Sedimentation survey of Fena Reservoir, Guam, Mariana Islands, 1979

Fena Reservoir, in south-central Guam, was constructed in 1950-51 to provide a dependable water supply for the U.S. Navy. At the request of the U.S. Navy, the U.S. Geological Survey conducted a sedimentation survey of the Fena Reservoir during the months of November and December 1979. The sedimentation survey showed that at the spillway elevation, the reservoir has a surface area of 195 acres and a volume of 7,863 acre-ft. Data from a network of 30 triangulation stations and 32 cross sections indicated a decrease of 440 acre-feet in reservoir capacity since 1949 due to the accumulation of sediment. Area capacity curves for 1949, 1973, and 1979 and a bathymetric map of the reservoir were constructed. The combination of denser water due to lower temperature and suspended sediment load appears to create a density current within the reservoir. Particle size analyses and unit-weight computation are provided to define the physical characteristics of the accumulated sediment. (Author 's abstract)