Secondary Outflow Versus Primary Outflow

[login67]

I have a scenario where in a storm sewer modeled as a pond discharges flows from the seocondary outlet but zero flow from the primary outlet despite the fact that the primary outlet invert is far below the secondary invert.The secondary outlet invert elevation is set at the catchbasin grate elevation. How is this possible? One w Thanks.ill expect the primary outlet to first discharge before the secondary. Your help is highly appreciated.

 

[psmart]

Have a close look at the pond summary report. A discharge multiplier of zero will effectively "turn off" the outlet. There could also be tailwater. Any of these conditions (and others) will be indicated in the summary report.

If you still have questions please post the HydroCAD project file or a PDF of the pond summary report.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[login67]

I looked at the discharge multiplier in the pond window as it is set to 1 and not zero. I have attached the file for your review. Thank you for all your help. You have been extremely supportive. Thanks again

 

[psmart]

There is no primary discharge because the pond's maximum WSE of 4.36' is below the 6.20' tailwater created by the storage invert in the next node.

The pond summary report tells all: Scroll down through the report to the device analysis:
Primary Outflow max=0.00 .... TW=6.20'

Looking at the downstream pond, the storage begins at 6.20', higher than the "upper" node. This creates a culvert tailwater condition that is never exceeded by the upper pond, so no culvert discharge occurs. Perhaps there's an error in the elevation data in the "lower" pond?

BTW, your overflow grate is currently not routed, to the entire outflow is basically discarded. I suspect you want to route the (secondary) overflow to the next node, along with the primary.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[login67]

You are right. I had the wrong tail water elevation in the downstream pond. I fixed it and it works. As always, thank you very much.