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