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Groundwater Resources in the Piedmont and Shenandoah Valley: A Comparison of Geologic Controls
on Groundwater Quality and Sustainability
PART I: Shenandoah ValleyEnhanced Understanding for Aquifer Health
Mark D. Kozar, USGS Washington WSC, Tacoma WA
Dick Yager, USGS New York WSC, Ithaca NY
Kurt J. McCoy, George Harlow, and Dave NelmsUSGS Virginia WSC, Richmond VA
http://www.swarpa.net/~danforth/photos/caves/wn_weddingcake.jpg
Whitings Neck Cave
CAVES OF THE EASTERN PANHANDLE
•Not that many caves–42 known caves in Jefferson County–48 known caves in Berkeley County
•Most are short and not of hydrological interest
Karst Continuum Model
3,300 mi2 300 mi2 10 mi2
Outline – Nested ModelingWhat is important for aquifer health depends on scale
Shenandoah Valley (Yager et al, 2009)
Opequon Creek(Kozar and Weary, 2009)
Leetown Science Center
(Kozar et al, 2007)
StructureShenandoah Valley Model
3,300 mi2
Yager, RM, Voss, CI, Southworth, S, 2009, Comparison of alternative representations of hydraulic-conductivity anisotropy in folded fractured-sedimentary rock: modeling groundwater flow in the Shenandoah Valley (USA): Hydrogeology Journal, v. 17, p. 1111-1131.
Shenandoah Valley Regional Conceptual
Model
(Yager et al., 2009)
Numerical RepresentationOf Regional
Scale Anisotropy
(Yager et al., 2009)
Groundwater flows along preferential
paths
Well Capture zones – Influence of Anisotropy
Meso Scale - Opequon Creek Model
Meso-Scale (300 mi2) Conceptual Model
Epikarst
Fractured Karst
Fractured Rock
Photo courtesy of Craig Wagnell (portaec.net)
Photo by Wil Orndorff
Influence of Lithology – ALL ROCKS ARE NOT ALIKE
Leetown Ground-Water Flow Model
Three layer model
Tectonic Deformation
KARST Vertical permeability
contrast
Fault Orientation
Fracture Orientations in the Leetown Area, WV
• Major fractures occur parallel to regional strike N. 20o E. and perpendicular to strike.
• Thrust faults parallel to strike and cross strike faults are especially important controls on ground-water flow.
Fractures mapped by a) Jones and Deike, 1981 and b) McCoy and others, 2005
Faults
Fold Hinges or Lithologic Contacts
Fracture-Flow
Deform
ation
Ort
hogo
nal F
ract
urin
gBed-limited permeability
Karst zones
Gradient
Leetown Surface Geophysics – AMT
Plan View
X-Sect View
Scale-Related Evolution of Conceptual Models
Primary Deposition
Heterogeneity Tectonic Deformation
3,300 mi2 300 mi2 10 mi2
Conclusions
Nested Models – Scale Dependent Controls on Flow
Basin Geometry
Orderly Preferential Flow Paths
Carbonate Heterogeneity
Not All Rocks are Alike
Fault Zone Hydrology
Important Routes to Drain The Aquifer