USGS Colorado Water Science Center

Geochemistry of Red Mountain Creek,
Colorado, Under Low-Flow Conditions,
August 2002

By Robert L. Runkel, Briant A. Kimball, Katherine
Walton-Day, and Philip L. Verplanck

USGS Scientific Investigations Report 2005-5101, 78 p., 37 figs.--ONLINE ONLY

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The citation for this report, in USGS format, is as follows:
Runkel, Robert L., Kimball, Briant A., Walton-Day, Katherine, and Verplanck, Philip L., 2005, Geochemistry of Red Mountain Creek, Colorado, under low-flow conditions, August 2002: U.S. Geological Survey Scientific Investigations Report 2005–5101, 78 p.


Red Mountain Creek, an acid mine drainage stream in southwestern Colorado, was the subject of a synoptic study conducted in August 2002. During the synoptic study, a solution containing lithium chloride was injected continuously to allow for the calculation of streamflow using the tracer-dilution method. Synoptic water-quality samples were collected from 48 stream sites and 29 inflow locations along a 5.4-kilometer study reach. Data from the study provide profiles of pH, concentration, and mass load with a high degree of spatial resolution. Despite the presence of 10 circumneutral inflows, pH remained below 3.4 at all stream sites. Concentration profiles indicate that dissolved concentrations of aluminum, cadmium, copper, lead, and zinc exceed chronic aquatic-life standards established by the State of Colorado along the entire study reach. Comparison of total recoverable and dissolved concentrations suggests that most constituents were transported conservatively. Exceptions to this pattern include arsenic, iron, molybdenum, and vanadium, four constituents that were subject to precipitation and(or) sorption reactions as the addition of a circumneutral tributary resulted in a slight increase in instream pH. Evaluation of data from the 29 inflow locations indicates a sharp contrast between the east and west sides of the watershed; inflows from the east side have high constituent concentrations and acidic pH, whereas inflows from the west side have lower concentrations and generally higher pH. Loading profiles, the product of streamflow and concentration, are used to rank potential sources of metals and acidity within the watershed. Four sources account for 83, 72, 70, 69, 64, and 61 percent of the aluminum, iron, arsenic, zinc, copper, and cadmium loading within the study reach, respectively. All four sources appear to be the result of surface inflows that have been affected by mining activities. The relatively small number of major sources and the fact that they are attributable to surface inflows are two factors that may facilitate effective remediation.




Purpose and Scope

Description of the Study Area



Tracer Injection and Synoptic Sampling

Loading Analysis

Geochemistry of Red Mountain Creek Under Low-Flow Conditions, August 2002

Constituent Concentration and pH

Mass Loads

Load Profiles

Major Sources of Metals

Other Potential Sources

Implications for Remediation

Additional Sources of Data

Summary and Conclusions

References Cited

Appendix 1. Estimating Streamflow Using the Tracer-Dilution Method

Appendix 2. Spatial Profiles of Concentration—Additional Constituents

Appendix 3. Total Recoverable Loads—Additional Constituents

Appendix 4. Additional Data—April 2003 and September 2004

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