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Modeling Workgroup

Scope and Purpose

The Chesapeake Bay Program integrated models include simulations of the airshed, watershed, estuary, living resources, and climate change. These integrated models assess effects of current and proposed watershed management on changes in nutrient and sediment loads delivered to the Bay, and the effect those changing loads have on water quality and living resources. The CBP Models assist CBP decision-makers in estimating the collective actions needed to achieve State and Federal water quality standards necessary to restore the Bay.

Core Values

The Modeling Workgroup has a responsibility to the Chesapeake Bay Program Partnership to provide state-of-the-art decision-support modeling tools that are built through community and participatory principles. The responsible planning and management of resources to provide the best available decision-support modeling tools requires the Modeling Workgroup members and participants to adhere to the core values of: 

  • Integration - Integration of most recent science and knowledge in air, watershed, and coastal waters to support ecosystem modeling for restoration decision making.
  • Innovation - Embracing creativity and encouraging improvement in the development and support of transparent and robust modeling tools.
  • Independence – Making modeling decisions on the basis of best available evidence and using the most appropriate methods to produce, run, and interpret models, independent of policy considerations.
  • Inclusiveness - Commitment to an open and transparent process and the engagement of relevant partners, that results in strengthening the Partnership’s decision making tools.

Overall CBP Model Framework

The CBP model framework is designed to address questions of how Chesapeake Bay water quality will respond to changes in watershed and airshed management actions.  In the first step of model scenario development, scenario management actions are interpreted by several models, including the Land Use Change Model, the Airshed Model, and Scenario Builder to produce input to the Watershed Model, as shown in the figure below.  The CBP Land Use Change Model, predicts changes in land use, sewerage, and septic systems given changes in land use policy. The Airshed Model, a national application of Community Multiscale Air Quality Model (CMAQ), predicts changes in deposition of inorganic nitrogen due to changes in emissions. The Scenario Builder software combines the output of these models with other data sources, such as the US Census of Agriculture, to generate inputs to the Watershed Model.  The Phase 5.3 Watershed Model predicts the loads of nitrogen, phosphorus, and sediment that result from the given inputs.The estuarine Water Quality and Sediment Transport Model (WQSTM) (also known as the Chesapeake Bay Model) predicts changes in Bay water quality due to the changes in input loads provided by the Watershed Model. As a final step, a water quality standard analysis system examines model estimates of DO, chlorophyll, and water clarity to assess in time and space the attainment of the Bay living resource-based water quality standards.


Additional information can be found at:

  • Lee Currey (Co-Chair), Maryland Department of the Environment
  • Dave Montali (Co-Chair), West Virginia Department of Environmental Protection
  • Lewis Linker (Coordinator), U.S. Environmental Protection Agency
  • Kyle Hinson (Staff), Chesapeake Research Consortium

  • Jesse Bash, U.S. Environmental Protection Agency
  • Mark Bennett, U.S. Geological Survey (USGS)
  • Karl Berger, Metropolitan Washington Council of Governments
  • Bill Brown, University of Delaware Cooperative Extension
  • Monir Chowdhury, District of Columbia Department of Energy & Environment (DOEE)
  • Mukhtar Ibrahim, Metropolitan Washington Council of Governments
  • Bill Keeling, Virginia Department of Environmental Quality
  • Ross Mandel, Interstate Commission on the Potomac River Basin (ICPRB)
  • George Onyullo, District of Columbia Department of Energy & Environment (DOEE)
  • Ben Sears, New York State Department of Environmental Conservation
  • Gary Shenk, U.S. Geological Survey (USGS)
  • Helen Stewart, Maryland Department of Natural Resources
  • Peter Tango, U.S. Geological Survey (USGS)
  • Ted Tesler, Pennsylvania Department of Environmental Protection
  • Harry Wang, Virginia Institute of Marine Science (VIMS)

Past Meetings & Events

  • April 26, 2016 to April 27, 2016 - April 2016 Modeling WG Quarterly Review
  • January 20, 2016 to January 21, 2016 - January 2016 Modeling WG Quarterly Review
  • November 3, 2015 to November 4, 2015 - November 2015 Modeling WG Quarterly Meeting
  • July 21, 2015 to July 22, 2015 - July 2015 Modeling WG Quarterly Meeting
  • April 22, 2015 to April 23, 2015 - April 2015 Modeling Quarterly Review
  • February 19, 2015 - Shallow Water Modeling Call
  • January 28, 2015 to January 29, 2015 - January 2015 Modeling Quarterly Review (Part 2)
  • January 14, 2015 to January 15, 2015 - January 2015 Modeling Quarterly Review (Part 1)
  • April 9, 2013 to April 10, 2013 - April 2013 Modeling Quarterly Review
  • January 8, 2013 to January 9, 2013 - January 2013 Modeling Quarterly Review
  • October 2, 2012 to October 3, 2012 - October Modeling Quarterly Review
  • January 11, 2012 - Modeling Team Quarterly Review

  • Phase 6 Beta 2 Draft Documentation - June 2016

    The Phase 6 Beta 2 Watershed Model is available for partnership review.  The purpose of making the draft documentation available to the Partnership is to provide the Partnership with a written record of the results of the many partnership decisions that have been made in the Management Board, the Modeling Workgroup, the Water Quality Goal Implementation Team, and the WQGIT’s many workgroups.

    A recording of the Phase 6 Beta 2 webinar that occurred on July 7, 2016 can be viewed using the following link:


    A recording of the Phase 6 Beta 1 webinar that occurred on March 10, 2016 can be viewed using the following link:



    Documentation pdf and excel files can be found here: ftp://ftp.chesapeakebay.net/Modeling/Phase6/Ph6Calibration_Beta2/20160401/Documentation/

    Calibration Plots

    Graphics showing the calibration to individual stations and aggregate statistics are found here: ftp://ftp.chesapeakebay.net/Modeling/gbhatt/Phase_6_Beta_2/

    Additional information is available using the following link: https://public.tableau.com/profile/bryan.chastain#!/vizhome/CBPNon-TidalV6/Non-TidalWaterQualityDashboard


    Inputs for Beta 2 were produced in April and do not reflect the latest versions of the nutrient spread and other partnership decisions that will be included in Beta 2. Inputs used in Beta 2 are available here: ftp://ftp.chesapeakebay.net/Modeling/Phase6/Ph6Calibration_Beta2/20160401/inputs/. A more conveniently summarized version of the the Beta 2 inputs can be found in excel files at this ftp site: ftp://ftp.chesapeakebay.net/Modeling/Phase6/Ph6Calibration_Beta2/20160401/inputs/ScenarioBuilder/

    Load Outputs

    The ‘AllLoads’ excel files are the annual average loads in raw format and can be found at this FTP site: ftp://ftp.chesapeakebay.net/Modeling/Phase6/Ph6Calibration_Beta2/20160401/

    Phase 6 Beta 1 - January 2016

    The Phase 6 Beta 1 Watershed Model is available for partnership review.  Draft documentation files are available in the series of attached documents below. Calibration plots are available on the CBP FTP site by constituent, or in a single file (hyperlinks below). Information and data regarding Scenario Builder inputs can also be accessed from another linked FTP below.

    Calibration Plots, by Constituent: ftp://ftp.chesapeakebay.net/Modeling/gbhatt/Phase_6_Beta_1/20151231_Calibration_Graphics/

    All Calibration Plots (large file size): http://ftp.chesapeakebay.net/Modeling/gbhatt/Phase_6_Beta_1/20151231_Calibration_Graphics/Calibration%20Graphics%20Binder%2020151231.pdf

    Scenario Builder Inputs: ftp://ftp.chesapeakebay.net/Modeling/Phase6

    The files represent the annual average loads from the calibration run.  The time period for calibration is 1985 through 2014.  The loads are provided as annual averages of 1985-2014 and 1991-2000.  Inputs change annually during the calibration run, so these are not meant to represent any particular year, but rather the average of the years indicated.  The loads are for information only and cannot be used to analyze the effect of model changes on any policies.  These effects can only be understood when the final versions of the entire modeling system including the estuarine model is run together.

    The ‘AllLoads’ excel files are the annual average loads in raw format and can be found at this FTP site: http://ftp.chesapeakebay.net/Modeling/Phase6/Ph6CalibrationFiles_20151109/20151109/
    The ‘Export Loads Comparison’ excel file (below) is a comparison with USGS-estimated loads at monitoring stations.

    The Chesapeake Bay Program’s Watershed Model is a participatory creation of the CBP Partnership. For Phase 6, this broad participation throughout the partnership has grown to include many workgroups. As such, the documentation also belongs to the Partnership and it has become necessary to make the draft documentation available in rough form to aid the development process.

    The purpose of making the draft documentation available to the Partnership at this early stage is to provide the Partnership with a written record of the results of the many partnership decisions that have been made in the Management Board, the Modeling Workgroup, the Water Quality Goal Implementation Team, and the WQGIT’s many workgroups.

    The February 1, 2016 version of the Phase 6 Beta 1 Watershed Model documentation is a rough draft of the documentation of a development version of the Phase 6 Watershed Model. The reader should be aware that there are significant omissions and there may also be significant errors due to the limited time available to prepare this documentation.

    Soil P data were made available to the CBPO from multiple sources. These included data from all counties in the watershed, but there was not a complete record for the entire time period and for all land uses. Also, the data were not grouped by land use for states other than PA and VA. The APLE model and the January 2016 Phase 6 Beta inputs were used to create the time series of soil P data for each county. The model, inputs, outputs, and graphical outputs are available at this ftp site: ftp://ftp.chesapeakebay.net/Modeling/gyactayo/aple6/  Each graphic contains a bias statistic. The results were used only where bias was less than 1. Otherwise, the long–term average for that county was used.

    Additional information regarding the Midpoint Assessment can be found here: http://timstest.tetratech-ffx.com/BayMidpointAssessment/

    Any questions should be directed to Lewis Linker or Kyle Hinson.

    FINAL Water Quality Model Calibration Run January, 2002

    Peer Reviews

    CMAQ Review Process: During the past three years, CMAS, in collaboration with EPA scientists, has organized two CMAQ review panel meetings etc. The first CMAQ review meeting was held during December 2003. The second meeting was held during May 2005. The review process usually starts by inviting a number of key scientists to participate in the process. The scientists are selected based on their expertise in accordance with the focus of the review session. After reviewing numerous reports and articles and completing their meeting in Research Triangle Park, North Carolina, the review panel prepares a comprehensive report on their findings and recommendations. EPA then responds to the comments of the reviewers. Final review reports are posted below.

    Congestion Mitigation and Air Quality (CMAQ) Model - Third Review (February, 2007)

    Peer Review Guidance

    The CBP models follow the peer review guidance developed by EPA’s Science Advisory Board (SAB) for regulatory models: http://www.epa.gov/spc/pdfs/modelpr.pdf  and the peer review guidance developed by the Ecological Society of America and endorsed by the American College of Preventive Medicine, American Fisheries Society, American Institute of Biological Sciences, American Public Health Association, American Society of Agronomy, American Society of Limnology and Oceanography, Association of Teachers of Preventive Medicine, Crop Science Society of America, Ecological Society of America, Estuarine Research Federation, Institute of Food Technologists, Soil Science Society of America, Society for Conservation Biology

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