CBP Climate Change Modeling III: Post-2025 decisions

May 7, 2024 - May 9, 2024
Arlington, Virginia

This workshop convened in-person on Tuesday-Thursday, May 7-9, 2024 at the Virginia Tech Executive Briefing Center (900 N Glebe Rd, Arlington, VA).

The Scientific and Technical Advisory Committee (STAC) hosted a 3-day workshop in May 2024 for the purpose of bringing Chesapeake Bay Program (CBP) managers and model developers together with experts in climate change, estuarine, and watershed science. Workshop participants were asked to develop recommendations to guide the development and application of CBP Total Maximum Daily Load (TMDL) models for climate change applications.

Questions to be addressed

The goal of the workshop is to develop recommendations for new or refined methods and modeling techniques to be completed and fully operational by 2025, to assess future impacts of projected climate change on watershed loads and estuarine processes, including the methodology for updating expected reductions in nutrient pollutant loads due to 2035 climate projections.

  • What recommendations from the first 2 workshops and review should carry through, be emphasized, or revised?
  • How should climate change analyses be approached in the next generation Phase 7 estuarine model now under development?
  • What areas of the watershed model need improvement (other than BMP response)?
  • What is our current understanding of phenology in the Chesapeake and how do we best incorporate it in the watershed, estuarine, and living resource models?
  • How to incorporate uncertainty in all models and the decision process?

A Programmatic Workshop

The CBP partnership’s Midpoint Assessment process resulted in CBP’s adoption of updated nutrient and sediment planning targets in 2018 consistent with the 2010 Chesapeake Bay TMDL allocations, and based on updates to the CBP’s suite of models. Consideration of the effects of climate change on the CBP partnership’s ability to reach Bay water quality goals was intended to be part of the 2017 Midpoint Assessment process, however, the partnership decided to delay decisions until additional climate effects modeling could be completed.

Guided by the STAC products as described below, the CBP’s Modeling Workgroup revised the CBP’s TMDL models and climate change application of the models to arrive at estimates of additional reductions necessary to defend Bay water quality standards against climate change through 2025 (Shenk, et al., 2021a). In October of 2020, the Management Board reached consensus on approval of the revised models and additional climate loads. Notably, the partnership acknowledged limitations in the science and modeling. Shallow open water was excluded from the climate change allocation. Questions arose around the model-projected versus observed climate change. The impact of climate change on management practice effectiveness remains largely unquantified. Draft models will be due for partnership review by the end of 2025 with decisions on new planning targets to be made in 2027.

STAC input to the 2020 climate process

  • 2016 STAC workshop on climate projections assessed available climate data for use in the CBP decision process (Johnson et al. 2016). Recommendations included the use of historical precipitation trends for 2025 while carefully considering evapotranspiration.
  • 2018 STAC workshop (Shenk et al., 2021b) generated specific near-term and long- term recommendations for watershed and estuarine modeling, and methods of model application. Many recommendations were incorporated during the 2020 climate modeling process, with some resulting publications (e.g., Bertani, et al. 2022, Hinson et al., 2022, Tian et al. 2021).
  • Review of the CBP’s proposed approach for dealing with climate change in the TMDL (Herrmann et al. 2018), generally approving of the methods but recommending a modification of methods for climate inputs.
  • Monitoring and Assessing Impacts of Changes in Weather Patterns and Extreme Events on BMP Siting and Design (Johnson et al. 2018)
  • CBP Modeling in 2025 and Beyond (Hood et al. 2019)
  • Reviews of the Phase 6 Watershed Model (Easton, et al. 2017) and the Water Quality Sediment Transport Model (Brady et al. 2018)
  • STAC review of BMP effectiveness under climate change (Hanson et al. 2022)
  • Comprehensive Evaluation of System Response (CESR): report webpage

Workshop Steering Committee: *STAC member

  • Gary Shenk (USGS, Chair): CBP Modeling team
  • Mark Bennett (USGS): CBP Climate Resiliency Workgroup Co-Chair; Director of the USGS VA/WV Water Science Center
  • *Zach Easton (Virginia Tech): Professor of Biological Systems Engineering; Chair of the CBP Agricultural Modeling Team
  • Marjy Friedrichs (VIMS): Research Professor
  • Jeni Keisman* (USGS): Chief, Hydrologic Impacts Branch
  • Lewis Linker (EPA CBPO): CBP Modeling Coordinator
  • Charles Stock (NOAA): Research Oceanographer, NOAA/Geophysical Fluid Dynamics Laboratory
  • Raymond Najjar, Jr. (PSU): Professor of Oceanography
  • Robert Sabo (EPA): Center for Public Health and Environmental Assessment, Office of Research and Development, ORCID iD

Presentations:

 

For more information, please contact Meg Cole, STAC Coordinator, colem@chesapeake.org.