Hennig Brandt's discovery of phosphorus (P) occurred during the early European colonization of the Chesapeake Bay region. Today, P, an essential nutrient on land and water alike, is one of the principal threats to the health of the bay. Despite widespread implementation of best management practices across the Chesapeake Bay watershed following the implementation in 2010 of a total maximum daily load (TMDL) to improve the health of the bay, P load reductions across the bay's 166,000-km(2) watershed have been uneven, and dissolved P loads have increased in a number of the bay's tributaries. As the midpoint of the 15-yr TMDL process has now passed, some of the more stubborn sources of P must now be tackled. For nonpoint agricultural sources, strategies that not only address particulate P but also mitigate dissolved P losses are essential. Lingering concerns include legacy P stored in soils and reservoir sediments, mitigation of P in artificial drainage and stormwater from hotspots and converted farmland, manure management and animal heavy use areas, and critical source areas of P in agricultural landscapes. While opportunities exist to curtail transport of all forms of P, greater attention is required toward adapting P management to new hydrologic regimes and transport pathways imposed by climate change. ; Public domain authored by a U.S. government employee
Extensive efforts to adaptively manage nutrient pollution rely on Chesapeake Bay Program's (Phase 6) Watershed Model, called Chesapeake Assessment Scenario Tool (CAST), which helps decision-makers plan and track implementation of Best Management Practices (BMPs). We describe mathematical characteristics of CAST and develop a constrained nonlinear BMP-subset model, software, and visualization framework. This represents the first publicly available optimization framework for exploring least-cost strategies of pollutant load control for the United States' largest estuary. The optimization identifies implementation options for a BMP subset modeled with load reduction effectiveness factors, and the web interface facilitates interactive exploration of >30,000 solutions organized by objective, nutrient control level, and for similar to 200 counties. We assess framework performance and demonstrate modeled cost improvements when comparing optimization-suggested proposals with proposals inspired by jurisdiction plans. Stakeholder feedback highlights the framework's current utility for investigating cost-effective tradeoffs and its usefulness as a foundation for future analysis of restoration strategies. ; United States Environmental Protection Agency (USEPA) Chesapeake Bay Program Office [CB96350501, CB96325901, CB96365601, CB96351401] ; Published version ; This material is based upon work funded wholly or in part by the United States Environmental Protection Agency (USEPA) Chesapeake Bay Program Office, including direct salary support for multiple partners within the USEPA-administered Chesapeake Bay Program (including co-authors Shenk and Linker as well as numerous assisting support staff) , assistance agreements CB96350501 to Chesapeake Research Consortium (CRC) , Inc. (co-authors Kaufman, Ball, Bosch, Ellis, Hobbs, Van Houtven, and McGarity) , CB96325901 and CB96365601 to the Uni-versity of Maryland Center for Environmental Science (co-author Asplen) , and CB96351401 to Pennsylvania State University (co-author Bhatt) . The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.; The authors thank Rich Batiuk and the modeling team at the Ches-apeake Bay Program Office (Cuiyin Wu, Andrew Sommerlot, Richard Tian, Isabella Bertani) for constructive input throughout the project. The authors thank and acknowledge Stuart Schwartz of the University of Maryland, Baltimore County, who was an original member of CRC's Advisory and Support Committee and provided important early contributions of both conceptual and practical nature. Many thanks to John Massey for technical support with cloud resources and batch processing and Megan McNeilly for User Experience improvements to the online decision-support tool. Further thanks to Brian Burch, Megan Thynge, Tim Paris, Martin Koslof, and the entire CBPO software development and information technology team.
The Chesapeake Bay is the largest, most productive, and most biologically diverse estuary in the continental United States providing crucial habitat and natural resources for culturally and economically important species. Pressures from human population growth and associated development and agricultural intensification have led to excessive nutrient and sediment inputs entering the Bay, negatively affecting the health of the Bay ecosystem and the economic services it provides. The Chesapeake Bay Program (CBP) is a unique program formally created in 1983 as a multi-stakeholder partnership to guide and foster restoration of the Chesapeake Bay and its watershed. Since its inception, the CBP Partnership has been developing, updating, and applying a complex linked modeling system of watershed, airshed, and estuary models as a planning tool to inform strategic management decisions and Bay restoration efforts. This paper provides a description of the 2017 CBP Modeling System and the higher trophic level models developed by the NOAA Chesapeake Bay Office, along with specific recommendations that emerged from a 2018 workshop designed to inform future model development. Recom-mendations highlight the need for simulation of watershed inputs, conditions, processes, and practices at higher resolution to provide improved information to guide local nutrient and sediment management plans. More explicit and extensive modeling of connectivity between watershed landforms and estuary sub-areas, estuarine hydrodynamics, watershed and estuarine water quality, the estuarine-watershed socioecological system, and living resources will be important to broaden and improve characterization of responses to targeted nutrient and sediment load reductions. Finally, the value and importance of maintaining effective collaborations among jurisdictional managers, scientists, modelers, support staff, and stakeholder communities is emphasized. An open collaborative and transparent process has been a key element of successes to date and is vitally important as the CBP Partnership moves forward with modeling system improvements that help stakeholders evolve new knowledge, improve management strategies, and better communicate outcomes. ; Chesapeake Bay Scientific and Technical Advisory Committee (STAC) via the Chesapeake Research Consortium; NSFNational Science Foundation (NSF) [1556661]; NASANational Aeronautics & Space Administration (NASA) [80NSSC17K0258 49A37A]; NOAANational Oceanic Atmospheric Admin (NOAA) - USA [NA15NMF4570252 NCRS-17] ; Published version ; The views expressed in this manuscript are those of the authors alone and do not necessarily reflect the views and policies of the U.S. Environmental Protection Agency. This article has been peer reviewed and approved for publication consistent with USGS Fundamental Science Practices (https://pubs.usgs.gov/circ/1367/).This review paper is based on information that was provided by 70 scientists and managers who participated in a workshop that was convened on January 17-19, 2018 at the National Conservation Training Center in Shepherdstown, West Virginia, USA. This workshop was funded by the Chesapeake Bay Scientific and Technical Advisory Committee (STAC) via the Chesapeake Research Consortium. The lead author would like to thank all of the workshop participants for their contributions to that workshop and this paper. In addition, special thanks go to STAC support personnel (specifically, coauthor Rachel Dixon and staff member Elaine Hinrichs) who handled all of the logistics involved in planning and running the workshop. The development of this paper was supported by NSF grant no. 1556661, NASA grant no. 80NSSC17K0258 49A37A and NOAA grant no. NA15NMF4570252 NCRS-17 to R. Hood. Additional support to coauthors was provided by multiple US Federal and State Agencies, and US Universities (see author affiliations above). This is UMCES contribution no. CN 6018. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ; Public domain authored by a U.S. government employee
