Forecasts for Bighorn River Basin inflows below average

The Bureau of Reclamation’s April forecast of the May through July runoff predicted for the Bighorn River Basin shows below average inflows for reservoirs.

The predictions are as follows:

•Bighorn Lake - Bighorn River June through July inflow to Bighorn Lake is forecast to be approximately 455,000 acre-feet (af), which is 59% of the 30-year average of 771,000 af.  As of June 1, Bighorn Lake is 84% full.

•Buffalo Bill Reservoir - Shoshone River June through July inflow to Buffalo Bill Reservoir is forecast at 400,000 af, which is 77% of the 30-year average of 517,600 af. As of June 1, Buffalo Bill is 75% full. *

•Boysen Reservoir - Wind River June through July inflow to Boysen Reservoir is forecast at 350,000 af, which is 81% of the 30-year average of 430,000 af. As of June 1, Boysen Reservoir is 72% full. *

•Bull Lake Reservoir - June through July snowmelt runoff into Bull Lake Reservoir from Bull Lake Creek is expected to be 100,000 af, which is 89% of the 30-year average of 112,000 af. As of June 1, Bull Lake Reservoir is 62% 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 Basin is a plateau region and intermontane basin, approximately 100 miles (160 km) wide, in north-central Wyoming. It is bounded by the Absaroka Range on the west, the Pryor Mountains on the north, the Bighorn Mountains on the east, and the Wind River and Granite Mountains on 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.