Yellowstone River Compact CommissionTechnical Committee Discussions

Sheridan County CourthouseSheridan, WYApril 24, 2007

Bighorn Reservoir operations and long term management discussions

RECLAMATIONManaging Water in the West

Yellowtail Unit and Bighorn Canyon National

Recreation Area

Long-Term Issues Group

Draft Problem Statement

• “The amount, timing, and location of water available in the Big Horn River system to support all required and desired uses including, but not limited to, tribal obligations, recreation, aquatic organisms, power generation, and irrigation is limited and variable. Our challenge is to take a new look at all uses and needs, while recognizing commitments to authorized project purposes and other legal obligations—including water rights.”

Draft Group Charter

• “The Big Horn River System Long-Term Coordinating Group has been formed to identify, explore, and recommend alternative courses of action to the federal and state agencies responsible for managing Big Horn River and Big Horn Reservoir resources for their consideration as part of long-term management strategies.”

Yellowtail Unit

• Authorization: Flood Control Act of Dec. 22, 1944 (ch.665 Stat. 887)

Senate Document 191—USACE/Reclamation plan for Missouri River Basin Development

• Project Purposes

– Flood Control – Hydropower – Irrigation – Recreation– Fish & Wildlife– Sediment storage

Bighorn Canyon National Recreation Area

Authorization: Public Law 89-664, October 15, 1966

Purpose

“In order to provide for public outdoor recreation use and enjoyment of the proposed Yellowtail Reservoir and lands adjacent thereto in the States of Wyoming and Montana by the people of the United States….”

OPERATIONS - A BALANCING ACT AMONG THE AUTHORIZED

PURPOSES OF THE YELLOWTAIL UNIT and the AUTHORIZED

PURPOSES OF THE BIGHORN CANYON NATIONAL RECREATION

AREA

Administration of the Yellowtail Unit and the Bighorn Canyon National Recreation

Area

Memorandum of Agreements between Reclamation and the Park Service:

December 1964 (signed by the Secretary)

Updated March 1972

Operating Requirements & Objectives

• Mandatory /Legal – Recognize all Senior Downstream Water Rights– Fulfill Compact obligation with Native American Tribes– Meet Contract Commitments for Stored Water – Dam Safety

• Operating Objectives– Maximize Power Generation Benefit– Maintain Storage Space for Flood Control – Maintain desired Lake levels for Recreation, Reservoir

Fishery and Waterfowl– Maintain desired River Flow levels for the River Fishery and

water quality

Bighorn Lake Inflow DistributionBased on 1967-2006 Data

Bighorn River Accretions less Depletions (Gain)

30%

Buffalo Bill

Release

28%

Boysen

Release

42%

Annual Total

Bighorn Lake Inflows2000-2006 Drought vs 1934-1940 Drought

1777

1348

10301208

1042

1848

1433

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7

Years

1,00

0 ac

re-f

eet 2000-2006

1934-1940

30 Year Avg

2000-2006 Avg

1934-1940 Avg

Annual Volume of Water Required to Meet River

Targets vs Drought Supply

1928

1566

1204

311

1384

1030

0

500

1000

1500

2000

2500

2500 cfs 2000 cfs 1500 cfs Storage 00-06 Avg 2004

1000

acr

e-fe

et

MULTIPURPOSE OBJECTIVESElevations Targets

• Sept – Oct: A Desired Lake Elevation of 3635 provides space for late summer and fall rainstorms, recreation enhancement and wildlife habitat

• March: Position Lake Level between 3605 and 3615 to provide good fall and winter generation, prepare reservoir for spring runoff and provide desired fishery flows. This also increases probability of raising pool during Walleye Spawning

• July: Fill reservoir to normal full level of 3640 to provide good water supply for all water uses while leaving adequate space to control summer and fall rain events.

MULTIPURPOSE OBJECTIVESDesired River Operating Range

• 1,500 cfs – Approximate discharge to provide “firm” power generation as identified in DPR and provide minimum target flow for river fishery. Provide more then adequate water for downstream irrigation demands. Protects Reservoir storage in low runoff years except for the period of 2002 - 2004

• 4,500 cfs – Provides optimum power generation (allows full peaking) while providing more then adequate water conditions for river fishery and irrigation needs

BIGHORN LAKEBIGHORN LAKE ELEVATION

3570.00

3575.00

3580.00

3585.00

3590.00

3595.00

3600.00

3605.00

3610.00

3615.00

3620.00

3625.00

3630.00

3635.00

3640.00

3645.00

Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Oct-07 Nov-07 Dec-07 Jan-08 Feb-08 Mar-08

Ele

vati

on

in F

eet

Most Probable

Sto

rag

e in

KA

F

Ok-A-Beh & Barry's Landing Minimum Boat Launch Elevation

Horseshoe Bend Minimum Boat Launch Elevation

Target Range for Flood Control

594.3

1137.5

1070.0

959.5

873.6

836.7

803.2

772.9

744.6

717.6

691.5

666.3

641.7

617.7

914.2

1011.0

Top of Joint-Use Conservation - 3640.00 (1,070.0 kaf)