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Scientific Investigations Report 2012–5017


Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10


Table 15. Summary of BEST variables and top models explaining patterns in diatom species relative abundance in the Molalla River, Oregon, July and August 2010.


[Algal taxa relative abundance values for July and August were averaged for this analysis. Abbreviation: D50, median particle size; mm, millimeter]


Variable Variable / model
correlation and
significance
Rho P =
Individual variables
Presence of local gravel bars 0.85
Maximum pH in September 0.84
2009 channel sinuosity 0.84
2009 specific bar area 0.71
Averaged active channel width 0.52
D50 particle size (mm) 0.39
Open canopy percent 0.35
Flood plain width (segment) 0.27
Low flow discharge (10 percent exceedance) 0.09
Presence of local streambed bedrock -0.07
Top combination models
Top 4-Variable Model 0.98 0.007
   Presence of local gravel bars
   Maximum pH in September
   Open canopy percent
   Presence of local streambed bedrock
Top 5-Variable Model 0.98 0.012
   Presence of local gravel bars
   2009 channel sinuosity
   D50 particle size (mm)
   Open canopy percent
   Presence of local streambed bedrock

First posted February 29, 2012

For additional information contact:
Director, Oregon Water Science Center
U.S. Geological Survey
2130 SW 5th Avenue
Portland, Oregon 97201
http://or.water.usgs.gov

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