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Old groundwater in parts of the upper Patapsco aquifer,Atlantic Coastal Plain, Maryland, USA: Evidence fromradiocarbon, chlorine-36 and helium-4

Hydrogeology

By:
, , , , , and
DOI: 10.1007/s10040-012-0871-1

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Abstract

Apparent groundwater ages along two flow paths in the upper Patapsco aquifer of the Maryland Atlantic Coastal Plain, USA, were estimated using 14C, 36Cl and 4He data. Most of the ages range from modern to about 500 ka, with one sample at 117 km downgradient from the recharge area dated by radiogenic 4He accumulation at more than one Ma. Last Glacial Maximum (LGM) water was located about 20 km downgradient on the northern flow path where the radiocarbon age was 21.5 ka, paleorecharge temperatures were 0.5 to 1.5 °C (a maximum cooling of about 12 °C relative to the modern mean annual temperature of 13 °C), and Cl-, Cl/Br, and stable isotopes of water were minimum. Low recharge temperatures (typically 5-7 °C) indicate that recharge occurred predominantly during glacial periods when coastal heads were lowest due to low sea-level stand. Flow velocities averaged about 1.0 ma-1 in upgradient parts of the upper Patapsco aquifer and decreased from 0.13 ma-1 to 0.04 ma-1 at 40 km and 80 km further downgradient, respectively. This study demonstrates that most water in the upper Patapsco aquifer is non-renewable on human timescales under natural gradients, thus highlighting the importance of effective water-supply management to prolong the resource.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Old groundwater in parts of the upper Patapsco aquifer,Atlantic Coastal Plain, Maryland, USA: Evidence fromradiocarbon, chlorine-36 and helium-4
Series title:
Hydrogeology
DOI:
10.1007/s10040-012-0871-1
Volume
20
Issue:
7
Year Published:
2012
Language:
English
Publisher:
Springer
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Branch of Regional Research-Eastern Region
Description:
26 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Hydrogeology
First page:
1269
Last page:
1294
Country:
United States
State:
Maryl
County:
Anne Arundel
City:
Baltimore
Additional Online Files(Y/N):
N