GenScn, which stands for GENeration and analysis of model simulation SCeNarios, was developed by the USGS to create simulation scenarios and analyze and compare the results of those scenarios in a graphical, interactive environment. The USGS developers said the Hydrological Simulation Program-Fortran, or HSPF, was used in the design of the GenScn system. HSPF is a highly versatile model used in simulating urban and rural watersheds. HSPF is contained in the GenScn program and is also available separately at the web site listed below. Other models can be adapted to use GenScn.

GenScn is documented in a new USGS report, "A Tool for the Generation and Analysis of Model Simulation Scenarios for Watersheds (GenScn)," published as USGS Water-Resources Investigations Report 98-4134, and is available for electronic retrieval on the World Wide Web.