Model Documentation

CAST-2019 version

CAST-2017d is updated to CAST-2019 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.

CAST-2019 Upgrades and Documentation

Phase 6 Calibration

The Final Chesapeake Bay Program Partnership Phase 6 CAST and Watershed Model documentation is posted as it becomes available. The documentation is for the time-averaged Watershed Model. CAST is the same as the Model. Creating and running scenarios in CAST is simply using an on-line interface to the Model. The documentation for the Model is the documentation for CAST. Due to the length of the documentation, it is divided into sections. Click on the links below to read through the different portions of the documentation. See Draft Beta 3 documentation for draft versions of sections coming soon. 

Click on the links below to read through the different portions of the Draft Beta 3 documentation for the Chesapeake Bay Program Partnership Phase 6 Watershed Model. All other portions of the Model Documentation are final and are available for download in the section above.

Phase 6 Model Performance

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

Suggested Citation

Chesapeake Bay Program, 2017. Chesapeake Assessment and Scenario Tool (CAST) Version 2017d. Chesapeake Bay Program Office, Last accessed [Month, Year].

Non-Tidal Water Quality Dashboard

Comparisons between the modeled and monitored data can be found on the non-tidal water quality dashboard. These visual representations show both the loads estimated from the U.S. Geologic Survey's Weighted Regressions on Time, Discharge and Season (WRTDS) and loads estimated from the time-variable Phase 6 Watershed Model.

Non-Tidal Water Quality Dashboard

Graphical Interface to the Phase 6 Watershed Model Inputs

Graphs and maps of the inputs to the Phase 6 Watershed Model for all versions, along with the option to download the source data, is provided to facilitate transparency and offer a common, public platform for reviewing data.

Due to the size of the datasets required to present this information, the Graphs and Maps have been divided into the following categories.

The calibration land use data is available on the Nutrient Applications link above. It is shown in maps with the ability to filter by sector, land use, and agency. The tabular land use for years between 1984 and 2013 may be downloaded using the link below.

Not all of the inputs are applied to each of the load sources. For example, manure nitrogen and phosphorus are not attributed to developed lands. Only leguminous plants fix nitrogen, so the fixed nitrogen input only applies to load sources that may contain crops or plants that are leguminous. The table of Loads by Load Source provides a ready reference of the inputs for each load source. 

Phase 6 Model Review Sessions

Webinar-based model review sessions provide the Chesapeake Bay Program Partnership with the opportunity to directly ask questions and provide feedback on the model. Click on the links below to view and hear the recorded webinars.