The recently completed Campos Novos Dam in southern Brazil failed last week to contain the water in its reservoir, releasing all the water impounded behind the 626-foot (202-meter) tall structure.
Aerial photographs released Tuesday by Friends of the Earth Brazil show major cracks at the base of the dam, suggesting irreparable damage.
"If this uncontrolled release had happened during the rainy season thousands of people could have been drowned," warned Glenn Switkes, International Rivers Network (IRN) Latin America campaigns director.
The US$671 million Campos Novos Dam is located on the Canoas River. It is the power behind a 880 megawatt hydroelectric generating station.
Campos Novos is the world's third tallest dam built with a concrete face filled in with rock. Switkes says this design has become increasingly common in recent years for very high dams.
The dam was built by a consortium led by Brazilian construction giant Camargo Correa and engineering consultants Engevix.
Major funders for the dam included the Inter-American Development Bank and the Brazilian state-owned National Bank for Economic and Social Development.
Campos Novos' 35 year build and operate concession was awarded in 1998. It is owned by Enercan, a consortium made up of Brazilian power company CPFL Energia with 48.7 percent; Brazilian aluminum makers CBA with 22.7 percent; metallurgy company CNT with 20 percent; and the state-controlled companies of Rio Grande do Sul CEEE with 6.5 percent, and Santa Catarina Celesc with two percent.
Almost as soon as the reservoir started filling up with water in October, it slowly began leaking. Engineers blamed a faulty diversion tunnel.
But last week the reservoir suddenly emptied, falling over 160 feet (53 meters) in a few days. That water raced down the parched riverbed and into the reservoir of a dam downstream that was almost empty due to a severe regional drought.
Enio Schneider, president of the Enercan consortium, said on June 22 saying that the dam itself was not threatened because the reservoir draining occurred through a diversion tunnel which "is an isolated structure" from the dam.
But aerial photographs taken on June 24 suggest that the tunnel failure has seriously undermined the dam's structural integrity.
The Movement of Dam Affected Peoples (MAB), which represent farmers who have lost land or been evicted by dams, had already written a letter in May to the dam's funders and environmental authorities warning them of continued leakage from the reservoir. They voiced worry about flood dangers for people downstream, but got no response.
Controversy has swirled around the Campos Novos project with allegations of miserly compensation for residents evicted to make way for the dam and reservoir.
Following round-ups of community leaders and violent police suppression of protests, the Brazilian MAB registered complaints with international agencies, and the United Nations launched an investigation of human rights violations at Campos Novos.
In total 750 families, about 3,000 people, have been displaced by the dam, and not all have received indemnifcation or resettlement.
Several thousand more people live downstream of the dam, but are not considered by the dam builders as eligible for compensation, even though fish resources and the fertility of the floodplain are affected by the dam's construction.
Switkes alleges that the consortium is failing to protect the residents who live downstream from a potentially catastropic dam failure that could wash their homes away if the dam failed during the rainy season.
"The company has been covering up the extent of the damage, the cost and time of repairing or rebuilding the dam, and the potential risks to people and property downstream," he said. "The company did not disseminate any information, despite the dangers posed by the weakened structure."
The consortium has sent engineering crews to the scene, and is in the process of deciding how to handle the situation.
Worried about the risks to the inhabitants of the cities in case the river overflows into the states of Santa Catarina and Rio Grande Do Sul, the Movement of Dam Affected Peoples sent a technical team to the site to follow the measures taken by the New Fields Energy S/A (Enercan), the company responsible for the workmanship of the dam.
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