Two Lakes : Dreams Realized
 

ANSWER TO U.S. CORPS OF ENGINEERS
CONCERN NUMBER 1


1979 Maximum Benefits
Discharge Data

Flood damage reduction provided by
the current plan would require unrealistic
operation of Ross Barnett Reservoir.
Releases are based on rainfall forecast data.
If events do not occur as forecast, lake
levels could be severly impacted.

     After the fact analysis of the 1979 and 1983 floods reveals that the Barnett Reservoir has the ability to reduce flow rates of these floods by an additional factor of 20%. This would have the effect of reducing flood damage by 50%. Preliminary study indicates that this can be accomplished by responding to rainfall as it is measured on the ground, not rainfall forecast data, and that it is not necessary to maintain the reservoir at levels lower than its normal winter pool level (296.0 feet).

     The limiting factor in use of the reservoir for flood control is not its depth or size, or the fact that it has an important recreational purpose. Difficulty in using the reservoir for flood control is created by fewer than 100 structures in the metropolitan area that are built at such low elevations that they are subject to flooding on a frequent basis. Prerelease of the reservoir, which is necessary to prevent flooding, must be withheld until the rainfall event has progressed to a point that it can safely be adjudged that these structures will flood anyway. This wasted time is the main limiting factor in using the reservoir for flood control. Despite this handicap, study at this point indicates that the reservoir can, at this time, reduce damage from floods such as the 1979 and 1983 events by an additional 50%. This is provided that an accurate prediction of reservoir inflow can be derived from rainfall data. At this time, we are doing a study to determine if this can be done.

     Construction of a flood control lake thru Jackson would, by itself, solve Jackson's flooding problem. This would, in turn, enable the reservoir to prerelease without regard to flooding in Jackson which would, in turn, make it much easier for the reservoir to lower flooding farther downstream, in Richland and Byram. The following spreadsheet shows that the reservoir had the unused capacity to reduce the 1979 flood from 120,000 to approximately 100,000 cfs.

 

 

- -

ACTUAL

-

PROJECTED

-

DATE

TIME

DISCHG

RESERVOIR

LAKE VOL

INFLOW

DSCHG

RESERVOIR

DESCRIPTION OF

 RAINFALL
- -

(CFPS)

LEVEL

CHNG(CFPS)

(CFPS)

(CFPS)

LEVEL

EVENTS

 TOTALS

4/10/1979

6:00AM

21700

297.66

 - - - - - --
-

7:00AM

 -

297.65

-3519

18181

 - --

1.5' average inches of rain had

 ----
-

8:00AM

 -

297.64

-3517

18183

 - --

fallen on the 8th.

 -------
-

9:00AM

 -

297.63

-3515

18185

 - - - -----
-

10:00AM

 -

297.63

-3514

18186

 - - - -
-

11:00AM

 -

297.62

-3512

18188

 - - - -
-

12:00PM

 -

297.61

-3510

18190

 - - - -
-

1:00PM

 -

297.60

-3508

18192

 - - - -
-

2:00PM

 -

297.59

-3506

18194

 - - - -
-

3:00PM

 -

297.58

-3504

18196

 - - - -
-

4:00PM

 -

297.58

-3503

18197

 - - - -
-

5:00PM

 -

297.57

-3501

18199

 - - - -
-

6:00PM

 -

297.56

-3499

18201

 - - - -
-

7:00PM

 -

297.55

-3497

18203

 - - - -
-

8:00PM

 -

297.54

-3495

18205

 - - - -
-

9:00PM

 -

297.53

-3494

18206

 - - - -
-

10:00PM

 -

297.53

-3492

18208

 - - - -
-

11:00PM

 -

297.52

-3490

18210

 - - - -
-

12:00AM

 -

297.51

-3488

18212

 - - - -
-

1:00AM

 -

297.50

-3486

18214

21700

295.5

normal level for flood prone

 -
-

2:00AM

 -

297.50

0

21700

21700

295.50

months

 -
-

3:00AM

 -

297.50

0

21700

21700

295.50

 - -
-

4:00AM

 -

297.50

0

21700

21700

295.50

flash flood warnings

 -
--

5:00AM

 -

297.50

0

21700

21700

295.50

(do not increase discharge

 -

4/11/1979

6:00AM

18500

297.50

0

18500

18500

295.50

above inflow levels) continue

 -
-

7:00AM

 -

297.49

-5172

13328

18500

295.49

maintaining normal reservoir

 -
-

8:00AM

 -

297.48

-5168

13332

18500

295.47

levels

 -
-

9:00AM

 -

297.46

-5164

13336

18500

295.46

 - -
-

10:00AM

15300

297.45

-5160

10140

15300

295.44

 - -
-

11:00AM

 -

297.46

2999

18299

15300

295.45

 - -
-

12:00PM

 -

297.46

3000

18300

15300

295.46

 - -
-

1:00PM

 -

297.47

3002

18302

15300

295.47

 - -
-

2:00PM

 -

297.48

3003

18303

15300

295.48

 - -
-

3:00PM

 -

297.49

3004

18304

15300

295.48

 - -
-

4:00PM

 -

297.49

3006

18306

15300

295.49

 - -
-

5:00PM

 -

297.50

3007

18307

15300

295.50

 - -
-

6:00PM

 -

297.51

3008

18308

15300

295.51

 - -
-

7:00PM

 -

297.52

3010

18310

15300

295.52

 - -
-

8:00PM

 -

297.52

3011

18311

15300

295.53

 - -
-

9:00PM

18500

297.53

3025

21525

18500

295.53

 - -
-

10:00PM

 -

297.53

-2073

16427

18500

295.53

 - -
-

11:00PM

21700

297.52

-2072

19628

21700

295.52

 - -
-

12:00AM

 -

297.67

62145

83845

21700

295.69

heavy rain hits 28 hours after

 2.2"
-

1:00AM

28100

297.81

58538

86638

28100

295.85

warning (rain totals 2.2")

 -
-

2:00AM

 -

297.81

0

28100

28100

295.85

small discharge increase is

 -
-

3:00AM

 -

297.82

4217

32317

28100

295.86

still allowing reservoir levels

 -
-

4:00AM

31300

297.82

0

31300

31300

295.86

to rise

 -
-

5:00AM

 -

297.96

59075

90375

31300

296.02

 - -

4/12/1979

6:00AM

33200

298.10

59576

92776

33200

296.18

confirmation of serious amounts

 4.1"
-

7:00AM

 -

298.14

17165

50365

33200

296.23

of rainfall (4.1" total)

 -
-

8:00AM

36200

298.17

12905

49105

36200

296.26

(monitors at selected sights

 -
-

9:00AM

 -

298.19

8618

44818

36200

296.28

could be used to confirm this)

 -
-

10:00AM

38850

298.21

8629

47479

38850

296.31

 - -
-

11:00AM

 -

298.21

0

38850

45000

296.29

gradual discharge increase

 -
-

12:00PM

 -

298.21

0

38850

50000

296.26

reservoir is filling up (4.8" total)

 4.8"
-

1:00PM

 -

298.22

4319

43169

55000

296.23

 - -
-

2:00PM

41100

298.22

0

41100

60000

296.18

boat owners advised that

 -
-

3:00PM

48275

298.40

77796

126071

70000

296.33

record breaking rainfall has

--
-

4:00PM

 -

298.39

-4368

43907

80000

296.23

occurred, continued rain in

 -
-

5:00PM

 -

298.39

0

48275

80000

296.15

forcast (8.4" total)

 8.4"
-

6:00PM

50375

298.38

-4366

46009

80000

296.06

boat owners warned

 -
-

7:00PM

 -

298.37

-6545

43830

80000

295.96

(calculations based on com-

 -
-

8:00PM

 -

298.35

-6539

43836

80000

295.87

puter model could be used to

 -
-

9:00PM

 -

298.34

-6533

43842

80000

295.77

predict upcoming inflows)

 -
-

10:00PM

 -

298.32

-6527

43848

80000

295.67

 - -
-

11:00PM

 -

298.31

-6521

43854

80000

295.57

(9.8" total)

 -
-

12:00AM

 -

298.29

-6516

43859

80000

295.48

 - 9.8"
-

1:00AM

 -

298.28

-6510

43865

80000

295.38

30 hours after rain begins

 -
-

2:00AM

 -

298.26

-6504

43871

80000

295.28

reservoir is stll at normal level

 -
-

3:00AM

 -

298.25

-6498

43877

80000

295.17

rain has ended (10.2" total)

 10.2"
-

4:00AM

 -

298.23

-6493

43882

80000

295.07

 - -
-

5:00AM

 -

298.22

-6487

43888

80000

294.97

 - -

4/13/1979

6:00AM

50375

298.20

-6481

43894

85000

294.85

emergency declared

 -
-

7:00AM

 -

298.19

-4317

46058

85000

294.74

computations in watershed

 -
-

8:00AM

 -

298.19

0

50375

85000

294.64

indicate that lake must be

-
-

9:00AM

52850

298.18

-4314

48536

85000

294.53

dropped to 292'(lowest limit)

 -
-

10:00AM

55125

298.18

0

55125

85000

294.44

 - -
-

11:00AM

57400

298.13

-21559

35841

85000

294.30

boats must be moved and

 -
-

12:00PM

62675

298.10

-12897

49778

85000

294.19

moorings freed

 -
-

1:00PM

65600

298.07

-12874

52726

85000

294.10

 - -
-

2:00PM

68075

298.00

-29985

38090

85000

293.95

 - -
-

3:00PM

72875

297.97

-12797

60078

90000

293.86

 - -
-

4:00PM

76150

297.86

-46838

29312

90000

293.67

 - -
-

5:00PM

78175

297.81

-21149

57026

90000

293.57

 - -
-

6:00PM

80875

297.72

-37954

42921

90000

293.42

 - -
-

7:00PM

85800

297.66

-25164

60636

90000

293.32

 - -
-

8:00PM

90750

297.55

-45966

44784

90000

293.18

 - -
-

9:00PM

96600

297.43

-49808

46792

90000

293.04

 - -
-

10:00PM

101325

297.30

-53561

47764

90000

292.90

 - -
-

11:00PM

 -

297.14

-65391

35934

90000

292.71

 - -
-

12:00AM

 -

297.03

-44508

56817

90000

292.60

 - -
-

1:00AM

 -

296.95

-32146

69179

90000

292.53

 - -
-

2:00AM

 -

296.84

-43976

57349

90000

292.42

calculations indicate that it

 -
-

3:00AM

 -

296.76

-31759

69566

90000

292.35

will take a rate of 95000cfs in

 -
-

4:00AM

 -

296.67

-35546

65779

90000

292.26

order to stay below a maximum

 -
-

5:00AM

 -

296.60

-27487

73838

95000

292.18

reservoir level of 299.7' at

 -

4/14/1979

6:00AM

101325

296.58

-7818

93507

95000

292.18

fill up

 -
-

7:00AM

 -

296.53

-19520

81805

95000

292.13

 - -
-

8:00AM

 -

296.53

0

101325

95000

292.16

30 hours after rain ends

-
-

9:00AM

 -

296.50

-11674

89651

95000

292.14

reservoir is at 292'

 -
-

10:00AM

101900

296.49

-3884

98016

95000

292.15

 - -
-

11:00AM

 -

296.48

-3881

98019

98000

292.15

inflow is greater than expected

 -
-

12:00PM

 -

296.49

3879

105779

98000

292.17

updated computations indicate

 -
-

1:00PM

 -

296.52

11643

113543

98000

292.23

that 98000cfs will be necessary

 -
-

2:00PM

 -

296.55

11666

113566

98000

292.29

 - -
-

3:00PM

104600

296.57

7793

112393

98000

292.34

 - -
-

4:00PM

107300

296.59

7803

115103

98000

292.40

 - -
-

5:00PM

110000

296.62

11719

121719

98000

292.48

 - -
-

6:00PM

112700

296.62

0

112700

98000

292.53

 - -
-

7:00PM

115400

296.60

-7828

107572

98000

292.56

 - -
-

8:00PM

118100

296.62

7818

125918

98000

292.66

 - -
-

9:00PM

120800

296.63

3914

124714

98000

292.75

 - -
-

10:00PM

 -

296.62

-3917

116883

98000

292.82

 - -
-

11:00PM

 -

296.63

3914

124714

98000

292.91

 - -
-

12:00AM

 -

296.65

7833

128633

98000

293.01

 - -
-

1:00AM

 -

296.70

19608

140408

98000

293.15

 - -
-

2:00AM

 -

296.71

3934

124734

98000

293.24

 - -
-

3:00AM

 -

296.75

15748

136548

98000

293.36

 - -
-

4:00AM

 -

296.80

19735

140535

98000

293.50

 - -
-

5:00AM

 -

296.84

15839

136639

98000

293.62

 - -

4/15/1979

6:00AM

120800

296.91

27789

148589

98000

293.78

 - -
-

7:00AM

 -

296.95

15951

136751

98000

293.90

 - -
-

8:00AM

124500

297.02

27985

152485

98000

294.07

 - -
-

9:00AM

 -

297.06

16063

140563

98000

294.20

 - -
-

10:00AM

 -

297.13

28181

152681

98000

294.37

 - -
-

11:00AM

 -

297.21

32349

156849

98000

294.54

 - -
-

12:00PM

 -

297.31

40640

165140

98000

294.74

 - -
-

1:00PM

 -

297.40

36805

161305

98000

294.93

 - -
-

2:00PM

 -

297.45

20562

145062

98000

295.06

 - -
-

3:00PM

 -

297.54

37126

161626

98000

295.24

 - -
-

4:00PM

 -

297.61

29037

153537

98000

295.40

 - -
-

5:00PM

 -

297.68

29162

153662

98000

295.55

 - -
-

6:00PM

 -

297.76

33471

157971

98000

295.72

 - -
-

7:00PM

 -

297.82

25226

149726

98000

295.86

 - -
-

8:00PM

115500

297.96

59075

174575

98000

296.06

 - -
-

9:00PM

112500

298.05

38299

150799

98000

296.20

 - -
-

10:00PM

 0-

298.13

34228

146728

98000

296.33

 - -
-

11:00PM

 -

298.20

30093

142593

98000

296.45

 - -
-

12:00AM

 -

298.29

38852

151352

98000

296.59

 - -
-

1:00AM

 -

298.37

34720

147220

98000

296.71

 - -
-

2:00AM

118500

298.50

56686

175186

98000

296.91

 - -
-

3:00AM

 -

298.53

13181

131681

98000

296.99

 - -
-

4:00AM

 -

298.62

39614

158114

98000

297.14

 - -
-

5:00AM

 -

298.70

35397

153897

98000

297.28

 - -

4/16/1979

6:00AM

 -

298.78

35562

154062

98000

297.42

52 hours after rain's end,

 -
-

7:00AM

118500

298.86

35726

154226

98000

297.55

continued application of

 -
-

8:00AM

 -

298.95

40377

158877

98000

297.70

monitored information

 -
-

9:00AM

124500

299.03

36076

160576

98000

297.85

confirms that 98000cfps

 -
-

10:00AM

119000

299.17

63421

182421

98000

298.05

is adequate to not exceed

 -
-

11:00AM

 -

299.20

13699

132699

98000

298.13

maximum lake level

 -
-

12:00PM

 -

299.30

45739

164739

98000

298.29

 - -
-

1:00PM

 -

299.36

27598

146598

98000

298.40

 - -
-

2:00PM

 -

299.43

32306

151306

98000

298.52

 - -
-

3:00PM

 -

299.50

32433

151433

98000

298.64

 - -
-

4:00PM

 -

299.55

23257

142257

98000

298.74

 - -
-

5:00PM

 -

299.60

23321

142321

98000

298.84

 - -
-

6:00PM

 -

299.64

18709

137709

98000

298.93

 - -
-

7:00PM

 -

299.68

18750

137750

98000

299.02

 - -
-

8:00PM

 -

299.72

18791

137791

98000

299.11

 - -
-

9:00PM

119700

299.76

18833

138533

98000

299.19

 - -
-

10:00PM

119700

299.77

4719

124419

98000

299.25

 - -
-

11:00PM

120250

299.78

4721

124971

98000

299.31

 - -
-

12:00AM

120250

299.79

4724

124974

98000

299.37

 - -
-

1:00AM

 -

299.77

-9453

110797

98000

299.40

 - -
-

2:00AM

 -

299.76

-4721

115529

98000

299.44

 - -
-

3:00AM

 -

299.74

-9437

110813

98000

299.46

 - -
-

4:00AM

120250

299.72

-9427

110823

98000

299.49

 - -
-

5:00AM

 -

299.72

0

120250

98000

299.54

 - -

4/17/1979

6:00AM

119000

299.71

-4708

114292

98000

299.57

 - -
-

7:00AM

 -

299.73

9411

128411

98000

299.64

 - -
-

8:00AM

 -

299.72

-4711

114289

98000

299.67

 - -
-

9:00AM

 -

299.69

-14125

104875

98000

299.69

 - -
-

10:00AM

118000

299.66

-14101

103899

98000

299.70

 - -
-

11:00AM

 -

299.65

-4693

113307

98000

299.73

Jackson gage reaches crest

 -
-

12:00PM

117000

299.61

-18760

98240

98000

299.73

5-1/2 days(134 hours) after rain

 -
-

1:00PM

 -

299.59

-9360

107640

98000

299.75

began, 4-1/2 days(108 hours)

 -
-

2:00PM

114600

299.55

-18698

95902

98000

299.75

after rain ended

 -
-

3:00PM

 -

299.54

-4664

109936

98000

299.77

 - -
-

4:00PM

111300

299.51

-13985

97315

98000

299.77

 - -
-

5:00PM

 -

299.48

-13962

97338

98000

299.77

 - -
-

6:00PM

108300

299.45

-13939

94361

98000

299.76

 - -
-

7:00PM

 -

299.40

-23192

85108

98000

299.74

 - -
-

8:00PM

105200

299.36

-18502

86698

98000

299.71

 - -
-

9:00PM

 -

299.34

-9230

95970

98000

299.71

 - -
-

10:00PM

102500

299.30

-18440

84060

98000

299.68

 - -
-

11:00PM

 -

299.28

-9199

93301

98000

299.67

 - -
-

12:00AM

95300

299.25

-13784

81516

95300

299.64

 - -
-

1:00AM

 -

299.24

-4587

90713

95300

299.63

 - -
-

2:00AM

 -

299.21

-13753

81547

95300

299.60

 - -
-

3:00AM

89400

299.18

-13729

75671

89400

299.57

danger subsides

 -
-

4:00AM

 -

299.18

0

89400

89400

299.57

inflow is decreasing

 -
-

5:00AM

 -

299.15

-13706

75694

89400

299.54

no rain in forcast

 -

4/18/1979

6:00AM

89400

299.10

-22805

66595

89400

299.49

 - -
-

7:00AM

 -

299.08

-9096

80304

89400

299.47

 - -
-

8:00AM

 -

299.02

-27258

62142

89400

299.41

 - -
-

9:00AM

83600

298.98

-18110

65490

83600

299.38

 - -
-

10:00AM

 -

298.97

-4517

79083

83600

299.37

 - -
-

11:00AM

 -

298.95

-9029

74571

83600

299.35

 - -
-

12:00PM

 -

298.91

-18038

65562

83600

299.31

 - -
-

1:00PM

 -

298.89

-8998

74602

83600

299.29

 - -
-

2:00PM

 -

298.86

-13482

70118

83600

299.26

 - -
-

3:00PM

 -

298.81

-22432

61168

83600

299.21

 - -
-

4:00PM

 -

298.77

-17894

65706

83600

299.17

 -- -
-

5:00PM

 -

298.71

-26779

56821

83600

299.11

 - -
-

6:00PM

 -

298.65

-26687

56913

83600

299.05

 - -
-

7:00PM

 -

298.59

-26594

57006

83600

298.99

 - -
-

8:00PM

 -

298.52

-30918

52682

83600

298.93

 - -
-

9:00PM

 -

298.46

-26394

57206

83600

298.87

 - -
-

10:00PM

 -

298.39

-30685

52915

83600

298.80

 - -
-

11:00PM

79600

298.33

-26194

53406

79600

298.74

 - -
-

12:00AM

 -

298.27

-26101

53499

79600

298.68

 - -
-

1:00AM

 -

298.20

-30344

49256

79600

298.61

 - -
-

2:00AM

 -

298.13

-30218

49382

79600

298.55

 - -
-

3:00AM

 -

298.05

-34392

45208

79600

298.47

 - -
-

4:00AM

 -

297.98

-29949

49651

79600

298.40

 - -
-

5:00AM

 -

297.91

-29824

49776

79600

298.33

 - -

4/19/1979

6:00AM

79600

297.82

-38184

41416

79600

298.24

 - -
-

7:00AM

70050

297.74

-33757

36293

70050

298.16

 - -
-

8:00AM

 -

297.72

-8398

61652

70050

298.15

 - -
-

9:00AM

67125

297.66

-25164

41961

62125

298.10

 - -
-

10:00AM

 -

297.63

-12536

54589

62125

298.08

 - -
-

11:00AM

61950

297.56

-29198

32752

61950

298.01

 - -
-

12:00PM

 -

297.54

-8306

53644

61950

297.99

 - -
-

1:00PM

56550

297.51

-12444

44106

56550

297.96

 - -
-

2:00PM

 -

297.49

-8281

48269

56550

297.94

 - -
-

3:00PM

 -

297.47

-8271

48279

56550

297.93

 - -
-

4:00PM

50250

297.44

-12391

37859

50250

297.90

 - -
-

5:00PM

 -

297.44

0

50250

50250

297.90

 - -
-

6:00PM

 -

297.42

-8245

42005

50250

297.88

 - -
-

7:00PM

 -

297.40

-8235

42015

50250

297.86

 - -
-

8:00PM

 -

297.38

-8225

42025

50250

297.84

 - -
-

9:00PM

47325

297.36

-8215

39110

47325

297.82

 - -
-

10:00PM

 -

297.34

-8204

39121

47325

297.80

 - -
-

11:00PM

 -

297.32

-9014

38311

47325

297.78

 - -
-

12:00AM

 -

297.30

-9410

37915

47325

297.75

 - -
-

1:00AM

 -

297.27

-9397

37928

47325

297.73

 - -
-

2:00AM

 -

297.25

-9384

37941

47325

297.71

 - -
-

3:00AM

 -

297.23

-9370

37955

47325

297.69

 - -
-

4:00AM

 -

297.20

-9357

37968

47325

297.67

 - -
-

5:00AM

44850

297.18

-9343

35507

44850

297.64

 - -
                 
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