(Fremont County, WY) — Reclamation’s May forecasts of the April through July runoff predicted for the Bighorn River Basin are as follows:
• Bighorn Lake – Bighorn River April through July inflow to Bighorn Lake is forecasted to be approximately 899,000 acre-feet (af), which is 73% of the 30-year average of 1,228,400 af. Approximately 113,000 af of the forecast volume was accumulated during April, which is 64% of the April average. As of May 1, Bighorn Lake is 79% full.*
• Buffalo Bill Reservoir – Shoshone River April through July inflow to Buffalo Bill Reservoir is forecast at 600,000 af, which is 81% of the 30-year average of 739,800 af. Approximately 24,000 af of the forecast volume was accumulated during April, which is 51% of the April average. As of May 1, Buffalo Bill is 58% full. *
• Boysen Reservoir – Wind River April through July inflow to Boysen Reservoir is forecast at 500,000 af, which is 83% of the 30-year average of 604,000 af. Approximately 37,400 af of the forecast volume was accumulated during April, which is 74% of the April average. As of May 1, Boysen Reservoir is 83% full. *
• Bull Lake Reservoir – April through July snowmelt runoff into Bull Lake Reservoir from Bull Lake Creek is expected to be 140,000 af, which is 99% of the 30-year average of 142,000 af. Approximately 2,600 af of the forecast volume was accumulated during April, which is 63% of the April average. As of May 1, Bull Lake Reservoir is 58% full. *
*Reservoir is considered “full” when the pool elevation is at top of active conservation or joint-use pool. The percentage is based on total reservoir volume below that level.
The Bighorn River Basin is bounded by the Absaroka Range on the west, the Pryor Mountains of Montana on the north, the Bighorn Mountains on the east, and the Wind River and Granite Mountains to the south. It is drained to the north by tributaries of the Bighorn River, which enters the basin from the southwest, and passes through a gap between the Owl Creek and Bridger Mountains as the Wind River before changing its name to the Bighorn River at Wedding of the Waters, south of Thermopolis.
Reclamation’s storage reservoirs in the basin have a combined storage capacity of 2.6 million acre-feet and most of that capacity is attributed to Bull Lake, Boysen and Buffalo Bill Reservoirs in Wyoming and Bighorn Lake in Montana. Hydropower is produced at Boysen Powerplant and four powerplants supplied by Buffalo Bill Reservoir in Wyoming and at Yellowtail Powerplant in Montana.
For additional information on Buffalo Bill, Boysen, and Bull Lake Reservoirs, contact Wyoming Area Manager Lyle Myler at 307-261-5671. For additional information on Bighorn Lake (Yellowtail), contact Montana Area Manager Ryan Newman at 406-247-7298.