Cottonwood Lake

About Cottonwood Lake

The primary purpose of Cottonwood Lake is grade stabilization. Grade stabilization dams prevent erosion by reducing the slope and velocity of water flowing through a channel. They're commonly used to stop gullies from deepening and to protect downstream land and infrastructure. The dam is owned by County Of Lyon (private). It impounds the Yellow Medicine River-tr near Hanley Falls.

The dam stands 9 feet tall, creates a reservoir covering 378 acres, has a maximum storage capacity of 3,582 acre-feet, and collects water from a drainage area of 20 square miles. Completed in 1960, the structure is well into its service life at over 50 years old.

This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. The most recent inspection on record was 11/14/2018.

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