# Model help:TopoFlow-Soil Properties Page

## TopoFlow-Soil Properties Page

This page contains information on several different methods for modeling the properties of soil as a porous media in hydrologic models. It contains relationships and tables of values that are used for modeling the process of infiltration. A discussion of several soil characteristic relations is followed by two tables of standard values from the literature. This information is helpful for setting parameters in hydrologic models such as TopoFlow

## Main equations

Effective saturation or scaled water content

 $\displaystyle{ \Theta_{e} = \left ( \theta - \theta_{r} \right ) / \left ( \theta_{s} - \theta_{r} \right ) }$ (1)

Transitional Brooks-Corey (Smith, 1990)

(1) Hydraulic conductivity

 $\displaystyle{ K \left (\Theta_{e}\right ) = K_{s} * \Theta_{e}^ \left ({\frac{\eta}{\lambda}}\right ) }$ (2)

 $\displaystyle{ \Psi \left(\Theta_{e} \right ) = \Psi_{B} [\Theta_{e}^ \left ({\frac{-c}{\lambda}}\right ) - 1]^ \left ({\frac{1}{c}}\right ) - \Psi_{A} }$ (3)

(3) Hydraulic conductivity

 $\displaystyle{ K \left (\Psi \right ) = K_{s} * \{ 1 + [\left (\Psi + \Psi_{A} \right ) / \Psi_{B}]^c \} ^ \left ({\frac{-\eta}{c}} \right ) }$ (4)

Standard Brooks-Corey (1964)

(1) Hydraulic conductivity

 $\displaystyle{ K \left (\Theta_{e}\right ) = K_{s} * \Theta_{e}^ \left ({\frac{\eta}{\lambda}}\right ) }$ (5)

 $\displaystyle{ \Psi \left(\Theta_{e} \right ) = \Psi_{B} * \Theta_{e}^ \left ({\frac{-1}{\lambda}}\right ) }$ (6)

(3) Hydraulic conductivity

 $\displaystyle{ K \left (\Psi \right ) = K_{s} * \{ \Psi / \Psi_{B}\} ^ \left (-\eta \right ) }$ (7)

van Genuchten (1980)

(1) Hydraulic conductivity

 $\displaystyle{ K \left (\Theta_{e}\right ) = K_{s} * \Theta_{e}^ \left ({\frac{1}{2}}\right ) [1 - \left ( 1 - \Theta_{e}^ \left ({\frac{1}{m}}\right )\right )^m]^2 }$ (8)

 $\displaystyle{ \Psi \left(\Theta_{e} \right ) = \left ( 1/ \alpha_{g} \right ) [\Theta_{e}^ \left ({\frac{-1}{m}}\right ) - 1]^ \left ({\frac{1}{n}}\right ) }$ (9)