Complexities of the Flow Complexities of the Flow System, System, Edwards Aquifer Edwards Aquifer Susan Hovorka, Bureau of Economic Geology with data from: Geary Schindel and Steve Johnson, Edwards Aquifer Authority J. P Nicot, Bureau of Economic Geology Steve Worthington, Worthington Associates Adrien Lindley and Thandar Phu, University of Texas at Austin
Complexities of the Flow System, Edwards Aquifer. Susan Hovorka, Bureau of Economic Geology with data from: Geary Schindel and Steve Johnson, Edwards Aquifer Authority J. P Nicot, Bureau of Economic Geology Steve Worthington, Worthington Associates - PowerPoint PPT Presentation
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Complexities of the Flow System, Complexities of the Flow System, Edwards AquiferEdwards Aquifer
Susan Hovorka, Bureau of Economic Geologywith data from:
Geary Schindel and Steve Johnson, Edwards Aquifer Authority
J. P Nicot, Bureau of Economic GeologySteve Worthington, Worthington Associates
Adrien Lindley and Thandar Phu, University of Texas at Austin
Purpose
• What is the scale, distribution , and hydrologic significance of heterogeneity in the Edwards aquifer?
• How much information can be extracted from existing data?
• Where are productive areas for future research to better answer this question?
Techniques
• Thin section petrography• Measurement of porosity and permeability core plugs from cores and
outcrops• Calibration of wireline logs using core plug data and
porosity/permeability transforms• Core examination• Fracture aperture measurement • Outcrop photograph digitization• Cave trend analysis• Calculation of permeability from specific capacity tests• Well hydrograph recession analysis• Pseudosynoptic analysis of troughs in the water level• Calcite saturation and other geochemical indicators
springflow, models must upscale transmissivity several orders of magnitude above estimated transmissivity from wells High transmissivity areas of Maclay and Land
overlain on well-test-derived permeability modelSWRI, 2002
Conduit Flow Dominates
• In wells with estimated transmissivity, matrix flow accounts for about 1% of total flow.
Mace and Hovorka, permeability from core compared topermeability calculated from specific capacity
Fractures and Caves are Obvious in Outcrop
From G. Schindel
Evolution of Karst, Confined Zone
Hovorka and Yeh
Karst features are found in the confined
aquifer
5 cm
Missing section, terra rosa,Off-scale caliper
Effects of faulting on permeability
QAa8500c
BureauofEconomic
Geology
Offset decreases cross-fault transmissivity
Fractures andbrecciation increasepermeability parallel to the fault
Caves
Fracturing focusesdevelopment of karst
Topographic Expression of Balcones Fault Zone, Austin