WATER-QUALITY ASSESSMENT OF THE RIO GRANDE

VALLEY, COLORADO, NEW MEXICO, AND TEXAS—

Surface-Water Quality, Shallow Ground-Water Quality, and

Factors Affecting Water Quality in the Rincon Valley,

South-Central New Mexico, 1994-95

National Water-Quality Assessment Program

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4188
U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4188

WATER-QUALITY ASSESSMENT OF THE RIO GRANDE

VALLEY, COLORADO, NEW MEXICO, AND TEXAS—

Surface-Water Quality, Shallow Ground-Water Quality, and

Factors Affecting Water Quality in the Rincon Valley,

South-Central New Mexico, 1994-95

National Water-Quality Assessment Program

By Scott K. Anderholm

Albuquerque, New Mexico

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does

not constitute endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be purchased

U.S. Geological Survey

Information Services

Box 25286

Denver, CO 80225-0286

District Chief

U.S. Geological Survey

Water Resources Division

5338 Montgomery Blvd. NE, Suite 400

Albuquerque, NM 87109-1311

from:

Information regarding research and data-collection programs of the U.S. Geological Survey is available

on the Internet via the World Wide Web. You may connect to the home page for the New Mexico District

Office using the URL http://nm.water.usgs.gov.
iii

FOREWORD

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and

timely scientific information that helps enhance and protect the overall quality of life and

facilitates effective management of water, biological, energy, and mineral resources.

Information on the quality of the Nation’s water resources is of critical interest to the

USGS because it is so integrally linked to the long-term availability of water that is clean

and safe for drinking and recreation and that is suitable for industry, irrigation, and habitat

for fish and wildlife. Escalating population growth and increasing demands for the

multiple water uses make water availability, now measured in terms of quantity and

quality, even more critical to the long-term sustainability of our communities and

ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program to

support national, regional, and local information needs and decisions related to waterquality management and policy. Shaped by and coordinated with ongoing efforts of other

Federal, State, and local agencies, the NAWQA Program is designed to answer: What is

the condition of our Nation’s streams and ground water? How are the conditions changing

over time? How do natural features and human activities affect the quality of streams and

ground water, and where are those effects most pronounced? By combining information

on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA

Program aims to provide science-based insights for current and emerging water issues.

NAWQA results can contribute to informed decisions that result in practical and effective

water-resource management and strategies that protect and restore water quality.

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more

than 50 of the Nation’s most important river basins and aquifers, referred to as study units.

Collectively, these study units account for more than 60 percent of the overall water use

and population served by public water supply and are representative of the Nation’s major

hydrologic landscapes, priority ecological resources, and agricultural, urban, and natural

sources of contamination.

Each assessment is guided by a nationally consistent study design and methods of

sampling and analysis. The assessments thereby build local knowledge about waterquality issues and trends in a particular stream or aquifer while providing an

understanding of how and why water quality varies regionally and nationally. The

consistent, multiscale approach helps to determine if certain types of water-quality issues

are isolated or pervasive and allows direct comparisons of how human activities and

natural processes affect water quality and ecological health in the Nation’s diverse

geographic and environmental settings. Comprehensive assessments on pesticides,

nutrients, volatile organic compounds, trace metals, and aquatic ecology are developed at

the national scale through comparative analysis of the Study-Unit findings.

The USGS places high value on the communication and dissemination of credible, timely,

and relevant science so that the most recent and available knowledge about water

resources can be applied in management and policy decisions. We hope this NAWQA

publication will provide you the needed insights and information to meet your needs and

thereby foster increased awareness and involvement in the protection and restoration of

our Nation’s waters.
iv

The NAWQA Program recognizes that a national assessment by a single program cannot

address all water-resource issues of interest. External coordination at all levels is critical

for a fully integrated understanding of watersheds and for cost-effective management,

regulation, and conservation of our Nation’s water resources. The program, therefore,

depends extensively on the advice, cooperation, and information from other Federal, State,

interstate, tribal, and local agencies, non-government organizations, industry, academia,

and other stakeholder groups. The assistance and suggestions of all are greatly

appreciated.

Robert M. Hirsch

Associate Director for Water
v

CONTENTS

Page

Foreword................................................................................................................................................................................ iii

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

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

Purpose and scope ....................................................................................................................................................... 2

Previous work .............................................................................................................................................................. 2

Acknowledgments ....................................................................................................................................................... 4

Description of study area....................................................................................................................................................... 4

Climate......................................................................................................................................................................... 4

Surface-water/irrigation system................................................................................................................................... 5

Ground-water hydrology ............................................................................................................................................. 9

Ground-water/surface-water relations ......................................................................................................................... 10

Land use/land cover..................................................................................................................................................... 13

Study design .......................................................................................................................................................................... 13

Methods ....................................................................................................................................................................... 15

Well site selection.............................................................................................................................................. 15

Well installation................................................................................................................................................. 17

Water sampling .................................................................................................................................................. 17

Bed-material sampling....................................................................................................................................... 17

U.S. Geological Survey National Water Quality Laboratory methods.............................................................. 17

Quality assurance/quality control of data .......................................................................................................... 18

Surface-water quality............................................................................................................................................................. 19

Field properties and common constituents .................................................................................................................. 20

Nutrients and dissolved organic carbon....................................................................................................................... 23

Trace elements ............................................................................................................................................................. 26

Pesticides ..................................................................................................................................................................... 26

Shallow ground-water quality................................................................................................................................................ 28

Field properties and common constituents .................................................................................................................. 28

Nutrients and dissolved organic carbon....................................................................................................................... 33

Trace elements ............................................................................................................................................................. 33

Radioactivity and radon-222........................................................................................................................................ 36

Volatile organic compounds......................................................................................................................................... 36

Pesticides ..................................................................................................................................................................... 36

Pesticides, pesticide metabolites, gross polychlorinated biphenols, and gross polychlorinated naphthalenes in

bed material ................................................................................................................................................... 38

Factors affecting water quality in the Rincon Valley............................................................................................................. 38

Common constituents .................................................................................................................................................. 39

Nutrients ...................................................................................................................................................................... 47

Trace elements ............................................................................................................................................................. 49

Radioactivity and radon-222........................................................................................................................................ 50

Volatile organic compounds......................................................................................................................................... 52

Pesticides ..................................................................................................................................................................... 52

Summary and conclusions ..................................................................................................................................................... 55

References ............................................................................................................................................................................. 57

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area ................................................ 91

Appendix B. Shallow ground-water-quality data for wells sampled in the Rincon Valley study area.................................. 109

Appendix C. Concentrations of pesticides and pesticide metabolites detected in bed-material samples from

selected sites in the Rincon Valley study area ......................................................................................................... 117
vi

FIGURES

Page

1. Map showing location of the Rincon Valley study area ............................................................................................ 3

2. Map showing location of major irrigation canals, drains, and surface-water and ground-water sampling

sites in the Rincon Valley study area........................................................................................................... 6

3-6. Graphs showing:

3. Mean daily discharge of the Rio Grande below Caballo Dam and diversions to Arrey Canal, 1993-95........... 7

4. Mean daily discharge of the Garfield Drain, Hatch Drain, and Rincon Drain, 1993-95.................................... 8

5. Relation between instantaneous discharge and river miles downstream from Caballo Dam, 1994-95 ............. 11

6. Relation between instantaneous discharge and river miles downstream from Caballo Dam,

January 5 and 6, 1994.................................................................................................................................. 12

7. Aerial photograph of land use/land cover in part of the Rincon Valley study area................................................... 14

8. Map showing location of agricultural land-use cells and wells sampled in the Rincon Valley study area ............... 16

9. Graph showing relation between dissolved-solids concentration in surface water and river miles downstream

from Caballo Dam, 1994-95.................................................................................................................................. 21

10. Box plots showing distribution of selected constituent concentrations in surface water in the Rincon Valley

study area............................................................................................................................................................... 22

11. Durov plot of surface-water composition in the Rincon Valley study area............................................................... 24

12-14. Graphs showing:

12. Relation between dissolved nitrite plus nitrate concentration in surface water and river miles downstream

from Caballo Dam, 1994-95 .......................................................................................................................... 25

13. Relation between dissolved organic carbon concentration in surface water and river miles downstream

from Caballo Dam, 1994-95 .......................................................................................................................... 27

14. Relation between DCPA concentration in surface water and river miles downstream from Caballo

Dam, 1994-95................................................................................................................................................. 29

15. Box plots showing distribution of selected constituent concentrations in shallow ground water in the Rincon

Valley study area ................................................................................................................................................... 30

16. Map showing dissolved-solids concentration in shallow ground water in the Rincon Valley study area ................. 31

17. Durov plot of shallow ground-water composition in the Rincon Valley study area.................................................. 32

18-20. Maps showing:

18. Dissolved nitrite plus nitrate concentration in shallow ground water in the Rincon Valley study area ............. 34

19. Dissolved uranium concentration in shallow ground water in the Rincon Valley study area ............................ 35

20. Concentrations of pesticides detected in shallow ground water in the Rincon Valley study area...................... 37

21-24. Graphs showing:

21. Relation between dissolved sulfate and chloride concentrations in surface water and shallow ground

water in the Rincon Valley study area............................................................................................................ 41

22. Relation between dissolved bicarbonate and chloride concentrations in surface water and shallow

ground water in the Rincon Valley study area ............................................................................................... 42

23. Relation between dissolved calcium and chloride concentrations in surface water and shallow ground

water in the Rincon Valley study area............................................................................................................ 43

24. Relation between dissolved sodium and chloride concentrations in surface water and shallow ground

water in the Rincon Valley study area............................................................................................................ 44

25. Plot showing relation between dissolved silica and chloride concentrations in surface water and shallow

ground water in the Rincon Valley study area....................................................................................................... 45

26. Plot showing relation between dissolved nitrite plus nitrate and ammonia concentrations in the Rio Grande,

drains, and shallow ground water in the Rincon Valley study area....................................................................... 48

27. Graph showing relation between gross alpha activity and dissolved uranium concentration in shallow

ground water in the Rincon Valley study area....................................................................................................... 51

28. Plot showing relation between (A) gross beta activity and dissolved potassium concentration and

(B) adjusted gross beta activity and dissolved uranium concentration in shallow ground water

in the Rincon Valley study area............................................................................................................................. 53
vii

TABLES

Page

1. Annual diversions and discharge in drains in the Rincon Valley study area, 1993-95.............................................. 60

2. Crops, in acres, irrigated in the Rincon Valley study area, 1993-95 ......................................................................... 60

3. List of common constituents, nutrients and organic carbon, trace elements, and pesticides analyzed for in

surface-water samples ........................................................................................................................................... 61

4. List of common constituents, nutrients and dissolved organic carbon, trace elements, radioactivity/radon,

volatile organic compounds, and pesticides analyzed for in ground-water samples............................................. 63

5. List of pesticides, pesticide metabolites, gross polychlorinated biphenols, and gross polychlorinated

naphthalenes analyzed for in bed-material samples.............................................................................................. 65

6. Constituents detected in field-blank samples and ranges of concentrations detected in field-blank, shallow

ground-water, and surface-water samples ............................................................................................................. 66

7. Relative-percent difference for replicate samples from surface-water and ground-water sites................................. 67

8. Percent recovery of spiked Group A pesticides......................................................................................................... 69

9. Percent recovery of spiked Group B pesticides......................................................................................................... 72

10. Percent recovery of spiked volatile organic compounds ........................................................................................... 74

11. Water-quality standards for the Rio Grande and ranges of concentrations in samples from the Rio Grande

and from drains in the Rincon Valley study area .................................................................................................. 75

12. Statistical summary of selected data for surface water in the Rincon Valley study area .......................................... 76

13. Statistical summary of selected data for wells sampled in the Rincon Valley study area ......................................... 83

14. Drinking water standard or lifetime health advisory for constituents detected in shallow ground water, range

of concentrations in shallow ground water, and percentage of shallow ground-water samples exceeding

standard or lifetime health advisory...................................................................................................................... 88

15. Saturation index for selected minerals and partial pressure of carbon dioxide in irrigation water and

shallow ground water in the Rincon Valley study area ......................................................................................... 90

CONVERSION FACTORS AND DATUMS

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

°C = (°F - 32) / 1.8

°F = (1.8 ⋅ ° C) + 32

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (∝S/cm at

25  ̊C).

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

88).

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

Multiply By To obtain

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

acre 0.004047 square kilometer (km2)

quart (qt) 0.9464 liter (L)

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

pound (lb) 0.4536 kilogram (kg)

cubic foot per second (ft3s) 0.02832 cubic meter per second (m3/s)

cubic foot per second per mile (ft3s/mi) 0.01760 cubic meter per second per kilometer (m3/s/km)

atmosphere, standard (atm) 101.3 kilopascal (kPa)
1

ABSTRACT

As part of the National Water-Quality

Assessment Program, surface-water and ground-water

samples were collected in 1994 and 1995 for analysis

of common constituents, nutrients, dissolved organic

carbon, trace elements, radioactivity, volatile organic

compounds, and pesticides to characterize surfacewater quality and shallow ground-water quality and to

determine factors affecting water quality in the Rincon

Valley, south-central New Mexico. Samples of surface

water were collected from three sites on the Rio Grande

and from sites on three agricultural drains in the Rincon

Valley in January 1994 and 1995, April 1994, and

October 1994. Ground-water samples were collected in

late April and early May 1994 from 30 shallow wells

that were installed during the investigation.

Dissolved-solids concentrations in surface water

ranged from 434 to 1,510 milligrams per liter (mg/L).

Dissolved-solids concentrations were smallest in water

from the Rio Grande below Caballo Dam and largest in

the drains. Nitrite plus nitrate concentrations ranged

from less than 0.05 to 3.3 mg/L as nitrogen, and

ammonia concentrations ranged from less than 0.015 to

0.33 mg/L as nitrogen in surface-water samples.

Trace-element concentrations in surface water

were significantly smaller than the acute-fisheries

standards. One or more pesticides were detected in 34

of 37 surface-water samples. DCPA (dacthal) and

metolachlor were the most commonly detected

pesticides. No standards have been established for the

pesticides analyzed for in this study.

Dissolved-solids concentrations in shallow

ground water ranged from 481 to 3,630 mg/L. All but 2

of 30 samples exceeded the secondary maximum

contaminant level for dissolved solids of 500 mg/L.

Water from about 73 percent of the wells sampled

exceeded the secondary maximum contaminant level

of 250 mg/L for sulfate, and water from about 7 percent

of the wells sampled exceeded the secondary

maximum contaminant level of 250 mg/L for chloride.

Nitrite plus nitrate concentrations ranged from less

than 0.05 to 33 mg/L as nitrogen in shallow ground

water. Water from about 17 percent of the well samples

exceeded the maximum contaminant level of 10 mg/L

as nitrogen for nitrite plus nitrate.

Trace-element concentrations in shallow ground

water generally were small (1 to 10 micrograms per

liter). The proposed maximum contaminant level of 20

micrograms per liter for uranium was exceeded in

about 13 percent of the samples. The secondary

maximum contaminant level of 300 micrograms per

liter for iron was exceeded in about 17 percent of the

samples and of 50 micrograms per liter for manganese

was exceeded in about 83 percent of the samples.

Samples from about 23 percent of the wells exceeded

the maximum contaminant level of 15 picocuries per

liter for gross alpha activity.

One or more pesticides were detected in water

from 12 of 30 wells sampled. The pesticides or

pesticide metabolites diazinon, metolachlor,

napropamide, p,p’-DDE, and prometon were detected

in one or more samples. Metolachlor and prometon

were the most commonly detected pesticides. Health

advisories for the pesticides detected in shallow ground

water (no maximum contaminant levels have been

established for the pesticides detected) are 10 to 300

times larger than the concentrations detected.

Infiltration, evaporation, and transpiration of

irrigation water are important factors affecting the

concentrations of common constituents in shallow

ground water in the Rincon Valley. Dissolution and

precipitation of minerals and mixing of shallow ground

water and inflow of ground water from adjacent areas

also affect the composition of shallow ground water

and water in the drains.

Relatively large nitrite plus nitrate

concentrations in several shallow ground-water

samples indicate leaching of fertilizers in some areas of

the Rincon Valley. Molybdenum and uranium

concentrations in part of the Rincon Valley are affected

by inflow of ground water to the valley from adjacent

areas. A large amount of the gross alpha activity in

shallow ground water is from uranium isotopes. Gross

beta activity increases with dissolved potassium,

WATER-QUALITY ASSESSMENT OF THE RIO GRANDE VALLEY,

COLORADO, NEW MEXICO, AND TEXAS—Surface-Water Quality,

Shallow Ground-Water Quality, and Factors Affecting Water Quality in

the Rincon Valley, South-Central New Mexico, 1994-95

By Scott K. Anderholm
2

indicating that part of the dissolved gross beta activity

is from potassium-40.

The detection of a larger number of different

pesticides in surface water than in ground water

indicates that pesticides are entering surface water as

runoff from fields or that the number of ground-water

samples collected and the time of year that the samples

were collected did not adequately represent the

composition of ground water in the Rincon Valley that

discharges to the drains.

On the basis of pesticide concentrations detected

in shallow ground water in the Rincon Valley, large

amounts of the pesticides analyzed for are not leaching

from land surface into ground water. There is some

indication that several pesticides are leaching

downward into shallow ground water (metolachlor and

prometon especially); however, the concentrations

detected in shallow ground water are significantly

smaller than any standards or health advisories issued

by the U.S. Environmental Protection Agency.

INTRODUCTION

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

implement the full-scale National Water-Quality

Assessment (NAWQA) Program in 1991. The Rio

Grande Valley was one of the first 20 NAWQA study

units selected for study of the status of and trends in the

quality of ground water and surface water. One of the

goals of the NAWQA Program is to provide a scientific

understanding of the natural and human factors

affecting the quality of ground water and surface water

in the Nation. Distinguishing the difference between

natural and human-related factors that affect water

quality can be difficult, especially in areas of mixed

land-use practices. Land-use activities can have

particularly significant effects on ground-water and

surface-water quality in areas where ground-water

recharge is occurring or where the ground-water

system discharges to surface-water bodies. Relations

between a particular land-use activity and water quality

can be directly assessed with the least difficulty in areas

with relatively homogeneous land use.

Surface-water quality and shallow ground-water

quality in the agricultural area of the Rincon Valley

were investigated as part of the Rio Grande Valley

NAWQA study. The Rincon Valley is similar to other

agricultural areas in the Rio Grande Valley study unit

and throughout the arid Western United States, and the

results of the investigation could be applicable to these

areas.

The Rincon Valley is located along the Rio

Grande in the southern part of the Rio Grande Valley

NAWQA study unit (fig. 1). The Rincon Valley was

chosen for study because land use in this area is

dominantly agricultural; vegetables, grains, cotton,

alfalfa, and pecan orchards are flood irrigated with

surface water diverted from the Rio Grande. Shallow

ground water and surface water were sampled because

they are in equilibrium, and a change in the amount or

quality of one affects the other. Seepage of water from

canals or irrigated land changes the depth to water and

the amount of ground water that discharges to surfacewater bodies; a change in the amount or quality of

surface water used for irrigation changes the depth to

water and the quality of ground water and surface

water.

Purpose and Scope

This report describes water quality and factors

affecting water quality in the Rincon Valley, southcentral New Mexico. Water quality in the Rincon

Valley was determined by collecting 37 surface-water

samples, 30 ground-water samples, and 3 bed-material

samples and analyzing these samples for a variety of

physical properties and inorganic and organic

constituents. As many as about 200 individual

constituents were measured or analyzed for in some of

the samples. Surface-water samples were collected

near the upstream ends and near the mouths of three

agricultural drains and from three sites on the Rio

Grande during four sampling events from January 1994

to January 1995. Shallow ground-water samples were

collected from 30 wells, which were installed for this

investigation, in April and May 1994. Bed-material

samples were collected from a site near the mouths of

the three drains in January 1995. Natural and humanrelated factors affecting water quality were determined

using the water-quality data collected.

Previous Work

Although few hydrologic studies have been

conducted in the Rincon Valley, the studies that have

been done are comprehensive. Conover (1954)

conducted an extensive study of the ground-water
RIO GRANDE

VALLEY

NATIONAL

WATER

QUALITY

ASSESSMENT

STUDY UNIT

Colorado

Texas

MAP

AREA

LOCATION MAP

New 

Mexico

Jornada

del M

uerto

Caballo

Mountains

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

107°20 ́ 107°10 ́ 107°00 ́

32°

40 ́

32°

30 ́

32°

50 ́

Caballo

Reservoir

Caballo

Dam

Percha Diversion

Dam

ARREY

DERRY

GARFIELD

SALEM

HATCH

RINCON

RADIUM SPRINGS

Rincon Valley

Study Area

Boundary

McLeod

Arroyo

Arroyo

Rincon

Placitas Arroyo

Angostura

Arroyo

Selden Canyon

Tonuco

Mountain

RINCON

VALLEY

Sierra de las Uvas

Leasburg Diversion Dam

Rio

Grande

Figure 1. Location of the Rincon Valley study area.
4

resources of the Rincon Valley that included

inventorying many wells in the area, examining the

interaction of ground water and surface water, and

presenting data on water-quality conditions in the

valley. Conover (1954, p. 79) noted that because of

evaporation and transpiration, ground water generally

has larger concentrations of dissolved ions than surface

water applied for irrigation.

Wilcox (1968) presented a summary for a 30-

year period of monitoring discharge and salt burden on

the Rio Grande that included the Rincon Valley. Wilcox

discussed a positive salt balance between Caballo Dam

and Leasburg Diversion Dam over this 30-year period,

indicating that more salt was removed from the Rincon

Valley than entered the valley from the Rio Grande.

King and others (1971) presented a discussion of

the geologic framework and geohydrology of the

Rincon Valley. They reported that no wells in the

Rincon Valley produce large quantities of water from

depths greater than 80 ft and that the basin-fill deposits

at depths greater than about 80 ft are fine grained (p.

58). King and others (1971, p. 58) also reported

ground-water inflow to the valley from the west near

Hatch and ground-water inflow from the east in the

southern Rincon Valley (Jornada del Muerto).

Wilson and others (1981) compiled data on the

water resources of the Rincon Valley and adjacent

areas. They reported that recharge from the Rio Grande

and irrigation canals affects the quality of ground water

and that ground-water discharge to drains affects the

volume and water quality in the Rio Grande.

Acknowledgments

The Board of Directors of the Elephant Butte

Irrigation District (EBID) supported the concept of this

study and their cooperation is greatly appreciated.

Michael Riley and Henry Magallanez of the EBID

assisted in site-selection approval for shallow wells and

provided information on land use, land ownership,

acreages of crops grown, and streamflow data. Conrad

Keyes assisted in approval for shallow wells on land

administered by the International Boundary and Water

Commission. R. David Fischer of the Natural

Resources Conservation Service assisted in the initial

planning stages of the study. The study would not have

been possible without the cooperation of the land

owners of the Rincon Valley who allowed access to

their lands for sampling and installation of shallow

wells. The support from the members of the Caballo

Soil and Water Conservation District also is greatly

appreciated.

DESCRIPTION OF STUDY AREA

The Rincon Valley study area is defined as the

Rio Grande erosional valley (Rio Grande flood plain)

from Caballo Dam on the north to Selden Canyon on

the south (fig. 1). The study area is about 38 mi long,

generally less than 2 mi wide, relatively flat, and is

bordered by steep bluffs 50 to 100 ft high. The active

channel of the Rio Grande, which is bounded by levees

throughout most of the Rincon Valley, is generally the

lowest point in the flood plain. The altitude of the Rio

Grande below Caballo Dam is about 4,170 ft above sea

level and at the north end of Selden Canyon is about

3,990 ft. A piedmont slope extends outward from the

steep bluffs that border the study area to adjacent

mountainous areas.

Several geographic features are adjacent to the

Rincon Valley. The Caballo Mountains and Tonuco

Mountain are on the east side of the valley. The Jornada

del Muerto, a large alluvial basin, also is adjacent to the

east side. The Sierra de las Uvas, a mountainous area,

is on the southwest side of the valley. Many ephemeral

channels (arroyos) enter the Rincon Valley from the

adjacent piedmont, but many of them have dams that

prevent storm runoff from flowing into the valley. In

Rincon Arroyo, one of the largest of the arroyos, runoff

is not impounded by a dam but is routed into the Rio

Grande.

Climate

The arid climate of the Rincon Valley is

characterized by clear skies, large daily fluctuations in

temperature, low relative humidity, and potential

evaporation exceeding precipitation throughout the

year (Tuan and others, 1969). Temperature can

fluctuate more than 39 °F in a 24-hour period, and daily

temperature fluctuations generally are largest in April

(Tuan and others, 1969, p. 71). The mean temperature

generally is coldest in December and January and

warmest in July (National Oceanic and Atmospheric

Administration, 1993). The mean annual precipitation

at Caballo Dam for 1961-90 was 10.17 in. (National

Oceanic and Atmospheric Administration, 1993). The

largest fraction of annual precipitation generally falls
5

in July, August, and September from intense

thunderstorms; the smallest fraction of annual

precipitation falls in March and April (National

Oceanic and Atmospheric Administration, 1993).

Mean annual potential evapotranspiration is the

amount of evapotranspiration that would occur in a

year in an area completely covered with vegetation and

no deficiency of water in the soil. Potential

evapotranspiration is generally assumed to be about

equal to free water-surface evaporation (Linsley and

others, 1975, p. 178). Potential evapotranspiration in

the Rincon Valley is about 75 in. per year (Farnsworth

and others, 1982), about seven times greater than

precipitation.

Surface-Water/Irrigation System

The Rio Grande is the main drainage through the

Rincon Valley (fig. 2). The only perennial tributaries to

the Rio Grande in the valley are manmade agricultural

drains (drains). Discharge in the Rio Grande has large

variation because it is generally controlled by releases

from Caballo Reservoir in response to demands for

irrigation water downstream. During most years, little

or no water is released from mid-October until January

(fig. 3). During periods of no releases from Caballo

Reservoir, discharge at the streamflow gage Rio

Grande below Caballo Dam is generally less than 10

ft3

/s. Discharge in the Rio Grande increases

downstream because of ground-water discharge to the

river and inflow from drains. Small releases (less than

500 ft3

/s) start in early to mid-January and increase

until about March 1 (fig. 3). From about March 1 until

mid-October, discharge at Rio Grande below Caballo

Dam is generally greater than 1,000 ft3

/s. The largest

discharges in the Rio Grande generally are in June,

July, and August (fig. 3).

Most surface water used for irrigation in the

Rincon Valley is diverted from the Rio Grande into the

Arrey Canal and Percha Lateral at Percha Diversion

Dam, which is about 1.5 mi downstream from the

streamflow gage below Caballo Dam (fig. 2). A small

amount of water also is diverted from the Rio Grande

below Caballo Dam into the Bonita Community Ditch,

which supplies water to fields in the northern part of the

valley. From 1993 to 1995, annual diversions into the

Arrey Canal ranged from 102,000 to 127,000 acre-ft,

and annual diversions into the Percha Lateral ranged

from 1,080 to 1,440 acre-ft (Michael Riley, Elephant

Butte Irrigation District, written commun., 1996) (table

1; all tables are in the back of the report). Diversion into

the Arrey Canal generally ranges from 200 to 300 ft3/s

during the irrigation season (mid-February to midOctober), which is about 10 percent of the mean daily

discharge in the Rio Grande (fig. 3).

A complex system of canals moves irrigation

water to individual fields in the Rincon Valley (fig. 2).

Most canals are constructed above the level of the fields

so water can be diverted into the fields by gravity.

Water leaks from these canals because the canals are

above the water table and are unlined. Part of this

leakage recharges shallow ground water.

Not all water diverted from the Rio Grande for

irrigation is used for crop irrigation. Leakage of water

from irrigation canals to shallow ground water,

evaporation from canal surfaces, and transpiration from

plants along the canals, which together are referred to

as canal losses, accounted for 29 to 57 percent of total

water diverted in the Rincon Valley from 1930 to 1975

(Conover, 1954, p. 138; Wilson and others, 1981, p.

505-506). Because of cancellation of water deliveries

after the water has been diverted into the irrigation

system, 2 to 35 percent of the diverted water is returned

to the river or the drains (canal-return flow). The

amount of irrigation water delivered to farms ranged

from 20 to 55 percent of the water diverted in the

Rincon Valley from 1930 to 1975 (Conover, 1954, p.

138; Wilson and others, 1981, p. 505-506). Water

applied to fields is consumed by crops (transpires or

becomes plant biomass), evaporates from the soil,

infiltrates and recharges shallow ground water, or flows

across the fields and into a drain.

Drains were constructed in the Rincon Valley to

maintain water levels below land surface by

intercepting and draining off shallow ground water.

The drains are open channels 10 to 15 ft below land

surface. The five drains in the Rincon Valley that

discharge water to the Rio Grande are the Fera Drain,

Garfield Drain, Hatch Drain, Angostura Drain, and

Rincon Drain (fig. 2). The Garfield, Hatch, and Rincon

drains are the longest drains and drain most of the

valley. The Hatch wastewater-treatment plant

discharges into the Hatch Drain east of Hatch (fig. 2).

Streamflow gages generally upstream from the mouth

are operated by the EBID at sites on these drains (fig.

2). Hydrographs of mean daily discharge of the

Garfield, Hatch, and Rincon Drains for 1993-95 are

shown in figure 4.
Figure 2. Location of major irrigation canals and drains and surface-water and ground-water 

 sampling sites in the Rincon Valley study area.

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

32°

40 ́

32°

50 ́

107°20 ́ 107°10 ́ 107°00 ́

Caballo Reservoir

ARREY

DERRY

Derry Warm

 Spring

GARFIELD

SALEM

HATCH

RINCON

Rincon Valley

study area

boundary

Rio Grande

 EXPLANATION

DRAIN

IRRIGATION CANAL

HATCH WASTEWATER-TREATMENT

 PLANT INFLOW

STREAMFLOW-GAGING STATION

SURFACE-WATER SAMPLING SITE-- Letters

 indicate site is on Rio Grande (RG);

 upstream site on drain (U);

 downstream site on drain (D);

 or additional site sampled in April 1994

 on Garfield Drain (DG)

GROUND-WATER SAMPLING SITE--Well 

 numbers in appendix B

Fera Drain

U

D

D

D

U

RG

U

DG

RG

RG

Caballo

Dam Bonita

Community

Ditch

Percha Diversion Dam

Percha Lateral Arrey

Canal

Rincon Drain

Tonuco

Drain

Angostura

Drain

Colorado

Drain

Hatch

Drain

Garfield Drain

18

20

21 22

29 28

27

26

25

24

23

30

1

9

10

11

17

14

16

15

12

13

19

8

7

3

2

4

5 6
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J 

1993 1994 1995

RIO GRANDE BELOW CABALLO

0

5,000

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

D

N

O

CES REP TEEF CI BUC

NI , E GRA

H

CSI D

YLI A

D

N

AE M

Figure 3. Mean daily discharge of the Rio Grande below Caballo Dam and diversions to Arrey 

 ( data from Elephant Butte Irrigation District).

Rio Grande

below Caballo Dam

Diversion to

Arrey Canal
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

1993 1994 1995

GARFIELD DRAIN

0

40

10

20

30

MEAN DAILY DISCHARGE, IN

C

U

BIC FEET PER

SEC

O

N

D

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

1993 1994 1995

HATCH DRAIN

0

40

10

20

30

MEAN DAILY DISCHARGE, IN

C

U

BIC FEET PER

SEC

O

N

D

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

1993 1994 1995

RINCON DRAIN

0

40

10

20

30

MEAN DAILY DISCHARGE, IN

C

U

BIC FEET PER

SEC

O

N

D

Figure 4. Mean daily discharge of the Garfield Drain, Hatch Drain, and Rincon Drain, 1993-95.
9

The hydrographs for the three main drains in the

Rincon Valley show the largest amount of discharge

generally in June, July, and August and the smallest

amount of discharge in December, January, and

February (fig. 4). Discharge increases from the

beginning of March until June and decreases from

August until December; discharge is relatively constant

from December until March. Most of the discharge in

the drains is due to ground-water discharge. The

increase in discharge in the drains during the irrigation

season suggests that ground water discharging to the

drains is derived from infiltration of water diverted

from the Rio Grande and that ground water moves

toward and discharges to the drains soon after the

irrigation diversions start. The relatively rapid

increases in discharge for short periods of time during

the irrigation season probably result from canal waste

discharged to the drain or water applied to a field that

runs off to a drain (tail water). The annual discharge at

the gages for each drain is similar and did not vary

substantially from 1993 to 1995 (table 1). The sum of

annual discharge from the drains to the Rio Grande

measured at the streamflow gages was about 15,000

acre-ft for 1993-95 (table 1). This is about 12 percent

of the annual diversion to the Arrey Canal (table 1).

Most discharge from the drains to the Rio Grande

occurs during the irrigation season when discharge in

the Rio Grande is greater than 1,000 ft3/s. During the

irrigation season, total discharge from the three drains

to the Rio Grande is small (about 30 ft3/s) relative to

discharge in the Rio Grande.

Ground-Water Hydrology

The Rincon Valley is underlain by basin-fill

deposits that can be divided into the Santa Fe Group of

Tertiary age and the overlying valley-fill deposits of

Quaternary age. The Santa Fe Group underlying the

Rincon Valley consists of clay-sized material and does

not yield substantial quantities of water (King and

others, 1971, p. 17). This fine-grained facies is as much

as 2,000 ft thick in the area near Hatch (King and

others, 1971, p. 17). Most of the Rincon Valley is

underlain by this fine-grained facies of the Santa Fe

Group.

The Quaternary valley fill, which generally is

less than 80 ft thick, consists of gravel, sand, silt, and

clay-sized sediment and is the aquifer used in the

Rincon Valley (King and others, 1971, p. 23-24). The

areal extent of the Quaternary valley fill is limited to the

Rincon Valley and the narrow arroyo channels adjacent

to the valley. Conover (1954, p. 26) reported the

average depth to clay or the Santa Fe Group to be less

than 70 ft below land surface in the Rincon Valley. The

lower 30 to 40 ft of the valley-fill deposits are relatively

coarse grained; above this coarse-grained material

there is much lateral variation in grain size and sorting

of the deposits.

Ground-water recharge to the Quaternary valleyfill deposits is from infiltration of precipitation, water

from the Rio Grande, and irrigation water and inflow of

ground water from adjacent areas. Although there is

some infiltration of precipitation, most recharge to the

Quaternary valley-fill deposits is from infiltration of

water from the Rio Grande, irrigation water in canals,

and irrigation water applied to fields but not consumed

by crops. Ground-water inflow from adjacent areas

occurs along the area north and west of Caballo Dam,

the arroyo channels adjacent to the Rincon Valley, the

area west of Hatch (King and others, 1971, p. 58), and

the Jornada del Muerto (King and others, 1971, p. 58;

Wilson and others, 1981, p. 62).

Discharge of ground water from the Quaternary

valley-fill deposits of the Rincon Valley is from

ground-water discharge to the Rio Grande and drains,

ground-water flow through Selden Canyon, groundwater pumpage, and evapotranspiration. Ground-water

discharge to the Rio Grande and drains probably

accounts for most of the total discharge of ground

water from the Rincon Valley. Ground-water flow

through Selden Canyon is probably small because of

the limited thickness of Quaternary valley-fill deposits

in the canyon (Conover, 1954, p. 78). Ground water

removed from storage as the result of ground-water

pumpage is replaced by infiltrating irrigation water

because ground-water levels have not significantly

changed in the Rincon Valley since installation of the

drains. The net effect of ground-water pumpage is a

reduction of drain flow in the area until water levels

return to levels controlled by the drains.

Evapotranspiration from ground water is probably

limited to areas of native vegetation because most crops

do not have roots extending to or below the zone of

saturation.

Ground-water movement in the Rincon Valley is

generally down the valley. In the shallow part of the

Quaternary valley-fill deposits, the interaction of the

Rio Grande, irrigation canals, irrigated fields, drains,

and irrigation wells has created many localized flow

systems. Ground-water flow in these localized systems
10

generally is from the irrigation canals or fields toward

the drains or, in some cases, toward the Rio Grande.

Ground-Water/Surface-Water

Relations

Infiltration of surface and (or) irrigation water is

the main source of ground-water recharge to the

ground-water system, and discharge of ground water to

the drains and to the Rio Grande is the main source of

discharge from the ground-water system; therefore, a

change in surface-water supplies affects the groundwater system and discharge to the drains. Because of

little variation in the amount of water diverted from the

Rio Grande and discharge from drains from 1993 to

1995 (table 1), the surface-water and ground-water

systems may have approached steady state. At steady

state, recharge to the ground-water system may be

approximately equal to discharge from the groundwater system.

The rapid increase in discharge in the drains at

the beginning of the irrigation season (March),

relatively large discharge in the drains during the

irrigation season (March-October), rapid decrease in

discharge in the drains after the irrigation season

(October-November), and small discharge in the drains

in December, January, and February (fig. 4) indicate

that increases or decreases in ground-water recharge

rapidly increase or decrease ground-water discharge to

the drains. During sampling in April and October 1994

(irrigation season), discharge increased from the

upstream to downstream sites on the Garfield, Hatch,

and Rincon Drains (fig. 5), indicating ground-water

discharge to the drains and (or) flow of tail water or

canal-return flow into the drains. As previously

discussed, the contribution of tail water and canalreturn flow in the drains is thought to be small.

Increases in drain discharge between the upstream and

downstream sites (on the drains) generally were larger

in April than in October, possibly because diversions

and recharge generally were larger in April than in

October (figs. 3, 4, and 5). The discharge in the drains

decreased from August to December (fig. 4), probably

in response to decreases in recharge and subsequent

decrease in ground-water discharge to the drains,

indicating that these drains quickly remove ground

water from the ground-water system. In December and

January discharge in the drains is at a minimum for the

year (fig. 4) probably because of little ground-water

discharge to the drains. During sampling in January

1994 and 1995, discharge in the Rincon Drain

increased about 5 ft3

/s between the upstream and

downstream sites (fig. 5), indicating ground-water

discharge. In January 1994 and 1995, discharge at the

upstream and downstream sites was essentially the

same (fig. 5) on both the Garfield and Hatch Drains,

indicating little or no ground-water discharge to either

drain.

Ground water discharges into the Rio Grande

when water is not being released from Caballo

Reservoir. On January 5, 1994, streamflow

measurements were made at 10 locations along the Rio

Grande to quantify ground-water/surface-water

interaction. These measurements were made in January

because water had not been released from Caballo

Reservoir since the middle of October (fig. 3),

discharge from drains to the Rio Grande was at an

annual minimum (less than or equal to 1 ft3/s at the

Garfield and Hatch Drains), and the amount of

evaporation and transpiration was at an annual

minimum. The streamflow measurements showed the

largest ground-water discharges to be along the Rio

Grande from Caballo Dam to about 24 mi downstream

(near Hatch) (fig. 6). Discharge increased from about 5

to 40 ft3/s in a distance of about 23 mi; thus, groundwater inflow was about 1.5 ft3/s per river mi. The rate

of inflow was relatively constant throughout this reach

of the Rio Grande (fig. 6). Wilson and others (1981, p.

66) reported that ground-water inflow in this same

reach was about 0.58 ft3

/s per mi in February 1974 and

1.2 ft3

/s per mi in January 1975.

The increase in discharge in the Rio Grande

downstream from the site near Hatch to the site above

the Rincon Drain (4 ft3

/s in about 14 mi) was much less

than in the reach upstream from Hatch (fig. 6). The

Hatch Drain also discharges into the Rio Grande in this

reach, which increases discharge in the Rio Grande. On

January 4, 1994, discharge to the Rio Grande from the

Hatch Drain was about 0.4 ft3/s or about 10 percent of

the measured increase in discharge (4 ft3/s). The rate of

ground-water discharge to the Rio Grande between the

Hatch and Rincon Drains is about 0.3 ft3

/s per river mi.

Wilson and others (1981, p. 66) reported a slight gain

in this reach in February 1974 and a slight loss in

January 1975.
0 

5 10 15 20 25 30 35

RIVER MILES DOWNSTREAM FROM CABALLO DAM

0

50

5

45

40

35

30

25

20

15

10

DNO

CES REP TEEF CI BUC NI , E GRAHCSI D SUOENAT NATSNI

Rio Grande

Garfield Drain

Hatch Drain

Rincon Drain

Figure 5. Relation between instantaeous discharge and river miles downstream from Caballo Dam, 199
Inflow of 

3

0.44 ft /s

from 

Hatch 

Drain

Hatch

Inflo

4.8 

from 

Rinc

Dra

50

40

30

20

10

0 5 10 15 20 25 30 35 

5

45

35

25

15

 RIVER MILES DOWNSTREAM FROM CABALLO DAM

D

N

O

CES REP TEEF CI BU

C

NI , E GRA

H

CSI D

Figure 6. Instantaneous discharge at selected sites on the Rio Grande, January 5 and 6, 1994.
13

The increase in discharge in the Rio Grande from

Caballo Dam to near Hatch due to ground-water

discharge and a lack of ground-water discharge to the

Garfield Drain probably mean that the Rio Grande

drains the ground-water system in this part of the

Rincon Valley during the winter months or

nonirrigation period. The altitude of the river channel

could be much lower than that of the channels of the

drains, which would cause ground water to move

toward the Rio Grande and water in the drain to

infiltrate and recharge the ground-water system in this

part of the Rincon Valley.

Land Use/Land Cover

Land use/land cover in the Rincon Valley is

predominantly agricultural but also includes the

categories residential, urban, vacant, roadways, and

water. An aerial photograph of the Salem area shows

that nonagricultural land use/land cover generally

occupies little of the area and is generally surrounded

by agricultural land use (fig. 7). Agricultural land use

can be characterized as areas with flood-irrigated

crops. Most of the area south and west of Salem in

figure 7 can be characterized as agricultural land use. In

most of the Rincon Valley, homes representing

residential land use are located on small parcels (less

than one-half acre) surrounded by fields. Home sites

can be identified in figure 7 by areas where fields

surround buildings and trees. Urban areas in the Rincon

Valley include Arrey, Derry, Garfield, Salem, and

Hatch (fig. 2). Hatch, which had a population of 1,136

in 1990 (U.S. Department of Commerce, 1991), is the

largest urban area in the Rincon Valley. Vacant land

includes the area between the levees that bound the Rio

Grande (fig. 7), areas of the arroyo channels that enter

the Rincon Valley, and areas of native vegetation that

are not irrigated. These areas are found throughout the

Rincon Valley, but, with the exception of the area

between the levees, do not represent large, contiguous

land areas. The water land-use/land-cover category

includes the Rio Grande, main canals, and drains.

The main crops grown in the Rincon Valley are

alfalfa, peppers, onions, wheat, cotton, and pecans

(table 2). Planting dates vary for these different crops;

for example, peppers and cotton are generally planted

in late March to early April, whereas some varieties of

wheat are planted in October. Fields planted in alfalfa

are generally left in alfalfa for several years. Pecan

orchards take several years to establish and once

established are generally not used for production of

other crops. Typical crop rotation in the Rincon Valley

is 2 years of peppers or onions followed by 1 year of

wheat or other grains.

Fertilizer generally is applied to crops several

times during the year. In the spring prior to or during

planting, fertilizer is applied or mixed into the soil. If

fertilizer is needed during the growing season, it

generally is added to irrigation water. This is generally

done by pumping or siphoning liquid fertilizer into the

irrigation canals used to irrigate the specific field.

The amounts of specific pesticides used in the

Rincon Valley are unknown. Although many pesticides

are labeled for specific crops that are grown in the

Rincon Valley, little information is available

concerning particular pesticides used in the valley.

STUDY DESIGN

To assess the quality of water in the Rincon

Valley and determine factors affecting water quality,

samples of surface water, ground water, and bed

material (sediment in channels of drains) were

collected and analyzed for a variety of constituents.

During collection of surface-water and ground-water

samples, specific conductance, pH, temperature,

dissolved oxygen, and alkalinity (field properties) were

measured in the field. Surface-water and shallow

ground-water samples were sent to the USGS National

Water Quality Laboratory (NWQL) for analysis of

common constituents, nutrients, organic carbon, trace

elements, and pesticides (tables 3 and 4). Pesticides

were analyzed using two methods (Zaugg and others,

1995; Werner and others, 1996) and are grouped as A

or B in tables 3 and 4 depending on which method was

used for analysis. Shallow ground-water samples were

also analyzed for radioactivity, 18 samples were

analyzed for radon-222, and 20 samples were analyzed

for volatile organic compounds (VOC’s) (table 4).

Samples of bed sediment were collected at the

downstream sampling sites on each drain in January

1995 for analysis of 21 pesticides or pesticide

metabolites, gross polychlorinated biphenols (PCB’s),

and gross polychlorinated naphthalenes (PCN’s) (table

5). The pesticide metabolites dacthal mono-acid; DDD;

deethyl atrazine; 2,6, -diethylaniline; and p,p’-DDE are

also included in tables 3, 4, or 5. Although DDD and

p,p’-DDE were occasionally used as pesticides, in this
Figure 7. Land use/land cover in part of the Rincon Valley.

107° 13 ́30 ́ ́

32° 

42 ́

30 ́ ́

32° 

41 ́

30 ́ ́

107° 12 ́30 ́ ́

Salem Lateral

Garfield Drain

Levee

Levee

Hatch Canal

Hatch Drain

Salem

Rio Grande

85

0

0

0.25

0.25

0.5

0.5

1 MILE

1 KILOMETER
15

report they are referred to as pesticide metabolites.

Water-quality data are presented in appendixes A, B,

and C. Only VOC’s and pesticides that were detected in

one or more samples are included in the appendixes.

Samples were collected from three sites on the

Rio Grande (fig. 2) to characterize water that enters the

Rincon Valley and is used for irrigation and to

determine changes in water quality as water moves in

the Rio Grande through the Rincon Valley. Surfacewater samples were collected from an upstream (near

the beginning of the drain) and downstream (near the

mouth of the drain) site on the Garfield, Hatch, and

Rincon Drains (fig. 2) to determine variations in the

quality of water in drains throughout the Rincon Valley.

These drains were sampled because they traverse a

large part of the Rincon Valley, and water in them

represents ground-water discharge from areas adjacent

to the drain.

 Surface-water samples were collected during

January 1994, April 1994, October 1994, and January

1995 to characterize water quality during three

different hydrologic conditions or seasons. During

sampling in January 1994 and 1995, no water was

released from Caballo Reservoir for irrigation and most

flow in the Rio Grande was the result of ground-water

and drain discharge. During sampling in April 1994,

flow in the Rio Grande and the drains was near the

maximum for the year, most of the crops were planted,

and the farmers were irrigating crops throughout the

Rincon Valley. During the October 1994 sampling,

water was being released from Caballo Dam, flow in

the drains was decreasing, and most crops were not

being irrigated.

Samples of shallow ground water were collected

from 30 wells, installed during this investigation, to

characterize the quality of recently recharged ground

water. Well screens were located at or just below the

water table to ensure that water from the upper part of

the ground-water system (recently recharged water)

was sampled.

Ground-water samples were collected from

April 18 to May 7, 1994. Although this is early in the

growing season for some crops, many of the fertilizers

and pesticides used are incorporated into the soil prior

to planting and could be leached by irrigation water to

the ground-water system early in the irrigation season.

Therefore, sampling shallow ground water early in the

irrigation season may increase the probability of

detecting agricultural chemicals in ground water

because of the suspected rapid movement of irrigation

water to the ground-water system.

Composite samples of bed material were

collected at the downstream sampling site on the drains

in January 1995 for analysis of 21 pesticides or

pesticide metabolites, PCB’s, and PCN’s. Pesticides in

bed material at the mouth of the drains could be the

result of sediment transport from fields to the drains or

the result of absorption of pesticides from water in the

drains or ground water moving through the bed of the

drains.

Methods

Methods used during this study also were used

by personnel of the other NAWQA study units to

ensure that data collected for the NAWQA Program are

compatible. These methods are discussed in detail in

Horowitz and others (1994), Shelton (1994), Koterba

and others (1995), and Lapham and others (1995).

Well Site Selection

To prevent bias in the data, the locations of

possible sites where wells would be installed for

shallow ground-water sampling were determined using

a computer program that randomly selected the

locations (Scott, 1990). The area of study was

delineated on a map to include the Rincon Valley from

Caballo Dam to the upper part of Selden Canyon (fig.

1). Land use within the study area was grouped into

two categories: agricultural or nonagricultural.

Agricultural land use included small areas of

residential, urban, vacant, roadways, and water land

use/land cover because the areas generally were small

and surrounded by agricultural land use.

Nonagricultural land use included the urban area of

Hatch, an area of native vegetation east of Hatch, and

the area between the levees that border the Rio Grande

where crops generally are not grown.

The area of agricultural land use was divided into

30 cells of equal size using a computer program (Scott,

1990) (fig. 8). A primary and three alternate sites in

each agricultural land-use cell were then randomly

selected from a population of 28 to 39 possible points

in each cell. The land owner of the primary or alternate

site was contacted; if a location at or within 500 ft of

the site was acceptable, a well was installed.
Figure 8. Location of agricultural land-use cells and wells sampled

 in the Rincon Valley study area.

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

107°20 ́ 107°10 ́ 107°00 ́

Caballo Reservoir

ARREY

GARFIELD

SALEM

HATCH

RINCON

RINCON

VALLEY

Rio

Grande

BOUNDARY OF AGRICULTURAL

 LAND-USE CELLS

WELL SAMPLED--Number indicates cell

3 number and well number (appendix B)

1

9

10

10

11

17

17

14

16

15

12

13

19

18 20

21

22

29

28

27

26

25

24

23

30

8

2

4

6

5

7

6

EXPLANATION

7

6 6

5

7

9

17

11

17

19

22

26

22

22

32°

40 ́

32°

50 ́
17

Well Installation

Wells were installed in March 1994 using a

hollow stem auger following protocols outlined by

Lapham and others (1995). A hole was augured to a

depth of about 10 ft below the top of the zone of

saturation. The wells were constructed using 2-in. PVC

pipe and 10 ft of PVC well screen. The top of the well

screen was set at the top of the zone of saturation. The

wells were developed within 2 weeks of installation

and allowed to stand for 2 to 3 weeks prior to sampling.

Well numbers were assigned to each well on the basis

of the agricultural land-use cell in which the well was

located (fig. 8 and app. B).

Water Sampling

The equal-width-increment sampling method

and a DH-81 1-liter teflon bottle sampler were used to

collect most surface-water samples following protocols

outlined by Shelton (1994). The samples for dissolved

organic carbon (DOC), total organic carbon, or

suspended organic carbon analysis were collected by

submerging a sample bottle below the water surface at

the center of flow. Ground water was sampled using a

1.8-in.-diameter stainless steel pump and teflon

discharge lines following protocols outlined by

Koterba and others (1995). The pump was set at a depth

2 to 5 ft below the initial water level in the well. After

three casing volumes of water had been pumped from

the well, specific conductance, pH, temperature,

dissolved oxygen, and turbidity were monitored until

these field properties stabilized (generally less than 10-

percent variation). When the field properties had

stabilized, samples were collected. Samples for

analysis of common constituents, nutrients, DOC, trace

elements, and radioactivity were filtered using a 0.45-

micron pore-size filter. Samples for pesticide analysis

were filtered using a 0.7-micron pore-size baked glass

fiber filter. VOC samples were not filtered but were

preserved using 2 drops of concentrated hydrochloric

acid. After collection of samples, sampling equipment

was cleaned following protocols outlined by Shelton

(1994) and Koterba and others (1995), and the clean

equipment was stored in plastic bags.

Bed-Material Sampling

Composite samples of bed material were

collected by obtaining subsamples at several locations

across the channel of a drain. A plastic tube was pushed

into the bed material to a depth of about 3 in. to obtain

subsamples. Subsamples were placed in a 0.5-liter jar

until the jar was filled. The jar was then chilled, stored,

and shipped on ice to the NWQL. The sampling tube

was cleaned after drain sampling using the same

procedure as that used for the surface-water sampling

bottles (Shelton, 1994).

U.S. Geological Survey National Water

Quality Laboratory Methods

All samples were analyzed at the USGS NWQL.

The methods used for analysis of common constituents

and nutrients are outlined in Fishman (1993). Trace

elements were analyzed by inductively coupled

plasma/mass spectrometer techniques (Faires, 1993).

Gross alpha and gross beta analytical methods are

described in Thatcher and others (1977). Radon-222

was analyzed by liquid scintillation counting. Methods

used for analysis of VOC’s are described in Rose and

Shroeder (1995). Group A pesticides were analyzed by

the C-18 solid-phase extraction method (Zaugg and

others, 1995), and group B pesticides were analyzed by

the Carbopak-B solid-phase extraction method

(Werner and others, 1996). Methods used for analysis

of pesticides in bed sediment are described in Wershaw

and others (1987). The NWQL has a quality-assurance

program (Friedman and Erdmann, 1982; Pritt and

Raese, 1992), but the specifics of the program are not

addressed in this report.

The minimum reporting level (MRL) or method

detection limit (MDL) for each constituent is

determined by the analytical methods used. The MRL

is the lowest measured concentration of a constituent

that may be reliably reported using a given analytical

method (Timme, 1995, p. 92) and is used when

documentation of an analytical method is not available.

The MDL’s in tables 3 and 4 were defined and

determined at the NWQL (Zaugg and others, 1995;

Peter Rogerson, National Water Quality Laboratory,

written commun., 1996). An MDL is the minimum

concentration of a particular analyte that can be

identified, measured, and reported with 99-percent

confidence that the analyte concentration is greater

than zero (Zaugg and others, 1995). In some samples, a

particular pesticide was positively identified at a

concentration less than the MDL; for these samples, the

concentration of the pesticide was estimated and the

confidence in the concentration measured is less than

99 percent. Constituents that were not measured at a
18

concentration equal to or greater than the MRL or

MDL or were not positively identified in a sample are

referred to as not detected.

Quality Assurance/Quality Control of Data

A quality-assurance program allowed evaluation

of the data to ensure that the sampling procedures and

characteristics of the water sampled (matrix bias or

interferences) were not resulting in poor-quality data.

Field-blank samples, replicate samples, and spike

samples were collected as part of the quality control

used in this investigation. The results of the qualityassurance program presented are a compilation of all

quality-assurance samples (surface-water and groundwater samples) collected during this investigation.

Seven field blanks were collected and sent to the

NWQL to ensure that chemical constituents were not

being introduced into samples as the result of sampling

and laboratory procedures. Field blanks were collected

using surface- and ground-water sampling equipment

following protocols described in Shelton (1994) and

Koterba and others (1995).

Results of the field-blank samples indicate that

many of the constituents were not detected or were

detected at concentrations significantly smaller than

those detected in the surface-water and ground-water

samples (table 6). This indicates that the sampling and

laboratory procedures used did not result in the

addition of these chemical constituents to the samples

at concentrations that would have an effect on

interpretation of the surface-water and ground-water

data. Nitrite, ammonia, phosphorus, aluminum,

chromium, iron, zinc, and methylchloride were

detected in the field-blank samples (table 6) at

concentrations near the MRL and in about the same

range as concentrations detected in some of the

surface-water or ground-water samples. Nitrite,

phosphorus, and iron were detected only in one of

seven field-blank samples at concentrations equal to or

slightly greater than the MRL, indicating that these

constituents were infrequently added to the samples as

a result of sampling or laboratory procedures.

Ammonia, aluminum, and zinc were detected in more

than one-half of the blank samples at concentrations

similar to those detected in many of the surface- and

ground-water samples, indicating that samples were

commonly contaminated. Ammonia concentrations in

the surface- and ground-water samples greater than

0.06 mg/L (two to three times higher than the

concentrations in the blanks (0.02

mg/L)) are indicative of ammonia in the samples;

however, concentrations smaller than 0.06 mg/L in the

surface- or ground-water samples could be due to

contamination. All aluminum and zinc concentrations

measured in the surface- and ground-water samples

could be the result of sample contamination; thus, they

are not discussed in this report. Methylchloride was

detected in both field-blank samples at concentrations

similar to those detected in ground-water samples, so

methylchloride was probably introduced into the

samples during sampling or in the laboratory and is not

present in ground water. Because methylene chloride

was not detected in any ground-water samples,

methylene chloride was probably in the organic-free

water used to prepare the field blanks (table 6).

Replicate samples are two samples split from

one sample. Seven pairs of replicate samples were sent

to the NWQL to determine precision of sampling

procedures or laboratory procedures for an individual

sample site. The relative-percent difference was

calculated for each pair of replicates. Relative-percent

difference is the difference in the concentration of an

analyte in the two samples divided by the average

concentration of the two samples multiplied by 100.

Minimum, median, and maximum relative-percent

differences for constituents analyzed in the replicates

are presented in table 7. Comparison of analytical

results for the replicate samples shows that the median

relative-percent difference was zero for most

constituents, indicating good precision of the sampling

and laboratory procedures. The trace elements

chromium, copper, and nickel had some of the largest

relative-percent differences. The measured

concentrations of these trace elements are in the same

range as the MRL or MDL. For these constituents, the

differences in concentrations in the replicate samples

could be from the analytical procedures used.

Surrogate compounds, which are generally not

found in the environment, were added at the time of

collection to all surface- and ground-water pesticide

samples to determine the precision and accuracy of the

analytical methods. Several surface- and ground-water

samples were spiked in the field or in the laboratory

(field or laboratory spikes); most of the pesticides or

VOC’s were analyzed for to evaluate the accuracy and

precision of the analytical method for different

compounds in different sample matrixes and to

evaluate degradation of compounds during shipping

and handling of the samples. Surrogate (or spike)
19

recoveries less than 100 percent indicate that not all the

surrogate (or spike) added to the sample is detected

(results biased low), and recoveries greater than 100

percent indicate that concentrations detected in the

sample are larger than the actual concentration in the

sample (results biased high).

For the three surrogates used for the group A

pesticide analysis, surrogate recoveries ranged from 68

to 132 percent (app. A and B), indicating acceptable

method performance. The surrogate recovery for the

surrogate used for group B pesticides ranged from 0 to

110 percent (app. A and B). The relatively small

surrogate recoveries for group B pesticides are not

necessarily indicative of poor performance of the

method because “the surrogates chosen did not perform

as expected for a variety of reasons, including coelution with target analytes, natural background

concentration, and poor reproducibility” (U.S.

Geological Survey National Water Quality

Assessment/ National Water Quality Laboratory

Quality Assurance Committee, written commun.,

1995). The results for group B pesticides could be

biased low on the basis of the surrogate recoveries.

The median percent recovery for most of the

spiked compounds for group A pesticide analyses

ranged from 75 to 120 percent (table 8), indicating little

bias in the analytical results. Many of the spiked

compounds used in the samples for group B pesticide

analyses (table 9) had relatively small recoveries. Low

spike recoveries were found in samples submitted to

the laboratory for group B pesticides analysis from

throughout the country, and the low spike recoveries

were evaluated by a quality-assurance committee (U.S.

Geological Survey National Water Quality

Assessment/National Water Quality Laboratory

Quality Assurance Committee, written commun.,

1995). The quality-assurance committee determined

that the recovery and precision for all compounds with

the exception of aldicarb, aldicarb sulfone, carbaryl,

carbofuran, methiocarb, 1-napthol, and oxamyl

“generally are high enough and consistent enough that

the data are acceptable for publication and useful for

data analysis” (U.S. Geological Survey National Water

Quality Assessment/National Water Quality

Laboratory Quality Assurance Committee, written

commun., 1995). The low spike recoveries could

indicate that the results for group B pesticides are

biased low.

The results of the six VOC spike samples show

that the percent recovery for the laboratory spikes

ranged from 70 to 115 and for the field spikes and field

spike replicates ranged from 30 to 85 percent (table

10). The smaller percent recovery for the field spikes

could be due to the procedures used in the field relative

to the procedures used in the laboratory or to

degradation of compounds during shipping and

handling prior to analysis. If the smaller recoveries in

the field spikes relative to laboratory spikes are the

result of degradation of compounds during shipping,

the results of the VOC analyses could be biased low.

The results for the spike samples (pesticides and

VOC’s) indicate that the methods used were

appropriate for most compounds and no significant

degradation of compounds occurred during shipping

and handling. Spiked compounds that have percent

recoveries less than 100 percent may be present in the

unspiked samples and not be detected, or the

concentrations measured in a sample may be smaller

than the actual concentration in the sample (biased

low). If recovery of a compound in the spiked samples

was consistently greater than 100 percent and the

compound was detected in an unspiked sample, the

reported concentration in the unspiked sample could be

larger than the actual concentration in the sample

(biased high).

SURFACE-WATER QUALITY

Surface-water-quality standards for the Rio

Grande, which are based on the designated uses of

water in the stream reach (New Mexico Water Quality

Control Commission, 1994), are compared to surfacewater quality in the Rincon Valley in the following

section. For the reach of the Rio Grande from below

Caballo Dam to 1 mi below Percha Diversion Dam, the

designated uses include irrigation, warm-water fishery,

livestock watering, wildlife habitat, and primary

contact recreation (New Mexico Water Quality Control

Commission, 1994, p. 13). For the reach of the Rio

Grande from 1 mi below Percha Diversion Dam to the

southern end of the Rincon Valley, the designated uses

include irrigation, limited warm-water fishery,

livestock watering, wildlife habitat, and secondary

contact recreation (New Mexico Water Quality Control

Commission, 1994, p. 13). Each designated use has

standards for specific constituents; some constituents

could be included in the standards for several

designated uses. For the constituents analyzed for

during this investigation, the standards for the two
20

different reaches are essentially the same with the

exception of pH and temperature (table 11). No State

water-quality standards have been established for water

in drains. Water quality in the drains is compared to the

standards (table 11), however, because discharge from

the drains can affect water quality in the Rio Grande.

The standards applicable to a particular river reach with

several use designations are those that protect and

sustain the most sensitive case, which in the Rincon

Valley are the fisheries standards (New Mexico Water

Quality Control Commission, 1994). Fisheries

standards include both acute and chronic standards.

Acute standards are designed to protect most species

from deleterious effects of contaminants for short

periods of time, are applied to single grab samples, and

shall not be exceeded. Chronic standards are designed

to protect most species from deleterious effects from

contaminants for extended periods of time, are applied

to the arithmetic mean concentration of four samples

collected on each of 4 consecutive days, and shall not

be exceeded more than once every 3 years (New

Mexico Water Quality Control Commission, 1994, p.

50). Because samples were not collected on 4

consecutive days during this investigation, data in this

report cannot be compared to chronic standards.

Field Properties and Common

Constituents

Specific conductance, a measure related to

dissolved-solids concentration, was generally larger in

samples from the drains than in samples from the Rio

Grande (app. A). The pH was generally larger in

samples from the Rio Grande than in samples from the

drains. In January, the pH generally increased

downstream in the Rio Grande; in April and October

there was no clear change in pH downstream. Water

temperature was similar in the Rio Grande and in the

drains and varied depending on the time of year

(warmer in the summer). Dissolved oxygen

concentrations showed relatively large variation during

different sampling events at a particular site (app. A).

In general, dissolved oxygen concentrations were

larger in water from the Rio Grande than in water from

the drains. At all sites, except those on the Garfield

Drain, dissolved oxygen concentrations were about

1 mg/L or more larger in January 1994 and 1995 than

in April 1994 or October 1994.

No samples from the Rio Grande or the drains

exceeded surface-water-quality standards for pH or

temperature. Dissolved oxygen was less than the

standard of 5 mg/L in five samples from the drains.

Dissolved-solids concentrations in surface water

ranged from 434 to 1,510 mg/L (table 12).

Concentrations were smallest in water from the Rio

Grande below Caballo Dam and largest in water from

the drains (app. A). Dissolved-solids concentrations in

the Rio Grande increased downstream from Caballo

Dam during all sampling events; the largest increases

were in January 1994 and 1995 (fig. 9). On the Hatch

and Rincon Drains, dissolved-solids concentrations

also were smaller at the upstream sampling sites than at

the downstream sampling sites during all sampling

events (fig. 9). The dissolved-solids concentration

increased downstream in the Garfield Drain in October

1994 and January 1995, but decreased in January 1994

(fig. 9). In April 1994, an additional site near the lower

end of the Garfield Drain was sampled; the dissolvedsolids concentration increased in the upper reach and

decreased in the lower reach. In general, the largest

increases in concentration between the upstream and

downstream sampling sites were in water from the

Hatch and Rincon Drains; the dissolved-solids

concentration in water from the drains was largest in

January. The smallest temporal variation in dissolvedsolids concentration at a sampling site was at both

sampling sites on the Hatch Drain and at the upstream

site on the Rincon Drain (fig. 9).

The concentrations of common constituents in

surface-water samples (fig. 10 and table 12) varied

widely. In general, the relative variation in dissolvedsolids concentration at a given site is similar to the

relative variation of individual common constituents.

Sulfate generally had the largest concentrations and the

most variation of the common constituents in surfacewater samples (fig. 10 and table 12). Bicarbonate and

sodium had the next largest concentrations.

Concentrations of magnesium, potassium, carbonate,

fluoride, and silica were smaller than concentrations of

the other common constituents (less than 40 mg/L) in

all samples (fig. 10 and table 12). The largest sulfate

concentrations generally were in samples from the

downstream sampling site on the Rincon Drain.

Sodium, potassium, and fluoride concentrations

generally were largest in samples from the upstream
0 

5 10 15 20 25 30 

RIVER MILES DOWNSTREAM FROM CABALLO DAM

400

1,600

900

800

700

600

500

1,000

1,100

1,200

1,300

1,400

1,500

RETI L REP S M

AR GI LLI M NI , NOI TART NECNO

C SDI L OS DEVL OSSI D

Rio Grande

Garfield Drain

Hatch Drain

Rinco

Figure 9. Relation between dissolved-solids concentration in surface wa

 and river miles downstream from Caballo Dam, 1994-95.
Figure 10. Distribution of selected constituent concentrations in surface water

 in the Rincon Valley study area.

75- PERCEN

NUMBER OF 

90-PERCEN

MEDIAN VA

25-PERCEN

10-PERCEN

M

UI CLA

C

M

UI SEN

G

A

M

ETA

N

OBRA

CI B

ETA

N

OBRA

C

EDI R OL H

C

ETAFL US

EDI R O

ULF

A

CI LI S

M

UI D

OS

M

UI SSAT OP

1,000

100

10

1

0.1

RETI L REP S M

AR GI LLI M

NI , N

OI TART NEC

N

O

C

*

**

**

*

*

*

*

*

*

*

*

**

*

***

*

*

*

*

*

*

*

*

*

*

*

**

(37)

(37)

(37)

(37)

(37)

(37)

(37)

(37)

(14)

(37)

(37)

EXPLANATION

OUTLIER
23

sampling site on the Garfield Drain (app. A). The

largest silica concentrations were generally from the

downstream Hatch Drain site. Silica concentrations in

samples collected from all sites on the Rio Grande in

April 1994 were about 10 times smaller than any other

silica concentrations measured during this

investigation.

A Durov plot of water compositions shows

variations in the percentage of different anions and

cations in each water sample (fig. 11) and can be used

to compare the compositions of a large number of

samples. The plot consists of two trilinear diagrams

that represent concentrations as percentages of major

cations or anions (in milliequivalents per liter) as a

point in each respective trilinear diagram. Projections

of the data points from the two trilinear diagrams to the

central rectangular plot intersect to define a point that

represents the major ion composition of each sample.

Projections from the central rectangular plot to two

adjacent rectangular plots are used to represent

variations in major compositions of the chosen

constituents, in this case dissolved solids.

In the Durov plot, most of the water has a similar

distribution of cations and anions, and the distribution

of cations does not change systematically with

variations in dissolved-solids concentrations. However,

the distribution of anions does change systematically

with variations in dissolved-solids concentration (fig.

11). Calcium and sodium account for about equal

percentages of total cations (40 percent). Magnesium

was similar (about 20 percent) in all samples. Sulfate

and bicarbonate plus carbonate account for about equal

percentages of the total anions (40 percent). Six

samples had percentages of calcium less than 30, which

generally were less than the percentage of calcium in

most samples; four of these samples were from the

upstream sampling site on the Garfield Drain and the

other two samples were from the Rio Grande below

Caballo Dam in January of 1994 and 1995. Samples

with larger dissolved-solids concentrations generally

have larger percentages of sulfate and smaller

percentages of bicarbonate plus carbonate (fig. 11).

Nutrients and Dissolved Organic

Carbon

The concentrations of dissolved nutrient species

in surface water in the Rincon Valley varied

considerably. Nitrite plus nitrate concentrations ranged

from less than 0.05 to 3.3 mg/L as nitrogen, and

dissolved ammonia concentrations ranged from less

than 0.015 to 0.33 mg/L as nitrogen in surface-water

samples (table 12 and app. A). Nitrite concentrations

were generally small (less than 0.11 mg/L as nitrogen),

indicating that nitrite accounts for a small amount of

nitrogen in the nitrite plus nitrate analyses.

Nitrite plus nitrate concentrations generally were

larger in samples collected from the drains than in

samples collected from the Rio Grande (fig. 12). At

sampling sites on the drains, nitrite plus nitrate

concentrations generally were largest in water from the

downstream sampling site on the Hatch Drain and

smallest in water from the sampling sites on the Rincon

Drain (fig. 12). Nitrite plus nitrate concentrations

generally increased downstream on the Hatch and

Rincon Drains and decreased downstream in the

Garfield Drain. Concentrations in samples from the Rio

Grande in April and October (irrigation season) were

smaller than concentrations in January (nonirrigation

season).

Ammonia concentrations generally were larger

in samples from the drains than from the Rio Grande

(app. A). In the Rio Grande, ammonia concentrations

were less than 0.1 mg/L as nitrogen and did not vary

consistently with time of year or between sampling

sites (app. A). The largest ammonia concentrations

were in samples from the upstream and downstream

sampling sites on the Hatch Drain in January 1995 and

the downstream sampling site on the Hatch Drain in

January 1994. Ammonia concentrations increased

downstream during all sampling periods at the two sites

on the Rincon Drain (app. A), but showed no clear

trend between the upstream and downstream sampling

sites on the other two drains.

The surface-water-quality standard for total

ammonia varies depending on the pH and temperature

of the sample (New Mexico Water Quality Control

Commission, 1994, p. 48). No samples were collected

for analysis of total ammonia so the results of this study

cannot be compared to the total ammonia standard.

 Ammonia plus organic nitrogen concentrations

in the Rincon Valley (app. A; table 12) showed no

trends or significant variation. Most ammonia plus

organic nitrogen concentrations were equal to or

slightly greater than the MRL of 0.2 mg/L as nitrogen.

There was little or no variation in phosphorous

and orthophosphate concentrations, which were equal

to or slightly greater than the MRL of 0.01 mg/L as

phosphorus at many sites. Water collected from the
DISSOLVED SOLIDS,

IN MILLIGRAMS PER LITER

PERCENTAGE OF

TOTAL CATIONS,

IN MILLIEQUIVALENTS PER LITER

PERCENTAGE OF

TOTAL ANIONS,

IN

MILLIEQUIVALENTS PER LITER

DISSOLVED SOLIDS,

IN

MILLIGRA

MS PER LITER

0

0 1,000

1,000

2,000

2,000

Figure 11. Surface-water composition in the Rincon Valley study area, April and October 1994.

IRRIGATION WATER

 (Rio Grande below Caballo

 Dam, April and October 1994)

SODIUM PLUS POTASSIUM

BICARBONATE PLUS CARBONATE
0 

5 10 15 20 25 30 35

RIVER MILES DOWNSTREAM FROM CABALLO DAM

0

3.5

0.5

1.0

1.5

2.0

2.5

3.0

, N

OI TART NEC

N

O

C ETARTI N SULP ETI RTI N

DEVL OSSI D

NE G

ORTI N SA RETI L REP S M

AR GI LLI M

NI

Figure 12. Relation between dissolved nitrite plus nitrate concentration in surface wat

 and river miles downstream from Caballo Dam, 1994-95.

Rio Grande

Garfield Drain

Hatch Drain

Rincon Drain
26

downstream sampling site on the Hatch Drain had

phosphorous and orthophosphate concentrations

ranging from 0.18 to 0.73 mg/L as phosphorus and

were much larger than concentrations measured at any

other sites.

DOC concentrations in water from the Rio

Grande generally were in the same range as those in

water from the drains (fig. 13). Concentrations

generally were smaller in samples collected in January

than in samples collected in April or October on the Rio

Grande. During all sampling on Garfield Drain, DOC

concentrations generally were smaller at the upstream

sampling site than at the downstream sampling site (fig.

13). Concentrations showed no clear pattern or trend

relative to sampling sites or time of sampling on the

Hatch and Rincon Drains.

Trace Elements

Concentrations of many trace elements in

surface water in the Rincon Valley were small or less

than the MRL (table 12). Aluminum, barium, boron,

bromide, copper, iron, manganese, molybdenum,

uranium, and zinc were detected in one or more

samples at concentrations larger than 10 ∝g/L (table

12). No samples had detectable concentrations of

antimony, beryllium, cobalt, or silver. Cadmium was

detected at a concentration of 6 ∝g/L in one sample,

and selenium was detected at a concentration of 1 ∝g/L

in one sample.

In general, there was little spatial or temporal

variation in the concentrations of arsenic, chromium,

copper, lead, molybdenum, nickel, and uranium.

Barium concentrations generally were largest in

samples from the Rio Grande and in samples from the

upstream sampling sites on the Hatch and Rincon

Drains (app. A). Boron concentrations generally were

largest in samples from the upstream sampling site on

the Garfield Drain and the downstream sampling site

on the Hatch and Rincon Drains (app. A).

Concentrations of iron, molybdenum, and uranium

were also larger in samples from the upstream site on

the Garfield Drain. Bromide concentrations generally

were largest in the samples from the drains and

smallest in samples from the Rio Grande in April and

October 1994 (app. A). Manganese concentrations

generally were smaller than 10 ∝g/L in samples from

the Rio Grande in April and October. Samples

collected at the upstream sampling sites on the Hatch

and Rincon Drains generally had the largest manganese

concentrations compared with samples from other

sites. Manganese concentrations generally were larger

in samples collected in January than in April or

October.

The acute fisheries standards for many trace

elements are dependent on the hardness (as CaCO3) of

the water (for example, dissolved copper std 1 ∝g/L =

e (0.9422 [ln(water hardness in mg/L as CaCO3)]-

1.464)) (New Mexico Water Quality Control

Commission, 1994). The standards listed in table 11

were calculated using a hardness of 150 mg/L as

CaCO3, which is less than the hardness of any of the

samples collected. The 32-∝g/L copper concentration

from the upstream site on the Rincon Drain exceeded

the standard calculated using a hardness of 150 mg/L.

The standard was recalculated using the actual

hardness of the sample (350 mg/L), and the measured

concentration was less than the recalculated standard

(58 ∝g/L). The trace-element concentrations in

surface-water samples were significantly smaller than

the acute fisheries standards (table 11).

Pesticides

Thirty-seven samples were analyzed for 88

pesticides or pesticide metabolites (hereinafter referred

to as pesticides) with MDL’s ranging from 0.001 to

0.050 ∝g/L (table 3). One or more pesticides were

detected in 34 of 37 samples (app. A). Thirteen of the

88 pesticides analyzed for were detected in one or more

samples. The most commonly detected pesticides,

DCPA (dacthal) and metolachlor, which are herbicides,

were each detected 27 times. Carbofuran, which is an

insecticide, was detected eight times. The degradation

product of DDT, p,p’-DDE, was detected seven times.

The herbicide EPTC was detected six times, and the

herbicides prometon and simazine were each detected

four times. Diazinon, an insecticide, was detected three

times. Chloropyrifos, an insecticide, and dacthal monoacid, a degradation product of DCPA, were each

detected twice. Atrazine, pendimethalin, and

trifluralin, which are herbicides, were each detected

once.

In general, pesticides were more commonly

detected in April 1994 in samples from the drains and

in January 1994 in samples from the Rio Grande than

during the other sampling events. More pesticide

detections were in samples from the downstream sites
0 

5 10 15 20 25 30 35

RIVER MILES DOWNSTREAM FROM CABALLO DAM

0.5

5.0

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

, N

OI T

A

R

T

NEC

N

O

C

N

O

B

R

A

C

CI N

A

G

R

O

DEVL O

S

SI D

N

O

B

R

A

C

S

A

RETI L REP S

M

A

R

GI LLI M

NI

Figure 13. Relation between dissolved organic carbon concentration in surface water 

 and river miles downstream from Caballo Dam, 1994-95.

Rio Grande

Garfield Drain

Hatch Drain

Rincon Drain
28

on the drains than in samples from the upstream sites

on the drains. Pesticides were detected more frequently

in samples from the downstream site on the Rincon

Drain and least frequently in samples from the

upstream site on the Rincon Drain and the site on the

Rio Grande below Caballo Dam.

The concentrations of pesticides detected

generally were small (less than 0.05 ∝g/L) (app. A).

Pesticide concentrations were generally larger in

samples from the drains than in samples from the Rio

Grande. Metolachlor was detected at a concentration of

0.41 ∝g/L in a sample from the Hatch Drain.

Metolachlor concentrations generally were larger in

samples from the downstream site on the Hatch Drain

and the downstream site on the Rincon Drain. DCPA

concentrations generally were larger in samples from

the downstream sites on the drains than in samples

from the upstream sites (fig. 14). DCPA concentrations

in samples from the Rio Grande generally were small

relative to concentrations in samples from the drains.

The New Mexico Water Quality Control Commission

(1994) has not established standards for the 13

pesticides detected.

SHALLOW GROUND-WATER

QUALITY

In the following discussion, shallow groundwater quality in the Rincon Valley is compared to U.S.

Environmental Protection Agency (USEPA) drinking

water standards although none of the wells sampled are

used for drinking water. Water from these wells is from

the shallow part of the aquifer, whereas most domestic

and irrigation wells in the area are completed in the

deeper parts of the aquifer. Shallow ground water could

move downward in the aquifer, however, and affect

water quality in deeper parts of the aquifer.

The USEPA has established national primary

drinking water regulations for constituents that, if

present in drinking water, may cause adverse human

health effects (U.S. Environmental Protection Agency,

1996). For regulated constituents, the regulations

specify either a maximum contaminant level (MCL) or

an action level that requires a treatment technique.

Treatment techniques are specified in place of MCL’s

when establishing a quantifiable level of a constituent

for compliance purposes is not economically or

technically feasible. Secondary maximum contaminant

levels (SMCL’s) are established for constituents that

can adversely affect the odor or appearance of water

and result in discontinuation of its use. SMCL’s

generally are established for aesthetic purposes and are

not based on adverse health effects. Health advisories,

which are also established by the USEPA, are

nonregulatory levels of constituents that can be used

for guidance when regulatory limits have not been

established. Health advisories are estimates of

concentrations that result in no known health effects

based on assumptions about body weight and amount

of drinking water consumed per day. Lifetime health

advisories used in this report assume a 70-year

exposure period for a person weighing about 155 lbs

and drinking about 2 qts of water per day.

Symbols representing different ranges in

concentrations are shown on maps in the following

sections to demonstrate areal variations in the

concentrations of selected constituents. The rationale

for grouping different concentration ranges (symbols)

is based on statistical summaries of the concentrations

for a particular constituent (table 13). Concentrations

between the maximum and 75th percentile are depicted

by a triangle pointing upward, concentrations between

the 25th percentile and the minimum are depicted by a

triangle pointing downward, and the remainder of the

concentrations are depicted by a square.

Field Properties and Common

Constituents

 The specific conductance of shallow ground

water ranged from 790 to 5,280 ∝S/cm. About 75

percent of the samples had a specific conductance

between 1,000 and 2,000 ∝S/cm (table 13). The pH

varied little in shallow ground water; about 80 percent

of the samples had a pH between 7.20 and 7.63. The

temperature of shallow ground water was between 15.4

and 18.7 °C in about 80 percent of the samples.

Dissolved oxygen concentrations generally were less

than 1 mg/L (table 13). The larger dissolved oxygen

concentrations were in samples from wells located near

irrigation canals.

Bicarbonate and sulfate concentrations generally

were the largest of the common constituents, and

sulfate concentrations generally had the largest

variation (fig. 15). Sodium and calcium concentrations

had the next largest concentrations of the common

constituents (fig. 15). Magnesium and potassium

concentrations were generally much smaller than
0 

5 10 15 20 25 30 35

RIVER MILES DOWNSTREAM FROM CABALLO DAM

0

0.22

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

RETI L REP S M

AR G

ORCI M

NI , APC

D

Figure 14. Relation between DCPA concentration in surface water

 and river miles downstream from Caballo Dam, 1994-95.

Rio Grande

Garfield Drain

Hatch Drain

Rincon Drain
30

sodium and calcium concentrations, and chloride

concentrations were generally smaller than the

bicarbonate and sulfate concentrations. Three samples

had fluoride concentrations between 2.6 and 2.9 mg/L

(wells 7, 8, and 25), which were much larger than those

detected in the rest of the samples (app. B). In general,

there was a small range in silica concentrations (table

13).

Dissolved-solids concentrations in shallow

ground water ranged from 481 to 3,630 mg/L (table

13). Some of the largest dissolved-solids

concentrations were in wells south and east of Rincon

(wells 25, 26, 27, and 29) (fig. 16). Dissolved-solids

concentrations can vary widely between wells a

relatively short distance apart (fig. 16; app. B). For

example, the dissolved-solids concentration in samples

from wells 25 and 26, which are about one-half mi

apart, differ by about 2,000 mg/L.

A Durov plot of water compositions indicates

little variation in the percentages of the different anions

(bicarbonate, sulfate, and chloride) and a relatively

constant percentage of magnesium in the samples;

there is, however, variation in the percentages of

calcium and sodium (fig. 17). Although the percentages

of anions in shallow ground water have little variation,

the samples with larger percentages of sulfate have

larger dissolved-solids concentrations (fig. 17). The

variation in percentages of calcium and sodium is not

related to dissolved-solids concentration.
Figure 16. Dissolved-solids concentrations in shallow ground water

 in the Rincon Valley study area.

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

107°20 ́ 107°10 ́ 107°00 ́

Caballo Reservoir

ARREY

GARFIELD

SALEM

HATCH

RINCON

Rincon Valley

study area

boundary

Rio

Grande

DISSOLVED-SOLIDS CONCENTRATION

 1,350 TO 3,630 MILLIGRAMS PER LITER--

 Number indicates well number (appendix B)

DISSOLVED-SOLIDS CONCENTRATION

 789 TO 1,349 MILLIGRAMS PER LITER--

 Number indicates well number (appendix B)

DISSOLVED-SOLIDS CONCENTRATION

 481 TO 788 MILLIGRAMS PER LITER--

 Number indicates well number (appendix B)

2

3

1

9

10

11 17

14

16

15

12

13

19 18

20

21 22

29

28

27 26

25

24

23

30

8

2

4

5 6

6

4

EXPLANATION

7

32°

40 ́

32°

50 ́
Figure 17. Shallow ground-water composition in the Rincon Valley study area, 

 April and October 1994.

BICARBONATE PLUS CARBONATE

DISSOLVED SOLIDS,

IN

MILLIGRA

MS PER LITER

PERCENTAGE OF TOTAL

CATIONS, IN MILLIEQUIVALENTS

PER LITER

4,000

2,000

0

IRRIGATION WATER

 (Rio Grande below Caballo

 Dam, April and October 1994)

0 2,000 4,000

DISSOLVED SOLIDS,

IN MILLIGRAMS PER LITER

MAGNESIUM

SODIUM PLUS POTASSIUM

CHLORIDE

C

ALCIU

M

SULFATE

PERCENTAGE OF TOTAL

ANIONS, IN

MILLIEQUIVALENTS

PER LITER
33

All but 2 of 30 samples exceeded the SMCL of

500 mg/L for dissolved solids. Chloride in water from

two wells (6.7 percent) exceeded the SMCL of 250

mg/L for chloride, and water from 22 wells (73

percent) equaled or exceeded the SMCL of 250 mg/L

for sulfate (table 14). The MCL for fluoride of 4 mg/L

was not exceeded in any samples.

Nutrients and Dissolved Organic

Carbon

Nitrite plus nitrate concentrations, which were

the largest of the analyzed nutrient concentrations,

ranged from less than 0.05 to 33 mg/L as nitrogen

(table 13). Nitrite concentrations were less than 0.11

mg/L as nitrogen, indicating nitrate as the dominant

nitrogen species in the nitrite plus nitrate analyses. The

distribution of nitrite plus nitrate concentrations had no

areal pattern in the Rincon Valley (fig. 18). In some

areas, dissolved nitrite plus nitrate concentrations

varied considerably in water from wells small distances

apart. For example, the nitrite plus nitrate

concentration in water from well 3 was 2.00 mg/L as

nitrogen and in water from well 4, which is about 700

ft from well 3, was 13.0 mg/L (app. B). Water from five

wells (about 17 percent) exceeded the MCL of 10

mg/L for nitrite plus nitrate as nitrogen (table 14).

Ammonia and ammonia plus organic nitrogen

concentrations were generally small (less than 0.1

mg/L and 0.4 mg/L as nitrogen, respectively) (table

13). The largest ammonia and ammonia plus organic

nitrogen concentrations generally were in samples

from wells south and east of Hatch in the southern part

of the Rincon Valley (app. B). Phosphorous and

orthophosphate concentrations were generally less

than 0.05 mg/L as phosphorus (table 13) and varied

little among the wells (app. B). The DOC

concentrations ranged from 1.1 to 5.3 mg/L (table 13)

and showed no areal pattern in shallow ground water.

Trace Elements

The concentrations of many trace elements were

small (less than 10 ∝g/L) in shallow ground water in the

Rincon Valley. Barium, bromide, copper, iron,

manganese, molybdenum, uranium, and zinc were the

only trace elements that were in one or more samples at

concentrations larger than 10 ∝g/L (app. B). Cadmium,

cobalt, and selenium were detected above the MRL in

three or fewer samples. No samples had detectable

concentrations of antimony, beryllium, lead, or silver.

Barium, bromide, copper, and molybdenum

were detected in all the samples (table 13). Iron was

detected in 21 samples, manganese in 28 samples, and

uranium in 27 samples. Barium concentrations were

largest in samples from wells 18 and 24. The bromide

concentration in water from well 25 was 0.97 mg/L,

which was much larger than the concentration in any

other samples. Copper concentrations generally were

less than 6 ∝g/L; however, samples from wells 25, 26,

and 27 had concentrations of 18, 11, and 21 ∝g/L,

respectively. A large copper concentration (32 ∝g/L)

was also detected in a surface-water sample from the

upstream sampling site on the Rincon Drain, which is

in the same area as wells 25, 26, and 27. Nineteen

samples had iron concentrations less than 10 ∝g/L

(app. B). Manganese concentrations were typically

larger than 100 ∝g/L. Samples with manganese

concentrations larger than 1,000 ∝g/L also generally

had large iron concentrations. The largest molybdenum

concentration was from well 7 (app. B), which is

located near the upstream sampling site on the Garfield

Drain where relatively large molybdenum

concentrations were also measured (app. A). In

general, the larger uranium concentrations were from

wells in the northern part of the Rincon Valley (fig. 19).

The concentrations of uranium, iron, and

manganese exceeded USEPA MCL’s or SMCL’s in

some instances (table 14). The proposed MCL of 20

∝g/L for uranium (U.S. Environmental Protection

Agency, 1996) was exceeded in about 13 percent of the

samples (four samples). The SMCL of 300 ∝g/L for

iron was exceeded in about 17 percent of the samples

(5 samples), and the SMCL of 50 ∝g/L for manganese

was exceeded in about 83 percent of the samples (25

samples) (table 14). Concentrations of cadmium and

molybdenum were in the same range but less than the

standards. Concentrations of the other trace elements

that have standards (aluminum, antimony, arsenic,

barium, beryllium, chromium, copper, lead, nickel,

selenium, silver, and zinc) were much smaller than

drinking water standards or health advisories (table

14).
Figure 18. Dissolved nitrite plus nitrate concentrations in shallow ground water 

 in the Rincon Valley study area.

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

107°20 ́ 107°10 ́ 107°00 ́

Caballo Reservoir

ARREY

GARFIELD

SALEM

HATCH

RINCON

Rincon Valley

study area

boundary

Rio

Grande

NITRITE PLUS NITRATE CONCENTRATION

 5.6 TO 33 MILLIGRAMS PER LITER AS NITROGEN--

 Number indicates well number (appendix B)

NITRITE PLUS NITRATE CONCENTRATION

 0.06 TO 5.5 MILLIGRAMS PER LITER AS NITROGEN--

 Number indicates well number (appendix B)

NITRITE PLUS NITRATE CONCENTRATION

 LESS THAN 0.05 TO 0.05 MILLIGRAM PER LITER 

 AS NITROGEN--Number indicates well number 

 (appendix B)

6

3

1

9

10

11 17

14

16

15

12

13

19 18

20

21 22 29

28

27 26

25

24

23

30

8

7

2

4

5 6

5

4

EXPLANATION

32°

40 ́

32°

50 ́
Figure 19. Dissolved-uranium concentrations in shallow ground water

 in the Rincon Valley study area.

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

107°20 ́ 107°10 ́ 107°00 ́

Caballo Reservoir

ARREY

GARFIELD

SALEM

HATCH

RINCON

Rincon Valley

study area

boundary

Rio

Grande

DISSOLVED-URANIUM CONCENTRATION

 14 TO 62 MICROGRAMS PER LITER--

 Number indicates well number (appendix B)

DISSOLVED-URANIUM CONCENTRATION

 4 TO 13 MICROGRAMS PER LITER--

 Number indicates well number (appendix B)

DISSOLVED-URANIUM CONCENTRATION

 LESS THAN 1 TO 3 MICROGRAMS PER LITER--

 Number indicates well number (appendix B)

5

3

1

9

10

11 17

14

16

15

12

13

19 18

20

21 22

29

28

27 26

25

24

23

30

8

2

4

5 6

3

9

EXPLANATION

7

32°

40 ́

32°

50 ́
36

Radioactivity and Radon-222

Gross alpha activity and gross beta activity were

measured in filtered samples, and radon-222

concentration was measured in unfiltered samples

(table 13 and app. B). Gross alpha activity is a measure

of all alpha radiation (positively charged helium nuclei)

in a sample. Gross beta activity is a measure of all beta

radiation (electrons or positrons) in a sample. Activity

is a measure of radiation emitted by a sample; it is not

a concentration. Several different substances in a

sample can emit alpha or beta radiation. All alpha or

beta radiation in a sample is measured and is reported

in terms of one particular substance that emits alpha or

beta radiation. Gross alpha activity is reported in terms

of the amount of natural uranium, in micrograms per

liter, that would emit the same radiation. Gross beta

activity is reported in terms of the equilibrium

strontium-90/yttrium-90 (Sr-90/Y-90) that would give

the same count rates.

Gross alpha activity ranged from 0.8 to 67 ∝g/L

as uranium (table 13). The largest gross alpha activities

were in samples from the northern part of the Rincon

Valley, where the largest uranium concentrations also

were detected. Gross beta activity ranged from 4.7 to

29 pCi/L as Sr-90/Y-90 (table 13). Gross beta activity

showed no areal pattern in the Rincon Valley.

Radon-222 concentrations ranged from 210 to

440 pCi/L in 18 samples. Twelve of 18 samples had

radon-222 concentrations ranging from 240 to 260

pCi/L, indicating a relatively small range in radon-222

concentrations throughout the Rincon Valley. No clear

areal pattern was apparent in radon-222 concentrations

in the valley.

The MCL for gross alpha activity is 15 pCi/L

(table 14) (U.S. Environmental Protection Agency,

1996). For gross alpha activity reported as equivalent

uranium in micrograms per liter, the mass to activity

conversion factor used to determine gross alpha

activity as uranium, in picocuries per liter, was 1.3

∝g/L per picocuries per liter. Samples from about 23

percent of the wells (seven wells) exceeded the MCL.

The MCL for gross beta activity is 4 millirems per year.

This MCL is based on an annual dose and cannot be

compared to the activity measured in the shallow

ground-water samples.

Volatile Organic Compounds

Twenty samples were analyzed for 60 VOC’s

with an MDL of 0.2 ∝g/L (table 4). Methylchloride (in

8 of 19 samples) and xylene (in 3 of 20 samples) were

the only VOC’s detected (app. B). Concentrations of

methylchloride detected in field-blank samples

indicate that contamination occurred during sampling

or analysis and that methylchloride detected in groundwater samples does not represent environmental

conditions. Xylene, which is a common compound in

many petroleum products such as gasoline, was

detected at concentrations ranging from 0.3 to 2.8

∝g/L (app. B). The MCL for xylene is 10,000 ∝g/L,

which is significantly larger than the concentration in

any ground-water sample (table 14).

Pesticides

Thirty samples were analyzed for 88 pesticides

with MDL’s ranging from 0.001 to 0.050 ∝g/L (table

4). One or more pesticides were detected in 12 of 30

samples (app. B). Five of the 88 pesticides analyzed for

were detected in one or more samples. Metolachlor (in

nine samples) and prometon (in five samples) were the

most commonly detected pesticides. Diazinon,

napropamide (an herbicide), and p,p’-DDE were each

detected once.

When pesticides were detected, the

concentrations generally were small (less than 0.1

∝g/L in 12 of 17 detections or less than or equal to 0.01

∝g/L in 8 of 17 detections) (app. B). Metolachlor was

the pesticide with the largest measured concentration

(5.4 ∝g/L in the sample from well 22). Two or more

pesticides were detected in samples from wells 4, 10,

22, and 28. In general, pesticides were detected less

frequently in samples from wells in the northern part of

the Rincon Valley (fig. 20).

Concentrations of pesticides detected in shallow

ground water in the Rincon Valley were less than

health-based standards established by the USEPA (U.S.

Environmental Protection Agency, 1996). The USEPA

has not established MCL’s for any pesticides detected

in the Rincon Valley but has established health

advisories for three of the pesticides (table 14). The

health advisory for diazinon is 0.6 ∝g/L, which is about

10 times the concentration detected in well 28. The

health advisory for metolachlor is 100 ∝g/L, which is

about 20 times the largest concentration of metolachlor
Figure 20. Concentrations of pesticides detected in shallow ground water

 in the Rincon Valley study area.

0

0

1

1

2

2

3

3

4

4

5 MILES

5 KILOMETERS

107°20 ́ 107°10 ́ 107°00 ́

Caballo Reservoir

ARREY

GARFIELD

SALEM

HATCH

RINCON

Rincon Valley

study area

boundary

Rio

Grande

PESTICIDE DETECTED

NO PESTICIDE DETECTED

ESTIMATED

All concentrations in

 micrograms per liter

EXPLANATION

E

Diazinon 0.077

Metolachlor E0.005

Prometon E0.01

Prometon E0.005

Napropamide 0.014

Metolachlor E0.005

 

Metolachlor 0.13

Metolachlor 0.010

Metolachlor 0.38

Metolachlor 0.018

Metolachlor E0.005

p, p’-DDD E0.002

Metolachlor 0.26

Prometon E0.009

Metolachlor 5.4

Prometon E0.012

32°

40 ́

32°

50 ́

37

3

1

9

10

11 17

14

16

15

12

13

19 18

20

21 22 29

28

27

26

25

24

23

30

8

2

4

5 6

7

Prometon E0.32
38

detected in shallow ground water (well 22). The health

advisory for prometon is 100 ∝g/L, which is about 300

times the largest concentration of prometon detected in

shallow ground water.

Pesticides, Pesticide Metabolites,

Gross Polychlorinated Biphenols,

and Gross Polychlorinated

Napthalenes in Bed Material

Bed-material samples were collected at the three

downstream sites on the drains in January 1995. DDT,

which is an insecticide that has been banned from use

in the United States since 1973, and DDD and

p,p’-DDE, which are common degradation products of

DDT, were the only compounds detected of 23

compounds analyzed for (table 5 and app. C). These

three compounds were detected at all three sites. DDT

was detected at concentrations ranging from 0.3 to 0.5

∝g/kg, DDD was detected at concentrations ranging

from 0.2 to 1.4 ∝g/kg, and p,p’-DDE was detected at

concentrations ranging from 1.5 to 44 ∝g/kg (app. C).

The presence of DDT indicates that it was probably

used in the area and has not completely degraded.

FACTORS AFFECTING WATER

QUALITY IN THE RINCON VALLEY

The quality of surface water used for irrigation

affects ground-water quality and the quality of ground

water affects surface-water quality because of

interaction between the surface- and ground-water

systems. Surface water infiltrates and recharges the

ground-water system, and ground water discharges to

the drains and the Rio Grande. Most recharge to the

ground-water system occurs during the irrigation

season when surface water is released from Caballo

Reservoir and diverted from the Rio Grande into the

canals. Recharge to the shallow ground-water system

results from infiltration of water applied to fields and

leakage from canals. Increases or decreases in recharge

result in rapid increases or decreases in ground-water

discharge to the drains.

The amount of ground-water discharge to the

drains and the subsequent amount of discharge from

the drains to the Rio Grande vary throughout the year

and are largest during June, July, and August (fig. 4).

During December, January, and February, groundwater discharge to the drains is small. Discharge in the

Rio Grande and the source of water in the Rio Grande

also vary throughout the year (fig. 3). During the

irrigation season (about March to mid-October), most

discharge in the Rio Grande is from releases from

Caballo Reservoir, and discharge from the drains to the

Rio Grande is a small percentage of total discharge in

the Rio Grande. From about mid-October to midJanuary, no water is released from Caballo Reservoir

and discharge in the Rio Grande is from ground-water

discharge and discharge from the drains. From midJanuary through February, releases from Caballo

Reservoir begin and slowly increase to more than 1,000

ft3

/s, resulting in varying mixtures of water from

Caballo Reservoir, ground-water discharge, and

discharge from the drains.

The quality of water diverted from the Rio

Grande during the irrigation season (irrigation water) is

an important factor affecting the quality of surface

water and shallow ground water in the Rincon Valley.

Irrigation water is the source of most ground-water

recharge and the starting composition from which

ground water evolves. The quality of water in the drains

throughout the year and of water in the Rio Grande

when no water is being released from Caballo

Reservoir is also related to irrigation water because

ground-water discharge accounts for most water in the

drains and Rio Grande at these times.

Comparing the quality of irrigation water,

shallow ground water, water in the drains, and water

from the Rio Grande when no water is being released

from Caballo Reservoir helps determine how irrigation

water quality changes (evolves) as it infiltrates to the

ground-water system, as ground water moves through

the aquifer to the drains or the Rio Grande, and as water

moves downstream in the drains and Rio Grande. Areal

variations in shallow ground-water quality, differences

in water quality in the drains, and temporal variations

in water quality at sites on drains can be useful for

determining factors that result in these areal or

temporal differences in water quality.

The composition of irrigation water was

assumed to be the average composition of water

samples from the Rio Grande below Caballo Reservoir

in April and October 1994 (app. A). No samples were

collected between April, near the beginning of the

irrigation season, and October, near the end of the

irrigation season, that could be used to document

changes in the composition of irrigation water during

the irrigation season. Comparison of the composition
39

of water in April to that of water in October indicates

little difference in most dissolved constituents.

Variations in the composition of irrigation water are

probably small during the irrigation season because the

two large reservoirs upstream from the Rincon Valley

tend to damp out large variations.

Common Constituents

 Concentrations of common constituents in

surface water and ground water are affected by natural

and human-related factors. Natural factors include

mineral dissolution, precipitation or weathering, ion

exchange, and mixing of water with different

compositions. Human-related factors include

composition of infiltrating irrigation water,

evapotranspiration resulting from crop irrigation, or

leaching of agricultural chemicals.

Dissolved-solids concentrations, which

essentially are the sums of concentrations of common

constituents, generally were smallest (about 450 mg/L)

in irrigation water (Rio Grande below Caballo Dam in

April and October 1994) (fig. 9). During the irrigation

season, ground-water discharge to the Rio Grande and

discharge from the drains to the Rio Grande have little

effect on dissolved-solids concentrations in the river

because the amount of water being released from

Caballo Reservoir is much larger than the amount of

ground-water discharge and discharge from the drains

to the Rio Grande. Dissolved-solids concentrations in

samples from the Rio Grande increased downstream

between Caballo Dam and above the Rincon Drain

about 30 mg/L in April 1994 and about 90 mg/L in

October 1994 (fig. 9).

Concentrations of dissolved solids generally

were larger and increased downstream in water from

the Rio Grande when no water was being released from

Caballo Reservoir (January 1994 and 1995) than

during the irrigation season (April and October 1994)

(fig. 9) because discharge of shallow ground water and

discharge from the drains account for most flow in the

Rio Grande. Dissolved-solids concentrations in

samples from the Rio Grande increased downstream

from Caballo Dam to above the Rincon Drain about

400 mg/L in January 1994 and about 300 mg/L in

January 1995. Dissolved-solids concentrations in

samples from the downstream sites on the drains were

larger than those in the Rio Grande (fig. 9).

Dissolved-solids concentrations varied in water

from different drains, from the upstream and

downstream sampling sites on a given drain, and

temporally at sites on drains (fig. 9). Concentrations

generally were largest in samples from the downstream

sampling site on the Rincon Drain and smallest in

samples from the upstream sampling site on the Hatch

Drain. The dissolved-solids concentration increased

downstream during all samplings on the Rincon and

Hatch Drains (fig. 9), indicating generally larger

dissolved-solids concentrations in ground water near

the downstream parts of the drains than at the upstream

parts. At the upstream and downstream sites on the

Rincon Drain, dissolved-solids concentrations

generally were larger in January than during April or

October 1994, indicating smaller concentrations in

ground water discharging to this drain during the

irrigation season (fig. 9).

Dissolved-solids concentrations in shallow

ground water ranged from 481 to 3,630 mg/L and

generally were larger in the southeastern part of the

Rincon Valley (fig. 16). The large variation in

dissolved-solids concentrations indicates differences in

the influence of particular factors or the number of

factors affecting the concentrations of common

constituents throughout the valley. Dissolved-solids

concentrations in samples from wells 17 (481 mg/L)

and 20 (486 mg/L) were about the same as those in

irrigation water (450 mg/L), indicating few factors

affecting the composition of water near these wells.

Water from wells 25 and 27 had much larger dissolvedsolids concentrations (3,630 and 2,420 mg/L) than the

rest of the surface-water and ground-water samples

(app. A and B); these samples may be affected by

different factors than the rest of the samples. King and

others (1971) and Wilson and others (1981, p. 62)

indicated ground-water inflow to the Rincon Valley

near well 25. This inflow is probably affecting shallow

ground water near well 25. Water from well 27 also

contains relatively large concentrations of dissolved

solutes (app. B). What factors are affecting water

quality in water from this well is not clear.

Because the Durov plots (figs. 11 and 17)

indicate only slight variations in the percentages of

major cations and anions (common constituents) in

most samples, similar factors could be affecting

common constituent concentrations. In general,

dissolved-solids concentrations are larger in water

from the drains and shallow ground water (figs. 11 and

17) than in irrigation water, possibly indicating

concentration of solutes during infiltration of irrigation

water.
40

Evapotranspiration (evaporation and

transpiration) of irrigation water could be an important

factor affecting the composition of common

constituents in shallow ground water and surface water.

Irrigation water applied to fields evaporates or is

transpired by plants during infiltration.

Evapotranspiration results in increases in constituents

but no change in the proportions of individual cations

or anions. If evapotranspiration is the only factor

affecting the concentrations of individual constituents,

the increases in concentrations are a function of the

amount of evapotranspiration that has occurred. For

example, if the volume of irrigation water is reduced by

one-half as the result of evapotranspiration, the

concentration of all dissolved constituents will double,

but the proportion of individual ions relative to other

ions will remain constant.

To compare the composition of irrigation water,

shallow ground water, water from the drains, and water

from the Rio Grande when no water was being released

from Caballo Reservoir (January of 1994 and 1995)

(nonirrigation season) and the effect of

evapotranspiration on irrigation water, dissolved

sulfate, bicarbonate, calcium, sodium, and silica

concentrations were plotted in relation to dissolved

chloride concentration (figs. 21-25). Chloride was used

in all plots because it is relatively conservative in water

and does not enter into many reactions (Hem, 1985, p.

118-120); therefore chloride concentration can be used

to estimate the effect of evapotranspiration.

Magnesium and potassium are not discussed because

the concentrations were small. Samples from wells 25

and 27 are not included in figures 21-25 because of the

large concentrations of solutes in samples from these

wells relative to the other samples.

 Evaporation paths of irrigation water (average

composition of samples collected from the Rio Grande

below Caballo Dam in April and October 1994) and

relatively dilute ground water (average composition

water from wells 1, 4, 9, and 22) have been calculated

and also plotted in figures 21-24 to demonstrate how

evapotranspiration affects water composition. If no

constituents are assumed to be added to or removed

from the starting solution (irrigation water or dilute

ground water) during evapotranspiration, the

evaporation paths represent concentrations of

constituents as irrigation water and dilute ground water

evapotranspire. A 2X concentration value is also shown

on the evaporation paths; this point represents the

concentrations of constituents in irrigation water or

dilute ground water after evapotranspiration of onehalf the original volume.

The plots show a wide range in sulfate,

bicarbonate, calcium, sodium, and chloride

concentrations in surface water and shallow ground

water. Because many of the samples plot along slopes

similar to the evaporation paths and are bounded by the

evaporation paths (figs. 21-24), evapotranspiration

could be an important factor affecting these

concentrations. Many samples have chloride

concentrations less than the 2X chloride concentrations

(fig. 21), indicating that the amount of irrigation water

that evapotranspires probably is less than one-half the

amount diverted. The scatter of points around the

evaporation paths indicates factors other than

evapotranspiration also affecting water composition.

 Water from wells 1, 4, 9, and 22 (dilute ground

water) has about the same concentration of chloride

(mean 72.5 mg/L) as irrigation water (mean 66 mg/L),

indicating little or no evapotranspiration of irrigation

water during infiltration near these wells (figs. 21-24).

Water from these wells represents irrigation water that

infiltrates through the root zone quickly prior to

evapotranspiration. The concentrations of sulfate,

bicarbonate, calcium, and sodium in the average

composition of water from these wells are about 70,

100, 50, and 30 mg/L larger, respectively, than those in

irrigation water (figs. 21-24), indicating factors other

than evapotranspiration causing increases in these

constituents during infiltration. Dissolution of minerals

such as gypsum (CaSO4) and calcite (CaCO3),

calcium/sodium ion exchange, or weathering of a

variety of silicate minerals could account for the

increases in these constituents.

Because most samples have sulfate

concentrations that plot above the evaporation path of

irrigation water (fig. 21), more sulfate may be in the

samples than can be accounted for by

evapotranspiration of irrigation water. The larger

sulfate concentrations in dilute ground water and most

of the other samples relative to irrigation water indicate

that increases in sulfate occur throughout the Rincon

Valley. Dissolution of minerals containing sulfur, such

as gypsum, or sulfur applied to fields as a soil

amendment could account for the increased sulfate.

The saturation index of gypsum was less than zero in

ground-water samples, indicating that gypsum, if

present in the soil zone or aquifer, would tend to

dissolve (table 15).
d

d

200 60 80 100 120 140 160 180

DISSOLVED CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

1,000

0

100

200300400

500

600700800

900 RETI L REP S M

A

R

GI LLI M NI , NOI TA

R

T NECNO

C ETAFL US DEVL OSSI D 8 17 22 19 430 1101 14 316 28 19

21

2

12

7

24

6

5

13

29

15

23

18

26

u

u

u u

u

u

d

u

U

20

d

d

d

u

d

d

d

d

d

Figure 21. Relation between dissolved sulfate and chloride concentrations in surface water and shallow ground water

in the Rincon Valley study area. 40

EXPLANATION

RIO GRANDE DURING NON- IRRIGATION SEASON (January

1994 and 1995)

EVAPORATION PATH OF

IRRIGATION WATER

EVAPORATION PATH OF

DILUTE GROUND WATER

DERRY WARM SPRING

2X CONCENTRATION REPRESENTING

EVAPOTRANSPIRATION OF

ONE-HALF THE ORIGINAL VOLUME

GARFIELD DRAIN--Letter indicates

upstream (u) or downstream (d) site

HATCH DRAIN--Letter indicates

upstream (u) or downstream (d) site

RINCON DRAIN--Letter indicates

upstream (u) or downstream (d) site

SHALLOW GROUND WATER--Number

indicates well number (appendix B)

IRRIGATION WATER (Rio Grande

below Caballo Dam, April and

October 1994)

2 points

2 points

41
40 200 60 80 100 120 140 160 180

DIS

S

OLVED

C

HLO

RIDE C

O

N

CEN

T

R

ATIO

N, IN

MILLIG

R

A

M

S PER LITER

100600100150200250300350400450500550

RETI L REP S MARGI LLI M NI , NOI TART NECNOC ETANOBRACI B DEVL OSSI D

20

1

2

7

2

4

28

16

6

6

19

13

29

12

2

7

21

5

24

23

26

15

18

14

8

3

11

u

u

u

u

u

u

d

d

d

d

d

d

d

d

u

u

u

u u

u

9

30

1

10

Fig

ure

2

2. R

elation b

etw

e

en dissolv

e

d

bicarb

onate

and chlorid

e concentrations in surface

w

ater and shallo

w

ground

w

ater

in the

Rincon V

alle

y stud

y

are

a.

EXPLA

N

ATIO

N

RIO

GRANDE DURING NONIRRIG

ATION SEASON (January 1994 and 1995)

EV

APORATION PATH OF

IRRIG

ATION W

ATER

EV

APORATION PATH OF DILUTE GROUND W

ATER

2X

C

ONCENTRATION

REPRESENTING

EV

APOTRANSPIRATION OF ONE-HALF THE ORIGINAL V

OLUME

G

ARFIELD DRAIN--Letter

indicates upstream (u) or downstream (d) site HATCH DRAIN--Letter indicates upstream (u) or downstream

(d) site RINC

ON DRAIN--Letter

indicates upstream (u) or downstream (d) site

SHALLO

W

GROUND W

ATER-- Number indicates well number

(appendix B)

IRRIG

ATION W

ATER

(Rio Grande below

Caballo Dam, April and October 1994)

d d

d

13

3 points ( ) , ,

d

3 points ( ) , ,

42
200 60 80 100 120 140 160 180 DISSOLVED CHLORIDE C

ONCENTRATION, IN MILLIGRA

MS PER LITER

40

40

240

60

80

100120140160180

200220

RETI L REP S MARGI LLI M NI , NOI TART NECNOC MUI CL AC DEVL OSSI D

17 20

22

1

9 4

10

2

8

8

11

30

14 16

3

21

24

6

6

2

7

,12

13,29

19

15

5

23

18

26

Fig

ure

2

3. R

elation b

etw

e

en dissolv

e

d calcium

and chlorid

e concentrations in surface

w

ater and shallo

w

ground

w

ater

in the

Rincon V

alle

y stud

y

are

a.

u u

u

u

u

u

u u

u u

u

d

d

d

d

d

d

d d d

d

d

d

d

d

EXPLA

N

ATIO

N

RIO

GRANDE DURING NONIRRIG

ATION SEASON (January 1994 and 1995)

EV

APORATION PATH OF

IRRIG

ATION W

ATER

EV

APORATION PATH OF DILUTE GROUND W

ATER

DERRY

W

ARM SPRING

2X

C

ONCENTRATION REPRESENTING

EV

APOTRANSPIRATION OF ONE-HALF THE ORIGINAL V

OLUME

G

ARFIELD DRAIN--Letter indicates upstream (u) or downstream (d) site HATCH DRAIN--Letter indicates upstream (u) or downstream (d) site RINC

ON DRAIN--Letter indicates upstream (u) or downstream (d) site

SHALLO

W

GROUND W

ATER--Number

indicates well number (appendix B)

IRRIG

ATION W

ATER (Rio Grande

below

Caballo Dam, April and October 1994)

3 points

3 points

43
u

200 40 60 80 100 120 140 160 180

DISSOLVED CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

350

0

50

100150200250300

R

E

TI L

R

E

P

S

M

A

R

GI L

LI M

NI , N

OI TA

R

T

N

E

C

N

O

C

M

UI D

O

S

D

E

V

L

O

S

SI D

17 20

22

1 9

4

30

28

16

10 1

3

4

11

8

19

24

6

12

21

2

7

23

u

u u

u

u u

13

u

d

d

d

d

d

d

d

d

d

Figure 24. Relation between dissolved sodium and chloride concentrations in surface water and

shallow ground water in the Rincon Valley study area.

EXPLANATION

RIO GRANDE DURING NON- IRRIGATION SEASON (January

1994 and 1995)

EVAPORATION PATH OF

IRRIGATION WATER

EVAPORATION PATH OF

DILUTE GROUND WATER

DERRY WARM SPRING

2X CONCENTRATION REPRESENTING

EVAPOTRANSPIRATION OF

ONE-HALF THE ORIGINAL VOLUME

GARFIELD DRAIN--Letter indicates

upstream (u) or downstream (d) site

HATCH DRAIN--Letter indicates

upstream (u) or downstream (d) site

RINCON DRAIN--Letter indicates

upstream (u) or downstream (d) site

SHALLOW GROUND WATER--Number

indicates well number (appendix B)

IRRIGATION WATER (Rio Grande

below Caballo Dam, April and

October 1994)

29

5

15

26

18

u

u

d

u

d d

3 points

d

44
200 40 60 80 100 120 140 160 180

DISSOLVED CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

RETI LREPSMARGI LLI MNI , NOI TARTNECNOCACI LI SDEVLOSSI D

35

50

10

15

20

2530

Figure 25. Relation between dissolved silica and chloride concentrations in surface water and shallow ground water

in the Rincon Valley study area.

EXPLANATION

RIO GRANDE DURING NON- IRRIGATION SEASON (January

1994 and 1995)

GARFIELD DRAIN

HATCH DRAIN

RINCON DRAINSHALLOW GROUND WATER

IRRIGATION WATER (Rio Grande

below Caballo Dam, April and

October 1994)

2 points

2 points

3 points

45

( )
46

The bicarbonate and chloride and calcium and

chloride plots (figs. 22 and 23) show that many of the

samples plot between the evaporation paths for

irrigation water and dilute ground water. Dilute ground

water had bicarbonate and calcium concentrations

greater than irrigation water, indicating increases in

bicarbonate and calcium concentrations during

infiltration. Bicarbonate concentrations in water can be

related to the partial pressure of carbon dioxide in the

soil zone or aquifer and dissolution/precipitation of

calcite. Dissolution/precipitation of calcite would also

affect calcium concentrations. The calculated partial

pressure of carbon dioxide in ground-water samples,

which reflects the partial pressure of carbon dioxide in

the aquifer, ranged from about 10-1.65 to 10 -2.42 atm,

whereas the calculated partial pressure of carbon

dioxide in irrigation water was about 10-3.2 atm (table

15), indicating larger partial pressures of carbon

dioxide in the aquifer relative to surface water in

contact with the atmosphere. Because the saturation

index of calcite in ground water and surface water

generally was equal to or greater than zero (table 15),

the water was probably in equilibrium with calcite. The

increase in bicarbonate and calcium concentrations in

the ground-water samples relative to irrigation water is

probably due to the larger partial pressure of carbon

dioxide in the soil zone/aquifer. Irrigation water

infiltrating through the soil zone would equilibrate with

the carbon dioxide in the soil zone and calcite, if

present, would tend to dissolve. The water would

dissolve calcite until the water was at calcite saturation

(saturation index equal to zero). Larger partial pressure

of carbon dioxide in the aquifer results in dissolution of

more calcite, which in turn results in larger bicarbonate

and calcium concentrations, as is seen in the sample

from well 5 (table 15 and figs. 22 and 23).

The sodium and chloride concentration plot (fig.

24) shows that many of the samples plot along and

between the evaporation paths of irrigation water and

dilute ground water. The sodium concentration in

dilute ground water is about 30 mg/L larger than in

irrigation water, indicating increases in sodium during

infiltration. The source of the sodium is unknown but

could be due to calcium/sodium ion exchange or

dissolution of sodium sulfate in the soil.

 Surface water and shallow ground water show

no linear trend in silica and chloride concentrations

(fig. 25), indicating that silica concentrations are not

affected by evapotranspiration (figs. 21-24). Dissolved

silica concentrations in most surface water and ground

water generally are larger than those in irrigation water.

Weathering or dissolution of silicate minerals is a

factor that could cause increases in dissolved silica,

bicarbonate, sodium, and calcium concentrations.

Because most shallow ground-water samples are

undersaturated with respect to amorphous silica (table

15), dissolution of amorphous silica during infiltration

may represent the source of silica in surface and ground

water.

The mixing of irrigation water and ground-water

inflow from areas adjacent to the Rincon Valley is

another factor that could affect water quality. The

composition of water at the upstream sampling site on

the Garfield Drain is probably affected by Derry Warm

Spring, which is located near the beginning of the

Garfield Drain and discharges into the drain. Water

from Derry Warm Spring contains 160 mg/L chloride,

309 mg/L sulfate, 52 mg/L calcium, and 303 mg/L

sodium plus potassium as sodium (Conover, 1954, p.

152-153) and probably represents the general

composition of ground-water inflow to the aquifer in

this part of the Rincon Valley. Water from well 7, which

is located along the Garfield Drain near Derry Warm

Spring, is also probably affected by ground-water

inflow in the area. Water from the upstream site on the

Garfield Drain and from well 7 has smaller calcium

concentrations (fig. 23) and larger sodium

concentrations (fig. 24) than other samples in the

Rincon Valley with similar chloride concentrations.

The composition of water from wells 25 and 26,

which are located in the southern area of the Rincon

Valley near the Rincon Drain, and of water from the

downstream sampling site on the Rincon Drain

generally had larger chloride and sulfate concentrations

than most water in the valley (fig. 21 and app. B).

Ground-water inflow from adjacent areas and irrigation

water are probably mixing in this area. The relatively

large dissolved-solids concentrations in water from the

downstream site on the Rincon Drain during January

(fig. 9) indicate that ground-water inflow from adjacent

areas affects the composition of water in the drain

during the nonirrigation season.

Fluoride concentrations in surface water and

shallow ground water generally range from 0.5 to 1.5

mg/L (app. A and B). Fluoride concentrations in

irrigation water (about 0.7 mg/L) are about the same as

those in many of the surface-water (median 0.8 mg/L)

and shallow ground-water (median 0.9 mg/L) samples,

indicating little concentration of fluoride by

evapotranspiration of irrigation water. Fluoride

concentrations in water from the upstream site on the

Garfield Drain (3.0 to 4.9 mg/L) and in water from well
47

7 (2.6 mg/L) are much larger than those in most other

samples collected in the Rincon Valley. Derry Warm

Spring, which contains large concentrations of fluoride

(5.8 mg/L) (Conover, 1954, p. 153), probably affects

the composition of water from well 7 and Garfield

Drain near the upstream sampling site.

Nutrients

Nutrients (nitrogen and phosphorous

compounds) in water can be from natural and humanrelated sources. Natural sources of nutrients include

plant material, minerals, animal wastes, production of

organic nitrogen compounds from nitrogen gas by

plants (nitrogen fixation), and precipitation. Humanrelated nutrient sources include emissions from

burning of fossil fuels, sewage effluent, and fertilizers.

In agricultural areas, leaching of fertilizers can result in

significant increases of nutrients in ground water and

surface water.

Nutrients can be removed from water by many

processes. Nitrogen and phosphorus are essential

nutrients to many plants and organisms and can be

removed from water to form biomass. In surface water,

uptake by plants and adsorption to clays and iron

oxides reduce dissolved nitrogen and phosphorous

concentrations. In ground water, biologically mediated

reactions can affect which forms of nitrogen are

present. Denitrification, which is the reduction of

nitrate to nitrogen gas (a stable compound that diffuses

out of the water), can be an important process that

removes nitrogen from ground water. Dissolved

phosphorous concentrations are generally small in

ground water because phosphorous minerals are

relatively insoluble (Freeze and Cherry, 1979, p. 422)

and phosphorus is adsorbed by clays in the soil zone/

aquifer.

The occurrence and movement of different forms

(species) of nitrogen, such as nitrate or ammonia, are

related to the oxidation/reduction state of the aqueous

environment. Under reducing conditions (anaerobic or

small dissolved oxygen) ammonia or ammonium (in

this report, ammonia includes ammonia and

ammonium) typically is most common, and under

oxidizing conditions (aerobic or presence of dissolved

oxygen) nitrate typically is most common. Nitrate is

usually found at larger concentrations in water than

ammonia because nitrate is very soluble and is not

adsorbed to clays or iron oxides, whereas ammonia

generally is removed rapidly by plants, is strongly

adsorbed to clay and iron oxides, and diffuses out of the

water.

 Nitrite plus nitrate concentrations ranged from

less than 0.05 to 33 mg/L as nitrogen, and ammonia

concentrations ranged from less than 0.01 to 0.33

mg/L as nitrogen in surface- and ground-water samples

(tables 12 and 13). Ammonia concentrations are

generally larger in samples with small nitrite plus

nitrate concentrations (fig. 26) as would be expected if

oxidation/reduction conditions control which form of

nitrogen is dominant. Ground-water samples with

ammonia concentrations larger than 0.05 mg/L as

nitrogen generally had dissolved oxygen

concentrations equal to or less than 0.2 mg/L (app. B),

indicating oxidation/reduction conditions controlling

nitrogen speciation in ground water. Because the

surface-water samples with ammonia concentrations

larger than 0.05 mg/L as nitrogen had dissolved oxygen

concentrations larger than 1 mg/L (app. A), factors

other than oxidation/reduction conditions may affect

ammonia concentrations in surface water. Irrigation

water (Rio Grande below Caballo Dam in April and

October) has small concentrations of nitrite plus nitrate

(less than 0.05 and 0.07 mg/L, respectively, as

nitrogen) and ammonia (0.01 and 0.08 mg/L as

nitrogen), indicating small nitrogen concentrations in

surface water entering the Rincon Valley and diverted

for irrigation. The small nitrogen concentrations in

irrigation water relative to nitrogen concentrations in

most other samples from the Rincon Valley indicate

natural and land-use factors affecting nitrogen

concentrations in the area.

The relatively small ammonia concentrations in

surface water and ground water indicate that natural

and land-use factors generally do not result in large

ammonia concentrations in the Rincon Valley. Some of

the largest ammonia concentrations were detected in

samples from the downstream site on the Hatch Drain

(app. A). These relatively large ammonia

concentrations (0.27 and 0.33 mg/L as nitrogen) could

be due to discharge from the Hatch wastewater

treatment plant.

Nitrite plus nitrate concentrations were generally

larger in ground water than in surface water (fig. 26),

although the median concentration of nitrite plus

nitrate in ground water (0.48 mg/L as nitrogen) was

similar to the median concentration in surface water

(0.44 mg/L as nitrogen). Twelve ground-water samples

and two surface-water samples (downstream site on the
Fig

ure

2

6. R

elation b

etw

e

en dissolv

e

d nitrite

plus nitrate

and

a

m

m

onia concentrations in the

Rio

Grand

e, drains, and shallo

w

ground

w

ater

in the

Rincon V

alle

y stud

y

are

a.

Drains and well locations in figure 2

IN MILLIG

R

A

MS PER LITER

AS NIT

R

O

GEN

DIS

S

OLVED

A

M

M

O

NIA

C

O

N

CEN

T

R

ATIO

N,

IN MILLIGRAMS PER LITER AS NITROGEN

DISSOLVED A

M

M

ONIA

C

ONCENTRATION,

, NOI TART NECNOC ETARTI N SULP ETI RTI N DEVL OSSI D

0.35 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0

0

34

8642

101214161820222426283032

NE GORTI N SA RETI L REP S MARGI LLI M NI

, NOI TART NECNOC ETARTI N SULP ETI RTI N DEVL OSSI D

NE GORTI N SA RETI L REP S MARGI LLI M NI

0 0.2 0.1

0

1.00.20.40.60.8

RIO

G

R

A

N

DE

D

R

AIN

S

S

H

ALLO

W

G

R

O

U

N

D

W

ATER

EXPLA

N

ATIO

N

48
49

Hatch Drain) had nitrite plus nitrate concentrations

equal to or greater than 2 mg/L as nitrogen (app. B; fig.

26). Nitrite plus nitrate concentrations were generally

larger in samples from the drains than in samples from

the Rio Grande (fig. 26). The larger nitrite plus nitrate

concentrations in the drains than in the Rio Grande

probably are due to larger nitrite plus nitrate

concentrations in ground water, which discharges to

the drains. Samples from the downstream site on the

Hatch Drain had much larger nitrite plus nitrate

concentrations in January than during April or October,

possibly because discharge from the Hatch wastewater

treatment plant is a larger part of total flow in the drain

in January than during April and October when flow in

the drains is larger.

Fertilizers are probably leaching downward to

the aquifer in some parts of the Rincon Valley on the

basis of large nitrite plus nitrate concentrations in

samples from some of the wells relative to irrigation

water. Elevated nitrite plus nitrate concentrations do

not seem to be located in one particular area of the

Rincon Valley (fig. 18), so leaching of fertilizers

probably is not limited to specific areas in the valley.

The large range and relatively wide variation in nitrite

plus nitrate concentrations in short distances (such as

well 3 with a concentration of 2.00 mg/L as nitrogen

and well 4 with a concentration of 13.0 mg/L) indicate

variations in leaching or chemical processes affecting

nitrogen concentrations in infiltrating irrigation water

and ground water.

Phosphorous concentrations in surface water and

ground water generally were small: 75 percent of the

surface-water samples had phosphorous concentrations

equal to or less than 0.02 mg/L (table 12), and 75

percent of the shallow ground-water samples had

phosphorous concentrations equal to or less than 0.05

mg/L (table 13). The relatively small phosphorous

concentrations in most surface-water and shallow

ground-water samples indicate that they are not

significantly affected by the application of phosphoruscontaining fertilizers in the Rincon Valley.

Samples from the downstream sampling site on

the Hatch Drain were the only surface-water samples

with phosphorous concentrations larger than 0.03

mg/L (app. A). The largest concentrations were in the

Hatch Drain in January when flows were smallest (app.

A). These large phosphorous concentrations probably

are due to inflow of treated effluent from the Hatch

wastewater treatment plant. Snoeyink and Jenkins

(1980, p. 301) indicated that phosphorous

concentrations range from 3 to 15 mg/L in domestic

wastewater. Healy (1995) measured phosphorous

concentrations as large as 3.9 mg/L in wastewater

treatment plant effluent in southern New Mexico.

Trace Elements

The sources and concentrations of trace elements

in water can be affected by natural and human-related

factors. Natural factors include dissolution of naturally

occurring minerals, adsorption, and complexing by

organic ligands. Some trace elements are relatively rare

and therefore generally are not naturally found in

water. The solubility of minerals containing trace

elements is probably one of the most important factors

affecting trace-element concentrations in water. Many

trace elements can exist in various oxidation states;

therefore, dissolved concentrations are related to

oxidation/reduction conditions of the subsurface.

Human activities that can affect the availability of

minerals that contain trace elements or trace-element

concentrations in water include mining, application of

pesticides (arsenic and copper were used as pesticides),

burning of fossil fuels, and improper disposal of

household and industrial wastes. Evapotranspiration

resulting from crop irrigation can also affect traceelement concentrations in water.

The concentrations of many trace elements were

small, not measurable, or had little spatial or temporal

variation in concentration; therefore, they are not

discussed. The trace elements barium, bromide, iron,

manganese, molybdenum, and uranium are discussed

in detail because they had measurable concentrations in

most samples and spatial variations in concentrations

among samples.

The concentration of barium in surface-water

and ground-water samples ranged from 29 to 120 ∝g/L

(tables 12 and 13). Because barium concentrations in

irrigation water (Rio Grande below Caballo Dam in

April and October 1994) were generally larger than

those in shallow ground water, concentrations probably

decrease (adsorption or mineral precipitation) during

infiltration of irrigation water. The concentration of

barium in water can be controlled by the solubility of

barite (BaSO4) and by ion exchange or adsorption by

clays (Robertson, 1991, p. 22). Irrigation water and

many ground-water samples have barite saturation

indexes greater than 0.5 (table 15), indicating that

barite tends to precipitate from these samples.
50

Bromide is relatively conservative in water and

probably is affected by evapotranspiration. Large

concentrations of bromide also can occur in geothermal

water. Anthropogenic sources include bromide

compounds used in gasoline or as fumigants (Hem,

1985, p. 146). Bromide concentrations in irrigation

water were about 0.06 mg/L (app. A) and in shallow

ground water ranged from 0.13 to 0.97 mg/L with a

median of 0.27 mg/L (table 13). Concentrations of

bromide generally were larger in ground water than in

drain water. On the basis of the amount of

evapotranspiration of irrigation water estimated using

concentrations of common constituents, bromide

concentrations generally are larger in ground water

than can be accounted for by concentration by

evapotranspiration. This means that the Rincon Valley

must have another source of bromide, possibly groundwater inflow from adjacent areas. Why concentrations

of bromide are larger in shallow ground water than in

drain water is not clear.

Iron and manganese minerals are very common

in the environment. Iron and manganese can exist in

several oxidation states and generally are more soluble

in the reduced form than in the oxidized form. Iron and

manganese concentrations detected in ground-water

samples (app. B) generally were much larger than those

in irrigation water (app. A), so irrigation water is

probably not the source of iron and manganese in the

valley. Manganese was detected at larger

concentrations in ground water (median about 370

∝g/L) and in surface water (median 159 ∝g/L) than iron

(ground-water median 6.5 ∝g/L; surface-water median

5 ∝g/L), indicating oxidation/reduction conditions in

which manganese has been reduced but iron has not.

The larger manganese concentrations in ground water

than in surface water are probably related to more

reducing conditions in the aquifer than in surface water

(app. A and B).

Molybdenum is present in many ore minerals

and is relatively soluble or mobile in water (Hem, 1985,

p. 140). In surface water and shallow ground water,

molybdenum concentrations generally ranged from 6

to 13 ∝g/L (app. A and B). Molybdenum

concentrations in irrigation water (6 and 7 ∝g/L, app.

A) generally were smaller than those in shallow ground

water (median 10.5 ∝g/L) and in the drains (generally

10 ∝g/L), possibly indicating molybdenum in irrigation

water concentrated by evapotranspiration. Samples

from the upstream sampling site on the Garfield Drain

and in water from well 7, located near the Garfield

Drain, had relatively large molybdenum concentrations

compared with water in other areas of the Rincon

Valley (app. A and B), possibly a result of mixing of

ground-water inflow from adjacent areas and shallow

ground water.

Uranium concentrations ranged from less than 1

to 62 ∝g/L in surface- and ground-water samples,

indicating that several factors could be affecting

uranium concentrations. Uranium can exist in different

oxidation states and generally is more soluble in the

oxidized form than in the reduced form (Hem, 1985, p.

148). Because the concentration of uranium in

irrigation water (about 3 ∝g/L, app. A) generally was

smaller than that in shallow ground water (median 8.5

∝g/L), uranium concentrations may increase during

infiltration/evapotranspiration of irrigation water.

Samples with uranium concentrations larger than about

10 ∝g/L are probably due to factors other than

concentration of irrigation water. The relatively large

uranium concentrations in samples from the upstream

sampling site on the Garfield Drain (12 to 20 ∝g/L) and

from well 7 (62 ∝g/L) indicate that ground-water

inflow from areas adjacent to the Rincon Valley may be

affecting uranium concentrations in water in this area.

Because most of the larger uranium concentrations in

ground water are in samples from wells in the northern

part of the Rincon Valley, ground-water inflow from

adjacent areas possibly affects uranium concentrations

in the northern part of the Rincon Valley.

Radioactivity and Radon-222

Radionuclides in water are from natural sources,

such as weathering of rocks and interaction of cosmic

rays with atmospheric particles, or from human

activities, such as testing of nuclear weapons and

industrial/medical uses of radionuclides. Human

activities also can indirectly affect radionuclide

concentrations in water. For example, human activities

that result in changes in the concentration of solutes in

water as a result of evapotranspiration could affect

radionuclide concentrations. The main alpha-emitting

substances in water are decay products of uranium and

thorium, which generally occur naturally. Gross betaemitting substances include potassium-40 and

radium-228, which occur naturally, and cesium-137

and strontium-90, which are related to human

activities. Radon-222 is in the uranium-238 decay

series and is the decay product of radium-226.
51

Radium-226 can be present in aquifer material or be

dissolved in ground water.

A plot of gross alpha activity and dissolved

uranium concentration shows a linear relation (fig. 27),

indicating that a large amount of the measured gross

alpha activity in shallow ground water is from

dissolved uranium. Three isotopes of uranium produce

alpha activity, and variations in the ratio of these

isotopes dissolved in water will result in different gross

alpha activities because the isotopes have different

half-lives (Thomas and others, 1993, p. 454). Most

shallow ground-water samples from the Rincon Valley

have dissolved gross alpha activity larger than alpha

activity estimated from the uranium concentration

assuming a uranium-234 to uranium-238 activity ratio

of 1 (data plot above the line; fig. 27), indicating that

the uranium-234 to uranium-238 activity ratio could be

greater than 1. Other alpha emitters such as radium-226

and thorium-230 dissolved in shallow ground water or

counting uncertainty during analysis could also

account for the larger gross alpha activity than would

be estimated from a uranium-234 to uranium-238

activity ratio of 1.

A plot of gross beta activity and dissolved

potassium concentration (fig. 28A) shows gross beta

activity increasing with increasing dissolved potassium

concentration, suggesting that some gross beta activity

is due to potassium-40. The beta activity (picocuries

per liter as Sr-90/Y-90) due to potassium-40 can be

estimated by multiplying the potassium concentration

(milligrams per liter) by 0.818, which assumes a

natural ratio of potassium-40 to total potassium of

0.0117 percent and a half-life of potassium-40 of 1.28

x 109 years (Thomas and others, 1993, p. 463). Welch

and others (1995) reported that radioactive decay of

dissolved uranium-238 in the sample between time of

collection and time of analysis results in the daughter

products thorium-234 and protactinium-234, which

decay and produce beta activity. These uranium-238

daughter products, which are relatively insoluble in

ground water but would be soluble in an acidified

sample, can result in significant beta activity in a
52

sample that is distinct from the beta activity of the

water when the sample was collected or distinct from

water in the aquifer. The effect of uranium-238

daughter products can be estimated by subtracting the

beta activity due to potassium-40 from the gross beta

activity and plotting the adjusted value against the

uranium concentration in the sample (fig. 28B). This

plot shows that in many samples most beta activity can

be accounted for by potassium-40 (adjusted values

close to zero). For samples in which the adjusted value

is greater than zero, the adjusted beta activity generally

increases with increasing uranium concentration,

indicating that uranium-238 daughter products account

for part of the gross beta activity in the samples (fig.

28B). Gross beta activity not accounted for by

potassium-40 and dissolved uranium could be due to

gross beta activity from radium-228 or from counting

uncertainty during analysis of the samples.

Radon-222, which is the result of decay of

radium-226, probably does not travel far from the

source because the half-life of radon-222 is about 4

days. Thomas and others (1993, p. 451) reported that

radium-226 is relatively immobile in water and that

most radium-226 probably is part of the aquifer

material. Because of the relatively small concentrations

of radon-222 in most ground water in the Rincon

Valley, uranium and therefore radium-226 probably are

not found in large concentrations in shallow aquifer

material in the valley.

Volatile Organic Compounds

VOC’s in water generally result from human

activities because most VOC’s do not occur naturally.

VOC’s come from a variety of sources including

gasoline, asphalt, paints, adhesives, solvents, wood

preservatives, dry-cleaning agents, pesticides,

cosmetics, and refrigerants. The presence of VOC’s in

ground water generally is due to leaching of VOC’s

applied to or spilled on the land surface, infiltration of

industrial or municipal wastewater, infiltration of

domestic septic-tank effluent, and infiltration of

precipitation containing VOC’s.

Xylene was detected in wells 16, 21, and 26.

These wells are adjacent to asphalt-covered roads.

Infiltration of runoff from the roads could be the source

of the xylene. The xylene concentration in water from

well 21 was 0.70 ∝g/L and from well 26 was 0.30 ∝g/L

(app. B). Well 26 was sampled on the same day and

immediately after well 21 was sampled, so the xylene

in water from well 26 could be due to carryover of

xylene on the equipment between the two wells.

Because of the small number of VOC detections,

human activities probably have not resulted in

widespread VOC contamination of the shallow aquifer.

Pesticides

Pesticides are used to control a wide variety of

pests (Meister, 1995), including insects (insecticides)

and weeds (herbicides). Approximately 1.1 billion lbs

of pesticides are used annually in the United States

(Barbash and Resek, 1996, p. 3). Although a large

number of pesticides are used that were not analyzed

for in the samples collected during this study, many of

the most widely used pesticides were analyzed for.

Many factors affect pesticides that are applied to

soil or crops. Many pesticides break down or are

transformed into common chemical constituents as the

result of biochemical, photochemical, or other

chemical processes (Barbash and Resek, 1996, p. 203).

Sometimes pesticides break down in steps and some of

the breakdown or degradation products can be toxic to

plants and organisms. Dacthal mono-acid, DDD, and

p,p’-DDE are degradation products that were detected

in samples from the Rincon Valley. Although these

compounds are generally not used as pesticides, they

are referred to as pesticides in the following discussion.

Pesticides can evaporate or volatilize from the soil or

crops to the atmosphere. Pesticides applied to soil or

crops can be leached by infiltrating irrigation water or

precipitation and transported to the ground-water

system. Runoff of irrigation water or precipitation from

fields where pesticides have been applied and ground

water discharging to drains can transport pesticides to

surface water. Many pesticides are adsorbed by organic

carbon or clay minerals, thereby reducing dissolved

concentrations and reducing the rate at which

pesticides move through the soil zone, ground-water

system, or surface-water body.

A larger number of pesticides were detected and

detected more frequently in surface water than in

ground water. Thirteen pesticides (nine herbicides and

four insecticides) were detected in one or more surfacewater samples, whereas only five pesticides (two

herbicides and three insecticides) were detected in
0 10 20 30 40 50 60 70

DISSOLVED URANIUM CONCENTRATION, IN MICROGRAMS PER LITER

18

0

2

4

6

8

10

12

14

16

G

R

O

S

S BETA

A

C

TIVIT

Y

A

DJU

S

TED FO

R

A

C

TIVIT

Y

D

UE

T

O PO

TA

S

SIU

M-40, IN PIC

O

C

U

RIES PER LITER

2 4 6 8 10 12 14 16 18 20 22

DISSOLVED POTASSIUM CONCENTRATION, IN MILLIGRAMS PER LITER

30

0

5

10

15

20

25

G

R

O

S

S BETA

A

C

TIVIT

Y, IN PIC

O

C

U

RIES PER LITER

A

S

S

T

R

O

N

TIU

M-90/Y

T

T

RIU

M-90

A

S

S

T

R

O

N

TIU

M-90/Y

T

T

RIU

M-90

0.818:1

Figure 28. Relation between (A) gross beta activity and dissolved potassium

 concentration and (B) adjusted gross beta activity and dissolved 

 uranium concentration in shallow ground water in the Rincon Valley

 study area.

A

B

53
54

ground-water samples (app. A and B). One or more

pesticides were detected in 34 of 37 surface-water

samples (92 percent) and in 12 of 30 ground-water

samples (40 percent). DCPA and metolachlor were the

most commonly detected pesticides in surface water,

and metolachlor was the most commonly detected

pesticide in ground water. DCPA was not detected in

any ground-water samples. The detection of a larger

number of different pesticides in surface water (13)

than in ground water (5) indicates that pesticides are

entering surface water as runoff from fields or that the

number of ground-water samples collected and time of

year that the samples were collected did not adequately

represent the composition of ground water in the

Rincon Valley that discharges to the drains. For

example, some of the largest DCPA concentrations

were detected in samples from the drains during the

irrigation season (April and October 1994, fig. 14), but

DCPA was not detected in any ground-water samples in

April/May 1994, indicating that ground-water inflow to

the drains is probably not the source of DCPA in the

drains. Flow of irrigation water across the fields and

into the drains could transport DCPA into the drains.

During the non-irrigation season (January 1994 and

1995), DCPA was also detected in samples from the

drains; however, no water would be flowing across the

fields during this time of the year. Whether DCPA in

the samples from the drains during the non-irrigation

season is due to ground-water discharge to the drains or

is leached from sediment in the drains is not clear.

Additional ground-water sampling throughout the year

would be required to determine the temporal variations

in pesticide concentrations in shallow ground water

and the source of DCPA in the drains.

Some pesticides detected in surface- and groundwater samples from the Rincon Valley could be

transported into the valley in irrigation water. Prometon

and simazine were detected in samples of irrigation

water (app. A). Prometon detected in water from well

17, which is near an irrigation ditch, is probably the

result of infiltration of irrigation water containing

prometon. In three of four other samples containing

prometon, the concentration was similar to that in

surface water (estimated 0.011 ∝g/L), indicating that

prometon in ground water could be from infiltrating

irrigation water (app. A and B).

Five pesticides (DCPA, EPTC, metolachlor,

prometon, and simazine) were detected during a

particular sampling period in water from two or more

sites on the Rio Grande, indicating transport of these

pesticides down the Rio Grande (app. A). The

concentrations of EPTC and metolachlor (January

1994) decreased as water moved downstream more

than can be accounted for by dilution from increased

discharge, possibly indicating adsorption or

transformations. The concentrations of DCPA,

prometon, and simazine detected in samples from the

Rio Grande were relatively constant as the water

moved downstream (app. A), indicating little dilution,

adsorption, or transformation as these pesticides

moved downstream.

Insecticides detected in surface water

(carbofuran, chlorpyrifos, diazinon, and p,p’-DDE)

generally were detected in April 1994 at drain sites

(app. A). Carbofuran, the most commonly detected

insecticide, was detected in samples from all drain sites

sampled in April 1994 and in a sample from the

upstream sampling site on the Garfield Drain in

January 1995. Chlorpyrifos was detected in April 1994

at the two downstream sampling sites on the Garfield

Drain. Carbofuran and chlorpyrifos were not detected

in any ground-water samples, possibly indicating that

these insecticides are adsorbed to material in the soil

zone and do not leach downward into ground water but

instead are transported into the drains by runoff from

fields. Diazinon was detected at the downstream

sampling site on the Rincon Drain in April 1994 and at

the downstream site on the Hatch Drain in January

1994. The pesticide degradation product p,p’-DDE was

detected in drain samples at small concentrations. Four

of seven samples in which p,p’-DDE was detected were

collected in April 1994. DDT and p,p’-DDE also were

detected in samples of bed material from the three

drains sampled in the Rincon Valley (app. C). Although

DDT was not analyzed for in surface-water samples,

DDT and p,p’-DDE could be leaching from bed

sediment in the drains, resulting in the p,p’-DDE

detected in surface water. Because p,p’-DDE was

detected in only one ground-water sample (well 29),

p,p’-DDE probably is not generally found in shallow

ground water; thus, ground-water discharge is probably

not the main source of p,p’-DDE in surface water.

Diazinon, metolachlor, napropamide, p,p’-DDE,

and prometon were detected in one or more groundwater samples (app. B); their presence indicates that

they are leaching from land surface into ground water

in the Rincon Valley. Diazinon, napropamide, and

p,p’-DDE were detected in only one ground-water

sample. The concentrations of prometon in four of five

samples where prometon was detected were in the
55

same range as those in irrigation water. Metolachlor,

the most commonly detected pesticide in ground water

and surface water, is probably the only pesticide that is

leaching from the soil zone into ground water on a

widespread basis. Metolachlor was detected in 6 of the

10 samples that had the largest nitrite plus nitrate

concentrations, indicating that nitrogen and

metolachlor are leaching into ground water in some

areas of the Rincon Valley.

On the basis of pesticide concentrations detected

in shallow ground water in the Rincon Valley, no large

amounts of pesticides are leaching from land surface

into ground water. Although there is some indication

that several pesticides are leaching into shallow ground

water (metolachlor and prometon especially), the

concentrations are significantly smaller than any

standards or health advisories issued by the USEPA.

SUMMARY AND CONCLUSIONS

As part of the National Water-Quality

Assessment Program, surface-water and ground-water

samples were collected in 1994 and 1995 for analysis

of common constituents, nutrients, dissolved organic

carbon, trace elements, radioactivity, radon-222,

VOC’s, and pesticides to characterize surface-water

and shallow ground-water quality and to determine

factors affecting water quality in the Rincon Valley,

south-central New Mexico. Samples of surface water

were collected from three sites on the Rio Grande and

from sites on three agricultural drains in the Rincon

Valley. Samples were collected in January of 1994 and

1995, in April of 1994, and in October of 1994.

Ground-water samples were collected in late April and

early May 1994 from 30 shallow wells that were

installed during the investigation.

The Rincon Valley is an agricultural area that

includes the area of the Rio Grande flood plain between

Caballo Reservoir and Seldon Canyon. Crops in the

Rincon Valley are irrigated with surface water diverted

into irrigation canals from the Rio Grande, which is the

main drainage in the valley. Flow in the Rio Grande is

controlled by releases from Caballo Reservoir. From

about mid-October to early January little or no water is

released from Caballo Dam into the Rio Grande. A

complex set of unlined irrigation canals are used to

move irrigation water from the point of diversion to

individual fields. Shallow ground water discharges into

open drains to maintain water levels below land

surface. The largest drain flow occurs in June, July, and

August during the peak of the irrigation season, and the

smallest flow occurs in December, January, and

February. When no water is being released from

Caballo Dam, all flow in the Rio Grande below Caballo

Dam is from ground-water discharge and discharge

from the drains to the river. The annual discharge to the

Rio Grande from the drains equals about 12 percent of

the water diverted to the Arrey Canal from the Rio

Grande.

The main aquifer in the Rincon Valley consists of

the Quaternary valley fill, which is about 80 ft thick and

consists of gravel, sand, silt, and clay. The main sources

of recharge to the aquifer are infiltration of water from

the Rio Grande, infiltration of water in irrigation

canals, and infiltration of water applied to fields.

Discharge from the aquifer is mainly the result of

discharge to the Rio Grande and drains. In the winter

months, ground water discharges to the Rio Grande,

but relatively little or no ground water discharges to the

Hatch and Garfield Drains. The surface-water and

ground-water systems are closely connected; therefore,

a change in surface-water supplies or surface-water

quality affects ground-water supplies or ground-water

quality.

Dissolved oxygen concentrations generally were

larger in samples from the Rio Grande than in samples

from the drains and generally were larger in samples

collected in January of 1994 and 1995 than in samples

collected in April and October of 1994. All samples

from the Rio Grande had dissolved oxygen

concentrations larger than 5 mg/L, which is the

surface-water-quality standard.

Dissolved-solids concentrations in surface water

ranged from 434 to 1,510 mg/L. Dissolved-solids

concentrations were smallest in water from the Rio

Grande below Caballo Dam and largest in the drains.

Sulfate concentrations generally were the largest and

had the most variation of the common constituents, and

bicarbonate and sodium had the next largest

concentrations in surface-water samples. Nitrite plus

nitrate concentrations ranged from less than 0.05 to 3.3

mg/L as nitrogen, and ammonia concentrations ranged

from less than 0.015 to 0.33 mg/L as nitrogen in

surface-water samples. Nitrite plus nitrate and

ammonia concentrations generally were larger in water

from the drains than in water from the Rio Grande.

Concentrations of many trace elements in

surface water in the Rincon Valley were small (less

than 10 ∝g/L). Aluminum, barium, boron, bromide,
56

copper, iron, manganese, molybdenum, uranium, and

zinc were the only trace elements analyzed for that

were in one or more samples at concentrations larger

than 10 ∝g/L. The trace-element concentrations in

surface water were significantly smaller than acutefisheries standards. One or more pesticides were

detected in 34 of 37 surface-water samples. Thirteen of

88 pesticides analyzed for in each sample were

detected in one or more samples. DCPA (dacthal) and

metolachlor were the most commonly detected

pesticides, and metolachlor was detected at the largest

concentration. No surface-water-quality standards have

been established for the pesticides analyzed for in this

study.

Although the wells sampled are not used for

drinking water, shallow ground-water quality in the

Rincon Valley was compared to MCL’s, SMCL’s, and

health advisories established for drinking water.

Dissolved-solids concentrations in shallow ground

water ranged from 481 to 3,630 mg/L. Some of the

largest dissolved-solids concentrations were in water

from wells south and east of Rincon. Dissolved-solids

concentrations in water from wells a short distance

apart have a relatively large variation. Bicarbonate and

sulfate concentrations generally were the largest of the

common constituents. All but 2 of 30 samples

exceeded the SMCL of 500 mg/L for dissolved solids.

Water from about 73 percent of the wells sampled

exceeded the SMCL of 250 mg/L for sulfate and from

about 7 percent of the wells sampled exceeded the

SMCL of 250 mg/L for chloride.

Nitrite plus nitrate concentrations ranged from

less than 0.05 to 33 mg/L as nitrogen, and ammonia

concentrations were generally less than 0.1 mg/L as

nitrogen in shallow ground water. Nitrite plus nitrate

concentrations showed no areal pattern and varied

considerably over short distances. Water from about 17

percent of the well samples exceeded the MCL of 10

mg/L for nitrite plus nitrate as nitrogen.

The concentrations of trace elements in shallow

ground water generally were small (less than 10 ∝g/L).

Barium, bromide, copper, iron, manganese,

molybdenum, and uranium were the only trace

elements analyzed for that were in one or more samples

at concentrations larger than 10 ∝g/L. The proposed

MCL of 20 ∝g/L for uranium was exceeded in about 13

percent of the samples, the SMCL of 300 ∝g/L for iron

was exceeded in about 17 percent of the samples, and

the SMCL of 50 ∝g/L for manganese was exceeded in

about 83 percent of the samples.

Gross alpha activity ranged from 0.8 to 67 ∝g/L

as uranium, and the largest gross alpha activities were

in samples from the northern part of the Rincon Valley.

Samples from about 23 percent of the wells exceeded

the MCL of 15 pCi/L. Gross beta activity ranged from

4.7 to 29 pCi/L as Sr-90/Y-90, and radon-222

concentrations ranged from 210 to 440 pCi/L in

shallow ground water.

Xylene was detected in 3 of 20 samples at

concentrations ranging from 0.3 to 2.8 ∝g/L. The MCL

for xylene is 10,000 ∝g/L, which is significantly larger

than any concentration detected in ground-water

samples in the Rincon Valley.

Five (diazinon, metolachlor, napropamide,

p,p’-DDE, and prometon) of the 88 pesticides or

pesticide degradation products analyzed for were

detected in one or more shallow ground-water samples.

One or more pesticides or degradation products were

detected in water from 12 of 30 wells sampled.

Metolachlor and prometon were the most commonly

detected pesticides. Health advisories for the pesticides

detected in shallow ground water are 10 to 300 times

larger than the concentrations detected.

Infiltration and evapotranspiration of irrigation

water are important factors affecting shallow groundwater quality in the Rincon Valley. Dissolution of

calcite and gypsum are potentially important factors

affecting the concentrations of common constituents.

In some areas of the Rincon Valley, ground-water

inflow from adjacent areas possibly influences the

composition of shallow ground water and water in the

drains. Although silica concentrations in ground water

and drain water could be affected by weathering and

dissolution of silicate rocks, silica concentrations do

not appear to be affected by evaporation and

transpiration.

Nitrate and ammonia concentrations generally

were small in surface water entering the Rincon Valley

(irrigation water), and nitrogen concentrations in water

in the Rio Grande did not increase from ground-water

discharge and drain discharge to the river during most

of the year. Because of relatively large nitrite plus

nitrate concentrations in several shallow ground-water

samples (as much as 33 mg/L), fertilizers may be

leaching to ground water in some areas of the Rincon

Valley. Wide variations in nitrite plus nitrate

concentrations in short distances indicate variations in

leaching or chemical processes affecting nitrogen

concentrations in ground water.
57

Phosphorous concentrations in surface water and

ground water in the Rincon Valley generally were less

than 0.05 mg/L as phosphorus, indicating that

phosphorous concentrations in the valley are not

significantly affected by application of phosphorouscontaining fertilizers. The largest phosphorous

concentrations were detected in samples from the

downstream sampling site on the Hatch Drain and are

probably due to inflow of treated effluent to the drain

from the Hatch wastewater treatment plant.

Because barium concentrations generally were

larger in irrigation water than in shallow ground water

or drain water, they probably decrease during

infiltration and evaporation of irrigation water.

Bromide concentrations in water in the Rincon Valley

are probably affected by evapotranspiration of

irrigation water and inflow of ground water from

adjacent areas. Although relatively large manganese

concentrations were detected in both surface water and

ground water, iron concentrations generally were

small, indicating oxidation/reduction conditions where

manganese has been reduced but iron has not.

Molybdenum and uranium concentrations were

relatively larger in samples from the upstream

sampling site on the Garfield Drain and from well 7,

indicating that ground-water inflow to the Rincon

Valley from adjacent areas influences the composition

of shallow ground water in this area.

A large amount of dissolved gross alpha activity

in shallow ground water is from uranium isotopes.

Because dissolved gross beta activity increases with

dissolved potassium concentration, part of the

dissolved gross beta activity is due to potassium-40.

Xylene was the only VOC detected in shallow

ground water. Infiltration of runoff from the roadways

adjacent to the wells could be the source of the xylene.

A larger number of different pesticides were

detected and detected more frequently in surface water

than in ground water. This indicates that pesticides are

entering surface water as runoff from fields or that the

number of ground-water samples collected and time of

year that the samples were collected did not adequately

represent the composition of ground water in the

Rincon Valley that discharges to the drains. Pesticides

may also be leaching from sediment in the drains,

resulting in the observed concentrations of pesticides in

surface water. Some of the pesticides detected could be

transported into the valley in irrigation water. Prometon

and simazine were detected in water that was diverted

into the irrigation canals.

The insecticide carbofuran was not detected in

ground-water samples but was detected in all samples

from the drain sites sampled in April 1994. This may

mean that carbofuran does not leach into ground water

but instead is transported into the drains by runoff from

fields.

On the basis of pesticide concentrations detected

in shallow ground water in the Rincon Valley, large

amounts of the pesticides analyzed for in this study are

not leaching into ground water. Although there is some

indication that several pesticides are leaching into

shallow ground water (metolachlor and prometon

especially), the concentrations detected in shallow

ground water are significantly smaller than any

standards or health advisories issued by the USEPA.

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U.S. Geological Survey Water-Supply Paper 1230,

200 p.

Drever, J.I., 1988, The geochemistry of natural waters:

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58

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59

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60

Table 1. Annual diversions and discharge in drains in the Rincon Valley study area, 1993-95

[Data from Elephant Butte Irrigation District. All values in acre-feet;

location of streamflow gages on drains shown in figure 2]

1993 1994 1995

Diversions

Arrey Canal 102,000 127,000 127,000

Percha Lateral 1,080 1,440 1,370

Drains

Garfield Drain 3,900 5,120 5,700

Hatch Drain 5,540 5,350 5,110

Rincon Drain 5,540 5,050 5,410

Table 2. Crops, in acres, irrigated in the Rincon Valley study area, 1993-95

[Data from Elephant Butte Irrigation District]

Crop 1993 1994 1995

Alfalfa hay 4,468 5,778 6,628

Barley 0 0 57

Cabbage 56 26 7

Carrots 55 0 0

Cotton, lint (Am, Pima) 588 969 1,067

Cotton, lint (upland) 590 640 809

Family gardens and orchards 32 34 18

Field crops (miscellaneous) 0 0 24

Hay (other) 92 39 31

Irrigated pasture 64 84 86

Lettuce 161 130 56

Nursery (total) 40 40 13

Oats 0 0 654

Onions, dry 2,495 1,912 1,982

Pecans 1,310 1,377 1,425

Peppers (all kinds) 3,776 2,833 2,145

Sileage or ensilage 911 1,165 901

Tomatoes (canning) 114 116 106

Vegetables (other) 0 40 79

Watermelons 0 0 54

Wheat 1,703 1,812 1,084
61

 COMMON CONSTITUENTS

Constituent Minimum reporting level (mg/L)

Calcium 0.02

Magnesium 0.01

Sodium 0.20

Potassium 0.1

Bicarbonate 0.1

Carbonate 0.1

Alkalinity 0.1

Sulfate 0.1

Chloride 0.1

Fluoride 0.1

Silica 0.01

Dissolved solids 1.0

NUTRIENTS AND ORGANIC CARBON

Nitrite 0.01

Nitrite plus nitrate 0.05

Ammonia 0.015

Ammonia plus organic nitrogen 0.2

Phosphorus 0.01

Orthophosphate 0.01

Total organic carbon 0.1

Suspended organic carbon 0.1

Dissolved organic carbon 0.1

TRACE ELEMENTS

Constituent Minimum reporting level (∝g/L)

Aluminum 1

Antimony 1

Arsenic 1

Barium 1

Beryllium 1

Boron 10

Bromide 10

Cadmium 1

Chromium 1

Cobalt 1

Copper 1

Iron 3

Lead 1

Manganese 1

Molybdenum 1

Nickel 1

Selenium 1

Silver 1

Uranium 1

Zinc 1

Table 3. List of common constituents, nutrients and organic carbon, trace elements, and

pesticides analyzed for in surface-water samples

[Minimum reporting level, minimum concentration of an analyte that can be reliably measured and reported by the

laboratory using a given analytical method (Timme, 1995). Method detection limit, minimum concentration of an

analyte that can be measured and reported with 99-percent confidence that the concentration of the analyte is greater

than zero (Zaugg and others, 1995). mg/L, milligrams per liter; mg/L, micrograms per liter. Pesticides listed in group

A extracted by C-18 solid-phase extraction cartridge and analyzed by gas chromatography/mass spectrometric

detector. Pesticides listed in group B extracted by Carbopak-B solid-phase extraction cartridge and analyzed by

high-performance liquid chromatography]
62

GROUP A

Name Method detection limit (∝g/L)

Acetochlor 0.002

Alachlor 0.002

Atrazine 0.001

Benfluralin 0.002

Alpha HCH 0.002

Butylate 0.002

Carbaryl 0.003

Carbofuran 0.003

Chlorpyrifos 0.004

Cyanazine 0.004

DCPA 0.002

p,p’-DDE 0.006

Deethyl atrazine 0.002

Diazinon 0.002

Dieldrin 0.001

2,6-Diethylaniline 0.003

Disulfoton 0.017

EPTC 0.002

Ethalfluralin 0.004

Ethoprop 0.003

Fonofos 0.003

Lindane 0.004

Linuron 0.002

Malathion 0.005

Methyl azinphos 0.001

Methyl parathion 0.006

Metolachlor 0.002

Metribuzin 0.004

Molinate 0.004

Napropamide 0.003

Parathion 0.004

Pebulate 0.004

Pendimethalin 0.004

Permethrin 0.005

Phorate 0.002

Prometon 0.018

Pronamide 0.003

Propachlor 0.007

Propargite 0.013

Propanil 0.004

Simazine 0.005

Tebuthiuron 0.010

Terbacil 0.007

Terbufos 0.013

Thiobencarb 0.002

Triallate 0.001

Trifluralin 0.002

 GROUP B

Name Method detection limit (∝g/L)

Acifluorfen 0.035

Aldicarb 0.016

Aldicarb sulfone 0.016

Aldicarb sulfoxide 0.021

Amiben 0.011

Bentazon 0.014

Bromacil 0.035

Bromoxynil 0.035

Carbaryl 0.008

Carbofuran 0.028

Chlorothalonil 0.035

Clopyralid 0.050

2,4-D 0.035

Dacthal mono-acid 0.017

2,4-DB 0.035

Dicamba 0.035

Dichlobenil 0.020

Dichlorprop 0.032

Dinoseb 0.035

Diuron 0.020

Esfenvalerate 0.019

Fenuron 0.013

Fluometuron 0.035

3-Hydroxycarbofuran 0.014

Linuron 0.018

MCPA 0.050

MCPB 0.035

Methiocarb 0.026

Methomyl 0.017

1-Naphthol 0.007

Neburon 0.015

Norflurazon 0.024

Ocresol 0.035

Oryzalin 0.019

Oxamyl 0.018

Picloram 0.050

Propham 0.035

Propoxur 0.035

Silvex 0.021

2,4,5-T 0.035

Triclopyr 0.050

Table 3. List of common constituents, nutrients and organic carbon, trace elements, and pesticides

analyzed for in surface-water samples--Concluded

PESTICIDES
63

COMMON CONSTITUENTS

Constituent Minimum reporting level (mg/L)

Calcium 0.02

Magnesium 0.01

Sodium 0.2

Potassium 0.1

Bicarbonate 0.1

Carbonate 0.1

Alkalinity 0.1

Sulfate 0.1

Chloride 0.1

Fluoride 0.1

Silica 0.01

NUTRIENTS AND DISSOLVED ORGANIC CARBON

Nitrite 0.01

Nitrite plus nitrate 0.05

Ammonia 0.015

Ammonia plus organic nitrogen 0.2

Phosphorus 0.01

Orthophosphate 0.01

Dissolved organic carbon 0.1

TRACE ELEMENTS

Constituent Minimum reporting level (∝g/L)

Aluminum 1

Antimony 1

Arsenic 1

Barium 1

Beryllium 1

Bromide 10

Cadmium 1

Chromium 1

Cobalt 1

Copper 1

Iron 3

Lead 1

Manganese 1

Molybdenum 1

Nickel 1

Selenium 1

Silver 1

Uranium 1

Zinc 1

RADIOACTIVITY/RADON

Constituent Minimum reporting level

Gross alpha activity as uranium 3.0 ∝g/L

Gross beta activity as

 strontium-90/yttrium-90 4.0 pCi/L

Radon-222 24 pCi/L

VOLATILE ORGANIC COMPOUNDS

Constituent Minimum reporting level (∝g/L)

Benzene 0.2

Bromobenzene 0.2

Bromochloromethane 0.2

Bromoform 0.2

Carbon tetrachloride 0.2

Chlorobenzene 0.2

Chlorodibromomethane 0.2

Chloroethane 0.2

Chloroform 0.2

Cis-1,2-dichloroethene 0.2

Cis-1,3-dichloropropene 0.2

Dibromochloropropane 1.0

1,2-Dibromoethane 0.2

Dibromomethane 0.2

1,3-Dichlorobenzene 0.2

1,4-Dichlorobenzene 0.2

Dichlorobromomethane 0.2

Dichlorodifluoromethane 0.2

1,1-Dichloroethane 0.2

1,2-Dichloroethane 0.2

1,1-Dichloroethylene 0.2

1,2-Dichloropropane 0.2

1,3-Dichloropropane 0.2

2,2-Dichloropropane 0.2

1,1-Dichloropropene 0.2

Ethylbenzene 0.2

Freon-113 0.2

Hexachlorobutadiene 0.2

Isopropylbenzene 0.2

Mesitylene 0.2

Methylbromide 0.2

Methylchloride 0.2

Methylene chloride 0.2

Methyl tert-butyl ether (MTBE) 0.2

Napthalene 0.2

N-butylbenzene 0.2

N-propylbenzene 0.2

O-chlorobenzene 0.2

O-chlorotoluene 0.2

P-chlorotoluene 0.2

P-isopropyltoluene 0.2

Pseudocumene 0.2

Sec-butylbenzene 0.2

Styrene 0.2

Tertbutylbenzene 0.2

1,1,1,2-Tetrachloroethane 0.2

1,1,2,2-Tetrachloroethane 0.2

Tetrachloroethylene 0.2

Toluene 0.2

1,2-Transdichloroethene 0.2

Trans-1,3-dichloropropene 0.2

1,2,3-Trichlorobenzene 0.2

1,2,4-Trichlorobenzene 0.2

1,1,1-Trichloroethane 0.2

1,1,2-Trichloroethane 0.2

Trichloroethylene 0.2

Trichlorofluoromethane 0.2

1,2,3-Tricloropropane 0.2

Vinyl chloride 0.2

Xylene 0.2

Table 4. List of common constituents, nutrients and dissolved organic carbon, trace elements,

radioactivity/radon, volatile organic compounds, and pesticides analyzed for in ground-water samples

[Minimum reporting level is the minimum concentration of an analyte that can be reliably measured and reported by

the laboratory using a given analytical method (Timme, 1995). Method detection limit is the minimum concentration

of an analyte that can be measured and reported with 99-percent confidence that the concentration of the analyte is

greater than zero (Zaugg and others, 1995). mg/L, milligrams per liter; ∝g/L, micrograms per liter; pCi/L, picocuries

per liter. Pesticides listed in group A extracted by C-18 solid-phase extraction cartridge and analyzed by gas

chromatography/mass spectrometric detector. Pesticides listed in group B extracted by Carbopak-B solid-phase

extraction cartridge and analyzed by high-performance liquid chromatography]
64

GROUP A

Name Method detection limit (∝g/L)

Acetochlor 0.002

Alachlor 0.002

Atrazine 0.001

Benfluralin 0.002

Alpha HCH 0.002

Butylate 0.002

Carbaryl 0.003

Carbofuran 0.003

Chlorpyrifos 0.004

Cyanazine 0.004

DCPA 0.002

p,p’-DDE 0.006

Deethyl atrazine 0.002

Diazinon 0.002

Dieldrin 0.001

2,6-Diethylaniline 0.003

Disulfoton 0.017

EPTC 0.002

Ethalfluralin 0.004

Ethoprop 0.003

Fonofos 0.003

Lindane 0.004

Linuron 0.002

Malathion 0.005

Methyl azinphos 0.001

Methyl parathion 0.006

Metolachlor 0.002

Metribuzin 0.004

Molinate 0.004

Napropamide 0.003

Parathion 0.004

Pebulate 0.004

Pendimethalin 0.004

Permethrin 0.005

Phorate 0.002

Prometon 0.018

Pronamide 0.003

Propachlor 0.007

Propargite 0.013

Propanil 0.004

Simazine 0.005

Tebuthiuron 0.010

Terbacil 0.007

Terbufos 0.013

Thiobencarb 0.002

Triallate 0.001

Trifuralin 0.002

 GROUP B

Name Method detection limit (∝g/L)

Acifluorfen 0.035

Aldicarb 0.016

Aldicarb sulfone 0.016

Aldicarb sulfoxide 0.021

Amiben 0.011

Bentazon 0.014

Bromacil 0.035

Bromoxynil 0.035

Carbaryl 0.008

Carbofuran 0.028

Chlorothalonil 0.035

Clopyralid 0.050

2,4-D 0.035

Dacthal mono-acid 0.017

2,4-DB 0.035

Dicamba 0.035

Dichlobenil 0.020

Dichlorprop 0.032

Dinoseb 0.035

Diuron 0.020

Esfenvalerate 0.019

Fenuron 0.013

Fluometuron 0.035

3-Hydroxycarbofuran 0.014

Linuron 0.018

MCPA 0.050

MCPB 0.035

Methiocarb 0.026

Methomyl 0.017

1-Naphthol 0.007

Neburon 0.015

Norflurazon 0.024

Ocresol 0.035

Oryzalin 0.019

Oxamyl 0.018

Picloram 0.050

Propham 0.035

Propoxur 0.035

Silvex 0.021

2,4,5-T 0.035

Triclopyr 0.050

Table 4. List of common constituents, nutrients and dissolved organic carbon, trace elements, radioactivity/radon,

volatile organic compounds, and pesticides analyzed for in ground-water samples--Concluded

PESTICIDES
65

Table 5. List of pesticides, pesticide metabolites, gross polychlorinated biphenols, and gross

polychlorinated naphthalenes analyzed for in bed-material samples

[Minimum reporting level is the minimum concentration of an analyte that can be reliably

measured and reported by the laboratory using a given analytical method

(Timme, 1995)]

Name

Minimum reporting level

(micrograms per

kilogram)

Aldrin 0.1

Chlordane 0.1

DDD 0.1

p,p’-DDE 0.1

DDT 0.1

Diazinon 0.2

Dieldrin 0.1

Endosulfan 0.1

Endrin 0.1

Ethion 0.2

Heptachlor 0.1

Heptachlor, epoxide 0.1

Lindane 0.1

Malathion 0.2

Methoxychlor 0.1

Methyl parathion 0.2

Mirex 0.1

Parathion 0.2

Gross polychlorinated biphenols (PCB’s) 1.0

Gross polychlorinated naphthalenes

(PCN’s)

1.0

Perthane 1.0

Toxaphene 10.0

Trithion 0.2
66

Table 6. Constituents detected in field-blank samples and ranges of concentrations detected in

field-blank, shallow ground-water, and surface-water samples

[MRL, minimum reporting level; MDL, method detection limit; mg/L, milligrams per liter;

∝g/L, micrograms per liter; --, no data; *, only 2 samples analyzed for constituent;

+, MRL changed to 0.015 mg/L after April/May sampling]

Constituent

MRL or

MDL

Number of

detections

at or above

MRL or

MDL

Range of

concentrations in

field-blank

samples

Range of

concentrations

detected in

shallow

ground

water

(app. B)

Range

of

concentrations

detected in

surface

water

(app. A)

Calcium (mg/L as Ca) 0.02 6 0.04-0.06 69-270 46-170

Magnesium (mg/L as Mg) 0.01 1 0.01 11-70 12-32

Alkalinity (mg/L as CaCO3) 0.1 7 1.1-1.6 140-560 140-350

Sulfate (mg/L as SO4) 0.1 1 0.2 130-1,700 120-630

Silica (mg/L as SiO2) 0.01 6 0.01-0.16 11-33 0.96-32

Nitrite (mg/L as N) 0.01 1 0.01 0.01-0.10 0.01-0.11

Ammonia, dissolved

(mg/L as N) 0.01+ 4 0.01-0.02 0.01-0.33 0.01-0.33

Phosphorus, dissolved

(mg/L as P) 0.01 1 0.01 0.01-0.13 0.01-0.73

Suspended organic carbon

(mg/L as C) 0.1 2* 0.1 -- 0.3-2.1

Dissolved organic carbon

(mg/L as C) 0.1 5 0.1-0.8 1.1-5.3 0.8-4.9

Aluminum (∝g/L as Al) 1 6 1-4 1-6 2-17

Chromium (∝g/L as Cr) 1 2 1-2 1-10 1-10

Iron (∝g/L as Fe) 3 1 4 3-1,900 3-61

Zinc (∝g/L as Zn) 1 6 1-7 1-14 1-11

Methyl chloride (∝g/L) 0.2 2* 0.3-0.4 0.2-0.5 --

Methylene chloride (∝g/L) 0.2 2* 0.2-0.3 -- --
67

Table 7. Relative-percent difference for replicate samples from surface-water and ground-water sites

[mg/L, milligrams per liter; deg C, degrees Celsius; ∝g/L, micrograms per liter;

pCi/L, picocuries per liter; --, no data]

pH,

laboratory

(standard

units)

Calcium,

dissolved

(mg/L as Ca)

Magnesium,

dissolved

(mg/L as

Mg)

Sodium,

dissolved

(mg/L as

Na)

Potassium,

dissolved

(mg/L as K)

Sulfate,

dissolved

(mg/L as

SO4)

Minimum 000000Median 000010Maximum 425522

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)

Bromide,

dissolved

(mg/L

as Br)

Silica,

dissolved

(mg/L

as SiO2)

Dissolved

solids,

residue at

180 deg C

(mg/L)

Nitrite,

dissolved

(mg/L

as N)

Nitrite+

nitrate,

dissolved

(mg/L

as N)

Ammonia,

dissolved

(mg/L

as N)

Ammonia

+organic

nitrogen,

dissolved

(mg/L

as N)

Minimum 000000000Median 0 0 12 010700Maximum 5 15 130 5 15 12 9 29 40

Phosphorus,

dissolved

(mg/L

as P)

Orthophosphate,

dissolved

(mg/L

as P)

Dissolved

organic

carbon

(mg/L

as C)

Aluminum,

dissolved

(∝g/L

as Al)

Antimony,

dissolved

(∝g/L

as Sb)

Arsenic,

dissolved

(∝g/L

as As)

Barium,

dissolved

(∝g/L

as Ba)

Beryllium,

dissolved

(∝g/L

as Be)

Cadmium,

dissolved

(∝g/L

as Cd)

Minimum 0 0 0 0 00100Median 0 0 0 10 00200Maximum 40 0 6 66 00400
68

Table 7. Relative-percent difference for replicate samples from surface-water and ground-water sites--Concluded

Chromium,

dissolved

(∝g/L

as Cr)

Cobalt,

dissolved

(∝g/L

as Co)

Copper,

dissolved

(∝g/L

as Cu)

Iron,

dissolved

(∝g/L

as Fe)

Lead,

dissolved

(∝g/L

as Pb)

Manganese,

dissolved

(∝g/L

as Mn)

Molybdenum,

dissolved

(∝g/L

as Mo)

Nickel,

dissolved

(∝g/L

as Ni)

Selenium,

dissolved

(∝g/L

as Se)

Minimum 0 0000 0 000Median 28 0 23 3 0 9 0 40 0Maximum 66 0 66 22 0 21 15 66 0

Silver,

dissolved

(∝g/L

as Ag)

Uranium,

dissolved

(∝g/L as U)

Zinc,

dissolved

(∝g/L

as Zn)

Gross alpha,

dissolved

(∝g/L as U)

Gross beta,

dissolved

(pCi/L as

Sr-90/Y-90)

Radon-222

(pCi/L)

Minimum 000804Median 0 0 0 16 0 7Maximum 0 6 57 22 15 25
69

Table 8. Percent recovery of spiked Group A pesticides

[--, no data]

Alachlor

Alpha

BCH Atrazine

Benfluralin Butylate Carbaryl Carbo- furan Chlor- pyrifos

Field spikes

Minimum 98 86 85 54 83 51 80 42Median 109 89 93 87 92 84 93 88Maximum 120 112 116 98 107 120 131 116

Laboratory spikes

Minimum 92 80 76 51 82 60 80 60Median 101 83 93 79 85 84 88 74Maximum 111 101 101 85 90 102 93 87

Cyanazine DCPA

Deethylatrazine Diazinon Dieldrin

2,6-

Diethylaniline Disulfoton EPTC

Field spikes

Minimum 67 94 23 62 73 74 59 79Median 105 104 35 90 77 92 116 90Maximum 143 146 57 112 121 107 139 125

Laboratory spikes

Minimum 74 85 25 52 69 83 73 78Median 93 101 37 87 73 89 126 84Maximum 112 130 52 92 76 99 138 118
70

Table 8. Percent recovery of spiked Group A pesticides--Continued

Sample type

Ethalfluralin Ethoprop Fonofox Lindane Linuron Malathion Methyl azinphos Methyl parathion

Field spikes

Minimum 77 81 48 62 58 45 51 60Median 96 93 87 89 85 90 101 101Maximum 116 116 116 143 121 103 177 152

Laboratory spikes

Minimum 67 87 79 80 63 53 51 56Median 89 90 83 84 81 83 84 78Maximum 92 109 109 143 85 93 121 102

Metolachlor Metribuzi n Molinate Napro- pamide p,p’-DDE Parathion Pebulate Pendi- methalin

Field spikes

Minimum 103 69 89 68 46 59 80 46Median 111 82 92 101 60 65 92 85Maximum 137 93 125 125 79 116 125 116

Laboratory spikes

Minimum 93 63 82 74 41 63 77 62Median 102 74 90 90 57 63 87 72Maximum 129 92 118 118 66 70 109 92
71

Table 8. Percent recovery of spiked Group A pesticides--Concluded

Permethrin Phorate Prometon Pronamide Propachlor Propanil Propargite Simazine

Field spikes

Minimum 33 52 89 62 86 80 63 69Median 52 81 107 83 92 95 77 101Maximum 101 93 125 170 116 125 187 125

Laboratory spikes

Minimum 25 60 89 64 77 76 66 89Median 48 87 109 86 86 93 72 93Maximum 106 91 111 160 92 109 80 110

Tebuthiuron Terbacil Terbufos Thio- bencarb Triallate Trifluralin

Field spikes

Minimum 71 15 63 63 80 66Median 90 144 90 93 89 89Maximum 303 426 131 170 103 98

Laboratory spikes

Minimum 70 72 86 81 73 61Median 87 163 92 87 85 76Maximum 193 368 93 151 92 92
72

Table 9. Percent recovery of spiked Group B pesticides

[--, no data]

Aldicarb

Aldicarb

sulfone

Aldicarb

sulfoxide Bentazon Bromacil

Bromoxynil Carbaryl Carbo- furan

Field spikes

Minimum 30 1 27 11 37 43 1 20Median 49 12 47 61 65 62 14 69Maximum 89 31 110 73 101 90 55 187

Laboratory spikes

Minimum 21 1 37 10 42 42 8.4 37Median 52 11 47 63 60 61 12 51Maximum 79 19 62 74 78 89 30 136

2, 4-D 2, 4-DB 2, 4, 5-T Dicamba Dichlorprop Dinoseb Diuron Ocresol

Field spikes

Minimum 43 24 40 11 39 36 17 39Median 68 38 62 41 60 57 42 60Maximum 113 44 118 213 77 77 62 74

Laboratory spikes

Minimum 55 27 3 8 41 39 22 49Median 63 38 45 46 59 57 41 53Maximum 108 44 104 79 70 63 60 75
73

Table 9. Percent recovery of spiked Group B pesticides--Concluded

Fenuron

Fluometuron Linuron MCPA Methiocarb Methomyl 1-Naph- thol Neburon

Field spikes

Minimum 43 35 60 35 7 34 1 21Median 87 69 132 59 19 71 3 52Maximum 229 117 190 72 69 96 56 79

Laboratory spikes

Minimum 52 36 75 49 9 40 1 34Median 87 61 108 54 20 55 5 54Maximum 168 92 165 76 40 83 25 70

Oxamyl Picloram Propham Propoxur Silvex

Field spikes

Minimum 2 5 68 21 46Median 7 44 143 52 62Maximum 71 53 196 190 80

Laboratory spikes

Minimum 1 20 76 25 44Median 18 51 119 61 64Maximum 52 58 172 141 72
74

Table 10. Percent recovery of spiked volatile organic compounds

Sample type

Bromoform Carbon te- trachloride

Chlorodibromomethane 1,4-Dichlo- robenzene 1,2-Dichlo- roethane Dichloro- bromo- methane 1,1- Dichloro- ethylene

Laboratory spike 100 72 87 100 87 87 115Field spike 85 48 70 80 70 70 60Field spike replicate 80 44 65 70 65 61 60Laboratory spike 75 72 74 95 78 70 100Field spike 55 44 52 70 57 48 60Field spike replicate 60 40 52 70 57 52 50

Sample type

Ethylbenzene MTBE Tetrachlo- roethylene

1,1,1-

Trichloroethane Trichlo- roethylene Vinyl chloride

Laboratory spike 76 92 76 95 95 96Field spike 60 72 56 60 65 30Field spike replicate 52 72 48 55 60 44Laboratory spike 88 76 88 90 95 113Field spike 64 56 56 60 65 57Field spike replicate 60 56 56 55 60 39
75

Table 11. Water-quality standards for the Rio Grande and ranges of concentrations in samples

from the Rio Grande and from drains in the Rincon Valley study area

[Standards from New Mexico Water Quality Control Commission, 1994. Trace element standards based on

the acute fisheries standard. <, less than; >, greater than; --, no data; *, value based on hardness of 150

milligrams per liter (mg/L) as CaCO3; deg C, degrees Celsius, ∝g/L, micrograms per liter]

Property/constituent

Standard for

Rio Grande

from below

Caballo Dam

to 1 mile

below Percha

Diversion

Dam

(fig. 2)

Standard for

Rio Grande

from 1 mile

below Percha

Diversion

Dam to

southern end

of Rincon

Valley

(fig. 2)

Range of

concentrations in

samples from

Rio Grande

below

Caballo Dam

(fig. 2)

Range of

concentrations in

samples from

Rio Grande

at Road 187

near Hatch

and Rio

Grande above

RinconDrain,

near Rincon

(fig. 2)

Range of

concentrations in

samples from

drains

(fig. 2)

pH 6.6-9.0 6.6-8.8 8.0-8.52 8.2-8.65 7.52-8.4

Temperature (deg C) <32.2 <34 11.0-15.5 5-19.5 4.5-24

Dissolved oxygen (mg/L) >5.0 >5.0 9.0-11.0 7.5-13.2 3.2-17.1

Aluminum (∝g/L as Al) 750 750 5-12 3-12 2-17

Arsenic (∝g/L as As) 20 20 2-3 <1-3 <1-3

Beryllium (∝g/L as Be) 130 130 <1 <1 <1

Boron (∝g/L as B) 50 50 -- 200-210 170-350

Cadmium (∝g/L as Cd) 6.2* 6.2* <1 <1 <1-6

Chromium (∝g/L as Cr) 2,420* 2,420* <1-3 1-5 1-10

Cobalt (∝g/L as Co) 1,000* 1,000* <1 <1 <1

Copper (∝g/L as Cu) 26* 26* 1 <1-3 <1-32

Lead (∝g/L as Pb) 137* 137* <1-3 <1-2 <1-3

Nickel (∝g/L as Ni) 2,510* 2,510* <1-3 <1-6 <1-9

Selenium (∝g/L as Se) 20 20 <1 <1 <1

Silver (∝g/L as Ag) 8.15* 8.15* <1 <1 <1

Zinc (∝g/L as Zn) 165* 165* 1-7 <1-5 <1-11
76

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90

Specific conductance,field (∝S/cm)

37 0 1,343 373 727 2,140 765 1,080 1,390 1,590 1,840

pH, field (standard units) 37 0 8.18 0.29 7.52 8.69 7.8 7.99 8.16 8.4 8.52pH, laboratory (standardunits)

37 0 7.79 0.17 7.3 8.1 7.6 7.7 7.8 7.9 8.0

Temperature, water (degC)

37 0 13.4 5.6 4.7 24.2 5.2 8 13.4 17.5 21.9

Oxygen, dissolved(mg/L)

37 0 9 3.2 3.2 17.1 4.8 7.5 8.8 10.4 14.2

Hardness, (mg/L CaCO3) 37 0 334 103 170 560 180 260 360 400 470

Calcium, dissolved(mg/L as Ca)

37 0 101 33 46 170 51 71 110 120 140

Magnesium, dissolved(mg/L as Mg)

37 0 20 5 12 32 13 15 20 23 27

Sodium, dissolved (mg/Las Na)

37 0 155.8 53.9 78 270 84 110 150 190 250

Sodium adsorption ratio 37 0 3.8 1.1 3 7 3 3 4 4 5Sodium percent 37 0 49 6.4 42 68 43 45 48 49 60Potassium, dissolved(mg/L as K)

37 0 8.4 3.3 5.2 17 5.7 6.1 6.8 9.8 13

[No. < MRL, total number of samples with concentration less than minimum reporting level; inst, instantaneous; ∝S/cm, microsiemens per centimeter at 25

degrees Celsius (deg C); mg/L, milligrams per liter; it. field, field measurement by incremental titration; gran field, field measurement by gran titration; ∝g/L,

micrograms per liter; <, less than. Summary statistics calculated using MRL or method detection limit concentration substituted for all less than values]
77

Bicarbonate, dissolved it.field (mg/L as HCO3)

37 0 285 69.8 158 422 172 249 297 332 368

Carbonate, dissolved it.field (mg/L as CO3)

14 11.2 5.7 4 24 4 8 10 16 18

Alkalinity, dissolved granfield (mg/L as CaCO3)

37 0 240 54.7 140 350 150 210 240 280 300

Sulfate, dissolved (mg/Las SO4)

37 0 300 121 120 630 130 230 310 370 440

Chloride, dissolved(mg/L as Cl)

37 0 110 32.4 62 180 70 78 110 130 150

Fluoride, dissolved(mg/L as F)

37 0 1.16 1.15 0.5 4.9 0.6 0.6 0.8 0.9 3

Silica, dissolved (mg/Las SiO2)

37 0 18.3 7.4 0.96 32 12 15 19 24 29

Dissolved solids, residueat 180 deg C (mg/L)

37 0 888 274 434 1,510 461 694 894 1,060 1,260

Nitrite, dissolved (mg/Las N)

37 7 0.03 0.03 <0.01 0.11 <0.01 0.01 0.03 0.04 0.08

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
78

Nitrite plus nitrate, dissolved (mg/L as N) 37 4 0.56 0.66 <0.05 3.3 <0.05 0.15 0.44 0.61 1.2

Ammonia, dissolved(mg/L as N)

37 2 0.09 0.07 <0.015 0.33 0.01 0.04 0.08 0.1 0.15

Ammonia + organicnitrogen, dissolved(mg/L as N)

37 4 0.33 0.16 <0.2 1.1 <0.2 0.2 0.3 0.3 0.5

Phosphorus, dissolved(mg/L as P)

37 17 0.05 0.13 <0.01 0.73 <0.01 <0.01 0.01 0.02 0.18

Orthophosphate, dissolved (mg/L as P) 37 17 0.05 0.14 <0.01 0.73 <0.01 <0.01 0.01 0.02 0.19

Total organic carbon(mg/L as C)

9 0 7.18 2.83 3.6 13 3.6 5.5 7.1 7.3 13

Suspended organiccarbon (mg/L as C)

19 0 0.74 0.49 0.3 2.1 0.3 0.3 0.6 1.1 1.5

Dissolved organic carbon(mg/L as C)

36 0 3.62 0.78 0.8 4.9 2.7 3.25 3.6 4.25 4.6

Aluminum, dissolved(∝g/L as Al)

37 0 5.8 3.3 2 17 3 4 5 7 11

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
79

Antimony, dissolved(∝g/L as Sb)

37 37 1 0 <1 <1 <1 <1 <1 <1 <1

Arsenic, dissolved (∝g/L

as As)

37 8 1.7 0.66 <1 3 <1 1 2 2 3

Barium, dissolved (∝g/L

as Ba)

37 0 77.9 18.7 37 120 59 64 75 91 110

Beryllium, dissolved(∝g/L as Be)

37 37 1 0 <1 <1 <1 <1 <1 <1 <1

Boron, dissolved (∝g/L

as B)

8 0 268 82.2 170 400 170 205 250 330 400

Bromide, dissolved(mg/L as Br)

28 0 0.17 0.07 0.06 0.31 0.07 0.11 0.17 0.22 0.26

Cadmium, dissolved(∝g/L as Cd)

37 36 1.1 0.8 <1 6 <1 <1 <1 <1 <1

Chromium, dissolved(∝g/L as Cr)

37 1 2.8 1.8 <1 10 1 2 2 3 6

Cobalt, dissolved (∝g/Las Co)

37 37 1 0 <1 <1 <1 <1 <1 <1 <1

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
80

Copper, dissolved (∝g/L

as Cu)

37 4 2.7 5 <1 32 <1 1 2 3 4

Iron, dissolved (∝g/L as

Fe)

37 8 10.8 12.2 <3 61 <3 4 5 15 28

Lead, dissolved (∝g/L asPb)

37 27 1.2 0.6 <1 3 <1 <1 <1 1 2

Manganese, dissolved(∝g/L as Mn)

37 0 273 295 2 1,220 6 63 159 459 758

Molybdenum, dissolved(∝g/L as Mo)

37 0 11.7 8.2 6 42 7 7 9 12 22

Nickel, dissolved (∝g/L as Ni)

37 7 3.1 2.3 <1 9 <1 1 2 5 7

Selenium, dissolved (∝g/L as Se)

37 36 1 0 <1 1 <1 <1 <1 <1 <1

Silver, dissolved (∝g/L as Ag)

37 37 1 0 <1 <1 <1 <1 <1 <1 <1

Uranium, dissolved(∝g/L as U)

37 0 6.7 3.9 3 20 3 5 5 8 12

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
81

Zinc, dissolved (∝g/L as Zn)

37 3 2.9 2.3 <1 11 1 1 2 3 6

Atrazine, dissolved(∝g/L)

37 36 0.001 0 <0.001 0.002 <0.001 <0.001 <0.001 <0.001 <0.001

Carbofuran, dissolved(∝g/L)

37 29 0.01 0.03 <0.003 0.15 <0.003 <0.003 <0.003 <0.003 0.05

Chlorpyrifos, dissolved(∝g/L)

37 35 0.004 0.001 <0.004 0.01 <0.004 <0.004 <0.004 <0.004 <0.004

Dacthal, mono-acid,dissolved (∝g/L)

36 34 0.02 0.03 <0.017 0.13 <0.02 <0.02 <0.02 <0.02 0.02

DCPA, dissolved (∝g/L) 37 12 0.02 0.05 <0.001 0.21 <0.002 <0.002 0.004 0.01 0.06

Diazinon, dissolved(∝g/L)

37 34 0.003 0.003 <0.001 0.02 <0.002 <0.002 <0.002 <0.002 0.002

EPTC, dissolved (∝g/L) 37 31 0.002 0.002 <0.001 0.01 <0.002 <0.002 <0.002 <0.002 0.004Metolachlor, dissolved(∝g/L)

37 10 0.03 0.07 0.002 0.41 <0.002 <0.002 0.007 0.02 0.06

Pendimethalin, dissolved (∝g/L) 37 36 0.01 0.005 <0.004 0.03 <0.004 <0.004 <0.004 <0.004 <0.004

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
82

p,p’-DDE, dissolved (∝g/

L)

37 30 0.01 0.002 <0.001 0.006 <0.002 <0.006 <0.006 <0.006 0.006

Prometon, dissolved(∝g/L)

37 33 0.02 0.003 <0.006 0.02 <0.01 <0.02 <0.02 <0.02 <0.02

Simazine, dissolved(∝g/L)

37 34 0.005 0 <0.005 0.005 <0.005 <0.005 <0.005 <0.005 <0.005

Trifluralin, dissolved(∝g/L)

37 36 0.002 0 E0.001 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

Table 12. Statistical summary of selected data for surface water in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90

Concluded
83

Table 13. Statistical summary of selected data for wells sampled in the Rincon Valley study area

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90

Well depth (feet) 30 -- 19.6 2.80 14.89 24.19 15.57 17.47 19.94 22.04 23.13Water level below landsurface (feet)

30 -- 8.24 2.38 3.92 12.28 5.62 6.3 7.97 10.11 11.95

Specific conductance, field(∝S/cm)

30 -- 1,714 859 790 5,280 1,000 1,270 1,495 1,932 2,270

pH, field (standard units) 30 -- 7.41 0.17 7.01 7.68 7.21 7.31 7.41 7.53 7.63Temperature water, (degreesCelsius)

30 -- 17.2 1.77 10 19.3 15.4 16.2 17.55 18.2 18.7

Oxygen, dissolved (mg/L) 30 -- 0.76 1.25 0.1 5.6 0.1 0.1 0.2 0.9 1.90Calcium, dissolved(mg/L as Ca)

30 0 135 51.5 69 270 76 97 130 160 210

Magnesium, dissolved(mg/L as Mg)

30 0 24.9 12.0 11 70 14.5 17 23.0 28.0 37.5

Sodium, dissolved(mg/L as Na)

30 0 205 157 73 920 100 120 170 230 285

Potassium, dissolved(mg/L as K)

30 0 8.52 4.12 3.7 21 5.0 5.8 7.4 9.6 14.5

Bicarbonate, dissolved(mg/L as HCO3)

30 0 368 128 174 694 199 269.5 342 356 546

Alkalinity, gran field(mg/L as CaCO3)

30 0 302 103 140 560 170 240 280 350 450

[No. < MRL, total number of samples with concentrations less than minimum reporting level (MRL); --, not applicable; mS/cm, microsiemens per

centimeter at 25 degrees Celsius; mg/L, milligrams per liter; gran field, field measurement by gran titration; <, less than; mg/L, micrograms per liter;

pCi/L, picocuries per liter. Summary statistics calculated using MRL or method detection limit concentration substituted for all less than values and

maximum detection limit for all greater than values]
84

Sulfate, dissolved(mg/L as SO4)

30 0 407 308 130 1,700 185 230 330 450 720

Chloride, dissolved(mg/L as Cl)

30 0 126 75 67 450 72 93 110 130 170

Fluoride, dissolved(mg/L as F)

30 0 1.05 0.65 0.5 2.9 0.5 0.6 0.9 1.1 2.2

Bromide, dissolved(mg/L as Br)

30 0 0.31 0.18 0.13 0.97 0.14 0.17 0.27 0.36 0.52

Silica, dissolved(mg/L as SiO2)

30 0 22.5 5.39 11 33 14 19.0 24 26 28.5

Dissolved solids (mg/L) 30 0 1,140 618 481 3,630 646.5 788 995 1,350 1,615Nitrite, dissolved(mg/L as N)

30 13 0.04 0.03 <0.01 0.10 <0.01 <0.01 0.02 0.06 0.09

Nitrite plus nitrate,dissolved (mg/L as N)

30 7 5.16 9.02 <0.05 33 <0.05 0.06 0.48 5.6 19

Ammonia, dissolved(mg/L as N)

30 3 0.08 0.09 <0.01 0.33 <0.01 0.02 0.03 0.1 0.24

Table 13. Statistical summary of selected data for wells sampled in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
85

Ammonia + organicnitrogen, dissolved(mg/L as N)

30 7 0.41 0.34 <0.2 1.5 <0.2 0.2 0.3 0.4 1

 Phosphorus, dissolved(mg/L as P)

30 10 0.03 0.03 <0.01 0.13 <0.01 <0.01 0.02 0.05 0.07

 Orthophosphate, dissolved(mg/L as P)

30 4 0.03 0.02 <0.01 0.06 <0.01 0.01 0.02 0.05 0.055

 Dissolved organic carbon(mg/L as C)

30 1 2.77 1.02 1.1 5.3 1.5 2.2 2.8 3.4 4

 Aluminum, dissolved(∝g/L as Al)

30 14 1.77 1.19 <1 6 <1 <1 1 2 3

 Antimony, dissolved(∝g/L as Sb)

30 30 1.1 0.4 <1 3 <1 <1 <1 <1 <1

 Arsenic, dissolved(∝g/L as As)

30 8 1.83 0.83 <1 4 <1 <1 2 2 3

 Barium, dissolved(∝g/L as Ba)

30 0 66.8 23.4 29 110 38 49 63.5 83 100

 Beryllium, dissolved(∝g/L as Be)

30 30 1.1 0.4 <1 <3 <1 <1 <1 <1 <1

Table 13. Statistical summary of selected data for wells sampled in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
86

Cadmium, dissolved(∝g/L as Cd)

30 28 1.2 0.66 <1 4 <1 <1 <1 <1 1.5

Chromium, dissolved(∝g/L as Cr)

30 2 4.27 1.93 <1 10 1.5 3 4 5 6.5

Cobalt, dissolved(∝g/L as Co)

30 29 1.13 0.57 <1 4 <1 <1 <1 <1 <1

Copper, dissolved(∝g/L as Cu)

30 0 4.83 4.45 1 21 2 3 4 5 8.5

Iron, dissolved (∝g/L as Fe) 30 9 222 484 <3 1,900 <3 <3 6.5 83 1,050

Lead, dissolved(∝g/L as Pb)

30 30 1.1 0.4 <1 <3 <1 <1 <1 <1 <1

Manganese, dissolved(∝g/L as Mn)

30 2 523 430 <1 2,130 9 172 370.5 1,000 1,370

Molybdenum, dissolved(∝g/L as Mo)

30 0 11.6 6.32 4 38 6 8 10.5 13 17.5

Nickel, dissolved(∝g/L as Ni)

30 1 2.23 1.33 <1 8 1 2 2 3 3

Selenium, dissolved(∝g/L as Se)

30 27 1.2 1.1 <1 7 <1 <1 <1 <1 <1

Table 13. Statistical summary of selected data for wells sampled in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90
87

Silver, dissolved(∝g/L as As)

30 30 1.1 0.4 <1 <3 <1 <1 <1 <1 <1

Uranium, dissolved(∝g/L as U)

30 3 12.1 13.4 <1 62 <1 3 8.5 14 30

Zinc, dissolved (∝g/L as Zn) 30 1 3.53 2.5 <1 14 2 2 3 4 5.5Gross alpha, dissolved(∝g/L as U)

30 0 14 13.8 0.8 67 2 3.9 11 18 33.5

Gross beta, dissolved(pCi/L as SR-90/Y-90)

30 0 11.8 5.83 4.7 29 5.9 7.2 10.5 14 21

Radon-222, total (pCi/L) 18 0 274 56.1 210 440 240 250 260 280 390

Table 13. Statistical summary of selected data for wells sampled in the Rincon Valley study area--Continued

Percentile

Property/constituent No.

No.

<

MRL Mean

Standard

deviation Minimum Maximum 10 25 50 75 90

Concluded
88

Table 14. Drinking water standard or lifetime health advisory for constituents

detected in shallow ground water, range of concentrations in shallow

ground water, and percentage of shallow ground-water samples

exceeding standard or lifetime health advisory

[F, final; D, draft; P, proposed; mg/L, milligrams per liter; ∝g/L, micrograms per liter; <, less than;

pCi/L, picocuries per liter; E, estimated]

Property/constituent

Drinking water

standard or lifetime

health advisory

(U.S. Environmental

Protection Agency,

1996)

Status of

standard

Range of

concentrations in

shallow ground

water

Samples

exceeding

standard or

advisory

(percent)

pH (standard units) 16.5 - 8.5 F 7.01-7.68 0

Sulfate (mg/L as SO4) 1250 F 130-1,700 73

Chloride (mg/L as Cl) 1250 F 67-450 6.7

Fluoride (mg/L as F) 24 F 0.50-2.9 0

Dissolved solids (mg/L) 1500 F 481-3,630 93.3

Nitrite (mg/L as N) 21 F <0.01 - 0.10 0

Nitrite plus nitrate

(mg/L as N)

210 F <0.05 - 33.0 16.7

Aluminum (∝g/L as Al) 150 - 200 F <1 - 6 0

Antimony (∝g/L as Sb) 26 F <1 - <3 0

Arsenic (∝g/L as As) 250 F <1 - 4 0

Barium (∝g/L as Ba) 22,000 F 29 - 110 0

Beryllium (∝g/L as Be) 24 F <1 - <3 0

Cadmium (∝g/L as Cd) 25 F <1 - 4 0

Chromium (∝g/L as Cr) 2100 F <1 - 10 0

Copper (∝g/L as Cu) 31,300 F 1 - 21 0

Iron (∝g/L as Fe) 1300 F <3 - 1,900 16.7

Lead (∝g/L as Pb) 315 F <1 - <3 0
89

1Secondary maximum contaminant level.

2Maximum contaminant level.

3Action level.

4Lifetime health advisory.

5Being remanded.

6Concentration in ∝g/L as uranium; multiply concentration by 0.77 to get concentration in pCi/L.

Manganese

(∝g/L as Mn)

150 F <1 - 2,130 83.3

Molybdenum

(∝g/L as Mo)

440 D 4 - 38 0

Nickel (∝g/L as Ni) 5100 F <1 - 8 0

Selenium (∝g/L as Se) 250 F <1 - 7 0

Silver (∝g/L as Ag) 1100 F <1 - <3 0

Uranium (∝g/L as U) 220 P <1 - 62 13.3

Zinc (∝g/L as Zn) 15,000 F <1 - 14 0

Gross alpha activity

(pCi/L)

215 F 60.8 - 67 23.3

Diazinon (∝g/L) 40.6 F <0.002 - 0.077 0

Metolachlor (∝g/L) 4100 F <0.002 - 5.4 0

Prometon (∝g/L) 4100 F E0.005 - 0.32 0

Xylene (∝g/L) 210,000 F <0.2 - 2.8 0

Table 14. Drinking water standard or lifetime health advisory for constituents

detected in shallow ground water, range of concentrations in shallow

ground water, and percentage of shallow ground-water samples

exceeding standard or lifetime health advisory--Concluded

[F, final; D, draft; P, proposed; mg/L, milligrams per liter; ∝g/L, micrograms per liter; <, less than;

pCi/L, picocuries per liter; E, estimated]

Property/constituent

Drinking water

standard or lifetime

health advisory

(U.S. Environmental

Protection Agency,

1996)

Status of

standard

Range of

concentrations in

shallow ground

water

Samples

exceeding

standard or

advisory

(percent)
90

Table 15. Saturation index for selected minerals and partial pressure of carbon dioxide in

irrigation water and shallow ground water in the Rincon Valley study area

[Values calculated using PHREEQE, Parkhurst and others, 1980]

Well

number

(fig. 8) Calcite Gypsum Barite Fluorite

Amorphous

silica Chalcedony

Partial pressure

of carbon

dioxide

(10-atmospheres)

Irrigation

water,

April 1994

0.77 -1.65 0.58 -1.53 -2.02 -1.15 -3.34

Irrigation

water,

October

1994

0.65 -1.67 0.54 -1.38 -0.91 -0.04 -3.21

1 0.03 -1.92 -0.07 -1.09 -0.90 -0.03 -2.18

2 0.15 -3.35 -1.94 -0.66 -0.57 0.29 -1.65

3 0.21 -1.77 -0.18 -0.92 -0.61 0.26 -2.01

4 0.11 -1.70 0.10 -0.94 -0.56 0.30 -2.06

5 0.51 -1.24 0.40 -1.09 -0.67 0.20 -1.87

6 0.38 -1.13 0.60 -0.90 -0.73 0.13 -2.09

7 0.36 -1.26 0.20 -0.09 -0.67 0.20 -1.90

8 0.11 -1.78 0.23 -0.00 -0.57 0.31 -2.03

9 0.11 -2.01 -0.27 -1.00 -0.60 0.27 -2.03

10 0.33 -1.35 0.58 -0.54 -0.64 0.22 -2.18

11 0.35 -1.15 0.44 -0.64 -0.69 0.18 -2.07

12 0.78 -0.94 0.50 -1.11 -0.69 0.18 -2.09

13 0.01 -2.25 -0.48 -1.09 -0.76 0.11 -2.15

14 0.39 -1.10 0.43 -1.16 -0.75 0.11 -2.02

15 0.14 -1.53 -0.07 -0.77 -0.61 0.26 -2.15

16 0.47 -1.08 0.50 -0.85 -0.68 0.18 -2.15

17 0.02 -1.56 0.32 -1.40 -0.85 0.01 -2.32

18 0.58 -0.74 1.03 -1.27 -0.79 0.10 -2.17

19 0.11 -2.94 -1.34 -0.57 -0.52 0.34 -1.90

20 0.09 -1.53 0.51 -1.54 -0.95 -0.08 -2.42

21 0.37 -1.67 -0.03 -0.61 -0.49 0.37 -1.80

22 0.13 -1.39 0.25 -0.87 -0.63 0.23 -2.28

23 0.49 -0.99 0.74 -1.39 -0.58 0.28 -2.24

24 0.28 -1.06 0.78 -1.40 -0.72 0.14 -2.22

25 -0.23 -3.46 -2.41 0.28 -0.58 0.28 -2.03

26 0.13 -0.54 0.40 -0.64 -0.59 0.27 -2.27

27 0.30 -1.74 -0.48 -1.07 -0.54 0.33 -1.95

28 0.18 -1.34 0.62 -1.23 -0.62 0.24 -2.17

29 0.11 -2.48 -1.09 -0.88 -0.57 0.30 -1.97

30 0.11 -2.50 -0.77 -0.70 -0.71 0.15 -1.95
91

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area

[inst., instantaneous; ∝S/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mm, millimeters; mg/L, milligrams per liter; it. field,

field measurement by incremental titration; gran field, field measurement by gran titration; ammonia + organic, dis., dissolved ammonia plus

organic nitrogen; ∝g/L, micrograms per liter; --, no data; <, less than; E, estimated; lat, latitude; long, longitude]

Date Time

Discharge,

inst.

(cubic

feet

per

second)

Specific

conductance,

field

(∝S/cm)

Specific

conductance,

laboratory

(∝S/cm)

pH

water,

whole,

field

(standard

units)

pH

water,

whole,

laboratory

(standard

units)

Temperature

water

(deg C)

Temperature

air

(deg C)

Barometric

pressure

(mm

of

Hg)

Oxygen,

dissolved

(mg/L)

Hardness,

total

(mg/L

as

CaCO3)

Calcium,

dissolved

(mg/L

as Ca)

08362500 Rio Grande below Caballo Dam (lat 32°53’05”N., long 107°17’31”W.)

01-03-94 1300 8.51 864 874 8.00 8.0 11.0 21.0 657 11.0 180 4604-20-94 0750 1,510 727 719 8.52 7.7 15.5 19.0 655 9.0 170 4910-24-94 1050 328 740 746 8.37 7.6 15.0 17.5 656 9.0 180 5001-03-95 1200 3.3 1,020 1,000 8.00 7.8 12.5 -- 655 10.7 220 61

324056107112103 Rio Grande at Road 187, near Hatch (lat 32°40’56”N., long 107°11’21”W.)

01-06-94 0810 38 1,290 1,280 8.20 7.9 5.0 10.0 653 9.4 360 11004-21-94 1140 1,140 745 734 8.47 8.0 19.5 26.0 657 8.4 180 5110-25-94 1100 302 819 823 8.65 8.0 15.5 14.5 660 9.0 200 5801-03-95 1245 36 1,280 1,280 8.50 7.8 9.0 10.0 662 13.2 360 110

323414106594903 Rio Grande above Rincon Drain, near Rincon (lat 32°34’14”N., long 106°59’49”W.)

01-05-94 1150 44 1,410 1,400 8.40 7.8 8.0 16.5 657 10.3 390 12004-22-94 0940 1,100 765 762 8.51 8.0 17.5 25.0 658 7.5 190 5410-26-94 1030 464 862 872 8.52 7.9 15.5 13.5 662 8.60 210 6101-03-95 1740 45 1,420 1,400 8.50 7.8 8.0 7.0 661 10.2 370 110

324708107164203 Garfield Drain SE of Derry (lat 32°47’08”N., long 107°16’42”W.)

01-04-94 0900 0.65 1,820 1,820 7.80 7.8 5.0 6.5 662 4.8 260 7004-20-94 1040 2.0 1,410 1,400 7.70 7.7 17.5 -- 656 4.9 260 7110-24-94 1340 2.83 1,660 1,680 7.92 7.6 19.0 25.5 656 14.2 270 7701-05-95 0815 0.73 1,730 1,650 8.00 7.6 8.0 -- 650 5.2 270 74
92

 Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Magnesium,

dissolved

(mg/L

as Mg)

Sodium,

dissolved

(mg/L

as Na)

Sodium

adsorption

ratio

Sodium

(percent)

Potassium,

dissolved

(mg/L

as K)

Bicarbonate,

dissolved

it.

field

(mg/L

as

HCO3)

Carbonate,

dissolved

it.

field

(mg/L

as CO3)

Alkalinity,

dissolved

granfield

(mg/L

as

CaCO3)

Sulfate,

dissolved

(mg/L

as SO4)

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)

08362500 Rio Grande below Caballo Dam (lat 32°53’05”N., long 107°17’31”W.)

01-03-94 15 110 4 57 5.2 248 -- 200 140 70 0.604-20-94 12 78 3 49 5.9 164 6 140 130 62 0.610-24-94 13 84 3 49 6.4 158 10 150 120 70 0.701-03-95 16 140 4 57 5.9 289 -- 230 130 98 0.8

324056107112103 Rio Grande at Road 187, near Hatch (lat 32°40’56”N., long 107°11’21”W.)

01-06-94 21 130 3 43 5.7 303 -- 240 300 95 0.604-21-94 13 79 3 48 5.7 180 4 150 130 65 0.610-25-94 14 93 3 49 6.3 174 8 166 140 74 0.701-03-95 20 130 3 44 6.5 297 24 280 280 91 0.6

323414106594903 Rio Grande above Rincon Drain, near Rincon (lat 32°34’14”N., long 106°59’49”W.)

01-05-94 23 150 3 45 6.1 246 16 230 340 110 0.604-22-94 13 83 3 48 6.1 168 8 150 130 65 0.610-26-94 15 97 3 49 6.2 172 11 160 160 78 0.701-03-95 22 150 3 47 6.6 266 8 230 320 120 0.6

324708107164203 Garfield Drain SE of Derry (lat 32°47’08”N., long 107°16’42”W.)

01-04-94 20 270 7 68 17 422 -- 350 340 150 4.904-20-94 19 190 5 60 13 342 -- 280 270 120 3.010-24-94 20 260 7 66 17 402 -- 330 320 140 4.301-05-95 20 250 7 65 17 411 -- 330 320 140 4.9
93

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Silica,

dissolved

(mg/L

as

SiO2)

Dissolved

solids

residue

at 180

deg C

(mg/L)

Nitrite,

dissolved

(mg/L

as N)

Nitrite

+

nitrate,

dissolved

(mg/L

as N)

Ammonia,

dissolved

(mg/L

as N)

Ammonia

+

organic,

dissolved

(mg/L

as N)

Phosphorus,

dissolved

(mg/L

as P)

Orthophosphate,

dissolved

(mg/L

as P)

Total

organic

carbon

(mg/L

as C)

Suspended

organic

carbon

(mg/L

as C)

Dissolved

organic

carbon

(mg/L

as C)

08362500 Rio Grande below Caballo Dam (lat 32°53’05”N., long 107°17’31”W.)

01-03-94 12 534 <0.01 0.12 0.01 <0.2 <0.01 <0.01 -- -- 3.304-20-94 0.96 434 <0.01 <0.05 0.01 0.2 <0.01 <0.01 -- 0.3 4.410-24-94 12 452 0.01 0.07 0.08 0.3 <0.01 <0.01 -- 2.1 4.401-03-95 15 605 <0.01 0.08 0.02 <0.2 <0.01 0.02 7.1 -- 3.6

324056107112103 Rio Grande at Road 187, near Hatch (lat 32°40’56”N., long 107°11’21”W.)

01-06-94 16 864 0.04 0.50 0.05 0.2 0.02 <0.01 -- -- 3.504-21-94 1.5 453 <0.01 <0.05 0.02 0.2 <0.01 <0.01 -- 0.6 4.610-25-94 13 510 0.01 0.11 <0.015 0.2 <0.01 <0.01 -- 1.5 4.001-03-95 16 828 0.02 0.25 0.02 <0.2 <0.01 <0.01 13 -- 3.8

323414106594903 Rio Grande above Rincon Drain, near Rincon (lat 32°34’14”N., long 106°59’49”W.)

01-05-94 14 922 0.02 0.40 0.09 0.2 <0.01 0.01 -- -- 3.504-22-94 1.8 461 <0.01 <0.05 0.04 0.3 <0.01 <0.01 -- 0.5 3.910-26-94 13 544 <0.01 0.08 <0.015 0.3 <0.01 <0.01 -- 1.3 3.501-03-95 15 894 0.01 0.15 0.02 <0.2 <0.01 <0.01 7.3 -- 3.1

324708107164203 Garfield Drain SE of Derry (lat 32°47’08”N., long 107°16’42”W.)

01-04-94 25 1,170 0.03 0.54 0.10 0.3 <0.01 <0.01 -- -- 2.704-20-94 19 856 0.05 0.61 0.07 0.3 <0.01 <0.01 -- 0.3 3.310-24-94 29 1,080 0.08 1.20 0.10 0.3 0.02 0.02 -- 0.4 2.901-05-95 26 1,110 0.04 0.86 0.14 0.3 <0.01 0.02 4.9 -- 3.0
94

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Aluminum,

dissolved

(∝g/L

as Al)

Antimony,

dissolved

(∝g/L

as Sb)

Arsenic,

dissolved

(∝g/L

as As)

Barium,

dissolved

(∝g/L

as Ba)

Beryllium,

dissolved

(∝g/L

as Be)

Boron,

dissolved

(∝g/L

as B)

Bromide,

dissolved

(mg/L

as Br)

Cadmium,

dissolved

(∝g/L

as Cd)

Chromium,

dissolved

(∝g/L

as Cr)

Cobalt,

dissolved

(∝g/L

as Co)

Copper,

dissolved

(∝g/L

as Cu)

Iron,

dissolved

(∝g/L

as Fe)

08362500 Rio Grande below Caballo Dam (lat 32°53’05”N., long 107°17’31”W.)

01-03-94 5 <1 2 63 <1 -- 0.08 <1 3 <1 1 504-20-94 6 <1 2 90 <1 -- 0.06 <1 1 <1 1 <310-24-94 12 <1 3 86 <1 -- 0.06 <1 <1 <1 1 501-03-95 8 <1 2 82 <1 -- -- <1 1 <1 1 7

324056107112103 Rio Grande at Road 187, near Hatch (lat 32°40’56”N., long 107°11’21”W.)

01-06-94 3 <1 1 78 <1 -- 0.21 <1 2 <1 2 604-21-94 9 <1 2 92 <1 -- 0.07 <1 5 <1 <1 610-25-94 11 <1 3 91 <1 -- 0.08 <1 1 <1 1 <301-03-95 3 <1 1 98 <1 200 -- <1 3 <1 2 <3

323414106594903 Rio Grande above Rincon Drain, near Rincon (lat 32°34’14”N., long 106°59’49”W.)

01-05-94 6 <1 2 81 <1 -- 0.22 <1 2 <1 2 404-22-94 12 <1 1 85 <1 -- 0.08 <1 3 <1 <1 710-26-94 9 <1 3 82 <1 -- 0.09 <1 1 <1 1 401-03-95 7 <1 <1 95 <1 210 -- <1 1 <1 3 <3

324708107164203 Garfield Drain SE of Derry (lat 32°47’08”N., long 107°16’42”W.)

01-04-94 3 <1 1 67 <1 -- 0.19 <1 2 <1 3 1504-20-94 7 <1 2 73 <1 -- 0.17 <1 6 <1 1 2810-24-94 5 <1 2 61 <1 -- 0.22 <1 2 <1 1 2201-05-95 3 <1 <1 59 <1 350 -- <1 3 <1 2 18
95

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Lead,

dissolved

(∝g/L

as Pb)

Manganese,

dissolved

(∝g/L

as Mn)

Molybdenum,

dissolved

(∝g/L

as Mo)

Nickel,

dissolved

(∝g/L

as Ni)

Selenium,

dissolved

(∝g/L

as Se)

Silver,

dissolved

(∝g/L

as Ag)

Uranium,

dissolved

(∝g/L

as U)

Zinc,

dissolved

(∝g/L

as Zn)

Atrazine,

dissolved

(∝g/L)

Carbofuran,

dissolved

(∝g/L)

Chlorpyrifos,

dissolved

(∝g/L)

Dacthal

monoacid,

dissolved

(∝g/L)

08362500 Rio Grande below Caballo Dam (lat 32°53’05”N., long 107°17’31”W.)

01-03-94 <1 63 9 <1 <1 <1 5 2 0.002 <0.003 <0.004 <0.01704-20-94 <1 6 6 1 <1 <1 3 2 <0.001 <0.003 <0.004 <0.01710-24-94 3 5 7 2 <1 <1 3 7 <0.001 <0.003 <0.004 <0.01701-03-95 <1 82 8 3 <1 <1 5 1 <0.001 <0.003 <0.004 <0.017

324056107112103 Rio Grande at Road 187, near Hatch (lat 32°40’56”N., long 107°11’21”W.)

01-06-94 1 480 7 <1 <1 <1 7 2 <0.001 <0.003 <0.004 <0.01704-21-94 <1 9 6 <1 <1 <1 3 1 <0.001 <0.003 <0.004 <0.01710-25-94 2 40 7 2 <1 <1 4 5 <0.001 <0.003 <0.004 <0.01701-03-95 <1 460 7 6 <1 <1 6 2 <0.001 <0.003 <0.004 <0.017

323414106594903 Rio Grande above Rincon Drain, near Rincon (lat 32°34’14”N., long 106°59’49”W.)

01-05-94 2 68 8 <1 <1 <1 6 3 <0.001 <0.003 <0.004 <0.01704-22-94 <1 2 7 <1 <1 <1 3 <1 <0.001 <0.003 <0.004 <0.01710-26-94 <1 3 7 3 <1 <1 3 4 <0.001 <0.003 <0.004 <0.01701-03-95 <1 51 7 5 <1 <1 5 2 <0.001 <0.003 <0.004 <0.017

324708107164203 Garfield Drain SE of Derry (lat 32°47’08”N., long 107°16’42”W.)

01-04-94 <1 159 42 3 <1 <1 20 4 <0.001 <0.003 <0.004 <0.01704-20-94 <1 287 22 1 <1 <1 12 1 <0.001 E0.018 <0.004 <0.01710-24-94 2 130 34 3 <1 <1 16 1 <0.001 <0.003 <0.004 --01-05-95 <1 100 34 4 <1 <1 16 2 <0.001 E0.003 <0.004 <0.017
96

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Group A pesticide

surrogates

Group

B

pesticide

surrogate

Date

DCPA,

dissolved

(∝g/L)

Diazinon,

dissolved

(∝g/L)

EPTC,

dissolved

(∝g/L)

Metolachlor,

dissolved

(∝g/L)

Pendimethalin,

dissolved

(∝g/L)

p,p’-

DDE,

dissolved

(∝g/L)

Prometon,

dissolved

(∝g/L)

Simazine,

dissolved

(∝g/L)

Trifluralin,

dissolved

(∝g/L)

Diazinon

(percent

recovery)

HCH

alpha

(percent

recovery)

Terbuthylazine

(percent

recovery)

BDMC

(percent

recovery)

08362500 Rio Grande below Caballo Dam (lat 32°53’05”N., long 107°17’31”W.)

01-03-94 E0.001 E0.001 <0.002 <0.002 <0.004 <0.006 <0.018 E0.004 <0.002 88 96 105 004-20-94 <0.002 <0.002 <0.002 <0.002 <0.004 <0.006 E0.011 <0.005 <0.002 90 88 108 010-24-94 <0.002 <0.002 <0.002 <0.002 <0.004 <0.006 <0.018 0.005 <0.002 92 83 100 E7.001-03-95 <0.002 <0.002 <0.002 <0.002 <0.004 <0.006 <0.018 <0.005 <0.002 101 99 131 83

324056107112103 Rio Grande at Road 187, near Hatch (lat 32°40’56”N., long 107°11’21”W.)

01-06-94 0.004 <0.002 0.010 0.024 <0.004 <0.006 <0.018 <0.005 <0.002 91 91 87 1704-21-94 <0.002 <0.002 <0.002 <0.002 <0.004 <0.006 E0.010 <0.005 <0.002 82 93 112 1010-25-94 0.007 <0.002 <0.002 <0.002 <0.004 <0.006 <0.018 <0.005 <0.002 99 89 97 001-03-95 0.003 <0.002 0.009 0.009 <0.004 <0.006 <0.018 <0.005 <0.002 99 95 107 56

323414106594903 Rio Grande above Rincon Drain, near Rincon (lat 32°34’14”N., long 106°59’49”W.)

01-05-94 0.004 <0.002 0.003 0.018 <0.004 <0.006 <0.018 <0.005 <0.002 86 89 86 1204-22-94 0.008 <0.002 <0.002 0.005 <0.004 <0.006 <0.018 <0.005 <0.002 100 96 106 3410-26-94 0.003 <0.002 <0.002 0.003 <0.004 <0.006 E0.006 0.005 <0.002 93 87 97 001-03-95 0.003 <0.002 0.004 0.009 <0.004 <0.006 <0.018 <0.005 <0.002 122 102 104 80

324708107164203 Garfield Drain SE of Derry (lat 32°47’08”N., long 107°16’42”W.)

01-04-94 0.008 <0.002 <0.002 0.062 <0.004 <0.006 <0.018 <0.005 <0.002 91 96 104 004-20-94 0.007 <0.002 <0.002 0.037 <0.004 <0.006 <0.018 <0.005 <0.002 92 88 109 8610-24-94 <0.002 <0.002 <0.002 0.034 <0.004 <0.006 <0.018 <0.005 <0.002 95 88 98 --01-05-95 <0.002 <0.002 <0.002 0.020 <0.004 <0.006 <0.018 <0.005 <0.002 115 97 116 72
97

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date Time

Discharge,

inst.

(cubic

feet

per

second)

Specific

conductance,

field

(∝S/cm)

Specific

conductance,

laboratory

(∝S/cm)

pH

water,

whole,

field

(standard

units)

pH

water,

whole,

laboratory

(standard

units)

Temperature

water

(deg C)

Temperature

air

(deg C)

Barometric

pressure

(mm

of

Hg)

Oxygen,

dissolved

(mg/L)

Hardness,

total

(mg/L

as

CaCO3)

Calcium,

dissolved

(mg/L

as Ca)

324255107142703 Garfield Drain at Road 390 near Salem (lat 32°42’55”N., long 107°14’27”W.)

01-06-94 1010 0.16 1,590 1,580 7.9 7.7 8.0 14.5 653 7.5 430 13004-20-94 1600 10.8 1,240 1,550 7.52 7.8 22.5 -- 654 8.8 400 12010-24-94 1600 6.17 1,660 1,700 8.05 7.8 18.0 21.0 656 7.8 450 14001-05-95 1040 0.62 1,840 1,860 8.3 8.1 9.0 -- 650 9.9 470 140

324154107124603 Garfield Drain at Road 391, near Salem (lat 32°41’54”N., long 107°12’46”W.)

04-20-94 1350 14 1,390 1,380 8.11 7.9 19.5 34.5 656 9.9 370 110

323931107042003 Rincon Drain 0.5 mile east of 140 near Rincon (lat 32°39’31”N., long 107°04’20”W.)

01-05-94 1430 0.05 1,470 1,470 8.3 7.8 13.0 21.0 659 17.1 400 12004-21-94 1630 0.87 1,220 1,190 8.01 7.8 22.5 -- 655 7.6 350 11010-25-94 1630 0.958 1,230 1,230 8.16 7.8 22.0 20.5 657 7.5 350 11001-04-95 0830 0.04 1,350 1,370 7.8 7.6 4.5 2.0 660 8.8 390 120

323410106594403 Rincon Drain at Rio Grande, near Rincon (lat 32°34’10”N., long 106°59’44”W.)

01-05-94 0920 4.8 1,890 1,910 8.3 7.9 11.0 4.5 559 11.5 490 15004-22-94 0800 15 1,530 1,540 7.88 7.3 18.0 17.5 658 3.2 390 12010-26-94 0840 10.6 1,890 1,910 8.04 7.8 12.5 11.0 662 5.1 510 16001-03-95 1330 4.5 2,140 2,170 8.4 7.6 13.5 14.5 660 14.2 560 170

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

01-04-94 1220 0.13 1,100 1,090 8.1 7.8 8.0 15.5 662 10.4 290 93

324105107122710 Hatch Drain SE of Road 391, near Salem (lat 32°41’05”N., long 107°12’27”W.)

04-21-94 1450 0.42 1,080 1,050 7.86 7.6 24.0 26.0 653 4.6 280 86
98

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Magnesium,

dissolved

(mg/L

as Mg)

Sodium,

dissolved

(mg/L

as Na)

Sodium

adsorption

ratio

Sodium

(percent)

Potassium,

dissolved

(mg/L

as K)

Bicarbonate,

dissolved

it.

field

(mg/L

as

HCO3)

Carbonate,

dissolved

it.

field

(mg/L

as CO3)

Alkalinity,

dissolved

granfield

(mg/L

as

CaCO3)

Sulfate,

dissolved

(mg/L

as SO4)

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)

324255107142703 Garfield Drain at Road 390 near Salem (lat 32°42’55”N., long 107°14’27”W.)

01-06-94 26 170 4 46 7.7 342 -- 280 370 120 0.904-20-94 24 180 4 49 8.9 344 -- 280 360 130 1.310-24-94 25 200 4 48 10 368 -- 300 390 140 1.401-05-95 28 210 4 49 10 361 4 300 440 150 1.5

324154107124603 Garfield Drain at Road 391, near Salem (lat 32°41’54”N., long 107°12’46”W.)

04-20-94 22 160 4 48 8.7 310 -- 250 310 110 1.1

323931107042003 Rincon Drain 0.5 mile east of 140 near Rincon (lat 32°39’31”N., long 107°04’20”W.)

01-05-94 24 150 3 45 6.8 322 10 280 350 110 0.604-21-94 19 120 3 42 6.8 277 -- 220 270 86 0.710-25-94 19 130 3 44 6.9 312 -- 250 270 91 0.701-04-95 22 140 3 43 6.6 332 -- 270 300 100 0.5

323410106594403 Rincon Drain at Rio Grande, near Rincon (lat 32°34’10”N., long 106°59’44”W.)

01-05-94 28 220 4 49 9.8 272 -- 220 550 160 0.704-22-94 23 170 4 48 9.8 254 -- 210 370 140 0.710-26-94 27 220 4 48 10 302 -- 240 510 170 0.801-03-95 32 250 5 49 13 218 18 210 630 180 0.8

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

01-04-94 15 110 3 44 5.3 265 -- 215 230 76 0.8

324105107122710 Hatch Drain SE of Road 391, near Salem (lat 32°41’05”N., long 107°12’27”W.)

04-21-94 15 110 3 46 6.0 254 -- 210 230 77 0.9
99

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Silica,

dissolved

(mg/L

as

SiO2)

Dissolved

solids

residue

at 180

deg C

(mg/L)

Nitrite,

dissolved

(mg/L

as N)

Nitrite

+

nitrate,

dissolved

(mg/L

as N)

Ammonia,

dissolved

(mg/L

as N)

Ammonia +

organic,

dissolved

(mg/L

as N)

Phosphorus,

dissolved

(mg/L

as P)

Orthophosphate,

dissolved

(mg/L

as P)

Total

organic

carbon

(mg/L

as C)

Suspended

organic

carbon

(mg/L

as C)

Dissolved

organic

carbon

(mg/L

as C)

324255107142703 Garfield Drain at Road 390 near Salem (lat 32°42’55”N., long 107°14’27”W.)

001-06-94 17 1,040 0.03 0.57 0.10 0.3 0.03 0.02 -- -- 3.6

04-20-94 19 1,030 0.03 0.53 0.11 0.4 0.01 <0.01 -- 0.7 4.410-24-94 24 1,140 0.03 0.71 0.07 0.3 0.01 0.01 -- 1.1 3.401-05-95 19 1,260 0.02 0.27 0.06 0.3 <0.01 0.01 10 -- 3.7

324154107124603 Garfield Drain at Road 391, near Salem (lat 32°41’54”N., long 107°12’46”W.)

04-20-94 15 892 0.03 0.48 0.09 0.3 <0.01 <0.01 -- 0.4 3.9

323931107042003 Rincon Drain 0.5 mile east of 140 near Rincon (lat 32°39’31”N., long 107°04’20”W.)

01-05-94 15 930 0.02 0.45 0.080 0.3 0.02 0.01 -- -- 4.204-21-94 21 788 0.01 0.40 0.06 0.3 <0.01 <0.01 -- 0.5 3.610-25-94 22 810 <0.01 0.32 0.06 0.3 0.02 0.02 -- 0.7 3.701-04-95 12 938 0.03 0.27 0.07 0.4 <0.01 <0.01 6.0 -- 2.7

323410106594403 Rincon Drain at Rio Grande, near Rincon (lat 32°34’10”N., long 106°59’44”W.)

01-05-94 22 1,320 0.03 0.44 0.14 0.3 0.03 0.02 -- -- 2.904-22-94 16 1,010 0.03 0.44 0.12 0.5 0.02 0.02 -- 0.8 4.910-26-94 24 1,300 0.02 0.63 0.10 0.3 0.02 0.02 -- 0.9 3.201-03-95 26 1,510 0.02 0.50 0.09 0.3 0.03 0.02 3.6 -- 3.3

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

01-04-94 21 736 0.05 0.69 0.15 0.4 0.03 0.030 -- -- 2.7

324105107122710 Hatch Drain SE of Road 391, near Salem (lat 32°41’05”N., long 107°12’27”W.)

04-21-94 19 694 0.01 <0.05 0.04 0.3 0.01 <0.01 -- 0.3 4.4
100

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Aluminum,

dissolved

(∝g/L

as Al)

Antimony,

dissolved

(∝g/L

as Sb)

Arsenic,

dissolved

(∝g/L

as As)

Barium,

dissolved

(∝g/L

as Ba)

Beryllium,

dissolved

(∝g/L

as Be)

Boron,

dissolved

(∝g/L

as B)

Bromide,

dissolved

(mg/L

as Br)

Cadmium,

dissolved

(∝g/L

as Cd)

Chromium,

dissolved

(∝g/L

as Cr)

Cobalt,

dissolved

(∝g/L

as Co)

Copper,

dissolved

(∝g/L

as Cu)

Iron,

dissolved

(∝g/L

as Fe)

324255107142703 Garfield Drain at Road 390 near Salem (lat 32°42’55”N., long 107°14’27”W.)

01-06-94 7 <1 <1 80 <1 -- 0.23 <1 3 <1 2 604-20-94 2 <1 1 70 <1 -- 0.21 <1 3 <1 3 1110-24-94 4 <1 2 62 <1 -- 0.26 <1 2 <1 1 401-05-95 2 <1 <1 71 <1 290 -- <1 3 <1 2 5

324154107124603 Garfield Drain at Road 391, near Salem (lat 32°41’54”N., long 107°12’46”W.)

04-20-94 4 <1 <1 64 <1 -- 0.17 <1 6 <1 1 10

323931107042003 Rincon Drain 0.5 mile east of 140 near Rincon (lat 32°39’31”N., long 107°04’20”W.)

01-05-94 3 <1 <1 110 <1 -- 0.16 <1 2 <1 2 504-21-94 17 <1 1 53 <1 -- 0.15 6 10 <1 32 3010-25-94 5 <1 2 100 <1 -- 0.15 <1 2 <1 <1 301-04-95 5 <1 <1 110 <1 210 -- <1 4 <1 2 5

323410106594403 Rincon Drain at Rio Grande, near Rincon (lat 32°34’10”N., long 106°59’44”W.)

01-05-94 4 <1 2 60 <1 -- 0.28 <1 2 <1 3 404-22-94 4 <1 2 72 <1 -- 0.20 <1 3 <1 4 1710-26-94 4 <1 2 73 <1 -- 0.31 <1 2 <1 2 <301-03-95 5 <1 2 63 <1 400 -- <1 1 <1 4 <9

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

01-04-94 3 <1 1 110 <1 -- 0.14 <1 2 <1 2 4

324105107122710 Hatch Drain SE of Road 391, near Salem (lat 32°41’05”N., long 107°12’27”W.)

04-21-94 6 <1 2 75 <1 -- 0.12 <1 6 <1 <1 61
101

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Lead,

dissolved

(∝g/L

as Pb)

Manganese,

dissolved

(∝g/L

as Mn)

Molybdenum,

dissolved

(∝g/L

as Mo)

Nickel,

dissolved

(∝g/L

as Ni)

Selenium,

dissolved

(∝g/L

as Se)

Silver,

dissolved

(∝g/L

as Ag)

Uranium,

dissolved

(∝g/L

as U)

Zinc,

dissolved

(∝g/L

as Zn)

Atrazine,

dissolved

(∝g/L)

Carbofuran,

dissolved

(∝g/L)

Chlorpyrifos,

dissolved

(∝g/L)

Dacthal

monoacid,

dissolved

(∝g/L)

324255107142703 Garfield Drain at Road 390 near Salem (lat 32°42’55”N., long 107°14’27”W.)

01-06-94 1 657 10 <1 <1 <1 8 2 <0.001 <0.003 <0.004 <0.01704-20-94 <1 178 13 1 <1 <1 9 3 <0.001 E0.048 0.005 <0.01710-24-94 1 128 13 5 <1 <1 8 9 <0.001 <0.003 <0.004 <0.01701-05-95 <1 277 12 8 <1 <1 8 2 <0.001 <0.003 <0.004 <0.017

324154107124603 Garfield Drain at Road 391, near Salem (lat 32°41’54”N., long 107°12’46”W.)

04-20-94 <1 33 11 2 <1 <1 8 2 <0.001 E0.15 0.010 <0.017

323931107042003 Rincon Drain 0.5 mile east of 140 near Rincon (lat 32°39’31”N., long 107°04’20”W.)

01-05-94 1 758 9 1 <1 <1 5 2 <0.001 <0.003 <0.004 <0.01704-21-94 <1 242 9 2 <1 <1 5 3 <0.001 E0.047 <0.004 <0.01710-25-94 <1 542 8 5 <1 <1 3 <1 <0.001 <0.003 <0.004 <0.01701-04-95 <1 1,220 6 9 <1 <1 3 1 <0.001 <0.003 <0.004 <0.017

323410106594403 Rincon Drain at Rio Grande, near Rincon (lat 32°34’10”N., long 106°59’44”W.)

01-05-94 3 341 10 2 <1 <1 5 2 <0.001 <0.003 <0.004 <0.01704-22-94 <1 129 8 2 <1 <1 5 5 <0.001 E0.052 <0.004 <0.01710-26-94 <1 224 9 6 <1 <1 5 3 <0.001 <0.003 <0.004 0.1301-03-95 <1 386 9 8 1 <1 5 2 <0.001 <0.003 <0.004 <0.017

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

01-04-94 <1 796 13 2 <1 <1 10 3 <0.001 <0.003 <0.004 <0.017

324105107122710 Hatch Drain SE of Road 391, near Salem (lat 32°41’05”N., long 107°12’27”W.)

04-21-94 <1 459 12 <1 <1 <1 7 1 <0.001 E0.019 <0.004 <0.017
102

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Group A pesticide

surrogates

Group

B

pesticide

surrogate

Date

DCPA,

dissolved

(∝g/L)

Diazinon,

dissolved

(∝g/L)

EPTC,

dissolved

(∝g/L)

Metolachlor,

dissolved

(∝g/L)

Pendimethalin,

dissolved

(∝g/L)

p,p’-

DDE,

dissolved

(∝g/L)

Prometon,

dissolved

(∝g/L)

Simazine,

dissolved

(∝g/L)

Trifluralin,

dissolved

(∝g/L)

Diazinon

(percent

recovery)

HCH

alpha

(percent

recovery)

Terbuth

ylazine

(percent

recovery)

BDMC

(percent

recovery)

324255107142703 Garfield Drain at Road 390 near Salem (lat 32°42’55”N., long 107°14’27”W.)

01-06-94 0.010 <0.002 <0.002 0.007 <0.004 <0.006 <0.018 <0.005 <0.002 91 85 84 2004-20-94 0.036 <0.002 <0.002 0.013 <0.004 <0.006 <0.018 <0.005 <0.002 79 91 110 2410-24-94 0.004 <0.002 <0.002 0.007 <0.004 <0.006 <0.018 <0.005 <0.002 90 85 89 E4.001-05-94 0.013 <0.002 <0.002 0.008 <0.004 <0.006 <0.018 <0.005 <0.002 132 115 126 47

324154107124603 Garfield Drain at Road 391, near Salem (lat 32°41’54”N., long 107°12’46”W.)

04-20-94 0.056 <0.002 <0.002 0.020 <0.004 E0.002 <0.018 0.005 <0.002 85 82 103 17

323931107042003 Rincon Drain 0.5 mile east of 140 near Rincon (lat 32°39’31”N., long 107°04’20”W.)

01-05-94 0.002 <0.002 E0.001 <0.002 <0.004 <0.006 <0.018 <0.005 <0.002 91 87 80 10004-21-94 <0.002 <0.002 <0.002 <0.002 <0.004 E0.001 <0.018 <0.005 <0.002 95 76 107 7610-25-94 <0.002 <0.002 <0.002 <0.002 <0.004 <0.006 <0.018 <0.005 <0.002 95 90 103 E1001-04-95 0.003 <0.002 <0.002 0.003 <0.004 <0.006 <0.018 <0.005 <0.002 95 114 111 64

323410106594403 Rincon Drain at Rio Grande, near Rincon (lat 32°34’10”N., long 106°59’44”W.)

01-05-94 0.004 <0.002 <0.002 0.008 <0.004 E0.002 <0.018 <0.005 E0.001 92 96.5 104 1004-22-94 0.17 0.004 <0.002 0.003 <0.004 E0.001 <0.018 <0.005 <0.002 98 83 114 8210-26-94 0.21 <0.002 <0.002 0.013 <0.004 E0.002 <0.018 <0.005 <0.002 98 89 97 1.001-03-95 0.007 <0.002 <0.002 0.003 <0.004 <0.006 E0.007 <0.005 <0.002 114 100 119 60

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

01-04-94 <0.002 <0.002 <0.002 <0.002 <0.004 <0.006 <0.018 <0.005 <0.002 86 94 97 34

324105107122710 Hatch Drain SE of Road 391, near Salem (lat 32°41’05”N., long 107°12’27”W.)

04-21-94 0.012 <0.002 <0.002 0.12 0.033 E0.001 <0.018 <0.005 <0.002 87 92 108 8.0
103

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date Time

Discharge,

inst.

(cubic

feet

per

second)

Specific

conductance,

field

(∝S/cm)

Specific

conductance,

laboratory

(∝S/cm)

pH

water,

whole,

field

(standard

units)

pH

water,

whole,

laboratory

(standard

units)

Temperature

water

(deg C)

Temperature

air

(deg C)

Barometric

pressure

(mm

of

Hg)

Oxygen,

dissolved

(mg/L)

Hardness,

total

(mg/L

CaCO3)

Calcium,

dissolved

(mg/L

as Ca)

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

10-25-94 0830 0.447 1,040 1,030 7.99 7.7 14.5 11.5 659 5.7 290 9301-04-95 0830 0.17 1,130 1,100 8.2 7.5 5.0 6.5 665 8.0 300 95

323917107055603 Hatch Drain at Rio Grande, near Hatch (lat 32°39’17”N., long 107°05’56”W.)

01-04-94 1450 0.44 1,690 1,690 8.7 8.1 8.0 14.0 662 15.3 390 12004-21-94 0730 7.5 1,540 1,530 7.94 7.6 16.0 12.0 658 4.7 400 12010-25-94 1450 3.76 1,570 1,580 8.36 8.0 16.0 19.0 659 8.50 420 13001-04-95 1150 0.02 1,530 1,540 8.5 7.9 7.0 5.5 658 11.4 370 110
104

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Magnesium,

dissolved

(mg/L

as Mg)

Sodium,

dissolved

(mg/L

as Na)

Sodium

adsorption

ratio

Sodium

(percent)

Potassium,

dissolved

(mg/L

as K)

Bicarbonate,

dissolved,

it.

field

(mg/L

as

HCO3)

Carbonate,

dissolved,

it.

field

(mg/L

as CO3)

Alkalinity,

dissolved,

granfield

(mg/L

as

CaCO3)

Sulfate,

dissolved

(mg/L

as SO4)

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

10-25-94 15 110 3 44 6.0 256 -- 210 220 75 0.8001-04-95 15 100 3 42 5.5 249 -- 200 240 80 0.70

323917107055603 Hatch Drain at Rio Grande, near Hatch (lat 32°39’17”N., long 107°05’56”W.)

01-04-94 23 190 4 50 10 342 -- 280 400 130 0.8004-21-94 24 170 4 48 8.0 321 -- 260 370 130 0.8010-25-94 23 180 4 48 8.8 311 16 280 370 130 0.9001-04-95 22 180 4 51 9.7 304 14 270 340 120 0.80
105

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Silica,

dissolved

(mg/L

as

SiO2)

Dissolved

solids

residue

at 180

deg C

(mg/L)

Nitrite,

dissolved

(mg/L

as N)

Nitrite

+

nitrate,

dissolved

(mg/L

as N)

Ammonia,

dissolved

(mg/L

as N)

Ammonia +

organic,

dissolved

(mg/L

as N)

Phosphorus,

dissolved

(mg/L

as P)

Orthophosphate,

dissolved

(mg/L

as P)

Total

organic

carbon

(mg/L

as C)

Suspended

organic

carbon

(mg/L

as C)

Dissolved

organic

carbon

(mg/L

as C)

Aluminum,

dissolved

(∝g/L

as Al)

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

10-25-94 25 680 0.05 1.10 0.11 0.20 0.02 0.03 -- 0.3 0.8 401-04-95 17 743 0.03 0.25 0.28 0.40 0.01 0.01 5.5 -- -- 3

323917107055603 Hatch Drain at Rio Grande, near Hatch (lat 32°39’17”N., long 107°05’56”W.)

01-04-94 32 1,170 0.11 3.30 0.06 0.50 0.73 0.73 -- -- 4.8 1104-21-94 23 1,040 0.08 0.54 0.27 0.60 0.18 0.19 -- 1.1 4.3 410-25-94 29 1,060 0.04 1.20 0.10 0.40 0.19 0.19 -- 0.3 4.0 401-04-95 29 1,030 0.09 2.60 0.33 1.1 0.37 0.40 7.2 -- 4.6 4
106

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Antimony,

dissolved

(∝g/L

as Sb)

Arsenic,

dissolved

(∝g/L

as As)

Barium,

dissolved

(∝g/L

as Ba)

Beryllium,

dissolved

(∝g/L

as Be)

Boron,

dissolved

(∝g/L

as B)

Bromide,

dissolved

(mg/L

as Br)

Cadmium,

dissolved

(∝g/L

as Cd)

Chromium,

dissolved

(∝g/L

as Cr)

Cobalt,

dissolved

(∝g/L

as Co)

Copper,

dissolved

(∝g/L

as Cu)

Iron,

dissolved

(∝g/L

as Fe)

Lead,

dissolved

(∝g/L

as Pb)

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

10-25-94 <1 2 93 <1 -- 0.15 <1 2 <1 1 15 301-04-95 <1 <1 120 <1 170 -- <1 4 <1 1 4 <1

323917107055603 Hatch Drain at Rio Grande, near Hatch (lat 32°39’17”N., long 107°05’56”W.)

01-04-94 <1 2 37 <1 -- 0.22 <1 3 <1 4 40 <104-21-94 <1 2 66 <1 -- 0.23 <1 3 <1 3 17 <110-25-94 <1 2 69 <1 -- 0.24 <1 2 <1 3 <3 <101-04-95 <1 3 45 <1 310 -- <1 2 <1 2 <3 <1
107

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Continued

Date

Manganese,

dissolved

(∝g/L

as Mn)

Molybdenum,

dissolved

(∝g/L

as Mo)

Nickel,

dissolved

(∝g/L

as Ni)

Selenium,

dissolved

(∝g/L

as Se)

Silver,

dissolved

(∝g/L

as Ag)

Uranium,

dissolved

(∝g/L

as U)

Zinc,

dissolved

(∝g/L

as Zn)

Atrazine,

dissolved

(∝g/L)

Carbofuran,

dissolved

(∝g/L)

Chlorpyrifos,

dissolved

(∝g/L)

Dacthal

monoacid,

dissolved

(∝g/L)

DCPA,

dissolved

(∝g/L)

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

10-25-94 483 10 3 <1 <1 5 <1 <0.001 <0.003 <0.004 <0.017 <0.00201-04-95 940 11 7 <1 <1 8 6 <0.001 <0.003 <0.004 <0.017 E0.001

323917107055603 Hatch Drain at Rio Grande, near Hatch (lat 32°39’17”N., long 107°05’56”W.)

01-04-94 41 10 2 <1 <1 7 11 <0.001 <0.003 <0.004 <0.017 0.01604-21-94 167 10 1 <1 <1 7 4 <0.001 E0.037 <0.004 <0.017 0.04610-25-94 99 12 5 <1 <1 6 1 <0.001 <0.003 <0.004 E0.11 0.07101-04-95 73 9 5 <1 <1 4 2 <0.001 <0.003 <0.004 <0.017 0.062
108

Appendix A. Surface-water-quality data for selected sites in the Rincon Valley study area--Concluded

Group A pesticide

surrogates

Group

B

pesticide

surrogate

Date

Diazinon,

dissolved

(∝g/L)

EPTC,

dissolved

(∝g/L)

Metolachlor,

dissolved

(∝g/L)

Pendimethalin,

dissolved

(∝g/L)

p,p’-

DDE,

dissolved

(∝g/L)

Prometon,

dissolved

(∝g/L)

Simazine,

dissolved

(∝g/L)

Trifluralin,

dissolved

(∝g/L)

Diazinon

(percent

recovery)

HCH

alpha

(percent

recovery)

Terbuth

ylazine

(percent

recovery)

BDMC

(percent

recovery)

324121107124603 Hatch Drain at Road 391, near Salem (lat 32°41’21”N., long 107°12’46”W.)

10-25-94 <0.002 <0.002 0.005 <0.004 <0.006 <0.018 <0.005 <0.002 86 80 88 0.0001-04-95 <0.002 <0.002 0.004 <0.004 E0.002 <0.018 <0.005 <0.002 106 104 110 70

323917107055603 Hatch Drain at Rio Grande, near Hatch (lat 32°39’17”N., long 107°05’56”W.)

01-04-94 0.022 <0.002 0.050 <0.004 <0.006 <0.018 <0.005 <0.002 95 97 115 1504-21-94 <0.002 <0.002 0.10 <0.004 <0.006 <0.018 <0.005 <0.002 80 95 118 2210-25-94 <0.002 0.009 0.027 <0.004 <0.006 <0.018 <0.005 <0.002 98 87 103 E9.001-04-95 <0.002 <0.002 0.41 <0.004 <0.006 <0.018 <0.005 <0.002 105 98 106 79
109

Appendix B. Shallow ground-water-quality data for wells sampled in the Rincon Valley study area

[∝S/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mm, millimeters; mg/L, milligrams per liter; it. field, field measurement by

incremental titration; gran field, field measurement by gran titration; ∝g/L, micrograms per liter; count, 2 sigma, 2-sigma percision estimate of

analysis; pCi/L, picocuries per liter; <, less than; >, greater than; --, no data; E, estimated]

Wellnumber(fig. 8) Latitude Longitude Date Time

Altitude of

land

surface

datum

(feet above

sea level)

Depth of

well (feet)

Waterlevel depth

below land

surface

(feet)

Specific

conductance,

field

(∝S/cm)

pH water,

whole field

(standard

units)

pH water,

whole

laboratory

(standard

units)

Temperature

water

(deg C)

Temperature air

(deg C)

1 32°47’14"N. 107°18’02"W. 04-25-94 1000 4,110 18.32 10.11 1,000 7.39 7.3 15.0 10.52 32°48’55"N. 107°18’46"W. 04-26-94 1340 4,135 22.87 11.02 2,180 7.10 7.2 19.0 23.03 32°49’55"N. 107°18’09"W. 04-19-94 1020 4,135 17.49 6.62 1,490 7.35 7.2 16.0 30.04 32°50’02"N. 107°18’12"W. 04-19-94 1420 4,135 20.27 7.80 1,200 7.37 7.2 18.0 24.55 32°51’23"N. 107°17’57"W. 05-03-94 0940 4,140 21.83 8.20 1,930 7.35 7.3 18.0 11.56 32°51’21"N. 107°17’26"W. 05-07-94 1140 4,140 20.9 9.50 1,450 7.53 7.6 18.5 25.07 32°47’38"N. 107°16’52"W. 04-26-94 0930 4,118 16.94 6.16 1,840 7.46 7.5 16.0 12.08 32°46’28"N. 107°16’34"W. 04-23-94 0850 4,108 15.04 6.77 1,380 7.41 7.5 15.0 14.59 32°46’12"N. 107°16’38"W. 04-23-94 1300 4,107 19.98 7.92 1,090 7.35 7.4 17.0 29.0

10 32°45’10"N. 107°16’26"W. 04-23-94 1620 4,104 18.35 8.15 1,270 7.63 7.4 19.0 29.5

11 32°44’19"N. 107°16’08"W. 04-24-94 1630 4,090 23.08 11.78 1,420 7.53 7.4 18.0 28.5

12 32°40’59"N. 107°12’23"W. 04-27-94 0940 4,060 19.89 6.97 1,700 7.68 7.7 18.0 12.513 32°41’22"N. 107°12’08"W. 04-28-94 0930 4,062 22.04 12.24 1,740 7.27 7.3 16.0 12.514 32°42’02"N. 107°14’31"W. 04-28-94 1430 4,075 24.19 12.28 1,500 7.48 7.5 18.0 20.515 32°42’36"N. 107°13’37"W. 05-02-94 1420 4,078 17.47 5.74 1,970 7.35 7.2 16.0 26.516 32°42’57"N. 107°14’26"W. 04-22-94 1530 4,080 20.27 8.02 1,400 7.59 7.6 18.0 28.017 32°44’22"N. 107°15’22"W. 05-02-94 1700 4,098 23.18 12.11 790 7.53 7.4 17.0 28.018 32°40’41"N. 107°10’00"W. 04-24-94 0900 4,053 16.06 5.48 2,270 7.64 7.4 10.0 16.019 32°40’21"N. 107°11’43"W. 04-27-94 1410 4,065 16.98 6.70 1,820 7.18 7.3 17.0 17.520 32°39’59"N. 107°07’54"W. 04-18-94 1430 4,050 20.76 9.61 800 7.62 7.4 16.0 30.021 32°39’26"N. 107°07’51"W. 05-06-94 0930 4,040 21.5 5.61 1,890 7.31 7.3 18.5 18.022 32°39’20"N. 107°06’46"W. 05-07-94 1430 4,050 22.9 11.2 1,000 7.54 7.6 18.5 27.523 32°35’27"N. 107°00’07"W. 05-04-94 0930 4,007 15.07 3.92 1,520 7.62 7.5 17.0 12.524 32°36’01"N. 107°01’00"W. 05-04-94 1230 4,008 14.89 5.63 1,360 7.51 7.5 17.5 31.525 32°37’22"N. 107°00’28"W. 05-04-94 1520 4,008 23.02 9.63 5,280 7.01 7.1 19.5 33.526 32°37’33"N. 107°01’10"W. 05-06-94 1230 4,008 18.1 6.45 2,270 7.40 7.4 18.0 28.527 32°38’02"N. 107°02’41"W. 05-06-94 1520 4,020 16.9 5.84 3,420 7.25 7.3 17.5 31.528 32°38’52"N. 107°03’38"W. 05-07-94 0830 4,027 18.3 8.74 1,160 7.50 7.5 17.5 13.029 32°39’17"N. 107°03’16"W. 05-05-94 1500 4,025 18.17 6.30 1,990 7.23 7.2 17.0 35.030 32°39’30"N. 107°04’14"W. 05-05-94 1000 4,030 23.25 10.78 1,290 7.23 7.6 18.5 15.5
110

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Continued

Well

number

(fig. 8) Latitude Longitude

Barometric

pressure

(mm of

Hg)

Oxygen,

dissolved

(mg/L)

Hardness,

total

(mg/L as

CaCO3)

Calcium,

dissolved

(mg/L as

Ca)

Magnesium,

dissolved

(mg/L as

Mg)

Sodium,

dissolved

(mg/L as

Na)

Sodium

adsorption

ratio

Sodium

(percent)

Potassium,

dissolved

(mg/L as

K)

Bicarbonate,

dissolved

it. field

(mg/L as

HCO3)

1 32°47’14"N. 107°18’02"W. 651 4.2 300 97 15 100 2 41 5.1 270

2 32°48’55"N. 107°18’46"W. 649 1.1 490 150 28 300 6 57 5.8 5233 32°49’55"N. 107°18’09"W. 656 0.2 420 130 24 170 4 46 5.5 3894 32°50’02"N. 107°18’12"W. 654 0.1 290 96 13 140 4 51 3.7 3035 32°51’23"N. 107°17’57"W. 655 0.2 620 200 30 200 3 41 7.4 5166 32°51’21"N. 107°17’26"W. 657 0.2 360 110 20 190 4 53 6.9 3437 32°47’38"N. 107°16’52"W. 650 0.2 350 100 24 260 6 61 16 5108 32°46’28"N. 107°16’34"W. 654 1.8 290 82 20 190 5 58 7.6 3779 32°46’12"N. 107°16’38"W. 653 0.1 310 98 15 100 2 41 5.6 321

10 32°45’10"N. 107°16’26"W. 651 0.2 250 72 17 160 4 57 9.3 338

11 32°44’19"N. 107°16’08"W. 649 0.3 310 99 15 170 4 54 7.0 255

12 32°40’59"N. 107°12’23"W. 652 0.1 470 150 22 200 4 48 6.9 47813 32°41’22"N. 107°12’08"W. 658 1.1 510 160 26 180 3 43 9.9 34114 32°42’02"N. 107°14’31"W. 655 0.2 390 120 23 160 4 46 7.6 38415 32°42’36"N. 107°13’37"W. 653 0.9 510 160 28 230 4 49 10 36516 32°42’57"N. 107°14’26"W. 652 0.7 390 120 23 140 3 43 7.2 33917 32°44’22"N. 107°15’22"W. 650 2.1 220 69 11 77 2 43 5.3 19918 32°40’41"N. 107°10’00"W. 653 0.1 610 180 40 270 5 48 13 43419 32°40’21"N. 107°11’43"W. 650 0.8 560 170 33 170 3 39 7.7 373

20 32°39’59"N. 107°07’54"W. 657 5.6 230 70 14 73 2 40 4.8 192

21 32°39’26"N. 107°07’51"W. 656 0.1 470 140 30 240 5 52 7.4 54622 32°39’20"N. 107°06’46"W. 656 0.1 260 80 15 110 3 47 4.2 22023 32°35’27"N. 107°00’07"W. 660 0.2 450 140 25 140 3 40 7.0 30024 32°36’01"N. 107°01’00"W. 658 0.3 430 130 25 110 2 35 6.3 25425 32°37’22"N. 107°00’28"W. 656 0.1 880 270 49 920 14 69 19 69426 32°37’33"N. 107°01’10"W. 657 0.2 620 220 18 250 4 46 13 17427 32°38’02"N. 107°02’41"W. 656 0.1 910 250 70 460 7 52 9.6 64128 32°38’52"N. 107°03’38"W. 658 1.3 290 89 17 120 3 45 21 26929 32°39’17"N. 107°03’16"W. 655 0.2 540 160 35 210 4 45 7.4 37430 32°39’30"N. 107°04’14"W. 660 0.2 440 140 23 100 2 32 8.4 327
111

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Continued

Well

number

(fig. 8) Latitude Longitude

Alkalinity,

dissolved,

gran field

(mg/L as

CaCO3)

Sulfate,

dissolved

(mg/L as

SO4)

Chloride,

dissolved

(mg/L as

Cl)

Fluoride,

dissolved

(mg/L as F)

Silica,

dissolved

(mg/L as

SiO2)

Dissolved

solids,

residue at

180 deg C

(mg/L)

Nitrite,

dissolved

(mg/L as

N)

Nitrite +

nitrate,

dissolved

(mg/L as

N)

Ammonia,

dissolved

(mg/L as

N)

1 32°47’14"N. 107°18’02"W. 220 200 72 0.70 12 664 <0.01 1.20 0.022 32°48’55"N. 107°18’46"W. 430 510 120 1.1 28 1,500 0.09 19.0 0.023 32°49’55"N. 107°18’09"W. 320 330 100 0.80 24 1,010 0.02 2.00 <0.014 32°50’02"N. 107°18’12"W. 250 200 77 0.90 28 776 0.10 13.0 <0.015 32°51’23"N. 107°17’57"W. 420 470 130 0.60 22 1,350 <0.01 <0.05 0.106 32°51’21"N. 107°17’26"W. 280 300 120 1.0 19 910 0.06 3.20 0.027 32°47’38"N. 107°16’52"W. 420 370 120 2.6 21 1,130 0.10 6.80 0.028 32°46’28"N. 107°16’34"W. 310 250 100 2.8 26 882 0.06 4.30 0.019 32°46’12"N. 107°16’38"W. 260 190 73 0.80 25 680 <0.01 <0.05 0.20

10 32°45’10"N. 107°16’26"W. 270 230 93 1.8 24 788 0.02 0.11 0.02

11 32°44’19"N. 107°16’08"W. 290 310 94 1.4 21 894 <0.01 0.12 0.02

12 32°40’59"N. 107°12’23"W. 390 370 120 0.70 21 1,150 0.01 <0.05 0.3313 32°41’22"N. 107°12’08"W. 280 450 130 0.60 17 1,200 0.03 1.20 0.0214 32°42’02"N. 107°14’31"W. 310 340 98 0.70 18 990 0.02 0.31 0.0215 32°42’36"N. 107°13’37"W. 300 480 150 0.90 24 1,370 0.06 19.0 0.0316 32°42’57"N. 107°14’26"W. 270 300 100 1.0 21 888 <0.01 0.23 0.0217 32°44’22"N. 107°15’22"W. 160 130 67 0.60 14 481 <0.01 0.21 0.0318 32°40’41"N. 107°10’00"W. 350 620 170 0.50 14 1,550 0.09 3.40 0.0519 32°40’21"N. 107°11’43"W. 300 380 110 1.1 30 1,280 0.03 33.0 0.02

20 32°39’59"N. 107°07’54"W. 160 130 72 0.50 11 486 <0.01 0.16 <0.0121 32°39’26"N. 107°07’51"W. 450 430 110 1.2 33 1,300 <0.01 <0.05 0.3122 32°39’20"N. 107°06’46"W. 180 180 68 1.1 24 629 0.06 9.60 0.0223 32°35’27"N. 107°00’07"W. 240 330 150 0.50 26 1,000 <0.01 <0.05 0.2524 32°36’01"N. 107°01’00"W. 210 310 120 0.50 19 868 <0.01 0.38 0.0825 32°37’22"N. 107°00’28"W. 560 1,700 450 2.9 27 3,630 0.05 0.57 0.1626 32°37’33"N. 107°01’10"W. 140 820 170 1.1 26 1,680 <0.01 <0.05 0.0527 32°38’02"N. 107°02’41"W. 520 980 290 0.60 29 2,420 <0.01 <0.05 0.2328 32°38’52"N. 107°03’38"W. 220 210 100 0.70 24 702 <0.01 0.05 0.1329 32°39’17"N. 107°03’16"W. 310 410 130 0.80 27 1,360 0.04 31.0 0.0430 32°39’30"N. 107°04’14"W. 270 270 83 1.0 20 854 0.08 5.60 0.03
112

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Continued

Well

number

(fig. 8) Latitude Longitude

Ammonia

+ organic,

dissolved

(mg/L as

N)

Phosphorus,

dissolved

(mg/L as

P)

Orthophosphate,

dissolved

(mg/L as P)

Dissolved

organic

carbon

(mg/L as

C)

Aluminum,

dissolved

(∝g/L as Al)

Antimony,

dissolved

(∝g/L as

Sb)

Arsenic,

dissolved

(∝g/L as

As)

Barium,

dissolved

(∝g/L as

Ba)

Beryllium,

dissolved

(∝g/L as

Be)

Bromide,

dissolved

(mg/L as

Br)

1 32°47’14"N. 107°18’02"W. <0.2 0.02 <0.01 2.1 1 <1 <1 66 <1 0.142 32°48’55"N. 107°18’46"W. 0.3 0.04 0.05 3.6 <1 <1 3 43 <1 0.503 32°49’55"N. 107°18’09"W. 0.2 <0.01 0.01 3.3 1 <1 1 52 <1 0.264 32°50’02"N. 107°18’12"W. 0.2 <0.01 0.01 2.8 2 <1 2 69 <1 0.155 32°51’23"N. 107°17’57"W. <0.2 <0.01 0.01 2.4 <1 <1 <1 100 <1 0.406 32°51’21"N. 107°17’26"W. 0.2 <0.01 0.01 1.4 3 <1 2 78 <1 0.317 32°47’38"N. 107°16’52"W. 0.3 <0.01 0.01 3.7 <1 <1 1 33 <1 0.278 32°46’28"N. 107°16’34"W. 0.2 0.05 0.06 2.2 <1 <1 3 83 <1 0.249 32°46’12"N. 107°16’38"W. 0.3 <0.01 0.02 2.2 <1 <1 <1 56 <1 0.23

10 32°45’10"N. 107°16’26"W. <0.2 0.07 0.05 2.2 2 <1 4 81 <1 0.17

11 32°44’19"N. 107°16’08"W. <0.2 0.02 0.02 2.6 5 <1 2 51 <1 0.21

12 32°40’59"N. 107°12’23"W. 0.5 0.05 0.06 3.1 <1 <1 2 55 <1 0.2713 32°41’22"N. 107°12’08"W. 0.2 <0.01 <0.01 3.0 2 <1 <1 94 <1 0.3014 32°42’02"N. 107°14’31"W. 0.3 <0.01 <0.01 2.9 2 <1 <1 52 <1 0.1315 32°42’36"N. 107°13’37"W. 0.4 0.05 0.05 3.7 <1 <1 3 49 <1 0.3616 32°42’57"N. 107°14’26"W. <0.2 0.06 0.05 2.4 2 <1 2 59 <1 0.2617 32°44’22"N. 107°15’22"W. <0.2 0.03 0.03 1.6 1 <1 2 61 <1 0.3618 32°40’41"N. 107°10’00"W. 0.3 <0.01 0.01 3.8 2 <1 <1 110 <1 0.4319 32°40’21"N. 107°11’43"W. 0.8 0.03 0.02 2.5 <1 <1 2 70 <1 0.3920 32°39’59"N. 107°07’54"W. <0.2 0.02 0.02 1.9 6 <1 2 85 <1 0.1321 32°39’26"N. 107°07’51"W. 1.2 0.13 0.05 3.4 <1 <1 <1 69 <1 0.3622 32°39’20"N. 107°06’46"W. 0.5 0.01 0.02 4.1 2 <1 1 44 <1 0.1323 32°35’27"N. 107°00’07"W. 1.2 0.01 <0.01 2.8 1 <1 <1 96 <1 0.2524 32°36’01"N. 107°01’00"W. 0.3 0.04 0.05 2.6 2 <1 3 110 <1 0.2225 32°37’22"N. 107°00’28"W. 0.3 0.03 0.04 4.1 <3 <3 2 35 <3 0.9726 32°37’33"N. 107°01’10"W. 1.5 0.08 0.02 1.1 <1 <1 2 29 <1 0.5327 32°38’02"N. 107°02’41"W. 0.7 0.07 0.05 5.3 <2 <2 3 49 <2 0.6328 32°38’52"N. 107°03’38"W. 0.3 0.05 0.06 2.6 2 <1 2 99 <1 0.1529 32°39’17"N. 107°03’16"W. 0.3 0.02 0.01 3.4 <1 <1 2 41 <1 0.3130 32°39’30"N. 107°04’14"W. 0.3 <0.01 0.01 2.7 <1 <1 1 82 <1 0.16
113

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Continued

Well

number

(fig. 8) Latitude Longitude

Cadmium,

dissolved

(∝g/L as

Cd)

Chromium,

dissolved

(∝g/L as Cr)

Cobalt,

dissolved

(∝g/L as

Co)

Copper,

dissolved

(∝g/L as

Cu)

Iron,

dissolved

(∝g/L as

Fe)

Lead,

dissolved

(∝g/L as

Pb)

Manganese,

dissolved

(∝g/L as

Mn)

Molybdenum,

dissolved

(∝g/L as

Mo)

Nickel,

dissolved

(∝g/L as

Ni)

Selenium,

dissolved

(∝g/L as

Se)

1 32°47’14"N. 107°18’02"W. <1 3 <1 2 5 <1 1 6 2 <1

2 32°48’55"N. 107°18’46"W. <1 7 <1 5 <3 <1 110 10 3 7

3 32°49’55"N. 107°18’09"W. <1 3 <1 3 8 <1 250 11 2 <1

4 32°50’02"N. 107°18’12"W. <1 4 <1 1 3 <1 28 9 2 <1

5 32°51’23"N. 107°17’57"W. <1 5 <1 4 1,200 <1 1,650 7 2 <16 32°51’21"N. 107°17’26"W. <1 1 <1 4 <3 <1 470 12 1 <1

7 32°47’38"N. 107°16’52"W. <1 5 <1 3 7 <1 230 38 2 1

8 32°46’28"N. 107°16’34"W. <1 4 <1 2 6 <1 220 15 2 <1

9 32°46’12"N. 107°16’38"W. <1 3 <1 2 1,100 <1 >1,360 9 <1 <1

10 32°45’10"N. 107°16’26"W. <1 5 <1 5 <3 <1 1,370 8 2 <1

11 32°44’19"N. 107°16’08"W. <1 4 <1 5 <3 <1 170 13 2 <1

12 32°40’59"N. 107°12’23"W. <1 6 <1 3 26 <1 1,350 11 2 <1

13 32°41’22"N. 107°12’08"W. 2 7 <1 5 100 <1 230 9 3 <114 32°42’02"N. 107°14’31"W. <1 5 <1 3 9 <1 710 11 2 <1

15 32°42’36"N. 107°13’37"W. <1 4 <1 6 <3 <1 77 17 3 <1

16 32°42’57"N. 107°14’26"W. <1 5 <1 3 83 <1 1,210 8 1 <1

17 32°44’22"N. 107°15’22"W. <1 2 <1 2 7 <1 <1 7 1 <1

18 32°40’41"N. 107°10’00"W. <1 4 <1 6 140 <1 920 17 3 <1

19 32°40’21"N. 107°11’43"W. <1 6 <1 4 <3 <1 17 10 2 120 32°39’59"N. 107°07’54"W. <1 3 <1 1 <3 <1 <1 5 1 <1

21 32°39’26"N. 107°07’51"W. <1 5 <1 6 1,900 <1 2,130 12 1 <1

22 32°39’20"N. 107°06’46"W. <1 <1 <1 2 <3 <1 210 16 2 <1

23 32°35’27"N. 107°00’07"W. <1 4 <1 3 980 <1 1,550 6 1 <124 32°36’01"N. 107°01’00"W. <1 3 <1 4 3 <1 950 4 2 <1

25 32°37’22"N. 107°00’28"W. <3 6 4 18 32 <3 >1,000 18 8 <1

26 32°37’33"N. 107°01’10"W. <1 3 <1 11 19 <1 300 18 3 <1

27 32°38’02"N. 107°02’41"W. 4 10 <2 21 1,000 <2 >1,000 9 4 <1

28 32°38’52"N. 107°03’38"W. <1 <1 <1 4 <3 <1 220 7 2 <1

29 32°39’17"N. 107°03’16"W. <1 5 <1 4 3 <1 440 12 3 <1

30 32°39’30"N. 107°04’14"W. <1 4 <1 3 5 <1 740 12 2 <1
114

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Continued

Well

number

(fig. 8) Latitude Longitude

Silver,

dissolved

(∝g/L as

Ag)

Uranium,

dissolved

(∝g/L as U)

Zinc,

dissolved

(∝g/L as

Zn)

Gross

alpha,

dissolved

(∝g/L as U)

Alpha,

count, 2

sigma,

dissolved

(∝g/L as U)

Gross beta,

dissolved

(pCi/L as

Sr-90/Y-90)

Beta count,

2 sigma,

dissolved

(pCi/L as

Sr-90/Y-90)

Radon222,

total

(pCi/L)

Radon222, count,

2 sigma

(pCi/L)

1 32°47’14”N. 107°18’02"W. <1 4 2 5.0 1.7 5.7 1.5 260 25

2 32°48’55"N. 107°18’46"W. <1 26 5 34 7.9 14 3.6 260 22

3 32°49’55"N. 107°18’09"W. <1 10 2 13 3.7 9.3 2.4 250 194 32°50’02"N. 107°18’12"W. <1 6 2 8.3 2.5 5.8 1.7 250 195 32°51’23"N. 107°17’57"W. <1 16 3 20 5.2 12 3.1 440 236 32°51’21"N. 107°17’26"W. <1 34 2 33 5.6 17 3.1 -- --7 32°47’38"N. 107°16’52"W. <1 62 2 67 10 29 5.0 290 238 32°46’28"N. 107°16’34"W. <1 13 2 15 3.8 6.8 2.0 -- --9 32°46’12"N. 107°16’38"W. <1 <1 1 1.9 1.2 5.9 1.6 -- --10 32°45’10"N. 107°16’26"W. <1 8 3 11 2.9 11 2.4 -- --11 32°44’19"N. 107°16’08"W. <1 10 5 11 3.1 9.4 2.3 240 2012 32°40’59"N. 107°12’23"W. <1 17 3 21 5.7 12 3.0 280 2313 32°41’22"N. 107°12’08"W. <1 13 3 21 5.0 10 2.5 -- --14 32°42’02"N. 107°14’31"W. <1 14 3 18 4.6 14 3.2 -- --15 32°42’36"N. 107°13’37"W. <1 15 4 18 4.6 13 3.1 240 2216 32°42’57"N. 107°14’26"W. <1 7 2 8.5 2.8 9.0 2.3 -- --17 32°44’22"N. 107°15’22"W. <1 2 2 3.8 1.4 7.2 1.5 390 2418 32°40’41"N. 107°10’00"W. <1 41 4 34 7.8 22 4.6 250 2919 32°40’21"N. 107°11’43"W. <1 14 5 14 4.5 15 3.5 260 22

20 32°39’59"N. 107°07’54"W. <1 3 <1 3.8 1.4 6.2 1.4 310 2221 32°39’26"N. 107°07’51"W. <1 <1 4 0.8 1.2 7.9 2.5 -- --22 32°39’20"N. 107°06’46"W. <1 3 2 3.9 1.4 4.7 1.3 -- --23 32°35’27"N. 107°00’07"W. <1 <1 4 2.0 1.5 6.3 1.9 210 1824 32°36’01"N. 107°01’00"W. <1 2 4 2.2 1.3 9.0 2.2 250 1825 32°37’22"N. 107°00’28"W. <3 6 14 7.9 8.4 23 7.0 260 1826 32°37’33"N. 107°01’10"W. <1 6 6 4.8 2.5 17 3.8 -- --27 32°38’02"N. 107°02’41"W. <2 9 8 13 5.6 12 4.3 -- --28 32°38’52"N. 107°03’38"W. <1 1 2 2.0 1.1 20 3.3 -- --29 32°39’17"N. 107°03’16"W. <1 12 3 13 3.9 11 2.9 260 1930 32°39’30"N. 107°04’14"W. <1 7 3 8.6 2.6 10 2.4 240 18
115

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Continued

Well

number

(fig. 8) Latitude Longtitude

Alpha

count, 2

sigma,

dissolved

(pCi/L as

Th-230)

Gross

beta,

dissolved

(pCi/L as

Cs-137)

Beta

count, 2

sigma,

dissolved

(pCi/L as

Cs-137)

Radon222,

total

(pCi/L)

Metolachlor,

dissolved

(∝g/L)

Diazinon,

dissolved

(∝g/L)

1 32°47’14"N. 107°18’02"W. 1.2 7.6 2.1 260 <0.002 <0.002

2 32°48’55"N. 107°18’46"W. 5.7 19 4.7 260 <0.002 <0.0023 32°49’55"N. 107°18’09"W. 2.6 13 3.2 250 <0.002 <0.002

4 32°50’02"N. 107°18’12’"W. 1.8 7.6 2.3 250 0.26 <0.0025 32°51’23"N. 107°17’57"W. 3.8 16 4.2 440 <0.002 <0.0026 32°51’21"N. 107°17’26"W. 4.0 22 4.1 -- <0.002 <0.0027 32°47’38"N. 107°16’52"W. 7.6 39 6.7 290 <0.002 <0.002

8 32°46’28"N. 107°16’34"W. 2.7 9.1 2.7 -- <0.002 <0.0029 32°46’12’"N. 107°16’38"W. 0.73 8.0 2.2 -- <0.002 <0.002

10 32°45’10"N. 107°16’26"W. 2.0 14 3.1 -- E0.005 <0.002

11 32°44’19"N. 107°16’08"W. 2.1 13 3.0 240 <0.002 <0.002

12 32°40’59"N. 107°12’23"W. 4.0 16 4.0 280 <0.002 <0.002

13 32°41’22"N. 107°12’08"W. 3.4 14 3.3 -- <0.002 <0.00214 32°42’02"N. 107°14’31"W. 3.2 19 4.2 -- 0.010 <0.00215 32°42’36"N. 107°13’37"W. 3.2 17 4.2 240 0.13 <0.002

16 32°42’57"N. 107°14’26"W. 1.9 12 3.1 -- <0.002 <0.00217 32°44’22"N. 107°15’22"W. 0.95 9.5 2.0 390 <0.002 <0.002

18 32°40’41"N. 107°10’00"W. 5.6 29 6.1 250 0.018 <0.00219 32°40’21"N. 107°11’43"W. 3.2 19 4.6 260 0.38 <0.002

20 32°39’59"N. 107°07’54"W. 0.96 8.3 1.9 310 <0.002 <0.00221 32°39’26"N. 107°07’51"W. 0.86 11 3.4 -- <0.002 <0.002

22 32°39’20"N. 107°06’46"W. 0.92 6.3 1.8 -- 5.4 <0.00223 32°35’27"N. 107°00’07"W. 1.0 8.4 2.6 210 <0.002 <0.00224 32°36’01"N. 107°01’00"W. 0.91 12 2.9 250 <0.002 <0.002

25 32°37’22"N. 107°00’28"W. 5.9 30 9.2 260 <0.002 <0.00226 32°37’33"N. 107°01’10"W. 1.7 23 5.1 -- <0.002 <0.002

27 32°38’02"N. 107°02’41"W. 4.0 16 5.7 -- <0.002 <0.00228 32°38’52"N. 107°03’38"W. 0.79 27 4.3 -- E0.005 0.077

29 32°39’17"N. 107°03’16"W. 2.8 14 3.8 260 <0.002 <0.00230 32°39’30"N. 107°04’14"W. 1.8 13 3.1 240 E0.005 <0.002
116

Appendix B. Shallow ground-water-quality data for selected sites in the Rincon Valley study area--Concluded

Group A pesticide

surrogates

Group B

pesticide

surrogate

Well

number

(fig. 8) Latitude Longitude

Napropamide,

dissolved

(∝g/L)

p,p’-

DDE,

dissolved

(∝g/L)

Prometon,

dissolved

(∝g/L)

Methylchloride,

total

(∝g/L)

Xylene

water

unfltrd rec

(∝g/L)

Diazinon

(percent

recovery)

HCH

alpha

(percent

recovery)

Terbuthylazine,

(percent

recovery)

BDMC

(percent

recovery)

1 32°47’14"N. 107°18’02"W. <0.01 <0.006 <0.018 <0.2 <0.20 89 93 114 --

2 32°48’55"N. 107°18’46"W. <0.01 <0.006 <0.018 <0.2 <0.20 91 70 100 110

3 32°49’55"N. 107°18’09"W. <0.01 <0.006 <0.018 <0.2 <0.20 101 89 109 24

4 32°50’02"N. 107°18’12"W. <0.01 <0.006 E0.009 <0.2 <0.20 102 90 110 6.05 32°51’23"N. 107°17’57"W. <0.01 <0.006 <0.018 0.3 <0.20 83 84 76 32

6 32°51’21"N. 107°17’26"W. <0.01 <0.006 <0.018 0.5 <0.20 84 88 94 28

7 32°47’38"N. 107°16’52"W. <0.01 <0.006 <0.018 <0.2 <0.20 90 68 93 100

8 32°46’28"N. 107°16’34"W. <0.01 <0.006 <0.018 <0.2 <0.20 86 80 100 80

9 32°46’12"N. 107°16’38"W. <0.01 <0.006 <0.018 -- -- 95 83 105 --

10 32°45’10"N. 107°16’26"W. 0.014 <0.006 <0.018 <0.2 <0.20 90 82 102 70

11 32°44’19"N. 107°16’08"W. <0.01 <0.006 <0.018 <0.2 <0.20 88 80 99 68

12 32°40’59"N. 107°12’23"W. <0.01 <0.006 <0.018 -- -- 90 87 89 8.0

13 32°41’22"N. 107°12’08"W. <0.01 <0.006 <0.018 -- -- 91 89 89 5614 32°42’02"N. 107°14’31"W. <0.01 <0.006 <0.018 -- -- 92 87 91 32

15 32°42’36"N. 107°13’37"W. <0.01 <0.006 <0.018 0.2 <0.20 92 79 90 26

16 32°42’57"N. 107°14’26”W. <0.01 <0.006 <0.018 <0.2 2.8 91 78 104 62

17 32°44’22"N. 107°15’22"W. <0.01 <0.006 E0.005 0.2 <0.20 87 76 89 26

18 32°40’41"N. 107°10’00"W. <0.01 <0.006 <0.018 -- -- 92 89 108 16

19 32°40’21"N. 107°11’43"W. <0.01 <0.006 <0.018 <0.2 <0.20 90 79 89 8.0

20 32°39’59"N. 107°07’54"W. <0.01 <0.006 <0.018 <0.2 <0.20 100 90 109 12

21 32°39’26"N. 107°07’51"W. <0.01 <0.006 <0.018 0.4 0.70 90 89 87 56

22 32°39’20"N. 107°06’46"W. <0.01 <0.006 E0.012 -- -- 90 88 90 50

23 32°35’27"N. 107°00’07"W. <0.01 <0.006 <0.018 -- -- 84 71 89 34

24 32°36’01"N. 107°01’00"W. <0.01 <0.006 <0.018 0.3 <0.20 100 83 96 12

25 32°37’22"N. 107°00’28"W. <0.01 <0.006 0.32 0.4 -- 96 76 98 26

26 32°37’33"N. 107°01’10"W. <0.01 <0.006 <0.018 -- 0.30 90 91 95 4627 32°38’02"N. 107°02’41"W. <0.01 <0.006 <0.018 -- <0.20 79 84 81 48

28 32°38’52"N. 107°03’38"W. <0.01 <0.006 E0.010 -- -- 90 84 99 44

29 32°39’17"N. 107°03’16"W. <0.01 E0.002 <0.018 -- -- 87 84 87 28

30 32°39’30"N. 107°04’14"W. <0.01 <0.006 <0.018 0.3 <0.20 87 80 85 34
117

Appendix C. Concentrations of pesticides and pesticide metabolites detected in bed-material samples

from selected sites in the Rincon Valley study area

[∝g/kg, micrograms per kilogram]

Site name Date

DDT

(∝g/kg)

DDD

(∝g/kg)

p,p’-DDE

(∝g/kg)

Rincon Drain at Rio Grande, near Rincon 01-03-95 0.4 1.4 44.0Hatch Drain at Rio Grande, near Hatch 01-04-95 0.3 0.6 4.8Garfield Drain at Road 390 near Salem 01-05-95 0.5 0.2 1.5