From: on behalf of Panel Registry Subject: FW: TNG registration of ...

• Projected changes to the magnitude of flow include increased winter and decreased
summer and fall streamflow, along with a diminished spring freshet volume. 37
• Warmer winter temperatures will cause more precipitation to fall as rain rather than
snow, resulting in increased winter runoff and decreased snowpack accumulation and
a tendency towards more pluvial(i.e. rain­fed) streamflow regimes. 38
• Reductions to spring peaks will occur primarily from reductions in snowpack and from
warmer temperatures causing an earlier spring melt.”
The changes to the flood and low‐flow volume producing mechanisms are different for
pluvial (rain­fed) and nival (snow­fed) systems. 39 Watersheds fed by rain are expected to
have
increased flood magnitude and frequency. 40 This response is primarily driven by
warmer, wetter winters, where instead of snow, precipitation falls as rain. 41
A decrease in the number and magnitude of flood events is predicted for many snow‐fed
watersheds, particularly those in the semi‐arid interior regions. 42 This decrease is driven by
the spring melt taking place earlier. Drier summers in combination with year‐round
warming are projected to increase water shortages in both pluvial and nival rivers because
of changes in rainfall timing and amounts, projected smaller snowpack and increased
evaporation. 43 Also an increase in the time elapsed between snowmelt and fall rain is
projected, which will extend the dry‐season low‐flow period. Interestingly, rain‐fed regimes
have been shown to have noticeably longer dry seasons as a result of changes in
temperature
and precipitation inputs. Because of this rain‐fed systems are considered
sensitive to climate change. 44
In terms of projected impacts in the XGCA, based on the above trends, from the
projected warmer temperatures and increase in precipitation for the Study Area, the
XGCA rivers will probably see an increase in winter flows and decreased later
summer flows. 45 Glaciers play a major role in determining low‐flows for 48 percent of the
monitored
rivers in BC (see section above). The influence of groundwater and glacier melt
on
low‐flows requires further study. 46
Groundwater 47
Groundwater plays a critical role in maintaining streamflows during summer months, which
sustain fish habitat, aquatic ecosystems, not to mention the animals and humans that
depend on them. Yet, despite these important qualities of groundwater, very little research
have been done to date on how climate change might affect groundwater resources in the
future. Concerning BC, for the
past decade a research program spearheaded by Simon
Fraser
University has focused on modeling recharge and groundwater‐streamflow
37 Hamlet, A.F. and Lettenmaier, D.P., (1999b).
38 Hamlet, A.F. and Lettenmaier, D.P., (1999b) and Whitfield, P.H., Reynolds, C.J. and Cannon, A.J., (2002b).
39 Loukas, A., Lampros, V. and Dalezios,
N.R., (2002a).
40 Loukas, A., Vasiliades, L. and Dalezios, N.R., (2004) and Whitfield, P.H., Reynolds, C.J. and Cannon,
A.J., (2002b).
41 Parson, E.A. et al., (2001b).
42 Cohen, S. and Kulkarni, T., (20010. And
Loukas, A., Vasiliades, L. and Dalezios, N.R., (2002b).
43 Parson, E.A. et al., (2001a).
44 Whitfield, P.H. and
Taylor, E., (1998).
45 Walker, I.J. and Sydneysmith, R. (2008).
46 Stahl, K. (2007).
47 Given the scarcity of available information and data, this section is primarily based on information in the
recent article by Diana Allen in Innovation May/June 2009, Impacts of Climate Change on Groundwater in BC.
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