Pre 2014 Blogs

groundwater-calculations-in-swmm (1)

Groundwater Calculations in SWMM

Hello Robert !

I am trying to incorporate groundwater in my model. Right now it is showing high negative groundwater error. Is the groundwater error calculated same as the continuity error ?

The Percent Error = 100.0 * (1.0 - totalOutflow / totalInflow)

What are the components and corresponding equations for inflow and outflow for groundwater ?I think the outflow is calculated as

QGW = A1(HGW - H*)B1 - A2(HSW - H*)B2 + A3(HGW HSW)

But how is the inflow calculated ? There are quite a few parameters used in aquifer data editor and groundwater data editor ( i.e. Conductivity slope, tension slope etc) I want to learn them in details. Can you suggest me any documentation for them?

I am following some of the regional modeling attempts for parameters who used XP-SWMM. And they used a lot of parameters like

' Fraction of evapo-transpiration assigned to upper zone, Maximum depth of significant
lower zone storage, Curve fitting parameter, Initial upper zone moisture , Coefficient for unquantified losses
Average slope of the tension versus soil moisture curve. '

It would be very helpful if I could  use this data in my SWMM model. Are they  denoted differently in SWMM? Please help.

bests,

Shams

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