Exfiltration - start above an elevation?
Exfiltration - start above an elevation?
(OP)
Can HydroCAD delay exfiltration from a basin until the water within it gets to a certain depth? The "Only above invert" is not the answer as that then excludes the bottom area as impervious. I only want to delay the start as required by MA DEP "static method" regs.
Therefore, a basin with invert 100, is required to fill to 102 THEN exfiltration can begin over the entire surface area. Can this be modeled?
Thanks
Therefore, a basin with invert 100, is required to fill to 102 THEN exfiltration can begin over the entire surface area. Can this be modeled?
Thanks





RE: Exfiltration - start above an elevation?
However, you should be able to model this situation using a "pump" outlet, which allows you to set a "turn on" elevation. You'll also need to use the DSI routing procedure to handle the change in the stage-discharge relationship when the exfiltration starts. But it can be done.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Exfiltration - start above an elevation?
1) If you can model your exfiltration with a constant flow (in CFS), then you would be able to set the exfiltration invert elevation anywhere you wish with effecting the flow rate.
2) If your primary objective is to model the pond draw-down, you could eliminate the inflow hydrograph entirely and set the starting elevation instead.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Exfiltration - start above an elevation?
http://www.mass.gov/dep/water/laws/v3c1f.doc
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Exfiltration - start above an elevation?
Do you feel that would work? I only have two small basins so this technique is fine for this particular project.
RE: Exfiltration - start above an elevation?
As happens with the "simplified" procedures in many regulations, they're really intended for manual evaluation, and often do not lend themselves to a simulation program like HydroCAD. Fortunately, the Mass DEP regs do provide "dynamic" alternatives that are better suited for numerical simulation.
Peter Smart
HydroCAD Software
www.hydrocad.net