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Depth‐ and Time‐Resolved Distributions of Snowmelt‐Driven Hillslope Subsurface Flow and Transport and Their Contributions to Surface Waters
Author(s) -
Tokunaga Tetsu K.,
Wan Jiamin,
Williams Kenneth H.,
Brown Wendy,
Henderson Amanda,
Kim Yongman,
Tran Anh Phuong,
Conrad Mark E.,
Bill Markus,
Carroll Rosemary W.H.,
Dong Wenming,
Xu Zexuan,
Lavy Adi,
Gilbert Ben,
Carrero Sergio,
Christensen John N.,
Faybishenko Boris,
Arora Bhavna,
SiirilaWoodburn Erica R.,
Versteeg Roelof,
Raberg Jonathan H.,
Peterson John E.,
Hubbard Susan S.
Publication year - 2019
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2019wr025093
Subject(s) - snowmelt , subsurface flow , geology , weathering , hydrology (agriculture) , snowpack , groundwater , tributary , snow , surface water , bedrock , precipitation , soil water , geomorphology , environmental science , soil science , geotechnical engineering , physics , cartography , environmental engineering , meteorology , geography
Abstract Major components of hydrologic and elemental cycles reside underground, where their complex dynamics and linkages to surface waters are obscure. We delineated seasonal subsurface flow and transport dynamics along a hillslope in the Rocky Mountains (USA), where precipitation occurs primarily as winter snow and drainage discharges into the East River, a tributary of the Gunnison River. Hydraulic and geochemical measurements down to 10 m below ground surface supported application of transmissivity feedback of snowmelt to describe subsurface flow and transport through three zones: soil, weathering shale, and saturated fractured shale. Groundwater flow is predicted to depths of at least 176 m, although a shallower limit exists if hillslope‐scale hydraulic conductivities are higher than our local measurements. Snowmelt during the high snowpack water year 2017 sustained flow along the weathering zone and downslope within the soil, while negligible downslope flow occurred along the soil during the low snowpack water year 2018. We introduce subsurface concentration‐discharge ( C‐Q ) relations for explaining hillslope contributions to C‐Q observed in rivers and demonstrate their calculations based on transmissivity fluxes and measured pore water specific conductance and dissolved organic carbon. The specific conductance data show that major ions in the hillslope pore waters, primarily from the weathering and fractured shale, are about six times more concentrated than in the river, indicating hillslope solute loads are disproportionately high, while flow from this site and similar regions are relatively smaller. This methodology is applicable in different representative environments within snow‐dominated watersheds for linking their subsurface exports to surface waters.