Basin Hydrology, Operations and 

2016 Hydrograph

Glen Canyon Technical Work Group

June 11, 2015
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Snow Conditions

Seasonal snowpack 

peaked at 74% on 

March 9th

As of June 11th

most of basin 

snowpack has melted
May was very wet!

• Slowed snowmelt 

• Some additional 

snow accumulation

• Widespread rainfall 

throughout the basin
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May forecast was 3.0 maf (42%) Mar Mid Mid-May forecast : 3.75 maf (52%) -Month: 4.85 maf (68%)
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Lake Powell 2015 Operating Tier

Upper Elevation Balancing

• Tier was set in August 2014

• April Adjustment to 

Balancing 

• Goal: balance contents of Lake 

Powell and Lake Mead by end of 

water year

– release 8.23 maf - 9.0 maf

– Currently projecting 9.0 maf release 
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June Forecast for WY 2015: 

8.5 maf (79%) 

Powell highly likely to release 

9.0 maf in WY 2015

May forecast for WY 2015

 Most: 6.4 maf (59%)

Min: 5.9maf (54%)

Max: 7.9 maf (73%)
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Water Year 2015 projections

Most: 9.0 maf release

Max: 9.0 maf release 

Min: 8.9 maf release 

June 24-Month Study modeling 

is currently underway.

Increase in forecast means 

Powell likely to show 9.0 maf 

release for WY 2016
DOI-DOE Hydrograph

Development 

for Water Year 2016

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2016 Projected Annual Release

(Based on April and May 2015 modeling, 

June modeling is currently underway)

• Min probable: 7.48 maf release 

(Mid-Elevation Release Tier – release is set for entire year)

• Most probable: 7.48 maf release (9.0 maf likely in 

June 24-Month Study)

(Upper Elevation Balancing Tier

with projected April adjustment to Balancing 8.23-9.0 maf release)

• Max probable: 9.0 maf release 

(Upper Elevation Balancing Tier

with projected April adjustment to Balancing 8.23-9.0 maf release)

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2016 Hydrograph 

Current 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 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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2016 Proposed Hydrograph 

11.7 maf release

• Lots of water to move: limited flexibility, minimal difference (not a 

likely scenario, given current hydrology)

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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)
2016 Hydrograph Next Steps

• Continue to coordinate with TWG and AMWG 

member agencies

• TWG present to AMWG August 26-7 with motion 

for approval to recommend to Secretary

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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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