This marks the first progress update toward revised nutrient pollution reduction targets using the Phase 6 version of the Chesapeake Bay Program’s Watershed Model, also known as the Chesapeake Assessment Scenario Tool (CAST). The Chesapeake Bay Program and its partners scheduled this shift to CAST to occur after the 2017 midpoint of tracking toward the Chesapeake Bay Total Maximum Daily Load (Bay TMDL). In addition to the revised targets, historic pollution-reducing practices and annual progress assessments were updated incorporating the new science, data and methods learned through the Phase 6 model.

As of 2018, nutrient pollution-reducing practices are in place to achieve 39 percent of the nitrogen reductions and 77 percent of the phosphorus reductions necessary to attain applicable water quality standards as compared to the 2009 baseline established by the U.S. Environmental Protection Agency (EPA) as part of the Bay TMDL.

According to CAST, pollution controls put in place in the Chesapeake Bay watershed between 2009 and 2018 lowered nitrogen loads 10 percent and phosphorus loads 13 percent. According to BMP and wastewater data from jurisdictions as well as watershed conditions in the model established by the partnership, this drop in estimated pollution loads between 2009 and 2018 is mostly due to upgrades to waste treatment facilities. For the short term, between 2017 and 2018, 55 percent of the nitrogen load reductions came from the agricultural sector.

Interactive Charts

Modeled Nitrogen Loads to the Chesapeake Bay (1985-2025)

Loads simulated using Watershed Model (Phase 6) and jurisdiction-reported data on wastewater discharges.

Modeled Phosphorus Loads to the Chesapeake Bay (1985-2025)

Loads simulated using Watershed Model (Phase 6) and jurisdiction-reported data on wastewater discharges.

Final sediment and source sector targets, based on the jurisdictions’ Phase III Watershed Implementation Plans (WIPs), are scheduled to be released by the partnership in the Fall of 2019. Sediment loads and targets will be included in next year’s progress update.

The Chesapeake Bay Program’s nutrient pollution load estimates were generated using CAST and wastewater discharge data reported by jurisdictions and calibrated using monitoring data. For detailed descriptions of the differences between the CAST and Phase 5 versions of the Watershed Model, please visit the CAST Model Documentation website.

Jurisdictions describe the steps they will take to reduce pollution and achieve the Bay TMDL allocations in their respective Watershed Implementation Plans (WIPs). Jurisdictions developed and submitted Phase I WIPs in 2010, Phase II WIPs in 2012 and Phase III WIPs in 2019.

Resource availability, location and other factors can influence a jurisdiction’s decision and ability to implement certain practices in certain sectors. A full listing of the practices to which each jurisdiction has committed and implemented historically is available for download. Programmatic milestones are maintained on the websites of each jurisdiction: Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia and the District of Columbia.

More information about nitrogen and phosphorus loads and practices can be found on the CAST website. The Chesapeake Bay Program also uses water quality monitoring data to report the partnership’s progress in attaining water quality standards and to examine trends in reducing nitrogen, phosphorus and sediment in the watershed.

Management Strategy

Participating partners have described the steps they will take to achieve the 2025 Watershed Implementation Plan (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; and
  • Adhering to the TMDL Accountability Framework.

Monitoring and assessing progress toward the 2017 WIP outcome occurred through the 2017 Midpoint Assessment. This review of our progress led to enhanced modeling tools that addressed emerging issues like climate change and the TMDL Accountability Framework helps provide confidence that the necessary pollution reductions will occur to achieve the 2025 WIP outcome.

As part of the Chesapeake Bay Program’s partnership-wide implementation of adaptive management, progress toward this outcome will again be reviewed and discussed by the Management Board in August of 2020.

Logic & Action Plan

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

Participating Partners

The Water Quality Goal Implementation Team leads the effort to achieve this outcome. It works in partnership with the Vital Habitats Goal Implementation Team and the Scientific, Technical Assessment and Reporting Team.

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
  • Natural Resources Conservation Service (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