Prepared in cooperation with Southwestern Energy Company

Simulated Effects of Existing and Proposed Surface-Water 

Impoundments and Gas-Well Pads on Streamflow and 

Suspended Sediment in the Cypress Creek Watershed, 

Arkansas

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2014–5057

Version 1.1, April 2016
Cover: Surface-water impoundment located in the Fayetteville Shale, central Arkansas 

(photograph provided by Southwestern Energy Company)
Simulated Effects of Existing and Proposed 

Surface-Water Impoundments and Gas-Well 

Pads on Streamflow and Suspended Sediment in 

the Cypress Creek Watershed, Arkansas

By Rheannon M. Hart

Prepared in cooperation with Southwestern Energy Company

Scientific Investigations Report 2014–5057

Version 1.1, April 2016

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

First release: 2014

Revised: April 2016 (ver 1.1) 

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

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

Suggested citation:

Hart, R.M., 2014, Simulated effects of existing and proposed surface-water impoundments and gas-well pads on 

streamflow and suspended sediment in the Cypress Creek watershed, Arkansas (ver. 1.1, April 2016): U.S. Geological 

Survey Scientific Investigations Report 2014–5057, 36 p., http://dx.doi.org/10.3133/sir20145057.

ISSN -2328-0328 (online)
iii

Contents

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

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

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

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

Hydrologic Simulation Program—FORTRAN Watershed Model Development..................................7

Subwatershed Delineation and Land Use ........................................................................................7

Pervious and Impervious Land Segments ........................................................................................9

Reach Characterization .......................................................................................................................9

Meteorological Data...........................................................................................................................10

Evaluation Methods for the Hydrologic Simulation Program—FORTRAN.........................................10

Hydrologic Simulation Program—FORTRAN Model Calibration .........................................................12

Streamflow Calibration ......................................................................................................................12

Suspended-Sediment Calibration ....................................................................................................14

Hydrologic Simulation Program–Fortran Model Limitations ................................................................18

Simulated Effects of Proposed Gas Extraction Activities on the Streamflow and 

Sedimentation within the Cypress Creek Watershed ..............................................................18

Scenario 1—Simulated Time Period Before Extensive Grazing Activities and No 

Gas-Extraction Activities .....................................................................................................19

Scenario 2—Simulated Time Period with Some Grazing Activities and No 

Gas-Extraction Activities .....................................................................................................25

Scenario 3—Simulated Time Period with Current Land-Use Conditions and No 

Gas-Extraction Activities .....................................................................................................27

Scenario 4—Simulated Time Period with Current Land-Use Conditions and Increased 

Gas-Extraction Activities .....................................................................................................29

Implications of the Four Scenarios Modeled for the Cypress Creek Watershed .............................31

Summary........................................................................................................................................................32

References....................................................................................................................................................33
iv

Figures

1. Map showing location of study area, Cypress Creek watershed, Arkansas .....................3

2. Map showing soil types within the study area, Cypress Creek watershed, 

Arkansas ........................................................................................................................................4

3. Map showing the 2006 land use and land cover with 2013 gas-well pads, pipelines,

and surface-water impoundments, location of a streamflow-gaging and a

water-quality sampling station, and withdrawal points within the study area,

Cypress Creek watershed, Arkansas ........................................................................................5

4. Map showing locations of the subwatersheds and reaches within the Cypress

Creek watershed used for the Hydrologic Simulation Program—FORTRAN model.........8

5. Map showing location of the Next Generation Radar (NEXRAD) grid, Cypress 

Creek watershed, Arkansas......................................................................................................11

6. Graph showing simulated and measured daily mean streamflow at the Cypress

Creek gage in the Cypress Creek watershed.........................................................................15

7. Graph showing exceedance probability of simulated and measured daily mean

streamflow at selected inflow stations in the Cypress Creek watershed.........................15

8. Graph showing simulated and measured suspended-sediment concentrations at

Cypress Creek near Birdtown...................................................................................................16

9. Map showing land-use types used in scenario 1, a time period before

extensive-grazing activities and no gas-extraction activities in the Cypress 

Creek watershed, Arkansas......................................................................................................20

10. Graph showing comparison of total streamflow volume for the calibration period

(July 8, 2009–September 2012) between the current-conditions simulation and

scenario simulations for the Cypress Creek watershed......................................................21

11. Graph showing comparison of yearly suspended-sediment load between the

current-conditions simulation and scenario simulations for the Cypress Creek

watershed ....................................................................................................................................22

12. Map showing land-use types used in scenario 2, a time period with some 

grazing but before any gas-extraction activities in the Cypress Creek watershed, 

Arkansas ......................................................................................................................................26

13. Map showing land-use types used in scenario 3, a time period with current

conditions but without any gas-extraction activities in the Cypress Creek

watershed, Arkansas .................................................................................................................28

14. Map showing potential future conditions of increased gas-extraction activities 

for scenario 4 in the Cypress Creek watershed, Arkansas .................................................30
v

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

yard (yd) 0.9144 meter (m)

Area

acre 4,047 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

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

acre-foot (acre-ft) 1,233 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)

Mass

ton per day (ton/d) 0.9072 metric ton per day

ton per day (ton/d) 0.9072 megagram per day (Mg/d)

Application rate

pounds per acre per year 

[(lb/acre)/yr]

 1.121 kilograms per hectare per year

[(kg/ha)/yr]

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

(NGVD 1929)

Tables

1. Land-use types and characteristics designated for pervious and impervious 

areas within subwatersheds, Cypress Creek watershed, Arkansas ...................................6

2. Withdrawals and surface-water impoundment volumes for use in the Cypress

Creek watershed model...............................................................................................................9

3. Summary of calibrated values for selected hydrology parameters for the

Hydrological Simulation Program—FORTRAN model of the Cypress Creek

watershed ....................................................................................................................................13

4. Hydrological Simulation Program—FORTRAN streamflow calibration results for 

the Cypress Creek watershed ..................................................................................................13

5. Land-use loading rates for the Hydrological Simulation Program—FORTRAN 

model of the Cypress Creek watershed..................................................................................14

6. Summary of calibrated values for suspended-sediment parameters for the

Hydrological Simulation Program—FORTRAN model of the Cypress Creek

watershed ....................................................................................................................................16

7. Measured and simulated suspended-sediment concentrations and

suspended-sediment calibration statistics for the Hydrological Simulation

Program—FORTRAN model at Cypress Creek near Birdtown ...........................................17

8. Summary of July 8, 2009–September 30, 2012 simulation results for land-use

change scenarios on Brewer Lake in the Cypress Creek watershed ...............................23

Simulated Effects of Existing and Proposed Surface-Water 

Impoundments and Gas-Well Pads on Streamflow and 

Suspended Sediment in the Cypress Creek Watershed, 

Arkansas

By Rheannon M. Hart

Abstract 

Cypress Creek is located in central Arkansas and is the 

main tributary to Brewer Lake, which serves as the primary 

water supply for Conway, Arkansas, and the surrounding 

areas. A model of the Cypress Creek watershed was developed 

and calibrated in cooperation with Southwestern Energy 

Company using detailed precipitation, streamflow, and 

discrete suspended-sediment data collected from 2009 through 

2012. These data were used with a Hydrologic Simulation 

Program—FORTRAN model to address different potential 

gas-extraction activities within the watershed. 

The calibrated Hydrologic Simulation Program—

FORTRAN model was used to simulate four land-use 

scenarios and examine the potential effects of these landuse changes on the streamflow and water quality within 

the Cypress Creek watershed. These simulated scenarios 

included (1) the conversion of all nonforested land to 

forest, representing a time period before extensive grazing 

activities and no gas-extraction activities; (2) a land-use 

change to that of 1949, representing a time period with some 

grazing activities and no gas-extraction activities; (3) a time 

period with current land-use conditions, but without any 

gas-extraction activities, that is, the exclusion of gas-well 

pads/pipelines, associated gravel roads, and surface-water 

impoundments; and (4) a time period with current landuse conditions, but with increased gas-extraction activities 

(for example, increased gas-well pad and surface-water 

impoundment activities) to represent a possible future natural 

gas full-development condition for the area.

A current-conditions simulation also was built and 

calibrated and represents the current conditions (2013) 

within the watershed. This simulation was used as the 

comparison basis for the four land-use scenarios described 

above. The current-conditions simulation used the 2006 

land-use conditions, which consisted primarily of forest and 

pasture, as well as the current (2013) 35 gas-well pads and 

pipelines and 6 surface-water impoundments, which account 

for approximately 1.6 percent of the land use. Simulating 

a time period before extensive-grazing activities and no 

gas-extraction activities for scenario 1 resulted in a decrease 

in suspended-sediment loads and volume of streamflow 

within the Cypress Creek watershed compared to the currentconditions simulation. Simulating a time period before any 

gas-extraction activities but with some grazing activities for 

scenario 2 also resulted in a decrease in suspended-sediment 

loads and volume of streamflow within the Cypress Creek 

watershed. Simulating current conditions, but without any 

natural gas-pad land use or related activities (including 

pipelines and associated gravel roads), for scenario 3 resulted 

in mostly unchanged suspended-sediment loads and volume of 

streamflow within the Cypress Creek watershed, as compared 

to the current-conditions simulation. Finally, simulating 

potential future conditions of increased gas-well pad and 

surface-water impoundment activities for scenario 4 resulted 

in a decrease (compared to the current-conditions simulation) 

in suspended-sediment loads and a slight increase of volume 

of streamflow within the Cypress Creek watershed.

The Arkansas Natural Resources Commission and 

the Arkansas Department of Environmental Quality list 

suspended sediment from “poor pastures” as a primary source 

of nonpoint-source pollution in north-central Arkansas, 

but unpaved (gravel) roads are another important source of 

suspended sediment. Because of the high sediment-loading 

rates associated with gravel roads and the large amount of 

pasture within the watershed, the factors most responsible for 

suspended sediment within the Cypress Creek watershed are 

likely associated more with the pastureland and gravel roads, 

than factors associated with gas-well pads/pipelines.

Introduction

Brewer Lake, located in central Arkansas, is an 

impoundment on Cypress Creek and serves as the city of 

Conway’s major drinking-water source. Brewer Lake was 

constructed in the early 1980s and was designed to provide 

16.75 million gallons per day (Mgal/d) of water to the city 

of Conway and the surrounding area that is serviced by 

the Conway County Regional Water District (U.S. Army 
2 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

Corps of Engineers, 2002). The Cypress Creek watershed, 

defined as the catchment area upstream from the Brewer 

Lake spillway, has experienced a notable increase in gasextraction activities in the last 6 years (Southwestern Energy 

Co., written commun., 2013). Concerns about the impacts 

that gas development could have on the drinking-water source 

have been raised, and the necessity to understand the effects 

of additional increases in gas activities needs to be addressed. 

Using streamflow data (collected in cooperation with Conway 

Corporation) and suspended-sediment data (collected in 

cooperation with Southwestern Energy Company [SWN]), the 

U.S. Geological Survey (USGS), in cooperation with SWN, 

developed and calibrated a model simulating streamflow and 

suspended sediment in the Cypress Creek watershed from 

July 8, 2009, through September 30, 2012, and has applied 

the model to evaluate four scenarios related to potential gasextraction activities within the watershed.

Purpose and Scope

The purpose of this report is to present the development 

and findings of a model used to simulate the effects of 

land-use changes resulting from gas-extraction activities 

on streamflow and sediment load within the Cypress Creek 

watershed. Descriptions are provided for the development 

and results of a Hydrologic Simulation Program—FORTRAN 

(HSPF) (Bicknell and others, 2001) watershed model 

(hereafter referred to as the “HSPF model”) of the Cypress 

Creek watershed. The HSPF model input data are described, 

followed by a discussion of the development, calibration, and 

application of the model. The HSPF model was developed 

to simulate streamflow and suspended sediment using data 

collected from July 8, 2009, through September 30, 2012. The 

calibrated HSPF model was used to simulate four scenarios, 

which represent a range of potential generalized land-use 

changes that could result from potential gas-extraction 

activities in the watershed; evaluation was conducted of 

possible effects of anthropogenic (human-induced) activities 

in the Cypress Creek watershed. The calibrated HSPF model, 

however, does not capture effects at small, localized scales, 

for example, the sediment load in a stream immediately 

downstream from a gas-well pad or a pipeline crossing.

Description of Study Area

Brewer Lake (fig. 1) is located in central Arkansas, 

10 miles (mi) northwest of the city of Conway, and serves as 

the city’s primary water supply. Brewer Lake was formed by 

the impoundment of Cypress Creek, which was completed 

September 1982, and comprises an area of approximately 

1,165 acres (1.8 square miles[mi2]) (Conway Corporation, 

2012). The lake shoreline is approximately 13 mi and the 

mean depth is approximately 20.2 feet (ft). Brewer Lake 

contains approximately 23,500 acre-feet (acre-ft) of water 

when the water surface is at the spillway (339.5 ft above 

National Geodetic Vertical Datum of 1929 [NGVD 29]) 

(Conway Corporation, 2012) and is used primarily for 

drinking water, but also for recreation and fish and wildlife 

habitat. The drainage area of Cypress Creek watershed, that is 

upstream from the Brewer Lake spillway located near USGS 

water-quality sampling station 07261110, is approximately 

36 mi2, including the reservoir surface (Conway Corporation, 

2012). Cypress Creek is approximately 22.3 mi long from its 

headwaters to the confluence with the larger Cadron Creek 

(fig. 1). Additionally, Brewer Lake is not included in the study 

area (that is, it is not explicitly modeled within the HSPF 

Cypress Creek watershed model). The study area ends at the 

mouth of Cypress Creek and other smaller tributaries flowing 

into Brewer Lake.

The Cypress Creek watershed lies entirely within the 

Arkansas Valley physiographic section (Fenneman and 

Johnson, 1946; fig. 1). The Arkansas Valley is the northern 

extent of the Ouachita Mountains in Arkansas (Arkansas 

Geological Survey, 2012). The Arkansas Valley consists of 

Pennsylvanian sedimentary rocks that have been compressed 

into well-developed east-west trending open folds (anticlines 

and synclines) and faults (Arkansas Geological Survey, 2012).

The soils in the watershed consist primarily of the Linker 

and Mountainburg series (U.S. Department of Agriculture, 

2012b; fig. 2). The Linker series is described as moderately 

deep, well-drained, moderately permeable soils that formed in 

loamy residuum weathered from sandstone. The Mountainburg 

series is described as shallow, well-drained, moderate to rapid 

permeable soils that formed in residuum of sandstone. Slopes 

are dominantly 1 to 15 percent but range upward to 30 percent 

(U.S. Department of Agriculture, 2012b).

According to the 2006 land-use data, 53.0 percent 

of the land-use area within the Cypress Creek watershed 

is forest (deciduous, evergreen, and mixed), 34.9 percent 

pasture, 4.1 percent roads (including both gravel and paved), 

0.9 percent shrub, 0.4 percent urban, and 5.1 percent water, 

including Brewer Lake (Arkansas Natural Resources 

Commission and University of Arkansas: Center for Advanced 

Spatial Technologies, 2009). The remaining land-use area 

(1.6 percent) is either gas-well pads/pipelines or surface-water 

impoundments (fig. 3, table 1). Surface-water impoundments 

were constructed to supply water for gas extraction activities. 

Currently (2013), there are 12 permitted no-discharge facilities 

that exist in the watershed. These include six confinedanimal feeding operations involving swine or dairy cattle 

(Arkansas Department of Environmental Quality, 2008), 

although chicken houses also have been observed within the 

watershed. Additionally, SWN provided permit information 

for four withdrawals located on Cypress Creek, as well as six 

withdrawals on the six gas-well surface-water impoundments; 

these locations and water volumes were included in 

model development and are described in more detail in 

the “Hydrologic Simulation Program—FORTRAN Model 

Calibration” section.
Description of Study Area 3

laf14-0633_fig01

Cypress Creek

Cadron Creek

Brewer Lake

07261090

07261110

Conway

Morrilton

National Oceanic and 

Atmospheric Administration 

National Climatic Data Center station

FAULKNER

VAN BUREN

CONWAY

PERRY

92°44' 42' 40' 38' 36' 34' 32' 30' 28' 92°26'

35°22'

20'

18'

16'

14'

12'

10'

08'

06'

35°04'

0 1.25 2.5 5 MILES

0 1.25 2.5 5 KILOMETERS

Base map imagery from 7.5 minute USGS GeoPDF orthoimagery.

Cypress Creek

watershed boundary and 

study area

Arkansas Valley

physiographic section

ARKANSAS

EXPLANATION

Stream

Watershed boundary

Water-quality sampling 

station and identification 

number

Streamflow-gaging station and 

water-quality sampling 

station and identification 

number 07261090

07261110

Figure 1. Location of study area, Cypress Creek watershed, Arkansas.
4 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

laf14-0633_fig02

Brewer Lake

Cypress Creek

Base from U.S. Geological Survey digitial data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

EXPLANATION

Soil

Barling

Cane

Dam

Enders

Leadvale

Linker

Mountainburg

Spadra

Taft

Stream

Watershed boundary

Figure 2. Soil types within the study area, Cypress Creek watershed, Arkansas.
Description of Study Area 5

laf14-0633_fig03

Cypress Creek

Brewer Lake

07261090

07261090

Impoundments

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS Land use land cover by Arkansas Natural Resources 

Commission and University of Arkansas: Center for 

Advanced Spatial Technologies, 2009

Base from U.S. Geological Survey digitial data, 2008, 

1:24,000 Universal Transverse Mercator projection, zone 15

EXPLANATION

Stream reach

Watershed boundary

Streamflow-gaging station

and water-quality sampling

station and identification 

number

Withdrawal points 

2006 Land use and

land cover

Deciduous forest

Evergreen forest

Gas-well pad

Mixed forest

Pasture

Road

Shrub

Urban

Water

Figure 3. The 2006 land use and land cover with 2013 gas-well pads, pipelines, and surface-water impoundments, location of a 

streamflow-gaging and a water-quality sampling station, and withdrawal points within the study area, Cypress Creek watershed, 

Arkansas.
Table 1. Land-use types and characteristics designated for pervious and impervious areas within subwatersheds, Cypress Creek watershed, Arkans[Current conditions consist of the 2006 land-use conditions and the 2013 gas-well pads, pipelines, and surface-water impoundments. Percentage does not total to 100 percent bec

Land use Current conditions total area (square miles) Current conditions land-use percentage Land-use percentage Time period before extensive grazing activities and no gas- extraction activities (scenario 1) Time period with some grazing activities and no gas- extraction activities (scenario 2) Time period with current land-use conditions and no g

extraction activiti

(scenario 3) 

Deciduous forest 10.3 28.9 59.4 36.2 29.1 Evergreen forest 7.0 19.6 40.6 39.8 20.0 Gas-well pads/pipelines 0.5 1.4 0.0 0.0 0.0 Mixed forest 1.6 4.5 0.0 0.0 4.5 Pasture 12.5 34.9 0.0 22.4 36.0 Gravel roads 1.5 4.1 0.0 1.5 4.0 Shrub 0.3 0.9 0.0 0.0 0.9 Urban 0.1 0.4 0.0 0.0 0.4 Surface-water impoundments 0.1 0.2 0.0 0.0 0.0 Brewer Lake 1.8 5.1 0.0 0.0 5.1 
Hydrologic Simulation Program—FORTRAN Watershed Model Development 7

Hydrologic Simulation Program—

FORTRAN Watershed Model 

Development

Hydrologic Simulation Program—FORTRAN is a 

watershed model developed to simulate the hydrologic 

and associated water-quality processes on a specified time 

step for pervious and impervious land surfaces and in 

streams (Bicknell and others, 2001). HSPF model also is a 

semilumped-parameter model that simulates spatial variability 

by discretizing the watershed into hydrologically similar 

land units based on relative similarity of land use, soils, 

topography, and other hydrologic characteristics. A water 

budget is calculated by the HSPF model, where inflows equal 

outflows plus or minus change in storage for each time step. 

Within the HSPF model, some parameters are set equal to 

measured or default values; however, most parameters are 

adjusted during the calibration process. A complete description 

of the mathematical equations and model variables can be 

found in Bicknell and others (2001).

Numerous datasets are required in the development 

of a HSPF model. Datasets compiled for this study include 

National Elevation Dataset (NED) (U.S. Geological Survey, 

2011) for use in delineating subwatersheds; the National 

Hydrography Dataset (NHD) (U.S. Geological Survey, 

2012a) that includes all the stream reaches within the Cypress 

Creek watershed; the 2006 Arkansas land-use map (Arkansas 

Natural Resources Commission and University of Arkansas: 

Center for Advanced Spatial Technologies, 2009); the Soil 

Survey Geographic database for each county within the 

watershed (U.S. Department of Agriculture, 2012a,b); and 

Next-Generation Radar (NEXRAD) hourly precipitation data 

(National Oceanic and Atmospheric Administration, 2012a), 

as well as other meteorological data including air temperature. 

Air temperature was obtained from the National Oceanic and 

Atmospheric Administration, National Climatic Data Center 

Morrilton station located approximately 11 mi southwest 

of the watershed (National Oceanic and Atmospheric 

Administration, 2012b) (fig. 1).

The USGS operates a continuous streamflow-gaging 

station and water-quality sampling station on Cypress Creek 

in north-central Arkansas. This streamflow-gaging station 

(fig. 3) was the only station used in the calibration process 

and is USGS station 07261090, Cypress Creek near Birdtown 

(hereafter referred to as Cypress Creek) (fig. 3). Continuous 

streamflow data were collected from Cypress Creek 

beginning on July 8, 2009. The streamgage was operated 

and streamflow was measured according to the methods 

described in Rantz and others (1982). Streamflow, in cubic 

feet per second (ft3/s), was computed every 15 minutes and 

averaged daily from 2009 through 2012 (and continues) at 

the site. All streamflow data described are available on the 

web at http://water.usgs.gov/ar/nwis. Water-quality samples, 

with corresponding instantaneous streamflows (streamflow 

at the time of sample collection), were collected during rise, 

peak, and fall flow conditions. Representative water-quality 

samples were collected using equal-width increment (EWI) 

techniques and discrete-sampling methods as outlined in the 

National Field Manual for the Collection of Water Quality 

Data (Wilde and others, 1999a). For EWIs, the stream cross 

section was divided into equal-increment widths, and samples 

were collected at the center of each increment by lowering 

and raising a sampler through the water column (Wilde and 

others, 1999a). Discrete (point) samples were collected at 

one location along the stream cross section by opening and 

closing a sampler at a specified depth (Wilde and others, 

1999a). The Cypress Creek water-quality sampling record 

began with approximately quarterly (occurring about every 

3 months) and high-flow event sampling from November 23, 

2010, through present (February 28, 2014) (U.S. Geological 

Survey, 2012b) following protocols outlined by Edwards and 

Glysson (1999). The USGS Missouri Water Science Center 

Sediment Laboratory in Rolla, Missouri, analyzed samples 

for suspended-sediment concentration following procedures 

established in Guy (1969). To maintain proper quality 

assurance and quality control (QA/QC) of water-quality data, 

protocols for instrument calibration (Wilde and Radke, 1998; 

Wilde and others, 1998a,b) and equipment cleaning (Wilde 

and others, 1998c) were followed. Streamflow data measured 

from July 8, 2009, through September 30, 2012, and waterquality data collected from November 23, 2010, through 

June 20, 2012, are presented in this report. 

Subwatershed Delineation and Land Use

The HSPF model requires a set of hydrologically 

similar land areas based on land use, surficial geology, 

soil characteristics, and other factors that represent the 

watershed. These hydrologically similar areas are grouped 

into subwatersheds containing pervious land segments 

(PERLND) and impervious land segments (IMPLND), each 

of which simulates the water-quantity and quality processes 

through the conceptual pathways of the hydrologic cycle 

(Ockerman and Heitmuller, 2010). Subwatersheds (fig. 4) 

were delineated based on NED and automatic delineation 

tools within a Geographic Information System (GIS) and were 

adjusted manually based on the NHD stream reaches and 

well-pad locations. There are a total of 105 subwatersheds, 

split between two HSPF models that are linked together 

(55 in the upper part and 50 in the lower part) (fig. 4), 

characterizing Cypress Creek’s watershed. Each subwatershed 

and its associated PERLND and IMPLND drain into a stream 

segment called a reach reservoir (RCHRES). There is one 

RCHRES per subwatershed and each RCHRES subsequently 

drains downstream (fig. 4). Land use was determined from the 
8 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

laf14-0633_fig04

Cypress Creek

Brewer Lake

3

32 38 37

7

11

24

4

54

48

1

19

18

40

13

10

39

55

17

12

14

22

49

33

27

15

29

8

52

36

25

43 44

53

21

31

6

28

34

51

5

20

47

30

50

41

9

23

46 42

2

16

35

26

45

10

43

12

3

49

49

45

38

50

24

4

44

48

34

46

32

35

39

33

15

20

14

27

8

40

21

19

31

9

23

5

18

16

11

42

26

7

36

29

1

25

17

2

6

47

41

37

13

30

22

28

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

Base from U.S. Geological Survey digitial data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15

EXPLANATION

Stream reach reservoir

(RCHRES)

Subwatershed boudary

and number

Watershed boundary

Figure 4. Locations of the subwatersheds and reaches within the Cypress Creek watershed used for the Hydrologic 

Simulation Program—FORTRAN model.
Hydrologic Simulation Program—FORTRAN Watershed Model Development 9

Arkansas 2006 land-use dataset (Arkansas Natural Resources 

Commission and University of Arkansas: Center for Advanced 

Spatial Technologies, 2009). The land use was categorized 

into nine PERLND types and five IMPLND types. IMPLNDs 

were assigned as a percentage of the PERLND based on 

the land-use datasets. Eleven of the subwatersheds were 

created to represent potential surface-water impoundments 

in the scenario simulations (shown as squares on fig. 4); 

the areas within these subwatersheds retained the same 

hydrologic features (land use, slope, and others) as that of the 

current-conditions simulation and were adjusted only during 

scenario simulations.

Pervious and Impervious Land Segments

The water-quality and quantity processes that occur 

on the land surface before entering a stream segment are 

simulated within each PERLND or IMPLND module. The 

processes that occur within the PERLNDs include water 

movement by three components: surface runoff, interflow, 

and groundwater; whereas, the processes that occur within 

the IMPLNDs include only surface runoff and no infiltration 

occurs. Runoff is simulated for each PERLND or IMPLND 

independently, and a water balance is calculated for each time 

step throughout the simulation. Surface runoff associated 

with the PERLNDS and IMPLNDs is routed into a RCHRES 

within the associated subwatershed. Interflow and groundwater 

within the PERLNDs account for water that is not evaporated 

or moved off the land surface from direct runoff. Interflow 

accounts for water that is directly infiltrated to the upper soil 

zone, is moved to overland flow from surface storage, or is 

removed from interflow storage to shallow subsurface flow. 

Groundwater accounts for the water that infiltrates to the lower 

soil zone and groundwater storage. The water retained as 

groundwater storage reappears as base flow or is lost from the 

system through deep percolation.

Reach Characterization

Within each subwatershed, water and associated waterquality constituents drain from the PERLNDs and IMPLNDs 

into a RCHRES. Each RCHRES (fig. 4) within the HSPF 

model is characterized by a piecewise linear function table 

(FTABLE) and is developed based on channel geomorphology, 

width, depth, length, slope, and roughness obtained from 

the NED and NHD for streamflow routing. FTABLEs are 

independent of the shape of the water body but serve to relate 

stage to surface area, channel volume, and discharge and are 

based on the one-dimensional kinematic wave theory for each 

RCHRES (Moore and Mohamoud, 2007; Bicknell and others, 

2001). The assumptions made to calculate water movement 

through a reach are (1) flow within a RCHRES is assumed to 

be well-mixed and unidirectional; (2) inflows enter a RCHRES 

at its upstream limit; and (3) precipitation, evaporation, and 

fluxes from the PERLNDs and IMPLNDs influence processes 

that occur within the RCHRES.

Within the Cypress Creek watershed, six subwatersheds 

(table 2) were represented as RCHRESs only, meaning 

there was no PERLND or IMPLND associated within the 

subwatershed (fig. 4). This was done to best represent surfacewater impoundments (fig. 3) within the watershed. Only 

surface-water impoundments that had a surface area greater 

than 3 acres were included because smaller ponds have 

negligible effects on the hydrology.

Table 2. Withdrawals and surface-water impoundment volumes for use in the Cypress Creek watershed model.

[RCHRES, Hydrologic Simulation Program—FORTRAN reach reservoir (RCHRES)]

RCHRES 2 RCHRES 9 RCHRES 23 RCHRES 26 RCHRES 35 RCHRES 42

Average depth (feet) 3.2 10 10.1 7.1 6.4 8.3

Area (acres) 3.3 10.5 17.5 5.1 5.2 8.4

Volume (acre-feet) 10.6 105.0 176.8 36.2 33.3 69.7

70 percent volume 7.39 73.50 123.73 25.35 23.30 48.80

Volume per second (ft3/s) 1.57 5.57 5.57 5.57 5.57 5.57

Days withdrawn per year1 5.0 13.0 22.0 5.0 4.0 9.0

1

Days withdrawn are for two times per year, once in spring and once in fall.
10 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

Meteorological Data

The sparseness of available rain-gage data in small 

watersheds has been a severe hindrance to accurate hydrologic 

modeling in the past; however, NEXRAD data were used 

as the precipitation input for the HSPF model (National 

Oceanic and Atmospheric Administration, 2008). As part of 

the NEXRAD program, the National Weather Service River 

Forecasting Centers produce gridded precipitation estimates; 

these estimates are known as Multisensor Precipitation 

Estimator (MPE) data (National Oceanic and Atmospheric 

Administration, 2010). MPE data are based from Doppler 

radar precipitation data and replace the earlier Stage III 

NEXRAD product (National Oceanic and Atmospheric 

Administration, 2008). The MPE algorithms provide better 

gage-correction biasing, mosaicking of radar data, and can 

incorporate satellite-derived precipitation estimates into the 

final MPE data product (National Oceanic and Atmospheric 

Administration, 2002). The MPE data offer precipitation 

estimates spatially averaged over grid cells of about 6 mi2 on 

a 1-hour time step (fig. 5). The Weather Surveillance Radar 

– 1998 Doppler (WSR–88D) that provides raw radar data 

for the Cypress Creek watershed is located approximately 

41 mi south of the watershed; a single WSR–88D beam 

has an effective range of approximately 143 mi (U.S. Army 

Corps of Engineers, 1994). The NEXRAD precipitation data 

provide hourly estimates in the Hydrologic Rainfall Analysis 

Project (HRAP) grid system, about a 2.5-mi grid in a Polar 

Stereographic map projection (Shedd and Fulton, 1993). The 

HRAP grid (Greene and Hudlow, 1982) is used to identify 

the location of each NEXRAD precipitation value. These 

spatially distributed precipitation data can be incorporated into 

watershed models as an improvement to using the sparse raingage networks to obtain rainfall data (Ockerman and Roussel, 

2009; Soong and others, 2005). 

The HRAP grid cells with the hourly MPE precipitation 

time series were intersected with each of the subwatersheds 

of the HSPF model using standardized functions within a 

GIS. The amount of precipitation for each subwatershed was 

determined by using a weighted average of the percentage 

of subwatershed area covered by each HRAP grid cell. For 

example, if the entire area of one subwatershed is within 

one HRAP grid cell, the subwatershed would receive a 

proportionate amount of precipitation equivalent to the amount 

of HRAP grid cell area covered by the subwatershed; if a 

subwatershed is split by more than one HRAP grid cell, each 

grid cell precipitation value is multiplied by the percentage of 

subwatershed area that falls within each HRAP cell, and then 

all products are summed together. 

During the model simulation time period of January 

2008 through September 30, 2012, Arkansas experienced the 

ninth driest year (2010) on record (1895–2011), with only 

39.1 inches of precipitation, and the wettest year (2009) on 

record, with 72.7 inches of precipitation (National Oceanic 

and Atmospheric Administration, 2012a); the average annual 

precipitation for Arkansas from 1895–2011 was 49.5 inches 

(National Oceanic and Atmospheric Administration, 2012a). 

Additional HSPF model input data included hourly potential 

evapotranspiration estimates determined from minimum and 

maximum daily temperature, as well as watershed latitude, 

using the Hamon method (Hummel and others, 2001) within a 

preprocessor (U.S. Environmental Protection Agency, 2003).

Evaluation Methods for the Hydrologic 

Simulation Program—FORTRAN

Various methods can be used to evaluate the acceptance 

criteria of model calibration. Model calibration is an iterative 

process of simulation, parameter evaluation, and adjustment 

to achieve an acceptable match of simulated and measured 

values. Model validation was not performed for the HSPF 

model because of the limited data for calibration (July 8, 

2009–September 30, 2012, at one USGS streamflow-gaging 

station). The calibration period (July 8, 2009–September 30, 

2012) included an extreme dry and wet year, a normal year, 

and a year when precipitation was slightly above normal. 

Randomly removing one or more years from the calibration 

dataset to use for validation would have potentially removed 

essential values needed to calibrate the model for the range 

of hydrologic conditions. Instead, all of the recent calibration 

data in the calibration process were included to obtain the 

most accurate representative model.

Several statistical methods calculated for the calibration 

period (July 8, 2009–September 30, 2012) for the USGS 

streamflow-gaging station were used to evaluate the HSPF 

model streamflow calibration including: streamflow volumes, 

Spearman’s rho, the Nash-Sutcliffe model efficiency 

coefficient (NSE), the Mean Absolute Error (MAE), Root 

Mean Square Error (RMSE), and Percent Bias (PBIAS). 

The HSPF model statistics for water-quality constituents 

(suspended sediment) included daily mean values, mean 

percent error, MAE, RMSE, NSE, and PBIAS for the 

daily values.

Spearman’s rho was calculated to determine the 

correlation between simulated and measured values of 

streamflow and suspended sediment (Helsel and Hirsch, 

2002). The NSE measures the magnitude of the differences 

between the measured and simulated values and is computed 

by equation 1:

( )

( )

2

=1

2

=1

measured value simulated value

1 

measured value measured value 

where

is time, in days; and

measured value is the average of all measured values.

T

t

T

t

NSE

T

− = −

−

∑

∑

(1)
Evaluation Methods for the Hydrologic Simulation Program—FORTRAN 11

laf14-0633_fig05

Cypress Creek

Brewer Lake

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

Base from U.S. Geological Survey digitial data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15

EXPLANATION

Stream reach

Subwatershed boudary

Watershed boundary

NEXRAD grid

Figure 5. Location of the Next Generation Radar (NEXRAD) grid, Cypress Creek watershed, Arkansas.
12 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

A NSE of 1 indicates model predictions are a perfect match 

to the observed data, and a NSE of equal to or less than 0 

indicates that the mean measured value is a better predictor 

than the simulated value and is considered unacceptable 

(Moriasi and others, 2007). MAE provides the error between 

the simulated and measured values and is computed by 

equation 2:

simulated value measured value . number of observations

MAE − = ∑ (2)

For example, a MAE of 17.3 ft3/s indicates that the 

mean difference between simulated streamflow and measured 

streamflow is 17.3 ft3/s. The RMSE indicates the spread of 

how far the simulated values deviate from the measured values 

and is computed by equation 3:

2 (simulated value measured value) . number of observations

RMSE − = ∑ (3)

For example, a RMSE of 8.25 ft3/s indicates that the 

simulated streamflow is within 8.25 ft3/s of the measured 

streamflow. PBIAS measures the average tendency of the 

simulated data to be larger or smaller than their observed 

counterparts (Gupta and others, 1999) and is computed by 

equation 4:

 

( )

1

=1

(measured value simulated value) 100 .

measured value

T

t

T

t

PBIAS = − × = ∑

∑

(4)

A PBIAS of 0 indicates optimal performance, with 

low-magnitude values indicating accurate model simulation 

(Moriasi and others, 2007).

Hydrologic Simulation Program—

FORTRAN Model Calibration

Hourly streamflow data and suspended sediment 

concentration data were used to calibrate the HSFP model. 

The model covered the period from July 8, 2009, through 

September 30, 2012, and used continuous streamflow and 

water-quality data from Cypress Creek (USGS station 

07261090) for calibration. Calibration is a necessary step 

to check the reliability of the model. Prior to calibration, 

meteorological data for the entire 2008 calendar year was 

input to the HSPF model, as well as the period leading up to 

the start of the modeling period (July 8, 2009) for the model 

to “warmup.” This warmup period is a necessary step to allow 

for soil moisture to stabilize and constituent accumulation 

and washoff to equilibrate. Comparisons between the currentconditions simulation and scenario simulations were made for 

the calibration period (July 8, 2009–September 30, 2012) for 

streamflow and suspended-sediment analyses.

For the HSPF model current-conditions simulation, 

several conditions were considered: 

1. The surface-water impoundments within the watershed 

(figs. 3–4) were withdrawn to 70 percent of their total 

volume over a variable period, two times per year (once in 

spring and once in summer) (table 2); 

2. Withdrawal from Cypress Creek occurred during the 

same time of year as item 1 (for 6.5 days, two times per 

year [once in spring and once in summer] at a rate of 

1.39 ft3/s when the simulated streamflow at the Cypress 

Creek streamflow-gaging station at the time of withdrawal 

was at least 12 ft3/s), simultaneously from four separate 

locations along Cypress Creek (fig. 3); and

3. The rates and volumes of withdrawal for items 1 

and 2 were determined based on the assumption that 

245 hydraulic fracturing jobs (7 wells per 35 pads) during 

the simulation period would occur, and 4.73 million 

gallons (14.5 acre-ft) of water would be needed for each 

gas well. The water demand of 4.73 million gallons is 

removed only from the surface-water impoundments and 

Cypress Creek, and no recycled water is assumed, which 

currently accounts, on average, for 35 percent of the total 

hydraulic fracturing volume (Southwestern Energy Co., 

written commun., 2011).

Streamflow Calibration

Several HSPF model parameters (table 3) govern the 

simulated flux of water into a RCHRES. Primary parameters 

that reflect soil conditions simulated from the PERLNDs (and 

therefore determine the distribution of available water for 

infiltration or for runoff) include lower zone nominal storage 

(LZSN), upper zone nominal storage (UZSN), infiltration 

capacity of soil (INFILT), and lower zone evapotranspiration 

(LZETP). Parameters that affect surface runoff simulated 

from IMPLNDs are length of assumed overland flow plane 

(LSUR), slope of the assumed overland flow plane (SLSUR), 

Manning’s n for assumed overland flow plane (NSUR), and 

the retention storage capacity of the surface (RETSC). 

The simulated total flow volume and average daily 

mean streamflow rate matched well with the measured data 

at the Cypress Creek gage. Streamflow calibration results 

(percent errors) for average daily mean flow rate and total 

flow volume (table 4) generally were within the acceptance 

rating criteria of “very good” (less than 10 percent) for HSPF 

model performance (Donigian, 2000). The measured average 

daily mean streamflow rate was 36.6 ft3/s for the period of 
Hydrologic Simulation Program—FORTRAN Model Calibration 13

Table 3. Summary of calibrated values for selected hydrology parameters for the Hydrological Simulation Program—FORTRAN 

model of the Cypress Creek watershed.

[PERLND, pervious land area; IMPLND, impervious land area; numbers in bold are HSPF default values (Bicknell and others, 2001)]

Parameter Land surface Description Values Units

AGWETP PERLND Fraction of remaining evapotranspiration from active groundwater 0.00 Dimensionless

AGWRC PERLND Base groundwater recession 0.85 1/day

BASETP PERLND Fraction of remaining evapotranspiration from base flow 0.18 Dimensionless

CEPSC PERLND Interception storage capacity 0.01–0.25 Inches

DEEPFR PERLND Fraction of groundwater inflow to deep recharge 0.46 Dimensionless

INFEXP PERLND Infiltration equation exponent 2.0 Dimensionless

INFILD PERLND Ratio of maximum and mean infiltration capacities 2.0 Dimensionless

INFILT PERLND Index to infiltration capacity of soil 0.035–0.057 Inches/interval

INTFW PERLND Interflow index 3.00–5.00 Dimensionless

IRC PERLND Interflow recession coefficient 0.45–0.55 1/day

KVARY PERLND Groundwater outflow modifier 2.9 1/inches

LSUR PERLND or IMPLND Length of assumed overland flow plane 200–400 Feet

LZETP PERLND Lower zone evapotranspiration 0.10–0.85 Dimensionless

LZSN PERLND Lower zone nominal storage 10.0–12.2 Inches

NSUR PERLND or IMPLND Manning’s n for assumed overland flow plane 0.3 Dimensionless

RETSC IMPLND Retention storage capacity 0.1 Inches

SLSUR PERLND or IMPLND Slope of assumed overland flow plane 0.005–0.291 Dimensionless

UZSN PERLND Upper zone nominal storage 0.69–0.76 Inches

Table 4. Hydrological Simulation Program—FORTRAN streamflow calibration results for the Cypress Creek 

watershed.

[acre-ft, acre-feet; ft3/s, cubic feet per second; <, less than]

Cypress Creek near Birdtown (07261090)

Calibration period July 8, 2009, to September 30, 2012

Streamflow volumes1 Measured Simulated Percent

error2

Total streamflow volume (acre-ft) 79,035 78,285 -0.95

Average daily mean streamflow rate (ft3/s) 36.6 34.5 -5.61

Total of highest 10 percent of daily streamflows (acre-ft) 56,318 58,653 4.15

Total of lowest 50 percent of daily streamflows (acre-ft) 571 670 17.4

Model-fit statistics1 Daily

Number of days 1,138

Spearman’s rho 0.70

p value <0.001

Nash-Sutcliffe model efficiency coefficient (NSE) 0.77

Mean absolute error (MAE) (ft3/s) 21.1

Root mean square error (RMSE) (ft3/s) 66.9

Percent bias (PBIAS) (percent) 5.60

1

Only paired data were used in statistical calculations; missing data were not used.

2

Percent error is simulated minus measured divided by measured times 100.
14 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

record, and the simulated average daily mean streamflow 

rate for the same time period (July 8, 2009–September 30, 

2012) was 34.5 ft3/s (fig. 6); this is an error of -5.61 percent 

(table 4). In general, based on the exceedance probability, 

simulated “low flows” (in this instance, flows with exceedance 

probabilities greater than 50 percent) were within the 

acceptance rating criteria of “fair” for the total of the lowest 

50 percent of daily streamflows (17.4 percent) for the Cypress 

Creek gage (table 4, fig. 7) (Donigian, 2000). Additionally, 

simulated and observed high flows (highest 10 percent of 

daily streamflows) were within the acceptance rating criteria 

of “very good” with a 4.15-percent difference at the Cypress 

Creek gage (table 4, fig. 6) (Donigian, 2000). Percentage 

error between the measured and simulated total streamflow 

volume was -0.95 percent (table 4), a performance rating of 

“very good” (Donigian, 2000). Temporally, the streamflow 

calibration matched the seasonal variability occurring during 

low streamflow conditions (streamflows not substantially 

influenced by runoff) (fig. 6), and the simulated peak flows 

generally undersimulated high streamflow conditions. 

Specifically, simulated values were higher than measured 

values for the highest 10 percent of daily streamflows (table 4) 

probably because simulated and measured values for the 

highest 10 percent of daily streamflows did not occur on the 

same day (fig. 6). 

Based on the additional model-fit statistics, the simulated 

and measured average daily mean streamflow rates matched 

well at the Cypress Creek gage. Performance ratings for the 

given statistics were reported by Moriasi and others (2007) 

and Donigian (2000) (table 4). For the Spearman’s rho (0.70), 

NSE (0.77), and PBIAS (5.60 percent), the model performance 

falls within the “satisfactory” and “very good” rating, 

respectively. The MAE and RMSE for the simulated average 

daily mean streamflow and the measured average daily mean 

streamflow rate were 21.1 and 66.9 ft3/s, respectively (table 4).

Suspended-Sediment Calibration

To calibrate suspended-sediment loads entering streams, 

it is desirable to calibrate loads from each of the land-use 

types to known values. However, no suspended-sediment 

studies have been conducted within the Cypress Creek 

watershed. As such, suspended-sediment loading rates 

from each land use were obtained from literature values, 

which can range substantially from study to study (Bureau 

of Land Management, 2006; Donigian and Love, 2003; 

U.S. Environmental Protection Agency, 1999; Maryland 

Department of the Environment, 2006; Scoles and others, 

2001; Tetra Tech Inc., 2004) (table 5). For the Cypress Creek 

watershed, the middle to upper range of the suspendedsediment loading rates reported in the literature for relative 

land uses was used for calibration (table 5). 

Two equations are used in the HSPF model to calculate 

the production, removal, and transport of suspended sediment 

from the land surface for three sediment size classes (sand, 

silt, and clay). These equations are included in the Agricultural 

Runoff Model (ARM) and Nonpoint Source (NPS) models 

developed by Donigian and Davis (1978) and Donigian 

and Crawford (1977), respectively, which are used in the 

HSPF model. The production of sediment is simulated by 

detachment of soil by precipitation, removal of sediment 

by scour of the soil matrix, and transport of the detached 

sediment by overland flow. Suspended-sediment load within 

a RCHRES is calculated from particle size, soil texture, 

settling velocity, density, and erodibility and is simulated by 

convection, scouring, and deposition. Value ranges and units 

for calibrated HSPF model suspended-sediment parameters 

are listed in table 6.

The mid- to upper-range suspended-sediment loading 

rates, as reported in the literature for different land uses, 

worked reasonably well to calibrate the suspended-sediment 

concentrations at the Cypress Creek gage. For suspendedsediment concentrations at Cypress Creek, the mean measured 

suspended-sediment concentration was 290.9 mg/L and 

the mean simulated suspended-sediment concentration was 

373.6 mg/L, with a mean percent error between the paired 

data of -0.8 percent (table 7; fig. 8). Additionally, percent 

error (relative to the measured value) ranged from -301.0 to 

99.9 percent (table 7). Based on Moriasi and others (2007), 

the PBIAS value (-28.5 percent) is “good” for sediment 

calibration. The MAE, RMSE, and Spearman’s rho for the 

paired-simulated suspended-sediment concentrations and 

the measured suspended-sediment concentrations were 

235.1 mg/L, 480.3 mg/L, and 0.72, respectively (table 7).

Table 5. Land-use loading rates for the Hydrological Simulation 

Program—FORTRAN model of the Cypress Creek watershed.

[Loading rates for constituents are sums of annual loads for the listed 

constituent divided by the acres for each land-use type; (ton/acre)/yr, ton 

per acre per year. Loading rate values are determined from given literature 

values (Bureau of Land Management, 2006; Donigian and Love, 2003; 

U.S. Environmental Protection Agency, 1999; Maryland Department of the 

Environment, 2006; Scoles and others, 2001; Tetra Tech Inc., 2004)]

Land use Suspended sediment 

([ton/acre]/yr)

Deciduous forest 0.48

Evergreen forest 0.39

Mixed forest 0.46

Gravel roads 1.7

Pasture 1.2

Pads 1.2

Shrub 1.1

Urban 0.89
Hydrologic Simulation Program—FORTRAN Model Calibration 15

laf14-0633_fig06

Measured value

Simulated value 

EXPLANATION

0 

500 

1,000 

1,500 

2,000 

2,500 

2008 2009 2010 2011 2012

Streamflow, in cubic feet per second 

Years

Figure 6. Simulated and measured daily mean streamflow at the Cypress Creek gage in the Cypress Creek 

watershed.

0.10 

1 

10 

100 

1,000 

10,000 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 

Daily mean streamflow, in cubic feet per second 

Exceedance probability 

Measured value

Simulated value 

EXPLANATION 

Figure 7. Exceedance probability of simulated and measured daily mean streamflow at selected inflow stations 

in the Cypress Creek watershed.
16 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

Table 6. Summary of calibrated values for suspended-sediment parameters for the Hydrological Simulation Program—

FORTRAN model of the Cypress Creek watershed.

[PERLND, pervious land surface, IMPLND, impervious land surface, RCHRES, stream reach; –, none; numbers in bold are Hydrologic Simulation Program—

FORTRAN default values (Bicknell and others, 2001)]

Parameter Land 

surface Description Values Units

KRER PERLND Coefficient of the soil-detachment equation 0.28–0.43 Complex

JRER PERLND Exponent of the soil-detachment equation 2.1 Complex

KSER PERLND Coefficient of the detached-sediment washoff equation 0.030–4.175 Complex

JSER PERLND Exponent of the detached-sediment washoff equation 1.50 Complex

AFFIX PERLND Fraction by which detached sediment decreases daily through soil 

compaction 0.06–0.45 1/day

COVER PERLND Fraction of the land surface shielded from rainfall erosion 0.50–0.95 –

NVSI PERLND Rate at which sediment enters detached storage from the atmosphere 0 Pound/acre-day

KEIM IMPLND Coefficient of the solids washoff equation 0.30–0.55 Complex

JEIM IMPLND Exponent of the solids washoff equation 2.00 Complex

ACCSDP IMPLND Solids accumulation rate 0.0005 Ton/acre-day

RHO RCHRES Density of the sediment particle 2.6 Gram/cubic centimeter

M (silt)1 RCHRES Erodibility coefficient of the sediment 0.001 Pound/square foot-hour

M (clay)1 RCHRES Erodibility coefficient of the sediment 0.0001 Pound/square foot-hour

W (silt and clay) RCHRES Settling velocity of the sediment particle in still water 0.0005–0.005 Inch/second

TAUCD (silt) RCHRES Critical bed shear stress for sediment deposition 0.002–8.6 Pound/square foot

TAUCS (silt) RCHRES Critical bed shear stress for sediment scour 0.03–9.0 Pound/square foot

TAUCD (clay) RCHRES Critical bed shear stress for sediment deposition 0.002–8.6 Pound/square foot

TAUCS (clay) RCHRES Critical bed shear stress for sediment scour 0.03–9.0 Pound/square foot

1

Calibration only parameter (U.S. Environmental Protection Agency, 2006).

Simulated value

Measured value

EXPLANATION

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

2008 2009 2010 2011 2012

Suspended sediment concentration, in milligrams per liter 

Years

Figure 8. Simulated and measured suspended-sediment concentrations at Cypress Creek near Birdtown.
Hydrologic Simulation Program—FORTRAN Model Calibration 17

Table 7. Measured and simulated suspended-sediment concentrations and suspended-sediment calibration statistics for the 

Hydrological Simulation Program—FORTRAN model at Cypress Creek near Birdtown.

[mg/L, milligrams per liter; the measured instantaneous concentrations, collected from October 1, 2010, through September 30, 2012, were averaged. Hourly 

simulated values were paired with measured values for the nearby observed hour]

Cypress Creek near Birdtown (07261090)

Calibration period October 1, 2010, to September 30, 2012

Sample date Time

Measured 

instantaneous 

discharge 

(ft3/s)

Measured 

suspendedsediment 

concentration 

(mg/L)

Simulated 

suspendedsediment 

concentration 

(mg/L)

Percent 

error 

between 

paired data 

(percent)

Absolute

error

(mg/L)

November 23, 2010 10:30 1.0 9.0 34.7 -285.3 25.7

February 24, 2011 17:17 300.0 817.0 5.4 99.3 811.6

February 24, 2011 20:30 722.0 997.0 1,039.6 -4.3 42.6

March 24, 2011 11:45 14.0 15.0 0.0 99.9 15.0

June 2, 2011 14:00 7.4 4.0 1.8 55.0 2.2

June 23, 2011 11:00 0.7 34.0 1.8 94.7 32.2

November 9, 2011 1:30 94.0 378.0 325.3 13.9 52.7

November 17, 2011 12:30 28.0 6.0 2.2 62.6 3.8

November 21, 2011 23:30 1,460.0 1,610.0 1,183.4 26.5 426.6

November 22, 2011 3:15 1,870.0 443.0 890.8 -101.1 447.8

November 22, 2011 16:45 256.0 65.0 23.4 64.0 41.6

February 22, 2012 12:20 35.0 17.0 6.7 60.6 10.3

March 8, 2012 15:25 2,740.0 595.0 1,839.1 -209.1 1,244.1

March 8, 2012 18:20 2,010.0 471.0 1,888.9 -301.0 1,417.9

March 9, 2012 10:00 264.0 64.0 36.1 43.6 27.9

March 13, 2012 11:30 107.0 20.0 1.7 91.4 18.3

March 21, 2012 10:30 1,600.0 250.0 180.5 27.8 69.5

June 6, 2012 15:30 0.0 7.0 7.9 -13.1 0.9

June 20, 2012 9:15 0.0 6.0 1.5 75.0 4.5

June 20, 2012 9:16 0.0 9.0 1.5 83.3 7.5

Paired data for hours with measured data

Water-quality

characteristic

Mean of 

measured 

data

(mg/L)

Mean of 

simulated

data

(mg/L)

Mean 

percent

error

(percent)

Mean 

absolute

error

(mg/L)

Root mean 

square

error

(mg/L) 

NashSutcliffe 

model 

efficiency

Percent

bias 

(percent)

Spearman’s

rho p value

Suspended sediment 

(mg/L)1

290.9 373.6 -0.8 235.1 480.3 -0.3 -28.5 0.72 <0.001

1

Suspended sediment LRL: 1 mg/L.
18 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

Hydrologic Simulation Program–

Fortran Model Limitations

An understanding of model limitations is essential 

for the effective use and interpretation of watershed 

models. The accuracy of the HSPF model is limited by the 

simplification of complexities with the physical properties 

of streamflow, hydrodynamics within the watershed, 

water-quality processes within the watershed, spatial and 

temporal discretization effects, and assumptions made in the 

formulation of the governing equations. Model accuracy is 

limited by subwatershed size, boundary conditions, accuracy 

of calibration, and parameter sensitivity; model accuracy also 

is limited by the availability of appropriate data and by the 

interpolations and extrapolations that are inherent in using data 

in any model. For example, streamflow and water quality can 

be simulated with reasonable accuracy at stream or reservoir 

locations with a streamflow- or water-quality gaging station; 

however, for tributaries that do not have gaging stations, 

adequacy of streamflow simulation is uncertain. Further, landuse sediment loading rates were assumed for the HSPF model 

(table 5), but site-specific data collection for different land-use 

types in the Cypress Creek watershed could improve model 

calibration. Field QA/QC samples, such as replicates, were not 

collected for this study; therefore, variability associated with 

sediment data collection is unknown. Although a model might 

be considered calibrated, calibration parameter values are not 

unique in yielding acceptable simulated values of streamflow 

or water-quality characteristics. 

Sensitivity analysis is the determination of the effects 

of small changes in calibrated model parameters on model 

results. A complete sensitivity analysis was not conducted for 

all model parameters in the Cypress Creek watershed model. 

The HSPF model includes more than 150 parameters (tables 3 

and 6 list subsets of the parameters; default values in Bicknell 

and others [2001] were used for several other parameters), 

and a complete sensitivity analysis would be a very lengthy 

process; however, many hydrodynamic and water-quality 

simulations were conducted as a component of model 

calibrations. Results from these simulations form the basis for 

the sensitivity analysis. 

For the HSPF model, parameter sensitivity is a function 

of the physical conditions of Cypress Creek’s watershed, 

such as climate, topography, soils, and vegetation. For the 

simulation of streamflow, LZSN and INFILT (both of which 

play a direct role in determining whether moisture on the land 

surface infiltrates, enters storage, or becomes runoff) typically 

are the most sensitive hydrologic parameters (Al-Abed 

and Whiteley, 2002; Ryu, 2009; Skahill, 2004; Skahill and 

Doherty, 2006). Parameters related to detachment and washoff 

of sediment from the land surface, as well as the parameters 

related to shear stress within the RCHRES, such as critical bed 

shear stress for sediment deposition (TAUCD) and critical bed 

shear stress for sediment scour (TAUCS), typically appeared 

to be among the most sensitive parameters for simulation 

of suspended sediment within the Cypress Creek watershed 

HSPF model. 

During storm events, it is difficult to be at a given site to 

sample the rising flow, which presumably corresponds with 

the peak in suspended-constituent concentration. As such, 

the model is limited by the paucity of data. To adequately 

predict and match simulated to measured values through 

entire stormflow events, samples would have to be collected 

along the entire stormflow hydrograph. Although overall 

positive linear relations are found, for example, between 

streamflow and suspended sediment, there usually is large 

variation between instantaneous measurements as a result 

of numerous variables. The resulting low coefficient of 

determination values normally will reflect this variation 

as a result of sampling timing, difficulty in collecting 

representative samples, and varying landscape characteristics. 

As such, the model may actually perform much better as 

a predictive tool (especially for seasonal or annual loads 

rather than instantaneous or daily concentrations) than is 

reflected in attempts at matching individual simulations to 

instantaneous measurements.

Simulated Effects of Proposed Gas 

Extraction Activities on the Streamflow 

and Sedimentation within the Cypress 

Creek Watershed

The calibrated HSPF model is referred to as “currentconditions simulation” in the following discussions of 

scenarios. Comparisons between the current-conditions 

simulation and four scenario simulations were made for the 

calibration period (July 8, 2009–September 30, 2012) for 

streamflow and suspended-sediment loads. The four scenarios 

represent simulated changes in land use and examine the 

potential effects of these land-use changes on the water quality 

within the Cypress Creek watershed. These scenarios are 

intended to represent: 
Simulated Effects of Proposed Gas Extraction Activities on Streamflow and Sedimentation within Cypress Creek Watershed 19

1. a time period before extensive grazing activities and no 

gas-extraction activities; 

2. a time period with some grazing activities and no gasextraction activities; 

3. a time period with current land-use conditions and no gasextraction activities; and 

4. a time period with current land-use conditions and 

increased gas-extraction activities (for example, increased 

gas-well pad and surface-water impoundment activities). 

To quantify the changes between the current-conditions 

simulation and the scenario simulations, several metrics 

were used to quantify changes in streamflow characteristics. 

These metrics included average daily mean, maximum, 

and minimum streamflow for the calibration period (July 8, 

2009–September 30, 2012); as well as average daily mean 

and maximum streamflow for spring flows (March, April, 

and May), representing a wet period; average daily mean 

and maximum streamflow for summer flows (July, August, 

and September), representing a dry period; average daily 

mean effective and peak bankfull streamflows; and average 

daily mean low-flow streamflows. The daily mean low-flow 

values were determined from the lowest 10th percentile of 

all the simulated flows. The daily mean effective and peak 

bankfull streamflows were those flows greater than 315 ft3/s 

and were determined by the U.S. Department of Agriculture 

Natural Resources Conservation Service (Thom Garday, U.S. 

Department of Agriculture Natural Resources Conservation 

Service, written commun., 2013). The 315 ft3/s cutoff 

serves solely as a guideline for comparing daily mean high 

streamflows between the current-conditions simulation and 

scenario simulations.

Scenario 1—Simulated Time Period Before 

Extensive Grazing Activities and No GasExtraction Activities

Scenario 1 simulated a time period before extensivegrazing activities and no gas-extraction activities; that is, 

conversion of all nonforested land in the watershed to forest. 

All areas of anthropogenically altered land, including gas-well 

pads/pipelines and surface-water impoundment areas, pasture 

area, all gravel road area, shrub area, and urban land-use 

area, were converted to forest (fig. 9). The converted land use 

was divided into approximately 40 percent evergreen forest 

and approximately 60 percent deciduous forest based on 

General Land Office survey notes of the Ouachita Mountain 

region during the time of settlement (Foti and Glenn, 1990). 

Because mixed-forest land use contains parameters for 

hydrology and water quality that represent both coniferous 

and deciduous, it was deemed unnecessary to add in a 

separate mixed-forest land use. Converting the gas-well pads/

pipelines (1.4 percent), pasture (34.9 percent), gravel roads 

(4.1 percent), shrub (0.9 percent), urban (0.4 percent), and 

surface-water impoundments (0.2 percent) land use (fig. 3) 

to forest increased the percentage of forested land in the 

watershed by approximately 47 percent (from approximately 

53 to approximately 100 percent) (fig. 9; table 1).

Suspended-sediment loads and volume of streamflow 

entering the area that comprised Brewer Lake, as simulated 

by the HSPF model for scenario 1, were lower than those 

for the current-conditions simulation. Simulated land-use 

changes for a time period before extensive-grazing activities 

and no gas-extraction activities resulted in a 13.9-percent 

decrease in total streamflow volume (from 113,461 acre-ft to 

97,660 acre-ft) from all tributaries flowing into the area that 

would be encompassed by Brewer Lake, had it existed, for the 

calibration period (July 8, 2009–September 2012) (fig. 10). 

Relatedly, there was a 43.3-percent decrease (from 7,645 tons/

year to 4,336 tons/year) in suspended-sediment load for the 

entire simulation from all tributaries flowing into the same 

area (fig. 11). Additionally, average daily mean streamflow, 

average daily mean bankfull streamflow, average spring and 

summer streamflows, and average daily mean low flows 

(10th percentile) all decreased with increasing forested land. 

Average suspended-sediment loads also decreased for the 

same flow conditions (table 8). The decrease in streamflow 

volume and related streamflow metrics probably was a 

result of differences in increased vegetative interception of 

precipitation, increased infiltration with increasing forested 

land, and resulting decreased soil erosion.
20 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

laf14-0633_fig09

Cypress Creek

3

32 38 37

7

11

24

4

54

48

1

19

18

40

13

10

39

55

17

12

14

22

49

33

27

15

29

8

52

36

25

43 44

53

21

31

6

28

34

51

5

20

47

30

50

41

9

23

42 46

2

16

35

26

45

10

43

12

3

49

49

45

38

50

24

4

44

48

34

46

32 35

39

33

15

20

14

27

8

40

21

19

31

9

23

5

18

16

11

42

26

7

36

29

1

25

17

2

6

47

41

37

13

30

22

28

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

Base from U.S. Geological Survey digitial data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

Land use land cover by Arkansas Natural Resources Commission and 

University of Arkansas: Center for Advanced Spatial Technologies, 2009

EXPLANATION

Land use and land cover

Deciduous forest

Evergreen forest

Stream reach reservoir 

(RCHRES)

Subwatershed boudary

and number

Watershed boundary

Figure 9. Land-use types used in scenario 1, a time period before extensive-grazing activities and no gas-extraction activities 

in the Cypress Creek watershed, Arkansas.
Simulated Effects of Proposed Gas Extraction Activities on Streamflow and Sedimentation within Cypress Creek Watershed 21

laf14-0633_fig10

113,461 

97,660 

105,420 

112,613 114,566 

0 

20,000 

40,000 

60,000 

80,000 

100,000 

120,000 

Current conditions

(consist of the 2006 land-use conditions

and the 2013 gas-well pads, pipelines, 

and surface-water impoundments)

Time period before extensive grazing

activities and no gas-extraction 

activities (scenario 1) 

Time period with some grazing 

activities and no gas-extraction 

activities (scenario 2)

Time period with current land-use 

conditions and no gas-extraction 

activities (scenario 3)

Time period with current land-use 

conditions and increased gas-extraction 

activities (scenario 4)

Volume, in acre-feet 

Figure 10. Comparison of total streamflow volume for the calibration period (July 8, 2009–September 2012) between 

the current-conditions simulation and scenario simulations for the Cypress Creek watershed.
22 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

laf14-0633_fig11

7,645 

4,336 

6,079 

7,675 

6,632 

0 

1,000 

2,000 

3,000 

4,000 

5,000 

6,000 

7,000 

8,000 

Sediment load, in tons per year

Current conditions

(consist of the 2006 land-use conditions

and the 2013 gas-well pads, pipelines, 

and surface-water impoundments)

Time period before extensive grazing

activities and no gas-extraction 

activities (scenario 1) 

Time period with some grazing 

activities and no gas-extraction 

activities (scenario 2)

Time period with current land-use 

conditions and no gas-extraction 

activities (scenario 3)

Time period with current land-use 

conditions and increased gas-extraction 

activities (scenario 4)

Figure 11. Comparison of yearly suspended-sediment load between the current-conditions simulation and scenario 

simulations for the Cypress Creek watershed.
Table 8. Summary of July 8, 2009–September 30, 2012 simulation results for land-use change scenarios on Brewer Lake in the Cypress Creek waters[Current conditions consist of the 2006 land-use conditions and the 2013 gas-well pads, pipelines, and surface-water impoundments. ft3/s, cubic feet per second; mg/L, milligramsignificant figures do not imply a level of accuracy attributed to the simulation results] Simulated metric Units Land use scenarios Current conditions Time period before extensive grazing activities and no gas- extraction activities (scenario 1) Time period with some grazing activities and no gas- extraction activities (scenario 2) Time period with current land-use conditions and no g

extraction activiti

(scenario 3) 

Simulation results for all streamflows (daily mean) Average streamflow ft3/s 48.4 41.7 45.0 48.1 

Maximum streamflow ft3/s 2,019.2 1,762.1 1,895.6 2,024.4 Minimum streamflow ft3/s 6.1 × 10-7 3.7 × 10-7 4.8 × 10-7 5.9 × 10-7 Coefficient of variation ft3/s 3.3 3.4 3.3 3.3 Average sediment load ton/day 20.9 11.9 16.6 21.0 Maximum sediment load ton/day 4,245.2 2,879.8 3,723.0 4,333.5 Minimum sediment load ton/day 0.0 0.0 0.0 0.0 Percentage of current condition average sediment load percent 100 56.9 79.4 100.5 

Simulation results for daily mean spring streamflows (March, April, May) Average streamflow ft3/s 70.7 63.0 66.9 70.3 

Maximum streamflow ft3/s 1,628.7 1,343.9 1,489.1 1,624.1 Average sediment load ton/day 37.5 23.4 31.2 37.8 Maximum sediment load ton/day 4,245.2 2,879.8 3,723.0 4,333.5 Percentage of current condition average sediment load percent 100 62.4 83.2 100.8 

Simulation results for daily mean summer streamflows (July, August, September) Average streamflow ft3/s 30.5 23.6 26.6 29.4 

Maximum streamflow ft3/s 1,823.8 1,529.1 1,675.7 1,828.2 Average sediment load ton/day 16.8 8.8 12.7 16.8 Maximum sediment load ton/day 3,934.5 2,184.6 2,993.7 3,943.2 Percentage of current condition average sediment load percent 100 52.6 75.6 100.0 

Simulation results for daily mean effective and peak bankfull streamflows (greater than 315 ft3/s) Number of stormflow values days 39 36 37 39 

Percentage of time flow occurred percent 3.3 3.0 3.1 3.3 Average streamflow ft3/s 734.9 693.8 721.0 738.2 Maximum streamflow ft3/s 2,019.2 1,762.1 1,895.6 2,024.4 Minimum streamflow ft3/s 325.8 320.2 322.7 320.2 Percentage of current condition average flow percent 100.0 94.4 98.1 100.4 Average sediment load ton/day 578.0 365.9 475.8 582.0 Maximum sediment load ton/day 4,245.2 2,879.8 3,723.0 4,333.5 Minimum sediment load ton/day 1.8 0.2 0.3 0.3 Percentage of current condition average sediment load percent 100 63.3 82.3 100.7 
Table 8. Summary of July 8, 2009–September 30, 2012 simulation results for land-use change scenarios on Brewer Lake in the Cypress Creek waters[Current conditions consist of the 2006 land-use conditions and the 2013 gas-well pads, pipelines, and surface-water impoundments. ft3/s, cubic feet per second; mg/L, milligramsignificant figures do not imply a level of accuracy attributed to the simulation results] Simulated metric Units Land use scenarios Current conditions Time period before extensive grazing activities and no gas- extraction activities (scenario 1) Time period with some grazing activities and no gas- extraction activities (scenario 2) Time period with current land-use conditions and no g

extraction activiti

(scenario 3) 

Simulation results for daily mean low streamflows (10th percentile) Number of stormflow values days 118 118 118 118 

Percentage of time flow occurred percent 10 10 10 10 Average streamflow ft3/s 0.03 0.01 0.02 0.03 Maximum streamflow ft3/s 0.07 0.05 0.07 0.07 Minimum streamflow ft3/s 0.0 0.0 0.0 0.0 Percentage of current condition average flow percent 100.0 33.3 66.7 100.0 Average sediment load ton/day 6.75E-5 4.30E-5 5.57E-5 1.14E-5 Maximum sediment load ton/day 1.46E-3 1.42E-3 5.51E-3 1.27E-3 Minimum sediment load ton/day 0.0 0.0 0.0 0.0 Percentage of current condition average sediment load percent 100 63.7 82.5 16.9 
Simulated Effects of Proposed Gas Extraction Activities on Streamflow and Sedimentation within Cypress Creek Watershed 25

Scenario 2—Simulated Time Period 

with Some Grazing Activities and No 

Gas-Extraction Activities

Scenario 2 simulated a time period before any gasextraction activities but with some grazing activities; that 

is, simulated conversion of the current condition land use 

within the Cypress Creek watershed to that of 1949 land use. 

Single-frame aerial photography from 1949 was obtained 

from Earth Resources Observation and Science (EROS) 

Center and digitized within GIS. The quality of the aerial 

photography was such that only four land-use classifications 

could be clearly distinguished: pasture, evergreen forest, 

deciduous forest, and gravel roads (fig. 12). Land-use 

areas that were not readily identifiable from the 1949 aerial 

photography were compared to the current land use (2010) 

aerial photography provided by SWN (Southwestern Energy 

Co., written commun., 2011) and were classified to the 

closest land use from the current land use. For example, if 

an unidentifiable area was identified on the current aerial 

photography as a deciduous forest land use, then the 1949 land 

use was classified as deciduous forest. For the change from 

the 2006 to the 1949 land-use conditions, the percentage of 

pastureland within the watershed decreased from 34.9 percent 

to 22.4 percent; the percentage of evergreen forest land within 

the watershed increased from 19.6 percent to 39.8 percent; 

the percentage of deciduous forest land within the watershed 

increased from 28.9 percent to 36.2 percent; and the 

percentage of gravel roads decreased from 4.1 percent to 

1.5 percent (table 1).

Suspended-sediment loads and volume of streamflow 

entering the area that comprised Brewer Lake simulated by 

the HSPF model for scenario 2 were lower than those for the 

current-conditions simulation. Simulated land-use changes 

to those of the conditions in 1949 resulted in a 7.1-percent 

decrease in total streamflow volume (from 113,461 acre-ft 

to 105,420 acre-ft) from all tributaries flowing into the area 

that would be encompassed by Brewer Lake, had it existed, 

for the calibration period (July 8, 2009–September 30, 2012) 

and a 20.5-percent decrease in suspended-sediment load 

(from 7,645 tons/year to 6,079 tons/year) for the calibration 

period from all tributaries flowing into the same area 

(figs. 10–11). Once again, these decreases are likely a result of 

increased forested land, which results in greater precipitation 

interception by the vegetative canopy and increased 

infiltration because of undisturbed conditions, that is, no 

anthropogenically created impervious areas. Additionally, 

average daily mean streamflow and average spring and 

summer streamflows were less than streamflows associated 

with the 2006 land use. The average daily mean streamflow 

for the effective and peak bankfull streamflows decreased 

slightly, and the number of stormflow values (number of days 

streamflow exceeded 315 ft3/s) decreased from 39 days to 37 

days relative to the current-conditions simulation. For scenario 

2, average suspended-sediment loads decreased for average 

daily mean streamflow, average daily mean low streamflow 

(10th percentile), and average spring and summer streamflows 

conditions from the current-conditions simulation (table 8).
26 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

laf14-0633_fig12

Cypress Creek

10

43

12

3

49

45

38

50

24

4

44

48

34

46

32 35

39

33

15

20

14

27

8

40

21

19

31

9

23

5

18

16

11

42

26

7

36

29

1

25

17

2

6

47

41

37

13

30

22

28

3

32 37 38

7

11

24

4

54

48

1

19

18

40

13

10

39

55

17

12

14

22

49

33

27

15

29

8

52

36

25

43 44

53

21

31

6

28

34

51

5

20

47

30

50

41

9

23

42 46

2

16

35

26

45

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

Base from U.S. Geological Survey digital data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15 Land use land cover by Arkansas Natural Resources Commission and 

University of Arkansas: Center for Advanced Spatial Technologies, 2009

EXPLANATION

1949 Land use and 

land cover (percentage total is not

100 percent because of rounding)

Deciduous forest (36.2 percent)

Evergreen forest (39.8 percent)

Gravel roads (1.5 percent)

Pasture (22.4 percent)

Stream reach reservoir 

(RCHRES)

Subwatershed boudary

and number

Watershed boundary

49

Figure 12. Land-use types used in scenario 2, a time period with some grazing but before any gas-extraction activities in the 

Cypress Creek watershed, Arkansas.
Simulated Effects of Proposed Gas Extraction Activities on Streamflow and Sedimentation within Cypress Creek Watershed 27

Scenario 3—Simulated Time Period with 

Current Land-Use Conditions and No GasExtraction Activities

Scenario 3 simulated current conditions, but without 

any natural gas-pad land use or related activities; that is, 

simulated the Cypress Creek watershed prior to any natural 

gas development. This was achieved by using land use of the 

current-conditions simulation and removing gas-well pads/

pipelines and surface-water impoundments and associated 

withdrawals. The gas-well pad or surface-water impoundment 

land use was converted to the land use adjacent to the pad or 

impoundment location. For example, if the gas-well pad was 

located in a pasture-type land use, the gas-well pad acreage 

was applied to the pasture acreage (fig. 13; table 1).

Suspended-sediment loads and volume of streamflow 

simulated by the HSPF model for scenario 3 were mostly 

unchanged compared to those for the current-conditions 

simulation. Simulated conversion of pads and surface-water 

impoundments to nearby land uses resulted in a 0.7-percent 

decrease in total streamflow volume (from 113,461 acre-ft 

to 112,613 acre-ft) for all tributaries flowing into Brewer 

Lake for the calibration period and a 0.4-percent increase 

in suspended-sediment load (from 7,645 tons/year to 7,675 

tons/year) from all tributaries flowing into Brewer Lake (figs. 

10–11). The small changes likely are a result of the small landuse change between the current-conditions simulation and 

current conditions, but without any natural gas-pad land use or 

related-activities (pipelines, surface-water impoundments, or 

associated gravel roads) scenario (scenario 3). 

Although there are 35 gas-well pads/pipelines and 

6 surface-water impoundments in the current-conditions 

simulation, the overall land use affected by the gas-well 

pads/pipelines is 0.5 percent of the watershed (table 1), 

and all of the surface-water impoundments are located on 

headwater streams (fig. 4). So, there is little overall effect 

on the volume of streamflow and suspended-sediment load 

within the Cypress Creek watershed for scenario 3. Except 

for an increase in the effective and peak bankfull streamflows 

for scenario 3, all other average daily mean streamflows 

were slightly less than or equal to values for the currentconditions simulation. Except for the average daily mean 

low streamflows (10th percentile), average daily mean 

suspended-sediment loads for the simulated time period with 

current land-use conditions and no gas-extraction activities 

scenario were slightly more or equal to the current-conditions 

simulation values (table 8).
28 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

laf14-0633_fig13

Cypress Creek

Brewer Lake

3

37 32 38

7

11

24

4

54

48

1

19

18

40

13

10

39

55

17

12

14

22

49

33

27

15

29

8

52

36

25

43

44

53

21

31

6

28

34

51

5

20

47

30

50

41

9

23

42 46

2

16

35

26

45

10

43

12

3

49

45

38

50

24

4

44

48

34

46

32 35

39

33

15

20

14

27

8

40

21

19

31

9

23

5

18

16

11

42

26

7

36

29

1

25

17

2

6

47

41

37

13

30

22 28

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

Land use land cover by Arkansas Natural Resources Commission and 

University of Arkansas: Center for Advanced Spatial Technologies, 2009

Base from U.S. Geological Survey digitial data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

EXPLANATION

Stream reach reservoir 

(RCHRES)

Subwatershed boudary

and number

Watershed boundary

2006 Land use and

land cover

Deciduous forest

Evergreen forest

Mixed forest

Pasture

Road

Shrub

Urban

Water

49

Figure 13. Land-use types used in scenario 3, a time period with current conditions but without any gas-extraction activities in 

the Cypress Creek watershed, Arkansas.
Simulated Effects of Proposed Gas Extraction Activities on Streamflow and Sedimentation within Cypress Creek Watershed 29

Scenario 4—Simulated Time Period with 

Current Land-Use Conditions and Increased 

Gas-Extraction Activities

Scenario 4 simulated potential future conditions of 

increased gas-well pad and surface-water impoundment 

activities; that is, simulated conversion of parts of the 

Cypress Creek watershed to include additional gas-well pads/

pipelines and additional surface-water impoundments and 

associated withdrawals (more pads, pipelines, and surfacewater impoundments and associated withdrawals than in 

the current-conditions simulation) to represent a possible 

natural gas full-development condition for the area. A total 

of 98 large gas-well pads (8 acres per pad) were added to the 

Cypress Creek watershed (fig. 14) based on infrastructure 

design that gas-well pads generally are placed at a density 

of approximately 3 pads per section (Southwestern Energy 

Co., written commun., 2013) for a total of 133 gas-well pads 

for the scenario (35 in the current-conditions simulation). 

Additionally, an approximate 475 acres (30 percent of the 

total gas-well pad land use) were also added to the gas-well 

pad land use to account for an increase in gas pipelines within 

the Cypress Creek watershed; furthermore, an additional 

66 acres were added to the gravel roads land use to account 

for increased gravel road acreage associated with increased 

gas activities (table 1). The additional 66 acres consist of 

the relatively short gravel roads connecting the gas pads to 

the already existing gravel roads. A total of 11 additional 

surface-water impoundments were placed within the Cypress 

Creek watershed (fig. 14) based on typical infrastructure 

design that water is not generally piped beyond a 3-mi radius 

(Southwestern Energy Co., written commun., 2011). The 

scenario surface-water impoundments are approximately 

8 acres each and with characteristics that are based on the 

current-conditions simulation surface-water impoundment that 

comprises RCHRES 42 (table 2). This particular RCHRES 

was selected to best represent a “typical” surface-water 

impoundment within the model. The percentage of upstream 

land affected by the addition of scenario surface-water 

impoundments within the Cypress Creek watershed was 

17.5 percent of the total land area.

Water-withdrawal assumptions used for the currentconditions simulation also were used for scenario 4 with 

modifications for potential future conditions of increased 

gas-well pad and surface-water impoundment activities. 

Water was withdrawn from the surface-water impoundments 

at the same rate as that of the current-conditions simulation; 

however, the water was withdrawn from ponds three times per 

year instead of two as was the case for the current-conditions 

simulation (see, “Hydrologic Simulation Program–FORTRAN 

Model Calibration” section). The additional 11 surface-water 

impoundments used for scenario 4 were given the withdrawal 

rate equal to that of RCHRES 42’s withdrawal rate (table 2); 

again, withdrawal occurred three times per year. Additionally, 

water was withdrawn from Cypress Creek for 14 consecutive 

days, three times per year, at the same four locations as in the 

current-conditions simulation and at the same rate (1.39 ft3/s).

Suspended-sediment loading rates simulated by the 

HSPF model for scenario 4 were lower than those for the 

current-conditions simulation; however, streamflow volume 

was higher for scenario 4 than for the current-conditions 

simulation. Simulated land-use changes with increased gaswell pads/pipelines and surface-water impoundments resulted 

in a 1.0-percent increase in total volume of streamflow 

(from 113,461 acre-ft to 114,566 acre-ft) from all tributaries 

flowing into Brewer Lake for the calibration period (July 8, 

2009–September 30, 2012) and a 13.3-percent decrease in 

suspended-sediment load (from 7,645 tons/year to 6,632 tons/

year) for the calibration period from all tributaries flowing 

into Brewer Lake (figs. 10–11). Even though there was a 

slight increase in volume of streamflow within the Cypress 

Creek watershed, there was a relatively large decrease in 

suspended-sediment load entering the lake. The small increase 

in volume of streamflow is largely because of the increase 

in impervious land-use area associated with the increase of 

gas-well pad land use. Additionally, impoundment watertrapping efficiency increased with the increase in number 

of surface-water impoundments. The average daily mean 

streamflows and summer streamflows increased; however, 

average daily mean effective and peak bankfull streamflows 

(greater than 315 ft3/s) decreased and average daily mean 

low streamflows (10th percentile) remained unchanged. 

Because peak flows decreased, the suspended-sediment 

carrying capacity of the streams also decreased during peak 

flow. Though, average daily mean low streamflows (10th 

percentile) remained unchanged, maximum low streamflows 

increased; suspended-sediment load during low streamflow 

conditions also increased. However, the increase in suspendedsediment loads during low streamflows was not enough to 

offset decreases during times of higher streamflow yielding 

a 13.3-percent decrease in overall suspended-sediment load 

entering Brewer Lake. Average daily mean suspendedsediment load, average daily mean spring suspended-sediment 

load, average daily mean summer suspended-sediment 

load, and average daily mean effective and peak bankfull 

suspended-sediment load all decreased between the currentconditions simulation and the simulation of potential future 

conditions of increased gas-well pad and surface-water 

impoundment activities (table 8).
30 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

Figure 14. Potential future conditions of increased gas-extraction activities for scenario 4 in the Cypress Creek watershed, 

Arkansas.

laf14-0633_fig14

Cypress Creek

Brewer Lake

51

10

43

12

3

49

49

45

38

50

24

4

44

48

34

46

32 35

39

33

15

20

14

27

8

40

21

19

31

9

23

5

18

16

11

42

26

7

36

29

1

25

17

2

6

47

41

37

13

30

22

28

3

37 32

38

7

11

24

4

54

48

1

19

18

40

13

10

39

55

17

12

14

22

49

33

27

15

29

8

52

36

25

43 44

53

21

31

6

28

34

51

5

20

47

30

50

41

9

23

46

42

2

16

35

26

45

36'

92°34'

92°38'

35°20'

16'

35°14'

18'

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

Base from U.S. Geological Survey digital data, 2008, 1:24,000

Universal Transverse Mercator projection, zone 15

EXPLANATION

Existing gas-well pads

Scenario 4 gas-well surface-water 

impoundments

Scenario 4 gas-well pads

Stream reach reservoir 

(RCHRES)

Subwatershed boundary

and number

Watershed boundary
Implications of the Four Scenarios Modeled for the Cypress Creek Watershed 31

Although there were an additional 11 surface-water 

impoundments added to scenario 4, most were placed at 

headwaters of small tributaries, upstream from most of 

the scenario pads (fig. 14). Though suspended sediment 

from gas-well pads was captured by these surface-water 

impoundments, the primary cause of decreased suspended 

sediment is attributed to one surface-water impoundment in 

particular, located in the central part of the watershed (fig. 14, 

subbasin 13). This particular surface-water impoundment 

captures the streamflow and suspended sediment from 

11 subbasins (totaling approximately 2,482 acres) and 13 

of the additional gas-well pads. Removing this surfacewater impoundment caused the average sediment load for 

the calibration period (July 8, 2009–September 30, 2012) to 

increase from 18.1 tons/day to 20.2 tons/day; the currentconditions simulation average sediment load was 20.9 tons/

day (table 8). Additionally, the largest change in streamflow 

with the removal of the centrally located surface-water 

impoundment occurred for the daily mean low streamflow 

(10th percentile). The maximum daily mean low streamflow 

decreased from 0.1 ft3/s with the surface-water impoundment 

to 0.08 ft3/s without the surface-water impoundment; the 

current-conditions simulation maximum daily mean low 

streamflow was 0.07 ft3/s (table 8).

Implications of the Four Scenarios 

Modeled for the Cypress Creek 

Watershed

The addition of gas-well pads/pipelines has been shown 

to have an effect on suspended sediment only immediately 

after construction; sedimentation will naturally decline as 

the site around the gas-well pad becomes revegetated and 

the readily available sediment supply diminishes (Williams 

and others, 2008). Within the Cypress Creek watershed, 

the overall area affected by the land-use change for the 

addition of gas-well pads/pipelines and associated gravel 

roads (approximately 1,315 acres out of approximately 

22,859 acres for scenario 4) is relatively minimal. The 

construction of additional surface-water impoundments also 

has varying effects on the hydrology of the system. The 

addition of surface-water impoundments within the Cypress 

Creek watershed caused the peak stormflow magnitude to 

decrease and summer low flows to increase, albeit, ever so 

slightly. Additionally, surface-water impoundments within the 

watershed tend to trap much of the surface-erosion sediment 

from various land-use activities. Although the model does 

not capture sediment loading or hydrologic effects at small, 

localized scales, a large source of sediment loading within the 

Cypress Creek watershed is potentially from agricultural and 

gravel road sources. 

Graphical representations of the various scenario 

outcomes reflect the effects of land-use changes on streamflow 

volume and suspended-sediment load for the Cypress Creek 

watershed (figs. 10–11). Dominant changes in land use 

prior to any natural gas development were primarily related 

to clearing of land because of growing pastoral activity 

(scenario 2). Scenario 1 (a completely forested scenario) 

resulted in a streamflow volume of 97,660 acre-ft of water, 

additional land clearing predominantly for pastoral purposes 

(scenario 2), resulted in a streamflow volume of 105,420 

acre-ft, an increase of 7.9 percent relative to scenario 1. The 

removal of existing gas-well pads/pipelines and surface-water 

impoundments from the current conditions scenario for the 

scenario 3 simulation resulted in a decrease of 848 acre-ft of 

streamflow volume, or a decrease of 0.7 percent. As mentioned 

above, surface-water impoundments tend to trap much of the 

surface-erosion sediment from various land-use activities 

in the watershed. Although suspended sediment was noted 

to increase with the transition from scenario 1 (completely 

forested) to scenario 3 (current conditions without natural-gas 

activities) by an increase of 3,339 tons/year (77.0 percent), 

the surface-water impoundments (scenario 4) resulted in an 

overall decrease in suspended-sediment load (from 7,675 tons/

year for scenario 3 to 6,632 tons/year of suspended sediment 

for scenario 4, a 13.6-percent decrease in suspended sediment) 

even with additional gas-well pads/pipelines. The modeled 

scenario for projected increase in gas-well pad/pipelines 

and surface-water impoundments had little overall effect on 

streamflow volume. However, it is possible for there to be 

areas where suspended-sediment loading increased, but these 

increases may not be apparent because of the model scale 

and approach. For example, suspended-sediment loads could 

increase immediately downstream from gravel roads, gas-well 

pads, or pipeline crossings. 

Changes in water quality also can occur with the changes 

in flow regime. For larger surface-water impoundments, 

Batalla and others (2004) have shown that altered flows can 

influence oxygen concentrations, temperature, suspended 

solids, and cycling of organic matter and other nutrients, 

as well as having direct impacts on biota. Furthermore, 

the surface-water impoundments act as traps for additional 

suspended sediment and sediment-associated constituents 

that would otherwise be transported downstream (Foster 

and others, 2012). 

Because of the high sediment-loading rates associated 

with gravel roads and the large amount of pasture within the 

watershed (tables 1 and 5), the factors most responsible for 

most of the suspended sediment within the Cypress Creek 

watershed are likely associated more with the pastureland 

and gravel roads, than factors associated with gas-well pads/

pipelines. Compared to forest land use, ratios of gully erosion 

to sheet erosion are higher in areas of agricultural land use 

(Missouri Department of Conservation, 2013). Furthermore, 

gravel roads can be a primary source of suspended sediment in 
32 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

a wide range of forested areas, and in a land use where natural 

erosion rates tend to be very slow, gravel roads in forested 

land have higher erosion rates and disrupt geomorphologic 

and hydrologic processes (Ramos-Scharrón and MacDonald, 

2005). Within the Cypress Creek watershed, the amount of 

land disturbed for the simulated potential future conditions 

of increased gas-well pad and surface water-impoundment 

activities was minimal, and the resulting effects were also 

minimal, based on the parameters and assumptions used in 

the HSPF model. The addition of gas-well pads/pipelines and 

associated gravel road for scenario 4 resulted in 6.9 percent 

of the total land area being disturbed. However, most of 

this “disturbed” 6.9 percent area was converted from the 

already “disturbed” pastureland use. The Arkansas Natural 

Resources Commission (2013) and the Arkansas Department 

of Environmental Quality (2008) list sediment from “poor 

pastures” as a primary concern related to nonpoint-source 

pollution in north-central Arkansas, and unpaved roads are 

another major source of sediment. The initial Nonpoint Source 

Pollution Assessment for Arkansas together with updates in 

1990 and again in 1997 indicated agricultural activities as 

a major source of waterbody impairment (for sediment) in 

the State (Arkansas Department of Environmental Quality, 

2008). In Arkansas, approximately 88 percent of rural 

roads are unpaved (Arkansas Department of Environmental 

Quality, 2008). Because of these major sources of suspended 

sediment and resultant changes in streamflow from cleared 

land, conversion of land associated with these particular types 

of land use suggests that, in regards to suspended sediment, 

gravel roads and pasture may be of equal or greater concern 

than construction of gas-well pads/pipelines for the Cypress 

Creek watershed.

Summary

Cypress Creek is located in central Arkansas and is the 

main tributary to Brewer Lake, which serves as the primary 

water supply for Conway, Arkansas. A model of the Cypress 

Creek watershed was developed and calibrated in cooperation 

with Southwestern Energy Company using detailed 

precipitation, streamflow, and discrete suspended-sediment 

data collected from 2009 through 2012. These data were used 

in conjunction with the Hydrologic Simulation Program—

FORTRAN model to address different potential gas-extraction 

activities within the Cypress Creek watershed. 

The calibrated Hydrologic Simulation Program—

FORTRAN model was used to simulate four land-use 

scenarios and examine the potential effects of these land-use 

changes on suspended sediment within the Cypress Creek 

watershed. These simulated scenarios included (1) the 

conversion of all nonforested land to forest, representing a 

time period before extensive grazing activities and no gasextraction activities; (2) a land-use change to that of 1949, 

representing a time period with some grazing activities and 

no gas-extraction activities; (3) a time period with current 

land-use conditions but without any gas-extraction activities, 

that is, the exclusion of gas-well pads/pipelines, associated 

gravel roads, and surface-water impoundments; and (4) a time 

period with current land-use condition but with increased 

gas-extraction activities to include an increased number of 

gas-well pads (from 35 in the current-conditions simulation to 

133 for scenario 4), pipelines, and surface-water impoundment 

activities (from 6 in the current-conditions simulation to 17 

for scenario 4) to represent a possible future natural gas fulldevelopment condition for the Cypress Creek watershed. 

The current conditions-simulation within the Cypress 

Creek watershed used the 2006 land use, which consisted 

primarily of forest and pasture, as well as the current 

(2012) 35 gas-well pads/pipelines and 6 large gas-well 

surface-water impoundments that compose approximately 

1.6 percent of the land use. Simulating a time period before 

extensive-grazing activities and no gas-extraction activities 

for scenario 1 resulted in a decrease in suspended-sediment 

loads and volume of streamflow within the Cypress Creek 

watershed, compared to the current-conditions simulation. 

Simulating a time period before any gas-extraction activities 

but with some grazing activities for scenario 2 also resulted 

in a decrease in suspended-sediment loads and volume of 

streamflow within the Cypress Creek watershed compared 

to the current-conditions simulation. These decreases are 

likely a result of increased forested land, which results in 

greater precipitation interception by the vegetative canopy 

and increased infiltration because of undisturbed conditions, 

that is, no anthropogenically created impervious areas. 

Simulating current conditions, but without any natural 

gas-well pad land use or related activities for scenario 3, 

resulted in mostly unchanged suspended-sediment loads and 

volume of streamflow within the Cypress Creek watershed, 

as compared to the current-conditions simulation. The overall 

land use affected by the gas-well pads and pipelines for the 

current-conditions scenario is 0.5 percent of the watershed, 

and all of the surface-water impoundments are located on 

headwater streams, so there is little overall effect on the 

volume of streamflow and suspended-sediment load within 

the Cypress Creek watershed when these features are removed 

for scenario 3. Finally, simulating potential future conditions 

of increased gas-well pad and surface-water impoundment 

activities for scenario 4 resulted in a decrease in suspendedsediment loads and a slight increase of volume of streamflow 

within the Cypress Creek watershed. The small increase in 

volume of streamflow is largely because of the increase in 

impervious land-use area associated with the increase of gaswell pad land use. Even though there was a slight increase in 

volume of streamflow within the Cypress Creek watershed, 

there was a relatively large decrease in suspended-sediment 

load entering the lake. The decrease in suspended-sediment 

loads was because of an increase in the water-trapping 

efficiency with the increase in number of surface-water 
References 33

impoundments. However, the calibrated Hydrologic 

Simulation Program—FORTRAN model does not capture 

effects at small, localized scales, for example, the sediment 

load in a stream immediately downstream from a gravel road, 

gas-well pad, or pipeline crossing. 

The Arkansas Natural Resources Commission and 

the Arkansas Department of Environmental Quality list 

sediment from “poor pastures” as a primary concern related 

to nonpoint-source pollution in north-central Arkansas. The 

initial Nonpoint Source Pollution Assessment for Arkansas 

lists agricultural activities as a major source of waterbody 

impairment (for sediment) in the State. Other sources 

of surface erosion are unpaved roads, in which the main 

constituent is sediment. Because of the high sediment-loading 

rates associated with gravel roads and the large amount of 

pasture within the watershed, the factors most responsible for 

suspended sediment within the Cypress Creek watershed are 

likely associated more with the pastureland and gravel roads, 

than factors associated with gas-well pads/pipelines.

References

Al-Abed, N.A., and Whiteley, H.R., 2002, Calibration of the 

Hydrologic Simulation Program Fortran (HSPF) model 

using automatic calibration and geographical information 

systems: Hydrological Processes, v. 16, p. 3169–3188.

Arkansas Department of Environmental Quality, 2008, 

Integrated monitoring and assessment report: Arkansas 

Department of Environmental Quality, variously paginated.

Arkansas Geological Survey, 2012, Stratigraphic summary 

of the Arkansas River Valley and Ouachita Mountains: 

Arkansas Geological Survey, accessed October 19, 2012, 

at http://www.geology.ar.gov/geology/strat_arkvalley_

ouachita.htm.

Arkansas Natural Resources Commission and University of 

Arkansas: Center for Advanced Spatial Technologies, 2009, 

2006 Arkansas land use/land cover, accessed March 13, 

2009, at http://www.cast.uark.edu/home/research/geomatics/

remote-sensing/arkansas-land-useland-cover.html.

Arkansas Natural Resources Commission, 2013, Nonpoint 

source pollution management program: accessed February 

25, 2013, at http://anrc.ark.org/divisions/water-resourcesmanagement/nonpoint-pollution/.

Batalla, J.R., Gomez, C.M., and Kondolf, G.M., 2004, 

Reservoir-induced hydrological changes in the Ebro 

River Basin (NE Spain): Journal of Hydrology, v. 290, 

p. 117–136.

Bicknell, B.R., Imhoff, J.C., Kittle, J.L., Jr., Jobes, T.H., 

Donigian, A.S., Jr., 2001, Hydrologic Simulation Program—

FORTRAN, user’s manual for version 12: Research 

Triangle Park, N.C., U.S. Environmental Protection Agency, 

National Exposure Research Laboratory, Office of Research 

and Development, 845 p.

Brenton, R.W., and Arnett, T.L., 1993, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory; determination of dissolved organic carbon 

by UV-promoted persulfate oxidation and infrared 

spectrometry: U.S. Geological Survey Open-File 

Report 92–480, 12 p.

Bureau of Land Management, 2006, Resource management 

plan amendment and environmental impact statement, 

Glenwood Springs Field Office, Roan Plateau Planning 

Area: Department of the Interior, Bureau of Land 

Management, variously paginated.

Childress, C.J.O., Foreman, W.T., Conner, B.F., and Maloney, 

T.J., 1999, New reporting procedures based on longterm method detection levels and some considerations of 

water-quality data provided by the U.S. Geological Survey 

National Water Quality Laboratory: U.S. Geological Survey 

Open-File Report 99–193, 19 p.

Cohn, T.A., 1988, Adjusted maximum likelihood estimation of 

the moments of lognormal populations from type 1 censored 

samples: U.S. Geological Survey Open-File Report 88–350, 

34 p.

Cohn, T.A., DeLong, L.L., Gilroy, E.J., Hirsch, R.M., and 

Wells, D.K., 1989, Estimating constituent loads: Water 

Resources Research, v. 2, no. 5, p. 937–942.

Cohn, T.A., Gilroy, E.J., and Baier, W.G., 1992, Estimating 

fluvial transport of trace constituents using a regression 

model with data subject to censoring: Proceedings of the 

Joint Statistical Meeting, Boston, Mass., August 9–13, 

1992, p. 142–151.

Conway Corporation, 2012, James H. Brewer Lake, accessed 

October 16, 2012, at http://www.conwaycorp.com/About/

History/BrewerLake.aspx.

Crawford, C.G., 1991, Estimation of suspended-sediment 

rating curves and mean suspended-sediment loads: Journal 

of Hydrology, v. 129, p. 331–348.

Dempster, A.P., Laird, N.M., and Rubin, D.B., 1977, 

Maximum likelihood from incomplete data via the EM 

algorithm: Journal of the Royal Statistical Society, series B, 

v. 39, no. 1, p. 1–38.
34 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

Donigian, A.S., Jr., 2000, HSPF training workshop handbook 

and CD, lecture #19—Calibration and verification 

issues, slide #L19–22: Environmental Protection Agency 

Headquarters, Washington Information Center, January, 

10–14, 2000, presented and prepared for U.S. EPA, Office 

of Water, Office of Science and Technology, Washington, 

D.C.

Donigian, A.S., Jr., and Crawford, N.H., 1977, Simulation of 

nutrient loadings in surface runoff with the NPS model: 

U.S. Environmental Protection Agency Ecological Research 

Series EPA–600/3–77–065, 110 p.

Donigian, A.S., Jr., and Davis, H.H., 1978, User’s manual 

for Agricultural Runoff Management (ARM) model: U.S. 

Environmental Protection Agency Report EPA–600/3–78–

080, 163 p.

Donigian, A.S., Jr., Imhoff, J.C., Bicknell, B.R., and Kittle, 

J.L., Jr., 1984, Application guide for Hydrological 

Simulation Program—FORTRAN (HSPF): Environmental 

Protection Agency Environmental Research Laboratory, 

EPA-600/3-84-065, 177 p.

Donigian, A.S., Jr., and Love, J.T., 2003, Sediment calibration 

procedures and guidelines for watershed modeling: 

Chicago, Illinois, WEF TMDL 2003, November 16–19, 

2003.

Edwards, T.K., and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. C2, 89 p.

Fenneman, N.M., and Johnson, D.W., 1946, Physical divisions 

of the United States (map): Washington, D.C., U.S. 

Geological Survey.

Fishman, M.J., ed., 1993, Field methods of analysis by the 

U.S. Geological Survey National Water Quality Laboratory; 

determination of inorganic and organic constituents in water 

and fluvial sediments: U.S. Geological Survey Open-File 

Report 93–125, 217 p.

Foster, G.M., Lee, C.J., and Ziegler, A.C., 2012, Sediment 

transport to and from small impoundments in northeast 

Kansas, March 2009 through September 2011: U.S. 

Geological Survey Scientific Investigations Report 2012–

5269, 38 p.

Foti, T.L., and Glenn, S.M., 1990, The Ouachita Mountain 

landscape at the time of settlement: Morrilton, Arkansas, 

Winrock International, Conference on Restoring Old 

Growth Forests in the Interior Highlands of Arkansas and 

Oklahoma, September 19–20, 1990.

Gilroy, E.J., Hirsch, R.M., and Cohn, T.A., 1990, Mean square 

error of regression-based constituent transport estimates: 

Water Resources Research, v. 26, no. 9, p. 2069–2077.

Greene, D.G., and Hudlow, M.D., 1982, Hydrometeorologic 

grid mapping procedures, in Johnson, A.I., and Clark, 

R.A., American Water Resources Association International 

Symposium on Hydrometeorology, Proceedings: Denver, 

Colorado, June 13–17, 1982, 20 p.

Gupta, H.V., Sorooshian S., and Yapo P.O., 1999, Status of 

automatic calibration for hydrologic models: Comparison 

with multilevel expert calibration: Journal of Hydrologic 

Engineering, v. 4, no. 2, p. 135–143.

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p.

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources: U. S. Geological Survey Techniques of 

Water-Resource Investigations, book 4, chap. A3, 523 p.

Hummel, P., Kittle, J., and Gray, M., 2001, WDMUtil, version 

2.0—A tool for managing watershed modeling time-series 

data: U.S. Environmental Protection Agency Contract 

No. 68–C–98–010, 157 p.

Likes, Jiri, 1980, Variance of the MVUE for lognormal 

variance: Technometrics, v. 22, no. 2, p. 253–258.

Maryland Department of the Environment, 2006, 

Maryland’s 2006 TMDL implementation guidance for 

local governments: Baltimore, Maryland, The Maryland 

Department of the Environment, accessed February 20, 

2013, at http://www.mde.state.md.us/programs/Water/

TMDL/TMDLImplementation/Documents/www.mde.state.

md.us/assets/document/final_TMDL_Implementation_

Guidance_for_LG.pdf.

Missouri Department of Conservation, 2013, Water quality: 

mdconline, accessed February 21, 2013, at http://mdc.

mo.gov/landwater-care/stream-and-watershed-management/

missouri-watersheds/south-grand-river/water-quality.

Moore, Keara, and Mohamoud, Yusuf, 2007, Two automated 

methods for creating hydraulic function tables (FTABLES): 

U.S. Environmental Protection Agency BASINS Technical 

Note 2, 14 p.

Moriasi, D.N., Arnold, J.G., VanLiew, M.W., Bingner, R.L., 

Hrmel, R.D., and Veith, T.L., 2007, Model evaluation 

guidelines for systematic quantification of accuracy in 

watershed simulations: American Society of Agricultural 

and Biological Engineers, v. 50, no. 3, p. 885–900.
References 35

National Oceanic and Atmospheric Administration, 2002, 

About the stage III data: Distributed Model Intercomparison 

Project, accessed January 26, 2012, at http://www.nws.noaa.

gov/oh/hrl/dmip/stageiii_info.htm.

National Oceanic and Atmospheric Administration, 2008, 

Archive of River Forecast Center operational NEXRAD 

data: NOAA Hydrologic Data System Group, accessed 

January 26, 2012, at http://dipper.nws.noaa.gov/hdsb/data/

nexrad/nexrad.html.

National Oceanic and Atmospheric Administration, 2010, 

ABRFC precipitation processing: National Weather Service 

River Forecast Center: accessed January 26, 2012, at http://

www.srh.noaa.gov/abrfc/?n=pcpn_methods.

National Oceanic and Atmospheric Administration, 2012a, 

Climate data online: NOAA National Climatic Data Center, 

accessed July 26, 2012, at http://www.ncdc.noaa.gov/cdoweb/.

National Oceanic and Atmospheric Administration, 2012b, 

Multi-sensor precipitation reanalysis: National Climatic 

Data Center, accessed January 26, 2012, at http://www.ncdc.

noaa.gov/oa/rsad/mpr.html.

Ockerman, D.J., and Heitmuller, F.T., 2010, Simulation of 

streamflow and suspended-sediment concentrations and 

loads in the lower Nueces River watershed, downstream 

from Lake Corpus Christi to the Nueces Estuary, South 

Texas, 1958–2008: U.S. Geological Survey Scientific 

Investigations Report 2010–5194, 50 p. 

Ockerman, D.J., and Roussel, M.C., 2009, Simulation of 

streamflow and water quality in the Leon Creek watershed, 

Bexar County, Texas, 1997–2004: U.S. Geological Survey 

Scientific Investigations Report 2009–5191, 50 p.

Ramos-Scharrón, C.E., and MacDonald, L.H., 2005, 

Measurement and prediction of sediment production from 

unpaved roads, St. John, US Virgin Islands: Earth Surface 

Processes and Landforms v. 30, p. 1283–1304.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow—Volume 1, Measurement of stage 

and discharge: U.S. Geological Survey Water-Supply 

Paper 2175, 284 p.

Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load 

estimator (LOADEST)—A FORTRAN program for 

estimating constituent loads in streams and rivers: U.S. 

Geological Survey Techniques and Methods, book 4, chap. 

A5, accessed July 2010, at http://pubs.er.usgs.gov/usgspubs/

tm/tm4A5.

Ryu, J.H., 2009, Application of HSPF to the distributed 

model intercomparison project—Case study: Journal of 

Hydrologic Engineering, v. 14, no. 8, p. 847–857.

Scoles, S., Anderson, S. Turton, D., and Miller, E., 2001, 

Forestry and water quality, A review of watershed 

research in the Ouachita Mountains: Stillwater, Oklahoma, 

Oklahoma State University, Oklahoma Cooperative 

Extension Service, Water-Quality Series Circular E–932, 

29 p.

Shedd, R.C., and Fulton, R.A., 1993, WSR–88D Precipitation 

processing and its use in National Weather Service 

hydrologic forecasting, in Engineering Hydrology, 

Proceedings of the Symposium, San Francisco, Calif., 

July 25–30, 1993: Proceedings, Hydraulics Division of the 

American Society of Civil Engineers.

Skahill, B.E., 2004, Use of the Hydrological Simulation 

Program—FORTRAN (HSPF) model for watershed studies: 

System-wide Modeling, Assessment, and Restoration 

Technologies, ERDC/TN SMART-04-1 September 2004, 

26 p.

Skahill, B.E., and Doherty, J., 2006, Efficient accommodation 

of local minima in watershed model calibration: Journal of 

Hydrology, v. 329, p. 122–139.

Soong, D.T., Straub, T.D., and Murphy, E.A., 2005, 

Continuous hydrologic simulation and flood-frequency, 

hydraulic, and flood-hazard analysis of the Blackberry 

Creek watershed, Kane County, Illinois: U.S. Geological 

Survey Scientific Investigations Report 2005–5270, 66 p.

Tetra Tech, Inc., 2004, Translation of SET loading estimates to 

Upper Neuse performance targets: Research Triangle Park, 

N.C., Tetra Tech, Inc., Memorandum dated February 19, 

2004.

U.S. Army Corps of Engineers, 1994, Flood-runoff analysis: 

U.S. Army Corps of Engineers Engineering Manual, 

EM 1110–2–1417, 214 p.

U.S. Army Corps of Engineers, 2002, Conway water supply 

study city of Conway, Arkansas: Section 22, Water 

Resource Development Act of 1974, July 2002, 35 p.

U.S. Department of Agriculture, 2012a, Official soil series 

descriptions: USDA-NRCS Soil Survey Division, accessed 

on September 4, 2012, at https://soilseries.sc.egov.usda.gov/

osdlist.asp.

U.S. Department of Agriculture, 2012b, Soil Survey 

Geographic (SSURGO) database: National Resources 

Conservation Service, accessed February 1, 2012, at http://

datagateway.nrcs.usda.gov/GDGOrder.aspx.
36 Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas

U.S. Environmental Protection Agency, 1999, Preliminary data 

summary of urban stormwater best management practices: 

Office of Water EPA–821–R–99–012.

U.S. Environmental Protection Agency, 2003, BASINS 

(Better Assessment Science Integrating Point and Nonpoint 

sources), accessed March 28, 2009, at http://www.epa.gov/

waterscience/basins/.

U.S. Geological Survey, 2011, National elevation dataset, 

accessed November 4, 2011, at http://ned.usgs.gov/.

U.S. Geological Survey, 2012a, National hydrogaphy dataset, 

accessed September 4, 2012, at http://nhd.usgs.gov/.

U.S. Geological Survey, 2012b, USGS water data for the 

Nation, accessed November 27, 2012, at http://waterdata.

usgs.gov/nwis.

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A9, available online at http://pubs.water.

usgs.gov/twri9A.

Wershaw, R.L., Fishman, M.J., Grabbe, R.R., and Lowe, 

L.E., eds., 1987, Methods for the determination of organic 

substances in water and fluvial sediments: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 5, chap. A3, 80 p.

Wilde, F.D., and Radke, D.B., 1998, Field measurements: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6, variously paginated.

Wilde, F.D., Radke, D.B., Gibs, Jacob, Iwatsubo, R.T., 1998a, 

Preparations for water sampling: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chap. A1, variously paginated.

Wilde, F.D., Radke, D.B., Gibs, Jacob, Iwatsubo, R.T., 1998b, 

Selection of equipment for water sampling: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A2, variously paginated.

Wilde, F.D., Radke, D.B., Gibs, Jacob, Iwatsubo, R.T., 1998c, 

Cleaning of equipment for water sampling: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A3, variously paginated.

Wilde, F.D., Radke, D.B., Gibs, Jacob, Iwatsubo, R.T., 1999a, 

Collection of water samples: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chap. A4, variously paginated.

Wilde, F.D., Radke, D.B., Gibs, Jacob, Iwatsubo, R.T., 1999b, 

Processing of water samples: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chap. A5, variously paginated.

Williams, H.F.L., Havens, D.L., Banks, K.E., and Wachal, 

D.J., 2008, Field-based monitoring of sediment runoff 

from natural gas well sites in Denton County, Texas, USA: 

Environmental Geology, v. 55, p. 1463–1471.

Wolynetz, M.S., 1979, Algorithm 139—Maximum likelihood 

estimation in a linear model with confined and censored 

data: Applied Statistics, v. 28, p. 195–206.
Publishing support provided by the U.S. Geological Survey 

Publishing Network, Lafayette and Tacoma Publishing Service Centers

For more information concerning the research in this report, contact the 

Director, Arkansas Water Science Center

U.S. Geological Survey 

401 Hardin Road

Little Rock, Arkansas 72211-3528 
Hart, R.M.— Simulated Effects on Streamflow and Suspended Sediment, Cypress Creek Watershed, Arkansas—Scientific Investigations Report 2014–5057, ver. 1.1

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20145057