Impact of Flow Regulation and 

Powerplant Effluents on the 

Flow and Temperature Regimes 

of the Chattahoochee River 

Atlanta to Whitesburg, Georgia
Impact of Flow Regulation and 

Powerplant Effluents on the 

Flow and Temperature Regimes 

of the Chattahoochee River 

Atlanta to Whitesburg, Georgia

By R. E. FAYE, H. E. JOBSON, and L. F. LAND

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1108

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Faye, Robert E

Impact of flow regulation and powerplant effluents on the flow and temperature regimes of the Chattahooehee 

River, Atlanta to Whitesburg, Georgia.

(Geological Survey professional paper 1108)

Supt. of Docs. no. : I 19.16:1108

"Open-file report 78-528."

Bibliography: p.

1. Thermal pollution of rivers, lakes, etc. Chattahooehee River. 2. Chattahooehee River Regulation. I. Jobson, Harvey E., joint author. II. Land, Larry F., joint author. III. Title. IV. Series: United States. 

Geological Survey. Professional paper 1108.

TD225.C35F39 614.7'72 78-27042

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402

Stock Number 024-001-03244-9
CONTENTS

Metric conversion table 

Abstract _________.

Introduction ____________________________________

Description of the problem __________________________

Scope of the study ______________________________________

Description of the study area __________________________________

Stream network and channel description _________________________

Streamflow and temperature characteristics _______________________

Flow and temperature models ___________________________

Calibration and verification ____________________________________

Flow model ________________________________________

Temperature model ________________________________

Impact of powerplant effluents on river temperatures August 1-8, 1976 ______

Computation of natural river temperatures __________________________

Computed river temperatures using year 2000 and critical drought flow conditions 

Summary and conclusions ___.____________________________________

Selected references ______________________________________

Tables summarizing data ______________________________________

Page 

V

1

1

1

3

4

5

5

16

17

17

18

25

26

35

37

45

47

ILLUSTRATIONS

FIGURE 1. Map of study area showing data-collection sites _____________

2. Diagrams showing selected channel 

cross sections of the Chatahoochee River from Atlanta to 

Whitesburg. A, River mile 302.97. 

B, River mile 259.87. C, River 

mile 281.79. D, River mile 293.92. 

E, River mile 268.34. F, River 

mile 298.77 _______________

3. Graph showing thalweg and low-flow 

profile of the Chattahoochee 

River Atlanta to Whitesburg__

4-6. Graphs showing mean daily streamflow in the Chattahoochee 

River during water year 

1976:

4. At Atlanta ________________

5. Near Fairburn _________

6. Near Whitesburg _________

7. Flow duration characteristics of the 

Chattahoochee River at Atlanta 

prior to and subsequent to the 

construction of Buford Dam ___

Page

9

10

10

11

Page

FIGURE 8-12. Graphs showing observed mean daily 

temperature of the Chattahoochee River and mean 

monthly air temperature at 

Atlanta during water year 

1976:

8. At Buford Dam ________

9. At Atlanta ____________

10. At the Plant McDonough 

intake ______ __ _______

11. At Georgia Highway 280 __

12. Near Fairburn ___ ___ _

13. Graph showing observed mean daily 

temperature of the Chattahoochee River and mean monthly 

air temperature at Atlanta, July 

1937-May 1938 _______________

14. Graphs showing observed and computed stages of the Chattahoochee River during the period 

July 12-19, 1976. A, At Atlanta. 

B, At the Atlanta water-supply 

facility. C, At the Plant McDonough outfall. D, Near Fairburn. E, Near Whitesburg ___

12

12

13

13

14

15

19

ill
IV CONTENTS

Page

FIGURE 15. Graph showing rated and computed 

discharge at the Chattahoochee 

River near Fairburn, July 12-

18. 1976 _______________ 21

16. Diagram showing computed stagedischarge relations for the Chattahoochee River near Fairburn, 

July 13, 1976 ____________ 22

17. Graph showing rated and computed 

discharge at the Chattahoochee 

River near Whitesburg, July 12-

19. 1976 _______________ 2,2

18. Diagram showing computed stagedischarge relation for the Chattahoochee River near Whitesburg, July 13-14, 1976 _____ 22

19. Graphs showing observed and computed stages of the Chattahoochee River during the period 

August 1-8, 1976. A, At Atlanta. 

B, At the Atlanta water-supply 

facility. C, Near Fairburn. D, 

Near Whitesburg _______ 24

20. Graphs showing observed and computed temperatures of the Chattahoochee River during the period August 1-8, 1976. A, At Atlanta. B, At the Plant McDonough intake. C, At Georgia 

Highway 280. D, Near Fairburn 

E, Near Whitesburg ______ 26

21. Graphs showing observed and computed temperatures of the Chattahooche© River during the period July 12-19, 1976. A, At Atlanta. B, At the Plant MeDonough intake. C, At Georgia 

Highway 280. D, Near Fairburn 

E, Near Whitesburg _____ 30

22. Graph showing heat added to the 

Chattahoochee River from Plants 

Atkinson-McDonough, August 1- 

8, 1976 _______________ 32

23. Graphs showing temperature of the 

Chattahoochee River with and 

without heat loads from Plants 

Atkinson-McDonough during the 

period August 1-8, 1976. A, At 

Georgia Highway 280. B, Near 

Fairburn. C, Near Whitesburg._ 33

24. Graph showing computed longitudinal 

temperature profiles in the study 

reach with and without heat 

loads from Plants Atkinson-McDonough, 0000 e.s.t, August 8, 

1976 __________________ 34

Page

FIGURE 25. Graph showing observed temperature 

of the Chattahoochee River at 

Georgia Highway 280 and the observed temperature of the same 

water upon arrival at the Fairburn gage _____________ 34

26. Graph showing 8-day mean natural 

and thermally altered temperatures of the Chattahoochee River 

from Atlanta to Whitesburg, 

August 1-8, 1976 _________ 35

27. Graph showing computed natural and 

observed temperatures of the 

Chattahoochee River, August 1- 

8, 1976 _______________ 36

28. Graphs showing computed temperatures of the Chattahoochee River 

using flows representing year 

2000 peak water-supply demands, 

year 2000 average wastewater 

returns, and August 1976 tributary flows. A, At the Plant McDonough intake. B, At Georgia 

Highway 280. C, Near Fairburn. 

D, Near Whitesburg _______ 38

29. Graphs showing computed temperatures of the Chattahoochee River 

using flows representing year 

2000 peak water-supply demands, 

year 2000 average wastewater 

returns, and 1954 drought tributary flows. A, At the Plant McDonough intake. B, At Georgia 

Highway 280. C, Near Fairburn. 

D, Near Whitesburg _______ 40

30. Graphs showing computed temperatures of the Chattahoochee River 

using flows representing year 

2000 average water-supply demands, year 2000 average wastewater returns, and August 1976 

tributary flows, A, At the Plant 

McDonough intake. B, At Georgia 

Highway 280. C, Near Fairburn. 

D, Near Whitesburg _______ 42

31. Graphs showing computed temperatures of the Chattahoochee River 

using flows representing year 

2000 average water-supply demands, year 2000 average wastewater returns, and 1954 drought 

tributary flows. A, At the Plant 

McDonough intake. B, At Georgia Highway 280. C, Near Fairburn. D, Near Whitesburg 44
TABLE 1. Periodic data-collection sites ______

2. Summary of climatologic data for 

Atlanta, 1941-70 _______________

3. Tributary network and daily mean 

discharges during specified periods

4. Mean monthly air temperatures at 

Atlanta for the period of record 

and for specified months during 

1937-38 and 1975-76, in degrees 

Celsius _______________

5. Mean monthly water temperatures 

during 1937-38 and 1975-76, in degrees Celsius ________________

CONTENTS

TABLES

Page 

3

14

15

TABLE 6. Estimated water-supply demands and 

wastewater flows for the year 2000

7. Estimated discharge at the Atlanta 

and Whitesburg gages using selected tributary and year 2000 

water-supply demands and wastewater flows ________ _ _

8. Cross section coordinates __________

9. Channel roughness coefficients and 

barrier heights ___________ __

10. Summary of meteorologic data July 

12-19 and August 1-8, 1976 _____

Page

35

37

48

50

51

CONVERSION FACTORS

[Factors for converting inch-pound units to metric units are shown to four significant figures. However, 

in the text, the metric equivalents are shown only to the number of significant figures consistent with 

the values for the inch-pound]

Inch-pound units Multiply by

ft (foot) 3.048X10-1

ft (foot) 3.048xlOa

ft/s (foot per second) 3.048X10"1 

ft:! /s (cubic foot per second) 2.832X10'3

in. (inch) 2.540xlO~2

in. (inch) 2.540X101

mi (mile) 1.609

mi2 (square mile) 2.590

tons (tons, short) 9.072xlO"1

tons/d (tons per day) 9.072xlO'1 

tons/ft3 (tons per cubic foot) 3.204X10'1

tons/yr (tons per year) 9.072xlO-1

°F (degrees Fahrenheit) 5/9 (F-32)

Metric

m (meter)

mm (millimeter)

m/s (meter per second)

m7s (cubic meter per second)

m (meter)

mm (millimeter)

km (kilometer)

km" (square kilometer)

t (metric tons)

t/d (metric tons per day)

t/m3 (metric tons per cubic meter)

t/yr (metric tons per years)

°C (degrees Celsius)

IMPACT OF FLOW REGULATION AND POWERPLANT EFFLUENTS ON THE 

FLOW AND TEMPERATURE REGIMES OF THE CHATTAHOOCHEE RIVER 

ATLANTA TO WHITESBURG, GEORGIA

By R. E. FAYE, H. E. JOBSON, and L. F. LAND

ABSTRACT

A calibrated and verified transient flow-temperature model 

was used to evaluate the effects of flow regulation and powerplant loadings on the natural temperature regime of the 

Chattahoochee River in northeast Georgia. Estimates were 

made of both instantaneous and average natural temperatures in the river during an 8-day period in August 1976. 

Differences between the computed average natural temperature and an independent estimate of natural temperature 

based on observed equilibrium temperatures were less than 

0.5° C. Downstream of the powerplants, the combined thermal 

effects of flow regulation and powerplant effluents resulted 

in mean daily river temperatures about equal to or less than 

computed mean natural temperatures. Thus the thermal 

impact of heated effluents was offset by the cooling effects of 

structural regulation. An independent analysis of historical 

river- and air-temperature data, although considerably less 

accurate than model computations, provided substantially 

the same result. The range and rates of change of computed natural diurnal temperature fluctuations were conisiderably less than those in the river at the time of this 

study in 1976. The models also were used to simulate summer river temperatures using estimated year 2000 flow conditions and meteorologic data collected during 1976. Except 

during periods of peak water-supply demand, differences between computed year 2000 river temperatures and observed 

1976 temperatures were less than 2°C.

INTRODUCTION

This study is one part of the U.S. Geological Survey's Intensive River-Quality Assessment of the 

upper Chattahoochee River basin (Cherry and 

others, 1976). The upper Chattahoochee River (fig. 

1) drains an area of 3,550 mi2 and extends from the 

northern basin divide to West Point Dam, a distance 

of about 250 river miles. The specific reach of interest to this study is about 40 mi long and is 

bounded on the upstream and downstream ends by 

the Atlantic and Whitesburg gages, respectively 

(table 1, fig. 1). About 980 mi 2 of the upper basin 

drain to this reach, including a large part of the 

Atlanta metropolitan area. River flow and river

temperature in the reach of interest are influenced 

mostly by tributary inflows, by effluents from wastewater-treatment facilities (WTF's) and thermal 

powerplants, by water-supply demands, and by regulation of the Chattahoochee River at Buford Dam 

(ng. 1).

On occasion in this text points on the Chattahoochee River will be designated by river mile (RM). 

Zero river mile (RM 000.00) is defined as the confluence of the Flint and Chattahoochee Rivers near 

the Georgia-Florida border (fig. 1).

Study results summarized in this report include 

an evaluation of the impact of flow regulation and 

heated effluents on the flow and temperature regimes 

of the Chattahoochee River. The methods of evaluation include the comparison of 1976 river temperatures with historical data as well as the use of transient, flow-temperature models.

DESCRIPTION OF THE PROBLEM

Since 1956, flow in the Chattahoochee River between Lake Sidney Lanier and West Point Lake 

(fig. 1) has been regulated and, to a large extent, 

dominated by hydropower releases from Buford 

Dam (fig. 1). Waves generated by such releases can 

be observed at gaging stations along the entire 

reach of the river between the reservoirs, a distance 

of more than 100 river miles. In the reach of interest 

(Atlanta gage to Whitesburg gage), regulated flows 

have fundamentally altered the "natural" flow and 

temperature regimes of the river. Examples of flow 

alteration include a general reduction in annual peak 

discharges and the enhancement of minimum low 

flows. Stream-temperature alterations occur because 

the turbine intake structures at Buford Dam use 

water from the hypolimnion and metalimnion zones 

of Lake Sidney Lanier. Consequently, winter stream 

temperatures downstream of the dam are warmer,
35°

FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

85° 84° 83°

EXPLANATION

10 Water-data station 

«— Hydrologfc boundary

34°

33°

7

Lake 

Sidney 

Lanier

——— -. __TENNESSEE^ . NORTH CAR^ 

ALABAMA ! GEORGIA " ———

UPPER

CHATTAHOOCHEE^i 

. %••' v RIVER BASIN CAPPS FERRY BRIDGE Fairbum

Whitesbug FLINT RIVER 

BASIN

INDEX MAP

Base from U.S Geological Survey 

Greater Atlanta Region 1 100,000, 1974 

Pheonix City 1 250,000, 1963 

Greanville 1 250,000, 1964 

Rome 1 250,000,1972

0 10 20 30 40 50 60 70 80 KILOMETERS

10 20 30 40 50 MILES

FIGURE 1.—Study area showing data-collection sites.

and summer temepratures are cooler than corresponding "natural" temperatures.

Morgan Falls Dam and Georgia Power's Plants 

Atkinsion-McDonough (table 1, fig. 1) also effect 

river flows and river temperatures in the study 

reach. Morgan Falls Dam, located about 40 mi downstream of Buford Dam, is a "run-of-the-river" 

hydropower facility that partially regulates river 

flows. The impact of such regulation on flow and 

stream temperatures in the study reach, however, 

is minimal. The Plants Atkinson-McDonough are 

thermal electric power facilities, that utilize river
INTRODUCTION

water in their operations. Heated effluents from 

boilers at the plants can raise stream temperatures 

by as much as 8°'C immediately downstream of their 

outfalls. In addition, quantities of river water are 

consumed in plant operation. The amounts consumed, however, are small and river flows downstream of the plants are not noticably effected.

Water-resource managers and regulatory agencies 

are concerned with stream temperatures under 

present (1976) and future conditions of water-supply and waste-load allocations and the impact of 

such temperatures on stream quality. Of particular 

interest to resource managers are stream temperatures during the late spring and summer months 

when tributary flows are low and ambient air temperatures are highest. Any negative impact of high 

stream temperatures on stream quality would be 

most evident during such periods. Also of interest 

are stream temperatures during a critical drought 

period when tributary contributions to the Chattahoochee River would be extremely low and the proportion of waste discharges in the total streamflow 

correspondingly high.

Of interest to regulatory agencies are comparisons 

of 1976 stream temperatures with "natural" temperatures; that is, temperatures occurring prior to 

construction of the powerplants and Buford Dam. 

On the one hand, the combined effects of stream

regulation and powerplant heat loads may presently 

produce lower than "natural" stream temperatures; 

even during the critical spring and summer months. 

On the other hand, heated effluents from the powerplants could be increasing stream temperatures excessively above "natural" conditions. The degree of 

future regulation of powerplant effluents may depend on which situation prevails.

The objectives of this study are to provide some 

insight into these problems and to investigate the 

relationship between transient flows and stream 

temperatures in the Chattahoochee River. Specific 

study objectives apply only to the reach between the 

Atlanta and Whitesburg gages and include:

1. The calibration and verification of deterministic, 

transient, flow and temperature models.

2. Use of the transient models to determine the impact of flow regulation and powerplant heat 

loadings on river temperatures using present 

(1976), future, and critical drought flow conditions.

3. A comparison of 1976 and computed "natural" 

stream temperatures.

SCOPE OF THE STUDY

Most of the data used in this study were collected 

by the U.S. Geological Survey and other agencies 

as part of routine data-collection programs. Such

TABLE 1.—Periodic data-collection sites

uses

station No. Station name

Map reference

No. River mile 

(fig. 1)

Data

02334430. 

02336000. 

02336020-

02336021_

02336300- 

02336380- 

02336450.

02336479.

02336480.

02336490.

02336526.

02336610.

02336651.

02336653.

02337070.

02337073.

02337170.

02337500.

02338000.

-Chattahoochee River at Buford Dam ______. 

.Chattahoochee River at Atlanta (Atlanta gage).

-Chattahoochee River at the Atlanta watersupply facility.

.Chattahoochee River at the Cobb County 

wastewater-treatment facility outfall.

.Peachtree Creek at Atlanta __________.

.Nancy Creek at Atlanta _____________.

.Chattahoochee River at the R. M. Clayton 

wastewater-treatment facility outfall.

-Chattahoochee River at the Plant McDonough 

intake.

-Chattahoochee River at the Plant McDonough 

outfall.

-Chattahoochee River at Georgia Highway 280 _. 

.Proctor Creek at Atlanta _____________. 

.Nickajack Creek near Mableton ____________

-Chattahoochee River at the South Cobb County 

wastewater-treatment facility outfall.

-Chattahoochee River at the Utoy Creek wastewater-treatment facility outfall. 

.Sweetwater Creek near Austell _______.

-Chattahoochee River at the Camp Creek wastewater-treatment facility outfall.

-Chattahoochee River near Fairburn (Fairburn gage).

-Snake Creek near Whitesburg _________.

-Chattahoochee River near Whitesburg 

(Whitesburg gage).

1__ 348.ia__.

2__ 302.97__.

3__ 300.62__.

Temperature

Stage, temperature

Stage, mean daily withdrawal

4____

5__ _____.

6__ _____.

7__ 300.24_.

8__ 299.23_.

9__ 299.15__.

10__ 298.77_.

11__ _____.

12__ _____.

13__ 294.28__.

300.56__ Mean daily discharge

Mean daily discharge 

Mean daily discharge 

Mean daily discharge

Temperature 

Stage

Temperature 

Mean daily discharge 

Mean daily discharge 

Mean daily discharge

291.48__ Mean daily discharge

15 __ ________

16 __ 283.78

17 __ 281.79 ___

19 __ 259.85 __

Mean daily discharge 

Mean daily discharge

Stage, temperature

Mean daily discharge 

Stage
FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

data are listed by type and station in table 1. Time 

series data were obtained for two 8-day periods in 

July and August 1976. These data include: (1) 

Hourly stage and stream temperatures at several 

stations on the Chattahoochee River; (2) hourly 

meteorologic data at one station; (3) mean daily 

effluent discharges at five wastewater-treatment 

facilities; (4) mean daily discharge at several gaged 

tributary streams; and (5) mean daily withdrawals 

from the Chattahoochee River at the Atlanta watersupply facility. Hourly meteorlogic data were collected at the R. M. Clayton WTF (table 1 and fig. 

1) and include wet and dry bulb air temperatures, 

long and short wave radiation, wind speed and direction, and rainfall. Meteorologic data used in this 

study are listed by parameter in the Summary of 

Data Section at the end of this report (table 10). 

Mean daily flows at the various WTF outfalls and 

at the water-supply facility were treated as tributary contributions and diversions, respectively. 

Measurements of streamflow in the larger tributaries draining to the study reach were made on 

July 12, 1976.

River cross-section and bed-elevation data at 

36 locations were obtained originally from the U.S. 

Army Corps of Engineers (1973). Channel widths 

and bed elevations at most of these locations were 

corrected using data collected during a field reconnaissance in May 1977 when flow conditions were 

low and generally steady. Cross-section data at five 

additional locations were collected during this reconnaissance along with the shading or barrier heights 

of the river banks and the trees lining the banks. 

Coordinates and barrier heights for all cross sections 

used in this study are listed in the Summary of 

Data Section at the end of this publication.

In general, data used in this report are dimensioned according to the units in which the data 

were reported or collected. Thus, river temperatures 

and most meteorologic data are expressed in metric 

unite, and channel, stages, and discharge data are 

given in inch-pound units. A list of metric to inchpound conversion factors is provided at the front of 

this report.

Symbols in this report are defined where they first 

appear in the text.

DESCRIPTION OF THE STUDY AREA

The area of interest to this study is the watershed draining to the Chattahoochee between the Atlanta and; Whitesburg gages (fig. 1). Fenneman 

(1938) places this entire area within the southern

Piedmont physiographic province and, more specifically, within the Atlanta Plateau. The topography 

of the study area is characterized by low hills separated by narrow valleys. Small mountains do occur 

along the northern divide, but summit elevations 

do not exceed 2,000 ft. The stream channel network 

draining to the Chattahoochee River is slightly dendritic and is not particularly influenced by basin 

geology. The channel of the Chattahoochee River, 

however, is extensively controlled by geologic structures and occupies or directly parallels the Brevard 

Fault through most of the study reach (Higgins, 

1968). Alluvial "bottomlands" are common along 

the Chattahoochee River and its major tributaries 

but generally are less than 1 mi in width. Total 

basin area drained by the study reach is 980 mi2 .

Climate on the Atlanta Plateau is significantly 

influenced by the proximity of the area to the Gulf 

of Mexico (fig. 1) and to a lesser degree by the 

Blue Ridge Mountains northeast of the study area 

(fig. 1). In general, the Gulf of Mexico is a moderating influence on area temperatures and is a source 

of moisture-laden winds that provide rainfall to the 

basin. The mountains affect the climate most directly 

by serving as partial barriers to the flow of air 

masses.

Summer temperatures on the Atlanta Plateau are 

generally mild. Daytime temperatures are highest 

from June through August but rarely exceed 100°F. 

Summer nights are cool with minimum temperatures 

seldom below 65°F. During the winter, the mountain 

barriers inhibit the southerly flow of polar air 

masses into the Chattahoochee River basin. Thus 

winter temperatures are moderate and extended 

periods of excessively cold weather are rare. Daytime temperatures are lowest from November 

through January and rarely exceed 60 °F. Subfreezing temperatures (<32°F) occur frequently but subzero (<0°F) temperatures are rare.

Average annual precipitation in the study area is 

in excess of 45 in. Most rainfall occurs in the winter 

and early spring months. Frozen precipitation in 

the form of sleet and snow is rare. During the 

summer, convective storms with short period® of 

intense rainfall are common. A summary of climatologic data for Atlanta is listed in table 2.

Land use in the study area is presently (1976) 

characterized by the urbanization of forests and 

agricultural lands. Urban, agricultural, and forest 

lands occupy 25, 13, and 59 percent of the land area, 

respectively. The remaining 3 percent of the area 

consists of wetlands and reservoirs. Major urban
DESCRIPTION OF THE STUDY AREA

TABLE 2.—Summary of climatologic data for Atlanta, 1941-70

Temperature <°F)

Month

April ... __ ... _ ..

May . __ . —— _______ 

June ______--.______ 

July _ — -———.-

August --_--. __ -_ _

October _--__--._ _ 

November .___ _ ._. 

December _ . _ __

Record totals _ 

Yearly 

Averages.

Mean 

daily 

maximum

51.4 __

54.5--..

61.1 ——

71.4--..

79.0- __ 

84.6 __ 

86.5 __ 

86.4---. 

81.2. .

72.5 .... 

61.9--.. 

52.7 __

70.3- ...

Mean 

daily 

minimum

33.4 __

35.5 __

41.1 __

50.7 __

59.2 ____ 

66.6 ____ 

69.4 __ . 

68.6 ____ 

63.4. ___

52.3 ____ 

40.8 ____ 

34.3 __

.51.3 __

Record 

high

72 __

79 __

85——

88 __

93 __

98 ____ 

98____ 

98_...

93. ...

88 __ 

84, __ 

77 - -

98_...

Record 

low

— 3 __

8 __

21 ____

26. ..

37 .... 

48 __ 

53--. 

56--- 

36- -.

29 __ 

14 __ 

I....

— 3 __

Precipitation 

(in)

Average 

daily 

mean

4.34 __

5.84 __

4.61. __

3.71 ____ 

3.67 — — 

4.90 __ 

3.54 ____ 

3.15--..

2.50 __ 

3.43 __ 

4.24 __

48.34 __

Record 

daily 

high

3 91

5.67 __

5.08 __

4.26 __

5.13 __ 

3.41 __ 

5.44 __ 

5.05 __ 

5.46.-..

3.27 .___ 

4.11 __ 

3.85. —

5.67 __

centers include Atlanta and Marietta (fig. 1) and 

are characterized by extensive residential communities separated by commercial, industrial, and transportation centers. Agricultural lands are generally 

located within the flood plains of the Chattahoochee 

River and its major tributaries. Grazing, row cropping, poultry feeding, and orcharding comprise the 

majority of agricultural activities. Forests consist 

mostly of oak, pine, and hickory. Forest undergrowth is extensive and includes dogwood, greenbriar, sassafras, and blackberry briars.

STREAM NETWORK AND CHANNEL 

DESCRIPTION

Throug-h the study reach, the Chattahoochee River 

channel is oriented to the southwest and is contained mostly within the zone of cataclasis of the 

Brevard Fault (Higgins, 1968). The channel between the gages at Atlanta and near Fairburn 

(table 1, fig. 1) drains most of the Atlanta metropolitan area and receives inflows from tributaries 

and wastewater-treatment facilities. Diversions 

from this reach occur at the Atlanta water-supply 

facility and at the Atkinson-McDonoug-h powerplants. Between the Fairburn and Whitesburg gages 

the Chattahoochee River drains mostly forests and 

farmlands and receives only tributary inflows. Each 

significant tributary and municipal and power facility in the study reach plus the locations of each 

respective confluence, outfall, or intake are listed in 

table 3.

Channel cross sections are rectangular to trapezoidal in shape and are characterized by high, steep 

banks and sand beds. Shoals and rock beds do occur, 

however, and are common in the vicinity of the

TABLE 3.—Tributary network and mean discharges during 

specified periods

Name

Atlanta water-supply facility .. 

Cobb County wastewater-treatment facility.

ment facility.

South Cobb County wastewatertreatment facility.

ment facility.

Sweetwater Creek _____________

ment facility. 

Camp Creek __________________

Pea Creek

Bear Creek (left bank) ... .___

Wolf Creek . __ _ . .

Snake Creek ...... — ._ — _-_.. 

Cedar Creek _ ...__--- _______

River 

mile

300.62 __ 

300.56 ____

300.52 __

300.24 ____

299.46

299.23 _-._

299.19 ..

299.15 __._

297.50 ____

295.13 ____

294.28.-..

291.57 __._

288.58 ____

283.54 ____ 

283.27 ...

281.48

97C QC

274.49 __._ 

273.46.--.

267.34...

261.72 -.-. 

261.25 ____

Discharge 

July 

12-19, 

1976 

(ftVs)

— 141 ——

12 ____

65——

76..--

8 ____

26 __

11 ___. 

22 ——

20 —— _

299 _ —— 

7——

20 ____ 

24. ..

29 ...

91

25 __ — 

100.. .

22 ——

67 ____ 

40 __—

Discharge 

August 

1-8, 

1976 

(fWs)

— 141 ____ 

12 ——

24——

124 __._

7 ___.

17 ____

11—— 

22 ——

13 ——

100 ____

7 _—

15 ____ 

17. ..

23 __

10 — .

17 ____

16 ____ 

70 ——

16 __

33 ——

27 __ -

Discharge 

1954 

Drought 

(ftf/s)

8 _____

1 ___

1 _____

1 _____

2 _____

1 _____ 

2 _____

6 __ _

1 _____

3— —

1 __ _ 

I. ...

1 ____

3 _____

3.——

Atlanta gage, downstream of the confluence with 

Nickajack Creek, and between Capps Ferry Bridge 

and the Whitesburg gage (fig. 1). Typical channel 

cross sections are shown in figure 2. Profiles of the 

channel thalweg and the water-surface altitude during steady, low flow are shown in figure 3. Several 

discontinuities occur in the profile—in particular at 

RM 300.62 and RM 299.10. At these locations, weirs 

have been constructed to create pumping pools for 

the intake structures of the Atlanta water-supply 

facility and the Atkinson-McDonough powerplants. 

Other discontinuities are the result of bedrock controls or the rapid decline of channel altitudes across 

a shoal or series of shoals.

STREAMFLOW AND TEMPERATURE 

CHARACTERISTICS

Streamflow through the study reach is greatly 

influenced by regulation at Buford Dam. During1 a 

typical week, hydropower is produced at the dam for 

several hours each weekday and infrequently on 

weekends. Each period of hydropower production is 

accompanied by the movement of water downstream 

in the form of a wave or pulse. The flow characteristics of each wave are directly related to the quantity of power produced and the length of the powerproduction period.

Hydrographs of mean daily discharge in the Chattahoochee River at Atlanta, near Fairburn, and near
FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA 

770

760

uj

Q

D

Q 

ill 

00

750

740

100 200

CHANNEL WIDTH, IN FEET

A

300

700

690

Q 

ill 

00

680

670

RM 259.87 

Whitesburg Gage

100 200 

CHANNEL WIDTH, IN FEET

B

300

FIGURE 2.—Selected channel cross sections of the Chattahoochee River from Atlanta to 

Whitesburg. A, RM 302.97. B, RM 259.87.

Whitesburg1 are shown in figures 4 through 6. The 

cyclic nature of the flows is apparent and reflects 

the weekly (7-day) period characterized by 5 days 

of power production at Buford Dam followed by 2 

days with little or no production. Anomalously high 

peaks on the hydrographs correspond to periods of 

high rainfall runoff.

The long term effects of regulation on streamflow 

are indicated by the flow duration curves in figure

7. Since regulation, peak flows are smaller in both 

magnitude and duration, and minimum, flows are 

larger.

Mean daily river temperatures at several stations 

on the Chattahoochee River are shown in figures 8 

through 12. Each graph represents mean daily river 

temperature computed from hourly measurements 

recorded during water year 1976. At most stations, 

the annual variation of river temperatures generally
STREAMFLOW AND TEMPERATURE CHARACTERISTICS

740

730

< 720

Q

LLJ 

CO

710

RM 281.79 

Fairburn Gage

100 200 

CHANNEL WIDTH, IN FEET

c

305;

750

t740

Q

LU 

QQ

730

720'

RM 293.92 

(Channelized Section)

100 200

CHANNEL WIDTH, IN FEET,

D

306

FIGURE 2.—Continued. C, RM 281.79. D, RM 293.92.

conforms to the monthly air-temperature trends indicated in table 2 and ranges from a low of about 

4°C in January to a high of about 24°C in July or 

August. Those temperatures showing the least variation (7 to 13°C) are at Buford Dam (fig. 8) and 

are most influenced by the metalimnion and hypolimnion temperatures, of Lake Sidney Lanier. River 

temperatures at Georgia Highway 280 show the 

largest annual variation (7° to 28°C) and are influenced to a great extent by heat loads from the 

Atkinson-McDonough powerplants. At any station, 

short term variations in river temperature can be 

large and are caused mostly by flow regulation, the

occurrence of storm runoff, cloud cover, and day-today changes in air temperature.

Changes in mean daily river temperature between 

stations can also be large and are influenced primarily by exchanges of thermal energy between the 

river and the atmosphere.

Temperatures of the Chattahoochee River at the 

Atlanta gage during the period July 1937 to May 

1938 were reported by Lamar (1944) and are shown 

in figure 13. A total of 294 daily temperature measurements were recorded. Each measurement was 

reportedly made between 1300 and 1930 h. Hourly 

temperature data collected at the Atlanta gage dur-
FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

720

710

< 700

O

LU 

GO

690

RM 268.34

100 200 300

CHANNEL WIDTH, IN FEET

£

400

760

750

o

D

Q

LU 

GO

740

730

100 200 

CHANNEL WIDTH, IN FEET

300

FIGURE 2.—Continued. E, RM 268.14. F, RM 298.77.

ing water year 1976 indicate that stream temperatures during- the afternoon and early evening depart 

from mean daily stream temeprature by 1.5°C or 

less. The same criterion applied to the 1937-38 

temperatures indicates that these data are representative of mean daily stream temperature within an 

error of 1.5 °C and, for comparative purposes, are 

treated accordingly in this text.

The comparision of river-temperature data at the 

Atlanta gage collected before (fig. 13) and after 

(fig. 9) the construction of Buford Dam provides 

some insight into the impact of flow regulation on 

river temperatures. During water years 1937-38, 

annual variations in river temperature at Atlanta

were considerably greater than those measured in 

water year 1976—ranging from 1.5 to 31 °C compared to 4.5 to 21.5°C. Also, annual extremes occurred at different times of the year. During water 

year 1976, the annual low and high temperatures 

occurred in January and August, respectively; corresponding months for the 1937-38 temperature extremes were December and July.

Some of the variability in river temperature attributed to flow regulation could also be caused by 

differences in meteorologic conditions. The actual 

meteorologic contribution to river temperatures cannot be determined; however, estimates can be made 

by comparing mean monthly air temperatures at At-
STREAMFLOW AND TEMPERATURE CHARACTERISTICS

760

750

740

730 

fc

LLJ 

LL.

? 720

LU 

O

< 710 

700 

690 

680

• Steady, low flow, water surface

• Thalweg

255 260 265 270 275 280 285

RIVER MILE

290 295 300 305

FIGURE 3.—Thalweg and low-flow profile of the Chattahoochee River—Atlanta to Whitesburg.

Oct Nov Jan Feb Mar Apr May June July Aug Sept

1975

FIGURE 4.—Mean daily streamflow in the Chattahoochee River at Atlanta during water year 1976.
MEAN DAILY STREAMFLOW, IN THOUSANDS 

OF CUBIC FEET PER SECOND

go>

£0

a 

2.

«<T

en

?So

3

3s 

1

a>

O

cr

£0

cr

8

o

cr

»S'

^

a>

fo 

^

|

g"

A

CL 

C 

2

W3 

^

!

«<

«o 

-<I

os

MEAN DAILY STREAMFL

OF CUBIC FEET P

-» -» 

O ^ 00 ISJ O) 

1 I I 
STREAMFLOW AND TEMPERATURE CHARACTERISTICS 11

36

32

28

o

z 

o

LU 24

EC

LU 

Q.

LU 

LU 

LL

5 20 

o

o

O

16

o

00

o

12

— — Prior to construction of Buford Dam

——— Subsequent to construction of Buford Dam

0.1 5 20 50 90 99 

PERCENTAGE OF TIME FLOW EQUALED OR EXCEEDED

99.99

FIGURE 7.—Flow duration characteristics of the Chattahoochee River at Atlanta prior to and subsequent to the construction of Buford Dam.
12 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

27

24

21

UJO 

u>

UJ 

UJ<r O

UJ

cc

D

i

ff

uj 9

< 6

Q

12

—— Mean monthly air temperature at Atlanta

Oct Nov 

1975

Dec Jan Feb Mar Apr May 

1976

June July Aug Sept

FIGURE 8.—Observed mean daily temperature of the Chattahoochee River at Buford Dam and mean monthly air temperature at Atlanta during water year 1976.

30

GJ24

LLJ 

UJ 

OC 

O 

UJ

Q

QC

UJ „-

a. 12

O

Z 6

I I————————— ~ T 

Mean monthly air temperature at Atlanta

Oct Nov' 

1975

Dec Jan Feb Mar ' Apr May 

1976

June July Aug Sept

FIGURE 9.—Observed mean daily temperature of the Chattahoochee River at Atlanta and mean monthly air temperature at

Atlanta during water year 1976.
STREAMFLOW AND TEMPERATURE CHARACTERISTICS 13

Mean monthly air temperature at Atlanta ,

O 1—

Oct Nov 

1975

FIGURE 10.—Observed mean daily temperature of the Chattahoochee River at the Plant McDonough intake

monthly air temperature at Atlanta during water year 1976.

30

27

I I I I 

—— Mean monthly air temperature at Atlanta

1 1

Oct Nov 

1975

Dec

I I I

Jan Feb Mar Apr

I

May 

1976

I I I

June July Aug

i

Sept „

FIGURE 11.—Observed mean daily temperature of the Chattahoochee River at Georgia Highway 280 and mean monthly air

temperature at Atlanta during water year 1976.
14 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

——— Mean monthly air temperature at Atlanta

Aug Sept

FIGURE 12.—Observed mean daily temperature of the Chattahoochee River near Fairburn and mean monthly air temperature at Atlanta during water year 1976.

lanta for the periods 1937-38 and 1975-76 (NOAA, 

1976). These data are listed in table 4 for the coincident months of river-temperature record. Winter 

air temperatures during 1975-76 were generally 

colder than corresponding temperatures for the 

period 1937-38 and summer and fall air temperatures were about the same or warmer. River temperatures at the Atlanta gage, however, show nearly opposite trends—being warmer during the winter of 

1975-76 and cooler during the summer and early 

fall. Thus, observed differences in river temperature 

at Atlanta during the periods 1937-38 and 1975-76 

would at best have been dampened or minimized by 

the prevailing meteorologic conditions and have for 

the most part been correctly attributed to flow regulation at Buford Dam.

For purposes of this study, "natural" river temperatures at a station are defined as those temperatures resulting from the combined thermal effect of 

atmospheric exchange and tributary inflow on 

stream waters between the headwaters and the station. Thus, by definition, "natural" temperatures 

cannot be significantly affected by upstream artificial heat sources or sinks. Application of this definition to the observed river-temperature data described previously (figs. 8-13) indicates that the 

1937-38 stream temepratures at the Atlanta gage 

(fig. 13) probably closely approximate natural temperatures and are considered as such in this text.

Mean monthly air temperatures at Atlanta are 

listed in table 4 and are shown graphically by horizontal lines on figures 8 to 13. Corresponding mean

TABLE 4.—Mean monthly air temperatures at Atlanta for the period of record and for specified months during 1937-38 and

1975-76, in degrees Celsius

Year ——

1937 _ _. _

1938 _ _ __

1975 _ _____

1976 _ _ _

1879-1975 __

Month

Jan.

6.1

3.6 

6.3

Feb.

10.8

10.8

7.6

Mar.

14.7

13.6 

11.4

Apr.

16.3

16.5 

16.3

May

18.6 

20.8

June

——

23.2 

24.6

July

26.4

24.7 

25.8

Aug.

26.4

24.4 

25.4

Sept.

21.8

21.0 

22.8

Oct.

14.9

17.4

17.1

Nov.

8.6

12.2

11.1

Dec.

6.2 

~6~3

7.0
STREAMFLOW AND TEMPERATURE CHARACTERISTICS 15

36

33

27

-—— Mean monthly air temperature at Atlanta

0

LLJ iu 24 

<r

D 18

DC

S 15

LU

> 12

Z 9 

5 6

July Aug Sept Oct 

1937

Nov Dec Jan Feb Mar Apr 

1938

May June

FIGURE 13.—Observed mean daily temperature of the Chattahoochee River and mean monthly air temperature at Atlanta—

July 1937 to May 1938.

TABLE 5.—Mean monthly water temperatures during 1937- 

38 and 1975-76, in degrees Celsius

Month

October _____ 

November _ _ 

December _ __ 

January _ _ _

February

March _ ____

May ________ 

June _______

July __ ____

August _ _

September

Q«

1*<3S 

oa~

11.0__ 

11.5— 

11.0—

7.5__

6.5 _

7.5

8.5

8.5__ 

9.5 _

9.5_

10.5 _

11.5_

Atlanta gage 

(1937-38)

17.7— 

10.2 —

7.2__ 

7.4 _

11.3—

14.4 _

17.4—

29.4

27.6

24.7 _

Atlanta gage 

(1975-76)

13.0— 

10.0— 

7.0—

9.0 —

11.5—

12.0

14.0— 

15.5

18.0 _

18.5

17.5 _

Ifo£ 

32

sr

<u •£•* 

§5 

E-S

16.0— 

13.5__ 

10.5— 

7.5 _

9.5

11.5 _

12.0 _

14.5__ 

16.0

18.5-

19.5

18.0

Georgia Highway 

(1975-76) 280 

18.5— 

15.5__ 

12.5— 

9.0__

11.0

13.0

13.5

16.5— 

18.5

21.0

22.0

20.0

Fairbum gage 

(1975-76)

18.5— 

15.0__ 

11.0—

11.0 _

13.0

1~8~6"

22.0

23.5

21.5

monthly river temperatures are listed by location 

and period of record in taible 5. Comparison of mean 

monthly air and water temperatures at the Atlanta 

gage during 1937-38 (fig. 9, tables 4 and 5) indicates that mean monthly natural stream temperatures are within ±3°C of mean monthly air temperatures. Similar relations have also been observed for 

the Severn River in England and for the Illinois 

River in data presented by Langford (1970) and 

Kothandaraman and Evens (1972), respectively. 

Application of this relation to the temperature data 

collected during 1975-76 implies that differences between mean monthly air and river temperatures in 

excess of 3°C result partly from artificial thermal 

alteration; that is from flow regulation and powerplant effluents. Thus, hydropower production appears to have a significant cooling effect on river 

temperatures at Buford Dam, especially through the 

period March to September, and warms the river 

significantly during the months of December and 

January (fig. 8). At the Atlanta gage (fig. 9), much 

of the cooling effect noted at Buford Dam has been 

dissipated, and the river temperatures more closely 

approximate a natural, annual pattern. The cooling 

effects of hydropower production are still noticable,
16 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER. GEORGIA

however, especially during the period April through 

September. Only slight differences in mean monthly 

river temperatures were noted between the Atlanta 

gage and the Plant McDonough intake (figs. 9 and 

10). These differences should be expected given the 

short distance between the stations and the absence 

of significant heat sources or sinks in the intervening 

reach. Comparison of mean monthly air and river 

temperatures at Georgia Highway 280 (fig. 11, 

tables 4 and 5) indicates that the combined effect 

of flow regulation and powerplant effluents results 

in mean river temperatures approximately equal to 

mean natural temperatures throughout most of the 

period February to October and greater than natural 

temperatures during December and January. Similar 

results were noted at the Fairburn gage (fig. 12).

Thus, in summary, comparisons of mean monthly 

air and river temperatures have indicated both the 

occurrence and magnitude of river temperature alterations that result from flow regulation at Buford 

Dam and heat loadings from the Atkinson-McDonough powerplants. Significant cooling below 

natural temperatures was noted downstream of Buford Dam, at the Atlanta gage, and at the Plant 

McDonough intake during the spring and summer 

months. Flow regulation produced warmer than 

natural river temperatures at the same stations during the winter. Downstream from the powerplants, 

the combined effect of flow regulation and powerplant heat loads was shown to produce river temperatures approximating natural conditions during 

much of the spring and summer and warmer than 

natural temperatures during the early winter 

months.

FLOW AND TEMPERATURE MODELS

Detailed descriptions of the flow and temperature 

models, their uses, and solution techniques are presented by Jobson and Keefer (1979) and Land 

(1978). Aspects of the models pertinent to this study 

are discussed below.

The flow model is a finite-difference approximation of the one-dimensional continuity and momentum equations for gradually varied flow. The forms 

used are identical to those presented by Amein and 

Fang (1970). The numerical technique used to solve 

the equations is referred to as fully forward, linear, 

implicit which computes the spatial derivatives at 

the forward time level and simultaneously solves for 

the unknown depths and velocities at the end of 

each time step.

Boundary conditions for the flow model were defined at the Atlanta and Whitesburg gages as discharge and stage, respectively. Discharge at the Atlanta gage was estimated from a rating curve and 

hourly stage measurements. Stability criteria, based 

on the variable distances between cross sections 

(table 8 in the Summary of Data) and expected flow 

velocities, required that boundary data be applied 

to the flow model at 15-min intervals. Such data 

were obtained by linear interpolation between the 

given hourly data.

Tributary inflows applied to the model were assumed constant during the various simulation 

periods.

Flow-geometry data are required by the model as 

a function of depth and include values of top width, 

wetted perimeter, and area of flow at each cross 

section. Top widths were computed by linear interpolation between data pairs of top width and depth 

provided for each cross section. Flow areas at each 

depth were computed by integrating the curve defined by the top width-depth relation. Wetted perimeters were determined using computed values of 

top width and depth and a skew coefficient. A detailed description of these techniques is provided by 

Land (1978).

The temperature model solves a finite-difference 

approximation of the one-dimensional equation describing the continuity of thermal energy in open 

channels. Jobson and Keefer (1979) present this 

equation in the form:

-&T VdT Dx-d"-T $T W faP ,.,. —— + —— = ——~ + -^—7 + r A (1)

QV Q& QX" \^> ppA. \sppA.

where T = stream temperature, £ = time, U = stream 

velocity, x = distance along the channel, Dx = a dispersion coefficient, </> r = the flux of thermal energy from 

the atmosphere to the water, Cp = the specific heat of 

water, p = the density of water, T^ = the top width of 

flow, A = the flow area, P = the wetted perimeter, and 

<£/} = the flux of thermal energy from the bed to the 

water. The solution technique used to solve this 

equation is a slight variation of the six-point implicit 

scheme of Stone and Brian (1963).

Data input from the flow model to the temperature model included top width, velocity, cross 

sectional area and tributary inflow at each section 

for each time step.

The solution scheme of the temperature model requires subreaches of equal length. In order to make 

the output of the flow model compatible with the 

temperature model, the flow data were interpolated 

to an equal grid spacing by use of a processor pro-
CALIBRATION AND VERIFICATION 17

gram. The logic of this program assured that the 

total instantaneous volume of water within any 

subreach was the same for both models.

Observed river temperatures at the Atlanta gage 

served as the necessary boundary condition for the 

temperature model. Temperatures of the tributary 

inflows were unavailable but were estimated by regression from the equation:

-12.25 (2)

where 2\=instantaneous tributary temperature, 

Tw& = instantaneous wet bulb temperature, and i is a 

time step indicator. Development of this equation 

was based on 41 instantaneous tributary temperature measurements made in the study area during 

the summer of 1976. Standard error of estimate of 

this regression is 3.2°C.

The flux of thermal energy between the bed and 

the water is small compared to other heat flux and 

was computed using the procedure outlined by 

Jobson and Keefer (1979).

The flux of thermal energy from the atmosphere 

to the water, $T, is the result of several processes 

and is generally described by the relation:

i _ i i ; i i , i . fO\ tyT — OAT — *Pb — >V — fyh ~"~ 0/»* ~"~ fy</ \*J /

where <£A- = net heat flux caused by incoming radiation from the sun and atmosphere, ^> 6 = heat flux 

caused by longwave radiation emitted by the water, 

<t> c = heat utilized by evaporation, <£/, = heat conducted 

from the water as sensible heat, <£/. = heat added by 

rain falling directly on the surface, and ^^heat 

added to the river by tributary inflow. Only the flux 

of incoming .solar radiation could be measured 

directly by meteorologic instruments. The flux of incoming atmospheric radiation was computed using 

the procedure outlined by Koberg (1964). The radiation flux emitted by the water surface (t£b ) was 

computed using the Steffan-Boltzman equation (Jobson and Keefer, 1979). Three percent of the incoming atmospheric radiation was assumed to be reflected while the percentage of solar radiation reflected was estimated from a complex relation between the azimuth and height of the sun, the azimuth of the subreach, width of the subreach, and 

the effective shading height of the riverbanks and 

trees along the banks (Jobson and Keefer, 1979). 

The heat flux caused by evaporation and conduction 

was computed using meteorologic data, Dalton's 

Law, and the analog of mass and heat transfer as 

explained by Bowen's ratio (Jobson and Keefer, 

1979). The wind function used in Dalton's Law is 

proportional to the wind function derived by Jobson

(1977a and b) from thermal data collected on the 

San Diego Aqueduct in southern California.

The combined heat load from the Atkinson-McDonough powerplants to the Chattahoochee River 

was not measured directly. Computation of instantaneous loads was originally accomplished using the 

observed temperature differential across the outfalls 

(Plant McDonough intake and Georgia Highway 

280) and corresponding instantaneous river flows 

computed by the flow model. Unfortunately, at low 

flow, it was determined that the recorded temperatures at the Plant McDonough intake were affected, 

to some extent, by the hot water discharges. The 

heat loads applied to the temperature model, therefore, were computed using the difference between the 

observed temepratures at Georgia Highway 280 and 

the model computed temperatures at the Plant McDonough intake.

CALIBRATION AND VERIFICATION

Flow, temperature, and meteorologic data collected during two 8-day periods beginning July 12, 

1976, and August 1, 1976, respectfully, were used 

to calibrate and verify the flow and temperature 

models.

FLOW MODEL

Calibration of the flow model was accomplished 

in two steps using stage data for the period July 

12-19, 1976, and discharge and flow-depth data collected during the May 1977 reconnaissance. The first 

step utilized the discharge and flow-depth data collected during the reconnaissance. The maximum 

measured depth at each cross section was added to 

the "known" thalweg altitude (U.S. Army Corps 

of Engineers, 1973) to form an "observed" watersurface profile. A smooth curve was then drawn 

through the plotted points matching the observed 

water-surface altitudes at bridges and gages where 

accurate altitude measurements were available. The 

measured depths were then subtracted from the 

smoothed profile to determine corrected bed altitudes. Starting at the downstream end of the study 

reach, individual Manning's roughness coefficients 

were selected on a trial and error basis at each cross 

section such that the flow model, run to steady state, 

accurately reproduced the observed depths and the 

"smoothed" water-surface profile. The roughness coefficients obtained in this way insured that the model 

computed realistic depths and velocities at low flow 

and provided a basis for computing corresponding 

coefficients during transient flow.
18 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

The second step of the calibration process was the 

development of a linear rate of change of roughness 

with stage at each cross section, which would allow 

the model to best predict the observed July 12-19 

stages in the river. Such rates were determined by 

trial and error. The range of computed Manning's 

n values for each cross section is listed in Table 9 

in the Summary of data.

The results of the flow-model calibration are illustrated in figure 14. Computed and observed stages 

are plotted at the Atlanta gage, the Atlanta watersupply facility, the Plant McDonough outfall, the 

Fainburn gage, and the Whitesburg gage. Phase differences between computed and observed stages are 

minimal and stage values are closely matched at both 

high and low flow. The model consistently overpredicts intermediate stage values at all stations, which 

suggests that the rate of change of roughness with 

stage is not linear as originally assumed. This error 

is largest at the Atlanta water-supply facility (0.5 

ft) and progressively decreases downstream to the 

Fairburn gage (0.2 ft).

Both rated and computed discharges at the Fairburn gage are shown in figure 15. In general, the 

agreement is good but the two discharges appear to 

be out of phase by about 2 h. In evaluating this apparent phase shift, it is well to remember that a 

rated discharge is dependent on an assumed unique 

relation between stage and discharge. For unsteady 

flow, such relations do not generally exist. For example, figure 16 shows the rating curve and the 

simulated stage-discharge relation at the Fairburn 

gage for the hydropulse of July 13, 1976. The model 

predicts greater discharges than the rating curve on 

the rising limb and smaller discharges on the falling 

limb, just as one would expect. The phase shift between rated and computed discharge at the river 

gage near Whitesburg is shown in figure 17. A shift 

of about 5 h is noted and at a given instant, can result in discharge differences of nearly 20 percent. 

Arbitrary manipulation of geometry and Manning's 

n data at several sections upstream of the Whitesburg gage indicated that the size of the phase shift 

is insensitive to changes in both channel volume and 

roughness. The simulated stage-discharge relation 

for flow at the Whitesburg gage during July 13-14, 

1976, is shown on figure 18.

Tributary inflows during the calibration period 

are listed in table 3 and were based on measured 

discharges obtained on July 12, 1976, adjusted to 

a weekly average using records at gaged streams.

The calibrated flow model was verified using measured stage data for the period August 1-8, 1976.

Simulated and observed stages are shown on figure 

19. Flow variations were less extreme in August 

than in July, and no stage data were available at 

the Plant McDonough outfall. A maximum error of 

0.7 ft between computed and observed stages occurred at the Atlanta water-supply facility on 

August 7. Differences between observed and computed stages at the Atlanta and Fairburn gages were 

less than 0.4 ft.

Plots of simulated and rated discharge for the 

verification period were similar to those presented 

for model calibration and are not shown in this text. 

A phase shift of about 2 h was observed at the 

Fairburn gage with a maximum difference between 

simulated and rated discharge of about 8 percent. 

The phase shift at Whitesburg was also about 2 h 

with a corresponding maximum difference between 

discharge of about 13 percent. The reduction in 

phase shift between the calibration and verification 

periods is not unexpected because the hysteretic nature of the stage-discharge relation usually decreases 

in proportion to the dynamic nature of the flow.

Although phase shifts occurred between comparisons of instantaneous computed and rated discharge 

at both the Fairburn and Whitesburg gages, computation of the total volume of water passing by each 

station using both the model and the raiting curve 

produced nearly equal values for both the calibration and verification periods.

Roughness relations, bed elevations, and channel 

geometry data at each cross section were exactly the 

same for the calibration and verification of the flow 

model. Tributary inflows during the verification 

period (table 3) were based on average daily discharges at the gaged streams and extrapolated discharges at ungaged streams.

Overall, the results of the calibration and verification of the flow model are considered to be good, 

and the flow model is considered an adequate predictive tool.

TEMPERATURE MODEL

The only parameter in the temperature model 

which could reasonably be varied for calibration 

purposes is the empirical wind function. The wind 

function is used in conjunction with the quasi-empirical Dalton's Law to compute heat flux due to 

evaporation (Jobson and Keefer, 1979). The effect 

of the wind function is highly variable but generally 

is largest for high river temperatures, and low discharges. Consequently, river-temperature and rneteorologic data collected for the period August 1-8, 

1976, were used to' calibrate the temperature model,
CALIBRATION AND VERIFICATION 19

760

LU

a

F 

<

LU

o

2

cc

CO

cc

LU

I

755

750

——— Observed

——— Computed

12 13 14 15 

JULY 1976

16 17 18 19

755

—— Observed

— — Computed

LU

a

P

< 750

LU

o

745

12 13 14 15 16 17 18 19

JULY 1976

B

FIGURE 14.—Observed and computed stages of the Chattahoochee River during the period July 12-19, 1976. 

A, At Atlanta. B, At Atlanta water-supply facility. C, At the Plant McDonough outfall. D, Near Fairburn. E, Near Whitesburg. Points A-F on each graph represent water particles traced through the study 

reach (see p. 24).
O 

§

s±

3

c

s.

WATER-SURFACE ALTITUDE, IN FEET

Ill

o>

(O

-J 

o>

00

WATER-SURFACE ALTITUDE

S

01

I T --~ I I I 

I I
DISCHARGE, IN THOUSANDS 

OF CUBIC FEET PER SECOND

£*

cr~

_i ^ 

o>
22 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

726

725

724

723

722

721

720

Rating curve

1 23456 

DISCHARGE, IN THOUSANDS OF CUBIC FEET PER SECOND

FIGURE 16.—Computed stage-discharge relation for the Chattahoochee River near Fairburn, July 13, 1976.

and corresponding data for the period July 12-19, 

1976, were used for model verification.

A wind function derived from thermal data collected on the San Diego Aqueduct in southern California has 'been .shown to be satisfactory for modelui 687

686

685

684

683

~ Rating curve

01 234567 

DISCHARGE, IN THOUSANDS OF CUBIC FEET PER SECOND

FIGURE 18.—Computed stage-discharge relation for the 

Chattahoochee River near Whitesburg, July 13-14, 1976.

ing river temperatures in the Chattahoochee River 

upstream of Atlanta (Jobson and Keefer, 1979). 

Optimum calibration of the temperature model for

<0 

»%

l-o- zfc

-111 ui u. 3

<m

2

12 13 14 15 16 

JULY 1976

17 18 19

FIGURE 17.—Rated and computed discharge at the Chattahoochee River near Whitesburg, July 12-19, 1976.
CALIBRATION AND VERIFICATION 23

this study was achieved by reducing this wind function by 30 percent.

The measured and computed temperatures for the 

calibration period are shown on figure 20. The computed and observed temperatures at Georgia Highway 280 are identical because the model used the 

observed temperature at this point to determine the 

heat loading from the Atkinson-McDonough powerplants. Unfortunately, no acceptable observed-temperature record was available at Whitesburg, and 

only the computed record is shown.

The first comparison of interest is at the Plant 

McDonough Intake (fig. 205). Comparing the computed temperature at the intake to the observed 

temperature at the Atlanta gage (fig. 20A) indicates 

that a maximum warming of about 1°C occurs 

around noon, but little cooling occurs at night. These 

results are expected because of the short travel times 

associated with the 3.8-mi reach between the intake 

and the Atlanta gage. On the other hand, a relatively 

large difference exists between the observed and computed temperatures at the intake. The observed 

values tend to be larger than expected, especially at 

night when, 'because of diminished surface exchange, 

the model results should be most accurate. A comparison of these occurrences with the stage data on 

figure 19A indicates that the maximum differences 

almost always occur at low flow. As discussed previously, both powerplant intakes and outfalls are located in a reach of the river ponded during low flow 

by a control structure (fig. 3, table 3). It was concluded, therefore, that some recirculation of heated 

river water occurs at low flow and that this recirculation influences the observed river temperatures 

at the plant McDonough intake. For this reason, the 

computed rather than the measured temperatures 

upstream of the powerplants were used to determine 

the instantaneous powerplant heat loads.

Comparison of the observed river temperatures at 

Georgia Highway 280 and the computed intake temperatures indicates the powerplants increased river 

temperatures by as much as 8.4°C during the calibration period (fig. 20).

The only independent measure of the adequacy 

of the temperature model is the difference between 

observed and computed river temperatures at the 

Fairburn gage. Comparison of these temperatures 

(fig. 20Z)) indicates the model consistently predicts 

lower then observed temperatures throughout the 

calibration period with the greatest differences occurring at the lower temperatures. The mean computation error for the 8-day period was 0.35°C with 

a standard deviation of 0.65°C. Phase differences between observed and computed temperatures were 

minimal. In assessing the accuracy of the temperature model the following points should be kept in 

mind:

1. Instrumentation error in measuring river temperatures was ±0.5°C.

2. Only hourly meterological data were available. 

Thus, on partly cloudy days, the measured 

solar radiation may not have been representative of actual conditions.

3. No measured tributary temperatures were available and, at low flow, tributary inflows between 

Georgia Highway 280 and the Fairburn gage 

amounted to 39 percent of the flow at Georgia 

Highway 280.

The temperature model was verified using rivertemperature and meteorologic data collected during 

the period July 12-19, 1976. Observed and computed 

river temperatures during the verification period are 

shown in figure 21. Diurnal variations in flow and 

temperature were more regular during July than in 

August. Low flows at the Atlanta gage, for example, 

always occurred between 2000 and 2400 h. At the 

Plant McDonough intake, the tendency for the observed temperatures to be larger than computed 

temperatures during low flow (0100 h or 0500 h) is 

obvious (fig. 21B). It again appears that recirculation occurred at low flow and that heated effluent 

water affected the observed temperatures.

Heated effluents from the Atkinson-McDonough 

powerplants increased river temperatures by as 

much as 6°C during the verification period.

A comparison of observed and computed temperatures at the Fairburn gage again serves as the model 

verification. The poorest comparisons at Fairburn 

occurred at 0300 h on July 17, 1976, and at midnight 

between July 17 and 18 (fig. 2LD). Maximum differences between computed and observed temperatures during these periods were — 1.34°C and

- 1.77°C, respectively. Inspection of the meteoirologic 

and flow-transport data relating to the water at 

Fairburn at the given times provides no satisfactory 

explanation for these large temperature differences. 

During the remainder of the calibration period computed river temperatures closely resemble observed 

temperatures. The mean computation error at the 

Fairburn gage during the verification period was

-0.36°C with a standard deviation of 0.72°C. Phase 

differences between observed and computed temperatures were minimal.

Simulation of various river temperature anomalies 

during the verification period serves as an indirect 

verification of the flow model. Consider the rapid re-
24 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

756

Ill

ffi 755

z

111

§ 754

K

< 753

in

o

2

5 752

cc

£ 751

750

——— Observed

——— Computed

AUGUST 1976 

A

751

in

ffi 750

Z

iiT

Q 749

748

cc in

I

747

746

745

—— Observed

•— Computed

AUGUST 1976

B

FIGURE 19.—Observed and computed stages of the Chattahoochee River during the period August 1-8, 1976. A, At Atlanta.

B, At the Atlanta water-supply facility.

ductions in temperature that occurred at the Atlanta 

gage on July 13-15, 1976, and that are noted on 

figure 21A by points A-B, C-D, and E-F. These 

temperature anomalies were traced through the 

study reach by analytically "tagging" individual 

fluid particles (points A, B, C, D, E, and F) and by 

noting the time of arrival of each particle at the 

various downstream stations. For example, the water 

that passed the Atlanta gage at 0100 h on July 13 

is identified as "A" on figure 21A, and its arrival 

time at each downstream station (figs. 21A-E) is

similarly identified. The spatial distribution of each 

particle relative to the given anomaly at the Atlanta 

gage is shown to be maintained throughout the study 

reach. Thus travel times are being closely simulated, 

and velocities computed by the flow model are close 

to the actual values. For reference purposes, the 

temporal locations of these water particles are also 

noted on figure 14. Note that water particles represented by points A, B, C, and D traversed the reach 

under relatively high flow conditions and that water 

particles represented by points E and F traversed
IMPACT OF POWERPLANT EFFLUENTS ON RIVER TEMPERATURES 25

720

AUGUST 1976 

C

688

UJ

O

F 687 

*

UJ UJ

^ £ 686

tn 685

UJ

684

Observed

AUGUST 1976 

D

FIGURE 19.—Continued. C, Near Fairburn. D, Near Whitesburg.

the reach when discharge was intermediate and 

nearly steady.

Given the temperature comparisons discussed 

previously and the limitations of the flow, meteorologic and river temperature data, the temperature 

model is considered calibrated and verified and suitable for use as a predictive tool.

IMPACT OF POWERPLANT EFFLUENTS ON 

RIVER TEMPERATURES-AUGUST 1-8, 1976

Heatioads from the Atkinson-McDonough powerplants were determined using computed flows and 

temperatures from the models and the observed river 

temperatures at Georgia Highway 280. Figure 22 

shows computed, instantaneous powerplant heat 

loads for the period August 1-8, 1976. Larger heat 

loads correspond to periods of greater electrical 

power demand, which for the period of interest includes most of the afternoon and evening hours when 

peak air-conditioning demands occurred.

River temperatures without heat loads from the 

powerplants were computed for the period August 1- 

8,1976, using the flow-temperature models. Figure 23 

shows computed, instantaneous river temperatures, 

with and without powerplant heat loads, at Georgia 

Highway 280 and at the Fairburn and Whitesburg 

gages. As expected, the impact of the heat loads was 

most severe at Georgia Highway 280 and progressively decreased downstream with increasing distance from the heat source. At Georgia Highway 

280, the maximum temperature difference between 

heated and unheated water was 8°C. 'Corresponding 

values at the Fairburn and Whitesburg gages were 

about 6°C and 2°C, respectively. A reach profile of 

computed river temperatures, with and without 

powerplant heat loads, is shown in figure 24 for 

August 8, 1976, at 0000 h. Temperature differences
26 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

24

22

CO 

CO

o

CO 

LU 

LU

g 20

LU 

Q

LU 18

<r LU . c Q. 16

Observed

i i i I i i i I i i i I i i i i i i i ——— l ——— I ——— I ——— l ——— I ——— I

45 

AUGUST 1976 

A

24

22

CO

D 

CO

LU 

O

CO 

LU 

LU

Observed 

Computed

18

14

AUGUST 1976 

B

FIGURE 20.—Observed and computed temperatures of the Chattahoochee River during the period August 1-8, 1976. A,

At Atlanta. B, At the Plant McDonough intake.

between, the curves represent the distribution of 

residual heat in the river at the given time due to 

powerplant effluents.

COMPUTATION OF NATURAL RIVER 

TEMPERATURES

Before discussing the computation of natural 'temperature conditions in the Chattahooohee River, 

some general relations and concepts important to the 

interpretation of forthcoming information will be reviewed. Once a particle of water obtains a given 

temperature by whatever process, it will remain at 

that temperature unless energy is transferred to or 

away from it. The major process by which thermal 

energy in river water can be gained or lost is 

through heat exchange with the atmosphere. Several 

physical processes are involved in this exchange, but 

the combined effect of all these processes can be approximated by the expression:

T =-K (T-TE) (4)
COMPUTATION OF NATURAL RIVER TEMPERATURES 27

32

30

28

n——i——i——i——r

LJJ 

LJJ

§ 26

LJJ

O

uj 24 

cc

(2

cc uj 22

20

18

Observed

AUGUST 1976

C

30

28

uj 24 

cc

< 

§ 22

20

Observed 

Computed

23456 

AUGUST 1976

D 

FIGURE 20.—Continued. C, At Georgia Highway 280. D, Near Fairburn.

where HT = total heat transfer from the atmosphere 

to the water; K = & positive surface exchange coefficient, T = the observed water temperature, and 

!T£ =the equilibrium temperature of the water. The 

surface exchange coefficient (If) is dependent on the 

temperature of the water as well as several meteorologic variables. The equilibrium temperature is the 

temperature toward which the observed water temperature will always move. It is also highly dependent on meteorologic conditions but independent 

of flow variables such as depth. Conversely, the observed water temperature is sensitive to flow depth
28 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

28

26

24

22

20

O 

£2

UJ DC CJ

LU

LU 

CC.

Computed

345

AUGUST 1976

E

FIGURE 20.—Continued. E. Near Whitesburg.

as well as meteorologic conditions. Consequently, 

equilibrium and observed river temperatures at any 

instant can be quite different.

Where the stream system is not subject to artificial thermal alteration, observed water temperatures 

equal natural river temperatures. Under these conditions, mean daily observed and mean daily equilibrium temperatures are nearly equal.

Where a river system is influenced by artificial 

heat sources or sinks, observed and natural river 

temperatures differ by some amount that will be 

called the excess temperature. Under such conditions, total heat exchange between the water and the 

atmosphere is a function of the natural heat exchange and the excess temperature. The magnitude 

of excess temperature at a particular station is a 

function of the magnitude of the artificial alteration and the distance to its source. Just as the observed river temperature always seeks the equilibrium temperature, artifically altered water temperatures tend to return to natural temperatures. This 

process is conveniently expressed by the relation :

where jffe = heat exchange between the water and the 

atmosphere due to excess temperature and 7^ = the 

natural river temperature.

Natural river temperatures tend to decrease with 

increasing altitude and latitude so it is probable that 

the long term natural river temperature at Whitesburg is slightly higher than at Atlanta. The model 

depends on meteorologic data collected at Atlanta, 

however, and all meteorologic conditions throughout 

the study reach are assumed to be uniform. It is also 

assumed that any variation in natural temperature 

with distance from Atlanta is negligible.

Direct measurements of natural river temperatures during the calibration period of August 1-8, 

1976, were impossible to obtain. On the other hand, 

information about natural temperatures can be 

obtained from available temperature data. Figure 

25 shows a plot of the observed river temperatures 

at Georgia Highway 280. Superimposed on these 

temperatures are the observed temperatures of the 

same water particles when they arrived at the Fairburn gage. Estimates of time of travel between the 

two stations were obtained from the flow model. The 

difference between the two curves represents the 

observed temperature change experienced by a water 

particle as it traveled the 17.0 mi from Georgia Highway 280 to the Fairburn gage. In the 8 days of 

record, 18 time periods occurred during which the 

water experienced no net temperature change as it 

traversed this reach of the river. These points are 

circled on figure 25. Because no net surface exchange 

occurred during these periods, the river temperature and the equilibrium temperature must have 

been equal. In other words, each time the curves 

intersect on figure 25, a direct measurement of the 

equilibrium temperature is available, averaged over 

the time of passage through the reach. The mean 

time of travel for the water particles represented 

by these intersections was 14.91 h with a standard 

deviation of 1.83 h. The mean of the equilibrium 

temperatures was 24.8°C with a standard deviation 

of 1.37°C.

Except for times of travel, these equilibrium temperatures were obtained independently of the flow 

and temperature models. The 18 points of intersection (fig. 25) are also more or less randomly distributed in time. Thus, the mean of these 18 tempera-
COMPUTATION OF NATURAL RIVER TEMPERATURES 29

tures (24.8°C) is considered a reasonably good estimate of the mean natural temperature of the Chattahoochee River between Atlanta and Whitesburg during the period August 1-8, 1976.

The average impact of flow regulation and powerplant effluents on river temperatures during the 

period August 1-8, 1976, is shown on figure 26. The 

sihort-diashed line connects the mean observed 'temperatures during the 8-day period. The 8-day mean 

computed river temperatures, which would have 

occurred without powerplant heat loads, are represented by the longer dashes and were computed from 

data presented in figure 23. The horizontal solid 

line at the top of the figure represents the mean 

natural temperature of 24.8°C, estimated from the 

18 measurements of equilibrium temperature. During the given 8-day period, mean observed river 

temperatures downstream of the powerplants are 

shown to nearly equal natural temperatures. Thus, 

on the average, the heat added by the Atkinson-McDonough powerplants almost balanced the cooling 

effect of flow regulation. The average warming effect 

of the plants is estimated to have been 0.5°C at the 

Plant McDonough intake, 4.2 °C at Georgia Highway 

280, 2.9°C at the Fairburn gage, and 1.6°C at the 

Whitesburg gage. Likewise, the average cooling that 

resulted from flow regulation at Buford Dam is estimated to have been 4.8°C at the Atlanta gage, 4.4°C 

at the McDonough intake, 4.3°C at Georgia Highway 280, 2.9°C at the Fairburn gage, and 1.9°C at 

the Whitesburg gage. Note, that excess temperatures 

resulting from both a heat sink (Lake Sidney 

Lanier) and a heat source (powerplants) are shown 

to approach natural temperatures with increasing 

distance from the point of thermal alteration.

The average combined thermal impact of flow 

regulation and powerplant effluents on river temperatures has been shown to be small when compared to natural temperatures. Equally important, 

however, are the instantaneous effects. One way to 

estimate the natural instantaneous temperature 

through the study reach is by use of the flow and 

temperature models. Computation of natural temperatures is complicated, however, by the fact that 

the upstream boundary condition is unknown and 

must also be simulated. Simulation of this boundary 

is accomplished by solving the thermal energy equation (equation 1) for a channel of infinite length 

upstream of the station of interest. Such a solution 

effectively removes the spatial derivatives from consideration and computes river temperatures only as 

a function of depth and surface exchange. Such 

temperatures are by definition natural temperatures.

These assumptions were used in conjunction with 

the flow and temperature models to solve the thermal 

energy equation for a long channel where geometry, 

flow, and meteorologic conditions at each cross section were identical and equal to observed conditions 

at the Atlanta gage during the period August 1-8, 

1976. Computed instantaneous river temperatures 

at the downstream end of this long reach were considered equal to natural temperatures at the Atlanta 

gage during the given period.

The set of computed natural river temperatures at 

the Atlanta gage was used to drive the temperature 

model and compute instantaneous natural river temperatures through the study reach for the period 

August 1-8, 1976. Graphs of natural and observed 

temperatures at the Atlanta gage, at the Plant McDonough intake, at Georgia Highway 280, and at 

the Fairburn gage are shown in figure 27. Only computed temperatures are shown for the Whitesburg 

gage.

The computed mean natural temperature for the 

entire reach during the 8-day period was 24.9 °C and 

is considered to be in excellent agreement with the 

previously determined estimate of 24.8°C. This close 

agreement between two independently determined 

mean natural temperatures indicates that the total 

surface exchange was accurately modeled and that 

the computed instantaneous temperature values are 

reasonably accurate.

Based on these comparisons, flow regulation upstream of Atlanta lowered the temperature of the 

Chattahoochee River by an average 4.8°C during the 

first 8 days of August 1976. Heated effluents from 

the Atkinson-McDonough powerplants raised the 

mean river temperature about 4.2°C during the 

same period. Thus, the net average combined effect 

of flow regulation and heat loads was small. On the 

other hand, dirurnal variations and associated nates 

of change for both natural and artifically altered 

water temperatures were large and quite different. 

In general, the larger variations and rates were associated with the altered temperatures and decreased 

downstream.

These results and conclusions based on model 

studies compare favorably with the conclusions 

drawn from previous comparisons of historical 

river- and air-temperature data. In both cases, significant cooling effects due to flow regulation at Buford Dam were noted at the Atlanta gage and the 

Plant McDonough intake during August 1976 (figs. 

9, 10, 27). Also noted, in both cases, was the close 

approximation of mean natural to mean observed 

temperatures at Georgia Highway 280 (figs. 11, 27).
30 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

24 i——i——i——i——|——i——i——i——i——i——i——i——i——i——i——i——i——i——i——r

22

20tv/

"i——i——i——i——i——i——i——i——i——r

UJ

o

LU 

QC 

O 

UJ

oc

oc

LU 

Q.

16

14

12 I i I i i I I I I I

12 13 14 15 

JULY 1976

16 17 18 19

26

24

22

i —— i —— i —— i —— i i —— i —— r55

LU

o

LU 

LU

LU

O

LU 18 

QC

D

2 16

LU

14

1?

i —— i —— i —— i —— i

i i i I i i i I i i i I i i i I i i i I i I i

12 13 14 15

JULY 1976 

B

16 17 18 19

FIGURE 21.—Observed and computed temperatures of the Chattahoochee River during the period July 12-19, 1976. A, At 

Atlanta, B, At the Plant McDonough intake. C, At Georgia Highway 280. D, Near Fairburn. E, Near Whitesburg. 

Points A-F on each graph represent water particles traced through the study reach (see p. 24).
COMPUTATION OF NATURAL RIVER TEMPERATURES 31

30 I——I——i——r

13 14 15 16 

JULY 1976

D 

FIGURE 21.—Continued.

17 18 19
HEAT FLOW, IN MILLIONS OF CALORIES PER SECOND

-» -»' NJ NJ 

O C71 O C71 

0000
«s TEMPERATURE, IN DEGREES CELSIUS TEMPERATURE, IN DEGREES CELSIUS TEMPERATURE, IN DEGR

OKJ

§.g*

!

S3 &

to »

oo CL 

co

'

C 

O

C

s£ -»

</)

> 

o

<Q ^
34 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

o

C/> 111

O 111

Q

24-

22

20

18

16

With powerplant loads 

Without powerplant loads

10 20 30 

DISTANCE DOWNSTREAM, IN MILES

40 50

FIGURE 24.—Computed longitudinal temperature profiles in the study reach with and without heat loads from Plants Atkinson-McDonough, 0000 e.s.t., August 8, 1976.

32

30

28 111 

O

111 111 g 26

ul 24

cc.

tr. 

ffi 22

20

—— Observed water temperature 

at Georgia Highway 280

—— Temperature upon arrival at 

Fairburn Gage

18 I——i——i

AUGUST 1976

FIGURE 25.—Observed temperature of the Chattahoochee River at Georgia Highway 280 and the observed temperature of

the same water upon arrival at the Fairburn gage.
COMPUTED RIVER TEMPERATURES AND CRITICAL DROUGHT FLOW CONDITIONS 35

25

*

Natural temperature

Ill 

o

</> 111 111 00 DC 23 

CD ill

LU 22 

oc

21

Average temperature for August 1-8, 1976

Temperature without powerplant 

loads, August 1-8, 1976

Observed temperature 

Computed temperature

CD

CO

3 § *J CO CMN

c >.

o ~

Z-l

O D)

5 o 

c O

JO 

Q.

<o

05

co 

CD

CD 

05

co 

CD

D 

JD

FIGURE 26.—Eight-day mean natural and thermally altered temperatures of the Chattahoochee River from Atlanta to Whitesburg, August 1-8, 1976.

Thus, both the analysis of historical data and the 

model studies, albeit grossly different in accuracy 

and sophistication, provided similar concluisionis regarding the impact of flow regulation and powerplant loadings on stream temperatures in the study 

reach.

COMPUTED RIVER TEMPERATURES USING

YEAR 2000 AND CRITICAL DROUGHT FLOW

CONDITIONS

The flow-temperature models were used to predict 

future river temperatures using year 2000 and 

critical drought flow conditions. Representative 

future water-supply demands and wastewater flows 

were obtained from the Atlanta Regional Commission (1976) and are listed in table 6. Additional 

wastewater treatment facilities to be added to the 

network by the year 2000 include Sweetwater Creek

TABLE 6.—Estimated water-supply and wastewater flows for 

the year 2000

Station

Buford Dam to Atlanta gage..

Atlanta water-supply facility ..

Cobb County wastewatertreatment facility.

R. M.. Clayton wastewatertreatment facility.

South Cobb County wastewater-treatment facility.

Utoy Creek wastewatertreatment facility.

Sweetwater Creek wastewater-treatment facility.

Camp Creek wastewatertreatment facility.

Annewakee Creek wastewater-treatment facility.

Regional interceptor _ _ .

Bear Creek wastewatertreatment facility.

£

300.62 _

300.56 __

300.56 __

294.28 _

291.48 ...

288.57 ...

283.78.. .

281.46 __

281.45 ...

274.48 ...

g£

3 ...

4 __

7 __

13 __

14 __

20_._

16 _

21 _

22 _

23 _

ois- 3s- -51-

840 __ 560 __ 36.0

164 __ 109 __ ._._

____ ____ 31

____ ____ 162

____ ____ 49

____ ____ 44

....._ .. __ 2.6

____ ____ 27

____ ...... 6.0

____ ____ 4S

.. __ .. __ 7.8
o

§•o

TEMPERATURE, IN DEGREES CELSIUS

O

99

o

8

sr
SUMMARY AND CONCLUSIONS 37

WTF, Annewakee Creek WTF, Bear Creek WTF, 

and a regional interceptor (fig. 1, table 6). Tributary flows used to predict future conditions are those 

listed in table 3 for the 1954 drought and for the 

period August 1-8, 1976. Observed tributary discharges during the 1954 drought were obtained from 

Thompson and Carter (1955). The various flow conditions used to simulate year 2000 temperatures in 

the Chattahooichee River are listed below. The letter 

designation for each condition is used later in this 

text to define various flow combinations The average 

projected wastewater flow for the year 2000 (table 

6) was used in each simulation. The letter designations are as follows:

Flow condition

Letter 

designation

1954 drought tributary flows A

August 1-8, 1976, tributary flows B

Year 2000 peak water-supply demand C

Year 2000 average water-supply demand D

Boundary conditions used to compute future flow 

conditions are listed in table 7. Estimated discharges 

at the Atlanta gage were based on a minimum regulated discharge from Buford Dam of 1,717 ft3 /s proposed for the year 2000 (Atlanta Regional Commission, 1976). Tributary inflows between the dam and 

the Atlantic gage of 0 and 25 ft3 /a were used and 

represent 1954 drought and August 1976 flow conditions, respectively. Discharge at the Whitesburg 

gage for the various flow combinations (table 7) 

was based on the given Atlanta gage discharge and 

a mass balance of tributary and flow diversion data 

listed in tables 3 and 6. All simulations of year 2000 

flows and river temperatures are based on steadystate flow conditions. Such conditions are represented, for the most part, by the discharge data in 

tables 3, 6, and 7 and by the water-surface profile 

in figure 3. All future river temperatures were predicted using temperature and meteorologic data observed during the period August 1-8, 1976.

Year 2000 river temperatures computed with the 

various flow combinations listed above are shown in 

figures 28 to 31. Temperatures at Georgia Highway 

280 and at the Fairburn and Whitesburg gages are 

shown with and without heat loads from Plants 

Atkinson-McDonough (fig. 22). Heat loadings from

TABLE 7.—Estimated discharge at the Atlanta and Whitesburg gages using selected tributary and year 2000 watersupply demands and wastewater flows

Discharge (ft3/s)

Flow combination ___ C-B C-A D-B D-A

Locations:

Atlanta gage __ 940 910 1,220 1,190 

Whitesburg gage _ 1,590 1,150 1,920 1,490

the powerplants impact river temperatures most significantly when river flows are lowest. Maximum 

temperature at Georgia Highway 280 is nearly 34°C 

using powerplant loads, peak water-supply demands, 

and 1954 drought flow conditions. Temperatures at 

the same station using the same flow conditions without powerplant loads are about 10 °C cooler. River 

temperatures computed using August 1976 tributary 

inflows, and average water-supply demands are not 

significantly different from those observed during 

the period August 1-8, 1976.

SUMMARY AND CONCLUSIONS

Transient flow-temperature models and independent comparisons of historical river- and air-temperature data were used to evaluate some of the effects 

of flow regulation and powerplant effluents on Chattahoochee River temperatures between Atlanta and 

Whitesburg, Ga. The flow-temperature models were 

used to estimate instantaneous and mean natural 

temperatures in the river during an 8-day period in 

August 1976. These, in turn, were compared to observed, thermally altered river temperatures. Such 

comparisons indicated that the combined thermal 

effects of flow regulation and powerplant effluents 

resulted in mean daily river temperatures downstream of the powerplants about equal to or less 

than computed natural temperatures. An independent analysis of historical river and air-temperature 

data provided the same basic 'Conclusion.

The models were also used to simulate river temperatures using estimated year 2000 flow conditions 

and temperature and meteorologic data collected 

during 1976. Except for periods of peak water-supply demand, simulated year 2000 river temperatures 

were little changed from observed 1976 temperatures.

SUMMARY AND CONCLUSIONS 39

28

26

With powerplant loads 

Without powerplant loads

tu 

<r

22

20

18

TIME, IN DAYS

c

w 28

tu 

O

tu

QC

D

tu

Q.

26

24

22

i i ' 'i ' ''r

—— With powerplant loads 

• Without powerplant loads

tu 20

TIME, IN DAYS 

D

FIGURE 28.—Continued. C, Near Fairburn. D, Near Whitesburg.
TEMPERATURE

-» -» N

<7> 00 O 

H

5 

m

Z

D 

>

C/)
TEMPERATURE, IN DEGREES CELSIUS TEMPERATURE, IN 

0 

s>

CL

Q 

2

2(T>

Sa

Hi 

|

5TCO

cr

H

2 

m

Z 

O

'5

O)

O z *>

o 

>
42 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

26

24

~\——\——i——i——r i——i——i——\——i——i——i——i——i——i——i——i——i——i——I——i——i——i——I——i——I

o

LLJ

g 22

LLJ 

O

uT 20 

oc

18

16 I I I I I I I I I I I I I J___L

TIME, IN DAYS 

A

With powerplant 

Without powerplant (

TIME, IN DAYS 

*B

FIGURE 30.—Computed temperatures of the Chattahoochee River using flows representing year 2000 average water-supply demands, year 2000 average wastewater returns, and August 1976 tributary flows. A, At the Plant McDonough 

intake. B, At Georgia Highway 280.
SUMMARY AND CONCLUSIONS 43

With powerplant loads 

Without powerplant loads

TIME, IN DAYS

c

28

UJ 

O

UJ

cc

UJ

cc.

26

24

22

20

With powerplant loads 

Without powerplant loads

TIME, IN DAYS 

D

FIGURE 30.—Continued. C, Near Fairburn. D, Near Whitesburg.
44 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

26

24

22

ul 20 

oc

16

TIME, IN DAYS 

A

With powerplant loads 

Without powerplant loads

TIME, IN DAYS 

B

FIGURE 31.—Computed temperatures of the Chattahoochee River using flows representing year 2000 average watersupply demands, year 2000 average wastewater returns, and 1954 drought tributary flows. A, At the Plant McDonough intake. B, At Georgia Highway 280.
SELECTED REFERENCES 45

28 ———

26

oyl 24

~i———i———r ~i———i———r

O

HI 

HI

oc 

a

HI

o

HI" 22 

oc

<

ocHI on

Q. ^U

18

~i———i———r

With powerplant loads 

Without powerplant loads

5

TIME, IN DAYS

c

28

26

24

22

20

HI

O

HI 

OC

o

HI

QC

D

' ' I ' ' ' I

With powerplant loads 

Without powerplant loads

TIME, IN DAYS 

D

FIGURE 31.—Continued. C, Near Fairburn. D, Near Whitesburg.

SELECTED REFERENCES

Amein, M. M., and Fang, C. S., 1970, Implicit flood routing 

in natural channels: Journal of the Hydraulics Division, 

American Society of Civil Engineers, v. 96, no. HY12.

Atlanta Regional Commission, 1976, Metropolitan Atlanta 

area water-supply review supplement, Appendix M, 

Water-supply plan for the Atlanta region; Part 1, 

Needs, sources and policies.

Cherry, R. N., Faye, R. E., Stamer, J. K., McGinty, H. K., 

1976, Plan for river quality assessment, upper Chattahoochee River basin, Georgia: American Water Works 

Association River Water Quality Assessment Seminar, 

proceedings, no. 20133.

Dyar, T. R., and Stokes, W. R., 1973, Water temperatures of 

Georgia streams: Atlanta, Ga., Georgia Department of 

Natural Resources 317 p.

Fenneman, N. M., 1938, Physiography of the eastern United 

States: New York, McGraw-Hill, 714 p.

Higgins, M. W., 1968, Geologic map of the Brevard Fault 

zone near Atlanta, Georgia: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map 1-511.

Jobson, Harvey E., 1973, The dissipation of excess heat from 

water systems: Journal of the Power Division, American 

Society of Civil Engineers, v. 99, no. Pol, p. 89-103.

———— 1977a, Bed conduction computation for thermal models: 

Journal of the Hydraulics Division, American Society of 

Civil Engineers, v. 103, no. HY10, p. 1213-1217.

1977b, Thermal model for evaporation from open channels: Congress of the International Association for 

Hydraulic Research, 17th, Baden-Baden, Germany, 

August 14-19, 1977, proceedings, p. 95-102.

Jobson, H. E., 1975, Canal evaporation determined by thermal 

modeling: American Society of Civil Engineers, San 

Francisco, Calif., proceedings, p. 729-43.

Jobson, H. E., and Reefer, T. N., 1977, Thermal modeling of 

highly transient flows in the Chattahoochee River near 

Atlanta, Georgia: Special Symposium on River Quality
46 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

Assessments, American Water Works Association, 

Tueson, Ariz., proceedings,

1979, Modeling highly transient flow, mass and heat

transport in the Chattahoochee River near Atlanta, 

Georgia, U.S. Geological Survey Open-File Report 79- 

270, 139 p.

Koberg, G. E., 1964, Methods to compute long-wave radiation from the atmosphere and reflected solar radiation 

from a water surface: U.S. Geological Survey Professional Paper 272-F, p. 107-136.

Kothandaraman, V., and Evans, R. L,, 1972, Use of airwater relationships for predicting water temperature: 

Illinois State Water Survey Investigation no. 69, p. 10.

Lamar, W. L., 1944, Chemical character of surface waters 

of Georgia: U.S. Geological Survey Water Supply Paper 

889-E, 327 p.

Land, L. F., 1978, Unsteady streamflow simulation using a

linear-implicit, finite-difference model: U.S. Geological 

Survey program documentation J879, 69 p.

Langford, T. E., 1970, The temperature of a British river upstream and downstream of a heated discharge from a 

power station: Hydrolbiologia, Vol. 35, p. 353-375.

National Oceanic and Atmospheric Administration (NOAA), 

1976, Local climatological data, Atlanta, Georgia: 5 p.

Stone, H. L., and Brian, P. L. T., 1963, Numerical /solution 

of covective transport problems: Journal of the American Institute of Chemical Engineers, v. 9, no. 3, p. 681- 

688.

Thomson, M. T., and Carter R. F., 1955, Surface-water resources of Georgia during the drought of 1954, Part I, 

Streamflow: Georgia Department of Mines and Geology 

Information Circular 17, 79 p.

U.S. Army Corps of Engineers, 1973, Flood plain information—Chattahoochee River, Buford Dam to Whitesburg, 

Georgia: Alabama, Mobile District, 16 p., 50 plates.
SUMMARY OF DATA—TABLES 8-10
48 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

TABLE 8.—Cross section coordinates

[Measurements in feet]

Horizontal 

distance

RM

20.0

40

55

70

85

100

115

130 

145

160

170

180

190

200

210

220

230

240

250

260

270

1280 

290

300

310

320

330

RM

0

10

20 

22 

30 

50 

100 

200 

300 

400 

430 

500 

520 

540 

560

RM

0

14 

40

100

140

200

220

244

264

RM

0

14

21 

29 

50 

70 

80 

100 

150

IQfl J-i/V

200

236

255

Altitude

302.97

767.0

762.0

760.5

755.3

751.9

750.7

750.9

749.7 

749.5

749.6

748.1

748.4

747.4

747.4

747.8

749.4

750.3

749.7

747.9

747.7

747.9

749.Q 

750.8

751.3

753.1

756.8

766.8

302.38

766

761

756 

752 

748 

750 

747 

748 

748 

751 

752 

753 

756 

761 

766

302.05

761.5

752.6 

746.5

743.4

747.1

747.7

746.8

752.6

762.3

300.98

761.4

752.0

747.1 

747.0 

746.0 

746.0 

741.0 

739.0 

739.6

74210 

744.4

752.0

762.7

Horizontal 

distance

RM

0

42

62

82

100

120

160

200 

240

280

320

340

360

373

386

RM

364

381

409

425

439 

459

510

559

610

659

687

705

RM

23

66 

82 

103 

118 

169| 

216 

265 

309 

325 

405

RM

210 

240 

£60

280

300 

320

340

360

380

400

410

430

RM

26

75

125 

175 

225 

256 

280 

325 

425 

460

RM

-20

0

Altitude

300.62

760

755

750

748

746

745

745

745 

745

745

746

748

750

755

760

300.44

762.6

760.2

748.9

748.3

740.1 

740.8

740.8

739.3

739.0

739.0

749.7

761.8

300.29

776.0

763.0 

761.2 

750.9 

743.3

741.01 

1735.01 

735.2 

750.9 

760.2 

764.2

299.94 

756.8 

742.2 

734.0

731.2

731.2 

734.7

734.9

734.5

735.7

734.1

740.2

7fifi i ou.o3 

299.56

765.7

738.1

733.7 

733.5 

733.9 

738.5 

752.9 

754.9 

753.9 

762.4

299.20

754.5

741.4

Horizontal 

distance Altitude

RM 299.20 Continued

15

55

105

125

175

185

210

RM

0

20

35

60

100

150

200

214

233

RM

0

20 

35

45

60

100

150

200

214

233

RM

85 

130 

140 

150 

160 

170 

180 

190 

200 

210 

220 

230 

240 

250 

260

270

280 

290

300

310

322.6

332

373

RM

-40

-29

0

50 

107 

139 

200 

218 

223 

260 

290

RM

0

15

735.9

733.1

733.9

735.6

729.6

730.8

755.5

299.10

754

744

740

739

739

740

741

744

755

298.93

755,1

745.5 

738.5

733.0

736.3

735.2

735,4

736.4

744.5

756.0

298.77

756.7 

736.2 

741.1 

739.8 

735.7 

734.3 

733.4 

734.1 

734.4 

735.4 

733.7 

733.6 

734.4 

735.1 

735.3

737.1

737.1 

738.3

737.7

739.1

741.1

744.2

754.7

298.10

762.5

757.0

755.0

731.8 

733.4 

733.3 

735.4 

755.8 

740.5 

760.1 

764.4

297.86

753.6

743.9

Horizontal 

distance Altitude

RM 297.86 Continued

30

50

100

150

200

214

222

RM

74

130

145

160

180

230

280

300

315

326

347

367

RM

0

15

16

30

50

77

90

100

150

165 

182 

183 

195

RM 

140 

152 

165 

190 

240 

290 

340 

355 

368

388

RM

0

25

40

100

150

200

240

254 

285

RM

0 

45 

100 

153 

165 

200 

248 

299

367 

398

423

450

737.9

735.4

736.9

736.0

736.2

743.9

752.2

297.73

757.7

751.3

741.6

735.7

733.7

734.9

734.7

733.8

736.5

741.7

755.2

759.2

297.06

754.0

745.8

739.3

734.8

734.8

734.5

732.3

735.8

734.1

736.0 

739.3 

746.2 

751.2

296.60

750.3 

742.9 

735.9 

736.4 

735.1 

735.5 

735.2 

736.0 

743.8

751.2

295.30

TKO O fO£.O

740.5

731.9

731.8

732.0

732.4

749.9

740.5 

74Q I ~t<y.yQ

294.70

769.5 

755.9 

752.0 

745.0 

738.3 

738.0 

735.8 

727.0

733.8 

755.3

757.8

768.7
TABLES SUMMARIZING DATA 49

TABLE 8.—Cross section coordinates—Continued

[Measurements in feet]

Horizontal 

distance

RM

55

86

100

197

300

311

330

400

RM

0

15

16

30

36

50

100

104

150

167

180

199

200

215

RM 

400

420

437

450 

470 

494 

510 

560 

575 

586

606

659

RM 

-20 

0 

10 

20 

30 

50 

100 

153 

170 

180

195

RM 

-9 

2

16 

28 

40

50

100 

150 

200 

210 

216 

233 

249 

270

RM

0

15

20

30

Altitude

293.92

753.5

742.0

731.6

729.0

730.9

742.0

749.4

750.4

293 .10

751.9

739.3

733.3

731.1

727.8

729.2

728.1

729.3

727.6

726.6

729.2

733.2

739.3

750.3

292.19 

751.6

737.9

729.8

728.2 

725.2 

726.2 

726.1 

727.4 

723.7 

729.5

737.9 •

755.6

290.54

746.4 

741.7 

737.0 

730.5 

724.7 

727.1 

725.5 

728.0 

722.7 

730.5

744.1

287.86

744.6 

741.5

732.0 

725.1 

721.8

724.6

724.8 

723.8 

724.1 

723.8 

725.9 

732.0 

741.9 

744.2

286.96

742.1

729.8

727.1

725.8

Horizontal 

distance Altitude

RM 286.96 — Continued

50

100

150

200

245

255

270

RM 

220

248

270

320

370

420

435

482

RM

0

5

30

80

95 

121 

150 

160

190

195

RM 

20 

50 

80 

110 

140

170

OAA ZUv

22(0 

245 

270 

290 

310 

330 

334 

337 

340 

355 

370 

390

410

430 

450 

470 

500

530 

565 

580

RM

0 

12 

20 

40 

70 

100 

150 

200

227 

235

RM

0

5

722.3

721.9

722.1

721.8

727.1

729.8

741.2

286.07 

739.9

718.0

719.9

720.8

721.1

720.0

721.0

738.9

284.32

735.1

720.7

717.8

718.2

716.7 

718.5 

719.2 

719.2

720.7

739.4

281.79

743.9 

738.2 

737.4 

736.3 

734.6

734.3

729.8 

719.5 

715.0 

714.1 

716.5 

715.3 

714.7 

714.9 

716.3 

716.8 

716.8 

716.9 

716.8

717.1

718.0 

722.3 

730.4 

736.5

739.2 

741.3 

743.8

281.07

737.9 

720.2 

722.5 

710.2 

716.1 

714.5 

714.8 

713.1

720.2 

735.6

279.99

733.6

722.1

Horizontal 

distance Altitude

RM 279.99 — Continued

23

35

60

100

200

210

225

230

RM

0

10

20

30

60

180

210

235

240

245

254

264

354

RM 

-65

-48

0

20

100 

150 

200 

260 

2,66 

271 

300

RM

-10 

3 

8 

30 

80 

120 

140 

180 

200 

230 

250 

260

RM

0 

30

44 

enou 

51 

69 

80

100

150 

200 

250 

300 

330 

352 

353 

365

376 

406

RM

0

20

714.3

711.7

714.7

715.5

715.6

716.2

722.1

735.1

277.95

734.0

720.8

710.8

708.3

710.8

710.8

711.7

711.8

713.8

714.7

720.8

727.8

729.3

274.12 

732.0 

728.5

725.4

713.7

713.3 

712.9 

712.7 

711.2 

719.9 

726.8 

732.2

272.20

727.2 

713.2 

710.5 

712.1 

710.9 

711.1 

710.8 

711.3 

712.5 

712.8 

713.2 

727.5

271.22

740.5 

728.5 

728.3

71 Q q

1 lO.O

713.5 

710.7 

710.5

709.7

711.5 

712.4 

711.0 

710.2 

709.3 

713.5 

718.3 

724.8

725.7 

739.5

270.86

716.5

712.5

Horizontal 

distance Altitude

RM 270.86 — Continued

40

60

80

100

120

140

160

180

200 

220

240

260

280

286

291

RM

-86

0

10

25

76

125

165 

240 

246 

253

RM

800 

900 

910 

925 

975 

1,000 

1,050

1,100

1,150 

1,210 

1,215 

1,235 

1,275

RM 

0 

14 

30 

80 

120 

170

210

222

244

RM

0 

10 

33

110

200 

224 

229 

250 

264

RM 

-20

0 

20

40

57

61

80

708.0

709.5

710.0

710.0

710.0

710.5

711.5

709.0

707.3 

700.5

710.0

710.0

710.5

711.0

716.5

27043

719.3

715.5

707.8

701.5

702.4

701.5

700.9 

700.4 

707.8 

716.6

268.34

710.8 

707.3 

704.1 

701.8 

701.6 

700.6 

698.3

698.6

699.7 

702.4 

704.1 

708.2 

712.7

266.02 

702.5 

698.1 

692.1 

692.7 

693.1 

693.4

692.9

698.1 

704.6

263.62

700.2 

690.2 

684.9

687.2

686.4 

684.9 

686.4 

690.1 

697.6

259.87 

699.6

692.6 

684.1

684.0

684.4

681.6

683.8
50 PLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

TABLE 8.—Cross section coordinates—Continued

[Measurements in feet]

Horizontal 

distance Altitude

RM 259.87— Continued

100

120

140

157

681.3

679.6

678.6

677.1

Horizontal 

distance Altitude

RM 259.87 — Continued

161

180

200

220

676.5

680.1

680.6

680.1

Horizontal 

distance Altitude

RM 259.87 — Continued

240

257

261

280

679.6

679.6

682.6

684.0

Horizontal 

distance Altitude

RM 259.87 — Continued

300

310

330

689.1

691.6

699.6

TABLE 9.—Channel roughness and barrier heights

River mile

302.79

302.38

302.05

300.98

300.62

300.44

300.29

299.94

299.56

299.20

299.10

298.93

298.77

298.10

297.86

297.73

297.06

296.60

295.30

294.70

293.92

293.10

292.19

290.54

287.86

286.96

286.07

284.32

281.79

281.07

279.99

277.95

274.12

272.20

271.22

270.86

270.43

268.34

266.02

263.62

259.85

Manninor's

Maximum

(S/W'3)

0.057

.055

.066

.050

.080

.051

.039

.039

.040

.042

.050

.038

.038

.033

.033

.031

.034

.034

.035

.035

.034

.039

.042

.047

.041

.038

.025

.027

.030

.025

.027

.025

.033

.028

.028

.058

.052

.080

.080

.040

.040

n

Minimum

0.032

.040

.029

.034

.056

.040

.039

.021

.040

.024

.021

.031

.030

.024

.026

.024

.028

.025

.026

.028

.023

.039

.021

.038

.026

.038

.025

.020

.025

.021

.024

.021

.026

.014

.026

.049

.037

.058

.060

.034

.030

Effective 

barrier 

height 

(ft)

50

45

40

30

60

20

15

15

15

10

20

25

15

25

25

25

20

20

15

15

10

15

30

25

20

15

30

50

40

40

40

50

60

40

40

40

40

60

50

40

25
TABLES SUMMARIZING DATA 51

TABLE 10.—Summary of meteorologic data, July 12-19 and August 1-8,1976

[Precipitation = 0.0 mm for entire period]

Time

Wind

speed

(m/s)

Short wave

radiation

(W/m^)

Long wave

radiation

<W/mB)

Air temperature

dry bulb <°C) wet bulb <°C)

Vapor

pressure

(KPa)

July 12, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.28

.30

.30

.30

1.33

1.89

.52

3.47

1.47

4.57

6.47

3.70

6.34

4.40

3.00

3.93

5.93

4.11

3.39

2.44

.81

2.48

2.17

2.52

0.0

0.0

0.0

0.0

0.0

24.2

141.8

344.0

558.2

727.5

860.4

1,023.1

906.6

905.5

769.2

647.3

438.5

224.2

67.0

0.0

0.0

0.0

0.0

0.0

372.5

372.5

372.5

372.5

372.5

372.5

372.5

375.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

372.5

22.6

21.8

21.8

20.5

20.8

21.0

22.0

23.3

25.7

26.8

28.1

29.3

29.5

29.9

31.1

29.6

29.4

29.4

28.7

27.1

25.8

25.0

23.7

23.2

21.0

20.9

20.5

19.7

19.7

19.9

20.4

21.0

21.7

22.3

22.3

22.3

21.2

21.4

22.4

21.3

22.1

22.4

22.2

22.0

22.0

21.9

21.1

21.0

2.46

2.45

2.39

2.28

2.27

2.30

2.37

2.45

2.53

2.62

2.60

2.58

2.38

2.41

2.57

2.40

2.54

2.59

2.57

2.56

2.58

2.57

2.46

2.45

July 13, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2.19

1.04

1.12

1.62

.30

.28

.67

3.60

2.81

4.59

4.73

3.00

3.41

2.19

4.73

5.89

3.74

2.75

.50

.57

.73

.28

.28

.59

0.0

0.0

0.0

0.0

0.0

26.4

98.9

302.2

526.4

738.5

913.2

951.6

989.0

286.8

253.8

611.0

415.4

254.9

83.5

0.0

0.0

0.0

0.0

0.0

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

22.3

21.8

21.2

21.0

20.6

20.5

21.9

23.5

25.2

26.6

27.3

28.0

29.2

29.8

30.1

29.6

30.4

30.3

29.4

25.4

24.1

22.0

21.0

19.1

20.4

19.8

19.9

20.0

19.7

19.3

19.9

21.2

21.4

21.7

21.6

22.1

22.2

21.3 .

21.0

21.5

21.0

20.5

20.3

19.6

18.4

18.4

17.6

16.7

2.36

2.27

2.30

2.32

2.28

2.21

2.29

2.48

2.48

2.51

2.48

2.56

2.56

2.39

2.34

2.43

2.33

2.25

2.23

2.18

2.02

2.05

1.95

1.89

July 14, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

0.30

.90

.71

1.18

.79

.28

1.04

.96

.28

.59

.30

2.83

2.57

1.80

.90

4.65

1.04

2.61

0.0

0.0

0.0

0.0

0.0

9.9

201.1

301.1

558.2

693.4

853.8

934.1

964.8

925.3

786.8

649.5

453.8

258.2

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

349.6

18.1

17.8

17.4

16.5

16.4

15.9

17.3

20.2

24.0

24.1

27.6

26.7

28.4

30.8

30.7

30.1

30.6

30.4

16.5

15.7

15.2

15.2

14.5

14.2

15.2

15.1

16.2

16.0

16.8

16.7

17.3

17.0

17.8

17.7

18.3

18.5

1.85

1.75

1.69

1.70

1.62

1.59

1.69

1.63

1.71

1.69

1.74

1.74

1.80

1.72

1.83

1.83

1.90

1.94
52 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

TABLE 10.—Summary of meteorologic data, July 12-19 and August 1-8, 1976—Continued

[Precipitation = 0.0 mm for entire period]

Time

1800

1900

2000

2100

2200

2300

Wind

speed

(m/s)

.36

.54

.28

.28

.28

.28

Short wave

radiation

(W/mP)

July

70.3

0.0

0.0

0.0

0.0

0.0

Lone wave

radiation

<W/m2)

14, 1976 — Continued

349.6

349.6

349.6

349.6

349.6

349.6

Air temperature

dry bulb <°C)

29.3

25.5

23.4

22.3

22.0

20.4

wet bulb <°C)

19.9

19.7

19.7

19.8

19.3

18.9

Vapor

pressure

(KPa)

2.17

2.20

2.23

2.26

2.19

2.15

July 15, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.28

.28

.28

.28

.28

.57

.28

.92

2.13

.59

3.10

1.91

2.79

1.20

4.03

6.96

2.28

2.83

1.91

1.37

.63

1.78

1.20

.87

0.0

0.0

0.0

0.0

0.0

16.5

149.5

325.3

500.0

579.1

769.2

880.2

893.4

627.5

407.7

656.0

235.2

146.2

111.0

0.0

0.0

0.0

0.0

0.0

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

371.8

20.3

20.7

19.5

18.7

18.1

18.3

20.4

24.1

26.0

27.5

29.2

29.6

30.1

31.1

30.1

29.8

29.5

28.3

28.9

25.7

24.9

24.9

23.8

22.9

18.6

19.0

. 18.0

18.0

17.5

17.8

18.8

21.0

21.9

22.4

23.1

22.6

22.6

22.4

22.5

21.5

22.0

21.3

21.9

22.3

21.9

20.7

20.1

19.6

2.11

2.16

2.03

2.05

1.98

2.02

2.14

2.43

2.56

2.62

2.72

2.63

2.62

2.57

2.60

2.43

2.52

2.42

2.51

2.63

2.57

2.37

2.29

2.22

July 16, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

1.93

.54

.28

1.56

1.49

1.39

1.45

2.61

2.92

4.11

6.49

5.89

5.76

5.04

3.14

5.43

3.62

1.99

.30

2.81

.30

2.48

1.51

1.08

0.0

0.0

0.0

0.0

0.0

7.7

157.1

350.5

549.5

709.9

868.1

307.7

1,003.3

985.7

844.0

237.4

182.4

130.8

23.1

0.0

0.0

0.0

0.0

0.0

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

363.5

22.4

21.7

20.8

20.7

20.6

20.3

21.3

23.8

25.0

26.5

27.7

28.3

29.5

29.6

29.7

30.1

20.7

22.4

22.4

20.9

20.3

19.6

19.3

19.6

19.6

19.9

19.8

19.5

19.6

19.5

19.8

21.0

20.6

21.0

21.2

21.3

20.9

20.6

21.5

21.0

18.2

19.3

19.4

18.2

18.2

18.3

18.2

18.4

2.23

2.29

2.29

2.24

2.26

2.25

2.28

2.44

2.35

2.39

2.41

2.42

2.33

2.28

2.43

2.34

2.05

2.18

2.20

2.04

2.05

2.08

2.07

2.09

July 17, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

1.29

.85

.30

1.86

1.35

.28

1.08

.34

2.34

0.0

0.0

0.0

0.0

0.0

6.6

83.5

127.5

311.0

361.4

3G1.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

19.8

19.1

19.4

18.8

19.7

19.6

19.7

20.2

21.9

18.4

18.0

18.5

17.9

18.6

19.0

19.0

19.4

19.6

2.09

2.04

2.11

2.03

2.12

2.18

2.18

2.23

2.24
TABLES SUMMARIZING DATA 53

TABLE 10.—Summary of meteorologic data, July 12-19 and August 1-8, 1976—Continued

[Precipitation = 0.0 mm for entire period]

Time

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

Wind

speed

(m/s)

1.27

.28

2.85

1.00

4.03

4.05

1.35

4.86

2.40

.28

.28

.28

.28

.30

.30

Short wave

radiation

(W/m2)

July

319.8

764.8

912.1

236.3

760.4

427.5

565.9

214.3

42.9

24.2

1.1

0.0

0.0

0.0

0.0

Long wave

radiation

(W/mS)

17, 1976 — Continued

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

361.4

Air temperature

dry bulb <°C)

23.9

25.7

26.9

30.1

28.9

27.8

30.5

27.5

25.8

24.6

23.1

22.2

20.4

19.8

19.1

wet bulb (°C)

21.0

21.1

20.7

21.3

19.9

19.6

21.4

20.3

19.7

19.6

19.9

19.5

18.7

18.7

18.2

Vapor

pressure

(KPa)

2.44

2.42

2.34

2.39

2.18

2.15

2.40

2.26

2.19

2.20

2.27

2.22

2.12

2.13

2.07

July 18, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.32

.28

.28

.73

.28

.28

.30

.83

.75

1.00

.38

.28

.67

.87

2.05

.52

1.06

1.41

1.12

.61

.28

.46

.28

.28

0.0

0.0

0.0

0.0

0.0

6.6

74.7

290.1

380.2

475.8

827.5

887.9

926.4

924.2

823.1

330.8

469.2

137.4

63.7

0.0

0.0

0.0

0.0

0.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

377.0

18.4

18.7

18.2

17.5

17.3

17.1

17.6

20.0

23.1

26.1

28.3

31.7

33.4

35.1

31.3

34.3

33.2

31.0

27.8

25.1

23.5

21.9

20.9

20.4

17.7

17.2

17.1

16.4

16.3

16.2

16.9

17.5

18.5

19.6

19.9

20.7

21.6

22.4

20.7

22.4

22.4

22.0

21.0

21.1

20.2

19.8

19.3

19.3

2.01

1.93

1.93

1.84

1.83

1.82

1.91

1.96

2.0-5

2.17

2.19

2.26

2.39

2.50

2.27

2.52

2.53

2.50

2.37

2.43

2.31

2.27

2.21

2.22

July 19, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.28

.28

.79

.40

.67

.30

.90

.28

.38

1.37

1.16

.36

.96

1.43

4.53

3.72

1.68

.54

1.72

.81

.67

.54

.28

.28

0.0

0.0

0.0

0.0

0.0

12.1

130.8

301.1

494.5

667.0

818.7

906.6

970.3

960.4

803.3

275.8

419.8

250.5

18.7

0.0

0.0

0.0

0.0

0.0

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

373.2

20.1

19.6

18.7

17.9

18.3

18.5

19.4

22.9

25.3

27.9

30.4

31.4

32.9

31.6

32.3

32.8

32.0

32.7

28.5

26.9

25.2

23.5

22.2

21.8

18.9

18.1

18.1

17.0

17.0

17.2

18.1

19.6

21.0

21.4

22.1

21.9

22.4

21.2

21.4

21.4

21.8

23.2

22.1

21.5

21.7

20.6

20.2

20.1

2.16

2.05

2.06

1.92

1.91

1.94

2.05

2.22

2.41

2.44

2.52

2.47

2.54

2.35

2.37

2.36

2.45

2.69

2.55

2.47

2.57

2.38

2.33

2.32
54 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

TABLE 10.—Summary of meteorologic data, July 12-19 and August 1-8, 1976—Continued

[Precipitation = 0.0 mm for entire period]

Time

Wind

speed

(m/s)

Short wave

radiation

(W/nv*) .

Long wave

radiation

<W/rri2)

Air temperature

dry bulb (°C) wet bulb <°C)

Vapor

pressure

(KPa)

August 1, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

1.22

2.63

4.01

.73

1.10

.28

1.45

1.49

1.64

1.35

2.25

3.12

1.35

4.21

3.51

1.97

2.11

.29

.90

.46

.48

.44

.48

.77

0.0

0.0

0.0

0.0

0.0

0.0

5.5

54.9

153.8

452.7

738.5

824.2

338.5

928.6

911.0

341.8

339.6

49.5

202.2

42.9

0.0

0.0

0.0

0.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0 .

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

463.0

21.1

21.0

21.4

21.1

20.7

21.0

20.6

21.0

22.5

24.4

25.9

27.7

29.0

29.6

29.8

30.9

31.2

29.5

24.3

25.0

23.6

22.7

22.4

22.3

20.0

20.2

20.7

20.5

20.3

20.2

19.9

20.4

21.0

21.6

22.5

22.3

22.5

22.6

" 22.7

23.2

22.4

22.4

22.8

22.9

22.2

22.0

21.6

21.4

2.32

2.35

2.42

2.40

2.37

2.35

2.31

2.38

2.46

2.53

2.67

2.60

2.62

2.62

2.64

2.71

2.56

2.59

2.74

2.75

2.65

2.63

2.56

2.53

August 2, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.36

.28

.28

.28

1.82

.38

.28

.48

.38

2.40

2.21

.81

.28

1.68

.40

3.86

2.03

1.74

2.89

1.47

1.47

.50

.52

2.36

0.0

0.0

0.0

0.0

0.0

0.0

7.69

106.6

270.3

439.6

667.0

731.9

974.7

633.0

816.5

549.5

617.6

144.0

202.2

0.0

0.0

0.0

0.0

0.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

21.9

21.2

20.1

19.9

19.6

19.5

19.2

19.5

21.6

22.8

24.8

28.2

29.8

28.4

28.4

27.4

30.0

26.8

26.6

25.6

23.8

22.7

21.9

21.0

20.6

20.0

19.7

19.5

19.2

18.7

18.6

18.9

19.9

20.4

20.4

22.1

22.2

20.9

21.8

20.6

21.9

21.0

20.3

19.8

18.7

18.2

18.0

17.9

2.40

2.31

2.28

2.26

2.21

2.14

2.13

2.17

2.29

2.35

2.32

2.56

2.55

2.35

2.50

2.31

2.49

2.39

2.28

2.21

2.07

2.01

2.00

2.00

August 3, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

3.10

.28

.28

2.17

3.74

1.31

.85

.83

.28

.28

.28

1.26

1.53

1.47

1.62

1.76

1.51

.83

0.0

0.0

0.0

0.0

0.0

0.0

0.0

104.4

242.9

522.0

772.5

660.4

993.4

484.6

865.9

753.8

600.0

405.5

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

21.5

22.3

21.8

21.7

21.0

21.1

20.2

20.8

21.3

21.8

23.1

24.3

26.1

29.5

27.3

29.4

28.4

29.5

19.1

18.3

17.7

16.4

17.2

15.7

16.5

16.9

17.3

17.6

18.2

19.1

19.4

20.8

18.9

21.0

20.5

20.9

2.17

2.03

1.95

1.78

1.90

1.69

1.81

1.86

1.91

1.94

2.01

2.12

2.14

2.31

2.04

2.35

2.28

2.33
TABLES SUMMARIZING DATA 55

TABLE 10.—Summary of meteorologic data, July 12-19 and August 1-8, 1976—Continued

[Precipitation = 0.0 mm for entire period]

Time

Wind

speed

(m/s)

Short wave Long wave

radiation radiation

(W/mS) (W/m^)

Air temperature

dry bulb <°C) wet bulb <°C)

Vapor

pressure

(KPa)

August 3, 1976 — Continued

1800

1900

2000

2100

2200

2300

.77

.34

1.78

1.00

1.90

1.45

198.9

38.5

0.0

0.0

0.0

0.0

448.0

448.0

448.0

448.0

448.0

448.0

28.6

26.9

23.8

21.3

19.9

19.2

21.2

20.4

19.6

19.4

18.5

18.0

2.39

2.29

2.21

2.22

2.10

2.04

August 4, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.73

.36

1.70

.28

.40

1.47

.32

2.03

1.06

.98

1.47

.28

.87

.67

1.16

2.17

.95

1.72

2.77

1.78

1.57

.50

.56

1.74

0.0

0.0

0.0

0.0

0.0

0.0

3.3

256.0

327.5

536.3

727.5

824.2

920.9

930.8

513.2

796.7

650.5

169.2

94.5

15.4

0.0

0.0

0.0

0.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

448.0

19.2

20.0

19.5

18.6

16.7

16.6

16.0

17.2

20.9

22.4

24.2

26.4

28.0

29.9

29.3

28.8

32.1

28.8

28.1

26.4

22.8

20.1

19.0

17.8

18.0

17.9

17.4

17.3

16.2

16.0

15.8

16.4

17.9

18.4

18.7

19.5

19.5

20.2

19.8

19.2

20.7

20.0

19.8

19.7

18.6

18.0

17.5

17.0

2.04

2.01

1.95

1.95

1.83

1.80

1.79

1.85

2.00

2.05

2.06

2.15

2.13

2.21

2.15

2.07

2.26

2.19

2.17

2.18

2.07

2.03

1.97

1.92

August 5, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

1.72

.32

2.09

1.00

.28

1.41

1.16

1.78

.83

1.37

1.16

.28

.75

.28

1.70

. 1.16

.32

.28

.28

.28

1.68

.28

1.35

.75

0.0

0.0

0.0

0.0

0.0

0.0 1.1

109.9

198.9

252.7

680.7

923.1

1,034.1

1,034.1

286.8

825.3

184.6

418.7

195.6

29.7

0.0

0.0

0.0

0.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

450.0

17.3

16.6

16.2

15.8

15.8

15.0

14.9

. 16.8

18.9

21.9

25.2

28.8

30.6

33.3

29.8

29.4

31.7

33.1

31.5

29.0

24.3

21.3

20.5

19.8

16.4

16.1

15.8

15.3

15.2

14.9

14.9

15.7

17.2

18.9

20.6

21.8

21.1

21.8

18.8

18.6

20.5

20.9

21.0

20.5

19.6

19.1

18.4

18.5

1.84

1.82

1.78

1.72

1.71

1.69

1.69

1.76

1.93

2.13

2.35

2.49

2.35

2.42

1.99

1.97

2.23

2.27

2.32

2.27

2.20

2.17

2.08

2.10

August 6, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1.20

.28

.71

.28

1.51

.28

.28

.28

.28

2.24

0.0

0.0

0.0

0.0

0.0

0.0

2.19

109.9

284.6

494.5

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

19.7

18.4

18.2 - 17.5

17.4

17.1

17.8

17.9

23.0

25.5

18.2

17.6

17.2

16.8

17.0

16.5

17.0

17.2

19.1

20.2

2.06

1.99

1.94

1.90

1.93

1.86

1.92

1.94

2.14

2.28
56 FLOW REGULATION AND POWERPLANT EFFLUENTS—CHATTAHOOCHEE RIVER, GEORGIA

TABLE 10.—Summary of meteorologic data, July 12-19 and August 1-8, 1976—Continued

[Precipitation = 0.0 mm for entire period]

Time

Wind

speed

(m/s)

Short wave

radiation

(W/m2 )

Long wave

radiation

(W/m2)

Air temperature

dry bulb <°C) wet bulb (°C)

Vapor

pressure

(KPa)

August 6, 1976 — Continued

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

1.10

.75

1.51

.28

2.25

.73

.73

1.00

.90

.79

.48

1.43

1.55

1.55

671.4

854.9

854.9

917.6

733.0

413.2

596.7

376.9

188.5

0.0

0.0

0.0

0.0

0.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

456.0

28.7

28.7

28.6

29.3

30.4

29.5

30.0

30.3

26.5

22.7

19.5

20.5

20.5

20.6

20.8

22.8

21.6

22.0

22.0

21.3

21.4

21.3

20.8

20.3

18.4

19.4

19.7

19.8

2.37

2.68

2.46

2.52

2.51

2.40

2.41

2.38

2.37

2.34

2.09

2.23

2.28

2.29

August 7, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

1.51

.95

1.41

1.12

.28

.28

.28

.90

.28

.77

.29

.29

1.66

2.11

1.41

2.09

.87

.36

.28

.50

1.41

1.80

.59

1.66

0.0

0.0

0.0

0.0

0.0

0.0

0.0

109.9

271.4

285.7

281.3

216.5

458.2

735.2

390.1

780.2

609.9

397.8

159.3

40.7

0.0

0.0

0.0

0.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

444.0

20.8

19.9

20.0

19.6

19.7

19.1

19.0

20.2

20.5

20.7

21.7

22.9

23.2

24.1

25.5

27.6

28.5

27.3

27.3

27.7

24.8

23.1

22.1

21.0

19.7

19.3

19.4

19.1

19.4

18.8

18.6

19.6

19.6

19.9

20.3

21.1

21.4

21.8

21.9

22.2

22.1

21.6

21.8

22.3

22.1

21.7

20.2

20.1

2.27

2.22

2.24

2.20

2.24

2.16

2.13

2.26

2.26

2.30

2.35

2.47

2.51

2.57

2.56

2.58

2.55

2.48

2.52

2.60

2.61

2.57

2.33

2.33

August 8, 1976

0000

0100

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.81

.71

.90

1.00

.32

1.28

.52

1.78

.28

2.07

.65

1.86

.32

1.97

.28

1.70

.69

.28

.67

.85

1.04

.67

1.12

1.68

0.0

0.0

0.0

0.0

0.0

0.0

0.0

105.5

291.2

487.9

702.2

856.0

942.9

749.5

224.2

872.5

660.4

409.9

205.5

29.7

0.0

0.0

0.0

0.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

445.0

20.4

19.8

19.8

19.3

19.2

18.5

18.1

19.2

19.6

21.7

22.9

23.5

26.0

27.2

26.4

26.9

26.9

26.2

26.6

24.9

23.1

21.4

21.0

20.1

19.5

19.0

18.9

18.2

18.5

18.1

17.7

18.4

18.6

19.4

19.5

19.0

19.9

19.5

19.2

18.7

19.4

18.5

19.2

18.7

17.9

17.4

16.9

17.1

2.25

2.18

2.16

2.07

2.11

2.06

2.01

2.10

2.12

2.21

2.21

2.12

2.22

2.14

2.10

2.02

2.13

2.00

2.10

2.05

1.96

1.92

1.85

1.90

ft U.S. Government Printing Office: 1979—311-344/135