U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2020–5020

Prepared in cooperation with the Three Affiliated Tribes

Characterization of Surface-Water and Groundwater Quality 

on the Fort Berthold Reservation, North Dakota, 2014–17
Cover. Aerial extent of agricultural pasture and oil production activity on the Fort Berthold 

Reservation, south of Mandaree, North Dakota, July 18, 2019 (upper left). Monitoring well site near an 

active oil production well on the Fort Berthold Reservation, Mandaree, North Dakota, August 16, 2016 

(lower right). Photographs by Robert Lundgren, U.S. Geological Survey. 
Characterization of Surface-Water and 

Groundwater Quality on the Fort Berthold 

Reservation, North Dakota, 2014–17

By Robert F. Lundgren and Mary J. Iorio

Prepared in cooperation with the Three Affiliated Tribes

Scientific Investigations Report 2020–5020

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Suggested citation:

Lundgren, R.F., and Iorio, M.J., 2020, Characterization of surface-water and groundwater quality on the Fort Berthold 

Reservation, North Dakota, 2014–17: U.S. Geological Survey Scientific Investigations Report 2020–5020, 37 p., 

https://doi.org/ 10.3133/ sir20205020.

ISSN 2328-0328 (online)
iii

Acknowledgments

The authors thank Tricia Pfeiffer (U.S. Environmental Protection Agency Region 8, Denver, 

Colorado), who has been involved with the project from the initial phases through the final data 

review and release. Tricia served admirably as the Three Affiliated Tribes water-quality lead and 

provided outstanding coordination among the laboratories and management personnel of the 

Three Affiliated Tribes, U.S. Geological Survey, and U.S. Environmental Protection Agency. The 

authors also gratefully acknowledge the landowners who granted access to their property for 

the acquisition of data.

The authors thank Anthony Ranalli (U.S. Geological Survey Hydrologist, Colorado Water Science 

Center, retired) who was instrumental in the development of this project while serving as the 

Tribal Liaison between the U.S. Geological Survey and U.S. Environmental Protection Agency 

and Joel Galloway (U.S. Geological Survey Supervisory Hydrologist, Dakota Water Science 

Center) for project technical guidance and coordination.

v

Contents

Acknowledgments........................................................................................................................................iii

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

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

Purpose and Scope ..............................................................................................................................3

Previous Studies ...................................................................................................................................3

Methods...........................................................................................................................................................3

Surface-Water Site Selection .............................................................................................................4

Groundwater Well Selection ...............................................................................................................4

Data Collection and Laboratory Analysis Methods ........................................................................4

Water-Quality Data Analyses ..............................................................................................................9

Characterization of Water Quality on the Fort Berthold Reservation .................................................14

Surface-Water Quality .......................................................................................................................15

Groundwater Quality ..........................................................................................................................20

Summary........................................................................................................................................................32

References Cited..........................................................................................................................................34

Appendix 1 Quality-Assurance Data and Summary Statistics for Water-Quality 

Constituents in Surface Water and Groundwater ....................................................................36

Appendix 2 Summary Statistics for Historical Water-Quality Constituents in Major 

Aquifers on Fort Berthold Reservation, North Dakota .............................................................37

Figures

1. Map showing sampling locations at U.S. Geological Survey streamgaging 

stations and groundwater wells on the Fort Berthold Reservation during 2014–17 ..........2

2. Graph showing daily mean streamflow and water-quality samples collected 

at streamgaging station Bear Den Creek near Mandaree, North Dakota (U.S. 

Geological Survey station number 06332515), 2014–17 ........................................................16

3. Maps showing spatial distribution of dissolved chloride concentrations, in 

milligrams per liter, for groundwater wells on Fort Berthold Reservation, North 

Dakota, 2014–17 ..........................................................................................................................24

4. Maps showing spatial distribution of dissolved solids concentrations, in 

milligrams per liter, for groundwater wells on Fort Berthold Reservation, North 

Dakota, 2014–17 ..........................................................................................................................25

5. Maps showing spatial distribution of dissolved sodium concentrations, in 

milligrams per liter, for groundwater wells on Fort Berthold Reservation, North 

Dakota, 2014–17 ..........................................................................................................................26

6. Maps showing spatial distribution of dissolved sulfate concentrations, in 

milligrams per liter, for groundwater wells on Fort Berthold Reservation, North 

Dakota, 2014–17 ..........................................................................................................................27

7. Maps showing spatial distribution of dissolved arsenic concentrations, in 

micrograms per liter, for groundwater wells on Fort Berthold Reservation, 

North Dakota, 2014–17 ...............................................................................................................28

8. Maps showing spatial distribution of dissolved iron concentrations, in 

micrograms per liter, for groundwater wells on Fort Berthold Reservation, 

North Dakota, 2014–17 ...............................................................................................................29
vi

9. Maps showing spatial distribution of dissolved manganese concentrations, 

in micrograms per liter, for groundwater wells on Fort Berthold Reservation, 

North Dakota, 2014–17 ...............................................................................................................30

10. Maps showing spatial distribution of dissolved ammonia concentrations, in 

milligrams per liter, for groundwater wells on Fort Berthold Reservation, North 

Dakota, 2014–17 ..........................................................................................................................31

Tables

1. Period of record for available surface-water data from U.S. Geological Survey 

streamgaging stations on the Fort Berthold Reservation, North Dakota ............................5

2. Site information for groundwater wells sampled on Fort Berthold Reservation, 

North Dakota, 2014–17 ........................................................................................................linked

3. List of field measurements and constituents analyzed from samples collected 

on the Fort Berthold Reservation, North Dakota, 2014–17 .....................................................7

4. Laboratory reporting levels for selected water-quality constituents in surface 

water and groundwater on Fort Berthold Reservation, North Dakota, 2014–17 ..............10

5. Drinking water-quality standards and health-based screening levels available 

for water-quality constituents analyzed on Fort Berthold Reservation, North 

Dakota, 2014–17 ..........................................................................................................................11

6. Summary statistics for historical streamflow measurements at surface-water 

sites on Fort Berthold Reservation, North Dakota, October 1973 to April 2014 ................15

7. Summary statistics for selected water-quality constituents at surface-water 

sites on Fort Berthold Reservation, North Dakota, 2014–17 ................................................17

8. Summary statistics for selected water-quality constituents in groundwater 

wells on Fort Berthold Reservation, North Dakota, 2014–17 ...............................................22

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

yard (yd) 0.9144 meter (m)

Area

acre 4,047 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

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

 °C = (°F – 32) / 1.8.
vii

Datum

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

(NAVD 88).

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

Supplemental Information

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).

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

or micrograms per liter (μg/L).

Abbreviations

EWI equal-width-increments

MCL maximum contaminant level

NWIS National Water Information System

SDWR secondary drinking water regulation

TAT Three Affiliated Tribes

EPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Characterization of Surface-Water and Groundwater 

Quality on the Fort Berthold Reservation, North Dakota, 

2014–17

By Robert F. Lundgren1 and Mary J. Iorio2

Abstract

The Fort Berthold Reservation is in west-central North 

Dakota and home to the Three Affiliated Tribes. The primary 

water-resources concerns on the Fort Berthold Reservation 

are associated with the different types of land uses from 

agricultural activities and the rapid development of oil and 

gas resources in western North Dakota. The Three Affiliated 

Tribes Environmental Department identified the need for 

long-term water-quality monitoring throughout the Fort 

Berthold Reservation to better understand the potential effects 

on surface-water and groundwater quality and to determine 

if water quality is changing with time. The U.S. Geological 

Survey, in cooperation with the Three Affiliated Tribes, identified surface-water sites and groundwater wells that represent 

the water resources in major drainages and the most utilized 

aquifers on the reservation. A water-quality monitoring program was designed to address data gaps and provide consistent 

long-term data that can be used to identify potential effects 

on water quality. During 2014–17, the initial water-quality 

sampling efforts associated with this program were completed. The efforts provide a current (2019) characterization of 

water-quality conditions in surface water and groundwater and 

can assist in establishing a long-term water-quality monitoring program.

Introduction

The Fort Berthold Reservation is a reservation in westcentral North Dakota that is home for the federally recognized 

Mandan, Hidatsa, and Arikara Nation, also known as the Three 

Affiliated Tribes (TAT; fig. 1). The Fort Berthold Reservation 

(hereafter referred to as "reservation") is on Lake Sakakawea 

in parts of Dunn, McKenzie, McLean, Mercer, Mountrail, 

and Ward Counties (fig. 1) and includes an area of about 

1,530 square miles or 980,000 acres (Mandan, Hidatsa, and 

1U.S. Geological Survey.

2Three Affiliated Tribes.

Arikara Nation, 2020). The lake is a critical tribal resource 

because it supplies drinking water to tribal members and 

provides recreational opportunities. Land use on the east side 

of the reservation is predominantly cropland and on the west 

side of the reservation is predominantly rangeland used for 

the cattle grazing. Agricultural land use on the reservation has 

the potential to introduce fertilizers, pesticides, and livestock 

waste into streams, groundwater, and Lake Sakakawea.

In addition to the potential effects of agricultural activities, the rapid development of oil and gas resources in western 

North Dakota combined with the corresponding transport of 

extracted products from that energy development also have 

increased the potential to adversely affect water resources on 

the reservation. The development of these resources requires 

the transportation of oil and produced water (a by-product of 

oil production) from oil fields to refineries, transport terminals, 

or disposal locations. Transportation is typically done via pipeline, rail, or truck. Although the density of energy development continues to increase outside the reservation boundaries 

(North Dakota Industrial Commission, 2017), the potential for 

catastrophic environmental and economic effects from spills 

and other anthropogenic activities is ever present, especially 

for the hydrologic processes within the reservation.

During 2017, 704 contained or uncontained spills in 

Dunn, McKenzie, Mountrail, and Mercer Counties were 

reported to the North Dakota Department of Environmental 

Quality (2018). In 2014, one of the largest spills in State history took place on the reservation near Mandaree, N. Dak. 

(fig. 1). A leaky pipeline spilled an estimated 1 million gallons of produced water that reached Bear Den Bay of Lake 

Sakakawea (Dalrymple, 2018b). In addition, about 3 million 

gallons of produced water were reported to have leaked from 

a pipeline in January of 2015, spilling into Blacktail Creek 

(not shown on map) above the confluence with the Missouri 

River upstream outside of the reservation. The spills to the 

environment are not always accidental. In January 2018, a 

trucking company paid a fine of $950,000 to the North Dakota 

Industrial Commission for illegally dumping produced water 

on a Williams County gravel road (Dalrymple, 2018a).

A primary goal of the TAT Environmental Department is 

to protect water quality. The different types of land use on the 

reservation have the potential to affect water quality of streams 
102°45’ 102° 47°55’ 47°30’ Fort Berthold Reservation NORTH DAKOTA 

Shell Creek–White Lake aquifer White Shield aquifer New Town East Fork Shell Creek aquifer aquifer MCKENZIE COUNTY DUNN COUNTY MOUNTRAIL COUNTY WARD COUNTY MERCER COUNTY MCLEAN COUNTY Base and aquifer layers from North Dakota Geographic Information Systems (GIS) Hub Data Portal, 2018 Universal Transverse Mercator projection, zone 14N North American Datum of 1983 Sanish aquifer Shell Creek 06337480 06337470 06332770 06332523 06332520 06332515 Mandaree Twin Buttes Plaza 

Makoti New Town Parshall 3 9 8 7 6 5 4 3 2 1 34 33 32 31 30 29 26 25 24 23 22 21 20 19 17 16 15 14 13 12 11 10 28 27 18 37 22 1806 1804 28 8 73 23 Deepwater Creek Deepwater Creek Squaw Creek Moccasin Creek Bear Den Creek Lake Sakakawea Lake Sakakawea 063374

00 2 4 6 8 2 4 6 8 10 KILOMETERS10 MILES East Fork Shell Creek Bear Den Bay Figure 1. Sampling locations at U.S. Geological Survey streamgaging stations and groundwater wells on the Fort Berthold Reservation 

during 2014–17.
Methods 3

and groundwater on the reservation and potentially affect 

Lake Sakakawea farther downstream. As a result of these 

water-resources concerns, the TAT Environmental Department 

identified the need for long-term water-quality monitoring of 

streams and groundwater throughout the reservation to better 

understand the potential effects of land use on surface-water 

and groundwater quality and to determine if water quality 

is changing with time. Therefore, a water-quality monitoring program was designed to address data gaps and provide 

consistent long-term data that can be used to identify potential 

effects on water quality. The U.S. Geological Survey (USGS), 

in cooperation with the Three Affiliated Tribes, identified 

surface-water sites and groundwater wells that represent the 

water resources in major drainages and the most utilized 

aquifers on the reservation. During 2014–17, the initial waterquality sampling efforts associated with this program were 

completed. The efforts provide a current (2019) characterization of water-quality conditions and can assist in establishing a 

long-term water-quality monitoring program.

Purpose and Scope

The purpose of this report is to provide a current (2019) 

characterization of surface-water and groundwater-quality 

data collected on the reservation during 2014–17. This report 

describes the study design, sampling methods, and statistical summaries of the water-quality data for a broad suite of 

inorganic and organic chemical constituents. Six surface-water 

sites on streams and 34 groundwater wells were sampled 

for 232 constituents that include major ions, nutrients, trace 

elements, and organic compounds. Of the 232 constituents, 

11 were selected for more detailed analyses and discussion 

based on their common association with agricultural and 

energy development land uses. These dissolved constituents 

are chloride, dissolved solids, sodium, sulfate, aluminum, 

arsenic, iron, manganese, ammonia, nitrate, and nitrite. The 

surface-water sites were sampled primarily during April, June, 

August, and October. The groundwater wells were primarily 

sampled once.

Previous Studies

Several previous studies were completed that described 

the water resources of the reservation. A study was done 

by Dingman and others (1954) that located adequate water 

supplies and sources of sand and gravel on the uplands of 

the reservation. The effects of land-use activity on the water 

quality of five drainage basins on and adjacent to the reservation were described in Macek-Rowland and Lent (1996). 

The five ephemeral streams in these basins were East Fork 

Shell Creek, Deepwater Creek, Bear Den Creek, Moccasin 

Creek, and Squaw Creek. The study documented variations 

in agricultural land-use patterns and spatial and temporal 

variability of selected nutrients, total organic carbon, selected 

pesticides, and selected bacteria concentrations in the five 

streams (Macek-Rowland and Lent, 1996). The land-use data 

also were compared to water-quality data to determine relations between agricultural land-use practices and surface-water 

quality on the reservation. Spatial and temporal variations in 

nonpoint-source contamination in surface water in the reservation area during 1990–93 were related to variations in land-use 

patterns and streamflow. Analysis of water-quality samples 

indicated that concentrations of nitrogen, phosphorus, and 

total organic carbon varied throughout the study area (MacekRowland and Lent, 1996).

The quantity, quality, and use of groundwater and 

surface-water resources of the reservation were characterized 

in a study by Cates and Macek-Rowland (1998). The study 

described the stratigraphy and distribution of aquifers underlying the reservation and the groundwater system that included 

the direction of movement, the recharge and discharge relations, the volume of groundwater in storage, the hydraulic 

properties of the aquifers, and the quality of groundwater. The 

study also documented the average streamflow, the year-toyear and seasonal variations in streamflow, and the quality of 

water in streams on the reservation and completed an inventory of the water use. The study data were collected between 

January 1990 and December 1992 and supplemented by 

historical data and information from previous investigations 

that are published in Wald and Cates (1995). No groundwaterquality monitoring on the reservation is known to have been 

completed since the Cates and Macek-Rowland (1998) study.

In 2013, a water-resources investigation was done by 

private consultants that was prepared for the TAT to provide 

a concise summary of the groundwater and surface-water 

resources, which focused primarily on quantity and availability, within the reservation (Tricia Pfeiffer, U.S. Environmental 

Protection Agency, written commun., 2017).

Methods

This section describes the methods used for selection of 

surface-water sites and groundwater wells, data collection, 

laboratory methods, and water-quality data analyses. In general, surface-water sites and groundwater wells were selected 

to represent the water resources in major drainages and the 

aquifers most used on the reservation. Water-quality samples 

collected on the reservation during 2014–17 were analyzed 

at the U.S. Environmental Protection Agency (EPA) Region 

8 Laboratory in Golden, Colorado, and the USGS National 

Water Quality Laboratory in Lakewood, Colo. Water-quality 

data were summarized in graphical and tabular form for 

selected constituents with available water-quality standards 

related to agricultural land uses and energy development.
4 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

Surface-Water Site Selection

Surface-water-quality samples were collected from 

six surface-water sites that were selected from previously 

established USGS streamgaging stations (table 1, fig. 1). Of 

the six sites selected, three are continuous-recording USGS 

streamgaging stations currently (2019) operated on the reservation. These three streamgaging stations are Bear Den Creek 

near Mandaree, N. Dak. (USGS station number 06332515), 

East Fork Shell Creek near Parshall, N. Dak. (USGS station number 06332523), and Deepwater Creek at mouth near 

Raub, N. Dak. (USGS station number 06332770). The three 

streamgaging stations are in drainage basins that drain into 

Lake Sakakawea. The Bear Den Creek streamgaging station 

has been continuously operated since 1966 and is west of Lake 

Sakakawea where rangeland is the major land use. The East 

Fork Shell Creek and Deepwater Creek streamgaging stations 

were operated from 1990 through 2013 and from 2016 to 

present (2019) and are northeast and east of Lake Sakakawea, 

respectively, where cropland is the major land use. The other 

three selected surface-water sites are not currently (2019) 

streamgaging stations, and instantaneous streamflow measurements were made concurrently with each sample collection. 

Streamflow data are available from the USGS National Water 

Information System (NWIS) database using the station numbers in table 1 (U.S Geological Survey, 2017).

Groundwater Well Selection

Reconnaissance of potential groundwater wells for 

sampling began in May 2014, and 34 wells were selected for 

sampling. Initially, groundwater wells were randomly selected 

using methods described by Scott (1990). The 1,530 squaremile study area of the reservation was divided into 20 equalarea cells, and 1 well in each cell was randomly selected from 

the population of all wells available from multiple databases 

using a program developed by Scott (1990). Well locations 

on the reservation were obtained from the USGS NWIS 

database (U.S Geological Survey, 2017) and North Dakota 

State Water Commission databases (North Dakota State Water 

Commission, 2014a; 2014b). The types of wells selected were 

used for domestic, stock (including flowing), monitoring, 

irrigation, and industrial water use. This randomized selection 

approach resulted in a network of wells that represents the 

most utilized aquifer units and had good spatial coverage of 

the area.

The selected wells were inspected for suitability for sampling; if the well could not be sampled without being affected 

by any type of treatment system or a pressure tank, the well 

was not selected for sampling because it would not represent 

water-quality conditions in the aquifer. Well construction 

information was obtained from driller’s logs (North Dakota 

State Water Commission, 2014b) and was used to confirm 

the aquifer where the well was completed. Permissions were 

obtained from the landowner for sampling. If permissions 

were not granted for the selected well or if a well was deemed 

unsuitable for sampling, alternate wells were sought as 

described by Scott (1990).

Locating appropriate wells for sampling using the 

random selection approach (Scott, 1990) presented several 

challenges. The Fort Berthold Rural Water System was partially constructed and currently (2019) supplies most of the 

municipal water on the reservation. The rural water system 

pumps raw water from Lake Sakakawea, and several water 

treatment plants treat the water to regulatory standards and 

provides treated water to most residents on the reservation 

(Bureau of Reclamation, 2016). With the development of the 

Fort Berthold Rural Water System and associated decrease in 

groundwater use, most of the landowners’ domestic wells were 

disconnected. In addition, many of the monitoring wells on the 

reservation that were drilled before the 1990s were destroyed, 

abandoned, or no longer existed.

Because of the challenges in locating appropriate wells 

using the random approach, additional wells were selected 

based on criteria that the well could be physically located, the 

well had construction information from a well driller’s log, 

the samples could be collected without the well being affected 

by any type of water treatment system or a pressure tank, 

and the landowner had granted permission. All wells selected 

were completed on the reservation in the Quaternary, lower 

Tertiary, or Upper Cretaceous aquifer systems. The aquifers 

included the New Town, Sanish, Shell Creek, Tongue River, 

and White Shield aquifers (contained in Quaternary-age 

glacial and fluvial sediments); the Fort Union and Sentinel 

Butte aquifers (contained in the lower Tertiary-age Fort Union 

Formation); and the Fox Hills aquifer (contained in the Upper 

Cretaceous-age Fox Hills Sandstone) (North Dakota State 

Water Commission, 2014a).

Data Collection and Laboratory Analysis 

Methods

Surface-water and groundwater samples were collected 

by USGS and TAT personnel using methods that follow USGS 

protocols (U.S. Geological Survey, variously dated). The six 

surface-water sites were sampled twice during 2014 (May 

and August) and four times per year (April, June, August, 

and October) during 2015–17. Samples were collected from 

11 groundwater wells in 2014; 9 groundwater wells in 2015; 

and 15 groundwater wells in 2017 (table 2, available for 

download at https://doi.org/10.3133/sir20205020). A well 

(map number 3, table 2) was sampled once in 2014 and once 

in 2017. This well was selected to be sampled twice because 

the well is in an area of dense energy development and comparisons could be made to previously collected water-quality 

samples.

Surface-water-quality samples were collected using the 

equal-width-increments (EWI) method with a depth integrated DH–81 sampler (Davis, 2005). The DH–81 sampler is 

constructed of a plastic bottle with plastic removable nozzles. 
Table 1. Period of record for available surface-water data from U.S. Geological Survey streamgaging stations on the Fort Berthold Reservation, Nort[Data available from U.S. Geological Survey (USGS) National Water Information System database (U.S. Geological Survey, 2017)]

USGS

station 

number

(fig. 1)

USGS station name

Latitude,

in decimal

degrees

Longitude,

in decimal

degrees

Elevation, 

in feet 

above

North 

American

Vertical 

Datum of 

1988

Drainage 

area, in 

square 

miles

Strea

06332515 Bear Den Creek near Mandaree, North Dakota1 47.787 –102.769 1,949 74 6/1966–pre06332520 Shell Creek near Parshall, North Dakota 48.053 –102.137 1,932 465 9/1965–9/106332523 East Fork Shell Creek near Parshall, North Dakota1 47.949 –102.215 1,890 360 7/1991–9/206332770 Deepwater Creek at mouth near Raub, North Dakota1 47.738 –102.108 1,832 220 4/1990–9/206337470 Moccasin Creek at mouth near Mandaree, North Dakota 47.600 –102.511 1,918 54 4/1990–8/106337480 Squaw Creek above mouth near Mandaree, North Dakota 47.641 –102.512 1,892 52 4/1990–8/1

1Continuous-recording streamgaging station.2October 2019.
6 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

The EWI method is used to collect samples that represent the 

vertical and horizontal variability of the constituents in a cross 

section of the stream channel. The EWI method involved the 

collection of vertically integrated, isokinetic (velocity entering 

the sampler nozzle at the same velocity of the stream) samples 

and dividing the channel width into equal sections (generally 

10). The EWI method is viable for stream velocities more than 

1.5 feet per second. For samples where the stream velocities 

were less than 1.5 feet per second, a multiple vertical method 

or a weighted-bottle method was used (U.S. Geological 

Survey, variously dated). The multiple vertical method was 

collected the same as an EWI method, but the sample was not 

collected isokinetically. With the weighted-bottle method, a 

plastic device that holds the collector bottle is lowered in the 

stream (usually from a bridge) in multiple locations across the 

width of the stream. All samples, except for those collected 

for volatile and semivolatile organic compound analyses, were 

composited in a plastic churn splitter and processed onsite. 

Whole-water (unfiltered) samples were collected from the 

churn through the spigot, and filtered samples were processed 

through a 0.45-micrometer capsule filter (U.S. Geological 

Survey, variously dated). For volatile organic compounds, 

a sampler was used that is specifically designed to collect nonaerated samples in 40-mL glass septum vials. The 

stainless-steel volatile organic compound sampler was placed 

in a wadeable area of the stream until the vials were filled. The 

sampler was removed and drops of hydrochloric acid were 

added to each vial until a pH of less than 2 (standard units) 

was achieved. In addition to constituent concentrations, field 

measurements of water temperature, pH, specific conductance, 

dissolved oxygen, turbidity, and alkalinity were made with 

each surface-water sample at the centroid of the stream. The 

field measurements were made using a multiparameter instrument that was calibrated daily prior to data collection (U.S. 

Geological Survey, variously dated).

Streamflow was measured at the six surface-water sites 

each time water-quality samples were collected using protocols described in Turnipseed and Sauer (2010). Instantaneous 

streamflow was determined either by direct measurement or 

from stage-discharge rating tables (Rantz and others, 1982), 

and the streamflow was used for describing the hydrologic 

conditions at the time of the discrete samples. All streamflow 

measurements and continuously recorded data are stored in the 

USGS NWIS database (U.S. Geological Survey, 2017).

Groundwater samples from nonmonitoring (domestic, 

stock, and industrial) wells were collected using the existing 

submersible pumps in the wells. Sampling points in the water 

systems were located before wells were exposed to any type 

of water treatment system or pressure tanks. Groundwater 

samples collected from wells that were flowing (artesian) used 

the natural pressure head of the well. Tubing was connected 

to the existing spigot for collection of the water samples. 

Groundwater samples collected from monitoring wells used a 

2-inch Grundfos portable submersible pump that was lowered 

to about 3 feet below static water surface and above the top of 

the screened interval of the well.

All groundwater sample water was pumped through 

a closed-circuit system using Teflon tubing and connectors 

inside the field vehicle to ensure stable environmental control. 

Samples were collected within a chamber bag using clean 

hands/dirty hands sampling techniques (U.S. Geological 

Survey, variously dated). In general, samples were collected 

after a minimum of three casing volumes of water were purged 

from the wells and field measurements (water temperature, 

pH, specific conductance, dissolved oxygen, and turbidity) were stable. Final readings of field measurements were 

recorded for the samples after stabilization. In addition to the 

field measurements, water levels were measured at monitoring 

wells before pumping and sample collection using a steel or 

electric tape (Cunningham and Schalk, 2011).

The groundwater- and surface-water-quality samples 

were analyzed at the EPA Region 8 Laboratory in Golden, 

Colo., and the USGS National Water Quality Laboratory in 

Lakewood, Colo. (table 3). Surface water and groundwater were analyzed for major ions, trace elements, nutrients, 

volatile and semivolatile organic compounds, gasoline and 

diesel range organics, dissolved and total organic carbon, and 

dissolved solids. The EPA Region 8 Laboratory in Golden, 

Colo., analyzed samples collected during 2014–15 for major 

ions, trace elements, nutrients, volatile and semivolatile 

organic compounds, gasoline and diesel range organics, dissolved and total organic carbon, and dissolved solids following procedures described in the EPA Region 8 Environmental 

Laboratory quality-assurance manual (Mark Burkhart, U.S. 

Environmental Protection Agency, written commun.; U.S. 

Environmental Protection Agency, 2012). For samples collected during 2016–17, the EPA Region 8 Laboratory was 

unable to analyze samples for nutrients, dissolved organic carbon, total organic carbon, and dissolved solids, and the USGS 

National Water Quality Laboratory in Lakewood, Colo., 

completed the analyses following procedures described in 

Maloney (2005) and Fishman and Friedman (1989). Dissolved 

solids samples collected during 2014–15 were analyzed at 

the EPA Region 8 Laboratory, and dissolved solids samples 

collected during 2016–17 were analyzed at the USGS National 

Water Quality Laboratory.

A total of 232 constituents were monitored in surface 

water and groundwater on the reservation. In this report, discussion and presentation of results focuses on 11 constituents 

selected based on their common association with agricultural 

and energy development land uses. These constituents are 

chloride, dissolved solids, sodium, sulfate, aluminum, arsenic, 

iron, manganese, ammonia, nitrate, and nitrite. Produced water 

from shale and tight gas formations typically contain high concentrations of some of these major ions and trace metals (U.S. 

Environmental Protection Agency, 2016).

Trace metals in streams exist in dissolved and particulate 

form. Water-quality samples were collected and analyzed for 

total (unfiltered) trace metals and dissolved (filtered) trace 

metals. The EPA Office of Water uses the dissolved fraction 

to set and measure compliance with water-quality standards. 

This approach is recommended because dissolved metals more 
Methods 7

Table 3. List of field measurements and constituents analyzed from samples collected on the Fort Berthold Reservation, North Dakota, 

2014–17.

[Samples were analyzed at the U.S. Environmental Protection Agency Region 8 Laboratory in Golden, Colorado, and the U.S. Geological Survey National Water 

Quality Laboratory in Lakewood, Colorado. CaCO3, calcium carbonate; --, not applicable; SO4, sulfate; N, nitrogen; P, phosphorus]

Field measurement or constituent

Field measurements

Groundwater level (feet below land surface) Specific conductance (microsiemens per centimeter 

at 25 degrees Celsius)

Alkalinity, incremental titration 

(milligrams per liter as CaCO3)

Water temperature (degrees Celsius) Dissolved oxygen (milligrams per liter) Streamflow (cubic feet per second)

pH (standard units) Turbidity (formazin nephelometric unit) --

Major ions (filtered, milligrams per liter)

Bromide Fluoride Sodium

Calcium Magnesium Sulfate as SO4

Chloride Potassium --

Dissolved solids Silica --

Nutrients (milligrams per liter)

Ammonia as N, filtered Orthophosphate as P, filtered Dissolved organic carbon, filtered

Nitrate as N, filtered Total nitrogen as N, unfiltered Total organic carbon, unfiltered

Nitrite as N, filtered Total phosphorus as P, unfiltered --

Trace elements (filtered and unfiltered, in micrograms per liter)

Aluminum Cobalt Silver

Antimony Copper Strontium

Arsenic Iron Thallium

Barium Lead Uranium

Beryllium Manganese Vanadium

Boron Molybdenum Zinc

Cadmium Nickel --

Chromium Selenium --

Organic constituents (unfiltered, micrograms per liter)

Diesel range organics m- and p-Xylene

Gasoline range organics Methacrylonitrile

1,1,1,2-Tetrachloroethane Methyl acrylate

1,1,1-Trichloroethane Methyl tert-butyl ether (MTBE)

1,1,2,2-Tetrachloroethane Methylene chloride

1,1,2-Trichloroethane Naphthalene

1,1-Dichloroethane n-Butylbenzene

1,1-Dichloroethene n-Propylbenzene

1,1-Dichloropropene o-Xylene

1,2,3-Trichlorobenzene p-Isopropyltoluene

1,2,3-Trichloropropane sec-Butylbenzene

1,2,4-Trichlorobenzene Styrene

1,2,4-Trimethylbenzene tert-Butylbenzene

1,2-Dibromo-3-chloropropane (DBCP) Tetrachloroethene

1,2-Dibromoethane (EDB) Toluene

1,2-Dichlorobenzene Toluene-d8

4-Bromophenyl phenyl ether

4-Chloro-3-methylphenol

4-Chloroaniline

4-Chlorophenyl phenyl ether

4-Nitroaniline

4-Nitrophenol

Acenaphthene

Acenaphthylene

Adamantane

Aniline

Anthracene

Azobenzene

Benzo[a]anthracene

Benzo[a]pyrene

Benzo[b]fluoranthene

Benzo[ghi]perylene
8 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

Table 3. List of field measurements and constituents analyzed from samples collected on the Fort Berthold Reservation, North Dakota, 

2014–17.—Continued

[Samples were analyzed at the U.S. Environmental Protection Agency Region 8 Laboratory in Golden, Colorado, and the U.S. Geological Survey National Water 

Quality Laboratory in Lakewood, Colorado. CaCO3, calcium carbonate; --, not applicable; SO4, sulfate; N, nitrogen; P, phosphorus]

Field measurement or constituent

Organic constituents (unfiltered, micrograms per liter)—Continued

1,2-Dichloroethane trans-1,2-Dichloroethene Benzo[k]fluoranthene

1,2-Dichloroethane-d4 trans-1,3-Dichloropropene Benzoic acid

1,2-Dichloropropane Trichloroethene (TCE) Benzyl alcohol

1,3,5-Trimethylbenzene Trichlorofluoromethane (CFC-11) Bis(2-chloroethoxy)methane

1,3-Dichlorobenzene Vinyl chloride Bis(2-chloroethyl)ether

1,3-Dichloropropane Xylenes (total) Bis(2-chloroisopropyl) ether

1,4-Dichlorobenzene d-Limonene Bis-(2-Ethylhexyl) adipate

2,2-Dichloropropane 1,2,4-Trichlorobenzene Bis(2-ethylhexyl) phthalate

2-Butanone 1,2-Dichlorobenzene Butyl benzyl phthalate

2-Chlorotoluene 1,2-Dinitrobenzene Carbazole

2-Hexanone 1,3-Dichlorobenzene Chrysene

4-Bromofluorobenzene 1,3-Dimethyladamantane Dibenz[a,h]anthracene

4-Chlorotoluene 1,3-Dinitrobenzene Dibenzofuran

4-Methyl-2-pentanone 1,4-Dichlorobenzene Diethyl phthalate

Acetone (2-propanone) 1,4-Dinitrobenzene Dimethyl phthalate

Acrylonitrile 1-Methylnaphthalene Di-n-butyl phthalate

Allyl chloride 2,3,4,6-Tetrachlorophenol Di-n-octyl phthalate

Benzene 2,3,5,6-Tetrachlorophenol Diphenylamine

Bromobenzene 2,4,5-Trichlorophenol Fluoranthene

Bromochloromethane 2,4,6-Tribromophenol Fluorene

Bromodichloromethane 2,4,6-Trichlorophenol Hexachlorobenzene

Bromoform 2,4-Dichlorophenol Hexachlorobutadiene

Bromomethane 2,4-Dimethylphenol Hexachlorocyclopentadiene

Carbon disulfide 2,4-Dinitrophenol Hexachloroethane

Carbon tetrachloride 2,4-Dinitrotoluene Indeno(1,2,3-cd)pyrene

Chlorobenzene 2,6-Dinitrotoluene Isophorone

Chlorodibromomethane 2-Butoxyethanol Naphthalene

Chloroethane 2-Butoxyethanol phosphate Nitrobenzene

Chloroform 2-Chloronaphthalene Nitrobenzene-d5

Chloromethane 2-Chlorophenol N-Nitrosodimethylamine

cis-1,2-Dichloroethene 2-Fluorobiphenyl N-Nitrosodi-n-propylamine

cis-1,3-Dichloropropene 2-Fluorophenol Pentachlorophenol

Dibromofluoromethane 2-Methylnaphthalene Phenanthrene

Dibromomethane 2-Methylphenol Phenol

Dichlorodifluoromethane 2-Nitroaniline Phenol-d6

Ethyl ether 2-Nitrophenol Pyrene

Ethylbenzene p-Cresol Pyridine

Hexachlorobutadiene 3,3 ́-Dichlorobenzidine Squalene

Iodomethane 3-Nitroaniline Terphenyl-dl4

Isopropylbenzene 4,6-Dinitro-2-methylphenol Terpineol
Methods 9

closely approximate the bioavailable fraction in the water 

column than total recoverable metals (U.S. Environmental 

Protection Agency, 1994). The EPA recommends that State 

water-quality standards be based on dissolved metals. Thus, 

the dissolved fractions of aluminum, arsenic, iron, and manganese are presented.

All water-quality data collected on the reservation during 2014–17 can be accessed from the Water Quality Portal 

database (National Water Quality Monitoring Council, 2018). 

Water-quality data analyzed by the USGS National Water 

Quality Laboratory and streamflow data also can be accessed 

from the USGS NWIS database using site numbers in tables 1

and 2 (U.S. Geological Survey, 2017).

Quality-assurance samples were collected to estimate 

reproducibility and potential for bias. Quality-assurance 

samples included 5 equipment blanks, 1 field blank, and 1 replicate sample. Equipment blanks were collected and reviewed 

prior to collection of the first environmental sample of the 

year. Equipment blanks were collected in a controlled environment to determine if the cleaning procedures for sample containers, sample collection equipment, and sample-processing 

procedures are sufficient to produce contaminant-free samples. 

Equipment blanks were collected from the surface-water sampling equipment, groundwater pumps, and associated tubing. 

The equipment was recleaned prior to collection of environmental samples. Field blanks were collected from the surfacewater and groundwater sampling equipment in the field at a 

sampling site. 

The replicate sample was analyzed to assess variability 

in sample processing and analytical methods. The analytical 

variability of replicate samples for constituents was assessed 

using relative percent difference (calculated as the absolute 

difference in concentration divided by the mean concentration multiplied by 100 for the environmental/replicate sample 

pair). Relative percent differences for dissolved chloride, 

dissolved solids, sodium, sulfate, aluminum, arsenic, iron, 

manganese, ammonia, nitrate, and nitrite were all less than 

10 percent (table 1.1), indicating satisfactory quality assurance on these constituents. Overall, the equipment blanks were 

satisfactory (near or less than detection level) with the exception of dissolved organic carbon and diesel range organics 

that had detections of 2,290 mg/L and 52.6 μg/L, respectively 

(table 1.2). The organic carbon detection was likely from 

residual methanol remaining during the cleaning procedure. 

The equipment blanks collected before and after this sample 

had nondetects for organic carbon, and results for environmental samples collected afterwards were in the same range 

as other environmental samples, indicating that field rinsing 

removed any remaining methanol. 

Quality-assurance sample data analyzed at the EPA 

Region 8 Laboratory can be accessed from the Water Quality 

Portal database (National Water Quality Monitoring Council, 

2018). Quality-assurance sample data for the 11 constituents 

selected for additional discussion are presented in table 1.1. 

The quality-assurance sample data for the constituents not 

selected for additional discussion are presented in table 1.2.

Water-Quality Data Analyses

Summary statistics (minimum, median, and maximum) 

for concentrations of all 232 compounds are presented in 

table 1.3. Several of the water-quality constituents had varying 

reporting levels. The reporting level is the “less than” value 

reported when concentrations are too low to be accurately 

quantified. The reporting level can change through time 

and among laboratories because of changes in sensitivity 

of laboratory equipment, changes in analytical methods, or 

changes in protocol for determining the reporting level. The 

reporting level is generally higher than the method detection 

limit, which is the lowest concentration for which a compound 

can be detected (but not necessarily accurately quantified; 

Childress and others, 1999). Summary statistics were determined based solely on the detected concentrations. The “less 

than” values were not included in the summary statistics and, 

therefore, a “less than” value was indicated as a nondetect. 

The number of nondetects can be determined by subtracting the number of detections from the number of samples. 

Reporting levels for the 11 selected constituents in surface 

water and groundwater, along with the most common reporting level, are summarized in table 4. Water-quality concentrations for groundwater samples of the 11 selected water-quality 

constituents were mapped using a geographic information system to represent the spatial distribution across the reservation.

Selected water-quality constituents were compared to 

EPA drinking water maximum contaminant levels (MCLs), 

secondary drinking water regulations (SDWRs), and drinking water equivalent levels (U.S. Environmental Protection 

Agency, 2018). An MCL is an enforceable standard that refers 

to the highest level or concentration that is allowed in drinking 

water for protection of health. An SDWR is a nonenforceable guideline and addresses either cosmetic or aesthetic 

effects, such as taste, odor, and color. A drinking water 

equivalent level is a lifetime exposure concentration protective of adverse, noncancer health effects, that assumes all of 

the exposure to a contaminant is from drinking water. USGS 

health-based screening levels also were included and are 

nonenforceable benchmark concentrations of contaminants in 

water (Norman and others, 2018). These health-based screening levels supplement Federal drinking-water standards and 

guidelines, which are not available for many of the hundreds 

of contaminants analyzed in sources of drinking water. Using 

health-based screening levels can provide a human-health 

context when evaluating the quality of sources of drinking 

water and can help prioritize monitoring efforts. The drinking water-quality standards and health-based screening levels 

are summarized in table 5. If multiple drinking water-quality 

standards and health-based screening levels were available 

for a constituent, the one with the lowest value was used for 

comparisons.

Chloride concentrations were analyzed to determine if 

concentrations exceeded the EPA SDWR of 250 milligrams 

per liter (mg/L; table 5). Chloride is present in all natural 

waters, but generally at low concentrations (Hem, 1985). In 
10 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

Table 4. Laboratory reporting levels for selected water-quality constituents in surface water and groundwater on Fort Berthold 

Reservation, North Dakota, 2014–17.

[Cl, chloride; <, less than; *, most of the analytical results used this laboratory reporting level; Na, sodium; SO4, sulfate; Al, aluminum; As, arsenic; Fe, iron; 

Mn, manganese]

Constituent Reporting levels

Chloride, dissolved (milligrams per liter as Cl) <0.2*, < 2, 4

Dissolved solids, residue on evaporation at 180 degrees Celsius

(milligrams per liter) <2

Sodium, dissolved (milligrams per liter as Na) <500*, < 1,000, <5,000, <10,000

Sulfate, dissolved (milligrams per liter as SO4) <0.5*, <5, <10, < 25, < 50

Aluminum, dissolved (micrograms per liter as Al) <100

Arsenic, dissolved (micrograms per liter as As) <1, <2*, < 4, < 5

Iron, dissolved (micrograms per liter as Fe) <100

Manganese, dissolved (micrograms per liter as Mn) <2

Ammonia, dissolved (milligrams per liter as nitrogen) <0.025*, <0.05

Nitrate, dissolved (milligrams per liter as nitrogen) <0.005

Nitrite, dissolved (milligrams per liter as nitrogen) <0.005

most surface streams, chloride concentrations are lower than 

those of sulfate or bicarbonate. Exceptions are where streams 

receive inflows of high-chloride groundwater, industrial waste, 

or are affected by oceanic tides.

Dissolved solids concentrations were analyzed to determine if concentrations exceeded the EPA SDWR of 500 mg/L 

(table 5). Dissolved solids are an important constituent to 

water purveyors and users because high concentrations of dissolved solids can cause changes to the taste of water and could 

have undesirable effects for hospitals, industrial facilities, and 

stream ecosystems (Hem, 1985). Dissolved solids in surface 

water result from natural dissolution of rocks and minerals or 

discharges from municipal, industrial, or agricultural sources 

(Hem, 1985). The primary constituents of dissolved solids 

are the cations (positively charges ions) calcium, magnesium, 

sodium, and potassium; the anions (negatively charged ions) 

sulfate, chloride, fluoride, nitrate, and those contributing to 

alkalinity; and several other constituents that are present in 

small quantities. Natural variability in dissolved solids concentrations depends on chemical characteristics of drainage-basin 

soils; composition of surficial material; and in some situations, the minerals in deeper geologic strata. Dissolved solids 

concentrations may be affected by different constituents in different locations in North Dakota. Usually the changes in dissolved solids concentrations are somewhat related to the rate 

of water streamflow and the rate of change of streamflow, but 

this correlation is complicated by other factors related to the 

hydrology and the geochemistry of the system (Hem, 1985).

Sodium concentrations were analyzed to determine 

if concentrations exceeded the taste threshold of 30 mg/L 

(table 5). Sodium tends to remain in solution when dissolved 

from weathering rocks and does not form precipitates that can 

reduce dissolved sodium concentrations (Hem, 1985). Cationexchange processes in freshwater systems tend to extract 

divalent ions from solution and replace them with monovalent ions, especially sodium (Hem, 1985). Also, sodium salts 

used for deicing roads can be transported to streams in runoff 

(Hem, 1985).

Sulfate concentrations were analyzed to determine if concentrations exceeded the EPA SDWR of 250 mg/L (table 5). 

Sulfate is an oxidized form of sulfur and occurs naturally in 

surface water as a result of weathering of metallic sulfides 

in igneous and sedimentary rocks (Hem, 1985). Soils across 

North Dakota have naturally high sulfur content that readily 

oxidizes to highly soluble sulfate ions (Franzen, 2019). Sulfate 

in streams may be affected by land-use changes that can 

increase or decrease the exposure of naturally occurring sulfur 

to surface runoff. In addition to natural sources, sulfate concentrations in streams may be increased as a result of human 

activities. The release of sulfur dioxide during the combustion of fossil fuels may increase stream sulfate concentrations 

(Smith and Alexander, 1986). The conversion of sulfur dioxide 

to particulate sulfate is assumed to be an aqueous-enhanced 

chemical reaction in the atmosphere (Lamb and others, 1987). 

Subsequent wet and dry deposition may increase concentrations of sulfate in surface water. High concentrations of sulfate 

affect the taste of drinking water and may cause laxative 

effects (Hem, 1985).

Aluminum concentrations were analyzed to determine if 

concentrations exceeded the EPA SDWR of 50 micrograms 

per liter (μg/L; table 5). Aluminum is the third-most abundant 

element in the Earth’s outer crust but rarely is detected in 

solution in natural water in a concentration greater than a few 

tenths or hundredths of a microgram per liter (Hem, 1985). 

Most natural waters have ample opportunity to dissolve aluminum because it is so abundant and so widely distributed (Hem, 

1985). Aluminum, when present in high concentrations such 

as downstream from industrial point sources of aluminum-rich 
Table 5. Drinking water-quality standards and health-based screening levels available for water-quality constituents analyzed on Fort Berthold Rese2014–17.[This table lists Chemical Abstract Service (CAS) Registry Numbers. The CAS recommends the verification of the CAS Registry Number through CAS Client ServicesSM. EPAAgency; USGS, U.S. Geological Survey; HBSL, health-based screening level; --, no data or standard; SDWR, secondary drinking water regulation; MCL, maximum contaminansodium; F, fluoride; SO4, sulfate; Al, aluminum; Sb, antimony; As, arsenic; Ba, barium; Be, beryllium; B, boron; DWEL, drinking water equivalent level; Cd, cadmium; Cr, chroFe, iron; Pb, lead; Mn, manganese; Mo, molybdenum; Ni, nickel; Se, selenium; Ag, silver; Sr, strontium; Ti, thallium; V, vanadium; Zn, zinc]

Field measurement or constituent

CAS

Registry

Number

EPA

water-quality standard1

Water-quality 

standard

Water-qua

standard t

Field measurements

Field pH (standard units) -- 6.5–8.5 SDWR Turbidity, field measurement, unfiltered water (formazin nephelometric unit) -- 5 MCL 

Major ions (dissolved is the sample filtered in the laboratory through 0.45-micrometer filter)

Chloride, dissolved (milligrams per liter as Cl) 16887–00–6 250 SDWR Dissolved solids, residue on evaporation at 180 degrees Celsius (milligrams per liter) -- 500 SDWR Sodium, dissolved (milligrams per liter as Na) 7440–23–5 30 Taste threshFluoride, dissolved (milligrams per liter as F) 7681–49–4 4 MCL Sulfate, dissolved (milligrams per liter as SO4) 14808–79–8 250 SDWR 

Trace elements (dissolved is the sample filtered in the field through 0.45-micrometer disposable cartridge filter)

Aluminum, dissolved (micrograms per liter as Al) 7429–90–5 50 SDWR Antimony, dissolved (micrograms per liter as Sb) 7440–36–0 6 MCL Arsenic, dissolved (micrograms per liter as As) 7440–38–2 10 MCL Barium, dissolved (micrograms per liter as Ba) 7440–39–3 2,000 MCL Beryllium, dissolved (micrograms per liter as Be) 7440–41–7 4 MCL Boron, dissolved (micrograms per liter as B) 7440–42–8 7,000 DWEL Cadmium, dissolved (micrograms per liter as Cd) 7440–43–9 5 MCL Chromium, dissolved (micrograms per liter as Cr) 7440–47–3 100 MCL Cobalt, dissolved (micrograms per liter as Co) 7440–48–4 -- -- Copper, dissolved (micrograms per liter as Cu) 7440–50–8 1,300 MCL Iron, dissolved (micrograms per liter as Fe) 7439–89–6 300 SDWR Lead, dissolved (micrograms per liter as Pb) 7439–92–1 15 MCL Manganese, dissolved (micrograms per liter as Mn) 7439–96–5 50 SDWR Molybdenum, dissolved (micrograms per liter as Mo) 7439–98–7 200 DWEL Nickel, dissolved (micrograms per liter as Ni) 7440–02–0 700 DWEL Selenium, dissolved (micrograms per liter as Se) 7782–49–2 50 MCL 
Table 5. Drinking water-quality standards and health-based screening levels available for water-quality constituents analyzed on Fort Berthold Rese2014–17.—Continued [This table lists Chemical Abstract Service (CAS) Registry Numbers. The CAS recommends the verification of the CAS Registry Number through CAS Client ServicesSM. EPAAgency; USGS, U.S. Geological Survey; HBSL, health-based screening level; --, no data or standard; SDWR, secondary drinking water regulation; MCL, maximum contaminansodium; F, fluoride; SO4, sulfate; Al, aluminum; Sb, antimony; As, arsenic; Ba, barium; Be, beryllium; B, boron; DWEL, drinking water equivalent level; Cd, cadmium; Cr, chroFe, iron; Pb, lead; Mn, manganese; Mo, molybdenum; Ni, nickel; Se, selenium; Ag, silver; Sr, strontium; Ti, thallium; V, vanadium; Zn, zinc] Field measurement or constituent CAS Registry Number EPA water quality standard1 

Water-quality standard Water-qua

standard t

Trace elements (dissolved is the sample filtered in the field through 0.45-micrometer disposable cartridge filter)—Continued Silver, dissolved (micrograms per liter as Ag) 7440–22–4 100 SDWR 

Strontium, dissolved (micrograms per liter as Sr) 7440–24–6 20,000 DWEL Thallium, dissolved (micrograms per liter as Ti) 7440–28–0 2 MCL Uranium, natural, dissolved (micrograms per liter) 7440–61–1 30 MCL Vanadium, dissolved (micrograms per liter as V) 7440–62–2 -- -- Zinc, dissolved (micrograms per liter as Zn) 7440–66–6 5,000 SDWR 

Nutrients (dissolved is the sample filtered in the field through 0.45-micrometer disposable cartridge filter) Ammonia, dissolved (milligrams per liter as nitrogen) 7664–41–7 30 Taste thresho

Nitrate, dissolved (milligrams per liter as nitrogen) 14797–55–8 10 MCL Nitrite, dissolved (milligrams per liter as nitrogen) 14797–65–0 1 MCL Nitrate plus nitrite, dissolved (milligrams per liter as nitrogen) -- 10 -- 

Organic constituents 1,2 Dichloroethane, unfiltered, recoverable (micrograms per liter) 107–06–2 5 MCL 

1,2 Dichloropropane, unfiltered, recoverable (micrograms per liter) 78–87–5 5 MCL Acetone, unfiltered, recoverable (micrograms per liter) 67–64–1 -- -- Benzene, unfiltered, recoverable (micrograms per liter) 71–43–2 5 MCL Bromoform, unfiltered, recoverable (micrograms per liter) 75–25–2 80 MCL Carbon disulfide, unfiltered, recoverable (micrograms per liter) 75–15–0 -- -- Carbon tetrachloride, unfiltered, recoverable (micrograms per liter) 56–23–5 5 MCL Chloroform, unfiltered, recoverable (micrograms per liter) 67–66–3 80 MCL Ethlybenzene, unfiltered, recoverable (micrograms per liter) 100–41–4 700 MCL Hexachlorobenzene, unfiltered, recoverable (micrograms per liter) 118–74–1 1 MCL Hexachlorocyclopentadiene, unfiltered, recoverable (micrograms per liter) 77–47–4 50 MCL Pentachlorophenol, unfiltered, recoverable (micrograms per liter) 87–86–5 1 MCL 
Table 5. Drinking water-quality standards and health-based screening levels available for water-quality constituents analyzed on Fort Berthold Rese2014–17.—Continued[This table lists Chemical Abstract Service (CAS) Registry Numbers. The CAS recommends the verification of the CAS Registry Number through CAS Client ServicesSM. EPAAgency; USGS, U.S. Geological Survey; HBSL, health-based screening level; --, no data or standard; SDWR, secondary drinking water regulation; MCL, maximum contaminansodium; F, fluoride; SO4, sulfate; Al, aluminum; Sb, antimony; As, arsenic; Ba, barium; Be, beryllium; B, boron; DWEL, drinking water equivalent level; Cd, cadmium; Cr, chroFe, iron; Pb, lead; Mn, manganese; Mo, molybdenum; Ni, nickel; Se, selenium; Ag, silver; Sr, strontium; Ti, thallium; V, vanadium; Zn, zinc]

Field measurement or constituent

CAS

Registry

Number

EPA

water quality standard1

Water-quality 

standard

Water-qua

standard t

Organic constituents—Continued

Styrene, unfiltered, recoverable (micrograms per liter) 100–42–5 100 MCL Toluene, unfiltered, recoverable (micrograms per liter) 108–88–3 1,000 MCL 1,2,4–Trichlorobenzene, unfiltered, recoverable (micrograms per liter) 120–82–1 70 MCL Vinyl chloride, unfiltered, recoverable (micrograms per liter) 75–01–4 2 MCL Xylenes, unfiltered, recoverable (micrograms per liter) 1330–20–7 10,000 MCL 

1U.S. Environmental Protection Agency, 2018.2Norman and others, 2018.
14 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

process water, has been recognized as a toxic agent to aquatic 

freshwater organisms (Hem, 1985). The environmental effects 

of aluminum are mainly a result of acidic precipitation—

acidification of catchments leads to increased aluminum 

concentrations in soil solution and freshwaters. In the aquatic 

environment, aluminum acts as a toxic agent on gill-breathing 

animals such as fish and invertebrates. Aluminum also seems 

to accumulate in freshwater invertebrates (Rosseland and others, 1990).

Arsenic concentrations were analyzed to determine if 

concentrations exceeded the EPA MCL of 10 μg/L (table 5). 

Arsenic occurs naturally as a trace component in many rocks 

and sediments. Arsenic has been used as a component of pesticides and may enter streams or groundwater through waste 

disposal or agricultural drainage (Hem, 1985). An important 

factor in the natural circulation of arsenic is the volatility 

of the element and some of its compounds (Hem, 1985). 

Discharge of arsenic-enriched groundwater may contaminate 

surface-water resources. If the arsenic is released from these 

geologic sources into groundwater depends on the chemical 

form of the arsenic, the geochemical conditions in the aquifer, 

and the biogeochemical processes that occur. Arsenic also 

can be released into groundwater as a result of human activities such as mining, various uses in industry, animal feed, and 

wood preservatives.

In a national study of groundwater quality, USGS 

researchers documented that arsenic was detected in nearly 

one-half of the wells sampled in parts of aquifers used for 

drinking-water supply at a concentration of 1 μg/L or greater 

(DeSimone and others, 2014). As part of the national study, 

a regional assessment was completed for water quality in 

the glacial aquifer system that underlies much of the northern United States (Warner and Ayotte, 2014). The primary 

importance of the glacial aquifer system is as a source of water 

for public supply to the population centers in the region, but 

the aquifer system also provides drinking water for domestic 

use to individual homes and small communities in rural areas. 

Results of the national study indicated that contaminants from 

geologic sources, most notably arsenic and manganese, were 

detected at concentrations of potential concern for human 

health in 20 percent of samples of untreated drinking water—

more than three times as frequently as contaminants from 

human activities. Consumption of drinking water containing 

high concentrations of arsenic and manganese has been associated with carcinogenic and neurological effects (Hem, 1985). 

Concentrations of arsenic and manganese in the glacial aquifer 

system are among the highest in the Nation (DeSimone and 

others, 2014).

Iron concentrations were analyzed to determine if 

concentrations exceeded the EPA SDWR 300 μg/L (table 5). 

Iron occurs from the decomposition of some rocks and in 

mine runoff. Iron can affect the suitability of water for public 

and industrial water supply and can harm aquatic organisms. The higher concentrations sometimes reported in such 

waters generally are particulates (Kennedy and others, 1974) 

small enough to pass through 0.45-micrometer porosity filter 

membranes (Hem, 1985). The most common form of iron in 

solution in groundwater is the ferrous ion.

Manganese concentrations were analyzed to determine if 

concentrations exceeded the EPA SDWR of 50 μg/L (table 5). 

The chemistry of manganese is similar to iron in that both 

metals participate in redox processes in weathering environments (Hem, 1985). Manganese is a naturally occurring 

substance present in many types of rocks and soil. As with 

other elements, manganese cannot break down in the environment. Manganese can only change its form or become attached 

or separated from particles. In water, most of the manganese 

tends to attach to particles in the water or settle into the sediment. Manganese is not present in the environment as a pure 

metal, but rather is combined with other substances such as 

oxygen, sulfur, and chlorine (Hem, 1985).

Ammonia, nitrate, and nitrite are inorganic forms of 

nitrogen commonly associated with agricultural land use 

(Hem, 1985). As fertilizers are applied to the land surface, 

plants eventually take up these mineral forms through their 

root systems and form plant proteins and other organic forms 

of nitrogen. Livestock eat crops and produce manure, which is 

returned to the soil, adding organic and mineral forms of nitrogen to the soil, which can be used again by the next crop. As 

such, these sources of nitrogen may, in part, affect the water 

resources of the reservation.

Characterization of Water Quality on 

the Fort Berthold Reservation

The intent of the reservation water-quality monitoring 

program for surface water and groundwater is to provide a 

scientific understanding of current (2019) conditions that may 

be used to evaluate potential effects from agricultural and 

energy development land uses. The program was not designed 

for compliance monitoring. However, comparisons to available water-quality standards were provided. Water-quality 

data for surface water and groundwater on the reservation are 

described in terms of summary statistics on constituent concentrations. Eleven constituents considered to be indicators of 

surface-water and groundwater quality on the reservation were 

selected for analysis. The constituents were selected based on 

their common association with agricultural and energy development land uses. These constituents are chloride, dissolved 

solids, sodium, sulfate, aluminum, arsenic, iron, manganese, 

ammonia, nitrate, and nitrite. Samples also were analyzed 

for additional constituents that are generally categorized as 

major ions, nutrients, trace elements, and organic compounds. 

Constituents in these categories generally were not detected 

or were detected infrequently. Therefore, these constituents 

are not discussed in this report, but the data are provided in 

tables 1.3 and 1.5.
Characterization of Water Quality on the Fort Berthold Reservation 15

Surface-Water Quality

Streamflow and surface-water-quality data were collected from six surface-water sites on the reservation during May 2014 through October 2017. Historical streamflow 

data are available from the USGS NWIS database (U.S. 

Geological Survey, 2017; table 6) and water-quality data are 

available from the Water Quality Portal database (National 

Water Quality Monitoring Council, 2018) and NWIS database 

(table 1.4) for various periods from 1966 to April 2014. The 

six surface-water sites represent the six major drainages that 

are on and around the reservation and that flow into Lake 

Sakakawea (fig. 1). The streams on the reservation generally 

are ephemeral and have extended periods of no flow. The six 

surface-water sites were sampled two times during 2014 (May 

and August) and four times per year (April, June, August, and 

October) during 2015–17. Water-quality sampling frequency 

and timing during 2015–17 was based on a design described 

as “level 3” sites in Galloway and others (2012) and similar to 

the North Dakota statewide sampling network that is operated 

by the North Dakota Department of Environmental Quality, 

the USGS, and the North Dakota State Water Commission 

(Joel Galloway, U.S. Geological Survey, written commun., 2019).

Streamflow data and water-quality samples are needed 

to understand the chemistry, loads, and trends in the streams. 

Data from the six surface-water sites help hydrologists to better understand the hydrology and water quality on the reservation. Streamflow either was continuously recorded from an 

existing streamgaging station or instantaneously measured 

concurrently with each sample collected. Daily mean streamflows for the three continuous-recording USGS streamgaging 

stations generally were higher during spring snowmelt and 

rainfall from April through June and generally were lower 

during fall and winter from October through March. This 

pattern is represented in figure 2 for the streamgaging station 

Bear Den Creek near Mandaree, N. Dak. (USGS station number 06332515). The water-quality samples collected during 

2014–17 also were displayed on figure 2 to show the range 

of streamflow during sample collection. In this case, streamflow ranged from less than 0.01 to 10 cubic feet per second. 

Historically, streamflows at the six sites ranged from a minimum of less than 0.01 cubic foot per second at several sites to 

a maximum of 1,570 cubic feet per second at the streamgaging station Shell Creek near Parshall, N. Dak. (USGS station 

number 06332520; table 6). The surface-water site that had the 

most historical streamflow measurements was the streamgaging station Bear Den Creek near Mandaree, N. Dak. (USGS 

station number 06332515; table 6).

Summary statistics for the 11 selected constituents in 

surface water are presented in table 7. Summary statistics for 

all constituents analyzed in surface water are presented in 

table 1.3. Summary statistics for historical water-quality constituents are presented in table 1.4. In general, higher concentrations of these 11 selected constituents may be attributed to 

low streamflow conditions. However, analyses of the relation 

between streamflow characteristics and water quality (loads 

and trends) is beyond the scope of this report.

The major ions that were selected for detailed discussion 

are dissolved chloride, dissolved solids, dissolved sodium, and 

dissolved sulfate. Each of these constituents were detected in 

all samples collected at the six surface-water sites (table 7). 

Dissolved chloride concentrations in all samples were less 

than the EPA SDWR of 250 mg/L (tables 5, 7). When detected, 

the median dissolved chloride concentrations ranged from 

4.3 mg/L at streamgaging station Squaw Creek above mouth 

near Mandaree, N. Dak. (USGS station number 06337480) to 

24.9 mg/L at streamgaging station East Fork Shell Creek near 

Parshall, N. Dak. (USGS station number 06332523; table 7). 

Dissolved solids concentrations exceeded the EPA SDWR 

of 500 mg/L in all samples from each site (tables 5, 7). The 

median dissolved solids concentrations tended to be greater 

in the western part of the reservation and lower in the eastern 

part of the reservation (table 7, fig. 1). The median dissolved 

solids concentrations ranged from 1,260 mg/L at streamgaging station Deepwater Creek at mouth near Raub, N. Dak. 

(USGS station number 06332770) to 3,370 mg/L at the Squaw 

Creek streamgaging station (USGS station number 06337480; 

Table 6. Summary statistics for historical streamflow measurements at surface-water sites on Fort Berthold Reservation, North 

Dakota, October 1973 to April 2014.

[Data available from U.S. Geological Survey (USGS) National Water Information System database (U.S. Geological Survey, 2017). <, less than]

USGS

station number 

(fig. 1)

Number of 

streamflow 

measurements

Streamflow, in cubic feet per second

Begin date End date

Minimum Median Maximum

06332515 318 0.01 0.25 1,100 11/1/1973 03/24/2014

06332520 99 0.02 2.5 1,570 10/1/1973 09/03/1981

06332523 117 0.01 1.8 542 07/10/1991 08/21/2013

06332770 115 0.02 2.2 921 04/18/1990 06/19/2013

06337470 19 <0.1 0.03 106 04/18/1990 08/11/1993

06337480 18 <0.1 0.025 60 04/18/1990 08/11/1993
16 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

Daily mean streamflow

Water−quality sample

EXPLANATION

0.01

0.10

1

10

100

Date

Streamflow, in cubic feet per second

2014 2015 2016 2017 2018

Figure 2. Daily mean streamflow and water-quality samples collected at streamgaging station Bear Den Creek near Mandaree, 

North Dakota (U.S. Geological Survey station number 06332515), 2014–17.

table 7). Dissolved sodium concentrations exceeded the 

EPA taste threshold of 30 mg/L in all samples from each site 

(tables 5, 7). The median dissolved sodium concentrations 

ranged from 268 mg/L at the Deepwater Creek streamgaging station (USGS station number 06332770) to 1,007 mg/L 

at the Squaw Creek streamgaging station (USGS station 

number 06337480; table 7). Dissolved sulfate concentrations 

exceeded the EPA SDWR of 250 mg/L in all samples from 

each site (tables 5, 7). The median dissolved sulfate concentrations ranged from 628 mg/L at the Deepwater Creek 

streamgaging station (USGS station number 06332770) to 

2,065 mg/L at the Squaw Creek streamgaging station (USGS 

station number 06337480; table 7).

Trace metals that were selected for discussion are dissolved aluminum, dissolved arsenic, dissolved iron, and 

dissolved manganese. Dissolved aluminum was detected in 17 

samples collected during 2014–17 from the 6 surface-water 

sites (table 7). Of the detected concentrations, all exceeded the 

EPA SDWR of 50 μg/L, and median dissolved aluminum concentrations ranged from 116 to 216 μg/L (table 7). Dissolved 

arsenic was detected in 58 samples collected during 2014–17 

from the 6 surface-water sites at concentrations that were less 

than the EPA MCL of 10 μg/L (tables 5, 7). When detected, 

the median dissolved arsenic concentrations ranged from 

2.0 μg/L at streamgaging station Moccasin Creek at mouth 

near Mandaree, N. Dak. (USGS station number 06337470) 

to 6.2 μg/L at the Deepwater Creek streamgaging station 

(USGS station number 06332770; table 7). Iron was detected 

in 22 samples collected from the 6 surface-water sites at 

concentrations that exceeded the EPA SDWR of 300 μg/L 

in 3 samples (table 7). When detected, the median dissolved 

iron concentrations ranged from 138 μg/L at the Deepwater 

Creek streamgaging station (USGS station number 06332770) 

to 250 μg/L at the Squaw Creek streamgaging station (USGS 

station number 06337480; table 7). Dissolved manganese 

was detected in 83 of 84 samples collected, and each of the 

6 surface-water sites had samples with concentrations that 

exceeded the EPA SDWR of 50 μg/L (table 7). When detected, 

the median dissolved manganese concentrations ranged 

from 20.9 μg/L at the Moccasin Creek streamgaging station 

(USGS station number 06337470) to 122 μg/L at the Squaw 

Creek streamgaging station (USGS station number 06337480; 

table 7).

Nutrients that were selected are dissolved ammonia, 

dissolved nitrate, and dissolved nitrite. Dissolved ammonia 

was detected in seven samples at concentrations that were 

less than the EPA taste threshold of 30 mg/L (tables 5, 7). 

When detected, the median dissolved ammonia concentrations ranged from 0.1 to 0.5 mg/L. Dissolved nitrate was 

detected in nine samples at concentrations that were less than 
Table 7. Summary statistics for selected water-quality constituents at surface-water sites on Fort Berthold Reservation, North Dakota, 2014–17.[USGS, U.S. Geological Survey; EPA, U.S. Environmental Protection Agency; SDWR, secondary drinking water regulation; nd, nondetect; MCL, maximum contaminant level]

USGS station

number

(fig. 1)

Number of

samples

EPA 

water-quality

standard1

EPA 

water-quality

standard type

Minimum Median Maximum Number of detections N

c

Chloride, dissolved (milligrams per liter)

06332515 14 250 SDWR 2.2 4.6 22.2 14 06332520 14 250 SDWR 6.8 11.2 26.3 14 06332523 14 250 SDWR 8.4 24.9 56.5 14 06332770 14 250 SDWR 6.8 12.7 20.2 14 06337470 14 250 SDWR 3.0 5.4 12.1 14 06337480 14 250 SDWR 0.4 4.3 13.3 14 

Dissolved solids, residue on evaporation at 180 degrees Celsius (milligrams per liter)

06332515 13 500 SDWR 1,570 2,200 2,570 13 06332520 13 500 SDWR 1,670 1,960 2,260 13 06332523 13 500 SDWR 1,880 2,070 2,800 13 06332770 13 500 SDWR 1,090 1,260 1,800 13 06337470 13 500 SDWR 1,010 1,480 2,380 13 06337480 13 500 SDWR 1,430 3,370 5,720 13 

Sodium, dissolved (milligrams per liter as sodium)

06332515 14 30 Taste threshold 452 620 740 14 06332520 14 30 Taste threshold 314 508 624 14 06332523 14 30 Taste threshold 185 515 665 14 06332770 14 30 Taste threshold 143 268 385 14 06337470 14 30 Taste threshold 265 373 2700 14 06337480 14 30 Taste threshold 411 1,007 1,470 14 

Sulfate, dissolved (milligrams per liter as sulfate)

06332515 14 250 SDWR 700 1,045 1,490 14 06332520 14 250 SDWR 694 878 1,210 14 06332523 14 250 SDWR 532 1,145 1,540 14 06332770 14 250 SDWR 464 628 949 14 06337470 14 250 SDWR 447 818 1580 14 06337480 14 250 SDWR 735 2,065 2,980 14 
Table 7. Summary statistics for selected water-quality constituents at surface-water sites on Fort Berthold Reservation, North Dakota, 2014–17.—Co[USGS, U.S. Geological Survey; EPA, U.S. Environmental Protection Agency; SDWR, secondary drinking water regulation; nd, nondetect; MCL, maximum contaminant level] USGS station number (fig. 1) Number of samples EPA water-quality standard1 EPA water-quality standard type Minimum Median Maximum Number of detections N

c

Aluminum, dissolved (micrograms per liter as aluminum) 06332515 14 50 SDWR 167 191 380 5 

06332520 14 50 SDWR 105 177 249 2 06332523 14 50 SDWR nd nd nd 0 06332770 14 50 SDWR 116 116 116 1 06337470 14 50 SDWR 103 216 527 6 06337480 14 50 SDWR 154 173 337 3 

Arsenic, dissolved (micrograms per liter as arsenic) 06332515 14 10 MCL 1.8 2.7 4.3 8 

06332520 14 10 MCL 2.0 3.5 7.3 10 06332523 14 10 MCL 2.2 5.0 6.0 11 06332770 14 10 MCL 2.1 6.2 8.4 12 06337470 14 10 MCL 1.8 2.0 2.4 8 06337480 14 10 MCL 2.0 4.1 6.7 9 

Iron, dissolved (micrograms per liter as iron) 06332515 14 300 SDWR 102 145 349 6 

06332520 14 300 SDWR 138 210 297 5 06332523 14 300 SDWR nd nd nd 0 06332770 14 300 SDWR 109 138 166 2 06337470 14 300 SDWR 146 178 375 6 06337480 14 300 SDWR 137 250 317 3 

Manganese, dissolved (micrograms per liter as manganese) 06332515 14 50 SDWR 3.2 21.8 75.3 14 

06332520 14 50 SDWR 22.3 46.7 115 14 06332523 14 50 SDWR 15.9 49.3 112 14 06332770 14 50 SDWR 3.3 47 114 14 06337470 14 50 SDWR 2.4 20.9 147 13 06337480 14 50 SDWR 45.7 122 191 14 
Table 7. Summary statistics for selected water-quality constituents at surface-water sites on Fort Berthold Reservation, North Dakota, 2014–17.—Co[USGS, U.S. Geological Survey; EPA, U.S. Environmental Protection Agency; SDWR, secondary drinking water regulation; nd, nondetect; MCL, maximum contaminant level]

USGS station

number

(fig. 1)

Number of

samples

EPA 

water-quality

standard1

EPA 

water-quality

standard type

Minimum Median Maximum Number of detections N

c

Ammonia, dissolved (milligrams per liter as nitrogen)

06332515 14 30 Taste threshold 0.1 0.5 0.9 2 06332520 14 30 Taste threshold 0.1 0.1 0.1 1 06332523 14 30 Taste threshold 0.1 0.1 0.1 1 06332770 14 30 Taste threshold 0.1 0.1 0.1 3 06337470 14 30 Taste threshold nd nd nd 0 06337480 14 30 Taste threshold nd nd nd 0 

Nitrate, dissolved (milligrams per liter as nitrogen)

06332515 5 10 MCL 0.016 0.016 0.016 1 06332520 5 10 MCL 0.013 0.076 0.081 3 06332523 5 10 MCL 0.182 0.182 0.182 1 06332770 5 10 MCL 0.010 0.199 0.387 2 06337470 5 10 MCL 0.019 0.268 0.517 2 06337480 5 10 MCL nd nd nd 0 

Nitrite, dissolved (milligrams per liter as nitrogen)

06332515 5 1 MCL 0.006 0.009 0.013 2 06332520 5 1 MCL 0.005 0.008 0.011 2 06332523 5 1 MCL 0.007 0.007 0.029 3 06332770 5 1 MCL 0.006 0.009 0.012 2 06337470 5 1 MCL 0.012 0.012 0.030 3 06337480 5 1 MCL 0.006 0.007 0.008 2 

1U.S. Environmental Protection Agency, 2018.
20 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

the EPA MCL of 10 mg/L (tables 5, 7). When detected, the 

median dissolved nitrate concentrations ranged from 0.016 

to 0.268 mg/L. Dissolved nitrite was detected in 14 samples 

at concentrations that were less than the EPA MCL of 1 mg/L 

(table 7). When detected, the median dissolved nitrite concentrations ranged from 0.007 to 0.012 mg/L.

Groundwater Quality

Groundwater-quality data were collected from 34 wells 

on the reservation during 2014, 2015, and 2017 (table 2). The 

sampled wells completed in the Quaternary aquifer system 

(contained in Quaternary-age glacial and fluvial sediments 

in the reservation) consisted of 3 wells in the White Shield 

aquifer, 4 wells in the Sanish aquifer, 6 wells in the Shell 

Creek aquifer, 1 well in the New Town aquifer, and 1 well 

in the Tongue River aquifer. The sampled wells completed 

in the lower Tertiary aquifer system consisted of 13 wells in 

the Sentinel Butte aquifer (contained in the Sentinel Butte 

Member of the Fort Union Formation) and 1 well in the Fort 

Union aquifer (contained in the Fort Union Formation). The 

sampled wells completed in the Upper Cretaceous aquifer 

system consisted of 5 wells in the Fox Hills aquifer (contained 

in the Fox Hills Sandstone). These 34 wells included domestic, stock, monitoring, and industrial wells that represent the 

most utilized aquifer units and had good spatial coverage on 

the reservation. Most of these wells were in the western part of 

the reservation (fig. 1).

Summary statistics for the 11 selected constituents in 

groundwater in the 34 wells completed in the Quaternary, 

lower Tertiary, or Upper Cretaceous aquifer systems are summarized in table 8. Summary statistics for all constituents 

analyzed in groundwater from the 34 wells are presented in 

table 1.5. The historical groundwater data predate the intensive energy development since the 2000s, and some of the 

data were collected in the 1950s. The most recent historical 

groundwater data for the wells on the reservation were prior 

to the early 1990s (Wald and Cates, 1995; Cates and MacekRowland, 1998). Summary statistics for these historical waterquality constituents in the major aquifers on the reservation 

are presented in table 2.1 (Cates and Macek-Rowland, 1998).

The major ions that were selected for additional discussion are dissolved chloride, dissolved solids, dissolved 

sodium, and dissolved sulfate. The only dissolved chloride 

concentration that exceeded the EPA SDWR of 250 mg/L was 

in a sample from a well completed in the Upper Cretaceous 

aquifer system (table 8; map number 34, fig. 3). The median 

dissolved chloride concentrations were 5.1, 2.6, and 237 mg/L 

in the Quaternary, lower Tertiary, and Upper Cretaceous 

aquifer systems, respectively. The Upper Cretaceous aquifer 

system had the highest dissolved chloride concentrations that 

ranged from 185 to 271 mg/L. Dissolved solids concentrations exceeded the EPA SDWR of 500 mg/L in samples from 

32 of 34 groundwater wells (table 8). The median dissolved 

solids concentrations were 1,710, 1,460, and 1,590 mg/L 

in the Quaternary, lower Tertiary, and Upper Cretaceous 

aquifer systems, respectively. The median dissolved solids 

concentrations were more than double the EPA SDWR of 

500 mg/L (tables 5, 8). The dissolved solids concentrations 

that exceeded the EPA SDWR of 500 mg/L were spatially 

distributed throughout the reservation and included all the 

major aquifer systems (fig. 4). Dissolved sodium concentrations exceeded the EPA taste threshold of 30 mg/L in samples 

from all groundwater wells (table 8). The median dissolved 

sodium concentrations were 513, 281, and 587 mg/L in the 

Quaternary, lower Tertiary, and Upper Cretaceous aquifer 

systems, respectively (table 8). The dissolved sodium concentrations that exceeded the EPA taste threshold of 30 mg/L 

were spatially distributed throughout the reservation and 

included all the major aquifer systems (fig. 5). Dissolved 

sulfate concentrations exceeded the EPA SDWR of 250 mg/L 

in samples from 21 of 35 groundwater wells (table 8). When 

detected, the median dissolved sulfate concentrations were 568 

and 302 mg/L in the Quaternary and lower Tertiary aquifer 

systems, respectively. Dissolved sulfate concentrations were 

reported as nondetects in the Upper Cretaceous aquifer system 

(table 8). The highest dissolved sulfate concentrations that 

exceeded the EPA SDWR of 250 mg/L were in the Quaternary 

and lower Tertiary aquifer systems and had dissolved sulfate 

concentrations of 2,300 and 2,310 mg/L, respectively (table 8, 

fig. 6). The groundwater well (map number 3, fig. 6) in the 

Quaternary aquifer system was sampled in 2014 and 2017, 

respectively.

Trace metals that were selected for discussion are dissolved aluminum, dissolved arsenic, dissolved iron, and 

dissolved manganese. All dissolved aluminum concentrations 

were reported as less than 100 μg/L, except for one sample 

collected from a well in the lower Tertiary aquifer system, 

with a concentration of 137 μg/L. Dissolved arsenic concentrations exceeded the EPA MCL of 10 μg/L in samples 

from 7 of 35 groundwater wells (table 8). When detected, the 

median dissolved arsenic concentrations were 8.9 and 3.5 μg/L 

in the Quaternary and Upper Cretaceous aquifer systems, 

respectively. Dissolved arsenic concentrations were reported 

as nondetects in the lower Tertiary aquifer system (table 8). 

The seven groundwater wells that exceeded the EPA MCL of 

10 μg/L generally were on the northern and eastern side of the 

reservation from monitoring wells in the Quaternary aquifer 

system (fig. 7). Dissolved iron concentrations exceeded the 

EPA SDWR of 300 μg/L in samples from 17 of 35 groundwater wells (table 8). When detected, the median dissolved iron 

concentrations were 1,220 and 230 μg/L in the Quaternary 

and lower Tertiary aquifer systems, respectively. Dissolved 

iron concentrations were reported as nondetects in the Upper 

Cretaceous aquifer system (table 8). The dissolved iron 

concentrations that exceeded the EPA SDWR of 300 μg/L 

were from wells in the Quaternary and lower Tertiary aquifer systems (fig. 8). Dissolved manganese concentrations 

exceeded the EPA SDWR of 50 μg/L in samples from 14 of 35 

groundwater wells (table 8). When detected, the median dissolved manganese concentrations were 104, 46.8, and 3.0 μg/L 
Characterization of Water Quality on the Fort Berthold Reservation 21

in the Quaternary, lower Tertiary, and Upper Cretaceous 

aquifer systems, respectively (table 8). The dissolved manganese concentrations that exceeded the EPA SDWR of 50 μg/L 

were from wells in the Quaternary and lower Tertiary aquifer 

systems (fig. 9).

Nutrients that were selected for discussion include dissolved ammonia, dissolved nitrate, and dissolved nitrite. None 

of the nutrient concentrations exceeded any water-quality 

standards. Dissolved ammonia was detected in 30 samples 

at concentrations that were less than the EPA taste threshold 

of 30 mg/L (table 8). When detected, the median dissolved 

ammonia concentrations were 0.6, 0.2, and 0.6 mg/L in the 

Quaternary, lower Tertiary, and Upper Cretaceous aquifer 

systems, respectively (table 8). Dissolved ammonia concentrations were detected in samples from wells in each of the aquifer systems (fig. 10). Nitrate was detected in only one sample, 

and nitrite was not detected in any samples. All dissolved 

nitrate and dissolved nitrite concentrations were less than the 

EPA MCL of 10 and 1 mg/L, respectively (table 8).
Table 8. Summary statistics for selected water-quality constituents in groundwater wells on Fort Berthold Reservation, North Dakota, 2014–17. [EPA, U.S. Environmental Protection Agency; Cl, chloride; SDWR, secondary drinking water regulation; Na, sodium; SO4, sulfate; Al, aluminum; nd, nondetect; As, arsenic; Mlevel; Fe, iron; Mn, manganese] Constituent EPA water-quality standard EPA water-quality standard type Number of samples Minimum Median Maximum N

det

Quaternary aquifer system Chloride, dissolved (milligrams per liter as Cl) 250 SDWR 16 1.1 5.1 164 

Dissolved solids, residue on evaporation at 180 degrees Celsius (milligrams per liter) 500 SDWR 15 777 1,710 2,980 Sodium, dissolved (milligrams per liter as Na) 30 Taste threshold 16 132 513 892 Sulfate, dissolved (milligrams per liter as SO4) 250 SDWR 16 181 568 2,300 Aluminum, dissolved (micrograms per liter as Al) 50 SDWR 16 nd nd nd Arsenic, dissolved (micrograms per liter as As) 10 MCL 16 2.5 8.9 30.1 Iron, dissolved (micrograms per liter as Fe) 300 SDWR 16 355 1,220 7,080 Manganese, dissolved (micrograms per liter as Mn) 50 SDWR 16 11 104 910 Ammonia, dissolved (milligrams per liter as nitrogen) 30 Taste threshold 16 0.2 0.6 1.4 Nitrate, dissolved (milligrams per liter as nitrogen) 10 MCL 10 0.006 0.006 0.006 Nitrite, dissolved (milligrams per liter as nitrogen) 1 MCL 10 nd nd nd 

Lower Tertiary aquifer system Chloride, dissolved (milligrams per liter as Cl) 250 SDWR 14 0.9 2.6 24.7 

Dissolved solids, residue on evaporation at 180 degrees Celsius (milligrams per liter) 500 SDWR 14 373 1,460 4,100 Sodium, dissolved (milligrams per liter as Na) 30 Taste threshold 14 61.2 281 1,660 Sulfate, dissolved (milligrams per liter as SO4) 250 SDWR 14 41 302 2,310 Aluminum, dissolved (micrograms per liter as Al) 50 SDWR 14 137 137 137 Arsenic, dissolved (micrograms per liter as As) 10 MCL 14 nd nd nd Iron, dissolved (micrograms per liter as Fe) 300 SDWR 14 104 230 5,080 Manganese, dissolved (micrograms per liter as Mn) 50 SDWR 14 3.2 46.8 5,530 Ammonia, dissolved (milligrams per liter as nitrogen) 30 Taste threshold 14 0.1 0.2 0.7 Nitrate, dissolved (milligrams per liter as nitrogen) 10 MCL 2 nd nd nd Nitrite, dissolved (milligrams per liter as nitrogen) 1 MCL 2 nd nd nd 
Table 8. Summary statistics for selected water-quality constituents in groundwater wells on Fort Berthold Reservation, North Dakota, 2014–17.—Co[EPA, U.S. Environmental Protection Agency; Cl, chloride; SDWR, secondary drinking water regulation; Na, sodium; SO4, sulfate; Al, aluminum; nd, nondetect; As, arsenic; Mlevel; Fe, iron; Mn, manganese]

Constituent

EPA 

waterquality

standard

EPA 

water-quality 

standard type

Number

of

samples

Minimum Median Maximum

N

de

Upper Cretaceous aquifer system

Chloride, dissolved (milligrams per liter as Cl) 250 SDWR 5 185 237 271 Dissolved solids, residue on evaporation at 180 degrees 

Celsius (milligrams per liter) 500 SDWR 5 1,470 1,590 1,750 

Sodium, dissolved (milligrams per liter as Na) 30 Taste threshold 5 569 587 636 Sulfate, dissolved (milligrams per liter as SO4) 250 SDWR 5 nd nd nd Aluminum, dissolved (micrograms per liter as Al) 50 SDWR 5 nd nd nd Arsenic, dissolved (micrograms per liter as As) 10 MCL 5 2.8 3.5 4.1 Iron, dissolved (micrograms per liter as Fe) 300 SDWR 5 nd nd nd Manganese, dissolved (micrograms per liter as Mn) 50 SDWR 5 3.0 3.0 3.0 Ammonia, dissolved (milligrams per liter as nitrogen) 30 Taste threshold 5 0.6 0.6 0.7 Nitrate, dissolved (milligrams per liter as nitrogen) 10 MCL 2 nd nd nd Nitrite, dissolved (milligrams per liter as nitrogen) 1 MCL 2 nd nd nd 

1U.S. Environmental Protection Agency, 2018.
Lake Sakakawea Plaza Ryder Makoti New Town Parshall Mandaree Twin Buttes 102°45’ 102° 47°55’ 47°30’ Lake Sakakawea 

New Town Parsha

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Lake Sakakawea 

New Town Parsha

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ 

12 10 34 24 

6 21 31 22 33 14 15 13 25 17 23 16 26 5 3 1 4 3 9 8 30 29 32 20 18 28 19 27 11 A. Quaternary aquifer system B. Lower Tertiary aquifer system 0 C. Upper Cretaceous aquifer system 0 4 8 12 16 4 8 12 16 20 KILOMETERS Base layers from North Dakota Geographic Information 20 MILES Systems (GIS) Hub Data Portal, 2018 Universal Transverse Mercator projection, zone 14N North American Datum of 1983 EXPLANATION Chloride, dissolved (milligrams per liter as chloride), with map number (table 2) Less than 0.2 (not detected) 0.2 to 250 Greater than 250 Fort Berthold Reservation Figure 3. Spatial distribution of dissolved chloride concentrations, in milligrams per liter, for groundwater wells on Fort Berthold Reservation, North 

A, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea

Plaza

Ryder

Makoti

New Town Parshall

Mandaree

Twin Buttes

102°45’ 102°

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

34

24

10

12

6

31 21

33

26 23

22

25 13

17

14

15

16

3

9

8

5

1

4

30

28 27

29 32

11

20

18

19

A. Quaternary aquifer system B. Lower Tertiary aquifer system

0 C. Upper Cretaceous aquifer system0 4 8 12 16

4 8 12 16

20 KILOMETERS

Base layers from North Dakota Geographic Information 20 MILESSystems (GIS) Hub Data Portal, 2018Universal Transverse Mercator projection, zone 14NNorth American Datum of 1983

EXPLANATION

Dissolved solids (milligrams 

per liter), with map number (table 2)

Fort Berthold Reservation

Less than 2 (not detected)2 to 500Greater than 500

Figure 4. Spatial distribution of dissolved solids concentrations, in milligrams per liter, for groundwater wells on Fort Berthold Reservation, North DaA, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea Plaza Ryder Makoti New Town Mandaree Twin Buttes 102°45’ 102° 47°55’ 47°30’ Lake Sakakaw

New Town Pars

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Lake Sakakaw

New Town Pars

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Parshall 

12 10 34 24 

6 31 21 22 33 14 15 13 25 17 23 16 26 5 3 1 4 3 9 8 30 29 32 20 18 28 19 27 11 A. Quaternary aquifer system B. Lower Tertiary aquifer system 0 C. Upper Cretaceous aquifer system 0 4 8 12 16 4 8 12 16 20 KILOMETERS Base layers from North Dakota Geographic Information 20 MILES Systems (GIS) Hub Data Portal, 2018 Universal Transverse Mercator projection, zone 14N North American Datum of 1983 EXPLANATION Sodium, dissolved (milligrams per liter as sodium), with map number (table 2) Fort Berthold Reservation Less than 0.5 (not detected) 0.5 to 30 (not detected) Greater than 30 Figure 5. Spatial distribution of dissolved sodium concentrations, in milligrams per liter, for groundwater wells on Fort Berthold Reservation, North D

A, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea

Plaza

Ryder

Makoti

New Town

Mandaree

Twin Buttes

102°45’ 102°

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Parshall

12

10

34

24

6

13

26

17

31

14

21

23

15 25

22

33

16

3

3

9

1

8

5

4

11

20

18

28

29

19

27

30

32

A. Quaternary aquifer system B. Lower Tertiary aquifer system

0 C. Upper Cretaceous aquifer system0 4 8 12 16

4 8 12 16

20 KILOMETERS

Base layers from North Dakota Geographic Information 20 MILESSystems (GIS) Hub Data Portal, 2018Universal Transverse Mercator projection, zone 14NNorth American Datum of 1983

EXPLANATION

Sulfate, dissolved (milligrams 

per liter as sulfate), with map number (table 2)

Fort Berthold Reservation

Less than 0.5 (not detected)0.5 to 250Greater than 250

Figure 6. Spatial distribution of dissolved sulfate concentrations, in milligrams per liter, for groundwater wells on Fort Berthold Reservation, North DA, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea Plaza Ryder Makoti New Town Mandaree Twin Buttes 102°45’ 102° 47°55’ 47°30’ Lake Sakakaw

New Town Pars

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Lake Sakakaw

New Town Pars

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Parshall 

34 12 10 24 

6 31 21 22 33 14 16 13 26 15 23 25 17 4 9 33 5 1 8 30 20 28 18 32 2719 11 29 A. Quaternary aquifer system B. Lower Tertiary aquifer system 0 C. Upper Cretaceous aquifer system 0 4 8 12 16 4 8 12 16 20 KILOMETERS Base layers from North Dakota Geographic Information 20 MILES Systems (GIS) Hub Data Portal, 2018 Universal Transverse Mercator projection, zone 14N North American Datum of 1983 EXPLANATION Arsenic, dissolved (micrograms per liter as arsenic), with map number (table 2) Fort Berthold Reservation Less than 2 (not detected) 2 to 10 Greater than 10 Figure 7. Spatial distribution of dissolved arsenic concentrations, in micrograms per liter, for groundwater wells on Fort Berthold Reservation, North 

A, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea

Plaza

Ryder

Makoti

New Town

Mandaree

Twin Buttes

102°45’ 102°

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Parshall

A. Quaternary aquifer system B. Lower Tertiary aquifer system

0 C. Upper Cretaceous aquifer system0 4 8 12 16

4 8 12 16

20 KILOMETERS

Base layers from North Dakota Geographic Information 20 MILESSystems (GIS) Hub Data Portal, 2018Universal Transverse Mercator projection, zone 14NNorth American Datum of 1983

EXPLANATION

Iron, dissolved (micrograms 

per liter as iron), with map number (table 2)

Less than 100 (not detected)100 to 300Greater than 300

Fort Berthold Reservation

12

10

34

24

6

21 31

22

33

14

15 13 25

17

23

16

26

5

3

1

4

3

9

8

30

29 32

20

18

28

19

27

11

Figure 8. Spatial distribution of dissolved iron concentrations, in micrograms per liter, for groundwater wells on Fort Berthold Reservation, North Daaquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea Plaza Ryder Makoti New Town Mandaree Twin Buttes 102°45’ 102° 47°55’ 47°30’ Lake Sakakaw

New Town Pars

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Lake Sakakaw

New Town Pars

Mandaree Twin Buttes 102°45’ 

47°55’ 47°30’ Parshall A. Quaternary aquifer system B. Lower Tertiary aquifer system 0 C. Upper Cretaceous aquifer system 0 4 8 12 16 4 8 12 16 20 KILOMETERS Base layers from North Dakota Geographic Information 20 MILES Systems (GIS) Hub Data Portal, 2018 Universal Transverse Mercator projection, zone 14N North American Datum of 1983 EXPLANATION Manganese, dissolved (micrograms per liter as manganese), with map number (table 2) Less than 2 2 to 50 Greater than 50 Fort Berthold Reservation 

12 10 34 24 

6 21 31 22 33 14 15 13 25 17 23 16 26 5 3 1 4 3 9 8 30 29 32 20 18 28 19 27 11 Figure 9. Spatial distribution of dissolved manganese concentrations, in micrograms per liter, for groundwater wells on Fort Berthold Reservation, N

A, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
Lake Sakakawea

Plaza

Ryder

Makoti

New Town

Mandaree

Twin Buttes

102°45’ 102°

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Lake Sakakaw

New Town

Pars

Mandaree

Twin Buttes

102°45’ 

47°55’47°30’

Parshall

A. Quaternary aquifer system B. Lower Tertiary aquifer system

0 C. Upper Cretaceous aquifer system0 4 8 12 16

4 8 12 16

20 KILOMETERS

Base layers from North Dakota Geographic Information 20 MILESSystems (GIS) Hub Data Portal, 2018Universal Transverse Mercator projection, zone 14NNorth American Datum of 1983

EXPLANATION

Ammonia, dissolved (milligrams 

per liter as nitrogen), with map number (table 2)

Less than 0.0250.025 to 30Greater than 30 (not detected)

Fort Berthold Reservation

12

10

34

24

6

21 31

22

33

14

15 13 25

17

23

16

26

5

3

1

4

3

9

8

30

29 32

20

18

28

19

27

11

Figure 10. Spatial distribution of dissolved ammonia concentrations, in milligrams per liter, for groundwater wells on Fort Berthold Reservation, NortA, Quaternary aquifer system; B, lower Tertiary aquifer system; and C, Upper Cretaceous aquifer system.
32 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

Summary

The Fort Berthold Reservation (hereafter referred to as 

"reservation"), in west-central North Dakota, is home to the 

Three Affiliated Tribes (TAT). The primary water-resources 

concerns on the reservation are the different types of land uses 

from agricultural activities and the rapid development of oil 

and gas resources in western North Dakota. A primary goal 

of the TAT Environmental Department is to protect the water 

quality in streams, groundwater, and Lake Sakakawea from 

these water-resources issues on the reservation. As a result of 

these concerns, the TAT Environmental Department identified 

the need for long-term water-quality monitoring throughout 

the reservation to better understand the potential effects on 

surface-water and groundwater quality and to determine if 

water quality is changing with time. Therefore, a water-quality 

monitoring program was designed to address data gaps and 

provide consistent long-term data that can be used to identify 

potential effects on water quality. During 2014–17, the initial 

water-quality sampling efforts associated with this program 

were completed. The efforts provide a current (2019) characterization of water-quality conditions and assist in establishing 

a long-term water-quality monitoring program

The U.S. Geological Survey, in cooperation with the 

TAT, identified surface-water sites and groundwater wells that 

represent the water resources in major drainages and the most 

utilized aquifers on the reservation. Surface-water-quality 

samples were collected from six surface-water sites that were 

selected from previously established U.S. Geological Survey 

(USGS) streamgaging stations. Of the six sites selected, three 

are continuous-recording U.S. Geological Survey streamgaging stations currently (2019) operated on the reservation. 

These three streamgaging stations are Bear Den Creek near 

Mandaree, N. Dak.; East Fork Shell Creek near Parshall, 

N. Dak.; and Deepwater Creek at mouth near Raub, N. Dak. 

The other three surface-water sites are not continuously operated streamgaging stations.

Reconnaissance of potential groundwater wells for 

sampling began in May 2014, and 34 wells were selected for 

sampling. Initially, groundwater wells were selected by dividing the area of the reservation into 20 equal-area cells, and 1 

well in each cell was randomly selected from the population of 

all wells available from multiple databases. Locating appropriate wells for sampling using the random selection approach 

presented several challenges in this area. With the development of the Fort Berthold Rural Water System and associated decrease in groundwater use, most of the domestic wells 

were disconnected and many of the monitoring wells on the 

reservation that were drilled prior to the 1990s were destroyed, 

abandoned, or no longer existed. Because of the challenges in 

locating appropriate wells using the random approach, additional wells were selected based on criteria that the wells could 

be physically located, the wells had construction information from a well driller’s log, the samples could be collected 

without the well being affected by any type water treatment or 

a pressure tank, and the landowner had granted permission.

Six surface-water sites on streams and 34 groundwater 

wells were sampled on the reservation for 232 constituents 

that include major ions, nutrients, trace elements, and semivolatile and volatile organic compounds. Of the 232 constituents, 11 were selected for more detailed analyses and discussion based on their common association with agricultural and 

energy development land uses. These dissolved constituents 

are chloride, dissolved solids, sodium, sulfate, aluminum, 

arsenic, iron, manganese, ammonia, nitrate, and nitrite.

In surface-water samples, chloride concentrations were 

less than the U.S. Environmental Protection Agency (EPA) 

secondary drinking water regulation (SDWR) of 250 milligrams per liter (mg/L), and median chloride concentrations ranged from 4.3 mg/L at streamgaging station Squaw 

Creek above mouth near Mandaree, N. Dak. (USGS station 

number 06337480) to 24.9 mg/L at streamgaging station 

East Fork Shell Creek near Parshall, N. Dak. (USGS station number 06332523). Dissolved solids concentrations 

exceeded the EPA SDWR of 500 mg/L at all surface-water 

sites. The median dissolved solids concentrations tended to 

be greater in the western part of the reservation and lower 

in the eastern part of the reservation. The median dissolved 

solids concentrations ranged from 1,260 mg/L at streamgaging station Deepwater Creek at mouth near Raub, N. Dak. 

(USGS station number 06332770) to 3,370 mg/L at the Squaw 

Creek streamgaging station. Sodium concentrations exceeded 

the EPA taste threshold of 30 mg/L at all surface-water sites. 

The median sodium concentrations ranged from 268 mg/L 

at the Deepwater Creek streamgaging station to 1,007 mg/L 

at the Squaw Creek streamgaing station. Sulfate concentrations exceeded the EPA SDWR of 250 mg/L at all surfacewater sites. The median sulfate concentrations ranged from 

628 mg/L at the Deepwater Creek streamgaging station to 

2,065 mg/L at the Squaw Creek streamgaging station.

Trace metals that were selected include dissolved aluminum, dissolved arsenic, dissolved iron, and dissolved manganese. Aluminum was detected in 17 samples collected during 

2014–17 from the 6 surface-water sites. When detected, all 

concentrations exceeded the EPA SDWR of 50 micrograms 

per liter (μg/L). When detected, the median aluminum concentrations ranged from 116 to 216 μg/L. Arsenic was detected in 

58 samples collected during 2014–17 from the 6 surface-water 

sites at concentrations that were less than the EPA maximum 

contaminant level (MCL) of 10 mg/L. When detected, the 

median arsenic concentrations ranged from 2 to 6.2 μg/L. Iron 

was detected in 22 samples collected from the 6 surface-water 

sites at concentrations that were less than the EPA SDWR 

of 300 μg/L. When detected, the median iron concentrations 

ranged from 138 to 250 μg/L. Manganese was detected in 83 

samples collected, and each of the 6 surface-water sites had 

samples with concentrations that exceeded the EPA SDWR 

of 50 μg/L. When detected, the median detected manganese 

concentrations ranged from 20.9 to 122 μg/L.

Nutrients that were selected include dissolved ammonia, dissolved nitrate, and dissolved nitrite. In surfacewater samples, ammonia was detected in seven samples at 
Summary 33

concentrations that were less than the EPA taste threshold of 

30 mg/L. When detected, the median ammonia concentrations 

ranged from 0.1 to 0.5 mg/L. Dissolved nitrate was detected 

in nine samples at concentrations that were less than the EPA 

MCL of 10 mg/L and when detected, the median nitrate concentrations ranged from 0.016 to 0.268 mg/L. Dissolved nitrite 

was detected in 14 samples at concentrations that were less 

than the EPA MCL of 1 mg/L and when detected, the median 

nitrite concentrations ranged from 0.007 to 0.012 mg/L.

Groundwater-quality data were collected from 34 wells 

on the reservation during 2014, 2015, and 2017. The sampled 

wells completed in the Quaternary aquifer system (contained 

in Quaternary-age glacial and fluvial sediments in the reservation) consisted of 3 wells in the White Shield aquifer, 4 wells 

in the Sanish aquifer, 6 wells in the Shell Creek aquifer, 1 

well in the New Town aquifer, and 1 well in the Tongue River 

aquifer. The sampled wells completed in lower Tertiary aquifer 

system consisted of 13 wells in the Sentinel Butte aquifer 

(contained in the Sentinel Butte Member of the Fort Union 

Formation) and 1 well in the Fort Union aquifer (contained in 

the Fort Union Formation). The sampled wells completed in 

the Upper Cretaceous aquifer system consisted of 5 wells in 

the Fox Hills aquifer (contained in the Fox Hills Sandstone). 

The 34 wells included domestic, stock, monitoring, and industrial wells that represent the most utilized aquifer units and had 

good spatial coverage on the reservation.

For groundwater samples, the major ions that were 

selected are dissolved chloride, dissolved solids, dissolved 

sodium, and dissolved sulfate. The only chloride concentration that exceeded the EPA SDWR of 250 mg/L was from a 

well completed in the Upper Cretaceous aquifer system. The 

median chloride concentrations were 5.1, 2.6, and 237 mg/L in 

the Quaternary, lower Tertiary and Upper Cretaceous aquifer 

systems, respectively. The Upper Cretaceous aquifer system 

had the highest chloride concentrations that ranged from 185 

to 271 mg/L. Dissolved solids concentrations exceeded the 

EPA SWDR of 500 mg/L in samples from 32 of 34 groundwater wells. The median dissolved solids concentrations 

were 1,710, 1,459, and 1,590 mg/L in the Quaternary, lower 

Tertiary, and Upper Cretaceous aquifer systems, respectively. 

The median dissolved solids concentrations were more than 

double the EPA SDWR of 500 mg/L. The dissolved solids 

concentrations that exceeded the EPA benchmark of 500 mg/L 

were spatially distributed throughout the reservation and 

included all the major aquifer systems. Dissolved sodium 

concentrations exceeded the EPA taste threshold of 30 mg/L 

in samples from all groundwater wells. The median detected 

sodium concentrations were 513, 281, and 587 mg/L in the 

Quaternary, lower Tertiary, and Upper Cretaceous aquifer 

systems, respectively. The dissolved sodium concentrations 

that exceeded the EPA taste threshold of 30 mg/L were spatially distributed throughout the reservation and included all 

the major aquifer systems. Dissolved sulfate concentrations 

exceeded the EPA SDWR of 250 mg/L in 21 of 34 groundwater wells. When detected, the median dissolved sulfate 

concentrations were 568 and 302 mg/L in the Quaternary and 

lower Tertiary aquifer systems, respectively. Dissolved sulfate 

concentrations were reported as nondetects in the Upper 

Cretaceous aquifer system. The highest detected sulfate concentrations that exceeded the EPA SDWR of 250 mg/L were in 

the Quaternary and lower Tertiary aquifer systems. A groundwater well in the Quaternary aquifer system was sampled 

twice and had sulfate concentrations of 2,300 and 1,730 mg/L 

in 2014 and 2017, respectively.

For groundwater samples, trace metals that were selected 

are dissolved aluminum, dissolved arsenic, dissolved iron, 

and dissolved manganese. All dissolved aluminum concentrations were reported as less than 100 μg/L, except for one 

sample collected from a well in the lower Tertiary aquifer 

system, with a concentration of 137 μg/L. Dissolved arsenic 

concentrations exceeded the EPA MCL of 10 μg/L in samples 

from 7 of 34 groundwater wells. When detected, the median 

dissolved arsenic concentrations were 8.9 and 3.5 μg/L in the 

Quaternary and Upper Cretaceous aquifer systems, respectively. Dissolved arsenic concentrations were reported as 

nondetects in the lower Tertiary aquifer system. The seven 

groundwater wells that exceeded the EPA MCL of 10 μg/L 

generally were on the northern and eastern side of the reservation from monitoring wells in the Quaternary aquifer system. 

Iron concentrations exceeded the EPA SDWR of 300 μg/L 

in 17 of 34 groundwater wells. When detected, the median 

dissolved iron concentrations were 1,220 and 230 μg/L in the 

Quaternary and lower Tertiary aquifer systems, respectively. 

Dissolved iron concentrations were reported as nondetects 

in the Upper Cretaceous aquifer system. The dissolved iron 

concentrations that exceeded the EPA SDWR of 300 μg/L 

were from wells in the Quaternary and lower Tertiary aquifer 

systems. Dissolved manganese concentrations exceeded the 

EPA SDWR of 50 μg/L in 14 of 34 groundwater wells. When 

detected, the median dissolved manganese concentrations 

were 104, 46.8, and 3 μg/L in the Quaternary, lower Tertiary, 

and Upper Cretaceous aquifer systems, respectively. The 

dissolved manganese concentrations that exceeded the EPA 

SDWR of 50 μg/L were from wells in the Quaternary and 

lower Tertiary aquifer systems.

For groundwater samples, nutrients that were selected are 

dissolved ammonia, dissolved nitrate, and dissolved nitrite. 

None of the nutrient concentrations exceeded any waterquality standards. Dissolved ammonia was detected in 30 

samples at concentrations that were less than the EPA taste 

threshold of 30 mg/L. When detected, the median dissolved 

ammonia concentrations were 0.6, 0.2, and 0.6 mg/L in the 

Quaternary, lower Tertiary, and Upper Cretaceous aquifer 

systems, respectively. Dissolved ammonia concentrations were 

detected from wells in each of the aquifer systems. Nitrate 

was detected in only one sample, and nitrite was not detected 

in any samples. All dissolved nitrate and dissolved nitrite 

concentrations were less than the EPA MCL of 10 and 1 mg/L, 

respectively.
34 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

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Appendix 1. Quality-Assurance Data and Summary Statistics for Water-Quality 

Constituents in Surface Water and Groundwater

This appendix contains a link listing of the qualityassurance data and summary statistics for water-quality 

constituents in surface water and groundwater for samples 

collected for the study and historical water-quality data for 

surface-water sites and are presented in the Microsoft Excel 

file available at https://dx.doi.org/10.3133/sir20205020. The 

Microsoft Excel file contains the following five tables:

36 Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17

Table 1.1. Quality-assurance data collected for selected constituents on Forth Berthold Reservation, North Dakota, 2014–17.

Table 1.2. Quality-assurance data collected for additional constituents on Fort Berthold Reservation, North Dakota, 2014–17.

Table 1.3. Summary statistics for water-quality constituents analyzed but not selected for additional discussion in surface water on 

Fort Berthold Reservation, 2014–17. 

Table 1.4. Summary statistics for historical water-quality constituents at surface-water sites on Fort Berthold Reservation, August 1966 

to April 2014.

Table 1.5. Summary statistics for water-quality constituents analyzed but not selected for additional discussion in groundwater on Fort 

Berthold Reservation, 2014–17.
Appendix 2 37

Appendix 2. Summary Statistics for Historical Water-Quality Constituents in 

Major Aquifers on Fort Berthold Reservation, North Dakota

This appendix contains a link listing of the historical 

water-quality constituents in major aquifers on Fort Berthold 

Reservation, North Dakota, and are presented in the Microsoft 

Excel file available at https://dx.doi.org/10.3133/sir20205020. 

The Microsoft Excel file contains the following table:

Table 2.1. Summary statistics for historical water-quality constituents in major aquifers on Fort Berthold Reservation, North Dakota.
For more information about this publication, contact:

Director, USGS Dakota Water Science Center

821 East Interstate Avenue, Bismarck, ND 58503

1608 Mountain View Road, Rapid City, SD 57702

605–394–3200

For additional information, visit: https://www.usgs.gov/centers/

dakota-water

Publishing support provided by the 

Rolla Publishing Service Center

Lundgren and Iorio—Characterization of Surface-Water and Groundwater Quality on the Fort Berthold Reservation, North Dakota, 2014–17—SIR 2020–5020

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20205020