Lake Helen, located in Sonoma, California, is a privately owned reservoir primarily used for water supply purposes. Constructed in 1966, the earth dam stands at a height of 39 feet and has a storage capacity of 192 acre-feet. The reservoir covers a surface area of 14 acres and is fed by the Tr Russian River, serving as a vital resource for irrigation and recreation in the area.

Managed by the Natural Resources Conservation Service, Lake Helen has a high hazard potential but is currently in satisfactory condition as of the last assessment in September 2017. The dam is regulated by the California Department of Water Resources and undergoes regular inspections to ensure its safety and compliance with state regulations. Despite its age, Lake Helen continues to play a crucial role in providing water for agricultural and recreational activities in the region.

With its picturesque location in Graton and close proximity to the San Francisco District, Lake Helen offers a serene retreat for water resource and climate enthusiasts. The dam's emergency action plan was last revised in February 2021, ensuring that necessary measures are in place to address any potential risks. As a vital component of the local water infrastructure, Lake Helen remains a key player in sustaining the surrounding ecosystem and supporting the community's water needs.