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Nitrogen in Rivers Entering Chesapeake Bay: Short-Term Flow-Adjusted Concentration Trends

Over the past decade, one-third of the monitoring sites in the Chesapeake Bay watershed have shown improving flow-adjusted trends in nitrogen concentrations. Between 2004 and 2013:

  • Three out of nine sites—including the Patuxent, Potomac and Susquehanna rivers—have shown improving trends for nitrogen concentrations
  • One site—the Choptank River—has shown degrading trends
  • Five sites—including the Appomattox, James, Mattaponi, Rappahannock and Pamunkey rivers—have shown minor changes that are not statistically significant

For more information, visit the U.S. Geological Survey’s Summary of Trends Measured at the Chesapeake Bay Tributary Sites: Water Year 2013 Update.


Short-Term Trend in Flow-Adjusted Total Nitrogen Concentration, 2004-2013

Map: Short-Term Trend in Flow-Adjusted Total Nitrogen Concentration, 2004-2013

Date created: Jan 07 2015 / Download

Over the past decade, one-third of the monitoring sites in the Chesapeake Bay watershed have shown improving flow-adjusted trends in nitrogen concentrations. Between 2004 and 2013: three out of nine sites—including the Patuxent, Potomac and Susquehanna rivers—have shown improving trends for nitrogen concentrations. One site—the Choptank River—has shown degrading trends. Five sites—including the Appomattox, James, Mattaponi, Rappahannock and Pamunkey rivers—have shown minor changes that are not statistically significant.

Importance

Excess nitrogen is among the leading causes of the Chesapeake Bay’s poor health. But nitrogen concentrations are highly variable, depending on the amount of water flowing in streams and rivers across the watershed. For this reason, scientists calculate flow-adjusted concentration trends to determine whether nitrogen concentrations have changed over time. By examining data that is presented independently of the effects of variations in stream flow, resource managers can better evaluate the changes in stream health that have and could continue to result from pollution-reducing practices or other activities in the watershed.

Goal

In 2014, the Chesapeake Bay Program adopted a goal to reduce pollution and achieve the water quality necessary to protect human health and support the region’s underwater resources. Resource managers hope to observe downward trends in flow-adjusted nitrogen concentrations at monitoring sites across the watershed.

Additional Information

The U.S. Geological Survey (USGS) works with Chesapeake Bay Program partners to monitor nutrients and sediment in the watershed. Data are collected, updated and interpreted each year. The update for water year 2013 (which took place between Oct. 1, 2012, and Sept. 30, 2013) includes data from nine River Input Monitoring (RIM) stations. Together, these stations—which are located on the Appomattox, Choptank, James, Mattaponi, Pamunkey, Patuxent, Potomac, Rappahannock and Susquehanna rivers—reflect loads delivered to the Bay from 78 percent of its watershed.

Because one goal of our restoration work is to reduce nitrogen, phosphorus and sediment loads to the Bay, downward trends in nutrient and sediment concentrations are considered improving conditions. Increasing trends are considered degrading conditions. Findings for trends in nutrient and sediment concentrations across the watershed through 2013 include:

One-third of the sites—including the James, Patuxent and Potomac rivers—are showing long-term improvements in both nitrogen and phosphorus concentrations. Five sites are showing long-term improvements in nitrogen concentrations, while three sites are showing long-term improvements in phosphorus concentrations. Over the past decade, nitrogen concentrations have improved at three sites, while phosphorus concentrations have shown little or no change at almost all of the sites.
One-third of the sites—including the Choptank, Patuxent and Potomac rivers—are showing long-term improvements in sediment concentrations. Over the past decade, sediment concentrations have shown little or no change at five sites and degrading conditions at four sites.

For more information, visit the U.S. Geological Survey’s Summary of Trends Measured at the Chesapeake Bay Tributary Sites: Water Year 2013 Update.

Contact

Scott Phillips
USGS Chesapeake Bay
(443) 498-5552

Source of Data

US Geological Survey

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Annapolis, Maryland 21403
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