textural classes

A discussion forum for RETC users. RETC is a program which can be used to analyze the soil water retention and hydraulic conductivity functions of unsaturated soils.
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Joined: Wed Feb 03, 2010 6:56 am
Location: Slovenia

textural classes

Post by saska.vidmar » Wed Feb 03, 2010 7:01 am

Inside the program used textural classes are defined as sand and smaller particles. How do we take into account grain sizes bigger than sand (gravel, pebbles)? Do we just assume a 100% composition of smaller particles? Have there been any known problems as a result of this?

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Joined: Wed Apr 24, 2002 7:22 pm
Location: USA

Post by rvang » Wed Feb 10, 2010 12:51 pm


There have been a number of studies suggesting that you can make a simple linear correction to the water retention curve (e.g., as predicted with pedotransfer functions, or measured) to account for the gravel content (i.e., by assuming that gravel contains no water); just correct the saturated and residual water contents. Corrections of the hydraulic conductivity are a bit more complicated. A good recent study is by Dann et al. in Vadose Zone Journal (2008, 8:651–663, doi:10.2136/vzj2008.0174). Look also at Khaleel and Relyea, 1997 (Correcting laboratory-measured moisture retention data for gravels. Water Resour. Res. 33:1875–1878), and references in those two papers.

Rien van G.

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