Gardner (1956) Fit 
Gardner (1956) permeability function for unsaturated soils is expressed as a function of suction:
aga: The aga field indicates fitting parameter for Gardner (1956) fit of the hydraulic conductivity function.
nga: The nga field indicates fitting parameter for Gardner (1956) fit of the hydraulic conductivity function.
k minimum: The value entered in this field represents the minimum allowable hydraulic conductivity. The minimum hydraulic conductivity should correspond to conditions encountered as the soil approaches residual conditions. A value of 1e14 m/s is typical of the point where vapour flow begins to dominates flow. A minimum hydraulic conductivity is less than 1e10 m/s may significantly increase the number of nodes used to obtain a solution. It is suggested that a minimum value of 1e10 m/s be entered for most practical problems.
Apply k minimum: The equation originally presented by Gardner (1956) did not have a limitation on the minimum allowable hydraulic conductivity. Applying a reasonable minimum to the unsaturated portion of the curve and dramatically improve numerical computations.
Gardner a: The Gardner (1956) a field indicated the parameter related to the breaking point of the function.
Gardner n: The Gardner (1956) n field indicated the slope of the function.
Gardner Error: The Gardner (1956) Error is the difference between the fitted results and the laboratory values in terms of R2.
The Estimate button is provided at the bottom of the dialog in order to allow the user to estimate the hydraulic conductivity.
The Graph button allows the user to display a graph of suction versus hydraulic conductivity. The interpolated curve will also be displayed. It should be noted that laboratory data will be interpolated on an arithmetic scale.
