Recent Progress: Increase

As of 2023, the best management practices (BMPs) in place Watershed-wide to reduce pollutant loads are estimated to achieve 57% of the nitrogen reductions, 67% of the phosphorus reductions and 100% of the sediment reductions needed to attain applicable water quality standards when compared to the 2009 loads. According to the Chesapeake Assessment Scenario Tool (CAST) version 19, BMPs (pollution controls) put in place in the Chesapeake Bay watershed between 2009 and 2023 are estimated to have reduced nitrogen loads by 16.9%, phosphorus loads by 17.3% and sediment loads by 5.8%, compared to 2009. As modeled based on the implementation of BMPs, the sediment load reductions have met the established target and nitrogen and phosphorus loads have decreased from 2022 to 2023, constituting an increase in overall progress.

Outlook: Off Course

At the Fall 2022 Executive Council meeting, it was acknowledged that the 2025 Watershed Implementation Plans (WIPs) outcome will not be met on time, and the indicators for this outcome continue to support the determination that it is off course. The outlook for pollutant loads is forecasted by comparing recent modeled progress for the 2023 progress year to the expected goal for the 2023 progress year, which is a 90% achievement of the 2025 planning target as compared to 2009. BMPs are in place to achieve 100% of the needed sediment load reductions for the Chesapeake Bay watershed as a whole. However, Delaware, New York and Pennsylvania have not met their statewide planning targets for sediment. Nitrogen and phosphorus modeled load reductions are well below 90% and thus off course for the Chesapeake Bay watershed as a whole, though the District of Columbia and West Virginia have met their statewide nitrogen and phosphorus targets.

The Modeled Load Reduction indicator (covering nitrogen, phosphorus and sediment loads) is used to estimate progress toward this outcome. This data is enhanced by considering the combination of modeled and observed load data reported under the Water Quality Standards Attainment and Monitoring Outcome’s Total Maximum Daily Load (TMDL) indicator and via the Monitored and Expected Total Reduction Indicator for the Chesapeake (METRIC) tool.

Modeled Loads Reduction Indicator: Improvement

This indicator reflects nutrient and sediment pollutant load estimates generated using the 2019 version of CAST, which is part of the Phase 6 suite of modeling tools (which includes baseline data up through the 2023 progress year) and wastewater discharge data reported by jurisdictions and calibrated using monitoring data. For detailed descriptions of CAST, please visit the CAST Model Documentation website.

Modeled Nitrogen Loads: Improvement

Nitrogen loads to the Bay decreased by an estimated 8.3 million pounds/year from 2022 to 2023 compared to the average load change of 3.2 million pounds/year over the 13 years from 2009 to 2022, indicating an increase in progress. Pollution controls implemented between 2009 and 2023 have reduced nitrogen loads to the Bay by an estimated 50.2 million pounds, a 16.9% reduction since 2009. By 2023, the BMPs in place are estimated to have achieved 57% of the nitrogen load reductions necessary to meet the 2025 target as compared to 2009 (the last modeled progress assessment prior to establishing the Bay TMDL).

Modeled Phosphorus Loads: Improvement

Phosphorus loads to the Bay decreased by an estimated 0.67 million pounds/year from 2022 to 2023, compared to the average load reduction of 0.2 million pounds/year between 2009 and 2022. This decrease in modeled phosphorus loads reflects an increase in recent progress. Pollution controls implemented between 2009 and 2023 have reduced phosphorus loads to the Bay by about 3.0 million pounds, a 17.3% reduction, since 2009. The BMPs in place as of 2023 are estimated to have achieved 67% of the phosphorus load reductions necessary to meet the 2025 target, as compared to 2009.

Modeled Sediment Loads: Achieved Bay-wide

Sediment load reduction goals have been met, with 100% of the reduction goal for sediment achieved Bay-wide. Sediment loads were 17,815 million pounds/year in 2023, below the planning goal for 2023 of 18,619 million pounds/year. Pollution controls implemented between 2009 and 2023 have achieved a reduction of an estimated 1096 million pounds, a 5.8% reduction since 2009.

Jurisdictions have described the steps they are taking to achieve the nutrient and sediment load reductions they committed to make in their respective Phase III WIPs. Jurisdictions developed and submitted Phase I WIPs in 2010, Phase II WIPs in 2012 and Phase III WIPs in 2019. New York and Pennsylvania amended their Phase III WIPs in 2021 and 2022, respectively.

Resource availability, location and other factors can influence a jurisdiction’s decision and ability to implement certain practices in certain sectors. More information about nitrogen, phosphorus and sediment loads and practices can be found in downloadable reports on the CAST website. Programmatic milestones are maintained and updated every two years on the websites of each jurisdiction: Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia and the District of Columbia. The current milestone period is 2023-2024.

Learn About Factors Influencing Progress

Management Strategy

Participating partners have described the steps they will take to achieve the 2025 WIP Outcome in their individual WIPs. To track the achievement of these outcomes, partners have committed to:

  • Collecting, verifying and reporting BMP data.
  • Evaluating the effectiveness of pollution controls.
  • Enhancing water quality monitoring efforts.
  • Adhering to the TMDL Accountability Framework (as explained in the Analysis & Methods).

Monitoring and assessing progress toward the 2017 WIPs outcome occurred through the 2017 Midpoint Assessment. This review of progress led to enhanced modeling tools that addressed emerging issues like climate change. The Accountability Framework aims to provide confidence that the necessary practices and controls will be in place and, therefore, applicable water quality standards will be attained.

As part of the Chesapeake Bay Program’s partnership-wide implementation of adaptive management, progress toward this outcome was reviewed and discussed by the Management Board in September 2022. It will be reviewed and discussed by the Management Board again in September of 2024.

Download Management Strategy (.pdf)

Logic & Action Plan

Chesapeake Bay Program partners have committed to taking a series of specific actions that will support the management approaches listed above.


  • Leading BMP Verification.
  • Supporting continued BMP implementation, tracking and reporting across all source sectors.
  • Upgrading and enhancing wastewater treatment plants and septic systems.
  • Guiding the development of jurisdictions’ trading and offset programs.
  • Providing permit and enforcement oversight across all sectors.
  • Improving temporal and regional patterns in water quality criteria attainment in tidal and nontidal waters.
  • Coordinating the Chesapeake Bay Program Nontidal Water Quality Monitoring Network.
  • Addressing gaps in monitoring programs.
  • Developing and applying new approaches for quantifying and explaining water quality trends in tidal waters.
  • Explaining the drivers of water quality trends in the watershed.
  • Continuing to enhance the Bay Program’s decision support tools (CAST, ChesapeakeProgress, the Chesapeake Bay Program watershed and estuary models).

Recently Completed


  • Quantified the relative effects of significant changes between CAST-19 and CAST-23 and explained results to stakeholder groups and jurisdictions in one-on-one meetings and more public sessions as well as formal Bay Program meetings.
  • Assessed changes to how, and when, the unaccounted additional loads are addressed in CAST-23 and the post-2025 Phase 7 Watershed Model.
  • Collaborated with stakeholders on state-proposed model changes like the extension of BMP credit durations, BMP “excess” in CAST and the introduction of newly reported BMPs.
  • Completed analysis for the 2023 Progress model assessment, including supporting jurisdictions’ National Environmental Information Exchange Network (NEIEN) submissions, reviewing Quality Assurance Project Plans (QAPPs) for accuracy and completeness related to verification and meeting with each jurisdiction about the quality of their data and modeling results.


  • Completed all analyses for the 2021 and 2022 Progress model assessment including supporting jurisdictions’ National Environmental Information Exchange Network (NEIEN) submissions, reviewing Quality Assurance Project Plans (QAPPs) for accuracy and completeness related to verification and meeting with each jurisdiction about the quality of their data and modeling results.
  • Created a Phase 7 Model Development page to document and track seven interrelated projects contributing to a full suite of modeling tools to be ready in 2027: High Resolution Land Use, Chesapeake Assessment Scenario Tool (CAST), Optimization, Agricultural Inputs, Watershed Modeling, Estuarine Modeling and Criteria Assessment.
  • Produced an array of information on trends of BMP implementation and loads that help signatory jurisdictions understand their progress and assist EPA with any continued oversight evaluations of progress and WIPs.
  • Updated each jurisdiction’s progress toward meeting priority BMP implementation commitments for the 2022-2023 Milestones for those practices identified in Phase III WIPs that account for the majority of the nitrogen reductions.
  • Finalized the numeric assessment and documentation of EPA’s evaluation of PA’s final amended Phase III WIP, leading to the publication of findings in November 2022.
  • Worked extensively with team members, jurisdictions, academics and outside fertilizer organizations to update agricultural and urban fertilizer application rates for CAST.
  • Updated the BMP Expert Panel Protocol.
  • Recommended a list of tributaries for the development of Multiple Tributary Models.
  • Supported the Chesapeake Bay Commission in their assessment of NRCS Climate Change Mitigation BMPs.

Learn About Logic & Action Plan

Participating Partners

The Water Quality Goal Implementation Team (GIT) leads the effort to achieve this outcome. It works in partnership with the Habitat GIT, Sustainable Fisheries GIT, Maintain Healthy Watersheds GIT, Enhance Partnering, Leadership and Management GIT and the Scientific, Technical Assessment and Reporting Team (STAR).

Participating partners include:

  • State of Delaware
  • State of Maryland
  • State of New York
  • Commonwealth of Pennsylvania
  • Commonwealth of Virginia
  • State of West Virginia
  • District of Columbia
  • Chesapeake Bay Commission
  • U.S. Department of Agriculture
  • U.S. Army Corps of Engineers
  • U.S. Department of Defense
  • U.S. Department of Homeland Security
  • U.S. Environmental Protection Agency
  • U.S. Geological Survey