Pond Storage Question
Pond Storage Question
(OP)
I have modeled a pond with an overflow weir as the secondary outlet at the top of the pond elevation and a culvert discharge as the primary outlet, located at the base of the pond. The question I have is that when I look at the Hydrograph table, there is water flowing through the overflow weir (secondary discharge) before the pond capacity has been reached. Can you please tell me why this is occuring and what this means? I have double checked that the base of the weir is at the top of the pond storage so it is not that the storage volume should be reduced due to the outlet location.





RE: Pond Storage Question
In general, you need to define enough storage to cover the entire range of possible operation. In the case of a weir outlet, this means that you must define storage to some point above the weir. Otherwise the pond will effectively be "capped" at the weir crest, and will not produce the behavior you expect.
To define storage above the weir, include the controlled volume upstream of the weir, bounded by an imaginary wall above the spillway. For further details please see www.hydrocad.net/overfilled.htm
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Pond Storage Question