1. Characterization of an Internal Drainage Basin Cave Using ArcGIS Brian Cowan

2. 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

3. Study Area University of Texas Study Area

4. 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

5. 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

6. 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

7. 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

8. 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

9. Frustration sets in… www.mediabistro.com

10. 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…

11. Benefits of Proposed Plan For an Internal Drainage Basin… Discrete Recharge = Precip - ET - Infiltration

12. 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

13. If Successful…