How does the Panama Canal work?

The canal crosses the isthmus of Panama, connecting the Atlantic and Pacific and saving ships the long passage around South America. It is not a sea-level cut. Ships enter a series of locks that raise them roughly 85 feet to the level of Gatun Lake, an artificial lake created by damming the Chagres River, cross the lake and the excavated Culebra Cut, then descend through locks on the far side. Each transit takes eight to ten hours. The lock chambers fill and empty entirely by gravity, using fresh water from the lake, with no pumps involved.

That water requirement is the canal's central vulnerability. Every transit sends tens of millions of gallons of fresh water to the sea, and the supply depends on rainfall in the watershed. Severe drought has repeatedly forced the authority to reduce daily transits and impose draft restrictions, which ripples through global shipping schedules and rates, and this has become a recurring rather than exceptional problem. Water-saving basins were included in the newer locks to recycle a portion.

The history is consequential. A French attempt in the 1880s under Ferdinand de Lesseps failed after enormous loss of life to yellow fever and malaria and financial collapse. The United States backed Panamanian separation from Colombia in 1903, secured rights to the zone, and completed the canal in 1914 after mosquito-control work by William Gorgas made the project survivable. The Torrijos-Carter Treaties of 1977 transferred control to Panama, completed in 1999. An expansion opened in 2016 added larger locks accommodating neo-Panamax vessels, and ship dimensions worldwide are still designed around canal constraints.