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Measuring Hydraulic Properties Using a Line Source I. Analytical Expressions
Author(s) -
Zhang Z.Fred,
Kachanoski R.Gary,
Parkin Gary W.,
Si Bingcheng
Publication year - 2000
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2000.6451554x
Subject(s) - hydraulic conductivity , reflectometry , line source , infiltration (hvac) , soil science , saturation (graph theory) , pressure head , inverse , hydraulic head , tracer , uniqueness , mathematics , environmental science , time domain , mechanics , mathematical analysis , geology , soil water , geotechnical engineering , physics , thermodynamics , geometry , optics , computer science , combinatorics , nuclear physics , computer vision
In situ measurement of soil hydraulic properties remains a challenge. This study presents new analytical expressions for estimation of soil hydraulic properties below a surface line source by means of multi‐purpose time domain reflectometry (TDR) probes and existing quasi‐analytical, steady‐state solutions for infiltration from a surface line source. Inverse procedures are used to estimate the inverse macroscopic capillary length scale, α, and the hydraulic conductivity at saturation, K s , from pressure head (ψ), water storage ( W ), and conservative ionic tracer travel time ( T ) measured via multi‐purpose TDR probes placed at several depths below a line source with constant flux of water. Soil water content at saturation, θ s , can also be estimated if prior information is available. The parameter and spatial sensitivities of each solution were calculated by means of sensitivity coefficients. The uniqueness of possible combinations of measurements to estimate α, K s , and θ s was tested by means of two‐dimensional response surfaces. Significant correlation exists between K s and θ s , and thus it is not possible to estimate both K s and θ s by globally minimizing the objective function. Combination approaches with W (i.e., ψ and W , T and W , or ψ and W and T ) give unique estimates of α and K s if either θ s is known or prior information on θ s is available.