Problem

How can I model a pumped pond with the Implicit or Explicit (SWMM) dynamic solver? (a pond that is drained with a pump instead of a pond outlet)

Note: for PondPack, see further below.

Solution

A pump is connected to a pond by way of a pond outlet node element with a pressure pipe between it, as seen in the figures below. Select your pond from the "upstream pond" field in the pond outlet node and choose "false" for "has control structure".

Pond > pond outlet node > pressure pipe > pump > pressure pipe

Single pump:

Pump Station (multiple ponds in parallel, associated with a pump station element for organizational purposes):

Note: if you encounter problems with pump results (especially when manifolded), try setting the pressure pipe between the pond outlet and the pump to be a virtual pipe (Is Virtual = True).

Modeling a Pumped Pond in PondPack

With PondPack, you may be able to model a pump with the "User Defined Rating Table" option in a composite outlet structure. For lower pond elevations where the pump is off, the corresponding flow would be zero, and then for elevations above which the pump is on, you would enter the expected pump flow rate.

The problem with this approach is that you would not be able to have any "band" in the control range. Meaning, as soon as the pond elevation rises above the first rating curve elevation that has the pump "turn on" (non-zero flow), if the elevation drops, it would immediately drop back to the zero flow (pump off) point, and you may see some oscillation. In a real system you may have some range between the pump on and off elevation, where for example the pond would need to drain some distance (or get near the bottom) before the pump turns back off.

So, if you need to model this type of situation where you need range between on and off controls, you may need to use SewerGEMS or CivilStorm, which can explicitly model the pump and pressure pipes connected to a pond.

See Also

How are pumps handled in each OpenFlows product?

Pond and pond outlet assumptions in StormCAD, SewerGEMS, CivilStorm  and SewerCAD