A WATER-RESOURCES DATA-NETWORK EVALUATION FOR

MONTEREY COUNTY, CALIFORNIA,

PHASE 3: NORTHERN SALINAS RIVER DRAINAGE BASIN

By William E. Templin and Randall C. Schluter

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 89-4123

Prepared in cooperation with the 

MONTEREY COUNTY FLOOD CONTROL AND 

WATER CONSERVATION DISTRICT

CM

iH

I

CO 

O

o

Sacramento, California 

1990
DEPARTMENT OF THE INTERIOR

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY

Dallas L. Peck, Director

For additional information write to:

District Chief 

U.S. Geological Survey 

Federal Building, Room W-2234 

2800 Cottage Way 

Sacramento, CA 95825

Copies of this report 

may be purchased from:

U.S. Geological Survey

Books and Open-File Reports Section

Box 25425

Building 810, Federal Center

Denver, CO 80225
CONTENTS

Page

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

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

Purpose, scope, and objectives ....................................... 2

Approach ............................................................. 6

Location of study area ............................................... 6

Limitations .......................................................... 7

Acknowledgments ...................................................... 7

Well-numbering system ................................................ 8

Climate ................................................................... 9

Land use .................................................................. 10

Water use ................................................................. 12

Precipitation networks .................................................... 18

Precipitation-quantity networks ...................................... 18

Precipitation conditions ........................................ 18

Objectives ...................................................... 19

Factors affecting design ........................................ 34

Precipitation maps .............................................. 34

Description ..................................................... 35

Possible additional monitoring .................................. 37

Precipitation-quality networks ....................................... 37

Objectives ...................................................... 37

Possible problems ............................................... 38

Acid rain and acid fog ..................................... 38

Pesticides ................................................. 39

Design .......................................................... 39

Surface-water networks .................................................... 40

Surface-water conditions ............................................. 40

Streamflow networks .................................................. 40

Objectives ...................................................... 40

Method of evaluation ............................................ 41

Criteria for site selection ..................................... 41

Description of streamflow-gaging stations ....................... 44

Salinas River at Soledad ................................... 44

Salinas River near Gonzales ................................ 46

Salinas River near Chualar ................................. 46

Salinas River near Spreckels ............................... 47

El Toro Creek near Spreckels ............................... 47

Alisal Creek near Salinas .................................. 48

Gabilan Creek near Salinas ................................. 48

Reclamation Ditch near Salinas ............................. 49

Santa Rita Creek at Santa Rita ............................. 49

Contents III
Page 

Surface-water networks Continued

Surface-water-quality networks ....................................... 53

Surface-water quality conditions ................................ 53

Objectives ...................................................... 53

Method of evaluation ............................................ 54

Station location and sampling frequency ......................... 55

Description ..................................................... 55

Stream-reach rating system ...................................... 57

Ground-water networks ..................................................... 58

Ground-water conditions .............................................. 58

Occurrence of ground water ...................................... 58

Ground-water flow ............................................... 60

Flow barriers ................................................... 61

Water-level changes ............................................. 61

Ground-water-quality conditions ................................. 62

Ground-water-level networks .......................................... 63

Objectives ...................................................... 63

Method of evaluation ............................................ 63

Well and network classification ................................. 64

Well-classification system ................................. 64

Network-classification system .............................. 67

Description ..................................................... 67

Possible additional monitoring .................................. 72

Ground-water-quality networks ........................................ 74

Objectives ...................................................... 74

Description ..................................................... 75

Possible additional monitoring .................................. 89

Summary and conclusions ................................................... 90

References cited .......................................................... 92

ILLUSTRATIONS

Page 

Figures 1-7. Maps showing:

1. Location of the study area .......................... 4

2. Land use and land cover in the northern Salinas

River drainage basin .............................. 11

3. Point and regional sources of concern for

possible water-quality degradation ................ 13

4. Mean annual precipitation in Monterey County ........ 20

5. Precipitation gages ................................. 36

6. Surface-water-quality monitoring sites and

streamflow-gaging stations ........................ 45

7. Ground-water geographic areas ....................... 59

8. Graph showing mean changes in autumn ground-water

levels, 1974-78 ........................................... 62

9. Map showing ground-water monitoring wells ................... 71

IV Contents
TABLES

Page 

Table 1. Generalized management and network objectives ................... 3

2. Major point-source dischargers to land .......................... 14

3. Ideal networks, priority, and pertinent data .................... 22

4. Precipitation gages ............................................. 32

5. Streamflow-gaging stations ...................................... 42

6. Surface-water-quality monitoring sites .......................... 50

7. Classification of ground-water networks ......................... 65

8. Inventory of ground-water-level networks ........................ 68

9. Network locations that presently do not have water-level

wells monitored by the Monterey County Flood Control and

Water Conservation District ................................... 73

10. Inventory of ground-water-quality monitoring networks ........... 76

11. Well summary and cross-reference to wells in ground-water

networks ...................................................... 83

12. Network locations that presently do not have wells monitored 

for ambient water-quality conditions by the Monterey County 

Flood Control and Water Conservation District ................. 89

CONVERSION FACTORS

For readers who prefer metric and International System (SI) units to 

inch-pound units, the conversion factors for the terms used in this report are 

as follows:

Multiply By

acre 0.4047

cubic foot per second (ft 3 /s) 0.02832

foot 0.3048 

gallon per minute (gal/min) 0.06308

gallon per day 0.06308

inch 25.4

inch per year (in/yr) 25.4

mile 1.609

square mile (mi 2 ) 2.590

Abbreviations;

yg/L microgram per liter

mg/L milligram per liter

To obtain 

hectare

cubic meter per second 

meter

liter per second 

liter per day 

millimeter 

millimeter per year 

kilometer 

square kilometer

Degree Celsius (°C) can be converted to degree Fahrenheit (°F) by the 

following formula:

°F = 1.8x°C+32.

Sea level; In this report, "sea level" refers to the National Geodetic 

Vertical Datum of 1929 (NGVD of 1929) a geodetic datum derived from a general 

adjustment of the first-order level nets of both the United States and Canada, 

formerly called Sea Level Datum of 1929.

Contents V
A WATER-RESOURCES DATA-NETWORK EVALUATION FOR MONTEREY COUNTY, 

CALIFORNIA, PHASE 3: NORTHERN SALINAS RIVER DRAINAGE BASIN

By William E. Templin and Randall C. Schluter

ABSTRACT

This report presents an evaluation of water-resources data-collection networks in the 

northern Salinas River drainage basin, Monterey County, California. The evaluation, done in 

cooperation with the Monterey County Flood Control and Water Conservation District, covers both 

quantity and quality monitoring by precipitation, surface-water, and ground-water networks. The 

report describes existing networks in the study area and possible additional data collection.

The study identified 34 precipitation gages in the study area, of which 20 are active. The 

stations are concentrated in the northwestern part of the study area. Data are lacking for the 

eastern and southern parts of the study area, as well as the southwestern slopes of the Gabilan 

Range. No precipitation-quality networks were identified. Possible data-collection efforts for 

precipitation quality include monitoring for acid rain and for pesticides in precipitation.

The study identified 10 streamflow-gaging stations, of which 6 are active. To meet the 

objectives for streamflow networks that are outlined in the report, all sites could be reactivated, and two of the inactive sites could be relocated to improve the reliability of the data. 

Besides these stations, nine possible additional streamflow-gaging sites were identified.

The Monterey County Flood Control and Water Conservation District samples one surface-water 

site for suspended sediment, specific conductance, and chlorides. Several agencies have done 

water-quality sampling in the past, but only five sites are active. Reactivation of the 45 

inactive sites might help to meet the various surface-water-quality objectives described in the 

report. Development of a stream-reach rating system also could help to identify parts of the 

study area most in need of sampling.

The Monterey County Flood Control and Water Conservation District maintains three networks 

to measure ground-water levels on a monthly basis, during peak irrigation, and at the end of 

the irrigation season. The District measures water levels in 318 wells. The only other network identified for this report was operated by the U.S. Geological Survey, and none of its 

five wells are active. The study identified 128 sections in which no ground-water-level 

monitoring is presently done. Well coverage is densest in the saltwater-intrusion areas near 

Castroville, California. Wells in the rest of the study area are more sparsely distributed and 

are concentrated down the center of the drainage basin in the alluvial ground-water basin.

The ideal initial baseline network of ground-water-quality wells would be an evenly spaced 

grid of index wells within each aquifer, with a density of one per section. Once baseline conditions were established, representative wells could be selected and monitored annually. As of 

1985, the Monterey County Flood Control and Water Conservation District monitored 379 study 

wells in the area for various water-quality conditions. Other networks monitor (or propose the 

monitoring of) 135 wells. The District collects samples in summer months to monitor saltwater 

intrusion near Castroville. Annual samples also are analyzed for chloride, specific conductance, 

and nitrate. Every 5 years, the District does a complete mineral analysis on each study well. 

Improvements in network coverage are suggested to better approximate ideal network coverage. The 

adequacy of wells in existing monitoring networks for representing actual conditions in the 

ground-water basins was not established conclusively. Possible redundancy of information from 

existing networks was not evaluated statistically. Despite these limitations, this report does 

provide a basis for assessing the adequacy of ground-water-level networks in the study area. The 

computerized Geographic Information System (GIS) that is planned for Monterey County could easily 

use the information in this report for the needed initial analysis of network adequacy. The 

feasibility of management and analysis of large complicated data bases (such as the ground water 

networks identified in this report) is substantially improved through the use of state-of-the-art 

GIS tools now available.

Abstract 1
INTRODUCTION

Continuing data collection and analysis are vital to efficient development 

and management of water resources. To insure that water managers have adequate 

information on conditions and trends, data-collection programs must be 

evaluated and updated periodically. Changes in population, land use, and 

agricultural practices may increase the demand for water, so that effective 

water management and supporting data collection become even more critical. 

Consideration of cost effectiveness, however, means that every site must count, 

and redundancy must be minimized. Water-resources management and monitoring 

are ever-changing, and periodic reevaluation is a necessary part of this 

process.

This report presents an evaluation of precipitation, surface-water, and 

ground-water monitoring networks in the northern Salinas River drainage basin 

of Monterey County, California (fig. 1). This report is third in a series of 

reports prepared in cooperation with the Monterey County Flood Control and 

Water Conservation District (MCFCWCD). The phase 1 report (Showalter and 

Hoffard, 1986) covers the southern Salinas River drainage basin, the phase 2 

report covers the north county and coastal areas of Monterey County (W.E. 

Templin, P.E. Smith, and R.C. Schluter, U.S. Geological Survey, written 

commun., 1989), and this report (phase 3) covers the northern Salinas River 

drainage basin (fig. 1).

Purpose, Scope, and Objectives

This report presents an evaluation of water-resources data-collection 

networks in the northern Salinas River drainage basin of Monterey County 

(fig. 1) . Possible additional monitoring is described for networks that 

presently do not meet objectives defined in this report. The report includes 

an evaluation of networks that monitor quantity and quality of precipitation, 

surface water, and ground water in the study area. The report also describes 

factors influencing water-resources network design in the area, including 

geology, climate, water use, hydrologic conditions, and land use. Generalized 

management and network objectives are summarized in table 1. These objectives, 

developed with significant assistance from the staff of the Monterey County 

Flood Control and Water Conservation District, guided the network evaluations 

and the preparation of this report.

2 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 1. Generalized management and network objectives

I. Generalized management objectives 

A. Precipitation networks

1. Determine regional variations to establish spatial and temporal trends for storm events and for 

average periods of time (such as daily, monthly, and annual totals).

2. Identify factors which may influence quantity or quality:

a. Determine the effects of the presence of natural and human-influenced point and regional

factors that may affect precipitation characteristics, such as lakes, reservoirs, oceans, 

estuaries, wetlands; regionally irrigated areas; multiple-story buildings; and industries 

with emissions into the air.

b. Determine the presence of measurement conditions that may affect measurement values, such as 

standard methods of gaging-station installation (gage types, distance above ground and away 

from structures, and sampling and analytical practices).

B. Streamflow networks

1. Determine benchmark flow characteristics, such as peaks and mean daily flows, for all major and 

minor streams.

2. Identify temporal and spatial trends.

3. Identify causes of quantity changes, such as annual precipitation variation, land use changes, 

instream uses, diversions, agricultural return, channel stabilization, or channelization.

4. Determine best management options among the various water uses, such as instream fish habitat,

recreation, ground-water recharge, or diversions for agricultural, industrial, or municipal and 

domestic uses.

C. Surface-water-quality networks

1. Determine ambient concentrations of all water-quality constituents.

2. Determine spatial and temporal trends.

3. Identify sources of constituents:

a. Native (soils and geologic parent materials).

b. Point sources (industrial, municipal and domestic, solid-waste disposal sites, and 

agriculturally related sites).

c. Nonpoint sources, including but not limited to applied agricultural chemicals (pesticides and 

herbicides from agricultural and forest land use and land cover categories); cumulative 

effects of septic systems, mines, urban runoff, underground storage tanks, and rainfall 

ground-water discharge from water sources of lower quality than streams.

4. Develop a management plan to control stream quality.

D. Ground-water-level networks

1. Determine regional water-level conditions to establish spatial and temporal trends.

2. Identify sources of pumpage and recharge.

3. Determine storage capacities and best management practices to prevent overdraft and saltwater 

intrusion.

E. Ground-water-quality networks

1. Determine regional ambient water-quality conditions to establish spatial and temporal trends.

2. Identify sources of ground-water use and potential contamination to minimize contaminant buildup, 

reduce and eliminate sources of contamination, prevent additional contamination, and improve 

degraded water conditions whenever possible.

II. Generalized network objectives for all networks

A. Ideal-network objectives (Pederson and others, 1978, p. 77).

1. Establish a data base for water quantity and quality to achieve management objectives.

2. Provide complete spatial and temporal coverage to satisfy all data needs of Monterey County Flood 

Control and Water Conservation District at an adequate level of accuracy.

B. Actual-network objectives (Moss and others, 1982, p. 1).

1. Optimum distribution of monitoring sites to provide a minimum-cost network or integrated 

information system that will attain a prespecified accuracy and reliability.

2. Maximum information within budgetary and time constraints.

Introduction 3
MOSS LANDING/;-:-:

/ ^::'SALiNA6tt£

n $m$mmz*

SACRAMENTO

V.

SAN FRANCISCO 

PHASE 2

__ A _MONTEREYj __ __ CO 

~SAN LUIS OBISPO CO '

20 MILES

20 KILOMETERS

MAP OF CALIFORNIA

FIGURE 1.-Location of the study area.

4 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
121°45'

R2E R3E

R4E

30'

T14S

T16S

36°30'

EXPLANATION

STUDY AREA BOUNDARY

10MILES

10 KILOMETERS

Introduction 5
Approach

The approach of this report is similar to the one used by Showalter and 

Hoffard (1986, p. 7) . In general, the principal steps include (1) assessment 

of data needs for the study areas, (2) design of ideal network coverage, (3) 

description and evaluation of existing networks, and (4) suggestion of improvements to network coverage. Specific approaches for each network evaluation 

vary considerably because of differences both in the level of knowledge about 

precipitation, surface water, and ground water in the study areas and in the 

general state of the art for each of the water-resources disciplines. For 

example, considerably more research has been completed in the specialities of 

streamflow and precipitation network evaluation than in water-quality and 

ground-water network evaluation.

Location of Study Area

Monterey County (fig. 1) is south of San Francisco in central coastal 

California. For the network evaluations, the Salinas River drainage basin was 

divided into the southern and northern parts. The study area for this report 

is the northern Salinas River drainage basin in Monterey County. Showalter and 

Hoffard (1986) reported on the southern basin.

The study area for this report is about 40 miles long, about 25 miles wide 

near Chualar, and about 600 mi 2 in area. The communities of Soledad, Gonzales, 

Chualar, Salinas, Castroville, and Moss Landing lie in the study area (fig. 1). 

The Salinas River is braided from its confluence with the Arroyo Seco near 

Soledad, meanders to near Spreckels, and is mostly straight or confined from 

Spreckels to Monterey Bay. The Salinas River drains an area of about 5,000 

mi 2 , which extends southward from its mouth about 150 miles. The basin rises 

in altitude from sea level at the mouth of the Salinas River to about 50 feet 

at Salinas and about 200 feet at Soledad, which is at the southern edge of the 

study area.

6 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Limitations

The lack of an up-to-date, computerized data base precluded the use of 

many sophisticated statistical and geographical tools for network evaluation. 

Efforts to identify current data-collection activities were restricted to 

reviews of such computerized data bases as STORET, U.S. Geological Survey 

Water-Data Storage and Retrieval System (WATSTORE), National Water Data 

Exchange (NAWDEX), and California Department of Water Resources Water 

Information System (WDIS); reviews of published versions of these data bases; 

and telephone interviews with water-resources agencies in the local area. An 

attempt was made to identify all hydro logic monitoring in the area, but the 

compilation of networks is not as thorough as is needed and was necessary for a 

ground-water-quality monitoring network design done in cooperation with the 

California State Water Resources Control Board (Templin, 1984). Monitoring 

activities change rapidly in location and number of sites as well as in the 

properties, characteristics, and constituents monitored. Consequently, 

periodic inventories of active data collection are vital to investigations of 

the sort undertaken for this report.

Acknowledgments

The authors appreciate the assistance of personnel of many agencies, 

without whom this report could not have been completed:

Association of Monterey Bay Area Governments

California Air Resources Control Board

California Department of Fish and Game

California Department of Food and Agriculture

California Department of Forestry

California Department of Health Services

California Department of Parks and Recreation

California Department of Water Resources

California Regional Water Quality Control Board

California Water Resources Control Board

Marina County Water District

Monterey Bay Air Pollution Control District

Monterey County Flood Control and Water Conservation District

Monterey County Health Department

Monterey County Planning Department

Northern Salinas Valley Mosquito Abatement District

Santa Cruz County Planning Department

U.S. Naval Postgraduate School

U.S. Soil Conservation Service

Introduction 7
Well-Numbering System

Wells are identified according to their location in the rectangular system 

for the subdivision of public lands. Identification consists of the township 

number, north or south; the range number, east or west; and the section number. 

Each section is divided into sixteen 40-acre tracts lettered consecutively 

(omitting the letters I and O), beginning with A in the northeast corner of the 

section and progressing in a sinusoidal manner to R in the southeast corner. 

Within the 40-acre tract, wells are numbered sequentially in the order in which 

they are inventoried. The final letter of the identification refers to the 

base line and meridian from which the well location is referenced. All wells 

in Monterey County are referenced from the Mount Diablo base line and meridian, 

and so the final letter in the official State well number of all wells in this 

report is M for Mount Diablo. The following diagram of the well-numbering 

system shows how well number 16S/2E-03A1M is derived.

16S/2E - 03A1M

8 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
The California Department of Water Resources (DWR) has sole authority for 

assigning official State well numbers. In some instances, the DWR has delegated this authority; the Monterey County Flood Control and Water Conservation 

District, for example, has been authorized to assign State well numbers. In 

order to assign a well number, the authorized agency needs the well location on 

the appropriate U.S. Geological Survey 7.5-minute quadrangle map and such 

well-construction information as completed drillers' logs and local-agency 

numbers. Accurate location and construction information on wells can enhance 

greatly the reliability of ground-water research.

CLIMATE

The northern Salinas River drainage basin (fig. 1) has a Mediterranean 

climate: temperatures are moderate all year; the rainy winter seasons are 

short; and the summers are cool and dry. The Pacific Ocean moderates weather 

conditions, but this influence decreases towards Soledad on the southern edge 

of the study area (fig. 1). Seasons are weakly defined, and temperature 

variations are small. At Salinas, more than 91 percent of the average annual 

precipitation falls during November through April (California Department of 

Water Resources, 1981a, p. 18). Annual precipitation actually can vary much 

more widely than the average annual precipitation values indicate. For 

example, annual precipitation at Salinas has ranged from a low of 5.74 inches 

to a high of 28.10 inches (Monterey County Planning Department, 1980, p. 9) .

The Salinas River drainage basin lies between the Sierra de Salinas and 

Santa Lucia Range to the west and south and the Gabilan Range to the northeast 

of the study area (fig. 1). Between March and October, northwesterly winds 

blow directly into the Salinas River drainage basin and parallel to the Santa 

Lucia Range. These winds cause upwelling of cold ocean water in Monterey Bay, 

and fog forms as saturated ocean air passes over the cold bay water. The fog 

moves along the coast and into the Salinas River drainage basin. Typically, 

the fog reduces temperatures and moderates the potential imbalance between the 

moisture-deficient conditions and the increased potential evapotranspiration 

during the growing season. The foggy, moisture-laden sea air usually warms and 

dries by the time it reaches the southern boundary of the study area at Soledad 

(Showalter and Hoffard, 1986, p. 8) . During the rainy season, the winds 

typically blow from the south to the north across the Santa Lucia Range, and 

the Salinas River drainage basin lies in the "rain shadow" of the mountains. 

Precipitation in the Salinas River drainage basin is typically less than in the 

coastal areas to the south and west on the other side of the Santa Lucia Range 

(fig. 1).

Climate 9
LAND USE

Land use can affect water quality at all stages of the hydrologic cycle. 

Industrial emissions and pesticides can enter the atmosphere and return in 

precipitation. Industrial and agricultural wastes can wash into streams or 

seep into ground water. Most water-supply contamination may result from point 

sources such as chemical spills, disposal of toxic consumer products, leaks 

from underground storage tanks, and nonpoint sources such as runoff from 

agricultural and urban land (Magnuson, 1983). Correlations between feed lots 

and nurseries and areas of nitrate contamination of ground water already have 

been substantiated in certain areas of Monterey County (Bruce LaClergue, 

Monterey County Flood Control and Water Conservation District, written commun., 

1984), and other similar correlations have been found in other areas of 

California, such as orchards and vineyards with DBCP (dibromochloropropane). 

Karubian (1974) suggested that because data on the quality of ground water 

commonly are sparse and usually expensive to obtain, a supplementary approach 

might be to estimate kinds, amounts, and trends of ground-water pollution by 

relating them to human activities. His preliminary research was on the methodology for estimating the polluting effects of human activities on ground 

water. In particular, he studied the effects of unlined sedimentation basins 

and lagoons used by pulp and paper, petroleum refining, and primary metals 

industries; wastewater ponds in phosphate mining; agricultural use of chemical 

fertilizers; and cattle feedlot operations. Land use is therefore an important 

consideration in water-quality data collection and network evaluation for 

Monterey County.

A generalized land-use and land-cover map (fig. 2) was prepared for the 

study area based on detailed U.S. Geological Survey maps (1976a, 1976b, and 

1978). Cropland, pasture, and other agricultural land (fig. 2) make up the 

highest percentage of the land use in the study area, followed by forest and 

range lands (fig. 2). Showalter and others (1984, p. 10) noted a distinct 

relation in the northern Salinas River drainage basin between the agricultural, 

range, and forest land uses and land slope. Agricultural land typically is 

flat, range land is rolling or steep, and forest land is steep in slope.

Urban areas and areas of orchards, vineyard, and nursery (fig. 2) also 

cover significant portions of land. Salinas is by far the largest urban area, 

followed by Santa Rita, Laguna Seca, Castroville, Spreckels, Gonzales, Moss 

Landing, and Soledad. There are three confined feeding areas between Gonzales 

and Soledad. Wetland areas lie in the Salinas River drainage. A major quarry 

lies northeast of Salinas, and several smaller quarries are scattered around 

the northern one-half of the study area.

More detailed (7.5 minute scale) land-use information also is available 

from the California Department of Water Resources land-use surveys that have a 

recurrence mapping interval of about 7 years (California Department of Water 

Resources, 1971). Land-use information is available for Monterey County by 

U.S. Geological Survey 7.5 minute quadrangle area for 1976, 1982, and will be 

available soon for 1989 (Fred Stumpf, California Department of Water Resources, 

oral commun., 1989).

10 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
121 °45'

R2E

R4E

MOM Land!

T13S

36°45'

T14S

T15S

T16S

36°30'

URBAN (RESIDENTIAL AND INDUSTRIAL)

AGRICULTURAL (CROPLAND AND PASTURE)

RANGELAND

FOREST LAND

WATER AND WETLANDS

ORCHARDS AND VINEYARDS

CONFINED FEEDING AREA

STUDY AREA BOUNDARY

10 MILES

10 KILOMETERS

FIGURE 2.-Land use and land cover in the northern Salinas River drainage basin 

(modified from U.S. Geological Survey, 1976a, 1976b, and 1978).

Land Use 11
Potential point and regional sources of water-quality degradation are 

shown in figure 3, and major point-source dischargers to land are noted in 

detail in table 2. Mineral deposits indicated on Hart's (1966, pi. 1) geologic 

map also may be point sources because of their natural constituents or the 

effects on them of human activities (such as leaching of trace elements from 

soils by irrigation activities).

WATER USE

Water and land use have similar effects on water quality. This relation 

in the study area was recognized as early as 1946 (California Department of 

Water Resources, 1946). Applications of water to agricultural fields is a 

major source of incidental ground-water recharge and flow in streams during 

summer months. The pesticides, fertilizers, and soil amendments used in 

agriculture and minerals leached from soils can have significant effects on 

surface- and ground-water quality.

The largest water use in the Salinas River drainage basin is irrigation, 

and the second largest is domestic and municipal (Showalter and others, 1984, 

p. 11) . Irrigation water is used primarily during the summer. Domestic and 

municipal use, by contrast, is fairly constant throughout the year, except for 

increases attributable to lawn watering in the summer months. About 89 percent 

of the water used in the Salinas Valley was from ground-water sources during 

1985 (W.E. Templin, U.S. Geological Survey, written commun., 1988), which was a 

decrease from 95 percent in 1969 (Showalter and others, 1984, p. 14).

Knowledge of land-use patterns can be used (especially for irrigated 

areas) to estimate locations and quantities of water use when detailed wateruse data are not available. The establishment and maintenance of a sitespecific water-use data base (including withdrawal, delivery, release, and 

return data as described in Templin, 1986) could add substantially to knowledge 

of the surface-water and ground-water hydrology of Monterey County.

12 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
121°45'

R2E R3E

R4E

30'

T14S

T16S

36°30';

EXPLANATION

TYPES OF POINT-SOURCES DISCHARGERS -

Number corresponds to site number in table 2 

A Industrial

O Airport

O Sewage treatment plant

13 Solid-waste disposal site

O Agricultural

STUDY AREA BOUNDARY

0 10MILES

0 5 10 KILOMETERS 

FIGURE 3.-Point and regional sources of concern for possible water-quality degradation.

Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif. 13
TABLE 2. Major point-source

[Modified from information on industrial dischargers under National Pollution Discharge Elimination System

Obispo, California. Sites are shown in figure 3.

Location; Township, range, and section are given. Sites are ordered by township, range, and section in

ascending order. 

Properties and constituents of concern:

Biochemical oxygen demand, 5-day test (BOD5 ) analysis recommended by California Regional Water Quality 

Control Boards; Dermer and others (1980) and Pye and others (1983, p. 181) suggest BOD 5 may not be 

appropriate for ground-water-quality monitoring 

Chlorine, total available, free available and/or dosage; see Industrial dischargers under National 

Pollution Discharge Elimination System permit

Site 

No.

1

2

*3

*4

5

6

7

8

*9

10

11

12

13

14

15

*16

17

Discharger

Industrial dischargers under

Kaiser Refractories

Pacific Gas and Electric

Santa Cruz Canning

Sea Products

Bud Antle, Marina

Union Ice

Sun Harvest

Salinas Industrial

Firestone Rubber

Salinas Tallow

Shippers Development Company

John Inglis, Salinas

Valley Cooling

Dalgety Foods

Merchants Refrigerating

Spreckels Sugar

Gonzales Potato

Location

National Pollution

13S/2E-18

13S/2E-18

13S/2E-18

13S/2E-18

14S/2E-8

14S/2E-9

14S/3E-33

15S/2E-12

15S/3E-13

15S/3E-3

15S/3E-3

15S/3E-4

15S/3E-9

15S/3E-10

15S/3E-11

15S/3E-17

16S/5E-28,29,32,33

Type of waste Disposal method

Discharge Elimination System permit

Process water

Cooling water

Food processing

do.

do.

Refrigerant cooling

Unknown

Industrial wastes

Unknown

Animal carcasses

Vegetable processing

do.

do.

Unknown

do.

Sugar refining

Vegetable processing

Ocean outfall

do.

do.

do.

Unknown

Discharge to 

Tembladero Slough

Unknown

Evaporation ponds 

(possibly Salinas 

River)

Percolation ponds

Unknown

do.

do.

do.

do.

do.

do.

Evaporation ponds

14 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
dischargers to land

permit provided by the California Regional Water Quality Control Board, Central Coastal Region, San Luis 

Site No., asterisk (*) indicates discharger site is closed. Do., ditto]

Properties and constituents of concern Continued

Flow, quantity of water entering or leaving the site (volume in gallons, monthly summaries of mean and

maximum daily flow)

pH, negative logarithm of the hydrogen ion (acid/base conditions) 

Total chlorinated pesticides, measured by summing the individual concentrations of aldrin, BHC, chlordane,

DDD, DDE, DOT, dieldrin, endrin, heptachlor, lindane, and polychlorinated biphenyls 

Toxicity concentration, as described in written and oral communications with California State Water

Resources Control Board and California Department of Fish and Game (1976)

Properties and constituents of concern 

Industrial dischargers under National Pollution Discharge Elimination System permit Continued

Effluent: Flow, pH, temperature (degrees Fahrenheit), turbidity, biochemical oxygen demand, total solids 

(dissolved, suspended, settleable), nitrogen (also may be used to indicate ammonia), arsenic, cadmium, 

chromium, copper, lead, mercury, nickel, silver, zinc, cyanide, phenolic compounds, polychlorinated 

biphenyls, total chlorinated pesticides, oil and grease, toxicity concentration

Receiving water: Light transmittance, pH, salinity, temperature (degrees Fahrenheit), turbidity, 

dissolved oxygen, coliform bacteria organisms

Bottom sediment: Benthic (bottom dwelling) organisms, particle-size analysis

Influent; pH, temperature (degrees Fahrenheit), total solids (dissolved, suspended, settleable), 

nitrogen (also may be used to indicate ammonia), arsenic, cadmium, chromium, copper, lead, mercury, 

nickel, silver, zinc, cyanide, phenolic compounds, oil and grease

Effluent: Flow, pH, temperature (degrees Fahrenheit), chlorine, total solids (dissolved, suspended, 

settleable), dissolved oxygen, nitrogen (also may be used to indicate ammonia), arsenic, cadmium, 

chromium, copper, total iron, lead, mercury, nickel, silver, zinc, toxicity concentration, cyanide, 

phenolic compounds, polychlorinated biphenyls, oil and grease

Unknown 

Do. 

Do. 

Do.

Do. 

Do.

Toxics

Unknown

Pesticides in wash/cooling water

Do.

Do.

Do.

Do. 

Pesticides

Do.

Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif. 15
TABLE 2. Major point-source

Site 

No.

18

19

20

21

22

23

Discharger

Other

Fritzscbe Field (Fort Ord 

Army Air Field)

Henningson Salvage

Salinas

Verticare 

(Quail Creek)

Puregrow

Berman Steel

Location Type of waste Disposal method

potential industrial dischargers

14S/2E-29

14S/3E-29

14S/3E-35

15S/4E-14

14S/3E-29

15S/4E-19

Municipal and domestic dischargers: 

National Pollution Discharge

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

Laguna Seca Recreation Area, 

Road Race Agte, Ranch Estates

Salinas, Main

Indian Springs

San Jerardo

Chualar Sanitation District

Gonzales

Soledad Correction Facility

Soledad, City of

Oak Hills

North Monterey County 

High School

Monte del Lago Mobile 

Home Park

Castroville Wastewater 

Treatment Plant

Salinas

Alisal

Bluff's Subdivision

Salinas Utilities (Toro

15S/2E-32

15S/3E-6

15S/3E-29

I5S/4E-9

16S/4E-3

16S/5E-29

17S/5E-12

17S/6E-29

13S/2E-23

13S/2E-29

13S/2E-35

13S/2E-29

14S/3E-33,34

15S/3E-17

15S/2E-11,12

15S/2E-13

Airplane maintenance 

and burn pit

Auto dismantling

Airplane maintenance

Airplane maintenance 

and crop dusting

Agricultural chemicals

Transformer insulation

Sewage treatment plants under 

Elimination System permit

Sewage

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

Land disposal

do.

do.

do.

do.

do.

Septic systems

Ocean outfall 

(historically to 

Salinas River)

Unknown

do.

do.

do.

do.

do.

Evaporation/percolation ponds and landsurface disposal

Unknown

Evaporation/percolation ponds

do.

Outfill

do.

do.

Outflow (overflow

Management) to Salinas River)

16 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
dischargers to land Continued

Properties and constituents of concern

Other potential industrial dischargers Continued

Trichloroethane and other similar solvents and unknown contaminants

Lead in soil and slough sediments 

Trichloroethane and other similar solvents 

Trichloroethane and other similar solvents and pesticides

Pesticides in shallow ground water

Polychlorinated biphenyls in soil (none found in ground water or surface water)

Municipal and domestic dischargers: Sewage treatment plants under 

National Pollution Discharge Elimination System permit Continued

Flow, sludge depths, total sludge volume, total usable storage, percent full, depth of effluent in drain 

fields

Do.

Do. 

Do. 

Do. 

Do. 

Do. 

Do.

Influent; Flow, sodium, chlorine, dissolved solids

Pond; Sodium, chlorine, dissolved solids, nitrogen (also may be used to indicate ammonia),

nitrate, ammonia 

Ground water; Ground-water levels, chlorine, dissolved solids, nitrogen (also may be used to

indicate ammonia), nitrate, ammonia 

Effluent; Coliform bacteria organisms

Unknown

Effluent; Flow, sodium, coliform bacteria organisms, chlorine, total solids (dissolved, suspended, 

settleable)

Do.

Do. 

Do. 

Do. 

Do.

Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif. 17
TABLE 2. Major point-source

Site 

No. Discharger Location Type of waste Disposal method

Municipal and domestic dischargers: Solid-waste disposal sites

40 Crazy Horse 13S/3E-15

(Phase 2 area)

Solid wastes Landfill

41 Lewis Road site Phase 2 area (off 

the map, north of 

Phase 3)

do. do.

42

43

44

45

46

47

48

49

Gonzales (Johnson Canyon Road)

Monterey Peninsula

U.S. Army, Fort Ord

Moon Glow Dairy

Fat City Feedyard

Trico Feeders

Mission Dairy

Hamby and Sons

16S/5E-22

14S/2E-7,8,17,18

15S/2E-5,6

Agricultural point

13S/2E-8,17

16S/5E-9

16S/5E-22

16S/5E-28

17S/6E-22

do.

do.

Solid and demolition 

wastes

sources

Dairy effluent

Feed lots 10, 15, 16

do.

do.

do.

do.

do.

do.

Land disposal

do.

do.

do.

do.

PRECIPITATION NETWORKS

Precipitation-Quantity Networks

Precipitation Conditions

Distribution of mean annual precipitation in the study area is uneven (fig. 4). 

The greatest precipitation has been recorded in the mountains along both sides of 

the Salinas River drainage basin where estimated mean annual totals range from 18 

to 75 in/yr. The scarcity of data and the extreme differences in areal distribution of precipitation at those altitudes make accurate estimates difficult, as can 

be seen in the three estimates of mean annual precipitation for the study area 

(fig. 4) . The lowest mean annual precipitation, recorded in the lower altitudes of 

the study area, is about 12 in/yr. More than 90 percent of the precipitation in the 

study area falls from November through April. From May to October, mean annual 

precipitation is normally less than 1 inch.

18 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
dischargers to land Continued

Properties and constituents of concern

Municipal and domestic dischargers: Solid-waste disposal sites Continued

Ground water; Two wells in Aromas Formation: Ground-water levels/ specific conductance/ pH/ bicarbonate/

chlorine/ nitrogen (also may be used to indicate ammonia) 

Leachate: Six monitoring wells: Ground-water levels/ flow/ specific conductance/ pH r chemical oxygen

demand/ chlorine/ nitrogen/ total Kjeldahl

Do.

Do.

Unknown 

Do.

Agricultural point sources Continued

Potassium, sulfate/ nitrate/ ammonia/ phosphate 

Do. 

Do. 

Do. 

Do.

Objectives

Precipitation-quantity networks have two major objectives: (1) to determine 

regional variations in precipitation to establish trends, and (2) to identify 

factors that may influence the quantity of precipitation in the region (table 1). 

Precipitation-quantity networks help to establish spatial and temporal trends 

for the short term/ as with storm intensity and duration, and in the long term/ 

as with mean daily/ monthly/ and annual precipitation. The networks also can 

help to determine the effects on precipitation of natural and artificial features/ 

such as lakes, reservoirs/ and other large water bodies; regionally irrigated 

areas; multiple-story buildings; and industrial emissions into the air. Finally/ 

precipitation-quantity networks determine the presence of measurement conditions that may affect the values obtained, such as standard methods of station 

installation, including precipitation-gage types; locations above ground and 

away from structures; and sampling and analytical practices (Linsley and others, 

1982, p. 61) .

Precipitation Networks 19
a

EXPLANATION

 30 LINE OF EQUAL MEAN ANNUAL

PRECIPITATION - Interval, in 

inches, is variable

 STUDY AREA BOUNDARY

FIGURE 4. Mean annual precipitation, in inches, in Nonterey County. A, modified from Rantz, 1969. B, modified from 

Nonterey County Planning Department, 1980 and 1981a. C, modified from Renard, 1983.

20 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
Monterey County's precipitation-quantity networks have a number of 

specific objectives, which are noted in table 3. These specific objectives 

include (1) measurement of regional ambient conditions to help in estimating 

ground-water recharge; (2) help in estimating water supply for agricultural, 

domestic, and industrial uses; (3) flood warning; and (4) provision of specific 

site data to aid erosion control, water-related engineering, water-rights 

management, and fire-hazard assessment.

The method of analysis used to evaluate precipitation-quantity networks 

involved the following steps: (1) design of an ideal network, which would 

give maximum coverage to the study area; (2) identification of existing precipitation-quantity monitoring; (3) examination of existing precipitation maps of the 

study area to identify discrepancies between maps and possible weaknesses in network 

coverage; and (4) description of possible additional precipitation-quantity 

monitoring in the study area.

Data needs for precipitation-quantity networks are presented in table 3 

in order of the priority of their specific network objectives. Network priorities 

reflect the precipitation-data uses reported by the Monterey County Flood Control 

and Water Conservation District (1977). The two primary data needs include (1) 

measurement of areal daily precipitation and (2) measurement of storm precipitation in 15- to 30-minute intervals. In the study area, precipitation data have been 

used principally for water-balance computations to determine ground-water recharge 

and to improve long-term estimates of water available for domestic and industrial 

uses. As a result, accurate estimates of monthly and annual precipitation seem most 

important. In this report, only mean annual precipitation is examined, using available precipitation maps to define spatial distribution. It was beyond the scope of 

this report to analyze the distribution of storm precipitation, but table 4 does 

identify the recording gages in the study area that could be used for this purpose.

Precipitation-quantity data, together with other climatic data (such as humidity, temperature, wind, and evapotranspiration), are needed to estimate water use 

and water supply. As of 1987, the only sites at which climatic data are known to 

be collected are near Spence (U.S. Department of Agriculture property) and at 

Soledad (U.S. Highway 101 near Camphora Gloria Road). Before 1978, climatic data 

also were collected at the Hartnell College East Campus site near Alisal Road in 

Salinas. Irrigation applied water and related climatic data were collected during 

the 1960's and 1970's from various sites as part of a county crop water-use study 

(Bruce LaClergue, Monterey County Flood Control and Water Conservation District, 

oral commun., 1988) .

The determination of water supply and water use also entails having information on the other climatic data as well as withdrawal and release information 

by water suppliers. If a local network of climatic data stations was established, the accuracy of estimates of water use would improve because the data 

used to calculate these estimates would be more accurate. The results of 

studies of phreatophyte water use (Anderson-Nichols and Co., 1985) also could 

benefit from improved climatic-data stations complemented by collection of data 

from mobile installations similar to those described by Simpson and Duell 

(1984) . Mobile agricultural water-use efficiency monitoring labs also are 

available that may be of use in Monterey County (Thomas Hawkins, California 

Department of Water Resources, oral commun., 1985).

Precipitation Networks 21
TABLE 3. Ideal networks,

[Priority points were developed for Monterey County Flood Control and Water Conservation District

Proposed monitoring components;

A, physical and indicator characteristics, such as temperature, pH, electrical conductivity, odor

B, common chemical analyses

Bio., biological (phytoplankton, zooplankton, algal growth potential, microplankton, fish tissue,

muscle, and other biological indicator analyses) 

BOD5 , biochemical oxygen demand, 5-day test 

CD, climatic data, such as rain, air temperature, solar radiation, evaporation, evapotranspiration,

relative humidity, wind movement

Proposed frequency;

A, annual

B, bimonthly

C, continuous

CS, continuous seasonally as needed

D, daily

M, monthly 

Q, quarterly 

T, twice annually 

W, weekly

Network 

name

Specific network objectives

Priority 

points

Data needs

Precipitation-quantity networks

Ala Ground-water recharge (regional 

ambient conditions

Alb Water-supply estimates (for agricultural, domestic, and industrial uses)

Ale Flood warning

Aid Specific site data for runoff determinations used in erosion control; 

designing culverts, levees, bridges, 

storm drains, flood channels, and 

dams; water-rights management; also 

rainfall duration for use in 

National Forest Fire Danger Rating 

Components

10 Areal daily storm precipitation (U.S. Army Corps 

of Engineers, 1957) and other climate data

9 do.

15- to 30-minute interval storm precipitation data 

do.

Precipitation-quality networks

A2a Effects on surface- and ground-water

quality (regional ambient conditions)

Daily wet and dry deposition volume and quality, 

and climate data

A2b Effects on vegetation and personal 

property

do.

Streamflow networks

Bla Ground-water recharge (regional 

ambient conditions)

Bib Water-use quantity

10 Long-term areal integrated information system of

continuous record and regional correlations with 

precipitation (Fontaine and others, 1983, p. 1)

9 do.

Blc Flood warning Telemetered stage record at key lake and stream 

locations

22 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
priority, and pertinent data 

(Showalter and Hoffard, 1986, tables 4 and 13) Abbreviations: ft, feet; do., ditto]

El, environmental isotopes, such as H2 , Ho (tritium), oxygen-18, and carbon-14 

F, sanitary (total-coliform and fecal-colIform bacteria viruses) 

FT, total flow, in gallons per day

G, all of the above quality constituents including trace elements, pesticides, and nutrients 

SD, continuous stage-discharge record, with periodic flow measurements to establish and maintain 

the relation

Ideal network

Site distribution Site density

Proposed 

monitoring 

component

Proposed 

frequency

Precipitation-quantity networks Continued

Countywide 

do.

One or two per township

do.

CD

CD

do. 

do.

do. 

Three per township

CD 

CD

Precipitation-quality networks Continued

do. One per township pH and pesticides 

CD

D during storms

C

do. do. pH and pesticides 

CD

D during storms 

C

Streamflow networks Continued

Major tributaries

All streams

do.

At first point of recharge, SD 

one per stream (also at 

major confluences)

Upstream and downstream 

from each point of 

inflow and outflow

do.

SD

SD, peak flow

C at 30-minute 

intervals

C at 30-minute 

intervals

C at 30-minute 

intervals

Precipitation Networks 23
TABLE 3. Ideal networks, priority,

Network 

name

Specific network objectives

Priority 

points

Data needs

Strearaflow networks Continued

Bid Water rights Continuous record upstream and downstream from 

all diversions (daily means, maximums, and 

minimum flows)

Ble Site data for design of storm drains, 

dams, levees, flood channels, 

bridges, and culverts

Blf Determine sediment transport

Periodically revised rainfall/runoff relations 

following significant land-use changes or cumulatively significant changes, including flood-plain 

elevations developed from network Bla (recharge)

Periodic nonstorm, during and after storm sediment 

samples to estimate rates of reservoir siltation 

and effects of levee construction, recent urban 

growth areas, and agriculturally fire disturbed 

areas

Big Manage irrigation diversions and 

recharge

Data generated in network Bid and continuous 

records of all agricultural return flows and 

diversions

Blh Instream use management/planning Data from network Bid

Bli Determine streamflow characteristics 

to develop regional relations to 

ungaged sites

Blj Manage municipal and industrial uses

25-year recurrence interval flood, drainage areas, 

mean annual precipitation (Riggs, 1973, p. 4)

Data from network Bid, and continuous records of 

all agricultural return flows and diversions

Blk Determine sediment-transport rates 

upstream from dams

Bll Potential hydropower plants

Network Blf data, supplemented with similar data 

upstream from dams

Site selection information and begin developing 

continuous record at sites

Surface-water-quality networks

B2a Monitor water quality for domestic 

and irrigation uses

10 Routine, periodic complete analyses

B2b Assess reservoir discharges for irrigation, domestic, and fish and 

wildlife uses

10 Routine periodic samples (during discharge periods) 

and determination of lake trophic levels (outside 

study area)

B2c Develop a water-quality baseline 

(regional ambient conditions)

Stream-reach rating system for priority based on 

specific needs. Complete analyses in relation 

to needs, with correlation to continuously 

measured indices, such as temperature and 

specific conductance

24 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
and pertinent data Continued

Ideal network

Site distribution Site density

Proposed 

monitoring 

component

Proposed 

frequency

Streamflow networks Continued

One station at each 

location of change in 

stream characteristics

Upstream and downstream from 

each point of inflow and 

outflow

SD C at 30-minute 

intervals

Countywide do. Network Aid, flow 

at sites (streams 

and bridges

Upstream and downstream 

from dams

Upstream and downstream 

from all diversions

do.

Two per diversion

Total sediment discharge D 

SD, water temperature C 

Trace elements M 

Bed and bank samples Q

for size analysis,

composition, and

sources

SD CS

Salinas River; other 

creeks as needed for 

water rights, appropriations, and water 

balance

All major drainages

Upstream and downstream 

from all diversions

As needed

do.

Two per diversion

SD C

Water temperature C

Total sediment discharge D

Low flow CS

SD C 

Precipitation volume, D 

in inches

SD

Upstream from dams 

(none in study area)

Site specific (none in 

phase 3 study area)

One per dam 

One per site

Total sediment discharge D

SD CS

Surface-water quality networks Continued

At all withdrawal locations One per location A 

B, trace elements 

Pesticides, nutrients 

F

C 

M 

B 

W

Salinas River

Salinas River 

Sloughs: Elkhorn,

Moro Cojo, Tembladero 

Reclamation Ditch

Two sites downstream from dam 

1-30 ft 

1-500 ft

In reaches of known hydraulic 

connection with ground water

Hydrogen sulfide, dissolved oxygen, water 

temperature, 

Quality:A,B

Quality:A,B,

water temperature, 

specific conductance

Precipitation Networks 25
TABLE 3. Ideal networks, priority,

Network 

name

Specific network objectives

Priority 

points

Data needs

Surface-water-quality networks Continued

B2d Determine flow and quality from 

specific creeks

8 Baseline for specific creeks with present or

potential for significant future development

B2e Determine trends for reservoir water 

quality

B2f Evaluate water-quality effects on 

instream uses (fish, recreation)

B2g Mosquito abatement

Water-quality monitoring, especially for effects 

of land uses (such as residential, timber 

harvest, forest fire, and mining) and natural 

geologic influences

Stage/discharge data from network Bla and waterquality data to compare existing conditions to 

standards established for each type of water use 

(Templin, 1986)

Data pertinent to growth and reproduction of 

mosquitos and other pest insects, also possibly 

data on chemical abatement methods used

Ground-water-level networks

Cla Determine each basin's water balance 

and seawater intrusion portion of 

inflow (regional ambient conditions)

Clb Determine effect of reservoir discharges on ground-water storage

Clc Determine ground-water storage in 

each basin

Cldl Determine accuracy of annual waterlevel measurements in monitoring 

changes in storage

10 Precipitation data from network Aid, streamflow

data from network Bla, collect pumpage and waterlevel trend data (inflow, outflow, and storage)

9 Streamflow data from network Bla, diversions data 

from network Bid, information on hydraulically 

connected areas from network B2c, water-level 

and pumpage data from network Cla

9 Water-level and pumpage data from network Cla,

perform pump and aquifer tests where not already 

available, interpret the data (Freeze and Cherry, 

1979, p. 343; Todd, 1980, p. 45 and 362). 

Geologic information on location of fresh waterbearing deposits and formation characteristics

7 Evaluation of existing water-level network and 

resultant data for its representativeness of 

regional conditions. Use of variables similar 

to what has been done by Sophocleous and others 

(1982) may be applicable to this analysis to 

determine the adequacy of current well densities 

for this purpose.

A correlation analysis of the recharge flow data 

from network Blj and the storage data from 

network Clc needs to be accomplished and an 

inflow/outflow/storage relation developed (Todd, 

1980, p. 361-363).

Use of available, or adaptable, management models 

(Bachmat and others, 1980, p. 39-40) could 

facilitate the effective use of available natural 

and financial resources

26 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
and pertinent data Continued

Ideal network

Site distribution Site density

Proposed 

monitoring 

component

Proposed 

frequency

Surface-water-quality networks Continued

Sloughs: Moro Cojo, 

Tembladero

Creeks: El Toro, Gabilan, 

Quail, Chualar, Johnson, 

Alisal, Natividad, San 

Miguel, Santa Rita

Reclamation Ditch

Chualar Reservoir 

Lakes: Espinosa, Carr, 

Merritt, Sherwood

Upstream from confluence with 

major tributary

Three sites on each lake

SD 

Quality:A,B

Quality:A,B; bio.

Salinas River 

Sloughs: Elkhorn, 

Moro Cojo, Tembladero

Lakes, streams, wetlands, 

stock ponds, industrial 

holding ponds, street 

drains

Sites near mouths, and 

downstream from all 

major diversions

As needed

SD, water temperature 

Quality:A,B 

Trace elements, 

pesticides

Quality:A, specific 

gravity, turbidity, 

BOD 5 , nutrients, bio.

Mosquito larvae and 

adults

Ground-water-level networks Continued

Subarea and countywide grid

Salinas Valley

One per subarea; 

as needed

As needed

Water levels C,T 

Pumpage (from meters) C 

and electrical usage

Water levels C,T

Pumpage C

SD M

Grid ground-water basins Density as needed to draw 

adequate contours

Water levels C,M,T

as needed

Salinas Valley Existing water-level 

monitoring sites

Water levels,

geologic formation 

characteristics

C,M

Precipitation Networks 27
TABLE 3. Ideal networks, priority,

Network 

name

Specific network objectives

Priority 

points

Data needs

Ground-water-level networks Continued

Cld2 Monthly water-level measurements in 

monitoring changes in storage due 

to seasonal pumping demands

Evaluation of existing water-level network and 

resultant data for its representativeness of 

regional conditions. Use of variables similar 

to what has been done by Sophocleous and others 

(1982) may be applicable to this analysis to 

determine the adequacy of current well densities 

for this purpose.

A correlation analysis of the recharge flow data 

from network Blj and the storage data from 

network Clc needs to be accomplished and an 

inflow/outflow/storage relation developed (Todd, 

1980, p. 361-363).

Use of available, or adaptable, management models 

(Bachmat and others, 1980, p. 39-40) could 

facilitate the effective use of available natural 

and financial resources

Cle Determine annual ground-water pumpage

Clf Determine annual consumptive use of 

applied water, phreatophytes, and 

precipitation in agriculture and 

urban areas

Clg Monitor ground-water flow patterns

Clh Determine ground-water outflow

(recharge) from streams and creeks

Cli Determine locations where river

percolation could be enhanced to 

increase ground-water storage

Cljl Determine aquifer characteristics

PG&E records and pumpage following Mitten (1976). 

Also collect pumpage from metered wells needed 

for networks Cla and Clc. Compare with 

California Department of Water Resources (1983a, 

p. 97-99) estimates based on land use

Land-use map (fig. 2) and determine areas of each 

land use, determine unit values of consumptive 

use for each land use, combine areas and values 

of interest (Todd, 1980, p. 361-362). See also 

California Department of Water Resources (1975, 

p. 5, 1982, 1983a, 1983b); Dunne and Leopold 

(1978, p. 95-162)

Requires information on topography, piezometric 

patterns, hydrochemical trends, environmental 

in the area isotopes, and soil/land surface 

features (Freeze and Cherry, 1979, p. 200-203).

Using information developed in networks Bla, Clc, 

Clg, and C2c, and determine baseflow, and use 

hydrograph separation to differentiate subsurface 

contributions

Using information from networks Clg and Clh, determine areas of recharge, storage, and discharge. 

Study the effects of increased artificial 

recharge in stream channels on storage and discharge down gradient. Use of a refined groundwater-flow model could be preferable to trial 

and error

A literature search needs to be conducted to determine the level of available information on aquifer properties for each ground-water basin. 

Where gaps exist, pumping tests need to be made, 

and the information used to determine hydraulic 

conductivity, storativity, and transmissivity 

(Todd, 1980, p. 78 and 124). Physical aquifer 

properties of thickness and confined or unconfined nature of the existing aquifers in each 

basin also need to be determined, if not already 

done, and noted in the literature search for this 

information category

28 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
and pertinent data--Continued

Ideal network

Site distribution Site density

Proposed 

monitoring 

component

Proposed 

frequency

Ground-water-level networks Continued

Salinas Valley Existing water-level 

monitoring sites

Water levels,

geologic formation 

characteristics

C,M

do. All wells in basin Metered pumpage and 

PG&E records

M,A

do. Climatic data stations, one CD

per area; 

Meters, one per well, and FT

one per customer supplied

C,D 

C,D

All ground-water basins

Salinas River; other 

creeks as needed

Wells as needed

As needed

Water levels, pumpage 

(from meters and electrical usage)

Quality:A,B,EI

SD, water levels, 

pumpage (from meters 

and electrical usage)

Salinas River; other 

creeks as appropriate 

(for example, Santa 

Rita Creek)

do. SD, water levels, 

pumpage (from meters 

and electrical usage)

All ground-water basins do. Storage coefficient 

(storativity), 

hydraulic conductivity, 

transmissivity

Precipitation Networks 29
TABLE 3. Ideal networks, priority,

Network 

name

Specific network objectives

Priority 

points

Data needs

Ground-water-level networks Continued

Clj2 Determine aquifer boundaries Need geologic information on flow barriers (faults 

and impermeable strata)

Clk Determine areas of influence or cone 

of depression for large and small 

wells

Need to know the influence of each well in the 

water-level networks on each other well in the 

network, if there is any influence, in order to 

evaluate that well's utility in the network

Ground-water-quality networks

C2a 

C2b 

C2cl

Determine water-quality baseline, 

including specific conductance

Determine distribution of nitrates in 

expected problem areas

Determine effect of ground-water

10 

9 

8

Establish regional networks of representative 

wells monitored annually for complete analyses

Would be done in network C2a 

Would entail study of geochemistry of streams and

quality on effluent (gaining) 

streams

C2c2 Determine the need for establishing a 

ground-water data base for tributary 

areas

C2d Develop a baseline of organics in 

ground water

C2e Determine regional effects of point 

sources and cumulative effects of 

point sources

C2f Determine regional effects of nonpoint 

sources (such as agricultural and 

urban areas)

C2g Determine native and human-caused

sources of radioactive substances

adjacent ground water (network Clg) for determination of which are losing or gaining and a 

comparison with baseline surface-water quality 

from network B2c

Use data gathered in networks B2c, B2d, and C2a to 

compare areal quality in tributary areas to the 

downstream ground-water basins to understand the 

influence of geologic parent materials and land 

uses in tributary areas on major basin groundwater quality

Need data on total organic carbon and volatile 

organic carbon for comparison with results from 

network Clg and known point sources to determine 

the relations at point sources to the surrounding 

environment

Collect data on the extent of point-source plumes, 

and compare with data from networks C2a and C2d

Study typical areas of land use to determine cause 

and effect of land-use practices

Regional analyses for indicators of broader categories of substances and more specific analyses 

where high values are noted

30 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
and pertinent data Continued

Ideal network

Site distribution Site density

Proposed 

monitoring 

component

Proposed 

frequency

Ground-water-level networks Continued

All ground-water basins As needed

do. do.

Storage coefficient 

(storativity) , 

hydraulic conductivity, 

transmissivity

Pump and aquifer tests, 

storage coefficient 

(storativity), 

hydraulic conductivity, transmissivity

All ground -water basins

Salinas Valley

All ground-water basins

Selected wells in recharge

Ground-water-qual i ty

Grid basins

networks Continued

G

Bound and grid septic tank A, nutrients, F, 

areas water levels

Wells as needed

As needed

Water levels, pumpage 

(from meters and 

electrical usage) 

Quality:A,B,EI

Quality:A,B,

Q

M

C

M

Q

points areas at points 

where tributaries enter 

the ground-water basin

geology, land use

Bound and grid all groundwater basins

do. Total organic carbon, 

volatile organic 

carbon, El

In areas of concentrations do. 

of point sources (table 2, 

figure 3)

Select major urban and do. 

agricultural areas from 

figure 2

Grid basin, more dense in do. 

industrial and military 

areas

As needed

do.

Gross: Alpha, Beta, 

radium, (Safe Drinking 

Water Act regulations, 

U.S. Environmental 

Protection Agency, 

1986)

As needed

As needed

Precipitation Networks 31
TABLE 4. Precipitation gages

[Data from California Department of Water Resources (1981b) and National Oceanic and Atmospheric 

Administration (1985). Gage numbers are assigned by the California Department of Water Resources. 

Site numbers refer to locations in figure 5. , no data available]

Operating agency:

3922 , U.S. National Weather Service

5003 , U.S. Department of Navy

5050, California Department of Water Resources

5115, Monterey County Flood Control and Water

Conservation District 

5702, Individual owner 

5706, Pacific Gas and Electric Company (PG&E)

Gage type;

Active: Gages where data are still being collected.

Nonrecording: Gages that collect rain, but must be read by someone.

Telemetered: Gages where records are transmitted in real-time to a central receiving location by

phone or satellite media. 

Recording: Gages having mechanical automatic recording capabilities (for example, paper tapes,

charts, or data logger computer equipment). 

Inactive; Gages where data have been collected (and records exist) but are not now known to be data

collection/measurement sites.

Location

Site 

No.

1

2

3

4

5

6

7

8

8a

9

10

lOa

11

12

13

Gage name

Associated Oil 6H

Associated Oil 7

Associated Oil 8

Castroville

Castroville Hardware

Castroville Wastewater 

Treatment Plant

Moss Landing 

PG&E Powerplant

Salinas 2 E

Salinas 3 E

Salinas-Miller

Spreckels Highway 

Bridge

Spreckels Highway 

Bridge

Spreckels

Associated Oil 7A

Salinas Airport 

(Federal Aviation

Operating 

Gage No. agency

0354-08

0354-09

0354-11

1585-01

1586-00

1586-25

5878-50

7668-00

7668-04

7669-60

8446-00

8446-04

8446-01

0354-10

7669-00

5702

5702

5702

5050

5702

5115

5706

3922

3922

5003

3922

3922

5702

5702

3922

Township/ 

range

17S/5E

16S/5E

15S/3E

13S/2E

13S/2E

13S/2E

13S/2E

14S/3E

14S/3E

15S/3E

15S/3E

15S/3E

15S/3E

15S/4E

14S/3E

Latitude/ 

longitude

36°27'12"/ 

121°22'12"

36°31'18"/ 

121°27'48"

360 37'48"/ 

121°41'00"

36 0 46'00"/ 

121°45'00"

36°46'00"/ 

121°45'30"

36°46'00'V 

121 0 46'00"

36°48'23"/ 

121°46'57"

36°40'00"/ 

121°37'00"

36 0 40'00"/ 

121°36'00"

360 35'55"/ 

121°37'44"

36°36'00"/ 

121°41'00"

36 0 36'00"/ 

121°41'00"

36 0 37'14"/ 

121°39'27"

36°36 I 42"/ 

121°33'54"

36 0 40'00"/ 

121 0 36'00"

Period 

of 

record

1923-30

1923-32

1923-31

1974

1931-61 

1931-39

1968- 

present

1980- 

p resent

1958-70

1970- 

present

1980- 

present

1905-80

1980- 

present

1961-80

1923-36

1873- 

present

Gage 

type

Inactive

Inactive

Inactive

Inactive

Inactive

Active 

recording

Active 

nonrecording

Inactive

Active 

recording

Active 

nonrecording

Inactive 

nonrecording

Active 

nonrecording

Inactive

Inactive

Active 

nonrecording

Administration)

32 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 4. Precipitation gages--Continued

Location

Site 

No.

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

Gage name

Chualar- Jacks Ranch

Soledad

Soledad (California 

Training Facility)

Soledad Milling Co.

Corral de Tierra 

Hendrichs

Salinas Golf and 

Country Club

Salinas Haney

Toro Regional Park

Monterey Bay Packing

Marina County 

Water District

Fort Ord

Salinas-Kaiser 

Refractories Quarry

Natividad (no. 40)

Los Laureles Grade, 

Leipper

Harper Canyon

Cannel Valley, 

Wallace, Jr.

Cannel Valley, 

El sherry

Los Laureles

Mount Toro

Gage No.

1751-00

8338-00

8338-01

8338-05

2047-00

7669-30

7669-40

8972-11

5370-00

3186-00

7669-50

5127-10

3778-80

1534-90

1534-05

Operating 

agency

5702

3922

5050

5702

5003

5115

5003

5115

5115

5003

3922

5115

5115

5003

5702

5003

5003

5115

5115

Township/ 

range

16S/4E

17S/6E

17S/5E

17S/6E

16S/3E

14S/3E

15S/2E

15S/2E

13S/2E

14S/1E

14S/2E

14S/3E

14S/3E

15S/2E

16S/2E

16S/2E

16S/2E

16S/2E

16S/3E

Latitude/ 

longitude

36°33'48"/ 

121°30'54"

36°26'00"/ 

121°19'00"

36 0 28'26"/ 

121°22'34"

36°25'42"/ 

121°19'54"

36°30'51"/ 

121 0 41'05"

36°45'00"/ 

121°38'00"

36 0 35'40"/ 

121 0 42'20"

36°41'57"/ 

121°48 I 21"

36 0 41'00"/ 

121°46'00"

36°41'34"/ 

121°37'29"

36°37'32"/ 

121°45'31"

36°34'03"/ 

121°42'00"

36 0 30'01"/ 

121°42 ? 13"

36 0 29'39"/ 

121°41'01"

36 0 33'00"/ 

121°43'00"

36°33 ? 00"/ 

121°38'00"

Period 

of 

record

1897- 

1931

1874- 

1980

1963-72

1916-39

1961- 

present

1968- 

present

1972- 

present

1969- 

present

1960- 

present

1970- 

present

1967-78

1958- 

present

1985- 

present

1972- 

present

1969- 

present

1960- 

present

1972- 

present

1968- 

present

1968- 

present

Gage 

type

Inactive

Inactive

Inactive

Inactive

Active 

nonrecording

Active 

recording

Active 

nonrecording

Active 

nonrecording

Active 

nonrecording

Active 

nonrecording

Inactive 

nonrecording

Active 

nonrecording

Active 

telemetered

Active 

nonrecording

Active 

nonrecording

Active 

nonrecording

Active 

nonrecording

Active 

recording

Active 

recording

Precipitation Networks 33
Factors Affecting Design

The density of a precipitation-quantity network can be determined from the 

spatial distribution of precipitation and the intended uses of the data 

(Linsley and others, 1982, p. 61). In hydrologic studies, precipitation data 

commonly are used to determine long-term mean precipitation, averaged for 

monthly, seasonal, or annual intervals. Mean precipitation is used in studies 

of water balance. Precipitation data also are used to determine total storm 

precipitation, which is used in flood-related studies. In general, studies 

requiring storm precipitation use a much denser network of precipitationquantity stations than studies requiring long-term mean precipitation.

A precipitation-quantity network usually is designed to give a representative picture of the distribution of precipitation for a given area. Generally, topography has the most influence on distribution of precipitation. 

Precipitation is typically more evenly distributed on level or gently sloping 

terrain than on rugged terrain. A mountainous area may therefore require a 

dense network of gages if accurate areal precipitation data are needed. The 

cost of installing and maintaining a network in mountainous areas can be high 

because gages may not be accessible and observers may not be readily available.

Many factors affect the measurement of precipitation data, such as standard methods of gaging-station installation, location, and density (including 

effects of different types of rain gages, distances above ground or away from 

structures) as well as sampling and analytical practices (Linsley and others, 

1982, p. 61). Other natural and artificial factors also may affect precipitation characteristics, including location of lakes, reservoirs, oceans, and 

other large water bodies; mountain ranges; and microclimatic factors such as 

irrigated regions, multiple-story buildings, industrial emissions into the air, 

wind patterns, and cloud-seeding operations. Showalter and Hoffard (1986, 

p. 25) gave information on selection of type of precipitation gage, maintenance, and operations that is appropriate for all Monterey County if other 

factors in site location and operation are kept in mind. Oltmann and others 

(1987, p. 7-8) describe their use of tipping-bucket rain-gaging instruments and 

how they operate. References to similar studies are important in maintaining 

and improving data collection functions.

Precipitation Maps

Several precipitation maps that include the study area are available 

(fig. 4) . Rantz (1969) compiled a statewide map of mean annual precipitation; 

the section of the map covering the study area was modified from a map by the 

U.S. Army Corps of Engineers (1957). Rantz' s (1969) map is not highly 

detailed. The interval of lines of equal precipitation in rugged terrain is 10 

inches and in level terrain 4 inches. More recently, the Monterey County

34 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Planning Department (1980 and 1981a) published a precipitation map in two 

reports. Intervals of lines of equal precipitation on this map range from 2 to 

5 inches. The most recent and detailed precipitation map of the study area was 

prepared by Renard (1983); this map has intervals ranging from 1 to 6 inches. 

Renard's (1983) map is based on 10 years of precipitation record (1969-79) and 

covers all the study area except south and east of Gonzales. The map is based 

on a dense network of precipitation gages, particularly in the Monterey 

Peninsula area. Many of the gages in the network are part of a network 

operated by Renard and a number of observers whom he has enlisted. These 

observers record daily rainfall totals in 2-month intervals after which they 

send the data to Renard, who maintains the data on file. The operating agency 

given for Renard's stations in table 4 is the U.S. Department of the Navy. 

Much of these data are not entered in the WDIS computer file operated by the 

California Department of Water Resources and are not readily available for 

review.

The maps published by Rantz (1969) and Monterey County Planning Department 

(1980 and 1981a) (fig. 4) are in fairly good agreement except in the southwestern part of the study area, but they disagree somewhat with the Renard 

(1983) map. This discrepancy probably is due to different periods of record, 

different gages used in analysis, and the limited amount of available data for 

this area. Specific gages used to prepare these maps are not known. Taken 

together, the three maps indicate some possible areas for additional network 

coverage, especially where differences occur among the maps; the maps also 

indicate a need for a well-documented and routinely updated official mean 

annual precipitation map and data base for Monterey County.

Description

The precipitation-quantity network, which includes all sites in the study 

area where data historically have been collected, is shown in figure 5 and 

summarized in table 4. These sites were identified initially through the 

California Department of Water Resources (1981b); this information was modified 

with input from the Monterey County Flood Control and Water Conservation 

District and it represents all currently known sources of precipitation data in 

the study area.

The Monterey County Flood Control and Water District, in cooperation with 

the California Department of Water Resources (DWR) and the National Weather 

Service (NWS), has installed nine telemetered recording gages in remote parts 

of the Monterey County as part of the ALERT network (eight of which are outside 

this report area). The primary purpose of these gages is flood warning, but, 

as the record for each gage becomes longer, the data also can be used for 

estimating mean precipitation totals in areas where data are presently lacking. 

The district maintains a network of eight gages in the area of this report. In 

1985, a telemetered recording gage was installed at the District headquarters 

(site 26, table 4 and fig. 5) . The other seven gages include four recording 

gages and three nonrecording gages in the study area.

Precipitation Networks 35
121°45'

R4E

T16S

36°30'i

25<

6

26

14

PRECIPITATION GAGE - Number corresponds T 17 S 

to site number in table 4

Active, nonrecording

Active, recording 

Active, telemetered 

Inactive

STUDY AREA BOUNDARY

T 18 S

10MILES 

_I

10 KILOMETERS

FIGURE 5.-Precipitation gages.

36 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
According to the California Department of Water Resources (1981b, 

p. 515-678), precipitation gages in or near the study area have been maintained 

by the California Department of Water Resources (two gages), the U.S. National 

Weather Service (seven gages), the U.S. Department of the Navy (seven gages), 

Pacific Gas and Electric Co. (one gage), and private individuals (nine gages). 

A total of 34 precipitation gages have been identified in the study area, 

including the 8 maintained by Monterey County Flood Control and Water District. 

Of these 34 stations, 20 are still active.

Possible Additional Monitoring

An improved network of recording precipitation gages in the study area 

could provide more basis for extending short-term records, estimating daily or 

hourly precipitation data for flood-damage studies, and precipitation duration 

and intensity studies. The areal distribution of the gages in the active and 

historic network (fig. 5 and table 4) indicates a concentration in the northwestern part of the study area; stations are sparse in the eastern and southern 

parts of the study area. There also is an apparent lack of data for the 

southwestern slopes of the Gabilan Range in the eastern part of the study area. 

The network might be modified by selecting 3 or 4 of the most representative 

gages from the II shown in figure 5 in the El Toro Creek basin area and 

locating some new gages along the eastern county boundary. In 1986, the Gloria 

Grade gage was installed and may help fill the data void for the southwestern 

slopes of the Gabilan Range. The ALERT network may help define the annual 

precipitation values in high elevation areas as the period of record increases. 

Additional solid-state recording precipitation instruments might be installed 

in strategically located drainages where large developments are being approved, 

for example, El Toro Creek basin. Rainfall-runoff correlations need to be 

maintained countywide. Many quality control factors need to be considered in 

developing rainfall-runoff correlations. Oltmann and Shulters (1989, p. 13) 

analyzed the correlations they developed in urban situations around the city of 

Fresno, California. Their discussion provides prime examples of specific 

situations to avoid to reduce data-collection inaccuracies.

Precipitation-Quality Networks 

Objectives

Generalized objectives for the precipitation-quality network are similar 

to those for the precipitation-quantity network (table 1) . These objectives 

include (I) determination of the actual precipitation quality and the effects 

of natural and artificial point and regional factors and (2) determination of 

conditions that affect measurement of precipitation quality. Specific objectives for the precipitation-quality network include (I) determination of the 

effects of precipitation quality on surface- and ground-water quality and (2) 

determination of the effects of precipitation quality on property (table 3) .

Precipitation Networks 37
Possible Problems

Little is known about precipitation quality in the Monterey area, and no 

known sampling network is operating at present (Jim Goodridge, California 

Department of Water Resources, oral commun., 1983; Harold Hillman, Monterey Bay 

Air Pollution Control District, oral commun., 1983; Doug Lawson, California Air 

Resources Control Board, oral commun., 1983). Air quality in the Monterey area 

generally has been considered good, and so concern for such problems as acid 

rain has not been great. Such concerns may arise in the future, and a data 

base could help precipitation-quality investigations. Nearby Santa Cruz County 

has considered sampling from the County's precipitation gages (Robert Coiling, 

Santa Cruz County Planning Department, Watershed Management Section, oral 

commun. , 1987) , but so far has not begun any sampling because no need has been 

identified. The following discussion indicates some concerns that a 

precipitation-quality network might address.

Acid rain and acid fog. One condition that a precipitation-quality 

network could monitor is acid rain and fog. A report by the Monterey County 

Planning Department (1981b) deals with air and water quality but makes no 

reference to the potential effects of acid rain or fog. A review of acid 

deposition research in California also shows no research activity in the 

Monterey County area (Western Oil and Gas Association, 1983), but acid fog 

conditions observed further south along the California coast may eventually be 

observed in this area.

Acidic gases in the atmosphere can derive from natural sources, such as 

volcanoes and forest fires, but this condition results especially from human 

activities, such as burning fossil fuels in powerplants and motor vehicles 

(U.S. Geological Survey, 1984, p. 61) . In areas fairly unaffected by industrial emissions, precipitation has a minimum pH of about 5.0. In California 

during 1981, the average pH of precipitation ranged from 5.2 to 5.8 at six 

sampling sites (U.S. Geological Survey, 1984, p. 62). In comparison, a 

retrieval from the U.S. Environmental Protection Agency's STORET file indicated 

that average ground-water pH for 1953-80 for Monterey County was 7.5.

In the Western United States, nitric acid is typically dominant in acid 

rain, whereas in the eastern United States sulfuric acid is dominant (Payton, 

1982). Even so, Melack and others (1982, p. 35) reported that "sulfuric acid 

contributed about twice the acidity of nitric acid" in the east-central Sierra 

Nevada in their study, which measured pH of convective-storm precipitation 

during the dry season of 1981. Values of pH in their study ranged from 3.7 to 

4.9.

38 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Pesticides. Pesticides in precipitation is another condition that a 

precipitation-quality network could monitor. A recent study in Fresno, 

California, found the insecticides diazinon, malathion, and parathion in precipitation samples in concentrations as high as 0.93, 0.11, and 1.0 yg/L, 

respectively (Oltmann and Shulters, 1989, p. 59) . The detection of these 

pesticides in precipitation was tentatively related to their application to 

dormant fruit trees by truck-mounted sprayers (Oltmann and Shulters, 1989, 

p. 36) . This method of application suspends large quantities of spray in the 

air, which may then move with wind currents. Other application methods, such 

as aerial crop dusting, may have similar results in certain areas, but probably 

will not have such high concentrations because of the greater potential for 

dispersion over a larger area.

Design

The ideal distribution of precipitation-quality sites is purely speculative at this time because no baseline data of precipitation quality in the 

study area are available at present. Precipitation-quality networks probably 

would be similar to regional networks for monitoring distribution of precipitation quantity. Possible specifications for an ideal network are presented in 

table 3. An ideal network might have only one sampling site per township, 

depending upon the results of a denser synoptic sampling project. Sampling 

would measure daily wet and dry deposition volume and quality, particularly for 

pH and pesticides. Samples would be taken daily and during storms. Ideally, 

this sampling would be coupled with continuous daily climatic-data collection. 

Spaite and others (1980, p. 2) suggest that acid rain may be chiefly a local 

phenomenon, and so specific local networks may need to be established.

Methods of sampling, data collection, and analysis have been established 

by several past studies of precipitation quality (Mehra, 1982; Melack and 

others, 1982; Strachan and Huneault, 1982; and Oltmann and others, 1987). 

These methods are not covered in detail in this report because methods vary 

with the specific type of data collected. A detailed review of the various 

methods might be undertaken before a network is established in the study area 

to assure that the data are representative and statistically sound.

The precipitation-quality network could be an initial selection of some of 

the active precipitation-quantity sites. The distribution of these sites 

initially could be one, two, or more sites per township to establish the baseline distribution of precipitation quality in the study area. After selecting 

standardized sampling methods and determining the constituents that could be 

monitored accurately at existing precipitation gages or after modifying the 

existing gages, a review of the data could help determine if enough sites were 

selected or if some sites could be discontinued. As monitoring progressed, the 

stations could be evaluated to determine how representative they were for 

measuring precipitation quality in each township or other selected area.

Precipitation Networks 39
SURFACE-WATER NETWORKS 

Surface-Water Conditions

Streamflow is closely related to precipitation and has about the same 

seasonal distribution. Streamflows are normally high during the rainy season 

(November to April), and flooding can be a problem during years of greaterthan-normal precipitation. Streamflows decline sharply in the summer months, 

and some streams dry up. Demand for water is greatest during the dry season 

when supplies are least plentiful. In the Salinas River drainage basin, water 

supply is an especially critical issue. Surface water is stored in reservoirs 

mainly in the southern Salinas River drainage basin (Showalter and Hoffard, 

1986) f south of this report's study area in Monterey and San Luis Obispo 

Counties. Reservoir releases are used to recharge ground water, which in turn 

is tapped for water supply. Thus, surface and ground water in the area are 

closely interrelated.

Streamflow Networks

Data needs for the Streamflow networks (table 3) are diverse. The 

highest-priority needs include (1) formation of an integrated information 

system of continuous Streamflow record, which can be correlated with precipitation; (2) use of telemetered stage recorders at key lakes and streams; and 

(3) periodic and continuous data collection relating to water use, storm 

runoff, and dam and hydroelectric sites. These and other data needs are 

outlined in table 3.

Objectives

Generalized management objectives for Streamflow networks (table 1) 

include (1) determination of benchmark flow characteristics such as peaks, mean 

daily flows, and low flows for all major and minor streams in the county; (2) 

identification of temporal and spatial trends in Streamflow, both seasonally 

and annually; (3) identification of the causes of changes in Streamflow, such 

as variation in annual precipitation, land use, instream water use, diversion, 

agricultural return flow, and channelizations; and (4) determination of the 

best use of surface water. Once the uses, timing, and volumes of use are 

identified, management decisions can be made on how best to allocate the 

resources among the various uses.

40 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
Specific streamflow-network objectives are more fully described in table 

3, along with priority rankings (Showalter and Hoffard, 1986) and other pertinent data. The objectives can be summarized to include (1) assessment of 

effects of streamflow on ground-water recharge; (2) measurement of surfacewater use; (3) flood warning; (4) data gathering for water-rights adjudication 

and design of storm-drain systems and flood-control structures; (5) determination of sediment transport; (6) management of irrigation diversions; (7) 

instream-use management and planning; (8) development of relations to ungaged 

sites; (9) management of irrigation, municipal, and industrial development; and 

(10) assessment of potential hydropower-plant sites.

Method of Evaluation

Following the example of Showalter and Hoffard (1986, p. 36) , an ideal 

network was developed that reflects generalized management and network objectives (table 1) as well as specific objectives and data needs (table 3) . 

Definitions of generalized ideal- and actual-network objectives are derived 

from Pederson and others (1978, p. 77) and Moss and others (1982, p. 1) , 

respectively. The various networks also were given priority points according 

to the scheme devised by Showalter and Hoffard (1986, p. 37) , and an ideal 

number of sites for each network was projected (table 3).

Available information on existing streamflow-gaging stations was collected, and existing sites were evaluated in terms of the objectives and data 

needs indicated by the ideal network (table 3) . The six sites in the study 

area where data presently are collected (table 5) are important to existing 

planning and management activities, so that continuation of all sites is indicated. Reactivation of the four discontinued sites also is indicated; two of 

these sites, Alisal Creek near Salinas and Salinas River near Gonzales, might 

be relocated to improve record quality. The existing sites are discussed in 

detail at the end of the streamflow-networks section of this report. 

Additional gages can be located to fulfill objectives described in table 3 as 

need and funds dictate they should be established.

Criteria for Site Selection

Site selection for a streamflow network is a complex process in which 

sometimes conflicting objectives and conditions must be reconciled (table 3). 

Information requirements for a streamflow-gaging station may include peak stage 

and low-flow discharge and depth or continuous record of stage and discharge. 

The selection of sites for streamflow-gaging stations is dictated by the 

requirements of a hydrologic network and the needs of water management (Carter

Surface-Water Networks 41
TABLE 5. Streamflow-gaging stations

[Sources of information include California Department of Water Resources (1981b, p. 20-163); 

U.S. Geological Survey (1974, p. 325; 1979, p. 59); Anderson and others (1985). Site 

numbers refer to locations in figure 6. Operating agency; 5000, U.S. Geological Survey 

(USGS); 5050, California Department of Water Resources (DWR); 5115, Monterey County Flood 

Control and Water Conservation District]

Site 

No.

1

2

3

4

5

6

7

8

9

10

Station name

Salinas River at 

Soledad

Salinas River near 

Gonzales

Salinas River near 

Chualar

Salinas River near 

Spreckels

El Toro Creek near 

Spreckels

El Toro Creek near 

Spreckels

Alisal Creek near 

Salinas

Gabilan Creek near 

Salinas

Reclamation Ditch 

near Salinas

Santa Rita Creek at 

Santa Rita

Station 

number 

(DWR, USGS)

D2-1500, 

11151700

D2-1325, 

11152200

D2-1310, 

11152300

D2-1220, 

11152500

D2-1180, 

11152540

D2-1170, 

11152550

D2-1225, 

11152570

D2-1240, 

11152600

D2-1009, 

11152650

D2-1007

Location

Operating 

agency

5000

5050

5000

5000

5000

5115

5000

5115/5000

5115/5000

5115

Township/ 

range

17S/6E

17S/5E

16S/4E

15S/3E

15S/2E

15S/3E

14S/4E

13S/3E

14S/2E

14S/3E

Latitude/ 

longitude

36°24 I 4011 / 

121°19 I 06"

36°29 I 12"/ 

121 0 28'06"

36°33 I 14I V 

121 0 32'53"

36°37'52 11 / 

121°40 I 17"

36°35'oo"/

121 0 42'50M

36°37 I 3011 / 

121°41 I 12"

se^i'ss 11 /

121°34 I 04"

36 0 45'21"/ 

121°36 I 34"

36°42 I 18"/ 

121°42'14 11

36°43'30"/ 

121°39 I 12"

Period 

of 

record

1968-78, 

1983-present

1976-80

1966-present

1900-01, 

1929-present

1961-present

1960-61

1965-74

1959-present

1968-present

1968-78

and Davidian, 1968, p. 2) . Station locations for a hydrologic network generally are chosen to take advantage of the best available conditions for stage 

and discharge measurements and for developing discharge ratings. Stations 

established for water-management purposes, by contrast, commonly have little 

freedom of site selection, and frequently records must be obtained under 

adverse hydraulic conditions. For example, many of the principal streams in an 

area may have been converted into a series of pools by the construction of 

dams, and yet dam operation may require precise records. Water management also 

may need records of tidal-affected reaches of stream channels for information 

on water supply, salinity repulsion, or waste-disposal contamination. 

Streamflow-gaging conditions may be poor in areas that have only sand-channel 

streams in which stage-discharge relations change continually. The Salinas 

River and Prunedale Creek in this study area are examples of this condition.

42 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Despite the problems in site selection, Carter and Davidian (1968, p. 2-3) 

proposed several criteria for selecting gaging-station locations:

1. Channel characteristics relative to a fixed and permanent 

relation between stage and discharge at the gage. A rock 

riffle or falls * * * indicates an ideal site. If a site 

on a stream with a movable bed needs to be accepted for 

example, a sand-channel stream it is best to locate the 

gage in as uniform a reach as possible, away from 

obstructions in the channel such as bridges.

2. Opportunity to install an artificial control.

3. Possibility of backwater from downstream tributaries or other 

sources. If a site where backwater occurs has been accepted, 

a uniform reach for measurement of slope needs to be sought, 

in addition to the proper placement of an auxiliary gage. 

Unsteady flow such as occurs in tidal-affected stream channels 

requires similar consideration but, in addition, line power 

needs to be available to insure simultaneous recording of 

stage at the two gages.

4. Availability of a nearby cross section where good discharge 

measurements can be made.

5. Proper placement of a stage gage with respect to the measuring 

section and to that part of the channel which controls the 

stage-discharge relation.

6. Suitability of existing structures for use in making high-flow 

discharge measurements, or the proper placement of a cableway 

for this purpose.

7. Possibility of flow bypassing the site in ground water or in 

flood channels.

8. Availability of line power or telephone lines where needed, for 

special instrumentation or for Telemark units.

9. Accessibility of the site by roads, particularly during flood 

periods.

Frequent discharge measurements are normally necessary for defining the 

stage-discharge relation at any given time. The stage-discharge relations are 

rarely permanent because of changes in the stream channel such as aquatic 

growth, debris or ice accumulation, and conditions of scour and fill. Consequently, the frequency of measurements ultimately relates to the needed 

reliability of the resulting data. As measurements and station visits become 

less frequent, the reliability of the resulting data decreases.

Surface-Water Networks 43
Description of Streamflow-Gaging Stations

There have been 10 streamflow-gaging stations operated in the study area 

(table 5 and fig. 6). Five active stations are operated by the U.S. Geological 

Survey: Salinas River at Soledad, Salinas River near Chualar, Salinas River 

near Spreckels, El Toro Creek near Spreckels, and Gabilan Creek near Salinas. 

One active station, Reclamation Ditch near Salinas, is operated by the Monterey 

County Flood Control and Water Conservation District. The District has operated two other discontinued streamflow-gaging stations in the study area. The 

station at El Toro Creek near Spreckels was replaced in 1961 by a nearby station operated by the U.S. Geological Survey. The other station, Santa Rita 

Creek at Santa Rita, was discontinued in 1978. The other two discontinued 

streamflow-gaging stations (table 5) are Alisal Creek near Salinas and Salinas 

River near Gonzales. Alisal Creek is a tributary in the Tembladero Slough 

basin. The station at Alisal Creek near Salinas was operated between 1965 

and 1974. The station was operated by the District from December 1965 to 

September 1970 and by the U.S. Geological Survey from October 1970 through 

September 1974. A small reservoir upstream from the station diverted water for 

irrigation during most flow periods and controlled all but high flows (U.S. 

Geological Survey, 1974, p. 325). The station at Salinas River near Gonzales 

operated from 1976 to 1980. In much of the study area, the Salinas River 

meanders in a wide, flat, braided channel, and so communication between gage 

and flow is difficult. This condition at the Gonzales station evidently led to 

discontinuation. Each station is described in the following sections, and the 

reasons for retaining or excluding them from future monitoring are discussed.

Salinas River at Soledad. The U.S. Geological Survey installed the 

streamflow-gaging station at Salinas River at Soledad (site 1 in table 5 and 

fig. 6) in October 1968. The station was inactive between October 1978 and 

September 1983. Ground-water withdrawals and small surface-water diversions 

are made upstream from this station; several large reservoirs also regulate 

flow (Anderson and others, 1985, p. 49). The drainage area for this station is 

3,563 mi 2 . The peak discharge, recorded on February 25, 1969, was 

106,100 ft 3 /s. The no-flow condition during March 9-16, 1977, was the minimum 

flow recorded at this station. Land use in this area is cropland and pasture 

(fig. 2). This station is about 1.2 miles upstream from the Soledad 

wastewater-treatment facility and less than 0.5 mile south of Soledad. Water 

quality was sampled infrequently at this station between 1971 and 1977 (site 20 

in table 6 and fig. 6) . The continued operation of this station is justified 

as part of the highest priority streamflow network for identification of 

ground-water recharge, as well as several other networks (table 3).

44 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
121°45'

R2E

R4E

121°30'

T14S

T16S

36°30'

EXPLANATION

SURFACE-WATER-QUALITY 

MONITORING SITES - Number 

corresponds to site number 

in table 6

17 Y Active

18 V Inactive

STREAMFLOW GAGING STATIONS -

Number corresponds to site

number in table 5 

o 

A Continuous record

Inactive 

STUDY AREA BOUNDARY 10MILES

0 5 10 KILOMETERS 

FIGURE 6. Surface-water-quality monitoring sites and streamflow-gaging stations.

Surface-Water Networks 45
Salinas River near Gonzales. The California Department of Water Resources 

(DWR) installed a station at Salinas River near Gonzales (site 2 in table 5 and 

fig. 6) in 1976. Streamflow has been measured there several times, but a peak 

of 43,000 ft 3 /s in 1978 shifted the main channel and destroyed communication 

between the gage and the stream. No stage-discharge relation was ever established for this site because of channel instability. Streamflow measurement 

was discontinued at the station in 1980 because of channel instability, funding 

reductions, and installation of the station near Chualar (Bill Mancebo, 

California Department of Water Resources, oral commun., 1985). From 1969 to 

1985, the DWR took water-quality samples twice a year at this site for the 

California State Water Resources Control Board (site 19 in table 6 and fig. 6). 

The California Department of Water Resources (1981b, p. 68 and 125) stated that 

a streamflow-gaging station has been in operation at this site since 1969, but 

the DWR did not verify this site for the present report. Upstream reservoirs 

typically discharge at rates that maximize recharge of Salinas aquifers, but by 

the time these flows reach Chualar much of the water already has percolated 

into the ground (Jagger, 1981, p. 25). Quantification of the remaining streamflow of the Salinas River between Soledad and Chualar might help to relate 

Streamflow to ground-water recharge in this area. Therefore, the relocation of 

a streamflow-gaging station at a suitable site is justified, if such a site can 

be found, to become a part of the highest priority Streamflow network, identifying ground-water recharge (table 3), as well as for determining conveyance 

capacity and sediment transport. Streamflow correlations may be possible, 

however, between the Gonzales station and the stations at Soledad and Chualar.

Salinas River near Chualar. The U.S. Geological Survey has operated the 

streamflow-gaging station at Salinas River near Chualar (site 3 in table 5 and 

fig. 6) since 1966. From October 1976 through December 1978, the gage was 

nonrecording. Since January 1979, a continuous water-stage recorder has been 

in operation. Daily discharge for 1976-78 has been determined by correlation 

of discharge measurements at this station with Salinas River near Soledad and 

Salinas River near Spreckels (Anderson and others, 1985, p. 55) . Low flow 

during the drought included periods of no flow during January through April 

1977 (U.S. Geological Survey, 1979, p. 71). The flow passing this station has 

been regulated partly by three upstream reservoirs, which are outside the study 

area. Large ground-water withdrawals and small surface-water diversions are 

made upstream of the Chualar station for municipal and irrigation uses. Water 

quality has been sampled at this station (site 17 in table 6 and fig. 6) since 

1977 as part of the U.S. Geological Survey's National Stream-Quality Accounting 

Network (NASQAN). Chemical water-quality analyses and sediment records have 

been available for this site since 1977. Biological, continuous watertemperature, and specific-conductance data are available for 1977-81. Because 

this station is downstream from diversions, it is needed for the following 

networks: ground-water recharge, water use, water rights, sediment transport, 

irrigation use, water balance, saltwater intrusion, instream use, and municipal 

and industrial use (table 3). The continued operation of the station therefore 

is highly justified, although improvements in record quality for high and low 

flows might be necessary.

46 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Salinas River near Spreckels. The U.S. Geological Survey installed the 

streamflow-gaging station at Salinas River near Spreckels (site 4 in table 5 

and fig. 6) in January 1900. Record was published as "Salinas River near 

Salinas" for 1900-01. The station was inactive after August 1901 until October 

1929. Upstream, large ground-water withdrawals and small surface-water diversions are made for municipal use and for irrigation of about 95,000 acres 

(Anderson and others, 1985, p. 58) . The drainage area for this station is 

4,156 mi 2 . The peak discharge, recorded on February 26, 1969, was 

83,100 ft 3 /s; a peak of 63,000 ft 3 /s was recorded on March 3, 1983. The minimum flow, recorded in 1983, was 181 ft 3 /s on December 21, but no flow was 

recorded on several occasions during 1929-40. Land use in this area is cropland and pasture (fig. 2). Water quality was monitored near this station 

between 1951 and 1977 (site 12 in table 6 and fig. 6) . Between October 1974 

and January 1977, water quality was monitored monthly as part of NASQAN. This 

station is about 1 mile downstream from the closed Spreckels sugar refinery 

and just downstream from the outfall for the Alisal sewage-disposal plant. 

Historically, low flow at this station represented primarily wastewater from 

these two sources. Laboratory work continues at the refinery site, but discharges are now minimal. The continued operation of this station is justified 

as part of the highest priority streamflow network for identification of 

ground-water recharge downstream from the Chualar station, as well as several 

other network categories (table 3).

El Toro Creek near Spreckels. The present streamflow-gaging station at 

El Toro Creek near Spreckels (site 5 in table 5 and fig. 6) is about 3 miles 

upstream from the original station (11152550) (site 6 in table 5 and fig. 6) . 

The U.S. Geological Survey operates the present station; the Monterey County 

Flood Control and Water Conservation District operated the old station until 

September 1961. The original station was installed in 1960, so that about 25 

years of record are available near this site. Seepage under the concrete 

control at the new station resulted in a poor record for 1983, and so the 

station was moved 700 feet downstream. The flow in El Toro Creek is extremely 

low during most of the year, but the peak flow for the period of record was 630 

ft 3 /s on March 2, 1983, even though the drainage area upstream from the station 

is only 31.9 mi 2 (Anderson and others, 1985, p. 59). Small stock ponds are the 

only regulation or diversion upstream from this site. This station is in a 

forested area between two residential areas, Ambler Park and Serra Village 

(fig. 6) . The station lies just inside the boundary of the Fort Ord Military 

Reservation and about 2 miles downstream from the Laguna Seca raceway. The 

continued operation of this station is justified as part of the highest 

priority streamflow network, identification of ground-water recharge, as well 

as several other networks (table 3).

Surface-Water Networks 47
Alisal Creek near Salinas. The Monterey County Flood Control and Water 

Conservation District operated the Alisal Creek near Salinas streamflow-gaging 

station (site 7 in table 5 and fig. 6) between December 1965 and September 

1970, when the U.S. Geological Survey assumed operation until September 1974. 

A small reservoir controls all but high flows passing this station (U.S. 

Geological Survey, 1974, p. 325) . Much of the flow of Alisal Creek probably is 

controlled by regulation of tributaries, including several small reservoirs and 

one diversion to a reservoir in the Natividad Creek drainage. The drainage 

area for this station is 14.2 mi 2 . The peak discharge is 780 ft 3 /s, recorded 

on April 1, 1974, the date of the peak of record for Gabilan Creek near Salinas 

(fig. 6) , which is still in operation. Land use in this area (fig. 2) is 

cropland and pasture; upstream from the station lie rangeland and forest. The 

original station was located on a bend of the creek where debris and sand 

tended to build up, reducing the quality of record (Wendell Ayers, U.S. 

Geological Survey, oral commun., 1985). If the station is reactivated, a 

change in location might alleviate this problem. A single water-quality sample 

was taken in 1974 from the Natividad Creek drainage downstream from the reservoir, which receives diversions from Alisal Creek (site 40 in table 6 and 

fig. 6) . Reestablishment of this station is justified as part of the highest 

priority streamflow network for identifying ground-water recharge, as well as 

for determining conveyance capacity and sediment transport (table 3).

Gabilan Creek near Salinas. The Monterey County Flood Control and Water 

Conservation District installed the streamflow-gaging station at Gabilan Creek 

near Salinas (site 8 in table 5 and fig. 6) in January 1959 and operated it 

until October 1970, when the U.S. Geological Survey assumed operation. A 

concrete control feature was installed on October 9, 1975, to improve the 

accuracy of stage-discharge monitoring. Diversions and small detention reservoirs upstream from the station provide some regulation of the flow (Anderson 

and others, 1985, p. 60). The drainage area for this station is 36.7 mi 2 ; the 

peak discharge, originally recorded on April 1, 1974, as 800 ft 3 /s, was later 

modified to 898 ft 3 /s (S.H. Hoffard, U.S. Geological Survey, oral commun., 

October 1985). A peak of 217 ft 3 /s was recorded at 0445 hours on March 3, 

1983. By contrast, El Toro Creek near Spreckels recorded a historic high flow 

of 630 ft 3 /s from the same storm, even though the drainage area for that station is smaller than for Gabilan Creek near Salinas. Comparisons could indicate differences in characteristics influencing runoff in the two drainages, 

such as distribution and intensity of precipitation. The land use in this area 

(fig. 2) is cropland and pasture. A tributary entering Gabilan Creek 0.3 mile 

upstream of the station partly drains from the largest strip-mine and quarry 

area in Monterey County. In 1973, a single water-quality sample was collected 

near this site (site 43 in table 6 and fig. 6) . The continued operation of 

this station is justified as part of the highest priority streamflow network 

(table 3) , identification of ground-water recharge, as well as several other 

networks.

48 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Reclamation Ditch near Salinas. The Monterey County Flood Control and 

Water Conservation District installed the streamflow-gaging station at 

Reclamation Ditch near Salinas (site 9 in table 5 and fig. 6) in March 1968 

and operated it until October 1970. The U.S. Geological Survey then operated 

the station until 1986 when the District assumed operation again. Reclamation 

Ditch is in the Tembladero Slough basin. The station measures drain flow 

mostly from Carr Lake (T. 14 S., R. 3 E., sec. 22); the water is used primarily 

for farming (Anderson and others, 1987, p. 71) . The drainage area for this 

station is 53.2 mi 2 , and the peak discharge, recorded on March 1, 1983, was 

524 ft 3 /s. The gage has a concrete control, but otherwise the ditch is 

unlined. The land use in this area is cropland and pasture (fig. 2) . Very 

infrequent water-quality samples were collected near this site before 1973 

(site 30 in table 6 and fig. 6) . The continued operation of this station 

is justified as part of the second-highest priority streamflow network, 

identification of water-use quantities, as well as several other network 

categories (table 3).

Santa Rita Creek at Santa Rita. The Monterey County Flood Control and 

Water Conservation District operated the streamflow-gaging station at Santa 

Rita Creek at Santa Rita (site 10 in table 5 and fig. 6) between October 1968 

and September 1978. Several small reservoirs in the Santa Rita Creek drainage 

probably influence flows at this station. The drainage area for this station 

is 4 mi 2 , according to the Monterey County Flood Control and Water Conservation 

District (1978, p. 31) , but California Department of Water Resources (1981b, 

p. 125) stated that the drainage area is 10.4 mi 2 . The 4-mi 2 drainage area has 

been verified recently (Bruce LaClergue, Monterey County Flood Control and 

Water Conservation District, oral commun., 1985). The peak discharge of 178 

ft 3 /s was recorded on April 1, 1974, the date of the peak of record for Gabilan 

Creek near Salinas (site 8 in table 5 and fig. 6) and Alisal Creek near Salinas 

(site 7 in table 5 and fig. 6). Land use in this area is primarily residential 

and industrial, but croplands and pastures also lie within the drainage area 

(fig. 2). Historically, infrequent streamflow measurements have reduced the 

quality of record at this station (S.H. Hoffard, U.S. Geological Survey, oral 

commun., 1985). Frequency of streamflow measurement can be established on a 

periodic schedule. To maintain the accuracy of continuous flow records, measurements must be frequent enough to detect changes in the stage-discharge 

relation; this might require six or more measurements per year, depending on 

the measured flow for the year. Reestablishment of the Santa Rita station is 

justified as part of the highest priority streamflow network for identifying 

ground-water recharge, as well as for several other networks (table 3). Urban 

development is concentrating in the immediate and upstream areas near this 

site, which may require improved data for various hydrologic planning needs.

Surface-Water Networks 49
TABLE 6. Surf ace-water-quality monitoring sites

[Site numbers refer to station locations in figure 6. , no data available]

Operating agency:

1257, Northern Salinas Valley

Mosquito Abatement District

5000, U.S. Geological Survey (USGS)

5050, California Department of

Water Resources (DWR) 

5115, Monterey County Flood Control and

Water Conservation District

Sampling frequency codes:

S, single, one-time sample

1. very infrequent (less than 

	5 analyses)

2. infrequent (5-25 analyses)

3. frequent (more than 25 analyses)

A, currently active

N, no sampling identified

Summary of sampling frequencies

Number

of 

Frequency stations Percent

S

1

2

3

N

Total. . . .

9

14

11

14

2

...50

18

28

22

28

4

100

Site 

No.

Station 

name

Station

number Oper- 

(DWR, ating 

USGS) agency

Sampling frequency

Location

 Number

Township/ Latitude/ Period of Before 1973- of

range longitude record 1973 present analyses Code

Salinas River near 

Bank from Mulligan 

Highway

Salinas River at 

Twin Bridges'

Salinas River 1.9 

miles above 

Highway 1 Bridge

Blanco Drive at Pump 

Lift 1

Salinas River at 

Blanco Drive

Salinas River at 

Blanco Road

D2-1100.30 5050

D2-1110.50 5050

D2-1110.70 5050

D2-1030.30 5050, 

5000

D2-1120.50 5050

1257

14S/1E 36°44'54"/ 1964 

121°48'06"

14S/2E 36°44'00"/ 1964-

121°46'42" present

14S/2E 36 0 43'06"/ 1964-77 

121°45'00"

14S/2E 36°42'36"/ 1970-75 

121°44'36"

14S/2E 36°42'24"/ 1964-77 

121°44'48"

14S/2E 1975-84

N

32

11

15

11

118

3,A

Salinas River at 

Blanco Road 1

Salinas Oxidation 

Pond 2

D2-1150.30 5050

1257

14S/2E 36 0 40'42"/ 1964-

121°44'42" present

15S/2E 1975-84

28

118

3,A

Salinas Oxidation 

Pond 1

1257 15S/2E 1975-84 118

10 Salinas River at 

Davis Road 1

11 El Toro Creek near 

San Benancio 

Bridge 1

12

13

14

Salinas River near

Spreckels

Salinas River at 

Highway 68

Spreckels Holding 

Pond, Old 1-E

D2-1160.20 5050 15S/2E

D2-1185.20 5050, 15S/2E 

5000

D2-1220.00 5050, 15S/3E 

11152500 5000

1257 15S/3E

1257 15S/3E

36°38'30"/ 1971-77 

121°42'00"

36°34'42"/ 1970-72 

121°43'12"

36°37'48"/ 1951-77 

121°40'42"

1975-84

1975-84

160

118

118

Footnotes at end of table.

50 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 6. Surface-water-quality monitoring sites Continued

Site 

No.

15

16

17

18

19

20

21

22

23

24

25

26

27

Station 

name

Spreckels Pond, 

5-6-W

Quail Creek above 

Old Stage Road

Salinas River near 

Chualar

Chualar Creek at Old 

Stage Road

Salinas River near 

Gonzales 1

Salinas River at 

Soledad

Old Salinas River 

above Tembladero 

Slough 1

Tembladero Slough at 

Molera Road 1 *

Tembladero Slough 

below sewage 

treatment plant

Tembladero Slough at 

Highway 183

Tembladero Slough at 

Preston 1 4

Merritt Lake drain 

at pump 1

Salinas Reclamation

Station 

number 

(DWR, 

USGS)

D2-1260.50

D2-1310.10 

11152300

D2-1290.50

D2-1325.10 

11152200

D2-1500 

11151700

D2-1006.50

D2-1006.30

D2-1006.52

D2-1006.60

D2-1009.20

Operating 

agency

1257

5050, 

5000

5050, 

5000

5050

5000

5115

5115

5050

Location

Township/ 

range

15S/3E

15S/4E

16S/4E

15S/4E

17S/5E

17S/6E

13S/2E

13S/2E

13S/2E

13S/2E

13S/2E

13S/2E

14S/2E

Latitude/ 

longitude

--

36°37'00"/ 

121°31'18"

36°33'14"/ 

121°32'53"

36°34'42"/ 

121°29'42"

36°29'12'7 

121°28'06"

36°24'40"/ 

121°19'06"

36°46'12"/ 

121°47'12"

36°46'18"/ 

121°47'12"

36°46'20"/ 

121°47'11"

36°45'06"/ 

121°44'12"

36°44'30'7

Sampling frequency

Number 

Period of Before 1973- of 

record 1973 present analyses Code

1975-84 N 3 118 3

1973 S N IS

1952-69 2 3 50 3, A 

1977-

present

1952-70 IN 41

1969- 2 3 59 3, A 

present

1971-77 22 92

1972-77 11 62

1970-78 2 2 14 2

1969-70 IN 31

1969-70 IN 31

1977-78 N 2 62

1970-75 21 92

1970-72 IN 21

Canal below Alisal 

Slough

28 Reclamation Canal at 

Tembladero Slough 1

29 Reclamation Canal at 

Highway 183 (Santa 

Rita lateral)

30 Salinas Reclamation 

Canal at San Jon 

Road

121°44'18"

11152650

14S/2E

5115 14S/3E

5115 14S/2E 36°42'18'7 1969-70 1 

121°42'14"

3 1

31 Salinas Reclamation 

Canal at Boronda 

Road

D2-1010.20 5050 14S/3E 36°41'24'7 1970 

121°40'48"

2 1

32 Salinas Reclamation 

Canal at Preston 

Street

D2-1011.50 5050 14S/3E 36°41'06'7 1974 

121°39'12"

1 S

33 Salinas Reclamation 

Canal at Main 

Street

5115 14S/3E 1969-70 3 1

Footnotes at end of table.

Surface-Water Networks 51
TABLE 6. Surface-water-quality monitoring sites Continued

Site 

No.

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

Station 

name

Salinas Reclamation

Canal at end Merced

Street

Sherwood Lake, east

shore

Natividad Creek at

East Laurel Drive

Salinas Reclamation

Canal at Alisal

Sewage Treatment

Plant

Salinas Reclamation

Canal at Airport

Boulevard 1

Salinas Airport

northeast moat

Alisal Creek at Old

Stage Road

Natividad Creek at

Old Stage Road

Gabilan Creek at

Natividad Bridge

Crossing

Gabilan Creek near

Santa Rita

San Miguel Creek east

of Backie Road

Old Salinas River

channel above

First Tide Gate 2

Moro Co jo Slough West

Bank, northeast of

Highway I 2

Moro Cojo Slough at

Railroad, south of

Dolan Road 2

Elkhorn Slough South

Bank, north of

Dolan Road2

Elkhorn Slough at

Highway 1 bridge 2

Elkhorn Slough at

Highway I 2

Station 

number Oper- 

(DWR, ating 

USGS) agency

D2-1015.50 5050

1257

D2-1264.50 5050

D2-1016.50

D2-1020.70

1257

D2-1255.50 5050,

5000

D2-1266.50 5050

D2-1261.50 5050

D2-1240.00 5000

D2-1060.20 5050

Dl-3111.30 5115

Dl-3114.3 5000

Dl-3113.3 5000

Dl-3116.3 5000

1257

Dl-3150.3 5000

Loc

Township/ 

range

14S/3E

14S/3E

14S/3E

14S/3E

15S/3E

14S/3E

14S/4E

14S/4E

14S/3E

13S/3E

13S/3E

13S/2E

13S/2E

13S/2E

13S/2E

13S/2E

13S/2E

Sampling frequency 

ation 

 Number

Latitude/ Period of Before 1973- of 

longitude record 1973 present analyses Code

36°40'30"/ 1970 IN 21

121°38'24"

1975-84 N 3 118 3

36°41'18"/ 1974 N S IS

121°37'30"

36°40'06"/ 1973-75 11 41

121°38'06"

36°39'42"/ 1970-77 2 N 62

121°37'18"

1975-84 N 3 118 3

36°41'30"/ 1952-74 2 S 11 2

121°34'06"

36°42'00"/ 1974 N S IS

121°34'24"

36°43'54"/ 1974 N S IS

121°36'42"

36°45'18"/ 1973 S N IS

121°36' 36"

36°46'01"/ 1970 S N IS

121°39'08"

36°48'00"/ 1977- N 1 10 1,A

121°47'15" present

36°47'51"/ 1977 N 1 21

121°45'58"

36°47'22"/ 1977 N 1 21

121°45'10"

36°48'48"/ 1977 N 1 21

121°44'40"

1975-84 N 3 118 3

36°48'36"/ 1953-70 2 N 21

121°47'00"

Site(s) recommended in Burau and others (1981, v. 1, p. 52-54).

2 Site(s) noted by W.E. Templin, P.E. Smith, and R.C. Schluter (U.S. Geological Survey, written commun., 1989) 

3 Called "at Nashua Road" (site 14) in Burau and others (1981). 

^Called "at Merritt Lake Drain" (site 15) in Burau and others (1981).

52 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Surface-Water-Quality Networks 

Surface-Water Quality Conditions

Quality of surface water in the Salinas River varies greatly with location (Monterey County Planning Department, 1981b / p. 127-128). The basin can 

be divided into two areas, a lower basin downstream from Chualar and an upper 

basin. Although the upper part has generally good quality, contamination does 

exist. Natural contamination is present in water draining from the east side 

of the Salinas Valley; water draining the Diablo Range (outside the study area) 

is typically high in mineral concentrations. Dissolved solids, which are 

minerals that remain combined with water after filtering, can be 10 times 

higher in concentration in water draining from the eastside range than in water 

from the westside. Surface-water quality also is affected by land use in 

the Salinas River basin. Communities and cities south of Chualar discharge 

their sewage into holding ponds before release into the river to prevent high 

nutrient discharges. Irrigated agriculture, a major land use in the Salinas 

River basin, demands a large part of the total water used from the Salinas 

River. About 20 to 50 percent of irrigation water returns to the river as 

surface drainage or to the ground water by percolation. High nutrient levels 

in the river are the result. Clean water coming from outside the study area 

(from Lake Nacimiento, Lake San Antonio, and the Arroyo Seco) flushes out 

these nonpoint sources of pollution, resulting in good-quality water from the 

upper Salinas River. The lower Salinas River does not benefit from this 

flushing action because summer water flows are limited to reaches upstream from 

Spreckels and State Highway 68 bridge.

Water quality in the lower Salinas River has been degraded by waste disposal, land development, and agricultural practices. The city of Salinas has 

two sewage outfalls on the Salinas River near the Highway 68 bridge (fig. 3) . 

Treated sewage and agricultural drainage comprise more than 90 percent of the 

summer flow of the Salinas River downstream of the Highway 68 bridge. 

Excessive nutrient buildup has resulted in eutrophication, large amounts of 

algae, sludge deposits, and foul odors. Because of such conditions, the State 

of California has listed the Salinas River from the community of Spreckels to 

Monterey Bay as one of the five dirtiest rivers in the State (Walter Wong, 

Monterey County Environmental Health Department, oral commun., 1980). During 

the winter rainy season, these conditions are improved as high flows produce 

good-quality water throughout the Salinas River.

Objectives

Generalized management and network objectives (table 1) for surface-water 

quality include (1) determination of ambient concentrations of water-quality 

constituents; (2) determination of spatial and temporal trends; (3) 

identification of native, point, and nonpoint sources of constituents; and (4) 

development of a surface-water-quality management plan.

Surface-Water Networks 53
Koryak (1980, p. 1) said that "the design of water-quality monitoring 

networks has traditionally been a subjective process. Decisions as to the 

number of stations in a network, station locations, sampling frequencies, and 

parameter coverage are based primarily on the intuitions and judgment of the 

individual designers." Koryak also stated that the initial step of network 

design, definition of objectives, probably was the most subjective and potentially controversial part of the process; he suggested two basic categories of 

water-quality monitoring objectives which require correspondingly different 

strategies.

The first category consists of water-quality characterization and trend 

identification, which require routine monitoring. Routine monitoring entails 

long-term, fixed-time increment sampling at permanent station locations for 

which no termination date is designated. The second category includes deterministic water-quality investigations, which entail synoptic monitoring. This 

type of monitoring often is required for regulatory enforcement, primarily 

involving effluent and receiving-water monitoring. Synoptic monitoring can be 

(1) scheduled, to measure chronic water-quality conditions; or (2) unscheduled, 

to measure acute conditions. Synoptic monitoring normally has a short-term or 

designated termination date. In this report, generalized management and network objectives for surface-water quality (table 1) have tried to accommodate 

both categories of monitoring objectives, as well as the objectives outlined by 

the United Nations Educational, Scientific, and Cultural Organization and 

others (1978, p. 25-27).

Method of Evaluation

The method used in this report to evaluate the surface-water-quality 

monitoring networks was (1) assessment of data needs of the area, (2) assessment of ideal-network coverage for the study area, (3) location and evaluation 

of existing and potential sites for surface-water-quality sampling, and (4) 

determination of possible improvements to network coverage. The ideal network 

summarized in table 3 follows the example of Ponce's (1980, p. 35) waterquality matrix in developing a systematic understanding of water-quality monitoring in the study area. An ideal network for monitoring surface-water 

quality would provide information on the general chemical quality, trace elements, bacteria, and all other potential contaminants at any stream site anywhere in the study area, at any time requested. Because such a saturation of 

information is impractical, an ideal network could be expected to produce more 

information than is being produced currently, but less than saturation level. 

An example of some of the potential needs for data is provided along with some 

preliminary priorities and other pertinent data in table 3. These networks and 

priorities should be reviewed and improved periodically as needs change and 

more information is gathered.

54 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Data needs for surface-water quality (table 3) include routine, periodic, 

complete analyses of stream and reservoir water to monitor for domestic, agricultural, and fish and wildlife uses. Ideally, sampling should (1) determine 

water quality of flow from reservoirs; (2) monitor for the effects of geology 

and land use on water-quality trends; and (3) establish baseline water-quality 

characteristics, such as temperature and specific conductance, for the entire 

basin and for specific streams. Data collection can assist in mosquito 

abatement, evaluate compliance with water-quality criteria and standards, and 

develop a water-quality rating system for stream reaches.

Station Location and Sampling Frequency

According to Brown and others (1970, p. 4-8), the overall needs of a 

data-collection program determine the location of a station and the frequency 

of sampling. If a sampling network is set up to measure overall water quality 

of a stream, sampling should represent the entire stream; sampling stations 

therefore should not be established where mixing of water is incomplete or 

where water composition differs significantly in the stream cross section. A 

sampling station may be set up to measure water quality at a specific intake 

point, but care should be taken not to mislead data users as to the representativeness of the sample for the entire stream. For most streams, sampling 

should be every day or two in some cases every few hours to ensure reliability of the record. Sampling may be infrequent for streams completely controlled by large storage reservoirs or by large constant ground-water inflow. 

To establish continuous water-quality conditions of a stream, continuous 

recording and telemetering equipment may be used in conjunction with periodic 

complete water-quality analyses. The use of the proper tools for the job (in 

this case instruments for the specific sample and desired analysis) commonly is 

taken for granted, but this approach can be a serious mistake. Reports by 

Skougstad and others (1979) and Claassen (1982) review various analytical and 

instrumentation approaches suggested for use in water-quality sampling.

Description

The Monterey County Flood Control and Water Conservation District 

(MCFCWCD) presently is sampling surface-water quality at one site for suspended 

sediment, specific conductance, and chlorides as requested routinely by the 

California Coastal Commission (site 45 in fig. 6 and table 6). The following 

agencies also have conducted surface-water-quality monitoring in the study 

area: the U.S. Geological Survey (USGS); the California Department of Water 

Resources (DWR); Monterey County Environmental Health Department; and the 

Northern Salinas Valley Mosquito Abatement District (fig. 6 and table 6).

Surface-Water Networks 55
Fifty sites were identified during this study as historic or recommended by 

other investigators for surface-water quality monitoring. A review of the 

sampling frequency was done (table 6) which indicates that most (36 sites, 72 

percent) sites have been sampled infrequently at best. As of 1985, only five 

monitoring sites were active: Salinas River at Twin Bridges (DWR), Salinas 

River at Blanco Road (DWR), Salinas River near Chualar (DWR and USGS), Salinas 

River near Gonzales (DWR), and Old Salinas River channel above First Tide Gate 

(table 6 and fig. 6). Sampling frequencies, locations, and results need to be 

reviewed periodically by local agencies to remain current with available information. The U.S. Environmental Protection Agency maintains a computerized 

system that can be accessed to obtain information on sampling locations, 

results, and frequencies in relation to various other related information 

(including waste dischargers and water-supply withdrawal locations) (Phil 

Daniels, California State Water Resources Control Board, oral commun., July 

1989). Additional data may be available from the California Regional Water 

Quality Control Board, Central Coastal Region, San Luis Obispo, as required by 

discharge permits. The stations identified for this report include 45 inactive 

and 5 active sites.

Showalter and others (1984, p. 54-55) suggested continued monthly sampling 

and sampling during storms at the streamflow-gaging station Salinas River near 

Chualar (11152300) (site 17 in table 6 and fig. 6) and Salinas River at Soledad 

(11151700) (site 20 in table 6 and fig. 6) for three reasons: (1) infiltration 

through stream channels is the major source of recharge to ground water; (2) 

streamflow records are available; and (3) sampling could correspond to regular 

streamflow measurement visits, thereby reducing additional costs. To meet 

specific data needs for future seawater intrusion problems, a routine longterm, deterministic program developing water-quality parameters to characterize 

the existing conditions also is important. Similar data are needed on Gabilan 

and Natividad Creeks for characterizing the quality of water currently 

recharging the ground-water basins in those areas. These streams would be 

likely candidates for high ratings in the stream-reach rating system discussed 

below.

Burau and others (1981, p. 54) recommended 13 sites in the study area for 

monthly or at least quarterly sampling for various environmentally hazardous 

substances and standard water analyses (table 6). These sites are included in 

table 6 and figure 6 as surface-water-quality sites 2, 4, 7, 10, 11, 12, 19, 

21, 22, 25, 26, 28, and 38. The authors then modified their proposed monitoring program to include quarterly water samples at five sites and annual 

water samples at eight sites (Burau and others, 1981, p. 75-76) . The list of 

constituents suggested for analysis included arsenic, boron, cadmium, lead, 

mercury, DDT, PCB's, and metabolites, 10 chlorinated hydrocarbons, parathions, 

and nitrates. Burau and others (1981) also suggested semiannual sampling at 

five sites with analysis of sediment, and tissue analyses from fish and crayfish. Wastewater from 12 known dischargers was recommended for quarterly 

sampling, and three marine-environment sites were recommended for semiannual 

sampling of sediment, water, and various plant and animal species.

56 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Since 1977, the California Department of Fish and Game and the California 

State Water Resources Control Board have monitored biological indicators of the 

quality of coastal bay and estuarine waters in Monterey County as part of the 

State Mussel Watch Program and the Toxic Substances Monitoring Program 

(California State Water Resources Control Board, 1984, p. 41-46). Surfacewater-quality sampling at the Salinas River near Gonzales station (site 19 in 

table 6 and fig. 6) has been ended, and sampling at Salinas River near Chualar 

(site 17 in table 6 and fig. 6) as part of the U.S. Geological Survey's 

National Stream-Quality Accounting Network (NASQAN) is used instead (Tom 

Lavenda, California State Water Resources Control Board, oral commun., 1985). 

The Geological Survey site could be used as an example of the frequency and 

constituents for sampling stream quality that is needed throughout Monterey 

County.

Although the objectives for surface-water-quality monitoring summarized in 

tables 1 and 3 are extensive, at present only five sites are active (sites 2, 

7, 17, 19, and 45 in table 6 and fig. 6) . Establishment of additional sites 

would be necessary to meet the proposed monitoring objectives. Possible 

sampling sites include the 45 inactive sites included in table 6, and further 

canvassing of the study area might identify other active sites. A stream-reach 

rating system would help to determine possible additional sites and establish 

the priority of the sites.

Stream-Reach Rating System

A method of determining priorities for individual streams and reaches of 

streams is needed so that Monterey County Flood Control and Water Conservation 

District can start to monitor additional surface-water-quality sites. Sanders 

(1980, p. 118) presented a method for selecting river reaches that need a 

sampling station. This method identified each major stream and subdivided the 

streams into tributaries. Each stream and tributary was assigned a rating of 

its need for monitoring on the basis of the number and types of diversions from 

and discharges into them. This approach is typical of what is needed in the 

design of a surface-water-quality-monitoring network for Monterey County. The 

drainage-basin numbering system proposed by Durbin and others (1978, p. 44-46) 

for small tributary streams of the Salinas River needs to be expanded to 

include separate reaches of the Salinas River itself. The use of stream reach 

numbers and segmentation of the U.S. Environmental Protection Agency would 

adequately meet the needs of Monterey County and lead to improved cooperation 

between local and Federal agencies with common interests. The result would 

provide an initial list of specific stream reaches that would need to be ranked 

by their priority of need for streamflow and surface-water-quality data. 

Beyond identifying all reaches of the Salinas River as higher priority than the 

25 other tributaries identified by Durbin and others (1978, p. 38) in the study 

area, the assignment of priorities to segments of streams is beyond the scope 

of this study.

Surface-Water Networks 57
GROUND-WATER NETWORKS 

Ground-Water Conditions

The conditions of ground water in the study area have been reported as 

early as 1946 (California Department of Water Resources, 1946). Hart (1966, p. 

5) describes the geology of the Salinas River drainage basin as "typical of the 

southern Coast Ranges, being structurally and stratigraphically complex." 

Durbin and others (1978, p. 15) divided the geologic formations of the area 

into three general units on the basis of their capacity to yield ground water. 

These geologic units are consolidated rocks, semiconsolidated deposits, and 

unconsolidated deposits. The consolidated rocks yield only a small quantity of 

water; the semiconsolidated deposits yield small to appreciable amounts of 

water; and the unconsolidated deposits, which form the prolific aquifers of the 

area, yield the most water. For a detailed discussion of the geology of the 

study area, the reader is referred to Hart (1966).

Occurrence of Ground Water

Many reports have been published on ground-water occurrence in specific 

geographic areas of Monterey County, and for convenience, this report uses the 

geographic names used historically by the Monterey County Flood Control and 

Water Conservation District and other agencies. The study area for this report 

includes the following geographic areas: El Toro Creek basin area, Pressure 

area, East Side area, and the northern one-half of Forebay area (fig. 7) .

Ground water in the El Toro Creek basin area occurs in six major geologic 

units in ascending order: the basal sand unit, the Monterey Formation, the 

Santa Margarita Sandstone, the Paso Robles Formation, the Aromas Sand, and 

alluvium, all of late Tertiary and Quaternary age (Anderson-Nichols and Co., 

1981, p. 15). The Santa Margarita Sandstone, Paso Robles Formation, and Aromas 

Sand are the principal sources of ground water for the area. Water-bearing 

units in the El Toro Creek basin area have extreme variability in permeability, 

no noted confinement, and some influence by faults (Anderson-Nichols and Co., 

1981, p. 15-20).

Ground-water occurrence in the Pressure, East Side, and Forebay areas is 

distinguished by three characteristics: (1) degree of confinement, (2) source 

of ground-water recharge, and (3) specific capacity of wells (Durbin and 

others, 1978, p. 8-9). According to Showalter and others (1984, p. 29) , the 

Pressure area contains a shallow, perched water table and at least three confined aquifers that are separated by interconnecting clay layers. These aquifers are formed of alluvium and the Paso Robles Formation or its equivalents.

58 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
121 °45'

R2E

PAJARO

PAJARO-SPRINGFIELD 

BASIN

T12S

EXPLANATION

GEOGRAPHIC AREA 

 GEOGRAPHIC AREA BOUNDARY

GROUND-WATER BASIN BOUNDARY 

STUDY AREA BOUNDARY

R4E

J21°30'

PACIFIC 

T15S GROVE

PRUNEDALE

MOSS LANDINGS 

T13S

EL TORO 

CREEK 

BASIN

TULARCITOS 

CREEK 

BASIN

R6E

SALINAS VlALLEY 

BASIN

CARMEL 

T16S

36°30'

T17S

T18S

10 MILES

_l

10 KILOMETERS

FIGURE 7. Ground-water geographic areas.

Ground-Water Networks 59
The confined aquifers are known as the 180-foot, 400-foot, and deep aquifers on 

the basis of the general depth to the top of each. The 180-foot and the 

400-foot aquifers are heavily used, and saltwater intrudes both aquifers in 

areas of heavy pumping near Monterey Bay. In 1981, the front of the advancing 

saltwater was about 4.6 miles inland in the 180-foot aquifer and about 1.8 

miles inland in the 400-foot aquifer. Continued monitoring provides important 

information on changes in this saltwater front over time, with changes in 

land-use and water-use management.

The aquifers of the Pressure area are recharged primarily by underflow 

from the Forebay area, direct percolation from Quail Creek at Spence, and percolation from shallower to deeper aquifers (Showalter and others, 1984, p. 32). 

Ground water in the East Side area is mostly semiconfined and in the Forebay 

area is mostly unconfined. The main source of recharge to the East Side and 

Forebay areas is infiltration from the Salinas River and its tributaries. Some 

recharge to the East Side, however, is attributed to underflow from the 

Pressure and Forebay areas. In the Forebay area, some recharge also is 

attributed to underflow from the southern Salinas River drainage basin. 

Modeling of ground water indicates that the Pressure area is recharged by 

upward movement of water from the deep zone (Hydrocomp, Inc., 1985, p. 35).

Average specific capacities, in gallons per minute, for the study area are 

as follows: Forebay area, 109; Pressure area 180-foot aquifer, 63; Pressure 

area 400-foot aquifer, not available; Pressure area deep aquifer and East Side 

area, 21 (Durbin and others, 1978, p. 8; Showalter and others, 1984, p. 32; 

Schmidt, 1985, p. 5).

Ground-Water Flow

The natural direction of ground-water flow in the Salinas River basin 

generally parallels the surface-water flow. Ground water in the Forebay area 

generally moves in a northwesterly direction along a fairly uniform gradient 

toward Gonzales, and in the East Side and Pressure areas, ground water moves in 

a northerly direction toward Chualar and Salinas (Leedshill-Herkenhoff, Inc., 

1985, p. 3-3). Localized pumping of wells, however, strongly influences threedimensional flow of ground water in the area. Near Salinas, ground-water 

movement turns eastward because of pumpage patterns. Significant parts of the 

Pressure and East Side areas have water-surface altitudes below sea level. 

Fresh ground water no longer flows westward toward the ocean because pumpage 

has reversed the typical flow gradient. This reversal in flow direction has 

allowed saltwater to intrude from the Pacific Ocean into the major producing 

aquifers near the mouth of the Salinas River.

60 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Anderson-Nichols and Co. (1981, p. 35) found that the flow of ground water 

in the El Toro Creek basin generally follows the pattern of surface drainage 

north along El Toro Creek and west towards Laguna Seca. A more even distribution of water-level measurements is needed to confirm the directions of 

ground-water flow in this area.

Flow Barriers

The only known barrier to ground-water flow in the study area is north of 

Salinas (T. 14 S., R. 3 E., sec. 14). Wells in the area indicate a faultcreated flow barrier that has offset the water table 130 feet (Showalter and 

others, 1984, p. 42) . In the El Toro Creek basin area, much of the hydrology 

is controlled by northwest-southeast trending folds and faults, such as the 

Harper Canyon, Harper, Chupines, and Corral de Tierra Faults (Anderson-Nichols 

and Co., 1981, p. 19-20). In particular, the Corral de Tierra Fault and the 

Chupines Fault influence the flow of ground water in the area.

Water-Level Changes

Showalter and others (1984, p. 44) summarized the changes in water levels 

that have been measured in the Salinas River basin since ground-water-level 

monitoring began in 1944. Between 1944 and 1980, measurements of the average 

water levels and potentiometric surfaces in the East Side, Pressure, and 

Forebay areas declined 43, 18, and 2 feet, respectively. Furthermore, 

according to Showalter and others (1984),

The decline in the East Side subarea has been most severe 

where transmissivities are low and recharge slow. Because 

saltwater intrusion was already a problem in the Pressure 

Area in 1944, an additional decline of 18 feet since then 

is serious. Water-level declines in the Pressure Area near 

the coast are somewhat stabilized by the intrusion of seawater. The rate of decline has not been constant over 

time. During the 1976-77 drought, the water levels dropped 

substantially throughout the basin. By 1980, the water 

levels in the Forebay * * * had recovered to their predrought levels, but the water levels in the Pressure Area 

and East Side had not.

The mean changes in autumn ground-water levels for the Salinas River 

drainage basin and El Toro Creek basin between 1973 and 1978 (fig. 8) indicate 

the effects of the 1976-77 drought on ground-water levels in these areas 

(Monterey County Flood Control and Water Conservation District, 1978, p. 12) .

Ground-Water Networks 61
10.0 I I 

Salinas River Basin 

El Toro Creek Basin

-10.0

1974 1975 1976 1977 1978 

YEAR

FIGURE 8.-Mean changes in autumn ground-water levels, 1974-78.

Ground-Water-Quality Conditions

The quality of ground water in 

the El Toro Creek basin is generally 

fair to poor; concentrations of dissolved solids, sulfate, chloride, 

nitrate, iron, and manganese commonly 

exceed California State drinking-water 

standards (Anderson-Nichols and Co., 

1981, p. 76). Water-quality problems 

have been noted in all areas of the El 

Toro Creek basin but most commonly in 

the Calera Canyon and Watson Creek 

basins. The problems presumably relate to the natural aquifer mineralogy 

of the area because current land use 

(fig. 2) does not indicate that known 

problems result from development.

Ground water in the East Side area from Gonzales to Castroville generally 

contains less than 1,000 mg/L (milligrams per liter) of dissolved solids 

(Showalter and others, 1984, p. 48). Ground-water type is principally sodium 

chloride or sodium calcium chloride but in a few scattered areas, it is calcium 

bicarbonate. The chloride dominance in some of these wells probably does not 

result from saltwater intrusion because the dissolved-solids concentration is 

low. North of Gonzales along the east side of the drainage basin, the ground 

water is dominantly of the sodium sulfate and calcium sulfate types (Showalter 

and others, 1984, p. 48 and pi. 5).

In the Pressure area, the 180-foot and 400-foot aquifers generally contain 

a similar water type, but water in the 180-foot aquifer has a higher 

dissolved-solids concentration (Showalter and others, 1984, p. 48) . In both 

aquifers, sodium calcium (or calcium sodium) bicarbonate water types dominate, 

but the 180-foot and 400-foot aquifers contain some calcium sulfate and calcium 

bicarbonate water types, respectively. Three conditions have affected 

adversely the quality of water in both aquifers: (1) percolation from 

irrigation, (2) downward migration of water through unsealed and otherwise 

poorly constructed wells, and (3) saltwater intrusion.

In the deep aquifer, water types are dominantly sodium bicarbonate (Ares, 

1982, p. 7). The available data indicate that the dissolved-mineral concentrations of water in the deep aquifer are within acceptable limits for class 1 

irrigation water. The high sodium content of the water, however, has created 

some concern about soil-permeability problems related to the long-term use of 

this water for irrigation. Boron levels detected in soil water extracts in 

areas irrigated with water from this aquifer indicate that careful monitoring 

and farming practices may be required for this aquifer to be a good source of 

supplemental irrigation water to the Castroville area (Ares, 1982, p. 2; Bruce 

LaClergue, Monterey County Flood Control and Water Conservation District, 

written commun., 1988).

62 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Ground-Water-Level Networks

Objectives

Generalized management and network objectives (table 1) for ground-water 

levels include (1) determination of regional water-level conditions to establish temporal and spatial trends; (2) identification of ground-water pumpage 

and recharge sources; and (3) determination of storage capacities and best 

management practices for preventing overdraft and saltwater intrusion.

The objectives for ground-water level networks (table 3) include the need 

for information on pumpage (ground-water use) as an indication of outflow from 

the region's aquifers. For ideal water-use efficiency, pumpage would be 

metered with permanently installed and routinely maintained flow-totalizing 

meters on each well. In the absence of flow meter data, ground-water withdrawals can be estimated in different ways. Unless the method used is specified, the results may not be comparable. For example, outflow could be 

determined from the correlation between electrical-use records and the 

approximate pumpage volume allowed by that electricity, or it could be 

determined from the approximate applications of water necessary for the 

production of specific crop types (M.J. Johnson, U.S. Geological Survey, oral 

commun., 1984). Depending on the assumptions made for the computation, 

significant differences can result. For example, outflow estimates can differ, 

depending on whether a high or low estimate of crop utilization of water is 

used. Similarly, if pumpage estimates are based on electrical usage, 

corrections made in the meter readings for other possible electrical uses may 

change outflow estimates significantly. In both cases, calculations of annual 

trends must be based on comparable periods, such as calendar years, water 

years, fiscal years, or rainfall years; the months included in the year used in 

the trend analysis must be explicit.

Method of Evaluation

Ground-water networks may be analyzed in at least three ways: qualitatively, quantitatively, and statistically. Two examples of qualitative analysis were provided by Blankenbaker and Farrar (1981, p. 6) and Winner (1981, 

p. 18) where characteristics of wells were discussed and the wells are assigned 

subjectively to qualitative categories. Showalter and others (1984) and 

Templin (1984) took a quantitative approach, in which numerical ratings were 

assigned to monitoring wells on the basis of the availability of wellconstruction information. A statistical method for network analysis was proposed by Karlinger and Skrivan (1978) and implemented by Sophocleous and others 

(1982) using the concept of kriging, which incorporates the use of regionalized 

variables and semivariograms to help decide the needed number of monitoring 

sites to attain the desired level of accuracy. Recent (1988) development 

of computerized data bases that incorporate mapped information in a relational environment would have been helpful in this evaluation. A geographic 

information system (GIS) can simplify problems encountered with manipulating 

and analyzing large spatial data bases while also incorporating historic 

information.

Ground-Water Networks 63
The method of analysis of ground-water networks used in this report is 

adapted from Showalter and others (1984) and Templin (1984). First, an ideal 

network was developed (table 3) that would encompass all known data needs for 

ground-water levels in the study area. Second, existing networks were identified, and wells and networks were classified according to well-construction 

data. Third, changes in network density were suggested to better approximate 

ideal-network coverage. Although statistical analysis of well networks is 

desirable, an evaluation of the type done by Karlinger and Skrivan (1978) or 

Sophocleous and others (1982) was beyond the scope of this report. The adequacy of wells in existing monitoring networks for representing actual conditions in the ground-water basins therefore has not been established 

conclusively nor has the possible redundancy of information from existing 

networks been evaluated statistically. Despite these limitations, this report 

does provide a basis for assessing the adequacy of ground-water-level networks 

in the study area.

Well and Network Classification

The networks operated by the Monterey County Flood Control and Water 

Conservation District were evaluated following an example of well and network 

classification established in recent work by Templin (1984). For the present 

report, only networks operated by the District were evaluated. Networks 

operated or proposed by others were provided as a source of supplemental wells 

that might be considered for inclusion in the the District networks.

Well classification system. For the networks maintained by the Monterey 

County Flood Control and Water Conservation District, each well was classified 

according to the availability of data concerning its construction and lithology 

(table 7) . The classification of each well was based on the availability of 

five key items of information:

1. Opening records (perforation intervals),

2. Well depth,

3. Casing record,

4. Sealing (record that a seal exists), and

5. Well-log availability.

Each well was classified according to which and how many of these five key 

items are available for that particular well as follows:

Class 1. All five key items are available and complete.

Class 2. The opening record is available, but any one or all of the remaining 

key items may be lacking or incomplete.

Class 3. The opening record is lacking, but one or more of the remaining key 

items is available.

Class 4. All five key items are lacking.

64 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 7. Classification of ground-water networks

Well Classification System: The classification of 

wells is based on the availability of five key 

items of information:

1. opening records (perforation intervals)

2. well depth

3. casing record

4. sealing (record that a seal exists)

5. well-log availability

Each well was classified according to which and 

how many of the five key items are available 

for that particular well, as follows: 

Class 1, all five key items are available and

complete

Class 2, the opening record is available, but any 

one or all of the remaining key items may be 

lacking or incomplete 

Class 3, the opening record is lacking, but one

or more of the remaining key items is available 

Class 4, all five key items are lacking.

Network Classification System: Each ground-water 

network was assigned to one of the following 

four classes on the basis of the relative number 

of class 1 and class 4 wells in the specific 

network. A class 1 well would be most preferred 

and a class 4 network would be least preferred. 

Class 1, more than 50 percent of the wells in

the network are class 1 wells. 

Class 2, 50 percent or less of the wells in the 

network are class 1 wells, and less than 50 

percent are class 4 wells.

Class 3, 50 percent of the wells in the network 

are class 1 wells, and 50 percent are class 4 

wells.

Class 4, 50 percent or more of the wells in the 

network are class 4 wells, and less than 50 

percent are class 1 wells.

Total 

number 

of wells

Well 

class

Well-class

Number 

of wells

distribution

Percent

Network 

class

Total 

number 

of wells

Well 

class

We 11 -class

Number 

of wells

distribution

Percent

Network 

class

Monterey County Flood Control and Water Conservation District

Autumn

Network Lla.

73 1 

2 

3 

4

Network Lib.

70 1 

2 

3 

4

Network

81 1 

2 

3 

4

Network

44 1 

2 

3 

4

Network Lie.

5 1 

2 

3 

4

Network

32 1 

2 

3 

4

water-level measurements

Pressure area,

1 

15 

33 

24

Pressure area,

27 

30 

7 

6

180-foot aquifer

1 2 

21 

44 

34

400-foot aquifer

39 2 

43 

10 

8

Lie. East Side area

2 

36 

35 

8

Lid. Forebay

2 

17 

10 

15

3 2 

44 

43 

10

area

4 2 

39 

23 

34

Pressure area, deep aquifer

4 

0 

0 

1

Llf. El Toro

11 

12 

4 

5

80 1 

0 

0 

20

Creek basin

34 2 

38 

12 

16

Monthly

Network L2a.

10 1 

2 

3 

4

Network L2b.

12 1 

2 

3 

4

water-level measurements

Pressure area, 180-foot

0 0 

1 10 

4 40 

5 50

Pressure area, 400- foot

5 42 

6 50 

1 8 

0 0

aquifer

4

aquifer

2

Network L2c. East Side area

16 1 

2 

3 

4

0 0 

8 50 

4 25 

4 25

2

Network L2d. Forebay area

9 1 

2 

3 

4

Network L2e.

5 1 

2 

3 

4

0 0 

3 33

1 11 

5 56

4

Pressure area, deep aquifer

5 100 

0 0 

0 0 

0 0

1

Network L2f. El Toro Creek basin

6 1 

2 

3 

4

3 50 

3 50 

0 0 

0 0

2

Ground-Water Networks 65
TABLE 7. Classification of ground-water networks Continued

Well-class distribution 

Total 

number Well Number Network 

of wells class of wells Percent class

Monterey County Flood Control and 

Water Conservation District 

August water-level measurements

Network L3a. Pressure area, 180-foot aquifer

38 1 

238

1 32 

3 19 50 

4 15 39

Network L3b. Pressure area, 400-foot aquifer

37 1 22 60 1 

2 9 24 

3 4 11

4

*^ C

Network Ql. U.S. Geological Survey 1

51 1 20 2 

2 1 20 

3 

400

3 60 

Network Q2. U.S. Army Health Service

210 

200 

04 

300 

4 2 100

Network Q3a. Monterey County Flood Control and 

Water Conservation District 

Summer network, monthly analyses (May-Sept.)

52 1 16 31 2 

2 15 29 

3 12 23 

4 9 17

Network Q3b. Monterey County Flood Control and 

Water Conservation District 

Summer network, annual analyses

366 1 63 17 2 

2 131 36 

3 102 28 

4 70 19

Well-class distribution 

Total 

number Well Number Network 

of wells class of wells Percent class

Network Q4. California Department of Health 

Services

30 1 9 30 2 

313 

2 11 37 

4 9 30

Network Q5. Monterey County Department of 

Environmental Health

19 1 10 53 1 

2 6 32 

3 

415

2 10 

Network Q6. California Regional Water

Quality Control Board, Central Coast Region

17 1 2 12 4 

2 2 12 

3 4 23 

4 9 53

Network Q7. California Water Service Company

25 

228 

1 20 80 1 

300 

4 3 12

Network Q8. Showalter and others (1984)

131 1 29 22 2 

2 47 36 

3 13 10 

4 42 32

Network Q9. Burau and others (1981) Monterey 

Basin Pilot Monitoring Project

63 1 23 37 2 

323 

2 21 33 

4 16 27

*No wells were sampled as of 1987 by the U.S. 

Survey, oral commun., 1987).

Geological Survey (Gail Keeter, U.S. Geological

The accuracy of this method of classification relies on drillers' logs and 

other sources of data. Improvements in the information used also can improve 

the results of this method. Therefore, if drillers accurately fill out the 

State-required log when wells are drilled, that source of data and the quality of 

subsequent ground-water data is more reliable.

66 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Network classification system. Each of the five ground-water networks 

maintained by the Monterey County Flood Control and Water Conservation District 

was assigned to one of the following four classes according to the relative 

number of class 1 and class 4 wells in the network (table 7) . A class 1 network is most preferred, and a class 4 network is least preferred. This classification system emphasizes use of wells having good information on their 

construction characteristics. This information helps the analyst know more 

about the data collected in these networks and the relation to the geohydrology 

of the area.

Class 1. More than 50 percent of the wells in the network are class 1 wells.

Class 2. 50 percent or less of the wells in the network are class 1 wells, 

and less than 50 percent are class 4 wells.

Class 3. 50 percent of the wells in the network are class 1 wells, and 

50 percent are class 4 wells.

Class 4. 50 percent or more of the wells in the network are class 4 wells, 

and less than 50 percent are class 1 wells.

The objective of this classification system is to eliminate all wells from 

the network that are not optimal for monitoring. Information exists on all 

wells with class 1 designations that can help validate the data collected from 

them. Ideally, all wells in all networks would have class 1 designations, and 

the networks would contain enough wells to provide the needed information.

Description

Three ground-water-level networks (table 8) are maintained by the Monterey 

County Flood Control and Water Conservation District in the northern Salinas 

River drainage basin: the autumn network, the monthly network, and the August 

network. The autumn network (table 8, networks Lla-f) is a set of wells usually measured in December or January to obtain static water-level measurements 

at the end of the irrigation season. The purpose of these measurements is to 

indicate the changes in ground-water storage during the preceding year. These 

changes in storage are considered the net result of all recharge and withdrawal 

from the individual aquifers. Wells in the autumn network are among those 

shown in figure 9.

Ground-Water Networks 67
TABLE 8. Inventory of ground-water-level networks

[Well class is explained in table 7. Dagger (t) indicates that area within 

section has been proposed for the location of a monitoring well]

Well 

No.

Well 

class

Well 

No.

Well 

class

Well 

No.

Well 

class

Well 

No.

Well 

class

Monterey County Flood Control and Water Conservation District

Autumn water-level networks

[Total well count, 305]

13S/2E-27L1 

27M1 

29R1 

33R1 

35L1

14S/2E-03C1

3F1

3K1

3R1

4A1

4R1

10K1

10P1

10R1

11G1

13B2

14E1

14L1

15G1

13S/2E-19H1 

19R1 

20J1 

21N1 

27P1 

29C2 

29D3 

29F2 

29M2 

30A1 

30H1 

30Q2 

31D2 

31G4 

31N2 

31P1 

32A2 

32C1

13S/2E-36F1 

13S/3E-35N1 

14S/3E-02E3 

3K1 

4E1 

4N1 

4Q1 

5B2 

6L1 

6L2 

6R1 

7A1 

8C1

Network Lla. Pressure area, 180-foot aquifer 

[Well count, 73]

14S/2E-16E2

17A1

21J1

21L1

22F1

22N1

22P2

23A1

23L1

24J1

26P1

27G2

28H2

34B1

36E1

14S/3E-19G1

19Q2

30N1

Network Lib.

13S/2E-32E3

32J3

33N3

14S/2E-03K2

3M2

4B1

4H1

5C2

5F4

5K1

5P2

6J3

7K1

7L3

8C3

8M2

10C1

12Q1

4

4

4

4

3

3

2

3

3

3

3

3

2

3

3

3

3

3

14S/3E-31F1

15S/2E-01Q1

2J1

12E2

15S/3E-09E3

13N1

14C1

16M1

18B1

18C2

22G1

25Q1

26F1

15S/4E-31A2

16S/4E-05M2

8B1

8J1

9A1

Pressure area, 400- foot

[Well

2

1

3

1

1

2

1

2

1

1

1

1

3

4

1

1

1

2

Network Lie

14S/3E-10F3

10Q1

10R2

11H1

12E1

14C1

14N1

15C1

15H3

16D1

16E1

22A1

24H1

[Well

2

2

2

2

2

3

3

3

2

3

2

2

2

count, 70]

14S/2E-15B1

15P1

17B2

26J3

27G3

34A1

34B3

35L2

36G1

14S/3E-18J1

31F2

15S/2E-01A3

2G1

12A1

15S/3E-04K3

6D2

6K1

. East Side area

count , 81 ]

14S/3E-24N1

24R1

25L1

25L2

27G2

36A1

36P2

14S/4E-30N1

30R1

31F1

15S/3E-02Q1

12E2

12F2

3

3

4

2

2

2

3

3

3

2

4

4

2

2

2

4

3

2

aquifer

1

2

2

4

1

2

2

1

2

2

2

1

2

2

2

2

3

3

4

3

2

3

3

2

2

3

3

3

2

2

16S/4E-13H1 

13R2 

15D1 

15R2 

16E1 

24C1 

25C1 

25P1 

27B2

16S/5E-19F1 

30E1 

31A1 

31M1 

31Q1 

32B2 

32C1 

32E1

17S/4E-01D1

15S/3E-07G1

8F1

8N3

15B1

16B3

18F1

18M2

28B1

15S/4E-19D2 

29D1 

29Q1 

29R1

16S/4E-02Q3

4C1

10R2

25G1

16S/5E-30J2

15S/3E-13G4 

15S/4E-05C1 

5M1 

6R1 

7A1 

7R1 

8C1 

8L1 

8N1 

8Q1 

9D1 

9J1 

9M1

68 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
TABLE 8. Inventory of ground-water-level networks--Continued

Well 

No.

15S/4E-14N1 

15D2 

15P2 

16D1 

16E2 

17P2 

20B2 

21F4

16S/5E-32H2 

32M1 

33Q1

17S/5E-01Q1 

2N2 

2N4 

3L1 

4K1 

4N1 

4R1 

5G1

13S/1E-36J1 

13S/2E-19Q3

16S/2E-03A1 

3G1 

3H1 

3J1 

4H1

16S/2E-01E1 

1L1 

1M1

Well 

class

Well 

No.

Well 

class

Well 

No.

Well 

class

Well 

No.

Well 

class

Monterey County Flood Control and Water Conservation District Continued 

Autumn water-level networks Continued

Network Lie.

15S/4E-21L2 

22L2 

24N3 

27G1 

33A1 

34L1 

36H1

East Side area Continued

3 15S/4E-36P1

3 36R2

2 16S/4E-01L1

3 16S/5E-05N1

2 7G1

2 8Q1

2 17P1

Network Lid. Forebay area 

[Well count, 44]

17S/5E-6Q1 

8L1 

9R1 

10Q1 

12E1 

13E1 

14D1 

21A1 

24G1 

25L1 

27A1

17S/5E-36F2 

36J1

17S/6E-16N1 

18G1 

19D1 

20E2 

27E3 

27K1 

28B1 

28K1 

29C1

Network Lie. Pressure area, deep aquifer 

[Well count, 5]

13S/2E-32E5 1 14S/2E-06L1 1

Network Llf. El Toro Creek basin 

[Well count, 32]

Corral de Tierra

16S/2E-04L1

9H1

9J1

10B1

10H1

16S/2E-02D1 

2D2 

2D3

16S/2E-10Q1 

10Q2 

15F2 

15J1 

15P1

San Benancio

16S/2E-02D5 

2G1 

2H1

16S/5E-17R1 

20G2 

20R1 

21R1 

27Q1 

28D1 

28P1

17S/6E-29K1 

29Q1 

30F1 

34E1 

35F1

18S/6E-05R2 

6M1 

7A1 

8R1 

9M1 

9M2

14S/2E-18E1

16S/2E-23H1 

24C1

16S/3E-17N1 

19L1 

19L2

16S/3E-07L1

7N1

17F2

Monterey County Flood Control and Water Conservation District

Monthly water-level networks

[Well count 58]

Network L2a.

13S/2E-33R1 3 14S/3E-31F1

14S/2E-03R1 4 15S/2E-01Q1

14L1 4 2J1

Network L2b.

13S/2E-21N1 1 13S/2E-32A2

30A1 1 14S/2E-08M2

31N2 1 12Q1

Pressure area, 180-foot aquifer 

[Well count, 10]

15S/3E-07C1 

16M1

Pressure area, 400-foot aquifer 

[Well count, 12]

14S/2E-34A1

14S/3E-18J1

31F2

15S/3E-25Q1 

16S/5E-30E1

15S/3E-16B3 

15S/4E-29Q1 

16S/4E-10R2

Ground-Water Networks 69
TABLE 8. Inventory of ground-water-level networks Continued

Well

No.

Well

class

Well Well Well

No. class No.

Well

class

Well

No.

Well

class

Monterey County Flood Control and Water Conservation District Continued

Monthly water-level networks Continued

14S/3E-06R1

9F3

15H3

24R1

17S/5E-02N4

3L1

5G1

13S/1E-36J1

13S/2E-19Q3

3

2

2

4

4

2

4

1

1

Network L2c. East Side area

[Well count, 16]

14S/3E-25L2 2 15S/4E-07R2

15S/3E-12E2 2 21L2

15S/4E-06R1 2 22L2

7R1 3 36P1

Network L2d. Forebay area

[Well count, 9]

17S/5E-36J1 4 17S/6E-19D1

17S/6E-16N1 2 28B1

Network L2e. Pressure area, deep

[Well count, 5]

13S/2E-31A2 1 13S/2E-32E5

2

3

3

4

3

4

aquifer

1

16S/5E-08Q1

20R1

27Q1

28D1

18S/6E-02N1

6M1

14S/2E-06L1

4

2

4

2

2

4

1

Network L2f . El Toro Creek basin

16S/2E-02D1

2G1

1

1

[Well count, 6]

16S/2E-02H1 1 16S/2E-15J1

10Q1 2

2 16S/2E-17N1 2

Monterey County Flood Control and Water Conservation District

August water-level networks

[Total well count, 75]

Network L3a. Pressure area, 180-foot aquifer

13S/2E-27L1

27M1

28 L2

33R1

35L1

14S/2E-03C1

3F1

3K1

3L1

3R1

4

4

2

3

3

4

3

4

4

4

[Well count, 38]

14S/2E-04A1 3 14S/2E-15H1

4R1 3 16E2

10K1 3 17A1

10P1 4 21J1

10R1 4 22F1

11G1 3 22P2

13B2 1 23A1

14E1 2 24J1

14L1 4 26P1

15G1 4 27G2

4

4

4

4

3

2

3

3

3

3

14S/2E-34B1

36E1

14S/3E-19G1

19Q2

30N1

31F1

15S/2E-01Q1

2J1

3

3

3

3

3

3

3

4

Network L3b. Pressure area, 400-foot aquifer

13S/2E-19H1

19R1

20J1

21N1

26L1

29C2

29F2

30A1

30H1

31D2

2

1

3

1

3

1

1

1

4

1

[Well count, 37]

13S/2E-31G4 1 14S/2E-04B1

31N2 1 4H1

31P1 2 5C2

32A2 2 5F4

32J3 1 5K1

33N3 3 5P2

34G1 1 6J3

34M1 1 7K1

14S/2E-03K2 1 8C3

3M2 1 8M2

Network L4. U.S. Geological Survey stream

response network 1

[Well count, 5]

2

1

2

1

1

1

1

3

1

1

channel/aquifer

14S/2E-10C1

15A1

15P1

17B2

26J3

34A1

15S/3E-06D2

1

1

2

2

4

2

2

17S/5E-23Ff (HI) 17S/5E-23F (H3D) 17S/5E-23F 

-23F (H2S)

(H4) 17S/5E-23F (H5)

Monthly water levels, January through September 1985. No wells active since 1985 (Lawrence F. 

Trujillo, U.S. Geological Survey, oral commun., 1987).

70 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
121°45'

R 2 E

R4E

30'

36°30'

MONTEREY COUNTY FLOOD CONTROL 

AND WATER CONSERVATION 

DISTRICT STUDY WELLS T 17 S

Water quality 

Water level

Water quality and water level 

OTHER INVENTORIED WELLS

Water quality - Query (?) indicates well 

proposed by Showalter and others (1984)

Water level

Water quality and water level

STUDY AREA BOUNDARY

10MILES

10 KILOMETERS

FIGURE 9. Ground-water monitoring wells,

Ground-Water Networks 71
The monthly network (table 8, networks L2a-f) consists of key wells measured throughout the year to determine the variations in ground-water levels. 

The changes in the water levels of wells in each ground-water basin are 

averaged, graphed, and compared with previous years to indicate trends 

(Monterey County Flood Control and Water Conservation District, 1977, p. 

40-41). It is not always possible to obtain static water-level measurements 

for every well each month because of the heavy use of wells for irrigation for 

long periods of time. Missing measurements, therefore, are estimated from 

known well characteristics and from measurements of nearby wells. Wells in the 

monthly network are among those shown in figure 9. These water levels need to 

be closely monitored soon after their collection to provide timely information 

for use in water-resources management, but staffing limitations have often 

prevented proper monitoring of the data in Monterey County.

The August network (table 8, networks L3a-b) consists of wells near the 

coast which are measured annually to determine the location and extent of 

ground-water troughs during the peak irrigation period. These troughs occur 

near the mouth of the Pajaro River and west of Salinas in the Pressure-area 

aquifers. According to Monterey County Flood Control and Water Conservation 

District (1977) , the troughs result from ground-water withdrawal in excess of 

recharge. The "August troughs" develop when "the water level in wells falls 

below sea level and water flows both from the direction of the ocean and from 

inland to fill the trough" (Monterey County Flood Control and Water Conservation District, 1977, p. 3). The location and depth of the troughs indicate the 

potential landward intrusion of saltwater from the ocean. The troughs vary in 

position and depth from year to year because of changes in pumping and recharge 

conditions. Wells in the August network are among those shown in figure 9. 

Besides the three District networks, the only other ground-water-level monitoring network identified was operated by the U.S. Geological Survey. Of the 

five wells that have been measured historically, none are currently measured 

(table 8, network L4).

Possible Additional Monitoring

Currently, water levels in 318 wells are being measured by the Monterey 

County Flood Control and Water Conservation District in the study area. The 

addition of the five wells installed by the U.S. Geological Survey could be 

beneficial to the understanding of ground-water and surface-water relations 

along the Salinas River. This study identified 128 sections (table 9) (each 

section is 1 mi 2 ) where no water levels currently are being measured. The 

addition of wells in these areas to create an evenly spaced monitoring grid 

would provide valuable data for use in subsequent analyses of the adequacy of 

the ground-water-level networks. An inventory of wells operating in these 

areas would determine if existing wells could be used or if wells need to be 

drilled specifically for water-level monitoring.

72 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 9. Network locations that 

presently do not have water-level 

 wells monitored by the Monterey 

County Flood Control and Water 

Conservation District

Township/

Range Section

T13S/R2E 16,17,18

T13S/R3E 30,31,32,33,34

T14S/R2E 1,2,25,33

T14S/R3E 1,13,17,20,21,23,26,28,29,32,33,

	34,35 

T14S/R4E 32

T15S/R2E 3,4,9,10,11,13,14,24,25,26,34,35,36

T15S/R3E 1,3,5,10,11,17,19,20,21,23,24,27,33,

	34,35,36

T15S/R4E 4,18,23,25,26,28,30,32,35

T15S/R5E 31

T16S/R2E 12,14,22

T16S/R3E 8,18

T16S/R4E 3,6,11,12,14,22,23,26,28

T16S/R5E 6,9,14,15,16,18,22,23,26,29,34,36

T17S/R4E 2,3,10,11,12,13,14,23,24,25,26,36

The well coverage in saltwaterintrusion areas near Castroville is 

denser than in other parts of the 

study area. In the saltwater-intrusion 

areas, continuous water-level recorders might be installed in a few of 

the currently monitored wells, and the 

remaining wells could be measured 

monthly until a correlation could be 

established between the monthly measurements and the continuous records. 

Wells in the rest of the study area 

are distributed more sparsely, but 

they are concentrated down the center 

of the drainage in the alluvial 

ground-water basin. To provide an 

even spatial distribution of each network in the study area, wells could be 

identified that are in sections that 

currently do not have water-level 

monitoring wells (table 9).

T17S/R5E 

T17S/R6E 

T18S/R5E 

T18S/R6E

7,11,15,16,23,26 

7,8,17,21,22,31,32 

1,2,3,4,5,9,10,11,12,13,14 

18

All available data from monitoring networks should be entered into a 

computer data-base management system. 

This would allow easier (and less manpower intensive) statistical analysis 

for extracting additional needed 

information. Analysis of variance,

cluster analysis, and other statistical applications, as well as the newest 

in geographic information system technologies, are readily available as software packages that usually are maintained on computers as tools for analyzing 

data. In addition, mechanical plotting of all wells from a computer file 

for each specific network objective within each basin or study area could 

provide spatial analyses that are often too time consuming and costly to be 

done routinely by hand.

The installation of continuous recorders at key wells could help to 

determine representative hydrographs for the various regions to ensure that 

measurements are timed appropriately to provide the highest priority data. 

Once the typical hydrograph for each region is determined, the measurement 

frequency may be reduced to semiannually or quarterly as long as the key wells 

are reinstalled with continuous recorders periodically to reconfirm their 

representativeness. For ground-water modeling uses, the highest priority 

water-level data are the measurements of the static levels midway between the 

highs and lows; these static levels usually occur in November (T.J. Durbin, 

U.S. Geological Survey, oral commun., 1984). Second priority are the summer 

low and winter high water levels, which may occur in September and March or 

April, respectively. Third priority is the midpoint in the declining hydrograph, which may occur in May. At least one continuously recorded well in each 

region within each aquifer would be needed to determine when these measurements 

should be made.

Ground-Water Networks 73
Measurement of wells during peak pumping periods can be difficult. At the 

time of measurement, many of the wells may be pumping or may have recently 

ceased pumping, and so accurate water-level measurement is difficult to obtain. 

The current practice is to make estimates of the water level at these wells on 

the basis of historic information on the water levels at that well in comparison with other nearby wells. Thorough study of each well in each network 

could determine whether the water-level measurements from a well are accurate 

enough for network use or whether an observation well should be installed 

nearby and used instead.

Ground-Water-Quality Networks 

Objectives

The generalized management objectives for ground-water quality (table 1) 

include (I) determination of the regional ambient water-quality conditions to 

establish spatial and temporal trends; and (2) identification of ground-water 

use and potential sources of contamination to minimize contaminant buildup, 

reduce and eliminate sources of contamination, prevent additional 

contamination, and improve degraded water-quality conditions whenever possible.

The highest-priority network goals (table 3) include determining (1) a 

ground-water-quality baseline, (2) distribution of nitrates in probable problem 

areas, (3) effects of ground-water quality on surface-water quality, and (4) 

effects of geology and land use in tributary areas on major-basin ground-water 

quality. Following the examples of Showalter and others (1984) and Templin 

(1984) , the information summarized in table 3 has been used to develop an 

ideal-network coverage for the study area. Suggestions for improving network 

coverage derive from this ideal conception.

Land use, geology, contamination sources, ground-water levels, and 

ground-water quality also should be considered in establishing ground-waterquality monitoring networks. For a network monitoring ambient conditions, the 

types of land use may affect the results of the ground-water-quality samples. 

For this reason, unless ambient ground-water conditions are uniformly affected 

by a specific land use within an area, specific wells showing effects of land 

use should be avoided in a baseline network. Such wells should be included in 

a separate network measuring the effects of point and regional contamination 

sources (table 3, networks C2f-g).

Existing data on geology, historic ground-water levels, and ground-water 

quality are important in identifying sources of naturally occurring minerals 

and trace elements, aquifers, direction of ground-water flow, and known distribution of specific water constituents. Identifying the locations of 

presently known and potential sources of contamination (fig. 3) is important in 

establishing a ground-water-quality monitoring network because such areas may 

affect ambient conditions. For example, a well selected to monitor baseline 

conditions probably should not be influenced by a known contamination source 

other than a natural source.

74 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
The goal for the ideal baseline network would be to form a spatially consistent grid of wells covering all basins with a density of one representative 

well per section (table 3); this regional network would be monitored quarterly 

until a baseline is established, and then wells representative of larger areas 

could be monitored at least annually to maintain the reliability of the network. The ideal nitrate network would consist of a grid of wells around 

locally concentrated septic-tank and other points and regional contamination 

areas in the Salinas River drainage basin. Sampling for a number of constituents and water levels would take place monthly. Line-source networks would 

be established on an as-needed basis in all basins in order to better characterize the linear effects of (1) ground-water quality on surface water and (2) 

surface-water quality of tributary area on regional ground-water quality. 

These networks would sample a number of constituents on a monthly basis; they 

also would work in conjunction with other networks continuously monitoring 

water levels and pumpage in order to determine the effects of line sources on 

ground-water and surface-water quality. Besides these highest priority networks, other ideal networks include baseline monitoring for organics in ground 

water, for regional and cumulative effects of point and nonpoint sources of 

contamination, and for natural and artificial sources of radioactive and other 

substances.

Description

The ground-water-quality networks identified for thi s report are inventoried in table 10. In addition to the monitoring by the Monterey County Flood 

Control and Water Conservation District (network Q3) , the following agencies 

also collect ground-water-quality data in the study area: the U.S. Geological 

Survey (network Ql) ; the U.S. Army Health Service, Fort Ord, California (network Q2) ; the California Department of Health Services (network Q4) ; the 

Monterey County Department of Environmental Health (network Q5); the California 

Regional Water Quality Control Board (network Q6) ; and the California Water 

Service Company (network Q7) . The networks proposed by Showalter and others 

(1984) (network Q8) and Burau and others (1981) (network Q9) also were included 

in table 10 for informational purposes. The compilation of networks and wells 

in tables 7, 8, 10, and 11 still may not include all the monitoring that is now 

active in the study area. The inclusion of these networks is intended to 

provide an initial point from which to progress in understanding the full 

extent of the active data collection. The extent of monitoring, overlap in 

monitoring, and the need for close coordination also is illustrated. The 

information collected by the California Regional Water Quality Control Board 

and the various public-supply networks should be incorporated into the data 

base maintained by Monterey County.

Ground-Water Networks 75
TABLE 10. Inventory of ground-water-quality monitoring networks

[Complete well number is given where available. Dagger (t) indicates that area within section has been 

proposed for the location of a monitoring well. An inspection of well log files and a field canvass 

are needed to determine if suitable wells exist in these locations. Networks identified by C.D. 

Farrar and P.M. Glenn (U.S. Geological Survey, written commun., 1980) or suggested by Showalter and 

others (1984). Networks from Farrar and Glenn were grouped in this report to condense all wells 

monitored by an agency as one network. Monitoring column abbreviations indicate the type of 

analysis that was being done at that well in 1980 and the reason for monitoring the well. 

Information on monitoring types and reasons was modified from Farrar and Glenn. Operating 

agency code is shown in parentheses following network name]

Monitoring type: 

B, common chemical 

C t trace elements (such as selenium) 

D, pesticides 

HM, heavy metals (such as arsenic, cadmium,

lead, mercury, zinc) 

I, combination of common chemical and

trace elements 

M f all or most of physical, common chemical,

trace elements, and sanitary 

N, nitrates 

P f combination of physical, common chemical,

and trace elements 

Z, other, not known

Monitoring reason;

1. public supply

2. base line data

3. saltwater intrusion

4. ground-water flow tracing

5. known contaminated

6. wastewater injection

7. SW/GW relations

8. nearby feed lot

9. nearby radioactive source

10. agricultural area

11. required by law

12. known dischargers

13. migration between aquifers

Well

Monitoring

Well No. class Type Reason

Well

Monitoring

Well

Monitoring

Well No. class Type Reason Well No. class Type Reason

Network Ql. U.S. Geological Survey (5000) 

[Total well count, 5]

13S/2E-29M2 

33R1

1 

3

B 

B

2 

2

14S/3E-18J1 

15S/2E-01Q1

2 

3

B 

B

2 

2

16S/5E-17R1 3 B 2

Network Q2. U.S. Army Health Service (USAHS) 

[Total well count, 2]

15S/2E-02N1 15S/2E-10A1 M

Network Q3a. Monterey County Flood Control and Water Conservation District (5115)

Summer network, monthly analyses (May-Sept.)

[Total well count, 52]

13S/2E-33R1

14S/2E-03R1

10R1

13S/2E-20J1 

20M2 

20P2 

21N1 

29C2 

29C4 

29D3 

29F2 

30H1

14S/3E-06R1 

15H3 

24R1 

25L2

Pressure area, 180-foot aquifer 

[Well count, 9]

14S/2E-14L1 4 B 3

16E2 4 B 3

14S/3E-31F1 3 B 3

Pressure area, 400-foot aquifer 

[Well count, 27]

13S/2E-30J1 

31D2 

31N2 

31P1 

32A1 

32A2 

32C1 

32E3 

32J3

East Side area 

[Well count, 10]

15S/3E-12E2 2 B

15S/4E-06R1 2 B

7R1 3 B

15S/2E-01Q1

2J1

15S/3E-16M1

13S/2E-32N1

14S/2E-08M2

12Q1

34A1

14S/3E-18J1 

31F2

15S/3E-16B3 

15S/4E-29Q1 

16S/4E-10R2

15S/4E-22L2

16S/5E-21R1

28D1

See footnotes at end of table.

76 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif,
TABLE 10. Inventory of ground-water-quality monitoring networks--Continued

Well

Monitoring

Well

Monitoring

Well

Monitoring

Well No. class Type Reason Well No. class Type Reason Well No. class Type Reason

Network Q3a. Monterey Flood Control and Water Conservation District (5115) Continued

17S/6E-16N1

13S/2E-19Q3

13S/2E-17H3

13S/2E-28M1 

29H1 

29R1 

33R1 

35L1

14S/2E-02M1 

3F1 

3R1 

10R1 

11D1 

11G1 

13B2 

13P1 

14J1 

14N2 

21J1 

22F1 

22N1 

22P2 

22Q1 

23A1 

23P1 

24J1 

24Q1 

25F1 

26C1 

26N3 

26P1 

27K1 

35G1 

35Q1 

36E1 

36H1 

36R1

14S/3E-19Q2 

29G2

Forebay area 

[Well count, 2]

17S/6E-19D1 3 B 3

Pressure area, deep aquifer 

[Well count, 2]

14S/2E-06L1 1 B 3

El Toro Creek basin 

[Well count, 2]

13S/2E-17J1 B

Network Q3b. Monterey Flood Control and Water Conservation District (5115)

Summer network, annual analyses

[Total well count, 366]

Pressure area, 180-foot aquifer 

[Well count, 107]

14S/3E-29L4 

30E1 

30F1 

30F2 

30N1 

31B1 

31F1

15S/2E-01K1

2Q1

12C1

12E2

15S/3E-05N1

5R1

6A3

7E1

7N1

8C1

9B1

9C1

9H1

9H2

9K1

10P1

10P3

10R2

13N1

14C1

14G1

14H1

14R1

15L1

16M1

17B1

17B2

17G1

18B1

15S/3E-21A1 

22F1 

22G1 

23E1 

25L1 

25Q1 

26D1 

26H2 

28G1 

35B5

15S/4E-32D2 

32E1

16S/4E-08J1 

9A1 

13K1 

14A1 

15D1 

15H2 

24A1 

25K1 

25Q1 

27G1 

36B1

16S/5E-19F1 

19R1 

30C1 

30E1 

30G1 

31A1 

31Q1 

32B2 

32C1 

32E1 

32M1

17S/4E-01D1

Ground-Water Networks 77
TABLE 10. Inventory of ground-water-quality monitoring networks Continued

Well

Monitoring

Well

Monitoring

Well

Monitoring

Well No. class Type Reason Well No. class Type Reason Well No. class Type Reason

Network Q3b. Monterey Flood Control and Water Conservation District (5115) Continued

13S/2E-20J1 

27L1 

27M1 

27P1 

28B1 

29C2 

29C4 

29D3 

29F2 

29J1 

29M2 

30H1 

30J1 

31D2 

31N2 

31P1 

32A1 

32A2 

32C1 

32E3 

32J3 

32N1 

33H3 

33N3

14S/2E-03M2 

4B1 

4E2 

5C2 

5F4 

5G2 

5K1 

5K2 

5P2

13S/3E-02N1

14S/3E-02E3

3K1

4E1

4N1

5B2

6L1

6L2

7A1

10F2

10F3

10P1

10Q1

10R2

11H1

12E1

14D1

16E1

16G1

16K2

17D1

Pressure area, 400-foot aquifer 

[Well count, 98]

2 15S/2E-01A3 1 B 2

2 2G1 2 B 2

2 12A1 2 B 2

2 15S/3E-04K3 2 B 2

2 4N3 2 B 2

2 6D2 2 B 2

2 6F2 1 B 2

2 6K1 3 B 2

2 7D2 3 B 2

2 7G1 3 B 2

2 8B4 1 B 2

2 8C6 2 B 2

2 8F1 2 B 2

2 8F7 1 B 2

2 8N3 2 B 2

2 15B1 2 B 2

2 16B3 1 B 2

2 18F1 2 B 2

2 15S/4E-29D1 3 B 2

2 29Q1 3 B 2

2 16S/4E-02Q3 2 B 2

2 4C1 2 B 2

2 10K1 2 B 2

2 10R2 2 B 2

2 11E2 2 B 2

2 12M1 3 B 2

2 13D1 2 B 2

2 14M1 2 B 2

2 14M2 2 B 2

2 24R1 4 B 2

2 25A1 2 B 2

2 16S/5E-30J2 4 B 2 

2

2 15S/4E-08L1 3 B 2

2 8N1 3 B 2

2 9N1 4 B 2

2 15D2 1 B 2

2 15P2 4 B 2

2 16D1 3 B 2

2 17B1 3 B 2

2 17P2 2 B 2

2 18L1 4 B 2

2 19D2 2 B 2

2 19H3 1 B 2

2 20B2 2 B 2

2 21B1 4 B 2

2 22J1 3 B 2

2 22L2 3 B 2

2 23M1 3 B 2

2 26G1 2 B 2

2 27G1 3 B 2

2 28C1 3 B 2

2 33A1 2 B 2

2 34G1 4 B 2

14S/2E-06B1

6J3

6R2

7F2

7K1

8A1

8C3

8M2

9L2

9N1

10C1

12Q1

15A1

15P1

16H1

17B2

24E1

24P2

25D3

26J3

28H2

34A1

34B3

35L2

36G1

36J2

14S/3E-18J1

20D1

28B2

28F2

30E3

31F2

31Q2

East

[Well

14S/3E-22A1

24H1

24N1

36A1

14S/4E-30N1

31F1

15S/3E-01L1

12E2

13 J2

26A1

26P1

27J1

28B2

15S/4E-05K1

5M1

6D4

6R1

7A1

7E2

7R1

8C1

4

1

1

1

3

1

1

1

1

1

1

2

1

2

1

2

2

2

2

4

2

2

2

1

2

2

2

2

2

2

2

2

2

Side

count

2

2

3

3

2

4

3

2

2

1

2

2

4

2

3

2

2

2

1

3

3

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

area

, 78]

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

78 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 10. Inventory of ground-water-quality monitoring networks Continued

Monitoring 

Well 

Well No. class Type Reason

Well

Monitoring

Well

Monitoring

Well No. class Type Reason Well No. class Type Reason

Network Q3b. Monterey Flood Control and

15S/4E-36H1

36P1

36R2

16S/4E-01L1

16S/5E-05N1

2

4

2

1

2

B

B

B

B

B

2

2

2

2

2

East Side

16S/5E-07G1

8F1

8Q1

17P1

17R1

Water Conservation District (5115) Continued

area Continued

2

4

4

2

2

B

B

B

B

B

2

2

2

2

2

16S/5E-20G2

27G1

27Q1

28D1

28P1

3

2

4

2

4

B

B

B

B

B

2

2

2

2

2

16S/5E-33F1 

33Q1 

35C1

17S/5E-01Q1 

2N4 

3B1 

4C1 

4K1 

4N1 

5G1 

6Q1 

9G1 

9Q1 

10A1 

10Q1

13S/1E-36J1 

13S/2E-19Q3

16S/2E-03A1 

3G1 

3H1 

3J1 

3J3 

4H1

15S/2E-24J1

16S/2E-01E1

1L1

1M1

13S/2E-15M1 

16D1

Forebay area 

[Well count, 45]

17S/5E-12E1 

12P3 

14D1 

14G1 

21A1 

23L1 

25L1 

36F2 

36J1

17S/6E-16N1 

17R1 

18G1 

19D1 

20K1 

20Q2

Pressure area, deep aquifer 

[Well count, 4]

13S/2E-32E5 1 B 2

El Toro Creek basin 

[Well count, 34]

Corral de Tierra

16S/2E-04L1 

10H1 

10Q1 

10Q2 

10Q3 

15F2

San

16S/2E-02D1 

2G1 

2H1 

12G1

1 B 

2 B 

2 B 

4 B 

4 B 

2 B

Benancio

1 B 

1 B 

1 B 

2 B

Moro Cojo 

13S/2E-17H3 4 B

17S/6E-20Q3 

27E3 

28B1 

28N1 

29C1 

29K1 

29Q1 

30F1 

32J2 

35F1 

35J1

18S/6E-05H1 

6M1 

7A1 

8R1

13S/2E-32M2

16S/2E-15J1 

15P1 

24C1 

24J1

16S/3E-17N1 

19L2

16S/3E-07L1

7N1

7N2

17F2

13S/2E-17J1

Ground-Water Networks 79
TABLE 10. Inventory of ground-water-quality monitoring networks Continued

Well

Monitoring

Well

Monitoring

Well

Monitoring

Well No. class Type Reason Well No. class Type Reason Well No. class Type Reason

Network Q4. California Department of Health Services (5060) 

[Total well count, 30]

13S/2E-28L2

33A12

33A2

14S/3E-09B1

9E1

9G22

9P3

10E3

10E4

19J1

2

4

4

2

2

4

1

2

2

1

B

P

B

P

P

P

P

B

P

I

1

1

1

1

1

1

1

1

1

1

14S/3E-19R1

26G3

26M1

26Q3

26Q4

27G32

35C2

35H2

15S/1E-23G2

15S/2E-24J32

2

1

2

2

2

4

2

2

1

4

I

P

P

P

P

P

P

P

I

P

1

1

1

1

1

1

1

1

1

1

15S/2E-25B12

25B2

25F1

16S/5E-29H1

29L1

29M12

17S/6E-21P1

28C1

28G5

28G6

4

1

1

4

1

4

4

3

1

4

P

P

P

I

I

P

P

P

I

P

1

1

1

1

1

1

1

1

1

1

Network Q5. Monterey County Department of Environmental Health (5116)

[Well count, 19]

13S/2E-20N1

13S/3E-30E1

14S/2E-01H1

14S/3E-08R1

16S/2E-03A1

4L1

9J1

1

2

2

4

2

1

1

B

P

B

B

B

P

P

1

1

1

1

1

1

1

16S/2E-12G1

12J1

14Q1

14R1

15L1

15L2

2

3

1

1

1

1

P

B

P

B

B

B

1

1

1

1

1

1

16S/2E-15R1

24G1

24G2

16S/3E-07N1

17S/5E-13A1

13B1

2

1

2

1

1

3

P

I

P

P

D

P

1

1

1

1

1

1

Network 0.6. California Regional Water Quality Control Board, Central Coast Region (8493)

[Total well count, 17]

13S/3E-15R1

27D1

14S/2E-16L1

16Q1

17J1

17J2

4

2

3

3

3

3

B

B

Z

Z

Z

Z

11

11

11

11

11

11

14S/2E-35N1

15S/2E-02B1

15S/3E-13N1

13P1

24C1

15S/4E-09L1

4

4

2

4

4

4

B

B

Z

Z

Z

B

11

11

11

11

11

11

16S/4E-24A1

25K1

16S/5E-26R1

17S/5E-14D1

17S/6E-21R1

1

1

4

4

4

B

B

B

B

B

11

11

11

11

11

Network Q7. California Water Service Company (5701) 

[Total well count, 25]

14S/3E-20F2

20L1

21E3

21L12

22D1

22E1

28M1

28M2

28M3

1

1

1

4

1

1

1

1

1

P

P

P

P

P

P

P

P

P

1

1

1

1

1

1

1

1

1

14S/3E-28N12

29P1

30R2

31L1

32B12

32N4

33G1

33Q1

4

1

1

1

4

1

1

1

P

P

P

P

P

P

P

P

1

1

1

1

1

1

1

1

14S/3E-34C1

35N1

15S/3E-03C1

3N2

3R2

5C2

5Q5

25F1

1

2

2

1

1

1

1

1

P

P

P

P

P

P

P

P

1

1

1

1

1

1

1

1

Well No.

13S/2E-31N2

32E3

32N1

32Q3

33H3

36J1

13S/3E-30P1

33Qf

Wol ncll1

class

1

2

1

1

2

1

4

4

Type

M

M

M

M

M

M

M

M

Monitoring

Reason

Network Q8. Showalter and

[Total well count

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

Monitoring

Well No.

others (1984)

, 131]

14S/2E-02M1

3M2

5F4

5P2

6J3

6R2

7F2

8C3

Wol WtzJ. 1J.

class

4

1

1

1

1

1

1

1

Type

M

M

M

M

M

M

M

M

Reason

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

See footnotes at end of table.

80 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 10. Inventory of o/round-water-quah'ty monitoring networks Continued

Well No.

14S/2E-08M2

9L2

9N1

10R1

12E1

12Q1

13P1

16E2

16H1

17B2

21L1

22P2

23F1

24E1

24P2

25D3

34A1

34B3

35L2

36E1

36G1

14S/3E-10F3

11H1

16K3

18J1

19H1

24Cf

25L2

28B2

28F2

30E1

30N1

31F2

31Q2

33G1

35H3

14S/4E-30Lf

32Gf

15S/2E-01A3

2A2

3C1

3C3

9Gf

12C2

14Af

25B2

15S/3E-03C1

4H4

5C2

5Q4

6F2

7G1

8F5

12F2

13J2

14H1

15B1

18F1

Well 

class

1

1

1

4

2

2

2

4

1

2

4

2

4

2

2

2

2

2

1

3

2

2

2

4

2

4

4

2

2

2

3

3

2

2

1

2

4

4

1

4

4

4

4

4

4

1

2

4

1

4

1

3

1

2

2

2

2

2

Monitoring

Type

Network Q8.

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

P

P

P

M

M

M,Z

M,Z

M,Z

M,Z

M,Z

P

P,Z

M,N,Z

M

M,N

M,N

M,N

M,N,Z

M,N

M,N

M,N

M,N

M,N,Z

Reason

Showalter and

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,3,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4,13

2,4

2,4

2,4

2,4,13

2,3,4,13

2,3,4,12,13

2,3,4,12,13

2,3,4,12,13

2,3,4,13

2,3,4,13

2,4

2,4,13

2,4,10,12,13

2,4,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,12,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

Well No.

Well 

class

Monitoring

Type Reason

others (1984 ) Continued

15S/3E-26H2

27J1

28G1

35B5

15S/4E-06D4

7A1

16E2

17P2

19H3

22L2

27G1

29Q1

33A1

15S/5E-30G1

30Pf

16S/3E-01Af

IGf

16S/4E-01Gf

8J1

13K1

14M2

15D1

24A1

25K1

27Ff

28Hf

28Qf

36B1

16S/5E-08F1

8Hf

9Pf

14Nf

ISLt

17Gt

17R1

27Ef

32B2

35C1

17S/5E-01Q1

3B1

4C1

6Q1

9Q1

10Q1

12P3

22Kf

24Gf

25L1

36F2

17S/6E-08Nf

20Q3

21N2

27K1

28N1

29C1

32G1

18S/6E-07A1

2

2

1

2

2

2

3

2

1

3

3

3

2

4

4

4

4

4

3

2

2

2

1

1

4

4

4

3

4

4

4

4

4

4

2

4

4

1

1

2

2

2

2

2

1

4

4

3

2

4

2

4

4

3

2

3

4

M,N,Z

M,N,Z

M,N,Z

M,N,Z

M

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

P

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M,N

M

M,N

M,N

M,N

M,N

P

P

M,N

P

M,N

P

P

P

M,N,HM,C

M,N,HM,C

M,N,HM,C

M,N,HM,C

M,N,HM,C

M,N,HM,C

M,N,HM,C

2,4,12,13

2,4,12,13

2,4,12,13

2,4,12,13

2,4,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10,12

2,4,13

2,4,10,13

2,4,10,13

2,4,10,13

2,4,10

2,4,10

2,4,10

2,4,10

2,4,10

2,4,10

2,4,10

2,4,10

2,4

2,4,10

2,4,12

2,4,12

2,4,12

2,4,12

2,4,12

2,4,10,12,13

2,4,12

2,4,12

2,4,12

2,4

2,4,12

2,4,12

2,4,10

2,4,10

2,4

2,4

2,4,12

2,4

2,4,12

2,4

2,4

2 4

2^4,10,12

2,4,10,12

2,4,12

2,4,10,12

2,4,10,12

2,4,10,12

2,4,10,12

Ground-Water Networks 81
TABLE 10. Inventory of ground-water-quality monitoring networks Continued

Well No.

Well 

class

Monitoring

Type Reason Well No.

Well 

class

Monitoring

Type Reason

Network Q9. Burau and others (1981) Monterey Basin Pilot Monitoring Project

[Total well count, 63]

13S/2E-28L2

33A1

33A2

14S/2E-08M2

12Q1

13P1

36G1

14S/3E-04E1

9B1

9E1

9G2

9P3

10E3

10E4

19J1

19R1

20F2

20L1

21E3

21L1

22D1

22E1

25L2

26D2

26M1

26Q3

26Q4

27G3

28M2

28M3

28N1

30R2

2

4

4

1

2

2

2

3

2

2

4

1

2

2

1

2

1

1

1

4

1

1

2

4

2

2

2

4

1

1

4

1

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M f N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M f N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

14S/3E-31L1

32B1

32N4

33G1

33Q1

34C1

35C2

35H2

35N1

15S/3E-03C1

3N2

3R2

5C2

5Q5

13N1

17P1

25F1

15S/4E-26G1

16S/4E 2 wells

3Q1

16S/5E-17P1

29H1

29M1

17S/5E-14D1

36F2

17S/6E-07Q1

21P1

28C1

28G5

28G6

1

4

1

1

1

1

2

2

2

2

1

1

1

1

2

4

1

2

4

4

2

1

4

4

2

4

4

3

1

4

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

M,N,HM,Z

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

1,2,10

iNo wells were sampled as of 1987 by the U.S. Geological Survey (Gall Keeter, U.S. Geological Survey, 

oral commun., 1987).

2Well shown on the California Department of Health Services (CDHS) retrieval dated November 21, 1983, 

which was received from the California State Water Resources Control Board, Data Management Department 

which maintains the computer files for CDHS. All other wells in Networks Q4-Q7 came from C.D. Farrar 

and F.M. Glenn (U.S. Geological Survey, written commun., 1980).

82 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 11. WeZZ summary and cross-reference to wells in ground-water networks

[Complete well number is given where available. Dagger (t) indicates that area within section has been proposed for the location 

of a monitoring well. An inspection of well-log files and a field canvass are needed to determine if suitable wells exist in 

these locations. Network numbers starting with "L" indicate ground-water-level networks from table 8. Network numbers starting 

with "Q" indicate ground-water-quality networks from table 10. Well classes were determined for each well based on the availability of information for each well (see table 7). All official State well numbers in Monterey County are assigned by Monterey 

County Flood Control and Water Conservation District. , no data available]

Monterey County Flood Control and Water Conservation District 

autumn water-level networks:

Lla, Pressure area, 180-foot aquifer

Lib, Pressure area, 400-foot aquifer

Lie, East Side area

Lid, Forebay area

Lie, Pressure area, deep aquifer

Llf, El Tore Creek basin

Monterey County Flood Control and Water Conservation District 

monthly water-level networks:

L2a, Pressure area, 180-foot aquifer

L2b, Pressure area, 400-foot aquifer

L2c, East Side area

L2d, Forebay area

L2e, Pressure area, deep aquifer

L2f, El Toro Creek basin

Monterey County Flood Control and Water Conservation District 

August water-level networks:

L3a, Pressure area, 180-foot aquifer 

L3b, Pressure area, 400-foot aquifer

U.S. Geological Survey:

L4, Stream channel/aquifer response network

Ql, Baseline data network, part of Statewide network

U.S. Army Health Service: 

Q2, Public supply network

Monterey County Flood Control and Water Conservation District 

water-quality networks:

Q3a, Summer network, monthly analyses

Q3b, Summer network, annual analyses

Q4, California Department of Health Services

Department of Health Services public supply networks:

Q5, Monterey County Department of Environmental Health,

public health network 

Q6, California Regional Water Quality Control Board, Central

Coast Region, discharger network

Q7, California Water Service Company, public supply network 

Q8, Showalter and others (1984) Salinas Valley network 

Q9, Burau and others (1981) Monterey Basin Pilot Monitoring

Project

Well 

No.

Well 

class

Network Nos. 

(tables 8 and 10)

Local 

identification

Well 

No.

Well 

class

Network Nos. 

(tables 8 and 10)

Local 

identification

13S/1E-36J1

13S/2E-15M1 

16D1 

17H3 

17J1 

19H1 

19Q3 

19R1 

20J1 

20M2 

20N1 

20P2 

21N1 

26L1 

27L1 

27M1 

27P1 

28B1 

28L2 

28M1 

29C2 

29C4 

29D3 

29F2 

29H1 

29J1 

29M2 

29R1 

30A1 

30H1 

30J1 

30Q2 

31A2 

31D2 

31G4 

31N2 

31P1 

32A1 

32A2 

32C1

Lle,L2e,Q3b Moss Landing 13S/2E 

Harbor District 

well

4

4

4

2

2

1

1

3

1

1

1

1

3

4

3

2

1

2

3

1

1

1

1

1

2

1

4

1

4

4

2

1

1

1

1

2

3

2

1

Q3b

Q3b

Q3a

Q3a

Lib

Lie

Lib

Lib

Q3a

Q5

Q3a

Lib

L3b

Lla

Lla

Lib

Q3b

L3a

Q3b

Lib

Q3a

Lib

Lib

Q3b

Q3b

Lib

Lla

Lib

Lib

Q3a

Lib

L2e

Lib

Lib

Lib

Lib

Q3a

Lib

Lib

,Q3b

,Q3b

,L3b

,L2e

,L3b

,L3b

,L2b

,L3a

,L3a

,Q3b

,Q4,

,L3b

,Q3b

,Q3a

,L3b

,Q1,

,Q3b

,L2b

,L3b

,Q3b

,L3b

,L3b

,L2b

,L3b

,Q3b

,L2b

,Q3a

,Q3a

,Q3a

,L3b

,Q3b

,Q3b

Q9

,Q3a

,Q3b

,Q3a

Q3b

,L3b

,Q3a

,Q3a

,L3b

,Q3a

,L3b

,Q3b

,Q3b

,Q3b

,Q3a

,Q3b

,Q3b

,Q3b

,Q3b

,Q3a,Q3b

,Q3b

,Q3a,Q3b

32E3 

32E5 

32J3 

32M2 

32N1 

32Q3 

33A1 

33A2 

33H3 

33N3 

33R1 

34G1 

34M1 

35L1 

36F1 

36J1

13S/3E-02N1 

15R1 

27D1 

30E1 

30P1 

33Qt 

35N1

14S/2E-01H1 

2M1 

3C1 

3F1 

3K1 

3K2 

3L1 

3M2 

3R1 

4A1 

4B1 

4E2 

4H1 

4R1 

5C2 

5F4 

5G2 

5K1 

5K2 

5P2

Llb,Q3a,Q3b,Q8

Lle,L2e,Q3b

Llb,L3b,Q3a,Q3b

Q3b

Q3a,Q3b,Q8

Q8

Q4,Q9

Q4,Q9

Q3b,Q8

Llb,L3b,Q3b

Lla,L2a,L3a,Ql,Q3a,Q3b

L3b

L3b

Lla,L3a,Q3b

Lie

Q8

Q3b

Q6

Q6

Q5

Lie

Q5

Q3b,Q8

Lla,L3a

Lla,L3a,Q3b

Lla,L3a

Llb,L3b

L3a

Llb,L3b,Q3b,Q8

Lla,L2a,L3a,Q3a,Q3b

Lla,L3a

Llb,L3b,Q3b

Q3b

Llb,L3b

Lla,L3a

Llb,L3b,Q3b

Llb,L3b,Q3b,Q8

Q3b

Llb,L3b,Q3b

Q3b

Llb,L3b,Q3b,Q8

No. 1 

No. 2

Ground-Water Networks 83
TABLE 11. Wen summary and cross-reference to wells 

in ground-water networks Continued

Well Well 

No. class

14S/2E-06B1

6J3

6L1

6R2

7F2

7K1

7L3

8A1

8C3

8M2

9L2

9N1

10C1

10K1

10P1

10R1

11D1

11G1

12E1

12Q1

13B2

13P1

14E1

14J1

14L1

14N2

15A1

15B1

15G1

15H1

15P1

16E2

16H1

16L1

16Q1

17A1

17B2

17J1

17J2

18E1

21J1

21L1

22F1

22N1

22P2

22Q1

23A1

23F1

23L1

23P1

24E1

24J1

24P2

24Q1

25D3

25F1

26C1

26J3

26N3

26P1

27G2

27G3

27K1

28H2

34A1

34B1

34B3

35G1

35L2

4

1

1

1

1

3

4

1

1

1

1

1

1

3

4

4

3

3

2

2

1

2

2

4

4

2

1

1

4

4

2

4

1

3

3

4

2

3

3

4

4

4

3

3

2

4

3

4

3

3

2

3

2

3

2

3

3

4

2

3

3

1

1

2

2

3

2

3

1

Network Nos. 

(tables 8 and 10)

Q3b

Llb,L3b,Q3b,Q8

Lle,L2e,Q3a

Q3b,Q8

Q3b,Q8

Llb,L3b,Q3b

Lib

Q3b

Llb,L3b,Q3b,Q8

Llb,L2b,L3b,Q3a,Q3b

Q8,Q9

Q3b,Q8

Q3b,Q8

Llb,L3b,Q3b

Lla,L3a

Lla,L3a

Lla,L3a,Q3a,Q3b,Q8

Q3b

Lla,L3a,Q3b

Q8

Llb,L2b,Q3a,Q3b,Q8,Q9

Lla,L3a,Q3b

Q3b,Q8,Q9

Lla,L3a

Q3b

Lla,L2a,L3a,Q3a

Q3b

L3b,Q3b

Lib

Lla,L3a

L3a

Llb,L3b,Q3b

Lla,L3a,Q3a,Q8

Q3b,Q8

Q6

Q6

Lla,L3a

Llb,L3b,Q3b,Q8

Q6

Q6

Lie

Lla,L3a,Q3b

Lla,Q8

Lla,L3a,Q3b

Lla,Q3b

Lla,L3a,Q3b,Q8

Q3b

Lla,L3a,Q3b

Q8

Lla

Q3b

Q3b,Q8

Lla,L3a,Q3b

Q3b,Q8

Q3b

Q3b,Q8

Q3b

Q3b

Llb,L3b,Q3b

Q3b

Lla,L3a,Q3b

Lla,L3a

Lib

Q3b

Lla,Q3b

Llb,L2b,L3b,Q3a,Q3b,Q8

Lla,L3a

Llb,Q3b,Q8

Q3b

Llb,Q3b,Q8

Local Well 

identification No.

--

--

__

14S/2E-35N1

35Q1

36E1

36G1

36H1

36J2

36R1

14S/3E-02E3

3K1

4E1

4N1

4Q1

5B2

6L1

6L2

6R1

7A1

8C1

8R1

9B1

9E1

9F3

9G2

9P3

10E3

10E4

10F2

10F3

10P1

10Q1

10R2

11H1

12E1

14C1

14D1

14N1

15C1

15H3

16D1

16E1

16G1

16K2

16K3

17D1

18J1

19G1

19H1

19J1

19Q2

19R1

20D1

20F2

20L1

21E3

21L1

22A1

22D1

22E1

24Ct

24H1

24N1

24R1

25L1

25L2

26D2

26G3

26M1

26Q3

26Q4

Well 

class

4

4

3

2

4

2

4

3

3

3

3

4

3

3

2

3

2

3

4

2

2

2

4

1

2

2

3

2

3

2

2

2

2

3

3

3

3

2

3

2

2

4

4

4

2

3

4

1

3

2

2

1

1

1

4

2

1

1

4

2

3

4

3

2

4

1

2

2

2

Network Nos. 

(tables 8 and 10)

Q6

Q3b

Lla,L3a,Q3b,Q8

Llb,Q3b,Q8,Q9

Q3b

Q3b

Q3b

Llc,Q3b

Llc,Q3b

Llc,Q3b,Q9

Llc,Q3b

Lie

Llc,Q3b

Llc,Q3b

Llc,Q3b

Llc,L2c,Q3a

Llc,Q3b

Lie

Q5

Q4,Q9

Q4,Q9

L2c

Q4,Q9

Q4,Q9

Q4,Q9

Q4,Q9

Q3b

Llc,Q3b,Q8

Q3b

Llc,Q3b

Llc,Q3b

Llc,Q3b,Q8

Llc,Q3b

Lie

Q3b

Lie

Lie

Llc,L2c,Q3a

Lie

Llc,Q3b

Q3b

Q3b

Q8

Q3b

Llb,L2b,Ql,Q3a,Q3b,Q8

Lla,L3a

Q8

Q4,Q9

Lla,L3a,Q3b

Q4,Q9

Q3b

Q7,Q9

Q7,Q9

Q7,Q9

Q7,Q9

Llc,Q3b

Q7,Q9

Q7,Q9

Q8

Llc,Q3b

Llc,Q3b

Llc,L2c,Q3a

Lie

Llc,L2c,Q3a,Q8,Q9

Q9

Q4

Q4,Q9

Q4,Q9

Q4,Q9

Local 

identification

__

--

--

--

No. 1

--

Rider Street

Alma Street

Wiren Street

front

Wiren Street

rear

84 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 11. Well summary and cross-reference to wells 

in ground-water networks Continued

Well 

No.

14S/3E-27G2

27G3

28B2

28F2

28M1

28M2

28M3

28N1

29G2

29L4

29P1

30E1

30E3

30F1

30F2

30N1

30R2

31B1

31F1

31F2

31 LI

31Q2

32B1

32N4

33G1

33Q1

34C1

35C2

35H2

35H3

35N1

36A1

36P2

14S/4E-30Lt

30N1

30R1

31F1

32Gt

15S/1E-23G2

15S/2E-01A3

1K1

1Q1

2A2

2B1

2G1

2J1

2N1

2Q1

3C1

3C3

9Gt

10A1

12A1

12C1

12C2

12E2

14At

24J1

24J3

25B1

25B2

25F1

15S/3E-01L1

2Q1

3C1

3N2

3R2

4H4

4K3

4N3

5C2

Well 

class

3

4

2

2

1

1

1

4

1

1

1

3

2

4

2

3

1

3

3

2

1

2

4

1

1

1

1

2

2

2

2

3

2

4

2

3

3

4

1

1

3

3

4

4

2

4

4

3

4

4

4

4

2

3

4

2

4

4

4

4

1

1

3

3

2

1

1

4

2

2

1

Network Nos. 

(tables 8 and 10)

Lie

Q4,Q9

Q3b,Q8

Q3b,Q8

Q7

Q7,Q9

Q7,Q9

Q7,Q9

Q3b

Q3b

Q7

Q3b,Q8

Q3b

Q3b

Q3b

Lla,L3a,Q3b,Q8

Q7,Q9

Q3b

Lla,L2a,L3a,Q3a,Q3b

Llb,L2b,Q3a,Q3b,Q8

Q7,Q9

Q3b,Q8

Q7,Q9

Q7,Q9

Q7,Q8,Q9

Q7,Q9

Q7,Q9

Q4.Q9

Q4,Q9

Q8

Q7,Q9

Llc,Q3b

Lie

Q8

Llc,Q3b

Lie

Llc,Q3b

Q8

Q4

Llb,Q3b,Q8

Q3b

Lla,L2a,L3a,Ql,Q3a

Q8

Q6

Llb,Q3b

Lla,L2a,L3a,Q3a

Q2

Q3b

Q8

Q8

Q8

Q2

Llb,Q3b

Q3b

Q8

Lla,Q3b

Q8

Q3b

Q4

Q4

Q4,Q8

Q4

Q3b

Lie

Q7,Q8,Q9

Q7,Q9

Q7,Q9

Q8

Llb,Q3b

Q3b

Q7,Q8,Q9

Local Well 

identification No.

35S/3E-05N1

East Laurel 5Q4

Drive 5Q5

5R1

6A3

6D2

6F2

6K1

1-04 7C1

7D2

7E1

7G1

7N1

8B4

8C1

8C6

8F1

8F5

8F7

8N3

9B1

9C1

9E3

9H1

9H2

9K1

10P1

10P3

Williams Road 10R2

Bardin Road 12E2

12F2

13G4

13J2

13N1

13P1

14C1

14G1

14H1

14R1

15B]

15L1

16B3

16M1

17B1

17B2

17G1

17P1

18B1

18C2

18F1

18M2

21A1

22F1

22G1

23E1

24C1

25F1

25L1

25Q1

S-l 26A1

Toro Park 26D1

26F1

26H2

26P1

27J1

28B1

28B2

28G1

35B5

15S/4E-05C1

5K1

5M1

Well 

class

4

4

1

3

4

2

1

3

2

3

4

3

3

1

3

2

2

1

1

2

3

4

2

3

3

3

3

3

3

2

2

4

2

2

4

3

3

2

3

2

3

1

3

3

4

3

4

3

2

2

2

2

3

4

3

4

1

2

4

1

4

2

2

2

2

4

4

1

2

2

2

3

Network Nos. 

(tables 8 and 10)

Q3b

Q8

Q7,Q9

Q3b

Q3b

Llb,L3b,Q3b

Q3b,Q8

Llb,23b

L2a

Q3b

Q3b

Llb,Q3b,Q8

Q3b

Q3b

Q3b

Q3b

Llb,Q3b

Q8

Q3b

Llb,Q3b

Q3b

Q3b

Lla

Q3b

Q3b

Q3b

Q3b

Q3b

Q3b

Llc,L2c,Q3a,Q3b

Llc,Q8

Lie

Q3b,Q8

Lla,Q3b,Q6,Q9

Q6

Lla,Q3b

Q3b

Q3b,Q8

Q3b

Llb,Q3b,Q8

Q3b

Llb,L2b,Q3a,Q3b

Lla,L2a,Q3a,Q3b

Q3b

Q3b

Q3b

Q9

Lla,Q3b

Lla

Llb,Q3b,Q8

Lib

Q3b

Q3b

Lla,Q3b

Q3b

Q6

Q?,Q9

Q3b

Lla,L2a,Q3b

Q3b

Q3b

Lla

Q3b,Q8

Q3b

Q3b,Q8

Lib

Q3b

Q3b,Q8

Q3b,Q8

Lie

Q3b

Llc,Q3b

Local 

identification

--

--

--

Ground-Water Networks 85
TABLE 11. Well summary and cross-reference to -wells 

in ground-water networks Continued

Well 

No.

15S/4E-06D4

6R1

7A1

7E2

7R1

7R2

8C1

8L1

8N1

8Q1

9D1

9J1

9L1

9M1

9N1

14N1

15D2

15P2

16D1

16E2

17B1

17P2

18L1

19D2

19H3

20B2

21B1

21F4

21L2

22J1

22L2

23M1

24N3

26G1

27G1

28C1

29D1

29Q1

29R1

31A2

32D2

32E1

33A1

34G1

34L1

36H1

36P1

36R2

15S/5E-30G1

30Pt

16S/2E-01E1

1L1

1M1

2D1

2D2

2D3

2D5

2G1

2H1

3A1

3G1

3H1

3J1

3J3

4H1

4L1

9H1

9J1

10B1

10H1

Well 

class

2

2

2

1

3

2

3

3

3

3

3

3

4

2

4

2

1

4

3

3

3

2

4

2

1

2

4

2

3

3

3

3

2

2

3

3

3

3

2

2

2

4

2

4

2

2

4

2

4

4

2

1

1

1

2

3

1

1

1

2

1

2

3

4

1

1

4

1

2

2

Network Nos. 

(tables 8 and 10)

Q3b,Q8

Llc,L2c,Q3a,Q3b

Llc,Q3b,Q8

Q3b

Llc,L2c,Q3a,Q3b

L2c

Llc,Q3b

Llc,Q3b

Llc,Q3b

Lie

Lie

Lie

Q6

Lie

Q3b

Lie

Llc,Q3b

Llc,Q3b

Llc,Q3b

Llc,Q8

Q3b

Llc,Q3b,Q8

Q3b

Llb,Q3b

Q3b,Q8

Llc,Q3b

Q3b

Lie

Llc,L2c

Q3b

Llc,L2c,Q3a,Q3b,Q8

Q3b

Lie

Q3b,Q9

Llc,Q3b,Q8

Q3b

Llb,Q3b

Llb,L2b,Q3a,Q3b,Q8

Lib

Lla

Q3b

Q3b

Llc,Q3b,Q8

Q3b

Lie

Llc,Q3b

Llc,L2c,Q3b

Llc,Q3b

Q8

Q8

Llf ,Q3b

Llf,Q3b

Llf ,Q3b

Llf ,L2f,Q3b

Llf

Llf

Llf

Llf ,L2f ,Q3b

Llf ,L2f ,Q3b

Llf ,Q3b,Q5

Llf ,Q3b

Llf ,Q3b

Llf,Q3b

Q3b

Llf ,Q3b

Llf ,Q3b,Q5

Llf

Llf,Q5

Llf

Llf ,Q3b

Local Well Well 

identification No. class

--

--

16S/2E-10Q1

10Q2

10Q3

12G1

12J1

14Q1

14R1

15F2

15J1

15L1

15L2

15P1

15R1

17N1

23H1

24C1

24G1

24G2

24J1

16S/3E-OlAt

IGt

7L1

7N1

7N2

17F2

17N1

19L1

19L2

16S/4E 2 wells

IGt

1L1

2Q3

3Q1

4C1

5M2

8B1

8J1

9A1

10K1

10R2

11E2

12M1

13D1

13H1

13K1

13R2

14A1

14M1

14M2

15D1

15H2

15R2

16E1

24A1

24C1

24R1

25A1

25C1

25G1

25K1

25P1

25Q1

27B2

27Ft

27G1

28Ht

28Qt

36B1

16S/5E-05N1

7G1

8F1

2

4

4

2

3

1

1

2

2

1

1

2

2

2

4

3

1

2

1

4

4

2

1

2

3

2

4

4

4

4

1

2

4

2

2

4

3

2

2

2

2

3

2

3

2

2

4

2

2

2

2

2

3

1

3

4

2

4

4

1

3

3

3

4

3

4

4

3

2

2

4

Network Nos. 

(tables 8 and 10)

Llf ,L2f ,Q3b

Llf ,Q3b

Q3b

Q3b,Q5

Q5

Q5

Q5

Llf ,Q3b

Llf ,L2f ,Q3b

Q5

Q5

Llf ,Q3b

Q5

L2f

Llf

Llf,Q3b

Q5

Q5

Q3b

Q8

Q8

Llf ,Q3b

Llf ,Q3b,Q5

Q3b

Llf ,Q3b

Llf ,Q3b

Llf

Llf ,Q3b

Q9

Q8

Llc,Q3b

Llb,Q3b

Q9

Llb,Q3b

Lla

Lla

Lla,Q3b,Q8

Lla,Q3b

Q3b

Llb,L2b,Q3a,Q3b

Q3b

Q3b

Q3b

Lla

Q3b,Q8

Lla

Q3b

Q3b

Q3b,Q8

Lla,Q3b,Q8

Q3b

Lla

Lla

Q3b,Q6,Q8

Lla

Q3b

Q3b

Lla

Lib

Q3b,Q6,Q8

Lla

Q3b

Lla

Q8

Q3b

Q8

Q8

Q3b,Q8

Llc,Q3b

Llc,Q3b

Q3b,Q8

Local 

identification

--

--

--

Chualar wells

--

--

86 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
TABLE 11. WeH summary and cross-reference to wells 

in ground-water networks Continued

Well 

No.

16S/5E-08Ht

8Q1

9Pt

14Nt

15Lt

17Gt

17P1

17R1

19F1

19R1

20G2

20R1

21R1

26R1

27Et

27G1

27Q1

28D1

28P1

29H1

29L1

29M1

30C1

30E1

30G1

30J2

31A1

31M1

31Q1

32B2

32C1

32E1

32H2

32M1

33F1

33Q1

35C1

17S/4E-01D1

17S/5E-01Q1

2N2

2N4

3B1

3L1

4C1

4K1

4N1

4R1

5G1

6Q1

8L1

9G1

9Q1

9R1

10A1

10Q1

Well 

class

4

4

4

4

4

4

2

3,2

4

3

3

2

3

4

4

2

4

2

4

1

1

4

3

4

3

4

4

4

3

2

4

4

2

3

2

3

1

3

1

2

4

2

2

2

4

2

2

4

2

3

3

2

3

3

2

Network Nos. 

(tables 8 and 10)

Q8

Llc,L2c,Q3b

Q8

Q8

Q8

Q8

Llc,Q3b,Q9

Llc,Ql,Q3b,Q8

Lla,Q3b

Q3b

Llc,Q3b

Llc,L2c

Llc,Q3a

Q6

Q8

Q3b

Llc,L2c,Q3b

Llc,L2c,Q3a,Q3b

Llc,Q3b

Q4,Q9

Q4

Q4,Q9

Q3b

Lla,L2a,Q3b

Q3b

Llb,Q3b

Lla,Q3b

Lla

Lla,Q3b

Lla,Q3b,Q8

Lla,Q3b

Lla,Q3b

Lid

Lld,Q3b

Q3b

Lld,Q3b

Q3b,Q8

Lla,Q3b

Lld,Q3b,Q8

Lid

Lld,L2d,Q3b

Q3b,Q8

Lld,L2d

Q3b,Q8

Lld,Q3b

Lld,Q3b

Lid

Lld,L2d,Q3b

Lld,Q3b,Q8

Lid

Q3b

Q3b,Q8

Lid

Q3b

Lld,Q3b,Q8

Local well 

identification NO.

17S/5E-12E1

12P3

13A1

13B1

13E1

14D1

14G1

21A1

22Kt

23Ft

23L1

24Gt

24G1

25L1

27A1

36F2

36J1

17S/6E-07Q1

08Nt

16N1

17R1

18G1

19D1

20E2

20K1

20Q2

20Q3

21N2

21P1

21R1

27E3

27K1

28B1

28C1

28G5

28G6

28K1

28N1

29C1

29K1

29Q1

30F1

32G1

32J2

34E1

35F1

35J1

18S/6E-02N1

5H1

5R2

6M1

7A1

8R1

9M1

9M2

Well 

class

1

1

1

3

4

4

2

2

4

2

4

4

3

2

2

4

4

4

2

4

2

3

2

2

2

2

4

4

4

2

4

4

3

1

4

3

3

2

3

2

3

3

2

4

4

4

2

4

4

4

4

4

3

2

Network Nos. 

(tables 8 and 10)

Lld,Q3b

Q3b,Q8

Q5

Q5

Lid

Lld,Q3b,Q6,Q9

Q3b

Lld,Q3b

Q8

L4 (5 wells)

Q3b

Q8

Lid

Lld,Q3b,Q8

Lid

Lld,Q3b,Q8,Q9

Lld,L2d,Q3b

Q9

Q8

Lld,L2d,Q3a,Q3b

Q3b

Lld,Q3b

Lld,L2d,Q3a,Q3b

Lid

Q3b

Q3b

Q3b,Q8

Q8

Q4,Q9

Q6

Lld,Q3b

Lld,Q8

Lld,L2d,Q3b

Q4,Q9

Q4,Q9

Q4.Q9

Lid

Q3b,Q8

Lld,Q3b,Q8

Lld,Q3b

Lld,Q3b

Lld,Q3b

Q8

Q3b

Lid

Lld,Q3b

Q3b

L2d

Q3b

Lid

Lld,L2d,Q3b

Lld,Q3b,Q8

Lld,Q3b

Lid

Lid

Local 

identification

--

--

--

The ground-water-quality monitoring program of the Monterey County Flood 

Control and Water Conservation District consists of a network of wells sampled 

monthly during the summer months (usually May to September) and a network of wells 

sampled annually during the summer. In the northern Salinas River drainage basin, 

saltwater intrusion has become an immediate and serious threat to ground-water use. 

Each year, samples are collected and a partial mineral analysis (for specific 

conductance, nitrogen nitrite, and chloride) is done monthly during the irrigation 

season to provide information on short-term trends in the water quality of this 

area (table 10) . The Pressure area 400-foot aquifer near Castroville is sampled

Ground-Water Networks 87
as part of the monthly-summer network, as are areas in the north-county part of 

the phase 2 study area. The coordination of water-level measurement along with 

water-quality sampling is important so the analyst of these data can better 

interpret their meaning. Well locations are shown in figure 9.

Additional water samples for complete mineral analyses are collected from 

some of these wells each summer to obtain a complete analysis on each well once 

every 5 years. The data from this network are used to provide information on 

the historical long-term trends in ground-water quality as shown by concentrations of chlorides, nitrates, and other water-quality characteristics. The 

Monterey County Flood Control and Water Conservation District relies on the 

California Department of Water Resources Title 22 classification system which 

indicates the limitations of ground water for domestic and agricultural purposes? this system is based on dissolved solids, chloride, percent sodium, and 

boron concentration ranges (Bruce LaClergue, Monterey County Flood Control and 

Water Conservation District, written commun., 1988). The quality of ground 

water is represented by the Monterey County Flood Control and Water 

Conservation District (1978, p. 17) in graphs of the mean changes in specific 

conductance concentrations from all wells in each aquifer or ground-water 

basin.

The approach used by Monterey County Flood Control and Water Conservation 

District (1978, p. 20) has some limitations. For example, average water 

quality in the Pressure area, measured in specific conductance, depends on the 

specific wells sampled and may not reflect real trends. As saltwater moves 

inland, specific conductance in wells increases at a higher than normal rate 

until the wells become unusable. Sampling of abandoned, salty wells is discontinued, and graphs of average water quality may indicate an improvement. 

The apparent improvement, however, merely reflects the exclusion of wells with 

high specific conductance which thereby lowers the average specific conductance 

for the area.

Averages of water-quality characteristics, therefore, cannot be relied on 

by themselves to indicate water quality for an area. The range of values of 

water-quality characteristics and the history of wells removed from the networks also needs to be indicated in order to have adequate knowledge of the 

regional quality of ground water for that specific characteristic. The data 

published prior to Monterey County Flood Control and Water Conservation 

District's (1978) report used electrical conductivity (EC) to indicate dissolved solids. The relation between electrical conductivity and dissolved 

solids varies with space and time, depending on their local relation. Determination of electrical conductivity also varies with the temperature of the 

water at the time of measurement; for this reason, the U.S. Geological Survey 

measures specific conductance (which is electrical conductivity adjusted to 

25 °C) to obtain a more standard indicator of water quality. Until 1978, these 

factors had not been addressed in Monterey County Flood Control and Water 

Conservation District annual data reports, and pre-1978 historical EC data may 

not be comparable to post-1978 specific conductance data. Use of the proper 

instruments and methodology, therefore, is extremely important in obtaining and 

analyzing the results of water-quality samples. The District staff are aware 

of the importance of proper use of instruments and analytical procedures and 

are working to improve all aspects of their operations.

88 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
Possible Additional Monitoring

At present, the Monterey County Flood Control and Water Conservation 

District monitors 379 wells for a limited range of water-quality constituents 

on a monthly or annual basis. This study identified 135 additional wells that 

have been monitored or recommended by other networks. The saltwater-intrusion 

areas near Castroville (fig. 3) have the densest distribution of wells. In 

these areas, a few of the currently monitored wells may be selected for the 

baseline network, and sampling at these wells may be expanded to include constituents needed for the baseline network. The distribution of wells in other 

areas is more sparse. For the baseline networks, wells could be added to 

provide an even spatial distribution; the 54 sections presently lacking wells 

for such a distribution are shown in table 12. An evenly spaced grid would 

require additional wells to be monitored in these sections. Additional wells 

also would improve the accuracy of a statistical evaluation of networks. 

Replacing wells having lower classifications (less information available about 

them) with higher class wells will improve the reliability of the resultant 

information.

Historic data are available for many of the constituents of concern. A 

thorough analysis of these data may make it be unnecessary to establish additional wells in all areas. The baseline network, however, is intended to 

identify temporal as well as spatial variations in the quality of the area's 

ground water, so that at least some key wells (as suggested by Showalter 

and Hoffard, 1986) could be established that have good water-quality correlations with unmonitored wells in these areas. Periodically, the correlations 

between those wells would be rechecked to retain confidence in network adequacy. Other factors to consider are the constituents to monitor and the frequency of sampling. The ideal network calls for monitoring a broad range of 

water-quality constituents on a quarterly basis. In reality, these 

requirements may not be financially 

feasible, but unless historic data or 

adequate well correlations are available, the ideal networks should be 

approximated as closely as possible.

An approach similar to the one by 

Karubian (1974) may be a valuable supplement to conventional ground-waterquality monitoring by sampling from 

wells. Further research would be 

helpful if done to see if Karubian was 

correct in hypothesizing that trends 

in ground-water pollution may be more 

easily deduced and predicted with 

greater confidence and lower cost by 

analyzing human activities than by 

extrapolating data from water-well 

sampling.

TABLE 12. Network locations that 

presently do not have wells 

monitored for ambient waterquality conditions by the 

Monterey County Flood Control 

and Water Conservation District

Township/Range Section

T13S/R2E

T13S/R3E

T14S/R3E

T15S/R2E

T15S/R3E

T15S/R4E

T16S/R4E

T16S/R5E

T17S/R5E

T17S/R6E

8,34

31,32,34,35

1,13,23

4,11,13,26,35,36

2,11,19,20,34,36

14,24,25,30,31,35

5,6,16,21,22,23,26,34,35

6,16,18,22,23,34

7,8,11,15,16,26,27

8,9,10,22,31

Ground-Water Networks 89
SUMMARY AND CONCLUSIONS

This report presents an evaluation of water-resources data-collection 

networks for precipitation, surface water and ground water in the northern 

Salinas River drainage basin of Monterey County, California. The evaluation 

includes an inventory of active data-collection networks and a description of 

possible additional monitoring. A set of ideal networks is described that 

would meet the data needs for water management in the study area.

The study identified 34 precipitation gages in the study area, of which 20 

are active. The stations are concentrated in the northwestern part of the 

study area. Data are lacking for the eastern and southern parts of the study 

area as well as the southwestern slopes of the Gabilan Range. No 

precipitation-quality networks were identified. Possible data-collection 

efforts for precipitation quality include monitoring for acid rain and for 

pesticides in precipitation.

The study identified 10 streamflow-gaging stations, of which 6 are active. 

To meet the objectives for streamflow networks that are outlined in the report, 

all sites could be reactivated, and two of the inactive sites could be 

relocated to improve the record.

The Monterey County Flood Control and Water Conservation District samples 

one surface-water site for suspended sediment, specific conductance, and 

chlorides. Several other agencies have done water-quality sampling in the 

past, but only five sites are active, counting the District's sites. Reactivation of the 45 inactive sites would help to meet the various 

surface-water-quality objectives described in the report. Development of a 

stream-reach rating system also could help to identify parts of the study area 

most in need of sampling.

The Monterey County Flood Control and Water Conservation District maintains three networks to measure ground-water levels on a monthly basis, during 

peak irrigation, and at the end of the irrigation season. The only other 

network identified for this report was run by the U.S. Geological Survey, and 

none of its five wells are active. The District measures water levels in 318 

wells. An ideal network would have evenly spaced wells throughout the study 

area. The study identified 128 sections in which no ground-water-level monitoring presently is done. Well coverage is densest in the saltwater-intrusion 

areas near Castroville, California. Wells in the rest of the study area are 

more sparsely distributed, but they are concentrated down the center of the 

drainage in the alluvial ground-water basin.

90 Water-Resources Data-Network Evaluation, Phase 3, Monterey County, Calif.
At present, the Monterey County Flood Control and Water Conservation 

District monitors 379 wells for a limited range of water-quality constituents 

on a monthly or annual basis. This study identified 135 additional wells that 

have been monitored or recommended by other networks. For the baseline networks, wells could be added to provide an even spatial distribution; the 54 

sections presently lacking wells for such a distribution are shown in table 12. 

Replacing wells having lower classifications (less information available about 

them) with higher class wells will improve the reliability of the resultant 

information.

To develop a water-resources information system that would meet the 

objectives outlined in tables 1 and 3, a regional computerized data base could 

be created for each of the six categories of hydrologic data evaluated in this 

report to bring together historic information with new information obtained 

from active monitoring. Additional historic and new data could be gathered 

about specific existing and potential problems. These data could be collected 

from historic reports as well as monitoring networks established for each of 

the objectives identified in table 3.

Computer software packages are readily available that include statistical 

applications (such as analysis of variance, multivariate linear regression, and 

cluster analysis) for use in analyzing data adequacy. More specialized analyses (such as kriging and regional analysis with semivariograms) also can be 

made to evaluate cost effectiveness and "worth" of data, but that would include 

adapting existing computer programs to fit the specific computer hardware being 

used. The combination of temporal and financial constraints with the absence 

of a coordinated data base prohibited use of these tools in this study.

The computerized Geographic Information System (CIS) that is planned for 

Monterey County could easily use the information in this report for the needed 

initial analysis of network adequacy. The feasibility of management and 

analysis of large complicated data bases (such as the ground-water networks 

identified in this report) is substantially improved through the use of 

state-of-the-art CIS tools now available.

The ability to plot mechanically all data-collection sites from a computer 

file for each specific network objective within each basin or study area provides spatial analysis capabilities that are often too time consuming and 

costly to be done routinely by hand. The acquisition and application of computer geographic information system (CIS) software and hardware that allow 

manipulation of data files is a requirement of modern hydrologic data-network 

evaluation that needs to be considered by the Monterey County Flood Control and 

Water Conservation District.

In conclusion, hydrologic data network evaluation requires that data are 

organized properly, contain adequate information on the specific sites, and are 

maintained routinely. The existing hydrologic networks will need to be 

reevaluated when the above criteria are met.

Summary and Conclusions 91
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