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Yellowtail Unit and the Bighorn River: Governmental Authorities and Operating Criteria

Sept 15, 2019

Lead Scientist

Ken Frazer

study objectives
  • Identify the key partners and stakeholders involved in the operation and management of the Bighorn River and reservoir system and look at the operating criteria they used in managing Yellowtail Dam and the Bighorn River.

  • Look at the evolution of changes in these operating criteria over time and recognize factors driving these changes.

  • Identify the authority and limitations each management agency has in system operations.


The Yellowtail Unit, consisting of Yellowtail Dam, the Afterbay Dam and Bighorn Lake (Yellowtail Reservoir) upstream of the dam was authorized under the 1944 Flood Control Act. Yellowtail Dam, closed in 1965, was constructed at the mouth of Bighorn Canyon in Montana with the upper end of Bighorn Lake extending into Wyoming. Before construction, the Bighorn River was a warm, turbid prairie stream contributing a high sediment load to the Yellowstone River. Construction of Yellowtail Dam completely changed the character of the Bighorn River downstream of the dam, creating a world-class tailwater trout fishery which ranks as one of the highest use fisheries in MT, and is an important economic driver in this part of MT. The high sediment load that moved down the Bighorn River is now trapped upstream of the dam and is creating major issues, especially in the upper end of the reservoir in Wyoming. 

The Bureau of Reclamation (BOR) retains primary authority over the operation and maintenance of the Yellowtail Unit and they control reservoir elevations and flow releases into the Bighorn River. The BOR shares flood control with the US Army Corps of Engineers and recreation management on Bighorn Canyon National Recreation Area with the National Park Service. Yellowtail Dam, part of Bighorn Lake, and the main tailwater section of the Bighorn River are located within the Crow Indian Reservation, and the Crow Tribe has senior rights on the water being released from Yellowtail Dam. The BOR is responsible 

for establishing Operating Criteria and putting together a management plan under which the Yellowtail Unit operates, while trying to balance their legal obligations and the expectations and interests of a diverse group of stakeholders. Demands and expectations of various user groups have changed over time based on water conditions in the Bighorn Drainage. The BOR has made a sincere effort to involve all interested stakeholders in their water management planning process and have made numerous changes to their operating criteria based on stakeholder input. They continue to look for new ways to improve water management  and forecasting, which should benefit the Bighorn River fishery. 


The operation and management of the Yellowtail Dam/Bighorn River system is complicated by the interests of a diverse group of stakeholders who have different interests and expectations related to river and reservoir management. It is important the BHRA understand the authorities, strengths and limitations each of the major management agencies and stakeholders have in the development of a long-term management plan for the Bighorn system. This will help them in forming partnerships with key players while developing and implementing the various programs identified in the Research Initiative. These partnerships will improve funding opportunities and increase the effectiveness of these programs while ensuring that the information collected reaches the proper management agencies where its utilization in developing future operational and management plans for the Bighorn system should provide benefits for all stakeholders.

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