Reclamation to Begin Jackson Lake Fall Flow Ramp Down Sept. 29

HEYBURN, Idaho - The Bureau of Reclamation will begin fall flow ramp-down operations at Jackson Lake Dam on Monday, Sept. 29, 2025.

The ramp-down schedule was developed in coordination with the Snake River agencies group during its annual fall meeting last week. The plan includes three outflow reductions per day over four days, starting from the current 2,100 cubic feet per second and concluding at 280 cfs by Thursday, Oct. 2, 2025.

Each of the 12 scheduled reductions is expected to lower the river stage by approximately 2.6 inches immediately downstream of the dam, resulting in a total stage change of about 31 inches (2.6 feet). Minor adjustments may follow in the coming weeks, based on final flow measurements taken by the U.S. Geological Survey to ensure winter outflows are accurately set at 280 cfs.

The Snake River agencies group-a collaborative body of federal, state, and local stakeholders-comprises representatives from Grand Teton National Park, the Wyoming State Engineer's Office, Wyoming Game and Fish Department, Idaho Water District 1, U.S. Army Corps of Engineers, Idaho State University's Stream Ecology Research Team, Trout Unlimited, and Reclamation water operations managers, among others. The group met regularly throughout the summer to coordinate river operations, including the ramp down.

Hydrological conditions in the Snake River headwaters upstream of Jackson Lake have remained below average since July, with baseflows tracking near the 10^th percentile. The region has received only 67% of average precipitation since May 1, contributing to the reduced inflows.

As of mid-September, Jackson Lake is at 69% of capacity and is projected to be approximately 65% full by the end of the month. Winter outflows are expected to remain at or above 280 cfs.

For more information on the fall flow ramp down, contact Reclamation's public affairs office at (208) 378-6203 or email: [email protected].

Current river and reservoir data are available at https://www.usbr.gov/pn/hydromet/uppersnake/.

For more information about Reclamation programs, please visit https://www.usbr.gov/pn/snakeriver/index.html.

Jackson Lake Dam is located on the Snake River in Grand Teton National Park near Moran, Wyoming. The dam is part of the Minidoka Project and was originally constructed in 1911. Parts of the dam were later replaced in 1989 under the authority of Reclamation's Safety of Dams Act.