Lake Hennessey is a freshwater reservoir located in the Napa Valley of California. The lake was named after one of the first settlers in the area, Charles Hennessey. The primary source of the lake's water is the Conn Creek watershed. The lake also receives water from the Rector Creek and Milliken Reservoir. The lake is managed by the Napa County Flood Control and Water Conservation District. The lake's water is used for agricultural purposes, including vineyards and orchards in the Napa Valley. The lake is also used for recreational activities such as fishing and boating. The lake's depth, size, and water quality make it an ideal location for water sports and fishing. The lake's hydrology is characterized by a surface flow and snowpack providers. The surface flow is a result of rainfall and snowmelt, while the snowpack providers are the Sierra Nevada Mountains.