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USGS Chesapeake Bay Activities

USGS study:  Groundwater delaying water-quality improvements on the Delmarva Peninsula and Chesapeake Bay

(Released November 2013)

Map showing the distribution of groundwater ages (return times) on the Delmarva Peninsula.

The map shows the distribution of groundwater ages (return times) on the Delmarva Peninsula (Sanford and Pope, 2013). The slow groundwater travel times will delay the benefits of water-quality practices to reduce nutrient in streams and portions of the Chesapeake Bay tidal waters.

New research by the U.S. Geological Survey conducted on the Delmarva Peninsula, which forms the Eastern Shore of the Chesapeake Bay, indicates it may take several decades for many water-quality management practices aimed at reducing nitrogen input to the Bay to achieve their full benefit due to the influence of groundwater.

The new study shows that ages of groundwater and associated nitrogen from the Delmarva Peninsula into the Chesapeake Bay range from less than a year to centuries (see map), with median ages ranging from 20 to 40 years. These groundwater age distributions are markedly older than previously estimated for areas west and north of the Bay, which has a median age of 10 years. The older ages occur because the porous, sandy aquifers on the Delmarva yield longer groundwater return times than the fractured-rock areas of the Bay watershed.

The USGS findings provide critical information on how long it may take to see the water-quality improvements in the Chesapeake Bay as more stringent practices are implemented to reduce nutrients and sediment under the Chesapeake total maximum daily load (TMDL).

Read the press release….

Read journal article in Environment, Science, & Technology…

Read an article by the Bay Journal….

Read the recent STAC report on lag times in the Chesapeake Bay watershed…

For additional information about this research, please contact Ward Sanford ( or Scott Phillips (

For additional information about USGS Chesapeake Bay studies, please contact Scott Phillips (

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