Abstract

The Stormwater Management Model (SWMM) is a dynamic rainfall-runoff model used for continuous simulation of runoff quantity and quality. SWMM has recently been redeveloped under a Cooperative Research and Development Agreement (CRADA) between CDM Inc. and the U.S. Environmental Protection Agency (USEPA). One of the purposes of the CRADA is to improve the numerical stability of the model without changing the fundamental characteristics of the EXTRAN solution or sacrificing the efficiency of its performance. Extensive QA/QC testing was performed as part of the CRADA to ensure consistency between the SWMM4 and SWMM5 solutions. (Dickinson et al., 2004; Rossman et al., 2003; Schade, 2002; Chan et al., 2003). Another aspect of QA/QC testing was to compare simulation runtimes between SWMM4 and SWMM5.

This chapter presents the computational speed comparison between SWMM4 (Huber & Dickinson, 1988) and SWMM5 (Rossman et al., 2003). Various SWMM4 historical applications were used and runtimes of SWMM4 and SWMM5 were plotted and compared by different calculation methods.

This chapter also describes the approach used to test the simulation speed in SWMM4 and SWMM5. All models were run on the same computer workstation for fairness in the comparison. The test computer was equipped with a commonly available Pentium® P4-1.6 GHz processor with 256Mb RAM. The SWMM4 models were run with SWMM499 and the new SWMM5 (version Beta E). To ensure data consistency, the historical SWMM4 applications were translated to SWMM5 input format, using the converter software distributed with the SWMM5 package. Results generated from the new SWMM5 were compared to those from the existing SWMM4 model as part of the speed test procedure.

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