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| Titel |
Towards understanding the spatial and temporal characteristics of stream, hillslope, and groundwater runoff processes in a Rocky Mountain headwater catchment in Alberta, Canada |
| VerfasserIn |
Sheena Spencer, Axel Anderson, Uldis Silins, Kevin Bladon, Adrian Collins |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090346
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| Publikation (Nr.) |
 EGU/EGU2014-4576.pdf |
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| Zusammenfassung |
| The eastern slopes of the Rocky Mountains produce the majority of the surface water supplies
for much of Alberta’s population. Groundwater inputs to rivers constitutes a large
component of flow in this headwater region, however limited knowledge of the
interaction of groundwater-surface water sources limits the ability to predict impacts of
climate and disturbance in this critical source water region. The objectives of this
study are to explore the spatial and temporal dynamics of surface, hillslope, and
deeper groundwater runoff processes using coupled tracer approaches to characterize
their interaction in regulating streamflow dynamics at stream reach and catchment
scales.
The study was conducted in Star Creek (10.4 km2), which is representative of
small-medium sized, front-range Rocky Mountain catchments. A network of climate stations
and 6 nested hydrometric-water quality sampling stations were used to collect 5 years (2009 -
2013) of meteorological, discharge (Q), and stream water quality data. Nested stream
gauging stations enabled characterization of the spatial and temporal pattern of Q and water
geochemistry (cations: Na+, Mg2+, Ca2+, K+, and anions: Cl-, and SO42-) along a
gradient of very steep, bedrock entrenched alpine stream reaches down through lower
gradient mid-montane alluvial stream reaches. The initial phase of this work uses the stream
gauging network to determine the difference in Q between stations, hydrograph
baseflow separation, and mixing model analyses of geochemical parameters. These
analyses suggest the runoff process is dominated by longer, deeper runoff flow
pathways (groundwater). Geologic information and a conceptual model of topographic
controls on hillslope-stream connectedness (after Jensco et al. 2009 and others) was
used to identify sites where concentrated hillslope flow may be connected with the
stream to aid in interpreting the spatial and temporal variation in Q and stream
geochemistry.
Strong longitudinal and seasonal patterns in Q were evident over 5 years showing that the
alpine reaches contributed 20-40%, steep mid-elevation reaches contributed 2-9%, and the
lowest elevation, alluvial reaches contributed 11-25% of total catchment Q. This was
consistent with baseflow separation of the 6 nested gauging stations which showed baseflow
comprised 67-70% in the alpine reaches, 70-71% in the steep mid-elevation reaches, and
increased to 75-80% in the lowest alluvial stream reach. Preliminary analysis of distributed
water geochemistry identified some parameters that displayed strong seasonal patterns with
over-winter groundwater contributions. Results from an end member mixing analysis using
these parameters were consistent with results from the hydrometric analysis suggesting large
groundwater contributions in the steepest upper reaches and increased groundwater
contributions in downstream reaches. Future work will focus on coupled tracing
approaches using a broader suite of geochemical end-members, along with higher
spatial resolution NaCl tracing studies, to better characterize groundwater-surface
water interactions reflecting hillslope, hyporheic, and deeper groundwater sources. |
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