TY - JOUR
T1 - Old-Aged groundwater contributes to mountain hillslope hydrologic dynamics
AU - Thiros, Nicholas E.
AU - Siirila-Woodburn, Erica R.
AU - Sprenger, Matthias
AU - Williams, Kenneth H.
AU - Dennedy-Frank, James P.
AU - Carroll, Rosemary W.H.
AU - Gardner, W. P.
N1 - Publisher Copyright:
© 2024 The Authors
PY - 2024/5
Y1 - 2024/5
N2 - Understanding connectivity between the soil and deeper bedrock groundwater is needed to accurately predict a watershed's response to perturbation, such as drought. Yet, the bedrock groundwater dynamics in mountainous environments are typically under-constrained and excluded from watershed hydrologic models. Here, we investigate the role of groundwater characterized with decadal and longer water ages on the hydrologic and mass-transport processes within a steep snow-dominated mountain hillslope in the Central Rocky Mountains (USA). We quantify subsurface and surface water mass-balance, groundwater flowpaths, and age distributions using the ParFlow-CLM integrated hydrologic and EcoSLIM particle tracking models, which are compared to hydrometric and environmental tracer observations. An ensemble of models with varied soil and hydrogeologic parameters reproduces observed groundwater levels and century-scale mean ages inferred from environmental tracers. The numerical models suggest soil water near the toe of the hillslope contains considerable (>60 % of the mass-flux) contributions from bedrock flowpaths characterized with water ages >10 years. Flowpath connectivity between the deeper bedrock and soil systems is present throughout the year, highlighting the potentially critical role of groundwater with old ages on processes such as evapotranspiration and streamflow generation. The coupled numerical model and groundwater age observations show the bedrock groundwater system influences the hillslope hydrodynamics and should be considered in mountain watershed conceptual and numerical models.
AB - Understanding connectivity between the soil and deeper bedrock groundwater is needed to accurately predict a watershed's response to perturbation, such as drought. Yet, the bedrock groundwater dynamics in mountainous environments are typically under-constrained and excluded from watershed hydrologic models. Here, we investigate the role of groundwater characterized with decadal and longer water ages on the hydrologic and mass-transport processes within a steep snow-dominated mountain hillslope in the Central Rocky Mountains (USA). We quantify subsurface and surface water mass-balance, groundwater flowpaths, and age distributions using the ParFlow-CLM integrated hydrologic and EcoSLIM particle tracking models, which are compared to hydrometric and environmental tracer observations. An ensemble of models with varied soil and hydrogeologic parameters reproduces observed groundwater levels and century-scale mean ages inferred from environmental tracers. The numerical models suggest soil water near the toe of the hillslope contains considerable (>60 % of the mass-flux) contributions from bedrock flowpaths characterized with water ages >10 years. Flowpath connectivity between the deeper bedrock and soil systems is present throughout the year, highlighting the potentially critical role of groundwater with old ages on processes such as evapotranspiration and streamflow generation. The coupled numerical model and groundwater age observations show the bedrock groundwater system influences the hillslope hydrodynamics and should be considered in mountain watershed conceptual and numerical models.
KW - Bedrock groundwater
KW - Environmental tracers
KW - Groundwater age
KW - Integrated hydrologic modeling
KW - Mountain hydrology
KW - Particle tracking
UR - http://www.scopus.com/inward/record.url?scp=85190402776&partnerID=8YFLogxK
U2 - 10.1016/j.jhydrol.2024.131193
DO - 10.1016/j.jhydrol.2024.131193
M3 - Article
AN - SCOPUS:85190402776
SN - 0022-1694
VL - 635
JO - Journal of Hydrology
JF - Journal of Hydrology
M1 - 131193
ER -