Donath Lake, also known as Louden Reservoir, is a private water resource located in Larimer County, Colorado. Managed by the USDA NRCS, this reservoir serves multiple purposes including irrigation, recreation, and water supply. Built in 1883, the earth dam stands at a height of 26 feet with a hydraulic height of 23 feet, providing a storage capacity of 1148 acre-feet and covering a surface area of 85 acres.

Situated on the Big Thompson River, Donath Lake plays a crucial role in the local water management system. With a spillway width of 25 feet and a maximum discharge of 380 cubic feet per second, the dam has been classified with a significant hazard potential and a moderate risk assessment level. Despite its age, the dam structure remains in satisfactory condition, as indicated by the last inspection conducted in July 2019. With state regulation, permitting, and enforcement in place, Donath Lake continues to be a vital resource for the surrounding community.

For water resource and climate enthusiasts, Donath Lake offers a fascinating glimpse into the historical development of irrigation infrastructure in Colorado. As a privately owned reservoir with a long-standing presence in the landscape, it serves as a reminder of the intricate balance between human needs and environmental stewardship. With its varied uses and significant storage capacity, Donath Lake highlights the importance of sustainable water management practices in the face of changing climate conditions.