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Tiber Reservoir -Lake EIweII

2002 Survey

U.S. Department of the InterIor

Bureau of Reclamation

Technical Service Center

Denver, Colorado September 2005
REPORT DOCUMENTATION PAGE Form Approved

_____________________________________________________________

0MB No. 0704-01 88

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

Sepienther_2005 Final __________________________________________

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Tiber Reservoir Lake Liwell

2002 Survey PR

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

II SUPPLEMENTARY NOTES

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

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

13. ABSTRACT (Maxiniu,n 200 v'ords)

The Bureau of Reclamation (Reclamation) surveyed Tiber Reservoir in June and July of 2002 to develop new

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

survey, conducted between reservoir elevation 2,991.9 (feet) and 2,995.4, 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 contour lines from the U.S. Geological Survey quadrangle

(USGS quad) maps and the reservoir water surface from a 2003 aerial survey of the reservoir (elevation 2,991.6).

As of July 2002, at joint use elevation 2,993.0, the surface area was 18,275 acres with a total capacity of 925,649

acre-feet. At maximum reservoir elevation 3,020.2 feet, the surface area was 25,407 acres with a total capacity of

1,515,522 acre-feet. Since initial filling in October of 1956, about 42,179 acre-feet of capacity loss has occurred

below elevation 2,993.0. A large portion of this loss is due to extensive shoreline erosion throughout the reservoir.

14. SUBJECT TERMS 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)

Prescribed by ANSI Std. 239-18

298-102
Tiber Reservoir -Lake EIweII

2002 Survey

Prepared by

Ronald L. Ferrari

ad

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 September 2005
ACKNOWLEDGMENTS

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

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

repOrt. Ronald Ferrari, Sharon Nuanes. and Tom Pruitt of TSC conducted the underwater

data collection. Ron Ferrari and Sharon Nuanes completed the data processing needed to

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

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

peer review of this documentation.

UNITED STATES DEPARTMENT OF THE

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.

ii
CONTENTS

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I'age

Introduction .

Summary and Conclusions .

Reservoir Operations 6

Hydrographic Survey Equipment and Method 6

Shoreline Erosion 8

Tiber Dam Datum 11

Multibeam Analysis 11

Reservoir Area and Capacity 12

Topography Development 12

Development of 2002 Contour Areas and Reservoir Volume 13

2002 Reservoir Analyses 14

References 15

TABLES

Table

I Reservoir sediment data summary (3 pages) 16-18

2 Tiber Reservoir 2002 Survey Summary (5 pages) 19-23

FIGURES

Figure

1 Tiber Dam location map 1

2 Lower Marias Unit of the Pick-Sloan Missouri Basin Project- Tiber Dam Plan 2

3 Lower Marias Unit of the Pick-Sloan Missouri Basin Project - Tiber Dam Sections 3

4 Survey vessel with mounted hydrographic equipment on Jackson Lake in Wyoming 7

5 Multibeam collection system 7

6 Eroded Material Forming a Shelf 9

7 Large Areas of Erosion Occurring Above Maximum Water Surface 9

8 Recent Eroded Material That Has Not Moved Further Into Reservoir 10

9 Eroded Bank Where the Eroded Material Has Deposited Below the Water Line 10

10 Tiber Reservoir topographic map 1 25

11 Tiber Reservoir topographic map 2 27

12 Tiber Reservoir topographic map 3 29

13 Tiber Reservoir topographic map 4 31

14 Tiber Reservoir topographic map 5 33

15 Tiber Reservoir topographic map 6 35

16 Tiber Reservoir topographic map 7 37

17 Tiber Reservoir topographic map 8 39

18 Tiber Reservoir topographic map 9 41

19 2002 area and capacity curves 43

111
Hungry Horsy , Lake Sherburne 

Clark C 

1 i kes 

\ Yellowtail Afterboy 

Yellowtail 

Figure 1 - Tiber Dam Location Map. 

Settlement of the spillway crest of Tiber Dm began following initial filling of the reservoir in 

1956. Reservoir operating level restrictions were imposed to safeguard the structure until 

repaired. The rate of settlement became more alarming following a 1964 flood. Measures to 

protect the structure were approved by Congress and initial construction began in 1967 with 

completion in 1970. The work consisted of modifying the canal outlet works for use as an 

auxiliary outlet works and closing the entrance channel of the spillway by a temporary earthfill 

cofferdam. For additional protection, the reservoir operating criteria was further revised and the 

active capacity was eliminated. Additional work was completed, 1976-8 1, that included 

replacing the upstream section of the spillway and raising the dam 5 feet (figures 2 and 3). 

Beginning in 1982, and continuing through 1983, Tiber Reservoir was filled to its original design 

capacity of elevation 2,993.0 feet and normal reservoir operations were restored. 
Space intentionally left blank due to security concerns 
Space intentionally left blank due to security concerns 
Tiber Reservoir is formed by Tiber Dam along with a dike that closes a saddle on the south rim

of the reservoir near the dam. The earthfihl dike is 16,650 feet long and has a maximum height

of 65 feet. The dam is a zoned earthfill structure whose dimensions are:

Hydraulic height1 189 feet Structural height 206 feet

Top width 45 feet Crest length 4,300 feet

Crest elevation 3,026 feet2

The spiliway, crest elevation 2,975, is located on the right abutment. The flows are controlled by

three 22- by 38-foot radial gates with top of gate elevation 3,012.5. The spiliway capacity is

68,470 cubic feet per second (cfs) at reservoir elevation 3,020.2.

The River Outlet Works (ROW) through the right abutment contains two discharge pipes, 22-

and 72-inch diameters that are controlled by a 24-inch gate value and a 5.0-foot square highpressure gate respectfully. The discharge capacity is 65 cfs for the 22-inch pipe and 1,540 cfs for

the 72-inch pipe at reservoir elevation 3,020.2.

The 22-inch diameter outlet pipe with 24-inch gate valve and 1 8-inch butterfly valve (BFV) has

not been operational since completion of the dam. The existing hydraulic operating system is

inadequate to operate the upstream, gate valve due to excessive friction losses in the piping

system. The Montana Area Office is planning to convert the 22-inch outlet pipe into a

ventilation system in 2006.

In 2003-2004, the ROW underwent extensive modification to incorporate the addition of a

Federal Energy Regulatory Commission (FERC) 7.5 MW powerplant, privately owned by Tiber

Montana, LLC. A bifurcation pipe was installed in the ROW tunnel at the downstream end to

divert flow from the existing 72-inch outlet pipe through a bifurcation and 96-inch BFV to the

powerplant. Releases from the regulating gate and powerplant enter directly into the ROW

stilling basin.

Under normal operation, river releases up to about 700 cfs will be primarily through the 7.5MW

FERC powerplant. River flows greater than 700 cfs will normally be released through the

auxiliary outlet works. However, if the auxiliary outlet works is not available for use, flows in

excess of the powerplant capacity are released through a combination of the ROW regulating

gate and powerplant.

An auxiliary outlet works, constructed as part of the safety of dams modification, is located

through the left abutment of the dam. The auxiliary outlet is controlled by a 7.25- by 9.25-foot

outlet gate with a capacity of 4,240 cfs at reservoir elevation 3,020.2.

'The definition of such terms as hydrauIic height," "structural height," etc. may be found in manuals such as Reclamation's

Design of Small Dams and Guidefor Preparation ofStanding Operating Procedures for Dams and Reservoirs, or ASCE's

Nomenclature for Hydraulics.

2Elevations in feet. All elevations based on the original project datum established by U.S. Bureau of Reclamation that was

determined to be 2.9 feet lower than the North American Vertical Datum of 1988 (NAVD88).

4
The drainage area above Tiber Dam is approximately 4,375 square miles and all is considered

sediment contributing. The reservoir, at elevation 2,990.0, is about 44 miles in length with an

average width of 1.6 miles. The total length includes 35 miles of the Marias River arm and 9

miles of the Willow Creek arm.

SUMMARY AND CONCLUSIONS

This Reclamation report presents the 2002 results of the survey of Tiber Reservoir. The primary

objective of the survey was to gather data to:

develop reservoir topography

compute area-capacity relationships

estimate storage depletion since dam closure

Prior to the underwater collection, the hydrographic survey crew conducted a RTK GPS survey

utilizing horizontal and vertical control established by the National Geodetic Survey (NGS) for

datum point "Tibi." This point is located near the dam and is not a high-order vertical datum.

Other NGS datums in the surrounding area found elevations in NAVD88 to be around three feet

higher than elevations in NGVD29. The 2002 hydrographic survey found the vertical project

datum established by Reclamation during construction to be 2.9 feet lower than NAVD88

assigned to "Tibi". All elevations are in feet and referenced to Reclamation's project vertical

datum.

The underwater survey, June and July of 2002, was conducted between reservoir elevation

2,991.9 and 2,995.4. The bathymetric survey used sonic depth recording equipment interfaced

with a RTK GPS capable of determining sounding locations within the reservoir. The system

continuously recorded depth and horizontal coordinates of the survey boat as it navigated along

grid lines covering Tiber Reservoir. The positioning system provided information to allow the

boat operator to maintain a course along these grid lines. The reservoir's water surface

elevations, recorded by the Reclamation reservoir gauge during the time of collection, were used

to convert the sonic depth measurements to reservoir bottom elevations. These gauge elevations

are tied to the Reclamation project datum.

The above-water area of Tiber Reservoir was developed by digitizing the developed contour

lines from the USGS quad maps and the reservoir water surface from rectified aerial photographs

flown July 4, 2003 at reservoir elevation 2,991.6. The 2003 aerial survey covered the entire

reservoir and provided valuable information about the extensive shoreline erosion that has

occurred on Tiber Reservoir.

The final 2002 Tiber Reservoir topography is a combination of the 2003 aerial water surface

contour, the USGS quad contours, and the 2002 underwater collected data. A computer graphics

program generated the 2002 reservoir surface areas at predetermined contour intervals from these

combined data sets. The 2002 area and capacity tables were generated by a computer program

that used the measured contour surface areas and a curve-fitting technique to compute area and

capacity at prescribed elevation increments (Bureau of Reclamation, 1985).

5
Tables 1 and 2 contain summaries of the Tiber Reservoir and watershed characteristics for the

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

925,649 acre-feel and a surface area of 18,275 acres at joint use reservoir water surface elevation

2,993.0. Since closure in October of 1957, the reservoir has an estimated volume change of

42,179 acre-feet below reservoir elevation 2,993.0. This volume represents a 4.4 percent change

in total capacity at this elevation.

RESERVOIR OPERATIONS

Tiber Dam operates to provide regulated flows downstream on the Marias River. The July 2002

capacity table shows 1,515,522 acre-feet of total storage below the maximum water surface

elevation 3,020.3. The 2002 survey measured a minimum lake bottom of around elevation

2,839. The following values are from the July 2002 capacity table:

• 186,799 acre-feet of surcharge between elevation 3,012.5 and 3,020.2

• 403,074 acre-feet of flood control between elevation 2,993.0 and 3,012.5.

• 258,436 acre-feet ofjoint use between elevation 2,976.0 and 2,993.0.

• 112,883 acre-foot of conservation storage between elevation 2,966.4 and 2,976.0.

• 534,709 acre-foot of inactive storage between elevation 2,870.0 and 2,966.4.

• 19,621 acre-foot of dead storage below 2,870.0.

Tiber Reservoir computed annual inflow and reservoir stage records are listed by water year on

table 1 for the operation period 1956 through 2002. The inflow values were computed by the

regional office and show annual fluctuations with a computed average inflow of 618,300 acrefeet per year. The maximum reservoir elevation was 3,005.6 in 1965 with a minimum elevation

of 2,953.8 in 1968.

HYDROGRAPHIC SURVEY EQUIPMENT AND METHOD

The hydrographic survey equipment was mounted in the cabin of a 24-foot trihull aluminum

vessel equipped with twin in-board motors (figure 4). The hydrographic system included a GPS

receiver with a built-in radio, a depth sounder, a helmsman display for navigation, a computer,

and hydrographic system software for collecting the underwater data. An on-board generator

supplied power to all the equipment. The shore equipment included a second GPS receiver with

an external radio. The GPS receiver and antenna were mounted on a survey tripod over a known

datum point and a 12-volt battery provided the power for the shore unit.

The Sedimentation and River Hydraulics Group uses RTK GPS with the major benefit being

precise heights measured in real time to monitor water surface elevation changes. The basic

output is from a RTK receiver are precise 3D coordinates in latitude, longitude, and height with

accuracies on the order of 2 centimeters horizontally and 3 centimeters vertically. The output is

on the GPS datum of WGS-84 that the hydrographic collection software converted into

Montana's state plane coordinates in NAD83. The RTK GPS system employs two receivers that

track the same satellites simultaneously just like with differential GPS.

6

positioning; a motion reference unit to measure the heave, pitch, and roll of the survey vessel; a

gyro to measure the yaw or vessel attitude; and a velocity meter to measure the speed of sound of

the reservoir water column. With the proper calibration, the data processing software utilizes all

the incoming information to provide an accurate detailed x, y, z data set of the lake bottom.

The Tiber Reservoir bathymetric survey collection was conducted in June and July of 2002

between water surface elevation 2,991.9 and 2,995.4 (Reclamation project datum). The survey

was run using the multibeam instrumentation described above where the survey system software

continuously recorded reservoir depths and horizontal coordinates as the survey vessel moved

across closely spaced grid lines covering the reservoir area. Most of the transects (grid lines)

were run along the original river alignment to the reservoir where the multibeam swaths

overlapped each other. The multibeam system could have provided full bottom coverage, but

time, budget, and access did not allow this to occur in all the shallow portions of the reservoir.

The loss of these additional data points did not have a significant impact on the area

computations since an extensive above water collection was not conducted for this study.

Additional data. in the upper shallow water reaches of the two inlets was also collected using a

single beam depth sounder. The depth sounder 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-cop.y 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.

Shoreline Erosion

The 2002 underwater survey revealed extensive shoreline erosion throughout the reservoir area.

During collection, the GPS boat positions were found to be at times outside the digitized USGS

quad contour locations indicating the boat was on solid ground. These USGS quad contours

were developed from aerial photography flown in the 1960's and at times, the position of the

boat was tens of feet outside their boundary. In addition, during the 2002 survey a major

windstorm occurred and the crew witnessed vertical sections of the shoreline collapsing into the

reservoir for days after. Even with the extensive shore erosion that has occurred since dam

closure, the survey vessel was able to hug the vertical banks in deep water conditions where

previous shore material had collapsed into the reservoir. It appears that over time the collapsed

material is washed further into the reservoir by the wave action, similar to ocean waves

smoothing the beaches. This is possible because the material dissipates in the water and consists

of little to no rock or large cobble. Following are views showing the shoreline erosion and its

affect on the reservoir, figure 6 through 9, from photographs taken by Sharon Nuanes in 2002.

8


The above photographs show several different stages of the shoreline erosion along the Tiber

Reservoir banks. lithe erosion occurred only below the reservoir high water mark, the total

volume of the reservoir would not he greatly affected. In this case, however, the gain in surface

area and resulting volume in the upper reservoir elevation zone is offset by the loss of surface

area and volume in the lower elevations of the reservoir. The eroded upper elevation shoreline

deposits in the lower elevations of the reservoir. The photographs show the large amount of

shore erosion above the maximum reservoir elevation, meaning that a portion of the loss of the

original total reservoir volume is due to the above reservoir shoreline erosion along with the

incoming river sediments. The only means to accurately measure the extent of the shoreline

erosion would be by an above water aerial survey.

For a vegetation study, an aerial survey was conducted on July 4 of 2003 at reservoir water

surface elevation 2,991 .6. The collected digital aerial photos were rectified, but no above water

contours were developed. As part of this analysis, the 2003 reservoir water surface image was

digitized to compute the surface area at elevation 2,991.6. The 2003 digitized surface area at

reservoir elevation 2,991.6 was 17,935 acres compared to the original computed surface area of

17,472 acres at the same elevation. The 2003 surface area was nearly 500 acres greater,

illustrating the extent of the shoreline erosion that has occurred throughout the reservoir.

Tiber Dam Datum

Prior to the underwater collection, the hydrographic survey crew conducted a RTK GPS survey

utilizing horizontal and vertical control at NGS datum point "Tib 1." Tib 1 is located near the

dam and is not a highly rated vertical control point. Other NGS vertical datums in the

surrounding area show the elevations in NAVD88 to be around three feet higher than the

elevations in NGVD29. The 2002 hydrographic survey found the vertical project datum

established by Reclamation during construction to be 2.9 feet lower than NA\TD88 elevation at

Tib 1. This was an average measured shift from multiple water surface shots compared to the

Reclamation gauge readings. All elevations in this report are in feet and referenced to the

Reclamation project vertical datum or gauge readings at the time of this survey. Following are

the NGS coordinates for "Tibi" used for this survey. The Montana's state plane coordinates are

in NADS3 and elevation in NAVD88.

North 1,486855.785

West 1,578,509.929

Elevation 3,025.51

Multibeam Analysis

The analysis started with processing all the collected raw multibeam bottom profile files. This

included applying all necessary correction information that was collected, such as the roll, pitch,

and yaw effects on the survey vessel. Other corrections included applying the field measured

sound velocity of the reservoir water column. All this information was used when converting all

the corrected depth data to elevations. All elevations in the final analysis were tied to the

Reclamation measured water surface elevation at the time of collection. Due to the massive
amount of data, the data set was filtered utilizing procedures within the collection and analysis

software that logically removed data points without adversely affecting the results. Quality

control and assurance of the data sets were accomplished by conducting field calibration as

required by the multiheam system and collecting velocity profile data for the areas being

surveyed.

RESERVOIR AREA AND CAPACITY

Topography Development

The topography of Tiber Reservoir was developed from the 2002 collected underwater data, the

digitized contours from the USGS quad maps, and the digitized 2003 aerial water surface

contour. The digitized USGS contour lines were used to supplement areas of the reservoir not

covered by the survey vessel due to shallow water conditions. The USGS quad maps were

developed from aerial photography dated in the 1960's because it was the only available data for

certain portions of the reservoir. ARC/INFO geographic information system software was used

to digitize the USGS quad contours. The digitized contours were transformed to Montana's

NAD 1983 state plane coordinates using the ARC/INFO PROJECT command. This same

method was used to digitize the reservoir water surface from the 2003 rectified digital aerial

photographs that were flown on July 4, 2003 at reservoir water surface elevation 2,991.6. These

rectified photographs were part of a vegetation study and no contours were developed. The

aerial water surface image did allow a complete contour to be digitized for the reservoir's water

surface elevation 2,991.6. The 2003 digitized surface area at elevation 2,991.6 was 17,935 acres

compared to the original computed surface area of 17,472 acres. The 2003 surface area was

nearly 500 acres greater due to the extensive shoreline erosion that has occurred throughout the

reservoir.

The digitized 2003 reservoir water surface, elevation 2,991.6, was used to perform a clip of Tiber

Reservoir triangular irregular network (TIN) such that interpolation was not allowed to occur

outside the enclosed polygon. This contour was selected since it was the closest data available to

represent the reservoir water surface at the time the 2002 underwater survey was conducted

(between reservoir elevation 2,992 and 2,995). The clip was assigned an elevation of 2,991.6.

Contours for the reservoir below elevation 2,991.6 were computed from the 2002 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 Users Documentation, (ESRI, 1992).

12
The linear interpolation option of the ARC/INFO TINCONTOUR command was used to

interpolate contours from the Tiher 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 hearing on the computation of surface areas and volumes for Tiber

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 elevation

2991.0 and below. The contour topography at 10-foot intervals is presented on figures 10

through 18.

Development of 2002 Contour Areas and Reservoir Volume

The 2002 contour surface areas for Tiber Reservoir were computed at 1-foot increments from

elevation 2,839.() to 2991.0. 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. For the purpose of this study,

the measured 2002 survey areas at 2-foot increments from elevation 2,839.0 through 2,985.0

were used to compute the new area and capacity tables. Due to the limited amount of 2002

shallow water data, the digitized surface area at elevation 2,991.6 was used to complete the area

and volume computations between elevation 2,985.0 and 2,991.6. Due to the absence of above

water data, this study assumed no change in original area from elevation 3,005.0 and above. The

area and capacity program computes the areas between the elevations by assuming a straight-line

interpolation between the input data set. For the 2002 study, this was the only means to compute

the areas between elevation 2,991.6 and 3,005.0.

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

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

data as described above were used as the control parameters for computing the 2002 Tiber

Reservoir capacity. Since this study did not collect above water data, the measured 2003 aerial

water surface contour area and the original surface areas from elevation 3,005.0 and above were

used to complete the area and capacity tables.

The ACAP8S 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 Tiber 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 a 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. Differentiating the capacity equations, which are of second order polynomial form, the

final area equations are derived:

13
y=a1a2x±a3x

where: y=capacity

x = elevation above a reference base

a = intercept

a and a = coefficients

Results of the Tiher Reservoir area and capacity computations are listed in table 1 and columns 4

and 5 of table 2. On table 2, columns 2 and 3 list the original surface areas and recomputed

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 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 19. As of July 2002, at

maximum reservoir elevation 3,020.2, the surface area was 25,407 acres with a total capacity of

1,515,522 acre-feet.

2002 RESERVOIR ANALYSES

Results of the Tiber Reservoir area and capacity computations are listed in table 1 and columns 4

and 5 of table 2. Columns 2 and 3 of table 2 list the original area and recomputed capacity

values. Column 6 lists the capacity differences between the original and 2002 computations.

Figure 19 is a plot of the Tiber Reservoir surface area and capacity values and illustrates the

differences between the two surveys. Since Tiber Dam closure in 1957, the measured total

volume change at reservoir elevation 2,993.0 is 42,179 acre-feet. The estimated average annual

rate of capacity lost for this period (44.8 years) was 941.5 acre-feet per year. The storage loss in

terms of percent of original storage capacity was 4.4 percent at elevation 2,993.0. The 2002 area

and capacity tables were generated assuming no change in area and capacity, since the original

survey, from elevation 3,005.0 and above. This is in all probability not the case, but the lack of

above water data only allows this assumption. As indicated before, there have been large areas

of shoreline erosion that has occurred above elevation 2,993 and in some areas it appears to have

occurred above maximum reservoir elevation 3,005. The only means to measure this would be

by an aerial topographic survey.

The 2002 survey noted the large areas of shoreline erosion by comparing with the original

contours. The 2003 aerial water surface contour was able to measure the erosion at elevation

2,991.6 that this study found to be around 500 acres. The shoreline erosion has enlarged the

surface area and volume of the upper elevations while decreasing the surface area and volume of

the lower reservoir elevations where the eroded material has deposited. If the shoreline material

only occurred within the reservoir boundary, the overall volume of the reservoir would not

significantly change due to the shoreline erosion. The volume would have redistributed within

the reservoir affecting the reservoir operation levels, but not the total volume. The 2002 survey

visually noted significant erosion above the normal maximum reservoir elevation. This material

has settled within the reservoir along with the inflowing sediments to reduce the original

capacity.

14
During the original planning of Tiber Reservoir, the estimated loss of total capacity of the

reservoir over the first 100 years of operation was 47,000 acre-feet. There is no information on

how this sediment inflow value was determined and what factors were used to compute this

value. The 2002 survey found a current volume loss of 42,179 acre-feet in the first 44.8 years of

reservoir operation below elevation 2,993.0. That is near the total 100-year estimate in less than

half the time, 44.8 years. As stated before, a large part of this volume is due to shoreline-eroded

material that this study is not able to distinguish from inflowing sediment. The 2002 survey

results did measure where the volume loss has occurred as illustrated on item 43 of

table 1. The study found that of the total volume of 42,179 acre-feet, 4.9 percent occurred below

dead storage elevation 2,870, 50.2 percent below inactive reservoir elevation 2,966.4, 22.1

percent below conservation elevation 2,976.0 and 22.8 percent below joint use elevation 2,993.0.

There is no information above elevation 2,991.6 feet to allow computing changes above this

elevation.

A resurvey of Tiber Reservoir should be considered in the future if major sediment inflow events

are observed or if the average annual rate of sediment accumulation requires further clarification.

Due to the extensive shoreline erosion, any new survey should include detailed above water

collection. Comparing the aerial data with the original values would make it possible to measure

the extent of the reservoir shoreline erosion.

REFERENCES

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

New York.

Bureau of Reclamation, 1981. Proj ect Data, Denver Office, Denver CO.

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

Service Center, Denver CO.

Bureau of Reclamation, 198 7(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, July 2002. Denver Office, Tiber Reservoir Area and Capacity Tables,

Lower Marias Unit, Great Plains Region, Billings, MT.

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

EM 1110-2-1003, Department of the Army, Washnigton DC,

(www.usace.army.millinet/usace-docs/eng-manuals/eml 110-2-1 003/toc.htm).

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

15
RESERVOIR SEDIMENT

DATA SUMMARY Tiber Reservoi,r

NAME OF RESERVOIR I

DATA SHEET NC.

D 1. OWNER reoo of Reclamation 2 STREAM Maras River 3 STATE Montana

A 4. SEC. 39 TWL 33) N' RANGE S S 5. NEAREST P.O. Cheater 6. COUNTY Liberty

N 7. OAT 48' 19' 01" LONG 111 0527" 8. TOP CF DAM ELEVATION 3,026.0' 9. SPILLWAY ORES"' EL 2,175.1

R 10. STORAGe 11. ELEVATION 12. ORIGINAL 13. ORIGINAL 14. GROSS 17. DATE

E ALLOCATION TOP OF POOL SURFACE AREA, AC CAPACITY, A? STORAGE ACRE- STDRACE

5 FEET BEGAN

a. SURCHANC3E 3,020.2' 29,414 187,741 1,555,898

R

b. FLOOD CONTROL 3,012.9 23,192 400,838 1,368,157 -

V

, 0/S7

c

C POWER ________________ _______________ ________________ ___________

I

d. JOINT LEA

__________

2,993.0

_____

17,886 267,994 967,319 15. DATE

R e. CONSERVATION 2,976.0 13,787 121,701 599,326 NORMAL

f. INACTIVIS 2,966.4 11,741 555,042 577,624 OPERATION

a. DEAD 2,870.0 1,535 21,582 21,582 _____________

17. LENGTH OF ESSERVOIR 444 Miles AVG. WIDTH OF RESERVOIR 1.5 M:LEs

B 18. TOTAL DRA1NAGE AREA 4,375 SQUARE MILES 22. MEAN ANNUAL PRECIPITATION 10.23' INCHES

A 19. NET SEDIMEN'I' CONTRIBUTING AREA 4,376 SQUARE MILES 23. MEAN ANNUAL RUNOFF 2.551 INCHES

S

20. LENGTH MILES AV. WIDTH 24. MEAN ANNUAL RUNOFF 618,300 ACRE-FEET

21. MAX. ELEVATION MUN. ELEVATION 25. ANNUAL TEMP. MEAN 59.9SF RANGE -53Fto 103'F5

S 26. DATE CF 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

___________________

10/97

_________________

Contour 5-ft 17,896 967,828 1.5

E

Y

7/02 44.8 44.8 Contour D( 2-ft 18,275 925,649 1.5

D 26. DATE OF 34. PERIOD 35. 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

7/02 618,300' 1,167,600 29,060,900 618,300 29,060,900

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

SURVEY ______________ _____________________________________________

a. TOTAL

_______________

b. AV. ANN.

_______________

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

7/02 42,17911 941.5 0.215 42,179 941.5 0.215

26. DATE OF 39. AV. DRY 40. SED. DEP. TONS/MI.:YR. 41. STORAGE LOSS, PCT. 42.

SURVEY MT. /FT') ______________ ___________________________________________

a. PERIOD j

______________

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

7/02 00911 4411

26. 43. DEPTH DESIGNATION RANGE BY RESERVOIR ELEVATION

DATE OF

SURVEY 2525-

2870

2870-

2966

2965-

2976

2976

2993

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

4.9 50.2 22.1 22.8

26. 44. REACH DESIGNATION PERCENT OF TOTAL oR:GINAL LENGTH OF RESERVOIR

SVEY 0-16 10-

20

20-

30

30-

40

40-

50

50-

60

60-

70

70-

80

80-

90

90-

100

100-

105

105-

110

110-

115

115-

120

120-

125

PERCENT OF TOTAL SEDIMENT' LOCATED WITHIN REACH DESIGNATION

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

16
45. RANGE IN R5.9RVC 5, ..

YEAR MAX '51V 80N. E'.EV. IN'FLOE, AR YEAR 'IRE. ELEV. MIN. ELEV. JX".OW, AR

1956 ______________ _____________

,.54,"5' 1587 2982.5 2969.2 0,,575

1958 . 94 272. 0 ',5,,P' 950 298.5 2971.3 '8,007

1960 '.. 20 . / 1 1951 2984.2 2072.5 13, 920

1962 2 7. 482,48 19,3 2980.0 2971.2 3)2,538

1964 0',. 2.73. 0 372,7'4 1968 3005. 2975.2

955 S' I. 27".8 79 1067 2984.8 2855.1

955 .75.' 2'.F , ,i37 959 2975.2 2956.3 71,280

1970 2; .. 2752. 0 •,i2, 70 1971 2)75.4 2967.4 /75, 927

1972 257 '. 2360.. 025,408 1973 2970.2 2960.8 341,915

1974 ,.1/ '. 2i1.E u04, .OC 1875 2993.9 2960.0 1.7,90,

1970 ,9/,,.. 205.1 784,703 1077 2969.4 2960.' 2 3,57

1978 297,. 29,2.9 768,800 079 2980.2 2961.2 71,744

1980 29'O .3 2962.9 570,79 1981 2972.5 2959.4 u0,330

1982 2978.0 2953.7 75,8E3 1983 2983.7 2975.2 300,728

1984 20/7.5 2073.7 254, )4 1985 2989.3 2975.2 357,556

1986 100..'. 207'?. 720,087 1)87 2988.5 2976.7 508,358

1988 2984.7 2075.0 27,22, 1989 2989.4 2973.3 641,313

1990 2/72. 2980. 740,777 1991 2995.5 2974.9 927,078

1992 2983.3 2974.8 204,349 1993 2991.2 2976.6 513,396

1994 2091.8 2979.7 540,830 1995 2995.3 2979.0 754,503

1996 '5,5,, 298?.' 977,705 1907 2995.5 2978. 843,373

1998 2932.7 2901.2 428,5.2 .999 2990.3 2975.6 434,990

2000 2)qS.0 2952.5 336,20) 2001 2983.4 2976.2 20, 948

2002 2970.5 1574,1 '1 &, 20

46. ELEVATION AREA - CAPACITY DATA FOR 2002 CAPACIY12

ELEVATION AREA CAPACITY ELEVATION AREA CAPACITY ELEVATION AREA CAPACITY

2,839 0 0 2,840 0 0 2,841 5. 0

2,842 4 3 2,843 8 9 2,844 30 25

2,045 51 68 2,846 92 140 2,847 134 253

2,848 15 413 2,849 238 625 2,650 290 687

2,851 341 _,204 2,852 405 1,577 2,852 468 2,014

2,854 549 2,523 2,855 529 3,112 2,850 91 3,772

2,857 753 4,404 2,858 812 5,277 2,859 871 8,118

2,860 928 7,017 2,861 986 7,974 2,862 1,046 8,990

2,863 ,106 :0,066 2,8o4 1,153 11,211 2,855 1,260 12,432

2,866 1,338 13,731 2,867 1,416 15,108 2,868 1,477 16,555

2,859 1,536 18,061 2,870 1,582 19,621 2,871 1,628 21,225

2,872 1,577 22,879 2,873 1,725 24,580 2,874 1,777 26,329

2,875 1.521 28,126 2,87, 1,089 29,981 2,877 1,95o 31,903

2,878 2,023 33,893 2,879 2,090 35,950 2,880 2,164 38,077

2,881 2,238 40,278 2,882 2,327 42,560 2,883 2,417 44,933

2,884 2,617 47,400 2,885 2,818 49,967 2,886 2,701 52,627

2,887 2,768 55,369 2,888 2,852 58,188 2,889 2,919 61,073

2,890 2,992 64,029 2,091 3,064 67,056 2,892 3,134 70,156

2,893 ,205 73,325 2,804 ',271 76,563 2,895 3,33, 79,856

2,896 3,405 83,237 2,897 3,473 86,67, 2,898 3,540 90,187

2,899 3,524 93,773 2,900 3,708 97,439 2,901 3,792 101,189

2,902 3,8,7 105019 2,903 3)42 108,923 2,904 4,020 12,904

2,905 4,098 116,963 2,906 4,178 121,101 2,907 4,258 125,319

2,908 4,327 129,,2 2,909 4,397 132,974 2,710 4,473 138,409

2,911 4,880 142,921 2,912 4,627 147,509 2,913 4,703 152,174

2,914 4,785 156,918 2,915 4,867 161,745 2,915 4,q50 55,661

2,917 5,064 171,676 2,918 5,188 176,792 2,919 5,272 182,013

2,920 5,377 187,337 2,921 6,483 192,768 2,922 5,580 198,299

2,923 5,677 203,928 2,924 8,777 209,655 2,925 6,877 215,482

2,926 5,962 221,402 2,927 6,048 227,407 2,928 6,147 233,504

2,929 5,246 239,701 2,930 6,350 245,999 2,931 6,454 252,400

2,932 6,567 258,9 2,933 5,580 2o5,538 2,934 6,792 272,27:

2,935 8,934 279,119 2,936 7,009 286,075 2,937 7,114 293,136

2,938 7,224 300,305 2,939 7,'34 307,584 2,340 7,444 34,972

2,94: 7,563 322,471 2,942 7,657 330,076 2,943 7,760 337,754

Table 1. - Reservoir sedioent data summary (page 2 of 3)

1/
2,944 .76 2,44 7, 951 '53,524 2, 45 2,1:2 351,575

2,947 .54 3o9,7 ,042 B,46 378,101 2,947) 9,59., 38r, 569

2,950 , '45, 7l ''451 s,so:' 403,906 2,952 8, :' 412,772

2,953 ', ,' 2,7S4 , 394 i, 7) 430,677 2,958 7, 440,103

2,95o 109 449,447 2, 9'7 '', 458,908 2,958 ),oS" 458,49

2,959 .7' 478,22., 2, 9,6 1, 905 488,087 2,931 10,054 498,075

2,962 .2 tOE, 95 2,Oo' 16,7 3 58,443 2,954 10,41 328,624

2,965 f' ,9,, '44 3,, ,6,7'3 550,013 2, 67 0, 71, 5,0,25

2,968 ,' 57,957 9 ,,,2 2 583,037 2,770 11,i5 594,429

2,971 7, i. 05,O,,' ,7: :3,'47 617,020 ,'f73 12,63: J20,9c

2,974 2, '2 242,1'S ,'7 l,iO o54,602 2, '7c, 12,70 t57,2

2,977 980,02' 2,17 13,_SI 573,054 2,979 13,39' 706,32,

2,980 '.7:7 71,88u, 2, 2: 14,U.,1 733,779 2,982 14,232 747,953

2,983 4, 7:2,350 .1, .4,7z9 776,976 2,985 14,"41 791,813

2,986 1', f) 80s,)E1 ,')7'1 15,84s 822,603 2,986 16,302 638,578

2,989 1,75' 85,20 2, ,9' 17,209 872,182 29)7. l7,C2 829,524

2,992 1,03.' 907,496 2,997 :8,275 925,649 2,994 18,617 944,045

2,995 77,76 9s2,58' 2,89' 19,003 991,566 2,997 19,246 1,000,690

2,998 1,48) 1,020,058 2,73') 13,732 1,039,665 3,000 19,778 1,359,521

3,001 26,218 1,079,517 3,002 20,4,0 1,099,950 3,763 20,703 1,120,538

3,004 20,94 l,4l,33 9,099 21,123 1,162,431 3,005 21,451 1,183,750

3,007 2 .712 .,20,,332 ',002 21,974 1,227,175 3,009 22,235 1,249,279

3,010 22,497 1,271,64o 7,011 22,7,4 1,294,275 3,012 23,031 1,317,174

3,013 23,293 1,340,339 3,014 23,5r6 1,363,771 3,015 23,633 1,387,471

3,Ole 24,3h l,4l1,45o 7,0,7 24,443 1,435,746 3,618 24,747 1,460,341

3,019 25,052 1,485,241 3,020 25,357 1,510,446 3,020.2 25,407 1,515,522

47. REMARKS AND REFERENCES

All elevations are in feet on tne oriCin1 project datorn establisned by Reclsmaton that were found, during

2002 survey, to be around 2.9 feet less then Inc KAVDS8. 0riginl construction 1955 57. Due to sttlng,

construction modificat.ons were conaucted, 1)7, 81, to the splllway and uso tr,at was raised 5 feet.

2 Splllwsy ci's: elevst_on. Controlled Ly radial gates wIth top of gate elevat:on 3,012.5.

Original are, and capacity values obtain from table dated September 1963.

35 milee from dam to upper Manes Rver plus 9 miles of Willow Creek from confluence of Msrias River at

elevation 2890.

Western Rog,onal Climate Center Data for Station 243489 located at Gibson Dan-, Montana

6 Calculated using mean annual runoff value of 618,300 acre feet, Item #24.

Average annual computed inflows by w.ter year, from 1956 through 2002.

8 original surface areas from 19e3 table at Joint use elevation 2993.0. The original capacity values were

recomputed by ACAP program for use of aetermining capacity loss.

2002 area and capacity values computed by ACAP program at elevation 2993.0. 2002 surface ares at elevation

2,993 is larger tnen original due to extensive shoreline erosion.

10 Annual ReclamatiOn computed inflows by water year, from 1956 through 2002. Maximum and minimum elevations

available from Reclamation records.

Capacity loss calculated oy comparing original recomputed capacity and 2002 capacity at reservoir elevation

2,993. 2002 survey had only one above water contour developed from a 2003 serial survey flown at reservo1r

elevation 2,992.6 feet. A portion of the measured lower elevation lossses are due to extensive shoreline

erosion.

12 Capacities computed by Reclamation' a AcAP computer program. Surface areas from elevation 3005 were

developed assuming no original surface area change.

48. AGENCY MAKING SURVEY Bureau of Reclamation

49. AGENCY SUPPLYING DATA Bureau of Reclamation DATE June 2005

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

2002 Survey Summary

--

2 3 4 5 6 -

7

Elevations Original Original 2002 2002 2002 ----

Percent of

Survey Capacity Survey Survey Volume Reservoir

LJ (acre-feet) gx3 jj.tI Change Oepth

3020.2 25407 1555429 25407 1515522 39,907 100.0

3020

-

25357 1550353 25357

- 1510446

- --

39,907 99 9

- -

3019 25052 1525148 25052 1485241 39,907 99.4

3018 24747 1500248 24747 1460341 39,907 98.9

3017 24443 1475653 24443 1435746 39,907 98.4

3016 24138 1451363 24138 1411456 39,907 97.8

3015 23833 1427278 23833 1387471 39,807 97.3

3014 23866 1403678 23566 1363771 39,907 96.8

3013 23299 138024 3299 1340339 39, 907

-

96.3

3012.5 23165 1368630 23165 1328723 39,907 96.1

3012 23031 1357081 23031 1317174 39,907 95.8

3011 22764 1334183 22764 1294276 39,907 95.3

3010 22497 1311553 22497 1271646 39,907 94.8

3009 22235 1289186 22235 1249279 39,907 94.3

3008 21974 1267082 21974 :227175 39,907 93.8

- -- -

3007 21712 1245239 21712 1205332 39,907 93.2

3006 21451 1223657 21451 1183750 39,907 92.7

3005 21189 1202338 21189 1162431 39,907 92.2

3004 20909 1181288 20946 1141363 39,925 91.7

3003 20629 1160519 20703 1120538 39,981 91.2

3002 20350 1140030 20460 1099956 40,074 90.7

3001 20070 1119820 20218 1079617 40,203 90.2

3000 19790 1099890 19975 1059521 40,369 89.7

2999 19529 1080231 19732 1039668 40,563 89.1

2998 19267 1060833 19489 1020058 40,775 88.6

2997 19006 1041696 19246 1000690 41,006 88.1

2996 18744 1022821 19003 981566 41,255 87.6

2995 18483 1004208 18760 962684 41,524 87.1

2994 18190 985871 18517 944045 41,826 86.6

2993 17896 967828 18275 925649 42,179 86.1

2992 17603 950079 18032 907496 42,583 85.6

2991 17309 932623 17662 889624 42,999 85.0

2990 17016 915460 17209 872188 43,272 84.5

2989 16794 898555 16755 855206 43,349 84.0

2988 16571 881873 16302 838678 43, 195

-

83.5

2987 16349 865413 15848 822603 42,810 83.0

2986 16126 849175 15395 806981 42,194 82.5

2985 15904 833160 14941 791813 41,347 82.0

2984 15660 817378 14729 776978 40,400 81.5

2983 15416 801840 14516 762356 39,484 80.9

2982 15171 786547 14288

-

747953 38,594 80.4

2981 14927 771498 14061 733779 37,719 79.

19
Tther Reservoir

2002 Survey Summary

2 3 4 5 6 7

Elevations Original Original 2002 2002 2092 Percent of

Survey Capacity Survey

i 1

Survey

L tI

Volume

Canae

Reservoir

2980 11683 756693

gi

:3727

.cs.

7:9886 36,807 79.4

2979 14459 742122 :3393 706326 35,796 78.9

2978 14235 727775 :3152 693054 34,721 78.4

2977 14010 713652 .2910 680023 33,629 77.9

2976 .3786 699754 12710 667213 32,541 77.4

2975 13562 686080 12510 654602 31,478 76.8

2974 13321 672638 12321 642186 30,452 76.3

2973 13081 659437 12132 629960 29,477 75.8

2972 12840 646477 11947 617920 28,557

2971 12600 633757 11761 606066 27,691 74.8

2970 12359 621278 11515 594428 26,850 74.3

2969 2182 609007 11268 583037 25,970 73.8

2968 12005 596913 11093 571857 25,056 73.3

2967 11829 584996 10918 560851 24,145 72.7

2966.4 11723 577931 10819 554330 23,601 72.4

2966 11652 573256 10753 550016 23,240 72.2

2965 11475 561693 10589 539344 22,349 71.7

2964 11306 550302 10451 528824 21,478 71.2

2963 11137 539081 10313 518443 20,638 70.7

2962 10968 528028 10183 508195 19,833 70.2

2961 10799 517144 10054 498076 19,068 69.7

2960 10630 506430 9925 488087 18,343 69.2

2959 10455 495887 9795 478226 17,661 68.6

2958 10281 485519 9659 468499 17,020 68.1

2957 10106 475326 9523 458908 16,418 67:6

2956 9932 465307 9403 449446 15,861 67.1

2955 9757 455462 9283 440103 15,359 66.6

2954 9600 445784 9170 430877 14,907 66.1

2953 9443 436262 9056 421764 14,498 65.6

2952 9286

-

426898

-

8929 412772

- -.

14,126 65.1

2951 9129 417690 8802 403906 13,784 64.5

2950 8972 408640 8669 395171 13,469 64.0

2949 8834 399737 8536 386569 13,168 63.5

2948 8695 390973 8400 378101 12,872 63.0

2947 8557 382347 8264 369769 12,578 62.5

2946 8418 373859 8122 361576 12,283 62.0

2945 8280 365510 7981 353524 11,986 61.5

2944 8164 357288 7870 345599 11,689 61.0

2943 8048 349182 7760 337784 11,398 60.5

2942 7931 341193 7657 330076 11,117 59.9

2941 7815 333320 7553 322471 10,849

-

59.4

2940 7699 325563 7444 314972 10,591 58.9

2939 7585 317920 7334 307584 10,336 58.4

20
Tiber Reservoir

2002 Survey Summary

2 3 4 5 6 7

Elevations Original Original 2002 2002 2002 Percent of

Survey

icreI

Capacity

L 1i

Survey

L 1

Survey

( -f t)

Volume Reservoir

2938

.

7471

t

310392

sxa

7224

acre ee

300305 10,087

2937 7348 302978 7114 293136 9,842 57.4

2936 7244 295677 7009 286075 9,602 56.9

2935 7130 288490 6904 279119 9,371 54.4

2934 7024 281413 6792 272271 9,142 55.8

2933 6918 274442 6680 265535 8,907 55.3

2932 6813 267576 6567 258911 8,665 54.8

2931 6707 260816 6454 252400 8,416 54.3

2930 6601 254163 6350 245999 8,164 53.8

2929 6503 247610 6246 239701 7,909 53.3

2928 6406 241156 6147 233504 7,652 52.8

2927 6308 234799 6048 227407 7,392 52.3

2926 6211 228539 5962 221402 7,137 51.7

2925 6113 222378 5877 215482 6,896 51.2

2924 5992 216325 5777 209655 6,670 50.7

2923 5871 210394 5677 203928 6,466 50.2

2922 5750 204583 5580 198299 6,284 497

2921 5629 198894 5483 192768

-

6,126 49.2

2920 5508 193325 5377 187337 5,988 48.7

2919 5420 187861 5272 182013 5,848 48.2

2918 5331 182486 5168 176792 5,694 47.6

2917 5243 177199 5064 171676 5,523 47.1

-

2916 5154 172000 4966 166661 5,339

-

46.6

2915 5066 166890 4867 161745 5,145 46.1

2914 4974 161870 4785 156918 4,952 45.6

2913 4882 156942 4703 152174 4,768 45.1

2912 4789 152107 4627 147509 4,5.98 446

2911 4697 147364 4550 142921 4,443 44.1

2910 4605 142713 4473 138409 4,304 43.5

2909 4507 138156 4397 133974 4,182 43.0

2908 4409 133698 4327 129612

-

4,086 42.5

2907 4312 129338 4258 125319 4,019 42.0

2906 4214 125075 4178 121101 3,974 41.5

2905 4116 120910 4098 116963 3,947 41.0

2904 4038 116833 4020 112904 3,929 40.5

2903 3960 112834 3942 108923 3,911 40.0

2902 3882 108913 3867 105019 3,894 39.4

2901 3804 105070 3792 101189 3,881 38.9

2900 3726 101305 3708 97439 3,866 38.4

2899 3664 97610 3624 93773 3,837 37.9

2898 3601 93978 3549 90187 3,791 37.4

2897 3539 90408 3473 86676 3,732 36.9

2896 3476 86900 3405 83237 3,663 36.4

21
Tiber Reservoir

2002 Survey Summary

2 3 4 5 6 7

Elevations Original Original 2002 2002 2002 Percent of

Survey Capacity Survey

( )

Survey

( f t)

Volume

CI

Reservoir

D th

2895

iI

34,

L-ia).

83455

acres

3336

acre- ee

79866

anne

3,589

ep

35.9

2896 3347 80075 3271 76553 3,512 353

2893 3280 76761 3205 73325 3,436 34.8

2892 33 73515 3134 70156 3,359 34.3

2891 3146 70335 3064 67056 3,279 33.8

2890 3079 67223 2992 64029 3,194 33.3

2889 2995 64185 2919 61073 3,112 32.8

2888 2911 61232 2852 58188 3,044 32.3

2887 2828 58363 2785 55369 2994 31.8

2886 2744 55577 2701 52627 2,950 31.3

2885 2660 52875 2618 49967 2,908 30.7

2884 2583 50254 2517 47400 2,854 30.2

2883 2506 47709 2417 44933 2,776 29.7

2882 2429 45242 2327 42560 2,682 29.2

2881 2352 42851 2238 40278 2,573 28.7

2880 2275 40538 2164 38077 2,461 28.2

2879 2193 38304 2090 35950 2,354 27.7

2878 2110 36152 2023 33893 2,259 27.2

2877 2028 34083 1956 -

31903 2,180 26.6

2876 1945 32097 1889 29981 2,116 26.1

2875 1863 30193 1821 28126 2,067 25.6

2874 1797 28362 1773 26329 2,033 25.1

2873 1732 26598 1725 24580 2,018 24.6

2872 1666 24899 1677 22879 2020 24.1

2871 1601 23265 1628 21226 2,039 23.6

2870 1535 -

21698 1582 19621 2,077 23.1

2869 1471 20195 1536 18061 2,134 22.5

2868 1406 18756 - 1477 16555 2,201 22.0

2867 1342 17382 1416 15108 2,274 21.5

2866 1177 16073 1338 13731 2,342 21.0

-

2865 1213 14828 1260 12432 2,396 20.5

2864 1143 13650 1183 11211 2,439 20.0

2863 1072 12542 1106 10066 2,476 19.5

^^^^ 1002 11505 1046 8990 2,515 19.0

2861 931 10539 986 7974 2,565 18.4

2860 861 9643 928 7017 2,626 17.9

2859 796 8814 871 6118 2,696 17.4

2858 731 8050 812 5277 2,773 16.9

2857 667 7351 753 4494 2,857 16.4

2856 602 6717 691 3772 2,945 15.9

2855 537 6148 629 3112 3,036 15.4

2854 508 5625 549 2523 3,102 14.9

2853 478 5132 468 2014 3,118 14.3

22
Tiber Reservoir

2002 Survey Summary

2 3 4 5 6 7

Elevations Original original 2002 2002 2002 Percent of

Survey Capacity Survey Survey Volume Reservoir

.Lx.ai lacre-feeti (acres) Laorej .e.tJ hang Depth

2852 449 4669 405 1577 3,092 13.5

281 419 4235 341 1204 3,03: 3.3

2850 390 3830 290 889 2,941 12.8

2849 375 3448 238 625 2,823 12.3

2848 360 3080 186 413 2,667 1.1.8

2847 344 2728 134 253 2,475 11.3

2846 329 2392 92 140 2,252 10.8

2845 314 2070 5. 68 2,002 10.2

2844 285 1771 30 28 1,743 9.7

2843 256 1500 8 9 1,491 9.2

2842 226 1259 4 3 1,256 8.7

2841 197 1048 0 0 1,048 8.2

-

2840 168 865 0 0 865 7.7

2839 148 707 0 0 707 7.2

2838 128 569 0 0 569 6.7

2837 108 451 0 0 451 6.1

2836 88 353 0 0 353 5.6

2835 68 275 0 0 275 5.1

2834 59 212 0 0 212 4.6

2833 49 158 0 0 158 4.1

2832 40 113 0 0 113 3.6

2831 30 78 0 0 78 3.1

2830 21 53 0 0 53 2.6

2829 17 34 0

- 0 34 2:0

2828 13 19 0 0 19 1.5

2827

- 8 8 0 0 8 1.0

2826 4

-

2 0

-

0 2 0.5

2825

- - -

0

-

0 0 0 0 0.0

Elevation of reservoir water surface.

2 Original reservoir surface area from 1963 area table.

3 original reservoir capacity recomputed from 1963 surface areas using ACAP.

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 195.2 feet.

23
.5

- -
7

iimir I I - I iher RrTcir t n-rrhic
N

/

Ii

LOCATION

N

I'

-

w - H

-

r

/, 5 _________

c

(

/ I

29
4,

4,

1/

li

/I

1t

Li

S

t540000-j--

LOCATION

B

1530000±

B

N

w E

S

Teat

a SJ SmV dWV

iOaI I. 55W

Horizontal datum bused on Montana s

State Plane Coordinate System. in

North Amer loan Datum of lOBS INADB3I

Vertical datum based on oriqinal

prolmct datum established by U S

Bureau of Reclamation which rs

25 feet lower than the NatIonal

American Vertical Datum of 101313 (NAVDAB)

31

1 m ira 1 - T1ar t) nenrirn,r tnnnnrnnkir man Kin zi.
3

Figure 14. fiber Reservoir toooranhic man. No. 5.
35

el, Co/acu'o JV29,

Fimiri' 1 c T1-,.-
Vrni-r 1 tc Th,,. P fc-rrnrQr%l1ip rnr
I ao; isioo isioooo'f

I

II

/1

/1 II

/1

II

Li

t'

/1

Sc5

ii

I

5/

II

ii

Sc,

\\

ii

ii

U moV iaO± ii OcUU

S

8 t*l yi

e/r' /c/kl

Horizontal datum based on lontana's

State Plane Coordinate System, 10

North AmerIcan Datum of 1983 NADB3I

Vertical datum based on original

project datum established by US

Bureau of Pet lamatlor which is

V.9 feet loser than the National

umericae Vertical Datum of 1988 NAVDABI

39

1-figure 17. - Tiber Reservoir tonoranhic man. No. 8.
,ni0000-fic

II

LOCATION

(

N

\\ ;//

e/ t/

/7 Horizontal datum based on Montanan

II State Pleoc Coordinate System, in

North Amercan [latuni of 1983 (NAEIB3I

H

// Vertical datum based on Original

protect datum Votoblished IV US

/7 Bureau of Reclamation ahiCh is

2 9 feet beer than the National

/1 American Vertical Datum of 1988 NAVDRB)

/1

Ii'

Ii

\\ 1/

1/ _________________________________________________

us

S/iI Wills

e*Jfl,. el/ely

2 1//tI i8d/1ME

\

MV/484

B § H T/8EKRS1ht'/!

aa0000-f- II _________________________________________________________

H L4AYllL /[C/V/CAL ,1/5PVVAL._

a/FLt[D8r, AP/'/?I2V/D -

Ocneer, Ca/of tfo J1HV29, 8OU 9

41

m 1 2 - Tbam. 1? nrsir rr morhii rnia'r% Nc
Area-Capacity Curves for Tiber Reservoir

Area (acres)

26000 23400 20800 18200 15600 13000 10400 7800

3025 ± -

301

29

j 29f

0)

'I0

w

2900

2875

2850

2825

0

5200 2600 0

3025

3000

2975

2950

2925

2900

2875

2850

4- 4 4 - L 1 2825

156000 312000 468000 624000 780000 936000 1092000 1248000 1404000 1560000

Capacity (acre-feet)

Figure 19. - 2002 area and capacity curves.