Upper Twin Lake in Napa, California, is a privately owned dam with a primary purpose of water supply. Constructed in 1987, this earth dam stands at a height of 19 feet and has a hydraulic height of 15 feet. The reservoir has a storage capacity of 63 acre-feet and covers an area of 6 acres. While the dam is regulated and inspected by the state, it has a low hazard potential and is currently in fair condition.

The dam on Upper Twin Lake serves multiple purposes including irrigation, recreation, and of course, water supply. Located on Tr Pope Creek, this dam plays a crucial role in managing water resources in the area. The surrounding environment benefits from the reservoir's presence, providing a habitat for various wildlife and recreational opportunities for visitors.

With its picturesque location and vital role in water management, Upper Twin Lake is a fascinating site for water resource and climate enthusiasts. Its low hazard potential and fair condition make it a reliable and essential infrastructure for the community. As efforts to manage water resources become increasingly important in the face of climate change, the role of dams like Upper Twin Lake will continue to be significant in ensuring water security for the region.