Bathymetric Study of Patillas Reservoir, Puerto Rico

Client: Puerto Rico Electric and Power Authorithy (PREPA)

Contract Period: 2016 (Project Duration: 4 months)

A sedimentation survey of Patillas reservoir (Lago Patillas) in the municipality of Patillas, Puerto Rico, has been prepared using field data collected from March 17 to April 1, 2016. This sedimentation study was performed to update the reservoir storage volume.

The reservoir bathymetric mapping was performed using a boat equipped with an integrated GPS – SONAR system downloading data to an onboard computer, and these data were post-processed in the office. Bathymetric survey was performed using Survey Case-200 S bathymetric survey equipment manufactured by Specialty Devices Inc. The system included the onboard computer, depth sounder (200 kHz), and GPS system


Sections were surveyed at 50-meter intervals starting at the dam and at the spillway, and extending upstream along the Río Grande de Patillas and Río Marín. A total of 83 cross sections were surveyed. Because of the reservoir drawdown, the upstream and lateral portions of the reservoir had inadequate water depth (or no water), and could not be surveyed by boat. In these areas, ground survey was performed by conventional GPS survey techniques using a roving GPS unit transported by foot, thereby surveying the entire reservoir area up to elevation 67.67 m.