Reporting from Johannesburg, South Africa — The spring, just over 20 miles northwest of Johannesburg, flows blood red.
It is toxic, highly acidic and full of heavy metals, so nasty that newly weaned impala and other animals in the Krugersdorp Game Reserve downstream can't drink the water — and some of them die of thirst.
The water, a poisonous legacy of the gold mining industry, is dead. Not one living organism survives in it.
Millions of gallons of the same kind of toxic water lie underneath Johannesburg, a city of nearly 4 million people, and it's rising 50 feet a month.
The technical term is acid mine drainage. If nothing is done, subterranean parking garages will fill with the toxic red water in about two years' time. Tunnels for electrical cables and underground railway stations will flood. And unnatural crimson streams will spring from the ground across the suburbs to the east of Johannesburg as the rising water escapes.
Although South Africa's government has resolved to act, experts are warning that unless work starts soon, in just months, it will be too late to build the pumps and water treatment plants needed.
"The government has had acid mine drainage on its urgent agenda since 2009 but has yet to act," said University of the Witwatersrand geology professor Terry McCarthy, who released a study on the problem Thursday in Johannesburg.
"We have to do something. We can't let things take their natural course."
The city of Johannesburg grew fat on gold.
It exploded in a gold rush after the metal was discovered in 1886. Gold mines operated along a 25-mile strip from Roodepoort to the west of Johannesburg to Boksburg to the east, as hundreds of mining companies gouged out a gigantic hole under the city and its suburbs.
The void, McCarthy calls it.
Flying into the city, you see gigantic heaps of earth left over from gold extraction. From the ground they loom like mountains. Unemployed men clamber up and down like ants on a giant anthill.
When rain falls, water runs off the hills and much of it is absorbed by the earth. The water turns toxic when it reacts with heavy metals underground.
When the mines were functioning, pumps siphoned the water away. But one by one the gold mines under Johannesburg were shut down as the gold ran out. The last one — which was pumping all the water from "the void" — was East Rand Proprietary Mines, which stopped pumping in 2008.
McCarthy warned that current mining operations in other parts of South Africa were doing even more damage, and would eventually pollute some of Johannesburg's main drinking water sources, the Vaal dam and Vaal River, posing greater costs for future generations.
"We are on the road to catastrophe," he said.
McCarthy said there was an urgent need for a geological survey to discover the lowest areas in Boksburg, the suburb that will be first affected if pumps aren't ready in time. He said it would take a year to get pumps and treatment plants installed.
He said some of the toxic water from the mines is polluted with uranium.
Environmental scientist Shan Holmes of Realsearch, a private environmental management company, said water resources around Johannesburg were grossly contaminated by mining.
"We haven't looked at the environmental impact and long-term consequences," she said. "We're only looking at the costs of water treatment."
Holmes said she had extensive contact with U.S. scientists engaged in dealing with similar problems in the United States as a consequence of mining.
"They have thrown a ton more money at [the problem] than we have. When I speak to American scientists, they can't believe it. They think I have got the numbers wrong," she said, referring to the level of acidity and toxicity in the water flowing out of defunct mines.
Stephan du Toit, an environmental specialist with the Mogale municipality near the Krugersdorp Game Reserve, said at a meeting Thursday that the water flowing through the reserve had extremely high sulfate concentrates.
"We've picked up terrapins 500 meters from the nearest water source, looking for alternative habitat," he said. "Not even a microorganism can survive in the water.
"The young [animals] weaning from their mothers come trying to drink the water, and they just refuse to drink the water. They try to go back to their mothers, and there's a struggle between the young and the mothers. They eventually die."