Merwin, located in Woodland, Washington, is a private hydroelectric dam on the Lewis River that was completed in 1931. With a dam height of 313 feet and a storage capacity of 422,000 acre-feet, Merwin serves multiple purposes including fish and wildlife pond management, hydroelectric power generation, and recreation. The dam is classified as an arch type, with a spillway width of 166 feet and controlled spillway type.

Managed by the Federal Energy Regulatory Commission, Merwin poses a high hazard potential and is considered to have a very high risk level. Despite its age, the dam's condition assessment is not available, and its last inspection was conducted in September 2020. The emergency action plan for the dam was last revised in February 2021, ensuring that necessary measures are in place to address any potential risks or emergencies that may arise.

For water resource and climate enthusiasts, Merwin presents an intriguing case study of a historic dam with significant storage capacity and operational capabilities. Its location on the Lewis River in Cowlitz County, Washington, provides a vital source of hydroelectric power while also supporting local wildlife and recreational activities. As efforts continue to monitor and manage the dam's risk levels, the importance of sustainable water resource management and infrastructure maintenance is underscored by Merwin's role in the region.