Subject: How Does the Green Ampt Initial Moisture Defiict Work in InfoSWMM and 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:
· Soil Moisture = IMD Max – (FUMax – FU)/Upper Soil Zone Depth
· 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
· IMD Max is the user defined Initial soil moisture deficit and is a fraction
Figure 1. How Soil Moisture changes over time.
Figure 2. Soil Moisture and IMD are related – the Soil Moisture has a maximum of IMDMax.