Lake Isabelle, located in Boulder, Colorado, is a privately owned reservoir with a primary purpose of irrigation. Built in 1925, this rockfill dam stands at a height of 38 feet and has a storage capacity of 738 acre-feet. The reservoir covers an area of 36 acres and is fed by the S F St Vrain Creek.

Despite its age, Lake Isabelle has a low hazard potential and its condition is currently not rated. The last inspection of the dam was conducted in 1990, but there have been no recent assessments. The risk assessment for the dam is classified as high, with a risk level of 2, although specific risk management measures are not detailed in the data provided.

Overall, Lake Isabelle serves as a vital water resource for irrigation purposes in the region, with a significant storage capacity and a history dating back to the early 20th century. Climate and water resource enthusiasts may find this reservoir intriguing due to its historical significance and role in supporting agricultural activities in the area.