Notes on ROSETTA ( from ROSETTA Help File, USDA-ARS Salinity Laboratory, Riverside, CA)

 

The present version of Rosetta is capable of predicting van Genuchten (1980) water retention and unsaturated hydraulic conductivity parameters, as well as to provide estimates of saturated hydraulic conductivity, Ks.

 

The van Genuchten water retention function is given by:
 

 

where q(h)  represents the water retention curve defining the water content, q  (cm3/cm3), as a function of the soil water pressure head h (cm), qr  and qs (cm3/cm3) are  residual and saturated water contents, respectively, while a  (1/cm) and n are curve shape parameters. This equation can be rewritten to yield the relative saturation, Se

 

 

This equation can then be used in conjunction with the pore-size distribution model by Mualem (1976) to yield the van Genuchten-Mualem model  (van Genuchten, 1980):

 

 

 

in which Ko is the matching point at saturation (cm/day) and similar, but not necessarily equal, to the saturated hydraulic conductivity, Ks. The parameter L (-) is an empirical pore tortuosity/connectivity parameter that is normally assumed to be 0.5 (Mualem, 1976). Rosetta predicts L and, in the majority of the cases L will be (cf. Kosugi, 1999; Schaap and Leij (1999).

 

In DRAINMOD, the routine for creating a soil file requires the following inputs: qs and qr (the saturated and  residual water contents), alpha, parameter n and L, Ko and Ks.  These values can be taken from the output of the ROSETA model