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Umatilla National Forest Watershed Vulnerability Assessment, Pacific Northwest Region (R6) Individual Value Ranking: Aquatic species vulnerability Aquatic species’ vulnerability was assessed using the number of focal aquatic species per subwatershed as the value metric. All sensitivity and threats variables, as used in the composite analysis, were used in this analysis. All climate factors, including winter and summer temperature and SWE, were also included in the analysis. Results were placed in three categories; high, medium, and low. Greatest vulnerability tends to be in subwatersheds with 3 focal aquatic species; however, not all subwatersheds with 3 focal aquatic species show high vulnerability. 218 Assessing the Vulnerability of Watersheds to Climate Change

Umatilla National Forest Watershed Vulnerability Assessment, Pacific Northwest Region (R6) FINE SCALE ANALYSIS FOR BULL TROUT Bull trout (Salvelinus confluentus) was used as our aquatic focal species in the WVA because bull trout require cold (≤ 17 °C) and relatively low gradient, pristine waters to rear and spawn. They have a small thermal niche and are very responsive to changes in stream temperature. Analysis of suitable habitat on the UNF is necessary because bull trout are on the edge of their bioclimatic envelope (Beever et al. 2010, Dunham et al. 2003); the UNF is a fairly low elevation, dry forest landscape. Bull trout populations in the southern parts of the UNF can also be described as peripheral populations or species that are at the geographic edge of their range; they often have increased conservation value because they maximize within-species biodiversity, retain important evolutionary legacies, and may provide a “gene pool” for future adaptation (Haak et al. 2010). Previous research suggests future stream temperature increases on the forest, but influences on distribution and abundance of stream organisms is not well documented (Rieman et al. 2007). To begin the analysis, current bull trout distributions were identified in the Umatilla, Walla Walla, Tucannon, Lookingglass, and North Fork John Day (NFJD) drainages. Previous stream surveys conducted by USFS and ODFW/WDFW were used to verify current bull trout distribution. Multiple Regression Stream Temperature Model A multiple regression stream temperature model developed by the RMRS was used to model historic, current and future (years 2033, 2058, 2080) suitable bull trout habitat. Stream temperature model information and methods to the can be found at www.fs.fed.us/rm/boise/AWAE/projects/stream_temperature.shtml The regression model used observed mean weekly maximum temperature (MWMT) and physical parameters or predictor variables and geomorphic variables that have direct effects on stream temperatures. (The regression equation and coefficients can be found at www.fs.fed.us/ccrc/wva/appendixes.) Physical metrics: • Water diversion • Wildfire – Used data from the last 20 years; ~4km from the stream. • Groundwater Dependent Ecosystems (resiliency): number of springs and wetlands per HU12, rated Geomorphic variables or metrics (National hydrologic data set): • Cumulative drainage area (km 2 ) • Slope (%) • Elevation (m) Observed Stream Temperature and Climate Data Observed summer MWMT were taken from 37 locations and provided a total of 333 stream observations. A separate regression model was developed to predict historic and future stream temperatures using the same physical and geomorphic predictor vales, however, air MWMT data (1979-2009) and flow (m 3 /s) data (1957-2009) were considered. (Details about this regression model are available at www.fs.fed.us/ccrc/wva/appendixes.) 219 Assessing the Vulnerability of Watersheds to Climate Change

Umatilla National Forest Watershed Vulnerability Assessment, Pacific Northwest Region (R6)<br />

Individual Value Ranking: Aquatic species vulnerability<br />

Aquatic species’ vulnerability was assessed using the number of focal aquatic species per subwatershed as<br />

the value metric. All sensitivity and threats variables, as used in the composite analysis, were used in this<br />

analysis. All climate factors, including winter and summer temperature and SWE, were also included in<br />

the analysis. Results were placed in three categories; high, medium, and low. Greatest vulnerability tends<br />

to be in subwatersheds with 3 focal aquatic species; however, not all subwatersheds with 3 focal aquatic<br />

species show high vulnerability.<br />

218 Assessing the Vulnerability of Watersheds to Climate Change

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