perco

Percolation coefficient

The percolation coefficient is input to limit percolation from the bottom soil layer due to an impermeable layer or high water table. Since percolation can be a slow process, that can occur over days or weeks, the percolation coefficient is highly non-linear and difficult to parameterize and calibrate. To make the input more linear, the following adjustments are applied.

perc_ln_co = log(-log(perco) + 5.6862

perco_lim = exp(-perc_ln_co)

Seepage through the bottom layer, as calculated based on hydraulic conductivity in the soil water routing equations, is multiplied by perco_lim.

A perco value of 0.0 does not allow any percolation from the soil and a value of 1.0 does not restrict percolation from the bottom soil layer.