A new open-source hydraulic solver has been created as a companion to the EPA Storm Water Management Model (SWMM). The new SWMM5+ hydraulic solver uses finite-volume algorithms with automated subdivision of the link-node system from a traditional EPA SWMM model. Partitioning of the 1D computational network across for parallel computation across any number of processors is accomplished with an integrated pre-processing algorithm designed with insights from graph theory. The new hydraulics algorithms are closely-coupled with the EPA-SWMM hydrology code. Using the new hydraulic solver requires coupled compiling of the EPA SWMM source code with the new SWMM5+ source code using the Intel OneAPI compiler. The new SWMM hydraulics and associated libraries for compilation are available in a Docker image that is compatible with Windows, Linux and (with some limitations) OSX. The key advantages of the new model are (i) parallelization across a large number of processors, and (ii) mass conservation to machine accuracy.
