Glen Canyon Dam Operatio

During Equalization

TWG Meeting 

January 28, 2016 
Presentation Overview 

• What is equalization? • Why hydrology matters • Recent example of equalization operatio• How "frequently" equalization releases o• Back to back wet years • Questions/Discussion 
What is Equalization? 

• It is an operating tier at Lake Powell 
What is Equalization? 

• If Powell elevation is projected to be abov

equalization level 

 release more than 8

until at the end of the water year, such th

• Powell storage = Mead Storage, or • Mead elevation = 1,105’, or • Powell elevation = equalization level – 20 ft, or • Powell elevation = equalization level 

• So... what is balancing? 

– Attempt balance the contents of Powell and M

the end of the water year 

• BUT Powell releases UP TO 9.0 maf 
How is Equalization determine

• August 24-Month Study Projection of La

Powell Jan 1 elevation >= equalization le

OR 

• April 24-Month Study projection of Lake 

September 30th elevation >= equalization 
What is Equalization?

• Equalization level increases 

each year of the interimperiod 

– With each passing year, 

reservoir has to be “more full” to trigger equalization 
August 

determination 
April 

determination 
Hydrology matters!
10 

Reservoir initial conditions matter 

• Powell • Mead 
13 

Water Year 2016 

Upper Elevation Balancing Tier 

Initial release of 8.23 maf 

Potential April adjustment 

to Equalization or Balancing 

April adjustment to 

Balancing releases 

April adju

Equalizati

No April 

Adjustment 
Unit 

Number 

Oct 

2015 

Nov 

2015 

Dec 

2015 

Jan 

2016 

Feb 

2016 

Mar 

2016 

Apr 

2016 

May 

2016 

Jun 

2016 

Jul 

2016 

1 2 3 4 5 6 7 8 

Units 

Available 6 7 7 7 5 5 6 6 7 7 

Capacity 

(cfs) 18,400 22,100 22,100 22.100 15,200 15,300 18,700 18,600 22,100 22,10

Capacity 

(kaf/month) 1,150 1,130 1,280 1,300 920 990 1,140 1,140 1,310 1,330 

Max (kaf) 1 -- -- -- 900 700 650 666 700 800 950 

Most (kaf) 2 600 577 857 900 700 650 666 700 800 950 

Min (kaf) 1 -- -- -- 900 700 650 666 700 800 950 

14 

Glen Canyon Power Plant Provisional Unit Outage Schedule for Wate

1 Projected release, based on January 2016 Min and Max Probable 

Inflow Projections and 24-Month Study model runs 

2 Projected release, based on January 2016 Most Probable Inflow 

Projections and 24-Month Study model runs 

(up

Maintenance matters 
Water Year 2011 

Review of Operations
---

Summary of Lake Powell and Lake Mead Op

Review of 24-Month Study 2011 Water Year Projections 

24-

Month 

Study 

Projected 

Powell 

WY 

Unreg 

Inflow 

Projected 

Powell 

Apr- Jul 

Unreg 

Inflow 

Projected 

Lake Powell 

EOWY 

Elevation 

w/ 8.23 maf 

Release 

Projected 

Glen 

Canyon 

WY 

Release 

Projected 

Amount 

of EQ 

Release 

Proje

Lak

Mea

EOW

Eleva

Jan 2011 

110% 

13.19 maf 

120% 

9.5 maf 3663.31 ft 11.36 maf 3.13 maf 1105.

Feb 2011 

105% 

12.60 maf 

113% 

9.0 maf 3657.85 ft 11.48 maf 3.25 maf 1105.

Mar 2011 

105% 

12.68 maf 

116% 

9.2 maf 3658.16 ft 11.63 maf 3.40 maf 1105.

Apr 2011 

109% 

13.11 maf 

120% 

9.5 maf 3662.63 ft 11.56 maf 3.33 maf 1105.

Oct-1 2011 

139% 

16.79 maf 

162% 

12.89 maf 3653.01 ft 12.52 maf 4.29 maf 1116.

In 2011, the Equalization Elevation is 3643 ft.
495 810 847 997 964 1033 940 1171 1377 1483 

Monthly Volumes in KAF (Water Year Total Release = 12.52 MA
WY 2011 WY 2012 
How frequent are high annual releases
Back to back large annual volume release

11.5 

15.3 

13.9 15.4 

11.6 

8.23 

Example Wet Scenario 

This is NOT our current forecast 
Summary 

• Equalization is an operating tier under th

interim guidelines 

• Hydrology matters 

– Hydrology (and forecast development) deter

how “spread out” the total annual volume is water year 

• Reservoir initial elevations matter • Maintenance matters • Releases can be 8.23 up to 12 maf, 15 m

or more 
Thank you!

Questions / Discussion
Extra Slides Follow
Equalization for 2011

Lake Powell Lake Powell 

Elevation Storage 

(ft) (maf) 

Observed 

EOWY 3653.01 17.593 

Condition 

Equalization 

EOWY 3643.00 16.360 

Objective 

Difference 10.01 1.233 

Equalization in 2011 was not achieved on September 30, 2011 due to powe

release limitations during water year 2011. The Equalization objective in 201

achieve a Lake Powell elevation on September 30, 2011 of 3643.00 fee
25 
August 

determination 

April 

determinatio 

n