Lake Hennessey

Lake Hennessey
Location of the reservoir in California, USA.
Location of the reservoir in California, USA.
Lake Hennessey
Location of the reservoir in California, USA.
Location of the reservoir in California, USA.
Lake Hennessey
LocationVaca Mountains,
Napa County, California
Coordinates38°28′52″N 122°22′24″W / 38.48111°N 122.37333°W / 38.48111; -122.37333[1]
TypeReservoir
Primary inflowsSage Creek, Chiles Creek, Moore Creek, Conn Creek
Primary outflowsConn Creek[2]
Catchment area54 sq mi (140 km2)[2]
Basin countriesUnited States
Max. length2 mi (3.2 km)
Max. width3,500 ft (1,100 m)
Surface area790 acres (320 ha)[2]
Water volume31,000 acre-feet (38,000,000 m3)[2]
Surface elevation322 feet (98 m)[1]

Lake Hennessey is a reservoir in the Vaca Mountains, east of St. Helena and the Napa Valley, within Napa County, California.

The reservoir is formed by Conn Creek Dam, built in 1948 (76 years ago) (1948) across Conn Creek. Construction of the earthen dam was authorized by the United States Congress when it passed the Flood Control Act of 1944 in order to mitigate flooding downstream in Napa, California.[3]

Funding for the dam was never appropriated by Congress, so in 1946 the City of Napa took on the project and built it at a cost of $550,000 plus $250,000 for the land. The cost of laying the 36 inches (910 mm) diameter pipeline from the dam to the city of Napa was $1.7 million. The 30 miles of pipe for the project was manufactured at the Basalt Rock Company plant located south of Napa.[4] The design of the dam did not include a way to drain water from the reservoir when it comes close to full capacity. Once the lake is full, water drains from a spillway causing potential flooding dangers downstream.[5] The reservoir and pipelines are maintained by the city of Napa, and it is its primary source of water. When the reservoir reaches its capacity, outflow reaches San Pablo Bay via Conn Creek to the Napa River.[6] The lake was named after Edwin R. Hennessey. Hennessey was a local civic leader who played a role in the development of the Conn Valley reservoir.[7]

  1. ^ a b U.S. Geological Survey Geographic Names Information System: Lake Hennessey
  2. ^ a b c d Cite error: The named reference DWR was invoked but never defined (see the help page).
  3. ^ http://www.countyofnapa.org/Pages/DepartmentContent.aspx?id=4294968277 County of Napa Flood Control District
  4. ^ Courtney, Kevin (October 17, 2004). "Napa Pipe plant loads its final rail car". Napa Valley Register. Napa, CA: Lee Enterprises, Inc. Retrieved September 24, 2011.
  5. ^ Goetting, Jay (January 28, 2006). "Lake Hennessey adds to flood flows, but officials say changes to Conn Dam unlikely, unhelpful". Napa Valley Register. Retrieved October 17, 2010.
  6. ^ http://www.napanow.com/chronhist.html/Napa Napa Now
  7. ^ Brennen, Nancy (October 17, 2010). "Examining the life of one of Napa's founding physicians". Napa Valley Register. Retrieved October 17, 2010.