Yellowtail Dam & Bighorn Lake

Billings, MontanaJanuary 2011

RECLAMATIONManaging Water in the West

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 flows for the river fishery and water

quality

Multipurpose Benefits• Water Rights

– Regulate stream flow and release water for irrigation• Compact Commitments with N. Cheyenne and Crow tribes• Industrial water supply

– 6,000 AF contract with PPL- MT• Flood control

– Flood protection Benefits= $113 million since construction (2007)• Hydropower

– 260 MW powerplant (8,000 cfs)– Peaking power supplied to two grid systems– Average Annual generation = 866.0 million kwhrs (1967-2007)– Average Annual power sales @ .023/kwhr = $20 million per year– Montana and Wyoming both benefit from power generated

• Fish & Wildlife– Lake fishery, river fishery, and waterfowl

• Recreation – Bighorn Canyon Recreation Area and Bighorn River

• Water Quality – Reduce high levels of nitrogen supersaturation– Sediment retention

BIGHORN LAKE STORAGE 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

Operational GoalsPrior to Review

• Desired lake elevations requested by lake interests– Minimum desired lake elevation recommended by the NPS

for the summer recreation season - 3617.– Minimum late fall lake elevation recommended by the

Wyoming Game and Fish to provide suitable waterfowl habitat - 3635.

– Draft reservoir to 3630 to prevent ice-jams from forming in low end of Shoshone River

– Maximum lake elevation recommended by the NPS for the summer recreation season to protect facilities - 3642.

– A rising reservoir level through the spring for walleye spawning.

Operational Goals (continued)

• Desired river flows requested by Montana FW&P by letter dated November 19, 1986• 2,500 cfs – to provide good spawning, rearing and cover

conditions in all major side channels.• 2,000 cfs - to provide adequate spawning and rearing

conditions in most side channels but cover for adult fish is limited.

• 1,500 cfs – to provide only main channel habitat and no side channel habitat

• Minimum release included in the 1962 Definite Planning Report for the Yellowtail Unit – 1,000 cfs

Operational Goals (continued)

• Power generation– Utilize available water supply to maximize generation at time of

greatest demand– Maximize reservoir head to provide the greatest generation per

unit of water

• Flood control– Coordinate operations with the Corps of Engineers to provide

system benefits– Draft water from the Joint-Use pool based on mountain snowpack

forecast to provide space for expected runoff while allowing the reservoir to fill to the top of the joint-use pool by end of July.

– Operate the Exclusive flood pool as directed by the Corps of Engineers to control rain flood events and high snowmelt runoff.

QUESTIONS & COMMENTS