Basin Hydrology, Reservoir 

Operations and 2020 

Hydrograph

October 21, 2019
90%

85%

54%

81%

76%

1 Percent of average based on the period of record from 1981-2010.

Available online at: www.usbr.gov/uc/water/basin/index.html

Basin Storage

As of 

10/18/19

Reservoir Forecast 

(kaf)

Percent of 

Average1

Fontenelle 1,024 95

Flaming Gorge 1,375 95

Blue Mesa 880 92

Navajo 810 75

Powell 9,500 88

Water Year 2020

Forecasted Unregulated Inflow

Issued October 2, 2019

2

Upper Basin Storage and Inflow
3

Lake Powell Inflow
4

Lake Powell Monthly Release
Lake Powell & Lake Mead Operational Table

Operational Tiers for Water/Calendar Year 20201

1 Lake Powell and Lake Mead operational tier determinations were based on August 2019 

24-Month Study projections and will be documented in the draft 2020 AOP.

3,618.56 ft

Jan 1, 2020 

Projection 1,089.40 ft

Jan 1, 2020

Projection

5
6

Release Scenarios 
7

Monthly Release Volumes
Most Probable End of CY 2019 

Projection: 3,609.83 feet (53% full)

Min/Max Range: 3,609.8 to 3,610.4 feet

Most Probable End of CY 2020 

Projection: 3,618.12 feet (56% full)

Min/Max Range: 3,585.4 to 3,657.97 feet

8

Powell Elevations
9

Most Probable End of CY 2019 

Projection: 1,088.59 feet (41% full)

Min/Max Range: 1,088.4 to 1,088.8 feet

Most Probable End of CY 2020 

Projection: 1,081.25 feet (39% full)

Min/Max Range: 1,081.25 to 1,121.36 feet

Mead Elevations
Glen Canyon Power Plant unit 

outage schedule for WY2020

Unit 

Number

Oct 

2019

Nov 

2019

Dec 

2019

Jan 

2020

Feb 

2020

Mar 

2020

Apr 

2020

May 

2020

Jun 

2020

Jul 

2020

Aug 

2020

Sep 

2020

1

2

3

4

5

6

7

8

Units 

Available 5 5/6 6/8 6 6 6 6 6 6 6 6 6

Capacity 

(cfs) 16,800 16,800

/22,520

20,500/

28,000 20,500 20,400 20,400 20,400 20,600 20,900 20,900 20,800 20,800

Capacity 

(kaf/month) 1,060 1,160 1,420 1,330 1,170 1,250 1,220 1,320 1,280 1,330 1,320 1,310

Max (kaf) 1 625 625 750 1,210 1,070 1,130 1,010 1,000 1,050 1,190 1,270 963

Most (kaf) 2 625 625 750 760 675 700 630 630 650 750 835 600

Min (kaf) 1 625 625 750 860 750 800 710 710 750 850 900 670

10

Glen Canyon Power Plant Planned Unit Outage Schedule for Water Year 2020

1 Projected release, based on Oct 2019 Min and Max Probable Inflow Projections and 24-Month Study model runs

2 Projected release, based on October 2019 Most Probable Inflow Projections and 24-Month Study model runs

8.23

9.0

11.89

(updated 10-09-2019)

MOST

MAX
11

September 2019 Hourly Releases
12

October 2019 Hourly Releases
13

November 2019 Hourly Releases
14

December 2019 Hourly Releases
Lake Powell Release Temperatures
Grand Canyon Water Temperatures
Penstock

Lake Powell Reservoir Temperature 

Profile
Historical Dissolved Oxygen
Penstock

Penstock

Penstock

5.0 mg/l

5.0 mg/l

5.0 mg/l

Dissolved 

Oxygen

10/12/2005

11/2/2005 Comparison

12/9/2005

5.0 mg/l
2

2

2 2

2

2 2 2 2

2

3

3

3

3

3

3

3

3

3

3 3

3 3

4

4

4

4 4

4

4 4 4 4

4

4

4

4

4

4

4

4

5

5

5

5

5 5

5

5

5 5

5

5

5

6

6

6

7

7

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

Km Upstream from Dam

Lake Powell Dissolved Oxygen, September 2005

3200

3250

3300

3350

3400

3450

3500

3550

3600

0

1

2

3

4

5

6

7

8

elevation, Ft

Penstock mg/L

Dissolved Oxygen, September 

2005
2

2

4

4

4

4 4

4

4

6

6

6

6

6

8

8

8

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

Km Upstream from Dam

Lake Powell Dissolved Oxygen, December 2005

3200

3250

3300

3350

3400

3450

3500

3550

3600

1

2

3

4

5

6

7

8

9

10

11

elevation, Ft

mg/L

Penstock

Dissolved Oxygen, December 

2005
Questions and Discussion