GCDAMP Technical Work 

Group

Basin Hydrology and Operations

January 22, 2021
2

Reservoir Percent 

Full

Storage

(maf)

Elevation

(feet)

Fontenelle 49 .162 6,480.73

Flaming 

Gorge 84 3.15 6,024.77

Blue Mesa 48 0.399 7,465.13

Navajo 63 1.07 6,035.95

Lake Powell 40 9.80 3,578.39

System 

Storage (incl. LC)

46 27.32

Upper Basin Storage (as of January 20, 2021)
Seasonal Precipitation and Soil Moisture

3
Seasonal Snow Conditions and Basin SWE

4
5

Upper Colorado Basin

Projected Operations 

for Water Year 2021 

Based on January 2021 

Modeling
6

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

Reservoir

Unregulated 

Inflow

(kaf)

Percent of 

Average1

Fontenelle 727 67

Flaming Gorge 900 62

Blue Mesa 670 70

Navajo 609 57

Powell 5,723 53

as of January 1, 2020

Water Year 2021

Forecasted Unregulated Inflow

Current SWE and WY2021 Forecast
7

Jan MM = 5.373 maf (50%) Jan MM = 3.45 maf (48%)
8
9
10

LTEMP Operational Flexibility
11
12

Most Probable End of WY 2022 Projection: 

3,578.18 feet (40% full)

Min/Max Range: 3,518.83 to 3,623.94 feet

Most Probable End of CY 2021 Projection: 

3,558.56 feet (34% full)

Min/Max Range: 3,537.16 to 3,578.41 feet
13

Drought Operations
14

• The January minimum probable forecast projects Powell to fall below 3525 feet in 

2022.

• Notification went out to the Basin States and the UCRC informing them of this 

event. 

• Model results do not initiate operational changes to Reclamation facilities. 

• Model results do initiate enhanced monitoring and coordination under the DROA. 

• Model results do initiate monthly analysis of min/most/max with the Upper Division States and the Commission. 

• The DROA enhanced monitoring and coordination will continue until either:

• (i) The minimum probable the minimum probable projected elevation remains above 3525' 

for 24 months; or

• (ii) the process moves to the next step when the most probable projected elevation indicates 

Powell elevations below 3,525 feet and a Drought Response Operations Plan is implemented. 

(Section II.A.4.b)

Drought Operations - Details
15

Most Probable End of CY 2021 Projection: 

1,069.75 feet (35% full)

Min/Max Range: 1,067.73 to 1,088.58 feet

Most Probable End of CY 2022 Projection: 

1,057.10 feet (31% full)

Min/Max Range: 1,054.45 to 1,080.00 feet
16

1 Projected release, based on January 2021 Most Probable Inflow Projections and 24-Month Study model runs.

2 Projected release, based on January 2021 Min and Max Probable Inflow Projections and 24-Month Study model runs.

3 Dependent upon availability to shift contingency reserves, which will increase capacity by 30-40MW (3%) at current efficiency. 

Unit Number Oct 

2020

Nov 

2020

Dec 

2020

Jan 

2021

Feb 

2021

Mar 

2021

Apr 

2021

May 

2021

Jun 

2021

Jul 

2021

Aug 

2021

Sep 

2021

1

2

3

4

5

6

7

8

Units Available 5 5/4 6 6 6 6 6 6 6 6 6/8 8/6

Capacity (cfs) 16,400 16,400

/12,200 19,800 19,600 19,500 19,400 19,300 19,400 19,600 19,500 19,300/26,400

26,300

/19,300

Capacity 

(kaf/month) 1,040 1,140 1,250 1,220 1,210 1,080 1,280 1,190 1,160 1,200 1,340 1,410

Max (kaf) 2 640 640 720 857 758 801 713 710 745 842 900 674

Most (kaf) 1 640 640 720 763 675 700 628 628 651 765 800 620

Min (kaf) 2 640 640 720 760 680 710 640 630 660 750 800 600

8.23

8.23

9.0

(updated 01-20-2021)

JAN MOST3

JAN MOST

Glen Canyon Power Plant Planned Unit Outage Schedule for Water Year 2021
17

1 Projected release, based on January 2021 Most Probable Inflow Projections and 24-Month Study model runs.

2 Projected release, based on January 2021 Min and Max Probable Inflow Projections and 24-Month Study model runs.

3 Dependent upon availability to shift contingency reserves, which will increase capacity by 30-40MW (3%) at current efficiency. 

Unit Number Oct 

2021

Nov 

2021

Dec 

2021

Jan 

2022

Feb 

2022

Mar 

2022

Apr 

2022

May 

2022

Jun 

2022

Jul 

2022

Aug 

2022

Sep 

2022

1

2

3

4

5

6

7

8

Units Available 6 6/5 5/6 6 4 6 8 7 6 6 6 4

Capacity (cfs) 19,200 19,200

/15,700

15,600/

19,100 19,000 12,000 18,800 25,800 23,000 19,800 19,800 19,700 12,500

Capacity 

(kaf/month) 1,170 1,030 1,110 1,150 730 1,240 1,540 1,440 1,250 1,220 1,210 800

Max (kaf) 2 643 642 715 763 675 713 635 632 663 749 800 600

Most (kaf) 1 480 500 600 723 639 675 601 599 628 709 758 568

Min (kaf) 2 480 500 600 723 639 675 601 599 628 709 758 548

7.48

7.48

8.23

(updated 01-20-2021)

JAN 

MOST3

JAN 

MOST

Glen Canyon Power Plant Planned Unit Outage Schedule for Water Year 2022
18

Water Quality
19
20

>16°C HBC Spawn

>12°C HBC Growth
Temperature Profile of Powell near GC Dam

21

Penstock

12/20/2020
Cross Sectional Temperature Profile of Powell

22

Penstock

12/20/2020
23
24

Upper Colorado Basin

Operational and WQ 

Historical Analysis of 

7.48 maf Releases
25
26
27
28



32

Questions/Discussion