What is the ILSAX Runoff Method and how does it differ from DRAINS?
SewerGEMS includes support for the ILSAX hydrological model as a runoff method, as one of the many runoff methods that it supports. The version of the ILSAX method used in SewerGEMS is the same version used in the DRAINS program. ILSAX is also the name of a freeware application that was superseded by DRAINS, but SewerGEMS implements only the hydrological method.
Once the overall runoff hydrograph is calculated, it is routed into the hydraulic model network and hydraulics are calculated based on the selected numerical solver: Implicit dynamic, Explicit dynamic (SWMM) or GVF-Convex (SewerCAD)*
*The GVF-Convex solver is only available in SewerCAD and SewerGEMS.
Since the ILSAX program is freeware, many users (typically in Australia) still use it and are familiar with it's runoff method. Therefore, such users can use this runoff method in SewerGEMS in order to produce familiar runoff hydrographs per the ILSAX standard method.