U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5128

Prepared in cooperation with the Strategic Environmental Research and Development Program

Storage Capacity of the Fena Valley Reservoir, Guam, 

Mariana Islands, 2014 
Main background photo

Cover. Main Cover Photo: Fena Valley Reservoir with view of intake-screen house and spillway. (Photograph by S.A. Wright, U.S. Geological 

Survey, February 24, 2014)

Upper right photo: Erosion on steep slopes in the Fena Valley Reservoir Watershed. (Photograph by M.D. Marineau, U.S. Geological Survey, 

February 22, 2014)

Middle right photo: Imong River upstream from the Fena Valley Reservoir. (Photograph by M.D. Marineau, U.S. Geological Survey , February 23, 

2014)

Lower right photo: U.S. Geological Survey hydrologist Mathieu Marineau surveying a section of the Imong River just upstream of the Fena 

Valley Reservoir. (Photograph by S.A. Wright, U.S. Geological Survey, February 23, 2014)

Upper right photo

Middle right photo

Lower right photo
Storage Capacity of the Fena Valley 

Reservoir, Guam, Mariana Islands, 2014

By Mathieu D. Marineau and Scott A. Wright

Prepared in cooperation with the Strategic Environmental Research and 

Development Program

Scientific Investigations Report 2015–5128

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Marineau, M.D., and Wright, S.A, 2015, Storage capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014: 

U.S. Geological Survey Scientific Investigations Report 2015–5128, 31 p., http://dx.doi.org/10.3133/sir20155128.

ISSN 2328-0328 (online)
iii

Acknowledgments

In particular, we are grateful to Mr. Danny Dungca (Department of Public Works, Naval 

Facilities Engineering Command Marianas) for general logistics, access to the U.S. Navy 

Base and reservoir, and providing copies of pre-construction documents. We would also like 

to acknowledge the military personnel at the U.S. Navy Explosive Ordnance Disposal Mobile 

Unit 5 for providing safety support, the personnel at the Water and Environmental Research 

Institute of the Western Pacific at the University of Guam Marine Laboratory for use of their 

watercraft, and Mr. Thomas Torres (Department of Land Management, Government of Guam) 

for providing survey benchmark information and for locating and marking benchmarks outside 

of the Naval Base Guam Ordnance Annex. This study was part of the Strategic Environmental 

Research and Development Program Project Number RC-2340.

Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

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

Purpose and Scope ..............................................................................................................................1

Description of Study Area ...................................................................................................................2

Previous Studies and Vertical Datum................................................................................................2

Data Collection...............................................................................................................................................4

Equipment...............................................................................................................................................4

Horizontal and Vertical Controls.........................................................................................................4

Coordinate systems.....................................................................................................................4

Temporary Benchmark................................................................................................................5

Bathymetric Survey..............................................................................................................................7

Temperature and Depth Profiles ........................................................................................................8

Data Analysis................................................................................................................................................11

Shallow-Water Survey, Spillway Elevation, and Shoreline Digitization ....................................11

Sound-Speed Corrections.................................................................................................................11

Bed-Elevation Calculation from Depth Soundings........................................................................11

Digital Elevation Model Development .............................................................................................13

Results ...........................................................................................................................................................14

Bathymetry...........................................................................................................................................14

Reservoir Storage Capacity ..............................................................................................................14

Summary........................................................................................................................................................21

References Cited..........................................................................................................................................22

Glossary.........................................................................................................................................................24

Appendix. National Geodetic Survey Datasheets..................................................................................25

Benchmark DH3061 ............................................................................................................................25

Benchmark DH3040 ............................................................................................................................27

Benchmark DK2736.............................................................................................................................28

Benchmark DH3034 ............................................................................................................................30
iv

Figures

1. Map showing the Fena Valley Reservoir and watershed, Guam..........................................3

2. Photographs showing temporary benchmark USGS-BM1, installed February 21, 

2014, near the boat launch area of the Fena Valley Reservoir, Guam..................................5

3. Photograph showing the spillway at the Fena Valley Reservoir, Guam ..............................6

4. Map showing the bathymetric boat-survey track, locations of topographic survey 

points at Imong River and Imong River Delta, and locations of conductivity, 

temperature, and depth (CTD) vertical profiles, Fena Valley Reservoir, Guam, 2014........9

5. Photograph showing sand deposition at Imong River Delta on the southern-most tip 

of the Fena Valley Reservoir, Guam.........................................................................................10

6. Photograph showing surveying of the Imong River between the Fena Valley 

Reservoir and the Imong River streamgage (station 16847000), Guam .............................10

7. Graphs showing examples of water temperature, salinity, density, and soundspeed profiles at three locations within the reservoir: A and B, cast from the 

downstream part of the reservoir near the dam (depth, 20.4 meters, 66.9 feet); 

C and D, cast from the middle part of the reservoir (depth, 12.5 meters, 41.0 feet); 

and E and F, cast from the upstream part of the reservoir (depth, 7.0 meters, 

23 feet)..........................................................................................................................................12

8. Graph showing maximum depths measured using the CastAway Conductivity, 

Temperature, and Depth profiler in relation to depths derived from the digital 

elevation model of the Fena Valley Reservoir, Guam, 2014..................................................13

9. Map showing bathymetry and 5-foot interval contours, based on the February 2014 

survey, Fena Valley Reservoir, Guam.......................................................................................15

10. Graphs showing A, stage-surface area curves for 1951 and 2014; and B, stagecapacity curves with live and dead storage capacity in 1951 and 2014 indicated, 

Fena Valley Reservoir, Guam ....................................................................................................20

Tables

1. Survey results for benchmarks used in the February 22, 2014, control survey from 

Talofofo Bay to Fena Valley Reservoir, Guam ..........................................................................6

2. Differences between published coordinates and 2014 surveyed coordinates, Fena 

Valley Reservoir, Guam................................................................................................................7

3. Rating table for surface area of the Fena Valley Reservoir, Guam, 2014 ..........................16

4. Rating table for storage capacity of the Fena Valley Reservoir, Guam, 2014 ...................18
v

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2)

Volume

acre-foot (acre-ft) 1,233 cubic meter (m3

)

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3

)

Flow rate

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3

/yr)

foot per second (ft/s) 0.3048 meter per second (m/s)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as 

°C = (°F – 32) / 1.8.

Datums

Vertical coordinate information is referenced to the 2004 Vertical Datum of Guam (GUVD04), 

which is referenced to the Mean Sea Level (MSL) calculated from the National Tidal Datum 

Epoch (NTDE) of 1983–2001 by Carlson and others (2009).

Previous datums used in historical surveys referenced elevation to the MSL tidal datum or to the 

mean lower low water (MLLW) tidal datum, although details on the precise elevation of the tidal 

datums used in the historical surveys is unknown.

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83) 

coordinates where the reference frame has been affixed to the stable Mariana tectonic plate 

[NAD 83(MA11)] (National Geodetic Survey, 2011).

Elevation, as used in this report, refers to distance above the vertical datum. 
vi

Abbreviations

ADCP Acoustic Doppler Current Profiler

CTD Conductivity, temperature, and depth

DEM Digital Elevation Model

GNSS Global Navigation Satellite System

GUVD04 Guam Vertical Datum of 2004

MLLW Mean Lower Low Water

MSL Mean Sea Level

NTDE National Tidal Datum Epoch

NAD83(MA11) North American Datum of 1983 (referenced to the Mariana tectonic plate)

PSS-78 Practical salinity scale 

RTK Real-time kinematic

SERDP Strategic Environmental Research and Development Program

USGS U.S. Geological Survey

UHF Ultra-high frequency
Storage Capacity of the Fena Valley Reservoir, Guam, 

Mariana Islands, 2014

By Mathieu D. Marineau and Scott A. Wright

Abstract

The Fena Valley Reservoir is in southern Guam and 

is the primary source of water for the U.S. Naval Base 

Guam and nearby village residents. Since the construction 

of the Fena Dam in 1951, sediment has accumulated in the 

reservoir and reduced its storage capacity. The reservoir was 

surveyed previously in 1973, 1979, and 1990 to estimate the 

loss in storage capacity. To determine the current storage 

capacity, the U.S. Geological Survey, in cooperation with 

the U.S. Department of Defense Strategic Environmental 

Research and Development Program, surveyed the bathymetry 

of the reservoir in February 2014.

The bathymetric survey was accomplished by making 

depth soundings using a boat-mounted, acoustic Doppler 

current profiler. Location during bathymetric data collection 

was determined using a single-base Global Navigation 

Satellite System-Real Time Kinematic survey. Vertical 

profiles of conductivity, temperature, and depth were collected 

periodically. The conductivity, temperature, and depth profiles 

were used to spatially and temporally adjust the sound-speed 

calculations used to determine depth from the soundings. 

Approximately 108 kilometers of transects with a total of 

about 380,000 depth soundings were surveyed. In addition, 

approximately 2,100 topographic survey points in shallow, 

wadable areas near the Imong River Delta were defined by 

using a Global Navigation Satellite System receiver attached 

to a fixed-length survey rod. Depth soundings and topographic 

survey points were compiled and interpolated to generate a 

digital-elevation model of the reservoir. Data extracted from 

the digital-elevation model were then tabulated to determine 

total reservoir capacity and create reservoir stage–surface area 

and stage–storage capacity tables.

Analyses of the bathymetric data indicate that the 

reservoir currently has 6,915 acre-feet of storage capacity. The 

engineering drawings of record show that the total reservoir 

capacity in 1951 was estimated to be 8,365 acre-feet. Thus, 

between 1951 and 2014, the total storage capacity decreased 

by 1,450 acre-feet (a loss of 17 percent of the original total 

storage capacity). The remaining live-storage capacity, 

or the volume of storage above the lowest-level reservoir 

outlet elevation, was calculated to be 5,511 acre-feet in 

2014, indicating a decrease of 372 acre-feet (or 6 percent) 

of the original 5,883 acre-feet of live-storage capacity. The 

remaining dead-storage capacity, or volume of storage below 

the lowest-level outlet, was 1,404 acre-feet in 2014, indicating 

a decrease of 1,078 acre-feet (or 43 percent) of the original 

2,482 acre-feet of dead-storage capacity.

Introduction

Fena Valley Reservoir, located in southern Guam, is 

owned and operated by the U.S. Navy. Construction of 

the Fena Dam began in 1950 and was completed in 1951. 

Previous surveys reveal a general decline in the Fena Valley 

Reservoir storage capacity. The U.S. Geological Survey 

(USGS), in cooperation with the U.S. Department of Defense 

Strategic Environmental Research and Development Program 

(SERDP), is investigating the potential effects of climate 

change on the water resources of Guam. In order to accurately 

predict surface-water availability by using a watershed model 

of southern Guam and a water-balance model of the reservoir, 

up-to-date reservoir capacity information is needed. The 

need for updated reservoir capacity data and the concern for 

reservoir sedimentation led to the initiation of this study.

Purpose and Scope

The USGS, in cooperation with the SERDP, conducted a 

bathymetric survey to determine the present storage capacity 

of the Fena Valley Reservoir and provide updated reservoir 

stage–surface-area and stage–capacity curves. 

The bathymetric survey was part of a more 

comprehensive study to investigate the effects of climate 

change on the water resources of Guam. Some of the other 

parts of the comprehensive study include downscaling climate 

projections, developing an updated watershed model for the 

island, and developing a quantitative assessment of how future 

changes in streamflow and sediment loads will affect the 

reservoir. 
2 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

In this report, the stage-storage and stage-capacity results 

from the 2014 reservoir capacity survey were compared with 

those from the 1949 pre-construction survey to provide 

some general context of the quantity of sediment that has 

been deposited in the reservoir since construction. A detailed 

interpretation of sedimentation rates and deposition patterns is 

not included in this report. 

Description of Study Area

The Fena Valley Reservoir is in southern Guam, 8.7 mi 

southwest of the capitol, Hagåtña, at approximately 13° 21ʹ N, 

144° 42ʹ E and lies within the Naval Base Guam Ordnance 

Annex (formerly the Naval Magazine), which is one of many 

facilities that are a part of Naval Base Guam, a consolidated 

U.S. Navy installation. At full capacity, the reservoir surface 

area extends approximately 0.30 square miles (mi2) and drains 

a watershed area of about 5.88 mi2. The reservoir was formed 

after the construction of the Fena Dam in 1951 and inundation 

of the Fena River Valley. The earthen dam is 85 feet (ft) tall 

and 1,050 ft in length. The reservoir currently serves as the 

primary source of water for Navy Base Guam and the civilian 

residents living in villages near the base in southern Guam. 

At the time of construction, the reservoir had an estimated 

total storage capacity of 8,365 acre-feet (acre-ft; based on 

digitization of 1949 stage-capacity curve from Frederic R. 

Harris, Inc., 1949). Live storage, sometimes called usable 

storage or water-supply storage, is water storage located above 

the lowest-level outlet, which is 37.00 ft below the spillway 

crest (Frederic R. Harris, Inc., 1949). The live-storage capacity 

at the time of construction was estimated to be 5,883 acre-ft. 

The 2,482 acre-ft of 1949 storage volume below the lowestlevel outlet is considered dead storage and is reserved for 

siltation.

Climate in Guam is characterized as warm and humid. 

Mean temperature is 84 degrees Fahrenheit (°F) and generally 

ranges from 79 to 89 °F (National Oceanic and Atmospheric 

Administration, 2014). Average annual precipitation is 

approximately 100 inches in southern Guam (Shade, 1983). 

Most of this precipitation falls between July and November; 

December through June is considered the dry season. 

Typhoons and tropical storms happen periodically and can 

deliver substantial amounts of precipitation in 24- to 48-hour 

periods.

The geology in the Fena Valley Watershed consists 

mostly of rocks in the Umatac Formation (primarily weathered 

rock of volcanic origin) and an older limestone formation 

in the higher elevations (Tracey and others, 1964). The 

surficial geology in the western-most part of the watershed 

appears to have high permeability (evidenced by the lack 

of any large surface-water features). Precipitation in this 

region seeps into the soil and underlying rock until it reaches 

the Umatac Formation, which has low permeability (Ward 

and others, 1965). The precipitation then resurfaces through 

springs that are found in the area of Fena Valley Reservoir. 

Although there are a few roads and facilities in the watershed, 

it remains largely undeveloped and covered with tall grasses 

and broad-leaf forests. The volcanic soils are highly erodible 

when denuded of vegetation (Kennedy Engineers Inc., 1973). 

Previous studies noted that wildfires (Shade, 1983; Nakama 

1992) and fires started by poachers (Kennedy Engineers Inc., 

1973) are common during the dry season and indicated that 

they are the primary underlying cause of erosion. During the 

survey, no direct evidence of wildfires was observed; however, 

several areas of recent soil erosion, in the form of translational 

earth slides, were noted on the steep slopes. The steep slopes 

are particularly vulnerable to this type of erosion (Schumm 

and Harvey, 2008), which could be triggered by saturated 

soil conditions following intense precipitation (Highland and 

Bobrowsky, 2008).

Three rivers drain into the reservoir from the south 

and west: the Imong, Almagosa, and Maulap Rivers (fig. 1). 

Streamflow discharge on all three of these rivers is monitored 

by USGS streamgages (station 16847000, Imong River near 

Agat; station 16848100, Almagosa River near Agat Guam; 

station 16848500, Maulup River near Agat Guam; fig. 1). 

The watershed draining to the reservoir does not extend far 

to the east, and there are no major tributary rivers on the east 

side. Water exiting the reservoir over the spillway enters the 

Maagas River and eventually drains east to the Pacific Ocean.

Previous Studies and Vertical Datum

The Fena Valley Reservoir was surveyed previously in 

1973, 1979, and 1990 (Kennedy Engineers Inc., 1973; Curtis, 

1984; Nakama, 1992, respectively) to determine the remaining 

storage capacity and estimate sedimentation rates. Previous 

surveys show a general but unsteady decline in the Fena 

Valley Reservoir storage capacity since completion of the dam 

in 1951.

The current official vertical datum is the Guam Vertical 

Datum 2004 (GUVD04); however, the dam construction 

predates this datum by several decades. Previous studies and 

the pre-construction engineering drawings of record used a 

variety of datums or did not indicate a datum. For example, 

the engineering drawings of record note that elevations 

were “corrected” to Mean Lower Low Water (MLLW) and 

designated MLLW as the elevation datum on one sheet; the 

vertical datum was not indicated on other sheets (Frederic 

R. Harris, Inc., 1949). Later studies either did not indicate 

a datum (Kennedy Engineers Inc., 1973) or used Mean Sea 

Level (MSL; Curtis, 1984; Nakama, 1992). In all cases, the 

same elevation of the spillway (111.35 ft) was reported but 

without referencing this elevation to a consistent datum. The 

original elevation measurement of the spillway crest was 

likely an error caused by using an unofficial MLLW datum, 

and that error has propagated through subsequent studies and 

local surveys.
Introduction 3

Sac15-0570_fig 01

Boat 

launch area

144°42' E 144°42'30" E 144°43' E

13°21'30"

13°21'

13°20'30"

0 0.1 0.2 0.3 0.4 MILE

0 0.1 0.2 0.3 0.4 KILOMETER

Fena watershed

boundary

GUAM

Hagåtña

Map location

Talofofo 

 Bay

Fena Dam

Spillway

Screen

 house

16848500

16848100

16847000

16849000

Benchmark RP21

Benchmark USGS-BM1

Naval Base Guam 

 Ordnance Annex

Base modified from U.S. Geological Survey and other

Federal and State digital data, various scales

Universal Transverse Mercator, zone 55N

North American Datum of 1983 (MA11)

Imagery courtesy of DigitalGlobe. ©2014.

10-meter Digital Elevation Map from Guam Coastal Atlas

 (http://www.guammarinelab.com/)

Fena Valley

Reservoir

Fena Valley

Reservoir

Maulap

Almagosa River

Imong River

River

Maagas

Maulap River aulap River

Almagosa RiverAlmagosa River

Imong River Imong River

River

Survey benchmark

Streamgage

Reservoir shoreline

Rivers

EXPLANATION

13°21'30"

144°40'

144°40'30"

144°41'30"

144°41'

13°20'30"

13°19'30"

13°21'

13°20'

13°19'

Figure 1. Fena Valley Reservoir and watershed, Guam.
4 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

During this study (2014), a control survey using the 

latest survey techniques was conducted to directly relate the 

elevation of the Fena Dam spillway crest to GUVD04 vertical 

datum (Carlson and others, 2009). The results of the spillway 

elevation differed from that reported in previous studies. 

Although there are several possible causes of survey error, 

the original survey also referenced an unofficial tidal datum. 

Tidal records from a specific 19-year period designated as a 

National Tidal Datum Epoch (NTDE) are required to compute 

tidal datums reliably (Gill and Schultz, 2001). Because the 

first known tidal station on Guam was not established until 

1948 (Department of Commerce, 1948), tidal records were not 

long enough at the time of reservoir construction to compute 

official tidal datums. Because there are no other known control 

surveys relating the spillway crest to GUVD04 or any other 

known benchmark, in this report only the results of the control 

survey conducted during this study are used. The precise 

elevation of the spillway, however, does not affect the capacity 

calculations of this study or previous studies since they all 

measure reservoir capacity relative to the spillway crest.

Data Collection

The equipment and methods used to collect the 

topographic and bathymetric data, which were used to 

calculate the reservoir storage capacity, are described in this 

section. All fieldwork was conducted during February 22–27, 

2014.

Equipment

The following is a list of equipment used during 

the bathymetric survey and establishment of a temporary 

benchmark.

• 14-ft McKee Craft fiberglass boat with 4-horsepower 

engine

• Sontek M9 HydroSurveyorTM acoustic Doppler current 

profiler (ADCP)

• Field laptop with Sontek HydroSurveyorTM software

• Trimble R7 Global Navigation Satellite System 

(GNSS) receiver, Ultra-High Frequency (UHF) radio, 

and Zephyr II antenna mounted to an adjustable-height 

tripod

• Trimble R10 GNSS receiver used as a rover mounted 

to the boat or used with a 2-meter fixed-length survey 

rod

• Trimble TSC3 hand-held controller, used to program 

the GNSS receivers and record data

• Sontek CastAwayTM conductivity, temperature, and 

depth (CTD) profiler

Horizontal and Vertical Controls

A temporary benchmark was established near the 

reservoir and used for horizontal and vertical control during 

this study. This section describes the coordinate systems used 

in this survey and the methods used to establish the temporary 

benchmark.

Coordinate systems

The vertical coordinate system used in this study is 

the Guam Vertical Datum of 2004 (GUVD04). GUVD04 is 

referenced to the MSL calculated from the NTDE of 1983–

2001 (Carlson and others, 2009). The horizontal geographic 

coordinate system used is the North American Datum of 

1983 adjusted by the National Geodetic Survey such that it is 

referenced to the Mariana tectonic plate; it is abbreviated as 

NAD83(MA11). NAD83(MA11) is used to define coordinates 

for Guam and the Northern Mariana Islands (National 

Geodetic Survey, 2011). The projected coordinate system 

used in figures in this report is NAD83(MA11) Universal 

Transverse Mercator zone 55 North.
Data Collection 5

Temporary Benchmark

The primary benchmark used for horizontal and vertical 

control at the Fena Dam is benchmark RP21 (fig. 1; Chui 

Yueng, U.S. Geological Survey, written commun., 2014; 

fig. 1). However, benchmark RP21 is not readily accessible 

from the boat launch area and is located below power lines, 

which can affect GNSS quality and distort measurements 

(Rydland and Densmore, 2012). In addition, surveymeasurement quality information on benchmark RP21 was 

not well documented. Therefore, a temporary benchmark 

(designated USGS-BM1) was installed near the boat launch 

area at the northwestern corner of the reservoir (fig. 1). 

Horizontal and vertical controls for the bathymetric survey 

were established by surveying from Guam Department 

of Land Management (Guam DLM) Benchmark DH3061 

(appendix 1; DH3061 is not shown in a figure), using a 

Level IV (Rydland and Densmore, 2012) single-base global 

navigation satellite system, real-time kinematics (GNSSRTK) survey, to temporary benchmark USGS-BM1 (fig. 1). 

Guam DLM Benchmark DH3061 was selected because of 

its proximity to the reservoir and because it was surveyed 

by Carlson and others (2009) during the establishment of 

GUVD04.

Temporary benchmark USGS-BM1 was installed 

February 21, 2014, and marked by a USGS brass plate (fig. 2). 

The asphalt surface of the boat launch parking lot was buried 

by about 6 inches of soil. To secure the brass plate, a 12-inch 

diameter hole was dug though the soil to the asphalt and 

backfilled with quick-setting concrete mix. The brass plate 

was installed in the concrete (fig. 2). Horizontal and vertical 

coordinates of temporary benchmark USGS-BM1 and other 

benchmarks were derived from averaging one or more survey 

measurements with occupation times typically between 10 and 

40 seconds.

The GNSS-RTK base station consisted of a Trimble 

R7 GNSS receiver with a dual frequency, Zephyr II antenna 

and UHF transmitting radio mounted on an adjustable height 

tripod. A laser tribrach was used to center the base station 

antenna above a benchmark. Each leg of the tripod was 

braced by sand bags to prevent movement during the survey. 

The rover consisted of a Trimble R10 Global GNSS receiver 

mounted to a 2-meter fixed-height survey rod. Data were 

logged on a Trimble TSC3 hand-held controller using Trimble 

Access Software (Trimble, 2013).

While the GNSS-RTK base station was set up on Guam 

DLM Benchmark DH3061 for the survey to temporary 

benchmark USGS-BM1, three nearby benchmarks (DH3034, 

DK2736, and DH3040; appendix 1) were surveyed as vertical 

and horizontal checks. Later, the GNSS-RTK base station 

was set over temporary benchmark USGS-BM1to perform 

elevation checks at additional benchmarks and to perform 

a single-base GNSS-RTK survey of the reservoir. Elevation 

checks were done for two additional benchmarks (GGN 2053 

and GGN 2054; table 1), which are outside of the Naval 

Base Guam Ordnance Annex near the entrance gate (Thomas 

Torres, Government of Guam, written commun., 2014). In 

addition, survey measurements were collected for benchmark 

RP21 (fig. 1) and the spillway crest (fig. 3). 

Horizontal and vertical coordinates for each benchmark 

and the spillway crest are listed in table 1. Differences 

between previously published coordinates and the coordinates 

of survey measurements made during this study are listed in 

table 2.

Sac15-0570_fig 02

Figure 2. Temporary benchmark USGS-BM1, installed February 21, 2014, near the boat launch area of the Fena Valley Reservoir, Guam. 

(Photographs by M.D. Marineau, February 22, 2014)
6 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Table 1. Survey results for benchmarks used in the February 22, 2014, control survey from Talofofo Bay to Fena Valley Reservoir, Guam.

Benchmark/

survey point Latitude1 Longitude1 Ellipsoid height2(feet)

Orthometric height3

(feet)

DH3040 13° 21ʹ 00.33332ʺ N 144° 46ʹ 09.66726ʺ E 216.47 40.84

DK2736 13° 20ʹ 32.74334ʺ N 144° 45ʹ 44.64012ʺ E 189.55 14.2

DH3034 13° 20ʹ 10.72125ʺ N 144° 45ʹ 44.64012ʺ E 184.25 8.8

USGS BM1 13° 21ʹ 45.11828ʺ N 144° 42ʹ 09.96910ʺ E 289.97 112.69

GGN 2053 13° 23ʹ 19.11545ʺ N 144° 41ʹ 13.24816ʺ E 576.83 399

GGN 2054 13° 23ʹ 12.01057ʺ N 144° 41ʹ 07.84761ʺ E 558.63 380.83

RP21 13° 21ʹ 46.35849ʺ N 144° 42ʹ 21.74374ʺ E 302.63 125.41

Spillway Crest4 13° 21ʹ 32.38333ʺ N 144° 42ʹ 20.82923ʺ E 287.77 110.63

Spillway Crest5 13° 21ʹ 31.86879ʺ N 144° 42ʹ 20.94531ʺ E 288.07 110.93

1

Symbols and letters °, ʹ, ʺ, N, and E refer to degrees, minutes, seconds, north and east, respectively.

2

Ellipsoid height referenced to North American Datum of 1983 (NAD83) referenced to the Mariana tectonic plate.

3

Orthometric height referenced to Guam Vertical Datum of 2004 (GUVD04) using GEOID12A (National Geodetic Survey, 2012).

4

Survey measurement at the northern end of the spillway crest.

5

Survey measurement at the center of the spillway crest.

Sac15-0570_fig 03

Figure 3. Spillway at the Fena Valley Reservoir, Guam. (Photograph by M.D. Marineau, February 21, 2014)
Data Collection 7

Table 2. Differences between published coordinates and 2014 surveyed coordinates, Fena Valley Reservoir, Guam.

[ft, feet; MSL, mean sea level; n/a, published coordinates were not available for comparison; NGS, National Geodetic Survey. Difference is published minus 

surveyed coordinates.]

Benchmark/

survey point

Latitude 

difference1

Longitude 

difference1

Orthometric height difference2

(ft)

Source of 

published data 

DH3040 n/a n/a –0.28 NGS datasheet

DK2736 –00° 00ʹ 0.00039ʺ 00° 00ʹ 0.00048ʺ –0.16 NGS datasheet

DH3034 n/a n/a –0.11 NGS datasheet

GGN 2053 00° 00ʹ 0.00886ʺ 00° 00ʹ 0.01389ʺ –0.05 Written communication3

GGN 2054 00° 00ʹ 0.00865ʺ 00° 00ʹ 0.01451ʺ 0.07 Written communication3

RP21 n/a n/a 0.42 Written communication4

Spillway crest5 n/a n/a 0.72 Written communication4

Spillway crest6 n/a n/a 0.42 Written communication4

1

Symbols and letters: °, ʹ, and ʺ, refer to degrees, minutes, seconds, respectively.

2

Orthometric height referenced to Guam Vertical Datum of 2004 (GUVD04) using GEOID12A (National Geodetic Survey, 2012); NGS datasheets are 

included in the appendix.

3

Thomas Torres, Government of Guam, written commun., 2014.

4

Elevation of RP21, 125.83 ft above MSL; spillway crest elevation, 111.35 ft above MSL (Ron Rickman and Chui Yueng, U.S. Geological Survey, written 

commun., 2014).

5

Survey measurement at northern end of Spillway Crest.

6

Survey measurement at center of Spillway Crest.

A USGS streamgage at the spillway (station 16849000, 

Fena Dam Spillway near Agat, Guam; fig. 1) monitors 

reservoir stage and is referenced to the spillway crest. In 

general, during the 4 days of the bathymetric survey, the 

reservoir was full. The change in stage was approximately 

0.16 ft.

Bathymetric Survey

Bathymetric data were collected using a boat-mounted 

Sontek M9 HydroSurveyorTM (M9) acoustic Doppler current 

profiler (ADCP). The ADCP was attached to the side of the 

14-ft fiberglass McKee Craft motorized boat at a depth of 

1.15 ft (measured from the water surface to the bottom of the 

ADCP) using an aluminum mount and wooden frame.

The M9 is equipped with nine transducers. One of the 

transducers is pointed directly below the ADCP, and the other 

eight are arranged as two sets of four transducers in Janus 

configurations with each transducer at a 25-degree slant angle. 

The center transducer (0.5 megahertz [MHz]) is designed 

to measure depth directly beneath the instrument, and the 

two sets of transducers in Janus configurations (1 MHz and 

3 MHz) are designed to measure three-dimensional velocity 

profiles. However, the angled transducers also record the 

depth to the bed such that the ADCP records five depth 

measurements per ping with the footprint dependent on water 

depth (larger footprint in deeper water). Internal compass data 

are used by the HydroSurveyor software (Sontek Inc., 2013) to 

horizontally locate the depths from the angled transducers with 

respect to instrument position. In addition to the horizontal 

position corrections, data from the pitch/roll sensor are used 

to make geometric corrections. During operation, the center 

transducer is always in use, whereas only one of the sets of 

four outer transducers is in use at any given time, depending 

on water depth and instrument settings. For depths up to 

5 meters (m; about 16.4 ft), the 3.0 MHz set of transducers 

is typically used, and for deeper waters (greater than 5 m), 

the second set of transducers, operating at 1.0 MHz, is used. 

The instrument was set to automatically switch from one set 

of transducers to the other depending on the detected water 

depth. The maximum depth that the 1.0-MHz transducers are 

capable of measuring is 40 m (about 130 ft). According to 

manufacturer specifications, the vertical accuracy of the M9 is 

0.02 m (0.07 ft) when using sound-speed corrections (Xylem 

Inc., 2012a). System checks and compass calibration of the 

ADCP were performed daily.

Data were recorded on a field laptop using 

HydroSurveyor software. Location was determined using a 

single-base GNSS-RTK survey. A Trimble R10 GNSS receiver 

mounted to the boat was configured to provide a 10 Hz 

National Marine Electronics Association data stream of vector 

track and ground speed data and global positioning system fix 

information data to the HydroSurveyorTM software. The GNSS 

base station was mounted over benchmark USGS-BM1. The 

HydroSurveyorTM software uses the coordinates from the R10 

GNSS, ADCP heading information, and measured depth to 

calculate the precise position of each depth sounding.
8 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

The approach for conducting the bathymetric survey was 

first to follow the entire shoreline as closely as possible, given 

dense vegetation and water depth. Distance to the shoreline 

was generally between 3 and 9 ft. After the shoreline depth 

data were collected, the center of the reservoir was surveyed 

by generally following a crisscross pattern (fig. 4). The 

real-time display of the boat position along with previously 

collected data on the field laptop were used to determine 

where to guide the boat to reduce data gaps. Deltaic deposits 

were found at the mouth of the Imong River (fig. 5). In 

these areas, the shallow water prevented use of the boat for 

surveying. Therefore, the R10 GNSS rover was used with a 

2-m (6.56-ft) survey rod (fig. 6) to survey the Imong River and 

delta. An outline of the reservoir with the location of all depth 

soundings and topographic survey points is shown in figure 4.

Temperature and Depth Profiles

The density of water is primarily affected by temperature 

in freshwater reservoirs. Changes in the density above and 

below a thermocline will affect the speed of sound underwater 

(referred to as “sound speed”). Sound-speed variation in the 

water column, if uncorrected, can introduce error in depth 

measurements collected using acoustically based survey 

instruments. A 10 °F decrease in temperature (from 65 °F to 

55 °F, for example) in freshwater can decrease the sound speed 

by about 54 ft per second (ft/s), or 1.1 percent, determined 

on the basis of calculations made using the Chen and Millero 

(1977) equation for sound speed. Thus, assuming the water 

column is the same temperature as the surface would cause an 

overestimate of sound speed leading to a biased-high estimate 

of depth (resulting in an overestimation of reservoir capacity). 

Most ADCPs are equipped with built-in temperature sensors 

that provide only near-surface temperature (Oberg and others, 

2005). Vertical profiles of conductivity, temperature, and depth 

CTD (referred to as “casts”) were collected using a Sontek 

CastAwayTM CTD profiler and were used to calculate the sound 

speed throughout the water column. Generally, a cast was 

collected at the start of the survey, during the survey whenever 

moving to a new location, and at the end of the survey (fig. 4). 

The CastAway CTD has an internal Global Positioning System 

(GPS) receiver for measuring the horizontal location of each 

cast. The CastAway CTD can operate in depths up to 100 m 

(about 328.1 ft) with an error of ±0.25 percent full scale and 

temperatures ranging from –5 to 45 °C (about 23 to 113 °F) 

with an error of ±0.05 °C (about ±0.09 °F) (Yellow Springs 

Instruments, 2010).
Data Collection 9

Sac15-0570_fig 04

CTD profile locations Reservoir shoreline

Rivers

Topographic survey path

Boat track

EXPLANATION 0 0.1 0.2 0.3 0.4 MILE

0.10 0.2 0.3 0.4 KILOMETER

144°41'30” E 144°42' E 144°42'30” E

13°21'30"

13°21'

13°20'30"

Almagosa RiverAlmagosa River

Imong RiverImong River

Maulap RiverMaulap River

Base modified from U.S. Geological Survey and other

Federal and State digital data, various scales

Imagery courtesy of DigitalGlobe. ©2014.

Universal Transverse Mercator, zone 55N

North American Datum of 1983 (MA11)

GUAM

Hagåtña

Map location

Figure 4. Bathymetric boat-survey track, locations of topographic survey points at Imong River and Imong River Delta, and locations of 

conductivity, temperature, and depth (CTD) vertical profiles, Fena Valley Reservoir, Guam, 2014.
10 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Sac15-0570_fig 05

Figure 5. Sand deposition at Imong River Delta on the southern-most tip of the Fena Valley Reservoir, Guam. (Photograph by M.D. 

Marineau, February 25, 2014)

Sac15-0570_fig 06

Figure 6. Surveying of the Imong River between the Fena Valley Reservoir and the Imong River streamgage (station 16847000), Guam. 

(Photograph by S.A. Wright, February 25, 2014)
Data Analysis 11

Data Analysis

Raw depth-sounding data were first corrected for changes 

in sound speed, resulting from potential thermoclines. The 

sound-speed corrected depth data were then converted to 

elevation and merged with topographic datasets and the 

shoreline data. The merged data were interpolated to obtain a 

1-meter (3.28-ft) resolution digital elevation model (DEM) of 

the survey. This DEM was used to compute capacity.

Shallow-Water Survey, Spillway Elevation, and 

Shoreline Digitization

Additional shallow-water survey measurements were 

processed in Trimble Business Center software (Trimble, 

2014). The coordinates of these points were then merged with 

bathymetric points. The spillway crest was also surveyed 

(tables 1 and 2) and found to have an average elevation of 

110.8 ft GUVD04.

The elevation of the spillway crest was surveyed by 

using a fixed-length survey rod with the R10 receiver. The 

spillway crest was surveyed in two locations, once near the 

northern wall of the spillway and once in the center of the 

spillway (tables 1 and 2). Results for these two spillway crest 

locations differed by about 0.3 ft, and neither corresponded 

with previously published survey elevations. The differences 

between the two survey elevations could be associated with 

multipath signals near the northern wall or could be due to 

difficulties in maintaining survey rod stability on the spillway 

crest. For this study, we averaged the two values and reported 

the surveyed elevation of the spillway crest as 110.8 ft 

GUVD04.

The shoreline, representing spillway elevation, was 

digitized from high-resolution satellite imagery of the 

reservoir (fig. 1), dated February 7, 2014, courtesy of 

DigitalGlobe Inc. (2014). The imagery was collected when 

the reservoir was near full capacity, which was based on 

USGS streamgage measurements recorded at the time. The 

bathymetric data were overlaid and reviewed to ensure that 

all points fell within the digitized shoreline. The shoreline 

was then converted to points at 1-meter (3.28-ft) intervals 

using ArcGISTM, assigned an elevation of 110.8 ft GUVD04 

(elevation the water surface when reservoir is at full capacity), 

and merged with the bathymetric and topographic data.

Sound-Speed Corrections

The HydroSurveyorTM software integrates multiple 

measurements made using the CastAwayTM CTD with the 

bathymetric data. Sound speed was calculated by using the 

Chen and Millero (1977) equation, and beam angle changes 

resulting from the presence of a thermocline were corrected 

for by using Snell’s Law (Joel Edelman, Sontek Inc., written 

commun., 2014). The HydroSurveyor software was used 

to apply sound-speed corrections to each depth sounding. 

Temperatures in the upper 10 ft of the water column were 

fairly uniform at about 85 °F. Below 10 ft to around 30 ft, 

temperatures dropped steadily to about 80 °F, indicating the 

presence of a thermocline. The average conductivity measured 

in the reservoir was 211 microsiemens per centimeter (μS/cm), 

and ranged from 176 to 260 μS/cm. The peak in conductivity 

occurred right around the thermocline; however, these changes 

in conductivity were considered low and had very little effect 

on sound-speed calculations. Average sound speed, calculated 

from the CTD profiles, was 4,940 ft/s and ranged from 4,925 

to 4,947 ft/s. Examples of the water temperature, salinity, 

density and sound-speed profiles for three locations within 

the reservoir are shown in figure 7. The salinity in these 

plots is shown using the practical salinity scale (PSS-78), 

and the conversion of conductivity to salinity is based on the 

international equation of state for seawater (United Nations 

Educational, Scientific, and Cultural Organization, 1981). This 

conversion was performed internally by the CastAway CTD 

(Xylem, 2012b).

Bed-Elevation Calculation from Depth 

Soundings

After sound-speed corrections were applied to the depth 

soundings, the measurements from the depth soundings 

were converted to reservoir bed elevations on the basis of 

the reservoir stage at the time of measurement. Changes in 

stage can affect the capacity calculations if not properly taken 

into account. For example, during the time of the survey, the 

reservoir surface area at the spillway elevation was estimated 

as 192.6 acres (on the basis of the shoreline digitization), and 

the maximum observed range in stage was 0.16 ft. Failure to 

consider this change in stage could introduce error as high as 

31 acre-ft in the storage-capacity estimate.

To account for the changes in stage, the corrected depth 

measurements were exported from the HydroSurveyorTM

program to an Excel® file (Microsoft Corp., 2010). The time 

stamp for each depth sounding was rounded to the nearest 

15-minute interval and cross-referenced to the gage-height 

measurement recorded at the spillway streamgage (Fena Dam 

Spillway near Agat, Guam, station 16849000; fig. 1). The 

vertical datum of the streamgage is referenced to the spillway 

such that a gage height of 0.0 ft corresponds to the spillway 

crest. The corresponding bed elevation, in ft GUVD04, for 

each depth sounding was then calculated using equation 1:

E S = +110 8. ft − D (1)

where

E is bed elevation, in ft GUVD04;

S is gage height recorded at the spillway, in ft; 

and

D is depth of sounding, in ft.
12 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Sac15-0570_fig 07

A B

C D

0.08 0.09 0.1 0.11 0.12

Practical Salinity Scale

0.08 0.09 0.1 0.11 0.12

Practical Salinity Scale

25 26 27 28 29 30

0

2

4

6

8

10

12

14

16

18

20

22

0

2

4

6

8

10

12

14

16

18

20

22

Temperature, in degrees Celsius

25 26 27 28 29 30

Temperature, in degrees Celsius

25 26 27 28 29 30

Temperature, in degrees Celsius

Depth below water surface, in meters Depth below water surface, in meters

0

2

4

6

8

10

12

14

16

18

20

22

Depth below water surface, in meters

0

2

4

6

8

10

12

14

16

18

20

22

Depth below water surface, in meters

0

2

4

6

8

10

12

14

16

18

20

22

Depth below water surface, in meters

E F

1,498 1,500 1,502 1,504 1,506 1,508 1,510

0

2

4

6

8

10

12

14

16

18

20

22

Sound speed, in meters per second

1,498 1,500 1,502 1,504 1,506 1,508 1,510

Sound speed, in meters per second

1,498 1,500 1,502 1,504 1,506 1,508 1,510

Sound speed, in meters per second

Depth below water surface, in meters

995

Density, in kilograms per cubic meter

995.5 996 996.5 997 997.5 998

995

Density, in kilograms per cubic meter

995.5 996 996.5 997 997.5 998

0.08 0.09 0.1 0.11 0.12

Practical Salinity Scale

995

Density, in kilograms per cubic meter

995.5 996 996.5 997 997.5 998

Figure 7. Examples of water temperature, salinity, density, and sound-speed profiles at three locations within the reservoir: A and B, 

cast from the downstream part of the reservoir near the dam (depth, 20.4 meters, 66.9 feet); C and D, cast from the middle part of the 

reservoir (depth, 12.5 meters, 41.0 feet); and E and F, cast from the upstream part of the reservoir (depth, 7.0 meters, 23 feet). Salinity is 

shown using the practical salinity scale (PSS-78). On plots A, C, and E, blue points indicate temperature and red points indicate salinity. 

On plots B, D, and F, green points indicate velocity and brown points indicate density.
Data Analysis 13

Digital Elevation Model Development

The bed elevation and additional topographic survey 

points in the Imong River and delta were merged and imported 

into ArcGISTM (ESRI Inc., 2013) as a shapefile. Erroneous bedelevation points, likely caused by sound-wave reflections from 

the CastAwayTM CTD, were removed from the dataset. A digital 

elevation model (DEM) was created in ArcGIS by using 

a nearest-neighbor interpolation algorithm. The elevation 

data from the DEM were then exported and tabulated in 

MATLAB® (The MathWorks Inc., 2014) to obtain the surface 

area and cumulative storage volume at 0.1-foot stage intervals. 

The bathymetric raster dataset was also used to generate 

contours at 5-foot intervals using an algorithm in ArcGIS. The 

contours were created only for the figure and were not used to 

calculate storage capacity. Contours smaller than about 50 ft 

are not shown.

The transducers in the Sontek M9 ADCP were calibrated 

by the manufacturer, and no calibration adjustments by the 

operator were needed. As an indirect check that the ADCP 

was functioning properly, we compared the maximum depth 

recorded in each CTD cast (referred to as “CTD-measured 

depth”) to the depth derived from the DEM (referred to as 

“DEM-derived depth”) at that location. Several of the casts 

collected had high horizontal-positioning error (greater than 

about 10 ft). This amount of error is acceptable for largescale adjustments of sound-speed corrections but not for 

comparisons to DEM-derived depths; therefore, casts with 

large horizontal error were not used in the comparison. 

Also, several of the casts were collected in areas with steep 

bed topography; in those areas if the boat drifted a few 

meters from the GPS-derived location of the cast while the 

CastAwayCTD was still underwater, the CTD-measured 

depth could differ significantly from the DEM-derived 

depth. Excluding the casts collected in areas with mildly 

sloped to steep bed topography, the average depth of the 

remaining casts was 35.08 ft with a range of 3.93–67.06 ft. 

On average, the CTD-measured depth was 0.40 ft deeper than 

the DEM-derived depth. Differences in depth could be due to 

instrumentation error, interpolation between depth soundings, 

or possibly from the CastAway CTD penetrating the soft bed 

material in the upper layers of sediment. In general, excluding 

the casts collected in areas with mildly sloped to steep bed 

topography, the DEM-derived depths and CTD-measured 

depths corresponded well. In addition to performing daily 

system checks on the ADCP, this indirect check against the 

CTD-measured depths provided additional assurance that the 

Sontek M9 ADCP was functioning properly.

Sac15-053_fig 08

0 10 20 30 40 50 60 70 80

CTD-measured max-depth, in feet

DEM-derived depths, in feet

0

10

20

30

40

50

60

70

80

All casts with low GPS error

Cast with low GPS error and in areas with generally flat terrain

1:1 line

EXPLANATION

Figure 8. Maximum depths measured using the CastAway Conductivity, Temperature, and Depth profiler in relation to depths derived 

from the digital elevation model of the Fena Valley Reservoir, Guam, 2014. Casts with Global Positioning System (GPS) error greater than 

10 feet were not included in this comparison. Depths from casts collected in areas with generally flat terrain, which would provide a 

better check against the digital elevation model (DEM)-derived depths, are shown by dark-green markers. (CTD, CastAway Conductivity, 

Temperature, and Depth).
14 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Results

In this section the results of the 2014 Fena Valley 

Reservoir capacity analysis are compared to the initial 

capacity. The 1951 stage-area and stage-capacity curves were 

digitized from the engineering drawings of record (Frederic R. 

Harris, Inc., 1949) by using PlotDigitizer software (Huwaldt 

and Steinhorst, 2012).

Bathymetry

Results of the 2014 bathymetric survey of the reservoir 

are shown in figure 9. Approximately 380,000 depth soundings 

and about 2,100 topographic points were used to create the 

bathymetric map with a point density generally ranging from 

0.02 to 0.21 points per ft2 (average about 1 point per 22 ft2). 

The bathymetric map shows that remnants of the Fena 

River channel are still fairly well defined in the northern 

two-thirds of the reservoir. However, significant sediment 

deposition has occurred in the southern part of the reservoir, 

particularly just downstream from the Imong and Almagosa 

Rivers, to the degree that sediment has completely buried the 

river channels in this area of the reservoir. Coarse sediment 

(cobbles, sand, and silt) typically settles out quickly near river 

mouths in a reservoir. In the Fena Valley Reservoir, the Imong 

River has the most pronounced deltaic deposits. The Almagosa 

River also contributes a large amount of sediment; however, 

there was very little noticeable sediment accumulation near the 

Maulap River mouth. On the basis of this evidence, the Imong 

River watershed probably contributes the greatest volume of 

sediment to the reservoir.

In the other parts of the reservoir, if sediment deposition 

has occurred, it is more uniformly distributed such that 

some detail of the underlying topography (prior to reservoir 

inundation) is visible in the bathymetric map. For example, in 

addition to the visible former Fena River channel, remnants of 

the retaining levees used during construction of the Fena Dam 

are also visible in the bathymetric map. These levees are in the 

downstream-most part of the reservoir, starting diagonally just 

south of the boat launch area, then following the northern bank 

of the former Fena River to the screen house.

Reservoir Storage Capacity

The total storage capacity of the Fena Valley Reservoir 

determined from the 2014 bathymetric survey was 

6,915 acre-ft. Rating tables for the surface area and reservoir 

volume at 0.1-foot stage intervals are provided in tables 3 and 

4. The reservoir volume is shown as a stage-capacity curve, 

along with the 1951 stage-capacity curve, in figure 10.

The total reservoir storage capacity has decreased 

from 8,365 acre-ft in 1951 to 6,915 acre-ft in 2014 (a loss 

of 17 percent). The live storage capacity has decreased 

from 5,883 acre-ft in 1951 to 5,511 acre-ft in 2014 (a loss 

of 6 percent), and the dead storage capacity has decreased 

from 2,482 acre-ft in 1951 to 1,404 acre-ft in 2014 (a loss 

of 43 percent). Seventy-five percent of the capacity loss 

was in the dead storage. The dead-storage area (defined as 

the reservoir bed which lies below the lowest-level outlet 

elevation) extends south from the dam to about the location 

of the former (that is submerged) confluence of the Almagosa 

River and the Fena River. On the basis of the historical rates of 

deposition, a greater portion of future sediment may still end 

up in the dead storage area; however, sedimentation in the live 

storage area (or usable storage) is likely to continue, which 

will affect reservoir management.

At this time we cannot estimate rates of sedimentation 

because of the uncertainty in the methods used during previous 

surveys, as well as unknowns regarding the watershed 

response to infrequent, but major, storms, which could deliver 

large volumes of sediment. Further analysis is needed to 

quantify the error associated with the previous surveys and 

then place those results in the context of the hydrologic history 

of the watershed.
0 0.20.1 0.3 KILOMETER

0 0.1 0.2 0.3 MILE

^

 Location

144°42' E 144°42'30" E

13°21'30”

13°20' 30”

13°21'

Base modified from U.S. Geological Survey and other

Federal and State digital data, various scales

Universal Transverse Mercator, zone 55N

North American Datum of 1983 (MA11)

Imagery courtesy of DigitalGlobe© 2014.

GUAM

Hagåtña

Map location

EXPLANATION

Elevation, in feet Guam Vertical 

Datum 2004 (GUVD04)

High: 110.8 Low: 40

5-foot interval contour

Figure 9. Bathymetry and 5-foot interval contours, based on the February 2014 survey, Fena Valley Reservoir, Guam.
16 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Table 3. Rating table for surface area of the Fena Valley Reservoir, Guam, 2014.

Stage 

(feet)1

Surface area 

(acres)

Intervals

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

42 0 0 0 0 0 0 0 0.1 0.2 0.2

43 0.3 0.3 0.3 0.4 0.4 0.4 0.5 0.5 0.6 0.6

44 0.6 0.7 0.7 0.8 0.8 0.8 0.9 1.0 1.0 1.1

45 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.2

46 2.3 2.4 2.5 2.7 2.8 2.9 3.0 3.1 3.2 3.3

47 3.4 3.5 3.6 3.7 3.8 3.8 3.9 4.0 4.1 4.2

48 4.2 4.3 4.4 4.5 4.6 4.6 4.7 4.8 4.9 5.0

49 5.0 5.1 5.2 5.3 5.4 5.4 5.5 5.6 5.7 5.8

50 5.9 6.0 6.1 6.2 6.4 6.5 6.7 6.9 7.0 7.3

51 7.5 7.7 7.9 8.1 8.4 8.7 8.9 9.2 9.5 9.8

52 10.0 10.3 10.6 11.0 11.3 11.6 12.0 12.4 12.8 13.2

53 13.7 14.1 14.5 15.0 15.4 15.9 16.3 16.8 17.2 17.7

54 18.2 18.6 19.1 19.5 20.0 20.5 21.0 21.5 22.1 22.6

55 23.1 23.7 24.3 24.8 25.4 26.0 26.7 27.2 27.8 28.4

56 28.9 29.5 30.0 30.6 31.2 31.7 32.3 32.8 33.4 33.9

57 34.5 35.1 35.7 36.3 36.9 37.6 38.2 38.8 39.4 40.1

58 40.8 41.5 42.1 42.8 43.4 44.1 44.8 45.4 46.0 46.7

59 47.3 47.9 48.6 49.2 49.8 50.4 50.9 51.5 52.0 52.6

60 53.1 53.5 54.0 54.5 55.0 55.5 55.9 56.4 56.8 57.3

61 57.7 58.1 58.5 59.0 59.4 59.8 60.2 60.6 61.1 61.5

62 62.0 62.4 62.9 63.4 63.8 64.3 64.8 65.3 65.8 66.3

63 66.7 67.2 67.6 68.1 68.5 69.0 69.4 69.9 70.4 70.8

64 71.3 71.7 72.2 72.6 73.1 73.5 74.0 74.4 74.8 75.2

65 75.7 76.1 76.5 77.0 77.4 77.8 78.2 78.6 79.0 79.4

66 79.8 80.2 80.6 81.0 81.4 81.8 82.1 82.5 82.8 83.2

67 83.6 84.0 84.3 84.7 85.1 85.5 85.8 86.2 86.5 86.9

68 87.2 87.6 88.0 88.3 88.7 89.1 89.4 89.7 90.1 90.4

69 90.7 91.0 91.4 91.7 92.0 92.3 92.6 92.9 93.1 93.4

70 93.7 94.0 94.3 94.5 94.8 95.1 95.4 95.6 95.9 96.2

71 96.5 96.8 97.1 97.4 97.7 98.0 98.3 98.6 99.0 99.3

72 99.6 100.0 100.3 100.6 100.9 101.2 101.5 101.8 102.0 102.3

73 102.6 102.8 103.1 103.3 103.6 103.8 104.1 104.3 104.6 104.8

74 105.1 105.4 105.7 106.0 106.2 106.5 106.8 107.1 107.3 107.6

75 107.8 108.1 108.3 108.6 108.8 109.1 109.3 109.6 109.8 110.1

76 110.3 110.6 110.8 111.1 111.3 111.6 111.8 112.1 112.3 112.6

77 112.8 113.1 113.4 113.6 113.9 114.1 114.4 114.6 114.9 115.1
Results 17

Table 3. Rating table for surface area of the Fena Valley Reservoir, Guam, 2014.—Continued

Stage 

(feet)1

Surface area 

(acres)

Intervals

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

78 115.4 115.6 115.9 116.1 116.4 116.6 116.9 117.2 117.4 117.7

79 117.9 118.2 118.4 118.7 118.9 119.2 119.4 119.7 119.9 120.2

80 120.4 120.6 120.9 121.1 121.3 121.6 121.8 122.0 122.3 122.5

81 122.8 123.0 123.3 123.6 123.8 124.1 124.3 124.6 124.9 125.1

82 125.4 125.7 125.9 126.2 126.4 126.6 126.9 127.1 127.3 127.5

83 127.8 128.0 128.2 128.4 128.6 128.8 129.1 129.3 129.5 129.7

84 130.0 130.2 130.4 130.6 130.8 131.1 131.3 131.5 131.7 131.9

85 132.1 132.3 132.5 132.7 132.9 133.1 133.3 133.5 133.7 134.0

86 134.2 134.4 134.6 134.8 135.0 135.2 135.4 135.7 135.9 136.1

87 136.3 136.5 136.7 136.9 137.1 137.4 137.6 137.8 138.0 138.3

88 138.5 138.7 139.0 139.2 139.4 139.7 139.9 140.1 140.4 140.6

89 140.9 141.1 141.3 141.5 141.8 142.0 142.2 142.4 142.7 142.9

90 143.1 143.3 143.5 143.8 144.0 144.2 144.4 144.6 144.8 145.1

91 145.3 145.5 145.7 145.9 146.1 146.4 146.6 146.8 147.1 147.3

92 147.5 147.7 148.0 148.2 148.4 148.7 148.9 149.1 149.4 149.6

93 149.8 150.1 150.3 150.6 150.8 151.0 151.3 151.5 151.8 152.1

94 152.3 152.6 152.8 153.1 153.3 153.6 153.9 154.1 154.4 154.6

95 154.9 155.2 155.4 155.7 155.9 156.2 156.4 156.7 157.0 157.2

96 157.5 157.8 158.0 158.3 158.6 158.8 159.1 159.4 159.6 159.9

97 160.2 160.4 160.7 161.0 161.2 161.5 161.8 162.0 162.2 162.5

98 162.7 163.0 163.2 163.5 163.7 164.0 164.2 164.4 164.7 164.9

99 165.1 165.3 165.6 165.8 166.0 166.3 166.5 166.7 166.9 167.2

100 167.4 167.7 167.9 168.1 168.3 168.5 168.8 169.0 169.2 169.5

101 169.7 170.0 170.2 170.4 170.7 170.9 171.2 171.4 171.7 171.9

102 172.1 172.3 172.6 172.8 173.0 173.2 173.4 173.7 173.9 174.2

103 174.4 174.6 174.8 175.0 175.2 175.4 175.7 175.9 176.1 176.4

104 176.6 176.8 177.1 177.3 177.5 177.7 178.0 178.2 178.4 178.6

105 178.8 179.1 179.3 179.5 179.7 180.0 180.2 180.4 180.6 180.8

106 181.0 181.3 181.5 181.7 182.0 182.2 182.5 182.7 182.9 183.2

107 183.4 183.6 183.7 184.0 184.2 184.4 184.6 184.8 184.9 185.1

108 185.3 185.5 185.7 185.9 186.0 186.2 186.4 186.6 186.7 186.9

109 187.0 187.2 187.4 187.6 187.7 187.9 188.1 188.3 188.5 188.7

110 189.0 189.4 189.8 190.2 190.6 190.9 191.2 191.5 192.6

Spillway Crest (110.8 feet GUVD04).

1

Elevation in feet referenced to Guam Vertical Datum of 2004 (GUVD04).
18 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Table 4. Rating table for storage capacity of the Fena Valley Reservoir, Guam, 2014.

Stage 

(feet)1

Storage capacity 

(acre-feet)

Intervals

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

42 0 0 0 0 0 0 0 0.1 0.1 0.1

43 0.1 0.1 0.2 0.2 0.3 0.3 0.3 0.4 0.5 0.5

44 0.6 0.6 0.7 0.8 0.9 1.0 1.0 1.1 1.2 1.4

45 1.5 1.6 1.8 1.9 2.1 2.2 2.4 2.6 2.8 3.0

46 3.3 3.5 3.8 4.0 4.3 4.6 4.9 5.2 5.5 5.9

47 6.2 6.5 6.9 7.3 7.6 8.0 8.4 8.8 9.2 9.7

48 10.1 10.5 10.9 11.4 11.9 12.3 12.8 13.3 13.8 14.3

49 14.8 15.3 15.8 16.3 16.8 17.4 17.9 18.5 19.1 19.7

50 20.2 20.8 21.5 22.1 22.7 23.4 24.0 24.7 25.4 26.1

51 26.9 27.7 28.5 29.3 30.1 31.0 31.9 32.8 33.7 34.7

52 35.7 36.8 37.8 38.9 40.1 41.2 42.4 43.7 44.9 46.3

53 47.6 49.0 50.5 52.0 53.5 55.1 56.8 58.4 60.2 61.9

54 63.7 65.6 67.5 69.5 71.5 73.5 75.6 77.8 80.0 82.2

55 84.6 86.9 89.4 91.8 94.4 97.0 100 102 105 108

56 111 114 117 120 123 126 129 133 136 139

57 143 146 150 154 157 161 165 169 173 177

58 181 185 189 193 198 202 207 211 216 220

59 225 230 235 240 245 250 255 260 265 270

60 276 281 287 292 297 303 309 314 320 326

61 331 337 343 349 355 361 367 373 379 385

62 391 398 404 410 417 423 430 436 443 449

63 456 463 469 476 483 490 497 504 511 518

64 525 532 540 547 554 562 569 576 584 591

65 599 607 614 622 630 637 645 653 661 669

66 677 685 693 701 709 717 726 734 742 750

67 759 767 776 784 793 801 810 818 827 836

68 844 853 862 871 880 889 898 907 916 925

69 934 943 952 961 970 979 989 998 1,007 1,017

70 1,026 1,035 1,045 1,054 1,064 1,073 1,083 1,092 1,102 1,112

71 1,121 1,131 1,141 1,150 1,160 1,170 1,180 1,190 1,200 1,209

72 1,219 1,229 1,239 1,250 1,260 1,270 1,280 1,290 1,300 1,311

73 1,321 1,331 1,341 1,352 1,362 1,372 1,383 1,393 1,404 1,414

74 1,425 1,435 1,446 1,456 1,467 1,478 1,488 1,499 1,510 1,521

75 1,531 1,542 1,553 1,564 1,575 1,586 1,597 1,608 1,619 1,630

76 1,641 1,652 1,663 1,674 1,685 1,696 1,707 1,718 1,730 1,741

77 1,752 1,764 1,775 1,786 1,798 1,809 1,820 1,832 1,843 1,855
Results 19

Stage 

(feet)1

Storage capacity 

(acre-feet)

Intervals

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

78 1,866 1,878 1,890 1,901 1,913 1,925 1,936 1,948 1,960 1,971

79 1,983 1,995 2,007 2,019 2,031 2,043 2,055 2,067 2,078 2,091

80 2,103 2,115 2,127 2,139 2,151 2,163 2,175 2,187 2,200 2,212

81 2,224 2,237 2,249 2,261 2,274 2,286 2,298 2,311 2,323 2,336

82 2,348 2,361 2,374 2,386 2,399 2,412 2,424 2,437 2,450 2,462

83 2,475 2,488 2,501 2,514 2,527 2,539 2,552 2,565 2,578 2,591

84 2,604 2,617 2,630 2,643 2,656 2,669 2,683 2,696 2,709 2,722

85 2,735 2,749 2,762 2,775 2,788 2,802 2,815 2,828 2,842 2,855

86 2,869 2,882 2,895 2,909 2,922 2,936 2,949 2,963 2,977 2,990

87 3,004 3,018 3,031 3,045 3,059 3,072 3,086 3,100 3,114 3,128

88 3,141 3,155 3,169 3,183 3,197 3,211 3,225 3,239 3,253 3,267

89 3,281 3,295 3,309 3,324 3,338 3,352 3,366 3,380 3,395 3,409

90 3,423 3,438 3,452 3,466 3,481 3,495 3,510 3,524 3,539 3,553

91 3,568 3,582 3,597 3,611 3,626 3,641 3,655 3,670 3,685 3,699

92 3,714 3,729 3,744 3,758 3,773 3,788 3,803 3,818 3,833 3,848

93 3,863 3,878 3,893 3,908 3,923 3,938 3,953 3,968 3,984 3,999

94 4,014 4,029 4,045 4,060 4,075 4,091 4,106 4,121 4,137 4,152

95 4,168 4,183 4,199 4,214 4,230 4,246 4,261 4,277 4,293 4,308

96 4,324 4,340 4,356 4,371 4,387 4,403 4,419 4,435 4,451 4,467

97 4,483 4,499 4,515 4,531 4,547 4,564 4,580 4,596 4,612 4,628

98 4,645 4,661 4,677 4,694 4,710 4,726 4,743 4,759 4,776 4,792

99 4,809 4,825 4,842 4,858 4,875 4,892 4,908 4,925 4,942 4,958

100 4,975 4,992 5,009 5,025 5,042 5,059 5,076 5,093 5,110 5,127

101 5,144 5,161 5,178 5,195 5,212 5,229 5,246 5,263 5,280 5,298

102 5,315 5,332 5,349 5,367 5,384 5,401 5,419 5,436 5,453 5,471

103 5,488 5,506 5,523 5,541 5,558 5,576 5,593 5,611 5,628 5,646

104 5,664 5,681 5,699 5,717 5,735 5,752 5,770 5,788 5,806 5,824

105 5,842 5,860 5,877 5,895 5,913 5,931 5,949 5,967 5,985 6,004

106 6,022 6,040 6,058 6,076 6,094 6,113 6,131 6,149 6,167 6,186

107 6,204 6,222 6,241 6,259 6,278 6,296 6,314 6,333 6,351 6,370

108 6,388 6,407 6,426 6,444 6,463 6,481 6,500 6,519 6,537 6,556

109 6,575 6,593 6,612 6,631 6,650 6,669 6,687 6,706 6,725 6,744

110 6,763 6,782 6,801 6,820 6,839 6,858 6,877 6,896 6,915

Spillway Crest (110.78 feet GUVD04).

1

Elevation in feet referenced to Guam Vertical Datum of 2004 (GUVD04).

Table 4. Rating table for storage capacity of the Fena Valley Reservoir, Guam, 2014.—Continued
20 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Sac15-0570_fig 10

Reservoir surface area, in acres

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

Reservoir capacity, in acre-feet (acre-ft)

(Live storage, 2014: 5,500 acre-ft)

(Dead storage,

2014: 1,400 acre-ft)

(Live storage, 1951: 5,900 acre-ft)

Elevation of lowestlevel water outlet 

(73.8 feet)

30

40

50

60

70

80

90

100

110

120

Water-surface elevation, in feet above Guam Vertical Datum, 2004

A

B

200 180 160 140 120 100 80 60 40 20 0

30

40

50

60

70

80

90

100

110

120

Water-surface elevation, in feet above Guam Vertical Datum, 2004

(Dead storage, 1951: 2,500 acre-ft)

EXPLANATION

1951 Surface area

2014 Surface area

EXPLANATION

2014 Storage capacity

1951 Storage capacity

Figure 10. A, stage-surface area curves for 1951 and 2014; and; B, stage-capacity curves with live and dead storage capacity in 1951 

and 2014 indicated, Fena Valley Reservoir, Guam.
Summary 21

Summary

Since construction of the Fena Dam in 1951, sediment 

has been accumulating in the Fena Valley Reservoir. The 

reservoir was surveyed prior to dam construction, as well as in 

1973, 1979, and 1990. In order to accurately predict surfacewater availability, up-to-date reservoir capacity information 

is needed by the U.S. Navy. In response, the U.S. Geological 

Survey (USGS), in cooperation with the U.S. Department of 

Defense Strategic Environmental Research and Development 

Program, surveyed the bathymetry of the reservoir in 

February 2014 to determine its current storage capacity and to 

create updated reservoir stage–surface area and stage–capacity 

curves.

Methods are presented for the collection of data on 

depth soundings, topographic survey points, and temperature 

and depth within the water column to correct the depth 

soundings. Depth soundings and topographic points were 

then interpolated to create a bathymetric map of the reservoir. 

During the February 2014 survey, data on approximately 

380,000 depth soundings, 2,100 topographic points, and 

45 conductivity, temperature, and depth (CTD) profiles 

were collected. Results from the CTD profiles show that 

temperature varied slightly, and salinity was relatively 

constant. The depth soundings were corrected for temperature 

gradients, merged with topographic survey points in the 

shallow areas of the Imong River, and spatially interpolated 

to create a bathymetric map of the reservoir in the form of 

a digital elevation model (DEM). Elevations from the DEM 

were tabulated to generate the stage–surface area and stage–

capacity tables presented in this report.

A control survey was conducted using Global Navigation 

Satellite System-Real-Time Kinematic receiver to check 

the elevations of the spillway and benchmark RP21 (which 

is used routinely for surveying dam settlement) and to 

establish a temporary benchmark at the boat launch area. 

The spillway crest elevation was surveyed at 110.8 feet (ft) 

Guam Vertical Datum of 2004 (GUVD04), and RP21 was 

surveyed at 125.41 ft. The survey measurements for the 

spillway-crest elevation and benchmark RP21 were lower 

than previously published by 0.42 and 0.57 ft, respectively. 

Survey measurements were checked against two additional 

benchmarks (GGN 2053 and GGN 2054) outside the Naval 

Base Guam Ordnance Annex near the entrance gate. The 

measurements made during this study were within 0.1 ft of 

the known elevation of those two benchmarks. We concluded 

that the original 1948 measurement of the spillway crest which 

used the Mean Lower Low Water (MLLW) as the datum was 

in error and that error has propagated through subsequent 

studies and local surveys. However, this does not affect the 

result of those previous surveys since they were surveyed 

relative to the spillway crest.

Results of the analysis of the bathymetric data indicate 

that the reservoir currently has a total storage capacity of 

6,915 acre-feet (acre-ft). The live-storage capacity was 

calculated as 5,511 acre-ft. Total reservoir capacity in 1951 

was estimated to be 8,365 acre-ft, and the live-storage capacity 

was estimated to be 5,900 acre-ft. Thus, between 1951 and 

2014, the total storage capacity decreased by 1,449 acre-ft, 

and the live-storage capacity decreased by 372 acre-ft 

(representing losses of 17 and 6 percent of the original 

capacity, respectively). Between 1951 and 2014, the deadstorage capacity decreased by 1,078 acre-ft, which represents 

a loss of 43 percent of the original 2,482 acre-ft dead-storage 

capacity. 

Although the overall reservoir capacity is continuing 

to decline, most of the sediment accumulation has occurred 

in the dead-storage area of the reservoir. On the basis of 

the historical rates of deposition, a greater portion of future 

sediment may still end up in the dead storage area; however, 

sedimentation in the live storage area (or usable storage) is 

likely to continue, which will affect reservoir management. 

Coarse sediment (cobbles, sand, and silt) typically settles out 

quickly near river mouths in a reservoir. In the Fena Valley 

Reservoir, the Imong River has the most pronounced deltaic 

deposits. The Almagosa River also contributes a large amount 

of sediment; however, there was little noticeable sediment 

accumulation near the Maulap River mouth. On the basis 

of this evidence, the Imong River watershed is probably the 

primary contributor of sediment to the reservoir. Over the 

lifetime of the reservoir, the average annual decrease in total 

reservoir capacity was 23.0 acre-feet per year. However, 

the sediment delivery is likely to happen at an unsteady 

rate and could be driven by strong tropical storms. At this 

time, sedimentation rates cannot be estimated because of 

the uncertainty in previous surveys and unknowns regarding 

watershed response to infrequent, but major, storms, which 

could deliver large volumes of sediment. Further analysis 

is needed to quantify the error associated with the previous 

surveys and then place those results in the context of the 

hydrologic history of the watershed.
22 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

References Cited

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Development of comprehensive geodetic vertical datums 

for the United States Pacific Territories of American Samoa, 

Guam, and the Northern Marianas: Surveying and Land 

Information Science, v. 69, no. 1, p 5–17.

Chen, C.T., and Millero, F.J., 1977, Speed of sound in 

seawater at high pressures: Journal of the Acoustical Society 

of America, v. 62, no. 5, p. 1129–1135.

Curtis, W.F., 1984, Sedimentation survey of Fena Reservoir, 

Guam, Mariana Islands, 1979: U.S. Geological Survey 

Water-Resources Investigation Report 84–4125, 15 p.

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station at Pier K, Apra Harbor, established March 10, 1948, 

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100307315, accessed July 16, 2014, at https://www.ncdc.

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Highland, L.M., and Bobrowsky, Peter, 2008, The landslide 

handbook—A guide to understanding landslides: U.S. 

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Kennedy Engineers. Inc., 1973, Fena watershed and reservoir 

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17 p.

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Database, NGS update, September 11, 2012, GEOID12A 

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ngs.noaa.gov/GEOID/GEOID12A/.

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Climatological report (monthly) for the Guam International 

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Engineers, Reston Va., 1132 p.
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Shade, P. J., 1983, Reconnaissance study of stream 

sedimentation, Southern Guam: U.S. Geological Survey 

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24 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Glossary

Conductivity The raw measurement of specific conductance 

of water which has not been compensated for temperature.

Dead storage The volume of storage that lies below the 

lower-level water outlet and therefore cannot be drained 

through normal dam operations. The dead storage is not usable 

for water-supply purposes; however, it could be useful for 

the storage of sediment such that sediment deposition in this 

region does not decrease the live-storage capacity.

Ellipsoid height The height above or below a mathematically 

defined surface or ellipsoid that provides a representation 

of the Earth. The height coordinate determined by a Global 

Navigation Satellite System (GNSS) observation is related 

to the surface of the ellipsoid and is then converted to an 

orthometric height using a geoid model. 

Live storage The volume of storage above the lower-level 

water outlet but below the spillway. 

Orthometric height The height of a point on the Earth’s 

surface measured as a distance along a plumb line and normal 

to gravity from that point to a geoid.
Appendix. National Geodetic Survey Datasheets

Benchmark DH3061

PROGRAM = datasheet95, VERSION = 8.3

1 National Geodetic Survey, Retrieval Date = FEBRUARY 19, 2014

 DH3061 ***********************************************************************

 DH3061 DESIGNATION - SABLAN CASTRO

 DH3061 PID - DH3061

 DH3061 STATE/COUNTY- GU/GUAM

 DH3061 COUNTRY - US

 DH3061 USGS QUAD - TALOFOFO (1975)

 DH3061

 DH3061 *CURRENT SURVEY CONTROL

 DH3061 ______________________________________________________________________

 DH3061* NAD 83(MA11) POSITION- 13 20 21.73008(N) 215 13 57.41925(W) ADJUSTED 

 DH3061* NAD 83(MA11) ELLIP HT- 97.358 (meters) (06/27/12) ADJUSTED

 DH3061* NAD 83(MA11) EPOCH - 2010.00

 DH3061* GUVD04 ORTHO HEIGHT - 43.884 (meters) 143.98 (feet) ADJUSTED 

 DH3061 ______________________________________________________________________

 DH3061 NAD 83(MA11) X - -5,070,192.569 (meters) COMP

 DH3061 NAD 83(MA11) Y - 3,580,951.707 (meters) COMP

 DH3061 NAD 83(MA11) Z - 1,461,985.268 (meters) COMP

 DH3061 LAPLACE CORR - -4.35 (seconds) DEFLEC12A

 DH3061 GEOID HEIGHT - 53.46 (meters) GEOID12A

 DH3061 VERT ORDER - FIRST CLASS II

 DH3061

 DH3061 FGDC Geospatial Positioning Accuracy Standards (95% confidence, cm)

 DH3061 Type Horiz Ellip Dist(km)

 DH3061 -------------------------------------------------------------------

 DH3061 NETWORK 4.08 5.08

 DH3061 -------------------------------------------------------------------

 DH3061 MEDIAN LOCAL ACCURACY AND DIST (014 points) 4.82 5.08 12.81

 DH3061 -------------------------------------------------------------------

 DH3061 NOTE: Click here for information on individual local accuracy

 DH3061 values and other accuracy information.

 DH3061

 DH3061

 DH3061.The horizontal coordinates were established by GPS observations

 DH3061.and adjusted by the National Geodetic Survey in June 2012.

 DH3061

 DH3061.NAD 83(MA11) refers to NAD 83 coordinates where the reference 

 DH3061.frame has been affixed to the stable Mariana tectonic plate. 

 DH3061

 DH3061.The horizontal coordinates are valid at the epoch date displayed above

 DH3061.which is a decimal equivalence of Year/Month/Day.

 DH3061

 DH3061.The orthometric height was determined by differential leveling and

 DH3061.adjusted by the NATIONAL GEODETIC SURVEY

 DH3061.in May 2005.

 DH3061
26 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

 DH3061.The X, Y, and Z were computed from the position and the ellipsoidal ht.

 DH3061

 DH3061.The Laplace correction was computed from DEFLEC12A derived deflections.

 DH3061

 DH3061.The ellipsoidal height was determined by GPS observations

 DH3061.and is referenced to NAD 83.

 DH3061

 DH3061. The following values were computed from the NAD 83(MA11) position.

 DH3061

 DH3061; North East Units Scale Factor Converg.

 DH3061;SPC GU - 182,228.850 101,883.254 MT 1.00000004 +0 00 14.4

 DH3061;UTM 55 - 1,475,753.271 258,170.163 MT 1.00032350 -0 30 55.3

 DH3061

 DH3061! - Elev Factor x Scale Factor = Combined Factor

 DH3061!SPC GU - 0.99998469 x 1.00000004 = 0.99998473

 DH3061!UTM 55 - 0.99998469 x 1.00032350 = 1.00030818

 DH3061

 DH3061 SUPERSEDED SURVEY CONTROL

 DH3061

 DH3061 NAD 83(1993)- 13 20 21.72936(N) 215 13 57.41964(W) AD(2004.00) A

 DH3061 ELLIP H (06/10/05) 97.315 (m) GP(2004.00) 3 2

 DH3061

 DH3061.Superseded values are not recommended for survey control.

 DH3061

 DH3061.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

 DH3061.See file dsdata.txt to determine how the superseded data were derived.

 DH3061

 DH3061_U.S. NATIONAL GRID SPATIAL ADDRESS: 55PBQ5817075753(NAD 83)

 DH3061

 DH3061_MARKER: Z = SEE DESCRIPTION

 DH3061_SETTING: 7 = SET IN TOP OF CONCRETE MONUMENT

 DH3061_MARK LOGO: GUAMLM

 DH3061_MAGNETIC: R = STEEL ROD IMBEDDED IN MONUMENT

 DH3061_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO

 DH3061+STABILITY: SURFACE MOTION

 DH3061_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR

 DH3061+SATELLITE: SATELLITE OBSERVATIONS - May 21, 2004

 DH3061

 DH3061 HISTORY - Date Condition Report By

 DH3061 HISTORY - 20040521 MONUMENTED GUAMLM

 DH3061

 DH3061 STATION DESCRIPTION

 DH3061

 DH3061’DESCRIBED BY GUAM DEPARTMENT OF LAND MANAGEMENT 2004 (TJT)

 DH3061’GENERAL STATION LOCATION- THE STATION IS LOCATED IN THE MUNICIPALITY

 DH3061’OF TALOFOFO.

 DH3061’ 

 DH3061’TO REACH NARRATIVE- TO REACH THE STATION FROM THE JUNCTION OF ROUTE 4

 DH3061’AND ROUTE 17, GO SOUTH ON ROUTE 4 FOR 3.5 MILE, STATION ON THE LEFT

 DH3061’SIDE OF ROUTE 4 AND 4A. THE STATION IS CENTER WITHIN TALOFOFO BAY

 DH3061’OVERLOOK.

 DH3061’ 

 DH3061’MONUMENT DESCRIPTION AND MEASUREMENTS- THE STATION IS 13.30M SOUTHEAST

 DH3061’FROM A CONCRETE POWER POLE, 23.70M SOUTHEAST FROM CENTERLINE OF ROUTE

 DH3061’4 AND 5.80M SOUTHWEST FROM THE NORTHEAST CORNER OF A STONE WALL.

 DH3061’ 
Appendix. National Geodetic Survey Datasheets 27

 DH3061’THE STATION IS A NO 4 REBAR PROJECTING 1/4 INCH SET IN CONCRETE

 DH3061’INSCRIBED DEL. LM 3-24-60 SABLAN CASTRO.

Benchmark DH3040

PROGRAM = datasheet95, VERSION = 8.3

1 National Geodetic Survey, Retrieval Date = FEBRUARY 19, 2014

 DH3040 ***********************************************************************

 DH3040 DESIGNATION - GGN 2669

 DH3040 PID - DH3040

 DH3040 STATE/COUNTY- GU/GUAM

 DH3040 COUNTRY - US

 DH3040 USGS QUAD - TALOFOFO (1975)

 DH3040

 DH3040 *CURRENT SURVEY CONTROL

 DH3040 ______________________________________________________________________

 DH3040* NAD 83(1986) POSITION- 13 21 00. (N) 215 13 51. (W) SCALED 

 DH3040* GUVD04 ORTHO HEIGHT - 12.365 (meters) 40.57 (feet) ADJUSTED 

 DH3040 ______________________________________________________________________

 DH3040 GEOID HEIGHT - 53.53 (meters) GEOID12A

 DH3040 VERT ORDER - FIRST CLASS II

 DH3040

 DH3040.The horizontal coordinates were scaled from a topographic map and have

 DH3040.an estimated accuracy of +/- 6 seconds.

 DH3040.

 DH3040.The orthometric height was determined by differential leveling and

 DH3040.adjusted by the NATIONAL GEODETIC SURVEY

 DH3040.in May 2005.

 DH3040

 DH3040; North East Units Estimated Accuracy

 DH3040;SPC GU - 183,410. 102,080. MT (+/- 180 meters Scaled)

 DH3040

 DH3040 SUPERSEDED SURVEY CONTROL

 DH3040

 DH3040.No superseded survey control is available for this station.

 DH3040

 DH3040_U.S. NATIONAL GRID SPATIAL ADDRESS: 55PBQ583769(NAD 83)

 DH3040

 DH3040_MARKER: DD = SURVEY DISK

 DH3040_SETTING: 7 = SET IN TOP OF CONCRETE MONUMENT

 DH3040_STAMPING: 2669

 DH3040_MARK LOGO: GUAMLM

 DH3040_MAGNETIC: N = NO MAGNETIC MATERIAL

 DH3040_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO

 DH3040+STABILITY: SURFACE MOTION

 DH3040_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR

 DH3040+SATELLITE: SATELLITE OBSERVATIONS - May 04, 2004

 DH3040

 DH3040 HISTORY - Date Condition Report By

 DH3040 HISTORY - 20040504 MONUMENTED GUAMLM

 DH3040

 DH3040 STATION DESCRIPTION

 DH3040

 DH3040’DESCRIBED BY GUAM DEPARTMENT OF LAND MANAGEMENT 2004 (TJT)

 DH3040’GENERAL STATION LOCATION- THE STATION IS LOCATED IN SUBURBAN OF IPAN,
28 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

 DH3040’THE MUNICIPALITY OF TALOFOFO.

 DH3040’ 

 DH3040’TO REACH NARRATIVE- TO REACH THE STATION FROM JUNCTION OF ROUTE 4 AND

 DH3040’ROUTE 17, GO SOUTH ON ROUTE 4 FOR 2.5 MILES, TO THE STATION ON THE

 DH3040’EAST SIDE OF ROUTE 4 AND ACROSS PAULINO HEIGHTS ROAD. THE MARK IS

 DH3040’SOUTH OF BUS SHELTER (YT-95).

 DH3040’ 

 DH3040’MONUMENT DESCRIPTION AND MEASUREMENTS- THE STATION IS 8.10M EAST OF

 DH3040’CENTERLINE OF ROUTE 4, 12.10M SOUTH OF A CONCRETE POWER POLE (PU-23-7)

 DH3040’AND 8.20M NORTH OF A TELEPHONE BOX.

 DH3040’ 

 DH3040’THE MARK IS A STANDARD 1993 GUAM GEODETIC NETWORK DISK

 DH3040’STAMPED--2669--, SET IN A CONCRETE POST.

 *** retrieval complete.

 Elapsed Time = 00:00:03

Benchmark DK2736

PROGRAM = datasheet95, VERSION = 8.4

1 National Geodetic Survey, Retrieval Date = MAY 14, 2014

 DK2736 ***********************************************************************

 DK2736 DESIGNATION - NUTZ

 DK2736 PID - DK2736

 DK2736 STATE/COUNTY- GU/GUAM

 DK2736 COUNTRY - US

 DK2736 USGS QUAD - TALOFOFO (1975)

 DK2736

 DK2736 *CURRENT SURVEY CONTROL

 DK2736 ______________________________________________________________________

 DK2736* NAD 83(MA11) POSITION- 13 20 32.74295(N) 215 13 43.41794(W) ADJUSTED 

 DK2736* NAD 83(MA11) ELLIP HT- 57.710 (meters) (06/27/12) ADJUSTED

 DK2736* NAD 83(MA11) EPOCH - 2010.00

 DK2736* GUVD04 ORTHO HEIGHT - 4.28 (meters) 14.0 (feet) LEVELING 

 DK2736 ______________________________________________________________________

 DK2736 GEOID HEIGHT - 53.44 (meters) GEOID12A

 DK2736 NAD 83(MA11) X - -5,070,340.329 (meters) COMP

 DK2736 NAD 83(MA11) Y - 3,580,540.231 (meters) COMP

 DK2736 NAD 83(MA11) Z - 1,462,305.433 (meters) COMP

 DK2736 LAPLACE CORR - -4.41 (seconds) DEFLEC12A

 DK2736 VERT ORDER - THIRD ?

 DK2736

 DK2736 FGDC Geospatial Positioning Accuracy Standards (95% confidence, cm)

 DK2736 Type Horiz Ellip Dist(km)

 DK2736 -------------------------------------------------------------------

 DK2736 NETWORK 1.28 1.45

 DK2736 -------------------------------------------------------------------

 DK2736 MEDIAN LOCAL ACCURACY AND DIST (004 points) 1.25 1.51 5.39

 DK2736 -------------------------------------------------------------------

 DK2736 NOTE: Click here for information on individual local accuracy

 DK2736 values and other accuracy information.

 DK2736

 DK2736

 DK2736.The horizontal coordinates were established by GPS observations

 DK2736.and adjusted by the National Geodetic Survey in June 2012.
Appendix. National Geodetic Survey Datasheets 29

 DK2736

 DK2736.NAD 83(MA11) refers to NAD 83 coordinates where the reference 

 DK2736.frame has been affixed to the stable Mariana tectonic plate. 

 DK2736

 DK2736.The horizontal coordinates are valid at the epoch date displayed above

 DK2736.which is a decimal equivalence of Year/Month/Day.

 DK2736

 DK2736.The orthometric height was determined by differential leveling.

 DK2736.The vertical network tie was performed by a horz. field party for horz.

 DK2736.obs reductions. Reset procedures were used to establish the elevation.

 DK2736

 DK2736.The X, Y, and Z were computed from the position and the ellipsoidal ht.

 DK2736

 DK2736.The Laplace correction was computed from DEFLEC12A derived deflections.

 DK2736

 DK2736.The ellipsoidal height was determined by GPS observations

 DK2736.and is referenced to NAD 83.

 DK2736

 DK2736. The following values were computed from the NAD 83(MA11) position.

 DK2736

 DK2736; North East Units Scale Factor Converg.

 DK2736;SPC GU - 182,567.325 102,304.569 MT 1.00000007 +0 00 17.7

 DK2736;UTM 55 - 1,476,088.020 258,594.666 MT 1.00032096 -0 30 52.5

 DK2736

 DK2736! - Elev Factor x Scale Factor = Combined Factor

 DK2736!SPC GU - 0.99999092 x 1.00000007 = 0.99999099

 DK2736!UTM 55 - 0.99999092 x 1.00032096 = 1.00031188

 DK2736

 DK2736|---------------------------------------------------------------------|

 DK2736| PID Reference Object Distance Geod. Az |

 DK2736| dddmmss.s |

 DK2736| DK2735 BIRU 35.002 METERS 15701 |

 DK2736| DH2964 CLQT 184.595 METERS 16031 |

 DK2736|---------------------------------------------------------------------|

 DK2736

 DK2736 SUPERSEDED SURVEY CONTROL

 DK2736

 DK2736 NAD 83(1993)- 13 20 32.74344(N) 215 13 43.41842(W) AD(2004.00) 1

 DK2736 ELLIP H (10/11/07) 57.708 (m) GP(2004.00) 4 2

 DK2736

 DK2736.Superseded values are not recommended for survey control.

 DK2736

 DK2736.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

 DK2736.See file dsdata.txt to determine how the superseded data were derived.

 DK2736

 DK2736_U.S. NATIONAL GRID SPATIAL ADDRESS: 55PBQ5859476088(NAD 83)

 DK2736

 DK2736_MARKER: DD = SURVEY DISK

 DK2736_SETTING: 0 = UNSPECIFIED SETTING

 DK2736_STAMPING: NUTZ 2007

 DK2736_MARK LOGO: USACE

 DK2736_MAGNETIC: N = NO MAGNETIC MATERIAL

 DK2736_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO

 DK2736+STABILITY: SURFACE MOTION

 DK2736_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR

 DK2736+SATELLITE: SATELLITE OBSERVATIONS - July 20, 2007
30 Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

 DK2736

 DK2736 HISTORY - Date Condition Report By

 DK2736 HISTORY - 20070720 MONUMENTED USACE

 DK2736

 DK2736 STATION DESCRIPTION

 DK2736

 DK2736’DESCRIBED BY US ARMY CORPS OF ENGINEERS 2007

 DK2736’STATION LOCATION - THE STATION IS LOCATED ALONG THE OCEAN-SIDE OF

 DK2736’ROUTE 4 IN THE MUNICIPALITY OF TALOFOFO, GUAM JUST NORTH OF TALOFOFO

 DK2736’BAY AT ASQUIROGA BAY.

 DK2736’ 

 DK2736’OWNERSHIP - GUAM DEPARTMENT OF PUBLIC WORKS TO REACH THE STATION

 DK2736’FROM THE INTERSECTION OF ROUTE 4 AND ROUTE 4A, TRAVEL NORTH ALONG

 DK2736’ROUTE 4 FOR 0.5 MI (0.8 KM) TOWARDS ASQUIROGA BAY (AWAY FROM TALOFOFO

 DK2736’BAY). THE BENCH MARK IS LOCATED ON THE OCEAN-SIDE OF ROUTE 4 AND ITS

 DK2736’ASSOCIATED GUARDRAIL. THE BENCH MARK SITS FLUSH IN A CONCRETE SLURRY

 DK2736’ADJACENT TO A U.S. ARMY CORPS OF ENGINEERS HURRICANE SHORE PROTECTION

 DK2736’PROJECT. AN OLD PILLBOX SITS ON THE NORTH SIDE OF ASQUIROGA BAY, AND

 DK2736’THE BAY IS A POPULAR SWIMMING/SNORKELING LOCATION.

 DK2736’ 

 DK2736’THE STATION IS AS FOLLOWS - 95 FT (29.0 M) AT AN ANGLE OF 340 FROM

 DK2736’CONCRETE POWER POLE DC-YP 45-600 84-11. - 40 FT (12.2 M) 4 INCHES (10

 DK2736’CM) AT AN ANGLE OF 263.5 FROM THE CENTERLINE OF ROUTE 4. - 50 FT (15.2

 DK2736’M) AT AN ANGLE OF 150 FROM CONCRETE POWER POLE DC-YP 45-600 84-13. - 9

 DK2736’FT (2.7 M) 6 INCHES (15 CM) AT AN ANGLE OF 263.5 FROM THE GUARDRAIL. -

 DK2736’19 FT (5.8 M) 6 INCHES (15 CM) ALONG THE GUARDRAIL IF I START

 DK2736’MEASURING FROM THE NORTH END OF IT.

 DK2736’ 

 DK2736’DESCRIBED BY JUSTIN PUMMELL, U.S. ARMY CORPS OF ENGINEERS, HONOLULU

 DK2736’DISTRICT PHONE (808) 438-7038 E-MAIL JUSTIN.D.PUMMELL USACE.ARMY.MIL

 *** retrieval complete.

 Elapsed Time = 00:00:04

Benchmark DH3034

PROGRAM = datasheet95, VERSION = 8.3

1 National Geodetic Survey, Retrieval Date = FEBRUARY 22, 2014

 DH3034 ***********************************************************************

 DH3034 DESIGNATION - GGN 2555

 DH3034 PID - DH3034

 DH3034 STATE/COUNTY- GU/GUAM

 DH3034 COUNTRY - US

 DH3034 USGS QUAD - TALOFOFO (1975)

 DH3034

 DH3034 *CURRENT SURVEY CONTROL

 DH3034 ______________________________________________________________________

 DH3034* NAD 83(1986) POSITION- 13 20 10. (N) 215 14 16. (W) SCALED 

 DH3034* GUVD04 ORTHO HEIGHT - 2.648 (meters) 8.69 (feet) ADJUSTED 

 DH3034 ______________________________________________________________________

 DH3034 GEOID HEIGHT - 53.48 (meters) GEOID12A

 DH3034 VERT ORDER - FIRST CLASS II

 DH3034

 DH3034.The horizontal coordinates were scaled from a topographic map and have

 DH3034.an estimated accuracy of +/- 6 seconds.
Appendix. National Geodetic Survey Datasheets 31

 DH3034.

 DH3034.The orthometric height was determined by differential leveling and

 DH3034.adjusted by the NATIONAL GEODETIC SURVEY

 DH3034.in May 2005.

 DH3034

 DH3034; North East Units Estimated Accuracy

 DH3034;SPC GU - 181,870. 101,320. MT (+/- 180 meters Scaled)

 DH3034

 DH3034 SUPERSEDED SURVEY CONTROL

 DH3034

 DH3034.No superseded survey control is available for this station.

 DH3034

 DH3034_U.S. NATIONAL GRID SPATIAL ADDRESS: 55PBQ576753(NAD 83)

 DH3034

 DH3034_MARKER: DD = SURVEY DISK

 DH3034_SETTING: 7 = SET IN TOP OF CONCRETE MONUMENT

 DH3034_STAMPING: 2555

 DH3034_MARK LOGO: GUAMLM

 DH3034_MAGNETIC: N = NO MAGNETIC MATERIAL

 DH3034_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO

 DH3034+STABILITY: SURFACE MOTION

 DH3034_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR

 DH3034+SATELLITE: SATELLITE OBSERVATIONS - May 04, 2004

 DH3034

 DH3034 HISTORY - Date Condition Report By

 DH3034 HISTORY - 20040504 MONUMENTED GUAMLM

 DH3034

 DH3034 STATION DESCRIPTION

 DH3034

 DH3034’DESCRIBED BY GUAM DEPARTMENT OF LAND MANAGEMENT 2004 (TJT)

 DH3034’GENERAL STATION LOCATION- THE STATION IS LOCATED IN THE MUNICIPALITY

 DH3034’OF TALOFOFO.

 DH3034’ 

 DH3034’TO REACH NARRATIVE- TO REACH THE STATION FROM JUNCTION OF ROUTE 4 AND

 DH3034’ROUTE 14, GO SOUTH ON ROUTE 4 FOR 0.5 MILES, TO THE STATION ON THE

 DH3034’NORTHWEST CORNER PAULINO HEIGHTS ROAD AND SOUTHWEST OF TALOFOFO SURF

 DH3034’BEACH PARK. THE STATION IS A CONCRETE MONUMENT FLUSH WITH SURFACE.

 DH3034’ 

 DH3034’MONUMENT DESCRIPTION AND MEASUREMENTS- THE STATION IS 6.60M SOUTHWEST

 DH3034’OF CENTERLINE OF ROUTE 4, 18.60M NORTHWEST OF A CONCRETE POWER POLE

 DH3034’AND 8.70M NORTHWEST OF CENTERLINE OF (AC) PAULINO HEIGHTS.

 DH3034’ 

 DH3034’THE MARK IS A STANDARD 1993 GUAM GEODETIC NETWORK DISK

 DH3034’STAMPED--2555--, SET IN A CONCRETE POST.

 *** retrieval complete.

 Elapsed Time = 00:00:08

Prepared by the Sacramento Publishing Service Center.

For more information concerning this report, contact:

Director

U.S. Geological Survey

California Water Science Center

6000 J Street, Placer Hall

Sacramento, CA 95829

or visit our Web site at:

http://ca.water.usgs.gov ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155128
Marineau and Wright—Storage Capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014—Scientific Investigations Report 2015–5128