THIEF VALLEY RESERVOIR

1992 SEDIMENTATION SURVEY

U.S. Department of the interior

Bureau of Reclamation
7-2090 (4-81)

Bweau of keclamation TECHNICAL REPORT STANDARD TITLE PAGE

1. REPORT NO. NMNTACeS$• 3. RECIPIENTS CATALOG NO.

4. TITLE AND SUBTITLE 5. REPORT DATE

h ll

March 1994

T ief Va ey Reservoir R RM DE

1992 Sedimentation Survey

6. PE FO ING ORGANIZATION CO

D-5753

7. AUTHOR(S) 8. PERFORMING ORGANIZATION

Ronald L. Ferrari REPORT NO.

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. WORK UNIT NO.

Bureau of Reclamation 11. CONTRACT OR GRANT NO.

Denver Office

Denver CO 80225 13. TYPE OF REPORT AND PERIOD COVERED

12. SPONSORING AGENCY NAME AND ADDRESS

DIBR

Same

14. SPONSORING AGENCY CODE

_________________________________________________________ D-5753

15. SUPPLEMENTARY NOTES

Microfiche and hard copy available at the Denver Office, Denver, Colorado

16. ABSTRACT

Thief Valley Reservoir was surveyed in June 1992 to compile field data for developing a

reservoir topographic map and computing a present storage-elevation relationship. The data

were also used to estimate the volume of sediment that has accumulated in the reservoir since

dam closure in February 1932. The 1992 bathymetric survey used sonic depth recording

equipment interfaced with an automated microwave positioning system that gave continuous

depth and sounding positions throughout the reservoir. The above-water reservoir area was

calculated from close interval cross sections measured from aerial photography. A new

reservoir contour map was developed by the computer graphics program Surface II using the

collected data.

As of June 1992, at reservoir spiliway crest elevation (feet) 3133.0, the surface area was 685.1

acres and the reservoir had a total capacity of 13,307 acre-feet. Since initial reservcnr storage

in February 1932, 1,798 acre-feet of sediment have been trapped in Thief Valley Reservoir,

resulting in an 11.9-percent loss in reservoir capacity. The average annual rate of sediment

accumulation since 1932 is 30.1 acre-feet.

17. KEY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS- reservoir area and capacity! sedimentation! reservoir surveys! sonar!

sediment distribution! contour area! reservoir area! sedimentation survey!

b. IDENTIFIERS- Thief Valley Reservoir!

c. COSATI Field/Group 13/B COWRR: 1302.66 SRIM:

18. DISTRIBUTION STATEMENT 19. SECURITY CLASS 21. NO. OF PAGES

(THIS REP0 15 UNCL4$S(FlED

20. SECURITY CLASS 22. PRICE

(THIS PASS)

UNCLASSFIED
THIEF VALLEY RESERVOIR

1992 SEDIMENTATION SURVEY

by

Ronald L. Ferrari

Sedimentation Section

Surface Water Branch

Division of Earth Sciences

Denver Office

Denver, Colorado

March 1994

A
ACKNOWLEDG MENTS

The Bureau of Reclamation prepared and published this report

under the supervision of Robert I. Strand, Head, Sedimentation

Section, Earth Sciences Division. Ronald Ferrari and Joseph

Lyons of the Denver Office conducted the hydrographic survey.

Personnel from the Columbia Basin Project Office of the Pacific

Northwest Region assisted during the hydrographic survey and

performed the required land survey for the hydrographic and

aerial data collection. Special thanks to Jerry Harrod and

Chuck Woodruff of the Columbia Basin Projects Office for the

field assistance during the hydrographic survey. Ronald Ferrari

completed the data processing needed to generate the new

topographic map and area-capacity tables. Robert I. Strand and

Joseph Lyons consulted in the engineering computations,

topographic map development, and report preparation.

U.S. Department of the Interior

Mission Statement

As the Nation's principal conservation agency, the Department of the

Interior has responsibility for most of our nationally-owned public

lands and natural resources. This includes fostering sound use of our

land and water resources; protecting our fish, wildlife, and biological

diversity; preserving the environmental and cultural values of our

national parks and historical places; and providing for the enjoyment

of life through outdoor recreation. The Department assesses our

energy and mineral resources and works to ensure that their

development is in the best interests of all our people by encouraging

stewardship and citizen participation in their care. The Department

also has a major responsibility for American Indian reservation

communities and for people who live in island territories under U.S.

administration.

The information contained in this report regarding commercial

products or firms may not be used for advertising or promotional

purposes and is not to be construed as an endorsement of any

product or firm by the Bureau of Reclamation.

The information contained in this report was developed for the

Bureau of Reclamation; no warranty as to the accuracy,

usefulness, or completeness is expressed or implied.

11
CONTENTS

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Page

9

Introduction 1

Summary and conclusions 2

Description of watershed 2

Reservoir operations 3

Survey method and equipment 3

Reservoir area and capacity 4

Original capacity 4

Development of 1992 contour areas 5

1992 revised storage capacity 5

Sediment analyses 6

References 7

Table

TABLES

1 Reservoir sediment data summary 8

2 Summary of 1992 survey results 10

FIGURES

Figure

1 Thief Valley Reservoir location map 11

2 Thief Valley Reservoir Dam, plan and section 12

3 Thief Valley Reservoir topographic map 13

4 1992 area and capacity curves 15

in
INTRODUCTION

Thief Valley Dam and Reservoir forms one of the major storage features of the Baker Project.

The dam is located on the Powder River in Union County, about 7 miles east of North Powder

and 16 miles north of Baker, Oregon (fig. 1).

Thief Valley Reservoir provides a supplemental irrigation supply for the Lower Division of

the Baker Project. The Lower Division of the Baker Project was approved by the President

on March 18, 1931. The facilities are operated and maintained by the Lower Powder River

Irrigation District. Other major facffities of the basin include Mason Dam and Phillips Lake,

located on the Powder River 11 miles southwest of Baker, Oregon. Phillips Lake supplies

supplemental irrigation water to the Upper Division of the Baker Project and is operated and

maintained by the Baker Valley Irrigation District.

Construction of Thief Valley Dam and Reservoir started September 12, 1931, and was

completed on May 6, 1932. Initial water storage began in February 1932. The dam is a

reinforced concrete, slab and buttress (Ambursen) structure. At dam crest elevation 3143.0,

Thief Valley Dam (fig. 2) has:

a structural height* of 73 feet

a hydraulic height of 48 feet

a top crest width of 7 feet

a crest length of 390 feet

The spillway is an uncontrolled overflow section located in the center of the dam and has a

crest elevation of 3133.0 and a length of 268.0 feet. The spillway design flow is 35,000 cubic

feet per second at maximum water surface elevation 3143.0.

The outlet works, located through the face of the dam's overflow section, are controlled by two

4.8- by 6-foot slide gates. The capacity of the outlet works is 2,440 cubic feet per second at

reservoir elevation 3143.0.

The 1992 reservoir survey measured a total storage capacity of 13,307 acre-feet and a surface

area of 685.1 acres at reservoir spiliway crest elevation 3133.0. During the 59.7 years since

dam closure (February 1932 to June 1992), the capacity loss caused by sediment

accumulation in the reservoir was estimated to be 1,798 acre-feet.

* The definition of terms such as "structural height," "hydraulic height," etc., may be found in manuals such as

Reclamation's Design of Small Dams and Guide for Preparation of Standing Operating Procedures for Dams and

Reservoirs, or ASCE's Nomenclature for Hydraulics.
SUMMARY AND CONCLUSIONS

This report presents the 1992 results of the first extensive sedimentation survey of Thief

Valley Reservoir by the Bureau of Reclamation. The primary objectives of the survey were

to:

• gather data needed for developing new reservoir topography

• compute area-capacity relationships

• estimate storage depletion caused by sediment deposition since Thief Valley Dam closure.

Standard land surveying methods were used to establish horizontal and vertical control

points for the aerial and hydrographic surveys. A local horizontal grid system was

established for both surveys using monumented control points located on the center line of

the dam axis overlooking the reservoir area These monuments are Reclamation bench

marks with 1929 National Geodetic Vertical Datums. The bathymetric survey was run using

sonic depth recording equipment interfaced with an automated survey system consisting of

a line-of-sight microwave positioning unit capable of determining sounding locations within

the reservoir. The system continuously recorded reservoir depth and horizontal coordinates

as the survey boat was steered across close spaced gridlines covering the reservoir area. The

positioning system provided information to allow the boat operator to maintain course along

these gridlines. Water surface elevations measured by the land surveyors at the time of data

collection were used to convert the sonic depth measurements to true lake bottom elevations.

The 1992 surface areas at predetermined 5-foot contour intervals were generated by a

computer graphics program that produced a new contour map of the reservoir (fig. 3). The

revised area and capacity tables were produced by a computer program that uses measured

contour surface areas and a curve-fitting technique to compute area and capacity at

prescribed elevation increments.

Table 1 contains a summary of reservoir watershed characteristics and sediment data for the

1992 survey. The 1992 survey determined that the reservoir has a storage capacity of 13,307

acre-feet and a surface area of 685.1 acres at spillway crest elevation 3133.0. Since closure

in February 1932, the reservoir has accumulated an estimated volume of 1,798 acre-feet of

sediment below spillway crest elevation 3133.0. This volume represents an 11.9-percent loss

in total capacity and an average annual loss of 30.1 acre-feet. These figures indicate that a

large amount of estimated sediment has accumulated in the reservoir since the original

survey, but uncertainties with the original reservoir area data create questions regarding

these sediment accumulation values. The 1992 survey established the present area-capacity

of Thief Valley Reservoir, and a resurvey should not be necessary unless major sediment

inflow occurs in the future.

DESCRIPTION OF WATERSHED

The Powder River that drains into Thief Valley Reservoir originates in northeastern Oregon

along the eastern slopes of the Blue Mountains. The watershed above the dam has a

drainage area of 910 square miles, of which a calculated 842 square miles contributed

sediment inflow during the study period. Sediment from the remaining drainage area was

trapped by Phillips Lake since water storage began in October 1967. The basin rises from

elevation 3094.0 feet at the outlet works to about 9,000 feet along the Elkhorn Ridge, which

forms the northeastern boundary of the Phillips Lake watershed.

2
The basin is elliptical in shape and lies in a south to north orientation. The western and

southern portion of the basin is forested and steep. Tree cover consists of larch, pine, fir, and

very little underbrush. The central portion consists of a rather broad open basin with

relatively flat terrain. The valley consists of pasture, alfalfa fields, rolling sagebrush covered

hills, and very few trees. Soils are loose and consist of a silty loam of moderate to deep

depths.

RESERVOIR OPERATIONS

The reservoir is a multiuse facility having (following values are from June 1992 area-capacity

tables):

7,488 acre-feet of exclusive flood control storage between elevations 3133.0 and 3143.0

13,307 acre-feet of active conservation storage between elevations 3094.0 and 3133.0

0 acre-feet of inactive storage below elevation 3094.0(1992 survey measured a minimum

elevation of 3093.8)

Records for Thief Valley Reservoir are very limited. The mean annual runoff of 177,500 acrefeet per year was obtained from Reclamation's project data book (Reclamation, 1981).

Records of the reservoir operation were only available from 1961 and ranged from a minimum

elevation of 3094.0 in 1961, 1966, 1967, and 1977 to a maximum elevation of 3134.8 in 1984.

The limited inflow and end-of-month stage records in table 1 show the extreme annual

fluctuation of the reservoir, and this type of operation is assumed to have occurred prior to

1961 also.

SURVEY METHOD AND EQUIPMENT

The Thief Valley Reservoir survey was completed using the contour method as outlined by

Blanton (1982). The procedure involved collecting adequate coordinate data for developing

a reliable contour map by photogrammetric and bathymetric survey methods. Columbia

Basin Project Office personnel used standard land surveying methods to establish horizontal

and vertical control points for both survey methods. A local horizontal grid system was

established for both surveys using monumented points located in the reservoir area. The

above water data were collected by aerial photography when the reservoir was nearly empty.

The field survey work for the bathymetric survey involved establishing a triangulation

network around the reservoir to provide horizontal and vertical control for all required grid

lines and shore stations. No range lines were previously established on the lake and it was

decided not to establish permanent range lines during this survey. Because of the size and

shape of the reservoir, any future survey would also employ the contour method; therefore,

permanent range line end markers were not necessary.

The hydrographic survey was run on June 4 and 5, 1992, with the reservoir at water surface

elevation 3121.9 and 3122.2, respectively. The bathymetric survey was run using sonic depth

recording equipment interfaced with an automated survey system consisting of a line-of-sight

microwave positioning unit capable of determining sounding locations within the reservoir.

This positioning system transmitted line-of-sight microwave signals to fixed shore stations

and converted the reply time to range distances, which the system data logger used to

compute the coordinate position of the sounding boat. The survey system continuously
recorded reservoir depth and horizontal coordinates as the survey boat moved across closespaced gridlines covering the reservoir area. To produce adequate data for developing

contours of Thief Valley Reservoir, grid spacing of 150 to 200 feet was selected. The system

gave directions to the boat operator to assist in maintaining course along the close-spaced

gridlines. During each run, the depth and position data were recorded on a floppy disk for

subsequent processing by Denver Office personnel. A graph plotter was used in the field to

track the boat and ensure adequate coverage during the cOllection process. Water surface

elevations surveyed at the time of collection were used to convert the sonic depth

measurements to true lake bottom elevations.

RESERVOIR AREA AND CAPACITY

Original Capacity

The original (1932) total capacity of Thief Valley Reservoir was reported as 17,600 acre-feet

with a surface area of 744.0 acres at spillway crest elevation 3133.0. The original values

were obtained from the Thief Valley Reservoir area and capacity table dated June 29, 1949.

The table indicated that the area values came from a acreage curve dated October 29, 1932.

Comparing the 1992 Thief Valley Reservoir surface area results with the original surface

areas found differences in the upper elevations of the reservoir that could not be explained.

The 1992 reservoir surface areas between elevations 3120.0 and 3133.0 were found to be

around 9 percent smaller then the original reported areas, and elevation 3135.0 was found

to be around 6 percent smaller. The field survey and operation of the reservoir gave no

reason to believe that the upper reservoir area would have silted in since dam closure. The

1992 survey confirmed the reported dam crest elevation of 3143.0. A comparison plot of the

1932 original areas with the 1992 areas appeared to indicate an approximate 4-foot elevation

shift between the two measurements.

3)50

3)45

3110

3135

3 30

3)25

3120

3115

3100

3095

2090

2085

3280

AREA (ACRES

808 760 721) 680 610 60)3 560 54) 480 480 40)3 360 320 280 240 160 120 8)) 60 U

- tAPRCIfl1flREfl - - - - __ -

Um1 I 7180318(68)190)4200)4

CAPFICITI ACRE-FEETI

4
Research of these differences found no clear answer that could explain them. For sediment

computation purposes, the original datum was shifted 4 feet, and the original capacity was

recalculated from the shifted area values. The original area of 763 acres at elevation 3135.0

became the area at elevation 3139.0. The elevation shift was completed for all of the original

surface areas as listed in column (4) of table 2. The recalculated capacity values are listed

in column (5) of table 2. The original stream bed elevation of 3085.0 was assumed to be the

same.

Development of 1992 Contour Areas

The 1992 contour surface areas for Thief Valley Reservoir were developed by generating a

contour map from the collected aerial and underwater coordinate data. Five-foot contour

intervals of the lake area were created by a computer graphics software program SURFACE

II (Kansas Geological Survey, 1978). A modification of this program by the Denver Office

calculated surface areas of the closed contours of the generated map. The fmal reservoir map

shown on figure 3 was prepared by the Denver Office Computer Drafting Unit of the Drafting

Section. The map scale is 1 inch = 500 feet with a contour interval of five feet.

1992 Revised Storage Capacity

The storage-elevation relationships based on the aerial and underwater survey data were

developed using the area-capacity computer program ACAP85 (Reclamation, 1985). Surface

areas at 5-foot contour intervals computed from aerial and underwater survey data were used

as control parameters for computing reservoir capacity. The program computes an area at

elevation increments of 0.01 to 1.0 foot by linear interpolation between the 5-foot contour

intervals. The program begins by testing the initial capacity equation over successive

intervals to ensure that the equation fits within an allowable error limit, which was set at

0.000001 for Thief Valley Reservoir. This capacity equation is then used over the full range

of intervals fitting within this allowable error limit. For the first interval at which the initial

allowable error limit is exceeded, a new capacity equation (integrated from the basic area

curve over that interval) tests the fit until it also exceeds the error limit. Thus, the capacity

curve is defined by a series of curves, each fitting a certain region of data. Final area

equations are derived by differentiating the capacity equations, which are of second order

polynomial form:

y a + a2x + aax2

where:

y capacity,

x = elevation above a reference base,

a = intercept, and

a2 and a3 = coefficients

Results of the 1992 Thief Valley Reservoir area and capacity computations are listed in table

1 and columns (6) and (7) of table 2. Listed in columns (4) and (5) of table 2 are the adjusted

original surface areas and recomputed capacity values. A separate set of 1992 area and

capacity tables has been published for the 0.01-, 0.1-, and 1-foot elevation increments

(Reclamation, 1992). A description of the computations and coefficients output from the

ACAP85 program is included with these tables. Both the original and 1992 area-capacity

curves are plotted on figure 4. As of June 1992, at reservoir spillway crest elevation 3133.0,

the surface area was 685.1 acres and the total capacity was 13,307 acre-feet.
SEDIMENT ANALYSES

Sediments have accumulated in Thief Valley Reservoir to a total volume of 1,798 acre-feet

since dam closure in February 1932. This volume indicates a large amount of accumulated

sediment since the original survey, but the problem with the original reservoir areas (see

original capacity section) creates questions regarding the accumulation value. The average

annual rate of sediment deposition between closure and June 1992(59.7 years) was 30.1 acrefeet, or 0.0338 acre-foot per square mile from the sediment-contributing drainage area. The

storage loss in terms of percent of original storage capacity was 11.9 percent. Table 1 and

2 summarize the Thief Valley Reservoir sediment accumulation and water storage data based

on the 1992 resurvey.

The Powder River downstream from Thief Valley Dam is a Federal Wild and Scenic River

and has a substantial rainbow trout fishery. In 1991, the Pacific Northwest Regional Office

conducted studies on the sediment releases from Thief Valley Reservoir. The study measured

the downstream water quality as the sediment deposits on the reservoir bottom were eroded

during extreme reservoir drawdown. The study concluded that maintenance of a 2,200 acrefoot minimum pool would prevent the downstream sedimentation problems. This value was

determined from the collected samples and the original capacity table.

The Sedimentation Section, using the 1991 samples and reservoir trap efficiency calculations,

concluded that to maintain the downstream water quality, a maximum release along with a

minimum pool elevation should be recommended. Also, the maintenance of the minimum

pool will increase the reservoir trap efficiency and the sediment buildup within the reservoir.

Over time, the sediment buildup within the reservoir will require the minimum pool elevation

to be increased to maintain the good downstream water quality.

It is recommended, for maintaining downstream water quality releases, that the reservoir

operation have a minimum pooi elevation of 3104.5 feet and that the maximum discharge not

exceed 75 cubic feet per second near the minimum pool level. It is also recommended that

periodic water samples be taken downstream during low reservoir pool conditions. These

samples will better determine the maximum discharge during these conditions plus monitor

the need of increasing the minimum pool elevation. The 1992 survey established the present

area-capacity of Thief Valley Reservoir, and a resurvey should not be necessary unless major

sediment inflows occur in the future.
REFERENCES

American Society of Civil Engineers,Nomenclature for Hydraulics, ASCE Headquarters, New

York, 1962.

Blanton, J.O. III, "Procedures for Monitoring Reservoir Sedimentation: Technical Guideline

for Bureau of Reclamation," Denver Office, Denver, CO, October 1982.

Bureau of Reclamation, Surface Water Branch, ACAP85 User's Manual, Denver Office,

Denver, Colorado, 1985.

Bureau of Reclamation, Guide for Preparation of Standing Operating Procedures for Bureau

of Reclamation Dams and Reservoirs, U.S. Government Printing Office, Denver, CO, 1987a.

Bureau of Reclamation, Design of Small Dams, U.S. Government Printing Office, Denver, CO,

1987b.

Bureau of Reclamation, Estimated Sediment Deposition in Mann Creek Reservoir, Mann Creek

Project, Pacific Northwest Region, Boise, Idaho, May 1987c,

Bureau of Reclamation, Denver Office, "Thief Valley Reservoir Area and Capacity Tables,

Baker Project," Pacific Northwest Region, Denver, CO, June 1992.

Kansas Geological Survey, SURFACE II GRAPHICS SYSTEM, Lawrence, Kansas, 1978.

7
RESERVOIR SEDIMENT

DATA SUMMARY Thief Valley Reservoir

NAME OF RESERVOIR

DATA SHEET NO.

1. OWNER Bureau of Reclamation' 2. STREAM Powder River 3. STATE Oregon

A 4. SEC. 26 1W?. 6 5. RANGE 40 E. 5. NEAREST P.O. North Powder 6. COUNTY Baker

H 7. LAT 452 00' 45" LONG 117' 46' 50" 8. TOP OF DAM ELEVATION 3143.02 9. SPILLWAY CREST ELEV. 3133.0

T 10. STOR.ALE 11. ELEVATION 12. ORIGINAL 13. ORIGINAL 4. GROSS STORAGE 15. DATE

E ALLOCATION TOP OF POOL SURFACE AREA, Ac CAPACITY, #2 ACRE- FEET STORAGE

BEGAN

a. FLOOD CONTROL 3143.0 895 8,400 26,000

R b. MULTIPLE USE ______________ ________________ 2 32

C. POWER

_______________ ________________

I

___ ______ __

R

d. WATER SUPPLY

___

16. DATE

e. GA N

______________ _______________ ______________ ________________

NORMAL

OPERATION

f. CONSERVATION 3133.0 740 17,400 17,600 BEGAN

g. INACTIVE 3094.0 90 200 200 2/32

17. LENGTH OF RESEK OIR 3.8 MILES AVG. WIDTH OF RL, RVOIR 0.28 MILES

18. TOTAL DRAINAGE AREA 910 SQUARE MILES 22. MEAN ANNUAL PRECIPITATION 10.5 INCHES

19. NET SEDIMENT CONTRIBUTING AREA 843' SQUARE MILES 23. MEAN ANNUAL RUNOFF INCHES

I

N

20. LENGTH MILES AV. WIDTH MILES 24. MEAN ANNUAL RUNOFF l77,SOO ACRE-FEET

-

21. MAX. ELEVATION 9000+ MIN. ELEVATION 3094 25. ANNUAL TEMP. MEAN 46'F RANGE -22'F to 102'F

r- 26. DATE OF 27. 28. 29. TYPE OF 30. NO. OF 31. SURFACE 32. CAPACITY 33. C/I

U SURVEY PER. ACCL. SURVEY RANGES OR AREA, AC. ACRE-FEET RATIO AF/AF

Ft YRS. YES. INTERVAL

Y 2/32 699.8' 15,105' .08

D

A 6/92 60.3 60.3 Contour (D) 5-FT 685.1 13,307 .07

T 26. DATE OF 34. PERIOD I 35. PERIOD WATER INFLOW, ACRE FEET WATER INFLOW TO DATE, AF A SURVEY ANNUAL

PRECIP.

a. MEAN ANN. b. MAX. ANN. c. TOTAL a. MEAN ANN. b. TOTAL

2/32 10.5 177,500 269,700' - - -

26. DATE OF 37. PERIOD CAPACITY LOSS, ACRE-FEET 38. TOTAL SEDIMENT DEPOSITS TO DATE, AF

SURVEY

a. TOTAL b. AV. ANN. c. /MI.2-YR. a. TOTAL b. AV. ANNUAL c. /MI.'-YR.

2/32 1,798 30.1 0.034' 1,798 30.1 0.034'

26. DATE OF 39. AV. DRY 40. SED. DEE'. TONS/MI.-YR. 41. STORAGE LOSS, PCT. 42. SEDIMENT

SURVEY WT. (#/FT3) INFLOW, PPM

a. PERIOD b. TOTAL TO a. AV. b. TOTAL TO a. b.

DATE ANNUAL DATE PER. TOT.

2/32 0.20' 11.9'

26.

DATE

43. DEPTH DESIGNATION RANGE IN FEET BELOW TOP OF CONSERVATION (ELEVATION

OF

SURVEY

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

26. 44. REACH DESIGNATION PERCENT OF TOTAL ORIGINAL LENGTH OF RESERVOIR

DATE

SURVEY

0-10 10-

20

20-

30

30-

40

40-

50

50-

60

60- I

70

70-

80

1 80- 90- 100- 105-

100 105 110

110-

115

115-

120

120-

125

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN REACH DESIGNATION

N/A

Table 1. - Reservoir sediment data summary (page 1 of 2).
45. RANGE IN RESERVOIR OPERATION '

WATER YEAR MAX. ELEV. MIN. ELEV. INFLOW • Al WATER ELEV. NIH. ELEV. INFLOW • Al

1961 3133.0 3094.0 - 1962 3133.0 - -

1963 3133.0 - 1964 - -

1965 3133.0 3096.0 - 1966 3133.0 3094.0 -

1967 3133.0 3094.0 - 1968 3133.0 3102.0 -

1969 3133.0 3105.4 - 1970 3133.0 3110.0 -

1971 3133.0 3114.0 - 1972 3133.0 3114.5 -

1973 3133.0 3104.0 - 1974 3133.0 3104.8 -

1975 3133.0 3111.7 - 1976 3133.0 3127.3 -

1977 3133.0 3094.0 - 1978 3133.0 3108.0 -

1979 3133.0 3110.0 124,210 1980 3133.0 3115.0 119,120

1981 3133.9 3109.6 138,410 1982 3134.4 3113.2 307,420

1983 3134.5 3128.1 306,770 1984 3134.8 3129.2 345,670

1985 3133.5 3114.4 161,200 1986 3134.2 3112.0 174,200

1987 3133.3 3097.5 53,920 1988 3133.4 3101.5 -

1989 3133.8 3106.0 - 1990 3133.5 3096.5 52,930

1991 3133.8 3101.6 64,910 1992 3133.4 3096.6 8/92 34,820 6/92

46. ELEVATION - AREA - CAPAI..ITY DATA FOR Cu 1GINAL CAPACITI II

ELEV. AREA CAP. ELEV. AREA CAP. ELEV. AREA CAP.

3085 0 0 3100 401.0 4,576 3130 714.1 15,616

3095 113.7 507 3115 478.0 6,774 3133 740.0 17,803

3100 231.1 1,369 3120 552.3 9,349 3135 763.0 19,310

3105 325.4 2,760 3125 620.1 12,280 ____________

46. ELEVATION - AREA - LAPACITY DATA FOR 1992 TOTAL CAPACITY

ELEV. AREA CAP. ELEV. AREA CAP. ELEV. AREA CAP.

3093.8 0 0 3105 143.2 514 3130 639.4 11,320

3100 35.8 66 3110 268.0 1,542 3133 685.1 13,307

3105 143.2 514 3115 415.9 3,251 3135 720.3 14,712

3110 268.0 1,542 3120 508.6 5,563 3140 767.9 18,433

____________ ____________ ____________

3125 577.5 8,278 3143 806.9 20,795

47. REMARKS AND REFERENCL.

Operated by Lower Powder River Irrigation District.

Top of parapet wall is elevation 3146.0.

Original area and capacity values estimated from drawing No. 115-100-2, Thief Valley Reservoir Area and Capacity

curves. Original topography not located.

Length and width of reservoir at elevation 3133.0.

Limited r.cords available. Presented values from Reclamation's project data book.

Represents loss of contributing area since dam closure at Phillips Lake in October 1967. Total drainage area of

above Phillips Lake Dam is 165 mi2. Net contributing area 843 mi2 910 m15 - l65mia (24.6 yrs/60.3 yrs).

Research concluded the original elevation versus area values should be adj usted (-) 4. 0 feet to better represent

the original reservoir conditions and for sediment computations. Adjusted original c apacity at elevation 3133.0

of 15,105 was computed by ACAP85 using adjusted surface area values.

* 1798 acre-feet 910 mi2 (35.7yrs)X + 843 mi2 (24.6yrs)X.

X 0.03378 AF/mi2-yr.

35.7 years of operation before Phillips Lake and 24.6 years after for a total of 60.3 years of operation.

Average annual and total sediment deposits of 30.1 and 1,798 respectfully divided by 1 5,105 Al (recalulated total

capacity at El. 3133 using adjusted surface area, see remark number 7.

'° Limited records available. End of month values.

II Original area-capacity table reported by Bureau of Reclamation.

48. AGENCY MAKING SURVEY Bureau of Reclamation

49. AGENCY SUPPLYING DATA Bureau of Reclamation DATE August 1993

Table 1. - Reservoir sediment data summary (page 2 of 2).
(1)

Elevation

(ft)

(2)

Original

Area

(acres)

(3)

Original

Capacity

(acre-ft)

(4)

Adjusted

Original Area

(acres)

(5)

Adjusted Original

Capacity

(acre-ft)

(6)

1992

Area

(acres)

(7)

1992

Capacity

(acre-if)

(8)

Measured

Sediment Volume

(acre-if)

(9)

Percent

Measured

Sediment

(10)

Percent

Reservoir

Depth

3143 - - - - 806.9 20,795 - - -

3140 - - - - 767.9 18,433 - - -

3139 - - 763.0 19,506 (758) 17,670 - - -

3135 763.0 19,310 725.2 16,530 720.3 14,712 - - -

3133 744.0 17,803 699.8 15,105 685.1 13,307 1,798 100.0 100.0

3130 714.1 15,616 638.8 13,097 639.4 11,320 1,777 100.0 93.8

3125 620.1 12,280 565.0 10,087 577.5 8,278 1,809 100.0 83.3

3120 552.3 9,349 493.6 7,441 508.6 5,563 1,878 100.0 72.9

3115 478.0 6,774 416.3 5,166 415.9 3,251 1,915 100.0 62.5

3110 401.0 4,576 341.4 3,272 268.0 1,542 1,730 96.2 52.1

3105 325.4 2,760 252.5 1,787 143.2 514 1,273 70.8 41.7

3100 231.1 1,369 137.4 812 35.8 66 746 41.5 31.2

3095 113.7 507 (69) 346 (2) 1 345 19.2 20.8

3093.8 (88)' 387 (61) (268) 0 0 268 14.9 18.3

3090 (50) 125 (35) 87 0 0 87 4.8 10.4

3085 0 0 0 0 0 0 0 0.0 0.0

(1) Elevation of reservoir water surface.

(2) Original reservoir surface area values estimated from 1932 area curves (Drawing 115-100-2).

(3) Original reservoir capacity recomputed using ACAP85.

(4) Original reservoir surface area values with a 4-foot datum adjustment to better represent original conditions.

(5) Original reservoir capacity computed by ACAP85 using adjusted original areas.

(6) Reservoir surface area from 1992 survey.

(7) 1992 calculated reservoir capacity from 1992 survey data.

(8) Measured sediment volume = column (5) - column (7).

(9) Measured sediment expressed in percentage of total sediment (1,798), measured at spillway crest El. 3133.0. 100% measured from El. 3115.0 and above.

1992 areas measured slightly greater then original at El. 3120, 3125, and 3130 probably because of difference in survey methods and bank erosion.

(10) Depth of reservoir expressed in percentage of total depth (48 feet).

1 Areas in ( ) computed by ACAP85.

Table 2. - Summary of 1992 survey results.
____________ ____________ __________________________

ft31E.

____________________ _________________________ __________________________

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UNION CO UNTY

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Figure 1. - Mann Creek Iocaton map.
Space intentionally left blank due to security concerns 
Figure 3. - Thief Valley Reservoir topographic map.

1)
AREA (ACRES)

-

3150

3145

3140

3135

3130

3125

Li

Li 3120

3115

ci: Q1

>

3110

Li

-J

Li 3105

3100

3095

3090

3085

3080

840800 760 720 580 640 600 560 520 480 440 400 360 320 280 24 0 200 160 120 80 40 C

--- ------

•

N

N

L

--

CAPACIT Y AREA

.

/

7

/

I7 -

--

-

/ ---

I

'I, '

- LEGEND

1992 SURVEY

1932 SURVEY

fl 200fl 4000 6000 8000 10000 12000 14000 16000 18000 20000

CAPACITY (ACRE-rEET)

Figure 4. - 1992 area and capacity curves.
Mission

The mission of the Bureau of Reclamation is to manage, develop, and

protect water and related resources in an environmentally and

economically sound manner in the interest of the American Public.