Sunday, August 10, 2008
Itaipú Dam , Brazil/Paraguay border, South America
Built between 1975 and 1991, the Itaipú Hydroelectric Power Plant is situated on the Paraná River between the cities of Guaira, Brazil, and Salto del Guaira, Paraguay. Including the reservoir created by its dam, the system extends about 125 miles (200 kilometers) along the river; it is the largest hydroelectric facility in the world. It supplies about a quarter of Brazil’s south, southeast, and west-central regional demand, and nearly 80 percent of Paraguay’s total electrical energy. In 1995 the American Society of Civil Engineers nominated Itaipú as one of the seven wonders of the modern world, on the basis of its “advances, engineering challenges and long-term significance.” Beyond the staggering scale of the engineering project, Itaipú is also important politically (because of the dual ownership of Brazil and Paraguay) and environmentally.
The two nations recognized the energy potential of the Paraná River, the seventh largest in the world, that forms their mutual border. In 1966 they signed the Ata do Iguaçu (Act Iguaçu), a joint statement agreeing to equally share the energy. In 1970, a consortium comprising the U.S. firm IECO and the Italian company ELC successfully tendered to conduct a thorough evaluation of resources, and in April 1973 the Treaty of Itaipú set out details for the creation of the power plant. A year later the Itaipú Binacional corporation was established to administer the financing, construction, and management of the dam. Construction work began in January 1975 and reached its peak in 1978, when about 40,000 people were engaged on the massive undertaking, described by one source as “a labor of Hercules.” The first of eighteen 700-mega-watt generating units (nine serve each country) was commissioned in December 1983, and Paraguay’s electrical grid went on-line in March 1984. Brazil followed in August, and the whole system, generating 12,600 megawatts, was operational by April 1991. Two more generators will be installed by 2003, bringing Itaipú’s capacity to 14,000 megawatts. The dam was projected to cost U.S.$3.4 billion but the final cost reached between $1.8 billion and $20 billion.
Itaipú’s complex series of dams was built after the Paraná was rerouted through a 1.3-mile-long (2.1-kilometer) diversion channel, completed in October 1978, which entailed removing over 50 million tons (45.5 million tonnes) of earth and rock. Together, the great walls stretch 4.8 miles (7.7 kilometers) across the Paraná River, impounding a 125-mile (170-kilometer) reservoir that holds 28.54 billion tons (26.4 billion tonnes) of water. Tourist brochures boast that the dams contain enough concrete to build five Hoover Dams and enough steel for 380 Eiffel Towers. The main hollow gravity-type concrete dam, with a crest height of 640 feet (196 meters), is connected to the spillway (on the right bank) by a concrete buttress-type wing dam, which in turn is linked to a small earth- and rock-fill dike. On the left bank another rock-fill structure links the main dam and an earth-fill dam. The partly submerged, 1,055-yard-long (968-meter) powerhouse sits on the riverbed at the toe of the main dam; fifteen of the generators are in the main powerhouse and the others on the diversion channel.
The resettlement of people—Ava-Guarani Indians and Mestisos—on reservations and the disruption of their lives have had undesirable social effects, both on the displaced people and their new neighbors. Among other consequences, especially in the early stages of dam construction, was the enormous impact on natural vegetation. The binational Forest Management Project, initiated in the late 1970s, aimed to maintain ecological equilibrium and sustainability within the surrounding forests. Reforestation programs and the creation of a number of forest reserves eventually reduced the potential damage by half. It is estimated that 11.5 million plant species were rescued. Fauna rescue and relocation programs saved thousands of animals, birds, and insects, representing over 400 species.
Captive breeding programs will eventually allow the release of rare and endangered creatures into their natural habitat. The Itaipú project has demonstrated that, with careful management, even large-scale socioeconomic development is compatible with environmental conservation.