Mathes, also known as Mathes Lake, is a federal-owned water resource located in Fort Madison, Iowa. Managed by the US Army, this recreational dam was completed in 1941 and stands at a height of 64 feet with a hydraulic height of 27 feet. The dam spans 1120 feet and has a maximum storage capacity of 1440 acre-feet, making it a vital water source for the surrounding area.

Situated on Long Creek, Mathes serves as a popular spot for outdoor activities and water recreation in Des Moines County. Despite its low hazard potential, the dam is regulated and inspected by the Iowa Department of Natural Resources. The spillway, with a width of 75 feet, is designed as uncontrolled, allowing for controlled release of excess water during high flow events. With a moderate risk assessment rating of 3, Mathes is monitored closely to ensure the safety and integrity of the structure for both residents and visitors alike.

While the condition assessment is currently listed as "Not Available," Mathes Dam undergoes frequent inspections every four years to assess any potential risks and ensure proper maintenance. With its strategic location and vital role in providing recreational opportunities and water storage, Mathes remains a significant asset in the management of water resources in the region.