<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:creator>Stephen R. Hinkle</dc:creator>
  <dc:date>2009</dc:date>
  <dc:description>Water samples for tritium/helium-3 age dating were collected from 12 shallow monitoring wells in the Portland basin, Oregon, in 1997, and again in 1998. Robust tritium/helium-3 apparent (piston-flow) ages were obtained for water samples from 10 of the 12 wells; apparent ages ranged from 1.1 to 21.2 years. Method precision was demonstrated by close agreement between data collected in 1997 and 1998. Tritium/helium-3 apparent ages generally increase with increasing depth below the water table, and agree well with age/depth relations based on assumptions of effects of recharge rate on vertical ground-water movement.</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3133/sir20095057</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>U.S. Geological Survey</dc:publisher>
  <dc:title>Tritium/Helium-3 Apparent Ages of Shallow Ground Water, Portland Basin, Oregon, 1997-98</dc:title>
  <dc:type>reports</dc:type>
</oai_dc:dc>