U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5113

Prepared in cooperation with the Bedford County Board of Supervisors and the

Virginia Department of Environmental Quality

Hydrogeology and Simulation of Groundwater Flow in 

Fractured-Rock Aquifers of the Piedmont and Blue Ridge 

Physiographic Provinces, Bedford County, Virginia
Front cover: Small waterfall on North Otter River in Bedford County, Virginia. Photograph by Don Hayes, U.S. Geological Survey.
Hydrogeology and Simulation of 

Groundwater Flow in Fractured-Rock 

Aquifers of the Piedmont and Blue Ridge 

Physiographic Provinces, Bedford County, 

Virginia

By Kurt J. McCoy, Bradley A. White, Richard M. Yager, and George E. Harlow, Jr.

Prepared in cooperation with the Bedford County Board of Supervisors and the 

Virginia Department of Environmental Quality

Scientific Investigations Report 2015–5113

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation:

McCoy, K.J., White, B.A., Yager, R.M., and Harlow, G.E., Jr., 2015, Hydrogeology and simulation of groundwater 

flow in fractured-rock aquifers of the Piedmont and Blue Ridge Physiographic Provinces, Bedford County, Virginia: 

U.S. Geological Survey Scientific Investigations Report 2015–5113, 54 p., http://dx.doi.org/10.3133/sir20155113.

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

ISBN 978-1-4113-3965-1
iii

Contents

Acknowledgments......................................................................................................................................viii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................2

Previous Investigations........................................................................................................................4

Hydrologic Data Collection ................................................................................................................5

Well Installation ...........................................................................................................................5

Groundwater Data .......................................................................................................................9

Borehole Logging.........................................................................................................................9

Well Construction Report Compilation.....................................................................................9

Streamflow Measurements ......................................................................................................9

Hydrogeology of Piedmont and Blue Ridge Aquifers ............................................................................10

Hydrogeologic Units...........................................................................................................................10

Cambro-Ordovician Metasedimentary Rocks.......................................................................14

Proterozoic Basement Crystalline Rocks ..............................................................................18

Late Proterozoic-Cambrian Cover Crystalline Rocks...........................................................18

Conceptual Model of Groundwater Flow........................................................................................19

Groundwater Response to Precipitation ........................................................................................23

Water Budget ......................................................................................................................................26

Inflows to Aquifer ......................................................................................................................26

Precipitation ......................................................................................................................26

Estimates of Recharge from Streamflow...............................................................................29

Effluent from Septic Systems..........................................................................................34

Outflows from Aquifer...............................................................................................................34

Water Use ..........................................................................................................................34

Evapotranspiration ...........................................................................................................34

Discharge to Surface Waters and Subsurface Outflow.............................................34

Simulation of Groundwater Flow ..............................................................................................................35

Model Design.......................................................................................................................................36

Boundary Conditions.................................................................................................................37

Hydraulic Properties .................................................................................................................39

Model Calibration................................................................................................................................41

Observations...............................................................................................................................41

Model Fit......................................................................................................................................41

Parameters..................................................................................................................................42

Model Application...............................................................................................................................42

Model Limitations ...............................................................................................................................42

Summary and Conclusions.........................................................................................................................45

References Cited..........................................................................................................................................46

Appendix 1. Borehole Geophysical Logs .................................................................................................49
iv

Figures

1. Map showing locations of stream-gaging and climate stations within the study area, 

Bedford County, Virginia..............................................................................................................3

2. Graph showing mean monthly precipitation at National Oceanic and Atmospheric 

Administration climate station Bedford 4 NW 440561, 1981–2010........................................4

3. Map showing locations of wells within the study area, Bedford County, Virginia............6

4. Diagram showing major hydrogeologic units, subunits, and geologic map units in 

Bedford County, Virginia............................................................................................................11

5. Map showing major hydrogeologic units and geologic map units in 

Bedford County, Virginia............................................................................................................12

6. Rose diagrams showing all linear features from selected wells in 

Bedford County, Virginia............................................................................................................13

7. Boxplots showing well characteristics by hydrogeologic unit in 

Bedford County, Virginia............................................................................................................14

8. Generalized conceptual model of the flow system in Blue Ridge fracture rock 

aquifers in Bedford County, Virginia........................................................................................20

9. Components of the groundwater-flow system and relative storage volumes in the 

regolith and fractured-rock aquifers of the Piedmont Physiographic Province, 

Bedford County, Virginia............................................................................................................21

10. Map showing groundwater levels in Bedford County, Virginia, December 2010 ............22

11. Graph showing water-level data from continuous monitoring wells and daily

precipitation from National Oceanic and Atmposheric Administration site 440561

in Bedford County, Virginia, 2009–2013 water years.............................................................24

12. Map showing average annual precipitation across Bedford County, Virginia,

based on parameter-elevation regressions on independent slopes model .....................27

13. Graph showing relation of discharge measured at partial-record station 02011600

Elk Creek at Route 668 near Goode, Virginia, with concurrent mean daily discharge

at long-term stream-gaging station 02061500 Big Otter River near

Evington, Virginia ........................................................................................................................30

14. Map showing effective recharge as base flow calculated at partial-record streamgaging stations in Bedford County, Virginia, 2006–2009.......................................................31

15. Graph showing relation of discharge measured at partial-record stations in the

Goose Creek Basin to concurrent mean daily discharge at long-term

stream-gaging station 02059500 Goose Creek near Huddleston, Virginia ........................32

16. Graph showing relation of discharge measured at partial-record stations in the

Big Otter River Basin to concurrent mean daily discharge at long-term

stream-gaging station 02061500 Big Otter River near Evington, Virginia ..........................33

17. Pie charts showing water-use estimates for Bedford County, Virginia,

1985–2005 .....................................................................................................................................35

18. Map showing model domain, boundary conditions, and hydrogeologic units

delineated in the Bedford County, Virginia, groundwater model.......................................36

19. Graph of section A-A’ showing thickness of model layers beneath areas with high 

relief, Bedford County, Virginia.................................................................................................38

20. Box plot showing distribution of hydraulic conductivity values computed from

specific capacity of crystalline bedrock wells in Bedford County, Virginia .....................40

21. Three-dimensional block diagram showing model layers and hydraulic

conductivity zones within model domain, Bedford County, Virginia..................................40
v

22. Graph showing residual plots for heads in Bedford County groundwater-flow

model: relation between simulated and observed values and relation between

simulated values and weighted residuals ..............................................................................41

23. Graph showing residual plot for flows in Bedford County groundwater-flow

model showing relation between simulated and measured values...................................41

24. Map showing distribution of annual recharge for steady-state conditions in

the Bedford County groundwater-flow model .......................................................................43

25. Map showing water table simulated for steady-state conditions by the

Bedford County groundwater-flow model..............................................................................44

26. Pie chart showing proportion of groundwater flow through major basins, 

Bedford County, Virginia............................................................................................................45

Tables

1. NOAA climate stations in Bedford County, Virginia................................................................2

2. Site information for monitoring wells in Bedford County, Virginia .......................................7

3. Streamflow measurement gages in Bedford County, Virginia............................................10

4. Descriptive statistics of hydrogeologic parameters by rock type associated with a 

selection of drilled water wells in Bedford County, Virginia ...............................................16

5. Water-level measurements from selected wells in Bedford County, Virginia..................25

6. Hydrologic budget components for select localities and basins in

Bedford County, Virginia............................................................................................................28

7. Hydraulic properties estimated and specified in Bedford County

groundwater-flow model ...........................................................................................................38

8. Simulated water budget for Bedford County groundwater-flow model............................45
vi

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

gallon (gal) 3.785 cubic decimeter (dm3) 

million gallons (Mgal) 3,785 cubic meter (m3)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Pressure

atmosphere, standard (atm) 101.3 kilopascal (kPa)

bar 100 kilopascal (kPa) 

pound per square inch (lb/in2) 6.895 kilopascal (kPa) 

Specific capacity

gallon per minute per foot 

[(gal/min)/ft)]

 0.2070 liter per second per meter 

[(L/s)/m]

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Transmissivity*

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d) 
vii

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: 

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: 

°C=(°F–32)/1.8

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

Datum

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
viii

Acknowledgments

The authors gratefully acknowledge the many individuals, establishments, and authorities in 

the county that permitted access to their wells to measure water levels during this study. The 

authors also thank the property owners that granted access to their property for collection of 

streamflow data. Special thanks are given to Frank J. Rogers, Deputy County Administrator of 

Bedford County, for his efforts with project logistics and support. Todd Fowler of the Bedford 

County Health Department provided well completion information and guidance in regards to the 

distribution of well yields.
Abstract

An annual groundwater budget was computed as part 

of a hydrogeologic characterization and monitoring effort 

of fractured-rock aquifers in Bedford County, Virginia, a 

growing 764-square-mile (mi2) rural area between the cities 

of Roanoke and Lynchburg, Virginia. Data collection in 

Bedford County began in the 1930s when continuous stream 

gages were installed on Goose Creek and Big Otter River, 

the two major tributaries of the Roanoke River within the 

county. Between 2006 and 2014, an additional 2 stream 

gages, 3 groundwater monitoring wells, and 12 partial-record 

stream gages were operated. Hydrograph separation methods 

were used to compute base-flow recharge rates from the 

continuous data collected from the continuous stream gages. 

Mean annual base-flow recharge ranged from 8.3 inches per 

year (in/yr) for the period 1931–2012 at Goose Creek near 

Huddleston (drainage area 188 mi2) to 9.3 in/yr for the period 

1938–2012 at Big Otter River near Evington (drainage area 

315 mi2). Mean annual base-flow recharge was estimated 

to be 6.5 in/yr for the period 2007–2012 at Goose Creek 

at Route 747 near Bunker Hill (drainage area 125 mi2) and 

8.9 in/yr for the period 2007–2012 at Big Otter River at 

Route 221 near Bedford (drainage area 114 mi2). Base-flow 

recharge computed from the partial-record data ranged from 

5.0 in/yr in the headwaters of Goose Creek to 10.5 in/yr in the 

headwaters of Big Otter River. 

A steady-state groundwater-flow simulation for Bedford 

County was developed to test the conceptual understanding of 

flow in the fractured-rock aquifers and to compute a groundwater budget for the four major drainages: James River, 

Smith Mountain and Leesville Lakes, Goose Creek, and Big 

Otter River. Model results indicate that groundwater levels 

mimic topography and that minimal differences in aquifer 

properties exist between the Proterozoic basement crystalline 

rocks and Late Proterozoic-Cambrian cover crystalline 

rocks. The Big Otter River receives 40.8 percent of the total 

daily groundwater outflow from fractured-rock aquifers in 

Hydrogeology and Simulation of Groundwater Flow in 

Fractured-Rock Aquifers of the Piedmont and Blue Ridge 

Physiographic Provinces, Bedford County, Virginia

By Kurt J. McCoy,1 Bradley A. White,2 Richard M. Yager,1 and George E. Harlow, Jr.1

Bedford County; Goose Creek receives 25.8 percent, the 

James River receives 18.2 percent, and Smith Mountain and 

Leesville Lakes receive 15.2 percent. The remaining percentage of outflow is attributed to pumping from the aquifer 

(consumptive use).

Introduction

Groundwater resources in Bedford County, Virginia 

(Va.), are increasingly relied upon to supply water to 

local communities, industry, and individual residences. 

Groundwater withdrawals from fractured-rock aquifers are 

the primary source of water for most rural households and 

the majority of the county’s residents. Since 2003, more than 

2,000 new wells have been permitted and drilled in Bedford 

County to meet the needs of individual residences (T.R. 

Fowler, Bedford County Health Department, oral commun., 

2012). The area has a growing rural population which has 

expanded from approximately 38,300 residents in 1985 to 

68,700 residents in 2010 (Maupin and others, 2014). To 

meet future water needs of individual residences, additional 

domestic development of these bedrock aquifers is likely. Previous hydrologic work in rural areas of the central Piedmont 

and Blue Ridge Physiographic Provinces of Virginia is 

limited, and basic knowledge of aquifer systems in this area 

is needed to support the expanding economy and growing 

population of Bedford County. 

From 2006 to 2014, the U.S. Geological Survey (USGS), 

in cooperation with the Bedford County Board of Supervisors 

and the Virginia Department of Environmental Quality 

(DEQ), collected hydrologic data in Bedford County to assess 

county-wide groundwater conditions and provide technical 

data and a scientific foundation that could be used as a basis 

for management and future planning of Bedford County 

water resources. A conceptual model of groundwater flow in 

Bedford County was developed based on (1) previous studies 

in the Piedmont and Blue Ridge fractured-rock aquifers, 

(2) compilation of existing data, and (3) results of new 

hydrologic data collected from wells and streams. Base-flow 

yields, general well construction information, and borehole 

1

U.S. Geological Survey.

2

Virginia Department of Environmental Quality.
2 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

logs were summarized to support conceptualization of 

geologic features controlling the occurrence of groundwater 

in the Piedmont and Blue Ridge fractured-rock aquifers of 

Bedford County. A numerical model simulating groundwater 

flow in the aquifers was constructed as a component of this 

investigation to evaluate the conceptual model and estimate 

steady-state groundwater budgets for areas within Bedford 

County that drain to the Big Otter River, Goose Creek, the 

James River, and Smith Mountain and Leesville Lakes. 

Purpose and Scope

This report provides a description of the hydrogeology 

and groundwater availability of the fractured-rock aquifer 

systems in Bedford County, Va. The primary purpose of the 

data collection and groundwater-flow simulation conducted as 

part of this study in Bedford County is to provide hydrogeologic information that can be used to guide the development 

and management of these important water resources in context 

of long-term aquifer inflows and outflows. The scope of this 

study included (1) the drilling of three new bedrock monitoring wells; (2) establishment of a continuous and biannual 

groundwater-level network; (3) continuous and partial-record 

measurement of stream discharge in the Big Otter River and 

Goose Creek Basins; and (4) borehole geophysical logging of 

five wells in Bedford County. Well completion reports from 

local and State health departments and archival State and 

Federal records were synthesized to document the variability 

in well construction and yields among hydrogeologic units. 

This report also documents the development of a 

numerical model to synthesize all currently available data 

and evaluate the conceptualization of groundwater flow in 

the fractured-rock aquifers of Bedford County at a scale of 

hundreds of square miles. Extrapolation of model results to 

smaller-scale domains would require more hydrogeologic 

detail than is currently (2015) available. 

Description of Study Area

Bedford County encompasses 764 square miles (mi2) in 

Virginia’s Piedmont and Blue Ridge Physiographic Provinces 

(fig. 1), two physiographic regions that extend over much of 

the central portion of Virginia. The two physiographic regions 

are defined by large topographic differences. The Piedmont 

is characterized by rolling and hilly terrain while the Blue 

Ridge has much steeper slopes. The Piedmont in Bedford 

County ranges in elevation from 800 feet (ft) to 2,100 ft above 

sea level, while elevations in the Blue Ridge are as much as 

4,000 ft. The county is bounded by the Blue Ridge Mountains 

on the west, the James River on the northeast, Smith Mountain 

and Leesville Lakes on the south, and Campbell County on the 

east. The county contains the headwaters of Goose Creek and 

Big Otter River, which are major tributaries to the Roanoke 

River. 

Bedford County has a mild climate with an average 

annual precipitation of 45.6 inches per year (in/yr) and a 

mean maximum daily temperature of 67.4 degrees Fahrenheit 

(PRISM Climate Group, Oregon State University, 2014). 

Climate station data for Bedford County were obtained 

from the National Oceanic and Atmospheric Administration 

(NOAA) National Climate Data Center (National Oceanic and 

Atmospheric Administration, 2014). Available precipitation 

data within or near Bedford County for which periods of data 

were available for the current normal climatological period 

1981–2010 included five sites (table 1; fig. 1). Two of the 

sites (Holcomb Rock and Lynchburg #2) are within the James 

River Basin, two of the sites (Bedford 4 NW and Bedford) 

are within the Big Otter River Basin, and the remaining site 

(Huddleston 4 SW) is within the Goose Creek Basin. 

Mean annual precipitation for the climatological period 

1981–2010 decreases in an easterly direction, ranging from 

46.5 in/yr (Holcomb Rock) to 41.5 in/yr (Lynchburg #2) 

(fig. 1; table 1). Mean monthly precipitation amounts among 

Table 1. NOAA climate stations in Bedford County, Virginia.

[Site locations shown in figure 1. Abbreviations: ft, feet above National Geodetic Vertical Datum of 1929; NOAA, National Oceanic and Atmospheric Administration; in/yr, inches per year; NAD 83, North American Datum of 1983]

 Station 

identification 

number

Station name

Latitude 

(decimal 

degrees)

Longitude 

(decimal 

degrees)

Datum Elevation 

(ft)

Operating 

agency

Period of record 

(calendar years)1

NOAA climatological 

period 1981–2010 

mean annual 

precipitation 

(in/yr)

440561 Bedford 4 NW 37.380 –79.561 NAD 83 1,220 NOAA 1973–2014 44.2

440551 Bedford 37.348 –79.523 NAD 83 975 NOAA 1948–2006 45.1

444039 Holcomb Rock 37.544 –79.403 NAD 83 620 NOAA 1960–2014 46.5

444148 Huddleston 4 SW 37.126 –79.526 NAD 83 1,045 NOAA 1950–2014 42.5

445117 Lynchburg #2 37.385 –79.229 NAD 83 740 NOAA 1997–2014 41.5

1

Discontinuous record and data gaps may exist within ranges of years.
Introduction 3

221

460

Town of 

Bedford

Terrapin

RO A NO

Elk Creek

JAMES

Back

Creek

ROANO

*

FLAT

Creek

RIVER

SMITH MOUNTAIN 

LAKE Leesville 

Lake

02061320

02061160

02060860

02060800

02060695

02060692 02060592

02059490

02059459

02059452

02059450 02059420

02061500

02061000

02059485

02059500 #

02059500 #

79°30' 02059490 V

79°15'

37°30'

37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Continuous stream-gaging station

Partial-record stream-gaging station

440561 NOAA climate station

440561

440551

444039

444148

445117

CAMPBELL COUNTY

FRANKLIN COUNTY

ROANOAKE 

COUNTY

BOTETOURT COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

FEET ABOVE NGVD 29

1,282

98

Roanoke

River

Rockcastle Creek

Mill

Creek

Creek

Creek

Creek

Creek

Falling

Island

Nininger

Goose

Creek

Creek

Enochs

Falling

Creek

Big

Little

Otter

Otter

River

River

Bore Auger

221

Day

Creek

Creek

Buffalo

Run

Lick

Run

Roaring

Creek

Ivy

501

Creek

Stony

Creek Johnson

BEDFORD COUNTY

Matts

Creek

Hunting Creek

VV

V

V

V #

V

V

V

V

V

V

V

#

#

#

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

PIEDMONT

VALLEY

AND 

RIDGE

COASTAL PLAIN

APPALACHIAN

PLATEAUS

BLUE RIDGE

Location of Bedford County and physiographic provinces in Virginia

43

682

695 644

122

643

663

622

811

43

24

619

746

608

122

626

634

Figure 1. Locations of stream-gaging and climate stations within the study area, Bedford County, Virginia.
4 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Previous Investigations

During the mid- to late 1990s, the USGS Regional 

Aquifer System Analysis (RASA) Program used discharge 

data from surface-water basins to calculate base-flow yields 

and effective recharge for the Blue Ridge and Piedmont 

Physiographic Provinces (Rutledge and Mesko, 1996; Nelms 

and others, 1997; Swain and others, 2004). Rutledge and 

Mesko (1996) found a positive correlation between rates of 

recharge and base flow, or the water-yielding capacity of 

rocks in the Piedmont. Base-flow yields in the Piedmont, 

however, are lower in comparison to yields in the adjacent 

Valley and Ridge and Blue Ridge Physiographic Provinces 

(Nelms and others, 1997). By using data from the stream 

gage at Goose Creek near Huddleston (02059500, fig. 1) in 

Bedford County, mean effective recharge rates calculated by 

hydrograph separation techniques ranged from 10.45 in/yr 

during 1961–1990 (Rutledge and Mesko, 1996) to 8.40 in/yr 

during 1956–1984 (Nelms and others, 1997). For Big Otter 

River near Bedford (02061000, fig. 1), the mean effective 

recharge rate was 11.48 in/yr for the period 1945–1960 

(Nelms and others, 1997). 

Sanford and others (2012) developed a series of regression equations for the entire State of Virginia to quantify 

components of the water budget on a watershed and locality 

basis, including the town of Bedford and Bedford County. 

0

1

2

3

4

5

6

7

Percentage of mean

annual precipitation

Mean

monthly precipitation

7.5

6.5

9.1 8.8 8.5 8.6

7.8

9.1

7.5 7.8

8.3

10.6

Bedford 4 NW 440561 mean annual precipitation = 44.2 in.

Mean monthly precipitation, in inches

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Figure 2. Mean monthly precipitation at National Oceanic and Atmospheric Administration climate station 

Bedford 4 NW 440561, 1981–2010.

all five climate stations are similar; the largest differences 

generally occur between the months of April and July. In 

the center of the county, the Bedford 4 NW station indicates 

that monthly precipitation amounts peak mid-summer with 

45 percent of annual precipitation falling during May through 

September; generally, precipitation amounts vary only slightly 

from month to month (fig. 2). Mean monthly precipitation is 

lowest from November through February.

Groundwater recharge calculated by regression methods was 

12.3 in/yr and 13.7 in/yr, respectively, for the town of Bedford 

and Bedford County. Their results for Bedford County indicate 

that 64.2 percent of average annual precipitation is lost to 

evapotranspiration processes or evaporation plus uptake 

by vegetation. Direct runoff to streams accounted for only 

8.3 percent of total annual precipitation. 

Heller (2008) summarized yields from public-supply 

wells in Virginia based on geologic province. Data indicated 

that public-supply wells from the Blue Ridge and Piedmont 

Physiographic Provinces were less likely to be high yielding 

(less than100 gallons per minute [gal/min]) than wells in 

other physiographic provinces in the State. Powell and Abe 

(1985) identified the major factors affecting well yields in the 

Piedmont of Virginia as topographic setting and the occurrence 

of clastic rock units; White (2012) later found topographic 

setting to also influence rates of recharge. In summarizing 

studies from the Piedmont in North Carolina and Maryland, 

neither Daniel and Payne (1990) nor Powell and Abe (1985) 

identified differences in the water-producing capacity of the 

various crystalline rock units in the Piedmont. 

The occurrence of groundwater in crystalline rocks 

depends on the location and density of permeable fractures, 

some of which may be localized along regional structures 

(Keane and Gilstrap, 2011). Fracture-related heterogeneities 

in the Blue Ridge Physiographic Province are ubiquitous at a 
Introduction 5

local scale (White, 2012) and can yield significant quantities 

of water if associated with faulting (Seaton and Burbey, 2005; 

White and Burbey, 2007). Fault zones have been observed to 

have permeabilities up to 6 orders of magnitude higher than 

the surrounding crystalline rock mass (Seaton and Burbey, 

2005) and strongly control recharge processes in the Blue 

Ridge Physiographic Province (White and Burbey, 2007). 

Lithology and structure are also important controls on 

groundwater yields in fractured rocks of the Piedmont Physiographic Province near Atlanta, Georgia (Chapman and others, 

1998; Williams and others, 2005). Chapman and others (2011) 

studied a developed area in the Piedmont of North Carolina 

where annual water-level fluctuations exceeded 200 ft. Prior 

to development, water levels fluctuated only 15 to 50 ft. They 

concluded that the occurrence of intermittent dry wells during 

a period of drought correlated with geologic structure and a 

temporary loss of groundwater in storage potentially related to 

increased pumpage at community wells.

Much of the conceptual understanding of groundwater 

storage in the regolith, or weathered overburden, overlying 

fractured rocks of the Piedmont was developed by Heath 

(1984) and later expanded by Daniel and Harned (1998). 

White and Burbey (2007) and Seaton and Burbey (2005) 

characterize regolith of the Blue Ridge Physiographic 

Province as having significant geologic variability with 

confined conditions often found along a thin transition zone 

at the top of bedrock. The interaction of shallow water stored 

in the regolith with deeper fractures varies depending on 

the hydrologic connection from recharge to discharge zones 

(White and Burbey, 2007). 

Hydrologic Data Collection 

Various hydrologic data from Bedford County have been 

collected by the USGS and the DEQ since 1930. The longest 

period of record in the study area is at continuous streamgaging station 02059500, Goose Creek near Huddleston, 

Va. Between 2006 and 2009, 12 partial-record streamflow 

gaging stations, 3 continuous groundwater-level observation 

wells, and 2 additional continuous stream-gaging stations 

were instrumented to record hydrologic data. Geologic data 

collected from 5 wells in Bedford County and more than 2,000 

well records are presented to investigate the geohydrology in 

Bedford County. 

Well Installation

Between May 13 and 15, 2008, monitoring wells were 

drilled at three county-owned locations for the purpose of 

monitoring water levels in an assumed recharge area of 

western Bedford County (site numbers 33G 1 SOW 224, 33G 

2 SOW 225, and 35H 1 SOW 226; fig. 3; table 2). All three 

wells were drilled as 10-inch (in.)-diameter boreholes to the 

depth of competent bedrock where a 6.625-in. inside-diameter 

black steel casing was seated, and the annulus space exterior 

to the casing was backfilled with a bentonite slurry to land 

surface. Below the casing interval, wells were completed as 

open boreholes drilled to various field-determined depths at 

which a desired yield was obtained from bedrock aquifers. 

Well cuttings were collected from each drill hole. Detailed 

lithologic descriptions were made at the site by DEQ personnel using a hand lens and a Munsell color chart. 

On October 16, 2011, well 35H 1 SOW 226 near 

Otterville, Va., was converted to a dual-zone groundwater 

monitoring well for independently monitoring hydraulic heads 

associated with transmissive fractures at 37 and 168 ft below 

land-surface datum. Interior 2-in. PVC monitoring wells were 

nested inside the open bedrock wellbore in a deep and shallow 

configuration with 10-ft sections of 0.2-in. slotted screen open 

to the transmissive fractures. Hydraulic heads were isolated by 

surrounding the screened intervals with #3 sand filter pack and 

placing bentonite pellets in lifts between the screened intervals 

of the deep and shallow 2-in. wells. Well 35H 1 SOW 226 was 

then discontinued, and the deep and shallow nested wells were 

assigned well numbers 35H 3 SOW 226A and 35H 4 SOW 

226B, respectively. 
6 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

221

460

Town of 

Bedford

Matts

Creek

Terrapin

RO A NO

Elk Creek

Hunting

Creek JAMES

Back

Creek

ROANO

*

FLAT

Creek

RIVER

SMITH MOUNTAIN 

LAKE Leesville 

Lake

#

#

79°30'

79°15'

37°30'

37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Well location and site number CAMPBELL COUNTY

FRANKLIN COUNTY

BEDFORD COUNTY

ROANOAKE 

COUNTY

BOTETOURT COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

Roanoke

River

Rockcastle Creek

Mill

Creek

Creek

Creek

Creek

Falling

Island

Nininger

Goose

Creek

Enochs

Creek

Falling

Creek

Big

Little

Otter

Otter

River

River

Bore Auger

221

Day

Creek

Creek

Buffalo

Run

Lick

Run

Roaring

Creek

Ivy

501

Creek

Stony

Creek Johnson

35J 5 36J 7

35J 4

35H 2 34H 6

33G 3

34G 3

34G 2

35G 4

36G 2

36H 1

36H 3

36H 2

36G 3

34H 4

34H 5

34H 7

34H 8

34H 9

34H 10

34H 11

35H 1 SOW 226

35H 3 SOW 226A

35H 4 SOW226B

34E 3

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

43

682

695

644

643

122

663

622

811

24 43

619

746

608

634

122

626

Creek

34F 1 34F 2

35G 2 35G 1

36G 1

36G 5

35F 1

35F 2

36G 4

Creek

34E 3

33F 2

34E 2 34E 1

33G 5

33G 7

33G 6

33G 4

33F 6

33F 3

33F 5 33F 4

32G 12

33G 2 SOW 225

33G 1 SOW 224

36G 2

PIEDMONT

VALLEY

AND 

RIDGE

COASTAL PLAIN

APPALACHIAN

PLATEAUS

BLUE RIDGE

Location of Bedford County and physiographic provinces in Virginia

Figure 3. Locations of wells within the study area, Bedford County, Virginia.
Introduction 7

Table 2. Site information for monitoring wells in Bedford County, Virginia.

[Site locations shown in figure 3. Abbreviations: USGS, U.S. Geological Survey; DDMMSS, degrees, minutes and seconds; Elev, elevation above National 

Geodetic Vertical Datum of 1929; ft, feet; ft-blsd, feet below land-surface datum; --, no data reported]

Site number USGS station 

number

Latitude 

(DDMMSS)

Longitude 

(DDMMSS)

Elev

(ft)

Well 

depth 

(ft-blsd)

Casing 

length 

(ft)

Screened 

interval 

(ft-blsd)

Water 

level data 

type 

Hydrogeologic unit

1

33G 1 SOW 224 372224079423601 372224 794236 930 101 51 -- hourly Cambro-Ordovician 

metasedimentary rocks

1

33G 2 SOW 225 372150079422301 372150 794223 1,070 201 95 -- hourly Proterozoic basement 

crystalline rocks

1, 2 35H 1 SOW 226 372543079295401 372543 792954 940 181 38 -- hourly Proterozoic basement 

crystalline rocks

35H 3 SOW 226A 372543079295402 372543 792954 940 181 -- 162–172 hourly Proterozoic basement 

crystalline rocks

35H 4 SOW 226B 372543079295403 372543 792954 940 50 -- 30–40 hourly Proterozoic basement 

crystalline rocks

32G 12 371621079482801 371621 794828 1,053 -- -- -- biannual Proterozoic basement 

crystalline rocks

33F 2 371019079375301 371019 793753 977 420 70 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

33F 3 371136079431901 371137 794319 823 -- -- -- biannual Proterozoic basement 

crystalline rocks

33F 4 371138079431601 371138 794316 882 385 60 -- biannual Proterozoic basement 

crystalline rocks

33F 5 371139079432001 371139 794320 844 445 31 -- biannual Proterozoic basement 

crystalline rocks

33G 3 372106079374501 372106 793745 946 305 60 -- biannual Proterozoic basement 

crystalline rocks

33G 4 371538079435501 371538 794355 997 246 32 -- biannual Proterozoic basement 

crystalline rocks

33G 5 371508079431001 371508 794310 1,009 260 78 -- biannual Proterozoic basement 

crystalline rocks

33G 6 371505079431301 371505 794313 985 280 42 -- biannual Proterozoic basement 

crystalline rocks

1 33G 7 371503079431701 371503 794317 982 300 55 -- biannual Proterozoic basement 

crystalline rocks

1 34E 1 370636079370601 370636 793706 940 350 85 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

34E 2 370645079341501 370645 793415 1,011 160 110 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

34E 3 370522079352601 370522 793526 932 -- -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

33F 6 371252079434501 371252 794345 998 700 55 -- biannual Proterozoic basement 

crystalline rocks

34F 1 371330079333001 371330 793330 911 254 -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

34F 2 371237079321901 371237 793219 923 -- -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

34G 2 371634079333501 371634 793335 1,002 -- -- -- biannual Proterozoic basement 

crystalline rocks

34G 3 372100079345901 372100 793459 955 -- -- -- biannual Proterozoic basement 

crystalline rocks

34H 4 372256079303001 372256 793030 1,055 -- -- -- biannual Proterozoic basement 

crystalline rocks

34H 5 372531079343701 372531 793437 1,319 181 60 -- biannual Proterozoic basement 

crystalline rocks
8 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Table 2. Site information for monitoring wells in Bedford County, Virginia.—Continued

[Site locations shown in figure 3. Abbreviations: USGS, U.S. Geological Survey; DDMMSS, degrees, minutes and seconds; Elev, elevation above National 

Geodetic Vertical Datum of 1929; ft, feet; ft-blsd, feet below land-surface datum; --, no data reported]

Site number USGS station 

number

Latitude 

(DDMMSS)

Longitude 

(DDMMSS)

Elev

(ft)

Well 

depth 

(ft-blsd)

Casing 

length 

(ft)

Screened 

interval 

(ft-blsd)

Water 

level data 

type 

Hydrogeologic unit

34H 6 372514079320801 372514 793208 1,006 450 21 -- biannual Proterozoic basement 

crystalline rocks

34H 7 372323079331301 372323 793313 853 450 -- -- biannual Proterozoic basement 

crystalline rocks

34H 8 372324079331701 372324 793317 854 413 -- -- biannual Proterozoic basement 

crystalline rocks

34H 9 372326079332001 372326 793320 857 500 -- -- biannual Proterozoic basement 

crystalline rocks

34H 10 372329079331901 372329 793319 861 450 -- -- biannual Proterozoic basement 

crystalline rocks

34H 11 372332079331801 372332 793318 865 500 -- -- biannual Proterozoic basement 

crystalline rocks

35F 1 371337079230701 371337 792307 858 305 65 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

35F 2 370929079284801 370929 792848 705 320 100 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

35G 1 371511079284901 371511 792849 874 -- -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

35G 2 371508079285501 371508 792855 881 240 40 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

35G 3 372150079263101 372150 792631 910 -- -- -- biannual Proterozoic basement 

crystalline rocks

35G 4 372102079292801 372102 792928 926 -- -- -- biannual Proterozoic basement 

crystalline rocks

35H 2 372539079285901 372539 792859 922 206 90 -- biannual Proterozoic basement 

crystalline rocks

35J 4 373108079233301 373108 792333 889 305 105 -- biannual Proterozoic basement 

crystalline rocks

35J 5 373138079250801 373138 792508 1,056 -- -- -- biannual Proterozoic basement 

crystalline rocks

36G 1 371819079180501 371819 791805 871 296 -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

36G 2 372214079185501 372214 791855 811 175 67 -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

36G 3 372143079222501 372143 792225 852 245 52 -- biannual Proterozoic basement 

crystalline rocks

36G 4 371625079202301 371625 792023 816 -- -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

36G 5 371627079202501 371627 792025 845 -- -- -- biannual Late Proterozoic-Cambrian 

cover crystalline rocks

36H 1 372246079220901 372246 792209 892 -- -- -- biannual Proterozoic basement 

crystalline rocks

36H 2 372244079210401 372244 792104 900 305 53 -- biannual Proterozoic basement 

crystalline rocks

36H 3 372508079221401 372508 792214 1,013 -- -- -- biannual Proterozoic basement 

crystalline rocks

36J 7 373151079213001 373151 792130 726 -- -- -- biannual Proterozoic basement 

crystalline rocks

1

 Denotes well with borehole geophysical log.

2

 Well later completed as a multiple-zone monitoring well.
Introduction 9

Groundwater Data

Pressure transducers with dataloggers were installed by 

the USGS in wells 33G 1 SOW 224 and 33G 2 SOW 225 

and by the DEQ in well 35H 1 SOW 226, and subsequently 

installed by the DEQ in wells 35H 3 SOW 226A and 35H 4 

SOW 226B to monitor and record water levels continuously. 

Water-level data were uploaded automatically via real-time 

satellite platforms to the USGS National Water Information 

System (NWIS, http://waterdata.usgs.gov/nwis) and field 

verified with manual tapedowns every 6 to 8 weeks. 

Synoptic surveys of water levels in 47 wells (table 2; 

fig. 3) distributed across Bedford County were conducted 

during 1-week periods in December 2010 and April 2011. 

Water levels were measured manually with a steel tape to the 

nearest one-hundredth of a foot. An electric tape was substituted for the steel tape in wells where the depth to water could 

not be successfully determined with the steel tape, typically 

because of moisture inside the well casing. At each visit, two 

water-level measurements were made, at least 5 minutes apart, 

to detect any short-term water-level fluctuations attributed 

to recent pumpage. The intent of the survey was to evaluate 

the seasonal water-table fluctuations across the county that 

coincide with periods of water-level lows in early winter and 

water-level highs in early spring. The water-level data were 

used to construct a water-level contour map for the county. 

Available well information was inventoried from well owner 

or local health department records. 

Borehole Logging

Borehole geophysical logging of the three wells 

constructed during this study, as well as two additional wells 

(table 2), included caliper; ambient and pumping fluid resistivity and temperature; ambient and pumping electromagnetic 

flow; multiparameter logs (gamma, formation resistivity); and 

acoustic televiewer (ATV) and borehole video. ATV, borehole 

video, and caliper logs were collected to characterize the locations and orientation of subsurface features in the fractured 

bedrock aquifers. ATV logging produces a high-resolution, 

magnetically oriented, digital image that was used to delineate 

and measure orientations of fractures at depth that intersect 

the borehole. When used in conjunction with other logs, data 

from the caliper logs are diagnostic in pinpointing locations 

of open and transmissive fractures. Ambient and pumping 

electromagnetic (EM) flow and fluid resistivity and temperature logs were run to ascertain the number and approximate 

position of transmissive fractures for four of the five wells in 

the study area. Gamma and formation resistivity logs were 

collected from all wells for evaluation of changes in rock type 

and formation competency adjacent to the wellbore. 

Well Construction Report Compilation

Digital water-well records were compiled from the 

Virginia Department of Health Virginia Environmental 

Information System (VENIS), the Virginia Department of 

Health Safe Drinking Water Information System (SDWIS), the 

USGS Groundwater Site Inventory (GWSI), the DEQ Virginia 

Water Use Data System (VWUDS), and the U.S. Environmental Protection Agency (EPA) Storage and Retrieval (STORET) 

database. The location accuracy and completeness of the 

water-well data vary within and among databases. Coordinate 

information for SDWIS public water supply wells is typically 

of Global Positioning System (GPS) or Differential Global 

Positioning System (DGPS ) quality, and location data for 

most of the wells originating in the GWSI and STORET 

databases were determined from locations using 7.5-minute 

quadrangles. Virginia Department of Health well data were 

located by assigning the coordinates for the tax parcel centroid 

associated with the well because original coordinate data were 

not given. A total of 2,140 well records were compiled and 

stored in a geographic information system (GIS) shapefile for 

geospatial analysis. 

Streamflow Measurements 

Streamflow was measured with continuous data recorders 

every 15 minutes at three gaging locations in Bedford County 

and one gaging location in Campbell County within the 

Roanoke River Basin (fig. 1; table 3). Two pre-existing stream 

gages—one on Goose Creek near Huddleston, Va. (02059500) 

and one on Big Otter River near Evington, Va. (02061500)—

had been in operation since 1930 and 1936, respectively. 

In 2006, two additional stream gages were established as 

part of the current investigation—one on Goose Creek at 

Route 747 near Bunker Hill, Va. (02059485) and the other on 

Big Otter River at Route 221 near Bedford, Va. (02061000). 

Partial-record streamflow measurements (sites where discrete 

streamflow measurements were obtained over a period of time 

without continuous data being recorded) were also conducted 

at 12 sites within the county (fig. 1; table 3). 
10 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Hydrogeology of Piedmont and Blue 

Ridge Aquifers

Hydrogeologic conditions and processes that control 

groundwater availability in the Piedmont and Blue Ridge 

fractured-rock aquifer systems in Bedford County were 

investigated by a synthesis of the literature and of data 

sources and analyses that are described in the following sections. The rates of groundwater inflow, outflow, and volume 

of water stored in Piedmont and Blue Ridge aquifers are 

defined by the prevailing climate conditions and topography 

and by the complex distributions of aquifer properties in the 

regolith and fractured-rock parts of the aquifer. 

Hydrogeologic Units

Piedmont and Blue Ridge fractured-rock aquifers 

within Bedford County were subdivided into three distinct 

hydrogeologic units following White (2012): (1) CambroOrdovician metasedimentary rocks, (2) Proterozoic basement 

crystalline rocks, and (3) Late Proterozoic-Cambrian 

cover crystalline rocks (figs. 4 and 5). For the Proterozoic 

basement crystalline rock and Late Proterozoic-Cambrian 

cover crystalline rock hydrogeologic units, subunits are 

defined by grouping geologic map units with similar 

metamorphic history or textural characteristics. While local 

Table 3. Streamflow measurement gages in Bedford County, Virginia.

[Site locations shown in figure 1. Abbreviations: USGS, U.S. Geological Survey; DDMMSS, degrees, minutes, and seconds; mi2, square miles]

Station 

number USGS station name Latitude (DDMMSS)

Longitude 

(DDMMSS)

Drainage 

area 

(mi2)

Station type Period of 

record

02059485 Goose Creek at Route 747 near Bunker Hill, VA 371559 793516 125 Continuous 2007–2012

02061000 Big Otter River at Route 221 near Bedford, VA 372150 792510 114 Continuous 2007–2012

02059500 Goose Creek near Huddleston, VA 371023 793114 188 Continuous 1931–2012

02061500 Big Otter River near Evington, VA 371230 791814 315 Continuous 1938–2012

02059420 North Fork Goose Creek at Route 460 near Montvale, VA 372214 794155 31.5 Partial Record 2006–2009

02059450 South Fork Goose Creek at Route 607 at Montvale, VA 372247 794350 11.0 Partial Record 2006–2009

02059452 Goose Creek at Route 726 near Irving, VA 372122 794132 46.8 Partial Record 2006–2009

02059459 Bore Auger Creek at Route 754 near Irving, VA 371826 794040 17.6 Partial Record 2006–2009

02059490 Stony Fork at Route 608 near Moneta, VA 371236 793833 7.01 Partial Record 2006–2009

02060592 Sheep Creek at Route 688 near Thaxton, VA 372316 793653 10.3 Partial Record 2006–2009

02060692 Stony Creek at Route 43 near Peaks of Otter, VA 372334 793319 14 Partial Record 2006–2009

02060695 Big Otter River at Route 43 near Peaks of Otter, VA 372323 793305 37 Partial Record 2006–2009

02060800 North Otter Creek at Route 643 near Cifax, VA 372526 792758 25.8 Partial Record 2006–2009

02060860 Oslin Creek at Route 644 near Cifax, VA 372340 792702 12 Partial Record 2006–2009

02061160 Elk Creek at Route 668 near Goode, VA 371950 792329 41 Partial Record 2006–2009

02061320 Little Otter River at Route 715 near Otter Hill, VA 371636 792606 66.4 Partial Record 2006–2009

hydrogeologic conditions are highly variable within and 

across all three hydrogeologic units, these groups warrant 

distinction because of differences in texture and structure 

that can influence the storage and movement of groundwater 

(Daniel and Payne, 1990). The three hydrogeologic units 

occur within the Blue Ridge Anticlinorium, a larger geologic 

feature in Virginia that is composed of a stack of northeastto southwest-striking thrust sheets (Bailey and others, 2006; 

Southworth and others, 2009).

Orientations of fractures and foliation (the preferential 

orientation of minerals and fabric in metamorphic rocks) 

were collected from borehole geophysical logs and plotted to 

describe general fracture trends of the three hydrogeologic 

units in the study area. Trends were assessed from borehole 

ATV geophysical log data collected in three wells in the 

Proterozoic basement crystalline rocks, one well in the Late 

Proterozoic-Cambrian cover crystalline rocks, and one well 

in the Cambro-Ordovician metasedimentary rocks (fig. 6). 

Foliation measurements were collected only in portions 

of wells that exhibited a metamorphic fabric or texture 

(schistosity and [or] cleavage) because of the inability of 

the ATV to resolve lineations present on otherwise smooth 

borehole wall. Fluid resistivity, fluid temperature, formation 

resistivity, natural gamma, EM flow, and ATV logs from the 

five wells are shown in Appendix 1. Several general statements can be made about the distribution and orientation of 

structural features collected from ATV logs in the study area: 
Hydrogeology of Piedmont and Blue Ridge Aquifers 11

1. Fracturing in the Proterozoic basement crystalline rocks 

appears to be systematic at the borehole level but not at 

a regional scale. Similar observations have been made 

by workers studying fracturing at the outcrop and the 

regional level elsewhere in the Blue Ridge (Bailey and 

others, 2003; Hasty and Bailey, 2005). 

2. A pervasive southeast dipping foliation can occur in 

bedrock wells across all hydrogeologic units. This foliation is more prevalent in the Late Proterozoic-Cambrian 

cover crystalline rocks and Cambro-Ordovician 

metasedimentary rocks, and fracturing related to foliation within these units may be a discernible regional 

trend.

3. Water-bearing fractures occur at a variety of orientations. Notable trends in the orientation of water-bearing 

fractures across all hydrogeologic units are as follows:

Zam; Ashe Formation 

ЄZmg; Moneta Gneiss1

ЄZmi; amphibolite 

ЄZmy,ЄZas; Alligator

 Back

 Formation

ЄCa; Candler Formation 

 of Evington Group 

Єu; Unicoi Formation of 

 Chilhowee Group

Yma; augen and flaser

 gneiss 

Rome/Waynesboro Formation

Yhm; biotite granitoid 

Ygb; biotite granofels

 and gneiss 

Ybg; biotite-granitoid

 gneiss 

Zsg, Zfg; granodiorite

Pzmy; mylonite

Yc, Ybc; charnockite

Ypg; layered gneiss

 and granulite

Zgd; granitic gneiss 

HYDROGEOLOGIC

UNIT

SUBUNIT GEOLOGIC MAP

 UNIT

Cambro-Ordovician 

metasedimentary 

rocks

Proterozoic basement 

crystalline rocks

Late ProterozoicCambrian cover 

crystalline rocks

Piedmont and Blue Ridge Fractured Rock Aquifers of Bedford County

Massive Crystalline Sedimentary Protolith Volcanic Protolith

Rock

Foliated Crystalline 

Rock

1Nomenclature conforms to current usage of Virginia Division of Geology and Mineral Resources

 a. Fractures parallel or subparallel to foliation (parting 

 along foliation or schistosity).

 b. Horizontal or subhorizontal water-bearing joints 

 (sheet jointing). 

c. Water-bearing fractures occurring as a component of 

 a conjugate fracture set (tectonically induced 

 fractures).

Similar trends have been noted in other locations along 

the Atlantic Seaboard by workers conducting hydrogeologic 

studies in crystalline rock (Chapman and others, 2005; 

Williams and others, 2005; Manda and others, 2008).

Figure 4. Major hydrogeologic units, subunits, and geologic map units in Bedford County, Virginia.
12 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Bedford County

ЄZmg

Ybg

Ybg

Ypg

Ygb

Yhm

Yhm

Yhm

Ygb

Yc, Ybc

Zgd

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

Town of 

Bedford

RO A NO

ROANO

*

FLAT

SMITH MOUNTAIN 

LAKE

#

#

#

79°30'

79°15'

37°30'

37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Cambro-Ordovician Meta-

 sedimentary Rocks

Ashe Formation (Zam)

Moneta Gneiss (ЄZmg)1

Amphibolite (ЄZmi)

Alligator Back Formation (ЄZmy,ЄZas)

Candler Formation of Evington Group (ЄCa)

Unicoi Formation of Chilhowee Group (Єu)

Late Proterozoic-Cambrian

Cover Crystalline Rocks

Augen and flaser gneiss (Yma)

Biotite granitoid (Yhm)

Biotite granofels and gneiss (Ygb)

Biotite-granitoid gneiss (Ybg)

Granodiorite (Zsg, Zfg)

Mylonite (Pzmy)

Charnockite (Yc, Ybc)

Layered gneiss and granulite (Ypg)

Granitic gneiss (Zgd)

Proterozoic Basement

Crystalline Rocks

FRANKLIN COUNTY

ROANOAKE 

COUNTY

BOTETOURT COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

CAMPBELL COUNTY

BEDFORD COUNTY

Zam

Yhm

Yhm

Ypg

Yc, Ybc Yc, Ybc

Yc, Ybc

Yc, Ybc

Ygb

Ygb

Pzmy

Zsg,Zfg

Єu

Єu

Єu

ЄZmg

ЄZmi

ЄCa

ЄZmy,ЄZas

ЄCa

ЄZmy,ЄZas

Zam

Zam

Zam

Yma

Ybg

Zgd

PEAKS

BLUE

RIDGE

FAULT

ROCKFISH

VALLEY

FAULT

BOWENS

CREEK

FAULT

OF OTTER FAULT

ЄZmi

UNNAMED FAULT

UNNAMED

FAULT

PIEDMONT

VALLEY

AND 

RIDGE

COASTAL PLAIN

APPALACHIAN

PLATEAUS

BLUE RIDGE

Location of Bedford County and physiographic provinces in Virginia

Fault

1Nomenclature conforms to current usage of Virginia

Division of Geology and Mineral Resources

Figure 5. Major hydrogeologic units and geologic map units in Bedford County, Virginia. 

[Modified from Henika (1997).]
Hydrogeology of Piedmont and Blue Ridge Aquifers 13

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

Town of 

Bedford

RO A NO

ROANO

*

FLAT

SMITH MOUNTAIN 

LAKE

79°30'

79°15'

37°30' 37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Cambro-Ordovician Meta-

 sedimentary rocks

Late Proterozoic-Cambrian

Cover Crystalline Rocks

FRANKLIN COUNTY

ROANOAKE 

COUNTY

BOTETOURT

COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

CAMPBELL COUNTY

BEDFORD COUNTY

35H 6 35H 2

33G 3 34G 3

34G 2

34F 1

34F 2

35G 4

35G 2 35G 1

35G 3

36H 1

36H 3

36H 2

36G 1

35G 3 36G 3

36G 5

35F 1

35F 2

36G 4

34H 4

33F 2

34E 1

33G 5

33G 7

33G 6

35H 5

34H 7

34H 8

34H 9

34H 10

34H 11

35H 1 SOW 226

35H 3 SOW 226A

35H 4 SOW226B

33G 1 SOW 224

33G 4 33F 2

33F 6

33F 4 33F 3

33F 5

5

10

N

90

180

270

N

90

180

270

N

90

180

270

N

90

180

270

20

40

15

30

45

5

10

15

20

Cambro-Ordovician metasedimentary rocks

Late Proterozoic-Cambrian cover crystalline rocks

Proterozoic basement crystalline rocks

EXPLANATION

Hydrogeologic Units

5

10

15

20 Percent of total linear features

270 90 Fracture azimuth

180

N

N

90

180

270

5

10

15

33G 7

33G 1 SOW 224

33G 2 SOW 225

34E 1

35H 1 SOW 226

34E 2

34E 3

35J 5 36J 7

35J 4

33G 2 SOW 225

Figure 6. Rose diagrams showing all linear features from selected wells in Bedford County, Virginia. [Fracture 

data obtained from acoustic televiewer logs. Geology modified from Henika (1997).]
14 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Cambro-Ordovician Metasedimentary Rocks

The Cambro-Ordovician-aged metasedimentary 

rocks occur in the valleys along the north and south forks 

of Goose Creek in the northwestern portion of the county 

(fig. 5) and are exposed at land surface where erosion has 

removed the overlying Proterozoic basement crystalline rocks 

(Henika, 1981). In Bedford County, Cambro-Ordovician 

metasedimentary rocks are composed predominantly of the 

Rome-Waynesboro Formation—an interbedded sequence of 

mudstone, argillite, quartzite, and dolomite. Carbonate rocks 

of the Elbrook Limestone, Conococheague Limestone, and 

the Stonehenge Limestone of Beekmantown Group occur in 

the extreme northwestern end of Bedford County and are also 

included in this unit. These rocks originated as cyclic shallow 

marine sequences deposited in a cratonic basin during the late 

Cambrian and early Ordovician (Butts, 1940). Subsequent to 

lithification, these rocks were folded and faulted during the 

mid- to late Paleozoic. In Bedford County, rocks of the RomeWaynesboro Formation are thrust over the younger carbonate 

units (Henika, 1981).

Well 33G 1 SOW 224 was drilled in the RomeWaynesboro Formation. All noted fractures in the well strike 

between 15° and 70°, and although no prevalent schistosity 

was noted in the well with the televiewer, these fractures 

strike in the same general direction as the foliation noted in 

wells 35H 1 SOW 226 and 34E 1, which are located in the 

Proterozoic basement crystalline rocks and Late ProterozoicCambrian cover crystalline rocks, respectively (fig. 6). Dip 

angles for noted fractures in well 33G 1 SOW 224 varied 

between 29° and 74°, with most dip angles greater than 50° 

(Appendix 1). Orientations for water-bearing fractures noted 

in well 33G 1 SOW 224 identified from EM flow and camera 

logging are coincident with the strikes and dip angles of other 

non-transmissive fractures in the well. Visual logs of the well 

via borehole camera show zones of complex folding and 

faulting with a persistent cleavage striking to the northeast. 

All open fractures observed on the camera log for well 

33G 1 SOW 224 occurred within carbonate intervals. 

The Rome-Waynesboro Formation was the only geologic 

unit in the Cambro-Ordovician metasedimentary rocks 

hydrogeologic unit with sufficient well completion data for 

summary evaluation. Wells drilled in the Rome-Waynesboro 

Formation are typically less than 300 ft deep (median well 

depth of 225 ft), with median yield of 20 gal/min, median 

depth to bedrock of 71.5 ft, and median casing depth of 108 ft 

(figure 7; table 4). Median depths for first and lowest reported 

water-bearing zones occur at 145 ft (15 wells) and 150 ft 

(7 wells), respectively, approximately 70 to 80 ft below the 

median depth to the bedrock interface.

1

Nomenclature conforms to current usage of Virginia Division of Geology and Mineral Resources

EXPLANATION

Upper outlier

75th Percentile

Number of values

Whiskers are 1.5 x interquartile range

Median

25th Percentile

Lower outlier

33

Data value shown when 

population less than 10

Proterozoic basement crystalline rocks

Augen and flaser gneiss

Biotite granitoid

Biotite granofels and gneiss

Biotite-granitoid gneiss

Granitoid

Mylonite

Chamockite

Layered gneiss and granulite

Granitic gneiss

Late Proterozoic-Cambrian cover crystalline rocks

Ashe Formation

Moneta gneiss1

Amphibolite

Alligator Back Formation

Candler Formation of Evington Group

Unicoi Formation of Chilhowee Group

Cambro-Ordovician metasedimentary rocks

Rome/Waynesboro Formation

Hydrogeologic unit summary statistics

75th percentile

Median

25th percentile

HYDROGEOLOGIC UNIT AND GEOLOGIC MAP UNIT

Figure 7. Well characteristics by hydrogeologic unit in Bedford County, Virginia.
Hydrogeology of Piedmont and Blue Ridge Aquifers 15

214 353 339 115 27 52 50 32 26 295 74 54 7 47 209 65

16 44 46 20 8 16 4 16 4 40 4 2 1 2 12 16

207 342 332 105 27 49 52 30 25 278 63 53 7 46 199 60

Augen and Flaser Gneiss

Layered Gneiss and Granulite

Biotite Granofels and Gneiss

Biotite Granitoid Gneiss

Mylonite

Granitic Gneiss

Charnockite

Biotite Granitoid

Alligator Back Formation

Candler Formation of Evington Group

Unicoi Formation of Chilhowee Group

Ashe Formation

Granodiortie

Amphibolite

Rome/Waynesboro

Moneta Gneiss

Augen and Flaser Gneiss

Layered Gneiss and Granulite

Biotite Granofels and Gneiss

Biotite Granitoid Gneiss

Mylonite

Granitic Gneiss

Charnockite

Biotite Granitoid

Alligator Back Formation

Candler Formation of Evington Group

Unicoi Formation of Chilhowee Group

Ashe Formation

Granodiortie

Amphibolite

Rome/Waynesboro

Moneta Gneiss

Reported yield, in gallons per minute

100

400

10

1.0

0.1

Depth, in feet below land surface Depth to bedrock, in feet below land surface

0

200

400

600

800

1,000

0

50

100

150

200

250

Figure 7. Well characteristics by hydrogeologic unit in Bedford County, Virginia.—Continued
16 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia Table 4. Descriptive statistics of hydrogeologic parameters by rock type associated with a selection of drilled water wells in Bedford County, Virginia. Hydrogeologic unit Proterozoic basement crystalline rocks Sub unit Foliated crystalline rock Massive crystalline rock Geologic map unit Augen and flaser gneiss Biotite- granitoid gneiss Biotite granofels and gneiss Layered gneiss and granulite Mylonite All foliated Biotite granitoid Charnockite Granitic gneiss Granodiorite All massive All Reported yield at drilling, in gallons per minute Median 10 10 10 10 10 10 8 7.5 7.5 5 7 10 Minimum 1 1 1 1 1 1 1 1 1 1 1 1 Maximum 200 150 300 191 80 300 95 100 60 60 100 300 Number of observations 207 342 332 105 27 1,013 49 52 30 25 156 1,169 Well depth, in feet Median 300 300 300 305 305 300 265 300 245 370 300 300 Minimum 65 54 80 60 75 54 65 125 100 95 65 54 Maximum 720 1,000 900 850 560 1,000 520 560 560 500 560 1,000 Number of observations 214 353 339 115 27 1,048 52 50 32 26 160 1,208 Depth to bedrock, in feet Median 75.5 63 53 33.5 20 54 62.5 70 53.5 21 52.5 53.5 Minimum 32 19 12 2 13 2 15 28 6 10 6 2 Maximum 240 140 110 147 88 240 90 150 82 36 150 240 Number of observations 16 44 46 20 8 134 16 4 16 4 40 174 Casing depth, in feet Median 75 67.5 63 70 65 68 60.5 60 65.5 40 60 66 Minimum 20 9 13 16 20 9 30 23 20 19 19 9 Maximum 160 180 140 148 120 180 103 124 100 80 124 180 Number of observations 199 292 302 102 20 915 40 42 26 23 131 1,046 Depth to first water-bearing zone, in feet Median 115 102 105 101 88 105 122 115 123 96.6 117 110 Minimum 42 40 31 29 35 29 50 70 50 38 38 29 Maximum 210 355 340 315 230 355 260 250 215 180 260 355 Number of observations 15 56 51 18 9 149 18 6 19 5 48 197 Depth to lowest water-bearing zone, in feet Median 180 205 185 196 110 192 209 170 210 199 202 195

Minimum 95 110 50 90 60 50 183 150 115 168 115 50Maximum 285 478 410 390 180 478 434 190 295 231 434 478Number of observations 8 33 37 10 4 92 6 2 10 2 20 112
Hydrogeology of Piedmont and Blue Ridge Aquifers 17

Table 4. Descriptive statistics of hydrogeologic parameters by rock type associated with a selection of drilled water wells in Bedford County, VA.—Continued 

Hydrogeologic unit Late Proterozoic-Cambrian cover crystalline rocks Cambro-Ordovician 

metasedimentary rocks Sub unit Sedimentary Protolith Volcanic Protolith

Hydrogeologic 

parameter

Alligator Back 

Formation

Ashe 

Formation

Candler 

Formation of 

Evington Group

Unicoi 

Formation of 

Chilhowee Group

All 

sedimentary Amphibolite Moneta gneiss1 All volcanic All Rome- Waynesboro Formation Elbrook Limestone

Reported yield at drilling, in gallons per minute

Median 12 10 10 12 10 12 7 8 10 20Minimum 1 1 1 5 1 2 1 1 1 2Maximum 200 50 100 35 200 68 112 112 200 100Number of observations 278 63 53 7 401 46 199 245 646 60

Well depth, in feet

Median 300 305 305 400 300 255 300 300 300 225 300Minimum 65 6 96 60 37 84 85 84 37 74 300Maximum 908 560 700 520 908 500 700 700 908 550 300Number of observations 295 74 54 7 429 47 209 256 685 65 1

Depth to bedrock, in feet

Median 54.1 72.7 62.5 13 57 37.5 66.2 57 58 71.5Minimum 10 52 60 13 10 20 14 14 10 4Maximum 100 92 65 13 100 55 95 95 100 196Number of observations 40 4 2 1 49 2 12 14 61 16

Casing depth, in feet

Median 71.6 64 79 87.2 70 68.1 71.1 68 70 108 82

Minimum 16 20 30 51 16 20 10 10 10 20 82Maximum 142 122 140 123 142 140 130 140 142 441 82Number of observations 158 66 52 7 383 43 198 241 624 56 1

Depth to first water-bearing zone, in feet

Median 160 136 105 140 145 175 138 132 142 145

Minimum 25 45 60 140 25 140 75 75 25 62Maximum 380 250 150 140 380 210 280 280 380 235Number of observations 47 4 2 1 54 2 12 14 68 15

Depth to lowest water-bearing zone, in feet

Median 220 200 150 225 240 181 185 202 150Minimum 53 150 150 53 230 92 92 53 100Maximum 440 250 150 440 250 320 320 440 260Number of observations 18 2 1 21 2 8 10 31 7

1Nomenclature conforms to current usage of Virginia Division of Geology and Mineral Resources.
18 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Proterozoic Basement Crystalline Rocks

Proterozoic-aged basement crystalline rocks occur to 

the northwest of a northeast-trending contact with the Late 

Proterozoic-Cambrian cover crystalline rocks (fig. 5). Proterozoic basement crystalline rocks within Bedford County are 

composed predominantly of biotite-rich gneisses surrounding 

pods of relatively undeformed granitic rocks to the south of 

the Rockfish Valley Fault, and more pyroxene-rich granulites, 

gneisses, and charnockitic rocks to the north of the Rockfish 

Valley Fault (Henika, 1997). These are the oldest rocks in 

the study area, and many bear evidence of multiple periods 

of deformation. These rocks are variably foliated, granitoid 

gneisses and granitoids defined by a characteristic crystalline 

structure as well as by their lowest stratigraphic position within 

the Blue Ridge Anticlinorium. Basement crystalline rocks 

include the augen and flaser gneiss (Yma), biotite-granitoid 

gneiss (Ybg), biotite granofels and gneiss (Ygb), biotite granitoid (Yhm), granitic gneiss (Zgd), charnockite (Yc,Ybc), layered 

gneiss and granulite (Ypg), mylonite (Pzmy), and granodiorite 

(Zsg, Zfg) geologic map units described in the geologic map of 

the Roanoke 30×60-minute quadrangle (Henika, 1997).

Fracturing within basement crystalline rocks is highly 

variable and dependent on the orientation of local stress fields 

in the rock imparted during deformation and exhumation, and 

in some cases by the presence or absence of metamorphic 

fabric (foliation and schistosity). Observations by the authors of 

basement outcrop within the study area and analysis of limited 

borehole geophysical log data obtained from three wells within 

the crystalline basement portion of the county indicate that 

jointing and parting along metamorphic fabric appear to be the 

predominant styles of fracturing within these rocks. 

Conjugate sets of fractures striking between 20° to 60° and 

210° to 230° were noted in well 33G 7 (fig. 6). Dip angles for 

noted fractures in well 33G 7 varied between 17° and 84° with 

the majority of noted fractures dipping at angles greater than 

50° (Appendix 1). Four of the six water-bearing fractures identified in well 33G 7 through EM flow and fluid logging have dip 

angles of 50° or less. The main water-producing zones for well 

33G 7 are associated with a steeply dipping fracture (dip angle 

of 72°) at 119 ft below land surface (bls) and a moderately 

dipping fracture (dip angle of 17°) at 135 ft bls. 

Conjugate fracture sets in well 33G 2 SOW 225 strike 

between 325° to 50° and 115° to 245°. Four water-bearing 

fractures were noted in well 33G 2 SOW 225. Two of the 

noted water-bearing fractures strike within the easterly dipping 

fracture set (strike angles of 26° and 343°), and two waterbearing fractures strike within the westward dipping fracture set 

(strike angles of 216° and 222°). Dip angles for noted fractures 

within well 33G2 SOW 225 vary between 11° and 74° with 

predominant dip angles for noted fractures ranging between 

50° and 70°. Three of the noted water-bearing fractures in well 

33G 2 SOW 225 have dip angles between 18° and 28° and 

collectively yielded about 3 gal/min during air lifting as the 

well was drilled. The main water-bearing fracture at 188 ft bls 

yielded approximately 10 gal/min and has a dip angle of 68°, 

which is coincident with the predominant dip of fracturing 

within the wellbore. 

Well 35H 1 SOW 226 was drilled in a mylonitic section of 

granodiorite and has a pervasive schistosity striking between 0° 

and 50° (Appendix 1). Two water-bearing zones were identified 

in this well—a nearly horizontal joint at 38 ft bls dipping at 

2° and striking at 17° that yielded less than 1 gal/min during 

air lifting and a joint at 169 ft bls striking at 201° and dipping 

northwest at nearly 20°. Yield from the lower fracture during 

air lifting was approximately 60 gal/min. EM flow and fluid 

profiling confirmed observations about the positions and yields 

of transmissive fractures recorded during drilling of the well. 

Wells drilled in the Proterozoic basement crystalline 

rocks typically have a median depth ranging from 300 to 305 ft 

(table 4; fig. 7) with median casing depth of 60 to 75 ft. Drilling 

depths of less than 300 ft are common for wells completed in 

the biotite granitoid and granitic gneiss map units, and drilling 

depths of greater than 350 ft and shallower casing depths 

(median value of 40 ft) can be expected for wells drilled in the 

granodiorite map unit. Reported median yield values for all 

rocks within the basement crystalline rocks ranged between 5 

and 10 gal/min. The highest reported well yield of 300 gal/min 

occurred in the biotite granofels and gneiss map unit. Reported 

water-bearing zones occur at median depths between 110 ft and 

195 ft, and median depth to bedrock occurs at 53.5 ft. 

Late Proterozoic-Cambrian Cover 

Crystalline Rocks

Late Proterozoic-Cambrian cover crystalline rocks occur 

primarily to the southeast of the northeast trending contact with 

the basement crystalline rocks and in smaller areas of the county 

along the northwestern borders with Botetourt, Rockbridge, 

Roanoke, and Amherst Counties (fig. 5). These rocks were 

unconformably extruded or deposited on basement crystalline 

rocks and include rocks of volcanic and sedimentary origin. 

The rocks in this hydrogeologic unit include the Alligator 

Back Formation (ЄZmy, ЄZas), amphibolite (ЄZmi), Moneta 

Gneiss (ЄZmg—nomenclature conforms to current usage of 

the Virginia Division of Geology and Mineral Resources), Ashe 

Formation (Zam), Candler Formation of the Evington Group 

(ЄCa), and Unicoi Formation of the Chilhowee Group (Єu) 

described in Henika (1997). 

Preserved textures in these rocks generally progress from 

coarse-grained conglomeratic metagraywacke and gneiss in the 

Ashe Formation to finer grained schistose and phyllitic rocks 

in the Alligator Back Formation and Candler Formation of the 

Evington Group. Along the northwestern border of the county, 

rocks of the Unicoi Formation of the Chilhowee group are composed of heterogeneous packages of coarse-grained basal units 

that typically fine upward into phyllitic and quartzose sequences 

(Henika, 1981). Well 34E 1 was completed in the Alligator Back 

Formation. Foliation was resolved with the optical televiewer 

throughout the well and strikes uniformly between 40° and 

60° with dip angles between 50° and 79° (fig. 6; Appendix 1). 
Hydrogeology of Piedmont and Blue Ridge Aquifers 19

Fracturing along and subangular to foliation is prevalent. A 

single transmissive joint at 292 ft bls strikes at 71° and dips 8°. 

Cascading conditions were observed in the well while camera 

logging. Cascading conditions indicate a downward hydraulic 

gradient between a flowing fracture observed on the camera log 

at 103 ft bls and the transmissive joint at 292 ft bls.

Wells drilled in the Late Proterozoic-Cambrian cover 

crystalline rocks have a median depth of 300 ft with a median 

casing depth of 70 ft (table 4; fig. 7). The median depth to 

bedrock in the Late Proterozoic-Cambrian cover crystalline 

rocks was 58 ft. Median well yields among geologic map units 

in the Late Proterozoic-Cambrian cover crystalline rocks range 

between 7 gal/min (Moneta Gneiss) and 12 gal/min (Alligator 

Back Formation, Unicoi Formation of the Chilhowee Group, 

and amphibolite). Median depths to first and lowest reported 

water-bearing zones are 142 and 202 ft, respectively. 

Low-yielding or seasonally dry wells have been reported in 

southeastern areas of the county (Todd Fowler, Bedford County 

Health Department, written commun., 2012) in areas underlain 

by Late Proterozoic-Cambrian cover crystalline rocks. A simple 

one-way analysis of variance (ANOVA) test on drillers’ well 

yields was conducted to assess the hypothesis that low-yielding 

wells were more common in Late Proterozoic-Cambrian cover 

crystalline rocks than in the Proterozoic basement crystalline 

rocks. Yields were binned by hydrogeologic unit, and the mean 

yields for Proterozoic basement crystalline rocks and Late 

Proterozoic-Cambrian cover crystalline rocks were found to be 

identical (fig. 7). The ANOVA test resulted in a p-value of 0.26 

that indicates no differences in well yields in the basement and 

cover crystalline rocks across the scale of the entire county. 

Daniel and Harned (1998) similarly found no difference in 

yields among crystalline rock units in the Piedmont of North 

Carolina. Reported low-yielding wells in the southeastern part 

of the county likely result from local heterogeneities of which 

insufficient data exist to characterize and which are not reflected 

in the current conceptual model. 

Conceptual Model of Groundwater Flow

In the Blue Ridge Physiographic Province, topography 

provides the driving force for groundwater flow, and the water 

table is generally a subdued reflection of the land surface 

(figs. 8, 9). The high density of streams in the Blue Ridge 

Physiographic Province is probably the result of the underlying 

low-permeability rocks. The porous nature of the overlying 

regolith material (overburden) and the sharp contrast in permeability with the underlying hydrogeologic units coupled with 

numerous streams and hilly terrain are probably conducive for 

the development of local flow systems. Groundwater discharges 

at low elevation points along small streams and headwater 

springs (White, 2012). Groundwater flow in the bedrock is 

primarily controlled by the irregular fracture network and steep 

terrain (Wright, 1990) and by the development of complex 

potentiometric head relations between recharge and discharge 

zones (White, 2012). Local flow systems may be controlled 

by stress relief or other brittle fracturing; however, beddingplane partings in metasedimentary rocks and foliations in the 

metamorphic rocks may facilitate more of a subregional- to 

regional-type flow. 

The groundwater-flow system of the Piedmont Physiographic Province can be idealized to consist of four components 

(fig. 9): (1) unsaturated regolith, (2) saturated regolith, 

(3) a transition zone between regolith and bedrock aquifer, and 

(4) fractured bedrock aquifer or hydrogeologic unit as described 

previously (Daniel and Harned, 1998). The regolith is a mantle 

of organic materials in surface soils, residuum, and saprolite, as 

well as alluvium and colluvium, that overlies bedrock in most 

locations. The sandy-clay residuum or saprolite that composes 

the majority of the regolith thickness is derived from in-place 

weathering of bedrock and commonly contains fragments of 

solid rock that is highly fractured near a transition zone (Daniel 

and Harned, 1998) to bedrock. Residuum is produced from the 

weathering of feldspars and micas found in crystalline rocks to 

clays and differs from saprolite, which is weathered material 

that retains the structural characteristics of the parent rock 

(Chapman and others, 2005). The thickness of the regolith may 

vary considerably from near zero to greater than 150 ft. The 

regolith and transition zone contain intergranular porosity that 

provides the majority of water storage within the Piedmont and 

Blue Ridge aquifers (Heath, 1980). Storage potential of the 

regolith is dependent on a number of factors, including topographic position, thickness of the material, hydraulic gradients, 

and orientation of relict structure (saprolite) (White, 2012). 

An abrupt change in storage potential occurs at the bedrock 

interface because of the reduction in porosity from typical 

values of 35 to 55 percent in the regolith to 1 to 3 percent in the 

fractured bedrock (Daniel and Harned, 1998) (fig. 9). Hydraulic 

gradients are downward in recharge areas where water stored in 

the regolith slowly leaks downward into the bedrock fractures 

or moves laterally along the interface towards discharge points. 

In discharge areas, hydraulic gradients are reversed, and water 

from the fractured bedrock flows upward into the regolith 

(White, 2012).

Groundwater-level altitudes that were measured in 

December 2010 in Bedford County range from about 

1,300 ft NGVD 29 in the northwest part of the county to about 

600 ft NGVD 29 in the southeastern part of the county (fig. 10). 

The water-level map shown in figure 10 assumes streams are a 

surficial expression of the water level in adjacent aquifers, and 

the water-level altitude associated with streams were assigned 

by using a 20-meter digital elevation model (DEM). Groundwater generally flows from northwest to southeast in Bedford 

County, although groundwater flows locally towards drainages 

in eastern portions of the county where surface-water channels 

are deeply incised. Although the spatial coverage of the wells 

used to measure groundwater levels as part of this study was 

limited, in general, groundwater divides appear coincident with 

surface-water divides that separate the county’s major surface 

drainages: Smith Mountain Lake, Goose Creek, Big Otter River, 

and the James River (fig. 10).
20 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Hydrogeologic unit

contact

Intermittent

spring

Perennial

spring

Alluvium and

colluvium

Land surface

Southeast

Northwest

Feet

1,400

1,200

1,000

800

600

1,400

1,200

1,000

800

600

0 500 1,000 1,500

Distance, in feet

2,000 2,500 3,000 3,500

Fractured rocks with 

low primary permeability

Regolith with high 

primary permeability

Figure 8. Generalized conceptual model of the flow system in Blue Ridge fracture rock aquifers in Bedford County, 

Virginia. [Modified from Nelms and Moberg (2010).]
Hydrogeology of Piedmont and Blue Ridge Aquifers 21

Fracture

Bedrock

structure

Unweathered

bedrock

Weathered

bedrock, boulders

Saprolite

Stress-relief

fracture

Water table

Transition

zone

Soil zone

Storage

in 

bedrock

Storage

in regolith

Regolith

Regolith

unsaturated

zone

Regolith

saturated

zone

Fractured

bedrock

Figure 9. Components of the groundwater-flow system and relative storage volumes in the regolith and fractured-rock aquifers of 

the Piedmont Physiographic Province, Bedford County, Virginia. [Modified from Heath (1984) and Daniel and Harned (1998).]
22 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

Town of 

Bedford

RO A NO

ROANO

*

FLAT

SMITH MOUNTAIN 

LAKE

#

79°30'

79°15'

37°30'

37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Line of equal water-level—Dashed

 where approximately located. Contour

 interval 200 feet

Well location and water-level altitude

 to the nearest foot

Land-surface elevation, in

 feet above NGVD 29 

FRANKLIN COUNTY

ROANOAKE 

COUNTY

BOTETOURT COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

CAMPBELL COUNTY

BEDFORD COUNTY

1,282

98

PIEDMONT

VALLEY

AND 

RIDGE

COASTAL PLAIN

APPALACHIAN

PLATEAUS

BLUE RIDGE

Location of Bedford County and physiographic provinces in Virginia

921

922

821

844

617

966

850

770

870

866

901

860

814

843

816

827

774

931

822

683

950 945

870

957

830

965 978

963

882

876

854 853

850

853

850

940

946

802 783

781

1,020

1,015

1,007

1,286

858

816

1,000

1,200

800

800

800

800

600

600

600

800

Figure 10. Groundwater levels in Bedford County, Virginia, December 2010.
Hydrogeology of Piedmont and Blue Ridge Aquifers 23

Groundwater Response to Precipitation

The fractured-bedrock aquifers in the study area respond 

to natural transient atmospheric conditions, and the response 

is measured as changes in groundwater levels and base-level 

conditions in streams. The range of natural water-level 

fluctuation in the fractured-rock aquifer system varies across 

Bedford County and is controlled by (1) the location and 

magnitude of recharge, (2) topographic relief, or position in 

the local flow system, (3) amount of evapotranspiration (ET), 

particularly during the growing season, (4) hydraulic properties of the aquifer, (5) groundwater discharge to springs and 

streams, and (6) the location of pumped wells. 

The differences between the December 2010 and 

April 2011 water levels measured at 47 wells averaged 

1.0 ft (table 5); seasonal water-level fluctuations between the 

two measurement time periods were minimal (as noted from 

continuous hourly groundwater levels recorded in the study 

area for this time period) and are less than the resolution 

of the 200-ft contour intervals shown in figure 10. With the 

exception of two wells (33F 5 and 34H 6) that are thought to 

be influenced by recent pumpage, the maximum change from 

December 2010 to April 2011 was 6.12 ft (table 5).

Daily water-level data from October 2009 through 

September 2013 in continuous monitoring wells 

33G 1 SOW 224, 33G 2 SOW 225, 35H 1 SOW 226, 

35H 3 SOW 226A, and 35H 4 SOW 226B are shown in 

figure 11 with daily precipitation data from NOAA site 

440561 Bedford 4 NW, the site closest to the three well 

locations (figs. 1, 3). The hydrographs for these wells indicate 

annual water-level variation of less than 10 ft, with subtle 

differences in amplitude and duration of interannual peaks. 

White (2012) prescribed the differences in response to 

precipitation to the variation in regolith storage, hydrologic 

communication with the surface, and depths of water-bearing 

fractures in the respective wells. 

Water-level variation attributed to changing climate 

conditions during the study period can be quantified by using 

the Standardized Precipitation Index (SPI) (McKee and 

others, 1993). In the SPI, raw observations of precipitation 

are transformed to follow a normal distribution, and a single 

numeric value, equivalent to the number of standard deviations the observed data differ from the long-term mean, is 

assigned to observed precipitation data. For Bedford County, 

a 3-month time period was used to calculate SPI values from 

the precipitation data collected at NOAA site 440561 Bedford 

4 NW, although a variety of time scales is possible. The SPI 

results during the water years 2009 to 2013 (fig. 11) indicate 

periods of below-normal precipitation during the winter of 

2008–2009 and from March 2010 through June 2011, and 

periods of above-normal precipitation from July 2011 through 

May 2012 and January 2013 through September 2013.

Wells 33G 1 SOW 224, 33G 2 SOW 225, and 

35H 1 SOW 226 had similar water-level trends that followed 

the 3-month SPI trends with broad peak lags of 3 to 4 months 

(White, 2012). The general absence of flashiness or response 

to individual precipitation events in the hydrographs of 

33G 1 SOW 224, 33G 2 SOW 225, and 35H 1 SOW 226 

for any of the years of record qualitatively implies either 

(1) a delayed response to subsurface flow within adjacent 

hillslopes, or (2) unconsolidated sediment in the regolith 

contains large accessible storage to modulate climatic inputs. 

For the first case, the rounded peaks are considered a result of 

an increase in distance, depth, or areal distribution of recharge 

to the aquifer. In the second case, permeability contrast at 

the bedrock interface likely provides additional moderation 

of the downgradient rate of leakage from the overlying 

regolith to the fractured-rock aquifers. Other factors such as 

prevailing and antecedent moisture conditions, hydrogeologic 

framework of the aquifer, proximity of a well to streams or 

other point of aquifer discharge, degree of aquifer confinement, or duration and intensity of seasonal events also may 

contribute to low-amplitude peaks and longer response times 

to precipitation. 

Winter precipitation is a critical source of recharge 

to aquifers and is directly related to base flow in receiving 

streams during later periods of low flow in late summer 

and early fall (Austin, 2014). The response of aquifers to 

cold-season recharge was evident in hydrographs following 

heavy snows in the winter of 2009–10. Water levels in 

33G 1 SOW 224 and 35H 1 SOW 226 rose approximately 

2 ft and nearly 6 ft in 33 G2 SOW 225, the highest water 

levels recorded during the study period (fig. 11). The 2009–10 

winter represents a weather extreme; however, the response 

of water levels to typical winter season precipitation have 

similar timing albeit lower magnitude of change than seen 

during the 2009–10 winter. 

Replacement of 35H 1 SOW 226 with the nested 

piezometers 35H 3 SOW 226A (168-ft fracture zone) 

and 35H 4 SOW 226B (37-ft fracture zone) resulted in 

measurement of a 4.5- to 9.9-ft head differential between 

fractures at 37 ft and 168 ft below land surface. This range 

of measurements equates to a downward vertical gradient of 

0.03 to 0.08. Water levels in the shallow fracture as measured 

in 35H 4 SOW 226B are more responsive to individual 

precipitation events than water levels in the deeper fracture 

measured in 35H 3 SOW 226A. 

On August 23, 2011, a magnitude 5.8 earthquake was 

recorded near Mineral, Va., approximately 110 miles (mi) 

northwest of well 33G 2 SOW 225. This event was one of 

the largest earthquakes recorded in the eastern United States. 

Water levels in 33G 2 SOW 225 instantaneously lowered 

0.74 ft in response to the propagation of seismic waves 

following the earthquake. Following the initial response to 

the earthquake, water levels in 33G 2 SOW 225 appeared 

to stabilize until September 26, 2011. During the next 

4 days, through September 30, 2011, water levels rose 

8.43 ft. The anomalous rise in water level followed the 

timing of the earthquake and daily rainfall totals of 4.8 in. 

(August 14, 2011) and 5.5 in. (September 6, 2011), the two 

highest daily rainfall totals observed during the study period. 
24 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Topography in mountainous settings has been related 

to differences in the range of water levels observed in valley 

and hilltop settings. Aquifer recharge and discharge are both 

largely driven by topography, such that valleys and hilltops 

serve as hydrologic boundaries. Proximity of wells to these 

boundaries is reflected in observed water levels. Seasonal 

water-level fluctuations tend to be greater in the elevated 

recharge areas and in areas underlain by low-permeability 

rocks; water levels in discharge areas near streams and springs 

and areas underlain by permeable rocks tend to fluctuate less 

(Nelms and Moberg, 2010). The water levels in Bedford 

County wells 33G 1 SOW 224 and 33G 2 SOW 225 exemplify 

these tendencies. Well 33G 2 SOW 225 is on a ridge at an 

elevation of 1,070 ft above mean sea level approximately 

0.7 mi southeast of well 33G 1 SOW 224, which is in the 

adjacent valley at an elevation of 930 ft above mean sea 

level. Depth to water in the valley setting ranges from about 

7 to 12 ft in 33G 1 SOW 224 and is much shallower than the 

measured range of depth to water of about 41 to 55 ft along the 

ridgeline in 33G 2 SOW 225 (fig. 11). 

Figure 11. Water-level data from continuous monitoring wells and daily precipitation from National Oceanic and 

Atmposheric Administration site 440561 in Bedford County, Virginia, 2009–2013 water years. Three-month Standardized Precipitation Index

Extremely wet

Extremely dry

Precipitation, in inches

Water-level depth, in feet below land surface

WATER YEAR

2009 2010 2011 2012 2013

35H 1 SOW 226 replaced by 

Otterville Research Station

wells 35H 3 SOW 226A and

35H 4 SOW 226B 

10/16/2011

0

10

20

30

40

50

60

3

2

1

–3

–2

–1

0

35H 1 SOW 226

33G 2 SOW 225

33G 1 SOW 224

440561

Bedford 4 NW

2

0

4

6

Aug. 23, 2011 

earthquake near 

Mineral, Va.

35H 4 SOW 226B

35H 3 SOW 226A

Dec. 2010 synoptic

water-level

measurement,

see fig. 10

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S
Hydrogeology of Piedmont and Blue Ridge Aquifers 25

Table 5. Water-level measurements from selected wells in Bedford County, Virginia.

[Site locations shown in figure 3. Abbreviations: USGS, U.S. Geological Survey; ft-blsd, feet below land-surface datum; —, no data reported]

Site number USGS station number

December 2010 April 2011 December 2010–April 2011 

change in water level 

Date (ft blsd) 

Water level 

(ft-blsd) Date Water level (ft-blsd)

32G 12 371621079482801 12/7/2010 46.48 4/18/2011 45.73 0.75

33F 2 371019079375301 12/6/2010 36.91 4/18/2011 37.46 –0.55

33F 3 371136079431901 12/6/2010 41.64 4/18/2011 41.22 0.42

33F 4 371138079431601 12/6/2010 79.7 4/18/2011 73.58 6.12

33F 5 371139079432001 12/6/2010 60.91 4/18/2011 48.05 12.86

33G 3 372106079374501 12/7/2010 0.57 4/18/2011 0.60 –0.03

33G 4 371538079435501 12/7/2010 33.51 4/18/2011 32.22 1.29

33G 5 371508079431001 12/7/2010 43.66 4/18/2011 39.81 3.85

33G 6 371505079431301 12/7/2010 6.85 4/18/2011 4.62 2.23

33G 7* 371503079431701 — — 6/21/2011 7.42 —

34E 2 370645079341501 12/10/2010 45.3 4/18/2011 45.04 0.26

34E 3 370522079352601 12/10/2010 81.54 4/18/2011 80.27 1.27

33F 6 371252079434501 12/7/2010 167.51 4/18/2011 170.21 –2.70

34F 1 371330079333001 12/7/2010 28.78 4/18/2011 29.51 –0.73

34F 2 371237079321901 12/7/2010 47.36 4/18/2011 49.22 –1.86

34G 2 371634079333501 12/7/2010 45.34 4/19/2011 46.37 –1.03

34G 3 372100079345901 12/8/2010 5.08 4/18/2011 3.59 1.49

34H 4 372256079303001 12/8/2010 196.73 — — —

34H 5 372531079343701 12/6/2010 33.29 4/18/2011 29.43 3.86

34H 6 372514079320801 12/6/2010 60.09 4/18/2011 41.07 19.02

34H 7 372323079331301 12/6/2010 2.9 4/18/2011 2.58 0.32

34H 8 372324079331701 12/6/2010 1.05 4/18/2011 3.59 –2.54

34H 9 372326079332001 12/6/2010 7.07 4/18/2011 6.16 0.91

34H 10 372329079331901 12/6/2010 6.97 4/18/2011 6.26 0.71

34H 11 372332079331801 12/6/2010 11.88 4/18/2011 11.16 0.72

35F 1 371337079230701 12/9/2010 41.6 4/18/2011 42.49 –0.89

35F 2 370929079284801 12/10/2010 88.22 4/18/2011 89.15 –0.93

35G 1 371511079284901 — — 4/18/2011 51.60 —

35G 2 371508079285501 12/10/2010 36.75 4/18/2011 37.04 –0.29

35G 3 372150079263101 12/8/2010 43.9 4/19/2011 45.05 –1.15

35G 4 372102079292801 12/8/2010 25.37 4/18/2011 28.23 –2.86

35H 2 372539079285901 12/8/2010 51.98 4/19/2011 51.03 0.95

35J 4 373108079233301 12/8/2010 67.29 4/19/2011 69.73 –2.44

35J 5 373138079250801 12/8/2010 41.07 4/19/2011 39.45 1.62

36G 1 371819079180501 12/9/2010 27.75 4/18/2011 29.88 –2.13

36G 2 372214079185501 12/9/2010 41.11 4/19/2011 42.40 –1.29

36G 3 372143079222501 12/9/2010 38.31 4/19/2011 37.33 0.98

36G 4 371625079202301 12/9/2010 42.28 4/18/2011 42.32 –0.04

36G 5 371627079202501 12/9/2010 18.47 4/18/2011 17.97 0.50

36H 1 372246079220901 12/9/2010 32.33 4/19/2011 33.24 –0.91

36H 2 372244079210401 12/9/2010 30.42 4/19/2011 29.80 0.62

36H 3 372508079221401 12/8/2010 82.38 4/18/2011 81.49 0.89

36J 7 373151079213001 12/8/2010 42.88 4/19/2011 42.12 0.76

*

 Single measurement made at well in June 2011.
26 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Water Budget

A water budget is an estimate of water entering and 

leaving a basin plus or minus storage changes for a given 

time period. Water enters a basin as precipitation and leaves 

as streamflow, ET, and diversions, such as surface-water 

withdrawals and groundwater pumpage. The conceptualization 

of flow in Bedford County suggests that groundwater and 

surface-water divides are coincident and that groundwater 

does not enter or leave a surface-water basin as underflow. 

Based on that conceptualization, a simple water budget for a 

typical watershed in Bedford County can be described by the 

following equation:

PR = ET + SF + ΔS, (1)

where

PR is the mean precipitation, in inches per year,

ET is the mean evapotranspiration, in inches per 

year,

SF is the mean streamflow, in inches per year, 

and

ΔS is the change in groundwater storage, in 

inches per year.

Streamflow can be divided into two components as

SF = RO + BF, (2)

where 

RO is runoff from land surface, in inches per 

year, and

BF is base-flow discharge from aquifers, in 

inches per year. 

For the purposes of this water-budget analysis, ΔS is assumed 

equal to zero because all recharge from precipitation is 

assumed to discharge to streams as base flow. All terms in 

the water-budget equation are known or can be estimated 

except ET, and the equation is solved for ET. Deviations from 

the assumptions of the equation, such as underflow between 

basins, and errors in other terms, are, therefore, included in 

ET. 

Inflows to Aquifer

Precipitation that falls on Bedford County is the sole 

source of inflow to the groundwater system. Climate records 

of precipitation and hydrologic records of streamflow are the 

most available data with which to assess the variability in 

hydrologic budget components of Bedford County. The magnitude and distribution of groundwater supplies in Bedford 

County was quantified by using streamflow data collected at 

continuous and partial-record stations and estimates of return 

flow from domestic wastewater systems. 

Precipitation

The PRISM (Parameter-elevation Regressions on 

Independent Slopes Model) Climate Group at Oregon State 

University provides yearly and monthly precipitation datasets 

(Daly and others, 2008). The average annual precipitation for 

Bedford County was extracted from the National PRISM data 

(fig. 12; PRISM Climate Group, Oregon State University, 

2014). The gridded precipitation data are based on a model 

of the National Weather Service (NWS) station data for the 

normal climatological period 1981–2010. Mean annual precipitation rates listed in table 6 are the average of 1981–2010 

PRISM precipitation normals (fig. 12) within respective locality or basin boundary defining polygon. PRISM data indicate 

that average precipitation ranges from 39.4 to 66.9 inches per 

year in Bedford County. The orographic influence of the Blue 

Ridge Mountains is shown by the higher values in the western 

portions of the Big Otter River Basin. The lowest values are 

found in the southeastern portion of Bedford County near the 

mouth of Goose Creek.
Hydrogeology of Piedmont and Blue Ridge Aquifers 27

221

460

Town of 

Bedford

SMITH MOUNTAIN 

LAKE Leesville 

Lake

79°30'

79°15'

37°30'

37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Average annual precipitation,

in inches

CAMPBELL COUNTY

FRANKLIN COUNTY

ROANOAKE 

COUNTY

BOTETOURT COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

Roanoke

River

Rockcastle Creek

Mill

Creek

Creek

Creek

Creek

Creek

Falling

Island

Nininger

Goose

Creek

Creek

Enochs

Falling

Creek

Big

Little

Otter

Otter

River

River

Bore Auger

221

Day

Creek

Creek

Buffalo

Run

Lick

Run

Roaring

Creek

Ivy

501

Creek

Stony

Creek Johnson

BEDFORD COUNTY

Matts

Creek

Hunting Creek

Physiographic province boundary

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

PIEDMONT

VALLEY

AND 

RIDGE

COASTAL PLAIN

APPALACHIAN

PLATEAUS

BLUE RIDGE

Location of Bedford County and physiographic provinces in Virginia

BLUE RIDGE

PIEDMONT

43

682

695 644

122

643

663

622

811

43

24

619

746

608

122

626

634

66.9

39.4

Figure 12. Average annual precipitation across Bedford County, Virginia, based on parameter-elevation regressions on 

independent slopes model (PRISM) (PRISM Climate Group, Oregon State University, 2014). The normal values are based on the 

National Weather Service’s current normal climatological period from 1981 to 2000.
28 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Table 6. Hydrologic budget components for select localities and basins in Bedford County, Virginia.

[—, not determined; na, not applicable; Rt, Route]

Evapotranspiration

 Locality or station name Station 

number

Mean 

annual 

precipitation, in 

inches1

Total, in 

inches 

per year

Riparian 

evapotranspiration, in 

inches per 

year

Runoff, in 

inches per 

year

Effective 

recharge, 

in inches 

per year

Baseflow 

index, in 

percent

Period of 

record

Bedford County, Virginia2 45.6 29.2 1.2 3.8 13.7 — na

City of Bedford, Virginia2 45 25.7 1.2 8.3 12.3 — na

Goose Creek Basin

Goose Creek near Huddleston, VA3 02059500 44.2 31.4 — 4.5 8.3 65 1931–2012

Goose Creek at Rt 747 near Bunker Hill, VA3 02059485 45.7 35.9 — 3.3 6.5 66 2007–2012

North Fork Goose Creek at Rt 460 near 

Montvale, VA4

02059420 46.4 38.7 — 2.7 5.0 65 2006–2009

South Fork Goose Creek at Rt 607 at Montvale, VA402059450 46.4 35.8 — 3.7 6.9 65 2006–2009

Goose Creek at Rt 726 near Irving, VA4 02059452 46.4 37.3 — 3.2 6.0 65 2006–2009

Bore Auger Creek at Rt 754 near Irving, VA4 02059459 46.2 35.6 — 3.7 6.9 65 2006–2009

Stony Fork at Rt 608 near Moneta, VA4 02059490 44.9 34.2 — 3.7 7.0 65 2006–2009

Big Otter River Basin

Big Otter River near Evington, VA3 02061500 44.6 30.5 — 4.7 9.3 66 1938–2012

Big Otter River at Rt 221 near 

Bedford, VA3

02061000 47.8 35.1 — 3.8 8.9 70 2007–2012

Sheep Creek at Rt 688 near Thaxton, VA5 02060592 50.2 42.0 — 2.7 5.4 66 2006–2009

Stony Creek at Rt 43 near Peaks of Otter, 

VA5

02060692 50.2 36.7 — 4.5 8.9 66 2006–2009

Big Otter River at Rt 43 near Peaks of Otter, 

VA5

02060695 50.2 37.8 — 4.2 8.2 66 2006–2009

North Otter Creek at Rt 643 near Cifax, VA5 02060800 50.4 34.6 — 5.3 10.5 66 2006–2009

Oslin Creek at Rt 644 near Cifax, VA5 02060860 45.9 34.4 — 3.9 7.6 66 2006–2009

Elk Creek at Rt 668 near Goode, VA5 02061160 45.5 34.3 — 3.8 7.5 66 2006–2009

Little Otter River at Rt 715 near Otter Hill, 

VA5

02061320 44.8 34.9 — 3.3 6.5 66 2006–2009

1

Data from 1981–2010 PRISM raster dataset (PRISM Climate Group, Oregon State University, 2014).

2

Data from Sanford and others (2012) chemograph separation.

3

Runoff, recharge, and BFI data computed using PART.

4

Denotes partial record station with value determined by log-log dischage relation with 02059500 Goose Creek near Huddleston, VA.

5

Denotes partial record station with value determined by log-log dischage relation with 02061500 Big Otter River near Evington, VA.
Hydrogeology of Piedmont and Blue Ridge Aquifers 29

Estimates of Recharge from Streamflow

Precipitation that infiltrates into the soil and percolates to 

the water table recharges the groundwater system. The amount 

of recharge depends on many factors, including antecedent 

soil-moisture conditions, the timing, duration, and intensity of 

precipitation, depth to the water table, and soil, regolith, and 

bedrock characteristics. Generally, recharge areas coincide 

with topographic highs in an area, whereas topographic lows 

are commonly discharge areas. Because of climatic variability, 

the amount of recharge is expected to vary from year to year. 

Because the water table is relatively shallow and streams 

in Bedford County are assumed to be gaining, or receiving 

groundwater discharge, base flow is used as an approximation 

of recharge. Annual recharge rates were estimated based on 

streamflow records and the hydrograph separation technique 

PART (Rutledge, 1998). PART was used to separate streamflow into its groundwater discharge (BF) and surface-runoff 

(RO) components and to estimate groundwater recharge 

under the previously mentioned assumptions. PART also 

generates annual estimates of base-flow index (BFI), which 

is the percentage of streamflow that is accounted for by BF. 

Streamflow data from the four continuous-record stream gages 

in the study area were analyzed for their respective entire 

periods of record (tables 3, 6). Graphical regression methods 

were used to relate measurements at the partial-record sites 

(table 3) to concurrent daily mean discharge at their respective 

downstream long-term continuous data stations (02061500 

Big Otter River near Evington or 02059500 Goose Creek 

near Huddleston; fig. 13). A curve was visually fitted to the 

data points, and mean base-flow discharge was estimated by 

transferring the mean base-flow discharge from the continuous 

stations through the relation line to the partial-record station 

based on the methods of Harlow and others (2005). 

Base-flow discharge is commonly assumed to be 

equivalent to effective recharge; however, it is not the total 

recharge for a basin. Total recharge is always larger than 

effective recharge and includes riparian evapotranspiration 

(RET), which is the quantity of water evaporated or transpired 

by plants in the riparian zone adjacent to streams. RET is also 

a component of total ET and is included in the ET component 

of the water-budget estimates presented in table 6.

Using PART, the average annual effective recharge 

for continuous stream gage 02059500, Goose Creek 

near Huddleston, Va., during the period 1931–2012 was 

8.3 in/yr (table 6), with base-flow discharge composing 

65 percent of mean streamflow. During the 2006–2009 period 

of partial-record station data collection, average annual 

effective recharge at continuous stream gage 02059500, 

Goose Creek near Huddleston, Va., was 5.4 in/yr, and BFI was 

67 percent. The 2006–09 average annual effective recharge 

at continuous stream gage 02059500 is a decrease from the 

1931–2012 average annual effective recharge at the gage 

by about 35 percent, which is equivalent to a decrease of 

approximately 26.9 million gallons per day (Mgal/d) over the 

188-mi2 drainage area.

Continuous stream gage 02059485, Goose Creek at 

Route 747 near Bunker Hill, Va., is upstream of 02059500 

about 4 mi south of the town of Bedford and was constructed in 

December 2006 as part of the current investigation (fig. 1). The 

average annual effective recharge for this station for 2007–12 

was 6.5 in/yr, with base-flow discharge composing 66 percent 

of mean streamflow. A log-log relation of base-flow discharge 

at five partial-record streamflow sites in the Goose Creek Basin 

(02059420, 02059450, 02059452, 02059459, and 02059490) 

and concurrent daily mean discharge at the continuous station 

02059500 Goose Creek near Huddleston, Va., yielded baseflow values ranging from 5.0 to 6.9 in/yr during the period 

2006–09 (table 6; figs. 14–15).

The average annual effective recharge for 02061500, Big 

Otter River near Evington, Va., during the period 1938–2012 

was 9.3 inches per year, with base-flow discharge composing 

66 percent of mean streamflow (table 6). During the 2006–09 

period of partial-record station data collection, average 

annual effective recharge at 02061500, Big Otter River near 

Evington, Va., was 6.5 in/yr, and BFI was 68 percent. The 

2006–09 average annual effective recharge at continuous 

stream gage 02061500 was a decrease from the 1938–2012 

average annual effective recharge by about 30 percent, which is 

equivalent to a decrease of approximately 26.9 Mgal/d over the 

315-mi2 drainage area. 

At 02061000, Big Otter River at Route 221 near Bedford, 

Va., the average annual effective recharge for 2007–12 was 

8.9 in/yr, with base-flow discharge composing 70 percent of 

mean streamflow. Partial-record streamflow measurements conducted at seven sites in the Big Otter River Basin (02060592, 

02060692, 02060695, 02060800, 02060860, 02061160, 

and 02061320) were evaluated with concurrent daily mean 

discharge values at station 02061500 Big Otter River near 

Evington, Va. The average annual effective recharge values for 

the seven partial-record stations ranged from 5.4 to 10.5 in/yr 

during the period (2006–09) (table 6; figs. 14 and 16).

Sanford and others (2012) computed water budgets at 

two gages in Bedford County by using chemograph separation 

techniques. They spatially extrapolated the computed water 

budgets across the entire State of Virginia through a regression 

analysis of ET and runoff with land use and basin characteristics. Sanford and others (2012) used political boundaries to 

summarize their water-budget results. Chemograph separation 

techniques by Sanford and others (2012) for the town of 

Bedford and Bedford County areas yielded approximately 

30 percent higher effective recharge values than those generated from PART for the period of record at 02059500 and 

02061500 (table 6). Hydrograph separation techniques are 

intuitive and follow the assumption that peak flows are dominated by surface-water runoff. Water in streams, however, will 

retain the chemical character of the groundwater and surfacerunoff inputs throughout the peak event. Where groundwater 

chemistry is known or can be established, stream chemograph 

separation techniques have been shown to consistently yield 

higher base-flow values (Sanford and others, 2012). 
30 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

y = 0.0651 * 1.1657

R2 = 0.9139

0.1

1

10

100

1 10 100 1,000

Discharge at 02061160 Elk Creek at Route 668 near Goode, Virginia,

in cubic feet per second

Discharge at 02061500 Big Otter River near Evington, Virginia, in cubic feet per second 

02061500 

Big Otter River near 

Evington, Va. 

mean 2007–2009 

base flow from 

PART 

(150 cfs)

Calculated 2007–2009

base flow for partialrecord station

02061160 

Elk Creek at Route 668 

near Goode, Va. 

 (22.5 ft3/s)

Figure 13. Relation of discharge measured at partial-record station 02011600 Elk Creek at 

Route 668 near Goode, Virginia, with concurrent mean daily discharge at long-term stream-gaging 

station 02061500 Big Otter River near Evington, Virginia.
Hydrogeology of Piedmont and Blue Ridge Aquifers 31

Town of 

Bedford

Terrapin

RO A NO

Elk Creek

JAMES

Back

Creek

ROANO

*

FLAT

Creek

RIVER

SMITH MOUNTAIN 

LAKE Leesville 

Lake

02061320

02061160

02060860

02060800

02060695 02060692 02060592

02059490

02059459

02059452

02059450

02059420

02061500

02061000

02059485

02059500 #

02059500 #

02059490 V

79°30'

79°15'

37°30'

37°30'

37°15' 37°15'

37°

79°30'

79°45'

37°

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Effective recharge, in inches per year

5.0–6.5

6.6–8.0

8.1–9.5

9.6–11.0

Continuous stream-gaging station

Partial-record stream-gaging station

CAMPBELL COUNTY

FRANKLIN COUNTY

ROANOAKE 

COUNTY

BOTETOURT COUNTY

ROCKBRIDGE

COUNTY

AMHERST COUNTY

City of 

Lynchburg

FEET ABOVE NGVD 29

1,282

98

Roanoke

River

Rockcastle Creek

Mill

Creek

Creek

Creek

Creek

Creek

Falling

Island

Nininger

Goose

Creek

Creek

Enochs

Falling

Creek

Big

Little

Otter

Otter

River

River

Bore Auger

Day

Creek

Creek

Buffalo

Run

Lick

Run

Roaring

Creek

Ivy

Creek

Stony

Creek Johnson

BEDFORD COUNTY

Matts

Creek

Hunting Creek

VV

V

V

V #

V

V

V

V

V

V

V

#

#

#

Base from Esri® Data and Maps, 2008;

Esri World Shaded Relief, 2014;

UTM Zone 17N projection

North American Datum of 1983

PIEDMONT

VALLEY

AND 

RIDGE

COASTAL PLAIN

APPALACHIAN

PLATEAUS

BLUE RIDGE

Location of Bedford County and physiographic provinces in Virginia

Figure 14. Effective recharge as base flow calculated at partial-record stream-gaging stations in Bedford County, Virginia, 

2006–2009.
32 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

0.1

1

10

100

0.1

1

10

100

1 10 100 1,000

Discharge at 02059500 Goose Creek near Huddleston, VA,

in cubic feet per second 

1 10 100 1,000

Discharge at 02059500 Goose Creek near Huddleston, VA,

in cubic feet per second 

A B

C

E

D

Discharge at 02059420 North Fork Goose Creek at

Route 460 at Montvale, VA, in cubic feet per second

Discharge at 02059450 South Fork Goose Creek at

Route 607 at Montvale, VA, in cubic feet per second

Discharge at 02059459 Bore Auger Creek at

Route 754 near Irving, VA, in cubic feet per second

R2 = 0.72

R2 = 0.67

Discharge at 02059452 Goose Creek at Route 726

 near Irving, VA, in cubic feet per second

0.1

1

10

100

0.1

1

10

100

0.1

1

10

100

R2 = 0.88

R2 = 0.82

Discharge at 02059490 Stony Fork at Route 608 

near Moneta, VA, in cubic feet per second

R2 = 0.77

Figure 15. Relation of discharge measured at partial-record stations in the Goose Creek Basin to concurrent mean daily discharge at 

long-term stream-gaging station 02059500 Goose Creek near Huddleston, Virginia.
Hydrogeology of Piedmont and Blue Ridge Aquifers 33

0.1

1

10

100

0.1

1

10

100

1 10 100 1,000

Discharge at 02061500 Big Otter River near Evington, VA,

in cubic feet per second 

Discharge at 02061500 Big Otter River near Evington, VA,

in cubic feet per second 

A B

C

E

D

Discharge at 02060592 Sheep Creek at

Route 688 at Thaxton, VA, in cubic feet per second

Discharge at 02060692 Stony Creek at

Route 43 near Peaks of Otter, VA,

in cubic feet per second

Discharge at 02060800 North Otter Creek at

Route 643 near Cifax, VA, in cubic feet per second

R2 = 0.90

R2 = 0.88

Discharge at 02060695 Big Otter River at Route 43

 near Peaks of Otter, VA, in cubic feet per second

0.1

1

10

100

0.1

1

10

100

0.1

1

10

100

R2 = 0.90 R2 = 0.77

Discharge at 02060860 Oslin Creek at Route 644 

near Cifax, VA, in cubic feet per second

R2 = 0.84

1 10 100 1,000

F

0.1

1

10

100

Discharge at 02061320 Little Otter River at Route 715

near Otter Hill, VA, in cubic feet per second

R2 = 0.98

Figure 16. Relation of discharge measured at partial-record stations in the Big Otter River Basin to concurrent mean daily discharge at 

long-term stream-gaging station 02061500 Big Otter River near Evington, Virginia.
34 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Effluent from Septic Systems

For a typical domestic household discharging to a septic 

system, 84 percent of the indoor water use is assumed to 

return to the aquifer (Horn and others, 2008). Approximately 

43,200 residents who relied on domestic wells for water 

supplies in Bedford County in 2005 (Kenny and others, 2009) 

are assumed to have also discharged wastewater to a typical 

household septic system. If per-capita use from domestic 

wells is 75 gallons per day (gal/d) (Hutson and others, 2004), 

then 2.8 Mgal/d (0.8 in/yr) of water is returned to the aquifer 

by infiltration from septic systems. Return flow from septic 

systems can potentially mitigate adverse effects of aquifer 

pumping, but the fate of water discharged into the shallow 

regolith by septic systems and the rate and timing at which 

wastewater will recharge to deeper bedrock aquifers are 

unknown.

Outflows from Aquifer

The hydrologic budget for any basin must balance the 

quantity of water entering the basin with the quantity of water 

leaving the basin. Outflows from aquifers in Bedford County 

include ET and groundwater withdrawals. Groundwater is an 

important source of freshwater withdrawn from the Piedmont 

and Blue Ridge fractured-rock aquifers for several uses, 

including drinking water, and for commercial, industrial, 

mining, and agricultural purposes. 

Water Use

Annual water-use data for Bedford County were compiled from the Virginia Water Use Data System (VWUDS), a 

State-mandated reporting system for surface- and groundwater 

withdrawals exceeding 10,000 gal/d in any single month. 

VWUDS provides data on specific water-use categories in 

Virginia that are summarized on a county level as part of the 

USGS national water-use estimates (Kenny and others, 2009). 

The USGS summary also includes computed daily estimated 

withdrawal rates attributed to private domestic use based 

on a published per-capita withdrawal coefficient of 75 gal/d 

(Hutson and others, 2004). All withdrawals are reported in 

million gallons per day. 

Bedford County relies on surface-water sources to 

meet most of its residential and industrial demands (fig. 17). 

Surface-water withdrawals primarily support industry along 

the James River and public drinking water supplies for the 

town of Bedford (Virginia Department of Environmental 

Quality, oral commun., 2012). Between the years of 1985 and 

2005, withdrawals from surface-water sources increased from 

12.8 to 13.6 Mgal/d (Kenny and others, 2009). The proportion 

of surface-water withdrawals with respect to total withdrawals, 

however, has steadily declined from 82 to 74 percent during 

this period (fig. 17).

Total groundwater withdrawals from bedrock aquifers in 

Bedford County increased from about 2.80 Mgal/d in 1985 to 

about 4.85 Mgal/d in 2005 (fig. 17; Kenny and others, 2009). 

Domestic withdrawals of groundwater also increased between 

1985 and 2005 from 2.37 Mgal/d to 3.24 Mgal/d, ranging from 

67 to 94 percent of the total, likely as a result of the increase 

in county population by 37,000 residents during that period. 

The domestic withdrawal estimate includes small community 

systems that supply less than the 10,000-gal/d State-mandated 

reporting limit. 

The town of Bedford operates five public-supply wells as 

a backup supply when surface-water sources are insufficient 

to meet public-supply demands. Groundwater used for public 

supply in Bedford County was less than 10 percent of the total 

public supply for 1985, 1995, and 2005 (fig. 17). Groundwater 

withdrawals used for public supply were about 0.17 Mgal/d, or 

6 percent of the total groundwater withdrawals, in 1985, and 

were about 0.07 Mgal/d, or 1 percent of the total groundwater 

withdrawals, in 2005 (Kenny and others, 2009). 

The proportion of groundwater use attributed to mining 

varied considerably between 1985 and 2005. Groundwater 

withdrawals for mining purposes from a single quarry dewatering operation accounted for 1.27 Mgal/d, or 26 percent of 

the total groundwater used, in 2005. Increases in groundwater 

withdrawals used in mining from 1985 to 2005 likely reflect 

inconsistencies in data reporting.

Evapotranspiration

For each basin, total ET was computed by subtracting 

the PART-derived mean streamflow at individual gages from 

the PRISM-derived mean value of precipitation (fig. 12) 

over the respective drainage areas for each gage (tables 3, 6). 

Long-term estimates of total ET accounted for 68 percent 

(30.5 in/yr) of precipitation falling in the Goose Creek Basin 

(station 02059500) and 71 percent (31.4 in/yr) of precipitation 

falling in the Big Otter River Basin (station 02061500). 

These estimates of total ET are within the previous range of 

ET values (23.7 to 31.5 in/yr) for Bedford County that were 

extrapolated from national datasets (Sanford and Selnick, 

2013). Most of the water removed by ET is rerouted to the 

atmosphere by plant uptake prior to reaching the groundwater 

table. RET or direct discharge from the water table by plant 

uptake is included in estimates of total ET, but cannot be 

estimated from the PART data. Rutledge and Mesko (1996) 

noted that RET generally ranges between 1 and 2 in/yr in the 

Appalachian Valley and Ridge, the Piedmont, and the Blue 

Ridge from Alabama to New Jersey, and Sanford and others 

(2012) estimated an RET of 1.2 in/yr for Bedford County 

(table 6). 

Discharge to Surface Waters and Subsurface Outflow

As previously discussed, groundwater discharges from 

the groundwater system in Bedford County as base flow to 

streams and rivers. In the previously described conceptual 

model, the rates of discharge to surface-water bodies 

are assumed to be equal to the rate at which the aquifer 

is recharged by precipitation, which ranges from 5.0 to 

13.7 in/yr (table 6) depending on the method of analysis and 
Simulation of Groundwater Flow 35

1985

2.80 Mgal/d

1995

3.47 Mgal/d

Surface water

74%

Groundwater

26%

Surface water

78%

Groundwater

22%

Surface water

82%

Groundwater

18%

2005

4.85 Mgal/d

Public supply

1%

Domestic supply

67%

Domestic supply

94%

Mining

26%

Mining

1%

Mining

7%

Livestock

1%

Livestock

1%

Irrigation

5%

Industrial

1%

Livestock

1%

Industrial

1%

Public supply

4%

Domestic supply

85%

Public supply

6%

Total Water Withdrawals

Groundwater Withdrawals Year

Figure 17. Water-use estimates for Bedford County, Virginia, 1985–2005 (from Kenny and others, 2009).

the prevailing climatic conditions. Stream gages permit direct 

measurement of stream discharge and estimation of base flow 

for areas draining to Big Otter River and Goose Creek. Direct 

groundwater discharge to the James River or Smith Mountain 

Lake are assumed to be similar in magnitude to that measured 

in the Big Otter River and Goose Creek drainages, but are 

more fully explored in the following sections of this report. 

Subsurface outflow, or groundwater that originates 

in Bedford County and discharges to surface-water bodies 

outside of the county, is assumed to be minimal. The northern 

and southern boundaries of Bedford County are major regional 

drains that likely function as controlling hydrologic boundaries on the outflow of adjacent fractured-rock aquifers. 

Simulation of Groundwater Flow 

Groundwater flow through the fractured-rock aquifer 

underlying Bedford County was simulated by using MODFLOW (Harbaugh, 2005), a three-dimensional finite-difference 

model. The application of MODFLOW was based on the 

common assumption that flow through the fracture network at 

the scale of miles can be represented as flow through porous 

media. This approach has been used in other simulation studies 

of groundwater flow through crystalline rocks (Tiedeman and 

others, 1997). The groundwater-flow model used a steady-state 

simulation to represent equilibrium conditions for the aquifer 

system in December 2010 (fig. 10), a period when water levels 

were near the median levels measured in continuous observation wells (fig. 11). Model simulations were used to compute a 

groundwater budget including sources of recharge and groundwater discharge for the four major drainages within the study 

area. Previously discussed groundwater budgets are constrained 

by watershed boundaries and do not include estimates for all 

areas in Bedford County. Model estimates therefore provide 

additional coverage of areas in Bedford County outside of 

gaged basins. 
36 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Model Design

The model domain was divided into a uniform grid of 

820-ft cells aligned along 229 rows and 280 columns. The 

grid was oriented at an azimuth of 320o to best align model 

boundaries with major surface-water features. The western 

model boundary coincided with the upper watershed divides 

of the major drainages: the James River, Big Otter River, 

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Hydrogeologic units

Cambro-Ordovician metasedimentary rock

Crystalline rock

Late Proterozoic-Cambrian cover rock

Proterozoic basement rock

Model boundary

Drain

General head boundary

Basin boundary

Pumped well

Observation well

Stream gage

79°30'

37°30' 37°30'

37°15'

37°

79°30'

79°15'

79°45'

79°45'

37°

79°15'

37°15'

#

#

#

#

A

A'

Active

model

boundary

James River

Goose

Creek 

SMITH MOUNTAIN

LAKE Leesville

Lake

Big Otter

River 

#

Model grid

boundary

Roanoke

River 

Figure 18. Model domain, boundary conditions, and hydrogeologic units delineated in the Bedford County, Virginia, 

groundwater model.

and Goose Creek (fig. 18). The northern and southern model 

boundaries were delineated along the James River and the 

Roanoke River, respectively. The eastern model boundary 

coincided with local surface-water divides of the major 

drainages downstream of the stream gages that were used 

to measure streamflow within the study area. The resulting 

975-mi2 model domain contains 40,424 active cells (fig. 18).
Simulation of Groundwater Flow 37

Boundary Conditions

Three model layers of increasing thickness with 

depth were used to represent the upper 655 ft of crystalline 

(Proterozoic basement and Late Proterozoic-Cambrian cover 

crystalline rocks) and Cambro-Ordovician metasedimentary 

rock aquifers. The model layers are parallel and were 

constructed to form a subdued reflection of the land surface. 

Model layer 1, the top layer, has minimum and maximum 

thicknesses of 130 and 425 ft, respectively, and represents the 

regolith and upper weathered portion of bedrock. In areas of 

high relief in the western portion of the model domain, the 

thickness of layer 1 reaches the maximum value of 425 ft and 

extends into unweathered bedrock so that the bottom of layer 1 

is smoother than the land surface (fig. 19). Model layers 2 and 

3 have uniform thicknesses of 200 and 330 ft, respectively, 

and represent the fractured bedrock aquifers.

The western, eastern, and bottom model boundaries were 

specified as no-flow (impervious to flow). Head-dependent 

(GHB) boundaries were specified in layer 2 to represent 

discharge to Smith Mountain Lake and Leesville Lake along 

the southern model boundary (fig. 18); the head elevation 

of the GHB boundaries were specified as the mean lake 

stages (795 and 615 ft, respectively). Drain boundaries were 

specified in layer 1 within the model domain and along the 

northern boundary to represent groundwater discharge to the 

major drainages. Head elevations of the drain boundaries were 

calculated from a 100-ft DEM. The conductance C of the GHB 

and drain boundaries is defined as

C KA

L = -------, (3)

where

K is hydraulic conductivity,

A is the cross-sectional flow area of the 

boundary, and

L is the flow-path length across the boundary. 

For the GHB boundary, the flow area A is WB where W is the 

cell width and B is the layer thickness. If the flow-path length 

L is assumed equal to W, then the conductance can be computed as KB, the transmissivity of the model cell.

For drain cells, the flow-path length L is the streambed 

thickness, which is assumed to be 3 ft. The flow area A was 

computed for each cell as the product of the length of the 

stream channel crossing the cell and an assumed stream width. 

Stream widths were based on the location of the channel 

within the drainage network. The widths of the channels of the 

James River and Roanoke River ranged from 16 to 330 ft. The 

widths of the channels of the Big Otter River and Goose Creek 

ranged from 16 to 65 ft. The hydraulic conductivities K for the 

GHB and drain boundaries were insensitive model parameters 

and were specified as 3 feet per day (ft/d) so that groundwater 

discharge through the boundaries was limited by the 1.3- to 

1.7-ft/d hydraulic conductivities of the adjacent crystalline 

fractured-rock aquifers (table 7).

The top model boundary represents recharge as a 

specified flux. The recharge rate was spatially variable and 

assumed to be proportional to the available water, calculated 

as the difference between mean annual precipitation from 

PRISM (Daly and others, 2008) and actual ET. ET was 

estimated from a regression based on national climate and 

land-cover data by Sanford and Selnick (2013). The proportion of the available water that was diverted to recharge (Rch) 

was estimated through model calibration, discussed further 

on. Values of Rch were estimated for three areas within the 

model domain with different degrees of relief, ranging from 

low to steep. Grid cells were assigned to low, moderate, or 

steep slope classes (less than 770 feet per mile [ft/mi], 770 to 

1,540 ft/mi, and more than 1,540 ft/mi, respectively) by using 

a 100-ft DEM to estimate the average surface slope within 

each cell. Pumping from 14 municipal wells was represented 

by constant flux boundaries in layer 2. Reported well depths 

from 7 of the 14 municipal wells averaged 366 ft. Pumping 

rates ranged from 1.3 to 12.6 Mgal/d and were estimated 

from average monthly groundwater withdrawals recorded in 

VWUDS for 2005.
38 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

0 10 20 30 40 45

2,000

1,000

0

Altitude above sea level, in feet

Distance along cross section, in miles

Vertical Exaggeration x20

Model layer:

1

2

3

A A'

Figure 19. Section A-A’ showing thickness of model layers beneath areas with high relief, Bedford County, Virginia. Location of 

section shown in figure 18.

Table 7. Hydraulic properties estimated and specified in Bedford County groundwater-flow model.

[ft/d, foot per day; ft, foot; Shaded values were specified]

Parameter Abbreviation Value

Approximate 

95-percent 

confidence interval

Coefficient 

of variation, 

percent

Horizontal hydraulic conductivity, ft/d

Cambro-Ordovician metasedimentary rocks Kh-carb 15

Proterozoic basement crystalline rocks Kh-base 1.9 0.7 to 1.9 51

Late Proterozoic-Cambrian cover crystalline rocks Kh-cover 1.1 0.3 to 2 32

Faults Kh-fault

1

2

Streambed KDRN 3

General head boundary KGHB 3

Vertical anisotropy

Kh/v-carb 5

Kh/v-base 78.5 26

Kh/v-cover 15.8 56

Kh/v-fault 2

Decay factor, ft–1

λcarb 7.6E-05

λcrystal 1.5E-4

Recharge factor, percent

Shallow slope Rchlow 0.645 40

Moderate slope Rchmod 0.418 60

Steep slope Rchsteep 0.125 73

Standard error of weighted residuals, ft

Water level 42.6

Flow 49.9 1

 Hydraulic conductivity perpendicular to fault specified as 0.02 ft/d.
Simulation of Groundwater Flow 39

Hydraulic Properties

Transmissivity was estimated from specific-capacity data 

from 22 wells drilled into Proterozoic basement crystalline 

rocks and Late Proterozoic-Cambrian cover crystalline rocks 

in Bedford County by using an equation from Todd and Mays 

(2005). Transmissivity values (T) ranged from 7 to 800 feet 

squared per day (ft2/d), with a mean value of 73 ft2/d. Corresponding values of horizontal hydraulic conductivity (Kh

) were 

computed by dividing the T values by the aquifer-saturated 

thickness intercepted by each well. The Kh values ranged from 

0.04 to 8.6 ft/d, with a mean value of 1.7 ft/d, and occupy the 

lower end of the range of mean values reported by Daniel and 

others (1997) for 1,153 wells in three topographic settings in 

fractured crystalline rocks in North Carolina (fig. 20).

The three hydrogeologic units presented earlier (CambroOrdovician metasedimentary rocks, Proterozoic basement 

crystalline rocks, and Late Proterozoic-Cambrian cover 

crystalline rocks) were each delineated as separate zones within 

the model domain and assumed to extend vertically through 

all model layers (figs. 18 and 21). Values of horizontal and 

vertical hydraulic conductivity (Kh and Kv) were estimated 

for each unit through model calibration. Horizontal hydraulic 

conductivity is assumed to be isotropic even though some 

borehole data indicate that the fracture networks within these 

units are aligned regionally along preferential directions (fig. 6). 

Available hydraulic conductivity data are insufficient, however, 

to characterize the differences in horizontal tensors. Hydraulic 

conductivity is assumed to be vertically anisotropic; values 

of vertical anisotropy (Kh/Kv) were estimated through model 

calibration. Assigned hydraulic conductivity values are intended 

only to characterize bulk aquifer properties at a regional scale. 

It is important to note that at the regional scale, data are also 

insufficient to define discrete fracture heterogeneities which 

may supply water at depth. 

In addition, a power function similar to that applied in the 

groundwater-flow model of the Shenandoah Valley by Yager 

and others (2008) was used to relate the decrease in hydraulic 

conductivity Kh in each hydrogeologic unit below a threshold 

depth D below the bedrock surface (fig. 21):

Kdepth = K10–λd (4)

where

Kdepth is the hydraulic conductivity [length/time] at 

depth D [length] below a threshold depth D, 

and

λ is a decay factor [length–1].

The threshold depth for each hydrogeologic unit was set as 

the depth to the bottom of layer 1. Two depth-decay factors 

λ were estimated through model calibration—one for the 

Cambro-Ordovician metasedimentary rock unit and one for 

the combined Proterozoic basement crystalline-rock and Late 

Proterozoic-Cambrian cover crystalline-rock units. 

The specified-thickness approximation (Sheets and others, 

2015) was used to compute transmissivity in model layer 1, 

which is assumed to be unconfined. With this approximation 

model, layer 1 is treated as confined with a specified thickness 

to facilitate the numerical convergence of the groundwater-flow 

equation. The specified thickness was obtained by multiplying 

the model layer 1 thickness by a factor (Satfactor) to account 

for partial saturation:

Satfactor

head bottom

thick

sim = − , (5)

where

headsim is the head computed by a prior simulation, 

bottom is the elevation of the bottom of model layer 1, 

and 

thick is the thickness of model layer 1.

Satfactor was set to 0.05 × thick in areas where the simulated 

head was below the bottom of model layer 1. The value of 

Satfactor was computed iteratively through a sequence of 

simulations until the computed headsim approached stable 

values. Model layers 2 and 3 were also treated as confined, but 

the full layer thicknesses were used to compute the transmissivity of each layer. The specified thickness assumption for model 

layer 1 is appropriate for the steady-state simulation because the 

effect of pumping on the saturated thickness is negligible.

The location of the public-supply wells along mapped 

faults in Bedford County (City of Bedford, Well System 

Drilling Report, unpub. data, 1981) suggests the potential for 

hydraulic conductivity along faults to be larger than that of the 

surrounding fracture network, thereby channeling groundwater 

flow parallel to the fault. Alternatively, faults could be sealed, 

thereby creating low-permeability barriers to flow perpendicular 

to the fault. Faults cutting Blue Ridge and Piedmont rocks are 

extremely complex and not currently well understood. Because 

the faults have experienced multiple phases of deformation, 

structural markers indicating the direction of fault displacement 

are often variable within individual fault systems. Regional 

fault systems such as the Rockfish Valley Fault system in 

the northeastern portion of Bedford County contain both 

extensional and compressional (younger) features (Simpson and 

Kalaghan, 1989; Bailey and Simpson, 1993; Tollo and others, 

2004), while the Bowens Creek Fault system to the southeast 

has a primarily dextral sense of shear with a younger compressional overprint (Edelman and others, 1987; Conley, 1989). The 

Blue Ridge and Peaks of Otter faults are thought to be primarily 

thrust related (Henika, 1981, 1997), while two unnamed faults 

in the central and northeastern portions of the county are shown 

to have a dextral sense of shear (Henika, 1997). 

The hydraulic properties of faults are insensitive model 

parameters and could not be estimated through model calibration because the faults mapped at a 1:100,000 scale are widely 

spaced (Henika, 1997) and appear to have little influence on 

regional groundwater flow. The hydraulic effects of faults, however, are known to be important locally (Seaton and Burbey, 

2005; White and Burbey, 2007), so hydraulic properties of 

faults were specified in the model to reflect larger horizontal 

and vertical hydraulic conductivities than those of the surrounding fracture network. Faults were also specified as horizontally 

anisotropic with the larger hydraulic conductivity value parallel 

to the fault and the smaller value perpendicular to the fault.
40 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

0

2

4

6

8

10

90th percentile

Number of observations

75th percentile

50th percentile

25th percentile

10th percentile

Outlier less than 10th percentile or

 greater than 90th percentile

Hydraulic conductivity estimated with

 Bedford County groundwater-flow

 model

EXPLANATION

22

Range reported

by Daniel and

others (1997)

Hydraulic conductivity, in feet per day

1.5 ft/d

22

Figure 20. Distribution of hydraulic conductivity values computed from specific capacity of crystalline 

bedrock wells in Bedford County, Virginia.

A

metasedimentary

rocks 

VERTICAL EXAGGERATION x 5

fault

Hydraulic conductivity,

in feet per day

EXPLANATION

basement crystalline

rocks 

cover crystalline

rocks 

A'

30

0.3

3

Figure 21. Model layers and hydraulic conductivity zones within model domain, Bedford County, Virginia. Location of 

section A’–A’ shown in figure 18.
Simulation of Groundwater Flow 41

Measured head, in feet Residual, in feet

Simulated head, in feet

A

B

1,300

1,200

1,100

1,000

900

800

700

600

150

100

50

0

–50

–100

–150

600 700 800 900 1,000 1,100 1,200 1,300

1:1 line

Figure 22. Residual plots for heads in Bedford County 

groundwater-flow model: (A) relation between simulated and 

observed values; (B) relation between simulated values and 

weighted residuals. Measured flow, in cubic feet per day

Simulated flow, in cubic feet per day

250

200

150

100

50

0

0 50 100 150 200 250

1:1 line

Figure 23. Residual plot for flows in Bedford County 

groundwater-flow model showing relation between simulated 

and measured values.

Model Calibration

The Bedford County groundwater-flow model was 

calibrated by adjusting hydraulic conductivity and recharge 

values to minimize the difference between simulated groundwater levels and discharges, and those observed in wells and 

at stream gages. Optimum values for model parameters were 

obtained through nonlinear regression by using UCODE 2005 

(Poeter and others, 2005).

Observations

The nonlinear regression compared simulated water 

levels with the water levels measured in 47 bedrock wells in 

December 2010. The open intervals of many of these wells 

are not known (table 2), but drilled wells in the study area 

are typically cased below bedrock (table 4; fig. 7). For wells 

where the open interval was unknown, the assumed measurement depth was computed as midway between land surface 

and the bottom of layer 1. The measurement depths of two 

wells (33G 2 SOW 225 and 34H 5), located in areas where the 

simulated water table was below the bottom of layer 1, were 

specified as midway between the top and bottom of layer 2. 

The weights assigned to all water-level measurements were 

equivalent to a 3-ft standard deviation in measurement error.

Simulated groundwater discharges to drain boundaries 

representing Big Otter River and Goose Creek were compared 

with average base flows computed by PART from streamflow 

measurements obtained from four continuous record streamflow gages (02059485, 02059500, 02061000, and 02061500) 

during the period 2007 through 2012 (table 6). Each stream 

was divided into an upstream and downstream reach based 

on the locations of the four stream gages (fig. 18). The flow 

observations were assigned weights based on an arbitrary 

coefficient of variation in measurement error of 1 percent. 

Although the accuracy of the flow measurements is less than 

this value, the resulting weights in flow observations resulted 

in weighted residuals (observed minus simulated values) 

that were comparable in magnitude with weighted residuals 

in heads, so that both observation groups influenced the 

regression equally.

Model Fit

Residual plots for heads and flows (observed minus 

simulated values) indicate that the model simulates the 

groundwater system reasonably well. Residual plots for 

heads (fig. 22) show little bias in model error with the mean 

weighted residual near zero. The standard error (SE) of the 

weighted residuals for water level is 42.6 ft, which is less than 

7 percent of the 685-ft range in head (table 7). Nearly all the 

simulated heads are within 100 ft of the measured value.

Simulated groundwater discharge to Big Otter River and 

Goose Creek closely match base flow estimated by PART 

for the period 2007 through 2012 with little bias (fig. 23). 
42 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Simulated flows are within 10 percent of the measured flow at 

three of the stream gages. The largest error (23 percent) is for 

the upstream gage on Big Otter River. At a scale of hundreds 

of square miles, the error in head and flow is acceptable for an 

exercise in conceptual understanding; however, extrapolation 

of model results to smaller-scale domains would require 

additional hydrogeologic detail than is currently (2014) 

available. 

Parameters

Fifteen parameter values were specified in the model, 8 of 

which were optimized through nonlinear regression (table 7). 

Coefficients of variation (cv) for the hydraulic conductivity 

parameters ranged from 26 to 56 percent. The cv for the 

recharge parameters ranged from 40 to 73 percent. These cv 

values indicate that the regression is relatively sensitive to most 

of the estimated parameters, but that the values are not particularly well estimated. Values of K for Proterozoic basement and 

Late Proterozoic-Cambrian cover crystalline rocks are similar 

(table 7), indicating little difference in permeability between 

these two units. Daniel and others (1997) reached a similar 

conclusion with respect to five hydrogeologic units delineated 

within crystalline rocks in North Carolina. The estimated 

depth-decay factor for crystalline rocks (5.5×10-4 ft–1) resulted in 

an 80 percent reduction in Kh at a depth of 400 ft in model layer 

3, which compares favorably with the range of 60 to 90 percent 

reduction in Kh at a depth of 300 ft estimated by Daniel and 

others (1997) for crystalline bedrock wells in North Carolina.

Estimated recharge factors ranged from about 42 percent 

of available water (PR–ET) for moderate to steep slopes, to 

64 percent of available water for shallow slopes. Recharge 

values applied to model cells ranged from 4 in/yr near streams 

and in the southeastern corner of the model domain, to 28 in/yr 

in isolated flat areas in uplands near the northwestern corner 

(fig. 24). The mean recharge value within the model domain 

was 9.4 in/yr, which is similar to the mean long-term base 

flow computed using hydrograph separation for Goose Creek 

(8.3 in/yr at continuous station 02059500) and Big Otter River 

(9.3 in/yr at continuous station 02061500). The spatial distribution of recharge reflects the grid resolution of the PRISM data 

used to estimate precipitation within the model domain (fig. 24).

Model Application

The hydraulic head distribution computed by using the 

Bedford County model indicates that groundwater flows 

towards the major drainages within the model domain and 

that the water table reflects the pattern of the stream network 

(fig. 25). The highest water levels are in the uplands along 

watershed divides and along the northwest model boundary. 

The distribution of head residuals indicates no spatial bias in the 

model (fig. 25). 

The water budget computed by the Bedford County 

model indicates that nearly all the recharge within each major 

watershed discharges to the drainage network within that 

watershed (table 8). The distribution of recharge and discharge 

is generally proportionate to the drainage area of the four major 

basins, although the Goose Creek and James River Basins 

derive about 7 percent of their discharge as underflow from 

adjacent watersheds. The Big Otter River receives 40.8 percent 

of the total daily groundwater outflow from fractured-rock 

aquifers in Bedford County; Goose Creek receives 25.8 percent, 

the James River receives 18.2 percent, and Smith Mountain and 

Leesville Lakes receive 15.2 percent (fig. 26). The volume of 

public-supply pumping within the model domain (not indicated 

in table 8) is a small part of the water budget and represents 

0.2 percent of the total groundwater outflow.

Model Limitations 

The Bedford County groundwater-flow model was 

constructed to represent recent (December 2010) steady-state 

conditions when recharge and water levels are near their longterm averages, and not extreme conditions, such as drought. The 

model could be modified to simulate transient conditions with 

varying recharge, but this would necessitate the specification of 

values for specific yield in the model. Continuous water-level 

monitoring for periods of 3 or more years at multiple wells 

could supply the required information to estimate this model 

parameter. Simulation of transient conditions could have the 

additional benefit of supporting an estimate of the volume of 

groundwater stored within the model domain.

The volume of pumping within the model domain is 

small and exerts little stress on the aquifer system. The values 

of hydraulic parameters estimated through model calibration 

are based on limited data, including base-flow volumes and 

water-level observations at 47 wells. The uncertainty in the 

parameter values is reflected by the relatively large coefficients 

of variation associated with the estimates. In addition, although 

the hydraulic conductivity of the fracture network varies over 

4 orders of magnitude, uniform values of Kh are specified 

within the model. As a result, computed water levels likely will 

differ from those measured locally in wells, as indicated by the 

standard error (45.6 ft) and scatter in the head residuals (fig. 22). 

Other approaches could include anisotropy in Kh to account for 

the preferential alignment of fractures noted in borehole logs 

(fig. 6). Finally, computed water levels are likely underpredicted 

in upland areas as a result of the specified-thickness approximation for model layer 1. More accurate results could be obtained 

by treating model layers 1 and 2 as convertible, that is, either 

confined or unconfined. This representation would require the 

application of the Newton solver (Niswonger and others, 2011), 

however, which does not support the depiction of directional 

permeability along faults that was used in the current model. 

Despite these limitations, the model provides accurate estimates 

of the rate and direction of regional groundwater flow and 

serves as a solid basis for future modifications to simulate the 

aquifer system in greater detail.
Simulation of Groundwater Flow 43

0 12.5 KILOMETERS

0 15 MILES

EXPLANATION

Annual recharge, in inches

Less than 5

5.1 to 7

7.1 to 9

9.1 to 11

11.1 to 13

13.1 to 15

More than 15

Stream

79°30'

37°30' 37°30'

37°15'

37°

79°30'

79°15'

79°45'

79°45'

37°

79°15'

37°15'

Active

model

boundary

James River

SMITH MOUNTAIN

LAKE

Model grid

boundary

Figure 24. Distribution of annual recharge for steady-state conditions in the Bedford County groundwater-flow model.
44 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

0 12.5 KILOMETERS

0 15 MILES

79°30’

37°30’ 37°30’

37°15’

37°

79°30’

79°15’

79°45’

79°45’

37°

79°15’

37°15’

EXPLANATION

Water-table altitude, in feet

Residual (difference between observed

and simulated water level), in feet

501 to 600

601 to 700

701 to 800

801 to 900

901 to 1,000

1,001 to 1,100

1,101 to 1,200

1,201 to 1,300

1,301 to 1,400

1,401 to 1,500

1,501 to 1,600

1,601 to 1,700

1,701 to 1,800

More than 1,800

Less than –50

–50 to –25

–24 to 24

25 to 50

More than 50

Active

model

boundary

Model grid

boundary

!

!

!

!

!

!

!

!!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

Figure 25. Water table simulated for steady-state conditions by the Bedford County groundwater-flow model.
Summary and Conclusions 45

Table 8. Simulated water budget for Bedford County groundwater-flow model.

[ft3/d, cubic foot per day] 

Source Inflow volume 

(105 ft3/d) Percent Discharge Outflow volume (105 ft3/d) Percent

Recharge Base flow

James River 9.8 16.9 James River 10.5 18.2

Big Otter River 23.5 40.5 Big Otter River 23.5 40.8

Goose Creek 14.1 24.3 Goose Creek 14.9 25.8

Smith Mountain & Leesville Lakes 10.6 18.3 Smith Mountain & Leesville Lakes 8.8 15.2

Total 58.0 100.0 57.7 100.0

James River

18.2%

Goose Creek

25.8%

Big Otter River

40.8%

Smith Mountain and 

Leesville Lakes

15.2%

Public-supply wells

0.2%

Note: Numbers may not add up to 100 percent because of independent rounding.

Figure 26. Proportion of groundwater flow through major basins, 

Bedford County, Virginia.

Summary and Conclusions

Groundwater resources in Bedford County, Virginia, 

include water that is stored in and flows through Piedmont 

and Blue Ridge regolith and fractured-rock aquifers. The 

fractured-rock aquifers in Bedford County were subdivided 

into three hydrogeologic units based on rock type: CambroOrdovician metasedimentary rocks, Proterozoic basement 

crystalline rocks, and Late Proterozoic-Cambrian cover 

crystalline rocks. Cambro-Ordovician metasedimentary 

rocks in the northwest part of the county have the highest 

driller-reported well yields, largest depth to bedrock, and 

highest model calibrated hydraulic conductivity of the three 

hydrogeologic units. Mean reported drillers’ well yields 

and model-calibrated hydraulic conductivity in Proterozoic 

basement and Late Proterozoic-Cambrian cover crystallinerock units were similar. Well characteristics and model results 

indicate little difference between the crystalline-rock units in 

Bedford County, a conclusion that is supported by findings 

in geologically similar areas of North Carolina. Reported 

seasonally dry wells or low-yielding wells in the southeastern 

portion of the county cannot be explained by rock type but 

likely reflect local heterogeneities that are beyond the scope of 

this study.

Groundwater levels for the period of study (2009–2013) 

were found to vary only a few feet in response to seasonal 

changes in climate conditions. Because the water level mimics 

land surface, groundwater flow is topographically driven. 

Groundwater flows from upland areas to local streams and 

rivers such that surface-water divides are coincident with 

groundwater divides. 

A water budget for the county shows model-calibrated 

recharge rates that mimic precipitation patterns and range from 

4 inches per year (in/yr) near streams to 28 in/yr in upland 
46 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

areas of the Blue Ridge Physiographic Province. The mean 

rate of recharge from model results is 9.4 in/yr, a value equivalent to the long-term mean from hydrograph separation of 

streamflow in the Big Otter River. An expanding rural population has resulted in an increase in the groundwater use in 

Bedford County from 2.80 million gallons per day (Mgal/d) to 

4.85 Mgal/d between 1985 and 2005. Evapotranspiration rates 

ranged from 30.5 to 31.4 in/yr based on streamflow and are 

within the higher end of the 23.7- to 31.5-in/yr range of values 

from national datasets. The percent volume of groundwater 

discharging from Piedmont and Blue Ridge fractured-rock 

aquifers of Bedford County is proportional to the drainage 

area of the four major basins: Big Otter River (40.8 percent), 

Goose Creek (25.8 percent), James River (18.2 percent), and 

Smith Mountain and Leesville Lakes (15.2 percent). 

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Appendix 1. Borehole Geophysical Logs
50 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia

Figure 1–1. Borehole geophsyical logs from well 33G 7 in Bedford County, Virginia.

 Dip Angle of Feature

0 90

ATV Image

° 072 ° 09 ° 081 ° 0 ° 0

Natural Gamma

RG-I PA 003 0

Caliper

6 8 INCH

Res(16N)

M- MHO 0004 0

Res (64N)

M- MHO 0004 0

Lateral

M- MHO 0004 0

Ambient Fluid Temp

F GED 95 55

Pumping Fluid Temp

F GED 95 55

Ambient Fluid Res

M- MHO 041 01

Pumping Fluid Res

M- MHO 041 01

Ambient Flow Stations

NI M/ LAG 53 53-

NI M/ LAG 53 53-

0.0

50.0

100.0150.0200.0250.0

DEGREES

Depth, in feet below land surface

7.63 ft below land 

surface 

on 6/22/2011 

Casing to 55 ft

below

land surface 

EXPLANATION

Transmissive fracture

Fracture

Foliation

Water level
Figure 1–2. Borehole geophsyical logs from well 33G 2 SOW 225 in Bedford County, Virginia.

 Dip Angle of Feature

0 90

ATV Image

° 072 ° 09 ° 081 ° 0 ° 0

Natural Gamma

RG-I PA 003 0

Caliper

6 8 INCH

Res (16N)

M- MHO 0004 0

Res (64N)

M- MHO 0004 0

Lateral

M- MHO 0004 0

Ambient Fluid Temp

Pumping Fluid Temp

Ambient Fluid Res

Pumping Fluid Res

Ambient Flow Stations

0.0

50.0

100.0150.0200.0

DEGREES

Depth, in feet below land surface

55 57 DEG F

55 57 DEG F

M- MHO 091 571

M- MHO 091 571

NI M/ LAG 5. 1 5. 1-

NI M/ LAG 5. 1 5. 1-

Pumping Flow Stations

EXPLANATION

Transmissive fracture

Fracture

Foliation

Water level

47.93 ft below 

land surface 

on 8/8/2008

Casing to

70 ft

below

land surface 

Appendix 1 51
52 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia Figure 1–3. Borehole geophsyical logs from well 35H 1 SOW 226 in Bedford County, Virginia. Dip Angle of Feature

0 90

ATV Image

° 072 ° 09 ° 081 ° 0 ° 0

Natural Gamma

RG-I PA 003 0

Caliper

6 8 INCH

Res(16N)

M- MHO 0004 0

Res (64N)

M- MHO 0004 0

Lateral

M- MHO 0004 0

Ambient Fluid Temp

Pumping Fluid Temp

Ambient Fluid Res

Pumping Fluid Res

Ambient Flow Stations

0.0

50.0

100.0150.0200.0

DEGREES

Depth, in feet below land surface

62 65 DEG F

62 65 DEG F

M- MHO 06 52

M- MHO 06 52

NI M/ LAG 5. 4 5. 4-

NI M/ LAG 5. 4 5. 4-

EXPLANATION

Transmissive fracture

Foliation

Water level

Pumping Flow Stations

18.65 ft below 

land surface 

on 9/3/2008

Casing to

38 ft

below

land surface 
Figure 1–4. Borehole geophsyical logs from well 33G 1 SOW 224 in Bedford County, Virginia.

 Dip Angle of Feature

0 90

ATV Image

° 072 ° 09 ° 081 ° 0 ° 0

Natural Gamma

RG-I PA 003 0

Caliper

INCH

Res(16N)

M- MHO 0004 0

Res (64N)

M- MHO 0004 0

Lateral

M- MHO 0004 0

Ambient Fluid Temp

Pumping Fluid Temp

Ambient Fluid Res

Pumping Fluid Res

Ambient Flow Stations

0.0

DEGREES

Depth, in feet below land surface 25.0 50.0 75.0

100.0

6 9

62 63 DEG F

62 63 DEG F M- MHO 7. 3 5. 3

M- MHO 7. 3 5. 3 NI M/ LAG 2 2-

NI M/ LAG 2 2-

EXPLANATION

Transmissive fracture

Fracture

Bedding

Water level

Pumping Flow Stations

11.63 ft below 

land surface 

on 7/31/2008

Casing to 51 ft

below

land surface 

Appendix 1 53
54 Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia Dip Angle of Feature

0 90

Caliper

6 9 INCH

Res(16N)

Res (64N)

Lateral

Ambient Fluid Temp

F GED 25 05

Ambient Fluid Res

DEGREES

Depth, in feet below land surface

ATV Image

° 072 ° 09 ° 081 ° 0 ° 0

Natural Gamma

RG-I PA 054 0

0.0

50.0

100.0150.0200.0250.0300.0

350.0

Res

MHO 0004 0 M- MHO 012 011

129.99 ft below 

land surface 

on 8/19/2010

Cascading water 

from fracture at

103.8 ft

below land surface

Casing to 85 ft

below

land surface 

EXPLANATION

Transmissive fracture

Fracture

Bedding

Foliation

Water level

Figure 1–5. Borehole geophsyical logs from well 34E 1 in Bedford County, Virginia.
Manuscript was approved on July 30, 2015

For further information about this publication, 

contact:

Director

USGS Virginia Water Science Center

1730 East Parham Road

Richmond, VA 23228

(804) 261-2600

Or visit the Virginia Water Science Center

Web site at http://va.water.usgs.gov

Publishing support provided by the USGS Science 

Publishing Network, Raleigh Publishing 

Service Center


Printed on recycled paper

McCoy and others—Hydrogeology and Simulation of Groundwater Flow in Fractured-Rock Aquifers, Bedford County, Virginia—Scientific Investigations Report 2015–5113

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155113