On 10 January 2014, I had the opportunity to travel through the Panama Canal from the Atlantic to the Pacific Ocean with nine alumnae from Smith College. As a civil engineer, this was an opportunity of a lifetime.
Unlike the Cape Cod and Suez Canals, passage through the Panama Canal is not at sea level. Instead, the ships are raised and lowered 85 feet at each end via a series of locks. From the Caribbean side, the ships go up through the locks, travel through Lake Gatun and the Gaillard Cut, and then step back down near Panama City before exiting into the Pacific. The 50-mile passage through the canal shaves 7,872 miles from a trip that would otherwise go around the tip of South America. The history and engineering of the canal are fascinating, and David McCullough’s book, The Path Between The Seas, provides a detailed account of the trials and triumphs of the decades of design and construction that culminated in the 1914 opening of the waterway.
As our ship approached the Gatun locks shortly after dawn, two men in a small rowboat pushed out into the water in front of us. They were carrying the lines that would connect us to the silver locomotives that traveled alongside to ensure that our 106-foot-wide ship remained centered in the 110-foot-wide lock. When the miter gates closed behind us, water from above flowed via gravity into the chamber and floated our ship up to the level of the next lock. The process repeats in reverse to lower the ships back down to sea level.
The locks are impressive and, along with the huge container ships and the Centennial Bridge, are the charismatic stars of the show. However, the real story of the Panama Canal is one of hydrology. 52 million gallons of water are required for each ship to make the trip through the canal. That’s 15% more water than Smith College uses in a year. The water originates as rainfall over the Panama Canal Watershed (PCW), arriving predominantly during the 8-month rainy season. The 165-square-mile Gatun Lake, created by damming the Chagres River, along with the more recently created Alajuela Lake, store the water so that it can also be used throughout the year. In addition to supporting the canal traffic, that water is also the supply for cities of Colón, Panama City, and San Miguelito; however, the 270 million cubic meters of drinking water is only one-tenth of the water used to support the canal locks.
The charge for our ship to pass from the Caribbean to the Pacific was $200,000, and the Panama Canal Authority (ACP) generates toll revenues of $1.8 billion on approximately 15,000 transits each year. Because of the economic importance of the canal, the ACP thinks carefully about the management of its watershed and is currently engaged in reforestation projects. These will reduce sediment loads and associated dredging costs in the canal and will also reduce the treatment needs for drinking water.
There is also some hope that the presence of forest will slow the movement of water through the watershed, providing steadier flows during the dry season while reducing runoff during the rainy season. These services provided by the landscape (often called environmental or ecosystem services) are especially important now, as the canal is currently undergoing a massive expansion of the locks to allow more and even larger vessels to pass through. A significant part of the project is the design and construction of water-reutilization basins that enable 60% of the water used to raise and lower the ships to be recycled.
The Panama Canal is one of the largest and most impressive civil engineering works ever undertaken. Even so, it was humbling, and in some ways reassuring, to see how much the path between the seas depends on nature. My trip through the canal is something I won’t ever forget.
Director, Center for the Environment, Ecological Design, and Sustainability
Professor, Picker Engineering Program
 Smith College, 2010. Sustainability and Climate Action Management Plan.
 Fotos, M., F. Chou, Q. Newcomer, 2007. Assessment of existing demand for watershed services in the Panama Canal watershed, Journal of Sustainable Forestry, 25 (1-2), pp. 175-193.