watervulnerability

Shasta Trinity National Forest Watershed Vulnerability Assessment, Pacific Southwest Region (R5)
Figure 9. Model used in the Shasta-Trinity NF Watershed Vulnerability Assessment. Note that stressors are limited
to those relative to climate change exposure.
WATER RESOURCE VALUES
Three resource issues were selected for analysis, warming, drying, and extreme events. The aquatic values
of focus are the aquatic habitats associated with lakes and streams (fish focus), ponds and springs
(sensitive aquatic species), and infrastructure (stream crossings and near-stream recreation facilities).
These resources are likely to be impacted by climate change in different ways. Fish populations are most
likely to be affected by warming of rivers and streams. Sensitive aquatic species are most likely to be
affected by the drying of ponds, small lakes, and springs. Infrastructure is at increased risk of damage
from runoff from extreme precipitation events.
Fisheries
Fish species on the Forest include several USFS-sensitive species as well as species listed as threatened
and endangered under the Endangered Species Act (ESA). ESA-listed species include Sacramento River
winter run Chinook, Central Valley spring- and fall-run Chinook, North Coast winter coho, Northern
California steelhead, and Great Basin Redband trout. The distribution of these species is shown in Figure
10. Impacts to these species are likely to occur as increased temperatures reduce the amount of suitable
habitat. California lakes have been found, on average, to be warming at 0.2 degrees per year over the past
several decades (Schneider et al. 2009). Warmer water temperatures and shifts in timing of hydrographs
will likely disturb breeding and rearing lifecycles, and also impact food-source organisms upon which the
species depend, resulting in additional stress. Increased stresses could result in loss of species already at
risk.
193 Assessing the Vulnerability of Watersheds to Climate Change