Is pristine mountain water always clean and pure? Can streams unaffected by human activities and livestock influences be unfit for human consumption, or fish? A new study by the CGS has some surprising answers. The study examines specific areas in Colorado that have natural surface-water of poor quality because of that local geological regime.
The report identifies streams in eleven headwater areas of Colorado where surface water is acidic and has high concentrations of metals well upstream of any significant human impact areas.
Through detailed geologic mapping, the type and intensity of hydrothermal alteration is examined and the geology is correlated with surface-water chemistry. Many of the areas exhibiting intense hydrothermal alteration also contain historic mine sites. Because acid rock drainage from natural sources and mine sites combine to cause severe downstream water quality problems, it is important to differentiate the natural, or background water quality so that realistic cleanup goals for total water quality may be set. Book, 112 pages, 2 plates. B-54