Climate Change and the Rocky Mountains - Impact of Global Changes on Mountains: Responses and Adaptation - page 435

Lettenmaier 1999, Lapp et al. 2005, Larson et al. 2011, MacDonald et al.
2011) as the proportion of rain to snow increases, altering the timing and
magnitude of snowmelt contributions to streamfl ow in mountainous
regions (Barnett et al. 2005). Shifts in the timing of snowmelt runoff are
likely to result in lower late-season streamfl ow conditions in mountain
regions (Huntington et al. 2012). Winter fl ooding is likely to increase due
to a higher proportion of winter rainfall (Goode et al. 2013) and mountain
glaciers will continue to be depleted in a warmer climate (Marshall et al.
2011). The effect of climate change is likely to be compounded by enhanced
landscape disturbance due to wildfi re and pest outbreaks (Flannigan et
al. 2005, Hicke and Jenkins 2008, Littell et al. 2009), signifi cantly affecting
water supply from snow-dominated regions. The anticipated reduction in
available water for both human and ecosystem needs poses a substantial
challenge for future water resource management in Rocky Mountain
ecosystems (Harma et al. 2011).
A particularly important feature of Rocky Mountain rivers is that they
have large contributions of groundwater to streamfl ow (Ward 1994). During
the summer groundwater-dominated mountain streams are very important
for the survival of aquatic organisms. This is largely due to the fact that at high
temperatures fi sh may experience reduced growth associated with depleted
oxygen, appetite, and enzyme effi ciency. In extreme cases, fi sh could even
die when thermal tolerances are exceeded. Therefore, the temperature of
the water, particularly cool water associated with groundwater upwelling
during summer controls habitat selection of many fi sh (Power et al. 1999).
Cunjak (1996) suggests the protection against extreme abiotic conditions
such as ice, reduced oxygen and streamfl ow fl uctuations during winter
periods are also critical to fi sh survival. Groundwater upwelling enables
fi sh to overwinter in streams which would not otherwise contain suitable
habitat in the absence of the relatively warm, oxygenated water provided
by groundwater (Brown et al. 2011). Changes in groundwater regimes
of the Rocky Mountains as a function of climate change have important
consequences for ecosystems and suggest this sensitive water-resource must
be accounted for when adaptively managing these systems.
Snow and the Terrestrial Ecosystem
Although glacier recession and glacial meltwater directly impact hydrology
and aquatic ecological interactions, it is the seasonal snowpack that exerts
the predominant infl uence on alpine terrestrial ecosystems. Thus, the
50-year downward trend in snow water equivalent of mountain snowpacks,
the earlier spring melt (up to four weeks), and the shift toward more rain,
even during winter, all have consequences for terrestrial vegetation in the
Rocky Mountains (Pederson et al. 2011). At the highest elevations, species