There are three types of RDII Response, six different parameters and an annual and optional twelve monthly sets of distinct parameters.
Subject: RDII Initial Abstraction in SWMM 5
The initial abstraction in each of the three components of RDII in SWMM 5 are updated at each time step. The initial abstraction (ia) is:
ia = iaMax - iaUsed
based on the maximum amount of ia, the ia used (iaUsed), the recovery rate (iaRecov) and the month and class of RDII. You can enter a value for iaMax, iaInit and iaRecov for each month.
The iaUsed at the beginning of the simulation is set equal to iaInit
and if there is no rainfall
Subject: The Groundwater flow in SWMM 5 Groundwater
The Groundwater flow in SWMM 5 is actually made up of three components:
1. A groundwater flow computed from the coefficient a1 and exponent b1
2. A groundwater flow computed from the coefficient a2 and exponent b2 and
3. A Surface Water / Groundwater Interaction coefficient a3
The total Groundwater flow is the sum of the flow from 1, 2 and 3 – normally 2 is the opposite of 1.
Subject: Exit, Other and Entrance Loss Values in SWMM 5
The entrance, exit and other losses in SWMM 5 are computed at the upstream, downstream and midpoint of the sections of the link. However, if the normal flow equation is used for the link during a time step then these losses are zero as the flow in the link is based solely on the upstream area and upstream hydraulic radius of the link. If you add loss coefficients and the normal flow equation is used then you will not see any change in the flow as you modify the loss coefficients.
Subject: Link Simulated Parameters used in either the Normal Flow or St Venant Equation of SWMM 5
St. Venant equation – this is the link attribute data used when the St. Venant Equation is used in SWMM 5. Simulated Parameters from the upstream, midpoint and downstream sections of the link are used.
Normal Flow Equation – this is the link attribute data used when the Normal Flow Equation is used in SWMM 5. Only simulated parameters from the upstream end of the link are used if the normal flow equation is used for the time step.
