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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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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

  • Qout of reach =

  • Qinto reach + Groundwater inputs + Surface runoff

  • -evaporation – transpiration - human use

  • Solve water balance for groundwater input


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


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


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


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


Horizontal profile by resistivity


Seismic wave velocity varies with material:


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


Wave generation example – sledge hammer


WSI = Water Seismic Index


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