Phase 5 Watershed Model

Phase 5, the latest version of the Chesapeake Bay Program's Watershed Model, is now under development. A number of improvements are being made from the previous version of the model, Phase 4.3; however, the most significant improvement is the scale in which the data are now available. We are developing a model that can be used on a fine scale, consistent with the scale needed for State developed TMDLs. In this way, watershed load analysis can be consistent between State-led basin and small tributary TMDLs, and the CBPO led overall assessment of Chesapeake Bay water quality. The level of collaboration with this model between the Environmental Protection Agency (EPA), the Chesapeake Bay Program (CBP), US Geological Survey (USGS), Interstate Commission on the Potomac River Basin (ICPRB), Maryland Department of the Environment (MDE), VA Department of Conservation and Recreation (DCR), and the University of Maryland (UMD) has allowed us to significantly improve the spatial and computational scale of the model.

Specific improvements include:

• Refined and updated rainfall, fertilizer, Best Management Practice (BMP), and landscape processes data. All data will be updated to 2002, allowing an 18 year simulation period from 1984 to 2002.
• Refined segmentation of land segments and river reaches including the simulation of all major reservoirs in the watershed.
• Additional land use simulations - there will be approximately 20 Phase 5 land uses, a two-fold increase from Phase 4.3. Phase 5 land use will include 12 different crop types, and several new BMP types will be directly simulated.

For more information see the model related publications by clicking on the publications tab on the top of this page. Featured publications include: the report Cross-Media Models of the Chesapeake Watershed and Airshed and Watershed Model Application to Calculate Bay Nutrient Loadings: Final Findings and Recommendations are particularly recommended as detailed background information on the Watershed Model

Draft Phase 5 Community Model Documentation

A preliminary working draft of the Phase 5 model is provided here for the user community. This draft documentation includes updates in October 2006, January 2007, April 2007, and July 2007. The documentation will be finalized by January 2008 when Phase 5 is approved for management application in Bay Program nutrient and sediment load assessments. Users of this draft information are warned that this information is preliminary, subject to change, and unsubstantiated by full and final reviews. These draft reports should be cited as “U.S. EPA, 2008. Chesapeake Bay Phase 5 Community Watershed Model In preparation EPA XXX-X-XX-008 Chesapeake Bay Program Office, Annapolis MD. January 2008."

Section 1: Watershed Model Overview
Section 1.1 – 1.10	Latest Draft: 3/21/08	12 MB .pdf	Download

Section 2: Meteorology and Precipitation
Section 2.1 – 2.31	Latest Draft: 3/21/08	4 MB .pdf	Download

Section 3: Land and River Segmentation
Section 3.1 – 3.7	Latest Draft: 3/21/08	8 MB .pdf	Download

Section 4: Land Use
Section 4.1 – 4.7	Latest Draft: 3/21/08	8.5 MB .pdf	Download

Section 7: Point Sources, Water Withdraws, and On-Site Waste Disposal Systems
Section 7.1 – 7.4	Latest Draft: 3/21/08	372 kb .pdf	Download

Section 9: Sediment Simulation
Section 9.1 – 9.7	Latest Draft: 3/21/08	757 kb .pdf	Download

Chesapeake Online Assessment Scenario Tool (VORTEX) Documentation
Vortex Watershed Data Tool Documentation	Latest Draft: 1/3/08	757 kb .doc	Download