EPA's Vessel General Permit and Small Vessel General

Table 2. Phenomena associated with projections of global climate change (adapted from
IPCC 2001 and Campbell-Lendrum Woodruff 2007).
Phenomenon
Higher maximum temperatures and a greater
number of hot days over almost all land areas
Higher minimum temperatures with fewer cold
days and frost days over almost all land areas
Reduced diurnal temperature range over most
land areas
Confidence in Observed
Changes (observed in the
latter 20 th Century)
Likely Very likely
Very likely Very likely
Very likely Very likely
Increased heat index over most land areas Likely over many areas
More intense precipitation events
Increased summer continental drying and
associated probability of drought
Increase in peak wind intensities in tropical
cyclones
Increase in mean and peak precipitation
intensities in tropical cyclones
Likely over many mid- to highlatitude
areas in Northern
Hemisphere
Likely in a few areas
Confidence in Projected
Changes (during the 21 st
Century)
Very likely over most
areas
Very likely over many
areas
Likely over most midlatitude
continental
interiors (projections are
inconsistent for other
areas)
Not observed Likely over some areas
Insufficient data Likely over some areas
Rising stream temperatures will likely reduce the quality and extent of freshwater salmon habitat.
The duration of periods that cause thermal stress and migration barriers to salmon is projected to
at least double by the 2080s for most analyzed streams and lakes (Littell et al. 2009). The
greatest increases in thermal stress (including diseases and parasites which thrive in warmer
waters) would occur in the Interior Columbia River Basin and the Lake Washington Ship Canal.
The combined effects of warming stream temperatures and altered stream flows will very likely
reduce the reproductive success of many salmon populations in Washington watersheds, but
impacts will vary according to different life-history types and watershed-types. As more winter
precipitation falls as rain rather than snow, higher winter stream flows scour streambeds,
damaging spawning nests and washing away incubating eggs for Pacific Northwest salmon.
Earlier peak stream flows flush young salmon from rivers to estuaries before they are physically
mature enough for transition, increasing a variety of stressors including the risk of being eaten by
predators.
As a result of these changes, about one third of the current habitat for either the endangered or
threatened Northwest salmon species will no longer be suitable for them by the end of this
century as key temperature thresholds are exceeded (Littell et al. 2009). As summer
temperatures increase, juvenile salmon are expected to experience reduced growth rates,
impaired smoltification and greater vulnerability to predators.
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