Basin Hydrology, 

Water Years 2018-2019 

Operations 

Glen Canyon Technical Work Group

January 25, 2018
Snow Conditions

67% of total 

average seasonal 

accumulation

As of 4/18/2018 

SWE is 74% of median

3
85%

61%

52%

72%

35%

1 Percent of average based on 1981-2010 period.

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

Reservoir Forecast

(KAF)

Percent 

of 

Average1

Fontenelle 970 134%

Flaming Gorge 1,070 109%

Blue Mesa 360 53%

Navajo 220 30%

Powell 3,300 46%

Upper Basin Storage

April to July 2018 Forecasted Inflow

Issued April 16, 2018

3

Basin Storage

As of 

04/22/2018
4

March Mid-Month: 3.1 maf (43%) April Mid-Month: 3.3 maf (46%)
5

Lake Powell 2018 Operating Tier

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 maf

3. Equalization: > 8.23 maf
August

determination

6

April 

determination
Water Year 2018 Operations: April 2018 24-Month Study

Upper Elevation Balancing

With an 8.23maf release pattern for 

WY2018, September 30, 2018 

projected elevations are:

Powell: 3605.64 (i.e, above 3575 ft) Mead: 1070.80 (i.e, below 1075 ft)

Therefore, Powell’s April adjustment is to Balancing, with releases not 

more than 9.0 maf and not less than 

8.23 maf in the Water Year.

April 2018 24-Month Study EXHIBIT run

7
8

Potential Lake Powell Release Scenarios 

Water Year 2018 Release Volume as a Function of Unregulated Inflow Volume 

based on April 2018 24-Month Study Conditions I I 

Water Vear 2018 

Powell releases controlled by ba lancing 2018 Most Probable 

9.5 contents of Powellseμ,o and Meadsev:;o WY Unreg Inflow= 5.6 mat (52%) 

(Release= 8.23 up to 9.0 maf) Powell Release= 9.0 maf 

// 

/ 

- / -

I • . -. >-, 

' \\ ----------------- ' ' ' 2018 Most Probable \\ 

I ' WY Unreg Inflow = 7. 76 mat (72%) -

M inimum Inflow Scenario Powell Release= 9.0 maf 

WY Unreg Inflow = 4.32 mat (40%) 

9.0 

8.5 

) ' Powell Release= 9.0 mat 

/ / ,, - c:oordi11:-1l~d op ... M;,iiri I i11t-: 

YTD Measured Unreg 

8.0 

Inflow = 2.29 mat 0 Probable Max (Apr 18) 

0 Probable M in (Apr 18) 

7.5 

• Most Proboble (Apr 18) 

D C:u11 1-:11I \/VY lJru !-!glunmu 

7.0 

0 2 4 6 8 10 

Potential Water Year Unregulated Inflow Volume (maf) 
9

1,600 

1,400 

1,200 

cnl 

.:.:: 

~ 1,000 

Q) 

E 

::, 

0 

> 800 

Q) 

(/) 

nl 

Q) 

Q) 

600 

Ct'. 

400 

200 

Projected Lake Powell Monthly Release Volume Distribution 

Release Scenarios for Water Year 2018 

Based on April 2018 modeling 

WY 2018 Release Scenarios 

Apr Probable Min 9.0 mat 

Apr Most Probable: 9.0 maf 

Apr Probable Max: 9.0 mat 

8/iO 

6·10 r,:=rn 

<O 

.... 

c:: 

nl 

' 

<O 

.... 

.Q 

(I) 

LL 

800 

<O 

.... 

... 

ro 

2 

<O 

.... 

c:: 

::, 

' 

o Probable Min • Most Probable im Probable Max 

900 

<O 

.... 

::, 

' 
10

Water Year 2018 projections

Most: 9.0 maf release

MIN: 9.0 maf release 

MAX: 9.0 maf release 

End of CY 2017 Elevation:

3622.85 feet (58% full) End of CY 2018 Projection:

3590.43 feet (45% full)

Min/Max Range: 3580 to 3612 feet

Water Year 2019 projections

Most: 9.0 maf release

MIN: 8.8 maf release 

MAX: 9.0 maf release 
Most Probable End of CY 2018 

Projection: 1,079.1 feet (38% full)

Min/Max Range: 1,077 to 1,081 feet

Most Probable End of CY 2019 

Projection: 1,074.6 feet (37% full)

Min/Max Range: 1,062 to 1,079 feet

11
Unit 

Number

Oct 

2017

Nov 

2017

Dec 

2017

Jan 

2018

Feb 

2018

Mar 

2018

Apr 

2018

May 

2018

Jun 

2018

Jul 

2018

Aug 

2018

Sep 

2018

1

2

3

4

5

6

7

8

Units 

Available 6 6/4 4/6 6 4/6 5/6 5/6 5/6 7 7 7 5

Capacity 

(cfs) 21,000 13,200 13,200 20,600 13,000 12,000 15,700 15,700 22,600 22,600 22,600 12,100

Capacity 

(kaf/month) 1,290 970 1,170 1,260 780 1,060 1,130 1,340 1,340 1,390 1,390 1,130

Max (kaf) 1 667 630 740 860 730 800 705 705 760 860 900 670

Most (kaf) 2 640 630 740 860 730 800 705 705 760 860 900 670

Min (kaf) 1 630 630 740 860 750 780 683 700 760 860 900 670

12

Glen Canyon Power Plant Planned Unit Outage Schedule for Water Year 2018

1 Projected release, based on Apr 2018 Min and Max Probable 

Inflow Projections and 24-Month Study model runs

2 Projected release, based on Apr 2018 Most Probable Inflow 

Projections and 24-Month Study model runs

9.0

9.0

9.0

(updated 4-11-2018)
Experimental Macroinvertebrate

Production Flow (Bug Flow)

• Approved by Assistant Sec. Water & Science on April 13.

– Experiment is for May through August

– Steady weekend flows.

– Normal hydropower production flows during week days.

– No monthly or weekly volumes flow changes.

– Week day fluctuating flows follow LTEMP guide lines.

13
14

"' "' "' "' "' "' ... a, co 0 "' .c,. a, a, 0 "' .c,. a, a, 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

en 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

;r 5/01 - Tu e 

(D 

Cl. 

C: 5,U2 - Wed 

ar I G) Cl. 

I 

5:U3 - Thu 

I -Cl) 0 

C: 5.104 - Fri 

. 

::I 

I '< 0 ;:o 51

U5 - Sat 

!!!. • I Cl) (D 5/06 - Sun ::I 

OJ 

.... '< "' (D 5/07 - Mon 

. 0 "' I ::I 5/08 - Tu e 

- I 0 5/09 -Wed Cl) 

[IJ 

I 3 C: 5/10 - Thu . 

'° I "Tl 

5/11 - Fri I 

0 I 0 :E 5112 - Sat C 

m I -, 

>< 511 3 - Sun '< "tJ (D 

:::,. 5/14 - Mon OJ 3 

(D I C 

3. 0 5/15 - Tu e <C ::0 Ill I 

IS- r+ 5/16 -Wed -n <D I OJ 0 I 

lfJ :r 5i17 - Thu 0 I "' C 

5/18-Fri 

--, I 'iJ I 5i19 - Sat Cl) 

)> 5/20 - Sun 

I 

--

Cl) 

a -, 

C: 5/21 - Mon ::I 

I!!. I I 5122 - Tu e ?:: 

0 I Cl) C: 5/23 - Wed '< 

I . 

::0 5124 - Thu 

- I'\) 

(D I 0 ar 5.1'25 - Fri -->. OJ 

"' _l • co (D 5/26 - Sat "' 
Water Year 2019

Projected Operations

15
Lake Powell 2019 Operating Tier Scenarios 

Based on April 2018 modeling 

Inflow 

Scenario

Operating Tier

Release Volume

Minimum

Probable

Upper Elevation Balancing

8.8 maf

Most

Probable

Upper Elevation Balancing

9.0 maf

Maximum 

Probable

Upper Elevation Balancing

9.0 maf

16
17

LTEMP Monthly Release Volumes 

1 /i!lfl 

1,10fl 

n uu 

-

~ " 

~ u 1000 

"' 0 

-0 "'

"' C: Rm 

"' ;;, 

0 

,::. 

,_ 

OJ 

V> 

"' bOO 

,!? 

"' "' 

4L\l 

() 

OCT NOV DEC JAN f EB MAR \1AY JUN JU_ AUG SEP 

Monthly J)P.r WYT~rgP.t, Mill iOM ot ~r.rP.-tP.P.t 

. , 8 /.48 • 8.B • Y a Y., 8 10., • 11 a n • B 8 14 
LTEMP Monthly Release Volumes

Month 7.00 7.48 8.23 9.00 9.50 10.50 11.00 12.00 13.00 14.00

OCT 480 480 640 640 640 640 640 640 640 640

NOV 500 500 640 640 640 640 640 640 640 640

DEC 600 600 720 720 720 720 720 720 720 720

JAN 660 720 760 860 920 1040 1100 1230 1350 1470

FEB 590 640 680 750 810 920 970 1080 1190 1300

MAR 620 675 710 800 860 970 1030 1150 1260 1370

APR 550 600 640 710 760 870 920 1020 1120 1220

MAY 550 600 630 710 760 860 910 1020 1120 1220

JUN 580 630 660 750 800 910 960 1060 1170 1280

JUL 650 710 750 850 900 1020 1080 1200 1320 1440

AUG 700 760 800 900 970 1090 1160 1280 1410 1540

SEP 520 565 600 670 720 820 870 960 1060 1160
1,600 

1,400 

1,200 

<P 

ro 

.:.:: 

~ 1,000 

<I) 

E 

::, 

g 800 

<I) 

rJ) 

ro 

<I) 600 <I) 

0:: 

400 

200 

Projected Lake Powell Monthly Release Volume Distribution 

Release Scenarios for Water Year 2019 

WY 2019 Release Scenarios 

Apr Probable Min 8.80 maf 

Apr Most Probable: 9.0 maf 

Apr Probable Ma)(; 9.0 maf 

co 

..--

8 

co 

..-

::?-

0 

z 

Based on April 2018 modeling 

0) 

..-

c: 

ro 

-, 

0) 

r-

..c 

Cl) 

LL 

O> 

..-

~ Probable Min • Most Probable l!3 Probable Max 

!JOU 
Unit 

Number

Oct 

2018

Nov 

2018

Dec 

2018

Jan 

2019

Feb 

2019

Mar 

2019

Apr 

2019

May 

2019

Jun 

2019

Jul 

2019

Aug 

2019

Sep 

2019

1

2

3

4

5

6

7

8

Units 

Available 6 8 6 6 6 4/6 6 7 8 8 8 6

Capacity 

(cfs) 19,100 26,100 19,100 19,100 19,100 12,200 19,000 22,700 26,100 26.100 26,100 19,100

Capacity 

(kaf/month) 1,240 1,550 1,200 1,170 1,060 1,140 1,190 1,480 1,550 1,600 1,600 1,180

Max (kaf) 1 640 640 720 860 750 800 710 710 750 850 900 670

Most (kaf) 2 640 640 720 860 750 800 710 710 750 850 900 670

Min (kaf) 1 640 640 720 830 740 780 700 690 720 820 870 655

20

Glen Canyon Power Plant Planned Unit Outage Schedule for Water Year 2019

1 Projected release, based on Apr 2018 Min and Max Probable 

Inflow Projections and 24-Month Study model runs

2 Projected release, based on Apr 2018 Most Probable Inflow 

Projections and 24-Month Study model runs

9.0

8.8

9.0

(updated 4-11-2018)

Possible HFE
Questions?

Paul Davidson

801-524-3642

PDavidson@usbr.gov

Hydraulic Engineer, Glen Canyon

Reclamation, Upper Colorado Region

Resource Management Division

Water Resources Group