Located in Madison County, Iowa, Sinnwell Dam is a privately owned structure designed by the Soil Conservation Service (SCS) with a primary purpose of fire protection, stock, or small fish pond. Completed in 1987, this earth dam stands at a height of 27 feet and spans 365 feet in length, with a storage capacity of 20 acre-feet. The dam is situated on the TR- Middle River and is regulated by the Iowa Department of Natural Resources, with state permitting, inspection, and enforcement in place to ensure its safety and compliance.

With a low hazard potential and a moderate risk assessment, Sinnwell Dam plays a crucial role in water resource management in the region. The dam's normal storage of 8 acre-feet and surface area of 1.4 acres provide valuable water resources for various purposes, while also serving as a protective barrier against potential flooding events. Despite its uncontrolled spillway type, Sinnwell Dam continues to be a vital asset for fire protection and stock water supply, highlighting its importance in both water resource management and climate resilience efforts in the area.