The U.S. Army Corps of Engineers Sacramento District is currently working to update the water control manual for Folsom Dam and reservoir. The manual must be updated to reflect physical and non-physical changes to the dam facility to help guide dam operators manage water releases under various scenarios. With the addition of a new auxiliary spillway currently under construction and increased forecasting capabilities, among other items, the water control manual must be updated to reflect those operational changes.
The Folsom Dam auxiliary spillway project is an approximately $900 million cooperative effort between the Corps and the U.S. Bureau of Reclamation, along with the state's Central Valley Flood Protection Board and the Sacramento Area Flood Control Agency, to improve the safety of Folsom Dam and reduce the flood risk for the Sacramento area. The spillway is scheduled to be completed in October 2017.
The auxiliary spillway is not intended to replace any of the main dam’s current functions or increase the capacity of the reservoir.
In addition to accounting for the new spillway, the water control manual update will develop new operational rules for dam safety and flood risk management, and ensure compliance with federal authorizations to reduce creditable space allocation from the current operating range of 400,000–670,000 acre-feet to 400,000–600,000 acre-feet. To put it simply, the existing dam infrastructure couldn’t release water fast enough so the current water control manual had to plan for scenarios in which the reservoir would have up to 670,000 acre feet of water. With the spillway and the increased capability to release water not only in larger amounts, but sooner based on forecasting, operators are anticipated to typically manage releases at lower reservoir levels.
The water control manual update is scheduled to be completed in 2017 to correspond with completion of auxiliary spillway construction so the increased flood operation capabilities provided by the spillway can be appropriately supported.