Warm Water? Science Plan

Temperature Monitoring
GCMRC Thermal Monitoring

• Glen Canyon Dam Forebay

– Monthly full water quality profiles

– Continuous monitoring at various depths since 2000

• Glen Canyon Dam Tailwater

– Continuous full water quality monitoring

• Draft Tubes

• Immediately below dam

• Lees Ferry

• Grand Canyon Thermal Monitoring

– 10 mainstem sites in Grand Canyon
Lees Ferry Daily Temperature 

64-76 Inflow Hydrograph (offset by 25)

Release Hydrograph

LF Temperature

LP Elevation

Penstock Elev. 3470 ft

Lake Powell Initial Filling Stage

Temp (deg C) and Discharge (x 10,000 cfs)

 0

 5

 10

 15

 20

 25

 30

 35

1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976

3350

3400

3450

3500

3550

3600

3650

3700
Filling Period 1964-1976

• Summer withdrawals from epilimnion

– Ended with filling to 3645 ft. in 1973

• Maximum temperatures in September

– Due to epilimnetic withdrawal

• Maximum temperatures reduced as 

reservoir filled

• High inflows in 1973 raised surface 

elevation away from penstock levels
Discharge (cfs)

197019711972197319741975197619771978197919801981198219831984198519861987

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

3430

3440

3450

3460

3470

3480

3490

3500

3510

3520

3530

3540

3550

3560

3570

3580

3590

3600

3610

3620

3630

3640

3650

3660

3670

3680

3690

3700

Lake Elevation (ft)

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

17.0

18.0

Temperature

@LeesFerry

pgp

LeesFerry:1970to1987

Lakeelevation

Discharge-cfs(Spillways&Inflow)

Temperature (°C)

g r\po \lfT em pDQ63 -cur2 .grf S. Hueftle 10/22/02 USGS- GCMRC
Current Conditions 1993-2003

• Summer withdrawals from hypolimnion

• Maximum temperatures in December

– Due to convective mixing of epilimnion

• Maximum winter temperatures affected by 

previous spring runoff volume

• 1999-2000 had similar inflow patterns as 1971-

1972 (but different lake elevations)

– Could serve as model for 2003 – similar projections
Forebay Profile – September 18, 2002

• Apr-Jul runoff 1.45 MAF

• Lowest runoff volume on 

record

• Very thin epilimnion

• 12°C water at 27 m
Forebay Profile – September 12, 1995

• Apr-Jul runoff 10.62 MAF

• Highest runoff volume 

since 1986

• Very thick epilimnion

• 12°C water at 59 m 

• 1995 conditions at 2002 

lake levels would have 

resulted in ~14°C releases
Forebay Profile – September 13, 2000

• Apr-Jul runoff 4.62 MAF

• Intermediate runoff 

volume

• Similar to 1972 runoff

– 4.06 MAF in 1972

– Last year of warm release

• Similar to projected 2003 

runoff of 5.67 MAF

• 12°C water at 35 m
975

1000

1025

1050

1075

1100

1125

975

1000

1025

1050

1075

1100

1125

Depth in Elev

ation (m)

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83

Temperature Profile (°C) in Lake Powell near Forebay, 1965 to August 2002 Grand Canyon Monitoring & Research C

S. Hueftle 10/22/02

Penstocks

Jet Tubes

Spillways (1112 m / 3648 ft)

84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02

Inflow/ Outflow

Spillways

Penstocks

Jet Tubes

84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02
975

1000

1025

1050

1075

1100

1125

975

1000

1025

1050

1075

1100

1125

Depth in Elevation (m)

3.0 °

4.0 °

6.0 °

6.5 °

7.0 °

8.0 °

9.0 °

10.0 

12.0 

14.0 

16.0 

18.0 

20.0 

22.0 

24.0 

26.0 

28.0 

30.0 

32.0 

33.0 

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83

Temperature Profile (°C) in Lake Powell near Forebay, 1965 to August 2002 Grand Canyon Monitoring & Research Center

S. Hueftle 10/21/02

Penstock Depth (1057.7 m / 3470 ft)

Jet Tube Depth (1028.4 m / 3374 ft)

Spillways (1112 m / 3648 ft)

Spillways (1112 m / 3648 ft)

84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02

Inflow/ Outflow

Lake Powell Thermal History

Note epilimnion thickness as related to inflow volume in 1993-1995
Dis

c

h

arg

e (cfs)

19

6

5

19

6

7

19

6

9

19

71

19

7

3

19

7

5

19

7

7

19

7

9

19

81

19

8

3

19

8

5

19

8

7

19

8

9

19

91

19

9

3

19

9

5

19

9

7

19

9

9

2

0

01

2

0

0

3

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

3430

3440

3450

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3490

3500

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3600

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3700

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

17.0

18.0

Temperature

@Lees Ferry

@Glen Cyn Dam

Effects of Lake Elevation And Dam Operations on Discharge Temperature

1964 to 2002, Project from 10/02 to 9/04 USGS- GCMRC S. Hueftle 10/22/02 Gr\ po \LF Te mp DQ6 3-cur2. grf

Discharge-cfs (Spillways)

T

e

m

p

erature (°C)

Projecte

d
Dis

c

h

arg

e (cfs)

19

8

7

19

8

8

19

8

9

19

9

0

19

91

19

9

2

19

9

3

19

9

4

19

9

5

19

9

6

19

9

7

19

9

8

19

9

9

2

0

0

0

2

0

01

2

0

0

2

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

3430

3440

3450

3460

3470

3480

3490

3500

3510

3520

3530

3540

3550

3560

3570

3580

3590

3600

3610

3620

3630

3640

3650

3660

3670

3680

3690

3700

L

k

El

ti

(ft)

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

17.0

18.0

Temperature

@Lees Ferry

Effects of Lake Elevation And Dam Operations on Discharge Temperature

Lees Ferry & Glen Cyn Dam: 1987 to 2002

Lake elevation

Discharge-cfs (JetTubes & Inflow)

T

e

m

p

erature (°C)

g r\po \lfTe mp DQ6 3- cur2 .gr f S. Hueftle 10/22/02 USGS- G

C

M

R

C

3609 ft: projected lake min in April '03
Factors Affecting Possibility of 

Warm Water Release

• Reservoir elevation 

– Proximity of thermocline to penstock depth

• Antecedent Hydrology

– High runoff causes thick layer of warm 

water near dam (closer to penstocks)

• Timing

– Maximum warming at depth occurs AugustSeptember
What are Chances of Warm 

Water Release in 2003?

• Probably LOW due to projected elevation and 

runoff

• Current projections:

– 5.67 MAF runoff (moderate)

• 12°C water expected at 35-40 meters

– Reservoir elevation of 3629 ft by Sept. 2003

• Penstock depth of ~47 meters

– Higher runoff could warm to greater depths

• But could raise thermocline away from penstocks

– Lower runoff could bring thermocline lower

• But would not allow as much warming at depth
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Glen Canyon Dam

SH HA BA

LD LU

TA KA

NA

PA

R132

R033

R076

R065

R246

R226

R194

R166

R087

R276

CRBD

CRLF

R061

GCMRC Thermal Monitoring Locations

Colorado River Mainstem
(Selected Stations)

STA R-15 R000 R061 R087 R226

Temperature (deg C)

 8.50

 9.00

 9.50

10.00

10.50

11.00

11.50

12.00

12.50

13.00

13.50

14.00

14.50

15.00

15.50

16.00

16.50

17.00

17.50

18.00

18.50

19.00

19.50

20.00

20.50

01JAN93 01JAN94 01JAN95 01JAN96 01JAN97 01JAN98 01JAN99 01JAN00 01JAN01 01JAN02 01JAN0

Grand Canyon Warming
Lake Powell Filling Releases 1965-1973

y = -0.0875x + 328.74

R

2

 = 0.9092

0

5

10

15

20

25

3500 3550 3600 3650 370

Reservoir Elevation (ft)

Water Temperature (C)
y = -0.0003x + 11.981

R

2

 = 0.8556

4

5

6

7

8

9

10

11

5000 10000 15000 20000 25000 3000

Dam Release (cfs)

Water Temp Increase (C)
Predicted Water Temperatures June 2004

Reservoir Elevation 3636'

0

4

8

12

16

20

24

5000 8000 11000 14000 17000 20000

Dam Release (cfs)

Water Temperature (C)

LCR Diamond Ck
Predicted June Water Temperatures

Reservoir Elevation 3620'

0

4

8

12

16

20

24

5000 8000 11000 14000 17000 20000

Dam Release (cfs)

Water Temperature (C)

LCR Diamond Ck