Water Resources of Colorado

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

by Roderick F. Ortiz and Sheryl A. Ferguson

Available from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver Federal Center, Denver, CO 80225, USGS Water-Resources Investigations Report 00-4170, 29 p., 1 fig.

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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.

Table of Contents



Purpose and Scope

Description of Study Area

Methods of Investigation

Data-Collection Methods

Data-Analysis Methods

Estimation of Hardness for Selected Sites

Lack of Dissolved-Metal Data for Selected Sites

Use of Censored Data

Comparison of Aggregated Data to Instream Standards

Comparison of Instantaneous Data to Instream Standards and Toxicological Reference Values

Summary Statistics for Selected Tributary Sites

Comparisons to Instream Standards and Toxicological Reference Values

pH Comparisons

Copper Comparisons

Iron Comparisons

Zinc Comparisons




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Water Resources of Colorado

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