As Panama embarks on a US$5.2 billion effort to widen the Panama Canal and double its shipping capacity by 2025, environmentalists and engineers alike are keeping their fingers crossed that the country won’t compromise a key watershed in the process.

Since the Panama Canal was completed in 1914, the Chagres River and Gatun Lake watershed has provided the all-important water needed to fill the locks of the world’s most important commercial canal. The watershed also has supplied drinking water for fast-growing Panama City, whose population now stands at two million.

The canal widening, which started last August and is scheduled to be completed in time to mark the canal’s 100th anniversary in 2014, involves building a third set of locks that will be 40% longer and 60% wider than the current lock system.

The locks are used to raise and lower ships heading to and from Gatun Lake, the transisthmian body of water that sits 26 meters (85 feet) above sea level and represents the majority of the 80-kilometer (50-mile) passage between the Atlantic and Pacific oceans. The new locks will accommodate so-called Post-Panamax ships, which can carry three times the cargo load of the largest vessels that currently squeeze through the canal.

But the new locks could also put an additional strain on the watershed. Even before the expansion project was proposed, the Panama Canal was already a water-guzzler, consuming some 55 million gallons of fresh water each time a ship passes through the locks. The canal averages 38 transits a day, for a total daily water consumption of more than 2 billion gallons. By comparison, the entire population of Panama City consumes around 200 million gallons of water each day, or roughly the same amount used by four ship passages through the locks.

The Panama Canal Authority, known here as ACP, its Spanish acronym, insists all of its studies show there is sufficient water to run the expanded canal at full capacity for a planning horizon of 25 years. Jorge de la Guardia, executive manager for the locks project, says independent studies conducted by the U.S. Army Corps of Engineers’ Hydrologic Engineering Center in Davis, California, confirm an adequate water supply with a “99% level of confidence.”

De la Guardia insists the canal does not waste water, as some conservationists allege. “There are lots of rivers that naturally dump that much water into the ocean each day,” he says. At the canal, he adds, “We’re not dumping water in the ocean, we are using it profitably.”

Still, those charged with safeguarding the watershed that supplies the canal warn Panama’s natural resources must be protected as a long-term investment, rather than viewed as a source of immediate commercial profit. “Without these natural resources, it’s difficult to imagine the country could prosper,” says Rosamaría Guerra, executive director of the Chagres National Park Foundation, which was created in 1985 to protect the main water basin supplying the Panama Canal.

Chagres National Park contains the sources of three rivers: the Chagres, the San Juan de Pequení and the Boquerón. Together, these rivers supply 40% of the water needed for the canal and 80% of the drinking water for Panama City and the city of Colón.

The 130,000-hectare (321,000-acre) park is also home to 114 species of mammals, 396 bird species, 95 reptile varieties and 79 species of amphibian, according to Guerra. The park’s diverse wildlife, including the endemic stripe-cheeked woodpecker (Piculus callopterus), the majestic harpy eagle (Harpia harpyja), the rare cocle salamander (Bolitoglossa schizodactyla) and the endangered brown-headed spider monkey (Ateles fusciceps), also have become an important ecotourism draw.

Last year, more than 100,000 tourists came to the area to nature-watch and visit villages of the indigenous Emberá people along the banks of the Chagres.

Guerra says conservation of the park isn’t enough; the area also needs to be reforested to maintain animal habitat and protect the watershed. She points out that the dry months of summer are becoming increasingly severe and falling water levels in the rivers and smaller lakes is “becoming more evident each year, and is a great source of concern to the people who live along the riverbanks.”

Failure to act now, she warns, could push the region past an ecological point of no return.

“People need to understand that reforestation is fundamental because it reestablishes affected ecosystems,” Guerra says. “If there is no forest, there will be no habitat for the animals or birds, which would mean an end to tourism, which would mean no more jobs would be created and those who have jobs would lose their source of income.”

Ocean commerce, therefore, should not be Panama’s only concern in protecting its forests and main watershed. Says Guerra: “This park plays a strategic role in [Panama’s] life, biodiversity, economy and culture.”

De la Guardia, the locks-project manager, insists the ACP considers environmental conservation a key to the long-term viability of the canal and to the financing of the canal expansion. He says lenders insisted on strict environmental assurances before agreeing to provide the US$2.3 billion required in outside financing for the project, and will monitor environmental-protection efforts.

The ACP’s conservation steps center on the design of the new lock system, which includes a series of basins that allow water to be reused from one lock chamber to the next. As a result, 60% of the water that enters the lock system from Gatun Lake will be reused in more than one chamber before eventually making its way to the sea. So instead of using 230% more water than the existing lock system (which, based on the size of the expanded locks, is how much more water they would require), the bigger locks will actually consume 7% less than the existing lock system, De la Guardia claims.

“It’s not the cheapest solution, but it makes sure we are maximizing the use of the existing watershed without affecting other areas,” De la Guardia says. “It would have been cheaper to build a new lake, but this was the solution that was the most environmentally and socially acceptable.”

Such environmental considerations, De la Guardia argues, mark a dramatic shift in the engineering paradigm employed in construction of the original canal at the beginning of the last century. The original lock system, he says, was designed entirely on previous ship-navigation experience, with no regard for environmental conservation. Still, he asserts, the engineers got lucky and unintentionally built a system that has protected Gatun Lake from serious levels of saltwater intrusion over the past century.

Had the original lock system been built with two chambers instead of three on each side of Gatun Lake, ocean water would have filtered into Gatun, making it a saltwater lake over the years. But De la Guardia says testing has shown that diluted salt water intrusion past the second chamber of the locks is completely flushed out by the third chamber, making the saline level in the lake “basically imperceptible.” (The smaller Miraflores Lake, which sits between the second and third locks on the Pacific side, does have an elevated saline count, independent studies show.) Says De la Guardia: “That wasn’t by design, but it turned out well.”

A century later, he asserts, engineers are not leaving such considerations to chance.

“This time everything is very scientific,” he says. “We have done very profound water-quality studies and we are developing a new three-dimensional model to monitor the quality of water in Gatun Lake.”

De la Guardia adds that if there is a measured increase in the lake’s saline content from the new locks, the whole system can be flushed and cleaned.

The head engineer says the ACP also is preparing for global-warming impacts by building the lock walls higher than originally planned in case ocean levels rise over the next century. “Climate change has been in the back of our minds, but it’s a difficult thing to measure,” De la Guardia says. More worrisome, he says, are the periodic El Niño drought cycles, especially since there has been a slight drop in the level of Gatun Lake since 1970.

Engineers say that as the population in Panama’s booming capital city continues to grow and shipping traffic increases, the water quality and levels of Gatun Lake will need to be checked continually.

In normal years, the area’s watershed will have enough water to supply the canal and the so-called third lane at full tilt, but the demand is growing. “By 2030 we are going to need to look for additional sources of water,” De la Guardia says.

John Reid, president of Conservation Strategy Fund, a nonprofit that specializes in applying economic expertise to developing-world conservation issues, analyzed the original canal-expansion proposal in 2000. Reid says the current plan is much less intrusive. The original plan called for the damming of three rivers and piping water from their reservoirs into Gatun Lake, a proposal that was extremely expensive and controversial—particularly among farmers it would displace.

Reid forecasts the environmental impact of the redesigned project will most likely be “modest in comparison,” adding that the canal expansion is less invasive than several other government damming and gold mine projects underway in other parts of Panama.

Reid also notes that in the case of the canal, everyone—regardless of motive—has a strong interest in preserving the watershed and its surrounding forest.

“The Canal Authority has an economic incentive to keep the watershed forest to prevent erosion [and silt buildup],” says Reid. (See Q&A—this issue.)

Indeed, the ACP claims it has an ambitious reforestation plan that will focus on the western edge of the watershed. There, land clearing by campesinos along several smaller rivers has boosted sedimentation and seasonal drying.

Yet some experts are less inclined to give the ACP the benefit of the environmental doubt. Ariel Rodríguez, a professor of zoology, ecology and environmental sciences at the University of Panama, questions the Canal Authority’s statistics, projections and intentions.

In addition to challenging the ACP’s figures regarding the salinity of the lake water, Rodríguez cites multiple comparative studies suggesting that by 2020, the canal’s real water consumption will be more than double what the ACP projects.

The professor also argues that the ACP is underestimating the increased water consumption of the region’s growing human population. Charges Rodríguez: “The ACP is expert in maintaining appearances and lying.”

According to Rodríguez, the current absence of organized opposition to the canal expansion is not due to a lack of grounds for objections but, rather, to a weak civil society in Panama. The professor also blames the national media, which benefited from the ACP’s strong advertising campaign prior to the referendum vote in Oct. 2006, for failing to inform the public about the project’s true risks.

Rodríguez acknowledges that a campaign to oppose the canal expansion has quieted considerably. Several formerly outspoken critics of the project did not respond to invitations to comment for this article.

However, if all goes according to the ACP’s long-term plan, environmentalists—or their children—might get a second chance to mount a strong anti- expansion plans in the future.

De la Guardia says a another canal expansion project is not out of the question 30 to 50 years from now. He adds: “We are building the third lane now, but we are already thinking of the fourth lane.”