In order to evaluate the evaporation estimates using Bellini plate atmometer, a comparison study was carried out from 1997 to 2001, we operated a side-by-side set of continuous measurements, in the lab clearing, comparing the Bellini plate atmometers and a 1.2-meter diameter, insulated, type-A evaporation pans of the type used by the Panama Canal Authority. Up to three Bellani-plate gages were located next to a Pan and observed for more than 5 years.