[2][3] The dam impounds the South Fork McKenzie River about 42 miles (68 km) east of Eugene, Oregon, creating Cougar Reservoir which has a storage capacity of 219,000 acre-feet (270,000,000 m3).

[2][3] The purpose of Cougar Dam is to provide flood risk management, hydropower, water quality improvement, irrigation, fish and wildlife habitat, recreation, storage, and navigation.

[5] From 2003 to 2005, state-of-the-art turbine runners were installed in the turbine-generator units at the Cougar powerhouse, and were designed to resist cavitation and operate efficiently at very large head ranges.

[3] The dam consists of a rock-fill embankment approximately 1,500 feet (460 m) long, a penstock to power two Kaplan turbines, an emergency spillway capable of a capacity of 76,140 cu ft/s (2,156 m3/s), a regulating outlet, and a diversion tunnel.

[9] In the fall, the reservoir level is considerably lower and the warmer water from the surface enters the intakes and makes the river downstream unnaturally warm which causes salmon eggs to hatch several months too early.

In order to help control the temperature of water discharged below the dam, the original intake tower was modified by adding a 302-foot (92 m) tall wet well.

[9] 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.