watervulnerability

Shasta Trinity National Forest Watershed Vulnerability Assessment, Pacific Southwest Region (R5)
CLIMATE CHANGE INFLUENCE ON HYDROLOGIC PROCESSES
Implications of climate change on water resources are very complex. Based on climate trends already
observed and discussion of potential effects of changing climate on hydrologic processes (Furniss et al,
2010), the team identified several changes. These were briefly addressed in the discussion of each
resource value, and are displayed in Figure 12. Next, the team considered how these changes might
influence key aquatic resource values. The assessment assumes the effects will be moderated in resilient
watersheds. These inter-relationships are shown in Table 3.
Figure 12. Summary of likely climate change effects on hydrologic processes, and on selected resource values
Stressors (Exposure)
Two elements were combined to rate exposure of watersheds to climate change. The first is temperature
increases predicted by the A2 Climate Scenario from the World Climate Research Programme's
(WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset. This is a
downscaled global temperature modeling output available from the University of California, Santa
Barbara. The second element of the exposure analysis was characterization of each stream and river
segment’s relative solar exposure. The NetMap Modeling Product (citation) was used for this
characterization.
Projected Temperature Increases
The CMIP3 multi-model dataset displayed below uses an A2 emission scenario represents a world that
has a self-reliant focus on local or regional concerns as opposed to cooperative global concerns; it’s also
driven by greater emphasis on economics than on environmental concerns. The result is temperatures at
the high end of the range of projections. Projected temperatures are displayed in Figure 13. Note that in
196 Assessing the Vulnerability of Watersheds to Climate Change