Mukwonago, also known as Phantom Lake, is a gravity dam located in Waukesha, Wisconsin, owned and regulated by the local government. Completed in 1848, this dam primarily serves as a recreational area for water enthusiasts in the region. With a height of 10 feet and a length of 250 feet, the dam has a storage capacity of 2,740 acre-feet and covers a surface area of 540 acres, with a drainage area of 60 acres.

The dam is equipped with a controlled spillway and has a maximum discharge rate of 1,270 cubic feet per second. Despite its age, the dam has been assessed as being in satisfactory condition with a low hazard potential. However, a very high risk assessment rating of 1 indicates potential vulnerabilities that may require further risk management measures. The dam has regular state inspections and enforcement measures in place to ensure its safety and functionality for both recreational use and water resource management in the area.

Overall, Mukwonago serves as a vital water resource for the community, offering opportunities for recreation while also highlighting the importance of proper dam maintenance and risk assessment in the face of changing climate conditions. As a historic structure with a rich history dating back to the 19th century, this dam stands as a testament to the intersection of water resource management and climate resilience in the region.