Chemical Degradation on 

Opposite Flanks of the 

Wind River Range 

Wyoming

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1535-E

Chemical Degradation on 

Opposite Flanks of the 

Wind River Range 

Wyoming

By CHARLES H. HEMBREE and FRANK H. RAINWATER

GEOCHEMISTRY OF WATER

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1535-E

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C.
CONTENTS

Page

Abstract_____________________-_-_------_-_-_________ E-1

Chemical degradation________________________________________.____ 1

Conclusions_ ____ _ ________________________________________________ 9

Literature cited.__ ______________________________________________ 9

ILLUSTRATIONS

FIGURE 1. Map of geology of the Wind River Range and location of

chemical-quality and streamflow stations_______________ E-2

2. Relation of dissolved-solids concentration to water discharge,

East Fork at New Fork, Wyo__________________ 6

3. Flow-duration curve for East Fork at New Fork, Wyo., 1914r-57

water years______________________________ _______ 7

TABLES

TABLE 1. Rates of chemical degradation and runoff on opposite flanks of

the Wind River Range, Wyo__________-.----______ E-4

2. Rate of degradation in selected areas__-___-_-_-_-__________ 8

m

5S5224-81

GEOCHEMISTRY OF WATER

CHEMICAL DEGRADATION ON OPPOSITE FLANKS OF 

THE WIND RIVER RANGE, WYOMING

By CHARLES H. HEMBREE and FRANK H. EAINWATER

ABSTRACT

The rate of degradation by solution on the northeast flank of the Wind River 

Range is twice that on the southwest flank about 49 and 26 tons per square 

mile per year, respectively. Conversely, the stream runoff on the southwest 

flank is about 1% times that on the northeast. This seeming anomaly is 

due principally to the erosive nature of a girdling band of pre-Tertiary rocks 

exposed on the northeast flank.

Five drainage basins are selected on the southwest side of the mountains 

and six on the northeast side as representative samples of the geologic terranes. The computed discharge-weighted concentrations of dissolved solids 

range from 25 to 34 parts per million on the southwest and from 37 to 276 

parts per million on the northeast.

Techniques used in the computations of chemical degradation rates include: 

adjustment of short-term flow-duration curves to a base 1914-57 period, correlation of chemical concentrations with water discharges, calculation of solute 

yield from flow duration curves and discharge-concentration correlations, and 

correction of gross yields for soluble material in precipitation.

CHEMICAL DEGRADATION

The term "chemical degradation" applies only to the removal of 

rock material by corrosion, or chemical erosion, and the subsequent 

transport of the dissolved products. Because of its setting and the 

amount of chemical, hydrologic, and geologic data available, the Wind 

Eiver Eange is an excellent pilot area for quantitative study of corrosion rates in different geologic and hydrologic environments.

The central part of the Wind Eiver Mountains is a rugged wilderness of granitic spires and massive buttresses that were formed 

by prolonged erosion of the anticlinal range. The higher, or more 

central, part is a large plateau that bears the imprint of past and 

present glaciation^ Myriad sparkling lakes of glacial origin form 

a band astride the sometimes indistinct continental divide. On the

B-l
E-2 GEOCHEMISTRY OF WATER

western side, where glaciers in times past have spilled off the high 

plateau into the valleys below, great glacier-gouged lakes protrude 

likes tongues from the mountain canyons. For a number of miles 

along the highest ridge, which reaches an altitude of 13,785 feet 

at the top of Gannett Peak, Dinwood, and Bull Lake Glaciers are 

still actively eroding their cirques.

The area of exposed granitic rocks is about 125 miles long and 

25 miles wide. (See fig. 1.) On the northeast side of the mountains,, 

erosion has stripped away the nearly horizontal Tertiary rocks,, 

which at one time almost covered the Paleozoic and Mesozoic rocks 

that dip steeply to the northeast. These latter rocks, of varying 

degrees of erosibility, form a broad band along the northeast side of 

the range. On the southwest side of the range, rocks of these ages

EXPLANATION 

Tertiary and Quaternary rocks 

Paleozoic and Mesozoic rocks

Geology from Geologic Map of Wyoming by 

J.D. Love, J.L.Weitz, and R.K.Hose, 1955

FIGURE 1. Map of geology of tbe Wind River Range and location of chemical-quality and

strcamflow stations.
CHEMICAL DEGRADATION, WIND EIVEK KANGE E-3

have not heen exposed by post-Tertiary erosion, and the Tertiary 

rocks and Pleistocene debris lap directly onto Precambrian granites.

Streams that carry away the precipitation that falls on the mountains start, almost without exception, in cirque lakes along the divide. 

At the southern end of the range near Atlantic City, the continental divide has an altitude of about 9,000 feet. The altitude gradually increases northward to Gannett Peak, and the increase in 

altitude is accompanied by an increase in precipitation and runoff. 

Runoff per unit area of Pine Creek above Fremont Lake, which 

drains the highest part of the mountains, is more than twice that 

of Little Sandy Creek near Elkhorn, which is near the south end 

of the range.

The basic data used in this study consist of records of chemical 

quality and streamflow at seven sites on the southwest side of the 

range and at eight sites on the northeast, as shown on figure 1. Of 

these, the five streams whose drainage basins upstream from sampling points are underlain predominantly by granites are selected as 

being representative of streams draining the southwest side of the 

mountains. On the northeast side, the six stations lying closest to 

the front are believed to form the most representative group. The 

streams above the 11 representative stations are affected very little, 

if at all, by diversions or return flow from irrigated land. Their 

drainage areas range from 21 to 94 square miles on the southwest 

flank and from 60 to 140 square miles on the northeast flank. (See 

table 1.)

As part of an investigation of the water resources of the Wind 

Eiver Basin to the north of the mountains, chemical-quality data 

were collected at many sites from 1948 to 1953. Analyses are published in a report by Colby, Hembree, and Eainwater (1956). In 

1957 and 1958, as a part of the investigations of the water resources 

of the Upper Colorado River Basin, the Geological Survey collected 

chemical-quality data at hundreds of sites. Chemical analyses that 

were used to compute the yield of dissolved solids from the southwest side of the Wind River Range are a part of these data.

The streamflow records were converted into tables of duration of 

flow by manual and electronic computations. Duration curves for 

the 1914-57 water-year period were then synthesized by correlation 

techniques, and the mean discharges, given in table 1, were computed from the synthetic records. The shortest period of measured 

record for the streamflow stations was 3 water years, and the longest 

was 43 water years. This 1914-57 period is assumed to be representative of a long-term base period of the same length and perhaps 

for an even longer period.
TABLE 1. Rates of chemical degradation and runoff on opposite flanks o

Station

Drainage 

area 

(sqmi)

Runofl

Mean 

water 

discharge 

(cfs)

Inches

Precipitation

Inches

Concentration 

(ppm)

Ratio of 

precipitation to 

runoff

Southwest side of Wind River Mountains

New Fork River below New Fork Lake, near

Big Sandy at Leckie Ranch near Big Sandy,

36.2

75.8

79.2

94.0

20.9

306

552

348

900

51.4

106

85.7

21.5

111

401

166

310

19.2

35.6

18.2

12.5

14.0

20.6

9.8

6.5

8.5

35

44

34

29

30

35

26

23

25

6

6

6

6

6

6

6

6

6

1.8

1.2

1 Q

2.3

2.1

9 7

3.5

Northeast side of Wind River Mountains

North Fork Little Wind River at Fort WaSouth Fork Little Wind River near Fort WaNorth Popo Agio River near Lander, Wyo 

57

50

222

127

118

140

714

640

331

971

44.5

17.2

284

113

123

112

155

182

99.3

154

10.6

4.7

17.4

12.1

14.1

11.3

13.3

3.9

3.7

3.8

31

22

33

27

26

28

29

20

18

19

6

6

6

6

6

6

6

6

6

6

2.9

4 7

1 Q

2.2

1.8

2.5

5.1

4.8
CHEMICAL DEGRADATION, WIND RIVER RANGE E-5

Snow and rain contain dissolved solids. In computing chemical 

degradation from an area, the dissolved solids contributed by precipitation must be subtracted. One method of correcting gross, or 

measured, degradation for small areas is to compute the mineral 

content of streamflow attributable to precipitation and subtract this 

amount from the measured concentration of dissolved solids. Although no measurements of dissolved solids in precipitation were 

made in the study area, analysis of data reported by Junge and 

Werby (1959) and other available information at points nearby, 

indicates that the annual average mineral content of precipitation 

on the Wind Kiver Eange is about 6 parts per million. This value 

is in good agreement with data collected by Eogers and Feth (1959) 

in the Sierra Nevada and Wasatch Mountains and by J. P. Miller 

(written communication) in the Sangre de Cristo Mountains.

The average precipitation over each drainage basin was estimated 

from records of precipitation and runoff, relation of runoff to precipitation, the general relation of precipitation to altitude, and maps 

of runoff and altitude. (See Oltman and Tracy, 1949.) Corrections 

of the gross dissolved-solids content of the representative streams 

ranged from 7 ppni for Pine Creek above Fremont Lake to 28 ppm 

for Willow Creek near Crowheart (table 1).

Samples of water for chemical analysis were collected at sites on 

the southwest flank at high, medium, and low stages of the streams. 

On the northeast flank the samples represented high and low stages. 

These data were used to establish relations between water discharge 

and chemical concentration. For many streams this inverse relation is very good. The form of the curve drawn through a plot 

of concentration versus water discharge, depends on the type of 

stream. Similar stream environments are conducive to similarly 

formed curves. The shape of the c^irve on figure 2 is typical of 

high mountain streams in this area. r. ?he similarity was helpful when 

curves were drawn for those streams where sampling did not cover 

the complete range of discharge.

To compute the gross yields of dissolved solids, the mean water 

discharge for the mean of selected tirie intervals was obtained from 

tables or curves of duration of streainflow for each station (fig. 3). 

Values of concentration for each of those water discharges were taken 

from the plot of concentration versus water discharge, and applicable discharges of dissolved solids were computed for each station. 

Weighted-mean concentrations were Ihen computed from the means 

of the dissolved-solids and water discharges.

The gross weighted-average concentrations of streams draining the 

granites on the southwest flank differed only slightly regardless of
E-6 GEOCHEMISTRY OF WATER

runoff per unit area or size of drainage area (table 1). Pine Creek 

above Fremont Lake drains an area of 76 square miles and has a, 

runoff of 36 inches and a weighted concentration of 25 ppm. Little 

Sandy Creek near Elkhorn has a drainage area of 21 square miles^ 

a runoff of 14 inches, and a weighted-average concentration of 29 

ppm. The net weighted-average concentration for these two streams 

was 18 ppm for Pine Creek and 16 ppm for Little Sandy Creek. 

J. P. Miller (written communication) also has found this same lack 

of correlation of concentration with size of drainage areas in terrains of uniform rock type in the Sangre de Cristo Eange in New 

Mexico.

The small divergence in dissolved-solids concentrations in waters 

from the granites is remarkable. Precipitation may have what has 

been called a solution potential for monolithogic terrains, and this potential is depleted rapidly when the water comes in contact with the 

rocks. Any solution subsequent to the rapid depletion of most of 

the solution potential is either extremely slow or nonexistent. In 

more exacting terms, the amount of material that will be dissolved 

depends on the controlling chemical equilibria between minerals and 

ionic species in solution.

Additional research in this phase of geochemistry should lead to 

fuller understanding of the processes of chemical degradation. Where

KTOfi

100 

K)

£

^

"^

ls

x

\

V ^ ^

~ 

10 100 1000 

WATER DISCHARGE, IN CUBIC FEET PER SECOND

FIGUBB 2. Relation of dlssolved-sollds concentration to water discharge, Bast Fork at

New Fork, Wyo.
CHEMICAL DEGRADATION, WIND KIVER RANGE E-7

the amount of water is sufficient to carry off the soluble products 

of weathering, as is evidently the situation high in the mountains, 

concentration of constituents in runoff may be essentially constant 

and controlled by the chemical equilibrium between the solutes and 

some solid phases. Where weathering is faster than removal of its 

soluble products, the products accumulate. The mineral content of 

waters from these areas is probably related directly to the accessibility 

of these soluble materials to the runoff. This type of degradation 

seems to apply to arid and semiarid environments.

iqpoo

Q

O 

O 

UJ 

to

cc 1000

UJ

s

10

\

K

I

GO Ql 05 I 2 5 10 20 40 60 80 90 95 9899 998 99.99

PERCENTAGE OF TIME THAT WATER DISCHARGE EQUALED OR

EXCEEDED VALUE SHOWN

FIGURE 3. Flow-duration curve for Bast Fork at New Fork, Wyo., 1914r-57 water years.
E-8 GEOCHEMISTRY OF WATER

The range in net yields from the individual representative drainage basins is considerable 16 to 46 tons on the southwest flank 

and 27 to 84 tons on the northeast flank. This spread raises the 

question of the significance between the regional averages of 26 and 

49 tons. Statistical tests show that the difference in these regional 

averages is significant at better than the 0.01 level.

A second approach to the subject of geology's influence on degradation is to move farther down the flanks and consider the combined 

drainages of 900 and 971 square miles on the southwest and northeast flanks, respectively (the last regional weighted averages on 

table 1). The yield from 900 square miles on the southwest that 

include areas of granites and Pleistocene and Tertiary rocks, was 

34 tons per square mile compared to 56 tons per square mile for an 

area of 971 square miles on the northeast underlain by granites and 

the more erosible rocks of Paleozoic, Mesozoic, and Tertiary ages. 

The net yield of water from the northeast flank (3.8 in.) is a little 

less than half the yield from the southwest flank (8.5 in.). Yet, 

the yield of dissolved solids from the northeast flank is still almost 

twice the yield from the southwest flank. The difference in the 

dissolved-solids yield must be due in part to the effect of the preTertiary rocks that are exposed on the northeast and not on the 

southwest side.

Degradation rates in relation to the modification of land forms 

always are fuel for interesting speculation. The time required to 

remove 1 foot of material in the drainage basin of Little Sandy Creek 

at the present rate of chemical degradation would be 137,000 years or 

almost three times the 48,000 years it would require to remove 1 

foot from the drainage basin of Pine Creek (table 2). If this 

differential rate of degradation were to continue, the north and higher 

part of the Wind River Range would be reduced to the same altitude as the south part of the Range, unless, as is probable, differential 

elevation of the mountains occurs or is occurring.

TABLE 2. Rate of degradation in selected areas

Areas

Pine Creek above Fremont Lake __ _

Bull Lake Creek near Lenore___ __ _ ____ _ _

Regional south west. ____ __ __ _______

Regional northeast __ ______ _ ____ ___ ____

Dissolved-solids 

yield (tons per 

SQ mi per year)

46

16

48

26

49

Time to remove 

1 ft of material 

(years)

48, 000

137, 000

46, 000

84, 000

45, 000
CHEMICAL DEGRADATION, WIND RIVER RANGE E-9

CONCLUSIONS

Long-term gross chemical degradation can be estimated from the 

regression of concentration of dissolved solids on streamflow and

the adjusted flow-duration curve. Di 

significantly contribute to the gross,

percent for the 15 drainage basins studied.

The control exerted by chemical equilibria between mineral and 

ionic species in solution is clearly demonstrated by the small divergence in concentration in waters from j rranites. The large divergence

in concentrations and yields in waters

east flanks is attributable to the weathering and erosional characteristics of the girdling band of pre-Terti ary sedimentary rocks exposed 

on the northeast flank.

LITERATURE

Colby, B. R., Hembree, 0. H., and Rainwa 

chemical quality of surface waters in 

Geol. Survey Water-Supply Paper 1373.

Junge, C. E., and Werby, R. T., 1959, The 

potassium, calcium, and sulfate in rain 

Jour, of Meteorology, v. 15, no. 5, p. 417-425

Oltman, R. E., and Tracy, H. J., 1949,

River Basin in Wyoming: U.S. Geol. Sur fey O:

Rogers, S. M., and Feth, J. H., 1959, Chemical 

Sierra Nevada, Calif., and the Wasat 

at the 1959 Western Snow Conf., April 1959,

O

,er, F. H., 1956, Sedimentation and 

;he Wind River Basin, Wyo.: U.S.

concentration of chloride, sodium, 

water over the United States:

Average annual runoff in the Wind 

lire. 66.

constituents in snow from the 

ch Mountains, Utah: Paper given

ssolved solids in precipitation 

or apparent, yield 8 to 45

from the southwest and northCITED