In cooperation with the U.S. Army Corps of Engineers

Reconnaissance of Mercury in Lakes, Wetlands, and

Rivers in the Red River of the North Basin,

North Dakota, March Through August 2001

Water-Resources Investigations Report 03-4078

U.S. Department of the Interior

U.S. Geological Survey

Red

River of

the

North

Minnesota

River

River

Mississippi

Missouri

River

River

Missouri

James

River

N O R T H D A K O T A M I N N E S O T A

S O U T H D A K O T A Big

Sioux

River

Devils

 Lake Lake

 Basin Basin

Sheyenne Sheyenne

 River River

 

 Basin Basin

Fargo

Grand Forks

 Red

 River River

 Of Of

 The The

 North North

 Basin Basin
U.S. Department of the Interior

U.S. Geological Survey

Reconnaissance of Mercury in Lakes, Wetlands, and

Rivers in the Red River of the North Basin, North

Dakota, March Through August 2001

By Steven K. Sando, G. J. Wiche, R. F. Lundgren, and Bradley A. Sether

Water-Resources Investigations Report 03-4078

In cooperation with the U.S. Army Corps of Engineers

Bismarck, North Dakota

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

Any use of trade, product, or firm names 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

Water Resources Division

821 East Interstate Avenue

Bismarck, ND 58503-1199

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Box 25286

Denver, CO 80225-0286
iii

CONTENTS

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

Introduction ...............................................................................................................................................................................................1

Description of study area...........................................................................................................................................................................3

Methods of study.......................................................................................................................................................................................4

Sample collection, processing, and analysis ......................................................................................................................................5

Quality assurance/quality control.......................................................................................................................................................7

Estimation of masses and loads..........................................................................................................................................................7

Results for quality-assurance/quality-control samples and for selected properties and constituents........................................................8

Quality-assurance/quality-control samples ........................................................................................................................................8

Field-measured properties and constituents.......................................................................................................................................9

Major-ion, trace-element, and suspended-sediment constituents ......................................................................................................9

Organic-carbon constituents.............................................................................................................................................................15

Mercury constituents in lakes, wetlands, and rivers................................................................................................................................16

Lakes and wetlands ..........................................................................................................................................................................17

Rivers ...............................................................................................................................................................................................26

Possible effects from Devils Lake outlet..........................................................................................................................................33

Summary and conclusions.......................................................................................................................................................................34

References ...............................................................................................................................................................................................37

Supplement 1. Results for field-measured properties and constituents for lake and wetland sites........................................................40

Supplement 2. Results for field-measured properties and constituents for river sites............................................................................43

Supplement 3. Results for major-ion, trace-element, and suspended-sediment constituents for lake and wetland sites.......................44

Supplement 4. Results for major-ion, trace-element, and suspended-sediment constituents for river sites ..........................................48

Supplement 5. Results for mercury and organic-carbon constituents for lake and wetland sites ..........................................................50

Supplement 6. Results for mercury and organic-carbon constituents for river sites..............................................................................52

FIGURES

1. Map showing location of study area and water-quality sampling sites..............................................................................................2

2. Graphs showing vertical profiles of field-measured properties and constituents at a representative deep

lake site (site 5, Devils Lake Main Bay) ..........................................................................................................................................12

3. Graphs showing vertical profiles of field-measured properties and constituents at a representative shallow

lake site (site 4, Devils Lake West Bay southwest)..........................................................................................................................13

4. Stiff diagrams showing average dissolved-solids concentrations and ionic proportions for water-quality

sampling sites...................................................................................................................................................................................14

5. Graphs showing concentrations of suspended sediment and organic carbon for river sites ............................................................16

6. Graphs showing concentrations of organic carbon for lake and wetland sites ................................................................................17

7. Graphs showing concentrations of methylmercury and ratios of whole-water methylmercury to

whole-water total mercury for lake and wetland sites......................................................................................................................18

8. Graphs showing concentrations of total mercury for lake and wetland sites...................................................................................20

9. Graphs showing masses of mercury constituents for lake and wetland sites...................................................................................23

10. Graphs showing concentrations of methylmercury and ratios of whole-water methylmercury to

whole-water total mercury for river sites .........................................................................................................................................27

11. Graphs showing concentrations of total mercury for river sites ......................................................................................................28

12. Graphs showing loads of mercury constituents for river sites .........................................................................................................30

13. Graph showing discharge and times of sampling for the Sheyenne River, Red River of the North, and

Red Lake River sites ........................................................................................................................................................................31

TABLES

1. Water-quality sampling sites ..............................................................................................................................................................4

2. Properties and constituents for which water-quality samples were analyzed ....................................................................................5

3. Concentrations of mercury and organic-carbon constituents in quality-assurance/quality-control

field-equipment blank samples...........................................................................................................................................................9

4. Analytical results for primary environmental samples and for quality-assurance/quality-control

replicate samples for major-ion and trace-element constituents ......................................................................................................10
iv

TABLES, Continued

5. Analytical results for primary environmental samples and for quality-assurance/quality-control

replicate samples for mercury and organic-carbon constituents ......................................................................................................11

6. Concentrations of mercury constituents for Devils Lake and Lake Ashtabula, 1991-93.................................................................21

7. Concentrations of mercury constituents for selected lakes in the Devils Lake and Sheyenne River

Basins, 1991-93................................................................................................................................................................................22

8. Statistically significant results of Spearman’s rank-correlation procedure to investigate relations between

mercury constituents and other water-quality properties and constituents for lake and wetland sites ............................................25

9. Nonexceedance frequencies for discharges at time of sampling for river sites ...............................................................................32

10. Statistically significant results of Spearman’s rank-correlation procedure to investigate relations between

mercury constituents and other water-quality properties and constituents for river sites ................................................................33
 1

Reconnaissance of Mercury in Lakes, Wetlands, and Rivers in the

Red River of the North Basin, North Dakota, March Through

August 2001

By Steven K. Sando, G. J. Wiche, R. F. Lundgren, and Bradley A. Sether

Abstract

Devils Lake rose dramatically during the 1990’s, causing extensive flood damages. Because of the potential

for continued flooding, the U.S. Army Corps of Engineers has been conducting studies to evaluate the feasibility

of constructing and operating an outlet from Devils Lake. The occurrence of mercury in lakes, wetlands, and

rivers and the potential for increased loading of mercury into the Sheyenne River as a result of a Devils Lake

outlet needed to be evaluated as part of the studies.

Sixteen lake, wetland, and river sites in the Devils Lake, Sheyenne River, Red River of the North, and Red

Lake River Basins were sampled and analyzed for mercury constituents and other selected properties and

constituents relevant to mercury aquatic chemistry. For the lake and wetland sites, whole-water methylmercury

concentrations ranged from less than 0.04 to 3.53 nanograms per liter and whole-water total mercury

concentrations ranged from 0.38 to 7.02 nanograms per liter. Conditions favorable for methylation of mercury

generally exist at the lake and wetland sites, as indicated by larger dissolved methylmercury concentrations in

near-bottom samples than in near-surface samples and by relatively large ratios of methylmercury to total

mercury (generally greater than 10 percent for the summer sampling period). Total mercury concentrations were

larger for the summer sampling period than for the winter sampling period for all lake and wetland sites. A

wetland site in the upper Devils Lake Basin had the largest mercury concentrations for the lake and wetland sites.

For the river sites, whole-water methylmercury concentrations ranged from 0.15 to 1.13 nanograms per liter

and whole-water total mercury concentrations ranged from 2.00 to 26.90 nanograms per liter. Most of the

mercury for the river sites occurred in particulate inorganic phase. Summer ratios of whole-water

methylmercury to whole-water total mercury were 35 percent for Starkweather Coulee (a wetland-dominated

site), near or less than 10 percent for the Sheyenne River sites, and less than 8 percent for the Red River of the

North and Red Lake River sites.

Although the number of samples collected during this investigation is small, results indicated an outlet from

Devils Lake probably would not have adverse effects on mercury concentrations in the Sheyenne River upstream

from Lake Ashtabula. However, because discharges in the Sheyenne River would increase during some periods,

loads of mercury entering Lake Ashtabula also would increase. Lake Ashtabula probably serves as a sink for

suspended sediment and mercury. Thus, a Devils Lake outlet probably would not have substantial effects on

mercury concentrations and loads in the downstream part of the Sheyenne River or in the Red River of the North.

More substantial effects could occur for Lake Ashtabula.

INTRODUCTION

The Devils Lake Basin is a closed subbasin (fig. 1) within the Red River of the North Basin. At an elevation of about

1,446.5 feet above National Geodetic Vertical Datum of 1929, Devils Lake begins to spill into Stump Lake; and at an

elevation of about 1,459 feet above National Geodetic Vertical Datum of 1929, the combined lakes begin to spill through

Tolna Coulee into the Sheyenne River (fig. 1).
 2

Since the end of glaciation about 10,000 years ago, Devils Lake has fluctuated between spilling and being dry.

Research by the North Dakota Geological Survey indicates Devils Lake has overflowed into the Sheyenne River at least

twice during the past 4,000 years and has spilled into the Stump Lakes several times (Bluemle, 1991; Murphy and others,

1997). John Bluemle, North Dakota State Geologist, concluded the natural condition for Devils Lake is either rising or

falling, and the lake should not be expected to remain at any elevation for a long period of time.

Recent conditions indicate the lake is in a rising phase. The lake rose more than 25 feet from February 1993 to July

2001, and flood damages in the Devils Lake Basin have exceeded $400 million (Vecchia, 2002). Because of the potential

for continued lake-level rises and the potential for additional damages, the U.S. Army Corps of Engineers, using authorities

provided to the Secretary of the Army, has been conducting engineering and environmental studies to evaluate the

feasibility of constructing and operating an outlet from Devils Lake. The occurrence of mercury in the Red River of the

North Basin and the potential for increased loading of mercury into the Sheyenne River as a result of a constructed outlet

from Devils Lake needed to be considered and evaluated as part of the studies. Therefore, the U.S. Geological Survey, in

cooperation with the U.S. Army Corps of Engineers, conducted a reconnaissance investigation of mercury in lakes,

wetlands, and rivers in the Red River of the North Basin. Specific objectives of the investigation were to (1) sample seven

sites in the Devils Lake Basin, five sites in the Sheyenne River Basin, and four sites in the Red River of the North Basin for

 EXPLANATION

Sheyenne River Basin

Devils Lake Basin

Red River of the North Basin

Water-quality sampling site--Site

number given in table 1

99 ̊ 97 ̊

95 ̊

49 ̊

47 ̊ 47 ̊

49 ̊

97 ̊

99 ̊

Grand

Forks

Webster

Warwick

Fargo

Red River

of

the

North

Upper

Red

Lake Devils

 Lake

River

River

Red

Lake

Sheyenne

Lake

Ashtabula

Stump

Lake

Tolna

Coulee

Baldhill

Dam

StarkweatherCoulee

Lower

Red

Lake

Mississippi R.

Kindred

Halstad

Emerson

East

Grand

Forks

Fisher

Base from U.S. Geological Survey

1:2,000,000, 1972

0 20 40 60 MILES 

8

2

3

1

4 5

7

6

9

10

11

12

14

15

16

13

N O R T H D A K O T A M I N N E S O T A

M A N I T O B A

S O U T H D A K O T A

6

Figure 1. Location of study area and water-quality sampling sites.

Sioux R.

Bois de

Tail

River

Otter
 3

mercury and selected constituents that affect the occurrence and partitioning of mercury in aquatic systems; (2) determine

concentrations and masses of mercury constituents in Devils Lake and Lake Ashtabula; (3) determine concentrations and

loads of mercury constituents at sites on the Sheyenne River, the Red River of the North, and the Red Lake River; (4)

compare mercury data collected during this investigation with data collected during 1991-93 at various locations in the

Devils Lake and Sheyenne River Basins and with data collected in other aquatic systems; and (5) relate mercury

concentrations in the Devils Lake and Red River of the North Basins to the current state of knowledge concerning mercury

toxicity, health effects, and effects on aquatic systems.

Mercury is a ubiquitous environmental contaminant and comes from many natural and anthropogenic sources.

Typically, mercury occurs in very low concentrations in surface waters, in both inorganic and organic forms. Inorganic

mercury is not particularly toxic but, under certain conditions, can be converted to organic mercury (methylmercury, a

potent neurotoxin) by bacterially-mediated methylation and then assimilated by aquatic organisms and magnified in the

food chain (Krabbenhoft and Rickert, 1995). Even very small amounts of inorganic mercury can cause problems in aquatic

ecosystems when conditions are suitable for methylation, which primarily occurs as a byproduct of bacterially-mediated

sulfate reduction. The primary conditions that are necessary for sulfate reduction (and, thus, methylation of mercury)

include the presence of adequate concentrations of sulfate and organic material and a lack of dissolved oxygen

(Krabbenhoft, 1996). These conditions do not have to be prevalent throughout a given aquatic ecosystem but must exist at

least in isolated microzones for methylation of mercury to occur.

Methylmercury, which is produced by methylation of inorganic mercury, is a potent form of organic mercury and is

among the most toxic and widespread contaminants affecting the Nation’s aquatic ecosystems (Brumbaugh and others,

2001). Methylation and bioaccumulation of mercury pose toxicological risks to both fish (Wiener and Spry, 1996) and

humans (U.S. Environmental Protection Agency, 1997). Because of serious concerns about methylmercury toxicity, the

U.S. Environmental Protection Agency recently reduced the recommended standard for methylmercury in fish tissue from

0.5 milligram per kilogram to 0.3 milligram per kilogram (U.S. Environmental Protection Agency, accessed February 8,

2001). Methylmercury contamination also has caused many states, including North Dakota, to issue fish-consumption

advisories. In North Dakota, an advisory was issued in the early 1990’s when elevated mercury concentrations were

detected in sport fish in Devils Lake.

This report presents the concentrations of mercury constituents for several lake, wetland, and river water-quality

sampling sites; the masses of mercury in the lakes and wetlands; and the loads of mercury transported in the rivers at the

times of sampling. The scope of the report is a reconnaissance-level assessment of the occurrence of mercury in the Red

River of the North Basin. Data in the report can be used to assess whether the introduction of water from Devils Lake is a

threat to human health and to aquatic-health systems of the Red River of the North Basin.

DESCRIPTION OF STUDY AREA

Characteristics of the Devils Lake and Red River of the North Basins have been described in detail by Wiche and Pusc

(1994) and Stoner and others (1993), respectively. Much of the following information was taken from their reports.

The Devils Lake Basin is a 3,810-square-mile closed basin in northeastern North Dakota. About 3,320 square miles of

the basin is tributary to Devils Lake, and the remainder is tributary to Stump Lake. The eastern, western, and northern

boundaries of the Devils Lake Basin are poorly defined low divides. The southern boundary is a series of recessional

moraines that lie between Devils Lake and the Sheyenne River.

The Red River of the North originates at the confluence of the Otter Tail and Bois de Sioux Rivers on the border

between North Dakota and Minnesota and then flows about 394 miles northward into Manitoba, Canada. The Red River of

the North has a drainage area of about 40,200 square miles near the Canadian border. Most tributaries to the Red River of

the North enter from the east, but the Sheyenne River, which constitutes a relatively large tributary, enters the Red River of

the North from the west. The Sheyenne River has a contributing drainage area of about 3,090 square miles, which is about

8 percent of the drainage area of the Red River of the North at the Canadian border. Mean annual flow for the Sheyenne

River is about 5 percent of mean annual flow at the border. The Red Lake River, another large tributary to the Red River of

the North, enters the Red River of the North from the east at East Grand Forks. The Red Lake River has a drainage area of

about 5,970 square miles, which is about 15 percent of the drainage area of the Red River of the North at the Canadian
 4

border. Mean annual flow for the Red Lake River is about 30 percent of mean annual flow at the border. The slope of the

Red River of the North ranges from about 1.3 feet per mile near the headwaters to about 0.2 foot per mile at the Canadian

border. The river meanders are mature, and the streambed is comprised mostly of clay- and silt-sized particles.

The climate of the Red River of the North Basin is continental and ranges from dry subhumid in the western part of the

basin to subhumid in the eastern part of the basin. The basin has cold winters and moderately warm summers. According

to the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Data Service

(1982), mean annual temperatures range from 37 to 43oF, and mean monthly temperatures range from -1oF in January in

the northern part of the basin to 73o

F in July in the southern part of the basin. Mean annual precipitation ranges from about

17 inches in the western part of the basin to about 26 inches in the eastern part of the basin. About three-fourths of the

annual precipitation falls from April through September. Mean annual net evaporation ranges from about 4 inches in the

eastern part of the basin to about 22 inches in the western part of the basin. Climatic characteristics of the Devils Lake

Basin are very similar to those in the western part of the Red River of the North Basin.

Geologic and topographic features of both the Devils Lake and Red River of the North Basins primarily are a result of

depositional and erosional effects of continental glaciation. Surficial geology consists of a thick mantle of glacial drift

(consisting of till and outwash) that is 150 to 300 feet thick in the Red River of the North Basin. Upland areas are

dominated by till that is composed mostly of clay and silt. Cretaceous-age marine sediments underlie the glacial drift in

most areas. Effects of glaciation in both the Devils Lake and Red River of the North Basins are indicated by the numerous

shallow depressions and potholes in the basins.

METHODS OF STUDY

Water samples were collected at 16 sites (table 1), including 1 wetland site in the upper Devils Lake Basin, 1 site on

Starkweather Coulee, 5 sites on Devils Lake, 3 sites on the Sheyenne River, 2 sites on Lake Ashtabula, 3 sites on the Red

River of the North, and 1 site on the Red Lake River. The water samples collected at these sites were analyzed for the

selected properties and constituents given in table 2.

Table 1. Water-quality sampling sites

[--, not determined]

Site number

(see figure 1 for location) Site name

Site

identification

number

Drainage area

(square miles)

1 Wetland site in upper Devils Lake Basin 482818098463800 --

2 Starkweather Coulee near Webster, North Dakota 05056239 310

3 Devils Lake West Bay near Pelican Lake 480818099100000 --

4 Devils Lake West Bay southwest 480306099140000 --

5 Devils Lake Main Bay 480147098572200 --

6 Devils Lake East Bay 480050098454100 --

7 East Devils Lake 475740098381600 --

8 Sheyenne River near Warwick, North Dakota 05056000 2,070

9 Lake Ashtabula near north end 471256097573900 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 05057500 7,470

11 Sheyenne River below Baldhill Dam, North Dakota 05058000 7,470

12 Sheyenne River near Kindred, North Dakota 05059000 8,800

13 Red River of the North at Fargo, North Dakota 05054000 6,800

14 Red River of the North at Halstad, Minnesota 05064500 21,800

15 Red Lake River at Fisher, Minnesota 05080000 5,678

16 Red River of the North at Emerson, Manitoba 05102500 40,200
 5

Sample Collection, Processing, and Analysis

Sampling for mercury in the natural environment poses many problems. Although mercury typically occurs in

extremely low concentrations in water, it also may be present in very low but problematic concentrations in the ambient

atmosphere (either in gaseous form or within airborne particles) and on surfaces near or in the sampling and processing

environment. Thus, extreme precautions are necessary during sample collection, and exposure of the water sample to

different collection/processing containers (or the ambient atmosphere) must be kept to a minimum. For this investigation,

two-person ultra-clean sampling procedures (“clean hands/dirty hands”; U.S. Environmental Protection Agency, 1996;

Olson and DeWild, 1999) were used to collect the water samples analyzed for mercury constituents. The collectors wore

clean TYVEK suits, shoulder-length polyethylene gloves, and wrist-length latex gloves. Sample bottles were contained

within double polyethylene bags. Any materials and containers that contacted the sample water were rigorously cleaned

using procedures described by Olson and DeWild (1999), the U.S. Environmental Protection Agency (2001), and DeWild

and others (2002).

Table 2. Properties and constituents for which water-quality samples were analyzed

Property or constituent Reporting level used in investigation

FIELD ANALYSES

Field-measured properties and constituents

(U.S. Geological Survey North Dakota District)

Specific conductance 10 microsiemens per centimeter

pH 0.1 standard unit

Water temperature 0.1 degree Celsius

Dissolved oxygen 0.1 milligram per liter

LABORATORY ANALYSES

Major-ion and selected trace-element constituents

(North Dakota Department of Health Laboratory)

Calcium, dissolved 0.1 milligram per liter

Magnesium, dissolved 0.1 milligram per liter

Sodium, dissolved 0.1 milligram per liter

Potassium, dissolved 0.1 milligram per liter

Alkalinity, dissolved 0.1 milligram per liter

Sulfate, dissolved 0.1 milligram per liter

Chloride, dissolved 0.1 milligram per liter

Iron, whole water 10 micrograms per liter

Manganese, whole water 10 micrograms per liter

Suspended-sediment constituents

(U.S. Geological Survey Iowa District Sediment Laboratory)

Suspended sediment 1 milligram per liter

Suspended sediment (finer than 0.062 millimeter) 1 percent

Mercury constituents

(U.S. Geological Survey Wisconsin District Mercury Laboratory)

Methylmercury, dissolved 0.04 nanogram per liter

Methylmercury, particulate 0.02 nanogram per liter

Methylmercury, whole water 0.04 nanogram per liter

Total mercury, dissolved 0.04 nanogram per liter

Total mercury, particulate 0.02 nanogram per liter

Total mercury, whole water 0.04 nanogram per liter

Organic-carbon constituents

(U.S. Geological Survey Wisconsin District Mercury Laboratory)

Organic carbon, dissolved 0.1 milligram per liter

Organic carbon, whole water 0.1 milligram per liter
 6

Lake and wetland sites were sampled once in mid-March during ice cover and inverse thermal stratification and once

in late summer during peak heating conditions. Sampling periods were selected to represent conditions most conducive for

the occurrence of methylmercury in lacustrine settings. In northern temperate lakes, large amounts of methylmercury

typically can be generated during winter stratification under ice (David Krabbenhoft, U.S. Geological Survey, oral

commun., 2000), primarily because the stratification is particularly stable and results in an extended period of nearsediment oxygen depletion. Although microbial metabolic rates are slowed in winter, conditions suitable for sulfate

reduction can continue for a long duration and can result in accumulation of methylmercury. During peak heating

conditions in late summer, wind-generated turbulence can disrupt thermal stratification in northern prairie lakes, and

stratification might not be as stable as during winter. However, microbial metabolic rates are high and available oxygen can

be consumed quickly in the process of breaking down organic material. Also, during calm periods, near-sediment oxygen

depletion can occur quickly, promoting sulfate reduction and accumulation of methylmercury.

Lake samples were collected through ice during the winter sampling trip and from a boat during the summer sampling

trip. During the winter sampling trip, a hole was drilled in the ice, upwind from any vehicles, using a pre-cleaned manual

steel auger. Several gallons of native lake water then were purged from the hole before sample collection. Vertical profiles

of field-measured properties and constituents (table 2) were made during each sampling trip. All lake samples were

collected using a rigorously cleaned peristaltic pump with Teflon tubing. Near-surface samples (taken about 3 feet below

the water surface) were collected at all sites during both sampling trips, and near-sediment samples (taken about 3 feet

above the lake bottom) were collected at four sites (sites 3, 5, 7, and 10) during both sampling trips.

Because the wetland site was inaccessible during the winter sampling trip, the first wetland sample was not collected

until after ice out. The second wetland sample was collected in late summer at about the same time that lake samples were

collected. The wetland sample was collected by wading to a point near the center of the wetland and using a rigorously

cleaned 1-liter Teflon bottle to obtain a grab sample.

River sites were sampled once in late April/early May during spring-runoff conditions and once in late summer during

low-flow/peak heating conditions. Because little is known about seasonal variability of mercury constituents in northern

prairie streams, sampling periods were selected to represent a wide range of flow and environmental conditions.

River samples were collected from a boat near the centroid of flow in the stream cross section, and field properties and

constituents (table 2) were measured at mid-depth near the centroid of flow. Because water samples analyzed for mercury

are susceptible to contamination, depth- and width-integrating procedures that require the transfer of a sample to multiple

containers in the field generally are not recommended for low-level mercury analysis. Also, flowing-water conditions are

problematic when using ultra-clean sampling procedures with a peristaltic pump. Thus, river samples were collected from

just below the water surface using rigorously cleaned 1-liter Teflon bottles to obtain grab samples. To minimize exposure

to the ambient atmosphere, collection bottles were submersed while capped, then uncapped and filled, and then recapped

while still submersed. For all sampling sites, water samples were collected for analysis of mercury constituents and then

for analysis of major-ion, trace-element, suspended-sediment, and organic-carbon constituents. Major-ion, trace-element,

suspended-sediment, and organic-carbon samples were collected using equipment and techniques that were similar to those

used for mercury samples. However, some of the extreme precautions, such as rigorous acid cleaning and double bagging

of sample bottles, that were necessary for collection of mercury samples were not used for collection of major-ion, traceelement, suspended-sediment, and organic-carbon samples. Because those constituents occur in much greater

concentrations than mercury, the potential for contamination is much less than for mercury.

Water samples were processed and analyzed for major-ion and selected trace-element constituents by the North

Dakota Department of Health Laboratory (NDDHL). To determine dissolved concentrations of major-ion constituents,

water samples were passed through 0.45-micrometer pore-size filters. Thus, in this report, for major-ion constituents,

“dissolved” is operationally defined as that part of a water sample that passes through a 0.45-micrometer filter. To

determine whole-water concentrations of trace-element constituents, water samples were not filtered before analysis and,

thus, included both dissolved and particulate phases. Quality-assurance and analytical procedures are described in the

NDDHL environmental methods handbook (North Dakota Department of Health, 2001).

Water samples were processed and analyzed for suspended-sediment constituents by the U.S. Geological Survey Iowa

District Sediment Laboratory. Analytical and quality-assurance procedures are described by Guy (1969) and Matthes and

others (1991).
 7

Water samples were processed and analyzed for mercury and organic-carbon constituents by the U.S. Geological

Survey Wisconsin District Mercury Laboratory (WDML), a class-100, clean-room facility. WDML quality-assurance

procedures (Wisconsin District Mercury Laboratory, 1999) are available at URL http://infotrek.er.usgs.gov/doc/mercury/

qa.html (accessed March 6, 2002). Water samples were analyzed at the WDML for determination of methylmercury

(Olson and DeWild, 1997c, 1997d) and total mercury (Olson and DeWild, 1997a). In this report, the term “total” with

respect to mercury refers to both the inorganic and organic forms combined. Analyses for organic-carbon constituents

were performed using procedures described by Olson and DeWild (1997b). To determine dissolved concentrations of

mercury and organic-carbon constituents, water samples were passed through ultra-clean, 0.7-nominal-pore-size, quartzfiber filters at the WDML within 24 hours of sample collection. Thus, in this report, for mercury and organic-carbon

constituents, “dissolved” is operationally defined as that part of a water sample that passes through a 0.7-micrometer filter.

To determine particulate concentrations of mercury constituents, known volumes of sample water were passed through

ultra-clean, 0.7-nominal-pore-size, quartz-fiber filters. The filter and retained particulate material were digested and the

resulting solution was analyzed. Mass/volume concentrations of particulate mercury constituents then were determined on

the basis of the original known volume of sample water filtered. To determine whole-water concentrations of mercury

constituents, dissolved and particulate concentrations were summed. If either the dissolved or particulate concentration for

a given sample was less than the reporting level, the concentration for the “less-than” fraction was assumed to be zero.

Quality Assurance/Quality Control

Quality-assurance/quality-control samples were collected to assess precision and accuracy of collected data. One

field-equipment blank sample and one replicate sample were collected during each sampling trip and analyzed for mercury

and organic-carbon constituents. Fewer quality-assurance/quality-control samples were collected for major-ion and traceelement constituents because those constituents are not as susceptible to contamination as mercury constituents. For

major-ion and trace-element constituents, one replicate sample was collected during the first lake-sampling trip and another

was collected during the first river-sampling trip. Blank samples were collected by passing ultra-clean water through the

collection and processing equipment used for primary environmental samples. Replicate samples were collected and

processed immediately after each primary environmental sample was collected and processed, and procedures used for

replicate samples were identical to those used for primary environmental samples.

Estimation of Masses and Loads

Coarse estimates of masses of mercury constituents for lake and wetland sites were calculated to investigate the

processing and fate of mercury in lakes and wetlands. Masses were estimated by multiplying lake and wetland volumes by

representative constituent concentrations and by a conversion factor (0.00123) to convert the sample concentration (in

milligrams per liter) to the total mass of the constituent in the given water body (in grams).

Volumes for the Devils Lake sites were estimated using records of the Devils Lake water-surface elevation at U.S.

Geological Survey gaging station 05056500 (Devils Lake near Devils Lake, N. Dak.) and elevation/capacity curves for

Devils Lake (Aldo V. Vecchia, U.S. Geological Survey, written commun., March 27, 2002). Volumes for the Lake

Ashtabula sites were estimated using records of water-surface elevation and elevation/capacity curves provided by the U.S.

Army Corps of Engineers (U.S. Army Corps of Engineers, 2002). The volume for the wetland site was estimated using a

visual estimate of surface area and the average depth of the wetland at the time of sampling.

Representative constituent concentrations were determined using the following guidelines. For lake and wetland sites

where only one sample in the vertical was collected (that is, for sites 1, 4, 6, and 9 where only a near-surface sample was

collected), constituent concentrations in that sample were assumed to represent constituent concentrations in the entire

water body represented by the sampling site. For example, for site 6 (Devils Lake East Bay), a single near-surface sample

was collected during each sampling trip. Constituent concentrations in that sample were assumed to represent constituent

concentrations in the entire water volume for Devils Lake East Bay for the sampling period. For lake and wetland sites

where two samples in the vertical were collected (that is, for sites 3, 5, 7, and 10 where near-surface and near-bottom

samples were collected), the proportion of the water column represented by each of the two samples was estimated by

inspecting the vertical profiles of field-measured properties and constituents. For example, for the winter sampling at

site 5 (Devils Lake Main Bay), field measurements of specific conductance, water temperature, and dissolved oxygen
 8

(supplement 1) indicate that the hypolimnion (where more reducing conditions would be expected to occur) existed from

about 39 to 46 feet below the water surface. That depth represented about 14 percent of the total water column. Thus, to

determine representative constituent concentrations for site 5, the near-bottom sample constituent concentrations were

multiplied by 0.14, and the near-surface sample constituent concentrations were multiplied by 0.86. The two

concentrations then were summed to obtain vertically-weighted constituent concentrations for that site. The verticallyweighted constituent concentrations were assumed to represent constituent concentrations in the entire water volume for

Devils Lake Main Bay for the sampling period. For samples in which constituent concentrations were less than the

reporting level, representative constituent concentrations were assumed to be zero.

Masses of mercury constituents for Devils Lake were estimated by summing masses for individual bays. Masses of

mercury constituents for Lake Ashtabula were estimated by summing masses for the two sampling sites on Lake

Ashtabula. Site 9 (Lake Ashtabula near north end) was assumed to represent 20 percent of the entire water volume for

Lake Ashtabula, and site 10 (Lake Ashtabula at Baldhill Dam, N. Dak.) was assumed to represent 80 percent of the entire

water volume for Lake Ashtabula.

Loads of mercury constituents for river sites were estimated by multiplying stream discharges at the times of sampling

by representative constituent concentrations and by a conversion factor (0.00245) to convert cubic feet per second and

nanograms per liter to grams per day. A single near-surface grab sample was collected for each river site, and constituent

concentrations in that sample were assumed to represent constituent concentrations in the entire water volume flowing past

the site at the time of sampling.

Mass estimates in this report should be considered coarse. The relatively small number of samples collected during

the investigation may not accurately represent spatial variability of mercury constituents in the water bodies, and errors in

volume estimates for the water bodies and analytical errors also may exist. However, for this reconnaissance-level

assessment of the occurrence of mercury in the Red River of the North Basin, the methods used to estimate the masses

probably are reasonable for assessing relative differences between different water bodies and between different sampling

periods. In addition, the near-surface grab sample collected for each river site may not accurately represent the vertical and

horizontal variability of mercury constituents in the rivers, and errors associated with discharge estimates and analytical

errors also may exist. However, load estimates for the river sites probably are reasonable and adequate for discerning

differences between sites and between different sampling periods.

RESULTS FOR QUALITY-ASSURANCE/QUALITY-CONTROL SAMPLES AND FOR SELECTED PROPERTIES AND

CONSTITUENTS

Field and analytical data collected during this investigation are given in supplements 1 through 6 at the back of the

report. Results for field-measured properties and constituents are given in supplement 1 for lake and wetland sites and in

supplement 2 for river sites. Laboratory analytical results for major-ion and selected trace-element constituents are given

in supplement 3 for lake and wetland sites and in supplement 4 for river sites, and laboratory analytical results for organiccarbon constituents are given in supplement 5 for lake and wetland sites and in supplement 6 for river sites.

Quality-Assurance/Quality-Control Samples

Concentrations of mercury and organic-carbon constituents in field-equipment blank samples (table 3) generally were

less than the reporting level and were substantially less than typical concentrations in the environmental samples

(supplements 5 and 6). A comparison of results for the primary environmental samples and the replicate samples generally

indicates good agreement (tables 4 and 5). A typical data-quality objective for the precision of replicate samples is a

relative percent difference (RPD) less than or equal to 20 percent (Taylor, 1987). Nearly all values for the replicate

samples had RPD values that met this criterion. However, one dissolved total mercury concentration and one dissolved

chloride concentration substantially exceeded the criterion, and one dissolved methylmercury concentration and one

particulate total mercury concentration slightly exceeded the criterion. Generally, problems in the quality-assurance/

quality-control data were few and probably did not interfere with evaluation of the data.
 9

Field-Measured Properties and Constituents

Vertical profiles of field-measured properties and constituents for lake and wetland sites (supplement 1) provide

information about general water-quality conditions and about the strength of thermal stratification. Thermal stratification

in lakes can be important to mercury chemistry because near-sediment oxygen depletion promotes sulfate reduction and

accumulation of methylmercury. Generally, the lake and wetland sites tended to be moderately alkaline (field-measured

pH values were between 6.8 and 8.7 standard units) and of relatively high ionic strength (field-measured specificconductance values were between 1,010 and 6,930 microsiemens per centimeter). Deep lake sites (represented by site 5,

Devils Lake Main Bay, fig. 2) generally showed relatively strong thermal stratification during both winter and summer

sampling periods. Field-measured properties at deep sites were typical of stratified conditions (fig. 2); specific

conductance increased near the bottom, and pH and dissolved oxygen decreased near the bottom. Shallow lake sites

(represented by site 4, Devils Lake West Bay southwest, fig. 3) did not show strong thermal stratification in either sampling

period, and field-measured properties tended to be similar at different depths.

Values for field-measured properties and constituents for river sites (supplement 2) were fairly typical of large streams

in the northern Great Plains and were similar to previously reported data for the Red River of the North Basin (Stoner and

others, 1998). The river sites tended to be moderately alkaline (field-measured pH values were between 7.6 and 8.4

standard units) and of moderate ionic strength (field-measured specific-conductance values were between 341 and 1,260

microsiemens per centimeter). Dissolved-oxygen concentrations generally were near saturation during spring-runoff

conditions and no more than moderately depleted (percent saturation greater than about 75 percent) during the summer

sampling period.

Major-Ion, Trace-Element, and Suspended-Sediment Constituents

Average dissolved-solids concentrations and ionic proportions for all sites are shown in figure 4. For the lake and

wetland sites in the Devils Lake Basin (sites 1 and 3 through 7), sodium and sulfate were dominant among the cations and

anions, respectively (fig. 4). Dissolved-solids concentrations and the dominance of those two ions generally increased

downstream through the Devils Lake system. For the Lake Ashtabula sites (sites 9 and 10), sodium, magnesium, and

calcium were about equal in dominance among the cations, and bicarbonate was slightly dominant among the anions.

However, sulfate concentrations still were relatively large and exceeded 200 milligrams per liter (supplement 3). Sulfate

concentrations are particularly important in mercury chemistry because methylation of mercury occurs as a byproduct of

sulfate reduction. Very high rates of sulfate reduction can result in an accumulation of sulfide (the end product of sulfate

reduction), which can strongly bind available mercury ions and make them unavailable for methylation of mercury. Thus,

although sulfate concentrations must be greater than about 2 milligrams per liter for sulfate reduction to occur (Gilmour

and Krabbenhoft, 2001), relatively large sulfate concentrations (greater than about 50 milligrams per liter; U.S. Department

of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service, 1996) can at times provide

accumulation of sulfide and inhibit methylation of mercury. For this investigation, sulfate concentrations for the lake and

Table 3. Concentrations of mercury and organic-carbon constituents in quality-assurance/quality-control field-equipment blank samples

[ng/L, nanograms per liter; mg/L, milligrams per liter; <, less than; ND, not determined]

Site number

(see figure 1

for location)

Site where blank was collected Date Time

Methylmercury,

dissolved

(ng/L)

Methylmercury,

particulate

(ng/L)

Total

mercury,

dissolved

(ng/L)

Total

mercury,

particulate

(ng/L)

Organic

carbon,

dissolved

(mg/L)

Organic

carbon,

whole

water

(mg/L)

7 East Devils Lake 03/14/01 1655 <0.04 ND 0.20 <0.02 ND ND

7 East Devils Lake 08/02/01 0950 <.04 <0.02 .20 <.02 0.1 0.1

15 Red Lake River at Fisher,

Minnesota

07/25/01 1340 <.04 <.02 .30 .30 <.1 <.1

16 Red River of the North at Emerson,

Manitoba

05/02/01 0735 <.04 <.02 .10 <.02 <.1 ND
 10

Table 4. Analytical results for primary environmental samples and for quality-assurance/quality-control replicate samples for major-ion and trace-element constituents[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; RPD, relative percent difference; μg/L, micrograms per liter; --, no data]

Site number

(see figure 1

for location)

Site name Date

Time Specific conductance (μS/cm) Calcium, dissolved (mg/L) Magnesium, dissolved (mg/L)

Primary Replicate Primary Replicate RPD (percent) Primary Replicate RPD (percent) Primary Replicate RPD (percent)

3 Devils Lake West Bay near

Pelican Lake

03/15/01 1155 1205 1,970 1,970 0 100 110 9.5 84 90 6.9

16 Red River of the North at

Emerson, Manitoba

05/02/01 0730 0740 539 536 -0.6 56 56 0 25 24 -4.1

Site number

(see figure 1

for location)

Site name Date

Time Sodium, dissolved (mg/L) Potassium, dissolved (mg/L) Alkalinity, dissolved (mg/L as CaCO3)

Primary Replicate Primary Replicate RPD (percent) Primary Replicate RPD (percent) Primary Replicate RPD (percent)

3 Devils Lake West Bay near

Pelican Lake

03/15/01 1155 1205 240 260 8.0 38 42 10.0 390 400 2.5

16 Red River of the North at

Emerson, Manitoba

05/02/01 0730 0740 18 18 0 8.2 7.9 -3.7 150 150 0

Site number

(see figure 1

for location)

Site name Date

Time Sulfate, dissolved (mg/L) Chloride, dissolved (mg/L) Solids, dissolved, sum of constituents (mg/L)

Primary Replicate Primary Replicate RPD (percent) Primary Replicate RPD (percent) Primary Replicate RPD (percent)

3 Devils Lake West Bay near

Pelican Lake

03/15/01 1155 1205 520 520 0 87 94 7.7 1,300 1,360 4.5

16 Red River of the North at

Emerson, Manitoba

05/02/01 0730 0740 110 110 0 12 0.4 -187.1 317 308 -2.9

Site number

(see figure 1

for location)

Site name Date

Time Iron, whole water (μg/L) Manganese, whole water (μg/L)

Primary Replicate Primary Replicate RPD (percent) Primary Replicate RPD (percent)

3 Devils Lake West Bay near

Pelican Lake

03/15/01 1155 1205 20 20 0 410 410 0

16 Red River of the North at

Emerson, Manitoba

05/02/01 0730 0740 -- 3,800 -- -- 130 --
 11

Table 5. Analytical results for primary environmental samples and for quality-assurance/quality-control replicate samples for mercury and organic-carbon constituents[ng/L, nanograms per liter; RPD, relative percent difference; <, less than; mg/L, milligrams per liter]

Site number

(see figure 1for location)

Site name Date

Time Methylmercury, dissolved (ng/L) Methylmercury, particulate (ng/L) Total mercury, dissolved (ng/L)

Primary Replicate Primary Replicate RPD (percent) Primary Replicate RPD (percent) Primary Replicate RPD (percent)

3 Devils Lake West Bay near

Pelican Lake

03/15/01 1155 1205 <0.04 <0.04 0 <0.02 <0.02 0 0.50 1.43 96.4

6 Devils Lake East Bay 08/02/01 0740 0750 .10 .13 26.3 .10 .09 10.5 .85 .97 13.2

16 Red River of the North at

Emerson, Manitoba

05/02/01 0730 0740 .06 .07 15.4 .10 .09 10.5 1.91 1.78 7.0

16 Red River of the North at

Emerson, Manitoba

07/26/01 0715 0725 .06 .07 15.4 .31 .34 9.2 1.13 1.06 6.4

Site number

(see figure 1

for location)

Site name Date

Time

Total mercury,

particulate

(ng/L)

Organic carbon,

dissolved

(mg/L)

Organic carbon,

whole water

(mg/L)

Primary Replicate Primary Replicate RPD (percent) Primary Replicate RPD (percent) Primary Replicate RPD (percent)

3 Devils Lake West Bay near

Pelican Lake

03/15/01 1155 1205 <0.02 <0.02 0 20.72 20.69 0.1 20.99 21.18 0.9

6 Devils Lake East Bay 08/02/01 0740 0750 .34 .45 27.8 19.22 20.02 4.1 19.57 19.84 1.4

16 Red River of the North at

Emerson, Manitoba

05/02/01 0730 0740 7.49 7.31 2.4 8.53 8.92 4.5 8.37 8.79 4.9

16 Red River of the North at

Emerson, Manitoba

07/26/01 0715 0725 21.30 22.49 5.4 9.44 9.42 0.2 9.42 9.30 1.3
 12

DEPTH BELOW WATER SURFACE, IN FEET

 EXPLANATION 

Winter sampling period Summer sampling period

Figure 2. Vertical profiles of field-measured properties and constituents at a

representative deep lake site (site 5, Devils Lake Main Bay).

0

-5

-10

-15

-20

-25

-30

-35

-40

-50

-45

0

-5

-10

-15

-20

-25

-30

-35

-40

-50

-45

0

-5

-10

-15

-20

-25

-30

-35

-40

-50

-45

0

-5

-10

-15

-20

-25

-30

-35

-40

-50

-45

8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8

pH, IN STANDARD UNITS

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER

-5 0 5 10 15 20 25

WATER TEMPERATURE, IN DEGREES CELSIUS

1,500 1,600 1,700 1,800 1,900 2,000 2,100 2,200 2,300 2,400 2,500

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER
 13

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-4

-3

-2

-1

0

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-4

-3

-2

-1

0

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-4

-3

-2

-1

0

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-4

-3

-2

-1

0

8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8

pH, IN STANDARD UNITS

DEPTH BELOW WATER SURFACE, IN FEET

0 1 2 3 5 6 7 8 9 10 11 12 13 14 15 4

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER

-5 0 5 10 15 20 25

WATER TEMPERATURE, IN DEGREES CELSIUS

1,500 1,600 1,700 1,800 1,900 2,000 2,100 2,200 2,300 2,400 2,500

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

 EXPLANATION 

Winter sampling period Summer sampling period

Figure 3. Vertical profiles of field-measured properties and constituents at a

representative shallow lake site (site 4, Devils Lake West Bay southwest).
 14

99 ̊ 97 ̊

95 ̊

49 ̊

47 ̊

49 ̊

47 ̊

97 ̊

99 ̊

Grand

Forks

Webster

Warwick

Red

Fargo

River

of

the North

Upper

Red

Lake Devils Lake

River

River

Red

Lake

Sheyenne

Lake

Ashtabula

Stump

Lake

Tolna

Coulee

Baldhill

Dam

StarkweatherCoulee

Lower

Red

Lake

Mississippi

R.

Kindred

Halstad

Emerson

Fisher

East

Grand

Forks

N O R T H D A K O T A M I N N E S O T A

M A N I T O B A

S O U T H D A K O T A

Sioux R. Bois de

Tail

River

Otter

Figure 4. Average dissolved-solids concentrations and ionic proportions for water-quality sampling sites.

0

SITE 16 DS 344

30 60 60 30

0

SITE 15 DS 214

30 60 60 30

0

SITE 13 DS 396

30 60 60 30 0

SITE 12 DS 566

30 60 60 30

Devils Lake

DEVILS LAKE

Pelican Lake

EastDevilsLake

CAVALIER CO.

RAMSEY CO.

NELSON CO.

WALSH CO.

TOWNER CO.

BENSON CO.

ROLETTE CO.

PIERCE CO.

Starkweather Coulee

Webster

Warwick

0

SITE 14 DS 440

30 60 60 30

0

SITE 9 DS 778

30 60 60 30

0

SITE 10 DS 923

30 60 60 30

0

SITE 8 DS 766

30 60 60 30

0

SITE 11 DS 629

30 60 60 30

0

SITE 6 DS 2,455

30 60 60 30

0

SITE 3 DS 1,070

30 60 60 30

0

SITE 2 DS 570

30 60 60 30 0

SITE 1 DS 1,097

30 60 60 30

0

CONCENTRATION, IN

MILLIEQUIVALENTS PER LITER

SITE 7 DS 4,998

30 60 60 30

Sodium plus

potassium

Magnesium

Calcium

Chloride

Dissolved solids, inmilligrams per liter

SulfateBicarbonateplus carbonate

0

SITE 5 DS 1,513

30 60 60 30

0

SITE 7 DS 4,998

30 60 60 30

0

SITE 4 DS 1,400

30 60 60 30

 EXPLANATIONSheyenne River BasinDevils Lake BasinRed River of the North BasinWater-quality sampling site--Sitenumber given in table 1
 15

wetland sites were much larger than the minimum concentration required for sulfate reduction and also were much larger

than concentrations reported to inhibit methylation of mercury. However, the ability of sulfide to bind with available

mercury ions also can depend on several other factors, including (1) the presence of either dissolved or particulate iron and

manganese, which have a strong affinity for sulfide (U.S. Department of Commerce, National Oceanic and Atmospheric

Administration, National Ocean Service, 1996); and (2) the presence of certain organic acids, which decrease mercury

binding by sulfide (Ravichandran and others, 1999). The biological and chemical interactions that affect sulfate reduction,

availability of mercury for methylation, and the inhibitory effects of sulfide on methylation of mercury are complex and

site specific.

Iron and manganese concentrations for the lake and wetland sites (supplement 3) were within typical ranges for

northern temperate lakes (Livingstone, 1963). The whole-water concentrations shown represent both dissolved and

particulate phases of the constituents because the water samples analyzed for the constituents were not filtered. However,

most of the iron and manganese probably was in dissolved phase as indicated by the small (generally less than

30 milligrams per liter; supplement 3) suspended-sediment concentrations. Near-bottom concentrations generally were

larger than near-surface concentrations, especially for manganese, indicating the occurrence of iron and manganese in

natural waters is sensitive to oxidation-reduction conditions. Reducing conditions near the bottom probably result in

release of adsorbed ions from oxide-surface sites on inorganic sediment particles and from organic material.

For the Sheyenne River sites (sites 8, 11, and 12), sodium, magnesium, and calcium were about equal in dominance

among the cations, and sulfate and bicarbonate were about equal in dominance among the anions (fig. 4). Dissolved-solids

concentrations decreased slightly in a downstream direction. For the Red River of the North and Red Lake River sites

(sites 13 through 16), magnesium and calcium were about equal in dominance among the cations for sites 13 and 14.

Magnesium decreased in proportion in a downstream direction, and calcium became dominant among the cations for

sites 15 and 16. Sulfate and bicarbonate were about equal in dominance among the anions at sites 13, 14, and 16, and

bicarbonate was dominant among the anions at site 15. Dissolved-solids concentrations generally decreased in a

downstream direction. Sulfate concentrations for the river sites ranged from about 15 to 290 milligrams per liter

(supplement 4) and were much larger than the minimum concentration required for sulfate reduction and generally larger

than the concentrations reported to inhibit methylation of mercury. However, as previously noted, the biological and

chemical interactions that affect sulfate reduction and the inhibitory effects of sulfide on methylation of mercury are

complex and site specific.

Whole-water iron and manganese concentrations for the river sites (supplement 4) were within previously reported

ranges for sites in the Red River of the North Basin (Britton and others, 1983). Much of the iron and manganese probably

was in particulate phase.

River sites tended to be fairly oxic and had moderate suspended-sediment concentrations (supplement 4). Suspendedsediment concentrations were within typical ranges for rivers in the Red River of the North Basin (Tornes and others, 1997)

and were largely dependent on discharge at the time of sampling. For sites in the upper part of the Sheyenne River Basin

(sites 8 and 11) (fig. 5), concentrations were small relative to the other river sites during both sampling periods. The

concentrations decreased between sites 8 and 11, probably indicating that Lake Ashtabula serves as a sediment sink.

Organic-Carbon Constituents

Most of the organic carbon in water samples from the lake and wetland sites was in dissolved phase. Dissolved

organic-carbon concentrations for the wetland site (site 1) ranged from about 20 to 30 milligrams per liter (supplement 5;

fig. 6). For the Devils Lake sites (sites 3 through 7), concentrations ranged from about 15 to 30 milligrams per liter and had

a median of about 20 milligrams per liter. For the Lake Ashtabula sites (sites 9 and 10), concentrations ranged from about

10 to 20 milligrams per liter and had a median of about 15 milligrams per liter. These concentrations generally were within

typical ranges for water bodies in the Red River of the North Basin (Tornes and others, 1997; Brigham and others, 1999).

Organic-carbon concentrations in water bodies in the Red River of the North tend to be larger than general concentrations

for water bodies across the United States (Britton and others, 1983), indicating that waters in the Red River of the North

probably have relatively high biological productivity. For this investigation, near-surface sample concentrations were

similar to near-bottom sample concentrations (fig. 6). Generally, concentrations decreased slightly between winter and

summer sampling periods, but for sites 1 and 9, concentrations increased slightly between sampling periods.
 16

Most of the organic carbon in water samples from the river sites was in dissolved phase, and concentrations increased

slightly between the spring and summer sampling periods (supplement 6; fig. 5). Organic-carbon concentrations generally

were within typical ranges for rivers in the Red River of the North Basin (Tornes and others, 1997; Brigham and others,

1999).

MERCURY CONSTITUENTS IN LAKES, WETLANDS, AND RIVERS

In this section, mercury concentrations, masses, and loads from the reconnaissance-level sampling of lakes, wetlands,

and rivers are presented and discussed. Results of the study are used to postulate possible effects from a Devils Lake outlet

on mercury occurrence.

0

5

10

15

20

25

0

2 8 11 12 13 14 15 16

5

10

15

20

25

CONCENTRATION, IN MILLIGRAMS PER LITER

SITE NUMBER

EXPLANATION

 Spring sampling period

 Summer sampling period

Figure 5. Concentrations of suspended sediment and organic carbon for river sites.

DISSOLVED ORGANIC CARBON

WHOLE-WATER ORGANIC CARBON

0

100

200

400

300

500

600

SUSPENDED SEDIMENT

NO DATA
 17

Lakes and Wetlands

Whole-water methylmercury concentrations in water samples from the lake and wetland sites ranged from 0.39 to

3.53 nanograms per liter for the wetland site (site 1), from less than 0.04 to 0.34 nanogram per liter for the Devils Lake

sites (sites 3 through 7), and from less than 0.04 to 0.46 nanogram per liter for the Lake Ashtabula sites (sites 9 and 10)

(supplement 5; fig. 7). Most of the sites had methylmercury concentrations that exceeded 0.10 nanogram per liter, which

might be considered the upper end of the range of typical aquatic concentrations throughout the United States

(Krabbenhoft and others, 1999). However, the concentrations generally were within typical ranges for natural lakes in the

Red River of the North Basin in Minnesota (Brigham and others, 1999; Brigham and others, 2002) except for the largest

concentration for the wetland site (site 1). That concentration (3.53 nanograms per liter) is near the largest reported

concentration in the Red River of the North Basin.

For the winter sampling period, most of the methylmercury in water samples from the lake and wetland sites was in

dissolved phase, and concentrations generally were less than the reporting level of 0.04 nanogram per liter (supplement 5;

fig. 7). However, concentrations at sites 1, 3, and 10 were moderately large. For the summer sampling period,

methylmercury concentrations (fig. 7) generally were greater than for the winter sampling period. The whole-water

methylmercury concentration (3.53 nanograms per liter) for the wetland site (site 1) was large, and the concentrations for

the remaining sites were moderately large. Wetlands have been reported to be favorable sites for production of

0

5

10

15

20

25

30

35

0

5

10

15

20

25

30

35

1 3 4 6 7 9 10 5

SITE NUMBER

CONCENTRATION, IN MILLIGRAMS PER LITER

DISSOLVED ORGANIC CARBON

WHOLE-WATER ORGANIC CARBON

 EXPLANATION

Winter sampling period

 Near-surface sample

 Near-bottom sample

Summer sampling period

 Near-surface sample

 Near-bottom sample

Figure 6. Concentrations of organic carbon for lake and wetland sites. NO DATA NO DATA NO DATA NO DATA NO DATA NO DATA

NO DATA NO DATANO DATA NO DATANO DATA NO DATANO DATA NO DATA
 18

1 3 4 6 7 9 10 5

SITE NUMBER

Figure 7. Concentrations of methylmercury and ratios of whole-water methylmercury to whole-water total mercury for lake and

wetland sites.

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

60

50

40

30

20

10

0

CONCENTRATION, IN NANOGRAMS PER LITER RATIO, IN PERCENT

NO DATANO DATANO DATANO DATANO DATANO DATANO DATA

NO DATANO DATANO DATANO DATANO DATANO DATANO DATA

NO DATANO DATANO DATANO DATANO DATANO DATANO DATA

NO DATANO DATANO DATANO DATANO DATANO DATANO DATA

 EXPLANATION

Winter sampling period

 Near-surface sample

 Near-bottom sample

Summer sampling period

 Near-surface sample

 Near-bottom sample

DISSOLVED METHYLMERCURY

PARTICULATE METHYLMERCURY

WHOLE-WATER METHYLMERCURY

MINIMUM REPORTING LIMIT IS 0.04 NANOGRAM

PER LITER; "LESS-THAN" VALUES ARE PLOTTED

AT ONE-HALF THE MINIMUM REPORTING LIMIT

MINIMUM REPORTING LIMIT IS 0.02 NANOGRAM

PER LITER; "LESS-THAN" VALUES ARE PLOTTED

AT ONE-HALF THE MINIMUM REPORTING LIMIT

MINIMUM REPORTING LIMIT IS 0.04 NANOGRAM PER LITER;

"LESS-THAN" VALUES ARE PLOTTED AT ONE-HALF THE

MINIMUM REPORTING LIMIT
 19

methylmercury (St. Louis and others, 1994; Hurley and others, 1995). The pattern of larger methylmercury concentrations

in summer than in winter differs from the seasonal pattern reported by Brigham and others (2002) for lakes and

impoundments in the Red River of the North Basin in Minnesota. In Brigham’s study, seasonal patterns of methylmercury

were characterized by concentrations that were largest in winter, smallest in spring and fall, and intermediate in summer.

However, Brigham and others (2002) showed a summer maximum for a single hypereutrophic lake, possibly indicating that

seasonal patterns of methylmercury are dependent on trophic status. The lakes and wetland sampled for this investigation

are hypereutrophic, which may account for the difference in the patterns of methylmercury. Dissolved methylmercury

concentrations generally were larger than particulate methylmercury concentrations in summer. However, summer

particulate methylmercury concentrations were relatively larger than winter concentrations, probably because of larger

amounts of suspended particulate organic and inorganic materials that adsorb mercury during summer. The summer

particulate methylmercury concentrations at site 3 were much larger than the dissolved concentrations, possibly indicating

that most of the methylmercury at site 3 is adsorbed to particulate material. Generally, near-bottom samples had larger

dissolved methylmercury concentrations than near-surface samples for both sampling periods, possibly indicating

production of methylmercury by sulfate reduction at the sediment-water interface and/or photodegradation of

methylmercury near the water surface.

Whole-water total mercury concentrations ranged from 1.43 to 7.02 nanograms per liter for the wetland site (site 1),

from 0.38 to 2.98 nanograms per liter for the Devils Lake sites (sites 3 through 7), and from 0.63 to 3.11 nanograms per

liter for the Lake Ashtabula sites (sites 9 and 10) (supplement 5; fig. 8). These concentrations are less than 10 nanograms

per liter, which might be considered the upper end of the range of typical aquatic concentrations throughout the United

States (Hurley and others, 1995; Krabbenhoft and others, 1999). Whole-water total mercury concentrations for the lakes

and wetland sampled for this investigation were similar to concentrations reported for natural lakes in the Red River of the

North Basin in Minnesota (Brigham and others, 1999; Brigham and others, 2002) and Wisconsin (Fitzgerald and Watras,

1989) and to previously reported concentrations for Devils Lake and Lake Ashtabula (table 6) and for other lake sites in the

Devils Lake and Sheyenne River Basins (table 7). However, detailed comparison of mercury concentrations from this

investigation with previously reported concentrations for Devils Lake and Lake Ashtabula is complicated by (1) differences

in sampling locations; (2) differences in the seasonal timing of sampling; and (3) the relatively small number of samples

collected.

Among the lake and wetland sites, the wetland site (site 1) had the largest whole-water total mercury concentrations

for both sampling periods (1.43 and 7.02 nanograms per liter for the winter and summer sampling periods, respectively).

Patterns in whole-water total mercury concentrations in near-surface samples relative to near-bottom samples were not

consistent either between sites, or for a given site, between sampling periods. For example, for the winter sampling period,

near-bottom concentrations were greater than near-surface concentrations for sites 3, 4, and 10, but near-bottom

concentrations were slightly less than near-surface concentrations for sites 5 and 7. For the summer sampling period, the

near-bottom concentration was greater than the near-surface concentration for site 7, but near-bottom concentrations were

less than near-surface concentrations for sites 3, 5, and 10. Generally, both dissolved and particulate total mercury

concentrations were larger for the summer sampling period than for the winter sampling period for the various sites.

Except for site 9, particulate total mercury concentrations were small (generally near or less than 0.1 nanogram per liter)

for all winter samples.

Masses of mercury constituents for the lake and wetland sites are shown in figure 9. For the wetland site (site 1),

methylmercury comprised a substantial part of total mercury for both the winter and summer sampling periods (about

25 percent for the winter sampling period and about 50 percent for the summer sampling period; fig. 7) and was almost

entirely in dissolved phase. The summer methylmercury concentration was about 10 times greater than the winter

methylmercury concentration, and most of the methylmercury comprising the increase was in dissolved phase. This

indicates that the wetland site has favorable conditions for methylation of mercury and that production of methylmercury in

the sediments is a primary factor governing mercury processes in the wetland. Although most of the mercury was in

dissolved phase, a substantial increase also occurred between winter and summer particulate total mercury masses (fig. 9).

For Devils Lake, the mass of mercury in winter was small relative to summer (fig. 9), and the mercury was mostly in

dissolved inorganic phase. The whole-water total mercury mass increased substantially (about 4 times) between winter

and summer, and relatively large increases also occurred in both dissolved and particulate methylmercury. At the shallow

more-upstream sites (sites 3 and 4), the increase in methylmercury between winter and summer was almost entirely in

particulate phase. The morphologic and limnologic characteristics at those sites may result in greater interaction and
 20

1 3 4 6 7 9 10 5

SITE NUMBER

Figure 8. Concentrations of total mercury for lake and wetland sites. CONCENTRATION, IN NANOGRAMS PER LITER

DISSOLVED TOTAL MERCURY

PARTICULATE TOTAL MERCURY

WHOLE-WATER TOTAL MERCURY

NO DATA NO DATA NO DATANO DATA NO DATA NO DATANO DATA NO DATA NO DATANO DATA NO DATA NO DATANO DATA NO DATA NO DATANO DATA NO DATA NO DATANO DATA NO DATA NO DATA

MINIMUM REPORTING LIMIT IS 0.04 NANOGRAM

PER LITER; "LESS-THAN" VALUES ARE PLOTTED

AT ONE-HALF THE MINIMUM REPORTING LIMIT

MINIMUM REPORTING LIMIT IS 0.04 NANOGRAM

PER LITER; "LESS-THAN" VALUES ARE PLOTTED

AT ONE-HALF THE MINIMUM REPORTING LIMIT

MINIMUM REPORTING LIMIT IS 0.02 NANOGRAM

PER LITER; "LESS-THAN" VALUES ARE PLOTTED

AT ONE-HALF THE MINIMUM REPORTING LIMIT

 EXPLANATION

Winter sampling period

 Near-surface sample

 Near-bottom sample

Summer sampling period

 Near-surface sample

 Near-bottom sample

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10
 21

Table 6. Concentrations of mercury constituents for Devils Lake and Lake Ashtabula, 1991-93[Wayne R. Berkas, U.S. Geological Survey, written commun., 2001; ng/L, nanograms per liter; --, no data]

Site number

(see figure 1

for location)

Site

identification

number

Site name Date

Methylmercury, dissolved

(ng/L)

Total mercury, dissolved

(ng/L)

Total mercury, whole water

(ng/L)

Near

surface

Middepth Near bottom Near surface Mid- depth Near bottom Near surface Mid- depth Near bottom

-- 480623099013400 Devils Lake Six Mile Bay 09/19/91 -- -- -- -- -- -- 2.80 -- ---- 480500098561000 Devils Lake Creel Bay 09/18/91 -- -- -- -- -- -- 2.60 -- --

03/22/93 -- -- 0.06 0.66 0.90 1.45 -- -- --

5 480147098572200 Devils Lake Main Bay 09/19/91 -- -- -- 2.10 -- .20 3.20 -- --

02/15/92 -- -- -- 1.00 1.00 1.00 2.30 1.70 2.0003/22/93 -- -- .10 .69 .90 .66 -- -- --

-- 480407098491900 Devils Lake East Bay West 09/19/91 -- -- -- 1.00 -- -- 1.30 -- --

7 475740098381600 East Devils Lake 09/18/91 -- -- -- 1.60 -- -- -- -- --

02/15/92 -- -- -- .40 1.80 1.00 1.10 2.00 1.0003/23/93 -- -- .09 .75 1.08 .13 -- -- --

10 05057500 Lake Ashtabula at Baldhill Dam,

North Dakota

03/10/93 -- -- -- .92 -- .50 -- -- --
 22

Table 7. Concentrations of mercury constituents for selected lakes in the Devils Lake and Sheyenne River Basins, 1991-93[Wayne R. Berkas, U.S. Geological Survey, written commun., 2001; ng/L, nanograms per liter; --, no data]

Site

identification

number

Site name Date

Methylmercury, dissolved

(ng/L)

Total mercury, dissolved

(ng/L)

Near surface Mid-depth Near bottom Near surface Mid-depth Near bottom

481335098492000 Sweetwater Lake near Webster 09/19/91 -- -- -- -- -- 11.40475150098210000 East Stump Lake near Perkin 09/18/91 -- -- -- -- -- 6.40475350098501300 Wood Lake 03/23/93 -- -- -- 0.45 -- 1.56474844098363800 Battle Lake 03/23/93 -- -- -- 2.51 -- --480032101314701 Rice Lake near Ryder 03/11/93 -- -- -- 1.59 -- --480137100011600 Round Lake north of Anamoose 03/11/93 -- -- -- -- -- .37470427098345800 Spiritwood Lake 03/15/93 0.03 0.04 -- .93 0.50 --473407097371600 Golden Lake 03/15/93 -- -- -- .64 -- --
 23

1 3 4 6 7 9 10 Devils

Lake

Lake

Ashtabula

5

SITE NUMBER

Figure 9. Masses of mercury constituents for lake and wetland sites.

DISSOLVED PHASE

PARTICULATE PHASE

WHOLE WATER

(DISSOLVED AND PARTICULATE PHASES COMBINED) 

 EXPLANATION

 

 Winter sampling period

 Summer sampling period

 Methylmercury

 Total mercury

0.01

0.1

1

10

100

1,000

10,000

0.01

0.1

1

10

100

1,000

10,000

0.01

0.1

1

10

100

1,000

10,000

MASS, IN GRAMS

CONCENTRATIONS LESSTHAN REPORTING LEVELCONCENTRATIONS LESSTHAN REPORTING LEVEL
 24

mixing between near-bottom areas and the entire water column, causing more particulate material (both organic and

inorganic), to which methylmercury adsorbs, to be suspended throughout the water column. At the deep more-downstream

sites (sites 5 and 6), the increase in methylmercury between winter and summer was substantial for both dissolved and

particulate phases. The characteristics at those sites may result in more stable stratification between the hypolimnion and

the upper water column, thus maintaining a larger part of methylmercury in dissolved phase. However, substantial

adsorption of methylmercury to particulate material still occurs. Most of the whole-water total mercury mass was in

dissolved inorganic phase (about 90 percent in winter and 50 percent in summer), indicating that (1) besides the

methylmercury that is being mobilized from the sediments by methylation of mercury, other important sources of mercury

exist and/or (2) the methylmercury that is being mobilized from the sediments is transformed to both dissolved and

particulate inorganic phases. Mechanisms that can transform methylmercury to inorganic mercury include microbiallymediated demethylation and photochemical degradation (Krabbenhoft, 1996; Krabbenhoft and others, 2000). Generally,

conditions suitable for methylation of mercury exist throughout the Devils Lake system. Ratios of whole-water

methylmercury to whole-water total mercury in summer near-bottom samples ranged from about 15 to 20 percent at the

Devils Lake sites (sites 3 through 7) (fig. 7). However, methylation of mercury in Devils Lake probably occurs at much

smaller rates than in the wetland, where the summer ratio was about 50 percent. It appears from this reconnaissance

investigation that mercury in Devils Lake exhibits an annual cycle with a summer maximum. Mercury may be removed

from the water column following the summer maximum by (1) adsorption to particulate material with subsequent

deposition to the sediments; (2) volatilization; and/or (3) uptake and bioaccumulation by aquatic organisms (Krabbenhoft

and Rickert, 1995).

For Lake Ashtabula, as for Devils Lake, the mass of mercury in winter was small relative to summer (fig. 9), and the

mercury was mostly in dissolved inorganic phase. Dissolved inorganic mercury accounted for about 80 percent of the total

mercury mass in winter and about 50 percent in summer. The whole-water total mercury mass increased substantially

between the winter and summer sampling periods (about 4 times), and relatively large increases also occurred in both

dissolved and particulate methylmercury. Methylmercury accounted for a relatively large proportion of total mercury in

Lake Ashtabula (fig. 7), especially at the deep site (site 10) near the dam. For site 9, the shallow more-upstream site, most

of the methylmercury was in dissolved phase. For site 10, the deep more-downstream site near the dam, the winter nearbottom sample had substantially larger methylmercury concentrations than the winter near-surface sample. However, the

summer near-bottom and near-surface samples had similar concentrations (fig. 7). Also, the ratio of whole-water

methylmercury to whole-water total mercury increased substantially between winter and summer near-surface samples.

Although field-measured properties and constituents showed fairly strong thermal stratification on the sampling days for

both the winter and summer sampling periods for site 10, the hydrologic and limnologic characteristics of Lake Ashtabula

(that is, the pattern of dam releases and the movement of water through the reservoir) may result in greater interaction and

mixing between near-bottom areas and the entire water column throughout the lake. Thus, methylmercury produced at the

sediment-water interface may be exposed to suspended material (to which it can adsorb) throughout the water column.

Lake Ashtabula probably has conditions favorable for methylation of mercury throughout most of the lake, and the

flowthrough characteristics of the reservoir may result in more even distribution of methylmercury throughout the water

column during summer.

Spearman’s rank-correlation procedure (Iman and Conover, 1983) was used to investigate relations between mercury

constituents and other water-quality properties and constituents for the lake and wetland sites (table 8). Concentrations for

all samples collected for the lake and wetland sites were included in the data set that was analyzed. Thus, sites where both

near-surface and near-bottom samples were collected had greater weight in the analysis than sites where only near-surface

samples were collected. However, differences between near-surface and near-bottom environments at a given site provide

useful information for discerning relations between mercury constituents and other water-quality properties and

constituents.

Generally, concentrations of individual mercury constituents in lakes and wetlands were correlated significantly with

other mercury constituents. This result might indicate that mercury is cycled between organic and inorganic phases and

also between dissolved and particulate phases. All mercury constituents were correlated positively with water temperature.

This result is consistent with observations of higher concentrations of mercury constituents in summer than in winter and

also might provide evidence that methylation plays an important role in contributing mercury to the water column.

Microbial breakdown of organic matter by sulfate reduction typically occurs at higher rates when temperatures increase

(Rheinheimer, 1974) and might result in higher mercury methylation rates. Most mercury constituents were correlated
 25

Table 8. Statistically significant results of Spearman’s rank-correlation procedure to investigate relations between mercury constituents and other

water-quality properties and constituents for lake and wetland sites

Mercury

constituent

Positive statistically significant correlations1

1

Statistical significance based on = 0.05; that is, p-value less than 0.05.

Negative statistically significant correlations1

Property or

constituent

Spearman’s

rho p-value Property orconstituent

Spearman’s

rho p-value

Dissolved

methylmercury

Particulate methylmercury 0.442 0.0304 Specific conductance -0.432 0.0344

Whole-water methylmercury 0.910 0 pH -0.531 0.0093

Dissolved total mercury 0.702 0.0006 Dissolved oxygen -0.540 0.0081

Particulate total mercury 0.401 0.0499

Whole-water total mercury 0.592 0.0037

Water temperature 0.448 0.0284

Whole-water manganese 0.480 0.0244

Particulate

methylmercury

Dissolved methylmercury 0.442 0.0304 Specific conductance -0.429 0.0354

Whole-water methylmercury 0.708 0.0005

Dissolved total mercury 0.616 0.0026

Particulate total mercury 0.862 0

Whole-water total mercury 0.822 0.0001

Water temperature 0.851 0

Suspended sediment 0.538 0.0268

Whole-water

methylmercury

Dissolved methylmercury 0.910 0 Specific conductance -0.593 0.0037

Particulate methylmercury 0.708 0.0005 Dissolved oxygen -0.417 0.0409

Dissolved total mercury 0.800 0.0001 Dissolved sulfate -0.432 0.0425

Particulate total mercury 0.620 0.0024

Whole-water total mercury 0.780 0.0001

Water temperature 0.678 0.0009

Suspended sediment 0.496 0.0411

Dissolved

total mercury

Dissolved methylmercury 0.702 0.0006

Particulate methylmercury 0.616 0.0026

Whole-water methylmercury 0.800 0.0001

Particulate total mercury 0.535 0.0088

Whole-water total mercury 0.859 0

Water temperature 0.611 0.0028

Suspended sediment 0.684 0.0048

Particulate

total mercury

Dissolved methylmercury 0.401 0.0499 Specific conductance -0.408 0.0452

Particulate methylmercury 0.862 0

Whole-water methylmercury 0.620 0.0024

Dissolved total mercury 0.535 0.0088

Whole-water total mercury 0.866 0

Water temperature 0.698 0.0006

Suspended sediment 0.620 0.0107

Whole-water

total mercury

Dissolved methylmercury 0.592 0.0037 Specific conductance -0.447 0.0285

Particulate methylmercury 0.822 0.0001

Whole-water methylmercury 0.780 0.0001

Dissolved total mercury 0.859 0

Particulate total mercury 0.866 0

Water temperature 0.739 0.0003

Suspended sediment 0.702 0.0039

α
 26

positively with suspended sediment, indicating the affinity for mercury to adsorb to particulate material and to cycle

between dissolved and particulate phases in the lakes and wetlands. Dissolved methylmercury was correlated negatively

with specific conductance, pH, and dissolved oxygen. Sulfate reduction occurs in low dissolved-oxygen environments, and

low pH values have been reported to be associated with methylation of mercury (U.S. Department of Commerce, National

Oceanic and Atmospheric Administration, National Ocean Service, 1996). The negative association between

methylmercury and specific conductance is unclear but may be related to sulfate inhibition of methylation. Sulfate

generally is the dominant anion contributing to the ionic strength of the lakes and wetlands sampled for this investigation.

Large concentrations of sulfate have been reported to inhibit methylation of mercury because of an accumulation of sulfide

that can bind available mercury ions (U.S. Department of Commerce, National Oceanic and Atmospheric Administration,

National Ocean Service, 1996). However, negative correlations between mercury constituents and sulfate individually

were not as strong as between mercury constituents and specific conductance. Also, the biological and chemical

interactions that affect sulfate reduction, availability of mercury for methylation, and the inhibitory effects of sulfide on

methylation of mercury are complex and site specific; previously reported patterns in sulfate inhibition of methylation do

not appear to directly apply to the lakes and wetlands sampled for this investigation.

Rivers

Whole-water methylmercury concentrations in water samples from river sites were relatively large and ranged from

0.45 to 1.13 nanograms per liter for the Starkweather Coulee site (site 2), from 0.20 to 1.44 nanograms per liter for the

Sheyenne River sites (sites 8, 11, and 12), and from 0.15 to 0.47 nanogram per liter for the Red River of the North and Red

Lake River sites (sites 13 through 16) (supplement 6; fig. 10). Most sites had methylmercury concentrations that exceeded

0.10 nanogram per liter, which might be considered the upper end of the range of typical aquatic concentrations throughout

the United States (Krabbenhoft and others, 1999). However, the concentrations were only slightly larger than

concentrations reported for streams in Wisconsin drainage basins that were dominated by wetlands, agriculture, and/or

forested areas (Hurley and others, 1995). Generally, methylmercury concentrations for most sites increased between

spring and summer for both dissolved and particulate phases, and most of the increase was caused by methylmercury in

particulate phase. Starkweather Coulee (site 2), which drains an area dominated by wetlands, had the largest dissolved

methylmercury concentrations for both sampling periods. The summer concentration for site 2 was very large, indicating

that conditions in the Starkweather Coulee channel or in water bodies that flow into the channel were favorable for

methylation of mercury. According to Hurley and others (1995), streams that drain wetland areas tend to have larger

methylmercury concentrations than streams that drain either agricultural or forested areas. Methylmercury concentrations

also were large for the Sheyenne River near Kindred (site 12). Concentrations increased between sites 11 and 12 for both

sampling periods, and most of the increase was caused by methylmercury in particulate phase. Thus, methylation

conditions may be favorable in the Sheyenne River channel between sites 11 and 12 or in water bodies that flow into that

reach. Also, methylmercury concentrations between sites 11 and 12 may be affected by channel hydraulics and

morphology and the degree to which sediments are resuspended and transported at the two sites. Lake Ashtabula is located

between sites 8 and 11 and methylmercury concentrations generally are similar between the two sites. However, for the

sampling period, methylmercury concentrations increased between the two sites. Also, the summer ratio of whole-water

methylmercury to whole-water total mercury for site 11 (13.5 percent) was larger than for either site 8 (3.5 percent) or

site 12 (11.0 percent) (fig. 10). These patterns may indicate favorable conditions for methylation of mercury in Lake

Ashtabula. Ratios of whole-water methylmercury to whole-water total mercury were less than 8 percent for the Red River

of the North or Red Lake River sites (fig. 10).

Whole-water total mercury concentrations ranged from 3.22 to 6.33 nanograms per liter for the Starkweather Coulee

site (site 2), from 2.00 to 17.84 nanograms per liter for the Sheyenne River sites (sites 8, 11, and 12), and from 5.73 to

26.90 nanograms per liter for the Red River of the North and Red Lake River sites (sites 13 through 16) (supplement 6;

fig. 11). Generally, the concentrations were small to moderately large. Only a few samples had concentrations that

exceeded 10 nanograms per liter, which might be considered the upper end of the range of typical aquatic concentrations at

locations where the dominant sources of mercury are naturally occurring or result from atmospheric deposition

(Krabbenhoft, 1996). Whole-water total mercury concentrations for rivers sampled for this investigation also were

generally similar to concentrations reported for uncontaminated streams in Wisconsin (Hurley and others, 1995); generally

similar to concentrations reported for the Minnesota River, which is in an agriculture-dominated basin in South Dakota,

Minnesota, and Iowa (Balogh and others, 1997); and generally larger than concentrations reported for the St. Croix and

upper Mississippi Rivers in Minnesota, which are in basins that are dominated by uncultivated forest and wetland areas
 27

40

30

20

10

0

0.01

0.1

1

10

0.01

0.1

1

10

0.01

0.1

1

10

SITE NUMBER

CONCENTRATION, IN NANOGRAMS PER LITER RATIO, IN PERCENT

DISSOLVED METHYLMERCURY

PARTICULATE METHYLMERCURY

WHOLE-WATER METHYLMERCURY

Figure 10. Concentrations of methylmercury and ratios of whole-water methylmercury to

whole-water total mercury for river sites.

EXPLANATION

 Spring sampling period

 Summer sampling period

2 8 11 12 13 14 15 16

SHEYENNE RIVER ENTERS

RED RIVER OF THE NORTH

IN INTERVENING REACH

LAKE ASHTABULA IS LOCATED

IN INTERVENING REACH

SHEYENNE RIVER ENTERS

RED RIVER OF THE NORTH

IN INTERVENING REACH

LAKE ASHTABULA IS LOCATED

IN INTERVENING REACH

SHEYENNE RIVER ENTERS

RED RIVER OF THE NORTH

IN INTERVENING REACH

LAKE ASHTABULA IS LOCATED

IN INTERVENING REACH
 28

0.1

1

10

100

0.1

1

10

100

0.1

1

10

100

SITE NUMBER

CONCENTRATION, IN NANOGRAMS PER LITER

DISSOLVED TOTAL MERCURY

PARTICULATE TOTAL MERCURY

WHOLE-WATER TOTAL MERCURY

Figure 11. Concentrations of total mercury for river sites.

EXPLANATION

 Spring sampling period

 Summer sampling period

2 8 11 12 13 14 15 16

SHEYENNE RIVER ENTERS

RED RIVER OF THE NORTH

IN INTERVENING REACH

LAKE ASHTABULA IS LOCATED

IN INTERVENING REACH

SHEYENNE RIVER ENTERS

RED RIVER OF THE NORTH

IN INTERVENING REACH

LAKE ASHTABULA IS LOCATED

IN INTERVENING REACH

SHEYENNE RIVER ENTERS

RED RIVER OF THE NORTH

IN INTERVENING REACH

LAKE ASHTABULA IS LOCATED

IN INTERVENING REACH
 29

(Balogh and others, 1998). For Starkweather Coulee (site 2) and the two most-upstream sites on the Sheyenne River

(sites 8 and 11), dissolved total mercury concentrations generally were similar to particulate total mercury concentrations.

For sites 12 through 16, particulate total mercury accounted for most of the whole-water total mercury. However,

particulate total mercury concentrations decreased between sites 8 and 11, possibly indicating that Lake Ashtabula acts as a

sink for that constituent. The large increase in particulate total mercury concentrations between sites 11 and 12 was similar

in magnitude to the increase in suspended-sediment concentrations for those sites (fig. 5) and probably indicates that

mercury at site 12 primarily is inorganic and adsorbed to suspended sediment. Total mercury concentrations for the

Sheyenne River and Red Lake River sites generally were similar for the spring and summer sampling periods, but

concentrations for the Red River of the North sites generally increased during the summer sampling period. The

differences between spring and summer concentrations may be a result of site-specific differences in composition of

suspended sediment and partitioning of mercury between dissolved and various particulate phases (Hurley and others,

1995). Whole-water total mercury concentrations at all sites were at levels that would not be considered extreme.

Loads of mercury constituents for the river sites are shown in figure 12. Consideration of the loads for the river sites is

particularly relevant to the purpose of this report. If an outlet from Devils Lake to the Sheyenne River is constructed,

discharge of the Sheyenne River downstream from the proposed diversion will increase. Although the mixing of water

from Devils Lake with the Sheyenne River may or may not result in substantial differences in concentrations of mercury

constituents in the Sheyenne River, the mixing will result in an increase in the load of mercury transported in the river. An

understanding of how loads of mercury constituents currently are transported in the Sheyenne River and the Red River of

the North will aid in assessing the effects of increased mercury loads downstream from the proposed outlet.

Direct comparison of loads between sampling sites within a given sampling period is complicated by relative

differences in discharge conditions that may have existed between the sites at the time of sampling. In addition to

discharge being a variable in the calculation of loads, discharge also can strongly affect mercury concentrations. Mercury

can readily adsorb to suspended particulate material and concentrations of suspended particulate material in streams is

strongly dependent on flow conditions (Grigal, 2002). Discharges for the Sheyenne River, Red River of the North, and Red

Lake River sites are shown in figure 13, and nonexceedance frequencies for the discharges at the time of sampling are given

in table 9. The nonexceedance frequencies provide information on flow conditions at the time of sampling relative to

typical flow conditions for that time of year. Nonexceedance frequencies were determined by statistically comparing

discharges on the specific day of sampling with daily discharges for the same day for the entire period of record for the site.

For example, a nonexceedance frequency of 90 percent for the Sheyenne River near Warwick (table 9) for April 30, 2001,

indicates that a discharge of 460 cubic feet per second exceeds 90 percent of all daily discharges recorded at the site on

April 30 for the entire period of record. Thus, a nonexceedance frequency of 90 percent would indicate much-abovenormal flow conditions for the given day.

The hydrographs and the times of sampling for the river sites (fig. 13) indicate that for the spring sampling period, all

samples were collected on receding limbs of large runoff events. Nonexceedance frequencies for the Sheyenne River, Red

River of the North, and Red Lake River sites ranged from 81 to 97 percent and indicate that spring flow conditions were

much-above normal. Flows steadily declined after the peak snowmelt runoff in early April except for a few relatively

minor runoff events. For the summer sampling period, flow conditions at all sites also were fairly similar. Generally, the

summer samples were collected near the peak or on receding limbs of relatively small runoff events. Nonexceedance

frequencies for the summer sampling period (table 9) ranged from 79 to 96 percent and again indicate that flow conditions

at all sites were much-above normal. Generally, flow conditions for both sampling periods were reasonably similar among

the different sites relative to timing with respect to runoff events and also relative to typical flow conditions for the given

times of year. Thus, coarse comparisons of loads of mercury constituents between the different sites are justified.

For Starkweather Coulee (site 2), the loads of total mercury decreased substantially between the spring and summer

sampling periods (fig.12), primarily because of a decrease in discharge of about 75 percent (supplement 2). However, even

with the substantial decrease in discharge, the load of dissolved methylmercury increased between spring and summer, and

the summer ratio of whole-water methylmercury to whole-water total mercury was 35 percent (fig. 10). Thus, the

observation that the Starkweather Coulee channel and/or water bodies that flow into the channel have favorable conditions

for methylation of mercury, especially during summer, is further supported.

For the Sheyenne River, loads of whole-water total mercury generally were small at sites 8 and 11 for both sampling

periods and increased substantially at site 12, especially for the spring sampling period (fig. 12). For the spring sampling
 30

2 8 11 13 15 16 12 14

SITE NUMBER

Figure 12. Loads of mercury constituents for river sites.

DISSOLVED PHASE

PARTICULATE PHASE

WHOLE WATER

(DISSOLVED AND PARTICULATE PHASES COMBINED) 

 EXPLANATION

 

 Spring sampling period

 Summer sampling period

 Methylmercury

 Total mercury

0.01

0.1

1

10

100

1,000

0.01

0.1

1

10

100

1,000

0.01

0.1

1

10

100

1,000

LOAD, IN GRAMS PER DAY
 31

10

100

1,000

10,000

100,000

3/1/2001 3/31/2001 5/1/2001 5/31/2001 7/1/2001 7/31/2001 8/31/2001 9/30/2001

 EXPLANATION

Site 8, station number 05056000, Sheyenne River near Warwick, North Dakota

Site 11, station number 05058000, Sheyenne River below Baldhill Dam, North Dakota

Site 12, station number 05059000, Sheyenne River near Kindred, North Dakota

Site 13, station number 05054000, Red River of the North at Fargo, North Dakota

Site 14, station number 05064500, Red River of the North at Halstad, Minnesota

Site 15, station number 05080000, Red Lake River at Fisher, Minnesota

Site 16, station number 05102500, Red River of the North at Emerson, Manitoba

Time of sampling

DISCHARGE, IN CUBIC FEET PER SECOND

Figure 13. Discharge and times of sampling for the Sheyenne River, Red River of the North, and Red Lake River sites.
 32

period, particulate total mercury loads were similar between sites 8 and 11 although discharge increased by about

60 percent between the two sites. For the summer sampling period, particulate and whole-water total mercury loads

decreased between sites 8 and 11 although discharges were similar between the two sites. These patterns possibly indicate

the effects of Lake Ashtabula as a mercury sink. The larger whole-water total mercury loads at site 12 occurred primarily

in the particulate inorganic phase and probably are a function of increased suspended-sediment transport at site 12. Ratios

of whole-water methylmercury to whole-water total mercury generally were near or less than 10 percent for the Sheyenne

River sites. The largest ratio for any Sheyenne River site (13.5 percent) was recorded at site 11 for the summer sampling

period and may indicate favorable conditions for methylation of mercury in Lake Ashtabula. The loads of whole-water

total mercury for site 12 decreased substantially between the spring and summer sampling periods, primarily because of a

decrease in discharge of about 82 percent (supplement 2).

For the Red River of the North, loads of total mercury increased substantially between sites 13 and 14 for both

sampling periods (fig. 12). The Sheyenne River enters the Red River of the North in the intervening reach, but the increase

in load between the two sites was much larger than can be accounted for by inputs from the Sheyenne River. For example,

the loads of whole-water total mercury transported in the Sheyenne River near Kindred (site 12) were about 70 and

10 grams per day for the spring and summer sampling periods, respectively, but the increases in loads between sites 13 and

14 were about 600 and 200 grams per day for the spring and summer sampling periods, respectively. The substantial

increase in load between sites 13 and 14 indicates that important sources of mercury, in addition to the Sheyenne River,

exist in the intervening reach. These sources of mercury may include contributions from other tributaries, flux of mercury

from stream sediments, atmospheric deposition, and various sources associated with the city of Fargo. Loads of mercury

for sites 14 and 16 were similar although a 70-percent increase in discharge occurred between the two sites during the

spring sampling period (supplement 2). This may indicate that tributary inflows between the two sites had negligible loads

of mercury and/or that various processes that remove mercury from the water column were occurring between the two

sites. Possible mechanisms for removal of mercury from the water column include volatilization, deposition in sediments,

and uptake by biota (Krabbenhoft and Rickert, 1995).

Table 9. Nonexceedance frequencies for discharges at time of sampling for river sites

[--, not determined]

Site number

(see figure 1

for location)

Site name Date

Discharge

(cubic feet

per second)

Nonexceedance

frequency

(percent)

2 Starkweather Coulee near Webster, North Dakota 04/30/01

07/24/01

220

56

89

70

8 Sheyenne River near Warwick, North Dakota 04/30/01

07/24/01

460

380

90

96

11 Sheyenne River below Baldhill Dam, North Dakota 05/01/01

07/24/01

720

370

81

84

12 Sheyenne River near Kindred, North Dakota 05/01/01

07/25/01

1,650

290

86

79

13 Red River of the North at Fargo, North Dakota 05/01/01

07/25/01

7,700

2,880

97

96

14 Red River of the North at Halstad, Minnesota 05/01/01

07/25/01

23,500

5,050

95

93

15 Red Lake River at Fisher, Minnesota 05/01/01

07/25/01

4,660

1,760

--

--

16 Red River of the North at Emerson, Manitoba 05/02/01

07/26/01

40,000

6,100

--

--
 33

Results of Spearman’s rank-correlation procedure (Iman and Conover, 1983) for the river sites (table 10) indicated

dissolved methylmercury was correlated positively with organic-carbon constituents and negatively with discharge. This

pattern may indicate that smaller tributaries in wetland-dominated basins may serve as primary areas for the production of

methylmercury and from which methylmercury is contributed to the river systems. Total mercury constituents generally

were correlated positively with discharge and suspended sediment. These relations, along with the fact that nearly all

mercury in the water at the river sites is in inorganic particulate phase (figs. 10 and 11), support previous observations that

processes that result in mobilization, suspension, and transport of sediment largely govern concentrations of total mercury

for the river sites. The strong correlation between whole-water total mercury concentrations and suspended-sediment

concentrations is similar to relations reported for sites on the Minnesota River (Balogh and others, 1997).

Possible Effects from Devils Lake Outlet

The proposed plans for an outlet from Devils Lake include pumping water from the southern part of Devils Lake West

Bay, an area represented by site 4 in this investigation, into the Sheyenne River channel in the reach between sites 8 and 9.

Although the number of samples collected during this investigation is small, results indicated concentrations of both

methylmercury and total mercury constituents for site 4 were less than concentrations for site 8 for both sampling periods.

Thus, an outlet probably would not have adverse effects on mercury concentrations in the Sheyenne River upstream from

Lake Ashtabula. However, because discharges in the Sheyenne River would increase during some periods, the loads of

mercury entering Lake Ashtabula also would increase. To completely evaluate the effects of the increased loads into Lake

Ashtabula, further data collection is needed. However, some general observations can be made. Lake Ashtabula probably

Table 10. Statistically significant results of Spearman’s rank-correlation procedure to investigate relations between mercury constituents and other

water-quality properties and constituents for river sites

Mercury constituent

Positive statistically significant correlations1

1

Statistical significance based on = 0.05; that is, p-value less than 0.05.

Negative statistically significant correlations1

Property or

constituent

Spearman’s

rho p-value Property orconstituent

Spearman’s

rho p-value

Dissolved methylmercury Whole-water methylmercury 0.6024 0.0200 Discharge -0.8542 0.0009

Dissolved organic carbon 0.7364 0.0044 Particulate total mercury -0.5287 0.0400

Whole-water organic carbon 0.7761 0.0027

Particulate methylmercury Dissolved calcium 0.5725 0.0270

Whole-water methylmercury 0.7294 0.0048

Particulate total mercury 0.6971 0.0071

Whole-water total mercury 0.7824 0.0025

Suspended sediment 0.6434 0.0164

Whole-water methylmercury Water temperature 0.6824 0.0084 Dissolved oxygen -0.5092 0.0480

Dissolved calcium 0.6416 0.0132

Dissolved methylmercury 0.6024 0.0200

Particulate methylmercury 0.7294 0.0048

Dissolved total mercury Whole-water manganese 0.7563 0.0489

Particulate total mercury Discharge 0.5853 0.0238 Dissolved potassium -0.5313 0.0391

Whole-water total mercury 0.9529 0.0002 Dissolved sulfate -0.5618 0.0292

Suspended sediment 0.8668 0.0012 Dissolved organic carbon -0.7029 0.0064

Whole-water organic carbon -0.7324 0.0045

Whole-water total mercury Suspended sediment 0.8758 0.0011 Dissolved organic carbon -0.6765 0.0064

Whole-water organic carbon -0.6971 0.0068

α
 34

serves as a sink for suspended sediment (fig. 5) and whole-water total mercury (fig. 11) and most of the whole-water total

mercury that occurs in the downstream part of the Sheyenne River originates downstream from Lake Ashtabula. Thus, a

Devils Lake outlet probably would not have substantial effects on mercury concentrations or loads in the downstream part

of the Sheyenne River or in the Red River of the North. More substantial effects could occur for Lake Ashtabula. Lake

Ashtabula is a hypereutrophic lake and conditions for methylation of mercury can be favorable, as evidenced by large

methylmercury concentrations and large ratios of whole-water methylmercury to whole-water total mercury (fig. 7). The

fact that loads of mercury in the Sheyenne River downstream from Lake Ashtabula are slightly less than loads upstream

from Lake Ashtabula may indicate that processes that prevent transport of methylmercury downstream are occurring in

Lake Ashtabula. These processes could include sedimentation, demethylation and subsequent volatilization, and/or uptake

and bioaccumulation by aquatic organisms (Krabbenhoft and Rickert, 1995). A detailed study of the mass balance of

mercury constituents in Lake Ashtabula and the Sheyenne River would be needed to fully address the fate of mercury in

Lake Ashtabula and the possible effects of a Devils Lake outlet on mercury in Lake Ashtabula.

SUMMARY AND CONCLUSIONS

Devils Lake rose dramatically during the 1990’s, and flood damages in the Devils Lake Basin have exceeded

$400 million. Because of the potential for continued lake-level rises and the potential for additional damages, the U.S.

Army Corps of Engineers has been conducting engineering and environmental studies to evaluate the feasibility of

constructing and operating an outlet from Devils Lake. The occurrence of mercury in the Red River of the North Basin and

the potential for increased loading of mercury into the Sheyenne River as a result of a constructed outlet from Devils Lake

needed to be considered and evaluated as part of the studies.

Water samples were collected at 16 lake, wetland, and river sites in the Devils Lake, Sheyenne River, Red River of the

North, and Red Lake River Basins and analyzed for selected field-measured properties and constituents and laboratorymeasured major-ion, trace-element, suspended-sediment, mercury, and organic-carbon constituents. Lake and wetland

sites were sampled in winter during ice cover and in late summer during peak heating conditions. River sites were sampled

during spring-runoff conditions and in late summer during low-flow/peak heating conditions.

Generally, the lake and wetland sites tended to be moderately alkaline and of relatively high ionic strength. Deep lake

sites generally showed relatively strong thermal stratification with substantial near-bottom dissolved oxygen depletion

during both winter and summer sampling periods, and shallow lake sites did not show strong thermal stratification in either

sampling period. River sites tended to be moderately alkaline and of moderate ionic strength. Dissolved-oxygen

concentrations generally were near saturation during spring-runoff conditions and no more than moderately depleted

during the summer sampling period. For all sampling sites, sulfate concentrations were much larger than the minimum

concentration required for sulfate reduction and also were much larger than concentrations reported to inhibit methylation

of mercury. However, biological and chemical interactions that affect sulfate reduction and the inhibitory effects of sulfide

on methylation of mercury are complex and site specific.

Whole-water methylmercury concentrations for the lake and wetland sites ranged from 0.39 to 3.53 nanograms per

liter for the wetland site, from less than 0.04 to 0.34 nanogram per liter for the Devils Lake sites, and from less than 0.04 to

0.46 nanogram per liter for the Lake Ashtabula sites. For the winter sampling period, most of the methylmercury in water

samples from the lake and wetland sites was in dissolved phase, and concentrations generally were less than the reporting

level of 0.04 nanogram per liter. Summer methylmercury concentrations generally were greater than winter

methylmercury concentrations, and the whole-water methylmercury concentration for the wetland site was large.

However, summer particulate methylmercury concentrations were relatively larger than winter concentrations, probably

because of larger amounts of suspended particulate organic and inorganic materials that adsorb mercury during summer.

Generally, near-bottom samples had larger dissolved methylmercury concentrations than near-surface samples for both

sampling periods, possibly indicating production of methylmercury by sulfate reduction at the sediment-water interface

and/or photodegradation of methylmercury near the water surface.

For the lake and wetland sites, whole-water total mercury concentrations ranged from 1.43 to 7.02 nanograms per liter

for the wetland site, from 0.38 to 2.98 nanograms per liter for the Devils Lake sites, and from 0.63 to 3.11 nanograms per

liter for the Lake Ashtabula sites. The wetland site had the largest whole-water total mercury concentrations for both

sampling periods (1.43 and 7.02 nanograms per liter for the winter and summer sampling periods, respectively). Both
 35

dissolved and particulate total mercury concentrations were larger for the summer sampling period than for the winter

sampling period for the various sites. Relative differences in total mercury concentrations between near-surface samples

and near-bottom samples varied among the sites.

For the wetland site, methylmercury comprised a substantial part of total mercury for both the winter and summer

sampling periods (about 25 to 50 percent) and was almost entirely in dissolved phase. The summer methylmercury

concentration was about 10 times greater than the winter methylmercury concentration, and most of the methylmercury

comprising the increase was in dissolved phase. This indicates that the wetland site has favorable conditions for

methylation of mercury and that production of methylmercury in the sediments is a primary factor governing mercury

processes in the wetland.

For Devils Lake, the mass of mercury in winter was small relative to summer, and the mercury was mostly in dissolved

inorganic phase. The whole-water total mercury mass increased substantially between winter and summer, and relatively

large increases also occurred in both dissolved and particulate methylmercury. At the shallow more-upstream sites, the

increase in methylmercury between winter and summer was almost entirely in particulate phase. The morphologic and

limnologic characteristics at those sites may result in greater interaction and mixing between near-bottom areas and the

entire water column, causing more particulate material, to which methylmercury adsorbs, to be suspended throughout the

water column. At the deep more-downstream sites, the increase in methylmercury between winter and summer was

substantial for both dissolved and particulate phases. The characteristics at those sites may result in more stable

stratification between the hypolimnion and the upper water column, thus maintaining a larger part of methylmercury in

dissolved phase. However, substantial adsorption of methylmercury to particulate material still occurs. Most of the wholewater total mercury mass was in dissolved inorganic phase, indicating that besides the methylmercury that is being

mobilized from the sediments by methylation of mercury, other important sources of mercury exist and/or methylmercury

that is being mobilized from the sediments is transformed to both dissolved and particulate inorganic phases. Generally,

conditions suitable for methylation of mercury exist throughout the Devils Lake system. Ratios of whole-water

methylmercury to whole-water total mercury in summer near-bottom samples ranged from about 15 to 20 percent at the

Devils Lake sites. It appears from this reconnaissance investigation that mercury in Devils Lake exhibits an annual cycle

with a summer maximum.

For Lake Ashtabula, as for Devils Lake, the mass of mercury in winter was small relative to summer, and the mercury

was mostly in dissolved inorganic phase. Dissolved inorganic mercury accounted for about 80 percent of the total mercury

mass in winter and about 50 percent in summer. The whole-water total mercury mass increased substantially between the

winter and summer sampling periods, and relatively large increases also occurred in both dissolved and particulate

methylmercury. Methylmercury accounted for a relatively large proportion of total mercury in Lake Ashtabula, especially

at the deep site near the dam. For the shallow more-upstream site, most of the methylmercury was in dissolved phase. For

the deep more-downstream site near the dam, the winter near-bottom sample had substantially larger methylmercury

concentrations than the winter near-surface sample. However, the summer near-bottom and near-surface samples had

similar concentrations. Also, the ratio of whole-water methylmercury to whole-water total mercury increased substantially

between winter and summer near-surface samples. Although field-measured properties and constituents showed fairly

strong thermal stratification at the deep more-downstream site, the hydrologic and limnologic characteristics of Lake

Ashtabula (that is, the pattern of dam releases and the movement of water through the reservoir) may result in greater

interaction and mixing between near-bottom areas and the entire water column throughout the lake. Thus, methylmercury

produced at the sediment-water interface may be exposed to suspended material (to which it can adsorb) throughout the

water column. Lake Ashtabula probably has conditions favorable for methylation of mercury throughout most of the lake,

and the flowthrough characteristics of the reservoir may result in more even distribution of methylmercury throughout the

water column during summer.

For the river sites, whole-water methylmercury concentrations were relatively large and ranged from 0.45 to

1.13 nanograms per liter for the Starkweather Coulee site, from 0.20 to 1.44 nanograms per liter for the Sheyenne River

sites, and from 0.15 to 0.47 nanogram per liter for the Red River of the North and Red Lake River sites. Generally,

methylmercury concentrations for most sites increased between spring and summer for both dissolved and particulate

phases, and most of the increase was caused by methylmercury in particulate phase. Starkweather Coulee, which drains an

area dominated by wetlands, had the largest dissolved methylmercury concentrations for both sampling periods, indicating

that conditions in the Starkweather Coulee channel or in the water bodies that flow into the channel were favorable for

methylation of mercury. Methylmercury concentrations also were large for the Sheyenne River near Kindred.
 36

Methylmercury concentrations in the Sheyenne River increased between the Sheyenne River below Baldhill Dam site and

the Sheyenne River near Kindred site for both sampling periods, and most of the increase was caused by methylmercury in

particulate phase. Thus, methylation conditions may be favorable in the Sheyenne River channel between those sites or in

water bodies that flow into that reach. Also, methylmercury concentrations between those sites may be affected by channel

hydraulics and morphology and the degree to which sediments are resuspended and transported at the two sites. Lake

Ashtabula is located between the Sheyenne River near Warwick site and the Sheyenne River below Baldhill Dam site.

Although methylmercury concentrations generally are similar between the two sites, patterns in the methylmercury

concentrations and in the ratios of whole-water methylmercury to whole-water total mercury may indicate favorable

conditions for methylation of mercury in Lake Ashtabula. Ratios of whole-water methylmercury to whole-water total

mercury were less than 8 percent for the Red River of the North and Red Lake River sites.

Whole-water total mercury concentrations ranged from 3.22 to 6.33 nanograms per liter for the Starkweather Coulee

site, from 2.00 to 17.84 nanograms per liter for the Sheyenne River sites, and from 5.73 to 26.90 nanograms per liter for the

Red River of the North and Red Lake River sites. For Starkweather Coulee and the two most-upstream sites on the

Sheyenne River, dissolved total mercury concentrations generally were similar to particulate total mercury concentrations.

For sites on the downstream part of the Sheyenne River and on the Red River of the North and the Red Lake River,

particulate total mercury accounted for most of the whole-water total mercury. However, particulate total mercury

concentrations decreased between the Sheyenne River near Warwick site and the Sheyenne River below Baldhill Dam site,

possibly indicating that Lake Ashtabula acts as a sink for that constituent. The large increase between the Sheyenne River

below Baldhill Dam site and the Sheyenne River near Kindred site was similar in magnitude to the increase in suspendedsediment concentrations for those sites and probably indicates that mercury in the Sheyenne River near Kindred is

inorganic and adsorbed to suspended sediment. Total mercury concentrations for the Sheyenne River and Red Lake River

sites generally were similar for the spring and summer sampling periods, but concentrations for the Red River of the North

sites generally increased during the summer sampling period. The differences between spring and summer concentrations

may be a result of site-specific differences in composition of suspended sediment and partitioning of mercury between

dissolved and various particulate phases.

For Starkweather Coulee, the loads of total mercury decreased substantially between the spring and summer sampling

periods, primarily because of a decrease in discharge of about 75 percent. However, the load of dissolved methylmercury

increased between spring and summer, and the summer ratio of whole-water methylmercury to whole-water total mercury

was 35 percent. Methylation conditions probably are favorable in the Starkweather Coulee channel or in water bodies that

flow into the channel.

For the Sheyenne River, loads of whole-water total mercury generally were small at the Sheyenne River near Warwick

and the Sheyenne River below Baldhill Dam sites for both sampling periods and increased substantially at the Sheyenne

River near Kindred site, especially for the spring sampling period. Patterns in particulate and whole-water total mercury

loads for the Sheyenne River near Warwick and the Sheyenne River below Baldhill Dam sites possibly indicate the effects

of Lake Ashtabula as a mercury sink. The larger whole-water total mercury loads at the Sheyenne River near Kindred site

occurred primarily in particulate phase and probably are a function of increased suspended-sediment transport at the site.

Although the ratios of whole-water methylmercury to whole-water total mercury generally were near or less than

10 percent for the Sheyenne River sites, the largest ratio (13.5 percent) was recorded at the Sheyenne River below Baldhill

Dam site for the summer sampling period and may indicate favorable conditions for methylation of mercury in Lake

Ashtabula. The loads of whole-water total mercury for the Sheyenne River near Kindred site decreased substantially

between the spring and summer sampling periods, primarily because of a decrease in discharge of about 82 percent.

For the Red River of the North, loads of total mercury increased substantially between the Red River of the North at

Fargo site and the Red River of the North at Halstad site for both sampling periods. The Sheyenne River enters the Red

River of the North in the intervening reach, but the increase in load between the two sites was much larger than can be

accounted for by inputs from the Sheyenne River. Other sources of mercury, including contributions from other tributaries,

flux of mercury from stream sediments, atmospheric deposition, and various sources associated with the city of Fargo, may

be contributing to the increases in mercury loads between Fargo and Halstad. Loads of mercury for the Red River of the

North at Halstad and the Red River of the North at Emerson sites were similar although a 70-percent increase in discharge

occurred between the two sites during the spring sampling period. This may indicate that tributary inflows between the two

sites had negligible loads of mercury or that various processes that remove mercury from the water column were occurring

between the two sites.
 37

The proposed plans for an outlet from Devils Lake include pumping water into the Sheyenne River channel. Although

the number of samples collected during this investigation is small, results indicated an outlet probably would not have

adverse effects on mercury concentrations in the Sheyenne River upstream from Lake Ashtabula. However, because

discharges in the Sheyenne River would increase during some periods, the loads of mercury entering Lake Ashtabula also

would increase. Lake Ashtabula probably serves as a sink for suspended sediment and whole-water total mercury, and

most of the whole-water total mercury that occurs in the downstream part of the Sheyenne River originates downstream

from Lake Ashtabula. Thus, a Devils Lake outlet probably would not have substantial effects on mercury concentrations or

loads in the downstream part of the Sheyenne River or in the Red River of the North. More substantial effects could occur

for Lake Ashtabula. Lake Ashtabula is a hypereutrophic lake and conditions for methylation of mercury can be favorable,

as evidenced by large methylmercury concentrations and large ratios of whole-water methylmercury to whole-water total

mercury. The fact that loads of mercury in the Sheyenne River downstream from Lake Ashtabula are slightly less than

loads upstream from Lake Ashtabula may indicate that processes that prevent transport of methylmercury downstream are

occurring in Lake Ashtabula. A detailed study of the mass balance of mercury constituents in Lake Ashtabula and the

Sheyenne River would be needed to fully address the fate of mercury in Lake Ashtabula and the possible effects of a Devils

Lake outlet on mercury in Lake Ashtabula.

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no. 9, p. 1418-1423.

Rheinheimer, Gerhard, 1974, Aquatic microbiology: New York, John Wiley and Sons, 184 p.
 39

St. Louis, V.L., Rudd, J.W.M., Kelly, C.A., Beaty, K.G., Bloom, N.S., and Flett, R.J., 1994, Importance of wetlands as sources of

methyl mercury to boreal forest ecosystems: Canadian Journal of Fisheries and Aquatic Sciences, v. 51, p. 1065-1076.

Stoner, J.D., Lorenz, D.L., Wiche, G.J., and Goldstein, R.M., 1993, Red River of the North Basin, Minnesota, North Dakota, and South

Dakota: Water Resources Bulletin, v. 29, no. 4, p. 575-615.

Stoner, J.D., Lorenz, D.L., Goldstein, R.M., Brigham, M.E., and Cowdery, T.K., 1998, Water quality in the Red River of the North

Basin, Minnesota, North Dakota, and South Dakota, 1992-95: U.S. Geological Survey Circular 1169, 33 p.

Taylor, J.K., 1987, Quality assurance of chemical measurements: Chelsea, Michigan, Lewis Publishers, 328 p.

Tornes, L.H., Brigham, M.E., and Lorenz, D.L., 1997, Nutrients, suspended sediment, and pesticides in streams in the Red River of the

North Basin, Minnesota, North Dakota, and South Dakota, 1993-95: U.S. Geological Survey Water-Resources Investigations

Report 97-4053, 70 p.

U.S. Army Corps of Engineers, 2002, Baldhill Dam and Reservoir near Valley City, ND: accessed March 29, 2002, at URL

http://www.mvp-wc.usace.army.mil/projects/Baldhill.shtml.

U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Data Service, 1982, Monthly

normals of temperature, precipitation, and heating and cooling degree days, 1941-70 (Minnesota, North Dakota, and South Dakota):

Asheville, North Carolina, Climatography of the United States, No. 81.

U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service, 1996, Contaminants in

aquatic habitats at hazardous waste sites--Mercury: NOAA Technical Memorandum NOS ORCA 100, 64 p.

U.S. Environmental Protection Agency, 1996, Method 1669--Sampling ambient water for trace metals at EPA water-quality criteria

levels: EPA Report 821/R-96-011, Office of Water, Engineering and Analysis Division (4303), Washington, D.C., 37 p.

U.S. Environmental Protection Agency, 1997, Mercury study report to Congress, volume V--Health effects of mercury and mercury

compounds: U.S. Environmental Protection Agency EPA-452/R-97-007, 349 p.

U.S. Environmental Protection Agency, Methylmercury--Ambient human health: accessed February 8, 2001, at URL

http://www.epa.gov/waterscience/criteria/methylmercury/factsheet.html.

U.S. Environmental Protection Agency, 2001, Method 1631, Revision D--Mercury in water by oxidation, purge and trap, and cold

vapor atomic fluorescence spectrometry, Draft method: EPA Report 821-R-01-033, Office of Water, Engineering and Analysis

Division, Washington, D.C., 46 p.

Vecchia, A.V., 2002, Simulation of a proposed emergency outlet from Devils Lake, North Dakota: U.S. Geological Survey WaterResources Investigations Report 02-4042, 129 p.

Wiche, G.J., and Pusc, S.W., 1994, Hydrology of the Devils Lake area, North Dakota: North Dakota State Water Commission Water

Resources Investigation 22, 24 p.

Wiener, J.G., and Spry, D.J., 1996, Toxicological significance of mercury in freshwater fish, in Beyer, W.N., Heinz, G.H., and Redmon,

A.W., eds., Environmental Contaminants in Wildlife--Interpreting Tissue Concentrations: Boca Raton, Florida, Lewis Publishers,

p. 297-339.

Wisconsin District Mercury Laboratory, 1999, Quality assurance plan: accessed March 6, 2002, at URL

http://infotrek.er.usgs.gov/doc/mercury/qa.html.
 40

Supplement 1. Results for field-measured properties and constituents for lake and wetland sites[mm, millimeters; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; e, estimated]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth at

sampling

location

(feet)

Measurement

depth

(feet)

Barometric

pressure

(mm of Hg)

Specificconductance,

field

(μS/cm

at 25°C)

pH,

field

(standard

units)

Temperature,

air

(°C)

Temperature,

water

(°C)

Oxygen,

dissolved

(mg/L)

Oxygen,

dissolved

(percent

saturation)

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- -- 720 1,290 7.7 17.0 13.3 6.2 63

07/31/01 0720 -- -- 714 1,900 6.8 23.0 21.7 1.2 15

3 Devils Lake West Bay near Pelican Lake 03/15/01 1130 17.1 2.6 728 2,000 7.8 3.0 .2 5.4 39

1131 -- 5.9 -- 1,960 7.7 -- 1.9 5.0 --1132 -- 9.8 -- 1,960 7.7 -- 2.6 4.0 --1133 -- 13.1 -- 1,990 7.7 -- 3.3 1.3 --1134 -- 16.4 -- 2,020 7.7 -- 3.4 1.1 --1135 -- 17.1 -- 2,020 7.6 -- 3.5 .7 --

08/01/01 1200 9.2 0 724 1,200 8.7 23.0 22.9 9.0 111

1201 -- 3.3 -- 1,210 8.7 -- 22.8 8.9 --1202 -- 6.6 -- 1,210 8.7 -- 22.8 8.8 --1203 -- 9.2 -- 1,200 8.7 -- 22.7 8.6 --

4 Devils Lake West Bay southwest 03/15/01 1410 12.8 3.3 730 2,340 8.2 7.0 -.1 13.0 93

1411 -- 6.6 -- 2,320 8.2 -- .1 13.2 --1412 -- 9.8 -- 2,330 8.2 -- .1 13.6 --1413 -- 12.8 -- 2,320 8.2 -- .9 10.9 --

08/01/01 1420 -- 0 -- 1,850 8.5 26.0 23.7 9.0 110

1421 -- 3.3 -- 1,850 8.5 -- 23.7 8.7 --1422 -- 6.6 -- 1,910 8.6 -- 23.7 8.6 --1423 -- 9.8 -- 1,950 8.6 -- 23.7 8.2 --1424 -- 13.1 -- 1,850 8.6 -- 23.7 8.1 --

5 Devils Lake Main Bay 03/14/01 1000 45.6 2.6 720 2,280 8.3 -2.5 -.1 12.6 92

1001 -- 5.9 -- 2,270 8.3 -- -.1 12.6 --1002 -- 9.8 -- 2,270 8.3 -- -.1 12.5 --1003 -- 13.1 -- 2,270 8.3 -- -.1 12.5 --1004 -- 16.4 -- 2,270 8.3 -- -.1 12.5 --1005 -- 19.7 -- 2,270 8.3 -- -.1 12.4 --1006 -- 23.0 -- 2,260 8.3 -- 0 12.4 --1007 -- 26.2 -- 2,260 8.3 -- .4 12.3 --1008 -- 29.5 -- 2,250 8.3 -- .9 11.4 --1009 -- 32.8 -- 2,240 8.3 -- 1.3 9.6 --1010 -- 36.1 -- 2,250 8.3 -- 1.7 7.4 --1011 -- 39.4 -- 2,290 8.3 -- 2.3 4.7 --1012 -- 42.7 -- 2,420 8.2 -- 2.8 3.2 --1013 -- 45.6 -- 2,500 8.2 -- 4.1 .4 --
 41

5 Devils Lake Main Bay--Continued 08/01/01 0815 48.9 0 725 2,040 8.2 19.0 22.0 8.1 98

0816 -- 3.3 -- 2,040 8.3 -- 22.0 7.8 --0817 -- 6.6 -- 2,040 8.4 -- 22.0 7.7 --0818 -- 13.1 -- 2,050 8.4 -- 22.0 7.7 --0819 -- 19.7 -- 2,050 8.4 -- 22.0 7.7 --0820 -- 26.2 -- 2,050 8.4 -- 22.0 7.7 --0821 -- 32.8 -- 2,050 8.4 -- 22.0 7.6 --0827 -- 39.4 -- 2,050 8.4 -- 21.9 7.3 --0828 -- 45.9 -- 2,100 8.1 -- 18.2 .5 --0829 -- 48.9 -- 2,100 8.0 -- 18.0 .4 --

6 Devils Lake East Bay 03/14/01 1310 36.4 3.3 722 3,660 8.4 1.5 -.1 10.7 --

1311 -- 6.6 -- 3,650 8.4 -- -.1 10.6 --1312 -- 9.8 -- 3,660 8.4 -- -.1 10.7 --1313 -- 13.1 -- 3,660 8.4 -- -.1 11.0 --1314 -- 16.4 -- 3,660 8.4 -- -.1 11.1 --1315 -- 19.7 -- 3,680 8.4 -- -.1 11.2 --1316 -- 23.0 -- 3,670 8.5 -- -.1 11.2 --1317 -- 26.2 -- 3,650 8.5 -- .1 11.1 --1318 -- 29.5 -- 3,640 8.5 -- .5 10.0 --1319 -- 32.8 -- 3,740 8.4 -- 1.6 6.1 --1320 -- 36.4 -- 4,020 8.4 -- 2.5 .7 --

08/02/01 0730 38.7 0 731 3,230 8.5 18.0 22.1 7.3 --

0731 -- 3.3 -- 3,230 8.5 -- 22.1 7.2 --0732 -- 6.6 -- 3,230 8.5 -- 22.1 7.1 --0733 -- 13.1 -- 3,250 8.5 -- 22.1 7.0 --0734 -- 19.7 -- 3,250 8.5 -- 22.1 6.9 --0735 -- 26.2 -- 3,250 8.5 -- 22.1 6.8 --0736 -- 32.8 -- 3,230 8.5 -- 22.0 5.0 --0737 -- 38.7 -- 3,230 8.4 -- 21.6 1.7 --

7 East Devils Lake 03/14/01 1525 49.2 3.0 724 6,930 8.4 4.0 -.2 9.3 68

1526 -- 6.2 -- 6,860 8.4 -- -.2 9.0 --1527 -- 9.2 -- 6,840 8.4 -- -.3 8.9 --1528 -- 13.1 -- 6,830 8.5 -- -.3 8.8 --1529 -- 16.4 -- 6,830 8.5 -- -.3 8.8 --1530 -- 19.7 -- 6,840 8.5 -- -.3 8.7 --1531 -- 23.0 -- 6,840 8.5 -- -.3 8.7 --1532 -- 26.2 -- 6,840 8.5 -- -.3 8.7 --1533 -- 29.5 -- 6,830 8.5 -- -.3 8.7 --1534 -- 32.8 -- 6,800 8.5 -- -.1 8.7 --1535 -- 36.1 -- 6,820 8.5 -- .1 8.7 --1536 -- 39.4 -- 6,830 8.5 -- .2 8.7 --1537 -- 42.7 -- 6,830 8.5 -- .3 8.7 --1538 -- 45.9 -- 6,850 8.5 -- .8 7.8 --1539 -- 49.2 -- 6,760 8.5 -- 1.7 4.6 --

Supplement 1. Results for field-measured properties and constituents for lake and wetland sites—Continued

[mm, millimeters; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; e, estimated]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth at

sampling

location

(feet)

Measurement

depth

(feet)

Barometric

pressure

(mm of Hg)

Specificconductance,

field

(μS/cm

at 25°C)

pH,

field

(standard

units)

Temperature,

air

(°C)

Temperature,

water

(°C)

Oxygen,

dissolved

(mg/L)

Oxygen,

dissolved

(percent

saturation)
 42

7 East Devils Lake--Continued 08/02/01 0920 51.5 0 731 6,000 8.3 22.0 21.9 9.5 115

0921 -- 3.3 -- 6,080 8.5 -- 21.9 8.0 --0922 -- 6.6 -- 6,080 8.5 -- 21.9 7.8 --0923 -- 13.1 -- 6,090 8.6 -- 21.9 7.7 --0924 -- 19.7 -- 6,090 8.6 -- 21.9 7.6 --0925 -- 26.2 -- 6,090 8.6 -- 21.9 7.5 --0926 -- 32.8 -- 6,080 8.6 -- 21.9 7.5 --0927 -- 39.4 -- 6,180 8.5 -- 19.6 4.0 --0928 -- 45.9 -- 6,280 8.3 -- 16.0 .6 --0929 -- 51.5 -- 6,280 8.3 -- 15.2 .5 --

9 Lake Ashtabula near north end 03/13/01 1430 8.2 3.0 e722 1,350 8.5 7.0 0 5.0 --

1431 -- 4.9 -- 1,360 8.5 -- 0 4.4 --1432 -- 6.6 -- 1,360 8.4 -- 0 4.3 --1433 -- 8.2 -- 1,360 8.4 -- 0 4.1 --

08/07/01 1100 8.9 0 e727 1,010 7.6 30.5 27.9 7.0 --

1101 -- 3.3 -- 1,100 7.7 -- 27.9 6.4 --1102 -- 6.6 -- 1,100 7.8 -- 27.9 5.9 --1103 -- 8.9 -- 1,100 7.8 -- 27.7 5.7 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1020 18.4 2.6 722 1,560 8.6 4.5 0 11.0 80

1021 -- 3.3 -- 1,550 8.5 -- .3 10.9 --1022 -- 6.6 -- 1,520 8.4 -- 1.0 10.7 --1023 -- 9.8 -- 1,500 8.2 -- 2.0 8.1 --1024 -- 13.1 -- 1,520 8.1 -- 2.6 6.3 --1025 -- 16.4 -- 1,710 8.0 -- 3.3 2.6 --1026 -- 18.0 -- 1,730 7.9 -- 3.5 1.8 --

08/07/01 1230 27.9 0 727 1,180 8.4 34.5 26.7 11.3 149

1231 -- 3.3 -- 1,180 8.4 -- 26.7 11.2 --1232 -- 6.6 -- 1,180 8.4 -- 25.6 9.6 --1233 -- 9.8 -- 1,180 8.3 -- 25.5 8.2 --1234 -- 13.1 -- 1,190 8.3 -- 25.4 7.5 --1235 -- 16.4 -- 1,190 8.3 -- 25.0 6.9 --1236 -- 19.7 -- 1,190 8.3 -- 24.7 5.9 --1237 -- 23.0 -- 1,190 8.3 -- 24.4 4.9 --1238 -- 26.2 -- 1,190 8.2 -- 23.6 .7 --1239 -- 27.9 -- 1,190 8.2 -- 23.5 .5 --

Supplement 1. Results for field-measured properties and constituents for lake and wetland sites—Continued

[mm, millimeters; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; e, estimated]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth at

sampling

location

(feet)

Measurement

depth

(feet)

Barometric

pressure

(mm of Hg)

Specificconductance,

field

(μS/cm

at 25°C)

pH,

field

(standard

units)

Temperature,

air

(°C)

Temperature,

water

(°C)

Oxygen,

dissolved

(mg/L)

Oxygen,

dissolved

(percent

saturation)
 43

Supplement 2. Results for field-measured properties and constituents for river sites[mm, millimeters; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; --, no data]

Site

number

(see

figure 1

for

location)

Site name Date Time

Discharge

(cubic

feet

per

second)

Barometric

pressure

(mm of Hg)

Specific

conductance,

field

(μS/cm at

25°C)

pH, whole

water, field

(standard

units)

Temperature,

air

(°C)

Temperature,

water

(°C)

Turbidity,

field, whole

water

(nephelometric

turbidity

units)

Oxygen,

dissolved

(mg/L)

Oxygen,

dissolved

(percent

saturation)

2 Starkweather Coulee near 04/30/01 1140 210 -- 808 8.2 17.5 13.5 -- 8.3 85

Webster, North Dakota 07/24/01 0845 55 -- 711 7.6 17.5 21.8 -- 5.5 65

8 Sheyenne River near Warwick, 04/30/01 1400 485 720 1,140 8.2 19.8 16.3 24 9.0 98

North Dakota 07/24/01 1020 361 730 1,260 8.0 20.9 25.2 85 5.6 71

11 Sheyenne River below Baldhill 05/01/01 0830 893 717 828 8.1 17.0 8.5 14 11.0 100

Dam, North Dakota 07/24/01 1240 382 732 1,130 8.4 20.0 24.6 20 7.4 93

12 Sheyenne River near Kindred, 05/01/01 1030 1,400 725 797 8.0 17.6 13.6 240 9.0 91

North Dakota 07/25/01 0830 253 742 985 8.2 18.9 23.3 150 8.0 97

13 Red River of the North at Fargo, 05/01/01 1200 7,670 726 621 7.8 19.0 14.9 -- 7.9 82

North Dakota 07/25/01 0950 2,400 742 649 7.8 25.0 26.5 270 5.8 74

14 Red River of the North at Halstad, 05/01/01 1345 23,500 726 661 7.9 18.1 14.2 -- 8.5 87

Minnesota 07/25/01 1130 5,060 743 526 7.8 25.8 26.4 510 5.7 73

15 Red Lake River at Fisher, 05/01/01 1515 4,660 727 411 8.1 19.2 15.3 95 9.4 99

Minnesota 07/25/01 1330 1,760 745 341 8.0 25.5 25.5 140 7.2 90

16 Red River of the North at 05/02/01 0730 40,000 734 531 7.9 10.0 12.8 -- 8.7 85

Emerson, Manitoba 07/26/01 0715 6,100 749 657 8.0 20.5 26.1 440 7.1 89
 44

Supplement 3. Results for major-ion, trace-element, and suspended-sediment constituents for lake and wetland sites[Samples were analyzed by the North Dakota Department of Health Laboratory; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; NS, near-surface sample collected about 3 feet below

water surface; NB, near-bottom sample collected about 3 feet above lake bottom; --, no data; μg/L, micrograms per liter; <, less than; mm, millimeter]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth at

 sampling

 location

(feet)

Depth to top

of sample

interval

(feet)

Specific

conductance

(μS/cm at

25°C)

pH, whole

water,

laboratory

(standard

units)

Calcium,

dissolved

(mg/L as Ca)

Magnesium,

dissolved

(mg/L as Mg)

NS NB NS NB NS NB NS NB NS NB

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- -- -- 1,290 -- 8.0 -- 60 -- 60 --

07/31/01 0715 -- -- -- 1,900 -- 7.2 -- 82 -- 90 --

3 Devils Lake West Bay near Pelican Lake 03/15/01 1155 17.1 6.0 16.4 1,970 2,060 8.1 8.0 100 100 84 87

08/01/01 1205 9.2 3.3 6.6 1,220 1,220 9.0 9.0 70 69 51 51

4 Devils Lake West Bay southwest 03/15/01 1430 12.8 10.5 -- 2,280 -- 8.4 -- 90 -- 88 --

08/01/01 1430 -- 3.3 -- 1,890 -- 8.9 -- 76 -- 72 --

5 Devils Lake Main Bay 03/14/01 1030 45.6 6.0 43.3 2,270 2,430 8.6 8.4 84 83 92 98

08/01/01 0845 48.9 45.9 -- 2,050 -- -- -- 71 -- 75 --

6 Devils Lake East Bay 03/14/01 1330 36.4 6.6 -- 3,640 -- 8.5 -- 85 -- 140 --

08/02/01 0740 38.7 3.3 -- 3,230 -- 8.8 -- 74 -- 120 --

7 East Devils Lake 03/14/01 1615 49.2 6.2 47.6 6,760 6,770 8.5 8.5 94 89 270 260

08/02/01 0935 51.5 3.3 48.2 6,060 6,180 8.8 8.6 81 84 220 230

9 Lake Ashtabula near north end 03/13/01 1450 8.2 6.2 -- 1,310 -- 7.8 -- 110 -- 57 --

08/07/01 1105 8.9 3.3 -- 1,120 -- 8.0 -- 66 -- 48 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1120 18.4 6.0 15.7 1,470 1,700 8.3 8.0 110 120 72 86

08/07/01 1240 27.9 3.3 24.6 1,190 1,190 8.6 8.5 70 71 54 54
 45

Supplement 3. Results for major-ion, trace-element, and suspended-sediment constituents for lake and wetland sites—Continued[Samples were analyzed by the North Dakota Department of Health Laboratory; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; NS, near-surface sample collected about 3 feet below

water surface; NB, near-bottom sample collected about 3 feet above lake bottom; --, no data; μg/L, micrograms per liter; <, less than; mm, millimeter]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth at

 sampling

 location

(feet)

Depth to top

of sample

interval

(feet)

Sodium,

dissolved

(mg/L as Na)

Potassium,

dissolved

(mg/L as K)

Alkalinity,

titration to

pH 4.5,

laboratory

(mg/L as CaCO3)

Sulfate,

dissolved

(mg/L as SO4)

NS NB NS NB NS NB NS NB NS NB

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- -- -- 140 -- 14 -- 270 -- 420 --

07/31/01 0715 -- -- -- 220 -- 16 -- 360 -- 700 --

3 Devils Lake West Bay near Pelican Lake 03/15/01 1155 17.1 6.0 16.4 240 260 38 40 390 430 520 520

08/01/01 1205 9.2 3.3 6.6 110 110 22 22 320 320 320 320

4 Devils Lake West Bay southwest 03/15/01 1430 12.8 10.5 -- 290 -- 44 -- 410 -- 650 --

08/01/01 1430 -- 3.3 -- 230 -- 36 -- 390 -- 510 --

5 Devils Lake Main Bay 03/14/01 1030 45.6 6.0 43.3 320 350 47 50 360 370 690 720

08/01/01 0845 48.9 45.9 -- 260 -- 39 -- 350 -- 560 --

6 Devils Lake East Bay 03/14/01 1330 36.4 6.6 -- 570 -- 76 -- 420 -- 1,300 --

08/02/01 0740 38.7 3.3 -- 480 -- 64 -- 430 -- 1,000 --

7 East Devils Lake 03/14/01 1615 49.2 6.2 47.6 1,300 1,200 150 140 530 540 2,700 2,700

08/02/01 0935 51.5 3.3 48.2 1,100 1,100 120 120 570 580 2,400 2,200

9 Lake Ashtabula near north end 03/13/01 1450 8.2 6.2 -- 120 -- 8.2 -- 460 -- 230 --

08/07/01 1105 8.9 3.3 -- 120 -- 11 -- 340 -- 270 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1120 18.4 6.0 15.7 150 180 15 15 460 550 310 370

08/07/01 1240 27.9 3.3 24.6 120 120 11 11 390 420 280 280
 46

Supplement 3. Results for major-ion, trace-element, and suspended-sediment constituents for lake and wetland sites—Continued[Samples were analyzed by the North Dakota Department of Health Laboratory; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; NS, near-surface sample collected about 3 feet below

water surface; NB, near-bottom sample collected about 3 feet above lake bottom; --, no data; μg/L, micrograms per liter; <, less than; mm, millimeter]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth at

 sampling

 location

(feet)

Depth to top

of sample

interval

(feet)

Chloride,

dissolved

(mg/L as Cl)

Solids,

dissolved,

sum of

constituents

(mg/L)

Iron, whole water

(μg/L as Fe)

Manganese,

whole water

(μg/L)

NS NB NS NB NS NB NS NB NS NB

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- -- -- 8.1 -- 863 -- 50 -- 110 --

07/31/01 0715 -- -- -- 6.5 -- 1,330 -- 20 -- 160 --

3 Devils Lake West Bay near Pelican Lake 03/15/01 1155 17.1 6.0 16.4 87 100 1,300 1,370 20 180 410 1,800

08/01/01 1205 9.2 3.3 6.6 36 45 802 808 150 130 120 110

4 Devils Lake West Bay southwest 03/15/01 1430 12.8 10.5 -- 130 -- 1,540 -- <10 -- 40 --

08/01/01 1430 -- 3.3 -- 99 -- 1,260 -- 210 -- 50 --

5 Devils Lake Main Bay 03/14/01 1030 45.6 6.0 43.3 120 130 1,570 1,650 10 30 <10 230

08/01/01 0845 48.9 45.9 -- 110 -- 1,320 -- <10 -- 20 --

6 Devils Lake East Bay 03/14/01 1330 36.4 6.6 -- 260 -- 2,660 -- <10 -- <10 --

08/02/01 0740 38.7 3.3 -- 220 -- 2,250 -- 70 -- 30 --

7 East Devils Lake 03/14/01 1615 49.2 6.2 47.6 520 530 5,290 5,320 40 40 <10 10

08/02/01 0935 51.5 3.3 48.2 490 490 4,670 4,710 <10 <10 <10 320

9 Lake Ashtabula near north end 03/13/01 1450 8.2 6.2 -- 17 -- 830 -- 210 -- 540 --

08/07/01 1105 8.9 3.3 -- 12 -- 727 -- 220 -- 160 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1120 18.4 6.0 15.7 22 28 954 1,140 110 50 320 1,100

08/07/01 1240 27.9 3.3 24.6 17 17 789 809 10 <10 130 310
 47

Supplement 3. Results for major-ion, trace-element, and suspended-sediment constituents for lake and wetland sites—Continued[Samples were analyzed by the North Dakota Department of Health Laboratory; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; NS, near-surface sample collected about 3 feet below

water surface; NB, near-bottom sample collected about 3 feet above lake bottom; --, no data; μg/L, micrograms per liter; <, less than; mm, millimeter]

Site

number

(see

figure 1

for

location)

Site name Date Time

Depth of

 lake at

 sampling

 location

(feet)

Depth to top

of sample

interval

(feet)

Suspended

sediment

(mg/L)

Suspended

sediment

(percent finer

than 0.062 mm)

NS NB NS NB NS NB

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- -- -- 4 -- 91 --

07/31/01 0715 -- -- -- 31 -- 97 --

3 Devils Lake West Bay near Pelican Lake 03/15/01 1155 17.1 6.0 16.4 -- -- -- --

08/01/01 1205 9.2 3.3 6.6 23 31 98 95

4 Devils Lake West Bay southwest 03/15/01 1430 12.8 10.5 -- -- -- -- --

08/01/01 1430 -- 3.3 -- 10 -- 98 --

5 Devils Lake Main Bay 03/14/01 1030 45.6 6.0 43.3 2 3 91 96

08/01/01 0845 48.9 45.9 -- 2 -- 88 --

6 Devils Lake East Bay 03/14/01 1330 36.4 6.6 -- 1 -- 85 --

08/02/01 0740 38.7 3.3 -- 5 -- 92 --

7 East Devils Lake 03/14/01 1615 49.2 6.2 47.6 4 -- 99 --

08/02/01 0935 51.5 3.3 48.2 29 154 100 100

9 Lake Ashtabula near north end 03/13/01 1450 8.2 6.2 -- -- -- -- --

08/07/01 1105 8.9 3.3 -- 8 -- 88 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1120 18.4 6.0 15.7 3 23 92 97

08/07/01 1240 27.9 3.3 24.6 3 4 79 86
 48

Supplement 4. Results for major-ion, trace-element, and suspended-sediment constituents for river sites[Samples were analyzed by the North Dakota Department of Health Laboratory; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; <, less than; μg/L, micrograms per liter;

mm, millimeters; M, presence verified, not quantified]

Site

number

(see

figure 1

for

location)

Site name Date Time

Specific

conductance

(μS/cm at

25°C)

pH, whole water,

laboratory

(standard

units)

Calcium,

dissolved

(mg/L as Ca)

Magnesium,

dissolved

(mg/L as Mg)

Sodium,

dissolved

(mg/L as Na)

Potassium,

dissolved

(mg/L as K)

Alkalinity,

titration to

pH 4.5,

laboratory

(mg/L as

CaCO3)

2 Starkweather Coulee near Webster, North Dakota 04/30/01 1140 816 8.3 80 38 36 19 200

07/24/01 0845 -- -- 76 42 59 13 170

8 Sheyenne River near Warwick, North Dakota 04/30/01 1400 1,140 8.4 63 52 120 11 360

07/24/01 1020 1,280 7.9 59 52 160 12 320

11 Sheyenne River below Baldhill Dam, North Dakota 05/01/01 0830 838 8.2 56 35 73 10 230

07/24/01 1240 1,150 8.4 74 55 120 12 310

12 Sheyenne River near Kindred, North Dakota 05/01/01 1030 793 8.2 64 32 60 10 230

07/25/01 0830 993 7.8 88 46 79 11 250

13 Red River of the North at Fargo, North Dakota 05/01/01 1200 626 7.6 62 32 19 7.6 140

07/25/01 0950 662 7.0 66 41 20 7.0 160

14 Red River of the North at Halstad, Minnesota 05/01/01 1345 672 7.9 68 35 24 8.2 170

07/25/01 1130 680 -- 80 44 26 9.2 210

15 Red Lake River at Fisher, Minnesota 05/01/01 1515 419 8.0 62 22 <3.0 4.3 160

07/25/01 1330 -- -- 49 17 3.0 2.9 150

16 Red River of the North at Emerson, Manitoba 05/02/01 0730 539 7.8 56 25 18 8.2 150

Replicate 0740 536 7.8 56 24 18 7.9 150

07/26/01 0715 665 7.0 61 33 26 5.9 160

Replicate 0725 -- -- -- -- -- -- --
 49

Supplement 4. Results for major-ion, trace-element, and suspended-sediment constituents for river sites—Continued[Samples were analyzed by the North Dakota Department of Health Laboratory; μS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; <, less than; μg/L, micrograms per liter;

mm, millimeters; M, presence verified, not quantified]

Site

number

(see

figure 1

for

location)

Station name Date Time

Sulfate,

dissolved

(mg/L as SO4)

Chloride,

dissolved

(mg/L as Cl)

Solids,

dissolved,

sum of

constituents

(mg/L)

Iron, whole

water

(mg/L as Fe)

Manganese,

whole water

(μg/L)

Suspended

sediment

(mg/L)

Suspended

sediment

(percent finer

than 0.062 mm)

2 Starkweather Coulee near Webster, North Dakota 04/30/01 1140 210 24 524 2,900 740 394 100

07/24/01 0845 290 28 616 M M 6 96

8 Sheyenne River near Warwick, North Dakota 04/30/01 1400 270 15 747 600 100 21 98

07/24/01 1020 290 15 786 M M 95 99

11 Sheyenne River below Baldhill Dam, North Dakota 05/01/01 0830 200 12 524 350 330 17 90

07/24/01 1240 270 14 734 M M 17 95

12 Sheyenne River near Kindred, North Dakota 05/01/01 1030 190 15 511 2,500 420 166 84

07/25/01 0830 220 19 622 4,100 570 211 96

13 Red River of the North at Fargo, North Dakota 05/01/01 1200 180 10 393 2,200 80 138 100

07/25/01 0950 160 11 400 M M 278 100

14 Red River of the North at Halstad, Minnesota 05/01/01 1345 170 12 425 3,400 130 -- --

07/25/01 1130 150 14 456 12,500 M 499 100

15 Red Lake River at Fisher, Minnesota 05/01/01 1515 50 5.4 244 2,900 130 133 95

07/25/01 1330 15 3.0 183 M M 116 98

16 Red River of the North at Emerson, Manitoba 05/02/01 0730 110 12 317 M M -- --

Replicate 0740 110 .4 308 3,800 130 302 100

07/26/01 0715 130 20 372 10 M 419 100

Replicate 0725 -- -- -- -- -- -- 100
 50

Supplement 5. Results for mercury and organic-carbon constituents for lake and wetland sites[Samples were analyzed by the U.S. Geological Survey Wisconsin District Mercury Laboratory; ng/L, nanograms per liter; NS, near-surface sample collected about 3 feet below water surface; NB, near-bottom samplecollected about 3 feet above lake bottom; --, no data; <, less than; mg/L, milligrams per liter]

Site

number

(see

figure 1

for

location)

Site name Date

Time

Methylmercury,

dissolved

(ng/L)

Methylmercury,

particulate

(ng/L)

Methylmercury,

whole water

(ng/L)

Total mercury,

dissolved

(ng/L)

NS NB NS NB NS NB NS NB NS NB

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- 0.35 -- 0.04 -- 0.39 -- 1.29 --

07/31/01 0715 -- 3.13 -- .40 -- 3.53 -- 5.31 --

3 Devils Lake West Bay near Pelican Lake 03/15/01 1155 1225 <.04 0.22 <.02 <0.02 <.04 0.22 .50 0.86

Replicate -- <.04 -- <.02 -- <.04 -- 1.43 --

08/01/01 1205 1210 <.04 .06 .21 .20 .21 .25 1.22 .68

4 Devils Lake West Bay southwest 03/15/01 1400 1430 <.04 <.04 <.02 .02 <.04 <.04 .34 .37

08/01/01 1430 -- <.04 -- .09 -- .09 -- .79 --

5 Devils Lake Main Bay 03/14/01 1030 1100 <.04 <.04 <.02 <.02 <.04 <.04 .40 .38

08/01/01 0840 0845 .06 .12 .06 .04 .12 .16 .79 .58

6 Devils Lake East Bay 03/14/01 1330 -- <.04 -- <.02 -- <.04 -- .41 --

08/02/01 0740 -- .10 -- .10 -- .20 -- .85 --08/02/01 Replicate -- .13 -- .09 -- .21 -- .97 --

7 East Devils Lake 03/14/01 1615 1645 <.04 <.04 <.02 <.02 <.04 <.04 .63 .64

08/02/01 0935 0940 <.04 .26 .03 .07 <.04 .34 .80 1.25

9 Lake Ashtabula near north end 03/13/01 1450 -- .06 -- <.02 -- .06 -- .53 --

08/07/01 1105 -- .37 -- .09 -- .46 -- 2.07 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1120 1150 <.04 .22 <.02 <.02 <.04 .22 .63 .88

08/07/01 1240 1245 .15 .21 .13 .05 .28 .27 .64 .68
 51

Supplement 5. Results for mercury and organic-carbon constituents for lake and wetland sites—Continued[Samples were analyzed by the U.S. Geological Survey Wisconsin District Mercury Laboratory; ng/L, nanograms per liter; NS, near-surface sample collected about 3 feet below water surface; NB, near-bottom samplecollected about 3 feet above lake bottom; --, no data; <, less than; mg/L, milligrams per liter]

Site

number

(see

figure 1

for

location)

Site name Date

Time

Total mercury,

particulate

(ng/L)

Total mercury,

whole water

(ng/L)

Organic carbon,

dissolved

(mg/L)

Organic carbon,

whole water

(mg/L)

NS NB NS NB NS NB NS NB NS NB

1 Wetland site in upper Devils Lake Basin 04/30/01 1030 -- 0.14 -- 1.43 -- 19.9 -- 18.7 --

07/31/01 0715 -- 1.71 -- 7.02 -- 30.7 -- 31.0 --

3 Devils Lake West Bay near Pelican Lake 03/15/01 1155 1225 <.02 0.03 .50 0.89 20.7 21.7 21.0 20.7

03/15/01 Replicate -- <.02 -- 1.43 -- 20.7 -- 21.2 --08/01/01 1205 1210 1.76 .92 2.98 1.61 14.7 14.7 15.4 15.7

4 Devils Lake West Bay southwest 03/15/01 1400 1430 .04 .22 .38 .59 19.3 19.0 20.0 19.5

08/01/01 1430 -- 1.07 -- 1.86 -- 17.2 -- 17.9 --

5 Devils Lake Main Bay 03/14/01 1030 1100 <.02 <.02 .40 .38 18.0 18.7 17.9 18.2

08/01/01 0840 0845 .32 .28 1.11 .86 14.1 14.6 14.1 14.7

6 Devils Lake East Bay 03/14/01 1330 -- <.02 -- .41 -- 24.3 -- 24.2 --

08/02/01 0740 -- .34 -- 1.20 -- 19.2 -- 19.6 --08/02/01 Replicate -- .45 -- 1.41 -- 20.0 -- 19.8 --

7 East Devils Lake 03/14/01 1615 1645 .07 <.02 .70 .64 32.5 32.5 32.2 32.9

08/02/01 0935 0940 .19 .48 .99 1.73 27.6 27.4 27.8 27.3

9 Lake Ashtabula near north end 03/13/01 1450 -- .55 -- 1.08 -- 8.7 -- 8.5 --

08/07/01 1105 -- 1.04 -- 3.11 -- 18.6 -- 18.1 --

10 Lake Ashtabula at Baldhill Dam, North Dakota 03/13/01 1120 1150 <.02 <.02 .63 .88 18.0 18.1 17.8 18.9

08/07/01 1240 1245 .31 .25 .96 .93 14.4 14.2 14.9 14.0
 52

Supplement 6. Results for mercury and organic-carbon constituents for river sites[Samples were analyzed by the U.S. Geological Survey Wisconsin District Mercury Laboratory; ft3/s, cubic feet per second; ng/L, nanograms per liter; mg/L, milligrams per liter; --, no data]

Site

number

(see

figure 1

for

location)

Site name Date Time Discharge (ft3/s)

Methylmercury,

dissolved

(ng/L)

Methylmercury,

particulate

(ng/L)

Methylmercury,

whole

water

(ng/L)

Total

mercury,

dissolved

(ng/L)

Total

mercury,

particulate

(ng/L)

Total

mercury,

whole

water

(ng/L)

Organic

carbon,

dissolved

(mg/L)

Organic

carbon,

whole

water

(mg/L)

2 Starkweather Coulee near Webster, North Dakota 04/30/01 1140 220 0.21 0.25 0.45 2.11 4.22 6.33 13.7 13.1

07/24/01 0845 56 .96 .17 1.13 2.57 .66 3.22 15.4 15.9

8 Sheyenne River near Warwick, North Dakota 04/30/01 1400 460 .19 .08 .27 1.31 1.11 2.42 14.1 13.1

07/24/01 1020 380 .13 .08 .21 2.32 3.53 5.85 21.3 20.9

11 Sheyenne River below Baldhill Dam, North Dakota 05/01/01 0830 720 .09 .12 .20 1.59 .97 2.56 11.2 10.8

07/24/01 1240 370 .18 .09 .27 .96 1.04 2.00 13.8 13.6

12 Sheyenne River near Kindred, North Dakota 05/01/01 1030 1,650 .08 .21 .29 1.60 16.25 17.84 8.7 8.8

07/25/01 0830 290 .47 .97 1.44 1.57 11.55 13.12 9.4 9.7

13 Red River of the North at Fargo, North Dakota 05/01/01 1200 7,700 .06 .14 .20 1.39 6.41 7.81 7.9 7.6

07/25/01 0950 2,880 .13 .35 .47 .95 15.31 16.27 9.1 9.3

14 Red River of the North at Halstad, Minnesota 05/01/01 1345 23,500 .08 .17 .25 1.54 11.49 13.04 8.4 8.1

07/25/01 1130 5,050 .07 .39 .46 1.09 25.81 26.90 8.2 7.9

15 Red Lake River at Fisher, Minnesota 05/01/01 1515 4,660 .11 .12 .23 1.32 4.41 5.73 11.6 11.2

07/25/01 1330 1,760 .29 .16 .45 1.56 4.30 5.86 15.6 15.8

16 Red River of the North at Emerson, Manitoba 05/02/01 0730 40,000 .06 .10 .16 1.91 7.49 9.40 8.5 8.4

05/02/01 Replicate -- .07 .09 .15 1.78 7.31 9.09 8.9 8.807/26/01 0715 6,100 .06 .31 .37 1.13 21.30 22.43 9.4 9.407/26/01 Replicate -- .07 .34 .41 1.06 22.49 23.55 9.4 9.3