A thick layer of toxic foam covers the surface of São Paulo's largest and most important Tiete River.
Untreated domestic runoff from 39 cities in the metropolitan area is killing aquatic river life as well as polluting riverbanks and emitting noxious odors in riverside communities.
Mata Atlantica, an NGO and activist group that has been pushing for the clean-up of the river for years, said on Wednesday (10/13) that the government has fallen behind in its plan to restore and clean up the river.
Malu Ribeiro, a spokesperson for the group, says the energy company controlling upriver dams opened the gates after rain caused a rise in reservoir waters.
"This is the result of an environmental crime, caused on 29 August, when the hydroelectric dams located in the metropolitan areas of São Paulo and the interior were opened," Ribeiro charged while inspecting the river.
Ribero claims that the company did not consider the accumulation of contaminated sediment at the bottom of the dam gates, which occurred after months of drought when the gates were closed due to low water levels.
The sudden release of water brought with it tons of chemicals and wastewater that had accumulated over months, leaving a toxic white foam on the surface of the river, emitting a cloud of sulfur and killing thousands of fish.
Tiete River, with a length of 1150 kilometers (714 miles) and a basin area of 150 thousand square kilometers (58,000 sq. miles), runs along the coast through São Paulo and dozens of smaller municipalities, feeding an important hydroelectric power plant that supplies energy to a large part of the region.
The river has been heavily polluted for decades, and government efforts to clean up the river have been insufficient, leaving residents and visitors complaining about noxious odors from rotting animals and plants affected by the pollutants in the water.
The NGO says the river lacks oxygen and is heavily polluted with toxic chemicals that could cause respiratory ailments to residents living nearby.