Basin Hydrology, Operations 

2018 Hydrograph 

Glen Canyon Technical Work Gro

August 30, 2017 
95% 

98% 

62% 

78% 

80% 

1 percent of average based on per

http://www.usbr.gov/uc/water/basin/index.html 

Basin Storage 

As of 

8/27/2017 

Upper Basin Storage 

April to July 2017 Ob

Reservoir 

Apr-J

Observ

(KAF

Fontenelle 1,719 

Flaming 

Gorge 2,214 

Blue Mesa 915 

Navajo 775 

Powell 8,174 
Peak inflow of 60,600 cfs 

Max elevation of 3635.8 ft on 

July 11th 


Reservoir Operations 

for Water Year 2018 
Lake Powell 2018 Operating Tie

Upper Elevation Balancing 

• Tier was set in August 2017

– Start with 8.23 maf release

• Use April 24-Month Study 

projections of end of water year storage to potentially adjust 

1. Stay with 8.23 maf 2. Balancing: 8.23 - 9.0 maf3. Equalization: > 8.23 maf
Water Year 2018 Operating Tie

Operating Tier determined with the August 2017 24-Mo

Powell Inflow 

Scenario 

WY 2018 

Release Projection 

Probable 

Minimum 

Upper Elevation Balancing Tie

w/ Projected April shift to Balancing 

9.0 maf release 

Most 

Probable 

Upper Elevation Balancing Tie

w/ Projected April shift to Balancing 

9.0 maf release 

Probable 

Maximum 

Upper Elevation Balancing Tie

w/ Projected April shift to Equalization 

13.8 maf release 
April adjustment to 

Balancing releases 

April adjust

Equalization 

No April 

Adjustment 
Water Year 2018 projections 

Most: 9.0 maf release 

Max: 13.8 maf release 

Min: 9.0 maf release 

End of CY 2017 Projection: 

3627.34 feet 

End of CY 2

363

(Range 3,5
End of CY 2017 Projection: 

1,083.5 feet (39% full) 

Range: 1,083.2 to 1,083.7 feet 

End of CY 2

1,079.5 fe

Range: 1,07

LTEMP Monthly Release Volumes 2

Month 7.00 7.48 8.23 9.00 9.50 10.50 11.00 12.00 OCT 480 480 640 640 640 640 640 640 6NOV 500 500 640 640 640 640 640 640 6DEC 600 600 720 720 720 720 720 720 7JAN 660 720 760 860 920 1040 1100 1230 1FEB 590 640 680 750 810 920 970 1080 1MAR 620 675 710 800 860 970 1030 1150 1APR 550 600 640 710 760 870 920 1020 1MAY 550 600 630 710 760 860 910 1020 1JUN 580 630 660 750 800 910 960 1060 1JUL 650 710 750 850 900 1020 1080 1200 1AUG 700 760 800 900 970 1090 1160 1280 1SEP 520 565 600 670 720 820 870 960 1

MIN & MOST
2018 Hydrograph 

Month LTEMP Release 

Volume, (kaf) 

Operational Considerations 

Release Volume, (kaf)* 

LTEMP Daily 

Fluctuations (cfs)*

OCT 640 630 5,700 NOV 640 630 5,700 DEC 720 740 6,700 JAN 860 860 7,700 FEB 750 750 6,800 MAR 800 800 7,200 APR 710 700 6,300 MAY 710 700 6,300 JUN 750 760 7,600 JUL 850 860 8,000 AUG 900 900 8,000 SEP 670 670 6,000 • *Modifications of monthly volumes reached between Reclamation and WAPA • **LTEMP Daily fluctuations determined by, 9 x monthly vol (Sep – May), and 10 x monthly vol (Jun • LTEMP Down ramp rates, 2,500 cfs/hr (all months) • Up-ramp rates, 4,000 cfs/hr (all months) 

Unit 

Number 

Oct 

2017 

Nov 

2017 

Dec 

2017 

Jan 

2018 

Feb 

2018 

Mar 

2018 

Apr 

2018 

May 

2018 

Jun 

2018 

Jul 

2018 

1 2 3 4 5 6 7 8 

Units 

Available 5 5 7 5 5 5 5 6/8 8 8 

Capacity 

(cfs) 17,200 17,200 17,200 17,200 17,200 17,200 17,200 21,600 28,700 28.70

Capacity 

(kaf/month) 1,270 1,140 1,410 1,240 1,120 1,060 1,010 1,610 1,710 1,760 

Max (kaf) 1 630 630 740 1,450 1,280 1,350 1,200 1,200 1,260 1,420 

Most (kaf) 2 630 630 740 860 750 800 700 700 760 860 

Min (kaf) 1 630 630 740 860 750 800 700 700 760 860 

Glen Canyon Power Plant Planned Unit Outage Schedule for Water 

1 Projected release, based on Aug 2017 Min and Max Probable 

Inflow Projections and 24-Month Study model runs 

2 Projected release, based on Aug 2017 Most Probable Inflow 

Projections and 24-Month Study model runs 

(up
Sand Budget Model Results 

• As of 8-24-2017, not enough sediment input to t

fall 2017 HFE 

• Still early in the season 
–

–

–– = –

= = 

–

–

Percent of Traces with Event or System ConditioResults from August 2017 CRSS1,2,3,4 (values in percent) 

Event or System Condition 2018 2019 202

Upper 

Basin 

– 

Lake 

Powell 

Equalization Tier 

Equalization annual release > 8.23 maf Equalization annual release = 8.23 maf 

20 

20 

0 

29 

29 

0 

Upper Elevation Balancing Tier 

Upper Elevation Balancing annual release > 8.23 maf Upper Elevation Balancing annual release 8.23 maf Upper Elevation Balancing annual release < 8.23 maf 

80 

75 

5 0 

68 

52 15 

1 

Mid-Elevation Release Tier 

Mid-Elevation Release – annual release 8.23 maf Mid-Elevation Release – annual release 7.48 maf 

0 

0 0 

3 

0 3 

Lower Elevation Balancing Tier 0 0 

Lower 

Basin 

– 

Lake 

Mead 

Shortage Condition any amount (Mead ≤ 1,075 ft) 

Shortage – 1st level (Mead ≤ 1,075 and ≥ 1,050) 

Shortage – 2nd level (Mead < 1,050 and ≥ 1,025) 

Shortage – 3rd level (Mead < 1,025) 

0 

0 0 

0 

15 

15 

0 

0 

Surplus Condition any amount (Mead ≥ 1,145 ft) 

Surplus – Flood Control 

0 

0 

0 

0 

Normal or ICS Surplus Condition 100 85 

1 Reservoir initial conditions based on results from the August 2017 most-probable 24-Month Study.2 Percentages computed from 110 hydrologic inflow sequences based on resampling of the observed natural flow record fr

110 traces analyzed.

3 Percentages shown may not sum to 100% due to rounding to the nearest percent.4 Percentages shown may not be representative of the full range of future 18 possibilities that could occur with different modeling assumptions. 
Questions?

Paul Davidson

801-524-3642

PDavidson@usbr.gov

Hydraulic Engineer, Glen Canyon

Reclamation, Upper Colorado Region

Resource Management Division

Water Resources Group
August 

determination 

April 

determination 
Water Year 2017 Operations: April 2017 24-Mon

Upper Elevation Balancing 

With an 8.23maf releasWY2017, September 30projected elevations arPowell: 3646.82 (i.e, abMead: 1072.07 (i.e, beTherefore, Powell’s Apis to Balancing, with remore than 9.0 maf and 8.23 maf in the Water Y

April 2017 24-Month Study EXHIBIT run 

* Modification of monthly volumes 

reached between Reclamation 

and WAPA 
Unit 

Number 

Oct 

2017 

Nov 

2017 

Dec 

2017 

Jan 

2018 

Feb 

2018 

Mar 

2018 

Apr 

2018 

May 

2018 

Jun 

2018 

Jul 

2018 

1 2 3 4 5 6 7 8 

Units 

Available 5 7 7 7 5 5 5 6/8 8 8 

Capacity 

(cfs) 16,100 23,400 23,400 23,400 16,200 16,000 16,000 27,000 27,000 27,00

Capacity 

(kaf/month) 1,060 1,390 1,440 1,290 920 980 1,040 1,520 1,610 1,660 

Max (kaf) 1 640 640 720 1,520 1,340 1,420 1,260 1,260 1,320 1,490 

Most (kaf) 2 640 640 720 1,160 1,020 1080 966 956 1,000 1,140 

Min (kaf) 1 640 640 720 860 750 800 710 710 750 850 

Glen Canyon Power Plant Planned Unit Outage Schedule for Water 

1 Projected release, based on Apr 2017 Min and Max Probable 

Inflow Projections and 24-Month Study model runs 

2 Projected release, based on Apr 2017 Most Probable Inflow 

Projections and 24-Month Study model runs 

(up
Paria Sand Load Dec 1 though Feb 13 Paria Sand Load July 1 though Feb 

Sediment Conditions As of 2-13-2015 

Sediment Model RAs of 2-13-2015 Have: ~18 ktons Need: several hundred k

(for the smallest H
If we end up with a 8.23 maf release instead of 9.

will need to reduce the remaining months by 7
Dave Trueman 

dtrueman@usbr.gov 

(801) 524-3759 

Manager 

Resource Management Division 

Upper Colorado Region 

Salt Lake City, UT 

Objective: better preserve August 

and September sand inputs for 

potential HFE in November. 

Typical 

greatest