page_title: Lake Berryessa
section_title: Geography
hierarchical_section_title: Lake Berryessa / Geography
caption_attribution_description: Monticello Dam spillway, Lake Berryessa
context_page_description: Lake Berryessa is the largest lake in Napa County, California. This reservoir in the Vaca Mountains was formed following the construction of the Monticello Dam on Putah Creek in the 1950s. Since the early 1960s, this reservoir has provided water and hydroelectricity to the North Bay region of the San Francisco Bay Area.
  The reservoir was named after the first European settlers in the Berryessa Valley, José Jesús and Sexto "Sisto" Berrelleza, who were granted Rancho Las Putas in 1843.
context_section_description: The lake is over 20,000 acres (80 km²) when full. It is approximately 25 km (15.5 miles) long and 5 km (3 miles) wide. It has approximately 265 km (165 miles) of shoreline.
  Near the dam on the southeast side of the reservoir is an open bell-mouth spillway, 72 feet (22 m) in diameter, which is known as the Glory Hole. The pipe has a straight drop of 200 feet (61 m), and the diameter shrinks down to about 28 feet (8.5 m). The spillway has a maximum capacity of 48,000 cfs (1360 m³/s). The spillway operates when there is excess water in the reservoir; in 2017 after heavy rains it started flowing, for the first time since 2006. It started flowing again in 2019 after heavy rains. In 1997 a woman was killed after being pulled inside the spillway.
caption: The spillway at Monticello Dam, Lake Berryessa, in operation, February 19, 2017
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