A torrent of muddy mining waste unleashed by a dam breach in southeastern Brazil is now heading down a small river with high concentrations of iron oxide. The breach, which killed at least 84 people, is threatening to contaminate a much larger river which provides drinking water to communities in five of the country's 26 states.

190127160139109

The release of the muddy waste has already turned the normally greenish water of the Parapoeba River brown about 18km downstream from the southeastern city of Brumadhinho, where the broken dam is located.

The Parapoeba flows into the much larger Sao Francisco River, which provides drinking and irrigation water to hundreds of municipalities and larger cities such as Petrolina in the state of Pernambuco, 1,400km away from Brumadhino in Minas Gerais State. In a Pataxco Ha-ha-hae indigenous community near the Paraopeba River, dead fish and refuse, including plastic sandals were visible along its banks on Tuesday.

The village chief said on Tuesday that Brazilian environmental agents warned his community to stop fishing in, bathing in and using river water for the plants they cultivate as food.

"We used the river to take baths, to fish, to water our plants and now we can't do any of that," said chief Hayo, who uses only one name. "We can't even water our plants because they say it damages the soil."

Communities at risk

As grieving relatives of the dead bury family members and searchers continue looking for 276 people who are missing, Brazilian authorities and companies involved with river water management are trying to figure out how to prevent the contamination

Their main focus is the Retiro Baixo hydroelectric dam and plant complex about 300km from Brumadinho. Officials and environmentalists hope the dam's reservoirs can be used to isolate the muck so it can be cleaned before the water is released to head further downstream to the Sao Francisco River.

"A lot of communities and cities in different states depend on that river to live," Carlos Rittl, a director at Brazil's Climate Observatory environmental nonprofit group, told the AP news agency.

The "wave" of muddy water and waste is expected to reach the dam between February 5 and February 10, Brazil's National Water Agency has said. Researchers from the Geological Survey of Brazil are monitoring the velocity of the mine waste and the estimate could change.

The contaminated water was unleashed on Friday when a dam storing iron ore waste for big Brazilian mining company Vale SA breached. Officials warned on Tuesday that the death toll was expected to rise significantly, with no one rescued alive since Saturday.

Vale said in a statement it was trying to find ways of containing the spread and planned to install a fabric barrier to retain residues where the river reaches the city of Para de Minas, about 40km from Brumadinho. The company may also build levees near the Brumadinho mine in an effort to prevent the sediment from moving.

'A huge effort'

Among those hired to try to keep the waste in place were experts who helped the company when a dam at another iron ore mine owned jointly by Vale and BHP Billiton ruptured in 2015, killing 19 people.

170518073228854

Rivers contaminated by mining tailings, which contain high levels of fine particles of iron ore or other heavy metals, can end up contaminated for years or decades, said Joao Paulo Machado Torres, a professor who heads the Environmental Biophysics programme at the Federal University of Rio de Janeiro.

He sampled water from the river contaminated by Vale's 2015 dam failure, which left 250,000 people without drinking water and killed thousands of fish.

Efforts are still under way to clean up the environmental damage from that dam failure, and Torres said repairing ecological damage from Friday's dam breach will take "a huge effort to bring any sort of life back."