Reclamation issues snowmelt forecast for Bighorn River, North Platte River Basins

Reclamation’s May forecast of the April through July runoff predicted for the Bighorn River Basin is as follows:

Bighorn Lake – Bighorn River April through July inflow to Bighorn Lake is forecast to be approximately 1,203,000 acre-feet (af), which is 96% of the 30-year average of 1,256,400 at.

Buffalo Bill Reservoir – Shoshone River April through July inflow to Buffalo Bill Reservoir is forecast at 750,000 af, which is 101% of the 30-year average of 742,600 at.


Boysen Reservoir – Wind River April through July inflow to Boysen Reservoir is forecast at 650,000 af, which is 105% of the 30-year average of 617,400 at.

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 94% of the 30-year average of 143,800 at.

Wind River – April through July snowmelt runoff into the Wind River above Bull Lake Creek is expected to be 450,000 af, which is 103% of the 30-year average of 437,900 at.

For additional information on Buffalo Bill, Boysen, and Bull Lake Reservoirs, contact Wyoming Area Manager Carlie Ronca at 307-261-5671. For additional information on Yellowtail Reservoir, contact Montana Area Manager Steve Davies at 406-247-7298.


The Wyoming Area Office of the Bureau of Reclamation has prepared the May snowmelt runoff forecasts and operating plans for the North Platte River Basin.

The April forecasts indicate the spring snowmelt runoff will be above average. Total April through July runoff in the North Platte River Basin above Glendo Dam is expected to be 1,002,000 acre-feet (af), which is 110% of the 30-year average.

The total conservation storage capacity of the North Platte Reservoir System is approximately 2,815,800 at. As of April 30, 2020, the combined storage content in the North Platte Reservoirs was 2,273,800 af, which is 129% of the 30-year average.


Current releases are 2,350 cubic feet per second (cfs) from Seminoe Reservoir through the Miracle Mile. Releases out of Gray Reef Reservoir are 2,500 cfs. Releases out of Guernsey Reservoir are 3,000 cfs. Based on current projections for the months of May, June, and July, the releases out of Seminoe Reservoir are expected to have already peaked at 3,200 cfs, while flows out of Gray Reef are expected to be in the range of approximately 2,000 to 3,000 cfs. Releases from Guernsey will be in the 3,000 to 5,200 cfs range. Pathfinder Reservoir is not expected to spill this spring.

h/t Wyoming State Geological Survey

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