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Estimating the Water Retention Shape Parameter from Sand and Clay Content
Author(s) -
Minasny Budiman,
McBratney Alex B.
Publication year - 2007
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/sssaj2006.0298n
Subject(s) - hydraulic conductivity , water content , soil science , water retention curve , shape parameter , parameterized complexity , water retention , pedotransfer function , particle size distribution , soil water , mathematics , infiltration (hvac) , function (biology) , particle size , environmental science , geotechnical engineering , materials science , geology , statistics , algorithm , composite material , paleontology , evolutionary biology , biology
This study developed an alternative way of estimating the van Genuchten water retention shape parameter n from a soil's sand and clay content. This estimation can be used to complement an infiltration experiment called the Beerkan method, which has been proposed for estimating the van Genuchten water retention function and Brooks–Corey hydraulic conductivity characteristic. To estimate the water retention shape parameter, the Beerkan method requires a distribution function fitted to particle‐size distribution data (more than five fractions) and a measurement of bulk density. Using three published databases, we were able to derive a neural network model that predicts the shape parameter and its uncertainty from sand and clay content. Its accuracy ranges from 0.2 to 0.4. This method is comparable to prediction using parameterized particle‐size distribution data. The response surface of n as a function of sand and clay content shows an increasing value of n with increasing sand content in a nonlinear way. We also show that using simpler methods for predicting shape parameter n does not influence the accuracy of the Beerkan method in estimating the soil hydraulic properties.