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An Index for Degree of Hysteresis in Water Retention
Author(s) -
Gebrenegus Thomas,
Ghezzehei Teamrat A.
Publication year - 2011
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/sssaj2011.0082n
Subject(s) - hysteresis , wetting , logarithm , degree (music) , imbibition , mathematics , richards equation , water content , index (typography) , soil science , soil water , statistics , thermodynamics , environmental science , geotechnical engineering , computer science , geology , mathematical analysis , physics , world wide web , acoustics , germination , botany , quantum mechanics , biology
Direct characterization of hysteresis in water retention (WR) is typically cumbersome and time consuming. Thus, such data are scarce, and even when available are typically ignored in unsaturated flow modeling. One reason for disregard of this ubiquitous and significant feature of WR is lack of a universally applicable index for the degree of hysteresis that allows a priori assessment of its effect on flow. In this note we show that the mismatch between the hydraulic capacity functions of the primary drainage and imbibition curves can serve as generalized index for degree of hysteresis ( H ). Moreover, we showed that hysteresis indices of a broad range of soils are linearly related with the natural‐logarithm of the van Genuchten n parameter ( r 2 = 0.73). This model allows predicting the degree of hysteresis and the missing hysteresis branch using only wetting or drying water retention data. The robustness of the proposed index was illustrated by comparing it with error in simulated moisture redistribution in a horizontal column that arises from ignoring hysteresis.