Infiltration Pond Oscillations

[PSVT]

Hi everyone,

I am having trouble figuring out why I am getting oscillations in my model of an infiltration pond. I've used custom stage data to represent the available storage. The available storage elevation is in excess of the peak water elevation during the design storm. I have infiltration occurring through the bottom of the pond represented by an exfiltration outlet with 2.5 in./hr rate.

I have tried setting the finer routing setting to 2 or 3 and adjusted my time increment down to 0.01 hr with no improvement.

I have noticed that the oscillations go away when I change from DSI to SI routing, but I still see oscillations with DSI routing even when I detach my pond from its downstream nodes. Right now I just have 2 subcatchments routed to the infiltration pond, and still see oscillations. I wish to use the DSI routing in my model because I need to account for tailwater effects in other areas of my site. Also, my results summary states that my pond inflow precedes pond outflow.

I would appreciate any help.

 

[psmart]

Exactly what warning messages are you getting?

Other conditions, such as overfilled storage, can trigger oscillations.

For details see

http://www.hydrocad.net/dsi.htm

If you need further assistance you can post your project file of send it to HydroCAD support.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[PSVT]

I am getting warning message #87
" oscillations may require finer routing or smaller dt" My current settings are set at dt =0.01 hr and finer routing =2. My model shows .6' freeboard, and I have tried adding extra storage to see if that would make the problem go away, but I still have oscillations in my outflow hydrograph.

 

[psmart]

Are there any other warnings?

For routing tips please see

http://www.hydrocad.net/dsi.htm

If you need further assistance you can post your project file of send it to HydroCAD support.

Peter Smart
HydroCAD Software

http://www.hydrocad.net