Folsom Lake 

2005 Sedimentation Survey 

U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Denver, Colorado January 2007 

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 

January 2007 

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

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Folsom Lake 

2005 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 Folsom Lake in the fall of 2005 via an interagency agreement with the U.S. 

Army Corps of Engineers (Corps of Engineers). The extensive surveys developed topographic imagery to study Folsom Dam, 

the wing and auxiliary dams, and the eight dikes that form Folsom Lake. This report presents the computed present storageelevation relationship (area-capacity tables) developed from the 2005 surveys. Unless noted, all elevations in this report are tied 

to the project vertical datum in feet that was determined to be 2.34 feet less than the North American Vertical Datum of 1988 

(NAVD88-05). 

The underwater survey was conducted from September 9 through 22, 2005 between lake elevations 437 and 441 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 developed by aerial photography under contract with Reclamation. The main body of the reservoir 

was flown on October 20, 2005 near reservoir elevation 430.2 (NAVD88-05) and high accuracy data was flown on 10/31/2005 

near reservoir elevation 427.1 (NAVD88-05). The 2005 topographic maps were developed from the combined data sets. All 

digital topographic images for these studies were tied to vertical datum NAVD88-05. For purpose of computing updated area 

and capacity tables, the topographic elevations were shifted 2.34 feet to match the project vertical elevations. The bathymetric 

survey measured a minimum elevation of 190. Lake contour surface areas were developed from elevation 490.0 and below. 

As of September 2005, at water surface elevation 466.0, the surface area was 11,140 acres with a total capacity of 966,823 acrefeet. Since initial closure in 1955, about 43,407 acre-feet of volume loss was measured by the 2005 survey. 

15. SUBJECT TERMS 

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

area/ sedimentation survey/ global positioning system/ lake/ multibeam/ 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 
ii
U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Sedimentation and River Hydraulics Group 

Denver, Colorado January 2007 

Folsom Lake 

2005 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. Corps of Engineers 

provided funding for conducting the detailed surveys of the Folsom Lake study area and 

for the analysis presented in this report. Terri Reaves, Chief of Reclamation’s MidPacific Region Surveys and Mapping Branch coordinated the collection and analysis of 

these extensive data sets. Ronald Ferrari of the Sedimentation Group, with assistance 

from staff of the Surveys and Mapping Branch, conducted the underwater data collection. 

The Surveys and Mapping Branch completed the topographic mapping of the merged 

data for these surveys. Ron Ferrari completed this report and the data processing needed 

to generate the reservoir only topography and area-capacity tables. Stacey Smith of the 

Mid-Pacific Region assisted in the computation of the operational values. This report 

includes comments, from December 2006 review, from the Corps of Engineers and MidPacific Region. Kent Collins of the Sedimentation Group 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 ..................................................................................... 3 

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

Reservoir Operations .............................................................................................. 6 

Hydrographic Survey Equipment and Method ....................................................... 6 

Reservoir Area and Capacity .................................................................................. 9 

Topography Development ................................................................................ 9 

Survey and Mapping Branch Processing .................................................... 9 

Sedimentation Group Processing.............................................................. 10 

Development of the 2005 Contours................................................................ 11 

Development of the 2005 Folsom Lake Surface Areas.................................. 11 

2005 Storage Capacity .................................................................................... 11 

2005 Reservoir Analyses ...................................................................................... 19 

References............................................................................................................. 26 

Appendix............................................................................................................... 27 

Index of Figures 

Page

Figure 1 - Folsom Lake location map. ................................................................................1 

Figure 2 - RTK GPS base station, WD48. ..........................................................................5 

Figure 3 - Survey vessel with mounted instrumentation on Jackson Lake in Wyoming....7 

Figure 4 - Multibeam collection system. ............................................................................7 

Figure 5 - Map index for the 2005 Folsom Lake survey...................................................12 

Figure 6 - Folsom Dam and lake topography, drawing 485-208-2058.............................13 

Figure 7 - Folsom Lake topography, drawing 485-208-2059...........................................14 

Figure 8 - Folsom Lake left wing dam and topography, drawing 485-208-2088. ............15 

Figure 9 - Folsom Lake topography, drawing 485-208-2089...........................................16 

Figure 10 - Folsom Lake and Dike 7 topography, drawing 485-208-2077.......................17 

Figure 11 - Folsom Lake topography, drawing 485-208-2078.........................................18 

Figure 12 - Folsom Lake area and capacity plots. ............................................................23 

Index of Tables 

Page

Table 1 - Reservoir sediment data summary (1 of 2)........................................................21 

Table 1 - Reservoir sediment data summary (2 of 2)........................................................22

Table 2 - Summary of 2005 survey results. ......................................................................25



Folsom Lake 2005 Sedimentation 

Survey 

Introduction 

Folsom Dam and reservoir are located on the American River approximately two 

miles upstream from the city of Folsom and 20 miles northeast of the city of 

Sacramento, California, figure 1. The dam is located in Sacramento County with 

portions of the lake also in El Dorado and Placer Counties. The reservoir 

provides a water supply for irrigation, domestic, municipal, industrial, and power 

production purposes. The reservoir also provides flood protection and recreation. 

Releases provide water quality control in the Sacramento-San Joaquin delta, 

maintain fish runs in the American River below the dam, and help maintain 

navigation along the lower reaches of the Sacramento River. Folsom Dam was 

constructed by the Corps of Engineers in the late 1940’s and transferred to 

Reclamation upon completion in a 1956 Memorandum of Understanding. A 1981 

Memorandum of Understanding made the Corps of Engineers responsible for any 

studies necessary to determine the structural adequacy of the dam. 

Figure 1 - Folsom Lake location map. 

1
Folsom Lake was created by the closure of Folsom Dam on February 25, 1955. 

Folsom Dam is a concrete structure flanked by two earth wing dams, Mormon 

Island Auxiliary Dam, and eight dikes with combined crest lengths of around 5 

miles. The concrete portion is a 1,400 foot straight gravity structure with a 

maximum structural height1 of 340.0 feet, a crest elevation of 480.52, and parapet 

wall elevation of 484.0 feet. The left wing dam is a zoned earthen embankment 

with a crest length of 2,100 feet and maximum height of 145 feet at crest 

elevation 480.5. The right wing dam is a zoned earthen embankment with a crest 

length of 6,700 feet and maximum height of 145 feet at crest elevation 480.5. 

Mormon Island Auxiliary Dam is located east of the main dam and is a zoned 

earthen embankment with a crest length of 4,820 feet and maximum height of 110 

feet at crest elevation 480.5. There are eight dikes located around the reservoir 

rim with crest elevations of 480.5 and ranging in maximum height from 15 to 105 

feet and length from 740 to 2,060 feet. 

The spillway is a gate-controlled overflow spillway divided by piers into eight 

equal sections and is located in the center gravity section of the dam at crest 

elevation 418.0. Flow is controlled by 42-foot wide radial gates that are 50-foot 

high in the service spillway area and 53-foot high in the emergency spillway area. 

The service spillway consists of the western-most five gates that discharge into a 

stilling basin in the original river channel below. The eastern most three gates 

make up the emergency spillway and discharge into a flip bucket that projects the 

discharge. The discharge capacity is 567,000 cubic feet per second (cfs); 

however, the levee system that protects the city of Sacramento downstream only 

allows a safe channel capacity of 115,000 cfs. 

The outlet works consists of eight 5-foot wide by 9-foot high gated sluice outlets 

located in the overflow spillway section of the dam. Four river outlet conduits are 

at invert elevation 280.0 and four are at invert elevation 210.0. The maximum 

discharge capacity, into the spillway stilling basin, is 27,800 cfs at reservoir 

elevation 466.0. 

Three 15.5-foot-diameter penstocks are located in the right non-overflow section 

of the concrete dam that carry water approximately 500 feet downstream to three 

generating units at the Folsom Power plant. The powerplant is the primary source 

of normal releases into the American River. 

The drainage area above Folsom Dam is approximately 1,861 square miles and 

1,020 square miles are considered sediment contributing. The total drainage area 

 

1

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

Reclamation’s Design of Small Dams and ASCE’s Nomenclature for Hydraulics. 

2

Elevations in feet. All elevations based on the original project datum established during construction that 

was found to be 2.34 feet lower than NAVD88-2005 (NAVD88-05). Unless noted, all listed elevations in 

feet and in project vertical datum. 

2
value is from the USGS water resource data (USGS, 1990). The non-sediment 

contributing area includes the normal surface area of Folsom Lake and drainage 

areas above the numerous dams located within the drainage basin above Folsom 

Dam. The drainage basin elevations range from approximately 10,400 feet at the 

headwaters to normal reservoir surface elevation 466.0. The reservoir is around 

28.0 miles in length and around 0.6 miles in width. 

Summary and Conclusions 

This Reclamation report presents the 2005 results of the survey of Folsom Lake. 

The primary objectives of the surveys were to gather data needed to:

$ develop lake topography 

$ develop detailed topography of the entrapment structures 

$ compute area-capacity relationships 

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

Reclamation was directed to survey Folsom Lake in the fall of 2005 by an 

interagency agreement with the Corps of Engineers. The extensive surveys 

developed detailed topography to be used for studies of Folsom Dam, Mormon 

Island Auxiliary Dam, the wing dams, and the eight dikes that form Folsom Lake. 

Aerial surveys covered upstream and downstream of the entrapment structures 

and extended up the north and south arms of the American River. Combined 

aerial and bathymetric survey data were used to develop the 2005 area and 

capacity tables of Folsom Lake formed by these entrapment structures. 

The underwater (bathymetric) survey was conducted from September 9 through 

22, 2005 between lake elevations 437 and 441 feet (project datum). The 

bathymetric survey used sonic depth recording equipment interfaced with a realtime kinematic (RTK) global positioning system (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 Folsom Lake. The positioning system provided information to allow the 

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

surface elevations (project datum), 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 project 

vertical datum that was found to be 2.34 feet lower than NAVD88-05. All area 

and capacity computations within this report are tied to the project vertical datum. 

The above-water topography was developed by aerial photography under contract 

with Reclamation. The main body of the reservoir was flown on October 20, 

2005 near reservoir elevation 430.2 (NAVD88-05) and high accuracy data was 

flown on October 31, 2005 near reservoir elevation 427.1 (NAVD88-05). All 

3
digital topographic images for these surveys were tied to vertical datum 

NAVD88-05. 

The 2005 Folsom Lake topography for this report is a combination of the 2005 

aerial and the shifted underwater data sets with elevations tied to NAVD88-05. 

For purpose of computing updated area and capacity tables, these topographic 

elevations were reduced 2.34 feet for the measured surface areas to match the 

project datum elevations. Since all past and present reservoir operations are tied 

to the project vertical datum, all elevations and resulting values were shifted to 

match the project datum elevations. Unless noted, all elevations in this report are 

tied to the project vertical datum in feet. 

In September 2005, Reclamation and Corps of Engineers, under the direction of 

the National Geodetic Survey, established an extensive geodetic control network 

for the entire project area in North American Datum of 1983 (NAD83) and 

NAVD88-05. This control network was established prior to all the 

photogrammetric work with the horizontal control in California state plane, zone 

2, in NAD83. This control network was established after the bathymetric survey 

was conducted and was used to adjust the processed bathymetric data to match the 

aerial survey’s horizontal and vertical datums. 

A computer graphics program generated the 2005 reservoir surface areas at 

predetermined contour intervals from these combined data sets. The 2005 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 project datum elevation increments (Bureau of Reclamation, 1985). 

Tables 1 and 2 contain summaries of the Folsom Lake and watershed 

characteristics for the 2005 survey. The 2005 survey determined that the 

reservoir has a total storage capacity of 966,823 acre-feet and a surface area of 

11,140 acres at joint use reservoir water surface elevation 466.0. Since initial 

closure in 1955, about 43,407 acre-feet of volume loss was measured by the 2005 

survey. 

Control Survey Data Information 

Reclamation’s Mid-Pacific Regional Surveys and Mapping Branch provided the 

control network information used by the bathymetric survey crew. The base 

station was set over marker “WD48,” located on the east wing dam, and was used 

throughout the duration of the survey, figure 2. The data collection was in 

California state plane coordinates, zone 2, NAD83 and the vertical was tied to 

National Geodetic Vertical Datum of 1929 (NGVD29). 

4
Figure 2- RTK GPS base station, WD48. 

In September of 2005, Reclamation and Corps of Engineers, under the direction 

of the National Geodetic Survey, surveyed an extensive geodetic control network 

for the entire project area in NAD83 and NAVD88-05. This control network was 

used for all of the photogrammetric work that followed, but was established after 

the bathymetric survey was conducted. The results of the 2005 geodetic control 

survey required a shift of the bathymetric data in the vertical and a slight shift in 

the horizontal coordinates to match the aerial survey data’s horizontal (NAV83) 

and vertical datums (NAVD88-05). The bathymetric data was tied to base station 

“WD48” and the following shifts were applied. 

NAD83/NGVD29 (project elevation) NAD83/NAVD88-05 Difference

North 2,019,300.82 2,019,301.29 (+) 0.47 

West 6,804,655.01 6,804,654.40 (-) 0.61 

Elevation: 481.04 483.38 (+) 2.34 

5
Reservoir Operations 

Folsom Dam operates to provide regulated diversion and downstream flows from 

the American River. The September 2005 capacity table shows 1,074,207 acrefeet of total storage below the maximum water surface elevation 475.4 feet. The 

2005 survey measured a minimum lake bottom near elevation 190. Since all past 

and present operations are tied to the project vertical datum, all elevations and 

resulting values in NAVD88-05 were shifted to match. The following values are 

from the September 2005 capacity table:

 $ 107,384 acre-feet of surcharge between elevation 466.0 and 475.4 feet. 

 $ 398,724 acre-feet of joint use between elevation 425.8 and 466.0 feet.

 $ 484,706 acre-foot of active storage between elevation 327.0 and 425.8 feet. 

 $ 83,387 acre-foot of inactive storage between elevation 205.5 and 327.0 feet. 

 $ 6 acre-foot of dead storage below 205.5 feet. 

Folsom Lake computed annual inflow and reservoir stage available records are 

listed by water year on table 1 for the operation period 1955 through 2005. The 

inflow values were computed by the Mid-Pacific Regional office and show annual 

fluctuation with a computed average inflow of 2,787,400 acre-feet per year. The 

maximum reservoir elevation was 467.2 recorded during water year 1963 with a 

minimum elevation of 347.6 recorded 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 3. 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 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 

California’s state plane, zone 2, coordinates in NAD83. The RTK GPS system 

6
Figure 3 - Survey vessel with mounted instrumentation on Jackson Lake in Wyoming.

employs two receivers that track the same satellites simultaneously just like with 

differential GPS. 

In 2001, the Sedimentation and River Hydraulics Group began utilizing an 

integrated multibeam hydrographic survey system. The system consists of a 

single transducer mounted on the center bow or forward portion of the boat. 

From the single transducer a fan array of narrow beams generate a detailed cross 

section of bottom geometry as the survey vessel passes over the areas to be 

mapped. The system transmits 80 separate 1-1/2 degree slant beams resulting in a 

120-degree swath from the transducer. The 200 kHz high-resolution multibeam 

echosounder system measured the relative water depth across the wide swath 

perpendicular to the vessel’s track. Figure 4 illuminates the swath of the sea floor 

that is about 3.5 times as wide as the water depth below the transducer. 

Figure 4 - Multibeam collection system. 

7
The multibeam system is composed of several instruments that are all in constant 

communication with a central on-board notebook computer. The components 

include the RTK GPS for 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 Folsom Lake bathymetric survey collection was conducted from September 9 

through September 22 of 2005 between water surface elevation 437 and 441 

(project datum). The survey was run using the multibeam instrumentation 

described above. The survey system software continuously recorded reservoir 

depths and horizontal coordinates as the survey vessel moved across close-spaced 

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

along the original river alignment of the reservoir where the multibeam swaths 

overlapped each other. In the shallower depths, around thirty feet and less, the 

swaths did not overlap. The multibeam system could have provided full bottom 

coverage not covered by these swaths, but time, budget, and access prevented this 

in the shallow water portions of the reservoir. Due to the cost and sensitivity of 

the multibeam transducer, the collection crew generally avoids collection in 

depths shallower than 10 feet. The loss of these additional data points did not 

have a significant impact on the area computations since they occurred in 

shallower areas of the reservoir where the bottom topography was generally 

flatter in nature. 

The 2005 collection of bathymetric data did not include single beam data in the 

shallow, less than 10 foot, areas of the reservoir. It was anticipated that the lake 

would be low enough during aerial collection to obtain enough overlap between 

the aerial and multibeam data sets, but this did not occur throughout the reservoir. 

Besides the shallow flat areas of the reservoirs some of the additional areas not 

covered included the upstream arms and coves of the reservoir. For these missed 

areas the contours between the surveyed data were interpolated using contouring 

software. These contours should not be considered reliable and would not meet 

most accuracy standards. To preserve the integrity of the data sets, interpolated 

points were not added to the shallow water areas. Also, these areas were small 

relative to the total reservoir area and would not have had a significant effect on 

the overall surface area computations. 

The first part of the analysis started with the processing of all the collected raw 

profile data files of the bottom. This included application of all necessary 

correction information that was collected, such as vessel location and the roll, 

pitch, and yaw effects on the survey vessel. Other corrections included 

application of the field measured sound velocity of the reservoir water column 

and then conversion of all corrected depth data to elevations. All elevations in the 

final processing were tied to the Reclamation measured water surface gauge 

8
elevations at the time of collection. During map processing, these bottom 

elevations were converted to NAVD88-05 datum by adding 2.34 feet. The 

geodetic survey also measured a slight shift in the horizontal coordinates (+) 0.47 

feet north and (-) 0.61 feet west that was also applied. 

Due to the massive amount of multibeam data collected, procedures within the 

collection and analysis software logically filtered data points without adversely 

affecting the results were utilized. Filtering mainly occurred in the flatter areas of 

the reservoir where the additional survey points were not necessary to map the 

bottom details of the reservoir. Quality control and assurance of the data sets 

were accomplished by conducting field calibration as required by the multibeam 

system and by collecting velocity profile data for the areas being surveyed. The 

processing of the multibeam data was conducted by Reclamation’s Sedimentation 

Group. The processed data in an x,y,z format was forwarded to the Surveys and 

Mapping Branch for topographic development. 

Reservoir Area and Capacity 

Topography Development 

Survey and Mapping Branch Processing 

The entire topography of 2005 Folsom Lake and the surrounding area were 

developed by the Reclamation’s Mid-Pacific Region Surveys and Mapping 

Branch. This included overseeing the contracting of the aerial collection and 

quality control. The aerial mapping included the upstream arms of the north and 

south forks of the American River and the high accuracy mapping of the dams 

and dikes that enclose the reservoir. Using standard photogrammetric processes 

the film diapositives were used for aerial triangulation and subsequent 3D data 

collection. Using AutoCAD, breaklines along with random and regularly gridded 

points were also compiled to create surface models for contour generation. For 

the bathymetric data, the processed x,y,z data points were shifted to match the 

aerial horizontal and vertical control datums which were in NAD83 and 

NAVD88-05 respectively. The bathymetry contours were developed using a 

hardclip boundary around the underwater data that was developed from the aerial 

data, contour elevation 430.0 (NAVD88-05). Due to the large data sets, the final 

contours were broken up into seven blocks or drawing files. The area blocks also 

included digital terrain model (DTM) files that contained the surface data in the 

form of breaklines along with the random and regular gridded points. These data 

files were forwarded to the Sedimentation Group for area and capacity 

computations and sediment inflow calculations. All data was tied to California 

state plane, zone 2, in NAD83 and the elevations tied to NAVD88-05. Additional 

files included the full orthorectified photos of the project area. Additional 

9
information on these coverage files and methods of processing are listed in the 

metadata file located in the appendix. 

Sedimentation Group Processing 

The Sedimentation Group uses ARCGIS (ESRI, 2006) to process data for 

developing reservoir topography and computing the resulting surface areas and 

volumes. To accomplish this, the 2005 Folsom Lake study area’s processed x,y,z 

data points were combined into one data set. This included the nearly nine 

million bathymetric data points that were shifted to match the aerial data datums. 

These bathymetric points were combined with the aerial data points, located 

within the DTM files, for developing the study area contours. 

The first step was to enclose all the combined data points within a hardclip 

polygon so that during contour development all interpretations would remain 

within the study area. The contours within this hardclip were developed from the 

combined aerial and underwater data sets using the triangular irregular network 

(TIN) surface-modeling package within ARCGIS. A TIN is a set of adjacent nonoverlapping 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 were interpolated along 

the triangle elements using the surface contouring option within ARCGIS. 

The aerial data of the dam and dikes is a very detailed set of points of the entire 

structures that are located beyond or downstream of the actual reservoir area. For 

the purpose of computing the surface area and capacity of the reservoir area only, 

a hardclip was developed to enclose the data points within the reservoir area only. 

This was accomplished by using the elevation 500.0 (NAVD88-05) contour 

developed from the entire study area survey points as described above. This 

contour is above the top of the dam, but was chosen for developing the updated 

reservoir surface areas since there have been discussions of possibly raising the 

existing structures and resulting reservoir levels. Using ARCGIS edit tools, the 

elevation 500.0 (NAVD88-05) contour was enclosed along the existing dike and 

dams by overlaying this contour onto the orthorectified photos. Once this 

polygon was developed and enclosed, elevation 500.0 (NAVD88-05) was 

assigned for the purpose of developing the reservoir TIN and resulting contours. 

Within this reservoir area elevation 500.0 (NAVD88-05) hardclip, a TIN was 

developed for the Folsom Lake reservoir area. From this TIN, the 2005 surface 

areas and volumes were computed at one-foot increments from elevation 500.0 

(NAVD88-05) and below. The contour data presented on these maps are tied to 

the vertical datum of NAVD88-05. All surface area and volume computations 

10
within this report were tied to the Folsom Lake project datum by shifting the 

elevations 2.34 feet lower than NAVD88-05. The vertical shift is necessary since 

past and present reservoir operations are tied to the project vertical datum. 

Development of the 2005 Contours 

Reclamation’s Survey and Mapping Branch in Sacramento developed the 2005 

contours of the Folsom Lake study area by combining the 2005 aerial and 

underwater data sets. These contours are presented on 204 detailed maps as 

illustrated on the index map, figure 5. The contours presented on these maps are 

tied to NAVD88-05 and are 2.34 feet higher than the project vertical datum and 

the horizontal coordinates are on the California State Plane, zone 2, in NAD83. 

Examples of maps are illustrated on figures 6 through 11. These maps are of the 

whole study area that extends upstream and downstream of the entrapment 

structures forming Folsom Lake. The metadata file in the appendix provides 

additional information on the creation of these maps. 

Development of the 2005 Folsom Lake Surface Areas 

The 2005 surface areas for Folsom Lake were computed at 1-foot increments 

from the TIN that covered the Folsom Lake area only. This TIN was developed 

within a hardclip area that included the existing elevation 500.0 (NAVD88-05) 

contour that was modified to run along the present alignment of the entrapment 

structures. These calculations were performed using the ARCGIS surface area 

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

from the TIN and takes into consideration all regions of equal elevation. For the 

purpose of computing the 2005 area and capacity tables for this report, the 

measured surface area elevations in NAVD88-05 where shifted down by 2.34 feet 

to match the project elevations. 

2005 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). For the purpose of this study, the measured 2005 survey 

areas at 3-foot increments from elevation 190.0.0 through 490.0 were used to 

compute the new area and capacity tables and were used as the control parameters 

for computing the 2005 Folsom Lake capacity. The ACAP program can compute 

the 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 0.000001 

for Folsom Lake. The capacity equation is then used over the full range of 

11
Figure 5 - Map index for the 2005 Folsom Lake survey. 

12
Figure 6 - Folsom Dam and lake topography, drawing 485-208-2058. 

13
Figure 7 - Folsom Lake topography, drawing 485-208-2059. 

14
Figure 8 - Folsom Lake left wing dam and topography, drawing 485-208-2088. 

15
Figure 9 - Folsom Lake topography, drawing 485-208-2089. 

16
Figure 10 - Folsom Lake and Dike 7 topography, drawing 485-208-2077. 

17
Figure 11 - Folsom Lake topography, drawing 485-208-2078. 

18
intervals fitting within this allowable error limit. For the first interval at which 

the initial allowable error limit is exceeded, a new capacity equation (integrated 

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

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

region of data. Differentiating the capacity equations, which are of second order 

polynomial form, derives final area equations: 

y = a1 + a2x + a3x

2 

 where: y = capacity 

x = elevation above a reference base 

a1 = intercept 

a2 and a3 = coefficients 

Results of the Folsom Lake area and capacity computations are listed in a separate 

set of 2005 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 1955, 1991, and 2005 area-capacity curves are listed on table 2 

and plotted on figure 12. As of September 2005, at top of joint use elevation 

466.0, the surface area was 11,140 acres with a total capacity of 966,823 acrefeet. 

2005 Reservoir Analyses 

Results of the 2005 Folsom Lake area and capacity computations are listed in 

table 1 and columns 8 and 9 of table 2. Columns 2 and 3 of table 2 list the 1955 

or original area and capacity values and column 4 and 5 list the 1991 surface and 

area and capacity results for Folsom Lake. Column 6 and 10 of table 2 list the 

capacity differences between the original and 1991 and 2005 survey results. 

Figure 12 is a plot of the Folsom Lake surface area and capacity values for the 

three surveys and illustrates the differences between the surveys. The 

comparisons show that the total reservoir capacity in 2005 is 45,871 acre-feet less 

in volume from the original volume at maximum reservoir elevation 475.4. 

Research into the original area and capacity data found 20-foot contour surface 

areas were used to compute the original volumes. For elevations 400 and below, 

the 20-foot contours were developed from U.S. Geologic Survey (USGS) river 

survey data collected in 1935-36. The 20-foot contours above elevation 400 came 

from 1940’s USGS quadrangle maps of the reservoir area. During the original 

planning of Folsom Lake, the 100 year estimated loss of total capacity of the 

reservoir below elevation 466.0 was 5.7 percent, a total of 58,000 acre-feet, or an 

annual average loss of 580 acre-feet. There was not any information on factors 

used to compute this sediment inflow value. The 2005 investigation found that 

19
the total drainage area into Folsom Lake is around 1,861 square miles and with 

several of the upstream reservoirs capturing sediment, it was computed that 1,020 

square miles of the drainage area contributes sediment inflow into Folsom Lake. 

There are several reservoirs operating as diversion structures that were assumed 

had no effect on sediment retention. It is assumed the original 100 year estimate 

took into account the upper reservoir effects, but to what degree is not known. 

The 2005 survey computed a loss of 43,407 acre-feet of storage during the first 

50.5 years of operation below joint use reservoir elevation 466.0. It is unknown 

how much of this loss is due to differences in the detail of the surveys. The 1991 

survey was a combination of an aerial survey conducted during low reservoir 

content (elevation 366), and a single beam bathymetric survey conducted at 

reservoir elevation 418. Parallel cross sections were run 200-feet apart to fill in 

the deeper reservoir area not covered by the aerial survey. The survey computed 

an average annual loss of 921.7 acre-feet, below elevation 466.0, over the first 

36.1 years of operation by comparing the original recomputed volume with the 

1991 computed volume. The 2005 survey computed an average annual loss of 

703.6 acre-feet, below elevation 466.0, for the 14.4 years of operation since the 

1991 survey. Even though the period is small between these surveys, the average 

annual loss of 703.6 acre-feet is a better representation for computing future 

losses since both surveys were of better detail than the original. There are many 

factors in the drainage basins that affect the annual sediment inflows, but it is 

recommended that the 703.6 acre-feet value be used as a basis for future 

prediction of reservoir losses. 

It is the general conclusion that the difference between the original and 2005 

surveys is due partially to sediment inflow, but the differences in the detail 

between the two surveys is also a factor. The 2005 survey is of greater detail and 

provides an accurate representation of the present reservoir volume as of 

September 2005. 

20
21

1. 1 2. American River 3. STATE: California

4. 5. Folsom 6. COUNTY: Sacramento

7. ° 42 ' 29 " ° 09 ' 22 " 8. 2 9. SPILLWAY CREST EL. 3

10. 11. 12. GROSS STORAGE 15

CAPACITY, AC-FT

a. 4

b.

c.

d. 16

e.

f.

g.

17. LENGTH OF RESERVOIR 6

18. 22. 7

19. NET SEDIMENT CONTRIBUTING AREA 8 23. MEAN ANNUAL RUNOFF 

20. LENGTH MILES AVG. WIDTH MILES 24. MEAN ANNUAL RUNOFF 9 ACRE-FEET

21. 25. °F °F7

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

26. DATE OF 35. 36

9

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.

09/21/05

0.091

0.90

4/15/91

 2/25/55

12 921.7 12 33,275 12

12

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

-YR.

12

a. 

12

101,568,200

MEAN ANN. b. TOTAL

33,275 12

0.84

3.29

12 0.90

100

105-

E 36.1 36.1

A 4/15/91 22.7 7

125

115-

105 120

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

120-

190.0-300.0

PER. PER.

20-ft 11,440 4

11,183

ELEVATION

1,861

Contour (D)

Contour (D)

1,020

DEAD

TOP OF POOL

FLOOD CONTROL

POWER

LONG 121

SURCHARGE

INACTIVE

STORAGE

ALLOCATION

425.8

JOINT USE

CONSERVATION

466.0

28

12.6

DEPTH DESIGNATION RANGE BY RESERVOIR ELEVATION

430.0-450.0

22.4

111

0- 110-

90 115

70-

80

10- 20- 80-

14.6 6.4 16.6

REACH DESIGNATION PERCENT OF TOTAL ORIGINAL LENGTH OF RESERVOIR

5.9

30-

300.0-327.0

2.5 6.1 15.4 19.9

 

370.0-390.0

90- 100-

390.0-410.0

0.085

410.0-430.0 450.0-466.0

4.30

327.0-350.0 350.0-370.0

60-

70

50-

10 20 30 40 60

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN REACH DESIGNATION

4/15/91

9/21/05

 

YRS YRS

10

34.

0.36 4

11 0.35

859.5

12 921.7 12

 

10,132

2,745,100

 

12 703.6

4/15/91

101,568,200

2,899,400 5,414,300

ACRE-FEET

TOP OF DAM ELEVATION:

11,440

MILES

2,787,400

INCHES

28.2

0.64

D

A 10 N RANGE

R

E

S

E

7 E

STREAM:

NEAREST P.O.

38

OWNER:

SEC

LAT

24

M

TWP.

Bureau of Reclamation

b.

PERIOD PERIOD WATER INFLOW, ACRE-FEET

MAX. ANN. TOTAL c.

S

R

V

O

I

R

B

A

SURFACE AREA, AC-FT

ORIGINAL 13. ORIGINAL 

411,211

8,946

2,035

20

2,795,100 6,541,200

MEAN ANNUAL PRECIPITATION

SQUARE MILES

SQUARE MILES

AVG. WIDTH OF RESERVOIR

475.4 11,931

5-ft 11

11,140 11 3-ft

976,955

966,823 0.35 11

1,010,230

to 112

33.

RATIO AF/AF

0.69

40,591,900

 /MI. a. 2 c. -YR.

a. AVG. ANNUAL

43,407

2,787,400 142,160,100

TOTAL SEDIMENT DEPOSITS TO DATE, AF

TYPE OF 

SURVEY

a. MEAN ANN.

Contour (D)

AVG. ANN.

R

14.4

9/21/05

50.5

ANNUAL

PRECIPITATION

N

S

a.

a. TOTAL b.

12

599,019

90,047

114

I 61 °F RANGE 17

327.0

205.5

26.

CAPACITY

WATER INFLOW TO DATE, AF

SURVEY

PERIOD CAPACITY LOSS, ACRE-FEET

TOTAL

PERIOD

U

DATE

OF

SURVEY

A

T

Y

SURVEY

9/21/05

SURVEY

26. 44.

DATE

OF

SURVEY

RESERVOIR SEDIMENT

DATA SUMMARY

Folsom Lake

NAME OF RESERVOIR 1

DATA SHEET NO.

DATE

STORAGE

480.5

14.

418.0

BEGAN

DATE NORMAL

2/25/55

OPERATIONS

BEGAN

MAX. ELEVATION MIN. ELEVATION ANNUAL TEMP, MEAN

12/6/19555

MILES

SURVEY

V 

D

9/21/05

109,848 1,120,078

 

AREA, AC. ACRE - FEET

1,010,230

89,933

114

508,972

TOTAL DRAINAGE AREA

INCHES

NO. OF

RANGES OR 

INTERVALS

SURFACE 32.

Table 1 - Reservoir sediment data summary (1 of 2). 
22

1

2

3

4

5

6

7

8

9

10

11

12

13

2,404,600

1982 465.0 419.1 6,112,800 1983 465.1 427.7 6,541,200

440.3 398.2 1,244,200

2002 452.8 378.9 1,865,200 2003 465.1 407.6

2000 448.9 416.3 2,722,500

463.6 416.0 3,431,000

455.6 394.4

1998 463.6 405.4 4,437,400

97

1976 443.7 403.1 1,142,300 1977 404.1 349.6 356,000

215.0 13 55 220.0 45 180 225.0

405.0 6,979 406,833 410.0 442,754 415.0 7,743

245.0 300 4,410 250.0 255.0 420

1,128 235.0 240.0 249

1966 457.7 416.3 1,516,500 1967 465.3 419.6 3,987,000

3,386,600

1964 464.6 403.0 1,914,300 1965 466.3 410.2 4,421,200

463.9 416.3 3,040,400

1962 460.7 394.5 2,171,000 1963 467.2 406.0

457.1 420.1 3,380,000 1971

1968 446.2 418.8 1,844,600 1969 455.7 406.5 4,548,800

1970

45. RANGE IN RESERVOIR OPERATION

8,874

0

1,128,679

2004

485.0 12,233 1,189,200

450.0

425.0 8,407 561,341

966,823

490.0 12,484 1,250,992

466.0 11,140

475.4 11,710

CAPACITY

465.0 11,084

435.0

ELEVATION AREA CAPACITY

696,955

455.0 10,515 847,700

440.0 9,574

11

427.0 8,612 578,359

3,037

7,976

480,578

543

205.0 1 6 210.0 2

795,889

955,710

1,931

10,208

9,239 649,918

190

7,381

36,611

354 6,049

190.0 0 0

2005 CAPACITY

ELEVATION AREA

 

440.7 399.6 1,794,700 465.4 391.4 3,204,000

1997

2005

1999

2001

1996 464.4 393.7 3,799,600 4,886,800

1994 424.0 370.9 1,041,500 1995 465.5 364.3 5,414,300

1992 440.0 360.3 1,086,500 1993 465.5 355.6 3,259,600

1990 425.8 359.0 1,345,000 1991 443.8 352.0 1,376,700

1988 415.0 369.1 962,400 1989 463.3 358.9 2,167,000

1,796,700

1986 465.7 413.1 4,573,400 1987 440.9 405.1 1,102,900

461.3 425.9 1,411,800

1984 464.5 426.8 4,159,100 1985 455.5 424.5

1980 424.7 3,971,800 1981

461.3 425.2 2,785,700

1978 347.6 2,963,100 1979 464.5 428.3 2,276,600

1974 424.4 4,407,800 1975

391.6 1,180,500

1972 421.8 2,067,900 1973 464.6 424.0 3,093,100

378.2 1,760,700 1961 458.9

466.6 400.0 2,296,600

1958 398.7 4,205,400 1959 456.2 387.3 1,315,400

1956 466.9 353.2 4,781,300 1957

710 19,191 280.0 785

460.0

3

520,142

604,610

745,632

900,996

275.0

136

1955 408.0 244.5

MIN. ELEV. INFLOW, AF

1,204,600

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

Constructed by the Corps of Engineers. Upon completion transferred to Reclamation to operate as part of the Central Valley Project.

Top of parapet wall at elevation 484.0. All elevations in feet based on original project datum that is 2.34 feet lower than NAVD88 (2005).

Spillway crest elevation 418.0. Elevation top of drum gates: five at 468.0 and three at 471.0 feet. 

Total length includes North Fork American River (16.3 miles) and South Fork American River (11.7 miles) at elevation 466.

13

200.0

420.0

430.0

445.0

480.0

YEAR MAX. ELEV.

49. Bureau of Reclamation September 2006

1991 bathymetric survey performed by Reclamation, 4/15/91 through 4/21/91 at elevation 418. Aerial on 10/10/90 at elevation 366.0

Surface area and capacity at joint use elevation 466.0.

Computed capacity loss, by comparing differences of surveys, is affected by the detail and methods of surveys.

48. AGENCY MAKING SURVEY Bureau of Reclamation

Climate records, Bureau of Reclamation Project Data Book, 1981. Values for Central Valley Project.

Total drainage area from USGS water year records. Loss of contributing areas due to closing of North Fork in 1941 (343 mi2

), French 

Computed inflows for water years 1955 through 2005. For water year 1955, inflow values for March through September 1955.

 Meadows in 1964 (34.2 mi2

), Hell Hole in 1965 (79.8 mi2), Loon Lake in 1963 (6.0 mi2), Caples Lake in 1924 (13.5 mi2), Silver Lake in 

 in 1876 (15.2 mi2

), Union Valley in 1962 (66.9 mi2), Ice House in 1959 (23.6 mi2), Slab Creek in 1967 (229.4 mi2), Lake Edison in 

 in 1961 (13.0 mi2

), and Folsom Lake surface area (17.9 mi2).

AGENCY SUPPLYING DATA DATE

10,801

11,973

Area and capacity calculated by BOR program ACAP for sediment computation purposes. Areas below elevation 400.0 based on 1935-36

Full power production with all generators began on December 6, 1955.

 Original data from 20-foot contour intervals. 1991 and 2005 data from more detailed aerial and underwater data.

Water year data provided by Reclamation's Mid Pacific Regional Office.

2005

230.0

SURVEY 195.0 0 1

46. ELEVATION - AREA - CAPACITY - DATA FOR

8,078

466.6

466.9

464.4

ELEVATION AREA CAPACITY

462.8

460.0

454.8

1960

260.0 489 10,253 265.0 560 12,869 630

395.0

270.0

6,202

22,932

1,062

9,894

15,844

390.0 5,835 310,921 341,024 400.0 6,576 372,964

285.0 864 27,051

290.0 952 30,585 295.0 300.0 1,184 42,226

305.0 1,304 48,449 310.0 1,426 55,271 315.0 1,554 62,715

320.0 1,691 70,823 325.0 1,841 79,646 327.0 1,907 83,393

330.0 2,015 89,273 335.0 2,216 99,838 340.0 2,428 111,443

345.0 2,646 124,123 350.0 2,886 137,943 355.0 3,168 153,060

360.0 3,519 169,747 365.0 3,914 188,313 370.0 4,346 208,980

375.0 4,726 231,679 380.0 5,104 256,241 385.0 5,466 282,681

470.0 11,380 1,011,844 475.0 11,687 1,074,207

 USGS survey resulting in 20-foot contour map. Areas above elevation 400.0 based on USGS quadrangle maps dated 1940's.

1,069,528

47. REMARKS AND REFERENCES

Table 1 - Reservoir sediment data summary (page 2 of 2). 
23

Area-Capacity Curves for Folsom Lake

190200210220230240250260270280290300310320330340350360370380390400410420430440450460470480

0 115000 230000 345000 460000 575000 690000 805000 920000 

Capacity (acre-feet)

Elevation (feet)

12000 10800 9600 8400 7200 6000 4800 3600 2400 

Area (acres)

20051991Original

Capacity Area

Figure 12 - Folsom Lake area and capacity plots. 
24
25

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

1991 2005 

Computed 1991 Total 2005 Sediment P

 Original Original 1991 1991 Sediment Percent 2005 2005 Sediment Percent Volume Co

Elevation Survey Capacity Survey Survey Volume Computed Survey Survey Volume Computed 1991-2005 S

Feet Acres Ac-Ft Acres Ac-Ft Ac-Ft Sediment Acres Ac-Ft Ac-Ft Sediment Ac-Ft 19

475.4 11931 1120078 11749 1084778 35300 11710 1074207 45871 10571 

470 11650 1056410 11432 1022185 34225 11380 1011844 44566 10341 466 11440 1010230 11183 976955 33275 100.0 11140 966823 43407 100.0 10132 460 11100 942610 10829 910928 31682 95.2 10801 900966 41644 95.9 9962 450 10500 834610 10240 805535 29075 87.4 10208 795889 38721 89.2 9646 440 9870 732760 9604 706360 26400 79.3 9574 696955 35805 82.5 9405 430 9240 637210 8932 613650 23560 70.8 8874 604610 32600 75.1 9040 

425.8 8946 599019 8629 576772 22247 66.9 8489 568099 30920 71.2 8673 

420 8540 548310 8191 527987 20323 61.1 8078 520142 28168 64.9 7845 410 7770 466760 7444 449815 16945 50.9 7381 442754 24006 55.3 7061 400 6850 393660 6638 379410 14250 42.8 6576 372964 20696 47.7 6446 390 6200 328410 5915 316613 11797 35.5 5835 310921 17489 40.3 5692 380 5280 271010 5196 261095 9915 29.8 5104 256241 14769 34.0 4854 370 4370 222760 4413 212978 9782 29.4 4346 208980 13780 31.7 3998 360 3690 182460 3609 173043 9417 28.3 3519 169747 12713 29.3 3296 350 3110 148460 3019 139493 8967 26.9 2886 137943 10517 24.2 1550 340 2590 119960 2514 111945 8015 24.1 2428 111443 8517 19.6 502 327 2035 90047 1950 83071 6976 21.0 1907 83393 6654 15.3 -322 300 1260 46310 1192 41465 4845 14.6 1184 42226 4084 9.4 -761 280 830 25560 784 22040 3520 10.6 785 22932 2628 6.1 -892 250 430 7260 338 5450 1810 5.4 354 6049 1211 2.8 -599 220 45 585 26 130 455 1.4 45 180 405 0.9 -50 

205.5 20 114 1 3 111 0.3 1 6 108 0.2 -3 

190 0 00 0 0 0.0 0 0 00.0 0

1 Elevation of reservoir water surface.2 Original reservoir surface areas.3 Original reservoir capacity computed using ACAP.4 1991 measured reservoir surface area.5 1991 reservoir capacity computed using ACAP.6 1991 computed sediment volume, column (3) - column (5).7 1991 measured sediment in percentage of total sediment, 33,275 acre-feet, by elevation.8 2005 measured reservoir surface area.9 2005 reservoir capacity computed using ACAP.

10 2005 measured sediment volume = column (3) - column (9).11 2005 measured sediment in percentage of total sediment, 43,407 acre-feet, by elevation.12 Measured sediment volume from 1991 to 2005, column (5) - column (9).13 Measured sediment in percentage my elevation from 1991 to 2005. Total sediment volume of 10,132 acre-feet.14 Depth of reservoir expressed in percentage of total depth (285.4), from maximum water surface.

Table 2 - Summary of 2005 survey results. 
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, Technical 

Service Center, Denver CO. 

Bureau of Reclamation, September 2005. Denver Office, Folsom Lake Area and Capacity 

Tables, Central Valley Project, Mid-Pacific Region, Sacramento, CA. 

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. 

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

Geological Survey, 1990. Water Resources Data California Water Year 1990, Water-Data 

Report CA-91-4, U.S. Geological Survey, Sacramento, CA. 

26
Appendix 

27
28
February 21, 2007 

Folsom Dam Raise 

Topography and Imagery 

Identification_Information: Citation: Citation_Information: Originator: U.S. Bureau of Reclamation. Publication_Date: May 2006 Title: 

Folsom Dam Raise - Topography and Imagery

Master Data files: 

 BR FSC 11 and 12 Master Topo Folsom Dam.dwg 

Geospatial_Data_Presentation_Form: Raster and Vector Data Online_Linkage: AM Teamworks and/or REDS Overview: 

Topography, Bathymetry and Imagery was developed to study the Dikes, the Wing Dams, Folsom Dam, and 

Mormon Island Auxiliary Dam along with the up-stream arms of the American River. 

The project consists of 1 Sheet Index @ 1:48000 on drawing number 485-208-1882 and 204 mapping sheets @ 

1:1200 on drawing numbers 485-208-1883 through 485-208-2086. 

 

Orthophotos for above water sheets in related sheet tiles are in .sid format with .sdw files for geo-referencing. 

 Project Datum: California Coordinate System, CCS, Zone 2, U.S. Survey Feet 

 Horizontal Datum: NAD 83 Vertical Datum: 

 NAVD 88 (2005) 

Process and Methodology Description: 

Ground Control: 

 The Bureau of Reclamation and the Army Corps of Engineers, under the direction of the National Geodetic 

Survey, performed an extensive geodetic control network in NAD83/NAVD88 encompassing the project. Aerial 

control was then established for the photogrammetric work. 

Aerial Photography: 

 Under contract with BOR, American Aerial Surveys, Ione, CA provided color vertical aerial photography 

as follows; BR-FSC-11@ 1:6000 flown for the Upstream Arms of the American River on 10-20-05 with a reservoir 

elevation of 430.2’. BR-FSC-12 @ 1:3600 flown for high accuracy mapping from Dike 1 to MIAD on 10-31-05 with 

a reservoir elevation of 427.1’. Aerial obliques of all structures were taken 12-05-05. 

Bathymetry: 

Bathymetric Data was collected in October 2005 using Real Time Kinetic Global Positioning System with a 

Multiple Beam Sonar Collection System by the Bureau of Reclamation Sedimentation and River Hydraulics Group 

from Denver, CO. The average reservoir elevation during data collection was 440’ giving reliable readings below 

approximately 425’. 

29
 The bathymetric data was collected prior to the completion of the Geodetic Network and was post 

processed to the final survey adjustment. To allow efficient contour generation, the data files were filtered. A 

Triangulated Irregular Network (TIN) was computed with the insertion of the photogrammetric water surfaces as a 

breakline around the perimeter. 

 Because the sensor could not collect data in shallow water, some of the upstream arm data was 

interpolated between the photogrammetric water surface information and the bathymetric data points which created 

anomalous contour data and should be considered unreliable. These areas will not meet any accuracy standards. 

This data was not edited or clipped out to keep vector work concatenated for area capacity and surface area 

calculations. 

Photogrammetry: 

 Using standard photogrammetric processes, film diapositives were used for aerial triangulation and 

subsequent 3D data collection. Breaklines and random and regularly gridded points were compiled to create 

surface models for subsequent contour generation. 

1 foot contours were produced from Dike 1 to Morman Island Auxiliary Dam, 2 foot contours cover the 

upstream arms and 5 foot contours reflect the bathymetry, all at a horizontal scale of 1:1200/1”=100’. 

Field surveys were performed to check final data and the results meet or exceed standards on above water 

data. 

Orthophotos: 

 Full orthorectification was performed using the photogrammetric surface information. Tif images were 

compressed to create .sid files with associated world files corresponding to the sheet layout and index. Any surface 

information outside of the contoured corridors were only collected for gross rectification for surrounding areas and 

said data and imagery will not meet mapping standards. 

Satellite Imagery: 

p0576North.sid and .sdw 

p0576South.sid and .sdw 

Date Flown: January 2004 

Pixel Size: 2 feet 

Prepared By: IntraSearch Inc. 

 MapMart 

 12424 East Weaver Place 

 Suite 100 

 Centennial, Colorado 80111 

 303-759-5050 

 303-759-0400 - fax 

 www.intrasearch.com 

 www.mapmart.com 

 info@intrasearch.com

Map Mart Project Number: 2004-p-0576 

Digital Take Line Information: 

 Information for a digital take line (NAD27) was extracted from (22) USACE drawings AM-1-13-490 dated 

January 1952 and (6) BOR drawings 485-208-254 through 485-208-259 dated October 1958. A simple 

transformation was performed to move this data into the current horizontal datum of NAD83. 

 This boundary data is limited by the condition of the records and was oftentimes not clearly visible, had 

obvious errors and omissions and was produced using survey and drafting methods suitable only for that particular 

timeframe. Some data manipulation was necessary to resolve minor issues of precision and newer technology. 

Major issues with no obvious resolution are noted. 

 Some field work was performed to check this data and without significant field verification we believe the 

take line data is now within a +/-10’ error ellipse but have no solutions for major discrepancies. The take line data 

should be considered informational only until a full boundary survey is performed. 

30
Horizontal Alignment Information: 

 Information for the construction of a digital horizontal alignment was taken from BOR’s Spec 896 book. 

 The horizontal alignment data is limited by the condition of the records and was oftentimes not clearly 

visible, had obvious errors and omissions and was produced using survey and drafting methods suitable only for 

that particular timeframe. Some data manipulation was necessary to resolve minor issues of precision and newer 

technology.

 

Data Management: Appropriate data files are referenced into the master AutoCAD file: 

BR FSC 11 and 12 Master Topo Folsom Dam.dwg

 Mapping Features_2d.dwg 

 Contour Data referenced into master AutoCAD file per contour blocks: 

 Contour Blk Dikes 1-3.dwg 

 Contour Blk Dikes 4-6.dwg 

 Contour Blk RWD-Dike7.dwg 

 Contour Blk Dikes8-MIAD.dwg 

 Contour Blk North and South Forks.dwg 

 Contour Blk North Fork Bathymetry.dwg 

 Contour Blk South Fork Bathymetry.dwg 

 Surface Data in the form of DTM breaklines and random and regularly gridded points are 

 available: 

 DTM Dikes 1-3.dwg 

 DTM Dikes 4-6.dwg 

 DTM RWD-Dike7.dwg 

 DTM Dikes8-MIAD.dwg 

 DTM North and South Forks.dwg 

 DTM North Fork Bathymetry.dwg 

 DTM South Fork Bathymetry.dwg 

 Additional Data Available: 

 Mapping Features_3d.dwg 

 Folsom Take Line 83.dwg 

 Waterlines (2d and 3d).dwg 

 Data Limitations: Terrain information outside the main contour corridors will not meet standards for vertical accuracy 

and is intended only to support gross orthorectification of surrounding areas. 

 

Data Duplication: USBR Surveys and Photogrammetry; Art Aguirre 978-5333 or AM Teamworks and/or REDS. Time_Period_Information: Calendar_Date: Date of Aerial Photography October 20 and 31, 2005

 Date of Bathymetry August 2005

Currentness_Reference: Current to the listed Calendar Date provided. See Data Quality for process steps. Status: Progress: Only current to the date specified. Maintenance_and_Update_Frequency: Updated as determined by USBR. Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -121.10.00 East_Bounding_Coordinate: -121.00.00 North_Bounding_Coordinate: 38.46.00 South_Bounding_Coordinate: 38.37.30 Access_Constraints: None. Use_Constraints: If used, please indicate that the database source was the U.S. Bureau of Reclamation. Point_of_Contact: 

31
Contact_Information: Contact_Person_Primary: Contact_Person: Terri Reaves Contact_Organization: U.S. Bureau of Reclamation, Design and Construction Contact_Position: Regional Chief of Surveys and Mapping

Contact_Voice_Telephone: (916) 978-5306 Contact_Facsimile_Telephone: (916) 978-5345 Contact_Electronic_Mail_Address: treaves@mp.usbr.gov Hours_of_Service: 7:00 AM - 4:00 PM M-F Contact_Instructions: Email your request to the above email address Data_Set_Credit: Bureau of Reclamation 

 Division of Design and Construction, Surveys and Mapping Branch 

 2800 Cottage Way Sacramento, CA 95825 916-978-5306 POC Terri Reaves 

Geodetic Survey and Ground Control 

 Frame Surveys and Mapping 

 17029 Lambert Rd. Ione, CA 95640 209-274-6500 POC Curtis Holmes

Aerial Photography 

 American Aerial Surveys 

 17029 Lambert Rd. Ione, CA 95640 209-274-6500 POC Curtis Holmes

Bathymetry 

 USBR - Reservoir Area and Upstream Arms - 5 foot contours 

 Sedimentation and River Hydraulics Group 

 Denver, Co 

 POC Ronald Ferrari 

 303-445-2551 

 

Photogrammetry 

 USBR - Dike 1 through MIAD - 1 foot contours 

 Surveys and Mapping Branch 

 Sacramento, CA 

 POC Terri Reaves 

 916-978-5306 

 American Aerial Surveys /Spectrum Mapping - North and South Forks - 2 foot contours

 17029 Lambert Rd. Ione, CA 95640 209-274-6500 POC Curtis Holmes

Orthophotos 

 Tri-State Surveying, Ltd., Inc.

 1925 East Prater Way Sparks, NV 89434-8938 775-358-9491 

32
 POC Mitch Bartorelli

Security_Information: Security_Classification_System: None Security_Classification: None Security_Handling_Description: None Native_Data_Set_Environment: AutoCAD 2005 Cross_Reference: Citation_Information: Title: None 

Data_Quality_Information: Digital databases created within the USBR were reviewed using existing quality standards. Logical_Consistency_Report: Data meets accuracy and quality standards within USBR, the National Standard for Spatial Data Accuracy 

(NSSDA) and the National Map Accuracy Standards (NMAS) for 1:1200 with 1, 2 and 5 foot contours.

Completeness_Report: This database represents the most current and up to date mapping for the Folsom Project up to the date of 

photography, October 2005. 

Horizontal_Positional_Accuracy: All horizontal positions meet or exceed NSSDA. Vertical_Positional_Accuracy: All vertical positions meet or exceed NSSDA. Lineage: Source_Information: Source_Scale_Denominator: 1:3600 photography and 1:6000 photography. Type_of_Source_Media: 

 Aerial Photography: American Aerial Surveys, Inc - Ione, California Zeiss RMK Top 15 Zeiss Pleogon a3/4 Camera Serial No. :141307 Lens Serial No. : 141329 Calibrated Focal Length 154.060 

Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: NAD83 Grid_Coordinate_System: California Coordinate System - Zone 2 Lambert: Scale_Factor_at_Central_Meridian: .999914672977 Longitude_of_Central_Meridian: -122.00.00 Latitude_of_Projection_Origin: 37.40.00 False_Easting: 6561666.667' False_Northing: 1640416.667' Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: Geodetic Reference System 1980 Semi-major_Axis: 20925604.4742' Denominator_of_Flattening_Ratio: 298.2572221008827 

Distribution_Information: Distributor: 

33
Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Bureau of Reclamation, Mid-Pacific Region, Design and Construction Contact_Person: Terri Reaves Contact_Position: Regional Chief of Surveys and Mapping Contact_Voice_Telephone: 916-978-5306 Contact_Facsimile_Telephone: 916-978-5345 Contact_Electronic_Mail_Address: treaves@mp.usbr.gov Hours_of_Service: 7:00 AM - 4:00 PM Contact_Instructions: Call or email for method of data transfer Distribution_Liability: This data set was designed for 1:1200 mapping with 1 foot contour coverage on Dike1 to Mormon Island 

Auxiliary Dam, 2 foot contour coverage on up-stream arms inside of USBR take line and 5 foot 

bathymetric contour coverage. Mapping was developed from the source documents following standard 

procedures of compilation, draft editing, map and orthophoto generation. Use of this data at scales and 

contour intervals which are more detailed than the source is not recommended. 

Metadata_Reference_Information: Metadata_Date: May 2006 Metadata_Review_Date: May 2006 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Terri Reaves Contact_Organization: U.S. Bureau of Reclamation, Mid-Pacific Region Contact_Position: Chief of Surveys and Mapping

Contact_Address: Address_Type: mailing address Address: US Bureau of Reclamation Terri Reaves - MP222 2800 Cottage Way W2916 City: Sacramento State_or_Province: CA Postal_Code: 95825 Country: USA Contact_Voice_Telephone: 916-978-5306 Contact_Facsimile_Telephone: 926-978-5345 Contact_Electronic_Mail_Address: treaves@mp.usbr.gov Hours_of_Service: 7:00 AM - 4:00 PM Contact_Instructions: Call or email Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time Metadata_Access_Constraints: None Metadata_Use_Constraints: If used, please indicate that the data source was the U.S. Bureau of Reclamation, Mid-Pacific Region. 

34