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

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. Groundwater Geochemistry.

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

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  1. Columbia Basin GWMA Subsurface Geologic Mapping and Hydrogeologic Assessment Project Progress ReportGroundwater 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. 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

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

  7. 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 (<20 %) is too small to offset withdrawals • Limited connection to surface recharge

  8. 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 >10,000 years) • No present-day surface recharge sources

  9. 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

  10. 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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