 Since Cougar Reservoir is built for flood control, the levels of the reservoir very greatly, causing the units to operate at heads between one third of the time and at heads between one fifth of the time.In 2002, the Corps began lowering the level of the reservoir for the construction of a temperature control facility.The reservoir level was lowered to an elevation below the turbine intakes, which put the powerhouse out of service and provided an opportunity to overhaul the turbine-generator units.