Here is a new tool, based on SWMM, that may be of interest. It provides non-modelers with a quick and easy way to rigorously estimate stormwater runoff volumes from their properties. For you SWMM experts, it offers an easy way to download long term rainfall data and monthly ET rates for use in your SWMM models.
EPA's National Stormwater Calculator is Now Available to the Public http://www.epa.gov/nrmrl/
EPA's National Stormwater Calculator is a desktop application that estimates the annual amount of rainwater and frequency of runoff from a specific site anywhere in the United States. Estimates are based on local soil conditions, land cover, and historic rainfall records. The Calculator accesses several national databases that provide soil, topography, rainfall, and evaporation information for the chosen site. The user supplies information about the site's land cover and selects the types of low impact development (LID) controls they would like to use.
Water Supply and Water Resources Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
|EPA National Stormwater Calculator Graphical User Interface