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Simple in situ determination of hydraulic conductivity by power function descriptions of drainage
Author(s) -
Chong SheKong,
Green Richard E.,
Ahuja Lajpat R.
Publication year - 1981
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/wr017i004p01109
Subject(s) - hydraulic conductivity , hydraulic head , drainage , infiltration (hvac) , power function , pressure head , soil science , soil water , conductivity , geotechnical engineering , pressure gradient , hydrology (agriculture) , geology , mechanics , environmental science , materials science , mathematics , thermodynamics , chemistry , mathematical analysis , physics , composite material , ecology , biology
A simple method is presented to calculate soil hydraulic conductivity, K(θ ), from in situ measurements during infiltration and redistribution. Equations for calculating K(θ ) and K(h ) were derived with the assumption of unit hydraulic gradient. The derivation employed power functions to describe the change of water content θ and pressure head h with time during the redistribution period. The validity of this assumption was tested because measured pressure head profiles during drainage showed that the total hydraulic head gradient varied from extremes of about 0.3 during the early stage of drainage to 2.0 after several days. Unit gradient was most frequently approached during the intermediate stages of drainage. K(θ ) values obtained with this simple method should therefore be most reliable at intermediate water contents. This expectation was confirmed by comparison of K(h ) values from the simple method with K values determined by the detailed Darcy method. The simple method appears to provide a practical means of characterizing K(θ ) of well‐drained soils, even when the surface is tilled and the conductivity at high water contents decreases with depth. Such methods are needed to adequately characterize large areas to which hydrologic models, which require K(θ ), are to be applied.