This dataset contains the shapefile of the bathymetric contours generated from field data collected in the Lago Caonillas between September and November 2012 by U.S. Geological Survey. The 2012 bathymetric survey was conducted using a bathymetric/land survey system, consisting of a global positioning system (GPS) coupled to a digital depth sounder. A total of 155 survey navigation lines were established at 50 meter (m) intervals, beginning at the dam and continuing upstream along the river branches of the reservoir. Geographic position (accuracy of less than 2 m) and water depths (accuracy of 2 centimeters [cm] ±1 percent of the measured depth) were acquired simultaneously using the GPS interfaced to the depth sounder. Data points were color-coded according to their specific depths, and same-color points were connected with a line to draw depth contours. Lago Caonillas is owned and operated by the Puerto Rico Electric Power Authority (PREPA) since 1996. Because of the importance of Lago Caonillas to the North Coast Superaqueduct, the U.S. Geological Survey (USGS), in cooperation with PRASA, conducted a sedimentation survey of Lago Caonillas between September and November 2012 to update estimates of the reservoir’s storage capacity.