Phase 7 Model Development
In ProgressThese updated modeling tools will be used by the Chesapeake Bay Program partnership to inform decisions related to the nutrient and sediment reduction goals outlined in the 2014 Chesapeake Bay Watershed Agreement.
Description
Currently in development, the Phase 7 Modeling Tools will be used by the partnership to inform decisions related to the nutrient and sediment reduction goals outlined in the 2014 Chesapeake Bay Watershed Agreement. Integral to this updated suite of tools is the ability to project changing environmental conditions through 2035. The model, which will be ready for use by 2028, consists of eight interrelated projects: (1) High Resolution Land Use, (2) Chesapeake Assessment Scenario Tool (CAST), (3) Optimization, (4) Agricultural Inputs, (5) Atmospheric Deposition Modeling, (6) Watershed Modeling, (7) Estuarine Modeling and (8) Criteria Assessment.
The development of the Phase 7 model is ongoing. Evolving plans and related documents will be posted here as they become available. Resources on the development of Phase 7 as a whole are posted in the side panel. Resources on specific components of the model can be found below.
More information on the role of the model in the Chesapeake Bay Program, and why this update is happening can be found on the Phase 7 Model Development webpage.
WQGIT Phase 7 Office Hours
The WQGIT organized optional sessions to facilitate comprehension of Phase 7 topics and updates. These topics continue to be discussed at the appropriate workgroup. Recognizing an interest to better understand these evolving methods, we provided these “office hours” as informal briefings and discussions for the WQGIT or other interested parties. Notes from all three sessions are compiled here.
- Friday, August 15, 1-2:30pm - BMP Excess, Land Use Loading Rate Ratios - Recording, Notes
- Monday, August 18, 1-2:30pm - Land Use Topics: Back-Cast Overview, Land Use aggregation, CAST Land Uses - Recording, Notes
- Monday, September 15, 1-2:30pm - Wastewater Topics: Exfiltration method, Septic/Sewer Model, SSO Loads, Boat Pump-Outs - Recording, Notes
Resources
High Resolution Land Use
- Phase 7 Land Use Aggregation - This presentation from the September 2025 WQGIT meeting outlining how different land use products relate to each other, and changes to the aggregation of High-Resolution Land Use/Land Cover to Phase 7 Land Uses.
- High-Res Land Use/Land Cover Data Update - This includes a new Land Use/Land Cover dataset representing 2021/2022, updates the 2013/2014 and 2017/2018 High-Resolution Land Use/Land Cover Data and Change Data. View the web viewer here.
- Hyper-Resolution Hydrology Database - This dataset identifies the location, dimensions, and connectivity of streams, ditches, and other waterways. View the web viewer here.
- Chesapeake Bay Watershed Historical Land Use (1985-2013) Workplan - The land data team developed a methodology for the land use for years prior to 2013. In 2013, 2017, and 2021, there are land cover/use data that is at the 1-meter scale. Prior to those years, the data available are much less detailed. This document describes the methodology for developing the back-cast land use for 1985 through 2012.
CAST
- Phase 7 Land Use/CAST Load Sources Crosswalk Table - This table shows the aggregation of High-Resolution Land Uses to Phase 7 Mapped Land Uses and the corresponding Phase 7 CAST Load Sources. It also includes loading rate ratios for each load source.
- Phase 7 CAST Load Sources - This presentation from the September 2025 WQGIT meeting outlines the Phase 7 CAST Load Sources by Agriculture, Developed, and Natural sectors, highlighting any new land uses and changes from Phase 6.