FEATURE-Johannesburg gold riches spawn acid water woes

* Acid water leakage could hit Johannesburg in coming months

* Government trying to figure out who pays the bill

* Economy could be eroded by toxic leakage problem

By Jon Herskovitz

JOHANNESBURG, Feb 8 (Reuters) - South Africa's city of gold, Johannesburg, may soon start being eaten away by acidic water flowing from the mines that created its astronomical fortunes.

Mines dug more than a century ago stretching about 40 km (25 miles) along one of the world's largest gold deposits have reached their water storage limit and will start leaking a toxic cocktail of chemicals in the coming months, independent experts and government officials have said.

If left unchecked, acidic mine water is expected to foul up works near the country's famed Apartheid Museum, flood basements in downtown Johannesburg and then seep into the streets of the city of about 4 million people.

"The threat of acid water decanting from old mine workings is a real and present danger. It poses a threat to our economy, environment, health and history," Terence McCarthy, a professor of geosciences at the University of Witwatersrand, wrote in a report.