Lake Spaulding No. 1, also known as Spaulding Main, is a private hydroelectric reservoir located in Washington, California. Built in 1912, this arch dam stands at a towering height of 276.5 feet and has a storage capacity of 74,773 acre-feet. The dam's primary purpose is hydroelectric power generation, utilizing the waters of the South Yuba River to produce clean energy.

Managed by the Federal Energy Regulatory Commission, Lake Spaulding No. 1 is a critical infrastructure with a high hazard potential. With a maximum storage capacity of 74,773 acre-feet and a surface area of 698 acres, this reservoir plays a significant role in water resource management and power generation in the Nevada County area. Despite its age, the dam is regulated and inspected by various state agencies to ensure its safety and structural integrity.

Situated in a picturesque location with a drainage area of 118 square miles, Lake Spaulding No. 1 serves as a vital water resource for the surrounding communities. Its historical significance, combined with its modern-day functionality for hydroelectric power generation, makes it a fascinating site for water resource and climate enthusiasts to explore and appreciate.