Thursday, May 29, 2008 - 3:00 PM
583

Integrated assessment of intermittent streams of the Colorado Plateau, Southern Utah

Anne M. D. Brasher, Utah Water Science Center, U.S. Geological Survey, 121 West 200 South, Moab, UT 84532 and David Thoma, Inventory and Monitoring Program, National Park Service, Northern Colorado Plateau Network, Zion National Park, Springdale, UT 84767.

Intermittent streams play a critical role in arid southwestern ecosystems of the U.S., where water is a scarce but vital resource.  Significant threats to these systems include grazing, off-road vehicle use, groundwater diversion, natural gas exploration, and fire.  Consequently, development of assessment criteria is a key management priority.  As the first step in this process we conducted integrated assessments in seven streams along the Colorado Plateau (southern Utah), representing a range of flow conditions from perennial to temporary.  At each site we measured water-quality, physical habitat, and collected both qualitative (multi-habitat) and quantitative (targeted-habitat) benthic macroinvertebrate samples.  At all sites, qualitative samples had higher taxa richness than quantitative samples.  Intermittent streams (typically a series of isolated pools) were dominated by ostracods, chironomids, molluscs, and annelids.  Perennial sites in streams with intermittent reaches were dominated by non-midge Diptera, Ephemeroptera, and Coleoptera.  Perennial streams with relatively large volume and flow velocity were dominated by Ephemeroptera and Diptera (especially simuliids).  Trichoptera were rare at most sites.  These results indicate that standard metrics (e.g. EPT, tolerant-taxa) may be inappropriate for streams of the Colorado Plateau, and that an index of biotic integrity for these systems may need to be stratified based on flow characteristics.


Web Page: Intermittent streams, arid southwest, macroinvertebrates

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