Characterization of water quality in selected tributaries of the Alamosa River, southwestern Colorado, including comparisons to instream water-quality standards and toxicological reference values, 1995-97

A comprehensive water-quality sampling network was implemented by the U.S. Geological Survey from 1995 through 1997 at 12 tributary sites to the Alamosa River. The network was designed to address data gaps identified in the initial ecological risk assessment of the Summitville Superfund site. Tributaries draining hydrothermally altered areas had higher median values for nearly all measured properties and constituents than tributaries draining unaltered areas. Colorado instream standards for pH, copper, iron, and zinc were in attainment at most tributary sites. Instream standards for pH and chronic aquatic-life standards for iron were not attained in Jasper Creek. Toxicological reference values were most often exceeded at Iron Creek, Alum Creek, Bitter Creek, Wightman Fork, and Burnt Creek. These tributaries all drain hydrothermally altered areas.