Pishkun Reservoir

2002 Survey

(

U.S. Department of the Interior

Bureau of Reclamation

Technical Service Center

Denver, Colorado August 2005
REPORT DOCUMENTATION PAGE Form Approved

0MB No. 0704-0188

AGENCY USE ONLY (Leave Blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

August 2005 Final __________________________________

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Pishkun Reservoir PR

2002 Survey

6. AUTHOR(S)

Ronald L. Ferrari and Sharon Nuanes ___________________________

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION

Bureau of Reclamation, Technical Service Center, Denver CO 80225-0007 REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING

Bureau of Reclamation, Denver Federal Center, P0 Box 25007, AGENCY REPORT NUMBER

Denver CO 80225-0007

DIBR

11. SUPPLEMENTARY NOTES

Hard copy available at Bureau of Reclamation Technical Service Center, Denver, Colorado

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

13. ABSTRACT (Ma.iinunz 200 words)

The Bureau of Reclamation (Reclamation) surveyed Pishkun Reservoir in June 2002 to develop new

reservoir topography and compute a present storage-elevation relationship (area-capacity tables). The

underwater survey was conducted at reservoir water surface elevation 4,369.9 feet (project datum). The

survey used sonic depth recording equipment interfaced with a real-time kinematic (RTK) global

positioning system (GPS) that gave continuous sounding positions throughout the underwater portion of the

reservoir covered by the survey vessel. The above-water topography was determined by digitizing the

developed reservoir contour line from the U.S. Geological Survey quadrangle (USGS quad) maps of the

reservoir area. The new topographic map of Pishkun Reservoir was developed from the combined digitized

USGS quad contour and June 2002 underwater measured topography. This study assumed no change from

elevation 4,370.0 (feet) and above. As of June 2002, at water surface elevation 4,370.0, the surface area

was 1,522 acres with a total capacity of 46,694 acre-feet. This study found little change from the original

published values. It is assumed the calculated changes are due to accuracy difference between the two

surveys and expected small sediment inflow to the offstream reservoir.

14. SUBJECTTERMS 15. NUMBER OF PAGES

reservoir area and capacity/ sedimentation! reservoir surveys! sonar! sediment distribution!

contour area! reservoir area! sedimentation survey! global positioning system! lake

______________________

16. PRICE CODE

17. SECURITY 18. SECURITY 19. SECURITY CLASSIFICATION 20, LIMITATION OF

CLASSIFICATION CLASSIFICATION ABSTRACT

OF REPORT OF ABSTRACT

OF THIS PAGE

UL UL UL

_____________________ UL ________________________

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescn'bedbv ANSI Std. 239-18

298-102
Pishkun Reservoir

2002 Survey

Prepared by

Ronald L. Ferrari

and

Sharon Nuanes

( '\

U.S. Department of the Interior

Bureau of Reclamation

Technical Service Center

Water Resources Services

Sedimentation and River Hydraulics Group

Water Supply, Use and Conservation Group

Denver, Colorado August 2005
ACKNOWLEDGMENTS

Reclamation's Sedimentation and River Hydraulics and the Water Supply, Use and

Conservation Groups of the Technical Service Center (TSC) prepared and published this

report. Ronald Ferrari and Tom Pruitt of TSC conducted the underwater data collection.

Ron Ferrari and Sharon Nuanes of the TSC completed the data processing needed to

generate the new topographic map, area-capacity tables and report. Sharon Nuanes of the

TSC developed the final topographic map. Kent Collins of the TSC performed the

technical peer review of this documentation.

UNITED STATES DEPARTMENT OF TILE

INTERIOR

The mission of the Department of the Interior is to protect

and provide access to our Nation's natural and cultural

heritage and honor our trust responsibilities to Indian tribes

and our commitments to island communities.

BUREAU OF RECLAMATION

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.

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 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Introduction .

Summary and Conclusions 3

Reservoir Operations 4

Hydrographic Survey Equipment and Method 5

Pishkun Datum 6

Reservoir Area and Capacity 6

Topography Development 6

Development of 2002 Contour Areas 7

2002 Storage Capacity 7

2004 Reservoir Analyses 8

References 9

TABLES

Table

1 Reservoir sediment data summary (page 1 of 3) 10

1 Reservoir sediment data summary (page 2 of 3) 11

1 Reservoir sediment data summary (page 3 of 3) 12

2 Summary of 2002 survey results 13

FIGURES

Figure

1 Pishkun Dikes Location

2 Pishkun Dikes 1, 2, and 3 2

3 Pishkun Dikes 4 through 8 3

4 Survey vessel with mounted hydrographic equipment on Jackson Lake in WY 5

5 Pishkun Reservoir topographic map 15

6 2002 area and capacity curves 17

Iii

Space intentionally left blank due to security concerns 
Space intentionally left blank due to security concerns 
system continuously recorded depth and horizontal coordinates of the survey boat as it was

navigated along grid lines covering Pishkun Reservoir. The positioning system provided

information to allow the boat operator to maintain a course along these grid lines. Water surface

elevations recorded by the reservoir gauge (tied to the Reclamation vertical datum) during the

time of collection were used to convert the sonic depth measurements to true reservoir bottom

elevations. The above-water topography was determined by digitizing the developed reservoir

contour line from the U.S. Geological Survey quadrangle (USGS quad) maps of the reservoir

area.

The 2002 Pishkun Reservoir topographic map is a combination of the USGS quad contour and

the underwater survey data. A computer graphics program generated the 2002 reservoir surface

areas at predetermined contour intervals from the collected data. The 2002 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 (Bureau

of Reclamation, 1985).

Tables 1 and 2 contain summaries of the Pishkun Reservoir and watershed characteristics for the

2002 survey. The 2002 survey determined that the reservoir has a total storage capacity of

46,694 acre-feet and a surface area of 1,522 acres at active conservation elevation 4,370.0.

RESERVOIR OPERATIONS

The Sun River Project uses the waters of the Sun River and its tributaries, stored and regulated

by Gibson, Pishkun, and Willow Creek Reservoirs, for irrigating about 93,000 acres of land lying

along the Sun River. Water stored in Gibson Reservoir is released into the river for diversion

downstream into the Pishkun Supply Canal, Willow Creek Feeder Canal, or the Fort Shaw

Canal. The Pishkun Supply Canal, heading at Sun River Diversion Dam, conveys water to

Pishkun or Willow Creek Reservoirs through the Willow Creek Feeder Canal, which stems from

the Pishkun Supply Canal and empties into a natural channel to the reservoir. Water released

from Pishkun Reservoir enters the Sun River Slope Canal, which branches into several main

canals for distribution to about 81,000 acres in the Greenfields Division.

The June 2002 capacity table shows 54,852 acre-feet of total storage below the maximum water

surface elevation 4,375.0. The 2002 survey measured a minimum lake bottom elevation of

4290.5. The following values are from the June 2002 capacity table:

8,158 acre-feet of surcharge between elevation 4,370.0 and 4,375.0.

30,686 acre-feet of conservation use between elevation 4,342.0 and 4,370.0.

16,008 acre-foot of dead storage below 4,342.0.

Pishkun Reservoir readily available inflow and end-of-month stage records in table 1, operation

period 1947 through 2002, show the calculated inflow and annual fluctuation for these years of

operation. The computed average inflow into the reservoir for these years was 227,240 acre-feet

per year. The maximum-recorded elevation was 4371.2 in 1949 and the minimum recorded was

4316.4 in 1991.

4

the shore as the boat traversed between transects. The survey vessel's guidance system gave

directions to the boat operator to assist in maintaining the course along these predetermined

lines. During each run, the depth and position data were recorded on the notebook computer

hard drive for subsequent processing.

The 2002 underwater data were collected by a depth sounder that was calibrated by lowering a

weighted cable below the boat with beads marking known depths. The depth sounder was

calibrated by adjusting the speed of sound, which can vary with density, salinity, temperature,

turbidity, and other conditions. The collected data were digitally transmitted to the computer

collection system via a RS-232 port. The depth sounder also produces an analog hard-copy chart

of the measured depths. These graphed analog charts were printed for all survey lines as the data

were collected and recorded by the computer. The charts were analyzed during post-processing,

and when the analog charted depths indicated a difference from the recorded computer bottom

depths, the computer data files were modified. The water surface elevations at the dam, recorded

by a Reclamation gauge, were used to convert the sonic depth measurements to true lake-bottom

elevations.

Pishkun Datum

Upon completion of the underwater survey, a RTK GPS survey was conducted to tie the

horizontal and vertical control of the hydrographic survey temporary point and the reservoir

water surface to the NGS control point "Choteau". The 2002 RTK GPS survey determined the

Reclamation vertical datum to be around 6.4 feet lower than NGVD88. Note that all elevations

in this report are tied to the Reclamation vertical elevations that were measured by the

Reclamation gauge during the time of collection.

RESERVOIR AREA AND CAPACITY

Topography Development

The topography of Pishkun Reservoir was developed from the 2002 collected underwater and a

digitized contour from the USGS quad map. The digitized USGS contour line was the Pishkun

Reservoir water surface labeled elevation 4,370.0. The USGS quad maps were developed from

aerial photography dated 1982. This study found the enclosed digitized contour area, with the

island surfaces removed, to be slightly less than the original surface area at elevation 4370.

ARC/INFO V7.0.2 geographic information system software was used to digitize the USGS quad

contour. The digitized contours were transformed to Montana's NAD 1983 state plane

coordinates using the ARC/INFO PROJECT command.

The digitized contour line was used to perform a clip of the Pishkun Reservoir triangular

irregular network (TN) such that interpolation was not allowed to occur outside the enclosed

polygon. This contour was selected since it was the only available data to represent the reservoir

water surface at the time the survey was conducted (near reservoir elevation 4,370). This clip

was performed using the hardclip option of the ARC/INFO CREATETIN command. Using

ARCEDIT, the underwater collected data and digitized contours from the quad maps were

plotted. Using select and move commands within ARCEDIT, the vertices of the clip were

6
shifted to fit all the collected underwater data. The clip was assigned an elevation of 4,370.0 to

reflect the original area of the developed polygons.

Contours for the reservoir below elevation 4,370.0 were computed from the underwater data set

using the triangular irregular network (TIN) surface-modeling package within ARC/INFO. A

TIN is a set of adjacent non-overlapping triangles computed from irregularly spaced points with

x,y coordinates and z values. TIN was designed to deal with continuous data such as elevations.

The TIN software uses a method known as Delaunay's criteria for triangulation where triangles

are formed among all data points within the polygon clip. The method requires that a circle

drawn through the three nodes of a triangle will contain no other point, meaning that sample

points are connected to their nearest neighbors to form triangles using all collected data. This

method preserves all collected survey points. Elevation contours are then interpolated along the

triangle elements. The TIN method is discussed in detail in the ARC/INFO V7.0.2 Users

Documentation, (ESRI, 1992).

The linear interpolation option of the ARC/INFO TINCONTOLJR command was used to

interpolate contours from the Pishkun Reservoir TIN. In addition, the contours were generalized

by filtering out vertices along the contours. This generalization process improved the

presentability of the resulting contours by removing very small variations in the contour lines.

This generalization had no bearing on the computation of surface areas and volumes for Pishkun

Reservoir since the areas were calculated from the developed TIN. The areas of the enclosed

contour polygons at one-foot increments were developed from the survey data for elevations

4,291.0 through 4,370.0. The contour topography at two-foot intervals is presented on figure 5.

Development of 2002 Contour Areas

The 2002 contour surface areas for Pishkun Reservoir were computed at one-foot increments

from elevation 4,291.0 to 4,370.0. The 2002 underwater survey measured a minimum reservoir

bottom elevation of 4,290.5. These calculations were performed using the ARC/INFO

VOLUME command. This command computes areas at user-specified elevations directly from

the TIN and takes into consideration all regions of equal elevation. As indicated above, the 2002

underwater survey data was collected near reservoir elevation 4,369.9. For the purpose of this

study, the measured 2002 survey areas at one-foot increments from elevation 4,291.0 through

4,370.0 were used to compute the new area and capacity tables. This study assumed no change

in original volume from elevation 4,370.0 and above. The area and capacity program was

adjusted to reflect this assumption for the computations between elevation 4,370 and 4,375.

2002 Storage Capacity

The storage-elevation relationships based on the measured surface areas were developed using

the area-capacity computer program ACAP85 (Bureau of Reclamation, 1985). The 2002

surveyed surface areas at one-foot contour intervals from reservoir elevation 4,291.0 to elevation

4,370.0 were used as the control parameters for computing the 2002 Pishkun Reservoir capacity.

A surface area was interpolated at elevation 4,375.0 to compute the volumes between elevations

4,370 through 4,375 with the assumption there has been little change since the original

computations.

7
The ACAP85 program can compute an area and capacity at elevation increments 0.01- to 1.0-

foot by linear interpolation between the given contour surface areas. The program begins by

testing the initial capacity equation over successive intervals to ensure that the equation fits

within an allowable error limit. The error limit was set at 0.00000 1 for Pishkun Reservoir. The

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 basic area curve over that interval) is utilized until it exceeds the error

limit. Thus, the capacity curve is defined by a series of curves, each fitting a certain region of

data. By diflèrentiating the capacity equations, which are of second order polynomial form, the

final area equations are derived:

y = a1 + a2x + a3x2

where: y = capacity

x = elevation above a reference base

a1 = intercept

a2 and a3 = coefficients

Results of the Pishkun Reservoir area and capacity computations are listed in table 1 and

colunms 4 and 5 of table 2. On table 2, column 3 lists the original capacities. A separate set of

2002 area and capacity tables has been published for the 0.01, 0.1 and 1-foot elevation

increments (Bureau of Reclamation, June 2002). A description of the computations and

coefficients output from the ACAP85 program is included with these tables. Both the original

and 2002 area-capacity curves are plotted on figure 6. As of June 2002, at elevation 4,375.0, the

surface area was projected to be 1,741 acres with a total computed capacity of 54,852 acre-feet.

2004 RESERVOIR ANALYSES

Results of the 2002 Pishkun Reservoir area and capacity computations are listed in table 1 and

columns 4 and 5 of table 2. Column 3 of table 2 lists the original capacity values for Pishkun

Reservoir and column 6 lists the capacity differences between the original and 2002

computations. Figure 6 is a plot of the Pishkun Reservoir capacity values for the two surveys

and illustrates the very small differences. These comparisons show that the total reservoir

capacity in 2002 is slightly greater in volume than the original published volume.

Research into the original values found surface areas and capacity curves along with an active

storage table dated June 6, 1940. The curves are presented on drawing number 28-600-1 dated

August 28 of 1942. Notes on the drawing indicate the curves represent visual capacity values

with a dead storage of 16,250 acre-feet. No other history on how these values were developed

was located.

The 2002 investigation found that the total drainage area into Pishkun Reservoir is around 9.7

square miles and all considered sediment contributing. The main source of water inflow is from

diversions and it is assumed this also contributes a small amount of sediment inflow. Due to the

unknowns of the original values, there are no means from the 2002 survey results to estimate

how much sediment has deposited within the reservoir since dam closure.
It is the general conclusion the small difference between the original and 2002 surveys is more

due to the differences in the detail of the two surveys and than due to sediment inflow. The 2002

survey is of sufficient detail in the underwater portion to represent the current volumes, but if a

more accurate representation is needed for the total reservoir, then more detailed collection is

needed in the above water area above elevation 4,370.

REFERENCES

American Society of Civil Engineers, 1962. Nomen clature for Hydraulics, ASCE Headquarters,

New York.

Bureau of Reclamation, 1981. Project Data, Denver Office, Denver CO.

Bureau of Reclamation, 1985. Surface Water Branch, ACAP85 User's Manual, Technical

Service Center, Denver CO.

Bureau of Reclamation, 1987(a). Guide for Preparation of Standing Operating Procedures for

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

Bureau of Reclamation, 1987(b). Design of Small Dams, U.S. Government Printing Office,

Denver CO.

Bureau of Reclamation, June 2002. Denver Office, Pishkun Reservoir Area and Capacity

Tables, Sun River Project, Great Plains Region, Billings, MT.

Corps of Engineers, January 2002. Engineer and Design - Hydrographic Surveying,

EM 1110-2-1003, Department of the Anriy, Washington DC,

(www.usace.army.mil/inetlusace-docs/eng-manuals/em 1110-2-1 003/toc.htm).

Environmental Systems Research Institute, Inc. (ESRI), 1992. ARC Command References.

9
RESERVOIR SEDIMENT

DATA SUMMARY Pishkun Reservoir

NAME OF RESERVOIR 1

DATA SHEET NO.

0 1. OWNER LOreuu RinatiGn 2. STREAM Off Stream 3. STATE Montana

A 4. SEC. 10 TWO. 22 N LANCE 7 H S. NEAREST P.O. Augusta 6. COUNTY Teton

F 7. DAT 47 t' LONG :T,2 29 48" 4. TOP OF DAM ELEVAT ION 4,380.0- 9. SPILLWAY CREST EL NA

R 10. STORAGO 11. ELEVAT: DN 12. ORIGINAL 13. ORIGINAL 14. GROSS 15. DATE

E ALLOCATION TOP OF POOL SURFACE AREA, AC CAPACITY, AF STORAGE ACHE- STORAGE

s

FEET BEGAN

E a. SURCHARGE ___________________ _________________ ___________________

R

b. FLOOD CONTROL

__________________

___________________ _________________ ___________________ 1/30 V

__________________

C. POWER _________________ ________________ _________________

0

z

0. JOINT USE

________________

_______________ ______________ ________________

16. DATE

R e. CONSERVATION 4,37C.U' 1,550 30,420 46,570 NORMAL

OPERATION

8. INACTIVE

g. DEAD 4,342.0 __________________

16,250 15,250 _____________

-

17. LENGTH OF RRSF.SVOTIR .7 Miles AVG. WIDTH OF RESERVOIR 1.4 MILES

B 18. TOTAL DRAINAGE AREA 9. 7 SQUARE MILES 22. MEAN ANNUAL PRECIPITATION l7.74 INCHES

A 19. NET SEDIMENT CONTP,:BUTING AREA 9.7 SQUARE MILES 23. MEAN ANNUAL RUNOFF INCHES

20. LENGTH MILES AV. WIDTH 24. MEAN ANNUAL RUNOFF 227,2406 ACRE-FEET

21. MAX. ELEVATION WIN. ELEVATION 25. ANNUAL TEMP. MEAN 4SF RANGE -49"F to 10SF4

S 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

R

V April, 1940 1,5S0 46,670 0.2

Y

6/02 Contour D) 1-ft l,522 46,694 0.2

O 26. DATE OF 34. PERIOD 39. PERIOD WATER INFLOW, ACRE FEET WATER INFLOW TO DATE, AF

A SURVEY ANNUAL

T PRECIP.

_____________

a. MEAN ANN.

_______________

b. MAX. ANN.

____________

C. TOTAL

__

a. MEAN ANN. b. TOTAL

A ______________________________________________ _______________________________

6/02 227,240' 322,888 12,725,500 227,240 12,729,900

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

SURVEY

a. TOTAL J

b. AV. ANN. J

C. /MI.-YR. a. TOTAL b. AV. ANNUAL C. /MI.-YR.

6/02

26. DATE OF 39. AV. DRY 40. SED. DEP. TONS/MI."-YR. 41. STORAGE LOSS, PCE. 42.

SURVEY WV. (# / FT __________________

a. PERIOD

_________________

0. TOTAL TO a. AV. b. TOTAL TO a. J

b.

6/02

26. 43. DEPTH DESIGNATION RANGE BY RESERVOIR ELEVAT:ON

DATE OF

SURVEY

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION H

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

0-10 10-

20

20-

30

30--

40

40-

50

50-

60

60-

70

70-

80

80-

90

90-

100

100-

1CS

105-

110

110-

119

115-

120

120-

129

PERCENT OF TOTAL SEDIMENT LOCATED W:THIN REACH DESIGNATION

Table 1. - Reservoir sediment data surrary (page 1 of 3)

10
45. RANGE SM RFCAVSTR OPERATION

YEAR FOX. ELEV. FIN. ELEV. INFLOW, AR YEAR MAX. ELEV, MIN. ELEV. INFLOW, AF

1946 1947 4371.0 4360.5 182,930

1948 iU. 4360.0 116,107 1949 4311.2 4360.5 220,479

1953 49/0.5 4360.0 157,727 1951 4370.9 4351.8 153,356

1952 _____________

4350.5 210,961 1953 4371.1 4356.0 160,020

1954 47.4 4362.4 225,145 1955 4368.1 4360.2 156,923

1956 4 . 4359.7 197,060 1957 4370.2 4366.5 205,233

1958 21 4355.5 193,251 1959 4359.5 4355.2 197,142

1960 4.'11.5 4349.7 229,238 1161 4368.2 4358.7 275,720

1962 11.9.7 436C.1 250,475 1953 4370.2 4360.8 763,416

1154 4970.6 4359.9 260,338 1965 4370.3 4352.4 214,629

1965 4 /12.5 4355.2 269,930 1967 4371.1 4351.0 217,554

1965 4970.5 4359.7 279,359 1969 4370.1 4359.5 292,238

1970 4370.5 4355.7 273, 119 1971 4370.5 4360.1 322,885

1972 4570.5 4360.5 303,857 1973 4370.9 4347,0 246,037

1974 4371.0 4346.7 305,852 1975 4371.0 4359.9 183,987

1976 '1959.5 4358.7 265,424 1977 4370.6 4354.4 197889

1978 4970.5 4361.6 212,457 1979 4370.0 4362.2 253,364

1980 4370.8 4350.8 204,935 1981 4370.3 4362.1 241,006

1982 437011 4359.1 196,993 1983 4370.0 4355.9 228,313

1984 4359.6 4356.7 254,164 1985 4370.8 4356.4 230,172

1986 4369.4 4357.5 216,442 1987 4371.1 4360.5 218,437

1988 4368.0 4344.5 227,391 1989 4367.8 4351.4 191,043

1990 4370.1 4361.2 239,904 1991 4370.2 4316.4 235,949

1992 4359.0 4361.2 251,807 1993 4369.6 4353.5 152,653

1994 4368.6 4342.0 219,889 1995 4370.3 4342.0 216,032

1996 4369.9 4357.5 259,579 1997 4370.9 4360.0 239,947

1998 4370.9 4361.7 263,155 1999 4370.37 4357.8 270,251

2000 4370.5 4351.8 263,573 2001 4370.86 4359.9 224,711

2002 4370.2 4356.5 234,896

___________

45. ELEVATION AREA - CAPACITY DATA FOR 2002 CAPACITY'°

ELEVATION AREA CAPACITY ELEVATION AREA CAPACITY ELEVATION AREA CAPACITY

4,290 0 0 4,291 5 3 4,292 47 29

4,293 57 80 4,294 64 141 4,295 71 209

4,296 78 283 4,297 84 364 4,298 89 451

4,299 94 542 4,300 100 640 4,301 106 742

4,302 111 850 4,303 118 965 4,304 124 1,085

4,305 134 1,214 4,306 143 1,353 4,307 152 1,500

4,308 161 1,657 4,309 170 1,822 4,310 180 1,997

4,311 110 2,182 4,312 199 2,376 4,313 210 2,590

4,314 221 2,798 4,315 234 3,023 4,316 248 3,264

4,317 261 3,519 4,318 277 3,788 4,319 292 4,072

4,320 327 4,382 4,321 348 4,719 4,322 366 5,075

4,323 382 5,451 4,324 400 5,842 4,325 417 6,250

4,326 434 6,676 4,327 453 7,120 4,328 472 7,582

4,329 494 8,065 4,330 516 8,569 4,331 536 9,095

4,332 552 9,540 4,333 566 10,199 4,334 580 10,772

4,336 598 11,361 4,336 619 11,969 4,337 639 12,598

4,336 656 13,246 4,339 675 13,911 4,340 691 14,594

4,341 707 15,293 4,342 723 16,008 4,343 739 16,739

4,344 756 17,486 4,345 776 18,252 4,346 797 19,039

4,347 816 19,845 4,348 836 26,672 4,349 857 21,518

4,350 882 22,388 4,351 906 23,282 4,352 930 24,200

4,353 956 25,143 4,354 988 26,115 4,358 1,023 27,120

4,356 1,061 25,152 4,357 1,100 29,242 4,358 1,142 30,363

4,359 1,187 31,528 4,360 1,230 32,736 4,361 1,273 33,988

4,362 1,316 35,283 4,363 1,355 36,618 4,364 1,385 37,988

4,365 1,408 39,386 4,366 1,422 40,803 4,367 1,447 42,241

4,368

4.375

1,456

1.741

43,730

54.852

4,369

_

1,497

____________

45,185.

___________

4,370 5,822 46,694

Table I. Reservoir sediment data summary (page 2 of 3)

II
47. REMARt(S AND nEFERENCES

Al elevaton,; of dikes arm in feet. end based on the orIginal project datum established by Reciamation that

were founc .irin 2002 survey to be urcund 1.4 feet less then the NAVDSS. Orginai constructIon 1930 31.

Eniarged in :)40.

An offstrea 'rvo:r witn no api1lwy.

Origna1 vi u. capacity base on enlargement of the reservoir completeo it Aprl 1940. 2002 area and

capacity fr 2202 underwater survey. 2002 surface area at elevatIon 4370 from a digitized USGS cuad mac.

Western Re Cmte Center cute for Station 2434f9 Gibson Dam, Montana

No calculat '1 nce majority of inflow from diversions. See remark

Annual comg d onflws by water yea:, tror 1947 tnrcugn 2002. Inflows from P:shkur dra:nege and overted

flows from te Cur River tnrouqr tnt DJiaw Creek Feeder Canal which stems from tne Piahun Suppy Canal.

Surface are. e capacty computed by ACAF program. Area ano capacity values anove elevation 470 were

.nterpolat'- uuing orig:nal capacIty vIues.

Annual Recl.reton computed inS lowe by water year, from 1947 through 2002. Inflows from ?:shkun drainage

and dvertec1 flowo from the Sun R1ver througn the Willow Creek Feeder Canal. Maximum and minimum elevations

availaole f:om R&clsmatiOn end of the rnontn water year records.

No computed v:lume change. Difference duo to some sediment inflow and different method of surveys.

Expect lit:I unange due to sedinent inflow since Pishkun is an offstrearr reservoir.

Capacities computed ay Reclamat.on' a AOAF computer program.

48. AGEECY MAKING SCAVEY Bureau of Reclamation

49. AGENCY SUPPLYING DATA Bureau of Reclamat:on DATE June 2005

Tabie i. Reservoir sediment data summary (page 3 of 3).

12
Table 2. - Summary of 2002 survey results

3 4 5 6 7

Elevations Original Original 2002 2002 2002 Percent of

L1

Survey

.LcsI

Capacity --

(acre-feet)

Survey

Ls1

Survey

Lacre-feet>

Volume Reservoir

Deth

4375 54827 1741 54852 -25 100.0

4370 1550 46670 1522 46694 -24 94.1

4365 39289 1408 39385 -96 88.2

4360 32833 1230 32736 97 82.4

4355 27349 1023 27120 229 76.5

4350 22624 882 22388 236 70.6

4345 18496 776 18252 244 64.7

4342 16250 723 16008 242 61.2

4340 691 14594 58.8

4335 598 11361 52.9

4330 - 516 8569 47.1

4325 -

417 6250 41.2

4320 327 4382 35.3

4315 234 3023 29.4

4310 180 1997 23.5

4305 - 134 1214 17.6

4300 100 640 11.8

4295 -

71 209 5.9

4290.5 0 0 0.6

1 Elevation of reservoir water surface.

2 Original surface area values for complete reservoir not located. Drawing

No. 28-600-1, Pishkun Reservoir Area and Capacity Curves.

3 Original reservoir capacity from June 1940 capacity

table (16,250 AF Inactive storage).

4 Reservoir surface area from 2002 survey.

5 Reservoir capacity computed from 2002 surface areas using ACAP.

6 Measured volume difference = column (3) - column (5). -

7 Depth of reservoir expressed in percentage of total depth of 79 feet.

13
2 2

\

4L

I

\\\ \\\\

\ ' = 4

/

=

\\

- -

= -

m

m

,

Taxr

,PP'?OV[D

______ ____ ____ ____ _____ ____________ ______________ _____ ___________ __________ _________

Oerer,Co/ro1o J1/NOJ,OO5

15

Figure 5. - Pishkun Reservoir topographic map.
1800

4380 -

4370

4360

4350

4340

>

w

4330

4320

4310

4300

4290 --

0

0

4380

4370

4360

4350

4340

4330

4320

4310

4300

_ _ - --- -- 4290

5500 11000 16500 22000 27500 33000 38500 44000 49500 55000

Capacity (acre4eet)

Figure 6. - 2002 area and capacity curves

Area-Capacity Curves for Pishkun Reservoir

Area (acres)

1620 1440 1260 1080 900 720 540 360 180