HydroCAD Stormwater Modeling - Since 1986

Modeling a SmartPOND Rotary Weir

HydroCAD-10.1 provides a new delayed outlet option that makes it easy to model rotating bucket weirs, such as the "SmartPOND" shown at right.  This product, manufactured by AutoFlow LLC and marketed by Convergent Water Technologies, is commonly used as an outlet control device for batch detention systems.

The rotating bucket is activated after a given water surface elevation and time delay have elapsed.  The bucket then begins to rotate at a preset rate depending on the desired release rate and/or detention time.  Flow is evaluated by the weir and orifice equations (depending on head) with the inlet moving from a horizontal to vertical orientation as the bucket rotates. 

Modeling the SmartPOND in HydroCAD

Because the discharge vs. head varies over time, modeling a SmartPOND outlet requires the use of a dynamic pond routing procedure. This also allows the outlet to respond to tailwater conditions created by a downstream reach or pond.

To setup a SmartPOND outlet in HydroCAD, create a new outlet device and select "Delayed Outlet".  A typical outlet screen is shown below:

Description: Text to appear on HydroCAD reports
Routing: Usually set to Primary
Discharge Multiplier: Normally set to 1

Trigger Elevation: Usually set just above the bottom of the pond.
Time Delay: Time to wait before the bucket starts to rotate
Opening Time: Time for bucket to move to fully open (lowered) position
Opening Step: Bucket is lowered at this interval
Invert Elevation: Lip of bucket in fully lowered position
Vertical Range: Set to bucket height
Rotary Weir: Must be checked
Inlet Size: Set for standard 24"x24" bucket inlet
Orifice Coefficient: Also used to determine weir coefficient, defaults to 0.6

Further Information

For further modeling information read about the delayed outlet device or click the the Help button on the outlet screen.

For further SmartPOND product information visit the AutoFlow or Convergent web sites.


HydroCAD is a registered trademark of HydroCAD Software Solutions LLC.
SmartPOND is a trademark of AutoFlow LLC
Images courtesy of AutoFlow LLC and Convergent Water Technologies

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