Thomas, also known as Lewis Lake or J L Thomas Reservoir, is a privately owned water structure located in Carbondale, Colorado. Constructed in 1938, this earth dam stands at a height of 32 feet and serves primarily for irrigation purposes, with a storage capacity of 292 acre-feet. The reservoir covers a surface area of 15 acres and is situated along the Thomas Creek-OS, providing essential water resources for the surrounding area.

Managed by the Colorado Department of Water Resources, Thomas Dam has a significant hazard potential and is classified as being in fair condition as of the last inspection in September 2020. The dam has undergone modifications in 1999 to enhance its foundation, hydraulic, and structural components. With an uncontrolled spillway and a maximum discharge capacity of 800 cubic feet per second, the reservoir plays a crucial role in water management and irrigation activities in Pitkin County.

Despite its moderate risk assessment, Thomas Dam is an important piece of infrastructure in the region, ensuring water supply for agricultural needs and offering recreational opportunities. With continued monitoring and maintenance, this reservoir remains a vital asset for water resource and climate enthusiasts interested in sustainable water management practices in Colorado.