Prepared in cooperation with the Triangle J Council of Governments Cape Fear River Flow 

Study Committee and the North Carolina Department of Environment and Natural Resources, 

Division of Water Resources

Determination of Flow Losses in the Cape Fear River 

between B. Everett Jordan Lake and Lillington, North 

Carolina, 2008–2010

Scientific Investigations Report 2012–5226

U.S. Department of the Interior

U.S. Geological Survey
Front cover. Left: Brad Huffman (USGS) towing a multifrequency electromagnetic sensor behind a boat on the Cape Fear River upstream 

from Lillington, North Carolina (N.C.), July 10, 2009. Top right: Wildlife on the diversion canal adjacent to Cape Fear River near Buckhorn 

Dam, September 9, 2009. Bottom right: Streamgage at USGS station 02098198 on Haw R below B. Everett Jordan Dam near Moncure, N.C., 

November 19, 2009. All photos by Curtis Weaver.

Back cover. Left: Industrial water withdrawal intake on Haw River below B. Everett Jordan Lake, June 24, 2009 (photo by Curtis Weaver).

Top right: Geoff Cartano (USGS) making discharge measurements at USGS station 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, N.C., April 27, 2009 (photo by Curtis Weaver). Middle right: Piezometer transect at Bradley Road near Lillington, N.C. (USGS 

station 352630078511401), July 21, 2009 (photo by Kristen McSwain, USGS). Bottom: B. Everett Jordan Dam, August 15, 2002 (photo by 

Bobby Ragland, USGS).
Determination of Flow Losses in the Cape 

Fear River between B. Everett Jordan Lake 

and Lillington, North Carolina, 2008–2010

By J. Curtis Weaver and Kristen Bukowski McSwain

Prepared in cooperation with the Triangle J Council of Governments Cape Fear 

River Flow Study Committee and the North Carolina Department of Environment 

and Natural Resources, Division of Water Resources

Scientific Investigations Report 2012–5226

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2013

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Weaver, J.C., and McSwain, K.B., 2013, Determination of flow losses in the Cape Fear River between B. Everett 

Jordan Lake and Lillington, North Carolina, 2008–2010: U.S. Geological Survey Scientific Investigations Report 

2012–5226, 76 p., http://pubs.usgs.gov/sir/2012/5226.
iii

Acknowledgments

Support for this study was provided by the North Carolina Division of Water Resources and with 

the following local cooperators who provided funding through the Triangle J Council of Governments Cape Fear River Flow Study Committee: Cape Fear Public Utility Authority, Town of Cary 

Water Resources, Chatham County Public Works, City of Durham Water Management, Public 

Works Commission of the City of Fayetteville, Harnett County Public Utilities, Town of Holly 

Springs Engineering, Lower Cape Fear Water and Sewer Authority, Town of Morrisville Engineering, Orange Water and Sewer Authority, City of Sanford Public Works, Wake County, and DuPont 

Company (Fayetteville Works).

The authors acknowledge Mr. Tom Fransen of the N.C. Division of Water Resources; Mr. Mike 

Schlegel and Mr. Sydney Miller (formerly) of the Triangle J Council of Governments; and 

Mr. Mick Noland of the Fayetteville Public Works Commission. Their foresight and leadership in 

areas of water management as well as their assistance and support of this study have improved 

the understanding of the complex flow patterns in this reach of the Cape Fear River.

The authors gratefully acknowledge the assistance provided by Ms. Ashley Hatchell and Mr. Tony 

Young of the U.S. Army Corps of Engineers, Wilmington District, during the study. Ms. Hatchell 

and Mr. Young collaborated with the U.S. Geological Survey on flow releases from Jordan Lake 

Dam during synoptic discharge measurement runs and other critical data-collection events.

Progress Energy Carolinas provided assistance in this investigation. The authors acknowledge 

Mr. Mick Greeson and Ms. Robin Bryson for their support in the operation of a streamgage on 

the diversion canal adjacent to the Cape Fear River. Mr. Greeson and Ms. Bryson were instrumental in providing data concerning water withdrawals from the Cape Fear River into a regional 

power plant and in obtaining permission to operate a cluster of groundwater piezometers on 

property owned by the company.

Water-use information provided by Mr. Don Rayno (North Carolina Division of Water Resources), 

Ms. Carolyn Underwood (Uniboard), Mr. Brad Crawford (Arclin), Mr. Brian Van Gelden (Moncure 

Plywood), Mr. Charles Powell, Mr. Marty Stewart (Perfomance Fibers), and Mr. Warren Paschal 

(General Shale Brick) allowed for a better understanding of the industrial water usage in the 

study area. Information concerning municipal water use from the Cape Fear River was provided 

by Mr. Victor Czar and Mr. Scott Christiansen (City of Sanford), and Mr. Charles Fiero and 

Mr. Allan O’Briant (Harnett County Public Utilities).

The authors also acknowledge Mr. William Brooks, owner of the Lockville Hydropower Dam, for 

providing information concerning the operations at this facility. Access to the Cape Fear River 

was made possible by the use of privately owned boat ramps graciously provided by Mr. Charles 

Stirewalt and Mr. Mike Taylor. Additionally, the authors thank Mr. Mike Taylor for allowing 

property access to monitor a cluster of groundwater piezometers.

v

Contents

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

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................4

Study Area and Possible Factors Affecting Flow Loss...................................................................4

Geologic Setting....................................................................................................................................8

Data Collection and Methods for Assessing Flow Patterns in the Cape Fear River ..........................8

Surface Water.......................................................................................................................................8

Flow Loss Analyses .....................................................................................................................9

Synoptic Discharge Measurements.........................................................................................9

Streamgage Data Collection....................................................................................................11

Analyses of Ratings and Measured Discharges ..................................................................12

Water Use ...................................................................................................................................13

Evaporation.................................................................................................................................13

Groundwater and Surface-Water Interaction ...............................................................................14

Electromagnetic Geophysical Survey ....................................................................................14

Groundwater Temperature.......................................................................................................15

Distributed-Temperature Sensing (DTS) Survey .........................................................15

Thermal Infrared (TIR) Survey ........................................................................................15

Piezometer Transects................................................................................................................16

Continuous Monitoring .............................................................................................................16

Results and Interpretation of Data ...........................................................................................................16

Surface Water.....................................................................................................................................16

Flow Loss Analyses ...................................................................................................................19

Synoptic Discharge Measurements.......................................................................................22

Streamgage Data Collection and Analyses...........................................................................40

Analyses of Ratings and Measured Discharges .........................................................40

Streamgage at Haw River below B. Everett Jordan Dam..........................................44

Stage-Only Streamgage on Cape Fear River at Buckhorn Dam...............................44

Water Use ...................................................................................................................................46

Lockville Hydropower Station ........................................................................................50

Regional Power-Plant Diversion and Flow through Diversion Canal.......................52

Evaporative Losses....................................................................................................................52

Comparisons of Water Use, Evaporation, and Flow-Loss Occurrences during 

2008–2010.......................................................................................................................54

Effects of Diversion Canal Flows on Cape Fear River at Lillington....................................54

Groundwater and Surface-Water Interaction ...............................................................................57

Electromagnetic Geophysical Survey ....................................................................................58

Groundwater Temperature.......................................................................................................58

Distributed Temperature Sensing (DTS) Survey..........................................................59

Thermal Infrared (TIR) Imaging ......................................................................................61

Hydrogeology..............................................................................................................................63

Continuous Monitoring .............................................................................................................64

Causes of Flow Losses Based on Results of Data Analyses.......................................................68

Summary and Conclusions.........................................................................................................................69
vi

Selected References...................................................................................................................................71

Appendix 1. A Brief Primer on Discharge Measurements and Ratings Analyses ........................75

Figures

1. Map showing location of study area between B. Everett Jordan Lake and

Lillington, North Carolina.............................................................................................................3

2. Drainage area and elevation profiles on the Haw and Cape Fear Rivers between

Jordan Lake Dam and Lillington, North Carolina.....................................................................4

3. Photograph of Cape Fear River at Buckhorn Dam near Corinth, North Carolina ..............8

4. Map showing lithotectonic geologic units in the Cape Fear River study area,

North Carolina ...............................................................................................................................9

5. Photograph showing an example of a diabase dike that vertically intrudes the

subsurface of a quarry near Cary, North Carolina................................................................10

6. Map showing locations upstream from Cape Fear River at Buckhorn Dam where

discharge measurements were made during the series of synoptic

measurements in 2009 ...............................................................................................................11

7. Map showing locations downstream from Cape Fear River at Buckhorn Dam

where discharge measurements were made during the series of synoptic

measurements in 2009 ...............................................................................................................12

8. Map showing locations of nearby National Oceanic and Atmospheric

Administration National Weather Service cooperative observer stations where

daily reference, open-water evaporation data were compiled for the study based

on the Penman-Monteith method ...........................................................................................15

9. Cross sections showing piezometer profiles and soils encountered at the regional

power plant transect near Corinth and Bradley Road transect near Lillington,

North Carolina .............................................................................................................................18

10. Graphs showing daily mean and instantaneous discharges in the Cape Fear River

and tributaries, North Carolina, during October 5–14, 2007, with daily and 7-day

flow losses based on daily discharge flow comparison 3 ...................................................21

11. Graphs showing daily mean and instantaneous discharges for days prior to and

following April 24, 1998, on which maximum flow loss occurred in the Cape Fear

River and tributaries, North Carolina, based on daily discharge flow comparison 3 .........21

12. Histograms of filtered flow-loss occurrences in the Cape Fear River determined in

flow comparison 3 based on daily mean discharge, flow-loss amount, percentage

of daily mean discharge, and month of occurrence.............................................................23

13. Graph showing discharges measured during a series of six synoptic discharge

measurements in 2009 on the Haw and Cape Fear Rivers between Jordan Lake

Dam and Lillington, North Carolina..........................................................................................24

14. Graph showing measured discharges on April 27, 2009, on the Haw and Cape

Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.............................24

15. Graph showing measured discharges on June 25, 2009, on the Haw and Cape

Fear Rivers between Jordan Lake Dam and Lillington, North Carolina............................25

16. Graph showing measured discharges on July 22, 2009, on the Haw and Cape Fear

Rivers between Jordan Lake Dam and Lillington, North Carolina......................................25

17. Graph showing measured discharges on August 18, 2009, on the Haw and Cape

Fear Rivers between Jordan Lake Dam and Lillington, North Carolina............................26

18. Graph showing measured discharges on September 9, 2009, on the Haw and

Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina ..................26
vii

19. Graph showing measured discharges on October 1, 2009, on the Haw and Cape

Fear Rivers between Jordan Lake Dam and Lillington, North Carolina............................27

20. Graphs showing average velocities and channel widths determined from the

series of synoptic measurements made during 2009 on the Haw and Cape Fear

Rivers between Jordan Lake Dam and Lillington, North Carolina......................................41

21. Graphs showing quality ratings of discharge measurements and percentage

differences from shifted, where applied, base rating at Deep River at Moncure,

North Carolina, during the 1982–2011 water years ...............................................................42

22. Graphs showing quality ratings of discharge measurements and percentage

differences from shifted, where applied, base rating at Cape Fear River at

Lillington, North Carolina, during the 1982–2011 water years.............................................43

23. Graphs showing full range of measured discharges at Haw River below B. Everett

Jordan Lake near Moncure, North Carolina, and measured discharges less than

2,000 cubic feet per second ......................................................................................................46

24. Graph showing instantaneous elevation of water surface on the Cape Fear River

at Buckhorn Dam near Corinth, North Carolina, November 2008 through July 2010 ......47

25. Graphs showing flow diversions at industrial facility on the Haw River during

2006–2010, and regional power plant during 2008–2010, North Carolina .........................49

26. Graphs showing water use reported for municipal facility F9 for 1986–2010, and

municipal facility F10 for 2006–2010 in the Cape Fear River study area, North Carolina........51

27. Graphs showing estimated open-water evaporation and equivalent flow loss in

the study reach from potential open-water evaporation based on the

Penman-Monteith model at five nearby National Oceanic and Atmospheric

Administration stations and pan-evaporation data for the Chapel Hill 2W 

NOAA station...............................................................................................................................53

28. Hydrograph showing effect of changes in instantaneous discharges at diversion

canal streamgage and Cape Fear River at Lillington, North Carolina, on

September 15–19, 2009 ..............................................................................................................55

29. Hydrograph showing effect of changes in instantaneous discharges at diversion

canal streamgage and Cape Fear River at Lillington, North Carolina, on November

1, 2009 ...........................................................................................................................................56

30. Hydrograph showing effect of changes in instantaneous discharges at diversion

canal streamgage and Cape Fear River at Lillington, North Carolina, on October

28, 2010 .........................................................................................................................................56

31. Hydrograph showing effect of changes in instantaneous discharges at diversion

canal streamgage and Cape Fear River at Lillington, North Carolina, on 

December 3, 2010........................................................................................................................57

32. Map showing locations of increased magnetic anomalies in the upstream reach

from Buckhorn Dam, North Carolina .......................................................................................59

33. Map showing locations of increased magnetic anomalies in the downstream

reach from Buckhorn Dam, North Carolina............................................................................60

34. Maps of results of the FO-DTS survey showing temperature of the river bottom on

August 12, 2009, at midnight, 0600 hours, noon, and 1800 hours in the Cape Fear

River near Raven Rock State Park, North Carolina..............................................................61

35. Map showing areas of groundwater discharge to the Cape Fear River between 

Jordan Lake Dam and Lillington, North Carolina, identified by thermal infrared 

imaging, February 27, 2010 ........................................................................................................62

36. Hydrographs showing daily precipitation measured at the Siler City Airport, daily

mean water level and calculated hydraulic gradients at the regional power plant

piezometer transect near Corinth, and daily mean streamflow measured in the

Cape Fear River at Lillington, North Carolina.........................................................................65
viii

37. Hydrographs showing daily precipitation measured at the Fayetteville Public

Works Commission Cooperative station, daily mean water level and calculated

hydraulic gradients at the Bradley Road piezometer transect near Lillington, and

daily mean streamflow measured in the Cape Fear River at Lillington, North Carolina.66

38. Cross section showing piezometers and interpolated lines of equivalent pressure

head under gaining- and losing-stream conditions at the regional power plant

transect near Corinth, North Carolina.....................................................................................67

39. Cross section showing piezometers and interpolated lines of equivalent pressure

head under gaining- and losing-stream conditions at the Bradley Road transect

near Lillington, North Carolina..................................................................................................68

1–1. Schematic showing theoretical shift in stage-discharge rating in response to

changes in river channel geometry.........................................................................................75

Tables

1. Continuous- and partial-record U.S. Geological Survey surface-water sites in the

Cape Fear River study area, North Carolina.............................................................................6

2. Characteristics of the piezometers and adjacent surface-water sites on the Cape

Fear River in Chatham and Harnett Counties, North Carolina.............................................17

3. Number of days with flow loss and flow-loss statistics for the Haw, Deep, and

Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina, for

the periods January 1963 to December 1970 and the 1983 - 2010 water years................20

4. Results of synoptic discharge measurements made on April 27, 2009, on the Haw

and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina...........28

5. Results of synoptic discharge measurements made on June 25, 2009, on the Haw

and Cape Fear Rivers between Jordan Lake Dam and Lillilngton, North Carolina..........30

6. Results of synoptic discharge measurements made on July 22, 2009, on the Haw

and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina...........32

7. Results of synoptic discharge measurements made on August 18, 2009, on the

Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina .............................................................................................................................34

8. Results of synoptic discharge measurements made on September 9, 2009, on the

Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina .............................................................................................................................36

9. Results of synoptic discharge measurements made on October 1, 2009, on the

Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina .............................................................................................................................38

10. U.S. Geological Survey discharge measurements made at Haw River below 

B. Everett Jordan Lake near Moncure, North Carolina, and reported hourly flow

releases from Jordan Lake Dam, December 2008 through December 2010.....................45

11. Summary of selected surface-water withdrawals and return point-source

discharges in the Cape Fear study reach, North Carolina...................................................48
ix

Conversion Factors

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)

yard (yd) 0.9144 meter (m)

Area

acre 4,047 square meter (m2

)

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

cubic foot per second (ft3

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

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)

Hydraulic gradient

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

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

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

(NGVD 29) and North American Vertical Datum of 1988 (NAVD 88) unless otherwise noted.

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

Altitude, as used in this report, refers to distance of groundwater level (or water table) above 

the vertical datum.

Elevation, as used in this report, refers to distance of surface-water level (stage or gage height) 

or land surface above the vertical datum.
x

Abbreviations

DMR discharge monitoring report

DTS distributed temperature sensing (survey)

EM electromagnetic

ET evapotranspiration

FAO Food and Agricultural Organization

FERC Federal Energy Regulatory Commission

FO-DTS fiber-optic distributed-temperature sensing

GPS global positioning system

Hz hertz

kW kilowatt

NOAA National Oceanic and Atmospheric Administration

NWIS National Water Information System

ppm parts per million

PVC polyvinyl chloride

PZ piezometer (groundwater transect)

RTK Real-Time Kinematic (GPS equipment)

TIR thermal infrared (imaging)

USACE U.S. Army Corps of Engineers

USGS U.S. Geological Survey
Determination of Flow Losses in the Cape Fear River 

between B. Everett Jordan Lake and Lillington, North 

Carolina, 2008–2010

By J. Curtis Weaver and Kristen Bukowski McSwain

Abstract

During 2008–2010, the U.S. Geological Survey conducted 

a hydrologic investigation in cooperation with the Triangle J 

Council of Governments Cape Fear River Flow Study Committee and the North Carolina Division of Water Resources 

to collect hydrologic data in the Cape Fear River between 

B. Everett Jordan Lake and Lillington in central North Carolina to help determine if suspected flow losses occur in the 

reach. Flow loss analyses were completed by summing the 

daily flow releases at Jordan Lake Dam with the daily discharges at Deep River at Moncure and Buckhorn Creek near 

Corinth, then subtracting these values from the daily discharges at Cape Fear River at Lillington. Examination of longterm records revealed that during 10,227 days of the 1983–

2010 water years,1 408 days (4.0 percent) had flow loss when 

conditions were relatively steady with respect to the previous 

day’s records. The flow loss that occurred on these 408 days 

ranged from 0.49 to 2,150 cubic feet per second with a median 

flow loss of 37.2 cubic feet per second. The months with the 

highest number of days with flow losses were June (16.7 percent), September (16.9 percent), and October (19.4 percent).

A series of synoptic discharge measurements made on 

six separate days in 2009 provided “snapshots” of overall flow 

conditions along the study reach. The largest water diversion 

is just downstream from the confluence of the Haw and Deep 

Rivers, and discharges substantially decrease in the main stem 

downstream from the intake point. Downstream from Buckhorn Dam, minimal gain or loss between the dam and Raven 

Rock State Park was noted.

Analyses of discharge measurements and ratings for two 

streamgages—one at Deep River at Moncure and the other at 

Cape Fear River at Lillington—were completed to address the 

accuracy of the relation between stage and discharge at these 

sites. The ratings analyses did not indicate a particular time 

during the 1982–2011 water years in which a consistent bias 

occurred in the computations of discharge records that would 

indicate false flow losses.

1 A water year is the 12-month period October 1 through September 30, designated by the calendar year in which the period ends. For example, the 2010 

water year began on October 1, 2009, and ended on September 30, 2010.

A total of 34 measured discharges at a streamgage on the 

Haw River below B. Everett Jordan Lake near Moncure were 

compared with the reported hourly flow releases from Jordan 

Lake Dam. Because 28 of 34 measurements were within plus 

or minus 10 percent of the hourly flow releases reported by 

the U.S Army Corps of Engineers, use of the current discharge 

computation tables for reporting Jordan Lake Dam flow 

releases is generally supported.

A stage gage was operated on the Cape Fear River at 

Buckhorn Dam near Corinth to collect continuous stage-only 

records. Throughout the study period, flow over the dam was 

observed along its length, and flow loss within the study reach 

is not attributed to river-level fluctuations at the dam.

Water-use information and (or) data were obtained for 

five industrial facilities, a regional power utility, two municipalities, one small hydropower facility on the Deep River, 

and one quarry operation also adjacent to the Deep River. The 

largest water users are the regional power producer, a small 

hydropower operation, and the two municipalities. The total 

water-use diversions for these facilities range from almost 

25.5 to 38.5 cubic feet per second (39.5 to 59.5 million gallons 

per day) during the winter and summer periods, respectively. 

This range is equivalent to 69 to 104 percent of the 37 cubic 

feet per second median flow loss.

The Lockville hydropower station is on the Deep River 

about 1 mile downstream from the streamgage near Moncure. 

Run-of-river operations at the facility do not appear to affect 

flow losses in the study reach. The largest water user in the 

study area is a regional power producer at a coal-fired powergeneration plant located immediately adjacent to the Cape Fear 

River just downstream from the confluence of the Haw and 

Deep Rivers. Comparisons of daily water withdrawals, supplied by the regional power producer, and discharge records at 

a streamgage on the diversion canal indicated many days when 

consumption exceeded the producer’s estimates for the cooling towers. Uncertainty surrounding reasonable estimates of 

consumption remained in effect at the end of the study. 

Data concerning evaporative losses were compiled using 

two approaches—an analysis of available pan-evaporation 

data from a National Weather Service cooperative observer 

station in Chapel Hill, North Carolina; and a compilation 
2 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

of reference open-water evaporation computed by the State 

Climate Office of North Carolina. The potential flow loss 

by evaporation from the main stem and the Deep River was 

estimated to be in the range of 4 to 14 cubic feet per second 

during May through October, equivalent to 10 to 38 percent of 

the 37 cubic feet per second median flow loss.

Daily water-use diversions and evaporation losses were 

compared to flow-loss occurrences during the period April 

2008 through September 2010. In comparing the surface-water, 

water-use, and evaporation data compiled for 2008–2010, it is 

evident that documented water diversions combined with flow 

losses by open-water evaporation can exceed the net flow gains 

in the study area and result in flow losses from the reach.

Analysis of data from a streamgage downstream from the 

regional power plant on the diversion canal adjacent to the Cape 

Fear River provided insight into the occurrence of an apparent flow loss at the streamgage at Lillington. Assessment of 

the daily discharges and subsequent hydrographs for the canal 

streamgage indicated at least 24 instances during the study when 

the flows suddenly changed by magnitudes of 100 to more than 

200 cubic feet per second, resulting in a noted time-lag effect on 

the downstream discharges at the Lillington streamgage, beginning 8 to 16 hours after the sudden flow change.

A fiber-optic distributed temperature-sensing survey was 

conducted on the Cape Fear River at the Raven Rock State 

Park reach August 12–14, 2009, to determine if the presence 

of diabase dikes were preferentially directing groundwater 

discharge. No temperature anomalies of colder water were 

measured during the survey, which indicated that at the time of 

the survey that particular reach of the Cape Fear River was a 

“no-flow” or losing stream.

An aerial thermal-infrared survey was conducted on the 

Haw and Cape Fear Rivers on February 27, 2010, from Jordan Lake Dam to Lillington to qualitatively delineate areas of 

groundwater discharge on the basis of the contrast between warm 

groundwater discharge and cold surface-water temperatures. Discharge generally was noted as diffuse seepage, but in a few cases 

springs were detected as inflow at a discrete point of discharge. 

Two reaches of the Cape Fear River (regional power 

plant and Bradley Road reaches) were selected for groundwater monitoring with a transect of piezometers installed within 

the flood plain. Groundwater-level altitudes at these reaches 

were analyzed for 1 water year (October 1, 2009, to September 

30, 2010). Data collected as part of this study represent only 

a brief period of time and may not represent all conditions 

and all years; however, the data indicate that, during the dry 

summer months, the Cape Fear River within the study area is 

losing an undetermined quantity of water through seepage.

Analyses completed during this investigation indicate a 

study reach with complex flow patterns affected by numerous 

concurrent factors resulting in flow losses. The causes of flow 

loss could not be solely attributed to any one factor. Among 

the factors considered, the occurrences of water diversions 

and evaporative losses were determined to be sufficient on 

some days (particularly during the base-flow period) to exceed 

the net gain in flows between the upstream and downstream 

ends of the study area. Losses by diversions and evaporation 

can exceed the median flow loss of 37 cubic feet per second, 

which indicates that flow loss from the study reach is real. 

Groundwater data collected during 2009–2010 indicate the 

possibility of localized flow loss during the summer, particularly in the impounded reach above Buckhorn Dam. However, no indication of unusual patterns was noted that would 

cause substantial flow loss by groundwater and surface-water 

interaction at the river bottom.

Introduction

Streamflows on large rivers are affected by a number of 

factors, including precipitation, evaporative losses, and underlying geologic and soils characteristics within a basin or along 

a given reach. Other factors include diversions to and from 

the rivers for water use as well as the impoundment of water 

behind structures (both actively regulated and run-of-river 

structures) that alter the normal regime of streamflow. The 

combined effects of these factors can result in complex flow 

patterns that indicate apparent or real flow losses for a reach 

of interest. One such reach suspected of being a losing reach 

is the Haw River and Cape Fear River between B. Everett 

Jordan Lake Dam (hereafter referred to as Jordan Lake Dam) 

and Lillington in Harnett County in central North Carolina 

(fig. 1). The Cape Fear River is formed at the confluence of the 

Haw and Deep Rivers. Real flow losses would reflect consumptive use somewhere within the intervening drainage area 

or the presence of a losing reach attributed to natural factors 

(underlying geology). Apparent flow losses would reflect flow 

dynamics that occur primarily as a result of water diversion 

through canals, storage, or potential flow regulations at the 

dams, and (or) measurement error at observation points.

In accordance with the U.S. Army Corps of Engineers’ 

(USACE) water-control plan, water is released from Jordan 

Lake Dam (fig. 1, site D1) to maintain a normal minimum 

target flow of 600 cubic feet per second (ft3/s), with a tolerance of plus or minus (+/–) 50 ft3

/s, at the U.S. Geological 

Survey (USGS) streamgaging station (or streamgage) on 

the Cape Fear River at Lillington (fig. 1, site 28) in Harnett 

County (Michael A. (Tony) Young, U.S. Army Corps of Engineers, written commun., December 20, 2011). The USACE 

estimates flow releases at Jordan Lake Dam based on a rating 

between the service gate openings in the intake tower and 

theoretically computed flows through the openings based on 

the lake level.

During some low-flow conditions, the sum of the estimated 

releases from Jordan Lake Dam and the observed streamflow at 

a second long-term streamgage on the Deep River at Moncure 

(fig. 1, site 3) in Chatham County is greater than the observed 

streamflow downstream at the streamgage at Lillington. In 

addition, flows at the Lillington streamgage have been observed 

to decrease by as much as 50 to 150 ft3/s over a period of 12 

to 24 hours for unknown reasons. Consequently, either the 
Introduction 3

target flow at Lillington is not met, or additional water must be 

released from Jordan Lake in an attempt to meet the target.

Repeated occurrences of suspected flow loss between Jordan Lake Dam and Lillington have raised questions about the 

factors that affect flows (or discharges) in this reach, whether 

or not flow losses are real, and the source(s) behind the flow 

losses. The difference between the inflow (sum of releases 

from Jordan Lake Dam and flow in the Deep River at Moncure) and outflow from the reach (flow in the Cape Fear River 

at Lillington) could be because either (1) flow is measured 

inaccurately at one or more of the three measurement locations; or (2) flow is lost from the reach as a result of surfacewater diversions, possible alterations because of impoundment 

behind dam structures, groundwater withdrawals, evaporative 

losses, recharge of the groundwater system, or some combination of these factors. 

During 2008–2010, the USGS conducted a hydrologic 

investigation in cooperation with the Triangle J Council of 

Governments Cape Fear River Flow Study Committee and 

the North Carolina Division of Water Resources to characterize natural and manmade factors that affect the study reach 

and to collect hydrologic data to help determine if the losses 

indicated in the initial analysis of data are real or apparent.

This study specifically addresses the USGS science strategy goal, “A Water Census of the United States: quantifying, 

forecasting, and securing freshwater for America’s Future” 

(U.S. Geological Survey, 2007a). The study also addresses the 

water census priority issue of the USGS 2011 Federal-State 

Water Cooperative Program, which helps to meet the goal of 

better understanding water availability and use (U.S. Geological Survey, 2010a). Finally, the study meets the science 

plan goal of the USGS North Carolina Water Science Center 

Figure 1. Location of study area between B. Everett Jordan Lake and Lillington, North Carolina.

$

$

$$

$

$ $ $

$

$

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.

7920’ 7910’ 78 79 50’ 

3540’

3530’

0 5 10 MILES

0 5 10 KILOMETERS

Apex

Cary

Jordan Lake

Shearon

CHATHAM Harris Lake

LEE

Holly

Springs

Angier

Lillington

FuquayVarina

Sanford

Broadway

WAKE

HARNETT

Study area boundary

Stage-only continuous-record

 station and number

Stage-discharge continuous-record

 station and number

Dam and number

Facility and number

Groundwater piezometer (PZ) and

 distributed temperature sensing

 (DTS) sites and number

EXPLANATION

$ D1 1

3

F5 F6

D2 F1

F2F3

F4 F7

F8

8

20

18

18

1

D1

F1

DTS

D3

F9

PZ1

DTS

PZ2

F10

28

Neills Cr.

Hector Cr.

Buckhorn

Cr.

Buckhorn

Res.

McKay

Island

Lick

Cr.

Cape

Haw R.

Deep

River

Fear

River

Raven Rock

State park

Shearon Harris

Power Plant

Moncure

Haywood

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale
4 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

(Bales and others, 2004) to understand increased demands 

on water resources through awareness of State and local 

water use, greatly enhancing the water-use database with 

an understanding of the regional, environmental, climatic, 

and economic factors affecting water use in North Carolina 

streams and rivers.

Purpose and Scope

The purpose of this report is to describe the causes of 

flow losses in the Cape Fear River between Jordan Lake Dam 

and Lillington, North Carolina. The report presents varied 

data-collection and data-analysis approaches selected to 

contribute toward an improved understanding of the possible 

causes of the flow losses. Results of the various approaches 

are interpreted to develop a conceptual model of the manmade or natural causes of the flow losses based on the new 

data collection and analysis.

The scope of the report includes results of flow analyses 

of long-term records for the 1983–2010 water years when 

losses were determined, description and results of the synoptic discharge measurements that were collected during 2009, 

assessments of water-use data compiled during the study, 

estimated losses by evaporation, and discussion concerning the groundwater data collected at two piezometer well 

clusters during 2009–2010. Results of a 2009 magnetometer 

survey and an aerial infrared flyover completed in February 

2010 also are presented.

Study Area and Possible Factors Affecting 

Flow Loss

The study area for this investigation is the intervening 

drainage area between Jordan Lake Dam near Moncure (fig. 1, 

site D1) and the USGS streamgages on the Deep River at 

Moncure (site 3) and Cape Fear River at Lillington (site 28). 

The drainage area along this 24.5-mile (mi) reach increases 

from 1,689 square miles (mi2) at Jordan Lake Dam to 3,464 mi2

at the Lillington streamgage (resulting in a 1,775-mi2

 difference 

in drainage area). The intervening drainage area in this reach 

includes the portion of the Deep River basin downstream from 

the Moncure streamgage (site 3), which has a drainage area of 

1,434 mi2. Accounting for this drainage area results in an intervening drainage area of 341 mi2

 for the study area.

As discussed in a subsequent section, the final study area 

did not include the basin upstream from a long-term USGS 

streamgage on Buckhorn Creek near Corinth (fig. 1, site 20). 

Buckhorn Creek is the largest tributary in the intervening 

drainage area. By not including this basin, the final intervening 

(ungaged) drainage area for this study is nearly 265 mi2.

Upstream from Buckhorn Dam (site D3), the Cape Fear 

River is characterized by fairly level water surfaces reflective of the lake setting. The average slope of the water surface 

between Jordan Lake Dam and Buckhorn Dam is approximately 0.5 foot per mile (ft/mi; fig. 2). Water depths range 

from 5–10 feet (ft) downstream from Jordan Lake Dam to 

20–25 ft just upstream from Buckhorn Dam. Downstream 

from Buckhorn Dam, the river bottom is characterized by rock 

Figure 2. Drainage area 

and elevation profiles on the 

Haw and Cape Fear Rivers 

between Jordan Lake Dam and 

Lillington, North Carolina.

Raven Rock

Hector CreekNeills Creek

State Park

Jordan Lake

NC Hwy. 42

Buckhorn Dam

Dam

Private boat

ramp

Deep River

regional power

Lick Creek

plant intake

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Drainage

area

profile

3,600

3,400

3,200

3,000

2,800

2,600

2,400

2,200

2,000

1,800

1,600

200

180

160

140

120

100

Drainage area, in square miles

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

Elevation,

smoothed

(LIDAR)

Elevation, in feet above NAVD 88
Introduction 5

outcrops of varying size, ranging from small cobbles to substantial boulders. Navigation using motorized craft is limited in 

this section of the river, particularly during base-flow conditions. Between Buckhorn Dam and the Lillington streamgage 

(site 28), the channel slope varies from about 7 ft/mi in the 

3-mi reach below the dam to about 1.6 ft/mi in the downstream 

most 11.5-mi reach (fig. 2).

A diversion canal runs adjacent to the Cape Fear River 

just downstream from the confluence of the Haw and Deep 

Rivers to immediately upstream from Buckhorn Dam. The 

area of the basin drained by the canal is approximately 

10.3 mi2. Water used in the regional power plant for cooling 

purposes travels the length of the canal about 6 mi before 

merging back into the Cape Fear River at the dam.

Streamflow records are available for five locations in the 

study area (table 1). Streamflow records were collected on the 

Deep River at Moncure (fig. 1, site 3) beginning in July 1930, 

and records were collected on the Cape Fear River at Lillington 

(site 28) beginning in December 1923. Prior to October 1992, 

streamflow records also were collected on the Haw River below 

B. Everett Jordan Dam near Moncure (site 1) and were published as Haw River near Haywood (USGS station 02098200) 

during the 1966–78 water years before and during the construction of Jordan Lake just downstream from the dam. Since April 

2008, continuous streamflow records have been collected at a 

streamgaging station (site 8) downstream from a power plant on 

a diversion canal adjacent to the Cape Fear River. Continuousrecord discharge also is measured on Buckhorn Creek (site 20) 

downstream from Shearon Harris Lake, which is owned and 

operated by the regional power producer to supply cooling 

water to the Shearon Harris Power Plant (fig. 1) in southwest 

Wake County. No active or inactive continuous groundwater 

monitoring sites are located within the study area.

Consideration of possible flow losses is complicated by 

several factors that may affect the overall flow patterns in the 

study reach. One factor is two low-head, run-of-river dams 

located in the study area. The Lockville Hydropower Dam 

(fig. 1, site D2) is on the Deep River about 2.7 mi upstream 

from the mouth of the river. The dam is used for hydropower 

generation at a power station (site F6) about 0.5 mi downstream from the dam. Ownership of the dam changed in 2003, 

and power production has occurred at this site since early 

2008. Further discussion about this dam and the operations are 

provided in a subsequent section.

Buckhorn Dam (figs. 1 (site D3), 3) is on the Cape Fear 

River, 13.8 mi upstream from the U.S. Highway 401 bridge and 

5.9 mi downstream from the confluence of the Haw and Deep 

Rivers. The dam, which is approximately 1,100 ft in length 

between the edges of the river, was completed and the reservoir was filled in 1908 (Ragland and others, 2003). This dam 

was used until December 1962 by a regional power producer 

to regulate flows for power production. The estimated surface 

area of the river upstream from the dam to Jordan Lake Dam 

and the Lockville Dam is about 460 acres. The volume of water 

in storage behind Buckhorn Dam is reported to be 69.7 million 

ft3 (Walters and others, 2006). The dam has been a run-of-river 

structure with no active regulation of downstream flows since 

December 1962 and continues to provide water storage for cooling purposes at the power plant.

Another factor that may affect possible flow losses is water 

withdrawals and return point-source discharges to and from the 

Haw and Cape Fear Rivers (or main stem) in the study area. The 

largest withdrawal is associated with the operation of the coalfired power plant (fig. 1, site F7) owned by a regional power 

producer located adjacent to the Cape Fear River just downstream from the confluence of the Deep and Haw Rivers. Water 

is withdrawn from the river into the plant and discharged to the 

diversion canal that runs generally parallel to the main stem, 

merging back into the river immediately upstream from Buckhorn Dam (site D3). The average daily withdrawal and return 

discharge in 1998 for the plant was about 207 and 204 million 

gallons per day (Mgal/d), respectively (Weaver, 2001). As previously noted, a streamgaging station (site 8) was installed on the 

canal in March 2008 to provide additional information about 

the flow through this facility. No major water withdrawals and 

return point-source discharges were identified or observed to or 

from the Deep River during the study period.

Two municipal withdrawals for water-supply purposes 

also occur in the study area. The first withdrawal is on the 

Cape Fear River upstream from N.C. Highway 42 (fig. 1, 

site F9), and the associated wastewater discharge is on Buffalo Creek, a tributary to the Deep River upstream from the 

study area. The second municipal withdrawal (site F10) is on 

the Cape Fear River upstream from the streamgage at Lillington (site 28), and the associated wastewater discharge is 

downstream from the streamgage and the study area. Because 

the associated wastewater discharges for these two withdrawals are located outside of the study area, the withdrawals for 

these two intakes were considered equivalent to 100 percent 

consumptive use within the study area. 

Water withdrawals and return discharges also are made by 

five private industries (fig. 1), four of which (sites F1–F4) are 

located on the Haw River upstream from its confluence with the 

Deep River. The fifth industry (site F8) withdraws water from 

the diversion canal adjacent to the Cape Fear River. Groundwater withdrawals by a quarry operation (site F5) upstream from 

the Lockville hydropower dam also were identified as a possible 

cause of flow loss, because groundwater is intercepted that 

would be otherwise discharged to the Deep River.

Geologic Setting

The geologic setting is complex in the study area because 

it is located near the Fall Line between the Piedmont and 

Coastal Plain Physiographic Provinces. The majority of the 

study area is in the Piedmont and includes the Mesozoic basin 

(44 percent) and members of the Carolina Terrane (Cary 

Sequence, 32.1 percent; Virgilina Sequence, 2 percent) and 

Crabtree Terrane (4.4 percent, fig. 4; Hibbard and others, 

2002). Coastal Plain sediments (17.5 percent) are present as 

a thin veneer in the southeastern part of the study area (fig. 4; 
6 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 1. Continuous- and partial-record U.S. Geological Survey surface-water sites in the Cape Fear River study area, North Carolina. [USGS, U.S. Geological Survey; °, degree; ′, minute; ′′, second; mi2, square mile; CR, continuous-record gaging station; PR, partial-record synoptic site; SO, stage only] Site index number (figs. 1, 6, 7) USGS station number Station name Latitude Longitude Drainage area, mi2 Site type Period of record Remarks

1 02098198 Haw R below B. Everett Jordan Dam near 

Moncure, NC

35°39′01′′ 79°03′58′′ 1,689 CR October 1965 to current Prior to October 1992, discharge 

records published; prior to September 1978, published as “Haw River near Haywood, NC” (USGS 02098200, located immediately downstream from current location of 02098198).

2 02098210 Haw River above Deep River near Haywood, NC 35°36′00′′ 79°03′03′′ 1,708 PR

3 02102000 Deep River at Moncure, NC 35°37′38′′ 79°06′57′′ 1,434 CR July 1930 to current Diurnal fluctuation and some regulation at low flow caused by small 

power plants upstream from station.

4 0210204915 Deep River above mouth near Moncure, NC 35°36′22′′ 79°03′57′′ 1,448 PR

5 02102050 Cape Fear River above powerplant intake 

near Moncure, NC

35°35′40′′ 79°03′08′′ 3,157 PR

6 02102082 Cape Fear River below powerplant intake 

near Moncure, NC

35°35′03′′ 79°03′05′′ 3,157 PR

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

35°34′11′′ 79°02′48′′ 3,166 PR

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

35°35′03′′ 79°02′28′′ 0.22 CR April 2008 to current

9 0210209450 Cape Fear powerplant discharge canal above 

juncture at Brickhaven, NC

35°34′21′′ 79°02′26′′ 1.32 PR

10 0210209475 Cape Fear powerplant discharge canal below 

dam at Brickhaven, NC

35°34′17′′ 79°02′32′′ 1.33 PR

11 0210209625 Unnamed stream between canal and Cape 

Fear River at Brickhaven, NC

35°34′15′′ 79°02′30′′ 1.33 PR

12 0210209650 Cape Fear powerplant discharge canal below 

juncture at Brickhaven, NC

35°34′12′′ 79°02′26′′ 1.00 PR

13 02102159 Lick Creek near Rosser, NC 35°33′33′′ 79°03′16′′ 45.6 PR

14 0210215960 Cape Fear River above NC Highway 42 

near Corinth, NC

35°33′02′′ 79°01′36′′ 3,226 PR
Introduction 

7

Table 1. Continuous- and partial-record U.S. Geological Survey surface-water sites in the Cape Fear River study area, North Carolina.—Continued[USGS, U.S. Geological Survey; °, degree; ′, minute; ′′, second; mi2, square mile; CR, continuous-record gaging station; PR, partial-record synoptic site; SO, stage only]

Site index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name Latitude Longitude

Drainage 

area,

mi2

Site

type Period of record Remarks

15 0210215995 Cape Fear powerplant discharge canal at NC 

Highway 42 near Corinth, NC

35°33′02′′ 79°01′24′′ 8.54 PR

16 02102176 Cape Fear powerplant discharge canal above 

mouth near Corinth, NC

35°32′36′′ 78°59′52′′ 10.3 PR

17 02102177 Cape Fear River upstream from Buckhorn 

Dam near Corinth, NC

35°32′27′′ 78°59′32′′ 3,234 PR

18 02102178 Cape Fear River at Buckhorn Dam near 

Corinth, NC

35°32′27′′ 78°59′21′′ 3,235 SO November 2008 to June 

2010

19 0210217810 Cape Fear River downstream from Buckhorn Dam near Corinth, NC 35°32′09′′ 78°59′04′′ 3,235 PR

20 02102192 Buckhorn Creek near Corinth, NC 35°33′35′′ 78°58′22′′ 76.3 CR June 1972 to current Flow regulated since December 1, 

1980, by Shearon Harris Lake

21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

35°29′13′′ 78°57′06′′ 3,354 PR

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

35°27′49′′ 78°52′59′′ 3,391 PR

23 02102278 Cape Fear River above Hector Creek near 

Chalybeate, NC

35°26′53′′ 78°51′54′′ 3,400 PR

24 02102280 Hector Creek near Chalybeate, NC 35°28′00′′ 78°51′29′′ 17.4 PR

25 02102283 Cape Fear R adjacent to Bradley Road near 

Lillington, NC

35°26′28′′ 78°51′16′′ 3,420 PR

26 02102289 Cape Fear River above Neills Creek near 

Lillington, NC

35°25′22′′ 78°49′38′′ 3,425 PR

27 02102480 Neills Creek near Lillington, NC 35°25′42′′ 78°49′27′′ 37.6 PR

28 02102500 Cape Fear River at Lillington, NC 35°24′22′′ 78°48′47′′ 3,464 CR December 1923 to current Flow regulated since September 1981 by B. Everett Jordan Lake
8 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Hibbard and others, 2002). Coastal Plain sediments that once 

covered the entire southeastern part of the study area have 

eroded as sea level declined and the Cape Fear River incised 

into the underlying Piedmont rocks.

Questions have been raised as to whether the underlying 

geologic setting could be a factor in flow losses in the study 

area. The presence of diabase dikes that intersect the river 

could act as impermeable boundaries to groundwater discharge (McSwain, 2009). Diabase dikes are high-angle, vertically intruded geologic features of mafic igneous rock with 

less thickness than length. The thickness of diabase dikes 

can vary from inches to tens of feet, and length can exceed 

many miles. As a result of weathering over time, diabase 

dikes become exposed at the surface (fig. 5) and can intersect 

river bottoms.

Diabase dikes were mapped previously by Burt and 

others (1978) in rocks of the Mesozoic basin and Carolina 

Terrane. As a result of rifting activity, isolated tabular diabase dikes may extend into the Mesozoic basin sedimentary 

rocks. Weaver and Pope (2001) noted that rocks and soils of 

the Mesozoic basin generally have low permeabilities, and 

perched water tables are common. Additionally, they noted 

that soils in the Mesozoic basin support a lower potential for 

sustained base flows, and they identified a number of streamflow sites in the Mesozoic basin that were determined to have 

7-day, 10-year low-flow discharges equal to zero flow. In the 

reach downstream from Buckhorn Dam (figs. 1, 4), the Cary 

sequence of the Carolina Terrane contains high-grade metamorphic gneiss and schist intruded by granite plutons and diabase dikes (Burt and others, 1978; Hibbard and others, 2002). 

Burt and others (1978) did not locate diabase dikes within the 

metamorphic slates of Crabtree Terrane, metamorphic volcanic and sedimentary rock of the Carolina Terrane, Virgilina 

sequence, or Coastal Plain sediments of the study area.

Data Collection and Methods for 

Assessing Flow Patterns in the Cape 

Fear River

Assessment of the flow patterns in the study reach 

required a multidiscipline approach. In addition to existing 

surface-water records, additional surface- and groundwater data were collected during the study to enable further 

analyses of flow into and out of the study area. Data also 

were collected regarding water use in the study area and the 

potential evaporative losses from the study reach. Elements 

of the study also included a geophysical survey, a distributed 

temperature-sensing survey, and an aerial infrared survey to 

help define the groundwater and surface-water interaction 

along the study reach. 

Surface Water

The collection of surface-water data involved the 

(1) operation of currently active streamgaging stations in the 

study area along with the reactivation of a site on the Haw 

River below Jordan Lake Dam, (2) activation of a stageonly streamgage on the Cape Fear River at Buckhorn Dam, 

(3) completion of synoptic discharge measurements along 

the main stem and selected tributaries, (4) estimation of 

flow losses by evaporation, and (5) compilation of available 

water-use information for industrial and municipal facilities 

adjacent to the Haw and Cape Fear Rivers in the study area. 

Evaluations of historical discharge records were completed to 

document the occurrence and magnitudes of suspected flow 

losses. Analyses of ratings at the two long-term streamgaging 

stations also were completed to determine if the computation 

of discharge records could result in falsely detected flow loss.

Flow Loss Analyses

Flow analyses were completed using historical USGS discharge records and flow releases reported by the USACE from 

Jordan Lake Dam to further characterize the magnitude and 

frequency of flow loss occurrences between the dam and the 

streamgage on the Cape Fear River at Lillington. Both instantaneous and daily discharge records available for the 1983–2010 

water years were compiled. When comparing flows at upstream 

and downstream locations, the upstream flow can be higher 

than the downstream flow due to a peak flow traveling along 

the reach. The time of travel and passage of peaks between 

upstream and downstream locations limit the usefulness of a 

comparison between simultaneous instantaneous discharges to 

assess the occurrence of flow losses. Likewise, using average 

flows over a large number of days (for example, 14- or 28-day 

average flows) also may result in the loss of detailed fluctuations in the comparisons. Therefore, both daily mean discharge 

records and 7-day average flows were used as the primary 

Figure 3. Figure 3. Cape Fear River at Buckhorn Dam (site D3) near 

Corinth, North Carolina. (Photo by J. Curtis Weaver on 

April 27, 2009)
Data Collection and Methods for Assessing Flow Patterns in the Cape Fear River 9

dataset for further analysis to identify days on which flow loss 

occurred and the magnitude of such losses.

Synoptic Discharge Measurements

A series of six synoptic discharge measurements were 

made during 2009 along the Haw and Cape Fear Rivers and 

selected tributaries to create a “snapshot” of the flow variations along the main stem. Completing the synoptic measurements helped to determine if similar flow variations among 

the series could identify a particular point along the main stem 

where flow losses were consistently evident.

The synoptic discharge measurements were made on April 

27, June 25, July 22, August 18, September 9, and October 1, 

2009. Tributaries were selected based on the amount of change 

in an intervening drainage area contributed by the tributary basin. 

For example, a discharge measurement was made on a tributary 

if the intervening drainage area increased by 5 percent or more. 

The following tributaries were selected: Deep River, Lick Creek, 

Buckhorn Creek, Hector Creek, and Neills Creek (fig. 1).

During the April 27 synoptic series, measurements were 

made at 20 locations in the study area, 13 of which were along 

the main stem. The additional 7 measurements were made 

on the adjacent diversion canal and the selected tributaries (2 

locations on the Deep River and 1 each on the four smaller 

tributaries). Post-synoptic processing of the April 27 measurements indicated a breach between the diversion canal and 

main stem at McKay Island. Following a detailed reconnaissance of the diversion canal on May 13, 6 new locations were 

Figure 4. Lithotectonic geologic units in the Cape Fear River study area, North Carolina (from Hibbard and others, 2006).

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.

7920’ 7910’ 78 79 50’ 

3540’

3530’

0 5 10 MILES

0 5 10 KILOMETERS

Pittsboro

Goldston

Apex

Cary

Jordan Lake

Shearon

Harris Lake

CHATHAM

LEE

Holly

Springs

Angier

Lillington

FuquayVarina

Sanford

Broadway

WAKE

HARNETT

Carolina Terrane (Cary

 sequence

Carolina Terrane (Virgilina

 sequence

Coastal Plain

Crabtree Terrane

Mesozoic (Triassic) basin

Study area boundary

Note: percentages shown

indicate the percentages

of geologic units relative

to the study area

EXPLANATION

Lithotectonic geology units

2%

44%

4.4%

32.1%

17.5%

Raven Rock

State park

Shearon Harris

Power Plant

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale
10 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

added for inclusion in the synoptic series: 1 location on the 

main stem and 5 locations on the adjacent diversion canal and 

unnamed stream (table 1, sites 7, 9, 11, 12, 15, 16) between 

the diversion canal and main stem that constituted the breach.

During the remaining five synoptic series (June 25, 

July 22, August 18, September 9, and October 1), measurements were made at 26 locations: 14 on the main stem and 

12 on the adjacent diversion canal (6) and the tributaries (6). 

Among the 26 locations, 17 and 9 sites were located upstream 

and downstream, respectively, from Buckhorn Dam (figs. 6, 7, 

respectively). Except for a few instances when equipment or the 

boat malfunctioned, measurements were made at each location 

during the synoptic series. As part of each synoptic series, the 

USGS collaborated with the Wilmington District USACE to set 

and maintain steady flow releases from Jordan Lake Dam as the 

measurements were collected. Efforts were made to complete 

each synoptic series within the course of a single day.

Velocity and corresponding discharge measurements 

were made in the water column using acoustic Doppler current 

profilers and velocimeters (Mueller and Wagner, 2009). Use 

of such equipment allowed the completion of measurements 

at all locations within 1 day. However, as discussed further 

in subsequent sections, the presence of backwater conditions, 

extremely low velocities, wind effects, and eddies in the main 

Figure 5. 

Figure 5. An example of a diabase dike (dark feature near center) that 

vertically intrudes the subsurface of a quarry near Cary, North Carolina. (Photo 

by Richard Bolich, North Carolina Division of Water Quality, April 5, 2005).
Data Collection and Methods for Assessing Flow Patterns in the Cape Fear River 11

stem upstream from Buckhorn Dam affected the quality of the 

discharge measurements at sites upstream from the dam. Following post-processing and review of the discharge measurements, some measurements were discarded because of poor 

measuring conditions.

Streamgage Data Collection

At the beginning of the study, four continuous-record 

streamgages were in operation and were used to provide 

additional data for assessment in the flow analyses (table 1, 

sites 3, 8, 20, 28). The collection of continuous discharge 

data also was reactivated at a streamgage on the Haw River 

just downstream from Jordan Lake Dam (site D1), which 

was previously operated from October 1965 to September 

1992 (published as USGS station 02098200, Haw River near 

Haywood prior to October 1978). Streamflow at this site is 

affected by backwater conditions, the effects of storage behind 

Buckhorn Dam and (or) inflow from the Deep River into the 

Cape Fear River. Thus, the streamgage was operated as an 

index-velocity station where velocity data and stage were collected to develop a rating for computing discharges.

Continuous stage-only records were collected on the 

Cape Fear River at Buckhorn Dam near Corinth (table 1, 

site 18) to determine whether water levels fell below the 

crest of the dam during periods of suspected flow loss. Data 

Figure 6. Locations upstream from Cape Fear River at Buckhorn Dam where discharge measurements were made during the series of 

synoptic measurements in 2009.

Study area boundary

Stage-only continuous-record station

 and number

Partial-record synoptic sites

Stage-discharge continuous-record

 station and number

Dam and number

Facility and number

Groundwater piezometer (PZ) and distributed

 temperature sensing (DTS) sites and number

EXPLANATION

$

18

1

15

D1

F1

PZ1

WAKE

CHATHAM

HARNETT

7910’ 79

Jordan Lake

Shearon

Harris Lake

$

$

$

$ $

$

$ $ $

7 12

13

10

11

9

6

5

2

4

8

 16

17 19

18

14

15

3

1

Moncure

Haywood

McKay

Island

Lick

Creek

Buckhorn

Creek

Diversion

canal

Diversion

canal

0 2.5 5 MILES

0 2.5 5 KILOMETERS

Cape

Haw

River

Deep

River

Fear

River

Buckhorn

Dam

3538’

3536’

3532’

3534’

PZ1

F9

F8

D3

D2

D1

F7

F3

F2

F1

F5 F6

F4

20

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.
12 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

collection began in November 2008 and continued, except 

for a brief interruption during January 2008 when recording 

equipment was stolen, until late June 2010 when the entire 

streamgage structure and recording equipment were stolen.

Analyses of Ratings and Measured Discharges

Analyses were completed on ratings and measured discharges for the 1982–2011 water years at the two long-term 

streamgages on the Deep River at Moncure and Cape Fear River 

at Lillington (figs. 6, 7, sites 3, 28, respectively). The analyses 

were completed to determine if the computation of discharge 

records could be a factor in flow loss. In other words, could there 

be a systematic bias in the process of developing and maintaining 

the ratings at the Moncure and Lillington streamgages, possibly 

resulting in questionable discharge records?

Discharge measurements made at each of the sites during this period were examined to understand the pattern of 

percentage differences between the measured discharges and 

the rating discharges and whether or not a rating shift was 

applied following the measurements. The trend of percentage 

differences (whether shifted or unshifted) during the period of 

analysis also was examined.

Additional information on discharge measurements and 

ratings analyses is provided in the appendix. Additional information on techniques for collecting and analyzing discharge 

records can be obtained from Rantz and others (1982, v. 1, 2), 

Mueller and Wagner (2009), Turnipseed and Sauer (2010), and 

U.S. Geological Survey (2010b). 

Figure 7. Locations downstream from Cape Fear River at Buckhorn Dam where discharge measurements were made during the series 

of synoptic measurements in 2009.

CHATHAM

LEE

HARNETT

WAKE

Buckhorn

Dam

79 7850’

16

17 19

18

Angier

Lillington

0 2.5 5 MILES

0 2.5 5 KILOMETERS

Cape

Fear

River

DTS

PZ2

Raven Rock

State park

3530’

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.

D3

$

21

22 24

23

25

27

F10

26

28

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale

Study area boundary

Stage-only continuous-record station

 and number

Partial-record synoptic sites

Stage-discharge continuous-record

 station and number

Dam and number

Facility and number

Groundwater piezometer (PZ) and distributed

 temperature sensing (DTS) sites and number

EXPLANATION

$

18

28

25

D3

F10

DTS

Hector

Creek

Neills

Creek
Data Collection and Methods for Assessing Flow Patterns in the Cape Fear River 13

Water Use

Water-use information was compiled during the investigation 

to characterize the number and magnitude of diversions and 

return flows that occur in the study reach. Because water-use 

diversions from the main stem have been known to occur, an 

understanding of the magnitudes of diversions (and the associated consumptive uses) could potentially identify all or part of 

the suspected flow losses.

After an initial assessment by the North Carolina Division 

of Water Resources (Don Rayno, North Carolina Division of 

Water Resources, oral commun., May 28, 2009), five industrial 

and two municipal facilities with intakes in the Haw or Cape 

Fear Rivers were identified and contacted in order to obtain 

detailed information. No major water withdrawals from or 

return point-source discharges to the Deep River were identified during the study period. Detailed water-use information, 

particularly with respect to water withdrawals, is commonly 

limited to hard-copy format when available and requires 

extensive effort to create an electronic file from paper records 

or the use of available anecdotal information to compose a 

general range of daily water use. Both methods were used in 

this investigation, although the latter method was the more 

common approach with four of the five industries.

Water-use information also was collected during the 

series of synoptic measurements to assess the streamflow 

conditions on each of the six dates. Facility records of water 

withdrawals (or use) and point-source discharge data were 

compiled. The study period coincided with a national economic recession, which affected water diversions such that 

those reported for most of the facilities during the study were 

lower than in the preceding years. 

Of particular note, Shearon Harris Power Plant is located 

in southwest Wake County (fig. 1) and is adjacent to Shearon 

Harris Lake, the largest impoundment in the study area. The 

lake is formed by the impoundment of Buckhorn Creek, the 

second largest tributary in the study area, and provides cooling 

water for power generation. The plant currently (2011) consists of one reactor. The 2008–2010 annual water-use reports 

filed with the North Carolina Division of Water Resources 

indicated that average daily withdrawal from the lake during 

these years ranged from 27.9 to 29.1 Mgal/d (43–45 ft3/s), 

and the average return point-source discharge to the lake 

ranged from 15.0 to 17.4 Mgal/d (23–27 ft3/s; North Carolina 

Department of Environment and Natural Resources, Division 

of Water Resources, 2007). Differences between diversions 

and returns indicate that the average water consumption from 

Shearon Harris Lake during 2008–2010 ranged from 10.5 to 

13.5 Mgal/d (16–21 ft3/s). Available discharge records from 

a long-term streamgage on Buckhorn Creek (fig. 1, site 20) 

downstream from the dam were used to provide insight into 

the net flow from the drainage basin into the study area. No 

detailed assessment of the water-use patterns at this facility 

were deemed necessary because the discharge records available at the streamgage accounted for the contributing streamflow from the basin.

Evaporation

Evaporation from the study reach was estimated during 

the investigation to determine the portion of suspected flow 

losses in the study reach that could be attributed to the transformation of water from a liquid state to a gaseous state and 

removed from the earth’s surface. Evaporation is recognized 

as an important source of water loss during droughts, particularly for operators of large reservoirs managing the balance of 

inflow to and outflow from impoundments. Losses by evaporation can exceed inflow to impoundments and result in conditions referred to as “negative inflow” to a reservoir. Evaporation from large rivers, such as the Haw and Cape Fear Rivers, 

likewise can be substantial as water surfaces in wide channels 

allow for extensive exposure of water to the atmosphere.

The evaporation process occurs in two ways: (1) evaporation of water directly from water bodies, and (2) evapotranspiration (ET) of water through trees and vegetation. Although 

evaporation occurs throughout the year, the process is cyclical with maximum evaporation occurring during the warmer 

months. At its peak during the summer months, evaporative losses from the stream channel can be on the order of 

0.2–0.3 inch per day (in/d). While this range may not appear 

substantial at first glance, evaporative losses of this magnitude 

on a daily basis during the course of a month can well exceed 

the normal precipitation for an area.

Two methods were used in this study to estimate the portion of flow losses in the study reach that could be attributed to 

open-water evaporation. The first method involved the compilation and analysis of available pan-evaporation data in the vicinity of the study area. The second method, the Penman-Monteith 

method (Penman, 1948; Monteith, 1965), was used to compute 

potential reference-crop ET using meteorological measures for 

a weather station nearby where climatic data are available. The 

Penman-Monteith method also can be used to determine reference open-water evaporation with adjustments of coefficients 

used in the method. It bears noting that evaporation determined 

by using the Penman-Monteith method is a calculated estimate, 

not a measured value as with pan-evaporation data.

Evaporation data commonly are collected by using the panevaporation method whereby a large stainless steel pan partially 

filled with a measure of water is placed in an open area and 

monitored daily to measure changes in water levels, in inches. 

The placement of the pan in an open area simulates a body of 

water such as an impoundment. Pan-evaporation rates, however, tend to overestimate actual evaporation from surface water 

because the pan temperature may be greater than the temperature 

of a natural water body. Farnsworth and Thompson (1982) determined that evaporation from a shallow lake, wet soil, or other 

moist natural surface is about 70 percent of the evaporation from 

a Class A pan under the same meteorological conditions.

Although such data provide a direct measure of evaporative losses, there are only nine National Oceanic and Atmospheric Administration (NOAA) weather stations in North 

Carolina where pan-evaporation data have been collected. 

The periods of record vary among the nine stations, and data 
14 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

at these stations generally are intermittent during the periods 

of record. One NOAA station with data during the investigation period (2008–10) is the Chapel Hill 2W station in Orange 

County within 30 mi of the study area. The second closest 

NOAA station with pan-evaporation data during the investigation period is located in Lumberton, Robeson County, more 

than 60 mi from the study area.

During the study, data from the Chapel Hill 2W NOAA 

weather station were determined to be the most complete with 

most daily observations recorded during the warmer months 

when evaporation is greatest. The Chapel Hill data also were 

considered to be most representative of evaporation in the 

study area because of the close proximity of the weather station. Pan-evaporation data for this site date back to March 

1949 and were available on an intermittent basis through July 

2008 at the time of analysis. The available pan-evaporation 

data for this station were compiled and analyzed, but because 

of the intermittent nature of daily pan-evaporation data, 

monthly median evaporation amounts were determined.

The limited pan-evaporation data near the study area 

resulted in the determination that use of computed referencecrop ET data based on the Penman-Monteith model could be 

used to assess evaporative losses from the study reach (Dr. Ryan 

Boyles, North Carolina State Climatologist, written commun., 

September 11, 2009). The Penman-Monteith method was specified in a document published by the United Nations Food and 

Agriculture Organization (FAO; Allen and others, 1998) as the 

standard method acceptable for estimating reference-crop ET 

losses for well-watered surfaces (State Climate Office of North 

Carolina, 2010). The reference surface is defined as a theoretical grass crop. Estimates are computed using meteorological 

observations of solar radiation, temperature, wind speed, and 

relative humidity. Using crop coefficients, the determination of 

ET losses can vary on the basis of the crop of interest and the 

particular growth stage during the growing season. 

The North Carolina State Climate Office has computed 

and compiled estimated potential daily open-water evaporative 

losses for NOAA stations across the State using the PenmanMonteith method (State Climate Office of North Carolina, 

2010). The daily evaporation amounts were obtained for five 

NOAA stations in the vicinity of the study area: Chapel HillWilliams Airport (NOAA station KIGX), Harnett County Airport (KHRJ), Lee County Airport (KTTA), Pope Air Force Base 

(KPOB) near Fayetteville, and Raleigh-Durham International 

Airport (KRDU; fig. 8).

The monthly median daily pan-evaporation amounts 

(adjusted by a pan coefficient of 0.7) for the Chapel Hill 2W 

station were applied to the estimated surface area of the Haw, 

Deep, and Cape Fear Rivers between Jordan Lake Dam and 

Lillington (fig. 1). Daily reference open-water evaporation 

data compiled for the five nearby NOAA stations using the 

Penman-Monteith method were averaged and applied to the 

estimated surface area. The surface area was estimated by 

creating a trace of river boundaries using computerized topographical maps. Applying the daily evaporation amounts to the 

surface area resulted in an estimated volume of water removed 

daily from the rivers. 

Groundwater and Surface-Water Interaction

From July 2009 to November 2010, several field investigative and monitoring methods were applied to describe the 

groundwater and surface-water interaction within the flood 

plain of the Cape Fear River. Elements of the study included a 

geophysical survey, a distributed temperature sensing survey 

and an aerial infrared survey to help define the groundwater 

and surface-water interaction along the study reach. Continuous groundwater monitoring also was conducted at two 

piezometer transects on the Cape Fear River.

Electromagnetic Geophysical Survey

A GEM 2 digital, multifrequency electromagnetic (EM) 

sensor was used during July and August 2009 to collect a continuous EM profile along the Haw, Deep, and Cape Fear Rivers 

within the study area. The focus of the survey was to identify 

locations of possible diabase dikes (fig. 5) intersecting the bottom of the river. 

The GEM 2 sensor has an electric coil that transmits a 

waveform at frequencies ranging between 300 and 24,000 hertz 

(Hz) that induces a magnetic field in susceptible rocks, such as 

diabase. The sensor receiver coil then measures the electrical 

conductivity of the response. Because of the multifrequency 

capability of the GEM 2, the sensor has the ability to penetrate 

to depths beneath the surface depending on the rock type 

encountered. At low frequencies, the waveform produced by 

the GEM 2 penetrates deeper into the earth, and the response 

is comparable to the response of a magnetometer (Geophex, 

Ltd., 2011). 

The GEM 2 sensor was equipped with a global positioning system (GPS) tracking device and towed behind a boat for 

approximately 53 mi along the main stem and the Deep River 

to trace variations or anomalies in the magnetic signal. Two 

26.5-mi-long survey lines were completed by towing the instrument along each side of most of the channel. Following the 

survey, the USGS Office of Groundwater Branch of Geophysics 

provided processing support to filter the signal data (Troy R. 

Brosten, U.S. Geological Survey, written commun., 2009). Raw 

data logged by the GEM 2 were recorded in sensor-specific 

units of parts per million. While multiple frequencies were 

collected during the survey, the frequency that displayed the 

deepest resolution for each reach was selected for data analysis. 

In the reach above Buckhorn Dam, the 450-Hz frequency was 

selected, and a frequency of 1,170 Hz was selected for the lower 

reach. A lower frequency was needed in the reach above Buckhorn Dam in order to penetrate the thick water column (greater 

than 20 ft in places) in the Cape Fear River. 

Groundwater Temperature

Additional characterization of the interaction between 

groundwater and surface water was conducted by evaluating 

thermal properties within the hyporheic zone of the Cape Fear 
Data Collection and Methods for Assessing Flow Patterns in the Cape Fear River 15

River. Two novel approaches, distributed-temperature sensing and 

thermal infrared imaging, were applied during this study to characterize the spatial and temporal variation of groundwater discharge.

Distributed-Temperature Sensing (DTS) Survey

Fiber-optic distributed-temperature sensing (FO-DTS) 

is a relatively new technology that can measure temperature 

with a spatial resolution of less than 1 yard along a fiber-optic 

cable that may be a mile or more long. Temperature precision of 0.1 degree Celsius (o

C) and a temporal resolution of 

90 seconds are attainable using FO-DTS technology. Physical 

principles of FO-DTS technology are described in Selker and 

others (2006). In this study, temperature data were collected 

using a SensorTran FO-DTS.

A 3,000-ft-long shielded telecommunication fiber-optic 

cable was deployed in a reach of the Cape Fear River near 

Raven Rock State Park during August 12–14, 2009 (fig. 1, 

site DTS). The fiber-optic cable was laid temporarily on the 

bed of the Cape Fear River in two lines parallel to the riverbank to measure differences in temperature along the lines 

over a 36-hour period, August 11–13, 2009. Temperature data 

were collected every 2.75 minutes at intervals of about 1.7 ft 

along the length of the fiber-optic cable.

Thermal Infrared (TIR) Survey

Thermal infrared (TIR) imaging has been used to 

remotely sense groundwater discharge and provide a noninvasive screening tool for the identification of groundwater 

Figure 8. Locations of nearby National Oceanic and Atmospheric Administration National Weather Service cooperative observer 

stations where daily reference, open-water evaporation data were compiled for the study based on the Penman-Monteith method.

GUILFORD

ALAMANCE

ORANGE DURHAM

WAKE

FRANKLIN

JOHNSTON

HARNETT

CUMBERLAND

SAMPSON

HOKE

MOORE

LEE

CHATHAM

RANDOLPH

Morrisville

Cary

Apex

Holly Springs Clayton

Smithfield

Selma

Four Oaks

Newton Grove

Coats

Angier

Erwin

Dunn

Spring Lake

Godwin

Falcon

Linden

Wade Fayetteville

Benson

Fuquay-Varina

Wake

Forest

Knightdale

Wendell

Zebulon

Garner

Robbins

Sanford

Siler City Pittsboro

Goldston

Staley

Liberty

Ramseur

Broadway

Carthage

Jackson

Springs

Whispering Pines

Southern

Pines

Taylortown

Pinehurst

FoxfireAberdeen

Village

Vass

7940’ 7930’ 7920’ 7910’ 7850’ 7840’ 7830’ 78 79 20’ 

Carrboro

Durham

Raleigh

Rolesville

Chapel Hill

Chapel Hill-Williams

Airport Raleigh-Durham

International Airport

Lee County

Airport

Open water

Study area boundary

NOAA National Weather Service

cooperative observer station

EXPLANATION

Harnett County

Airport

Pope

Air Force

Base

3550’

3540’

3530’

3520’

0 5 10 MILES

0 5 10 KILOMETERS

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.

Jordan

Lake

Shearon

Harris Lake

Shearon Harris

Power Plant

Raven Rock

State Park

Cape

Fear

River

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale
16 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

seeps over a large geographic area (Banks and others, 1996). 

To locate areas of seepage that contribute groundwater to the 

Cape Fear River, a high-resolution, low-altitude airborne TIR 

survey was performed during the early-morning hours on February 27, 2010. The 24.5-mi reach of the Haw and Cape Fear 

Rivers extending from B. Everett Jordan Dam to Lillington 

was investigated using TIR.

A USGS contractor collected the TIR imagery using a 

FLIR® Systems, Inc. digital infrared camera with 1 megapixel 

resolution (1024 x 1024) mounted on a fixed wing aircraft. The 

camera measured radiant energy (in the infrared wave band) 

emitted from the water surface and stored the readings as values 

of pixels in a digital image, whereas a standard thermometer 

measures kinetic energy through direct contact with an object or 

fluid. In a TIR image, land and water features are distinguishable because of differences in radiant temperature. To minimize 

interference caused by reflected solar thermal energy, the TIR 

survey was conducted in the pre-dawn hours during a winter 

month when the temperature of the groundwater was warmer 

than the ground surface and surface water. Additionally, the air 

temperature did not exceed 3 oC and no measurable precipitation occurred within the preceding 36-hour period at the KRDU 

weather station (Raleigh-Durham International Airport, fig. 8). 

The river surface was not frozen, and the instantaneous gage 

height measured at the Cape Fear River at Lillington (fig. 1, 

site 28) did not exceed 4.0 ft at the time of image collection. 

The TIR imagery was collected in one flight using a 

series of passes to gather enough overlapping imagery to cover 

the entire river surface plus a 50-ft buffer on each side of the 

river. A georeferenced photo mosaic of overlapping digital 

TIR imagery was assembled by the contractor at the end of 

imagery collection. Groundwater seepage was depicted on the 

images as lighter (warmer) areas compared to darker (cooler) 

surrounding areas.

Piezometer Transects

Piezometer transects were installed at two locations on the 

Cape Fear River to monitor water levels in the flood plain and 

river (fig. 1, PZ1, PZ2) and determine the variability of groundwater and surface-water interaction. A piezometer is a well that 

has a short screen so the water level represents hydraulic head 

in only a small part of the groundwater system (Winter and 

others, 1998). Clustering a group of piezometers at different 

depths at the same location is referred to as a piezometer nest 

(or transect) and allows data collection that can be used to 

interpret the movement of water within the transect. 

To install the piezometers, individual boreholes were 

excavated in the flood-plain and river-bed sediments by jetting, using a high-velocity stream of water either to a specific 

depth or to resistance by consolidated material. A centrifugal 

pump supplied a pressurized stream of water through a jetting 

tube to excavate a 6-inch (in.) diameter hole and remove the 

liquefied sediment. The Cape Fear River was the water source 

used for jetting. Because of the cohesive nature of the floodplain sediments, a temporary casing was not needed to prevent 

sediments from collapsing back into the hole. 

After each borehole was excavated to the prescribed 

depth, a 1.5-in. diameter schedule 40 polyvinyl chloride 

(PVC) piezometer casing was placed in the borehole. All of 

the piezometers were constructed with a 0.01-in. machineslotted well screen with a 1-ft length. Clean medium-sized 

(no. 2) filter sand was poured into the annular space between 

the PVC casing and the borehole wall to a level approximately 

0.25 ft above the top of the well screen. A seal of bentonite 

pellets, hydrated with water obtained from the Cape Fear 

River, was placed on top of the sand filter pack to the floodplain or river-bed surface. After installation, the altitude of 

each piezometer was determined by using traditional survey 

techniques referenced to the altitude of a nearby temporary 

benchmark established by using GPS satellites. Construction 

details for each piezometer are listed in table 2.

In order to monitor horizontal and vertical groundwaterflow paths in the flood plain, the piezometers were installed 

along a high- to low-topographic profile perpendicular to the 

river edge and following a presumed flow path from recharge 

(flood-plain terrace) to discharge areas (river; fig. 9). In the 

riverbed, a nest of piezometers was installed at increasing 

depths to monitor water levels (vertical gradients).

Continuous Monitoring

Monitoring of groundwater level and river stage was 

conducted at each piezometer transect. Groundwater-level and 

river-stage data were collected on a continual basis by using 

an absolute (nonvented) self-logging submersible pressure 

transducer. Consequently, groundwater-level and river-stage 

data were corrected using barometric pressure data recorded 

onsite. The pressure transducers were field checked every 

4 to 6 weeks and corrected to measurements made with an 

electric tape to ensure accurate reading, according to methods 

described in Freeman and others (2004). Vertical and horizontal gradients were calculated by comparing water-level altitudes. Continuous and periodic groundwater-level and riverstage data are stored in the USGS National Water Information 

System (NWIS) database (U.S. Geological Survey, 2001).

Results and Interpretation of Data 

The multidiscipline data collection and analyses completed 

for this investigation revealed that flow losses occur in the 

reach of the Cape Fear River between Jordan Lake Dam and the 

USGS streamgage at Lillington (fig. 1, site 28). The results of 

this investigation are discussed in the following sections.

Surface Water

Several methods were applied during the study to aid in 

understanding the occurrence of suspected flow losses and 

to identify possible causes. Examination of the streamflow 

records collected along the study reach coupled with six series 
Data Collection and Methods for Assessing Flow Patterns in the Cape Fear River 17

Table 2. Characteristics of the piezometers and adjacent surface-water sites on the Cape Fear River in Chatham and Harnett Counties, North Carolina.[NAVD 88, North American Vertical Datum of 1988; in., inch; PZ, piezometer; °, degree; ′, minute; ′′, second; PVC, polyvinyl chloride, schedule 40 casing; H, hyporheic; R, river; FP, flood plain; NA, 

not applicable]

Site

identification

number

Station

name

Latitude Longitude Construction date

Landsurface 

elevation 

(feet above

NAVD 88)

Top of 

casing 

elevation 

(feet above

NAVD 88)

Casing 

material

Casing 

diameter 

(inches)

Screened 

interval

(feet below 

land surface)

Screen type

Zone 

monitored

From To

PZ1, Regional power plant transect (profiles shown in fig. 9

A)

353304079013401 CH-231 Cape Fear PE-1U 35°33′04.1′′ 79°01′34.5′′ Oct. 1, 2009 156.71 162.75 PVC 1.5 0.96 1.96 0.01-in. slotted PVC

H

353304079013402 CH-232 Cape Fear PE-1M 35°33′04.1′′ 79°01′34.5′′ Oct. 1, 2009 156.73 162.47 PVC 1.5 3.98 4.98 0.01-in. slotted PVC

H

353304079013403 CH-233 Cape Fear PE-1D 35°33′04.1′′ 79°01′34.5′′ Oct. 1, 2009 156.69 162.61 PVC 1.5 6.98 7.98 0.01-in. slotted PVC

H

353304079013404 CH-234 Cape Fear PE-1R 35°33′04.1′′ 79°01′34.5′′ Oct. 1, 2009 156.65 162.57 PVC 1.5 0.00 0.01-in. slotted PVC

R

353304079013405 CH-235 Cape Fear PE-2 35°33′04.1′′ 79°01′34.5′′ Oct. 1, 2009 159.26 163.15 PVC 1.5 5.84 6.84 0.01-in. slotted PVC FP

353304079013406 CH-236 Cape Fear PE-3 35°33′04.1′′ 79°01′34.5′′ Oct. 1, 2009 159.98 163.65 PVC 1.5 4.59 5.59 0.01-in. slotted PVC FP

PZ2, Bradley Road transect (profiles shown in fig. 9

B)

352630078511401 HR-060 Cape Fear BR-1D 35°26′29.4′′ 78°51′14.9′′ Aug. 11, 2009 107.01 113.96 PVC 1.5 2.75 3.75 0.01-in. slotted PVC

H

352630078511402 HR-061 Cape Fear BR-1U 35°26′29.4′′ 78°51′14.9′′ Aug. 11, 2009 106.80 113.80 PVC 1.5 0.50 1.50 0.01-in. slotted PVC

H

352630078511403 HR-062 Cape Fear BR-1R 35°26′29.4′′ 78°51′14.9′′ Aug. 11, 2009 106.37 113.8 PVC 1.5 0.00 0.01-in. slotted PVC

R

352630078511404 HR-063 Cape Fear BR-2 35°26′29.5′′ 78°51′14.9′′ Aug. 11, 2009 107.76 114.21 PVC 1.5 3.25 4.25 0.01-in. slotted PVC

H

352630078511405 HR-064 Cape Fear BR-3 35°26′29.5′′ 78°51′14.8′′ Aug. 11, 2009 112.57 115.17 PVC 1.5 7.15 8.15 0.01-in. slotted PVC FP

352630078511406 HR-065 Cape Fear BR-4 35°26′29.6′′ 78°51′14.8′′ Aug. 11, 2009 114.23 117.91 PVC 1.5 6.07 7.07 0.01-in. slotted PVC FP

0210215960

(site 14, fig. 6)

Cape Fear River above 

NC Highway 42 near Corinth, NC

35°33′02.68′′ 79°01′36.42′′ Aug. 11, 2009 156.70 NA NA NA NA NA NA

R

02102283

(site 25, fig. 7)

Cape Fear River adjacent 

to Bradley Road near Lillington, NC

35°26′28.92′′ 78°51′16.85′′ Apr. 27, 2009 106.75 NA NA NA NA NA NA

R
18 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

166

164

162

160

158

156

154

152

150

148

146

Altitude, in feet above NAVD 88

0 2 4 6 8 10 12 14 16 18 20

Sandy clay loam

Clay

Loam

Sand

Sand and gravel

Cape Fear River

 HR-062 BR-1R

Riverbed piezometers

 HR-061 BR-1U

 (destroyed Nov. 2009)

 HR-0601 BR-1D

Flood plain piezometers

 HR-063 BR-2

 HR-064 BR-3

 HR-065 BR-4

EXPLANATION

Piezometer screened interval

CH-232

CH-234

CH-233

CH-231

CH-235

CH-236

Cape Fear

River

Land surface

Land surface

118

116

114

112

110

108

106

104

102

100

98

0 4 8 16 18 20

Distance, in feet

24 28 32 36 40 44

HR-062

HR-060

HR-061 HR-063

HR-064

HR-065

Cape

Fear

River

A

B

Figure 9. 

Cape Fear River

 CH-234 PE-1R

Riverbed Piezometers

 CH-231 PE-1U

 CH-232 PE-1M

 CH-233 PE-1D

Flood plain Piezometers

 CH-235 PE-2

 CH-236 PE-3

EXPLANATION

Piezometer screened interval

Figure 9. Piezometer profiles and soils encountered at the (A) regional power plant transect (PZ1) near Corinth 

and (B) Bradley Road transect (PZ2) near Lillington, North Carolina (sites shown in fig. 1).
Results and Interpretation of Data 19

of synoptic discharge measurements provided information 

concerning the magnitudes of flow losses and whether or not 

the losses consistently occurred at a given location. Water use 

was examined and open-water evaporative losses were estimated, both of which were determined to cause flow losses in 

the study area. Review of the measured discharges and ratings 

at the two long-term streamgages at Moncure and Lillington 

did not indicate any systematic bias in the stage-discharge 

ratings used to compute discharge records. Results of the 

surface-water analyses are provided in the following sections.

Flow Loss Analyses

The first analyses in the study focused on developing 

an understanding of the magnitude and frequency of flow 

losses by using flow-release data reported by the USACE 

from Jordan Lake Dam and discharge records at three USGS 

streamgaging stations (fig. 1, sites 3, 20, 28). Recent and historical records based on active and discontinued stations were 

examined to document the differences in the number of days 

of flow loss in varying periods of record. The flow loss analyses of daily discharge records confirmed the flow loss between 

the upstream and downstream ends of the study reach but did 

not provide insight into possible causes of the losses.

For the purposes of this study, the quantification of flow 

losses was determined by summing the daily discharges at 

Jordan Lake Dam, Deep River at Moncure, and Buckhorn 

Creek near Corinth (fig. 1, sites D1, 3, 20, respectively) and 

subtracting this value from the discharge at Cape Fear River at 

Lillington (site 28). As defined in this report, positive net differences indicate a gain in flow between the upstream inputs 

and the streamgage at Lillington, whereas negative net differences indicate a possible flow loss between these locations. 

Net differences in flow were determined for a 1-day time scale 

using daily mean discharge or flow release and for a 7-day 

time scale using 7-day average discharge or flow release.

Three flow comparisons were completed to evaluate 

periods of potential flow loss using records for the 1983–2010 

water years as well as two comparisons based on records from 

January 1963 to December 1970 (prior to Jordan Lake construction) for discontinued streamgages (table 3). The period 

1963–70 was specifically chosen because it corresponds to the 

time after active regulation by Buckhorn Dam ceased but prior 

to the start of construction on Jordan Lake.

The first historical flow comparison was made using 

data from the discontinued streamgage on the Haw River 

near Pittsboro (USGS station 02097000; drainage area 

1,310 mi2), which was operated October 1928–September 

1973 and discontinued during the construction of Jordan Lake 

because the streamgage was located in the inundation area. 

The second historical flow comparison was made using data 

from the discontinued streamgage on the Haw River near 

Haywood (USGS station 02098200; drainage area approximately 1,700 mi2

), which was operated October 1965–September 1978. The location of the discontinued streamgage 

near Haywood is downstream from the current streamgage 

below Jordan Lake Dam (fig. 1, site 1). In each historical 

comparison, the discharges at the discontinued streamgages 

were summed with the discharges at Deep River at Moncure 

(site 3) and compared with corresponding discharges at Cape 

Fear River at Lillington (site 28). Among the 2,922 possible 

days for comparison during January 1963–December 1970, 

a total of 2,922 and 1,918 days, respectively, were available 

for flow comparisons 1 and 2 for all three streamgages. The 

smaller number of days available in flow comparison 2 is 

because the period of record for the Haywood streamgage 

began in October 1965.

Flow comparisons 3, 4, and 5 were completed using data 

for the 1983–2010 water years. This period includes the presence of Jordan Lake and Shearon Harris Lake, which affect 

part of the input flows into the study area. Input flows for 

flow comparisons 3 and 5 were daily flow releases reported 

for Jordan Lake Dam (fig. 1, site D1) and the discharges at 

Deep River at Moncure (site 3) and Buckhorn Creek near 

Corinth (site 20). The differences between flow comparisons 

3 and 5 were that input flows were compared to same-day and 

next-day (1-day lag) discharges, respectively, at the Lillington streamgage (site 28). Completing a comparison based on 

next-day discharges at the Lillington streamgage allowed for 

consideration of travel time in flow between Jordan Lake Dam 

and Lillington. Flow comparison 4 was made using data from 

the USGS streamgage on the Haw River below Jordan Lake 

(site 1) for one of the input flows in place of flow releases 

reported for the dam; however, comparisons based on data 

from the USGS streamgage below Jordan Lake are limited in 

terms of available record (1983–92 water years). As discussed 

in subsequent sections, comparisons using data collected during the 2008–2010 water years at this streamgage could not be 

completed because of technical concerns with the velocity data 

collected during the study. Nevertheless, the occurrence of 

flow loss noted in this comparison reinforces the recognition 

that flow loss is part of the overall flow dynamics in this reach.

For each flow comparison, the number of days of flow 

loss were tabulated (table 3) for two categories: the number 

of days of flow loss during the period of interest regardless 

of the preceding flow conditions upstream from the study 

area and the number of days of flow loss based on a filtered 

comparison in which daily records for flow releases at Jordan 

Lake Dam (site D1) and discharges at Deep River at Moncure 

(site 3) both changed less than 5 percent from the previous 

day’s records. The filter was applied to examine the days 

when little to no temporal change in flow occurred, indicating 

that no peak flow was passing through the study area along 

the main stem. For the number of days of flow loss filtered, 

the minimum, median, and maximum flow losses were 

tabulated (table 3).

In all comparisons, the number of days of flow loss 

based on a filtered assessment is substantially less than the 

number of days of flow loss based on a nonfiltered assessment (table 3). For example, in flow comparison 3, among 

10,227 days during the 1983–2010 water years, flow loss 

occurred on a total of 2,941 days (28.8 percent) based on 
20 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

comparison of the daily mean discharge between the inputs 

and the Lillington streamgage (site 28). However, flow loss 

occurred on 408 days (4.0 percent) when conditions were 

relatively steady with respect to the previous day’s records. 

The flow loss during these 408 days ranged from 0.49 to 

2,150 ft3/s, with a median flow loss of 37.2 ft3/s (table 3). In 

terms of 7-day average discharge, the number of days of flow 

loss for this comparison was determined to be 2,350 days 

(23.0 percent) and 647 days (6.3 percent) for the nonfiltered 

and filtered assessments, respectively. The flow loss on these 

647 days ranged from 0.07 to 1,450 ft3/s, with a median flow 

loss of 37.4 ft3/s (table 3). An example of flow loss can be seen 

in the daily and unit hydrographs for October 5–14, 2007, a 

period during which drought conditions occurred (fig. 10). 

Both daily and 7-day flow losses occurred on all days during 

this period, and daily flow losses were computed.

Examination of the maximum flow loss amounts, particularly for flow comparisons 3 and 5 (table 3), indicates the 

filtered assessments did not filter out all nonpeak-flow conditions, because flow losses at this magnitude are not true flow 

losses. The maximum flow loss determined for comparison 

3 highlighted an interesting occurrence in the flow patterns 

at the Lillington streamgage where flows decreased and then 

increased again by about 5,000 ft3/s within a 36-hour period 

during April 23–25, 1998 (fig. 11). Limited information is 

available to fully explain this unusual flow pattern, suspicion 

of possible sudden changes in flow release were confirmed 

by the USACE (Terry Brown, U.S. Army Corps of Engineers 

(retired), written commun., December 16, 2009). Of note, the 

lake elevation for Jordan Lake on April 21, 1998, exceeded 

220 ft, more than 4 ft above the guide curve elevation of 

216 ft used in daily lake-management operations (fig. 11A). 

Table 3. Number of days with flow loss and flow-loss statistics for the Haw, Deep, and Cape Fear Rivers between Jordan Lake Dam 

and Lillington, North Carolina, for the periods January 1963 to December 1970 and the 1983 - 2010 water years.

[USGS, U.S. Geological Survey; ft3/s, cubic foot per second; flow comparisons discussed in detail in report. Number of days flow loss filtered refers to days in 

which changes in flow at upstream sites were less than 5 percent from previous day.]

Flow loss based on daily mean discharge Flow loss based on 7-day average discharge

Number of 

days flow 

loss and 

percentage 

of days with 

flow at all 

sites

Number of 

days flow 

loss filtered and 

percentage 

of days 

with flow 

at all sites

Minimum,

 in ft3

/s

(date)

Median,

in ft3

/s

Maximum,

 in ft3

/s

(date)

Number of 

days flow 

loss and 

percentage 

of days 

with flow 

at all sites

Number of 

days flow 

loss filtered and 

percentage 

of days 

with flow 

at all sites

Minimum,

 in ft3

/s

(date)

Median,

in ft3

/s

Maximum,

 in ft3

/s

(date)

Flow comparison 1: Haw River near Pittsboro (USGS station 02097000) plus Deep River at Moncure (site 3) compared to Cape Fear River at Lillington (site 28), 2,922 days with flow at all 3 sites among 2,922 possible days during period of interest (January 1963 through December 1970)

391 3 1.0 5.0 26.0 179 33 0.14 5.1 78.1

13.4% 0.1% (4/24/1968) (10/11/1968) 6.1% 1.1% (9/18/1968) (8/17/1966)

Flow comparison 2: Haw River near Haywood (USGS station 02098200) plus Deep River at Moncure (site 3) compared to Cape Fear River at Lillington (site 28), 1,918 days with flow at all 3 sites among 2,922 possible days during period of interest (January 1963 through December 1970)

417 17 1.0 33.0 100 318 90 1.1 16.4 740

21.7% 0.9% (9/21/1968) (2/1/1966) 16.6% 4.7% (9/29/1968) (3/19/1968)

Flow comparison 3: Jordan Lake Dam flow releases (site D1), Deep River at Moncure (site 3), and Buckhorn Creek near Corinth (site 20) compared to 

Cape Fear River at Lillington (site 28), 10,227 days with flow at all 4 sites among 10,227 possible days during period of interest (1983-2010 water years)

2,941 408 0.49 37.2 2,150 2,350 647 0.07 37.4 1,450

28.8% 4.0% (9/11/1989) (4/24/1998) 23.0% 6.3% (11/28/2007) (4/25/2003)

Flow comparison 4: Flows at Haw River below Jordan Lake dam (site 1), Deep River at Moncure (site 3), and Buckhorn Creek near Corinth 

(site 20) compared to Cape Fear River at Lillington (site 28), 2,069 days with flow at all 4 sites among 3,653 possible days during period of 

interest (1983-1992 water years)

1,182 169 1.8 92.0 433 1,111 296 0.52 85.2 1,030

57.1% 8.2% (11/23/1984) (10/24/1988) 53.7% 14.3% (11/27/1984) (3/7/1989)

Flow comparison 5: Jordan Lake dam flow releases (site D1), Deep River at Moncure (site 3), and Buckhorn Creek near Corinth (site 20) compared to next-day Cape Fear River at Lillington (site 28) in effort to look at possible losses on a 1-day adjusted time scale, 10,226 days with 

flow at all 4 sites among 10,227 possible days during period of interest (1983-2010 water years)

3,775 394 0.18 43.2 3,330 3,191 656 0.09 38.0 1,900

36.9% 3.9% (8/26/2008) (11/25/2006) 31.2% 6.4% (7/11/2009) (4/26/2003)
Results and Interpretation of Data 21

Figure 10. (A) Daily mean and (B) instantaneous discharges 

in the Cape Fear River and tributaries, North Carolina, during 

October 5–14, 2007, with daily and 7-day flow losses based on 

daily discharge flow comparison 3.

EXPLANATION

1,000

100

10

212.00

211.75

211.50

211.25

211.00

210.75

210.50

210.25

210.00

212.00

211.75

211.50

211.25

211.00

210.75

210.50

210.25

210.00

300

250

200

150

100

50

0

6 7 8 9

October 2007

Type of flow loss

5 10 11 12 13

6 7 8 9

October 2007

5 10 11 12 13 14

Jordan Lake Dam flow releases

Deep River at Moncure

Cape Fear River at Lillington

Jordan Lake elevation (U.S. Geological Survey)

Flow loss (daily)

Flow loss (daily filtered)

Flow loss (7-day)

Flow loss (7-day filtered)

Flow loss amount (cubic feet per second) 

Discharge, in cubic feet per second

Jordan Lake elevation, in feet above NGVD 29

A

B

Figure 11. (A) Daily mean and (B) instantaneous discharges 

for days prior to and following April 24, 1998, on which maximum 

flow loss occurred in the Cape Fear River and tributaries, North 

Carolina, based on daily discharge flow comparison 3.

EXPLANATION

Jordan Lake Dam flow releases

Deep River at Moncure

Cape Fear River at Lillington

Jordan Lake elevation (U.S. Geological Survey)

Flow loss (daily)

Flow loss (daily filtered)

Flow loss (7-day)

Flow loss amount (cubic feet per second) 

100,000

10,000

1,000

100

221

220

219

218

217

216

215

221

220

219

218

217

216

215

12,000

10,000

8,000

6,000

4,000

2,000

0

21 22 23 24

April 1998

20 25 26 27 28

April 1998

23 24 25

Discharge, in cubic feet per second

Jordan Lake elevation, in feet above NGVD 29

A

B

Type of flow loss
22 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

An elevation at this level typically results in actions to reduce 

the lake level as rapidly and safely as possible, which is 

reflected in the daily hydrograph for April 21–22, 1998. The 

lake elevation stabilized between the mid-day hours on April 

23 and 24, suggesting a sudden and substantial change in flow 

releases from Jordan Lake Dam (fig. 11B). No hourly flow 

data were initially available for this period to confirm the sudden change in discharge at Lillington. Flow releases estimated 

by the USACE (Ashley Hatchell, U.S. Army Corps of Engineers, written commun., June 28, 2011), however, confirm the 

sudden and substantial changes in the flow releases on April 

23–24. Information provided with the estimated flow releases 

also included a historical note referencing heavy rain in the 

lower part of the Cape Fear River basin, indicating that the 

sudden changes may have been made to help mitigate high 

flows in the lower part of the basin.

Flow losses determined in flow comparison 3 based on 

the daily mean discharges were selected for further inspection 

using statistical histograms to assess the frequency of several factors related to the flow loss determined in the filtered 

assessment (fig. 12). Approximately 61 percent of the flow 

loss days occurred when the daily mean discharge at the Lillington streamgage (site 28) was at the target flow of 600 ft3

/s 

or less. In terms of flow loss amounts, the histogram indicates 

that approximately 64 percent of the flow losses are 50 ft3/s or 

less. Expressed as a percentage of the daily mean discharge at 

the Lillington streamgage, nearly 68 percent of the flow losses 

constitute 10 percent or less of the Lillington flows. In terms 

of days of occurrence during the calendar year, about 82 percent of the flow loss days were during the months of May 

through October. The months with the highest number of days 

of flow loss were June (16.7 percent), September (16.9 percent), and October (19.4 percent). Information gleaned from 

the histograms indicates the majority of flow losses occurred 

during the warm season months, particularly during the baseflow months of September and October. The histograms also 

indicate that a majority of the flow losses accounted for less 

than 10 percent of the daily mean discharge at the Lillington 

streamgage.

Synoptic Discharge Measurements

A series of synoptic discharge measurements were made 

at selected locations along the main stem between Jordan Lake 

Dam (fig. 1, site D1) and the Lillington streamgage (site 28) 

on six different occasions in 2009 (fig. 13). The purpose of 

each series of synoptic measurements was to create a “snapshot” of the flow conditions along the main stem to determine 

if a particular pattern could be detected that might identify 

a consistent flow-loss location, thereby leading to further 

investigation into the cause(s) for flow loss at that location. 

Because the flow analyses indicated the majority of flow 

losses occurred under base-flow conditions during the warmer 

months, all synoptic-measurement series except the April 27 

series were conducted under these conditions on June 25, 

July 22, August 18, September 9, and October 1, 2009 

(figs. 14–19; tables 4–9). The completion of each synopticmeasurement series indicated that the largest change in the 

main-stem flow occurs immediately downstream from the 

regional power-plant intake (fig. 1, site F7). However, the 

synoptic measurements did not indicate any other location 

where another previously unknown flow loss was observed 

consistently on each date.

Discharge measurements were made by using acoustic 

measuring equipment and USGS techniques (Mueller and 

Wagner, 2009; U.S. Geological Survey, 2010b). For each 

measured discharge collected during the synoptic series on the 

main stem and the Deep River, the velocity, standard deviation, 95-percent confidence interval, and percentage of change 

in discharge from the next upstream discharge on the main 

stem are summarized in tables 4–9. The standard deviation and 

measured discharge were used to compute the coefficient of 

variation, which was used with the number of passes completed during the measurement across the section (typically 

four or eight) to compute a 95-percent confidence interval of 

measurement uncertainty. Following the review procedures, 

the discharge measurements for three sites (6, 7, and 14) on 

June 25 (table 5) and one site (17) on October 1 (table 9) were 

deemed unreliable and, therefore, were not used in further 

analyses.

The first series of synoptic measurements made on 

April 27 were not at base-flow conditions but provided insight 

in preparing for the remaining five series of synoptic measurements. The discharges at the Lillington streamgage ranged 

from 300 to 600 ft3/s for the five series of measurements made 

during June through October and was about 1,400 ft3/s for the 

April 27 measurements (fig. 13). Known diversions for water 

use—both withdrawals and return point-source discharges—

were compiled and documented when available for each series 

of synoptic measurements (tables 4–9).

The measured discharges highlight some challenges 

associated with attempting to create a profile of discharges 

along the Haw and Cape Fear Rivers, particularly between the 

confluence of the Haw and Deep Rivers and Buckhorn Dam. 

Under ideal circumstances, the measured discharges would be 

expected to accurately characterize the changes in discharges 

due to confluences with tributaries and to diversions along a 

given riverine reach.

Among the series of six synoptic measurements, the sum 

of the measured discharges at site 2 on the Haw River and 

site 4 on the Deep River (tables 4–9) were +5.5, +3.7, –3.7, 

–20, –0.3, and –13.9 percent different from the measured discharge at site 5 on the Cape Fear River just downstream from 

the confluence and upstream from the intake at site F7 (fig. 6). 

Assessment of the 95-percent confidence intervals for the measured discharges at these three sites indicated that the interval 

of measurement uncertainty was greater than 8 percent for part 

of or all three sites on each of the synoptic-measurement dates 

with the exception of April 27, which was the date with the 

highest range of flows measured (fig. 13). As indicated in the 

surface-water quality-assurance plan for the USGS North Carolina Water Science Center (U.S. Geological Survey, 2010b), 
Results and Interpretation of Data 23

Figure 12. 

201–300

301–400

401–500

501–600

601–700

701–800

801–900

901–1,000

1,001–2,000

2,001–3,000

3,001–4,000

4,001–5,000

5,001–6,000

6,001–7,000

7,001–8,000

8,001–9,000

9,001–10,000

10,001–12,500

12,501–15,000

15,001–17,500

17,501–20,000

200

150

100

50

0

Daily mean discharge, in cubic feet per second

A

200

150

100

50

0

C

160

140

120

100

80

60

40

20

0

Flow loss amount, in cubic feet per second

Number of days

Flow loss as percentage of daily mean discharge, in percent

B

100

80

60

40

20

0

Months of flow loss occurrence

D

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

1–5

6–10

11–15

16–20

21–25

26–30

31–35

36–40

41–45

46–50

51–55

56–60

61–65

66–70

71–75

76–80

81–85

86–90

91–95

96–100

1–25

26–50

51–75

76–100

101–250

251–500

501–750

751–1,000

1,001–1,500

1,501–2,000

2,001–2,500

Figure 12. Filtered flow-loss occurrences in the Cape Fear River determined in flow comparison 3 based 

on (A) daily mean discharge, (B) flow-loss amount, (C) percentage of daily mean discharge, and (D) month 

of occurrence.
24 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Figure 13. Discharges measured during a series of six synoptic discharge measurements in 2009 on the Haw and Cape Fear Rivers 

between Jordan Lake Dam and Lillington, North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

1,600

1,400

1,200

1,000

800

600

400

200

0

Discharge, in cubic feet per second

April 27, 2009

June 25, 2009

July 22, 2009

August 18, 2009

September 9, 2009

October 1, 2009

Jordan Lake

Dam

Deep River

regional power

 plant intake

Lick Creek

Raven Rock

Hector Cr

Neills Cr

State Park

private

NC Hwy 42

boat ramp

EXPLANATION

Buckhorn

Dam

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Figure 14. Measured discharges on April 27, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

1,600

1,400

1,200

1,000

800

600

400

200

0

Discharge, in cubic feet per second

April 27, 2009

0.1–0.25

0.26–0.50

0.51–1.0

Greater than 1.0

Upper and lower bars

surrounding measurement

correspond to range

between upper and

lower limits of 95-percent

confidence interval

Average velocity,

in feet per second

Note: Discharges

plotted by color based

on average velocity

determined in

measurement, as

detailed in explanation

Jordan Lake

Dam

Deep River

regional power

plant intake

Lick Creek

Raven Rock

State Park

Hector Cr

Neills Cr

private

NC Hwy 42

boat ramp

EXPLANATION

Buckhorn

Dam

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane
Results and Interpretation of Data 25

Figure 15. Measured discharges on June 25, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Jordan Lake

Dam

Deep River

regional power

plant intake

Lick Creek

Raven Rock

Hector Cr

Neills Cr

State Park

private

NC Hwy 42

boat ramp

June 25, 2009

Less than or

 equal to 0.1

0.11–0.25

0.26–0.50

0.51–1.0

Upper and lower bars

surrounding measurement

correspond to range

between upper and

lower limits of 95-percent

confidence interval

Average velocity,

in feet per second

Note: Discharges

plotted by color based

on average velocity

determined in

measurement, as

detailed in explanation

EXPLANATION

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Buckhorn

Dam

Figure 16. Measured discharges on July 22, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Jordan Lake

Dam

Deep River

regional power

plant intake

Lick Creek

Raven Rock

State Park

Hector Cr

Neills Cr

private

NC Hwy 42

boat ramp

July 22, 2009

Less than or equal to 0.1

0.11–0.25

0.26–0.50

0.51–1.0

Upper and lower bars

surrounding measurement

correspond to range

between upper and

lower limits of 95-percent

confidence interval

Average velocity,

in feet per second

EXPLANATION

Note: Discharges

plotted by color based

on average velocity

determined in

measurement, as

detailed in explanation

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Buckhorn

Dam
26 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Figure 17. Measured discharges on August 18, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Deep RiverLick Creek

Raven Rock

Hector CrNeills Cr

State Park

private

NC Hwy 42

boat ramp

Note: Discharges

plotted by color based

on average velocity

determined in

measurement, as

detailed in explanation

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

August 18, 2009

Less than or equal to 0.1

0.11–0.25

0.26–0.50

0.51–1.0

Upper and lower bars

surrounding measurement

correspond to range

between upper and

lower limits of 95-percent

confidence interval

Average velocity,

in feet per second

EXPLANATION

regional power

plant intake

Buckhorn

Dam

Jordan Lake

Dam

Figure 18. Measured discharges on September 9, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Deep RiverLick Creek

Raven Rock

State Park

Hector CrNeills Cr

private

NC Hwy 42

boat ramp

Note: Discharges

plotted by color based

on average velocity

determined in

measurement, as

detailed in explanation

September 9, 2009

Less than or equal to 0.1

0.11–0.25

0.26–0.50

0.51–1.0

Upper and lower bars

surrounding measurement

correspond to range

between upper and

lower limits of 95-percent

confidence interval

Average velocity, 

in feet per second

EXPLANATION

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

regional power

plant intake

Buckhorn

Dam

Jordan Lake

Dam
Results and Interpretation of Data 27

Figure 19. Measured discharges on October 1, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, 

North Carolina.

30 25 20 15 10 5 0

Distance upstream from USGS station 02102500 on Cape Fear River at Lillington, in river miles

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Jordan Lake

Dam

Deep River

regional power

plant intake

Lick Creek

Raven Rock

State Park

Hector Cr

Neills Cr

private

NC Hwy 42

boat ramp

Note: Discharges

plotted by color based

on average velocity

determined in

measurement, as

detailed in explanation

October 1, 2009

Less than or equal to 0.1

0.11–0.25

0.26–0.50

0.51–1.0

Upper and lower bars

surrounding measurement

correspond to range

between upper and

lower limits of 95-percent

confidence interval

Average velocity,

in feet per second

EXPLANATION

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Buckhorn

Dam

acoustic discharge measurements with 95-percent confidence 

intervals exceeding 8 percent are rated as poor. The flow 

dynamics associated with the confluence of two large basins 

(Deep and Haw Rivers) in a backwater reach during base-flow 

conditions on five of the six series of measurements were 

reflected in the quality rating of the measured discharges at 

these locations.

Comparisons of the differences in measured discharges 

between sites 5 and 6 on the Cape Fear River upstream and 

downstream, respectively, from the intake at site F7 (fig. 6) 

with the reported water withdrawals also highlighted challenges 

during the synoptic measurements. Differences in measured discharges between sites 5 and 6 on April 27, July 22, August 18, 

September 9, and October 1 were 60, 83, 106, 66, and 68 percent, respectively, of the reported water withdrawals. For five of 

the six synoptic measurements, the reported water withdrawals 

were identical – about 396 ft3/s. As discussed in a subsequent 

section, reported water withdrawals at site F7 were questioned when compared to the discharge records at the USGS 

streamgage on the adjacent diversion canal downstream from 

the regional power plant (fig. 6, site 8). Comparisons between 

the reported withdrawals and the differences in measured discharges at sites 5 and 6 were, therefore, limited because of the 

questions concerning the accuracy of the withdrawal data.

Several noticeable patterns can be seen in the graphs 

of each of the series of synoptic measurements (figs. 14–19) 

when inspected from an overall “big picture” perspective. 

The largest water diversion occurs just downstream from 

the confluence of the Haw and Deep Rivers where water is 

withdrawn for cooling purposes at the regional power plant 

(fig. 6, site F7). Discharges measured during the synoptic 

measurements decreased substantially in the main stem downstream from the power-plant intake point. Downstream from 

Buckhorn Dam, little gain or loss is evident between the dam 

and Raven Rock State Park (fig. 7, site 22), although minor 

fluctuations in flow patterns occur between the State park and 

the Lillington streamgage (fig. 7, site 28). What is clear in the 

graphs is that flows in the Cape Fear River between the intake 

point below the confluence and Buckhorn Dam are governed 

by the water diversion through the regional power plant. 

Upon release from the plant, the flow travels approximately 

6.3 mi along a diversion canal that drains into the main stem 

immediately upstream from Buckhorn Dam.

Following the synoptic measurements on April 27, 2009, 

a breach was discovered between the diversion canal and Cape 

Fear River near the northern end of McKay Island (fig. 6). 

Thus, flow was measured in the unnamed stream (fig. 6, 

site 11) between the canal and river during the remaining 

five synoptic measurements. The measured discharges in the 

unnamed stream ranged from 43 to 52 percent of the measured 

discharge at the next upstream canal site (site 9). Although 

a few other smaller breaches between the canal and Cape 

Fear River were noted during the field operations, none was 

observed to be as large as the breach near McKay Island.
28 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 4. Results of synoptic discharge measurements made on April 27, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina. [USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second; ft/s, foot per second; change, in percent, computed as difference in measured discharge from next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (F), fair; (G), good; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)] Site index number (figs. 1, 6, 7) USGS station number Station name Main stem river miles upstream from Lillington streamgage (site 28) Measured discharge Measured discharge, in ft3/s Average velocity, in ft/s Standard deviation, in ft3/s 95-percent confi- dence interval of measurement uncertainty, in percent (measurement rating) Lowest discharge in 95-percent confidence interval, in ft3/s Highest discharge in 95-percent confidence interval, in ft3/s Change, in percent Sites above Buckhorn Dam

1 02098198 Haw R below B. Everett Jordan Dam near 

Moncure, NC

24.3 859 0.91 29.3 5.5 (F) 812 906 DA

F1 Industrial NA Withdrawal: 0.24 ft3/s Return: 0.1 ft3/s

F2 Industrial NA Withdrawal: Not recorded Return: Not recorded

F3 Industrial NA Withdrawal: Not recorded Return: 0.08 ft3/s

F4 Industrial NA Withdrawal: 0.03 ft3/s Return: 0 ft3/s

2 02098210 Haw River above Deep River near Haywood, NC 20.7 835 0.34 31.3 6.0 (F) 785 885 -2.8

3 02102000 Deep River at Moncure, NC DA 448 1 -- -- -- -- -- DA

F6 Hydropower power generation NA Power generation online all day.

4 0210204915 Deep River above mouth near Moncure, NC DA 432 0.18 34.9 6.5 (F) 404 460 DA

5 02102050 Cape Fear River above powerplant intake near 

Moncure, NC

20.3 1,200 0.35 18.8 2.5 (G) 1,171 1,231 43.8

F7 Regional power utility NA Withdrawal: 395.77 ft3/s Return: 338.68 ft3/s

6 02102082 Cape Fear River below powerplant intake near 

Moncure, NC

19.4 960 0.22 22.9 3.8 (G) 923 997 -20.1

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

18.4 -- -- -- -- -- -- DA

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

DA 339 1 -- -- -- -- -- DA

F8 Industrial NA Withdrawal: 0 ft3/s Return: No return discharge

9 0210209450 Cape Fear powerplant discharge canal above 

juncture at Brickhaven, NC

DA -- -- -- -- -- -- DA

10 0210209475 Cape Fear powerplant discharge canal below 

dam at Brickhaven, NC

DA -- -- -- -- -- -- DA

11 0210209625 Unnamed stream between canal and Cape Fear 

River at Brickhaven, NC

DA -- -- -- -- -- -- DA

12 0210209650 Cape Fear powerplant discharge canal below 

juncture at Brickhaven, NC

DA -- -- -- -- -- -- DA

13 02102159 Lick Creek near Rosser, NC DA 5.26 0.105 -- -- -- -- DA
Results and Interpretation of Data 29

Table 4. Results of synoptic discharge measurements made on April 27, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.—Continued[USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second; ft/s, foot per second; change, in percent, computed as difference in measured discharge from 

next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (F), fair; (G), good; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)]

Site 

index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name

Main stem

 river miles 

upstream from 

Lillington 

streamgage 

(site 28)

Measured discharge

Measured 

discharge, 

in ft3/s

Average 

velocity,

in ft/s

Standard 

deviation, 

in ft3/s

95-percent confidence interval of 

measurement 

uncertainty, 

in percent

(measurement 

rating)

Lowest 

discharge in 

95-percent 

confidence 

interval, in 

ft3/s

Highest 

discharge in 

95-percent 

confidence 

interval, in 

ft3/s

Change, 

in percent

14 0210215960 Cape Fear River above NC Highway 42 near 

Corinth, NC

16.7 1,140 0.21 41.1 5.8 (F) 1,076 1,208 DA

F9 Municipal NA Withdrawal: 10.84 ft3/s Return: 0.59 ft3/s 2

15 0210215995 Cape Fear powerplant discharge canal at NC 

Highway 42 near Corinth, NC

DA -- -- -- -- -- -- DA

16 02102176 Cape Fear powerplant discharge canal above 

mouth near Corinth, NC

DA -- -- -- -- -- -- DA

17 02102177 Cape Fear River upstream from Buckhorn Dam 

near Corinth, NC

14.6 1,210 0.16 26.5 3.5 (G) 1,168 1,252 6.0

Sites at or below Buckhorn Dam

18 02102178 Cape Fear River at Buckhorn Dam near Corinth, 

NC

14.3

19 0210217810 Cape Fear River downstream from Buckhorn 

Dam near Corinth, NC

14 1,230 0.53 27.9 3.6 (G) 1,189 1,279 2.0

20 02102192 Buckhorn Creek near Corinth, NC DA 25.9 0.58 -- -- -- -- DA21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

10. 1,330 0.79 14.5 1.7 (G) 1,304 1,350 7.5

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

5.9 1,270 0.91 35 4.4 (G) 1,217 1,329 -4.1

23 02102278 Cape Fear River above Hector Creek near Chalybeate, NC 4.2 1,290 1.03 55.2 6.8 (F) 1,206 1,382 1.6

24 02102280 Hector Creek near Chalybeate, NC DA 6.31 0.729 -- -- -- -- DA

25 02102283 Cape Fear R adjacent to Bradley Road near Lillington, NC 3.4 1,360 0.71 37.3 4.4 (G) 1,302 1,422 5.3

26 02102289 Cape Fear River above Neills Creek near Lillington, NC 1.4 1,340 0.69 30.4 3.6 (G) 1,295 1,393 -1.3

27 02102480 Neills Creek near Lillington, NC DA 11.4 0.164 -- -- -- -- DA

F10 Municipal NA Withdrawal: 23.73 ft3/s Return: Outside of study area

28 02102500 Cape Fear River at Lillington, NC 0.0 1,400 0.7 46.3 5.3 (F) 1,321 1,469 3.8

1Computed DAily discharge at this site for indicated DAte.2Reported return discharge associated with water-treatment plant operations, not the wastewater-treatment operations that discharge to a tributary to the Deep River upstream from the study area.
30 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 5. Results of synoptic discharge measurements made on June 25, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillilngton, North Carolina. [USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic feet per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good, (P), poor, (F), fair (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)] Site index number (figs. 1, 6, 7) USGS station number Station name Main stem river miles upstream from Lillington streamgage (site 28) Measured discharge Measured discharge, in ft3/s Average velocity, in ft/s Standard deviation, in ft3/s 95-percent confi- dence interval of measurement uncertainty, in percent (measurement rating) Lowest discharge in 95-per- cent con- fidence interval, in ft3/s Highest discharge in 95-per- cent con- fidence interval, in ft3/s Change, in percent Sites above Buckhorn Dam

1 02098198 Haw R below B. Everett Jordan Dam near 

Moncure, NC

24.3 164 0.16 5.5 2.7 (G) 160 168 DA

F1 Industrial NA Withdrawal: 0.36 ft3/s Return: 0.11 ft3/s

F2 Industrial NA Withdrawal: 0 ft3/s Return: Not recorded

F3 Industrial NA Withdrawal: 0.36 ft3/s Return: 0.02 ft3/s

F4 Industrial NA Withdrawal: 0.15 ft3/s Return: 0 ft3/s

2 02098210 Haw River above Deep River near Haywood, NC 20.7 185 0.06 20.2 11.5 (P) 164 206 12.8

3 02102000 Deep River at Moncure, NC DA 236 1 -- -- -- -- -- DA

F6 Hydropower power generation NA Power generation offline all day.

4 0210204915 Deep River above mouth near Moncure, NC DA 262 0.11 27.1 16.5 (P) 219 305 DA

5 02102050 Cape Fear River above powerplant intake near 

Moncure, NC

20.3 431 0.15 10.4 3.9 (G) 414 448 133.0

F7 Regional power utility NA Withdrawal: 395.77 ft3/s Return: 329.4 ft3/s

6 02102082 Cape Fear River below powerplant intake near 

Moncure, NC

19.4 -- -- -- -- -- -- -- --

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

18.4 -- -- -- -- -- -- -- --

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

DA 325 1.05 10.8 5.3 (F) 308 342 DA

F8 Industrial NA Withdrawal: 0 ft3/s Return: No return discharge

9 0210209450 Cape Fear powerplant discharge canal above 

juncture at Brickhaven, NC

DA 332 1.33 2.1 1.0 (G) 329 335 DA

10 0210209475 Cape Fear powerplant discharge canal below 

dam at Brickhaven, NC

DA 0.034 0.008 -- -- -- -- DA

11 0210209625 Unnamed stream between canal and Cape 

Fear River at Brickhaven, NC

DA 149 1.45 7.4 4.0 (G) 143 155 DA

12 0210209650 Cape Fear powerplant discharge canal below 

juncture at Brickhaven, NC

DA 178 0.97 4.1 3.7 (G) 171 185 DA

13 02102159 Lick Creek near Rosser, NC DA .33 0.008 -- -- -- -- DA
Results and Interpretation of Data 31

Table 5. Results of synoptic discharge measurements made on June 25, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillilngton, North Carolina.—Continued[USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic feet per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from 

next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good, (P), poor, (F), fair (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)]

Site 

index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name

Main stem

 river miles 

upstream from 

Lillington 

streamgage 

(site 28)

Measured discharge

Measured 

discharge, 

in ft3/s

Average 

velocity,

in ft/s

Standard 

deviation, 

in ft3/s

95-percent confidence interval of 

measurement 

uncertainty, 

in percent

(measurement 

rating)

Lowest 

discharge 

in 95-percent confidence 

interval, 

in ft3/s

Highest 

discharge 

in 95-percent confidence 

interval, 

in ft3/s

Change, 

in percent

14 0210215960 Cape Fear River above NC Highway 42 near 

Corinth, NC

16.7 -- -- -- -- -- -- -- --

F9 Municipal NA Withdrawal: 12.48 ft3/s Return: 0.59 ft3/s 2

15 0210215995 Cape Fear powerplant discharge canal at NC 

Highway 42 near Corinth, NC

DA 207 0.79 14.6 5.6 (F) 195 219 DA

16 02102176 Cape Fear powerplant discharge canal above 

mouth near Corinth, NC

DA 190 0.62 5.9 5.0 (G) 181 199 DA

17 02102177 Cape Fear River upstream from Buckhorn 

Dam near Corinth, NC

14.6 160 0.02 22. 22.0 (P) 125 195 DA

Sites at or below Buckhorn Dam

18 02102178 Cape Fear River at Buckhorn Dam near 

Corinth, NC

14.3

19 0210217810 Cape Fear River downstream from Buckhorn 

Dam near Corinth, NC

14 357 0.22 52.6 11.8 (P) 315. 399 123.1

20 02102192 Buckhorn Creek near Corinth, NC DA 0.0 -- -- -- -- -- DA

21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

10 411 0.333 9.6 3.7 (G) 396 426 15.1

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

5.9 401 0.497 22.5 4.5 (G) 383 419 -2.4

23 02102278 Cape Fear River above Hector Creek near 

Chalybeate, NC

4.2 397 0.519 18.3 3.7 (G) 382 412 -1.0

24 02102280 Hector Creek near Chalybeate, NC DA 1.17 0.205 -- -- -- -- DA

25 02102283 Cape Fear R adjacent to Bradley Road near 

Lillington, NC

3.4 410 0.313 18.5 3.6 (G) 396 426 3.5

26 02102289 Cape Fear River above Neills Creek near Lillington, NC 1.4 428 0.338 11.5 4.3 (G) 410 446 4.1

27 02102480 Neills Creek near Lillington, NC DA 1.61 0.024 -- -- -- -- DA

F10 Municipal NA Withdrawal: 25.39 ft3/s Return: Outside of study area

28 02102500 Cape Fear River at Lillington, NC 0.0 384 0.19 22 4.6 (G) 366 402 -10.3

1Computed daily discharge at this site for indicated date.2 Reported return discharge associated with water-treatment plant operations, not the wastewater-treatment operations that discharge to a tributary to the Deep River upstream from the study area.
32 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 6. Results of synoptic discharge measurements made on July 22, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina. [USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence intercal: (G), good; (F) fair; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)] Site index number (figs. 1, 6, 7) USGS station number Station name Main stem river miles upstream from Lillington streamgage (site 28) Measured discharge Measured discharge, in ft3/s Average velocity, in ft/s Standard deviation, in ft3/s 95-percent confi- dence interval of measurement uncertainty, in percent (measurement rating) Lowest discharge in 95-per- cent con- fidence interval, in ft3/s Highest dicharge in 95-per cent con- fidence interval, in ft3/s Change, in percent Sites above Buckhorn Dam

1 02098198 Haw R below B. Everett Jordan Dam near 

Moncure, NC

24.3 430 0.38 13.2 4.9 (G) 409 451 DA

F1 Industrial NA Withdrawal: 0.33 ft3/s Return: 0.1 ft3/s

F2 Industrial NA Withdrawal: 0 ft3/s Return: 0 ft3/sF3 Industrial NA Withdrawal: Not recorded Return: 0.06 ft3/sF4 Industrial NA Withdrawal: 0.11 ft3/s Return: 0 ft3/s

2 02098210 Haw River above Deep River near Haywood, NC 20.7 436 0.17 16 5.9 (F) 410 462 1.4

3 02102000 Deep River at Moncure, NC DA 164 1 -- -- -- -- -- DA

F6 Hydropower power generation NA Power generation online between midnight and 03:00, then between 13:00 and 16:00; offline 

during remainder of day.

4 0210204915 Deep River above mouth near Moncure, NC DA 193 0.09 15.3 6.3 (F) 181 205 DA

5 02102050 Cape Fear River above powerplant intake 

near Moncure, NC

20.3 653 0.22 28.9 7.1 (F) 607 699 49.8

F7 Regional power utility NA Withdrawal: 395.77 ft3/s Return: 338.53 ft3/s

6 02102082 Cape Fear River below powerplant intake 

near Moncure, NC

19.4 320 0.09 13 6.5 (F) 299 341 -51.0

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

18.4 294 0.067 10 5.4 (F) 278 310 -8.1

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

DA 355 1.02 3.9 1.8 (G) 349 361 DA

F8 Industrial NA Withdrawal: 0 ft3/s Return: No return discharge

9 0210209450 Cape Fear powerplant discharge canal above 

juncture at Brickhaven, NC

DA 319 1.34 11.1 3.7 (G) 307 331 DA

10 0210209475 Cape Fear powerplant discharge canal below 

dam at Brickhaven, NC

DA -- -- -- -- -- -- DA

11 0210209625 Unnamed stream between canal and Cape 

Fear River at Brickhaven, NC

DA 160. 1.5 3.7 3.7 (G) 154 166 DA

12 0210209650 Cape Fear powerplant discharge canal below 

juncture at Brickhaven, NC

DA 202 1.06 4.8 1.9 (G) 198 206 DA
Results and Interpretation of Data 33

Table 6. Results of synoptic discharge measurements made on July 22, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.—Continued[USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from 

next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence intercal: (G), good; (F) fair; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)]

Site 

index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name

Main stem

 river miles 

upstream from 

Lillington 

streamgage 

(site 28)

Measured discharge

Measured 

discharge, 

in ft3/s

Average 

velocity,

in ft/s

Standard 

deviation, 

in ft3/s

95-percent confidence interval of 

measurement 

uncertainty, 

in percent

(measurement 

rating)

Lowest 

discharge 

in 95-percent confidence 

interval, 

in ft3/s

Highest 

dicharge 

in 95-per

cent confidence 

interval, 

in ft3/s

Change, 

in percent

13 02102159 Lick Creek near Rosser, NC DA -- -- -- -- -- -- DA14 0210215960 Cape Fear River above NC Highway 42 near 

Corinth, NC

16.7 442 0.08 13.3 4.8 (G) 421 463 50.3

F9 Municipal NA Withdrawal: 11.77 ft3/s Return: 1.01 ft3/s 2

15 0210215995 Cape Fear powerplant discharge canal at NC 

Highway 42 near Corinth, NC

DA 198 0.785 1.8 1.4 (G) 195 201 DA

16 02102176 Cape Fear powerplant discharge canal above 

mouth near Corinth, NC

DA 194 0.604 7.4 6.1 (F) 182 206 DA

17 02102177 Cape Fear River upstream from Buckhorn 

Dam near Corinth, NC

14.6 393 0.06 31.2 6.4 (F) 368 418 -11.1

Sites at or below Buckhorn Dam

18 02102178 Cape Fear River at Buckhorn Dam near 

Corinth, NC

14.3

19 0210217810 Cape Fear River downstream from Buckhorn 

Dam near Corinth, NC

14 577 0.312 22.6 6.3 (F) 541 613 46.8

20 02102192 Buckhorn Creek near Corinth, NC DA 0.57 0.02 -- -- -- -- DA

21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

10 569 0.437 2.4 0.7 (G) 565 573 -1.4

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

5.9 583 0.669 6.2 1.7 (G) 573 593 2.5

23 02102278 Cape Fear River above Hector Creek near 

Chalybeate, NC

4.2 564 0.536 30.2 4.3 (G) 540 588 -3.3

24 02102280 Hector Creek near Chalybeate, NC DA 0.84 0.171 -- -- -- -- DA

25 02102283 Cape Fear R adjacent to Bradley Road near 

Lillington, NC

3.4 568 0.374 36 5.1 (F) 539 597 0.7

26 02102289 Cape Fear River above Neills Creek near 

Lillington, NC

1.4 581 0.431 13 3.6 (G) 560 602 2.3

27 02102480 Neills Creek near Lillington, NC DA 1.18 0.019 -- -- -- -- DA

F10 Municipal NA Withdrawal: 20.27 ft3/s Return: Outside of study area

28 02102500 Cape Fear River at Lillington, NC 0.0 609 0.39 26 6.8 (F) 567 651 4.8

1Computed daily discharge at this site for indicated date.2Reported return discharge associated with water-treatment plant operations, not the wastewater-treatment operations that discharge to a tributary to the Deep River upstream from the study area.
34 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 7. Results of synoptic discharge measurements made on August 18, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina. [USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good; (F), fair; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)] Site index number (figs. 1, 6, 7) USGS station number Station name Main stem river miles upstream from Lillington streamgage (site 28) Measured discharge Measured discharge, in ft3/s Average velocity, in ft/s Standard deviation, in ft3/s 95-percent confi- dence interval of measurement uncertainty, in percent (measure- ment rating) Lowest discharge in 95-per- cent con- fidence interval, in ft3/s Highest discharge in 95-per- cent con- fidence interval, in ft3/s Change, in percent Sites above Buckhorn Dam

1 02098198 Haw R below B. Everett Jordan Dam near 

Moncure, NC

24.3 443 0.41 12.6 4.6 (G) 423 463 DA

F1 Industrial NA Withdrawal: 0.33 ft3/s Return: 0.09 ft3/s

F2 Industrial NA Withdrawal: Not recorded Return: 0 ft3/sF3 Industrial NA Withdrawal: 0.31 ft3/s Return: 0.1 ft3/sF4 Industrial NA Withdrawal: 0.2 ft3/s Return: 0 ft3/s

2 02098210 Haw River above Deep River near Haywood, NC 20.7 411 0.15 16.2 6.3 (F) 385 437 -7.2

3 02102000 Deep River at Moncure, NC DA 90.3 0.07 10.8 9.6 (P) 82 99 DA

F6 Hydropower power generation NA Power generation offline all day.

4 0210204915 Deep River above mouth near Moncure, NC DA 101 0.05 24.2 19.2 (P) 82 120 DA

5 02102050 Cape Fear River above powerplant intake 

near Moncure, NC

20.3 639 0.19 34.8 8.7 (P) 583 695 55.5

F7 Regional power utility NA Withdrawal: 395.77 ft3/s Return: 337.29 ft3/s

6 02102082 Cape Fear River below powerplant intake 

near Moncure, NC

19.4 219 0.06 14.1 10.3 (P) 196 242 -65.7

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

18.4 312 0.067 80.4 41.2 (P) 183 441 42.5

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

DA 351 1.02 2.1 1.0 (G) 348 354 DA

F8 Industrial NA Withdrawal: 0 ft3/s Return: No return discharge

9 0210209450 Cape Fear powerplant discharge canal 

above juncture at Brickhaven, NC

DA 341 1.33 2.6 1.2 (G) 337 345 DA

10 0210209475 Cape Fear powerplant discharge canal 

below dam at Brickhaven, NC

DA -- -- -- -- -- -- DA

11 0210209625 Unnamed stream between canal and Cape 

Fear River at Brickhaven, NC

DA 157 1.43 3.2 3.2 (G) 152 162 DA

12 0210209650 Cape Fear powerplant discharge canal 

below juncture at Brickhaven, NC

DA 182 0.95 0.4 0.3 (G) 181 183 DA

13 02102159 Lick Creek near Rosser, NC DA 0.18 0.011 -- -- -- -- DA
Results and Interpretation of Data 35

Table 7. Results of synoptic discharge measurements made on August 18, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.—Continued[USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from 

next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good; (F), fair; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)]

Site 

index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name

Main stem

 river miles 

upstream from 

Lillington 

streamgage 

(site 28)

Measured discharge

Measured 

discharge, 

in ft3/s

Average 

velocity,

in ft/s

Standard 

deviation, 

in ft3/s

95-percent confidence interval of 

measurement 

uncertainty, 

in percent

(measurement rating)

Lowest 

discharge 

in 95-percent confidence 

interval, 

in ft3/s

Highest 

discharge 

in 95-percent confidence 

interval, 

in ft3/s

Change, 

in percent

14 0210215960 Cape Fear River above NC Highway 42 

near Corinth, NC

16.7 391 0.08 26.8 11.0 (P) 348 434 25.3

F9 Municipal NA Withdrawal: 10.27 ft3/s Return: 0.53 ft3/s 1

15 0210215995 Cape Fear powerplant discharge canal at 

NC Highway 42 near Corinth, NC

DA 182 0.68 4.9 4.3 (G) 174 190 DA

16 02102176 Cape Fear powerplant discharge canal 

above mouth near Corinth, NC

DA 184 0.6 5.3 4.6 (G) 176 192 DA

17 02102177 Cape Fear River upstream from Buckhorn 

Dam near Corinth, NC

14.6 300 0.04 101 26.9 (P) 219 381 -23.3

Sites at or below Buckhorn Dam

18 02102178 Cape Fear River at Buckhorn Dam near 

Corinth, NC

14.3

19 0210217810 Cape Fear River downstream from Buckhorn Dam near Corinth, NC 14 485 0.26 23.1 7.6 (F) 448 522. 61.7

20 02102192 Buckhorn Creek near Corinth, NC DA 0.0 -- -- -- -- -- DA21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

10 514 0.403 11.5 3.6 (G) 496 532 6.0

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

5.9 510 0.498 16.8 5.3 (F) 483 537 -0.8

23 02102278 Cape Fear River above Hector Creek near 

Chalybeate, NC

4.2 -- -- -- -- -- -- DA

24 02102280 Hector Creek near Chalybeate, NC DA 0.81 0.225 -- -- -- -- DA

25 02102283 Cape Fear R adjacent to Bradley Road near 

Lillington, NC

3.4 532 0.369 18.1 5.4 (F) 503 561 DA

26 02102289 Cape Fear River above Neills Creek near 

Lillington, NC

1.4 517 0.382 21.5 6.7 (F) 483 551 -2.8

27 02102480 Neills Creek near Lillington, NC DA 1.78 0.027 -- -- -- -- DA

F10 Municipal NA Withdrawal: 20.7 ft3/s Return: Outside of study area

28 02102500 Cape Fear River at Lillington, NC 0.0 512 2 -- -- -- -- -- DA

1Reported return discharge associated with water-treatment plant operations, not the wastewater-treatment operations that discharge to a tributary to the Deep River upstream from the study area.2Computed daily discharge at this site for indicated date.
36 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 8. Results of synoptic discharge measurements made on September 9, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina. [USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good; (F), fair; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)] Site index number (figs. 1, 6, 7) USGS station number Station name Main stem river miles upstream from Lillington streamgage (site 28) Measured discharge Measured discharge, in ft3/s Average velocity, in ft/s Standard deviation, in ft3/s 95-percent con- fidence interval of measurement uncertainty, in percent (measure- ment rating) Lowest discharge in 95-percent confidence interval, in ft3/s Highest dis- charge in 95-percent confidence interval, in ft3/s Change, in percent Sites above Buckhorn Dam

1 02098198 Haw R below B. Everett Jordan Dam near 

Moncure, NC

24.3 274 0.29 7.9 4.6 (G) 261 287 DA

F1 Industrial NA Withdrawal: 0.35 ft3/s Return: 0.07 ft3/s

F2 Industrial NA Withdrawal: 0 ft3/s Return: 0 ft3/sF3 Industrial NA Withdrawal: 0.17 ft3/s Return: 0.05 ft3/sF4 Industrial NA Withdrawal: 0.09 ft3/s Return: 0 ft3/s

2 02098210 Haw River above Deep River near Haywood, NC 20.7 266 0.09 5.9 3.5 (G) 257 275 -2.93 02102000 Deep River at Moncure, NC DA 86 1 0.0 0.0 -- (P) -- -- DA

F6 Hydropower power generation NA Power generation offline all day.

4 0210204915 Deep River above mouth near Moncure, NC DA 90.1 0.04 10 8.9 (P) 82 98 DA5 02102050 Cape Fear River above powerplant intake 

near Moncure, NC

20.3 355 0.11 23 10.4 (P) 318 392 33.5

F7 Regional power utility NA Withdrawal: 213.82 ft3/s Return: 178.08 ft3/s

6 02102082 Cape Fear River below powerplant intake 

near Moncure, NC

19.4 217 0.05 10.5 7.9 (F) 197 231 -39.7

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

18.4 211 0.05 10.9 8.3 (P) 194 228 -1.4

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

DA 170 0.68 2.9 2.7 (G) 165 175 DA

F8 Industrial NA Withdrawal: 0 ft3/s Return: No return discharge

9 0210209450 Cape Fear powerplant discharge canal above 

juncture at Brickhaven, NC

DA 179 0.88 3.8 3.4 (G) 173 185 DA

10 0210209475 Cape Fear powerplant discharge canal below 

dam at Brickhaven, NC

DA -- -- -- -- -- -- DA

11 0210209625 Unnamed stream between canal and Cape 

Fear River at Brickhaven, NC

DA 77 0.89 2.2 4.6 (G) 73 81 DA

12 0210209650 Cape Fear powerplant discharge canal below 

juncture at Brickhaven, NC

DA 98.3 0.73 1 1.7 (G) 97 100 DA

13 02102159 Lick Creek near Rosser, NC DA 0.0 -- -- -- -- -- DA
Results and Interpretation of Data 37

Table 8. Results of synoptic discharge measurements made on September 9, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.—Continued[USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from 

next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good; (F), fair; (P), poor (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)]

Site 

index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name

Main stem

 river miles 

upstream from 

Lillington 

streamgage 

(site 28)

Measured discharge

Measured 

discharge, 

in ft3/s

Average 

velocity,

in ft/s

Standard 

deviation, 

in ft3/s

95-percent confidence interval 

of measurement 

uncertainty, 

in percent

(measurement rating)

Lowest 

discharge in 

95-percent 

confidence 

interval, 

in ft3/s

Highest discharge in 

95-percent 

confidence 

interval, 

in ft3/s

Change, in 

percent

14 0210215960 Cape Fear River above NC Highway 42 near 

Corinth, NC

16.7 -- -- -- -- -- -- DA

F9 Municipal NA Withdrawal: 11.28 ft3/s Return: 0.61 ft3/s 2

15 0210215995 Cape Fear powerplant discharge canal at NC 

Highway 42 near Corinth, NC

DA 104 0.47 4 6.1 (F) 98 110 DA

16 02102176 Cape Fear powerplant discharge canal above 

mouth near Corinth, NC

DA 102 0.34 3.3 5.2 (F) 97 107 DA

17 02102177 Cape Fear River upstream from Buckhorn 

Dam near Corinth, NC

14.6 250 0.04 108 34.6 (P) 164 336 DA

Sites at or below Buckhorn Dam

18 02102178 Cape Fear River at Buckhorn Dam near 

Corinth, NC

14.3

19 0210217810 Cape Fear River downstream from Buckhorn Dam near Corinth, NC 14 346 0.2 19.6 4.5 (G) 330 362 38.4

20 02102192 Buckhorn Creek near Corinth, NC DA 0.0 -- -- -- -- -- DA

21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

10 395 0.317 17.6 7.1 (F) 367 423 14.2

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

5.9 422 0.613 17.7 3.4 (G) 408 436 6.8

23 02102278 Cape Fear River above Hector Creek near 

Chalybeate, NC

4.2 424 0.423 29.8 5.6 (F) 400 448 0.5

24 02102280 Hector Creek near Chalybeate, NC DA 4.67 0.147 -- -- -- -- DA25 02102283 Cape Fear R adjacent to Bradley Road near 

Lillington, NC

3.4 404 0.26 17.6 7.0 (F) 376 432 -4.7

26 02102289 Cape Fear River above Neills Creek near 

Lillington, NC

1.4 358 0.297 14.7 3.3 (G) 346 370 -11.4

27 02102480 Neills Creek near Lillington, NC DA 13.2 0.165 -- -- -- -- DA

F10 Municipal NA Withdrawal: 18.91 ft3/s Return: Outside of study area

28 02102500 Cape Fear River at Lillington, NC 0.0 403 0.3 41.6 8.3 (P) 370 436 12.6

1 Computed daily discharge at this site for indicated date.2 Reported return discharge associated with water-treatment plant operations, not the wastewater-treatment operations that discharge to a tributary to the Deep River upstream from the study area.
38 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina Table 9. Results of synoptic discharge measurements made on October 1, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina. [USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (P), poor; (F), fair; (G), good (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)] Site index number (figs. 1, 6, 7) USGS station number Station name Main stem river miles upstream from Lillington streamgage (site 28) Measured discharge Measured discharge, in ft3/s Average velocity, in ft/s Standard deviation, in ft3/s 95-percent con- fidence interval of measurement uncertainty, in percent (measure- ment rating) Lowest discharge in 95-percent confidence interval, in ft3/s Highest discharge in 95-percent confidence interval, in ft3/s Change, in percent Sites above Buckhorn Dam

1 02098198 Haw R below B. Everett Jordan Dam near Moncure, NC 24.3 214 0.23 12 8.9 (P) 196 234 DA

F1 Industrial NA Withdrawal: 0.28 ft3/s Return: 0.05 ft3/s

F2 Industrial NA Withdrawal: 0 ft3/s Return: 0 ft3/sF3 Industrial NA Withdrawal: 0.21 ft3/s Return: 0.11 ft3/s

F4 Industrial NA Withdrawal: 0.63 ft3/s Return: 0.01 ft3/s

2 02098210 Haw River above Deep River near Haywood, NC 20.7 204 0.08 17.9 7.0 (F) 190 218 -5.1

3 02102000 Deep River at Moncure, NC DA 82 1 -- -- -- -- -- DA

F6 Hydropower power generation NA Power generation offline all day.

4 0210204915 Deep River above mouth near Moncure, NC DA 68.9 0.033 22.5 26.1 (P) 51 87 DA

5 02102050 Cape Fear River above powerplant intake 

near Moncure, NC

20.3 317 0.1 17.9 9.0 (P) 288 346 55.4

F7 Regional power utility NA Withdrawal: 395.77 ft3/s Return: 316.87 ft3/s

6 02102082 Cape Fear River below powerplant intake 

near Moncure, NC

19.4 46.2 0.01 20.5 35.5 (P) 30 63 -85.4

7 02102090 Cape Fear River above railroad bridge near 

Rosser, NC

18.4 40.8 0.01 30.9 60.6 (P) 16 66 -11.7

8 02102094 Cape Fear powerplant discharge canal near 

Brickhaven, NC

DA 309 0.95 7.7 4.0 (G) 297 321 DA

F8 Industrial NA Withdrawal: 0 ft3/s Return: No return discharge

9 0210209450 Cape Fear powerplant discharge canal 

above juncture at Brickhaven, NC

DA 308 1.25 5.5 2.9 (G) 299 317 DA

10 0210209475 Cape Fear powerplant discharge canal 

below dam at Brickhaven, NC

DA -- -- -- -- -- -- DA

11 0210209625 Unnamed stream between canal and Cape 

Fear River at Brickhaven, NC

DA 159 1.51 8.2 4.1 (G) 152. 166 DA

12 0210209650 Cape Fear powerplant discharge canal 

below juncture at Brickhaven, NC

DA 154 0.84 5.6 5.8 (F) 145 163 DA

13 02102159 Lick Creek near Rosser, NC DA 1.66 0.057 -- -- -- -- DA
Results and Interpretation of Data 39

Table 9. Results of synoptic discharge measurements made on October 1, 2009, on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.—Continued[USGS, U.S. Geological Survey; main stem refers to the Haw and Cape Fear Rivers; ft3/s, cubic foot per second, ft/s, foot per second; change, in percent, computed as difference in measured discharge from 

next upstream measured discharge on main stem; DA, doesn’t apply; NA, not available; --, not measured; measurement rating determined from base uncertainty at 95-percent confidence interval: (P), poor; (F), fair; (G), good (http://nc.water.usgs.gov/usgs/info/qaplan/surface.html)]

Site 

index 

number

(figs.

1, 6, 7)

USGS 

station 

number

Station name

Main stem

 river miles 

upstream from 

Lillington 

streamgage 

(site 28)

Measured discharge

Measured 

discharge, 

in ft3/s

Average 

velocity,

in ft/s

Standard 

deviation, 

in ft3/s

95-percent confidence interval 

of measurement 

uncertainty, 

in percent

(measurement rating)

Lowest 

discharge in 

95-percent 

confidence 

interval, 

in ft3/s

Highest 

discharge in 

95-percent 

confidence 

interval, in 

ft3/s

Change, 

in percent

14 0210215960 Cape Fear River above NC Highway 42 

near Corinth, NC

16.7 76 0.014 49.5 52.1 (P) 36 116 86.3

F9 Municipal NA Withdrawal: 10.85 ft3/s Return: 0.09 ft3/s 1

15 0210215995 Cape Fear powerplant discharge canal at 

NC Highway 42 near Corinth, NC

DA 152 0.611 3.6 3.8 (G) 146 158 DA

16 02102176 Cape Fear powerplant discharge canal 

above mouth near Corinth, NC

DA 149 0.51 3.3 3.6 (G) 144 154 DA

17 02102177 Cape Fear River upstream from Buckhorn 

Dam near Corinth, NC

14.6 -- -- -- -- -- -- -- --

Sites at or below Buckhorn Dam

18 02102178 Cape Fear River at Buckhorn Dam near 

Corinth, NC

14.3

19 0210217810 Cape Fear River downstream from Buckhorn Dam near Corinth, NC 14 285 0.18 71.6 26.4 (P) 210 360 DA

20 02102192 Buckhorn Creek near Corinth, NC DA 0.8 0.03 -- -- -- -- DA21 02102240 Cape Fear River adjacent to Bay Street near 

Cokesbury, NC

10 309 0.263 21 7.1 (F) 287 331 8.4

22 02102265 Cape Fear River at Raven Rock State Park 

group camp, NC

5.9 302 0.513 19.8 10.5 (P) 270 334 -2.3

23 02102278 Cape Fear River above Hector Creek near 

Chalybeate, NC

4.2 311 0.408 6.2 3.2 (G) 301 321 3.0

24 02102280 Hector Creek near Chalybeate, NC DA 4.09 0.146 -- -- -- -- DA25 02102283 Cape Fear R adjacent to Bradley Road near 

Lillington, NC

3.4 325 0.204 10.1 5.0 (G) 309 341 4.5

26 02102289 Cape Fear River above Neills Creek near 

Lillington, NC

1.4 318 0.262 10.3 5.2 (F) 302 334 -2.2

27 02102480 Neills Creek near Lillington, NC DA 6.05 0.082 -- -- -- -- DA

F10 Municipal NA Withdrawal: 18.6 ft3/s Return: Outside of study area

28 02102500 Cape Fear River at Lillington, NC 0.0 327 0.24 11.4 5.6 (F) 309 345 2.8

1 Computed daily discharge at this site for indicated date.2 Reported return discharge associated with water-treatment plant operations, not the wastewater-treatment operations that discharge to a tributary to the Deep River upstream from the study area.
40 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

During each series of synoptic measurements, discharge 

measurements also were made on selected tributaries where 

the contributing drainage area exceeded 5 percent of the drainage area of the main stem just upstream from the confluence. 

The selected tributaries include the Deep River, Lick Creek, 

Buckhorn Creek (fig. 6, sites 4, 13, 20, respectively), Hector Creek and Neills Creek (fig. 7, sites 24, 27, respectively). 

Measured discharges and average velocities are listed in 

tables 4–9. Not including the Deep River, measured discharge 

values at the four remaining tributaries were less than 5 percent and did not provide substantial flow contributions to the 

main stem, particularly during base-flow conditions. 

In addition to the reduced flows downstream from the 

power-plant intake, average velocities from the measurements 

varied along the main stem (fig. 20; tables 4–9). Between the 

power-plant intake and Buckhorn Dam, the average velocities determined from the measurements were lower than along 

any other part of the main stem. For the synoptic measurements conducted during June through October, the average 

velocities in this reach were less than 0.1 foot per second 

(ft/s). In addition to the increased channel width between the 

intake point and Buckhorn Dam, the amount of storage in the 

channel upstream from Buckhorn Dam results in very slow 

water travel along this reach during base-flow conditions. The 

average velocities in the diversion canal adjacent to the main 

stem commonly ranged from 0.5 to about 1.5 ft/s at the canalmeasurement sites (tables 4–9). Average velocities in the reach 

downstream from Buckhorn Dam increased from about 0.2 or 

0.3 ft/s to a range of about 0.5 to almost 0.7 ft/s at the measurement sites at Raven Rock (fig. 7, site 22) and above Hector Creek (site 23), then decreased to a range of 0.2 to 0.4 ft/s 

toward the Lillington streamgage (site 28). These variations in 

average velocity downstream from Buckhorn Dam were attributed to changes in channel widths on the main stem between 

Raven Rock State Park and the Lillington streamgage (fig. 20) 

as well as minor variations in the channel slope (fig. 2). While 

changes in velocities do not factor into a determination of flow 

loss, an understanding of the velocity patterns determined 

from the series of synoptic measurements emphasizes recognition of the complex flow patterns in the reach.

Streamgage Data Collection and Analyses

In the years leading up to this study, questions were 

raised about the accuracy of the discharge records at the USGS 

streamgages used in the determination of possible flow losses. 

Questions also were raised concerning the determination of 

flow releases for Jordan Lake Dam operated by the USACE. 

Therefore, a comparison of the stage-discharge ratings and 

the measured discharges used to compute discharge records 

was completed for Deep River at Moncure (fig. 1, site 3) 

and Cape Fear River at Lillington (fig. 1, site 28). In addition to the rating analyses for these two sites, velocity data 

at the streamgage on the Haw River below B. Everett Jordan 

Dam (site 1) downstream from Jordan Lake and stage data 

at Cape Fear River at Buckhorn Dam near Corinth (site 18) 

were collected. Analyses completed on the ratings at the two 

streamgages (sites 3 and 28) did not indicate the presence of 

bias in the discharge computations that would result in the 

occurrence of false flow losses. Comparisons of discharge 

measurements collected on the Haw River below Jordan 

Lake Dam provided general support of the current USACE 

discharge-computation tables used for reporting flow releases 

from the dam.

Analyses of Ratings and Measured Discharges

Analyses of discharge measurements and ratings for 

the two streamgages at Deep River at Moncure (site 3) and 

Cape Fear River at Lillington (site 28) were completed as part 

of this investigation to verify the accuracy of the computed 

discharges. USGS personnel responsible for the operation of 

the streamgages were routinely called upon to make special 

visits to the sites to verify their accuracy and functionality, as 

was the case for the Lillington streamgage (site 28) during the 

years leading up to this study. The analyses were completed to 

determine if a systematic bias existed in the discharge records, 

possibly giving a false computation of flow loss between 

upstream and downstream ends of the study reach. For the 

streamgage at Cape Fear River at Lillington (site 28) at the 

outlet of the study reach, such a bias would be indicated by 

consistently positive percentage differences over time (following any rating shifts), meaning the base rating discharges 

would be consistently lower than the measured discharges. 

Such a pattern could potentially result in an apparent flow loss 

due to differences between the measured discharge and the 

discharge computed using the stage-discharge rating. However, for the streamgage at Deep River at Moncure (one of the 

inputs, site 3), a bias would be indicated by shifted percentage 

differences that are consistently negative, meaning the base 

rating discharges would be consistently higher than the measured discharges obtained during the streamgage inspections.

Assessment of stage-discharge ratings focused on 

discharge measurements and ratings after February 1982, 

the month during which lake levels at Jordan Lake initially 

reached normal pool elevation. Two ratings were used during 

the 1982–2011 water years at Deep River at Moncure (site 3). 

A total of 99 discharge measurements were made at this site 

during the same period and ranged in magnitude from 27.9 to 

21,500 ft3/s (fig. 21A). The measurements made during this 

period were rated as good (40 percent), fair (44 percent), or 

poor (16 percent). Among these measurements, 66 were below 

500 ft3/s; the distribution of these measurement ratings as 

good, fair, or poor was 25, 55, and 20 percent, respectively.

Percentage differences at Deep River at Moncure 

(site 3) during the 1982–2011 water years ranged from about 

–7.5 percent to nearly +19 percent with values within plus or 

minus (+/–) 5 percent for 85 measurements (fig. 21B). For the 

measurements followed by a temporary rating shift (indicated 

by X symbol in fig. 21B), the percentage differences indicated 

are the shifted percentage differences. The measurement with 

a percentage difference of almost 19 percent was rated as 
Results and Interpretation of Data 41

Figure 20. (A) Average velocities and (B) channel widths determined from the series of synoptic measurements 

made during 2009 on the Haw and Cape Fear Rivers between Jordan Lake Dam and Lillington, North Carolina.

30 25 20 15 10 5 0

Distance upstream from U.S. Geological Survey station 02102500 on Cape Fear River at Lillington, in river miles

800

700

600

500

400

300

200

100

0

Channel width, in feet

Deep RiverLick CreekHector CrNeills Cr

private

NC Hwy 42

boat ramp

30 25 20 15 10 5 0

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Average velocity, in cubic feet per second

April 27, 2009

June 25, 2009

July 22, 2009

August 18, 2009

September 9, 2009

October 1, 2009

Jordan Lake

Dam

Deep Riverregional power

plant intake

Lick Creek

Raven Rock

Hector Cr

Neills Cr

State Park

Jordan Lake

Dam

regional power

plant intake

Raven Rock

State Park

private

NC Hwy 42

boat ramp

EXPLANATION

Buckhorn

Dam

Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Buckhorn

Dam

April 27, 2009

June 25, 2009

July 22, 2009

August 18, 2009

September 9, 2009

October 1, 2009

EXPLANATION

B Mesozoic (Triassic) Basin

Carolina Terrane

(Cary sequence) Crabtree Terrane

Figure 20. 

A
42 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

poor because of equipment malfunction, and the measurement 

was not used to apply a rating shift. A total of 53 rating shifts 

were applied during the period, and 17 shifts were positive and 

36 were negative (fig. 21B). Among the 66 measurements less 

than 500 ft3/s, rating shifts were applied after 45 measurements 

were completed, and 14 shifts were positive and 31 were negative. Whether shifted or unshifted, percentage differences at the 

Moncure streamgage do not indicate a particular time during the 

1982–2011 water years when the values were either consistently 

positive or negative (fig. 21B). The majority of the percentage differences and corresponding shifts were negative, which 

would support the hypothesis that possible false computations 

of flow loss occur due to the discharge records at the Moncure 

streamgage. However, when examining the temporal trend in the 

percentage differences for measurements less than 500 ft3/s, there 

was no indication of a long-term temporal bias in which the values were negative (fig. 21B). The absence of negative bias indicates that flow losses in the study reach are not attributable to the 

computation of discharge records at the Moncure streamgage.

Four ratings have been used for the Cape Fear River at 

Lillington streamgage (site 28) since December 1976. A total 

of 103 discharge measurements made at this streamgage during the 1982–2011 water years range from 133 to 28,800 ft3

/s 

(fig. 22A). The measurements made during this period 

were rated as excellent (1 percent), good (47 percent), fair 

(42 percent), or poor (11 percent). Among these measurements, 51 were measured at discharges of 1,000 ft3

/s or less. 

Among these 51 discharge measurements, the distribution of 

Figure 21. Quality ratings of (A) discharge measurements and (B) percentage differences from shifted, where applied, base 

rating at Deep River at Moncure (site 3), North Carolina, during the 1982–2011 water years.

1985 1990 1995 2000 2005 2010

20

15

10

5

0

–5

–10

Percentage difference 

EXPLANATION

25,000

20,000

15,000

10,000

5,000

0

Good

Fair

Poor

Water Year

Discharge, in cubic feet per second

Discharge measurement

quality rating

A

B

Note: Percentage differences where temporary

rating shift was applied are shifted percentage

differences. Where no rating shift was applied,

unshifted percentage differences are indicated.

Good

Fair

Poor

Good

Fair

Poor

Temporary rating shift applied

Discharges greater than or equal to

500 cubic feet per second

EXPLANATION

Discharges less than 500 cubic feet

per second

1985 1990 1995 2000 2005 2010

Water Year
Results and Interpretation of Data 43

measurement ratings as excellent, good, fair, or poor was 2, 

43, 47, and 8 percent, respectively.

Percentage differences for the 103 measurements at the 

Cape Fear River at Lillington streamgage (site 28) during the 

1982–2011 water years ranged from about –10 percent to about 

+16 percent, with values within +/– 5 percent for 79 of the 103 

measurements (fig. 22B). A total of 24 rating shifts were applied, 

and 23 shifts were positive and 1 was negative (fig. 22B). Among 

the 51 measurements less than 1,000 ft3/s, rating shifts were 

applied after 11 measurements were completed, and 10 shifts 

were positive and 1 was negative. The percentage differences, 

whether shifted or unshifted (shifted values are indicated by X 

symbol in fig. 22B), likewise do not indicate a particular time 

during the 1982–2011 water years when the values were either 

consistently positive or negative (fig. 22B). When examining just 

the 51 measurements less than 1,000 ft3/s, there is likewise no 

indication of bias in the percentage differences during this period. 

The majority of shifts were positive, which lends support to the 

hypothesis that possible false computations of flow loss occur 

due to the discharge records at the Lillington streamgage. However, relatively few shifts were applied at this site; all but one 

of the shifts occurred during and following the 2001 water year 

(fig. 22B). Where shifts were not applied to the rating, the current 

ratings in effect at the time of measurement were regarded as 

appropriate for the continual computation of discharge records. 

The absence of shifts further indicates that no long-term temporal 

bias has occurred in the ratings at the Lillington streamgage that 

could result in false computation of flow losses.

Figure 22. Quality ratings of (A) discharge measurements and (B) percentage differences from shifted, where applied, base 

rating at Cape Fear River at Lillington (site 28), North Carolina, during the 1982–2011 water years.

30,000

25,000

20,000

15,000

10,000

5,000

0

Discharge, in cubic feet per second

EXPLANATION

Excellent

Good

Fair

Poor

Discharge measurement

quality rating

A

B

Good

Fair

Poor

Excellent

Good

Fair

Poor

Temporary rating shift applied

Discharges greater than or equal to

1,000 cubic feet per second

EXPLANATION

Discharges less than 1,000 cubic feet

per second

1985 1990 1995

Water Year

2000 2005 2010

1985 1990 1995

Water Year

2000 2005 2010

20

15

10

5

0

–5

–10

Percentage difference 

Note: Percentage differences where temporary

rating shift was applied are shifted percentage

differences. Where no rating shift was applied,

unshifted percentage differences are indicated.
44 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Streamgage at Haw River below B. Everett Jordan Dam

Questions concerning suspected flow losses in the years 

prior to this investigation indicated some concerns about the 

accuracy of reported flow releases from Jordan Lake Dam. To 

assess the accuracy of flow releases, a streamgage on the Haw 

River below B. Everett Jordan Dam near Moncure (site 1), 

operated since 1992 for stage-only records, was converted to a 

discharge-record site in November 2008. Streamflow records 

for this site were published from October 1965 to October 

1992. Prior to October 1978, the site was operated 0.3 mi 

downstream from the dam with records published under the 

name of Haw River near Haywood (USGS station 02098200).

The effects of storage behind Buckhorn Dam extend 

upstream to Jordan Lake Dam. The result of this storage creates a backwater effect that prevents a normal stage-discharge 

relation from being established. High flows traveling down the 

Deep River also create a backwater effect on Haw River flows 

immediately downstream from Jordan Lake Dam. When the 

Haw River streamgage was operated previously as a discharge 

station, the site was operated as a “slope station” because an 

auxiliary gage was located downstream from the primary or 

base streamgage. Stage records collected at both locations 

allowed the determination of a slope between the two points, a 

variable used in the computation of discharge records.

The streamgage operated at this location during the 

study was an index-velocity site, whereby continuous velocity records are collected in one or more volume samples in 

the channel and used to establish a relation with the average 

velocities determined by individual discharge measurements. 

A second relation is developed between water stage and crosssectional area of the channel. Discharge is then computed by 

multiplying the average velocity from the first relation by the 

area determined from the second relation.

Channel velocities are collected by using acoustical 

transducers that emit sound waves into the channel; returning sound waves from moving particles in the flow are used 

to compute an index velocity based on the Doppler principle. 

Flow releases from the dam often resulted in entrained air 

bubbles in the water column at the cross section where the 

velocity transducers were located. When this phenomenon 

occurred, the velocity data displayed such a wide range in 

variability that questions arose concerning the ability of the 

instrumentation to obtain accurate velocity data needed to 

compute the discharge. Following a review (during the latter 

part of the investigation) of the index-velocity data collected at 

this streamgage, records of daily discharge computed for this 

site were deemed unreliable. Nearing the end of the investigation, plans were underway to relocate the streamgage approximately 1.25 mi downstream at the U.S. Highway 1 bridge 

where reconnaissance discharge measurements indicated more 

suitable conditions for index-velocity streamgage operations 

were likely.

Following the review, a focus was placed on comparison of individual measured discharges and the reported 

hourly flow releases from Jordan Lake Dam. A total of 34 

discharge measurements were collected during the study at 

the streamgage downstream from Jordan Lake Dam (site 1). 

Measured discharges ranged from 94.7 to 9,970 ft3/s (table 10; 

fig. 23A), and 25 of these measurements were less than 

2,000 ft3/s. Comparison of the USGS measured discharges and 

USACE-supplied flow releases indicated that the measured 

discharges ranged from 75 to about 140 percent of the concurrent hourly flow releases among the 34 measurements, and 

the values were within +/– 10 percent for 28 measurements. 

Among the 6 measurements with differences greater than 

10 percent, explanation for the differences lies in changes in 

hourly flow releases close to the time of measurement.

Flow releases from Jordan Lake Dam were made through 

service gates located in the intake tower immediately upstream 

from the dam. Tables of predetermined discharges based on 

lake level and gate openings are used to determine the opening necessary for a given discharge. Adjustments to the gate 

openings are completed using mechanical adjustment and 

visual inspection of a scale linked to each opening. When 

attempting to set the flow for a relatively small release amount 

(for example, during drought conditions), adjustments to the 

gates may be a matter of 1 to 2 in., making verification of the 

desired opening more challenging for personnel. According to 

the USACE, at a lake level of 216 ft above NGVD 29 (and at 

lower levels), each 1-in. gate opening equates to an approximate difference of 30 ft3

/s in discharge magnitude (Ashley 

Hatchell, U.S. Army Corps of Engineers, written commun., 

March 2, 2010). The occurrence of 28 of 34 measurements 

being within +/- 10 percent of the reported hourly flow releases 

provides general support of the current discharge computation 

tables used for reporting Jordan Lake Dam flow releases.

Stage-Only Streamgage on Cape Fear River at Buckhorn Dam

An absence of stage data on the Cape Fear River at Buckhorn Dam raised questions about whether flow losses could be 

attributed to fluctuations in the water surface at this structure. 

In other words, the question to be answered is whether the 

water surface declines to levels below the spillway crest, 

thereby resulting in flow losses measured at the Lillington 

streamgage (site 28).

During the study, a stage-only streamgage was operated on the Cape Fear River at Buckhorn Dam near Corinth 

(site 18) to collect continuous stage data. No records of 

discharge were collected at this site. Except for one week 

during January 2009, the station was operated from November 24, 2008, to June 25, 2010, when the gage and recording 

equipment were lost due to theft. A temporary stage gage was 

installed to continue data collection during the latter stages 

of the investigation. Data from the temporary gage provided 

additional data through July 31, 2010. Stage records were 

converted into elevations following a survey that determined 

the station datum for the site, which was referenced to the 

elevation of a temporary benchmark established using RealTime Kinematic (RTK) GPS equipment. The elevation of the 

station datum was determined to be 156.49 ft above NAVD 88 
Results and Interpretation of Data 45

Table 10. U.S. Geological Survey discharge measurements made at Haw River below B. Everett Jordan Lake near Moncure, North 

Carolina, and reported hourly flow releases from Jordan Lake Dam, December 2008 through December 2010.

[ft3/s, cubic feet per second; measurement rating determined from base uncertainty at 95-percent confidence interval: (G), good; (F) fair; (P), poor 

(http://nc.water.usgs.gov/usgs/info/qaplan/surface.html); hrs., hours; NR, none recorded]

Date

Time of 

measurement

Measured 

discharge,

in ft3

/s

Stage, 

in feet

Measurement

rating

Reported 

hourly flow 

release,

in ft3

/s

Time Comments

12/3/2008 1058 1,710 4.66 G 1,573 1100 NR

12/15/2008 1138 1,690 4.54 G 1,407 1100 Substantial adjustments in flow release between 1000 

and 1500 hrs (from 303 to 4,592 ft3

/s).

12/15/2008 1212 3,300 5.88 G 3,024 1300 Substantial adjustments in flow release between 1000 

and 1500 hrs (from 303 to 4,592 ft3

/s).

12/15/2008 1455 5,030 7.16 G 4,592 1500 Substantial adjustments in flow release between 1000 

and 1500 hrs (from 303 to 4,592 ft3

/s).

3/4/2009 1109 4,220 8.60 G 4,242 1200 Measurement made during increase in stage from 

8.23 ft at 1100 hrs to 8.64 ft at 1115 hrs to 8.74 ft at 

1130 hrs.

3/5/2009 1137 6,200 9.00 G 6,080 1100 NR

3/17/2009 1057 1,450 6.18 G 1,550 1100 Substantial adjustment in flow release between 1300 

and 1400 (from 608 to 2,512 ft3

/s).

4/22/2009 1010 838 3.90 G 788 1000 NR

4/27/2009 1233 859 3.74 G 787 1200 NR

6/25/2009 1052 164 3.19 F 130 1100 NR

7/22/2009 0750 430 3.34 G 420 0800 NR

8/18/2009 1015 443 3.28 G 417 1000 NR

9/9/2009 0926 274 3.18 P 288 0900 NR

9/30/2009 1033 94.7 3.03 P 127 1100 Flow releases from Jordan Lake dam adjusted between 

1000 and 1400 hrs.

9/30/2009 1122 169 3.06 F 127 1100 Flow releases from Jordan Lake dam adjusted between 

1000 and 1400 hrs.

9/30/2009 1142 167 3.05 F 127 1100 Flow releases from Jordan Lake dam adjusted between 

1000 and 1400 hrs.

9/30/2009 1224 270 3.08 F 192 1200 Flow releases from Jordan Lake dam adjusted between 

1000 and 1400 hrs.

9/30/2009 1244 273 3.06 G 192 1200 Flow releases from Jordan Lake dam adjusted between 

1000 and 1400 hrs.

10/1/2009 0850 214 3.10 F 223 0800 NR

11/3/2009 1018 193 3.14 F 193 1000 NR

11/6/2009 0858 134 3.15 G 128 0900 NR

11/6/2009 0948 124 3.13 G 128 0900 NR

11/17/2009 1105 7,570 9.82 G 7,404 1100 NR

11/17/2009 1124 7,470 9.82 G 7,404 1100 NR

11/19/2009 0944 9,970 11.48 G 9,950 0900 NR

11/19/2009 1000 9,830 11.46 G 9,946 1000 NR

1/13/2010 1107 419 3.37 F 393 1100 NR

2/23/2010 0950 2,830 5.86 G 2,958 1000 NR

2/26/2010 1110 124 3.80 G 131 1100 NR

4/22/2010 0934 414 3.37 G 425 0900 NR

6/8/2010 1350 693 3.56 G 658 1300 NR

8/11/2010 1020 487 3.31 G 522 1000 NR

8/11/2010 1059 501 3.31 G 522 1100 NR

12/8/2010 1804 380 3.34 G 393 1800 NR
46 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

with an accuracy of 0.15 ft. The left end of the dam crest was 

surveyed at an elevation of 157.25 ft.

The crest length of Buckhorn Dam is almost 1,700 ft 

with a structural height of 25 ft (North Carolina Department of 

Environment and Natural Resources, 2010). Aerial photographs 

(from Google Earth) indicate the crest of the dam between the 

edges of the river is approximately 1,100 ft in length.

Stage data collected during the study and converted to a 

continuous record of elevation ranged from 157.32 ft on October 9 and 12, 2009, to 161.42 ft on February 6, 2010 (fig. 24). 

Throughout the study period, flow over the dam was observed 

along its length and is confirmed by the minimum recorded 

elevation being at a slightly higher elevation than that surveyed 

for the left end (facing downstream) of the dam crest. During 

the nearly 20-month period of record for this station, there 

were 14 days when flow loss was computed using the methods 

described in previous sections. Among these 14 days, the stage 

ranged from 0.14 to 1.89 ft above the left end of the dam crest. 

This range indicates that flow loss in the study reach is not 

attributed to a decrease in stage below the dam crest.

Water Use

Developing an understanding of the flows in the study 

area required an assessment of available water-use records of 

diversions that affect the discharges in the Haw and Cape Fear 

Rivers. The diversion records for the study area, and particularly along the main stem, raised questions in the year prior to 

the study about whether flow losses could be attributed to water 

use. Using the median flow loss of 37 ft3/s (table 3; flow comparison 3, daily discharge) as a point of reference, water-use 

analyses completed during the investigation indicated that total 

diversions were equivalent to 69 and 104 percent of the median 

flow loss during the winter and summer periods, respectively. 

Figure 23. (A) Full range of measured discharges at Haw River below B. Everett 

Jordan Lake near Moncure (site 1), North Carolina, and (B) measured discharges 

less than 2,000 cubic feet per second.

12,000

10,000

8,000

6,000

4,000

2,000

0

0 500 1,000 1,500 2,000

2,000

1,500

1,000

500

0

U.S. Geological Survey measured discharge, in cubic feet per second

0 2,000 4,000 6,000 8,000 10,000 12,000

Hourly flow releases, in cubic feet per second (reported by Army Corps of Engineers)

EXPLANATION

Discharge, in ft3/s

Equal line reference

A

B

Figure 23. 

EXPLANATION

Discharge, in ft3/s

Equal line reference
Results and Interpretation of Data 47

Near the beginning of the study, an initial assessment of 

water users within or near the study area was completed (Don 

Rayno, North Carolina Division of Water Resource, oral commun., May 28, 2009). Using information from this assessment, 

water-use information and (or) data were obtained for five 

industrial facilities—a regional power utility, two municipalities, one small hydropower facility on the Deep River, and one 

quarry operation adjacent to the Deep River (table 11). Data 

indicate that the level of water consumption—the portion of 

water withdrawals not returned to the rivers by way of return 

point-source discharges—varies among these facilities.

The compilation of water-use data indicates that the largest 

users are the regional power producer, the small hydropower 

facility that operates in a run-of-river mode, and the two municipalities (table 11). Water use at the regional power plant and 

small hydropower facility is for power-generation purposes. 

Only part of the water through the regional power plant is 

consumed, and no water consumption occurs in the run-of-river 

operations at the hydropower facility. Water use at these two 

facilities is discussed in further detail in subsequent sections.

Most of the facilities do not directly measure the water 

withdrawals from the rivers. Rather, water use between an offstream storage location and the facility is compiled and made 

available for reporting to regulatory agencies. Water use at both 

municipal intakes is measured between the storage pond and 

the water-treatment facilities. Expansion of the water-treatment 

plant at one of the municipal facilities was underway during 

the investigation. By the end of the study, pump flowmeters 

were in position to directly measure future water withdrawals 

from the Cape Fear River. Likewise, water-use information 

available for four of the five industrial users was monitored 

between an onsite fire pond and (or) storage facility and the 

facility itself. Paper records of direct water withdrawals from 

the river are available for one industrial facility (fig. 6, site F4); 

however, major facility expansion during the investigation 

altered the daily operations such that water-use data reported 

for the synoptic series are not typical of normal operations. 

Among the privately owned facilities for which water-use data 

were sought during the investigation, only data on a daily scale 

were obtained in electronic format for facilities F1 and F7 for 

2006–2010 (fig. 25A) and 2008–2010 (fig. 25B), respectively. 

Changes in daily water use at facility F1 that were attributed 

to the economic recession during the study period were noted 

with a decrease from 0.4–0.5 ft3/s to 0.3–0.4 ft3/s beginning 

in early 2009 (fig. 25A). Water use at the regional power plant 

(fig. 25B) is discussed further in a subsequent section.

A quarry operation (fig. 1, site F5) is located adjacent to 

the Deep River just downstream from the streamgage on the 

Deep River at Moncure (site 3). Information obtained from the 

environmental compliance representative for the quarry indicated that reported water withdrawals are from the quarry pit, 

with most of the withdrawn water attributed to the accumulation 

of precipitation runoff in the quarry pit (David Lee, Wake Stone 

Corporation, Geologist/Environmental Supervisor oral commun., 

Figure 24. Instantaneous elevation of water surface on the Cape Fear River at Buckhorn Dam near Corinth (site 18), North 

156

157

158

159

160

161

162

Elevation, in feet above NAVD 88

Elevation of left end dam crest at 157.25 feet above NAVD 88

Nov. Dec. Jan. Feb. Mar. May April Nov. Dec.

2008 2009 2010

JulyJune Aug. Sept. Oct. Jan. Feb. Mar. MayApril JulyJune Aug. Sept.

Figure 24. 

Note: breaks in the line indicate no data.

Carolina, November 2008 through July 2010.
48 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Table 11. Summary of selected surface-water withdrawals and return point-source discharges in the Cape Fear study reach, North Carolina.

[ft3/s, cubic foot per second; Mgal/d, million gallons per day (1 Mgal/d is equivalent to 1.5472 ft3/s); NPDES, National Pollutant Discharge Elimination System; <, less than; ~, approximately; NA, not applicable; ND, no data; USGS, U.S. Geological Survey; WTP, water-treatment plant; WWTP, wastewater-treatment plant. Facility name and specifc diversion location not identified in accordance with federal security regulations. Reported withdrawals or water usage for 

facililties are based on electronic records (period indicated in Remarks) and (or) anecdotal information provided by facility]

Site 

index 

number

(figs.

1, 6, 7)

Facility type Source of

water supply

Withdrawals or 

water usage,

ft3

/s

(Mgal/d)

Destination of

return

point-source

discharge

Return

point-source

discharge,

ft3

/s

(Mgal/d)

Permitted

NPDES

discharge,

ft3

/s

(Mgal/d)

F1 Industrial Haw River 0.3 to 0.45

(0.2 to 0.3)

Haw River 0.08 to 0.15

(0.05 to 0.1)

0.37

(0.24)

Remarks: Facility manufactures polyester fiber used in tire cord market. Water usage and point-source discharge data are based on electronic records 

obtained for 2006-2010 calendar years (fig. 25A). Water usage since early 2009 has declined to about 0.2 Mgal/d due to economic downturn.

F2 Industrial Haw River < 0.1

(< 0.06)

Haw River See Remarks 0.01

(0.006)

Remarks: Facility manufactures plywood used for wood products. Water is pumped from Haw River into fire pond with overflow to the Haw 

River; pump is manually turned on and off as needed. No records of water withdrawals or usage or pump run times are maintained. Pump 

capacity was stated to be about 300-400 gallons per minute. Return point-source discharage to Haw River from on-site waste pond is 

managed for company by way of contract and is not continuous, being used as needed. The company is advised by the contractor when to 

complete a return discharge. 

F3 Industrial Haw River < 0.4

(< 0.25)

Haw River < 0.15

(< 0.1)

0.15

(0.1)

Remarks: Facility manufactures resins used in the furniture industry. Water usage and point-source discharge data are based on information obtained during on-site visits. No records of water withdrawals or usage or pump run times are maintained. Two pumps are used to 

withdraw water (rated 300 gallons per minute, but more likely running at about 170 to 180 gallons/min due to wear and tear on pumps 

over time).

F4 Industrial Haw River ~ 1.5

(~ 1.0)

Haw River 0.03

(0.02)

Not limited

Remarks: Facility manufactures particle board and medium density fiber board. Water usage and point-source discharge data are based on 

information obtained during on-site visits. Paper records are maintained in on-site files, but no electronic data were available for water 

withdrawals or usage. Average daily withdrawal in 2008 reported to N.C. Division of Water Resources ranged from 0.45 to 1.5 ft3

/s (0.3 to 

1.0 Mgal/d). Major facility expansions were underway during the study period. Following the expansions, daily withdrawals are projected 

to increase to about 3 ft3

/s (2 Mgal/d), and the return point-source discharge likely will increase to about 0.4 ft3/s (0.25 Mgal/d). Part of 

treated water is spray discharged onto adjacent fields owned by company.

F5 Quarry Water collected at 

bottom of quarry

~ 0.2 to ~ 0.45

(0.14 to 0.3)

Unnamed tributary to Deep 

River

0 to ~ 0.45

(0 to 0.3)

See Remarks

Remarks: Water usage and point-source discharge data are based on information for 2009 reported to N.C. Division of Water Resources. 

Return point-source discharge occurs under Stormwater General Permit with no specified discharge limit. According to quarry management, most of water withdrawn from quarry is rainwater runoff collected at bottom. Water withdrawn from the quarry is discharged to an 

unnamed tributary to the Deep River adjacent to the quarry or routed to a process-water reservoir for later use in stone washing and dust 

suppression operations.

F6 Hydropower power 

generation

Deep River ~ 250 to ~ 550

(~ 160 to ~ 355)

NA NA See Remarks

Remarks: Small hydropower operation is located about 1 mile downstream from USGS streamgage on Deep River near Moncure (site 3). 

General range in water use corresponds to discharges through turbine when in operation. Water is return discharged to the Deep River 

after passage through turbine. Water usage information listed for this facilty is estimated flow in 0.5-mile canal between dam and powerhouse. Water is return discharged to Deep River by way of flow through turbine. See text for further discussion concerning this facility.

F7 Regional power 

utility

Cape Fear River ~ 290 to ~ 400

(~ 190 to ~ 260)

Diversion canal adjacent to 

Cape Fear River

ND Not limited

Remarks: Facility is largest water user in the study area. Withdrawal information is based on daily average of 15-minute interval intake volumes estimated using adjusted pump curves developed by regional power producer in late 2010 (fig. 25B). Pumping varies during the year 

according to power demands, highest in the summer and lowest during the winter. No long-term information was obtained on the return 

point-source discharge, which is located downstream from USGS streamgage on discharge canal adjacent to the Cape Fear River (site 8), 

because of the presence of this gaging station. See text for further discussion concerning this facility.
Results and Interpretation of Data 49

May 17, 2010). The reported point-source discharge is to an 

unnamed tributary to the Deep River. No daily records of water 

withdrawal were obtained during the study; however, the 2009 

annual water-use report filed with the North Carolina Division 

of Water Resources indicated that both average daily water 

withdrawals and return point sources were less than 0.3 Mgal/d 

(0.45 ft3/s; North Carolina Division of Water Resources, 2009). 

Information concerning irrigation withdrawals in North 

Carolina has been limited historically, as State regulations 

exempt agricultural operations from reporting requirements 

for water withdrawals and usage. However, one exception is 

a 2007 report filed with the State agency for a farm operation 

near the Cape Fear River near Lillington (Don Rayno, North 

Carolina Division of Water Resources, oral commun., May 

28, 2009). Average daily withdrawals during June through 

August were reported at about 1.2 Mgal/d (about 2 ft3/s; North 

Carolina Division of Water Resources, 2007). No observations of irrigation piping into the main stem were observed in 

field operations during the study period. Aerial photographs 

indicate limited occurrences of agricultural land cover immediately adjacent to the main stem.

The combined maximum daily water withdrawal or usage 

is about 3 ft3/s (about 2 Mgal/d) for the five industries and 

quarry operation. Similarly, the combined minimum return 

point-source discharge is less than 0.5 ft3/s (about 0.3 Mgal/d), 

implying the maximum water consumption among the six 

facilities would be about 2.5 ft3/s (about 1.6 Mgal/d). Even 

adjusting for the projected increases in water withdrawals and 

Figure 25. Flow diversions at (A) industrial facility (site F1) on the Haw River during 2006–2010, and (B) regional power 

plant (site F7) during 2008–2010, North Carolina.

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0

Flow diversion, in cubic feet per second

Water usage

Return point-source discharge

EXPLANATION

Jan.

Mar.

May

June

Sept.

Nov.

Jan.

Mar.

May

June

Sept.

Nov.

Jan.

Mar.

May

June

Sept.

Nov.

Jan.

Mar.

May

June

Sept.

Nov.

Jan.

Mar.

May

June

Sept.

Nov.

2006 2007

500

450

400

350

300

250

200

150

100

50

0

Flow, in cubic feet per second

Apr. July Oct. Jan. Apr. July Oct. Jan. Apr. July Oct.

2008 2009 2010

2008 2009 2010

Daily withdrawal (ft3/s)

02102094 (daily discharge, ft3/s)

EXPLANATION

A. Site F1

B. Site F7

Figure 25. 
50 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

return discharges at facility F4 following major expansions during the study period, the maximum water consumption among 

the industrial users is less than 4.0 ft3/s (about 2.6 Mgal/d).

Water withdrawals at the two municipal water-supply 

intakes (sites F9, F10) represent 100 percent consumption in 

the study area because the return point-source discharges from 

corresponding wastewater-treatment plants are located outside 

of the study area. The return point-source discharge for facility 

F9 is on a tributary to the Deep River upstream from site 3 

near Moncure (fig. 6), and the return point-source discharge 

for facility F10 is downstream from site 28 at Lillington 

(fig. 7). Monthly (facility F9) and daily (facility F10) wateruse data in electronic format were available for these two 

intakes and provided some insight about variations in water 

use through the calendar year. As with most of the other industries examined during the investigation, water use is monitored 

between a storage reservoir and the water-treatment plants 

for both municipalities, although major expansion completed 

during the study period at one of the water-treatment plants 

(facility F10) included the installation of pump flowmeters for 

monitoring future water withdrawals directly from the river.

Since 2000, the amount of water use associated with the 

upstream municipal intake (facility F9) has ranged from 9 

to 12 ft3/s (5.8 to 7.8 Mgal/d) during the winter and summer 

periods, respectively (fig. 26; table 11). Of note in the data 

for 1986–2010 calendar years provided for this municipal 

intake, average water use increased approximately 67 percent 

between 1986 and 2000, rising from 6 to 10 ft3/s (about 3.9 to 

6.5 Mgal/d). Data indicate water-use patterns have been level 

since 2000 with a slight decline during 2005–2010, a reflection 

of changes in water use following recent drought periods.

Water use associated with the downstream municipal 

intake (facility F10) during 2006–2010 typically ranged from 

14 to 24 ft3/s (9.0 to 15.5 Mgal/d) during the winter and summer 

periods, respectively (fig. 26; table 11). Following the recent 

expansions at the downstream municipal intake (facility F10), 

increased pumping at this facility alone ranged from 24 to about 

35 ft3/s (15.5 to 22.6 Mgal/d) beginning in early 2010 (fig. 26).

Combining the range of withdrawals for just the two 

municipalities indicates that from 23 to 36 ft3/s (35.6 to 

55.7 Mgal/d) is removed from the study area during the winter 

and summer periods, respectively. When adding the maximum 

water consumption of about 2.5 ft3/s (about 1.6 Mgal/d) for 

the five industries and quarry operation, the total water-use 

diversions can range from almost 25.5 to 38.5 ft3/s (39.5 to 

59.6 Mgal/d) during the winter and summer periods, respectively. This range in water-use diversions is equivalent to 69 

to 104 percent of the 37 ft3/s median flow loss (table 3, flow 

comparison 3, daily discharge).

Lockville Hydropower Station 

The Lockville hydropower station (fig. 6, site F6) is on 

the Deep River about 1 mi downstream from the Moncure 

streamgage (site 3). A small low-head dam across the river, 

constructed in the mid-1800s, is 0.5 mi upstream from the 

powerhouse (built in the early 1920s) and connected by a 

canal built between the two structures. Ownership of the dam, 

canal, and powerhouse has changed hands during previous 

decades and most recently in 2003. No hydropower generation 

occurred from 2003 to early 2008 while equipment repairs and 

upgrades were completed by the current (2011) owner.

Hydropower generation at the station, regulated for 

operation by the Federal Energy Regulatory Commission 

(FERC), occurs on a continual basis except during instances 

when insufficient streamflow prevents operation of the 

turbines or when operations have been stopped for the repair 

or protection of equipment. The powerhouse contains two 

turbines capable of generating 750 kilowatts (kW) of power, 

but only one is being used currently (2011) to generate power 

(William Brooks, owner, Lockville hydropower station, oral 

commun., November 9, 2009).

Onsite visits on two separate occasions were completed 

during the study in an attempt to understand the operations 

at this facility and the effects of hydropower operations on 

downstream flows. The minimum flow release from the dam 

mandated by the State of North Carolina is 70 ft3/s, and it 

occurs through a gate opening that is locked in a fixed position 

in the dam. A stage sensor installed on the dam monitors the 

water level behind the dam and controls the ability to operate the turbine. When the lake level is 3 in. above the crest at 

the sensor, operation of the turbine begins to transition so that 

by the time the lake level is within 1 in. of a threshold at the 

top of the dam, the turbine has stopped and no further power 

generation occurs.

Power generation is not efficient when the discharge is 

less than 250 ft3/s as measured at the upstream streamgage 

on the Deep River near Moncure (site 3; William D. Brooks, 

owner, Lockville hydropower station, oral commun., November 9, 2009). On the basis of a recent streamflow analysis 

completed for this streamgage, this discharge is between the 

70th and 75th exceedance percentiles of daily mean discharges, 

which implies that power generation is limited at or below 25 

to 30 percent of the lowest daily discharges recorded at the 

Moncure streamgage during the 1930–2010 water years. No 

formal discharge-turbine rating is available; however, some 

general ranges were obtained during the second onsite visit. 

Approximately 140 kW of power is generated at about 250 ft3/s 

of discharge through the turbine. The owner of the power plant 

states that the most power that can be efficiently generated is 

about 600 kW. This level of power generation requires about 

a 550 ft3/s discharge through the turbine. Thus, under the current operation of one turbine, the discharge diverted through 

the canal between the dam and powerhouse during maximum 

power generation is between 500 and 600 ft3/s.

The discharge release from the turbine into the Deep River 

is subject to backwater effects caused by storage upstream from 

Buckhorn Dam and (or) large flow releases from Jordan Lake 

Dam, which also create backwater conditions on the Deep River 

from its mouth to the hydropower operation. To meet FERC 

regulations, hydropower operations must be completed in a runof-river manner with no peaking cycles permitted.
Results and Interpretation of Data 51

Records maintained to document the water level at the 

dam (as detected by a continuous sensor) and amount of 

power generated are not required to be submitted to FERC or 

any other regulatory agency. Records were not made available 

for the full study period but were made available for selected 

dates (William Brooks, owner, Lockville hydropower station, 

oral commun., January 27, 2011).

During the series of six synoptic measurements completed 

in 2009, hydropower generation only occurred on two dates 

(April 27 and July 22). No power generation occurred during 

the remaining four synoptic dates (June 25, August 18, September 9, and October 1). Records indicate power generation 

occurred all day on April 27 and during limited hours on July 

22. Instantaneous discharges on April 27 at the upstream 

streamgage on the Deep River (site 3) were between 400 and 

500 ft3/s. On July 22, the turbine was operated between the 

hours of 1300 and 1600 until the water level at the sensor on 

the dam declined to less than 1 in. above the top of the dam, 

resulting in the shutdown of the turbine. The instantaneous discharge at the streamgage was steady at 162 ft3

/s for the 3 hours 

of operation on this date. This supports the assumption that 

power generation is inefficient below a discharge of 250 ft3/s, 

but further data are needed to confirm this conclusion. While 

no numerical flow-routing models were completed as part of 

Figure 26. Water use reported for (A) municipal facility F9 for 1986–2010, and (B) municipal facility F10 for 2006–2010 in 

the Cape Fear River study area, North Carolina.

14

12

10

8

6

4

2

0

Monthly mean water use, in cubic feet per second

Jan. 1986

Oct. 1986

July 1987

April 1988

Jan. 1989

Oct. 1989

July 1990

April 1991

Jan. 1992

Oct. 1992

July 1993

April 1994

Jan. 1995

Oct. 1995

July 1996

April 1997

Jan. 1998

Oct. 1998

July 1999

April 2000

Jan. 2001

Oct. 2001

July 2002

April 2003

Jan. 2004

Oct. 2004

July 2005

April 2006

Jan. 2007

Oct. 2007

July 2008

April 2009

Jan. 2010

Oct. 2010

40

35

30

25

20

15

10

5

0

Daily water use, in cubic feet per second

A

B

Jan. 1, 2006

Feb. 15, 2006

April 1, 2006

May 16, 2006

June 30, 2006

Aug. 14, 2006

Sept. 28, 2006

Nov. 12, 2006

Feb. 10, 2007

Mar. 27, 2007

May 11, 2007

June 25, 2007

Aug. 9, 2007

Sept. 23, 2007

Nov. 7, 2007

Dec. 27, 2006

Dec. 22, 2007

Feb. 5, 2008

Mar. 21, 2008

May 5, 2008

June 19, 2008

Aug. 3, 2008

Sept. 17, 2008

Nov. 1, 2008

Jan. 30, 2009

Mar. 16, 2009

April 30, 2009

June 14, 2009

July 29, 2009

Sept. 12, 2009

Dec. 16, 2008

Oct. 27, 2009

Dec. 11, 2009

Jan. 25, 2010

Mar. 11, 2010

April 25, 2010

June 9, 2010

July 24, 2010

Sept. 7, 2010

Oct. 22, 2010

Dec. 6, 2010

Jan. 20, 2011

Figure 26. 
52 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

this study to confirm the effects of hydropower generation, 

the release of discharge into a backwater-affected reach under 

presumed run-of-river operations does not appear to be a major 

factor behind flow losses in the study reach.

Regional Power-Plant Diversion and Flow through 

Diversion Canal

The largest water user in the study area is a regional 

power producer that generates electricity at two separate facilities. The first is a coal-fired power-generation plant immediately adjacent to the Cape Fear River just downstream from 

the confluence of the Haw and Deep Rivers (fig. 1, site F7). 

As previously discussed, the second facility is the Shearon 

Harris Plant adjacent to Shearon Harris Lake, an impoundment 

of Buckhorn Creek, the second largest tributary in the study 

area. Because of available continuous discharge records at the 

streamgage on Buckhorn Creek near Corinth (site 20) downstream from Shearon Harris Lake Dam, a detailed assessment 

of water-use patterns at this facility was deemed unnecessary 

for the objectives of this study.

At the first facility operated by the regional power 

producer, water is withdrawn from the Cape Fear River and 

passed through the plant for cooling purposes before being 

discharged into the diversion canal adjacent to the main stem. 

After discharge from the plant, the water is passed through 

cooling towers as needed during June through September 

to reduce the temperature prior to final release to the canal. 

From the plant to the canal mouth immediately upstream from 

Buckhorn Dam, the diversion canal is 6.3 mi long and drains 

about 10.3 mi2 of the study area (site 16). The dam, which was 

constructed in 1908 (Ragland and others, 2003), has provided 

a storage of water for the cooling operations and was actively 

regulated until December 1962 when it changed to a run-ofriver mode of operation. Buckhorn Dam is approximately 

5.75 mi downstream from the intake for the power plant.

The diversion canal was extended in 1954, and the added 

distance to its current mouth above Buckhorn Dam allows 

additional cooling time of the heated water released from 

the plant. The original canal mouth is approximately 1.75 mi 

downstream from the intake on the main stem, making the 

original canal distance about 2.25 mi.

The regional power producer compiles and submits 

discharge monitoring report (DMR) data to State regulatory 

agencies to track daily water withdrawals. The DMR data 

for the period April 2008 to December 2010 were compiled 

and coupled with concurrent daily discharge records at the 

continuous-record streamgage on the canal (site 8) in an effort 

to determine estimates of water consumption between the 

intake and streamgage. Estimated differences between the 

intake and canal discharge data typically were in the range of 

30 to 50 ft3/s (20 to about 30 Mgal/d) with values as high as 

75 to 100 ft3/s (about 50 to 65 Mgal/d). These ranges are much 

higher than the approximately 13.4 ft3/s (8.65 Mgal/d) estimate 

in water loss from the cooling towers (Robin Bryson, Progress 

Energy Carolinas, written commun., November 30, 2009).

The regional power producer expressed concern that these 

comparisons are limited because of the methods used to calculate the daily withdrawals. Because the pump intake logs are 

used to estimate the flow discharged into the diversion canal, 

these estimates can only provide a daily “snapshot” of the flow 

volume through the plant and should not be used for making daily comparisons with the continuous discharge records 

observed at the canal streamgage (site 8; Robin Bryson, Progress Energy Carolinas, written commun., August 26, 2011).

Uncertainty in the amount of water consumption during 

the study prompted the regional power producer to undertake 

measures to adjust and validate pump curves used for estimating withdrawal amounts. These measures were completed 

in September 2010, and adjusted pump curves were applied 

to DMR data beginning in December 2010 near the end of 

the investigation. The regional power producer reported that 

percentage change between the old and newly adjusted pump 

flows among the varying combinations of pumps ranged from 

-7 percent to almost 43 percent (average 17.6 percent). Using 

the adjusted pump curves, the regional power producer also 

provided new estimates of the withdrawal volumes (at 15-minute intervals) for April 2008 through December 2010 (Robin 

Bryson, Progress Energy Carolinas, written commun., August 

30, 2011). These estimates were used to calculate daily average withdrawal amounts for a second comparison with daily 

mean discharges at the canal streamgage (site 8).

The second comparisons between the withdrawal 

data for the period of interest (based on the adjusted pump 

curves) and the discharge records at the canal streamgage 

(site 8) indicated a smaller range, typically from 10 to 40 ft3/s 

(6.5 to 25.8 Mgal/d) with some amounts exceeding 50 ft3/s 

(32.3 Mgal/d) on some days (fig. 25B). A large part of this 

range still exceeds the approximately 13.4 ft3/s (8.65 Mgal/d) 

estimate in water loss from the cooling towers provided by the 

regional power producer. The regional power producer continued to express concern about the utility of these comparisons to 

estimate water loss from the facility even after the pump curve 

adjustments were made (Robin Bryson, Progress Energy Carolinas, written commun., August 30, 2011). Thus, uncertainty 

surrounding reasonable estimates of consumption remained in 

effect at the end of the study. Further resolution of this issue 

requires the collection of additional data after December 2010. 

Following the investigation, it was learned the power company 

is tentatively planning to close the regional power plant by 

mid-2013 because of changing environmental regulations and 

economic conditions (Mick Greeson, Progress Energy Carolinas, written commun., September 7, 2011).

Evaporative Losses

Evaporation is part of the hydrologic cycle (U.S. Geological Survey, 2011b), and it is understood that part of the 

flow loss from rivers is attributed to the removal of water 

from the earth’s surface. Evaporation from the main stem was 

estimated during this study to understand the portion of flow 

losses attributed to this process. Evaporation analysis indicates 
Results and Interpretation of Data 53

that the estimated range in flow loss due to open-water evaporation from the main stem and the Deep River is between 10 

and 38 percent of the 37 ft3/s median flow loss (table 3; flow 

comparison 3, daily discharge) during the months from May 

through October.

Data on evaporative losses were compiled through two 

approaches: (1) an analysis of available pan-evaporation data 

for the Chapel Hill 2W NOAA weather station in Orange 

County and (2) a compilation of estimated open-water 

evaporation computed and compiled by the State Climate 

Office of North Carolina (2010) using the Penman-Monteith 

method used for computing reference crop evapotranspiration. 

Because of the intermittent nature of the data at the Chapel 

Hill 2W NOAA weather station, available records were sorted, 

and statistics were determined by month. The monthly median 

pan-evaporation amounts were adjusted by a pan coefficient 

of 0.7 (Farnsworth and Thompson, 1982). Adjusted monthly 

median evaporation on the basis of the Chapel Hill data ranged 

from 0.05 inch per day (in/d) during the winter to 0.15 in/d 

during the summer (fig. 27A). The monthly medians then were 

multiplied by the surface areas determined for the Haw, Deep, 

and Cape Fear Rivers in the study area to compute a volume of 

water loss (expressed as equivalent daily flow in cubic feet per 

second) due to estimated open-water evaporation (fig. 27B) 

during the 3 years (2008–2010) corresponding to the study 

period. Equivalent daily flow loss from the main stem and the 

Deep River on the basis of the pan-evaporation data ranged 

from about 2–3 ft3/s during December through February to 

about 7–8 ft3/s during June through August (fig. 27B).

During the investigation, records of estimated daily 

open-water evaporation computed using the Penman-Monteith 

method were obtained from databases maintained by the 

State Climate Office of North Carolina (2010). This method 

estimates reference crop evapotranspiration rates for a wellwatered reference surface on the basis of physical atmospheric 

observations of solar radiation, temperature, wind speed, 

and relative humidity. Daily records were accessed for five 

nearby NOAA stations in the vicinity of the study area: Chapel 

Hill-Williams Airport (NOAA station KIGX), Harnett County 

Airport (KHRJ), Lee County Airport (KTTA), Pope Air Force 

Base (KPOB), and Raleigh-Durham International Airport 

(KRDU, fig. 8). The daily open-water evaporation estimates 

among the five sites using the Penman-Monteith method were 

averaged to determine a regional evaporation amount. Daily 

evaporation based on the Penman-Monteith data ranged from 

about 0.06 in/d during the winter to 0.25 and 0.3 in/d during 

the summer (fig. 27A). As with the pan-evaporation method, 

the averaged values were then multiplied by the surface area 

determined for the main stem and the Deep River to compute a volume of water loss. The equivalent daily flow-loss 

estimates on the basis of the Penman-Monteith method ranged 

from about 2 ft3/s during December through February to about 

11–14 ft3/s during June through August (fig. 27B).

Comparison of the daily flow losses indicates substantial 

differences between the two methods for computing evaporation, particularly during the summer months. Discussion of the 

differences between the methods is beyond the scope of this 

report; however, the differences during the summer months 

Figure 27. (A) Estimated open-water evaporation and (B) equivalent flow loss in the study reach from potential open-water 

evaporation based on the Penman-Monteith model at five nearby National Oceanic and Atmospheric Administration (NOAA) stations 

and pan-evaporation data for the Chapel Hill 2W NOAA station (State Climate Office of North Carolina, 2010). Estimated open-water evaporation, in inches per day

A EXPLANATION

Potential open-water evaporation

based on Penman-Monteith method

Adjusted pan evaporation data

for Chapel Hill 2W National

Oceanic and Atmospheric

Administration station

Chapel Hill-Williams Airport

Raleigh Durham Airport

Lee County Airport

Harnett County Airport

Pope Air Force Base

Chapel Hill pan evaporation

EXPLANATION

Flow loss based on potential

open-water evaporation, in

cubic feet per second

Flow loss based on pan

evaporation, in cubic feet

per second

B

J F M A M J J

2008

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

2009

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

2010

A S O N D

0.400

0.350

0.300

0.250

0.200

0.150

0.100

0.050

0

Equivalent flow loss, in cubic feet per second 18

16

14

12

10

8

6

4

2

0
54 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

highlight the uncertainty and complexities associated with 

estimating the portion of flow loss due to evaporation from 

the study reach. Part of the uncertainty is due to the recognition that no pan-evaporation data have been collected within 

the study area. Pan coefficients used to adjust pan-evaporation 

data vary by season during the course of a year (Yonts and 

others, 1973) and vary on the basis of the type of water body 

(river as opposed to lake with large fetch) for which evaporation estimates are needed (David I. Stannard, U.S. Geological 

Survey, oral commun., November 9, 2011). Evaporation estimates based on the Penman-Monteith method for locations far 

from water bodies tend to be higher than actual evaporation, 

because of the different meteorological measures used in the 

method, than would be measured closer to the water surfaces 

(David I. Stannard, U.S. Geological Survey, oral commun., 

November 9, 2011). The NOAA stations for which PenmanMonteith estimates were compiled were all located at airport 

facilities as opposed to nearby water bodies. For the purposes 

of this study, both methods were considered, by estimating 

the potential flow loss from the study reach due to evaporation from the main stem and the Deep River, to be in the range 

of 4 to 14 ft3/s during May through October (fig. 27B). The 

flow-loss analyses completed during this study indicate that 

82 percent of flow-loss days occurred during these months. 

The estimated range in flow loss due to open-water evaporation is equivalent to 10 to 38 percent of the 37 ft3

/s median 

flow loss (table 3; flow comparison 3, daily discharge).

Comparisons of Water Use, Evaporation, and 

Flow-Loss Occurrences during 2008–2010

Comparisons were made of daily water-use diversions 

and evaporation losses with flow-loss occurrences during the 

period April 2008 through September 2010. This period was 

chosen because of its concurrence with the period of record at 

the streamgage on the adjacent diversion canal (table 1, site 8). 

The comparison was completed to assess how the magnitude 

of total losses due to water consumption and evaporation compared to calculated flow losses.

During the period of interest, flow analyses indicated 

289 days of flow-loss occurrences at the streamgage on Cape 

Fear River at Lillington (site 28). Filtered daily flow losses 

occurred on 34 days during the same period (filtered for days 

of steady flow conditions at the upstream inputs relative to 

the previous day). Flow losses ranged from 0.5 ft3/s (September 22, 2010) to about 140 ft3

/s (February 21, 2010) with a 

median flow loss of 20.7 ft3/s. Although the maximum flow 

loss met the criteria applied to filtered flow analyses, the flow 

loss actually is not a true flow loss because it occurred 2 days 

after an adjusted flow release of 4,000 ft3/s at Jordan Lake 

Dam on February 19, 2010.

Among the 34 days of filtered flow losses, the total wateruse diversions for the five industries and two municipalities 

exceeded the computed flow losses on 26 days. With evaporative losses added, the total losses exceeded the computed flow 

losses at the streamgage on 1 and 2 additional days, depending 

on whether evaporative losses are based on the pan-evaporation 

data or the Penman-Monteith computations, respectively. For the 

remaining 6 days when total losses from water use and evaporation did not exceed the computed flow losses at the streamgage, 

flow losses could be attributed to the addition of water consumption from the regional power plant (facility F7) on 2 other days 

during the period of interest. Among these 6 days, the balance of 

unaccounted flow loss after adjustments for water-use diversions 

and evaporative losses ranged from about 7 to 104 ft3/s, less than 

16 ft3/s on 4 of the 6 remaining days.

Water consumption from the power plant could not be 

determined reliably (based on the data provided from the 

facility) during the study as previously discussed. However, 

water consumption from the facility could account for part of 

the flow losses on at least 3 of the 6 remaining days, which 

occurred during August 2009 at a time when the water consumption rates from the facility can be among the highest during the year. The remaining 3 days were during the winter and 

early spring following the passage of higher flows along the 

main stem and likely a peak flow passing through the system.

In comparing the surface-water, water-use, and evaporation data compiled for 2008–2010, it is evident that documented water diversions combined with losses from openwater evaporation can exceed the net flow gain in the study 

area. The median flow loss was determined to be 37 ft3/s 

(table 3; flow comparison 3, daily discharge), which is slightly 

greater than the combined municipal water withdrawals of 

23 to 36 ft3/s. The effects of open-water evaporation from the 

main stem and the Deep River during July through August 

equals between 4 and 14 ft3/s of equivalent flow loss removed 

from the hydrologic system. Summing the two ranges of water 

diversions and evaporation provides a total range of 27 to 

50 ft3/s of equivalent flow loss. The small magnitude of measured discharges from the four smaller tributaries during the 

series of synoptic measurements also confirm that net gain in 

flow along the study reach is limited, particularly under baseflow conditions during warmer months.

Effects of Diversion Canal Flows on Cape Fear 

River at Lillington

The operation of the streamgage on the diversion canal 

(fig. 6, site 8) downstream from the regional power plant (facility 

F7) provided additional insight into the occurrence of an apparent flow loss at the streamgage at Lillington (fig. 7, site 28). As 

previously discussed, the diversion canal travels adjacent to the 

Cape Fear River allowing heated waters from the power plant 

sufficient time to cool before merging into the main stem.

In the years leading up to the investigation, sudden 

decreases in the instantaneous streamflow would occasionally be observed in the Cape Fear River at Lillington (site 28), 

often prompting an inquiry by the USACE about the rapid 

changes. During the latter stages of the investigation, a 

connection was established between the occasional sudden 
Results and Interpretation of Data 55

changes in canal flow and downstream flows at the Lillington streamgage. From time to time, some or all of the pumps 

used to withdraw water into the regional power plant (facility 

F7) are stopped for durations ranging from one-half day to 

about 2 days, mainly based on the run times of the generating 

units in response to power demands. Changes due to pumping 

adjustments can be observed in the discharge records at the 

streamgage on the diversion canal (site 8) downstream from 

the power plant.

An assessment of the daily discharges and subsequent 

inspection of the instantaneous-value hydrographs for the 

canal streamgage (site 8) indicate at least 24 instances from 

the start of data collection in April 2008 through December 

2010 during which the flows suddenly decreased, and then 

increased shortly thereafter, by magnitudes of 100 to more 

than 200 ft3/s. Flows at the Lillington streamgage (site 28) during 14 of these instances were in the high-flow range above 

1,000 ft3/s. Thus, changes in the canal flow were “masked” 

by the larger flows in the main stem. Flows at the Lillington 

streamgage during the remaining 10 instances, however, were 

at or below 600 ft3/s. At these discharges, the above-referenced 

changes in the canal discharges were determined to affect the 

pattern of discharges at the Lillington streamgage.

The scope of this investigation did not include flow 

routing or model development that would permit in-depth 

assessment of the effects of starting or stopping main-stem 

withdrawals and subsequent canal discharges on main-stem 

flows downstream. For the 10 instances during the period of 

interest when effects were noted, however, visual inspection of 

the instantaneous hydrographs permitted a qualitative assessment of this cause-and-effect relation. The changes in flows 

are illustrated in 4 of the 10 instances (figs. 28–31).

Multiple oscillations in the discharges at the Cape Fear 

River at Lillington (site 28) during September 15–19, 2009, 

echo the pattern of adjusted discharges in the diversion canal 

for the same period (fig. 28). Little to no changes in discharge 

occurred in the flow releases from Jordan Lake Dam (site D1) 

or at the streamgage at Deep River at Moncure (site 3) during 

the period. Variations in canal discharge ranged from 150 to 

200 ft3/s with decreases typically occurring over a period of 

a few hours and increases occurring over a slightly longer 

period. The decreases and increases in discharge at the Lillington streamgage ranged from 40 to 60 ft3

/s. The hydrograph 

for this period indicates that flows at the Lillington streamgage 

increased on a time-lagged basis when the discharge through 

the diversion canal substantially decreased. In a similar manner, discharges at the Lillington streamgage appear to decrease 

in response to a corresponding increase in discharge through 

the diversion canal.

The magnitude and duration of discharge changes at the 

Lillington streamgage (site 28) are governed by the magnitude 

and timing of changes in canal discharge (fig. 28). Hydrographs for three other selected dates (figs. 29–31) confirm this 

pattern. On November 1, 2009, the canal discharge decreased 

during the morning by approximately 150–200 ft3

/s, which 

resulted in an increase in discharge of about 60 ft3/s at the 

Lillington streamgage beginning about 8 hours later (fig. 29). 

When the canal discharge increased on the following midnight, however, the effects on discharge at the Lillington 

streamgage are not as evident (or are indeterminate) given 

that discharges were already in a declining pattern beginning 

at hour 2200 on November 1. The hydrograph for this date 

also indicates the discharges at Deep River at Moncure (site 3) 

were in recession from October 31 into the early morning 

hours of November 1 (fig. 29).

On October 28, 2010, the canal discharge decreased during the morning by approximately 250 ft3

/s, which resulted 

in an increase in discharge of about 90 ft3/s at the Lillington 

streamgage about 8 hours later (fig. 30). Between noon and 

1900, the canal discharge increased about 350 ft3/s. At about 

2030 (about 8 hours after the initial increase), the discharge 

at the Lillington streamgage declined about 150 ft3/s over a 

Figure 28. Effect of changes 

in instantaneous discharges at 

diversion canal streamgage (site 8)

and Cape Fear River at Lillington

(site 28), North Carolina, on 

September 15–19, 2009.

500

450

400

350

300

250

200

150

100

50

0

Discharge, in cubic feet per second

15 16

September 2009

17 18 19

Jordan Lake flow releases

Deep River at Moncure (site 3)

Cape Fear River at Lillington (site 28)

Discharge canal (site 8)

EXPLANATION

Figure 28. 

Note: Multiple changes in discharge at Cape Fear River at

Lillington following repeated pumping changes
56 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Figure 29. Effect of changes in instantaneous discharges at diversion canal streamgage (site 8) and Cape Fear River at Lillington

(site 28), North Carolina, on November 1, 2009.

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Oct. 31 Nov. 1

Indeterminate

Nov. 2

Jordan Lake flow releases

Deep River at Moncure (site 3)

Cape Fear River at Lillington (site 28)

Discharge canal (site 8)

Note: Vertical red lines indicate

time elapsed between stoppage 

of pumping and resulting change

in discharge at the Lillington

streamgage. Vertical blue lines

indicate time elapsed between

resumption of pumping and

change in discharge.

EXPLANATION

Note: Change in Cape Fear River at Lillington discharge at 8 hours pre- and

indeterminate hours post-pumping changes, 60 cubic feet per second preand indeterminate amount post adjustment

Figure 30. Effect of changes in instantaneous discharges at diversion canal streamgage (site 8) and Cape Fear River at Lillington

(site 28), North Carolina, on October 28, 2010.

900

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Oct. 27 Oct. 28 Oct. 29

Jordan Lake flow releases

Deep River at Moncure (site 3)

Cape Fear River at Lillington (site 28)

Discharge canal (site 8)

EXPLANATION

Note: Change in Cape Fear River at Lillington discharge 8 hours preand 8 hours post-pumping changes, 90 cubic feet per second pre-and

150 cubic feet per second post adjustment

Note: Vertical red lines indicate

time elapsed between stoppage 

of pumping and resulting change

in discharge at the Lillington

streamgage. Vertical blue lines

indicate time elapsed between

resumption of pumping and

change in discharge.
Results and Interpretation of Data 57

period of 16 hours. The hydrograph for this date also indicates 

little to no changes in the discharge at Deep River at Moncure 

(site 3) or in flow releases from Jordan Lake Dam (fig. 30).

The hydrograph for December 3, 2010, indicates the 

canal discharge decreased by approximately 100 ft3/s during 

the morning, which resulted in an increase in discharge of 

about 60 ft3/s at the Lillington streamgage about 7 hours later 

(fig. 31). Beginning at 1230, the canal discharge increased 

about 375 ft3/s. At about 0230 (approximately 15 hours after 

the initial increase), the discharge at the Lillington streamgage 

declined about 80 ft3/s over a period of 15 hours. The hydrograph for this date also indicates little to no changes in the 

discharge at Deep River at Moncure (site 3) or in flow releases 

from Jordan Lake Dam (fig. 31) through the period during 

which the canal discharge decreased then increased again. 

However, beginning at about 1500 on December 3, the discharge at the Deep River streamgage began to increase, and 

the discharge at the Lillington streamgage correspondingly 

began to rise almost 24 hours later on December 4 (fig. 31).

These hydrographs indicate that when discharge through 

the canal is decreased or stopped for a short period, that 

amount of discharge is immediately available for travel in the 

Cape Fear River, which results in an increase in discharge at 

the downstream Lillington streamgage (site 28) beginning 

about 8 hours later after the main-stem channel storage has 

been satisfied. When discharge from the Cape Fear River is 

subsequently diverted back into the canal, there usually is 

(but not always) a time-lagged decrease on the downstream 

discharges at the Lillington streamgage beginning about 8 to 

16 hours later. Part of the longer time lag may be due in part 

to the time to refill (satisfy storage in) the diversion canal. As 

observed by USGS field personnel, the channel was nearly 

empty when the discharge substantially decreased in response 

to a stoppage in pumping operations. Another factor affecting 

the lag time may be the interaction of flows and, consequently, 

travel time between the diversion and the main stem affected 

by the storage immediately upstream from Buckhorn Dam.

Groundwater and Surface-Water Interaction

Rivers gain water from or lose water to the underlying 

aquifer depending on climate, geologic setting, changes in 

streambed slope, meanders in the stream, and hydrologic gradients between the river and the aquifer. As part of this study, several complementary methods were applied to assess conditions 

of gain or loss through groundwater and surface-water interaction within regional (large scale) and local (small scale) confines 

of the Cape Fear River. Regional groundwater characteristics 

over the entire 24.5-mi river study reach were assessed using 

an EM-induction geophysical survey of the channel bottom to 

identify possible locations of diabase dikes. The EM-induction 

survey enabled selection of a suitable location for deployment of a FO-DTS survey that measured local changes in the 

temperature of riverbed sediments near exposed diabase dikes. 

A regional aerial flyover of the Cape Fear and Haw Rivers was 

Figure 31. Effect of changes in instantaneous discharges at diversion canal streamgage (site 8) and Cape Fear River at Lillington

(site 28), North Carolina, on December 3, 2010.

800

700

600

500

400

300

200

100

0

Discharge, in cubic feet per second

Dec. 2 Dec. 3 Dec. 4

Jordan Lake flow releases

Deep River at Moncure (site 3)

Cape Fear River at Lillington (site 28)

Discharge canal (site 8)

EXPLANATION

Note: Change in Cape Fear River at Lillington discharge at 7 hours preand 15 hours post-pumping changes, 60 cubic feet per second pre- and

80 cubic feet per second post adjustment

Note: Vertical red lines indicate

time elapsed between stoppage 

of pumping and resulting change

in discharge at the Lillington

streamgage. Vertical blue lines

indicate time elapsed between

resumption of pumping and

change in discharge.
58 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

conducted using infrared techniques to detect regional groundwater discharge by measuring variations in water temperature 

near the flood-plain sediments. Additionally, three reaches of 

the Cape Fear River were selected for local groundwater-level 

monitoring using a transect of piezometers installed in the flood 

plain to determine the validity of the underlying assumption 

that the groundwater-flow system near the Cape Fear River is 

functioning in “gaining-stream” conditions. These groundwatermeasurement methods differ in resolution and time scale from 

the methods applied to the surface-water data collection. The 

groundwater data-collection methods applied to the subsurface 

yield point estimates at a small scale. The groundwater data 

collected during this investigation indicate the possibility of 

localized flow loss during the summer, particularly in the reach 

above Buckhorn Dam. However, there was no indication of 

unusual patterns that would cause substantial flow loss from 

the study reach as a result of groundwater and surface-water 

interaction at the river bottom.

In humid regions, such as those present in North Carolina, a typical river receives groundwater discharge by the 

seepage of groundwater into the riverbanks or riverbed (base 

flow; Winter and others, 1998; Weaver and Pope, 2001; 

LeGrand, 2004). Under these gaining-stream conditions, 

the groundwater level near the river is higher than the water 

level in the stream channel, which causes stream discharge to 

increase in a downstream direction even if no tributaries are 

present. If the river is a “losing stream,” the groundwater level 

near the river is below the river level. Streams can be gaining 

streams along one river reach and losing streams along another 

reach, depending on the relation to the water table. 

Under conditions of drought, storm events, abrupt 

changes in channel gradient (both natural and those caused by 

manmade diversions), nearby groundwater pumping, evaporation, and transpiration of groundwater by vegetation, a river 

reach can alternate between losing and gaining on a daily 

or seasonal basis. During storm events, water can overflow 

the river onto the streambank as the river stage rises causing 

surface water to infiltrate into the groundwater beneath the 

flood plain and resulting in temporary localized changes to the 

water-table altitude. These differences in flow dynamics and 

variations in underlying geologic units can influence regional 

and local groundwater interaction.

Electromagnetic Geophysical Survey

A geophysical survey of the 24.5-mi river bottom in the 

study reach was conducted to identify possible locations of 

diabase dikes. A GEM–2 EM-induction geophysical instrument was used at base-flow conditions to map the presence 

of diabase dikes that may act as impermeable boundaries to 

groundwater discharge. Because of the higher iron and magnetite content in diabase dikes, compared to the surrounding 

geologic material, these geologic features beneath riverbed 

sediments can be mapped as higher variations in conductivity and magnetic susceptibility in the lower frequency EM 

response.

 The majority of the detected anomalies in the geophysical survey results were located downstream from Buckhorn 

Dam (figs. 32–33) in the Carolina Terrane, Cary sequence 

rocks, while relatively few occurrences were detected 

upstream in the Mesozoic (Triassic) basin rocks. In the Haw 

and Cape Fear Rivers of the upper reach, the numerous conductive anomalies detected along the left side (when viewed 

in the downstream direction) likely resulted from variations in 

water-column thickness or instrument drift. Many anomalies 

were detected on both sides of the Haw River in the upper 

reach 1.75 mi downstream from Jordan Lake Dam and in areas 

where electric power-transmission lines spanning the river 

affected the instrument.

On the Cape Fear River, the depth penetration of the 

GEM–2 instrument may have been limited by deeper watercolumn depths in the main stem, particularly on the reach 

between State Highway 42 and Buckhorn Dam. In addition 

to more occurrences of increased magnetic anomalies in the 

lower reach, there also were more occurrences of increased 

signal detections along both sides of the Cape Fear River 

channel between Buckhorn Dam and the streamgage at Lillington (fig. 33, site 28). Examination of the mapped survey in 

the lower reach indicates increased magnetic signals on both 

sides of the channel.

Previous geologic mapping by Burt and others (1978) 

in central North Carolina covers the northwest part of the 

study area and indicates that diabase dikes typically strike 

northwest-southeast (fig. 32). Given that the orientation of the 

main stem is similar to these previously mapped dikes, it is 

inconclusive whether the conductive anomalies in the lower 

reach correspond to one or more diabase dikes in this reach. 

Although detailed geologic maps of diabase dike outcrops 

were not available for the lower reaches, multiple locations of 

mapped conductive anomalies from the EM survey indicate 

the potential presence of these relatively impermeable hydrologic boundaries, most notably between Buckhorn Dam and 

the confluence with Buckhorn Creek in Raven Rock State Park 

(including the group camp area near the downstream end of 

the park boundary) and in the reach abetween PZ2 and Lillington (fig. 33). Because of the clustering of conductive anomalies, presence of riffles, and relatively shallow river depths 

identified using the GEM2 EM-induction tool, the group camp 

area in Raven Rock State Park was selected as the location for 

the FO-DTS survey.

Groundwater Temperature

Two heat-tracer methods were employed to delineate 

groundwater discharge zones in the study area—a DTS survey 

of a 1-mi long reach of the Cape Fear River and a thermal 

infrared survey of the Haw and Cape Fear Rivers. Temperature traditionally has been shown to be an excellent tracer of 

groundwater movement (Stonestrom and Constantz, 2003). 

Natural variations in streamwater temperature patterns are 

used to assess the interaction of river water with shallow 

groundwater. The temperatures of surface-water bodies are 
Results and Interpretation of Data 59

variable and change daily in response to seasonal and meteorological changes, whereas groundwater temperatures are relatively stable year round. Groundwater discharge into surface 

water can be recognized as a cold signature in the summer and 

a warm signature in the winter. These methods of measuring 

differences in temperature can be used to identify areas of 

groundwater discharge (gaining-stream conditions) into the 

Cape Fear River but generally cannot distinguish between noflow and losing reaches. 

Distributed Temperature Sensing (DTS) Survey

About 3,000 ft of fiber optic cable was deployed on the 

bed of the Cape Fear River at the Raven Rock State Park reach 

(fig. 33, site DTS) to evaluate if potential effects of diabase 

dikes, delineated from the EM geophysical survey, could be 

preferentially directing groundwater discharge. Continuous 

temperature measurements were made by the FO-DTS from 

1800 hours on August 11 through 1000 hours on August 13, 

Figure 32. Locations of increased magnetic anomalies in the upstream reach from Buckhorn Dam, North Carolina.

X

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.

LEE

CHATHAM

WAKE

HARNETT

McKay

Island

Fear

Cape

Haw

Deep

River

River

Mesozoic

(Triassic)

basin

Carolina Terrane

(Virgilina sequence)

Shearon

Harris Lake

Carolina

Terrane

(Cary

sequence)

River

Jordan Lake

79 7905'

Magnetic anomaly signals

 transitioning from low

 (yellow) to high (red)

Study area

Faults

Diabase dikes

Geologic unit boundary

Power transmission lines

Dam and number

Groundwater piezometer (PZ) and

 distributed temperature sensing

 (DTS) sites and number

EXPLANATION

D1

D2

PZ1

D3

0 2.5 5 MILES

0 2.5 5 KILOMETERS

PZ1

D3

Buckhorn

Dam

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale

Haywood

Moncure

35

38'

35

36'

35

34'
60 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Figure 33. Locations of increased magnetic anomalies in the downstream reach from Buckhorn Dam, North Carolina.

469 to 486 ft3/s. Water temperatures measured near the riverbed 

during the survey ranged from about 28 to 34 oC.

The FO-DTS data are displayed as colored thermal transects in figure 34 at four different time periods on August 12. 

No temperature anomalies of colder water were measured during the survey, which indicates that at the time of the survey, 

the Cape Fear River was a no-flow or losing stream in that 

particular river reach. If groundwater discharge were entering 

the Cape Fear River through riverbed seepage, a persistent 

cold temperature anomaly (about 15 to 20 oC) would have 

been identified. 

2009. The cable was laid in a U-shape pattern along the bottom 

of the riverbed, paralleling the right riverbank (fig. 34). At the 

Raven Rock State Park reach, the riverbed was composed of 

exposed bedrock and was devoid of sediment, with the exception of a limited quantity of sand-sized particles that accumulated around boulders. The cable crossed three large shallowly 

submerged quartz-boulder shoals and six conductive anomalies 

identified during the EM geophysical survey. The stage of the 

Cape Fear River at the Lillington streamgage (site 28) was 

low and stable (base-flow conditions) and fluctuated less than 

0.03 ft over the 3-day survey with a daily mean discharge from 

CHATHAM

LEE

HARNETT

WAKE

Buckhorn

Dam

79 7850’

Angier

Lillington 0 2.5 5 MILES

0 2.5 5 KILOMETERS

Cape

Fear

River

DTS

PZ2

Raven Rock

State park

3530’

D3

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale

Magnetic anomaly signals

 transitioning from low

 (yellow) to high (red)

Study area

Dam and number

Groundwater piezometer (PZ) and

 distributed temperature sensing

 (DTS) sites and number

Stage-discharge continuous-record

 station and number

EXPLANATION

D3

DTS

28

28

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.
Results and Interpretation of Data 61

Figure 34. Results of the FO-DTS survey showing 

temperature of the river bottom on August 12, 2009, 

at (A) midnight, (B) 0600 hours, (C) noon, and

(D) 1800 hours in the Cape Fear River near Raven 

Rock State Park, North Carolina.

EXPLANATION

28.50–29.49

29.50–30.49

30.50–31.49

31.50–32.49

32.50–33.49

Temperature in,

degrees Celsius

0 100 200 300 400 500 MILES

0 25 50 100 150 KILOMETERS

7852’53”

3527’45”

3527’38”

7852’45” 7852’53”

3527’45”

3527’38”

7852’45”

7852’53”

3527’45”

3527’38”

7852’45” 7852’53”

3527’45”

3527’38”

7852’45”

A B

C D
62 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

It should be noted that the lack of observed groundwater seepage during the survey does not imply that this reach 

is a no-flow or losing stream at all times during the year. It 

does suggest that, under conditions similar to those present 

during the survey (high ambient temperature, low river stage, 

high ET processes, and low flow), this reach is not a gaining stream. Additionally, the FO-DTS survey was unable to 

discern losing-stream conditions, because the fiber-optic cable 

could not be deployed vertically beneath the river to measure 

temperature gradient with depth. The presence of competent 

bedrock instead of riverbed sediments lining the channel 

made vertical temperature measurements impossible in this 

reach.

Thermal Infrared (TIR) Imaging

A regional TIR aerial flyover of the Cape Fear and Haw 

Rivers was conducted on February 27, 2010, to detect regional 

groundwater discharge by qualitatively measuring variations 

in water temperature near the flood-plain sediments. The application of remote temperature sensing in rivers is a relatively 

recent development that has proven effective for assessing 

stream temperature patterns (Banks and others, 1996; Belknap 

and Naiman, 1998; Torgersen and others, 2001). Conventional 

methods of in-stream temperature measurement by placing 

data recorders in the stream are useful in evaluating groundwater and surface-water interaction but generally are spatially 

limited (Stonestrom and Constantz, 2003). The spatial data 

needed to map sources of thermal heterogeneity at the large 

watershed scale are facilitated by airborne TIR imaging. With 

TIR, differences in temperature can be used to qualitatively 

identify areas of groundwater discharge (gaining-stream conditions) into the Cape Fear River but generally cannot distinguish between no-flow and losing reaches. Areas interpreted 

from the TIR images as groundwater seepage (gaining stream) 

are shown in figure 35.

Figure 35. Areas of groundwater discharge to the Cape Fear River between Jordan Lake Dam and Lillington, North Carolina, identified 

by thermal infrared imaging, February 27, 2010.

7920’ 7910’ 78 79 50’ 

3540’

3530’

0 5 10 MILES

0 5 10 KILOMETERS

Apex

Cary

Jordan Lake

CHATHAM

LEE

Holly

Springs

Angier

Lillington

FuquayVarina

WAKE

HARNETT

Buckhorn

Cr.

Cape

Fear

River

Moncure

Haywood

Groundwater

seepage

Regional power plant

discharge canal

Groundwater

seepage

Unnamed tributary

fed by groundwater

 seepage

Study area boundary

Groundwater seepage area

Seep

EXPLANATION

Goldston

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale

Location of study area in Chatham, Lee, Wake,

and Harnett Counties in North Carolina.
Results and Interpretation of Data 63

The TIR survey conducted as part of this study proved 

highly effective for qualitatively examining the spatial distribution of stream temperature. Four areas of groundwater discharge were present in the study area—between Jordan Lake 

Dam and the confluence of the Haw and Deep Rivers, between 

McKay Island and Buckhorn Dam, above Raven Rock State 

Park, and above the city of Lillington. Groundwater discharge 

was noted generally as diffuse groundwater seepage, which 

displays in TIR imagery as warmer temperatures present on 

the surface water across an area close to the riverbank. In two 

locations just downstream from Raven Rock State Park, discrete points of groundwater discharge (springs) were detected. 

Two closeups of TIR images that display the warmer groundwater seepage are shown in figure 35. Of immediate notice 

in one of the TIR images is the temperature contrast between 

the flows in the main stem and the adjacent diversion canal, a 

reflection of the much warmer water temperatures in the canal 

as it flows downstream from the regional power plant (fig. 35).

The TIR imagery collected as part of this study represents 

hydrologic conditions present at one point in time and does 

not represent conditions throughout the entire year. The TIR 

imagery does indicate, however, that under some hydrologic 

conditions during the winter, much of the study area is gaining 

an undetermined quantity of water through groundwater seepage in selected reaches along the main stem.

Hydrogeology

Groundwater availability and monitoring were not considered for much of the regional study area because of access 

restrictions and limited availability of long-term monitoring 

wells. Instead, three reaches of the Cape Fear River were 

selected for local groundwater monitoring using a transect of 

piezometers installed in the flood plain (locations PZ1, DTS, 

and PZ2; figs. 6, 7). The groundwater investigation focused on 

the calculation of local hydraulic gradients between the flood 

plain and the Cape Fear River to determine the validity of 

the underlying assumption that the groundwater-flow system 

near the Cape Fear River is functioning under gaining-stream 

conditions, as suggested by the LeGrand (2004) conceptual 

model.

The regional power plant reach is located in Chatham 

County about 8 mi downstream from Jordan Lake Dam 

(site PZ1, fig. 6). The river stage in this reach is highly 

controlled by backwater created by Buckhorn Dam, which is 

located about 2 mi downstream. The right riverbank (looking 

downstream) is a high, steeply cut bank (over 7 ft of exposed 

face) at typical base-flow stage, whereas the left bank gently 

slopes away from the river to a broad, flat flood plain. In the 

area of the regional power plant reach, the Cape Fear River 

is about 350 ft wide and the water depth at base flow exceeds 

10 ft. A transect of piezometers was installed on the left bank 

perpendicular to the edge of the river to monitor horizontal 

and vertical groundwater flow through the flood-plain sediments. The arrangement and depth of piezometers are shown 

in figure 9A and construction details are listed in table 2. Three 

piezometers were installed within the bed of the Cape Fear 

River (CH–231, CH -232, and CH–233) to monitor vertical 

groundwater gradients. Two piezometers were installed on 

the flood plain (CH–235 and CH–236) to monitor horizontal 

groundwater flow. One piezometer was installed in the bottom 

of the water column of the Cape Fear River (CH–234) to act 

as a reference for river stage.

The soil in the area of the regional power plant reach has 

been mapped as Riverview silt loam (Hayes, 2006), very deep, 

well-drained soil formed in alluvium on flood plains. Soil borings collected near the piezometers generally agree with this 

classification but indicate that soils in this location are slightly 

darker in color and finer in texture than typical Riverview silt 

loam (fig. 9A). The regional power plant reach was selected 

for monitoring because of the potential for a “losing reach” in 

this area resulting from the artificially high river stage raised 

by Buckhorn Dam. 

The Raven Rock State Park reach is in Harnett County, 

about 8 mi downstream from Buckhorn Dam (fig. 7; 

site DTS). In this area, the width of the Cape Fear River can 

exceed 450 ft and is generally shallow, with water column 

depths less than 3 ft during base-flow conditions. Similar to 

the regional power plant reach, the channel wall on the right 

bank is high and steep (over 10 ft high at base-flow conditions), leading to a broad, flat flood plain that merges into 

steep upland slopes, whereas the left bank gently slopes away 

from the river into a flat flood plain. The Raven Rock State 

Park reach was selected because many magnetic anomalies 

were identified by the EM geophysical survey of the river 

in this area, potentially associated with diabase dikes that 

may serve as impermeable boundaries to groundwater flow 

(fig. 33).

An attempt was made to install a transect of piezometers 

at the Raven Rock State Park reach; however, several logistical complications prevented the installation. The bottom of the 

river in this location is devoid of sediment, and the exposed 

bedrock prevented the installation of piezometers in the river. 

Additionally, the right riverbank was inaccessibly high and 

steep, making it unsuitable for piezometer installation. While 

the left riverbank was accessible, the depth to bedrock was 

too shallow to install piezometers near the river. Ultimately, 

the intention to install a piezometer transect was abandoned in 

favor of conducting a thermal survey in this location.

The Bradley Road reach is in Harnett County about 3 mi 

upstream from the Lillington streamgage (fig. 7, site PZ2). 

Similar to the Raven Rock State Park reach, the right riverbank is high and steep (over 10 ft high at base-flow conditions) with an overlying flat flood-plain terrace. The left 

riverbank is more accessible as it slopes away from the river 

over several natural terraces to a broad, flat flood plain. In the 

area of the Bradley Road reach, the Cape Fear River is about 

300 ft wide, and the water-column thickness at base flow is 

less than 10 ft. A transect of piezometers was installed on the 

left riverbank perpendicular to the edge of the river to monitor 

horizontal and vertical groundwater flow through the floodplain sediments (fig. 9B); construction details are listed in 
64 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

table 2. Two piezometers were installed within the bed of the 

Cape Fear River (HR–060 and HR–061) to monitor vertical 

groundwater gradients. Three piezometers were installed on 

the flood plain (HR–063, HR–064, and HR–065) to monitor 

horizontal groundwater flow. One piezometer was installed 

in the water column of the Cape Fear River (HR–062) to 

act as a reference for river stage. Unfortunately, piezometer 

HR–061 was destroyed soon after installation during a storm 

in November 2009. 

The soil in the area of the Bradley Road reach has been 

mapped as Chewacla loam (Spangler, 1994), a very deep, 

somewhat poorly drained soil formed in alluvium of Piedmont 

river valleys (fig. 9B). Soil borings collected near the piezometers generally agree with this classification but indicate that 

soils in this location are slightly more yellow in color and 

coarser in texture than typical Chewacla loam. The Bradley 

Road reach was selected for comparison to the regional power 

plant transect because it was likely representative of a typical 

gaining reach where diabase dikes were not delineated by the 

EM survey.

Continuous Monitoring

Groundwater levels and river-stage altitudes were monitored in piezometers installed at the regional power plant reach 

from October 2009 to November 2010 and at the Bradley 

Road reach from August 2009 to November 2010 to facilitate the calculation of hydraulic gradients between the flood 

plain and the Cape Fear River. Hydrographs of continuous 

water-level altitudes and river-stage elevations collected at the 

regional power plant and Bradley Road reaches are shown in 

figures 36, 37. Water-level altitudes measured in all piezometers were affected by their proximity to the Cape Fear River 

and rainfall events. Seasonal climatic trends typical of groundwater-level fluctuations across the southeastern U.S. Piedmont 

are not readily discernible as a result of surface-water releases 

from Jordan Lake (U.S. Geological Survey, 2011b).

Throughout the study period, water-level altitudes were 

variable between piezometers as a result of fluctuations in 

river stage and groundwater discharge, but distinctions can be 

noted when transect locations are compared. The Cape Fear 

River stage in the regional power plant reach fluctuated about 

6 ft (fig. 36B) during the monitoring period of October 2009 to 

November 2010, while river stage in the Bradley Road reach, 

the fluctuation was about 15 ft (fig. 37B) during the monitoring period of August 2009 to November 2010. The smaller 

fluctuation in river stage in the regional power plant reach is 

a direct result of being located upstream from Buckhorn Dam 

where the fluctuation in stage is limited. At the regional power 

plant reach, all of the piezometers were intermittently inundated by the Cape Fear River for a few days during the period 

from November 2009 to February 2010 when the river stage 

exceeded the land-surface elevation of all the piezometers 

(fig. 36B). In contrast, most of the piezometers in the Bradley 

Road reach located about 11 mi below Buckhorn Dam were 

inundated by surface water from November 2009 to March 

2010, with only brief periods when land surface was exposed 

at the piezometers (fig. 37B). 

Changes in river stage had a noticeable effect on groundwater levels in both reaches. In the regional power plant reach, 

a decline in river stage resulted in a release of groundwater 

from bank storage and gaining-stream conditions several 

times in January, February, March, and April 2010 (fig. 36C). 

During periods of base flow, however, when the stage of the 

Cape Fear River is relatively stable and the air temperature is 

warm (greater than 70 °F), the flora populating the flood plain 

take up shallow groundwater through evapotranspiration (ET). 

Under these conditions in the regional power plant reach, the 

groundwater level in the flood plain quickly declined below 

the elevation of the river (losing-stream conditions). This 

effect is most noticeable in October 2009 and from June to 

September 2010 (fig. 36C). During the summer months in the 

regional power plant reach, it is not uncommon for groundwater altitudes measured in the flood-plain piezometers (fig. 36B, 

CH–235, CH–236) to be more than 3 ft lower than the Cape 

Fear River. In contrast, groundwater altitudes measured in 

piezometers at different depths in the bed of the Cape Fear 

River (fig. 36B, CH–231, CH–232) are rarely more than 1 ft 

lower than the river level (but still losing-stream conditions).

Changes in river stage had a similar effect on groundwater levels at the Bradley Road reach. A sudden decline in 

river stage resulted in a release of groundwater from bank 

storage and gaining-stream conditions several times in January, March, and April 2010 (figs. 37B, C). Unlike in regional 

power plant reach, periodic groundwater discharge (gainingstream conditions) continued into May and June 2010. Similar 

to the regional power plant reach, when the stage of the Cape 

Fear River in the Bradley Road reach was relatively stable at 

base-flow conditions, the air temperature was warmer, and the 

flora populating the flood plain removed groundwater through 

ET, which resulted in decreased groundwater levels in the 

flood plain below the elevation of the river (losing-stream conditions). This effect was noticeable in August and September 

2010 when temperatures were warmest and ET processes were 

dominant (fig. 37C). In the Bradley Road reach, groundwater 

altitudes measured in the flood-plain piezometers (fig. 37B, 

HR–063, HR–064, HR–065) were generally less than 1 ft 

lower than the river during the summer months, and groundwater altitudes measured in the streambed of the Cape Fear 

River (fig. 37B, HR–060) were rarely more than 0.25 ft lower 

than the river during the summer. 

Water-level altitudes in the regional power plant and 

Bradley Road reaches were analyzed over a 1-year period 

from October 1, 2009, to September 30, 2010 (water year 

2010) to determine the percentage of time the reach was in 

gaining-stream or losing-stream conditions. Piezometers at 

both reaches were installed in vertical nests (different depths 

at the same location) and horizontal transects (different locations at similar depths) to enable mean daily vertical and horizontal hydraulic gradients to be computed between the river 

and groundwater (figs. 36C, 37C). If the mean daily horizontal and vertical gradients were negative, the groundwater 
Results and Interpretation of Data 65

Figure 36. (A) Daily precipitation measured at the Siler City Airport (SILR), (B) daily mean water level and (C) calculated 

hydraulic gradients at the regional power plant piezometer transect (PZ1) near Corinth, and (D) daily mean streamflow 

measured in the Cape Fear River at Lillington (site 28), North Carolina.

Gaining stream

Losing stream

CH-232 PE-1M

CH-233 PE-1D

Calculated hydraulic gradient between

the Cape Fear River and riverbed and flood plain piezometers

Riverbed 

CH-235 PE-2

CH-236 PE-3

Flood Plain

EXPLANATION

Blank where data are missing

CH-231 PE-1U

CH-234 PE-1R CH-231 PE-1U

CH-232 PE-1M

CH-233 PE-1D

Cape Fear River Riverbed Piezometers

CH-235 PE-2

CH-236 PE-3

Flood Plain Piezometers

EXPLANATION

Land surface altitude at CH-236

Example of

“gaining stream”

conditions

Example of

“losing stream”

conditions

Blank where data are missing

Figure 36.

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

2010 Water Year

Daily mean water-level altitude NAVD 88, in feet

100,000

10,000

1,000

100

Daily mean streamflow, in

cubic feet per second Calculated hydraulic gradient, in feet per feet

3.0

2.5

2.0

1.5

1.0

0.5

0

164

162

160

158

156

154

152

0.6

0.5

0.4

0.3

0.2

0.1

0

–0.1

–0.2

–0.3

–0.4

–0.5

–0.6

Daily precipitation,

 in inches

2009 2010

A

B

C

D
66 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Figure 37. (A) Daily precipitation measured at the Fayetteville Public Works Commission (313017) Cooperative station,

(B) daily mean water level and (C) calculated hydraulic gradients at the Bradley Road piezometer transect (PZ2) near Lillington, 

and (D) daily mean streamflow measured in the Cape Fear River at Lillington (site 28), North Carolina.

2010 Water Year

Gaining 

stream

Losing 

stream

Blank where data are missing

HR-062 BR-1R

HR-060 BR-1D

Cape Fear River

Riverbed Piezometer

HR-063 BR-2

HR-064 BR-3

HR-065 BR-4

Flood Plain Piezometers

EXPLANATION

Land surface altitude

at CH-236

Example of

“gaining stream”

conditions

Example of

“losing stream”

conditions

Blank where data are missing

Calculated hydraulic gradient between

the Cape Fear River and riverbed and flood plain piezometers

Riverbed 

HR-063 BR-2 HR-065 BR-4

HR-064 BR-3

Flood Plain

EXPLANATION

HR-060 BR-1D

Figure 37. 

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

Daily mean water-level altitude NAVD 88, in feet

100,000

10,000

1,000

100

Daily mean streamflow, in

cubic feet per second Calculated hydraulic gradient, in feet per feet

3.0

2.5

2.0

1.5

1.0

0.5

0

126

124

122

120

118

116

114

112

110

108

0.15

0.10

0.05

0

–0.05

–0.10

–0.15

Daily precipitation,

 in inches

2009 2010

A

B

C

D
Results and Interpretation of Data 67

flow was downward and outward from the river to the bed 

and flood-plain sediments, indicating the hydraulic head was 

less at depth and losing-stream conditions were assigned for 

the day. Conversely, if the groundwater flow was upward 

and toward the river from the bed and flood-plain sediments, 

the mean daily horizontal and vertical gradients were positive, indicating the hydraulic head was greater at depth and 

gaining-stream conditions were assigned for the day. It was 

also possible for a reach to be gaining in the vertical direction but losing in the horizontal direction or vice versa. This 

condition most likely occurs when the vertical or horizontal gradients are reversing because of changes (increase or 

decrease) in streamflow from impoundment releases or precipitation events but also may occur because the piezometers 

in the transect intercept different parts of the groundwaterflow path during these events. For example, the vertical flow 

path beneath the river may have a positive gradient (gaining 

stream) because of regional groundwater recharge at higher 

altitudes, yet the horizontal flow path may have a negative 

gradient (losing stream) because of a rapid rise in river stage. 

The category “both” was assigned to this condition (figs. 36B, 

C, 37B, C). The distribution of hydraulic head under gaining- and losing-stream conditions as measured on April 20 

and August 25, 2010, in the regional power plant and Bradley 

Road reaches, respectively, is displayed in figures 38, 39. 

Note that the hydraulic gradient under losing-stream conditions on August 25, 2010, in the regional power plant reach is 

about five times greater than under gaining-stream conditions 

measured on April 20, 2010 (fig. 38). In contrast, the hydraulic gradient in the Bradley Road reach is similar in magnitude 

under both gaining- and losing-stream conditions (fig. 39).

Figures 36C and 37C display the distribution of losingand gaining-stream conditions during the monitoring period. 

For water year 2010, the Cape Fear River in the regional 

power plant reach was in a losing-stream condition 38 percent 

of the year, a gaining-stream condition 26 percent of the year, 

and both 28 percent of the year. In the Bradley Road reach 

during the same period, the Cape Fear River was in a losingstream condition 13 percent of the year, a gaining-stream condition 34 percent of the year, and both 43 percent of the year. 

Figure 38. Piezometers and interpolated lines of equivalent pressure head under gaining- and losing-stream conditions at the regional 

power plant transect (PZ1) near Corinth, North Carolina (location shown in fig. 1).

166

164

162

160

158

156

154

152

150

148

146

Altitude, in feet above NAVD 88

0 5 10 15 20

Distance, in feet

Cape Fear River

 CH-234 PE-1R

Riverbed piezometers

 CH-231 PE-1U

 CH-232 PE-1M

 CH-233 PE-1D

Flood plain piezometers

 CH-235 PE-2

 CH-236 PE-3

EXPLANATION

Piezometer screened interval

CH-232

157.92

157.21

CH-234

157.51

157.68

CH-233

158.15

156.73 CH-231

157.85

157.25

CH-235

157.89

155.06

CH-236

157.73

155.08

CH-236

157.73

155.08

Cape Fear

River

155.5

156.0

156.5

157.0

157.6

157.7

157.8

157.9

157.5

158.1

158.0

Figure 38. 

Line of equivalent pressure

head, April 20, 2010

(gaining stream conditions)

Line of equivalent pressure

head, August 25, 2010

(losing stream conditions)

Piezometer identification number

Mean daily water level,

April 20, 2010

Mean daily water level,

August 25, 2010

Land

surface
68 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

Not enough water-level data were available to calculate a gain 

or loss during part of July and August 2010 and intermittently 

throughout the study period because of pressure transducer 

failures in both the regional power plant and Bradley Road 

reaches, which resulted in a loss of 8 percent and 10 percent 

of data for the year, respectively. Both vertical and horizontal 

gradients were frequently two to three times greater under 

both gaining and losing conditions in the regional power 

plant reach than those calculated for the Bradley Road reach. 

This difference is likely because of differences in soils in the 

reaches (fig. 9). Soils in the regional power plant reach contain 

more silt and clay, derived mostly from Mesozoic basin sedimentary rocks ( Hayes, 2006), which retard the movement of 

water more than the sandy loam soils, derived from metamorphic rocks of the Cary sequence of the Carolina Terrane 

(Spangler, 1994) in the Bradley Road reach. 

Water-level data collected for more than 1 year at the 

Progress Energy and Bradley Road reaches indicate that differing hydrologic conditions occur in each reach. During water 

year 2010, the regional power plant reach lost water through 

groundwater seepage from the Cape Fear River into the underlying aquifer and adjacent flood plain on about three times as 

many days as the Bradley Road reach, with most of the losing 

days occurring during the summer months when ET processes 

increased. In contrast, the Bradley Road reach gained water 

through groundwater discharge from the underlying aquifer 

and adjacent flood plain on about 30 more days during water 

year 2010 than in the regional power plant reach, and most of 

these days occurred during the late spring. 

Causes of Flow Losses Based on Results of Data 

Analyses

Consideration of all data collected and (or) analyzed during this investigation indicates a study reach with complex flow 

patterns affected by numerous factors and resulting flow losses. 

Flows often are affected concurrently by several factors, and 

so the causes of flow loss could not be solely attributed to any 

one factor as the primary cause. The factors considered in this 

investigation were (1) computation of discharges at streamgages 

in the study reach and flow releases from Jordan Lake Dam, 

(2) effects of diversion and (or) storage at Buckhorn Dam and 

the Lockville hydropower station, (3) water use associated with 

industrial and municipal intakes in the study area, (4) losses 

Figure 39. Piezometers and interpolated lines of equivalent pressure head under gaining- and losing-stream conditions at the Bradley 

Road transect (PZ2) near Lillington, North Carolina (location shown in fig. 1). Altitude, in feet above NAVD 88

Cape Fear River

 HR-062 BR-1R

Riverbed piezometers

 HR-061 BR-1U

 (destroyed Nov. 2009)

 HR-060 BR-1D

Flood plain piezometers

 HR-063 BR-2

 HR-064 BR-3

 HR-065 BR-4

110.4

110.2

110.0

109.6

109.8

109.4

109.2

109.4

109.6

109.8

Land

surface

EXPLANATION

Piezometer screened interval

118

116

114

112

110

108

106

104

102

100

98

0 4 8 16 18 20

Distance, in feet

24 28 32 36 40 44

Cape

Fear

River

HR-065

110.53

109.04

HR-064

110.20

HR-063 109.24

109.45

109.66

HR-060

109.43

109.70

HR-062

109.36

109.83

HR-061

HR-065

110.53

109.04

Line of equivalent pressure

head, April 20, 2010

(gaining stream conditions)

Line of equivalent pressure

head, August 25, 2010

(losing stream conditions)

Piezometer identification

number

Mean daily water level,

April 20, 2010

Mean daily water level,

August 25, 2010
Summary and Conclusions 69

by evaporation from the study reach, and (5) groundwater and 

surface-water interaction along the study reach. Analyses of 

flow data completed for the 1983–2010 water years indicate the 

median flow loss is 37 ft3/s, based on the assessment of days 

when steady conditions were in effect (that is, little to no change 

in flow conditions from the previous day).

Water diversions and evaporative losses were determined 

to be sufficient on some days (particularly during base-flow 

periods) to exceed the net gain in flows between the upstream 

and downstream ends of the study reach. While consumptive use associated with the regional power plant adjacent to 

the study reach was not fully quantified during the investigation, the net consumptive use associated with five industrial and two municipal intakes was computed to be about 

2.5 ft3/s (about 1.6 Mgal/d) and from 23 to 36 ft3/s (35.6 to 

55.7 Mgal/d), respectively. Potential flow loss from openwater evaporation in the study reach was estimated to be in the 

range of 4 to 14 ft3/s during May through October. The summation of these ranges clearly exceeds the median flow loss of 

37 ft3/s, indicating flow loss from the study reach due to water 

diversions and evaporation is real. Ratings analyses completed 

for the streamgages at Deep River at Moncure (site 3) and 

Cape Fear River at Lillington (site 28) did not indicate any 

particular time during the 1982–2011 water years when the use 

of stage-discharge ratings resulted in computed discharges that 

indicated false flow losses. Similarly, discharge measurements 

made at the streamgage on the Haw River downstream from 

Jordan Dam provided general confirmation of the reported 

flow releases from Jordan Lake.

Groundwater data collected during 2009–2010 indicate 

the possibility of localized flow loss during the summer, 

particularly in the reach above Buckhorn Dam. No indication of unusual patterns was evident, however, that would 

cause substantial flow loss as a result of groundwater and 

surface-water interaction at the river bottom. At the regional 

power plant piezometer reach upstream from Buckhorn Dam, 

the groundwater level quickly declined below the river level 

during the base-flow period in late summer and early fall, 

which indicates losing-stream conditions. Groundwater-level 

altitudes measured in the flood-plain piezometers were commonly more than 3 ft lower than the Cape Fear River during 

the summer months. In contrast, groundwater-level altitudes 

measured in the Bradley Road piezometers were rarely more 

than 1 ft lower than the river stage, although still representative of losing-stream conditions. During the year of data collection, the Cape Fear River was in a losing-stream condition 

38 and 13 percent of the year at the regional power plant and 

Bradley Road reaches, respectively. The higher percentage at 

the regional power plant reach is attributed to storage in the 

impounded reach upstream from Buckhorn Dam.

The distributed temperature survey completed August 

2009 on the Cape Fear River at Raven Rock State Park indicated that, under conditions similar to those present during 

the survey (high ambient temperature, low river stage, high 

ET processes, and low flow), the study reach is not gaining. In 

contrast, the aerial TIR survey completed February 27, 2010, 

indicated that under some hydrologic conditions during the 

winter, much of the study reach gained an undetermined quantity of water through groundwater seepage in selected reaches 

along the main stem.

Summary and Conclusions

During 2008–2010, the U.S. Geological Survey (USGS) 

conducted a hydrologic investigation in cooperation with the 

Triangle J Council of Governments Cape Fear River Flow 

Study Committee and the North Carolina Division of Water 

Resources to collect hydrologic data to help determine if 

suspected flow losses in the Cape Fear River between B. 

Everett Jordan Lake and Lillington, North Carolina, are real or 

apparent. During some low-flow conditions, the sum of flow 

releases from Jordan Lake Dam and observed streamflow at a 

long-term streamgaging station on the Deep River at Moncure 

in Chatham County is greater than the observed streamflow 

downstream at the streamgage at Lillington. In addition, flows 

at the Lillington streamgage have been observed to decrease 

by 50 to 150 ft3/s over a period of 12 to 24 hours for unknown 

reasons. Assessment of the flow patterns in the study reach 

required a multidiscipline approach for surface-water and 

groundwater data collection and analyses.

Net differences in flows between the upstream and downstream extents of the study reach were determined by summing the daily discharges at Jordan Lake Dam, Deep River at 

Moncure, and Buckhorn Creek near Corinth and subtracting 

that sum from the discharge at Cape Fear River at Lillington. 

Among 10,227 days during the 1983–2010 water years, flow 

loss occurred on 2,941 days (28.8 percent) based on comparison of the daily discharge between the inputs and the Lillington streamgage. However, flow loss occurred on 408 days 

(4.0 percent) during conditions that were relatively steady with 

respect to records for the previous day. The flow loss among 

these 408 days ranged from 0.49 to 2,150 ft3/s with a median 

flow loss of 37.2 ft3/s. In terms of flow-loss amounts, analyses 

of histograms indicated that approximately 64 percent of the 

flow losses were 50 ft3/s or less. The months with the highest 

number of days with flow losses were June (16.7 percent), 

September (16.9 percent), and October (19.4 percent).

Part of the surface-water data collected during the study 

included discharge measurements made at selected locations 

along the main stem between Jordan Lake Dam and the Lillington streamgage during a series of six synoptic measurements in 2009. The series of synoptic measurements were 

conducted on April 27, June 25, July 22, August 18, September 9, and October 1. Several patterns were noticeable from 

the graphed data of each series of measurements when viewed 

from a greater perspective. The largest water diversion for 

use as cooling water at the regional power plant occurs just 

downstream from the confluence of the Haw and Deep Rivers. 

Downstream from Buckhorn Dam, little gain or loss was noted 

between the dam and Raven Rock State Park, although some 
70 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

minor fluctuations in flow patterns appeared to occur between 

the State park and the Lillington streamgage.

Analyses of discharge measurements and ratings for the 

two streamgages at Deep River at Moncure and Cape Fear 

River at Lillington were completed as part of this investigation 

to address a concern that computed discharge records at these 

two sites could perhaps be inaccurate, resulting in false flow 

loss. A total of 99 discharge measurements were made at the 

Moncure streamgage during the 1982–2011 water years, ranging from 27.9 to 21,500 ft3

/s; 66 measured discharges were 

500 ft3/s or less. Among these 66 measurements, rating shifts 

were applied after 45 measurements were completed; 14 shifts 

were positive, and 31 shifts were negative. A total of 103 discharge measurements were made at the Lillington streamgage 

during the same period, ranging from 133 to 28,800 ft3/s; 51 

measured discharges were 1,000 ft3/s or less. Among these 51 

measurements, rating shifts were applied after 11 measurements were completed; 10 shifts were positive, and 1 shift was 

negative. Examination of the percentage differences (whether 

shifted or unshifted) at both streamgages likewise did not indicate a particular time during the 1982–2011 water years when 

the values were consistently positive or negative, and no bias 

was indicated that could result in falsely computed flow losses.

A comparison was made between 34 measured discharges at a streamgage on the Haw River below B. Everett 

Jordan Lake near Moncure and reported hourly flow releases 

from Jordan Lake Dam. The discharge measurements ranged 

from 94.7 to 9,970 ft3/s, and 25 measurements were less than 

2,000 ft3/s. Comparison of these measurements and flow 

releases indicates the measured discharges ranged from 75 

to about 140 percent of the concurrent hourly flow releases 

among the 34 measurements and within plus or minus 10 percent for 28 measurements, which provides general support of 

the current discharge computation tables used for reporting 

Jordan Lake Dam flow releases. 

A stage gage was operated during the study on the Cape 

Fear River at Buckhorn Dam near Corinth to collect continuous 

stage-only records. Elevation computed from stage records collected during the study ranged from 157.32 ft on October 9 and 

12, 2009, to 161.42 ft on February 6, 2010. Flow over the dam 

was observed along its length during the study, and the above 

range in stage records indicates that flow loss in the study reach 

is not attributed to river-level fluctuations at the dam.

Water-use information and (or) data were obtained for 

five industrial facilities, a regional power plant, two municipalities, one small hydropower facility on the Deep River, and 

one quarry operation adjacent to the Deep River. The largest 

water users are the regional power plant, the small hydropower 

facility, and the two municipalities. 

Water-use data collected at the five industrial facilities 

during the study indicate the maximum water consumption 

among these facilities is about 2.5 ft3/s (about 1.6 Mgal/d). 

Combining the range of withdrawals for the two municipalities indicates that from 23 to 36 ft3

/s (35.6 to 55.7 Mgal/d) was 

removed from the study reach during the winter and summer 

periods. When adding the maximum water consumption for 

all five industries and quarry operation, the total water-use 

diversions ranged from almost 25.5 to 38.5 ft3/s (39.5 to 

59.5 Mgal/d) during the winter and summer periods. This 

range in water-use diversions is equivalent to 69 to 104 percent of the 37 ft3

/s median flow loss.

The Lockville hydropower station is on the Deep River 

about 1 mi downstream from the streamgage near Moncure. 

Under the current (2011) operation of one turbine, the discharge diverted through the canal between the dam and powerhouse during maximum power generation is between 500 and 

600 ft3/s. Information obtained during two visits to the facility 

indicated that run-of-river operations did not appear to be a 

major factor behind flow losses in the study reach.

The largest water user in the study area is a regional 

power producer at a coal-fired power generation plant located 

immediately adjacent to the Cape Fear River just downstream from the confluence of the Haw and Deep Rivers. 

Data describing daily water withdrawals were supplied by the 

regional power producer and compared to discharge records at 

a USGS streamgage on the diversion canal downstream from 

the power plant. Estimated differences between the intake and 

canal discharge data (or consumptive losses) typically ranged 

from 10 to 40 ft3/s (6.5 to about 25.8 Mgal/d) with amounts 

exceeding 50 ft3/s (32.3 Mgal/d) on some days. A large part 

of this range is higher than the approximately 13.4 ft3/s 

(8.65 Mgal/d) estimate in water loss from the cooling towers 

provided from engineers with the regional power producer. 

Uncertainty surrounding reasonable estimates of consumption 

remained in effect at the end of the study.

Data concerning evaporative losses were compiled by using 

two approaches: (1) analysis of available pan-evaporation data 

from a collection station nearby in Chapel Hill, N.C., and (2) compilation of reference open-water evaporation data computed by 

the State Climate Office of North Carolina using the PenmanMonteith method. Comparison of estimated evaporative losses 

indicated substantial differences between the two methods of 

computing evaporation, particularly during the summer months. 

Both methods were considered by estimating the potential flow 

loss by evaporation from the main stem and the Deep River to be 

in the range of 4 to 14 ft3/s during May through October, equivalent to 10 to 38 percent of the 37 ft3

/s median flow loss.

Daily water-use diversions and evaporation losses were 

compared to flow-loss occurrences during the period April 

2008 to September 2010. The comparison was completed to 

assess how the magnitude of total losses from water consumption and evaporation compared to calculated flow losses. 

During the period of interest, flow analyses indicated 289 days 

of flow loss occurrences at the streamgage on the Cape Fear 

River at Lillington, with filtered flow losses occurring on 

34 days during the same period. Among these 34 days, the 

total consumptive water-use diversions for the five industries 

and two municipalities exceeded the computed flow losses 

on 26 days. With evaporative losses added, the total losses 

exceeded the computed flow losses on 2 additional days.

During the latter stages of the investigation, a connection 

was established between the occasional sudden changes in flow 
Selected References 71

at the streamgage on the diversion canal adjacent to the Cape 

Fear River and downstream flows at the Lillington streamgage, 

resulting in an apparent flow loss. An assessment of the daily 

discharges and subsequent inspection of the instantaneousvalue hydrographs for the canal streamgage indicated at least 

24 instances from the start of data collection in April 2008 

through December 2010 when the flows inexplicably decreased 

or increased by 100 to more than 200 ft3/s. For 10 of these 24 

instances, flows at the Lillington streamgage were at or below 

600 ft3/s. The instantaneous hydrographs showed a fairly consistent cause-and-effect relation. Inspection of the hydrographs 

indicated that, when discharge through the canal decreased 

or stopped for a short period, that amount of discharge was 

immediately available for travel in the Cape Fear River, which 

resulted in increased discharge at the downstream Lillington 

streamgage beginning about 8 hours later. When discharge from 

the Cape Fear River was diverted into the canal, there was a 

time-lagged decrease in discharges downstream at the Lillington 

streamgage beginning anywhere between 8 and 16 hours later.

Several complementary methods were applied to assess 

conditions of gain or loss through groundwater and surfacewater interaction within regional (large scale) and local (small 

scale) confines of the Cape Fear River. A geophysical survey 

using the GEM–2 digital multifrequency electromagneticinduction instrument was completed on the main stem during 

2009. The geophysical survey was used to identify possible locations of magnetic anomalies indicating the presence of diabase dikes (altering groundwater discharge from 

or recharge to a river), thereby enabling increased focus on 

reaches where additional groundwater data, in particular the 

distributed temperature sensing survey, could be collected. 

Inspection of mapped anomalies from the study-area scale 

revealed that most occurrences of increased magnetic anomalies were detected downstream from Buckhorn Dam in the 

Carolina terrane, Cary sequence rocks and relatively few 

occurrences were detected upstream.

About 3,000 ft of fiber-optic cable was deployed on the 

bed of the Cape Fear River at the Raven Rock State Park reach 

August 11–13, 2009, to determine if the presence of diabase 

dikes could be preferentially directing groundwater discharge. 

The average water depth was 1.84 ft and ranged from 0.48 to 

3.83 ft. Over the 40 hours of temperature monitoring with the 

fiber-optic distributed temperature sensor (FO-DTS), water 

temperatures were dominated by the diurnal effects of solar 

heating and night-time cooling. No temperature anomalies of 

colder water were measured during the survey, which indicated that at the time of the survey, the Cape Fear River was a 

no-flow or losing stream in that particular river reach.

An aerial thermal-infrared survey was conducted over 

the Haw and Cape Fear Rivers on February 27, 2010, from 

Jordan Lake Dam to Lillington to qualitatively delineate areas 

of preferential discharge on the basis of the contrast between 

warm groundwater discharge and cold surface-water temperatures. Discharge generally was noted as diffuse seepage, but in a 

few cases springs were detected as inflow as a discrete point of 

discharge.

Two reaches of the Cape Fear River were selected for 

groundwater monitoring, each with a transect of piezometers installed in the flood plain (regional power plant and 

Bradley Road). Water-level altitudes at the regional power 

plant and Bradley Road reaches were analyzed over a 1-year 

period from October 1, 2009, to September 30, 2010 (water 

year 2010). In the regional power plant reach, the Cape Fear 

River was in a losing-stream condition 38 percent of the year, 

a gaining-stream condition 26 percent of the year, and both 

conditions 28 percent of the year. In the Bradley Road reach 

during the same period, the Cape Fear River was in a losingstream condition 13 percent of the year, a gaining-stream condition 34 percent of the year, and both conditions 43 percent 

of the year. Groundwater data collected as part of this study 

represent only a brief period of time and may not represent 

conditions present at all times and for all years. However, the 

data indicated that during the winter, the study area gained an 

undetermined quantity of water through seepage.

Consideration of all data collected and (or) analyzed 

during this investigation indicates a study reach with complex 

flow patterns affected by numerous factors and resulting flow 

losses. Flows often are affected concurrently by several factors, and the causes of flow loss could not be solely attributed 

to any one factor as the primary cause. Water diversions and 

evaporative losses were determined to be sufficient on some 

days (particularly during base-flow periods) to exceed the net 

gain in flows between the upstream and downstream ends of 

the study reach. Losses due to diversions and evaporation can 

exceed the median flow loss of 37 ft3/s, indicating flow loss 

from the study reach is real. Groundwater data collected during 2009–2010 indicate the possibility of localized flow loss 

during the summer, particularly in the impounded reach above 

Buckhorn Dam. No indication of unusual patterns was evident, 

however, that would cause substantial flow loss as a result of 

groundwater and surface-water interaction at the river bottom.

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Appendix 1 75

In operating a streamgage, records of gage height (or 

stage) are collected and applied to a stage-discharge rating to 

determine the discharge associated with a given stage. The 

stage-discharge rating relates the stage and discharge values 

for a specific site. The rating is established over time with the 

collection of discharge measurements made at the streamgage 

over the range of stages expected at the site. Because of everchanging conditions in the channel, ratings are dynamic and 

typically evolve over time as additional discharge measurements are made and used to further update the relation between 

stage and discharge. For example, channel scour resulting from 

a large flood event may be sufficient to warrant a revised rating 

for a streamgage, while flow events of lesser magnitude may 

result in a temporary “shift” of the rating (fig. 1–1).

Discharge records at USGS streamgages commonly 

are based on the use of a stage-discharge relation (or rating), 

which defines the relation between the stage and discharge 

for a specific location on a stream. The establishment and 

maintenance of a stage-discharge rating for a streamgage is 

an on-going process requiring the continual collection and 

evaluation of discharge measurements over time. As discharge 

Appendix 1. 

100

10

1

1 10 100 1,000 10,000 100,000

Shifted rating

Discharge, in cubic feet per second

Best rating

Channel cross section

Water surface

Individual discharge

measurements obtained

over time

In this example, the lower end of the

stage-discharge rating (blue)

undergoes a negative or left shift

(red) in response to channel fill

Example scour hole in cross

section filled following

high-flow event

Stage, in feet

Channel bottom

measurements are collected at a streamgage, the rating is 

developed and reanalyzed to determine if the current rating is 

appropriate or if a temporary “rating shift” is needed. A number of factors govern the strength and stability of a rating, one 

of the most notable being the materials that make up the channel bottom at the streamgage. The channel bottom material 

at the Moncure and Lillington streamgages is characterized 

generally by rocks of varying sizes ranging from small cobbles 

to large boulders. The process of scour and fill under the range 

of discharges that can occur on a stream may result in a temporary rating shift following a moderate- to high-flow event. 

Temporary rating shifts also may be required when debris is 

lodged in the channel following storm events, aquatic growth 

in the channel, or beaver-dam activity. If the temporary shift 

remains in effect over the course of time after additional discharge measurements have been obtained, then a new stagedischarge rating may be established for the streamgage.

When a discharge measurement is made at a streamgage, 

the discharge is computed and three initial steps are completed 

by the hydrographer. The first is to establish the quality of the 

measurement by using one of four assessments (excellent, 

Appendix 1. A Brief Primer on Discharge Measurements and Ratings Analyses

Figure 1–1. Schematic 

showing theoretical shift in 

stage-discharge rating in 

response to changes in river 

channel geometry.
76 Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina

good, fair, or poor). For measurements made using mechanical 

velocity meters, the quality is based on the number of sections, 

percentage of discharge within each section, the mean velocity, and occurrence of angle coefficients (U.S. Geological Survey, 2010b). For discharge measurements made using acoustic 

meters, the measurement quality is based on the calculated 

95-percent confidence interval of base measurement uncertainty (in percent). For all measurements, the condition of 

equipment, field measuring conditions, and the hydrographer’s 

judgment also factor into the quality of the measurement.

If the base uncertainty for an acoustic measurement is 

less than or equal to 5 percent, the measurement rating is good 

(U.S. Geological Survey, 2010b). If the base uncertainty is 

between 5 and 8 percent, the measurement rating is fair. If 

the base uncertainty is greater than 8 percent, the measurement rating is poor. Although the assessment is somewhat 

subjective, the rating of a measurement is an important step 

and reflects the hydrographer’s characterization of the overall 

quality of the measurement. The measurement quality rating 

is useful in determining whether any temporary shifts need 

to be applied to the stage-discharge rating in effect for the 

streamgage, which affects the discharge records that are computed on the basis of the rating.

In the modern environment of real-time streamflow dissemination, current streamflow data are determined using a 

base rating curve and a temporary rating shift (if needed and 

where applicable) as indicated by the most recent discharge 

measurement(s). This is a critical point of consideration when 

assessing the accuracy of discharge data continuously being 

provided through real-time capabilities. Until the next discharge measurement is made at a gaging station, any temporary shift applied to a rating remains in effect until the next 

measurement can be processed and reviewed to determine if a 

shift is still necessary. Real-time discharge data, therefore, are 

considered provisional and subject to revision pending subsequent analysis as additional discharge measurements become 

available. Because provisional discharge data can be subject 

to an unknown percentage difference from the base rating, the 

possibility exists that incorrect assessments of flow loss can 

occur until the next measurement is made.

The second step completed by the hydrographer following a discharge measurement is to compute an unshifted

percentage difference between the measured discharge and base 

rating discharge. This value is computed by subtracting the 

base rating discharge from the measured discharge, dividing by 

the base rating discharge, and expressing the result as a percentage. A positive unshifted percentage difference indicates the 

measured discharge is higher than the base rating discharge, 

and a negative unshifted percentage difference indicates the 

measured discharge is lower than the base rating discharge.

Based on the quality assigned to the discharge measurement, the magnitude of percentage difference, and other 

factors observed during the field inspections, the hydrographer may apply a temporary shift to align the base rating with 

observed conditions at the time of the measurement. Although 

rare, the hydrographer may elect not to use the measurement 

to apply any shift in the rating and resulting computation of 

discharge records. 

A shift is measured in stage units (feet) and corresponds 

to the equivalent change in stage necessary to bring the base 

rating discharge in sync with the measured discharge, resulting in a shift-adjusted rating. Following the shift, a shifted 

percentage difference between the measured discharge and the 

shift-adjusted-rating discharge is computed using the approach 

described above for the unshifted percentage difference.

More information documenting the computation of 

discharge at USGS streamgaging stations is available in Rantz 

and others (1982, v. 1, 2).
Manuscript approved October 2, 2012

For more information about this publication, contact:

 Director

 USGS North Carolina Water Science Center

 3916 Sunset Ridge Road

 Raleigh, North Carolina 27607

 phone: (919) 571-4000

 fax: (919) 571-4041

Or visit the North Carolina Water Science Center

Web site at: http://nc.water.usgs.gov

Prepared by the Raleigh Publishing Service Center

A PDF version of this publication is available online at

http://pubs.usgs.gov/sir/2012/5226
Weaver and Bukowski McSwain—Determination of Flow Losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, N.C.—Scientific Investigations Report 2012–5226