Total discharge time

[arabojan]

I was wondering how can calculate total discharge time for a detention pond to completely be empty for example after 10 years storm, I am using PondPack for my calculation.

 

[RWF7437]

I don't use PondPack but a general answer to your question is offered. Plot the inflow and outflow hydrographs from your pond routing. Then measure the time from the point where the two hydrographs intersect to the point where the outflow hydrograph reaches zero outflow. This distance, in hours or minutes, is the time to empty.

good luck

 

[arabojan]

thnaks so much

 

[cvg]

most consider the drain time to begin when rainfall stops. So you might consider measuring the time from when the rainfall stops, till the end of your outflow hydrograph. You may also want to cut off at a certain point as the remaining flow will likely infiltrate into the ground. Usually I don't continue beyond say 6" deep in the basin - assuming you can infiltrate at least that much water into the ground.