Columbia Basin GWMA Subsurface Geologic Mapping and Hydrogeologic Assessment Project Progress Report Groundwater Geochemistry - PowerPoint PPT Presentation

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Columbia Basin GWMA Subsurface Geologic Mapping and Hydrogeologic Assessment Project Progress Report Groundwater Geochemistry

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Deeper (605') well in basalt (Wanapum and uppermost Grande Ronde) Static ... The lower part of the basalt aquifer system has not been recharged since the end ... – PowerPoint PPT presentation

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Title: Columbia Basin GWMA Subsurface Geologic Mapping and Hydrogeologic Assessment Project Progress Report Groundwater Geochemistry


1
Columbia Basin GWMA Subsurface Geologic Mapping
and Hydrogeologic Assessment Project Progress
Report Groundwater Geochemistry
  • Dimitri Vlassopoulos
  • SS Papadopulos and Associates
  • Portland, Oregon
  • Presented at GWMA Board Meeting, Othello, WA
  • January 22, 2009

2
Groundwater Geochemistry
  • Major ion chemistry
  • Changes along flow path
  • Relative age
  • Recharge sources
  • Mixing
  • Stable Isotopes
  • Water sources (precipitation/runoff, surface
    water)
  • Ancient (glacial) versus modern recharge
  • Atmospheric tracers (groundwater age-dating)
  • Radiocarbon, tritium, CFCs, SF6
  • Groundwater age (time since recharged)
  • Mixing of old and young water (pumping effects)

3
GWMA Well Sampling 2008
4
Groundwater Geochemistry, Age and Recharge
  • Geochemical data can identify the source(s) of
    groundwater
  • ancient groundwater
  • surface water recharge (lakes, rivers, canals)
  • irrigation water recharge
  • Age-dating methods can be used to determine the
    length of time groundwater has been in the
    subsurface
  • Direct information on the relative amounts of old
    and young water drawn by pumping wells

5
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6
Royal City
  • Wells 1, 2
  • Shallow-cased water supply wells completed in
    Wanapum
  • Static water levels steady
  • Mixture of older and young water (recharged
    since 1950s)
  • Recharge from Frenchman Hills sufficient to
    sustain withdrawals

7
Moses Lake
  • Well 18
  • Supply well completed in Wanapum (Frenchman
    Springs)
  • Static water levels stable
  • Mostly young water (post-1950s)
  • Direct connection to East Low Canal through
    Roza/Upper Frenchman Springs flow zones

8
Moses Lake
  • Well 17
  • Supply well completed in upper Grande Ronde
    (Sentinel Bluffs)
  • Static water levels declining
  • Mixture of old and young water (average
    recharge age 6,000 years)
  • Recharge from young water component (lt20 ) is
    too small to offset withdrawals
  • Limited connection to surface recharge

9
Odessa
  • Irrigation well 20 miles east of Moses Lake
  • Well completed in Lower Grande Ronde (Umtanum and
    Ortley)
  • Static water levels declining
  • Old water (recharge age gt10,000 years)
  • No present-day surface recharge sources

10
Horseshoe Bend
  • Irrigation Wells
  • Shallow (132) well in use since 1948
    (Roza/Alluvium)
  • Deeper (605) well in basalt (Wanapum and
    uppermost Grande Ronde)
  • Static water levels stable
  • Predominantly young water in shallow well,
    predominantly older water in deeper well
  • Relatively low groundwater use area
  • Connection to surface recharge (Sprague Lake)
    sufficient to recharge shallow well

11
However
  • MOST of the groundwater in the Lower Grande Ronde
    aquifers is more than 10,000 years old
  • The lower part of the basalt aquifer system has
    not been recharged since the end of the last ice
    age (!)
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