Currently, the 27 shutters cannot be individually and independently raised automatically. Instead, shutters are bolted together so that the 9 shutters comprising each vertical column have a 3-2-4 configuration. This means that the top three, middle two, and bottom four panels are bolted together and are raised as a unit.
Temperature management provides protection to endangered and threatened fishery species and provides suitable habitat for fish hatchery operations. The current shutter configuration results in larger than desired changes in release temperature, which can adversely affect fisheries and other aquatic life. The proposed refinement of the shutter system would allow finer control of release temperature changes, which would benefit the downstream fisheries as well as conserve cold water pool, thus allowing temperature control to be effective for a longer time into the fall. This would also have an added benefit of minimizing the frequency of times when power bypass may be necessary to maintain temperatures below Nimbus Dam.
The U.S. Bureau of Reclamation operates Folsom Lake for flood protection, water supply use, power generation, recreation, and environmental purposes, including water temperature management in the Lower American River. Thermal stratification of Folsom Lake affords the opportunity for selective withdrawal of water of various temperatures at different elevations. A temperature device structure at Folsom Dam blends the selected waters for desired downstream performance. Seasonal temperature strategies are developed annually, depending on the hydrologic year type, storage conditions, cold-water reserves and fishery objectives.
Operational challenges to temperature management include uncertain future hydrologic, downstream water demands, and meteorological conditions. Additional challenges include balancing trade-offs between water release volumes, different fishery species, power generation and water temperature. To assist in temperature management, computational tools are employed to project the efficiency of cold-water reserve use, future downstream temperature performance, physical shutter operations and bypass of power generation. Drought periods are particularly challenging for temperature management due to limited water supply and cold-water reserves.
The U.S. Army Corps of Engineer’s design for the new Temperature Control Device is approximately 35% complete and may change as it gets to 65%. The design is intended to automate the process of changing the position of the shutters. The project will involve replacing the existing system with two 13-foot-tall panels in each of 5 new vertical tracks. These new tracks and panels will be placed between the three piers comprising the existing temperature control structures on each of the three Folsom power penstocks. By expanding and reconfiguring the number of temperature control panels within the temperature control system, operators would be able to preserve the amount of cold water behind Folsom Dam and deliver the water downstream as needed to promote a suitable aquatic habitat for downstream fish and fisheries. Next steps will include the development of 65% Plans and Specifications and the Design Documentation Report.