Inflow hydrograph in the pond

Question

Hi 
 when I am using pond maker in the sewerGems , in the "Storage Estimate" I get the following capture for the inflow hydrograph!

Scott Kampa · Accepted Answer

Hello Hamid, 
 
As Jesse mentioned, a fixed inflow is not valid when using Pondmaker, since Pondmaker assumes a typical hydrograph like you see from your catchment itself. However, you have a fixed inflow of 400 L/s applied to MH-1. If you want to use Pondmaker, you cannot have this inflow. 
 
If you remove the fixed inflow, further adjustments still need to be made in order to use Pondmaker. Pondmaker assumes that you are sizing a pond so that the outflow from the pond in a post-development situation matches well with the outflow from a predevelopment situation. However, in your model, the design scenario and the target scenario are the same. This is not valid. You would need to either create a new predevelopment scenario or you would need to set "Target Flow/Volume Source" in Step 1 of PondMaker to "User-defined". If you use the user-defined peak flow option, you would then be able to enter a target peak flow and target peak volume in the table at the bottom of PondMaker. This will typically be less than the peak flow and volume you see in the post-development scenario, otherwise there is no reason to build a pond. 
 
If you need to have the fixed inflow at MH-1, you will likely need to size the pond using another method. 
 
Here is a link on how to use Pondmaker: communities.bentley.com/.../using-pondmaker 
 
Note that the sample model referenced at the end of the TechNote will only open in PondPack and not in SewerGEMS. 
 
Regards, 
Scott