NetSTORM’s eponymous module extends the STORM concept to a network of linked control structures, such as found in an urban collection system. The runoff volume calculation presented above is modified to include inflow from an upstream control structure. The NetSTORM module also allows specification of dry weather flow (Qdwf), either as a constant input, or read from an external time series:
Vt = (C i + (1 – C) max (0, i – fc)) A Dt + St-1 + Vus + Qdwf Dt (7)
Upstream inflow (Vus) may come either from a treated volume or from an overflow volume, depending on how the model connectivity is specified. This allows the model to simulate an interceptor sewer with multiple CSO regulators upstream of another regulator such as a pump station or wastewater treatment plant, and also allows it to simulate an overflow collection conduit that has several tributary regulators. Alternatively, the same concept may be extended to any collection system with multiple control structures. The NetSTORM module does not offer built-in facility sizing computations as the simpler STORM module does. The NetSTORM module permits the use of multiple rain gages for analysis of large systems.
Results from NetSTORM analysis yields hourly overflow volumes for each simulated control structure, as well as a summary of overflow activity for each storm in the meteorologic record. The results can be post-processed within the program’s GUI to obtain summary storm and overflow statistics such as annual overflow by month, overflow volume, duration, and frequency at each control structure, and annualized percent capture.