Berkeley Pit, an open pit copper mine, Butte, Montana
Source: NASA Earth Observatory
A report in today's New York Times says there may be huge deposits of valuable minerals in Afghanistan (remind me of why that war was started), and the country could enjoy substantial wealth from their exploitation. Several skeptics have questioned the news, but assuming it is true, exploitation, if it happens in the not too distant future, is neither going to be easy nor cheap. The war has demonstrated the problems of a country with minimal transportation infrastructure, where electricity is sporadic even in larger places, and where political control is far from firmly established. Another problem could be the absence of adequate water supplies.
Most types of mining use vast quantities of water and often contaminate that water. Hydraulic processes use water to dislodge ore. In the California and later the Yukon gold rushes in North America huge areas were damaged by hydraulic processes, and more than a century and a half later some of the water flowing over the abandoned workings contains quantities of mercury dangerous for humans. More recently hydraulic mining was used in Malaysia to dislodge tin ores where dredging of river bottoms has also been utilized.
While hydraulic techniques are limited to ores at or near the earth's surface, underground and deep pit mining also demand large quantities of water to wash and treat ores, and sometimes to carry crushed ore from a mine considerable distances to processing facilities. Deep pit mines, like the Berkeley pit in Butte, Montana shown above, are potentially hazardous for nearby streams and rivers. The pits can fill with water, and the water can become highly toxic. Water flooding the abandoned Montana pit is so toxic that birds landing on its surface have reportedly died! Sitting close the Continental Divide, water released and ground water seeping out from the mine could contaminate either the Missouri River drainage or the Columbia drainage and make use of river water problematic far downstream.
Even when the processes do not use much water, mining can harm water supplies as mining wastes pollute lakes, streams and aquifers. Breaking into ore bodies can unleash previously trapped underground aquifers contaminated with arsenic and other toxic elements and chemicals. Ores in contact with surface water also unleash contaminants, and very toxic materials are used in some mining processes, including cyanide and arsenic.
