Merritt Reservoir

2003 Survey

U.S. Department of the Interior

Bureau of Reclamation

Technical Service Center

Denver, Colorado September 2004
REPORT DOCUMENTATION PAGE Form Approved

0MB No. 0704-0 188

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

I September 2004 Final ________________________________

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Merritt Reservoir

2003 Survey PR

6. AUTHOR(S)

Ronald L. Ferrari ________________________

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 DJBR

II. SUPPLEMENTARY NOTES

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

12a. DISTRIBUTION/A VAILABILITY STATEMENT 12b. DISTRIBUTION CODE

13. ABSTRACT (Ma.rimum 200 words)

The Bureau of Reclamation (Reclamation) surveyed Merritt Reservoir in June of 2003 to develop a topographic map and

compute a present storage-elevation relationship (area-capacity tables). The underwater survey was conducted near lake

elevation 2,945.6 feet (project datum). The underwater survey used sonic depth recording equipment interfaced with a global

positioning system (GPS) that gave continuous sounding positions throughout the underwater portions of the reservoir covered by

the survey vessel. The above-water topography was determined by digitizing the developed reservoir contour lines from the U.S.

Geological Survey quadrangle (USGS quad) map of the reservoir area. The new topographic map of Merritt Reservoir was

developed from the combined digitized USGS quad contours and June 2003 underwater measured topography. This study

assumed no change from elevation 2,945 (feet) and above due to lack of 2003 above water data.

As of June 2003, at maximum water surface elevation 2,949.8, the surface area was 3,222 acres with a total capacity of 78,375

acre-feet. Since dam closure on February 19, 1964, about 7,886 acre-feet of change have been estimated below elevation

2,946.0, resulting in a 10.6 percent loss in reservoir volume. This study assumed the calculated change is due to accuracy

difference between the two surveys, the lack of updated above water topography, shoreline erosion, and sediment inflow.

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
Merritt Reservoir

2003 Survey

by

Ronald L. Ferrari

Sedimentation and River Hydraulics Group

Water Resources Services

Technical Service Center

Denver, Colorado

September 2004
ACKNOWLEDGMENTS

The Bureau of Reclamation's (Reclamation) Sedimentation and River

Hydraulics Group of the Technical Service Center (TSC) prepared and

published this report. Ronald Ferrari and Shraon Nuanes of the TSC

conducted the hydrographic survey. Ron Ferrari of the TSC completed

the data processing needed to generate the new topographic map and areacapacity tables. 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.

FJ FoR THE

*RSOJ =. -

UREREC

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

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Page

Introduction 1

Summary and Conclusions 2

Reservoir Operations 3

Hydrographic Survey Equipment and Method 3

Merritt Reservoir Datum 5

Reservoir Area and Capacity 5

Topography Development 5

Development of 2003 Contour Areas 6

2003 Storage Capacity 6

Reservoir Sediment Analyses 7

References 8

TABLES

Table

1 Reservoir sediment data summary (page 1 of 2) 9

1 Reservoir sediment data summary (page 2 of 2) 10

2 Summary of 2003 survey results 11

FIGURES

Figure

I Merritt Reservoir location map 2

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

3 Merritt Reservoir topographic map 13

4 Merritt Reservoir topographic map 15

S Merritt Reservoir topographic map 17

6 2003 area and capacity curves 19

111
INTRODUCTION

Merritt Dam and Reservoir are located in north central Nebraska in Cherry County. The dam,

formed on the Snake River, is located about 8 miles southwest of Burge and 23 miles southwest

of Valentine, Nebraska (fig. 1). The reservoir is located at the confluence of Boardman Creek

and Snake River. The dam, reservoir, and facilities are part of the Ainsworth Unit of the

Missouri River Basin Project.

Merritt Dam was constructed from August 1961 thru May 1964 with initial storage beginning on

February 19 of 1964. The dam is a zoned earthfill structure whose dimensions are:

Hydraulic height' 115 feet Structural height 126 feet

Top width 30 feet Crest length 3,222 feet

Crest elevation 2,956.0 feet2

The spiliway is an ungated morning-glory structure that consists of a concrete intake structure,

concrete conduit, concrete stilling basin, and outlet channel. The spiliway crest elevation is

2,946.0 and provides a discharge of 2,080 cubic feet per second (cfs) at maximum reservoir

elevation 2,949.8. A river outlet works consists of a concrete intake structure, concrete conduit,

gate chamber, access shaft and house, 54-inch diameter steel pipe, control house and stilling

basin with a discharge capacity of 730 cfs. The canal outlet works consist of a 78-inch diameter

steel pipe and concrete control house. The discharge capacity is 580 cfs and discharges into the

Ainsworth Canal.

The drainage area above Merritt Dam is around 660 square miles and all is considered sediment

contributing. The basin has very little elevation relief, from approximately 3,800 feet at the

headwaters to the normal water surface elevation of 2,946 feet. The drainage area is comprised

primarily of sand dunes covered with grasses with some reports stating that due to the large sand

dunes, less than ten percent of the drainage area contributes to the actual runoff. The reservoir is

around 15.8 miles in length and around 0.3 miles in width.

1The definition of such terms as "hydraulic height," "structural height," etc. may be found in manuals such as

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

Reservoirs, or ASCE's Nomenclature for Hydraulics.

2Elevation levels are shown in feet. All elevations shown in this report are based on the original project datum

established by U.S. Bureau of Reclamation that was reportedly tied to the National Geodetic Vertical Datum of 1929

(NGVD29). The 2003 survey confirm that Reclamation's datum was tied to NGVD29 and around 1.0 feet less than the

North American Vertical Datum of 1988 (NAVD88).
SUMMARY AND CONCLUSIONS 

This Reclamation report presents the 2003 results of the survey of Merritt Reservoir. The 

primary objectives of the survey were to gather data needed to: 

develop reservoir topography 

compute area-capacity relationships 

estimate storage depletion due to sediment deposition 

-- 

NEBRASKA 

\ Trenton 

Figure 1 - Merritt Reservoir location map. 

A Real-time Kinematic (RTK) GPS control survey established a temporary horizontal and 

vertical control point near the reservoir for the hydrographic survey. The RTK GPS control base 

was set on the National Geoldetic Survey (NGS) datum point "Y 43 1" located several miles fiom 

the lake. The horizontal control was established in Nebraska state plane coordinates, north zone, 

in the North American Datum of 1983 (NAD83) and the vertical control was tied to the North 

American Vertical Datum of 1988 (NAVD88) and the Reclamation project datum. All 

elevations in this report are referenced to the Reclamation project or construction datum that, for 

this study, was tied to the NGVDD and around 1.0 feet less than the NAVD88. 

The underwater survey was conducted in June of 2003 near reservoir water surface elevation 

2,945.6. The bathyrnetric survey was run using sonic depth recordmg equipment interfaced with 

a differential global positioning system (DGPS) capable of determining sounding locations 

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

survey boat as it was navigated along grid lines covering Merritt 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 

dahun) 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

previously developed contour lines from the U.S. Geological Survey quadrangle (USGS quad)

maps of the reservoir area.

The 2003 Merritt Reservoir topographic map is a combination of the USGS quad contours and

the underwater survey data. A computer graphics program using the collected reservoir data

generated the 2003 reservoir surface areas at predetermined contour intervals. The 2003 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 Merritt Reservoir and watershed characteristics for the

2003 survey. The 2003 survey determined that the reservoir has a total storage capacity of

66,726 acre-feet and a surface area of 2,909 acres at active conservation elevation 2,946.0. Since

closure in February of 1964, the reservoir has an estimated volume change of 7,886 acre-feet

below reservoir elevation 2,945.0. This volume represents a 10.6 percent loss in total original

capacity at this elevation.

RESERVOIR OPERATIONS

Merritt Reservoir is part of the Ainsworth Unit of the Pick-Sloan Missouri Basin Program that

supplies water for irrigating 34,540 acres of land in the Ainsworth Irrigation District. The June

2003 capacity table shows 78,375 acre-feet of total storage below the maximum water surface

elevation 2,949.8. The 2003 survey measured a minimum lake bottom elevation of 2,848.2.

The following values are from the June 2003 capacity table:

• 11,649 acre-feet of surcharge between elevation 2,946.0 and 2,949.8.

• 62,064 acre-feet of conservation use between elevation 2,896.0 and 2,946.0.

• 3,888 acre-foot of inactive storage between elevation 2,875.0 and 2,896.0.

• 774 acre-foot of dead storage below 2,875.0.

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

period 1968 through 2003, show the calculated inflow and annual fluctuation for these years of

operation. The computed average inflow into the reservoir for these years of record was 183,100

acre-feet per year. The maximum reservoir elevation was 2,946.8 recorded in May of 1982 with

a minimum elevation of 2,916.4 recorded in September of 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 2). 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

3
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. . 

Figure 2 - Survey vessel with mounted hydrographic equipment on Jackson Lake in Wyoming 

The Sedimentation and River Hydraulics G~oup uses RTK GPS with the major benefit being 

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

outputs from an 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, which the hydrographic collection software converted into 

Nebraska's NAD83 state plane north zone coordinate system. The RTK GPS system employs 

two receivers that track the same satellites simultaneously just like with differential GPS. 

Merritt Reservoir's hydrographic survey was conducted on June 4 through 7 of 2003 near water 

surface elevation 2,945.6 (Reclamation project datum). The bathyrnetric survey was run using 

sonic depth recording equipment, interfaced with an RTK GPS, capable of determining sounding 

locations within the reservoir. The survey system sohe continuously recorded reservoir 

depths and horizontal coordinates as the survey boat moved across closely spaced grid lines 

covering the reservoir area. Most of the transects (grid lines) were run somewhat perpendicular 

to the downstream alignment of the reservoir at around 300-foot spacing. Data was also 

collected along 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 underwater data set includes about 935,000 

data points. 

The 2003 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.

Merritt Reservoir Datum

Prior to the underwater survey, a RTK GPS survey was conducted from the NGS control point

"Y 431" to tie horizontal and vertical control to a temporary point and the reservoir water

surface. All vertical information for this study is referenced to the Reclamation reservoir water

surface gauge measurements that were found to be tied to NGVD29. The RTK GPS water

surface measurement found the NGS vertical of NAVD88 to be around 1.0 feet higher then the

Reclamation gauge readings. The reported vertical shifts were from this one time RTK GPS

survey.

RESERVOIR AREA AND CAPACITY

Topography Development

The topography of Merritt Reservoir was developed from the 2003 collected underwater and the

digitized contours from the USGS quad maps. The digitized USGS contour lines were the

Merritt Reservoir water surface labeled elevation 2,946 and the elevation 2940 contour. These

USGS quad maps were developed from aerial photography dated 1980. This study found the

enclosed digitized surface area of the labeled 2946 contour, with the islands surfaces removed, to

correspond to the original surface area at elevation 2,943.8. The enclosed digitized surface area

of the labeled 2940 contour corresponds to the original surface area at elevation 2935.

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

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

coordinates, north zone, using the ARC/INFO PROJECT command.

The digitized 2946 contour line was used to perform a clip of Merritt 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 available data to represent the

reservoir water surface at the time the survey was conducted, which was near reservoir elevation

2,945.6. 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. The plot showed that the underwater data did not lie completely within this

clip, which required modifications to include the entire underwater data set. Modified areas

included the shoreline around the islands and some of the shoreline of the reservoir. It is

assumed these changes were due to erosion along these shorelines. Using select and move

5
commands within ARCEDIT, the vertices of the clip were shifted to fit all the collected

underwater data. The clip was assigned an elevation of 2,943.8 to reflect the original area of the

developed polygons.

Contours for the reservoir below elevation 2,943.8 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 greater detail in the ARC/INFO V7.0.2 Users

Documentation, (ESRI, 1992).

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

interpolate contours from the Merritt 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 Merritt

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

2,849.0 through elevation 2,940.0. The 2003 study assumed no change in area, since the original

survey, for elevation 2,945.0 and above. The contour topography at 2-foot intervals is presented

on figure 3 through 5.

Development of 2003 Contour Areas

The 2003 contour surface areas for Merritt Reservoir were computed at 1-foot increments from

elevation 2,849.0 to 2,940.0. The 2003 underwater survey measured a minimum reservoir

bottom elevation of 2,848.2. 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 2003

underwater survey data was collected near reservoir elevation 2,946.5. For the purpose of this

study, the measured 2003 survey areas at 2-foot increments from elevation 2,850.0 through

2,940.0 were used to compute the new area and capacity tables. This study assumed no change

in original area from elevation 2,945.0 and above. The area and capacity program computed the

areas between elevation 2,940.0 and 2,945.0 by assuming a straight-line interpolation.

2003 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 2003

6
surveyed surface areas at 2-foot contour intervals from reservoir elevation 2,850.0 to elevation

2,940.0 were used as the control parameters for computing the 2003 Merritt Reservoir capacity.

Since this study did not collect above water data, the original surface areas for elevation 2,945.0

and 2,950.0 were used to complete the area and capacity table. The 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 Merritt 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

defmed by a series of curves, each fitting a certain region of data. Differentiating the capacity

equations, which are of second order polynomial form, derives final area equations:

y a1 + a2x + a3x2

where: y = capacity

x = elevation above a reference base

a1 = intercept

a2 and a3 = coefficients

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

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

original capacities. A separate set of 2003 area and capacity tables has been published for the

0.01, 0.1 and 1-foot elevation increments (Bureau of Reclamation 2003). A description of the

computations and coefficients output from the ACAP85 program is included with these tables.

Both the original and 2003 area-capacity curves are plotted on figure 6. As of June 2003, at

elevation 2,946.0, the surface area was 2,909 acres with a total capacity of 66,726 acre-feet.

RESERVOIR SEDIMENT ANALYSES

Figure 6 is a plot of Merritt Reservoir original surface area and capacity versus the 2003

measured surface area and capacity that illustrates the differences between the two surveys.

Since Merritt Dam closure in February of 1964, the measured total volume change at reservoir

elevation 2,945.0 was estimated to be 7,886 acre-feet. The estimated average annual rate of

capacity lost for this period (39.3 years) was 200.7 acre-feet per year. The storage loss in terms

of percent of original storage capacity was 10.6 percent at spiliway crest elevation 2,946.0. It

must be noted that the 2003 area and capacity tables were generated assuming no change in

original area and capacity from elevation 2,945.0 and above which in all probability is not the

case.

The original estimated 100 years of sediment accumulation for Merritt Reservoir was 12,000

acre-feet below elevation 2946.0. The 2003 study estimated an annual inflow of sediment of

200.7 acre-feet per year for a total sediment accumulation of 20,000 acre-feet in the first 100

7
years of operation. From table 1 and 2, the 2003 study shows that of the total computed sediment

27.3 percent, or 2,156 acre-feet, has accumulated below dead storage elevation 2,896.0 with the

rest accumulating in the active storage areas between elevation 2896.0 and 2946.0. In the active

zone, 35.6 percent or 2,804 acre-feet between elevation 2,896.0 and 2930.0 and 37.1 percent or

2,926 acre-feet between elevation 2930.0 and 2946.0. From table 1, range in reservoir operation,

it appears that for most years of operation the minimum reservoir elevation is near or above

elevation 2,930 causing the majority of the sediment inflow to settle and accumulate in the upper

portion of the reservoir on the Snake River arm.

For this study the computed storage loss or sediment accumulation since Merritt Dam closure

was determined by comparing the newly computed reservoir capacity with the original reported

capacities. On a Reclamation area - capacity curve for Merritt Reservoir, drawing 7 19-705-3, it

states that the original topography was developed on 5-foot contour intervals from aerial

photography and the original topography data was corrected for the dam location. This is noted

since the 2003 sediment accumulation results assume reliable original data. An above water

survey should be conducted if better information is needed for elevation 2,940.0 and above. A

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

are observed.

REFERENCES

American Society of Civil Engineers, 1962. Nomenclature 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, 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 ofSmail Dams, U.S. Government Printing Office,

Denver CO.

Bureau of Reclamation, June 2003. Denver Office, Merritt Reservoir Area and Capacity

Tables, Ainsworth Unit, Great Plains Region, Billings, MT.

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

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

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

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

8
RESERVOIR SEDIMENT

DATA SUMMARY Merritt Reservoir

NAME OF RESERVOIR 1

DATA SHEET NO.

D 1. OWNER Bureau of Reclamation 2. STREAM Snake River 3. STATE Nebraska

A 4. SEC. 29 THE . 31 N RANGE 30 H 5. NEAREST P.O. Surge 6. COUNTY Cherry

N 7. LAT 42 38 06" LONG 100° 52 18" 8. TOP OF DAN ELEVATION 2,956.0' 9. SPILLWAY CREST EL 2,946.02

R 10. STORAGE 11. ELEVATION 12. 2002 13. 2002 14.GROSS STORAGE 15. DATE

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

S BEGAN

E

a. SURCHARGE 2,949.8 3,222 11,650 86,140

R

V

b. FLOOD CONTROL

2/19/64

o

C POWER

d. JOINT USE

_______________ ________________ 16. DATE

R e. CONSERVATION 2,946.0 2,906 67,690 74,490 NORMAL

f. INACTIVE 2,896.0 415 5,190 6,800 OPERATION

. DEAD 2,875.0 119 1,610 1,610 9964

- 17. LENGTH OF RESERVOIR 15.8 MILES AVG. WIDTH OF RESERVOIR 0.3 MILES

B 18. TOTAL DRAINAGE AREA 660 SQUARE MILES 22. MEAN ANNUAL PRECIPITATION 216 INCHES

A

19. NET SEDIMENT CONTRIBUTING AREA 660 SQUARE MILES 23. MEAN ANNUAL RUNOFF 5.2 INCHES

S

20. LENGTH MILES AV. WIDTH 24. MEAN ANNUAL RUNOFF 183,1008 ACRE-FEET

____ 21. MAX. ELEVATION MI M. ELEVATION 25. ANNUAL TEMP. MEAN 49°F RANGE -33°F to 112°F6

5 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

________________________________________________________________________________________

E 2/64 Contour CD) 5-ft 2,909 74,612 .41

Y

6/03 39.3 Contour CD) 2-ft 2,909 66,726 .36

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

6/03 21 183,1000 201,600 6,591,000 183,100 6,591,000

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.

6/03 7,88611 200.7 0.3 7,886 200.7 0.3

26. DATE OF 39. AV. DRY 40. SEC. DEP. TONS/MI.°-YR. 41. STORAGE LOSS, POT. 42.

SURVEY MT. )#/FT') ______________

a. PERIOD

______________

b. TOTAL TO

_____________

a. AV. j

_______________

b. TOTAL TO

______

a.

______

b.

6/03 10.611

26. 43. DEPTH DESIGNATION RANGE BY RESERVOIR ELEVATION

DATE

OF 2845- 2870- 2890- 2896- 2910- 2920- 2930- 2940-

StJRVE 2870 2890 2896 2910 2920 2930 2940 2946

crest

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

6/03 8.1 14.1 5.1 11.6 8.2 15.9 27.5 9.5

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

DATE

OF 0-10 10- 20- 30- 40- 50- 60- 70- 80- 90- 100- 105- 110- 115- 120-

SURVE 20 30 40 50 60 70 80 90 100 105 110 115 120 125

Y PERCENT OF TOTAL SEDIMENT LOCATED WITHIN REACH DESIGNATION

Table 1. - Reservoir sediment data summary (page 1 of 2).
45. RANGE IN RESERVOIR OPERATION'0 ____________ ___________

YEAR MAX. ELEV. MIN. ELEV. INFLOW, AF YEAR MAX. ELEV. MIN. ELEV. INFLOW, AF

1968 2,946.1 2,916.4 160,200 1969 2,945.9 2925.0 163,200

1970 2,945.9 2,930.8 173,000 1971 2,946.2 2,932.1 174,500

1972 2,946.2 2,941.2 176,800 1973 2,946.3 2,931.6 174,700

1974 2,946.0 2,930.3 171,100 1975 2,946.2 2,926.4 171,400

1976 2,946.8 2,927.4 162,700 1977 2,946.2 2,937.3 169,200

1978 2,946.2 2,936.9 167,700 1979 2,946.0 2,937.1 164,500

1980 2,946.2 2,928.5 184,100 1981 2,946.7 2937.7 174,800

1982 2,946.8 2,934.8 187,000 1983 2,946.5 2,939.0 195,300

1984 2,945.8 2,936.4 200,800 1985 2,946.7 2,935.9 192,200

1986 2,944.8 2,932.6 200,000 1987 2,944.0 2,929.9 197,000

1988 2,945.8 2,933.6 195,800 1989 2,946.1 2,930.1 186,900

1990 2,946.2 2,936.2 184,100 1991 2,946.2 2,932.1 182,500

1992 2,946.2 2,932.1 191,900 1993 2,946.0 2,939.5 188,900

1994 2,946.0 2,943.2 176,900 1995 2,946.7 2,931.7 191,300

1996 2,946.4 2,929.8 195,700 1997 2,946.5 2,937.2 201,600

1998 2,946.5 2,934.1 195,200 1999 2,945.9 2,927.6 196,600

2000 2,946.6 2,924.8 185,600 2001 2,946.2 2,928.0 196,800

7 '315 7 0 7(017 2056 1 7026 2

46. ELEVATION - AREA - CAPACITY DATA FOR 2003 CAPJCITY'

ELEVATION AREA CAPACITY ELEVATION AREA CAPACITY ELEVATION AREA CAPACITY

2,848.2 0 0 2,850 0 0 2,852 1 1

2,854 1 3 2,856 6 10 2,858 11 27

2,860 20 59 2,862 27 106 2,864 34 168

2,866 41 242 2,868 48 331 2,870 57 436

2,872 65 558 2,874 74 698 2,876 83 856

2,878 93 1,032 2,880 106 1,231 2,882 129 1,466

2,884 153 1,748 2,886 180 2,081 2,888 212 2,474

2,890 240 2,926 2,892 270 3,435 2,894 307 4,012

2,896 343 4,562 2,898 381 5,386 2,900 426 6,194

2,902 472 7,092 2,904 519 8,083 2,906 577 9,178

2,908 635 10,390 2,910 695 11,720 2,912 771 13,186

2,914 846 14,803 2,916 923 16,572 2,918 988 18,484

2,920 1,053 20,525 2,922 1,126 22,704 2,924 1,204 25,033

2,926 1,295 27,533 2,928 1,397 30,225 2,930 1,503 33,125

2,932 1,626 36,254 2,934 1,765 39,646 2,936 1,896 43,307

2,938

7946

2,025

2909

47,228

66726

2,940

2949.8

2,155

6,222

51,407

78,776

2,945 2,826 63,859

________

47. REMARKS AND REFERENCES

All elevations in feet and based on original project datu m that were tied to NGVD29.

2 Uncontrolled morning- glory overflow spillway.

Original values computed from 5-foot contours developed f rom aerial photography.

' Total of main stream, Snake River, and two smaller arms t hat make up the reservoir a t elevation 2946.

From USGS water year records, 1981. Report states runoff affected by large presence of sand dunes with only

forty four square miles contributing to water runoff.

6 Bureau of Reclamation Project Data Book, 1981. Values fo r Ainsworth Unit.

Calculated using mean annual runoff value of 183,100 AF, item 24, 1968 through 2003. (See remark 86.

8 Annual computed inflows by water year from readily available records from 1968 through 2003.

Surface area & capaci ty at elevation 2,946.0, top of active conservation, by indicat ed year. The original

capacity was recomputed and the 2003 values computed by BOR program ACAP.

10 Maximum and minimum elevationa and annual computed inflows by water year from 1968 through 2003 (BOR

available records

All sediment computations are computed by comparing the 2003 results with the original results at spillway

crest elevation 2,94 6.0. This assumed the original data is of a reliable accuracy. The 2003 survey

assumed no change si nce the original survey from elevati on 2,945 and above. Comput ed storage lose is due

accuracy differences between original and 2003 surveys and due to accumulation of s ediment.

12 Capacities computed by Reclamation's ACAP computer program.

48. AGENCY MAKING SURVEY Bureau of Reclamation

49. AGENCY SUPPLYING DATA Bureeu of Reclamation DATE September 2004

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

10
2 3 4 5 6 7 8

-

2003 2003 Percentof

Elevations Original Original 2003 2003 Sediment Percent of Reservoir

Survey Capacity Survey Survey Volume Sediment Depth

(feet) (acres) (acre-feet) (acres) (acre-feet) (acre-feet)

2,949.8 3222 86261 3222 78375 100.0

2,946.0 2909 74612 2909 66726 7886 100.0 96.4

2,945.0 282 71745 2826

-

63859

-

7886

_-

100.0 95.4

2,940.0 2454 58545 2155 51407 7138 90.5 90.6

- -- -----

2,938.0 2284 53807 2025 6579 83.4 88.7

2,935.0 2030 47335 1831 41444 74.7 85.9

2,930.0 1670 38085 1503 33125 4960 62.9 81.1

2,925.0 1370 30485 1250 --

26260 4225

----

53.6 76.3

2,920.0 1132 24230

1

1053 20525 3705 47.0 71.6

2,915.0 944 19040 13669 3371 42.7 66.8

2,910.0756 14790

____

695

____

11720 62.0

2, 905.01 603 11393 548 8616 2777 35.2 57.3

2,900.0 497 8643 426 6194

,

2449 31.1 52.5

2,896.0 415 6818 343 4662 2156 27.3 48.7

_ - --

2,895.0 395 6413

--- - 325 4328 2085 26.4 47.7

2,890.0 301 4673 240 2926 1747 22.2 42.9

-

2,885.0 232 3340 167 1908 1432 18.2 38.2

170 23 106 1231 1104 14.0 33.4

2,875.0 119 1613 79 774L 839 10.6 28.6

2,870.0 95 1078 57 436 642 8.1 23.9

2,865.0 73 658 37 - -

203 -

5.8 19.1 -

2,860.052

-

345 9 59 286 36 14.3

2,8

-

29 -

-

143 4 5 -

138 -

1.7

2,850.0 14 35 0 0 35 0.4 4.8

__

' - :- - -----

1 Elevation of reservoir water surface.

tOriginal reser 2 voir surface area.

3 Original reservoir capacity recomputed using ACAP.

4 Reservoir surface area from 2003 survey.

5 Reservoir capacity computed using ACAP.

6 Measured sediment volume = column (3) -

-- - ------ - - ---- - -

column (5).

7 Measured sediment expressed in percentage of total sediment 7,886.

8 Depth of reservoir expressed in percentage of total depth of 104.8 feet.

Table 2. - Summary of 2003 survey results

11
,ooooo+

- -1

/' Merritt

Dam

' I '

Land ing

rip

N

w E

S

a ,, ,

,/ø 1fSR'

/

or

/

2

MQ

TTjgR 0/I

jJJjf /

''Br I

01F1'ID HI

L

Pionr - Mrrft PQ,r1rr t orrhi 1
/

o,J y\5

LS

\\

J

otoooe

N

w

E

S

Gal

a

v i*V 2IV

Ge/, /./

Zontal datum based on Nebraska's

State Plane Coordinate System,

North Zone, (NADB3)

Vertical datum based on original

project datum established by U5

Buresu Of Reclamation .hlch IS

reported to be tied to the National

Geodetic Verticalbatum of 1925 (NGVO2S)

Trim 2003 survey found Reclamations

datum to be around 1,0 feet lea than

the North Amaerican Vertical Datum of

1998 (NAVD8B)

ayvg ijmf7

tIf I t25W/R

TI if SIR roll

tWA?/81i__,, [('1*/Oil 4°At?1'___

t'1I[('K[i2

_

OG7f'ef, Co/oraoio 5/P 2,9. 2009

Figure 4. -' Merritt Reservoir topographic n
3

lOl0000•+ Q4

0

- 01

lo t0000-fN

Location

_

:- E

l0oo /

S ft

NoZoote datrn, booed or Nebrooto's

State Prle COordr,ote Systelo,

// North Zorte. (N0083)

1f Vertcai datum based on or'1groa]

//

pr'o)ect datunt established by U S

Bureau of Reclanoatlon WI-lOch 10

& J6 lw 1/ r'eporteo to be toed to the N5tiorsi

GeodetIc VerticalDotont of 1325 (5GV023)

/7

The 2003 suroey fourd Rec4lnattOrlS

datom to be around 1.0 feet IsOS thSh

/7 the North American VertIcel D5tm of

1988 (NAVD88)

// _______________________________________________

8' '-,

Wfl.lRY

SWKQ4WflN

,ayri WR

ft

,47i91TT!f5, VVO/l

/7

ria,vic.ii APPkVV4L_

tY/[CK[D BY APM?OV[D

nrsr,Co/orcoS1P,22l

____

17

Figure 5. - Merritt Reservoir topographic map.
3300

2,955.0

2,935.0

2,915.0

C,

0

>

-

.Q .2895.0

w

2,875.0

2,855.0

2,835.0

0

2970 2640

Cal

8800

Area-Capacity Curves for Merritt Reservoir

Area (acre)

2310 1980 1650 1320 990 0

------ 2,955.0

660 330

)acity

-- -C

Area

200

Ori

3 Survey

ginal Survey

17600

2,935.0

2,915.0

2,895.0

2,875.0

- 2,855.0

--- ---------- ----- --- ---- ---- 2,835.0

26400 35200 44000 52800 61600 70400 79200 88000

Capacity (acre-feet)

Figure 6. - 2003 area and capacity curves.