Round Valley, also known as Round Valley Reservoir, is a privately owned dam located in Belfast, California. Built in 1892, this earth dam stands at a height of 45 feet and has a maximum storage capacity of 5500 acre-feet, primarily serving as a water supply for irrigation purposes. With a significant hazard potential, the dam is under state regulation and inspection by the California Department of Water Resources, ensuring its structural integrity and safety.

Situated on Round Val Cr, with a drainage area of 10.6 square miles, Round Valley Reservoir covers a surface area of 420 acres and has a hydraulic height of 40.4 feet. Despite its age, the dam has been assessed as satisfactory in condition as of September 2017, with regular inspections conducted to monitor its safety. The reservoir's emergency action plan has been updated most recently in January 2021, highlighting the importance of preparedness in the event of a potential risk or emergency situation.

Owned by private entities, Round Valley plays a crucial role in providing water resources to the surrounding area, contributing to agricultural irrigation and water supply needs. With its historical significance dating back over a century, the dam stands as a testament to the importance of sustainable water management practices in the face of evolving climate challenges.