5.1.6  Maximum and Potential Percolation

The maximum amount of moisture available for percolation (i.e., maximum percolation) is the adjusted precipitation less overland runoff:



where    I_max(j) is the maximum amount of moisture available for percolation in the j-th month (cm).

Potential percolation is the maximum percolation (I_max(j)) less PET.  Therefore, the maximum percolation is first used to satisfy the demands of PET before soil moisture recharge or deep-drainage percolation can occur.  Potential percolation is expressed as follows:



where

I_pot(j)     is the potential percolation for the j-th month (cm)
E_pj         is the potential evapotranspiration rate for the j-th month (mm d^-1).

The factor (n_dj/10) in Equation 5.30 is needed to convert PET rate (mm d^-1) to PET (cm).  Note that potential percolation is positive during wet seasons and negative during dry seasons.