El Vado Reservoir 

2007 Sedimentation Survey 

U.S. Department of the Interior 

Bureau of Reclamation 

Technical Service Center 

Denver, Colorado July 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 July 2008 

El Vado 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. Ronald Ferrari of the Sedimentation Group and Sharon Nuanes of the Water 

Resources Planning and Operations Support Group of the TSC conducted the bathymetry 

survey of the reservoir in June of 2007. Anthony Vigil of Reclamation’s Albuquerque 

Area Office of the Upper Colorado Region was the study coordinator with additional 

field support provided by Chama Field Division personnel. Ron Ferrari completed the 

data processing to generate the new reservoir topography and resulting area-capacity 

tables. Kent Collins of the Sedimentation Group 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/.

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) 

 July 2008 

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

5a. CONTRACT NUMBER 

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4. TITLE AND SUBTITLE 

El Vado 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 

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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 El Vado Reservoir in June 2007 to develop updated reservoir topography and compute the present 

storage-elevation relationship (area-capacity tables). The underwater survey, conducted near water surface elevation 6,900 

(project datum in feet), 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. Digitized reservoir contours from the U.S. Geological Survey quadrangle (USGS quad) maps were used to 

compute the reservoir areas and resulting capacities from elevation 6,902.0 through 6,912.0. 

As of June 2007, at elevation 6,902.0, the surface area was 3,232 acres with a total capacity of 190,820 acre-feet. Since the 

January 1935 dam closure, about 7,382 acre-feet of change has occurred below elevation 6,902.0 due to sediment deposition, 

resulting in a 3.7 percent loss in reservoir volume. Unknowns in the detail and accuracy of the previous surveys introduce 

uncertainty to the sediment computation values. The 2007 study used the contour method for collection and analysis resulting in 

a larger computed reservoir volume than the 1984 study that used the range line method for collection and analysis. 

15. SUBJECT TERMS 

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

area/ RTK GPS/ multibeam/ 

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a. REPORT b. ABSTRACT a. THIS PAGE 

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Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
Table of Contents 

Page 

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

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

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

Reservoir Operations........................................................................................................................ 

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

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

Topography Development....................................................................................................... 

Lateral Distribution ................................................................................................................. 

Development of the 2007 El Vado Reservoir Surface Areas.................................................. 

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

2007 Reservoir Sediment Analyses................................................................................................ 

References...................................................................................................................................... 

Index of Figures 

Page 

 

Figure 1 - Reclamation reservoirs located in New Mexico. ............................................................. 

Figure 2 - Temporary Point set near reservoir, June 2007................................................................ 

Figure 3 - Survey Vessel with Mounted Instrumentation on El Vado Reservoir, New Mexico....... 

Figure 4 - Multibeam Collection System. ....................................................................................... 

Figure 5 – El Vado Reservoir 2007 survey data points. ................................................................. 

Figure 6 - El Vado Reservoir Contour Map, 1 of 2........................................................................ 

Figure 7 - El Vado Reservoir Contour Map, 2 of 2........................................................................ 

Figure 8 - El Vado Reservoir Sedimentation Ranges Developed in 1984...................................... 

Figure 9 - Range Line 1, Rio Chama.............................................................................................. 

Figure 10 - Range Line 2, Rio Chama............................................................................................ 

Figure 11 - Range Line 3, Rio Chama............................................................................................ 

Figure 12 - Range Line 4, Rio Chama............................................................................................ 

Figure 13 - Range Line 6, Rio Chama and Boulder Creek............................................................. 

Figure 14 - Range Line 7, Rio Chama and Boulder Creek............................................................. 

Figure 15 - Range Line 8, Rio Chama and Boulder Creek............................................................. 

Figure 16 - Range Line 10, Rio Chama.......................................................................................... 

Figure 17 - Range Line 11, Rio Chama.......................................................................................... 

Figure 18 - Range Line 14, Rio Chama.......................................................................................... 

Figure 19 - Range Line 15, Rio Chama.......................................................................................... 

Figure 20 - Range Line 16, Rio Chama.......................................................................................... 

Figure 21 - Range line 20, Rio Chama. .......................................................................................... 

Figure 22 - Range line 22, Rio Chama. .......................................................................................... 

Figure 23 - Range Line 5, Boulder Creek. ..................................................................................... 

Figure 24 - Range Line 9, Boulder Creek. ..................................................................................... 

Figure 25 - Range Line 12, Boulder Creek. ................................................................................... 

Figure 26 - Range Line 13, Boulder Creek. ................................................................................... 

Figure 27 - Range line 17, Boulder Creek...................................................................................... 

Figure 28 - Range line 18, Boulder Creek...................................................................................... 

Figure 29 - Range line 19, Boulder Creek...................................................................................... 

Figure 30 – El Vado Reservoir Area and Capacity Plots ...............................................................
35

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Index of Tables 

Page 

Table 1 - Reservoir Sediment Data Summary (page 1 of 2)...........................................................

Table 2 - Summary of 2007 Survey Results...................................................................................
El Vado Reservoir 

2007 Sedimentation Survey 

Introduction 

El Vado Dam, located on the Rio Chama in New Mexico, is about 10 miles 

southwest of the town of Tierra Amarilla, 78 miles northwest of Santa Fe, and 28 

miles south of the Colorado-New Mexico state line (Figure 1). El Vado Dam, 

designated a New Mexico Civil Engineering Landmark, was built by the Middle 

Rio Grande Water Conservancy District in 1934-35 and rehabilitated by 

Reclamation in 1954-55. Reclamation installed new outlet works in 1965-66 to 

accommodate additional water for the San Juan-Chama Project that is diverted 

through Heron Reservoir, located upstream. The reservoir’s primary purpose is to 

provide storage for supplemental irrigation to the Middle Rio Grande Valley and 

San Juan-Chama Project water for irrigation, municipal, and industrial use. The 

project also provides flood control, hydroelectric power, recreation, and fish and 

wildlife benefits. 

Figure 1 - Reclamation reservoirs located in New Mexico (Reclamation, 2008). 

1
The dam, constructed between 1933 and 1935, has a rolled gravelfill and steel 

membrane. The embankment is compacted gravelfill with a rockfill zone at the 

downstream toe and a cobblefill zone downstream. The upstream face is covered 

with 0.25-inch-thick steel plate that is anchored to a cutoff wall at the toe and a 

steel parapet anchored to steel bracing set in concrete on the crest of the dam. 

The dam’s dimensions, in feet, are: 

 Hydraulic height1 156.5 Structural height 230 

 Crest length 1,326 Crest elevation2

 6,914.5 

An emergency spillway, located about one mile west of the dam, is an unlined 

channel with a fuseplug in a topographic saddle. The crest length is 630 feet at 

crest elevation 6,906.0 with a discharge capacity of 11,209 cubic-feet-per-second 

(cfs) at elevation 6,909.0. The service spillway is a gated crest structure with a 

36- by 24-foot high radial gate, crest length of 36 feet, and chute length of 956 

feet at crest elevation 6,879.0. The discharge capacity of the service spillway is 

18,200 cfs at elevation 6,909.0. The river outlet works, constructed by 

Reclamation in 1965, is located at the west end of the dam in the right abutment. 

It consists of four 5- by 9-foot high pressure slide gates discharging through a 13-

foot wide by 13- to 15-foot high horseshoe-shaped downstream tunnel section 

terminating in a concrete flip bucket in the right abutment. The discharge 

capacity at elevation 6,909.0 is 6,870 cfs. A bypass consists of a 14-inch pipe 

with a 14-inch high-pressure guard gate and 12-inch jet-flow gate valve that allow 

small outlet works releases at a capacity of 42 cfs at elevation 6,908.0. The 

hydroelectric powerplant consists of a 670-foot long penstock and a 96-inch 

diameter welded steel pipe extending from the valve chamber to the powerhouse 

with a maximum capacity of about 1,000 cfs. 

El Vado Dam impounds natural drainage water from the Rio Chama and Boulder 

Creek along with diverted San Juan basin water released through Heron 

Reservoir, located upstream on the Rio Chama arm. The total drainage above El 

Vado Reservoir is 783 square miles bounded by the Continental Divide on the 

west and San Juan Mountains on the east. The basin can be divided into four 

subbasins: Boulder Creek drainage area flows directly into El Vado Reservoir and 

is 95 square miles (mi2

); Willow Creek drainage area is controlled by Heron Dam 

(closure in October 1970) and is 193 mi2

; Rio Chama drainage area is 492 mi2; 

and the fourth subbasin is located west of El Vado Reservoir, drains into Stinking 

Lake and is considered non-contributing (Reclamation, 2004). 

 

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

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

Dams and Reservoirs, or ASCE’s Nomenclature for Hydraulics.

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

about 7.8 feet to match the National Geodetic Vertical Datum of 1929 (NGVD29) and 12.0 feet to match 

North American Vertical Datum of 1988 (NAVD88).

2
Summary and Conclusions 

This Reclamation report presents the results of the June 2007 survey of El Vado 

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

$ develop reservoir topography 

$ compute area-capacity relationships 

$ estimate storage depletion due to sediment deposition 

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 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 NGS control point called 

“DAM” that is located on a high point on the right bank near the dam alignment. 

NGS rated this point as third order horizontal with the vertical rounded to the 

nearest foot. Coordinates were computed by an OPUS solution and from this base 

additional control points were established and checked during the survey. 

The horizontal control for this study was in feet, New Mexico Central state plane 

coordinates, in the North American Datum of 1983 (NAD83). The vertical 

control, in feet, was tied to NAVD88 and the El Vado Dam project or 

construction (project) vertical datum. All elevations in this report are referenced 

to the project vertical datum that is 7.8 feet lower than NGVD29 and around 12.0 

feet lower than NAVD88. 

The June 2007 underwater survey was conducted near reservoir elevation 6,900, 

measured by the Reclamation gage at the dam. The bathymetric survey used 

sonic depth recording equipment interfaced with a RTK GPS for determining 

sounding locations within the reservoir. The system continuously recorded depth 

and horizontal coordinates as the survey boat navigated along grid lines covering 

El Vado Reservoir. The positioning system also provided information to allow 

the boat operator to maintain a course along these grid lines. The initial abovewater topography was determined by digitizing contour lines from the USGS 

quads of the reservoir area. 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. 

El Vado Reservoir topographic map is a combination of the adjusted digitized 

contours and the 2007 underwater survey data. A computer graphics program 

generated the 2007 reservoir surface areas at predetermined contour intervals 

from the collected reservoir area. The 2007 area and capacity tables were 

produced by a computer program that used measured contour surface areas and a 

3
curve-fitting technique to compute area and capacity at prescribed elevation 

increments (Bureau of Reclamation, 1985). 

Tables 1 and 2 contain summaries of the El Vado Reservoir and watershed 

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

reservoir has a total storage capacity of 213,090 acre-feet with a surface area of 

3,517 acres at maximum water surface elevation 6,908.6 and a storage capacity of 

190,820 acre-feet with a surface area of 3,232 acres at normal water surface 

elevation 6,902.0. Since closure in January 1935, the reservoir has an estimated 

volume change of 7,382 acre-feet below reservoir elevation 6,902.0. This volume 

change represents a 3.7 percent loss in total original capacity at this elevation. 

The unknown quality of the previous survey data introduces uncertainty into the 

volume change calculations as it is difficult to determine what portion is due to 

sediment deposition and what portion is due to differences in survey collection 

methods. 

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 

surveys. 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 NGS control point called “DAM”, located on a high point on 

the right bank near the dam. This point was rated as third order horizontal with 

the vertical rounded to the nearest foot. Accurate coordinates were obtained for 

the “DAM” point using OPUS and from this base additional points were 

established and checked during the June 2007 bathymetric survey, Figure 2. 

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 El Vado Dam project vertical datum. All elevations in this report are 

referenced to the project vertical datum that is 7.8 feet lower than NGVD29 and 

about 12.0 feet lower than NAVD88. Following is the OPUS solution for NGS 

point “DAM” that was used for setting control for the 2007 bathymetric survey. 

 NAD83/NAVD88 NAD27/NGVD29

North 2,035,143.10 North 2,035,077.12 

East 1,497,633.14 East 357,387.20 

Elevation 7,002.51 Elevation 6,998.41 

4
Figure 2 - Temporary Point set near reservoir, June 2007. 

The point data information was converted from NAD83/NAVD88 using the U.S. 

Army Corps of Engineers conversion program CORPSCON. For this location the 

difference between NAVD88 and NGVD29 was around 4.1 feet. During the 2007 

hydrographic survey, RTK GPS water surface measurements, in NAVD88, 

measured the average shift to match the water surface gage readings to be around 

11.9 to 12.0 feet, resulting in a 7.8 to 7.9 foot shift between the gage readings and 

NGVD29. This measured vertical difference agreed with several Reclamation 

references and control surveys that indicated the shift was 7.8 feet between 

NGVD29 and the project vertical datum (Reclamation, 2006). 

Reservoir Operations 

El Vado Reservoir is part of the Middle Rio Grande Project designed to provide 

storage for irrigation, municipal water, and flood control. The reservoir’s primary 

purpose is to provide storage for supplemental irrigation to the Middle Rio 

Grande Valley and San Juan-Chama Project water for irrigation, along with 

municipal and industrial uses. The 2007 survey determined that the reservoir has 

a total storage capacity of 213,090 acre-feet with a surface area of 3,517 acres at 

maximum water surface elevation 6,908.6. The computations above elevation 

6,902.0 were accomplished from the digitized above water contours from the 

5
USGS quads around the reservoir area. The 2007 survey measured a minimum 

lake bottom elevation of 6,766. The following values are from the June 2007 

capacity table: 

 $ 22,270 acre-feet of surcharge pool storage between elevation 6,992.0 and 6,908.6 

 $ 190,396 acre-feet of multiple use pool storage between elevation 6,775.0 and 6,902.0 

 $ 424 acre-feet of dead pool storage below elevation 6,775.0. 

The computed annual inflow and reservoir stage records for El Vado Reservoir 

are listed by water year in Table 1 for the available period starting in 1966. The 

inflow values were computed by the Upper Colorado Region for the 1984 analysis 

and are available through 1987. The values show the annual fluctuation with a 

computed average annual inflow of 287,731 acre-feet. The data shows the 

reservoir has not operated above elevation 6,902 since 1966. The USGS water 

resource records list the maximum recorded reservoir content at around 205,000 

acre-feet in 1948, which would be about reservoir elevation 6,906. Table 1 shows 

a few years where the reservoir was drawn down near dead pool elevation 6,775. 

Since the 1984 survey the reservoir was drawn down to elevation 6,796.8 during 

the years 2002 and 2003. 

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. 

6
Figure 3 - Survey Vessel with Mounted Instrumentation on El Vado Reservoir, New Mexico. 

The El Vado Reservoir bathymetric survey was conducted from June 10 through 

June 16 of 2007 between water surface elevation 6,900.0 and 6,900.2 (project 

datum). The bathymetric survey was conducted using sonic depth recording 

equipment, interfaced with a RTK GPS, capable of determining sounding 

locations within the reservoir for the single beam collection. The survey system 

software continuously recorded reservoir depths and horizontal coordinates as the 

survey boat moved along closely-spaced grid lines covering the reservoir area. 

Most transects (grid lines) were run somewhat parallel to the upstreamdownstream 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. Data was collected along 

the shore by the survey vessel for the majority of the reservoir. During each run, 

the depth and position data were recorded on the laptop computer hard drive for 

subsequent processing. 

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 

7
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. 

Figure 4 - Multibeam Collection System. 

The multibeam system is composed of several instruments all in constant 

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

include the RTK GPS for positioning; a motion reference unit to measure the 

heave, pitch, and roll of the survey vessel; a gyro to measure the yaw or vessel 

attitude; and a velocity meter to measure the speed of sound 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. 

8
Due to weather and time issues, the multibeam system was utilized on El Vado 

Reservoir during the last two days of collection only, June 15 and 16 of 2007. 

The multibeam surveyed areas mainly included the main channel from the dam 

upstream to the Rio Chama River, a few of the side coves, and the area around the 

mouth of the Boulder Creek. The collection concentrated on the deeper portions 

of the reservoir to provide more detailed mapping than what was provided by the 

single beam coverage. Figure 5 shows the reservoir areas covered by the 

multibeam and single beam collection systems along with the location of the 

sediment range lines. 

The multibeam soundings, combined with the single beam soundings created a 

detailed data set of around 1,870,000 x,y,z points representing the reservoir 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 

overlapping in the deeper areas 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 rest 

of the reservoir to be surveyed by this method. Even though the multibeam data 

provided more detail of the reservoir bottom versus the single beam data set, a 

comparison of the surface area and volume computation results in common areas 

covered found the differences were not significant between the two methods. 

The underwater collected data was processed using the hydrographic system 

software that was also 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 El Vado Reservoir map development. 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). 

9
10
11

Figure 5 - El Vado Reservoir 2007 survey data points. 
12
13

Reservoir Area and Capacity 

Topography Development 

The topography of El Vado Reservoir was developed from 2007 bathymetric 

survey data and digitized contours from the USGS quad maps. The USGS quad 

contours, labeled elevation 6,910 and 6,920 were developed from aerial 

photography dated 1976. These contours represent elevations in NGVD29 and 

were converted to project vertical elevations 6,902 and 6,912 respectfully. The 

6,902 clip was slightly adjusted to ensure all 2007 underwater data was enclosed 

within the polygon. The modified elevation 6,902 contour was assigned a more 

precise elevation of 6,902.0 and was used as a hard boundary for the 2007 

developed contours, allowing contour mapping within the reservoir area outlined 

by this hardclip contour only. The hardclip was used during the triangular 

irregular network (TIN) development to prevent interpolation outside the enclosed 

polygon. The 6,902.0 contour was selected for the hardclip boundary since it was 

the closest data available to represent the measured water surface during the 2007 

underwater survey, elevation 6,900. 

Contours for the reservoir below elevation 6,902.0 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 

was used to interpolate contours from the El Vado Reservoir TIN. The surface 

areas of the enclosed contour polygons at one-foot increments were computed 

from for elevations 6,766.0 through 6,902.0. The surface area of the modified 

digitized 6,902.0 contour was less than one percent different from the surface area 

used for the 1984 study at the same elevation. Since the digitized surface area 

was so close to the 1984 survey result, and because there were no visual signs of 

change of this contour due to a sediment delta, it was decided to assume no 

change and use the 1984 surface area for this study. For computing the capacity 

above elevation 6,902, the measured surface area of the digitized USGS quad 

contour elevation 6,912 was used. The reservoir contour topography at 2-foot 

intervals from elevation 6,902.0 and below is presented in Figures 6 and 7. The 

ARCGIS software developed contours directly from the TIN using all the 
14

enclosed data points, resulting in a jagged representation of the contours. For 

presentation purposes the contour lines were smoothed using the smooth line 

option within ARCMAP. The smoothing process did not affect the reported 

surface areas since they were computated directly from the TIN using all the data 

points. 

Lateral Distribution 

Profiles of the 21 previously surveyed sedimentation range lines were developed 

during this study to provide a visual representation of the lateral sediment 

deposition change since the 1944 and 1984 surveys (Figures 9 through 29). The 

location of the range lines along with the data points collected during this study 

are presented on Figure 5 and on Figure 8 of the 1984 contour and range line 

maps. The range line locations were visually determined from the reservoir 

sedimentation range system maps developed for the 1984 study, drawing number 

163-518-4988. The digital range line plots were recreated by digitizing the 1944 

and 1984 sedimentation range plots presented in an April, 1987 memorandum 

forwarding the results of the 1984 survey to the Albuquerque Area Office 

(Reclamation, 1987). It appears the 1944 and 1984 cross section profiles are 

plotted from left to right bank looking downstream. 

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 the projected range lines. These stored points 

within 10 feet of the projected range line alignment. The point density of each 

profile depended on available data near the cross section. 

The Range Line plots provided valuable insight into changes in lateral sediment 

distribution over time. Range Lines 1, 2, 3, 4, 6, 7, 8, 10, 11, 14, 15, 16, 20, and 

22 (located on the Rio Chama reach of the reservoir) indicated that little to no 

change has occurred since 1984 due to sediment deposition. Range lines 6, 7, and 

8 also extended into the Boulder Creek reach of the reservoir. The survey of 

range line 20 and 22, located in the upper reach of the Chama area, showed an 

increase in area due to erosion of the previous measured sediment deposits. The 

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

periods of low reservoir content since 1984 and clear water releases from Lake 

Heron. 

Range lines 5, 6, 7, 8, 9, 12, 13, 17, 18, and 19 are located on Boulder Creek arm 

of the reservoir and show a similar pattern to the Rio Chama arm, little to no 

change. Range lines 12 and 18 measured a slight change since the 1984 survey, 

but not a significant change considering the time period between surveys. Overall 

the sediment range line plots illustrate why the 2007 computed surface areas and 

resulting capacity are similar to the 1984 study results. The 2007 study actually 

measured a slight increase in capacity, likely due to the greater detail compared to 

the 1984 study. The 1984 study utilized a range line survey and a mathematical 

method to compute changes in the surface areas between the range lines. 
15

Figure 6 - El Vado Reservoir Contour Map, 1 of 2. 
16
17

Figure 7 - El Vado Reservoir Contour Map, 2 of 2. 
18
19

Figure 8 - El Vado Reservoir Sedimentation Ranges Developed in 1984. 
20
El Vado Reservoir - Range Line 1

6,725

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

6,950

6,975

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 9 - Range Line 1, Rio Chama. 

El Vado Reservoir - Range Line 2

6,725

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

6,950

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,250

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 10 - Range Line 2, Rio Chama. 

21
El Vado Reservoir - Range Line 3

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,250 3,500 3,750 4,000

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 11 - Range Line 3, Rio Chama. 

El Vado Reservoir - Range Line 4

6,830

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

0 100 200 300 400 500 600 700 800 900

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 12 - Range Line 4, Rio Chama. 

22
El Vado Reservoir - Range Line 6

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

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

1944

1984

2007

Figure 13 - Range Line 6, Rio Chama and Boulder Creek. 

El Vado Reservoir - Range Line 7

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

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

1944

1984

2007

Figure 14 - Range Line 7, Rio Chama and Boulder Creek. 

23
El Vado Reservoir - Range Line 8

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 15 - Range Line 8, Rio Chama and Boulder Creek. 

El Vado Reservoir - Range Line 10

6,750

6,775

6,800

6,825

6,850

6,875

6,900

6,925

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 16 - Range Line 10, Rio Chama. 

24
El Vado Reservoir - Range Line 11

6,775

6,800

6,825

6,850

6,875

6,900

6,925

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 17 - Range Line 11, Rio Chama. 

El Vado Reservoir - Range Line 14

6,780

6,800

6,820

6,840

6,860

6,880

6,900

6,920

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,250

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 18 - Range Line 14, Rio Chama. 

25
El Vado Reservoir - Range Line 15

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 19 - Range Line 15, Rio Chama. 

El Vado Reservoir - Range Line 16

6,800

6,820

6,840

6,860

6,880

6,900

6,920

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,250

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 20 - Range Line 16, Rio Chama. 

26
El Vado Reservoir - Range Line 20

6,820

6,830

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 21 - Range line 20, Rio Chama. 

El Vado Reservoir - Range Line 22

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 22 - Range line 22, Rio Chama. 

27
El Vado Reservoir - Range Line 5

6,820

6,830

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 23 - Range Line 5, Boulder Creek. 

El Vado Reservoir - Range Line 9

6,820

6,830

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 24 - Range Line 9, Boulder Creek. 

28
El Vado Reservoir - Range Line 12

6,830

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 25 - Range Line 12, Boulder Creek. 

El Vado Reservoir - Range Line 13

6,840

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 26 - Range Line 13, Boulder Creek. 

29
El Vado Reservoir - Range Line 17

6,850

6,860

6,870

6,880

6,890

6,900

6,910

6,920

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

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 27 - Range line 17, Boulder Creek. 

El Vado Reservoir - Range Line 18

6,860

6,870

6,880

6,890

6,900

6,910

6,920

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,250 3,500 3,750

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 28 - Range line 18, Boulder Creek. 

30
El Vado Reservoir - Range Line 19

6,870

6,880

6,890

6,900

6,910

6,920

0 250 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,250

Distance - Feet

Elevation - Feet

1944

1984

2007

Figure 29 - Range line 19, Boulder Creek. 

31
32
Development of the 2007 El Vado Reservoir Surface 

Areas 

The 2007 surface areas for El Vado Reservoir were computed at 1-foot 

increments directly from the reservoir TIN from elevation 6,766.0 through 

6,902.0. The TIN was developed from collected and interpolated data sets within 

the hardclip polygon created from the previously described digitized 6,902.0 

contour. Surface area calculations were performed using ARCGIS commands 

that compute areas at user-specified elevations directly from the TIN. For the 

purpose of this study, the measured survey areas at 2- and 5-foot increments from 

elevation 6,766.0 through 6,900.0 were used in computing the new area and 

capacity tables. The 1984 surface area at elevation 6,902.0 was used since it 

appeared no significant change had occurred at this elevation since 1984. 

Table 1 provides a summary of surveys that have been conducted on El Vado 

Reservoir including 1935 (original), 1944, 1967, 1984, and 2007 results. The area 

and capacity curves for all of these surveys are plotted on Figure 30. The table 

and plots show interesting results from all of these surveys. The 1967 results 

actually showed a slight increase in surface area at elevation 6,902.0 while the 

other survey results showed a similar surface area at the same elevation. There 

was limited literature available on the past surveys, but several located notes 

mentioned uncertainty in the results from previous surveys. The original surface 

areas were measured from developed contours that were later adjusted during the 

1944 study. The 1984 El Vado Reservoir surface areas were computed using the 

range width ratio method that is explained in more detail in Chapter 9 of the 

Sedimentation Groups Erosion and Sedimentation Manual (Ferrari and Collins, 

2006). 

As part of the 2007 analysis, the USGS quad contours developed from 1970 aerial 

photographs of the reservoir area were digitized. The elevation 6,902 digitized 

contour was slightly adjusted to enclose all 2007 survey data, resulting in a 

computed surface area less than one percent different from the 1944 and 1984 

results. For this study the 1984 surface area at elevation 6,902.0 was used. It was 

assumed the 1984 study measured the reservoir surface areas between ranges as 

presented in drawing number 163-518-4988, Figure 8. For computing reservoir 

data above elevation 6,902.0, the measured surface area of the digitized USGS 

quad contour 6,920 (elevation 6,912 in project datum) was used. This resulted in 

a 2007 computed volume of 22,270 acre-feet within the reservoir surcharge zone, 

slightly less than the previous published volume of 23,078 acre-feet within this 

same zone (Reclamation, 2006). 

33
34
35

1. 2. 3. STATE New Mexico

4. 5. Tierra Amarilla 6. COUNTY

7. ° 35 ' # " ° 44 ' 00 " 8. 9. SPILLWAY CREST EL 1

10. 11. 12. GROSS STORAGE 15

CAPACITY, AC-FT

a. 2

b.

c.

d. 16

e.

f.

g.

17. LENGTH OF RESERVOIR 3

18. TOTAL DRAINAGE AREA 4 22.

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

20. LENGTH MILES AVG. WIDTH MILES 24. MEAN ANNUAL INFLOW 5

21. 25. °F °F7

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

2

26. DATE OF 35. 36

26. DATE OF 37. 38.

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

-YR 41. STORAGE LOSS, PCT. 42 SEDIMENT 

(#/FT3

) b. TOTAL b. TOTAL TO INFLOW, PPM

TO DATE DATE a. PER. b. TOT.

43.

6879.0

ACRE-FEET

BEGAN

8 to 30

221,280

01/1935

3,232

ANNUAL TEMP, MEAN °F

CAPACITY

56

186,252

3,230

196,500

198,202

32.

ACRE - FEET

0.4

-20

DATE NORMAL

Rio Arriba

ORIGINAL DATE

STORAGE

6914.5

14.

BEGAN

 

23

23

3,380

1

DATA SHEET NO.

RESERVOIR SEDIMENT

DATA SUMMARY

El Vado Reservoir NAME OF RESERVOIR

SURVEY

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

 

Y

D

287,731

PERIOD WATER INFLOW, ACRE-FEET

MEAN ANN.

WATER INFLOW TO DATE, AF

SURVEY

PERIOD CAPACITY LOSS, ACRE-FEET

TOTAL

SURVEY

6/1984

SURVEY

8 to 30

V

R

1944 

S AREA, AC.

1/1935

U

PER.

YRS

SURVEY PER. SURVEY

6

a.

a. TOTAL

6/2007

MAX. ANN.

544,130

b.

a. b.

0.66

0.65

0.68

0.69

33.

OPERATIONS

to 108

4,619

49.5

197,533

MAX. ELEVATION

SQUARE MILES

MIN. ELEVATION

INCHES

INCHES

287,731

TOP OF POOL

FLOOD CONTROL

SURCHARGE 6,908.6

R

E

O

E

S

R

12,000+

I INACTIVE 6,775.0

DEAD

S

R

B

17.4

MEAN ANNUAL PRECIPITATION

N

I

50

A 602

AVG. WIDTH OF RESERVOIR

3,320

JOINT USE

CONSERVATION

349

V

TOP OF DAM ELEVATION

193,583

ORIGINAL 13.

23,078

SURFACE AREA, AC-FT

STREAM Rio Chama

1A TWP. 28N

D OWNER Middle Rio Grande Conservation District

A

LONG

SEC

M LAT 36 106

RANGE 2E

MILES

6,902.0 198,202

4,619

ACRE-FEET

RATIO AF/AF

0.69

RANGE

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

-YR.

0.401

190,820

c. TOTAL a. 

3,232

6/1984 9 6/2007

11,950 7 241

 

6/1984

DEPTH DESIGNATION RANGE IN FEET BELOW AND ABOVE CREST ELEVATION

90-100

6/2007

26.

DATE

OF

DATE

54-39 CR+11 11+23

 

C-9

0.051

39-24 24.9

 3.72

40-50 50-60 80-90

 

0-10 10-20 20-30 30-40 60-70

STORAGE

ALLOCATION

ELEVATION

873

11.7

SQUARE MILES

Multiple Use

MILES

6/1984

6/2007

PRECIPITATION

72.5

ANNUAL

34. PERIOD

 

 Range (D)

Contour (D)

Range (D)

TYPE OF 

49.5

23.0

11/1967

Contour (D)

NO. OF

RANGES OR 

INTERVALS

6741.5

YRS

SURFACE

1944

11/1967

E

A

A

T

114-99 99-84 84-69

287,731

TOTAL SEDIMENT DEPOSITS TO DATE, AF

13,954,950

 /MI.2

-YR.

MEAN ANN. b. TOTAL

 

13,954,950

8 0.401

0.169

241

102

 0.122

7 11,950 8

AVG. ANNUAL

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN DEPTH DESIGNATION

129-114 69-54

 

NEAREST P.O.

2-ft

a.

7,382

a. PERIOD

115- 120-

 

70-80 105- 110-

PERCENT OF TOTAL SEDIMENT LOCATED WITHIN REACH DESIGNATION

AVG. ANN. c.

6.03

Table 1 - Reservoir Sediment Data Summary (page 1 of 2). 
36

 

1

2

3

4

5

6

7

8

9

10

11

6,880.0 2,493.1 123,017 6,885.0 2,655 135,887 6,890.0 2,853 149,658

6,870.0 2,111 100,026 6,875.0 2,296 111,044

6,845.0 1,517

31,598 6,830.0 1,200 37,314

6,840.0

6,825.0

1982 6,878.5 6,866.2 475,450 1983 6,888.1 6,876.3 461,100

6,873.0 6,809.4

2002 6,875.4 6,796.8 2003 6,892.8 6,796.8

2000

107,770

6,900.2 6,854.8

6,900.0 6,835.2

574,650

6,877.2 6,855.8

1998 6,900.0 6,859.3

6,800.0 617

1976 6,898.4 6,852.2 272,130 1977 6,877.2 6,810.0

6,795.0 548 6,897

6,785.0 386

6,790.0 477.3 4,333

165 1,006

3,232

6,775.0 92 424 6,780.0

164,358 6,900.0 3,170 179,849 6,902.0

6,810.0 788 6,815.0 880

25,619 6,825.0 1,073 30,725

6,814.3 6,775.2 165,180

6,830.0 1,169 36,328

CAPACITY

6,812.0 6,775.1 199,430 1971

1968 6,812.0 6,775.0 237,230 1969 6,812.0 6,775.0 321,070

1970

45. RANGE IN RESERVOIR OPERATION

715

84.1

2004

 

6,855.0

6,795.0 557 7,310

114,202

 

6,875.0 2,369

2,927

6,870.0 2,166

6,810.0

1,739

ELEVATION AREA CAPACITY

21,718

6,860.0 1,856 82,830

6,815.0 903

57,569

2,275

6,800.0 631 10,273

20,992

186,252

2,422

9,810

6,780.0 144 1,051 6,785.0 346

73,849

102,868

809 17,437

1,399 50,276

1,082

16,828

2007

6,765.0 0 0

 CAPACITY

ELEVATION AREA

2006 6,883.0 6,842.7

46. ELEVATION - AREA - CAPACITY - DATA FOR

6,900.2 6,842.6

6,824.4 6,820.0 2005 6,892.8

1999

6,900.0 6,826.1 2001

1996 6,893.3 6,837.2

 1995 6,897.3 6,853.9

1997

1992 6,900.2 6,868.0 1993 6,900.2 6,848.4

 1991 6,898.3 6,870.1

1989 6,898.8 6,873.4

568,580

1988 6,900.0 6,877.7

1987 6,897.4 6,879.7 377,664

172,810

1984 6,885.6 6,877.6 461,500 1985 6,896.2 6,877.8

1980 6,864.4 544,130 1981

174,506 1975 6,896.2 6,854.8 424,880

1978 6,813.9 300,060 1979 6,896.2 6,839.0 529,330

1974 6,845.8

1972 6,775.3 162,440 1973 6,896.3 6,812.4 469,210

6,835.0 1,259.9 42,399 6,840.0 1,373 48,982 6,845.0 1,473 56,098

13,106

1986 6,899.9 6,897.8

1990

SURVEY 6,770.0 56

4,667

13,633

65,436

92,464

43,552

26,448

6,819.1 1967 6,814.7 6,775.2

MIN. ELEV. INFLOW, AF

6,758.6 230,790 172,900

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

For weighted contributing area of 736.6 sq. miles.

2007 surface area and capacity values above elevation 6,902.0 computed using USGS quad contour results.

Data for calendar year with elevation being end-of month occurrence. Inflows are cumulative sums of computed inflows using a 

 reservoir budget method.

2007 detailed contour survey computed a greater volume than 1984 range line survey. Range line comparisons (1984 and 2007) 

 show minimum change between surveys.

10

1966

6,775.0

6,790.0

6,805.0

6,850.0

YEAR MAX. ELEV.

49. Bureau of Reclamation June 2008

AGENCY MAKING SURVEY

AGENCY SUPPLYING DATA DATE

48. Bureau of Reclamation

REMARKS AND REFERENCES

Maximum annual from 1966-84.

Loss below elevation 6,902.0. Uncertainty of validity of original and following values. Some studies considered 1944 most accurate.

Top of movable spillway gate, el. 6,902.0. All elvations tied to project datum. Add 7.8 ft to match NGVD29 and 12.0 ft to match NAVD88.

Original capacity values adjusted using 1944 survey results. Questions on survey method and related accuracy of the different surveys.

 1984 study projected 23,078 AF of capacity between elevation 6902.0 (Top Active Conservation Pool) to elevation 6908.6. 

7.1 miles of Rio Chama arm + 4.6 miles of Boulder Creek arm = 11.7 miles.

Removes Heron Reservoir drainage basin of 188 sq. miles and 83 sq. miles of non-contributing area. Heron Reservoir clousre in Oct. 1970.

Beginning in 1972, inflow includes water released from Heron Reservoir which also stores transbasin diversions.

47.

2,000

1,630

3,051

6,835.0

6,865.0

6,895.0

1,296

6,820.0 985

6,895.0

2007

6,805.0

6,850.0

6,820.0

497

701.4

3,026.6

1,578.4

969.9

129

6,812.3

ELEVATION AREA CAPACITY

6,893.0

6,858.8

6,900.0 6,862.8

6,877.2

 

63,727

1994 6,900.7 6,867.3

6,878.3

1984

480

 

SURVEY 6,766.0 0 6,770.0 38 41 11 0

6,855.0 1,668 6,860.0 1,797 80,506

6,865.0 1,949.9 89,873

71,843

6,880.0

6,905.0

2,563

3,361

2,744

6,908.6 3,517

3,136

126,565 6,890.0 154,009

200,710

139,820

213,090

6,885.0

168,983 6,900.0 184,452 6,902.0 3,232 190,820

Table 1 - Reservoir Sediment Data Summary (page 2 of 2). 
37

Area-Capacity Curves for El Vado Reservoir

6,750.06,770.06,790.06,810.06,830.06,850.06,870.06,890.06,910.0

0 21000 42000 63000 84000 105000 126000 147000 168000 189

Capacity (acre-feet)

Elevation (feet)

3,500 3,150 2,800 2,450 2,100 1,750 1,400 1,050 700 3

Area (acres)

2007198419671944

Capacity Area

Figure 30 - El Vado Reservoir Area and Capacity Plots 
38
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 0.000001 for El Vado 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 El Vado 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, 2007). A 

description of the computations and coefficients output from the ACAP program 

is included with these tables. The original (1935), 1944, 1967, 1984, and 2007 

area-capacity relationships are listed on Table 2. The curves for all surveys 

except for the original, due to limited data, are plotted on Figure 30. As of June 

2007, at conservation use elevation 6,902.0, the surface area was 3,232 acres with 

a total capacity of 190,820 acre-feet. 

39
40
41

1 2 3 4 5 6 7 8910 11 12 

1967 1984 

1935 Sediment 1967 Sediment 1984 

 Original 1944 1944 1967 1967 Volume Percent 1984 1984 Volume Percent 

Elevation Capacity Area Capacity Area Capacity Since 1944 Computed Area Capacity Since 1944 Computed 

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

6,908.6 

6,905.0 3,480 206,780 

6,902.0 198,202 3,230 197,533 3,380 196,500 1,033 100.0 3,232 186,252 11,281 100

6,900.0 3,180 191,154 3,310 189,810 1,344 130.1 3,170 179,849 11,305 100

6,895.0 3,010 175,719 3,140 173,690 2,029 196.4 3,027 164,358 11,361 100

6,890.0 161,750 2,850 161,019 2,950 158,470 2,549 246.8 2,853 149,658 11,361 100

6,885.0 2,660 147,155 2,760 144,210 2,945 285.1 2,655 135,887 11,268 99

6,880.0 135,053 2,490 134,286 2,580 130,850 3,436 332.6 2,493 123,017 11,269 99

6,875.0 2,290 122,285 2,390 118,430 3,855 373.2 2,296 111,044 11,241 99

6,870.0 112,194 2,110 111,253 2,190 107,000 4,253 411.7 2,111 100,026 11,227 99

6,865.0 1,960 101,044 2,020 96,490 4,554 440.9 1,950 89,873 11,171 99

6,860.0 92,808 1,810 91,649 1,870 86,770 4,879 472.3 1,797 80,506 11,143 986,855.0 1,700 82,825 1,760 77,690 5,135 497.1 1,668 71,843 10,982 97

6,850.0 75,979 1,600 74,618 1,650 69,160 5,458 528.4 1,578 63,727 10,891 966,845.0 1,490 66,886 1,540 61,180 5,706 552.4 1,473 56,098 10,788 956,840.0 61,183 1,390 59,680 1,430 53,770 5,910 572.1 1,373 48,982 10,698 946,835.0 1,320 52,912 1,330 46,880 6,032 583.9 1,260 42,399 10,513 936,830.0 46,183 1,230 46,603 1,230 40,480 6,123 592.7 1,169 36,328 10,275 916,825.0 1,130 40,729 1,140 34,540 6,189 599.1 1,073 30,725 10,004 886,820.0 34,886 1,020 35,358 1,030 29,110 6,248 604.8 970 25,619 9,739 866,815.0 930 30,455 940 24,180 6,275 607.5 880 20,995 9,460 83

6,810.0 25,788 850 26,005 840 19,730 6,275 607.5 788 16,828 9,177 81

6,805.0 770 21,904 740 15,770 6,134 593.8 701 13,106 8,798 78

6,800.0 17,987 710 18,191 650 12,290 5,901 571.2 617 9,810 8,381 746,795.0 630 14,805 580 9,240 5,565 538.7 548 6,897 7,908 70

6,790.0 11,793 570 11,765 520 6,510 5,255 508.7 477 4,333 7,432 656,785.0 510 9,015 440 4,100 4,915 475.8 346 2,275 6,740 59

6,780.0 6,924 470 6,577 320 2,190 4,387 424.7 144 1,051 5,526 496,775.0 400 4,472 140 1,060 3,412 330.3 84 480 3,992 35

6,770.0 3,182 300 2,765 100 490 2,275 220.2 56 129 2,636 23

6,765.0 200 1,502 50 130 1,372 132.8 0 0 1,502 13

6,760.0 855 120 691 0 0 691 66.9 0 0 691 6

6,755.0 70 210 0 0 210 20.3 0 0 210 1

6,750.0 23 20 23 0 0 23 2.2 0 0 23 0

6,740.0 0 0 0 0 0 0 0.0 0 0 0 0

1 Reservoir water surface elevation tied to project or construction datum, add 7.8 feet to match NGVD29 and 12.0 feet to match NAVD82 Original capacity readjusted based on corrections of original traverse in May 1944.3 1944 reservoir surface area, measured by contour method. 1944 survey data used to adjust original 1935 upper contours, but accura4 1944 reported reservoir capacity.5 1967 reservoir surface area.6 1967 reported reservoir capacity.7 1967 computed sediment volume, column (4) - column (6), Since 1944. Due to limited information on original data, 1944 considered 8 1967 measured sediment in percentage of total sediment (1,033 AF at elevation 6902.0). Maximum measured deposition (6,275 AF) at 9 1984 reservoir surface area.

10 1984 reported reservoir capacity.11 1984 computed sediment volume, column (4) - column (10), Since 1944. Due to limited information on original data, 1944 considered 12 1984 measured sediment in percentage of total sediment (11,281 AF at elevation 6,902.0).13 2007 measured reservoir surface area. 2007 surface areas at elevation 6,902.0 and 6,912.2 developed from USGS quad contours.14 2007 reservoir capacity computed using ACAP.15 2007 measured sediment volume, column (2) - column (14), Since 1935 (original survey).

15a 2007 measured sediment volume, column (4) - column (14), Since 1944. Due to limited information on original data, 1944 considered 

16 2007 measured sediment in percentage of total sediment (6,713 AF at elevation 6,902.0). Maximum measured deposition (9,404 AF) a17 Depth of reservoir expressed in percentage of total depth, 162.0 feet, from water surface 6,902.0.

Table 2 - Summary of 2007 Survey Results. 
42
2007 Reservoir Analyses 

Results of the 2007 El Vado Reservoir area and capacity computations are listed 

in Table 1 and columns 13 and 14 of Table 2. Column 2 in Table 2 lists the 

original capacity values that were adjusted from the 1944 resurvey results. There 

was limited information on the original reservoir survey, but it was assumed it 

consisted of 10-foot contour intervals developed from a plane table survey. 

Columns 3 and 4 list the 1944 survey area and capacity values. The 1944 survey 

was conducted to correct the original survey and was considered the base for 

comparisons with the 1967, 1984, and 2007 resurveys showing the sediment 

deposition pattern. Column 15a lists the capacity differences between the 1944 

and 2007 survey results that are due to sediment deposition and methods of 

collection. Figure 30 is a plot of the El Vado Reservoir surface area and capacity 

values for the 1944, 1967, 1984, and 2007 surveys, illustrating the differences and 

reservoir area and capacity patterns. 

Table 1 shows the total capacity at elevation 6,902.0 for all known surveys along 

with the computed differences. The total reservoir capacity in 2007 is 7,382 acrefeet less than the original (1935) volume at reservoir elevation 6,902.0. It must be 

noted that the 2007 area and capacity tables were generated assuming no surface 

area change since the 1984 survey at elevation 6,902.0. Assuming no change at 

elevation 6,902.0 is probably not entirely accurate, but any loss due to sediment 

deposition above this elevation is not significant since the range line comparison 

plots show little to no change of the upper range lines. For the 2007 study, the 

USGS quad contour 6,912 (labeled 6,920 on the USGS quad) was digitized to 

compute the surface area and was used to calculate the area and capacity of the 

reservoir from elevation 6,902.0 to 6,912.0. This computation method resulted in 

a smaller surcharge capacity than previous publications, but no information on 

how the previous capacity was computed could be located. On the Chama arm, 

the comparison plots measured scour of the previously deposited sediments in the 

upper reservoir that occurred during low reservoir drawdown and clean water 

releases from Heron Reservoir. Questions as to the accuracy of these USGS 

digitized surface areas can only be answered with a detailed aerial survey of the 

reservoir area. 

During the planning phase for El Vado Reservoir, the original estimated 100 year 

sediment accumulation for was around 30,100 acre-feet at elevation 6,902.0, an 

average annual loss of 301 acre-feet. Table 1 list the sediment computation 

results of the 1984 and 2007 surveys that measured an average annual loss of 241 

and 102 acre-feet respectfully. The 2007 survey measured a larger reservoir 

capacity than the 1984 survey, resulting in a much lower computed average 

annual loss. It is assumed much of the computed differences are due to the 

accuracy differences between the survey methods along with sediment deposition. 

43
During the 2007 analysis limited files and notes on the details of the previous 

surveys were located. The May 1944 survey found errors in the original boundary 

survey and topography which necessitated the resurvey and adjustments of the 

original upper elevation topography. This adjustment resulted in corrected 

original capacities for comparison with the 1944 and subsequent surveys. In May 

and June of 1944 a plane table survey of the original reservoir boundary was 

conducted and 22 sediment ranges were established. Depth soundings were 

collected along the newly established sediment ranges and the original capacity 

based on the adjusted original contours was recomputed to be 198,202 acre-feet at 

elevation 6902.0. During the 1984 survey, the range lines were resurveyed and 

the differences used to compute the change of the original surface areas between 

the range lines, resulting in a computed 1984 reservoir capacity of 186,252 at 

elevation 6902.0. 

For the 2007 analysis, the hard copies of the range lines plots were digitized for 

comparisons between the three surveys. As seen from these plots, Figures 9 

through 29, there was little or no change between the 1984 and 2007 surveys for 

the majority of the range lines. A few of the range lines located in the upper 

Chama reach actually showed a gain in volume due to scouring of the previously 

deposited sediments. This is the reach were Heron Reservoir is located, which 

began trapping sediment for a large portion of this part of the basin after dam 

closure in 1970. For the Boulder Creek area only a few of the range lines 

indicated a small change in 2007 due to sediment deposition since 1984. If the 

1984 range line computation method could have been recreated using the 2007 

range line data, only a very slight loss of total reservoir capacity would likely 

have been computed between 1984 and 2007. The method utilized in the 1984 

computations only analyses the data at each range line and mathematically 

computes the surface area change between the range line locations. The 2007 

study used the contour method were survey data was collection throughout the 

reservoir area, providing detailed topography of the current reservoir geometry 

and current reservoir volume. 

The results of the 2007 El Vado Reservoir study provide up-to-date surface area 

and capacity information for the entire reservoir. Besides obtaining information 

along the previous established sediment range line alignments, the 2007 survey 

collected detailed data between these ranges throughout the reservoir area that 

was covered by the survey vessel. The resulting data set produced up-to-date 

reservoir information and represents the area and capacity of El Vado Reservoir 

as of June 2007. To compute the annual sediment inflow values more accurately, 

a future survey using the contour or similar method should be conducted. 

Overall, the range line comparison plots indicated that little sediment has 

deposited within the reservoir area since 1944 with an even smaller rate of 

deposition since the 1984 survey. A resurvey should be scheduled no sooner than 

the year 2027 unless a significant change in the sediment basin runoff is noted. 

An example of such change would be if a large basin fire occurred upstream of El 

Vado Reservoir. 

44
45

References 

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Headquarters, New York. 

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, 1987(c). El Vado Reservoir Area and Capacity Tables 

Memorandum, From Chief, Division of Planning Technical Service to Project 

Superintendent, New Mexico. 

Bureau of Reclamation, 2004. Hydrologic Hazard, El Vado Dam New Mexico,

Flood Hydrology and Meteorology Group, Denver, CO. 

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City, UT. 

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

(www.usbr.gov/dataweb). 

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(www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-1003/toc.htm). 

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

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www.usbr.gov/pmts/sediment