How is Capillary Suction Head Used in SWMM 5 Green-Ampt?

Subject:   How is Capillary Suction Head Used in SWMM 5 Green-Ampt?

How sensitive is the infiltration loss and rate to the capillary suction head parameter in the SWMM 5 Green-Ampt  infiltration method.   Figure         1 shows how the total infiltration loss and total loss rate vary as you change the suction head from 12 to 6 to 3 inches.    Internally the suction head is used in infil.c of SWMM 5 by adding the suction head to the ponded water on the pervious area in the parameter c1 of the implicit Green-Ampt SWMM5 solution.

C1 =  (Suction Head + Depth of Ponded Water) * IMD or Initial Moisture Deficit

Figure 1.  The sensitivity of the total infiltration loss to the capillary suction head in a continuous simulation