Lake Aloha Auxiliary No. 4, also known as Medley Lakes Auxiliary No. 4, is a private water resource located in El Dorado County, California, near South Lake Tahoe. This hydroelectric facility, completed in 1917, serves multiple purposes including hydroelectric power generation and irrigation. The dam, a rockfill structure standing at 9 feet tall with a structural height of 8.5 feet, contributes to the storage of water in the South Fork American River watershed.

With a storage capacity of 5063 acre-feet and a surface area of 630 acres, Lake Aloha Auxiliary No. 4 plays a crucial role in water management and conservation in the region. Although classified as having a low hazard potential, its risk assessment is considered high, emphasizing the importance of regular inspections and adherence to safety protocols. Managed by the Federal Energy Regulatory Commission, this dam is subject to state regulations and inspections to ensure its integrity and safety for the surrounding community and environment.