Johnston Dam in Keosauqua, Iowa, is a private-owned earth dam completed in 2005 by USDA NRCS. With a height of 29 feet and a length of 220 feet, this dam serves the primary purpose of grade stabilization along a tributary to the Des Moines River. The dam has a storage capacity of 29 acre-feet and covers a surface area of 2 acres, with a low hazard potential and a condition assessment of "Not Rated".

Situated in Van Buren County, Iowa, Johnston Dam plays a crucial role in managing water resources and preventing erosion in the area. The dam is equipped with spillways and outlet gates to regulate water flow and ensure safety during periods of high discharge. Although the dam has not been rated for its condition, its design and construction by USDA NRCS reflect a commitment to sustainable water management practices. For water resource and climate enthusiasts, Johnston Dam stands as an example of effective infrastructure for environmental conservation and management.