Tracing Reclaimed Water in the Menifee, 

Winchester, and Perris-South Ground-Water 

Subbasins, Riverside County, California

By Charles A. Kaehler and Kenneth Belitz

Sacramento, California

2003

Water-Resources Investigations Report 03-4039

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the

EASTERN MUNICIPAL WATER DISTRICT 5009-28
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

For additional information write to:

District Chief

U.S. Geological Survey

Placer Hall—Suite2012

6000 J Street

Sacramento, CA 95819-6129

http://ca.water.usgs.gov

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286
Contents iii

CONTENTS

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

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

Background ................................................................................................................................................. 3

Purpose and Scope ...................................................................................................................................... 6

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

Methods of Sample Collection and Analysis..................................................................................... 6

Quality Control .................................................................................................................................. 7

Description of the Study Area..................................................................................................................... 7

Acknowledgments....................................................................................................................................... 8

Inorganic and Organic Tracers............................................................................................................................. 8

Inorganic Tracers ........................................................................................................................................ 9

Inorganic-Constituent Mixing Models............................................................................................... 10

Organic Tracers........................................................................................................................................... 11

Tracing Reclaimed Water in the Three Subbasins............................................................................................... 14

Menifee Subbasin........................................................................................................................................ 16

Winchester Subbasin................................................................................................................................... 25

Perris-South Subbasin ................................................................................................................................. 33

Summary and Conclusions................................................................................................................................... 44

References Cited .................................................................................................................................................. 45

Table 1.................................................................................................................................................................. 49
iv Figures

FIGURES

Figure 1. Map showing location of the Menifee, Winchester, and Perris-South ground-water subbasin 

study area, Riverside County, California........................................................................................... 4

Figure 2. Map showing selected wells and reclaimed-water storage ponds, and regional water-reclamation

facilities, in the Menifee, Winchester, and Perris-South ground-water subbasins, Riverside 

County, California ............................................................................................................................. 5

Figure 3. Graph showing example boron/chloride-ratio mixing curves based on boron/chloride ratio plotted 

against chloride and on boron/chloride ratio plotted against fraction reclaimed water..................... 12

Figure 4. Graph showing example mixing curves and hypothetical field data based on boron/chloride ratio 

plotted against chloride and on boron/chloride ratio plotted against fraction reclaimed water......... 13

Figure 5. Block diagram showingconceptual model of reclaimed-water infiltration, ground-water flow, 

and well positions .............................................................................................................................. 15

Figure 6. Diagram showing Piper trilinear plot of major-ion concentrations for samples from selected 

wells in the Menifee ground-water subbasin, Riverside County, California..................................... 17

Figure 7. Map showing Stiff diagrams for selected wells and reclaimed-water storage ponds, and the 

Sun City reclamation facility, Menifee subbasin, Riverside County, California .............................. 18

Figure 8. Map showing water-level contours, directions of ground-water flow, and wells with ultravioletabsorbance data in the Menifee subbasin, Riverside County, California .......................................... 20

Figure 9. Graph showing delta deuterium plotted against delta oxygen-18 for selected wells in the 

Menifee subbasin, Riverside County, California............................................................................... 22

Figure 10. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved organic 

carbon for selected wells in the Menifee subbasin, Riverside County, California............................ 22

Figure 11. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved chloride for 

selected wells in the Menifee subbasin, Riverside County, California.............................................. 23

Figure 12. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved boron for 

selected wells in the Menifee subbasin, Riverside County, California.............................................. 24

Figure 13. Graph showing boron/chloride ratio plotted against dissolved chloride for selected wells in 

the Menifee subbasin, California, without and with a superimposed mixing curve.......................... 25

Figure 14. Graph showing estimation of fraction reclaimed water, plotted against boron/chloride ratio, 

generated using a two-end-member mixing model for water in the vicinity of the Sun City 

storage ponds, Menifee subbasin, Riverside County, California....................................................... 26

Figure 15. Diagram showing Piper trilinear plot of major-ion concentrations for selected wells in the 

Winchester subbasin, Riverside County, California.......................................................................... 27

Figure 16. Map showing Stiff diagrams for selected wells and reclaimed-water storage ponds, and the 

Temecula reclamation facility, Winchester subbasin, Riverside County, California........................ 28

Figure 17. Map showing water-level contours, directions of ground-water flow, and wells with ultravioletabsorbance data in the Winchester subbasin, Riverside County, California ..................................... 29

Figure 18. Graph showing delta deuterium plotted against delta oxygen-18 for selected wells in the 

Winchester subbasin, Riverside County, California.......................................................................... 31

Figure 19. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved organic

carbon for selected wells in the Winchester subbasin, Riverside County, California ....................... 31

Figure 20. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved chloride for 

selected wells in the Winchester subbasin, Riverside County, California......................................... 32

Figure 21. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved boron for

selected wells in the Winchester subbasin, Riverside County, California......................................... 32

Figure 22. Graph showing Boron/chloride ratio plotted against dissolved chloride for selected wells in 

the Winchester subbasin, Riverside County California, without and with superimposed 

mixing curves..................................................................................................................................... 34
Figures v

Figure 23. Graph showing estimation of fraction reclaimed water using a two-end-member mixing model 

in the vicinity of the Winchester storage ponds, Winchester subbasin, Riverside County, 

California ........................................................................................................................................... 35

Figure 24. Diagram showing Piper trilinear plot of major-ion concentrations for selected wells in the 

Perris-South ground-water subbasin, Riverside County, California ................................................. 36

Figure 25. Map showing Stiff diagrams for selected wells and reclaimed-water storage ponds, and the

Perris Valley reclamation facility, Perris-South subbasin, Riverside County, California................. 37

Figure 26. Map showing water-level contours, directions of ground-water flow, and wells with ultravioletabsorbance data in the Perris-South subbasin, Riverside County, California ................................... 39

Figure 27. Graph showing delta deuterium plotted against delta oxygen-18 for selected wells in the 

Perris-South subbasin, Riverside County, California........................................................................ 41

Figure 29. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved chloride for 

selected wells in the Perris-South subbasin, Riverside County, California....................................... 41

Figure 28. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved organic 

carbon for selected wells in the Perris-South subbasin, Riverside County, California ..................... 41

Figure 30. Graph showing ultraviolet-absorbance at 254 nanometers plotted against dissolved boron for 

selected wells in the Perris-South subbasin, Riverside County, California....................................... 41

Figure 31. Graph showing boron/chloride ratio plotted against dissolved chloride for selected wells in 

the Perris-South subbasin, Riverside County California, without and with superimposed

mixing curves .................................................................................................................................... 42

Figure 32. Graph showing estimation of the fraction reclaimed water using a two-end member mixing model

in the vicinity of the Trumble Road storage pond, Perris-South subbasin, California...................... 43
vi Tables

TABLES

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins,

Riverside County, California ............................................................................................................ 50

Table 2. Dissolved-solids (residue on evaporation) and chloride concentrations for selected wells located 

adjacent to the Sun City Ponds, Menifee subbasin, Riverside County, California............................ 21

Table 3. Calculated percentage of reclaimed water in ground water at selected wells located adjacent to 

the Sun City Ponds, Menifee subbasin, Riverside County, California .............................................. 24

Table 4. Dissolved-solids (residue on evaporation) and chloride concentrations for selected wells

located adjacent to the Winchester Ponds, Winchester subbasin, Riverside County,

California ........................................................................................................................................... 30

Table 5. Calculated percentage of reclaimed water in ground water at selected wells located adjacent

to the Winchester ponds, Winchester subbasin, Riverside County, California ................................. 33

Table 6. Dissolved-solids (residue on evaporation) and chloride concentrations for selected wells in the 

vicinity of the reclaimed-water ponds, Perris-South subbasin, Riverside County, California .......... 40
Conversion Factors, Vertical Datum, and Abbreviations vii

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

CONVERSION FACTORS

Temperature in degrees Celsius (oC) may be converted to degrees Fahrenheit (oF) as follows:

oF=1.8 oC+32.

Specific conductance is given microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25oC).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or 

micrograms per liter (μg/L). 

VERTICAL DATUM

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. 

Altitude, as used in this report, refers to distance above or below sea level.

ABBREVIATIONS

D or 2H deuterium

DOC dissolved organic carbon

18O oxygen-18

EDTA ethylenediaminetetraacetic acid 

LAS linear alkylbenzene sulfonate 

MBAS metheylene blue activated substances 

Multiply By To obtain

acre 0.4047 hectare

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

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

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

foot (ft) 0.3048 meter

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

square foot (ft2) 0.09290 square meter

foot squared per minute(ft2/min) 0.00155 meter squared per second 

cubic foot (ft3) 0.02832 cubic meter 

gallon (gal) 3.785 liter

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

inch (in.) 2.54 centimeter

inch (in.) 25.4 millimeter

mile (mi) 1.609 kilometer

square mile(mi2) 2.590 square kilometer 
viii Conversion Factors, Vertical Datum, and Abbreviations

MCL maximum contaminant level (U.S. Environmental Protection Agency, 1990,

Drinking water regulations and health advisories)

μg/L microgram per liter

μS/cm microsiemen per centimeter at 25 oCelsius

MEQ/L milliequivalents per liter

mg/L milligram per liter

nm nanometer

RWRF regional water-reclamation facility

TOC total organic carbon 

TOX total organic halide 

UV-A ultraviolet absorbance 

Organizations

EMWD Eastern Municipal Water District

USGS U.S. Geological Survey
Well-Numbering System ix

WELL-NUMBERING SYSTEM

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

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

section number. Each section is divided into sixteen 40-acre tracts lettered consecutively (except I and O), 

beginning with "A" in the northeast corner of the section and progressing in a sinusoidal manner to "R" in the 

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

final letter refers to the base line and meridian. In California, there are three base lines and meridians; Humboldt 

(H), Mount Diablo (M), and San Bernardino (S). All wells in the study area are referenced to the San Bernardino 

base line and meridian (S) Well numbers consist of 15 characters and follow the format 005S003W024F02S. In 

this report, well numbers are abbreviated and written 5S/3W-24F2. Wells in the same township and range are 

referred to only by their section designation (for example, 24F2). The following diagram shows how the number 

for well 05S/3W-24F2 is derived.

D C B A

E F G H

M L K J

N P Q R

6 5 4 3 2 1

7 8 9 10 11 12

18 17 16 15 14

19 20 21 22 23 24

30 29 28 26 25

31 32 33 34 35 36

27

R1W R1E

T3S

T2S

T1S

R2W

RANGE

TOWNSHIP

R4W R3W

T4S

T5S

R3W

SECTION 24

T5S

BASE LINE

MERIDIAN

24 13

5S/3W-24F2

Well-numbering diagram (Note: maps in this report use abbreviated well numbers such as "24F2")
Abstract 1

Tracing Reclaimed Water in the Menifee, Winchester, 

and Perris-South Ground-Water Subbasins, Riverside 

County, California

By Charles A. Kaehler and Kenneth Belitz

ABSTRACT

As a component in the management of water 

resources in the Menifee, Winchester, and PerrisSouth subbasins in Riverside County, California, 

ponds are operated by the Eastern Municipal 

Water District for the temporary storage of 

reclaimed water that is produced by several 

regional water-reclamation facilities. A primary 

goal of this study was to evaluate the potential for 

using various ground-water constituents or 

characteristics as tracers of reclaimed water that 

has infiltrated from the storage ponds into the 

ground water in the three subbasins. A secondary 

goal was to estimate the degree to which the 

infiltrated reclaimed water has mixed with the 

native ground water. The evaluation of potential 

tracers and the estimation of mixing focused on 

data from wells located relatively close to the 

ponds. 

The most useful constituents and 

characteristics for evaluation of the fate and 

mixing of reclaimed water in the Menifee, 

Winchester, and Perris-South subbasins are majorion composition, stable isotopes of hydrogen and 

oxygen, ultraviolet absorbance (UV-A), chloride 

concentration, and boron/chloride ratio plotted 

against chloride concentration. Emphasis in this 

study was placed on evaluating the utility of UV-A 

as a tracer and boron/chloride ratios in estimating 

the fraction of reclaimed water in ground water. 

In the Menifee subbasin, major-ion data, 

stable isotopes, chloride, UV-A, and 

boron/chloride ratio are all useful in identifying 

reclaimed water, and the results based on these 

indicators are consistent with each other. The 

results suggest that values of UV-A greater than or 

equal to 0.007 indicate the presence of reclaimed 

water in the Menifee subbasin. Ground-water 

samples with UV-A greater than 0.007 are 

estimated to consist of about 75 to 100 percent 

reclaimed water, on the basis of chloride-mixing 

calculations and boron/chloride-versus-chloride 

mixing calculations.

In the Winchester subbasin, results based on 

the same factors used in the Menifee subbasin are 

less conclusive; nevertheless, UV-A can be used as 

a tracer. The results suggest that values of UV-A 

greater than 0.01 indicate the presence of 

reclaimed water. Values from 0.006 to 0.01 may 

indicate the presence of reclaimed water; however, 

water from wells not likely to have reclaimed 

water may also have UV-A values in this range. 

Ground-water samples with UV-A greater than 

0.01 seem to contain about 25 percent reclaimed 

water (range 6 to 32 percent), on the basis of the 

consistency of the results of three types of mixing 

calculations—chloride alone, boron/chloride 

versus chloride, and UV-A. 
2 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

In the Perris-South subbasin, the potential 

tracers are not as conclusive in identifying 

reclaimed water in the subsurface as in the 

Menifee and Winchester subbasins. The lessconclusive results are a consequence of the 

multiple, spatially distributed sources of reclaimed 

water; the relative absence of wells close to the 

reclaimed-water pond; and the short period of 

operation (about 1 year) of the pond at the time of 

sampling. Mixing calculations suggest that 

ground-water samples with elevated UV-A values 

(greater than 0.01) in the Perris-South subbasin 

could contain as much as 40 to 65 percent 

reclaimed water. 

INTRODUCTION

Artificial recharge of ground water using treated 

reclaimed water has been an increasingly important 

aspect of water management in recent years, as the 

need for reuse of water has grown. Common 

mechanisms that result in recharge of ground water 

include injection of water into recharge wells, 

percolation of reclaimed water from infiltration ponds, 

and percolation of reclaimed water applied as 

irrigation. In many situations where reclaimed water 

recharges ground water, information regarding the 

quantity, fate, or impact of the reclaimed water is 

needed by water managers.

Previous studies of percolated reclaimed water 

indicate that the percolated water may have a beneficial 

or an adverse effect on ground-water quality. For 

example, results of a study at East Meadow, Long 

Island, New York, suggest that concentrations of 

nitrate-nitrogen and several low-molecular-weight 

hydrocarbons decreased at a location recharged with 

reclaimed water; however, concentrations of sodium 

and chloride in the reclaimed water increased 

somewhat relative to the unaffected ground water, but 

remained within drinking-water standards (Schneider 

and others, 1987). In a study near Tallahassee, Florida, 

increases in nitrate and chloride concentrations in 

ground water were attributed to irrigation using 

reclaimed water (Pruitt and others, 1988). In a third 

study, ground-water quality was generally degraded by 

reclaimed water used for irrigation in Alameda County, 

California (Sylvester, 1983). 

In a study of ground-water quality near artificialrecharge basins that receive reclaimed water and (or) 

stormwater and imported water in Los Angeles County, 

California (Schroeder and others, 1997), which was 

done after the present study’s data-collection and 

analysis phases, it was concluded that (1) significant 

correlations exist between elevated (above natural 

background levels) concentrations of chloride, boron, 

and nitrogen back-calculated to the time of recharge, 

and that these constituents were indicators for the 

presence of reclaimed water in the sampled wells; and 

(2) bacterial numbers in wells near the recharge ponds 

were generally less than in wastewater-impacted 

aquifers elsewhere, and were strongly correlated with 

aqueous organic carbon concentration and weakly 

correlated with distance from the recharge ponds. 

Analysis of organic data from the same study area 

(Barber and others, 1997) indicated that: (1) 

concentrations of dissolved organic carbon (DOC) 

were greater in production wells near the recharge 

ponds than in an upgradient background well; (2) total 

organic halide (TOX), not detected in the background 

well, was present at concentrations as great as 14.6 

mg/L in the production wells; (3) concentrations of 

ethylenediaminetetraacetic acid (EDTA), if assumed to 

be a conservative tracer, can be used to estimate the 

percentage of reclaimed water in the sampled wells; 

and (4) fluorescent whitening agents were highly 

correlated with DOC and EDTA.

The results of these, and other, studies indicate 

that the movement and effect of percolated reclaimed 

water can vary from site to site. The variability from 

site to site may be dependent on the chemical 

characteristics of the reclaimed water relative to those 

of the pre-existing ground water; the chemical and 

physical characteristics of the soil and aquifer matrix 

through which the ground water travels; or the amount 

and distribution of reclaimed water. In the study 

reported herein, selected constituents were evaluated as 

indicators of the presence of reclaimed water in ground 

water.
Introduction 3

Background

The Eastern Municipal Water District (EMWD), 

located in the San Jacinto and Santa Margarita Basins 

in southwestern Riverside County, California, serves a 

population of nearly 500,000 in a service area that 

exceeds 550 mi2 (fig. 1). The EMWD provides water, 

obtained from local wells and imported from non-local 

surface-water sources, for domestic and irrigation uses. 

In addition, EMWD operates five regional waterreclamation facilities (RWRFs) that treat wastewater. In 

1995, the five RWRFs had a combined reclaimed-water 

production of 31,900 acre-ft/yr, all of which (except 

evaporated or percolated storage-pond water) was used 

within the EMWD service area--mostly for agricultural 

irrigation or irrigation of golf courses. Because demand 

for the reclaimed water is seasonal, storage ponds have 

been constructed at three areas: near the town of 

Winchester (Winchester subbasin); at the Sun City 

RWRF (Menifee subbasin); and at the Perris Valley 

RWRF (including the Trumble Road pond) (PerrisSouth subbasin) (figs. 1, 2). Approximately 13,000 

acre-ft of reclaimed water is estimated by the EMWD 

to be lost annually to evaporation and to percolation to 

the ground-water system through operation of the 

storage ponds (Behrooz Mortazavi, EMWD, oral 

commun., 1995). 

Although some of the ponds have been in 

operation for more than 25 years, little is known about 

the amount of water percolating and its effect on 

ground-water quality. The ponds and RWRFs are 

located in subbasins in which the ground water is 

characterized by relatively high dissolved-solids 

concentrations. Although the quality of reclaimed 

water percolating from those ponds is generally better 

than that of the ground water near the percolation site, 

the reclaimed water may have higher concentrations of 

some individual constituents. 

Mechanisms used by the EMWD in managing 

the quantity and chemical quality of water resources in 

the Menifee, Winchester, and Perris-South subbasins 

(and surrounding areas) include pumping of ground 

water, importation of surface water from distant 

sources, treatment of wastewater, storage of reclaimed 

water in unlined ponds, delivery of reclaimed water for 

irrigation, and extraction and desalting of poor-quality 

ground water. Owing to the role of reclaimed water in a 

number of these mechanisms, the EMWD needs 

information regarding the quantity of reclaimed water 

that recharges the ground-water system, and regarding 

the subsurface mixing of percolated reclaimed water 

and ground water. These issues continue to be 

important as regulations evolve and as conjunctive-use 

and desalting projects are planned and implemented. 

Specifically, there is a need to develop methods of 

tracing reclaimed water in the subsurface to determine 

the percent of mixing with ground water at various 

locations. Development of methods for quantifying the 

amount of reclaimed water percolating from ponds 

would be potentially useful to water managers for 

estimating possible recharge credits.

Previously, the U.S. Geological Survey (USGS), 

in cooperation with the EMWD, conducted the first 

phase of this study to investigate the quantity and fate 

of water percolation from selected reclaimed-water 

storage ponds to the ground-water system. As a product 

of the first phase, Burton and others (1996) presented 

(1) data on historical water quality, historical and thencurrent (1995) water levels, and construction 

specifications of existing wells; (2) borehole-lithologic 

descriptions and depth-to-bedrock data; (3) maps 

showing general directions of ground-water flow 

determined on the basis of water-level data collected 

during the study; and (4) pond water-level data and 

infiltration estimates, using water budgets, for one 

storage pond at each site. These data were used, in part, 

to quantify the rates of percolation from the storage 

ponds. The study revealed that the rates were variable, 

and in particular, dependent on the management actions 

that affect water levels in the ponds. In the present 

phase of the study, chemical tracers were used to 

evaluate percolation from the ponds in an effort to 

provide results that integrate percolation rates over a 

longer period of time than that of the estimates made in 

the first phase.
4 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Lake

Perris

Lake

Elsinore

Murrieta Creek

Warm

Creek

Springs

San Jacinto River

60

74

79

79

91 60

15

15

10

215

San Bernardino

Mountains

San Bernardino

San Jacinto Mountains San Jacinto Mountains

Menifee

subbasin

PerrisSouth

subbasin

Santa Ana Mountains Santa Ana Mountains

Hemet

Beaumont

Winchester

Perris

Riverside

Temecula

Winchester

subbasin

Riverside

San Diego

California

Study

Area

San Francisco

33°

45'

33°

30'

34°

00'

117°15' 117°00' 116°45'

0

0 2 4 6 KILOMETERS

2 4 6 MILES

Ground-water

 subbasin boundary

EXPLANATION

Base from U.S. Geological Survey digital elevation data, 1:100,000, 1981-89: Universal Transverse Mercator

Projection, zone 11. Shaded relief base from 1:250,000 scale Digital Elevation Model: sun illumination from

northwest at 30 degrees above horizon

Figure 1. Location of the Menifee, Winchester, and Perris-South ground-water subbasin study area, Riverside County, California.
Introduction 5

1

4

1

19

12 10 8 9 11 7

25 30

29

28 27 26

36 31 32 33 34 35

14

2

11

23

26

35

2

10 11 9

4 3

34

27

28

21 22

16 15

20

29

30

19

13 18

12

24

25

36

12

7

31

9

8

1 6 5 3

10

17

33 32

6 5

7 8

1

36 31

12

25

36

1

12

13

25 30

24

35 35

12

26

14

10 11

21

13

5 6

7

4 3

8

25

23

15

24

9

20

27

22

2

18

29

32 33 34

28

17 16

R3W R3W

R2W

R4W

T4S

T5S

T5S

T6S

Briggs Rd

Warren Rd

Menifee Rd

Goetz Rd

Murrieta Rd

Antelope Rd

Florida Ave

Newport Rd

San Jacinto Ave

Winchester Rd

Case Rd

McCall Rd

Simpson Ave

Ellis Ave

74

79

74

215

San Diego Aqueduct

Canal

Railroad

Canyon

Reservoir

Menifee Lakes

San Jacinto

River

Trumble Rd

Pond

Winchester

Ponds

Salt Creek

Perris

Valley Storm Drain

Skiland Lake

Sun City

Ponds

33°

47'

30"

117°12'30"

33°

42'

30"

33°

45'

33°

40'

Winchester

Homeland

Perris

Sun

City

Base map obtained from Santa Ana Watershed Project Authority (digitized by James M. Montgomery,

Engineers) from U.S. Geological Survey 1:24,000 quadrangles Perris, Romoland, and Winchester,

1953, photorevised 1979. Universal Transverse Mercator projection, Zone 11

117°07'30" 117°02'30"

0

0

4 MILES

4 KILOMETERS

DOMENIGONI

 VALLEY

Double Butte

PERRIS VALLEY

VALLEY

MENIFEE

Winchester

subbasin

Menifee

subbasin

PerrisSouth

subbasin

3R1

24F2–4

28M1–4

32A1 32B1 32C1

32H1

32G1

32L1

30D2 30C1

30G3

36P2

35N2

34Q2

3N1 4M1

9E1

9H1

9H2

33Q1

4A1 3C1

26N1

3L1

17R1

2M2

11D1

11M2

9Q1

16F1

15L1

14P1 24C1

30G2

1J2 2G2

2A1

2E1 5E1

30H2

29L2

29L3

29N1

Sun City

RWRF

Perris

Valley

RWRF

EXPLANATION

Unconsolidated

 deposits

Consolidated

 rocks

Reclaimed-water storage pond

Area shown on subbasin maps

Regional Water Reclamation

 Facility

Ground-water subbasin boundary

Well and abbreviated number, with type of data collected—

Well with water-quality data including UV absorbance

Multiple-completion well with water-quality data

 including UV absorbance

Well with water-quality data but no UV absorbance

3R1

24F2–4

3L1

Lakeview Mts

Figure 2. Selected wells and reclaimed-water storage ponds, and regional water-reclamation facilities, in the Menifee, Winchester, and Perris-South groundwater subbasins, Riverside County, California.
6 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Purpose and Scope

The primary goal of the second phase of the 

reclaimed-water study done by the USGS in 

cooperation with the EMWD was to trace the fate and 

mixing of reclaimed water from selected storage ponds 

in the Menifee, Winchester, and Perris-South subbasins 

by identifying constituents or characteristics of the 

reclaimed water that may be useful as tracers. The 

purpose of this report is to present (1) the inorganic, 

organic, and isotopic water-quality data collected in 

1995 from treatment plants, reclaimed-water storage 

ponds, and wells; (2) an assessment of the suitability of 

analyzed constituents and characteristics for use as a 

tracer of infiltrated reclaimed water in vicinity of the 

storage ponds; and (3) an estimate of the degree to 

which the infiltrated reclaimed water has mixed with 

the pre-existing ground water. 

Approach

After historical water-quality, water-level, and 

well-construction information were compiled in the 

first phase of the study (Burton and others, 1996), a 

network of 47 wells was established for water-quality 

sampling. The wells were selected on the basis of (1) 

broad areal distribution (varying distances, from 

immediately adjacent to a pond site to about 4 mi 

distant); (2) depth of the perforated interval; and (3) 

accessibility for sampling. The location of the network 

wells is shown in figure 2.

Water samples collected from the network wells, 

the three RWRFs, and the three pond sites in July and 

August 1995 were analyzed for major ions, trace 

metals, pH, alkalinity, and stable isotopes of hydrogen 

and oxygen. To determine if organic compounds might 

be useful as tracers of reclaimed water that has 

infiltrated from the storage ponds, samples from each 

of the RWRFs, the three selected ponds, and a subset of 

the network wells were analyzed for a suite of organic 

compounds: samples from the RWRFs, the ponds, and 

37 wells were analyzed for total organic carbon (TOC) 

and dissolved organic carbon (DOC); samples from 27 

wells were analyzed for methylene blue activated 

substances (MBAS); samples from the RWRFs, the 

ponds, and 9 wells were analyzed for caffeine and 

linear alkylbenzene sulfonate (LAS); samples from the 

RWRFs, the ponds, and 28 wells were analyzed for 

ultraviolet absorbance (UV-A) at 254 nm (nanometers); 

and samples from the RWRFs and the ponds were 

analyzed for ethylenediaminetetraacetic acid (EDTA). 

The results of the analyses were evaluated to 

determine which of the compounds best serves as a 

tracer for infiltrated reclaimed water in the study area. 

The water-quality results, including the tracer data, 

were used to infer the degree to which infiltrated 

reclaimed water has mixed with pre-existing ground 

water, taking into consideration factors such as local 

and regional flow directions, location and depth of the 

sampled wells, and location of areas where ground 

water has been recharged by percolation of reclaimed 

water from storage ponds or from lands irrigated with 

reclaimed water. In each of the subbasins, emphasis 

was placed on interpretation of the data collected from 

wells near the storage ponds. 

Methods of Sample Collection and Analysis 

Ground-water samples were collected from wells 

using protocols modified from the National Field 

Manual for the Collection of Water-Quality Data (U.S. 

Geological Survey, 1997). To ensure that each well had 

been completely purged, approximately three casing 

volumes of water were removed prior to sample 

collection. Water samples from each treatment plant 

were collected into a 4-liter amber glass bottle using 

automated compositors over a 6- to 8-hour period. The 

samples were chilled at 4°C during the collection 

process. Water samples from reclaimed-water storage 

ponds were collected by dipping a polyethylene bottle 

attached to a handle into the pond at four to six points 

within a 600-ft reach. The subsamples obtained by each 

dipping were composited in a churn splitter. 

Samples collected for determination of major 

ions, nutrients, and trace elements were filtered using a 

0.45-μm capsule filter. The cations and trace-element 

samples were adjusted to a pH of 2 using nitric acid. 

The samples were shipped on ice to the USGS National 

Water-Quality Laboratory (NWQL) for analysis by 

various methods (Fishman and Friedman, 1989; 

Fishman, 1993). DOC and UV-A samples were filtered 

through a 0.45-μm silver filter. MBAS, LAS, and 

caffeine samples were filtered through a 1-μm glassfiber filter and preserved with 2-percent formalin. 

These samples were shipped on ice to a USGS organics 

research laboratory in Boulder, Colorado. 
Introduction 7

DOC was determined using ultraviolet-promoted 

persulfate oxidation and infrared spectrometry 

(Brenton and Arnett, 1993). UV-A was determined 

using a spectrophotometer. MBAS concentrations were 

determined using a miniaturized version of a method 

described by Wershaw and others (1983). LAS and 

caffeine were analyzed by solid-phase extraction and 

gas chromatography/mass spectrometry (Trehy and 

others, 1990; Barber and others, 1995). Unfiltered 

samples were shipped to the USGS Isotope Laboratory 

in Reston, Virginia, for analysis of stable isotopes 

(deuterium and oxygen-18) using methods described 

by Epstein and Mayeda (1953) and Coplen and others 

(1991). 

Quality Control 

Replicate samples were collected at five wells to 

assess variability of the analyses for nutrients, major 

ions, and trace elements. For this assessment, the mean 

relative standard deviation (MRSD), which is defined 

as 100 times the standard deviation divided by the 

mean concentration for each replicate pair of samples, 

was used. The MRSDs were less than 5 percent for 22 

of 32 constituents. Values of MRSD less than 20 

percent are considered acceptable in this study. MRSDs 

were greater than 20 percent for three constituents--

lithium (21 percent), lead (28 percent), and zinc (39 

percent). MSRDs that exceeded 20 percent generally 

were for low measured concentrations at or near the 

laboratory reporting levels. This may indicate 

analytical uncertainty at low measured concentrations.

Description of the Study Area

The study area includes parts of the groundwater subbasins in which the three EMWD storagepond sites are located: the Menifee subbasin, the 

Winchester subbasin, and the Perris-South subbasin 

(figs. 1, 2). The ground-water subbasins, located 20–25 

mi southeast of Riverside, California, are part of the 

San Jacinto ground-water basin and are in the upper 

Santa Ana River drainage basin. The boundaries of the 

basins and subbasins were previously outlined by the 

California Department of Water Resources (1979). 

Well-defined surface-water drainages in the study area 

consist solely of the San Jacinto River and Salt Creek. 

The downstream part of the ephemeral San Jacinto 

River flows southwestward across the Perris-South 

subbasin and into the northern end of Railroad Canyon 

Reservoir. The ephemeral Salt Creek flows westward 

through the Winchester subbasin, through the Menifee 

subbasin, and into the eastern end of the Railroad 

Canyon Reservoir (fig. 2). 

The 40-mi2 Menifee subbasin, which contains 

the Sun City RWRF, is bounded by metamorphic rocks 

on the west and by igneous rocks on the south and east 

(NBS/Lowry, 1987). Alluvium in the Menifee subbasin 

is about 600 ft thick in the Sun City area and more than 

800 ft thick in the vicinity of Menifee Lakes (Biehler 

and Lee, 1995; NBS/Lowry, 1987). The boundary with 

the Perris-South subbasin to the north is in an area of a 

bedrock constriction about 1 mi north of Sun City 

(California Department of Water Resources, 1979). 

The Sun City RWRF and ponds are located in the 

southwest part of the subbasin, and are bordered on the 

north and northeast by suburban development 

(including a golf course), to the south and east by the 

Salt Creek flood plain and suburban development, and 

to the west by bedrock hills.

The 20-mi2 Winchester subbasin includes about 

12 mi2 of relatively level alluvial valley floor and is 

bounded by granitic and undifferentiated metamorphic 

rocks (California Department of Water Resources, 

1959, plate B–1B). The project study area includes the 

western half of the subbasin. The boundaries of the 

Winchester subbasin coincide with surface-water 

drainage divides, except in areas where valley-floor 

alluvium is contiguous with neighboring basins. 

Alluvium-filled constrictions were selected as 

boundaries between the Winchester subbasin and the 

Perris-South subbasin to the northwest, the Menifee 

subbasin to the southwest, and the Hemet subbasin to 

the east (fig. 1) (California Department of Water 

Resources, 1964). Saturated alluvium that fills the 

constrictions connects the subbasins hydrologically in 

the subsurface. Alluvium in the Winchester subbasin is 

estimated to be as much as 500 to 900 ft thick (Biehler 

and Lee, 1994). Depth to water generally ranged from 

6 to 75 ft in 1994-95 (Kaehler and others, 1998). The 

Winchester reclaimed-water storage ponds are located 

in the northwestern part of the subbasin, and are 

bordered to the north by the Lakeview Mountains 

(fig. 2) and to the east, south, west and northwest by 
8 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

agricultural and livestock land uses. The storage ponds, 

which receive water from the Temecula RWRF (located 

about 15 mi to the south in the Santa Margarita Basin), 

had been in operation for 2 to 3 years at the time data 

were collected for the study.

The 50-mi2 Perris-South subbasin is bounded on 

the west and east primarily by granitic mountains 

(Lang, 1979). The study area includes the southern 

two-thirds of the subbasin, the northern boundary of 

which is an arbitrary line extending westward from the 

northern end of Lake Perris (fig. 1). Boundaries with 

the Winchester subbasin to the southeast and the 

Menifee subbasin to the south have been defined in 

alluvium-filled constrictions (California Department of 

Water Resources, 1979). Alluvium in the Perris-South 

subbasin is more than 800 ft thick in places (Biehler 

and Lee, University of California, Riverside, written 

commun., 1996). The Trumble Road pond is located 

about 2 mi southeast of the town of Perris, and about 1 

mi northeast of the Perris Valley RWRF (fig. 2). 

Additional ponds are present at the Perris Valley 

RWRF site, which had been in operation about 30 years 

at the time data were collected for this study. The area 

surrounding the Trumble Road pond, which had been 

in operation for only 1 year, is used primarily for 

agriculture and contains some rural residences.

Acknowledgments

The authors gratefully acknowledge the help of 

Jeffrey Hale, Alfred Javier, Stephen Crombie, and other 

EMWD personnel for their help in compiling data, for 

permitting use of EMWD equipment, and for providing 

access to EMWD facilities. The authors also 

acknowledge the many well owners for their 

cooperation in obtaining water-level measurements and 

collecting water samples.

INORGANIC AND ORGANIC TRACERS

One of the principal objectives of the study was 

to assess the suitability of selected constituents and 

characteristics, determined from ground-water- and 

reclaimed-water samples, for use as a tracer of 

reclaimed water that has percolated from storage ponds 

in the three subbasins. These chemical constituents can 

be either naturally occurring or the result of human 

activity. The use of tracers that may be added to surface 

water (such as dye) or that may be injected into ground 

water (such as bromide, sulfur hexafluorine, or noble 

gases), specifically to trace movement or mixing, was 

not within the scope of this study. 

In any given hydrologic setting, a useful 

chemical tracer, if present, has one or more of the 

following characteristics: (1) it is present and 

detectable in at least one of the waters being compared, 

prior to mixing; (2) the concentration or amount is 

measurable; (3) a contrast, or recognizable difference, 

in concentration exists between the subject waters; (4) 

it is conservative (the concentration or amount does not 

change owing to chemical reaction or other processes, 

either with time or distance of travel); or (5) the 

concentration or amount changes at a known rate. An 

example of a commonly used tracer is dissolved 

chloride; chloride is particularly useful because it is 

conservative over a wide range of conditions. Other 

examples of conservative tracers include the stable 

isotopes of water: deuterium and oxygen-18. Generally, 

conservative tracers are easier to use and model, but the 

use of non-conservative tracers may also be beneficial. 

Examples of tracers that may be non-conservative 

under some conditions include easily exchanged or 

reactive ions such as calcium, magnesium, boron, 

dissolved oxygen, or nitrogen. Commonly, several 

tracers or indicators are used in combination in an 

investigation to provide supporting or independent 

lines of evidence for mixing. Some tracers might be 

useful as qualitative indicators of the presence or 

absence of a water source; others might be useful for 

quantitatively estimating the percentage mixing of a 

water source.

In addition to categorizing tracers as 

conservative or non-conservative, potential tracers can 

be divided into two types: inorganic and organic. 

Organic tracers are generally distinguished from 

inorganic tracers by the presence of carbon compounds. 

Organic compounds generally are non-conservative.

Reclaimed water may contain different inorganic 

and organic constituents than does native ground water. 

In the San Jacinto Basin, reclaimed water generally 

differs from native ground water in ionic and isotopic 

(deuterium and oxygen-18) composition because 

reclaimed water includes water imported from the 
Inorganic and Organic Tracers 9

Colorado River or from northern California. In 

addition, organic compounds in reclaimed water are 

different than organic compounds present in native 

ground water because the compounds in reclaimed 

water are added to water by humans, and may not be 

completely removed during treatment. Examples of 

added organic compounds include caffeine and 

components of detergents. Organic compounds also 

may be present in surface-water sources, both local and 

imported, that are not present in native ground water. 

The differences in composition, whether inorganic or 

organic, between reclaimed water and native ground 

water may be useful for tracing reclaimed water in the 

subsurface.

Inorganic Tracers

Potential inorganic tracers that were measured in 

ground-water- and reclaimed-water samples include 

major ions, nutrients, stable isotopes of hydrogen and 

oxygen, and trace elements. Other properties measured 

were temperature, specific conductance, dissolvedsolids concentration, alkalinity, and pH. 

The major ions included in the analyses were 

calcium, magnesium, sodium, potassium, sulfate, 

chloride, fluoride, bromide, and silica. As mentioned 

previously, conservative ions have the best potential as 

tracers. However, the use of major ions as tracers may 

be constrained if the concentrations of the major ions 

vary significantly either areally or vertically. Another 

difficulty is that the amounts introduced into the 

ground-water system may vary with time; under these 

circumstances, historical and (or) time-series waterquality data would be needed if mixing is to be 

assessed.

The analyzed nutrients included nitrate, nitrite, 

ammonia, and phosphorus. Dissolved nutrients 

commonly are non-conservative because they tend to 

be transformed during reduction and oxidation 

processes. The concentrations of dissolved nutrients 

may also vary over a wide range in a subbasin owing to 

the influence of past and present land use, where 

activities such as feed-lot operations, agriculture, or use 

of reclaimed water for irrigation may have contributed 

nutrients to the ground water.

Oxygen-18 (18O) and deuterium (2H or D), 

naturally occurring stable isotopes of oxygen and 

hydrogen, can be used in studies to determine the 

source of ground water or to trace its movement. Some 

examples of southern California ground-water studies 

that utilized isotope data include Izbicki and others 

(1995, 1998), and Izbicki and Martin (1997). The 

abundances of oxygen-18 and deuterium are expressed 

as ratios of per mil (parts per thousand) differences 

relative to an internationally agreed standard, the 

Vienna Standard Mean Ocean Water (VSMOW) 

(Gonfiantini, 1978), using delta notation (δ). The δ18O 

and δD abundances in precipitation are linearly 

correlated around the world because almost all 

precipitation originates as evaporation from the ocean. 

The linear correlation can be graphed, and is known as 

the meteoric water line (Craig, 1961a,b). Oxygen-18 

and deuterium have a greater atomic mass than that of 

the more common respective isotopes, oxygen-16 and 

hydrogen. As a result, their abundances in 

precipitation, relative to the average over time present 

in water vapor originating from seawater, are 

influenced by local differences in the temperature of 

condensation, which is in turn influenced by factors 

such as altitude, latitude, and climatic regime. The 

isotopic composition of surface water also can be 

affected by partial evaporation of the lighter isotopes, 

leaving the water enriched in the heavier isotopes 

through the process of fractionation. In these ways, 

isotopic composition reflecting source and evaporative 

history of the water is imprinted up until the time of 

recharge. Following recharge, the isotopic composition 

may reflect the mixing of the recharged water with the 

native ground water. Consequently, isotopic-abundance 

data from ground-water samples may be useful for 

tracing movement of recharged water in the subsurface.

A trace element is an element, associated with 

minerals, that may be found at low concentration—

typically parts per billion—in water. The dissolved 

trace elements included in the analyses were arsenic, 

barium, berylium, boron, cadmium, chromium, cobalt, 

copper, iron, lead, lithium, manganese, molybdenum, 

nickel, silver, strontium, vanadium, and zinc. As with 

major ions, the natural variability of dissolved traceelement concentrations tends to be large within a 

ground-water basin. An additional complication in the 

use of trace elements to investigate subsurface mixing 
10 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

or movement of reclaimed water is that the traceelement characterization, or “signal,” of reclaimed 

water commonly is not distinct. However, a trace 

element that may be distinctive in reclaimed water is 

boron, especially in settings where boron 

concentrations are higher in reclaimed water than in the 

native ground water. In addition, boron is likely to be a 

conservative tracer: it is not removed during (septic 

system) treatment (Flynn and Barber, 2000) or likely 

sorbed during ground-water transport (Barber and 

others, 1988). However, the utility of boron as a tracer 

may be limited if there is significant spatial variability 

in the concentration of boron in the native ground 

water.

Inorganic-Constituent Mixing Models

Inorganic constituents may be useful indicators 

of mixing between two types of water. If the 

concentration of a single constituent in one water (end 

member) is sufficiently different than the concentration 

in the other water (second end-member), then that 

constituent may be suitable as a quantitative indicator 

of mixing. For example, chloride, a conservative tracer, 

is commonly used as a single constituent in two-endmember mixing models. 

If the concentration of a constituent in a groundwater sample is the result of mixing between two 

distinct end-me mbers, then the concentration in the 

sample is a linear function of the concentration in the 

two end-members. If the two end-members are 

reclaimed water and native ground water, then the 

concentration of a mixture is: 

(1)

where

Equation 1 can be rearranged so that the fraction 

of reclaimed water in the ground-water sample is a 

function of the concentration observed in the groundwater sample and the concentrations observed in the 

two end-members (reclaimed water and native ground 

water):

. (2)

If the concentration of a single constituent varies 

significantly in one of the end-member water types, it 

may be possible to use two constituents simultaneously 

in a two-end-member mixing model. A twoconstituent, two-end-member mixing model is most 

appropriate when the ratio between constituents within 

each of the water types is relatively constant and when 

each constituent behaves conservatively. For example, 

in some basins, the concentrations of boron and 

chloride in native ground water may vary over a wide 

range, and yet the boron/chloride ratio may remain 

relatively constant. However, when two end-members, 

each with constant boron/chloride ratios, are mixed, the 

ratio of the mix will not be a linear function of the 

boron/chloride ratios of the two end-members. Instead, 

the boron/chloride ratio of the mix must be calculated 

from the boron and chloride concentrations of the mix:

 (3a)

 (3b)

 

, (3c)

where

Cmix is concentration of the constituent in 

the mixture,

Freclaimed is fraction of reclaimed water in the 

mixture,

Creclaimed is concentration of the constituent in 

the reclaimed water,

(1–Freclaimed) is fraction of native ground water in the 

mixture, and

Cnative is concentration of the constituent in 

the native ground water.

Cmix FreclaimedCreclaimed 1 Freclaimed ( ) – Cnative = + ,

Bmix, Breclaimed, 

and Bnative

are boron concentration in the mix, 

reclaimed water, and native ground 

water, respectively,

Clmix, Clreclaimed, 

and Clnative

are chloride concentration in the 

mix, reclaimed water, and native 

ground water, respectively, and

Rmix is ratio of boron to chloride.

Freclaimed Cmix Cnative – Creclaimed Cnative = ⁄ ( ) –

Bmix= Freclaimed Breclaimed 1 Freclaimed ( ) – Bnative +

Clmix Freclaimed Clreclaimed = +

1 Freclaimed ( ) – Clnative

Rmix Bmix Clmix = ⁄
Inorganic and Organic Tracers 11

Given equations 3a to 3c, a family of mixing 

curves can be calculated (fig. 3A). Each of the example 

curves originates at a reclaimed-water end-member 

assumed to have a single value of boron concentration 

and a single value of chloride concentration, but 

terminating at different points. The terminal point for 

each mixing curve has a different chloride 

concentration, but the same boron/chloride ratio. The 

different terminal points can be conceptualized as 

either representing different ground-water endmembers, or as representing a ground water with 

spatially variable boron and chloride concentrations.

If a set of field samples plot along a single 

mixing curve (fig. 3A), then the samples may represent 

a native ground water—with an initial chloride 

concentration indicated by the terminal point of the 

curve—that has been mixed with differing proportions 

of the reclaimed water. The fraction of reclaimed water 

present in each of the samples can then be estimated 

using an accompanying plot (fig. 3B). The 

accompanying plot shows the boron/chloride ratio of 

the mix as a function of the fraction of reclaimed water, 

and is based on equations 3a to 3c. For a native ground 

water with a specified initial chloride value, there is a 

unique relation between the fraction of reclaimed water 

and the boron/chloride ratio (fig. 3B).

A set of field data may not plot on a single 

mixing curve owing to a number of factors, including 

natural variability in the ratio of boron to chloride, or 

non-conservative behavior of boron. In these cases, a 

range for the fraction of reclaimed water can be 

established. For example, if a data point plots beneath a 

mixing curve (fig. 4A), then one can shift the point to 

the right or upward. These two shifts provide two 

projected points that plot on the mixing curve (fig. 4A). 

The values of boron/chloride ratio from the projected 

points provide bounds for the fraction of reclaimed 

water (fig. 4B). Alternatively, if a point plots above a 

mixing curve, then one can shift the point to the left or 

downward; in this manner, two projected points are 

identified, which, in turn, provide the range for the 

fraction of reclaimed water.

If a shifted data point has a relatively high 

boron/chloride ratio, then the estimated fraction of 

reclaimed water is relatively insensitive to the initial 

chloride concentration of the native ground water 

(fig. 3B). For example 1 in figure 3B, the fraction of 

reclaimed water ranges from about 92 percent to about 

99 percent for a corresponding range in initial chloride 

concentration of 500 mg/L to 4,000 mg/L. In contrast, 

if a shifted data point has a relatively low 

boron/chloride ratio, then the estimated fraction of 

reclaimed water is relatively sensitive to the initial 

chloride concentration of the native ground water 

(fig. 3B). For example 2 in figure 3B, the fraction of 

reclaimed water ranges from about 25 percent to about 

75 percent for a corresponding range in initial chloride 

concentration of 500 mg/L to 4,000 mg/L. 

Organic Tracers

The potential exists for reclaimed water to 

contain any number of the hundreds of the organic 

compounds that are used in urban, agricultural, and 

industrial environments. These compounds commonly 

include pesticides, herbicides, solvents, detergents, 

pharmaceuticals, and hydrocarbons. Analysis for large 

numbers of organic compounds can become cost 

prohibitive, even if the number of samples is small. To 

determine if an organic compound might be used as a 

tracer for movement of reclaimed water that has 

infiltrated from the storage ponds, a suite of organic 

compounds were analyzed for samples from each of 

the RWRFs, the three selected ponds, and subsets of 

the network wells. The analyses included total organic 

carbon (TOC), dissolved organic carbon (DOC), 

metheylene blue activated substances (MBAS), linear 

alkylbenzene sulfonate (LAS), 

ethylenediaminetetraacetic acid (EDTA), caffeine, and 

ultraviolet absorbance (UV-A) at 254 nm.

 The various forms of dissolved carbon may 

serve as tracers if there are contrasts in concentrations 

in reclaimed water in comparison with native ground 

water. TOC, a measure of the concentration of all forms 

of organic carbon present in a sample, generally is less 

in ground water than in reclaimed water owing to the 

many sources of both biogenic and synthetic organic 

compounds contributed to reclaimed water, and to the 

incomplete removal of organic carbon during 

treatment. In addition, ground water generally is 

expected to have lower TOC values than those of 

reclaimed water owing to adsorption and 

biodegradation processes during ground-water 

recharge and movement (Flynn and Barber, 2000). 
12 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

A

0

0.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

0.5

1.0

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

100% Reclaimed Water

Mixing curve with

Cl0 = 1,000

Mixing curve with

Cl0 = 2,000 Mixing curve with

Cl0 = 4,000 Native ground-water,

initial boron/chloride ratio = 0.2

Mixing curve with

Cl0 = 500

Chloride concentration of

native-ground-water end-member

Example field-data point

Native-ground-water end-member

Reclaimed-water end-member

EXPLANATION

Cl0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1

FRACTION RECLAIMED WATER

BORON/CHLORIDE RATIO TIMES 1,000

Chloride concentration of native-ground-water end-member

EXPLANATION

Mixing curve with

Cl0 = 2,000

Mixing curve with

Cl0 = 4,000

Example 1 : Sample with B/Cl = 2.5

Example 2: Sample

with B/Cl = 0.5

Mixing curve with

Cl0 = 500

Mixing curve with

Cl0 = 1,000

Cl0

B

Estimated fraction of reclaimed water for example 2

Estimated fraction of reclaimed water for example 1

Figure 3. Example boron/chloride-ratio mixing curves. (A) Calculated family of mixing curves based on boron/chloride ratio plotted against chloride. One 

end- member is defined by boron and chloride values for reclaimed water, and the other end-member is defined by values for native ground water with chloride 

concentrations of 500, 1,000, 2,000, and 4,000 mg/L, respectively; all native ground waters have a B/Cl = 0.2. (B) Calculated family of mixing curves based on 

boron/chloride ratio plotted against fraction reclaimed water. The two diamonds represent the fraction of reclaimed water for a ground-water sample with a 

B/Cl = 2.5 mixed with two different native ground waters. The four circles represent the fraction of reclaimed water for a ground-water sample with a B/Cl = 0.5 

and four different native ground waters.
Inorganic and Organic Tracers 13

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

A

0

0.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

0.5

1.0

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

100% Reclaimed Water Chloride concentration of

native-ground-water end-member

Hypothetical field data

Lower range of B/Cl ratio

Upper range of B/Cl ratio

Example point for which a range of

boron/chloride ratios is estimated

Native-ground-water end-member

Reclaimed-water end-member

EXPLANATION

Cl0

Lower range of B/Cl ratio

Upper range of B/Cl ratio

Lower bound of fraction reclaimed water

Upper bound of fraction reclaimed water

Mixing curve with

Cl0 = 4,000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1

FRACTION RECLAIMED WATER

BORON/CHLORIDE RATIO TIMES 1,000

Chloride concentration of

native-ground-water end-member

EXPLANATION

Mixing curve with

Cl0 = 4,000

Cl0

B

Figure 4. Example mixing curves and hypothetical field data. (A) Calculated mixing curve based on boron/chloride ratio plotted against chloride. Example of 

projecting a field-sample data point onto the mixing curve. (B) Calculated mixing curve based on boron/chloride ratio plotted against fraction reclaimed water. 

Example of use of the curve to estimate the fraction of reclaimed water.
14 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

MBAS, LAS, and EDTA (organic components of 

detergents) and caffeine, might be expected to be 

present in reclaimed water, and therefore are potential 

tracers. However, these compounds also have 

limitations. MBAS may not be a reliable tracer of 

reclaimed water owing to chloride interference 

(Burkhardt and others, 1995). LAS, degradable under 

aerobic conditions, is non-conservative. EDTA was 

found to be a useful indicator of infiltrated municipal 

wastewater in Los Angeles County, California (Barber 

and others, 1997); Barber and others (1997) assumed 

that EDTA was a conservative tracer because it is not 

believed to undergo significant biodegradation or to 

sorb strongly to sediments. A potential drawback to the 

use of caffeine as tracer is that it can be removed from 

water biologically, and therefore is non-conservative.

Measurement of the absorption of light, such as 

ultraviolet-light absorbance at selected wavelengths, 

can show qualitative differences in the composition of 

DOC from different sources. For example, the 

absorption properties of synthetic detergent organic 

compounds are different than those of natural organic 

material. The absorbance is related to the molecular 

structure of specific functional groups within complex 

carbon molecules, and to the concentration of those 

molecules. Maximum absorbance generally occurs at a 

wavelength of about 254 nm and is indicative of 

aromatic rings that form the building blocks of many 

organic compounds (Izbicki and others, 2000). 

Elevated DOC concentrations can be associated with 

reclaimed water in some situations (Barber and others, 

1997; Leenheer and others, 2001). In some previous 

studies, UV-A measurements have been used as a 

surrogate for DOC concentrations (California 

Department of Water Resources, 1994), with variable 

results. In another study (Izbicki and others, 2000), 

UV-A was compared with DOC concentrations to 

examine qualitative differences in DOC composition 

between early-season and late-season stormflows. In 

the present study, an objective was to determine if UVA can be used as an indicator of infiltrated reclaimed 

water in the three subbasins, either with or without 

elevated values of DOC. Because DOC can include a 

wide range of different compounds, each of which may

absorb UV energy differently, the UV-A measured in 

ground-water samples may not be a simple function of 

DOC concentration.

TRACING RECLAIMED WATER IN THE 

THREE SUBBASINS

Reclaimed water is introduced to the groundwater flow systems in the Menifee, Winchester, and 

Perris-South subbasins by two principal mechanisms: 

percolation from storage ponds and from irrigation of 

fields. Preliminary analysis of the water-quality data 

collected for this study indicates that reclaimed water 

originating as percolation from ponds is more easily 

traced than is reclaimed water applied as irrigation. 

Percolation from ponds is a more localized source, and 

the local history of irrigation using reclaimed water is 

not as well documented. Therefore, our analysis 

focuses primarily on water samples collected from the 

ponds and from wells located near the ponds.

When interpreting water-quality data, both the 

proximity of the sampled wells to the reclaimed-water 

storage ponds and the depth of the perforated intervals 

of the sampled wells should be considered. A 

generalized conceptual-model diagram (fig. 5) shows a 

hypothetical plume of reclaimed water infiltrating from 

a pond, and examples of some possible welllocation/depth combinations representing a variety of 

theoretical sampling situations relative to the plume. 

For example, in the conceptual model, well 3 would be 

the well with the highest proportion of reclaimed water, 

and therefore highest concentration of reclaimed water 

indicators. Other wells with a deep perforated interval, 

such as wells 5 and 6, also can show relatively elevated 

proportions of reclaimed water even though they are 

located relatively far from the ponds. In the conceptual 

model, wells with perforated intervals located above 

the plume, such as wells 2 and 7, will contain little to 

no reclaimed water (and reclaimed water indicators), 

even if these wells are located close to the ponds. In 

contrast, well 8, located away from the plume 

associated with the pond, can contain some reclaimed 

water due to infiltration from the overlying field 

irrigated using reclaimed water. This conceptual model 

illustrates the importance of considering the hydrologic 

position of wells relative to sources of reclaimed water.
Tracing Reclaimed Water in the Three Subbasins 15

Water samples were collected from three 

Regional Water Reclamation Facilities (RWRFs), from 

three sets of storage ponds that receive water from the 

treatment facilities, and from selected ground-water 

wells in the Menifee, Winchester, and Perris-South 

subbasins (fig. 2). These samples were analyzed for 

major ions, nutrients, selected trace elements, stable 

isotopes of hydrogen and oxygen, and organic carbon. 

Also, some of the samples were analyzed for ultraviolet 

absorbance (UV-A) at a wavelength of 254 nm, 

methylene blue active substances (MBAS), linear 

alkylbenzene sulfonate (LAS), and caffeine, each of 

which might be useful as an organic tracer of infiltrated 

reclaimed water. The results of the water-quality 

analyses are given in table 1 (at back of report).

Several of the organic compounds analyzed 

were not used in this study for evaluating the presence 

of reclaimed water in the subsurface. MBAS analysis 

was run for 27 ground-water samples, but MBAS was 

not analyzed for the samples from the RWRFs or 

storage ponds; MBAS was detected at similar 

concentrations in all 27 ground-water samples. 

Therefore, MBAS was not suitable as a tracer for 

reclaimed water in this study. LAS was detected in 

three ponds and one of the RWRFs, but not in any of 

the nine well samples for which this analysis was run. 

Therefore, LAS was not suitable as a tracer. Owing to 

logistical problems, EDTA analysis in the present study 

was done only for the RWRFs and the three pond sites. 

Analysis for caffeine was done for samples from the 

RWRFs, the three ponds, and nine wells. Caffeine was 

found at, or slightly above, the detection limit in 

samples from 1 RWRF and 2 ponds, and in none of the 

11 wells for which this analysis was run. Therefore, 

caffeine was not suitable as a tracer of reclaimed water 

in this study.

Bedrock

Saturated

zone

Groundwater

flow

Unsaturated

zone

Reclaimed-water

storage pond Field irrigated with

reclaimed water

Wells with varying

perforation depths

1

3

2

4 5 6

7 8

Figure 5. Conceptual model of reclaimed-water infiltration, ground-water flow, and well positions.
16 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Menifee Subbasin

Ground-water quality in the Menifee subbasin is 

generally poor. The concentration of dissolved solids 

(residue on evaporation) exceeded 500 mg/L in 17 of 

the 18 wells sampled, and exceeded 1,000 mg/L in 16 

of the wells. The median concentration was about 

2,400 mg/L. In contrast, the dissolved-solids 

concentration in the reclaimed-water samples obtained 

from the Sun City RWRF and Sun City Pond no.7 was 

763 (computed) and 864 mg/L, respectively. 

A trilinear diagram (Piper, 1944) of water 

analyses from the Menifee subbasin (fig. 6) shows that 

the chemical composition is variable. No predominant 

water type exists for the subbasin. Two groups can be 

identified on the basis of anions: a low-sulfate group 

and a low-bicarbonate group. Within the low-sulfate 

group, chloride and bicarbonate each range from about 

10 to about 90 percent. Within the low-bicarbonate 

group, chloride ranges from about 20 to about 80 

percent, and sulfate ranges from about 10 to about 60 

percent. Unlike the anions, there is some tendency 

toward one predominant cation: sodium accounts for 

more than 50 percent of the cations in about half of the 

samples. Water samples from the RWRF and the pond 

show the presence of all three major anions in about 

equal proportions (fig. 6), and show sodium as the 

predominant cation. Consequently, major-ion 

composition alone is not sufficient as an indicator of 

the presence of reclaimed water in the subsurface of the 

Menifee subbasin.

Stiff diagrams for water samples from the 

Menifee subbasin, like the Piper trilinear diagram, 

show that the chemical composition in the Menifee 

subbasin is variable. The Stiff diagrams plotted on a 

map (fig. 7), unlike the trilinear diagram, are able to 

show the spatial and vertical (where multiplecompletion wells were sampled) variability of chemical 

composition. In general, both ground water close to the 

ponds and reclaimed water tend to have lower 

concentrations of dissolved ions than does ground 

water farther from the ponds (fig. 7). These patterns 

suggest that selected constituents may be useful as 

indicators in the Menifee subbasin.

Selected chemical constituents may be useful as 

tracers of reclaimed water if the hydrology of the flow 

system is understood. Reclaimed water in the Menifee 

subbasin enters the ground-water flow system 

primarily as infiltration from the Sun City storage 

ponds, which are located in the southwestern part of the 

subbasin. Ground-water flow (fig. 8) based on 1995 

data from Burton and others (1996, figs. 10, 11, and 

table 3) is away from the storage ponds, both toward 

the northeast and the southwest. Given the opposite 

directions of flow in the vicinity of the ponds, a 

ground-water divide likely is located in that area. The 

precise location of the ground-water divide is not 

known, but the 1995 ground-water-level data indicate 

that it was near the southwest edge of the ponds. It is 

likely that the location of the divide shifts in response 

to management of water levels in the ponds.

Major-ion data from wells located near the ponds 

indicate mixing of reclaimed water and downgradient 

native ground water. Ground water downgradient and 

near the ponds (wells 32B1, 32C1, 32G1, and 32H1) is 

lower in dissolved-solids concentration than is water in 

the well that is located upgradient and near the ponds 

(32L1) (fig. 7, and table 2). Also, there is a shift in 

chemical composition: the dominant anion is chloride 

in the upgradient well, and sulfate in the downgradient 

wells. The lowering of dissolved-solids concentrations 

and shift in chemical composition along the flow path 

indicate mixing of relatively saline, sodium/calciumchloride native ground water, and relatively fresh 

sodium-sulfate reclaimed water. The high 

concentration of dissolved solids at well 32A1 suggests 

that the dissolved-solids concentration of native ground 

water can vary widely.
Tracing Reclaimed Water in the Three Subbasins 17

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

20

40

0

60

80

100

100

80

60

40

20

0

0

20

40

60

80

100

80

60

100

40

20

0

60

80

100

20

40

0

100

80

60

40

20

0

CALCIUM

PERCENT

CALCIUM PLUS MAGNESIU

SULFATE PLUS CHLORIDE

M

SODIUM PLUS POTASSIUM

MAGNESIUM

PERCENT

CHLORIDE, FLUORIDE, NO2 + NO3

SULFATE

PERCENT

CARBONATE PLUS BICARBONATE

Menifee Subbasin,

including USGS Multiple-completion Well 28M1-4

28M1

28M2

28M3

28M4

1J2

32A1

34Q2

35N2

2G2

32H1

32L1

32G1

5E1 2E1

36P2 32B1

32C1

2A1

28M3

28M3

28M1

28M2

28M1

28M2

Well

USGS Multiple-completion well

Well with UV-A ≥ 0.1

Pond

RWRF

Regional water reclamation

facility (RWRF) and storage

pond

Figure 6. Piper trilinear plot of major-ion concentrations for samples from selected wells in the Menifee ground-water subbasin, Riverside County, 

California.
18 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

23

26

35

2

4 3

34

28 27

21 19 20 22

29

30

31

32 33

6 5 1

36

25

24

18 17 16 15 14 13

R3W R3W

T5S

T6S

Goetz Rd

Antelope Rd

Newport Rd

Case Rd

McCall Rd

215

Briggs Rd

Menifee Lakes

Salt Creek

Sun City

Ponds

864

28M3

3,800

28M2

1,510

28M1

1,080

28M4

2,850

35N2

2,960

34Q2

3,390

32G1

2,450

32H1

1,260

32A1

9,610

32C1

2,330

32B1

804

32L1

4,580

24F2-4

5E1

335

24C1

685

36P2

1,700

1J2

3,350

2A1

3,550

2E1

1,070

2G2

1,090

14P1

1,160

15L1

435

16F1

1,730

17R1

1,390

Sun City

RWRF

c 802

Sun

City

VALLEY

MENIFEE

0

0

2 MILES

2 KILOMETERS

Location of map shown in figure 2.

Figure 7. Stiff diagrams for selected wells and reclaimed-water storage ponds, and the Sun City reclamation facility, Menifee subbasin, Riverside County, 

California.
Tracing Reclaimed Water in the Three Subbasins 19

In the Menifee subbasin, stable isotopes of 

hydrogen and oxygen (fig. 9) are useful for 

distinguishing between ground water and reclaimed 

water. Eighteen wells in the subbasin were sampled for 

analysis of stable isotopes; 15 of the analyses plot 

along or near the global meteoric water line, indicating 

recharge from local precipitation. In contrast, analyses 

of reclaimed-water samples from the Sun City RWRF 

and storage ponds plot to the right and below the global 

meteoric water line, reflecting both the isotopically 

lighter original source of the reclaimed water (water 

imported from the Colorado River) and its evaporative 

history. Water from the remaining three wells (32B1, 

32C1, and 32H1) has an isotopic composition similar 

to that of the water from the RWRF and storage pond 

(fig. 9), suggesting the presence of reclaimed water in 

the subsurface at these well locations. These are three 

of the four wells that are physically close to and 

downgradient from the storage ponds, and that show a 

decrease in dissolved-solids and chloride 

concentrations from 1993 (Burton and others, 1996, 

table 2) to 1995 (table 1). Water from the fourth well 

(32G1) is shifted away from the meteoric water line, 

but not as much as water from the other three wells.

Ultraviolet absorbance (UV-A) also is useful for 

identifying the presence of reclaimed water in the 

subsurface. The UV-A values for reclaimed water from 

the Sun City RWRF and storage pond are 0.17 and 

0.15, respectively (rounded, table 1). The three groundwater samples that are isotopically similar to the 

reclaimed-water samples (wells 32B1, 32C1, and 

32H1) have UV-A values ranging from 0.02 to 0.06. A 

fourth well, 32G1, has a UV-A value of 0.007, and also 

has stable isotope values that are shifted away from the 

meteoric water line toward the values of reclaimed 

water (fig. 9). In contrast, water from well 32L1, 

located near and upgradient from the ponds, has an 

isotopic composition and a UV-A value (0.003) that are 

similar to those of ground water from wells located 

relatively far from the storage ponds, thus suggesting 

the absence of reclaimed water at that location. All four 

of the downgradient wells located near the ponds have 

chemical compositions indicative of the presence of 

reclaimed water. These results suggest that the 

threshold value for UV-A as an indicator of the 

presence of reclaimed water in ground water in the 

Menifee subbasin is approximately 0.007.

Cations Anions

Sodium and potassium

Magnesium

Calcium

Chloride and fluoride

Sulfate

Bicarbonate

0

Stiff Diagram

Well and number - Number in italics is dissolvedsolids concentration, in milligrams per liter.

c indicates calculated from specific conductance

Area of irrigation with reclaimed water

Differences in shape reflect difference in chemical composition.

(Stiff, 1951)

Milliequivalents per liter

100 100

34Q2

3,390

Unconsolidated deposits

Consolidated rocks

Reclaimed-water storage pond

Regional water reclamation facility

Ground-water subbasin boundary

EXPLANATION

USGS multiple-completion well - Sequence

number is from deepest to shallowest.

28M1-4

Figure 7.—Continued.
20 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

23

26

35

2

4 3

34

28 27

21 19 20 22

30 29

31

32 33

6 5 1

36

25

24

18 17 16 15 14 13

R3W R3W

T5S

T6S

Goetz Rd

Antelope Rd

Newport Rd

Case Rd

McCall Rd

Briggs Rd

Menifee Lakes

Sun City

Ponds

1,397

Salt Creek

1,350

1,400

1,400

1,350

1,400

1,390

1,390

?

?

?

?

?

?

?

?

?

?

Sun City

RWRF

28M1-4

32A1

1,378

32G1

1,394 32L1

1,398 34Q2

1,354 36P2

1,333

35N2

1,340

32H1

1,383

32B1

1,392 32C1

1,397

2G2 1J2

2A1

1,327

2E1

1,335

5E1

36E1

1,383

25K1

1,426

1E1

1,331

3C1

1,359

33K1

1,378

29J1

1,375

31R1

1,388

36P1

35R1 1,330

1,333

36N2

1,330

Sun

City

VALLEY

MENIFEE

0

0

2 MILES

2 KILOMETERS

215

Location of map shown in figure 2

See figures 17 and 26 for continuation of contours

in the Winchester and Perris-South subbasins

to the east and north, respectively.

24F4

1,418

Figure 8. Water-level contours, directions of ground-water flow, and wells with ultraviolet-absorbance data in the Menifee subbasin, Riverside County, 

California.
Tracing Reclaimed Water in the Three Subbasins 21

Table 2. Dissolved-solids (residue on evaporation) and chloride concentrations for selected wells located adjacent to the Sun City Ponds, Menifee 

subbasin, Riverside County, California

[Site name: RWRF, Sun City Regional Water Reclamation Facility; POND, Sun City Reclaimed Water Storage Pond no.7; abbreviated State well numbers, all 

are 5S/3W-____(see “Well-Numbering System” at front of report); perforated interval in feet below land surface, from Burton and others (1996); water-quality 

data collected in summer 1995; mg/L, milligrams per liter; —, no data]

1Dissolved-solids value computed using method described by Fishman and Friedman (1989).

Site name or 

State well No.

Perforated

interval Dissolved solids (mg/L) Chloride

(mg/L)

Location of well 

relative to ponds

RWRF — 7631 130 —

POND — 864 160 —

32L1 200–220 4,580 1,600 Upgradient (near)

32B1 200–220 804 130 Downgradient

32C1 200–220 2,330 430 Downgradient

32G1 200–220 2,450 520 Downgradient

32H1 200–220 1,260 150 Downgradient

Figure 8.—Continued.

34Q2

1,354 Abbreviated well number

Water-level altitude (1995), in feet above

sea level

Abbreviated well number

Water-level altitude (1995), in feet above

sea level

Well with other water-quality data

Abbreviated well number

Water-level altitude (1995), in feet above

sea level

Well with water-level data only

2E1

1,335

1E1

1,331

Well with UV-Absorbance data - Larger

dot indicates well with UV-A > 0.01

USGS multiple-completion well - Sequence

number is from deepest to shallowest.

Water-level contour - Dashed where approximately located; queried where uncertain.

Contour interval is 10 feet

Direction of ground-water flow

1,400 ?

28M1-4

Unconsolidated deposits

Consolidated rocks

Reclaimed-water storage pond

Regional water reclamation facility

Ground-water subbasin boundary

EXPLANATION
22 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

As shown in figure 10, ground-water samples 

can have elevated values of UV-A (indicating the 

presence of reclaimed water) without having elevated 

values of dissolved organic carbon (DOC). The four 

wells with elevated UV-A values have DOC values 

within the range of DOC observed in wells not having 

elevated UV-A. The lack of correspondence between 

UV-A and DOC may occur for two reasons: (1) UV-A 

at 254 nm is sensitive only to certain types of organic 

matter; and (2) other dissolved compounds also may 

absorb ultraviolet light (Izbicki and others, 2000; 

California Department of water Resources, 1994; 

Krazner and others, 1996). Therefore, in some cases, 

UV-A is a better indicator than is DOC for tracing 

reclaimed water. Also, in those cases, the common 

practice of dividing UV-A values by DOC 

concentrations (Leenheer and others, 2001) may lessen 

the usefulness of UV-A as a tracer.

As noted previously, reclaimed water in the 

Menifee subbasin is characterized by relatively low 

concentrations of chloride and elevated values of 

UV-A. Wells with high UV-A (and water that is 

isotopically similar to reclaimed water) also have low 

chloride concentrations (wells 32B1, 32H1, 32C1, and 

32G1) (fig. 11). However, wells with low chloride 

concentrations do not necessarily contain reclaimed 

water. For example, wells 36P2, 28M1, and 28M2 have 

intermediate values of UV-A (0.003 to 0.007) and 

values of chloride that are even less than those for the 

RWRF and pond. These wells, which are located in 

areas of irrigation with reclaimed water, but not near 

the ponds, are perforated at depths starting at 365 ft or 

more below land surface; therefore, they may not 

contain a large percentage of reclaimed water, and the 

low chloride values may simply represent those of 

native ground water in that part of the subbasin.

Menifee Subbasin

DELTA OXYGEN-18, IN PER MIL

DELTA DEUTERIUM, IN PER MIL

-12 -10 -8 -6 -4

-40

-50

-60

-70

-80

-90

Storage Pond

Regional Water

Reclamation Facility

32H1

32C1

32B1

28M2

36P2

32G1

32L1

32A1

28M3

28M4

35N2

2A1

1J2 2G2

5E1

28M1

2E1

Global Meteoric

Water Line

Wells with

UV-A ≥ 0.01

Evaporative EXPLANATION Trend Line

Menifee Subbasin

DISSOLVED ORGANIC CARBON, IN MILLIGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

0.001

0 6 8 10 12

32B1

32H1

32C1

32G1

34Q2

32L1

32A1

36P2

28M4

28M3

28M1 28M2

2 4

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

Figure 9. Delta deuterium plotted against delta oxygen-18 for selected 

wells in the Menifee subbasin, Riverside County, California. Figure 10. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved organic carbon for selected wells in the Menifee subbasin, 

Riverside County, California.
Tracing Reclaimed Water in the Three Subbasins 23

The UV-A values for samples from the four 

wells with water that is isotopically similar to that of 

reclaimed water help to distinguish, and suggest 

mixing, between native ground water and reclaimed 

water. One way to estimate the extent of mixing, and to 

evaluate UV-A as a tracer, is to compare two sets of 

mixing calculations: one using chloride, a known 

conservative constituent, and the other using UV-A. 

The estimated percent reclaimed water, calculated on 

the basis of chloride concentrations, at the four 

downgradient wells ranges from 75 to 102 percent 

(table 3). When calculated using UV-A instead of 

chloride, the estimated percent reclaimed water in 

ground water at the same well sites ranges from 3 to 

38 percent. Comparison of these two sets of 

calculations shows that UV-A is a non-conservative 

tracer. In addition, the mixing calculations based on 

chloride (a conservative tracer) suggest that a minimum 

mixture of about 75-percent reclaimed water might be 

needed for a recognizable UV-A signal to be seen in 

ground water in the Menifee subbasin. (A minimum of 

75 percent reclaimed water might be needed because 

the UV-A based percent reclaimed water for that same 

sample is only 3 percent (table 3); water that contains 

less than 75 percent reclaimed water may not 

necessarily have an elevated UV-A value.)

Boron, a trace element, also is useful for 

identifying the presence of reclaimed water in the 

subsurface in the Menifee subbasin. Wells with 

elevated UV-A also have relatively high concentrations 

of boron, as shown in figure 12: the same four wells for 

which the presence of reclaimed water is indicated by 

isotope and UV-A data (wells 32B1, 32C1, 32H1, and 

32G1) have higher concentrations of dissolved boron 

than do all but one of the wells (35N2) tested for boron 

in the Menifee subbasin, and the boron concentrations 

from these four wells are similar to those from the 

RWRF and pond. However, elevated values of boron do 

not necessarily indicate reclaimed water, as shown by 

the UV-A and boron data for well 35N2 (high boron, 

low UV-A) and wells 32L1, 32A1, and 36P2 (high 

boron and intermediate-to-low UV-A) (fig. 12).

The ratio of boron to chloride can be used to 

trace reclaimed water in the Menifee subbasin, and to 

estimate the extent of mixing at specific locations.A 

plot of boron/chloride versus chloride concentrations 

(fig. 13A) suggests threshold values for indicating the 

presence of reclaimed water: all of the wells with 

elevated UV-A plot within a region approximately 

defined by boron/chloride ratios above 1.0 and chloride 

concentrations ranging from 130 mg/L (the value for 

the RWRF reclaimed water) to 520 mg/L.

Menifee Subbasin

CHLORIDE, IN MILLIGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

≤0.001

0 2,000 3,000 4,000 1,000

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

32B1

32H1

32C1

32G1

34Q2

32L1

32A1

36P2

28M4

28M3

28M1

28M2

Figure 11. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved chloride for selected wells in the Menifee subbasin, Riverside 

County, California.
24 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

The proportion of reclaimed water in a groundwater sample can be estimated from the observed 

boron/chloride ratios and chloride values of the sample 

and hypothetical boron/chloride mixing curves. For 

example, the mixing curve in figure 13B shows the 

result of mixing native ground water, assumed to be 

represented by the boron and chloride concentrations 

measured at well 32L1, and reclaimed water, 

represented by the concentrations measured in the Sun 

City storage-pond sample. The wells with elevated 

UV-A (32C1, 32G1, 32H1, and 32B1) plot relatively 

close to the calculated mixing curve, suggesting that 

these ground-water samples are mixes of the two 

proposed end-members. Given the proposed mixing 

model, water from wells 32C1 and 32G1, with 

boron/chloride ratios of about 1, consists of nearly 80 

percent reclaimed water (fig. 14 and table 3). Water 

from wells 32H1 and 32B1, with boron/chloride ratios 

greater than 2.5, consists of about 98 percent reclaimed 

water. The percentages based on boron/chloride ratios 

are similar to the percentages based on chloride alone 

(table 3). This correspondence is expected for data 

points that plot relatively close to a single mixing 

curve.

Table 3. Calculated percentage of reclaimed water in ground water at selected wells located adjacent to the Sun City Ponds, Menifee subbasin, 

Riverside County, California

[Percentages based on a two-end-member mixing model; chloride and UV-A values for reclaimed-water end-member based on data collected at Sun City pond 

no.7; values of chloride, UV-A, and boron/chloride ratio for native-ground-water end member based on data collected at well 32L1, located upgradient from 

the Winchester ponds; well No, abbreviated State well number: all are 5S/3W-____(see “Well-Numbering System” at front of report); UV-A, ultraviolet 

absorbance at 254 nanometers; —, no data]

State well No.

Percent

reclaimed water

based on chloride

Percent 

reclaimed water 

based on UV-A

Percent

reclaimed water 

based on boron/chloride

ratio

32L1 0 0 —

32B1 102 38 98

32C1 81 13 80

32G1 75 3 80

32H1 101 17 98

Menifee Subbasin

BORON, IN MICROGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

≤0.001

0 200 300 600 100 400 700 500

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

32B1

32H1

32C1

32G1

35N2 32A1

32L1

36P2

28M1

28M3

28M2

28M4

34Q2

Figure 12. Ultraviolet-absorbance at 254 nanometers plotted against dissolved 

boron for selected wells in the Menifee subbasin, Riverside County, California.
Tracing Reclaimed Water in the Three Subbasins 25

Winchester Subbasin

Ground-water quality in the Winchester subbasin 

is generally poor. The concentration of dissolved solids 

(residue on evaporation) exceeds 1,000 mg/L in 10 of 

the 11 wells sampled in the central and western parts of 

the subbasin (table 1), with a median concentration of 

about 3,300 mg/L. In contrast, the dissolved-solids 

concentration in the samples obtained from the 

Temecula RWRF and Winchester Storage Pond B are 

686 and 772 mg/L, respectively. A Piper trilinear plot 

for samples from the Winchester subbasin (fig. 15) 

indicates that the ground water ranges from calciumchloride to sodium-chloride composition; there is no 

predominant anion in the reclaimed water, but sodium 

is the predominant cation. As in the Menifee subbasin, 

major-ion composition alone is not sufficient for 

identifying the presence of reclaimed water in the 

subsurface. However, Stiff diagrams (fig. 16) do 

indicate that concentrations and chemical composition 

vary spatially, both areally and vertically. Therefore, 

selected constituents may be useful as indicators of 

reclaimed water in the subsurface if the ground-water 

hydrology is understood.

Menifee Subbasin

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

4.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2,000 3,000 4,000 1,000

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

32B1

32H1

32C1

32G1

34Q2

35N2

1J2 32L1 32A1

2A1

5E1

2E1

2G2

36P2

28M4

28M3

28M1

28M2

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

4.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2,000 3,000 4,000 1,000

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Mixing curve with well

32L1 as native ground-water

end-member

Regional Water

Reclamation Facility

32B1

32H1

32C1

32L1

32G1

A

B

Figure 13. Boron/chloride ratio plotted against dissolved chloride for selected 

wells in the Menifee subbasin, California, without and with a superimposed 

mixing curve. (A) Boron/chloride ratio plotted against dissolved chloride. (B) 

Boron/chloride ratio plotted against dissolved chloride with a superimposed 

mixing curve. Mixing curve is based on well 32L1 as representative of native 

ground water and the RWRF as representative of reclaimed water.
26 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Ground-water flow in the Winchester subbasin is 

generally from east to west (fig. 17, 1995 data). In the 

immediate vicinity of the Winchester Storage Ponds 

there is a southwesterly component of flow away from 

the ponds, indicating recharge to the ground water from 

the ponds. The influence of this recharge can be seen in 

the general differences in water quality between wells 

located downgradient and upgradient from the ponds. 

Ground-water levels in the vicinity of the ponds vary 

with time (Burton and others, 1996, figs. 10, 11, and 

table 3), and therefore flow directions also vary with 

time. Indeed, the Winchester Storage Ponds sometimes 

receive ground-water inflow (Burton and others, 1996). 

Water quality, however, tends to reflect long-term 

trends. Ground water from wells located downgradient 

and relatively near the ponds (wells 30C1, 30G3, 30D2, 

and 30G2) is lower in dissolved-solids concentration, 

particularly sodium and chloride, than is water from the 

well located upgradient and near the ponds (30H2) 

(table 4; figs. 16, 17). The lowering of dissolved-solids 

concentrations along the flow path indicates dilution of 

relatively saline ground water with relatively fresh 

reclaimed water. Also shown in table 4 are 

concentrations of dissolved solids and chloride in 

samples from two wells (29L2 and 29L3) that are 

farther upgradient from the ponds than 30H2; the lower 

concentrations at 29L3 might reflect natural variability 

or the influence of reclaimed water from a source other 

than the storage ponds, such as irrigation using 

reclaimed water.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1

FRACTION RECLAIMED WATER

BORON/CHLORIDE RATIO TIMES 1,000

Mixing curve with well 32L1 as

native ground-water end-member

(Cl = 1,600 mg/L, B/Cl = 2.67)

Wells 32H1 and 32B1 with B/Cl ≥ 2.67

Wells 32C1 and 32G1 with B/Cl ~ 1.0

Figure 14. Estimation of fraction reclaimed water, plotted against boron/chloride ratio, generated using a two-end-member mixing model for water in the 

vicinity of the Sun City storage ponds, Menifee subbasin, Riverside County, California.
Tracing Reclaimed Water in the Three Subbasins 27

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

20

40

0

60

80

100

100

80

60

40

20

0

0

20

40

60

80

100

80

60

100

40

20

0

60

80

100

20

40

0

100

80

60

40

20

0

CALCIUM

PERCENT

CALCIUM PLUS MAGNESIU

SULFA

M

TE PLUS CHLORIDE

SODIUM PLUS POTASSIUM

MAGNESIUM

PERCENT

CHLORIDE, FLUORIDE, NO2 + NO3

SULFATE

PERCENT

CARBONATE PLUS BICARBONATE

Pond

RWRF

24F2

24F3

29N1

24F3

24F2 24F2 24F3

Well

USGS Multiple-completion well

Well with UV-A ≥ 0.1

29L2

29L3

30H2

30G2

30C1

24F4

30D2

30G3

Winchester Subbasin,

including USGS Multiple-completion Well 24F2-4

Regional water reclamation

facility (RWRF-Temecula)

and storage pond

Figure 15. Piper trilinear plot of major-ion concentrations for selected wells in the Winchester subbasin, Riverside County, California.
28 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

19

14

23

26

35 36 31

30

25

24

13

20 21

18 17 16

29

32 33

28

R3W R2W

T5S

T5S

Briggs Rd

Case Rd

Simpson Ave

Menifee Rd

Menifee Lakes

Salt Creek

29J1

33D1

36E1

25K1

Winchester

Ponds

772

Temecula Regional

Water Reclaimation

Facility (approximately

15 miles south) serving

Winchester ponds

686

24F2

395

24F4

1,330

24F3

2,520

30C1

2,290

30G3

2,320

30D2

3,330

14P1

1,160

24C1

685

30G2

4,570

30H2

6,430 29L2

6,440

29L3

29N1 4,620

3,850

0 2 MILES

30C1

2,290

Well and number - Number in italics is dissolvedsolids concentration, in milligrams per liter

Area of irrigation with reclaimed water

Unconsolidated deposits

Consolidated rocks

Reclaimed-water storage pond

Ground-water subbasin boundary

Double

Butte

0 2 KILOMETERS

EXPLANATION

USGS multiple-completion well - Sequence

number is from deepest to shallowest.

24F2-4

Cations Anions

Sodium and potassium

Magnesium

Calcium

Chloride and fluoride

Sulfate

Bicarbonate

0

Stiff Diagram

Differences in shape reflect difference in chemical composition.

(Stiff, 1951)

Milliequivalents per liter

100 100

Location of map

shown in figure 2.

Figure 16. Stiff diagrams for selected wells and reclaimed-water storage ponds, and the Temecula reclamation facility, Winchester subbasin, Riverside County, 

California.
Tracing Reclaimed Water in the Three Subbasins 29

19

14

23

26

35 36 31

30

25

24

13

20 21

18 17 16

29

32 33

28

R3W R2W

T5S

T5S

Briggs Rd

Case Rd

Simpson Ave

Menifee Rd

Menifee Lakes

Salt Creek

Winchester

Ponds

1,438

1,400

1,400

1,350

1,450

1,440

?

30D2

30C1

1,437

30G3

1,436

36P2

1,333

14P1

24C1

30G2

1,437

30H2

30H3 1,442

1,440

29L2

29L3

29N1

1,442

24F4

1,418

24F3

1,375

24F2

1,400

30H1

1,443

30A1

1,445

29J1

1,447

33D1

1,450

36E1

1,383

25K1

1,426

36P1

1,330

35R1

1,333

36N2

1,330

30B1

1,447

30B2

1,445

34Q2

1,354 Abbreviated well number

Water-level altitude (1995), in feet above sea level

Abbreviated well number

Water-level altitude (1995), in feet above sea level

Well with other water-quality data

Abbreviated well number

Water-level altitude (1995), in feet above sea level

Well with water-level data only

2E1

1,335

1E1

1,331

Well with UV-Absorbance data - Larger

dot indicates well with UV-A > 0.01

USGS multiple-completion well - Sequence

number is from deepest to shallowest.

Water-level contour - Dashed where approximately

located; queried where uncertain. Contour intervals

are 10 feet and 5 feet

Direction of ground-water flow

1,400

1,445

?

24F2-4

Unconsolidated deposits

Consolidated rocks

Reclaimed-water storage pond

Ground-water subbasin boundary

EXPLANATION

Double

Butte

0

0

2 MILES

2 KILOMETERS

Location of map shown in figure 2

See figures 8 and 26 for continuation of contours

in the Menifee and Perris-South subbasins

to the west and north, respectively.

Figure 17. Water-level contours, directions of ground-water flow, and wells with ultraviolet-absorbance data in the Winchester subbasin, Riverside County, 

California.
30 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

In the Winchester subbasin, the stable isotopes of 

hydrogen and oxygen are not as useful for 

distinguishing between ground water and reclaimed 

water as in the Menifee subbasin. For example, groundwater samples from wells 30C1 and 30H2 have nearly 

identical isotopic values even though the two wells are 

located downgradient and upgradient from the ponds, 

respectively (fig. 18). In general, no clear distinction in 

isotopic composition is evident between wells located 

upgradient or downgradient, or near or far from the 

ponds. The relative lack of utility in using hydrogen 

and oxygen isotopes as indicators of mixing primarily 

is a consequence of the relative similarity in isotopic 

composition of the reclaimed water and native ground 

water in this subbasin. This similarity may be attributed 

to a relatively high proportion of local ground water 

used for water supply in the service area of the 

Temecula RWRF.

In the Winchester subbasin, the difference in 

isotopic composition between water from the Temecula 

RWRF and the Winchester storage ponds is larger than 

the range observed in the ground water. This relatively 

large difference is another factor limiting the 

usefulness of hydrogen and oxygen isotopes as tracers 

in the Winchester subbasin. The relatively large 

difference in isotopic compostion between water from 

the RWRF and the storage ponds may be a function of 

the effects of evaporation on the isotopic composition 

of the pond water and the 21-day difference in 

sampling dates for the pond and the RWRF. In the 

absence of a distinguishing isotopic characteristic for 

the reclaimed water in the Winchester subbasin, it is 

difficult to use stable isotopes to identify the presence 

of reclaimed water in the subsurface.

 In the Winchester subbasin, as in the Menifee 

subbasin, the presence of reclaimed water in the 

subsurface is suggested by elevated values of UV-A. 

Six ground-water samples were analyzed for UV-A 

(fig. 19). Two of the samples (30C1 and 30G3) are 

from wells that are near and downgradient from the 

ponds, and have relatively high values of UV-A 

(greater than or equal to 0.02). Three samples are from 

the USGS multiple-depth cluster-well site (24F2-4) 

located relatively far from the ponds, and have 

relatively low UV-A values ranging from 0.003 to 

0.008. The sixth well, 30D2, is downgradient from the 

ponds, but farther than are 30C1 and 30G3, and the 

well is perforated over a relatively large depth interval. 

The UV-A value for this well is relatively low (0.004). 

Although the distance of 30D2 from the ponds is less 

than 0.5 mi, this distance is relatively large because the 

ponds had only been in use for 2 to 3 years at the time 

of sampling. In this subbasin, UV-A values greater than 

0.01 are likely indicators of the presence of reclaimed 

water.

Table 4. Dissolved-solids (residue on evaporation) and chloride concentrations for selected wells located adjacent to the Winchester Ponds, Winchester 

subbasin, Riverside County, California

[Site name: RWRF, Temecula Regional Water Reclamation Facility; Pond, Winchester Storage Pond B; well number, abbreviated State well number: all are 

5S/2W-____(see “Well-Numbering System” at front of report); perforated interval in feet below land surface, from Burton and others, 1996; mg/L, milligrams 

per liter; —, no data]

1 Several perforated intervals: 50–70, 100–120, 160–180 feet. 2 Several perforated intervals: 130–190, 210–230, 270–370 feet.

Site name

or State well No.

Perforated

interval

Dissolved solids

(mg/L)

Chloride

(mg/L) Location of well relative to pond

RWRF — 686 130 —

POND — 772 180 —

29L2 — 6,440 2,400 Upgradient

29L3 50–1801 4,620 1,900 Upgradient

30H2 50–70 6,430 2,500 Upgradient (near)

30C1 130–3702 2,290 830 Downgradient

30G3 52–72 2,320 730 Downgradient

30D2 40–355 3,330 790 Downgradient (far)

30G2 50–70 4,570 1,400 Downgradient (far)
Tracing Reclaimed Water in the Three Subbasins 31

In the Winchester subbasin, as in the Menifee 

subbasin, the presence of reclaimed water in the 

subsurface is not indicated by elevated values of DOC. 

The two wells with UV-A values greater than 0.01 and 

the four wells with UV-A less than 0.01 all have DOC 

values of 1.2 mg/L or less (fig. 19). The ponds and 

RWRF have DOC values greater than 7 mg/L.

Ground-water chloride concentrations in the 

Winchester subbasin are spatially variable, which may 

be due to natural variability or to the mixing of 

reclaimed water with native ground water. The two 

ground-water samples with elevated values of UV-A 

(wells 30C1 and 30G3), which suggest the presence of 

reclaimed water, have chloride concentrations (fig. 20) 

that are dissimilar to those for reclaimed water (pond 

and RWRF). In addition, these same two wells have 

chloride values that are bracketed by, and similar to, 

three other wells that do not have elevated values of 

UV-A. A fourth sample (well 24F2) with non-elevated 

UV-A has a chloride concentration even lower than that 

of the reclaimed water. This well, which is perforated 

near the alluvium/weathered-bedrock contact, may 

include ground water from the underlying fracturedbedrock flow system. 

In the Winchester subbasin, as in the Menifee 

subbasin, we used chloride concentrations and UV-A 

values to estimate the percentage of reclaimed water in 

the subsurface. Using the chloride value at well 30H2 

(located upgradient from the ponds) as an end-member, 

the calculated percentage of reclaimed water in the 

three wells located downgradient and near the ponds 

ranges from 72 to 76 per cent (table 5, column 1). If the 

lowest value of UV-A obtained in the Winchester Basin 

(0.003 at well 24F4) is used as an end-member (in 

place of chloride at well 30H2), then the fraction of 

reclaimed water ranges from 2 to 29 percent (table 5, 

column 2). If the chloride value at well 24F4 is used as 

representative of native ground water, then the 

calculated percentages all are negative (table 5, 

column 3). These discrepancies could be due to 

variability in chloride concentrations and UV-A values 

in the native ground water or to the use of different 

wells as representative of the native ground water—the 

discrepancies may indicate that UV-A is a nonconservative tracer.

Boron concentrations in the Winchester 

subbasin, like chloride concentrations, are not 

generally indicative of the presence of reclaimed water 

in the subsurface. Ground-water samples with UV-A 

values similar to those measured in reclaimed water 

have boron concentrations that are dissimilar to that of 

the reclaimed water (fig. 21). In addition, the boron 

concentrations for reclaimed water from the RWRF and 

storage ponds (540 and 590 mg/L, respectively) are in 

the middle of the range of concentrations in native 

ground water in the Winchester subbasin (40 to 1,300 

mg/L) (table 1). 

30G2

30H2

30G3

30D2

24F2

24F3

30C1

24F4

Winchester Subbasin

DELTA OXYGEN-18, IN PER MIL

DELTA DEUTERIUM, IN PER MIL

-12 -10 -8 -6 -4

-40

-50

-60

-70

-80

-90

Global Meteoric

Water Line

29L3

Wells with

UV-A ≥ 0.01

EXPLANATION

Evaporative

Trend Line

Storage

Pond

Regional Water

Reclamation Facility

24F4

24F2

24F3

30D2

30C1 30G3

Winchester Subbasin

DISSOLVED ORGANIC CARBON, IN MILLIGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

0.001

0 6 2 4 8 10 12

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

Figure 18. Delta deuterium plotted against delta oxygen-18 for selected 

wells in the Winchester subbasin, Riverside County, California.

Figure 19. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved organic carbon for selected wells in the Winchester subbasin, 

Riverside County, California.
32 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Interpretation of a plot of boron/chloride ratio 

versus chloride (fig. 22A) also is inconclusive with 

regard to tracing reclaimed water. The two wells with 

elevated UV-A (30C1 and 30G3) have boron/chloride 

ratios that are dissimilar to that of the reclaimed water 

and, in fact, the ratios are equal to or less than those of 

samples from wells not thought to contain reclaimed 

water (wells 29N1, 29L3, 28L2, and 24F2). These low 

values may indicate that boron is not conservative in 

this subbasin. However, it is nevertheless still 

illustrative to calculate mixing curves for the 

Winchester subbasin.

The upper curve in figure 22B shows the result of 

mixing native ground water, assumed to be represented 

by the boron and chloride concentrations measured in 

the sample from well 30H2, with reclaimed water, 

represented by the concentrations measured in the 

Winchester storage-pond sample. None of the groundwater data points, with the exception of well 30G2, plot 

near the mixing curve. Most significantly, the data for 

the two wells that have elevated UV-A (30C1 and 

30G3) plot far below this mixing curve, suggesting that 

there is a negligible percentage of reclaimed water 

present. This is in contradiction with the results based 

on using chloride alone (table 5, column 1).

This contradiction indicates that the mixing 

model using well 30H2 as an end member may be 

inappropriate. 

An alternative mixing curve, using well 24F3 as 

representative of the native ground water, also is shown 

in figure 22B. Well 24F3 is downgradient of the wells 

that have elevated UV-A (30C1 and 30G3), and may be 

representative of the native ground-water present prior 

to mixing with reclaimed water. This hypothesis is 

supported by the lower boron/chloride ratio and higher 

chloride concentration at well 24F3 than at the two 

wells with elevated UV-A. The two wells with elevated 

UV-A (30C1 and 30G3) plot near, but below, the 

alternative mixing curve. If the two points are shifted to 

the right onto the curve (thus holding the 

boron/chloride ratio constant), then the estimated 

percentage of reclaimed water present is less than 10 

percent (figs. 22B, 23). If the two points are shifted 

upward onto the curve (thus holding chloride constant), 

then the estimated percentage of reclaimed water is 

about 30 percent. These values are consistent with the 

percentages based on using chloride alone (table 5, 

column 4—well 24F3 end-member) and are consistent 

with the percentages based on using UV-A (table 5, 

column 5). This consistency suggests that ground water 

sampled from well 24F3 is an appropriate end-member.

Winchester Subbasin

CHLORIDE, IN MILLIGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

0.001

0 2,000 3,000 1,000

Wells with

UV-A ≥ 0.01

EXPLANATION

24F4

24F2

24F3

30D2

30G3 30C1

Storage Pond

Regional Water

Reclamation Facility

Figure 20. Ultraviolet-absorbance at 254 nanometers plotted against dissolved 

chloride for selected wells in the Winchester subbasin, Riverside County, 

California.

Winchester Subbasin

BORON, IN MICROGRAMS PER LITER

UV-ABSORBANCE AT 254 NAOMETERS

1.0

0.1

0.01

0.001

0 200 300 600 100 400 700 500

Wells with

UV-A ≥ 0.01

EXPLANATION

24F2

24F4

24F3 30D2

30C1

30G3

Storage Pond

Regional Water

Reclamation Facility

Figure 21. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved boron for selected wells in the Winchester subbasin, Riverside 

County, California.
Tracing Reclaimed Water in the Three Subbasins 33

The results using 24F3 as an end-member

(fig. 22B and table 5, column 6), suggest that UV-A can 

be elevated in samples that have relatively low 

percentages of reclaimed water. Well 30D2, located 

downgradient and near the pond, but lacking an 

elevated UV-A value, plots on the 24F3 mixing curve; 

the estimated percentage of reclaimed water is about 30 

percent (fig. 22B; and table 5, column 6). This value is 

consistent with the percentage calculated using 

chloride alone (table 5, column 4). 

The data point for the RWRF plots along an 

upward extension of the two mixing curves (fig. 22B), 

suggesting that the water in the storage pond at the time 

of sampling (1995) may have been a mixture of 

reclaimed water and some fraction of native ground 

water. This result is consistent with a previous finding 

of upward movement of ground water into the 

Winchester pond in the same general time frame as the 

sampling (Burton and others, 1996). If the RWRF is 

used as the reclaimed-water end-member, then the 

resulting mixing curves are quite similar to those 

shown in figure 22B; the only significant difference is 

that the curves extend beyond the point representing 

the storage pond and terminate at the point representing 

the RWRF. If the RWRF had been used as the 

reclaimed-water end-member, then the fraction of 

reclaimed water in the storage pond would be about 

97 percent; the fraction of ground water would be about 

3 percent. The computation of fractions at the wells, 

reported previously, remain virtually the same. 

Perris-South Subbasin

Ground-water quality in the Perris-South 

subbasin is generally poor. The concentration of 

dissolved solids (residue on evaporation) exceeds 500 

mg/L in 18 of the 19 wells sampled, and exceeds 1,000 

mg/L in 16 of the wells. The median concentration is 

about 1,700 mg/L. In contrast, the dissolved-solids 

concentration in the sample obtained from the Trumble 

Road Storage Pond is 599 mg/L. A Piper trilinear plot 

(fig. 24) for samples from the Perris-South subbasin 

indicates that the native ground-water type ranges from 

calcium-chloride to sodium-chloride; there is no 

predominant anion in the reclaimed water, but sodium 

is the predominant cation. As in the Menifee and 

Winchester subbasins, major-ion composition alone is 

not sufficient as an indicator of the presence of 

reclaimed water in the subsurface.

Table 5. Calculated percentage of reclaimed water in ground water at selected wells located adjacent to the Winchester ponds, Winchester subbasin, 

Riverside County, California

[Percentages based on a two-end-member mixing model; chloride and UV-A values for reclaimed-water end-member based on data collected at Winchester 

Pond B (table 1); values of chloride and UV-A for native-ground-water end-member based on data collected at well 30H2, located upgradient of the Winchester 

ponds, and at wells 24F4 and 24F3, located far downgradient of the ponds; value of boron/chloride ratio for native-ground-water end-member based on data 

collected at well 24F3; State well number: abbreviated State well number; all are 5S/2W-____, except for 5S/3W-24F3 and -24F4 (see “Well-Numbering 

System” at front of report); UV-A, ultraviolet absorbance at 254 nanometers; B, boron; Cl, chloride; —, no data]

1 Not reported because chloride concentration at well 30H2 is higher than at well 24F4, resulting in a negative percentage. 2 Not reported because chloride concentration at well 30H2 is higher than at well 24F3, resulting in a negative percentage. 3 Not reported because UV-A value at well 30D2 is lower than at well 24F3, resulting in a negative percentage.

Calculated percent reclaimed water in ground water

State well No.

Column 1:

based on 

chloride

at well 30H2 

end-member

Column 2:

based on UV-A 

at well 24F4 

end-member

Column 3:

based on chloride 

at well 24F4 

end-member

Column 4:

based on chloride 

at well 24F3 

end-member

Column 5:

based on UV-A

at well 24F3 

end-member

Column 6:

based on B/Cl ratio 

at well 24F3 

end-member

30H2 0 — —(1) —(2) — —

30C1 72 29 —(1) 21 25 6 to 32

30G3 76 27 —(1) 33 24 6 to 32

30D2 74 2 —(1) 26 —(3) 32
34 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Figure 22. Boron/chloride ratio plotted against dissolved chloride for 

selected wells in the Winchester subbasin, Riverside County California, 

without and with superimposed mixing curves. (A) Boron/chloride ratio 

plotted against dissolved chloride. (B) Boron/chloride ratio plotted against 

dissolved chloride with a superimposed mixing curve. Mixing curves are 

based on wells 24F3 or 30H2 as representative of native ground water and 

the storage pond as representative of reclaimed water.

Winchester Subbasin

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

4.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2,000 3,000 1,000

Wells with

UV-A ≥ 0.01

EXPLANATION

24F2

24F4 24F3

30D2

30H2

30G3 30C1

30G2

29N1

29L3 29L2

Storage Pond

Regional Water

Reclamation Facility

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

4.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2,000 3,000 1,000

Wells with

UV-A ≥ 0.01

EXPLANATION

30H2

30C1

24F3

30G3

Storage Pond

Regional Water

Reclamation Facility

A

B

Mixing curve with well

24F3 as native ground-water

end-member

Mixing curve with well

30H2 as native ground-water

end-member
Tracing Reclaimed Water in the Three Subbasins 35

Although Stiff diagrams show spatial variability 

of dissolved-solids concentrations and composition in 

ground water sampled across the Perris-South subbasin 

(fig. 25), this variability likely is due to natural 

conditions as well as to the influence of infiltrated 

reclaimed water. In the vicinity of the Perris Valley 

RWRF and Trumble Road Pond, ground-water flow 

generally is from the southwest to the northeast 

(fig. 26). Ground water having relatively low dissolvedsolids concentration is located in areas that may receive 

recharge from reclaimed-water sources (for example, 

wells 16F1, 9Q1, 9E1, and 9H1, located in or near 

fields irrigated with reclaimed water or near the Perris 

Valley RWRF ponds) as well as in areas unlikely to 

receive recharge from reclaimed-water sources (wells 

15L1, 14P1 and 11D1, located relatively far from 

reclaimed-water sources) (fig. 25). These wells have 

similar concentrations of specific ions, particularly 

chloride, sodium, and calcium (tables 1 and 6). 

Similarly, ground water having relatively high 

dissolved-solids concentration also is located in areas 

both near to and far from reclaimed-water sources 

(wells 4M1 and 20N1). The absence of systematic 

spatial variation, either in concentration or 

composition, may be due to the complexities of 

spatially separated ponds; the short period of time 

(1 year) that the Trumble Road Pond was in operation 

prior to the sampling date; and the presence of a field 

irrigated with reclaimed water located upgradient from 

the RWRF. 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1

FRACTION RECLAIMED WATER

BORON/CHLORIDE RATIO TIMES 1,000

B/Cl = 0.32 (well 30D2, and shift wells 30C1 and 30G3 upward)

B/Cl = 0.11 (shift wells 30C1 and 30G3 to the right)

Mixing curve with well 24F3 as

native ground-water end-member

(Cl = 110 mg/L, B/Cl =0.0007)

Range of fraction reclaimed water

present in ground-water samples

from wells 30C1 and 30G3

EXPLANATION

Figure 23. Estimation of fraction reclaimed water using a two-end-member mixing model in the vicinity of the Winchester storage ponds, Winchester 

subbasin, Riverside County, California.
36 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

20

40

0

60

80

100

100

80

60

40

20

0

0

20

40

60

80

100

80

60

100

40

20

0

60

80

100

20

40

0

100

80

60

40

20

0

CALCIUM

PERCENT

CALCIUM PLUS MAGNESIU

SULFATE PLUS CHLORIDE

M

SODIUM PLUS POTASSIUM

MAGNESIUM

PERCENT

CHLORIDE, FLUORIDE, NO2 + NO3

SULFATE

PERCENT

CARBONATE PLUS BICARBONATE

Pond

RWRF

4A1

33Q1

26N1

3L1

9H1

4M1

2M2

3C1

14P1

9H2

9E1

17R1

16F1

24C1

15L1

3R1

9Q1

11D1

Well

Well with UV-A ≥ 0.1

Regional water reclamation

facility (RWRF) and storage

pond

Figure 24. Piper trilinear plot of major-ion concentrations for selected wells in the Perris-South ground-water subbasin, Riverside County, California.
Tracing Reclaimed Water in the Three Subbasins 37

4

29 28

27 26

33 35 32 34

14

2

11

16 15

9

8 7

18

19

5

6

3

10

17

25

36

1

12

13

21 22 23 20 24

R3W

T4S

T5S

Murrieta Rd

Menifee Rd

Antelope Rd

San Jacinto Ave

Case Rd

Ellis Ave

215

74

74

Goetz Rd

San Jacinto

River

Perris

Valley Storm

Drain

Skiland Lake

Trumble

Road

Pond

599

3R1

1,150

4M1

5,760

9E1

1,930

9H1

2,100

9H2

1,370

33Q1

3,890

4A1

2,470 3C1

3,780

24F2-4

3N1

3,260

26N1

9,650

3L1

1,640

17R1

1,390

2M2

2,820

11D1

541

9Q1

1,500

16F1

1,730

15L1

435

14P1

1,160

24C1

685

Perris

Valley

RWRF

0

0

2 MILES

2 KILOMETERS

117°12'30"

Perris

PERRIS

VALLEY

(no data)

Location of map shown in figure 2.

Figure 25. Stiff diagrams for selected wells and reclaimed-water storage ponds, and the Perris Valley reclamation facility, Perris-South subbasin, Riverside 

County, California.
38 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

The stable isotopes of hydrogen and oxygen

(fig. 27) are not useful for distinguishing between 

ground water and reclaimed water in the Perris-South 

subbasin. Ground water from all wells plot parallel to, 

and below, the global meteoric water line; none of the 

wells appear to have a greater proportion of reclaimed 

water than any of the others. The lack of differentiation 

may be due to the similarity in isotopic composition in 

the reclaimed water and native ground water. Of the 

three subbasins, reclaimed water from the Perris Valley 

RWRF and storage pond plot closest to the global 

meteoric water line. The lack of differentiation among 

ground-water samples may also arise because the 

difference in isotopic composition between water from 

the RWRF and the storage pond is larger than the range 

observed in the subbasin ground water. In the absence 

of a distinguishing isotopic characteristic for a source 

of water, it is difficult to identify the presence of that 

source in the native ground water.

In the Perris-South subbasin, UV-A is less 

conclusive for identifying the presence of reclaimed 

water in the subsurface (fig. 28) than in the Menifee 

and Winchester subbasins. The UV-A values for 

reclaimed water from the Perris Valley RWRF and 

Trumble Road storage pond are 0.111 and 0.126, 

respectively. Two of the sampled wells (9H1 and 4A1) 

have UV-A values greater than 0.01; both are located in 

the general vicinity of the ponds (fig. 26). However, 

four wells (9E1, 9H2, 3N1, and 3C1), also located in 

the vicinity of the ponds, have UV-A values ranging 

from <0.001 to 0.009. Three wells (4M1, 3R1, and 

33Q1), generally located away from the ponds, have 

UV-A values ranging from 0.005 to 0.009. 

Cations Anions

Sodium and potassium

Magnesium

Calcium

Chloride and fluoride

Sulfate

Bicarbonate

0

Stiff Diagram

Well and number - Number in italics is

dissolved-solids concentration,

in milligrams per liter.

Area of irrigation with reclaimed water

Differences in shape reflect difference in chemical composition.

(Stiff, 1951)

Milliequivalents per liter

100 100

Unconsolidated deposits

Consolidated rocks

Reclaimed-water storage pond

Regional water reclamation facility

(includes storage ponds)

Ground-water subbasin boundary

EXPLANATION

3R1

1,150

Figure 25.—Continued.
Tracing Reclaimed Water in the Three Subbasins 39

4

29 28

27 26

33 35 32 34

14

2

11

16 15

9

8 7

18

19

5

6

3

10

17

25

36

1

12

13

21 22 23 20 24

R3W

T4S

T5S

Murrieta Rd

Menifee Rd

Antelope Rd

San Jacinto Ave

Case Rd

Ellis Ave

215

74

74

Goetz Rd

San Jacinto

River

Trumble

Rd

Pond

Perris

Valley Storm

Drain

Skiland Lake

3R1

1,319

3N1

1,323

4M1

1,327

9E1

1,333

9H1

1,327

9H2

1,326

33Q1

1,322

4A1

1,317 3C1

1,311

3L1

1,319

26N1

1,279

Perris

Valley

RWRF

2M1

1,308

10N1

1,329

34Q1

1,302

33E1

1,322

26F1

1,276

26M1

1,277

1,300

1,350

1,400

1,350

?

?

?

?

?

?

?

?

?

?

?

?

117°12'30"

Perris

PERRIS

VALLEY

0

0

2 MILES

2 KILOMETERS

24F4

1,418

24F3

1,375

24F2

1,400

24F4

1,418

24F3

1,375

24F2

1,400

Location of map shown in figure 2

See figures 8 and 17 for continuation of contours

in the Menifee and Winchester subbasins

to the south and east, respectively.

Figure 26. Water-level contours, directions of ground-water flow, and wells with ultraviolet-absorbance data in the Perris-South subbasin, Riverside County, 

California.
40 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

EXPLANATION

Area of irrigation with reclaimed water

Unconsolidated deposits

Consolidated rocks

Reclaimed-water storage pond

Regional Water Reclamation Facility

Ground-water subbasin boundary

Water-level contour - Dashed where

approximately located; queried where

uncertain. Contour interval is 10 feet

Direction of ground-water flow

1,400 ?

34Q1

1,302

Abbreviated well number

Water-level altitude (1995),

in feet above sea level

Abbreviated well number

Water-level altitude (1995),

in feet above sea level

Well with other water-quality data

Abbreviated well number

Water-level altitude (1995),

in feet above sea level

Well with water-level data only

3L1

1,319

10N1

1,329

Well with UV-Absorbance data - Larger

dot indicates well with UV-A > 0.01

Figure 26.—Continued.

Table 6. Dissolved-solids (residue on evaporation) and chloride concentrations for selected wells in the vicinity of the reclaimed-water ponds, PerrisSouth subbasin, Riverside County, California 

[Site name: RWRF, Perris Valley Regional Water Reclamation Facility; Pond, Trumble Road Pond; State well number (see “Well-Numbering System” at front of 

report); wells listed in general upgradient to downgradient order; perforated interval in feet below land surface, from Burton and others,1996; mg/L, milligrams 

per liter; —, no data]

Site name or State well No. Perforated 

interval

Dissolved solids

(mg/L)

 Chloride 

(mg/L)

RWRF — — 120

POND — 599 130

5S/3W-17R1 ?–370 1,390 390

5S/3W-16F1 — 1,730 680

5S/3W-9Q1 180–600 1,500 430

5S/3W-9E1 220–240 1,930 610

5S/3W-9H2 240–250 1,370 520

5S/3W-9H1 220–240 2,100 860

5S/3W-3N1 290–310, 

555–575

3,260 1,300

5S/3W-3L1 230–250 1,640 710

5S/3W-4A1 190–210 2,470 1,200

5S/3W-3C1 230–250 3,780 2,100
Tracing Reclaimed Water in the Three Subbasins 41

4A1

4M1

9Q1

24C1

3C1

3L1

3R1

9H2

9H1

9E1

3N1

33Q1

Perris-South Subbasin

DELTA OXYGEN-18, IN PER MIL

DELTA DEUTERIUM, IN PER MIL

-12 -10 -8 -6 -4

-40

-50

-60

-70

-80

-90

Global Meteoric

Water Line

Evaporative

Trend Line

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

Perris-South Subbasin

CHLORIDE, IN MILLIGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

≤0.001

0 7,000 1,000 2,000 3,000 4,000 5,000 6,000

4A1

9H1

3R1

3C1 4M1 9E1

9H2

33Q1

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation Facility

3N1

4A1

9H1 3R1

4M1, 3C1

9E1

9H2

3N1

33Q1

Perris-South Subbasin

DISSOLVED ORGANIC CARBON, IN MILLIGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

≤0.001

0 6 2 4 8 10 12

Wells with

UV-A ≥ 0.01

EXPLANATION

Storage Pond

Regional Water

Reclamation

Facility

Perris-South Subbasin

BORON, IN MICROGRAMS PER LITER

UV-ABSORBANCE AT 254 NANOMETERS

1.0

0.1

0.01

≤0.001

0 200 300 600 100 400 700 500

Wells with

UV-A ≥ 0.01

EXPLANATION

4A1

4M1

9H1

3R1

3C1

9E1

9H2

33Q1

Storage Pond

Regional Water

Reclamation Facility

3N1

Figure 27. Delta deuterium plotted against delta oxygen-18 for selected 

wells in the Perris-South subbasin, Riverside County, California.

Figure 29. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved chloride for selected wells in the Perris-South subbasin, 

Riverside County, California.

Figure 28. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved organic carbon for selected wells in the Perris-South subbasin, 

Riverside County, California.

Figure 30. Ultraviolet-absorbance at 254 nanometers plotted against 

dissolved boron for selected wells in the Perris-South subbasin, 

Riverside County, California.
42 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Plots of UV-A versus chloride, and UV-A versus 

boron, are insufficient for identifying the presence of 

reclaimed water in the subsurface in the Perris-South 

subbasin (figs. 29, 30). The chloride concentrations at 

the two wells that have elevated UV-A (9H1 and 4A1) 

are relatively low; however, other wells also have 

relatively low chloride concentrations. Consequently, 

we do not calculate the fraction reclaimed water using 

chloride (or UV-A) in the Perris-South subbasin, as was 

done in the Menifee and Winchester subbasins. The 

boron concentrations at the two wells with elevated 

UV-A have boron concentrations dissimilar to that of 

the reclaimed water. Of greater significance, the boron 

concentration of the reclaimed water (430 to 490 mg/L) 

is not an end-member; ground water in the Perris-South 

subbasin can have boron concentrations lower or 

higher than that of the reclaimed water 

(30 to 820 mg/L, table 1).

Figure 31. Boron/chloride ratio plotted against dissolved chloride for selected 

wells in the Perris-South subbasin, Riverside County California, without and with 

superimposed mixing curves. (A) Boron/chloride ratio plotted against dissolved 

chloride. (B) Boron/chloride ratio plotted against dissolved chloride with 

superimposed mixing curves. Mixing curves are based on wells 3C1 and 4M1 as 

representative of native ground water and the storage pond as representative of 

reclaimed water.

Perris-South Subbasin

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

4.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 7,000 1,000 2,000 3,000 4,000 5,000 6,000

Wells with

UV-A ≥ 0.01

EXPLANATION

4A1

9H1

3C1

3N1

2M2

33Q1

15L1

14P1

9Q1

9H2

3R1

9E1

16F1

3L1

17R1

11D1

24C1

4M1 26N1

Storage Pond

Regional Water

Reclamation Facility

A

CHLORIDE, IN MILLIGRAMS PER LITER

BORON/CHLORIDE RATIO TIMES 1,000

4.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 7,000 1,000 2,000 3,000 4,000 5,000 6,000

Wells with

UV-A ≥ 0.01

EXPLANATION

4A1

9H1

3C1

17R1

4M1

Storage Pond

Regional Water

Reclamation Facility

B

Mixing curve with well

3C1 as native ground-water

end-member

Mixing curve with well

4M1 as native ground-water

end-member
Tracing Reclaimed Water in the Three Subbasins 43

In the Perris-South subbasin, as in the 

Winchester and Menifee subbasins, the presence of 

reclaimed water in the subsurface is not indicated by 

elevated values of DOC. Both of the wells with UV-A 

values greater than 0.01 (9H1 and 4A1) have DOC 

values less than 1 mg/L (fig. 28). The ponds and RWRF 

have DOC values greater than 7 mg/L.

In the Perris-South subbasin, as in the 

Winchester subbasin, a plot of boron/chloride ratio 

versus chloride (fig. 31A) is not conclusive for 

identifying the presence of reclaimed water in the 

subsurface. The two wells that have elevated UV-A 

(9H1 and 4A1) have boron/chloride ratios that are 

dissimilar to that of the reclaimed water. Instead, the 

data for wells 9H1 and 4A1 plot close to the wells 

thought not to contain reclaimed water. Nevertheless, 

evaluation of the data using mixing curves may still be 

useful. 

0.0

0.5

1.0

1.5

2.0

3.0

2.5

4.0

3.5

0 0.2 0.4 0.6 0.8 1

FRACTION RECLAIMED WATER

BORON/CHLORIDE RATIO TIMES 1,000

B/Cl = 0.18 (shift wells 9H1

and 4A1 to the right)

B/Cl = 0.4 (shift wells 9H1

and 4A1 upward)

Range of fraction reclaimed water

present in ground-water samples

from wells 9H1 and 4A1

Mixing curve with well 3C1 as

native ground-water end-member

EXPLANATION

Figure 32. Estimation of the fraction reclaimed water using a two-end member mixing model in the vicinity of the Trumble Road storage pond, Perris-South 

subbasin, California.
44 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Two wells were chosen as possibly 

representative of the native ground-water component 

present at the locations that have elevated UV-A. These 

wells, 4M1 and 3C1, were chosen because they have 

chloride concentrations greater, and boron/chloride 

ratios lower, than those of the wells with elevated UVA. Consequently, mixing curves using one of these 

wells as an end-member and reclaimed water as the 

other, have the possibility of passing through or close 

to the wells with elevated UV-A (fig. 31B). The two 

wells with elevated UV-A (4A1 and 9H1) plot 

relatively far below the mixing curve that is based on 

end-member-well 4M1, and relatively close to the 

mixing curve based on well 3C1. These results suggest 

that water from well 3C1 is the more likely 

representative of the native ground-water component at 

wells 4A1 and 9H1. Well 4A1 is virtually on the 

mixing curve, and the fraction of reclaimed water is 

about 40 percent (fig. 32). If well 9H1 is shifted to the 

right onto the 3C1-mixing-curve, the fraction of 

reclaimed water is about 40 percent (fig. 32); if the 

point is shifted upward, then the fraction is about 65 

percent. These results suggest that the ground water 

with elevated UV-A in the Perris-South subbasin could 

consist of 40 to 65 percent reclaimed water. However, 

the two-end-member model might not be valid in this 

subbasin, as indicated by the relatively large amount of 

variation in chloride concentrations and boron/chloride 

ratios observed at other wells nearby. Also, boron may 

not be conservative in this subbasin.

SUMMARY AND CONCLUSIONS

As a component in the management of water 

resources in the Menifee, Winchester, and Perris-South 

subbasins, ponds are operated by the Eastern Municipal 

Water District for the temporary storage of reclaimed 

water that is produced by several regional waterreclamation facilities (RWRFs). Although some of the 

ponds have been in operation for more than 25 years, 

the amount of water percolating and its effect on 

ground-water quality are not well understood. 

Therefore, there is a need to develop methods of tracing 

reclaimed water in the subsurface that can be used in 

the study area. 

A primary goal of the study was to evaluate the 

potential for using various constituents or 

characteristics, measured in ground-water samples, as 

tracers of reclaimed water that has infiltrated from the 

storage ponds into the ground water in the three 

subbasins. A secondary goal was to estimate the degree 

to which the infiltrated reclaimed water has mixed with 

the native ground water. The evaluation of potential 

tracers and the estimation of mixing focused on data 

from wells located relatively close to the ponds. 

 The water samples collected from the three 

RWRFs, three sets of storage ponds, and selected 

ground-water wells were analyzed for major ions, 

nutrients, selected trace elements, stable isotopes of 

hydrogen and oxygen, and organic carbon. Also, some 

of the samples were analyzed for ultraviolet absorbance 

(UV-A) at a wavelength of 254 nm, methylene blue 

active substances (MBAS), linear alkylbenzene 

sulfonate (LAS), and caffeine. 

The most useful constituents and characteristics 

for evaluation of the fate and mixing of reclaimed water 

in the Menifee, Winchester, and Perris-South subbasins 

are major-ion composition (as expressed in Stiff 

diagrams), stable isotopes of hydrogen and oxygen, 

UV-A, chloride concentration, and plots of 

boron/chloride ratios versus chloride concentrations. 

Emphasis was placed on evaluating the utility of UV-A 

as a tracer and the utility of boron/chloride ratios for 

estimating the percentage of reclaimed water in ground 

water. The use of UV-A is convenient because analysis 

of samples for UV-A is relatively easy and inexpensive.

In the Menifee subbasin, major-ion data, stable 

isotopes, chloride, UV-A, and boron/chloride ratio are 

all useful in identifying reclaimed water, and the results 

based on these indicators are consistent with each 

other. In water from wells near, and downgradient 

from, the ponds, stable-isotope values and ionic 

composition are shifted relative to native ground water; 

have lower chloride concentration; have elevated UVA; and plot on a single boron/chloride mixing curve. 

The results suggest that values of UV-A greater than or 

equal to 0.007 indicate the presence of reclaimed water 

in the Menifee subbasin. Ground-water samples with 

UV-A greater than 0.007 consist of about 75 to 100 

percent reclaimed water, on the basis of chloridemixing calculations and boron/chloride-versus-chloride 

mixing calculations.
References Cited 45

In the Winchester subbasin, results based on the 

same factors used in the Menifee subbasin are less 

conclusive; nevertheless, UV-A can be used as a tracer. 

Values of UV-A greater than 0.01 indicate the presence 

of reclaimed water. Values from 0.006 to 0.01 may 

indicate the presence of reclaimed water; however, 

water from wells not likely to have reclaimed water 

may also have UV-A values in this range. Groundwater samples with UV-A greater than 0.01 appear to 

contain about 25 percent reclaimed water (range 6 to 

32 percent), on the basis of the consistency of the 

results of three types of mixing calculations—chloride 

alone, boron/chloride versus chloride, and UV-A. 

In the Perris-South subbasin, the potential tracers 

are not as conclusive in identifying reclaimed water as 

in the Menifee and Winchester subbasins. The inability 

to identify tracers may be a consequence of the 

multiple, spatially distributed sources of reclaimed 

water; the relative absence of wells close to the 

reclaimed-water pond; and the short period of 

operation (about 1 year) of the pond at the time of 

sampling. Mixing calculations suggest that groundwater samples with elevated UV-A values (greater than 

0.01) in the Perris-South subbasin could contain as 

much as 40 to 65 percent reclaimed water. However, 

the assumptions on which these numbers are based are 

not as appropriate as in the other two subbasins.

The results of this study indicate that UV-A can 

be used as a qualitative indicator of the presence of 

reclaimed water. Mixing calculations based on chloride 

and on boron/chloride ratios indicate that UV-A is not 

conservative, and therefore UV-A is not suitable for 

estimating the fraction of reclaimed water in the 

subsurface. The results also suggest that boron/chloride 

ratios are useful for estimating the fraction of 

reclaimed water. The accuracy of the estimates depends 

primarily on correctly identifying the boron/chloride 

ratio—and secondarily the chloride concentration—of 

the native ground water present prior to mixing. 

Resampling of selected wells located close to the 

reclaimed-water ponds, and sampling of additional 

wells, would provide updated estimates of the fraction 

of reclaimed water and confirm the usefulness of UV-A 

and boron/chloride ratios as tracers of reclaimed water.

REFERENCES CITED

Barber, L.B., II, Thurman, E.M., Schroeder, M.P., and 

LeBlanc, D.R., 1988, Long-term fate of organic 

micropollutants in sewage-contaminated groundwater: 

Environmental Science and Technology, v. 22, no. 2, p. 

205–211.

Barber, L.B., II, Leenherr, J.A., Tabor, C.F., Jr., Brown, G.K., 

Noyes, T.I., and Noriega, M.C., 1995, Organic 

compounds and sewage-derived compounds, in Moody, 

J.A. ed., Chemical data for water samples collected 

during four upriver cruises on the Mississippi River 

between New Orleans, Louisiana, and Minneapolis, 

Minnesota: U.S. Geological Survey Open-File Report 

94-523, p. 211–297.

Barber, L.B., II, Brown, G.K., Kennedy, K.R., Leenheer, 

J.A., Noyes, T.I., Rostad, C.E., and Thorn, K.A., 1997, 

Organic constituents that persist during aquifer storage 

and recovery of reclaimed water in Los Angeles 

County, California: Proceedings, American Water 

Resources Association symposium, Conjunctive Use of 

Water Resources—Aquifer Storage and Recovery, 

October 19-23, 1997, Long Beach, California, 

Technical Publication Series TPS, v. 97-2, p. 261–272.

Biehler, S., and Lee, T.C., 1994, Subsurface structure of the 

Winchester basin, Riverside County, California: 

Department of Earth Sciences, University of California, 

Riverside, California, 47 p.

_________ 1995, Subsurface structure of the Menifee basin, 

Riverside County, California: Department of Earth 

Sciences, University of California, Riverside, 

California, 59 p.

Brenton, R.W., and Arnett, T.L., 1993, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory--Determination of dissolved organic carbon 

by UV-promoted persulfate oxidation and infrared 

spectrometry: U.S. Geological Survey Open-File 

Report 92-480, 12 p.

Burkhardt, M.R., Cinotto, P.J., Frahm, G.W., Woodworth, 

M.T., and Pritt, J.W., 1995, Methods of analysis by the 

U.S. Geological Survey National Water Quality 

Laboratory--Determination of methylene blue active 

substances by spectrophotometry: U.S. Geological 

Survey Open-File Report 95-189, 20 p.

Burton, C.A., Kaehler, C.A., and Christensen, A.H., 1996, 

Well-construction, water-quality, and water-level data, 

and pond-infiltration estimates, for three ground-water 

subbasins, Riverside County, California: U.S. 

Geological Survey Water-Resources Investigations 

Report 96-4294, 114 p.
46 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

California Department of Water Resources, 1959, Santa Ana 

River Investigations: Bulletin No. 15, 207 p.

_______1964, Ground water quality objectives, San Jacinto 

River Valley, Riverside County, California, plate.

_______1979, Ground water quality conditions in Menifee, 

Winchester, and Perris South subareas: District Report, 

March, 1979, 82 p.

_______1994, Five-year report of the municipal water 

quality investigations program: variously paged.

Coplen, T.B., Wildman, J.D., and Chen, J., 1991, 

Improvements in the gaseous hydrogen-water 

equilibration techniques for hydrogen isotope ratio 

analysis: Analytical Chemistry v. 63, p. 910–912.

Craig, H., 1961a, Isotopic variation in meteoric waters: 

Science, v. 133, p. 1702–1703.

_______ 1961b, Standard for reporting concentrations of 

deuterium and oxygen-18 in natural waters: Science, 

v. 133, p. 1833–1834

Epstein, S. and Mayeda, T., 1953, Variation of O-18 content 

of water from natural sources: Geochemica et 

Cosmochemica Acta v. 4, p. 213–224.

Fishman, M.J., 1993, Methods of analysis by the U.S. 

Geological Survey National Water Quality 

Laboratory—Determination of inorganic and organic 

constituents in water and fluvial sediments: U.S. 

Geological Survey Open-File Report 93-125, 217 p.

Fishman, M.J., and Friedman, L.C., 1989, Methods for 

determination of inorganic substances in water and 

fluvial sediments: U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 5, chap. A1, 

545 p.

Flynn, J.L., and Barber, L.B., 2000, Quality of ground water 

and surface water in an area of individual sewage 

disposal system use near Barker Reservoir, Nederland, 

Colorado, August-September 1998: U.S. Geological 

Survey Open-File Report 00-214, 8 p.

Gonfiantini, R., 1978, Standards for stable isotope 

measurements in natural compounds: Nature, v. 271, 

p. 534–536.

Izbicki, J.A., Martin, Peter, and Michel, R.L., 1995, Source, 

movement, and age of groundwater in the upper part of 

the Mojave River basin, California, USA: in Adar, 

E.M., and Leibundgut, Christian, Application of tracers 

in arid zone hydrology, Vienna, Austria, August 22–26, 

1994, Proceedings: Wallingford, England,

Izbicki, J.A., and Martin, Peter, 1997, Use of isotopic data to 

evaluate recharge and geologic controls on the 

movement of ground water in Las Posas Valley, Ventura 

County, California: U.S. Geological Survey WaterResources Investigations Report 97-4035, 12 p.

Izbicki, J.A., Danskin, W.R., and Mendez, G.O., 1998, 

Chemistry and isotopic composition of ground water 

along a section near the Newmark area, San 

Bernardino, California: U.S. Geological Survey WaterResources Investigations Report 97-4179, 27 p.

Izbicki, J.A., Mendez, G.O., and Burton, C.A., 2000, 

Stormflow chemistry in the Santa Ana river below 

Prado Dam and at the diversion downstream from 

Imperial Highway, Southern California, 1995-98: 

U.S. Geological Survey Water-Resources Investigations 

Report 00-4127, 92 p.

Kaehler, C.A., Burton, C.A., Rees, T.F., and Christensen, 

A.H., 1998, Geohydrology of the Winchester subbasin, 

Riverside County, California: U.S. Geological Survey 

Water-Resources Investigations Report 98-4102, 90 p.

Krazner, S.W., Crouse, J.P., Buffle, Jacques, and Perdue, 

E.M., 1996, Three approaches for characterizing NOM: 

Journal of American Water Works Association, v. 88,

p. 66–79.

Lang, D.J., 1979, Water-resources data, 1970-75, for Perris 

Valley and vicinity, Riverside County, California: U.S. 

Geological Survey Open-File Report 79-1256, 127 p.

Leenheer, J.A., Rostad, C.E., Barber, L.B., Schroeder, R.A., 

Anders, R., and Davisson, M.L., 2001, Nature and 

chlorine reactivity of organic constituents from 

reclaimed water in groundwater, Los Angeles County, 

California: Environmental Science and Technology, 

v. 35, p. 3869–3876.

NBS/Lowry, 1987, feasibility of well recharge of reclaimed 

water and well extraction of groundwater for Menifee 

Village irrigation: Irvine, California, NBS/Lowry, 

Engineers and Planners.

Piper, A.M., 1944, A graphic procedure in the geochemical 

interpretation of water analyses: American Geophysical 

Union transactions, v. 25, p. 914–923.

Pruitt, J.B., Elder, J.F., and Johnson, I.K., 1988, Effects of 

treated municipal effluent irrigation on ground water 

beneath sprayfields, Tallahassee, Florida: U.S. 

Geological Survey Water-Resources Investigations 

Report 88-4092, 35 p.
References Cited 47

Schneider, B.J., Ku, H.F.H., and Oaksford, E.T., 1987, 

Hydrologic effects of artificial recharge experiments 

with reclaimed water at East Meadow, Long Island, 

New York: U.S. Geological Survey Water-Resources 

Investigations Report 85-4323, 79 p.

Schroeder, R.A., Anders, R., Bohlke, J.K., Michel, R.L., and 

Metge, D.W., 1997, Water quality at production wells 

near artificial-recharge basins in Montebello Forebay, 

Los Angeles County, California: in, Proceedings of 

AWRA Symposium, Conjunctive Use of Water 

Resources: Aquifer Storage and Recovery, Kendall, 

D.R., Ed., American Water Resources Association, 

Herndon, Va., p. 273–284.

Stiff, H.A., 1951, The interpretation of chemical water 

analysis by means of patterns: Journal of Petroleum 

Technology, v. 3, no. 10, p.15–17.

Sylvester, M.A, 1983, Land application of wastewater and its 

effect on ground-water quality in the LivermoreAmador Valley, Alameda County, California: U.S. 

Geological Survey Water-Resources Investigations 

Report 82-4100, 58 p.

Trehy, M.L., Gledhill, W.E., and Orth, R.G., 1990, 

Determination of linear alkylbenzenesulfonates and 

dialkyltetralinsulfonates in water and sediment by gas 

chromatography/mass spectrometry: Analytical 

Chemistry, v. 62, p. 2581–2586.

U.S. Environmental Protection Agency, 1990, Drinking 

water regulations and health advisories: U.S. 

Environmental Protection Agency Office of Water, EPA 

882-R-94-001, 11 p.

U.S. Geological Survey, 1997 to present, National field 

manual for the collection of water-quality data: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chaps. A1–A9, 2 v., variously 

paged. [Also available online at 

http://pubs.water.usgs.gov/twri9A. Chapters originally 

were published from 1997 to 1999; updates and 

revisions are ongoing and are summarized at: 

http://water.usgs.gov/owq/FieldManual/mastererrata.ht

ml]

Wershaw, R.L., Fishman, M.J., Grabbe, R.R., and Lowe, 

L.E., 1983, Methods for the determination of organic 

substances in water and fluvial sediments, U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 5, chap. A3: U.S. Geological 

Survey Open-File Report 82-1004, 173 p.
48 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

THIS PAGE LEFT BLANK INTENTIONALLY
TABLE 1 49

TABLE 1
50 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and South Perris subbasins, Riverside County, California—Continued

Site name or 

State well No. Date

Specific 

conductance,

field

(μS/cm)

pH,

field

(standard units)

Water

temperature

(

o

C)

Hardness

(mg/L as CaCO3)

Calcium,

dissolved

(mg/L)

Menifee subbasin

Sun City RWRF 07/03/95 1,230 7.0 11.1 260 64

Sun City Storage Pond 07/03/95 1,380 7.1 24.5 300 70

5S/3W-28M1S 07/20/95 1,750 7.2 23.1 230 64

5S/3W-28M2S 07/20/95 2,370 6.9 22.5 440 110

5S/3W-28M3S 07/20/95 5,540 6.3 22.5 2,300 670

5S/3W-28M4S 07/20/95 4,160 6.4 21.6 1,500 400

5S/3W-32A1S 08/01/95 12,400 5.9 24.3 5,100 1,500

5S/3W-32B1S 08/03/95 1,280 7.2 21.6 77 17.0

5S/3W-32C1S 08/02/95 3,230 6.8 24.4 820 250

5S/3W-32G1S 07/19/95 3,590 6.6 21.7 620 160

5S/3W-32H1S 08/02/95 1,770 6.5 21.7 460 120

5S/3W-32L1S 07/28/95 6,910 6.4 22.7 1,600 450

5S/3W-34Q2S 07/28/95 4,230 6.6 23.5 1,500 410

5S/3W-35N2S 08/01/95 4,310 5.9 25.5 1,500 350

5S/3W-36P2S 08/01/95 2,610 6.3 26.0 1,000 220

6S/3W-01J2S 08/15/95 4,670 6.5 21.5 1,700 480

6S/3W-02A1S 07/26/95 4,910 6.3 23.3 1,700 470

6S/3W-02E1S 07/27/95 1,730 6.1 28.9 660 170

6S/3W-02G2S 07/26/95 1,750 6.9 23.1 530 140

6S/3W-05E1S 08/15/95 517 7.4 24.0 150 43.0

Winchester subbasin

Temecula RWRF 07/20/95 1,120 7.5 13.1 190 50

Winchester Storage Pond 06/29/95 1,240 9.3 26.0 210 53

5S/2W-29L2S 08/11/95 9,550 6.6 21.0 2,000 390

5S/2W-29L3S 08/14/95 7,270 6.2 21.5 1,900 410

5S/2W-29N1S 07/12/95 5,320 6.0 22.7 1,700 440

5S/2W-30C1S 07/28/95 3,370 7.1 22.8 1,100 290

5S/2W-30D2S 07/19/95 4,440 6.3 22.6 1,900 530

5S/2W-30G2S 07/07/95 6,550 6.6 21.2 1,600 410

5S/2W-30G3S 08/02/95 3,660 6.7 20.5 1,100 290

5S/2W-30H2S 07/06/95 9,430 6.3 22.0 2,200 550

5S/3W-24F2S 07/21/95 690 8.0 24.6 70 24.0

5S/3W-24F3S 08/03/95 3,780 6.3 23.9 1,600 470

5S/3W-24F4S 07/21/95 1,970 6.8 35.0 650 180

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California

[State well number: See “Well-Numbering System” in “Contents” section; RWRF, regional water-reclamation facility; for well-construction information and 

water-level data, see Burton and others, 1996, tables 1 and 3; μS/cm, microsiemens per centimeter at 25oC; oC, degrees Celsius; mg/L, milligrams per liter; 

μg/L, micrograms per liter; per mil, parts per thousand; TOC, total organic carbon; DOC, dissolved organic carbon; nm, nanometer; MBAS, metheylene blue 

activated substances; LAS, linear alkylbenzene sulfonate; <, actual value less than value shown; e, estimated; c, calculated from specific conductance; —, no 

data] 
Table 1 51

Perris-South subbasin

Perris Valley RWRF 07/03/95 804 7.6 13.1 120 29

Trumble Road Storage Pond 06/30/95 990 7.9 26.5 160 39

4S/3W-26N1S 08/24/95 13,900 7.4 27.1 3,700 1,400

4S/3W-33Q1S 07/25/95 6,060 7.5 21.7 1,100 340

5S/3W-02M2S 08/17/95 4,470 7.0 23.0 1,800 460

5S/3W-03C1S 07/17/95 6,450 7.6 24.2 1,600 540

5S/3W-03L1S 07/17/95 2,770 7.2 23.6 770 240

5S/3W-03N1S 07/24/95 4,800 6.4 25.6 1,700 490

5S/3W-03R1S 07/18/95 1,900 7.3 23.5 590 160

5S/3W-04A1S 07/18/95 4,260 7.5 22.8 500 160

5S/3W-04M1S 07/26/95 17,500 6.4 21.5 6,400 1,900

5S/3W-09E1S 07/26/95 2,780 6.9 23.1 990 280

5S/3W-09H1S 07/25/95 3,190 6.5 24.1 860 240

5S/3W-09H2S 07/27/95 2,180 6.4 24.1 740 200

5S/3W-09Q1S 08/22/95 2,270 6.3 25.6 760 220

5S/3W-11D1S 08/09/95 859 7.5 23.3 260 68.0

5S/3W-11M2S 08/30/95 1,390 6.8 23.0 — —

5S/3W-14P1S 08/10/95 1,750 6.1 22.3 610 170

5S/3W-15L1S 08/11/95 663 6.7 22.5 190 51.0

5S/3W-16F1S 08/09/95 2,570 7.1 22.3 960 270

5S/3W-17R1S 07/24/95 1,920 7.2 25.1 780 170

5S/3W-24C1S 08/04/95 963 6.8 24.9 310 89.0

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and South Perris subbasins, Riverside County, California—Continued

Site name or 

State well No. Date

Specific 

conductance,

field

(μS/cm)

pH,

field

(standard units)

Water

temperature

(

oC)

Hardness

(mg/L as CaCO3)

Calcium,

dissolved

(mg/L)
52 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Magnesium,

dissolved

(mg/L)

Sodium,

dissolved

(mg/L),

Potassium,

dissolved

(mg/L)

Alkalinity,

(mg/L as 

CaCO3)

Sulfate,

dissolved

(mg/L)

Chloride,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Bromide,

dissolved

(mg/L)

Menifee subbasin

Sun City RWRF 25 150 16.0 e140 240 130 0.4 0.04

Sun City Storage Pond 29 170 16.0 150 270 160 .3 .14

5S/3W-28M1S 17.0 330 13.0 780 14.0 86.0 .3 .31

5S/3W-28M2S 40.0 400 19.0 1,200 13.0 110 .3 .27

5S/3W-28M3S 160 230 23.0 570 410 1,400 .1 2.30

5S/3W-28M4S 120 290 7.50 240 280 1,200 .2 1.80

5S/3W-32A1S 320 900 38.0 840 690 3,700 <.1 12.0

5S/3W-32B1S 8.30 230 1.00 200 200 130 .3 .20

5S/3W-32C1S 47.0 420 6.30 190 900 430 .2 .68

5S/3W-32G1S 54.0 550 5.10 240 840 520 .4 1.00

5S/3W-32H1S 38.0 210 5.40 130 540 150 .3 .22

5S/3W-32L1S 120 910 8.80 320 810 1,600 .3 .03

5S/3W-34Q2S 120 430 11.0 230 700 1,000 .3 .31

5S/3W-35N2S 150 390 13.0 610 500 850 .2 1.70

5S/3W-36P2S 120 250 10.0 1,440 13.0 95.0 .3 .08

6S/3W-01J2S 130 370 11.0 280 790 1,000 .3 2.00

6S/3W-02A1S 130 390 11.0 240 840 1,100 .3 1.90

6S/3W-02E1S 58.0 120 8.20 560 100 170 .3 .50

6S/3W-02G2S 43.0 150 5.50 220 180 300 .4 .71

6S/3W-05E1S 10.0 44.0 1.80 120 36.0 38.0 .5 .18

Winchester subbasin

Temecula RWRF 16 160 14.0 170 150 130 .5 .12

Winchester Storage Pond 18 200 14.0 220 170 180 .5 .28

5S/2W-29L2S 240 1,460 5.60 410 1,300 2,400 .2 4.50

5S/2W-29L3S 220 870 9.30 370 840 1,900 .2 3.60

5S/2W-29N1S 150 510 9.70 150 950 1,200 .1 2.60

5S/2W-30C1S 94.0 220 5.80 120 260 830 .3 1.60

5S/2W-30D2S 140 200 7.70 170 950 790 .1 1.60

5S/2W-30G2S 140 900 6.50 120 1,200 1,400 .2 2.70

5S/2W-30G3S 91.0 360 4.50 160 600 730 .3 1.30

5S/2W-30H2S 210 1,300 7.90 120 1,200 2,500 .2 4.60

5S/3W-24F2S 2.40 110 3.60 120 17.0 110 .4 .42

5S/3W-24F3S 95.0 150 10.00 260 86.0 1,000 <.1 1.60

5S/3W-24F4S 48.0 98.0 6.40 88 28.0 510 .1 1.20
Table 1 53

Perris-South subbasin

Perris Valley RWRF 11 110 12.0 e102 81 120 0.2 0.07

Trumble Road Storage Pond 14 140 13.0 138 110 130 .3 .18

4S/3W-26N1S 50.0 1,400 17.0 56 200 4,700 .9 7.60

4S/3W-33Q1S 71.0 750 10.0 36 100 1,900 .2 4.30

5S/3W-02M2S 160 120 16.0 120 190 1,300 .4 2.30

5S/3W-03C1S 57.0 130 14.0 71 100 2,100 <.1 4.10

5S/3W-03L1S 42.0 210 9.20 190 31.0 710 .1 1.60

5S/3W-03N1S 110 280 16.0 — 37.0 1,300 .2 2.80

5S/3W-03R1S 46.0 120 7.10 390 22.0 450 .4 1.30

5S/3W-04A1S 25.0 650 7.70 350 200 1,200 .1 2.70

5S/3W-04M1S 400 1,300 21.0 220 340 6,100 <.1 2.10

5S/3W-09E1S 71.0 160 4.50 270 150 610 .2 1.20

5S/3W-09H1S 62.0 270 7.40 150 48.0 860 .1 1.90

5S/3W-09H2S 57.0 120 6.60 210 50.0 520 .1 1.20

5S/3W-09Q1S 50.0 150 7.50 420 44.0 430 .2 .98

5S/3W-11D1S 21.0 62.0 6.10 140 17.0 150 .4 .53

5S/3W-11M2S — — — 180 — — — —

5S/3W-14P1S 45.0 100 4.10 180 68.0 380 .2 .89

5S/3W-15L1S 16.0 49.0 2.40 81 82.0 85.0 .3 .32

5S/3W-16F1S 68.0 140 3.50 140 73.0 680 .2 1.40

5S/3W-17R1S 85.0 74.0 4.00 160 180 390 .2 .81

5S/3W-24C1S 20.0 63.0 4.50 110 28.0 200 .2 .47

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Magnesium,

dissolved

(mg/L)

Sodium,

dissolved

(mg/L),

Potassium,

dissolved

(mg/L)

Alkalinity,

(mg/L as 

CaCO3)

Sulfate,

dissolved

(mg/L)

Chloride,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Bromide,

dissolved

(mg/L)
54 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Silica,

dissolved

(mg/L)

Dissolved 

Solids,

residue

(mg/L)

Nitrate,

NO2 + NO3

dissolved

(mg/L as N)

Nitrite,

dissolved

(mg/L as N)

Ammonia,

dissolved

(mg/L as N)

Phosphorus,

ortho,

dissolved

(mg/L)

Arsenic,

dissolved

(μg/L)

Barium,

dissolved

(μg/L)

Menifee subbasin

Sun City RWRF 12.0 c802 8.28 0.72 3.90 2.40 2 59

Sun City Storage Pond 13.0 864 2.70 .70 3.00 2.10 2 62

5S/3W-28M1S 37.0 1,080 <.05 <.010 .03 .29 2 430

5S/3W-28M2S 51.0 1,510 <.05 <.010 .02 1.00 12 590

5S/3W-28M3S 59.0 3,800 1.50 <.010 .34 1.80 1 120

5S/3W-28M4S 69.0 2,850 4.80 <.010 .16 .46 1 75.0

5S/3W-32A1S 43.0 9,610 .77 .020 .40 <.01 <1 400

5S/3W-32B1S 45.0 804 1.90 <.010 <.01 .09 2 25.0

5S/3W-32C1S 48.0 2,330 1.10 .020 <.01 .03 1 38.0

5S/3W-32G1S 51.0 2,450 2.20 <.010 .02 .04 8 25.0

5S/3W-32H1S 54.0 1,260 1.70 <.010 <.01 .08 2 18.0

5S/3W-32L1S 54.0 4,580 2.30 <.010 .11 .02 <1 <100

5S/3W-34Q2S 51.0 3,390 7.40 .010 .12 <.01 <1 39.0

5S/3W-35N2S 73.0 2,960 1.90 <.010 .08 .08 3 200

5S/3W-36P2S 89.0 1,700 3.40 .020 .05 .10 2 630

6S/3W-01J2S 52.0 3,350 6.30 <.010 .10 .05 1 70.0

6S/3W-02A1S 57.0 3,550 5.30 <.010 .12 .06 <1 44.0

6S/3W-02E1S 65.0 1,070 2.60 <.010 .03 .06 2 180

6S/3W-02G2S 56.0 1,090 5.20 <.010 .03 .06 1 74.0

6S/3W-05E1S 38.0 335 10.0 <.010 .04 .08 6 190

Winchester subbasin

Temecula RWRF 20.0 686 2.90 <.010 .04 4.20 4 45.0

Winchester Storage Pond 14.0 772 1.34 .060 <.01 .56 6 23.0

5S/2W-29L2S 64.0 6,440 1.80 <.004 .06 .04 <1 <100

5S/2W-29L3S 56.0 4,620 1.25 .050 .12 <.01 <1 <100

5S/2W-29N1S 60.0 3,850 16.0 <.010 .12 .06 1 20.0

5S/2W-30C1S 48.0 2,290 6.60 <.010 .03 .06 3 180

5S/2W-30D2S 63.0 3,330 13.0 <.010 .08 .07 1 36.0

5S/2W-30G2S 60.0 4,570 13.0 <.010 .08 .09 1 26.0

5S/2W-30G3S 56.0 2,320 3.30 <.010 .02 .13 3 25.0

5S/2W-30H2S 60.0 6,430 13.0 <.010 .11 .48 3 33.0

5S/3W-24F2S 30.0 395 5.70 <.010 <.01 .16 1 36.0

5S/3W-24F3S 69.0 2,520 13.0 <.010 .09 .87 1 510

5S/3W-24F4S 49.0 1,330 14.0 <.010 .02 1.00 1 570
Table 1 55

Perris-South subbasin

Perris Valley RWRF 19 — 4.42 0.080 0.61 2.50 1 14

Trumble Road Storage Pond 19 599 3.28 .120 .23 1.40 1 34

4S/3W-26N1S 17.0 9,650 0.59 <.010 .54 <.01 2 300

4S/3W-33Q1S 13.0 3,890 2.50 <.010 .02 <.01 <1 300

5S/3W-02M2S 37.0 2,820 21.0 <.010 .07 .03 1 380

5S/3W-03C1S 11.0 3,780 3.00 <.010 .20 <.01 <1 200

5S/3W-03L1S 35.0 1,640 5.50 <.010 .03 <.01 <1 710

5S/3W-03N1S 43.0 3,260 1.08 .020 .08 <.01 <1 1,100

5S/3W-03R1S 44.0 1,150 9.90 <.010 .02 <.01 3 450

5S/3W-04A1S 17.0 2,470 3.60 <.010 .05 <.01 <1 100

5S/3W-04M1S 46.0 5,760 1.90 <.010 .72 .02 <1 200

5S/3W-09E1S 58.0 1,930 7.50 <.010 .05 .02 <1 120

5S/3W-09H1S 63.0 2,100 7.80 <.010 .05 .02 <1 150

5S/3W-09H2S 68.0 1,370 8.00 <.010 .04 .04 <1 130

5S/3W-09Q1S 55.0 1,500 6.80 <.010 .05 <.01 <1 360

5S/3W-11D1S 52.0 541 7.60 <.010 <.01 .03 2 390

5S/3W-11M2S — — — — — — — —

5S/3W-14P1S 62.0 1,160 8.50 <.010 <.01 .05 1 210

5S/3W-15L1S 61.0 435 6.40 <.010 .03 .05 2 44.0

5S/3W-16F1S 46.0 1,730 11.0 <.010 <.01 .02 <1 300

5S/3W-17R1S 60.0 1,390 5.70 <.010 <.01 <.01 <1 81.0

5S/3W-24C1S 54.0 685 4.90 <.010 <.01 .04 2 200

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Silica,

dissolved

(mg/L)

Dissolved 

Solids,

residue

(mg/L)

Nitrate,

NO2 + NO3

dissolved

(mg/L as N)

Nitrite,

dissolved

(mg/L as N)

Ammonia,

dissolved

(mg/L as N)

Phosphorus,

ortho,

dissolved

(mg/L)

Arsenic,

dissolved

(μg/L)

Barium,

dissolved

(μg/L)
56 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Berylium,

dissolved

(μg/L)

Boron,

dissolved

(μg/L)

Cadmium,

dissolved

(μg/L)

Chromium,

dissolved

(μg/L)

Cobalt,

dissolved

(μg/L)

Copper,

dissolved

(μg/L)

Iron,

dissolved

(μg/L)

Lead,

dissolved

(μg/L)

Menifee subbasin

Sun City RWRF <0.5 440 <1 <5 <3 <10 13 <10

Sun City Storage Pond <.5 500 2 <5 3 <10 <3 10

5S/3W-28M1S <.5 210 <1 <5 <3 <10 48 10

5S/3W-28M2S <1.0 220 <2 <10 <6 <20 160 <20

5S/3W-28M3S <1.5 210 <3 <15 <9 <30 <9 <30

5S/3W-28M4S <1.5 130 <3 <15 <9 <30 36 100

5S/3W-32A1S <10 340 <4 1.4 13 <1 590 <4

5S/3W-32B1S <.5 530 <1 <5 4 <10 <3 30

5S/3W-32C1S <1.0 430 <2 <10 <6 <20 <6 <20

5S/3W-32G1S <1.0 580 <2 <10 <6 <20 14 30

5S/3W-32H1S <.5 400 <1 <5 <3 <10 <3 <10

5S/3W-32L1S <10 380 <1 2.0 <1 2.0 30 2

5S/3W-34Q2S <1.5 160 <3 <15 16 <30 2,800 <30

5S/3W-35N2S <1.5 610 <3 <15 <9 <30 130 70

5S/3W-36P2S <1.0 330 <2 <10 8 <20 180 40

6S/3W-01J2S <1.5 290 <3 <15 <9 <30 <9 <30

6S/3W-02A1S <2.0 410 <4 <20 <12 <40 45 <40

6S/3W-02E1S <.5 160 <1 <5 <3 <10 62 <10

6S/3W-02G2S <.5 80 <1 <5 <3 <10 37 <10

6S/3W-05E1S <.5 80 <1 <5 <3 <10 6 <10

Winchester subbasin

Temecula RWRF <.5 540 2 <5 <3 <10 9 20

Winchester Storage Pond <.5 590 3 <5 5 <10 <3 10

5S/2W-29L2S <10 1,300 <.01 1.6 <1 <1 10 <2

5S/2W-29L3S <10 1,100 <1 1.7 6 <1 21,000 <2

5S/2W-29N1S <1.5 1,300 <3 <15 <9 <30 <9 <30

5S/2W-30C1S <1.0 90 <2 <10 <6 <20 87 30

5S/2W-30D2S <1.5 250 <3 <15 <9 <30 10 70

5S/2W-30G2S <2.0 230 <4 <20 <12 <40 <12 <40

5S/2W-30G3S <1.0 90 <2 <10 <6 <20 <6 <20

5S/2W-30H2S <5.0 170 20 <50 <30 <100 <30 <100

5S/3W-24F2S <.5 70 <1 <5 <3 <10 9 <10

5S/3W-24F3S <1.0 80 <2 <10 <6 <20 <6 20

5S/3W-24F4S <.5 40 <1 <5 <3 <10 <3 <10
Table 1 57

Perris-South subbasin

Perris Valley RWRF <0.5 430 2 <5 <3 <10 18 <10

Trumble Road Storage Pond <.5 490 2 <5 <3 <10 5 <10

4S/3W-26N1S <10 820 <1 <5 <1 <1 310 <2

4S/3W-33Q1S <10 600 <2 1 <1 <1 10 <2

5S/3W-02M2S <1.5 250 <3 <15 <9 <30 21 <30

5S/3W-03C1S <10 70 <1 <1 <1 <1 <10 5

5S/3W-03L1S <1.0 70 <2 <10 <6 <20 < 6 <20

5S/3W-03N1S <1.5 260 <3 <15 20 <30 9,100 <30

5S/3W-03R1S <.5 110 1 <5 <3 <10 6 20

5S/3W-04A1S <1.5 210 3 <15 12 <30 <9 60

5S/3W-04M1S <10 300 <4 3.7 <1 1.0 30 <4

5S/3W-09E1S <1.0 90 <2 <10 <6 <20 8 <20

5S/3W-09H1S <1.0 170 <2 <10 <6 <20 <6 60

5S/3W-09H2S <1.0 190 <2 <10 <6 <20 9 30

5S/3W-09Q1S <.5 210 <1 <5 <3 10.0 84 <10

5S/3W-11D1S <.5 70 3 <5 <3 <10 13 20

5S/3W-11M2S — — — — — — — —

5S/3W-14P1S <.5 150 1 <5 <3 <10 9 30

5S/3W-15L1S <.5 60 3 <5 <3 <10 <3 <10

5S/3W-16F1S <.5 60 1 <5 <3 <10 <3 10

5S/3W-17R1S .5 70 <1 <5 <3 <10 <3 <10

5S/3W-24C1S <.5 30 <1 <5 <3 <10 13 20

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Berylium,

dissolved

(μg/L)

Boron,

dissolved

(μg/L)

Cadmium,

dissolved

(μg/L)

Chromium,

dissolved

(μg/L)

Cobalt,

dissolved

(μg/L)

Copper,

dissolved

(μg/L)

Iron,

dissolved

(μg/L)

Lead,

dissolved

(μg/L)
58 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Lithium,

dissolved

(μg/L)

Manganese,

dissolved

(μg/L)

Molybdenum,

dissolved

(μg/L)

Nickel,

dissolved

(μg/L)

Silver,

dissolved

(μg/L)

Strontium,

dissolved

(μg/L)

Vanadium,

dissolved

(μg/L)

Zinc,

dissolved

(μg/L)

Menifee subbasin

Sun City RWRF 43 5.0 20 <10 1 790 <6 59

Sun City Storage Pond 42 5.0 30 <10 <1 830 <6 11

5S/3W-28M1S 26 160 20 <10 <1 1,700 <6 <3

5S/3W-28M2S 39 280 30 <20 <2 3,100 <12 <6

5S/3W-28M3S 48 640 60 <30 <3 8,500 20 <9

5S/3W-28M4S 27 370 <30 <30 <3 2,300 <18 <9

5S/3W-32A1S 150 4,600 <2.0 3.0 <1 17,000 100 200

5S/3W-32B1S 7 35.0 20 <10 1 130 43 6

5S/3W-32C1S 8 65.0 <20 <20 <2 1,700 24 13

5S/3W-32G1S 48 180 30 <20 <2 1,200 <12 19

5S/3W-32H1S 43 41.0 <10 <10 <1 780 25 110

5S/3W-32L1S 40 80.0 1.2 24 <1 3,100 39 180

5S/3W-34Q2S 34 53.0 <30 <30 <3 2,100 <18 14

5S/3W-35N2S 140 530 40 50 <3 1,600 <18 3,600

5S/3W-36P2S 200 1,200 <20 <20 <2 1,100 28 3,900

6S/3W-01J2S 37 <3.0 40 <30 4 2,300 <18 38

6S/3W-02A1S 49 4.0 <40 110 <4 2,300 <24 <12

6S/3W-02E1S 80 520 10 30 <1 1,000 10 6

6S/3W-02G2S 24 19.0 20 <10 <1 740 11 15

6S/3W-05E1S 30 2.0 30 <10 4 160 12 17

Winchester subbasin

Temecula RWRF 23 4 10 <10 <1 490 22 38

Winchester Storage Pond 22 1 20 <10 <1 470 <3 <3

5S/2W-29L2S 30 10 9.0 1.0 <1 2,700 64 <10

5S/2W-29L3S 60 3,100 15 6.0 <1 2,800 40 10

5S/2W-29N1S 66 1,200 <30 <30 <3 2,900 <18 10

5S/2W-30C1S 17 8.0 30 <20 <2 1,400 <12 <6

5S/2W-30D2S 36 5.0 <30 <30 <3 3,400 <18 <9

5S/2W-30G2S 44 4.0 <40 <40 <4 2,200 <24 13

5S/2W-30G3S <8 <2.0 <20 <20 <2 1,400 <12 11

5S/2W-30H2S 53 14.0 <100 <100 <10 3,100 <60 <30

5S/3W-24F2S 6 52.0 30 10 <1 200 <6 <3

5S/3W-24F3S 38 14.0 <20 <20 <2 2,000 16 13

5S/3W-24F4S 8 <1.0 20 <10 <1 1,100 16 <3
Table 1 59

Perris-South subbasin

Perris Valley RWRF 13 8.0 20 <10 <1 220 <6 35

Trumble Road Storage Pond 13 7.0 <10 <10 <1 290 <6 29

4S/3W-26N1S 50 50.0 20 2.0 <2 14,000 150 210

4S/3W-33Q1S 30 <10.0 <1.0 <1.0 <1 2,800 46 <10

5S/3W-02M2S 50 <3.0 <30 <30 <3 1,900 31 82

5S/3W-03C1S 20 <10.0 <1.0 <1.0 <1 4,800 47 <10

5S/3W-03L1S 29 <2.0 <20 <20 <2 1,700 16 <6

5S/3W-03N1S 32 2,400 <30 <30 <3 3,300 <18 <9

5S/3W-03R1S 7 <1.0 <10 <10 <1 950 64 5

5S/3W-04A1S 29 <3.0 <30 <30 8 1,300 <18 <9

5S/3W-04M1S 60 <10 4.0 1.0 7 12,000 160 <10

5S/3W-09E1S <8 <2.0 <20 <20 <2 1,600 26 6

5S/3W-09H1S 18 <2.0 <20 <20 <2 1,400 19 10

5S/3W-09H2S 16 15.0 20 <20 <2 1,200 15 <6

5S/3W-09Q1S 25 67.0 <10 <10 1 1,600 14 350

5S/3W-11D1S 6 <1.0 30 <10 <1 370 48 410

5S/3W-11M2S — — — — — — — —

5S/3W-14P1S 20 1.0 20 <10 <1 960 20 10

5S/3W-15L1S 14 <1.0 <10 <10 3 290 21 <3

5S/3W-16F1S 7 <1.0 20 20 <1 1,600 20 210

5S/3W-17R1S 10 <1.0 20 <10 2 890 47 95

5S/3W-24C1S 17 2.0 <10 <10 <1 410 16 11

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

Lithium,

dissolved

(μg/L)

Manganese,

dissolved

(μg/L)

Molybdenum,

dissolved

(μg/L)

Nickel,

dissolved

(μg/L)

Silver,

dissolved

(μg/L)

Strontium,

dissolved

(μg/L)

Vanadium,

dissolved

(μg/L)

Zinc,

dissolved

(μg/L)
60 Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

2H/1H,

ratio

(per mil)

18O/16O

ratio

(per mil)

TOC,

(in mg/L)

DOC,

(in mg/L)

Ultraviolet

absorbance,

(at 254 nm)

MBAS,

(in μg/L)

LAS,

(in μg/L)

Caffeine,

(in μg/L)

Menifee subbasin

Sun City RWRF −82.80 −10.1 9.4 10.5 0.172 — <0.1 0.09

Sun City Storage Pond −67.40 −7.34 10.2 10.2 .149 — .1 .09

5S/3W-28M1S −62.40 −9.03 2.9 2.2 .004 0.079 — —

5S/3W-28M2S −61.40 −8.89 3.8 4.5 .004 .131 — —

5S/3W-28M3S −54.30 −7.63 1.4 1.5 .001 .464 — —

5S/3W-28M4S −51.70 −7.48 1.1 .9 .003 .339 — —

5S/3W-32A1S −52.30 −7.61 2.2 1.9 .001 — <.1 <.05

5S/3W-32B1S −70.40 −8.64 2.3 2.4 .058 .279 — —

5S/3W-32C1S −74.60 −8.84 1.8 1.7 .022 .432 — —

5S/3W-32G1S −57.90 −7.74 1.5 1.3 .007 — <.1 <.05

5S/3W-32H1S −81.80 −9.44 1.7 1.8 .028 .325 — —

5S/3W-32L1S −51.50 −7.52 1.2 1.2 .003 — <.1 <.05

5S/3W-34Q2S −49.80 −7.06 1.2 1.2 .005 — <.1 <.05

5S/3W-35N2S −52.90 −7.61 1.7 1.6 <.001 .396 — —

5S/3W-36P2S −58.00 −8.41 3.2 3.4 .004 .139 — —

6S/3W-01J2S −51.40 −7.18 — — — — — —

6S/3W-02A1S −51.80 −7.36 — — — — — —

6S/3W-02E1S −53.50 −7.65 0.9 .9 — .205 — —

6S/3W-02G2S −49.70 −6.94 — — — — — —

6S/3W-05E1S −46.10 −6.74 — — — — — —

Winchester subbasin

Temecula RWRF −61.20 −7.93 8.2 8.8 .114 — <.1 <.05

Winchester Storage Pond −43.80 −4.92 7.7 7.8 .065 — .7 <.05

5S/2W-29L2S −52.00 −7.15 1.3 1.3 — .648 — —

5S/2W-29L3S −54.10 −7.39 1.6 1.3 — .557 — —

5S/2W-29N1S −51.90 −7.42 — — — — — —

5S/2W-30C1S −51.10 −7.31 .7 .7 .021 .516 — —

5S/2W-30D2S −58.40 −7.99 .8 .8 .004 — <.1 <.05

5S/2W-30G2S −60.40 −8.29 — — — — — —

5S/2W-30G3S −55.70 −7.50 1.2 1.2 .020 .391 — —

5S/2W-30H2S −51.40 −7.25 — — — — — —

5S/3W-24F2S −59.10 −8.41 .7 .7 .008 .188 — —

5S/3W-24F3S −54.60 −8.01 .7 .8 .006 1.041 — —

5S/3W-24F4S −50.70 −7.32 .7 .7 .003 .478 — —
Table 1 61

Perris-South subbasin

Perris Valley RWRF −66.7 −8.72 9.3 8.7 0.126 — 0.04 <0.05

Trumble Road Storage Pond −54.2 −6.64 6.9 7.2 .111 — 1.1 .05

4S/3W-26N1S −62.3 −8.56 — — — — — —

4S/3W-33Q1S −60.8 −8.60 .5 .5 .005 0.697 — —

5S/3W-02M2S −56.0 −7.41 — — — — — —

5S/3W-03C1S −60.0 −8.38 .5 .5 .006 .618 — —

5S/3W-03L1S −53.9 −7.67 .6 — — .410 — —

5S/3W-03N1S −59.8 −8.59 .7 .7 <.001 .421 — —

5S/3W-03R1S −53.4 −7.59 .9 .9 .009 — <.1 <.05

5S/3W-04A1S −62.5 −8.45 .8 .8 .018 — — —

5S/3W-04M1S −56.1 −7.87 .7 .7 .006 1.208 — —

5S/3W-09E1S −53.1 −7.10 1.3 1.1 .009 — <.1 <.05

5S/3W-09H1S −50.80 −7.12 .8 .8 .013 — <.1 <.05

5S/3W-09H2S −52.60 −7.40 .7 .7 .002 — <.1 <.05

5S/3W-09Q1S −53.60 −7.64 1.4 1.2 — .276 — —

5S/3W-11D1S −51.00 −7.25 .8 .7 — .216 — —

5S/3W-11M2S −51.60 −7.21 — — — — — —

5S/3W-14P1S −51.60 −7.26 — — — — — —

5S/3W-15L1S −49.10 −6.62 .6 .6 — .180 — —

5S/3W-16F1S −51.00 −6.92 — — — — — —

5S/3W-17R1S −51.00 −7.07 .6 .6 — .249 — —

5S/3W-24C1S −53.00 −7.54 .5 — — .216 — —

Table 1. Water-quality data for selected wells in the Menifee, Winchester, and Perris-South subbasins, Riverside County, California—Continued

Site name or

State well No.

2H/1H,

ratio

(per mil)

18O/16O

ratio

(per mil)

TOC,

(in mg/L)

DOC,

(in mg/L)

Ultraviolet

absorbance,

(at 254 nm)

MBAS,

(in μg/L)

LAS,

(in μg/L)

Caffeine,

(in μg/L)