Yellowtail Dam & Bighorn Lake Water Supply & Operations Meeting Billings, Montana October 9, 2008...

Yellowtail Dam & Bighorn Lake Water Supply & Operations Meeting

Billings, Montana

October 9, 2008

RECLAMATIONManaging Water in the West

Purpose of Meeting Public outreach / education regarding

Yellowtail Dam & Bighorn Lake

Recap operations during water year 2008

Present operation scenarios for fall / winter 2008-2009

Obtain feedback / comment from public & interested parties

Meeting Agenda6:00 pm Doors open

6:30 pm Introductions, Welcome, and Meeting Objectives

6:40 pm Recap of Water Year 2008

7:15 pm Fall & Winter Reservoir Operation Scenarios

8:00 pm Facilitated Public Discussion

8:30 pm Adjourn

The Montana Area Office is responsible for managing the water supplies and administering Reclamation programs for Reclamation projects located in Montana east of the continental divide.

The Montana Area Office monitors hydrologic and climatic conditions, prepares inflow projections and operation plans, and directs water releases and lake level management at Yellowtail Dam & Bighorn Lake.

Yellowtail Dam, Bighorn Lake and Afterbay

Yellowtail Dam and Bighorn Lake

Visitor Center Powerplant

Bighorn Lake

Spillway Inlet

Yellowtail Dam, Bighorn Lake and Afterbay

Visitor Center

Yellowtail Dam

Substation

Yellowtail Afterbay Dam

Yellowtail Afterbay Dam and Afterbay

Bighorn Canal

Radial Gates

Sluice Gates

Afterbay Dam

Afterbay

Sewage Lagoons

Bighorn Reservoir AllocationsDam CrestElev. 3660.0

Top of Inactive Elev. 3547.00 (493,584 Acre-Feet)

SURCHARGE - 52,829 Acre-Feet Top of Exclusive Flood Elev. 3657.00 (1,328,360 AF)

EXCLUSIVE FLOOD CONTROL - 258,331 Acre-FeetTop of Joint Use Elev. 3640.00 (1,070,029 Acre-Feet)

JOINT USE - 240,342 Acre-Feet

Top of Active Conservation Elev. 3614.00 (829,687 Acre-Feet)

Top of Dead Elev. 3296.50 (16,008 Acre-Feet)

Maximum Water Surface or Top of Surcharge Elev. 3660.00 (1,381,189 Acre-Feet)

ACTIVE CONSERVATION - 336,103 Acre-Feet

INACTIVE CONSERVATION - 477,576 Acre-Feet

DEAD - 16,008 Acre-Feet

Streambed Elev. 3166.0

Spillway crest Elev. 3593.00

River Outlet Elev. 3300.0

WILDLIFE INDUSTRIALAGRICULTURE MUNICIPALRECREATIONFISH POWER

Powerplant Penstock Elev. 3450.00

Irrigation Outlet Elev. 3400.00

Bighorn Lake Annual Inflow Distribution(based on 1967-2005 data)

Bighorn Gain30%

Buffalo Bill Release

28%

Boysen Release

42%

OPERATIONS - Balancing the needs of the competing interests

Mountain Snowpack

Precipitation

Inflow to Bighorn Lake

Bighorn River Releases

Bighorn Lake Storage Conditions

Recap of Water Year 2008

Mountain Snowpack Conditions

0.0

2.0

4.0

6.0

8.0

10.0

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14.0

16.0

18.0S

ep Oct

Nov

Dec

Jan

Feb Mar

Apr

May

Jun

Jul

Aug

Sep

End of Month Date

Sn

ow

Wa

ter

Eq

uiv

ale

nt

(I

nc

he

s)

20072008Average


Peaked on 5/5 @ 110% of average


2008 Annual Inflow = 2,132.7 kaf (90% of average)

Historic Average Inflow = 2,372.7 kaf


2008 April-July Inflow = 1,298.3 kaf (117% of average)

Historic Average Inflow = 1,192.8 kaf


April-July Inflow – 1,298.3 kaf (117% of average)

Annual Inflow – 2,132.7 kaf (90% of average)

Oct-March Inflow – 520.6 kaf (57% of average)

10/07 Oct-Mar Forecast – 493.9 kaf (54% of average)


Average River Release = 2,728 cfs (87% of average)

2000-2007 Average River Release = 1,922 cfs

Historic Average River Release = 3,135 cfs


Peaked on 7/13 at 3642.50 feet

Ended year at 0.2 feet below full pool

Ended year 10.3 feet higher than in 2007

Summary of Water Year 2008• Water year started out with good precipitation – October well above

average but dropped to well below average during November.• Fall & winter releases were scheduled and maintained at 1,900 cfs.• Mountain precipitation above average during December-March.

Precipitation dropped to below average in April but well above average in May.

• October-March inflows were 57% of average totaling 520.6 kaf.• April-July inflows were 117% of average totaling 1,298.3 kaf.• On May 6 releases were reduced to 1,500 cfs to conserve storage.• Bighorn Lake reached a low level at elevation 3607.54 on May 8.• Bighorn Lake rose nearly 35 feet from May 8 to June 13, reaching a

peak elevation of 3642.50.• Record rains began around May 21 and continued into early June. The

rain accompanying the mountain snowmelt caused inflows to reach a peak of 14,130 cfs on May 24.

• On May 24 releases were gradually increased from 1,500 cfs to nearly 9,700 cfs by June 18.

• By the middle of July, releases were reduced from 6,200 cfs to 3,000 cfs and to 2,500 cfs by August 1. Releases are currently 2,700 cfs.

• Since June 13, storage has slowly declined to elevation 3640 by August 12 and has essentially remained full until present.

• Annual inflows were 90% of average totaling 2,132.7 kaf.• Storage in Bighorn Lake ended the water year at elevation 3639.8

which is 0.2 foot below full.

Bighorn Lake Conditions(as of October 1, 2008)

Elevation 3639.82 ft = 0.18 feet below full pool

Storage 1,067,800 af = 100% full

Inflows = 2,550 cfs

Total Outflow = 2,700 cfsRiver = 2,700 cfsCanal = 0 cfs

Boysen Reservoir Conditions(as of October 1, 2008)


Storage 628,800 af = 85% full

Inflows = 550 cfs

Total Outflow = 700 cfs

Buffalo Bill Reservoir Conditions(as of October 1, 2008)


Storage 484,400 af = 75% full

Inflows = 275 cfs

Total Outflow = 1,740 cfsRiver = 1,290 cfsHeart Mtn. Canal = 450

Water Supply Forecasts

• Fall forecasts rely heavily upon statistical information and analysis

• Reclamation monitors snow pack data each month from mid-October through May

• By about February 1 snow pack becomes a major factor

• Monthly plans are adjusted as needed based on snow data & anticipated normal spring precipitation

• Significant changes to operation plans may be needed

Bighorn Lake Inflow Forecast – Water Year 2009



2008 Actual Oct-Mar Inflows – 520.6 kaf (57% of average)

Bighorn Lake Operation Scenarios


Most Probable Inflow

• October – March Inflow forecast at 674.2 kaf (74% of average)

• Maintain fall and winter release at 2,500 cfs through March

• Reservoir level expected to drop to elevation 3618 by the end of March (typical flood control target is 3605 to 3614).

• Power generation during October – March would total 351.0 GWHrs.

Most Probable Inflow & 2500 cfs Release


Minimum Probable Inflow




• Generation during October – March would total 347.0 GWHrs.

Minimum Probable Inflow & 2500 cfs Release

Most and Minimum Probable Inflow & 2500 cfs Release

Most & Minimum Probable Inflow & 2500 cfs Release


Maximum Probable Inflow




• Generation during October – March would total 353.3 GWHrs.

Maximum Probable Inflow & 2500 cfs Release

All 3 Probable Inflow Scenarios & 2500 cfs Release

Question: What is the effect of a release rate other than 2500 cfs ?

Response: We looked at the most probable runoff condition with release rates of 2400, 2500, and 2600 cfs.

Most Probable Inflow with 3 Release Rates

Discussion & Comments

The information presented at this meeting can be found on the Montana

Area Office website at: www.usbr.gov/gp/mtao/yellowtail/index.cfm.

Please mail comments to:

Ms. Paula A. Holwegner

Bureau of Reclamation

2900 4th Avenue North, Suite 501

Billings, MT 59107

fax your comments to: 406-247-7338

or email your comments to: [email protected]

by October 13, 2008

Comments ?

http://www.usbr.gov/gp/mtao/yellowtail/index.cfm

mailto:[email protected]

Reclamation’s Internet Website

http://www.usbr.gov/gp/water/

• near real-time data available through the HYDROMET data system• summaries and plots of historical data• annual reservoir operating plan publication• monthly water supply reports• project data• snow plots• links to related internet sites

Yellowtail Dam & Bighorn Lake Water Supply & Operations Meeting Billings, Montana October 9, 2008...

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