Prepared in cooperation with the South Carolina Department of Health and Environmental Control

Low-Flow Frequency and Flow Duration of Selected

South Carolina Streams in the Catawba-Wateree and 

Santee River Basins through March 2012

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2014–1113
Cover: Rocky Creek at Great Falls, South Carolina, taken on September 21, 2011.
Low-Flow Frequency and Flow Duration 

of Selected South Carolina Streams in the 

Catawba-Wateree and Santee River Basins 

through March 2012

By Toby D. Feaster and Wladmir B. Guimaraes

Prepared in cooperation with the South Carolina Department of Health 

and Environmental Control

Open-File Report 2014–1113

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Feaster, T.D., and Guimaraes, W.B., 2014, Low-flow frequency and flow duration of selected South Carolina streams 

in the Catawba-Wateree and Santee River Basins through March 2012: U.S. Geological Survey Open-File Report 

2014–1113, 34 p., http://dx.doi.org/10.3133/ofr20141113.

ISSN 2331-1258 (online)
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................3

Previous Studies ...................................................................................................................................3

Description of the Study Area ............................................................................................................3

Low-Flow Statistics .......................................................................................................................................4

Analytical Approach.............................................................................................................................4

Quality Assurance and Quality Control .............................................................................................8

Results of Quality Assurance and Quality Control Analyses................................................8

Diversions.............................................................................................................................................10

Frequency Analysis ............................................................................................................................10

Record-Extension Technique............................................................................................................14

Partial-Record Type Analysis............................................................................................................16

Flow-Duration Analysis......................................................................................................................16

Analytical Considerations...........................................................................................................................16

Stations on the Main Stem of the Catawba and Wateree Rivers ...............................................17

Stations 02146750, McAlpine Creek below McMullen Creek near Pineville, NC, and 

0214678175, Steele Creek at Secondary Road 1441 near Pineville, NC........................17

Stations 02171500, Santee River near Pineville, SC, 02171700, Santee River near 

Jamestown, SC, and 02172002, Lake Moultrie Tailrace Canal at 

Moncks Corner, SC................................................................................................................17

Considerations for Accuracy of Low-Flow Statistics ............................................................................17

Comparison with Previously Published Low-Flow Statistics ...............................................................18

Summary........................................................................................................................................................19

References Cited..........................................................................................................................................19
iv

Figures

1. Map showing the eight major river basins in South Carolina as defined by the 

South Carolina Department of Health and Environmental Control.......................................2

2. Streamgaging stations in the Catawba-Wateree and Santee River Basins 

of South Carolina, as well as the physiographic provinces, and 8-digit 

hydrologic-unit code boundaries...............................................................................................5

3. Annual minimum 7-day average streamflow at unregulated U.S. Geological

Survey streamgaging stations analyzed in this investigation: 02146750, 

McAlpine Creek below McMullen Creek near Pineville, NC; 0214678175, 

Steele Creek at Secondary Road 1441 near Pineville, NC; 02147500, 

Rocky Creek at Great Falls, SC; and 02148300, Colonels Creek 

near Leesburg, SC ........................................................................................................................9

4. Annual minimum 7-day average streamflow at regulated U.S. Geological Survey 

streamgaging stations in South Carolina: 02146000, Catawba River near Rock Hill; 

02147020, Catawba River below Catawba; 02148000, Wateree River near Camden; 

02148315, Wateree River below Eastover; 02171500, Santee River near Pineville; 

02171700, Santee River near Jamestown; and 02172002, 

Lake Moultrie Tailrace Canal at Moncks Corner...................................................................11

5. Ratio of median weekday to median 7-day weekly streamflow and the median 

weekend to median 7-day weekly streamflow at U.S. Geological Survey streamgaging 

stations 02146000, Catawba River near Rock Hill, SC, and 02148000, Wateree River

near Camden, SC. .......................................................................................................................12

6. Low-flow frequency curve for the annual minimum 7-day average streamflow 

for the U.S. Geological Survey streamgaging station 02146750, McAlpine Creek 

below McMullen Creek near Pineville, NC. ...........................................................................13

7. Flow-duration curves for U.S. Geological Survey South Carolina streamgaging 

stations 02148300, Colonels Creek near Leesburg, SC, 02135300, Scape Ore Swamp 

near Bishopville, SC, and 02169570, Gills Creek at Columbia, SC, for the concurrent 

period from July 26, 1968, to September 30, 1980, in cubic feet per second and cubic 

feet per second per square mile. .............................................................................................15

Tables

1. South Carolina Department of Health and Environmental Control (SCDHEC) schedule 

for basin data analysis and statistics availability....................................................................2

2. Low-flow statistics for continuous-record streamgaging stations in the Catawba, 

Wateree, and Santee River Basins of South Carolina..........................................................22

3. Eight-digit hydrologic unit code subbasins, subbasin name, drainage area in

South Carolina, and number of U.S. Geological Survey continuous-record 

streamgaging stations analyzed for the Catawba-Wateree and Santee River

Basins of South Carolina .............................................................................................................6

4. Streamgaging stations in the Catawba-Wateree and Santee River Basins of

South Carolina that were considered for computations of low-flow statistics .................7

5. Differences between the annual minimum 7-day average streamflow with a

10-year recurrence interval in this report and previously published values for

continuous-record streamgaging stations in the Catawba-Wateree and

Santee River Basins of South Carolina ...................................................................................18
v

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3

) 0.02832 cubic meter (m3)

Flow rate

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)

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

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27) 

or 1983 (NAD 83).
vi

Abbreviations

CR Continuous record

HUC Hydrologic unit code

loratio Ratio of the 10th percentile to the 50th percentile of the average 7-day flows

MOVE.1 Maintenance of Variance Extension, Type 1

NCDENR North Carolina Department of Environment and Natural Resources

NPDES National Pollutant Discharge Elimination System

PR Partial record

Q7min Annual minimum 7-day average streamflow

QAQC Quality assurance and quality control

SCDNR South Carolina Department of Natural Resources

SCDHEC South Carolina Department of Health and Environmental Control

TMDL Total maximum daily load

USGS U.S. Geological Survey

WWQMS Watershed Water Quality Management Strategy

7Q2 Annual minimum 7-day average streamflow with a 2-year recurrence interval

7Q10 Annual minimum 7-day average streamflow with a 10-year recurrence interval
Low-Flow Frequency and Flow Duration of Selected 

South Carolina Streams in the Catawba-Wateree and 

Santee River Basins through March 2012

By Toby D. Feaster and Wladmir B. Guimaraes

Abstract

Part of the mission of both the South Carolina Department of 

Health and Environmental Control and the South Carolina Department 

of Natural Resources is to protect and preserve South Carolina’s water 

resources. Doing so requires an ongoing understanding of streamflow 

characteristics of the rivers and streams in South Carolina. A particular 

need is information concerning the low-flow characteristics of streams, 

which is especially important for effectively managing the State’s 

water resources during critical flow periods, such as during the historic 

droughts that South Carolina has experienced in the past few decades.

In 2008, the U.S. Geological Survey, in cooperation with the 

South Carolina Department of Health and Environmental Control, 

initiated a study to update low-flow statistics at continuous-record 

streamgaging stations operated by the U.S. Geological Survey in South 

Carolina. This report presents the low-flow statistics for 11 selected 

streamgaging stations in the Catawba-Wateree and Santee River Basins 

in South Carolina and 2 in North Carolina. For five of the streamgaging 

stations, low-flow statistics include daily mean flow durations for the 

5-, 10-, 25-, 50-, 75-, 90-, and 95-percent probability of exceedance and 

the annual minimum 1-, 3-, 7-, 14-, 30-, 60-, and 90-day mean flows 

with recurrence intervals of 2, 5, 10, 20, 30, and 50 years, depending on 

the length of record available at the streamgaging station. For the other 

eight streamgaging stations, only daily mean flow durations and (or) 

exceedance percentiles of annual minimum 7-day average flows are 

provided due to regulation. In either case, the low-flow statistics were 

computed from records available through March 31, 2012. 

Of the five streamgaging stations for which recurrence interval 

computations were made, three streamgaging stations in South 

Carolina were compared to low-flow statistics that were published 

in previous U.S. Geological Survey reports. A comparison of the 

low-flow statistics for the annual minimum 7-day average streamflow 

with a 10-year recurrence interval (7Q10) from this study with the 

most recently published values indicated that two of the streamgaging 

stations had values lower than the previous values and the 7Q10 for 

the third station remained unchanged at zero. Low-flow statistics are 

influenced by length of record, hydrologic regime under which the data 

were collected, analytical techniques used, and other factors, such as 

urbanization, diversions, and droughts that may have occurred in the 

basin.

Introduction

Low-flow stream statistics are used by South Carolina State 

agencies, such as the South Carolina Department of Health and 

Environmental Control (SCDHEC) and the South Carolina Department of Natural Resources (SCDNR), for many applications, including 

determining waste-load allocations for point sources, development 

of total maximum daily loads (TMDLs) for streams, determining the 

quantity of water that can be withdrawn safely from a particular stream, 

and preparing the State Water Plan. In addition, low-flow statistics 

are useful for improving the general level of understanding of natural 

and regulated stream systems. The droughts of the past few decades 

in South Carolina (South Carolina Department of Natural Resources, 

2013) have heightened awareness of the importance of having up-todate statistics for making critical water-resources decisions. 

Because of the importance of these applications, it is critical 

to effectively measure and document stream base-flow data for use 

in updating low-flow statistics on a regular basis, preferably about 

every 10 years. Low-flow statistics, as defined in this report, are 

annual minimum daily mean streamflow averaged over designated 

time periods (Riggs, 1972). The use of “average” with respect to 

the low-flow statistics in this report refers to the arithmetic mean. 

Low-flow statistics for streams in South Carolina have not been 

updated in a systematic way since 1987. In 2008, the U.S. Geological 

Survey (USGS), in cooperation with the SCDHEC, initiated a study to 

update low-flow statistics at continuous-record streamgaging stations 

(hereafter referred to as stations in this report) operated by the USGS 

in South Carolina. The investigation was originally planned (2008) 

for a period of 5 years to coincide with the SCDHEC Watershed 

Water Quality Management Strategy (WWQMS) for monitoring and 

assessment of eight major river basins in South Carolina (fig. 1), which 

is completed every 5 years (South Carolina Department of Health and 

Environmental Control, 2009; table 1). However, in 2010, the schedule 

for updating the low-flow statistics was modified at the request of the 

SCDHEC. The remaining basins will now be assessed by the USGS 

on a two-year schedule, and the results will be published during the 

second year (table 1). 
2 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

EXPLANATION

Major river basin

Pee Dee

Broad

Saluda

Santee

Edisto

Salkehatchie

Savannah

N 0 20 40 60 80 MILES

0 20 40 60 80 KILOMETERS

Catawba-Wateree

Base from 1:500,000-scale hydrography dataset

 and 1:250,000-scale watershed boundary dataset

Albers Equal Area projection; central meridian –96 00 00;

 rotation angle –8.5; datum NAD 27

NORTH CAROLINA

GEORGIA

Figure 1.

ATLANTIC

OCEAN

Figure 1. The eight major river basins in South Carolina as defined by the South Carolina Department of Health and 

Environmental Control.

Table 1. South Carolina Department of Health and Environmental 

Control (SCDHEC) schedule for basin data analysis and statistics 

availability.

SCDHEC basin name 

(fig. 1)

Data analysis, 

year1

Low-flow information 

available, year1

Pee Dee 2008 2009

Broad 2009 2010

Saluda and Edisto 2010 and 2011 2012

Catawba-Wateree and Santee 2012 and 2013 2014

Savannah and Salkehatchie 2014 and 2015 2016

1

The year is the Federal fiscal year, which begins on October 1 and ends on 

September 30, and is designated by the calendar year in which the period ends. 

For example, year 2012 is the 12-month period from October 1, 2011, through 

September 30, 2012.
Introduction 3

Purpose and Scope

The purpose of this report is to present updated lowflow statistics at continuous-record (CR) stations in the 

Catawba-Wateree and Santee River Basins of South Carolina. 

Depending on the length of record available at the CR stations, 

the report presents estimates of annual minimum 1-, 3-, 7-, 

14-, 30-, 60-, and 90-day average streamflows with recurrence 

intervals of 2, 5, l0, 20, 30, and 50 years. Low-flow statistics 

are presented for 4 of the 11 selected CR stations in the two 

basins. In addition, daily flow durations for the 5-, 10-, 25-, 

50-, 75-, 90-, and 95-percent probabilities of exceedance are 

presented for these stations (table 2, p. 22). For seven CR

stations located on regulated streams, only daily flow durations and (or) exceedance percentiles of annual minimum

7-day average flow are presented.

The scope of this report includes unregulated and 

regulated streams in the Catawba-Wateree and Santee River 

Basins of South Carolina. In order for the low-flow statistics 

to be updated for CR stations included in the previous 

study (Zalants, 1991a, 1991b), at least 3 years of additional 

streamflow data had to be collected after 1987. Of the new 

CR stations for which data were collected after 1987, only the 

stations that had at least 5 years of data were included. 

Daily mean streamflow data for this study were collected through March 31, 2012, which is the end of the 2011 

climatic year. The climatic year is a continuous 12-month 

period during which a complete annual cycle occurs and 

is arbitrarily selected for the presentation or analysis of 

data relative to hydrologic or meteorological phenomena 

(Langbein and Iseri, 1983). The climatic year is usually 

designated by the calendar year during which most of the 

12 months occur. For this investigation, the climatic year is the 

12-month period from April 1 through March 31 and is designated by the year in which the period begins. For example, the 

2011 climatic year is the period from April 1, 2011, through 

March 31, 2012. In South Carolina, minimum streamflows 

typically occur in the fall months (September, October, and 

November) and, therefore, use of the climatic year, as defined, 

prevents the annual low-flow cycle from being artificially 

placed in separate years. 

Previous Studies

Previous reports by Stallings (1967), Johnson and 

others (1968), Bloxham and others (1970), Bloxham (1976, 

1979, 1981), Barker (1986), Zalants (1991a, b), Feaster and 

Guimaraes (2009, 2012), and Guimaraes and Feaster (2010) 

described the low-flow frequency and flow-duration streamflows for selected CR stations in South Carolina. 

Stallings (1967) presented low-flow statistics for 61 CR 

stations and 83 other sites where flow was measured during 

the 1954 drought. Johnson and others (1968) focused on the 

low-flow statistics of streams in Pickens County. Low-flow 

streamflow measurements from 1945 through 1967 were 

presented for 32 partial-record (PR) stations. The PR stations 

were correlated with four index stations to estimate annual 

minimum 7-day average streamflow with 2- and 10-year 

recurrence intervals (7Q2 and 7Q10, respectively). 

Bloxham and others (1970) presented magnitude and 

frequency of low-flow streamflows for 9 CR stations in 

Spartanburg County, and streamflow measurements were 

presented for 63 sites. At 35 of the 63 sites, correlation 

methods were used with index stations to estimate the 7Q2 and 

7Q10. Bloxham (1976) used 6 index stations from the upper 

Coastal Plain Physiographic Province to estimate the 7Q2 and 

7Q10 at 54 PR stations and miscellaneous-measurement sites. 

Bloxham (1979) used data through the 1976 climatic year to 

compute low-flow frequency and flow-duration estimates at 

71 CR stations in South Carolina.

Bloxham (1981) estimated the 7Q2 and 7Q10 at 113 PR 

stations in the Piedmont and lower Coastal Plain Provinces of 

South Carolina. Barker (1986) detailed the establishment of 

361 PR stations with measurements made from August 1980 

through July 1986. Zalants (1991a) provided estimates of 

the 7Q2 and 7Q10 at 564 PR stations and 27 CR stations 

on streams in the Blue Ridge, Piedmont, and upper Coastal 

Plain Provinces in South Carolina and parts of North Carolina 

and Georgia. Zalants (1991b) provided estimates of annual 

minimum 1-, 3-, 7-, 14-, 30-, 60-, and 90-day average streamflows with recurrence intervals of 2 to 50 years, depending on 

the length of record, for 55 CR stations in South Carolina for 

which at least 5 years of unregulated daily mean streamflow 

data were available through the 1986 climatic year. 

Feaster and Guimaraes (2009), Guimaraes and Feaster 

(2010), and Feaster and Guimaraes (2012) presented low-flow 

statistics for 17, 23, and 25 CR stations in the Pee Dee River, 

Broad River, and Saluda-Congaree-Edisto River Basins in 

South Carolina, respectively. Low-flow estimates for the Pee 

Dee River, Broad River, and Saluda-Congaree-Edisto River 

Basins were generated using daily mean flow data through the 

2006, 2007, and 2008 climatic years, respectively. In addition, 

daily flow durations of the 5- to 95-percent probabilities of 

exceedance were presented for most of these stations. Much 

of the general information for this report was taken directly 

from Feaster and Guimaraes (2009, 2012) and Guimaraes and 

Feaster (2010).

Description of the Study Area

The study area for this report includes the CatawbaWateree and Santee River Basins of South Carolina. The 

basins encompass approximately 6,240 square miles (mi2

) and 

include all or part of eight 8-digit (subbasin) hydrologic units 

(Eidson and others, 2005; fig. 2; table 3).

Although the majority of the Catawba River Basin 

is located in the Piedmont Province of North and South 

Carolina, the headwaters of the basin begin in the Blue Ridge 

Province of North Carolina (fig. 2). In North Carolina, the 

Catawba River Basin encompasses approximately 3,300 mi2
4 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

(North Carolina State University, 2013) and flows into 

South Carolina through Lake Wylie. In South Carolina, 

the Catawba River Basin encompasses approximately 

1,070 mi2

 and includes drainage from York, Lancaster, 

Chester, and Fairfield Counties (South Carolina 

Department of Health and Environmental Control, 

2012). Downstream from Lake Wylie, the Catawba 

River is joined by four major tributaries: Sugar Creek, 

Twelvemile Creek, Waxhaw Creek, and Cane Creek. 

Other than Cane Creek, these tributaries predominately 

drain from North Carolina with Sugar Creek being the 

most urbanized of the basins with significant drainage 

from Charlotte, N.C. (Feaster and others, 2003). Land 

use in the Catawba River Basin is predominantly forest 

(60 percent) and agriculture (23 percent) with about 

14 percent considered to be urban (South Carolina 

Department of Health and Environmental Control, 2012).

The Wateree River Basin encompasses approximately 1,260 mi2

 and includes drainage from Fairfield, 

Kershaw, Richland, Lancaster, and Lee Counties in 

South Carolina (South Carolina Department of Health 

and Environmental Control, 2012; fig. 2). Formed by 

the convergence of Big Wateree Creek and the Catawba 

River, the Wateree River flows through Lake Wateree, 

which is the southernmost of 11 major reservoirs located 

along the Catawba River corridor (Feaster and Conrads, 

2000). Approximately 3 miles downstream from the 

Lake Wateree Dam, the Wateree River crosses the Fall 

Line, which is the name given the boundary between 

the Piedmont and upper Coastal Plain Provinces. This 

boundary is generally characterized by a series of rapids 

or falls where the streams transition from the more resistant rocks of the Piedmont to the deeper valleys worn 

into the softer sediments of the Coastal Plain Province 

(Cooke, 1936). Land use in the Wateree River Basin is 

predominantly forested land/wetland (72 percent) and 

agriculture (18 percent) with about 7 percent being 

considered urban (South Carolina Department of Health 

and Environmental Control, 2012). The basin includes 

four major subwatersheds: Grannies Quarter Creek, 

Sawneys Creek, Twentyfive Mile Creek, and Big Pine 

Tree Creek.

The Santee River Basin originates at the confluence 

of the Congaree and Wateree Rivers. The basin begins 

in the upper Coastal Plain Province but is predominantly 

located in the lower Coastal Plain Province and encompasses approximately 1,280 mi2

. The Santee River Basin 

includes drainage from eight South Carolina counties: 

Berkeley, Calhoun, Charleston, Clarendon, Georgetown, 

Orangeburg, Sumter, and Williamsburg (South Carolina 

Department of Natural Resources, 2009). Land use in 

the Santee River Basin is predominantly forested land/

wetland (62 percent) and agriculture (14 percent) with 

about 11 percent being water (South Carolina Department of Health and Environmental Control, 2005). The 

Santee River flows directly into Lake Marion. From 

1941 to 1985, most of the flow from Lake Marion 

(about 80 percent of the long-term average flow of the 

Santee River) was diverted to the Cooper River through 

a diversion canal to Lake Moultrie for the purpose of 

hydroelectric power generation (Patterson and others, 

1996; South Carolina Department of Natural Resources, 

2009). This diversion of flow had the unintended 

consequences of substantially increasing sediment in 

the Charleston Harbor and also altering the salinity 

characteristics of the lower Santee and Cooper Rivers. 

To mitigate the sedimentation and salinity problems, a 

rediversion canal was completed about 1985, restoring 

much of the previously diverted flow back to the lower 

Santee River. 

The SCDHEC also includes the Ashley and Cooper 

River Basins as part of the Santee River Basin (fig. 2). 

The Cooper River Basin encompasses 843 mi2

 and 

is completely contained in the lower Coastal Plain 

Province. Predominant land-use types include about 

67 percent forested lands (wetlands), 16 percent water, 

and 8 percent urban (South Carolina Department of 

Health and Environmental Control, 2013). The Ashley 

River Basin encompasses 894 mi2

 and also is completely 

contained in the lower Coastal Plain Province. Predominant land-use types include about 55 percent forested 

lands (wetlands), 15 percent nonforested wetland, 

10 percent urban, and 9 percent water. 

Low-Flow Statistics

Hydrologic information on the availability of 

streamflow under low-flow conditions is essential for 

the effective management of water resources. Low-flow 

statistics that define the magnitude and frequency of 

low-flow events typically are provided as a minimum 

average streamflow over some designated time period at 

a streamgaging location. For example, one of the most 

common low-flow statistics is the annual minimum 7-day 

average streamflow with a 10-year recurrence interval 

(7Q10). In terms of probability of occurrence, there is 

a one-tenth or 10-percent probability that the annual 

minimum 7-day average streamflow in any single year 

will be equal to or less than the estimated 7Q10 value for 

a specific location (Riggs, 1985).

Analytical Approach

The analyses of CR stations included in this study 

were based on four categories of stations: (1) long-term 

record stations; (2) short-term record stations that have at 

least 10 years of record; (3) stations that have between 5 

and 10 years of record, which were analyzed for a limited 

set of low-flow statistics by using techniques typically 

used in analyzing PR stations; and (4) regulated stations. 
Low-Flow Statistics 5

ORANGEBURG

BULLOCH

JENKINS

SCREVEN

ALAMANCE

ALEXANDER

AVERY

BUNCOMBE

BURKE

CABARRUS

CALDWELL

CATAWBA

CHATHAM

CLEVELAND GASTON

GUILFORD

IREDELL

LINCOLN

MCDOWELL

MECKLENBURG

MITCHELL ORANGE

RANDOLPH

ROWAN

RUTHERFORD

UNION

WATAUGA

WILKES

YANCEY

ALLENDALE

BARNWELL

BERKELEY

CALHOUN

CHARLESTON

CHESTER

CLARENDON

COLLETON

DORCHESTER

FAIRFIELD

GEORGETOWN

KERSHAW

LANCASTER

LEE

RICHLAND SUMTER

WILLIAMSBURG

YORK

Santee River

Wateree Ri ver

Catawba River

Lake

Moultrie

Sugar Creek

Lake

Norman

Lake Marion

Charleston

Greenville

Greenwood

Branchville

03050101

Charlotte

03050102

03050209

03050111

03050112

03050202

03050201

Piedmont

Blue

Ridge

Upper

Coastal Plain

Lower

Coastal Plain

NORTH CAROLIINA

SOUTH CAROLINA

GEORGIA

TN

NC

SC

GA

ATLANTIC

OCEAN

ATLANTIC

OCEAN

EXPLANATION

Basin and subbasin and associated

 hydrologic unit code

Physiographic province boundary

Low-flow statistics were computed

Noted in text but low-flow statistics

 were not computed

USGS streamgaging station and number

02172035

02147020

03050102

82° 81° 80° 79°

36°

35°

34°

33°

Base from ESRI® Data & Maps, 2010

U.S. Environmental Protection Agency River Reach File, 1:500,000

Watershed Boundary Dataset, 1:24,000

Universal Transverse Mercator projection, zone 17

0 10 20 30 40 MILES

0 10 20 30 40 KILOMETERS

Lake

Wateree 

02147000 Twelvemile Creek

Waxhaw Creek

Cane Creek

Big Wateree

Creek

Sawneys

Creek

Twenty-Five

Mile Creek

Grannies Quarter

Creek

Big Pine Tree Creek

LAKE

WATEREE

DAM 

Ashley

River

Charleston

Harbor

Cooper

River

Santeee

River

Congaree

River

02171500

02172002

02172035

02171700

02171680

Area

Shown

Lake Wylie

Rock

Hill

02148000

02148300

02148315

03050104

02146000

02147020

02147500

02146750

0214678175

03050103

02146110

021459367

021473426

021473428

0214676115

02146800

85

26

77

20

95

95

77

85

Fall

Line

Figure 2. Streamgaging stations in the Catawba-Wateree and Santee River Basins of South Carolina, as well as the 

physiographic provinces, and 8-digit hydrologic-unit code boundaries.
6 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

Table 3. Eight-digit hydrologic unit code subbasins, subbasin 

name, drainage area in South Carolina, and number of U.S. 

Geological Survey continuous-record streamgaging stations 

analyzed for the Catawba-Wateree and Santee River Basins of 

South Carolina.

[HUC, hydrologic unit code; mi2, square mile; USGS, U.S. Geological 

Survey; Subbasins in bold text are wholly contained in South Carolina]

Eight-digit 

(subbasin) 

HUC number 

(fig. 2)

Subbasin 

name

Drainage area 

in South Carolina, in mi2

USGS 

continuousrecord 

streamgaging stations 

analyzed

03050101 Upper Catawba 191 0

03050103 Lower Catawba 1,360 5

03050104 Wateree 1,260 3

03050111 Lake Marion 548 0

03050112 Santee 761 2

03050201 Cooper 1,260 1

03050202 Stono 389 0

03050209 Bulls Bay 468 0

Total 6,240 11

Typically, low-flow statistics are computed at CR 

stations if at least 10 years of record are available; 

however, computing low-flow statistics from long-term 

records is preferred because the long-term records are 

considered to be more representative of a broad range 

of hydrologic conditions. Thus, long-term streamgaging data are better suited for trend assessments and 

statistical estimates. The USGS uses a value of 30 years 

of streamflow record to designate long-term streamgages 

(U.S. Geological Survey, 2013b). 

 For CR stations with short-term records (those which 

have at least 10 years of record but less than about 30 years, 

representing the second category of stations), the lowflow statistics can possibly be improved by using record 

extension or augmentation methods (Hirsch, 1982) based 

on correlations with long-term stations. This approach is 

particularly beneficial if the streamflow data at the shortterm record station were collected during an unusually dry, 

wet, or otherwise unrepresentative period. As a result, the 

record-extension techniques allow a more representative 

range of low-flow conditions at the site. If two long-term 

record stations are located on the same stream and one of 

the stations has many more years of record that includes 

different hydrologic conditions, it also may be beneficial to 

extend the long-term record station that has the least years 

of record. There were no stations in the Catawba-Wateree 

and Santee River basins for which extensions of short-term 

or long-term stations were applied. 

A standard PR station is a site where limited streamflow data are collected on a systematic basis over a period 

of years for use in hydrologic analyses. For low-flow 

analyses, typically 10 to 20 base-flow measurements are 

made over a period of several years. Then, mathematical 

or graphical techniques are used to correlate the base-flow 

measurements with concurrent daily mean flows at a CR 

station (index station; Riggs, 1972; Zalants, 1991a). As 

noted by Riggs (1972), such a relation can be used to 

define a limited set of low-flow statistics at the PR station 

but should not be used to define an entire frequency curve 

because to do so would imply a greater accuracy than is 

warranted. Consequently, only the annual minimum 7-day 

average low-flow statistics with 2- and 10-year recurrence 

intervals (7Q2 and 7Q10, respectively) usually are estimated at PR stations (U.S. Geological Survey, 1979). 

This report and study include only CR stations. As 

with standard PR stations, however, similar techniques 

can be used to correlate daily mean flows at CR stations 

that have more than 5 years but less than 10 years of CR 

streamgaging data. In Feaster and Guimaraes (2009, 2012) 

and Guimaraes and Feaster (2010), such CR stations were 

referred to as PR stations and represented a third category 

of stations that were analyzed. Similar to the analyses at 

standard PR stations, only the 7Q2 and 7Q10 low-flow 

statistics were estimated at such CR stations. However, 

no PR stations were analyzed in the Catawba-Wateree and 

Santee River Basins because no suitable index stations were 

found. Index station criteria will be discussed later in the 

report.

A fourth category of stations included in this study 

are CR stations on regulated streams. If an assessment of 

the daily mean flow at a regulated station indicates that the 

pattern of regulation has been relatively consistent, and if 

the logarithms of the N-day flows (where N is the number 

of days used to compute the annual minimum average 

flow) are consistent with a Pearson Type III distribution, 

low-flow statistics can be computed for that period using 

similar techniques as is used for the unregulated stations 

(Riggs, 1972). The techniques used for estimating lowflow statistics at PR sites usually are applicable only to 

unregulated streams and, therefore, should not be applied 

to streams that are highly regulated, such as for power 

generation. In addition, the low-flow statistics for regulated 

streams are relevant to similar future regulation patterns 

and would not be applicable if the future regulation patterns 

were altered significantly. For the Catawba-Wateree and 

Santee River Basins, none of the regulated stations were 

considered appropriate for computing low-flow frequency 

statistics. Consequently, only daily duration flows and (or) 

exceedance of annual minimum 7-day average flows were 

computed. Information regarding regulation at applicable 

CR stations is provided in the “Remarks” sections for 

stations listed in table 2. All stations considered for computations for low-flow statistics in the Catawba-Wateree 

and Santee River Basins are listed in table 4 along with the 

period of record and drainage area.
Low-Flow Statistics 7

Table 4. Streamgaging stations in the Catawba-Wateree and Santee River Basins of South Carolina that were considered for 

computations of low-flow statistics.

[mi2, square miles; Q7min, annual minimum 7-day average flow]

Streamgaging 

station number 

(fig. 2)

Station name Period of record

Number of 

climatic years 

of record

Drainage 

area 

(mi2

)

Remarks

Stations for which low-flow statistics were computed

02146000 Catawba River near Rock 

Hill, SC

Oct. 1895–Sept. 1902, 

and Apr. 1942–Mar. 

2012

70 3,050 Duration of daily flow and exceedance 

percentiles of Q7min only.

02146750 McAlpine Creek below 

McMullen Creek near 

Pineville, NC

Apr. 1974–Mar. 2012 38 92.4 Although located in North Carolina, 

this station was analyzed instead of 

station 0214676115, which is located 

downstream, due to a substantial influence of wastewater treatment plant 

discharge that occurs between stations 

02146750 and 0214676115.

0214678175 Steele Creek at Secondary 

Road 1441 near 

Pineville, NC

May 1998–Mar. 2012 14 6.91

02147000 Catawba River near 

Catawba, SC

Oct. 1967–Jan.1992 24 3,530 The record was combined with 

02147020.

02147020 Catawba River below 

Catawba, SC

Jan. 1992–Sept. 1994, 

and Oct. 1995–Mar. 

2012

21 3,540 Duration of daily flow and exceedance 

percentiles of Q7min only.

02147500 Rocky Creek at Great 

Falls, SC

Mar. 1951–Sept. 

1981, and Oct. 

1986–Mar. 2012

56 194 Zero flows.

02148000 Wateree River near 

Camden, SC

Oct. 1929–Sept. 1983, 

and May 1984–

Mar. 2012

83 5,070 Duration of daily flow and exceedance 

percentiles of Q7min only.

02148300 Colonels Creek near 

Leesburg, SC

Sept. 1966–Sept. 

1980, and Feb. 

2004–Oct. 2007

18 40.2

02148315 Wateree River below 

Eastover, SC

July 1968–Mar. 2012 39 5,590 Exceedance percentiles of Q7min only.

02171500 Santee River near 

Pineville, SC

May 1942–Mar. 2012 70 14,700 Duration of daily flow and exceedance 

percentiles of Q7min only.

02171680 Wedboo Creek near 

Jamestown, SC

Sept. 1966–Feb. 

1972, and Feb. 

1973–Sept. 1992

24 17.4

02171700 Santee River near 

Jamestown, SC

Oct. 1986–Mar. 2012 25 10,750 Duration of daily flow and exceedance 

percentiles of Q7min only.

02172002 Lake Moultrie Tailrace 

Canal at Moncks 

Corner, SC

Oct. 1978–Sept. 2000, 

and Oct. 2001–Mar. 

2012

34 14,800 Duration of daily flow and exceedance 

percentiles of Q7min only.
8 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

 Quality Assurance and Quality Control

For this study, a quality assurance and quality control 

(QAQC) analysis was done on the annual minimum 7-day 

average streamflow data for the CR stations that had a 

minimum of 10 years of record. The data at each station were 

reviewed for homogeneity, which implies relatively stable 

basin conditions during the period of record. The Kendall’s 

tau test was used to assess the homogeneity of the record at 

each station (Helsel and Hirsch, 1992). The Kendall’s tau test 

provides an independent measure of the monotonic relation 

between the “X” value (date) and the “Y” value (annual 

minimum 7-day average streamflow). A null hypothesis is 

made that the two variables are independent of each other and 

if the hypothesis is rejected, the independence of the variables 

is substantiated. A calculated probability value (p-value) 

estimates the probability of rejecting the null hypothesis. In 

this study, the independence of the two variables is considered 

statistically significant when the “p-value” is less than or equal 

to 0.05. If a trend (nonhomogeneity) was indicated, additional 

assessments were used to determine if the trend may have 

been caused by a short-term condition. For example, if the 

station record happened to begin or end under extreme conditions (excessively wet or dry), the test may indicate a trend, 

but additional analysis that excludes the extreme events may 

indicate no trend. Trends at unregulated stations may result 

from changes in climatic cycles, land use, groundwater pumping, or other practices that may affect groundwater levels. 

For stations downstream from a major source of regulation, 

such as a dam, the data were assessed for gross trends, which 

may indicate a long-term change in the pattern of regulation 

(William Kirby, U.S. Geological Survey, written commun., 

June 6, 2005). Additionally, some investigations have shown 

that substantial urbanization can lead to a reduction in low 

flows (U.S. Environmental Protection Agency, 2009). Final 

decisions to include or exclude data from a specific station 

analyses were made by using hydrologic judgment based on 

the results of the QAQC analyses and other available information, such as comparisons with other long-term stations. 

The QAQC analyses included the use of several computer 

programs that were developed by using commercial statistical 

software (SAS Institute, Inc., 1989). The components of the 

QAQC reviews that were conducted for the CR stations are as 

follows:

• Plot of the ratios of median daily mean flows during 

the weekend (Saturday and Sunday) and entire week 

(Sunday through Saturday), and work week (Monday 

through Friday) and entire week against climatic year. 

These plots are useful for regulated streams and can 

show if the discharge patterns differ from week days to 

weekends.

• The Kendall’s tau test to check for trends in the annual 

minimum 7-day average streamflow data over time.

• Plot of the annual minimum 7-day average streamflow 

against climatic year, which is used along with the 

Kendall’s tau results to assess potential trends.

• Plot of the relation of the ratio of the 10th percentile to 

the 50th percentile of the average 7-day flows (loratio) 

against climatic year, which is useful for graphically 

assessing potential trends.

• Plot of the relation of the 50th percentile of the average 

7-day flow against climatic year. This plot is useful 

for assessing potential changes in the median average 

7-day flow over time.

• Plot of the relation of the cumulative loratio against 

climatic year. A significant change in the slope of this 

relation indicates a change in flow patterns.

• Plot of the relation of the cumulative 50th percentile 

of the average 7-day flow against climatic year. A 

significant change in the slope of this relation indicates 

changes in the median average 7-day flow patterns.

Results of Quality Assurance and Quality Control 

Analyses

A trend analysis, as described previously, was made 

for all stations in the investigation using a p-value of 0.05, 

which is the probability of obtaining the computed test 

statistic, or one even less likely, when the null hypothesis is 

true (Helsel and Hirsch, 1992). For the Kendall’s Tau trend 

analysis in this study, the null hypothesis is that there is no 

trend in the annual minimum 7-day average flow data. For 

the following unregulated stations, the analyses indicated a 

trend in the annual minimum 7-day average streamflow for 

the period of record analyzed: 0214678175, Steele Creek at 

Secondary Road 1441 near Pineville, NC; 02147500, Rocky 

Creek at Great Falls, SC; and 02148300, Colonels Creek 

near Leesburg, SC. A trend was not indicated at 02146750, 

McAlpine Creek below McMullen Creek near Pineville, 

NC. As can be seen in figure 3, the annual minimum 7-day 

average flows for the unregulated streamgages have been 

historically low in recent years as a result of substantial dry 

periods that have occurred in the Southeast during the last 

several decades. Consequently, it is likely that these trends 

are a reflection of these streamgage records ending in these 

historically dry periods. If these periods are actually part of 

a short-term hydrologic regime and not reflective of a shift 

in long-term climatic conditions, when viewed in terms of 

longer timeframes, the periods may just be part of a much 

longer term oscillation (Feaster and Guimaraes, 2009, 2012; 

Guimaraes and Feaster, 2010; Lins and others, 2010). As can 

be seen at station 02147500, after the historic drought in the 

1950s, the hydrologic regime moved back into a period of 

more well sustained low flows (fig. 3). 
Low-Flow Statistics 9

02146750

0214678175

02147500

02148300

15

10

5

0

0.50

0.40

0.30

0.20

0.10

0

50

40

30

20

10

0

35

30

25

20

15

10

5

0

Annual minimum 7-day average flow, in cubic feet per second

1950 1954 1958 1962 1966 1970 1974 1978 1982

Climate year

1986 1990 1994 1998 2002 2006 2010 2014

Figure 3. Annual minimum 7-day average streamflow at unregulated U.S. Geological Survey streamgaging 

stations analyzed in this investigation: 02146750, McAlpine Creek below McMullen Creek near Pineville, NC; 

0214678175, Steele Creek at Secondary Road 1441 near Pineville, NC; 02147500, Rocky Creek at Great Falls, SC; 

and 02148300, Colonels Creek near Leesburg, SC.
10 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

For the regulated streamgages, interpretations of trend analyses 

are a bit more complicated. Streamflows at regulated stations also 

are influenced by changes in climatic patterns, but those changes 

can be mitigated, enhanced, or even offset by changes in regulation 

patterns. Nonetheless, assessments in the flow patterns are useful 

to help determine the appropriateness of a frequency analysis at 

a regulated streamgage. Thus, the trend test also was done for the 

regulated streamgages. For the following regulated streamgages, no 

trend was indicated in the annual minimum 7-day average flows: 

02146000, Catawba River near Rock Hill, SC; 02147020, Catawba 

River below Catawba, SC; 02148000, Wateree River near Camden, 

SC; 02148315, Wateree River below Eastover, SC; and 02171700, 

Santee River near Jamestown, SC (fig. 4). Trends were indicated for 

02171500, Santee River near Pineville, SC, and 02172002, Lake 

Moultrie Tailrace Canal at Moncks Corner, SC (fig. 4). 

Unlike the unregulated streamgages shown in figure 3, the 

regulated streamgages on the Catawba and Wateree River reflect 

an increase in the annual minimum 7-day average flows in recent 

years (fig. 4). This increase is likely due to changing regulation 

patterns associated with minimum flow releases, which is discussed 

further in the Analytical Considerations section. Additionally, the 

substantial modifications to the hydrology in the Santee River Basin 

are reflected in the various flow patterns shown for station 02171500 

(fig. 4) and are discussed in that section. 

One additional change in regulation patterns reflected in 

the analysis of streamflow at the longer term streamgages on the 

Catawba and Wateree Rivers (stations 02146000 and 02148000, 

respectively) is the changes that have occurred in regulation patterns 

between the weekend and weekday flows (fig. 5A, B). The USGS 

first reported those variations in a previous investigation relating 

to water quality on the Wateree River (Feaster and others, 2003). 

At that time, operators of the hydroelectric plant indicated that 

no conscious effort had been made to change the weekend flow 

patterns during the timeframe from the early 1970s to the early 

1990s but that it was likely a reflection of the hydroelectric plants 

transitioning from a mainly base-load power generation operation 

to a more varied power generation operation to meet peak energy 

needs (William Stroud, Duke Energy, written commun., 1998).

Diversions

Diversions from natural streamflows occur for a variety of 

reasons. Some diversions are the result of water-supply withdrawals, 

manufacturing, point-source discharges, and agricultural needs, 

such as irrigation. Diversions by manufacturers are sometimes 

confined to short distances along rivers. Water may be taken from 

the river channel, passed through the manufacturing plant for use in 

processing, cooling, or dilution of wastes, and then returned to the 

river. Therefore, in many cases, consumptive losses from diversions 

by manufacturers may be negligible (Ries, 1994). Thus, the effects 

of diversions to the streamflow regime of a river are variable and 

depend not only on where the diversions occur but also on the final 

outcome of the diverted water. 

Ries (1994) noted that water diverted from a stream or adjacent 

aquifer for municipal supplies is returned to the basin as effluent 

from individual septic systems or from wastewater- treatment 

plants within the basin and generally causes little loss of water 

to the basin; however, such diversions may affect the temporal 

pattern of streamflows. Diversions from one basin to another reduce 

streamflow in the donor basin and increase streamflow in the 

receiving basin. Diversions between subbasins of a larger basin can 

substantially affect streamflows in the subbasins, but if consumptive 

losses are negligible, streamflows in the larger basin may be nearly 

unaffected. 

The various diversion scenarios described above indicates 

that a proper accounting of all diversions in a basin is typically 

difficult; therefore, most USGS low-flow analyses are made on 

the flow data as measured at the station without adjustments for 

diversions. For this study, diversion data, when available, were 

obtained from the SCDHEC and assessed to determine significance. 

Diversions upstream from a station were considered significant if 

the average annual diversion equaled or exceeded 10 percent of the 

mean annual minimum 1-day streamflow for the period of record. 

The assumptions for this comparison were that the diversion and 

streamflow data are of similar quality and were measured with the 

same frequency and based on concurrent periods of record. If these 

conditions did not exist, assessments still were made and comments 

were noted in table 2 regarding the diversions, but no adjustments 

were made to the low-flow estimates. 

Frequency Analysis

Low-flow frequency statistics at CR stations are computed by 

fitting a series of annual minimum N-day average streamflows to 

some known statistical distribution, where N can equal any number 

from 1 to 365. Low-flow frequency statistics for this study were 

computed by fitting logarithms (base 10) of the annual minimum 1-, 

3-, 7-, 14-, 30-, 60-, and 90-day average streamflows to a Pearson 

Type III distribution, which also is referred to as a log-Pearson 

Type III distribution. Fitting the distribution requires calculating the 

mean, standard deviation, and skew coefficient of the logarithms 

of the N-day streamflows. Estimates of the N-day non-exceedance 

flows for a specified recurrence interval T are computed by using the 

following equation: 

 (1)

where 

QT is the N-day low flow, in cubic feet per 

second, and T is the recurrence interval, in 

years; 

X is the mean of the logarithms of the annual 

minimum N-day average streamflows; 

K is a frequency factor that is a function of 

the recurrence interval and the coefficient 

of skew; and 

S is the standard deviation of the logarithms 

of the annual minimum N-day average 

streamflows.

logQ X KS T = +
Low-Flow Statistics 11

02146000 02171500

2,500

2,000

1,500

1,000

500

0

3,500

3,000

2,500

2,000

1,500

1,000

500

0

2,000

1,500

1,000

500

0

4,000

3,000

2,000

1,000

0

700

600

500

400

300

200

100

0

8,000

6,000

4,000

2,000

0

1,500

1,000

500

0

Annual minimum 7-day average flow, in cubic feet per second

Figure 4.

02147020 02171700

02148000 02172002

02148315

1925 1935 1945 1955 1965 1975 1985 1995 2005

Climate year

2015

1925 1935 1945 1955 1965 1975 1985 1995 2005

Climate year

2015

Figure 4. Annual minimum 7-day average streamflow at regulated U.S. Geological Survey streamgaging stations in South Carolina: 

02146000, Catawba River near Rock Hill; 02147020, Catawba River below Catawba; 02148000, Wateree River near Camden; 02148315, 

Wateree River below Eastover; 02171500, Santee River near Pineville; 02171700, Santee River near Jamestown; and 02172002, Lake 

Moultrie Tailrace Canal at Moncks Corner.
12 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Ratio Ratio

Median weekday flows/median 7-day weekly flows

Median weekend flows/median 7-day weekly flows

EXPLANATION

Median weekday flows/median 7-day weekly flows

Median weekend flows/median 7-day weekly flows

EXPLANATION

A. (02146000, Catawba River near Rock Hill, S.C.)

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

B. (02148000, Wateree River near Camden, S.C.)

19301925 19401935 19501945 19601955 19701965 19801975 1985 1990 1995 20052000 2010 2015

Figure 5. Ratio of median weekday to median 7-day weekly streamflow and the median weekend 

to median 7-day weekly streamflow at U.S. Geological Survey streamgaging stations (A) 02146000, 

Catawba River near Rock Hill, SC, and (B) 02148000, Wateree River near Camden, SC.
Low-Flow Statistics 13

Low-flow statistics typically are presented as a set of 

non-exceedance probabilities or, alternatively, recurrence 

intervals along with the associated low-flow values. The 

non-exceedance probability is defined as the probability 

that a flow at a given station will be equal to or less than 

the associated low-flow value once in a 1-year period and 

is expressed as a decimal fraction less than 1.0 or as a 

percentage less than 100. Recurrence interval is defined as 

the average interval of years (usually referred to as the return 

period) during which flows at a given station will be equal to 

or less than the associated low-flow value once. For example, 

a low-flow value at a given station with a non-exceedance 

probability of 0.10 indicates that flows at that station have a 

10-percent chance of being equal to or less than the low-flow 

value once in any given year. Recurrence interval and nonexceedance probability are the mathematical inverses of one 

another; therefore, a flow with a non-exceedance probability 

of 0.10 has a recurrence interval of 1 divided by 0.10 or 

10 years. It should be emphasized that recurrence intervals, 

regardless of length, always refer to an average period of 

time (or years) in which flows at a given station will be equal 

to or less than the associated low-flow value once. A 10-year 

recurrence interval does not imply that the low-flow value 

will have a non-exceedance every 10 years; it does indicate, 

however, that the average time between recurrences is equal 

to 10 years. Consequently, an observed interval between a 

non-exceedance of the 7Q10 may be as short as 1 year or 

may be considerably longer than 10 years.

The low-flow frequency curve is generated by application of equation 1 to a set of annual minimum N-day average 

flows for a range of specified return periods. To estimate 

low-flow statistics for recurrence intervals greater than the 

period of record, these frequency curves must be extended. 

For this study, the following criteria were used to limit the 

extension of the curves based on the period of record at 

the station, and the following criteria were established for 

extending frequency curves: 

1. Curves for stations with 10 or more years of annual lowflow streamflow record but less than 20 years of record 

were extended to a recurrence interval of 20 years; 

2. Curves for stations with 20 or more years of record but 

less than 30 years of record were extended to a recurrence 

interval of 30 years; and 

3. Curves for stations with 30 or more years of record 

were extended to a recurrence interval of 50 years. No 

data were compiled for recurrence intervals greater than 

50 years.

An example of the frequency curve using the log-Pearson 

Type III curve-fitting procedure is illustrated in figure 6.

100.00

10.00

1.00

0.10

0.9999 0.998 0.99 0.98 0.95 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.05 0.02 0.01 0.002 0.0001

Non-exceedance probability

Annual minimum 7-day average flow, in cubic feet per second

Figure 6. Figure 6. Low-flow frequency curve for the annual minimum 7-day average streamflow for the U.S. Geological Survey streamgaging 

station 02146750, McAlpine Creek below McMullen Creek near Pineville, NC.
14 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

Record-Extension Technique

Streamflow statistics often are needed to estimate probabilities of occurrences for periods much longer than the actual 

measured period of record. Consequently, short records that may 

have been collected during an unusually dry, wet, or otherwise 

unrepresentative period may not represent the more desirable 

fuller range of potential hydrologic regimes. Under certain 

conditions, it is possible to extend or augment a short record by 

using a correlated station having a longer record. The extended 

record at the short-term record station will better reflect low-flow 

conditions over a longer period and provide better estimates of 

low-flow statistics at that station. The record extension can be 

accomplished in the following manner. 

If a linear relation between the logarithms of the N-day 

flows at a short-term record station is determined to be 

significantly correlated to a concurrent set of the N-day flows 

at a long-term record station, or index station, a mathematical 

record-extension method known as the Maintenance of Variance 

Extension, Type 1 (MOVE.1) method (Hirsch, 1982) can be 

used to extend the record at the short-term record station. The 

MOVE.1 relation maintains the mean and the variance of the 

data at the short-term record station and, therefore, allows for 

the generation of a longer-term set of data that will possess the 

statistical characteristics of the actual measured data from the 

short-term record. 

The MOVE.1 equation is 

 

 , (2)

 

where

Yi is the logarithm of the estimated N-day 

flow for the short-term record station;

Y is the mean of the logarithms of N-day 

flows for the concurrent period at the shortterm record station;

Sy is the standard deviation of the logarithms 

of N-day flows for the concurrent period at 

the short-term record station;

Sx is the standard deviation of the logarithms 

of N-day flows for the concurrent period 

at the long-term record station or index 

station;

Xi is the logarithm of the flow statistic or 

observed N-day flow at the index station; 

and

X is the mean of the logarithms of the N-day 

flows for the concurrent period at the index 

station.

In order for an index station to be considered for this study, 

it had to have (1) a minimum of 10 years of concurrent record 

relative to the short-term record station, (2) similar basin geology 

as the short-term record station, and (3) a basin less than 10 

times larger than the size of the smaller basin (Telis, 1991). A 

minimum correlation coefficient between concurrent flows has 

not been developed for the MOVE.1 technique; however, similar 

correlation studies have used values ranging from 0.70 to 0.80 

(Hydrology Subcommittee of the Interagency Advisory Committee on Water Data, 1982; Stedinger and Thomas, 1985; Ries, 

1994; Nielsen, 1999). In addition, if the record at the short-term 

record station or available index station included zero flows, 

record extensions were not applied because including such values 

in record-extension techniques has not be adequately tested (Julie 

Kiang, U.S. Geological Survey Office of Surface Water, written 

commun., January 26, 2010). 

For gaging stations that have relatively long records, such 

as 30 years or more, record extension may still be beneficial if 

an index station is available that has additional record collected 

under hydrologic conditions that are not included in the record 

being analyzed. Currently, there are no standard criteria for 

assessing when use of MOVE.1 is warranted with respect to 

improvement in the low-flow statistics at such stations. Therefore, 

for this investigation, an arbitrary criterion was set. The 7-day 

low-flow statistics at the index station were computed using 

the complete period of record and the period of record that was 

concurrent with the station of interest. If the average difference in 

the 7-day low-flow statistics for the two periods at the index station was greater than 10 percent, MOVE.1 was used to augment 

the record at the station of interest. Otherwise, no augmentation 

was done. On the basis of this criterion, no station records were 

augmented for the Catawba-Wateree and Santee River Basins. 

At station 02148300, three additional years of record were 

collected since the previous investigation by Zalants (1991b). 

An assessment was made to determine if the station was suitable 

for record augmentation. The findings indicated that the station 

was not suitable for a record extension due to substantial influence at the lower flow range from upstream discharges. Two 

National Pollutant Discharge Elimination System (NPDES) 

permitted facilities discharge upstream from station 02148300 

and are considered to have minor environmental impacts and, 

therefore, do not require discharge reporting (Wade Cantrell, 

South Carolina Department of Health and Environmental 

Control, written commun., 2014). A graphical comparison of 

duration curves for a concurrent period of record (July 26, 1968, 

to September 30, 1980) at station 02148300 was made with two 

potential index stations that are located in the same physiographic 

province: 02135300, Scape Ore Swamp near Bishopville, SC, and 

02169570, Gills Creek at Columbia, SC (fig. 7). The comparison 

showed that for the higher daily mean flows, the duration curves 

tend to be parallel indicating similar flow patterns. However, 

for the lower daily mean flows, the slope of the duration curve 

for station 02148300 was flatter than those of the other two 

stations (fig. 7A). When plotted on the basis of streamflow per 

square mile, the distinction is even more pronounced with the 

duration curve for station 02148300 crossing the duration curves 

for stations 02135300 and 02169570 (fig. 7B) indicating higher 

runoff per square mile for the lower flows, which is assumed to 

be from the upstream NPDES discharges. Consequently, it was 

determined that station 02148300 was not suitable for record 

augmentation.

Y Y

S

S i X X y

x

= + ( ) i −
Low-Flow Statistics 15

10,000

1,000

100

10

1

100

10

1

0.10

0.01

Daily mean flow, in cubic feet per second Daily mean flow, in cubic feet per second per square mile

02148300

02135300

02169570

EXPLANATION

02148300

02135300

02169570

EXPLANATION

A

B

Percentage of time indicated streamflow was equaled or exceeded

0 10 20 30 40 50 60 70 80 90 100

Figure 7. Flow-duration curves for U.S. Geological Survey South Carolina streamgaging stations 02148300, 

Colonels Creek near Leesburg, SC, 02135300, Scape Ore Swamp near Bishopville, SC, and 02169570, Gills 

Creek at Columbia, SC, for the concurrent period from July 26, 1968, to September 30, 1980, in (A) cubic feet 

per second and (B) cubic feet per second per square mile. 
16 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

Partial-Record Type Analysis

As previously discussed, when limited streamflow data 

are collected on a systematic basis over a period of years for 

use in hydrologic analyses, the data-collection site is called a 

partial-record (PR) station (Zalants, 1991a). With respect to 

low-flow statistics, once a sufficient number of base-flow measurements have been made over a reasonable period of time, 

techniques can be used to transfer low-flow statistics from an 

index station to the PR station (Riggs, 1972). If the relation 

between the flows at the PR station and the index station is 

linear, mathematical correlation methods, such as MOVE.1, 

can be used (Hirsch, 1982). If the relation is nonlinear, then a 

graphical correlation described by Riggs (1972) can be used. 

The MOVE.1 technique can be used to establish a 

relation between the concurrent daily mean flows. In order 

to use daily mean flows that are representative of low-flow 

conditions, only concurrent flows that are less than or equal 

to the 90-percent flow duration at the index station were used 

in the MOVE.1 analysis. That relation is then used to transfer 

a limited set of low-flow statistics from an appropriate index 

station to the PR station. Similar criteria as were described 

for extending the record at a short-term record station can be 

used with the exception of the concurrent-record length. U.S. 

Geological Survey Office of Surface Water Technical Memorandum No. 86.02 (U.S. Geological Survey, 1985) recommended that only the 7Q2 and 7Q10 statistics be estimated for 

the PR stations. Because of the limited records available at the 

PR stations, providing a broader set of statistics would imply 

an accuracy that is not warranted. 

The same MOVE.1 equation (eq. 2) as described previously is used to transfer the low-flow characteristic from the 

index station to the PR station. The difference is that now Xi

is the low-flow characteristic computed from the index or 

long-term record station, and Yi is the low-flow characteristic 

estimated at the PR station. Seven CR stations in the CatawbaWateree or Santee River Basins had at least 5 years but less 

than 10 years of record (table 4). For three of those stations, 

021459367, Big Dutchman Creek at Rock Hill, SC; 02146110, 

Manchester Creek at Rock Hill, SC; and 021473428, Wildcat 

Creek below Rock Hill, SC, no suitable index station was 

found. Two additional CR stations, 021473426, Tools Fork 

Creek near Rock Hill, SC, and 02172035, Turkey Creek above 

Huger, SC, that had at least 5 years but less than 10 years 

of record experienced zero flows and, therefore, were not 

considered suitable for record extensions. Two additional CR 

stations, 0214676115, McAlpine Creek at Secondary Road 

2964 near Camp Cox, SC, and 02146800, Sugar Creek near 

Fort Mill, SC, had at least 5 years but less than 10 years of 

record for which the streamflows are substantially influenced 

by wastewater treatment plant discharges and, consequently, 

were not considered suitable for record extensions.

Flow-Duration Analysis

Flow durations represent the percentage of time that a 

specified streamflow is equaled or exceeded during a given 

period (Searcy, 1959). Flow durations are computed by sorting 

the daily mean flows for the period of record from the largest 

value to the smallest value and assigning each streamflow value a rank, starting from 1 to the largest value. The frequencies 

of exceedance are then computed using the Weibull formula 

for computing plotting position (Helsel and Hirsch, 1992):

 P = 100 * [M / (n+1)], (3)

where

P is the probability that a given flow will be 

equaled or exceeded (percentage of time),

M is the ranked position (dimensionless), and

n is the number of events for the period of 

record (dimensionless).

Flow durations are a summary of the past hydrologic 

events. Yet, if the streamflow during the period for which the 

duration curve is based is a sufficiently long period of record, 

the statistics can be used as an indicator of probable future 

conditions (Searcy, 1959). In order to compare flow durations 

at different stations or in different basins, flow-duration 

estimates can be normalized by drainage area to represent 

a streamflow per unit area. Again, it should be noted that 

the most useful comparisons will be those based on similar 

lengths of record from similar hydrologic periods.

Flow durations for this report are presented in tabular 

form for the 5-, 10-, 25-, 50-, 75-, 90-, and 95-percent 

exceedances (table 2). To be consistent with the low-flow 

statistics, flow durations were computed based on the climatic 

year using daily mean flows through March 2012. 

Analytical Considerations

Streamflow statistics computed at CR stations are based 

on historical streamflow records but can be useful for making 

decisions about the future if it can be reasonably assumed that 

the future streamflow patterns are likely to be relatively similar 

to historical streamflow patterns. Thus, streamflow statistics 

computed from records that capture a wide range of hydrologic 

conditions are more desirable. When a stream is influenced by 

regulation, techniques for estimating low-flow statistics that 

are similar to those used for analysis of natural streams can be 

applied; however, consistency in the regulation patterns also 

must be considered. If assessments of the historical streamflow 

records indicate that the regulation patterns have been relatively 

consistent and if the logarithm of the annual minimum flows for 

a given averaging period are consistent with a Pearson Type III 

distribution, low-flow statistics can be computed for the regulated station with the understanding that using those statistics for 

future planning assumes relatively similar regulation patterns 

will occur in the future (Riggs, 1972). Special considerations for 
Considerations for Accuracy of Low-Flow Statistics 17

the low-flow analyses included in this report are discussed in the 

following sections.

Stations on the Main Stem of the Catawba and 

Wateree Rivers

Station 02146000, Catawba River near Rock Hill, SC, has 

daily mean flow data from October 1895 to September 1902, 

which reflect unregulated conditions, and April 1942 to the 

current year (2013), which reflect regulated conditions. The 

reservoirs upstream from station 02146000 were built at various 

dates between 1915 and 1963 (U.S. Army Corps of Engineers, 

2012). In 2003, Duke Energy began the relicensing process for its 

hydroelectric projects located in the Catawba and Wateree River 

Basins (Duke Energy, 2006). Part of the comprehensive relicensing agreement dated December 22, 2006, provides for minimum 

flow releases from the hydroelectric plants. Consequently, 

the low-flow statistics that could be generated from historical 

streamflow records collected prior to this agreement may not be 

reflective of future conditions. As a result, low-flow frequency 

statistics were not generated for the following stations: 02146000, 

Catawba River near Rock Hill, SC; 02147000, Catawba River 

near Catawba, SC; 02147020, Catawba River below Catawba, 

SC; 02148000, Wateree River near Camden, SC; and 02148315, 

Wateree River below Eastover, SC. However, the duration of 

daily flow and exceedance percentiles of annual minimum 7-day 

average flows were generated to provide a historical perspective 

of streamflows at the stations (table 2). The drainage areas for 

stations 02147000 and 02147020 differ by less than 1 percent; 

consequently, for the flow duration analysis, the data from those 

two stations were combined. For station 02148315, Wateree River 

below Eastover, SC, the daily mean flows only represent those 

that are confined to the main channel. As a result, streamflows 

greater than 10,000 cubic feet per second (ft3

/s) are not reported 

(U.S. Geological Survey, 2011).

Stations 02146750, McAlpine Creek below 

McMullen Creek near Pineville, NC, and 

0214678175, Steele Creek at Secondary Road 1441 

near Pineville, NC

Stations 02146750 and 0214678175 are located in North 

Carolina and, thus, are not under the jurisdiction of the SCDHEC 

water-quality monitoring program. However, because a number 

of USGS stations that are located in the Catawba River Basin in 

and around Rock Hill, SC, do not currently have sufficient lengths 

of record to compute low-flow frequency statistics, low-flow 

frequency statistics were computed for stations 02146750 and 

0214678175 (tables 2 and 4). For nearby ungaged basins with 

similar basin characteristics, the statistics from stations 02146470 

and 0214678175 may be useful for providing low-flow estimates 

at the ungaged sites, using techniques such as the drainage-area 

ratio method (U.S. Geological Survey, 2013a).

Stations 02171500, Santee River near Pineville, 

SC, 02171700, Santee River near Jamestown, SC, 

and 02172002, Lake Moultrie Tailrace Canal at 

Moncks Corner, SC

The hydrology of the Santee River Basin has undergone 

substantial changes since the construction of Lake Marion and 

Lake Moultrie around 1941 and the implementation of the 

rediversion canal beginning around 1985 (Patterson and others, 

1996; South Carolina Department of Natural Resources, 2009). 

Because of these extensive hydrologic modifications, low-flow 

frequency statistics were not computed for stations 02171500, 

02171700, and 02172002. However, the duration of daily flow and 

exceedance percentiles of annual minimum 7-day average flows 

were generated to provide a historical perspective of streamflows 

at the three stations (table 2).

Considerations for Accuracy of 

Low-Flow Statistics

With respect to streamflow statistics, the period of collected 

record can be thought of as a sample, or small portion of the 

population, which represents all possible measurements. Statistics 

allow for making inferences about the characteristics of the 

population based on samples from the population. For example, 

statistical measures, such as mean, standard deviation, or skew 

coefficient, can be described in terms of the sample and then used 

to make inferences about the population from which the sample 

was obtained. Statistical measures computed from the sample 

record are estimates of what the measure would be if the entire 

population were known and used to compute the given measure. 

Consequently, the accuracy of low-flow statistics at streamgaging 

stations is related to the lengths of records (samples from the 

population) upon which the statistics are based. The longer the 

period of record at a streamgaging station that covers a broad 

range of hydrologic conditions, the more accurate or reflective of 

long-term conditions the low-flow statistics will be.

The streamflow statistics for short-term records are much 

more sensitive to extreme hydrologic events than those for longterm records. As a result, streamflow statistics, whether high or 

low, from one 10-year period may differ significantly from another 

10-year period (Dalrymple, 1960). Thus, a long-term record is 

always more desirable when computing streamflow statistics. 

Comparisons showing the effects of record length and hydrologic 

conditions on low-flow statistics using several long-term stations 

with record lengths of 77, 70, and 70 years were provided in 

Feaster and Guimaraes (2009), Guimaraes and Feaster (2010), and 

Feaster and Guimaraes (2012), respectively. A suitable unregulated 

station with a similar length of record was not available for a 

comparable analysis for the Catawba-Wateree and Santee River 

Basins.
18 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

Comparison with Previously Published 

Low-Flow Statistics

Low-flow frequency statistics are influenced by length 

of record, hydrologic regime under which the data were 

collected, analytical techniques used, and other factors, 

such as urbanization, diversions, and droughts that may 

have occurred in the basin. The last systematic update of 

low-flow statistics in South Carolina included data through 

March 1987 (the 1986 climatic year). Since that time, several 

substantial droughts have occurred, including one of the 

most severe droughts in recent history that occurred between 

1998 and 2002 and a more recent drought from 2006 to 2009 

(South Carolina Department of Natural Resources, 2004, 

2013). Less severe droughts were reported in 1988, 1990, 

1993, and 1995 (Mizzell, 2008). 

Of the 12 stations included in this study, only 3 had 7Q10 

values computed in previous publications (Bloxham (1979) or 

Zalants (1991b)). The most recent previously published 7Q10 

values for these two stations were compared with the current 

values, and percent differences were computed as follows:

Percent difference = [(current 7Q10 – previous 7Q10) 

/ previous 7Q10] x 100

As computed, the percent difference indicates the percentage of change from the previously published 7Q10 value. 

For station 02148300, Colonels Creek near Leesburg, SC, 

the 7Q10 decreased –28.5 percent (from 13 ft3

/s to 9.3 ft3/s) 

from the value published by Zalants (1991b). It should be 

noted, however, that the additional data for that station were 

collected from April 2004 through March 2007 (table 5). For 

station 02147500, Rocky Creek at Great Falls, SC, the 7Q10 

decreased –71.0 percent (from 1.0 ft3/s to 0.29 ft3/s) from the 

value published by Zalants (1991b). The additional data at 

station 02147500 were from April 1987 to March 2012 and, 

thus, included the severe droughts of the last decade or so. Of 

the 10 smallest annual minimum 7-day average flows from 

the 56 years of record analyzed, 7 occurred between climatic 

years 2000 and 2011 with the other three lowest annual 

minimum 7-day average flows occurring in 1954, 1956, and 

1957. For station 02171680, Wedboo Creek near Jamestown, 

SC, additional data were collected from April 1987 through 

September 1992; however, the additional years of record did 

not change the 7Q10 value of zero.

(4)

Table 5. Differences between the annual minimum 7-day average streamflow with a 10-year recurrence interval in this report 

and previously published values for continuous-record streamgaging stations in the Catawba-Wateree and Santee River Basins of 

South Carolina.

[USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CY, climatic year]

USGS streamgaging station 

number and name

Previous estimate from 

Bloxham (1979), in ft3

/s

Previous estimate from 

Zalants (1991b), in ft3/s

Current (CY 2011) 

estimate, in ft3/s

Percent difference from 

most recent estimate to 

current estimate

02147500, Rocky Creek at 

Great Falls, SC

1.8 1.0 0.29 –71.0

02148300, Colonels Creek near 

Leesburg, SC

11.5 13 9.3 –28.5

02171680, Wedboo Creek near 

Jamestown, SC

0.0 0.0 0.0 0.0
References Cited 19

Summary

This report, prepared in cooperation with the South 

Carolina Department of Health and Environmental Control, 

provides updated low-flow statistics at continuous-record 

streamgaging stations operated by the U.S. Geological 

Survey in the Catawba-Wateree and Santee River Basins 

of South Carolina. The continuous-record streamgaging 

stations included in this study were analyzed based on 

four categories of stations: (1) long-term record stations; 

(2) short-term record stations that have at least 10 years 

of record; (3) stations that have between 5 and 10 years of 

record and that were analyzed for a limited set of low-flow 

statistics, using techniques typically used in analyzing 

partial-record stations; and (4) regulated stations. For this 

investigation, record extension techniques were not used 

due to conditions not being met that warranted applying 

such techniques. Based on the length of record available 

at the continuous-record streamgaging stations, low-flow 

frequency statistics were estimated for consecutive 1-, 

3-, 7-, 14-, 30-, 60-, and 90-day average minimum flows 

with recurrence intervals of 2, 5, l0, 20, 30, and 50 years. 

Additionally, daily flow durations for the 5-, 10-, 25-, 

50-, 75-, 90-, and 95-percent probabilities of exceedance 

were computed for the stations. For the Catawba-Wateree 

and Santee River Basins, none of the regulated stations 

were considered appropriate for computing low-flow 

N-day frequency statistics; consequently, only exceedance 

percentiles of annual minimum 7-day flows and daily flow 

durations were computed.

Of the 13 streamgaging stations included in this 

study, 3 stations had 7Q10 low-flow statistics that were 

previously published in U.S. Geological Survey reports: 

02147500, Rocky Creek at Great Falls, SC, 02148300, 

Colonels Creek near Leesburg, SC, and 02171680, 

Wedboo Creek near Jamestown, SC. Comparison of the 

7Q10 values for these three stations as published by 

Zalantas (1991b) showed that for station 02147500, the 

7Q10 decreased from 1.0 ft3

/s to 0.29 ft3/s, a percent 

difference of –71.0 percent; for station 02148300, the 

7Q10 value decreased from 13 ft3

/s to 9.3 ft3/s, a percent 

difference of –28.5 percent; and for station 02171680, the 

7Q10 remained unchanged at 0.0 ft3

/s.

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22 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

Table 2. Low-flow statistics for continuous-record streamgaging stations in the Catawba, Wateree, and 

Santee River Basins of South Carolina.

[lat, latitude; long, longitude; ft, feet; mi, mile; mi2, square mi; ft3, cubic feet; SCDHEC, South Carolina Department 

of Health and Environmental Control; USGS, U.S. Geological Survey; ft3

/s, cubic feet per second; water year, the 

12-month period from October 1 through September 30 and designated by the year in which the period ends] 

Notes: The station low-flow statistics are presented in the following pages in numerical order by station number.

See figure 2 for location of the streamgaging stations.

 
Table 2 23

STATION NAME AND NUMBER.—02146000 Catawba River near Rock Hill, SC

LOCATION.—Lat 34°59′05′′, long 80°58′27′′ referenced to North American Datum of 1927, York County, SC, Hydrologic 

Unit 03050103, near right bank, at upstream side of foot bridge and just downstream from U.S. Highway 21, 3.5 mi downstream 

from Lake Wylie Dam, 5.0 mi northeast of Rock Hill, 7.5 mi upstream from Sugar Creek, and at river mile 137.6.

DRAINAGE AREA.—3,050 mi2.

PERIOD OF RECORD.—October 1895 to September 1902, April 1942 to current year.

PERIOD OF ANALYSIS.—April 1942 to March 2012. 

REMARKS.—Flow regulated by Lake Wylie (usable capacity, 2,520,500,000 ft3). 

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

1,390 1,280 1,100 1,020 963 884 785 696 609

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time (cubic feet per second)

5 10 25 50 75 90 95

10,000 8,380 5,650 3,090 1,320 860 718
24 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

STATION NAME AND NUMBER.--02146750 McAlpine Creek below McMullen Creek near Pineville, NC 

LOCATION.--Lat 35°03'59.39", long 80°52'11.46" referenced to North American Datum of 1983, Mecklenburg County, NC, 

Hydrologic Unit 03050103, on right bank, 150 ft downstream from McMullen Creek, 735 ft upstream from effluent outfall, and 

2.1 mi south of Pineville.

DRAINAGE AREA.—92.4 mi2. 

PERIOD OF RECORD.—April 1974 to current year. 

PERIOD OF ANALYSIS.—April 1974 to March 2012. 

REMARKS.— The SCDHEC requested this station be analyzed along with 0214678175, Steele Creek at Secondary Road 1441 

near Pineville, NC, in place of station 0214676115, McAlpine Creek at SR 2964 near Camp Cox, SC, and 02146800, Sugar 

Creek near Fort Mill, SC, due to those stations having substantial influence from upstream wastewater treatment plant discharges.

On the basis of review of withdrawal and discharge data provided by the North Carolina Department of Environment and Natural 

Resources (NCDENR), there are no significant diversions upstream.

MAGNITUDE AND FREQUENCY OF ANNUAL FLOWS

Recurrence 

intervals 

(years)

Lowest average flow for indicated number of consecutive days

(cubic feet per second)

1 3 7 14 30 60 90

2 4.0 4.4 5.3 6.5 11 19 27

5 1.6 1.9 2.4 3.3 5.3 11 16

10 0.93 1.1 1.4 2.1 3.5 7.9 12

20 0.55 0.66 0.88 1.5 2.4 6.2 9.6

30 0.41 0.50 0.68 1.2 2.0 5.4 8.4

50 0.28 0.35 0.49 0.91 1.5 4.6 7.3

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time

(cubic feet per second)

5 10 25 50 75 90 95

613 241 67 30 15 7.9 5.1
Table 2 25

STATION NAME AND NUMBER.--0214678175 Steele Creek at Secondary Road 1441 near Pineville, NC 

LOCATION.--Lat 35°06′18′′, long 80°57′13′′ referenced to North American Datum of 1983, Mecklenburg County, NC, 

Hydrologic Unit 03050103, on right bank, upstream from culvert on Secondary Road 1441 (Carowinds Boulevard), 4.5 mi west 

of Pineville.

DRAINAGE AREA.—6.91 mi2. 

PERIOD OF RECORD.—May 1998 to current year. 

PERIOD OF ANALYSIS.—May 1998 to March 2012. 

REMARKS.—The SCDHEC requested this station be analyzed along with 02146750, McAlpine Creek below McMullen Creek 

near Pineville, NC, in place of station 0214676115, McAlpine Creek at SR 2964 near Camp Cox, SC, and 02146800, Sugar 

Creek near Fort Mill, SC, due to those stations having substantial influence from upstream wastewater treatment plant discharges. 

Station 0214678175 is an urbanized basin. On the basis of review of withdrawal and discharge data provided by NCDENR, there 

are no significant diversions upstream.

MAGNITUDE AND FREQUENCY OF ANNUAL FLOWS

Recurrence 

intervals 

(years)

Lowest average flow for indicated number of consecutive days

(cubic feet per second)

1 3 7 14 30 60 90

2 0.15 0.17 0.20 0.32 0.59 1.5 2.0

5 0.09 0.10 0.11 0.19 0.32 0.91 1.2

10 0.06 0.07 0.08 0.13 0.23 0.69 0.90

20 0.05 0.05 0.06 0.10 0.17 0.55 0.71

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time

(cubic feet per second)

5 10 25 50 75 90 95

28 12 3.8 1.5 0.64 0.35 0.25
26 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

STATION NAME AND NUMBER.—02147020 Catawba River below Catawba, SC

LOCATION.—Lat 34°50′10′′, long 80°52′47′′ referenced to North American Datum of 1927, York County, SC, Hydrologic 

Unit 03050103, on right bank, 1.5 mi downstream from Twelvemile Creek, 2.2 mi southeast of Catawba, and at river mile 121.3.

DRAINAGE AREA.—3,540 mi2.

PERIOD OF RECORD.—January 1992 to September 1994 and October 1995 to current year. 

PERIOD OF ANALYSIS.—October 1967 to September 1994 and October 1995 to March 2012. 

REMARKS.—Because of minor differences in drainage areas (less than 1 percent), the record at 02147020 was combined with 

the record at 02147000, Catawba River near Catawba, SC (October 1967 to January 1992; drainage area = 3,530 mi2

). Flow 

regulated by Lake Wylie (usable capacity, 2,520,500,000 ft3). 

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

1,780 1,420 1,230 1,190 1,120 1,020 960 885 811

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time (cubic feet per second)

5 10 25 50 75 90 95

11,500 9,620 6,590 3,550 1,650 1,070 933
Table 2 27

STATION NAME AND NUMBER.--02147500 Rocky Creek at Great Falls, SC 

LOCATION.--Lat 34°33′55′′, long 80°55′12′′ referenced to North American Datum of 1927, Chester County, SC, Hydrologic 

Unit 03050103, on left bank, 350 ft downstream from Turkey Branch, 1.0 mi west of Great Falls, and at river mile 1.8. 

DRAINAGE AREA.--194 mi2

.

PERIOD OF RECORD.—March 1951 to September 1981, and October 1986 to current year. 

PERIOD OF ANALYSIS.—April 1951 to March 1981, and April 1987 to March 2012. 

REMARKS.— On the basis of review of withdrawal and discharge data provided by the SCDHEC, there are no significant 

diversions upstream. 

MAGNITUDE AND FREQUENCY OF ANNUAL FLOWS

Recurrence 

intervals 

(years)

Lowest average flow for indicated number of consecutive days

(cubic feet per second)

1 3 7 14 30 60 90

2 8.1 8.2 8.9 12 17 22 27

5 0.97 0.88 1.3 2.2 4.2 8.2 11

10 0.06 0.11 0.29 0.64 1.5 4.3 6.1

20 0.0 0.0 0.05 0.19 0.53 2.3 3.6

30 0.0 0.0 0.01 0.09 0.29 1.6 2.6

50 0.0 0.0 0.0 0.04 0.13 1.1 1.8

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time

(cubic feet per second)

5 10 25 50 75 90 95

612 315 128 56 26 12 6.9
28 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

STATION NAME AND NUMBER.—02148000 Wateree River near Camden, SC

LOCATION.—Lat 34°14′40′′, long 80°39′15′′ referenced to North American Datum of 1927, Kershaw County, SC, Hydrologic 

Unit 03050104, on downstream side of pier of downstream bridge on U.S. Highway 1, 1,500 ft downstream from Five and 

Twenty Creek, 4,000 ft upstream from Seaboard Coast Line Railroad bridge, 2.2 mi west of Camden, 7.4 mi downstream from 

Wateree Dam, and at river mile 68.8.

DRAINAGE AREA.—5,070 mi2.

PERIOD OF RECORD.—October 1929 to September 1983, and May 1984 to current year. 

PERIOD OF ANALYSIS.—October 1929 to September 1983, and May 1984 to March 2012.

REMARKS.—Flow regulated by powerplant at Wateree Reservoir (usable capacity, 2,794,000,000 ft3).

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

2,080 1,640 1,460 1,320 1,140 1,010 922 824 506

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time (cubic feet per second)

5 10 25 50 75 90 95

15,400 12,700 7,830 4,550 2,160 1,140 711
Table 2 29

STATION NAME AND NUMBER.--02148300 Colonels Creek near Leesburg, SC 

LOCATION.--Lat 34°00′25′′, long 80°43′58′′ referenced to North American Datum of 1927, Richland County, SC, Hydrologic 

Unit 03050104, on SC Highway 262 bridge, 0.2 mi above Jumping Run Creek, and 1.9 mi southwest of Leesburg.

DRAINAGE AREA.—40.2 mi2.

PERIOD OF RECORD.—September 1966 to September 1980, and February 2004 to October 2007. 

PERIOD OF ANALYSIS.—April 1967 to March 1980, and April 2004 to March 2007. 

REMARKS.— No withdrawal or discharge data were available from the SCDHEC for this station. However, flow-duration 

curve analyses indicate that the effects of upstream point-source discharges may be substantial at lower flows. 

MAGNITUDE AND FREQUENCY OF ANNUAL FLOWS

Recurrence 

intervals 

(years)

Lowest average flow for indicated number of consecutive days

(cubic feet per second)

1 3 7 14 30 60 90

2 16 17 17 19 21 25 27

5 11 11 12 13 15 18 20

10 8.8 9.0 9.3 10 12 15 17

20 7.1 7.2 7.5 8.2 9.9 13 15

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time

(cubic feet per second)

5 10 25 50 75 90 95

97 76 51 35 24 17 13
30 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

STATION NAME AND NUMBER.—02148315 Wateree River below Eastover, SC

LOCATION.—Lat 33°49′42′′, long 80°37′14′′ referenced to North American Datum of 1927, Richland County, SC, Hydrologic 

Unit 03050104, on right bank, 1.3 mi upstream from Southern Railway bridge, 1.8 mi northeast of Wateree, 4.5 mi southeast of 

Eastover, and at river mile 10.8.

DRAINAGE AREA.—5,590 mi2. 

PERIOD OF RECORD.—July 1968 to current year. 

PERIOD OF ANALYSIS.—July 1968 to March 2012. 

REMARKS.—Flow regulated by powerplant at Wateree Reservoir (usable capacity, 2,794,000,000 ft3). Flow represents only 

that portion of the flow confined to the main channel, which is less than about 10,000 ft3/s. At times of high flow, bankfull 

capacity is exceeded in the intervening channel reach; therefore, daily mean flows greater than 10,000 ft3/s are not determined 

and duration of daily flow analysis not made. 

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

2,170 1,960 1,670 1,580 1,430 1,300 1,210 1,090 1,020
Table 2 31

STATION NAME AND NUMBER.—02171500 Santee River near Pineville, SC

LOCATION.—Lat 33°27′15′′, long 80°08′30′′ referenced to North American Datum of 1927, Berkeley County, SC, Hydrologic 

Unit 03050112, on right bank 2.4 mi downstream from Lake Marion Dam, 3.0 mi upstream from Dead River, 6.7 mi west of 

Pineville, and at mile 85.0.

DRAINAGE AREA.—14,700 mi2.

PERIOD OF RECORD.—May 1942 to current year. 

PERIOD OF ANALYSIS.—May 1942 to March 2012. 

REMARKS.—Flow records for 1987–2004 water years are computed by utilization of a one-dimensional unsteady flow 

simulation model (Schaffranek and others, 1981). Flow completely regulated by Lake Marion. Water is diverted above the station 

from Lake Marion through the Diversion Canal into Lake Moultrie for power generation and navigation, and then discharged into 

the Cooper River basin and lower Santee River. During periods of incomplete gage-height record, values of daily mean flow

from Lake Marion Hydro and Spillway were obtained from the South Carolina Public Service Authority. These values are shown 

as estimated daily flows. Seepage from north dike of Lake Marion Dam bypasses station through Little River. 

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

591 534 507 496 480 471 446 430 390

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time (cubic feet per second)

5 10 25 50 75 90 95

11,500 1,130 653 562 515 492 472
32 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

STATION NAME AND NUMBER.--02171680 Wedboo Creek near Jamestown, SC 

LOCATION.--Lat 33°19'50", long 79°48'10" referenced to North American Datum of 1983, Berkeley County, SC, Hydrologic 

Unit 03050112, at culvert on State Highway 45, 1.4 mi southeast of Alvin, 3.3 mi upstream from Santee River, and 7.5 mi 

northeast of Jamestown. 

DRAINAGE AREA.—17.4 mi2. 

PERIOD OF RECORD.—September 1966 to February 1972, February 1973 to September 1992.

PERIOD OF ANALYSIS.—April 1967 to March 1912.

REMARKS.—No known regulation or diversion upstream.

MAGNITUDE AND FREQUENCY OF ANNUAL FLOWS

Recurrence 

intervals 

(years)

Lowest average flow for indicated number of consecutive days

(cubic feet per second)

1 3 7 14 30 60 90

2 0.19 0.21 0.25 0.27 0.45 0.71 1.0

5 0.0 0.0 0.0 0.02 0.13 0.27 0.45

10 0.0 0.0 0.0 0.0 0.05 0.15 0.29

20 0.0 0.0 0.0 0.0 0.0 0.09 0.20

30 0.0 0.0 0.0 0.0 0.0 0.07 0.16

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time

(cubic feet per second)

5 10 25 50 75 90 95

60 35 12 3.2 1.0 0.43 0.15
Table 2 33

STATION NAME AND NUMBER.—02171700 Santee River near Jamestown, SC

LOCATION.—Lat 33°18′17′′, long 79°40′42′′ referenced to North American Datum of 1927, Berkeley County, SC, Hydrologic 

Unit 03050112, at downstream side of bridge on U.S. Highway 17A, 0.7 mi below Wittee Branch, 0.1 mi upstream from 

Seaboard Coastline Railroad, 1.5 mi northeast of Jamestown, and at river mile 36.4.

DRAINAGE AREA.—10,750 mi2.

PERIOD OF RECORD.—October 1986 to current year. 

PERIOD OF ANALYSIS.—October 1986 to March 2012. 

REMARKS.—Flow affected by regulation from Lake Marion and rediversion from St. Stephens powerplant. Astronomical tides 

cause cycles of approximately 24.8 hours at this site during periods of low to medium flow. During periods of higher flow, the 

tidal influence is overcome by basin runoff. October 2005 to current year, tidal effects were removed from unit value flows using 

the Godin filter. Daily mean flow computed from filtered values. Flow records for 1987–2000 water years were computed by 

utilization of a one-dimensional flow simulation model (Schaffranek and others, 1981).

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

1,060 984 880 868 824 792 708 567 534

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time (cubic feet per second)

5 10 25 50 75 90 95

27,500 24,000 14,700 4,600 1,040 782 655
34 Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012

STATION NAME AND NUMBER.—02172002 Lake Moultrie Tailrace Canal at Moncks Corner, SC

LOCATION.—Lat 33°12′54′′, long 79°58′29′′ referenced to North American Datum of 1927, Berkeley County, SC, Hydrologic 

Unit 03050201, on upstream side of left fender pier, under U.S. Highway 52 bridge, 2.2 mi below Lake Moultrie Pinopolis Dam, 

and at river mile 45.8. 

DRAINAGE AREA.—14,800 mi2.

PERIOD OF RECORD.—October 1978 to September 2000 and October 2001 to current year. 

PERIOD OF ANALYSIS.—October 1978 to September 2000 and October 2001 to March 2012. 

REMARKS.—Discharge affected by regulation from Lake Moultrie Pinopolis Dam. Discharge records for the 1979–2001 water 

years computed by utilization of a one-dimensional unsteady flow simulation model (Schaffranek and others, 1981). 

ANNUAL MINIMUM 7-DAY AVERAGE FLOW

EXCEEDANCE PERCENTILES OF ANNUAL 7-DAY MINIMUM FLOWS

Annual 7-day minimum flow exceeded for indicated percentiles (cubic feet per second)

10 20 30 40 50 60 70 80 90

4,320 4,020 3,700 3,450 3,140 2,960 2,890 2,360 1,980

DURATION OF DAILY FLOW

Flow equaled or exceeded for indicated percentage of time (cubic feet per second)

5 10 25 50 75 90 95

21,200 14,900 7,130 5,100 4,030 2,960 2,230
Table 2 35

For further information about this publication contact:

Director 

USGS South Carolina Water Science Center

Stephenson Center, Suite 129 

720 Gracern Road 

Columbia, SC 29210-7651

Or visit the South Carolina Water Science Center Web

site at http://sc.water.usgs.gov/

Prepared by the Raleigh Publishing Service Center
Feaster and Guimaraes—Low-Flow Frequency and Flow Duration, Catawba-Wateree and Santee River Basins through March 2012—Open-File Report 2014–1113

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141113