Hydrology, metals, and aquatic physical habitat in the Upper Animas watershed, Colorado

The Upper Animas River watershed in southwestern Colorado is a watershed with historic mining districts with many small mines and mills and a few larger mines and mills. The numbers of trout may be limited by high flows during the spring runoff period and by winter streamflows. In some locations there are large particles on the stream surface that may provide cover to trout. but the presence of fines in the substrate in some areas and the presence of large particles on the surface probably limits use of the subsurface by fish. During some parts of the year metals in the interstecial waters are toxic to many aquatic animas when the stream waters are much less toxic. The concentration of copper and zinc appear to be constant during streamflows that cause the bed material would be moved by the high discharges. Copyright 2004 ASCE.