(Fremont County, WY) — Reclamation’s June 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 908,000 acre-feet (af), which is 74% of the 30-year average of 1,228,400 af. Approximately 332,300 af of the forecast volume was accumulated during April and May, which is 69% of the April and May average. As of June 1, Bighorn Lake is 86% full.
Buffalo Bill Reservoir – Shoshone River April through July inflow to Buffalo Bill Reservoir is forecast at 660,000 af, which is approximately 89% of the 30-year average of 740,000 af. Approximately 158,000 af of the forecast volume was accumulated during April and May, which is 67% of the April and May average. As of June 1, Buffalo Bill is 62% full. *
Boysen Reservoir – Wind River April through July inflow to Boysen Reservoir is forecast at 525,000 af, which is 87% of the 30-year average of 604,000 af. Approximately 126,000 af of the forecast volume was accumulated during April and May, which is 66% of the April and May average. As of June 1, Boysen Reservoir is 80% full. *
Bull Lake Reservoir – April through July snowmelt runoff into Bull Lake Reservoir from Bull Lake Creek is expected to be 135,000 af, which is approximately 95% of the 30-year average of 142,000 af. Approximately 25,000 af of the forecast volume was accumulated during April and May, which is 74% of the April and May average. As of June 1, Bull Lake Reservoir is 69% 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 Office at 307-261-5671. For additional information on Bighorn Lake (Yellowtail), contact Montana Area Office at 406-247-7296.