MODEL DOCUMENTATION

Phase 7

The development of the Phase 7 Suite of Models is ongoing. Related resources, relevant planning documents, and information on specific projects within the Suite of Models can be found on the Phase 7 Development webpage. More information on the role of these Models in the Chesapeake Bay Program and the purpose of the Phase 7 update can be found on the Modeling Page

Materials related to the Phase 7 Watershed Model will be provided below as they become available. Please note that Phase 7 Watershed Model input data and associated visualizations are draft for Partnership review and are subject to change prior to the release of the Phase 7 Suite of Models.

Phase 6

The Phase 6 Watershed Model represents the current Model of record. Information on CAST version updates under the Phase 6 Model, including the most recent version (CAST-23), is available below. You can also view Phase 6 Model documentation, information related to the STAC review of the Phase 6 Watershed Model, Phase 6 Watershed Model input data, and more.

Suggested Citation

Chesapeake Bay Program, 2024. Chesapeake Assessment and Scenario Tool (CAST) Version 2023, Phase 6-[7.XX.X See bottom of any page for specific version number]. Chesapeake Bay Program Office, Last accessed [Month, Year].

CAST-23 version

CAST-23 is planned to be the last model update to the phase 6 suite of models. This follows the decision to update the CAST schedule, which was approved by the Water Quality Goal Implementation Team, Management Board, and Principals' Staff Committee. The decision can be found in the September 26, 2023 PSC meeting minutes. CAST-23 contains all the planned updates for CAST-21 plus:

Additional CAST-23 related resources are linked below.

CAST-21 version

BMPs in progress scenarios are pulled from the National Environmental Information Exchange Network (NEIEN), and used to update that year's progress data. This means that new inspections, new cumulative BMPs in any year, and new annual BMPs are used for that year's progress. The prior years' progress scenarios are not updated. However, when changing to a new version of CAST, all years' progress scenarios are updated to include new BMP history.

CAST-19 version

CAST-17d is updated to CAST-19 with changes to data and BMPs used in the Phase 6 model for the milestone period. This follows the Principals' Staff Committee decision of July 9, 2018 that changes are made only in advance of the two-year milestone period. The decision can be found in the July 9, 2018 PSC meeting minutes. These changes were agreed to by the WQGIT and its workgroups. The changes are limited in scope so that they do not: 1) impact modeled runoff during the 1993-1995 critical period; or 2) alter the base conditions (land uses, septics, animals, etc.) from 1984 through 2013. Preservation of these estimates enables a consistent assessment of how new management actions and changes in base conditions have influenced loads over time.

Dynamic Watershed Model and CAST-17 documentation

The documentation is for the dynamic and time-averaged Watershed Model. CAST is the same as the time-averaged Phase 6 Model. Creating and running scenarios in CAST is simply using an on-line interface to the time-averaged Model.

Model Performance

More information on the Watershed Model can be found at the Modeling Workgroup page.

STAC Review

Changing Environmental Conditions

Results of updated methods, techniques, and studies that are used to develop an estimate of pollutant load changes (nitrogen, phosphorus, and sediment) due to 2025 changing environmental conditions. Planning targets for the TMDL, changing environmental conditions, and Local Area Planning Goals are available.

Changing Environmental Conditions Documentation

Phase 6 Watershed Model Input Data

Phase 6 Watershed Model input data is available below and includes Tableau-based visualizations of Phase 6 Model Inputs, Inputs by Load Source, and Source Data.