Pond Exfiltration Design
Exfiltration is classified as an outlet device and is
incorporated into a pond's stage-discharge curve. But exfiltration
is usually directed to the discarded outflow to prevent
further routing. There are two design methods to determine
exfiltration, shown below:
1. Constant exfiltration Flow: The flow value (cfs or cms) is
applied whenever there is water in the pond, or only when the water
level is at or above the specified invert elevation.
2. Exfiltration Velocity: The velocity (in/hr or mm/hr) is
multiplied by the exfiltration area at a given elevation to
determine the final exfiltration flow.
The exfiltration area may be defined in three ways: 1) Pond Bottom
Area, which allows the exfiltration only through the bottom of
pond; 2) Water Surface Area, which assumes the exfiltration is
downward; 3) Pond Wetted Area, which allows the exfiltration occur
through all exposed surfaces regardless of slope. You may also
choose to exclude the area of the pond that lies at or below the
specified invert elevation, which is useful in preventing
exfiltration through impervious (lower) regions of the pond.
There are two ways to enter the pond parameters. If you elect to
input the stage-storage curve, the program will determine the
bottom and side areas automatically.
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Pond Exfiltration Design
Dialog
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Stage-Discharge Result
Dialog
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Exfiltration Design
Report
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Pulldown Menu Location: Structure > Pond Exfiltration
Design
Keyboard Command: exfilcalc
Prerequisite: None