UNITED STATES

DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION

SEDIMENTATION SURVEYS

OF

PATHFINDER AND SEMINOE RESERVOIRS

NORTH PLATTE RIVER, WYOMING

Sedimentation Section Report

HYDROLOGY BRANCH

I

PROJECT PLANNING DIVISION

DENVER, COLORADO a

MAY 1953
UNITED STATES

DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION

SEDIMENTATION SURVEYS

OF

PATHFINDER AND SEMINOE RESERVOIRS

NORTH PLATTE RIVER, WYOMING

By

LOUIS M. SEAVY

and

FRANK K. ILLK

Sedimentation Section

Hydrology Branch

Project Planning Division

May 1953

.....

PATHFINDER DAM

-p - r - ., - - ,- •

-

P

-' •-• .•

- •

-- (.-__ f' ••ø..•._•.••••.•J.

.j•__J_4_J

,- ,_•_ -.-:.; ;• - -•

J:

I..- •.' I• - -

.• a. - • &

.7) '-4

- - -. -- -

- F

M.-- c--' F

:

-

/,

*

7__.

c_ - - -

-

_____ -' ----

- .

--- -

A

CONTENTS

.......................

....................

....................

........................

....................

..............

...............

...................

....................

...................

....................

................

.................

.............

......................

.....................

......................

......................

.......................

.....................

.....................

........................

..................

........

..............

.................

.............

.......

.........

..................

.............

SEDIMENTATION SURVEYS

OF

PATHFINDER AND SEMINOE RESERVOIRS

Page

Introduction 1

Acknowledgements 1

Purpose and Scope 1

Ownership 2

Location of Dams 2

Location of Pathfinder Reservoir 2

Location of Seminoe Reservoir 2

Purpose Served

Pathfinder Dam 3

Seminoe Dam 3

Description of the Dams

Pathfinder Dam 3

Seminoe Dam 4

Description of the Lakes

Pathfinder Reservoir 4

Seminoe Reservoir 6

Description of the Drainage Area 7

Geology 9

Topography 9

Climate 24

Rainfall 24

Runoff 24

Land Cover 25

Land Use 25

Soils 25

History of the Surveys 25

Sediment Distribution--Pathfinder Reservoir 27

Longitudinal Distribution 27

Lateral Distribution 27

Sediment Disposition Curve 28

Volume Weight and Mechanical Analysis 28

Statistical Summary--Pathfinder Reservoir 37

Explanation of Results in Statistical Summary- -

Pathfinder Reservoir 38

Summary for Pathfinder Reservoir 39

1
CONTENTS- -Continued

.........

.................

........

.........

..........

..............

.......................

...................

...............

................

................

...................

.......

........

......

.....

....................

..........

......

.......

.....

............

...........

.....

...........

......

Sediment Distribution- -Seminoe Reservoir

Longitudinal Distribution

Lateral Distribution

Sediment Disposition Curve

Volume Weight and Mechanical Analysis

Sediment Sample Data--Seminoe Reservoir

Statistical Summary, Seminoe Reservoir

Summary for Seminoe Reservoir

Bibliography

ILLUSTRATIONS

Figure

Frontispiece- -Pathfinder Dam

Page

39

39

44

44

51

54

55

56

58

Page

1. Seminoe Dam 5

(a) Downstream view 5

(b) Upstream view 5

2. Map of drainage area 8

3. Geologic Map 10

4. Map of Pathfinder Reservoir (in 6 sheets) 11 -16

5. Map of Seminoe Reservoir (in 7 sheets) 17-23

6. Longitudinal profiles- -Pathfinder Reservoir 29

7. Typical Cross-sections--Pathfinder Reservoir . . 30

8. Sediment Disposition Curves, Pathfinder Reservoir 31

9. Sediment Size Analysis--Pathfinder Reservoir 33

10. Area-Capacity tables and curves- -Pathfinder

Reservoir 40

11. Sand Dunes--Pathfinder Reservoir 41

12. Stream bank erosion--Pathfinder Reservoir 42

13. Longitudinal profiles --Seminoe Reservoir 43

14. Typical Cross-sections--Seminoe Reservoir 45

15. Bank erosion near Seminoe Dam 46

16. Sand Dunes- -Seminoe Reservoir 47

17. Sand Dunes and Shoreline--Seminoe Reservoir 48

18. Shoreline Seminoe Reservoir and North Platte River

downstream from Seminoe Dam 49

19. Sediment Disposition Curve- -Seminoe Reservoir. . 50

20. Area-Capacity tables and curves- -Seminoe Reservoir 52

21. Sediment Size Analysis--Seminoe Reservoir 53

11
CONTENTS- -Continued

......

.......

.......

........

Tables

Table

No. Page

1. Sediment Sample Data- -Pathfinder Reservoir 32

2. Statistical Summary--Pathfinder Reservoir 37

3. Sediment Sample Data- -Seminoe Reservoir 54

4. Statistical Summary--Seminoe Reservoir 55

INTROD IJCTION

This report presents the results of an investigation of sedimentation in the Pathfinder and Seminoe Reservoirs on the North Platte

River in Wyoming. The investigation was conducted by the Sedimentation Section, Hydrology Branch, Project Planning Division, Bureau of

Reclamation, Denver, Colorado, in cooperation with the District Office,

Casper, Wyoming, a district of Region 7, Bureau of Reclamation, Denver,

Colorado. The investigation was made under the authority of the Reclamation Act of 1902 and amendments thereto. The field work was initiated

on March 21, 1950, and was continued intermittently until April 14, 1951.

A copy of the original map of Pathfinder Reservoir made prior

to the closure of Pathfinder Dam in 1909, and a copy of the original map

of Seminoe Reservoir made prior to the closure of the Seminoe Dam in

1939, were used in analyzing the data obtained during this investigation.

In addition to using the above maps the results of the 1931 reconnaissance

survey of Pathfinder Reservoir were also used. The reconnaissance survey of 1931 was made by the Corps of Engineers, tiS. Department of the

Army, during their, "Silt Investigation in the Missouri River Basin."

ACKNOWLEDGMENTS

Messrs. Dale W. Henry and Joe M. Lara of the Sedimentation

Section, Hydrology Branch, Project Planning Division, Denver, Colorado, assisted in the compilation of data and the preparation of charts

for this report.

The helpful advice given the writers by the following persons

of the Bureau of Reclamation who reviewed this report is also acknowledged:

Mr. IJ. Matthews, District Manager; Mr. Nels P.

Nelson, Superintendent, Water and Land; and Mr.

Ed H. George, Planning Engineer, Casper Wyoming

Mr. John A. Keimig, Regional Planning Engineer,

Region 7, Denver, Colorado

Messrs. H.S. Riesbol and W. M. Borland, Hydrology

Branch, Project Planning Division, Denver, Colorado

PURPOSE AND SCOPE

The purpose of this investigation waS: (1) to obtain the

necessary data for preparing new area capacity tables for Pathfinder

and Seminoe Reservoirs, (2) to determine the sediment yield for the

drainage areas above Seminoe and Pathfinder Reservoirs, and (3) to

obtain information on the sediment disposition in these reservoirs.

The analysis of these data should provide information needed for the

proper operation of the reservoirs, aid in estimating the useful lives

of the reservoirs, and assist in the design of other structures relative to increasing the usefulness of the projects. Information may

also be furnished relative to the requirement of upstream measures

of control for reducing the rates of sediment contribution
RT-TTP

Both Pathfinder and Seminoe Reservoirs and Dams are owned

by the United States Government and are operated by the Bureau of

Reclamation, U.S. Department of the Interior.

LOCATION OF DAMS

Pathfinder and Seminoe Dams are located on the North Platte

River approximately 47 and 55 miles, respectively, southwest of Casper,

Wyoming. Their relative location is shown on Drainage Map, Figure 2,

page 8.

LOCATION OF PATHFINDER RESERVOIR

Natrona County, Wyoming

T3ON, R85W, Sects. 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36

T3ON, R84W, Sect. 31

T29N, R84W, Sects. 5, 6, 7, 8, 9, 16, 17, 19, 20, 21, 22, 23,

26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36

Carbon County, Wyoming

T28N, R84W, Sects. 4, 5, 6, 7, 8, 9, 10, 15, 16, 17, 18, 19,

20, 21, 28, 29, 30, 31, 32, 33

T28N, R85W, Sects. 1, 11, 12, 13, 14, 23, 24, 25, 26

T27N, R84W, Sects 5, 6, 7, 8, 18, 19, 20, 29, 30, 32, 33

T27N, R85W, Sects. 12 and 13

T26N, R84W, Sects. 4, 5, 8, 9

The res ervoir map is shown by Figure 4, pages 11 - 16.

LOCATION OF SEMINOE RESERVOIR

Carbon County, Wyoming

T25N, R83W, Sects. 30, 31, 32

T25N, R84W, Sects. 9, 10, 15, 16, 21, 22, 23, 24, 25, 26,

27, 28, 34, 35, 36

T24N, R82W, Sects. 31 and 32

T24N, R83W, Sects, 7, 16, 17, 18, 19, 20, 21, 22, 25, 26,

27, 28, 29, 34, 35, 36

2
T24N, R84W, Sects. 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13,

14, 15, 16, 17, 18, 19, 20, 22, 23, 24,

25, 26, 27, 28, 33, 35, 36

T24N, R85W, Sects. 13 and 14

T23N, R82W, Sects. 5 and 6

T23N, R83W, Sects. 1, 2, 19, 30

T23N, R84W, Sects. 1, 2, 3, 4, 10, 11, 13, 14, 15, 16, 22, 23,

24, 25, 26, 27, 28, 31, 32, 33, 34, 35

T23N, R85W, Sects. 36

T22N, R84W, Sects. 4, 5, 6,

T22N, R85W, Sects. 1, 2, 3, 10, 11

The res ervoir map is shown by Figure 5, pages 17 - 23.

PURPOSE SERVED

Pathfinder Dam was constructed to store irrigation water for

the North Platte Projecf. This project, comprising approximately

236, 000 acres of irrigated land, is located more than 170 miles downstream from the dam. The project lands are in Goshen County, Wyoming, and Morill, Sioux, and Scotts Bluff Counties of Nebraska.

Storage water is also supplied to lands under private canals

in accordance with the provisions of the Warren Act of February 21,

1911 (36 Stat. 9251). Eight irrigation districts or canal companies,

irrigating about 108, 000 acres of land have permanent contracts for

supplemental water. Eight additional districts or canal companies,

irrigating about 35, 000 acres of land, have annual or temporary contracts for supplemental water.

Power is alsO generated with the water released for irrigation

purposes.

Seminoe Dam was constructed to store water of the North

Platte River for use in developing power and for the irrigation of

lands in the Kendrick Project. The irrigable area of the project was

divided into two units, of which the first unit contains about 22, 000

acres of land and the second unit may contain up to 15, 000 acres.

DESCRIPTION OF THE DAMS

Pathfinder Dam, illustrated by the Frontispiece, is a masonry,

arch-gravity type dam situated in a deep narrow granite canyon. The

dam has a structural height of 214 feet, a hydraulic height of 184 feet,

the base width is 96. 5 feet, and the width at the crest is 10.9 feet.

3
The crest of the dam is 432 feet long and the elevation of the crest is

5, 858. 1 feetl/ above sea level (USGS datum).

The spiliway is a concrete weir, 650 feet long with a capacity

of 65, 000 cfs. The spiliway is located at the north end of the dam. The

elevation of the crest of the spillway is 5850. 1 feet.

The outlet works consist of two tunnels, one on the north side

and the other on the south side of the canyon. The sill of the trashrack

for the north tunnel is at elevation 5668. 1. The flow through the north

tunnel is controlled by two balanced needle valves. The sill of the

trashrack for the south side tunnel is at elevation 5719. 6. The outlet

of the south tunnel is controlled by six balanced Ensign-type valves.

Pathfinder Dike is located about one-fourth miles south of the

dam. The dike is earth fill with a concrete core wall, The dike is

1, 650 feet long with a structural height of 38 feet and a hydraulic height

of 20 feet.

Seminoe Dam, illustrated by Figure 1, page 5, is a concretearch type diam. This dam is also located in a deep narrow canyon. The

dam has the following dimensionsin feet:

Structural height 295 Crest width 17

Hydraulic height 195 Crest length 530

Base width 85

The elevation of the crest of the dam is 6361 feet.

The spillway is an inclined tunnel controlled at the inlet by

three fixed-wheel gates. Each gate is 14 x 50 feet. The elevation of

the gate sills, which is also the elevation of spillway crest, is 6307

feet. The elevation of the top of the spiliway gates is 6357 feet.

DESCRIPTION OF THE LAKES

Pathfinder Reservoir: The 1950 Reservoir Map, Figure 4,

Sheets 1 through 6 is shown on pages 11 - 16, inclusive. The lake,

beginning at Pathfinder Dam is confined in a narrow deep canyon and

is less than 500 feet in width. However, immediately above the dam

the lake broadens abruptly to a width of one half mile or more. About

one and one-half miles west of the dam the lake is restricted between

the base of a mountain and a rock point. Above this restriction the

lake opens into a large basin formed by the confluence of Sand Creek,

Canyon Creek, and the Sweetwater River with the North Platte River.

The basin is approximately 8 miles long in a SSW direction and has a

1/ Based on this survey; add 1.9 feet to convert to original Pathfind Dam Project datum.

4
r

;J

. #ii

(a) Downstream view - Outlet to spillway tunnel left foreground and

powerhouse near center of photo. j;

#!!#I • 4;

a

(b) Upstream view - Crane tower and spillway near right edge of photo,

three penstock trash racks near center, and outlet trash rack left of center.

SEMINOE DAM

FIGURE 1, PAGE 5
maximum width of 3 miles. The North Platte River enters this basin

approximately midway along the east side, 7-1/2 miles above the dam,

through a relatively narrow rugged channel varying in width from 1/4

to 1/2 mile. Four and one-half miles above the entrance to the basin

the lake narrows into a canyon section that is approximately 500 feet

wide for a distance of about 1-3/4 miles. Continuing upstream the

lake gradually widens to a width of approximately 1 mile and stays

approximately this wide nearly to the upper end, and then narrows to

the head of the back water 10 miles above the narrows or 24 miles

above the dam.

The Sweetwater River arm enters the basin from the north

through a rugged canyon approximately 1/2 mile wide. Three and onehalf miles north of its confluence with the North Platte River the lake

narrows to a width of 800 feet and turns sharply to the west. Immediately thereafter it widens to a width of 1 mile for a distance of 3 miles,

and then widens again to its maximum width of 1-1/2 miles at the point

where Horse Creek enters the reservoir 13.5 miles above the dam.

Then the lake narrows gradually to a width of 300 feet at a distance of

18 miles from the darn. The lake againwidens slightly before tapering

down to reach the spillway crest line 19 miles above the dam.

The south half of the aforementioned basin is in the wide flat

valley through which Sand Creek enters the reservoir. The basin has

a width of nearly two miles to its upper end, 4 miles above the confluence of Sand Creek and the North Platte River.

At the NE part of the basin between the point that the North

Platte enters and leaves the basin is the Canyon Creek arm. This arm

is approximately 1 mile wide at its mouth but narrows rapidly to the

head of impounded water 3.3 miles above the confluence of Canyon

Creek and the North Platte River.

Seminoe Reservoir: The 1950 Reservoir Map, Figure 5, Sheets

1 through V is shown on pages 17 - 23,inclusive, The main body of the

lake above Seminoe Dam is on the North Platte River. In addition to the

main body of the lake there is one major arm formed by the confluence

of the Medicine Bow River with the North Platte River. The other small

tributaries of the lake are of minor consequence.

The principal body of the lake at the top of spillway gates,

elevation 6357, is approximately 40 miles in length and the Medicine

Bow arm is 24 miles in length. The original area of the lake at

elevations 6357 and 6340 was 20, 045 and 15, 280 acres, respectively.

The 1950 area of the lake at elevation 6340, the upper limit of this

survey is 15, 200 acres.

The principal body of the lake extends from the dam in a

southerly direction to the head of the backwater. The Medicine Bow

arm joins the east side of the lake at a distance of about 8 miles air

line or 17. 2 river miles upstream from the dam.

6
Beginning at the dam the lake is confined to a narrow canyon

for a distance of about 2 miles. Upstream from this reach the lake

abruptly increases in width, from less than 600 feet to one mile or

larger. Approximately 4 miles farther upstream or about 6 miles

above the dam, the lake is pinched in by another canyon section which

extends for about one mile. At this point the lake again widens to a

mile or more in width and remains approximately at this larger width

for the next 6 miles. The lake, although generally having a narrower

width above this point and becoming smaller as the head of backwater

is approached, occasionally exceeds a mile in width and averages more

than 1/2 mile in width.

The Medicine Bow arm, approximately 2 miles in width where

it joins the North Platte, has a narrow section between 5 and 6 miles

above its confluence with the North Platte. Immediately above this

narrow section the Medicine Bow arm reaches a width of a mile, then

gradually narrows in the upper portions of the arm as the head of backwater is approached.

Description of the Drainage Area

A map of the drainage area is presented by Figure 2, page 8.

The headwaters of the North Platte River begin at the Continental Divide

in north central Colorado, south of Walden, Colorado. The initial course

of the stream, situated between the Medicine Bow Mountains and the

Park Range, is in a northwesterly direction, for about 50 miles through

Colorado and for 70 miles into Wyoming. At this point about 12 miles

northeast of Rawlins, Wyoming, the stream course changes to an easterly

direction. It continues east for a few miles until it reaches Seminoe

Reservoir. Then its course is in a northerly direction through Seminoe

Reservoir and Dam, Kortes Reservoir and Dam, and through Pathfinder

Reservoir to Pathfinder Dam.

The major tributaries to the North Platte River in the drainage

area are the Medicine Bow River and the Sweetwater River. The Medicine Bow River has a drainage area of approximately 2, 310 square miles.

It flows in a northwesterly direction and empties into the east side of

Seminoe Reservoir. The Sweetwater River has a drainage area of

approximately 2, 270 square miles at the Geological Survey gaging station

which is situated about four miles upstream from the spillway crest line

of Pathfinder Reservoir. The Sweetwater River flows in an easterly

direction to empty into the west side of Pathfinder Reservoir. Its

origin is along the east side of the Continental Divide in the southwestern

edge of the Shoshone National Forest, about 20 miles southwest of

Lander, Wyoming.

The total drainage area above Pathfinder Dam is approximately

14, 600 square miles. The contributing drainage area above Pathfinder

Dam including the reservoir area is approximately 10, 700 square miles.

This latter area may be divided into 3 parts as follows: 7, 348 square

miles of drainage area above Seminoe Dam; about 2 square miles of

drainage area between Seminoe Dan-i and the stream gaging station

7
---------------

PL Ar r

ff

\

7

cc '-;:\ ) e:I: S I A0002A 0A

-F 5A

510

PATHFINDER DAM

/

F

I

- S A A -/

SI AK1

I

I

_ I,:

-Noo-Coobvf6a

C

_______ _____ ______ ______

'.-' I

____________ _________ __________ WYOMING

COLORADO

05

6I_IERNSEY

42

0 5 0 ID 20 30 40

SCALE OF MILES

05

EXPLANATION

Dra nage Area Pathfinder Reservoir

Dra nage Area Seminoe Reservoir

Discharge Stotios

• Weather Station

KEY MAP

FIGURE 2, PAGE
located 1, 000 feet downstream from Kortes Dam; and 3, 350 square miles

between this gaging station and Pathfinder Dam. The run-off above

Seminoe Darn has been controlled by Seminoe Darn since April 3, 1939.

However, Kortes Darn, located only 2 miles below Seminoe Dam, did not

impound water until September 1950. The recent completion date of Kortes

Dam obviates the necessity of considering the effect it would have on the

sedimentation in Pathfinder Dam based on this investigation. As the

capacity of Kortes Reservoir is only 4, 800 acre-feet and because of the

small intervening drainage area between Kortes and Seminoe Dams, the

future effect that Kortes Dam will have on the sedimentation in Pathfinder

Reservoir will be quite small.

Geology - The geology of the North Platte River drainage basin is depicted

by Figure 3,1/ page 10. On this map a separation has been made of the

area contributing sediment to Pathfinder Reservoir, the noncontributing

area, and the total area upstream from Pathfinder Dam.

The approximate percentage of the sediment contributing area

for Pathfinder Reservoir is divided as follows:

(a) 25. 3 percent from Pre-Cambrian rocks consisting of

granite, schist, and gneiss.

(b) 4. 4 percent from the Paleozoic rocks consisting of

consolidated sediments, quartzite, limestone, and sandstone.

(c) 3. 9 percent from Mesozoic formations consisting of

sediments moderately to loosely consolidated, such as shale, siltstone, sandstone, and some limestone.

(d) 66. 4 percent from formations of Cenozoic age divided as

follows: 64. 5 percent tertiary sediments, loosely consolidated

siltstone, sandstone, and shale; 0. 2 percent tertiary lava; and

1. 7 percent of Quarternary and Recent river alluvium, terrace

material, and sand dunes.

The above percentages vary considerably for the total drainage

area above Pathfinder Dam as may be noted on Figure 3. For instance,

the alluvium, terrace material, and sand dunes for the total contributing

area amount to 5. 4 percent. Reservoir deposition of eolian deposits

from sand dunes adjacent to Seminoe Reservoir is of particular importance. Later in the report such deposition is discussed in detail.

Topography - The topography of the basin ranges from the rugged mounfins along the Continental Divide bordering the western and southern sides

of the basin to the rough rolling land interspersed with numerous mountainous areas on the northern and eastern sides of the basin. Elevations

throughout the area are high, ranging from 12, 000 feet above sea level

at the headwaters of the North Platte River to 5, 850 feet at Pathfinder Dam.

1/ This Figure with certain modifications is based on the geologic

maprepared by the Bureau of Reclamation, Casper District, Casper,

Wyoming.

9
Al

.05

.3

42

0s

KEY MAP

WYOMING

COLORADO

0 5 0 0 20 20 4.0 - 50

EXPL ANATION SCALE OF MILES

PERCENT OF PERCENT OF

PAIOFmDFR TOTAL

C9TR8UTNG CONTRIBUTING

AREA AREA

25 3 33 [g-:.] Pre-Combriaro- 6Tarofe, AChING, asd 3fleiSS

Poeozoic- SedIments consohdted 3uartzlte, 4 'O\o1oLLi

,

InsesIorle, saIsdstone.

3 9 21 7 :-i MesozoIc-Sediments moerot&y to osey Consoh&1+ed. __________________________________________________

flJ shede sIitstoI4 scSlIstc4Ie And scone Omastone CNIIFD 034 TES

QEP44IMENT OF THE INTERIOR

80NE40 OF RECLAUA 3/ON

T

TOrt/Ory- SedImentS ooSey consahdated, P50jT PLANNiNG DIVISION - I-IYDROEOGY

64 5 4 6

j slitOtone sandstone SlId shale SEDIMENTATION SECTION

GEOLOGIC MAP

_____ PATHFINDER AND SEMINOE RESE

0 2 0 5 11. Trtrary- Lava DRAINAGE AREA

7 54 [ ]

RecentRivero{luorum, ternace material,

208M/I rc&a

TWOEEA -. '5

FIGURE 3, PAGE 1
---------- ---

thPte

30 29 /53t 27

8-848 \..__-__ e-90L 26 25

/ Fl/n I -5lSEO,l / Lee

r L- d // -

7

N sn.

-

/

I

fl1

___

--- / -

- __ __ __ _ _____

C 8/8 8/

-698lL INDEX TO SHEETS -•-_--

(

I

/ ) [JN L A

/

C-38& /

31 t32- (34 35

--

36

-if / I

/ -

/

A0/'

-

)

7/

I

/ I \

-

j j _^_, 7

ss\ _.--------teo cootuo- or enor Ii,,. o let,.

J/z ---_---------- east, (I950) Contour ,nfervOl

/ '-i #-398---eft-5*. Ssdin,.ntot,o,, roepe

T,-ogiorsn l\I\ -4-- Recovered section COtO#r

I

-.----,----.---- Foote/in.

------,-- P,p, 1,58

-4-----$-----4----- Telephone l,n.

7

0 O S

SCALE 08 VEEr

000Jccr 004MSOWC O,VI5,OW-Hr000LL,hr 904300

5ELCOAENTZTION SECT/ON

CCCL SEDIMENTATiON SURVEY OF PATHFINDER RESERVOIR

SoS/,nr I nnr0nrt,I or n9So,ml5n Ol/tIOSt, 050 900500/, CANNON AND NATRONA COUNTIES, WYOMING

oAr. 110 5/03,5 nIle/I torn0 OS/I --33/ Cocet RESERVOIR TOPOSRAFflY MAY 1', /930 - APAIL 3, /95/

0RAWN 411, - sueM,rrro frj

roacrn - ¶T5 AT COMAE NOES #n-aS'

SiL4 - -

/5/Cr/i

1

.1 I I L

LL

P 5p Cee* eetata H -

rv

^,

________ : ::

-i--

£

9

2

6 ' _çcr.

:Iç INDEX To SHEETS

£

___

-

-

/ I

33

EXPLANATION

_-fltO Contour o 00004 Irne of 500.

,.,o (5950) Contour ,50&vO5

R-I300----0R-SSL S.d,oMntof,oo rouQe

A Tn TrSoflWdOtIoe nor,o,,

±

0100

/C5OJFC7 SASH/NC 0 V/S/ON 05,050/255? 0040025

SEIIr/MhNT4TI&N oor/oo

SEDWENTATIOW SURVEY OF PATHFINDER RESERVOIR

CR8ON 4N0 NATRONA COUNTIES, WYOMING

r/OTE RESERVO05 TOP000SFRY MsIY 0 /950 APRIL /3, /95/

Sector net 000 Sr/C-Nfl at opo/na,morel000r059 as /7 990900 0naw s n/i / hoNor, .//CSO05u//s__ ,q

?he)I .ero tot 90t,d nt/Old Aura0 900 - /9 515ur,ey

to./0r S 01550005050 'a)9ausa ts.*oVsnt-9

OflEctEr <Md 00500/20 /0 -1

V//Sb - 0

IIS.aUrsr. N, I-/0Ua1I
/

/

Rch ml. R-251 c _m

ç,ni

'5

5

N A

/

2/L

fl

32 30 ___-

. . . INDEX To SHEETS

\\\\\

.

/\

(

7 / -

A

ZOL

I

/

/_

N

25

-21R

\\

///

/////

1100 o, ,,oo

/

-___-.---_Ss.t 1,9501 ContOur, Ye vol

/

0-220 (3-.08-22C S.dimel,tat,on range

/ a rr,ongo;or,oa station

/

- /±

nOraer

'or OCT OYAN%,flX,,OClO,00 01011NO&YSPONCH

SF V'O,TITRIIN SECTION

SEDiMENTATION SURVEY OF PATHFINDER RESERVOIR

,nlno,,rn,OT,-proln1 11005 05 10 ooorn, CARBON AND NATRONA COUNYIES WYOMING

'001 00n I 111 OnT04 1011117 dl IQO 19511101 RE5ERVCIN TOGRAPHY MAY 7, 550 APRIL 3, 1921

00005 - OOuTOOj

or,', no - 0-,ao,io ,S1/ 'n-







Climate (l)* - The winters in the drainage area are long and severe.

The annual frost free period is 100 days or less. The average annual

temperature at Pathfinder and Seminoe Dams is approximately 45. 50 F

and 42. 80 F, respectively. The average annual temperature is lower

at the higher elevation in the basin. For instance at South Pass City,

Wyoming, near the headwaters of the Sweetwater River the average

annual temperature is 34. 20 F.

Rainfall - The average precipitation over the basin is light. Most of

the precipitation falls as snow. The average annual precipitation for

six weather stations selected throughout the basin is given below:

STATION

Pathfinder Dam

Saratoga, Wyoming

Oregon Trail Crossing, Wyoming

Seminoe Dam

Encampment, Wyoming

South Pass City, Wyoming

AVG. AN. PRECIP.

10.2 inches

14.8 inches

9.7 inches

8.2 inches

ll..1 inches

12.1 inches

Runoff (2) - The amount of inflow and outflow for Pathfinder Reservoir

for the period June 1909 (since the beginning of storage) to April 3,

1939, (the beginning of storage in Seminoe Reservoir which is upstream

from Pathfinder Reservoir) was 40, 299, 500 and 38, 725, 500 acre-feet,

respectively. The average annual inflow and outflow for Pathfinder

Reservoir during the same period were 1, 350, 500 and 1, 297, 800 acrefeet, respectively.

During the period April 3, 1939, through July 1950 (the average date of the survey soundings) the inflow and outflow for Pathfinder

Reservoir were 10, 366, 800 and 9, 561, 100 acre-feet, respectively.

The average annual inflow and outflow for Pathfinder Reservoir for the

same period were 921, 490 acre-feet and 849, 880 acre-feet, respectively.

The average annual amount of water contributed to Pathfinder

Reservoir by the Sweetwater River, based on 9 years of record at the

Geological Survey gaging station located 5 miles upstream from the highwater line of Pathfinder Reservoir, was 79, 400 acre-feet.

The amount of the inflow and outflow for Seminoe Reservoir

for the period April 3, 1939, (since the beginning of storage) to Sep..

tember 16, 1950, (the average date of the survey soundings) was

10, 382, 300 acre-feet and 9,217, 100 acre-feet, respectively. The

average annual inflow and outflow for Seminoe Reservoir for the same

period were 906, 800 acre-feet and 805, 000 acre-feet, respectively.

*Numbers in parentheses, as (1) above, refer to bibliography

references.

24
During the above period about 15 percent of the inflow into

Seminoe Reservoir was contributed by the Medicine Bow arm. Most

of the remaining 85 percent of inflow was contributed by the North

Platte River.

Land Cover - Land cover in the basin consists principally of range

grasses and sagebrush at lower elevations, and sparse to dense

stands of pine in the mountains. Large areas, especially along the

Sweetwater River, are so arid that vegetation of any kind is sparse.

Land Use - Light precipitation and short growing seasons limit the

ue ffFe land. It is principally devoted to grazing. Most of the

ranches in the area do have small irrigated meadows to produce hay,

but actual cultivation is very limited in extent.

Soils (3) - Approximately 50 percent of the soils of the drainage basin

are of the Navajo-Chipeta type. This soil type is associated with the

high desert plateaus of semi-arid regions. This soil is developed

over sandstones, shales and limestones and has a great variety of

color.

The remaining 50 percent of the soils are almost equally

divided and consist of the Bingham-Avon, Underwood Babb, Macammom

Deschutes, and Helmer-Santa-Benewah types. These soils vary considerably but generally are thin, coarse to stony, or gravelly soils

associated with mountainous regions.

History of the Surveys

The survey of Pathfinder and Seminoe Reservoirs was performed by the Sedimentation Section, Hydrology Branch, Denver,

Colorado, and the Planning Section of the Casper, Wyoming, District

Office of Region 7, both of the Bureau of Reclamation. The field work

was carried out at intervals from March 21, 1950, to April 14, 1951.

The field work was performed, under the direction of Frank

K. 111k, Engineer, by the following personnel of the Hydrology Branch;

Richard W. Vaughan, Assistant Chief of Party, Jack C. Bessee, James F.

King, Carl R. Miller, and Edward Lewandowski. The latter 3 men participated during only a part of the survey period. In addition several

laborers were furnished by the Casper Office to assist the party. The

field parties engaged in the survey furnished by the Casper District Office

were under the direction of Donald B. Woltersdorf and John E. Larsen.

The survey work on Pathfinder Reservoir was divided in the

following manner. The Casper Office personnel established and triangulated the primary horizontal control net, monumented the range ends,

ran level control to all range end monuments and took profiles of the

ranges from the range ends to the water surface. The Sedimentation

Section field party established the ranges, performed the secondary triangulation to locate the range ends, sounded the reservoir, and mapped

the crest contour.

25
The survey was initiated by extending the existing Geological

Survey triangulation systems to cover the reservoir area with a secondorder triangulation net comprising 26 stations. This net was plotted on

plane table sheets at a scale of 1 inch = 1, 000 feet and the range ends

were located by plane table triangulation.

Sixty-two sedimentation ranges were established, of these 56

were profiled by obtaining soundings by use of an 808J Fathometer. The

other ranges were profiled by use of an engineer level, level rods, and

an engineer chain. To improve the underwater detail, approximately

130 miles of additional sounding lines were run between ranges and

located by sextant angles from the boat with shore triangulation stations

or range ends.

The crest contour (elevation 5850. 1) of the lake, the 5855 contour

and such lower contours as were exposed at time of survey were mapped

on the plane table sheets.

On August 17, 1950, the soundings were completed on Pathfinder

Reservoir and for statistical purposes the average date of survey for

Pathfinder Reservoir was based on the average date of the survey soundings. This was July 1950.

However, the shore line mapping for Pathfinder Reservoir

which was also accomplished by the Sedimentation Sectionts party was

discontinued to obtain soundings at Seminoe Reservoir. This mapping

was resumed after soundings were obtained at Seminoe Reservoir but

was discontinued because of inclement weather on December 13, 1950.

Shore line mapping was resumed again on April 2, 1951, and was completed by the Sedimentation Sectionts party on April 13, 1951.

The survey field work on Seminoe Reservoir was divided in a

different manner from the field work for Pathfinder Reservoir in that

only the hydrographic work, consisting of soundings and sediment sampling was scheduled for accomplishment by the Sedimentation Survey

Party of the Hydrology Branch. The remainder of the field work, similar

to that accomplished on Pathfinder Reservoir, was scheduled to be

accomplished by personnel of the Casper, Wyoming, District Office.

Sufficient control for initiating the soundings on Seminoe

Reservoir was completed by the District parties by August 17, 1950.

On this date the Sedimentation Survey party moved to Seminoe Reservoir

and began obtaining reservoir soundings. Sounding of the inundated portion of this reservoir, which includes 47 sediment ranges and 150 miles

of random soundings between the sediment ranges, was completed by

this party on October 16, 1950.

Because of the work load in the Casper Office and the limited

number of personnel to accomplish it, and since the depletion of Seminoe

Reservoir because of sediment deposition appeared small based on the

soundings made, the completion of Seminoe Reservoir was deferred.

26
The work deferred consists principally of topographic mapping of the

upper 17 feet of reservoir elevation, which would entail levels to the

sedimentation range ends, profiles of the portion of ranges above the

reservoir stage when the soundings were made (August 17 to October 16,

1950), and the mapping of the shore line of the lake.

Since the soundings for Seminoe Reservoir did not extend above

elevation 6340 feet, changes in area and capacity of Seminoe Reservoir

are based on data below this elevation rather than below elevation 6357,

the top of the spillway gates. For statistical purposes in computing the

average amount of sediment contributed by the drainage area above

Seminoe Reservoir and deposited below elevation 6340 feet, the averaged

date of the resurvey of Seminoe Reservoir is September 16, 1950, the

mean date for the soundings.

SEDIMENT DISTRIBUTION, PATHFINDER RESERVOIR

Longitudinal distribution. The variation of the thickness of

the sediment in Pathfinder Reservoir is presented graphically by

Figure 6, page 29, which shows the original and the 1950 longitudinal

profiles of the thaiweg of the main arm and principal tributaries of the

lake. The original profile does not extend to crest elevation on this

graph as in several instances the contour closures on the stream bed

were not shown on the original map. Such contours were broken at the

edge of the stream banks. The depth of sediment near the dam is

approximately 20 feet and on the North Platte River arm nine miles

upstream from the dam the maximum depth of sediment is almost 30

feet. The maximum depth of sediment on the Sweetwater River arm is

approximately 15 feet, at a distance of 9-1/2 miles upstream from the

dam.

Lateral distribution. The lateral distribution oi the sediment

in Pathfinder Reservoir is depicted by Figure 7, page 30. Cross sections

of the North Platte River arm 4. 3 and 10. 7 miles upstream from the dam

and a cross section of the Sweetwater River arm 7. 2 miles upstream

from the dam are shown. The original and the 1931 profiles were drawn

by the Corps of Engineers during their 1931 "Silt Investigation" of Pathfinder Reservoir. Data for constructing the 1950 profiles were obtained

from the contour map based on our 1950 survey of the reservoir. It is

apparent that some of the variations between the original, the 1931, and the

1950 profiles are caused by the errors derived from the determination of

the exact location of the cross sections on the different maps. The locations of these cross sections are the sites of the 1931 sediment ranges.

These ranges were not permanently marked in the field and were of a

reconnaissance nature so the mapping accuracy would also account for

some of the variation of the profiles for the three surveys. However,

the general lateral sediment distribution can be observed by studying

these cross sections. The sediment deposits appear to be confined

principally to the channel portion of the reservoir. Inadequate data

were available from the original and the 1931 surveys to determine the

quantity of delta deposits. Field observation did not reveal delta deposits

of any consequence.

27
Sediment disposition curve. A sediment disposition curve for

Pathfinder Reservoir is p ented by Figure 8, page 31. The standard

design curve (4), Type II curve, and Type III are also shown for comparison. The sediment disposition curve for Pathfinder Reservoir

indicates scour in the top 10 percent of reservoir depth. It is believed

that the irregularities in the Pathfinder Reservoir disposition curve

are caused by discrepancies in the original map. Even more irregularities were noted when a disposition curve was plotted from data obtained during the 1931 reconnaissance resurvey.

Volume weight and mechanical analysis. During the 1931 "Silt

Investigation of Pathfinder ReservoirT tIiFe to five samples of the sediment deposited in the reservoir were obtained along 10 sediment ranges

in the North Platte River arm and along 5 sediment ranges in the Sweetwater River arm A mechanical analysis was made of each sample

obtained. In this report the samples for each sediment range have been

composited, The results are shown on Table 1, page 32. An analysis

of the observed densities is also illustrated by a graph, see Figure 9,

page 33.

28



---

tj

'2

_

107 _______ ________ ________

Sptl/way Crest Elevation-- -

________ ________ ________ ________ ________ ________

EXPLANATION

p Pathfinder reservoir

curve

--ti Design curve Sc - - --a Type H curve

x Type curve

70 ____________

60

I0

30 _____ z

2

-

-

C

p

30 NOTES *

The design curve, type , curve and type

curve are shown in A progress

report an the disposition of sediment in

20 the reservoir " by Arthur W Vant Hu/,

5' 5 DI, Bureau of Reclamation, Project

Planning Civision, hydroIagy Branch,

Sedimentation Section, Ion /950

Elevations refer to Pathfinder Reservoir

0 20 30 40 50 60 70 80 90 100 110 20

SEDIMENT - % TOTAL

PROJECT PLAwNING 0/ VISION-CYOROLOA/ NRANCW

$ EO/M$WTAT/oN SEc TON

SEDIMENT DISPOSITION CURVES

PATHFINDER RESER VOIR

AND OTHER TYPES

9

585010

- -----.------ -

5834.75 / /f

/

V

- 0

0

-5eso.

/ -p-

/ -'---- /

0

______

'

-

580357 71 - O0 •

/

çlE '

Q_ _ 4_' -57800

/

___

-

/

/

r7o - - - - - -

/ /

577255

/ / 0 / -_ / / -

----

- 575704

/ -/ /

V

574153

/

/

'

/

i - ..--.--- ----------- ________ ________.-

5726 0/

----- ... -

-

___________

5710,51

5695 00
Table 1

MECHANICAL ANALYSIS OF PATHFINDER RESERVOIR BED SEDIMENT

(Samples Obtained by Corns of Engineers Department of the Army, 1931)

Cmposite Prc eat - Mean Percent sand Percent gravel

Sample No smaller size Percent Percent silt Very Very

and Lcatin taaa 1/64 mm clay VF&F M&C fine Fine Medium Coarse coarse Granule Pebble

North Platte

River

1 (H-i) 17.2 0.0911 11,9 05.3 15.2 35.4 15.6 04.3 02.2 02.7 02.4 05.0

2 (H-3) 48.8 .0225 39.0 09.9 04.3 18.7 10.1 10,3 06.1 01.6 00.0 00.0

3 (F-5) 51.6 .0907 39.4 12.3 04.2 09.5 06.5 06.0 21.8 00.3 00.0 00.0

4 (R-7) 26.6 .1301 19.3 07.3 06.8 12.3 23.9 17.0 13.3 00.1 00.0 00.0

5 (R-13) 89.4 .00369 53.7 35.6 02.9 02.3 03.7 01.7 00.1 00.0 00.0 00.0

6 (R-19) 09.7 .0867 05.4 04.4 16.5 34.1 34.9 03.8 00.8 00.1 00.0 00.0

7 (R-21) 33.9 .1481 17.6 16.3 07.1 07.8 19.3 26.9 04.9 00.1 00.0 00.0

8 (H-23) 00,8 .2888 00.3 00.5 02.1 06.7 29.5 49.2 04.3 01.0 01.2 05.2

9 (R-15) 79.5 .00417 48.8 30.7 09.9 07.7 02.6 00.3 00.0 00.0 00.0 00.0

10 (R-17) 59.8 .01104 33.6 26.2 18.8 17.0 03.7 00.7 00.0 00.0 00.0 00.0

Sw e e twa t e r

River

11 (1A) 79.5 .0022 67.8 11.7 02.1 06.4 04.4 04,4 02.1 01.1 00.0 00.0

12 (4A) 68.6 .0051 44.5 24.1 12.3 16.5 01.6 00.6 00.3 00.1 00.0 00.0

13 (8A) 00. 6 . 1524 00. 2 00.4 07.4 28.6 55.9 06.6 00.6 00. 2 00. 1 00. 0

14 (12A) 01.0 .1369 00.5 00.5 12.6 33.3 47.5 04.0 01.1 00.4 00.1 00.0

15 (16A) 00.2 .8557 00. 1 00.1 00.2 00.3 05.3 24.4 33,3 21.7 11.6 03.0

In order to convert the quantity of sediment deposited in Pathfinder Reservoir into volume weight, pounds per cubic foot, the method

presented by Lane and Koelzer (5) was used. The first step was the

division of the sediment into three fractions, clay, silt, and sand. The

small percent of gravel found in a few of the samples was added to the

sand fraction. For the 15 composite samples the following percentages

were obtained:

Mean for

North Platte River Arm Sweetwater River Arm Pathfinder Res.

Size (10 samples) (5 samples) (j5sarnples)

Clay 26.9 22.6 25.5

Silt 23.6 14.3 20.5

Sand 49.5 63.1 54.0

The second step was the selection of the weight for each fraction

which is given after one year of consolidation and which varies for reservoirs of different operation conditions.

The third step was the selection of constants, K, to be used in

computing the consolidation of each fraction of the sediment over a

period of years. These constants are also based on the size of the sediment particles and on reservoir operating conditions.

The density values selected were those given for a reservoir

normally having a moderate drawdown. The weights, Wl, in pounds per

cubic foot after one year of deposition under this condition are 46, 74, and

93 for clay, silt, and sand, respectively. The consolidation factors, K,

for each fraction of the sediment for the operation condition selected were

10. 7, 2. 7, and 0 for clay, silt, and sand, respectively. The formula used

to determine the average weight of the sediment after a period of time was

W = Wi + 0.4343 K [T (loge T)_l1 where W average unit weight of

the sediment after T years of deposition. This is a slight modification of

the Lane and Koelzer formula that was made by Miller and Moody. (6)

The results obtained by use of the modified formula agree closely with

the results obtained by use of the original formula which is

W = W1 + K log 10 T. The degree of accuracy of the modified formula

has been checked by comparing computed volume weight of reservoir

sediment deposits with the volume weight obtained by laboratory analysis

of undisturbed reservoir sediment samples. For sediment where the clay

fraction does not exceed 25 percent of the total sample, the variation between the results of the laboratory analysis and the formula is usually

within 5 percent.

The volume weight of the

arm, the Sweetwater River arm,

sediment for Pathfinder Reservoir

given below:

sediment for the North Platte River

and the average volume weight of the

by use of the modified formula are

34
North Platte River Arm

_

_

_

_

_

_

(Weight after one year) W1 (46 x 0.269) + (74 x 0.236) + (93 x 0.495)

75.84 lbs/ft3

(Consolidation factor) K = (10.7 x 0.269) + (2.7 x 0.236) + (Ox 0.495) = 3.52

Then the average weight in 1931 or after 22 years,

W 75.84 + 0.4343 (3. 52) [ (loge 22)_lI 79.27 lbs/ft3

and the average weight in 1950 or after 41 years,

W = 75. 84 + 0.4343 (3. 52) [ (loge 41)-li = 80. 12 lbs/ft3

Sweetwater River Arm

(Weight after one year) W1 = (46 x 0.226) + (74 x 0. 143) + (93 x 0.631)

79.66 lbs/ft3

(Consolidation factor) K = (10.7 x 0.226) + (2.7 x 0.143) + (0 x 0.631) 2.81

Then the average weight in 1931,

(loge 22)11 W = 79.66 + 0.4343 (2.81) = 82.39 lbs/ft3 [

and the average weight in 1950,

W 79.66 + 0. 4343 (2.81) (loge 41)_i] 83.08 lbs/ft3 [

Pathfinder Reservoir

(Weight after one year) W1 (46 x 0. 255) + (74 x 0. 205) + (93 x 0.540)

77. 12 lbs/ft3

(Consolidation factor) K (10. 7 x 0.255) + (2.7 x 0.205) + (0 x 0.540) 3.28

Then the average weight in 1931,

W = 77.12 + 0. 4343 (3.28) (loge 22)1] 80.24 lbs/ft3 [

in 1939,

W = 77. 12 + 0. 4343 (3. 28) (loge 30)_i] = 80.66 lbs/ft3 [

and the average weight in 1950,

(loge 41)_li W = 77.12 + 0.4343 (3.28) = 81.08 lbs/ft3 [

35
Summarizing the above information on the mechanical analysis

and volume weight of sediment deposits the following is noted:

The average weight of the sediment in Pathfinder Reservoir

In 1950 was approximately 81 pounds per cubic foot and it was composed

of 54 percent sand. The average density of the sediment increased

about 4 pounds per cubic foot in 41 years.

36
Table 2

STATISTICAL SUMMARY

PATHFINDER RESERVOIR

___________________________________________________ Quantity Unit

Age!/ 41. 1 years

Water shed/

Area, 1909-1939 10, 700 sq mi (a)

Area, 1939-1950 3,350 sq mi (b)

Reservoir

Area at crest stage, original 22, 600 acres

Area at crest stage, preseit 22, 000 acres

Original storage capacity../ 1,056,300 ac-ft

Present storage capacity 1, 015, 900 ac-ft

Original storage capacity per sq mi, drainage area 98. 7 ac-ft (a)

Present storage capacity per sq mi, drainage area 94. 9 ac-ft (a)

Present storage capacity per sq mi, drainage area 303. 2 ac-ft (b)

Sedimentation

Total sediment 40, 400 ac-ft

Accumulation per year average, 1909-1931-1939 1,250 ac-ft (a)

Accumulation per year average, 1939-1950 263. 6 ac-ft (b)

Accumulation per year per 100 square miles of

drainage area: 1909-1939 11. 7 ac-ft (a)

1939-1950 7.9 ac-ft (b)

Accumulation per year per acre of drainage area,

1909-1939 7.96 cu-ft

@ 80.66 lbs per cu ft, 1909-1939 0.32 tons

1939-1950 5.36 cu-ft

@ 81.08 lbs per cu ft, 1939-1950 0.22 tons

Depletion of storage

Loss of original capacity per year, 1909-1939 0. 12 percent

1939-1950 0. O25percent

Loss of original capacity to date of survey 3. 82 percent

1/ Based on beginning of storage in June 1909 and average date of

soundingfor this survey, July 1950.

2/ (a) Includes contributing area above present location of Seminoe

- Dam (30 years) 1909-1939.

(b) Based on drainage area between Pathfinder Dam and U. S.

Geological Survey gaging station 1, 000 feet downstream from

Kortes Dam. Kortes Dam is approximately 2 miles downstream from Seminoe Dam.

3/ The original storage capacity for Pathfinder Reservoir based on

the origiiial reservoir map was 1, 070, 000 acre-feet.

The original storage capacity for Pathfinder Reservoir, 1, 056, 300

acre-feet, shown in this table is the adjusted original storage capacity dictated

by the 1950 resurvey. The additional data on this sheet are based on the same

adjustment - see explanation of statistical summary on following pages.

37
Explanation of Results in Statistical Summary for Pathfinder Reservoir

Although an accurate detail survey was made of Pathfinder

Reservoir in 1950 it has been a difficult task to determine closely the

amount and disposition of the sediment deposits in the reservoir. The

reason these difficulties were experienced was because of the low degree of accuracy used in making the original map which should be designated as a preliminary survey and because the 1931 survey was of a

reconnaissance nature.

The capacity of Pathfinder Reservoir derived from the original map, made in 1903 or six years before storage began, is 1,070,000

acre-feet. A direct comparison between the original map and the map

based on the 1950 survey indicates that the capacity of 1,070, 000 acre -

feet based on the original map is too large and consequently that the resultant sediment volume, 54, 000 acre-feet, is also too great. The figures shown on the preceding page, in Table 2, Statistical Summary--

Pathfinder Reservoir, are believed to be a closer approximation of the

original reservoir capacity and sediment deposition.

These data were obtained as follows:

(a) The map based on the 1950 survey was selected as a base

map and the cross sections of the 40 sediment ranges surveyed by

the Corps of Engineers in 1931 was compared with equivalent cross

sections derived from the original and the 1950 maps.

(b) The original capacity of the reservoir, the capacity of the

reservoir in 1931, and the capacity of the reservoir in 1950 were

computed by the range method(7) and by use of the cross sections

for the appropriate years.

(c) Since these cross sections were not ideally located to compute the volume by the range method, the results were adjusted by

a factor chosen to make the volume computed by the range method,

using the 1950 cross sections, agree with the volume computed by

the contour method from the 1950 map.

The adjusted reservoir capacities are 1, 056, 300 acre-feet for

1909; 1,028,700 acre-feet for 1931; and 1,015, 900 acre-feet for 1950.

Based on these capacities the sediment deposition from 1909 to 1931 is

27, 600 acre-feet and the sediment deposition from 1931 to 1950 is 12,800

acre-feet. The total sediment deposition from 1909 to 1950 is 40, 400

acre-feet, rather than 54, 000 acre-feet which was determined by the

use of the original map with no adjustment.

The annual amount of sediment deposition for the period 1909-

1931 is approximately 1, 250 acre-feet. By extending this annual rate of

sediment deposition until 1939, when storage began at Seminoe Reservoir

upstream from Pathfinder Reservoir, the amount of sediment deposition

in Pathfinder Reservoir by 1939 was 37, 500 acre-feet or the capacity of

Pathfinder Reservoir in 1939 was 1, 018, 000 acre-feet.

38
During the period 1939-1950,

eration, the annual amount of sediment

1,018,800 - 1,015,900 ervoir was -

11

with Seminoe Reservoir in opdeposition in Pathfinder Res263. 6 acre-feet.

The estimated quantity of sediment deposited in Pathfinder

Reservoir, based upon the 1931 reconnaissance survey by the Corps

of Engineers, was 52, 000 acre-feet, or approximately 2, 360 acrefeet annually. An analysis of the 1950 survey data indicates that these

figures are too large.

Summary for Pathfinder Reservoir

Information obtained during this investigation and the reappraisal of prior surveys indicate that the original capacity of Pathfinder Reservoir was 1,056, 300 acre-feet, its capacity in 1939 was

1., 018, 000 acre-feet and its capacity in 1950 was 1,015, 900 acre-feet.

An area and capacity table and curves based on the 1950 survey is

presented by Figure 10, page 40. The sediment yield from the original drainage area was 0. 12 acre-feet per square mile annually and

the sediment yield from its present drainage area is 0. 08 acre-feet

per square mile annually.

The loss of the original reservoir capacity to date of present

survey, 1950, or in 41. 1 years, is 3. 82 percent. Based on the rate of

sediment deposition in Pathfinder Reservoir since storage began upstream in Seminoe Reservoir, the future storage loss in Pathfinder

Reservoir will be only 1 percent in 40 years.

It is believed that an appreciable percentage of the sediment

deposited in Pathfinder Reservoir resulted from wind action. The

large areas of eolian deposits adjacent to the shore line show evidence

of considerable movement, see Figure 11, page 41. Wave action along

stretches of the shore has also moved sediment into the reservoir, see

Figure 12, page 42. However, the total amount of sediment that has

been deposited in Pathfinder Reservoir is small in comparison with the

total storage capacity and since the amount of deposition that has occurred since the construction of Seminoe Dam has been greatly reduced,

it follows that sediment deposition from wind action in Pathfinder Reservoir is of minor importance.

SEDIMENT DISTRIBUTION, SEMINOE RESERVOIR

Longitudinal distribution. The variation of the thickness of

the sediment for a portion of Seminoe Reservoir is presented graphically by Figure 13, page 43. The 1950 longitudinal profile of the thaiweg of the North Platte River arm of the reservoir is shown from the

dam extending upstream to the closure of the 6340 contour. The 1950

longitudinal profile of the thalweg of the Medicine Bow River arm is

shown from its confluence with the North Platte River also extending

upstream to the 6340 contour. Insufficient data were presented for the

stream beds of the North Platte River and the Medicine Bow River to

completely delineate the original thalweg of these two streams. However,

39
AREA IN THOUSANDS OF ACRES 1950 URVY

0 2 4 6 8 /0 /2 /4 /6 /8 20 22 24 *1vation Area Storage

585C

5840

5830

5820

58! 0

5800

5790

5780

I5770

5760

5750

5740

5730

5720

57/0

5700

5690

5680

5670

Jii _

I• SOUTH OUTLET

/T / -

____ ____

____ -

€ ELEV. VALVE NO. 3-5744.2

- € ELEV. VAL.VENO.2-5741.I

- € ELEV. VALVE NO. I 5738.0

j

_____ ____ _____ _____ _____ ____ _____ _____

NOTE: Elevations are based on the elevation of 5,848.16 feet for u. S. G. S.

_____ ____ ____ ____ _____

BM 5848 at Pathfinder Dam. To convert these elevations to the original

construction datum add 1.9 feet to the elevations shown.

____ ____ ____ - For example the spi/Iway crest elevation of 5850. 1 (as shown)

+1.9 :58520 (original construction darum.)

_____

---NORTH OUTLET TR4SHRACK SILL ELEV. 5668.!

0 I 2 3 4 5 6 7 8 9 /0 II /2

GAPACTY IN HUNDRED - THOUSAND ACRE-FEET

reoi cre -ere-iei

5855 23,839 1,128,178

585O]. 22,011 1,015,876

5845 20,431 90'7,673

5840 18,835 809,534

5835 17,153 719,598

5830 15,528 637,931

5825 13,902 564,396

5820 12,465 498,512

5e].5 11,180 439,428

5R10 9,938 386,664

5805 8,932 339,513

5800 8,108 296,931

5795 7,291 258,453

5790 6,680 223,538

5785 5,988 191,883

5780 5,513 163,138

5775 5,040 136,%5

5770 4,632 112,594

5765 4,027 90,966

5760 3,599 71,912

5755 3,097 55,187

5750 2,621 40,909

5745 2,139 29,030

5740 1,573 19,786

5735 1,120 13,085

5730 818 8,261

5725 497 5,008

5720 351 2,899

5715 169 1,626

5710 123 898

5705 79 395

5700 37 111

5695 7 12

5690 0

5685

5680

5675

5670

**Area and capa city at and below this

elevation is negligible based on

1950 survey

FIGURE 10, PAGE 4
'- -

-

-

-p -. -

.- -

4,

.

;

TSAND DUNES

IN NARROWS NORTH PLATTE RIVER ARM

PATHFINDER RESERVOIR

About 12 miles upstream from Pathfinder Dam.

Sediment is contributed to Reservoir by wind and wave action

upon sand dunes in this vicinity.

FIGURE 11, PAGE 41
I,

--.- -

t S _ go

-..

-. - -

- - ..--- -....--- --

-

- -

-

- - -

-

£- __ __ _-J. - - - -- - -

- •-•- - - - -

---

.- - - -. -- - .- - -. .-

e

-

.

;.:

- -- 4;;- - .

- .- -'•;-,-

- .- -.-•L. - --.. - - -- - --- -

-.- -.- --. -

.,_;;.- ------i.__

-- - -:-.-; '.---- -: - - - - .-,--,.. -

-- - ---- -

-- - - - -

--'

(a) Location is on North Platte River Arm

between Ranges Nos. 11 and 12.

11

(b) Location is on North Platte River Arm

between Ranges Nos. 17 and 18.

STREAM BANK EROSION

PATHFINDER RESERVOIR

FIGURE 12, PAGE 42
z0

'O

uJ

-J

uJ I

ZI 0

I->

Ui

-J

WIIISS

-El 6357. Top of spi/Iwoy qotes

SCALE OF MILES

3360

1350

.340

4330

2320

3310

3300

3290

3290

1270

0

I8260

Ui

-j

1250

'

3240

1230

3220

3210

1200

6190

l60

3170

IS0

6150

EXPLJ4NA TION

0-0 Profile Originol Tho/weg, based on /929

survey

a a Profile Present Tho/weg, based on /950

survey

S Profile ThoIweg, based on /942 partial

survey

Elevation of woter surface, token from

mops based on /929 survey

0 Elevation of stream bank near chonn/,

tren from mops based on 1929 survey

NOTES

Contour closures in the slream channel were not shown

on mops, hosed on the /929 survey, above devotion

6270 and 6280 for the North Platte and the

Medicine Bow Rivers, respectively. Contour closures

on the North Platte River were also omitted

for elevations 6/70, 6/80 and 6/90

DEPARTMENT OF THE INTERIOR

IURE*U OF RECLAMATION

OJECT PLANNING DI VI$:0N4(YDAOLOG V bRANCH

SEDIMENTATION SECTION

LONGITUDINAL PROFILE

NORTH PLATTE AND MEDICINE bOW RIVERS - SEMINOE RESERVOIR

DRAWN ?- SU6P4TtEO4?fCc?7- -. - - -

TCED

CJECKED

- ____ .p*owo

-

DENVEI, COLORADO JAN ZR. •53 I

FIGURE 13, PAGE 43
on the North Platte River arm the depth of the sediment deposits near

the dam resulting from bank caving, the depth of eolian deposits between Sediment Ranges Nos. 8 and 9, and the depth of stream-borne

deposits between Sediment Ranges Nos. 13 and 16 are shown. The

maximum depths of these three types of sediment deposits, measured

at the locations described above, were approximately 35, 50, and 8

feet, respectively.

A partial survey of the delta area of Seminoe Reservoir was

made in 1942 and the longitudinal profiles of the thalweg of both the

North Platte River and the Medicine Bow River determined by this

survey are also shown on Figure 13. A comparison between the 1950

and the 1942 longitudinal profiles shows several feet of delta deposits

in the channel of both streams for this period.

Lateral distribution. The lateral distribution of the sediment

in Seminô PeservoirTdepicted by Figure 14, page 45. The cross

section of Sediment Range No. 1 -A shows the sediment deposits resulting from bank erosion. Two views of the shore line in the vicinity of

this range where bank slides have occurred are shown on Figure 15,

page 46. It will be noted by the crack shown in Figure 15 (a) that an

additional amount of bank movement into the reservoir is imminent.

The cross section of Sediment Range No. 8A, Figure 14, illustrates the lateral distribution of eolian deposits between Sediment

Ranges Nos. 8 and 9. A distant view of the left bank of the reservoir

in the vicinity of Range No, 8A, between Ranges Nos. 8 and 9, is presented by Figure 16 (a), page 47. An idea of the extent of the sand

dune in the vicinity of this cross section can be obtained from this figure. The sandy shore line, upstream from Range 8A, and a close-up

view of the sand dune shown in Figure No. 16 (a) are depicted by Figure No. 17. Eolian deposits as measured by Sediment Range No. 8A

are about 70 feet in depth at Station 10+00. These deposits extend from

the left bank out into the lake for a distance of approximately 1, 000 feet

or to within about 350 feet of the shore line on the right bank of the lakes,

The right end of Range 8A in contrast to the left end is on a rocky hog

back, It is shown by Figure 18 (a), page 49. On the right bank in this

vicinity there are no sand dunes and only wave erosion near the lake

surface is noted.

The lateral distribution of sediment in Seminoe Reservoir consisting principally of water-borne sediment is also shown on Figure 14

by cross sections of Ranges Nos. 2, 15, 21, and 39. Cross sections of

the latter two ranges show sediment deposits in the stream channel for

the period 1942 to 1950, for the North Platte River arm and the Medicine Bow River arm, respectively. When cross sections of ranges

above elevation 6340 are obtained, additional information pertaining to

delta deposits in Serninoe Reservoir can be presented.

Sediment disposition curve. A sediment disposition curve for

Seminoe Reservoir is shown h7TTire 19, page 50. Many irregularities in sediment deposition are noted.

44

(a) Scarred bank shows where material has slipped into

reservoir. Crack to right of scar shows beginning of new

land slide. Location about 200' upstream from Range No. 1.

(b) Land slide left bank of reservoir about 500

feet upstream from Range End R-l-L.

BANK EROSION NEAR SEMINOE DAM

FIGURE 15, PAGE 46
(a) Location - Left side of Reservoir vicinity of Range No.

8-A.

(b) Location is downstream from Range No. 8, adjacent to

Road from Sinclair, Wyo. to Sei-ninoe Reservoir,

SAND DUNES SEMINOE RESERVOIR

FIGURE 16, PAGE 47
-'S

- \.

. p

I'...

S.

.5 .

k'

.

(a) Close-up - Sand Dune shown in Figure 16, Near Range End

R-8A L, Seminoe Reservoir.

-

-..------- '

•

.-

-

- _

(b) Left shoreline about 1000 feet upstream from Range No.

8 A, Seminoe Reservoir

SAND DUNE & SHORELINE

SEMINOE RESERVOIR

FIGURE 17, PAGE 48
L -

(a) Shoreline opposite Sand Dune, shown by

Figure 16A. Note wave erosion and lack of sand.

. (b) North Platte River

' .

below Dam - View looking

downstream. The channel

I

-

is well armored and con-

. - - fined between narrow

. - i4 i- Canyon Walls.

Ill

4

- -

:

T

SHORELINE SEMINOE RESERVOIR

A ND

NORTH PLATTE RIVER DOWNSTREAM

FROM SEMINOE DAM

FIGURE 18, PAGE 49 liue,-ior - ReImation - Denvr Colc.
I

Top of Spiliwoy ates- '1 I I I Mapping during the /950 survey did not extend

357

ab ove e leva tion 6340. Fie ld observations indicated A cre-Feet

sediment deposition above this eIevwas

90

_____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____

insignificant ________________________ _____ _____ T _____ _____ 6337

_____ _____ ____

4280 Acre- Feet of scour shown above elevation 6320 /0,360 Acre Feet

-

____ _____ _____ ____ _____ ____ ____ _____

- results partially from bank erosibn, but If a/so esu/ls

fromerrorsnotedontheor/gina/mop----

--

80 _____ _____ _____ _____ _____ 6317

Si/I of Spi//way Gates---.

70 ____ ____ ____ Sediment derived from sand dunes ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ 6 2 97

influenced shape of sediment dis- u.

____ ____ ____ ____ ____ ____ ____ ____

position curve ------------- ----, ____

-

____ ____ ____ ____ ____ ____ ____

2

I-
(a) The area and capacity curves and tables, Figure 20, page

52, based on the original and the lt50 survey list 5, 600 and 5, 830

acre-feet of capacity, respectively, at elevation 6210. A review

of the longitudinal profiles and cross sections previously described

shows that this indicated scour below elevation 6210 did not occur

but results from an error in the original map or failure to map the

stream channel.

(b) The 825 acre-feet of scour shown between elevations 6240

and 6260 also results from discrepancies in the original map. A

20-foot vertical section (Figure 14) in the eolian deposition lies in

this limit.

(c) The sediment disposition curve between elevations 6260

and 6310 or between 52 and 77 percent of the depth of the reservoir

is fairly uniform. This indicates that there are no serious original

mapping errors between these limits or that sufficient uniform sediment deposition has occurred to prevent such errors from being

noticeable.

(d) A scour of 1, 280 acre-feet is shown between elevations

6320 and 6340. Field observations indicate that wave erosion and

bank caving have occurred along the shore line of the lake and that

actually some scour has occurred between these limits. It is believed, however, that errors noted in the original map account for

the larger portion of this capacity gain which is listed as scour.

A resume of the factors described concerning the sediment

disposition curve for Seminoe Reservoir indicates that the 9, 080 acrefeet of sediment shown is the minimum sediment deposition that occurred.

Probably a more realistic figure would be approximately 10, 100 acrefeet. This figure would be obtained by adjusting the original map to reflect no scour below 52 percent of the reservoir depth. The operation

level of Seminoe Reservoir during period 1939-1950 does not indicate

that scour below 52 percent of the reservoir depth is reasonable.

Volume weight and mechanical analysis. During the 1950 survey of Seminoe Reservoir only three samples of the sediment deposited

in the reservoir were obtained. The field locations of the samples were

on Sediment Ranges Nos. 36, 37, and 39 of the Medicine Bow River arm.

The samples were obtained by use of a small pipe sediment sampler: (8)

The size of each sample obtained was 8 inches in length and 1/2-inch in

diameter. The data pertaining to these samples are given in Table No.

3 on the following page.

A graph based on the data from these samples is shown by Figure 21, page 53.

51
22 20

-_-__---_ __ _-

f

-

4 2

AREA 0 00 ACRES

0 8 6 4 2 0

D

S

. ;F----

J ___: i4r

1

--

r____ Mox $5 El 6357, rop o

I

gj//wcyqole

-

:-.

[TT

II

. S •

.

-

..

.

:

:

..

''-

:

---:--

::

-

5

i

.

.

I

r: :

.

.

:: f:

t:.

___

:

___

:

___

± __i

: :

: : ::

&30

6330 -___ ___ ___ -

__ __-__

-

__ __ __

I

__

Ei

__ -- -- 340

- - - -___ ___ ___ ___ ___ ___

6320 ____ - - ____ ____ ____ ____ ____ ____ - ____ ____ ____ ____ ____ ____ ____

-- -

Spifiwoy El 5307 -

-

6310

- - -

___ ____ ___ ____ ___ ____ ____ ___ 5310

CIT YI95O k - - I ±1

630C _ ___ _ _ _ _ __ _

-

:E -CAPACITY /9 39 iiiii: iii -ij -- -- ii-- -

-

6291 --- 8290
u s STA NDARD SIEVE SIZ E S I N CH E S

0 0 0 0

:

0 0

2

0 o o o r'- ,

o s)

0 1) 0 W

cJ -- L'-

C- 0 ?- D o 04 05 0 6 0 7 0e0 L

9 O 2 4

; :

.

I

.

00 T 1

[

i: :

9C

T

0

r £ r L :; : :

1

, . ,

V f

r ± T

i

r

- f

J t J8C

i

20

L j L , t

:

t t :

: f

t i

i

j ;

,

:

1

' H 1

7G - - - -

-

. 30 H -

t H i i I I i i i r I I

J

j if

€G '

I i i : L

i H

t :

j

I I i I

- - - - 4 f ' - - - Ii r +

H

I.J ItI

.

I

-

.

: . .

° 50 J

< cI4

! ,

-

- ..

-.--. [ I 1I II ' .-

1

-- - -

I FlI ' 4

JllTt !I 11'L .

' ci d

• [ .I J [r :

I , . ' ii. 40 60

F!1 . .

II

i}l J j 4

70

I

:

T

11'

u 1 [ Ii :

F H

1

4 r

0 I H J , . . 2 .

II tw [ . . . - H

,

i1

I 1 A

i llJ i1

d FJ L F

10 90

iI[fFtI - iiii i:

0_ :: _ 0 C Q 8-o_

..

r- .o

•: ci F O N w'2 g § g . .

PARTICLE SIZE - MILLIMETERS f DEP4RrMENTCF1-HE/NTERIOR

LI

Fue JMdiurn Coof7Fine co Med,um Core Coarse Very FneFin Med.

inoe ResTS

AMERIC4? GEOPHYSICAL UNION (.AG.U) CLASSIFICATION d1C Bov Arm

:

[N#ccitowo

FIGURE 21, PAGE 53
Table No. 3

SEDIMENT SAMPLE DATA OF SEMINOE RESERVOIR

Medicine Bow River, Wyoming

Mecnanlcal J-naiyses

Sample Range Date Volume Percent of grade sizes mm

No No Sampled weight .295 .147 .07 .037 .019- .009- .005- .0-

(lb/cu ft)

______

.589 .295 .147 .074 .037 .019 .009 .005

1

______

36

_________

Oct 1950

_________

45.6 0. 1 0.0 0.2 0.8 4.8 15. 1 12.6 66.4

2 37 Oct 1950 34. 8 0. 1 0. 3 0.2 0. 8 8. 7 16. 9 12. 8 60. 2

3 38 Oct 1950 44.8 0.3 0.4 1.4 11.7 10.6 12.0 7.0 56.6

*Average 41.6

The average percent of clay for the three samples obtained in the Medicine Bow River arm of

Seminoe Reservoir is 56. 7 percent. The estimated volume weight per cubic foot for the three samp1e, by

use of the modified Lane Koelzer formula and the initial weight for the particle sizes listed by Trask

clay 13 pounds, silt 76 pounds, and sand 88 pounds, gives an average weight of 45. 32.

Since the three samples listed above are not believed to be representative of the average sediment

deposits in Seminoe Reservoir, a weight of 65 pounds per cubic foot which is roughly an average between the

weight of the samples obtained in Medicine Bow River arm and the weight of the samples obtained in Pathfinder Reservoir, was used to convert the volume of sediment in Seminoe Reservoir from cubic feet to tons.
Table 4

STATISTICAL SUMMARY

SEMINOE RESERVOIR

1/ AgeWater shedReservoir

Area at top of spillway gates, elev 6357, Original

Area at elev 6340, Original

Area at elev 6340, Present

Original storage capacity, top of spillway gates

Original storage capacity, elev 6340

Present storage capacity, elev 6340

S edimentation/

Total sediment

Accumulation per

Accumulation per

Accumulation per

Accumulation per

65 pounds per ci

year average

year per 100 sq mi drainage are

year per acre of drainage area

year per acre of drainage at

ft (estimated)

11.45 years

7, 348 sq mi

20,045 acres

15,280 acres

15,200 acres

1,020,000 ac-ft

722,000 ac-ft

712,920 ac-ft

9,080 ac-ft

793 ac-ft

10.8 ac-ft

7.35 cu-ft

Depletion of storage/

Loss of original capacity per year

Loss of original capacity to date of survey

0.24 tons

0. 08 percent

0. 89 percent

1/ Based on beginning of storage on April 3, 1939 and the average

date of s6ündings made during this survey, September 16, 1950.

2/ Based on 7, 350 square miles listed as the contributing drainage

area upsfieam from the U. S. Geological Survey gaging station 1, 000 feet

downstream from Kortes Dam. Two square miles deducted for drainage

area between Seminoe Dam and gaging station. Does not include non-contributing drainage area outlined on Drainage Map, Figure 2.

3/ Items under ItSedimentationt are based on the sediment measured

below elation 6340 during the 1950 survey.

4/ Items under tDepletion of storage are based on the original storage capa&ty at the top of spillway gates. Sediment deposition between the top

of the spillway gates and elevation 6340 is believed to be small.

55
SUMMARY FOR SEMINOE RESERVOIR

The 1950 survey of Seminoe Reservoir extended from the

stream bed of the reservoir to elevation 6340 or 17 feet below the top

of the spiliway gates. A comparison between the original survey and

the 1950 survey between these limits indicates a loss of 9, 080 acrefeet of storage capacity or a loss of 1.26 percent of the original storage

capacity below elevation 6340 in 11.45 years.

Field observations indicate that in general erosion rather than

deposition has occurred between elevations 6340, the top limit of

the 1950 survey, and elevation 6357, the top of the spillway gates. The

net change in the reservoir capacity for this period between these limits

is believed to be small. At elevation 6340 the surface area in 1950 is

80 acres less than the area obtained during the original survey. This

decrease in area at this elevation results from deposition of material

removed from higher elevation by wave action, wind action, and bank

caving as well as from stream-transported sediment.

The quantity of eolian deposition in the North Platte River arm

of Seminoe Reservoir in the vicinity of Sediment Range No. 8A, about

10 miles upstream from the dam, is approximately 3, 100 acre-feet.

This is about one-third of the total sediment measured by the 1950 survey. It lies between cross sections selected at a location of 3700 feet

upstream and 2900 feet downstream, respectively, from Sediment Range

No. 8A and between the contour elevations of 6220 and 6290. It is recommended that the contributing sand dune area at Range 8A be investigated

by the Soil and Moisture Branch or appropriate officials of Region 7 relative to evaluating the worth of a treatment program to reduce the future

loss of reservoir storage from this sediment source.

A detailed economic study of the monetary loss because of storage depletion resulting from eolian deposits was not made for use in this

report. However, for illustrative purposes, if it is assumed that the

replacement cost per acre-foot of storage including dam, right-of-way,

appropriate power facilities, etc. is $40 per acre-foot; then the loss in

value to the Project represented by the loss of storage capacity in the

vicinity of Sediment Range No. 8A in 11.45 years equal 40 x 3, 100 =

$124, 000, and the annual loss equals $10, 830. If no treatmenj is given to

this sand dune area the potential loss over a period of years is believed

to be of sufficient magnitude to warrant further investigations of this area.

If a treatment program is recommended and it is successfully executed,

consideration should then be given to treatment of the sand dune area

shown by Figure 16 (b) to obviate the future necessity of relocating the

access road to Seminoe Dam which is threatened by the shifting of this

sand dune.

In attempting to evaluate the effect of sediment on Seminoe Reservoir and also Pathfinder Reservoir, a considerable amount of time and

expense was involved in making a fair appraisal of the changes which

occurred during the periods between the original and present surveys.

The present policy of the Bureau of Reclamation and other Federal Agencies is to make an accurate reservoir survey and install permanent

56
monuments at survey stations, denoting the ends of sediment ranges,

prior to the closure of the dam. On reservoirs where this type of survey has been made, the cost and difficulties involved in evaluating the

amount and disposition of sediment in the reservoir, the changes in

the stream regimen upstream from the reservoir and downstream from

the dam, and the preparation of new area and capacity tables are a

minimum. In addition, accurate data for use in designing new structures may be obtained.

57
BIBLIOGRAPHY

(1) Climatological Data, Wyoming Section, Weather Bureau, United

States Department of Commerce.

(2) Water Supply Papers, Surface Water Supply of the U. S., Part 6,

Missouri River Basin, Geological Survey, United States Department of the Interior.

(3) Soils and Men, Yearbook of Agriculture, 1938, United States Department of Agriculture.

(4) Van't Hul, Arthur W., A Progress Report on the Disposition of

Sediment in Reservoirs, Bureau of Reclamation, January 1950.

(5) Lane, E. W. and Koelzer, V. A., Density of Sediment Deposited

in Reservoirs, Report No. 9, A cooperative study by Federal

Agencies, published in November 1943 at St. Paul U. S. Engineer District Sub-Office Hydraulic Laboratory, University of

Iowa, Iowa City, Iowa.

(6) Miller, Carl R., Determination of the Unit Weight of Sediment for

use in Sediment Volume Computations, Bureau of Reclamation,

February 17, 1953.

(7) Eakin, H. M., revised by Brown, Carl B.,, Silting of Reservoirs,

Technical Bulletin 524, United States Department of Agriculture,

Washington, D.C., United States Government Printing Office,

1939.

(8) Seavy, Louis M., Sedimentation Survey of Tongue River Reservoir,

Bureau of Reclamation, August 1949.

58

Interior - Reclamation - Denver Cob.