the older alluvium also contains a significant 

amount of fine-grained arkosic sands and clays that are 

derived from erosional reworking of the underlying Morales 

Formation.

The CVKR borehole penetrated terrestrial siliciclastic 

sediments that are alluvial fan and stream deposits. The 

geophysical logs indicated a distinct drop-off in resistivity 

at about 365 ft bls, which was interpreted as the contact 

of younger alluvium overlying more consolidated older 

alluvium. Sediments encountered in the CVKR borehole at 

depths of 365–620 ft bls, correlating to the top of the Older 

Alluvium, were much more consolidated than expected from 

the descriptions of these units published on the geologic 

maps. A paleosol (buried soil horizon) was encountered at the 

CVKR site at approximately 505 ft bls, further subdividing the 

sequence of consolidated older alluvium (fig. 3). The highest 

level of natural gamma radioactivity was observed within, and 

just above, this paleosol. This paleosol was not encountered at 

the other drill sites.

On the basis of an absence of distinctive changes in either 

the geophysical logs or mineralogy of the sediments, the 

CVKR wellbore did not reach the Morales Formation. The 

core collected from the bottom of the borehole contained 

interbedded clay, sand, and sandstone. Two oil and gas 

exploration holes drilled 1,500 ft and 4,300 ft to the northwest 

of the CVKR borehole have geophysical logs that begin about 

1,400 ft bls (California Division of Oil, Gas and Geothermal 

Resources, accessed in July 2009, at http://owr.conservation.

ca.gov/WellSearch/WellSearch.aspx). Geophysical logs from 

these wells showed they were both in Morales Formation at 

this depth. If similar conditions exist beneath the CVKR site, 

this places a lower bound on the thickness of older alluvium at 

the CVKR site.

The CVBR borehole penetrated terrestrial siliciclastic 

sediments that are alluvial fan and stream deposits (fig. 4). The 

well penetrated an upper 30-ft thick section of sandy gravel 

with high and variable resistivity on borehole geophysical 

logs that can be interpreted as recent deposits (fig. 4). This 

thin layer of younger alluvium, consistent with the position of 

this well, is in the uplands on the southern edge of the valley, 

which are mapped as underlain by older alluvial deposits. 

The geophysical logs had an interval of moderate resistivity 

response between 30 ft bls and 240 ft bls that we interpreted 

as more consolidated older alluvium (fig. 4). The interval 

between 260 ft bls and 595 ft bls is characterized by silty 

sands, with some intervals of gravelly sands, and generally 

low-resistivity values on borehole geophysical logs. This 

interval was interpreted to be part of the older alluvium; it 

could correlate to the older, deformed alluvium of Vedder and 

Repenning (1975). This interval appeared to be lithologically 

similar to the underlying Morales Formation and could be 

composed, in large part, from sediments derived from erosion 

of the Morales Formation.

The contact between the older alluvium and the Morales 

Formation at CVBR was interpreted to be at about 595 ft 

bls and was below the deepest elevated resistivity values 

(fig. 4). Below this point, resistivity values were generally 

low, and the lithology is uniformly silty clay. No distinctive 

changes in the mineralogy of the sediments were observed at 

this site. The core collected from the bottom of the borehole 

contained a clay with minor fine sand and a silty very fine 

to medium sand. An oil and gas exploration well 2,900 ft 

to the northwest of CVBR was reported to have an electriclog response interpreted as Morales Formation at 840 ft bls, 

Figure 7. Sonic velocity and bulk density of core CVKR-1C-1 

collected from the bottom of the Cuyama Valley Kirschenmann 

Road (CVKR) borehole, Cuyama Valley, Santa Barbara County, 

California.

0

10

20

30

40

50

60

70

80

90

100

0.5 1 1.5 2 2.5

Increment, in cemtimeters

Velocity, in kilometers per second

1 1.5 2 2.5 3

Density, in grams per cubic centimeter
24 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12

where the geophysical logging of this hole began (California 

Division of Oil, Gas and Geothermal Resources, accessed 

on July, 2009, at http://owr.conservation.ca.gov/WellSearch/

WellSearch.aspx). The top of the Morales Formation in this oil 

and gas exploration well is shallower than 840 ft bls, which is 

generally consistent with the interpreted top of the Morales in 

CVBR.

The CVFR borehole penetrated terrestrial siliciclastic 

sediments that are alluvial fan and stream deposits (fig. 5). 

The upper 75 ft of the hole are characterized by sandy gravel, 

granules to medium pebbles, and medium to very coarse 

sand with relatively high values of resistivity; this interval 

can be interpreted as recent deposits and younger alluvium. 

Deposits below 75 ft bls are also coarse-grained, but contain 

minor amounts of silt and clay and had less resistivity on 

geophysical logs; these deposits were interpreted as older, 

more consolidated alluvium. The relatively thin interval of 

younger alluvium is consistent with the location of this well 

near the mapped surface expression of the contact between 

younger and older alluvium.

The contact between the older alluvium and the underlying 

Morales Formation at CVFR was interpreted to be at 560 ft 

bls on the basis of the lack of pebbles and gravel and overall 

drop in resistivity values to consistently low values below this 

depth (fig. 5). No distinctive changes in the mineralogy of the 

sediments were observed at this site. 

Geophysical logs from well CUY-06, on the east side 

of the Cuyama River 1.25 mi east-southeast of the CVFR 

site, showed a similar drop in resistivity at about 600 ft bls, 

which was interpreted as the depth of the contact between 

the older alluvium and the Morales Formation. Geophysical 

logs from an oil and gas exploration hole drilled 1-mi eastsoutheast of the CVFR borehole (California Division of Oil, 

Gas and Geothermal Resources, accessed on July, 2009, at 

http://owr.conservation.ca.gov/WellSearch/WellSearch.aspx) 

showed high resistivity values typical of younger alluvium to a 

depth of 1,100 ft bls, below which an abrupt drop in resistivity 

values to low values typical of the Morales Formation was 

observed. This well, very close to the active channel of the 

Cuyama River, could record the local presence of a channel 

scoured through the older alluvium, placing young alluvial 

channel fill directly on the Morales Formation.

Water-Quality

Groundwater samples were collected from the 12 

monitoring wells (4 wells at each of the 3 multiple-well 

monitoring sites), 27 selected domestic and supply wells, and 

2 springs (fig. 8). In addition, four surface-water samples were 

collected (fig. 8). Samples were analyzed for as many as 53 

constituents, including field parameters (water temperature, 

specific conductance, pH, dissolved oxygen, and alkalinity); 

major and minor ions; nitrate; trace elements; stable isotopes 

of hydrogen and oxygen; tritium and carbon-14 activities; and 

species of arsenic, iron, and chromium. Selected water-quality 

constituents results are presented. Water-quality results not 

presented in this report are available through the USGS NWIS 

web site.

Field and Laboratory Methods

Sampling was done by USGS personnel, and all samples 

were collected, handled, and preserved following written 

USGS field procedures (U.S. Geological Survey, variously 

dated). Prior to sampling, water-level measurements were 

made, and at least three well-casing volumes were purged 

from the well. For monitoring wells, a portable submersible 

pump was used for purging and sampling the well; for 

domestic and supply wells, samples were collected from the 

discharge of the installed pump before it entered a storage tank 

or any treatment. Specific conductance, pH, and temperature 

were monitored during the purging process. Samples were 

collected only after these parameters had stabilized. Stability 

was attained when three successive measurements taken 

at intervals of 5 minutes or more differed by less than 5 

percent for specific conductance, 0.1 units for pH, and 0.2°C 

for temperature. Purge logs, field measurements, and other 

information related to sample collection are on file at the 

USGS office in San Diego, California.

During sample collection, water from the pump was 

diverted into a special sample-collection chamber designed 

to minimize contamination. Most water samples intended 

for routine analyses (major and minor ions, nutrients, and 

trace elements) were pressure-filtered in the field through a 

polyethersulfone (PES) membrane capsule filter having a pore 

size of 0.45 μm. Laboratory samples intended for the analysis 

of pH, specific conductance, and acid-neutralizing capacity 

were not filtered. Polyethylene bottles were used to contain 

most samples and were rinsed three times with filtered native 

water prior to filling. Samples for nutrient determinations were 

collected in dark, opaque polyethylene bottles and preserved 

on ice to inhibit bacterial growth. Samples for cations and 

selected trace element determinations were collected in 

acid-rinsed polyethylene bottles and preserved by acidifying 

the sample to a pH less than 2 with a small volume of 

concentrated nitric acid. Samples for anion determination were 

collected in a natural polyethylene bottle and did not require 

preservation. Samples were shipped to the USGS National 

Water Quality Laboratory (NWQL) in Lakewood, Colorado, 

for analysis following standard methods outlined by Fishman 

and Friedman (1989), Fishman (1993), Struzeski and others 

(1996), Garbarino (1999), and Garbarino and others (2006). 

Water samples for analysis of stable isotopes of hydrogen 

and oxygen (δ2

H and δ18O) were collected in 60-mL glass 

bottles. These samples were not filtered. The bottles were not 

rinsed, but were sealed with a special polyseal (conical) cap to 

minimize exchange with the atmosphere. These samples were 

shipped to the USGS Stable Isotope Laboratory in Reston, 

Virginia, for analysis according to methods outlined by Coplen 
Water-Quality 25

166

166

33

33

Cuyama

Ventucopa

New Cuyama

Kern

County

Ventura

County

Santa Barbara

County

San Luis Obispo

County

119°50’ 119°40’ 119°30’ 119°20’

35°

34°

50’

34°

40’

Reyes Creek

Cuyama

Creek

Sierra Madre Mountains

Tehachapi

Cuyama Valley

groundwater

basin

Cuyama River

Caliente Range

Mts

EXPLANATION

0 5 10 Miles

0 5 10 Kilometers

Shaded relief base created from 30-m digital elevation model from USGS National 

Elevation Dataset (NED), North America Vertical Datum 1988 (NAVD88)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009 

Albers Projection, NAD83

Cuyama groundwater basin zones

Caliente Northern-Main

Central Sierra Madre Foothills

Northeast Ventucopa Uplands

Northwestern Sierra Madre Foothills

Northern Ventucopa Uplands

Southern Sierra Madre Foothills

Southern Ventucopa Uplands

Southern-Main

Western Basin

Site type

Spring

Surface-water site

U.S. Geological Survey 

monitoring site

Water-quality site

SW-04

SW-03

SW-02

SW-01

SP-02

SP-01

CUY-01

CUY-26

CUY-20

CUY-02

CUY-04 CUY-05

CUY-22

CUY-23 CUY-07

CUY-08 CUY-21

CUY-24

CUY-25

CUY-06

CUY-12

CUY-03

CUY-19

CUY-18

CUY-17

CUY-11

CUY-63

CUY-61

CUY-16 CUY-64

CUY-14

CUY-28 CUY-13

CVKR 1-4

CVBR 1-4

CVFR 1-4

and others (1991). The results of these determinations are 

expressed in terms of per mil relative to Vienna Standard 

Mean Ocean Water (Gonfiantini, 1984). The estimates of 

precision (two-sigma) for δ2H and δ18O are 2 are 0.2 per mil, 

respectively.

Water samples intended for the analysis of tritium were 

collected in one-L polyethylene bottles. The samples were 

not filtered. Bottles were not rinsed and care was taken not 

to aerate the sample during collection. Samples were sealed 

with a polyseal (conical) cap to minimize exchange with 

the atmosphere. These samples were analyzed at the USGS 

Isotope Tracers Laboratory in Menlo Park, California, or at the 

University of Miami (through arrangements with the NWQL), 

by gas counting (or liquid scintillation) after electrolytic 

enrichment as described by Ostlund and Dorsey (1977) and 

Ostlund and others (1987). The activity of tritium is reported 

in terms of picocuries per liter (pCi/L) plus or minus the 1 

sigma combined standard uncertainty (CSU). Tritium values 

less than the sample-specific critical level (ssLC) are reported 

as non-detections.

Water samples for analysis of δ13C and carbon-14 isotopes 

were collected in either a 500-milliliter (mL) or one-liter (L) 

plastic coated glass bottle fitted with a polyseal cone cap. 

Samples were filtered in the field through PES membrane 

Figure 8. The location of multiple-well monitoring sites, 

domestic and supply wells, springs, and surface water sites 

with available water-quality data, Cuyama Valley, Santa 

Barbara County, California.
26 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

capsule filter having a pore size of 0.45 micrometer (μm). The 

bottle was bottom-filled and allowed to overflow to several 

times the bottle volume, then sealed with a special Teflonsepta cap and held on ice. δ13C and carbon-14 of the dissolved 

inorganic carbon were analyzed by the National Ocean 

Sciences Accelerator Mass Spectrometry Facility (NOSAMS) 

in Woods Hole, Mass., by accelerator mass spectrometry 

(through arrangements with the NWQL). Results of the δ13C 

determination are reported in per mil relative to the Vienna 

PeeDee belemnite standard (Coplen, 1994). The activity 

of carbon-14 expressed as percent modern carbon (pmc) is 

reported with a 1-sigma estimate of precision relative to the 

1950 National Bureau of Standards (NBS) oxalic acid standard 

(Stuiver and Polach, 1977; Wigley and Muller, 1981). 

Water samples intended for analysis of chromium species 

were collected by using a 10-mL syringe with an attached 

0.45-μm disk filter. After the syringe was thoroughly rinsed 

and filled with native water, 4 mL were forced through the 

disk filter; the next 2 mL of native water was slowly filtered 

into a small centrifuge vial and analyzed for total chromium. 

Hexavalent chromium, Cr (VI), was then collected by 

attaching a small cation-exchange column to the syringe filter, 

and after conditioning the column with 2 mL of sample water, 

two mL were collected in a second centrifuge vial. Vials for 

both constituents were preserved with 7.5 Normal (N) nitric 

acid (Ball and McCleskey, 2003a and 2003b). Water samples 

intended for analysis of arsenic and iron species were filtered 

into 250-mL polyethylene bottles that were covered with tape 

to prevent light exposure and preserved with 6 N hydrochloric 

acid. Total chromium, total arsenic, total iron, and the 

dissolved concentration of either the reduced or the oxidized 

species of the element were analyzed at the USGS National 

Research Program (NRP) Trace Metal Laboratory (TML) in 

Boulder, Colorado, by using various techniques of ultraviolet 

visible (UV-VIS) spectrophotometer and atomic absorbance 

spectroscopy (Stookey, 1970; Ball and McCleskey, 2003a and 

2003b; McCleskey and others, 2003). 

Comparison Benchmarks

Concentrations of constituents detected in groundwater 

samples were compared with U.S Environmental Protection 

Agency (USEPA) and California Department of Public Health 

(CDPH) regulatory and non-regulatory drinking-water healthbased benchmarks and benchmarks established for aesthetic 

purposes (California Department of Public Health, 2012a 

and 2012b; U.S. Environmental Protection Agency, 2012a 

and 2012b). The chemical data presented in this report are 

meant to characterize the quality of the untreated groundwater 

within the primary aquifer system of the Cuyama Valley 

groundwater basin and are not intended to represent the treated 

drinking water delivered to consumers by water purveyors. 

The chemical composition of treated drinking water can differ 

from untreated groundwater because treated drinking water 

can be subjected to disinfection, filtration, mixing with other 

waters or exposure to the atmosphere prior to its delivery 

to consumers. Comparisons of untreated groundwater to 

benchmarks are for illustrative purposes only and are not 

indicative of compliance or non-compliance with drinkingwater regulations. Three benchmarks—maximum contaminant 

level, secondary maximum contaminant level, and public 

health goal—are used for comparisons. The maximum 

contaminant level (MCL) is a legally enforceable standard 

that applies to public-water systems and is designed to protect 

public health by limiting the levels of contaminants in drinking 

water. MCLs established by the USEPA are the minimum 

standards with which states are required to comply, and 

individual states may choose to set more stringent standards. 

The CDPH has established MCLs for additional constituents 

not regulated by the USEPA, as well as lowered the 

benchmark concentrations for a number of constituents with 

MCLs established by the USEPA. In this report, a benchmark 

set by the USEPA is labeled “MCL-US,” and one set by the 

CDPH that is more stringent than the MCL-US is labeled 

“MCL-CA.” The secondary maximum contaminant level 

(SMCL) is a non-enforceable standard applied to constituents 

that affect the aesthetic qualities of drinking water, such as 

taste, odor, and color, or the technical qualities of drinking 

water, such as scaling and staining. Both the USEPA and the 

CDPH define SMCLs, but unlike MCLs, SMCLs established 

by the CDPH are not required to be at least as stringent 

as those established by USEPA. In this report, the USEPA 

SMCLs (SMCL-US) are used unless the SMCLs established 

by the CDPH (SMCL-CA) have a lower value. The public 

health goal (PHG) is a non-enforceable standard set by the 

California Office of Environmental Health Hazard Assessment 

(OEHHA). In this report, the public health goal (OEHHAPHG) is listed for hexavalent chromium (Cr-VI), which does 

not have a MCL or SMCL; for constituents that have a MCL, 

the OEHHA-PHG is typically orders of magnitude lower 

than the MCL. The benchmark type and benchmark level are 

included in all tables with water-quality data.

Selected Chemical Attributes

Water-quality data indicated that the groundwater in the 

alluvial aquifer system generally has high concentrations 

of total dissolved solids and sulfate. Concentrations greater 

than the SMCL-US for total dissolved solids (greater than 

500 mg/L) were observed in samples collected from 38 of 39 

wells (97 percent); concentrations greater than the SMCL-US 

for sulfate (greater than 250 mg/L) were observed in samples 

collected from 37 of 39 wells (95 percent; table 8). 

Table 8. Results for analyses of major and minor ions, silica, 

and total dissolved solids in samples collected from selected 

sites, Cuyama Valley groundwater basin, Santa Barbara County, 

California. 

Table available separately as Microsoft Excel® at 

http://pubs.usgs.gov/sir/2013/5108.
Water-Quality 27

Concentrations greater than the MCL-US for 

nitrate were observed in 5 of the 39 wells (13 percent; 

table 9). Concentrations greater than the MCL-US for 

arsenic were observed in 4 of 33 wells (12 percent; table 

10). Concentrations of fluoride greater than the MCL-CA of 

2 mg/L were observed in one well (CUY-20; table 8). 

Table 9. Results for analyses of stable isotopes, tritium and 

carbon-14, estimated age since recharge, and nitrate in samples 

collected from selected sites, Cuyama Valley groundwater basin, 

Santa Barbara County, California.

Table available separately as Microsoft Excel® at 

http://pubs.usgs.gov/sir/2013/5108.

Table 10. Results for analyses of arsenic, iron, and chromium 

speciation and dissolved oxygen in samples collected from 

selected well sites, Cuyama Valley, Santa Barbara County, 

California.

Table available separately as Microsoft Excel® at 

http://pubs.usgs.gov/sir/2013/5108.

Five wells (CVKR-2, CVBR-1, CVBR-2, CVBR-3, 

CUY21) had concentrations of manganese greater than the 

SMCL-US of 50 μg/L; one of these wells (CUY-21) also had 

concentrations of iron greater than the SMCL-US of 300 μg/L 

(table 10). One well (CUY-20) had concentrations of chloride 

greater than the SMCL-US of 250 mg/L (table 8), and one 

well (CVKR-4) had concentrations of aluminum greater than 

the SMCL-US of 50 mg/L (table 10).

Major Ions

Piper diagrams show the relative abundance of major 

cations and anions (on a charge equivalent basis) as a percentage of the total ion content of the water (Piper, 1944). Piper 

diagrams often are used to define groundwater type (Hem, 

1992). In this report, the dominant cation and anion species 

are used to describe the water type of a water sample when a 

single cation or anion composes more than 60 percent of the 

total cations or anions, respectively. Where no one cation or 

anion exceeds 60 percent, the first and second most abundant 

cations or anions are given for description purposes.

The samples from CVKR were characterized as calciummagnesium sulfate waters (fig. 9A) and had total dissolvedsolids concentrations ranging from 1,480 to 1,930 mg/L 

(table 8). The samples from CVBR were calcium-magnesium 

sulfate waters and had total dissolved-solids concentrations 

ranging from 772 to 1,560 mg/L. The samples from CVFR 

also were calcium-magnesium sulfate waters and had total 

dissolved-solids concentrations ranging from 1,140 to 

1,480 mg/L. At the CVFR site, total dissolved-solids increased 

with depth, but the highest concentrations were observed in 

samples collected from the shallowest wells at the CVKR and 

CVBR sites. The majority of the other groundwater samples 

also were calcium-magnesium sulfate waters (fig. 9B). A few 

samples had a lesser abundance of calcium and magnesium 

and a greater abundance of sodium (fig.9B), which is 

consistent with loss of calcium and magnesium from solution 

by means of ion exchange with sodium attached to clays; this 

process is commonly observed in groundwater with longer 

residence times and abundant clays in the subsurface. 

Nitrate

Samples from all 12 monitoring wells, 27 additional wells, 

2 springs, and 2 surface-water sites were analyzed for nitrate. 

Nitrate concentrations reported as nitrogen (NO3

-N) ranged 

from less than 0.02 to 45.3 mg/L (table 9). Five of the samples 

(CVKR-4, CUY-04, -07, -20, and -61) had concentrations 

greater than the MCL-US of 10 mg/L.

At the CVKR site, nitrate concentrations ranged from 0.45 

to 15.2 mg/L and decreased with depth. At the CVBR site, 

nitrate concentrations were 1.01 mg/L in the shallowest well 

and were below the detection limit of 0.04 in the three deeper 

wells. At the CVFR site, nitrate concentrations ranged from 

estimated values of 0.53 to 1.37 mg/L and, generally, increased 

with depth.

Irrigation return flows are a possible source of the 

high nitrate concentrations detected in the Cuyama Valley 

groundwater basin. A majority of the agricultural activity 

within the Cuyama Groundwater basin lies within the Caliente 

Northern-Main and Southern-Main zones and within the 

northern half of the Southern Ventucopa Uplands. Four of the 

wells (CVKR-4, CUY-4, -07, -61) where the nitrate levels were 

greater than the MCL were in the Southern-Main zone (fig. 8) 

in the center of the agricultural land-use area. A decrease in 

concentrations with depth at the CVKR site, in the center of 

the Southern-Main zone, indicated the source of higher nitrate 

concentrations is likely to be near the surface. Four wells 

(CUY-2, -16, -21, -28), where the observed nitrate levels were 

the lowest, below 0.15 mg/L, were south of the Southern-Main 

zone, outside of the agricultural-use area. Low concentrations 

of nitrate, less than 0.02 mg/L, in the surface-water samples 

indicated that surface-water recharge was not a source of high 

nitrate.

Isotope Analyses

Oxygen-18 (18O) and deuterium (2H) are naturally occurring 

stable isotopes of oxygen and hydrogen. The isotopic ratios are 

expressed in delta notation (δ) as per mil (parts per thousand) 

differences relative to the standard known as Vienna Standard 

Mean Ocean Water (VSMOW) (Gonfiantini, 1978). The δ2

H 

and δ18O composition of precipitation throughout the world is 

linearly correlated because most of the world’s precipitation 

is derived from the evaporation of seawater. This linear 

relationship is known as the global meteoric water line (Craig, 

1961). The stable isotope ratios of oxygen and hydrogen in 

groundwater reflect the altitude, latitude, and temperature of 

recharge and the extent of evaporation before the water entered 

the groundwater system. Isotope ratios were analyzed from 

water samples collected from all of the monitoring sites, 21 

selected wells, 4 surface-water collection sites, and 2 springs.

The isotope samples from the three deeper CVKR wells 

became progressively lighter (more negative), indicating 

that groundwater does not move freely between the different 

flow paths of the older alluvium and that the units within the 
28 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

80

100

20

0

60

40

40

60

20

0

80

100

20

40

60

80

20

0

80

100

40

60

60

40

80

100

20

0

100

80

60

40

20

0

0

100

0 20 40 60 80 100

0

20

40

60

80

100

100

80

60

40

20

0

100 80 60 40 020

Bicarbonate (HCO3

) + Carbonate (CO3

) 

Calcium (Ca) + Magnesium (Mg)

Chloride (Cl) + Fluoride (F) + Sulfate (SO4

)

Sodium (Na) +Potassium (K)

Chloride (Cl) + Fluoride (F)

Sulfate (SO4

)

Calcium (Ca)

Magnesium (Mg)

Percent milliequivalents per liter

80

100

20

0

60

40

40

60

20

0

80

100

20

40

60

80

20

0

80

100

40

60

60

40

80

100

20

0

100

80

60

40

20

0

0

100

0 20 40 60 80 100

0

20

40

60

80

100

100

80

60

40

20

0

100 80 60 40 020

Bicarbonate (HCO3

) + Carbonate (CO3

) 

Calcium (Ca) + Magnesium (Mg)

Chloride (Cl) + Fluoride (F) + Sulfate (SO4

)

Sodium (Na) +Potassium (K)

Chloride (Cl) + Fluoride (F)

Sulfate (SO4

)

Calcium (Ca)

Magnesium (Mg)

Percent milliequivalents per liter

EXPLANATION A

CVBR-1 

CVBR-2 

CVBR-3 

CVBR-4 

CVFR-1 

CVFR-2 

CVFR-3 

CVFR-4 

U.S. Geological Survey well 

CVKR-1 

CVKR-2 

CVKR-3 

CVKR-4 

EXPLANATION

B Other wells by zone 

Caliente Northern-Main

Central Sierra Madre Foothills

Northeast Ventucopa Uplands

Northwestern Sierra Madre Foothills

Northern Ventucopa Uplands (no data)

Southern Sierra Madre Foothills

Southern Ventucopa Uplands

Southern-Main

Western Basin

Figure 9. Piper diagrams depicting major-ion composition for groundwater samples, Cuyama Valley, California, collected from A, the 

selected multiple-well monitoring sites; and B, multiple-well monitoring sites, domestic and supply wells grouped by zone.
Water-Quality 29

formations could have different sources of recharge (fig. 10A). 

The isotopic composition of the sample from the shallow well 

(CVKR-4) was similar to the composition of a surface-water 

sample collected from the nearby Cuyama River (SW-02), 

indicating a larger contribution from surface-water sources to 

this shallower depth interval than to the deeper wells at this 

site.

The isotope samples from the four CVBR wells were, in 

general, lighter in deuterium than the CVKR wells (fig. 10A). 

The range in values among the four wells also indicated that 

groundwater does not move freely between the older alluvium 

and the Morales Formation and that the units could have 

different sources of recharge. 

The isotope samples from the four CVFR wells were 

the heaviest (least negative) from the three multiple-well 

monitoring sites (fig. 10A). The slightly different isotopic 

composition of the sample from the deep well (CVFR-1) 

indicated that groundwater might not move freely between 

units within the Morales Formation. The isotopic compositions 

of the four samples were between the compositions of the 

two surface-water samples collected from the nearby Cuyama 

River (SW-02 and SW-04), indicating the source of recharge 

could be the Cuyama River. The substantial difference in 

isotopic values between the SW-02 and SW-04 sites, which 

were relatively near each other on the Cuyama River, could 

reflect that SW-04 was sampled in late August, when 

evaporative effects on surface water would be expected to 

be greatest; in contrast, SW-02 was sampled in early April. 

Evaporation causes isotopic values to move to the right of the 

meteoric water line, and the isotopic composition of SW-04 is 

consistent with evaporative modification (fig. 10A). Because 

streamflow is higher in the spring, when evaporative effects 

are less, it is logical that recharge from Cuyama River water 

would have an isotopic composition closer to SW-02, a spring 

value, than SW-04, a summer value. 

Restricted movement of water between units was also 

supported by the wide variability among the isotope samples 

from the other supply wells in the basin (fig. 10B). Samples 

from the Central Sierra Madre Foothills tended to be heavier 

(less negative) than most of the other samples. Samples from 

the Southern Ventucopa Uplands were similar to each other, 

indicating the same source of recharge. Samples from the 

Southern-Main and Northwestern Sierra Madre zone were 

typically lighter than samples from the Southern Ventucopa 

Uplands zone and trended along or below the meteoric 

water line, with the latter zone being lighter in deuterium. 

Isotope ratios for most samples from the Southern-Main 

zone were between the lightest samples from the Central 

Sierra Madre Foothills and most of the samples from the 

Southern Ventucopa Uplands, indicating that water in most of 

the Southern-Main zone could include a mixture of sources 

of recharge from the other two zones. Samples from the 

Southern-Main zone showed greater variation in isotope 

values than the other zones (fig. 10B), which is consistent 

with groundwater in this zone being derived from a variety of 

upgradient recharge sources.

Age Dating

Water samples from all of the wells at the CVKR, CVBR, 

and CVFR sites were analyzed for tritium and carbon-14. Ten 

other wells (CUY-01 through -08,-11, and -12) were analyzed 

for tritium, and twenty wells (CUY-01 through -08,-11, -12, 

and -17 through 26) and one spring (SP-01) were analyzed 

for carbon-14 (table 9). Tritium and carbon-14 activities 

provide information about the age (time since recharge) of 

groundwater. Tritium is a short-lived radioactive isotope 

of hydrogen; therefore, tritium concentrations above the 

detection level (0.3 picocuries per liter) indicate the presence 

of water recharged since the early 1950s, or recent recharge 

(Plummer and others, 1993; Clark and Fritz, 1997).

Samples from CVKR-3, CVKR-4, and CVBR-3 contained 

tritium concentrations near the detection level of 0.3 pCi/L, 

indicating recent recharge. Samples from CVKR-1, CVKR-2, 

CVBR-1, CVBR-2 and CVBR-4 contained concentrations 

less than 0.3 pCi/L, indicating that the water from these wells 

was recharged prior to the early 1950s. Post-1950s recharge 

in CVKR-3 and CVKR-4 was supported by relatively high 

NO3

-N concentrations in samples from these wells (table 9). 

Samples from all four wells at the CVFR site contained 

relatively high concentrations of tritium, indicating that the 

water from these wells contains water recharged since the 

1950s. Tritium concentrations at the CVFR site increased 

with depth. The presence of modern water throughout the 

depth profile is most likely caused by local pumping. Pumping 

at depth can alter the natural flow paths and draw younger 

water from the edges of the basin under the shallower, nonpumped units or can draw younger water down to the pumped 

depths from above. Greater groundwater flows in the deeper 

depth intervals are consistent with the measured temperature 

gradients at CVKR and CVBR; however, fluctuations in 

temperature gradients at CVFR were greatly subdued relative 

to these sites, indicating lateral groundwater fluxes at CVFR 

are relatively modest. However, the isotopic data from CVFR 

were consistent with recharge derived from Cuyama River 

water at all depths. Because the CVFR site has an unsaturated 

zone that is nearly 570 ft thick with some clay layers (fig. 5), it 

is most likely that recharge from the Cuyama River followed 

horizontal and vertical flow paths through the saturated aquifer 

between the river and CVFR to reach these monitoring wells. 

Tritium was detected in 14 of the 20 water samples 

collected from other wells (table 9). Tritium concentrations 

in these samples ranged from 0.43 to 9.0 pCi/L. The presence 

of tritium in most of the wells indicated that recent recharge 

contributes to the water resources in all zones in the Cuyama 

Valley groundwater basin.

Carbon-14 is a radioactive isotope of carbon with a 

half-life of about 5,700 years (Godwin, 1962). Carbon-14 

activities are used to determine the age (time since recharge) 

of groundwater on time scales ranging from recent to more 

than 20,000 years before present (Izbicki and Michel, 2003). 

Carbon-14 ages presented in this report do not account for 

changes in carbon-14 activities resulting from chemical 
30 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 10. Isotopic composition of water samples, Cuyama Valley, California, collected from A, selected multiple-well monitoring sites 

and surface-water sites, and B, multiple-well monitoring sites, domestic and supply wells, grouped by zone and springs.

−80

−75

−70

−65

−60

−55

−50

−11 −10.5 −10 −9.5 −9 −8.5 −8 −7.5

delta Deuterium, in per mil 

delta Oxygen-18, in per mil 

Global Meteoric Water

D = (O) 8 + 10 

A

−80

−75

−70

−65

−60

−55

−50

−11 −10.5 −10 −9.5 −9 −8.5 −8 −7.5

delta Deuterium, in per mil 

delta Oxygen-18, in per mil 

Global meteoric water line

D = (O) 8 + 10 

B

SW-01 

SW-02 

SW-03 

SW-04 

CVBR-1 

CVBR-2 

CVBR-3 

CVBR-4 

CVFR-1 

CVFR-2 

CVFR-3 

CVFR-4 

U.S. Geological Survey well Surface-water site

CVKR-1 

CVKR-2 

CVKR-3 

CVKR-4 

Other wells by zone

Central Sierra Madre Foothills

Northeast Ventucopa Uplands

Northwestern Sierra Madre Foothills

Southern Sierra Madre Foothills

Southern Ventucopa Uplands

Southern-Main Zone

Western Basin Zone

Outside basin boundary 

Springs

SP-01

SP-02 
Water-Quality 31

reactions or mixing and, therefore, are considered uncorrected 

ages. In general, uncorrected carbon-14 ages are older than the 

actual ages of the water after correction. Uncorrected ages (in 

years before present) were calculated by multiplying 8,033 by 

the natural log (ln) of the percent modern carbon expressed 

as a decimal as shown in the following equation (Stuiver and 

Polach, 1977):

Estimated age = 8,033 * ln (percent modern carbon/100 

percent)

Uncertainties in the initial value of carbon-14 in recharge 

waters add uncertainties to the groundwater-age estimations 

using carbon-14; without more comprehensive geochemical 

modeling, the carbon-14 ages are to be treated as relative 

estimates of age rather than accurate, absolute estimates of 

age. Water from the CVKR and CVFR monitoring wells (near 

the Cuyama River) was found to be younger than the water 

from the CVBR monitoring wells (4 miles away from the 

Cuyama River). Estimated carbon-14 ages for the CVKR, 

CVBR, and CVFR sites ranged from 3,600 to 6,400, 20,900 to 

31,200, and 2,700 to 3,100 years before present, respectively. 

Estimated ages increased with depth at the CVKR and CVBR 

sites. The samples from CVKR-3 and -4, CVBR-3, and CVFR1, -2, -3, and -4 contained water with detectable tritium (recent 

recharge) and an uncorrected carbon-14 age of more than 

2,700 years before present, indicating that these wells receive 

groundwater of different ages that are mixed in the sampled 

groundwater. In these mixed samples, tritium activities 

were less than 0.55 pCi/L in CVKR-3, and -4, and CVBR-3;

these samples could contain relatively small amounts of 

modern water. The carbon-14 value in CVBR-3 was an order 

of magnitude less than in CVKR-3, -4; this comparison 

indicated that the water at CVBR-3 is primarily very old 

with a small fraction of modern water and that CVKR-3 and 

-4 could contain mixtures of water that do not span as wide a 

range of ages. The samples from CVFR had tritium activities 

that were an order of magnitude higher than CVKR-3, and 

-4, and CVBR-3; consequently, fractions of modern water in 

CVFR wells are likely to be much larger than in CVKR-3, and 

-4, and CVBR-3.

Estimated carbon-14 ages for the other 20 sites ranged 

from 600 (CUY-03) to 38,300 (CUY-23) years before 

present (table 9). In general, the youngest water was found 

in wells in the Southern Ventucopa Uplands; this zone is a 

source of recharge for the Cuyama Valley and the presence 

of younger water is expected. The oldest water was found 

in wells in the Southern-Main, Northwestern Sierra Madre 

Foothills, and Central Sierra Madre Foothills zones. This is in 

contrast to the observation of Singer and Swarzenski (1970) 

that a substantial component of regional flow was northward 

from the Sierra Madre Mountains. If a significant portion of 

the flow is from the Sierra Madres, water in this flow path 

would be expected to be younger than what was observed, 

unless formations deeper than the Morales Formation, 

previously thought to be non-water-bearing, are contributing 

to groundwater discharge from the Sierra Madres toward the 

Southern-Main zone.

Arsenic, Iron, and Chromium Species

Arsenic, chromium, and iron can be different species 

depending on the oxidation-reduction state of the groundwater. 

The oxidized and reduced species have different solubilities in 

groundwater and can have different effects on human health. 

The relative proportions of the oxidized and reduced species 

of each element can be used to aid in interpretation of the oxidation–reduction conditions of the aquifer, which affect the 

mobility of many constituents. Concentrations of dissolved 

arsenic, chromium, and iron, and the dissolved concentration 

of either the reduced or the oxidized species of the element are 

reported in table 10. The concentration of the other species can 

be calculated by difference. The concentrations measured by 

the NWQL are considered to be more accurate determinations 

of dissolved arsenic, iron, and chromium. For some samples, 

the concentrations of total arsenic, total iron, and total 

chromium were measured by the TML and the NWQL using 

different sample collection and analytical methods; therefore, 

the total concentrations reported from the TML in table 10 

could be different than those reported by the NWQL. The data 

from TML were primarily used to identify the predominant 

oxidation-reduction species present in the samples, which is 

useful for understanding the geochemical environment and 

processes affecting trace-element concentrations in the system. 

Concentrations of total arsenic [As(T)] were greater 

than the MCL-US of 10 micrograms per liter (μg/L) in well 

samples analyzed at the NWQL from 4 of 33 wells. The 

highest concentration of arsenic, 67.1 μg/L, was in well 

CUY-23, which is in the Southern-Main zone and screened 

in both the younger and older alluvium; this sample had the 

oldest groundwater age in the study area, with no detected 

tritium, and an uncorrected carbon-14 age of 38,300 years 

before present (table 9), as well as the deepest bottom of 

perforations at 2,120 ft bls (table 2). Concentrations of 

arsenic in the CVBR-2 and CVBR-1 samples were 58.1 and 

37.7 μg/L, respectively. The CVBR multiple-well monitoring 

site is in the Northwestern Sierra Madre Foothills zone, and 

both wells are screened in the Morales Formation and have 

uncorrected carbon-14 ages older than 25,000 years before 

present. An arsenic concentration of 44.0 μg/L was observed 

in well CUY-02, which is in the Northwestern Sierra Madre 

Foothills, is screened in both the older alluvium and Morales 

Formation, and contained water that had an uncorrected 

carbon-14 age of 33,400 years before present. The next 

highest concentrations of arsenic in groundwater—8.6 and 

5.6 μg/L—were measured for CVBR-3, which is in the 

Northwestern Sierra Madre Foothills and screened in the 

older alluvium, followed by CUY-21, with a total arsenic 

concentration of 3.5 ug/L, which is in the Central Sierra Madre 

Foothills and screened in the Morales. The surface-water 

sample collected from the Cuyama River at site SW-04 in the 

southern end of the Southern Ventucopa Uplands contained a 

total concentration of 0.51 μg/L, indicating that surface-water 

recharge potentially is not a source of the arsenic. The four 

highest concentrations of arsenic were found in water that is 
32 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

older than 25,000 years, indicating that arsenic concentrations 

are higher in groundwater that has had more time to mobilize 

the arsenic.

Concentrations of total chromium [Cr(T)] ranged from 

no detections to 2.2 μg/L, less than the MCL-CA threshold 

50 μg/L. The highest concentration of Cr(T), 2.2 μg/L, 

was observed in well CUY-20, which is outside of the 

basin boundary (fig. 8). All of the wells inside the basin 

had concentrations of Cr(T) less than or equal to 1.3 μg/L. 

Concentrations of hexavalent chromium [Cr(VI)], however, 

were greater than the OEHHA-PHG of 0.02 μg/L in 20 of 

the samples. Concentrations of Cr(VI) ranged from 0.1 to 

1.7 μg/L. Concentrations of Cr(VI) were greater than the 

concentrations of Cr(T) in five of the samples. The difference 

in values can be attributed to the different methods of analysis 

used and the level of error (0.1 μg/L for each method) in the 

laboratory analysis. In these five samples, all concentrations 

of Cr(VI) and Cr(T)) were very near the detection limit 

(0.1 μg/L), and the laboratory measurement error can 

account for the differences. The three remaining samples had 

detections of Cr(VI) below the reporting limit of 0.1 μg/L.

Hydrology

Hydrologic data analyzed as part of this study included 

rainfall records, stream-discharge records, water-level records, 

and estimates of hydraulic properties. Rainfall records include 

monthly and annual rainfall totals and provide information 

on seasonal and annual variability in precipitation. Streamdischarge records include daily mean discharge measurements 

from three stream gaging stations and provide information on 

seasonal variability in surface-water flows and the potential 

stream losses (recharge) to the groundwater system. Waterlevel records include quarterly manual depth-to-water 

measurements collected from the 12 monitoring wells and 

55 domestic and supply wells and time-series data collected 

from the monitoring wells and 8 domestic and supply wells. 

Water-level measurements, manual and time-series, provide 

information on the seasonal responses of the aquifer system to 

pumping. Estimates of hydraulic properties include hydraulic 

conductivity and transmissivity estimated from aquifer tests 

performed on the 12 monitoring wells and 51 domestic and 

supply wells. Estimates of hydraulic properties of the Cuyama 

Valley aquifer provide insight into the rates of groundwater 

movement.

Rainfall Gaging Stations

The annual rainfall data in this report are presented by 

“water year.” A water year is defined as the 12-month period 

from October 1 of any given year through September 30 of the 

following year. The water year is designated by the calendar 

year in which it ends. Thus, the year ending September 30, 

1999, is called the “water year 1999.” Historical yearly and 

monthly rainfall totals from three rainfall gages operating 

in Santa Barbara County and one rainfall gage operating in 

Ventura County are shown in figures 11 and 12, respectively. 

The Caltrans, New Cuyama gage (Station 402), and the 

Cuyama Fire Station gage (Station 436) are near the city of 

New Cuyama; the Santa Barbara Canyon gage (Station 347) is 

in Santa Barbara County; and the Ozena Guard Station (NWS) 

gage (Station 174A) is near the Cuyama River in the southern 

half of the Southern Ventucopa Uplands (fig. 2). Rainfall 

records for Stations 402 and 436 are available from water-year 

1955 to the present. Records for Station 347 are available from 

water-year 1905 through water-year 1980, and from wateryear 1997 to the present. Rainfall records for Station 174A are 

available from water-year 1980 through July 2008. The official 

monthly and yearly rainfall records for the Santa Barbara 

County stations are published by the Santa Barbara County 

Flood Control District. The data are available for public access 

at http://www.countyofsb.org/pwd/. The monthly and yearly 

rainfall records for the Ventura County stations are published 

by the Ventura County Watershed Protection District and are 

available for public access at http://www.vcwatershed.net/

hydrodata. 

Analysis of the annual rainfall showed that Stations 402 

and 436, in the valley, received less rainfall than Stations 

347 and 174A in the uplands to the south (fig. 11). Stations 

402 and 436 received approximately the same amount of 

rainfall. Annual totals for the two sites averaged 8 inches and 

range from less than 2 inches (Station 436) to over 20 inches 

(Station 402) per year. Station 174A typically received the 

most rainfall. Annual rainfall totals at Stations 174A averaged 

almost 19 inches and ranged from about 5 to over 44 inches 

per year. Annual rainfall totals at Stations 347 averaged over 

12 inches and ranged from about 4 to over 32 inches per year. 

Averaging the total annual rainfall from all stations since 

records began at multiple sites in 1954 indicated that the 

highest annual rainfall in the Cuyama Valley was during 

water-years 1958, 1969, 1978, 1983, 1995, and 1998 (fig. 11). 

Records from the only station to exist prior to 1954 (Station 

347) showed an annual rainfall of over 32 inches during water 

year 1941, the highest observed at that station.

Streamflow Gaging Stations

Daily discharge data from three streamflow gaging stations 

in the Cuyama Valley drainage are available (figs. 13–14). 

Two gaging stations are on the Cuyama River: one is south 

of Ventucopa and measures surface-water flow into the 

valley from the Cuyama River, and the second site is near 

Buckhorn Canyon, west of the valley, and measures all 

surface flow out of the valley. The third gaging station is in 

Santa Barbara Canyon. The station on the Cuyama River 

near Ventucopa (SW-04) has historic data from October 

1945 through September 1958. The site was reestablished on 

August 24, 2009. The station near Buckhorn Canyon (SW05) was established on October 1, 1959. The station in Santa 

Barbara Canyon (SW-03) was established on October 1, 2009. 
Hydrology 33

Figure 11. Historic annual rainfall graphs from four rainfall stations in the study area, Cuyama Valley, Santa Barbara County, California. 

0

5

10

15

20

25

30

35

40

45

50

Annual water-year precipitation total, in inches

Water year

1940 1950 1960 1970 1980 1990 2000 2010

Station 402

Station 436

Station 347

Station 174A

Figure 12. Monthly rainfall graphs for three rainfall stations in the study area from June 2008 to March 2012, Cuyama Valley, Santa 

Barbara County, California.

0

1

2

3

4

5

6

7

Date 2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Monthly precipitation total, in inches

Station 402

Station 436

Station 347
34 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Locations of these gaging stations, with the exception of 

SW-05, are shown in figure 1. Data collected from these sites 

are available online at http://waterdata.usgs.gov/ca/nwis.

Cuyama River

Records from the Ventucopa station (fig. 13) showed the 

streamflow is perennial, but varies seasonally. Higher flow, 

averaging between 2 and 200 cubic feet per second (cfs), 

generally is observed during the wet season, or December 

through May; lower flow, averaging below 2 cfs, is observed 

during the dry season, or the remainder of the year. Flow 

observed during the dry season of 2011 was greater than that 

of 2010. Three flow events exceeding 100 cfs were observed 

between September 2009 and March 2012. High flows of 875 

and 1,020 cfs were observed in January and December of 

2010, respectively. A sustained increase in flow was observed 

between March 20 and April 9, 2011. While four distinct peaks 

were observed, flows exceeded 30 cfs during the entire period 

and averaged 136 cfs for the 21-day period.

Records from the Buckhorn Canyon station showed the 

streamflow is not continuous and varies seasonally. Higher 

flow, averaging between 2 and 200 cfs is observed through 

most of the wet season, while flow during the dry season 

averaged less than 2 cfs, and it is typically dry late in the 

season. Flows exceeding 1500 cfs were observed during the 

wet season of 2011, but high flows were typically below 

200 cfs.

Periods when the inflow from the Cuyama River (SW-04) 

was equal to or greater than the Cuyama River outflow 

(SW-05) indicated that the surface water was recharging 

the groundwater system. Simplistically, it can be assumed 

that if the inflow and outflow along the Cuyama River are 

equal, then the total of all other inflow to the Cuyama Valley, 

such as from Apache, Quanta, Santa Barbara, and Salisbury 

Canyon, represents the total amount of potential recharge. 

In general, surface water flowing into the Cuyama Valley 

from the Cuyama River is about equal to the amount of water 

flowing out, indicating that some degree of recharge from 

streams is typical. There are periods when outflow exceeds 

inflow, which indicate some combination of significant input 

Figure 13. Daily discharge graphs for two streamflow gaging stations (11136500 and 11136800) on the Cuyama River, Cuyama Valley, 

Santa Barbara County, California.

2008 2009 2010 2011

0.01

0.05

0.1

0.5

1

5

10

50

100

500

1,000

1,500

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

Mean discharge, in cubic feet per second

Date 

11136500 Daily mean discharge, Cuyama River 

near Ventucopa

11136500 Measured discharge, Cuyama River 

near Ventucopa

11136800 Daily mean discharge, Cuyama River 

below Buckhorn Canyon near 

Santa Maria

11136800 Measured discharge, Cuyama River 

below Buckhorn Canyon near 

Santa Maria
Hydrology 35

from tributaries, baseflow, and return flow from bank storage. 

Periods when inflow exceeds outflow indicate significant 

recharge from streams; the longest such period was from 

October 2011 to March 2012 (fig. 13).

Santa Barbara Canyon

Santa Barbara Canyon drains the southwest flanks of the 

Sierra Madre Mountains and represents the largest of the 

surrounding watersheds that flow into Cuyama Valley as a 

tributary to the Cuyama River (fig. 14). Streamflow records 

showed seasonality, with continuous flow generally ranging 

between 1 and 20 cfs through most of the wet season and no 

flow during the dry season. Flow was observed during the dry 

season of 2011, but was less than 0.5 cfs. The highest flow on 

record at this site, about 300 cfs, was measured in late March 

of 2011.

Groundwater Levels

Water levels, measured as depth to water below land 

surface, were routinely measured in all 12 monitoring wells 

and in an additional 56 selected wells in the Cuyama Valley 

(table 1). Thirty-three of the additional wells had water-level 

records prior to January 1, 2008; some records date as far back 

as August 1941 (table 11). Twenty of the wells were equipped 

with instrumentation to automatically measure and record the 

depth to water at regular time intervals (time-series; table 1). 

The water-level measurements in this report are given in feet 

with reference to land-surface datum (LSD). LSD is a datum 

plane that is approximately at land surface at each well. The 

elevation of the land-surface datum is given in table 11. Users 

of the data are encouraged to access site information through 

the USGS NWIS Web at http://waterdata.usgs.gov/nwis/.

Table 11. Summary of sites with manual water-level 

measurements including period of record, number of observation, 

and minimum and maximum observed water levels for selected 

wells, Cuyama Valley, Santa Barbara County, California.

Table available separately as Microsoft Excel® at 

http://pubs.usgs.gov/sir/2013/5108.

Figure 14. Daily discharge graphs for streamflow gaging stations (11136600) in Santa Barbara Canyon, Cuyama Valley, Santa Barbara 

County, California.

11136600 Daily mean discharge, Santa Barbara Canyon Creek near Ventucopa

11136600 Measured discharge, Santa Barbara Canyon Creek near Ventucopa

2008 2009 2010 2011

0.01

0.05

0.1

0.5

1

5

10

50

100

500

1,000

1,500

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

Mean discharge, in cubic feet per second

Date 
36 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Manual Measurements

Manual water-level measurements were typically taken 

once every 3 months in all wells shown in figure 15. Water 

levels were measured and recorded to within 0.01 foot 

by using a calibrated electric or steel tape. A summary 

of the available water-level data is presented in table 11, 

including land-surface elevation, period of record, number 

of measurements, and the minimum and maximum observed 

water levels.

Hydrographs for most wells showed seasonal fluctuations 

in water levels. Water levels generally declined during the 

summer months, coinciding with the peak of the agricultural 

season, and recovered during the winter months, when 

agricultural pumping is at a minimum. Several wells on 

the outer edges of the basin and in the Southern Ventucopa 

Uplands showed delayed responses, with the highest levels in 

the summer and lowest in the winter. 

A comparison of the highest annual measured water 

levels since January 2008 in the 56 domestic and supply 

wells showed that 16 wells had a declining trend, 7 wells 

had an upward trend, 8 wells had a reversal from downward 

to upward trends, 1 well had a reversal from upward to 

downward trend, and 9 wells showed no trend. Records 

from the remaining 15 wells were insufficient to determine 

a trend. Water-level declines in the 16 wells with downward 

trends ranged from about 6 feet in several wells to over 30 

feet (CUY-07). Downward water-level trends were observed 

in five zones; 7 of the 16 wells were in the Southern-Main 

zone (CUY-04, -06, -07, -50, -51, -56, and -59), 4 were in the 

Central Sierra Madre Foothills (CUY-21, -24, -25, and -48), 

and 3 were in the Southern Ventucopa Uplands (CUY-03, -12, 

and -46). Water-level increases in the seven wells with upward 

trends ranged from less than 1 foot in several wells to about 8 

feet (CUY-47). Two of the seven wells showing upward trends 

were in the Southern Ventucopa Uplands (CUY-31, and -35), 

two were in the Northeast Ventucopa Uplands (CUY-17, and 

-36), two were in the Southern-Main zone (CUY-08, and -27), 

and one was in the Southern Sierra Madre Foothills (CUY-47). 

The eight wells showing a reversal from declining to rising 

water levels were all in the Southern Ventucopa Uplands 

(CUY-13, -19, -30, -38, -39, -40, -42, and -43). Water levels 

declined from 2008 through the summer of 2010, began to rise 

early in 2012, and continued to rise throughout the summer 

of 2012. The observed rise in these wells ranged from 5 to 

15 feet. The rise in water level indicated that the aquifers 

receive recharge under certain conditions; this rise only in the 

Southern Ventucopa Uplands indicates that the water table 

in this zone could be relatively well-connected with recharge 

sources.

Time-Series Water Levels

All 12 monitoring wells and 8 additional wells were 

equipped with instrumentation to automatically measure 

and record the depth to water at regular time intervals, 

typically every hour or 15 minutes (fig. 15). The computed 

unit values, and daily maximum, minimum, and median 

values for all time-series water-level data for these sites are 

available through the USGS NWIS Web. Periodic manual 

measurements of water levels were made to verify the timeseries data. Seventeen wells with time-series water-level data 

are presented as time-series plots. Three wells (CUY-04,-55, 

and -60) with time-series records shorter than 6 months are not 

presented in this report. 

Time-series data presented in this report are the computed 

hourly unit values, as opposed to daily statistical values. 

Including the computed hourly values, even those water levels 

affected by pumping can cause the hydrograph to appear 

cluttered or “fuzzy,” especially when the x-axis is compressed. 

The hourly data display the entire range of water levels 

observed in the well under static and pumping conditions, and 

indicate when pumping and recovery are occurring. Most data 

gaps, denoted in grey on the hydrographs, were caused by the 

water level in the well dropping below the level of the sensor; 

consequently, the water level during these gaps is known to be 

deeper than the last measurement before the data gap.

The pumping of nearby irrigation wells directly influenced 

water levels in all of the CVKR (fig. 16) and CVBR (fig. 17) 

wells. During the period of record (2009–12), data showed a 

seasonal pattern, with water levels declining between March 

and August, coinciding with the peak of the agricultural 

season, and rising between September and February, when 

nearby irrigation and related pumping were at a minimum.

At the CVKR site, water levels in the three deeper wells 

(CVKR-1, -2, and -3) varied as much as 60 feet between 

March and August, while water levels in the shallowest well 

(CVKR-4) varied by about 25 ft over the same period (fig. 16). 

Water levels showed a decline in the seasonally high levels 

over the period of record. Manual measurements made in late 

February 2012 showed a decline of over 30 feet compared to 

those made in early March 2009. Vertical hydraulic gradients 

were upward during the winter months and reversed to 

downward gradients during the irrigation season.

Seasonal patterns at the CVBR site were similar to those 

at the CVKR site. Water levels in the three deeper wells 

(CVBR-1, -2, and -3) varied by as much as 90 feet between 

March and August, while water levels in the shallowest well 

(CVBR-4) varied by about 40 ft over the same period (fig. 17). 

Water levels showed a decline in the seasonally high levels 

over the period of record. Manual measurements made in late 

February of 2011 showed a decline of about 5 feet compared 

to those made in early March of 2010. Vertical hydraulic 

gradients were upward during the winter months and reversed 

to downward gradients during the irrigation season. Short-term 

fluctuations in water levels were larger at CVBR than CVKR, 

which is consistent with CVBR being more strongly affected 

by pumping in close proximity to the monitoring wells than 

CVKR.

Observations at the CVFR site indicated that water levels 

did not show short-term (daily) variability from nearby 

pumping as seen at the other sites, but did show similar 
Hydrology 37

166

166

33

33

Cuyama

Ventucopa

New Cuyama

Kern

County

Ventura

County

Santa Barbara

County

San Luis Obispo

County

119°50’ 119°40’ 119°30’ 119°20’

35°

34°

50’

34°

40’

Reyes Creek

Cuyama

Creek

Sierra Madre Mountains

Tehachapi

Cuyama Valley

groundwater

basin

Cuyama River

Caliente Range

Mts

EXPLANATION

Time-series site

Manual water level

0 5 10 Miles

0 5 10 Kilometers

Shaded relief base created from 30-m digital elevation model from USGS National 

Elevation Dataset (NED), North America Vertical Datum 1988 (NAVD88)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009 

Albers Projection, NAD83

Cuyama groundwater basin zones

Caliente Northern-Main

Central Sierra Madre Foothills

Northeast Ventucopa Uplands

Northwestern Sierra Madre Foothills

Northern Ventucopa Uplands

Southern Sierra Madre Foothills

Southern Ventucopa Uplands

Southern-Main

Western Basin

CUY-74

CUY-27

CUY-75

CUY-62 CUY-01

CUY-26

CUY-56

CUY-55

CUY-57 CUY-51 CUY-20

CUY-02

CUY-04

CUY-05

CUY-22 CUY-50 CUY-16 CUY-58 CUY-59

CUY-07

CUY-54

CUY-52

CUY-53

CUY-21 CUY-08 CUY-49

CUY-24

CUY-48 CUY-25

CUY-06

CUY-45 CUY-46

CUY-12

CUY-03

CUY-38 CUY-73

CUY-19

CUY-39 CUY-47

CUY-40 CUY-44 CUY-13

CUY-18 CUY-43

CUY-34

CUY-35

CUY-33 CUY-36

CUY-17

CUY-32

CUY-30

CUY-31

CUY-11

CVKR 1-4

CVBR 1-4

CUY-60

CVFR 1-4

Figure 15. The location of multiple-well monitoring sites, 

domestic, and supply wells with available water-level data, 

Cuyama Valley, Santa Barbara County, California.
38 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 17. Water-level hydrograph from multiple-well monitoring site Cuyama Valley Bell Road (CVBR) from September 29, 2009, to 

March 5, 2012, Cuyama Valley, California.

270

280

290

300

310

320

330

340

350

360

370

380

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

Gray blocks are gaps in data—

water level is known to be

below the level of the sensor

CVBR #3 failed to record

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CVBR-1 (830–850)

CVBR-2 (730–750)

CVBR-3 (540–560)

CVBR-4 (360–380) 

Figure 16. Water-level hydrograph from multiple-well monitoring site Cuyama Valley Kirschenmann Road (CVKR) from April 8, 2009, to 

February 20, 2012, Cuyama Valley, California.

360

370

380

390

400

410

420

430

440

450

460

470

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

CVKR#2 failed to record

Gray blocks are gaps in data—

water level is known to be

below the level of the sensor

Continuous

recording

Well

(depth,in feet)

Manual

water

level

CVKR-1 (960–980)

CVKR-2 (760–780)

CVKR-3 (600–620)

CVKR-4 (440–460) 
Hydrology 39

seasonal and longer-term changes. Similar to CVKR and 

CVBR, the vertical hydraulic gradients were upward during 

the winter months and reversed to downward gradients during 

the irrigation season; however, the gradients at the CVFR site 

were notably smaller. The gradient reversal at this location 

indicated that water levels at this site were influenced by 

local pumping but were not as strongly affected as CVKR 

and CVBR. Seasonal water levels in the wells varied about 

15 feet between March and September (fig. 18). Water levels 

showed a decline in the seasonally high levels over the period 

of record by about 10 feet per year.

Time-series data from well CUY-02 (fig. 19) in the 

Northwestern Sierra Madre Foothills zone showed no 

discernible trend over the period of record. Seasonally high 

water levels rose slightly between 2009 and 2010, were 

similar between 2010 and 2011, then declined by almost 

25 ft between 2011 and 2012; this pattern correlates to the 

relative duration of seasonal pumping of the well, which 

was apparent on the hydrograph (fig. 19). In 2009, daily 

pumping in this well started in late June and continued for 

about 5 months. Because of the data gap between early 

August 2009 and April 2010, caused by a probe failure, the 

entire pumping season did not show, but manual water-level 

measurements indicated pumping stopped sometime before 

mid-November. This pumping cycle correlated with the 

observed rise. In 2010, daily pumping in this well covered 

the same period: pumping started in early June and continued 

until early November. Comparison of the daily records, 

however, indicated the pump was operated more frequently 

during the first 30 days of operation in 2010 than in 2009. 

This pumping cycle correlated with the observed static water 

levels. In 2011, daily pumping in this well covered a longer 

time span: pumping started a month earlier, in mid-May, 

and continued through November. A comparison of the daily 

records indicated the pump was operated more during 2011 

than 2010. This pumping cycle correlated with the observed 

decrease in water levels. The increased irrigational pumping 

510

520

530

540

550

560

570

580

590

600

610

620

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CVFR-1 (960–980)

CVFR-2 (810–830)

CVFR-3 (680–700)

CVFR-4 (590–610) 

Figure 18. Water-level hydrograph from multiple-well monitoring site Cuyama Valley Foothill Road (CVFR) from October 27, 2009, to 

February 28, 2012, Cuyama Valley, California.
40 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

of other wells in the Northwestern Sierra Madre Foothills 

zone, reported during the summer of 2011 by several residents, 

also could have contributed to the observed decline in water 

levels. Irrespective of cause, the change in the pumping, and 

possibly recharge, conditions between 2010 and 2011 in the 

Northwestern Sierra Madre Foothills zone resulted in changes 

from static and overdraft conditions; these patterns were 

evident in both CVBR and CUY-02.

Time-series data from wells CUY-05 (fig. 20) and CUY-07 

(fig. 21) in the Southern Main zone showed a more detailed 

record of the steady decline in water level than was observed 

in the manual measurements. These hydrographs showed the 

seasonal highs and lows that are expected, and the year-toyear seasonal highs showed a steady decline in water levels. 

A decline of approximately 2.5 feet per year was observed 

at CUY-05 (fig. 20) between 2010 and 2012, and a decline 

of about 7 feet per year was observed at CUY-07 (fig. 21) 

between 2010 and 2012. Water levels in well CUY-05 showed 

high daily variability associated with the active pumping 

during the period of record, while water levels in the nonpumped well CUY-07 showed low daily variability. The lower 

variability in CUY-07 likely reflected the effects of regional 

pumping rather than local pumping effects near CUY-07.

Time-series water-level data from two wells, CUY-12 and 

CUY-35 in the Southern Ventucopa Uplands zone, showed 

a rise in water levels during the spring of 2012 compared to 

earlier spring high water levels. At CUY-12 (fig. 22), the 3 

to 4 foot per year of decline in water levels observed over 

the previous 2 years did not continue into 2012. Generally, 

increasing water levels at CUY-35 (fig. 23) corresponded with 

the high-flow events observed at the stream gage station on the 

Cuyama River near Ventucopa (11136500) between December 

2009 and February 2012 (fig. 13). At CUY-35 (fig. 23), an 

increase of approximately 27 feet corresponded with a highflow event in late March and early April 2011. A water-level 

increase of over 5 feet was observed at CUY-35 shortly after 

a December 2010 flow event. The correspondence of rising 

groundwater and river levels indicates that the Southern 

Ventucopa Uplands zone is strongly hydraulically connected 

to the Cuyama River.

0

50

100

150

200

250

300

350

400

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

(Note scale change)

Gray blocks are gaps in data—

water level is known to be

below the level of the sensor

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CUY-02 (340–790)

Figure 19. Water-level hydrograph from CUY-02, from January 1, 2008, to March 23, 2012, Cuyama Valley, California.
Hydrology 41

Figure 20. Water-level hydrograph from CUY-05, from January 1, 2008, to February 28, 2012, Cuyama Valley, California.

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

200

210

220

230

240

250

260

270

280

290

300

310

Gray block is gap in data— 

water level is known to be 

below the level of the sensor

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CUY-05 (unknown)

Figure 21. Water-level hydrograph from CUY-07, from January 1, 2008, to February 21, 2012, Cuyama Valley, California.

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

420

430

440

450

460

470

480

490

500

510

520

530

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CUY-07 (250–750)
42 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 22. Water-level hydrograph from CUY-12, from January 1, 2008, to March 5, 2012, Cuyama Valley, California.

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

30

40

50

60

70

80

90

100

110

120

130

140

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CUY-12 (unknown)

Figure 23. Water-level hydrograph from CUY-35, from January 1, 2008, to March 6, 2012, Valley, California.

Date 

2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M

2010 2011 2012

Depth to water, in feet below land surface

60

70

80

90

100

110

120

130

140

150

160

170

Continuous

recording

Well

(depth, in feet)

Manual

water

level

CUY-35 (unknown)
Hydrology 43

Historic Water Levels

Historic water-level data, some dating back to the early 

1940s, were compiled for 16 sites in the Cuyama Valley. 

Analysis of the long-term trends indicated that 10 wells 

showed a declining trend, 3 wells showed no trend, and 3 

wells showed a rising trend (fig. 24). 

All six wells in the South-Main zone showed declines 

over the period of record. Well CUY-04 showed the largest 

decline—over 300 feet between 1960 and 2001, for an average 

decline of over 7 ft per year. Well CUY-75 declined nearly 

200 ft from 1954 to 2007, for an average decline of almost 

4 ft per year. Wells CUY-27, -54, and -56 declined about 

100 feet over the period of record, for an average decline of 

between 1 and 2 ft per year. Large water-level declines were 

not limited to the South-Main zone. Well CUY-62, in the 

Caliente Northern-Main zone, declined over 100 feet between 

1947 and 2007, for an average decline of almost 2 ft per year. 

Well CUY-60, in the Western Basin zone, declined over 80 ft 

between 1945 and 2012, an average decline of over 1 ft per 

year. Well CUY-24, in the Central Sierra Madre foothills zone, 

declined approximately 30 feet between 1983 and 2012, for an 

average decline of about 1 ft per year.

Two of the wells that showed an increase in water levels, 

CUY-13 and -74, are in the Southern Ventucopa Uplands zone, 

which further indicated that this zone can respond quickly 

to periods of increased recharge. The third well that had an 

increase in water levels, well CUY-36, is in the Northeast 

Ventucopa Uplands zone. The record for well CUY-36 was 

limited, and it cannot be determined if the fluctuations in water 

levels that were observed in the Southern Ventucopa Uplands 

also occurred in this well. 

Wells CUY-13, -30, -39, -46, and -74, in the Southern 

Ventucopa Uplands, showed cyclical fluctuations in water 

levels. Declines in water levels over a 5 to 12 year period were 

followed by a marked rise. Well CUY-74 showed an increase 

in water level of over 116 feet between December 1977 and 

May 1978. Other rapid increases in water levels over a short 

time included 58 feet over 3 months in 1958, 74 ft over 2 

months in 1969, and 68 feet over 4 months in 1983. Well 

CUY-32, also in the Southern Ventucopa Uplands, did not 

show cyclical fluctuations in water levels.

Increases in water levels observed in the Southern 

Ventucopa Uplands corresponded to increased annual 

precipitation. The marked water-level rises in well CUY74 observed in 1958, 1969, 1978, and 1983 correlated with 

above average rain-fall totals during the respective years. 

Although increases in water levels were associated with 

increased precipitation (fig. 11), all of the marked increases 

were associated with annual rainfall totals exceeding 20 in/yr 

at either Station 347 or 174A. The 25-ft rise in water level 

at CUY-35 (fig. 23) in late March 2011 correlated with an 

above average monthly rainfall of over 5 inches at Station 34 

(fig. 12). A similar monthly rainfall in December 2010 also 

correlated to an increase in water level of 5 ft at CUY-35. 

This indicated that recharge to the aquifer system in the 

Southern Ventucopa Uplands is highly dependent on periods 

of increased annual rainfall and stream levels.

Aquifer Tests

Aquifer tests were performed on the monitoring wells and 

selected domestic and supply wells in the Cuyama Valley 

groundwater basin (fig. 25). Slug tests on the monitoring wells 

were done by using physical displacement. Historic pump test 

data for 51 wells were collected and analyzed to estimate the 

aquifer transmissivity.

Slug Tests 

Hydraulic conductivity estimates for the aquifer materials 

proximate to the screened intervals of the three multiple-well 

monitoring sites (CVKR, CVBR, and CVFR) were obtained 

by using physical displacement “slug” tests. These tests 

are useful for determining aquifer properties around smalldiameter wells that have short screened intervals. Unlike 

longer-term tests, the results are based on small changes 

in water level measured over short periods and, therefore, 

represent the hydraulic response from only a small volume of 

aquifer material next to the well screen.

The slug used for the displacement of volume was a 

1.05-inch outer diameter PVC pipe 63 inches long. The pipe 

was filled with sand for weight and sealed at both ends with 

pointed capes. The slug displacement was 0.0327 cubic feet 

(ft3), which resulted in an equivalent head displacement 

of approximately 1.50 ft in a 2-inch well. The initial head 

displacement observed for some tests differed from the 

calculated equivalent head displacement. The cause of the 

difference is uncertain. The observed initial head displacement 

was used for processing the results. 

Computations were performed by using existing 

spreadsheet-based tools (Halford and Kuniansky, 2002). The 

selection of the most appropriate method to analyze the data 

was based on a preliminary analysis of the slug test data and 

comparison with predicted responses from different methods. 

Wells CVKR-1, -2, and -3 were analyzed by using methods 

developed by James Butler of the Kansas Geological Survey 

(Butler and others, 2003) for formations of high hydraulic 

conductivity. All other wells were analyzed by using methods 

developed by Green and Shapiro (1998), with the exception of 

CVFR-4 . The water level in CVFR-4 was below the top of the 

sand pack at the time of testing; therefore, it was considered 

unconfined and was analyzed by using methods developed by 

Bouwer and Rice (1976) for unconfined wells. 

The following assumptions were made for the interpretation 

of slug test data: the volume of water is displaced 

instantaneously at t = 0, and the well is of finite diameter and 
44 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 24. Historic water-level hydrographs from 16 selected domestic and supply wells, Cuyama Valley, Santa Barbara County, 

California.Water level, in feet below land surface

Year Year

CUY-56 (Southern-Main) CUY-57 (Southern-Main)

CUY-60 (Western Basin)

CUY-74 (Southern Ventucopa Uplands) CUY-75- (Southern-Main)

Note scale change

CUY-62 (Caliente Northern-Main)

CUY-04 (Southern-Main)

Note scale change CUY-13 (Southern Ventucopa Uplands)

CUY-24 (Central Sierra Madre Foothills) CUY-27 (Southern-Main) 

CUY-30 (Southern Ventucopa Uplands) CUY-32 (Southern Ventucopa Uplands)

CUY-36 (Northeast Ventucopa Uplands)

CUY-39 (Southern Ventucopa Uplands)

CUY-46 (Southern Ventucopa Uplands) CUY-54 (Southern-Main)

50

100

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350

400

450

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360

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200

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0

0

0

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0

 20

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1950 1960 1970 1980 1990 2000 2010 1940 1950 1960 1970 1980 1990 2000 2010
Hydrology 45

166

166

33

33

Cuyama

Ventucopa

New Cuyama

Kern

County

Ventura

County

Santa Barbara

County

San Luis Obispo

County

119°50’ 119°40’ 119°30’ 119°20’

35°

34°

50’

34°

40’

Reyes Creek

Cuyama

Creek

Sierra Madre Mountains

Tehachapi

Cuyama Valley

groundwater

basin

Cuyama River

Caliente Range

Mts

0 5 10 Miles

0 5 10 Kilometers

EXPLANATION Shaded relief base created from 30-m digital elevation model from USGS National 

Elevation Dataset (NED), North America Vertical Datum 1988 (NAVD88)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009 

Albers Projection, NAD83

Cuyama groundwater basin zones

Caliente Northern-Main

Central Sierra Madre Foothills

Northeast Ventucopa Uplands

Northwestern Sierra Madre Foothills

Northern Ventucopa Uplands

Southern Sierra Madre Foothills

Southern Ventucopa Uplands

Southern-Main

Western Basin

Site type

U.S. Geological Survey 

monitoring site

Pump-test site

PT-52

PT-53

PT-51 PT-50 PT-49

PT-26

PT-45

PT-43

PT-42

PT-41

PT-44

PT-40

PT-39

PT-38

PT-37

PT-36 PT-35

PT-31

PT-34

PT-32

PT-30

PT-24

PT-23

PT-22

PT-21

PT-20

PT-19

PT-16

PT-15

PT-14

PT-13

PT-12 PT-11

PT-10 PT-18

PT-17

PT-09

PT-08

PT-07 PT-02

PT-48

PT-47

PT-54

PT-46 PT-25

PT-28

PT-29

PT-27 PT-05

PT-04

PT-03

PT-01

CVKR 1-4

CVBR 1-4

CVFR 1-4

Figure 25. The location of multiple-well monitoring sites, 

domestic and supply wells with aquifer test data, Cuyama 

Valley, Santa Barbara County, California.

fully penetrates the aquifer. It is also assumed that the aquifer 

is confined, homogeneous, isotropic, and of uniform thickness; 

the flow within each aquifer is horizontal and radially 

symmetric; and that the response is influenced over the entire 

screened interval. Thus, for these calculations, the aquifer 

thickness is assumed to equal the length of the screened 

interval of the monitoring well.

For wells analyzed after Butler and others (2003), the 

type curve can be automatically or manually fit to match the 

observed response by using the spreadsheet tool to adjust 

the dimensionless dampening coefficient and the hydraulic 

conductivity. The accuracy of the fit between the match curve 

and the measured response curve is characterized best by 

the residual standard error. For wells analyzed after Green 

and Shapiro (1998), the type curve can be automatically or 

manually fit to match the observed response by adjusting the 

storage coefficient and the hydraulic conductivity. For wells 

analyzed after Bouwer and Rice (1976), the type curve can be 

automatically or manually fit to match the observed response 

by adjusting the hydraulic conductivity (K).

Slug tests from each well were analyzed and grouped on 

the basis of the shape of each type curve. Similarly shaped 

type curves were grouped together. For each approach, 

the individual tests were manually examined; tests that 
46 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

contained errors were removed from the batch. For each well, 

the results from all valid tests were averaged to estimate 

K for the given well. Common errors included measured 

displacements varying greatly from the calculated equivalent 

head displacement, irregular recoveries, and tests containing 

anomalous readings. 

Slug test results from the monitoring wells indicated that 

horizontal hydraulic conductivities ranged from about 1.5 feet 

per day (ft/d) for the CVBR-4 well to 28 ft/d for the CVKR-3 

well (table 12). The median hydraulic conductivity of 15 ft/d 

observed for the wells in the older alluvium was almost 

five times greater than the median hydraulic conductivity 

observed in the Morales Formation (3.1 ft/d). The relatively 

low hydraulic conductivity values estimated in the Morales 

Formation probably reflect the greater degree of cementation 

and induration. None of the wells tested was screened in the 

younger alluvium.

Pump Tests

To better understand hydraulic properties of the local 

aquifer system, transmissivity (T) of the aquifer was estimated 

at 51 wells screened in the water-bearing units of the Cuyama 

Valley groundwater basin (table 13). The data used for the 

analysis were from historical pump efficiency tests performed 

on irrigation wells between 1941 and 1966. Data from these 

tests were analyzed by using the Jacob’s equations to estimate 

T of the aquifer material around the well (Jacob, 1946).

Most of the tests were done by Pacific Gas and Electric 

(PG&E) as a service to the customers for the purpose of 

maximizing the well efficiency and aiding in the protection of 

the electrical grid. Water pumping accounts for approximately 

80 percent of the energy consumed by PG&E’s agricultural 

customers and is a significant load to the electrical system 

(Pacific Gas and Electric, 2006). PG&E has performed free 

well-efficiency tests of water-pumping systems for their 

customers since 1911. The data—date and time, static and 

pumping water levels, total lift, discharge, specific capacity, 

kilowatt input, kilowatt-hour per acre-foot (ac-ft), and plant 

efficiency—were provided to the USGS for analysis. The 

overall condition of the well was not noted; it was assumed 

that wells were fully developed and in good working 

condition. 

A common approach for analyzing short-term single-well 

pumping test data is the use of the Jacob’s Method (Jacob, 

1946) to estimate the transmissivity of the aquifer. Although 

this method makes various assumptions (including the aquifer 

is infinitely large, homogeneous, isotropic, confined, and 

unconsolidated), it still provides a reasonable first-order 

approximation of the transmissivity of the aquifer near the 

well. Because drawdown data seldom fall in a straight line 

when plotted on a linear time scale (Bear, 1979), the method 

assumes that steady-state conditions are eventually reached, 

and the time since pumping began is plotted on a log cycle. It 

is assumed from the PG&E data that the reported water level 

was measured after a static condition had been reached, and 

the pump was allowed to run for at least one log-time cycle 

(for example, 1, 10, 100; or 30, 300 min, and so on). This 

technique allows for an estimation of transmissivity from 

specific capacity by taking the flow rate and drawdown of a 

well, at one log cycle apart, and applying Jacob’s Equation for 

straight-line drawdown, as shown (Roscoe Moss Company, 

1990).

Table 13. Summary of pump-test estimates of hydraulic 

properties for selected well sites, Cuyama Valley, Santa Barbara 

County, California.

Table available separately as Microsoft Excel® at 

http://pubs.usgs.gov/sir/2013/5108.

Table 12. Summary of slug-test estimates of hydraulic properties for selected multiple-well monitoring sites, Cuyama Valley, Santa 

Barbara County, California.

[Depth in feet below land surface, see table 1 for definitions of common well names. Abbreviations: Qoa, Older alluvium; QTm, Morales Formation; ft/day, feet per day; USGS, U.S. 

Geological Survey]

Common well 

name

Tested 

by

Number of 

tests

Date 

of test

(mm/dd/yyyy)

Top 

of 

screen

Bottom 

of 

screen

Formation 

at top 

of screen

Formation at 

bottom

of screen

Method 

of 

analysis

Hydraulic 

conductivity 

(ft/d)

CVKR-1 USGS 17 3/22/2009 960 980 Qoa Qoa Butler, Garnett and Healey, 2003 18

CVKR-2 USGS 17 3/23/2009 760 780 Qoa Qoa Butler, Garnett and Healey, 2003 22

CVKR-3 USGS 14 3/23/2009 600 620 Qoa Qoa Butler, Garnett and Healey, 2003 28

CVKR-4 USGS 15 3/23/2009 440 460 Qoa Qoa Greene and Shapiro, 1998 9.3

CVBR-1 USGS 20 11/4/2009 830 850 QTm QTm Greene and Shapiro, 1998 3.3

CVBR-2 USGS 19 11/5/2009 730 750 QTm QTm Greene and Shapiro, 1998 2.6

CVBR-3 USGS 17 11/5/2009 540 560 Qoa Qoa Greene and Shapiro, 1998 12

CVBR-4 USGS 18 11/4/2009 360 380 Qoa Qoa Greene and Shapiro, 1998 1.5

CVFR-1 USGS 20 11/4/2009 960 980 QTm QTm Greene and Shapiro, 1998 9.9

CVFR-2 USGS 20 11/5/2009 810 830 QTm QTm Greene and Shapiro, 1998 3.0

CVFR-3 USGS 20 11/5/2009 680 700 QTm QTm Greene and Shapiro, 1998 6.8

CVFR-4 USGS 20 11/5/2009 590 610 QTm QTm Bouwer and Rice, 1976 1.6
Geomechanical Activity 47

2.303

4

Q T x

π s = D

where

T is transmissivity (gallons per day per foot or 

square meters per day),

	 Ds is drawdown (feet or meters),

Q is well discharge (gallons per minute or liters 

per second).

Adding the conversion from gallons per minute (gpm) to 

gallons per day (gpd) allows for the flow (Q) to be entered in 

the standard unit of gpm while transmissivity (T) is calculated 

in the conventional units of gallons per day per foot (gpd/ft). 

Simplifying the resulting equation yields the following: 

264Q T

s = D

The median transmissivity estimates from pump-test 

analyses of the supply wells ranged from 560 to 163,400 

gallons per day per foot (gal/d/ft). The median transmissivity 

of 15,700 gal/d/ft for wells in the younger alluvium was 

three times that of the older alluvium (5,000 gal/d/ft). Wells 

screened in both the younger and older alluvium had a median 

transmissivity of 11,300 gal/d/ft. Data from wells screened 

solely in the Morales Formation were not available to be 

analyzed; however, transmissivity estimates from two wells 

screened in both the older alluvium and Morales Formation 

averaged 4,900 gal/d/ft. 

Pump tests were repeated for some wells over a span 

of several years. Analysis of the results indicated that 

transmissivity typically decreased over time, with a few 

exceptions. These temporal changes in transmissivity are 

likely due to physical deterioration of the well, but could also 

be influenced by declines in water levels over time, the loss of 

storage due to land subsidence, or both.

Geomechanical Activity

Geomechanical data collected from the study area included 

continuously operating global positioning system (GPS) and 

interferometric synthetic aperture radar (InSAR) data. The 

geomechanical data were used to estimate the rate of vertical 

land movement in the Cuyama Valley groundwater basin to 

determine if it is subsiding. Data from 5 GPS stations and 

133 unique interferograms were analyzed. Estimates of land 

subsidence for the Cuyama Valley provided insight into the 

response of the aquifer system to groundwater withdrawal. 

GPS Data

The horizontal and vertical motion of the Earth’s tectonic 

activity in California is monitored by a continuously operating 

network of GPS stations that are operated by various groups, 

including government agencies and education consortiums. 

Stations within the Cuyama study area were installed as part of 

Southern California Integrated GPS Network (SCIGN), which 

was designed to monitor plate boundary deformation and 

seismic hazards throughout Southern California (Hudnut and 

others, 2002). The GPS stations generally were constructed by 

using a stable monument embedded in the ground to a depth of 

approximately 10 meters to minimize signal noise and employ 

a standard choke ring antenna for the GPS receiver (Hudnut 

and others, 2002). The receiver detects signals transmitted by 

GPS satellites in orbit around the earth and determines the 

distance between the satellites to the receiver based on the 

travel time of the signal (U.S. Geological Survey Earthquakes 

Hazards Program, 2012). The station position (latitude, 

longitude, and elevation) is determined by triangulation of 

the distances to at least four GPS satellites (U.S. Geological 

Survey Earthquakes Hazards Program, 2012). 

Variations in the position of a GPS station can result 

from tectonic motion and from deformation associated with 

fluid pumping from anthropogenic activities—in this case, 

groundwater withdrawal. A study of continuous GPS data 

from sites in southern California determined that measured 

seasonal horizontal and vertical motion across a basin were 

consistent with simple elastic movement of the basin material 

responding to aquifer pumping and recharge (Bawden and 

others, 2001). “GPS sites on the margin... undergo seasonal 

horizontal motion toward and away from the basin, while sites 

within the basin undergo seasonal uplift and subsidence.” 

(Bawden and others, 2001, pg. 814). Seasonal motion showing 

fluctuating compression and expansion of the aquifer sediment 

is a result of elastic, or reversible, deformation and is the 

result of fluctuations in the pore-fluid pressure in the aquifer 

sediments that are less any previous maximum fluctuations 

(Galloway and others, 1999). Generally, elastic deformation is 

correlated with water-level changes and associated pumping. 

Inelastic, or irreversible, deformation occurs when the porefluid pressure is reduced to a value lower than the previous 

minimum pressure; in response, the aquifer sediments are 

permanently rearranged and the pore volume is reduced 

(Galloway and others, 1999). Generally, inelastic deformation 

is indicated by a multi-year trend of decline in the elevation 

of the land surface and does not correlate with water level 

recovery. 

The GPS stations used for the study, shown in figure 2, 

were Cuyama Valley High School (CUHS), Ventucopa 

Station (VCST), McPherson_CS2008 (P521), Bitter Creek 

Wildlife Refuge (BCWR), and OZST_SCGN_CS2000 

(OZST). GPS stations within the Cuyama Valley study area 

are maintained by the USGS, and the data are available online 

at http://earthquake.usgs.gov/monitoring/gps/ (accessed 

July 12, 2012). Post-processing of data collected from the 

GPS network stations can include cleaning, filtering, and 

de-trending for each position component (north, east, and 

up for a local Cartesian coordinate system). The data were 

cleaned to remove outliers that deviate significantly relative 
48 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

to an average position measurement, filtered to remove 

systemic errors that increase the signal noise, and de-trended 

to remove the regional tectonic signal (N. King, oral commun., 

2012). Regionally, filtered data were the most appropriate for 

comparison with estimates of subsidence from InSAR (see 

next section, “InSAR Data”). 

Comparison of the annual velocity in the north and east 

directions for all GPS stations in the Cuyama study area 

indicated the land surface is moving northwest at an average 

rate of almost 36 millimeters per year (mm/yr; table 14). The 

stations in the valley (CUHS, VCST, and OZST) are moving 

northwest at nearly the same velocity (about 25 mm/yr). 

P521, in the mountains to the west of the basin, is moving at a 

slightly faster velocity (about 29 mm/yr) toward the northwest 

direction; BWCR, in the hills to the east of the basin, is 

moving at a slightly slower velocity (about 22 mm/yr) toward 

the northwest. This indicates that there is movement consistent 

with the San Andreas fault system, with regional compression 

still occurring around this “pull-apart” basin. 

The annual velocity in the up direction for all GPS 

monitoring stations was positive, with the exception of CUHS, 

indicating a general net upward motion for the land surface in 

the region. The annual velocity at VCST, OZST, and BCWR 

was 0.7 mm/yr (table 14), indicating the valley is moving 

upward at the same rate as the area to the east and slightly 

slower than the mountains to the west (annual velocity at P521 

was 1.3 mm/yr). The annual velocity at CUHS is −7.5 mm/

yr, indicating significant downward motion at this location 

relative to the region. The daily land surface position in the up 

coordinate for CUHS (raw data from the USGS Earthquakes 

Hazard Program) showed a downward trend over the period 

of record and cyclic variability over shorter periods (fig. 26). 

The measured displacement at CUHS between December 

5, 2002, and May 22, 2008, was −40 mm. It is likely that 

this downward trend, or subsidence, represents inelastic 

deformation and indicates compaction and reduced storage 

capacity of the aquifer sediments; a significant component of 

the seasonal fluctuations represented elastic deformation, as 

evidenced by various periods of partial recovery.

The cyclic variability in the daily land surface position in 

the north, east, and up directions for CUHS also indicated 

the aquifer sediments in the area had experienced elastic 

deformation. The variability in the north and east directions 

Table 14. Annual velocities and associated uncertainties for selected GPS monitoring stations in the Cuyama study area, reported 

from the regionally filtered data from the U.S. Geological Survey Earthquakes Hazard Program for the period of record, Cuyama Valley, 

Santa Barbara County, California.

[mm/yy; millimeters per year]

GPS 

monitoring 

station

P521 

(McPherson_CS2008)

CUHS 

(Cuyama Valley 

High School)

VCST 

(Ventucopa Station)

OZST 

(OZST_SCGN_CS2000)

BCWR 

(Bitter Creek 

Wildlife Refuge)

Velocity 

(mm/yr)

Uncertainty 

(mm/yr)

Velocity 

(mm/yr)

Uncertainty 

(mm/yr)

Velocity 

(mm/yr)

Uncertainty 

(mm/yr)

Velocity 

(mm/yr)

Uncertainty 

(mm/yr)

Velocity 

(mm/yr)

Uncertainty 

(mm/yr)

North 29.10 0.50 24.70 0.30 24.50 0.30 24.60 0.30 21.50 0.30

East –27.40 0.50 –28.00 0.30 –25.10 0.30 –26.80 0.30 –22.00 0.30

Up 1.30 0.50 –7.50 0.30 0.70 0.30 0.70 0.30 0.70 0.30

of the de-trended data correlated with the variability in 

the up direction (fig. 27). As noted by Bawden and others 

(2001), elastic deformation in a basin will result in horizontal 

motion near the edge of the basin as the surface is pulled 

inward toward the center of subsidence and pushed outward 

during expansion. Cyclic deformation at CUHS in the 

north and east direction indicated elastic deformation of the 

aquifer sediments. The cyclic variation in the position of 

the land surface at CUHS also correlated with water-level 

measurements in nearby wells, which supports the conclusion 

that elastic deformation was caused by groundwater 

withdrawals. Water levels at well CUY-57 from 2000 to 

2008 followed the de-trended up data; higher water levels 

occurred close in time to surface expansion, and lower water 

levels occurred close in time to surface compression (fig. 27). 

In 2011, motion in all directions increased substantially 

and corresponded to compression of the aquifer sediments 

(fig. 27). Likewise, in 2011, water levels from CUY-05 and 

CUY-58 sharply declined, and the surface compressed at the 

highest rate during the period of record (fig. 27).

InSAR Data

Interferometric synthetic aperture radar (InSAR) is a 

satellite-based remote sensing technique that can detect 

centimeter-level land-surface deformation over hundreds 

of square kilometers at a spatial resolution (pixel size) of 

90 meters or better and a height resolution of 5–10 mm 

(Bawden and others, 2003). Synthetic aperture radar (SAR) 

imagery is produced by reflecting radar signals off a target 

area and measuring the two-way travel time to the satellite. 

SAR imagery has two components: amplitude and phase. 

The amplitude is the measure of the RADAR signal intensity 

returned to the satellite and shows roads, mountains, and other 

features because of their varying reflective properties. The 

phase component is the percentage of the sine wavelength that 

intersects the land-surface and is proportional to the line-ofsite distance from the land surface to the satellite (range). 

There are two forms of interferometric processing: 

conventional and persistent scatterer (PS InSAR). The 

conventional InSAR technique uses two SAR scenes of 

the same area taken at different times and differences the 
Geomechanical Activity 49

 −100

 −80

 −60

 −40

 −20

 0

 20

 40

 60

 80

100

2000 2001 2002

Date

2003 2004

JAN JULY JAN JULY JAN JULY JAN JULY JAN JULY

2005 2006 2007

JAN JULY JAN JULY JAN JULY

2008 2009

JAN JULY JAN JULY

2010 2011 2012

JAN JULY JAN JULY JAN

Cuyama High School (CUHS) GPS station, 31-day average

Bitter Creek Wildlife Refuge (BCWR), 31-day average

OZST_SCGN_CS2000 (OZST), 31-day average

Ventucopa Station (VCST), 31-day average 

McPherson_CS2008 (P521), 31-day average

Cuyama High School (CUHS) daily value 

Date and land-surface position, for comparison with 

InSAR

Daily land surface position, up coornidate, in millimeters

December 5, 2002

27.2

May 22, 2008

−12.9

CUHS is expressed in daily and 31-day running averages; all others are in 31-day running averages. 

Figure 26. Land-surface position, up coordinate, in millimeters, for the GPS stations Cuyama High School (CUHS), Ventucopa Station 

(VCST), McPherson_CS2008 (P521), Bitter Creek Wildlife Refuge (BCWR), and OZST_SCGN_CS2000 (OZST), Cuyama Valley, Santa 

Barbara County, California.

phase portion of the SAR signal, resulting in maps called 

interferograms that show relative land-surface elevation 

change (range change) between the two SAR acquisition dates 

(Sneed and Brandt, 2007). If the land surface has moved away 

from the satellite (subsidence), a slightly longer portion of 

the wavelength is reflected back to the satellite. Conversely, 

if the land surface has moved closer to the satellite (uplift), 

a slightly shorter portion of the wavelength is reflected back 

to the satellite. The PS InSAR technique requires many more 

SAR —usually 20 or more—that are processed together to 

determine, in part, the amplitude variance across the entire 

data stack (all of the SAR images) for each pixel. Pixels 

with relatively high amplitude variance (in time) are filtered 

from the data set, resulting in a list of relatively “stable” 

points, or persistent scatterers (PS). The differential phase is 

then calculated in a manner identical to that of conventional 

InSAR, except that the differential phase is only calculated for 

each “stable” point, rather than across the entire image. 

InSAR signal quality is dependent on topography, ground 

cover, land-use practices, atmospheric artifacts, time span of 

the interferogram, and orbit geometry, among other factors. 

Areas with high topographic relief can result in blocked 

radar signal in the line-of-sight (shadows). Densely forested 

areas are prone to poor signal quality because RADAR 

cannot effectively penetrate thick vegetation, and it either 

gets absorbed or reflects back to the satellite from random 

depths within the canopy, which leads to spatially incoherent 

signals. Certain land-use practices, such as farming, also cause 

spatially incoherent signal. The tilling, plowing, or flooding 

of farm fields causes large and non-uniform land-surface 

change that affect the amount of RADAR signal reflected back 

to the satellite and cannot be resolved with InSAR. Urban 

centers, however, generally have high signal quality because 

roads and buildings have high reflectivity (amplitude) and 

remain relatively uniform throughout the InSAR timescale. 

Non-uniform atmospheric water-vapor, such as clouds or fog, 

slows the radar signal, causing a phase shift that can lead 

to inappropriate deformation interpretations. Atmospheric 

artifacts can be identified by using multiple independent 

interferogram pairs, or by stacking interferograms. 

Stacking interferograms involves adding together several 

back-to-back shorter term images into a longer term time 

series for either select points or for the entire image. Long 

time span interferograms (generally 2 years or more) usually 
50 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 27. Daily detrended land-surface position, in millimeters, for the GPS station Cuyama High School (CUHS) for the A, north; B, 

east; and C, up direction; and D, water levels in selected wells near CUHS, in feet below land surface, Cuyama Valley, Santa Barbara 

County, California.

 −30

 −20

 −10

 20

10

0

30

2000 2001 2002 2003 2004

JAN JULY JAN JULY JAN JULY JAN JULY JAN JULY

2005 2006 2007

JAN JULY JAN JULY JAN JULY

2008 2009

JAN JULY JAN JULY

2010 2011 2012

JAN JULY JAN JULY JAN

 −30

 −20

 −10

 20

10

0

30

2000 2001 2002 2003 2004

JAN JULY JAN JULY JAN JULY JAN JULY JAN JULY

2005 2006 2007

JAN JULY JAN JULY JAN JULY

2008 2009

JAN JULY JAN JULY

2010 2011 2012

JAN JULY JAN JULY JAN

 −30

 −20

 −10

 20

10

0

30

2000 2001 2002 2003 2004

JAN JULY JAN JULY JAN JULY JAN JULY JAN JULY

2005 2006 2007

JAN JULY JAN JULY JAN JULY

2008 2009

JAN JULY JAN JULY

2010 2011 2012

JAN JULY JAN JULY JAN

Detrended CUHS displacement, in millimeters Water level in feet below land surface

A

B

C

Date

325

 300

275

 200

225

250

175

2000 2001 2002 2003 2004

JAN JULY JAN JULY JAN JULY JAN JULY JAN JULY

2005 2006 2007

JAN JULY JAN JULY JAN JULY

2008 2009

JAN JULY JAN JULY

2010 2011 2012

JAN JULY JAN JULY JAN

D

CUY-58,

July 8, 2008,

377.9 

CUY-57

CUY-05 - 31 day moving average

CUY-58
Geomechanical Activity 51

have poor signal quality because more non-uniform change 

is likely to have occurred in both urban and non-urban areas 

and are, therefore, generally not used (Sneed and Brandt, 

2007). Stacking is very beneficial in reducing these timedependent errors. The agricultural fields in the study area 

produce significant random noise across the imagery, which 

obscures good-quality points. The PS InSAR technique has 

the inherent ability to account for many of the anthropogenic 

effects because pixels with relatively high amplitude variance 

are removed early in the processing. The use of multiple, 

independent interferograms and stacking were used in the 

interpretation of both the conventional and PS InSAR imagery 

to account for atmospheric and time-dependent errors. 

Strict orbital control is required to precisely control the 

look angle and position of the satellite. Successful application 

of the InSAR technique is contingent on looking at the same 

point on the land-surface from the same position in space, 

such that the horizontal distance between each satellite pass, or 

perpendicular baseline, is minimized. Perpendicular baselines 

generally greater than about 200 meters (m) usually produce 

excessive topographic effects (Sneed and Brandt, 2007). The 

relatively flat topography of the study area, however, allowed 

some images with perpendicular baselines of up to about 

500 m to be successfully interpreted.

Understanding an interferogram image is not intuitive. An 

interferogram is a map that represents the change in the lineof-site distance between the land-surface and the satellite. This 

change is manifested as a set of repeating color fringes that 

indicate the magnitude and direction of deformation. In the 

case of ENVISAT (C-band), each complete color fringe (for 

example, purple, blue, cyan, green, yellow, red) represents 

28.3 millimeters (mm) of deformation. The progression of 

colors indicates whether the change is uplift or subsidence. For 

example, a change resulting in a mound-shaped increase of 

85 mm in height would appear as concentric rings alternating 

in color. Starting from outside the “bulls-eye” and working 

inward, there would be three complete color fringes; the colors 

would progress from red to yellow through purple, then the 

sequence would repeat twice more, indicating about 85 mm 

of uplift (three fringes times 28.3 mm is equal to 84.9 mm). 

If the shape were a depression, the color sequence would 

be reversed. One might think of the different colors as lines 

of topography, but instead of elevation, the changing colors 

represent the magnitude and direction of deformation. The 

more deformation there is, the larger number of color fringes 

are drawn. 

For this study, data from the European Space Agency’s 

(ESA) ENVISAT satellite were acquired through the InSAR 

and GeoEarthScope data archives. These archives are operated 

through UNAVCO, a consortium of educational, public, and 

non-profit institutions whose goal is to use various precision 

land- and space-based technologies to identify and understand 

land deformation across the United States. For the period of 

this study, the side-looking 5.6 centimeter (cm) wavelength 

satellite orbited the earth at an altitude of approximately 800 

kilometer (km) and had a 35-day repeat cycle. Tight orbital 

control is required in order to precisely control the look angle 

and position of the satellite, which consumes relatively large 

quantities of fuel. In October 2010, however, ESA made 

adjustments to ENVISAT’s orbit parameters in an attempt 

to extend its lifespan by 3 years, primarily by reducing fuel 

consumption. As a consequence, the satellite look angle is no 

longer controlled. Although the orbital changes did not affect 

the functionality of the SAR instruments, the lack of tight 

orbital control makes interferogram generation using post 

October 2010 data unlikely.

For this study, 30 SAR images were used to produce a total 

of 152 interferograms (77 conventional, and 75 PS InSAR), 

42 of which (20 conventional, and 22 PS InSAR) were of 

sufficient quality for interpretation. Both the conventional and 

PS InSAR techniques were used to produce 19 interferogram 

pairs; in all, 133 unique interferograms were generated. The 

133 interferograms spanned from December 5, 2002, to May 

22, 2008, and each represented differences in time ranging 

from 35 to 665 days. No compatible SAR data were available 

from June 2008 to September 2010. 

Data from the continuous GPS site CUHS (fig. 2) were 

used to calibrate InSAR interpretations. However, day-to-day 

GPS height solutions varied by as much as about plus or minus 

13 mm likely because of variable atmospheric conditions, 

random walk noise, and other effects not directly related to 

land-surface-elevation change (Zerbini and others, 2001; 

Williams and others, 2004; Langbein, 2008). To minimize 

this high-frequency variability to allow better correlation of 

GPS heights to InSAR measurements, a correction was used: 

the height values for the 15 days prior to and following the 

observed date were combined into a 31-day running average. 

The relatively large day-to-day variations in GPS heights were 

thus minimized, while maintaining a height resolution similar 

to that of InSAR (within about 5 mm) and the long-term 

deformation magnitudes evident in the GPS data. 

The construction of the InSAR time series involved 

selecting interferograms on the basis of image quality and the 

minimization of time gaps and overlaps and combining them 

to form longer-term time series. Various combinations of 28 

of the previously mentioned 42 interferograms were combined 

into 8 different time series. Each time series contained 

between 8 and 11 interferograms. Gaps or overlaps were 

never more than 70 days and were accounted for by using 

simple linear interpolation (for example, if the subsidence 

rate before a 35-day gap was 50 mm/yr, and it was 30 mm/

yr after the gap, a rate of 40 mm/yr (or approximately 4 mm) 

was added to the time series for that period). The resultant 

time series (fig. 28) was the average of these eight individually 

constructed time series.

Five points were selected from the Cuyama Valley on the 

basis of geographic distribution and proximity to wells. The 

resultant InSAR time series (fig. 28B) for these five points (fig. 

29) showed a total maximum detected subsidence of about 65 

mm between December 5, 2002, and May 22, 2008, at point 

five (which, if constant, would extrapolate to a rate about 12 

mm/yr) compared to about 40 mm (about 8 mm/yr) at CUHS 
52 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 28. Vertical deformation in Cuyama Valley, Santa Barbara County, 

California, relative to A, first SAR acquisition for the Cuyama High School (CUHS) 

continuous GPS station; and B, selected reference points.

Point 1

Point 2

Point 3

Point 4

Point 5

GPS-CUHS (31 day ave)

InSAR at CUHS

B

2002 2003 2004 2005

Year

2006 2007 2008

Vertical deformation relative to first sar acquisition, in millimeters 

−70

−60

−50

−40

−30

−20

−10

0

10

20

30

2002 2003 2004 2005

Year

2006 2007 2008

Vertical deformation relative to first sar acquisition, in millimeters 

−70

−60

−50

−40

−30

−20

−10

0

10

20

30 A (fig. 28A), which is approximately 7 km to the 

east of point five. An interferogram spanning 

December 5, 2002–January 9, 2003, that was 

used in the construction of the averaged time 

series indicated a local short-term maximum 

subsidence magnitude of approximately 15 mm 

near point four. Two interferograms not used 

in the construction of the long-term time 

series spanning December 9, 2004–January 

13, 2005, and December 29, 2005–February 

2, 2006, (fig. 28B) indicated a local maximum 

uplift of approximately 10 mm (about 100 

mm/yr) at points one and three, respectively. 

Interferograms between December 5, 2002, 

and May 22, 2008, showed the area of primary 

deformation approximately 3 kilometers to 

the southeast of the GPS site CUHS. The 

size and location of this feature appeared to 

be dependent, in part, on the timespan of the 

interferogram, which could reflect seasonal 

variations in pumping (figs. 29 and 30). 

Interferograms beginning in summer and ending 

in winter generally showed uplift (fig. 30B). 

Interferograms beginning in winter or spring 

and ending in summer or fall generally showed 

subsidence (figs. 29A–B, 30A, 31).

A qualitative analysis of the InSAR imagery, 

with respect to nearby faulting and oil-field 

production, was also completed (fig. 31). The 

primary faults in question were the Morales 

fault on the northern boundary of Cuyama 

Valley, the Russell fault to the west, the 

Rehoboth fault in the central portion of the 

basin, and the South Cuyama fault on the 

southern boundary of Cuyama Valley (fig. 31). 

In a few interferograms, there was an apparent 

deformation to the north of the range-front 

Morales fault, but this is more likely attributed 

to the parallax effect from relatively large 

perpendicular baselines than true land-surface 

elevation change because the signal mirrors 

that of the topography and is not consistent 

throughout the InSAR time span. The South 

Cuyama fault on the southern boundary of the 

basin showed no tendency to create sharp phasechange ramps (lineaments) in interferograms 

parallel to the fault itself. Both the Morales 

and South Cuyama faults are thrust faults, with 

older alluvium and the Morales Formation 

extending beneath exposed consolidated rocks 

in the range blocks. It is likely that these faults 

showed no INSAR response because the basinfill units were not truncated below the map-view 

trace of the fault. The Santa Barbara Canyon 

fault is too far to the south and east of the 

primary deforming areas to show a fault-related 
Geomechanical Activity 53

Figure 29. Conventional InSAR interferogram images for Cuyama Valley, Santa Barbara County, California, from A, May 18, 2006, to 

October 25, 2007; and B, February 7, 2008, to April 17, 2008.

166

33

166

33

Ref Pt. 1 Ref Pt. 2 Ref Pt. 3

Ref Pt. 4

Ref Pt. 5

Ref Pt. 1 Ref Pt. 2 Ref Pt. 3

Ref Pt. 4

Ref Pt. 5

VCST

VCST

0

0 1 2 3 4 5 Miles

1 2 3 4 Kilometers 5

Relative 

Subsidence Uplift

+28 mm 0 −28 mm

May 18, 2006, to October 25, 2007

119°45’ 119°40’ 119°35’ 119°30’

35°0’

34°55’

34°50’

Fault

Reference point

Continuous GPS site

Cuyama groundwater

 basin boundary

CUHS

CUHS

119°45’ 119°40’ 119°35’ 119°30’

35°0’

34°55’

34°50’

EXPLANATION

~35 mm subsidence

~25 mm subsidence

February 7, 2008, to April 17, 2008

A

B

mm is millimeter
54 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Figure 30. Persistent scatterer InSAR interferogram images for Cuyama Valley, Santa Barbara County, California, from A, May 13, 2004, 

to August 26, 2004; and B, August 31, 2006, to February 22, 2007.

166

33

166

33

Ref Pt. 1 Ref Pt. 2 Ref Pt. 3

Ref Pt. 4

Ref Pt. 5

Ref Pt. 1 Ref Pt. 2 Ref Pt. 3

Ref Pt. 4

Ref Pt. 5

VCST

VCST

0

0 1 2 3 4 5 Miles

1 2 3 4 Kilometers 5

Relative 

Subsidence Uplift

+28 mm 0 −28 mm

May 13, 2004, to August 26, 2004

119°45’ 119°40’ 119°35’ 119°30’

35°0’

34°55’

34°50’

Fault

Cuyama groundwater

 basin boundary

CUHS

CUHS

119°45’ 119°40’ 119°35’ 119°30’

35°0’

34°55’

34°50’

EXPLANATION

~20 mm subsidence

~25 mm uplift

August 31, 2006, to February 22, 2007

A

B

Reference point

Continuous GPS site

mm is millimeter
Geomechanical Activity 55

Figure 31. Persistent scatterer InSAR interferogram images for Cuyama Valley, Santa Barbara County, California, from March 9, 2006, 

to November 29, 2007.

166

33

119°55’ 119°50’ 119°45’ 119°40’ 119°35’ 119°30’

35°

5’

35°

0’

34°

55’

34°

50’

0 1 2 3 4 5 Miles

543210 Kilometers

Faults

Relative 

Subsidence Uplift

0 -28 mm

mm is millimeter

+28 mm 

Russell Ranch Oil Field

CUHS

March 9, 2006, to November 29, 2007

Rehoboth Farms fault

Morales fault

South Cuyama fault

Russell fault

Turkey Trap Ridge fault Graveyard Ridge fault

Whiterock 

Santa Barbara

Canyon fault

fault

response. The Rehoboth Farms fault trends northwest/

southeast and approximately bisects Cuyama Valley. It is 

apparent from InSAR that this fault is not a significant barrier 

to groundwater flow because the majority of interferograms 

showed symmetrical subsidence or uplift on both sides of this 

fault. The last fault that is of concern in the study area is the 

Russell fault, which runs roughly parallel to the Russell Ranch 

oil field. Similar to the other faults, the Russell fault did not 

appear to be acting as a barrier to groundwater flow. As with 

the South Cuyama fault, the primary areas of deformation did 

not typically extend far enough to the west to be truncated 

by the Russell fault, if it were to act as a groundwater-flow 

barrier. Subsidence detected by InSAR did not appear to be 

caused by hydrocarbon extraction from the Russell Ranch 

oil field because the primary subsidence feature lies 10 

kilometers or more to the east of the 8-km long by 1-km 

wide oil field. Subsidence caused by oil and gas extraction is 

largely restricted to the area of the oil field itself, as compared 

to the regional-scale subsidence that is typical of regional 

groundwater-extraction effects (Coplin and others, 1999). 
56 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12 

Summary and Conclusions

To better assess the water resources of the Cuyama 

Valley groundwater basin, Santa Barbara County, California, 

geologic, lithologic, geophysical, water-quality, and hydraulic 

data were collected from three groundwater multiple-well 

monitoring sites constructed in Cuyama Valley. Additional 

water-quality and hydraulic data were collected and compiled 

from 2008 to 2012 from selected domestic and supply wells, 

springs, and surface-water sites. Geomechanical processes in 

the Cuyama Valley were also analyzed. 

Three multiple-well monitoring sites, CVKR, CVBR, 

and CVFR, were installed in the study area to test specific 

conditions related to the geologic and hydrologic system. Data 

collected from multiple-well monitoring sites wells provided 

information on vertical differences in geology, water-quality, 

water levels, and hydraulic properties at the same location; 

these vertical profiles at multiple locations helped characterize 

the three-dimensional groundwater system.

Analysis of the generalized lithologic characterization and 

geophysical logs collected from the monitoring sites indicated 

the water-bearing units are composed of alternating layers of 

alluvial fan and stream deposits consisting of unconsolidated 

to partly consolidated sand, gravel, silt, clay, and occasional 

cobbles that range from less than 1 foot to more than 20 feet 

thick. At the CVKR site, the contact of younger and older 

alluvium is 365 ft bls; the contact of the older alluvium and the 

Morales Formation is deeper than 1,003 ft bls. At the CVBR 

site, the contact of recent and older alluvium is 30 ft bls; the 

contact of the older alluvium and the Morales Formation is 

595 ft bls. At the CVFR site, the contact of younger and older 

alluvium is 75 ft bls; the contact of the older alluvium and the 

Morales Formation is 560 ft bls. Thus, structure, deposition, 

and erosion have resulted in considerable variation in the 

depth and thickness of these units in the valley.

Deviations in temperature-gradient logs indicated that the 

local geothermal gradient is influenced by the movement of 

groundwater. Changes in the temperature gradients were used 

to identify several flow zones at each site. At the CVKR and 

CVBR sites, flow generally decreased with depth, whereas at 

the CVFR site, a majority of the flow is in the deeper zones.

Water-quality samples indicated poor water quality, with 

respect to total dissolved solids and sulfate, throughout the 

Cuyama Valley, whereas poor water quality with respect to 

other constituents was less prevalent. Concentrations greater 

than the USEPA secondary drinking-water standard (SMCL) 

were observed for total dissolved solids in 97 percent of 

the samples and for sulfate in 95 percent of the samples. 

Concentrations greater than the USEPA primary drinking 

standard (MCL) were observed for nitrate in 13 percent 

the samples and for arsenic in 12 percent of the samples. 

Concentrations of total chromium [Cr(T)] were not greater 

than the MCL-CA of 50 μg/L in any of the samples; however, 

concentrations of hexavalent chromium [Cr(VI)] greater than 

the PHG were observed in 95 percent of the samples (the 

PHG is a non-regulatory threshold, and PHGs are typically 

orders of magnitude lower than MCLs). Nitrate concentrations 

decreased with depth at the CVKR site, indicating the source 

was near surface. Four of the five wells where nitrate levels 

were greater than the MCL were in the Southern-Main zone 

in center of the agricultural land-use area. Wells with the 

lowest nitrate levels were on the edges of the agricultural 

land-use areas, indicating the source of nitrate was likely from 

irrigation return flows. Low concentrations of nitrate (NO3

-N), 

less than 0.02 mg/L, in the surface-water samples indicated 

that natural surface-water recharge was not a source of high 

nitrate concentrations. 

The isotope data indicated that groundwater does not 

move freely among the different flow-paths within the older 

alluvium or the Morales Formations, and that these units 

could have different sources of recharge. The range in isotope 

values observed at the different depths at the CVKR, CVBR, 

and CVBR indicated the water does not readily flow vertically 

between the water-bearing units. The relation between isotope 

values and depths also indicated that these units could have 

different sources of recharge. Variations in isotope values 

among the three monitoring sites indicated movement of water 

between different zones also could be restricted. The isotope 

samples from the four CVBR wells were, in general, lighter 

in deuterium than the CVKR wells, whereas isotope samples 

from the four CVFR wells were the heaviest collected in the 

basin. Comparison of values from other supply wells in the 

basin also supported restricted lateral flow between zones 

that could be controlled by the structural compartments of the 

basin.

Tritium concentrations and carbon activities showed a wide 

range in groundwater age for the basin. Concentrations of 

tritium in the samples ranged from 0.9 to 9.0 pCi/L, while time 

since recharge ranged between 600 and 38,000 years before 

present. The youngest water was collected in the Southern 

Ventucopa Uplands, and the oldest water was collected in the 

Northwestern Sierra Madre Foothills. Tritium concentrations 

in samples indicated the presence of some recent recharge in 

the CVKR-3, CVKR-4, and CVBR-3 wells and the absence 

of modern water in the CVKR-1, CVKR-2, and CVBR-3 

wells. Tritium concentrations in samples from all four CVFR 

indicated a higher percentage of recent recharge. Tritium 

levels at the CVFR site increased with depth, indicating that 

the percentage of younger water at depth was most likely 

caused by local pumping. Estimated carbon-14 ages for the 

CVKR, CVBR, and CVFR sites ranged from 2,700 to 31,200 

years before present. Samples from CVKR-3 and 4, CVBR-3, 

and CVFR-1, -2, -3, and -4 were all older than 2,700 years 

before present but also contained detectable levels of tritium, 

indicating that water from these wells is a mix of differently 

aged groundwater from different sources. 

Arsenic concentrations ranged from less than 0.2 to 

71.4 μg/l. The highest concentration sample was collected 

from a well in the Southern-Main zone that was screened 

in both the younger and older alluvium. A surface-water 

sample collected from the Cuyama River contained arsenic 

concentrations of 0.51 μg/l. Variation in the concentration of 
Summary and Conclusions 57

arsenic across zones and formations was observed. Elevated 

arsenic concentrations were observed in water recharged 

more than 22,000 years before present, indicating that arsenic 

concentrations are higher in groundwater that has had more 

time to mobilize the arsenic.

Water-level data indicated water levels fluctuated 

seasonally by as much as 80 feet, and water-level differences 

between aquifers were as great as 40 feet during the peak of 

the pumping season. Hydrographs showed downward vertical 

hydraulic gradients during the peak of the pumping season. 

The water-level hydrographs indicated different water-level 

changes and relations between aquifers in different parts of 

the basin. A comparison of the highest level observed each 

year since January 2008 showed a variation in water-level 

trends, with some levels declining, some rising, and some 

reversing. Declines from 6 to over 30 feet were observed in 

the Southern-Main zone and Central Sierra Madre Foothills. 

Rises in water levels from less than 1 to about 8 feet were 

observed the Southern Ventucopa Uplands and Northeast 

Ventucopa Uplands. Reversal from declining to rising water 

levels was only observed in the Southern Ventucopa Uplands 

and indicated that this zone could have the only viable source 

of recharge (from the Cuyama River) for the Cuyama Valley 

under the current conditions.

Time-series water-level data showed a seasonal pattern of 

declining levels coinciding with the peak of the agricultural 

season and rising water levels when nearby irrigation and 

related pumping were at a minimum. The pumping of nearby 

irrigation wells directly influenced water levels in all of the 

CVKR and CVBR wells. Water-level data from all of the 

monitoring sites showed a decline in the seasonally high levels 

over the period of record and showed a vertical hydraulic 

gradient reversal from upward during the winter months to 

downward during the irrigation season. Observations at the 

CVKR site showed water levels in the three deeper wells 

varied by as much as 60 ft seasonally, while water levels in 

the shallowest well varied by about 25 ft. Water levels in all 

wells showed a decline of over 20 ft between 2009 and 2012. 

Observations at the CVBR site showed water levels in the 

three deeper wells varied by as much as 90 ft seasonally, while 

water levels in the shallowest well varied by about 40 ft. Water 

levels in all wells showed a decline of over 5 ft between 2010 

and 2012. Observations at the CVFR site showed water levels 

in all wells varied by as much as 15 ft seasonally. Water levels 

in all wells showed a decline of over 20 ft between 2010 and 

2012.

Water-level rises and declines observed in the Sierra 

Madre Foothills zone correlated to the duration of seasonal 

pumping of the wells. Increased pumping in 2011 resulted 

in a water-level decline of over 25 ft in 1 year. Changes in 

the pumping, and possible the recharge, conditions between 

2010 and 2011 in Northwestern Sierra Madre Foothills zone 

can be the difference between static and overdraft conditions. 

Time-series data from two wells in the Southern Main Zone 

showed a detailed record of the steady decline in water level. 

The hydrographs showed the seasonal highs and lows that 

were expected; however, the year-to-year seasonal high 

showed a steady decline in water levels of approximately 2.5 

and 7 ft per year. Time-series data from two wells showed a 

rise in water levels in the Southern Ventucopa Uplands zone 

during the spring of 2012. Observations showed the rise 

began in late March 2012 and rose over the 25 ft in one well 

in about 1 month. This marked rise in water level over a short 

period indicated that this zone responds quickly to periods of 

increased recharge, possibly from the Cuyama River.

Historic water level data, dating back to the early 1940s, 

showed long-term trends. Data indicated that nine wells had 

declining water levels, four wells had relatively static levels, 

and three wells had rising water levels. All of the wells in the 

wells in the South-Main zone had declines in water levels over 

the period of record. The largest decline of 300 ft, averaging 

7.25 ft per year, was observed between 1960 and 2001. 

However, large declines in water levels were not limited to 

the Southern Main zone. In the Caliente Northern-Main zone, 

a decline of over 130 feet, for an average decline of 1.7 ft 

per year, was observed. In the Western Basin zone, a decline 

of over 80 ft, for an average decline of 1.2 ft per year, was 

observed. In the Southern Sierra Madre zone, a decline of over 

30 ft, for an average decline of 0.9 ft per year, was observed. 

Declines were not observed in all zones of the basin. Two of 

the wells in the Southern Ventucopa Uplands zone showed 

an increase in water levels, while five others showed slow 

declines followed by a marked rise in water levels—over 100 

ft in one case—indicating that this zone responds quickly to 

periods of increased recharge. 

Slug-test data from the monitoring wells indicated that 

horizontal hydraulic conductivities range from 1.5 to 28 ft/

day. The median hydraulic conductivity of 15 ft/day observed 

for the wells in the older alluvium was almost five times 

higher than the median hydraulic conductivity of 3.1 ft/day 

in the Morales formation. Pump-test data from supply wells 

indicated that transmissivities range from 560 to 163,400 

gal/d/ft. The median transmissivity of 15,700 gal/d/ft for 

the wells in the younger alluvium was three times higher 

than the median transmissivity of 5,000 gal/d/ft in the older 

alluvium. Tests were repeated on some wells over a span of 

several years. Analysis of the results indicated that hydraulic 

conductivity typically decreased over time. These temporal 

changes in hydraulic conductivity are likely due to well 

performance, but also could be influenced by the declines in 

water levels over time.

Daily discharge data from stream-flow gaging stations in 

the Cuyama Valley drainage showed the stream flows vary 

seasonally. Records from the Cuyama River, where it enters 

and exits the basin, showed a higher flow, averaging between 2 

and 200 cubic feet per second (cfs), through most of the winter 

months, while there was lower flow, below 2 cfs, during the 

summer months. Summer flow rates in 2011 were greater 

than in 2010. High flows of almost 900 cfs were observed in 

January and December of 2010. Changes in water levels in 

well CUY-35, in the Southern Ventucopa Uplands, correlated 

with high-flow events, while the extended-flow event 
58 Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12

corresponded with the 25-foot increase in water level at this 

well. In general, surface water flowing into the valley from 

the Cuyama River was equal to the amount of water flowing 

out of the valley, indicating that all other sources of inflow 

to the Cuyama Valley would be sources of recharge. Starting 

in October 2011, there was a net increase of inflow into the 

valley along the Cuyama River compared to the outflow, 

indicating that surface water was recharging the groundwater 

system.

Data collected from continuously operating GPS stations 

indicated that the Cuyama study area is slowly moving 

northwest. Stations in the mountains to the west of the valley, 

in the hills to the east of the valley, and in the Southern 

Ventucopa uplands showed a net upward motion for the 

land surface in the region. The CUHS, in the Southern-Main 

zone showed an annual velocity of −7.5 mm/yr (downward), 

indicating significant downward motion at this location 

relative to the region. The cyclic variability in the daily landsurface position in the lateral and vertical directions for CUHS 

indicated the aquifer sediments in the area had experienced 

elastic deformation. However, a longer-term downward trend 

likely represents inelastic deformation and indicates reduced 

storage capacity in the aquifer sediments. In 2011, motion in 

all the directions increased substantially and corresponded to 

compression of the aquifer sediments. The cyclic variation in 

the position of the land surface at CUHS also correlated with 

water-level measurements in nearby wells, which supports 

the conclusion that elastic deformation was caused by 

groundwater withdrawals. 

InSAR data showed local and regional changes that 

appeared to be dependent, in part, on both the time span 

of the interferogram, seasonal variations in pumping, and 

geological uplift. Long-term InSAR time series showed a total 

detected subsidence rate of approximately 12 mm per year 

at one location, while short InSAR time series showed uplift 

of approximately 10 mm per year at several locations. The 

resultant InSAR time series for five selected points showed a 

total maximum detected subsidence of about 40 mm (about 

8 mm/yr) at CUHS. Interferograms showed that a local 

maximum deformation bowl typically forms approximately 

3 kilometers to the southeast of the CUHS GPS site. The 

size and location of this feature appear to be dependent, in 

part, on both the timespan of the interferogram and seasonal 

variations in pumping. A qualitative analysis of the InSAR 

imagery with respect to nearby faulting production showed 

the Rehoboth Farms fault trend is not a significant barrier 

to groundwater flow because the majority of interferograms 

showed symmetrical subsidence or uplift on both sides of this 

fault. A qualitative analysis with respect to the local Russell 

Ranch oil field, which runs roughly parallel to the Russell 

fault, indicated that subsidence did not appear to be caused by 

hydrocarbon extraction and that the fault did not appear to be a 

contributing barrier to groundwater flow.
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U.S. Geological Survey

California Water Science Center

6000 J Street, Placer Hall

Sacramento, CA 95819

dc_ca@usgs.gov

or visit our Web site at:

http://ca.water.usgs.gov
Everett and others—Geology, Water-Quality, Hydrology, and Geomechanics of the Cuyama Valley Groundwater Basin, California, 2008–12—SIR 2013-5108