Water Quality Standards Attainment and Monitoring
Continually improve our capacity to monitor and assess the effects of the management actions being taken to implement the Chesapeake Bay Total Maximum Daily Load (Bay TMDL) and improve water quality. Use monitoring results to report annual progress being made in attaining water quality standards and trends in reducing nutrients and sediment in the watershed.
Progress
Recent Progress: Increase
Analysis of tidal and nontidal water quality monitoring data are showing mixed results across the suite of key indicators that assess whether management actions are having the expected reduction in nutrient and sediment loads and corresponding improvements in water quality. Funding has been identified to address long-term funding shortfalls for the water quality monitoring program; however, additional funding is needed to sustain these efforts. Progress is increasing with new reports and scientific journal publications focused on Bay health improvements and watershed factors affecting trends in nutrient and sediment pollution.
Outlook: On Course
This outcome is on course as efforts continue to support the monitoring and annual reporting of water quality standards attainment. This includes monitoring and reporting on dissolved oxygen, water clarity/submerged aquatic vegetation (SAV) and chlorophyll a for tidal waters of Chesapeake Bay, as well as key trends in nutrients and sediment concentrations and loads delivered from the watershed. These efforts include sustaining the operation of four monitoring programs that combine to provide necessary data to assess the outcome’s indicators: the (1) tidal water quality network (over 150 stations); (2) shallow water monitoring program in the tidal Bay; (3) 123 stations of the nontidal water quality monitoring network, including the nine River Input Monitoring (RIM) sites located at the fall line of the nine major tributaries entering the Bay; and (4) 188 survey lines of the SAV annual survey. The Scientific, Technical Assessment and Reporting (STAR) team conducted a 2021-2022 Chesapeake Bay monitoring program review at the request of the Principals’ Staff Committee to identify resource needs for sustaining, updating, and expanding these networks to meet decision support needs of the Bay Program. The Chesapeake Bay Program Office updated grants and interagency agreements to increase funding addressing inflation effects to sustain and grow the networks.
While this outcome’s progress and outlook are not determined based on the levels of water quality standards attainment or nutrient and sediment pollution loads, the indicators associated with this outcome have their own set of targets outside of the outcome language. This outcome reports on trends in standards attainment and nutrient and sediment pollution loads along with progress toward the outcome goal.
Indicators
Four indicators are used to assess change over time for measuring the effectiveness of our management actions to improve water quality:
- water quality standards attainment for dissolved oxygen, water clarity/submerged aquatic vegetation and chlorophyll a in tidal waters of the Bay.
- annual total nutrient and sediment pollution loads delivered to the Bay.
- monitored nutrient and sediment trends in the watershed.
- Bay TMDL progress, combining monitored and modeled data to estimate the progress of nitrogen and phosphorus load reductions in response to implemented management practices.
Water Quality Standards Attainment: Improvement
The current Bay-wide attainment score is 29.8%, meaning that 29.8% of tidal waters are estimated to have met water quality standards during the 2020-2022 assessment period. This is a slight increase from the estimated 28.1% from the 2019-2021 assessment period. The 29.8% score shows a slight rebound in the assessment status that has otherwise been falling since the record high of 42.2% was achieved during the 2015-2017 assessment period. Overall, the long-term trend is one of statistically significant improvement from 1985 to 2022.
Water Quality Standards Attainment (1985-2022)
Water quality is evaluated using three parameters: dissolved oxygen, water clarity or underwater grass abundance, and chlorophyll a (a measure of algae growth).
Periods of improvement and decline in the combined measure of water quality correlate with significant changes in rainfall patterns across the region, affecting nutrient and sediment pollution delivered to the Bay. The resulting nutrient and sediment loads affect the prevalence of algal blooms that impact water clarity and dissolved oxygen concentrations in the tidal waters of the Bay. Higher than average river flows entering the Bay delivered abundant nutrient and sediment loads in 2018 and 2019 (see Pollution Loads and River Flow to the Chesapeake Bay (1985-2022)) that resulted in poorer water clarity, reductions in SAV area and lower dissolved oxygen levels in the Bay. More average weather patterns occurred from 2020 to 2022, and thus the recent decrease and subsequent rebound in the indicator score were anticipated.
The indicator score combines evaluations of dissolved oxygen conditions, water clarity with submerged aquatic vegetation, and chlorophyll a measures. Looking at the individual parameter assessments for 2020-2022, major increases in attainment occurred for deep channel and migratory fish spawning and nursery habitats for dissolved oxygen measures. However, shallow water bay grasses/water clarity attainment saw a moderate decline in attainment relative to the preceding period.
The estimated water quality standards attainment of 29.8% for 2020-2022 remains far below the 100% attainment necessary to fully support survival, growth, and reproduction of its living resources. For the Bay and its tidal tributaries to function as a healthy ecosystem and be taken off of the impaired waters listings under Sections 303(d) and 305(b) of the Clean Water Act, all applicable water quality criteria must be met simultaneously as defined in the water quality standards of Maryland, Virginia, Delaware and Washington D.C. Segment-level assessment results of water quality standards attainment can be accessed and visualized through the Chesapeake Bay Water Quality Standards Attainment Deficit and Chesapeake Bay Water Quality Standards Attainment Indicator visualization tools.
Annual Nutrient and Sediment Pollution Loads to the Bay: Improvement
During 2022, average river flow to the Bay measured 47.2 billion gallons per day, a 7.6 billion gallon per day decrease from 2021, and a 10% decrease from the 1985-2022 mean. The corresponding nutrient and sediment loads entering the Bay in 2022 were approximately 253 million pounds of nitrogen, 13.4 million pounds of phosphorus, and 14.2 billion pounds of sediment. All of these are below both their 1985-2022 means and their 2021 levels, and thus represent an improvement.
Pollution Loads and River Flow to the Chesapeake Bay (1990-2022)
River and Watershed Input of Pollution Loads. Years denote the water year measured between October 1 and September 30.
Nutrient and sediment loads delivered from the watershed into the Bay are one of many factors that influence water quality and are influenced by land use, land management, and river flow. Generally, when the watershed receives more rain and river flows increase, the water carries more sediment and nutrient pollution than usual, as shown by the high flows and nutrient and sediment loads to the Bay in 2018 and 2019.
The source of the information of loads and river flow to the Bay includes the loads from the nine RIM stations in nine major rivers entering the Bay, point source discharges into tidal waters, and an estimate of nonpoint source below the RIM stations from the Chesapeake Bay Program’s Watershed Model, the Chesapeake Assessment Scenario Tool (CAST-2019).
Monitored Nutrient and Sediment Trends in the Watershed: Mixed
Nutrient and sediment loads are monitored from 123 river and stream stations throughout the Chesapeake Bay watershed. Water-quality samples collected from this nontidal network are used to calculate trends, which describe how loads of nitrogen, phosphorus and sediment have changed over time. The US Geological Survey (USGS) computes trends at nontidal monitoring stations every year or every other year. Monitored trend results show a mixture of responses across the watershed; loads at some stations have decreased while loads at other stations have increased. Learn more about this monitoring network and the most recent load and trend results from the USGS.
Chesapeake Bay Total Maximum Daily Load Indicator: Improvement
The Bay TMDL indicator combines monitored and modeled data to estimate the progress of nitrogen and phosphorus annual loading rate reductions (millions of pounds per year) in response to implemented management practices. The indicator addresses the following questions:
- What reductions have been observed in the monitoring data?
- What reductions are expected from past management actions but have not been observed due to known lags in implementation action and environmental response?
- What reductions are needed from planned future management actions?
- What reductions are expected but not yet observed in monitoring?
To provide quantitative answers to these questions, this indicator leverages modeling data from CAST along with monitoring data, including river discharge and water quality measurements, wastewater loads and atmospheric deposition (only nitrogen) to tidal waters. CAST integrates knowledge of land use, nutrient inputs and watershed processes to estimate load reductions in response to implemented management practices. However, the expected reductions often differ from the reductions observed in the rivers due to factors including uncertainty in CAST, uncertainty in monitored trends, natural lags between implementation of management practices and eventual attainment of water quality improvements, as well as the impacts of climate change and infill of Conowingo Reservoir. By quantifying the effects of some of these factors – lag times, climate change and infill of Conowingo Reservoir – this indicator can help bridge the gap between the monitored reduction and model-estimated reduction.
Also, a comprehensive effort has been made to compile and analyze data sets for the watersheds of the Chesapeake Bay Nontidal Network (NTN) stations, including 83 stations for nitrogen and 66 stations each for phosphorus and sediment. These station-level results, available through the Monitored and Expected Total Reduction Indicator for the Chesapeake (METRIC) tool, can help resource managers gauge expectations on the trajectory and pace of reduction progress at a localized scale.
The Bay TMDL indicator uses 1995 as the baseline year because it marks the end of the 1993-1995 critical period used for assessing attainment of water quality standards in the Bay TMDL. It divides the total annual loading rate reductions required to meet the Bay TMDL planning targets into categories:
- Implemented and Realized refers to reductions due to actions in the Watershed Implementation Plans (WIPs) that have been both estimated in the models and seen in monitoring data.
- Implemented but Lagged refers to nitrogen and phosphorus reductions that are expected in the future due to actions that have already taken place, but not yet been realized due to natural lag times.
- RIM Expected but Not Seen refers to reductions in the RIM watershed due to actions in the WIPs that are estimated to have occurred in the models but have not been seen in the monitoring data.
- Future Implementation refers to expected nitrogen and phosphorus reductions planned in the WIPs, but not yet reported as implemented.
- WIP Shortfall refers to the difference between the nitrogen and phosphorus reduction goals under the Bay TMDL and the reductions the jurisdictions planned in their WIPs.
- Climate Adjustment refers to the additional reduction amount required to offset the impact of climate change, including increased delivery of nitrogen and phosphorus to the Bay and the decreased ability of the Bay to absorb nutrients while maintaining water quality standards.
- Conowingo Adjustment refers to the additional reduction amount required to offset the filling of the Conowingo reservoir that increased the nitrogen and phosphorus passing through it.
- Tidal Deposition Reduction Realized refers to observed nitrogen reductions in atmospheric deposition to tidal waters.
- Tidal Deposition Reduction Unimplemented refers to expected future nitrogen reductions in atmospheric deposition to tidal waters.
Nitrogen
For nitrogen, a total reduction of the annual loading rate by 145.07 million pounds is required compared to 1995 to achieve the Bay TMDL planning target. The Bay TMDL planning target includes a 10.33 million pound per year increase to account for the increased delivery due to the Conowingo Reservoir infill (+6.01 million pounds) and climate change (+4.32 million pounds). As of 2021, implemented management actions are yielding annual load reductions of 77.64 million pounds per year (i.e., implemented and observed in the monitoring data). Implemented management actions are expected to yield additional annual load reductions of 13.92 million pounds per year, but these reductions have not yet been realized in the monitoring data due to natural lags between nutrient application and the subsequent delivery to streams. In addition, annual load reductions of 42.26 million pounds per year are expected from planned future implementation of management actions. The last total reduction of the annual loading rate required to meet the target is 7.92 million pounds per year from tidal atmospheric deposition, of which 6.50 million pounds per year have been realized in 2021.
From 1995 to 2021, the reduction of nitrogen loading rates has been trending toward meeting the Bay TMDL planning target. Specifically, the category “implemented and realized” and “tidal deposition reduction realized” have increased over time, whereas the category “future implementation” has decreased over time as more of the planned actions to meet the Bay TMDL planning target are completed.
Bay TMDL Indicator: Total Nitrogen
This indicator combines monitored and modeled data to estimate the progress of annual pollution loading rate reductions since 1995 in response to implemented management practices.
Phosphorus
For phosphorus, a total reduction of the annual loading rate by 9.33 million pounds is required compared to 1995 to achieve the Bay TMDL planning target. The Bay TMDL planning target includes a 0.80 million pounds per year increase to account for the increased delivery due to Conowingo Reservoir infill (+0.26 million pounds) and climate change (+0.54 million pounds). In 2022, implemented management actions are yielding estimated annual load reductions of 2.40 million pounds per year (i.e., implemented and observed in the monitoring data). Implemented management actions are expected to yield additional annual load reductions of 1.74 million pounds per year, but these reductions have not yet been realized in the monitoring data due to natural lags. In addition, annual load reductions of 1.82 million pounds per year are expected from planned future implementation of management actions. Lastly, annual load reductions of 2.57 million pounds per year have been estimated by the model while accounting for lag times, but have not been observed in the monitoring data, which represents an unknown response gap and implies unknown sources and/or processes that may need to be examined and incorporated in the future refinements of CAST.
Like nitrogen, the reduction of phosphorus loading rates since 1995 has been trending toward meeting the Bay TMDL planning target. Specifically, the category “implemented and realized” has increased over time, whereas the category “future implementation” has decreased over time as more of the planned actions to meet the Bay TMDL planning target are completed.
Bay TMDL Indicator: Total Phosphorus
This indicator combines monitored and modeled data to estimate the progress of annual pollution loading rate reductions since 1995 in response to implemented management practices.
Summary
There are multiple factors affecting attainment of water quality standards and response of nutrients to management actions in the watershed. The Chesapeake Bay Program water quality standards attainment indicator showed improvement in the Bay’s tidal waters after four consecutive years of degrading results. This indicator is influenced by the amount of nutrient and sediment pollution washed into the Bay each year as well as management efforts to control nutrient pollution. This indicator shows an improving trend in the long term since 1985. The trends of nitrogen, phosphorus and sediment loads at nontidal monitoring sites show mixed results in the watershed response to management actions. Studies are improving the understanding of the factors affecting water quality response to nutrient reduction efforts in the watershed. Recent studies identified water quality improvements resulting from point source upgrades and reduced air deposition of nitrogen, but management challenges are recognized in addressing nonpoint sources of nutrients delivered to rivers and the Bay from agricultural and urban lands.
Management Strategy
To achieve the Water Quality Standards Attainment and Monitoring outcome, participating partners have committed to:
- Analyzing water quality trends in the Chesapeake Bay and its watershed.
- Explaining the factors affecting water quality trends in the Bay and its watershed.
- Enhancing Chesapeake Bay Program models using our improved understanding of water quality trends.
- Informing management strategies to improve water quality.
- Adhering to the Bay TMDL Accountability Framework.
- Investing in enhanced monitoring efforts in the Bay and its watershed.
Assessing progress toward achieving the outcome will occur through analysis of data collected from monitoring networks that track river flow, nitrogen, phosphorus, and sediment in the watershed; air deposition of nitrogen and phosphorus; water quality conditions in tidal waters relative to established water quality standards; conditions of tidal habitats; changes in climate and the health of living resources.
Logic & Action Plan
Chesapeake Bay Program partners have committed to taking a series of specific actions that will support the management approaches listed above.
Ongoing
- Leading Best Management Practice (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 assessment of temporal and regional patterns in non-tidal waters and water quality criteria attainment in tidal waters.
- Coordinating the Chesapeake Bay Program Tidal and Non-tidal 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.
- Communicating the factors affecting trends and understanding responses to management practices.
- Contributing to understanding of co-benefits of water-quality restoration to selected habitats and living resources.
Recently Completed
2023
- Conducted field investigation of factors affecting stream condition in southeastern Pennsylvania.
- Established continuous (measurements on an hourly basis) water quality monitoring in a nontidal network of nine major RIM Program sites.
- Deployed three water quality sensors in Chesapeake Bay for the summer season.
- Developed a two-year nutrient limitation project in the Bay.
- Developed a multiyear satellite-monitoring protocol development and regional test case project.
- Published studies on management results in nutrient and sediment reduction efforts and water quality impacts of climate change, land use and population growth.
2022
- Conducted a field investigation of factors affecting stream conditions on the Eastern Shore of Maryland.
- Created a project team to create a tool that tracks water quality over space and time.
- Created the Hypoxia Collaborative Team, focused on enhanced high temporal frequency water quality monitoring in the Bay.
- Completed the 2021-2022 Monitoring Review, at the Principal’s Staff Committee request, to enhance core Bay Program monitoring networks.
- Successfully deployed seasonal testing for new investment in high temporal frequency water quality monitoring sensors in deep waters.
- Published studies on various topics related to trends in nutrient and nitrogen in the Bay watershed as well as impacts on hypoxia (see the Analysis & Methods document for publication details).
2021
- Conducted field investigation of factors affecting stream conditions in the Shenandoah Valley.
- Published the STAC Workshop Report on satellite monitoring opportunities for submerged aquatic vegetation in Chesapeake Bay and a study on nutrient limitation patterns in the mainstem of the Bay.
- Developed and awarded new six-year funding for the EPA-funded Community Science program through the Chesapeake Monitoring Cooperative.
Participating Partners
The Water Quality Goal Implementation Team leads the effort to achieve this outcome. It works in partnership with 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