U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2017–5068

Prepared in cooperation with the Bureau of Land Management

Geochemical Characterization of Groundwater 

Discharging from Springs North of the Grand Canyon, 

Arizona, 2009–2016
Cover. Schmutz Spring as seen by helicopter in August 2009, photo by Donald J. Bills.
Geochemical Characterization of Groundwater 

Discharging from Springs North of the Grand Canyon, 

Arizona, 2009–2016

By Kimberly R. Beisner, Fred D. Tillman, Jessica R. Anderson, Ronald C. Antweiler, and Donald J. Bills

Prepared in cooperation with the Bureau of Land Management

Scientific Investigations Report 2017–5068

U.S. Department of the Interior

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

RYAN K. ZINKE, Secretary

U.S. Geological Survey

William H. Werkheiser, Acting Director

U.S. Geological Survey, Reston, Virginia: 2017

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Suggested citation:

Beisner, K.R., Tillman, F.D., Anderson, J.R., Antweiler, R.C., and Bills, D.J., 2017, Geochemical characterization of 

groundwater discharging from springs north of the Grand Canyon, Arizona, 2009–2016: U.S. Geological Survey Scientific Investigations Report 2017–5068, 58 p., https://doi.org/10.3133/sir20175068.

ISSN 2328-0328 (online)
iii

Acknowledgments

The geochemical investigation presented in this report was supported by the U.S. Geological 

Survey (USGS) Toxic Substances Hydrology Program and the Bureau of Land Management. The 

report benefitted greatly from input from James Paces and Nick Paretti.
iv

Contents

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

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

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

Purpose and Scope ..............................................................................................................................2

Study Area..............................................................................................................................................2

Geologic Setting...........................................................................................................................2

Breccia Pipe Formation and Geochemistry ............................................................................4

Radioisotope Geochemistry.......................................................................................................5

Groundwater Occurrence and Movement ..............................................................................5

Climate...........................................................................................................................................6

Methodology...................................................................................................................................................6

Field.........................................................................................................................................................6

Analytical................................................................................................................................................6

Quality Assurance.................................................................................................................................7

Laboratory Selection...................................................................................................................7

Data Analysis.........................................................................................................................................8

Results .............................................................................................................................................................9

Quality Assessment..............................................................................................................................9

Environmental Samples .....................................................................................................................11

Parameters and Major Ions .....................................................................................................11

Trace Elements...........................................................................................................................13

Multivariate Analysis .......................................................................................................31

Isotopic and Radioactivity Analysis........................................................................................35

Radiochemistry...........................................................................................................................35

Strontium Isotopes ...........................................................................................................35

Oxygen and Hydrogen Stable Isotopes.........................................................................40

Groundwater Ages ....................................................................................................................41

Carbon-14...........................................................................................................................41

Tritium ................................................................................................................................41

Discussion.....................................................................................................................................................48

Evidence for Water Rock Interaction with Implication for Flowpaths.......................................48

Springs with Elevated Uranium and Selenium Concentrations ..................................................49

Springs with a Possible Component of Geothermal Fluids..........................................................52

Conclusions...................................................................................................................................................52

References Cited..........................................................................................................................................52

Appendixes 1–6............................................................................................................................................58
v

Figures

1. Map of study area with uranium mining withdrawal areas and spring sample 

locations identified by the geologic unit they discharge from..............................................3

2. Schematic of breccia pipe..........................................................................................................4

3. Graph of uranium activity ratio values from the U.S. Geological Survey National 

Research Program Lab versus USGS contract labs.............................................................11

4. Box plots of temperature, pH, and specific conductance...................................................12

5. Box plots of major cation concentrations; calcium, magnesium, potassium, 

and sodium...................................................................................................................................14

6. Box plots of major anion concentrations; bicarbonate, chloride, fluoride, 

and sulfate ...................................................................................................................................15

7. Piper plot representing major ion composition for spring samples...................................16

8. Maps of trace element concentration for arsenic, selenium, and uranium 

from spring samples ..................................................................................................................17

9. Box plots of trace element concentrations............................................................................21

10. Box plots of trace element concentrations grouped by geologic unit of 

spring discharge .........................................................................................................................26

11. Nonmetric multidimensional scaling plot for spring samples with polygons 

outlining geologic unit of spring discharge............................................................................32

12. Correlogram including the Kendall’s tau value for elemental pairs, where 

values with an X are not statistically significant with p >0.05.............................................33

13. Cluster dendrogram for spring samples .................................................................................34

14. Map of gross alpha radioactivity from spring samples with different symbols 

by geologic unit of spring discharge .......................................................................................36

15. Box plots of distribution of gross alpha radioactivity for all spring sites and 

divided by rock unit of spring discharge.................................................................................37

16. Box plots of distribution of gross beta radioactivity for all spring sites and 

divided by rock unit of spring discharge.................................................................................38

17. Graph showing uranium activity ratio data plotted against reciprocal uranium 

concentrations dissolved in spring samples collected from 2009 to 2016 ........................39

18. Graph showing strontium isotope ratio relative to the reciprocal strontium 

concentration for spring samples............................................................................................40

19. Stable isotope ratios for spring samples................................................................................40

20. Graphs of carbon data from spring water including 14C versus δ13C, 14C versus 

1/dissolved inorganic carbon, and δ13C versus 1/dissolved inorganic carbon ...............42

21. Boxplot of tritium for all samples and divided by rock unit of spring discharge..............47

22. Graph of tritium versus uncorrected carbon-14 values.......................................................48

23. Graph of selenium versus uranium from spring samples ....................................................50

24. Graph of strontium isotope ratio relative to uranium concentration for 

spring samples ............................................................................................................................51
vi

Tables

1. Standard reference samples reported by the U.S. Geological Survey National Research 

Program Laboratory in Boulder, Colorado outside of ± 2 Z-value threshold...........................8

2. U.S. Environmental Protection Agency water-quality standards for drinking water........9

3. Results of field blank analysis ..................................................................................................10

4. Results of water-sample replicate variability analysis ........................................................11

5. Median and mean values for trace elements from 36 samples from springs 

discharging north of the Grand Canyon from the Toroweap and Hermit 

Formations, Coconino Sandstone, Supai Group, and Redwall Limestone 

sampled for this study................................................................................................................20

6. Groundwater corrected age values ........................................................................................45

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)

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

gallon (gal) 3.785 cubic decimeter (dm3) 

International System of Units to U.S. customary units

Multiply By To obtain

Volume

liter (L) 33.81402 ounce, fluid (fl. oz)

liter (L) 2.113 pint (pt)

liter (L) 1.057 quart (qt)

liter (L) 0.2642 gallon (gal)

liter (L) 61.02 cubic inch (in3) 

Conversion Factors

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

°F = (1.8 × °C) + 32.

Tritium (3H) concentrations are given in units of picocuries per liter. The conversion of picocuries 

per liter to Tritium Units (TU), based upon a tritium half-life of 12.32 years (Lucas and Unterweger, 

2000), is: 1 TU = 3.22 picocuries per liter.

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).
Abstract

A geochemical study was conducted on 37 springs discharging from the Toroweap Formation, Coconino Sandstone, 

Hermit Formation, Supai Group, and Redwall Limestone north 

of the Grand Canyon near areas of breccia-pipe uranium mining. Baseline concentrations were established for the elements 

As, B, Li, Se, SiO2, Sr, Tl, U, and V. Three springs exceeded 

U.S. Environmental Protection Agency drinking water standards: Fence Spring for arsenic, Pigeon Spring for selenium 

and uranium, and Willow (Hack) Spring for selenium. The 

majority of the spring sites had uranium values of less than 

10 micrograms per liter (μg/L), but six springs discharging 

from all of the geologic units studied that are located stratigraphically above the Redwall Limestone had uranium values 

greater than 10 μg/L (Cottonwood [Tuckup], Grama, Pigeon, 

Rock, and Willow [Hack and Snake Gulch] Springs). The geochemical characteristics of these six springs with elevated uranium include Ca-Mg-SO4

 water type, circumneutral pH, high 

specific conductance, correlation and multivariate associations 

between U, Mo, Sr, Se, Li, and Zn, low 87Sr/86Sr, low 234U/238U 

activity ratios (1.34–2.31), detectable tritium, and carbon isotopic interpretation indicating they may be a mixture of modern and pre-modern waters. Similar geochemical compositions 

of spring waters having elevated uranium concentrations are 

observed at sites located both near and away from sites of uraniummining activities in the present study. Therefore, mining does 

not appear to explain the presence of elevated uranium concentrations in groundwater at the six springs noted above. The 

elevated uranium at the six previously mentioned springs may 

be influenced by iron mineralization associated with mineralized breccia pipe deposits. Six springs discharging from the 

Coconino Sandstone (Upper Jumpup, Little, Horse, and Slide 

Springs) and Redwall Limestone (Kanab and Side Canyon 

Springs) contained water with corrected radiocarbon ages as 

much as 9,300 years old. Of the springs discharging water 

with radiocarbon age, Kanab and Side Canyon Springs contain 

tritium of more than 1.3 picocuries per liter (pCi/L), indicating they may contain a component of modern water recharged 

after 1952. Springs containing high values of tritium (greater 

than 5.1 pCi/L), which may suggest a significant component 

of modern water, include Willow (Hack), Saddle Horse, Cottonwood (Tuckup), Hotel, Bitter, Unknown, Hole in the Wall, 

and Hanging Springs. Fence and Rider Springs, located on the 

eastern end of the study area near the Colorado River, have 

distinctly different geochemical compositions compared to 

the other springs of the study. Additionally, water from Fence 

Spring has the highest 87Sr/86Sr for samples analyzed from this 

study with a value greater than those known in sedimentary 

rocks from the region. Strontium isotope data likely indicate 

that water discharging at Fence Spring has interacted with Precambrian basement rocks. Rider Spring had the most depleted 

values of stable O and H isotopes indicating that recharge, if 

recent, occurred at higher elevations or was recharged during 

earlier, cooler-climate conditions.

Introduction

Grand Canyon National Park in Arizona is a United 

Nations World Heritage Site (United Nations Educational, 

Scientific and Cultural Organization [UNESCO], 2016) and 

an international tourist destination. The Grand Canyon region 

is a home or sacred place of origin to many Native Americans 

and its cultural significance extends back thousands of years. 

The Colorado River, which runs through Grand Canyon, is 

a primary source of drinking and irrigation water for millions of people in the United States and Mexico. The Grand 

Canyon region is also believed to host some of the highest 

grade uranium ore in the United States (Alpine and Brown, 

2010). In 1956, high-grade uranium ore was discovered in the 

Orphan Lode copper mine, just 3.2 kilometers (km) west of 

Grand Canyon Village (fig. 1), initiating the era of uranium 

exploration and mining in the area (Alpine and Brown, 2010). 

Uranium exploration and mining activity roughly tracked the 

price of uranium over time, with increasing prices and activity 

beginning in the late 1970s and declining prices and activity in 

Geochemical Characterization of Groundwater 

Discharging from Springs North of the Grand Canyon, 

Arizona, 2009–2016

By Kimberly R. Beisner, Fred D. Tillman, Jessica R. Anderson, Ronald C. Antweiler, and Donald J. Bills
2 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

the early 1990s. A brief uranium price spike in 2007 prompted 

renewed interest in deposits in the area, and by 2009 over 

10,000 mining claims had been located in the Grand Canyon 

region (U.S. Department of the Interior, 2012). In 2012, thenU.S. Secretary of the Interior Ken Salazar signed a Record 

of Decision (ROD) to withdraw over 1 million acres in three 

segregation areas of Federal land (north, east, and south) in the 

Grand Canyon region from new uranium mining activities for 

the next 20 years, subject to valid existing rights (fig. 1; U.S. 

Department of the Interior, 2012). A key factor in the decision 

for the withdrawal was the limited amount of scientific data 

and resulting uncertainties on the potential effects of uranium 

mining activities on cultural, biological, and water resources 

in the area.

Since 2012, the U.S. Geological Survey (USGS) has 

planned and conducted scientific investigations to address the 

uncertainties of potential uranium-mining impacts noted in 

the ROD. Investigations related to regional water resources 

include gaining a better understanding of the direction and 

rate of groundwater flow in the area, and understanding what 

constitutes background—or naturally occurring—concentrations

of uranium and associated trace elements in groundwater 

(referred to as baseline data in this report). There are limited 

groundwater data available from the Grand Canyon area, 

owing to the remoteness of the area and depth to the regional 

groundwater system (more than 3,000 feet [ft] in some areas). 

Water-quality data collected from springs are the primary 

source of information for the Grand Canyon region groundwater studies because of the lack of groundwater wells.

Purpose and Scope

Trace element concentrations in groundwater north of the 

Grand Canyon are not well understood. Springs were used to 

represent groundwater in this study as there are few groundwater wells to sample in the study area. Previous studies have 

investigated springs in the Snake Gulch and Jumpup Canyon 

areas, which includes Horse, Pigeon, Rock, Slide, Table Rock, 

Upper Jumpup, Willow (Snake Gulch), and Wildband Springs 

(fig. 1) where elevated uranium concentrations occur in some 

spring samples (Billingsley and others, 1983; Hopkins and 

others, 1984; Beisner and others, 2017). Knowledge gained 

from the spring studies in the Snake Gulch and Jumpup 

Canyon areas directed the approach to analyzing a larger 

data set for springs discharging north of the Grand Canyon, 

an area with mined and unmined mineralized breccia pipe 

deposits. Springs discharging from geologic units (Toroweap 

Formation, Coconino Sandstone, Supai Group, and Redwall 

Limestone) associated with breccia-pipe deposits north of 

the Grand Canyon were chosen to evaluate the geochemistry 

of the spring water in order to establish baseline values for 

trace element concentrations and to understand the recharge 

characteristics, geochemical reactions, and flowpaths as the 

groundwater circulates through these units.

The purpose of this report is to establish baseline trace 

element concentrations and geochemical characteristics for 

springs discharging from the Toroweap Formation, Coconino 

Sandstone, Supai Group, and Redwall Limestone north of the 

Grand Canyon and south of the Utah border. Spring sites with 

anomalous chemical characteristics are identified and characterized to understand possible sources. This report includes 

springs sampled by USGS between 2009 and 2016. Spring 

samples collected in 2009 are presented in Bills and others 

(2010) and are included in this study with more recent samples 

as part of a focused study scope in this report. Spring water 

geochemistry reflects past hydrologic and geochemical conditions, as groundwater moves from areas of recharge along geochemically reactive flowpaths. Spring geochemistry represents 

a snapshot based on the age of the water and the contribution 

of water of different ages, and it may take time for changes in 

the groundwater system to propagate to the spring. 

Study Area

The study area is located north of the Grand Canyon and 

south of the border with Utah, near the north and east segregation withdrawal areas. The area contains known mineralized 

breccia pipe deposits, some of which have been mined (fig. 1).

Geologic Setting

The study area is located within the southern part of the 

Colorado Plateau physiographic province. Geologic descriptions in this and the next paragraph are from Billingsley and 

others (2008) unless otherwise noted. Geologic units of interest for this report are Paleozoic sedimentary strata that have 

a regional dip of about 1° to 2° north-northeast on the west 

side of the study area. Geologic units are warped by anticlinal 

and synclinal folds, of which the Kaibab Anticline is a large 

scale north- trending and plunging anticline that elevates the 

Paleozoic strata as much as 2,000 ft higher than the surrounding plateaus east and west of the structure. The east side of the 

Kaibab Anticline is marked by the East Kaibab Monocline and 

the west side is marked by the Muav and Big Springs Faults, 

which have a general north-south strike and strata offset by as 

much as 1,200 ft down to the west. Monoclines developed in 

response to the Laramide orogeny along pre-existing Proterozoic fault zones (Huntoon, 2003). Extensional stresses from 

Miocene to the present time have resulted in normal faulting, which displaces strata down to the west, also along the 

pre-existing Proterozoic fault zones. There are several normal 

faults and minor folds in the study area that commonly parallel 

the northeast and northwest trending bedrock joints and fractures, which are vertically continuous through all Paleozoic 

strata exposed in the study area.

Paleozoic units discussed in this report include, in order 

from oldest to youngest: Redwall Limestone (Mississippian), 

Supai Group (Upper Mississippian, Pennsylvanian, and Lower 

Permian), Hermit Formation (Lower Permian), Coconino 
Introduction 

3

Swamp

Powell

OakBig

Warm

Saddle Horse

Cottonwood 

(Tuckup)

Schmutz Hotel

Willow(Hack)

Mountain Sheep

Bitter

Cottonwood (Sowats)

Upper Jumpup Lower Jumpup

# # # #

E

E

E

E EEE

Buck Farm Canyon

Fence

Vaseys Hanging

Hole in the wallUnknown

Rider

Grama

Rock

Water Canyon

Wildband

Pigeon

Table Rock

Side Canyon

27 Mule

Willow

(Snake G)

Showerbath

Kanab

Slide

Horse

Boulder

Little

111°40' 112°0' 112°20' 112°40' 113°0' 113°20'

36°40'

36°20'

36°0'

 Toroweap Formation Coconino Sandstone Hermit Formation Supai Group Redwall Limestone

Geologic unit of spring discharge

Known mineralized depositsMined deposits

EXPLANATION

0 5 10 15 20 25 KILOMETERS0 5 10 5 20 25 MILES

The base map from Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community

Figure 1. Study area with uranium mining withdrawal areas (red outline) and spring sample locations identified by the geologic unit they discharge from. Location of mineralized breccia pipes can be found in the following references; Alpine, 2010; Brown and others, 1992; Chenoweth, 1986, 1988; Verbeek and others, 1988; Wenrich and others, 1988, 1990, 1997; Sutphin and Weinrich, 1989; VanGosen and Weinrich, 1989, 1991; Finch and others, 1990; Wenrich, 1992; Wenrich and Aumente-Modreski, 1994; Gardner, 1998; Mazeika, 2002; Ross and Moreton, 2012.
4 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Sandstone (Lower Permian), Toroweap Formation (Lower 

Permian), and Kaibab Formation (Lower Permian). Several 

units are subdivided into distinct members presented here 

but not subdivided in this report. The Redwall Limestone 

includes the Whitmore Wash, Thunder Springs, Mooney Falls, 

and Horseshoe Mesa Members, and generally is composed 

of limestone with some chert and dolomite beds. The Supai 

Group includes the Watahomigi Formation (Upper Mississippian and Lower Pennsylvanian), Manakacha Formation 

(Middle Pennsylvanian), Wescogame Formation (Upper Pennsylvanian), and the Esplanade Sandstone (Lower Permian). 

The Supai Group is generally composed of sandstone, calcareous sandstone, dolomitic sandstone, siltstone, mudstone, 

conglomerate, dolomite, limestone, and chert. The Hermit 

Formation is composed of siltstone, sandstone, and calcareous 

sandstone; the unit gradually thickens westward and northward, and the sandstone beds gradually thin or pinch out from 

north to south. The Coconino Sandstone is a fine grained, well 

sorted quartz sandstone that pinches out to the north, the pinch 

out is visible in the upper reaches of Kanab Creek and north of 

Warm Spring. In some areas, where the Coconino Sandstone is 

absent, the Toroweap Formation rocks unconformably overly 

the Hermit Formation. The Toroweap Formation includes the 

Seligman, Brady Canyon, and Woods Ranch Members. The 

Toroweap Formation is generally composed of gypsiferous 

siltstone, sandstone, gypsum, limestone, dolomite, and chert. 

The Kaibab Formation includes the Fossil Mountain and 

Harrisburg Members; the formation is generally composed of 

gypsiferous siltstone, gypsum, limestone, cherty limestone, 

and chert beds. 

Breccia Pipe Formation and Geochemistry

Solution-collapse features known as breccia pipes are 

found throughout this region of Arizona. Breccia pipes are 

thought to form by dissolution and karst development in the 

underlying Redwall Limestone unit, with progressive collapse moving upwards through time into overlying rock units, 

forming a rubble (breccia) filled column that can be as much 

as 3,000 ft or more in height (Alpine and Brown, 2010; fig. 2). 

Breccia pipes are roughly circular in plan view, about 300 ft in 

Perched waterbearing zone

Redwall-Muav 

aquifer

(This aquifer 

extends below the 

stratigraphic 

column into the 

Cambrian Muav 

Limestone.)

0-600

Range of thickness, 

in feet

50-1,200

300-400

450-700

0-400

0-300

30-400

100-200

200-250

150-200

180-230

130-150

0-400

30-90

(Average 300 feet)

Kaibab

Formation

Toroweap

Formation

PERMIAN

299–251 Ma

PENNSYLVANIAN

318–299 Ma

MISSISSIPPIAN

359–318 Ma

DEVONIAN

416–359 Ma

Harrisburg Member

Fossil Mountain Member

Woods Ranch Member

Brady Canyon Member

Seligman Member

Coconino Sandstone

Hermit Formation

Esplanade Sandstone

Wescogame Formation

Manakacha Formation

Watahomigi Formation

Surprise Canyon

 Formation

 (Mississippian) Redwall Limestone

Temple Butte Formation Supai Group

uranium ore

Diameter of surface depression

Holocene alluvium

Esplanade

 surface

Figure 2. Schematic of breccia pipe. Modified from Van Gosen and Wenrich (1989) and Alpine and Brown (2010).
Introduction 5

diameter, and are often characterized by inward dipping beds 

along the margins (Otton and VanGosen, 2010). Other collapse 

features found throughout the Grand Canyon region include 

sinkholes and localized shallow collapse caused by dissolution 

of gypsum in the Kaibab and Toroweap Formations (Billingsley and others, 2008). In the absence of breccia exposed at the 

surface, the most effective way to determine if a breccia pipe 

underlies a collapse feature is by obtaining geologic core from 

drilling.

Some breccia pipes contain concentrated deposits of 

uranium, copper, silver, lead, zinc, cobalt, and nickel minerals (Wenrich, 1985; Wenrich and others, 1989; Finch and 

others, 1992). Uranium mineralization in breccia pipes likely 

occured after early mineralizing fluids moved through the 

pipe, creating reducing conditions within areas of the pipe that 

are amenable to reduction of oxidized uranium (U(VI)) and 

formation of lower solubility U(IV) minerals such as uraninite (Weinrich, 1985; Huntoon, 1996). Ore grade deposits are 

most commonly located in breccia adjacent to the Coconino 

Sandstone, Hermit Formation, and the upper members of the 

Supai Group (Otton and VanGosen, 2010). Mining of breccia 

pipe ore zones for copper, lead, zinc, and silver in the Grand 

Canyon region began in the 1860s, with uranium mining 

beginning in the 1950s.

Radioisotope Geochemistry

The most common radionuclides in groundwater are 222Rn, 226Ra, 238U, and 234U of the 238U decay series, and 228Ra of 

the 232Th decay series (Zapecza and Szabo, 1987). The occurrence of radionuclides in groundwater depends on the presence and solubility of the parent element in the decay series of 

each daughter element (Focazio and others, 2001). Uranium is 

most soluble in bicarbonate-rich oxidizing groundwater with 

low total dissolved solids content, and solubility is enhanced 

by association with carbonate, phosphate, and fluoride ions, 

or with organic compounds (Langmuir, 1978; Zapecza and 

Szabo, 1987). Uranium is less mobile in reducing groundwater, while radium is most mobile in chloride-rich reducing 

groundwater with high total dissolved solids content (Tanner, 

1964; Zapecza and Szabo, 1987). Gross alpha and gross beta 

activity measurements are used in drinking water regulations 

as a general screening tool to indicate the need for additional 

analysis of specific radionuclides. Radionuclides measured for 

this study include alpha emitters 226Ra, 234U, 235U, and 238U, and 

beta emitter 228Ra.

Erosion and mining expose fresh uranium ore surfaces 

to the hydrosphere. When exposed to oxygen in the air or in 

water, dissolution of uranium is expected. Conditions that 

favor uranium mobility in groundwater are dissolved oxygen 

and dissolved carbonate, both present in northern Arizona 

aquifers. The isotopic composition of uranium can be used to 

help evaluate whether uranium in surface water and groundwater samples is derived from the natural dissolution processes 

from uranium-bearing rock units of the Grand Canyon region, 

or from anthropogenic activities at active, on-standby, and 

abandoned uranium mines.

Natural uranium consists of three isotopes 238U, 235U, and 234U with relative abundances of approximately 99.27 percent, 

0.72 percent, and 0.0057 percent, respectively. Unlike the 

235U/238U ratio, which exhibits an extremely small range of 

variation in nature, 234U/238U can vary widely in natural waters. 

This variation is a result of processes related to the radioactive 

decay of daughter 234U from parent 238U such as alpha recoil, 

where during alpha decay of 238U the recoiling 234Th nuclei 

can be ejected from the solid to aqueous phase and then decay 

to 234U. These processes result in the preferential mobility of 234U relative to 238U during interactions between water and 

solid phases (Faure and Mensing, 2005). Uranium in undisturbed rocks and minerals older than approximately 1 million 

years reaches a state of radioactive equilibrium where the 

rate of decay of the short-lived 234U is limited by the rate of 

decay of the long-lived 238U parent. As a result, the 234U/238U 

activity ratio (UAR) is expected to equal unity (defined as 

secular equilibrium or UAR = 1.0). Solid phases subjected to 

water-rock interaction will be depleted in 234U relative to 238U 

and will have UAR values of equal to or less than 1.0. Bulk 

dissolution of the solid phase in a chemically aggressive environment (for example, fresh mill tailings or fresh exposures of 

ore) is likely to release uranium that has an isotopic composition similar to that of the rock (in other words, a UAR value 

close to 1.0). In contrast, water-rock interaction under less 

chemically aggressive conditions typical of natural flowpaths 

in aquifer rock that have been subjected to thousands of years 

of water/rock interaction allows preferential incorporation of 

234U into groundwater resulting from various recoil processes 

associated with production of 234U through alpha decay. As 

a result, most near-surface waters have 234U/238U AR values 

in excess of 1.0. Therefore, water in contact with high-grade 

uranium ore having a recent history of oxidation and leaching 

is likely to represent a mixture of material with UAR’s both 

greater than and less than 1.0. Groundwater in aquifers with 

long residence times and long flow paths will typically have 

higher UAR than aquifers with shorter residence times and 

short flow paths. Most natural groundwater has UAR’s greater 

than 1.0. Typical values fall in the 1–3 range but values in 

excess of 10 are possible (Kronfeld, 1974; Osmond and Cowart, 

1976; Szabo, 1982).

Groundwater Occurrence and Movement

Groundwater in the area occurs in locally perched aquifers of limited extent, which in this study includes spring discharge from the Toroweap and Hermit Formations, Coconino 

Sandstone, and Supai Group. Some springs discharge from 

Quaternary surficial deposits, which are limited in extent, and 

springs in this report are classified according to the adjacent 

stratrigraphic unit from Billingsley and others (2008). The 

deeper regional Redwall-Muav aquifer is several hundred feet 

below the perched groundwater (fig. 2). Springs discharging 

from the Redwall Limestone were included as there were 
6 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

enough for statistical analysis, whereas there were not enough 

springs sampled from the Muav Limestone for this study. 

Groundwater in perched aquifers discharges at several springs 

in the area or may migrate deeper into the subsurface (Bills 

and others, 2010).

Water in the Redwall Limestone is confined in some parts 

of the study area, as seen from pressure head encountered 

during well drilling, and is understood to be old water without 

a modern component (Bills and others, 2010). In some areas 

of the study, water may move quickly through the subsurface 

down to the Redwall Limestone. For example, dye tracers 

placed in a sinkhole on the Kaibab Plateau appeared after a 

year at Vasey’s Paradise (Jones and others, 2016).

Climate

The climate in the study area is semiarid to arid with temperature decreasing and precipitation increasing with increasing elevation. Average annual temperature at Page, Ariz. was 

15.4 °C for January 1997 through December 2008 (Western 

Regional Climate Center, 2016). Freezing winter temperatures 

are common on the Kaibab Plateau and summer temperatures 

may exceed 38 °C in the inner canyons of the area. Average 

annual precipitation ranges from 500–800 millimeters (mm) 

on the Kaibab Plateau to less than 300 mm in the Kanab Creek 

canyon (PRISM Climate Group, 2015). The ratio of annual 

evaporation to precipitation is about 2:1 in the higher altitudes 

on the Kaibab Plateau and as much as 5:1 at lower elevations 

near Snake Gulch (Farnsworth and others, 1982; Alpine and 

Brown, 2010; PRISM Climate Group, 2015).

Methodology

Field

Water samples were collected from 37 spring sites 

between August 2009 and May 2016, and spring characteristics are included in appendix 1. Thirteen springs were sampled 

more than one time during the sampling period. Water samples 

were collected following standard U.S. Geological Survey 

protocols (U.S. Geological Survey, variously dated). Field 

parameters including pH, water temperature, specific conductance, dissolved oxygen, and barometric pressure were 

measured on site just before water samples were collected. 

Spring discharge was measured by using volumetric techniques. Water samples were filtered (0.45 micrometers [μm]) 

for major cations; trace and rare earth elements; alkalinity; 

carbon-14; uranium, radium and strontium isotopes; and gross 

alpha and beta radioactivity. All samples, except for major 

anions, alkalinity, and carbon-14, were preserved to pH<2 by 

using ultrapure nitric acid. Unfiltered samples were collected 

for tritium and stable isotopes. Alkalinity titrations were performed in the field with the incremental equivalence method 

(U.S. Geological Survey, variously dated).

Three samples, Upper Jumpup (2009), Willow (Hack) 

(2012), and Kanab Spring (2009) were analyzed by a large 

volume method for radium isotopes, with detection limits less 

than 4 pCi/L, which involves passing at least 100 gallons through 

a series of filters including, in order, a 0.2 μm polypropylenemedium filter, and two manganese-impregnated acrylic fiber 

cartridges. The first cartridge primarily extracts the radium, 

and the second is used to check the efficiency of the first 

(Kraemer, 2005).

Analytical

Water samples were analyzed for major, trace, and 

rare-earth elements by the USGS National Research Program 

Laboratory in Boulder, Colo. (USGSTMCO) and at the USGS 

National Water Quality Laboratory (USGSNWQL). Analytical 

methods from the USGSTMCO included inductively coupled 

plasma-mass spectrometry (ICP-MS) to analyze for Al, As, B, 

Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Ga, Gd, Ho, 

La, Li, Lu, Mn, Mo, Nd, Ni, P, Pb, Pr, Rb, Re, Sb, Se, Sm, Sn, 

Sr, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, and Zr (Garbarino and Taylor, 1996; Taylor, 2001). An inductively-coupled 

plasma optical emission spectrophotometer (ICP-OES) was 

used to analyze for Ca, Fe, K, Mg, S, and SiO2 (Garbarino and 

Taylor, 1979). Anions Cl, F, NO3, and SO4 were analyzed by 

ion chromatography. Samples were analyzed in triplicate and 

the average was used for the final value.

Water samples analyzed for major and trace elements at 

the USGSNWQL include Buck Farm Canyon, Fence, Hanging, Hole in the Wall, Rider, and Unknown Springs. Analytical 

methods from the USGSNWQL included ICP-MS to analyze 

for Al, Sb, As, Ba, Be, B, Cd, Cr, Co, Cu, Pb, Li, Mo, Ni, Se, 

Ag, Sr, Tl, W, U, V, and Zn (Garbarino and others, 2006). 

ICP-AES was used to analyze for Ca, Fe, K, Mg, Mn, and 

Na (Fishman, 1993). Anions Cl, F, and SO4 were analyzed 

by ion chromatography, and SiO2 was evaluated by discrete 

analyzer colorimetry (Fishman and Friedman, 1989). Nitrate 

(NO3) + nitrite (NO2) was analyzed by colorimetry (Patton 

and Kryskalla, 2011). USGSNWQL reports values between 

their method detection level and laboratory reporting level 

as an estimated value, denoted with an E. Comparison of the 

USGSTMCO and USGSNWQL are described in the quality 

assurance section of this report.

Stable isotope ratios (δ18O and δ2H) were measured at the 

USGS Reston Stable Isotope Laboratory following methods 

by Révész and Coplen (2008a,b). Uncertainties reported at 

the 2-sigma level are 0.2 per mil (‰) for oxygen and 2‰ for 

hydrogen isotopic ratios relative to Vienna Standard Mean 

Ocean Water. Strontium isotope ratios (87Sr/86Sr) were measured by the USGS National Research Program Laboratory 

in Menlo Park, Calif. using methods described in Bullen 

and others (1996) with precision of ±0.00002 or better at the 

95 percent confidence level.

The USGS National Research Program Laboratory in 

Reston, Va., analyzed UAR using quadrapole ICP-MS mass 
Methodology 7

spectrometric methods described in Kraemer and others 

(2002) for samples of Wildband, Pigeon, Rock, Slide, Willow (Snake Gulch), Upper Jumpup, Rider, Schmutz, Willow 

(Hack), Grama, Hotel, Mountain Sheep, Lower Jumpup, Buck 

Farm Canyon, Side Canyon, Showerbath, Kanab, Hole in the 

Wall, Hanging, Fence, and Unknown Spring near Hanging 

Springs collected between 2009 and 2012. Multiple laboratories were used to analyze the 234U/238U activity ratio (UAR) 

owing to changes of the USGS contract laboratory. Uranium 

isotopes (234U, 235U, and 238U) were measured using alphacounting methods (ASTM D 3972) by Eberline Services in 

Richmond, Calif. for samples from 2011 and 2012; by Test 

America in Richland, Wash. in 2014; and by ALS Environmental in Fort Collins, Colo. in 2015 and 2016. Details of 

laboratory comparisons and determination of final UAR values 

are presented in the Quality Assessment section.

Total gross alpha was analyzed by counting using the 230Th curve and total gross beta was analyzed by counting 

using the 137Cs curve following U.S. Environmental Protection 

Agency (EPA) method 900.0 (U.S. Environmental Protection 

Agency, 1980) at Eberline Services in Richmond, Calif. for 

samples from 2009 and 2012; by Test America in Richland, 

Wash. in 2014; and by ALS Environmental in Fort Collins, 

Colo. in 2015 and 2016.

Radium isotopes (226Ra and 228Ra) were analyzed by the 

USGS National Research Program Laboratory in Reston, Va. 

for samples collected in 2009 through 2012 using methods 

described in Bills and others (2010). Three samples, Upper 

Jumpup (2009), Willow (Hack) (2012) and Kanab Spring 

(2009), were analyzed by a large volume method described in 

the field section of this report and analytical details are documented in Kraemer (2005).

Carbon-14 and 13/12C were analyzed by the National 

Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) 

at Woods Hole Oceanographic Institution. Carbon-14 values 

reported by the NOSAMS as absolute percent modern (pM) 

were denormalized using equation 5 of Plummer and others 

(2012) to percent modern carbon (pmc). NetpathXL was used 

to calculate corrected groundwater ages using model (11), 

“Revised F&G solid ex” (Parkhurst and Charlton, 2008). Values used in the calculation of groundwater age were 14C values 

of 0 pmc for carbonate and 100 pmc for soil CO2, and δ13C 

values of -1.1‰ for the Toroweap and Hermit Formations and 

Coconino Sandstone, -2‰ for the Supai Group, and -1.8‰ for 

the Redwall Limestone carbonate (Monroe and others, 2005; 

Bills and others, 2007) and -17‰ and -22‰ for soil CO2 (Hart 

and others, 2010).

Tritium (3H) is a useful tracer for determining if there 

is a component of water recharged during the period of 

nuclear bomb testing in the 1950s and 1960s when tritium 

values peaked and subsequently declined over the following 

decades. Tritium values have stopped decreasing in recent 

(after 1992) precipitation, and average values of tritium in 

precipitation range from 16.4 pCi/L in Camp Verde to 28.7 

pCi/L in Flagstaff (Eastoe and others, 2012). Tritium was 

measured on the majority of samples, but was not collected for 

samples in 2011. Tritium was measured at the USGS Menlo 

Park Tritium Lab using the electrolytic enrichment liquid 

scintillation counting method (Thatcher and others, 1977) 

with a detection limit of 0.5 pCi/L. Values below the laboratory detection level are reported including zero and negative 

values (McCurdy and others, 2008). The half-life of tritium is 

12.32 years (Lucas and Unterweger, 2000), so the age of the 

modern component of water can be quantified if the starting 

value is known. Tritium was assessed with a categorical age 

classification—as there is a large variation of tritium values in 

precipitation in northern Arizona—where less than 1.3 pCi/L 

is considered pre-modern (before 1952), greater than 12.8 pCi/L 

is modern (primarily after 1952), and values between the 

thresholds indicate a possible mixture of pre-modern and modern water. Additionally, a combination of measured tritium and 

geochemically corrected 14C were used to categorize springs 

based on age and calculate preliminary groundwater age estimates for select springs.

Quality Assurance

Quality assurance samples included blank and replicate 

samples evaluated based on methods from Mueller and others 

(2015). Five field blank samples were analyzed for major ion 

and trace element analysis by the USGSNWQL, and four field 

blank samples were analyzed by the USGSTMCO between 

2009 and 2015. Two equipment blanks were also collected for 

this project between 2010 and 2011. A threshold of 10 times 

the greatest blank concentration was used, where environmental sample concentrations above the threshold likely contain 

less than 10 percent influence from contamination and are not 

likely to be substantially affected by high bias, while concentrations below the threshold may contain more than 10 percent 

contamination and may be affected by high bias from sampling equipment and (or) field conditions.

There were 22 replicate water sample pairs analyzed 

for major ions and trace elements by the USGSTMCO. 

Replicate variability among all samples was determined for 

each element by calculating the standard deviation for each 

replicate pair and taking the average of the standard deviations and calculating a 90 percent confidence interval. Results 

from quality assurance samples are presented in the Quality 

Assessment section.

Laboratory Selection

At the beginning of this project in 2009, four laboratories were chosen to analyze splits of water samples for major 

ions and trace elements (Bills and others, 2010). Labs used 

included the (1) USGS National Research Program Laboratory in Boulder, Colo. (USGSTMCO), (2) USGS National 

Water Quality Laboratory in Lakewood, Colo. (USGSNWQL), 

(3) USGS National Research Program Laboratory in Reston, 

Va., and (4) Northern Arizona University. A decision was 

made to choose only one laboratory for analysis of subsequent 
8 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

samples collected after 2014 for this project. Laboratory selection was based on laboratory quality-control data. 

The USGSTMCO and USGSNWQL participate in the 

USGS Office of Water Quality Branch of Quality Systems 

(BQS) Inter-laboratory standard reference sample (SRS) 

comparison study where numerous labs across the country 

complete a round robin standard reference sample analysis and 

comparison. The USGS National Research Program Laboratory and Northern Arizona University do not participate in 

the USGS BQS Inter-laboratory SRS comparison study, and 

were therefore excluded from selections for future analysis 

as part of this project. The SRS data are statistically analyzed 

using methods from Hoaglin and others (1983), where a most 

probable value (MPV) is calculated for each analyte that represents the median excluding less than values, F-pseudosigma 

(fps) that approximates the standard deviation when data has 

a Gaussian distribution, Z value which is calculated as the 

reported value minus the MPV divided by the fps and the 

percent difference of a given laboratory reported value relative to the MPV, and are presented in U.S. Geological Survey 

(2016a). Standard reference sample data are considered acceptable if they have Z values within ±2. The USGSTMCO was 

chosen as the sole laboratory for analysis of major ions and 

trace elements for samples collected by this project starting in 

2014 based on performance in the SRS program, which gave 

acceptable values for all certified SRS for trace elements (U.S. 

Geological Survey, 2016a). Most major ion analysis from SRS 

at USGSTMCO were within the acceptable range except for 

the four samples analyzed between 2012 and 2015 presented 

in table 1 (U.S. Geological Survey, 2016a). No samples were 

analyzed in 2013 for this project and the other SRS reported 

values of potassium and sodium reported by the USGSTMCO 

with Z values outside the ±2 threshold are within variability 

(calculated from environmental sample replicate pairs) of 

the MPV.

Seven samples collected in fall 2009 from Buck Farm 

Canyon, Fence, Hanging, Hole in the Wall, Rider, Unknown 

and Vaseys Springs were analyzed for major and trace elements by the USGSNWQL but not the USGSTMCO; the 

USGSNWQL data for these samples are used in this report. 

All major and trace element concentrations reported for fall 

2009 standard reference samples by both the USGSNWQL 

and USGSTMCO were within ±2 Z-value and the percent 

difference between the two lab reported values were within 

±15 percent (appendix 2). Based on this laboratory qualitycontrol data, it is acceptable to combine the USGSNWQL data 

for these samples with the USGSTMCO data.

Data Analysis

As the majority of trace elements had one or more values 

below a laboratory reporting level, with several elements containing multiple reporting levels, specific statistical methods 

(Helsel, 2012) for data with values below a threshold (laboratory reporting level) were used to analyze the majority of 

analytes presented in this study. Select trace elements (Si, As, 

Ba, B, Sr, Li, and U) did not have any data below the laboratory reporting level for the data set used in this paper.

Boxplots for elements with censored data (value reported 

as less or greater than a threshold) were made using the 

cenboxplot function from the NADA software package (Lee, 

2015) in the R statistical computing environment (R Core 

Team, 2015). Outlier data points on boxplots were defined 

for this study as greater than 1.5 times the interquartile range 

(IQR). Chemical analysis from spring samples was analyzed 

for each element to determine the Kaplan-Meier model of 

the data using the cenfit function from the NADA package 

in R (Lee, 2015). A p-value threshold of 0.05 (95 percent 

confidence level) was used to indicate statistical significance 

for all mentioned statistical tests.

Robust regression on order statistics (ROS) using the 

cenros function from the NADA package in R (Lee, 2015) was 

used to calculate the median, mean, and standard deviation for 

trace elements for the first sample collected from each spring 

in the data set.

Spring samples were grouped by geologic unit of 

discharge and compared using the cendiff function from the 

NADA package in R (Lee, 2015). The cendiff function uses 

the Peto-Prentice test (Helsel and Lee, 2006) to determine 

whether there were significant differences between the groups 

for elements with censored data. An analysis of variance 

(ANOVA) was run for the elements without censored values 

and the TukeyHSD function was used to determine which 

groups were statistically different.

Table 1. Standard reference samples reported by the U.S. Geological Survey National Research Program Laboratory in Boulder, 

Colo. (USGSTMCO) outside of the ±2 Z-value threshold.

[F-, indicates a less than value was reported for a standard reference sample; MPV, most probable value]

Standard reference 

sample number 

Date Elements and associated Z-value Difference in concentration from 

MPV, in milligrams per liter

M-202 Spring 2012 Na (–2.99) –1.11

M-208 Fall 2013 K (–3.29), Mg (–2.16), Na (F-) K (0.86), Mg (–0.8)

M-212 Fall 2014 Na (–2.80) –1.015

P-64 Spring 2015 K (–3.29) –0.079
Results 9

Non-metric multidimensional scaling (NMDS) was used 

to reduce the complex data structure (many samples and many 

elements) to represent the pairwise dissimilarity between 

objects in a low-dimensional space (Buttigieg and Ramette, 

2014). The following elements, As, Cd, Cu, Li, Mn, Mo, Pb, 

Se, Sr, U, V, and Zn were used for multivariate comparison 

based on the distinction between breccia pipe uranium mining 

sediment leachate and spring chemistry from Beisner and 

others (2017). Uscores of the data were determined using the 

uscore function for R using the default to calculate the ranks 

of the scores (Helsel, 2012, 2016). The NMDS was performed 

on the uscores using the metaMDS function from the vegan 

package in R (Oksanen and others, 2016) using euclidean distance, zerodist = add and autotransform = false (Helsel, 2012). 

NMDS stress values less than or equal to 0.1 are considered 

fair, while values equal to or below 0.05 indicate good fit and 

values near or greater than 0.2 are deemed suspect (Buttigieg 

and Ramette, 2014).

The elements used in the NMDS analysis were then 

evaluated for correlation using the cenken function from the 

NADA package in R (Lee, 2015). Kendall’s tau correlation 

coefficients were included in a correlogram using the corrplot 

package in R (Wei and Simko, 2016). A cluster analysis was 

also used to identify similar groups in the spring samples by 

evaluating minimum differences within groups and maximum 

differences among groups using the hclust function for the elements used in the NMDS analysis. The Calinski criterion was 

used to determine the number of clusters that maximizes the 

difference between clusters, while minimizing the differences 

within clusters with the cascadeKM function of the vegan 

package in R (Oksanen and others, 2016). The anosim function was used to statistically evaluate whether or not groups 

of samples have significantly different concentration patterns 

(Helsel, 2012).

Water sample concentrations were compared to EPA 

drinking water standards presented in table 2 (U.S. Environmental Protection Agency, 2017). Springs are not utilized 

for public drinking water supply sources, but they are often 

located in remote locations where they may be the only source 

of water available to hikers.

Results

Quality Assessment

Spring sample quality assurance results are presented 

in appendixes 2–5, and are archived in the USGS National 

Water Information System database (U.S. Geological 

Survey, 2016b).

Table 2. U.S. Environmental Protection Agency (2017) waterquality standards for drinking water.

[Values presented in units used in this report. NA, not available; MCL, 

maximum contaminant level; SMCL, secondary maximum contaminant 

level]

Element Units

Primary 

drinkingwater 

standard

Secondary 

drinkingwater 

standard

MCL SMCL

Aluminum μg/L NA 50–200

Antimony μg/L 6 NA

Arsenic μg/L 10 NA

Barium μg/L 2,000 NA

Beryllium μg/L 4 NA

Cadmium μg/L 5 NA

Chloride mg/L NA 250

Chromium μg/L 100 NA

Copper μg/L 1,300 1,000

Fluoride mg/L 4 2

Iron μg/L NA 300

Lead μg/L 15 NA

Manganese μg/L NA 50

Mercury μg/L 2 NA

Nitrate (NO3) mg/L 10 NA

pH NA 6.5–8.5

Selenium μg/L 50 NA

Silver μg/L NA 100

Sulfate (SO4) mg/L NA 250

Thallium μg/L 2 NA

Total dissolved solids 

(TDS) mg/L NA 500

Uranium μg/L 30 NA

Zinc μg/L NA 5,000

226 and 228Radium pCi/L 5 NA

Alpha particles pCi/L 15 NA

Beta particles Millirems/

year

4 NA
10 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Constituents detected in field blank samples (value 

reported above laboratory detection level) are presented in 

table 3 and all blank results in appendix 3 along with a suggested threshold for contamination (concentration threshold 

for influence in table 3) based on a value 10 times the greatest blank concentration. Environmental sample concentrations above the threshold likely contain less than 10 percent 

contamination and are not likely to be substantially affected by 

high bias, while concentrations below the threshold may contain more than 10 percent contamination and may be affected 

by high bias from sampling equipment and conditions.

None of the environmental samples from this study had 

concentrations of major ion values less than the concentration 

threshold for influence for elements with blank detections. 

For trace elements, no environmental samples had values less 

than the concentration threshold for influence for B, Ba, and 

Sr. Environmental samples had greater than 50 percent of 

the samples with values less than the concentration threshold 

for influence for Al, Be, Cd, Co, Cr, Cu, Mn, Pb, Sb, and Zn 

(table 3). Blank detections for cobalt and chromium were only 

measured by samples submitted to the USGSNWQL, which 

accounts for 6 of the 52 environmental samples. The blank 

sample data indicate that the potential influence from contamination bias is random and not systematic at either lab.

Two equipment blanks that were analyzed at the 

USGSNWQL had less constituents detected compared with the 

field blanks and consisted of detections of cobalt (0.046 and 

0.12 μg/L) and manganese (E 0.14 and 0.23 μg/L) in each equipment blank, which were less than the highest field blank detection. Tungsten had a reported estimated value (E 0.019 μg/L) 

in one equipment blank. Tungsten was not used for analysis 

in this report as there were 15 samples with no reported 

value. Laboratory reporting levels are generally lower at the 

USGSTMCO than the USGSNWQL, and elements with blank 

detections from USGSTMCO were lower than the laboratory 

reporting level from the USGSNWQL with the exception of 

one sample from 2009 at Lower Jumpup Spring for calcium, 

where the blank detection at USGSTMCO was 0.11 and was 

<0.02 at USGSNWQL (appendix 3).

Replicate pair results are presented in appendix 4. Replicate variability among all samples was determined by calculating the standard deviation for each replicate pair and taking 

the average of the standard deviations of all replicate pairs. 

The 90 percent confidence intervals about a single sample are 

Table 3. Results of field blank analysis.

[mg/L, milligrams per liter; μg/L, micrograms per liter; E, estimated value, greater than lab detection level and less than lab reporting level; USGSTMCO, 

USGS National Research Program Laboratory in Boulder, Colo.; USGSNWQL, USGS National Water Quality Laboratory in Lakewood, Colo.; four total 

blanks were analyzed by USGSTMCO and five by USGSNWQL; blank detection indicates a value reported greater than the laboratory detection level]

Constituent

Number of blanks with value 

greater than lab detection level

Concentration range of blank 

detections

Concentration 

threshold for 

influence

Units

Percent of 

environmental 

samples below 

USGSTMCO USGSNWQL USGSTMCO USGSNWQL threshold

Calcium 1 0 0.11 1.1 mg/L 0

Chloride 2 0 0.01–0.02 0.2 mg/L 0

Sodium 1 0 0.005 0.05 mg/L 0

Sulfate 1 0 0.034 0.34 mg/L 0

Silica 2 0 0.009–0.11 1.1 mg/L 0

Aluminum 2 0 0.16–0.45 4.5 ug/L 94

Boron 1 0 0.4 4 ug/L 0

Barium 2 0 0.01 0.1 ug/L 0

Beryllium 1 0 0.007 0.07 ug/L 100

Cadmium 2 0 0.001–0.005 0.05 ug/L 100

Cobalt 0 3 0.031–0.182 1.82 ug/L 100

Chromium 0 1 0.07 0.7 ug/L 60

Copper 3 0 0.015–0.12 1.2 ug/L 88

Manganese 1 1 0.07 0.32 3.2 ug/L 92

Lead 2 0 0.005 0.05 ug/L 77

Antimony 3 0 0.006–0.026 0.26 ug/L 96

Strontium 1 0 0.3 3 ug/L 0

Zinc 2 2 0.1–2 E1.4–E1.5 20 ug/L 96
Results 11

presented in table 4; there is a 90 percent confidence that the 

true value of any individual measurement for any constituent 

listed in table 2 will lie within the range given in table 4.

Values of UAR determined for 16 paired samples 

(appendix 5) analyzed by USGS and contract labs (Eberline 

Services, Test America, and ALS Environmental) were similar: 

differences ranged from 0 to 0.191 with an average deviation 

of 0.013 UAR values, over a range of UAR values from 0 to 

10.2 with an average of 0.9 percent difference (fig. 3). If two 

UAR values were available for a single water sample, the 

value determined by the USGS National Research Program 

Laboratory was used.

Environmental Samples

Spring sample environmental results are presented in 

appendix 6 and are archived in the USGS National Water 

Information System database (U.S. Geological Survey, 

2016b).

Parameters and Major Ions

Water from springs sampled for this study had pH ranging from 6.6 to 8.6, moderately high specific conductance 

that varied over a wide range (300–3,610 microsiemens 

per centimeter [μS/cm]) (fig. 4), and measurable dissolved 

oxygen. Water temperatures generally were higher in springs 

discharging from lower stratigraphic units than in upper stratigraphic units. Water in springs discharging from the Toroweap 

Formation, Coconino Sandstone, and Hermit Formation was 

significantly different from springs discharging from the Redwall Limestone (fig. 4A). Hotel Spring hosted in Supai Group 

rocks had the greatest water temperature of 28 °C in July 

2011. The median value for Supai Group springs (18.3 °C) 

was substantially lower than the median value obtained for 

springs discharging from the Redwall Limestone (21.5 °C; fig. 

4A). For some springs measured more than once, temperatures 

varied depending on the time of year the sample was collected. 

For example, temperature in the Pigeon Spring pool ranged 

from 8.3 °C in March, to 20 °C in September, and 11.8 °C in 

November (Beisner and others, 2017). More temporal samples 

would be needed to determine which springs had seasonal 

temperature fluctuation.

The pH values varied over a similar range at springs 

discharging from all geologic units (fig. 4B) and statistical differences between the groups were not determined as the data 

did not fit a lognormal distribution. Specific conductance was 

Table 4. Results of water-sample replicate variability analysis.

[mg/L, milligrams per liter; μg/L, micrograms per liter; beryllium, bismuth, 

cobalt, and nickel did not have more than four replicate pairs with values 

above the laboratory reporting limit and therefore the variability was not 

quantified for these elements] 

Element

Variability 

(90 percent 

confidence)

Variability units

Aluminum ± 0.27 μg/L

Arsenic ± 0.10 μg/L

Boron ± 3.84 μg/L

Barium ± 0.46 μg/L

Calcium ± 8.26 mg/L

Cadmium ± 0.01 μg/L

Chlorine ± 0.33 mg/L

Chromium ± 0.17 μg/L

Copper ± 0.09 μg/L

Fluorine ± 0.03 mg/L

Iron ± 7.50 μg/L

Potassium ± 0.16 mg/L

Lithium ± 1.52 μg/L

Magnesium ± 2.86 mg/L

Manganese ± 0.07 μg/L

Molybdenum ± 0.27 μg/L

Sodium ± 1.42 mg/L

Lead ± 0.003 μg/L

Sulfate (SO4) ± 6.19 mg/L

Antimony ± 0.003 μg/L

Selenium ± 0.72 μg/L

Silica (SiO2) ± 0.35 mg/L

Strontium ± 60.1 μg/L

Thallium ± 0.02 μg/L

Uranium ± 0.47 μg/L

Vanadium ± 0.15 μg/L

Zinc ± 0.76 μg/L

Figure 3. Uranium activity ratio (UAR) values from 

the U.S. Geological Survey (USGS) National Research 

Program Lab versus USGS contract labs.

1

2

3

4

5

6

1 2 3 4 5 6

234Uranium /238Uranium, activity ratio, USGS 

National Research Program Lab 

234Uranium/238Uranium, activity ratio, contract laboratories

 Toroweap Formation

 Coconino Sandstone

 Hermit Formation

 Supai Group

 Redwall Limestone

Geologic unit of spring discharge

EXPLANATION
12 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

greatest in springs discharging from the Toroweap Formation and significantly different from springs discharging from 

the Coconino Sandstone and Redwall Limestone, which had 

lower values (fig. 4C). Willow (Snake Gulch) and Cottonwood 

(Tuckup) Springs specific conductance values were outliers 

(greater than 1.5 times the interquartile range) compared to the 

other springs discharging from the Coconino Sandstone and 

Supai Group respectively (fig. 4C).

Spring discharge varied across the study area. Several 

springs were slow seeping springs with flow rates ranging 

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values

Buck Farm

Canyon

Willow

(Snake Gulch)

Cottonwood

(Tuckup)

a b

p = 0.003

a a a,b

p = 0.006

C a b a,b a,b b

B

A

30

25

20

15

10

5

0

9

8.5

8

7.5

7

6.5

6

4,000

3,000

2,000

1,000

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

0

Specific conductance, in microsiemens

per centimeter pH Temperature, in degrees Celsius

Figure 4. Temperature (A), pH (B), and specific conductance (C). The interquartile range (IQR) 

is the 25th to 75th percentile. Letters a and b indicate significantly different groups and a,b are not 

distinct from either group where the p-value indicates the significance of the test for difference 

between groups.
Results 13

from less than a gallon a minute to several gallons per 

minute. Springs with high flow rates ranging from 200 to 

730 gallons per minute were primarily discharging from the 

Redwall Limestone.

Water discharging from the Toroweap Formation had 

significantly higher values of calcium, magnesium, and 

fluoride compared to springs discharging from other units 

(figs. 5 and 6) most notably the Coconino Sandstone (calcium, 

magnesium) and Redwall Limestone (calcium, magnesium, 

and fluoride). Willow (Snake Gulch) Spring had several elements (calcium, magnesium, sodium, and sulfate) which were 

outliers compared to the remaining springs discharging from 

the Coconino Sandstone (figs. 5A,B,D and 6D). Cottonwood 

(Tuckup) Spring had high outlier values for calcium, magnesium, and sulfate (fig. 5A,B,D). Rider and Fence Spring 

had high outlier values for potassium, sodium, and chloride 

(figs. 5C,D and 6B). Fence Spring had a high outlier value and 

Rider Spring had a low outlier value for bicarbonate (fig. 6A). 

Fluoride had a high outlier for Rider Spring (fig. 6C). Lower 

Jumpup and Saddle Horse Springs had high and low outlier 

values, respectively, for fluoride (fig. 6C).

Most spring waters were characterized by calcium and 

magnesium as the dominant cations and sulfate and bicarbonate as the dominant anions (fig. 7). Rider and Fence Springs 

had distinctly different water type classifications compared 

with the other spring samples in this study, with a larger 

proportion of sodium and potassium and chloride. All springs 

discharging from the Toroweap Formation sampled for this 

study had a dominant sulfate anion, which may be due to 

gypsum dissolution from the host rocks (Beisner and others, 

2017). Coconino Sandstone springs varied primarily with 

respect to the proportion of bicarbonate. In Big Springs the 

dominant anion was bicarbonate; in Upper Jumpup, Horse, 

Slide, Willow (Snake Gulch), and Rider Springs the dominant 

anion was sulfate; and Little, Boulder, and Warm Springs were 

a mixture of the two (fig. 7). Hermit Formation springs also 

varied with respect to bicarbonate; in Swamp, Powell, and 

Oak Springs the dominant anion was bicarbonate and the other 

springs were dominated by sulfate (fig. 7). Two Supai Group 

springs (Hotel and Saddle Horse Springs) had a higher proportion of magnesium compared with other Supai Group springs. 

In Saddle Horse Spring the dominant anion was bicarbonate, 

whereas Hotel Spring contained a mixture of bicarbonate and 

sulfate anion waters and had a slightly higher proportion of 

chloride compared to the other springs. The rest of the Supai 

Group springs contained dominantly sulfate anion waters 

except for Cottonwood Spring (Sowats), which was a mixture 

of bicarbonate and sulfate (fig. 7). Redwall Limestone springs 

also varied with respect to bicarbonate proportion; in Hole in 

the Wall, Hanging, and Unknown near Hanging Springs the 

dominant anion was bicarbonate. The other springs were a 

mixture of bicarbonate and sulfate, except for Side Canyon 

Spring, in which the dominant anion was sulfate (fig. 7).

Trace Elements

Three springs exceeded the EPA drinking water standard 

(table 2); Fence Spring for arsenic, Pigeon Spring for selenium and uranium, and Willow (Hack) Spring for selenium 

(figs. 8–10, table 5).

Median and mean values for all springs discharging north 

of the Grand Canyon from the Toroweap and Hermit Formations, Coconino Sandstone, Supai Group, and Redwall Limestone sampled for this study are listed in table 5. For all of the 

trace elements quantified in table 5 there are springs that are 

statistical outliers. Elements that were not statistically quantified had a majority (greater than 50 percent) of samples with 

values less than the threshold of influence from blank samples 

(Al, Be, Cd, Co, Cr, Cu, Mn, Pb, Sb, and Zn) or did not fit a 

lognormal distribution (Ba, Fe, Mo, and Ni).
14 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Figure 5. Major cation concentrations; calcium (A), magnesium (B), potassium (C), and sodium (D). The interquartile 

range (IQR) is the 25th to 75th percentile. Letters a and b indicate significantly different groups and a,b are not distinct 

from either group where the p-value indicates the significance of the test for difference between groups.

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values

700

600

400

500

300

200

100

0

300

250

150

200

100

50

0

20

15

5

10

0

200

150

50

100

0

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

Calcium, in milligrams per liter Magnesium, in milligrams per liter Potassium, in milligrams per liter Sodium, in milligrams per liter

Willow

(Snake Gulch)

Cottonwood

(Tuckup)

Willow

(Snake Gulch)

Cottonwood

(Tuckup)

Rider

Fence

Rider

Fence

Willow

(Snake Gulch)

p = 0.01

a b a,b a,b b

p = 0.005

a b a,b a,b b

p = 0.31

a a a a a

p = 0.52

a a a a a

A

B

C

D
Results 15

Figure 6. Major anion concentrations; bicarbonate (A), chloride (B), fluoride (C), and sulfate (D). The interquartile 

range (IQR) is the 25th to 75th percentile. Letters a and b indicate significantly different groups and a,b are not 

distinct from either group where the p-value indicates the significance of the test for difference between groups.

400

500

300

200

100

0

250

150

200

100

50

0

2

1.5

0.5

1

0

2,500

2,000

500

1,000

1,500

0

Bicarbonate, in milligrams per liter Chloride, in milligrams per liter Fluoride, in milligrams per liter Sulfate, in milligrams per liter

A

B

C

D

Rider

Fence

Rider

Fence

Rider

Lower

Jumpup

Saddle

Horse

Cottonwood

Willow (Tuckup) (Snake Gulch)

p = 0.53

a a a a a

p = 0.07

a a a a a

p = 0.30

a a a a a

p = 0.15

a a a a a

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone
16 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Calcium(Ca) Chloride(Cl) + Fluoride(F)

100 80 60 40 20 0 0 20 40 60 80 100

13

52

33

30

9, 20,21

49,50,51

35,36

37

1 Table Rock Spring

2 Wildband Spring

3 Water Canyon Spring

4,5,6 Pigeon Spring

7,8 Upper Jumpup Spring

9 Big Spring

10 Little Spring

11 Boulder unnamed Spring

12 Horse Spring

13 Rider Spring

14,15,16 Slide Spring

17 Warm Springs

18,19 Willow Spring (Snake Gulch)

20 Swamp Spring

21 Powell Spring

22,23 Schmutz Spring

24 27 Mule

25,26,27 Willow Spring (Hack Canyon)

28,29 Grama Spring

30 Oak Spring

31,32 Rock Spring

33 Saddle Horse Spring

34 Cottonwood Spring (Tuckup Canyon)

35,36 Hotel Spring

37 Cottonwood Sowats

38,39 Mountain Sheep Spring

40 Bitter Spring

41,42 Lower Jumpup Spring

43 Buck Farm Canyon Spring

44 Side Canyon Spring

45,46 Showerbath Spring

47,48 Kanab Spring

49 Unknown Spring near Hanging Springs

50 Hole in the Wall Spring

51 Hanging Spring

52 Fence Spring

38-42

10,11,17 43

7,8,12,14-16

24

44

45-48

1-6,18,19,22,23,25-29,31,32,34

Numbers Site Name Numbers Site Name

 Toroweap Formation

 Coconino Sandstone

 Hermit Formation

 Supai Group

 Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

Magnesium (Mg)

Chloride (Cl) + Fluoride (F) + Sulfate (SO4

)

Sodium (Na) + Potassium (K)

Calcium (Ca) + Magnesium (Mg)

Bicarbonate (HCO3

) + Carbonate (CO3

)

Sulfate (SO4

)

0

20

40

60

80

20

40

60

80

80

60

40

100

20

100

80

60

40

20

0

0

20

40

60

80

20

40

60

80

100

100

80

60

40

20

80

60

40

20

0

Figure 7. Major ion composition for spring samples.
Results 17 Figure 8. Trace element concentration for arsenic (A), selenium (B), and uranium (C) from spring samples. Location of mineralized breccia pipes can be found in the following references; Alpine, 2010; Brown and others, 1992; Chenoweth, 1986, 1988; Verbeek and others, 1988; Wenrich and others, 1988, 1990, 1997; Sutphin and Weinrich, 1989; VanGosen and Weinrich, 1989, 1991; Finch and others, 1990; Wenrich, 1992; Wenrich and Aumente-Modreski, 1994; Gardner, 1998; Mazeika, 

2002; Ross and Moreton, 2012.

The base map from Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community

Swamp

Powell

Oak

Big

Warm

Saddle Horse

Cottonwood (Tuckup)

Schmutz Hotel

Willow(Hack)

Mountain Sheep

Bitter

Cottonwood (Sowats)

Upper Jumpup

Lower Jumpup

!

! !!

!!

! !!

! !

!

!

!

!

!

!

!

!

! !

!!

!

! !

!

! ! !

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

! !

! !

!

# # # #

E

E

E

E EEE

Buck Farm Canyon

Fence

Vaseys Hanging

Hole in the WallUnknown

Rider

Grama

Rock

Water Canyon

Wildband

Pigeon

Table Rock

Side Canyon

27 Mule

Willow

(Snake Gulch)

Showerbath

Kanab

Slide

Horse

Boulder

Little

Toroweap FormationCoconino SandstoneHermit FormationSupai GroupRedwall Limestone

Less than 1.01.0 to 1.92.0 to 2.93.0 to 4.95 to 9.910 to 14Equal to or greater than 15

Arsenic concentration, in 

micrograms per liter 

0 5 10 15 20 25 KILOMETERS0 5 10 5 20 25 MILES

111°40' 112°0' 112°20' 112°40' 113°0' 113°20'

36°40'36°20'

A

36°0'

EXPLANATION

Known mineralized depositsMined deposits
18 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, ArizonaThe base map from Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, 

METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community

Swamp

Powell

Oak

Big

Warm

Saddle Horse

Cottonwood 

(T

Schmutz

uckup)

Hotel

Willow(Hack)

Mountain Sheep

Bitter

Cottonwood (Sowats)

Upper Jumpup

Lower Jumpup

!

! !

!

!!

! !!

! !

!

!

!

!

!

!

!

!

!

! !

!!

!

! !

!

! ! !

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

! ! ! !

!

#

#

#

#

E

E

E

E

EE

E

Buck Farm Canyon

Fence

Vaseys Hanging

Hole in the 

Wall

Unknown

Rider

Grama

Rock

Water Canyon

Wildband

PigeonTable Rock

Side Canyon

27 Mule

Willow

(Snake Gulch)

Showerbath

Kanab

Slide

Horse

Boulder

Little

0 5 10 15 20 25 KILOMETERS0 5 10 5 20 25 MILES

111°40' 112°0' 112°20' 112°40' 113°0' 113°20'

B

36°40'36°20'

36°0'

Toroweap FormationCoconino SandstoneHermit FormationSupai GroupRedwall Limestone

Less than 1.01.0 to 4.95.0 to 9.910 to 2930 to 4950 to 59Equal to or greater than 60

Selenium concentration, in 

micrograms per liter 

EXPLANATION

Known mineralized depositsMined deposits

Figure 8. Trace element concentration for arsenic (

A), selenium (

B), and uranium (

C) from spring samples. Location of mineralized breccia pipes can be found 

in the following references; Alpine, 2010; Brown and others, 1992; Chenoweth, 1986, 1988; Verbeek and others, 1988; Wenrich and others, 1988, 1990, 1997; Sutphin and Weinrich, 1989; VanGosen and Weinrich, 1989, 1991; Finch and others, 1990; Wenrich, 1992; Wenrich and Aumente-Modreski, 1994; Gardner, 1998; Mazeika, 2002; Ross and Moreton, 2012.—Continued
Results 19 Figure 8. Trace element concentration for arsenic (A), selenium (B), and uranium (C) from spring samples. Location of mineralized breccia pipes can be found in the following references; Alpine, 2010; Brown and others, 1992; Chenoweth, 1986, 1988; Verbeek and others, 1988; Wenrich and others, 1988, 1990, 1997; Sutphin and Weinrich, 1989; VanGosen and Weinrich, 1989, 1991; Finch and others, 1990; Wenrich, 1992; Wenrich and Aumente-Modreski, 1994; Gardner, 1998; Mazeika, 

2002; Ross and Moreton, 2012.—Continued

Swamp

Powell

Oak

Big

Warm

Saddle Horse

Cottonwood 

(Tuckup)

Schmutz Hotel

Willow(Hack) Mountain Sheep BitterCottonwood (Sowats)

Upper Jumpup Lower Jumpup

!

! !!

!!

! !!

! !

!

!

!

!

!

!

!

!

!

! !

!!

!

! !

!

! ! !

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

! !

! !

!

# # # #

E

E

E

E EEE

Buck Farm Canyon

Fence

Vaseys Hanging

Hole in the WallUnknown

Rider

Grama

Rock

Water Canyon

Wildband

Pigeon

Table Rock

Side Canyon

27 Mule

Willow

(Snake Gulch)

Showerbath

Kanab

Slide

Horse

Boulder

Little

The base map from Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community

!

0 5 10 15 20 25 KILOMETERS0 5 10 5 20 25 MILES

111°40' 112°0' 112°20' 112°40' 113°0' 113°20' C

36°40'36°20'

36°0'

Toroweap FormationCoconino SandstoneHermit FormationSupai GroupRedwall Limestone

Less than 1.01.0 to 1.92.0 to 4.95.0 to 9.910 to 1920 to 29Equal to or greater than 30

Uranium concentration, in 

micrograms per liter 

EXPLANATION

Known mineralized depositsMined deposits
20 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona EPA MCL = 10

0 10 20 30 40 50

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

0 2 4 6 8 10

0 50 100 150 200 250

12 14 16 18

Barium, in micrograms per liter Arsenic, in micrograms per liter Antimony, in micrograms per liter Aluminum, in micrograms per liter

A

B

C

D

Figure 9. Trace element concentrations. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E ), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium 

(J), manganese (K), molybdenum (L ), 

selenium (M), silica (N), strontium (O), 

thallium (P), uranium (Q), vanadium 

(R), and zinc (S). Vertical dashed line 

indicates the highest laboratory reporting 

level for the dataset. Dashed lines around 

box and whiskers indicate that values are 

less than the highest laboratory reporting 

level. U.S. Environmental Protection 

Agency maximum contaminant level 

(EPA MCL) indicates the drinking water 

standard value for elements were the 

standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th percentile.

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values
Results 21

Figure 9. Trace element concentrations. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E ), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium 

(J), manganese (K), molybdenum (L ), 

selenium (M), silica (N), strontium (O), 

thallium (P), uranium (Q), vanadium (R), 

and zinc (S). Vertical dashed line indicates 

the highest laboratory reporting level for 

the dataset. Dashed lines around box and 

whiskers indicate that values are less 

than the highest laboratory reporting level. 

U.S. Environmental Protection Agency 

maximum contaminant level (EPA MCL) 

indicates the drinking water standard 

value for elements were the standard is 

exceeded. The interquartile range (IQR) is 

the 25th to 75th percentile.—Continued

Copper, in micrograms per liter Cobalt, in micrograms per liter Cadmium, in micrograms per liter Boron, in micrograms per liter

EFGH0 0.01 0.02 0.03 0.04

0 100 200 300 400 500 600 0 0.2 0.4 0.6 0.8 1.0 1.2 4 0 1 2 3 4

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values
22 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Figure 9. Trace element concentrations. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium 

(J), manganese (K), molybdenum (L ), 

selenium (M), silica (N), strontium (O), 

thallium (P), uranium (Q), vanadium 

(R), and zinc (S). Vertical dashed line 

indicates the highest laboratory reporting 

level for the dataset. Dashed lines around 

box and whiskers indicate that values are 

less than the highest laboratory reporting 

level. U.S. Environmental Protection 

Agency maximum contaminant level 

(EPA MCL) indicates the drinking water 

standard value for elements were the 

standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th 

percentile.—Continued

Molybdenum, in micrograms per liter Manganese, in micrograms per liter Lithium, in micrograms per liter Lead, in micrograms per liter

I

J

K

L

0 0.05 0.1 0.15 0.2

0 50 100 150

0.25 0.3

0 50 100 150 200 250 300 350 400

0 5 10 15 20

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values
Results 23

Figure 9. Trace element concentrations. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium 

(J ), manganese (K), molybdenum (L ), 

selenium (M), silica (N), strontium (O), 

thallium (P), uranium (Q), vanadium 

(R), and zinc (S). Vertical dashed line 

indicates the highest laboratory reporting 

level for the dataset. Dashed lines around 

box and whiskers indicate that values are 

less than the highest laboratory reporting 

level. U.S. Environmental Protection 

Agency maximum contaminant level 

(EPA MCL) indicates the drinking water 

standard value for elements were the 

standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th 

percentile.—Continued

Thallium, in micrograms per liter Strontium, in micrograms per liter Silica, in micrograms per liter Selenium, in micrograms per liter

MNOP

EPA MCL = 50

0 0.1 0.2 0.3 0.4

0 2,000 4,000 6,000 8,000 10,000 0 5 10 15 20 25 0 10 20 30 40 50 60 70 80

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values
24 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Figure 9. Trace element concentrations. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium 

(J), manganese (K), molybdenum (L ), 

selenium (M), silica (N), strontium (O), 

thallium (P), uranium (Q), vanadium 

(R), and zinc (S). Vertical dashed line 

indicates the highest laboratory reporting 

level for the dataset. Dashed lines around 

box and whiskers indicate that values are 

less than the highest laboratory reporting 

level. U.S. Environmental Protection 

Agency maximum contaminant level 

(EPA MCL) indicates the drinking water 

standard value for elements were the 

standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th 

percentile.—Continued

Zinc, in micrograms per liter Vanadium, in micrograms per liter Uranium, in micrograms per liter

Q

R

S

0 2 4 6 8 10

0 5 10 15 20 25

0 20 40 60 80 100 EPA MCL = 30

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values
Results 25

Aluminum, in micrograms per liter Antimony, in micrograms per liter Arsenic, in micrograms per liter Barium, in micrograms per liter

ABCD

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

EPA MCL = 10

Rider

Fence

Hotel

Big

Powell

p = 0.23

aaaaa

p = 0.05

aaaaa

0

0.1

0.2

0.3

0.405

10

15

200

50

100

150

250

200

0.50

10

20

30

40

50

0.6

0.7

p = 0.08

p = 0.24

aaaaa

aaaaa

Horse Powell

Grama Cottonwood (Tuckup)

Cottonwood (Tuckup)

Figure 10. Trace element concentrations 

grouped by geologic unit of spring discharge. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium (J), 

manganese (K), molybdenum (L ), selenium 

(M), silica (N), strontium (O), thalium (P), 

uranium (Q), vanadium (R), and zinc (S). 

Horizontal dashed line indicates the highest 

laboratory reporting level for the dataset. 

Dashed lines around box and whiskers 

indicate that values are less than the highest 

laboratory reporting level. U.S. Environmental 

Protection Agency maximum contaminant 

level (EPA MCL) indicates the drinking 

water standard value for elements were the 

standard is exceeded. The interquartile range 

(IQR) is the 25th to 75th percentile.

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile
26 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Figure 10. Trace element concentrations 

grouped by geologic unit of spring discharge. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E ), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium (J), 

manganese (K), molybdenum (L ), selenium 

(M), silica (N), strontium (O), thalium (P), 

uranium (Q), vanadium (R), and zinc (S). 

Horizontal dashed line indicates the highest 

laboratory reporting level for the dataset. 

Dashed lines around box and whiskers 

indicate that values are less than the highest 

laboratory reporting level. U.S. Environmental 

Protection Agency maximum contaminant 

level (EPA MCL) indicates the drinking 

water standard value for elements were 

the standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th percentile.—

Continued

Boron, in micrograms per liter Cadmium, in micrograms per liter Cobalt, in micrograms per liter Copper, in micrograms per liter

E

F

G

H

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

Fence

p = 0.31

a a a a a

0

0.01

0.02

0.03

0.04

0

100

200

300

400

500

600

0

0.2

0.4

0.6

0.8

1.0

1.2

0

1

2

3

4

Horse

Rider

Powell

Warm

Powell

Mountain Sheep

p = 0.09

p = 0.30

p = 0.10

a a a a a

a a a a a

a a a a a

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile
Results 27

Figure 10. Trace element concentrations 

grouped by geologic unit of spring discharge. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E ), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium (J), 

manganese (K), molybdenum (L ), selenium 

(M), silica (N), strontium (O), thalium (P), 

uranium (Q), vanadium (R), and zinc (S). 

Horizontal dashed line indicates the highest 

laboratory reporting level for the dataset. 

Dashed lines around box and whiskers 

indicate that values are less than the highest 

laboratory reporting level. U.S. Environmental 

Protection Agency maximum contaminant 

level (EPA MCL) indicates the drinking 

water standard value for elements were 

the standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th percentile.—

Continued

Lead, in micrograms per liter Lithium, in micrograms per liter Manganese, in micrograms per liter Molybdenum, in micrograms per liter

I

J

K

L

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

Rider

Fence

0

0.05

0.10

0.15

0.20

0

100

200

300

0

50

100

150

0

5

10

15

20

25

400

0.25

0.30

Horse

27 Mule

Cottonwood (Tuckup)

Horse

27 Mule Lower Jumpup

Rider

Willow (Snake Gulch)

Side Canyon

p = 0.0007

p = 0.51

p = 0.004

p = 0.03

a a a a a

a b b a,b a,b

a b a,b a,b b

a b a,b a,b b

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile
28 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona Selenium, in micrograms per liter Silica, in milligrams per liter as SiO2 Strontium, in micrograms per liter Thallium, in micrograms per liter

M

N

O

P

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

EPA MCL = 50

2,000

0

4,000

6,000

8,000

10,000

5

0

10

15

20

25

10

0

20

30

50

40

70

60

Lower

Jumpup

Pigeon

Willow

(Hack)

Cottonwood

(Tuckup)

Willow

(Snake Gulch) Cottonwood

(Tuckup)

Side

Canyon

p = 0.0004

a b b a,b b

p = 0.08

a a a a a

p = 0.25

a a a a a

p = 0.52

a a a a a

0

0.1

0.2

0.3

0.4

Horse

Figure 10. Trace element concentrations 

grouped by geologic unit of spring discharge. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E ), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium (J), 

manganese (K), molybdenum (L ), selenium 

(M), silica (N), strontium (O), thalium (P), 

uranium (Q), vanadium (R), and zinc (S). 

Horizontal dashed line indicates the highest 

laboratory reporting level for the dataset. 

Dashed lines around box and whiskers 

indicate that values are less than the highest 

laboratory reporting level. U.S. Environmental 

Protection Agency maximum contaminant 

level (EPA MCL) indicates the drinking 

water standard value for elements were 

the standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th percentile..—

Continued

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile
Results 29

Uranium, in micrograms per liter Vanadium, in micrograms per liter Zinc, in micrograms per liter

QRS

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

50

10

15

20

25

3020468

10

12

200

40

60

100

80

USEPA MCL = 30

Willow

(Snake Gulch)

Buck Farm

Canyon

Grama

Cottonwood

(Tuckup)

Cottonwood

(Tuckup)

p = 0.62

aaaaa

p = 0.11

aaaaa

p = 0.37

aaaaa

Kanab

Figure 10. Trace element concentrations 

grouped by geologic unit of spring discharge. 

Aluminum (A), antimony (B), arsenic 

(C), barium (D), boron (E), cadmium (F ), 

cobalt (G), copper (H), lead (I), lithium (J), 

manganese (K), molybdenum (L ), selenium 

(M), silica (N), strontium (O), thalium (P), 

uranium (Q), vanadium (R), and zinc (S). 

Horizontal dashed line indicates the highest 

laboratory reporting level for the dataset. 

Dashed lines around box and whiskers 

indicate that values are less than the highest 

laboratory reporting level. U.S. Environmental 

Protection Agency maximum contaminant 

level (EPA MCL) indicates the drinking 

water standard value for elements were 

the standard is exceeded. The interquartile 

range (IQR) is the 25th to 75th percentile.—

Continued

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile
30 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Table 5. Median and mean values for trace elements from 36 samples from springs discharging north of the Grand Canyon from the 

Toroweap and Hermit Formations, Coconino Sandstone, Supai Group, and Redwall Limestone sampled for this study. Springs exceeding 

the U.S. Environmental Protection Agency drinking water standard are shown in italic. 

[–, not presented as data do not meet requirements for a robust statistical determination; μg/L, micrograms per liter; mg/L, milligrams per liter]

Element Median Mean Standard 

deviation Minimum Maximum Percent censored Springs with outliers

Aluminum 

(μg/L)

– – – <0.2 57 19

Antimony 

(μg/L)

– – – <0.04 and 0.013 0.68 17

Arsenic (μg/L) 1 1.8 2.8 0.3 16.4 0 Fence, Hotel, Rider

Barium (μg/L) – – – 7.7 249 0

Beryllium 

(μg/L)

– – – <0.0008 0.045 72

Boron (μg/L) 61.5 127.3 150 10 580 0 Fence, Rider, Water 

Canyon

Cadmium 

(μg/L)

– – – <0.001 0.041 50

Chromium 

(μg/L)

– – – <0.08 4 25

Cobalt (μg/L) – – – <0.1 1.2 and <4 61

Copper (μg/L) – – – <0.007 4 25

Iron (μg/L) – – – <0.8 226 44

Lead (μg/L) – – – <0.005 0.33 25

Lithium (μg/L) 18.5 37 62 0.8 355 0 Fence, Water 

Canyon

Manganese 

(μg/L)

– – – 0.02 190 42

Molybdenum 

(μg/L)

– – – <1 and 0.223 22 3

Nickel (μg/L) – – – <0.3 and 0.19 7 69

Selenium 

(μg/L)

6.1 12.8 16.1 <0.6 72 3 Pigeon, Willow 

(Hack)

Silica (in mg/L 

as SiO2)

11 11.5 3.4 7 24 0 Lower Jumpup, 

Water Canyon, 

Wildband

Strontium 

(μg/L)

1,220 2,086 2,323 54 9,030 0 Rock, Water Canyon, 

Wildband, Willow 

(Hack)

Thallium 

(μg/L)

0.03 0.06 0.08 <0.01 0.46 19 Table Rock

Uranium 

(μg/L)

3.6 7.6 15.4 0.37 92 0 Cottonwood 

(Tuckup), Grama, 

Pigeon, Willow 

(Hack)

Vanadium 

(μg/L)

1.15 1.7 2.1 <0.1 11 3 Bitter, Hotel, Saddle 

Horse

Zinc (μg/L) – – – <0.09 25 19
Results 31

The results from this study were compared with the 

descriptive statistics for more than 2,100 groundwater samples 

from across the United States (Lee and Helsel, 2005), which 

present statistical values for the following elements, As, Ba, 

Co, Cr, Cu, Mo, Ni, Pb, Se, and Zn. Measured values for the 

same elements from our study were less than the maximum 

values in the Lee and Helsel (2005) study. The median and 

mean values of the elements from our study were generally 

within the IQR of the Lee and Helsel (2005) study with the 

following exceptions; chromium, copper, and lead median 

values were slightly lower than the 25th percentile, the mean 

of molybdenum was between the 75th and 90th percentile, and 

the median and mean of selenium were greater than the 95th 

percentile. Seiler and others (2003) analyzed groundwater 

samples from the National Irrigation Water Quality Program 

in the western United States for Al, As, B, Cd, Cr, Cu, Pb, Mo, 

Se, Ag, U, and Zn. Measured and median values of the select 

elements from this study were within the reported range and 

all medians were less than data from Seiler and others (2003).

Billingsley and others (1983) conducted a study in the 

Snake Gulch area, which sampled several springs included 

in this study and concentration comparisons are presented 

in Beisner and others (2017). Billingsley and others (1983) 

defined uranium concentrations based on concentration 

contrasts; between 1–9 μg/L was considered background, 

10–40 μg/L was weakly anomalous, and greater than 40 μg/L 

was strongly anomalous. Using the Billingsley and others 

(1983) criteria, most springs from this study have background 

uranium concentrations. Cottonwood (Tuckup), Grama, Rock, 

and Willow (Hack and Snake Gulch) Springs have weakly 

anomalous concentrations and Pigeon Spring has strongly 

anomalous concentrations. Data from this study indicate that 

uranium values greater than 14 μg/L are statistical outliers 

(>1.5 IQR) and may be a good determination of anomalous 

concentrations for future studies in the area. The Billingsley 

and others (1983) study also calculated ranges for zinc 

and all values from this study were within the 1.8–50 μg/L 

background concentration range.

Multivariate Analysis

A multivariate analysis was conducted on the data to 

understand dissimilarity between spring sites. The following 

elements, As, Cd, Cu, Li, Mn, Mo, Pb, Se, Sr, U, V, and Zn, 

were used for multivariate comparison based on separation 

within springs near Snake Gulch and between mining leachate and spring chemistry from principal component analysis 

analysis in Beisner and others (2017).

The NMDS analysis of the spring data resulted in 2 

convergent solutions after 20 tries with a stress of 0.16 (fig. 11) 

which falls between a fair and suspect result (Buttigieg and 

Ramette, 2014). Elements associated near uranium were 

molybdenum, strontium, selenium and lithium, and springs 

with higher uranium loading were farther from springs 

influenced by arsenic, cadmium, copper, lead, and manganese 

(fig. 11). Elemental correlations were calculated using Kendall’s tau and indicate that there are significant positive correlations between the following elements—lithium, molybdenum, 

selenium, strontium, uranium and zinc—as well as between 

lead and manganese, and cadmium, copper, and lead (fig. 12).

An ANOSIM analysis on the spring samples relative to 

the geologic unit of spring discharge group resulted in a test 

statistic value of 0.14 and a p-value of 0.017, indicating there 

is a difference between at least two of the groups. A cluster 

analysis was also run on the same elements used in the NMDS 

analysis (fig. 13). The Calinski criterion indicates that two 

is the correct number of distinct groups, and the difference 

between the groups is driven by higher values of Mo, Li, Se, 

Sr, U, and Zn for the group on the right side of the dendrogram 

in figure 13.
32 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

−40 −20 0 20 40

−40

−20

0

20

40

Nonmetric multidimensional scaling 1

Nonmetric multidimensional scaling 2

Coconino

Hermit

Redwall

Supai

Toroweap

Cu

As

Pb

V

Cd

U

Mn

Mo

Sr

SeLi

Zn

23

1

21

14

2

6

22

15

30

16

18

4

34

3

33

13

24

11

9

12

17

36

35

31

19

5

20

10

7

28

32

8

25

26

29

27

Numbers Site name

1 Table Rock Spring

2 Wildband Spring

3 Water Canyon Spring

4 Pigeon Spring

5 Upper Jumpup Spring

6 Big Spring

7 Little Spring

8 Boulder Spring

9 Horse Spring

10 Rider Spring

11 Slide Spring

12 Warm Springs

13 Willow Spring (Snake Gulch)

14 Swamp Spring

15 Powell Spring

16 Schmutz Spring

17 27 Mule Spring

18 Willow Spring (Hack Canyon)

Numbers Site name

19 Grama Spring

20 Oak Spring

21 Rock Spring

22 Saddle Horse Spring

23 Cottonwood Spring (Tuckup Canyon)

24 Hotel Spring

25 Cottonwood Spring (Sowats)

26 Mountain Sheep Spring

27 Bitter Spring

28 Lower Jumpup Spring

29 Buck Farm Canyon Spring

30 Side Canyon Spring

31 Showerbath Spring

32 Kanab Spring

33 Unknown Spring near Hanging Springs

34 Hole in the Wall Spring

35 Hanging Spring

36 Fence Spring

Stress = 0.16

EXPLANATION

Figure 11. Spring samples with polygons outlining geologic unit of spring discharge. As, 

arsenic; Cd, cadmium; Cu, copper; Li, lithium; Mn, manganese; Mo, molybdenum; Pb, lead; 

Se, selenium; Sr, strontium; U, uranium; V, vanadium; Zn, zinc.
Results 33

Figure 12. Correlogram including the Kendall’s tau value for elemental pairs, where values with an X are not statistically 

significant with p >0.05.

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

VZnSeLiSrMoUMnCuCdPb

As

V

Zn

Se

Li

Sr

Mo

U

Mn

Cu

Cd

0.03 −0.08

−0.11

−0.16

−0.14

0.38

0.1

0

0.26

0.4

−0.12

−0.13

0.33

0.51

0.68

−0.01

−0.15

0.28

0.58

0.61

0.68

−0.08

−0.17

0.3

0.57

0.64

0.68

0.71

−0.13

0.02

0.04

0.06

0.11

0.15

0.09

0.08

−0.2

0.12

0.04

−0.08

−0.1

−0.05

−0.13

−0.1

0.17

−0.12

−0.07

−0.03

−0.09

0.08

0.05

0.01

−0.01

0.12

0.23

−0.16

−0.04

0.15

0.04

0.13

0.21

0.17

0.15

0.26

0.24

0.26
34 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona 24 2729 14 35 3334

6

15

22

12

25

8

20

19

2

23

3

17

1036

26

4

1819

1321

1628

7

11

32

5

3031

0

10

20

30

40

50

Cluster Dendrogram

hclust (*, "average")

Height

Numbers Site name

1 Table Rock Spring

2 Wildband Spring

3 Water Canyon Spring

4 Pigeon Spring

5 Upper Jumpup Spring

6 Big Spring

7 Little Spring

8 Boulder Spring

9 Horse Spring

10 Rider Spring

11 Slide Spring

12 Warm Springs

13 Willow Spring (Snake Gulch)

14 Swamp Spring

15 Powell Spring

16 Schmutz Spring

17 27 Mule Spring

18 Willow Spring (Hack Canyon)

Numbers Site name

19 Grama Spring

20 Oak Spring

21 Rock Spring

22 Saddle Horse Spring

23 Cottonwood Spring (Tuckup Canyon)

24 Hotel Spring

25 Cottonwood Spring (Sowats)

26 Mountain Sheep Spring

27 Bitter Spring

28 Lower Jumpup Spring

29 Buck Farm Canyon Spring

30 Side Canyon Spring

31 Showerbath Spring

32 Kanab Spring

33 Unknown Spring near Hanging Springs

34 Hole in the Wall Spring

35 Hanging Spring

36 Fence Spring

EXPLANATION

Figure 13. Cluster dendrogram for spring samples.
Results 35

Isotopic and Radioactivity Analysis

Radiochemistry

Gross-alpha radioactivity in samples from seven 

springs—Pigeon, Willow (Snake Gulch), Willow (Hack), 

Grama, Rock, Mountain Sheep (2011), and Lower Jumpup 

(2009) Springs—equaled or exceeded the EPA drinking water 

standard of 15 pCi/L (figs. 14 and 15). Pigeon, Willow (Snake 

Gulch), and Rock Springs had samples with values that were 

statistical high outliers for all spring sites for gross alpha 

radioactivity (fig. 15A). Radioactivity was not measured at 

Water Canyon Spring, therefore, data from only three springs 

discharging from the Toroweap Formation were available and 

descriptive statistics could not be calculated for this rock unit. 

Water from Willow (Snake Gulch) Spring had an elevated concentration of gross-alpha radioactivity, which represents a high 

statistical outlier for springs discharging from the Coconino 

Sandstone (fig. 15B).

Measurements of gross-beta radioactivity in water 

samples are reported in terms of the 137Cs curve. Gross beta 

radioactivity was greater than 15 pCi/L, the activity at which 

the USEPA requires testing for drinking water suppliers for 

selected individual beta-emitting radionuclides (Lappenbusch 

and Cothern, 1985), at four spring sites including Pigeon, Willow (Hack), Cottonwood (Tuckup), and Fence Springs. Pigeon 

and Cottonwood (Tuckup) Springs were statistical high outliers for all spring sites for gross beta radioactivity (fig. 16A). A 

sample from Fence Spring with a value of 15.4 pCi/L represents a statistical high outlier for springs discharging from the 

Redwall Limestone (fig. 16B).

Radium-226 and -228 concentrations were measured on 

samples from most springs and all had values less than the 

detection limit of 4 pCi/L. Three samples—Upper Jumpup 

(2009), Willow (Hack) (2012) and Kanab Spring (2009)—

were sampled using a large-volume radium reduction method, 

which provides lower detection limits (Kraemer, 2005). These 

samples yielded 226Ra activities between 0.19 and 0.245 pCi/L, 

and 228Ra concentrations between 0.016 and 0.122 pCi/L.

Fifty-one groundwater samples collected from 36 springs 

between 2009 and 2016 have UAR values ranging from 1.34 

to 6.71. Figure 17 shows the UAR data plotted against reciprocal dissolved-uranium concentrations and an expanded plot 

showing the range of higher uranium concentrations. Samples 

from the Toroweap Formation have low UAR values, whereas 

springs from the other units have a large range of UAR values. 

Some springs were sampled more than once and repeat samples are similar (fig. 17). The lowest UAR was from Cottonwood (Tuckup) Spring, although the concentration of uranium 

was greater at Pigeon and Willow (Hack) Springs. Generally, 

there is an inverse relation between uranium concentration and 

UAR, where UAR is lower for higher uranium concentrations 

(fig. 17).

Strontium Isotopes

Strontium isotope ratios (87Sr/86Sr) provide a means for 

understanding the different rock types that groundwater may 

have interacted with along its flowpath. Values of 87Sr/86Sr 

measured in spring water samples are within the range of 

values observed for sedimentary rocks in the region, from 

the Redwall Limestone to the Kaibab Formation (0.70756–

0.71216; Monroe and others, 2005; Bills and others, 2007). 

The exception is water from Fence Spring, which had a 

substantially more radiogenic (higher proportion of 87Sr) value 

of 0.71417 (fig. 18). Samples were not collected for strontium 

isotopic ratios from Saddle Horse and Water Canyon Springs.

Values of 87Sr/86Sr for most springs—excluding Fence 

Spring—fell into two general groups, those having higher 

strontium concentrations (greater than 350 μg/L) and lower 

87Sr/86Sr values (less than 0.7095) (group 1), or those with 

lower strontium concentrations (less than 90 μg/L) and higher 

87Sr/86Sr values (greater than 0.7095) (group 2) (fig. 18). 

Springs discharging from the Toroweap Formation and Supai 

Group all have characteristics of group 1. Springs discharging 

from the Coconino Sandstone, Hermit Formation, and Redwall 

Limestone rock units have samples that fall into both groups. 

The group 1 springs discharging from the Redwall Limestone 

include Buckfarm Canyon, Side Canyon, Showerbath, and 

Kanab Springs, and have strontium isotopic ratios similar to 

the average of the Redwall Limestone rocks (0.70875; Monroe 

and others, 2005; Bills and others, 2007). Group 2 includes 

two springs discharging from the Hermit Formation (Swamp 

and Powell Springs), one from the the Coconino Sandstone 

(Big Spring), and four springs discharging from the Redwall 

Limestone (Unknown, Hole in the Wall, Hanging, and Vaseys 

Springs).
36 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona Swamp Powell Oak Big Warm Saddle Horse Cottonwood (Tuckup) Schmutz Hotel Willow (Hack) Mountain Sheep BitterCottonwood (Sowats) Upper Jumpup Lower Jumpup

!

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!!

!

! !

!

! ! !

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

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!

!

! ! ! !

!

#

Buck Farm Canyon

Fence

Vaseys Hanging

Hole in the WallUnknown

Rider

Grama

Rock Wildband

Pigeon

Table Rock

Side Canyon

27 Mule

Willow

(Snake Gulch)

Showerbath

Kanab

Slide

Horse

Boulder

Little

111°40' 112°0' 112°20' 112°40' 113°0' 113°20'

36°40'

36°20'

36°0'

0 5 10 15 20 25 KILOMETERS0 5 10 5 20 25 MILES

The base map from Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community

Toroweap FormationCoconino SandstoneHermit FormationSupai GroupRedwall Limestone

Less than 1.01.0 to 1.92.0 to 4.95.0 to 9.910 to 1415 to 29Equal to or greater than 30

Gross apha radioactivity, in 

picocuries per liter 

EXPLANATION

Known mineralized depositsMined deposits

Figure 14. Gross alpha radioactivity from spring samples with different symbols by geologic unit of spring discharge. Location of mineralized breccia pipes can be found in the following references; Alpine, 2010; Brown and others, 1992; Chenoweth, 1986, 1988; Verbeek and others, 1988; Wenrich and others, 1988, 1990, 1997; Sutphin and Weinrich, 1989; VanGosen and Weinrich, 1989, 1991; Finch and others, 1990; Wenrich, 1992; Wenrich and AumenteModreski, 1994; Gardner, 1998; Mazeika, 2002; Ross and Moreton, 2012.
Results 37

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

20

0

40

60

80

100

120

EPA MCL = 15

EPA MCL = 15

A

B

Gross alpha activity, in picocuries per liter

Gross alpha activity, in picocuries per liter

0 20 40 60 80 100 120

Willow

(Snake Gulch)

Willow

(Snake Gulch)

Rock Pigeon

Figure 15. Distribution of gross alpha radioactivity for all spring sites (A) and divided by rock unit of 

spring discharge (B). EPA MCL, U.S. Environmental Protection Agency maximum contaminant level. 

The interquartile range (IQR) is the 25th to the 75th percentile.
38 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Figure 16. Distribution of gross beta radioactivity for all spring sites (A) and divided by rock unit of 

spring discharge (B). The interquartile range (IQR) is the 25th to the 75th percentile.

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

A

B

Gross beta activity, in picocuries per liter 137Cesium curve

5

0

10

15

20

25

30

Gross beta activity, in picocuries per liter 137Cesium curve

0 5 10 15 20 25 30

Cottonwood (Tuckup) Pigeon

Fence
Results 39

0

87654321

0 1 2 3

1/Dissolved uranium, in micrograms per liter

Geologic unit of spring discharge

 Toroweap Formation Coconino Sandstone Hermit Formation Supai Group Redwall Limestone

EXPLANATION

Saddle Horse

Big Warm

Vaseys

Unknown

Hole in the Wall

Hanging

Powell

Fence

Oak

Swamp

27 Mule

Cottonwood (Sowats)

Boulder

Slide Little

Horse

Upper Jumpup

Secular equilibrium

3210

0 0.25 0.50

1/Dissolved uranium, in micrograms per liter

234Uranium/238Uranium, activity ratio

234Uranium/238Uranium, activity ratio

Secular equilibrium

Buck Farm Side Canyon

Showerbath Kanab

Cottonwood (Tuckup)

Bitter

Hotel

Mountain Sheep

Lower Jumpup

Rider

Willow (Snake Gulch)

Pigeon

Wildband

Table Rock

Rock

Schmutz

Grama

Willow (Hack)

Inset area

Figure 17. Uranium activity ratio data plotted against reciprocal uranium concentrations dissolved in spring samples collected from 2009 to 2016. Dashed area represents the area for the inset graph.
40 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Oxygen and Hydrogen Stable Isotopes

The stable isotopes of oxygen and hydrogen can give a 

general indication of recharge elevation and evaporation. A 

local meteoric water line (LMWL) of δ2H=7.4 δ18O+6.5 was 

developed for Grand Canyon National Park at Hopi Point 

(Pendall, 1997), which plots to the left of the global meteoric 

water line (GMWL; Craig, 1961) (fig. 19). All spring samples 

plot to the right of the LMWL and most plot to the right of 

the GMWL except Cottonwood (Tuckup), Swamp, Powell, 

Unknown, Hole in the Wall, Hanging, Fence, Warm, and Big 

Springs. Four springs (Water Canyon, Wildband, Bitter, and 

Hotel) plot farther to the right from the GMWL compared 

with other springs. Rider Spring is notable in that isotopic 

ratio is the most depleted of all the springs samples (δ18O of 

–15.61 per mil, δ2H of –125 per mil).

For springs discharging from the same rock unit groups, 

there are some general similarities and differences within each 

group. Toroweap Formation springs sampled for this study fell 

into two groups, one group (Table Rock and Pigeon Springs) 

had values in the middle range of all spring samples and one 

group had values farther to the right of the LMWL (Water 

Canyon and Wildband Springs). Coconino Sandstone springs 

generally have stable isotope values in the middle of the 

range of all spring samples (–12.23 to –11.67 δ18O and –91.9 

to –87.9 δ2H) except for springs with more depleted values; 

Rider Spring, mentioned earlier, and Big and Warm Springs 

(–13.56 to -13.26 δ18O and -98.1 to -96.8 δ2H, respectively) 

which discharge on the Kaibab Plateau topographically 

above the surface expression of the Big Springs Fault. Hermit 

Formation springs span a large range of stable isotopic values 

Figure 18. Strontium isotope ratio relative to the reciprocal strontium concentration for spring 

samples; values from rock samples in Bills and others (2007) and Monroe and others (2005). Solid lines 

represent rock, average value; dashed lines, minimum and maximum values.

0.7070

0.7080

0.7090

0.7100

0.7110

0.7120

0.7130

0.7140

0.7150

0 0.005 0.01 0.015 0.02

87Strontium/ 86Strontium 

1/ Strontium

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Toroweap Formation

Kaibab Formation

 Toroweap Formation

 Coconino Sandstone

 Hermit Formation

 Supai Group

 Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

–130

–120

–110

–100

–90

–80

–70

–60

–16 –15 –14 –13 –12 –11 –10 –9 –8 –7 –6

δ18O, in per mil

δ2H, in per mil

 Toroweap Formation

 Coconino Sandstone

 Hermit Formation

 Supai Group

 Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

Figure 19. Stable isotope ratios (δ18O and δ2H) for spring 

samples. Global meteoric water line (solid line) from Craig 

(1961) and local meteoric water line (dashed line) from 

Pendall (1997).
Results 41

with Swamp, Powell, and Oak Springs having more depleted 

stable isotopic values and Schmutz, Grama, and Willow 

(Hack) Springs having more enriched stable isotopic values. 

Supai Group springs generally plot near the middle range of 

spring values except for two sites (Bitter and Hotel Springs) 

that are more enriched and show strong evaporative signatures. Redwall Limestone springs plot in two general groups, 

one (Hanging, Unknown near Hanging, Hole in the Wall and 

Fence Springs) with a more depleted signature between the 

GMWL and LMWL, and one group in the middle range of the 

spring samples (Buck Farm Canyon, Side Canyon, Showerbath, and Kanab Springs). The depleted-isotopic group springs 

discharge in a similar geographic area (fig. 1) and may indicate 

a similar recharge elevation location.

Groundwater Ages

Carbon-14

Groundwater age is inferred from 14C with corrections 

based on total dissolved inorganic carbon (the sum of inorganic carbon species; carbonic acid, bicarbonate, and carbonate) and δ13C. Graphs of carbon species were made according 

to Han and others (2012) and Han and Plummer (2016) to 

understand the potential processes influencing carbon water 

chemistry at the spring sample sites before interpretation of 

groundwater age (fig. 20, table 6). The colored lines on figure 

20 represent the “zero age” lines, which are determined by 

the 14C and δ13C values of the soil gas and solid carbonate. 

Samples that plot within the zero age lines on figure 20A have 

a zero radiocarbon age, which may be explained by geochemical reaction with no radiocarbon decay; samples above the 

zero age area are likely mixtures containing some 14C recharge 

water, and samples below the zero age (radiocarbon age area) 

may have a radiocarbon age greater than zero, which indicates 

the presence of old water that has undergone radiocarbon 

decay (Han and Plummer, 2016). Results from NetpathXL 

are presented in table 6 for both values of δ13C in carbonate 

rock and soil gas for the uncorrected age (user-defined) and 

Revised Fontes and Garnier (solid exchange) (Han and Plummer, 2013).

Samples from several sites plot in the region below the 

zero age area, indicating that they may be old waters that 

could have undergone 14C decay (fig. 20A) (Han and others, 

2012). Sites with a possible radiocarbon age using the values 

of δ13C in the soil gas CO2 and carbonate rock of –22 and –1.1 

and –1.8 per mil (Coconino and Redwall springs respectively) 

are Slide, Horse, Little, Upper Jumpup, and Kanab Springs. 

Sites with a possible radiocarbon age using –17 for δ13C in the 

soil gas CO2 and –1.1 (Toroweap Formation and Coconino 

Sandstone springs) and –1.8 per mil (Redwall Limestone 

springs) include all of the sites listed previously as well as the 

following sites: Pigeon, Warm, and Fence Springs. Showerbath and Boulder Springs are near the radiocarbon zero-age 

area and may have a radiocarbon age depending on the soil 

and rock values used in the age correction (fig. 20, table 6).

Tritium

Tritium values ranged from –0.9 pCi/L (which is below 

the reporting limit of 0.5 pCi/L) to 11.5 pCi/L. The tritium 

data indicate that the groundwater present at the spring sites 

was either primarily recharged prior to 1952 (pre-modern) or 

is a mixture of modern and pre-modern waters.

Bitter Spring had the highest tritium value of 11.5 pCi/L 

and is just below the threshold for being categorized as primarily modern water. None of the spring samples had tritium 

values that were statistical outliers from the entire dataset 

(fig. 21A). Tritium values were greater than the 75th percentile 

of the data (5.1 pCi/L) for the following springs, Willow 

(Hack), Saddle Horse, Cottonwood (Tuckup), Hotel, Bitter, 

Unknown, Hole in the Wall, and Hanging. Willow (Hack) 

Spring was a high statistical outlier (6.38 pCi/L) for springs 

discharging from the Hermit Formation (fig. 21B). The tritium 

values generally increased with deeper rock units, springs 

discharging from the Supai Group and Redwall Limestone had 

the highest median values.
42 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Figure 20. Carbon data from spring water including 14C versus δ13C (A), 14C versus 1/dissolved inorganic carbon (B), and 

δ13C versus 1/dissolved inorganic carbon (C). The solid horizontal and vertical gray lines represent Tamers X and (or) Y. 

The colored angled lines represent the zero age lines, which are determined by the carbon-14 and δ13C values of the soil 

gas and solid carbonate.

δ13C, in per mil

14 Carbon, in percent modern carbon 

0

20

40

60

80

100

120 

–20 –18 –16 –14 –12 –10 –8 –6 –4 –2 0

Upper Jumpup

Wildband

Pigeon

Table Rock

Big

Little

Warm

Boulder

Slide

Horse

Powell

Swamp

Willow (Snake Gulch)

27 Mule

Willow (Hack)

Schmutz

Grama

Oak

Rock

Saddle

Horse

Hotel

Cottonwood (Tuckup)

Cottonwood (Sowats)

Mountain Sheep

Bitter

Lower

Jumpup

Buck Farm

Canyon

Unknown

Hole in

the Wall Hanging

Side Canyon

Showerbath

Kanab

Fence

Toroweap Formation

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Geologic unit of spring discharge

–22 per mil Soil CO2 –17 per mil

Toroweap, Coconino, Hermit 

Supai

Redwall

EXPLANATION

A
Results 43

Figure 20. Carbon data from spring water including 14C versus δ13C (A), 14C versus 1/dissolved inorganic carbon (B), and 

δ13C versus 1/dissolved inorganic carbon (C). The solid horizontal and vertical gray lines represent Tamers X and (or) Y. The 

colored angled lines represent the zero age lines, which are determined by the carbon-14 and δ13C values of the soil gas 

and solid carbonate. —Continued

1/Dissolved inorganic carbon, in milligrams per liter

14 Carbon, in percent modern carbon 

0

20

40

60

80

100

120 

0 0.005 0.01 0.015

Toroweap Formation

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

B
44 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

1/Dissolved inorganic carbon, in milligrams per liter

–20

–18

–16

–14

–12

–10

–8

–6

–4

–2

0

0 0.005 0.01 0.015

Toroweap Formation

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

C

δ13C, in per mil

Figure 20. Carbon data from spring water including 14C versus δ13C (A), 14C versus 1/dissolved inorganic carbon (B), and 

δ13C versus 1/dissolved inorganic carbon (C). The solid horizontal and vertical gray lines represent Tamers X and (or) Y. The 

colored angled lines represent the zero age lines, which are determined by the carbon-14 and δ13C values of the soil gas 

and solid carbonate. —Continued
Results 45

Table 6. Groundwater corrected age values.—Continued[pCi/L, picocuries per liter; pM, absolute percent modern (normalized); pmc, percent modern carbon (denormalized); R, radiochemistry non-detect; NA, not applicable; B.P., before present]

USGS site number Common name Sample date Tritium (pCi/L) Tritium error (pCi/L) Denor- malized 14C (pmc) Normal- ized 14C (pM) 14C error (pM) 13C (per mil) Uncor- rected age

Minimum 

corrected 

age, in years 

B.P. (–22 per 

mil soil 

δ13C - CO2)

Maximum 

corrected 

age, in years 

B.P. (–17 per 

mil soil 

δ13C - CO2)

Average 

overlying 

rock unit 

δ13C 

(per mil)

Categorical 

determination

364242112274701 Table Rock Spring 8/27/2015 1.5 0.27 30.06 29.09 0.16 –4.92 9,935 NA NA –1.1 Possible mixture364259112303201 Wildband Spring 11/6/2012 1.8 0.42 105.76 102.3 0.27 –4.94 –463 NA NA –1.1 Possible mixture364327112303101 Pigeon Spring 3/15/2012 1.3 0.41 13.60 13.12 0.11 –3.77 16,496 –1,175 969 –1.1 Possible mixture364327112303101 Pigeon Spring 11/7/2012 0.9 0.26 11.20 10.81 0.14 –3.69 18,095 –420 1,776 –1.1 Pre-modern

364327112303101 Pigeon Spring 9/10/2014 0.8 0.29 13.45 12.99 0.07 –4.15 16,586 –1,904 418 –1.1 Pre-modern363450112325001 Upper Jumpup 

Spring

8/27/2009 R –0.9 0.89 22.11 21.44 0.19 –6.24 12,474 67 2,279 –1.1 Pre-modern

363450112325001 Upper Jumpup 

Spring

7/7/2015 NA 21.30 20.67 0.08 –6.31 12,783 323 2,536 –1.1

363607112205201 Big Spring 5/11/2016 2.71 0.41 66.76 65.31 0.15 –10.27 3,340 NA NA –1.1 Possible mixture363741112350501 Little Spring 11/10/2015 R 0 0.28 22.07 21.45 0.09 –7.18 12,492 1,567 3,791 –1.1 Pre-modern363756112350101 Boulder Spring 11/10/2015 R –0.1 0.32 46.08 44.94 0.14 –8.86 6,406 –2,400 –177 –1.1 Pre-modern363901112341601 Horse Spring 8/25/2015 0.3 0.27 15.43 14.95 0.09 –5.61 15,450 1,537 3,818 –1.1 Pre-modern

363907111471701 Rider Spring 8/25/2009 0.6 0.96 NA NA NA NA NA NA NA NA Pre-modern363922112334501 Slide Spring 8/27/2009 R 0 0.89 8.86 8.59 0.09 –6.01 20,031 7,058 9,302 –1.1 Pre-modern363922112334501 Slide Spring 8/25/2015 0.4 0.31 9.34 9.06 0.07 –6.26 19,601 6,978 9,222 –1.1 Pre-modern364143112184501 Warm Springs 8/26/2015 1.4 0.3 41.93 40.85 0.13 –8.34 7,186 –2,183 1 –1.1 Possible mixture364210112310501 Willow Spring 

(Snake Gulch)

3/15/2012 1.9 0.43 67.38 65.32 0.2 –6.01 3,264 NA NA –1.1 Possible mixture

364210112310501 Willow Spring 

(Snake Gulch)

11/7/2012 1.7 0.39 66.32 64.64 0.16 –8.69 3,395 NA NA –1.1 Possible mixture

361959112210401 Swamp Spring 11/12/2015 2.2 0.42 84.26 82.41 0.21 –10.25 1,416 NA NA –1.1 Possible mixture362045112212801 Powell Spring 11/12/2015 2.5 0.36 91.00 89.49 0.22 –12.95 780 NA NA –1.1 Possible mixture362143112551201 Schmutz Spring 8/25/2009 1.6 0.96 38.99 37.79 0.2 –6.14 7,787 NA NA –1.1 Possible mixture363014112325201 27 Mule Spring 4/22/2016 R –0.5 0.48 81.39 80.02 0.18 –12.75 1,702 NA NA –1.1 Pre-modern363357112440801 Willow Spring 

(Hack Canyon)

8/26/2009 6.4 0.96 70.45 68.11 0.31 –4.84 2,895 NA NA –1.1 Possible mixture

363357112440801 Willow Spring 

(Hack Canyon)

11/8/2012 5 0.34 71.38 69.07 0.17 –5.11 2,787 NA NA –1.1 Possible mixture
46 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona Table 6. Groundwater corrected age values.—Continued [pCi/L, picocuries per liter; pM, absolute percent modern (normalized); pmc, percent modern carbon (denormalized); R, radiochemistry non-detect; NA, not applicable; B.P., before present] USGS site number Common name Sample date Tritium (pCi/L) Tritium error (pCi/L) Denor- malized 14C (pmc) Normal- ized 14C (pM) 14C error (pM) 13C (per mil) Uncor- rected age Minimum corrected age, in years B.P. (–22 per mil soil 

δ13C - CO2

)

Maximum 

corrected 

age, in years 

B.P. (–17 per 

mil soil 

δ13C - CO2

)

Average 

overlying 

rock unit 

δ13C 

(per mil)

Categorical 

determination

363521112394601 Grama Spring 8/10/2011 NA 84.82 82.3 0.29 –6.53 1361 NA NA –1.1363521112394601 Grama Spring 11/8/2012 3.4 0.3 83.92 81.41 0.2 –6.38 1449 NA NA –1.1 Possible mixture364038112201001 Oak Spring 11/10/2015 R 0.0 0.29 55.58 54.28 0.16 –9.52 4856 NA NA –1.1 Pre-modern364101112340601 Rock Spring 9/2/2009 1.3 0.93 48.35 46.76 0.3 –5.02 6007 NA NA –1.1 Possible mixture361344113032001 Saddle Horse Spring 9/9/2014 7.5 0.53 100.93 98.52 0.2 –9.32 –77 NA NA –2 Possible mixture361944112551001

Cottonwood Spring 

(Tuckup Canyon) 4/8/2016 5.8 0.66 86.81 84.89 0.22 –10.11 1170 NA NA –2 Possible mixture

362157112451601 Hotel Spring 8/25/2009 7.3 0.96 76.12 74.17 0.3 –8.72 2255 NA NA –2 Possible mixture363110112314601

Cottonwood Spring 

(Sowats) 4/22/2016 R –0.4 0.54 59.83 58.36 0.17 –8.86 4246 NA NA –2 Pre-modern

363115112342601

Mountain Sheep 

Spring 9/1/2009 2.9 0.86 74.23 72.55 0.34 –10.24 2463 NA NA –2 Possible mixture

363135112330601 Bitter Spring 11/14/2015 11.5 1.4 97.45 95.93 0.22 –13.46 214 NA NA –2 Possible mixture363209112350801

Lower Jumpup 

Spring 8/28/2009 0.4 0.89 84.31 82.61 0.3 –11.48 1411 NA NA –2 Pre-modern

362434111533601

Buck Farm Canyon 

Spring 8/23/2009 4.2 0.57 58.98 57.62 0.23 –10 4364 NA NA –1.8 Possible mixture

362702112394701 Side Canyon Spring 8/26/2009 1.4 0.89 11.10 10.75 0.1 –5.7 18172 2,595 5,052 –1.8 Possible mixture362723112382801 Showerbath Spring 8/26/2009 5.1 0.96 38.79 37.8 0.18 –8.74 7828 –1,975 437 –1.8 Possible mixture

362802112374601 Kanab Spring 8/26/2009 2.2 0.93 30.02 29.21 0.21 –7.97 9946 –973 1,450 –1.8 Possible mixture

362827111504101

Unknown Spring 

near Hanging Springs 8/21/2009 6.2 0.64 56.48 55.19 0.25 –10.16 4723 NA NA –1.8 Possible mixture

362831111504401

Hole in the Wall 

Spring 8/22/2009 5.1 0.64 58.08 56.75 0.27 –10.12 4492 NA NA –1.8 Possible mixture

362837111504201 Hanging Spring 8/22/2009 5.6 0.61 58.99 57.62 0.26 –9.95 4363 NA NA –1.8 Possible mixture363123111503101 Fence Spring 8/20/2009 2.6 1.6 13.50 13.02 0.12 –3.68 16,554 –8,851 –6,362 –1.8 Possible mixture
Results 47

 Tritium values are generally higher in samples with high 14C values, but there are tritium values as high as 5.1 pCi/L for 

spring samples with 14C carbon-14 values less than 50 percent 

modern carbon (fig. 22). Waters with tritium and low 14C 

carbon-14 values may represent a mixture of modern and 

pre-modern water. The following samples do not have tritium 

values above the reporting limit of 0.5 pCi/L and likely do 

not have a component of modern water (post-1952): Upper 

and Lower Jumpup, Little, Boulder, Horse, Slide, 27 Mule, 

Oak, and Cottonwood (Sowats) Springs (table 6). Of the 

aforementioned springs, 27 Mule, Oak, Cottonwood (Sowats), 

and Lower Jumpup have 14C values greater than 50 percent 

modern carbon, ranging from 55.58 to 84.31 pmc. These 

springs may include water that was recharged prior to 1952, 

but is not old enough to be dated using radiocarbon techniques. The springs also fall within the zero age area of figure 

20 for given soil gas and rock values, and may indicate some 

equilibrium condition with respect to carbon that precludes 

radiocarbon age determination. Two springs, Pigeon and 

Rider, have tritium values below 1.3 pCi/L, which are categorically determined to be pre-modern. These springs may have a 

very small component of modern water or may include water 

recharged in the decades prior to 1952.

EXPLANATION

Outlier

+1.5 IQR

–1.5 IQR

75th percentile

mean

median

25th percentile

Spring sample

values

Tritium, in picocuries per liter

Tritium, in picocuries per liter

A

B

Toroweap

Formation

Coconino

Sandstone

Hermit

Formation

Supai

Group

Redwall

Limestone

Willow

(Hack)

12

10

8

6

4

2

0

–2 0 2 4 6 8 10 12

Figure 21. Tritium for all samples (A) and divided by rock unit of spring discharge (B). The 

interquartile range (IQR) is the 25th to the 75th percentile.
48 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Discussion

Evidence for Water Rock Interaction with 

Implication for Flowpaths

The hydrologic system in the area is generally understood 

to consist of a series of perched aquifers of limited extent situated above unsaturated rock, with the regional Redwall-Muav 

aquifer below (Bills and others, 2010). This study evaluated 

the chemistry of water collected by the USGS between 2009 

and 2016 discharging from perched springs in the Toroweap 

and Hermit Formations, Coconino Sandstone, and Supai 

Group, and regional springs in the Redwall Limestone.

A conceptual model of the flowpath to each spring is 

important to understand differences in chemistry compared to 

general trends of spring groups. General chemical characteristics for this data set are explored and specific springs with 

unique chemistry are discussed. More information is needed to 

be able to model the evolution of water through the subsurface 

for each individual spring, but the analysis in this report can 

provide a basis for that understanding, which is beyond the 

scope of this report.

Lower values of specific conductance in water discharging from springs in the Coconino Sandstone compared to 

water discharging from the overlying Toroweap Formation 

(fig. 4C) are likely caused by lower calcium, magnesium, and 

sulfate concentrations (figs. 5A,B and 6D). Fresher groundwater (lower specific conductance) in Coconino Sandstone 

springs may indicate that flow has not been affected greatly 

by water-rock interactions with gypsum present in the Kaibab 

and Toroweap Formations, and may indicate that water may 

move through the overlying units fairly quickly. Willow 

(Snake Gulch) Spring is an exception for Coconino Sandstone 

springs, and has a geochemical composition more similar to 

waters discharging from the Toroweap Formation (see fig.7).

Strontium concentrations were low (less than 90 μg/L) 

and strontium isotope ratios were high (greater than 0.7095) 

for Big, Swamp, Powell, Unknown, Hole in the Wall, Hanging, and Vaseys Springs discharging from Coconino Sandstone, 

Hermit Formation, and Redwall Limestone. This may indicate 

that the water discharging at these springs is not interacting 

with Kaibab or Toroweap Formation rocks for very long, as 

springs discharging from the Toroweap Formation have high 

strontium concentrations (greater than 1,900 μg/L) and low 

Toroweap Formation

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

–2

0

2

4

6

8

10

12

14

0 20 40 60 80 100 120

Tritium, in picocuries per liter 

14Carbon, in percent modern carbon

Figure 22. Tritium versus uncorrected carbon-14 values.
Discussion 49

strontium isotopic ratios (less than 0.70852). Saddle Horse 

Spring, which discharges from the Supai Group, had a low 

strontium concentration of 117 μg/L, but the strontium isotope 

ratio was not measured. The low strontium concentration may 

indicate that Saddle Horse Spring has similar characteristics 

to the aforementioned springs, and resampling may clarify 

the connections. There was some variation in the strontium 

isotopic values within rocks collected from the same geologic 

unit (Monroe and others, 2005; Bills and others, 2007), so 

additional analysis of strontium isotopic values in rock units 

from this study area would help with the interpretation of 

groundwater interaction.

All spring samples plot to the right of the LMWL and 

most also plot to the right of the GMWL suggesting that the 

water has undergone evaporation or that the springs were 

recharged by different moisture sources (fig. 19). Soil water 

near Red Butte, Ariz. (just south of the Grand Canyon) 

collected as part of another study plotted to the right of the 

LMWL—indicating evaporation influence (Pendall, 1997)—

which suggests that the evaporation signature of the spring 

groundwater samples might result from groundwater infiltration. Localized water cycling, such as groundwater discharge 

that infiltrates and later emerges at another spring, could also 

contribute to the evaporative signature observed at the springs 

in this study. Springs that plot to the left or near the GMWL 

include Cottonwood (Tuckup), Swamp, Powell, Unknown, 

Hole in the Wall, Hanging, Fence, Warm and Big Springs. 

With the exception of Cottonwood (Tuckup) Spring, the 

aforementioned springs also have more depleted stable isotope 

values (less than –13 per mil δ18O). These springs are located 

on the margin of the Kaibab Plateau uplift and may indicate 

that the water discharging at these springs was recharged at a 

higher elevation. The isotopic ratio of Rider Spring is the most 

depleted of all of the spring samples (–15.61, –125 per mil), 

indicating that the water discharging at Rider Spring recharged 

at a distinctly higher elevation or from a colder climate compared to the other springs and that the water has undergone 

some evaporation, as it plots to the right of the GMWL.

Elevated tritium values (greater than 1.3 pCi/L) in 

groundwater discharging from stratigraphically lower rock 

units (Supai Group and Redwall Limestone springs; fig. 21) 

may indicate that a component of modern recharge can quickly 

(on the order of decades) move through the upper stratigraphic 

units to lower stratigraphic units. Rapid recharge would likely 

require flow through fractures or other preferential pathways. 

A general trend of increasing tritium concentrations with 

stratigraphic depth (fig. 21) indicates that some component of 

modern recharge (>28.4 pCi/L) is present in the system and 

might suggest that high tritium associated with the bomb–peak 

is discernable in groundwater and gradually infiltrating to 

greater depth in the study area.

Corrected 14C activities and interpreted ages indicate 

that most springs discharging from the Hermit Formation, 

Supai Group, and Redwall Limestone do not have waters 

with radiocarbon age. Side Canyon, Showerbath, and Kanab 

Springs suggest a mixture of water with a radiocarbon age and 

modern water (table 6). Springs with a possible component 

of water with a radiocarbon age from this study discharge 

from the Toroweap Formation and Coconino Sandstone. The 

calculated corrected groundwater ages are sensitive to the 

value of δ13C in the soil gas CO2 and carbonate rock, with 

the oldest ages using a soil gas value of –17 per mil. Using 

a soil gas value of –22 per mil decreases the corrected age 

for the springs and also results in negative ages for some of 

the samples, indicating that the correction methods are not 

appropriate for calculating the groundwater age or that the 

sample plots near the zero age line. There was some variation 

in the δ13C data from Monroe and others (2005) and Bills and 

others (2007), so analysis of δ13C in rock units from this study 

area would help with the interpretation of the age dating of 

the groundwater. A soil gas CO2 value of –22 per mil for δ13C 

was used based on the values from Hart and others (2010) 

for C3–plant–dominated areas in Utah and –17 per mil for a 

more arid area of the study. The biome for the majority of the 

study area is Great Basin Conifer, which is dominated by C3 

plants; the Great Basin Desert Scrub biome is present in lower 

elevations on the west side of the study area (Arizona Game 

and Fish Department, 2015). The plant communities have been 

consistent for the last 14,040 yr B.P. in the area to the north 

of the Grand Canyon (Anderson and others, 2000), which 

includes springs with the range of corrected groundwater ages. 

Appelo and Postma (2005) report –27 per mil for δ13C of C3 

plants and some arid–zone C4 plants have a heavier δ13C value 

of –13 per mil (Farquhar and others, 1989; Vogel, 1993). The 

–17 and –22 per mil values may represent a mixture of C3 and 

C4 plants, and provides a good estimation for the age of the 

groundwater in this study. Soil gas δ13C values for the study 

area would help better constrain the age of the groundwater 

at the sampled sites. A more detailed understanding of water–

rock interactions along flowpaths contributing to discharge at 

the springs described in this study would result in better age 

constraints, and would likely need to be conducted separately 

for each spring.

Springs with Elevated Uranium and Selenium 

Concentrations

Groundwater discharge from springs including Cottonwood (Tuckup), Grama, Pigeon, Rock, and Willow (Hack 

and Snake Gulch) Springs had uranium concentrations greater 

than 10 μg/L (fig. 8C), which was considered to be above the 

threshold for anomalous uranium concentrations for the Snake 

Gulch area by Billingsley and others (1983). Groundwater 

from these springs were dominated by Ca-Mg-SO4, and the 

specific conductance of these springs ranged from 2,350 to 

3,440 μS/cm. These springs were more closely associated 

with each other compared with other springs in this study on 

the basis of U, Mo, Sr, Se, and Li in a multivariate analysis 

(fig. 11), and U was significantly positively correlated with 

Li, Mo, Se, Sr, and Zn (fig. 12). The 87Sr/86Sr values in these 

springs ranged from 0.70775 to 0.70852 and UAR values in 

these springs ranged from 1.34 to 2.31. Groundwater from 

all of these springs had detectable tritium ranging from 0.8 to 

6.38 pCi/L, and interpretation of carbon data (fig. 20) from 

these springs indicate they may contain mixtures of modern 
50 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

and pre-modern waters. Pigeon Spring may contain water with 

a radiocarbon age, depending on the parameters (soil gas CO2

and rock δ13C) used to calculate groundwater age. The tritium 

values from multiple samples at the site fall within the premodern and possible mixture classification (table 6).

Springs with elevated uranium concentrations also tend 

to have elevated selenium concentrations (figs. 8 and 23). 

Selenium and uranium are positively correlated with a Kendall’s Tau value of 0.57 that is significant at the <0.05 p-value 

threshold (fig. 12). Selenium is known to be concentrated in 

fine-grained marine sedimentary rocks of Late Cretaceous age 

(Seiler and others, 2003). Although there are no rocks of Cretaceous age present in the study area, Seiler and others (2003) 

suggest that any marine deposit formed in a shallow, biologically productive environment may be seleniferous. Selenium is 

commonly associated with Ca, Mg, SO4, Na, and U in waters 

from the western United States (Seiler and others, 2003).

Mazeika (2002) analyzed the geochemistry associated 

with mineralization in the Sage breccia pipe south of Grand 

Canyon. Selenium was associated with iron mineralization 

of the breccia pipe. The highest selenium concentrations 

were present in the Coconino Sandstone from core near the 

Sage breccia pipe and just below the Toroweap Formation/

Coconino Sandstone contact as disseminated pyrite changes 

to iron oxide sandstone (Mazeika, 2002). Other high selenium 

concentrations were found in some high-uranium samples at 

stratigraphic levels in the pipe equivalent to rocks of the Hermit Formation and Esplanade Sandstone (Mazeika, 2002).

Similar geochemical compositions of spring waters 

having elevated uranium concentrations are observed at sites 

located both near, and away from, sites of uranium-mining 

activities in the present study. In a principal component analysis of leachates of uranium-mining associated material from 

Pigeon Mine and groundwater springs (Horse, Pigeon, Rock, 

Slide, Table Rock, Upper Jumpup, Warm, Wildband, and Willow [Snake Gulch] Springs) near the Pigeon Mine, selenium 

was more associated with the groundwater spring samples 

than the mining waste material (Beisner and others, 2017). In 

that study, there was no evidence for physical movement of 

water from the nearby Pigeon Mine towards Pigeon Spring, 

which has elevated uranium and selenium concentrations. 

Additionally, uranium concentrations in the mine associated 

material leachates were orders of magnitude greater than 

values in spring water, whereas selenium concentrations in the 

two components were of similar magnitude. Therefore, simple 

dilution was not considered to be a plausible explanation. 

Mining does not appear to explain the presence of elevated 

uranium concentrations in groundwater at springs noted here. 

However, there is the possibility that changes in groundwater 

chemistry associated with uranium mining activity had not 

arrived at spring discharge locations at the time of sampling 

for this study.

Figure 23. Selenium versus uranium from spring samples.

Toroweap Formation

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80

Uranium, in micrograms per liter 

Selenium, in micrograms per liter
Discussion 51

Values of 87Sr/86Sr in uranium ore of the Orphan Mine are 

substantially more radiogenic (0.76288; Balboni and others, 

2016) than any of the unmineralized Paleozoic sedimentary 

rocks (0.70756-0.71216; Monroe and others, 2005; Bills and 

others, 2007) from the region, as is waste rock associated with 

the uranium ore (Balboni and others, 2016). The elevated 

87Sr/86Sr signatures of the uranium ore likely reflect a component of fluids that have interacted with Precambrian basement 

rocks as part of the ore forming process. Ludwig and Simmons 

(1992) came to a similar conclusion using lead isotopes from 

galena within uranium-mineralized breccia pipes. None of the 

groundwater samples with high uranium concentrations (>10 μg/L) 

from this study have 87Sr/86Sr values much greater than those 

observed in the Paleozoic host rocks (fig. 24). On the contrary, 

groundwater samples with elevated uranium concentrations 

tend to have 87Sr/86Sr values lower than the mean value for 

rock units. Therefore, there is no clear indication from 87Sr/86Sr 

data that water having interacted with uranium ore or waste 

rock similar to material from the Orphan Mine forms a significant contribution to current spring discharge sampled in this 

study. However, the results do not preclude a small component 

of water interacting with mining material to be present at the 

sampled springs. A previous study of Pigeon and associated 

springs found no physical or geochemical evidence indicating 

that elevated uranium concentrations were related to processing at the nearby Pigeon Mine (Beisner and others, 2017). 

Strontium isotopes may serve as an important indicator of contribution from water interacting with uranium mine material 

for future samples from other springs or resampling of springs 

over time in the study area.

Conceptually, groundwater in the Grand Canyon region 

can be subdivided into (1) nonmineralized natural groundwater, unaffected by mining; (2) mineralized groundwater in 

areas where paleo-passage of hydrothermal fluids has deposited residual sulfides and metal sulfates, which on dissolution 

result in higher solute concentrations of uranium and other 

trace elements than in nonmineralized natural groundwater; 

and (3) anthropogenically altered groundwater, where disturbance of the natural system has influenced the chemistry of 

either mineralized or nonmineralized receiving waters. Differentiating between mineralized and nonmineralized groundwater chemistry at a mine site can be challenging if there is an 

overprint of past and (or) current mining on naturally mineralized conditions. Other considerations that aid in the evaluation 

are spatial distributions, sample types, and other chemical 

compositions of the water at the sites.

Figure 24. Strontium isotope ratio relative to uranium concentration for spring samples.

Toroweap Formation

Coconino Sandstone

Hermit Formation

Supai Group

Redwall Limestone

Geologic unit of spring discharge

EXPLANATION

0.7070

0.7080

0.7090

0.7100

0.7110

0.7120

0.7130

0.7140

0.7150

0 10 20 30 40 50 60 70 80 90 100

87Strontium/ 86Strontium

Uranium, in micrograms per liter
52 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Springs with a Possible Component of 

Geothermal Fluids

Fence and Rider Springs have elevated concentrations 

of As, B, Cl, Li, K, and Na that statistically outlie the ranges 

exhibited by other springs discharging from the Redwall 

Limestone and Coconino Sandstone, respectively (fig. 10). 

Crossey and others (2009) demonstrated that Ba, Li, F, B, and 

As are consistently higher in CO2-charged springs, and that 

those characteristics are consistent with contributions from 

a component of more deeply circulating geothermal fluid. 

Fence Spring also has the highest 87Sr/86Sr value of all samples 

in this study. The observed value of 0.71417 is significantly 

greater than the highest strontium isotopic ratio for any of the 

Paleozoic sedimentary rocks of the Grand Canyon. Crossey 

and others (2006) and Patchett and Spencer (2001) indicate 

that Proterozoic basement rocks contain radiogenic strontium 

isotopic ratios greater than 0.714. Basement rocks from the 

Verde Valley in Arizona have 87Sr/86Sr values that range from 

0.7300 to 0.7800 (Johnson and others, 2011). Crossey and others (2006) suggest that springs with elevated 87Sr/86Sr, such as 

Fence Spring, may include a component of deeply circulating 

groundwater that has interacted with Precambrian basement 

rocks.

Conclusions

Baseline water chemistry was established for springs discharging north of the Grand Canyon from the Toroweap Formation, Coconino Sandstone, Hermit Formation, Supai Group, 

and Redwall Limestone in an area that includes uranium 

mining from breccia pipes. Of the 37 total springs sampled 

in this study, 3 springs had trace element concentrations that 

exceeded the USEPA drinking water standards: Fence Spring 

(arsenic), Pigeon Spring (selenium and uranium), and Willow 

(Hack) Spring (selenium). The majority of the spring sites 

had groundwater uranium concentrations less than 10 μg/L, 

but six springs discharging from all geologic units except the 

Redwall Limestone had uranium values greater than 10 μg/L 

(Cottonwood [Tuckup], Grama, Pigeon, Rock, and Willow 

[Hack and Snake Gulch] Springs). Geochemical characteristics of those springs include a Ca-Mg-SO4

 water type, 

circumneutral pH, high specific conductance, correlation and 

multivariate associations between U, Mo, Sr, Se, Li, and Zn, 

low 87Sr/86Sr, low 234U/238U activity ratios (1.34–2.31), detectable tritium, and carbon isotope interpretation indicating they 

may be mixtures of modern and pre-modern waters. Similar 

geochemical compositions of spring waters having elevated 

uranium concentrations are observed at sites located both near, 

and away from, sites of uranium-mining activities in the present study. Therefore, mining does not appear to explain the 

presence of elevated uranium concentrations in groundwater at 

the six springs noted previously. The elevated uranium at the 

six previously mentioned springs may be related to iron mineralization associated with mineralized breccia pipe deposits.

Springs containing old water datable by radiocarbon 

methods discharge from the Coconino Sandstone (Upper Jumpup, Little, Horse, and Slide Springs) and Redwall Limestone 

(Kanab and Side Canyon Springs) and have corrected 14C ages 

as much as 9,300 years old. Select springs with old apparent 

groundwater ages (Kanab and Side Canyon Springs) that also 

contain tritium above 1.3 pCi/L may possibly indicate that 

some component of modern water recharged after 1952 is 

present in spring discharge, but could also indicate all premodern water. In contrast, springs containing high tritium concentrations (greater than 5.1 pCi/L) indicate the presence of 

a significant component of modern water and include Willow 

(Hack), Saddle Horse, Cottonwood (Tuckup) Hotel, Bitter, 

Unknown, Hole in the Wall, Hanging and Bitter Springs.

Fence and Rider Springs are located on the eastern end 

of the study area near the Colorado River and have a distinct 

geochemistry compared to the other springs of the study. 

These springs have elevated values of As, B, Cl, Li, K, and 

Na, which may indicate a component of geothermal fluids. 

Additionally, Fence Spring has the most radiogenic strontium 

isotopic composition (87Sr/86Sr) of all samples analyzed from 

this study. Similarly, elevated 87Sr/86Sr values have not been 

identified in any of the Paleozoic sedimentary rocks exposed 

in the area. The high 87Sr/86Sr is most likely derived from a 

groundwater component that has interacted with Precambrian 

crystalline basement rocks. Rider Spring has the most depleted 

values for stable O and H isotopes, indicating that recharge 

water originated at higher elevations or from a previous, 

cooler climate relative to other analyzed springs.

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58 Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona

Appendixes 1–6

Appendixes 1–6 are presented as Excel table files, and are available for download at https://doi.org/10.3133/sir20175068.

Appendix 1. Spring sample site characteristics.

Appendix 2. Standard reference sample performance for USGS National Water Quality 

 Laboratory (USGSNWQL) and USGS National Research Program Laboratory 

 in Boulder, Colo. (USGSTMCO) for Fall 2009.

Appendix 3. Blank data from USGS National Water Quality Laboratory (USGSNWQL) and 

 USGS National Research Program Laboratory in Boulder, Colo. (USGSTMCO).

Appendix 4. Replicate sample data from USGS National Research Program Laboratory in 

 Boulder, Colo. (USGSTMCO).

Appendix 5. Replicate sample data from USGS National Research Program Laboratory in 

 Reston, Va. and contract labs for uranium activity ratio.

Appendix 6. Spring sample results.
Menlo Park and Lafayette Publishing Service Centers 

Manuscript approved June 20, 2017 

Edited by Katherine Jacques 

Design and layout by James E. Banton
Beisner and others—Geochemical Characterization of Groundwater Discharging from Springs North of the Grand Canyon, Arizona—Scientific Investigations Report 2017–5068

ISSN 2331-1258 (online)

https://doi.org/10.3133/sir20175068