Prepared in cooperation with the

Arkansas Game and Fish Commission

SIMULATION OF HYDRODYNAMICS, TEMPERATURE, 

AND DISSOLVED OXYGEN IN BULL SHOALS LAKE, 

ARKANSAS, 1994-1995

Water-Resources Investigations Report 03-4077

U.S. Department of the Interior

U.S. Geological Survey
SIMULATION OF HYDRODYNAMICS, TEMPERATURE, 

AND DISSOLVED OXYGEN IN BULL SHOALS LAKE, 

ARKANSAS, 1994-1995

By Joel M. Galloway and W. Reed Green

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 03-4077

Prepared in cooperation with the

Arkansas Game and Fish Commission

Little Rock, Arkansas

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey, WRD Branch of Information Services

401 Hardin Road Box 25286

Little Rock, Arkansas 72211 Denver Federal Center

Denver, Colorado 80225

The use of firm, trade, and brand names in this report is for identification purposes only and 

does not constitute endorsement by the U.S. Geological Survey.
Contents III

CONTENTS

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

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

Purpose...................................................................................................................................................... 3

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

Acknowledgments..................................................................................................................................... 3

Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake .............................. 3

Model Implementation.............................................................................................................................. 3

Computational Grid ......................................................................................................................... 4

Boundary and Initial Conditions...................................................................................................... 6

Hydraulic and Thermal Boundary Conditions........................................................................ 6

Chemical Boundary Conditions.............................................................................................. 9

Initial Conditions .................................................................................................................... 9

Model Parameters ............................................................................................................................ 9

Other Model Options ....................................................................................................................... 9

Model Calibration ...................................................................................................................................12

Hydrodynamics and Temperature ..................................................................................................12

Dissolved Oxygen..........................................................................................................................14

Sensitivity Analysis .......................................................................................................................18

Model Applications.................................................................................................................................19

Summary ..........................................................................................................................................................23

References........................................................................................................................................................24

ILLUSTRATIONS

Figure 1. Map showing location of Bull Shoals Lake and the White River Basin in Arkansas and

Missouri........................................................................................................................................ 2

2. Plot showing idealized model segments, layers, and branches for the CE-QUAL-W2

reservoir model............................................................................................................................. 4

3. Plot showing side view, top view, and face view from the dam of the computational grid

of Bull Shoals Lake used in CE-QUAL-W2................................................................................ 5

4-23. Graphs showing:

4. Relation between water-surface elevation and volume and water-surface elevation and

surface area in Bull Shoals Lake .................................................................................................. 6

5. Annual mean streamflow for the White River near Branson, Missouri, upstream from

Bull Shoals Lake, 1952-1995 ....................................................................................................... 7

6. Daily inflow and hourly dam outflow for Bull Shoals Lake, January 1994 through

December 1995 ............................................................................................................................ 8

7. Simulated and measured water-surface elevations near the Bull Shoals Lake dam,

January through December 1994 and January through December 1995....................................12

8. Relation between simulated and measured water temperatures in the water column near

the Bull Shoals Lake dam, January through December 1994 ....................................................13
IV Contents

9. Relation of difference between simulated and measured water temperatures near the 

Bull Shoals Lake dam to measured water temperature, sampling date, and water depth,

January through December 1994 ............................................................................................... 14

10. Relation between simulated and measured water temperatures in the water column

near the Bull Shoals Lake dam, January through December 1995............................................ 15

11. Relation of difference between simulated and measured water temperatures near the Bull

Shoals Lake dam to measured water temperature, sampling date, and water depth,

January through December 1995 ............................................................................................... 15

12. Relation between simulated and measured dissolved-oxygen concentrations in the water

column near the Bull Shoals Lake dam, January through December 1994............................... 16

13. Relation of difference between simulated and measured dissolved-oxygen concentrations near

Bull Shoals Lake dam to measured dissolved-oxygen concentrations, sampling date, and water 

depth, January through December 1994 .................................................................................... 17

14. Relation between simulated and measured dissolved-oxygen concentrations in the water column

near the Bull Shoals Lake dam, January through December 1995............................................ 17

15. Relation of difference between simulated and measured dissolved-oxygen concentrations

near Bull Shoals Lake dam to measured dissolved-oxygen concentrations, sampling date, and

water depth, January through December 1995 .......................................................................... 18

16. Vertical temperature distributions near the Bull Shoals Lake dam on July 7, 1994 and

January 20, 1995, showing calibrated model profiles and profiles as a result of

differing model parameters........................................................................................................ 19

17. Vertical dissolved-oxygen concentration distributions near the Bull Shoals Lake dam on

July 7, 1994, and January 20, 1995, showing calibrated model profiles and profiles as a

result of differing model parameters.......................................................................................... 20

18. Simulated water-surface elevations resulting from increased minimum flow scenarios ............. 20

19. Relation of difference between water-surface elevations predicted from increased

minimum flow scenarios and calibrated model water-surface elevation with time................... 21

20. Simulated water temperature differences between increased minimum flow scenarios

and the calibrated model ............................................................................................................ 21

21. Simulated and estimated water temperatures in Bull Shoals Lake outflow and measured

temperatures downstream from Bull Shoals Lake dam ............................................................. 21

22. Simulated dissolved-oxygen concentration differences between increased minimum

flow scenarios and calibrated model.......................................................................................... 22

23. Simulated and estimated dissolved-oxygen concentrations in Bull Shoals Lake

outflows ..................................................................................................................................... 22

TABLES

Table 1. Hydraulic and thermal input parameters specified for Bull Shoals Lake model .............................. 7

2. Rate coefficients used in water-chemistry and biological simulations and other parameters

specified as input in the Bull Shoals Lake model...................................................................... 10
Contents V

Degrees Celsius (° C) may be converted to degree Fahrenheit (° F) by using the following equation:

° F = 1.8(° C) + 32

Degrees Fahrenheit (° F) may be converted to degree Celsius (° C) by using the following equation:

° C = 0.55(° F – 32)

In this report vertical coordinate information is referenced to the National Geodetic Vertical datum of 1929 (NGVD of 1929). 

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

Constituent concentrations in water are in milligrams per liter (mg/L).

CONVERSION FACTORS AND VERTICAL DATUM

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

hectare (ha) 2.471 acre

square meter (m2) 10.76 square foot (ft2)

square kilometer (km2) 0.3861 square mile (mi2)

liter (L) 0.2642 gallon (gal)

cubic meter (m3) 35.31 cubic foot (ft3)

gram (g) 0.03527 ounce (oz)

kilogram (kg) 2.205 pound (lb)
Abstract 1

SIMULATION OF HYDRODYNAMICS, TEMPERATURE, AND 

DISSOLVED OXYGEN IN BULL SHOALS LAKE, ARKANSAS, 

1994-1995

By Joel M. Galloway and W. Reed Green

ABSTRACT

Outflow from Bull Shoals Lake and other White 

River reservoirs supports a cold-water trout fishery of 

substantial economic yield in north-central Arkansas 

and south-central Missouri. The Arkansas Game and 

Fish Commission has requested an increase in existing 

minimum flows through the Bull Shoals Lake dam to 

increase the amount of fishable waters downstream. 

Information is needed to assess the impact of increased 

minimum flows on temperature and dissolved-oxygen 

concentrations of reservoir water and the outflow.

A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model was 

developed and calibrated for Bull Shoals Lake, located 

on the Arkansas-Missouri State line. The model simulates water-surface elevation, heat transport, and dissolved-oxygen dynamics. The model was developed to 

assess the impacts of proposed increases in minimum 

flow from 4.6 cubic meters per second (the existing 

minimum flow) to 22.6 cubic meters per second (the 

increased minimum flow). Simulations included 

assessing the impact of (1) increased minimum flows 

and (2) increased minimum flows with increased initial 

water-surface elevation of 1.5 meters in Bull Shoals 

Lake on outflow temperatures and dissolved-oxygen 

concentrations.

The increased minimum flow simulation (without increasing initial water-surface elevation) increased 

the water temperature and dissolved-oxygen concentration in the outflow. Conversely, the increased minimum flow and increased initial water-surface elevation 

(1.5 meters) simulation decreased outflow water temperature and dissolved-oxygen concentration through 

time. However, results from both scenarios for water 

temperature and dissolved-oxygen concentration were 

within the boundaries of the error between measured 

and simulated water column profile values.

INTRODUCTION

Bull Shoals Lake (fig. 1) is a large, deep-storage 

reservoir located on the White River on the border of 

Arkansas and Missouri. Bull Shoals Lake dam was 

completed in 1951 and operated by the U.S. Army 

Corps of Engineers (USACE) for the purposes of flood 

control and hydroelectric power. In addition to aforementioned uses, the reservoir is used for fish and wildlife habitat, recreation, and water supply. The outflows 

from Bull Shoals Lake, and other White River reservoirs, also support a cold-water trout fishery of substantial economic yield in north-central Arkansas and 

south-central Missouri. The Arkansas Game and Fish 

Commission (AGFC) has requested an increase in minimum flows through Bull Shoals Lake dam to increase 

the amount of fishable waters downstream. Proposed 

changes in reservoir operations, such as increased minimum flows through the dam and increased water storage, have caused concerns about the sustainability of 

cold water temperature and dissolved oxygen in the 

bottom water (hypolimnion) of Bull Shoals Lake. 

Increases in water temperature and decreases in dissolved oxygen could have potential negative impacts 

on the cold-water trout fisheries in the downstream outflow. Comprehensive information is needed to address 

temperature and dissolved-oxygen dynamics of Bull 

Shoals Lake and the effects of increased minimum 

flow.

Bull Shoals Lake is the most downstream in a 

chain of major reservoirs on the White River mainstem. 

Upstream from Bull Shoals are Lake Taneycomo, Table 

Rock Lake, and Beaver Lake. Norfork Lake is located 

downstream on the North Fork River, a tributary to the 

White River (fig. 1). A study was conducted by the U.S. 

Geological Survey (USGS) in cooperation with the 

AGFC to characterize the hydrodynamics, temperature, 

and dissolved-oxygen concentrations in Bull Shoals 

Lake and to simulate the effect of reservoir operations 

on temperature and dissolved-oxygen concentrations in 
2 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

0 10 20 Miles

0 10 20 Kilometers

MISSOURI

ARKANSAS

STUDY

AREA

37o

36o

94o 93o 92o

BEAVER

LAKE

TABLE ROCK

LAKE

LAKE

TANEYCOMO

BULL SHOALS

LAKE

NORFORK

LAKE

Norfork

Flippin Harrison

Branson

Eureka

Springs

Bentonville

White River

White River

14

14

14

14

14

7

76

76

125

125

95

5

5

5

5

95

Ava

Swan

Swan

Creek

Creek

North Fork

Cr

Bear Creek

Hampton

Creek

ite

River

Little Beaver

Beaver

Creek

Creek

Creek

Big

Cowskin

TANEY

OZARK

BOONE

92 30 o 93o

0

0 10

10

20 KILOMETERS

20 MILES

o 36 30’

37 o

EXPLANATION

USGS STREAMFLOW

GAGING STATION

NATIONAL CLIMATIC

DATA CENTER

METEOROLOGIC

STATION

723446

07053500

160

1

MISSOURI

ARKANSAS

Bull Shoals

Lake

Forsyth

Little

W.

Sugerloaf

Cr.

Cr.

Lead

Hill

Sugerloaf

Moccasin Cr.

Shoal Cr.

E.

Spring

S.

BASIN

BOUNDARY

Fk Spring

Fork

Cr

Figure 1. Location of Bull Shoals Lake and the White River Basin in Arkansas and Missouri.
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 3

the reservoir and outflow. A hydrodynamic model of 

Bull Shoals Lake was developed using the USACE CEQUAL-W2 software program (Cole and Buchak, 1995) 

to simulate the expected minimum flow scenarios. This 

study was conducted in conjunction with other studies 

evaluating the impacts of reservoir operations on temperature and dissolved-oxygen concentration in Norfork (Galloway and Green, 2002), Table Rock, and 

Beaver Lakes (Haggard and Green, 2002). These studies will provide a better understanding of the hydroand water-quality dynamics within each reservoir system. In addition, calibrated models developed for these 

studies will provide the basis and framework for future 

water-quality modeling. As more data are collected in 

both the reservoirs and tributaries, the calibrated models can be modified to assess the nutrient assimilative 

capacity of the reservoir, nutrient limitations, and the 

effect of increases in nutrient loading on reservoir 

trophic status.

Purpose

The purpose of this report is to describe a model 

of hydrodynamics, temperature, and dissolved oxygen 

in Bull Shoals Lake for the simulation period of January 1994 through December 1995. Water temperature 

and dissolved-oxygen concentration results from 

model applications simulating two proposed minimum 

flow scenarios are presented and compared to a calibrated, base condition.

Description of Study Area

Bull Shoals Lake was impounded in 1951 on the 

White River, southeast of the city of Branson, Missouri. The primary inflows into Bull Shoals Lake are 

Little North Fork River, Beaver Creek, and the White 

River; several smaller tributaries also flow into the reservoir (fig. 1). The watershed has a drainage area of 

15,675 km2 at the Bull Shoals Lake dam. Bull Shoals 

Lake contains 4,194 million m3 of water at the elevation of the current conservation pool (199.3 m above 

NGVD of 1929) and the surface area is 184 km2

. The 

length of the reservoir is 130 km from the Lake Taneycomo dam to the Bull Shoals Lake dam. The depth of 

the reservoir at the dam at conservation pool elevation 

is about 63 m, and the average depth through the reservoir is 23 m. On average, the hydraulic retention time 

of Bull Shoals Lake is about 0.75 year (Green, 1996). 

Acknowledgments

Edward Buchak and Rajeev Jain of J.E. Edinger 

Associates, Inc., Jerad Bales of the USGS, and Tom 

Cole of the USACE provided valuable guidance on 

model development and applications. John Kielczewski of the USACE provided much of the inflow and 

outflow and water-surface elevation data used to 

develop and calibrate the model. 

SIMULATION OF HYDRODYNAMICS,

TEMPERATURE, AND DISSOLVED

OXYGEN IN BULL SHOALS LAKE

A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model using 

CE-QUAL-W2 was developed for Bull Shoals Lake 

and calibrated based on hydrologic records and vertical 

profiles of temperature and dissolved oxygen measured 

near the Bull Shoals Lake dam from January 1994 

through December 1995. The CE-QUAL-W2 model 

simulates water-surface elevation and vertical and longitudinal gradients in water-quality constituents. The 

model includes routines for temperature, dissolved 

oxygen, and more than 20 other parameters, including 

algae, carbon dioxide, coliform bacteria, detritus, inorganic carbon, iron, labile and refractory dissolved 

organic matter, nitrite plus nitrate as nitrogen, pH, 

phosphorus, sediment, suspended solids, total dissolved solids, and a conservative tracer (Cole and 

Buchak, 1995). Calibration and simulation of waterquality parameters other than water temperature and 

dissolved oxygen, such as nitrogen, phosphorus, algal 

production, and organic matter, are beyond the scope of 

this study. 

Model Implementation

Implementation of the CE-QUAL-W2 model for 

Bull Shoals Lake included development of the computational grid, specification of boundary and initial conditions, and preliminary selection of model parameter 

values. Model development and associated assumptions in the selection of boundary and initial conditions 

are described, and specific values of model parameters 

are given in this section.
4 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Computational Grid

The computational grid is the geometric scheme 

(fig. 2) that numerically represents the space and volume of the reservoir. The model extends 130 km from 

the upstream boundary (Lake Taneycomo dam) to the 

downstream boundary (Bull Shoals Lake dam). The 

grid geometry was developed by digitizing preimpoundment elevation contours of the land surface or 

reservoir bottom from USGS 7.5-minute and 15-

minute quadrangle maps (fig. 3). Sixty-two computational segments exist along the mainstem of the White 

River in Bull Shoals Lake, whereas, 10 segments are in 

the Little North Fork River and 4 segments are in the 

Big Creek and Shoal Creek branches. In addition, five 

other embayments (branches), including Bear Creek, 

West Sugarloaf Creek, East Sugarloaf Creek, Spring 

Creek, and Moccasin Creek, are modeled with three 

computational segments each. Volumes of the smaller 

embayments not included in the computational grid 

were added to associated mainstem segments so that 

reservoir volume was preserved.

Figure 2. Idealized model segments, layers, and branches for the CE-QUAL-W2 reservoir model.
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 5

B.

Penstock

A.

213 2

9

15

23

31

39

46

54

62

70

206

198

190

182

174

166

158

142

150

ELEVATION, IN METERS ABOVE NGVD OF 1929

LAYER NUMBER

136

0 10 20 30 40 50 60 70 80 90 100 110 120 130

DISTANCE FROM DAM, IN KILOMETERS

78

C.

B.

Penstock

Figure 3. Side view (A), top view (B), and face view from the dam (C) of the computational grid of Bull Shoals Lake used in 

CE-QUAL-W2.
6 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Segment geometry varied along the upstreamdownstream gradient (fig. 3). Segment length was based 

in part on segment width. Segments ranged in length 

from 1,208 to 4,446 m, and orientation of the longitudinal axis relative to north was determined for each segment. Segment widths at the reservoir surface ranged 

from 264 m in the headwaters to more than 4,400 m. 

Each segment was divided vertically into 1-m layers. 

Depth from the elevation of the top of the flood-control 

pool to the reservoir bottom ranged from 19 m at the 

upstream boundary to 76 m near Bull Shoals Lake dam. 

Relations between water-surface elevation and volume 

and surface area in the Bull Shoals Lake model grid 

were similar to USACE preimpoundment data (U.S. 

Army Corps of Engineers, 1960) (fig. 4).

Figure 4. Relation between water-surface elevation and 

volume and water-surface elevation and surface area in Bull 

Shoals Lake.

Boundary and Initial Conditions

Hydraulic, thermal, and chemical boundary conditions are required in CE-QUAL-W2. The boundaries 

of the Bull Shoals Lake model included the reservoir 

bottom, the shoreline, tributary streams, the upstream 

boundary (Lake Taneycomo dam), the downstream 

boundary (Bull Shoals Lake dam), and the water-surface 

elevation of the reservoir. Initial water-surface elevation 

of the reservoir, water temperature, and selected waterquality constituent concentrations also are required.

Hydraulic and Thermal Boundary Conditions

The reservoir bottom is assumed to be an immobile and impermeable boundary. That is, the bottom sediments are stationary and not resuspended by flow, and 

ground-water discharge to the reservoir or recharge 

from the reservoir to ground water is negligible. The reservoir bottom extracts energy from water movement by 

causing resistance to water flow; this phenomenon varies with the magnitude of flow. A single, empirical coefficient (Chezy resistance coefficient) is applied to the 

reservoir bottom in all computational segments (table 

1).

Heat exchange between the reservoir bottom and 

the overlying water column is computed from (1) the 

sediment temperature, (2) the simulated temperature of 

the overlying water, and (3) bottom-water heat exchange 

coefficient (table 1). The sediment temperature and the 

exchange coefficient are assumed to be temporally and 

spatially constant. A reasonable estimate of sediment 

temperature is the annual average water temperature 

near the sediment-water interface; a value of 7.0 °C was 

used in the Bull Shoals Lake model. In general, heat 

exchange from the reservoir bottom is about two orders 

of magnitude less than surface heat exchange (Cole and 

Buchak, 1995).

The reservoir shoreline is defined as a boundary 

across which there is no flow. The exact position of the 

shoreline changes during model simulation because of 

changing water-surface elevation. SURFACE AREA, IN MILLION SQUARE METERS

0 100 200 300 400

WATER-SURFACE ELEVATION, IN METERS ABOVE NGVD OF 1929

140

160

180

200

220

240

US ARMY CORPS OF 

ENGINEERS BATHYMETRY

MODEL BATHYMETRY

VOLUME, IN MILLION CUBIC METERS

0 2000 4000 6000 8000 10000

140

160

180

200

220

240

US ARMY CORPS OF 

ENGINEERS BATHYMETRY

MODEL BATHYMETRY

, , , , ,
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 7

Table 1. Hydraulic and thermal input parameters specified for Bull Shoals Lake model

[m0.5/s, meter to the one-half power per second; (watts/m2)/° C, watts per square meter per degree Celsius; ° C, degrees Celsius;

m2/s, square meter per second]

Parameter Computational purpose Value

Constant or

time variable

Chezy resistance

coefficient

Represents turbulent exchange of energy at the 

reservoir bottom

70 m0.5/s Constant

Bottom – water heat 

exchange coefficient

Computes heat exchange between reservoir bottom and overlying water7.0x10-8

(watts/m2)/° C

Constant

Sediment temperature Represents the reservoir bottom (sediment) temperature7.0 ° C Constant

Wind – sheltering

coefficient 

Reduces wind speed to effective wind speed at 

water surface

0.7

(dimensionless)

Constant

Horizontal eddy viscosity Represents laterally averaged longitudinal turbulent exchange of momentum1 m2/s Constant

Horizontal eddy

diffusivity

Represents laterally averaged longitudinal turbulent mixing of mass and heat1 m2/s Constant

Annual streamflow recorded at the USGS 

streamflow-gaging station near Branson, Missouri (station number 07053500; fig. 1), on the White River indicates that inflow to Bull Shoals Lake during the 1994 

and 1995 modeling time period was above average (fig. 

5). Annual mean streamflow for the White River from 

1952 through 1995 ranged from 23.7 to 234.7 m3

/s. 

The average annual mean streamflow for this time 

period was 110.4 m3

/s. Annual mean streamflow for 

the 1994 and 1995 modeling time period was 149.3 and 

149.0 m3

/s, respectively (Reed and others, 1995; 

Hauck and others, 1996, 1997).

Figure 5. Annual mean streamflow for the White River near 

Branson, Missouri, upstream from Bull Shoals Lake, 1952-

1995.

1955 1960 1965 1970 1975 1980 1985 1990 1995

ANNUAL MEAN STREAMFLOW,IN CUBIC METERS PER SECOND

0

50

100

150

200

250

AVERAGE
8 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Daily reservoir inflows used in the model (fig. 6) 

were calculated by the USACE (John Kielczewski, 

U.S. Army Corps of Engineers, written commun., 

1999) based on daily average outflows and changes in 

reservoir water-surface elevations. The daily inflow 

was distributed into one major branch (White River) 

and eight minor branches according to drainage area 

Daily reservoir inflows used in the model (fig. 6) were 

calculated by the USACE (John Kielczewski, U.S. 

Army Corps of Engineers, written commun., 1999) 

based on daily average outflows and changes in reservoir water-surface elevations. The daily inflow was 

distributed into one major branch (White River) and 

eight minor branches according to drainage area size. 

Approximately 70 percent of the inflow was distributed 

to the White River, 23 percent was evenly distributed 

along the reservoir shoreline, and 7 percent was distributed among the eight smaller branches. Total mean reservoir inflow from January 1, 1994, through December 

31, 1995, was estimated to be 208.7 m3

/s, whereas, the 

estimated median reservoir inflow for the same period 

was 162.4 m3/s. The estimated reservoir inflow 

exceeded 514 m3/s 10 percent of the time.

Figure 6. Daily inflow (top) and hourly outflow (bottom) for 

Bull Shoals Lake, January 1994 through December 1995. 

Inflow and outflow data provided by the U.S. Army Corps of 

Engineers.

The downstream boundary for the Bull Shoals 

Lake model consists of the outflow from Bull Shoals 

Lake dam. Hourly outflow data (fig. 6) were calculated 

by the USACE (John Kielczewski, U.S. Army Corps of 

Engineers, written commun., 1999) using stage-discharge relations and hourly power generation records. 

The mean and median reservoir outflow for the modeling period (January 1994 to December 1995) was 210.6 

and 126.6 m3

/s, respectively. The reservoir outflow 

exceeded 597 m3/s 10 percent of the time for the modeling period. The vertical extent and distribution of 

flow in the release zone near the Bull Shoals Lake dam 

(downstream boundary) were simulated using penstock 

(point) dam release flow, the outflow rate, and the simulated density gradient upstream from the dam in the 

reservoir. The release structure was simulated as a 

point release, and the middle of the structure was at an 

elevation of 163 m above NGVD of 1929, model layer 

51 (fig. 3). 

Hydraulic input parameters at the water surface 

included evaporation, wind stress, and surface heat 

exchange. All meteorological data required for these 

computations were measured at Harrison, Arkansas 

(station number 723446, National Climatic Data Center, Asheville, North Carolina; fig. 1), and generally 

were recorded at hourly intervals. Evaporation in the 

model was computed from a time series of water-surface temperatures, dewpoint temperatures, wind 

speeds, surface-layer widths, and length of the segments. Wind stress was computed from a time series of 

wind speeds and directions, the orientation of the computational segment, and a wind-sheltering coefficient 

(table 1). The wind-sheltering coefficient is time variable and reduces the effect of wind on the reservoir 

because of topographic or vegetative sheltering; however, in the Bull Shoals Lake model this coefficient was 

held constant. Surface heat exchange was computed in 

the model from reservoir latitude and longitude, and 

from a time series of measured air temperatures, dewpoint temperatures, cloud covers, and wind speeds and 

directions. In the original meteorological dataset, cloud 

cover was recorded as clear (CLR), scattered (SCT), 

broken (BKN), and overcast (OVC). The model 

requires cloud cover to be entered as a number ranging 

from 0.0 to 10.0. In the Bull Shoals Lake model, cloud 

cover was recorded as: CLR = 0.0, SCT = 1.0, BKN = 

3.6, and OVC = 7.8. The simulated surface-water temperature and loss of heat through evaporation were 

included in the heat budget.

DISCHARGE, IN CUBIC METERS PER SECOND

0

200

400

600

800

1000

1200

1400

1600

1800

Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan 

0

200

400

600

800

1000

1200

1400

1600

INFLOW

OUTFLOW

1994 1995

y t t y

,

,

,

,

,

,

,

,

,
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 9

Chemical Boundary Conditions

A time series of concentrations of selected constituents at all inflow boundaries is required for model 

operation. Boundary data for all tributaries and 

branches included dissolved oxygen, ammonia as 

nitrogen, nitrite plus nitrate as nitrogen, total phosphorus, and a conservative tracer concentrations. Because 

of the small amount of available water-quality data, 

annual average concentrations were estimated based on 

similar values reported from the White River by Evans 

and others (1995) and Porter and others (1996, 1997) 

and used for all inflow boundary constituents except 

dissolved oxygen. Dissolved-oxygen concentrations at 

the inflow boundaries were set to the concentration for 

100 percent saturation for the given water temperature. 

Exchange of dissolved oxygen occurs at the 

water surface of the reservoir and is affected by wind 

speed and direction, water temperature, water-surface 

elevation above NGVD of 1929, and the molecular diffusivity of oxygen gas. Atmospheric nutrient inputs 

were not included in this model, and constituent inputs 

from the reservoir bottom were generally computed 

within the model based on the value of selected parameters (table 2) and the constituent concentrations in the 

overlying waters.

Initial Conditions

Initial water-surface elevation and velocity, temperature, and constituent concentrations for each computational segment are required prior to initiating 

model simulation. Initial water-surface elevation was 

set to the value measured at the Bull Shoals Lake dam 

on January 1, 1994. Initial velocities were assumed to 

be zero. The water was assumed to be isothermal 

throughout the reservoir and equal to the water temperature measured near the dam (10.0 °C). Initial constituent concentrations also were assumed to be uniform 

throughout the reservoir and equal to values measured 

near the dam on December 30, 1993 (Evans and others, 

1995).

Model Parameters

Parameters are used to describe physical and 

chemical processes that are not explicitly modeled and 

to provide chemical kinetic rate information for the 

model. Many parameters cannot be measured directly 

and often are adjusted during the model calibration process until simulated values agree with measured observations.

Most of the relevant hydrodynamic and thermal 

processes are modeled in CE-QUAL-W2; thus, relatively few hydraulic and thermal parameters are adjustable. The horizontal eddy viscosity describes turbulent 

exchange of momentum, and the horizontal eddy diffusivity describes turbulent mixing of mass and heat 

(table 1). Other parameters such as Chezy resistance, 

bottom-water heat exchange, bottom temperature, and 

wind-sheltering coefficients were discussed previously 

(table 1). In general, reservoir models are relatively 

insensitive to changes in the horizontal eddy viscosity 

and diffusivity. However, the thermal processes are relatively sensitive to changes in bottom-heat exchange 

and temperature, and the wind-sheltering coefficient.

Sixty-one chemical and biological rate coefficients and other parameters are required for the application of CE-QUAL-W2 (table 2). Most of the 

parameter values were based on suggestions given in 

the CE-QUAL-W2 manual (Cole and Buchak, 1995), 

and all the parameters are temporally and spatially constant. Some of the parameters have suggested ranges, 

and selected parameters were adjusted, within reasonable limits, until simulated values agreed with measured observations (calibration).

Other Model Options

The maximum computational time step (interval) was limited to 1 hour because the input data were 

sometimes supplied at this interval. The modelselected computational interval generally was about 5 

minutes. Model calculations occurred at time steps 

smaller than the boundary conditions that were provided, and linear interpolation occurred between values 

for all input conditions except meteorological data. The 

meteorological data were assumed to remain constant 

between measured values. The ‘QUICKEST’ numerical scheme (Leonard, 1979) was used for solving the 

transport equations, and a Crank – Nicholson scheme 

(Roache, 1982) was used to solve the vertical advection 

equation.
10 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Table 2. Rate coefficients used in water-chemistry and biological simulations and other parameters specified as input in the 

Bull Shoals Lake model

[m, meters; *, dimensionless; d, day; Q10, temperature correction factor; m/d, meters per day; watts/m2, watts per square meter; oC, degrees Celsius;

(g/m2)/d, grams per square meter per day; BOD, biochemical oxygen demand; mg/L, milligrams per liter]

Parameter/rate coefficient Computational purpose Value

Light extinction coefficient for water Amount of solar radiation absorbed in the surface layer 0.24/m

Light extinction coefficient for organic solids Amount of solar radiation absorbed in the surface layer 0.01/m

Light extinction coefficient for inorganic solids Amount of solar radiation absorbed in the surface layer 0.01/m

Fraction of incident solar radiation absorbed at

water surface

Amount of solar radiation absorbed in the surface layer 0.24*

Coliform decay rate Decay rate for coliforms, temperature dependent 1.4/d

Coliform decay rate temperature coefficient A Q10 formulation modifies coliform decay rate 1.04*

Suspended solids settling rate Settling rates and sediment accumulation in reservoir 2 m/d

Algal growth rate Maximum gross algal production rate, uncorrected for

respiration, mortality, excretion or settling; temperature

dependent

1.5/d

Algal mortality rate Maximum algal mortality rate; temperature dependent 0.01/d

Algal excretion rate Maximum algal photorespiration rate, which becomes labile

dissolved organic matter

0.01/d

Algal dark respiration rate Maximum algal dark respiration rate 0.02/d

Algal settling rate Representative settling velocity for algal assemblages 0.14 m/d

Saturation light intensity Saturation light intensity at maximum algal photosynthesis

rate 500 watts/m2

Fraction of algal biomass lost by mortality to detritus Detritus and dissolved organic matter concentrations;

remaining biomass becomes labile dissolved organic

matter

0.8*

Lower temperature for algal growth Algal growth rate as a function of water temperature 1.0 oC

Fraction of algal growth at lower temperature Algal growth rate as a function of water temperature 0.10*

Lower temperature for maximum algal growth Algal growth rate as a function of water temperature 15.0oC

Fraction of maximum growth at lower temperature Algal growth rate as a function of water temperature 0.99*

Upper temperature for maximum algal growth Algal growth rate as a function of water temperature 35.0 oC

Fraction of maximum growth at upper temperature Algal growth rate as a function of water temperature 0.99*

Upper temperature for algal growth Algal growth rate as a function of water temperature 40.0 oC

Fraction of algal growth at upper temperature Algal growth rate as a function of water temperature 0.10*

Labile dissolved organic matter decay rate Dissolved-oxygen loss and production of inorganic carbon,

ammonia, and phosphate from algal decay; temperature

dependent

0.12/d

Labile to refractory decay rate Transfer of labile to refractory dissolved organic matter 0.001/d

Maximum refractory dissolved organic matter

decay rate

Dissolved-oxygen loss and production of inorganic carbon,

ammonia, and phosphate from decay of refractory dissolved organic matter; temperature dependent

0.001/d

Detritus decay rate Dissolved-oxygen loss and production of inorganic carbon,

ammonia, and phosphate from decay of particulate organic

matter, temperature dependent

0.06/d

Detritus settling velocity Loss of particulate organic matter to bottom sediment 0.35 m/d

Lower temperature for organic matter decay Organic matter decay as a function of temperature 5.0 oC

Fraction of organic matter decay at lower temperature Organic matter decay as a function of temperature 0.10*

Lower temperature for maximum organic matter decay Organic matter decay as a function of temperature 30.0 oC

Fraction of maximum organic matter decay at

lower temperature

Organic matter decay as a function of temperature 0.99*

Sediment decay rate Decay rate of organic matter in bed sediments 0.08/d
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 11

Sediment oxygen demand Zero-order sediment oxygen demand for each

computational segment

3.0 (g/m2)/d

5-day BOD decay rate Effects of BOD loading on dissolved oxygen 2.0/d

BOD temperature rate coefficient Adjusts 5-day BOD decay rate at 20oC to ambient

temperature

1.047*

Ratio of 5-day BOD to ultimate BOD Effects of BOD loading on dissolved oxygen 1.85*

Release rate of phosphorus from bottom sediments Phosphorus balance; computed as a fraction of

sediment oxygen demand

0.015*

Phosphorus partitioning coefficient Describes sorption of phosphorus on suspended solids 1.2*

Algal half-saturation constant for phosphorus The phosphorus concentration at which the uptake rate

is one-half the maximum uptake rate; upper concentration at which algal growth is proportional to phosphorus

concentration

0.005 mg/L

Release rate of ammonia from bottom sediments Nitrogen balance; computed as a fraction of the sediment

oxygen demand 

0.2*

Ammonia decay rate Rate at which ammonia is oxidized to nitrate 0.12/d

Algal half-saturation constant for ammonia Nitrogen concentration at which the algal uptake rate is

one-half the maximum uptake rate; upper concentration

at which algal growth is proportional to ammonia concentration

0.014 mg/L

Lower temperature for ammonia decay Ammonia nitrification as a function of temperature 5.0 oC

Fraction of nitrification at lower temperature Ammonia nitrification as a function of temperature 0.1*

Lower temperature for maximum ammonia decay Ammonia nitrification as a function of temperature 20.0 oC

Fraction of maximum nitrification at lower

temperature

Ammonia nitrification as a function of temperature 0.99*

Nitrate decay rate Rate at which nitrate is denitrified; temperature dependent 1.0/d

Lower temperature for nitrate decay Denitrification as a function of temperature 5.0 oC

Fraction of denitrification at lower temperature Denitrification as a function of temperature 0.1*

Lower temperature for maximum nitrate decay Denitrification as a function of temperature 20.0 oC

Fraction of maximum denitrification at lower

temperature

Denitrification as a function of temperature 0.99*

Iron release from bottom sediments Iron balance; computed as a fraction of sediment oxygen demand 0.5*

Iron settling velocity Particulate iron settling velocity under oxic conditions 2.0 m/d

Oxygen stoichiometric equivalent for ammonia

decay

Relates oxygen consumption to ammonia decay 4.57*

Oxygen stoichiometric equivalent for organic

matter decay

Relates oxygen consumption to decay of organic matter 1.4*

Oxygen stoichiometric equivalent for dark

respiration 

Relates oxygen consumption to algal dark respiration 1.4*

Oxygen stoichiometric equivalent for algal growth Relates oxygen production to algal growth 1.4*

Stoichiometric equivalent between organic matter

and phosphorus

Relates phosphorus release to decay of organic matter 0.011*

Stoichiometric equivalent between organic matter

and nitrogen

Relates nitrogen release to decay of organic matter 0.08*

Stoichiometric equivalent between organic matter

and carbon

Relates carbon release to decay of organic matter 0.45*

Dissolved-oxygen limit Dissolved-oxygen concentration below which anaerobic

processes such as nitrification and sediment nutrient

releases occur

0.1 mg/L

Table 2. Rate coefficients used in water-chemistry and biological simulations and other parameters specified as input in the 

Bull Shoals Lake model--Continued

[m, meters; *, dimensionless; d, day; Q10, temperature correction factor; m/d, meters per day; watts/m2, watts per square meter; oC, degrees Celsius;

(g/m2)/d, grams per square meter per day; BOD, biochemical oxygen demand; mg/L, milligrams per liter]

Parameter/rate coefficient Computational purpose Value
12 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Model Calibration

Successful model application requires model calibration that includes comparing model (simulated) results 

with observed (measured) reservoir conditions. If possible, 2 or more years of water-quality data should be used 

for adequate model calibration. Bull Shoals Lake model 

calibration was achieved by adjusting model parameters 

and, in some cases, estimated input data for the 2-year 

period of January 1994 through December 1995.

Two statistics were used to compare simulated and 

measured water-surface elevation, water temperature, and 

dissolved-oxygen concentration. The absolute mean error 

(AME) indicates the average difference between simulated and measured values and is computed by equation 1:

(1)

An AME of 0.5 °C means that the simulated temperatures 

are, on average, within + 0.5 °C of the measured temperatures. The root mean square error (RMSE) indicates the 

spread of how far simulated values deviate from the measured values and is computed by equation 2:

(2)

An RMSE of 0.5 °C means that the simulated temperatures are within 0.5 °C of the measured temperatures 

about 67 percent of the time.

Hydrodynamics and Temperature

Simulated water-surface elevations in Bull Shoals 

Lake were adjusted to the measured water surface for the 

model period January 1994 to December 1995 (fig. 7). 

The water-surface elevations were corrected to the measured values by adjusting the unmeasured inflow into the 

lake that was distributed to all the segments within a 

branch. Inflow was either added or subtracted so that the 

simulated water-surface elevation reflected the measured 

water-surface elevation. By correcting the distributed 

inflow, the thermodynamics could be calibrated without 

the uncertainty incurred with having differences between 

simulated and measured elevations.

Figure 7. Simulated and measured water-surface elevations 

near the Bull Shoals Lake dam, January through December 

1994 and January through December 1995.

AME Σ Simulated Value Measured Value –

Number of Observations = ----------------------------------------------------------------------------------------------------

RMSE Σ( ) Simulated Value Measured Value –

Number of Observations ------------------------------------------------------------------------------------------------------2

=

1994

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

196

198

200

202

204

206

208

1995

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

WATER-SURFACE ELEVATION, IN METERS ABOVE NGVD OF 1929

196

198

200

202

204

206

208

SIMULATED

MEASURED

SIMULATED

MEASURED
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 13

The heat budget in the model is computed from 

inflow water temperature, air-water surface heat 

exchange (determined from air and dew-point temperature, cloud cover, wind speed and direction, and 

organic and inorganic solids concentration) and bottom-water heat exchange. Organic and inorganic solids 

indirectly affect heat distribution by reducing light penetration. Thus, water temperature calibration cannot be 

performed independently from water chemistry computations, but water temperature can still be simulated 

neglecting the effects of solids on heat distribution.

Vertical distribution of water temperature affects 

vertical mixing of dissolved and suspended materials 

and can be used to define the general location of the 

epilimnion and hypolimnion of the reservoir. During 

the thermal stratification season (May-November) the 

epilimnion and hypolimnion typically are separated by 

a thermocline, in which there is a relatively large 

change in temperature over a small change in depth. A 

strong thermocline existed near the Bull Shoals Lake 

dam during June through November in 1994 and 1995. 

All simulated water temperatures (711) in 1994 

were compared with corresponding measured temperatures near the Bull Shoals Lake dam (Evans and others, 

1995; Porter and others, 1996). Simulated water temperatures reproduced seasonal variations observed in 

the water column near the dam (fig. 8), even for complex temperature profiles. Simulated water temperatures ranged from 5.7 to 28.0 °C, whereas measured 

water temperatures ranged from 5.9 to 28.4 °C. Simulated water temperatures in the vertical profile generally (79 percent) were within 1°C of measured 

temperatures. The AME and RMSE between simulated 

and measured water temperature were 0.67 and 0.89 

°C, respectively. The difference between simulated and 

measured temperature ranged from -2.2 to 4.0 °C, and 

the average and median differences both were -0.2 °C.

03/23/94 05/10/94 06/08/94 07/07/94

09/13/94

0 5 10 15 20 25 30

09/27/94

0 5 10 15 20 25 30

10/12/94

0 5 10 15 20 25 30

10/18/94

0 5 10 15 20 25 30

11/14/94

0 5 10 15 20 25 30

12/06/94

TEMPERATURE, IN DEGREES CELSIUS

0 5 10 15 20 25 30

01/27/94

60

50

40

30

20

10

0

08/17/94

0 5 10 15 20 25 30

DEPTH, IN METERS

60

50

40

30

20

10

0

11/01/94

0 5 10 15 20 25 30

DEPTH, IN METERS

60

50

40

30

20

10

0

AME = 0.33

RMSE = 0.36

AME = 0.31

RMSE = 0.37

AME = 0.58

RMSE = 0.72

AME = 0.93

RMSE = 1.16

AME = 1.05

RMSE = 1.18

AME =0.92

RMSE = 1.22

AME = 0.87

RMSE = 1.04

AME =0.79

RMSE =1.13

AME =0.60

RMSE = 0.82

AME =0.74

RMSE =0.90

AME = 0.52

RMSE = 0.71

AME = 0.48

RMSE = 0.58

AME =0.58

RMSE = 0.62

EXPLANATION

MEASURED

SIMULATED

Figure 8. Relation between simulated and measured water temperatures in the water column near the Bull Shoals Lake dam, 

January through December 1994.
14 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Although the calibrated model closely simulated 

water temperature near the Bull Shoals Lake dam in 

1994, with most simulated temperatures within 1°C of 

the measured temperatures, the accuracy and precision 

of simulated temperatures varied with temperature, season, and depth (fig. 9). Simulated water temperatures 

were less than measured temperatures more often when 

measured temperatures were less than 17 °C. Conversely, simulated water temperatures were greater than 

measured temperatures more often when measured 

temperatures were greater than approximately 17 °C. 

Error in simulated water temperatures was greater during the thermal stratification season (May through 

November). Simulated temperatures generally were 

less than measured temperatures at all depths, except 

between depths of 46 to 54 meters where simulated 

temperatures tended to be greater than measured temperatures. 

Figure 9. Relation of difference between simulated and 

measured water temperatures near the Bull Shoals Lake 

dam to (A) measured water temperature, (B) sampling date, 

and (C) water depth, January through December 1994.

All simulated temperatures (654) in 1995 were 

compared with corresponding measured temperatures 

(Porter and others, 1996; 1997) (fig. 10). Simulated 

water temperatures ranged from 5.8 to 29.1 °C, 

whereas measured water temperatures ranged from 6.7 

to 30.5 °C. Simulated water temperatures generally (58 

percent) were within 1°C of measured temperatures. 

The AME and RMSE between simulated and measured 

water temperature were 0.94 and 1.13 °C, respectively. 

The difference between simulated and measured temperatures ranged from -2.4 to 4.0 °C, and the average 

and median differences were -0.4 and -0.6 °C, respectively. 

Simulated water temperatures were similar to 

measured temperatures in 1995 (fig. 11). Simulated 

water temperatures during 1995 were less than measured temperatures more often when measured temperatures were less than 18 °C, and were greater than 

measured temperatures when temperatures were greater 

than 18 °C. From January 1995 through the stratification season (May to November), simulated water temperatures generally were less than measured water 

temperatures. Near the end of the stratification season, 

simulated water temperatures were greater than measured water temperatures. Simulated water temperatures generally were less than measured temperatures 

below depths of 20 m and near the water surface. However, as in 1994, most (58 percent) simulated temperatures were within 1 °C of the measured temperature.

Dissolved Oxygen

Simulation of the complex biochemical reactions 

affecting chemical and physical transport processes in 

the Bull Shoals Lake model are expressed in part within 

the simulated dissolved-oxygen results. The supply of 

nitrogen, phosphorus, and light regulates algal growth 

and the production of oxygen; photosynthesis is the 

only internal source of oxygen in the water-chemistry 

computations. Boundary sources of oxygen include the 

dissolved-oxygen concentration in the reservoir inflows 

and oxygen exchange at the air-water interface. Several 

sinks of oxygen exist including nitrification (conversion 

of ammonia to nitrate), algal and microbial respiration, 

organic matter decay (for example, detritus, labile and 

refractory dissolved organic matter), and sediment oxygen demand. These processes combined with the waterchemistry computations are used to simulate the complex vertical profiles of dissolved oxygen in Bull Shoals 

Lake. 

WATER DEPTH, IN METERS

0 10 20 30 40 50 60

-6

-4

-2

0

2

4

6

MEASURED TEMPERATURE, IN DEGREES CELSIUS

0 5 10 15 20 25 30

-6

-4

-2

0

2

4

6

1994

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

SIMULATED MINUS MEASURED TEMPERATURE, IN DEGREES CELSIUS -6

-4

-2

0

2

4

6

A

C

B
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 15

Figure 10. Relation between simulated and measured water temperatures in the water column near the Bull Shoals Lake dam, 

January through December 1995.

03/22/95 05/17/95 06/14/95 07/11/95

09/14/95

0 5 10 15 20 25 30

60

50

40

30

20

10

0

09/27/95

0 5 10 15 20 25 30

10/11/95

0 5 10 15 20 25 30

10/24/95

0 5 10 15 20 25 30

12/13/95

0 5 10 15 20 25 30

01/20/95

DEPTH, IN METERS

60

50

40

30

20

10

0

08/16/95

11/07/95

0 5 10 15 20 25 30

TEMPERATURE, IN DEGREES CELSIUS

AME =1.37

RMSE =1.37

EXPLANATION

AME =0.91

RMSE =1.05

AME =1.12

RMSE =1.21

AME =0.82

RMSE =0.92

AME =1.28

RMSE =1.51 AME =1.39

RMSE =1.66

AME =1.00

RMSE =1.24

AME =0.97

RMSE =1.11

AME =0.69

RMSE =0.82

AME =0.54

RMSE =0.67

AME =0.58

RMSE =0.74

AME =0.50

RMSE =0.64

MEASURED

SIMULATED

WATER DEPTH, IN METERS

0 10 20 30 40 50 60

-6

-4

-2

0

2

4

6

MEASURED TEMPERATURE, IN DEGREES CELSIUS

0 5 10 15 20 25 30 35

-6

-4

-2

0

2

4

6

1995

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

SIMULATED MINUS MEASURED TEMPERATURE, IN DEGREES CELSIUS

-6

-4

-2

0

2

4

6

A

C

B

Figure 11. Relation of difference between simulated and measured water temperatures near the Bull Shoals Lake dam to (A) 

measured water temperature, (B) sampling date, and (C) water depth, January through December 1995.
16 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Simulated dissolved-oxygen concentrations near 

the Bull Shoals Lake dam exhibited the same general 

patterns and magnitudes as measured concentrations 

(fig. 12). All simulated dissolved-oxygen concentrations (711) for 1994 were compared to corresponding 

measured concentrations (Evans and others, 1995; Porter and others, 1996). Simulated dissolved-oxygen concentrations ranged from 0.0 to 11.4 mg/L, whereas, 

measured dissolved-oxygen concentrations ranged 

from 0.1 to 11.1 mg/L. Simulated dissolved-oxygen 

concentrations in the vertical profile generally (61 percent) were within 1 mg/L of measured concentrations. 

The AME and RMSE between simulated and measured 

dissolved-oxygen concentrations were 1.13 and 1.71 

mg/L, respectively. The difference between simulated 

and measured concentrations ranged from -8.6 to 7.6 

mg/L, and the average and median differences were -

0.2 and -0.1 mg/L, respectively. 

Differences between simulated and measured 

dissolved-oxygen concentrations were compared to 

corresponding measured dissolved-oxygen concentrations, sampling date, and the water depth (fig. 13). Simulated dissolved-oxygen concentrations typically were 

less than measured values at concentrations less than 5 

mg/L and greater than measured values at concentrations greater than 5 mg/L. Errors in simulated dissolved-oxygen concentration were greater near the end 

of the thermal stratification season (SeptemberNovember) and during turnover (December). Simulated dissolved oxygen concentrations generally were 

less than measured concentrations at all depths.

Figure 12. Relation between simulated and measured dissolved-oxygen concentrations in the water column near the Bull 

Shoals Lake dam, January through December 1994.

03/23/94 05/10/94 06/08/94 07/07/94

09/13/94

0 2 4 6 8 10 12

09/27/94

0 2 4 6 8 10 12

10/12/94

0 2 4 6 8 10 12

10/18/94

0 2 4 6 8 10 12

11/14/94

0 2 4 6 8 10 12

12/06/94

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER

0 2 4 6 8 10 12

01/27/94

60

50

40

30

20

10

0

08/17/94

0 2 4 6 8 10 12

DEPTH, IN METERS

60

50

40

30

20

10

0

11/01/94

0 2 4 6 8 10 12

DEPTH, IN METERS

60

50

40

30

20

10

0

AME = 0.15

RMSE = 0.20

AME = 0.67

RMSE = 0.69

AME = 0.89

RMSE = 0.96

AME = 0.96

RMSE = 1.22

AME = 1.62

RMSE = 2.11

AME =1.41

RMSE = 1.84

AME = 2.07

RMSE = 3.06

AME =1.25

RMSE = 1.62

AME = 1.33

RMSE = 1.75

AME = 0.89

RMSE = 1.05

AME = 1.12

RMSE = 2.15

AME = 0.82

RMSE = 0.94

AME = 1.55

RMSE = 2.49

EXPLANATION

MEASURED

SIMULATED
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 17

Figure 13. Relation of difference between simulated and 

measured dissolved-oxygen concentrations near Bull Shoals 

Lake dam to (A) measured dissolved-oxygen concentrations, 

(B) sampling date, and (C) water depth, January through 

December 1994.

Simulated dissolved-oxygen concentrations were 

similar to measured dissolved-oxygen concentrations in 

1995 (fig. 14), but differences were somewhat less in 

1995 than in 1994. Seasonal variations in simulated dissolved-oxygen concentration were reproduced despite 

pronounced differences in the vertical distribution. All 

simulated dissolved-oxygen concentrations (654) were 

compared with corresponding measured concentrations 

near the Bull Shoals Lake dam (Porter and others, 1996, 

1997). Simulated values ranged from 0.0 to 11.1 mg/L 

whereas, measured dissolved-oxygen concentrations 

ranged from 0.0 to 13.1 mg/L. Simulated dissolvedoxygen concentrations in the vertical profile generally 

(67 percent) were within 1 mg/L of measured concentrations. The AME and RMSE between simulated and 

measured dissolved-oxygen concentrations were 0.94 

and 1.37, respectively. The difference between simulated and measured dissolved-oxygen concentrations 

ranged from -6.9 to 6.7 mg/L, and the average and 

median differences were -0.2 and -0.1 mg/L, respectively. 

0 10 20 30 40 50 60

-10

-8

-6

-4

-2

0

2

4

6

8

10

MEASURED DISSOLVED-OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

0 2 4 6 8 10 12

-10

-8

-6

-4

-2

0

2

4

6

8

10

1994

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

SIMULATED MINUS MEASURED DISSOLVED-OXYGEN

CONCENTRATION, IN MILLIGRAMS PER LITER -10

-8

-6

-4

-2

0

2

4

6

8

10

A

C

B

Figure 14. Relation between simulated and measured dissolved-oxygen concentrations in the water column near the Bull 

Shoals Lake dam, January through December 1995.

03/22/95 05/17/95 06/14/95 07/11/95

09/14/95

0 2 4 6 8 10 12

60

50

40

30

20

10

0

09/27/95

0 2 4 6 8 10 12

10/11/95

0 2 4 6 8 10 12

10/24/95

0 2 4 6 8 10 12

12/13/95

0 2 4 6 8 10 12

01/20/95

DEPTH, IN METERS

60

50

40

30

20

10

0

08/16/95

11/07/95

0 2 4 6 8 10 12

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER

AME =0.91

RMSE =0.95

AME =1.33

RMSE =1.37

AME =0.30

RMSE =0.41

AME =0.52

RMSE =0.71

AME =1.03

RMSE =1.19

AME =1.81

RMSE =2.46

AME =1.09

RMSE =1.27

AME =1.06

RMSE =1.53

AME =0.72

RMSE =0.97

AME =0.34

RMSE =0.76

AME =1.05

RMSE =1.85

AME =1.18

RMSE =1.71

EXPLANATION

MEASURED

SIMULATED
18 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

On average, simulated dissolved-oxygen concentrations in 1995 were less than measured concentrations (fig. 15). Simulated dissolved-oxygen 

concentrations were less than measured concentrations 

through most of the stratification season. Near the end 

of the stratification season and during turnover, simulated concentrations were typically greater than measured concentrations. Simulated dissolved-oxygen 

concentrations often were less than measured concentrations near the water surface and greater than measured concentrations near the lake bottom. Despite 

these tendencies, simulation of dissolved-oxygen concentration in the vertical profile near the Bull Shoals 

Lake dam followed the same general patterns as measured concentrations.

Figure 15. Relation of difference between simulated and 

measured dissolved-oxygen concentrations near Bull Shoals 

Lake dam to (A) measured dissolved-oxygen concentrations, (B) sampling date, and (C) water depth, January 

through December 1995.

Sensitivity Analysis

Sensitivity analysis is the determination of the 

effects of small changes in calibrated model parameters 

and input data on model results. A complete sensitivity 

analysis for all model parameters in the Bull Shoals 

Lake model was not conducted because the Bull Shoals 

Lake model includes more than 60 parameters (tables 1 

and 2). However, many hydrodynamic, temperature, 

and dissolved-oxygen simulations were conducted as a 

component of model development and calibration. 

Results from these simulations and information from 

previous modeling studies (Bales and Giorgino, 1998; 

Giorgino and Bales, 1997; Green, 2001; Haggard and 

Green, 2002) in other reservoirs were used to identify 

several parameters for evaluation in the sensitivity 

analysis. The sensitivity of simulated water temperature and dissolved-oxygen concentration near the dam 

to changes in the wind-sheltering coefficient (WSC), 

bottom-water heat exchange coefficient (CBHE), light 

extinction (α), sediment-oxygen demand (SOD), and 

changes in inflow temperature and dissolved-oxygen 

concentrations was assessed.

Water temperature in the Bull Shoals Lake 

model was most sensitive to changes in the WSC, α,

and inflow water temperature (fig. 16). Wind speed in 

the calibrated Bull Shoals Lake model was adjusted

(WSC = 0.7) from the meteorological data recorded at 

Harrison, Arkansas; that is, the effective wind speed 

was 70 percent of the recorded wind speed at Harrison. 

During thermal stratification, more vertical mixing was 

simulated when the WSC was increased (1.0) and less 

vertical mixing was simulated when the WSC was 

decreased (0.5). Changes in the α affected vertical 

water temperature profiles during stratification. 

Increasing α slightly elevated the thermocline and 

decreasing α lowered the thermocline. Changes in 

inflow water temperature also affected vertical water 

temperature profiles near the dam during stratification. 

Surface-water temperatures were not impacted as much 

by changes in inflow water temperatures as was the 

position of the thermocline and hypolimnetic temperatures. The combination of WSC and α appear to be the 

driving factors in the model responsible for the development, duration, and vertical location of the thermocline in Bull Shoals Lake near the dam.

WATER DEPTH, IN METERS

0 10 20 30 40 50 60

-8

-6

-4

-2

0

2

4

6

8

MEASURED DISSOLVED-OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

0 2 4 6 8 10 12

-8

-6

-4

-2

0

2

4

6

8

1995

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

SIMULATED MINUS MEASURED DISSOLVED-OXYGEN

CONCENTRATION, IN MILLIGRAMS PER LITER -8

-6

-4

-2

0

2

4

6

8

A

C

B
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 19

Figure 16. Vertical temperature distributions near the Bull Shoals Lake dam on July 7, 1994 (top), and January 20, 1995 

(bottom), showing calibrated model profiles and profiles as a result of differing model parameters.

Wind-Sheltering

Coefficient (WSC)

5 10 15 20 25 30

60

50

40

30

20

10

0

WSC = 0.7

(calibrated value)

WSC = 0.5

WSC = 1.0

Coefficient of Bottom

Heat Exchange (CBHE)

WATER TEMPERATURE, IN DEGREES CELSIUS

5 10 15 20 25 30

CBHE = 7E-8

(calibrated value)

CBHE = 7E-9

CBHE = 7E-7

Light Extinction

Coefficient ( 

5 10 15 20 25 30

α = 0.24

(calibration value)

α = 0.38 

α = 0.10

EXPLANATION

Inflow Water

Temperature (ITEMP)

5 10 15 20 25 30

1.0 x ITEMP

(calibration value)

0.75 x ITEMP

1.25 x ITEMP

5 10 15 20 25 30

DEPTH, IN METERS BELOW WATER SURFACE

60

50

40

30

20

10

0

5 10 15 20 25 30 5 10 15 20 25 30 5 10 15 20 25 30

January 20, 1995

July 7, 1994

In the Bull Shoals Lake model, dissolved-oxygen concentrations were most affected by changes in 

the WSC and FSOD (fig. 17). FSOD is the fraction of 

the zero-order SOD rate and is applied to adjust SOD 

equally among all segments. Changes in the WSC and 

FSOD had the greatest effect on dissolved-oxygen concentrations near the thermocline and throughout the 

hypolimnion. The α regulates the amount of light penetrating the water, indirectly affecting dissolved-oxygen concentrations by influencing algal production. 

Changes in α and inflow dissolved-oxygen concentrations had little effect on vertical distribution of dissolved oxygen near the dam.

Many other parameters indirectly affect dissolved-oxygen concentrations through algal dynamics; 

however, examination of all of these parameters is 

beyond the scope of this report given that so many 

assumptions were made in evaluating dissolved-oxygen concentrations near the dam. Regardless, algal 

dynamics play a substantial role in the dissolved-oxygen conditions near the Bull Shoals Lake dam. 

Model Applications

The calibrated Bull Shoals Lake model was used 

to assess the impacts of increased minimum flow on 

water-surface elevation and on temperature and dissolved-oxygen concentrations in the Bull Shoals Lake 

outflow waters. Two scenarios were simulated, including (1) an increase in the outflow of Bull Shoals Lake 

dam from the existing minimum flow of 4.6 m3/s to 

22.6 m3

/s, and (2) an increase in water-surface elevation of Bull Shoals Lake of 1. 5 m to correct for the volume displaced by the additional minimum flow.
20 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Figure 17. Vertical dissolved-oxygen concentration distributions near the Bull Shoals Lake dam on July 7, 1994 (top), and 

January 20, 1995 (bottom), showing calibrated model profiles and profiles as a result of differing model parameters.

Wind-Sheltering

Coefficient (WSC)

0 2 4 6 8 10 12

60

50

40

30

20

10

0

WSC = 0.7

(calibrated value)

WSC = 0.5

WSC = 1.0

Fraction of Sediment

Oxygen Demand (FSOD)

DISSOLVED OXYGEN CONCENTRATION, IN MILLIGRAMS PER LITER

0 2 4 6 8 10 12

FSOD = 1.75

(calibrated value)

FSOD = 0.5

FSOD = 2.5

Light Extinction

Coefficient ( 

0 2 4 6 8 10 12

α = 0.24

(calibration value)

α = 0.38

α = 0 10

EXPLANATION

Inflow Dissolved

Oxygen Concentration

(IDO)

0 2 4 6 8 10 12

1.0 X IDO

(calibration value)

0.75 X IDO

1.25 X IDO

0 2 4 6 8 10 12

DEPTH, IN METERS BELOW WATER SURFACE

60

50

40

30

20

10

0

0 2 4 6 8 10 12 0 2 4 6 8 10 12 0 2 4 6 8 10 12

January 20, 1995

July 7, 1994

When 22.6 m3/s was applied as the minimum 

amount of outflow (increased minimum flow scenario), 

mean annual outflow increased from 210.6 to 215.1 m3

/

s, about a 2 percent increase. Approximately 37 percent 

of the hourly outflow data required an increase to 22.6 

m3

/s. Average annual outflow increased from 6,641 to 

6,782 million m3

, which is equivalent to 141 million m3

per year increase, or about 3.4 percent of reservoir volume at conservation pool elevation. The water-surface 

elevation at the end of 1994 was reduced 0.79 m and at 

the end of 1995 was reduced about 1.5 m (figs. 18 and 

19) from the initial elevation on January 1, 1994 

(168.79 m). When 1.5 m of water was applied to the initial elevation (increased minimum flow with increased 

water-surface elevation scenario), the difference by the 

end of 1994 was 0.77 m greater than the calibrated 

model without the increased minimum flow and by the 

end of 1995 only 0.04 m greater than the calibrated 

model (fig. 19).

Figure 18. Simulated water-surface elevations resulting from 

increased minimum flow scenarios.

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

ELEVATION, 

IN METERS ABOVE 

NGVD OF 1929 194

196

198

200

202

204

206

208

Calibrated Model

Increased Minimum Flow Scenario

Increased Minimum Flow with Increased 

Water-Surface Elevation Scenario

EXPLANATION

1995
Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake 21

Simulated temperature in the outflow water differed little between the increased minimum flow scenarios and the calibrated model (figs. 20 and 21). 

Absolute maximum difference in outflow water temperature between the increased minimum flow scenario 

and the calibrated model was 3.03 °C and between the 

increased minimum flow with increased water-surface 

elevation and the calibrated model was 1.03 °C. The 

maximum temperature differences occurred at the end 

of the stratification season in November 1994 and 

1995. This could be attributed to the difference in the 

timing of turnover, when the lake goes from a stratified 

condition to a well-mixed condition. Turnover occurs 

within a short time period and the timing could be 

affected by the difference in flow conditions from the 

calibrated model to the minimum flow scenarios. Overall, temperature differences for both scenarios were 

within the AME and RMSE between simulated and 

measured water-column profile temperature differences reported in the “Model Calibration” section of 

this report. Simulated outflow temperatures were similar to estimated outflow temperatures from water-column profiles measured upstream from the dam (George 

Robins, Southwestern Power Administration, written 

commun., 2000) and to measured downstream outflow 

temperatures (USGS station number 07054501) (fig. 

21). Water temperature in the dam outflow increased 

slightly (less than 0.2 °C, on average) with increased 

minimum flow. Conversely, with the increase in watersurface elevation plus the increased minimum flow, 

water temperature in the dam outflow decreased 

slightly (less than 0.1 °C, on average) through time during the stratification season.

Figure 19. Relation of difference between water-surface 

elevations predicted from increased minimum flow scenarios 

and calibrated model water-surface elevation with time.

Figure 20. Simulated water temperature differences 

between increased minimum flow scenarios and the 

calibrated model.

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

SCENARIO ELEVATION MINUS

CALIBRATED MODEL

ELEVATION, IN METERS

-2.0

-1.6

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

1.6

2.0

Increased Minimum Flow Scenario

Increased Minimum Flow with Increased 

Water-Surface Elevation Scenario

EXPLANATION

1995

MINIMUM FLOW WATER TEMPERATURE DIFFERENCE

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

SCENARIO MINUS CALIBRATED 

OUTFLOW WATER TEMPERATURE, 

IN DEGREES CELSIUS

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1995

MINIMUM FLOW WITH INCREASED WATER-SURFACE

 ELEVATION WATER TEMPERATURE DIFFERENCE

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

SCENARIO MINUS CALIBRATED 

OUTFLOW WATER TEMPERATURE, 

IN DEGREES CELSIUS -1.0

-0.5

0.0

0.5

1.0

1995

Figure 21. Simulated and estimated water temperatures in Bull 

Shoals Lake outflow and measured temperatures downstream from 

Bull Shoals Lake dam.

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

TEMPERATURE,

IN DEGREES CELSIUS

4

6

8

10

12

14

16

18

20

Calibrated Model

Minimum Flow Scenario

Minimum Flow with Increased 

Water-Surface Elevation Scenario

Measured Outflow

Above Dam Water-Column Profile Estimate

EXPLANATION

1995
22 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Simulated dissolved-oxygen concentrations in 

the outflow water differed little between the two 

increased minimum flow scenarios and the calibrated 

model (figs. 22 and 23). Absolute maximum difference 

in outflow dissolved oxygen between the increased 

minimum flow scenario and the calibrated model was 

4.34 mg/L and between the increased minimum flow 

with increased water-surface elevation and the calibrated model was 2.02 mg/L. The maximum dissolvedoxygen concentration differences occurred at the end of 

the stratification season in November 1994 and 1995. 

The differences could be attributed to the difference in 

timing of the turnover, caused by the changes in flow 

condition from the calibrated model to the minimum 

flow scenarios. Overall, dissolved-oxygen concentration differences for both scenarios generally were about 

the same as the AME and RMSE between simulated 

and measured water-column profile dissolved-oxygen 

differences reported in the “Model Calibration” section 

of this report. Simulated outflow dissolved-oxygen 

concentrations were similar to estimated outflow concentrations from water-column profiles measured 

upstream from the dam (George Robins, Southwestern 

Power Administration, written commun., 2000) (fig. 

23). Simulated dissolved-oxygen concentrations in the 

dam outflow increased slightly with the addition of 

increased minimum flow (less than 0.05 mg/L, on average). Conversely, with the increase in water-surface 

elevation and the increased minimum flow, simulated 

dissolved-oxygen concentrations in the dam outflow 

decreased slightly (less than -0.05 mg/L, on average) 

during the simulation period.

Small changes in water temperature and dissolved-oxygen concentration compared to the calibrated, base condition were simulated for the two 

increased minimum flow scenarios. However, the 

changes were similar to the error between simulated 

and measured temperature and dissolved-oxygen concentrations determined for model calibration.

Figure 22. Simulated dissolved-oxygen concentration 

differences between increased minimum flow scenarios and 

calibrated model.

MINIMUM FLOW DISSOLVEDOXYGEN CONCENTRATION DIFFERENCE

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

SCENARIO MINUS CALIBRATED OUTFLOW 

DISSOLVED OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER -1

0

1

2

3

4

5

MINIMUM FLOW WITH INCREASED WATER-SURFACE 

ELEVATION DISSOLVED-OXYGEN CONCENTRATION DIFFERENCE

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

SCENARIO MINUS CALIBRATED OUTFLOW

DISSOLVED OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER -2

-1

0

1

2

1995

1995

Figure 23. Simulated and estimated dissolved-oxygen concentrations 

in Bull Shoals Lake outflows.

1994

JAN MAR MAY JULY SEPT NOV MAR MAY JULY SEPT NOV

DISSOLVED-OXYGEN 

CONCENTRATION,

IN MILLIGRAMS PER LITER

0

2

4

6

8

10

12

14

Calibrated Model

Minimum Flow Scenario

Minimum Flow with Increased 

Water-Surface Elevation Scenario

Above Dam Water-Column Profile Estimate

EXPLANATION

1995
Summary 23

SUMMARY

Outflow from Bull Shoals Lake and other White 

River reservoirs support a cold-water trout fishery of 

substantial economic yield in north-central Arkansas 

and south-central Missouri. Proposed increases in minimum flows released from the dam have caused concerns about the sustainability of cold-water 

temperature and dissolved oxygen in the bottom water 

of Bull Shoals Lake. Increases in water temperature 

and decreases in dissolved oxygen could have potentially negative impacts on the cold-water trout fisheries 

in the downstream outflow. The U.S. Geological Survey, in cooperation with the Arkansas Game and Fish 

Commission, conducted a study to assess the impact of 

additional minimum flows on the hydrodynamics, temperature, and dissolved-oxygen concentrations in Bull 

Shoals Lake and on temperature and dissolved-oxygen 

concentrations in the downstream outflow.

A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model was 

developed for Bull Shoals Lake, Arkansas. The model 

was calibrated using hydrologic records and vertical 

profiles of temperature and dissolved oxygen measured 

in or near Bull Shoals Lake from January 1994 through 

December 1995. The model simulates water-surface 

elevation, water temperature, and dissolved-oxygen 

concentration. The model simulated temperatures generally within 1 °C of the measured temperatures. The 

AME and RMSE between simulated and measured 

water temperature for 1994 were 0.67 and 0.89, respectively, and for 1995 were 0.94 and 1.13, respectively. 

The model simulated dissolved-oxygen concentrations 

generally within 1 mg/L of the measured concentrations. The AME and RMSE between simulated and 

measured dissolved-oxygen concentrations for 1994 

were 1.13 and 1.71, respectively, and for 1995 were 

0.94 and 1.37, respectively.

 The Bull Shoals Lake model was developed to 

assess the impacts of proposed increases in minimum 

flows from 4.6 m3/s (the existing minimum flow) to 

22.6 m3

/s (the increased minimum flow). Scenarios 

included assessing the impact of (1) increased minimum flows and (2) increased minimum flows with 

increased water-surface elevation of 1.5 m greater than 

the initial water-surface elevation on outflow temperatures and dissolved-oxygen concentrations. With the 

increased minimum flow, water temperatures and dissolved oxygen concentrations increased in the outflow. 

Conversely, increased minimum flow with increased 

water-surface elevation decreased the outflow water 

temperature and dissolved-oxygen concentrations. 

However, these results were within the boundaries of 

the error between simulated and measured water temperature and dissolved-oxygen concentrations for the 

calibrated model.

This model provides the basis and framework for 

future water-quality modeling of Bull Shoals Lake. As 

additional data are collected in the reservoir and tributaries, the calibrated model can be modified to assess 

the nutrient assimilative capacity of the reservoir, nutrient limitation, and the effect of increases in nutrient 

loading on reservoir trophic status.
24 Simulation of Hydrodynamics, Temperature, and Dissolved Oxygen in Bull Shoals Lake, Arkansas, 1994-1995

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