Harry Strunk Lake 

2006 Sedimentation Survey 

U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Denver, Colorado December 2006 

i

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering 

and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, 

including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson 

Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to 

comply with a collection of information if it does not display a currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE 

December 2006 

2. REPORT TYPE 3. DATES COVERED (From – To) 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Harry Strunk Lake 

2006 Sedimentation Survey 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

5e. TASK NUMBER 

6. AUTHOR(S) 

Ronald L. Ferrari 

5f. WORK UNIT NUMBER 

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

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

8. PERFORMING ORGANIZATION REPORT 

NUMBER 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

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

11. SPONSOR/MONITOR'S REPORT 

NUMBER(S) 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

13. SUPPLEMENTARY NOTES 

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

14. ABSTRACT 

The Bureau of Reclamation (Reclamation) surveyed Harry Strunk Lake in May 2006 to develop new reservoir 

topography and compute a present storage-elevation relationship (area-capacity tables). The 2006 underwater 

survey, conducted between reservoir elevation 2,365.7 and 2,365.9 feet (project datum), 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. Above-water 

topography was mapped by digitizing a reservoir contour from the U.S. Geological Survey quadrangle (USGS quad) 

maps of the reservoir area. Using the 2006 survey data, the digitized contour was adjusted throughout the reservoir 

due to shoreline erosion and in the upper reservoir area due to the sediment delta. Due to the lack of above water 

data, this study assumed no change since the 1981 range line survey from elevation 2,366.1 and above. 

As of May 2006, at conservation pool elevation 2,366.1, the surface area was 1,840 acres with a total capacity of 

34,647 acre-feet. Since dam closure on August 8, 1949, about 6,473 acre-feet of sediment has accumulated below 

elevation 2,366.1, resulting in a 15.7 percent loss in reservoir volume. 

15. SUBJECT TERMS 

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

area/ sedimentation survey/ global positioning system/ lake/ bathymetry

16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON 

a. REPORT b. ABSTRACT a. THIS PAGE 

17. LIMITATION 

OF ABSTRACT

18. NUMBER 

OF PAGES 

19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Sedimentation and River Hydraulics Group 

Denver, Colorado December 2006 

Harry Strunk Lake 

2006 Sedimentation Survey 

prepared by 

Ronald L. Ferrari 
Mission Statements 

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. 

___________________________ 

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

water and related resources in an environmentally and economically sound 

manner. 

Acknowledgments 

Reclamation's Sedimentation and River Hydraulics Group (Sedimentation Group) of the 

Technical Service Center (TSC) prepared and published this report. Ronald Ferrari of the 

TSC and Mark Rouse of the McCook Field Office in the Great Plains Region conducted 

the bathymetric survey. Ron Ferrari of the TSC completed the data processing needed to 

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

developed digital data sets needed for the final topographic map. Dave Varyu developed 

a table that provides more accurate means to present the summary of the reservoir 

sediment data. Kent Collins of the TSC performed the technical peer review of this 

documentation. 

Reclamation Report 

This report was produced by the Bureau of Reclamation’s Sedimentation and 

River Hydraulics Group (Mail Code 86-68540), PO Box 25007, Denver, 

Colorado 80225-0007. http://www.usbr.gov/pmts/sediment/ 

Disclaimer 

No warranty is expressed or implied regarding the usefulness or completeness of 

the information contained in this report. References to commercial products do 

not imply endorsement by the Bureau of Reclamation and may not be used for 

advertising or promotional purposes. 
Table of Contents 

Page

Introduction.........................................................................................................................1 

Summary and Conclusions .................................................................................................2 

Control Survey Data Information .......................................................................................4 

Reservoir Operations ..........................................................................................................4 

Hydrographic Survey Equipment and Method ...................................................................5 

Reservoir Area and Capacity ..............................................................................................6 

Topography Development............................................................................................6 

Shoreline Erosion .........................................................................................................9 

Development of the 2006 Harry Strunk Lake Surface Areas.....................................11 

2006 Storage Capacity................................................................................................12 

2006 Reservoir Sediment Analyses..................................................................................12 

References.........................................................................................................................18

18

Index of Figures 

Figure 1 - Reclamation Reservoirs located in Nebraska.....................................................1 

Figure 2 - Survey vessel with mounted instrumentation on Jackson Lake in Wyoming....5 

Figure 3 - Harry Strunk Lake topographic map..................................................................8 

Figure 4 - Eroded Shoreline................................................................................................9 

Figure 5 - Large areas of erosion occurring above normal reservoir water surface, 

elevation 2,366. ........................................................................................................10 

Figure 6 - View of shoreline erosion over extensive area of reservoir. ............................10 

Figure 7 - Typical sediment deposition profile.................................................................13 

Figure 8 - Harry Strunk Lake area and capacity plots. .....................................................17

Index of Tables

Table 1 - Reservoir sediment data summary (page 1 of 2). ..............................................14 

Table 2 - Summary of 2006 survey results. ......................................................................16 

iv
Harry Strunk Lake 2006 

Sedimentation Survey 

Introduction 

Medicine Creek Dam and Harry Strunk Lake are principal features of the 

Frenchman-Cambridge Division of the Pick-Sloan Missouri Basin Program 

located in southwestern Nebraska. Additional storage features are Swanson and 

Hugh Butler Lakes, and Enders Reservoir. The four dams, reservoirs, and 

irrigation systems provide storage to irrigate 66,161 acres of project lands, flood 

control, fish and wildlife conservation, and recreation along the Republican River 

and its three tributaries of Red Willow and Medicine Creeks, and the Frenchman 

River. 

Medicine Creek Dam and Harry Strunk Lake in Frontier County on Medicine 

Creek are located about seven miles northwest of Cambridge and 60 miles south 

east of North Platte, Nebraska (figure 1). 

Figure 1 - Reclamation Reservoirs located in Nebraska. 

1
Medicine Creek Dam is an earthfill structure that was completed in August of 

1949. The dam’s dimensions are as follows: 

 Hydraulic height1

 86 feet Structural height 165 feet 

 Crest length 5,665 feet Crest elevation 2,415.0 feet2

The spillway, crest elevation 2,386.2, is a concrete uncontrolled ogee overflow 

crest located in the left abutment of the dam (Bureau of Reclamation, 1964). The 

discharge capacity is 97,800 cubic feet per second (cfs) at maximum reservoir 

elevation 2,408.9. A slot 13 feet wide and 20.1 feet deep is provided between the 

two center piers of the spillway and has a crest elevation of 2,366.1 feet, the 

normal reservoir water surface. The discharge capacity is 3,780 cfs through the 

13-foot center notch with the reservoir at elevation 2,386.2. 

A river outlet works is located near the right abutment and consists of a concrete 

horseshoe conduit 8-feet diameter containing operating valves and a 44-inch steel 

pipe for controlled releases from the reservoir. The discharge capacity is 390 cfs 

at spillway crest elevation 2,366.1. 

The drainage area above Medicine Creek Dam is approximately 880 square miles 

of which only 642 square miles is considered contributing runoff. The additional 

238 square miles of sand hill area yields base flows through the subsurface 

drainage, (Bureau of Reclamation, 2003). The reservoir extends 8.5 miles up 

Medicine Creek at reservoir elevation 2,366.1 with an average reservoir width of 

0.34 miles (Bureau of Reclamation, 1964). 

Summary and Conclusions 

This Reclamation report presents the 2006 results of the survey of Harry Strunk 

Lake. The primary objectives of the survey were to gather data needed to:

$ develop lake topography 

$ compute area-capacity relationships 

$ estimate storage depletion, by sediment deposition, since dam closure 

The on-line positioning user service (OPUS) with real-time kinematic (RTK) 

global positioning system (GPS) control survey established a horizontal and 

 

1

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

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

and Reservoirs, or ASCE’s Nomenclature for Hydraulics.

2

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

Reclamation that was reported to be the National Geodetic Vertical Datum of 1929 (NGVD29) and around 

0.9 feet lower than the North American Vertical Datum of 1988 (NAVD88).

2
vertical control network near the reservoir for the hydrographic survey. OPUS is 

operated by the National Geodetic Survey (NGS) and allows users to submit GPS 

data files where it is processed with known point data to determine positions of 

points relative to the national control network. Initially, the GPS base was set 

over Reclamation brass cap “155 RP” that is located near the right abutment of 

the dam. To begin the collection process, an absolute position with the single 

GPS unit was measured. This position data was later corrected using the base 

station data, collected throughout the day, submitted to OPUS. During the 

bathymetric survey, three base station locations were used and all three sites were 

submitted to the OPUS web site for computations and verified, with good results, 

using RTK GPS. The horizontal control was in Nebraska state plane coordinates 

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

to the National American Vertical Datum of 1988 (NAVD88) and the 

Reclamation project vertical datum. All elevations in this report are referenced to 

Reclamation’s project or construction vertical datum that appears to be tied to the 

National Geodetic Vertical Datum of 1929 (NGVD29) that is around 0.9 feet 

lower than NAVD88. 

The May 2006 underwater survey was conducted between reservoir elevation 

2,365.7 and 2,365.9. The bathymetric survey used sonic depth recording 

equipment interfaced with RTK GPS for 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 Harry Strunk Lake. 

The positioning system provided information to allow the boat operator to 

maintain a course along these grid lines. Water surface elevations recorded by 

Reclamation’s reservoir gauge during the time of collection were used to convert 

the sonic depth measurements to reservoir bottom elevations. The above-water 

topography was determined by digitizing existing contour lines from the USGS 

quad of the reservoir area. During the bathymetric survey the boat location 

plotted outside these contours indicating extensive shoreline erosion has occurred 

throughout this reservoir. The contour locations where adjusted where this 

occurred. The previous surveys also documented shoreline erosion (Bureau of 

Reclamation, 1964). 

The Harry Strunk Lake topographic map is a combination of the adjusted 

digitized contour and the 2006 underwater survey data. A computer graphics 

program generated the 2006 reservoir surface areas at predetermined contour 

intervals from the collected reservoir area. The 2006 area and capacity tables 

were produced by a computer program that used 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 Harry Strunk Lake and watershed 

characteristics for the 2006 survey. The 2006 survey determined that the 

reservoir has a total storage capacity of 193,020 acre-feet and a surface area of 

5,784 acres at surcharge pool elevation 2,408.9. Since closure in August 1949, 

3
the reservoir has an estimated volume change of 6,473 acre-feet below 

conservation reservoir elevation 2,366.1. This volume represents a 15.7 percent 

loss in total original capacity at this elevation. 

Control Survey Data Information 

Prior to the bathymetric survey, a control network was set by the bathymetric 

survey crew and used throughout the survey. Initially, the RTK GPS base station 

was set over marker “155 RP” that is located in an open field near the right 

abutment of dam. The coordinates for this point were determined by processing 

the first day of collected raw data through the NGS service OPUS. During the 

bathymetric survey, three base station locations were used and all three sites were 

submitted to the OPUS web site for computations and verified with RTK GPS 

measurements. The horizontal control was in Nebraska state plane coordinates in 

NAD83 and the vertical control was tied to NAVD88 and the Reclamation project 

vertical datum. All elevations in this report are referenced to Reclamation’s 

project or construction vertical datum that is reference to NGVD29 and around 

0.9 feet lower than NAVD88. Following are the coordinates determined during 

this survey at the indicated locations. 

 Elevation Elevation 

Location North West (NAVD88) (NGVD29) 

155-RP 198,278.56 1,577,534.323 2,402.57 

Westmaster 197,860.39 1,575,856.569 2,418.39 2,417.502 

Section 35 220,592.17 1,575,428.521 2,477.26 

RL1-R 198,437.22 1,577,411.486 2,405.12 2,404.22 

Reservoir Operations 

Harry Strunk Lake is part of the Frenchman-Cambridge Division of the PickSloan Missouri Basin Program that provides storage for irrigation, flood control, 

fish and wildlife conservation, recreation and sediment control. The May 2006 

capacity table shows 193,020 acre-feet of total storage below the maximum water 

surface elevation 2,408.9, table 2. The 2006 survey measured a minimum lake 

bottom elevation of 2,320.1. The following values are from the May 2006 

capacity table: 

 $ 105,659 acre-feet of surcharge between elevation 2,386.2 and 2,408.9. 

 $ 52,714 acre-feet of flood control between elevation 2,366.1 and 2,386.2.

 $ 26,750 acre-foot of active storage between elevation 2,343.0 and 2,366.1. 

 $ 4,489 acre-foot of inactive storage between elevation 2,335.0 and 2,343.0. 

 $ 3,408 acre-foot of dead storage below 2,335.0. 

4
Harry Strunk Lake computed annual inflow and reservoir stage records are listed 

by calendar year on table 1 for the operation period August 1949 through May 

2006. The inflow values were computed by the Great Plains Regional Office and 

show annual fluctuation with a computed average inflow of 46,300 acre-feet per 

year. The maximum reservoir elevation was 2,374.1, recorded during water year 

1960, and after initial filling, minimum recorded elevation was 2,340.4 during 

water year 1978. 

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 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 instrumentation on Jackson Lake in Wyoming. 

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 from a RTK receiver are precise 3-D 

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 

5
Nebraska’s state plane coordinates in NAD83. The RTK GPS system employs 

two receivers that track the same satellites simultaneously just like with 

differential GPS. 

Harry Strunk Lake hydrographic survey was conducted in May of 2006 between 

reservoir elevation 2,365.7 and 2,365.9 (Reclamation project datum). The 

bathymetric survey was conducted using sonic depth recording equipment, 

interfaced with a RTK GPS, capable of determining sounding locations within the 

reservoir. The survey system software continuously recorded reservoir depths 

and horizontal coordinates as the survey boat moved along closely spaced grid 

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

parallel along an upstream-downstream river alignment of the reservoir at around 

150-foot spacing. Data was collected along the shore by the survey vessel for the 

majority of the reservoir. 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 2006 underwater data was collected by a depth sounder that was calibrated by 

lowering an instrument that measured the sound velocity of the reservoir water 

column. The individual depth soundings were adjusted by the speed of sound of 

the measurements that can vary with density, salinity, temperature, turbidity, and 

other conditions. The soundings were further verified by lowering a weighted 

cable below the boat with beads marking known depths. The collected data were 

digitally transmitted to the computer collection system via a RS-232 port. The 

depth sounder also produced an analog hard-copy chart of the measured depths. 

These graphed analog charts were analyzed during post-processing, and when the 

analog charted depths indicated a difference from the computer recorded 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. Additional information on 

collection and analysis procedures can be found online, (Corps of Engineers, 

January 2002) and (Ferrari, R.L., 2006). 

Reservoir Area and Capacity 

Topography Development 

The topography of Harry Strunk Lake was developed from the 2006 collected 

underwater data and the digitized contour from the USGS quad maps developed 

from aerial photography dated 1952. The digitized contour line was elevation 

2,366 and the enclosed contour area, with the island surfaces removed, was within 

a few percent of the 1951 survey surface area results at the same elevation. The 

6
2006 survey data was used to adjust the digitized contour due to the above water 

sediment delta that had formed since 1952 in the upper reservoir area and the 

extensive shoreline erosion that has occurred throughout this reservoir. The best 

means to truly develop this contour and the rest of the above water reservoir area 

would be by a detailed aerial survey. 

The adjusted contour, elevation 2,366, was used to perform a hardclip around the 

2006 data of Harry Strunk Lake. This hardclip was used during the triangular 

irregular network (TIN) development so interpolation did not occur outside the 

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

available to represent the water surface during the 2006 survey. Using 

ARCEDIT, the 2006 underwater and the digitized 2,366 contour were plotted. 

The plot showed that the underwater data did not lie completely within the 

original elevation 2,366 contour from the USGS quad maps. The 2,366 contour 

was modified to include the entire underwater data set within the enclosed 

polygon. Using select and move commands within ARCEDIT, the vertices of the 

clip were shifted to contain the 2006 underwater data. This adjusted clip was 

assigned an elevation of 2,366. 

Contours for the reservoir below elevation 2,366 were computed from the 2006 

data sets using the triangular irregular network (TIN) surface-modeling package 

within ARC/INFO. A TIN is a set of adjacent non-overlapping triangles 

computed from irregularly spaced points with x,y coordinates and z values. TIN 

was designed to deal with continuous data such as elevations. The TIN software 

uses a method known as Delaunay's criteria for triangulation where triangles are 

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

circle drawn through the three nodes of a triangle will contain no other point, 

meaning that sample points are connected to their nearest neighbors to form 

triangles using all collected data. This method preserves all collected survey 

points. Elevation contours are then interpolated along the triangle elements. The 

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

Documentation, (ESRI, 1992). 

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

used to interpolate contours from the Harry Strunk Lake TIN. The areas of the 

enclosed contour polygons at one-foot increments were developed from the 

survey data for elevations 2,322.0 through 2,362.0. Since no complete reservoir 

aerial data was collected, this study assumed no change in reservoir surface area, 

since the 1981 survey, for elevation 2,366.0 and above. Since there was limited 

underwater data collected during the 2006 survey, above elevation 2,362, this 

study only used surface area development from elevation 2,362 and below. The 

reservoir contour topography at 2-foot intervals is presented on figure 3.

7
8

Figure 3 - Harry Strunk Lake topographic map. 
Shoreline Erosion 

The 2006 underwater survey witnessed extensive shoreline erosion throughout the 

reservoir area. During collection, the GPS boat positions were found at times to 

be outside the digitized USGS quad contour locations, indicating the boat was on 

solid ground. The USGS quad contour was developed from aerial photography 

flown in the 1950’s and at times, the position of the boat was tens of feet outside 

their boundary. Even with the extensive shore erosion that has occurred since 

dam closure, the survey vessel was able to maneuver close to the vertical banks in 

deep water conditions where previous shore material had collapsed into the 

reservoir. It appears that over time the collapsed material washes 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 pictures showing the shoreline erosion and its 

affect on the reservoir, figures 4 through 6. 

Figure 4 - Eroded Shoreline. 

 

9
Figure 5 - Large areas of erosion occurring above normal reservoir water surface, elevation 2,366. 

Figure 6 - View of shoreline erosion over extensive area of reservoir. 

10
The above photographs show the extent of the shoreline erosion that has occurred 

throughout the reservoir. If the erosion were just below the reservoir high water 

mark, the total volume of the reservoir would not be greatly affected. In that case, 

the gain in surface area and resulting volume in the upper reservoir elevation zone 

would be offset by the loss of surface area and volume in the lower elevations of 

the reservoir due to the depositing material from the banks. The photographs 

(figures 4 through 6) show a large amount of the eroded material above the 

normal or conservation reservoir elevation 2366.1, meaning that a portion of the 

loss of the original total reservoir volume is due to material from reservoir 

shoreline erosion along with incoming river sediments. The only means to 

accurately measure the extent of the shoreline erosion would be by an extensive 

above water survey. 

The shoreline erosion was previously documented in the 1962 sedimentation 

survey report, with photographs and cross section plots of several of the sediment 

rangelines revealing the extensive impact of the reservoir wave action. The banks 

are composed of loessial soil which exhibits the characteristic of being able to 

stand on almost vertical slopes, but offers little or no resistance to the erosive 

force of the waves (Bureau of Reclamation, 1964). It is assumed the majority of 

the bank erosion occurred during the initial filling and early years of the reservoir, 

but it still occurs today to a lesser extent. 

Development of the 2006 Harry Strunk Lake Surface 

Areas 

The 2006 surface areas for Harry Strunk Lake were computed at 1-foot 

increments, from elevation 2,321.0 through 2,366.0, directly from the TIN that 

covered the Harry Strunk Lake within the hard clip area only. This TIN was 

developed within the hardclip area that included the digitized elevation 2,366.0 

contour that was modified for the shoreline erosion that has occurred throughout 

the lake area. These calculations were performed using the ARCGIS surface area 

and volume command that computes areas at user-specified elevations directly 

from the TIN and includes all regions of equal elevation. For the purpose of this 

study, the measured 2006 survey areas at 1-foot increments from elevation 

2,321.0 through 2,362.0 were used to compute the new area and capacity tables. 

There were insufficient 2006 surveyed data points, for accurate computer 

development of surface areas at elevations above 2,362.0. Straight line 

interpolation was used to compute the surface areas between elevations 2,362.0 

and 2,366.0. This study assumed no change in surface area, since the 1981 

survey, from elevation 2,366.0 and above. 

11
2006 Storage Capacity 

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

developed using the area-capacity computer program ACAP (Bureau of 

Reclamation, 1985). The ACAP program can compute the area and capacity at 

elevation increments from 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 0.000001 for Harry Strunk Lake. 

The capacity equation is then used over the full range of intervals fitting within 

the allowable error limit. For the first interval at which the initial allowable error 

limit is exceeded, a new capacity equation (integrated from basic area curve over 

that interval) is utilized until it exceeds the error limit. Thus, the capacity curve is 

defined by a series of curves, each fitting a certain region of data. Differentiating 

the capacity equations, which are of second order polynomial form, final area 

equations are derived: 

y = a1 + a2x + a3x

2 

 where: y = capacity 

x = elevation above a reference base 

a1 = intercept 

a2 and a3 = coefficients 

Results of the Harry Strunk Lake area and capacity computations are listed in a 

separate set of 2006 area and capacity tables and have been published for the 

0.01, 0.1 and 1-foot elevation increments (Bureau of Reclamation 2006). A 

description of the computations and coefficients output from the ACAP program 

is included with these tables. The original, 1951, 1962, 1981, and 2006 areacapacity relationships are listed on table 2 and the curves are plotted on figure 8. 

As of May 2006, at conservation use elevation 2,366.1, the surface area was 1,840 

acres with a total capacity of 34,647 acre-feet. 

2006 Reservoir Sediment Analyses 

Results of the 2006 Harry Strunk Lake area and capacity computations are listed 

in table 1 and columns 10 and 11 of table 2. Columns 2 and 3 of table 2 list the 

original area and capacity values and the results from the 1951, 1962, and 1981 

surveys are also listed. Column 12 lists the capacity differences between the 

original and 2006 survey results due to sediment inflow and bank erosion. Figure 

8 is a plot of the Harry Strunk Lake surface area and capacity values for all the 

listed surveys and illustrates the differences between the surveys. The 

comparisons show that the total reservoir capacity in 2006 is 6,473 acre-feet less 

than the original volume at conservation reservoir elevation 2,366.1. 

12
It must be noted that the 2006 area and capacity tables were generated assuming 

no surface area change, since the 1981 survey, from elevation 2,366.0 and above. 

This is all probably not the case, but it is assumed any loss due to sediment 

deposition above this elevation would not be significant since the previous 

surveys. The only means to measure this would be by an extensive above water 

survey. 

The estimated 100 years of sediment accumulation for Harry Strunk Lake was 

31.8 percent or 30,000 acre-feet at flood control elevation 2,386.2. This computes 

to an annual loss of 300 acre-feet. Table 1 show that the 1962 survey measured 

an average annual loss of 321.3 acre-feet at conservation reservoir elevation 

2,366.1. Since 1962, the 1981 and 2006 surveys measured a significantly less 

average annual loss of reservoir capacity. The 2006 survey measured an average 

annual loss of 42.3 acre-feet, at elevation 2,366.1, since the 1981 survey. Since 

closure the average annual loss was computed to be 114.0 acre-feet by the 2006 

study analysis. Additional research would be needed to determine the reason for 

such a drop in average annual loss, but the initial significant impact of the 

shoreline erosion and the different methods of surveys would be two issues to 

address. 

Figure 7 illustrates a typical reservoir sediment deposition profile where the pivot 

point of the depositing delta is near the normal water surface of the reservoir that 

for Harry Strunk Lake is near elevation 2,360 (Bureau of Reclamation, 1982). 

The 1962 survey developed a longitudinal profile of the upstream river showing 

this pivot point occurring just upstream of Mitchell Creek. The 2006 contours 

show that this pivot has only moved a little downstream of Mitchell Creek, 

indicating that the annual sediment inflow since 1962 has decreased (figure 3). 

Figure 7 - Typical sediment deposition profile. 

13
1. 2. Medicine Creek 3. STATE Nebraska

4. 5. Cambridge 6. COUNTY Frontier

7. ° 22 ' 40 " ° 13 ' 00 " 8. 1 9. SPILLWAY CREST EL 2

10. 11. 12. GROSS STORAGE 15

CAPACITY, AC-FT

a. 3

b.

c.

d. 16

e.

f.

g.

17. LENGTH OF RESERVOIR 4

18. TOTAL DRAINAGE AREA 5 22. 6

19. NET SEDIMENT CONTRIBUTING AREA 5 23. MEAN ANNUAL RUNOFF 7 INCHES

20. LENGTH MILES AVG. WIDTH MILES 24. MEAN ANNUAL RUNOFF 7 ACRE-FEET

21. 25. °F °F6

26. DATE OF 27. 28. 29. 30. 31. C/

3

8

9

26. DATE OF 35. 36

7

26. DATE OF 37. 38.

26. DATE OF 39.AVG. DRY WT. 40. SED. DEP. TONS/MI.2

-YR 41. STORAGE LOSS, PCT. 42 SEDIMENT 

(#/FT3

) b. TOTAL b. TOTAL TO INFLOW, PPM

TO DATE DATE a. PER. b. TOT.

43.

56.7

5/81

5/06

10

11

NO. OF

RANGES OR 

INTERVALS

105,734 199,935

94,201

AREA, AC.

R

SURVEY

V 2 10/51 .2 2.2

D

BEGAN

MAX. ELEVATION MIN. ELEVATION ANNUAL TEMP, MEAN

8/1949

MILES

BEGAN

DATE NORMAL

8/1949

OPERATIONS

DATA SHEET NO.

DATE

STORAGE

2415.0

RESERVOIR SEDIMENT

DATA SUMMARY

Harry Strunk Lake NAME OF RESERVOIR

DATE

OF

SURVEY

5/00

SURVEY

26. 44.

DATE

OF

SURVEY

A

T

Y

SURVEY

ACRE - FEET

32.

26.

CAPACITY

WATER INFLOW TO DATE, AF

SURVEY

PERIOD CAPACITY LOSS, ACRE-FEET

5,249

6,120

29,751 41,120

11,369

6,120

I

N

S

a.

 /MI. a. TOTAL 2 b. AVG. ANN. c. -YR.

0.07

5,416

PERIOD

U

TYPE OF SURFACE

SURVEY

a. MEAN ANN.

31.7 34

TOTAL SEDIMENT DEPOSITS TO DATE, AF

ANNUAL

PRECIPITATION

920,000 52,700 1,671,600

a. AVG. ANNUAL

6,473

0.10

RATIO AF/AF

0.89

0.75

to 110

33.

36,847

35,704 0.77

41,120

39,226

Contour (D)

Range (D)

Contour (D) 10 - ft 1,918

1 - ft 11

31

1,840

52 °F RANGE -22

5,780

3,486

2,408.9

2,343.0

2,335.0

1,918

793

530

960,600

14.

2,386.2 53,081

SURFACE AREA, AC-FT

ORIGINAL 13. ORIGINAL 

S

R

V

O

I

R

2,366.1

S

E

STORAGE

ALLOCATION

74,200

34.

18.4

b.

PERIOD PERIOD WATER INFLOW, ACRE-FEET

MAX. ANN. c.

56,500 105,400

40

OWNER

SEC

LAT

25

M

TWP.

1

26 W

STREAM

NEAREST P.O.

TOP OF DAM ELEVATION

D

A 5N RANGE

B

A

R

E

38,300

2386.2

ACRE-FEET

56,500

6/06 75,200 2,632,200

5/81

751,600

50,000

13.2

5/81 62.1

42.3 12 6/06

1,143

JOINT USE

CONSERVATION

1,057

10/51

a. TOTAL

0.85

0.80

170.9

114.2

321.3 12

YRS YRS

25.0

12/62

8/49

12/62

5/81

10/51 71.4 2,084

0.0

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN REACH DESIGNATION

10 20 30 40

60-

70

50-

60

70.3 475

0.28 15.7

0.42

2,408.9

2,400.0

2,340.0

2,330.0

2,350.0

2,340.0

2,400.0

2,386.2

2,360.0 2,375.0

90- 100-

2,366.1

30-

2330.0-

15.6 19.1 13.2 4.9

2,350.0 2,360.0

0.4

2,320.1

16.2 17.5

2,301.0

REACH DESIGNATION PERCENT OF TOTAL ORIGINAL LENGTH OF RESERVOIR

12.0

111

0- 110-

90 115

70-

80

10- 20- 80-

8.5 MILES

1.1

DEPTH DESIGNATION RANGE BY RESERVOIR ELEVATION

2,366.1

2,386.2

2,375.0

MEAN ANNUAL PRECIPITATION 20

46,300

INCHES

SQUARE MILES 1.16

SQUARE MILES

AVG. WIDTH OF RESERVOIR

100

Bureau of Reclamation

LONG

SURCHARGE

INACTIVE

DEAD

TOP OF POOL

FLOOD CONTROL

POWER

0.34

ELEVATION

880

34 1,768

34,647

Range (D) 1,842

Range (D)

642

PER. PER.

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

120-

125

115-

105 120

2320.1-

100

105-

6/06

E 11.1 13.3

A 12/62

12/62 4,273

6,396

0.27

10.4 4,404

14,063

0.50

0.18

751,600

TOTAL

1,840

a. MEAN ANN. b. TOTAL

14,063

b. AVG. ANN. c. /MI.2

-YR.

46,300

12 321.3 0.50

12

735

4,273

2,084

0.78

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

14
15

1

2

3

4

5

6

7

8

9

10

11

12

 erosion throughout the reservoir.

30,400

1982 2,367.7 2,361.0 39,200 1983 2,368.0 2,355.6 39,800

2,367.1 2,352.6 37,700

2002 2,366.6 2,347.2 28,800 2003 2,365.3 2,348.1

2000 2,367.6 2,352.0 35,900

45,300

1998 2,368.3 2,351.2 35,600 2,368.2 2,352.0 40,600

2,368.8 2,353.0

2,334.0 420

1976 2,367.0 2,343.2 40,300 1977 2,368.0 2,345.4

2,332.0 363 2,191

2,360.0 1,359

2,330.0 307 1,520

2,356.0 1,190 19,975 2,358.0 1,274 22,441

2,340.0 594 5,994 2,342.0 2,343.0 680

444 3,408 2,336.0 475 2,338.0 530

1966 2,367.1 2,363.1 57,800 1967 2,369.9 2,362.6 74,200

64,400

1964 2,367.8 2,354.0 49,100 1965 2,367.3 2,356.0 57,600

2,367.2 2,351.5 42,000

1962 2,372.7 2,356.6 105,400 1963 2,369.7 2,353.8

2,367.0 2,350.6 42,800 1971

1968 2,367.1 2,357.2 50,000 1969 2,370.0 2,358.7 71,500

1970

45. RANGE IN RESERVOIR OPERATION

1,840

135

171,175

2004

2,408.9 5,783 193,020

2,385.0

2,364.0 1,643 30,989

145,247

2,409.0 5,793 193,599

2,400.0 4,952

CAPACITY

2,395.0 4,397

2,370.0

ELEVATION AREA CAPACITY

54,052

2,386.2 3,483 87,361

2,375.0 2,518

961

2,366.0 1,832 34,463

4,874

7,897

25,075

2,976

2,326.0 196 512 2,328.0 255

83,250

121,875

3,369

2,140 42,407

643 7,235

3,867

782 10,083

1,029

2,320.1 0 0

2006 CAPACITY

ELEVATION AREA

2006 2,365.4 2,357.5 8,700

2,359.9 2,356.7 28,600 2,366.6 2,350.7 30,900

1997

2005

1999

2001

1996 2,368.3 2,349.8 44,100 41,900

1994 2,368.2 2,354.0 41,600 1995 2,368.3 2,348.3 38,400

1992 2,365.4 2,348.6 34,200 1993 2,371.5 2,362.6 75,200

1990 2,367.2 2,348.7 30,100 1991 2,367.1 2,348.5 35,300

1988 2,367.6 2,355.0 41,700 1989 2,367.2 2,351.8 34,700

35,300

1986 2,367.5 2,350.9 38,800 1987 2,367.6 2,352.3 39,000

2,367.8 2,346.6 42,900

1984 2,368.4 2,354.6 48,800 1985 2,367.5 2,355.3

1980 2,345.2 39,200 1981

2,368.6 2,350.5 46,200

1978 2,340.4 43,900 1979 2,368.1 2,341.4 48,400

1974 2,348.9 36,800 1975

2,354.0 48,300

1972 2,352.4 41,600 1973 2,367.5 2,351.1 51,300

2,353.2 74,700 1961 2,368.0

2,371.9 2,352.5 68,000

1958 2,363.7 47,700 1959 2,367.4 2,354.8 40,800

1956 2,363.5 2,348.2 41,100 1957

2,369.2

2,357.3 38,800

1954 2,366.1 2,354.0 39,900 1955 2,347.4 37,400

2,372.4 2,362.5 100,300

1952 2,364.9 41,300 1953 2366.5

2,362.6

2,367.4

2,300.0 17,800

2,390.0

182

27,893

34,647

67,587

101,277

1951

MIN. ELEV. INFLOW, AF

1950 2,329.3 50,100

1949 2,329.2

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

47.

48. Bureau of Reclamation

All elevations are in feet based on original project datum that is around 1 foot lower than NAVD88.

Spillway crest elevation 2,386.2 of four 50-foot wide ungated openings located at left abutment. Structure consist of 13-foot center notch 

Elevations from Reservoir Capacity Allocation table. Original surface areas and capacity values recomputed using ACAPprogram.

Bureau of Reclamation's Project Data Book, 1981.

REMARKS AND REFERENCES

 computations. Range line method showed some consolidation of sediments in lower reservoir area and extensive reservoir bank

12

2,324.0

2,362.0

2,366.1

2,380.0

2,405.0

YEAR MAX. ELEV.

49. Bureau of Reclamation October 2006

Surface area and capacity at elevation 2,366.1. 1981 survey produced new area-capacity curves by range line method. No report of results.

All 2006 capacities computed by Reclamation's ACAP computer program. 1-foot surface area data from elevation 2,321.0 through 2,362.0.

 Assumed no change since 1982 survey in upper elevations. Surface area results from 1982 survey used for elevation 2,366.0 and the

 1951 results not used due to questions on upper elevation data. All survey results recomputed using ACAP for comparison 

 to the loss in the lower elevation zones of the reservoir. 2006 survey also documents extensive shoreline erosion.

AGENCY MAKING SURVEY

Mean annual runoff of 46,300 acre-feet, item 24, August 1949 through May 2006. From Reclamation's Great Plains Region by calendar year. 

Surface area and capacity at elevation 2,366.1, spillway crest elevation. 1951 survey obtained data to prepare new area-capacity curves.

Surface area and capacity at elevation 2,366.1. 1962 survey obtained data to prepare updated area-capacity curves and sediment

 Results don't conform to other surveys, leading to questionable results in upper reservoir elevations. 

AGENCY SUPPLYING DATA DATE

3,842

5,419

Length at elevation 2,366.1.

Total drainage area 880 mi2

 with 642 mi2 considered contributing to surface runoff. Values from SOP (Standard Operation Procedures).

 10-foot increments from elevation 2,370.0 through 2,400.0.

Due to differences of detail between original and following resurveys, computing capacity loss by comparing differences is questionable.

2006

2,335.0

SURVEY

13

2,322.0 28 15

46. ELEVATION - AREA - CAPACITY - DATA FOR

1,453

2,367.9

2,374.1

2,367.1

ELEVATION AREA CAPACITY

2,367.2

2,368.4

2,369.2

1960

2,344.0 713 8,593 2,346.0 2,348.0 875 11,739

2,350.0 955 13,571 2,352.0

 purposes. 1962 survey shows extensive loss due to sedimentation. 1962 also documented extensive shoreline erosion that contributes

1,100 17,684

 with crest elevation 2,366.1.

15,554 2,354.0

2,896

Table 1 - Reservoir sediment data summary (page 2 of 2).
16

1 2 3 4 5 6 7 8 9 10 11 12 

 Original Original 1951 1951 1962 1962 1981 1981 2006 2006 Sediment Pe

Elevation Survey Capacity Survey Survey Survey Survey Survey Survey Survey Survey Orig-06 Se

Feet Acres Ac-Ft Acres Ac-Ft Acres Ac-Ft Acres Ac-Ft Acres Ac-Ft Ac-Ft T

2408.9 5780 199935 6205 197493 5749 194832 5784 194080 5784.0 193020 6915 2405.0 5418 178100 5608 174458 5462 172971 5419 172234 5419.0 171175 6925 2400.0 4955 152167 4823 148381 4981 146864 4952 146306 4952.0 145247 6920 2390.0 3850 108140 3908 104908 3847 102674 3842 102336 3842.0 101277 6863 2386.2 3486 94201 3457 90916 3451 88807 3483 88420 3483.0 87361 6840 2380.0 2893 74427 2915 71281 2854 69291 2896 68646 2896.0 67587 6840 2370.0 2173 49097 2054 46678 2113 44559 2140 43466 2140.0 42407 6690 2366.1 1918 41120 1768 39226 1842 36847 1840 35705 1840.0 34647 6473 2360.0 1519 30637 1459 29461 1445 26839 1371 25911 1358.9 25075 5562 2350.0 1047 17807 1046 16943 924 15101 911 14501 954.6 13571 4236 2340.0 684 9155 684 8388 605 7539 611 6891 594.5 5994 3161 2330.0 377 3852 380 3108 352 2781 352 2076 306.6 1520 2332 2320.1 174 1122 135 547 120 483 58 47 0.0 0 1122 2320.0 172 1105 132 533 118 471 55 41 0.0 0 1105 2318.5 150 863 104 356 96 311 0 0 0.0 0 863 2315.0 99 427 38 108 44 66 0 0 0.0 0 427 2312.0 55 196 18 24 0 0 0 0 0.0 0 196 

2310.0 26 115 4 2 0 0 0 0 0.0 0 115 

2309.0 23 90 0 0 0 0 0 0 0.0 0 90 

2305.0 11 22 0 0 0 0 0 0 0.0 0 22 

2301.0 0 0 0 0 0 0 0 0 0.0 0 0 

1 Elevation of reservoir water surface.2 Original reservoir surface areas.3 Original reservoir capacity recomputed using ACAP.4 1951 measured reservoir surface area. (Questions on upper elevation surface areas)5 1951 reservoir capacity recomputed by ACAP.6 1962 measured reservoir surface areas.7 1962 reservoir capacity recomputed by ACAP.8 1981 measured reservoir surface areas.9 1981 reservoir capacity.

10 2006 reservoir surface areas. (Elevation 2366.1 and above from 1981 survey results).11 2006 reservoir capacity computed using ACAP.12 2006 computed sediment volume, column (3) - column (11). 13 Measured sediment in percentage my elevation from original to 2006. Total sediment volume of 6,473 acre-fe14 Depth of reservoir expressed in percentage of total depth (107.9), from maximum water surface.

Table 2 - Summary of 2006 survey results. 
Area-Capacity Curves for Harry Strunk Lake

2300.02310.02320.02330.02340.02350.02360.02370.02380.02390.02400.02410.0

0 21000 42000 63000 84000 105000 126000 147000 168000 

Capacity (acre-feet)

Elevation (feet)

5800.0 5220.0 4640.0 4060.0 3480.0 2900.0 2320.0 1740.0 1160.0 

Area (acres)

2006198119621951original

17

Figure 8 - Harry Strunk Lake area and capacity plots.
References 

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

New York. 

Bureau of Reclamation, 1964. Denver Office, The 1962 Sedimentation Survey of Harry 

Strunk Lake Nebraska, Denver, CO. 

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

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

Service Center, Denver CO. 

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

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

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

Denver CO. 

Bureau of Reclamation, December 2003. Standing Operating Procedures (SOP), Medicine 

Creek Dam and Harry Strunk Lake, Frenchman-Cambridge Division of the Pick-Sloan 

Missouri Basin Program, Great Plains Region, Billings, MT. 

Bureau of Reclamation, May 2006. Harry Strunk Lake Area and Capacity Tables, 

Frenchman-Cambridge Division of the Pick-Sloan Missouri Basin Program, 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/em1110-2-1003/toc.htm). 

ESRI, 2006. Environmental Systems Research Institute, Inc. (www.esri.com) 

Ferrari, R.L., 2006. Reconnaissance Technique for Reservoir Surveys, U.S. Bureau of 

Reclamation, Denver, Colorado. http://www.usbr.gov/pmts/sediment/projects/index.html

18