 The dam impounds the South Fork McKenzie River about east of Eugene, Oregon, creating Cougar Reservoir which has a storage capacity of .The purpose of Cougar Dam is to provide flood risk management, hydropower, water quality improvement, irrigation, fish and wildlife habitat, recreation, storage, and navigation.In 2005, the Willamette temperature control facility was constructed to help regulate the water temperature released to the river below Cougar Dam in an attempt to reduce the negative effects on salmon migration.