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Reducing Nitrogen Pollution

Computer simulations show that pollution controls put in place in the Chesapeake Bay watershed between July 2009 and June 2014 lowered nitrogen loads six percent, from 282.66 million pounds in 2009 to 266.83 million pounds in 2014. Excess nitrogen is one of the leading causes of the Bay’s poor health, and reducing nutrient pollution will be critical to achieving our clean water goals.

These pollution loads were simulated using the Chesapeake Bay Program’s Watershed Model (Phase 5.3.2) and wastewater discharge data reported by watershed jurisdictions. These simulations were calibrated using monitoring data.







December 06, 2011

What is an algae bloom and how does it form? Charlie Poukish from the Maryland Department of the Environment explains what fuels algae blooms and how they can spell trouble for underwater life.



December 06, 2011

When rainfall runs across roads, lawns and golf courses, it can pick up pollutants before it enters local waterways. Mike Fritz from the Chesapeake Bay Program explains why so-called “stormwater runoff” is a major source of pollution to the Chesapeake Bay and what we can do to prevent it.



December 06, 2011

Old wastewater treatment plants can contribute nitrogen and phosphorous to the Chesapeake Bay, but plants across the watershed are being upgraded. Alan Quimby from the Queen Anne’s County (Md.) Department of Public Works explains how these upgrades will help the Bay.



December 06, 2011

Air pollution affects each of the 17.7 million people who live in the Chesapeake Bay watershed. But it doesn’t just cloud the air we breathe. Airborne pollutants can also harm our land and water, fueling the growth of harmful algae blooms that create oxygen-depleted dead zones in the Bay. Randy Mosier from the Maryland Department of the Environment (MDE) explains how our watershed is affected by the “airshed” that surrounds it, and how airborne pollutants fall onto our land and into our water.

Importance

Excess nitrogen is one of the leading causes of the Chesapeake Bay’s poor health. When nitrogen and phosphorus enter rivers, streams and the Bay, they fuel the growth of algae blooms that lead to low-oxygen “dead zones” that are harmful to fish, shellfish and other aquatic life. In general, nitrogen and phosphorus reach the Bay through three sources: wastewater treatment plants; urban, suburban and agricultural runoff; and air pollution. The Total Maximum Daily Load (TMDL) limits the amount of nutrients that can enter the Bay if it is to achieve water quality standards.

Goal

The Chesapeake Bay Total Maximum Daily Load (TMDL), which was incorporated into the Chesapeake Bay Watershed Agreement, limits the amount of nutrients and sediment that can enter the Bay to levels that would achieve water quality standards. Under this “pollution diet,” Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia and the District of Columbia must describe the steps they will take to reduce pollution in individual Watershed Implementation Plans (WIPs). Pollution control efforts that would achieve at least 60 percent of the pollution reductions necessary to restore the Bay compared to 2009 should be in place by 2017. Those efforts that would achieve all of the pollution reductions necessary should be in place by 2025, when computer-simulated nitrogen loads to the Bay should reach 207.57 million pounds.

Computer simulations show that pollution controls put in place in the Chesapeake Bay watershed between July 2009 and June 2014 lowered nitrogen loads six percent, from 282.66 million pounds in 2009 to 266.83 million pounds in 2014. The 2014 nitrogen loads were 29.22 million pounds higher than the 2017 Interim Target of 237.61 million pounds and 59.26 million pounds higher than the 2025 Planning Target of 207.57 million pounds.

The Chesapeake Bay Program takes an adaptive approach toward environmental restoration and is incorporating the latest science and monitoring data into a midpoint assessment of the Total Maximum Daily Load (TMDL). In 2018, watershed jurisdictions will develop Phase III Watershed Implementation Plans (WIPs) that will take findings from the midpoint assessment into account and address any modifications to ensure pollution control efforts that would achieve the pollution reductions necessary to restore the Bay are in place by 2025.

Additional Information

Measuring progress and pollution loads

The Chesapeake Bay Program measures progress toward reducing pollution using nutrient and sediment control tracking data that have been reported to the Chesapeake Bay Program by our partners. Through the Watershed Model (Phase 5.3.2), we use computer simulations to estimate the amount of nitrogen, phosphorus and sediment delivered to the Bay following the implementation of efforts to reduce these pollutants from wastewater treatment plants; septic tank discharges; urban, suburban and agricultural runoff; and air pollution.

Pollution loads can be influenced by land use and weather conditions. The Watershed Model uses long-term average weather conditions to estimate the impact of nutrient and sediment controls on agricultural, urban and forested lands; onsite septic systems; and atmospheric deposition. The Watershed Model uses actual wastewater discharge data (which is influenced by weather conditions) to estimate wastewater pollution entering the Bay. Watershed Model simulations help us better understand the effects of our management actions on pollution loads and are important in developing “what-if” scenarios we can use to project future impacts of our actions on water quality.

Because the computer simulations that generate the Reducing Nitrogen, Phosphorus and Sediment indicators use long-term average conditions, it is possible for these indicators to report pollution loads that differ from those that are reported by the indicators that monitor actual nitrogen, phosphorus and sediment loads in a given year.

Additional notes on data

Atmospheric deposition was simulated using the Chesapeake Bay Airshed Model (which combines a regression model for estimates of wet deposition and a continental-scale air quality model for estimates of dry deposition). Atmospheric deposition that is the U.S. Environmental Protection Agency’s responsibility to reduce is calculated by subtracting watershed loads assuming that existing requirements under the Clean Air Act are fully implemented (known as “allocation air”) from watershed loads and actual atmospheric deposition.

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