USGS Modeling of Watershed Systems (MOWS)
http://wwwbrr.cr.usgs.gov/projects/SW_MoWS/software/oui_and_mms_s/prms.shtml
USGS 1997. Precipitation-Runoff and Streamflow-Routing Models for the Willamette River Basin, Oregon, U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 95-4284. (pdf)