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interation under different scenarios of climate change and the overall understanding of
climate‐groundwater‐surface water interactions in BC. 48 To date, four case studies in BC
have
been completed to quantify potential impacts of future climate changes on
groundwater recharge and groundwater levels.
However, none of the assessments carried out pertained to the XGCA or the Chilcotin
Habitat Management Area. Given the scarcity of information related to the groundwater
situation in the XGCA, the following are therefore general observations from these other
assessments. While some of these findings may be very relevant for how climate change will
impact the groundwater resources in the XGCA, they should still be considered with a high
degree of uncertainty, as any given groundwater aquifer has unique physical properties (i.e.
the geology), geometry (i.e. the control of broad flow patterns), and the nature of
connection
with surface water (i.e., can be a highly dynamic water source and sink for
groundwater).
The following are some of the
main findings of these assessments:
• Of importance to the Xeni Gwet’in, groundwater systems in the interior regions
of BC will be particularly sensitive to climate change owing to shifts in the
timing and amount of precipitation, and the strong dependence of rates of
evapotranspiration, snow accumulation and snowmelt on temperature.
• In the spring, an increase in temperatures will kick off the growing season earlier,
and lead to increased rates of evapotranspiration.
• In the summer
and early fall, higher temperatures will limit groundwater
recharge even more
than presently observed.
• In the winter, loss of snowpack and timing of snowmelt in the spring can
potentially have significant impacts on the amount and timing of spring
runoff. As a result, these shifts will influence groundwater recharge both in
the valley bottom and in the upland areas.
If groundwater levels are reduced ‐ brought about either by increased extraction (i.e. for
agricultural or human consumption) or lower recharge ‐ the consequence could be a
reduction in summer baseflow to stream corridors. Even if changes in recharge amounted
to only a few millimeters per year, when summed across an entire aquifer, a significant
about of stored groundwater could be lost, which, subsequently, would lead to a significant
reduction in the contribution of groundwater to baseflow. Furthermore, a shift in peak
stream
flow will occur due to earlier snowmelt. The consequent longer baseflow period will
demand a higher groundwater contribution to sustain the flow.
In glacierized catchments – such as some of the catchments within the XGCA ‐, it is likely
that glacier‐fed rivers will experience a shift from a glacial regime with high flows in mid
and late summer to a regime that responds to the summer dry period with streamflow
recession, low flows and increased temperatures. In such areas, groundwater will become
an increasingly important source of water for sustaining baseflow during the summer
months. As a result, according to Allen (2009, “summer low flows in the streams may be
exacerbated by the decreasing groundwater levels and diminished glacier cover, and
streamflow may become inadequate to meet economic needs such as domestic
consumption,
irrigation, as well as ecological functions such as in­stream habitat for
fish and other aquatic species [emphasis added].”
48 Allen, Diana M. (2009)
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