Investigating groundwater flow and storage within a proglacial moraine in the Canadian Rockies using multiple geophysical methods
Abstract
Unconsolidated sedimentary deposits like talus slopes and moraines play an important yet largely undetermined role in storing and transmitting groundwater within alpine watersheds. To investigate their subsurface flow regime, and in conjunction with ongoing hydrological and chemical measurements, we have undertaken several geophysical surveys over a characteristic moraine-talus field within the Lake O'Hara alpine watershed, located in Yoho National Park, British Columbia. Here, we present results from multiple electrical resitivity, ground-penetrating radar (GPR), and seismic refraction lines recorded across the toe of a proglacial moraine deposit that is discharging groundwater into a nearby pond. Groundwater chemistry data sampled from the pond indicate separate flowpaths within the moraine that originate from at least three distinct sources. Model inversions of the electrical resistivity lines and the processed GPR profiles allow us to delineate the bedrock topography that underlies the moraine. A topographic depression within the bedrock surface is interpreted to control groundwater flow from within the interior of the moraine-talus field to the pond. By comparing a P-wave velocity tomogram determined from inversion of seismic refraction data with a coincident GPR profile, we show that in places the bedrock exhibits a low-velocity (<2000 m/s) weathering layer of up to 5 m in thickness. A corresponding electrical resistivity tomogram indicates that the weathered layer may be partially saturated with groundwater. Based on our interpreted datasets, we suggest that: 1) the underlying bedrock topography controls much of the groundwater flow through the moraine to the groundwater outlet pond, and 2) the fractured weathering layer of the shallow bedrock has the capacity to store some of this groundwater.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2009
- Bibcode:
- 2009AGUSMCG12A..06M
- Keywords:
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- 0925 Magnetic and electrical methods (5109);
- 0935 Seismic methods (3025;
- 7294);
- 1829 Groundwater hydrology;
- 1835 Hydrogeophysics