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Water resources and hydrochemistry of the Alluvial and Sparta aquifers of the Grand Prairie region
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Water resources and hydrochemistry of the Alluvial and Sparta aquifers of the Grand Prairie region

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My master's thesis defense presentation from April 2002, University of Arkansas Department of Geosciences

My master's thesis defense presentation from April 2002, University of Arkansas Department of Geosciences

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  • Going to attempt to sum up 2.5 years of research This picture is typically of what you can see in the Grand Prairie region….this is a Sparta-aquifer irrigation well, with a jug of drip oil sitting there and the vent, which is where I was able to acquire the sample in most of my wells

Transcript

  • 1. Water resources and hydrochemistry of the Alluvial and Sparta aquifers of the Grand Prairie region Chad D. Cooper, Ralph K. Davis, Kenneth F. Steele University of Arkansas, Department of Geosciences Arkansas Water Resources Center
  • 2. The Problem
    • Multiple ground-water uses
    • Ground-water level declines
    • Critical Ground-Water Area as of 1998
    • Salinization may be related to ground-water level decline
    • Water-quality variations resulting from lower water levels can impact all uses
  • 3. Objectives
    • Delineate spatial distribution and magnitude of varying water quality conditions as related to areas of ground-water level decline
    • Determine areas of ground-water salinization (high in chloride, SpC, TDS)
    • Examine varying water-quality conditions spatially over the study area
    • Provide baseline water-quality data to water users of the region
  • 4. Physiography of Study Area
    • Approximately 8,900 square kilometers
    • Little to no relief
    • Dominated by agricultural production
  • 5. 1999 Land Use/Land Cover (summer)
  • 6. Water level, Alluvial aquifer, spring 1998
    • Declines in Alluvial:
      • 1915-1933 – up to 60 feet, Arkansas Co.
      • 1938-1953 – from 10-20 feet
      • 1955-1961 – from 3-10 feet
      • 1969-1996 - 32 feet, Lonoke Co.
  • 7. Wells completed in the Alluvial aquifer
    • About 7,000 wells!
  • 8. Water level, Sparta aquifer, spring 1998
    • Declines in Sparta:
      • 1949 – 50 feet near Pine Bluff
      • 1958-1965 – 160 feet at Pine Bluff
      • 1969-1999 – 70 feet+ in Arkansas Co.
      • 1988-1999 – almost 20 feet in Lonoke Co.
  • 9. Wells completed in the Sparta aquifer
    • About 325 wells
    • (and rising)!
  • 10. Sample Sites
    • July/Aug 2000
    • 78 Alluvial
    • 39 Sparta
    • 8 QA/QC
    • Analyses at WQL of AWRC
  • 11. Ground-water quality, Alluvial aquifer
    • Good to acceptable
    • Calcium-magnesium-bicarbonate type
    • No MCL’s exceeded
    • SMCL’s exceeded: Mn (0.05 mg/L)
    • Fe (0.3 mg/L)
    • Chloride: 3-172 mg/L
  • 12. Ground-water quality, Sparta aquifer
    • Better
    • Range from Ca-Na-HCO 3 type to Na-HCO 3 type
    • No MCL’s exceeded
    • SMCL’s exceeded: Mn (0.05 mg/L)
    • Fe (0.3 mg/L)
    • Chloride: 2-56 mg/L
  • 13. Salinization related to declines? Cl, Alluvial Aquifer Cl, Sparta Aquifer
  • 14. Salinization related to declines? TDS, Alluvial Aquifer TDS, Sparta Aquifer
  • 15. Spatial trends, Sparta aquifer GW FLOW Lonoke Jefferson Arkansas Prairie
  • 16. Spatial trends, Sparta aquifer Ionic Strength Calcium Saturation
  • 17. Spatial trends, Sparta aquifer Transect Location Results GW FLOW
  • 18. Spatial trends, Alluvial aquifer Conductivity vs. Well Depth
  • 19. Spatial trends, Alluvial aquifer Ionic Strength Calcium Saturation 37 of 78 samples saturated
  • 20. Spatial trends, Alluvial aquifer pH vs. Ca Saturation pH~6.85
  • 21. Spatial trends, Alluvial aquifer pH vs. Iron pH~6.85
  • 22. Results and Conclusions
    • Salinization not widespread
    • Water quality for both aquifers:
      • Alluvial: Acceptable, with high Cl and Fe
      • Sparta: Better, lower Cl and Fe
    • Varying hydrochemistry not result of
    • ground-water level declines
    • Varying hydrochemistry is instead result of geochemical evolution along flowpath
  • 23. Results and Conclusions
    • Dominant processes:
      • Alluvial: Ca saturation, precipitation of calcium- and iron-rich cements
      • Sparta: Ca saturation, precipitation of calcium-rich cement; cation exchange
    • Future work:
      • Combine and compare with other datasets from the region
      • Statistical analysis of spatial data
      • Examine relationships with rivers
      • Iron in the Alluvial aquifer?
  • 24. Acknowledgements
    • Arkansas Water Resources Center (AWRC)
    • Water Quality Lab, AWRC
    • Arkansas Soil and Water Conservation Commission
    • United States Geological Survey, Little Rock
    • Arkansas Department of Environmental Quality
    • Center for Advanced Spatial Technologies, University of Arkansas
  • 25. Questions?