Storage capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014

Scientific Investigations Report 2015-5128
Prepared in cooperation with the Strategic Environmental Research and Development Program
By:  and 



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.

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.,

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract.
  • Introduction
  • Data Collection
  • Data Analysis
  • Results
  • Summary
  • References Cited
  • Glossary
  • Appendix. National Geodetic Survey Datasheets.
Publication type Report
Publication Subtype USGS Numbered Series
Title Storage capacity of the Fena Valley Reservoir, Guam, Mariana Islands, 2014
Series title Scientific Investigations Report
Series number 2015-5128
DOI 10.3133/sir20155128
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) California Water Science Center
Description vi, 31 p.
Other Geospatial Fena Valley Reservoir, Guam, Mariana Islands
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details