Text Size: A  A  A

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

Seventy percent of long-term stream monitoring sites in the Chesapeake Bay Watershed have improving flow-adjusted concentrations of nitrogen. Between 1985 and 2012:

  • 21 out of 30 sites show improving flow-adjusted trends for nitrogen concentrations
  • 3 sites show degrading trends
  • 6 sites show small changes that are not statistically significant

For more information go to the U.S. Geological Survey's webpage, Summary of Trends and Yields Measured at the Chesapeake Bay Nontidal Network Sites: Water Year 2012 Update


Long-Term Trend in Flow-Adjusted Total Nitrogen Concentration, 1985-2012

Map: Long-Term Trend in Flow-Adjusted Total Nitrogen Concentration, 1985-2012

Date created: Jan 02 2014 / Download

Long Term Trend: Seventy percent of long-term stream monitoring sites in the Chesapeake Bay Watershed have improving flow-adjusted concentrations of nitrogen. Between 1985 and 2012: - 21 out of 30 sites show improving flow-adjusted trends for nitrogen concentrations, - 3 sites show degrading trends, and - 6 sites show small changes that are not statistically significant.

Importance

Nitrogen concentrations are highly variable, depending on the amount of water flowing in streams and rivers throughout the Bay watershed. Therefore, scientists calculate flow-adjusted trends to determine whether concentrations have changed over time.  By removing the effects of natural variations in streamflow, resource managers can evaluate the changes in stream health that may result from nutrient-reduction actions or other changes within the watershed.

Goal

The goal is to observe downward trends in flow-adjusted nitrogen concentrations at monitoring sites across the Bay watershed.

Additional Information

The U.S. Geological Survey (USGS), works with partners in the Chesapeake Bay Program (CBP) to operate the Nontidal water-quality monitoring network. This network is designed to measure changes in nutrients and sediment in the Chesapeake Bay watershed. The nutrient and sediment data are updated and interpreted each year. The update of 2012 information includes:

  • Long-term trends in concentrations (1985-2012)
  • Short-term trends in concentrations (2003-2012)
  • Yields as an indicator of the relative loads among watersheds (2008-2012)

Because the goals of Bay restoration efforts are to reduce nitrogen, phosphorus and sediment reaching the Bay, downward trends in concentration are considered improving conditions, while increasing trends are considered degrading conditions. The major findings for nutrient and sediment concentration trends and yields in the Chesapeake Bay watershed through 2012 are:

  • Across the watershed, about 70 percent of the sites are showing long-term improvements in nitrogen and phosphorus. Over the past 10 years, nitrogen conditions have improved at about one half of the sites, while phosphorus concentrations show little or no change at more than one half of sites.
  • The amount of improvement for sediment concentrations is smaller than the nutrients with 28 percent showing an improvement over the long-term and 10 percent showing improvements over the last decade. Just under half of the sites show little change over the long term or past decade. However, 41 percent show degrading flow-adjusted sediment concentrations over the past 10 years.
  • Nitrogen, phosphorus and sediment yields at Chesapeake monitoring sites are highly variable. High yielding sites for nutrients are located in portions of the Susquehanna, Potomac and Rappahannock watersheds as well as the Eastern Shore. The lowest sediment yielding sites are located on the Eastern Shore and the York River Basin.

Contact

Scott Phillips
USGS Chesapeake Bay
(443) 498-5552

Source of Data

US Geological Survey

410 Severn Avenue / Suite 112
Annapolis, Maryland 21403
Tel: (800) YOUR-BAY / Fax: (410) 267-5777
Directions to the Bay Program Office
Terms of Use | Privacy Policy
©2012 Chesapeake Bay Program | All Rights Reserved