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Scientific Investigations Report 2006–5101–D

U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5101–D

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Table 3. Spearman’s rank correlations between urban indicator and water-chemistry metrics and select environmental variables, Willamette River basin and surrounding area, Oregon and Washington.

[See appendix A for variable definitions. Correlation coefficients were considered strong when absolute value ≥ (bolded and shaded) and moderate when 0.66 > rho ≥ 0.5 (bolded). Abbreviations: ROADDEN, road density; TEQ, toxic equivalents; SPMD, semipermeable membrane device. Symbols: ≥, greater than or equal to; >, greater than]

Stream and reach-scale variables Urban indicators
Urban intensity
index (UII)
Impervious area
(percent)
POPDEN00 Urban + agriculture
(percent)
ROADDEN
Hydrologic variation metrics
Number of falling events > 5×median (PeriodF5) 0.69 0.64 0.68 0.52 0.70
Number of falling events > 9×median (PeriodF9) .69 .65 .67 .51 .71
Number of rising events > 5×median (PeriodR5) .65 .62 .65 .48 .68
Richards-Baker Flashiness Index (Rb-flash) .56 .49 .55 .41 .53
Water temperature metrics
Minimum temperature (95th percentile) 0.56 0.51 0.56 0.44 0.53
Habitat metrics
Mean embeddedness (riffle and runs) 0.59 0.58 0.57 0.57 0.49
Mean width/depth ration (riffle and runs) -.51 -.51 -.52 -.47 -.49
Percent riffle habitat -.63 -.61 -.63 -.57 -.55
Percent large substrate -.30 -.23 -.30 -.24 -.27
Mean habitat heterogeneity .30 .21 .29 .20 .28

Stream and reach-scale variables Water-chemistry variables
Summer-time
dissolved oxygen
Dissolved
organic
carbon
Total
insecticides
Total
pesticides
TEQ
(SPMD)
Average
specific
conductance
Sulfate
concentration
Total
nitrogen
concentration
Hydrologic variation metrics
Number of falling events > 5×median (PeriodF5) -0.45 0.71 0.71 0.50 0.70 0.42 0.56 0.40
Number of falling events > 9×median (PeriodF9) -.40 .62 .68 .48 .67 .49 .66 .43
Number of rising events > 5×median (PeriodR5) -.37 .60 .65 .45 .68 .34 .52 .40
Richards-Baker Flashiness Index (Rb-flash) -.40 .70 .62 .46 .63 .39 .53 .30
Water temperature metrics
Minimum temperature (95th percentile) -0.53 0.67 0.57 0.42 0.45 0.28 0.32 0.22
Habitat metrics
Mean embeddedness (riffle and runs) -0.66 0.46 0.36 0.39 0.41 0.69 0.55 0.52
Mean width/depth ration (riffle and runs) .50 -.34 -.26 -.10 -.24 -.59 -.50 -.35
Percent riffle habitat .84 -.60 -.39 -.33 -.49 -.61 -.57 -.46
Percent large substrate .48 -.21 -.12 -.06 -.00 -.36 -.14 -.05
Mean habitat heterogeneity -.61 .38 .29 .25 .18 .31 .14 -.05

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