Deep Creek No 1, also known as Deep Creek Lower Reservoir, is a privately owned water resource located in Twin Falls, Idaho. This dam was completed in 1911 and serves the primary purpose of storing water for various other uses. Constructed with an earth core and stone foundation, the dam stands at a height of 17.6 feet with a hydraulic height of 13.4 feet. With a storage capacity of 88 acre-feet and a surface area of 19 acres, this reservoir plays a crucial role in supporting the local water supply and ecosystem.

Managed by the Idaho Department of Water Resources, Deep Creek No 1 is regulated, permitted, and inspected to ensure its safety and functionality. The dam has a low hazard potential and is rated in fair condition as of the last assessment in 2019. Its spillway type is uncontrolled, with a width of 6 feet, and it has other controlled outlet gates. Despite its age, the dam continues to meet modern regulatory standards, and measures are in place for risk management and emergency response. Positioned within the Deep Creek Sinks watershed, this reservoir contributes to the overall water management strategy in the region.

Deep Creek No 1 serves as a vital infrastructure for water storage and management in the area, with a moderate risk assessment rating. The dam's association with the Sacramento District of the US Army Corps of Engineers highlights its importance for water resource management at the federal level. With a history dating back over a century, this reservoir remains a key component of the local water supply network and plays a critical role in supporting the surrounding environment and community. As climate change continues to impact water resources, the maintenance and regulation of structures like Deep Creek No 1 will be essential for ensuring water security and resilience in the face of evolving climatic conditions.