The gravity of the situation - Letters

Cruise Travel, Nov-Dec, 2002 by Lou Erlich

In an otherwise good article "Eco-Cruising in Central America" (Cruise Travel, October 2002), author Glen Petrie says of the Panama Canal: "We learned how the jungle watershed on the hills around the Chagres River provides a continual supply of water to flood the locks. Only this freshwater is used, not seawater, to prevent salt corrosion." Huh?

This has nothing to do with corrosion and everything to do with the fact that Gatun Lake is geographically higher than sea level, by 85 feet, and therefore water flowing under the power of gravity allows vessels to transit the canal without the need to expend both money and energy pumping water anywhere along the way. The flow is controlled by the system of locks.

Lou Erlich, Richboro, PA

Glen Petrie elaborates: Mr. Erlich is quite right about the convenience of gravity to flood the locks being a key benefit of the canal's design. Early designs considered using some seawater and were rejected for this reason, as well as the corrosion issue. As the excellent canal guide aboard our Pacific Explorer cruise pointed out, a system using only freshwater has kept the mechanics in perfect condition 88 years later. Another interesting fact: the same watershed generates electricity for the motors that open and close the lock gates--conservation ahead of its time.