DETAILED STUDY OF IRRIGATION DRAINAGE 

IN AND NEAR WILDLIFE MANAGEMENT AREAS, 

WEST-CENTRAL NEVADA, 1987-90

Part B. Effect on Biota in Stillwater and 

Fernley Wildlife Management Areas 

and Other Nearby Wetlands

Robert J. Hallock and Linda L. Hallock, Editors 

U.S. Fish and Wildlife Service

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 92-4024B

U.S. GEOLOGICAL SURVEY,

U.S. FISH AND WILDLIFE SERVICE,

U.S. BUREAU OF RECLAMATION, and

U.S. BUREAU OF INDIAN AFFAIRS

Carson City, Nevada 

1993
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

DALLAS L. PECK, Director

Any use of trade names in this publication is for descriptive purposes 

only and does not imply endorsement by the U.S. Government.

For additional information 

write to:

District Chief

U.S. Geological Survey

333 West Nye Lane, Room 203

Carson City, NV 89706-0866

Copies of this report can be 

purchased from:

U.S. Geological Survey

Earth Science Information Center

Open-File Reports Section

Box 25286, MS 517

Denver Federal Center

Denver, CO 80225-0046
CONTENTS

Page

ABSTRACT .......................................................................................................................................................................... 1

INTRODUCTION .............................................................. 3

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

Purpose and Scope ..................................................................................................................................................... 4

Study Area ..........................................................................................................................................................^ 5

Acknowledgments ..................................................................................................................................................... 5

ESTIMATED HISTORICAL CONDITIONS OF THE LOWER

CARSON RIVER WETLANDS ..................................................................................................................................... 7

Linda L. Kerley, Geoffrey A. Ekechukwu, and Robert J. Hallock 

U.S. Fish and Wildlife Service 

Estimated Historical Carson River Flow and Wetland Sizes ................................................................................................ 7

Unregulated Flow of the Carson River ...................................................................................................................... 7

Average Historical Size of Carson Lake ................................................................................................................... 10

Flow Through Stillwater Slough ............................................................................................................................... 11

Average Historical Size of Stillwater Marsh ............................................................................................................. 11

Estimated Flow into Carson Sink Wetlands .............................................................................................................. 12

Estimated Size of Carson Sink Wetlands .................................................................................................................. 12

Estimated Historical Water Quality ...................................................................................................................................... 13

Vegetation .............................................................................._^ 17

Wildlife ................................................................................................................................................................................. 18

Present/Projected Wetland Conditions .................................................................................................................................. 19

TOXICITY OF IRRIGATION DRAINAGE AND ITS EFFECT

ON AQUATIC ORGANISMS ........................................................................................................................................ 21

Susan E. Finger, Steven J. Olson, and Ann C. Livingstone 

U.S. Fish and Wildlife Service

Methods ............................................................ 21

Sample Collection ..................................................................................................................................................... 21

Toxicity Assessments ................................................................................................................................................ 23

Chemical Analyses ................................................................................................................................................... 23

Results of Toxicity Tests ....................................................................................................................................................... 25

Paiute Diversion Drain and D-Line Canal ................................................................................................................ 25

TJ Drain ..................................................................................................................................................................... 25

Well Near TJ Drain .................................................................................................................................................... 28

Hunter Drain............................................................................................................................................................... 29

Lead Lake ......................................................................................................................................................^ 31

Stillwater Point Diversion Drain and Stillwater Point Reservoir .............................................................................. 32

Effect of Irrigation Drainage on Aquatic Organisms ............................................................................................................ 35

Ionic Composition ..................................................................................................................................................... 37

CONTENTS
Page

BIOLOGICAL PATHWAYS:

MOVEMENT OF SELENIUM AND MERCURY ........................................................................................................ 39

Robert J. Hallock, Howard L. Burge, and Peter L. Tuttle 

U.S. Fish and Wildlife Service 

Study Areas .......................................................................................................................................................................... 39

Approach and Methods ......................................................................................................................................................... 44

Results .................................................................................................................................................................................. 44

Bioaccumulation and Biomagnification of Selenium and Mercury .......................................................................... 45

Selenium and Mercury Pathways .............................................................................................................................. 46

Duration of Selenium Contamination ....................................................................................................................... 50

Contaminant Source Areas ....................................................................................................................................... 51

EFFECTS OF BORON, MERCURY, AND SELENIUM

ON WATERFOWL PRODUCTION .............................................................................................................................. 55

Linda L. Hallock, C. Anne Janik, and Linda L Kerley 

U.S. Fish and Wildlife Service 

Approach .............................................................................................................................................................................. 55

Methods ................................................................................................................................................................................ 55

Hatch Success and Teratogenesis............................................................................................................................... 57

Trace Elements in Eggs ............................................................................................................................................. 57

Trace Elements in Juvenile Duck Livers .................................................................................................................. 59

Nest Success......................................................................................................................................................^ 62

Waterfowl Production ............................................................................................................................................... 63

MERCURY AND SELENIUM IN EDIBLE TISSUE

OF WATERFOWL .......................................................................................................................................................... 65

Robert J. Hallock, Howard L. Burge, and Peter L. Tuttle 

U.S. Fish and Wildlife Service 

Approach and Methods ......................................................................................................................................................... 65

Mercury Accumulation in Waterfowl ....................................................................................................................... 66

Selenium Accumulation in Waterfowl ...................................................................................................................... 68

OVERALL SUMMARY OF EFFECT OF IRRIGATION DRAINAGE ON BIOTA ......................................................... 71

Robert J. Hallock and Linda L. Hallock 

U.S. Fish and Wildlife Service

REFERENCES CITED ........................................................................................................................................................ 72

SUPPLEMENTAL WATER-QUALITY DATA FROM TOXICITY STUDY .................................................................... 77

Figures

1. Map showing general physiographic features in the study area and western Nevada........................................... 2

2. Reproduction of early map showing configuration of the lower Carson River basin before development........... 8

3. Graph showing mean monthly flow and quartile statistics, Carson River gage

near Fort Churchill, water years 1919-69.............................................................................................................. 9

4. Map showing locations of toxicity sampling sites and important hydrologic

features in and near Stillwater Wildlife Management Area.................................................................................. 22

IV CONTENTS
Page

5-7. Graphs showing:

5. Cumulative mortality of freshwater organisms in undiluted surface-water

samples collected in and near Stillwater Wildlife Management Area........................................................... 35

6. Changes in specific conductance in Lead Lake and selected drains during toxicity study........................... 36

7. Relations between specific conductance and mortality of bluegills, fathead

minnow larvae, and daphnids........................................................................................................................ 37

8-10. Maps showing locations of:

8. Sampling sites for drift and biota in and near Stillwater Wildlife Management Area................................... 40

9. Sampling sites for drift and biota in and near Fernley Wildlife Management Area...................................... 41

10. Additional sampling sites for detritus and algae in and near Stillwater and

Fernley Wildlife Management Areas and Carson Lake................................................................................. 42

11-13. Diagrams showing arithmetic means, medians, and ranges of selenium 

concentrations in composite samples from:

11. Input drains, Lead Lake, and downgradient wetlands, and generalized flow path

in Stillwater Wildlife Management Area....................................................................................................... 47

12. A-Drain, South Pond, and downgradient wetlands, and generalized flow path

in Fernley Wildlife Management Area.......................................................................................................... 48

13. Hunter Drain, Stillwater Wildlife Management Area.................................................................................... 50

14. Map showing selenium concentrations in detritus samples from in and

near Stillwater and Fernley Wildlife Management Areas..................................................................................... 52

15. Map showing mercury concentrations in detritus samples from in and near

Stillwater and Fernley Wildlife Management Areas............................................................................................. 53

16-18. Diagrams showing:

16. Concentrations of selenium in duck eggs and liver tissue of juvenile ducks................................................. 62

17. Concentrations of mercury in edible portions of shoveler ducks................................................................... 67

18. Concentrations of mercury in edible portions of various duck species.......................................................... 68

Tables

1. Estimated historical (predevelopment) wetland acreage compared to 

projected wetland acreage at Carson Lake and the combined wetlands of 

Stillwater Marsh and Carson Sink ....................................................................................................................... 11

2. Estimated historical (predevelopment) and recent or projected 

water quantity and dissolved-solids concentrations and loads for 

Carson River, Carson Lake, and Stillwater Marsh ............................................................................................... 15

3. Concentration factors between wetland units and recent and 

projected concentrations of dissolved solids, Stillwater Wildlife 

Management Area ................................................................................................................................................ 20

4. Analytical reporting limits for selected inorganic constituents in water .............................................................. 24

5. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids after exposure 

to water from Paiute Diversion Drain diluted with reconstituted water and 

water from D-Line Canal ..................................................................................................................................... 25

6. Ranges of water-quality measurements in surface-water samples collected daily,

August 10-18, 1988, for aquatic toxicity tests...................................................................................................... 26

7. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed

to water from TJ Drain diluted with reconstituted water ..................................................................................... 27

8. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed

to water from TJ Drain diluted with water from D-Line Canal ........................................................................... 28

9. Concentrations of inorganic constituents in ground water collected from

U.S. Geological Survey well DH-102B in the vicinity of TJ Drain, August 17, 1988 ........................................ 29

10. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed

to water from Hunter Drain diluted with reconstituted water .............................................................................. 30

11. Cumulative mortality of saltwater species exposed to water from Hunter Drain

diluted with reconstituted water ........................................................................................................................... 31

CONTENTS \
Page

12. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed

to water from Lead Lake diluted with reconstituted water .................................................................................. 32

13. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed

to water from Stillwater Point Diversion Drain diluted with reconstituted water ................................................ 33

14. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed

to water from Stillwater Point Diversion Drain diluted with water from Stillwater Point Reservoir .................. 34

15. Sampling sites for drift, detritus, and algae .......................................................................................................... 43

16. Hatch success of artificially incubated waterfowl eggs collected in the study area, 1988 ................................... 57

17. Summary of data on concentrations of boron, mercury, and selenium, including

minimums, maximums, and means, for waterfowl eggs collected in the study area............................................ 58

18. Effect levels and characteristics of boron, mercury, and selenium concentrations

in waterfowl eggs and juvenile waterfowl livers .................................................................................................. 59

19. Summary of data on concentrations of boron, mercury, and selenium, including

minimums, maximums, and means, for juvenile waterfowl livers collected in the study ................................... 60

20. Nest success of ducks in the study area, 1988 ...................................................................................................... 63

21. Nest-success rates from various other studies and from the present study ........................................................... 64

22. Estimated waterfowl production in the study area, 1988 ...................................................................................... 64

23. Water-quality measurements for daily composite water samples from

Paiute Diversion Drain, August 1988 ................................................................................................................... 78

24. Water-quality measurements for daily composite water samples from TJ Drain, August 1988 .......................... 79

25. Water-quality measurements for daily composite water samples from D-Line Canal, August 1988 ................... 80

26. Water-quality measurements for daily instantaneous water samples from Lead Lake, August 1988 .................. 81

27. Water-quality measurements for daily composite water samples from Hunter Drain, August 1988 ................... 82

28. Water-quality measurements for daily composite water samples from Stillwater

Point Diversion Drain, August 1988 .................................................................................................................... 83

29. Water-quality measurements for daily instantaneous water samples from Stillwater

Point Reservoir, August 1988 ............................................................................................................................... 84

VI CONTENTS
CONVERSION FACTORS, VERTICAL DATUM, DEFINITION, 

AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To obtain

acre

acre-foot (acre-ft)

acre-foot per acre (acre-ft/acre)

acre-foot per acre per year (acre-ft/acre/yr)

acre-foot per year (acre-ft/yr)

foot (ft)

foot per year (ft/yr)

gallon (gal)

inch (in.)

mile (mi)

ounce(oz)

square foot per second (ftVs)

square mile (mi2)

ton per year (ton/yr)

yard

4,047

1,233

0.3048

0.3048

0.001233

0.3048

0.3048

3.785

25.4

1.609

0.02957

0.9072

2.59

0.9072

0.9144

square meter

cubic meter

cubic meter per square meter

cubic meter per square meter per year

cubic hectometer per year

meter

meter per year

liter

millimeter

kilometer

liter

square meter per second 

square kilometer 

megagram per year 

meter

Temperature: Degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) by using the formula °F = [1.8(°C)]+32.

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929, formerly called "SeaLevel Datum of 1929"), which is derived from a general adjustment of the first-order leveling networks of the United States and Canada.

Definition: The term "water year" refers to the 12-month period October 1 through September 30, during which a complete annual hydrologic 

cycle normally occurs. The water year is designated by the calendar year in which it ends. Thus, the year ending September 30,1988, is 

called the "1988 water year."

Abbreviated water-quality units used in this report:

L (liter)

|lg/g (microgram per gram)

mL (milliliter)

mg/L (milligram per liter)

ppt (part per thousand)

NTU (Nephelometric turbidity unit)

mg/kg (milligram per kilogram)

(1m (micrometer)

|lg/L (microgram per liter)

g(gram)

(iS/cm (microsiemen per centimeter at 25°C)

g/L (gram per liter)

kg (kilogram)

CONTENTS VII
DETAILED STUDY OF IRRIGATION DRAINAGE 

IN AND NEAR WILDLIFE MANAGEMENT AREAS, 

WEST-CENTRAL NEVADA, 1987-90

Part B. Effect on Biota in Stillwater and 

Fernley Wildlife Management Areas 

and Other Nearby Wetlands

Robert J. Hallock and Linda L. Hallock, Editors

Abstract

A water-quality reconnaissance investigation during 1986-87 found high concentrations 

of several potentially toxic elements in water, 

bottom sediment, and biota in and near Stillwater 

Wildlife Management Area (WMA). These 

results prompted the U.S. Department of the 

Interior to initiate a more detailed study in 1988 

to determine the hydrogeochemical processes 

that control water quality in the Stillwater WMA 

and other nearby wetlands, and the resulting 

effects on biota, especially migratory birds.

The average historical size of the natural 

wetlands at Carson Lake and Stillwater Marsh, 

the water quantity, and the average dissolvedsolids concentration and load in the water in these 

wetlands were estimated. Present wetland size is 

about 10 percent of historical size; the dissolvedsolids load in these now-isolated wetlands has 

increased only moderately, but the concentration 

has increased more than seven-fold. Wetland 

vegetation has diminished and species composition has shifted to predominantly salt-tolerant 

species in many areas. Decreased vegetative cover 

for nesting is implicated in declining waterfowl

production. Decreases in numbers or virtual 

absence of several wildlife species are attributed 

to degraded water quality.

Toxicity tests established that water in 

some drains and wetland areas was acutely toxic 

to some fish and invertebrates. Toxicity is attributed to the combined presence of arsenic, boron, 

lithium, and molybdenum. Rapid fluctuations in 

specific conductance and atypical ionic composition, which may increase acute toxicity, were 

observed in some drainwater. A strong relation 

was found between trace elements and both 

daily and average specific conductance.

Biological pathways are involved in the 

transport of mercury and selenium. Concentrations of selenium and mercury in drainwater were 

very low to below analytical reporting limits, but 

these elements had bioaccumulated in plants, and 

selenium had biomagnified in one trophic level 

(invertebrates) up to 10,000-fold. Selenium and 

mercury accumulated in plants, detritus, and invertebrates had been transported through irrigation 

drains to large wetland areas frequented by 

waterfowl and other wildlife, but no evidence of 

expected long-term selenium build-up since development was found in the wetlands. Several source 

areas of selenium and mercury were identified.

Abstract 1
Hatch success of both artificially 

incubated and field-reared duck eggs was 

90 percent or greater; no teratogenesis was 

observed. Boron and selenium concentrations 

in eggs were generally low all below adverse 

effect levels. Mercury concentrations were also 

low except in eggs from Stillwater WMA, where 

about 30 percent of the eggs contained concentrations above the adverse effect level. Boron, mercury, and selenium concentrations in pre-flight 

juvenile ducks ranged from insignificant to levels 

associated with impaired survival. Boron concentrations were at or below effect levels in various 

duck species, but above effect level in coots 

(Fulica americana). Mercury concentrations in 

birds from Stillwater WMA, Carson Lake, and 

Carson Valley were above effect levels. Mean 

concentrations of selenium ranged from 30 to 

77 micrograms per gram (Jig/g) in birds from 

Fernley WMA and Massie and Mahala Sloughs, 

all above effect level. Survival of juvenile birds 

that had accumulated selenium, however, was 

not reduced. Field nest success was 26 percent 

and estimated overall production was about 2,400 

ducklings from 6,800 breeding pairs. This poor 

production was attributed primarily to drought 

conditions and dissolved-solids accumulation 

that caused vegetative loss and exposed the 

nests to predators.

Maximum concentrations of mercury in 

muscle and liver tissue of waterfowl harvested 

from Carson Lake and Fernley WMA were 

15.5 and 38.9 Jig/g, wet weight, respectively, 

which exceeded the established human health 

criterion of 1.0 Jig/g. Selenium concentrations 

in livers of juvenile waterfowl from Fernley 

WMA and Massie Slough were four times 

the established criterion for human health.

INTRODUCTION

In the last several years, concern has been 

increasing about the quality of irrigation drainage, and 

its potential adverse effects on human health, fish, and 

wildlife. Recent studies at several National Wildlife 

Refuges and Wildlife Management Areas (WMA) 

throughout the western United States have identified

elevated concentrations of selenium and other trace 

elements that are a potential threat to biota within 

the management areas (Knapton and others, 1988; 

Lambing and others, 1988; Peterson and others, 1988; 

Radtke and others, 1988; Schroeder and others, 1988; 

Stephens and others, 1988; Wells and others, 1988; 

Hoffman and others, 1990; and Setmire and others, 

1990). In 1988, the U.S. Department of the Interior 

(DOI) directed the U.S. Geological Survey, U.S. Fish 

and Wildlife Service, U.S. Bureau of Reclamation, and 

the U.S. Bureau of Indian Affairs to implement detailed 

studies that would provide information useful for mitigating the negative effects of irrigation-drainage water. 

The detailed studies were to provide information on 

(A) toxic constituents, (B) their effects on biota, and 

(C) a summary of significant findings.

The Stillwater WMA (and other nearby 

wetlands) in west-central Nevada (fig. 1) is one of 

several areas in the western United States selected for 

detailed examination of the mobilization, transport, 

and fate of potentially toxic constituents involving 

the biotic and abiotic environment.

Background

The changes that have occurred in the wetlands 

associated with the Newlands Irrigation Project in the 

Carson Desert are widely recognized and are partly 

summarized in a report by the U.S. Department of 

the Interior (1988). An overview of the increment of 

change that may be ascribed to irrigation drainage was 

needed to place the related DOI irrigation-drainage 

studies in perspective.

Prior to these investigations, few studies had 

documented the effects of the toxic components of irrigation drainage on biota in and near Stillwater WMA. 

The first comprehensive study of irrigation-induced 

water-quality problems was made during 1986-87 by 

Hoffman and others (1990). Henny and Herron (1989) 

studied irrigation-drainage-related contaminants in 

white-faced ibis (Plegadis chihi) at Carson Lake.

Several contaminants found in irrigation 

drainage are known to directly affect fish and invertebrates, and thus indirectly, birds; both fish and invertebrates are important in the diets of many migratory 

birds at Stillwater WMA. Aquatic invertebrates are 

a frequent food source for birds during reproduction 

because ingested invertebrates provide high energy 

food for rapid growth of young birds in preparation for 

migration. Salinity is often high at Stillwater WMA, 

and both water and biota contain elevated levels of

2 Detailed Study of Irrigation Drainage Effect on Biota
Humboldt 

WMA

Carson City J?

f /

Garson 

Valley

EXPLANATION

OPEN WATER

WETLANDS, INCLUDING

OPEN WATER 

PLAYA

GENERALIZED AREA OF 

CARSON DESERT

----- GENERALIZED BOUNDARY OF

WILDLIFE MANAGEMENT AREA (WMA)

A GAGING STATION 10312000 

NEAR FORT CHURCHILL

Figure 1 . General physiographic features in the study area and western Nevada (Modified from Lico, 1992).

INTRODUCTION
potentially toxic trace elements (Hoffman and others, 

1990, p. 76-77). At Stillwater WMA, Largemouth bass 

(Micropterus salmoides), which once supported a 

popular sport fishery, are gone and the diverse fish 

forage base supporting American white pelicans 

(Pelecanus erythrorhynchos) is greatly reduced 

(U.S Fish and Wildlife Service, 1988, p. 132).

Some water-quality components associated with 

irrigation drainage may directly affect migratory birds. 

Both selenium and mercury have bioaccumulated and 

biomagnified in migratory bird tissues from the study 

area to the extent that reproduction may fail (Hoffman 

and others, 1990, p. 60,67,72,77; Eisler, 1985, p. 38). 

High concentrations of selenium were found in juvenile migratory birds confined to wetlands that commonly contained less than the analytical reporting limit 

(<1.0 fig/L) of dissolved selenium concentrations in 

water. In these same wetlands, selenium concentrations in sediment (< 1.2 fig/g) were well below the 

level of concern (4.0 fig/g) recommended by Lemly 

and Smith (1987, p. 9). Selenium was found in shallow 

ground water affected by irrigated agriculture in and 

near the headwaters of TJ Drain (U.S. Bureau of 

Reclamation, 1987, p. B14). Most of the mercury in 

the study area originated from 19th century mining 

and milling practices in the middle Carson River basin 

(Smith, 1943, p. 247). The distribution of mercury 

throughout the study area is associated with floodways and channels of the Carson River that existed 

before construction of the Newlands Irrigation Project. 

Low concentrations of mercury were found in filtered 

sample water from the study area. The highest concentration of mercury in water, reported by Hoffman and 

others (1990, p. 36), was 1.1 fig/L in Lead Lake in 

Stillwater WMA.

Reproductive life phases are typically sensitive 

and vulnerable to the effects of contaminants. Traceelement toxicity is a possible contributing factor to the 

steady decline in waterfowl production in wetlands 

maintained by drainage from the Newlands Irrigation 

Project (U.S. Department of the Interior, 1988, 

p. E-7-E-10). In addition to the white-faced ibis found 

to be accumulating selenium and mercury in the breeding grounds at Carson Lake (Henny and Herron, 1989, 

p. 1032), deformed ibis chicks have been observed at 

Stillwater WMA (U.S. Fish and Wildlife Service, 

Fallen, Nev., unpublished data, 1987). Dead and dying 

waterfowl found in Carson Sink and in various parts 

of this study area (Stillwater WMA, Humboldt WMA, 

and Carson Lake) had selenium levels in liver tissue 

sufficiently high to cause toxicosis (> 30 fig/g),

although necropsy reports did not identify selenium 

toxicosis as the immediate cause of death (Rowe and 

Hoffman, 1990, p. 39; Hoffman and others, 1990, 

p. 74). The primary effect of excessive dietary 

selenium on mallards (Anas platyrhynchos) is 

reproductive reduced reproductive efforts, hatch 

rates, and duckling survival (Lemly and Smith, 1987, 

p. 5). Chronic sublethal mercury concentrations are 

also related to reduced reproductive success (Heinz, 

1979, p. 398; Finley and Stendell, 1978, p. 54). Laboratory studies of boron as a dietary supplement showed 

reduced hatch rates, hatch weights, growth rates, and 

duckling survival (Smith and Anders, 1989, p. 943). 

Selenium, mercury, and boron were found in migratory 

birds, food-chain organisms, and sediment in the study 

area during the reconnaissance study by Hoffman 

and others (1990, p. 58, 62).

Wildlife from study-area wetlands have been 

used as food by humans for more than 4,000 years 

(Kelly, 1988, p. 11). Although the wetlands no longer 

support a popular fishery, harvest and consumption of 

waterfowl continues. When potential toxic elements, 

such as mercury and selenium, accumulate in waterfowl tissues, a concentration may be reached at which 

human consumption is inadvisable. During 1986-87, 

Hoffman and others (1990, p. 77) found indications 

that juvenile migratory birds, including waterfowl, in 

and near Stillwater WMA and Carson Lake were accumulating mercury and selenium in liver and muscle 

tissue. Some of the concentrations exceeded established criteria for human health. Cooper and others 

(1985, p. 56) identified a possible threat to human 

health from mercury in fish fillets taken from various 

wetlands in the Newlands Irrigation Project area, 

including Stillwater WMA.

Purpose and Scope

This report presents findings of the five 

detailed study elements that evaluate general and 

specific effects of irrigation drainage on biota and 

mechanisms or linkages related to these effects in 

wetlands in and near Stillwater WMA. The primary 

purpose in studying these wetlands was to assist remediation efforts in support of migratory waterfowl, a 

Federal trust responsibility; the common theme of 

these five elements is the possible adverse effects 

of irrigation drainage on migratory waterfowl. The 

five study elements, in order of presentation in this 

report, examine the historical conditions of the wetlands compared to the present, determine which

4 Detailed Study of Irrigation Drainage Effect on Biota
potentially toxic trace elements are present in the 

area, explore pathways by which the trace elements 

move through the wetlands, determine the effects 

of the contaminants on waterfowl production, and 

consider human-health implications.

Because of the length and scope of this report, 

those primarily interested in the collective findings of 

all the studies may wish to pass the detailed sections 

and proceed directly to the summary section at the back 

of this report. The more technically oriented reader 

may wish to examine the individual sections for more 

detail.

This investigation was made and the report 

authored by U.S. Fish and Wildlife Service scientists. 

The report is published by the U.S. Geological Survey 

to maintain continuity with the other detailed-study 

reports for the area (Rowe and others, 1991; Lico, 

1992; and Hoffman, in press). While the period of 

study was 1988-90, some biological data collected in 

1987 were used to assess the concentrations of mercury 

and selenium in waterfowl.

Study Area

The Carson Desert hydrographic area (Rush, 

1968, pi. 1) occupies a mostly flat area of about 

2,020 mi2 in the lower Carson River drainage basin. 

The area is about 70 mi east of Reno, and is one of 

the largest basin-fill valleys in northern Nevada. 

The Carson Desert includes natural wetlands at Carson 

Lake and within the artificial boundaries of Stillwater 

WMA Stillwater Marsh and the southern part of the 

Carson Sink (fig. 1). The Carson Sink is a nearly 

barren, flat, salt-encrusted playa occupying an area of 

about 400 mi2 on the northern boundary of Stillwater 

WMA. In abnormally high precipitation years, wetlands may emerge in the Sink, supported by flow of 

the Carson River and, on occasion, overflow from the 

Humboldt River.

Historically, these wetlands were supported 

primarily by the Carson River, but since completion 

of the Newlands Irrigation Project, additional water 

has been imported from the Truckee River drainage 

basin to the Carson River by way of the Truckee Canal. 

The Carson River is a major tributary draining the 

eastern slopes of the central Sierra Nevada. As with 

most rivers associated with the Great Basin, its annual 

discharge patterns are highly variable.

Biological samples were collected from 

additional wildlife areas because of their proximity 

to Stillwater WMA, and because they are maintained

by a combination of ground water and drainage from 

DOI irrigation projects. These other areas include the 

largely Project-created wetlands at Fernley WMA near 

Fernley, Nev., about 30 mi west of Stillwater WMA; 

Massie and Mahala Sloughs, about 25 mi west of 

Stillwater WMA; and the natural wetlands at Humboldt 

WMA (fig. 1).

Summary descriptions of climate, geology, soils, 

water use, hydrologic setting, wetland areas, and wildlife use were reported by Hoffman and others (1990) 

and Lico (1992).

Acknowledgments

The authors of this report gratefully 

acknowledge the following individuals who 

provided valuable assistance during the course 

of these investigations: Ron Crunkilton, Missouri 

Department of Conservation, for providing bluegills 

for the study; Rod Parrish, U.S. Environmental 

Protection Agency Laboratory, Gulf Breeze, Fla., 

for providing saltwater species; and Eugene Greer 

and Glenn Wylie, National Fisheries Contaminant 

Research Center, Columbia, Mo., for providing fathead 

minnow larvae and daphnids, respectively. The maintenance staff at the Stillwater National Wildlife Refuge 

provided valuable assistance in setting up the mobile 

toxicity testing facility. Mark Kaiser assisted in the 

analysis of data and provided valuable suggestions 

on parts of this report.

The following people also assisted in the study 

by providing data, information, or technical reviews 

of parts of this report: Roy Leach and Norman A. 

Saake, Nevada Department of Wildlife; James J. 

Cooper, Nevada Division of Environmental Protection; 

Theodore G. Roefs and Thomas Strekal, U.S. Bureau 

of Reclamation; Ronald M. Anglin, Timothy Bowman, 

C. Clifford Creger, Gerald Deutscher, Leslie Dubec, 

Eugene E. Duffney, Charles J. Henny, Earnest Lantos, 

Delven D. Lee, A. Dennis Lemly, Kenneth Merritt, 

Craig Stockwell, and Steven P. Thompson, all with the 

U.S. Fish and Wildlife Service; and Lyman F. McConnell and Willis Hyde of the Truckee-Carson Irrigation 

District.

And, finally, we thank Ray J. Hoffman, Study 

Team Leader, and Carol A. Myers, Technical Editor, 

of the U.S. Geological Survey for their substantial 

efforts in making this a more concise and cohesive 

document.

INTRODUCTION
ESTIMATED HISTORICAL CONDITIONS OF THE 

LOWER CARSON RIVER WETLANDS

To evaluate the effect of irrigation drainage 

on the wetlands of the lower Carson River, Carson 

Lake, Stillwater Marsh, and associated intermittent 

wetlands in the Carson Sink (fig. 1), an estimate was 

needed of the conditions prevailing before the onset of 

irrigation and development. These estimated historical 

wetland conditions were then compared to present and 

projected wetland conditions. To do this, it was necessary to distinguish between effects resulting from irrigation and those resulting from wetland management 

practices. Climatic changes, extreme variability of the 

streamflow of the Carson River, the cyclic nature of 

this variation, and the presence of lands irrigated with 

Carson River water upstream of the Newlands 

Irrigation Project are important considerations for 

the determination of historical conditions.

The historical flow, seasonal variation, average 

wetland size, and water quality were estimated on the 

basis of extrapolations from data in existing records, 

reports by early explorers, and archaeological findings. 

Early reports and evidence from archaeological sites 

were used to estimate the types and abundance of vegetation and wildlife historically present. Present conditions were determined from data collected for this 

study and from other recent State and Federal reports 

and data, particularly data analysis compiled in April 

1988 by the U.S. Fish and Wildlife Service at Stillwater 

Wildlife Management Area for OCAP (Operating 

Criteria and Procedures) of the Newlands Project 

(U.S. Fish and Wildlife Service, 1988), which are 

summarized in Appendix E of the Final Record of 

Decision (U.S. Department of the Interior, 1988).

ESTIMATED HISTORICAL CARSON RIVER 

FLOW AND WETLAND SIZES

Commonly, the flow path of the unregulated 

Carson River was to Carson Lake, out through 

Stillwater Slough into Stillwater Marsh, then terminated in Carson Sink, as discussed by Morrison (1964, 

p. 104) and Russell (1885, p. 44-45) and shown in 

figure 2. That flow pattern will be followed in this discussion, with alternating consideration of inflow quantities, wetland sizes, and probable water losses along 

the downgradient flow path.

Unregulated Flow of the Carson River

Systematic records of streamflow and water 

quality of the Carson River and associated wetlands 

have been kept only during this century. Data extrapolated from the existing streamflow records were used 

to estimate a representative annual average volume of 

water inflow to the wetlands before the initiation of irrigation (pre-1860) in the Carson Desert. This predevelopment inflow was then used to estimate an average 

wetland acreage that would have been maintained 

primarily by inflow of the Carson River. Because 

the annual streamflow of the Carson River is highly 

variable, the extrapolation included the following 

information, estimates, and assumptions:

lrThe term "average" is used here to indicate a representative 

situation sometimes stable, sometimes subject to extreme fluctuation; it does not mean a mathematical average or a usual or 

"normal" situation.

ESTIMATED HISTORICAL CONDITIONS Kerley and others
_^_ fo!-~Vvi£ -X^ --- .-z^'V'-ii-""'^ I1 .rv-te i;i 

 '&/£ 

- -- * ;- -- 

*%*M

jff~i ' - ; ;.. ^C«%^ pj\. ^saJ^^?^^- -.£*-:-::-.;./7^Js: - 1 ^- -: ^ _ _ /-'u- V"*IQJ '^^^ ->=Zs <- -i«=:."*»s- i . i-i'-K-, i'lv -._ - JT . -^1 - ^s^w r^fe^V®^^ ^^-:J/^VH:-^- <*xv. S^ %^s^ &%> ?m? '-7:1.^1- g^^^l4§^^t| ' r ' :; ^%; V"

*

Lahontan Beach 

Playas 4^>

Julius Bien & Co. Llth.

CARSON DESERT, NEVADA.

Scale oIMIes

Interval between 

Contours 1000 feet.

Figure 2. Reproduction of early map showing configuration of the lower Carson River basin before development (1880's). Note differences in 

name designations: in particular, "North Carson Lake," which is now part of Stillwater Marsh and Carson Sink, and "South Carson Lake," now 

designated simply Carson Lake. (Illustration was published in 1885 as Plate VII by I.C. Russell in U.S. Geological Survey Monograph 11, a 

report on ancient Lake Lahontan.)

8 Detailed Study of Irrigation Drainage Effect on Biota
(1) The average annual streamflow of the Carson 

River near Fort Churchill (U.S. Geological Survey 

station 10312000, approximately 50 river miles 

upstream from Carson Lake; fig. 1) was about 

270,000 acre-ft (rounded) for the period of record, 

1911-88 (Pupacko and others, 1989, p. 117).

(2) The average annual streamflow of the Carson 

River to Carson Lake and the connected Stillwater 

Marsh before agricultural development (pre-1860) 

was estimated to be equal to the present average 

annual streamflow near Fort Churchill plus the average annual flow of all water now consumed by agriculture upstream of that point. Other historical water 

losses, primarily seepage and evapotranspiration from 

the formerly more extensive wetlands associated with 

the upper river, were probably equal to other modern 

losses. These losses include seepage and evapotranspiration from reservoirs and canals, municipal 

uses, and agricultural uses in excess of the Alpine 

Decree1 (Garry Stone, Federal Water Master, oral 

communication, 1990).

lrThe Alpine Decree is the adjudication of the Carson River 

water rights (California Department of Water Resources, 1991).

(3) About 56,000 acres are irrigated along the 

Carson River above Fort Churchill, with an annual 

evapotranspiration rate of 2.5 acre-ft/acre, as calculated from the Alpine Decree (California Department 

of Water Resources, 1991, p. 126), which results in 

an estimated 140,000 acre-ft of water being diverted 

from the Carson River and consumed annually. This 

amount is in agreement with the findings of Brown 

and others (1986, p. 30) that about 137,000 acre-ft of 

water may be consumed annually from the area above 

Lahontan Reservoir.

Thus, adding the estimate of agricultural 

consumptive use (about 140,000 acre-ft) to the 

Carson River discharge at Fort Churchill (about 

270,000 acre-ft), the historical, unregulated annual 

average discharge of the Carson River at Fort Churchill 

was approximately 410,000 acre-ft. Based on the 

1911-1988 period of record, the flow ranged from 

about 90,000 acre-ft/yr (sum of Carson River inflows 

above Fort Churchill [U.S. Geological Survey, 1978]) 

to about 940,000 acre-ft/yr (800,000, rounded [Frisbie 

and others, 1984, p. 127], plus 140,000). Seasonal 

variations in Carson River flows for the period of 

record (1919-1969) are discussed by Glancy and 

Katzer (1976, p. 34-42) and shown for the Fort 

Churchill station in figure 3 of this report.

1,600

OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEP

Figure 3. Mean monthly flow and quartile statistics, Carson River gage 

near Fort Churchill, USGS station 10312000, water years 1919-69. 

Modified from Glancy and Katzer (1976, p. 35).

ESTIMATED HISTORICAL CONDITIONS Kerley and others
Average Historical Size of Carson Lake

The areal extent of wetlands at Carson Lake 

when maintained by the entire average annual flow 

of the Carson River was dependant primarily on the 

annual evapotranspiration rates, wetland morphology, 

and magnitude of seasonal inflow. Natural variation in 

the course of the river where it entered the Carson 

Desert is discussed by Morrison( 1964, p. 104). During 

recent geologic time, the Carson River usually flowed 

southeastward toward Carson Lake. As observed by 

Russell (1885, p. 44-45) in the mid 1800's, the Carson 

River also flowed northward to Carson Sink (North 

Carson Lake in fig. 2). The frequency of such flowpath changes over geologic time is unknown.

From his camp on Stillwater Slough in 1859, 

Simpson (1876, p. 85) observed a distinct line of cottonwood trees along the Carson River where it entered 

Carson Lake. E.M. Kern, a topographer with the 

Fremont Expedition of 1845, also reported seeing trees, 

probably cottonwoods, at the mouth of the Carson 

River from across the lake (Spence and Jackson, 1973, 

p. 51). These trees, large enough to be visible from a 

distance of at least 5 mi, as calculated from the map in 

figure 2, are an indication that a relatively stable geographic configuration of the lower Carson River had 

existed for 20-50 years prior to Kern's visit. For purposes of the present analysis, Carson Lake is assumed 

to have been a permanent wetland feature.

The maximum depth of Carson Lake at full 

pool is 10 ft, with the lake-bottom altitude at 3,909 ft 

above sea level (Hart and Bixby, 1922, p. 13) and the 

rim altitude at 3,919 ft (Morrison, 1964, p. 104). The 

maximum surface area of Carson Lake at the rim is 

about 34,000 acres. Russell (1885, p. 44-45; 1895, 

p. 108) observed the Carson Desert in the early 1880's, 

after the onset of early irrigation and after the Carson 

River had split with one part bypassing Carson Lake, 

thus reducing inflow to the lake. He described Carson 

Lake as varying in size and depth with the alternation 

of the seasons, generally outflowing through Stillwater 

Slough (1885, p. 68-69). The lake was discharging 

through the slough in June 1881, had an open water 

area of about 26,000 acres in 1882, and by September 

1883, much of the lake appeared to be a swamp 

(Russell, 1885, p. 45, 69). Because emergent vegetation in this region is typically found where water 

depths are less than 3 ft, by September 1883 the surface 

of Carson Lake probably was at least 7 ft below its natural rim. This inferred difference in water level is

greater than the evapotranspiration rate of 5 ft/yr 

(U.S. Department of the Interior, 1988, p. A-31). 

Outflow from Carson Lake in 1882 was nonexistent, 

as noted by Russell (1885, p. 45, 69). Apparently, the 

lake, at the time of his estimate of about 26,000 acres, 

was smaller than its maximum of 34,000 acres. About 

one fourth of the adjacent marsh, which was above the 

normal maximum lake-surface altitude, was probably 

intermittently flooded and may have covered about 

4,000 additional acres (fig. 2). For purposes of this 

discussion, then, the maximum wetland acreage of 

Carson Lake and the adjacent marsh land is estimated 

to have been about 38,000 acres.

Large variations in the Carson River streamflow, 

both seasonal and annual, would have affected the size 

of Carson Lake seasonally. Typically, the seasonal 

flow patterns vary from low flow from August through 

November, to a slow increase through March, and 

finally to a spring peak late in April that falls off by July 

(fig. 3). Seasonally diminishing streamflows of the 

Carson River usually limit agriculture in the basin 

above Fort Churchill by July 15 (Carry Stone, 

Federal Water Master, oral comrnun., 1990).

The summer and fall streamflow in the Carson 

River may regularly have been insufficient to maintain 

Carson Lake, and the lake size may have peaked at the 

rim in early summer, then decreased. The estimated 

4,000 acres of adjacent marsh is assumed, for purposes 

of this discussion, not to change in size. The seasonal 

variation noted by Russell (1885, p. 68-69) may have 

been usual. Richard Burton, in 1860 (1963, p. 551), 

found the water to be about a mile away from a Pony 

Express station (at the southwestern edge of the lake), 

but the following summer DeQuille (1963, p. 28) 

observed that the water was again up to the dock of the 

station. A summer-fall evaporative loss of 3 ft in depth 

would have reduced the surface of Carson Lake from a 

possible maximum of about 34,000 acres to about 

29,000 acres. The lake size also has been periodically 

reduced by drought (Morrison, 1964, p. 104; Russell, 

1895, p. 108). Thus, on the basis of the discussion 

above, the historical average wetted surface area of 

both open water and adjacent marsh at Carson Lake 

was less than the historical maximum, 38,000 acres, 

and is conservatively estimated to be 27,000 acres 

(table 1). This lesser acreage amount is used in 

the subsequent water-consumption estimate for 

Carson Lake.

10 Detailed Study of Irrigation Drainage Effect on Biota
Table 1 . Estimated historical (predevelopment) wetland acreage compared to 

projected wetland acreage at Carson Lake and the combined wetlands of 

Stillwater Marsh and Carson Sink

{All values have been rounded]

Wetland Acreage

Wetland area

Predevelopment estimate 

(1845-60) Projected 

average1

Range Average

Carson Lake

(South Carson Lake in figure 2)

Stillwater Marsh and Carson Sink 

(North Carson Lake and adjacent 

marsh lands in figure 2)

TOTAL (rounded)

225,000-338,000 27,000 5,000

20-200,000 120,000 4 11,000

150,000 16,000

1 U.S. Fish and Wildlife Service, 1988, p. 19, fig. 21.

2 Estimated minimum size associated with the 1911-88 period of Carson River flow records.

3 Includes about 4,000 acres of adjacent marsh land.

4 Includes 3,000 acres of historical Stillwater Marsh located within the Canvasback Gun Club 

(C. Clifford Creger, U.S. Fish and Wildlife Service, written commun., 1992).

Flow Through Stillwater Slough

In 1861, DeQuille described Stillwater Slough 

as 60 ft wide, with vertical banks 8-10 ft high, having 

no grass along the stream, and cutting through the 

barren sandy plain with only scattered clumps of sage 

and greasewood, which is typical of an intermittent 

waterway in this area (DeQuille, 1963, p. 36-37). The 

absence of hydrophytic vegetation in this channel also 

supports the contention that summer-fall flow in the 

Carson River was regularly insufficient to maintain 

flow through Stillwater Slough. Evapotranspiration 

losses at Carson Lake reduced the flow of the Carson 

River before it discharged through Stillwater Slough 

to Stillwater Marsh. These losses also decreased the 

duration of flow in the Carson River system below 

Carson Lake. With 27,000 acres average surface area 

and an evapotranspiration rate of 5 ft/yr, Carson Lake 

would have consumed about 140,000 acre-ft of water 

per year. Subtracting this from the unregulated average 

annual flow in the Carson River, about 410,000 acre-ft, 

leaves an annual average flow of 270,000 acre-ft to 

pass through Stillwater Slough into the wetlands 

Stillwater Marsh plus Carson Sink.

Average Historical Size of Stillwater Marsh

The wetted area of Stillwater Marsh and the 

downgradient playa wetlands (much of Carson Sink) 

were more variable in size than Carson Lake because 

of the cumulative evapotranspiration losses in these 

shallow, sequentially distributed wetlands (Morrison, 

1964, p. 104). Because there are no early quantitative 

estimates of the size of Stillwater Marsh a series of 

interconnecting wetlands and ponds flowing generally 

from south to north, the average size of the Marsh 

must be estimated using other approaches. Archaeological evidence and pollen cores indicate that a relatively permanent marsh existed in the Stillwater area 

for the last 4,000 years (Kelly, 1988; Warburton and 

others, 1990, p. 74), an area known to have been 

regularly inhabited by man, and by other waterdependent species.

Stillwater Marsh was called Stillwater Lakes 

by Morrison (1964, p. 104). That observation implies 

enough water depth (at least 3 ft) to possibly preclude 

the growth of emergent vegetation and maintain open 

water areas. Minor variations in topographic elevations (5-15 ft) may be responsible for the formation 

of these "lakes" at Stillwater Marsh (Raven and Elston, 

1989, p. 33). These depressions, by their proximity

ESTIMATED HISTORICAL CONDITIONS Kerley and others 11
to flow from Stillwater Slough and by retaining 

water, gave a degree of permanence to these wetlands 

compared to the relatively flat areas of Carson Sink.

Raven and Elston (1989, p. 64, 69) have 

defined two broad categories of historical wetlands 

at Stillwater, namely "marsh" and "playa," based 

on soil types and hydrologic characteristics. Both 

wetland types supported human occupation and waterdependant biota. "Marshes" were those areas which 

characteristically had enough differences in topography to maintain a combination of open water, 

emergent vegetation, and upland sites suitable for 

human habitation. In the absence of detailed land 

surveys prior to development of Lahontan Valley, 

the historical amount of each wetland type is uncertain. 

Elevations determined from U.S. Geological Survey 

7.5-minute quadrangle maps indicate that up to 

55,000 acres of wetlands were possible in what is 

now (1993) the Stillwater National Wildlife Refuge. 

Therefore, wetland acreage could have ranged from 

0 to 55,000 acres. Classification of wetland types on 

current U.S. Geological Survey 7.5-minute quadrangle 

maps indicates that wetlands at full pool consisted of 

an average of approximately 15,000 acres of marsh 

and 40,000 acres of playa (C. Clifford Creger, U.S. 

Fish and Wildlife Service, Fallen, Nev., written commun., 1992). These areas are consistent with a predictive model based largely on soil types, hydrology, 

and topography developed by Raven and Elston (1990, 

p. 123-34).

Carson River inflow through Stillwater Slough 

was seasonally intermittent. Parts of Stillwater Marsh 

were subjected to seasonal drying, as were the margins 

of Carson Lake. Although a graded change in evaporation losses would be predicted as the marsh diminished, 

it is conservatively estimated that 75 percent of this 

wetland, about 11,000 acres, would remain wetted and 

lose water at a rate of 5 acre-ft/yr. This lesser acreage 

is used only in the subsequent water consumption estimate for Stillwater Marsh.

Stillwater Marsh would have been dry only 

once during the period of record for the Carson River 

(1911-198 8), resulting from the drought of water-years 

1976-77.

Estimated Flow into Carson Sink Wetlands

Average water loss by evapotranspiration from 

the estimated 15,000 (full-pool) acres of Stillwater 

Marsh would have been 56,000 acre-ft, assuming that 

25 percent of the area was seasonally dry. Thus, 

the 270,000 acre-ft of Carson River water entering the 

marsh by way of Stillwater Slough each year would be 

further reduced to an average of about 210,000 acre-ft 

before entering wetlands in the Carson Sink.

Estimated Size of Carson Sink Wetlands

Wetland acreage in the Carson Sink maintained 

by Carson River water was, as it is now, generally 

ephemeral. Ephemeral wetlands are typically shallow, 

receiving only a few inches of water at the distal edges, 

and tend to evaporate completely or nearly so 

before the next inflow season. Under unregulated 

conditions, average Carson River flow would have 

refilled Carson Lake and Stillwater Marsh and begun 

to flow into the Carson Sink during winter. Most flow 

would have reached the sink following spring snow 

melt or occasional rain-on-snow events. During the 

spring, wetlands in the southeastern portion of the 

Carson Sink may have been characterized by having 

large volumes of flowing water relatively low in dissolved solids. This portion of Carson Sink wetlands 

may have been wetted for as long as 6 months in most 

years. In response to decreasing Carson River inflow 

and increasing evapotranspiration rates in the summer, 

the palustrine regime would have ceased and the wetlands would have rapidly receded in size and depth to 

zero or some variable minimum size. Wetlands at 

the advancing edge of water during peak flow events 

would have been the most ephemeral, persisting only 

a few weeks.

Approximately 40,000 acres of playa wetlands 

on the Carson Sink within the confines of the present 

(1993) Stillwater National Wildlife Refuge also contain human occupation sites and evidence of waterdependent biota (C. Clifford Creger, U.S. Fish and 

Wildlife Service, Fallen, Nev., written commun., 

1992).

Two accounts of water on the Carson Sink 

provide a basis from which to estimate an average wetland depth. This, combined with the average Carson 

River inflow, is used to estimate the average size of 

wetlands in the Carson Sink.

12 Detailed Study of Irrigation Drainage Effect on Biota
During September 1929, Sperry (1929, p. 1-3) 

surveyed the wetlands on the Carson Sink at the mouth 

of the Carson River. At that time, the river emptied into 

the Sink in the vicinity of what is now Fallen NWR, 

adjacent to Still water and topographically similar 

mostly flat with shallow sloughs and low rises. 

Sperry considered the water supply to be deficient that 

year and below normal, and reported the water to be 

mostly less than 1 ft deep, with a few ponds 2.5-3 ft 

deep. In addition to alkali bulrush (Scirpus maritimus) 

beds, he saw blackened basal stalks that "coat long 

reaches of the higher ground and indicate an enormous 

extension of big beds during wet seasons." His observation of "carpets" of sago pondweed (Potamogeton 

pectinatus), some in mature fruit, left exposed by the 

receding waters, indicates that the water receded rapidly and suggests fairly rapid decreases in wetland size 

in the fall.

During the 1980's, the Carson Sink was 

inundated by flood flows from both the Carson and 

Humboldt Rivers. This is considered an anomalous 

event; flooding on that scale last occurred in the 1860's. 

The 1980's occurrence created unusual physical and 

water-quality conditions, and is of interest here primarily because of observations of water depth made at 

various times during the inundation.

Between July 1984 and February 1985, flood 

water inundating Carson Sink and Stillwater Marsh 

covered about 212,000 acres of surface area to a maximum depth of nearly 12 ft (Rowe and Hoffman, 1990, 

p. 37). At that size, the average depth would have been 

8 ft and the volume about 1,700,000 acre-ft. In midJanuary of 1987, water in the Carson Sink had receded 

to less than 180,000 surface acres, with an average 

depth of 2 ft and a maximum of 6 ft (Rowe and 

Hoffman, 1990, p. 37). The volume of water in 

the Carson Sink would then have been less than 

360,000 acre-ft.

Although it is recognized that wetlands on 

the Carson Sink were dynamic, an average depth is 

needed to estimate the extent of wetlands which may 

typically have been maintained by the Carson River. 

Based on the observations by Sperry (1929) and 

Rowe and Hoffman (1990), 2 ft is a reasonable estimate for an average depth. Using this 2-ft depth, the 

210,000 acre-ft inflow from the Carson River could 

have seasonally flooded an average of 105,000 surface 

acres of wetlands on Carson Sink. This area represents

an average of maximum wetland sizes that could be 

anticipated from the flows of the 1911-1988 period 

of record for the Carson River.

The Carson Sink wetlands may have varied 

in size from 0 to 190,000 surface acres, based on fluctuations of the Carson River alone during the 78-year 

period of record. The low point, zero, would have 

occurred with flow similar to that of water-year 1977 

(the second year of the 1976-77 drought) when 

the Carson River flow would not have reached the 

Carson Sink. The maximum, 190,000 acres, is based 

on the flow of the Carson River during water-year 

1983. The adjusted flow of the Carson River at Fort 

Churchill in water-year 1983 was about 940,000 acre-ft 

(800,000 acre-ft, rounded [Frisbie and others, 1984, 

p. 127], plus 140,000 acre-ft from assumption no. 3 

in the subsection "Estimated Historical Carson River 

Flow and Wetland Sizes"), and the inflow to the 

sink from the Carson River through Stillwater Marsh 

is estimated to have been about 750,000 acre-ft. 

Based upon a linear relationship of surface areas 

and water volumes observed by Rowe and Hoffman 

(1990), this 750,000 acre-ft would have inundated 

about 190,000 surface acres on the Carson Sink, with 

an average depth of nearly 4 ft and a maximum of 8 ft. 

Some of this water would be expected to remain on 

the sink into the following year. Under these extreme 

hydrologic conditions, parts of Stillwater Marsh also 

would be flooded.

ESTIMATED HISTORICAL 

WATER QUALITY

Little information about the historical water 

quality of the lower Carson River system exists, but 

explorers and local residents of the mid to late 1800's 

reported good water (presumably potable, in the 

historical sense), plentiful vegetation, and abundant 

wildlife at various locations in the lower Carson River 

basin and its wetlands.

In June 1859, Simpson (1876, p. 85) visited 

Carson Lake and wrote the following:

ESTIMATED HISTORICAL CONDITIONS Ker/ey and others 13
We are encamped at the head of the 

outlet from Carson Lake into the sink of 

Carson, where our only fuel is dry rush. This 

outlet is about 50 feet wide and 3 or 4 feet 

deep, and voids the lake rapidly into its sink, 

which is some 10 or 15 miles to the northeast 

of us. The water is of a rather whitish, milky 

cast, and though not very lively, is yet quite 

good. The Carson River to the northwest, 

where it empties into the lake, can be seen 

quite distinctly, marked out by its line of 

green cottonwoods.

The name of the river and lake was 

given by Colonel Fremont, in compliment to 

Kit Carson, one of his celebrated guides.

The alluvial bottom about Carson Lake 

is quite extensive and rich, as the luxuriant 

growth of rushes shows, and could, I think, 

be easily irrigated. The only drawback to its 

being unexceptionable for cultivation in every 

part is its being somewhat alkaline in places, 

particularly toward its southern portion. 

Curlew, pelican, and ducks, and other 

aquatic birds frequent the locality, and 

the lake is filled with fish.

Wuzzie George, a Native American residing 

in Lahontan Valley in the early 1900's and a keen 

observer of natural things, referred to the abundance 

of submergent vegetation in the Stillwater marshes 

(U.S. Fish and Wildlife Service, 1952, p. 19), an indication of water clarity. Hart and Bixby (1922, p. 15) 

found Carson Lake in 1922 to be slightly alkaline, with 

very little accumulation of salts on the edges, and with 

"vegetation [that]... indicates the absence of an excess 

of harmful salts." At Stillwater Marsh, the remains of 

freshwater clams (Anadonta sp.\ fish, mink (Mustela 

5/7.), and river otter (Lutra sp.) in archaeological sites 

indicate the marsh had higher water quality than at 

present. The wetland ecosystem in the southern inflow 

area of Stillwater Marsh would have flourished with 

natural flushing, but water in the ephemeral wetlands 

on the Carson Sink would have accumulated salts. The 

fluctuating north and west margins of this ephemeral 

marsh probably resembled the barren areas associated 

with current managed wetlands, where water with dissolved solids concentrated beyond the tolerance level 

of aquatic plants is disposed of through evaporation.

Historical water-quality conditions were 

estimated using period-of-record data on streamflow 

and dissolved solids for the Carson River at the Fort 

Churchill gage. The average measured dissolvedsolids concentration at the Fort Churchill gage for the 

period 1970-88, the only data available, was 218 mg/L 

and ranged from 70 to 454 mg/L (Ray J. Hoffman, 

U.S. Geological Survey, written comrnun., 1990). 

Although the average Carson River streamflow 

measured at Fort Churchill has decreased because 

of upstream diversions, the recent average dissolvedsolids load at Fort Churchill (about 90,000 ton/yr) is 

assumed, for the purpose of the present analysis, to 

be about equal to the average historical dissolvedsolids load. Although predevelopment loads did not 

include post-development contributions of dissolved 

solids from irrigation returns and sewage disposal, 

this assumption should result in a reasonable estimate 

of an upper limit for predevelopment dissolved-solids 

loads and concentrations. The average historical 

(1845-1860) concentration of dissolved solids entering 

Carson Lake is estimated to be about 170 mg/L. This 

concentration was determined by computing the ratio 

of the average volume of water for the period 1970-88 

to the historical volume of water, then multiplying by 

the average dissolved-solids concentration for the 

period of record and adding an estimate for natural 

accretion (see footnotes 7 and 8 in table 2):

(300,000 acre-ft / 410,000 acre-ft) 218 mg/L 

+ 10 mg/L = 170 mg/L (rounded). 1

Historically, an estimated annual average of 

about 410,000 acre-ft of water reached Carson Lake 

by way of the Carson River; most of it overflowed 

to Stillwater Marsh. The water entering Carson Lake, 

with an estimated dissolved-solids concentration of 

170 mg/L, carried a probable dissolved-solids load 

of about 95,000 ton/yr to the wetlands (table 2). This 

estimated load to the wetlands provides a benchmark 

for understanding baseline water-quality conditions 

that existed in Carson Lake, Stillwater Marsh, and 

the Carson Sink.

lrThe estimated historical dissolved-solids concentrations 

presented in this section are intended solely as a historical 

baseline for comparison with existing water quality of wetlands in the lower Carson River basin receiving irrigation 

drainage. Because of variation of flow and the high evaporation 

rate, the average conditions described herein may have been 

greatly exceeded at times; thus, the estimated predevelopment 

concentrations should not be used to set downstream waterquality standards.

14 Detailed Study of Irrigation Drainage Effect on Biota
Table 2. Estimated historical (predevelopment) and recent or 

projected water quantity and dissolved-solids concentrations and 

loads for Carson River, Carson Lake, and Stillwater Marsh. 

(Estimated historical dissolved-solids concentrations should not 

be used to set water-quality standards for wetlands in the 

study area)

[Abbreviations: acre-ft, acre-feet; ft/yr, foot per year; mg/L, milligrams per liter; 

ton/yr, tons per year]

Carson River

at Fort

Churchill

gaging station

Carson

Lake

Stillwater

Marsh

Water quantity (acre-ft) 

Historical (1845-60) ^10,000 2410,000 3 270,000

Recent (1970-88) or 

projected by OCAP4 5300,000 625,000 655,000

Dissolved-solids concentration (mg/L) 

Historical (1845-60) 7 160 7'8 170 7'8270

Recent(1970-88) or 

projected by OCAP4 7220 91,170 9 1,170

Dissolved-solids load (ton/yr)10 

Historical (1845-60) 89,000 95,000 99,000

Recent (1970-88) or 

projected by OCAP4 90,000 40,000 88,000

1 Estimated historical unregulated discharge at Fort Churchill gage (average 

annual streamflow for period of record plus upstream consumptive use; see text for 

details).

2 All of Carson River flow estimated to enter Carson Lake.

3 Water entering Stillwater Marsh estimated by using total inflow to Carson Lake 

(410,000 acre-ft), minus evaporation rate (5 ft/yr) multiplied by average wetland 

acreage of Carson Lake (27,000, rounded; table 1).

4 OCAP (Operating criteria and procedures for Newlands Project) projection 

for 1992 and beyond (U.S. Fish and Wildlife Service, 1988).

5 Recent (1970-88) annual average (R.J. Hoffman, U.S. Geological Survey, 

written commun., 1990).

6 Estimated acreage projected for OCAP (table 1) multiplied by evaporation rate 

(5 ft/yr). L

7 Calculated from quantity and loads: C = 

Of

where

C is concentration, in mg/L;

L is load, in ton/yr;

Q is quantity (streamflow), in acre-ft; and

/is factor for converting mg/L to tons (0.00136).

8 Estimate includes calculated natural accretion of dissolved solids along the 

stream channel (R.J. Hoffman, U.S. Geological Survey, written commun., 1990).

9 U.S. Fish and Wildlife Service, 1988, p. 51.

10 All values calculated from estimated discharge and concentration 

(L = CXQXf).

ESTIMATED HISTORICAL CONDITIONS /Cer/ey and others 15
The average wetted surface area of Carson 

Lake (27,000 acres) would have lost, through evapotranspiration, about 140,000 acre-ft of water annually. 

This loss of water from Carson Lake would have 

increased the dissolved-solids concentration in the 

remaining 270,000 acre-ft of water to about 260 mg/L 

as it discharged through Stillwater Slough. Because of 

its shallow depth and shape, Carson Lake would have 

exchanged water easily with the inflow. The average 

flow of the Carson River was about 2.5 times greater 

than the lake's maximum volume, thus long-term concentration of dissolved solids in Carson Lake would 

not have occurred, and the dissolved-solids load 

leaving the lake would have been similar to the inflow, 

about 95,000 ton/yr. Because the average volume 

of the outflow from Carson Lake is about 10 times 

the volume of Stillwater Marsh, essentially the same 

dissolved-solids load would have passed through the 

Marsh into Carson Sink. The dissolved-solids concentrations, however, would have been higher and more 

variable in these lower wetlands than in Carson Lake.

Several early reports are available that describe 

water quality in Stillwater Slough and Carson Lake. 

Kern (Fremont Expedition of 1845) said of the water 

at the outlet of Carson Lake that it was "indifferently 

good" (Spence and Jackson, 1973, p. 52). Stillwater 

Slough water was described as "quite good" by 

Simpson (1876, p. 85). DeQuille, in the summer 

of 1861, described the water at the south end of 

Carson Lake as having the taste of decayed tules, but 

found the water in the upper slough to have a "touch 

of alkali" and at the lower end at the mouth of the 

sink, "a strong alkali twang"; he sent an Indian several 

hundred yards into the marsh for drinking water (1963, 

p. 28, 38, 42). After 60 years of agricultural activities 

(1862-1922), the dissolved-solids concentration of the 

water in Carson Lake was still only about 1,000 mg/L 

(Hart and Bixby, 1922, p. 15). For comparison, the 

maximum permissible dissolved-solids concentration 

in Nevada public water supplies is 1,000 mg/L. 

Dissolved-solids concentrations would have fluctuated 

seasonally when the lake surface regularly dropped 

below its natural rim in the fall and during droughts. 

As an example, Professor F.W. Clarke found a 

dissolved-solids concentration of about 1,500 mg/L 

in a water sample collected from Carson Lake in 

October 1863, a year after the Carson River was 

diverted from the lake during the floods of 1862 

(Russell, 1885, p. 44, 69).

Approximately half the streamflow of the 

Carson River would have come during peak snowmelt runoff from April through mid-July, then in most 

years would have diminished abruptly. This pattern 

would have resulted in dissolved-solids concentrations 

that were more variable in Stillwater Marsh than in 

Carson Lake. In most instances, dissolved-solids concentrations in Carson Lake and much of Stillwater 

Marsh would not have been a limiting factor to the 

biota known to have existed in the system. From 

examination of pollen in a core of Lead Lake sediment, 

scientists of the Desert Research Institute found that the 

wetland water had been alternately brackish and fresh 

(Warburton and others, 1990, p. 73-74). Because of 

the irregular topography of Stillwater Marsh, some 

wetland areas may have been poorly flushed and 

occasionally bypassed by the flow of the Carson River.

Although Carson Lake and Stillwater Marsh 

currently are hydrologically isolated, the dissolvedsolids loads projected under OCAP were summed 

(128,000 ton/yr) and compared to historical load 

(99,000 ton/yr) to assess the extent of change. 

While the projected load is estimated to increase somewhat about 30 percent over the historical load, the 

projected concentration would increase greatly about 

400 percent. Such a large increase in concentration is 

significant because living organisms respond physiologically to concentration rather than to load. Although 

the historical dissolved-solids concentration in Carson 

Lake would have increased as a result of evapotranspiration, the concentration in the water as it was flushed 

into Stillwater Marsh may have averaged 270 mg/L 

(see footnotes 7 and 8 in table 2) because of the higher 

river flows at that time. This concentration would have 

been representative of conditions throughout most of 

Stillwater Marsh following the spring flow peak.

The extrapolated estimates and existing reports 

indicate that the predevelopment water supply was 

probably adequate and of suitable quality to support 

healthy wetlands and their associated plants, fish, 

and wildlife. In the absence of agricultural irrigation, 

which has been shown to mobilize salts and trace 

elements such as arsenic, boron, selenium, molybdenum, and lithium (Hoffman and others, 1990, p. 31-38), 

and a corresponding increase in dissolved-solids concentrations, the water reaching Carson Lake and 

Stillwater Marsh in predevelopment time (pre-1860) 

was of better quality than water reaching the wetlands 

today.

16 Detailed Study of Irrigation Drainage Effect on Biota
Historical water quality in the ephemeral 

wetlands of Carson Sink, however, would have 

varied greatly. Under a representative average condition, 210,000 acre-ft of fresh water (about 270 mg/L, 

dissolved solids) would have passed into these ephemeral wetlands, flushing the area near Still water Marsh. 

Regular flushing in the spring would have created 

conditions favorable for aquatic vegetation and many 

forms of wildlife. Sperry (1929, p. 1-2) reported a 

wide variety of both submergent and emergent vegetation and wildlife in the sink, including extensive beds 

of alkali bulrush and sago pond weed. Alkali bulrush 

tolerates brackish water ranging from a specific conductance of 995 uS/cm (about 650 mg/L, dissolved 

solids) to 25,800 uS/cm (about 16,800 mg/L, dissolved 

solids). Sago pondweed grows in water containing as 

much as 16,800 mg/L, dissolved solids (25,800 uS/cm; 

Stewart and Kantrud, 1972, p. D5, D21, and D25). 

Archaeological sites that were occupied by humans 

are found in the playa habitat within the Carson Sink. 

These sites are similar to those in Stillwater Marsh, 

indicating the presence of wetland plants and animals 

(C. Clifford Creger, U.S. Fish and Wildlife Service, 

Fallen, Nev., written commun., 1992). Thus, these 

sites probably had potable water, in the historical sense, 

during periods of human use.

Water-quality characteristics are different 

when the Carson Sink is filled. Such an event, 

anomalous under current managed conditions, 

occurred between 1982 and 1988 when large 

quantities of relatively dilute flood water from both 

the Carson and Humboldt Rivers filled Carson Sink 

to a depth of nearly 12 ft (average 8 ft). In July 1983, 

specific conductance of flood water in the Carson 

Sink near Humboldt Slough was 4,700 uS/cm (about 

3,100 mg/L, dissolved solids), but by January 1987 

water in the Carson Sink had reached a dissolvedsolids concentration of 20,000 mg/L (Rowe and 

Hoffman, 1990, p. 37). This concentration cannot be 

accounted for by evaporative water loss alone; much 

of the dissolved solids probably resulted from redissolving salts previously deposited in the sink. During 

this event, no vascular aquatic plants grew in the sink. 

Fish flourished during the first years, then perished 

when the dissolved-solids concentrations of water 

became intolerably high as the water evaporated. 

A similar cycle probably occurred in the 1860's; 

the water in Carson Sink was 20 ft deep in 1863, 

according to Morrison (1964, p. 104).

In summary, the historical condition of the 

Carson River-Carson Sink system was a flushthrough pattern with most of the runoff occurring 

in the spring. Runoff flowed into Carson Lake, overflowed into Stillwater Marsh, and then created extensive ephemeral wetlands in the Carson Sink. Almost 

the entire 410,000 acre-ft (average annual flow) of 

Carson River with a probable low average (<300 mg/L) 

concentration of dissolved solids, entered the wetlands. 

The wetlands would have been largest in the spring, 

decreasing by evapotranspiration through the summer 

and fall. Salts deposited primarily in the sink by evaporating water would have been redissolved by the flushing action of subsequent spring peak flows and carried 

farther out into the sink. The distal edges of the 

wetlands would normally have been brackish, and 

the farthest reaches, at times, even more saline.

VEGETATION

Early reports of the study area describe a 

biologically productive marsh with a great diversity 

of vegetation. In 1845, when Kern reported timber 

at the mouth of the Carson River, he also described 

Carson Lake as bordered by "a thick growth" of 

bulrush about 30-40 yards wide at the mouth of the 

river (Spence and Jackson, 1973, p. 51-52). Simpson 

(1876, p. 85-86) called the alluvial bottom around the 

lake in 1859 "extensive and rich, as the luxuriant 

growth of rushes shows." Bailey (1898, p. 3) described 

Stillwater Marsh as "... half shallow lake, half tule 

swamp [which] extends for 20 miles along the valley 

bottom and furnishes enough salt grass, sedges, and 

tules to winter many thousand head of stock and a 

breeding ground for great numbers of water and 

shore birds."

Early in this century, Sperry (1929, p. 1-3) 

described the vegetation in the southwestern part of 

Carson Sink. At that time, alkali bulrush dominated 

the marsh, and cattail (Typha sp.) was common. Spike 

rush (Eleocharis acicularis) was abundant. Open 

water areas contained abundant stands of sago pondweed, horned pondweed (Zannichellia palustris), 

and algae. The old high-water line was marked by 

iodine brush (Allenrofea sp.), below that was a bank 

of pickle weed (Salicornia sp.), and all around, even 

out in the mudflats, were patches of salt grass 

(Distichlis spicata).

ESTIMATED HISTORICAL CONDITIONS Ker/ey and others 17
Wuzzie George described Stillwater Marsh of 

the early 1900's as abundant in both submergent and 

emergent vegetation; alkali bulrush was the most 

common emergent, followed by hardstem bulrush 

(Scirpus acutus) and cattails (U.S. Fish and Wildlife 

Service, 1952, p. 19).

At Stillwater Marsh, inflow water was 

sufficient to maintain luxurient wetland vegetation 

until 1967 when regular winter water releases from 

Lahontan Reservoir for power generation were discontinued. During the early 1950's, cattails were the dominant emergent species in the marsh, followed by alkali 

bulrush, then hardstem bulrush, at a ratio of 4.5:1.5:1 

(U.S. Fish and Wildlife Service, Fallen, Nev., 1952, 

written commun.). A quantitative survey in Stillwater 

Marsh in 1959 found a diversity of vegetation. Emergent vegetation was then dominated by alkali and 

hardstem bulrushes and submergent plants by horned 

pondweed, sago pondweed, and western pondweed 

(Potamogetonfiliformis). Other submergent plants 

observed by the U.S. Fish and Wildlife Service 

included coontail (Ceratophyllum demersum), 

muskgrass (Chara sp.), widgeon grass (Ruppia maritima), and curly-leaf pondweed (Potamogeton crispus). 

Some submergent plants, such as horned and sago 

pondweeds and widgeon grass, are relatively insensitive to high concentrations of dissolved solids (Stewart 

and Kantrud, 1972, p. D25; Steward and others, 1963, 

p. 50). The abundance of these submergent plants, as 

well as more sensitive species in Stillwater Marsh in 

1959, indicates the presence of a mixture of fresh and 

brackish water at that time (U.S. Fish and Wildlife 

Service, 1969).

In the Stillwater WMA, coontail and other 

less salt-tolerant pondweeds that were abundant in 

the 1959 survey have decreased, not only in total 

abundance but also relative to the more tolerant 

species, such as widgeon grass and sago pondweed. 

The abundance of some plants, such as western pondweed, is correlated with freshwater inflow. Cattails 

are extremely sensitive to increased dissolved-solids 

concentrations, whereas alkali and hardstem bulrushes 

tolerate higher concentrations (Stewart and Kantrud, 

1972, p. D21); cattails in Stillwater WMA are now 

found only in scattered patches.

Information from U.S. Geological Survey 

topographic maps (Carson Lake and Fallen quadrangles) published in 1951 indicates that vegetation has 

also diminished at Carson Lake by about 50 percent 

in the last 30 years. Today, much of Carson Lake is a

pasture for livestock. Much of the remaining water 

area is entirely devoid of vascular aquatic vegetation, 

and emergent vegetation is reduced to relatively small 

stands of bulrush near the inflow from drains.

WILDLIFE

Historically, the wetlands of the Carson LakeStillwater area supported a large and diverse assemblage of animals as well as plants. Archaeological 

studies have determined that the wetland areas were 

used extensively by native people for a period exceeding 4,000 years (U.S. Department of the Interior, 1988, 

p. Fl; Kelly, 1988, p. 11), an indication that the early 

(pre-1860) wetlands were a more productive and reliable habitat than those existing today. Little information is available to quantify the abundance of wildlife 

in the study area prior to irrigation diversion, but 

reports from early explorers and archeologists indicate 

that populations and diversity of wildlife were much 

greater than exist today.

According to Simpson (1876, p. 85), the marsh 

supported abundant fish populations. Simpson wrote, 

"... the lake is filled with fish...[the Indians] have piles 

of fish lying about drying, principally chubs and mullet." DeQuille (1963, p. 33) saw Indians with "several 

fine strings offish" in 1861 and the Indians fishing 

nearby were having "first-rate luck"; one had caught 

four nice fish in a few minutes. Fish bones are commonly found in archaeological sites, suggesting that 

fish were a significant food source for the people; skeletal remains of tui chub (Gila bicolor) and tahoe sucker 

(Catostomus tahoensis) are abundant at archaeological 

sites in Stillwater Marsh (Greenspan, 1988, 

p. 315-326). Both fish species are tolerant of wide 

ranges of dissolved solids. Lahontan cutthroat trout 

(Onchorhynchus clarki henshawi), although not 

widely distributed, were found in some Stillwater 

archaeological sites (Smith, 1985, p. 177). Lahontan 

cutthroat trout are tolerant of dissolved solids up to 

approximately 12,000 mg/L (Taylor, 1972, p. 7), but 

are sensitive to high water temperature. Historical 

water quality in Carson Lake and the southern part of 

Stillwater Marsh should not have been a limiting factor 

in the survival and distribution of cutthroat trout at 

most times, but changing habitat and water temperature 

resulting from water-level fluctuations may have been.

18 Detailed Study of Irrigation Drainage Effect on Biota
River otter and mink, both fish-eating animals, 

were present and used by the native people (Schmitt, 

1988, p. 272). Pelicans (Pelecanus erythrorhynchos), 

also fish eaters, were "characteristic" of the area 

(Simpson, 1876, p. 86).

Freshwater clams and aquatic snails 

(gastropods) were once abundant throughout the wetlands. Simpson (1876, p. 86) observed in 1859 that 

the shores of Carson Lake were covered with clam 

shells, and Russell (1885, p. 69) reported various species of freshwater clams and snails in Carson Lake. 

Drews (1988, p. 329-333) found evidence that clams 

were a food item at various sites in Stillwater Marsh. 

Sperry (1929, p. 3), surveying the adjoining wetland in 

Carson Sink in 1929 (now Fallen NWR), found that 

clams, frogs (Rana sp.), and snails (Physa sp.) were 

common, and that muskrats (Ondatra sp.) were 

reported as abundant throughout Carson Sink.

Mink and otters are absent from the wetlands 

today, as are frogs and turtles. Muskrats are no longer 

abundant. Fish populations are greatly reduced, and 

the species composition has changed since historical 

times. Most of the native fishes are now absent from 

most areas; Lahontan cutthroat trout are entirely 

absent. Several species of non-native fishes, primarily 

sport fish, were introduced early in the century, but 

most have decreased to remnant numbers. Introduced 

Largemouth bass (Micropterus salmoides) was a 

major fishery until the 1970's, when the population 

virtually disappeared. Today, only remnant populations of freshwater clams remain in Stillwater Point 

Reservoir and in the D-line Canal, the areas with the 

lowest dissolved-solids concentration.

Historical references record the abundance 

of pelicans, curlews (Numenius americanus), other 

shore birds, ducks, geese, and other aquatic birds 

(Simpson, 1876, p. 85-86; Bailey, 1898, p. 3; DeQuille, 

1963, p. 28-32). Shore birds, including curlew, are 

largely insectivorous and tend to frequent shallow, 

sparsely vegetated ephemeral water areas and mud 

flats wetland types that historically covered thousands of acres on the Carson Sink in the spring and 

are now scarce. None of the birds are entirely absent 

today, but none could be termed abundant and some, 

such as the curlew, are uncommon.

PRESENT/PROJECTED 

WETLAND CONDITIONS

Court-ordered Operating Criteria and 

Procedures (OCAP) for the Newlands Project, to 

be fully in effect in 1992, were evaluated in detail by 

the U.S. Department of the Interior (1988). An estimate of projected wetland conditions was made, based 

on data for inflow of water from all sources available 

for wetland maintenance between 1967 and 1986 and 

on surveys of varying reliability, made in September 

for many years, of all major wetlands in the area. The 

managed wetlands at Carson Lake and Stillwater 

Marsh (Stillwater WMA and Canvasback Gun Club) 

under the 1992 institutional (OCAP) constraints, are 

used here to represent present/projected wetland conditions. It is important to note that the Carson River 

no longer flows through Carson Lake and thence to 

Stillwater Marsh. Both wetlands are isolated; are 

maintained with drainwater, operational releases, 

and occasional flood flows; and are manipulated 

with man-made water-control structures.

Recent (1967-1986) average wetland sizes for 

Carson Lake and Stillwater Marsh were 10,000 and 

14,000 acres, respectively. Under OCAP, flow to 

these primary wetlands, and their average size, are 

reduced about 50 percent (U.S. Department of the 

Interior, 1988, p. E5; U.S. Fish and Wildlife Service, 

1988, fig. 5, p. 52). Under projected managed conditions, an average 25,000 acre-ft of water would maintain about 5,000 wetland acres at Carson Lake, and 

an average 55,000 acre-ft of water in Stillwater WMA 

Marsh (including the Canvasback Gun Club) would 

maintain about 11,000 acres of wetlands. This projected total of average wetland sizes in Carson Lake 

and Still water Marsh (16,000 acres) is about 11 percent 

of the estimated historical sum of 150,000 average wetland acres in and near Carson Lake, Stillwater Marsh 

and Carson Sink. Present wetland conditions are not 

directly comparable to historical conditions because 

most of the water now available is used for maintenance of permanent wetlands. In contrast to the natural 

pattern of the unregulated, historical Carson River 

(fig. 3), with an abrupt spring runoff peak, the water 

to Stillwater WMA, dictated by agricultural practice, 

comes in a reduced, protracted flow from March 

through November, without a substantial flushing flow 

in the spring (U.S. Fish and Wildlife Service, 1988, 

fig. 8). In addition, much of the remaining flow is

ESTIMATED HISTORICAL CONDITIONS Ker/ey and others 19
managed by artificial structures to create permanent 

wetlands consuming about 5 acre-ft/acre of water per 

year. Because of this management, present wetlands 

are smaller but more permanent than historical wetlands supported by a given amount of water. To allow 

comparison, under OCAP the average 16,000 acres 

projected to remain in Carson Lake and Stillwater 

Marsh would require at least 80,000 acre-ft/yr of water. 

However, the dissolved-solids concentrations in the 

inflow water of Stillwater Marsh and Carson Lake 

are now, respectively, about four to seven times 

greater than historical concentrations; wetland 

flushing is restricted only to years with exceptionally 

high streamflow.

Water quality projected for the wetlands was 

described by the U.S. Fish and Wildlife Service (1988, 

p. 50). Dissolved-solids concentrations in water entering primary wetlands would average 1,170 mg/L, as 

projected for OCAP. The dissolved-solids concentration of the Carson Lake inflow is about seven times 

the estimated historical concentration of 170 mg/L of 

solids for the Carson River, and the Stillwater Marsh 

inflow is about four times more concentrated than the 

estimated 270 mg/L historical Stillwater inflow by way 

of Stillwater Slough. Again, the reader is cautioned 

that the historical estimates are just that estimates 

and should not be used beyond that intended for 

this report.

In Stillwater WMA, dissolved solids are 

progressively concentrated through evapotranspiration 

as inflow water is stored for waterfowl use then moved 

through sequentially arranged ponds (table 3). These 

are historical ponds with water-control structures 

added. Under past management practices, the initial 

wetland would concentrate inflowing dissolved solids 

by nearly four times, to about 4,600 mg/L, and the next 

sequential wetland would further concentrate dissolved 

solids by six times, to about 28,000 mg/L (U.S. Fish 

and Wildlife Service, 1988, table 7).

Present concentrations of dissolved solids would 

rarely have occurred in the historical flow-through wetlands at Carson Lake and Stillwater Marsh, but they 

may have routinely occurred in parts of the more 

ephemeral wetlands in the Carson Sink. For example, 

high dissolved-solids concentrations were measured in 

the Carson sink during the 1980's (Rowe and Horrman, 

1990, p. 37). Present water-quality conditions in parts 

of Carson Lake and Stillwater Marsh are limiting to 

some aquatic plants and animals. In addition, trace 

elements toxic to fish and invertebrates are being 

released from Carson Desert soils by agricultural drainage and are entering these wetlands, as discussed in the 

next section on toxicity.

In summary, the pattern of water flow, quality 

of the water, and the size and quality of the resultant 

wetlands, as well as vegetation and wildlife, have all 

changed dramatically since the onset of irrigation in 

the late 1800's.

Table 3. Concentration factors between wetland units and recent and 

projected concentrations of dissolved solids, Stillwater Wildlife 

Management Area

[Values are based on data collected by the U.S. Fish and Wildlife Service (1988)]

Wetland unit1

Wetland inlet flow

Primary unit

Secondary unit

Tertiary unit

Recent

average

dissolved 

solids (mg/L) 

(1967-1986)

600

2,360

14,180

28,400

Approximate

concentration 

factor

22

4

6

2

Projected

average 

dissolved 

solids (mg/L)

1,170

4,610

27,600

55,200

1 Primary, secondary, and tertiary units refer to a series of shallow ponds that receive 

water progressively more concentrated with dissolved solids.

2 Initial change in dissolved-solids concentrations resulting from irrigation practices.

20 Detailed Study of Irrigation Drainage Effect on Biota
TOXICITY OF IRRIGATION DRAINAGE AND ITS 

EFFECT ON AQUATIC ORGANISMS

The wetlands in Stillwater Wildlife Management 

Area (WMA) are managed primarily to support 

migratory waterfowl. Many water-dependent migratory birds require a variety of fish and invertebrates 

in their diets. As a result of irrigation drainage, water 

in Stillwater WMA has an unnaturally high salinity, 

and both water and biota contain elevated concentrations of potentially toxic trace elements that can affect 

fish and invertebrates (Hoffman and others, 1990, 

p. 76-77). For example, Stillwater WMA can no longer 

sustain a Largemouth bass (Micropterus salmoides) 

population (U.S. Fish and Wildlife Service, 1988, 

p. 132), and invertebrate density is low. Toxicity 

tests were conducted to assess the suitability of 

water from various drains and wetland areas to 

support fish and invertebrates.

METHODS 

Sample Collection

Water samples were collected at sites in 

Stillwater WMA on Paiute Diversion Drain, D-Line 

Canal, Hunter Drain, Lead Lake, Stillwater Point 

Diversion Drain, Stillwater Point Reservoir, and TJ 

Drain (including one USGS well near TJ Drain). 

Sampling sites are shown in figure 4.

Composite water samples were collected daily 

from each drain location during August 9-18, 1988. 

Each sample consisted of water collected at 15-minute 

intervals during a 24-hour period by an ISCO model 

2710 automatic composite sampler. Water was 

pumped from the drain through Teflon tubing into 

19-L, acid-washed, glass collection containers. The 

containers were held in ice baths during the collection 

period to keep the samples at approximately 4°C during 

the day. Water samples from Lead Lake and Stillwater 

Point Reservoir were collected daily as "instantaneous" 

samples and, as such, represent the quality of the water

at the time of sampling. Onsite toxicity tests were 

made with portions of these samples collected daily 

from each location. Principal constituents and properties of each water sample (temperature, pH, dissolved 

oxygen, hardness, alkalinity, turbidity, specific conductance, salinity, and calcium, sulfate, and chloride) were 

measured on-site daily. Ammonia and nitrate were 

measured near the beginning, middle, and end of the 

toxicity tests.

A portion of the composite water collected 

daily was used for determination of additional 

inorganic constituents (magnesium, sodium, potassium, silica, phosphorus, arsenic, barium, boron, 

lithium, mercury, molybdenum, selenium, strontium, 

vanadium, and zinc). These subsamples were collected 

in 1-L, linear polyethylene bottles that had been previously washed with soap and water, rinsed with tap 

water, soaked in concentrated nitric acid, and rinsed 

twice with deionized water. Samples were filtered 

through a 0.4-|im polycarbonate filter and preserved 

with 2 mL of ultrapure nitric acid for in the laboratory 

analysis. Chemical analyses of the water were made 

by Environmental Trace Substances Research Center 

(Columbia, Mo.). Spiked samples, blanks, and 

replicates prepared onsite were included as qualityassurance samples (Peden, 1986).

A one-time collection of water from an 

observation well near TJ Drain was made by U.S. 

Geological Survey personnel using a bailer and according to standard methods (Claasen, 1982). The well 

water, which represented potential seepage to the drain, 

was tested for acute toxicity and analyzed for traceelement concentrations.

A one-time collection of water from all drains 

also was made for analysis of potentially toxic manmade organic constituents. Analysis was made by 

the U.S. Geological Survey National Water Quality 

Laboratory, Denver, Colo. The data are on file at the 

U.S. Geological Survey, Nevada District Office, 

Carson City.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 21
39°40' 

39°30'

Fallen National 

Wildlife Refuge

R. 29 E. R. 30 E. R. 31 E. R. 32 E.

EXPLANATION

OPEN WATER

STILLWATER NATIONAL WILDLIFE REFUGE -- 

AS defined July 1 990. Western boundary is 

dotted line

PRIVATELY OWNED LAND WITHIN 

REFUGE -Includes Canvasback Gun Club

BOUNDARY OF WILDLIFE MANAGEMENT AREA

BOUNDARY OF FALLON INDIAN RESERVATION 

North boundary coincides with that of adjacent 

Wildlife Management Area

SITE OF TOXICITY SAMPLE

Figure 4. Locations of toxicity sampling sites and important hydrologic features in and near Stillwater Wildlife Management 

Area. (Map modified from Lico, 1992.)

22 Detailed Study of Irrigation Drainage Effect on Biota
Toxicity Assessments

Toxicity tests were made using a portion of 

the daily composite water sample from each location 

to renew the test solution daily throughout the test 

period. The species tested were bluegills (Lepomis 

macrochirus), larval fathead minnows (Pimephales 

promelas), and daphnids (Daphnia magnd). Daphnids 

and fathead minnow larvae were obtained from cultures at the National Fisheries Contaminant Research 

Center (NFCRC), Columbia, Mo., and were maintained onsite in well water (hardness, 283 mg/L as 

CaCO3 ; alkalinity, 255 mg/L as CaCO3 ; pH, 7.8) that 

had been transported from NFCRC. Bluegills (<0.1 g) 

were obtained from the Missouri Department of 

Conservation, shipped to Stillwater WMA, and transferred into the NFCRC well water for 48 hours of 

observation prior to use. Using Hunter Drain water, 

in which salinity exceeded 15 ppt, additional tests were 

made with salt-tolerant species sheephead minnow 

(Cyprinodon variegatus) larvae, and mysid shrimp 

(Mysidopsis bahid). These organisms were obtained 

from the U.S. Environmental Protection Agency 

(USEPA) Laboratory in Gulf Breeze, Fla.

Tests were made as static renewals under 

appropriate 10-day test procedures (USEPA, 1985; 

American Society for Testing Materials, 1988). All 

organisms were fed freshly hatched brine shrimp 

(Artemid) twice daily. Tests with daphnids and 

fathead minnow larvae included 2 replicates per 

treatment and 10 organisms per replicate. Tests with 

bluegills consisted of 2 replicates per treatment and 

5 organisms per replicate. Treatments included fullstrength water and dilutions of 50,25, and 12.5 percent. 

Dilution water for each test was reconstituted to the 

appropriate hardness, alkalinity, specific conductance, 

and pH for that test-location water by the addition of 

major cations and anions using Instant Ocean and 

deionized water. By reconstituting dilution water to 

the same ionic composition as the drainwater, consistent concentrations of constituents such as calcium, 

magnesium, sodium, potassium, chloride, and sulfate 

were maintained for all treatments for each sampling 

site. All sampling sites were evaluated using this 

reconstituted water as a diluent and as a control. In 

addition, Paiute, TJ, and Stillwater Point Diversion 

Drains were also assessed by using water into which 

they discharged (Paiute and TJ into D-Line, and 

Stillwater Point Diversion Drain into Stillwater Point 

Reservoir) as diluent and control. The NFCRC well 

water provided a second control to evaluate the condition of test organisms throughout the tests. Dissolvedoxygen concentrations exceeded 40 percent saturation 

in all tests. Acceptability of a test required that control 

mortality not exceed 10 percent.

Evaluation of potential toxicity problems in the 

Stillwater area included a total of 35 concurrent tests on 

water samples:

Sample site Dilution source

Number 

of tests

Paiute Diversion Drain 

Paiute Diversion Drain 

TJ Drain 

TJ Drain

Stillwater Point Diversion 

Drain

Reconstituted water 3

D-Line Canal water 3

Reconstituted water 3

D-Line Canal water 3

Reconstituted water 3

Stillwater Point Diversion 

Drain

Stillwater Point Reservoir

Lead Lake

Hunter Drain

D-Line Canal

TJ Drain ground water

Stillwater Point 

Reservoir water

Reconstituted water

Reconstituted water

Reconstituted water

Reconstituted water

Undiluted water

3

3

3

5

3

3

During the tests, mortality was recorded daily 

for each species. Bluegills were weighed and measured to assess growth at the initiation and termination 

of the test. A subsample of daphnids was preserved on 

the first day of the test and the surviving adults were 

also preserved on the final day of the test for later 

examination. For daphnids, time to first brood production, total number of broods, and number of young per 

brood were recorded as measures of reproductive success. Temperature, pH, and dissolved oxygen were 

measured daily in each beaker prior to renewal of test 

solutions.

Chemical Analyses

Principal constituents and properties, along 

with ammonia and nitrate, were determined using 

standard methods (magnesium, sodium, potassium, 

silica, phosphorus, arsenic, barium, boron, lithium, 

mercury, molybdenum, selenium, strontium, 

vanadium, and zinc).

TOXICITY OF IRRIGATION DRAINAGE Finger and others 23
Filtered water samples to be analyzed for 

inorganic constituents were digested in 100-mL borosilicate glass beakers that had been cleansed by a concentrated nitric acid, 30-minute, reflux cycle. About 

40 mL of the digested sample was combined with 

15 mL of concentrated nitric acid and 2.5 mL of concentrated perchloric acid, then evaporated over low 

heat until only 1 mL remained. This digestate was 

diluted to 50 mL with ultrapure water and analyzed 

for selenium and arsenic by hydride generation atomic 

absorption. The remaining digestate was analyzed 

for additional elements with an inductively coupled 

plasma spectrophotometer. Mercury was determined 

by cold vapor atomic absorption. Analytical procedures are described in detail by the U.S. Fish and 

Wildlife Service (1985).

All results were within 20 percent of confidence 

intervals for certified or recommended concentrations 

for the reference materials. Of the samples analyzed, 

10 percent were blanks and 20 percent were blind

replicates and spiked samples. No values for blanks 

exceeded analytical reporting limits for any element 

(table 4).

Daily water-quality measurements for the seven 

surface-water sites are presented in the supplemental 

data tables at the back of this report. A summary of 

ranges is shown in table 6.

Water samples for analysis of manmade 

organic constituents were extracted three times in the 

laboratory at both acidic and basic pH with methylene 

chloride. The extracts were concentrated to about 

1 mL, combined with an internal standard, and analyzed by gas-chromatography, electron-impact, mass 

spectrometry. Surrogate compounds were added to 

each sample prior to extraction to verify method recoveries (Wershaw and others, 1987). The analytical 

results are discussed in the subsection titled "Stillwater 

Point Diversion Drain and Still water Point Reservoir."

Table 4. Analytical reporting limits for selected inorganic constituents in 

water (from Environmental Trace Substances Research Center, Columbia, Mo.)

[All units in micrograms per liter, except where indicated; mg/L milligrams per liter]

Element Concentration Element Concentration

Calcium (mg/L)

Magnesium (mg/L)

Sodium (mg/L)

Potassium (mg/L)

Sulfate (mg/L)

Silica (mg/L)

Chloride (mg/L)

Phosphorus (mg/L)

Aluminum

Antimony

Arsenic

Barium

Beryllium

Bismuth

Boron

Cadmium

Chromium

Cobalt

0.002

.002

.02

1

1

.01

.15

.10

30

40

.5

1

1

60

20

2

10

10

Copper

Iron

Lead

Lithium

Manganese

Mercury

Molybdenum

Nickel

Selenium

Silver

Strontium

Thallium

Tin

Titanium

Tungsten

Vanadium

Zinc

2

5

40

.5

5

.3

20

100

.3

20

4

3

10

4

2

2

2

24 Detailed Study of Irrigation Drainage Effect on Biota
RESULTS OF TOXICITY TESTS

Paiute Diversion Drain and D-Line Canal

beryllium, bismuth, chromium, cobalt, copper, iron, 

nickel, silver, tin, titanium, thallium, and tungsten did 

not exceed reporting limits.

Water from Paiute Diversion Drain diluted with 

D-Line Canal water was not acutely toxic to bluegills, 

fathead minnow larvae, or daphnids (table 5). No substantial mortality occurred in tests with water from 

Paiute Diversion Drain regardless of dilution water, 

and no mortality was recorded for any species exposed 

to water from D-Line Canal. No sublethal responses 

were identified in daphnids exposed to water from 

either location. Daphnids produced equal numbers of 

young in all treatments, with one brood produced in 

every treatment on day 8. For all treatments, mean 

number of young per brood ranged from 8.1 to 9.4. 

Microscopic examination of adults at the end of the test 

revealed production of eggs for a second brood and 

substantiated the continued reproductive development 

that would be expected in healthy organisms. Concentrations of constituents in Paiute Diversion Drain and 

D-Line Canal water were similar, and daily fluctuations 

in water quality were minimal during the study period 

(table 6). Neither mercury nor selenium was detected 

in any water sample. In addition, aluminum, antimony,

TJ Drain

Water from TJ Drain was acutely toxic to 

bluegills, fathead minnow larvae, and daphnids 

(tables 7 and 8). Cumulative mortality in 100-percent 

TJ Drain water was similar for fathead minnows and 

bluegills, and ranged from 85- to 90-percent mortality 

after 9 days of exposure. No mortality was observed 

in well-water controls, reconstituted-water controls, 

or 100 percent D-Line Canal water also used as control. 

Daphnids were more sensitive than were fish species to 

the two highest drain-water concentrations. Total 

mortality of daphnids occurred in full-strength drainwater after 6 days and in the 50-percent dilution by 

the end of the test; no substantial mortality occurred 

in the 12.5-percent dilution. No daphnid reproduction 

occurred in the TJ Drain water regardless of dilution 

water. Control daphnids in reconstituted water reproduced on day 8, with a mean brood size of 9.6; a first 

brood (9.3 young) was also produced on day 8 in the 

D-Line Canal control water.

Table 5. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids after exposure 

to water from Paiute Diversion Drain diluted with (A) reconstituted water1 and (B) water from 

D-Line Canal

Cumulative mortality of species after tests (percent)

Species 

(and number sampled)

Bluegills (10) 

Fathead minnow larvae (20) 

Daphnids (20)

Proportion of drain water in sample

100 

percent

50 

percent

25 

percent

12.5 

percent

A. Drainwater, diluted with reconstituted water

0 0 10 0 

0000 

0 0 10 0

0 

percent

10 

0

5

NFCRC 

wellwater 

control2

0 

0 

0

B. Drainwater, diluted with D-Line Canal water

Bluegills (10)

Fathead minnow larvae (20)

Daphnids (20)

10

0

10

10

0

0

1 Deionized water reconstituted to the same hardness, alkalinity, specific conductance, and pH as the Paiute Diversion 

Drain water.

2 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 25
Table 6. Ranges of water-quality measurements in surface-water samples collected daily, August 10-18, 1988, for a

9

a. 

CO

I 

o

CD

fi>

f»o' 

a

(O

I

[Abbreviations: NTU, nephelometric turbidity units; ppt, parts per thousand; J-lS/cm, microsiemens per centimeter at 25°C; J-lg/L, micrograms pe

per liter.]

Specific Conductance (jiS/m)

pH, field (units)

Turbidity (NTU)

Dissolved oxygen (mg/L)

Calcium (mg/L)

Magnesium (mg/L)

Hardness (mg/L as CaCO3 )

Sodium (mg/L)

Potassium (mg/L)

Alkalinity (mg/L as CaCO3 )

Sulfate (mg/L)

Chloride (mg/L)

Silica (mg/L)

Salinity (ppt)

Phosphorus (mg/L)

Arsenic (ug/L)

Barium (ug/L)

Boron (^g/L)

Lithium (ug/L)

Mercury (ug/L)

Molybdenum (ng/L)

Selenium (ng/L)

Strontium (ug/L)

Vanadium (^ig/L)

Zinc (ug/L)

Paiute 

Diversion 

Drain

370-480

7.5-8.6

15-35

6.8-9.7

31-36

10-13

110-140

62-84

2.8-5.4

111-158

52-85

50-70

5.8-7.2

0.1-0.3

<0.1-0.2

10-20

70-90

520-760

50-60

<0.3

<20-20

<0.3

350-410

10

20-70

D-Line 

Canal

350-610

8.6-9.4

3-9

9.0-10.3

26-32

9-11

94-130

83-110

5.4-9.4

113-174

47-130

12-50

5.9-7.6

0-0.5

<0.1

40-50

40-60

620-810

50-60

<0.3

<20-20

<0.3

340-370

10-20

10-40

TJ Drain

6,100-14,900

8.4-8.6

2-8

7.4-10.9

140-310

160-410

1,100-2,500

1,900-4,700

29-57

217-319

880-3,600

2,700-6,200

0.1-3.8

4.1-13.0

0.4-1.0

110-170

50-110

6,800-17,000

340-760

<0.3

270-670

0.9-1.6

3,200-7,900

10-20

10-90

Hunter Drain

410-27,500

8.0-8.8

7-37

5.6-8.8

32-390

10-250

110-2,300

98-8,600

4.0-210

102-276

52-2,900

84-13,000

5.0-13

0.0-28

<0. 1-0.9

20-190

50-100

810-49,000

60-2,300

<0.3

20-1,300

<0.3-3.6

390-10,400

10-30

10-90

Lead Lake

5,100-6,100

8.6-8.9

37-96

5.6-9.2

64-74

90-103

570-680

980-1,100

29-33

227-272

360-680

1,200-1,800

5.1-7.5

3.1-4.2

0.20-0.37

100-130

110-140

5,000-6,000

340-390

<0.3

110-130

<0.3

1,800-2,000

20

10-40

Stillw

Poi

Diver

Dra

470-7

8.2-8

21-5

8.3-9

42-5

12-1

140-2

120-2

7.3-1

114-3

110-

43-6

11-

0.2-0

0.20-0

40-5

60-7

860-1

60-1

<0

30-5

0.4-0

450-6

20

40-1

1 Analyzed by Environmental Trace Substances Research Center, Columbia, Mo. These water-quality data do not necessarily conform to U

guidelines for reporting significant figures.
Table 7. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed to water from TJ 

Drain diluted with reconstituted water1

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Bluegills (10) 1

2

3

4

5

6

7

8

9

Fathead minnow larvae (20) 1

2

3

4

5

6

7

8

9

Daphnids (20) 1 

2

3

4

5

6

7

8

9

Proportion of drainwater in sample

100 

percent

0 

0

20

40

50

70

90

90

90

20

20

20

20

45

45

60

60

85

10

25

25

60

95

100

50 

percent

0 

0

20

30

30

30

50

50

70

0

0

10

20

20

30

30

40

45

0 

0

20

30

30

40

75

80

100

25 

percent

0 

0

0

10

10

10

30

30

30

0

0

0

10

10

20

20

20

20

0 

0

0

10

15

20

25

25

25

12.5 

percent

0 

0

0

0

0

10

10

10

20

0

0

0

0

0

10

10

10

10

0 

0

0

0

0

10

10

10

10

0 

percent

0 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0 

0

0

0

0

0

0

0

0

NFCRC 

 wellwater 

control2

0 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0 

0

0

0

0

0

0

0

0

1 Deionized water reconstituted to the same hardness, alkalinity, specific conductance, and pH as the TJ Drain water.

2 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

A dose-response pattern was evident for all 

species regardless of dilution water. Although the 

fluctuating salinity was undoubtedly stressful to test 

organisms, survival of organisms in controls with identical salinity fluctuations strongly suggests that mortalities in drainwater did not result from exposure to 

salinity alone.

Concentrations of trace elements fluctuated 

throughout the exposure period, but concentrations of 

arsenic, boron, lithium, and molybdenum were consistently higher in TJ Drain water than in Paiute Diversion 

Drain or D-Line Canal water, where no mortality was

observed. Levels of arsenic in TJ Drain consistently 

exceeded 100 |Xg/L and boron concentrations reached 

a maximum level of 16,700 |Xg/L. Concentrations of 

dissolved selenium ranged from 0.9 to 1.6 ^lg/L; the 

highest concentrations were on day 4 when salinity 

was highest, and the lowest concentrations were on the 

day of lowest salinity. No mercury was detected in any 

sample. In addition, aluminum, antimony, beryllium, 

bismuth, chromium, cobalt, copper, iron, nickel, silver, 

tin, titanium, thallium, and tungsten did not exceed 

reporting limits. Ranges of concentrations of other 

constituents are reported in table 6.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 27
Table 8. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed to water from TJ 

Drain diluted with water from D-Line Canal

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Bluegills (10) 1

2

3

4

5

6

7

8

9

Fathead minnow larvae (20) 1

2

3

4

5

6

7

8

9

Daphnids (20) 1

2

3

4

5

6

7

8

9

Proportion of drainwater in sample

100 

percent

0

0

20

40

50

70

90

90

90

0

10

25

40

60

75

80

80

85

0

0

35

60

100

50 

percent

0

0

20

30

30

30

50

50

60

0

0

10

15

20

40

40

40

40

0

0

20

45

50

70

70

100

25 

percent

0

0

0

10

10

10

30

30

30

0

0

0

0

5

10

10

10

10

0

0

0

10

15

30

30

30

30

12.5 

percent

0

0

0

0

0

10

10

10

20

0

0

0

0

0

10

10

10

10

0

0

0

0

0

10

10

10

10

0 

percent

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NFCRC 

wellwater 

control1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

Well Near TJ Drain

Ground water from the USGS well DH-102B, 

near TJ Drain (Hoffman and others, table 3), was 

the most toxic of the water tested. The test was 

conducted as a static nonrenewal with the one 5-gal 

sample. Salinity of the ground water was 7.9 ppt and 

specific conductance was 12,000 ^,8/cm; the water 

was tested with bluegills, larval fathead minnows, and 

daphnids. All organisms exposed to 100-, 50-, 25-, 

and 12.5-percent ground water died within 24 hours of 

exposure. No mortality occurred in any controls. The 

ionic composition and water quality of TJ Drain ground 

water was different from that of TJ Drain surface water 

(table 6). The ground water was harder; the calcium

level was about two-fold higher than that of the drainwater and was more highly buffered (higher alkalinity). 

In addition, the pH of the ground water (7.0) was lower 

than that of the drainwater (8.4-8.6).

Concentrations of arsenic in the ground water 

(table 9) were higher than in any drainwater tested. 

Concentrations of lithium and molybdenum were 

higher in ground water than those measured in TJ Drain 

surface water. No selenium or mercury was detected in 

the ground-water sample, but concentrations of boron 

were high. Survival of freshwater control organisms in 

the reconstituted water with a salinity of 7.9 ppt indicates that the observed mortality was probably induced 

by the presence of trace elements in the ground water.

28 Detailed Study of Irrigation Drainage Effect on Biota
Table 9. Concentrations of inorganic constituents in ground water collected from 

U.S. Geological Survey well DH-102B in the vicinity of TJ Drain, August 17, 19881

[Except where indicated, all values are in micrograms per liter; mg/L, milligrams per liter.}

Element Concentration Element Concentration

Calcium (mg/L)

Magnesium (mg/L)

Sodium (mg/L)

Potassium (mg/L)

Silica (mg/L)

Phosphorus (mg/L)

Aluminum

Antimony

Arsenic

Barium

Beryllium

Bismuth

Boron

Cadmium

Chromium

Cobalt

Copper

544

268

2,390

87

36.1

0.80

<30

<40

560

48

<1

<60

24,400

<2

<10

<10

<2

Iron

Lead

Lithium

Manganese

Mercury

Molybdenum

Nickel

Selenium

Silver

Strontium

Thallium

Tin

Titanium

Tungsten

Vanadium

Zinc

<5

<40

1,640

1,440

<0.3

1,150

<100

<0.3

<20

13,300

<3

<10

<20

<2

<2

57

1 These water-quality data do not necessarily conform to U.S. Geological Survey guidelines for 

reporting significant figures

Hunter Drain

Hunter Drain water was acutely toxic to all 

species tested. This was the only water with salinity 

high enough to allow tests with saltwater species. 

Neither freshwater nor saltwater organisms survived 

in treatments of 100-percent or 50-percent drainwater. 

All species died quickly; 90 percent of the mysids, 

daphnids, and sheephead minnows died after 48 hours 

of exposure. After 9 days, at least 40 percent of every 

species had died in all dilutions (tables 10,11).

The water quality in Hunter Drain was highly 

variable (table 6). Salinity ranged from 0 to 28 ppt. 

The highest salinity was measured on days 3,4, and 5 

under conditions of low flow when there was no visible 

discharge of irrigation water to the drain. During this 

3-day period, the seepage of ground water into Hunter 

Drain was evident along the banks of the drain. The 

addition of operational spill water to the drain on day 6 

was apparently responsible for the reduction in salinity 

and conductivity. All the bluegills died on day 4, after

24 hours of exposure to Hunter Drain water when 

salinity was 28 ppt, which was more than twice as 

high as on the previous day. Only 10 percent of the 

fish died on day 4 in other treatments exposed to this 

level of salinity, but the cumulative mortality of 

20 percent in the controls on day 5 is probably related 

to the high salinity.

Survival, even for one day, of any bluegill at a 

salinity of 28 ppt was unexpected, based on accepted 

salt tolerances of the species. The ionic content of 

water in Hunter Drain and other Stillwater locations 

differed from that of seawater, which is typically used 

to estimate salinity tolerances of freshwater organisms. 

Although the test organisms were apparently more 

tolerant of salinity with these ionic ratios than of a 

similar salinity in seawater, it is probable that continued exposure to elevated salinity would have reduced 

survival in control water. It is unlikely that daily fluctuations in water quality of the magnitude experienced 

here would be tolerated by the tested species for an 

extended period.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 29
Table 10. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed to water from 

Hunter Drain diluted with reconstituted water1

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Bluegills (10) 1

2

3

4

5

6

7

8

9

Fathead minnow larvae (20) 1

2

3

4

5

6

7

8

9

Daphnids (20) 1

2

3

4

5

6

7

8

9

100 

percent

0

0

100

25

40

65

70

100

25

90

100

Proportion of drainwater in sample

50 

percent

0

0

10

60

80

80

100

10

50

85

90

90

100

20

50

85

90

90

100

25 

percent

0

0

10

10

30

30

50

60

60

0

0

0

20

30

45

60

60

60

0

0

0

15

30

50

50

60

75

12.5 

percent

0

0

0

10

10

20

20

30

40

0

0

0

10

10

25

25

25

40

0

0

0

10

10

25

25

25

50

0 

percent

0

0

0

10

20

20

20

20

20

0

0

0

0

0

0

0

0

0

0

0

0

0

10

10

10

10

10

NFCRC 

wellwater 

control2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1 Deionized water reconstituted to the same hardness, alkalinity, specific conductance, and pH as the Hunter Drain water.

2 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

Tests with saltwater species sheephead 

minnow larvae and mysid shrimp were initiated 

when salinity first exceeded 15 ppt on day 3. Total 

mortality of both species occurred in the 100-, 50-, 

and 25-percent dilutions after 7 days of exposure 

(table 11). The saltwater organisms were exposed 

under conditions of static renewal during the first 

72 hours, but because the salinity of the drainwater 

decreased to 7 ppt on day 6, testing continued without 

renewal for the remainder of the 7-day exposure 

period. Dissolved-oxygen concentrations of the test 

water exceeded 6.4 mg/L throughout the study and pH 

ranged from 8.4 to 8.5. Mortality of both species of at 

least 55 percent occurred in all drain-water dilutions; 

no mortality occurred in the well-water controls.

Higher levels of trace-element concentrations 

corresponded with the higher levels of salinity. During 

days with elevated salinity, concentrations of arsenic 

in Hunter Drain were similar to those measured in TJ 

Drain; levels of boron and lithium in Hunter Drain 

were higher than at any other location, and molybdenum nearly so (table 6). Concentrations of dissolved selenium ranged from below detection limits 

to 3.6 (ig/L and were highest during periods of highest 

salinity. No mercury was detected in samples from 

Hunter Drain. In addition, aluminum, antimony, beryllium, bismuth, chromium, cobalt, copper, iron, nickel, 

silver, tin, titanium, thallium, and tungsten did not 

exceed reporting limits.

30 Detailed Study of Irrigation Drainage Effect on Biota
Table 11. Cumulative mortality of saltwater species (sheephead minnow larvae and mysid shrimp) exposed to water 

from Hunter Drain diluted with reconstituted water1

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Sheephead minnow larvae (20) 4

5

6

7

8

9

Mysid shrimp (20) 4

5

6

7

8

9

Proportion of drainwater in sample

100 

percent

60

90

100

70

90

100

50 

percent

45

65

75

100

50

65

90

100

25 

percent

25

40

55

80

100

20

35

50

70

100

12.5 

percent

20

35

40

50

55

55

20

15

30

55

60

60

0 

percent

0

0

0

0

0

0

0

0

0

5

5

10

NFCRC 

wellwater 

control2

0

0

0

0

0

0

0

0

0

0

0

0

1 Deionized water reconstituted to the same hardness, alkalinity, specific conductance, and pH as the Hunter Drain water.

2 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

Lead Lake

Water from Lead Lake was moderately toxic 

to all species tested; the death rate accelerated after 

4 days (table 12). Survival rates of bluegill and fathead 

minnow larvae were similar; the lowest level of effect 

occurred in the 25-percent dilution. Daphnids were 

more sensitive to the toxic components in the water 

than were the fish, and died sooner. No species died in 

the 12.5-percent dilution or in the controls. Total survival of all organisms in the reconstituted control 

water, where salinity was similar to that in the Lead 

Lake water treatments, suggests that salinity alone did 

not account for the observed mortality.

Reproduction of daphnids was delayed in all 

treatments. No young were produced by daphnids in 

any Lead Lake water treatment and there was no evidence of development of a first brood in any individuals examined at the termination of the exposure. Young

were produced in both the reconstituted and well-water 

controls on day 9. Mean number of young per brood in 

these controls was 8.9 and 9.2, respectively.

Levels of trace elements did not fluctuate 

markedly throughout the exposure period. Concentrations of selenium and mercury were below analytical 

reporting levels. In addition, aluminum, antimony, 

beryllium, bismuth, chromium, cobalt, copper, iron, 

nickel, silver, tin, titanium, thallium, and tungsten 

did not exceed reporting limits. Concentrations of 

arsenic, boron, lithium, and molybdenum were consistently higher in Lead Lake water than in either Paiute 

Diversion Drain or D-Line Canal, where no mortality 

was observed. The concentrations of these four trace 

elements, which were associated with water hardness 

and specific conductance, appear to be strongly influenced by inflow from TJ Drain. Concentrations of salts 

in Lead Lake may be naturally increased by evaporative loss, but the addition of water from TJ Drain 

does not enhance the water quality of Lead Lake.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 31
Table 12. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed to water from Lead 

Lake diluted with reconstituted water1

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Bluegills (10) 1

2

3

4

5

6

7

8

9

Fathead minnow larvae (20) 1

2

3

4

5

6

7

8

9

Daphnids (20) 1

2

3

4

5

6

7

8

9

Proportion of drainwater in sample

100 

percent

0

20

20

30

30

30

40

40

60

0

20

20

25

25

30

40

60

60

0

20

20

25

30

30

45

60

80

50 

percent

0

0

0

0

20

20

20

30

30

0

0

5

5

5

15

20

25

30

0

0

5

5

15

15

30

35

45

25 

percent

0

0

0

0

0

10

10

10

10

0

0

5

5

10

10

10

15

15

0

0

5

5

10

10

15

20

20

12.5 

percent

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0 

percent

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NFCRC 

wellwater 

control2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1 Deionized water reconstituted to the same hardness, alkalinity, specific conductance, and pH as the Lead Lake water.

2 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

Still water Point Diversion Drain and 

Still water Point Reservoir

Test organisms were differentially sensitive 

to water from Stillwater Point Diversion Drain. The 

water was toxic to bluegills and marginally toxic to fathead minnow larvae and daphnids (tables 13 and 14). 

Mortality occurred after an extended exposure to drainwater; no mortality of any species occurred during the 

first 3 days of exposure. Bluegill mortality reached 

80 percent in undiluted water from Stillwater Point 

Diversion Drain. In the tests where drainwater was 

diluted with reconstituted water (table 13), no appreciable mortality occurred in the 12.5-percent dilution, 

but in tests using water from Stillwater Point 

Reservoir as a diluent, 20 percent of the fish died in 

the 12.5 percent dilution (table 14). In controls, no 

bluegills died in well water, 10 percent died in reconstituted water (table 13), and 20 percent died in Stillwater 

Point Reservoir water (table 14). Cumulative mortality 

of fathead minnow larvae and daphnids exposed to 

Stillwater Point Diversion Drain water diluted with 

reconstituted water (table 13) was lower than that of 

bluegills and ranged from 5 to 30 percent. Mortality 

of fathead minnows and daphnids exposed to Stillwater 

Point Diversion Drain water diluted with Stillwater

32 Detailed Study of Irrigation Drainage Effect on Biota
Point Reservoir water (table 14) ranged from 10 to 

30 percent and was much lower than bluegill mortality, 

but generally higher than in tests using reconstituted 

water (table 13) as a diluent (5-30 percent), but with 

no clear pattern of dose response. No fathead minnow 

larvae or daphnids died in the reconstituted or the wellwater controls, but in Stillwater Point Reservoir water 

controls, mortality was 25 percent (table 14).

The range in concentrations of the constituents 

in Stillwater Point Diversion Drain and Stillwater Point 

Reservoir remained less variable during the study than 

those in TJ and Hunter Drains (table 6). The ambient

water was well oxygenated and of moderately low 

specific conductance. Turbidity in Stillwater Point 

Diversion Drain was similar to Paiute Diversion Drain. 

Concentrations of constituents also were similar to 

those found in Paiute Diversion Drain and in D-Line 

Canal (table 6). Mercury and selenium concentrations 

in Stillwater Point Diversion Drain were at or below 

analytical reporting levels. In addition, aluminum, 

antimony, beryllium, bismuth, chromium, cobalt, 

copper, iron, nickel, silver, tin, titanium, thallium, 

and tungsten did not exceed reporting limits.

Table 13. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed to water from 

Stillwater Point Diversion Drain diluted with reconstituted water1

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Bluegills (10) 1

2

3

4

5

6

7

8

9

Fathead minnow larvae (20) 1

2

3

4

5

6

7

8

9

Daphnids (20) 1

2

3

4

5

6

7

8

9

Proportion of drainwater in sample

100 

percent

0

0

0

20

40

40

40

60

80

0

0

0

5

5

10

10

15

30

0

0

0

0

10

10

15

15

25

50 

percent

0

0

0

20

30

30

30

30

40

0

0

0

0

5

10

10

10

10

0

0

0

0

10

10

10

10

10

25 

percent

0

0

0

10

20

20

20

20

20

0

0

0

10

10

10

10

10

10

0

0

0

10

10

10

10

10

10

12.5 

percent

0

0

0

0

0

10

10

10

10

0

0

0

0

0

0

0

5

5

0

0

0

0

0

0

0

5

5

0 

percent

0

0

0

0

0

0

10

10

10

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NFCRC 

wellwater 

control2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1 Deionized water reconstituted to the same hardness, alkalinity, specific conductance, and pH as the Stillwater Point Diversion 

Drain water.

2 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 33
Table 14. Cumulative mortality of bluegills, fathead minnow larvae, and daphnids exposed to water from 

Stillwater Point Diversion Drain diluted with water from Stillwater Point Reservoir

Cumulative mortality of species in tests (percent)

Species Exposure 

(and number sampled) (days)

Bluegills (10) 1

2

3

4

5

6

7

8

9

Fathead minnow larvae (20) 1

2

3

4

5

6

7

8

9

Daphnids (20) 1

2

3

4

5

6

7

8

9

Proportion of drainwater in sample

100 

percent

0

0

0

30

60

60

60

70

80

0

0

0

10

10

15

20

25

30

0

0

0

10

10

15

25

25

25

50 

percent

0

0

0

20

20

20

20

30

40

0

0

0

15

15

20

20

20

25

0

0

0

20

20

20

20

20

25

25 

percent

0

0

0

10

10

10

10

20

20

0

0

0

10

15

15

15

15

20

0

0

0

10

10

10

10

10

20

12.5 

percent

0

0

0

0

0

0

10

10

20

0

0

0

0

10

10

10

15

25

0

0

0

0

0

0

0

0

20

0 

percent

0

0

0

0

0

0

0

10

20

0

5

10

10

10

15

20

20

25

0

5

5

10

10

20

20

25

25

NFCRC 

wellwater 

control 1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1 Well water from National Fisheries Contaminant Research Center, Columbia, Mo.

Because mortality in water from Stillwater 

Point Diversion Drain was higher than in apparently 

similar water from Paiute Diversion Drain and D-Line 

Canal, water samples from all drain sites were collected August 17, 1988, for chemical analysis of manmade organic constituents. No organic constituent was 

found at concentrations that might be expected to cause 

adverse effects on the test organisms. Consistent levels 

of phenols (2.6-5.4 (ig/L) were detected in every 

sample, which suggests incidental contamination 

during sample collection or chemical analysis. Results 

from these analyses did not explain the mortality 

observed in Stillwater Point Diversion Drain water.

Mortality in undiluted water from 

Stillwater Point Reservoir was low, but consistent 

(20-25 percent). No substantial mortality of any 

species occurred in dilutions of Stillwater Point Reservoir water. Daphnids reproduced equally in all treatments on day 9, with the mean number of young per 

brood ranging from 8.0 to 9.5. The reservoir water was 

turbid, ranging from 168 to 580 NTU's, which may 

have stressed the test organisms in the 100-percent 

treatment. Concentrations of boron, lithium, and 

molybdenum in the reservoir (table 6) were generally 

similar to those in Stillwater Point Diversion Drain 

water. Concentrations of arsenic were only slightly

34 Detailed Study of Irrigation Drainage Effect on Biota
lower than those in Lead Lake and TJ Drain and may 

have contributed to the observed mortality. Arsenic 

concentrations in the reservoir were approximately 

twice those in Stillwater Point Diversion Drain.

EFFECT OF IRRIGATION DRAINAGE 

ON AQUATIC ORGANISMS

Water from Hunter and TJ Drains and ground 

water from the well near TJ Drain was acutely toxic to 

all species tested (fig. 5). On the basis of effects of 

the drainwater on cumulative mortality and daphnid 

reproduction, the "No Observed Effect Concentration" 

(NOEC) 1 for both Hunter and TJ Drains was less than 

12.5 percent drainwater. Lead Lake water was moderately toxic to all species tested, with an NOEC of 

25 percent drainwater for both fish species and an 

NOEC of less than 12.5 percent for daphnids. In 

tests with Stillwater Point Diversion Drain water 

diluted with Stillwater Point Reservoir water, where 

mortality occurred in every treatment, an NOEC 

was not established, but in tests with Stillwater Point 

Diversion Drain water diluted with reconstituted water, 

the NOEC was 25 percent for daphnids and fathead 

minnows and 12.5 percent for bluegill. Water 

samples from Paiute Diversion Drain and D-Line 

Canal were not toxic to the species tested.

1 A time-independent measure that describes the threshold 

concentration below which predefined effects are not observed.

100

80

60

40

20

BLUEGILLS

FATHEAD MINNOW 

LARVAE

DAPHNIDS

PAIUTE

DIVERSION

DRAIN

D-LINE 

CANAL

LEAD 

LAKE

STILLWATER STILLWATER 

POINT POINT

DIVERSION RESERVOIR 

DRAIN

Figure 5. Cumulative mortality of freshwater organisms in undiluted surface-water samples collected in and near Stillwater Wildlife Management Area, August 1988. Data for Paiute Diversion Drain 

and D-Line Canal showed no mortality.

TOXICITY OF IRRIGATION DRAINAGE Finger and others 35
In both Hunter and TJ drains, dramatic daily 

fluctuations in water quality were measured, and 

specific conductance ranged from 410 to 27,500 ^iS/cm 

(about 270 to 17,900 mg/L dissolved solids) in Hunter 

Drain and from 6,100 to 14,900 ^iS/cm (about 4,000 to 

9,700 mg/L dissolved solids) in TJ Drain (fig. 6). 

Control organisms in reconstituted water, where conductance was similar to that of the drainwater, survived 

exposure to daily fluctuations of similar magnitudes. 

Saltwater organisms, sheephead minnow larvae and 

mysids, did not survive in Hunter Drain water although

the salinity was within their range of tolerance. 

A dose-response relationship was evident in TJ drainwater when diluted with reconstituted water of a similar salinity and when salinity was decreased by dilution 

with water from D-Line Canal. From 85 to 100 percent 

of the organisms died in Lead Lake water; controls with 

similar specific conductance (that is, salinity) showed 

no mortality. Although the elevated salinity in tests 

with drainwater from both locations undoubtedly 

stressed the organisms, the results suggest that salinity 

alone does not account for the mortality observed.

30,000

13 14 15 

DATE (AUGUST 1988)

16 17 18

Figure 6. Changes in specific conductance in Lead lake and selected drains during toxicity study 

August 10-18,1988.

36 Detailed Study of Irrigation Drainage Effect on Biota
In general, higher concentrations of trace 

elements corresponded to higher levels of specific 

conductance (fig. 7). In addition, subjective comparison of cumulative mortalities and concentrations of 

trace elements at each location suggested that the 

concentrations or arsenic, boron, lithium, and molybdenum were higher at locations where appreciable 

mortality occurred. No single trace element was 

present in concentrations that were acutely toxic to 

the species tested (U.S. Environmental Protection 

Agency, 1986); therefore, the toxicity is attributed to 

the interactive effects of the aggregate trace elements 

present. This conclusion is supported by the results 

of Dwyer and others (1990, p. 18) who exposed striped 

bass (Morone saxatilis) to these elements and also to 

copper and strontium, both by single element and in 

combination. Individually, these six elements were 

not acutely toxic to the bass in the concentrations 

found at Stillwater WMA, but in aggregate were 

acutely toxic.

Ionic Composition

In assessing the hazard to aquatic organisms, 

the ionic composition of the water should also be considered. For example, in a study subsequent to this one 

that used striped bass in water reconstituted to resemble 

Pintail Bay in Stillwater WMA, Dwyer and others 

(1990, 1992) concluded that the unusually low hardness of this saline water did not diminish toxicity of the 

combined trace elements arsenic, boron, copper, 

lithium, molybdenum, and strontium.

In the present study, water from the shallow 

well near TJ Drain was acutely toxic to bluegills, 

larval fathead minnows, and daphnids. This ground 

water was classified as hard, with the calcium concentration about two-fold higher than the nearby TJ Drain 

water. Mortality is attributed primarily to a combination of toxic trace elements regardless of the benefit of 

increased hardness. In follow-up work by Dwyer and 

others (1990, p. 26), using water from five additional 

wells in and near Stillwater WMA, acute toxicity 

to striped bass a salt tolerant species was 

demonstrated.

Thus, salinity alone may not explain the 

mortality observed in certain drainwater, but rather 

a mixture of trace elements and atypical ion ratios 

(compared to seawater; Ingersoll and others, 1992).

20

I 1 1 I

LLJ

10

2,500 5,000 7,500 10,000 12,500

03

DC 

LLJ

Q_

Q

LLJ 

Q 

DC 

LLJ

CO

^

2

>-

K

£

DC 

O

20 o"

I 15

-J

5

i 10 z

Q

S5 5

1

0

i i i i i i

(H) ~

© _

-

- © ©

/-<pL

V' i i i i i

2,500 5,000 7,500 10,000 12,500

1 I I I

1 1 1 1

0 2,500 5,000 7,500 10,000 12,500

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER 

CENTIMETER AT 25°CELSIUS

Figure 7. Relations between specific conductance 

and mortality of bluegills (r=0.88), fathead minnow 

larvae (r=0.93), and daphnids (r=0.97) for water 

from Paiute Diversion Drain (P), D-Line Canal 

(DL), TJ Drain (TJ), Hunter Drain (H), Lead Lake 

(L), Stillwater Point Diversion Drain (D), and 

Stillwater Point Reservoir (S).

TOXICITY OF IRRIGATION DRAINAGE Finger and others 37
BIOLOGICAL PATHWAYS:

MOVEMENT OF SELENIUM AND MERCURY

Some potentially toxic trace elements in 

irrigation drainage are known to biomagnify up the 

foot chain, thus affecting wildlife of an area, particularly waterfowl. Selenium and mercury are important 

trace elements in the study area and both are known 

to biomagnify.

STUDY AREAS

Three areas were selected for in-depth study of 

biological pathways: TJ Drain/Lead Lake and Hunter 

Drain/Goose Lake systems in Stillwater WMA (fig. 8), 

and A-Drain and ponds of the Fernley WMA (fig. 9). 

These lakes and ponds include emergent wetlands and 

are managed with water-control structures. Additional 

samples were collected from other wetlands and from 

irrigation drains throughout the Fallon agricultural 

area of the Newlands Irrigation Project area (table 15, 

fig. 10) to provide a broader scope of the extent of 

high selenium and mercury concentrations.

Lead Lake, which has three major water sources, 

is the most hydrologically complex of the areas. It is a 

1,000-acre, initial wetland unit that receives irrigation 

drainage directly before much of the water evaporates 

and constituents become concentrated; therefore, its 

water quality is commonly better than that in the connecting wetlands downgradient. However, Lead Lake 

has a history of avian botulism and unexplained fish 

and migratory bird deaths, and most of the emergent 

vegetation has perished in the last 30 years. Selenium 

was found in the headwaters of the recently constructed 

(1982-1983) TJ Drain, which ultimately discharges 

into Lead Lake (U.S. Bureau of Reclamation, 1987,

p. B14). Selenium accumulation in juvenile migratory 

birds from Lead Lake was documented by Hoffman 

and others (1990, p. 67).

Hunter Drain was included in the pathways 

study because refuge biologists had noted exceptionally high specific conductance (Steven P. Thompson, 

U.S. Fish and Wildlife Service, oral commun., 1988) 

and selenium concentrations above effect level in some 

juvenile birds from Goose Lake, at the drain terminus 

(Hoffman and others, 1990, p. 66). This 9-mile drain, 

which serves only about 180 acres of irrigated land, is 

a relatively simple flow system. Discharge is typically 

less than 1 ftVs, but operational releases occasionally 

cause flow peaks of relatively fresh water.

Fernley WMA, near Stillwater WMA, was 

studied because selenium in livers of juvenile migratory birds exceeded effect levels (Hoffman and others, 

1990, p. 67). About 40 percent of the inflow is ground 

water from Truckee Canal seepage (Van Denburgh and 

Arteaga, 1985, p. 6), which passes through the same 

ancient lake-bed sediments as does the drainage from 

the Stillwater Wildlife Management Area. Most of the 

water enters the wetlands through A-Drain (from irrigation drainage) and discharges into South Pond, then 

into a series of connecting ponds (fig. 9).

Most of the additional samples for selenium 

and mercury were collected principally from drains 

throughout the irrigation area about 60,300 acres 

served by about 350 mi of drainage ditches. Sites were 

selected to represent, approximately, each 1- to 2-mi2 

area of irrigated land in the study area. These sites 

are shown in fig. 10 and listed in table 15.

BIOLOGICAL PATHWAYS RJ. Hallock and others 39
118°40' 118°30'

39°40' 

39°30'

Fallen National 

Wildlife Refuge

R. 29 E. R. 30 E. R. 31 E. R. 32 E.

EXPLANATION

^B OPEN WATER

 HI STILLWATER NATIONAL WILDLIFE REFUGE -

**"*** As defined July 1990. Western boundary is 

^^^ dotted line

PRIVATELY OWNED LAND WITHIN 

«ffl REFUGE -Includes Canvasback Gun Club

 BOUNDARY OF WILDLIFE MANAGEMENT AREA

- - - BOUNDARY OF FALLON INDIAN RESERVATION - 

North boundary coincides with that of adjacent 

Wildlife Management Area

-PI SAMPLING SITE, AND NUMBER, FOR DRIFT AND 

b BIOTA (TABLE 15)

Figure 8. Location of sampling sites for drift and biota in and near Stillwater Wildlife Management Area. Sites are listed 

in table 15. (Map modified from Lico, 1992.)

40 Detailed Study of Irrigation Drainage Effect on Biota
119° 051

39°40' 

39° 35'

EXPLANATION

^^| OPEN WATER

[ J^j WETLANDS, INCLUDING OPEN WATER

KXSM PLAYA

 - BOUNDARY OF WILDLIFE 

MANAGEMENTAREA

69O SAMPLING SITE AND NUMBER (TABLE 15)

Figure 9. Location of sampling sites for drift and biota in and near Fernley Wildlife Management Area. Sites are listed 

in table 15. (Map modified from Lico, 1992.)

BIOLOGICAL PATHWAYS RJ. Hallock and others 41
39 U 45

118° 30'

O

I<D

a(A

I 

O

to

D>

39 U 30' 

39 15'

EXPLANATIONI OPEN WATER

>=^ WETLANDS, INCLUDING "^^ OPEN WATER

AGRICULTURAL LANDS 

PLAYA

WILDUFE MANAGEMENT 

AREA BOUNDARY

43

R. 25 E. R. 26 E. R. 27 E. R. 28 E. R. 29 E. R. 30 E.

SAMPLING SITE 

fTABLE 15)

Figure 10. Location of additional sampling sites for detritus and algae in and near Stillwater and Fernley Wildlife Management Areas and Carson Lake. 

Site names are listed in table 15. (Map modified from Seiler and Allander, in press.)
Table 15. Sampling sites for drift, detritus, and algae

[Locations are shown in figures 8, 9, and 10; data were published by Rowe and others (1991, tables 20, 21)]

Fallen agricultural area

2. Old Reservoir

3. Soda Lake Drain

4. Upper L Drain

5. South Carson River Drain

6. Sheckler Deep Drain

7. Upper West Side Drain

8. Upper Diagonal 2 Drain

9. Upper Diagonal Drain

10. Gummow Drain

11. Carson Lake I Extension Drain

12. Carson Lake Drain

13. Carson Lake 1A Drain

14. A1 Drain

15. Mussi Drain

16. F2 Drain

17. Shaffner Drain

18. ERB Drain

19. Lower Soda Lake Drain

20. Paiute Extension Branch 1 Drain

21. Harmon I Deep Drain

22. S-Line Reservoir

23. New River Extension Drain

24. Upper Harmon Deep Drain

25. Harmon 2 Drain

26. New River Drain

27. Upper New River Drain

28. LD Drain

29. Mid L Drain

30. L3 Drain

31.L2Drain

32. Upper Diagonal Drain1

33. Middle L Drain

34. LB Drain

35. L Branch 1 Deep Drain

36. Lower L Drain

37. Mid Carson Lake Drain

38. A-Line Canal

39. Pierson Drain

40. Jl Deep Drain

41. Yarbrough Drain

42. Carson Lake Branch 3 Drain

43. Carson Lake Branch 1 Drain

44. Downs Drain

54. R2 Drain

55. Upper Paiute Drain

58. Harmon Deep Drain

59. S2G Drain

60. Harmon Reservoir

61. SIB Drain

62. Lower Diagonal 1 Drain

63. Lower Diagonal Drain

Carson Lake area

45. Lower Carson Lake Drain

46. Holmes Branch 2 Drain

47. Holmes Drain

48. NE Carson Lake

67. Carson Lake, Sprig Pond

Stillwater Wildlife Management Area

49. Patrick Drain

50. Kent Lake Extension Drain

51. Lower Stillwater Slough

52. Paiute Branch 3 Drain

53. SI Deep Drain

56. S2C Drain

57. Upper Stillwater Slough

64. Paiute Branch 1 Drain

65. Stillwater Point Reservoir

66. Upper TJ Drain

76. Big Indian Lake

77. Cattail Lake

78. D-Line Canal

79. Dry Lake East

80. Dry Lake West

81. Hunter Drain

82. Hunter Drain South1

83. Lead Lake

84. Likes Lake

85. Papoose Lake

86. Paiute Drain

87. Pintail Bay

88. South Lead Lake

89. South Nutgrass

90. Stillwater Point Reservoir

91. Swan Lake Check

92. TJ Drain

93. Tule Lake

94. West Nutgrass

Fernley Wildlife Management Area

68. Lower A-Drain1

69. Upper A-Drain1

70. Fernley drain, west

71. Fernley WMA, East Pond

72. Fernley WMA, North Pond

73. Fernley WMA, South Pond

Background and other sites

1. Sheckler Reservoir

74. North Mahala Slough

75. South Mahala Slough

95. Carson River Below Lahontan

1 Some sites were mislabeled in tables 20 and 21 of Rowe and others (1991): Site 32, Upper Diagonal Drain 

(sample number 88926), was mislabeled as site 63, Lower Diagonal Drain; site 82, Hunter Drain South (sample 

89058), was mislabeled as site 81; site 68, Lower A-Drain (samples 89067 and 89202), was mislabeled as Fernley 

Drain; and site 69, Upper A-Drain (sample 88171), was mislabeled as Fernley South Drain.

BIOLOGICAL PATHWAYS RJ. Hallock and others 43
APPROACH AND METHODS

On the basis of the findings of Hoffman and 

others (1990) that concentrations of selenium and 

mercury in filtered water samples were low, it was 

thought that selenium, and possibly mercury, were 

moving through biological pathways and that transport 

was through organic rather than inorganic forms. No 

uniform set of plants or animals was found in all study 

sites, and living organisms were not always available; 

therefore, organically rich detritus was sampled to provide continuity throughout the study areas. Because it 

is lightweight, detritus transports easily down irrigation 

drainage ditches through routine operational releases 

and other peak flows. Living plant material, principally 

filamentous algae, and drift also were collected where 

available. Definitions of detritus and drift and the sampling procedures used are described by Rowe and 

others (1991, p. 11-13).

Qualitative analysis of the digestive tracts in 

birds was made to verify that organisms included 

in trace-element analysis were indeed diet items of 

migratory birds. The birds were primarily coots 

(Fulica americana), black-necked stilts (Himantopus 

mexicanus), and avocets (Recurvirostra americana), 

but ducks also were examined. The extent of digestion 

of the gut contents was a major variable because the 

elapsed time between collection and preservation 

varied widely.

A one-time estimate of the standing crop of 

vegetation (filamentous algae and submergent vascular 

plants) throughout the TJ Drain system was made 

August 27,1990. The drain was divided into 1.0-mi 

segments, and the width of the drain was measured at 

0.5-mi intervals. Transects were made at the midpoint 

of each segment as determined by measuring with a 

vehicle odometer. The transects consisted of either 

three or five evenly spaced sample sites across the 

width of the drain. Five samples were collected where 

drain width exceeded 10 ft. A Surber square-foot sampler was used to define the individual sample area. 

The attached net captured the vegetation after it was 

severed by the investigator and released into the current. Composite plant samples were frozen in 1-gal 

jars. Samples were later thawed, hand rinsed, drained, 

and weighed wet. Dry weights were obtained by drying in an oven at 104°C until weight remained constant.

To determine the source areas of selenium 

and mercury, sample points were selected throughout 

the drainage system in such a way that each point

represented drainage from about a 1-2-mi2 area of 

irrigated land. From these sites, organic detritus 

and filamentous algae, if present, were collected and 

analyzed. Although many of the managed wetland 

units were dry because of the drought, the wetlands 

sampled contained water. To identify source areas 

where selenium and mercury are most available biologically, the data sets for both detritus and filamentous 

algae were displayed through a geographicinformation system.

RESULTS

Examination of the upper digestive tracts of 

66 migratory birds from Carson Lake and Stillwater 

WMA confirmed that algae, vegetation, mixed drift, 

and insects were consumed by migratory birds in the 

study area. Content of the digestive tracts varied considerably between species and between individuals of 

the same species. Leeches (hirunids), ostracods, and 

daphnids (Daphnia magna) found in drift were not 

found in gut contents, but these relatively soft-bodied 

organisms may have been fragmented in the gizzard 

and therefore difficult to identify. Seeds of emergent 

vascular plants were found in digestive tracts of ducks. 

Digestive tracts of 11 black-necked stilts were examined and found to contain primarily water boatmen 

(corixids). No adult brine flies (Z)j/?tera)were found 

in the black-necked stilt digestive tracts examined, 

but stilts have been observed feeding heavily on brine 

flies at times in Hunter Drain (Steven P. Thompson, 

Stillwater WMA, U.S. Fish and Wildlife Service, 

oral commun., 1988).

Because plant material dominated the biomass in 

the drains and wetlands, detritus was assumed to be primarily of plant origin, with associated microorganisms, 

and did indeed contain recognizable plant and animal 

parts. Organically rich sediment, varying in depths at 

the soil-water interface, was the lightest fraction of the 

bottom sediment (typically 85-90 percent water). 

Because of its light-brown color, detritus appeared to 

be oxygenated and in chemical contact with the water 

column. Detritus was in direct contact with the most 

abundant benthic insect larvae in the study areas, 

midge (Chironomus sp.) and brine flies; invertebrates 

were not typically found in anaerobic sediments below 

the detrital layers at the sampled locations. All data 

collected were reported by either Hoffman and others 

(1990) or Rowe and others (1991).

44 Detailed Study of Irrigation Drainage Effect on Biota
Detritus sampling was a significant factor in 

establishing the biological pathways by which selenium and mercury moved into wildlife. A total of 

112 composite detritus samples from all sites were 

analyzed. The concentrations of selenium and 

mercury, respectively, ranged from <0.09 to 8.04 

and from <0.04 to 97.8 jig/g, dry weight.

Exceptionally high concentrations of mercury 

(26-98 jig/g) were found in three detritus samples 

from Indian Lakes within Stillwater WMA and from 

ten irrigation-drain samples. Long and Morgan (1990, 

p. 41) suggest that concentrations greater than or equal 

to 1.0 jig/g mercury, dry weight, in sediment would 

adversely affect exposed invertebrates. This criterion 

was exceeded in 47 of 112 (42 percent) of the detritus 

samples analyzed (Rowe and others, 1991).

Lemly and Smith (1987, p. 9) predicted 

reproductive failure or mortality in fish and waterfowl exposed to sediment containing selenium concentrations greater or equal to 4.0 jig/g, dry weight, 

because of food-chain bioaccumulation. This criterion 

was exceeded in only 4 of the 112 detritus samples 

(4 percent); 3 of those were from Fernley WMA.

Filamentous algae were not present at all 

detritus sampling sites. The concentrations of 

mercury and selenium in 87 algae samples ranged 

from <0.02 to 10.4 and from <0.06 to 5.6 ^ig/g, dry 

weight, respectively. The criteria used to evaluate 

mercury and selenium concentrations in algae are 

based on dietary bioaccumulation in fish and birds. 

The effect criterion for mercury in bird diets is 

0.39 M-g/g, dry weight (Heinz, 1979, p. 395; Hoffman 

and others, 1990, p. 26), and for selenium in fish diet 

is 5.0 jig/g, dry weight (Lemly and Smith, 1987, 

p. 9) The mercury criterion was exceeded in 49 of 

87 (56 percent) filamentous algae samples. The 

selenium criterion was exceeded in only two samples.

Samples of drift were taken for qualitative 

biological pathway evaluations. The rates of drift 

movement were not quantified and the data are qualitative. Most of the 55 samples were taken from the 

Lead Lake, Fernley WMA, and Hunter Drain systems. 

Sample contents and volumes were highly variable 

between sites and within sites sampled at various times, 

but most macroinvertebrates and aquatic plants were in 

drift. The exception emergent aquatic plants were 

not identified in drift, but may have contributed to the 

undifferentiated detritus parts. Dominant parts of drift 

included algae, submergent vascular plants, detritus,

daphnids, ostracods, amphipods (Gammarus s/?.), 

corixids, chironomids, brine flies, leeches, 

and odonates.

Selenium was detected in most drift samples, 

with the highest concentration (10.0 jig/g, dry weight) 

found in daphnids from South Pond in Fernley WMA. 

Eight of the 55 (15 percent) samples contained concentrations of selenium greater than the 5.0 jig/g dietary 

criterion that has been shown to cause reproductive 

failure or mortality in fish through food-chain bioconcentration (Lemly and Smith, 1987, p. 9). Concentrations in seven of these samples were greater than 

7.0 jig/g, dry weight. This concentration in the diet 

also may cause reproductive failure or mortality in 

some migratory birds (GJ. Smith, U.S. Fish and 

Wildlife Service, oral commun., 1989).

Although no attempt was made to establish 

contaminant loading estimates in aquatic drift, a onetime estimate of the standing crop of all vegetation 

in TJ drain was made August 27,1990. The instantaneous standing crop of vegetation in the 17-mi-long TJ 

Drain was about 15,500 kg (17 tons), dry weight. Using 

the selenium concentration range of 0.61-2.1 jig/g for 

vegetation, there was at that time between 9.5 and 

31.9 g of selenium fixed in vegetation. This estimate 

was made several days after a high discharge event 

when there was visual evidence that large quantities 

of algae and vascular plants had recently been flushed 

downstream. Selenium is also found in invertebrates 

and other animals and in detrital matter, but no attempt 

was made to estimate the standing crop of these groups 

because little remained after the discharge.

Brine fly adults were sampled where available. 

Six of the twelve samples (50 percent) contained selenium in excess of the 7.0 jig/g, dry weight, dietary criterion for birds (GJ. Smith, U.S. Fish and Wildlife 

Service, oral commun., 1989).

Bioaccumulation and Biomagnification 

of Selenium and Mercury

Selenium concentrations in filtered water samples from the general study area, including the lower 

TJ Drain and Lead Lake, were at or below the analytical reporting limit of 1.0 jig/L (Hoffman and others, 

1990, p. 77). Higher selenium concentrations, as much 

as 46 jig/L, were found in filtered sample water from 

the headwaters of the TJ Drain system (Tokunaga and 

Benson, 1991, p. 20, 28). Similarly, in California at

BIOLOGICAL PATHWAYS RJ. Hallock and others 45
the Grasslands Water District and Kesterson National 

Wildlife Refuge, dissolved selenium was quickly 

absorbed into biota, primarily plants, resulting in low 

concentrations in water (Presser and Ohlendorf, 1987, 

p. 811,815).

Selenium and mercury are not homogeneously 

distributed in the water or surficial soils within the 

study area (U.S. Bureau of Reclamation, 1987, p. B14; 

Ronald R. Tidball, U.S. Geological Survey, oral 

commun., 1989). Selenium concentrations in water 

are not a reliable indicator of the magnitude of contamination of selenium in organic matter (Hoffman and 

others, 1990, p. 77). Evidence of bioaccumulation of 

mercury in biota was found where dissolved mercury 

concentrations in water were below the analytical 

reporting limit (1990, p. 36, 60).

Both selenium and mercury are known to 

bioaccumulate in detritus. Lemly and Smith (1987, 

p. 5) discussed the potential importance of detritus 

pathways leading to fish and migratory birds in situations where selenium may not be detectable in water. 

Depending on waterway morphology and flow, 

detritus may accumulate and be available to 

consumers for several years.

Maximum observed concentrations of selenium 

and mercury in detritus were 8 and 98 |ig/g, dry weight, 

respectively. Sites with high selenium concentrations 

in detritus correlate with sites where Hoffman and 

others (1990, p. 67-70) found high selenium concentrations in juvenile bird livers and muscle. The highest 

mercury concentration found in detritus was from 

Indian Lakes, which corresponds to data from Cooper 

and others (1985, p. 57) that showed elevated mercury 

concentrations in fish and fish fillets from Indian Lakes. 

Detritus appears to be a useful medium with which 

to qualitatively assess the spatial distribution of 

biologically available selenium and mercury.

Filamentous algae and vascular aquatic 

plants also may bioaccumulate selenium (Presser 

and Ohlendorf, 1987, p. 811; Lemly and Smith, 1987, 

p. 4) or mercury (Eisler, 1987, p. 21), or selenium and 

mercury (Hoffman and others, 1990, p. 62). In this 

study, concentrations of selenium and mercury in algae 

were similar to those in detritus at the same locations. 

Algae were widespread and nearly as useful as detritus 

in understanding the dynamics of selenium and mercury movement in irrigation drains and wetlands.

Biomagnification of selenium was documented 

in juvenile black-necked stilts from Lead Lake 

(Hoffman and others, 1990, p. 67). Data from the

following section on waterfowl production show that 

selenium concentrations in juvenile bird (cinnamon 

teal [Anas cyanoptera] and coot) tissues were greater 

than 10,000 times those found in water, and that some 

migratory birds had accumulated selenium to levels 

at which mortality or reproductive impairment would 

be expected.

In the Stillwater study area, bioaccumulation 

appeared to occur primarily in the irrigation drains. 

Biomagnification also occurred in drains, but was 

more evident in the initial wetlands, as was the situation in Grasslands Water District, California, where 

the largest concentrations of selenium were found 

in animal tissue collected in the initial wetlands 

to receive selenium-bearing water (Presser and 

Ohlendorf, 1987, p. 815).

Selenium and Mercury Pathways

Algae and other aquatic vegetation have been 

observed moving down the drains. Much of this movement appears to be associated with peak discharges 

resulting from operational spills or heavy rainfall. 

Assessments of the vegetation standing crops in TJ 

Drain followed a large storm that apparently had 

flushed large quantities of vegetation downstream 

to Lead Lake. About 15,500 kg, dry weight, of 

vegetation remained.

The biological components actually being 

transported were isolated in the drift samples. The 

irregular mixture of vegetation and invertebrates in 

these samples makes the data appropriate only for 

qualitative evaluation. Analysis of drift samples indicates that selenium was being bioaccumulated in 

plants, biomagnified in invertebrates, and that both 

components in drift and detritus were transported 

to wetlands by drain flow.

Figure 11 illustrates the flow path of selenium 

in particulate matter to downgradient wetlands. The 

TJ Drain appears to be the largest contributor of selenium to Lead Lake. Paiute Diversion Drain seasonally 

supports large biomasses of algae and vascular plants, 

which also may be an important source of selenium 

to Lead Lake. Biological samples from wetland sites 

downgradient of Lead Lake, which are maintained by 

Lead Lake water, were generally lower in selenium 

than those from Lead Lake.

46 Detailed Study of Irrigation Drainage Effect on Biota
D-LINE CANAL TJ DRAIN PAIUTE DIVERSION DRAIN

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EXPLANATION

I I MAXIMUM-MINIMUM 

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0 NO SAMPLE COLLECTED

Figure 11. Generalized flow path in Stillwater Wildlife Management Area and selenium concentrations in 

composite samples from input drains, Lead Lake, and downgradient wetlands. Data from Hoffman and 

others (1990, table 19) and Rowe and others (1991, tables 20 and 21).

BIOLOGICAL PATHWAYS RJ. Hallock and others 47
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Figure 12. Generalized flow path and selenium concentrations in composite samples from A-Drain, 

South Pond, and downgradient wetlands, Fernley Wildlife Management Area. Data from Hoffman and 

others (1990, table 19) and Rowe and others (1991, tables 20 and 21).

48 Detailed Study of Irrigation Drainage Effect on Biota
Water is lost through evapotranspiration from 

Lead Lake and from managed ponds or wetlands downgradient to the extent that dissolved solids are concentrated two to six times in each successive wetland 

(U.S. Fish and Wildlife Service, 1988, p. 51). This 

process is cumulative, and dissolved-solids concentrations in the last wetland frequently exceed concentrations in seawater. Data on organically bound selenium 

from this study and on dissolved selenium (Hoffman 

and others, 1990, p. 37) do not conform to the simple 

evaporative patterns predicted from these concentration processes. Dissolved selenium is not a conservative variable; it was least present in water in the 

downgradient wetlands where dissolved solids were 

the most concentrated. Presser and Ohlendorf (1987, 

p. 811) also found that selenium distribution in sequentially arranged ponds was inversely related to that 

which would be predicted through evaporative models. 

Therefore, evapotranspiration does not appear to 

be an important mechanism contributing to selenium 

concentration in surface water.

Inorganic sediment deposition also is not 

believed to be playing an important role in selenium 

pathways within Lead Lake. Organic pathways were 

probably more effective at removing selenium from 

water than inorganic processes in the Grasslands 

Water District (Presser and Ohlendorf, 1987, p. 811). 

Although Lead Lake has received selenium-bearing 

drift for 7 years from TJ Drain and for more than 

40 years from Paiute Diversion Drain, selenium concentrations in the upper 2-3.5 in. of the bottom sediment in Lead Lake averaged only 0.65 jo,g/g (mg/kg: 

Hoffman and others, 1990, p. 113), near the median 

range of concentrations in various organisms and 

detritus in Lead Lake. These concentrations suggest 

that, in this system, selenium is not accumulating or 

immobilizing in inorganic sediment over the long term. 

Roots of aquatic plants could have an active role in 

mobilizing selenium out of inorganic sediment (Lemly 

and Smith, 1987, p. 4), but most of the rooted aquatic 

plant beds have perished from Lead Lake over the last 

30 years.

Organically bound selenium concentrations 

recorded in biota from Lead Lake are similar to those 

of the imported organisms and detritus found in drains 

(fig. 11). This indicates that an equilibrium between 

import and export exists in Lead Lake, which has been 

continuously flooded for about 10 years. Even with 

significant evaporative concentration processes, selenium concentrations in organisms from wetlands

downgradient from Lead Lake are lower than those 

within the lake. Selenium volatilization may be a 

component of such an equilibrium (Ohlendorf, 1989, 

p. 139). Frankenberger and Thompson-Eagle (1989, 

p. 2) have documented volatilization of selenium from 

saline evaporation-pond water. The bacteria and fungi 

that were acting on the available selenium to cause this 

process were particularly effective in protein-rich environments. Organic detritus is a protein source and may 

facilitate volatilization of selenium in the study areas.

The selenium hazard to fish and wildlife in 

the Lead Lake system is largely determined by both 

concentration and length of exposure. Habitat size 

and configuration are important physical variables that 

determine the extent of wildlife use and exposure. The 

TJ Drain system is about 17 mi long, contains about 20 

surface acres of flowing water, and attracts small numbers of migratory birds, primarily ducks. Conversely, 

Lead Lake covers about 1,000 acres and supports thousands of waterfowl. Because of relatively limited use, 

direct exposure of waterfowl to selenium in the TJ 

Drain is of lesser concern.

Concentrations of selenium in all types of 

biological samples from Fernley WMA were generally 

greater than those from the Lead Lake system. The 

relative concentrations of selenium in various organisms and spatial relationships are shown in figure 12. 

The relative concentrations of selenium in A-Drain, 

South Pond, and downgradient wetlands resemble the 

pattern described for the Lead Lake system but, like 

the Grasslands Water District (Presser and Ohlendorf, 

1987, p. 815), bioaccumulation was greatest in the 

initial wetland.

Concentrations of selenium in drift, algae, and 

adult brine flies in Hunter Drain in Stillwater WMA 

(fig. 13) are comparable to those in both Fernley WMA 

and TJ Drain.

Mercury released to the Carson River in the late 

1800's by gold and silver milling practices has contaminated the river sediment downstream of the Comstock 

mining district near Virginia City, Nev. (Smith, 1943; 

Cooper and others, 1985). Contaminated sediment is 

present over a large part of the Carson Desert, terminus 

of the Carson River. Mercury was deposited in the area 

through flooding prior to the construction of Lahontan 

Dam in 1915, and remains biologically available within 

Indian Lakes to this day. However, it appears that mercury export through the D-line Canal, a ditch that feeds 

the Indian Lakes, was minimal. The median concentration of mercury in composite detritus samples from

BIOLOGICAL PATHWAYS RJ. Hallock and others 49
Indian Lakes, in Stillwater WMA, was about 53 |ig/g, 

dry weight. In contrast, the median mercury concentration in detritus from the D-line Canal downstream from 

Indian Lakes was only 0.13 |ig/g, which is comparable 

to background sites and at a level about 400 times 

lower than that in Indian Lakes.

Mercury concentrations found in 89 detritus 

and 76 algae samples from drains within the area 

ranged from <0.04 to 38.6 u.g/g, and <0.02 to 10.4, 

respectively. Most of these high concentrations were 

from drainage/wetland systems not previously studied 

in detail for selenium accumulation. The mechanism(s) through which mercury was sorbed onto or into 

detritus and algae was not determined. Although drift 

was not examined in these drains, mercury was found 

in algae and detritus from drift moving down the drains 

in the area. Many of the samples with high mercury 

concentrations are from sites in drains upgradient of 

Carson Lake. Juvenile migratory birds have been 

shown to bioaccumulate mercury in Carson Lake 

(Hoffman and others, 1990, p. 61). Adult shoveler 

ducks (Anas clypeatd) feeding in Carson Lake have 

also been shown to bioaccumulate mercury. (See the 

section in this report, "Mercury and Selenium in Edible 

Tissue of Waterfowl. 11 )

In the three drainage systems examined in detail 

(Paiute, D-Line, and TJ Drains), biological pathways 

particularly detritus and algae were associated with 

the transport of selenium from irrigated lands (source 

areas) through drains to managed wetlands. Mercury 

also accumulated in detritus and algae in some drains. 

Because detritus and algae are transported in drift in 

similar drains in this project, biological pathways are 

thought to be involved in the movement of mercury 

from source areas to managed wetlands.

Duration of Selenium Contamination

Paiute Drain, which discharges to Lead Lake, 

provides additional information on the possible duration of selenium contamination in agricultural drainages. The Paiute Drain system (fig. 8) was constructed 

between 1913 and 1950. Median concentrations of

selenium in animal drift from Paiute Drain were 

approximately half those of nearby younger TJ Drain 

and slightly less than half those from Hunter Drain 

(figs. 11 and 13).

The release of high concentrations of selenium 

in the shallow ground water, if present, in the first 

1-5 years following construction of new drains, followed by the long-term release of lower concentrations 

would be expected (Gilliom and others, 1989, p. 123). 

The water-quality history of Paiute Drain is unknown, 

but it is apparent that after more than 40 years, selenium continues to be released into the water, incorporated into biota, and transported to Lead Lake (fig. 11). 

Similarly, after about 40 years of irrigation drainage, 

soils near Hunter Drain continue to release selenium 

into the water, and bioaccumulation occurs in this drain 

(ng. 13).

HUNTER DRAIN

10

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17.9 f

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11.1-

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% ° &, /A. V 

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EXPLANATION

| I MAXIMUM-MINIMUM 

X MEDIAN 

A MEAN 

 SINGLE SAMPLE

FIGURE 13. Selenium concentrations 

in composite samples from Hunter 

Drain in Stillwater Wildlife Management 

Area.

50 Detailed Study of Irrigation Drainage Effect on Biota
Contaminant Source Areas

Selenium and mercury are heterogenously 

distributed in irrigated soils within the Newlands 

Project area (R.R. Tidball, U.S. Geological Survey, 

oral commun., 1989). Here, source areas associated 

with biological pathways are irrigated land upgradient 

from or at sampling sites in drains that carried concentrations equal or exceeding 1.0 |ig/g, dry weight, of 

selenium or mercury.

Figure 14 shows the spatial distribution of 

selenium in detritus throughout the study area Selenium concentrations in algae generally correlate with 

those in detritus. Areas having selenium concentrations >1.0 |ig/g, dry weight, were defined as source 

areas or areas of high selenium availability. The 

1.0 |ig/g concentration was selected principally 

because of the capacity of selenium to biomagnify up 

the food chain. This concentration was the average for 

plants from TJ Drain. Four general source areas of high 

selenium concentration were identified: near the city 

of Fallen, north and east of S-Line Reservoir, Fallen 

Indian Reservation, and the Fernley agricultural area 

(fig. 9). Areas of high concentrations of arsenic and 

boron in detritus and algae coincided with the same 

areas of high selenium concentration (Rowe and 

others, 1991).

Areas having mercury concentrations > 1.0 |ig/g, 

dry weight, in detritus, were defined as source areas or 

areas of high mercury availability. Mercury concentrations greater than 1.0 |ig/g were found in both detritus 

(fig. 15) and algae in an area near Carson Lake along 

the historical Carson River channel, south of Fallen. 

This fan-shaped area, generally northwest of Carson 

Lake, is the area which may have received sediment 

from the Carson River prior to 1900, before the construction of dams that diverted the flow of the river 

(see fig. 2). Other areas of high concentrations are 

along the Carson River, Stillwater Slough, and New 

River Drain.

The occurrence of selenium and mercury in 

detritus and algae associated with irrigation drainage 

is indicative of the bioavailability of those elements, 

and suggests an upgradient source. Furthermore, the 

magnitude of bioaccumulation at one site can be compared with another to indicate source areas of more 

or less contamination. Additional information on 

the annual load of organically bound selenium and 

mercury from the agricultural drains to receiving 

wetlands would be more definitive.

BIOLOGICAL PATHWAYS RJ. Hallock and others 51
39"45

118° 30'

s?

CDa

CQ

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39°30' 

39 15

EXPLANATIONI OPEN WATER

.i;-.- I WETLANDS, INCLUDING ^*p '1 OPEN WATER

AGRICULTURAL LANDS 

PLAYA

WILDLIFE MANAGEMENT 

AREA BOUNDARY

0.6 SELENIUM CONCENTRATION, 

IN MICROGRAMS PER GRAM, 

DRY WEIGHT

R. 25 E. R.26E R. 27 E. R. 28 E. R.29E. R. 30 E.

FIGURE 14. Concentrations of selenium in detritus samples from in and near Stillwater and Fernley Wildlife Management Areas. (Map modified from Seller 

and Allander, in press.)
39°45'

118° 30'

00

6

o ogII

CA fon §.

39 301 

39°15'

EXPLANATION

OPEN WATER

aF^Tl WETLANDS. INCLUDING

- ^ OPEN WATER

| | AGRICULTURAL LANDS 

PLAYA

WILDLIFE MANAGEMENT 

AREA BOUNDARY

0.6 MERCURY CONCENTRATION, 

IN MICROGRAMS PER GRAM, 

DRY WEIGHT

R. 25 E. R. 26 E. R. 27 E. R. 28 E. R.29E. R.30E.

FIGURE 15. Concentrations of mercury in detritus samples from in and near Stillwater and Femley Wildlife Management Areas and adjacent wetlands. 

(Map modified from Seiler and Allander, in press.)
EFFECTS OF BORON, MERCURY, AND SELENIUM 

ON WATERFOWL PRODUCTION

Waterfowl are typically most sensitive to 

environmental stress during their reproductive phases 

(egg formation, incubation, and juvenile growth) and 

are more vulnerable to the effects of trace elements 

during that time. Trace-element toxicity is a possible 

contributing factor to the steady decline of waterfowl 

production in wetlands that are maintained by drainage 

from the Newlands Irrigation Project. Livers from 

juvenile waterfowl and shorebirds collected from 

these wetlands in 1986-87 contained concentrations 

of boron, mercury, and selenium that have been associated with various harmful effects (Hoffman and others 

1990, p. 53, 60, 67). The available literature concerning the effects of trace-element concentrations in eggs 

and juvenile waterfowl is limited, but some information is available about the effect levels of boron, 

mercury, and selenium. Concentrations of 20 trace 

elements were determined in this study in 1988 and 

presented by Rowe and others (1991, table 20). Of 

those elements, this section will consider only boron, 

mercury, and selenium. Evaluations of these three 

elements in eggs and juvenile duck livers and of 

hatch success, teratogenesis, nest success, and duckling production were made to determine the extent 

of the effects of these trace- elements on waterfowl 

reproduction.

APPROACH

Six separate wetlands were included in the 

waterfowl production study: Still water, Fernley, 

and Humboldt Wildlife Management Areas (WMAs); 

Carson Lake; and Massie and Mahala Sloughs (fig. 1). 

All of these areas receive irrigation drainage, ground 

water, or both, from U.S. Bureau of Reclamation 

Projects. Humboldt WMA is maintained primarily 

by irrigation return flow from the Humboldt Irrigation 

Project. The other five study areas receive irrigation 

return flow from the Newlands Irrigation Project 

(Hoffman and others, 1990).

Background sites were selected in Carson 

Valley, outside the study area, and at S-Line Reservoir, 

near the study area. The wetlands in Carson Valley 

are about 1,000 ft higher than the valley floors of the 

study area, thus presenting a history of soil development unaffected by ancient Lake Lahontan. Although 

S-Line Reservoir is located within the Fallon agricultural area, it is maintained primarily with Carson River 

water taken from Coleman Diversion Reservoir which 

contains only small amounts of irrigation return water.

This study was made in 1988 during the 

second year of a drought. Both irrigation drainwater 

and operational releases in the study area were greatly 

reduced because of the tight management of irrigation 

water; agricultural diversions were reduced to 

70 percent of normal in response to the drought. Thousands of wetland acres dried up, reducing nesting and 

feeding habitat. Waterfowl congregated on the remaining wetlands, where reduced vegetative cover exposed 

nests to increased predation. Dissolved solids, including trace elements, concentrated in the drainwater 

and remaining ponds as evaporation reduced the 

water volume.

The number of samples collected in this 

study was low, primarily because nests that were 

not destroyed by predators were extremely difficult to 

locate in the available habitat. Nest predators were an 

ongoing problem, commonly destroying previously 

located nests between study visits.

Nests of six species of ducks cinnamon teals 

(Anas cyanopterd), gadwalls (Anas strepera), mallards 

(Anas platyrhynchos), pintails (Anas acuta), redhead 

ducks, and ruddy ducks (Aythya americana and Oxyura 

jamaicensis) were surveyed, as were nests of American coots (Fulica americana).

METHODS

Surveys to locate as many duck and coot nests 

as possible were conducted, on foot, in the various 

nesting habitats from early May through June. Peak

WATERFOWL PRODUCTION L.L Hallock and others 55
nesting periods in this area typically range from 

April 10 to June 20 for ducks and from May 1 to June 

15 for coots. All study sites had suitable nesting habitat 

for the various waterfowl common to the area. Redhead and ruddy ducks and American coots build nests 

in and over water in bulrush (Scirpus sp.) and cattails 

(Typha sp.), and other duck species use a variety of 

upland and marsh vegetation.

After the nests were located and identified by 

species, one egg was taken from each nest for traceelement analysis. Two additional eggs were collected 

from duck nests containing seven or more eggs for artificial incubation under controlled conditions to determine hatch success. Nests with six or fewer eggs were 

revisited and, if the clutch size had increased to seven, 

the additional two eggs were collected at that time. 

Coot eggs were not collected for artificial incubation 

because the incubator was adjusted for duck eggs 

and coots were of secondary interest. All eggs were 

marked for identification and floated in water to determine incubation stage and expected hatch dates 

(Westerkov, 1950). Eggs collected for trace-element 

analysis were immediately refrigerated and those for 

incubation were placed in a Koolatron (a temperaturecontrolled, padded container) for transportation to 

the incubator.

Eggs for trace-element analysis were 

volumetrically measured by water displacement. 

The eggs were then opened, using a scalpel cleansed 

with acetone followed by a distilled- or deionizedwater rinse. The circumference of the egg was scribed 

with the scalpel and the contents dropped directly into 

a nitric-acid-washed, pre-weighed, 2-oz glass jar. 

The degree of embryonic development was recorded, 

and the samples were weighed, labeled, and frozen for 

shipment. All egg samples were analyzed for traceelements by the U.S. Fish and Wildlife Service, 

Patuxent Analytical Control Facility, Laurel, Md., 

or their contract laboratories. The resulting data had 

appropriate quality-assurance documentation attached. 

All trace elements were analyzed by inductively coupled plasma emission spectroscopy, except for mercury, which was analyzed by the cold-vapor technique, 

and selenium, which was analyzed by hydride 

generation (U.S. Fish and Wildlife Service, 1985).

The incubator (a Petersime Model No. 4) was 

checked twice daily to monitor temperature and humidity and to remove any newly hatched ducklings. Eggs 

that remained unhatched approximately 10 days after 

expected hatch dates, and eggs that pipped but did not 

hatch, were removed and refrigerated for examination.

Embryos and ducklings were examined for gross 

abnormalities of the eyes, beak, wings, and feet, and 

were then frozen in individual plastic bags. Mallard 

eggs of known age from game-farm birds maintained 

on a contaminant-free diet were used as incubation 

controls.

Coot nests were rechecked prior to expected 

hatch date and a second egg was collected from those 

nests still containing eggs. Embryos from these eggs 

were examined for deformities and then frozen.

To determine if juvenile birds accumulated 

trace elements after hatching, livers of juvenile ducks, 

coots, and black-necked stilts (Himantopus mexicanus) 

from both background and study-area wetlands were 

analyzed. Sixty preflight ducklings, 45 juvenile coots, 

and 12 juvenile stilts were collected from the study 

areas, and 5 ducklings and 6 coots were collected from 

the background areas. The birds were frozen and later 

partially thawed for dissection. The liver from each 

bird was removed using a scalpel rinsed with acetone 

followed by a distilled- or deionized-water rinse. The 

liver was placed in a nitric-acid washed, preweighed, 

2-oz glass jar, then weighed, labeled, and frozen for 

shipment. Juvenile stilt livers were so small that two 

were combined to make a minimum sample weight; 

therefore, each data point for liver (figs. 16,17) 

represents two birds.

Nest success is defined as the probability of 

production of one or more live juveniles from a nesting 

attempt. The nest-success rate was calculated by dividing the number of successful nests by the total number 

of nests. To determine nest success, each duck nest was 

checked at 7-10 day intervals for evidence of successful hatching. A feathered-egg membrane pulled away 

from the shell was used as an indicator of successful 

hatching. Coot nests were rechecked at least once, 

either at hatching time or just after.

Duckling production was estimated by 

conducting brood surveys in each study area from 

the fourth week of June through the third week of 

July the peak hatching period Survey routes were 

predetermined to include areas of high brood use, 

particularly shorelines and clumps of vegetation, and to 

ensure adequate visibility by the investigator. Surveys 

started about 6:00 a.m., during the most active feeding 

time. Most routes were walked or driven, using binoculars or a spotting scope as necessary. In areas inaccessible by land, an airboat was used. Data on duck 

species, duckling numbers, and age classes at each 

site were recorded.

56 Detailed Study of Irrigation Drainage Effect on Biota
Hatch Success and Teratogenesis

Duck eggs for incubation and subsequent 

examination were collected from 41 nests; two eggs 

per nest were collected where possible. A total of 

81 eggs were incubated 69 from study-area sites and 

12 from background sites. Eggs from the background 

sites had a hatch-success rate of 92 percent. Of the 

69 eggs from the study sites, 62 hatched a success 

rate of 90 percent. This rate for artificially incubated 

duck eggs is in the range expected for eggs from 

healthy populations (Charles J. Henny, U.S. Fish and 

Wildlife Service, oral commun., 1990). Hatch success 

is summarized in table 16 by species and area.

The eight eggs that failed to hatch seven 

from the study area and one from the background 

site were examined for deformities. Five contained 

embryos, all well developed with no gross deformities 

(Charles J. Henny, U.S. Fish and Wildlife Service, oral 

commun., 1990). The three eggs that failed to develop 

may have been infertile. The 62 ducklings were also 

examined and no gross external deformities were 

observed. Thirty-one coot eggs from separate nests

were collected just prior to expected hatch. Of these 

eggs, 24 had well-developed embryos and all 31 

appeared to be normal. Based on these data, levels 

of trace elements in the eggs probably were below 

effect levels for teratogenesis and mortality.

Trace Elements in Eggs

Eisler (1990,1987, and 1985) has summarized 

the available literature on the effects of boron, mercury, 

and selenium, respectively, on wildlife, including specific references for duck eggs (table 18). One of the 

common effects that each of these trace elements has 

on embryonic development is reduced hatch weight.

Concentrations of trace elements were 

determined for 62 duck eggs and 68 coot eggs. 

Five of the duck eggs were from the background 

site in Carson Valley and were well below the effect 

level for boron, mercury, and selenium. These data 

are reported by Rowe and others (1991, table 20) 

and are summarized in table 17 in this report.

Table 16. Hatch success of artificially incubated waterfowl eggs collected in the study area, 1988

[In each two-line data group, the top number (in parentheses) is total incubated eggs; bottom number is percentage hatched; , 

no data; WMA, Wildlife Management Area]

Location

Stillwater WMA

Fernley WMA

Humboldt WMA

Mahala Slough

Massie Slough

TOTAL

Carson Valley

Cinnamon 

teal

(6) 

100

(6) 

100

(2) 

100

(10) 

80

(2) 

100

(26) 

92

~

Gadwall Mallard Pintail

(2) 

100

--

(2) 

100

(2) 

100

--

(6) 

100

Study Sites

(4) (4) 

75 100

-

(3) 

100

(2) 

100

--

(9) (4) 

89 100

Background Site

(12) 

92

Redhead

(2) 

100

(6) 

67

(8) 

88

--

(2) 

100

(18) 

83

--

Ruddy

(2) 

100

--

--

(4) 

75

--

(6) 

83

--

Total, all 

species

(20) 

95

(12) 

83

(15) 

93

(18) 

89

(4) 

100

(69) 

90

(12) 

92

WATERFOWL PRODUCTION /../.. Hallock and others 57
The primary effects of high levels of boron are 

on growth, behavior, and brain biochemistry (Eisler, 

1990, p. 19). Mallard ducklings from eggs with a boron 

concentration of 13 |lg/g, dry weight, showed reduced 

hatch weights (Smith and Anders, 1989, p. 945). Eggs 

with boron concentrations of 49 |lg/g, dry weight, 

showed significantly reduced hatch rates and juveniles 

from those eggs had higher mortality rates (Smith and 

Anders, 1989, p. 945). These effect levels came from 

feeding studies and are the arithmetic means resulting 

from experimental concentrations in feed, so no data on 

intermediate concentrations are available.

The boron concentrations found in eggs in this 

study (maximum, 19.4 |lg/g, dry weight) were all 

well below the level known to adversely affect hatch 

success (49 |ig/g, dry weight). This correlates with 

the incubator hatch rate of 90 percent observed in this 

study. Three redhead duck eggs (5 percent), all collected in Mahala Slough, had boron concentrations 

above 13.0 |ig/g, dry weight, the level associated with 

reduced hatch weight. Overall, coot eggs had higher 

boron concentrations than duck eggs. Ten percent of 

the coot eggs, primarily those from Fernley WMA, 

had boron concentrations above the effect level for 

reduced hatch weight.

Table 17. Summary of data on concentrations of boron, mercury, and selenium, including minimums, maximums, and means 

for waterfowl eggs collected in the study area

[Abbreviations: (ig/g, micrograms per gram; C. teal, cinnamon teal; WMA Wildlife Management Area.]

Trace-element concentration (jxg/g, dry weight)

Location Species

Number 

of 

samples Minimum

Boron

Maximum

Mean

Minimum

Mercury

Maximum

Mean

Minimum

Selenium

Maximum

Mean

Study Sites

Stillwater WMA

Fernley WMA

HumboldtWMA

Mahala Slough

Massie Slough

C. teal

Gadwall

Mallard

Pintail

Redhead

Ruddy

Coot

C. teal

Mallard

Redhead

Coot

C. teal

Gadwall

Mallard

Redhead

C. teal

Gadwall

Mallard

Redhead

Ruddy

C. teal

Redhead

Ruddy

3

1

2

2

1

2

25

2

1

3

27

2

1

1

6

9

1

3

7

7

1

1

1

3.2

2.0

1.7

2.3

5.7

1.1

5.5

1.7

3.1

3.2

4.4

2.8

3.9

10.2

3.1

1.5

7.6

<0.8

4.2

<0.8

1.7

1.8

2.1

4.8

2.0

2.2

3.7

5.7

1.2

15.7

4.8

3.1

5.4

14.3

5.2

3.9

10.2

9.6

7.6

7.6

0.9

19.4

3.1

1.7

1.8

2.1

4.1

2.0

2.0

3.0

5.7

1.2

9.3

3.3

3.1

4.2

7.7

4.0

3.9

10.2

9.6

4.1

7.6

0.6

11.7

2.1

1.7

1.8

2.1

1.6

0.5

1.7

0.4

1.7

0.2

0.1

0.2

0.2

<0.1

0.1

0.4

0.2

0.5

0.1

0.2

0.3

0.3

0.1

0.1

0.1

0.4

0.1

6.2

0.5

3.7

0.5

1.7

0.5

0.4

0.7

0.2

0.1

1.36

0.5

0.2

0.5

1.74

1.1

0.3

2.1

1.2

2.7

0.1

0.4

0.1

4.5

0.5

2.7

0.5

1.7

0.4

0.1

0.5

0.2

0.3

0.2

0.5

0.2

0.5

0.5

0.6

0.3

1.1

0.6

0.6

0.1

0.4

0.1

2.0

1.8

2.1

2.5

1.8

2.1

4.4

7.6

8.9

8.8

1.9

2.8

3.1

3.0

3.0

2.0

4.6

1.3

1.2

1.2

8.0

3.6

7.4

2.3

1.8

2.1

2.9

1.8

2.9

12.2

10.1

8.9

10.9

4.48

3.7

3.1

3.0

3.7

7.4

4.6

8.4

8.5

5.7

8.0

3.6

7.4

2.2

1.8

2.1

2.7

1.8

2.5

8.7

8.8

8.9

9.9

2.9

3.2

3.1

3.0

3.2

4.4

4.6

4.0

3.7

3.3

8.0

3.6

7.4

Background Site

Carson Valley Mallard 5 <0.8 1.9 0.7 0.2 0.6 0.3 0.7 2.3 1.4

58 Detailed Study of Irrigation Drainage Effect on Biota
Table 18. Effect levels and characteristics of boron, mercury, and selenium concentrations in 

waterfowl eggs and juvenile waterfowl livers

[Hg/g, micrograms per gram]

Mercury 

Selenium3

Eggs Liver tissue

Constituent

Boron1

Effect level 

frig/g, dry 

weight)

13 

49

Characteristic sign 

or result

Reduced hatch weight 

Reduced hatch rate and 

juvenile survival

Effect level 

(\iglg, dry 

weight)

17

Characteristic sign 

or result

Reduced reproduction and 

duckling growth

3.1 Reduced hatch rate and 

juvenile survival

15 Teratogenesi s and embryo 

mortality

4.3 Reduced reproduction and 

survival rates

9 Reduced reproduction and 

juvenile survival

1 Smith and Anders, 1989.

2 Heinz, 1979. 

3 LemlyandSmith, 1987.

Mercury concentrations of 3.1 |ig/g, dry weight, 

in black duck (Anas rubripes) eggs are associated with 

significantly reduced hatch rate and duckling survival 

(Heinz, 1979, p. 398). Mercury residues found in duck 

and coot eggs in this study were low except in those 

collected in Stillwater WMA. Three (27 percent) of 

the 11 duck eggs from Stillwater WMA had mercury 

concentrations above the effect level. The nest siblings 

of these eggs cinnamon teal and pintail hatched in 

the incubators.

All selenium concentrations found in duck and 

coot eggs were below 15 |ig/g, dry weight. The level 

at which teratogenesis or embryo mortality (Lemly 

and Smith, 1987, p. 9), or reproductive problems in 

the laying hen (Heinz and others, 1989, p. 427) can 

be expected is 15-18 |ig/g, dry weight.

The concentrations of potentially harmful trace 

elements in duck and coot eggs in all areas were low, 

with the exception of mercury in those from Stillwater 

WMA and, with that exception, probably are not a 

factor in waterfowl production. The adults of these 

species normally do not overwinter in these wetlands; 

they arrive shortly before nesting and apparently 

are not sufficiently exposed to the trace elements to 

accumulate enough to deposit significant amounts 

in their eggs.

Trace Elements in Juvenile Duck Livers

Eisler (1990, 1987, and 1985) summarized the 

available literature on the effects and concentrations 

of boron, mercury, and selenium in livers of juvenile 

waterfowl (table 18).

It was assumed that juvenile waterfowl collected 

preflight had been feeding in the vicinity and that the 

trace-element concentrations in their tissues reflected 

existing conditions in the wetlands. Juvenile ducks, 

coots, and black-necked stilts were taken from study 

areas where eggs had been collected, and livers were 

analyzed for concentrations of trace elements. Data 

were obtained for 65 preflight ducklings, 52 juvenile 

coots, and 12 juvenile stilts. Complete data are presented by Rowe and others (1991, table 20) and are 

summarized in this report (table 19).

In boron feeding studies, mallard ducklings 

with liver concentrations of 17 |ig/g, dry weight, 

showed reduced weight gain (Smith and Anders, 1989, 

p. 945). In this study, boron concentrations in blacknecked stilt livers (6 composite samples) were below 

4 |ig/g, dry weight. Concentrations of boron in duck 

livers also were below the effect level, varying widely 

throughout the study area from 1.1 to 15.1 |ig/g. Coot 

livers showed higher boron concentrations than duck 

livers, as high as 34.5 |ig/g. Concentrations of boron 

were at or above effect level in 10 percent of the coot

WATERFOWL PRODUCTION LL. Hallock and others 59
livers. The highest boron concentrations were from 

Fernley WMA, where three of the seven coots collected had concentrations above effect level, and 

reduced growth rates could be expected. Boron 

levels in juvenile birds were not high enough to 

affect waterfowl reproduction

Levels of boron concentration varied; in some 

instances concentrations were higher in eggs than in 

juvenile livers from the same area. These data suggest 

that some adult birds may have acquired boron elsewhere in the fly way prior to their arrival and egg 

laying in the study areas.

Table 19. Summary of data on concentrations of boron, mercury, and selenium, including minimums, maximums, and means, 

for juvenile waterfowl livers collected in the study

[Abbreviations: ug/g, micrograms per gram; C. teal, cinnamon teal; WMA, Wildlife Management Area.]

Trace-element concentration (ng/g, dry weight)

Location Species

Number 

of 

Samples Minimum

Boron

Maximum

Mean

Minimum

Mercury

Maximum

Mean

Minimum

Selenium

Maximum

Mean

Study Sites

Stillwater WMA

Fernley WMA

Humboldt WMA

Carson Lake

Mahala Slough

Massie Slough

Coot

C. teal

Mallard

Pintail

Redhead

Ruddy

Coot

C. teal

Stilt

Coot

C. teal

Gadwall

Mallard

Redhead

Coot

C. teal

Mallard

Redhead

Ruddy

Stilt

Coot

Redhead

Ruddy

Stilt

Redhead

10

5

2

1

2

1

7

4

3

12

6

1

7

3

10

1

4

4

4

1

6

3

6

2

7

5.8

<2.0

5.1

5.9

5.0

1.8

7.5

2.4

2.0

<2.0

1.8

4.0

2.7

3.0

1.6

7.9

<2.0

0.8

2.1

1.7

3.7

3.7

<0.8

3.4

4.4

22.1

4.4

9.8

5.9

6.0

1.8

34.5

12.1

3.5

8.0

5.1

4.0

10.0

6.1

6.8

7.9

5.3

15.1

3.9

1.7

7.0

9.3

2.4

3.8

13.6

11.1

3.2

7.5

5.9

5.5

1.8

16.8

8.1

2.5

4.5

3.2

4.0

5.9

4.8

4.9

7.9

3.9

5.9

3.3

1.7

5.4

6.5

1.4

3.6

6.8

2.0

1.4

2.7

1.8

2.4

2.1

0.3

<0.1

0.4

0.2

0.4

0.8

0.3

0.6

2.0

5.6

1.4

0.9

<0.1

7.9

0.2

0.1

0.1

2.0

<0.1

5.7

3.5

3.0

1.8

6.4

2.1

0.5

0.1

1.0

3.2

1.6

0.8

0.7

0.8

8.8

5.6

6.0

5.1

2.4

7.9

1.19

0.7

0.5

13.9

0.5

4.0

2.2

5.6

1.8

4.4

2.1

0.4

0.1

0.7

0.7

1.0

0.8

0.5

0.8

5.3

5.6

3.4

2.3

1.5

7.9

0.8

0.4

0.2

8.0

0.3

3.4

4.0

7.4

6.6

6.7

6.4

26.4

26.4

17.0

7.8

11.9

16.0

7.2

9.1

2.6

8.7

4.4

4.4

6.9

13.2

7.6

8.2

5.4

52.0

17.5

5.9

6.8

9.0

6.6

13.9

6.4

36.0

35.3

35.3

13.0

17.5

16.0

23.0

13.3

6.3

8.7

6.6

7.0

8.2

13.2

15.0

20.4

10.4

102.0

43.5

4.4

5.6

8.2

6.6

10.3

6.4

30.9

30.3

28.4

10.1

15.1

16.0

12.8

11.6

4.4

8.7

5.1

5.6

7.6

13.2

9.6

13.5

7.9

77.0

30.7

Background Sites

Carson Valley

S-Line Reservoir

Mallard

Coot

C. teal

4

7

1

1.2

1.6

1.5

2.8

7.3

1.5

2.2

3.9

1.5

1.3

0.8

9.4

2.4

4.3

9.4

1.6

2.9

9.4

2.3

2.9

5.6

3.5

5.3

5.6

3.0

4.3

5.6

60 Detailed Study of Irrigation Drainage Effect on Biota
Data are not available for establishing an 

effect level for mercury concentration in juvenile 

waterfowl liver, but for adult mallard liver, an effect 

level of 4.3 (ig/g, dry weight, for decreased reproductive success can be derived from existing data (Heinz, 

1979, p. 396; Hoffman and others, 1990, p. 26). 

Stilt, duck, and coot livers from Fernley WMA and 

Humboldt WMA and Massie and Mahala Sloughs had 

mercury concentrations generally below 1 (ig/g. Moderate concentrations of mercury in ducks, coots, and 

stilts were found in Carson Valley (mean 1.6 (ig/g, 

dry weight) and in S-Line Reservoir (3.67 (ig/g, dry 

weight). Mercury concentrations were above the effect 

level in 70 percent of the coots and 31 percent of the 

ducks from Carson Lake and 40 percent of the coots 

from Stillwater WMA. The highest mercury concentration found in this study, 13.9 |ig/g, dry weight, was 

in a stilt sample (livers of two birds, combined) from 

Mahala Slough, an anomalous sample because no other 

samples from Mahala Slough showed high mercury 

concentrations, and Mahala Slough had not received 

direct Carson River water containing mining discharge. 

One of the birds in this sample probably was an adult 

that had moved into Mahala Slough from one of the 

nearby mercury-source areas.

The incidence of elevated mercury concentrations in birds was restricted to areas that had received 

mercury-contaminated sediment of the Carson River 

before construction of the Newlands Irrigation Project, 

including Carson Lake and Stillwater WMA. Mercury 

concentrations in bird livers from those areas are high 

enough that a negative effect on waterfowl production 

could be expected.

Data in the literature on the biological effects 

of selenium on waterfowl are more available. The 

effects are primarily on reproduction, but selenium 

toxicosis has been documented elsewhere since the 

1930's. Selenium concentrations of 9 (ig/g, dry weight, 

in livers of adult birds are known to be associated with 

decreased reproductive success and reduced juvenile 

survival (table 19; Lemly and Smith, 1987, p. 8). 

Selenium concentrations in livers establish 95 percent 

of equilibrium with dietary concentration in 7-8 days 

and return to background level 9-10 weeks after dietary 

intake stops (Heinz and others, 1990, p. 376). Selenium concentrations in livers of preflight juveniles, 

therefore, reflect the selenium in the food chain in 

the area.

Selenium concentrations in bird livers from 

Carson Valley and S-Line Reservoir (background 

sites), and Carson Lake were below the effect level

for reduced reproduction (9.0 |H/g, dry weight). Twenty 

percent of the ducks from Stillwater WMA had selenium concentrations at or above effect level (fig. 16). 

In birds from Mahala Slough, concentrations of selenium above the effect level were found in 56 percent 

of the ducks, 33 percent of the coots, and both stilt 

samples. Concentrations in the two stilt samples 

(composite) were 52.0 and 102.0 (ig/g (mean, 77 (ig/g, 

dry weight), the highest found in this study and in the 

range where toxicosis and mortality have been documented elsewhere (Heinz and others, 1987, p. 429; 

1988, p. 566). Livers from 83 percent of the ducks 

and 67 percent of the coots collected in Humboldt 

WMA had selenium concentrations above the effect 

level, as high as 23 |Llg/g, dry weight. High concentrations of selenium were also found in livers of cinnamon 

teal (mean, 30.0 (ig/g, dry weight) and coots (mean, 

30.9 |ig/g, dry weight) from Fernley WMA, and in 

redhead ducks (mean, 30.7 |ig/g, dry weight) from 

Massie Slough.

The two areas with the highest average 

concentrations of selenium in bird livers were Fernley 

WMA and Massie Slough, where every bird taken had 

concentrations between 17.0 and 43.5 (ig/g (mean, 

30.4 (ig/g, dry weight).

Decreased survival of juvenile birds is 

anticipated in areas where liver concentrations are 

consistently above effect levels. Decreased juvenile 

survival and, thus, decreased waterfowl production, 

is anticipated in Fernley and Humboldt WMAs and 

Mahala and Massie Sloughs, and to a lesser extent in 

Stillwater WMA.

The concentrations of selenium residues found 

in juvenile livers were consistently higher than those 

found in eggs from the same areas, indicating juvenile 

uptake in all areas.

The combined effect of concentrations of two 

or more trace elements is not well understood. High 

boron concentrations were found with high selenium 

concentrations only in Fernley WMA. Selenium and 

boron have been considered to biochemically operate 

independently (Patuxent Wildlife Research Center, 

1987, p. 28), but there is recent evidence that boron 

and selenium interact synergistically to produce more 

severe toxicological effects (David Hoffman, Patuxent 

Wildlife Research Center, written commun., 1990). 

With the exception of the anomalous stilt sample from 

Mahala Slough, high concentrations of mercury and 

selenium, in eggs or juvenile livers, were not found 

in the same areas.

WATERFOWL PRODUCTION LL. Hallock and others 61
STILLWATER WMA

EGG 

LIVER

FERNLEY WMA

EGG 

LIVER

HUMBOLDT WMA

EGG 

LIVER

MAHALA SLOUGH

C/"*/"*

LIVER

MASSIE SLOUGH

EGG 

LIVER

CARSON VALLEY

EGG 

LIVER

C

1

ft 

i 1 AmYA

1 i 

i YA i

i AX-i

LiJ 

§

o

!_&_! W njflSi u.

I xg. I LU

LiJ

IJ 

1

) 10

I I I I I I I

 U|

I 

I 

I

 '!

i i

i

YA I

XT '

I i

' ! '

i i i i i i 

|i

LiJ I

^i 

LiJ

SII I

20

I I

I I MINIMUM-MAXIMUM

A MEAN 

X MEDIAN

A Y I

I I

30 40

SELENIUM, IN MICROGRAMS PER GRAM, DRY WEIGHT

Figure 16. Concentrations of selenium in duck eggs and liver tissue of juvenile ducks collected in 

Stillwater, Fernley, and Humboldt Wildlife Management Areas, Mahala and Massie Sloughs, and at 

the background site. Effect levels for eggs and liver, 9 and 15 micrograms per gram, respectively, 

are described by Lemly and Smith (1987, table 2) and are summarized in table 18 of this report. 

Abbreviation: WMA, Wildlife Management Area.

Nest Success

Nest-success rate, by species, for each study area 

is summarized in table 20. The nest-success data from 

all study sites were combined, because of small sample 

sizes, and compared with data from nesting surveys 

conducted in Stillwater WMA in 1968-1970 (Napier, 

1974), 1983 (Evans, 1983, p. 18-19), and 1987-1988 

(Stillwater WMA, unpublished data); these comparisons are shown in table 21. The nest-success rate found 

in this study, 26 percent for the combined study sites, 

is comparable to the success rate of 25 percent determined for Stillwater WMA by the WMA staff. The 

nest-success rate at Stillwater has shown a general 

downward trend from 43-52 percent in 1968-70 to 

25 percent in 1988.

No relation could be established between the 

nest-success rates in the various study sites and the 

trace-element concentrations in eggs or juvenile livers 

from those sites. The nest failure observed during this 

study appeared to be caused primarily by predation 

exacerbated by loss of habitat and the lack of vegetative cover in and near the remaining wetlands.

62 Detailed Study of Irrigation Drainage Effect on Biota
Table 20. Nest success of ducks in the study area, 1988

[In each two-line data group, the top number (in parentheses) is total nests examined; bottom number is percentage of nests 

hatching at least one young; , no data; WMA, Wildlife Management Area.]

Location

Stillwater WMA

Fernley WMA

Humboldt WMA

Mahala Slough

Massie Slough

TOTAL

Cinnamon 

teal

(3) 

100

2) 

0

(2) 

0

(9)

22

(1) 

100

(17) 

35

Gadwall Mallard

(1) 

0

--

(1) 

100

(1)

0

-

(3) 

33

Study Sites

(2) 

50

(1) 

0

(1) 

100

(3) 

33

-

(7) 

43

Pintail Redhead

(2) (1) 

100 0

(3) 

0

(6) 

50

(1) 

0

(1) 

100

(2) (12) 

100 33

Ruddy

(2) 

0

--

--

(5) 

20

(1) 

0

(8) 

13

Total

(11) 

55

(6) 

0

(10) 

0

(19) 

21

(3) 

67

(49) 

26

Background Site

Carson Valley - (6) 

83

- ~ (6) 

83

Waterfowl Production

A survey of waterfowl breeding pairs, conducted 

annually in mid-May by the Nevada Department of 

Wildlife, found 6,810 breeding pairs of various species 

of ducks in the study area in 1988 (Nevada Department 

of Wildlife, unpublished data, 1988). The low number 

of duck nests (49) found in this study, and the difficulty 

experienced in finding even that number, suggests that 

most of the breeding pairs present in mid-May did not 

nest. Nesting habitat in the study area and in other 

traditional nesting areas is greatly reduced from that 

available in the recent past (U.S. Department of the 

Interior, 1988). This lack of habitat may be 

preventing many pairs from nesting.

Observed duckling production from all study 

areas except Stillwater WMA was 579 birds. Brood 

production in Stillwater WMA, estimated by the 

Stillwater staff, was about 1,800 ducklings (U.S. Fish 

and Wildlife Service, Fallon, Nev., unpublished data, 

1988), for a total estimated production of about 2,400 

waterfowl (table 22). The brood counts in Fernley

WMA, Humboldt WMA, and Carson Lake were 

close to estimates made by the Stillwater WMA staff. 

Duckling production in 1988 was considerably lower 

than production experienced in previous years 

(U.S. Fish and Wildlife Service, Fallon, Nev., 

unpublished data, 1988).

Waterfowl production typically fluctuates, and 

is dependant on a variety of factors, including the availability of suitable wetland nesting habitat and predator 

populations. Decreased water flow to the wetlands, 

management choices about use of the remaining water, 

and elevated dissolved-solids concentrations shown 

to cause vegetative losses (U.S. Fish and Wildlife 

Service, 1988, p. 74) are all probable contributing 

factors to decreases in nesting habitat. The continuing 

decrease in waterfowl production observed in the study 

area in recent years is associated with decreased feeding and nesting habitat that results in waterfowl nesting 

in marginal areas, and to increased predation rates 

resulting from a concentration of predators foraging in 

reduced wetland areas.

WATERFOWL PRODUCTION LL Hallock and others 63
Table 21 . Nest-success rates from various other studies and from the 

present study

[In each two-line data group, the top number (in parentheses) is total nests examined; 

bottom number is percentage of nests hatching at least one young.]

Other studies

_ , . (Stillwater Wildlife Management Area) Duck species

1 968-1 9701 19832

Cinnamon Teal (43-56) 

49-56

Gadwall (19-42) 

16-43

Mallard (1-7) 

0-43

Pintail (2-4) 

50-80

Redhead (4-7) 

57-100

Ruddy (1-3) 

67-100

TOTAL (87-118) 

43-54

1 Napier, 1974. 

2 Evans, 1983. 

3 Unpublished data from U.S.

(100) 

28

(23) 

13

(7) 

57

(6) 

17

(11) 

91

(5) 

60

(152) 

32

19873

(7) 

29

(17) 

6

(5) 

20

(5) 

0

(7) 

14

(2) 

0

(43) 

33

Fish and Wildlife Service,

Table 22. Estimated waterfowl production in the study area,

Site

Stillwater WMA1

Fernley WMA

HumboldtWMA

Mahala Slough

Massie Slough

Carson Lake

TOTAL

Cinnamon _ . teal Gadwa"

300 310

31 0

45 36

12 14

50 26

45 18

483 404

1988

Mallard Pintail

66

11

17

12

50

24

180

173

0

0

6

8

1

188

19883

(25) 

32

(26) 

8

(15) 

33

(7) 

29

(3) 

67

(1) 

0

(77) 

25

Fallen, Nev.

Redhead

150

0

0

12

50

32

244

Present 

study 

(all sites) 

1988

(17) 

35

(3) 

33

(7) 

43

(2) 

100

(12) 

33

(8) 

13

(49) 

26

Ruddy Other

690 82

0 0

0 0

30 0

5 0

44 0

769 82

Total

1,771

42

98

86

189

164

2,350

1 Estimates from U.S. Fish and Wildlife Service, Fallen, Nev. (unpublished data). All other data are from this study.

64 Detailed Study of Irrigation Drainage Effect on Biota
MERCURY AND SELENIUM IN EDIBLE TISSUE 

OF WATERFOWL

The reconnaissance study during 1986-87 

found indications that juvenile migratory birds, including waterfowl, in and near Still water WMA and Carson 

Lake were accumulating mercury and selenium in liver 

and muscle tissue and some of the concentrations 

exceeded established criteria for public-health warnings (Hoffman and others, 1990, p. 60-62, 66-70). 

Waterfowl taken from these areas are routinely consumed by hunters. Further sampling done in October 

1987 and in 1989 for the detailed study found continued high concentrations of mercury and selenium in 

edible tissues of waterfowl that could affect public 

health. Accumulation of selenium and mercury 

between waterfowl species within wetland systems 

and between different wetlands supporting the same 

species varied. This study focused primarily on 

Stillwater WMA and Carson Lake, the largest public 

waterfowl-hunting areas associated with the Newlands 

Irrigation Project, but because waterfowl are 

also hunted at nearby Fernley WMA and at Massie 

and Mahala Sloughs, those areas were included in 

the present study (fig. 1).

APPROACH AND METHODS

Ducks of various ages harvested in mid-October 

1989 at the beginning of waterfowl-hunting season, 

were considered to be representative of waterfowl consumed by humans. Most ducks evaluated in this study 

were contributed by hunters passing through USFWS 

check stations near Stillwater WMA and Carson Lake 

during the opening weekends of the waterfowl seasons; 

species included were shovelers (Anas clypeata), mallards (Anas platyrhynchos), green-winged teals (Anas 

crecca), canvasbacks (Aythya valisineria), and redhead 

ducks (Aythya americana). Shovelers, late summerearly fall migrants that rarely nest in the study area,

were collected from Carson Lake during August 1989 

soon after they arrived and again in mid-October 

1989. The mercury and selenium concentrations of 

the August birds served as a baseline against which to 

establish the increase in concentration of these trace 

elements between August and the mid-October hunting 

season. Green-winged teals also were collected in 

October 1989 from Carson Lake.

Whole ducks were identified, tagged, stored on 

ice in the field, and frozen in the laboratory on the date 

of collection. The ducks were thawed and later dissected. To prevent cross contamination, rubber gloves 

were worn and stainless-steel instruments were rinsed 

in acetone, then distilled or deionized water. Tissue 

samples were weighed and refrozen in labeled, nitricacid-rinsed 2-oz jars. Concentrations of mercury and 

selenium in muscle, liver, and skin were evaluated.

Tissue samples were analyzed by the U.S. 

Fish and Wildlife Service, Patuxent Analytical Control 

Facility, Laurel, Md., or its contract laboratories. The 

resulting data had appropriate quality-assurance documentation attached. Mercury was analyzed by coldvapor techniques and selenium was analyzed by 

hydride generation. Associated procedures used are 

described by the U.S. Fish and Wildlife Service (1985). 

Data were reported by the laboratory in micrograms per 

gram, dry weight. Because the purpose of this section 

of the report is to compare concentrations found with 

established criteria or action levels for human consumption, all data have been converted to wet weight, 

by dividing by 3.6 (Lemly and Smith, 1987, p. 7). 

An action level is a concentration of a contaminant in 

animal tissue used for human food at which responsible 

agencies take action. It is derived from a hazard-risk 

assessment and includes a safety margin for the 

population deemed most likely to consume the food 

involved. Typically, with wildlife not involved in 

commerce, the action taken is posting of public health

EDIBLE TISSUE OF WATERFOWL RJ. Hallock and others 65
warnings. Analysis of variance was used to examine 

temporal relations of contaminant levels. A statistical 

significance of 0.1 was selected.

Action levels established by the U.S. Food and 

Drug Administration (PDA) and the State of California 

were used to evaluate the potential threat to human 

health. The U.S. PDA (1984, p. 1) action level for mercury in edible animal tissue is 1.0 |ig/g, wet weight, and 

the State of California action level for selenium is 

2.0 ug/g, wet weight (Fan and others, 1988, p. 544).

During the October 1987 sampling period, 

mallards, redheads, and shovelers were collected from 

both Carson Lake and Stillwater WMA. Canvasbacks 

were collected only from Stillwater WMA. The data 

were published by Rowe and others (1991). The action 

level for mercury concentrations was exceeded in 

almost half of the ducks sampled. Selenium concentrations exceeded the action level in less than 15 percent 

of the samples. Mercury and selenium concentrations 

were highest in liver, lower in muscle, and least in skin 

samples. Concentrations in skin never exceeded the 

action levels. Muscle is of greatest concern because it 

is the preferred tissue of most humans who consume 

ducks; liver and skin are less frequently eaten.

Mercury Accumulation in Waterfowl

Hoffman and others (1990, p. 60-62) found 

that mercury concentrations in liver and muscle tissue 

of juvenile mallards and liver tissue of coots (Fulica 

americand) and black-necked stilts (Himantopus 

mexicanus) collected in 1986 and 1987 from Carson 

Lake exceeded the action level. Juvenile birds, too 

young to migrate, were assumed to have acquired 

most of this mercury locally through diet. Henny and 

Herron (1989, p. 1043) documented accumulation of 

mercury in white-faced ibis (Plegadis chihi) which 

feed in fields near Carson Lake. Mercury concentrations in liver tissue of juvenile black ducks (Anas 

rubripes) were found to nearly double in 4 weeks 

when the ducks were fed a diet containing 3 |ig/g mercury, and the rate of accumulation in liver was greater 

than in muscle (Finley and Stendell, 1978, p. 60).

Mercury concentrations in shoveler ducks 

collected in October 1987 from Carson Lake exceeded 

the action level (or public-health criterion of 1.0 |ig/g, 

wet weight; 3.6 |lg/g, dry weight) in every liver sample 

and in 90 percent of the muscle samples (fig. 17). 

Mercury concentrations in shoveler muscle and liver 

from the October 1987 data set were the basis for the 

Nevada State Health Officer's decision to post a publichealth warning specific to shoveler ducks at Carson 

Lake in 1989. The mean concentrations of mercury 

in shoveler muscle and liver from Carson Lake were, 

respectively, about 6 and 18 times the action level of 

1.0 ^lg/g, wet weight. At the request of the State Health 

Officer, shovelers were again analyzed by the 

Department of the Interior in 1989. The concentrations 

of mercury in muscle were lower, but still averaged 

three times the action level, and the public-health 

warning stayed in effect. Concentrations exceeding 

the action level for mercury were also found in some 

shovelers from Stillwater WMA (fig. 17), in some 

green-winged teal from Carson Lake, and in mallards 

from both locations (fig. 18).

The shoveler ducks collected from Carson 

Lake in mid-August 1989 for baseline data had a mean 

concentration of mercury in muscle tissue of 1.1 |lg/g, 

wet weight (fig. 17), significantly lower (p=<0.05) 

than the 5.9 (Xg/g mercury level found in shoveler 

ducks collected in October 1987. A lesser, but still 

significant difference (p=0.08) was found between the 

shovelers collected in August 1989 and those collected 

in October 1989. The shovelers collected in October 

1989 contained a mean of 2.8 |ig/g, wet weight, 

mercury in muscle tissue.

The significant difference (p=<0.05) found 

between the 1987 and the 1989 mercury concentrations 

in shovelers from Carson Lake may be related to wetland availability. In 1987, both the Island Unit and 

Sprig Pond in Carson Lake contained water, but in 

1989 only Sprig Pond was flooded. Composite sediment data gathered by Hoffman and others (1990, 

p. 113) indicated that mercury was twice as abundant 

in the Island Unit (18 mg/kg) as in Sprig Pond 

(9 mg/kg). The time of shoveler arrival and exposure 

(up to 8 weeks) was similar in both years.

66 Detailed Study of Irrigation Drainage Effect on Biota
CARSON LAKE

Oct. 1987

MUSCLE (10)

LIVER (10)

SKIN (2)

Aug. 1989 

MUSCLE (10)

Oct. 1989 

MUSCLE (10)

STILLWATER WMA

Oct. 1987

MUSCLE (12)

LIVER (9)

SKIN (2)

H MINIMUM-MAXIMUM

A MEAN

X MEDIAN

0 5 10 15

MERCURY, IN MICROGRAMS PER GRAM, WET WEIGHT

FIGURE 17. Concentrations of mercury in edible portions of shoveler ducks collected at 

Stillwater WMA and Carson Lake. Number of samples in parentheses. The action level is 

1.0 microgram per gram, wet weight (U.S. Food and Drug Administration, 1984, p. 1).

20

Differences in mercury concentrations between 

duck species was apparent in October 1987, when 

the widest variety of species was collected (figs. 17 

and 18). Shovelers from Carson Lake had the highest 

concentrations of mercury, with all liver samples and 

90 percent of the muscle samples exceeding the action

level. Mercury concentrations in mallards from Carson 

Lake exceeded the action level in 70 percent of the 

liver and 20 percent of the muscle samples. Mean and 

median mercury concentrations were below the action 

level in muscle tissue of green-winged teal, redheads, 

and canvasbacks (fig. 18).

EDIBLE TISSUE OF WATERFOWL RJ. Hallock and others 67
CARSON LAKE

MALLARD

October 1987

MUSCLE (10)

LIVER (10) 

SKIN (2)

REDHEAD

October 1987

MUSCLE (3) 

LIVER (3) 

SKIN (2) 

GREEN-WINGED TEAL

October 1989

MUSCLE (10) 

STILLWATER WMA

MALLARD

October 1987 

MUSCLE (10)

LIVER (10)

SKIN (2)

REDHEAD

October 1987 

MUSCLE (10) 

LIVER (10) 

SKIN (2)

CANVASBACK

October 1987

MUSCLE (3) 

LIVER (3)

i I I I I

i 1 X \/ ak A iI 

^

i-X-A i

^

h->^4r< 1

Y4

Y A

*

 jfcj | 1 MINIMUM-MAXIMUM 

-^^ | A MEAN 

*& X MEDIAN

1 11

01 234 5 

MERCURY, IN MICROGRAMS PER GRAM, WET WEIGHT

Figure 18. Concentrations of mercury in edible portions of various duck species collected 

at Stillwater WMA and Carson Lake during the opening week of waterfowl season, October 

1987. Number of samples in parentheses. The action level is 1.0 microgram per gram, wet 

weight (U.S. Food and Drug Administration, 1984, p. 15).

Selenium Accumulation in Waterfowl

Although Hoffman and others (1990, p. 66-70) 

reported selenium concentrations much higher than the 

action level of 2.0 (ig/g, wet weight, in liver tissue of 

various juvenile migratory birds from the study area, 

less than 15 percent (8 of 58) of livers from various 

waterfowl collected in October 1987 from Carson Lake 

and Stillwater WMA exceeded 2.0 (ig/g. However,

within this data set, 10 shoveler livers taken on October 

17,1987, contained a mean selenium concentration of 

2.2 (ig/g and ranged from 0.8 to 3.8 (ig/g. Shovelers 

are fall migrants believed to have been in these wetlands up to 6 weeks prior to collection. None of the 

muscle samples from these birds contained selenium 

concentrations above 2.0 (ig/g (Rowe and others, 1991, 

p. 118-151).

68 Detailed Study of Irrigation Drainage Effect on Biota
Fernley WMA could not be evaluated during 

the 1989 hunting season because it was dry by midOctober and, therefore, contained no ducks. However, 

during July 1988, juvenile cinnamon teal (Anas cyanoptera) and coots with mean selenium concentrations 

in livers of 8.4 and 8.6 (ig/g, wet weight, respectively, 

were collected from Fernley WMA. Selenium in livers 

of juvenile redhead ducks from Massie and Mahala 

Sloughs averaged 8.5 (ig/g and 3.7 (ig/g, wet weight, 

respectively, as reported in the preceding section on 

waterfowl production. In a study of mallards, Heinz 

and others (1990, p. 374) found that after 81 days on a 

selenium-rich diet, concentrations of selenium were

slightly higher in muscle than in liver tissues. This 

suggests that by October, at the start of hunting season, 

if the juvenile ducks had remained in Fernley WMA 

and Massie Slough they might have had selenium 

concentrations in muscle that were higher than the 

concentrations found in July (>8.0 (ig/g), which was 

already more than four times the established humanhealth criteria.

Differing lengths of waterfowl residence in the 

wetlands may account for some of the variability in the 

data from this study. Other important factors determining intake of potentially toxic constituents are dietary 

preferences and the specific wetlands selected by birds.

EDIBLE TISSUE OF WATERFOWL RJ. Hallock and others 69
OVERALL SUMMARY OF EFFECT OF IRRIGATION 

DRAINAGE ON BIOTA

Important findings of the five biologically 

related study elements addressing possible adverse 

effects of irrigation drainage on biota in and near 

Stillwater WMA are summarized here. The goal 

of the investigation was to (1) determine the effects 

of irrigation drainage on migratory waterfowl that 

frequent these wetlands and (2) provide information 

for resource-management decisions and subsequent 

remediation strategies. Major findings of the studies, 

in order of presentation, are:

 Historical wetlands in Carson Lake,

Stillwater Marsh, and Carson Sink averaged 

about 150,000 acres. Under the Operating 

Criteria and Procedures mandates, fully implemented in 1992, only about 10 percent, or 

15,000 wetland acres, are projected to remain 

in nearly permanent impoundments.

 Average dissolved-solids concentration 

in drainwater entering these wetlands has 

increased about seven-fold from the estimated 

historical 170 mg/L to a current average of 

1,170 mg/L. This increase in concentration 

has occurred largely through evapotranspiration associated with irrigated agriculture. 

Although the annual dissolved-solids load 

has decreased in these now-isolated wetlands, 

the increased concentrations have adversely 

affected the various plants, invertebrates, fish, 

and wildlife that were once abundant in the 

historical wetlands.

 During acute-toxicity tests, organisms in 

control water survived wide fluctuations in 

specific conductance that ranged from 410 to 

27,500 |LlS/cm (252 to 17,900 mg/L dissolved 

solids). Organisms in undiluted drainwater 

samples subjected to similar fluctuations in 

dissolved-solids concentrations did not survive. Surface water from TJ and Hunter 

Drains and ground water from a shallow

well near TJ Drain were acutely toxic to 

all test organisms.

 Analysis of undiluted drainwater showed 

that four potentially toxic elements arsenic, 

boron, lithium, and molybdenum were representative of the overall levels of toxicity in the 

water tested. Strong, positive relations were 

found between the aggregate of arsenic, boron, 

lithium, and molybdenum and both daily and 

average dissolved-solids concentration. Thus, 

specific conductance may be a useful measure 

of surface-water quality for management of 

fish and invertebrate populations in 

Stillwater WMA.

 Within drains, both mercury and selenium 

are being bioaccumulated in plants and plant 

detritus and biomagnified in invertebrates by 

factors of up to 10,000 times the concentrations measured in associated drainwater.

 Mercury and selenium are being transported 

in living organisms and their detritus. Transport is from irrigated land, by way of irrigation 

drains, to large wetlands where most migratory 

birds, fish, and other wildlife are exposed to 

these elements.

 Source areas of mercury and selenium in the 

Newlands Irrigation Project area are areas generally upgradient from sampling sites in drains 

where concentrations exceeded concern levels 

of 1.0 |Llg/g, dry weight, in detritus.

 Although selenium continues to be released 

from some irrigated soils more than 40 years 

after initiation of irrigation, and is being carried by plants and invertebrates through the 

drains, no evidence was found to indicate a 

long-term build up of selenium in the sediment 

and biota of downgradient wetlands.

OVERALL SUMMARY 71
 Potential contaminant concentrations in 

waterfowl eggs from the study sites were generally below published effect-level criteria and 

would not be expected to affect bird production. Consistent with these data, no teratogenesis was observed in embryos or hatchlings. 

The hatch rate of waterfowl eggs was normal, 

90 percent or more, at both study and background sites.

 Concentrations of boron, mercury, and 

selenium at adverse effect levels were found 

in juvenile migratory birds from several study 

sites. Concentrations of selenium as high as 

30 |ig/g were found in duck and coot livers 

from Fernley WMA and Massie Slough, and 

77 |ig/g in black-necked stilt livers from 

Mahala Slough. Decreased survival and, thus, 

production may be expected among birds containing selenium concentrations in this range.

 Nest success was poor throughout the study 

areas, averaging only 26 percent. Loss of 

feeding habitat and nesting cover caused by 

drought, increased dissolved-solids concentrations, and predation are the primary reasons 

for reduced nest success. Thus, waterfowl 

production is now much reduced compared 

to historical conditions.

 Shoveler ducks harvested by hunters from 

Carson Lake had accumulated mercury in 

muscles and livers, 5.9 and 17.8 times greater, 

respectively, on average, than the 1.0 |ig/g, 

wet weight, action level for human consumption. In response to the elevated mercury concentrations, the State of Nevada posted humanhealth warnings at Carson Lake specific to 

shoveler ducks.

 Concentrations of selenium in juvenilewaterfowl livers from Fernley WMA and 

Massie Slough in July 1988 averaged more 

than 8.0 |ig/g, wet weight, or more than four 

times the 2.0 ^lg/g, wet weight, criterion for 

human consumption. Because of drought, no 

birds were present in these areas in October 

1989 for collection and evaluation; thus, the 

potential for human-health concerns in these 

areas could not be fully evaluated.

REFERENCES CITED

American Society for Testing Materials, 1988, Standard 

practice for conducting acute toxicity tests with fishes, 

macroinvertebrates, and amphibians: Philadelphia, 

ASTM Designation E 729-88, 20 p.

Bailey, Vernon, 1898, Nevada: Carson Lake Valley

(Wadsworth, Ragtown and Stillwater) Physiography: 

Unpublished manuscript, Smithsonian Institution 

Archives, Record Unit 7176, U.S. Fish and Wildlife 

Service, 1860-1961, Field Reports, Box 69, Folder 14, 

3 p.

Brown, W.M., Nowlin, J.O., Smith, L.H., and Flint, M.R., 

1986, River quality assessment of the Truckee and 

Carson River system, California and Nevada 

Hydrologic characteristics: U.S. Geological Survey 

Open-File Report 84-576, 201 p.

Burton, R.F, 1963, The City of the Saints and across the 

Rocky Mountains to California: New York, Alfred A. 

Knopf, Inc., facsimilie of the 1861 edition, 654 p.

California Department of Water Resources, 1991, Carson 

River atlas: Sacramento, Calif., State of California, 

126 p.

Claassen, H.C., 1982, Guidelines and techniques for 

obtaining water samples that accurately represent 

the water chemistry of an aquifer: U.S. Geological 

Survey Open-File Report 82-1024, 49 p.

Cooper, J.J., Thomas, R.O., and Reed, S.M., 1985, Total 

mercury in sediment, water, and fishes in the Carson 

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REFERENCES CITED 75
SUPPLEMENTAL WATER-QUALITY DATA 

FROM TOXICITY STUDY

SUPPLEMENTAL WATER-QUALITY DATA FROM TOXICITY STUDY 77
Table 23. Water-quality measurements for daily composite water samples from Paiute Diversion Drain, August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

ug/L, micrograms per liter; uS/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(uS/cm)

420

370

480

390

400

400

400

383

430

Hardness

120

110

130

120

130

140

130

130

130

Salinity 

(ppt)

0.2

.2

.3

.2

.1

.1

.1

.1

.2

Lithium

0.06

.05

.06

.06

.06

.06

.06

.06

.06

Field 

PH

7.5

8.4

8.3

8.0

8.3

8.5

8.5

8.6

8.6

Sodium

72

62

84

68

75

79

72

82

73

Nitrate 

asN

<0.01

<.01

<.01

Molybdenum

0.02

<.02

.02

<.02

.02

.02

<.02

<.02

.02

Onsite 

mobile lab 

PH

8.2

8.2

8.4

8.3

8.1

8.4

8.5

8.6

8.6

Potassium

3.8

2.8

3.9

4.9

5.4

5.3

4.4

4.7

3.9

Ammonia 

asN

0.16

.06

.04

Selenium 

(H9/L)

<0.3

.3

.3

.3

.3

.3

.3

.3

.3

Turbidity 

(NTU)

31

35

33

32

16

15

25

20

18

Alkalinity

142

111

146

133

138

145

158

135

157

Phosphorus

0.1

<.l

.1

.1

.1

.1

.1

.2

<.l

Strontium

0.37

.35

.40

.37

.40

.41

.38

.41

.40

Dissolved 

oxygen

6.8

8.9

7.7

7.3

9.7

8.9

8.8

9.0

8.7

Sulfate

85

68

64

60

72

72

52

52

60

Arsenic

0.01

.02

.02

.02

.02

.02

.02

.02

.02

Vanadium

0.01

.01

.01

.01

.01

.01

.01

.01

.01

Calcium

33

31

35

33

35

36

35

35

36

Chloride

63

58

50

55

60

60

65

70

65

Barium

0.08

.08

.08

.08

.09

.08

.07

.07

.08

Zinc

0.07

.03

.03

.05

.04

.05

.03

.02

.03

Magnesium

11

10

12

11

12

12

11

13

11

Silica

5.8

6.3

7.0

6.7

6.6

6.9

6.8

7.2

6.6

Boron

0.58

.52

.76

.58

.60

.63

.60

.55

.61

78 Detailed Study of Irrigation Drainage Effect on Biota
Table 24. Water-quality measurements for daily composite water samples from TJ Drain, August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

ug/L, micrograms per liter; uS/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(uS/cm)

8,100

12,000

11,800

14,900

11,000

6,100

7,200

13,700

14,300

Hardness

1,300

1,900

2,000

2,500

1,800

1,100

1,300

1,900

1,700

Salinity 

(ppt)

6.5

10.0

10.0

13.0

9.2

5.0

4.1

8.9

9.2

Lithium

0.40

.62

.57

.76

.55

.34

.38

.67

.46

Field 

PH

8.5

8.5

8.6

8.5

8.6

8.4

8.4

8.5

8.6

Sodium

2,000

3,500

3,300

4,700

3,400

1,900

1,900

4,000

2,900

Nitrate 

asN

<0.01

<01

<01

Molybdenum

0.32

.54

.45

.67

.45

.27

.38

.67

.46

Onsite 

mobile lab 

PH

8.5

9.0

8.5

8.3

8.4

8.1

8.3

8.4

8.4

Potassium

29

42

40

57

43

29

29

50

39

Ammonia 

asN

0.11

.02

.16

Selenium 

(H9/L)

1.2

1.3

1.2

1.6

1.1

1.1

.9

1.3

1.5

Turbidity 

(NTU)

2

3

2

3

2

4

4

3

8

Alkalinity

232

289

263

319

276

224

217

292

244

Phosphorus

0.7

1.0

.8

1.0

.8

.4

.4

1.0

.8

Strontium

4.0

6.2

5.8

7.9

5.7

3.2

3.5

7.0

4.9

Dissolved 

oxygen

7.4

8.4

8.7

8.7

9.2

8.3

8.9

8.7

10.9

Sulfate

1,400

2,900

2,900

3,600

1,600

880

1,500

1,600

1,600

Arsenic

0.11

.13

.12

.17

.15

.13

.11

.14

.12

Vanadium

0.02

.02

.02

.02

.02

.02

.01

.02

.02

Calcium

180

260

240

310

230

140

160

290

210

Chloride

2,700

4,800

4,900

6,200

4,700

3,800

5,800

4,900

4,800

Barium

0.08

.11

.11

.10

.07

.05

.05

.11

.08

Zinc

0.05

.07

.09

.01

.03

.02

.02

.02

.02

Magnesium

200

320

300

410

290

160

180

360

250

Silica

2.1

.9

2.0

.6

.1

3.7

2.9

.8

3.8

Boron

7.8

13

12

17

12

6.8

6.8

14

10

SUPPLEMENTAL WATER-QUALITY DATA FROM TOXICITY STUDY 79
Table 25. Water-quality measurements for daily composite water samples from D-Line Canal, August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

ug/L, micrograms per liter; jiS/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(uS/cm)

600

490

610

400

425

380

350

445

470

Hardness

94

100

110

100

120

110

98

130

110

Salinity 

(ppt)

0.5

.4

.5

.0

.2

.1

.0

.0

.1

Lithium

0.06

.06

.06

.06

.06

.05

.05

.05

.05

Field 

PH

8.6

9.3

9.2

9.2

9.2

9.0

9.0

8.7

9.4

Sodium

110

110

100

97

110

84

87

96

83

Nitrate 

asN

<0.01

.01

.01

Molybdenum

0.02

.02

.02

.02

.02

.02

.02

.02

<.02

Onsite 

mobile lab 

PH

8.7

9.0

9.0

9.0

8.9

8.1

9.1

8.7

9.3

Potassium

9.4

8.6

8.3

8.2

8.4

6.3

6.2

5.4

6.5

Ammonia 

asN

0.10

.04

.05

Selenium 

(H9/L)

0.3

.3

.3

.3

.3

.3

.3

.3

.3

Turbidity 

(NTU)

4

5

4

3

4

3

6

9

9

Alkalinity

149

156

165

155

157

135

125

174

113

Phosphorus

<0.1

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

Strontium

0.37

.34

.36

.34

.37

.34

.34

.36

.34

Dissolved 

oxygen

9.2

10.0

9.5

9.2

10.3

9.8

10.0

9.0

9.9

Sulfate

110

110

60

56

130

68

47

100

48

Arsenic

0.05

.05

.05

.05

.04

.04

.04

.05

.04

Vanadium

0.02

.02

.02

.02

.02

.01

.01

.01

.02

Calcium

30

26

28

26

29

28

27

32

30

Chloride

50

12

50

43

47

40

36

45

45

Barium

0.06

.05

.05

.04

.04

.05

.05

.05

.05

Zinc

0.03

.01

.01

.01

.01

.01

.01

.04

.02

Magnesium

11

11

11

10

11

10

10

10

9

Silica

6.9

7.0

6.6

5.9

5.9

6.0

7.2

7.3

7.6

Boron

0.76

.78

.74

.79

.81

.70

.77

.75

.62

80 Detailed Study of Irrigation Drainage Effect on Biota
Table 26. Water-quality measurements for daily instantaneous water samples from Lead Lake, August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

ug/L, micrograms per liter; uS/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(uS/cm)

6,100

6,000

5,900

5,300

5,600

5,100

5,300

5,900

5,300

Hardness

580

570

630

580

600

600

610

640

680

Salinity 

(PPt)

3.5

3.5

3.8

3.2

3.5

4.2

3.1

3.5

3.3

Lithium

0.36

.36

.37

.34

.37

.34

.36

.39

.34

Field 

PH

8.9

8.8

8.9

8.8

8.6

8.9

8.9

8.9

8.9

Sodium

1,000

1,000

1,100

1,000

1,100

980

1,000

1,100

1,100

Nitrate 

asN

<0.01

.01

.05

Molybdenum

0.11

.11

.12

.11

.12

.11

.11

.12

.13

Onsite 

mobile lab 

PH

8.8

9.2

8.9

8.8

8.8

8.8

8.9

9.0

8.9

Potassium

32

32

33

31

33

30

31

33

29

Ammonia 

asN

0.14

.14

.24

Selenium fog/i.)

0.3

.3

.3

.3

.3

.3

.3

.3

.3

Turbidity 

(NTU)

62

96

59

63

53

37

53

50

43

Alkalinity

227

272

257

266

256

249

258

258

227

Phosphorus

0.2

.2

.2

.2

.2

.2

.2

.4

.2

Strontium

1.9

1.9

1.9

1.8

1.9

1.8

1.8

2.0

2.0

Dissolved 

oxygen

9.2

7.2

6.8

5.6

7.1

5.7

6.9

8.5

8.6

Sulfate

430

600

680

400

520

470

360

410

560

Arsenic

0.12

.12

.13

.11

.11

.10

.11

.11

.10

Vanadium

0.02

.02

.02

.02

.02

.02

.02

.02

.02

Calcium

67

69

71

65

68

64

67

68

74

Chloride

1,300

1,400

1,200

1,700

1,400

1,300

1,800

1,800

1,800

Barium

0.14

.13

.13

.12

.13

.12

.13

.13

.11

Zinc

0.02

.04

.01

.02

.02

.02

.02

.04

.02

Magnesium

96

97

100

92

98

90

96

103

103

Silica

6.9

7.5

6.9

6.8

6.8

6.3

6.4

7.3

5.1

Boron

6.0

5.4

5.6

5.2

5.5

5.0

5.3

5.7

5.4

SUPPLEMENTAL WATER-QUALITY DATA FROM TOXICITY STUDY 81
Table 27. Water-quality measurements for daily composite water samples from Hunter Drain, August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

H-g/L, micrograms per liter; ^.S/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(nS/cm)

12,000

13,900

27,500

22,000

25,000

8,000

410

600

1,200

Hardness

860

1,100

2,300

1,800

200

660

110

140

170

Salinity 

(ppt)

9.5

12

28

18

23

7.0

.0

1.0

1.0

Lithium

1.0

1.2

2.0

2.2

2.3

.86

.06

.08

.08

Field 

PH

8.3

8.4

8.5

8.8

8.7

8.7

8.0

8.3

8.2

Sodium

3,600

4,500

7,600

8,200

8,600

3,200

98

180

200

Nitrate 

asN

<0.01

.04

.05

Molybdenum

0.46

.59

1.1

1.2

1.3

.47

.02

.04

.06

Onsite 

mobile lab 

PH

8.2

8.9

8.4

8.7

8.5

8.6

8.0

8.2

8.3

Potassium

89

110

180

200

210

76

4.8

4.9

4

Ammonia 

asN

0.30

.10

.15

Selenium 

(^9/L)

2.2

2.3

2.1

3.5

3.6

2.1

<.3

<.4

.4

Turbidity 

(NTU)

14

7

37

13

8

14

19

14

10

Alkalinity

223

250

242

255

276

179

255

124

102

Phosphorus

0.6

.6

.6

.8

.9

.6

<.l

<.l

<.l

Strontium

5.0

6.0

9.6

10.2

10.4

4.1

.39

.51

.89

Dissolved 

oxygen

7.0

6.2

7.4

6.3

5.6

7.5

8.2

8.4

8.8

Sulfate

1,200

1,300

2,000

2,900

2,900

1,200

52

130

200

Arsenic

0.06

.07

.11

.17

.19

.06

.02

.02

.03

Vanadium

0.02

.02

.02

.03

.02

.02

.01

.01

.02

Calcium

190

220

350

380

390

160

32

35

38

Chloride

4,200

7,000

11,000

10,000

13,000

3,700

84

190

310

Barium

0.10

.09

.10

.09

.09

.07

.08

.05

.05

Zinc

0.09

.06

.01

.06

.01

.08

.02

.02

.02

Magnesium

100

130

230

240

250

100

10

13

15

Silica

5.0

13

14

13

14

9.0

7.6

6.8

6.8

Boron

20

25

43

46

49

18

.81

1.3

1.2

82 Detailed Study of Irrigation Drainage Effect on Biota
Table 28. Water-quality measurements for daily composite water samples from Stillwater Point Diversion Drain, 

August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

|4.g/L, micrograms per liter; |4.S/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(|xS/cm)

700

550

620

710

470

520

510

580

720

Hardness

140

200

150

150

150

150

140

160

160

Salinity 

(PPt)

0.5

.5

.5

.8

.5

.2

.2

.2

.4

Lithium

0.06

.07

.06

.10

.06

.06

.06

.06

.07

Field 

PH

8.4

8.5

8.3

8.4

8.2

8.3

8.4

8.6

8.5

Sodium

140

150

130

270

120

140

120

120

160

Nitrate 

asN

<0.01

.05

.04

Molybdenum

0.03

.03

.03

.05

.03

.03

.03

.03

.04

Onsite 

mobile lab 

pH

8.4

8.3

8.4

8.4

8.4

8.3

8.4

8.4

8.5

Potassium

8.8

8.8

8.6

13

8.6

7.9

7.7

7.3

8.6

Ammonia 

asN

0.21

.50

.44

Selenium 

(^9/L)

0.4

.5

<.4

.6

.5

<.4

.5

<.4

.4

Turbidity 

(NTU)

39

36

35

32

54

25

37

23

21

Alkalinity

234

227

114

312

211

210

210

221

245

Phosphorus

0.2

.2

.3

.3

.2

.2

.2

.2

.2

Strontium

0.52

.51

.48

.67

.46

.47

.45

.46

.52

Dissolved 

oxygen

9.0

8.5

8.4

8.3

8.9

8.7

8.9

9.6

8.4

Sulfate

130

140

120

110

110

120

140

150

140

Arsenic

0.05

.05

.04

.04

.04

.04

.04

.04

.05

Vanadium

0.02

.02

.02

.02

.02

.02

.02

.02

.02

Calcium

48

47

45

51

43

42

43

44

47

Chloride

60

63

63

58

50

55

55

43

48

Barium

0.07

.07

.07

.06

.07

.07

.07

.07

.07

Zinc

0.04

.06

.05

.10

.04

.06

.07

.04

.04

Magnesium

14

14

13

18

12

13

12

13

14

Silica

13

14

12

12

12

11

12

12

13

Boron

0.99

1.2

1.1

1.8

.86

.99

.88

.91

1.1

SUPPLEMENTAL WATER-QUALITY DATA FROM TOXICITY STUDY 83
Table 29. Water-quality measurements for daily instantaneous water samples from Stillwater Point Reservoir, 

August 1988

[Concentrations in milligrams per liter except as indicated. All mercury concentrations were below analytical reporting limit. Abbreviations: 

Ug/L, micrograms per liter; ^iS/cm, microsiemens per centimeter at 25°C; NTU, Nephelometric turbidity units; ppt, parts per thousand.]

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Date

August 10

11

12

13

14

15

16

17

18

Specific 

conductance 

(uS/cm)

2,510

1,950

1,710

2,270

2,000

2,210

1,590

1,720

2,020

Hardness

160

160

160

150

170

140

170

160

130

Salinity 

(PPt)

1.7

1.2

1.3

1.5

1.2

1.9

.9

1.1

1.2

Lithium

0.11

.12

.10

.13

.12

.13

.10

.11

.13

Field 

PH

9.1

9.0

9.1

9.1

9.1

9.2

9.1

9.0

9.2

Sodium

360

480

310

440

410

460

310

340

420

Nitrate 

asN

<0.01

.01

<.01

Molybdenum

0.05

.07

.05

.06

.06

.07

.05

.05

.06

Onsite 

mobile lab 

PH

8.9

9.0

9.1

9.1

9.0

9.1

9.1

9.1

9.2

Potassium

17

21

15

19

18

20

15

15

18

Ammonia 

asN

0.15

.18

.18

Selenium 

(H9/L)

0.5

.6

.6

.4

.4

.5

.6

.5

.4

Turbidity 

(NTU)

410

580

390

280

200

260

190

240

170

Alkalinity

261

263

289

298

300

292

291

292

235

Phosphorus

<0.1

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

Strontium

0.57

.55

.54

.54

.55

.52

.54

.53

.57

Dissolved 

oxygen

8.8

8.9

8.2

8.3

8.3

8.2

8.8

8.4

10.2

Sulfate

120

240

150

180

140

190

100

190

190

Arsenic

0.09

.11

.08

.11

.10

.11

.08

.09

.10

Vanadium

0.03

.03

.03

.03

.03

.03

.02

.02

.03

Calcium

35

24

35

26

30

22

36

31

28

Chloride

300

310

310

550

380

480

480

410

450

Barium

0.10

.11

.11

.10

.10

.09

.09

.09

.12

Zinc

0.01

.01

.05

.02

.01

.01

.01

.02

.02

Magnesium

18

20

16

18

18

18

16

17

21

Silica

11

11

12

10

10

10

10

11

11

Boron

2.2

3.0

2.3

2.9

2.6

2.9

2.0

2.2

2.7

84 Detailed Study of Irrigation Drainage Effect on Biota