Design of the New Spillway for the Panama Canal

When the current spillway of the Gatun Lake of the Panama Canal was designed in the early 1900’s, very little information was available concerning the hydrology and hydraulics of the Chagres river. The current spillway capacity was designed based on discharges calculated from historical flood elevations along the river and a maximum operational lake level. In following years, the maximum operating level was raised to satisfy additional water demands and accommodate increasing vessel drafts.

As part of the preparation of an overall Master Plan for expansion of the Panama Canal, the Panama Canal Authority (ACP) studied a number of options to upgrade the Canal infrastructure and existing infrastructure limitations, including the current capacity of Gatun Spillway. After more than one hundred years of operation, a significant amount of hydrologic data has been collected. Different studies have found that the current spillway capacity is insufficient to safely handle maximum floods.

The international standards, for dams such as Gatun, indicate that the spillway must be designed to meet the Probable Maximum Flood (PMF). Therefore, additional spillway capacity was needed in order to meet this criterion and to protect the Lake and the viability of the Canal system itself. This paper analyzes the main hydraulic aspects of the design of the new spillway, including the comparison of the results of a three dimensional numerical modeling and the physical model built for the project.