Assessing the Condition of Riverine Systems Using Multimetric Indices: An Example from Oregon's Calapooia Basin

Streams and rivers of the Western United States are susceptible to the combined influences of climate change and an expanding human population.  Empirical tools for assessing instream conditions play a critical role in monitoring change, preventing degradation, and mitigating impacts to help ensure the resilience of our freshwater communities.  Previous efforts have made notable progress towards integrating quantitative methods into multimetric indices (MMIs) developed for national and regional assessments, and provide a quantifiable view of varying conditions across the landscape.  To explore how well the sparse distribution of sample sites used in large-scale assessments represent conditions that may be highly variable at finer spatial resolutions, we use data from various locations within Oregon’s Calapooia basin.  We investigate multiple established methods for deriving MMIs using taxon-specific tolerances to disturbance and metrics developed for the Western mountains.  We examine and compare spatial patterns in condition estimates based on different biological and physical characteristics (fish, macroinvertebrates, habitat).  Applying MMIs at fine spatial resolution can provide a better understanding of both the natural landscape patterns in freshwater assemblages, and the anthropogenic effects influencing them. This understanding can help guide and prioritize restoration and management.