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Introduction
Recently, the hydrologic community has been struggling with the
“old water” paradox, i.e., how do watersheds store water for weeks or
months but then release it in minutes or hours in response to
rainfall inputs? Understanding this fundamental question is a
critical step to evaluating carbon and nutrient cycling in
watersheds. Developing a theoretical basis that can generate
realistic predictions has proved elusive. The problem is further
compounded because, although both base-flow and stormflow comprise
old water, the chemical signatures are often very different. If
water cannot be tracked through a watershed with certainty, our
ability to simulate carbon and nitrogen cycling is compromised. The
development of experimental watersheds and hydraulic expertise will
provide important insights to this challenge.
Research Plan
Our goal is to understand the influence of spatial and temporal
variability of earth materials and soil properties on the “old
water” paradox. Specific questions include:
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What pathways does high-elevation snowmelt take to reach valley
bottom aquifers? We will assess groundwater recharge,
evapotranspiration, transient storage, and surface runoff within experimental watersheds using hydrologic, geochemical,
and geophysical techniques.
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What control does spatial and temporal variability of soil
hydraulic properties have on watershed-scale water cycling? We
will assess the spatial and temporal variability of soil
hydraulic properties within experimental watershed using in situ test results
and continuous pressure head and moisture content test pit data,
and laboratory tests on undisturbed soil cores.
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What degree of sophistication is required to adequately
parameterize and simulate hydrologic and solute fluxes at
various scales? We will develop a comprehensive hydrologic model
and test the effects of uncertainty and data paucity on model
results investigated.
Dry Creek Experimental Watershed Website |
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