Questions about this article, topic, or product? Click here.

Modeling stormwater gate valve open and closure controls

	Product(s):	SewerGEMS, CivilStorm
	Version(s):	V8i, CONNECT Edition
	Area:	Modeling

Problem

How do I model a gate valve opening and closing based on a logic such as pressure at a pressure transducer (water level in an upstream manhole for example) or based on time (for example open a penstock after a storm).

Solution

This can be done using the Explicit (SWMM) numerical solver (selected in your calculation options) with SWMM Control Sets. After selecting the SWMM solver, define a start control structure on your downstream conduit such as an orifice with a particular label that will be referenced in the SWMM controls.

Next, Go to Components > SWMM Extensions > Controls sets. In here you will need to define two control rules; one to set the setting of the orifice to 0 when the level reaches the point when the gate should close, and another to set the setting to 1 when the orifice should be fully open. For example:

RULE A

IF NODE WW-1 DEPTH <= 0.1
THEN ORIFICE OR SETTING = 0}

RULE B
IF NODE WW-1 DEPTH > 3
THEN ORIFICE OR SETTING = 1

You can read more about SWMM control syntax in the Help or in the EPA-SWMM documentation
Time based controls can also be used (see article below for more)
You may need to use a wetwell upstream instead of a manhole for storage.
For orifice and weir controls, a conduit control structure needs to be used. If you are modeling an outlet structure of a pond, you will need to select "no" for the pond outlet structure's "has control structure" and model a start control structure on the conduit downstream of the pond outlet node.
If using metric units, some versions of the program still require the depths in the control sets to be entered in feet.
In at least one previous case, high continuity error was seen. The continuity error was much better if the gate wasn't opened all the way (80% versus 100%). In this case, try enlarging the full orifice diameter
to compensate. You may be able to further reduce the continuity error by reducing the routing timestep.

Example: a penstock/gate in a pond starts closed and opens up after a storm event, to let the pond's water into the storm drain system: