Technical Report No. SRH-2008-4 

Elephant Butte Reservoir 

2007 Sedimentation Survey 

U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Denver, Colorado September 2008 
U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Water and Environmental Resources Division 

Sedimentation and River Hydraulics Group 

Denver, Colorado September 2008 

Technical Report No. SRH-2008-4 

Elephant Butte Reservoir 

2007 Sedimentation Survey 

prepared by 

Ronald L. Ferrari 
ACKNOWLEDGMENTS

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

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

this report. Kent Collins and Ronald Ferrari of the Sedimentation Group conducted the 

bathymetry survey of the reservoir in October of 2007. Wayne Treers of Reclamation’s 

El Paso Field Office of the Upper Colorado Region was the study coordinator. Ron 

Ferrari completed the data processing to generate updated surface areas, new reservoir 

topography, and resulting area-capacity tables. Kent Collins performed the technical peer 

review of this documentation. 

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 in the interest of the American public. 

Reclamation Report 

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

River Hydraulics Group (Mail Code 86-68240), PO Box 25007, Denver, 

Colorado 80225-0007, www.usbr.gov/pmts/sediment/. 

Cover drawing by Mr. Peter Hurd (1904-1984).

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.
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1. REPORT DATE (DD-MM-YYYY) 

 September 2008 

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

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Elephant Butte Reservoir 

2007 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 

8. PERFORMING ORGANIZATION REPORT 

NUMBER 

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

Bureau of Reclamation, Denver Federal Center, PO Box 25007 

Denver, CO 80225-0007 11. SPONSOR/MONITOR'S REPORT 

NUMBER(S) 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

Reclamation surveyed Elephant Butte Reservoir in October 2007 to develop updated reservoir topography and compute the 

present storage-elevation relationship (area-capacity tables). The underwater survey was conducted near water surface elevation 

4,327 feet (project datum). The project datum is 43.3 feet less than the National Geodetic Vertical Datum of 1929 (NGVD29) 

and 45.5 feet less than the North American Vertical Datum of 1988 (NAVD88). The underwater survey used sonic depth 

recording equipment interfaced with a real-time kinematic (RTK) global positioning system (GPS) that provided continuous 

sounding positions throughout the underwater portion of the reservoir covered by the survey vessel. The reservoir topography 

was determined by importing digital images of the contour lines from the U.S. Geological Survey quadrangle (USGS quad) 

maps of the reservoir area, 2004 and 2007 aerial data that covered large portions of the reservoir, and 2007 bathymetric data. 

As of October 2007, at reservoir water surface elevation 4,407.0 feet, the surface area was 35,825 acres with a total capacity of 

2,024,586 acre-feet. Since 1915 and the initial reservoir filling, 610,214 acre-feet of sediment have accumulated in Elephant 

Butte Reservoir. Since the last reservoir survey in 1999, the reservoir volume has increased 1,228 acre-feet due to the 

dewatering and resulting compaction of the previous measured sediments that have been exposed during the extended drought 

conditions. The average annual rate of sediment accumulation since 1915 is 6,575.6 acre-feet compared to the 1999 study 

computation of 7,253.2 acre-feet.

15. SUBJECT TERMS 

reservoir area and capacity/ sedimentation/ reservoir surveys/ global positioning system/ sounders/ contour 

area/ RTK GPS/ multibeam/ 

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 
Table of Contents 

Page 

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

Summary and Conclusions............................................................................................................... 3 

Control Survey Data Information..................................................................................................... 5 

Reservoir Operations........................................................................................................................ 5 

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

Development of the 2007 Elephant Butte Reservoir Surface Areas............................................... 25 

Width adjustment method ....................................................................................................... 26 

Reservoir Sediment Distribution .................................................................................................... 27 

Lateral Distribution ................................................................................................................. 27 

Longitudinal Distribution........................................................................................................ 73 

Reservoir Area and Capacity.......................................................................................................... 77 

2007 Storage Capacity ............................................................................................................ 77 

2007 Analyses of Results........................................................................................................ 87 

2007 Topography Development..................................................................................................... 88 

Elephant Butte Data Sets and TIN Development.................................................................... 88 

Elephant Butte Contour Development .................................................................................. 105 

Elephant Butte 2007 Topography Surface Areas and Capacity Computations and 

Comparisons.......................................................................................................................... 123 

References.................................................................................................................................... 129 

Bureau of Reclamation, 2008. Project Data, Denver Office, Denver CO. .................................. 129 

(www.usbr.gov/dataweb). ............................................................................................................ 129 

ESRI, 2006. Environmental Systems Research Institute, Inc. (www.esri.com)......................... 129 

Appendix I.................................................................................................................................... 131 

Index of Figures 

Page 

Figure 1 - Bureau of Reclamation reservoirs in New Mexico.......................................................... 1 

Figure 2 - Elephant Butte Reservoir end of month water surface elevations. .................................. 7 

Figure 3 - Survey Vessel with mounted instrumentation on El Vado Reservoir, New Mexico. ...... 9 

Figure 4 - Multibeam collection system......................................................................................... 10 

Figure 5 - Elephant Butte Reservoir range line location map, 1 of 6. ............................................ 13 

Figure 6 - Elephant Butte Reservoir range line location map, 2 of 6. ............................................ 15 

Figure 7 - Elephant Butte Reservoir range line location map, 3 of 6. ............................................ 17 

Figure 8 - Elephant Butte Reservoir range line location map, 4 of 6. ............................................ 19 

Figure 9 - Elephant Butte Reservior range line location map, 5 of 6. ............................................ 21 

Figure 10 - Elephant Butte Reservoir range line location map, 6 of 6. .......................................... 23 

Figure 11 - Width adjustment method for revising contour areas. ................................................. 27 

Figure 12 - Range Line 90.............................................................................................................. 31 

Figure 13 - Range Line 89.............................................................................................................. 31 

Figure 14 - Range Line 88.............................................................................................................. 32 

Figure 15 - Range Line 87.............................................................................................................. 32 

Figure 16 - Range Line 86.............................................................................................................. 33 

Figure 17 - Range Line 85.............................................................................................................. 33 

Figure 18 - Range Line 84.............................................................................................................. 34 

Figure 19 - Range Line 83.............................................................................................................. 34 

Figure 20 - Range Line 82.............................................................................................................. 35 

Figure 21 - Range Line 81.............................................................................................................. 35 

Figure 22 - Rnage Line 80.............................................................................................................. 36 
Figure 23 - Range Line 79.............................................................................................................. 36 

Figure 24 - Range Line 78.............................................................................................................. 37 

Figure 25 - Range Line 77.............................................................................................................. 37 

Figure 26 - Range Line 76.............................................................................................................. 38 

Figure 27 - Range Line 75.............................................................................................................. 38 

Figure 28 - Range Line 74.............................................................................................................. 39 

Figure 29 - Range Line 73.............................................................................................................. 39 

Figure 30 - Range Line 72.............................................................................................................. 40 

Figure 31 - Range Line 71.............................................................................................................. 40 

Figure 32 - Range line 70............................................................................................................... 41 

Figure 33 - Range Line 69.............................................................................................................. 41 

Figure 34 - Range Line 68.............................................................................................................. 42 

Figure 35 - Range Line 67.............................................................................................................. 42 

Figure 36 - Range Line 66.............................................................................................................. 43 

Figure 37 - Range Line 65.............................................................................................................. 43 

Figure 38 - Range Line 64.............................................................................................................. 44 

Figure 39 - Range Line 63.............................................................................................................. 44 

Figure 40 - Range Line 62.............................................................................................................. 45 

Figure 41 - Range Line 61.............................................................................................................. 45 

Figure 42 - Range Line 60.............................................................................................................. 46 

Figure 43 - Range Line 59.............................................................................................................. 46 

Figure 44 - Range Line 58.............................................................................................................. 47 

Figure 45 - Range Line 57.............................................................................................................. 47 

Figure 46 - Range Line 56.............................................................................................................. 48 

Figure 47 - Range Line 55.............................................................................................................. 48 

Figure 48 - Range Line 54.............................................................................................................. 49 

Figure 49 - Range Line 53.............................................................................................................. 49 

Figure 50 - Range Line 52.............................................................................................................. 50 

Figure 51 - Range Line 51.............................................................................................................. 50 

Figure 52 - Range Line 50.............................................................................................................. 51 

Figure 53 - Range Line 49.............................................................................................................. 51 

Figure 54 - Range Line 48.............................................................................................................. 52 

Figure 55 - Range Line 47.............................................................................................................. 52 

Figure 56 - Range Line 46.............................................................................................................. 53 

Figure 57 - Range Line 45.............................................................................................................. 53 

Figure 58 - Range Line 44.............................................................................................................. 54 

Figure 59 - Range Line 43.............................................................................................................. 54 

Figure 60 - Range Line 42.............................................................................................................. 55 

Figure 61 - Range Line 41.............................................................................................................. 55 

Figure 62 - Range Line 40.............................................................................................................. 56 

Figure 63 - Range Line 39.............................................................................................................. 56 

Figure 64 - Range Line 38.............................................................................................................. 57 

Figure 65 - Range Line 37.............................................................................................................. 57 

Figure 66 - Range Line 36.............................................................................................................. 58 

Figure 67 - Range Line 35.............................................................................................................. 58 

Figure 68 - Range Line 34.............................................................................................................. 59 

Figure 69 - Range Line 34.............................................................................................................. 59 

Figure 70 - Range Line 33.............................................................................................................. 60 

Figure 71 - Range Line 32.............................................................................................................. 60 

Figure 72 - Range Line 31.............................................................................................................. 61 

Figure 73 - Range Line 30.............................................................................................................. 61 

Figure 74 - Range Line 29.............................................................................................................. 62 

Figure 75 - Range Line 28.............................................................................................................. 62 

Figure 76 - Range Line 27.............................................................................................................. 63 

Figure 77 - Range Line 26.............................................................................................................. 63 

Figure 78 - Range Line 25.............................................................................................................. 64 
Figure 79 - Range Line 24.............................................................................................................. 64 

Figure 80 - Range Line 23.............................................................................................................. 65 

Figure 81 - Range Line 22.............................................................................................................. 65 

Figure 82 - Range Line 21.............................................................................................................. 66 

Figure 83 - Range Line 20.............................................................................................................. 66 

Figure 84 - Range Line 19.............................................................................................................. 67 

Figure 85 - Range Line 18.............................................................................................................. 67 

Figure 86 - Range Line 17.............................................................................................................. 68 

Figure 87 - Range Line 16.............................................................................................................. 68 

Figure 88 - Range Line 15.............................................................................................................. 69 

Figure 89 - Range Line 14............................................................................................................. 69 

Figure 90 - Range Line 13.............................................................................................................. 70 

Figure 91 - Range Line 12.............................................................................................................. 70 

Figure 92 - Range Line 11.............................................................................................................. 71 

Figure 93 - Range Line 10.............................................................................................................. 71 

Figure 94 - Range Line 9................................................................................................................ 72 

Figure 95 - Elephant Butte Reservoir Longitudinal Profiles. ......................................................... 75 

Figure 96 - Elephant Butte Reservoir Area and Capacity Plots ..................................................... 85 

Figure 97 - Elephant Butte Reservoir TIN, 1 of 8. ........................................................................ 89 

Figure 98 - Elephant Butte Reservoir TIN, 2 of 8. ........................................................................ 91 

Figure 99 - Elephant Butte Reservoir TIN, 3 of 8. ......................................................................... 93 

Figure 100 - Elephant Butte Reservoir TIN, 4 of 8. ...................................................................... 95 

Figure 101 - Elephant Butte Reservoir TIN, 5 of 8. ....................................................................... 97 

Figure 102 - Elephant Butte Reservoir TIN, 6 of 8. ....................................................................... 99 

Figure 103 - Elephant Butte Reservoir TIN, 7 of 8. ..................................................................... 101 

Figure 104 - Elephant Butte Reservoir TIN, 8 of 8. ..................................................................... 103 

Figure 105 - Elephant Butte 2007 Reservoir Topography, 1 of 8. .............................................. 107 

Figure 106 - Elephant Butte 2007 Reservoir Topography, 2 of 8. .............................................. 109 

Figure 107 - Elephant Butte 2007 Reservoir Topography, 3 of 8. .............................................. 111 

Figure 108 - Elephant Butte 2007 Reservoir Topography, 4 of 8. .............................................. 113 

Figure 109 - Elephant Butte 2007 Reservoir Topography, 5 of 8. .............................................. 115 

Figure 110 - Elephant Butte 2007 Reservoir Topography, 6 of 8. .............................................. 117 

Figure 111 - Elephant Butte 2007 Reservoir Topography, 7 of 8. .............................................. 119 

Figure 112 - Elephant Butte 2007 Reservoir Topography, 8 of 8. .............................................. 121 

Figure 113 - Elephant Butte Reservoir Contour and Range Line Comparison Plots.................... 127 

Index of Tables 

Page 

Table 1 - Reservoir Sediment Summary Sheets (1 of 3). ............................................................... 79 

Table 2 - 2007 Elephant Butte Reservoir Survey Summaries. ....................................................... 83 

Table 3 - Elephant Butte Reservoir Contour and Range Line Comparisons................................ 125

Elephant Butte Reservoir 

2007 Sedimentation Survey

Introduction 

Elephant Butte dam and reservoir are located in Sierra County on the Rio Grande 

River about 4 miles northeast of Truth or Consequences and 125 miles north of El 

Paso, Texas in south central New Mexico (Figure 1). Elephant Butte Dam was 

one of the first major structures built by Reclamation after its formation in 1902. 

Elephant Butte Reservoir is the principal storage component of the originally 

authorized single purpose Rio Grande Project. 

Truth or Consequences

Figure 1 - Bureau of Reclamation reservoirs in New Mexico. 

Elephant Butte Dam construction began in 1908 and was completed in 1916 with 

water storage operations beginning in January 1915. The dam is a concrete 

straight gravity structure with a top elevation of 4,414.0 feet1. There is a parapet 

wall on both the upstream and downstream sides of the dam crest with top of wall 

elevation 4,419.0. The dam’s dimensions, in feet, are: 

 

1

Elevations are shown in feet. Unless noted, all elevations in this report are based on the original project 

datum established by Reclamation which is 43.3 feet lower than NGVD29 and 45.5 feet lower than

NAVD88.

1
 Hydraulic height2 193 Structural height 301 

 Top width 18 Crest length 6,914.5 

 Crest elevation 4,414.0 Top of parapet wall 4,419.0 

A zoned earthfill and rockfill dike is located in a saddle about one mile northwest 

of the dam. The dike has a paved crest with dimensions, in feet, as follows: 

 Structural height 59 Top width 20 

 Crest length 2,000 Crest elevation 4,425.0 

The dam’s spillway is located in the right abutment and consists of a concrete 

approach apron, an uncontrolled ogee crest weir structure, and a concrete chute. 

The weir with crest elevation 4,407.0 is separated into five equal bays by concrete 

piers which support a highway bridge. Four 10.33-foot cylinder gates control four 

10-foot diameter concrete conduits through the base of the weir. The weir and 

conduits provide discharge into a concrete-lined chute that discharges into an 

unlined stilling basin. At water surface elevation 4,419.0, the spillway provides a 

maximum discharge of 47,500 cubic feet per second (cfs) with 39,300 cfs over the 

weir crest and 8,200 cfs through the four conduits. 

The service outlet works are located in the dam near the left abutment and consist 

of an intake structure shared with the sluice and penstock inlets. There are four 

service conduits: two upper conduits at centerline elevation 4,290.0 and two lower 

conduits at centerline elevation 4,234.0. The combined capacity of the service 

outlets is 4,680 cfs at water surface elevation 4,407.0. The sluice outlet works are 

located in the dam near the left abutment and consist of a shared intake structure, 

trashracks, two slide gates, and two conduits through the dam with centerline 

elevation 4,234.0. The sluice outlet capacity is 2,200 cfs at water surface 

elevation 4,314.0. 

The generation penstock outlets consist of an intake structure and trashrack that 

are shared with the service and sluice outlets. The penstock outlets consist of six 

penstocks embedded in the dam at the lower left abutment. The three upper 

penstocks have inlets centered at elevation 4,264.7 and the three lower penstocks 

have inlets centered at elevation 4,234.0. The penstocks are joined in pairs (one 

upper and one lower) near the downstream face of the dam to form three larger 

penstocks that enter the powerplant. The capacity of the penstock outlets is 2,400 

cfs at reservoir water surface elevation 4,407.0. 

The total drainage area above Elephant Butte Dam is 25,923 square miles (mi2

). 

A flood study, completed in 1984, as a part of the SEED (Safety Evaluation of 

Existing Dams) program, of Elephant Butte Dam, computed a sediment 

contributing area of 12,023 mi2

. Subtracting the area of Elephant Butte Reservoir 

 

2

 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
(57 mi2

) would result in a net contributing area of 11,966 mi2. Sediment from the 

remaining upstream areas are considered trapped by upstream dams including 

Jemez Canyon with a drainage area of 1,034 mi2

 that closed in 1953; Galisteo 

with a drainage area of 596 mi2

 that closed in 1970; and Cochiti with a drainage 

area of 11,960 mi2

 that closed in 1970. A noncontributing area of 310 mi2 along 

the river channel exists between Albuquerque and Belen. The USGS gauge at 

Elephant Butte Reservoir reports a total drainage area of 29,445 mi2

 with 2,940 

mi2 located in the closed basin of the San Luis Valley, Colorado. This would 

represent a total drainage area of 26,505 mi2

 compared to above reported drainage 

area of 25,923 mi2

. This study did not conduct research to explain this difference. 

The sediment contributing area of 11,966 mi2 was used for this study to be 

consistent with the past sediment computation results (Reclamation, 2000). 

Summary and Conclusions 

This Reclamation report presents the results of the October 2007 survey of 

Elephant Butte Reservoir. The 2007 survey was the thirteenth survey of the 

reservoir that provides results from a range line analysis similar to the past 

surveys of the reservoir. This study also provides results from a contour analysis 

that generated new reservoir topography from extensive above and below water 

data that covered much of the reservoir area. 

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

 • compute area-capacity relationships 

 • estimate storage depletion due to sediment deposition 

 • develop reservoir topography 

A control survey was conducted using the on-line positioning user service 

(OPUS) and RTK GPS to establish a horizontal and vertical control network near 

the reservoir for the bathymetric survey. OPUS is operated by the National 

Geodetic Survey (NGS) and allows users to submit GPS data files that are 

processed with known point data to determine positions relative to the national 

control network. The GPS base was set over a temporarily driven piece of rebar 

in an area called Dillard Circle that is located on the west bank overlooking the 

reservoir. The OPUS generated coordinates were verified by RTK GPS 

observation shots on the NGS datum point “V 86” that is located on a dike west of 

the dam. The coordinates for this point were processed using OPUS, and from 

this base the bathymetric survey was conducted. 

The horizontal control was established in New Mexico state plane coordinates, 

central zone, on the North American Datum of 1983 (NAD83). The vertical 

control was tied to NAVD88. RTK GPS water surface measurements were 

periodically collected and a comparison of the reservoir water surface recorded by 

the Reclamation gage found they were around 45.5 feet higher. NGS published 

3
data in the study area shows the NAVD88 elevations are around 2.2 feet higher 

than NGVD29 elevations. These values compare well with the previous studies 

that noted a 43.3 feet difference between the NGVD29 datum and the 

Reclamation project datum. 

The October 2007 underwater survey was conducted near reservoir elevation 

4,327 that was measured by the Reclamation gage at the dam. The 2007 survey 

was conducted with the reservoir nearly seventy feet lower than the 1999 survey 

that was conducted near reservoir elevation 4,395. The bathymetric survey used 

sonic depth recording equipment interfaced with a RTK GPS for determining 

sounding locations within the reservoir that could be navigated by the survey 

boat. Due to the low reservoir content, the survey vessel was only able to 

navigate upstream near sediment range line 65 that is located downstream of the 

area of the reservoir called the “Narrows.” The system continuously recorded 

depth and horizontal coordinates as the survey boat navigated along previously 

established sediment range lines that have been resurveyed during prior studies. 

Additional grid lines that covered much of the underwater portion of reservoir 

were also surveyed for mapping purposes. The positioning system provided 

information to allow the boat operator to maintain a course along these lines. The 

water surface elevations recorded by Reclamation’s reservoir gage and confirmed 

by RTK GPS measurements during the time of collection were used to convert the 

sonic depth measurements to reservoir bottom elevations. 

Standard surveying techniques were used to measure the upper reservoir sediment 

range lines not covered during the 2007 bathymetric survey. These surveys were 

conducted under contract with Reclamation’s Albuquerque Area Office and 

included surveys on land, small boat bathymetry, and aerial LiDAR (Light 

Detection And Ranging) collected in 2004 and 2007. Computer programs were 

used to generate the range line data and resulting surface areas presented in this 

report and to conduct the analysis for developing the 2007 capacity tables with 

resulting sediment volumes also presented in this report. Since the LiDAR did 

not cover the total reservoir area, the decision was made to use the collected range 

line data and the range line width adjustment method versus the contour method 

for this study (Ferrari and Collins). Detailed Elephant Butte Reservoir 

topography was developed by combining scanned USGS quad contours, the 

contract surveys of the above water reservoir area, and the 2007 bathymetric data 

sets. 

The 2007 area and capacity tables were produced from a computer program that 

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

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

results were generated by the range line width adjustment method that has been 

used since the 1980 Elephant Butte survey. Some form of the range line 

collection and analysis method has been used for all past reservoir studies. 

Tables 1 and 2 contain summaries of the Elephant Butte Reservoir and watershed 

characteristics for the 2007 survey. The 2007 survey determined that the 

reservoir has a total storage capacity of 2,024,586 acre-feet with a surface area of 

4
35,825 acres at water surface elevation 4,407.0. Since closure in January 1915, 

the reservoir has an estimated volume change of 610,214 acre-feet below 

reservoir elevation 4,407.0. This volume change represents a 23.16 percent loss 

in total original capacity at this elevation. 

Control Survey Data Information 

A control survey was conducted using OPUS and RTK GPS to establish a 

horizontal and 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 that are processed with known point data to 

determine positions relative to the national control network. Initially, the GPS 

base was set over a temporarily driven piece of rebar on the west bank 

overlooking the reservoir. The coordinates for this point were processed using 

OPUS, and from this base additional points were established and checked during 

the survey using OPUS. The OPUS generated coordinates were further verified 

by RTK GPS observations on the NGS datum point “V 86” located on a dike west 

of Elephant Butte Dam. 

The horizontal control, in NAD83, was tied to the New Mexico central state plane 

coordinate system in feet. The vertical control in feet was tied to NAVD88 and 

the Elephant Butte Dam project vertical datum. Unless noted all elevations in this 

report are referenced to the project vertical datum that is 43.3 feet lower than 

NGVD29 and 45.5 feet lower than NAVD88. 

Reservoir Operations 

Elephant Butte Reservoir is part of the Rio Grande Project that provides storage 

for irrigation, flood control, and recreation. The October 2007 capacity was 

2,024,586 acre-feet of total storage below water surface elevation 4,407.00, the 

conservation pool elevation. There is a prudent flood reservation space of 25,000 

acre-feet from elevation 4,406.30 to 4,407.00 during winter months of October 1 

through March 31, and 50,000 acre-feet from elevation 4,405.59 through 4,407.00 

during summer months of April 1 through September 30. The 2007 survey 

measured a minimum lake bottom elevation near the dam of 4,244.00. 

Elephant Butte Reservoir computed annual inflow and reservoir stage records are 

listed by water year on table 1 for the period 1915 through 2007. The inflow 

values show the annual fluctuation with a computed average inflow for the total 

period of 853,600 acre-feet and since the 1999 survey of 504,200 acre-feet. The 

table list the maximum reservoir elevation was 4,409.2 in 1942 and since 1942, 

the minimum reservoir elevation was 4,258.0 in 1954. Since the last survey in 

1999 the maximum recorded reservoir elevation was 4,397.6 with the minimum 

5
6

elevation 4,294.0 during water year 2004. Figure 2 plots the end of month water 

surface elevations for the period of record. The plot shows the fuller reservoir 

period from 1980 through 2000 with the dramatic drop in reservoir elevation that 

followed with the lowest elevation in 2004. 

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, single and 

multibeam depth sounders, helmsman display for navigation, computer, and 

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

generator supplied power to all the boat 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 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 New 

Mexico’s state plane coordinates, central zone in NAD83. The RTK GPS system 

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

differential GPS. 

The Elephant Butte Reservoir bathymetric survey was conducted the first part of 

October 2007 near water surface elevation 4,327. 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 the previously established sediment 

range lines using a single beam sounder and along closely-spaced grid lines 

covering the deeper portion of the reservoir using a multibeam depth sounder. 

For mapping purposes, most transects (grid lines) were run somewhat parallel to 

the upstream-downstream alignment of the reservoir at around 200-foot spacing. 

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 laptop computer hard drive for 

subsequent processing.
7

Elephant Butte Water Surface Elevation 

426042804300432043404360438044004420

1910 1920 1930 1940 1950 1960 1970 1980 1990 

Year

Elephant Butte W ater Surface Elevation (ft)

Figure 2 - Elephant Butte Reservoir end of month water surface elevations. 
8

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Figure 3 - Survey Vessel with mounted instrumentation on El Vado Reservoir, New Mexico. 

The single beam depth sounder for the 2007 underwater data was calibrated by 

lowering a weighted cable below the boat with beads marking known depths. The 

collected data were digitally transmitted to the computer collection system 

through a RS-232 port. The single beam 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 gage, were used to convert the sonic depth measurements to true 

lake-bottom elevations. 

In 2001, the Sedimentation 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 generates a detailed cross section of bottom geometry as 

the survey vessel passes over the areas 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 measures the 

relative water depth across the wide swath perpendicular to the vessel’s track. 

Figure 4 illustrates the swath of the sea floor that is about 3.5 times as wide as the 

water depth below the transducer. 

9
Figure 4 - Multibeam collection system. 

The multibeam system is composed of several instruments all in constant 

communication with a central on-board laptop 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 through the vertical 

profile of the reservoir water. The multibeam sounder was calibrated by lowering 

an instrument that measured the sound velocity through the reservoir water 

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

the measurements, which can vary with density, salinity, temperature, turbidity, 

and other conditions. With 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 multibeam surveyed areas primarily included the main channel from the dam 

upstream near range line 73 along with a few of the side coves, Figures 5 through 

10. The collection concentrated on the deeper portions of the reservoir to provide 

more detailed mapping than what was provided by the single beam coverage 

during the 1999 survey. The single beam collection system was used to collect 

the 2007 underwater data along the sediment range line alignment that included 

range lines 65 through 90. For mapping purposes, single beam data was also 

collected along the shoreline and the wide portion of the reservoir from range line 

73 upstream to range line 65 before it became too shallow for boat access. 

The multibeam and single beam soundings, combined with the LiDAR data 

created a detailed data set of over 21 million x,y,z points that represented the 

majority of the reservoir. These data sets were used to generate reservoir 

topography for this study. The multibeam survey system software continuously 

recorded reservoir depths and horizontal coordinates as the survey vessel moved 

along closely-spaced grid lines covering the reservoir area. Most transects (grid 

lines) were run parallel to the reservoir alignment with the multibeam swaths 

10
overlapping in the deeper areas of the reservoir to provide full bottom coverage of 

the areas surveyed. The multibeam system could have provided more detailed 

bottom coverage throughout the reservoir, but time and budget did not allow for 

the remainder of the reservoir to be surveyed by this method. There was also 

concern of damaging the multibeam transducer when surveying lines near the 

shore at the time of the 2007 survey. Due to the clarity of the reservoir water at 

the time of this survey, the survey vessel hit bottom on several occasions. 

The underwater collected data was processed using the same hydrographic system 

software used during the data collection. The analysis applied all measurements, 

such as vessel location and corrections for the roll, pitch, and yaw effects. The 

other corrections included applying the sound velocity through the reservoir water 

column and converting all depth data points to elevations using the measured 

water surface elevation at the time of collection. To make it more manageable, 

the massive amount of multibeam data was filtered into 5-foot cells or grids of the 

reservoir area surveyed by the multibeam system. The multibeam data was 

combined with the single beam data to produce the x,y,z data set used for 2007 

Elephant Butte Reservoir underwater map development. This data was filtered 

further by removing points in the flat bottom portions of the reservoir that were 

not necessary to produce detailed accuracy in these areas. Additional information 

on collection and analysis procedures is included in Engineering and Design: 

Hydrographic Surveying (Corps of Engineers, January 2002) and Reservoir 

Survey and Data Analysis (Ferrari and Collins, 2006). 

For the range lines upstream of range line 65, standard surveying techniques were 

used to map the reservoir areas. These surveys were conducted under contract 

with Reclamation’s Albuquerque Area Office and included land, small boat 

bathymetry, and aerial LiDAR (Light Detection And Ranging) surveys. The 

LiDAR was collected in 2004 and 2007. During all of these surveys, the upper 

reservoir pool was below the “Narrows,” meaning the small boat bathymetry was 

within the inflow channel. The 2004 LiDAR was collected near reservoir water 

surface elevation 4,340 and covered the above water reservoir area from range 

line 78 upstream to range line 23. The 2007 LiDAR covered the reservoir area 

from range line 23 upstream beyond range line 9 that represents the upper extent 

of the reservoir boundary. The LiDAR resulted in detailed x,y,z data sets of the 

bare earth in the above water portion of the reservoir. Since 1999 and the 

drawdown of the reservoir due to drought, the upper reach has become heavily 

vegetated. There were some issues with the bare earth LiDAR data due to the 

thick blanket of vegetation in some areas of the reservoir along with reflection off 

the top of existing water pools, but overall, this analysis found very good results 

when the 2007 developed range lines were plotted against the 1999 surveys. 

Previous studies of the 2004 LiDAR data set found very favorable results when 

comparing the LiDAR with standard land collection data (Aubuchon, 2005, 

Appendix I). The LiDAR did not cover the whole reservoir, but is the first data 

set to account for the shoreline erosion changes that have occurred throughout 

most of the reservoir. The LiDAR is the best information available on the current 

geometry of the reservoir not covered by the survey vessel. 

11
12

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13

Figure 5 - Elephant Butte Reservoir range line location map, 1 of 6. 
14

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Figure 6 - Elephant Butte Reservoir range line location map, 2 of 6. 

15
16

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17

Figure 7 - Elephant Butte Reservoir range line location map, 3 of 6. 
18

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19

Figure 8 - Elephant Butte Reservoir range line location map, 4 of 6. 
20

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21

Figure 9 - Elephant Butte Reservoir range line location map, 5 of 6. 
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23

Figure 10 - Elephant Butte Reservoir range line location map, 6 of 6. 
24

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Development of the 2007 Elephant 

Butte Reservoir Surface Areas 

As previously discussed, the 2007 study analysis for computing the reservoir 

surface areas and resulting capacity used both the range line and contour methods 

(Ferrari and Collins, 2006). For the 1999 study, the contour method was 

attempted, but lack of above water data (except for the USGS quad maps) did not 

allow computation of accurate topography even though the underwater survey 

was conducted near reservoir full condition (elevation 4,395). Since the 1999 

survey, the reservoir content has severely decreased due to the persistent drought 

in New Mexico. In 2004 the reservoir level dropped to elevation 4,294, exposing 

previously measured reservoir bottom sediments and allowing them to dewater 

and compact. The October 2007 reservoir study was conducted near reservoir 

elevation 4,327 allowing the survey vessel to measure the wetted bottom from 

range line 90 upstream to range line 65. The remaining upstream range lines have 

been exposed to the atmosphere since the extreme drawdown except for the 

wetted perimeter of the river inflows. To complete the 2007 analysis, data 

collected by contracted surveys were utilized and included: 

• 2004 LiDAR data, collected near reservoir water surface elevation 

4,300, covered from range line 78 upstream to range line 23 

• 2007 LiDAR data covered from range line 23 upstream to beyond 

range line 9 and the very upper reach of the reservoir 

• 2004, 2005 and 2007 range line data that mainly covered the wetted 

perimeter of several of the range lines using small boat bathymetric 

systems. For a few reaches, range line land survey data that extended 

above the water level was collected. The results from these above water 

surveys were compared with the LiDAR data sets with very good results 

(Aubuchon, 2005, Appendix I). 

The combined LiDAR data sets covered about eighty five percent of the reservoir 

shore line area, but for consistency with past survey analysis, it was determined 

the range line width adjustment method would be used to generate the 2007 study 

results. If future surveys are conducted with the same above water detail, contour 

volume comparisons may be the best method for computing the updated reservoir 

capacity and resulting sediment deposition. 

25
Width adjustment method 

For some of the previous Elephant Butte Reservoir resurveys, new contour maps 

were drawn from the range-line survey data. These contours between the 

collected range-lines for the updated maps were drawn using the original contour 

map as a guide or control and estimating the new contour location based on 

changes that occurred at each range-line. This method was eventually abandoned 

for the constant factor method, which was further modified to the width 

adjustment method (Ferrari and Collins, 2006). Since the 1980 study, some form 

of the width adjustment method has been used for the Elephant Butte Reservoir 

analysis. 

In the width adjustment method, illustrated on Figure 11, the new contour area, 

A1, between any two ranges is computed by applying an adjustment factor to the 

original contour area, A0, between the two ranges. This adjustment factor is 

defined as the ratio of the new average width to the original average width for 

both upstream and downstream ranges at the specified contour. The revised 

segmented surface areas for each contour are then summed for the whole 

reservoir. The summarized segmented surface area versus elevation becomes the 

basic input for volume computations. 

A comparison of the simultaneous plots of original range profiles against the 

resurveyed range profiles indicates the lateral distribution of the sediment at the 

measured points. Where these plots indicate changes have occurred on the side 

slopes of the reservoir, an engineering judgment decision is required to determine 

whether the change is due to survey inaccuracies or due to actual deposition or 

erosion. 

On the original full scale base topography map of the reservoir, finalized location 

of all reservoir sediment ranges were marked. This divided the reservoir into 

storage segments defined by adjacent range-lines and/or by terminal ends of the 

reservoir, such as the dam or upstream ends of surface area contours. For the 

1957 sedimentation study, planimetering determined the original segmental 

contour surface areas between boundaries for each 10-foot contour from a water 

surface of 4,410.0 to the lowest contour area within each segment. For the 

original and 2007 measured range lines the width for all contours for each 

segment was computed for the 10-foot contour intervals. From these values, 

adjustment factors were computed by dividing the new survey average width by 

the original survey average width for each contour interval within each segment. 

The new segmental contour areas were computed by multiplying the original 

contour area by the adjustment factor. All segment areas were added together to 

develop the new contour elevation versus 2007 surface areas used in the 

area-capacity computations. 

26
Initial Survey New Survey

Ao = Contour Area A1 = Contour Area (Computed) 

Wo' = Downstream Width W1′ = Downstream Width 

Wo′′ = Upstream Width W1′′ = Upstream Width 

( ) ( )⎥

⎦

⎤ ⎢

⎣

⎡

+

+ = "

0

'

0

"

1

'

1

1 WW

WW A

Figure 11 - Width adjustment method for revising contour areas. 

Reservoir Sediment Distribution 

Lateral Distribution 

Ground profiles of the 82 reservoir sedimentation ranges are shown on Figures 12 

through 94. These profiles illustrate the general lateral distribution of sediments 

in the reservoir. Plots are from left to right looking upstream to be consistent with 

previous survey reports. The plots illustrate the survey results from the original, 

1999, and 2007 surveys. The original and other profiles do not fully agree in the 

lateral direction for all ranges mainly due to the fact the original profiles were 

transcribed from a 1915 topographic map with a contour interval of 10 feet. 

During the 1988 survey, the above-water portions of each range line from each 

range end to the water edge were measured. For the main portion of the reservoir, 

27
range line 79 through 90, the results from the 1988 survey were used to develop 

the range line plots for the areas not covered by the1999 survey. 

Using tools within ARCGIS, the 2007 cross sections were located and profiles 

were developed by cutting lines through the surveyed data points. The routine 

stored the nearest data points along each sediment range line alignment. The 

stored point density, within 5 feet of the projected range line alignment, was 

dependent on available data near the cross section, which for the LiDAR data sets 

was very dense. This routine was used for range lines 9 through 78 where LiDAR 

was available, and from the plots one can see a very good comparison throughout 

the range lines. The LiDAR produced portions of the range lines compared very 

well along the steep banks of the 1999 plots that were developed from the 1988 

land survey data and one would not expect change there due to sediment 

deposition. To account for changes at each range line, the latest bathymetric 

survey data was inserted into the LiDAR developed range lines. For range lines 

65 through 78 this included the October 2007 bathymetry. For most cases 

upstream of range line 65, data inserted into the LiDAR included the changes in 

the inflowing river channel geometry from the contract surveys of some of the 

range lines (the latest contract surveys were also conducted in 2007). 

The range line plot comparisons illustrate some interesting results when 

comparing the 1999 and 2007 survey results. The plots appear to indicate 

minimal change from range line 90 upstream through range line 73, but the 2007 

computations did measure a small increase of sediment volume in this portion of 

the reservoir. From range line 72 upstream through 65, located in the upper reach 

of the reservoir pool during the time of the 2007 survey, a delta has formed since 

the 1999 survey. This is the area where the reservoir widens significantly 

downstream of the “Narrows,” meaning the inflow velocities decrease and 

inflowing sediments deposit, forming a new reservoir delta. 

The range line plots upstream of 65 show varied results with the 2007 sediment 

level plotting below the 1999 results in many cases. This is likely due to 

significant compaction or consolidation of the previous deposited sediments that 

occurred since 1999 from the long exposure and drying out during the recent low 

reservoir content period. In some cases the average consolidation across the 

range line was as much as five feet. As shown on some of the plots, the river has 

scoured the previously deposited sediments in these upper range lines during this 

period of low reservoir content, but the biggest impact on the 2007 capacity 

computations resulted from the large areas of sediment consolidation that 

increased the reservoir volume of these portions of the reservoir. This is not the 

first time this significant consolidation has occurred. The 1957 survey was 

conducted after an extended drought and ten years after the last survey in 1947. 

The 1957 study measured an increase in total reservoir volume since the 1947 

survey of over 9,000 acre-feet (Bureau of Reclamation, 1960). 

28
Also apparent on the plots are the low flow conveyance channel dikes that have 

been developed over the years to convey river inflows to the reservoir. 

Channelization in the headwaters of Elephant Butte Reservoir began in the 1950s 

when severe drought conditions and salt cedar infestation resulted in the river 

channel becoming disconnected from the reservoir pool. The river disconnection 

has always been an issue at the headwaters of Elephant Butte. Some of the 

contributing factors for the occurrence of disconnection are the valley slope being 

very slight, the incoming sediment load high, and vegetation growth extremely 

aggressive. During dry climactic periods when the reservoir pool surface area 

decreases rapidly, all of these factors make it difficult for the river channel to cut 

its own channel to the reservoir pool. 

With the channelization work 1950s and the 1960s, in combination with an 

increasing reservoir pool, the river was able to maintain a connection of its own 

until the early 1990s when New Mexico entered another period of dry conditions, 

resulting in the construction of two temporary channels. In the summer of 2000, 

construction began on additional temporary channels which are illustrated on the 

following plots. 

29
30

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31

Elephant Butte Reservoir - Range Line 90

4,200

4,250

4,300

4,350

4,400

4,450

4,500

4,550

4,600

4,650

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 12 - Range Line 90. 

Elephant Butte Reservoir - Range Line 89

4,200

4,250

4,300

4,350

4,400

4,450

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 13 - Range Line 89. 
32

Elephant Butte Reservoir - Range Line 88

4,200

4,250

4,300

4,350

4,400

4,450

4,500

4,550

4,600

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 14 - Range Line 88. 

Elephant Butte Reservoir - Range Line 87

4,200

4,250

4,300

4,350

4,400

4,450

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 15 - Range Line 87. 
33

Elephant Butte Reservoir - Range Line 86

4,200

4,250

4,300

4,350

4,400

4,450

4,500

4,550

4,600

4,650

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 16 - Range Line 86. 

Elephant Butte Reservoir - Range Line 85

4,200

4,250

4,300

4,350

4,400

4,450

4,500

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 17 - Range Line 85. 
34

Elephant Butte Reservoir - Range Line 84

4,200

4,250

4,300

4,350

4,400

4,450

4,500

4,550

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 18 - Range Line 84. 

Elephant Butte Reservoir - Range Line 83

4,225

4,275

4,325

4,375

4,425

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 19 - Range Line 83. 
35

Elephant Butte Reservoir - Range Line 82

4,225

4,275

4,325

4,375

4,425

4,475

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 22,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 20 - Range Line 82. 

Elephant Butte Reservoir - Range Line 81

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 22,500 25,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 21 - Range Line 81. 
36

Elephant Butte Reservoir - Range Line 80

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 17,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 22 - Range Line 80. 

Elephant Butte Reservoir - Range Line 79

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 23 - Range Line 79. 
37

Elephant Butte Reservoir - Range Line 78

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 24 - Range Line 78. 

Elephant Butte Reservoir - Range Line 77

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 25 - Range Line 77. 
38

Elephant Butte Reservoir - Range Line 76

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 17,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 26 - Range Line 76. 

Elephant Butte Reservoir - Range Line 75

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 27 - Range Line 75. 
39

Elephant Butte Reservoir - Range Line 74

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 28 - Range Line 74. 

Elephant Butte Reservoir - Range Line 73

4,225

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 29 - Range Line 73. 
40

Elephant Butte Reservoir - Range Line 72

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 30 - Range Line 72. 

Elephant Butte Reservoir - Range Line 71

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 31 - Range Line 71. 
41

Elephant Butte Reservoir - Range Line 70

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 32 -Range Line 70. 

Elephant Butte Reservoir - Range Line 69

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 2,000 4,000 6,000 8,000 10,000 12,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 33 - Range Line 69. 
42

Elephant Butte Reservoir - Range Line 68

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 34 - Range Line 68. 

Elephant Butte Reservoir - Range Line 67

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 35 - Range Line 67. 
43

Elephant Butte Reservoir - Range Line 66

4,250

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 36 - Range Line 66. 

Elephant Butte Reservoir - Range Line 65

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 37 - Range Line 65. 
44

Elephant Butte Reservoir - Range Line 64

4,320

4,345

4,370

4,395

4,420

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 38 - Range Line 64. 

Elephant Butte Reservoir - Range Line 63

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 39 - Range Line 63. 
45

Elephant Butte Reservoir - Range Line 62

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 40 - Range Line 62. 

Elephant Butte Reservoir - Range Line 61

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 41 - Range Line 61. 
46

Elephant Butte Reservoir - Range Line 60

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 42 - Range Line 60. 

Elephant Butte Reservoir - Range Line 59

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 43 - Range Line 59. 
47

Elephant Butte Reservoir - Range Line 58

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 44 - Range Line 58. 

Elephant Butte Reservoir - Range Line 57

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 45 - Range Line 57. 
48

Elephant Butte Reservoir - Range Line 56

4,275

4,300

4,325

4,350

4,375

4,400

4,425

0 100 200 300 400 500 600 700 800 900 1,000 1,100

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 46 - Range Line 56. 

Elephant Butte Reservoir - Range Line 55

4,275

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 47 - Range Line 55. 
49

Elephant Butte Reservoir - Range Line 54

4,300

4,325

4,350

4,375

4,400

4,425

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 48 - Range Line 54. 

Elephant Butte Reservoir - Range Line 53

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 49 - Range Line 53. 
50

Elephant Butte Reservoir - Range Line 52

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 50 - Range Line 52. 

Elephant Butte Reservoir - Range Line 51

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 51 - Range Line 51. 
51

Elephant Butte Reservoir - Range Line 50

4,300

4,325

4,350

4,375

4,400

4,425

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 52 - Range Line 50. 

Elephant Butte Reservoir - Range Line 49

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 53 - Range Line 49. 
52

Elephant Butte Reservoir - Range Line 48

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 54 - Range Line 48. 

Elephant Butte Reservoir - Range Line 47

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

4,525

4,550

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 55 - Range Line 47. 
53

Elephant Butte Reservoir - Range Line 46

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

4,525

4,550

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 56 - Range Line 46. 

Elephant Butte Reservoir - Range Line 45

4,300

4,325

4,350

4,375

4,400

4,425

4,450

4,475

4,500

4,525

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 8,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 57 - Range Line 45. 
54

Elephant Butte Reservoir - Range Line 44

4,300

4,325

4,350

4,375

4,400

4,425

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 58 - Range Line 44. 

Elephant Butte Reservoir - Range Line 43

4,320

4,330

4,340

4,350

4,360

4,370

4,380

4,390

4,400

4,410

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 59 - Range Line 43. 
55

Elephant Butte Reservoir - Range Line 42

4,320

4,330

4,340

4,350

4,360

4,370

4,380

4,390

4,400

4,410

4,420

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 60 - Range Line 42. 

Elephant Butte Reservoir - Range Line 41

4,325

4,345

4,365

4,385

4,405

4,425

4,445

4,465

4,485

4,505

4,525

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 61 - Range Line 41. 
56

Elephant Butte Reservoir - Range Line 40

4,335

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 62 - Range Line 40. 

Elephant Butte Reservoir - Range Line 39

4,335

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 63 - Range Line 39. 
57

Elephant Butte Reservoir - Range Line 38

4,335

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 64 - Range Line 38. 

Elephant Butte Reservoir - Range Line 37

4,335

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 65 - Range Line 37. 
58

Elephant Butte Reservoir - Range Line 36

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 66 - Range Line 36. 

Elephant Butte Reservoir - Range Line 35

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 67 - Range Line 35. 
59

Elephant Butte Reservoir - Range Line 34

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Distance - Feet

Elevation - Feet

1915

1999

2007

2007 Contract

2007 LiDAR

Ponded area that appears 

shallow in some areas

Figure 68 - Range Line 34 with notes. 

Elephant Butte Reservoir - Range Line 34

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 69 - Range Line 34. 
60

Elephant Butte Reservoir - Range Line 33

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 70 - Range Line 33. 

Elephant Butte Reservoir - Range Line 32

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 8,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 71 - Range Line 32. 
61

Elephant Butte Reservoir - Range Line 31

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 72 - Range Line 31. 

Elephant Butte Reservoir - Range Line 30

4,345

4,355

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 73 - Range Line 30. 
62

Elephant Butte Reservoir - Range Line 29

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 74 - Range Line 29. 

Elephant Butte Reservoir - Range Line 28

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 75 - Range Line 28. 
63

Elephant Butte Reservoir - Range Line 27

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 76 - Range Line 27. 

Elephant Butte Reservoir - Range Line 26

4,365

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 77 - Range Line 26. 
64

Elephant Butte Reservoir - Range Line 25

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 78 - Range Line 25. 

Elephant Butte Reservoir - Range Line 24

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

4,495

4,505

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 79 - Range Line 24. 
65

Elephant Butte Reservoir - Range Line 23

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 80 - Range Line 23. 

Elephant Butte Reservoir - Range Line 22

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 81 - Range Line 22. 
66

Elephant Butte Reservoir - Range Line 21

4,375

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 82 - Range Line 21. 

Elephant Butte Reservoir - Range Line 20

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 83 - Range Line 20. 
67

Elephant Butte Reservoir - Range Line 19

4,385

4,395

4,405

4,415

4,425

4,435

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 84 - Range Line 19. 

Elephant Butte Reservoir - Range Line 18

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Distance - Feet

Elevation - Feet

1915

1999

2007

2007

Adjusted

Figure 85 - Range Line 18. 
68

Elephant Butte Reservoir - Range Line 17

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Distance - Feet

Elevation - Feet

1915

1999

2007

2007

Unadjusted

Figure 86 - Range Line 17. 

Elephant Butte Reservoir - Range Line 16

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 87 - Range Line 16. 
69

Elephant Butte Reservoir - Range Line 15

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 88 - Range Line 15. 

Elephant Butte Reservoir - Range Line 14

4,385

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 89 - Range Line 14. 
70

Elephant Butte Reservoir - Range Line 13

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

4,485

4,495

4,505

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 90 - Range Line 13. 

Elephant Butte Reservoir - Range Line 12

4,395

4,405

4,415

4,425

4,435

4,445

4,455

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 91 - Range Line 12. 
71

Elephant Butte Reservoir - Range Line 11

4,395

4,405

4,415

4,425

4,435

4,445

4,455

4,465

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 92 - Range Line 11. 

Elephant Butte Reservoir - Range Line 10

4,405

4,415

4,425

4,435

4,445

4,455

4,465

4,475

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 93 - Range Line 10. 
72

Elephant Butte Reservoir - Range Line 9

4,405

4,415

4,425

4,435

4,445

4,455

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

Distance - Feet

Elevation - Feet

1915

1999

2007

Figure 94 - Range Line 9. 
Longitudinal Distribution 

To illustrate the sediment distribution throughout the reservoir, a longitudinal 

profile was plotted for the original, 1988, 1999, and 2007 reservoir conditions 

(Figure 95). The difference between the original thalweg and the 1988, 1999, and 

2007 thalweg represents the sediment encroachment into the reservoir since the 

dam closed in 1915. The plot shows the greatest depths of longitudinal sediment 

deposits since 1915 occurring in 1988 and 1999 between 14 to 16 miles upstream 

of the dam. The deposit pattern in this region was influenced by the “Narrows” 

area located between 15 and 20 miles above the dam when the reservoir pool 

extends upstream. 

For this same reach the 2007 longitudinal plot is lower than the 1988 and 1999 

plots. Looking at the lateral distribution plots of the range lines in this area, range 

line 50 through 60, one can see this is a reach of the reservoir where the inflow 

channel has cut through the previously deposited sediments. The 2007 plot shows 

sediment deposition since 1999 occurring around mile 6 upstream to around mile 

13. When the reservoir is full, the “Narrows” divide the reservoir into 2 large 

water bodies. The “Narrows” have an average width of 0.36 miles compared to 

an average width of 1.39 miles for the overall reservoir. A major factor 

influencing the longitudinal pattern of the reservoir is the operational water 

surface. From 1950 through 1968 there was a severe drought in the region where 

the reservoir was held at a much lower stage, allowing the inflowing sediment to 

be deposited in the lower reaches of the reservoir. Another severe regional 

drought began in 1999 and the lateral and longitudinal plots show the affect of the 

sediment deposition more downstream towards the dam. The plot of the 1999 and 

2007 thalweg illustrates where the majority of sediments have deposited over the 

last 8 years: in the upper reservoir area above mile 34 and the reach downstream 

of the narrows where the reservoir water surface has fluctuated since the 1999 

drawdown. 

73
74

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75

Elephant Butte Reservoir Longitudinal Profiles

1915, 1988, 1999, 2007 Comparison

420042204240426042804300432043404360438044004420

262830323436384042 24 

1416182022 

Distance Upstream of Dam (miles)

Elevation (ft)

1915 Original Survey1988 Survey1999 Survey2007 Survey

RL 10

RL 20

RL 50

RL 60

RL 30

RL 40

The Narrows

Nogal Canyon

Figure 95 - Elephant Butte Reservoir Longitudinal Profiles. 
76

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Reservoir Area and Capacity 

2007 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 0.00001 for Elephant Butte 

Reservoir. 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. Through differentiation of 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 Elephant Butte Reservoir area and capacity computations are listed 

in a separate set of 2007 area and capacity tables and have been published for the 

0.01, 0.1 and 1-foot elevation increments (Bureau of Reclamation, 2008). A 

description of the computations and coefficients output from the ACAP program 

is included with these tables. The original (1915) and 2007 results are listed on 

table 1. The original, 1988, 1999, and 2007 area-capacity relationships are listed 

on Table 2. The curves for these surveys are plotted on Figure 96. As of October 

2007, at elevation 4,407.0, the surface area was 35,825 acres with a total capacity 

of 2,024,586 acre-feet. 

77
78

This page intentionally left blank.
79

1. 2. 3. STATE New Mexico

4. 5. Truth or Consequences 6. COUNTY

7. ° 09 ' 1 5 " ° 11 ' 28 " 8. 1 9. SPILLWAY CREST EL

10. 11. 12. GROSS STORAGE 15

CAPACITY, AC-FT

a. 

b.

c. 2

d. 16

e.

f.

g.

17. LENGTH OF RESERVOIR

18. TOTAL DRAINAGE AREA 22. 3

19. NET SEDIMENT CONTRIBUTING AREA 4 23. MEAN ANNUAL RUNOFF 5

20. LENGTH MILES AVG. WIDTH MILES 24. MEAN ANNUAL INFLOW 6

21. 25. °F °F7

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

7

7

7

7

8

26. DATE OF 35. 36

7

7 

7

8

26. DATE OF 37. 38.

9

10

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.

13,300

10,166.7

23.21

16.24

6,575.6 0.548

673

16.59 673

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN REACH DESIGNATION

PERIOD

751

a. AVG. ANNUAL

5.4

428,020

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

10/2007

610,214

2/12/57

4/14/1999

 0.386

2/28/47 0.514

a.

11,103,200

4,285,400

437,000

892,281

79,210,000

0.605

AVG. ANN.

7,253.2

39,114,548

0.522

75,219,280

 /MI.2 c. -YR.

8.9

E 9.8 42.1

A 

84.3

A

0.392

8.7

97-

9.9

77-

97

9.6 9.3

27-

197

611,442

2/12/57

OF 137- 117-

a.

0.362

26.

DATE

0.250 23.16

10/2007

SURVEY

2/28/47

4/14/1999

2/28/47

2/12/57

4/14/1999

10/2007

SURVEY

2/12/57

Contour (D)

8.5

Range (D)

Range (D)

Range (D)

305

1/6/1915

36,584

RANGES OR 

YRS

PER. PER.

YRS

SURVEY

a.

991,354

441,776

PRECIPITATION

MEAN ANN.

34. PERIOD

TYPE OF 

MIN. ELEVATION

NO. OF

Contour (D)

82 (RL)

25923

504,200

ANNUAL

4/1999

10/2007 92.8

42.2

SURVEY

LONG 107

SURCHARGE

STORAGE

ALLOCATION

ELEVATION

0-10 10-20 20-30 30-40 60-70 70-80 105- 110-

77 57

57-

 2.6

0.275

7.0

7-

137 117 17

crest37 2737- 17-

15.6 16.0

10.9

12.2 8.5

10.6

11.9

9.5 12.1 15.5

50-60 90-100 115- 120-

182

60

40-50 80-90

9.1

DATE

10/2007

SURVEY

26. 44.

4/1999

9

REACH DESIGNATION PERCENT OF TOTAL ORIGINAL LENGTH OF RESERVOIR

5.3

3,010

DEPTH DESIGNATION ELEVATION RANGE IN FEET

8.4

183,422

-1,228

4,346.5

9

437,200 0.522

-9,180

13,535.6

2,440,000

INTERVALS

AREA, AC.

MAX. ANN.

35,984

36,772

TOP OF POOL

3 W

ACRE-FEET

INCHES

INCHES

MILES

8.29

853,600

0.62

RANGE

Bureau of Reclamation STREAM

30

Rio Grande

NEAREST P.O.

I MAX. ELEVATION

JOINT USE

CONSERVATION

S

A

B SQUARE MILES

11996 SQUARE MILES

MILES AVG. WIDTH OF RESERVOIR

U

N 10000

S SURVEY

R

V

R MULTIPLE USE

O

I 3,215

2,631,585

DEAD

4,407.0 40,064

INACTIVE 4,231.5 420

E FLOOD CONTROL

R

E

S

ORIGINAL

SURFACE AREA, AC-FT

13.

3,215

2,634,800

2,206,780

2,634,800

MEAN ANNUAL PRECIPITATION

4100.5

41 1.39

85

32.3

2,023,358

2,197,600

64

32.

ACRE - FEET

2.37

BEGAN

DATE NORMAL

33.

OPERATIONS

2/1/15

111

1,776,999

b.

PERIOD WATER INFLOW, ACRE-FEET

13,535.6

944,365

1,036,000 4,307,318

7,506,600

c. TOTAL a. 

35,825

WATER INFLOW TO DATE, AF

2,024,586 2.37

MEAN ANN. b. TOTAL

1,077,623 34,807,230

AVG. ANN. /MI.2

-YR. TOTAL b.

930,191

853,600

TOTAL SEDIMENT DEPOSITS TO DATE, AF

a.

 1,154,862

TOTAL b.

PERIOD CAPACITY LOSS, ACRE-FEET

c.

R

4/28/47 32.3

ANNUAL TEMP, MEAN °F RANGE -16

SURFACE CAPACITY

Y

D

T

V

RESERVOIR SEDIMENT

DATA SUMMARY

Elephant Butte Reservoir NAME OF RESERVOIR 1

M

D

A TWP. 13 S

OWNER

SEC

LAT 33

DATA SHEET NO.

10-ft

10-ft (CI) 40,064

90 Feet

82 (RL)

4414.0

14.

4407.0

ACRE-FEET

ORIGINAL DATE

STORAGE

TOP OF DAM ELEVATION

2.59

2.57

Sierra

RATIO AF/AF

3.09

1/6/15

to

BEGAN

Table 1 - Reservoir Sediment Summary Sheets (1 of 3). 
80

 

2003 4,331.9 4,303.3 244,600 2004 4,324.2 4,294.0 365,700

2001 4,383.2 4,361.9 452,300 2002 4,365.9 4,320.1 273,100

1999 4,398.1 4,392.4 870,500 2000 4,397.6 4,377.6 361,100

1997 4,401.5 4,395.2 943,200 1998 4,404.5 4,393.1 919,200

1995 4,406.6 4,403.9 1,385,000 1996 4,406.5 4,394.2 525,700

1993 4,405.7 4,398.4 1,254,000 1994 4,406.0 4,401.1 1,776,000

1991 4,392.4 4,380.6 1,043,000 1992 4,405.7 4,391.4 1,167,000

1989 4,405.1 4,393.4 478,200 1990 4,397.5 4,380.3 347,100

1987 4,406.6 4,402.7 1,732,000 1988 4,406.7 4,401.4 930,300

1985 4,404.4 4,392.0 1,542,000 1986 4,407.2 4,402.8 1,576,000

1983 4,383.6 4,364.8 1,262,000 1984 4,392.3 4,381.0 1,052,000

824,300

1961 4,329.1 4,302.0 437,700 1962 4,329.8 4,304.4 748,100

4,380.5 4,363.8 1,280,000

1981 4,378.1 4,354.3 341,700 1982 4,364.7 4,354.3

1979

174,800

4,314.7 4,290.2 385,100

4,353.0 4,318.0 580,900

164,200

4,339.0

4,360.9

4,260.0 3,157

1955 4,295.5 4,276.6 257,900 1956 4,304.4 4,268.4

4,250.0 1,684 15,800

4,407.0 40,060

4,240.0 671 4,660

37,328 2,363,900

11,894

4,390.0 33,451 2,010,300 4,400.0

4,310.0 10,202 380,800 4,320.0

4,280.0 6,145 4,290.0 7,715

982,500

1945 4,385.6 4,372.3 851,500 1946 4,375.7 4,339.5 224,900

441,600 1944 4,385.7 4,369.2

4,346.1 4,315.5 364,100

1941 4,399.2 4,324.3 2,440,000 1942 4,409.2 4,397.0 2,322,000

1947 4,339.4 4,311.9 419,200 1948 4,349.2 4,313.1 1,036,000

4,351.3 4,329.7 1,031,000 1950

4,325.2 4,295.8

ELEVATION

0

2005

1977 243,200

AREA

2007 4,347.8

 

45. RANGE IN RESERVOIR OPERATION

1943 4,399.0 4,380.8

CAPACITY ELEVATION AREA CAPACITY

2,960

 

202,100

490,800

2,634,800

39,700

4,220.0 98 490 4,230.0 376

132,800

 

 

4,324.4 612,800

46. ELEVATION - AREA - CAPACITY - DATA FOR

4,340.7 4,308.5 515,000

 

4,344.2 4,309.9 944,400

1976

2006

1978

4,365.0 4,305.9 1,427,000 1980

4,312.2 451,400

1975 4,345.9 4,326.1 875,900

4,355.5 4,319.2 1,309,000 1974

729,200

1971 4,326.4 4,271.2 413,100 1972 4,319.0 4,297.7 427,900

787,600 1970 4,339.4 4,303.0

1968 4,319.7 4,295.1 646,230

821,700

1967 4,321.8 4,293.0 391,600

1966 4,338.3 4,311.0 725,340

563,400

1963 4,327.5 4,282.1 405,500 1964 4,299.2 4,275.5

1959 4,334.5 341,900 1960

286,800 1954 4,297.3 4,258.0

4,322.4

198,500

1957 4,267.1 972,300 1958 4,373.3 4,336.2 1,391,000

1953 4,283.2

4,323.2 333,100

1951 4,262.3 132,900 1952 4,324.6 4,261.6 967,000

4,351.2

917,600

615,700 1940 4,357.0

1936 4,354.9

1932

872,900

1937 4,333.9 1,597,000 1938 4,377.1 4,365.6 1,004,000

1935

4,384.5

4,331.8

4,367.8

4,351.8

4,342.2

4,374.2 1,440,000

1933 4,365.0 717,000 1934 4,325.0 298,300

1931 4,349.7 418,000

4,322.8

1965 4,323.0 4,277.5

4,377.9

1949

4,380.7

4,378.4

2,756,600

78,600

285,400

4,321.8 1,302,250 1916 4,346.8 4,306.6 1,421,000

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

6

1915

4,210.0

4,410.0

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

4,300.0

4,270.0

4,330.0

4,360.0

SURVEY

41,283

4,691

8,923

 

ELEVATION AREA CAPACITY

4,220.5

4,337.1

4,335.0 4,308.8

4,362.8

1969

1973

1939

14,240 621,400

1915

0

4,315.8

4,340.0 16,595 775,600 4,350.0 19,194 954,400

22,563 1,162,100 4,370.0 26,620 1,408,000 4,380.0 30,191 1,692,800

4,372.3

1925

1927

1929

4,382.1

4,374.0

4,374.8

1,180,000

1926

1928 773,000

4,378.1

4,379.1

4,384.5 930,000

4,354.6 1,120,000

4,359.7

1930

4,354.7

4,363.0

4,353.7 1,240,000

321,000

1917 4,353.8 4,331.8 1918 4,337.0 4,290.3 379,100

1919 4,358.8 4,285.5 1,527,000 1920 4,393.9 4,350.9 1,970,000

1,305,000

1,662,000

1921 4,392.5 4,377.5 1,470,000 1922 4,389.5 4,370.7 1,044,000

1923 4,377.4 4,366.5 964,000 1924 4,395.8 4,368.9

Table 1 – Reservoir Sediment Summary Sheets (2 of 3).
81

1

2

3

4

5

6

7

8

9

10

 Measured total storage measured a gain of 9,180 acre-feet since 1947 survey. Attributable to compaction of previous measured sediments 

 located in the upper reservoir area that had long term exposure and dewatering due to low reservoir content. 

Computed annual inflow from 1/1915 through 10/2008. Annual inflow records from different sources, used published values in 1999 Elephant Butte

 Vertical Datum of 1988. There is a parapet wall on upstream and downstream sides of the dam crest with top elevation 4,419.0.

 (October 1 - March 31), which is used for prudent flood control space. Surface area at elevation 4231.5 estimated.

 Used 1988 and previous study results to be consistent. Represents loss of contributing area since closing of Jemez Dam in 1953 (1,034 mi2).

 Galisteo Dam in 1970 (596 mi2), Cochiti in 1973 (11,960 mi2), noncontributing area (310 mi2), and reservoir area (57 mi2.

4,380.0 24,726.9 1,218,927 4,385.0 26,453.1 1,346,877 4,390.0 28,179.2 1,483,458

4,395.0 30,256.8 1,629,548 4,400.0 32,334.5 1,786,026

 

10,072.6

4,407.0 35,825.5 2,024,586

4,410.0 37,321.6

271,301 4,325.0 319,690 4,330.0 10,862.6 372,028

155,549 4,310.0 7,097.8 189,399 4,315.0 8,190.2 227,619

2007

4,216.9

0

ELEVATION AREA CAPACITY

2,134,307

SURVEY

14,899.4

2,298.6

 

19,499.7

4,290.0

4,320.0

6,442.1

9,282.7

4,275.0

4,305.0

All elevations are project datum which is 43.3 feet less than National Geodetic Vertical Datum of 1929 and 45.5 feet less than North American 

 

47. REMARKS AND REFERENCES

Calculated using mean annual runoff value of 853,600 acre-feet (item 24).

 

Irrigation and power water supply, except the top 50,000 acre-feet in the summer (April 1- September 30) and the top 25,000 acre-feet in the winter

49. Bureau of Reclamation August 2008

AGENCY MAKING SURVEY

AGENCY SUPPLYING DATA DATE

48. Bureau of Reclamation

4,245.0

4,350.0

4,365.0

 

BOR Project Data Book, 1981. Annual precipitation at dam, 8.71 inches (1936-1992) from NOAA/NWS. Reclamation site: http://dataweb.usbr.gov. 

Previous studies report total drainage area as 25,923 mi2

 while USGS gage data at dam indicated 29,445 mi2 with 2,940 mi2 as non contributing.

 Sediment Survey report from 1915 through 1998.

 Measured total storage measured a gain of 1,228 acre-feet since 1999 survey. Attributable to compaction of previous measured sediments 

 located in the upper reservoir area that had long term exposure and dewatering due to low reservoir content. 

Values for 1915, 1947, 1957, and 1999 survey results from previous published results of Elephant Butte surveys. (www.usbr.gov/pmts/sediment)

2007 survey results.

630,803

888,062

29,084

74,961

46. ELEVATION - AREA - CAPACITY - DATA FOR

41,179

 

 

21,130.9 989,638

4,355.0 16,383.9

AREA

12,996.5

4,250.0 56.5 141 4,255.0 402.4 1,288

4,360.0 17,868.4 794,642

55,974

124,978

558,684

18,194

4,375.0 22,928.9 1,099,788

CAPACITY ELEVATION AREA CAPACITY

4,370.0

709,011

ELEVATION

0.0

4,280.0 2,539.5 4,285.0 3,378.2

4,295.0 5,001.6 98,008 4,300.0 5,786.4

4,335.0 11,929.5 429,008 4,340.0 491,323 4,345.0 13,948.0

4,260.0 748.2 4,165 4,265.0 1,402.9 9,542 4,270.0 2,057.6

Table 1 – Reservoir Sediment Summary Sheets (3 of 3).
82

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83

1 2 3 4 5 6 7 8 910 11 

1915 1915 1988 1988 1999 1999 

 Original Original 1988 1988 Sediment Percent 1999 1999 Sediment Percen

Elevation Area Capacity Area Capacity Volume Computed Area Capacity Volume Comput

Feet Acres Ac-Ft Acres Ac-Ft Ac-Ft Sediment Acres Ac-Ft Ac-Ft Sedime

4,407.0 40,060 2,634,800 36,643 2,065,010 569,790 100.0 35,984 2,023,358 611,442 14,400.0 37,328 2,363,900 33,433 1,819,744 544,156 95.5 32,051 1,785,235 578,665 4,390.0 33,451 2,010,300 28,697 1,509,096 501,204 88.0 27,788 1,486,042 524,258 4,380.0 30,191 1,692,800 24,890 1,241,164 451,636 79.3 24,323 1,225,489 467,311 4,370.0 26,620 1,408,000 20,994 1,011,742 396,258 69.5 20,856 999,593 408,407 4,360.0 22,563 1,162,100 18,011 816,715 345,385 60.6 17,765 806,489 355,611 4,350.0 19,194 954,400 14,872 652,300 302,100 53.0 14,784 643,744 310,656 4,340.0 16,595 775,600 13,210 511,890 263,710 46.3 13,046 504,591 271,009 4,330.0 14,240 621,400 11,260 389,537 231,863 40.7 11,169 383,516 237,884 4,320.0 11,894 490,800 9,535 285,562 205,238 36.0 9,563 279,857 210,943 4,310.0 10,202 380,800 7,503 200,374 180,426 31.7 7,434 194,872 185,928 4,300.0 8,923 285,400 6,205 131,833 153,567 27.0 6,063 127,388 158,012 4,290.0 7,715 202,100 4,263 79,490 122,610 21.5 4,171 76,222 125,878 4,280.0 6,145 132,800 2,660 44,873 87,927 15.4 2,562 42,561 90,239 4,270.0 4,691 78,600 2,142 20,861 57,739 10.1 2,107 19,220 59,380 

4,260.3 3,302 40,717 1,007 5,590 35,127 6.2 860 4,831 35,886 

4,260.0 3,157 39,700 971 5,293 34,407 6.0 822 4,579 35,121 

4,250.0 1,684 15,800 55 160 15,640 2.7 63 157 15,643 

4,245.0 1,178 10,230 8 3 10,227 1.8 0 0 10,230 

4,244.2 1,096 9,339 0 0 9,339 1.6 0 0 9,339 

4,240.0 671 4,660 0 0 4,660 0.8 0 0 4,660 

4,230.0 376 2,960 0 0 2,960 0.5 0 0 2,960 

4,220.0 98 490 0 0 490 0.1 0 0 490 

4,210.0 0 0 0 0 00.0 0 0 0

1 Reservoir water surface elevation. Elevations tied to project datum that is 43.3 feet less than NGVD29 and 45.5 feet 2 Original, 1915 reservoir surface area.3 Original, 1915 reservoir capacity.4 1988 reservoir surface area.5 1988 reservoir capacity.6 1988 computed sediment volume, column (3) - column (5).7 1988 measured sediment in percentage of total sediment of 569,790 acre-feet.8 1999 reservoir surface area.9 1999 reservoir capacity.

10 1999 computed sediment volume, column (3) - column (9).11 1999 measured sediment in percentage of total sediment of 611,442 acre-feet.12 2007 measured reservoir surface area.13 2007 reservoir capacity computed using ACAP.14 2007 measured sediment volume, column (3) - column (13).15 2007 measured sediment in percentage of total sediment of 610,214 acre-feet.16 Depth of reservoir expressed in percentage of total depth, 197 feet, from maximum water surface 4,407.0.

Table 2 - 2007 Elephant Butte Reservoir Survey Summaries. 
84

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85

Area-Capacity Curves for Elephant Butte Reservoir

4,210.04,230.04,250.04,270.04,290.04,310.04,330.04,350.04,370.04,390.04,410.0

0 280000 560000 840000 1120000 1400000 1680000 1960000 2240000 252

Capacity (acre-feet)

Elevation (feet)

42,000 37,800 33,600 29,400 25,200 21,000 16,800 12,600 8,400 4,

Area (acres)

200719991988Original

Capacity

Area

Figure 96 - Elephant Butte Reservoir Area and Capacity Plots 
86

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2007 Analyses of Results 

The Elephant Butte Reservoir original, 1988, 1999, and 2007 area and capacity 

values are illustrated on Figure 96 and the results are listed on Tables 1 and 2. 

These presentations illustrate the capacity change that has occurred during the 

92.8 years of reservoir operations. This study found that as of October 2007, at 

reservoir water surface elevation (feet) 4,407.0, the surface area was 35,825 acres 

with a total capacity of 2,024,586 acre-feet. Since the reservoir’s 1915 initial 

filling, 610,214 acre-feet of sediment have accumulated in Elephant Butte 

Reservoir. The average annual rate of sediment accumulation since 1915 is 6,576 

acre-feet. These results were computed using the range line width area 

adjustment method. The range line method has been used been used in one form 

or another for all past surveys. Using like analysis methods for the 2007 survey 

was the best means to show change over time. 

Since the last reservoir survey in 1999, the 2007 survey measured a net capacity 

gain of 1,228 acre-feet. Comparing the results of the 1999 and 2007 surveys 

showed a greater sediment deposit downstream of the “Narrows” and in the very 

upper reach near range lines 9 through 20. Over the last 8.5 years since the 1999 

survey, the reservoir has been at very low stages, operating below the “Narrows.” 

The areas from the “Narrows” upstream seldom saw the river overflow its banks 

and the bulk of the incoming sediment was conveyed to the lower reservoir. 

These types of results were also seen during the 1957 survey that was conducted 

after a 10 year drought cycle (Bureau of Reclamation, 1960). During these 

periods the continual draw-down of the reservoir had a significant effect on the 

compaction of reservoir sediments. The deposits were exposed to the sun for 

prolonged periods where they dried, compacted, and increased the initial unit 

weight, resulting in an increase of the volume computations. Since the 1999 

survey, similar conditions have occurred, resulting in an increase volume due to 

consolidation of previous deposited sediments. 

The results presented on Table 1 and Table 2 were computed using the range line 

collection and the width area adjustment analysis method. These same methods 

were previously used for the 1980, 1988, and 1999 surveys. These methods were 

the best means to measure and illustrate changes that have occurred over these 

time frames. The following sections are the results of the contour analysis that 

compared very well with the 2007 overall results. 

87
88

2007 Topography Development 

Elephant Butte Data Sets and TIN Development 

The topography of Elephant Butte Reservoir was developed from 2007 

bathymetric survey data, digitized contours from the USGS quad maps, and the 

2004 and 2007 LiDAR data sets. All elevations presented on the following 

drawings are tied to the NAVD88 vertical datum that is 45.5 feet higher than 

Elephant Butte Dam project datum. This means the top of the dam at project 

elevation 4,414.0 would be elevation 4,459.5 feet in vertical datum NAVD88. 

The USGS 10-foot quad contours represent elevations in NGVD29 and were 

shifted to NAVD88 by adding 2.2 feet to their assigned elevation. The USGS 

quad contours do not provide the detail of the LiDAR data sets, but were the only 

means to map the areas not covered. There were also small coves upstream of 

range line 78 that the LiDAR data sets did not cover. In these reaches the USGS 

quad contours were used to interpolate data points to force contour closure. Even 

though there are areas that were not covered by the TIN data sets, an estimated 85 

percent of the reservoir was covered. The LiDAR provided the most recent data 

to map the actual reservoir geometry above the 2007 bathymetry. The LiDAR 

takes into account the bank changes that have occurred over the years not 

represented by the range line survey and analysis. 

The LiDAR data was processed as bare earth, but at times the water surface and 

top of vegetation were mapped where the LiDAR couldn’t penetrate. In the areas 

of the data sets where the 2007 bathymetry overlaid the LiDAR, the overlapping 

LiDAR data points where removed. This method removed all of the LiDAR 

water surface data points, plus provided the most up to date reservoir volume 

since the lower reservoir LiDAR data set was flown in 2004. To force contour 

development within the reservoir area, a hardclip contour was developed that ran 

along the dam and dike alignments in the downstream reservoir areas. This clip 

was assigned an elevation of 4,480.0 (NAVD88) and was used as a hard boundary 

for the 2007 developed contours. This boundary allowed contour mapping within 

the reservoir area as outlined by the hardclip contour. The hardclip was used 

during the triangular irregular network (TIN) development to prevent 

interpolation outside the enclosed polygon. Figures 97 through 104 are 

illustrations of the developed TIN of the reservoir. Figure 97 shows the USGS 

quad contours that were imported into the processed data sets to develop the 2007 

Elephant Butte topographic maps from the dam upstream to where the LiDAR 

began. 
89

Figure 97 - Elephant Butte Reservoir TIN, 1 of 8. 
90

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91

Figure 98 - Elephant Butte Reservoir TIN, 2 of 8. 
92

This page left blank intentionally. 
93

Figure 99 - Elephant Butte Reservoir TIN, 3 of 8. 
94

This page left blank intentionally. 
95

Figure 100 - Elephant Butte Reservoir TIN, 4 of 8. 
96

This page left blank intentionally. 
97

Figure 101 - Elephant Butte Reservoir TIN, 5 of 8. 
98

This page left blank intentionally. 
99

Figure 102 - Elephant Butte Reservoir TIN, 6 of 8. 
100

This page left blank intentionally. 
101

Figure 103 - Elephant Butte Reservoir TIN, 7 of 8. 
102

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103

Figure 104 - Elephant Butte Reservoir TIN, 8 of 8. 
104

This page left blank intentionally. 
Elephant Butte Contour Development 

Contours at reservoir elevation 4,470 (NAVD88) and below were developed from 

the TIN generated within ARCGIS. A TIN is a set of adjacent non-overlapping 

triangles computed from irregularly spaced points with x,y coordinates and z 

values. A TIN is 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 all the data points are connected to their nearest 

neighbors to form triangles. This method preserves all the collected data points. 

The TIN method is described in more detail in the ARCGIS user’s 

documentation, (ESRI, 2007). The linear interpolation option of the ARCGIS 

TIN and CONTOUR commands were used to interpolate contours from the 

Elephant Butte Reservoir TIN. The contours were developed from the TIN at tenfoot increments from elevations 4,390 (NAVD88) through 4,470.0 and are 

presented in Figures 105 through 112. The ARCGIS software developed contours 

directly from the TIN using all the enclosed data points, resulting in some jagged 

representations of the contours. For presentation purposes the contour lines were 

smoothed by removing the smaller developed contour lines. The contours can be 

further smoothed using a smooth line option within ARCMAP, but overall the 

following maps are a good representation of the reservoir topography. The 

smoothing processes did not affect the reported surface areas of the topography 

since they were computed directly from the TIN using all the data points. The 

following figures present the developed 10-foot contours from elevation 4,470 

(NAVD88) and below. The horizontal control is in New Mexico central state 

plane coordinates in NAD83. The contours are presented from the dam upstream 

in a north to south alignment. 

105
106

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107

Figure 105 - Elephant Butte 2007 Reservoir Topography, 1 of 8. 
108

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109

Figure 106 - Elephant Butte 2007 Reservoir Topography, 2 of 8. 
110

This page left blank intentionally.
111

Figure 107 - Elephant Butte 2007 Reservoir Topography, 3 of 8. 
112

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Figure 108 - Elephant Butte 2007 Reservoir Topography, 4 of 8. 
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Figure 109 - Elephant Butte 2007 Reservoir Topography, 5 of 8. 
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Figure 110 - Elephant Butte 2007 Reservoir Topography, 6 of 8. 
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Figure 111 - Elephant Butte 2007 Reservoir Topography, 7 of 8. 
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Figure 112 - Elephant Butte 2007 Reservoir Topography, 8 of 8. 
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Elephant Butte 2007 Topography Surface Areas and 

Capacity Computations and Comparisons 

The 2007 surface areas for Elephant Butte Reservoir were computed at 5-foot 

increments directly from the reservoir developed TIN from elevation 4,385 

(NAVD88) through 4,470 (NAVD88). The TIN was developed from collected 

and interpolated data sets within the hard clip polygon created from the previously 

described TIN and resulting contour maps. Surface area calculations were 

performed using ARCGIS commands that compute areas at user-specified 

elevations directly from the TIN using all the data points. For the purpose of this 

study, the computed survey areas at 5-foot increments were shifted to the project 

vertical datum by reducing the elevations by 45.5 feet. The resulting surface 

areas versus elevation were input into the ACAP program for computing the 

resulting Elephant Butte 2007 capacity using the contour method. ACAP was 

also used to compute the 2007 range line analysis results. The volume differences 

are due to measured surface area difference only. 

Table 3 and Figure 113 list and illustrate a comparison between the range line and 

contour methods. Comparison of the results of the two methods was favorable. 

The contour method computed a reservoir capacity of 2,008,244 acre-feet at 

elevation 4,407 compared to the range line method of 2,024,586 acre-feet. The 

difference is 16,342 acre-feet or less than 1 percent between the two analysis 

methods. The contour method was affected in the lower end of the reservoir 

where LiDAR coverage was not available, but overall the results are very good. It 

is recommended that future aerial surveys should cover the lower portion of the 

reservoir to the dam. Ideally the whole reservoir should be flown at one time, but 

budgets usually prevent such extensive coverage for larger reservoirs. Obtaining 

LiDAR type collection from the dam upstream to where the 2004 LiDAR 

coverage began will allow upper contours to be developed with more confidence. 

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125

1 2 3 4 5 6 7 8 910 11 

TOPOGRAPHIC CONTOUR METHOD WIDTH ADJUSTMENT METHOD

1915 1915 2007 2007 2007 TOPO 2007 TOPO 2007 2007 D

 Original Original TOPOGRAPHIC TOPOGRAPHIC Sediment Percent 2007 2007 Sediment Percent Ra

Elevation Area Capacity Area Capacity Volume Computed Area Capacity Volume Computed Con

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

4,407.0 40,060 2,634,800 35,629 2,008,244 626,556 100.0 35,826 2,024,586 610,214 100.0 4,400.0 37,328 2,363,900 32,270 1,770,350 593,550 94.7 32,335 1,786,026 577,874 94.7 4,390.0 33,451 2,010,300 27,860 1,470,855 539,445 86.1 28,176 1,483,458 526,842 86.3 4,380.0 30,191 1,692,800 24,585 1,209,347 483,453 77.2 24,727 1,218,927 473,873 77.7 4,370.0 26,620 1,408,000 21,012 981,920 426,080 68.0 21,131 989,638 418,362 68.6 4,360.0 22,563 1,162,100 17,810 787,407 374,693 59.8 17,868 794,642 367,458 60.2 4,350.0 19,194 954,400 14,912 625,406 328,994 52.5 14,899 630,803 323,597 53.0 4,340.0 16,595 775,600 13,205 484,635 290,965 46.4 12,997 491,323 284,277 46.6 4,330.0 14,240 621,400 11,034 363,744 257,656 41.1 10,863 372,028 249,372 40.9 4,320.0 11,894 490,800 9,084 262,751 228,049 36.4 9,283 271,301 219,499 36.0 4,310.0 10,202 380,800 7,032 182,694 198,106 31.6 7,098 189,399 191,401 31.4 4,300.0 8,923 285,400 5,502 119,613 165,787 26.5 5,786 124,978 160,422 26.3 4,290.0 7,715 202,100 3,891 72,824 129,276 20.6 4,217 74,961 127,139 20.8 4,280.0 6,145 132,800 2,556 41,019 91,781 14.6 2,539 41,179 91,621 15.0 4,270.0 4,691 78,600 1,998 18,332 60,268 9.6 2,058 18,194 60,406 9.9 

4,260.3 3,302 40,717 781 5,356 35,361 5.6 1,141 6,999 33,718 5.5 

4,260.0 3,157 39,700 753 5,126 34,574 5.5 748 4,165 35,535 5.8 

4,250.0 1,684 15,800 221 663 15,137 2.4 57 141 15,659 2.6 

4,245.0 1,178 10,230 37 18 10,212 1.6 0 0 10,230 1.7 

4,244.2 1,096 9,339 0 1 9,338 1.5 0 0 9,339 1.5 4,240.0 671 4,660 0 0 4,660 0.7 0 0 4,660 0.8 

4,230.0 376 2,960 0 0 2,960 0.5 0 0 2,960 0.5 

4,220.0 98 490 0 0 490 0.1 0 0 490 0.1 

4,210.0 0 0 0 0 00.0 0 0 00.0 

1 Reservoir water surface elevation. Elevations tied to project datum that is 43.3 feet less than NGVD29 and 45.5 feet less th2 Original, 1915 reservoir surface area.3 Original, 1915 reservoir capacity.4 2007 reservoir surface area by contour method.5 2007 reservoir capacity by contour method using ACAP.6 2007 contour computed sediment volume, column (3) - column (6).7 2007 contour measured sediment in percentage of total sediment of 626,556 acre-feet.8 2007 measured reservoir surface area by range line method.9 2007 reservoir capacity by range line method using ACAP.

10 2007 measured sediment volume, column (3) - column (10).11 2007 measured sediment in percentage of total sediment of 610,214 acre-feet.12 Computed difference between the 2007 range line method and 2007 contour method.13 Depth of reservoir expressed in percentage of total depth, 197 feet, from maximum water surface 4,407.0.

Table 3 - Elephant Butte Reservoir Contour and Range Line Comparisons 
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Area-Capacity Curves for Elephant Butte Reservoir

4,210.04,230.04,250.04,270.04,290.04,310.04,330.04,350.04,370.04,390.04,410.0

0 280000 560000 840000 1120000 1400000 1680000 1960000 2240000 2520

Capacity (acre-feet)

Elevation (feet)

42,000 37,800 33,600 29,400 25,200 21,000 16,800 12,600 8,400 4,2

Area (acres)

2007 RANGE LINE METHOD2007 CONTOUR METHODORIGINAL (1915)

Capacity

Area

Figure 113 - Elephant Butte Reservoir Contour and Range Line Comparison Plots. 
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References 

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

Headquarters, New York. 

Bureau of Reclamation, 1960. Elephant Butte Reservoir 1957 Reservoir Survey, 

Rio Grande Project, New Mexico, UC Region, Salt Lake City, UT. 

(www.usbr.gov/pmts/sediment). 

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, 2000. Elephant Butte Reservoir 1999 Reservoir Survey, 

Rio Grande Project, New Mexico, UC Region, Salt Lake City, UT. 

(www.usbr.gov/pmts/sediment). 

Bureau of Reclamation, 2006. Standing Operating Procedures (SOP), Elephant 

Butte Dam, Rio Grande Project, New Mexico, UC Region, Salt Lake City, UT. 

Bureau of Reclamation, 2007. Elephant Butte Reservoir Area and Capacity 

Tables, Rio Grande Project, Upper Colorado Region, Salt Lake City, UT. 

Bureau of Reclamation, 2008. Project Data, Denver Office, Denver CO. 

(www.usbr.gov/dataweb). 

Corps of Engineers, 2002. Engineering 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. and Collins, K. (2006). Reservoir Survey and Data Analysis, 

Chapter 9, Erosion and Sedimentation Manual, Bureau of Reclamation, 

Sedimentation and River Hydraulics Group. Denver, Colorado. 

www.usbr.gov/pmts/sediment 

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Appendix I 

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