Groundwater Resources in the
Piedmont and Shenandoah Valley:
A Comparison of Geologic Controls
on Groundwater Quality and Sustainability
PART I: Shenandoah Valley
Enhanced 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 Nelms
USGS Virginia WSC, Richmond VA
Karst Continuum Model
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
Whitings Neck Cave
http://www.swarpa.net/~danforth/photos/caves/wn_weddingcake.jpg
Outline – Nested Modeling
What is important for aquifer health depends on scale
Shenandoah Valley
(Yager et al, 2009)
3,300 mi2
Opequon Creek
(Kozar and Weary, 2009)
300 mi2
Leetown
Science Center
(Kozar et al, 2007)
10 mi2
Shenandoah
Valley Model
3,300 mi2
Structure
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. 11111131.
Shenandoah Valley
Regional Conceptual
Model
(Yager et al., 2009)
Numerical Representation
Of Regional
Scale Anisotropy
Groundwater flows
along preferential
paths
(Yager et al., 2009)
Well Capture zones – Influence of Anisotropy
Meso Scale - Opequon Creek Model
Meso-Scale (300 mi2) Conceptual Model
Photo courtesy of Craig Wagnell (portaec.net)
Epikarst
Fractured
Karst
Fractured
Rock
Photo by Wil Orndorff
Influence of Lithology – ALL ROCKS ARE NOT ALIKE
Leetown GroundWater 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
Karst zones
Fold Hinges or
Lithologic
Contacts
Deformation
Orthogonal Fracturing
Faults
Fracture-Flow
Bed-limited permeability
Leetown Surface
Geophysics – AMT
Plan View
X-Sect View
Scale-Related Evolution of Conceptual Models
Primary
Deposition
3,300 mi2
Heterogeneity
300 mi2
Tectonic
Deformation
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