The Chesapeake Bay Program (CBP) Modeling Workgroup has just completed several years of active model development in support of the CBP partnership’s 2017 Midpoint Assessment. The Midpoint Assessment applies the newly developed Phase 6 Suite of Modeling Tools in support of managing the historic 2010 TMDL (Total Maximum Daily Load) of the Chesapeake Bay Watershed.

The different phases of CBP modeling are meant to address new and emerging watershed management challenges in the Bay. Phase 5, which was applied by the CBP partnership from 2010 to 2017, served well for the development of the Phase 2 Watershed Implementation Plans (WIPS) by CBP partner jurisdictions, but was becoming outdated in several regards. Therefore, in parallel to the Phase 5 application in the assessment of watershed restoration progress to 2017, the CBP partnership’s Modeling Workgroup worked, in cooperation with the CBP Modeling Team, on the development of the Phase 6 Model.

The Modeling Workgroup tackled three main challenges in the Phase 6 development. First, with a growing body of evidence showing that Conowingo Dam has become less effective at trapping sediments, the Phase 6 Models were modified to properly reflect this to allow proper consideration of the implications for future Phase 3 WIP development. Secondly, the Phase 6 Suite of Modeling Tools incorporated the estimated influence of future climate change on Chesapeake water quality. And finally, the Modeling Workgroup aimed to modify the modeling approach — especially as related to watershed modeling, control of nutrient inputs, and “crediting” of best management practices — in new ways that would be more flexible, appropriate, and useful for jurisdictions as they update their watershed implementation plans. In short, Phase 6 was designed to use new knowledge and facilitate the development of new management strategies. Phase 6 will take what was learned from the 2017 Midpoint Assessment and will be used to implement the watershed restoration plans through 2025.

Throughout the process of model development and application, the Modeling Workgroup has been working with the Scientific Technical Advisory Committee (STAC). The STAC provides valuable workshops and guidance to the Bay Program on how to proceed on many aspects of developing a state-of-the-science model assessment system for the Chesapeake. In addition, STAC provides the CBP independent peer reviews of the final CBP models. One outcome of this is that the CBP Workgroup will be focusing, in the year ahead on final Phase 6 Model documentation, response to STAC’s peer reviews, and documentation of the Midpoint Assessment technical findings, even while already looking ahead to the development of a Phase 7 Model to respond to the Chesapeake management challenges in 2025 and beyond. (Note: Coordination of STAC is a CRC activity.)

One of the co-chairs of the Modeling Workgroup, Lee Currey of the Maryland Department of the Environment (MDE), will be stepping down from his role this year. Fortunately Lee will remain a member of the Workgroup and will continue to provide his valuable experience and guidance. Mark Bennett of the U. S. Geological Survey has been nominated as the next co-chair. Mark already serves as chair of the Climate Resiliency Workgroup, and the two workgroups often collaborate on the assessment of the estimated influence climate change has on the watershed and the water quality of the tidal Bay.