Bureau of Reclamation

05/18/2026 | Press release | Distributed by Public on 05/18/2026 11:32

Reclamation issues snowmelt forecast for Bighorn River Basin

WASHINGTON - Reclamation's May Forecast of the May through July water runoff predicted for the Bighorn River Basin is as follows:

  • Bighorn Lake - Bighorn River May through July inflow to Bighorn Lake is forecast to be approximately 407,000 acre-feet (af), which is 38% of the 30-year average of 1,061,000 af. As of May 1, Bighorn Lake is 78% full.
  • Buffalo Bill Reservoir - Shoshone River May through July inflow to Buffalo Bill Reservoir is forecast at 450,000 af, which is 64% of the 30-year average of 705,000 af. As of May 1, Buffalo Bill is 68% full. *
  • Boysen Reservoir - Wind River May through July inflow to Boysen Reservoir is forecast at 160,000 af, which is 29% of the 30-year average of 553,400 af. As of May 1, Boysen Reservoir is 71% full. *
  • Bull Lake Reservoir - May through July snowmelt runoff into Bull Lake Reservoir from Bull Lake Creek is expected to be 100,000 af, which is 72% of the 30-year average of 139,500 af. As of May 1, Bull Lake Reservoir is 33% 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.

Bureau of Reclamation published this content on May 18, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on May 18, 2026 at 17:32 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]