U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5072

Salinization of the Upper Colorado River—

Fingerprinting Geologic Salt Sources
COVER: Uncompahgre River near Ridgway, Colorado.

 Photograph by John G. Elliott, U.S. Geological Survey, July 20, 2005.
Salinization of the Upper Colorado River—

Fingerprinting Geologic Salt Sources

By Michele L. Tuttle and Richard I. Grauch

Scientific Investigations Report 2009–5072

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Tuttle, M.L., and Grauch, R.I., 2009, Salinization of the upper Colorado River—Fingerprinting geologic salt sources: 

U.S. Geological Survey Scientific Investigations Report 2009–5072, 62 p.
iii

Contents

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

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

Methods...........................................................................................................................................................2

Sample Collection.................................................................................................................................2

Analytical Procedures..........................................................................................................................2

Results .............................................................................................................................................................4

Flow and Solute Loads.........................................................................................................................4

Piper Diagrams......................................................................................................................................5

Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River

Above Cisco, Utah............................................................................................................................6

Eagle River.............................................................................................................................................7

Eagle River Near Minturn, Colorado.........................................................................................7

Eagle River at Avon, Colorado ...................................................................................................8

Eagle River at Gypsum, Colorado..............................................................................................8

Geochemical Evolution Along the Eagle River........................................................................8

Roaring Fork River at Glenwood Springs, Colorado........................................................................9

Gunnison River....................................................................................................................................10

Uncompahgre River............................................................................................................................10

Uncompahgre River Near Ouray, Colorado...........................................................................10

Uncompahgre River Near Ridgway, Colorado ......................................................................10

Uncompahgre River at Delta, Colorado .................................................................................10

Geochemical Evolution Along the Uncompahgre River......................................................12

Gunnison River Below Gunnison Tunnel, Colorado.......................................................................13

North Fork of the Gunnison River Below Paonia, Colorado.........................................................13

Lower Gunnison River........................................................................................................................13

Gunnison River at Delta, Colorado..........................................................................................13

Gunnison River Near Grand Junction, Colorado ..................................................................14

Geochemical Evolution Along the Gunnison River........................................................................14

Dolores and San Miguel Rivers........................................................................................................16

San Miguel River at Uravan, Colorado...................................................................................16

Dolores River at Dolores, Colorado ........................................................................................16

Dolores River at Bedrock, Colorado .......................................................................................16

Dolores River Near Cisco, Utah...............................................................................................17

Geochemical Evolution Along the Dolores River..................................................................18

Geochemistry in Main Stem Colorado River Above Cisco, Utah .........................................................19

Colorado River Near Kremmling, Colorado ....................................................................................19

Colorado River Above Glenwood Springs, Colorado ....................................................................19

Colorado River Near Cameo, Colorado ...........................................................................................20

Plateau Creek Near Cameo, Colorado ............................................................................................21

Colorado River Near Colorado-Utah State Line.............................................................................21

Colorado River Near Cisco, Utah .....................................................................................................21

Geochemical Evolution of the Colorado River Above Cisco........................................................22
iv

Fingerprinting Major Geologic Salt Sources...........................................................................................23

Evaporites in the Eagle Valley Evaporite.........................................................................................24

Evaporites in the Paradox Formation ..............................................................................................24

Salts Derived From Weathering of the Mancos Shale.................................................................25

Dolores River Watershed .........................................................................................................25

Gunnison River Watershed ......................................................................................................25

Colorado River Headwater-Plateau Watershed...................................................................26

Summary........................................................................................................................................................26

Acknowledgments ......................................................................................................................................26

References Cited..........................................................................................................................................27

Appendix I. Chemical and Isotopic Data for All Water Samples Collected in This Study............30

Appendix II. Chemical Loads for Major Chemical Elements and Total Solutes .............................50

Appendix III. Chemical, Isotopic, and Mineralogical Data for All Geologic Samples

Collected in This Study..................................................................................................................53

Figures

1. Map showing study area and sampling locations ..................................................................3

2. Schematic of flow during high-water, irrigation, and base flows ........................................4

3. Schematic of total solute loads during high-water, irrigation, and base flows .................5

4. Piper plots for water during high-water flow, irrigation flow, and base flow.....................6

5. Index map for watersheds considered in this study...............................................................7

6. Map of the Eagle River watershed ............................................................................................7

7. Cross plots showing relations between isotopic composition of δ2H and

δ18O of water and δ18O and δ34S of dissolved sulfate in the Eagle River..............................8

8. Map of Roaring Fork River watershed ......................................................................................9

9. Maps of the upper Gunnison River, North Fork of the Gunnison River,

Uncompahgre River, and lower Gunnison River watersheds .............................................11

10. Isotope data for the Uncompahgre River ...............................................................................12

11. Isotope data for the Gunnison River, North Fork of the Gunnison River,

and lowermost Uncompahgre River........................................................................................15

12. Map of the upper and lower Dolores River watersheds and the San Miguel

River watershed..........................................................................................................................17

13. Isotope data for the Dolores and San Miguel Rivers............................................................18

14. Maps of Colorado River headwater, Colorado River headwater-plateau,

and the Westwater Canyon watersheds ................................................................................20

15. Total load at stations along the Colorado River and at confluences

with tributaries ............................................................................................................................23

16. Isotopic composition of water and sulfate along the main stem of the upper

Colorado River at and above Cisco..........................................................................................24

Tables

1. Methods of chemical analyses ..................................................................................................3

2. Approximate distances of major tributary confluences on the Colorado River

downstream from the Kremmling station .................................................................................7
v

3–9. Summary of geochemical parameters for:

 3. Eagle River at Minturn ..........................................................................................................8

 4. Eagle River at Avon ...............................................................................................................9

 5. Eagle River at Gypsum..........................................................................................................9

 6. Roaring Fork River at Glenwood Springs.........................................................................10

 7. Uncompahgre River near Ouray .......................................................................................12

 8. Uncompahgre River near Ridgeway ................................................................................13

 9. Uncompahgre River at Delta .............................................................................................13

10. Stream flow, total salt load, and SO4 load for irrigation water in the

Uncompahgre watershed..........................................................................................................14

11–21. Summary of geochemical parameters for:

 11. Gunnison River below Gunnison Tunnel..........................................................................14

 12. North Fork of the Gunnison River below Paonia ............................................................15

 13. Gunnison River at Delta......................................................................................................16

 14. Gunnison River near Grand Junction...............................................................................16

 15. San Miguel River at Uravan...............................................................................................18

 16. Dolores River at Dolores ....................................................................................................19

 17. Dolores River at Bedrock ...................................................................................................19

 18. Dolores River near Cisco....................................................................................................19

 19. Colorado River near Kremmling ........................................................................................21

 20. Colorado River above Glenwood Springs........................................................................21

 21. Colorado River near Cameo...............................................................................................21

22. Sulfate loads and isotopic composition of contributions between

the stations above Glenwood Springs and near Cameo on the

upper Colorado River .................................................................................................................22

23–25. Summary of geochemical parameters for:

 23. Plateau Creek near Cameo ................................................................................................22

 24. Colorado River near the Colorado-Utah State line ........................................................22

 25. Colorado River near Cisco .................................................................................................23

26. The 2005 estimated dissolution rates for halite and gypsum in major

geologic units and a comparison of the derived solutes to the estimated

annual Colorado River load at Cisco .......................................................................................26

Appendix Tables

AI–1. Metadata for reported concentrations ...................................................................................30

AI–2. Elements not reported in Appendix 1 ......................................................................................31

AI–3. Chemical and isotopic data for all water samples collected in this study........................32

AII–1. Conductivity and chemical load (tonnes/day) for major chemical elements ...................50

AIII–1. Metadata for reported concentrations ...................................................................................53

AIII–2. Chemical data for all geologic samples..................................................................................54

AIII–3. Sulfur isotope data for selected geologic samples ..............................................................59

AIII–4. Mineralogical data for selected geologic samples ..............................................................61

Salinization of the Upper Colorado River—Fingerprinting 

Geologic Salt Sources

By Michele L. Tuttle and Richard I. Grauch

Abstract

Salt in the upper Colorado River is of concern for a 

number of political and socioeconomic reasons. Salinity limits 

in the 1974 U.S. agreement with Mexico require the United 

States to deliver Colorado River water of a particular quality 

to the border. Irrigation of crops, protection of wildlife habitat, 

and treatment for municipal water along the course of the river 

also place restrictions on the river’s salt content.

Most of the salt in the upper Colorado River at Cisco, 

Utah, comes from interactions of water with rock formations, 

their derived soil, and alluvium. Half of the salt comes from the 

Mancos Shale and the Eagle Valley Evaporite. Anthropogenic 

activities in the river basin (for example, mining, farming, petroleum exploration, and urban development) can greatly accelerate 

the release of constituents from these geologic materials, thus 

increasing the salt load of nearby streams and rivers. Evaporative 

concentration further concentrates these salts in several watersheds where agricultural land is extensively irrigated.

Sulfur and oxygen isotopes of sulfate show the greatest 

promise for fingerprinting the geologic sources of salts to the 

upper Colorado River and its major tributaries and estimating the relative contribution from each geologic formation. 

Knowing the salt source, its contribution, and whether the 

salt is released during natural weathering or during anthropogenic activities, such as irrigation and urban development, 

will facilitate efforts to lower the salt content of the upper 

Colorado River.

Introduction

Nearly 33 million people and 4 million acres of farmland in the United States and 3 million people and 500,000 

farmland acres in Mexico depend on the Colorado River 

(U.S. Department of Interior, 2005). The Colorado River is 

considered one of the most stressed rivers in the world because 

of increasing salinization (Serageldin, 2000), transporting 

9 million tons of dissolved salt each year. Roughly half of 

this salinity is from irrigation of agricultural fields, reservoirs, 

industry, and urbanization, and half from natural weathering. 

Salinity damages are estimated at $306 million in the United 

States alone (U.S. Department of Interior, 2005) and $1 billion 

per year overall (U.S. Water News Online, 1995). In accordance with requirements of the Clean Water Act, one million 

tons of salt per year have been controlled as of 2004, with a 

target control of 1.8 million tons per year by 2025, set by the 

Salinity Control Forum in 2002 (cited in U.S. Department of 

Interior, 2005). Achieving this target control standard requires 

identification of natural nonpoint sources (soils, geologic formations, and stream channels and banks) and an understanding 

of processes by which salinization occurs during irrigation and 

natural weathering. Evaluating the impact of these nonpoint 

sources is difficult; however, recent application of diagnostic 

geochemical tracers yielded successful results in other river 

systems (Vengosh, 2004).

In 2005, an estimated 5.8 million tons of salt was 

acquired by the Colorado River in the upper Colorado River 

basin (http://www.usbr.gov/uc/progact/salinity/index.html), 

a large portion of which is the focus of this study. The upper 

Colorado River and its tributary watersheds are located in 

mostly sparsely populated areas in mountainous terrain or in 

valleys that support agriculture; therefore, most solutes come 

primarily from geologic sources (such as rocks, soils, alluvium, and pediments). River reaches that travel through larger 

communities (Grand Junction being the largest with a population of around 126,000 at the time of this report) undoubtedly 

acquire some solutes from point sources such as municipal 

waste or industrial effluent; however, these contributions 

are small relative to those from geologic sources (Spahr and 

others, 2000).

Solutes in ground and surface water are released from 

geologic sources through natural weathering, or anthropogenic 

activities such as land development, mining, and irrigation. 

The major elements that make up the largest proportion of 

solutes in ground and surface water are calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chloride (Cl), sulfate 

(SO4), and bicarbonate (HCO3). These solutes are generally 

conservative in water, although precipitation of calcite can 
2 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

occur and Ca and Mg can be adsorbed during cation exchange 

reactions (Plummer and others, 2003). Dissolution of carbonate rocks (calcite—CaCO3

 and dolomite—CaMg(CO3)2) 

release Ca, Mg, and HCO3; gypsum (CaSO4•2H2O) and 

anhydrite (CaSO4) release Ca and SO4; halite (NaCl) releases 

Na and Cl; and silicate minerals release Na, Ca, Mg, K, and 

HCO3. During oxidation, sulfide minerals release SO4 and 

various metals. Reactions on the surfaces or in the interlayers 

of clay minerals preferentially release sodium and potassium 

relative to other cations.

The scientific objective of this study was two-fold: 

(1) develop diagnostic geochemical tracers for the major 

geologic sources of salt to the upper Colorado River and 

(2) demonstrate the use of these tracers to understanding 

contributions of nonpoint geologic sources of salt to the upper 

Colorado River. Our strategy was to collect water samples from 

major Colorado River tributaries and along reaches of the upper 

Colorado River during snowmelt runoff (high-water flow), 

maximum diversion and irrigation-return (irrigation flow), and 

base stream flow (base flow). Calculated loading of chemical 

constituents along with geochemical tracers (element suites, 

element ratios, and stable isotopes) are applied to distinguish 

salinity sources, the quantity of salt generated from the source, 

and its composition. The data represent three snapshots in time 

and are not meant to represent an overall average of water 

quality. Our results show that, although element ratios help 

support the identification of various geologic contributions to 

the upper Colorado River salt load, the isotopes of sulfate are 

the most useful for identifying and quantifying specific sources. 

Trace elements help identify contributions from weathering 

of mineral deposits or mining waste, water isotopes are used 

to evaluate the effect of evaporation on increasing loads, and 

“available” concentrations assess elements dissolved plus those 

associated with geologic materials in suspension that dissolve 

when acidified. The latter results have important implications 

for health of organisms as several environments where acidification can occur are in animal lungs and stomach, plant root 

zones, and amended soil.

Methods

Sample Collection

Stations (fig. 1) were chosen to balance coverage of 

the upper Colorado River system above Cisco, Utah, with 

available analytical funds and maximum watershed information. Samples were collected in 2005. At each station, flow, 

conductivity, and pH were measured in the field. The last 

two parameters were also measured in the laboratory; laboratory results compared favorably with field values (only 

laboratory measurements are reported to decrease variability 

inherent when using different field meters). Six water samples 

were collected at each station—two unfiltered and unacidified for alkalinity and water isotopes, two filtered (0.45 μm) 

and unacidified for sulfur isotopes and major anions, one 

unfiltered and acidified for available cations,1 and one filtered 

(0.45 μm) and acidified for dissolved cations. “High-water” 

samples were collected in May during the period when snowmelt results in high stream flow.2

 “Irrigation” samples were 

collected in mid-July to mid-August when some tributaries 

of the upper Colorado River are affected by diversion and/or 

return of irrigation water. “Base flow” samples were collected 

in mid-October to late November during the period when 

runoff from irrigation and storms is approaching its minimum. 

Samples were filtered and acidified in the field, packed in ice, 

and shipped to the laboratory. Upon receipt, samples were 

refrigerated until analyzed.

Point-source waters (Glenwood Springs hot springs 

and Rifle Uranium Mill monitoring wells) were collected 

identically to stream samples. Composites of geologic 

samples were collected, transported to the laboratory, and 

split for various analyses.

Analytical Procedures

Water samples were analyzed for alkalinity (titration), 

anions (ion chromatography and gravimetrically), cations 

(inductive coupled plasma–atomic emission spectrometry 

and inductive coupled plasma–mass spectrometry), and stable 

isotopes of water and dissolved sulfate (mass spectrometry) 

(table 1). Charge balances were all less than 10 percent (average 3 percent), excepting three samples that were between 

17 and 25 percent (Colorado River at Kremmling high water, 

Eagle River at Avon base flow, and Gunnison River below 

tunnel base flow). These three waters are dilute, and uncertainty in the bicarbonate analysis is suspected.

Geologic samples were completely digested using a 

lithium metaborate fusion or four-acid digestion (hydrochloric, nitric, perchloric, and hydrofluoric acids) and analyzed for 

major elements by ICP–AES and for minor and trace elements 

by ICP–MS (Taggert, 2002). A split was also analyzed for 

mineral identification and morphology under the SEM–EDX. 

Sulfur and oxygen isotopic composition was determined on 

individual sulfur species (oxygen only measured on the sulfate) 

and reported in standard delta notation3 (Tuttle and others, 1986; 

1

In this study, available cations include dissolved cations plus those dissolved 

or desorbed upon acidification. For this analysis, water samples are collected, 

acidified, and then filtered (0.45 μm) just prior to analysis by ICP–MS and 

ICP–AES.

2

Sampling periods were chosen to coincide with synoptic sampling for other 

studies and may not always represent the ideal sampling period.

3

δ(‰) = (Rsample–Rstandard) × 1,000, where R is the ratio of 34S:32S, 2H:1H, 

or 18O:16O, and the standards are V-CDT (Vienna Cañon Diablo Troilite) and 

V-SMOW (Vienna Standard Mean Ocean Water).
Methods 3

Figure 1. Map showing study 

area and sampling locations. Red 

dots, river-water samples at stream 

gaging stations; blue stars, pointsource water sample locations; 

green stars, geologic sample 

locations. Data for base map are 

from the National Elevation Dataset, 

available from http://ned.usgs.gov/; 

and the National Atlas, available 

from http://nationalatlas.gov/.

Table 1. Methods of chemical analyses, their abbreviation used in the appendixes, and publication references to the procedures.

[References: 1, Taggert (2002); 2, Tuttle and others (1986); 3, Giesemann and others (1995)]

Methods Abbreviation Reference

Carbon/hydrogen/nitrogen commercial analyzer CHN

Cold vapor atomic adsorption spectrometry CVAA 1

Combustion: SGS Laboratories (formerly XRAL), Toronto, Canada COMB1 1

Combustion: USGS COMB2 1

Coulometric titration CT 1

Energy dispersive X-ray fluorescence EDX 1

Graphite furnace GF 1

Gravimetric GRAV 2

Hydride generation atomic adsorption spectrometry HYD 1

Ion chromatography IC 1

Inductive coupled plasma–atomic emission spectrometry ICP–AES 1

Inductive coupled plasma–mass spectrometry ICP–MS 1

Ion selective electrode ISE 1

Mass spectrometry MS 3

Scanning electron microscopy–energy dispersive X-ray fluorescence SEM–EDX

Sulfur speciation Sspec 2

40°

39°

38°

37°

109° 108° 107° 106°

McPhee

Reservoir

Cisco

Bedrock

Mack

Grand

Junction

Gateway

Uravan

Dolores

Glenwood

Springs

Carbondale

Cameo

Paonia

Montrose

Delta

Gypsum

Minturn

Tunnel

Avon

Kremmling

Ridgway

Ouray

U T A H

C O L O R A D O

Study

area

COLORADO

UTAH

0

0 50 KILOMETERS

50 MILES
4 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Giesemann and others, 1995). Hydrogen and oxygen isotopes of 

water were commercially analyzed and reported in standard delta 

notation3 relative to V-SMOW.

Results

Individual chemical and isotopic results are presented in Appendixes I and III. In this study, we report two 

concentrations for each cation—aqueous (aq), which is 

operationally defined as dissolved (the filtered sample), and 

available (avail), which is defined as the dissolved concentration at the time of sampling plus those elements that 

dissolve or exchange upon acidification of the sample (the 

unfiltered sample). In this report, “available” data are only 

discussed with respect to transport of metals adsorbed to 

oxides and clays.

Flow and Solute Loads

Solute (chemical) loads in 103 kg/d (tonnes solute/day) 

(Appendix II) have been calculated for all major chemical 

constituents (aqueous and available) as the product between 

chemical concentration and flow at the time of sampling. 

Segment schematics for flow and total loads are shown in 

figures 2 and 3. When a constituent concentration remains 

constant, loads increase or decrease with flow rates. In 

Figure 2. Schematic of flow in cubic feet per second (cfs) during high-water, irrigation, and base flows (not to scale). Also included 

are flows from irrigation diversion through the Gunnison Tunnel into the Uncompahgre watershed (dashed line; Paul Davidson, Bureau 

of Reclamation, written commun., 2007) and flows from the Ridgway State Dam at Colona (X symbol; USGS stream gaging data at 

http://waterdata.usgs.gov/nwis/uv?09147500). “Added” values are the increase in flow (calculated as the difference between stations 

along the Colorado River and represents added flow not directly measured in this study). CR, Colorado River; ER, Eagle River; RF, Roaring 

Fork River; PC, Plateau Creek; GR, Gunnison River; NF, North Fork of the Gunnison River; UR, Uncompahgre River; SM, San Miguel River; 

DR, Dolores River.

x

Flow (cfs)

High-water flow

Irrigation flow

Base flow

CR-Kremmling

 1230

980

750 Added

330

1760

900

2190

70

135

(310)

680

265

2450

(890)

(115)

Added

Added

Added

ER-Minturn 635, 90, 85

ER-Gypsum

3630

870

420

ER-Avon 2180, 455, 205

CR-Glenwood 7050, 1920, 1400

CR-Cameo 10900, 5020, 2480

PC-Cameo 1430, 160, 145

GR-Grand Jct

GR-Delta

6410

960

880

NF-Paonia

5190

695

200

GR-Tunnel 744, 524, 394

UR-Colona 480, 450, 50

UR-Delta

5980

1570

1530

470

755

240

UR-Ouray

250

110

25

State line

SM-Uravan

18000

7430

4420

1250

215

135

UR-Ridgway

340

195

75

Irrigation diversion 865, 940, 0

RF-Glenwood

3520

1340

765

DR-Bedrock 1300, 80, 45

DR-Dolores 3920, 245, 120

DR-Cisco 1950, 270, 195

CR-Cisco 22400, 6810, 4500
Results 5

Figure 3. Schematic of total solute loads (tonnes solutes/day) during high-water, irrigation, and base flows (not to scale). Also included 

are loads from irrigation diversion through the Gunnison Tunnel into the Uncompahgre watershed (dashed line) and percent of the 

Colorado River load for lowermost tributary stations. “Added” values are loads acquired between stations along the Colorado River not 

attributable to measured loads in tributaries sampled. CR, Colorado River; ER, Eagle River; RF, Roaring Fork River; PC, Plateau Creek; GR, 

Gunnison River; NF, North Fork of the Gunnison River; UR, Uncompahgre River; SM, San Miguel River; DR, Dolores River.

some cases, however, loads vary in a more complex manner 

because concentrations in the water actually change as stream 

flow conditions change (for example, concentrations related to 

snow-melt runoff during high-water flow versus those related 

to ground-water discharge during base flow).

Piper Diagrams

Piper diagrams, which are used to define water type in 

a standard format, are shown in figure 4. The blue line on these 

plots tracks the evolution of the upper Colorado River from 

its headwater station at Kremmling to the farthest downstream 

station sampled at Cisco. The major cation (>50 percent on 

meq basis) in water during high-water flow conditions is Ca 

(fig. 4A); the major anion is HCO3 in all but four samples where 

SO4 is the dominant anion. Therefore, most of these samples 

during high water are calcium-bicarbonate water except for 

the four calcium sulfate waters in the Uncompahgre River and 

the lowermost Gunnison.4 The two lowermost Colorado River 

samples plot just outside the calcium bicarbonate water field 

and are technically a mixed-water type.

During irrigation-flow conditions, all headwater 

samples are calcium bicarbonate water, except for the headwater of the Uncompahgre River (fig. 4B). All water in the 

Uncompahgre River, water in the Gunnison River below its 

headwater stations, and water at the San Miguel River station 

4

Specific water types are defined as having at least 50 percent of the cation 

and anion on a milliequivalent (meq) basis. Mixed water types are those with 

no cation and/or anion that are >50 percent on a meq basis.

CR-Kremmling

310 (2%)

365 (4%)

280 (4%)

1560 (9%)

495 (6%)

810 (8%)

Added

Added

2690 (16%)

1800 (22%)

1620 (17%)

Added 

725 (4%)

1665 (20%)

2270 (24%)

Added

1820 (11%)

(890) (–11%)

675 (7%)

ER-Minturn 635, 90, 85

ER-Gypsum

1310 (8%)

500 (6%)

370 (4%)

ER-Avon 395, 455, 205

CR-Glenwood 3180 (19%), 1360 (17%), 1469 (15%)

CR-Cameo 7450 (44%), 4170 (51%), 3870 (40%)

PC-Cameo 575 (3%), 175 (2%), 190 (2%)

GR-Grand Jct

5150 (30%)

2540 (31%)

2090 (22%)

3310

1630

2370

GR-Delta

NF-Paonia

1210

240

145

UR-Delta GR-Tunnel 270, 205, 240

935

1730

760

UR-Ouray

State line

13900 (82%)

8550 (105%)

8420 (82%)

800

220

205

SM-Uravan

DR-Bedrock 930, 175, 70

DR-Dolores 1160, 115, 70

DR-Cisco 1280 (8%), 445 (5%), 535 (6%)

CR-Cisco 17000, 8170, 9630

UR-Ridgway

250 

200 

100

95

70

30

Irrigation diversion 380, 370, 0 

Total load (tonnes solutes/day)

(percent of load at 

Colorado River, Cisco)

High-water flow

Irrigation flow

Base flow

RF-Glenwood

1580 (9%)

1010 (12%)

790 (8%)
6 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Figure 4. Piper plots for water at all stations sampled in this study during (A) high-water flow, (B) irrigation flow, and 

(C) base flow. Data are plotted on a milliequivalent basis. CR, Colorado River; ER, Eagle River; RF, Roaring Fork River; 

PC, Plateau Creek; GR, Gunnison River; UR, Uncompahgre River; SM, San Miguel River; DR, Dolores River.

are of a calcium sulfate type. The Dolores River water at 

Bedrock is a sodium chloride type, whereas all other waters 

are of a mixed type. All Colorado River water below its 

headwater station is a mixed type; however, at the ColoradoUtah State line and at Cisco, the water approaches the 

SO4 field.

During base-flow conditions, headwater samples 

remain calcium bicarbonate water, except at the Uncompahgre 

River headwater station (fig. 4C). All of the Uncompahgre 

River and the San Miguel River stations remain calcium 

sulfate water. The Dolores River at Bedrock and Cisco is 

sodium chloride water. Water at all other stations is of a 

mixed type. The largest change in water type in the Colorado 

River is at Glenwood Springs, where the water type moves 

toward the Cl field and is very similar to Colorado River water 

at Cameo.

Geochemistry at Stations Along 

Tributary Watersheds to the Upper 

Colorado River Above Cisco, Utah

The following discussion of individual tributary results 

has been organized by watershed. Watersheds for each tributary, 

as well as those for the upper Colorado River within the study 

area, are indexed with a number in the map in figure 5. Geologic descriptions of these watersheds were taken from Warner 

and others (1985), Hintz and others (2000), and Day and others 

(1999). Estimates for the distance of each confluence considered in our study from the uppermost Colorado River sample at 

Kremmling are in table 2. The data presented herein characterize 

nearly 350 km of the upper Colorado River.

80

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80

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60

80

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60

40

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60

80

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80

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40

60

80

20

40

60

80

80

60

40

20

20

40

60

80

20

40

60

80

20

40

60

80

20

40

60

80

20

40

60

80

HCO3

Ca HCO Cl Na+K 3

Mg SO4

Ca + Mg

Cl + SO4

Na+K

Ca Na+K HCO3 Cl Ca Na+K HCO3 Cl

Mg SO4

Na+K

HCO

Na+K

3

HCO3

Mg SO4

Ca + Mg

Cl + SO4

Ca + Mg

Cl + SO4

Piper plot—Base flow

Piper plot—High-water flow Piper plot—Irrigation flow

C

A B

EXPLANATION

CR-Kremmling

ER-Minturn

ER-Avon

ER-Gypsum

CR-Glenwood Spg.

RF-Glenwood Spg.

CR-Cameo

PC-Cameo

GR-tunnel

GR-NF

GR-Delta

UR-Ouray

UR-Ridgway

UR-Delta

GR-Grand Jct.

CR-Colo.-Utah

DR-Dolores

DR-Bedrock

SM-Uravan

DR-Cisco

CR-Cisco
Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River Above Cisco, Utah 7

Eagle River

Three stations were sampled within the Eagle River 

watershed (fig. 6)—near or at Minturn, Avon, and Gypsum. 

The flow of the Eagle River is not controlled by any major 

reservoirs. The rocks upstream from Minturn are metamorphic 

and carbonate rocks, some mineralized. Between Minturn 

and Avon, rocks are predominately sedimentary and include 

carbonates, sandstones, and shales. Below Avon, the Eagle 

River crosses large expanses of Pennsylvanian Eagle Valley 

Evaporite composed of thick salt beds (mostly gypsum at 

the surface with halite at depth) and some sandstone and 

shale. Starting along the tributary at Vail and continuing 

downstream past Avon, the river valley is heavily developed 

with recreational communities. Some historic mining of base 

and precious metal ore occurred in the upper reaches of this 

watershed, and gypsum (Eagle Valley Evaporite) and volcanic 

cinder are mined in the lower portion of the river valley.

Figure 5. Index map for watersheds considered in this study 

(numbered 1 to 12). This map and those for watersheds listed 

were downloaded from http://www.epa.gov/surf/.

2

3

6 4

9

10

11

12

7

8

5

1

Denver

Colorado Springs

Pueblo

1

2

3

4

5

6

7

8

9

10

11

12

Colorado River headwaters

Eagle River

Roaring Fork River

Upper Gunnison River

North Fork of the Gunnison River

Uncompahgre River

Lower Gunnison River

Colorado River headwater-plateau

Upper Dolores River

San Miguel River

Lower Dolores River

Westwater Canyon

Table 2. Approximate distances of major tributary confluences 

on the Colorado River considered in this study downstream from 

the Kremmling station.

Confluence Distance

(km)

Eagle River 80

Roaring Fork River 112

Plateau Creek 215

Gunnison River 250

Dolores River 345

Eagle River Near Minturn, Colorado

The conductivity at this station is low (less than 

140 μS/cm), and the water is a calcium bicarbonate type 

(fig. 4; table 3). Waters at this station contain relatively high 

concentrations of dissolved and available Fe, Mn, and Zn 

(table AI–3). These metal concentrations, which are related 

to historic mining in the headwater area (for example, Eagle 

mine), decrease downstream. The Ca:SO4 ratio (table 3) at 

this station during high-water flow is consistent with most 

Ca being derived from the dissolution of minerals other 

than gypsum and the Na:Cl ratio with halite dissolution. 

Exposure of the Eagle Valley Evaporite does not occur in 

the watershed at or upstream from this station. Although 

speculative, the application of deicer mixtures that contain 

halite could explain the ratio during high-water flow, as much 

of the upstream watershed is in areas where winter highway maintenance includes deicing roads along the stream. 

Deicer contamination was also suggested by a concentration 

in shallow aquifers in the urban corridor on the east side of 

the continental divide (Flynn, 2003). During irrigation and 

base-flow conditions (periods when deicer is not being applied 

to the roads), the Na:Cl ratio increases slightly suggesting 

another source of sodium, and the Ca:SO4 ratio decreases 

suggesting an additional source of sulfate. Isotopes for the 

dissolved sulfate (fig. 7) are relatively constant during irrigation and base flow (the sulfate concentration at high-water 

flow was too low for isotope measurement). Isotope values 

are consistent with sulfate derived from oxidation of sulfide 

ores (fig. 7) predominately with atmospheric oxygen (Taylor 

and Wheeler, 1994).

Figure 6. Map of the Eagle River watershed (no. 2 on fig. 5), 

showing adjacent sampled watersheds, Minturn (the uppermost 

stream station), Avon (6 km from Minturn), and Gypsum (50 km 

from Minturn); the latter is the lowermost station in the watershed. 

Red dots, stations sampled. This and all subsequent watershed 

maps modified from those at http://www.epa.gov/surf/.

Gypsum

Avon

Vail

Roaring Fork River

Minturn

Colorado River Headwaters
8 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Table 3. Summary of geochemical parameters for the Eagle River 

at Minturn.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Eagle River

at Minturn HW IRR BF

Charge balance (percent) –9 2 1

Conductivity (μS/cm) 105 140 110

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 115 25 18

Percent CR load at Cisco 1 <1 <1

Ca:SO4 (molar basis) 5.7 4.1 3.1

Na:Cl (molar basis) 1.1 1.4 1.2

Evaporation no no no

SO4 source mineralization mineralization mineralization

Figure 7. Cross plots showing relations between isotopic composition of δ2H and δ18O of water and the GMWL 

(left) and δ18O and δ34S of dissolved sulfate in the Eagle River (ER) at three sampling stations during three 

flow seasons (right). HW, high-water flow; Irr, irrigation flow; BF, base flow. Hydrogen and oxygen isotopes 

measured relative to V-SMOW and sulfur isotopes relative to V-CDT.

Eagle River at Avon, Colorado

During high-water flow, the water at this station has a composition very similar to that at Minturn (fig. 4); however, the load 

at Avon increases by 3.5 times that at Minturn because the flow 

increases by a similar amount (table 4). During irrigation conditions, the Ca:SO4

 ratio decreases (table 4) as the SO4 concentration more than doubles (although still a small concentration), 

whereas concentrations of the other major elements change only 

slightly. The source of the additional sulfate is isotopically heavier 

than that at Minturn (fig. 7), suggesting that some dissolution of 

Pennsylvanian evaporites (δ34SSO4 = 14 ‰ and δ18OSO4 = 11 ‰; 

table AIII–2) is contributing to the salt load. The Na:Cl ratios during all flow conditions are near one, consistent with dissolution of 

halite in the Eagle Valley Evaporite.

Eagle River at Gypsum, Colorado

The conductivity of water at this station is between 2 

and 2.5 times that at Avon under all flow conditions (table 5). 

During high-water flow, the river water is a calcium bicarbonate 

type. During irrigation and base flow, a higher proportion of sulfate changes the water to a mixed anion type with Ca continuing 

to be the predominant cation (fig. 4). The Ca:SO4 ratios (table 5) 

are lower than at Avon and are highest during high-water 

flow. The dissolution of gypsum in the Eagle Valley Evaporite 

contributes a greater proportion of sulfate during irrigation and 

base-flow conditions as evident from the dramatic rise in the 

δ34SSO4 and δ18OSO4 values (fig. 7).

Geochemical Evolution Along the Eagle River

The composition of the Eagle River between Minturn and 

Avon changes little (fig. 4); however, there is an increase in sulfate proportion at Gypsum, especially during irrigation and base 

flow. The increased flow during high water increases the load of 

the river by over three times that during irrigation or base flow. 

Between Avon and Gypsum, HCO3(aq) and SO4(aq) concentrations 

increase as well as concentrations of many of the “available” 

elements (table AI–3). “Available” element concentrations significantly influence loads during high flow as soil and fine rock 

particles are carried in the more turbulent runoff. These particles 

consist of detrital components rich in resistate minerals containing Ba, rare earths, Sc, Si, Ti, and in oxides and oxide coatings 

rich in Al, Fe, Mn, and adsorbed metals such as Cd, Co, Cr, 

Eagle Evap.

–138

–136

–134

–132

–130

–128

–126

–124

–122

–120

–118

–8

–6

–4

–2

0

2

4

6

8

10

12

δ2H ‰

δ18OSO4 ‰

–19 –18.5 –18 –17.5 –17 –16.5 –16 –2 0 2 4 6 8 10 12 14

δ34SSO4 δ18OH20 ‰ ‰

ER-Minturn, Irr

ER-Minturn, BF ER-Minturn, HW

ER-Gypsum, HW ER-Gypsum, Irr

ER-Avon, Irr ER-Gypsum, BF

ER-Avon, BF ER-Avon, HW

EXPLANATION
Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River Above Cisco, Utah 9

Cu, Ni, V, and Zn. During base-flow conditions, significant 

concentrations of evaporite-related elements such as those from 

halite (Na and Cl) and from gypsum (Ca, Sr, and SO4) influence 

the load primarily through discharge of ground water that has 

flowed through Eagle Valley Evaporite.

The δ2H and δ18O values of the Eagle River water for all 

flow conditions fall on or very close to the global meteoric 

water line (GMWL; represented by δ2H ‰ = 8δ18O ‰ + 10 ‰ 

relative to SMOW; Craig, 1961) (fig. 7). Little evaporation of 

the water takes place along the river, and the variation in position along the water line among flow conditions reflects changing proportions of water derived from snowmelt during high 

flow (isotopically lighter values5) to ground-water discharge 

during base flow (isotopically heavier values).

Spatial and temporal variation in the sulfate isotopic composition among the three stations along the Eagle River results in 

a line, except for the Eagle River at Gypsum during high-water 

flow (fig. 7). The evolution of the sulfate derived principally 

from sulfide oxidation is distinct from that derived from Eagle 

Valley Evaporite, and mixing of these two sources is evident from 

this linear relation. It is possible that during high-water flow, an 

additional source contributes to the sulfate, causing the isotopic 

Table 4. Summary of geochemical parameters for the Eagle River 

at Avon.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Eagle River at Avon HW IRR BF

Charge balance (percent) 3 2 17

Conductivity (μS/cm) 100 130 190

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 395 105 100

Percent CR load at Cisco 2 1 1

Ca:SO4 (molar basis) 4.8 2.4 1.9

Na:Cl (molar basis) 0.86 0.98 0.96

Evaporation no no no

SO4 source mineralization

+ evaporites

mineralization

+ evaporites

mineralization

+ evaporites

Table 5. Summary of geochemical parameters for the Eagle River 

at Gypsum.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Eagle River at Gypsum HW IRR BF

Charge balance (percent) 9 –2 –3

Conductivity (μS/cm) 190 360 555

Water type Ca-HCO3 mixed mixed

Load (tonnes solutes/day) 1,310 500 370

Percent CR load at Cisco 8 6 4

Ca:SO4 (molar basis) 2.6 1.6 1.4

Na:Cl (molar basis) 1.3 1.2 1.1

Evaporation no no no

Dominant SO4 source evaporites evaporites evaporites

5

In this report, isotopically lighter refers to a depletion in the heavier isotope (2

H, 18O, or 34S), resulting in a smaller δ value relative to the appropriate 

standard, and conversely, isotopically heavier refers to an enrichment in the 

heavier isotope, resulting in a larger δ value.

composition to deviate from the linear trend. Unfortunately, 

sulfate concentrations were too low in the samples collected 

from the Eagle River at Minturn and Avon during high water to 

analyze for isotopes to confirm this additional source. Isotope 

mass-balance calculations indicate that the source of the dissolved 

sulfate at Avon during irrigation and base flow is 60 percent from 

the upstream source (presumably sulfide oxidation that would be 

consistent with the lighter isotope compositions) and 40 percent 

from evaporites. At Gypsum, 75 percent of the sulfate is from 

evaporites and 25 percent from an upstream source.

Roaring Fork River at 

Glenwood Springs, Colorado

Flow in the Roaring Fork River (fig. 8) is regulated by 

Reudi Reservoir east of the town of Basalt. The geology in 

this watershed is mostly igneous rocks in the headwaters, 

Pennsylvanian and Permian rocks, including evaporites, and 

Cretaceous Mancos Shale in the lower portions of the watershed. The water type at this station is calcium bicarbonate 

during high-water and irrigation flow and a mixed type with 

increasing sulfate and chloride contributions during base flow 

(fig. 4, table 6). During irrigation and base flow, the Ca:SO4

and Na:Cl ratios (table 6) look very similar to those in the 

Colorado River above Glenwood Springs. During high water, 

both ratios are higher, likely due to an increased contribution 

from igneous rocks in the headwaters during runoff (HCO3

contribution is larger as well). The sulfate isotope data (see 

fig. 16 in Geochemical Evolution of the Colorado River Above 

Cisco) fall on a mixing trend of sulfate derived from Eagle 

Valley Evaporite and likely crystalline rocks upstream. Isotope 

measurements show that Mancos Shale contributes little 

sulfate to this river.

Figure 8. Map of Roaring Fork River watershed (no. 3 on fig. 5) 

showing adjacent sampled watersheds. Red dot, station sampled. 

Map modified from http://www.epa.gov/surf/.

Glenwood

Springs

Carbondale

Eagle River

Colorado River

Headwater

North Fork

Gunnison River

Basalt

Aspen

Colorado River

Headwater-Plateau
10 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Gunnison River

The Gunnison River and its tributaries flow through six 

watersheds. Seven stations within four of these watersheds 

were sampled (fig. 9). The flow in the Gunnison River is 

controlled by dams on Taylor River, the mainstream Gunnison 

River, Muddy Creek, and Uncompahgre River.

Uncompahgre River

Uncompahgre River Near Ouray, Colorado

The flow of the water at this station (fig. 9) is not 

controlled by reservoirs upstream. The geology within the 

watershed upstream is volcanic rock that is mineralized in 

places. The conductivities at this station are higher than any 

others in the headwater group and waters are of a different 

type (calcium sulfate instead of calcium bicarbonate; fig. 4, 

table 7). This difference likely reflects the intense mining in 

this area related to Tertiary mineralization in the watershed. 

The volcanic rocks along the Uncompahgre River upstream 

from this station are highly altered with large mining reclamation sites in and along the drainage. Oxidation of sulfide 

ores and dissolution of primary and secondary gypsum in 

ores related to these deposits and alteration zones are likely 

the source of sulfate (see isotope discussion below). Water 

at this station also contains relatively high concentrations of 

dissolved Cd, Co, Cu, Ni, and Zn (only Cd and Zn exceed the 

chronic freshwater maximum contaminant level of 0.25 μg/L 

and 120 μg/L, respectively; EPA, 2006), as well as high 

concentrations of available base-metal concentrations (Cu(avail), 

Fe(avail), Mn(avail), Pb(avail), and Zn(avail)). The metal concentrations 

decrease with distance downstream and are not anomalous 

in the Gunnison River downstream from its confluence with 

the Uncompahgre. The Na:Cl ratios (table 7) are greater than 

one indicating that sodium is probably being derived from the 

volcanic rocks. The Ca:SO4 ratios of near one are consistent 

with sulfate being derived predominately from primary gypsum and/or secondary gypsum that formed following oxidation of sulfides. Pyrite in mineralized areas across the divide 

from the Uncompahgre headwaters has an average δ34Spy of 

Table 6. Summary of geochemical parameters for Roaring Fork 

River at Glenwood Springs.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Roaring Fork River

at Glenwood Springs HW IRR BF

Charge balance (percent) 0.4 –0.6 –3

Conductivity (μS/cm) 250 440 600

Water type Ca-HCO3 Ca-HCO3 mixed

Load (tonnes solutes/day) 1,580 1,010 790

Percent CR load at Cisco 9 12 8

Ca:SO4 (molar basis) 2.2 1.7 1.6

Na:Cl (molar basis) 1.7 1.3 1.2

Evaporation no no no

Dominant SO4 source evaporites evaporites evaporites

–3 per mil, and cogenetic gypsum has an average of 16 per 

mil (Nordstrom and others, 2007) compared to the 2.9 per 

mil in sulfate at our station during high water (fig. 10). From 

high water to irrigation flow to base flow, there is a small, but 

systematic shift to isotopically heavier sulfate (δ34SSO4 = 2.9 

to 4.1 to 6.8 ‰, respectively), accompanied by a similar 

small increase in δ18OSO4 (–4.3 to –3.3 to –1.6 ‰).These data 

suggest that the sulfate in the Uncompahgre River at Ouray 

could be derived from both sulfide oxidation and primary 

gypsum dissolution upstream, with gypsum dissolution 

becoming more important during low stream flow. The isotope 

values at the station may also reflect the input of sulfate in 

Canyon Creek, an upstream tributary, which has a δ34SSO4 of 

7.3 ‰ and a δ18OSO4 value of –1.6 ‰ (Tuttle, unpub. data). A 

change in the proportion of this tributary contribution could 

explain the shift in isotope values among flow conditions. 

Unfortunately, we do not have adequate data to test these 

two hypotheses.

Uncompahgre River Near Ridgway, Colorado

The flow of the Uncompahgre River at this station is 

not controlled by reservoirs. The geology along this reach of 

the Uncompahgre River consists predominantly of Tertiary 

volcanics and Permian, Triassic, and Jurassic sedimentary 

rocks. The marine, Cretaceous age Mancos Shale crops out 

at the downstream end of this stretch of the river. The Ca:SO4

ratio is near one (table 8), suggesting that the source of these 

solutes is gypsum, and the Na:Cl ratios are three or greater, 

indicating that the sodium likely is sourced from the volcanic 

rocks upstream. Ratios are similar under different flow conditions, suggesting that similar sources of solutes are likely. The 

isotope values for dissolved sulfate (fig. 10) are essentially the 

same from high-water flow to irrigation flow and are somewhat lighter than those at Ouray, suggesting a new source 

of sulfate, although the dominant source is still the same as 

at Ouray. This new source of sulfate is the Mancos Shale, 

which contains sulfate with negative δ34SSO4 values (average 

of –21 ‰; Tuttle, unpub. data). During base flow, the isotopes 

in the sulfate evolve to heavier values as seen in the Ouray 

isotopes, reflecting either the change from sulfide to primary 

gypsum as the dominant source in the headwaters or a change 

in the proportion of tributary flow upstream.

Uncompahgre River at Delta, Colorado

The flow of the Uncompahgre River at Delta is controlled 

by a reservoir upstream (below the station near Ridgway and 

just above the town of Colona), and, during high-water flow 

and irrigation conditions, by contributions of water diverted 

for irrigation from the Gunnison River just above the tunnel 

station (see discussion below). The geology in this lower portion of the watershed is dominated by the Cretaceous Dakota 

Sandstone and Mancos Shale. Selenium concentrations exceed 

the Colorado State freshwater chronic standard of 4.6 μg/L 

(CDPHE, 2003) during all flow regimes. The Ca:SO4 ratios 
Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River Above Cisco, Utah 11

are all less than one, and at base flow, fall to 0.7 (table 9). 

The Na:Cl ratios are high and, together with the low Ca:SO4

ratios, suggest that dissolution of sodium sulfate efflorescent 

salts contributes to these solutes. These highly soluble salts are 

common on and in Mancos soils and form during weathering 

when CaSO4 dissolves and Ca exchanges for Na on the marine 

clays (this process in the Mancos Shale is described in Tuttle 

and others, 2005). Although Na-salt dissolution plays a role in 

solute loading at this station, it does not alter the water from a 

predominantly calcium sulfate type. Isotopes of sulfate (–18 to 

–15 ‰; fig. 10) substantiate that the dominant source of sulfate 

is oxidation products from sulfides in the Mancos Shale during 

weathering. Evaporation of irrigation water is reflected in the 

water isotopes (fig. 10).

Figure 9. Maps of upper Gunnison River (no. 4), North Fork of the Gunnison River (no. 5), Uncompahgre River (no. 6), and lower 

Gunnison River (no. 7) watersheds (numbers refer to locations shown on fig. 5) showing adjacent sampled watersheds. The farthest

upstream sample on the Gunnison River (Tunnel station) is 80 miles above confluence with the Colorado River (CR). The Paonia station 

is in the North Fork of the Gunnison watershed and three stations (Ouray, Ridgeway, and Delta stations) are in the Uncompahgre 

watershed. Red dots, stations sampled. Maps modified from http://www.epa.gov/surf/.

San Miguel

River

Upper

Gunnison

River

Lower

Gunnison

River

North Fork

Gunnison River

Delta

Olathe

Montrose

Ridgway

Ouray

Uncompahgre 

River

North Fork

Gunnison River

Lower

Gunnison 

River

Gunnison

Diversion

tunnel

Uncompahgre River Watershed (6)

Lower Gunnison River Watershed (7)

Colorado River 

Headwater/Plateau

Westwater

Canyon

Upper

Dolores 

River

San Miguel

River

Upper

Gunnison

River

North Fork

Gunnison

River

Upper Gunnison River Watershed (4)

Delta

Grand

Junction

Uncompahgre 

River

Clifton

COLORADO

Lower

Dolores 

River

North Fork Gunnison River Watershed (5)

Roaring Fork

River

Colorado River

 Headwater/Plateau

Lower

Gunnison

River

Marble

Hotchkiss

Paonia

Upper Gunnison

River
12 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Geochemical Evolution Along

the Uncompahgre River

The water in the Uncompahgre River is calcium sulfate 

water throughout the entire year (fig. 4). During high water, 

concentrations of dissolved major anions and cations increase 

from the headwaters (Ouray) to the confluence with the 

Gunnison River whereas most trace metals decrease. Available Fe, SiO2

, and Ti increase downstream (table AI–3), but 

few available metal concentrations mirror this trend, suggesting that the metals are not adsorbed to iron, silica, or titanium 

oxides being carried in the river. Between Ridgway and Delta, 

available trace metals (Co, Pb, rare earths, Se, and V) increase 

Table 7. Summary of geochemical parameters for the 

Uncompahgre River near Ouray.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Uncompahgre River

near Ouray HW IRR BF

Charge balance (percent) 21 18 4

Conductivity (μS/cm) 235 395 625

Water type Ca-SO4 Ca-SO4 Ca-SO4

Load (tonnes solutes/day) 96 72 31

Percent CR load at Cisco 1 1 <1

Ca:SO4 (molar basis) 1.0 0.94 0.89

Na:Cl (molar basis) 2.4 2.4 2.5

Evaporation no no no

Dominant SO4 source mineralization mineralization mineralization

Figure 10. Isotope data for the Uncompahgre River including water isotopes for the diversion + reservoir water 

(calculated using isotope mass-balance equations). HW, high-water flow; Irr, irrigation flow; BF, base flow. Hydrogen 

and oxygen isotopes measured relative to V-SMOW and sulfur isotopes relative to V-CDT.

as well as does available Al and Mn. This relation suggests 

that the metals are associated with Al2O3 and MnO2. A similar 

suite of elements increases or (decreases) from Ouray to 

Delta during irrigation season with a few exceptions, notably 

SO4, which only increases from Ridgway to Delta. During 

base flow, most metals, with the exception of Se and available Fe, decrease as the water flows to Delta. The increase of 

SO4 between Ridgway and Delta is still evident during this 

flow period.

Water isotopes (fig. 10) indicate that little evaporation takes place along this reach of the river except between 

Ridgway and Delta during irrigation flow. The starting 

isotopic composition of the irrigation water (diversion + 

reservoir in fig. 10) was estimated with mass-balance calculations using the composition of diversion water (see section on 

Gunnison River below Gunnison Tunnel) and Uncompahgre 

River water at Ridgway. The large isotope shift in water in 

the Uncompahgre River at Delta during the irrigation period 

is due to return of water that has undergone evaporation during 

the irrigation process. Positioning along the GMWL for the 

other data reflects snowmelt runoff versus rain and groundwater discharge. A stream-flow budget (table 10) shows that, 

during high-water and irrigation flow, only 35 to 55 percent 

of the water delivered by diversion and stream flow returns 

to the Uncompahgre River. Although some of the diverted 

water is lost to consumptive use and some is lost as irrigationreturn to the Gunnison River, much of the water is lost through 

–18 –17 –16 –15 –14 –13 –20 –15 –10 –5 0 5 10

δ34SSO4 δ ‰ 18OH20 ‰

–124

–122

–120

–118

–116

–114

–112

–110

–5

–4.5

–4

–3.5

–3

–2.5

–2

–1.5

–1

δ18OSO4 ‰

δ2H ‰

Ridgway, Irr

Ridgway, HW

Ridgway, BF

Ouray, Irr

Ouray, HW

diversion + reservoir

 (calculated)

Delta, Irr Ouray, BF

Delta, HW

Delta, BF

EXPLANATION
Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River Above Cisco, Utah 13

evapotranspiration processes as indicated by its isotopic signature. Some of this loss returns as irrigation water that slowly 

enters the Uncompahgre River as groundwater discharge during base flow, accounting for the nearly four-fold increase of 

flow at Delta compared to that discharged from the Ridgway 

reservoir upstream (no diversion occurred during base flow).

The influence of the Mancos Shale on the evolution of the 

isotopic composition of sulfate in the Uncompahgre River can 

be seen by the smaller decrease in the δ34SSO4 at the Ridgway 

station compared to the Ouray station and the marked decrease 

at the Delta station (fig. 10). The isotope values at the Delta 

station do not change dramatically from one flow condition to 

the next indicating that the Mancos Shale influenced all sampling. Calculations, using isotopic data, estimate that between 

87 and 90 percent of the sulfate load in the Uncompahgre 

River at Delta is released from the Mancos Shale. During 

irrigation-flow conditions, this accounts for 31 percent of the 

Colorado River sulfate load at Cisco; whereas flow during the 

same time only accounts for 10 percent of that at Cisco. The 

evolution of the sulfate data among different flow conditions 

at the other two upstream stations is likely due to a change of 

source (see discussions above).

Gunnison River Below 

Gunnison Tunnel, Colorado

The discharge of the Gunnison River below the Gunnison 

Tunnel is entirely controlled by Crystal Dam on Morrow Point 

Reservoir. During irrigation season, water is diverted to the 

Uncompahgre watershed through the Gunnison Tunnel above 

this station.6 The geology in the watershed above the dam is 

mostly crystalline rocks (metamorphic and volcanic). The 

Ca:SO4 and Na:Cl ratios (table 11) are three times greater than 

expected for dissolution of gypsum and halite, respectively. 

Contributions of Ca and Na from weathering of crystalline 

rocks upstream explain these elevated ratios. The isotopic 

composition of dissolved sulfate at this station (fig. 11) changes 

very little as flow conditions change due to homogenization in 

the two large reservoirs immediately upstream (Morrow Point 

and Blue Mesa). These values likely reflect in part mineralization upstream. In the Lake City area drained by a tributary to 

the Gunnison River, water heavily affected by mineralization 

averages δ34SSO4 = –4 ‰ (Michele Tuttle, unpub. data).

North Fork of the Gunnison River Below

Paonia, Colorado

The flow of water at this station is, in part, controlled by 

the upstream reservoir on Muddy Creek. Most rocks in this watershed are sedimentary in origin and low-sulfur, Tertiary age coal 

is actively mined. Cretaceous Mancos Shale crops out in the 

lowermost portion of the watershed. The moderate Ca:SO4 and 

relatively high Na:Cl ratios (table 12) suggest that dissolution of 

sodium sulfates such as thenardite (Na2SO4) associated with the 

Mancos Shale may contribute solutes to the river, decreasing the 

Ca:SO4 ratio and increasing the Na:Cl ratio. The isotopic composition of the sulfate in the river during base flow (δ34SSO4 = –11 ‰; 

fig. 11) is consistent with a portion of the sulfate derived from 

oxidation of sulfides in marine shale. No sulfate isotope data are 

available for other times of the year, because recovered sulfate 

was too low for analyses.

Lower Gunnison River

Gunnison River at Delta, Colorado

This station is just above the confluence of the Gunnison 

River with the Uncompahgre River in Delta. The geology below 

the Gunnison Tunnel consists of metamorphic rocks about 

halfway to Delta and then Jurassic and Cretaceous sedimentary 

rocks, including the Mancos Shale. Selenium concentrations 

exceed Colorado’s freshwater chronic standard of 4.6 μg/L 

during base flow. During irrigation and base-flow conditions, 

the Ca:SO4 and Na:Cl ratios (table 13) are similar to those of 

the Uncompahgre at Delta, indicating that the Mancos Shale 

contributes significantly to the salt load under these flow 

conditions (also confirmed by sulfate isotopes). Ratios during 

6

The flow of this diversion is considered in the discussion on the 

Uncompahgre River.

Table 8. Summary of geochemical parameters for the Uncompahgre 

River near Ridgeway.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Uncompahgre River

near Ridgway HW IRR BF

Charge balance (percent) –0.1 –2.5 4.9

Conductivity (μS/cm) 420 565 680

Water type Ca-SO4 Ca-SO4 Ca-SO4

Load (tonnes solutes/day) 250 200 100

Percent CR load at Cisco 1 2 1

Ca:SO4 (molar basis) 1.2 1.2 0.94

Na:Cl (molar basis) 3.0 3.4 3.7

Evaporation no no no

Dominant SO4 source mineralization mineralization mineralization

Table 9. Summary of geochemical parameters for the Uncompahgre 

River at Delta.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Uncompahgre River

at Delta HW IRR BF

Charge balance (percent) –3 –3 0.9

Conductivity (μS/cm) 1,070 1,150 1,530

Water type Ca-SO4 Ca-SO4 Ca-SO4

Load (tonnes solutes/day) 935 1,730 760

Percent CR load at Cisco 6 21 8

Ca:SO4 (molar basis) 0.85 0.87 0.68

Na:Cl (molar basis) 8.3 5.7 8.1

Evaporation no yes no

Dominant SO4 source Mancos

Shale

Mancos

Shale

Mancos

Shale
14 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

high water suggest a mixture of solutes from the North Fork 

and solutes picked up from the Mancos Shale (the North Fork 

accounts for 80 percent of the water in the Gunnison River at 

Delta during this period).

Gunnison River Near Grand Junction, Colorado

There are no reservoirs on the Gunnison River between 

Delta and its confluence with the Colorado River. The geology in 

the area consists predominantly of Cretaceous Mancos Shale and 

Dakota Sandstone and some Jurassic and Triassic sedimentary 

rocks. During high-water flow, conductivities increase relative to 

those at Delta indicating an addition of salts. During base flow, 

conductivities are lower (table 14) than at the upstream station at 

Delta 715 compared to 1,080 μS/cm indicating that more dilute 

water is entering the river from tributaries downstream from 

Delta. The Ca:SO4 and Na:Cl ratios (table 14) at all times are 

Table 10. Stream flow, total salt load, and SO4 load for irrigation water diverted from the Gunnison River (Diversion), the Uncompahgre 

River below reservoir (Reservoir), and for the Uncompahgre River (UR) at Delta. Diversion flows provided by Paul Davidson, Bureau of 

Reclamation (written commun., 2007 ); reservoir release estimated with data for the USGS Uncompahgre River flow-gaging station at 

Colona below the reservoir (data available at http://waterdata.usgs.gov/nwis/uv?09147500). Gain/(loss) was calculated by subtracting 

the actual flow measured at Delta (UR, Delta) from the sum of Diversion and Reservoir (predicted flow). Gain/loss is then reported as the 

percentage of predicted flow (diversion plus reservoir).

Flow Diversion

cfs

Reservoir

cfs

UR, Delta

cfs

Gain/(loss) cfs,

Delta

Percent

predicted flow

High water 865 480 470 (875) –65

Irrigation 940 450 765 (625) –45

Base flow 0 50 240 190 +380

Total

salt load

Diversion

tonnes/day1

Reservoir

tonnes/day2

UR, Delta

tonnes/day

Diversion + reservoir 

tonnes/day

Gain

tonnes/day

High water 330 435 935 765 170

Irrigation 370 405 1,730 775 955

Base flow 0 45 760 45 715

Sulfate

load

Diversion

tonnes/day1

Reservoir

tonnes/day2

UR, Delta

tonnes/day

Diversion + reservoir

tonnes/day

Gain

tonnes/day

High water 38 190 430 230 200

Irrigation 44 175 790 220 570

Base flow 0 20 380 20 360

1

Chemistry for diversion water is discussed in the section below on the Gunnison River below the Gunnison Tunnel.

2

No chemistry was available for water released from the dam so compositional averages of the water during the three flow conditions (weighted with respect 

to flow) at the Ridgway station (major contributor to the reservoir) were used for the released water (averages: 160 mg/L SO4 and 370 mg/L total dissolved 

solids). Use of these averages is based on the hypothesis that the reservoir tends to homogenize heterogeneity related to seasonal flow.

Table 11. Summary of geochemical parameters for the Gunnison 

River below Gunnison Tunnel.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Gunnison River

below tunnel HW IRR BF

Charge balance (percent) –7 –0.4 25

Conductivity (μS/cm) 195 205 200

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 275 205 240

Percent CR load at Cisco 2 3 3

Ca:SO4 (molar basis) 3.3 3.3 2.8

Na:Cl (molar basis) 3.8 3.6 3.2

Evaporation no no no

Dominant SO4 source mineralization mineralization mineralization

similar to those in the Gunnison River at Delta; however, during 

high water, there is likely a greater contribution of Na and SO4

from the Mancos than recorded in the ratios at Delta. The δ34SSO4

values are around –17 ‰ and point to the Mancos Shale as the 

dominant source of sulfate (fig. 11).

Geochemical Evolution Along 

the Gunnison River

During all three flow regimes, the North Fork of the 

Gunnison and the Gunnison River below the tunnel are calcium 

bicarbonate water types; however, the North Fork water trends 

more toward Mg and Na than the tunnel water (fig. 4). At the 

Delta station and downstream, the Gunnison River becomes 

a calcium sulfate water type as it picks up sulfate from the 

Mancos Shale. During high-water flow, the total solute load 

in the Gunnison River doubles from the North Fork station 

to the Delta station and nearly doubles again to the Grand 

Junction station (table AII–1). These increases are much larger 

than can be explained from the sum of solutes from upstream 

stations, indicating that additional solutes are acquired through 

groundwater and other tributary input. The same pattern is 

observed during irrigation and base flow in the Gunnison River 

at Delta. At the station near Grand Junction, the solute load is less 

than the sum of solutes in the Gunnison River at Delta and in the 

Uncompahgre River at Delta, indicating that some of the load 

has been removed by diversion or alluvium recharge prior to the 

inflow of the more dilute water discussed above.

During high-water flow, available metal concentrations 

(table AI–3) are much higher in the North Fork than in the 

Gunnison River at the tunnel because the water at the tunnel 

is being directly released from Crystal Dam and does not 
Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River Above Cisco, Utah 15

transport sediment with oxide coatings. The sediment transported in the North Fork consists of detrital components 

rich in resistate minerals containing Ba, rare earths, Sc, Si, 

and Ti and in oxides and oxide coatings rich in Al, Fe, Mn, 

and adsorbed metals such as Cd, Co, Cr, Cu, Ni, V, and Zn. 

Although Al(avail) and Fe(avail) concentrations decrease some 

between Delta and Grand Junction, most trace-metal available concentrations remain similar to concentrations upstream. 

Except for the Uncompahgre River at Delta during irrigation 

flow, metal concentrations drop dramatically after high flow, 

indicating that these metals preferentially are transported in 

the Gunnison River in the spring runoff adsorbed onto aluminum and iron oxides.

Although most of the water isotopes cluster around the 

meteoric water line, evaporation is evident in the Uncompahgre 

River at Delta during irrigation flow (fig. 11). The water isotopes 

on the North Fork of the Gunnison during base flow is above the 

GMWL. This relative increase in δ2H relative to δ18OH20 often 

accompanies methanogenesis. Methanogenesis feasibly could 

occur in this watershed because of the occurrence of coal, however, this explanation is highly speculative.

The sulfate oxygen isotope data occur in a very narrow range (–3 to –1 ‰) (fig. 11). Conversely, the sulfur 

isotopes span a fairly broad range (–19 to –3 ‰). The δ34SSO4

values in water at the Gunnison Tunnel are a result of the 

Figure 11. Isotope data for the Gunnison River, North Fork, lowermost station on the Uncompahgre River, and 

calculated δ2H and δ18O values for irrigation water in the Uncompahgre watershed. HW, high-water flow; Irr, 

irrigation flow; BF, base flow; GR, Gunnison River; NF, North Fork of the Gunnison River; UR, Uncompahgre River. 

Hydrogen and oxygen isotopes reported relative to V-SMOW and sulfur isotopes relative to V-CDT.

–16.5 –16 –15.5 –15 –14.5 –14 –13.5 –13 –22 –20 –18 –16 –14 –12 –10 –8 –6 –4 –2

δ18OH20 ‰ δ34SSO4 ‰

–120

–118

–116

–114

–112

–110

–108

–106

–104

–102

–5

–4

–3

–2

–1

0

δ2H ‰

δ18OSO4 ‰

UR-Delta, Irr

UR-Delta, BF UR-Delta, HW

NF, HW NF, Irr

GR-Grand Jct., Irr NF, BF

GR-Grand Jct., BF GR-Grand Jct., HW

GR-Tunnel, HW GR-Tunnel, Irr

GR-Delta, Irr GR-Tunnel, BF

GR-Delta, BF GR-Delta, HW

Diversion. + reservoir

 (calculated)

EXPLANATION

Table 12. Summary of geochemical parameters for the North 

Fork of the Gunnison River below Paonia.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

North Fork of the

Gunnison below Paonia HW IRR BF

Charge balance (percent) –0.8 –11 9

Conductivity (μS/cm) 115 170 310

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 1,210 240 145

Percent CR load at Cisco 7 3 2

Ca:SO4 (molar basis) 4.9 2.1 2.0

Na:Cl (molar basis) 2.9 9.3 4.5

Evaporation no no no

Dominant SO4 source no data no data Mancos Shale

+ ?

geology upstream including mineralization in the Lake City 

area (δ34SSO4 of –4 ‰). Sulfate in the Gunnison River downstream from the tunnel is derived mostly from sulfate salts 

in the Mancos Shale (δ34SSO4 average of –21 ‰). Sulfate in 

the North Fork was insufficient for isotopic analyses during 

high-water and irrigation-flow conditions. The isotopic 

composition during base flow indicates a mixture of sulfate 

from the Mancos Shale and another source, possible Tertiary 

coal upstream of the station (no sulfur isotopic composition 

of sulfur in such coal was available).
16 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Dolores and San Miguel Rivers

Maps of the watersheds of the Dolores River are in 

figure 12. The San Miguel River is the only major tributary 

to the Dolores River. The flow of the Dolores River is largely 

controlled by the McPhee Reservoir upstream from the 

Dolores-San Miguel confluence.

San Miguel River at Uravan, Colorado

The flow of water at this station (fig. 12) is partially 

affected by small reservoirs upstream (for example, Taylor Lake, 

a damned natural lake near the headwaters). The watershed 

(fig. 12) is underlain by volcanic rocks near the headwaters and 

Pennsylvanian to Jurassic and Cretaceous rocks in the lower portion. Mancos Shale crops out in some tributaries along the entire 

stretch of the river. The Ca:SO4 and Na:Cl ratios (table 15) look 

similar to those in the Uncompahgre near the Ridgway station. 

Tributaries to the Uncompahgre from the west drain similar rocks 

as the San Miguel in the upper portion of its watershed. The 

Ca:SO4 ratios drop to one or below after high-water flow suggesting that gypsum dissolution alone controls these solutes. Under 

all three flow conditions, the sulfate isotopes (fig. 13) are slightly 

lighter than those for sulfate in the Dolores River headwaters, 

suggesting that there may be a small component of sulfate derived 

from the Mancos Shale. However, most of the sulfate is derived 

Table 13. Summary of geochemical parameters for the Gunnison 

River at Delta.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Gunnison River

at Delta HW IRR BF

Charge balance (percent) –3 –4 0.6

Conductivity (μS/cm) 280 900 1,080

Water type Ca-HCO3 Ca-SO4 Ca-SO4

Load (tonnes solutes/day) 3,310 1,630 1,910

Percent CR load at Cisco 19 20 20

Ca:SO4 (molar basis) 1.3 0.84 0.72

Na:Cl (molar basis) 4.4 7.2 7.2

Evaporation no no no

Dominant SO4 source Mancos

Shale

Mancos

Shale

Mancos

Shale

Table 14. Summary of geochemical parameters for the Gunnison 

River near Grand Junction.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Gunnison River near

Grand Junction HW IRR BF

Charge balance (percent) 4 4 4

Conductivity (μS/cm) 455 855 715

Water type Ca-SO4 Ca-SO4 mixed

Load (tonnes solutes/day) 5,150 2,540 2,090

Percent CR load at Cisco 30 31 22

Ca:SO4 (molar basis) 1.1 0.88 0.81

Na:Cl (molar basis) 7.4 6.5 5.2

Evaporation no no no

Dominant SO4 source Mancos

Shale

Mancos

Shale

Mancos

Shale

from weathering of mineralized rocks in the upper portion of the 

watershed, similar to those that supply sulfate in the headwaters 

of the Uncompahgre and Dolores Rivers.

Dolores River at Dolores, Colorado

The flow of water at this station is not regulated by any 

significant reservoirs upstream. The geology in the watershed 

upstream is varied with predominantly Pennsylvanian and 

Permian sedimentary rocks. During high-water flow, the water 

is a calcium bicarbonate type (fig. 4) with a high Ca:SO4 ratio 

(table 16) that decreases during irrigation and base flow. Similar δ34SSO4 values during all flow conditions suggest a common 

source of sulfate (fig. 13). These isotope values are similar 

to those in the Animas watershed (average δ34Spyrite of –3 ‰; 

Nordstrom and others, 2007), a parallel drainage to the east 

that is extensively mineralized.

Dolores River at Bedrock, Colorado

The flow of this stretch of the river is controlled by 

McPhee Reservoir. The dominant geologic unit at the 

Bedrock station is the Paradox Formation of the Hermosa 

Group, which contains beds of anhydrite, halite, and some 

potash. Similar rocks are exposed in the Gypsum Valley 

upstream. The Mancos Shale is aerially extensive in the 

Disappointment Creek catchment, which drains into the 

Dolores River upstream from Bedrock in the spring and 

intermittently during monsoon season in the late summer 

(G. Breit, oral commun., 2007). The Dolores River water at 

Bedrock transitions from a Ca-HCO3 type during high water 

to a Na-Cl water during irrigation and base-flow conditions 

(fig. 4). This transition is likely due to a large release of water 

from the McPhee Reservoir during high spring runoff (2,000 

to more than 4,000 cfs; May through June, 2004) compared 

to very low release during the rest of the year (<100 cfs) 

(http://www.usbr.gov/uc/wcao/water/rsvrs/ds/mcphee.html). 

No chemistry is available between McPhee Reservoir and 

Bedrock, so an average of chemistry for all three flow conditions, weighted with respect to flow at the Dolores station, was 

used as the composition of reservoir outflow. The Ca:SO4 ratio 

(table 17) is greater than one indicating that Ca has an additional source other than dissolution of gypsum in the Mancos 

Shale or anhydrite in the Paradox Formation. The Na:Cl ratio 

during high water is greater than one, indicating that halite dissolution is not the sole Na source; dissolution of sodium sulfates in the Mancos Formation in Disappointment Valley may 

contribute to the increase. During irrigation and base flow, as 

the water type changes to a Na-Cl water (fig. 4), the Na:Cl 

ratio is essentially one (table 17), indicating that the primary 

source of solutes under these flow conditions is dissolution of 

halite in the Paradox Formation. The sulfur isotopic composition varies systematically among high-water, irrigation, 

and base-flow conditions (fig. 13). During high-water flow, 

δ34SSO4 is isotopically light (–13 ‰). Mixing of the sulfate 

in the Dolores River at Dolores (δ34SSO4 = –3.4 ‰) with the 

increased load acquired along the flow to Bedrock, supports 
Geochemistry at Stations Along Tributary Watersheds to the Upper Colorado River Above Cisco, Utah 17

Dolores River Near Cisco, Utah

The confluence of the Dolores River with the Colorado 

River is just upstream from our most downstream Colorado River 

station near Cisco. There are no dams on the Dolores River downstream from Bedrock to this station; however, intercept of shallow 

saline ground water in the Paradox Valley and injection into deep 

wells occurs to help decrease the flow of salt to the Colorado 

River. This interception/injection is part of the Colorado River 

Basin Salinity Control Program Paradox Valley Unit operated 

by the Bureau of Reclamation. The unit was designed to remove 

128,000 tons of salt annually (62 percent of the salt released to 

the Dolores River from the Paradox Formation as it crosses the 

Paradox Valley; http://www.usbr.gov/dataweb/html/paradox.html). 

Chafin (2003) reports that 90 percent of the salt between 1988 

and 2001 was removed.

The water at the Cisco station is a calcium bicarbonate type 

during high-water flow, a mixed type during irrigation flow, and 

a sodium chloride type during base flow (fig. 4). During highwater flow, the Ca:SO4

 and Na:Cl ratios (table 18) look similar 

to those in the river at Bedrock. During irrigation and base-flow 

conditions, both Ca:SO4 and Na:Cl ratios approach one, suggesting that the primary sources of solutes are gypsum/anhydrite 

dissolution and halite dissolution. The halite is derived from the 

Paradox Formation. The isotopes of sulfate (fig. 13) indicate 

that the source of the sulfate is a mixture from the Mancos Shale 

(dominant source), anhydrite from the Paradox Formation, and 

mineralization upstream.

Figure 12. Map of the upper and lower Dolores River watersheds 

and the San Miguel River watershed showing adjacent sampled 

watersheds. Red dots, stations sampled. Black dashed line 

is the border between Utah and Colorado. Maps modified from 

http://www.epa.gov/surf/.

the hypothesis that the sulfate during high-water flow in the 

Dolores River at Bedrock is a mixture of that from upstream 

(45 percent) and from the Mancos Shale (55 percent). During 

irrigation, the δ34SSO4 value increases significantly to 2.3 ‰, 

suggesting that dissolution of anhydrite in the Paradox 

Formation (δ34SSO4 of 13 ‰; Claypool and others, 1980; Tuttle 

and others, 1996) contributes to the sulfate mix. This result is 

consistent with dissolution of halite in related evaporite beds 

during this time of year. The base flow δ34SSO4 value decreases 

to –1.2 ‰, indicating that anhydrite contributes a smaller 

proportion of sulfate during this time of the year.

Westwater

Canyon

Lower 

Gunnison River

Upper 

Dolores River

Lower

Dolores River

San Miguel

River

Lower 

Gunnison River

Uncompahgre

River

Nucla

Naturita

Lower

Dolores River

Upper

Dolores River

Telluride

Upper Dolores River Watershed (9)

San Miguel River Watershed (10)

Lower 

Gunnison River

San Miguel

River

Uncompahgre

River

UTAH

COLORADO UTAH

COLORADO

Nucla

Dolores

Bedrock

Cortez

Olatha

Lower Dolores River Watershed (11)
18 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Geochemical Evolution Along the Dolores River

Below the Dolores station, the water type of the Dolores 

River changes during the year from a calcium bicarbonate 

type during high water to a mixed or sodium chloride type 

during irrigation and base flow (fig. 4). This change reflects 

the input of solutes from salts derived from the Mancos 

Shale and Paradox Formation. During high water, transported 

sediment consists of components rich in resistate minerals 

containing Ba, rare earths, Si, and Ti, and in oxides and oxide 

Table 15. Summary of geochemical parameters for the San Miguel 

River at Uravan.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

San Miguel River

at Uravan HW IRR BF

Charge balance (percent) –0.9 –1 0.8

Conductivity (μS/cm) 350 565 750

Water type Ca-HCO3 Ca-SO4 Ca-SO4

Load (tonnes solutes/day) 800 220 205

Percent CR load at Cisco 5 3 2

Ca:SO4 (molar basis) 1.5 1.0 0.92

Na:Cl (molar basis) 2.8 3.1 3.0

Evaporation no no no

Dominant SO4 source mineralization mineralization mineralization

Figure 13. Isotope data for the Dolores and San Miguel Rivers. HW, high-water flow; Irr, irrigation flow; BF, base 

flow; SM, San Miguel River; DR, Dolores River. Hydrogen and oxygen isotopes reported relative to V-SMOW and 

sulfur isotopes relative to V-CDT.

coatings rich in Al, Fe, and Mn, and adsorbed metals such 

as Cd, Co, Cr, Cu, Ni, V, and Zn (table AI–3). During the 

irrigation season, the Dolores River below McPhee Reservoir 

is also high in many of these available metals even though 

the flow has decreased dramatically. This is especially evident 

at the Bedrock station. The cause for the transport of sediment in the Dolores during such low-flow conditions is not 

readily apparent.

Figure 13 shows that most of the water in the Dolores 

River falls on the GMWL with respect to its isotopic composition. The small deviation of water at Bedrock and Cisco 

during irrigation flow suggests that the water has undergone 

some evaporation.

The isotopes of sulfate in the San Miguel River at Uravan 

and the Dolores River at Dolores are similar and largely controlled by mineralization in the upper portion of these watersheds 

(fig. 13); however, in the San Miguel watershed, dissolution of 

salts in the Mancos Shale soil contribute a small proportion of 

the sulfate. The influence of the Mancos Shale in the vicinity of 

Disappointment Valley during high-water flow and the Paradox 

Formation evaporites in the Paradox Valley during irrigation flow 

is evident in the Dolores River at Bedrock. The composition of 

sulfate in the Dolores River near Cisco is a mixture of the sulfate 

in the river at Bedrock and the sulfate in the San Miguel River.

–16 –15 –14 –13 –12 –11 –10 –14 –12 –10 –8 –6 –4 –2 0 2 4

δ34SSO4 δ18OH20 ‰ ‰

–3

–2

–1

0

1

2

3

4

5

6

–110

–105

–100

–95

–90

–85

δ18OSO4 ‰

δ2H ‰

SM-Uravan, HW SM-Uravan, Irr

DR-Cisco, Irr SM-Uravan, BF

DR-Cisco, BF DR-Cisco, HW

DR-Bedrock, HW DR-Bedrock, Irr

DR-Delores, Irr DR-Bedrock, BF

DR-Delores, BF DR-Delores, HW

EXPLANATION
Geochemistry in Main StemColorado River Above Cisco, Utah 19

Table 16. Summary of geochemical parameters for the Dolores 

River at Dolores.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Dolores River

at Dolores HW IRR BF

Charge balance (percent) 4 –1 –6

Conductivity (μS/cm) 155 265 330

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 1,160 115 71

Percent CR load at Cisco 7 1 <1

Ca:SO4 (molar basis) 6.3 3.2 3.0

Na:Cl (molar basis) 1.2 1.3 1.3

Evaporation no no no

Dominant SO4 source mineralization mineralization mineralization

Table 17. Summary of geochemical parameters for the Dolores 

River at Bedrock.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Dolores River

at Bedrock HW IRR BF

Charge balance (percent) 0.9 2 –4

Conductivity (μS/cm) 400 1,510 1,010

Water type Ca-HCO3 Na-Cl Na-Cl

Load (tonnes solutes/day) 930 175 69

Percent CR load at Cisco 5 2 <1

Ca:SO4 (molar basis) 2.1 1.8 2.5

Na:Cl (molar basis) 1.6 .95 1.0

Evaporation no yes yes

Dominant SO4 source Mancos

Shale

Paradox

Formation

Paradox Formation 

+ Mancos Shale

Geochemistry in Main Stem

Colorado River Above Cisco, Utah

Maps of the main stem Colorado River watersheds sampled in this study are shown in figure 14. Also included in this 

discussion section is Plateau Creek, a tributary to the Colorado 

River within the Colorado River headwater-plateau watershed.

Colorado River Near Kremmling, Colorado

The Colorado River near Kremmling station is located in 

the upper portions of the Colorado River headwater watershed 

(fig. 14). The composition of the water sampled at this station 

is considered the Colorado River headwaters natural baseline for this study as the station is the farthest upstream site 

sampled and is the least impacted by anthropogenic activities, 

although there are five major reservoirs located upstream. The 

similarity in conductivities during irrigation and base flow 

indicates minimal influence from irrigation in this watershed.

The dominant geology in this and tributary watersheds

is igneous and metamorphic rocks; however, there are some 

exposures of Permian, Jurassic, Cretaceous, and Tertiary 

Table 18. Summary of geochemical parameters for the Dolores 

River near Cisco.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Dolores River,

Cisco HW IRR BF

Charge balance (percent) –0.2 7 –4

Conductivity (μS/cm) 375 1,070 1,750

Water type Ca-HCO3 mixed Na-Cl

Load (tonnes solutes/day) 1,280 445 535

Percent CR load at Cisco 8 5 6

Ca:SO4 (molar basis) 1.8 0.96 1.3

Na:Cl (molar basis) 1.7 0.89 1.1

Evaporation no yes no

Dominant SO4 source Mancos

Shale

Paradox

Formation

Paradox Formation

+ Mancos Shale

sedimentary rocks. This station has calcium bicarbonate 

water (fig. 4) with Ca:SO4 and Na:Cl ratios varying little 

throughout the year (table 19). Ratios of Ca:SO4 and Na:Cl 

are two or greater and consistent with crystalline rock sources 

that release bicarbonate as well as these cations. The δ34SSO4

values of dissolved sulfate (see fig. 16 in Geochemical 

Evolution of the Colorado River Above Cisco) at this station 

vary little with changing flow conditions and are intermediate 

at about –5 ‰; however, the δ18OSO4 is larger during high flow. 

The δ34SSO4 and δ18OSO4 values during base flow (see fig. 16 in 

Geochemical Evolution of the Colorado River Above Cisco) 

are assumed to be the starting composition of sulfate in the 

Colorado River.

Colorado River Above

Glenwood Springs, Colorado

The Colorado River above Glenwood Springs station is 

downstream from the confluence of the Colorado River with the 

Eagle River (fig. 14). There are no dams on the Colorado River 

between Kremmling and this station. Hot springs occur and 

discharge water along a portion of the Colorado River upstream 

from this station. As was the case at the Kremmling station, 

there is no influence due to irrigation as observed in the similar 

conductivities during irrigation and base flow.

The geology along the stretch of the Colorado from 

Kremmling halfway to this station consists mostly of igneous 

and metamorphic rocks. From that point downstream to the 

sampling station, sedimentary rocks of Cambrian through 

Permian age dominate; they include the Eagle Valley Evaporite 

and mudstones/sandstones of the Maroon Formation. Some 

Cretaceous Mancos Shale and Dakota Sandstone also crop out. 

The water is a calcium bicarbonate type during high-water flow 

and a mixed type during other flow conditions, moving more 

toward a sodium chloride type water during base flow (fig. 4). 

This change reflects the high content of Na and Cl in the hot 

spring water, which is overwhelmingly a sodium chloride water 
20 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

type (Glenwood Springs (GW) hot spring data in table AI–3 and 

in Eisenhauer, 1983). The trends in the Ca:SO4 and Na:Cl ratios 

(table 20) throughout the year mimic those in the Eagle River at 

Gypsum, suggesting that the source of the additional salts to the 

Colorado River (fig. 3) are similar to those to the downstream 

portion of the Eagle River. Sulfur isotopic compositions (see 

fig. 16 in Geochemical Evolution of the Colorado River Above 

Cisco) suggest a mixture of two sources of sulfate during irrigation and base flow—that inherited from the Kremmling station 

and a major contribution from the Eagle Valley Evaporite. 

Colorado River Near Cameo, Colorado

The Colorado River below the station above Glenwood 

Springs is not controlled by any large reservoirs; however, in 

Glenwood Canyon, the water is diverted and returned to the 

river to generate hydroelectric power. The Roaring Fork River 

and numerous hot springs enter the Colorado River upstream 

from this station. The geology along this stretch of the river 

changes from Mississippian limestone and metamorphic 

rocks in Glenwood Canyon to Tertiary rocks of the Wasatch 

and Green River Formations, which are variegated nonmarine mudstone and lacustrine oil shale, respectively, to the 

Cretaceous coal-bearing Mesaverde Formation in De Beque 

Canyon just above Cameo. The water at this station is a 

calcium bicarbonate type during high-water flow and a mixed 

type during the rest of the year as it picks up greater proportions of sodium and chloride from Eagle Valley Evaporite 

(fig. 4). The Ca:SO4and Na:Cl ratios (table 21) are very 

similar to those in the Colorado River at the station above 

Glenwood Springs.

Sulfur isotopes (see fig. 16 in Geochemical Evolution 

of the Colorado River Above Cisco) are similar to those in 

the Roaring Fork during high-water flow and to those at 

the station above Glenwood Springs during irrigation and 

base-flow conditions. The isotopic data combined with the 

sulfate load data have been used to estimate the sulfate isotopic composition of all sulfate unaccounted for in table 22. 

Sulfate from this unknown source(s) has an isotopic signature of 7.1, 3.4, and 6.5 ‰ during high-water, irrigation, and 

base-flow conditions, respectively (table 22). Possibilities 

that may contribute in varying proportions to this unknown 

sulfate load are sulfate in mudstones of the Wasatch Formation 

(–13 to –40 ‰; Tuttle, unpub. data) and oxidized sulfides in 

the Green River Formation (average 15 to 35 ‰; Tuttle and 

Goldhaber, 1993), both of which crop out along the river 

and in tributary watersheds through this stretch; sulfur in the 

Mesaverde Formation that crops out in De Beque Canyon and 

associated tributaries (1.5 to 3.5 ‰; table AIII–3); sulfate in 

ground water associated with the abandoned Rifle Uranium 

Mill sites (–6.5 to 2.4 ‰; table AI–3); and, possibly, produced 

water related to gas drilling (unknown isotopic composition). Additional detailed sampling along this stretch would 

be needed to quantify relative contributions from these 

possible sources.

Figure 14. Maps of Colorado River (CR) headwater (no. 1 on 

fig. 5), Colorado River headwater-plateau and Westwater Canyon 

watersheds (nos. 8 and 12, respectively on fig. 5) showing 

adjacent sampled watersheds. Black dashed line is the border 

between Utah and Colorado. Red dots, stations sampled. Maps 

modified from http://www.epa.gov/surf/.

Colorado River Headwater Watershed (1)

Roaring 

Fork River

Eagle

River

Kremmling

Granby

Glenwood

Springs

CR

HeadwaterPlateau

Grand

Junction

Glenwood

 Springs

North Fork

Gunnison

River

Westwater

Canyon

Roaring 

Fork

River

CR Headwater

Clifton

Rifle

Lower

Gunnison

River

Colorado River Headwater-Plateau (8)

Westwater Canyon (12)

Lower 

Gunnison

River

CR HeadwaterPlateau

Lower

Dolores

River

UTAH COLORADO

UTAH COLORADO

Fruita
Geochemistry in Main StemColorado River Above Cisco, Utah 21

Plateau Creek Near Cameo, Colorado

The flow of Plateau Creek is controlled, in part, by several small reservoirs. The geology upstream is predominantly 

mudstones of the Tertiary Wasatch Formation and basalt. The 

water is calcium bicarbonate type during high-water flow 

and a mixed type during other times of the year (fig. 4) with 

a greater proportion of magnesium, but the dominant anion 

remains HCO3, consistent with weathering of basaltic material. 

The Ca:SO4 and Na:Cl ratios (table 23) are high, also consistent with weathering of basalt. Isotopes of sulfate (see fig. 16 

in Geochemical Evolution of the Colorado River Above Cisco) 

do not vary and are similar to those in the Colorado River 

near Kremmling during high water and in the Dolores River at 

Dolores during irrigation and base flow; the dominant geology 

upstream from these two stations is also crystalline rocks, the 

likely source of this signature.

Colorado River Near Colorado-Utah State Line

The flow of the river downstream from Cameo is not 

dramatically affected by reservoirs; however, during irrigationflow conditions, water diversion and return occurs. The 

Gunnison River is a major tributary entering along this stretch. 

The river below Cameo enters the Grand Valley where intense 

Table 19. Summary of geochemical parameters for the Colorado 

River near Kremmling.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Colorado River,

Kremmling HW IRR BF

Charge balance (percent) 24 –2 3

Conductivity (μS/cm) 140 210 200

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 310 365 280

Percent CR load at Cisco 2 4 3

Ca:SO4 (molar basis) 2.2 2.6 2.2

Na:Cl (molar basis) 2.6 2.0 2.4

Evaporation no no no

Dominant SO4 source various

sources

various

sources

various

sources

Table 20. Summary of geochemical parameters for the Colorado 

River above Glenwood Springs.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Colorado River,

Glenwood Springs HW IRR BF

Charge balance (percent) 7 –4 7

Conductivity (μS/cm) 250 515 565

Water type Ca-HCO3 mixed mixed

Load (tonnes solutes/day) 3,180 1,570 1,460

Percent CR load at Cisco 19 19 15

Ca:SO4 (molar basis) 3.0 2.0 1.7

Na:Cl (molar basis) 1.4 1.2 1.2

Evaporation no no no

Predominant SO4 source evaporites evaporites evaporites

agricultural irrigation occurs. The Mancos Shale is the predominant rock in the valley with overlying Tertiary terrestrially 

deposited rocks high in the tributary drainages. The water type 

is mixed (fig. 4); however, during high-water flow, the river 

is closer to a calcium bicarbonate type, and during irrigation 

and base flow, sodium and sulfate occur in greater proportions. Selenium concentrations are at the State of Colorado's 

freshwater chronic standard of 4.6 μg/L during the three flow 

regimes (table AI–3). The Ca:SO4 ratio (table 24) decreases to 

one during irrigation and base flow, suggesting that dissolution 

of gypsum occurs during these flow conditions. The Ca:SO4

ratio is slightly higher than one during high-water flow and is 

likely due to a mixture of higher ratios in upstream Colorado 

River water and ratios of about one in Gunnison River water. 

The Na:Cl ratios are near two (table 24), reflecting the high 

ratios in the Gunnison River and Plateau Creek. Isotopes of 

sulfate (see fig. 16 in Geochemical Evolution of the Colorado 

River Above Cisco) support a mixture of sulfate derived from 

dissolution of salts in the Mancos Shale and sulfate derived 

upstream from the Grand Valley (Colorado River near Cameo).

Colorado River Near Cisco, Utah

The Dolores River enters the Colorado River upstream 

from our most downstream sampling station on the Colorado 

River (near Cisco). There are no reservoirs along this 

stretch of the Colorado River. In this area, the geology is 

dominated by Jurassic and Triassic sedimentary rocks. The 

Mancos Shale does crop out in some of the smaller tributary 

drainages to the north of the river. The water is a mixed type 

throughout the year (fig. 4). Additional loading of solutes 

from the State-line station to this station is due to input from 

the Dolores River and is most evident during high-water 

flow and is relatively insignificant during other times of the 

year. During high water, the Ca:SO4 ratio (table 25) at this 

station is lower than in the Dolores River (table 18) and at 

the State-line station (table 24). The sulfate isotopes during 

high-water flow (see fig. 16 in Geochemical Evolution of the 

Colorado River Above Cisco) are within the range expected 

for mixing of the Dolores River and upstream Colorado River 

waters, so the additional sulfate would have to be from a 

Table 21. Summary of geochemical parameters for the Colorado 

River near Cameo.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Colorado River,

Cameo HW IRR BF

Charge balance (percent) –2 –2 –0.4

Conductivity (μS/cm) 395 525 920

Water type Ca-HCO3 mixed mixed

Load (tonnes solutes/day) 7,450 4,170 3,870

Percent CR load at Cisco 44 51 40

Ca:SO4 (molar basis) 2.3 1.8 1.4

Na:Cl (molar basis) 1.4 1.3 1.3

Evaporation no no no

Predominant SO4 source ? (see text) evaporites evaporites
22 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Table 22. Sulfate loads and isotopic composition of contributions between the stations above Glenwood Springs and near Cameo on 

the upper Colorado River.

[HW, high-water flow; Irr, irrigation flow; BF, base flow; CR, Colorado River; V-CDT, Vienna Cañon Diablo Troilite]

Station

SO4 load

(tonnes/day)

δ34SSO4 ‰

(V-CDT)

HW Irr BF HW Irr BF

Colorado River above Glenwood Springs1 360 295 245 2.3 6.0 6.7

Hot springs, Glenwood Springs 352 352 352 15.3 15.3 15.3

Roaring Fork, Glenwood Springs 335 255 215 7.2 8.9 9.5

Colorado River near Cameo 1,160 775 700 5.9 6.7 7.9

Unknown source 430 190 205 7.1 3.4 6.5

1

Includes sulfate load from hot springs near Dotsero.

2

Calculated from data in Eisenhaur (1983) and from this study. Flow and composition of spring water are assumed to be constant during the year.

Table 23. Summary of geochemical parameters for Plateau Creek 

near Cameo.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Plateau Creek,

Cameo HW IRR BF

Charge balance (percent) 1 3 2

Conductivity (μS/cm) 195 520 590

Water type Ca-HCO3 Ca-HCO3 Ca-HCO3

Load (tonnes solutes/day) 575 175 190

Percent CR load at Cisco 3 2 2

Ca:SO4 (molar basis) 5.5 3.8 2.8

Na:Cl (molar basis) 5.8 7.5 7.7

Evaporation no no no

Predominant SO4 source Basalt Basalt Basalt

similar source as that in the Dolores and upstream Colorado 

Rivers. The Na:Cl ratios (tables 18, 24, and 25) indicate that 

dissolution of sodium sulfates similar to those found upstream 

may be added along this river stretch explaining the anomalously low Ca:SO4

 ratio.

Geochemical Evolution of the Colorado River 

Above Cisco

In the headwaters of the upper Colorado River, the water 

is a Ca-HCO3 type (fig. 4). The water type does not change 

dramatically during high-flow conditions. During irrigation 

and base flow, however, the water evolves toward a calcium 

chloride type as it flows through the Eagle Valley Evaporite 

and toward a calcium sulfate type as it flows through the 

Mancos Shale. From its headwaters to the station near Cisco, 

Utah, the conductivity of the Colorado River throughout 

our sampling transect increases between 3.4 and 6 times, 

while the load increases between 22 and 50 times (fig. 15). 

The load during high-water flow is much greater than during 

other times of the year because the flow is so much greater; 

loads during irrigation and base flow are nearly identical. 

The Gunnison River during high-water flow adds the greatest 

load to the Colorado River. In the upper portion of the study 

area (0 to 250 km), loads increase more or less linearly with 

distance. Starting at Cameo, loads added per kilometer of 

river increase at a greater rate as the river and its tributaries 

flow through the Mancos Shale and as the amount of irrigated 

land increases.

During high water, the Colorado River carries sediment 

rich in Al and Fe oxides, accounting for the greater available 

trace-metal concentrations (table AI–3). Aqueous Se concentrations exceed the Colorado freshwater chronic standard of 

4.6 μg/L at downstream stations during base flow.

The isotopes of water (fig. 16) fall along the GMWL 

trend indicating that evaporation does not significantly affect 

the salt load in the upper Colorado River above Cisco (fig. 16). 

Evolution of the isotopes of sulfate (fig. 16) dissolved in the 

Colorado River is systematic and depends on the geologic 

formation through which it is flowing. There appear to be 

three main sources of sulfate—sulfate derived from crystalline 

rock formations similar to those in the headwaters (starting 

composition, fig. 16), the Eagle Valley Evaporite, and the 

Mancos Shale. Mixing between starting composition and 

Eagle Valley Evaporite is evident in the Colorado River below 

Kremmling to Cameo, in the Eagle River, and the Roaring 

Fork River. The impact of the Mancos Shale on the sulfate 

load in the Colorado River below Cameo and in the Gunnison 

River is dramatic as shown by the shift in the sulfate isotopes 

(fig. 16). 

Table 24. Summary of geochemical parameters for the Colorado 

River near the Colorado-Utah State line.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Colorado River,

Colorado-Utah State line HW IRR BF

Charge balance (percent) –2 –4 –9

Conductivity (μS/cm) 435 685 1,090

Water type mixed mixed mixed

Load (tonnes solutes/day) 13,900 8,550 8,420

Percent CR load at Cisco 82 105 87

Ca:SO4 (molar basis) 1.4 1.1 1.1

Na:Cl (molar basis) 2.1 1.9 2.1

Evaporation no no no

Predominant SO4 source Mancos

Shale

Mancos

Shale

Mancos

Shale
Fingerprinting Major Geologic Salt Sources 23

Fingerprinting Major Geologic 

Salt Sources

Major geologic influences on the chemistry of the Colorado 

River are evident in the evolution of the water from a calcium 

bicarbonate type near its headwaters (weathering of crystalline 

rocks) toward a sodium chlorite type as it flows through Eagle 

Valley Evaporite that includes halite, toward a calcium sodium 

sulfate type as it and tributaries flow through the sulfate-rich 

Mancos Shale and bedded evaporites (halite and anhydrite) of the 

Paradox Formation. Sodium, chloride, calcium, and sulfate loads 

and sulfur isotopic compositions have been used to fingerprint 

these major salt contributors and to quantitatively determine their 

relative influence on solutes in the Colorado River.

Chloride is generally a minor contributor to salt loads in 

the upper Colorado River, accounting for only 6 to 14 percent 

of the total solute load at the Colorado River station near 

Cisco. It is less than 5 percent of the load at any one station 

except for those where the river flows through Eagle Valley 

Evaporite (Eagle River, Roaring Fork River, Colorado River 

headwater, and Colorado River headwater-plateau watersheds), or Paradox Formation evaporites (upper and lower 

Dolores River watersheds). At stations within these watersheds, values increase from 5 percent of the total load during 

high-water flow in the Dolores River to over 40 percent during 

irrigation flow. Although 40 percent is a high proportion of 

the total load, the contribution of chloride at this station to 

the load in the upper Colorado River near Cisco is still only 

2 percent.

Sulfate, on the other hand, is a major contributor, 

accounting for 25 to 30 percent of the solute load in the 

Colorado River near Cisco. In watersheds containing significant expanses of Mancos Shale (Gunnison and Uncompahgre 

Rivers), sulfate makes up nearly half of the total load. 

Although most sulfate comes from gypsum, some sulfate 

is derived from the dissolution of anhydrite and thenardite. 

In most cases, we are not able to constrain how much of 

the sulfate came from each mineral. Therefore, all mineral 

weights are reported on a gypsum basis. If all sulfate is 

derived from anhydrite, then using gypsum values results 

in an overestimation of 20 percent of the amount of mineral 

dissolved. If all is from thenardite, we overestimated the 

amount by 17 percent.

Table 25. Summary of geochemical parameters for the Colorado 

River near Cisco.

[HW, high-water flow; IRR, irrigation flow; BF, base flow; CR, Colorado River]

Colorado River,

Cisco HW IRR BF

Charge balance (percent) 10 0.8 –10

Conductivity (μS/cm) 430 725 1,230

Water type mixed mixed mixed

Load (tonnes solutes/day) 17,000 8,170 9,580

Percent CR load at Cisco 100 100 100

Ca:SO4 (molar basis) 1.1 0.99 0.98

Na:Cl (molar basis) 1.5 1.5 1.8

Evaporation no no no

Predominant SO4 source Mancos

Shale

Mancos

Shale

Mancos

Shale

Figure 15. Total load at stations along the Colorado River and at confluences 

with tributaries. River kilometers are estimated distance from the Colorado River 

near Kremmling, Colo., station. CR, Colorado River; ER, Eagle River, RF, Roaring 

Fork River; PC, Parachute Creek; GR, Gunnison River; and DR, Dolores River.

0 50 100 150 200 250 300 350 400 450

KILOMETERS DOWNSTREAM

CR

Kremmling

ER

Gypsum

RF

Glenwood

PC

Cameo

GR

Grand Jct.

DR

Cisco

CR

Glenwood

CR

Cameo

CR

CO/UT

CR

Cisco

STATION

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

TOTAL LOAD (TONNES/DAY)

Irrigation

High water

Base flow
24 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Evaporites in the Eagle Valley Evaporite

The major input of chloride to the Colorado River is dissolution of halite related to the Eagle Valley Evaporite upstream 

from Cameo. Based on our limited sampling, we estimate that 

1,210 tonnes of halite dissolve per day contributing Cl to the 

Colorado River during high-water flow, 1,060 tonnes of halite 

per day during irrigation flow, and 1,340 tonnes of halite per 

day during base flow.7 These values are fairly similar, and if 

we assume their average represents an average daily contribution, then 439,000 tonnes of halite in the Eagle Valley Evaporite 

are dissolved and added to the Colorado River annually. Using 

sulfate loads and isotopic compositions, we estimate that at least 

345,000 tonnes of gypsum from the Eagle Valley Evaporite 

are dissolved and added annually as well. The total amount of 

solutes derived from these evaporites as estimated in this study 

is 784,000 tonnes solutes/year (18 percent of the estimated 

annual load of the Colorado River at Cisco). Chafin and Butler 

(2002) derived an estimate of 817,000 tonnes/year using a very 

different approach. Considering the number of assumptions in 

both approaches and that the data are from different years, these 

estimates are very similar.

Figure 16. Isotopic composition of water and sulfate along the main stem of the upper Colorado River at and above Cisco and at farthest 

downstream stations of major tributaries. Solid line connects the starting composition and two major sources of sulfate to the Colorado River–

Starting Comp, starting composition at Kremmling station (farthest upstream on Colorado River); evap., evaporites (Eagle Valley Evaporite); and 

Mancos Shale. CR, Colorado River; ER, Eagle River, RF, Roaring Fork River; PC, Parachute Creek; GR, Gunnison River; DR, Dolores River; HW, 

high-water flow; Irr, irrigation flow; BF, base flow. In the case of the Dolores River, the evaporite contribution is from the Paradox Formation 

with a similar isotopic composition to that in the Eagle Valley Evaporite. Hydrogen and oxygen isotopes reported relative V-SMOW and sulfur 

isotopes relative to V-CDT.

7

Estimates based on Cl loads in the Colorado River at Cameo, Colo., 

minus loads for the Colorado River near Kremmling, Colo., and Eagle River 

near Minturn, Colo.

Evaporites in the Paradox Formation

A similar analysis was used to determine the amount 

of salt derived from the Paradox Formation in the upper 

Dolores River watershed. Assuming that 58 percent of the 

chloride in the Dolores River at Bedrock comes from dissolution of halite (load at Bedrock minus load calculated for 

McPhee Reservoir), 60 tonnes of halite per day are dissolved 

and added to the river during high flow. During irrigation 

and base-flow conditions, 100 percent of the Na and Cl is 

assumed to have been derived from halite as the load from the 

McPhee Reservoir is negligible. Under these conditions, 115 

and 35 tonnes of halite per day, respectively, dissolve and enter 

the river. Assuming that the average of these three amounts 

estimates a daily average throughout the year, 25,600 tonnes 

of Paradox Formation halite dissolve per year upstream 

from the Bedrock station. Calculations indicate that between 

−19 −18 −17 −16 −15 −14 −13 −12 −20 −15 −10 −5 0 5 10 15

δ18OH20 ‰ δ34SSO4 ‰

−135

−130

−125

−120

−115

−110

−105

−100

−95

−8

−3

2

7

12

δ18OSO4 ‰

δ2H ‰

Evap.

Mancos

Shale

Starting 

Comp

CR-Cisco, BF CR-Cisco, Irr CR-Cisco, HW

DR-Cisco, BF DR-Cisco, Irr DR-Cisco, HW

CR-Utah-Colo., BF CR-Utah-Colo., Irr CR-Utah-Colo., HW

GR-Grand Jct, BF GR-Grand Jct, Irr GR-Grand Jct, HW

PC-Cameo, BF PC-Cameo, Irr PC-Cameo, HW

CR-Cameo, BF CR-Cameo, Irr CR-Cameo, HW

RF-Glenwood Spg., HW RF-Glenwood Spg., HW RF-Glenwood Spg., HW

CR-Glenwood Spg., BF CR-Glenwood Spg.,Irr CR-Glenwood Spg., HW

ER-Gypsum, BF ER-Gypsum, Irr ER-Gypsum, HW

CR-Kremmling, BF CR-Kremmling, Irr CR-Kremmling, HW

EXPLANATION
Fingerprinting Major Geologic Salt Sources 25

the Bedrock and Cisco stations, a portion of the load of the 

Dolores River is lost during high- and irrigation-flow conditions. This loss may be due to recharge of the alluvium aquifer 

of the Paradox Valley (Chafin, 2003). Under base-flow conditions in the year we sampled, sodium and chloride increase 

dramatically in a molar ratio of one. This increase suggests 

that during base flow, additional solutes from the dissolution 

of 215 tonnes of halite per day are added to the river between 

these two stations (loads adjusted to exclude solutes carried 

by the San Miguel River). Assuming base-flow conditions 

for a third of the year, this amount is equal to 26,200 tonnes 

of halite. The total amount of Paradox halite dissolved and 

solutes added to the Dolores River from McPhee Reservoir 

to Cisco is estimated at 51,800 tonnes per year. 

The Paradox Formation evaporites also include bedded 

anhydrite that contributes to the calcium and sulfate load along 

the Dolores River. Sulfate isotopes were used to determine 

the relative contribution of Paradox anhydrite (δ34S of 13 ‰ 

and δ18O of around 16 ‰; Claypool and others, 1980; Tuttle 

and others, 1996). Dissolution of anhydrite in the Paradox 

Formation above the Bedrock station is small, consistent with 

findings reported in Chafin (2003). Sulfate isotopes indicate 

that negligible dissolution of anhydrite occurs during highwater flow. During irrigation flow and base flow, solutes from 

the dissolution of 12 and 8 tonnes anhydrite per day, respectively, are added to the Dolores River. An average of these 

daily rates indicates that about 2,430 tonnes of anhydrite dissolve in a year (3,100 tonnes per year on a gypsum basis).

During high water, the loss of a portion of the Dolores 

River flow across the Paradox Valley precludes calculation of 

contributions of specific salts; however, sulfate isotopes at the 

Cisco station indicate that 90 percent of the sulfate is acquired 

from the San Miguel River and 10 percent from upstream. 

During irrigation and base flow, the sulfate load at Cisco is 

equal to the sum of the load at the Bedrock and the San Miguel 

stations, indicating that negligible sulfate is acquired as the 

Dolores River crosses the Paradox Valley. Sulfate loads indicate that 81 (irrigation flow) and 90 (base flow) percent of the 

sulfate in the Dolores River is from San Miguel River flow.

Salts Derived From Weathering 

of the Mancos Shale

Gypsum and highly soluble thenardite (Na2SO4) are common weathering products associated with the Mancos Shale. 

Both salts are found in soils derived from the shale. Gypsum 

is also found along fractures and bedding planes in shale in the 

unsaturated zone. This deeper gypsum is thought to be related 

to historic weathering of the shale when the water table was 

higher and/or the climate wetter (Tuttle and others, 2008). The 

sulfur isotopes of all salt are very similar to that of pyrite in the 

Mancos Shale (average of –21 ‰), but the δ18O of the deeper 

gypsum is isotopically lighter (–10 ‰) than the sulfate salts 

found in the soil (–3 ‰) (Tuttle and others, 2005). 

In the Dolores River watershed, we had good control 

on the source of sodium, and we were able to determine sulfate 

derived from gypsum and sulfate derived from thenardite. In 

all the other watersheds, however, we were unable to differentiate between sulfate derived from these two minerals; therefore, 

all Mancos Shale calculations in these watersheds and totals at 

our most downstream station were made on a gypsum basis, 

realizing that some of the sulfate is indeed from dissolution of 

thenardite.

Dolores River Watershed

In the Dolores River watershed, a portion of the sulfate is derived from the Mancos Shale. By assuming that 

the sodium acquired between the McPhee Reservoir and the 

Bedrock station during high-water flow, and not attributed 

to halite, is from dissolution of salt in the Mancos, we can 

calculate the amount of thenardite (Na2SO4) separately from 

the gypsum. Calculations indicate that dissolution of 64 tonnes 

of thenardite per day (78 t/d gypsum equivalent) is needed to 

supply this sodium load. Dissolution of 57 tonnes of gypsum 

per day accounts for the remainder of the sulfate load acquired 

between these two points during high-water flow. Isotopic 

composition of this sulfate indicates that it comes from Mancos soil. During irrigation flow and base flow, thenardite does 

not contribute salt to the Dolores River, but gypsum along 

bedding planes deeper in the Mancos Shale does. Isotopes 

indicate that 40 and 30 percent, respectively, of the sulfate 

load at the Bedrock station comes from dissolution of 8 tonnes 

of gypsum per day during irrigation flow and 3 tonnes of 

gypsum per day during base flow.

It appears that gypsum in the Mancos Shale soil also 

contributes sulfate to the San Miguel River (estimated 

15 percent at our sampling station). This percentage translates 

to 66, 25, and 24 tonnes of gypsum per day being dissolved 

and solutes added to the river during high-water, irrigation, 

and base flows, respectively. It is possible that, during highwater flow, some of the sulfate may come from thenardite as 

well, although we have no way to quantify the amount. During 

high-water flow, dissolution of 200 tonnes of gypsum per day 

is needed to account for the sulfate load in the Dolores River 

attributed to the Mancos Shale. This amount drops dramatically to 33 and 27 tonnes per day during irrigation and base 

flow, respectively. Based on an average daily rate, this represents 31,600 tonnes of gypsum per year.

Gunnison River Watershed

About half of the solutes and most of the sulfate in the 

Gunnison River are derived from weathering of the Mancos 

Shale. Using sulfate isotopes, we calculate that during high 

water, 87 percent of the sulfate in the Uncompahgre River 

at Delta is derived from Mancos Shale. During irrigation 

and base flow, the proportions increase slightly to 90 and 

89 percent respectively. Using the same method, we calculate 
26 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Table 26. The 2005 estimated dissolution rates for halite and 

gypsum in the Eagle Valley, Paradox, and Mancos Formations 

estimated in this study and a comparison of the derived solutes 

to the estimated annual Colorado River (CR) load at Cisco.

Formation Halite

(tonnes/a)

Gypsum

(tonnes/a)

Percent of

CR annual load

(Cisco)

Eagle Valley Evaporite 439,000 343,000 18

Paradox Formation 51,800 3,100 1

Mancos Shale, total 1,400,800 33

Dolores River 31,600 1

Gunnison River 777,5001 18

Colorado River 

headwater/plateau

591,700 14

1

An estimated 40,200 tonnes per year of additional gypsum dissolved 

and the sulfate removed from the Gunnison River between Delta and Grand 

Junction stations during irrigation and base-flow conditions due to alluvium 

recharge or water diversion.

that 88, 90, and 95 percent of the sulfate in the Gunnison River 

at Delta during high-water, irrigation, and base flows, respectively, is from Mancos Shale. The amount of gypsum dissolution required to supply this sulfate at the Uncompahgre and 

Gunnison Rivers confluence a short distance downstream from 

these two stations is 2,190 (high-water flow), 2,410 (irrigation 

flow), and 2,120 (base flow) tonnes of gypsum per day. Again, 

assuming that the average of the amounts during different flow 

conditions approximates the daily average throughout the year, 

dissolution of 817,600 tonnes of gypsum is required to supply 

the sulfate.

During high-water flow, additional sulfate is picked 

up by the Gunnison River between the confluence with the 

Uncompahgre River and the Gunnison River near Grand 

Junction station. Isotopic composition of the sulfate indicates 

that most of it is from Mancos soil and represents an additional dissolution of 830 tonnes of gypsum per day. During 

irrigation and base-flow conditions, 22 and 29 percent of the 

sulfate load is lost over this reach due to alluvium recharge 

or diversion with no return. Summing the amount of sulfate 

in the Gunnison River at Delta and in the Uncompahgre River, 

adding in the sulfate acquired below their confluence during 

high-water flow, and subtracting that lost during irrigation and 

base flow, we calculate an average of 1,190 tonnes of sulfate 

per day from Mancos Shale was supplied to the Colorado 

River by the Gunnison River. This represents the dissolution 

of an estimated 777,500 tonnes of Mancos Shale gypsum per 

year (from base-flow data for Gunnison and Uncompahgre 

Rivers at Delta), 224,500 tonnes of which was lost to assumed 

alluvial recharge in the lower Gunnison River stretch. Warner 

and others (1985) used data from 1977–78 to calculate that 

the Gunnison River base flow contributed 736,000 tonnes of 

solutes per year. Using just our base-flow data, we calculate 

773,400 tonnes of solutes per year, a value that agrees well 

with Warner and others (1985).

Colorado River Headwater-Plateau Watershed

As the Colorado River enters the Grand Valley (reach 

below Cameo station), it flows through a landscape dominated 

by Mancos Shale. The Colorado River provides irrigation 

water that supports extensive agriculture on Mancos Shale in 

the valley. We estimate from sulfate isotopes that 62 (highwater flow), 67 (irrigation flow), and 65 (base flow) percent 

of the sulfate load at the Colorado-Utah State line station is 

derived from Mancos Shale soil. Using these percentages 

and the sulfate loads at this station, minus the sulfate loads 

of the Gunnison River at Grand Junction attributed to the 

Mancos Shale, we calculate a minimum of 1,190, 1,520, and 

2,150 tonnes of gypsum per day dissolved in the Grand Valley 

and contributed sulfate to the Colorado River during highwater, irrigation, and base flows, respectively. These values are 

minimums as some of the sulfate load may have been removed 

during recharge of alluvium. Assuming the average of these 

amounts reasonably estimates the daily average throughout the year, then 591,700 tonnes of gypsum in the Grand 

Valley dissolved and the solutes were added to the Colorado 

River in 2005.

Summary

In 2005, the amount of salt (halite and gypsum) dissolved 

from the Eagle Valley Evaporite, Paradox Formation, Mancos 

Shale, and their associated soils is shown in table 26. Collectively, dissolution of these salts account for just over half of 

the solutes in the Colorado River at the station near Cisco. The 

Mancos Shale generates about 33 percent of the solutes, the 

Eagle Valley Evaporite generates 18 percent of the solutes, and 

the Paradox Formation generates only 1 percent. 

Acknowledgments 

The authors wish to thank Patrick Lambert, District Chief 

of the Utah Water Science Center, and Paul von Guerard (retired) 

and Greg O’Neill, Chiefs for Grand Junction and Lakewood 

USGS Colorado Water Science Center field offices, respectively. 

Without the field support of Patricia Solberg, Ron Tibbetts, 

Clay Thompson, and David Grey (USGS), this study would not 

have been possible. We wish to thank U.S. Department of Energy 

personnel for obtaining ground-water samples from the Rifle 

mill site, especially Richard Bush, Dick Dayvault, Dave Traub, 

and Emile Better; Stephen Onorofskie for arranging sampling of 

gypsum from the American Gypsum mines in the Eagle Valley 

Evaporite; and Tonya Hammond for arranging access to the Snow 

Cap Coal Company property. Thanks to Cyrus Berry (USGS) 

for help with logistics and Bridget Ball (USGS) for GIS support. 

The manuscript benefited greatly from the thoughtful reviews of 

Richard Wanty and Paul von Guerard.
References Cited 27

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28 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

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Appendixes
30 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Table A1–1. Metadata (analytical method, detection limit, the number of samples with censored data, the percent of samples with 

replaced values, and the replacement value) for reported concentrations. Replacement (red) values (0.5 × detection limit) are used when 

censored values were reported for ≤20 percent of the samples (14 samples or less). For elements with the number censored = “many,” 

less than concentrations are reported.

[IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission spectrometry; na, not 

analyzed]

Element Method Detection limit No. censored Percent replaced Replacement

NO3 IC 0.08 mg/L 14 20 0.04 mg/L

Al ICP–MS 2 μg/L 13 19 1 μg/L

Al ICP–AES 10 μg/L many na 

B ICP–AES 5 μg/L many na

Cd ICP–MS 0.02 μg/L many na

Cd (raw) ICP–MS 6 10 0.01 μg/L

Ce ICP–MS 0.01 μg/L 8 13 0.005 μg/L

Ce (raw) ICP–MS 0.01 μg/L 1 2 0.005 μg/L

Co ICP–MS 0.02 μg/L 3 5 0.01 μg/L

Co (raw) ICP–MS 0.02 μg/L 1 2 0.01 μg/L

Cr ICP–MS 0.1 μg/L many na

Cr (raw) ICP–MS 0.1 μg/L many na

Cs ICP–MS 0.02 μg/L many na

Cs (raw) ICP–MS 0.02 μg/L 9 14 0.01 μg/L

Dy ICP–MS 0.005 μg/L many na

Dy (raw) ICP–MS 0.005 μg/L 1 2 0.003 μg/L

Er ICP–MS 0.005 μg/L many na

Er (raw) ICP–MS 0.005 μg/L 2 3 0.003 μg/L

Eu ICP–MS 0.005 μg/L 3 4 0.003 μg/L

Eu (raw) ICP–MS 0.005 μg/L 2 3 0.003 μg/L

Fe ICP–MS 50 μg/L many na

Fe (raw) ICP–MS 50 μg/L 8 13 25 μg/L

Gd ICP–MS 0.005 μg/L many na

Gd (raw) ICP–MS 0.005 μg/L 1 2 0.003 μg/L

Ho ICP–MS 0.005 μg/L many na

Ho (raw) ICP–MS 0.005 μg/L 11 17 0.003 μg/L

La ICP–MS 0.01 μg/L many na

La (raw) ICP–MS 0.01 μg/L 1 2 0.005 μg/L

Li ICP–AES 1 μg/L 2 3 0.5 μg/L

Mo ICP–MS 2 μg/L many na

Mo (raw) ICP–MS 2 μg/L many na

Mn ICP–AES 10 μg/L many na

Nd ICP–MS 0.01 μg/L 9 14 0.005 μg/L

P ICP–MS 0.01 mg/L many na

P (raw) ICP–MS 0.01 mg/L many na

Pb ICP–MS 0.05 μg/L many na

Pr ICP–MS 0.01 μg/L many na

Pr (raw) ICP–MS 0.01 μg/L 2 3 0.005 μg/L

Se ICP–MS 1 μg/L many na

Se (raw) ICP–MS 1 μg/L many na

Sm ICP–MS 0.01 μg/L many na

Sm (raw) ICP–MS 0.01 μg/L 2 3 0.005 μg/L

Tb ICP–MS 0.005 μg/L many na

Tb (raw) ICP–MS 0.005 μg/L 12 19 0.003 μg/L

Ti ICP–MS 0.5 μg/L 8 13 0.3 μg/L

Y ICP–MS 0.5 μg/L many na

Y (raw) ICP–MS 0.5 μg/L 10 16 0.3 μg/L

Yb ICP–MS 0.005 μg/L many na

Yb (raw) ICP–MS 0.005 μg/L 3 5 0.003 μg/L

Zn ICP–AES 10 μg/L many na

Appendix I. Chemical and Isotopic Data for All Water Samples Collected

in This Study
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 31

Table AI–2. Elements not reported in Appendix 1, because all reported values were less than detection 

limit, or the few values reported were very near the detection limit. In some instances where the available 

concentrations did not meet this criteria, concentrations for the few samples were reported.

[ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission spectrometry]

Element Method Detection

limit

Ag, Ag (raw) ICP–MS 3 μg/L

Ag ICP–AES 1 μg/L

As, As (raw) ICP–MS 1 μg/L

As ICP–AES 100 μg/L

Be, Be (raw) ICP–MS 0.05 μg/L

Be ICP–AES 10 μg/L

Bi, Bi (raw) ICP–MS 0.2 μg/L

Cd ICP–AES 5 μg/L

Co ICP–AES 10 μg/L

Cr ICP–AES 10 μg/L

Cu ICP–AES 11 μg/L

Fe ICP–AES 20 μg/L

Ga, Ga (raw) ICP–MS 0.05 μg/L

Ge, Ge (raw) ICP–MS 0.05 μg/L

Lu, Lu (raw) ICP–MS 0.1 μg/L

Mo ICP–AES 20 μg/L

Nb, Nb (raw) ICP–MS 0.2 μg/L

Ni ICP–AES 10 μg/L

P ICP–AES 0.1 mg/L

Pb ICP–AES 50 μg/L

Sb ICP–AES 50 μg/L

Sb, Sb (raw) ICP–MS 0.3 μg/L

Ta, Ta (raw) ICP–MS 0.02 μg/L

Th, Th (raw) ICP–MS 0.2 μg/L

Ti ICP–AES 50 μg/L

Tl, Tl (raw) ICP–MS 0.1 μg/L

Tm, Tm (raw) ICP–MS 0.005 μg/L

V ICP–AES 10 μg/L

W, W (raw) ICP–MS 0.5 μg/L

Zr, Zr (raw) ICP–MS 0.2 μg/L
32 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Station

ID Station name Site name WS # Flowcondition N. lat ° W. long ° Date

09058000 Colorado River near Kremmling, Colo. CR-Kremmling 1 High water 40.0367 –106.4394 5/24/05

09058000 Colorado River near Kremmling, Colo. CR-Kremmling 1 Irrigation 40.0367 –106.4394 8/30/05

09058000 Colorado River near Kremmling, Colo. CR-Kremmling 1 Base flow 40.0367 –106.4394 10/12/05

09064600 Eagle River near Minturn, Colo. ER-Minturn 2 High water 39.5539 –106.4019 5/26/05

09064600 Eagle River near Minturn, Colo. ER-Minturn 2 Irrigation 39.5539 –106.4019 7/29/05

09064600 Eagle River near Minturn, Colo. ER-Minturn 2 Base flow 39.5539 –106.4019 10/20/05

09067005 Eagle River at Avon, Colo. ER-Avon 2 High water 39.6317 –106.5219 5/26/05

09067005 Eagle River at Avon, Colo. ER-Avon 2 Irrigation 39.6317 –106.5219 7/26/05

09067005 Eagle River at Avon, Colo. ER-Avon 2 Base flow 39.6317 –106.5219 10/19/05

09069000 Eagle River at Gypsum, Colo. ER-Gypsum 2 High water 39.6500 –106.9517 5/24/05

09069000 Eagle River at Gypsum, Colo. ER-Gypsum 2 Irrigation 39.6500 –106.9517 7/26/05

09069000 Eagle River at Gypsum, Colo. ER-Gypsum 2 Base flow 39.6500 –106.9517 10/20/05

09071750 Colorado River above Glenwood Springs, Colo. CR-Glenwood 1 High water 39.5606 –107.2997 5/23/05

09071750 Colorado River above Glenwood Springs, Colo. CR-Glenwood 1 Irrigation 39.5606 –107.2997 7/28/05

09071750 Colorado River above Glenwood Springs, Colo. CR-Glenwood 1 Base flow 39.5606 –107.2997 10/21/05

09085000 Roaring Fork at Glennwood Springs, Colo. RF-Glenwood 3 High water 39.5436 –107.3289 6/3/05

09085000 Roaring Fork at Glennwood Springs, Colo. RF-Glenwood 3 Irrigation 39.5436 –107.3289 7/29/05

09085000 Roaring Fork at Glennwood Springs, Colo. RF-Glenwood 3 Base flow 39.5436 –107.3289 10/27/05

09105000 Plateau Creek near Cameo, Colo. PC-Cameo 8 High water 39.1833 –108.2672 6/3/05

09105000 Plateau Creek near Cameo, Colo. PC-Cameo 8 Irrigation 39.1833 –108.2672 7/14/05

09105000 Plateau Creek near Cameo, Colo. PC-Cameo 8 Base flow 39.1833 –108.2672 10/27/05

09095500 Colorado River near Cameo, Colo. CR-Cameo 8 High water 39.2392 –108.2656 6/3/05

09095500 Colorado River near Cameo, Colo. CR-Cameo 8 Irrigation 39.2392 –108.2656 7/13/05

09095500 Colorado River near Cameo, CO Colo. CR-Cameo 8 Base flow 39.2392 –108.2656 10/27/05

09134100 North Fork Gunnison River below Paonia, Colo. GR-NF 5 High water 38.8575 –107.6219 5/24/05

09134100 North Fork Gunnison River below Paonia, Colo. GR-NF 5 Irrigation 38.8575 –107.6219 7/5/05

09134100 North Fork Gunnison River below Paonia, Colo. GR-NF 5 Base flow 38.8575 –107.6219 11/30/05

09128000 Gunnison River below Gunnison Tunnel, Colo. GR-Tunnel 4 High water 38.5292 –107.6483 6/24/05

09128000 Gunnison River below Gunnison Tunnel, Colo. GR-Tunnel 4 Irrigation 38.5292 –107.6483 7/20/05

09128000 Gunnison River below Gunnison Tunnel, Colo. GR-Tunnel 4 Base flow 38.5292 –107.6483 10/17/05

09144250 Gunnison River at Delta, Colo. GR-Delta 7 High water 38.7531 –108.0778 5/27/05

09144250 Gunnison River at Delta, Colo. GR-Delta 7 Irrigation 38.7531 –108.0778 8/11/05

09144250 Gunnison River at Delta, Colo. GR-Delta 7 Base flow 38.7531 –108.0778 11/30/05

09146020 Uncompahgre River near Ouray, Colo. UR-Ouray 6 High water 38.0433 –107.6825 6/14/05

09146020 Uncompahgre River near Ouray, Colo. UR-Ouray 6 Irrigation 38.0433 –107.6825 8/10/05

09146020 Uncompahgre River near Ouray, Colo. UR-Ouray 6 Base flow 38.0433 –107.6825 11/18/05

09146200 Uncompahgre River near Ridgway, Colo. UR-Ridgway 6 High water 38.1839 –107.7453 6/14/05

09146200 Uncompahgre River near Ridgway, Colo. UR-Ridgway 6 Irrigation 38.1839 –107.7453 8/10/05

09146200 Uncompahgre River near Ridgway, Colo. UR-Ridgway 6 Base flow 38.1839 –107.7453 11/18/05

09149500 Uncompahgre River at Delta, Colo. UR-Delta 6 High water 38.7419 –108.0803 5/27/05

09149500 Uncompahgre River at Delta, Colo. UR-Delta 6 Irrigation 38.7419 –108.0803 8/11/05

09149500 Uncompahgre River at Delta, Colo. UR-Delta 6 Base flow 38.7419 –108.0803 11/29/05

09152500 Gunnison River near Grand Junction, Colo. GR-Grand Jct. 7 High water 38.9833 –108.4500 6/2/05

09152500 Gunnison River near Grand Junction, Colo. GR-Grand Jct. 7 Irrigation 38.9833 –108.4500 7/12/05

09152500 Gunnison River near Grand Junction, Colo. GR-Grand Jct. 7 Base flow 38.9833 –108.4500 10/31/05

09163500 Colorado River near Colorado-Utah State Line CR-State line 8 High water 39.1328 –109.0264 6/1/05

09163500 Colorado River near Colorado-Utah State Line CR-State line 8 Irrigation 39.1328 –109.0264 7/11/05

09163500 Colorado River near Colorado-Utah State Line CR-State line 8 Base flow 39.1328 –109.0264 10/26/05

09166500 Dolores River at Dolores, Colo. DR-Dolores 9 High water 37.4725 –108.4969 5/25/05

09166500 Dolores River at Dolores, Colo. DR-Dolores 9 Irrigation 37.4725 –108.4969 7/19/05

09166500 Dolores River at Dolores, Colo. DR-Dolores 9 Base flow 37.4725 –108.4969 10/3/05

Table AI–3. Chemical and isotopic data for all water samples collected in this study.

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 33

Site

name

AA meter

discharge

CFS

Electrode

conductivity

μS/cm

Electrode

pH

Mass spec.

δ18O(H20) ‰

Mass spec.

δ2H ‰

Titration HCO3

mg/L

IC

Cl mg/L

CR-Kremmling 1,230 140 7.13 –16.8 –125 62 2.3

CR-Kremmling 980 211 8.20 –16.8 –126 72 5.0

CR-Kremmling 750 200 8.20 –16.8 –126 78 4.5

ER-Minturn 634 103 7.42 –18.4 –137 45 1.7

ER-Minturn 91 140 7.61 –17.1 –128 70 1.7

ER-Minturn 86 110 7.60 –16.3 –120 52 2.3

ER-Avon 2,180 100 7.37 –18.4 –135 47 2.5

ER-Avon 457 131 7.53 –16.7 –122 50 3.0

ER-Avon 206 190 8.00 –16.4 –120 120 6.1

ER-Gypsum 3,630 191 7.57 –18.2 –133 86 4.5

ER-Gypsum 871 360 7.54 –16.8 –122 82 22

ER-Gypsum 418 555 8.70 –16.2 –119 99 47

CR-Glenwood 7,050 248 7.50 –17.5 –129 105 10

CR-Glenwood 1,920 515 7.75 –16.6 –124 110 55

CR-Glenwood 1,404 565 8.10 –16.5 –123 175 64

RF-Glenwood 3,520 251 7.62 –17.2 –125 88 5.0

RF-Glenwood 1,340 440 7.89 –16.8 –123 120 19

RF-Glenwood 764 600 8.40 –16.4 –121 140 42

PC-Cameo 1,430 195 7.70 –16.0 –115 26 2.0

PC-Cameo 158 520 8.21 –14.8 –109 22 6.4

PC-Cameo 145 590 8.30 –14.5 –107 35 8

CR-Cameo 10,900 397 7.64 –16.9 –124 83 28

CR-Cameo 5,020 527 7.91 –17.0 –124 105 55

CR-Cameo 2,480 920 8.20 –16.2 –120 115 135

GR-NF 5,190 117 7.42 –16.3 –118 175 2.0

GR-NF 696 171 7.59 –16.3 –118 200 2.0

GR-NF 199 310 7.90 –15.1 –105 250 5.2

GR-Tunnel 744 194 7.74 –15.8 –118 55 2.0

GR-Tunnel 524 204 7.54 –15.8 –118 67 2.0

GR-Tunnel 394 200 7.80 –15.9 –118 175 2.4

Station

ID Station name Site name WS # Flowcondition N. lat ° W. long ° Date

09171100 Dolores River near Bedrock, Colo. DR-Bedrock 9 High water 38.3569 –108.8328 5/31/05

09171100 Dolores River near Bedrock, Colo. DR-Bedrock 9 Irrigation 38.3569 –108.8328 7/28/05

09171100 Dolores River near Bedrock, Colo. DR-Bedrock 9 Base flow 38.3569 –108.8328 11/15/05

09177000 San Miguel at Uravan, Colo. SM-Uravan 10 High water 38.3572 –108.7122 6/1/05

09177000 San Miguel at Uravan, Colo. SM-Uravan 10 Irrigation 38.3572 –108.7122 7/29/05

09177000 San Miguel at Uravan, Colo. SM-Uravan 10 Base flow 38.3572 –108.7122 11/15/05

09180000 Dolores River near Cisco, Utah DR-Cisco 11 High water 38.7972 –109.1944 6/23/05

09180000 Dolores River near Cisco, UTUtah DR-Cisco 11 Irrigation 38.7972 –109.1944 8/5/05

09180000 Dolores River near Cisco, UTUtah DR-Cisco 11 Base flow 38.7972 –109.1944 11/8/05

09180500 Colorado River near Cisco, UTUtah CR-Cisco 12 High water 38.8106 –109.2928 5/21/05

09180500 Colorado River near Cisco, UTUtah CR-Cisco 12 Irrigation 38.8106 –109.2928 7/12/05

09180500 Colorado River near Cisco, UTUtah CR-Cisco 12 Base flow 38.8106 –109.2928 11/21/05

Glenwood Springs hot spring GW hot spring 39.55088 –107.32206 8/16/05

Rifle Uranium Mill monitoring well 305 RUM 305 4/25/06

Rifle Uranium Mill monitoring well 310 RUM 310 4/26/06

Rifle Uranium Mill monitoring well 590 RUM 590 4/26/06

Rifle Uranium Mill monitoring well 855 RUM 855 4/26/06

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
34 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site

name

AA meter

discharge

CFS

Electrode

conductivity

μS/cm

Electrode

pH

Mass spec.

δ18O(H20) ‰

Mass spec.

δ2H ‰

Titration HCO3

mg/L

IC

Cl mg/L

GR-Delta 6,410 279 7.59 –16.0 –117 76 3.9

GR-Delta 960 900 8.15 –15.7 –114 90 11

GR-Delta 878 1,080 8.00 –14.9 –110 175 15

UR-Ouray 252 234 7.24 –17.1 –123 82 2.0

UR-Ouray 110 395 6.99 –15.9 –112 175 3.9

UR-Ouray 27 625 7.40 –15.7 –114 205 7.3

UR-Ridgway 342 420 7.66 –16.7 –120 110 5.0

UR-Ridgway 193 566 7.80 –15.6 –112 160 6.5

UR-Ridgway 76 680 7.90 –15.7 –113 145 8.4

UR-Delta 470 1,067 7.78 –15.1 –112 100 11

UR-Delta 767 1,150 7.92 –13.2 –112 280 18

UR-Delta 242 1,530 8.00 –15.0 –112 330 22

GR-Grand Jct. 5,980 455 7.69 –15.7 –115 120 4.6

GR-Grand Jct. 1,570 853 7.74 –15.4 –114 120 11

GR-Grand Jct. 1,530 715 8.20 –15.1 –113 190 13

CR-State line 18,000 433 7.77 –16.5 –120 120 18

CR-State line 7,430 684 7.93 –16.5 –121 135 40

CR-State line 4,420 1,087 8.10 –15.6 –116 175 70

DR-Dolores 3,920 157 7.43 –14.9 –105 78 2.2

DR-Dolores 247 263 8.04 –14.4 –102 105 6.5

DR-Dolores 122 330 8.10 –12.7 –89 115 11

DR-Bedrock 1,300 400 7.62 –13.4 –97 135 18

DR-Bedrock 82 1,508 7.54 –11.6 –86 155 365

DR-Bedrock 46 1,010 8.10 –12.6 –94 155 190

SM-Uravan 1,250 351 7.52 –15.1 –108 105 4.3

SM-Uravan 217 567 7.83 –14.6 –106 120 6.4

SM-Uravan 134 750 8.10 –14.0 –102 185 13

DR-Cisco 1,950 376 7.54 –14.6 –105 115 14

DR-Cisco 270 1,071 7.63 –12.7 –96 155 150

DR-Cisco 193 1,745 8.00 –13.6 –99 205 330

CR-Cisco 22,400 431 7.41 –15.8 –116 135 21

CR-Cisco 6,810 724 7.48 –16.1 –120 140 55

CR-Cisco 3,500 1,230 8.10 –15.8 –116 175 120

GW hot spring na 34,200 6.66 –18.0 –134 585 10,500

RUM 305 na 1,420 7.44 na na 145 95

RUM 310 na 1,860 7.23 na na 205 185

RUM 590 na 4,770 6.79 na na 135 190

RUM 855 na 2,480 6.81 na na 105 175

Site name IC

F mg/L

IC

NO3 mg/L

IC

SO4 mg/L

ICP–MS

SO4 mg/L

ICP–MS

SO4 (avail.) mg/L

Gravimetric

SO4 mg/L

Mass spec.

δ34S(SO4) ‰

Mass spec.

δ18O(SO4) ‰

CR-Kremmling 0.6 0.3 11 6 9.0 12 –4.0 –0.5

CR-Kremmling 2 0.3 24 26 22 29 –3.7 –5.9

CR-Kremmling 0.08 0.4 24 23 22 28 –6.1 –5.5

ER-Minturn 0.1 1 5.5 3 4.0 2.9 ins ins

ER-Minturn 0.1 0.6 9.3 8 6.0 9.3 –1.3 –5.7

ER-Minturn 0.3 0.2 9.2 7.0 5.0 9 0.5 –4.3

ER-Avon 0.1 0.7 6 4 5.0 2.6 ins ins

ER-Avon 0.1 0.3 15 13 12 16 4.8 0.6

ER-Avon 0.2 0.7 31 31 27 33 5.2 1.2

ER-Gypsum 0.1 0.8 20 18 18 21 5.4 5.8

ER-Gypsum 0.2 1 58 56 49 63 10.3 7.3

ER-Gypsum 0.8 1.9 99 105 105 105 10.2 8.3

CR-Glenwood 0.1 0.9 20 18 17 21 2.3 4.7

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 35

Site name IC

F mg/L

IC

NO3 mg/L

IC

SO4 mg/L

ICP–MS

SO4 mg/L

ICP–MS

SO4 (avail.) mg/L

Gravimetric

SO4 mg/L

Mass spec.

δ34S(SO4) ‰

Mass spec.

δ18O(SO4) ‰

CR-Glenwood 0.4 0.8 56 55 55 63 6.0 4.0

CR-Glenwood 0.8 0.8 64 71 67 72 6.7 5.0

RF-Glenwood 0.2 1 36 33 31 39 7.2 4.4

RF-Glenwood 0.3 0.7 76 67 66 78 8.9 6.4

RF-Glenwood 0.8 0.04 110 115 110 115 9.5 7.3

PC-Cameo 0.6 0.4 8.7 8 7.0 9.4 –2.6 1.6

PC-Cameo 2 0.04 31 30 31 36 –2.3 0.7

PC-Cameo 0.5 0.04 45 46 39 48 –2.4 0.5

CR-Cameo 0.2 2 39 38 36 44 5.9 2.9

CR-Cameo 0.3 0.04 56 55 55 63 6.7 5.0

CR-Cameo 1.4 0.04 110 120 115 115 7.9 5.4

GR-NF 0.1 2 7.4 5 6.0 6.0 ins ins

GR-NF 0.1 0.2 21 29 19 25 ins –3.0

GR-NF 0.5 0.6 41 40 34 42 –11.8 –3.0

GR-Tunnel 0.6 1 18 18 16 21 –3.9 –2.2

GR-Tunnel 0.6 0.04 19 18 18 21 –3.1 –1.2

GR-Tunnel 0.1 0.04 22 22 16 24 –4.2 –2.1

GR-Delta 0.2 1 54 55 51 62 –15.2 –2.4

GR-Delta 0.6 2 300 325 285 300 –17.6 –2.9

GR-Delta 1.2 5.9 435 415 385 625 –17.4 –1.5

UR-Ouray 0.2 0.9 79 78 61 80 2.9 –4.3

UR-Ouray 0.5 0.8 160 165 140 160 4.1 –3.3

UR-Ouray 0.4 1.2 295 260 170 295 6.8 –1.6

UR-Ridgway 0.4 1 120 125 110 125 –1.4 –2.9

UR-Ridgway 0.6 1 180 190 165 185 –2.3 –2.7

UR-Ridgway 0.6 1.2 280 246 245 275 0.0 –1.4

UR-Delta 0.7 8.3 395 415 345 375 –17.8 –2.3

UR-Delta 1 8.9 440 470 370 420 –18.2 –2.6

UR-Delta 2.7 14.7 665 245 615 645 –18.4 –3.1

GR-Grand Jct. 0.3 2 120 140 120 130 –15.8 –2.2

GR-Grand Jct. 0.6 3 285 315 270 300 –16.9 –2.1

GR-Grand Jct. 1.3 2.0 225 235 215 235 –16.6 –3.0

CR-State line 0.3 2 78 87 65 86 –9.7 –1.1

CR-State line 0.5 2 145 165 150 155 –10.9 –0.7

CR-State line 2.6 3.6 235 290 280 290 –12 –1.2

DR-Dolores 1 1 8.4 7 7.0 7.7 –3.4 0.0

DR-Dolores 0.2 0.04 28 25 27 30 –3.1 –2.2

DR-Dolores 0.5 0.04 37 38 32 39 –1.0 –1.1

DR-Bedrock 2.0 5 51 51 46 59 –12.8 –1.5

DR-Bedrock 0.7 2 63 50 50 57 2.3 5.7

DR-Bedrock 1.4 0.04 57 67 50 57 –1.2 3.3

SM-Uravan 0.3 1 74 84 62 80 –5.8 –0.6

SM-Uravan 0.4 0.04 170 175 155 175 –4.8 0.1

SM-Uravan 1.3 0.04 260 270 255 265 –3.6 –0.8

DR-Cisco 0.3 0.9 57 56 49 65 –6.5 –1.2

DR-Cisco 1 0.04 190 155 155 175 –3.7 1.8

DR-Cisco 3.0 2.1 200 230 205 210 –1.7 0.9

CR-Cisco 0.3 2 90 61 54 72 –9.6 –0.6

CR-Cisco 0.6 2 155 150 145 150 –10.2 –1.4

CR-Cisco 2.7 4.0 270 295 265 275 –9.9 –1.0

GW hot spring 125 55 1,300 1,270 1,270 na 15.3 134

RUM 305 3.6 3.4 425 410 405 na –6.8 1.2

RUM 310 41 .04 685 645 590 na –6.5 1.5

RUM 590 41 93 1,000 2,440 2,180 na 2.8 6.6

RUM 855 7.3 295 2,570 1,120 1,020 na 2.4 6.8

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
36 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–AES

Al μg/L

ICP–MS

Al μg/L

ICP–MS

Al (avail.) μg/L

ICP–AES

B μg/L

ICP–AES

Ba μg/L

ICP–MS

Ba μg/L

ICP–MS

Ba (avail.) μg/L

ICP–AES

Ca mg/L

ICP–MS

Ca mg/L

CR-Kremmling <10 12 1,450 <5 18 18 69 11 10

CR-Kremmling <10 1.0 53 <5 36 23 40 26 26

CR-Kremmling <10 2 2 6.7 34 18 22 25 22

ER-Minturn 33 47 240 <5 37 34 39 13 13

ER-Minturn <10 19 37 <5 43 42 40 16 16

ER-Minturn 12 16 57 <5 33 32 34 13 12

ER-Avon 47 51 685 <5 38 35 50 13 12

ER-Avon 15 28 79 <5 31 31 31 15 15

ER-Avon <10 7.3 160 5.4 46 47 49 26 24

ER-Gypsum 22 32 4,640 <5 34 32 105 22 22

ER-Gypsum <10 9.8 145 <5 37 35 42 40 39

ER-Gypsum 22 3.0 130 14 41 41 44 61 58

CR-Glenwood 14 17 5,040 <5 35 32 110 26 25

CR-Glenwood <10 8.3 870 <5 48 48 58 44 46

CR-Glenwood <10 2.2 195 16 43 42 45 52 45

RF-Glenwood <10 20 585 <5 41 37 52 34 33

RF-Glenwood <10 8.1 130 <5 47 45 47 55 55

RF-Glenwood <10 1.0 21 15 56 53 51 82 73

PC-Cameo <10 25 4,110 <5 44 42 92 19 20

PC-Cameo <10 3.0 450 <5 110 110 130 48 49

PC-Cameo <10 1.0 430 53 122 115 120 60 52

CR-Cameo <10 23 2,640 <5 44 41 84 38 37

CR-Cameo <10 4.9 420 <5 43 43 54 42 42

CR-Cameo <10 1.0 130 31 51 49 50 71 65

GR-NF 11 24 9,160 <5 33 30 145 15 15

GR-NF 13 28 125 <5 30 29 34 18 18

GR-NF <10 1.0 555 37 83 77 85 42 34

GR-Tunnel <10 33 165 <5 38 35 40 25 25

GR-Tunnel <10 4.1 63 <5 35 35 38 25 26

GR-Tunnel <10 2.8 22 9.4 40 37 36 30 26

GR-Delta <10 18 6,780 <5 40 37 110 29 30

GR-Delta <10 1.0 495 <5 44 44 57 94 105

GR-Delta <10 1.0 1,500 110 53 53 58 130 130

UR-Ouray 40 46 1,350 <5 36 33 37 34 34

UR-Ouray 25 35 2,430 <5 47 46 51 62 63

UR-Ouray 23 25 3,790 17 46 45 46 120 110

UR-Ridgway 52 63 1,200 <5 38 35 47 61 61

UR-Ridgway 39 53 1,340 <5 48 47 61 83 90

UR-Ridgway 40 26 1,690 41 39 40 40 115 110

UR-Delta <10 11 8,660 24 58 53 215 130 140

UR-Delta <10 2.7 4,750 44 54 53 78 145 160

UR-Delta <10 1.0 125 175 37 35 36 210 190

GR-Grand Jct. <10 18 5,530 <5 52 50 110 53 53

GR-Grand Jct. <10 1.0 220 <5 46 45 53 96 105

GR-Grand Jct. <10 5.8 88 71 49 49 48 78 76

CR-State line <10 14 5,070 <5 50 47 110 43 44

CR-State line <10 6.7 695 <5 50 49 72 64 65

CR-State line 26 1.0 390 82 56 52 55 110 105

DR-Dolores 24 32 6,110 <5 66 61 225 21 22

DR-Dolores <10 9.9 47 <5 94 90 105 37 37

DR-Dolores 17 18 39 29 104 105 105 50 46

DR-Bedrock <10 11 2,460 <5 86 81 170 43 44

DR-Bedrock 26 26 7,930 <5 218 205 510 49 47

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 37

Site name ICP–MS

Ca (avail.) mg/L

ICP–MS

Cd μg/L

ICP–MS

Cd (avail.) μg/L

ICP–MS

Ce μg/L

ICP–MS

Ce (avail.) μg/L

ICP–MS

Co μg/L

ICP–MS

Co (avail.) μg/L

ICP–MS

Cr μg/L

CR-Kremmling 18 0.03 0.09 0.09 5.6 0.08 1.0 <1

CR-Kremmling 26 0.04 0.04 0.005 0.20 0.04 0.07 4.2

CR-Kremmling 22 0.05 0.04 0.01 0.005 0.02 0.01 3.3

ER-Minturn 13 0.13 0.18 0.15 0.54 0.08 0.15 <1

ER-Minturn 14 0.14 0.16 0.07 0.16 0.15 0.14 <1

ER-Minturn 11 0.16 0.21 0.10 0.25 0.11 0.16 <1

ER-Avon 14 0.04 0.16 0.16 1.3 0.06 0.38 <1

ER-Avon 14 0.03 0.04 0.05 0.21 0.05 0.08 <1

ER-Avon 22 0.05 0.10 0.02 0.37 0.04 0.16 <1

ER-Gypsum 35 <0.02 0.76 0.10 8.6 0.08 2.5 <1

ER-Gypsum 40 <0.02 0.06 0.02 0.41 0.04 0.16 <1

ER-Gypsum 56 <0.02 0.06 0.02 0.34 0.03 0.14 <1

CR-Glenwood 36 <0.02 0.55 0.07 9.9 0.14 2.7 <1

CR-Glenwood 46 0.02 0.06 0.02 2.4 0.16 0.56 <1

CR-Glenwood 42 <0.02 0.05 0.02 0.51 0.06 0.20 <1

RF-Glenwood 35 <0.02 0.11 0.06 1.5 0.04 0.33 1.0

RF-Glenwood 53 0.02 0.06 0.01 0.3 0.05 0.08 <1

RF-Glenwood 67 0.03 0.04 0.01 0.07 0.01 0.02 <1

PC-Cameo 24 <0.02 0.05 0.13 7.6 0.09 1.3 <1

PC-Cameo 48 <0.02 0.02 0.04 1.3 0.11 0.27 <1

PC-Cameo 46 <0.02 0.02 0.02 0.81 0.08 0.32 <1

CR-Cameo 45 <0.02 0.17 0.02 4.9 0.08 1.1 <1

CR-Cameo 41 0.02 0.05 0.02 1.0 0.05 0.21 <1

CR-Cameo 58 0.03 0.04 0.01 0.31 0.05 0.13 <1

GR-NF 17 <0.02 0.15 0.21 20 0.08 2.9 <1

GR-NF 17 <0.02 0.01 0.04 0.42 0.11 0.09 <1

GR-NF 32 <0.02 0.01 0.02 1.5 0.11 0.39 <1

GR-Tunnel 25 <0.02 0.01 0.02 0.34 0.04 0.07 <1

GR-Tunnel 25 <0.02 0.01 0.005 0.18 0.03 0.04 <1

GR-Tunnel 23 <0.02 0.01 0.005 0.06 0.01 0.02 <1

GR-Delta 35 <0.02 0.14 0.15 13 0.12 2.2 <1

GR-Delta 93 <0.02 0.07 0.01 1.9 0.16 0.42 <1

GR-Delta 125 <0.02 0.61 0.005 7.2 0.15 1.4 <1

Site name ICP–AES

Al μg/L

ICP–MS

Al μg/L

ICP–MS

Al (avail.) μg/L

ICP–AES

B μg/L

ICP–AES

Ba μg/L

ICP–MS

Ba μg/L

ICP–MS

Ba (avail.) μg/L

ICP–AES

Ca mg/L

ICP–MS

Ca mg/L

DR-Bedrock 13 1.0 710 40 161 165 170 59 60

SM-Uravan <10 24 2,250 <5 53 51 89 44 45

SM-Uravan <10 16 515 <5 49 49 64 73 74

SM-Uravan <10 4.4 83 51 58 56 55 105 100

DR-Cisco 30 52 3,260 <5 67 61 130 41 42

DR-Cisco <10 13 7,110 <5 130 135 245 69 76

DR-Cisco 21 3.5 895 68 108 100 105 96 105

CR-Cisco 18 34 6,270 <5 63 61 160 42 42

CR-Cisco 12 7.9 930 <5 53 55 80 59 64

CR-Cisco <10 2.6 535 86 70 59 61 120 110

GW hot spring <10 1.0 3.2 1,490 74 78 89 440 690

RUM 305 na 1.0 2.0 na na 36 37 na 140

RUM 310 na 1.0 2.6 na na 32 31 na 220

RUM 590 na 6 8.2 na na 16 15 na 635

RUM 855 na 16 15 na na 23 20 na 505

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
38 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–MS

Cr (avail) μg/L

ICP–MS

Cs μg/L

ICP–MS

Cs (avail.) μg/L

ICP–MS

Cu μg/L

ICP–MS

Cu (avail.) μg/L

ICP–MS

Dy μg/L

ICP–MS

Dy (avail.) μg/L

ICP–MS

Er μg/L

ICP–MS

Er (avail.) μg/L

CR-Kremmling 1.4 <0.02 0.33 0.84 6.2 0.009 0.33 0.006 0.16

CR-Kremmling <1 <0.02 0.01 0.67 1.1 <0.005 0.02 <0.005 0.01

CR-Kremmling 3.4 <0.02 0.01 1.8 0.55 <0.005 0.003 <0.005 0.003

ER-Minturn <1 <0.02 0.04 2.6 3.7 0.03 0.06 0.02 0.03

ER-Minturn <1 <0.02 0.01 1.6 2.0 0.01 0.02 0.005 0.01

ER-Minturn <1 <0.02 0.01 1.7 2.6 0.01 0.02 0.008 0.01

ER-Avon 1.4 <0.02 0.09 2.1 4.1 0.03 0.12 0.02 0.06

ER-Avon <1 <0.02 0.01 1.8 2.2 0.008 0.02 <0.005 0.01

ER-Avon <1 <0.02 0.05 1.5 2.5 0.005 0.03 <0.005 0.02

ER-Gypsum 5.4 <0.02 0.58 1.5 11 0.02 0.78 0.01 0.34

ER-Gypsum <1 <0.02 0.02 1.1 5.0 <0.005 0.04 <0.005 0.02

ER-Gypsum <1 <0.02 0.02 1.4 1.8 <0.005 0.05 <0.005 0.03

CR-Glenwood 5.6 <0.02 0.70 0.93 10 0.01 0.78 0.008 0.34

CR-Glenwood 1.1 <0.02 0.18 0.95 2.0 0.005 0.15 <0.005 0.06

CR-Glenwood <1 <0.02 0.06 0.88 2.2 <0.005 0.06 <0.005 0.02

Site name ICP–MS

Ca (avail.) mg/L

ICP–MS

Cd μg/L

ICP–MS

Cd (avail.) μg/L

ICP–MS

Ce μg/L

ICP–MS

Ce (avail.) μg/L

ICP–MS

Co μg/L

ICP–MS

Co (avail.) μg/L

ICP–MS

Cr μg/L

UR-Ouray 32 0.73 0.86 0.02 1.6 2.5 2.6 <1

UR-Ouray 58 1.01 1.2 0.12 2.2 4.5 4.7 <1

UR-Ouray 100 1.1 1.3 0.09 2.4 6.1 6.3 <1

UR-Ridgway 59 0.32 0.48 0.02 1.8 0.81 1.1 <1

UR-Ridgway 82 0.29 0.55 0.02 2.5 1.2 1.9 <1

UR-Ridgway 105 0.45 0.59 0.02 1.2 2.5 2.7 <1

UR-Delta 160 <0.02 0.45 0.03 19 0.26 3.2 1.0

UR-Delta 170 0.02 1.2 0.02 21 0.22 4.7 <1

UR-Delta 175 <0.02 0.01 <0.01 0.33 0.15 0.2 <1

GR-Grand Jct. 60 <0.02 0.14 0.05 9.8 0.16 1.6 <1

GR-Grand Jct. 90 <0.02 0.05 0.02 0.66 0.13 0.19 <1

GR-Grand Jct. 65 <0.02 0.01 0.04 0.49 0.12 0.15 <1

CR-State line 53 <0.02 0.22 0.03 9.7 0.12 1.6 1.0

CR-State line 63 <0.02 0.10 0.01 2.6 0.09 0.52 <1

CR-State line 93 0.02 0.08 0.005 1.0 0.10 0.33 <1

DR-Dolores 27 0.04 0.52 0.21 16 0.08 2.5 <1

DR-Dolores 34 0.03 0.06 0.01 0.17 0.02 0.03 <1

DR-Dolores 40 <0.02 0.04 0.02 0.11 0.01 0.03 <1

DR-Bedrock 70 <0.02 0.42 0.04 7.9 0.16 2.0 <1

DR-Bedrock 76 <0.02 0.38 2.7 20 0.14 3.6 <1

DR-Bedrock 51 <0.02 0.07 0.02 2.1 0.10 0.37 <1

SM-Uravan 46 0.04 0.38 0.04 4.2 0.11 0.89 1.2

SM-Uravan 66 0.02 0.18 0.005 1.6 0.10 0.45 <1

SM-Uravan 88 0.03 0.04 0.01 0.22 0.09 0.11 <1

DR-Cisco 49 <0.02 0.27 0.05 5.9 0.06 1.2 1.0

DR-Cisco 86 <0.02 0.21 0.02 13 0.15 2.4 <1

DR-Cisco 90 <0.02 0.06 0.02 1.7 0.10 0.33 <1

CR-Cisco 56 <0.02 0.32 0.06 13 0.05 2.2 1.4

CR-Cisco 64 <0.02 0.07 0.005 2.1 0.09 0.41 <1

CR-Cisco 98 0.02 0.04 0.02 1.1 0.12 0.29 <1

GW hot spring 550 <0.02 0.02 0.02 0.02 0.26 0.02 <1

RUM 305 150 2.7 2.7 0.04 0.05 2.4 2.5 5.5

RUM 310 205 1.0 1.0 0.08 0.13 2.3 2.4 6.5

RUM 590 565 24 22 1.1 1.1 20 18 6.4

RUM 855 465 4.8 4.4 0.08 0.08 1.6 1.3 4.5

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 39

Site name ICP–MS

Cr (avail) μg/L

ICP–MS

Cs μg/L

ICP–MS

Cs (avail.) μg/L

ICP–MS

Cu μg/L

ICP–MS

Cu (avail.) μg/L

ICP–MS

Dy μg/L

ICP–MS

Dy (avail.) μg/L

ICP–MS

Er μg/L

ICP–MS

Er (avail.) μg/L

RF-Glenwood <1 <0.02 0.10 0.88 1.8 0.02 0.15 0.009 0.07

RF-Glenwood <1 <0.02 0.06 0.66 0.95 <0.005 0.03 <0.005 0.01

RF-Glenwood <1 0.02 0.03 0.78 0.83 <0.005 0.01 <0.005 0.005

PC-Cameo 3.1 <0.02 0.23 1.0 4.2 0.03 0.47 0.02 0.23

PC-Cameo <1 <0.02 0.04 1.4 1.9 0.007 0.07 <0.005 0.04

PC-Cameo <1 <0.02 0.02 1.0 1.6 <0.005 0 <0.005 0.051

CR-Cameo 2.4 <0.02 0.33 0.86 3.9 0.008 0.39 0.005 0.17

CR-Cameo <1 0.04 0.16 1.3 1.4 <0.005 0.08 <0.005 0.03

CR-Cameo <1 0.10 0.15 0.94 1.1 <0.005 0.04 <0.005 0.02

GR-NF 5.3 <0.02 0.66 1.1 8.8 0.04 1.2 0.02 0.58

GR-NF <1 <0.02 0.01 0.93 0.76 0.01 0.04 0.009 0.03

GR-NF <1 <0.02 0.07 0.69 1.4 0.005 0.13 <0.005 0.05

GR-Tunnel <1 <0.02 0.02 0.84 1.2 0.005 0.03 <0.005 0.01

GR-Tunnel <1 <0.02 0.01 1.2 1.8 <0.005 0.02 <0.005 0.01

GR-Tunnel <1 <0.02 0.01 0.92 1.1 <0.005 0.006 <0.005 0.003

GR-Delta 4.0 <0.02 0.41 1.2 6.4 0.03 0.89 0.02 0.40

GR-Delta <1 <0.02 0.12 1.5 2.7 <0.005 0.18 <0.005 0.08

GR-Delta 1.9 <0.02 0.08 2.4 4.6 <0.005 0.83 <0.005 0.35

UR-Ouray <1 0.40 0.50 5.2 66 <0.005 0.15 <0.005 0.06

UR-Ouray <1 0.78 0.96 6.4 105 0.006 0.22 <0.005 0.10

UR-Ouray <1 2.7 2.7 9.0 135 0.005 0.25 <0.005 0.11

UR-Ridgway <1 0.18 0.40 6.0 27 <0.005 0.13 <0.005 0.05

UR-Ridgway <1 0.18 0.46 4.6 42 <0.005 0.23 <0.005 0.10

UR-Ridgway <1 0.99 1.05 5.4 58 <0.005 0.13 <0.005 0.05

UR-Delta 5.9 <0.02 1.1 2.4 15 0.01 1.2 <0.005 0.54

UR-Delta 5.5 <0.02 0.26 2.3 15 0.006 2.1 <0.005 0.90

UR-Delta <1 <0.02 0.03 2.7 3.1 <0.005 0.03 <0.005 0.01

GR-Grand Jct. 3.8 <0.02 0.52 1.5 6.0 0.01 0.67 0.01 0.30

GR-Grand Jct. <1 <0.02 0.05 1.9 2.4 0.005 0.06 <0.005 0.02

GR-Grand Jct. <1 <0.02 0.04 1.2 1.4 0.009 0.05 0.005 0.02

CR-State line 3.9 <0.02 0.55 2.2 6.2 0.009 0.65 0.006 0.29

CR-State line <1 <0.02 0.14 1.3 2.6 <0.005 0.22 <0.005 0.10

CR-State line <1 <0.02 0.05 1.7 2.5 <0.005 0.12 <0.005 0.05

DR-Dolores 3.9 <0.02 0.94 1.8 10 0.051 1.1 0.03 0.51

DR-Dolores <1 0.17 0.23 0.69 0.8 <0.005 0.02 <0.005 0.01

DR-Dolores <1 0.27 0.31 0.94 1.3 <0.005 0.02 <0.005 0.01

DR-Bedrock 2.7 <0.02 0.16 1.1 6 0.005 0.84 <0.005 0.38

DR-Bedrock 4.0 <0.02 0.13 2.7 16 0.15 2.0 0.04 0.83

DR-Bedrock <1 <0.02 0.07 1.1 2.1 <0.005 0.15 <0.005 0.07

SM-Uravan 1.7 <0.02 0.39 2.4 9.3 0.01 0.29 0.007 0.13

SM-Uravan <1 <0.02 0.08 1.6 3.3 <0.005 0.11 <0.005 0.06

SM-Uravan <1 <0.02 0.01 1.8 2.0 <0.005 0.02 <0.005 0.01

DR-Cisco 2.3 <0.02 0.36 2.3 7.5 0.008 0.45 <0.005 0.20

DR-Cisco 4.8 <0.02 0.84 1.9 8.6 0.006 0.81 <0.005 0.37

DR-Cisco 1.1 <0.02 0.13 1.5 2.4 <0.005 0.12 <0.005 0.05

CR-Cisco 5.2 <0.02 0.66 4.3 14 0.005 0.89 <0.005 0.39

CR-Cisco 1.3 <0.02 0.19 1.4 3.0 <0.005 0.14 <0.005 0.06

CR-Cisco <1 <0.02 0.09 1.7 3.0 0.005 0.08 <0.005 0.03

GW hot spring 1.0 59 73 4.1 7.6 0.006 0.005 <0.005 0.006

RUM 305 4.2 0.28 0.29 7.0 8.0 0.01 0.009 0.006 0.007

RUM 310 5.9 0.70 0.68 3.2 3.4 0.02 0.02 0.02 0.02

RUM 590 5.8 10 9.5 18 17 0.20 0.21 0.13 0.13

RUM 855 4.9 0.17 0.16 7.0 7.1 0.03 0.02 0.02 0.02

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
40 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–MS

Eu μg/L

ICP–MS

Eu (avail.) μg/L

ICP–MS

Fe μg/L

ICP–MS

Fe (avail.) μg/L

ICP–MS

Gd μg/L

ICP–MS

Gd (avail.) μg/L

ICP–MS

Ho μg/L

ICP–MS

Ho (avail.) μg/L

ICP–AES

K mg/L

ICP–MS

K mg/L

CR-Kremmling 0.006 0.11 51 2,700 0.009 0.46 <0.005 0.05 1.0 0.90

CR-Kremmling 0.003 0.01 <50 140 <0.005 0.02 <0.005 0.003 1.6 1.6

CR-Kremmling 0.003 0.003 <50 25 <0.005 0.003 <0.005 0.003 1.7 1.6

ER-Minturn 0.01 0.02 <50 345 0.04 0.08 0.005 0.01 0.72 0.64

ER-Minturn 0.01 0.01 310 485 0.02 0.02 <0.005 0.003 0.59 0.6

ER-Minturn 0.006 0.01 222 555 0.01 0.03 <0.005 0.005 0.80 0.73

ER-Avon 0.02 0.05 63 785 0.054 0.18 0.006 0.02 0.58 0.49

ER-Avon 0.007 0.01 101 190 0.01 0.03 <0.005 0.003 0.55 0.52

ER-Avon 0.006 0.02 <50 325 0.007 0.05 <0.005 0.006 0.96 0.88

ER-Gypsum 0.01 0.27 <50 6,170 0.03 1.2 0.005 0.12 0.88 0.79

ER-Gypsum 0.006 0.02 <50 230 <0.005 0.06 <0.005 0.007 1.3 1.2

ER-Gypsum 0.007 0.02 <50 245 0.005 0.08 <0.005 0.008 2.0 1.9

CR-Glenwood 0.01 0.27 <50 6,600 0.02 1.2 <0.005 0.13 1.1 1.1

CR-Glenwood 0.008 0.06 <50 1,020 <0.005 0.23 <0.005 0.02 2.2 2.0

CR-Glenwood 0.007 0.02 <50 265 <0.005 0.09 <0.005 0.01 2.3 2.1

RF-Glenwood 0.01 0.05 <50 730 0.02 0.23 <0.005 0.02 0.81 0.77

RF-Glenwood 0.007 0.01 <50 180 <0.005 0.04 <0.005 0.005 1.2 1.2

RF-Glenwood 0.007 0.01 <50 25 <0.005 0.01 <0.005 0.003 1.7 1.5

PC-Cameo 0.02 0.16 <50 2,900 0.04 0.71 0.005 0.08 1.4 1.3

PC-Cameo 0.02 0.04 <50 390 0.01 0.12 <0.005 0.02 3.7 3.8

PC-Cameo 0.02 0.05 <50 315 0.005 0.15 <0.005 0.02 4.1 3.7

CR-Cameo 0.009 0.14 <50 2,280 0.008 0.6 <0.005 0.06 1.3 1.4

CR-Cameo 0.006 0.03 <50 410 0.005 0.13 <0.005 0.01 1.7 1.7

CR-Cameo 0.008 0.02 <50 125 0.005 0.06 <0.005 0.007 3.1 2.9

GR-NF 0.02 0.44 <50 8,290 0.04 1.9 0.007 0.20 0.9 0.91

GR-NF 0.008 0.02 <50 105 0.01 0.06 <0.005 0.008 4.6 4.7

GR-NF 0.01 0.05 <50 660 <0.005 0.20 <0.005 0.02 1.1 0.99

GR-Tunnel 0.006 0.01 <50 110 0.008 0.04 <0.005 0.003 1.6 1.6

GR-Tunnel 0.005 0.01 <50 25 <0.005 0.02 <0.005 0.003 1.4 1.4

GR-Tunnel 0.005 0.006 <50 25 <0.005 0.009 <0.005 0.003 1.5 1.4

GR-Delta 0.01 0.31 <50 5,770 0.03 1.3 0.005 0.14 1.5 1.5

GR-Delta 0.007 0.06 <50 757 0.006 0.27 <0.005 0.03 3.9 4.0

GR-Delta 0.007 0.26 <50 1,870 <0.005 1.2 <0.005 0.14 4.1 4.0

UR-Ouray 0.006 0.05 <50 1,370 <0.005 0.23 <0.005 0.02 0.59 0.57

UR-Ouray 0.009 0.07 <50 2,420 0.007 0.32 <0.005 0.04 0.84 0.86

UR-Ouray 0.007 0.08 <50 1,280 0.006 0.38 <0.005 0.04 1.4 1.3

UR-Ridgway 0.006 0.05 <50 925 <0.005 0.20 <0.005 0.02 1.3 1.3

UR-Ridgway 0.007 0.08 <50 1,690 0.005 0.34 <0.005 0.04 1.6 1.7

UR-Ridgway 0.005 0.04 <50 1,250 <0.005 0.18 <0.005 0.02 2.0 1.8

UR-Delta 0.01 0.44 <50 7,780 0.007 1.9 <0.005 0.20 3.2 3.4

UR-Delta 0.009 0.59 <50 7,450 <0.005 2.89 <0.005 0.35 4.5 4.8

UR-Delta 0.005 0.01 <50 145 <0.005 0.04 <0.005 0.006 4.0 3.5

GR-Grand Jct. 0.01 0.23 <50 4,410 0.02 1.1 <0.005 0.11 2.0 2.1

GR-Grand Jct. 0.007 0.02 <50 175 0.006 0.07 <0.005 0.01 2.8 3.1

GR-Grand Jct. 0.009 0.02 <50 125 0.02 0.10 <0.005 0.007 3.3 3.3

CR-State line 0.009 0.22 <50 4,370 0.01 0.99 <0.005 0.1 1.6 1.7

CR-State line 0.007 0.07 <50 870 0.005 0.32 <0.005 0.04 2.2 2.3

CR-State line 0.007 0.04 <50 405 <0.005 0.17 <0.005 0.02 3.8 3.4

DR-Dolores 0.02 0.39 <50 5,140 0.066 1.7 0.008 0.18 0.94 0.92

DR-Dolores 0.01 0.02 <50 25 <0.005 0.03 <0.005 0.003 1.4 1.3

DR-Dolores 0.02 0.02 <50 25 <0.005 0.02 <0.005 0.003 1.9 1.9

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 41

Site name ICP–MS

K (avail.) mg/L

ICP–MS

La μg/L

ICP–MS

La (avail.) μg/L

ICP–AES

Li μg/L

ICP–MS

Li μg/L

ICP–MS

Li (avail.) μg/L

ICP–AES

Mg mg/L

ICP–MS

Mg mg/L

ICP–MS

Mg (avail.) mg/L

ICP–AES

Mn μg/L

CR-Kremmling 1.9 0.05 2.7 2.6 3.1 6.8 1.8 1.7 3.0 51

CR-Kremmling 1.6 <0.01 0.11 6.2 5.6 6.3 4.7 4.6 4.3 <10

CR-Kremmling 1.7 0.01 0.005 6.7 5.6 7.3 4.4 4.3 4.3 <10

ER-Minturn 0.66 0.10 0.27 1.0 1.3 1.4 4.7 4.5 3.9 28

ER-Minturn 0.55 0.04 0.09 1.2 1.0 1.8 5.6 5.7 4.8 99

ER-Minturn 0.76 0.05 0.13 0.5 1.0 1.5 4.9 4.8 4.5 90

ER-Avon 0.71 0.16 0.73 2.0 1.4 2.2 3.2 2.9 3.2 10

ER-Avon 0.52 0.04 0.14 2.0 1.4 2.3 3.8 3.9 3.4 12

ER-Avon 0.89 0.01 0.20 5.2 3.9 5.2 7.3 7.3 6.8 44

ER-Gypsum 1.9 0.08 3.9 1.4 2.2 7.6 4.4 4.2 6.3 13

ER-Gypsum 1.2 0.02 0.20 3.6 3.2 4.2 7.3 7.2 7.0 10

ER-Gypsum 1.9 <0.01 0.15 3.8 2.6 5.4 12 11 11 <10

CR-Glenwood 2.4 0.04 4.5 3.4 3.7 9.3 5.4 5.3 7.3 43

CR-Glenwood 2.2 0.01 0.98 6.8 7.2 9.4 8.2 8.7 8.7 13

CR-Glenwood 2.1 0.01 0.22 8.2 5.6 8.6 10 9.6 9.3 13

RF-Glenwood 0.87 0.05 0.7 3.1 3.7 4.2 5.3 5.2 4.8 <10

RF-Glenwood 1.2 <0.01 0.15 5.8 5.5 5.4 8.6 8.7 8.2 <10

RF-Glenwood 1.5 0.01 0.04 8.1 5.6 8.4 14 12 12 <10

PC-Cameo 2.1 0.08 3.2 3.0 3.8 6.9 6.3 6.6 7.7 <10

PC-Cameo 3.8 0.02 0.52 13 12 17 23 24 23 <10

PC-Cameo 3.7 0.01 0.33 16 15 18 32 30 27 <10

CR-Cameo 2.1 0.02 2.1 6.8 6.4 9.7 8.8 9.0 11 <10

CR-Cameo 1.7 0.01 0.46 7.6 8.9 12 8.6 9.1 8.8 <10

CR-Cameo 2.8 <0.01 0.13 17 17 20 17 15 14 <10

GR-NF 2.7 0.13 8.7 0.5 1.5 7.2 2.7 2.7 4.3 12

GR-NF 0.61 0.03 0 12 12 3.4 5.0 5.0 4.6 11

GR-NF 1.1 0.01 0.61 5.8 4.1 6.3 11 11 10 39

GR-Tunnel 1.6 0.02 0.15 4.3 4.8 4.9 5.5 5.5 4.9 <10

GR-Tunnel 1.4 <0.01 0.09 3.7 4.7 6.0 5.2 5.3 5.1 <10

GR-Tunnel 1.3 <0.01 0.03 5.5 5.1 6.2 6.3 6.0 5.1 <10

GR-Delta 2.7 0.08 5.7 9.0 9.6 15 8.5 8.7 11 18

GR-Delta 3.8 <0.01 0.76 41 42 49 31 33 29 26

GR-Delta 3.8 <0.01 2.8 60 56 67 42 39 36 10

Site name ICP–MS

Eu μg/L

ICP–MS

Eu (avail.) μg/L

ICP–MS

Fe μg/L

ICP–MS

Fe (avail.) μg/L

ICP–MS

Gd μg/L

ICP–MS

Gd (avail.) μg/L

ICP–MS

Ho μg/L

ICP–MS

Ho (avail.) μg/L

ICP–AES

K mg/L

ICP–MS

K mg/L

DR-Bedrock 0.01 0.27 <50 3,750 0.01 1.2 <0.005 0.14 2.2 2.3

DR-Bedrock 0.1 0.65 <50 4,260 0.36 3.0 0.02 0.33 13 13

DR-Bedrock 0.03 0.08 <50 660 <0.005 0.26 <0.005 0.02 5.1 5.0

SM-Uravan 0.01 0.11 <50 1,580 0.01 0.47 <0.005 0.04 1.2 1.2

SM-Uravan 0.008 0.04 <50 415 <0.005 0.17 <0.005 0.02 1.6 1.6

SM-Uravan 0.009 0.01 <50 53 <0.005 0.03 <0.005 0.003 2.1 1.9

DR-Cisco 0.01 0.15 <50 2,660 0.006 0.68 <0.005 0.07 1.7 1.7

DR-Cisco 0.02 0.34 83 4,110 0.005 1.4 <0.005 0.15 5.5 5.9

DR-Cisco 0.02 0.06 <50 715 <0.005 0.20 <0.005 0.02 11 12

CR-Cisco 0.01 0.29 <50 5,560 0.009 1.3 <0.005 0.14 1.7 1.7

CR-Cisco 0.009 0.06 <50 885 <0.005 0.22 <0.005 0.02 2.4 2.7

CR-Cisco 0.01 0.04 <50 470 0.005 0.13 <0.005 0.01 5.2 4.5

GW hot spring 0.01 0.01 <50 <50 0.005 0.006 <0.005 <0.005 160 160

RUM 305 0.003 0.006 <50 25 <0.005 0.006 <0.005 <0.005 5.9 na

RUM 310 0.007 0.008 710 820 0.01 0.02 0.005 0.005 7.7 na

RUM 590 0.04 0.05 <50 25 0.34 0.33 0.05 0.05 19 na

RUM 855 0.005 0.003 280 300 0.03 0.03 0.008 0.007 9.5 na

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
42 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–MS

Mn μg/L

ICP–MS

Mn (avail.) μg/L

ICP–MS

Mo μg/L

ICP–MS

Mo (avail.) μg/L

ICP–AES

Na mg/L

ICP–MS

Na mg/L

ICP–MS

Na (avail.) mg/L

ICP–MS

Nd μg/L

ICP–MS

Nd (avail.) μg/L

ICP–MS

Ni μg/L

CR-Kremmling 45 320 <2 <2 3.9 3.8 5.8 0.05 2.7 0.8

CR-Kremmling 1.8 31 20 17 6.8 6.6 6.1 0.005 0.13 0.9

CR-Kremmling 11 11 20 14 7.3 7.1 7.4 0.01 0.01 0.9

ER-Minturn 25 40 <2 <2 1.2 1.2 1.1 0.16 0.36 0.7

ER-Minturn 97 89 <2 <2 1.4 1.5 1.3 0.06 0.11 1.0

ER-Minturn 87 105 <2 <2 1.7 1.8 1.8 0.08 0.17 0.8

ER-Avon 9.3 73 <2 <2 1.5 1.4 1.5 0.23 0.95 0.7

ER-Avon 12 19 <2 <2 1.8 1.9 1.7 0.05 0.13 1.0

ER-Avon 43 71 <2 <2 3.8 3.8 3.7 0.02 0.23 0.9

ER-Gypsum 12 275 <2 <2 3.8 3.8 3.8 0.13 5.5 1.2

ER-Gypsum 9.6 26 <2 <2 17 17 16 0.02 0.25 1.0

ER-Gypsum 8.6 28 <2 <2 34 34 34 0.02 0.26 1.6

CR-Glenwood 38 295 <2 <2 9.2 8.9 8.3 0.06 5.9 1.6

CR-Glenwood 13 60 9.5 9.6 41 42 40 0.02 1.3 2.1

Site name ICP–MS

K (avail.) mg/L

ICP–MS

La μg/L

ICP–MS

La (avail.) μg/L

ICP–AES

Li μg/L

ICP–MS

Li μg/L

ICP–MS

Li (avail.) μg/L

ICP–AES

Mg mg/L

ICP–MS

Mg mg/L

ICP–MS

Mg (avail.) mg/L

ICP–AES

Mn μg/L

UR-Ouray 0.56 0.02 0.79 12 13 12 2.2 2.2 1.8 213

UR-Ouray 0.81 0.12 1.0 28 30 29 3.2 3.2 2.9 307

UR-Ouray 1.3 0.1 1.1 68 54 68 5.0 4.2 4.1 360

UR-Ridgway 1.3 0.01 0.88 28 29 29 6.3 6.2 5.2 94

UR-Ridgway 1.6 0.02 1.1 42 43 44 9.2 9.6 8.3 130

UR-Ridgway 1.8 0.02 0.56 67 59 71 11 10 9.9 185

UR-Delta 6.0 0.02 8.2 61 59 70 32 33 28 30

UR-Delta 5.1 <0.01 8.5 65 63 74 35 37 31 23

UR-Delta 3.4 <0.01 0.14 120 92 110 63 48 48 50

GR-Grand Jct. 3.3 0.03 4.1 20 21 26 14 15 17 16

GR-Grand Jct. 2.9 <0.01 0.29 42 43 51 27 29 25 <10

GR-Grand Jct. 3.1 0.02 0.17 31 31 35 30 29 26 38

CR-State line 2.9 0.02 4.2 11 13 17 11 12 14 <10

CR-State line 2.3 <0.01 1.1 19 22 27 17 18 17 <10

CR-State line 3.3 <0.01 0.40 42 39 44 34 31 27 <10

DR-Dolores 2.4 0.16 7.3 3.3 4.2 8.2 3.1 3.1 4.9 14

DR-Dolores 1.2 0.01 0.1 13 14 18 5.3 5.3 5.0 10

DR-Dolores 1.8 0.01 0.06 22 24 27 7.4 7.7 6.9 <10

DR-Bedrock 3.0 0.02 3.1 14 16 20 9.0 9.4 13 <10

DR-Bedrock 14 1.47 9.2 17 17 33 13 13 18 11

DR-Bedrock 4.9 0.01 0.92 30 32 35 16 17 15 10

SM-Uravan 1.7 0.03 1.9 9.8 11 12 9.6 10 10 21

SM-Uravan 1.5 <0.01 0.72 21 23 27 18 18 16 11

SM-Uravan 1.8 <0.01 0.1 34 33 37 33 31 28 24

DR-Cisco 2.7 0.02 2.6 11 12 14 8.6 8.7 10 <10

DR-Cisco 8.8 0.01 5.9 22 23 39 19 20 23 <10

DR-Cisco 11 0.01 0.72 30 27 31 31 34 29 <10

CR-Cisco 3.4 0.04 5.5 10 11 17 10 10 13 <10

CR-Cisco 2.8 <0.01 0.91 18 21 27 16 17 17 <10

CR-Cisco 4.4 <0.01 0.45 46 38 41 39 36 32 11

GW hot spring 170 0.01 0.01 850 630 795 83 87 105 47

RUM 305 5.9 0.03 0.03 na 35 36 na 61 62 na

RUM 310 7.1 0.07 0.10 na 53 50 na 110 105 na

RUM 590 17 0.82 0.79 na 95 86 na 62 55 na

RUM 855 8.4 0.08 0.07 na 35 31 na 28 25 na

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 43

Site name ICP–MS

Mn μg/L

ICP–MS

Mn (avail.) μg/L

ICP–MS

Mo μg/L

ICP–MS

Mo (avail.) μg/L

ICP–AES

Na mg/L

ICP–MS

Na mg/L

ICP–MS

Na (avail.) mg/L

ICP–MS

Nd μg/L

ICP–MS

Nd (avail.) μg/L

ICP–MS

Ni μg/L

CR-Glenwood 13 30 6.0 4.5 50 50 54 0.02 0.34 1.8

RF-Glenwood 4.4 30 <2 <2 5.5 5.4 4.8 0.07 0.93 1.1

RF-Glenwood 5.2 12 <2 <2 16 16 15 0.01 0.19 1.6

RF-Glenwood 3.2 6 <2 <2 37 33 33 0.01 0.05 1.6

PC-Cameo 6.2 83 <2 <2 7.2 7.5 7.7 0.13 3.9 1.4

PC-Cameo 4.3 33 2.9 3.2 30 31 29 0.03 0.62 1.9

PC-Cameo 5.9 40 2.7 <2 43 40 38 0.02 0.54 1.9

CR-Cameo 4.9 72 <2 <2 26 26 27 0.02 2.9 1.5

CR-Cameo 3.4 24 4.0 4.2 44 45 42 0.02 0.57 1.2

CR-Cameo 3.7 14 4.6 3.8 110 110 99 0.005 0.23 1.8

GR-NF 12 195 <2 <2 3.7 3.7 4.2 0.19 10 0.8

GR-NF 10 17 <2 <2 12 12 6.7 0.05 0.27 1.0

GR-NF 35 62 <2 <2 17 15 14 0.02 0.88 1.2

GR-Tunnel 3.3 18 <2 <2 5 4.9 4.4 0.02 0.16 0.9

GR-Tunnel 1.6 13 <2 <2 4.5 4.6 4.4 0.01 0.10 0.9

GR-Tunnel 0.80 5.8 <2 <2 5.4 5.0 4.6 0.005 0.03 0.8

GR-Delta 17 150 <2 <2 12 11 12 0.12 6.9 1.5

GR-Delta 24 61 2.3 1.9 49 51 43 0.02 1.1 3.0

GR-Delta 12 120 2.4 <2 70 70 67 0.005 5.3 4.2

UR-Ouray 205 205 <2 <2 3 3.1 2.6 0.02 0.96 3.0

UR-Ouray 305 315 <2 <2 6.0 6.1 5.3 0.05 1.2 4.9

UR-Ouray 375 390 <2 <2 14 12 13 0.03 1.4 7.3

UR-Ridgway 91 120 <2 <2 9.9 9.8 8.1 0.005 1.0 2.5

UR-Ridgway 130 170 <2 <2 15 15 12 0.01 1.5 2.6

UR-Ridgway 185 195 <2 <2 22 20 21 0.01 0.74 4.6

UR-Delta 28 260 3.6 4.0 58 59 46 0.03 9.8 4.7

UR-Delta 23 415 3.7 <2 65 66 48 0.02 13 3.7

UR-Delta 49 56 3.5 3.4 115 115 115 0.005 0.18 5.7

GR-Grand Jct. 16 125 <2 <2 21 22 22 0.06 5.3 2.2

GR-Grand Jct. 9 23 2.4 2.4 44 46 40 0.01 0.39 2.6

GR-Grand Jct. 37 44 <2 <2 45 44 40 0.05 0.39 2.4

CR-State line 5.2 125 <2 2.1 24 25 24 0.03 5.2 2.0

CR-State line 2.2 47 3.8 2.7 46 48 43 0.005 1.5 1.7

CR-State line 4.4 30 3.9 2.4 94 94 92 0.005 0.71 3.6

DR-Dolores 13 385 <2 <2 1.6 1.7 2.5 0.22 8.5 1.0

DR-Dolores 9.7 22 <2 <2 5.2 5.3 4.8 0.01 0.11 0.9

DR-Dolores 0.40 20 <2 <2 9.0 9.3 8.7 0.02 0.08 1.5

DR-Bedrock 4.9 120 2 <2 19 19 20 0.03 5.2 2.6

DR-Bedrock 11 375 2.1 <2 225 225 225 1.52 13 1.9

DR-Bedrock 11 30 <2 <2 125 125 120 0.01 1.3 2.2

SM-Uravan 20 130 <2 <2 7.7 7.9 7.7 0.04 2.2 1.6

SM-Uravan 11 77 2.1 <2 13 13 11 0.01 0.87 1.9

SM-Uravan 24 29 <2 <2 26 25 23 0.005 0.14 3.1

DR-Cisco 1.7 120 <2 <2 15 15 15 0.03 3.3 1.8

DR-Cisco 2.4 240 3.1 3.0 87 87 87 0.01 7.5 3.1

DR-Cisco 10 27 2.4 2.4 230 230 205 0.01 0.97 4.1

CR-Cisco 0.20 170 2.2 1.9 20 20 20 0.04 6.8 2.0

CR-Cisco 0.3 36 4.2 4.5 48 54 52 0.01 1.1 2.2

CR-Cisco 11 24 4.5 4.5 140 140 105 0.01 0.59 4.2

GW hot spring 54 50 <2 <2 150 120 165 0.01 0.01 8.2

RUM 305 265 265 39 17 na 120 125 0.03 0.03 2.7

RUM 310 1,380 1,330 43 37 na nr nr 0.05 0.08 2.6

RUM 590 9,980 9,110 2,130 1,950 na nr nr 0.76 0.70 12

RUM 855 1,410 1,240 1,600 1,470 na 180 164 0.06 0.06 7.4

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
44 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–MS

Ni (avail.) μg/L

ICP–MS

P mg/L

ICP–MS

P (avail.) mg/L

ICP–MS

Pb μg/L

ICP–MS

Pb (avail.) μg/L

ICP–MS

Pr μg/L

ICP–MS

Pr (avail.) μg/L

ICP–MS

Rb μg/L

ICP–MS

Rb (avail.) μg/L

CR-Kremmling 2.0 0.03 0.1 <0.05 2.7 0.01 0.65 0.61 4.8

CR-Kremmling 0.5 <0.01 <0.01 <0.05 0.20 <0.01 0.03 1.1 1.3

CR-Kremmling 0.6 <0.01 <0.01 0.08 0.05 <0.01 0.005 1.1 1.3

ER-Minturn 0.6 <0.01 <0.01 0.3 1.9 0.03 0.08 0.39 0.76

ER-Minturn 0.5 0.02 <0.01 0.2 0.58 0.01 0.02 0.52 0.55

ER-Minturn 0.7 <0.01 <0.01 0.2 0.94 0.02 0.04 0.68 0.79

ER-Avon 1.0 <0.01 0.02 0.2 11 0.05 0.21 0.34 1.6

ER-Avon 0.6 0.02 0.02 0.2 0.40 0.01 0.03 0.54 0.63

ER-Avon 1.4 <0.01 <0.01 <0.05 0.86 <0.01 0.05 0.69 1.0

ER-Gypsum 8.3 0.01 0.2 0.09 16 0.02 1.2 0.38 7.8

ER-Gypsum 0.7 <0.01 0.02 0.06 0.68 <0.01 0.06 0.61 0.90

ER-Gypsum 1.8 0.03 0.03 0.06 0.72 <0.01 0.05 0.88 1.1

CR-Glenwood 8.7 0.01 0.2 0.06 12 0.01 1.31 0.65 8.9

CR-Glenwood 2.2 0.02 0.05 0.06 1.1 <0.01 0.31 1.1 3.1

CR-Glenwood 1.9 <0.01 <0.01 0.05 0.54 <0.01 0.08 1.5 1.8

RF-Glenwood 1.0 <0.01 0.02 0.1 3.9 0.02 0.21 0.62 1.6

RF-Glenwood 0.9 <0.01 0.01 0.1 1.3 <0.01 0.04 1.0 1.3

RF-Glenwood 1.6 <0.01 <0.01 0.2 0.61 <0.01 0.01 1.4 1.4

PC-Cameo 4.0 0.03 0.1 <0.05 1.7 0.03 0.90 0.46 4.8

PC-Cameo 1.3 0.03 0.06 0.08 0.40 <0.01 0.16 1.7 2.5

PC-Cameo 2.0 <0.01 <0.01 <0.05 0.40 <0.01 0.11 1.7 2.2

CR-Cameo 3.6 <0.01 0.1 <0.05 3.7 <0.01 0.61 1.2 4.9

CR-Cameo 0.8 <0.01 0.02 0.2 1.2 <0.01 0.14 2.2 3.1

CR-Cameo 1.5 <0.01 <0.01 0.06 0.40 <0.01 0.04 4.4 4.8

GR-NF 6.8 <0.01 0.2 0.06 6.5 0.04 2.4 0.36 11

GR-NF 0.4 0.06 <0.01 0.06 0.2 <0.01 0.06 0.84 0.44

GR-NF 1.4 <0.01 0.01 <0.05 0.89 <0.01 0.19 0.27 1.0

GR-Tunnel 0.4 <0.01 0.01 <0.05 0.20 <0.01 0.04 1.4 1.8

GR-Tunnel 0.4 <0.01 <0.01 0.06 0.2 <0.01 0.02 1.3 1.6

GR-Tunnel 0.5 <0.01 <0.01 <0.05 0.05 <0.01 0.005 1.2 1.4

GR-Delta 6.0 0.01 0.2 <0.05 4.7 0.02 1.6 0.64 7.2

GR-Delta 2.1 <0.01 0.04 <0.05 1.3 <0.01 0.26 2.4 3.7

GR-Delta 7.9 <0.01 0.2 <0.05 3.3 <0.01 1.1 2.0 4.2

UR-Ouray 2.3 <0.01 <0.01 <0.05 6.2 <0.01 0.21 1.5 1.7

UR-Ouray 4.0 <0.01 <0.01 <0.05 8.2 0.01 0.29 3.1 3.5

UR-Ouray 7.3 <0.01 <0.01 <0.05 4.7 <0.01 0.31 7.5 7.8

UR-Ridgway 1.6 <0.01 0.02 <0.05 4.8 <0.01 0.23 1.8 2.6

UR-Ridgway 2.4 <0.01 0.05 <0.05 7.6 <0.01 0.33 2.7 3.6

UR-Ridgway 5.0 <0.01 <0.01 <0.05 3.1 <0.01 0.16 4.8 5.0

UR-Delta 10 0.06 0.4 <0.05 13 <0.01 2.3 1.3 16

UR-Delta 15 0.03 0.5 <0.05 18 <0.01 2.8 1.8 9.9

UR-Delta 5.5 <0.01 0.01 <0.05 0.40 <0.01 0.05 1.8 2.0

GR-Grand Jct. 5.5 <0.01 0.2 0.07 4.6 <0.01 1.2 1.0 7.3

GR-Grand Jct. 1.4 <0.01 <0.01 <0.05 0.66 <0.01 0.09 1.6 2.1

GR-Grand Jct. 1.6 <0.01 <0.01 <0.05 0.20 <0.01 0.08 2.1 2.3

CR-State line 5.0 0.01 0.2 0.09 7.1 <0.01 1.2 0.95 7.3

CR-State line 1.9 <0.01 0.05 0.06 1.9 <0.01 0.35 1.8 3.2

CR-State line 3.0 <0.01 <0.01 <0.05 0.83 <0.01 0.14 2.7 3.4

DR-Dolores 5.7 <0.01 0.2 0.2 19 0.05 2.0 0.78 9.0

DR-Dolores 0.4 <0.01 <0.01 <0.05 0.20 <0.01 0.03 3.8 4.2

DR-Dolores 1.0 <0.01 <0.01 <0.05 0.2 <0.01 0.02 5.9 6.3

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 45

Site name ICP–MS

Ni (avail.) μg/L

ICP–MS

P mg/L

ICP–MS

P (avail.) mg/L

ICP–MS

Pb μg/L

ICP–MS

Pb (avail.) μg/L

ICP–MS

Pr μg/L

ICP–MS

Pr (avail.) μg/L

ICP–MS

Rb μg/L

ICP–MS

Rb (avail.) μg/L

DR-Bedrock 7.8 <0.01 0.2 <0.05 4.7 <0.01 1.1 0.82 4.4

DR-Bedrock 7.9 <0.01 0.3 0.07 15 0.34 2.9 3.8 13

DR-Bedrock 2.6 <0.01 0.02 <0.05 0.85 <0.01 0.28 1.4 2.3

SM-Uravan 1.9 <0.01 0.08 0.1 14 <0.01 0.51 0.55 3.3

SM-Uravan 1.0 <0.01 0.01 0.3 4.2 <0.01 0.20 0.84 1.7

SM-Uravan 2.0 <0.01 <0.01 0.06 0.40 <0.01 0.03 0.92 1.1

DR-Cisco 3.7 <0.01 0.1 0.1 11 <0.01 0.75 0.68 4.8

DR-Cisco 6.1 0.03 0.2 0.07 6.8 <0.01 1.8 1.4 12

DR-Cisco 3.6 0.03 0.03 <0.05 0.87 <0.01 0.22 2.8 4.0

CR-Cisco 7.4 0.01 0.2 0.09 11 <0.01 1.5 0.83 9.1

CR-Cisco 1.8 <0.01 0.05 0.07 1.5 <0.01 0.26 1.8 3.4

CR-Cisco 3.6 0.01 0.03 <0.05 0.60 <0.01 0.14 3.2 3.9

GW hot spring 0.4 <0.01 <0.01 <0.05 0.08 <0.01 <0.01 680 610

RUM 305 3.1 0.02 0.03 <0.05 0.05 <0.01 <0.01 7.4 7.7

RUM 310 2.7 <0.01 <0.01 <0.05 <0.05 0.01 0.02 7.5 7.5

RUM 590 12 0.02 0.02 <0.05 <0.05 0.14 0.15 150 145

RUM 855 7.1 0.6 0.6 <0.05 <0.05 0.01 0.02 11 11

Site name ICP–MS

Sc ug/L

ICP–MS

Sc (avail.) ug/L

ICP–MS

Se μg/L

ICP–MS

Se (avail.) μg/L

ICP–AES

SiO2 mg/L

ICP–MS

SiO2 mg/L

ICP–MS

SiO2 (avail.) mg/L

ICP–MS

Sm μg/L

ICP–MS

Sm (avail.) μg/L

CR-Kremmling 1.4 3.2 <1 <1 9.8 11 20 0.02 0.51

CR-Kremmling 0.9 0.9 <1 <1 7.0 7.8 6.6 <0.01 0.03

CR-Kremmling 1.1 1.2 <1 <1 9.0 8.4 10 <0.01 0.005

ER-Minturn 0.8 0.9 <1 <1 6.2 6.1 5.8 0.03 0.08

ER-Minturn 0.8 0.7 <1 <1 5.2 5.8 4.6 0.01 0.02

ER-Minturn 0.6 0.7 <1 <1 5.8 4.6 5.3 0.02 0.03

ER-Avon 0.7 1.2 <1 <1 5.3 5.4 7.4 0.05 0.18

ER-Avon 0.6 0.6 <1 <1 3.9 4.4 4.0 0.01 0.03

ER-Avon 0.6 0.7 <1 <1 4.9 3.9 4.7 <0.01 0.05

ER-Gypsum 0.8 4.7 <1 <1 5.8 6.2 23 0.03 1.2

ER-Gypsum 0.6 0.7 <1 <1 5.1 4.9 5.2 <0.01 0.07

ER-Gypsum 0.8 0.8 <1 <1 6.3 4.9 6.0 <0.01 0.06

CR-Glenwood 1.0 5.3 <1 <1 7.8 8.4 27 0.02 1.3

CR-Glenwood 1.1 1.6 <1 <1 7.8 8.6 13 <0.01 0.24

CR-Glenwood 1.0 1.0 <1 <1 8.3 6.3 8.0 <0.01 0.08

RF-Glenwood 0.8 1.2 <1 <1 6.5 7.0 7.6 0.02 0.21

RF-Glenwood 0.9 0.8 <1 <1 6.9 7.4 8.0 <0.01 0.04

RF-Glenwood 1.0 1.0 <1 <1 9.0 6.8 7.6 <0.01 0.02

PC-Cameo 1.8 4.9 <1 <1 14 15 31 0.04 0.77

PC-Cameo 3.2 2.9 <1 <1 26 26 31 <0.01 0.13

PC-Cameo 3.3 3.1 <1 <1 30 23 27 <0.01 0.12

CR-Cameo 1.0 2.9 <1 <1 7.6 8.4 19 <0.01 0.6

CR-Cameo 0.7 0.8 <1 <1 5.3 5.5 8.4 <0.01 0.12

CR-Cameo 0.8 0.8 <1 <1 7.1 5.3 6.3 <0.01 0.05

GR-NF 1.2 8.0 <1 <1 9.4 10 42 0.05 2.0

GR-NF 1.1 0.7 <1 <1 8.8 8.6 8.7 0.01 0.05

GR-NF 1.2 1.3 <1 <1 11 8.6 11 <0.01 0.18

GR-Tunnel 1.5 1.6 <1 <1 12 13 11 <0.01 0.04

GR-Tunnel 1.3 1.0 <1 <1 9.5 10 11 <0.01 0.02

GR-Tunnel 1.0 0.9 <1 <1 9.5 7.4 7.8 <0.01 0.005

GR-Delta 1.4 6.3 1.2 1.3 11 12 38 0.03 1.4

GR-Delta 1.8 1.6 4.4 4.6 13 15 17 <0.01 0.25

GR-Delta 1.8 2.3 9.2 9.5 14 12 17 <0.01 1.2

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
46 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–MS

Sc ug/L

ICP–MS

Sc (avail.) ug/L

ICP–MS

Se μg/L

ICP–MS

Se (avail.) μg/L

ICP–AES

SiO2 mg/L

ICP–MS

SiO2 mg/L

ICP–MS

SiO2 (avail.) mg/L

ICP–MS

Sm μg/L

ICP–MS

Sm (avail.) μg/L

UR-Ouray 0.9 1.1 <1 <1 6.5 7.2 6.7 <0.01 0.21

UR-Ouray 1.1 1.1 <1 <1 8.1 8.7 9.4 <0.01 0.25

UR-Ouray 1.3 1.6 <1 <1 11 8.9 11 <0.01 0.30

UR-Ridgway 1.1 1.8 <1 <1 8.5 9.3 11 <0.01 0.19

UR-Ridgway 1.3 1.5 <1 1.0 10 11 13 <0.01 0.32

UR-Ridgway 1.2 1.5 1 1.1 11 8.6 11 <0.01 0.14

UR-Delta 1.8 9.7 8.6 11 14 16 53 0.01 2.0

UR-Delta 2.0 5.1 9.0 9.1 15 17 38 <0.01 2.8

UR-Delta 2.0 2.1 18 19 17 12 15 <0.01 0.05

GR-Grand Jct. 1.6 6.1 2.3 2.2 13 15 36 0.02 1.1

GR-Grand Jct. 1.2 1.0 4.4 5.0 8.7 9.4 10 <0.01 0.09

GR-Grand Jct. 1.6 1.3 3.9 4.0 14 11 13 0.01 0.10

CR-State line 1.3 5.1 1.8 1.9 9.8 11 31 0.01 1.1

CR-State line 1.0 1.2 2.8 2.8 7.6 8.0 12 <0.01 0.33

CR-State line 1.3 1.3 5.0 5.0 12 8.6 11 <0.01 0.15

DR-Dolores 0.7 4.7 <1 <1 5.3 5.8 27 0.06 1.8

DR-Dolores 0.6 0.6 <1 <1 4.7 4.6 5.2 <0.01 0.03

DR-Dolores 0.8 0.7 <1 <1 6.5 5.4 5.8 <0.01 0.02

DR-Bedrock 0.8 2.8 1.2 1.1 6.0 6.8 15 0.01 1.1

DR-Bedrock 0.7 5.4 2.2 1.8 5.4 5.5 51 0.41 2.9

DR-Bedrock 0.6 1.0 2.1 1.9 5.2 4.2 7.2 <0.01 0.27

SM-Uravan 1.0 2.7 1.0 <1 7.9 9.1 17 0.01 0.47

SM-Uravan 0.8 0.8 <1 <1 6.5 6.6 9.3 <0.01 0.18

SM-Uravan 0.9 0.8 1.0 1.1 7.8 6.0 6.9 <0.01 0.03

DR-Cisco 0.8 3.3 1.1 1.0 6.4 7.1 20 <0.01 0.72

DR-Cisco 1.0 5.3 1.6 1.3 6.4 7.4 45 <0.01 1.5

DR-Cisco 1.0 1.4 2.4 2.1 6.6 6.4 9.8 <0.01 0.21

CR-Cisco 1.1 5.9 1.6 1.8 8.0 8.5 34 <0.01 1.3

CR-Cisco 1.0 1.4 2.7 2.4 6.7 7.6 14 <0.01 0.23

CR-Cisco 1.6 1.7 4.3 3.9 13 9.9 13 <0.01 0.12

GW hot spring 5.9 6.3 <1 <1 31 31 39 <0.01 <0.01

RUM 305 1.5 1.6 62 60 na 19 19 <0.01 <0.01

RUM 310 2.2 2.1 6.1 7.9 na 27 25 <0.01 <0.01

RUM 590 0.9 0.9 89 84 na 10 9.0 0.13 0.13

RUM 855 2.7 2.5 1,560 1,450 na 32 30 0.01 0.01

Site name ICP–AES

Sr μg/L

ICP–MS

Sr μg/L

ICP–MS

Sr (avail.) μg/L

ICP–MS

Tb μg/L

ICP–MS

Tb (avail.) μg/L

ICP–MS

Ti ug/L

ICP–MS

Ti (avail.) ug/L

ICP–MS

U μg/L

ICP–MS

U (avail.) μg/L

ICP–MS

V μg/L

CR-Kremmling 93 86 180 <0.005 0.06 0.3 8.7 0.34 1.0 0.6

CR-Kremmling 150 140 155 <0.005 0.003 0.8 1.3 0.3 0.89 1.4

CR-Kremmling 145 135 160 <0.005 0.003 0.6 0.6 0.28 0.31 1.2

ER-Minturn 49 43 46 0.005 0.01 0.7 5.5 0.49 0.48 0.3

ER-Minturn 63 58 55 <0.005 0.003 0.3 0.9 0.69 0.54 <0.5

ER-Minturn 55 52 56 <0.005 0.005 0.3 1.2 0.43 0.47 <0.5

ER-Avon 48 41 50 0.007 0.02 0.7 20 0.48 0.60 <0.5

ER-Avon 74 71 68 <0.005 0.003 0.3 2.2 0.54 0.46 <0.5

ER-Avon 130 130 135 <0.005 0.005 0.3 5.3 0.55 0.7 <0.5

ER-Gypsum 150 135 200 <0.005 0.15 0.6 66 0.62 1.1 0.5

ER-Gypsum 375 350 405 <0.005 0.008 0.8 2.7 0.56 0.75 <0.5

ER-Gypsum 585 585 605 <0.005 0.009 1.5 2.6 0.92 1.1 <0.5

CR-Glenwood 170 150 210 <0.005 0.15 0.6 63 0.72 1.1 0.8

CR-Glenwood 385 380 395 <0.005 0.03 1.1 20 1.4 1.4 0.8

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 47

Site name ICP–AES

Sr μg/L

ICP–MS

Sr μg/L

ICP–MS

Sr (avail.) μg/L

ICP–MS

Tb μg/L

ICP–MS

Tb (avail.) μg/L

ICP–MS

Ti ug/L

ICP–MS

Ti (avail.) ug/L

ICP–MS

U μg/L

ICP–MS

U (avail.) μg/L

ICP–MS

V μg/L

CR-Glenwood 435 405 415 <0.005 0.01 1.1 2.3 1.1 1.2 <0.5

RF-Glenwood 220 200 230 <0.005 0.03 0.8 5.4 0.77 0.74 <0.5

RF-Glenwood 390 370 380 <0.005 0.003 1.1 2.8 1.5 1.4 <0.5

RF-Glenwood 605 555 555 <0.005 0.003 1.8 2.1 2.0 2.0 <0.5

PC-Cameo 170 165 195 0.005 0.09 0.6 51 0.94 1.0 1.4

PC-Cameo 535 515 540 <0.005 0.02 0.7 3.7 3.6 4.0 3.2

PC-Cameo 685 605 630 <0.005 0.02 0.7 0.9 3.4 4.4 3.0

CR-Cameo 260 245 300 <0.005 0.07 0.8 14 1.1 1.2 0.9

CR-Cameo 335 325 335 <0.005 0.02 0.9 7.7 1.4 1.4 0.6

CR-Cameo 635 565 580 <0.005 0.008 1.8 2.2 1.7 2.1 0.7

GR-NF 125 120 165 0.007 0.23 0.6 73 0.25 0.61 0.6

GR-NF 140 135 150 <0.005 0.01 0.6 0.6 0.36 0.4 0.6

GR-NF 360 305 320 <0.005 0.02 0.6 5.4 1.1 1.2 <0.5

GR-Tunnel 140 135 150 <0.005 0.01 0.6 3.1 1.0 0.96 0.9

GR-Tunnel 140 140 145 <0.005 0.003 0.3 1.1 1.1 1.2 0.6

GR-Tunnel 170 140 150 <0.005 0.003 0.3 0.6 0.88 1.0 0.5

GR-Delta 260 240 290 0.005 0.16 1.3 39 1.3 1.5 0.9

GR-Delta 945 945 1,010 <0.005 0.04 4.6 6.3 5.4 5.7 1.2

GR-Delta 1,330 1,280 1,390 <0.005 0.16 6.8 5.6 6.0 8.2 1.2

UR-Ouray 485 440 465 <0.005 0.03 1.2 3.1 <0.1 0.14 <0.5

UR-Ouray 895 850 910 <0.005 0.04 2.1 4.6 <0.1 0.29 <0.5

UR-Ouray 1,670 1,600 1,650 <0.005 0.05 4.0 4.5 0.10 0.44 <0.5

UR-Ridgway 780 715 780 <0.005 0.02 1.9 19 0.52 0.52 <0.5

UR-Ridgway 1,060 1,030 1,110 <0.005 0.04 2.5 4.8 0.69 0.92 <0.5

UR-Ridgway 1,450 1,480 1,510 <0.005 0.02 3.7 5.1 0.79 0.98 <0.5

UR-Delta 1,460 1,410 1,720 <0.005 0.23 6.0 77 8.2 7.6 1.9

UR-Delta 1,510 1,470 1,640 <0.005 0.39 6 7.1 7.6 8.2 2.1

UR-Delta 2,330 2,200 2,230 <0.005 0.006 9.4 11 13 13 0.7

GR-Grand Jct. 520 495 540 <0.005 0.12 2.2 53 2.8 2.6 1.2

GR-Grand Jct. 1,000 990 1,050 <0.005 0.01 4.3 5.1 5.5 5.5 1.5

GR-Grand Jct. 740 685 715 <0.005 0.01 3.6 4.0 5.2 5.3 0.9

CR-State line 375 360 415 <0.005 0.12 1.3 48 1.9 2.0 1.2

CR-State line 620 610 655 <0.005 0.04 2.2 4.3 3.1 3.1 1.2

CR-State line 1,140 1,040 1,080 <0.005 0.02 4.8 4.7 4.4 5.5 1.0

DR-Dolores 190 175 225 0.008 0.21 0.5 39 0.22 0.42 <0.5

DR-Dolores 345 325 330 <0.005 0.003 0.3 0.9 0.32 0.33 <0.5

DR-Dolores 460 435 450 <0.005 0.003 0.7 0.8 0.50 0.46 <0.5

DR-Bedrock 410 395 515 <0.005 0.15 0.9 4.4 1.3 1.6 1

DR-Bedrock 620 585 745 0.04 0.40 1.2 1.6 2.4 7.6 4.4

DR-Bedrock 770 720 740 <0.005 0.03 1.0 3.6 3.4 3.8 1.0

SM-Uravan 460 445 5.0 <0.005 0.06 1.4 28 0.98 0.92 0.6

SM-Uravan 965 945 970 <0.005 0.02 2.5 4.0 1.2 1.3 <0.5

SM-Uravan 1,410 1,270 1,300 <0.005 0.003 4.4 4.4 1.7 2.3 <0.5

DR-Cisco 430 405 455 <0.005 0.08 1.2 30 1.2 1.3 1

DR-Cisco 915 945 1,030 <0.005 0.18 2.8 56 2.7 3.0 2.7

DR-Cisco 1,240 1,130 1,140 <0.005 0.02 4.3 10 3.8 3.8 0.7

CR-Cisco 365 350 425 <0.005 0.16 1.3 46 1.9 2.1 1.6

CR-Cisco 580 620 660 <0.005 0.03 2.3 13 3.3 3.1 1.2

CR-Cisco 1,300 1,040 1,050 <0.005 0.02 5.2 9.7 6.0 6.0 1.0

GW hot spring 6,420 9,050 7,950 <0.005 <0.005 23 16 0.3 0.17 <0.5

RUM 305 na 2,130 2,180 <0.005 <0.005 4.0 4.2 55 55 470

RUM 310 na 2,610 2,540 <0.005 <0.005 6.6 6.1 245 225 12

RUM 590 na 2,020 1,870 0.04 0.04 23 21 54 50 470

RUM 855 na 1,070 995 <0.005 <0.005 12 11 87 83 13,800

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
48 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site name ICP–MS

V (avail.) μg/L

ICP–MS

Y μg/L

ICP–MS

Y (avail.) μg/L

ICP–MS

Yb μg/L

ICP–MS

Yb (avail.) μg/L

ICP–MS

Zn μg/L

ICP–MS

Zn μg/L

ICP–MS

Zn (avail.) μg/L

CR-Kremmling 4.0 0.05 1.6 0.006 0.13 <10 2.1 17

CR-Kremmling 0.3 0.01 0.08 <0.005 0.01 <10 1.2 3.5

CR-Kremmling 1 0.02 0.01 <0.005 0.003 10 2.6 5.0

ER-Minturn 0.5 0.13 0.28 0.01 0.02 56 54 52

ER-Minturn 0.3 0.05 0.08 <0.005 0.01 70 65 76

ER-Minturn 0.3 0.06 0.12 0.006 0.01 82 83 105

ER-Avon 1.0 0.16 0.55 0.01 0.04 15 12 49

ER-Avon 0.3 0.04 0.10 <0.005 0.01 12 8.2 16

ER-Avon 0.3 0.02 0.16 <0.005 0.01 27 26 53

ER-Gypsum 8.8 0.13 3.5 0.01 0.26 <10 4.3 135

ER-Gypsum 0.7 0.03 0.23 <0.005 0.01 12 6.4 14

ER-Gypsum 0.7 0.03 0.24 <0.005 0.02 12 4.3 17

CR-Glenwood 9.8 0.07 3.6 0.007 0.27 10 1.8 99

CR-Glenwood 2.2 0.03 0.60 <0.005 0.05 24 3.1 7.7

CR-Glenwood 0.9 0.03 0.27 <0.005 0.02 <10 1.5 6.6

RF-Glenwood 1.1 0.09 0.73 0.01 0.06 12 6.4 13

RF-Glenwood 0.5 0.03 0.13 <0.005 0.01 <10 3.6 5.0

RF-Glenwood 0.3 0.04 0.07 <0.005 0.003 14 5.3 3.4

PC-Cameo 5.1 0.16 2.0 0.02 0.18 <10 0.7 15

PC-Cameo 3.8 0.07 0.36 <0.005 0.03 <10 1.4 27

PC-Cameo 3.4 0.04 0.50 <0.005 0.04 <10 0.7 3

CR-Cameo 4.4 0.05 1.7 <0.005 0.12 <10 3.0 43

CR-Cameo 1.2 0.03 0.34 <0.005 0.02 <10 3.6 6.2

CR-Cameo 0.9 0.03 0.18 <0.005 0.01 <10 1.3 2.8

GR-NF 10 0.22 5.3 0.02 0.42 18 13 32

GR-NF 0.5 0.08 0.22 0.006 0.02 505 545 1.5

GR-NF 1.2 0.04 0.55 0.006 0.04 <10 1.8 4.3

GR-Tunnel 1.0 0.04 0.16 0.005 0.02 <10 0.7 2.0

GR-Tunnel 0.7 0.03 0.09 <0.005 0.01 <10 1.1 5.0

GR-Tunnel 0.5 0.02 0.04 <0.005 0.003 <10 0.8 1.4

GR-Delta 8.4 0.16 3.8 0.01 0.30 <10 1.6 23

GR-Delta 2.8 0.05 0.76 <0.005 0.05 10 2.5 6.8

GR-Delta 7.3 0.03 3.9 <0.005 0.24 13 2.1 19

UR-Ouray 0.5 0.03 0.74 <0.005 0.04 135 125 200

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
Appendix I. Chemical and Isotopic Data for All Water Samples Collectedin This Study 49

Site name ICP–MS

V (avail.) μg/L

ICP–MS

Y μg/L

ICP–MS

Y (avail.) μg/L

ICP–MS

Yb μg/L

ICP–MS

Yb (avail.) μg/L

ICP–MS

Zn μg/L

ICP–MS

Zn μg/L

ICP–MS

Zn (avail.) μg/L

UR-Ouray 0.8 0.04 0.99 <0.005 0.07 180 195 290

UR-Ouray 0.3 0.05 1.3 <0.005 0.08 205 215 335

UR-Ridgway 1.0 0.03 0.6 <0.005 0.04 49 38 99

UR-Ridgway 1.5 0.03 1.0 <0.005 0.07 29 24 105

UR-Ridgway 0.3 0.03 0.63 <0.005 0.04 54 49 145

UR-Delta 19 0.07 5.9 0.006 0.38 16 5.3 57

UR-Delta 20 0.06 9.1 <0.005 0.65 12 2.3 67

UR-Delta 1.1 0.04 0.17 <0.005 0.01 16 5.8 5.3

GR-Grand Jct. 8.5 0.09 2.9 0.008 0.22 13 4.6 26

GR-Grand Jct. 2.0 0.04 0.25 <0.005 0.02 <10 1.5 3.7

GR-Grand Jct. 1.0 0.06 0.21 0.005 0.01 <10 2.3 2.7

CR-State line 7.7 0.06 2.7 0.005 0.21 15 6.8 25

CR-State line 2.7 0.04 0.94 <0.005 0.07 <10 1.1 8.9

CR-State line 1.9 0.04 0.54 <0.005 0.04 12 1.6 5.1

DR-Dolores 7.9 0.26 5.1 0.02 0.35 12 5.5 89

DR-Dolores 0.3 0.04 0.09 <0.005 0.01 <10 3.5 6.2

DR-Dolores 0.3 0.03 0.08 <0.005 0.01 <10 2.6 5.5

DR-Bedrock 8.2 0.05 3.9 <0.005 0.26 16 10 28

DR-Bedrock 42 0.56 7.8 0.01 0.56 <10 1.2 34

DR-Bedrock 3.0 0.03 0.63 <0.005 0.04 <10 1.1 4.4

SM-Uravan 3.1 0.07 1.3 0.005 0.09 16 12 73

SM-Uravan 1.2 0.03 0.52 <0.005 0.03 12 5.0 29

SM-Uravan 0.3 0.03 0.10 <0.005 0.01 15 10 12

DR-Cisco 6.5 0.04 1.9 <0.005 0.14 10 4.8 49

DR-Cisco 13 0.04 3.3 <0.005 0.23 13 4.6 29

DR-Cisco 2.6 0.04 0.53 <0.005 0.04 12 3.5 7.7

CR-Cisco 11 0.04 3.8 <0.005 0.26 82 75 42

CR-Cisco 2.9 0.03 0.60 <0.005 0.05 12 5.5 9.3

CR-Cisco 1.7 0.04 0.34 <0.005 0.02 14 3.1 6.8

GW hot spring <0.5 0.09 0.07 <0.005 0.01 23 3.6 4.4

RUM 305 480 0.10 0.12 0.008 0.01 na 13 12

RUM 310 12 0.46 0.47 0.01 0.01 na 81 78

RUM 590 425 3.6 3.46 0.06 0.07 na 430 400

RUM 855 12,500 0.31 0.3 0.02 0.02 na 14 13

Table AI–3. Chemical and isotopic data for all water samples collected in this study.—Continued

[Site name is an abbreviation for station name; WS#, watershed number (see fig. 5 for location); red values are replacement values; na, not analyzed; nr, not reported; 

CFS, cubic feet per second; IC, ion chromatography; ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, inductive coupled plasma–atomic emission 

spectrometry; (avail.), available loads (operationally defined as total dissolved after acidification of unfiltered sample); ins, insufficient sample; hydrogen and oxygen 

isotopes reported relative to V-SMOW and sulfur isotope values relative to V-CDT]
50 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Appendix II. Chemical Loads for Major Chemical Elements and Total Solutes

Table AII–1. Conductivity and chemical load (tonnes/day) for major chemical elements.

[(aq), dissolved loads; (avail); available loads (operationally defined as total dissolved after acidification); Al (aq), Mn (aq) <1 tonne/day. Full station name 

in Table AI–3]

Station

ID

Site

name

Flow EC

μS/cm

HCO3

(aq)

Cl

(aq)

SO4

(aq)

Al

(avail)

Ca

(aq)

Ca

(avail)

Fe

(avail)

K

(aq)

K

(avail)

Mg

(aq)

Mg

(avail)

09058000 CR-Kremmling High water 140 185 7 35 4 31 55 8 3 6 5 9

09058000 CR-Kremmling Irrigation 210 170 12 69 <1 62 61 <1 4 4 11 10

09058000 CR-Kremmling Base flow 200 145 8 51 <1 40 40 <1 3 3 8 8

09064600 ER-Minturn High water 105 70 3 4 <1 20 19 1 1 1 7 6

09064600 ER-Minturn Irrigation 140 16 <1 2 <1 4 3 <1 <1 <1 1 1

09064600 ER-Minturn Base flow 110 11 <1 2 <1 2 2 <1 <1 <1 1 1

09067005 ER-Avon High water 100 250 13 14 4 66 75 4 3 4 16 17

09067005 ER-Avon Irrigation 130 56 3 18 <1 17 16 <1 1 1 4 4

09067005 ER-Avon Base flow 190 61 3 17 <1 12 11 <1 <1 <1 4 3

09069000 ER-Gypsum High water 190 760 40 185 41 190 305 55 7 17 37 56

09069000 ER-Gypsum Irrigation 360 175 47 135 <1 82 86 <1 3 3 15 15

09069000 ER-Gypsum Base flow 555 100 48 105 <1 59 57 <1 2 2 12 11

09071750 CR-Glenwood High water 250 1,800 180 360 87 435 625 115 19 41 91 125

09071750 CR-Glenwood Irrigation 515 520 260 295 4 215 215 5 9. 11 41 41

09071750 CR-Glenwood Base flow 565 610 220 245 1 155 145 1 7 7 33 32

09085000 RF-Glenwood High water 250 760 43 335 5 285 300 6 7 7 45 41

09085000 RF-Glenwood Irrigation 440 400 62 255 <1 180 170 1 4 4 29 27

09085000 RF-Glenwood Base flow 600 260 79 215 <1 135 125 <1 3 3 23 22

09105000 PC-Cameo High water 195 360 7 33 14 71 84 10 5 7 23 27

09105000 PC-Cameo Irrigation 520 110 2 14 <1 19 19 <1 2 1 9 9

09105000 PC-Cameo Base flow 590 115 3 17 <1 18 16 <1 1 1 11 10

09095500 CR-Cameo High water 395 3,250 745 1,160 70 995 1,210 61 37 56 240 290

09095500 CR-Cameo Irrigation 525 1,460 675 775 5 520 505 5 21 21 110 110

09095500 CR-Cameo Base flow 920 1,150 820 700 <1 395 355 1 18 17 94 84

09134100 GR-Northfork High water 115 695 25 77 115 190 210 105 12 34 35 54

09134100 GR-Northfork Irrigation 170 115 3 42 <1 30 29 <1 8 1.0 8 8

09134100 GR-Northfork Base flow 310 86 3 20 <1 17 15 <1 1 1 5 5

09128000 GR-tunnel High water 195 140 4 38 <1 46 46 <1 3 3 10 9

09128000 GR-tunnel Irrigation 205 115 3 27 <1 34 32 <1 2 2 7 6

09128000 GR-tunnel Base flow 200 170 2 21 <1 29 22 <1 1 1 6 5

09144250 GR-Delta High water 280 1,280 61 965 105 470 550 91 23 43 135 170

09144250 GR-Delta Irrigation 900 415 26 705 1 245 220 2 9 9 77 67

09144250 GR-Delta Base flow 1,080 445 32 890 3 280 270 4 9 8 83 77

09146020 UR-Ouray High water 235 16 1 49 1 21 19 1 <1 <1 1 1

09146020 UR-Ouray Irrigation 395 6 1 43 <1 17 16 1 <1 <1 1 1

09146020 UR-Ouray Base flow 625 2 <1 19 <1 7 7 <1 <1 <1 <1 <1

09146200 UR-Ridgway High water 420 70 4 105 1 51 49 1 1 1 5 4

09146200 UR-Ridgway Irrigation 565 50 3 87 1 43 39 1 1 1 5 4

09146200 UR-Ridgway Base flow 680 22 2 51 <1 20 20 <1 <1 <1 2 2

09149500 UR-Delta High water 1,070 205 13 430 10 160 185 9 4 7 38 32

09149500 UR-Delta Irrigation 1,150 380 34 790 9 300 320 14 9 10 69 59

09149500 UR-Delta Base flow 1,530 150 13 380 <1 115 105 <1 2 2 29 28

09152500 GR-GJ High water 455 1,620 67 1,900 81 775 875 65 30 48 220 245

09152500 GR-GJ Irrigation 855 610 42 1,150 1 405 345 1 12 11 110 96

09152500 GR-GJ Base flow 715 550 49 880 <1 285 245 <1 12 12 110 96

09163500 CR-CO/UT High water 435 5,230 795 3,790 225 1,940 2,310 190 74 130 530 605
Appendix II. Chemical Loads for Major Chemical Elements and Total Solutes 51

Table AII-1. Conductivity and chemical load (tonnes/day) for major chemical elements.—Continued

[(aq), dissolved loads; (avail); available loads (operationally defined as total dissolved after acidification); Al (aq), Mn (aq) <1 tonne/day. Full station name 

in Table AI–3]

Field

No. Site Flow EC,μS/cm)

HCO3

(aq)

Cl

(aq) 

SO4

(aq)

Al

(avail)

Ca

(aq)

Ca

(avail)

Fe

(avail) 

K

(aq)

K

(avail)

Mg

(aq)

Mg

(avail)

09163500 CR-CO/UT Irrigation 685 2,440 725 2,820 13 1,190 1,150 16 42 42 325 310

09163500 CR-CO/UT Base flow 1,090 1,910 755 3,140 4 1,140 1,000 4 36 35 335 295

09166500 DR-Dolores High water 155 745 21 74 59 210 255 49 9 23 30 47

09166500 DR-Dolores Irrigation 265 63 4 18 <1 22 20 <1 1 1 3 3

09166500 DR-Dolores Base flow 330 35 3 12 <1 14 12 <1 1 1 2 2

09171100 DR-Bedrock High water 400 425 57 185 8 140 220 12 7 9 30 42

09171100 DR-Bedrock Irrigation 1,510 31 73 11 2 9 15 1 3 3 3 4

09171100 DR-Bedrock Base flow 1,010 17 21 6 <1 7 6 <1 1 1 2 2

09177000 SMR-Uravan High water 350 320 13 245 7 140 140 5 4 5 32 31

09177000 SMR-Uravan Irrigation 565 63 3 93 <1 39 35 <1 1 1 9 8

09177000 SMR-Uravan Base flow 750 60 4 87 <1 33 29 <1 1 1 10 9

09180000 DR-Cisco High water 375 555 67 310 16 200 230 13 8 13 42 48

09180000 DR-Cisco Irrigation 1,070 100 99 115 5 50 57 3 4 6 13 15

09180000 DR-Cisco Base flow 1,745 98 155 99 <1 50 42 <1 5 5 16 14

09180500 CR-Cisco High water 430 7,350 1,150 3,930 345 2,290 3,060 305 92 185 560 720

09180500 CR-Cisco Irrigation 725 2,340 915 2,500 16 1,060 1,070 15 44 47 290 290

09180500 CR-Cisco Base flow 1,230 1,950 1,330 3,040 6 1,210 1,090 5 60 59 390 365

Site Flow Mn

(avail)

Na

(aq)

Na

(avail)

SiO2

(aq)

SiO2

(avail)

Total

(aq)

% CR

Cisco

CR-Kremmling High water 1 11 18 32 60 310 2

CR-Kremmling Irrigation <1 16 15 19 16 365 4

CR-Kremmling Base flow <1 13 14 15 19 280 3

ER-Minturn High water <1 2 2 9 9 115 <1

ER-Minturn Irrigation <1 <1 <1 1 1 25 <1

ER-Minturn Base flow <1 <1 <1 1 1 18 <1

ER-Avon High water <1 8 8 29 39 395 2

ER-Avon Irrigation <1 2 2 5 4 105 1

ER-Avon Base flow <1 2 2 2 2 100 1

ER-Gypsum High water 2 33 34 55 205 1,310 8

ER-Gypsum Irrigation <1 35 34 10 11 500 6

ER-Gypsum Base flow <1 34 35 5 6 370 4

CR-Glenwood High water 5 155 145 145 470 3,180 19

CR-Glenwood Irrigation <1 195 185 40 62 1,570 19

CR-Glenwood Base flow <1 170 185 22 27 1,460 15

RF-Glenwood High water <1 47 41 60 65 1,580 9

RF-Glenwood Irrigation <1 51 48 24 26 1,010 12

RF-Glenwood Base flow <1 61 61 13 14 790 8

PC-Cameo High water <1 26 27 52 110 575 3

PC-Cameo Irrigation <1 12 11 10 12 175 2

PC-Cameo Base flow <1 14 13 8 10 190 2

CR-Cameo High water 2 695 720 225 510 7,450 44

CR-Cameo Irrigation <1 545 515 68 105 4,170 51

CR-Cameo Base flow <1 670 600 32 38 3,870 40

GR-Northfork High water 2 47 53 130 540 1,210 7

GR-Northfork Irrigation <1 20 11 15 15 240 3

GR-Northfork Base flow <1 7 7 4 6 145 2

GR-tunnel High water <1 9 8 24 21 275 2

GR-tunnel Irrigation <1 6 6 13 14 205 3

GR-tunnel Base flow <1 5 4 7 8 240 3

GR-Delta High water 2 180 195 195 600 3,310 19
52 Salinization of the Upper Colorado River—Fingerprinting Geologic Salt Sources

Site Flow Mn

(avail)

Na

(aq)

Na

(avail)

SiO2

(aq)

SiO2

(avail)

Total

(aq)

% CR

Cisco

GR-Delta Irrigation <1 120 100 34 40 1,630 20

GR-Delta Base flow <1 150 145 25 37 1,910 20

UR-Ouray High water <1 2 2 4 4 96 1

UR-Ouray Irrigation <1 2 1 2 3 72 1

UR-Ouray Base flow <1 1 1 1 1 31 <1

UR-Ridgway High water <1 8 7 8 9 250 1

UR-Ridgway Irrigation <1 7 6 5 6 200 2

UR-Ridgway Base flow <1 4 4 2 2 100 1

UR-Delta High water <1 68 53 18 60 935 6

UR-Delta Irrigation 1 125 91 32 71 1,730 21

UR-Delta Base flow <1 68 68 7 9 760 8

GR-GJ High water 2 320 315 215 535 5,150 30

GR-GJ Irrigation <1 175 155 36 40 2,540 31

GR-GJ Base flow <1 165 150 42 47 2,090 22

CR-CO/UT High water 6 1,080 1,070 495 1,380 13,900 82

CR-CO/UT Irrigation 1 865 775 145 215 8,550 105

CR-CO/UT Base flow <1 1,020 995 93 115 8,420 87

DR-Dolores High water 4 16 24 56 260 1,160 7

DR-Dolores Irrigation <1 3 3 3 3 115 1

DR-Dolores Base flow <1 3 3 2 2 71 <1

DR-Bedrock High water <1 60 63 22 48 930 5

DR-Bedrock Irrigation <1 45 45 1 10 175 2

DR-Bedrock Base flow <1 14 14 <1 1 69 <1

SMR-Uravan High water <1 24 23 28 51 800 5

SMR-Uravan Irrigation <1 7 6 4 5 220 3

SMR-Uravan Base flow <1 8 8 2 2 205 2

DR-Cisco High water 1 70 70 34 95 1,280 8

DR-Cisco Irrigation <1 57 58 5 30 445 5

DR-Cisco Base flow <1 110 97 3 5 535 6

CR-Cisco High water 9 1,110 1,070 465 1,870 17,000

CR-Cisco Irrigation 1 895 860 125 225 8,170

CR-Cisco Base flow <1 1,540 1,170 110 150 9,630

Table AII-1. Conductivity and chemical load (tonnes/day) for major chemical elements.—Continued

[(aq), dissolved loads; (avail); available loads (operationally defined as total dissolved after acidification); Al (aq), Mn (aq) <1 tonne/day. Full station name 

in Table AI–3]
Appendix III. Chemical, Isotopic, and Mineralogical Data for All Geologic Samples Collected in This Study 53

Appendix III. Chemical, Isotopic, and Mineralogical Data for All Geologic 

Samples Collected in This Study

Table AIII–1. Metadata (analytical method, detection limit, the number of samples with censored data, the percent of samples with 

replaced values, and the replacement value) for reported concentrations. 

[Replacement (red) values (0.5 × detection limit) are used when censored values were reported for ≥20 percent of the samples (14 samples or less). For elements 

with the number censored = “many,” less than concentrations are reported. For tables AIII–1—4: ICP–MS, inductive coupled plasma–mass spectrometry; ICP–AES, 

inductive coupled plasma–atomic emission spectrometry; HYD, hydride generation atomic adsorption spectrometry; COMB, combustion; CVAA, cold vapor atomic 

adsorption spectrometry; GF, graphite furnace; ISE, ion selective electrode; nd, not determined; ins, insufficient sample]

Element Method Detection limit Number censored Percent censored Replacement

As HYD 0.6 mg/kg 1 6 0.3 mg/kg

As ICP–MS 1 mg/kg 1 6 0.5 mg/kg

Ba ICP–AES 10 mg/kg 5 28

Ba ICP–MS 6 mg/kg 2 11 3 mg/kg

Be ICP–MS 0.1 mg/kg 1 6 0.05 mg/kg

Bi ICP–MS 0.04 mg/kg 5 28

C (CO3) COMB 0.003 mg/kg 8 44

Cd ICP–MS 0.01 mg/kg 6 33

Cl ICE 50 mg/kg 7 39

Cr ICP–AES 10 mg/kg 3 17 5 mg/kg

Cr ICP–MS 1 mg/kg 4 22 0.5 mg/kg

F ISE 20 mg/kg 1 6 10 mg/kg

Fe ICP–AES 0.01 % 1 6 0.01 %

Hg CVAA 0.02 mg/kg 12 67

La ICP–MS 0.5 mg/kg 3 17 0.3 mg/kg

Li ICP–MS 1 mg/kg 1 6 0.5 mg/kg

Mg ICP–AES 0.01 % 1 6 0.01 %

Mg ICP–MS 0.01 % 1 6 0.005 %

Na ICP–AES 0.01 % 2 11 0.005 %

P ICP–MS 50 mg/kg 7 39

Sb ICP–MS 0.05 mg/kg 2 11 0.03 mg/kg

Se HYD 0.2 mg/kg 4 22

Sn ICP–MS 0.1 mg/kg 1 6 0.05 mg/kg

Th ICP–MS 0.2 mg/kg 3 17 0.1 mg/kg

Ti ICP–AES 0.01 % 5 28

Ti ICP–MS 0.01 % 5 28

Tl GF 0.1 mg/kg 4 22

U ICP–MS 0.1 mg/kg 3 17 0.05 mg/kg

V ICP–MS 1 mg/kg 2 11 0.5 mg/kg

W ICP–MS 0.1 mg/kg 2 11 0.05 mg/kg

Y ICP–MS 0.1 mg/kg 1 6 0.05 mg/kg

Zn ICP–AES 1 mg/kg 1 6 0.5 mg/kg

Zr ICP–AES 10 mg/kg 3 17 5 mg/kg

Elements removed from table as values below detection limit

Element Technique Detection limit

Ag ICP–MS 1 mg/kg

P ICP–AES 0.01 %

In ICP–MS 0.02 mg/kg

Te ICP–MS 0.1 mg/kg

Nb ICP–AES 10 mg/kg

Y ICP–AES 10 mg/g
Table AIII–2. Chemical data for all geologic samples collected in this study. Sample no. Site Location Sample type 

AGEM-1B American Gypsum Eagle mine near surface—hi-grade ore massive gypsum in Eagle Valley Evap. 3AGEM-2 American Gypsum Eagle mine deeper low-grade massive gypsum in Eagle Valley Evap. 3BW-2A-S Badger Wash (Mancos Shale) near entrance to Basin 2A efflorescent salt 3BW-2A-G Badger Wash (Mancos Shale) near entrance to Basin 2A surface gypsum 3BW-3B-S Badger Wash (Mancos Shale) near entrance to Basin 3B efflorescent salt 3SC-1 Mesaverde Fm. Snowcap coal coal on outcrop outside mine coal 3SC-2 Mesaverde Fm. Snowcap coal shale on outcrop outside mine shale 3SM 1 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) fine white powder 3SM 2 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) yellow popcorn salt 3SM 3 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) gray popcorn salt (cemented) 3SM 4 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) gray-yellow hard layer (ash?) 3SM 5 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) soft gray (ash-feeling) salt 3SM 6 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) massive white salt (lowermost) 3SM 7 GGNCA sulfur mine–Dakota Fm. middle working (the ridge) massive xl mat—white salt 3SM 12 GGNCA sulfur mine–Dakota Fm. lower workings "S face" ss with native S 3SM 17-S GGNCA sulfur mine–Dakota Fm. lower workings pond in main drainage efflorescent salt from bank 3I-70-1 Salts on Mesaverde Fm. I-70 parking (between Cameo and Debeque) massive efflorescent salt 3I-70-2 Salts on Mesaverde Fm. I-70 parking (between Cameo and Debeque) efflorescent salt scrapping 3

Sample no. Date sampled Al % ICP–AES Al % ICP–MS As mg/kg HYD As mg/kg ICP–MS Ba mg/kg ICP–

AGEM-1B 8/17/07 0.02 0.02 1.5 2 <10 AGEM-2 8/17/07 0.03 0.03 1.6 4 <10 BW-2A-S 8/17/07 3.9 3.5 6.4 4 450 BW-2A-G 8/17/07 0.05 0.07 1.6 3 <10 BW-3B-S 8/17/07 3.4 3.7 5.4 6 370 SC-1 8/18/07 6.2 4.9 1.5 0.5 620 SC-2 8/18/07 8.1 8.6 5.3 5 1,690 SM 1 8/18/07 0.62 0.64 2.8 2 40 SM 2 8/18/07 6.5 6.2 12 13 <10 SM 3 8/18/07 7.0 6.3 3.1 3 40 SM 4 8/18/07 2.6 2.7 88 115 40 SM 5 8/18/07 5.0 4.2 6.0 6 20 SM 6 8/18/07 1.2 1.2 6.4 6 20 SM 7 8/18/07 nd nd 0.7 nd nd SM 12 8/18/07 0.56 0.47 83 68 40 SM 17-S 8/18/07 2.9 2.7 120 140 <10 I-70-1 8/18/07 2.2 2.1 4.3 3 320 I-70-2 8/18/07 1.6 1.6 0.3 2 190 
Table AIII–2. Chemical data for all geologic samples collected in this study.—Continued Sample no. Be mg/kg ICP–MS Bi mg/kg ICP–MS Ca % ICP–AES Ca % ICP–MS C (tot) % COMB 

AGEM-1B 0.05 <0.04 24 27 0.02 AGEM-2 0.1 <0.04 29 31 0.09 BW-2A-S 1.4 0.19 4.9 4.2 2.1 BW-2A-G 0.1 <0.04 23 21 0.06 BW-3B-S 1.0 0.19 4.4 4.9 2.1 SC-1 3.7 0.45 0.02 0.02 43 SC-2 1.7 0.59 0.05 0.05 4.5 SM 1 0.2 0.05 1.4 1.3 nd SM 2 4.0 0.08 0.11 0.12 0.06 SM 3 3.6 0.81 0.16 0.14 0.56 SM 4 1.3 1.26 0.14 0.15 0.11 SM 5 0.5 0.13 0.13 0.11 0.22 SM 6 0.2 <0.04 0.31 0.33 0.18 SM 7 nd nd nd nd nd SM 12 0.1 0.14 0.11 0.1 0.11 SM 17-S 2.3 <0.04 0.3 0.27 0.12 I-70-1 0.6 0.04 1.3 1.3 0.41 I-70-2 0.5 0.08 3.1 3.1 nd 

Sample no. Cd mg/kg ICP–MS Ce mg/kg ICP–MS Cl mg/kg ISE Co mg/kg ICP–MS Cr mg/kg ICP–AES 

AGEM-1B <0.1 0.29 <50 0.6 5 AGEM-2 <0.1 0.38 100 0.4 10 BW-2A-S 0.4 30 120 4.6 50 BW-2A-G <0.1 0.56 <50 0.9 5 BW-3B-S 0.4 34 190 4.2 40 SC-1 0.2 29 150 5.3 20 SC-2 0.2 92 90 5.7 60 SM 1 <0.1 9.7 nd 1.3 10 SM 2 1.2 24 <50 36 20 SM 3 1.4 25 <50 27 10 SM 4 0.8 13 60 7.8 20 SM 5 0.2 21 <50 1.7 20 SM 6 <0.1 7.4 810 1.7 10 SM 7 ins nd nd nd nd SM 12 0.3 19 <50 0.2 5 SM 17-S 0.2 4.8 <50 2.5 20 I-70-1 <0.1 31 360 1.7 20 I-70-2 0.2 17 nd 2.2 20 
Table AIII–2. Chemical data for all geologic samples collected in this study.—Continued Sample no. F mg/kg ISE Fe % ICP–AES Fe % ICP–MS Ga mg/kg ICP–MS Hg mg/kg CVAA K % ICP–AES K % ICP

AGEM-1B 10 0.005 0.01 0.12 <0.02 0.01 0.02 AGEM-2 60 0.03 0.02 0.17 <0.02 0.01 0.0BW-2A-S 540 1.55 1.3 9.8 <0.02 1.5 1.4 BW-2A-G 30 0.02 0.02 0.22 <0.02 0.03 0.04 BW-3B-S 520 1.31 1.5 7.6 0.02 1.3 1.5 SC-1 270 0.17 0.15 13 0.14 0.2 0.1SC-2 840 1.51 1.8 20 0.11 2.3 2.4 SM 1 nd 0.23 0.25 1.7 <0.02 0.08 0.0SM 2 130 3.2 3.3 14 <0.02 0.4 0.3SM 3 560 0.41 0.39 3.8 0.77 0.18 0.14 SM 4 260 21.4 21 37 0.54 3.8 3.9 SM 5 110 2.5 2.5 15 <0.02 0.57 0.52 SM 6 90 0.91 1 3.0 <0.02 0.42 0.4SM 7 nd nd nd nd <0.02 nd nd SM 12 40 0.12 0.08 1.1 1.1 0.02 0.0SM 17-S 60 0.94 0.92 8.9 <0.02 0.44 0.3I-70-1 130 0.49 0.51 4.5 <0.02 1.2 1.2 I-70-2 nd 0.35 0.36 3.4 <0.02 0.78 0.7

Sample no. Mg % ICP–AES Mg % ICP–MS Mn mg/kg ICP–MS Mo mg/kg ICP–MS Na % ICP–AES Na % ICP–M

AGEM-1B 0.005 0.005 5 0.18 0.03 0.01 AGEM-2 0.1 0.09 6 0.69 0.005 0.02 BW-2A-S 1.8 1.5 235 1.3 1.64 1.3 BW-2A-G 0.02 0.02 17 0.09 0.02 0.02 BW-3B-S 1.6 1.8 185 1.2 2.78 2.5 SC-1 0.12 0.11 23 1.1 0.2 0.13 SC-2 0.39 0.45 40 1.2 0.82 0.76 SM 1 11 10 31 0.18 0.005 0.02 SM 2 1.1 1.1 740 0.45 1.02 0.81 SM 3 1.5 1.5 735 0.82 0.1 0.08 SM 4 0.24 0.24 170 16 1.1 0.97 SM 5 0.37 0.37 71 0.35 0.68 0.49 SM 6 6.3 7.2 24 0.28 9.85 8.3 SM 7 nd nd nd nd nd nd SM 12 0.01 0.01 11 0.32 0.05 0.01 SM 17-S 2.0 2.0 99 0.4 12.9 10.7 I-70-1 0.54 0.57 110 0.23 13.6 11.9 I-70-2 1.3 1.4 65 0.87 18 14.9 
Table AIII–2. Chemical data for all geologic samples collected in this study.—Continued

Sample no. Ni mg/kg ICP–MS P mg/kg ICP–MS Pb mg/kg ICP–MS Rb mg/kg ICP–MS S % ICP–MS S (tot) % COM

AGEM-1B 1.5 <50 1.2 0.6 22 17 AGEM-2 1.2 180 1.0 1.3 23 23 BW-2A-S 18 710 15 66 1.4 1.11 BW-2A-G 1.7 <50 0.6 1.4 23 17 BW-3B-S 18 960 15 59 2.4 1.59 SC-1 13 <50 13 6 0.49 0.78 SC-2 16 450 30 160 0.82 0.6 SM 1 2.6 <50 4.5 4 14 nd SM 2 43 <50 8.1 8.8 11 14 SM 3 27 <50 5.9 8.4 8.8 12 SM 4 15 100 81 86 14 12 SM 5 4.7 170 4.9 27 7.05 17 SM 6 3.9 <50 2.3 12 18 16 SM 7 nd nd nd nd nd nd SM 12 0.9 160 11 0.7 1.2 18 SM 17-S 6.8 210 1.3 7.9 18 19 I-70-1 4.8 310 10 43 8.9 8.2 I-70-2 5.8 140 6.5 25 13 nd 

Sample no. Sc mg/kg ICP–MS Se mg/kg Hydride Si % ICP–AES Sn mg/kg ICP–MS Sr mg/kg ICP–AES Sr mg/kg ICP–

AGEM-1B 0.4 <0.2 0.02 0.05 1,230 1,210 AGEM-2 0.4 <0.2 0.03 0.1 1,440 1,250 BW-2A-S 6.1 1.2 28 1.2 190 175 BW-2A-G 0.6 0.5 0.17 0.1 380 350 BW-3B-S 4.7 1 27 1.0 150 155 SC-1 5.2 1.8 8.5 1.1 30 18 SC-2 9.2 1.7 27 2.4 140 135 SM 1 0.5 0.7 2.3 0.4 60 53 SM 2 6.5 0.5 0.82 0.4 30 27 SM 3 2.8 1.4 5.3 0.6 40 36 SM 4 4.6 0.9 4.3 3.5 100 96 SM 5 3.9 <0.2 5.5 0.6 160 140 SM 6 0.7 0.2 3.1 0.3 130 130 SM 7 nd <0.2 nd nd nd nd SM 12 0.8 0.3 33 0.4 30 21 SM 17-S 3.7 0.6 1.7 0.2 120 105 I-70-1 1.7 3.6 22 0.5 220 210 I-70-2 1.4 7.9 12 0.4 450 120 
Table AIII–2. Chemical data for all geologic samples collected in this study.—Continued Sample no. Ti % ICP–MS Tl mg/kg GF Tl mg/kg ICP–MS U mg/kg ICP–MS V mg/kg ICP–MS W mg/kg ICP–

AGEM-1B <0.01 0.4 <0.1 0.05 0.5 0.1 AGEM-2 <0.01 <0.1 <0.1 0.05 0.5 1.3 BW-2A-S 0.12 0.6 0.5 2.5 72 0.6 BW-2A-G <0.01 <0.1 <0.1 0.05 1.0 0.05 BW-3B-S 0.11 0.5 0.5 2.3 73 0.6 SC-1 0.12 <0.1 0.1 4.6 27 0.3 SC-2 0.31 1.1 1.1 5.5 120 1.7 SM 1 0.02 <0.1 <0.1 0.6 3 0.3 SM 2 <0.01 0.6 0.5 0.7 6 0.05 SM 3 0.04 1 0.8 0.9 7 1.5 SM 4 0.05 6.3 6.5 1.0 41 1.2 SM 5 0.04 0.4 0.3 0.6 27 0.3 SM 6 0.02 0.6 0.6 0.9 7 0.2 SM 7 nd nd nd nd nd nd SM 12 0.04 0.3 0.3 5.9 3 0.6 SM 17-S <0.01 0.2 0.2 1.0 36 0.2 I-70-1 0.09 0.2 0.2 0.9 24 0.5 I-70-2 0.05 ins 0.2 0.8 17 0.4 

Sample no. Zn mg/kg ICP–MS Zr mg/kg I

AGEM-1B 0.5 5 AGEM-2 1 5 BW-2A-S 59 260 BW-2A-G 1 5 BW-3B-S 63 270 SC-1 42 140

SC-2 56 210

SM 1 11 30

SM 2 280 10SM 3 195 60

SM 4 64 80SM 5 33 70

SM 6 21 40

SM 7 nd nSM 12 13 100

SM 17-S 59 10

I-70-1 18 140I-70-2 19 80
Table AIII–3. Sulfur isotope data for geologic samples collected in this study. [S(H20), sulfate that dissolves in water; S(HCl), sulfate that dissolves in acid; S(elem), elemental sulfur; S(av), sulfur in monosulfide minerals; S(DI), sulfur in disulfide minerals sucBlanks indicate no data; oxygen isotopes reported relative to V-SMOW and sulfur isotopes relative to V-CDT] Sample no. Site Location Sample type lat 

AGEM-1A American Gypsum Eagle mine near surface gypsum (var. selenite) 39.67597 –AGEM-1B American Gypsum Eagle mine near surface–hi-grade ore massive gypsum 39.67597 –AGEM-2 American Gypsum Eagle mine deeper low-grade massive gypsum 39.67597 –BW-3BS Badger Wash near entrance to Basin 3B salts 39.34320 –BW-2AG Badger Wash near entrance to Basin 2A gypsum 39.3316 –BW-2AS Badger Wash near entrance to Basin 2A salt 39.3317 –SM-1 Sulfur mine middle working (the ridge) fine white powder 38.79016 –SM-2 Sulfur mine middle working (the ridge) yellow popcorn salt 38.79016 –SM-3 Sulfur mine middle working (the ridge) white-gray popcorn salt 38.79016 –SM-4 Sulfur mine middle working (the ridge) gray-white-yellow hard layer 38.79016 –SM-5 Sulfur mine middle working (the ridge) soft gray (ash-feeling) salt 38.79016 –SM-6 Sulfur mine middle working (the ridge) lowermost white salt 38.79016 –SM-7 Sulfur mine middle working (the ridge) massive xl mat–white salt 38.79016 –SM-8 Sulfur mine middle working (the ridge) massive siliceous layer 38.79016 –SM-9 Sulfur mine middle working (the ridge) yellow-white massive salt 38.79016 –SM-10 Sulfur mine middle working (the ridge)–down stream cherty silicified layer 38.79016 –SM-11 Sulfur mine middle working (the ridge)–down stream S(native) on fractures 38.79016 –SM-12 Sulfur mine lower workings "S face" sandstone with native S 38.78923 –SM-17 Sulfur mine lower workings pond in main drainage salts from bank 38.78923 –SC-1 Snowcap coal coal on outcrop outside mine coal 39.1423 –SC-2 Snowcap coal shale on outcrop outside mine shale 39.1423 –I-70-1 Mesa Verde I-70 parking (between Cameo/Debeque) massive salt 39.19412 –I-70-2 Mesa Verde I-70 parking (between Cameo/Debeque) salt scraping 39.19412 –
Table AIII–3. Sulfur isotope data for geologic samples collected in this study.—Continued [S(H20), sulfate that dissolves in water; S(HCl), sulfate that dissolves in acid; S(elem), elemental sulfur; S(av), sulfur in monosulfide minerals; S(DI), sulfur in disulfide minerals sucBlanks indicate no data; oxygen isotopes reported relative to V-SMOW and sulfur isotopes relative to V-CDT] Sample δ34S(H20)‰ δ18O(H2O) %S (HCl-1N) δ34S(HCl)‰ %S(elem) δ34S(ele)‰ %S(AV) δ34S(AV)‰ 

AGEM-1A 14.5 12.6 8.2 14.5 AGEM-1B 14.3 11.5 7.8 14.1 AGEM-2 13.7 10.2 13 13.6 BW-3BS –20.9 –9.0 0.014 nd BW-2AG –22.7 –2.9 7.9 –22.8 BW-2AS –17.0 –8.6 0.019 nd SM-1 –6 –7.5 0.027 nd SM-2 –1.5 –4.0 –2.0 0.004 nd SM-3 –3.7 –4.6 0.003 nd SM-4 1.7 –5.0 nq –3.2 0.006 nd SM-5 1.3 nd 0.008 nd SM-6 –18.9 –3.7 0.014 nd SM-7 –1.5 13.6 0.087 nd SM-8 SM-9 SM-10 SM-11 SM-12 nq –0.4 6.2 4.5 0.67 2.80 SM-17 –7.4 2.9 0.025 ndSC-1 nq 3.7 0.003 nd 0.0003 nd SC-2 nq –1.5 0.008 nd 0.0010 nd I-70-1 3.4 –3.6 0.011 ndI-70-2 3.6 –2.9 0.014 nd
Table AIII–4. Mineralogical data for selected geologic samples collected in this study. Data on elements present in the samples are based on examielectron microscope (SEM) equipped with an energy dispersive X-ray fluorescence detector. Elements are listed in order of abundance, except O, whMineral identification is based on morphology and element suites. [*, amount of hydroxyl present in each sample was not determined and may have changed between the time of sample collection and SEM examination] Sample Site Location Sample type Elements* 

AGEM-1A American Gypsum Eagle mine near surface gypsum (var. selenite) nd AGEM-1B American Gypsum Eagle mine near surface–hi-grade ore massive gypsum nd AGEM-2 American Gypsum Eagle mine deeper low-grade massive gypsum nd BW-3BS Badger Wash near entrance to Basin 3B salts NaSO, CaSO BW-2AG Badger Wash near entrance to Basin 2A gypsum CaSO BW-2AS Badger Wash near entrance to Basin 2A salt NaSO SM-1 Sulfur mine middle working (the ridge) fine white powder NaAlSO, MgAlSO, Fe(NaSiKSM-2 Sulfur mine middle working (the ridge) yellow popcorn salt MgSO, CaSO SM-3 Sulfur mine middle working (the ridge) white-gray popcorn salt AlMgSO, AlSO, MgAlSO, Ca

FeSO, NaAlSO, AlSiSO SM-4 Sulfur mine middle working (the ridge) gray-white-yellow hard layer AlMgSO, AlSO SM-5 Sulfur mine middle working (the ridge) soft gray (ash-feeling) salt AlSO, FeSO, KFeAlMgSO 

SM-6 Sulfur mine middle working (the ridge) lowermost white salt NaMgSO, S, MgSO, NaAlSO

AlMgSO, KAlSO 

SM-7 Sulfur mine middle working (the ridge) massive xl mat—white salt MgAlSO, MgFeAlSO, AlSO SM-8 Sulfur mine middle working (the ridge) massive siliceous layer SM-9 Sulfur mine middle working (the ridge) yellow-white massive salt SM-10 Sulfur mine middle working (the ridge)–down stream cherty silicified layer SM-11 Sulfur mine middle working (the ridge)–down stream S (native) on fractures SM-12 Sulfur mine lower workings “S face” sandstone with native S SM-17 Sulfur mine lower workings pond in main drainage salts from bank NaSO, NaFeSO, NaAlSO, NaSC-1 Snowcap coal coal on outcrop outside mine coal nd SC-2 Snowcap coal shale on outcrop outside mine shale nd I-70-1 Mesa Verde I-70 parking (between Cameo/Debeque) Salt scraping–massive and dendritic NaSO rounded xls I-70-2 Mesa Verde I-70 parking (between Cameo/Debeque) salt scraping–massive white salt, some dendritic xls NaSO, CaSO, NaCaSO, NaM
Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

Manuscript approved for publication, March 13, 2009

Edited by Thomas Judkins

Graphics and layout by Joy Monson

For more information concerning this publication, contact:

Team Chief Scientist, USGS Crustal Imaging and Characterization

Box 25046, Mail Stop 964

Denver, CO 80225

(303) 236-1312

Or visit the Crustal Imaging and Characterization Team Web site at:

http://crustal.usgs.gov/

This publication is available online at:

http://pubs.usgs.gov/sir/2009/5072/