Geophysical Measurements to Determine the Hydrologic Partitioning of Snowmelt on a Snow‐Dominated Subalpine Hillslope

In subalpine watersheds of the intermountain western United States, snowpack melt is the dominant water input to the hydrologic system. The primary focus of this work is to understand the partitioning of water from the snowpack during the snowmelt period and through the remainder of the growing seas...

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Bibliographic Details
Published in:Water resources research 2018-06, Vol.54 (6), p.3788-3808
Main Authors: Thayer, Drew, Parsekian, Andrew D., Hyde, Kevin, Speckman, Heather, Beverly, Dan, Ewers, Brent, Covalt, Matt, Fantello, Nadia, Kelleners, Thijs, Ohara, Noriaki, Rogers, Trent, Holbrook, W. Steven
Format: Article
Language:English
Subjects:
Aquifers
Coniferous trees
Electrical resistivity
Fluxes
Geophysics
Growing season
hillslope
hydrogeophysics
Hydrologic processes
Hydrology
Moisture content
Overland flow
Partitioning
Regolith
Seismic velocities
Snow
Snowmelt
Snowpack
Soil
Temporal variations
Tomography
Transpiration
Unconfined aquifers
Uptake
Vadose water
Vertical flow
Vertical mixing
Water budget
Water content
Water resources
Water uptake
Watersheds
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Summary:In subalpine watersheds of the intermountain western United States, snowpack melt is the dominant water input to the hydrologic system. The primary focus of this work is to understand the partitioning of water from the snowpack during the snowmelt period and through the remainder of the growing season. We conducted a time‐lapse electrical resistivity tomography (ERT) study in conjunction with a water budget analysis to track water from the snow‐on through snow‐off season (May–August 2015). Seismic velocities provided an estimate of regolith thickness while transpiration measurements from sap flow in conifer trees provided insight into root water uptake. We observed four hydrologic process‐periods and found that deep flow and tree water fluxes are the primary pathways through which water moves off of the hillslope. Overland flow and interflow were negligible. We observed temporal changes in vadose zone water content more than 3.0 m below the surface. Our results show that vertical flow through the thin soil mantle overlaying coarse colluvial regolith was the primary pathway to a local unconfined aquifer. Key Points On a historically glaciated subalpine hillslope underlain by metamorphic geology, most water moves as deep flow Based on water inputs and changes in vadose zone storage, we find four distinct functional hydrologic periods during the year Electrical and seismic geophysical data, tree water flux measurements, and hydrologic observations enable interpretation of water partitioning
ISSN:0043-1397
1944-7973
DOI:10.1029/2017WR021324