watervulnerability

Helena National Forest Watershed Vulnerability Assessment, Northern Region (R1)
Composite Watershed Vulnerability
Cutthroat trout will experience the same changes in temperature that bull trout experience because they
too inhabit headwater streams. Summer maximum air temperatures were predicted to increase by
approximately 2 °C uniformly across the forest for the 2030-2059 predictive period and approximately 5
°C uniformly for the 2070-2099 predictive period. These temperature changes are assumed to have little
impact on cutthroat populations; however there could be a net positive effect due to the predicted decrease
in invasive populations (Figure 5).
Figure 5. Composite watershed sensitivity rating for Westslope cutthroat trout with invasive fish species (bull trout
and brown trout) habitat overlay
Water Resource Value: Infrastructure
Sensitivity
Based on the indicators used to determine sensitivity (Table 5), a rank was developed to show those
watersheds that are least resilient (most sensitive). The overall sensitivity score was determined by
calculating the average of the ranked values given to each of the sensitivity factor. Density of high value
near-stream developments (table 5) were used to characterize infrastructure value (Figure 6).
56 Assessing the Vulnerability of Watersheds to Climate Change