Basin Hydrology, Operations and 

2016 Hydrograph

Glen Canyon Technical Work Group

April 21, 2015
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Snow Conditions Snowpack peaked at 

~74% on March 9th

As of April 20th

~56% of average
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Mar Mid Apr Mid-Month: 4.85 maf (68%) -Month: 3.40 (47%)
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Lake Powell 2015 Operating Tier

Upper Elevation Balancing

• Tier was set in August 2014

– 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
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6

April
7

Water Year 2015 projections

Most: 9.0 maf release

Max: 9.0 maf release 

Min: 8.9 maf release 
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DOI-DOE Hydrograph

Development 

for Water Year 2016

9
2016 Hydrograph Concepts

• Objective– retain sand inputs high in the system 

in anticipation of a potential fall HFE

• Target lower August through September releases

• Avoid shifting “extra” water to June (which cools 

temperatures at the mouth of the LCR)

• Move water from August to other equal value 

months for hydropower (Dec/Jan)

• Learn from past years’ experience

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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 months of 

greatest sand input

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12

Typical months of higher 

release volumes:

July and August

(also Dec, Jan)
Decreasing releases in the 

1,000kaf to 800kaf range can 

significantly decrease sand 

transport. Less difference seen at 

lower flow volumes.

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Lake Powell 2016 Operating Tier Scenarios 

Based on April 2015 modeling 

Inflow 

Scenario

Operating Tier

Release Volume

Minimum

Probable

Mid-Elevation Release

7.48 maf

Most

Probable

Upper Elevation Balancing

9.0 maf

Maximum 

Probable

Upper Elevation Balancing

9.0 maf

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2016 Hydrograph 

Current DOI-DOE Proposal

Annual Release 

Volume June August September

less than 9.0 maf 600 kaf -

650 kaf 800 kaf 600 kaf

9.0 maf –

less than 9.5 maf 800 kaf 900 kaf

(was 850) 700 kaf

9.5 maf –

less than 10 maf 900 kaf 900 kaf 700 kaf

10 maf and greater 900 kaf or 

more

900 kaf or 

more

800 kaf

or more

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2016 Proposed Hydrograph 

7.48 maf release

Release is already low in June, Aug and Sep, no difference

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2016 Proposed Hydrograph 

8.23 maf release

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2016 Proposed Hydrograph 

9.0 maf release

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Screening Tool Analysis

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Typical 9.0 MLFF Modified 9.0 year Proposal

Month

Monthly 

Volume 

(kaf)

Total 

Sediment 

Transport 

(MT)

Total 

Hydropower 

Value 

(1000$)

Temp at 

RM61 

(deg C) Month

Monthly 

Volume 

(kaf)

Total 

Sediment 

Transport 

(MT)

Total 

Hydropower 

Value 

(1000$)

Temp at 

RM61 

(deg C)

Oct 600 14,614 15,858 11.4 Oct 600 14,614 15,858 11.4

Nov 600 15,869 15,343 10.6 Nov 600 15,869 15,343 10.6

Dec 800 41,620 20,972 10.0 Dec 900 77,431 23,762 10.0

Jan 800 41,620 19,536 9.9 Jan 900 77,431 22,102 9.9

Feb 650 25,345 15,906 10.3 Feb 700 33,365 17,096 10.3

Mar 650 19,397 15,459 10.8 Mar 650 19,397 15,459 10.8

Apr 600 15,869 13,209 11.3 Apr 600 15,869 13,209 11.3

May 650 19,397 14,825 11.8 May 700 25,355 15,871 11.7

Jun 800 45,598 19,428 12.1 Jun 800 45,598 19,428 12.1

Jul 1000 113,929 30,588 12.1 Jul 950 94,279 29,197 12.2

Aug 1050 136,707 32,491 11.9 Aug 900 77,431 28,169 12.1

Sep 800 45,598 22,360 11.8 Sep 700 27,671 19,715 12.0

Total 9000 535,564 235,977 Total 9000 524,310 235,210

-767 hydropower diff

Annual 535,564 Annual 524,310 -11,254 sed diff (annual

Jul-Nov 326,718 Jul-Nov 229,864 -96,854 sed diff (Jul-Nov)

Aug-Sep 182,305 Aug-Sep 105,102 -77,203 sed diff (Aug - Sep)
Screening Tool Analysis

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Original 9.0 maf year Proposal (Presented at Feb AMWG) Modified 9.0 year Proposal

Month

Monthly 

Volume 

(kaf)

Total 

Sediment 

Transport 

(MT)

Total 

Hydropower 

Value 

(1000$)

Temp at 

RM61 

(deg C) Month

Monthly 

Volume 

(kaf)

Total 

Sediment 

Transport 

(MT)

Total 

Hydropower 

Value 

(1000$)

Temp at 

RM61 

(deg C)

Oct 600 14,614 15,858 11.4 Oct 600 14,614 15,858 11.4

Nov 600 15,869 15,343 10.6 Nov 600 15,869 15,343 10.6

Dec 900 77,431 23,762 10.0 Dec 900 77,431 23,762 10.0

Jan 900 77,431 22,102 9.9 Jan 900 77,431 22,102 9.9

Feb 700 33,365 17,096 10.3 Feb 700 33,365 17,096 10.3

Mar 650 19,397 15,459 10.8 Mar 650 19,397 15,459 10.8

Apr 600 15,869 13,209 11.3 Apr 600 15,869 13,209 11.3

May 700 25,355 15,871 11.7 May 700 25,355 15,871 11.7

Jun 800 45,598 19,428 12.1 Jun 800 45,598 19,428 12.1

Jul 1000 113,929 30,588 12.1 Jul 950 94,279 29,197 12.2

Aug 850 63,078 26,728 12.2 Aug 900 77,431 28,169 12.1

Sep 700 27,671 19,715 12.0 Sep 700 27,671 19,715 12.0

Total 9000 529,607 235,159 Total 9000 524,310 235,210

51 hydropower diff

Annual 529,607 Annual 524,310 -5,297 sed diff (annual

Jul-Nov 235,161 Jul-Nov 229,864 -5,297 sed diff (Jul-Nov)

Aug-Sep 90,749 Aug-Sep 105,102 14,353 sed diff (Aug - Sep)
2016 Proposed Hydrograph 

11.7 maf release (unlikely)

• Lots of water to move: limited flexibility, minimal difference

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2016 Hydrograph Next Steps

• Consider Feedback from TWG

• Continue to coordinate with DOI-DOE agencies

• Present to AMWG in May for review

• Draft motion to TWG in June

– TWG discuss and make recommendation to AMWG in June

• TWG present recommendation to AMWG in 

August for approval

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Questions?

Katrina Grantz

801-524-3635

kgrantz@usbr.gov

Hydraulic Engineer, Glen Canyon

Reclamation, Upper Colorado Region

Resource Management Division

Water Resources Group

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