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Surface Investigations of Groundwater

Surface Investigations of Groundwater. John Walton Fall, 2010. Remote sensing, example of phreatophytes. Salt Cedar – Rio Grande. Salt Cedar. Grows over shallow water table areas High amount of evapotranspiration Water balance component. Q out of reach =

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Surface Investigations of Groundwater

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  1. Surface Investigations of Groundwater John Walton Fall, 2010

  2. Remote sensing, example of phreatophytes

  3. Salt Cedar – Rio Grande

  4. Salt Cedar • Grows over shallow water table areas • High amount of evapotranspiration • Water balance component • Qout of reach = • Qinto reach + Groundwater inputs + Surface runoff • -evaporation – transpiration - human use • Solve water balance for groundwater input

  5. Groundwater Input to Rio Grande – Fort Quitman to Amistad Reservoir • Assume steady state system where groundwater recharge equals discharge • Take measured surface water flows and diversions • Estimate ET from Salt Cedar/Mesquite/cane bosque area • Divide groundwater input by drainage basin area to obtain large scale groundwater recharge rates • Answer: ~ 1 cm/year

  6. Thermal Infrared Mapping of Coastal-Aquifer Seeps and Associations between Seeps and Coastal Habitats

  7. Assumes fresh water in pores; 10X decrease for salt water

  8. Resistivity •  The potential difference between electrodes placed in the ground is measured. When an electric current is passed between two electrodes placed outside the measurement electrodes a potential difference is created. • Deeper penetration of the electrical field occurs as the electrodes are spaced further apart.  • Interpretation of this data can be complex in some cases

  9. Horizontal profile by resistivity

  10. Seismic wave velocity varies with material:

  11. Seismic location of water table, waves travel more rapidly in water saturated material; waves travel deeper at wider spacing

  12. Wave generation example – sledge hammer

  13. WSI = Water Seismic Index

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