A typical interconnected and hydraulically interdependent pond system is shown to the right.  The smaller ponds (in drainage basins A, B, C and D) are used for pollution abatement while the larger ponds (in basins E, F, G and H) are for flood attenuation. 

Control structures are used in the smaller ponds to capture the "first flush" and slowly meter it out.  The larger ponds are connected by either equalizer pipes (E to F and F to G) or by control structures at strategic locations (G to H and beyond H).  The control structures in the larger ponds are used to restrict the overall rate of discharge from the system as well as to maintain aesthetic water levels in the ponds.  

This entire system is hydraulically interdependent meaning that downstream water levels influence upstream water levels and hydraulics.

Aerial ©2007, Google 

This photograph shows the stormwater treatment pond "A" (in the foreground) connected to the larger detention pond "E" (in the background) by a control structure.  The four large pipes with mitered end sections in the distance connect pond E to pond F and tend to equalize storage between them.

ICPR Modeling Considerations

ICPR's basic building blocks are Basins, Nodes and Links. 

Hydrologic parameters such as drainage areas, runoff curve numbers and times of concentration are prepared for each basin and then runoff hydrographs for various storm events are generated and assigned to the individual nodes in the system.

There are two key data requirements for nodes in this model: (1) stage-area tables for each pond to reflect the amount of storage that's available; and, (2) initial stages.  Initial stages are the starting water levels in each pond (at "time zero" for the various simulations) and are typically governed by the various control structures.  Ponds E, F and G are connected together with equalizer pipes, so the initial stage for all of them would be the same and determined from the control structure connecting pond G to pond H.  All other initial stages are based on their respective control structures.

There are only two different link types for this system: (1) pipes; and, (2) drop structures.  Pipes are used for the connection from node E to F and from node F to G.  All other links in this model are drop structures.  A drop structure link is a composite structure consisting of one or more weirs in series with a pipe.  ICPR balances the losses through the pipe barrel with the losses across the weir(s) to determine the flow rate for the structure at each time step.