Parallel Ponds & Simultaneous Routing

[Joe_]

Refer to attached PDF for a diagram. I've also attached a HydroCAD file.
I'm trying to model two (2) earthen ponds/chambers. The ponds will be separated by a berm but connected by a level pipe that is intended to control how much flow enters the second pond.
The first pond/chamber was going to be a dry pond and the second pond/chamber was going to be a bio-retention pond.
Knowing the water elevation in the second chamber is desired.
I'm using the Simultaneous Routing procedure based on how the ponds are connected.

My intention was that flow will enter the first pond first and then be dispersed into the second pond. Smaller flows would first be forced to go through the bio-retention pond and routed through a small controlling orifice. This is one aspect that I'm having trouble with - I think I need to have this controlling orifice on the bio-retention side but routed to a device on the dry pond side?
The elevation of this controlling orifice is currently below my dry pond elevation but I'm not sure how to prevent flow from going through it, on the dry pond side, without first going through the bio-retention side. Do I need a third node of just a catch basin to assist in the modeling?
The other issues are my unfamiliarity with the Simultaneous Routing procedure and I am occasionally getting some oscillation errors when adjusting some things.

I appreciate any help provided.

 

[psmart]

The connecting pipe is easy. That's just a culvert outlet from the first (dry) pond. But you seem to be also be feeding water through the perforated underdrain, into the media and presumably into the upper part of the pond as it fills up? So the same media is actually receiving water from both ponds? I also assume your also have exfiltration from the second pond into the surrounding ground?

If this is true, your outlet setup for each pond would be:

Pond 1:
Device#1=Culvert, routing=Primary (this is the open pipe)
Device#2=Culvert, routing=Secondary (this feeds the media layer)
Device#3=Controlling orifice, routing=Device#2
Device#4=Side orifice, routing=Device#2
Device#5=Top of riser, routing=Device#2

Primary and secondary outlets are both routed to Pond 2.

Pond2:
Device#1=Exfiltration, routing=Discarded

However, you should definitely be using DSI and not SimRoute, which is needed only for circular (looping) flows. For details see www.hydrocad.net/tailwater.htm

 

[Joe_]

Thank you for your reply Psmart.
My apologies, looking back on my post I left out some other details.
I've attached a revised diagram.
My intention was that flow will enter the first pond first and then be dispersed into the second pond. Smaller flows would first be forced to go through the bio-retention pond and routed through a small controlling orifice. The smaller flows/events will be forced into the bio-retention pond, but larger flows/events will (partially) exit via an orifice & outlet pipe in the first pond.
The intent with the controlling orifice is that any flow that goes through it, has first passed through the bio-retention side.
I know that with this conceptual setup, some larger events will go through the bio-retention side and thats ok.
I will not have any exfiltration. Even though I have a "bio-retention" I'll need to assume that I have an impermeable liner.

I've seen another example of this concept but the example had a separate outlet structure (concrete structure with orifices) for each Pond. I'm not opposed to that but my first instinct was that maybe this concept could only have one "outlet structure" (concrete structure).

 

[psmart]

OK, so the "outlet pipe" at the bottom of the control structure is the final discharge, and the bioretention area is basically "offline" storage.

You could try:

Pond 1 = "Dry Pond"
Device#1=Culvert (connecting pipe), routing=Primary (routed to pond 2)
Devcie#2=Rectangular orifice, routing=Secondary (routed to pond 3)

Pond 2 = Bioretention area
Device#1="Controlling orifice" ,routing=Primary (routed to pond 3)

Pond 3 = Inside of riser control structure (zero-storage)
Device#1="Outlet Pipe",routing=Primary (final discharge)

In this scenario I am ignoring the influence of the media, assuming that the "controlling orifice" will always be the control point.

For stability use DSI routing, not SimRoute. Since this setup does not involve circular flows you do not need SimRoute.