Characterization of an Internal Drainage Basin Cave Using ArcGIS

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Characterization of an Internal Drainage Basin
Cave Using ArcGIS

• Brian Cowan

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Study Area

• In the Recharge Zone of the Edwards Aquifer
  Barton Springs Segment
• Flint Ridge Cave
• City of Austin Water Quality Protection Land
• Somewhere in South Austin

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Study Area
University of Texas
Study Area
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Importance of Study Area

• Flint Ridge is one of the largest recharge
  features in the South Austin area
• Internal Drainage Basin
• Cave is only outlet for basin
• Large amount of recharge
• Discrete Flow Over-land flow
• Relatively large portion of aquifer recharge from
  internal drainage basins

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Importance of Study Area

• Home to the Cicurina cueva cave spider
• Impacts Barton Springs
• Barton Springs Salamander
• Flow
• Quality
• Impacts the Edwards Aquifer
• Pollution can travel long distances in karst
  aquifers

City of Austin
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Original Plan

• Use ArcHydro to automatically delineate basin
  area
• Basin area too small!
• 50 acres in size
• Relief of basin may also play a roll in
  difficulties

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Original Plan

• Flow accumulation in basin based on fake
  rainfall
• Again, not able to delineate basin with ArcGIS
• Theory Apply fake rainfall data to delineated
  basin area to determine total amount of
  precipitation landing in basin. By subtracting
  known values of infiltration and
  evapotranspiration at the site I could calculate
  total volume of discrete recharge

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Original Plan

• After proving that the recharge values could be
  calculated, apply actual data to the model
• NEXRAD data would be used
• Compare model output with actual measured values

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Frustration sets in
www.mediabistro.com
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Benefits of Proposed Plan

• Remotely measure discrete recharge of internal
  drainage basins (and other geological settings).
• Characterize the normal percentage infiltration
  for area of interest
• Obtain evapotranspiration and precipitation data
  for study area

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Benefits of Proposed Plan

• For an Internal Drainage Basin
• Discrete Recharge Precip - ET - Infiltration

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A New Direction

• Determine area of study site in the field
• Artificially create a basin of the same size in
  the same location
• Apply NEXRAD data to the model
• Compare with measured results to determine
  feasibility

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If Successful
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