Appendix I discusses the Chesapeake Bay Phase IV Watershed Model operating procedures. The Phase IV Watershed Model is a comprehensive package for simulation of watershed hydrology and water quality based on the Hydrological Simulation Program - FORTRAN (HSPF) code. The phase IV Watershed Model allows the integrated simulation of land and soil contaminant runoff processes with instream hydraulic and sediment-chemical interaction. The Phase IV Watershed Model partitions the Chesapeake Bay into 86 segments. Each segment is divided in ten land uses and load sources which are: high tillage, low tillage, hayland, pasture, forest, pervious urban, inpervious urban, animal waste, atmospheric deposition, and point sources. The model generates daily nonpoint source edge-of-stream (EOS) nutrient loads for each land use on a unit area basis and daily nutrient loads delivered to the bay. The simulation of the entire Chesapeake Bay Basin necessitates the run of 29 separate input decks. Each input deck, as it is currently design, can simulate up to 3 segments of the basin. The simulation time is 12 years and spans from January, 1984 to December, 1995.

"Prepared by the Nutrient Subcommittee of the Chesapeake Bay Program"--Cover. "September 1998." "A Report of the Chesapeake Bay Program Modeling Subcommittee Annapolis, MD."