Using Tracers to Investigate Seasonal Variation of Flow Components
in the Canadian Rocky Mountains
Chris Hopkinson1, Mike English1, and Gordon J. Young1
The research presented is concerned with determining the usefulness of stable isotopic data for the
purpose of ascertaining contributions of glacier ice melt to river flow in the Bow Valley in the Cana-
dian Rockies. Using δ18O as a tracer and simple mixing models, an attempt has been made to better
understand groundwater and baseflow interactions with surface inputs of snow and rainfall and sur-
face outputs to the river channel. The ultimate aim of this research, although not this presentation, is
to produce a model of groundwater surface water interaction based largely on the hydrogeochemical
data collected.
From May 1996 to November 1997, approximately 180 water samples were collected from various
form of baseflow, springs, and from wells), lake inflows and outflows, river tributaries, and the Bow
River itself have all been collected. An attempt has been made to isotopically characterize the major
flow component sources of snow, ice, and rain and then both temporal and spatial patterns within
groundwater and river flow samples have been investigated. It is found that increasing snow fall
pack also continues to lighten groundwater flowing from springs and extracted from deep wells into
late summer. This suggests a lag time of perhaps several months for much of the snowmelt to tran-
scend groundwater aquifers in this region. Only relatively small proportions of rainfall are found in
these groundwater sources because a substantial amount is thought to be lost to evaporation and also
surface runoff when the water table is relatively high.
δ18O signatures of water draining both Peyto and Bow Lakes in the headwater regions display little
seasonal variability, possibly suggesting a relatively high level of mixing compared to the more
"piston-like" dynamics of localized groundwater. This low variability in output signature might
mean that lakes display the amalgamation of all flow components all year round, i.e., they may
provide an isotopic "overview" of hydrological processes upstream.
The seasonal δ18O signature for the Bow River at Banff reflects the changing dominance from win-
ter baseflow to spring melt to summer rainfall. However, near-baseflow values during the mid to late
summer period of substantial rainfall has led to the hypothesis that icemelt in the headwaters during
this time is buffering the rainfall signature further downstream. The results presented have provided
some insight into groundwater/surface runoff processes following spring snowmelt and during sum-
mer glacial melt in a mountainous basin, but few conclusions can be drawn at this stage. It is felt that
using isotopic and ionic tracers combined with other hydrometeorological mass balance techniques
for the goal of accomplishing a reasonable separation of seasonal flow components, in order to
quantify the relative glacial contribution, can be attained. To this end, further field work is currently
being implemented to study geochemical tracers and their relation to hydrological processes in two
headwater basins in the Bow Valley; one heavily glacierised and one nonglacierised.
1Cold
Regions Research Centre, Wilfrid Laurier University, Waterloo, Ontario, N2L 3C5, Canada.
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