Percolation ZPERC   A factor used to define the proportional increase from saturated to dry lower zone soil moisture conditions.  This parameter indicates, when used with other parameters, the maximum percolation rate possible when upper zone storages are full and the lower zone soil moisture is 100% deficient. REXP   An exponent determining the rate of change of the percolation rate as the lower zone deficiency ratio varies from 1.4 to 3.5

NOMINAL VALUE 175mm 2.5