A Little Applied Geochemistry and Some Useful Physical Characteristics

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A Little Applied GeochemistryandSome Useful
Physical Characteristics

• Relating to Karst Aquifers

Ralph O. Ewers, Ph.D. Peter J. Idstein,
M.S. ewc_at_mis.net
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Spring and Karst Aquifer Types
Schuster and White, 1971
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Conduit Flow Springs vs. Diffuse Flow Springs
Schuster and White, 1971
After Jacobsen and Langmuir, 1974
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Conduit Flow Springs vs. Diffuse Flow Springs
Schuster and White, 1971
These unfortunate names have prompted comments
such as This is a diffuse flow aquifer and
therefore it must be an equivalent porous medium.
Therefore, our wells should work properly and we
can even model this aquifer in the standard
granular aquifer manner.
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Conduit Flow Springs vs. Diffuse Flow Springs
Schuster and White, 1971

• These unfortunate names have prompted comments
  such as
• This is a diffuse flow aquifer and therefore it
  must be an equivalent porous medium. Therefore,
  our wells should work properly and we can even
  model this aquifer in the standard granular
  aquifer manner.
• The response of a person familiar with carbonate
  aquifers
• Only a tiny fraction of the carbonate aquifers
  of the world are truly equivalent porous media.
• Traditional methods in very highly fractured
  carbonates or those possessing significant
  inter-granular permeability may appear to predict
  tolerable head response and production values.
• Traditional methods do not provide useful
  predictions relative to contaminant transport in
  most carbonates.

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Quick-flow Recharge vs. Seepage Recharge
Schuster and White, 1971
After Jacobsen and Langmuir, 1974
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Coefficients of Variation
Jacobsen and Langmuir, 1974
Variable Quick-flow Rech. Seepage Recharge
Temperature 26.9 1.4
Ca 25.5 6.4
Mg 27.6 2.0
Total Hardness 26.0 4.8
Na 25.9 24.3
K 16.0 9.8
HCO3- 28.6 2.7
SO4-- 12.7 17.8
Cl- 17.7 29.0
NO3- 32.0 19.9
pH 1.7 0.6
Discharge 175 26.3
SI c 18.5 16.1
Pco2 8.7 2.4
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Coefficients of Variation
Jacobsen and Langmuir, 1974
Variable Quick-flow Rech. Seepage Recharge
Temperature 26.9 1.4
Ca 25.5 6.4
Mg 27.6 2.0
Total Hardness 26.0 4.8
Na 25.9 24.3
K 16.0 9.8
HCO3- 28.6 2.7
SO4-- 12.7 17.8
Cl- 17.7 29.0
NO3- 32.0 19.9
pH 1.7 0.6
Discharge 175 26.3
SI c 18.5 16.1
Pco2 8.7 2.4
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Coefficients of Variation
Jacobsen and Langmuir, 1974
Variable Quick-flow Rech. Seepage Recharge
Temperature 26.9 1.4
Ca 25.5 6.4
Mg 27.6 2.0
Total Hardness 26.0 4.8
Na 25.9 24.3
K 16.0 9.8
HCO3- 28.6 2.7
SO4-- 12.7 17.8
Cl- 17.7 29.0
NO3- 32.0 19.9
pH 1.7 0.6
Discharge 175 26.3
SI c 18.5 16.1
Pco2 8.7 2.4
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Hydraulic Conductivity Measurements In Karst
(Quinlan, Worthington and Davies, 1992 Teutsch
and Sauter, 1992 Worthington, 1992)
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Sinkholes DO NOT Define Karst

• Many demonstrably karst aquifers do not have them
• Conduits formed by dissolution of the carbonate
  rock do define them.

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Sinkholes DO NOT Define Karst

• Many demonstrably karst aquifers do not have them
• Conduits formed by dissolution of the carbonate
  rock do define them.

18Miles
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High Level Overflow Routes Between Basins May
Complicate a Site
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Traditional Potentiometric Surface Maps are
Reliable ONLY at Regional Scale
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Groundwater Flow is CONVERGENTIn Karst, Not
Divergent and Dispersive
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Digital Data Loggers

• An Asset in Understanding Karst Aquifers

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A typical Installation with auto-sampler
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Campbell 21X and CR-10 Series
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Stage SensorDruck Pressure Transducer
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Conductivity SensorA Simple Proprietary Device
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Temperature SensorPlatinum Resistance Thermometer
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Typical Data-Logger Program
Measure 10 seconds Measure 10 Seconds Measure 10
Seconds
Calculate 2 Minute Average
Compare To Previously Stored Value
Same
Different
Store New Value
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A phreatic conduit system
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An epiphreatic or vadose conduit system
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END

• Part 4