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QUANTIFYING THE REGIONAL EFFECTS OF MINE DRAINAGE ON STREAM ECOLOGICAL CONDITION IN THE COLORADO ROCKIES FROM PROBABILITY SURVEY DATA
Citation:
Herlihy, A. T., J M. Lazorchak, F H. McCormick, D J. Klemm, M E. Smith, W. T. Willingham, AND L. P. Parrish. QUANTIFYING THE REGIONAL EFFECTS OF MINE DRAINAGE ON STREAM ECOLOGICAL CONDITION IN THE COLORADO ROCKIES FROM PROBABILITY SURVEY DATA. Presented at EMAP Symposium on Western Ecological Systems, San Francisco, CA, April 5-9, 1999.
Description:
Runoff from both active and inactive metal mining has contaminated waters and sediments in the Southern Rockies Ecoregion. In 1994 and 1995, as part of its Regional Environmental Monitoring and Assessment Program (REMAP), the USEPA conducted a probability survey of wadeable streams in the mineral belt portion of the Southern Rockies in Colorado. Over the two summers of the study, samples were collected from 73 probability sites (representing 6,630 km of streams) and 13 hand-picked sites for indicators of fish and macroinvertebrate assemblages, physical habitat, and sediment and water chemistry and toxicity. Using stream chemistry, sites were classified into Least Disturbed, Mixed Impacts, and Mine Drainage Impacted Chemical Classes. The study area had roughly equal stream lengths in each of the three classes. Overall, an estimated 1,844 km (28%) of stream length had a sulfate signature of mine drainage, 438 km (7%) exceeded state Zn criteria and 375 km (6%) had water toxic to the test organisms. Sites with elevated metals and toxicity were concentrated in the mine drainage chemical class. Water column toxicity tests (48 hour fathead minnow and Ceriodaphnia survival) were better indicators of mine drainage stress than sediment toxicity test (seven day Hyalella azteca survival). Also, stream macroinvertebrate assemblages were more sensitive to mine drainage stressors than fish assemblages. The synoptic survey data gathered in the REMAP project provides a useful framework and baseline for assessing the extent of mine drainage impacts in the Colorado Rockies.