Glen Canyon Dam Hydropower 

Production and Value

Status & Trends, 2019

S. Clayton Palmer

WAPA/CRSP
Glen Canyon Powerplant

Capacity: 1,320 MW

Energy: 3,978 GWhs (10-year average annual) 
Status and Trends

Recent variables affecting hydropower metrics

• Recent decrease in power efficiency

[hydropower head = elevation of Lake Powell – elevation of GCD 

tailrace]

Variation in power efficiency effects electrical 

generation, capacity & net firming purchases

•Impacts of the Summer, 2018 Bug Flow 

Experiment on Hydropower
Hydropower efficiency

Presentation title 4
Lake Powell Elevation Affects Power Efficiency:

The efficiency in turning Acre Feet into Megawatt hours

3700 3584
Important Lake Powell Elevations

EOY 19 3584

Min Power
GCD Hydropower Head

From first electrical production 1963 - 2019

Presentation title 7

45.00%

55.00%

65.00%

75.00%

85.00%

95.00%

105.00%

Dec-63

Apr-65

Aug-66

Dec-67

Apr-69

Aug-70

Dec-71

Apr-73

Aug-74

Dec-75

Apr-77

Aug-78

Dec-79

Apr-81

Aug-82

Dec-83

Apr-85

Aug-86

Dec-87

Apr-89

Aug-90

Dec-91

Apr-93

Aug-94

Dec-95

Apr-97

Aug-98

Dec-99

Apr-01

Aug-02

Dec-03

Apr-05

Aug-06

Dec-07

Apr-09

Aug-10

Dec-11

Apr-13

Aug-14

Dec-15

Apr-17

Aug-18

Jul, 83

Mar, 05

Jul, 11

Jul, 1

Apr, 64

7

% of full power head
GCD Hydropower Head

From the beginning of current drought 1999 - 2019

Presentation title 8

75.00%

80.00%

85.00%

90.00%

95.00%

100.00%

Apr-99

Oct-99

Apr-00

Oct-00

Apr-01

Oct-01

Apr-02

Oct-02

Apr-03

Oct-03

Apr-04

Oct-04

Apr-05

Oct-05

Apr-06

Oct-06

Apr-07

Oct-07

Apr-08

Oct-08

Apr-09

Oct-09

Apr-10

Oct-10

Apr-11

Oct-11

Apr-12

Oct-12

Apr-13

Oct-13

Apr-14

Oct-14

Apr-15

Oct-15

Apr-16

Oct-16

Apr-17

Oct-17

Apr-18

Oct-18

Apr-19

Jul, 18

% of full power head

Mar, 14
GCD Hydropower Head

2014 - 2019

Presentation title 9

76.00%

78.00%

80.00%

82.00%

84.00%

86.00%

88.00%

90.00%

Mar-14

May-14

Jul-14

Sep-14

Nov-14

Jan-15

Mar-15

May-15

Jul-15

Sep-15

Nov-15

Jan-16

Mar-16

May-16

Jul-16

Sep-16

Nov-16

Jan-17

Mar-17

May-17

Jul-17

Sep-17

Nov-17

Jan-18

Mar-18

May-18

Jul-18

Sep-18

Nov-18

Jan-19

Mar-19

May-19

Jul-19

Sep-19

Mar, 14

Jul, 18

Jul, 19

% of full power head
The Effect of Power Efficiency on GCD Energy Production

Date

Lake Powell 

Elevation 

(ft)

Energy 

production in a 

9.0 maf year

(GWh) 

Percentage of 

production vs 

full powerhead

July, 1983 3,707.40 4,617 101.25%

Mar., 2005 3,555.90 3,378 74.09%

Jan., 2014 3,578.69 3,575 78.39%

Jan., 2018 3,619.38 3,916 85.89%

Jul., 2019 3,583.66 3,620 79.98%
Summer, 2018 

Macroinvertabrate

Experiment

“Bug flow” experiment

Presentation title 11
Development of the experiment

• The Bug Flow experiment was developed out of a joint 

scientific effort to understand the relationship between 

load-following flows and the aquatic food base. 

• This cooperative study was joined by GCMRC, Reclamation, 

WAPA, and Utah State University’s Bug Lab.

• Interest in studying low-volume, steady flows were 

implemented during the weekend, when electrical power 

has less value in favor of moving water to on-peak hours 

during the week, when additional power production is 

needed .

• This cooperative effort can serve as a templet of a “Project 

N” approach to the development of GCD operational 

experiments. 

Presentation title 12
13

Modeling input for the 

Bugflow Experiment – Summer, 2018

Sunday Monday Tuesday Wednesday Thursday Friday Saturday
Illustration of Bug Flows

May, 2018

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0.00

2,000.00

4,000.00

6,000.00

8,000.00

10,000.00

12,000.00

14,000.00

16,000.00

Water relase (cfs)

May 2018

Power release (cfs)
Results of the experiment

• The Argonne estimates that the 2018 Bug Flows 

had a financial impact of $165,000. 

• This dollar amount is relatively small given the 

assumptions used in the modeling process. 

• The 2018 Bug Flow experiment produced benefits 

to hydropower in the months of May and June, and 

costs to hydropower in July and August. The month 

of June turned out to be of particular benefit to 

hydropower. 

Presentation title 15
Results (cont.)

• These results are a function of the patterning of 

water releases. 

• Also, the result reflects the differences between 

weekday and weekend energy prices. Electrical 

energy prices are lower, and the weekday/weekend 

difference is less, in May and June 2018 than they 

were in July and August 2018. 

• To arrive at a positive financial outcome to 

hydropower, weekend electricity prices must be 

substantially lower than weekday prices. 

Presentation title 16
The import of the difference between 

weekday and weekend prices

Presentation title 17

0

10

20

30

40

50

60

70

May June July Aug.

Weighted average Energy Price ($/MWh)

Weekend On-Peak Sale Price Weekend On-Peak Purchase Price Weekday Off-Peak Purchase Price
Additional considerations

• The impact of capacity improvements during 

weekdays was not included 

• This is because capacity is – currently – above required 

capacity margins in the WECC region

• A word of caution: 

• A different set of weekend/weekday prices would 

produce a different result. 

Presentation title 18
Questions ?