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Ground Water and Its Influence on Nitrogen Delivery to the Chesapeake Bay

The USGS has recently completed a multi-year study of the discharge, nitrogen transport, and age of ground water into streams of the Chesapeake Bay watershed. The findings of the study have been summarized in a fact sheet “The Influence of Ground Water on Nitrogen Delivery to the Chesapeake Bay, Online Publication - FS-091-03” and a comprehensive technical report “Residence Times and Nitrate Transport in Ground Water Discharging to Streams in the Chesapeake Bay Watershed, Water-Resources Investigations Report 03-4035” Copies of the reports are being mailed to many in the Chesapeake Bay Community and are also available by sending an E-mail to shartsoe@usgs.gov.

Some of the major findings of the study include:

• Resource managers need to understand the “lag time” between implementation of management practices and improvement in water quality in the Bay to help develop future nutrient- and sediment-reduction strategies. One factor affecting the lag time is the influence of ground water on the transport of nitrogen to streams in the Bay watershed.
• Ground water supplies a significant amount (about half) of water and nitrogen to streams in the watershed and is therefore an important pathway for nitrogen to reach Chesapeake Bay.
• The age of ground water in shallow aquifers in the Chesapeake Bay watershed ranges from modern (less than 1 year) to more than 50 years, with a median age of 10 years.
• In addition to ground water, stream water will be influenced by surface runoff and soil water. Runoff and soil water both have very young ages (hours to months) and supply, on average, about half of the water to a stream.
• Proposed water-quality criteria in the Bay probably will not be met by 2010 due to the time needed to implement management practices and the effect of ground water and other watershed properties on nutrient transport.

The Annapolis Capital: Groundwater hinders bay recovery effort 3/1/2004

The Salisbury (MD) Daily Times: Groundwater hinders Chesapeake Bay recovery 2/25/2004

Capital News Service: Groundwater hinders Chesapeake Bay recovery 2/25/2004

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