If there is no control structure, a pond in SewerCAD is treated just like a manhole node; the steady flow routing is passing through the pond the same as passing through a manhole. All flow elements are passed through the pond and the steady routing calculation is continued downstream.

The outlet control structures are ignored (no control hydraulics are performed). Flow(in) = Flow(out).

If there is no control structure, the HGL is the value calculated by the gradually varied flow profiler and the input pond initial elevation is ignored.

If there is a control structure and the initial elevation is larger than the one given by the outlet pipe profile calculation then the initial elevation is set as the pond HGL.

The existing Inflow(Wet Collection) in the pond is kept and you caninput a Fixed load for steady state simulations.

Results are the same as a manhole node in SewerCAD.

There is no head loss or infiltration for a pond.

During Extended Period Simulation:

The engine performs storage routing for a pond when the convex routing comes to the pond node.

The pond initial elevation is the start pond HGL for the storage routing and the inflow hydrograph is determined from the upstream convex routing.

AE-Q curve is loaded for the pond outlet (the first curve of the EQT curves based on the fundamental GVF assumption that there are no backwater effects).

Then the Gradually Varied Flow (GVF) engine performs the storage routing to determine the pond outflow hydrograph and the pond elevations for each hydrologic time step.

This pond outflow hydrograph continues the downstream convex routing.

For the profile, the pond elevation time series determined from the storage routing will be compared with the HGL calculated by GVF profiler and the larger value will be used as the pond HGL for the time.

In the case where the outlet has no control structures, the outlet conduit data is used to generate an E-Q curve for the outlet.

The infiltration calculation assumes the pond has outlet control structures since there is no pond routing without control structures. The behavior is the as same as the Dynamic Wave engine.

If the pond type is of elevation-volume, there will be an error message for the average type infiltration.

During Steady State Simulation:

This scenario is treated very similarly to the way it is handled in StormCAD (see ”Ponds in StormCAD’).

If there is no control structure, a pond is treated just like a manhole node; the steady flow routing is passed through the pond the same as it would pass a manhole. All flow elements are passed through the pond and the steady routing calculation is continued downstream.

During steady state simulation, if there is a control structure:

1. The pond outflow will be determined by an EQT curve using the pond initial elevation and assuming a very low tailwater.
2. The pond outflow will become a wet weather flow and all system unit flows are set to 0 from this point.
3. The pond HGL will use the user-specified pond initial elevation.