Characterization of an Internal Drainage Basin Cave Using
Characterization of an Internal Drainage Basin Cave Using Arc. GIS Brian Cowan
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
Study Area University of Texas Study Area
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
Importance of Study Area • Home to the Cicurina cueva cave spider • Impacts Barton Springs – Barton Springs Salamander – Flow – Quality City of Austin • Impacts the Edwards Aquifer – Pollution can travel long distances in karst aquifers
Original Plan • Use Arc. Hydro to automatically delineate basin area – Basin area too small! – 50 acres in size • Relief of basin may also play a roll in difficulties
Original Plan • Flow accumulation in based on “fake” rainfall – Again, not able to delineate basin with Arc. GIS – 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
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
Frustration sets in… www. mediabistro. com
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…
Benefits of Proposed Plan For an Internal Drainage Basin… Discrete Recharge = Precip - ET - Infiltration
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
If Successful…
- Slides: 14