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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

 

Image003
Figure 1.  How FTOT, FU and F change over time

Image004
Figure 2.  A closer look at how FTOT or F and FU Change over time in a Green Ampt Pervious Area Simulation.

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  • Subject:   How Does Green Ampt Initial Moisture Defiict 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:

    ·         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

    Image005
    Figure 1.  How Soil Moisture changes over time.



    Image006
    Figure 2.  Soil Moisture and IMD are related – the Soil Moisture has a maximum of IMDMax.




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