The original dam was constructed of rockfill and completed in 1910. It was 42 feet (13 m) tall from the bottom of the foundation to the crest, 32 ft (10 m) if measured from the crest to the original stream bed. It was replaced with a concrete dam near the old dam in 2002. The old dam had deteriorated and the water level was kept low to prevent it from failing. Its crest is at the same height as the old dam and the reservoir's capacity is about the same. There is a small hydroelectric plant at the dam with a capacity of 3 MW. The dam is owned by the United States Bureau of Reclamation.

The dam and reservoir were created to reduce flows into the reclaimed wetlands of Tule Lake. It also reduces flows into Tule Lake Sumps in the Tule Lake National Wildlife Refuge.

The reservoir created by the dam has a very large surface area, 25,760 acres (104.2 km²), and its average depth at maximum capacity is only about 20 feet (6 m), so it has a very high rate of evaporation. In 1998, 74,500 acre-feet (91,900,000 m³) of water from the reservoir evaporated, more than any other lake in the state besides Shasta Lake, which has over 8 times the volume. Because of this, Clear Lake Reservoir is not an efficient water storage reservoir. This is a problem since the dam now provides water for irrigation in the eastern half of the Klamath Basin.

The reservoir is in Modoc National Forest and Clear Lake National Wildlife Refuge, so recreation opportunities are limited.

• List of dams and reservoirs in California
• List of largest reservoirs of California
• List of lakes in California

• California Department of Water Resources (XLS)
• "California State Water Resources Control Board" (PDF). Archived from the original (PDF) on 2006-10-04. (1.02 MiB)
• Herald News
• United States Bureau of Reclamation