The Hydrology of Mine Pit Lakes

If you ever have the opportunity to visit a world-class, open-pit mine, do it. Whether horrified or proud, there’s no substitute for looking into a 1,500-foot deep, two-mile long, man-made abyss to grasp the magnitude of human industriousness. Most of the large mines extend below the water table and will eventually fill with groundwater to form pit lakes. About forty pit lakes are expected to form in Nevada, predicted to range in size from mere puddles up to 400,000 acre-feet; and there may be another couple dozen that will form in other states across the Southwest. If you believe the groundwater models, most of these will be terminal basins – net sinks that pull in groundwater from all sides, evaporatively concentrating solutes in the lake. No need to rush, of course, because these pit lakes are expected to remain for thousands of years. This, of course, is the problem. – Houston Kempton, Integral Consulting, Inc., Boulder, CO