S-X, also known as Essex Reservoir, is a privately owned dam located in Canby, California. Completed in 1917, this earth dam stands at a height of 45 feet and serves primarily for water supply purposes, including irrigation. With a storage capacity of 4,225 acre-feet and a surface area of 330 acres, S-X plays a vital role in managing water resources in the region.

Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, S-X is state-regulated, inspected, and enforced to ensure its structural integrity and safety. The dam is situated on the Tr Pit River, within the Modoc County, and falls under the jurisdiction of the San Francisco District of the US Army Corps of Engineers. Despite being categorized as low hazard potential, S-X undergoes regular inspections to maintain its satisfactory condition and mitigate any risks associated with its operation.

As a significant component of the local water infrastructure, S-X contributes to the sustainable management of water resources in the area. Its historical significance, combined with its operational efficiency and regulatory oversight, underscores the importance of maintaining and monitoring dams like S-X to meet the water supply needs while safeguarding against potential hazards and emergencies. For water resource and climate enthusiasts, S-X represents a critical piece of the puzzle in ensuring the resilience and reliability of water systems in California.