Mongolia's nomadic herders are concerned about the future of already-limited water supplies due to Rio Tinto's $6 billion Oyu Tolgoi, the world's largest undeveloped copper-gold project in the South Gobi desert region.

Oyu Tolgoi was 94 percent complete in July and is slated for commercial production in the first half of 2013. The Mongolian government holds a 34 percent stake in the project, expected to account for about 30 percent of Mongolia's annual economic output.

The mine, in the South Gobi desert region, holds an estimated 41 billion pounds of copper and 21 million ounces of gold, The New York Times reports.

The region covers an area of 135 square miles and is home to 3.8 million livestock, including camels, horses, cows, sheep and goats, which require some 31,600 cubic meters of water each day.

That compares with the water needs of an estimated 10,000 cubic meters per day for residents in the sparsely populated region.

Extracting copper from the mine, however, is a water-intensive process.

A World Bank assessment indicated that in 2010, Oyu Tolgoi used about 67,000 cubic meters of water a day and the government-owned Tavan Tolgoi coal mine consumed 76,000 cubic meters daily.

D. Enkhat, director of Mongolia's ministry of environment and green development, says that the water consumption for Oyu Tolgoi is closely monitored and doesn't exceed the maximum allowance of 230 gallons a second for the construction phase, Inter Press News Agency reports.

Still, each mine's water consumption was more than double that of all the livestock in the entire region, says the IPS report.

Shar, a herdsman who like many Mongolians goes by just one name, told the Australian Broadcasting Corp. that prior to the development of Oyu Tolgoi, animals would drink from open water sources.

"This was a pristine natural environment. But Oyu Tolgoi has closed off these old open water sources which it owns now," Shar said. In their place, the herdsman said, Oyu Tolgoi has built two or three wells but he has heard rumors that those may be closed by winter.

As for the deep aquifer, Cameron McRae, Rio Tinto's director in Mongolia and also the chief executive of Oyu Tolgoi, told ABC that "we don't actually know if it recharges but if it doesn't recharge then we're only going to draw down on it by 20 percent in the first 30 years of the operation and nobody else uses that aquifer so it's not a shared water resource that others were using at the time of the discovery."