How Does Green Ampt Cumulative Event Infiltration work in SWMM 5?

Subject:   How Does Green Ampt Cumulative Event Infiltration work in SWMM 5?

This graph shows the values of the internal SWMM 5 parameters for Green Ampt Infiltration for the pervious area of a Subcatchment during a simulation.  The parameters are:

·         F or FTOT which is the cumulative event infiltration at the start of a time interval in the internal units of feet in SWMM 5,
·         FU or current moisture content of the upper zone of the of the soil
·         FUMAX which is the saturated moisture content of the upper zone in feet and stays constant during the simulation 

Figure 1.  How FTOT, FU and F change over time

Figure 2.  A closer look at how FTOT or F and FU Change over time in a Green Ampt Pervious Area Simulation.