Anderson Reservoir

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Coordinates: 37°9.9′N 121°37.8′W / 37.1650°N 121.6300°W / 37.1650; -121.6300
Anderson Reservoir
Anderson reservoir, California.jpg
Country United States
State California
County Santa Clara
District Santa Clara Valley Water District
City Morgan Hill, California
River Coyote Creek
Coordinates 37°9.9′N 121°37.8′W / 37.1650°N 121.6300°W / 37.1650; -121.6300

Anderson Reservoir is a man-made lake along Coyote Creek in Santa Clara County, California, near Morgan Hill.[1] Anderson Dam was built in 1950 to provide drinking water for Santa Clara county; the lake has also become a source of recreation to nearby residents.[2] Anderson Reservoir is the largest man-made lake in Santa Clara County. It is sometimes called Anderson Lake.[3]

A 3,144-acre county park surrounds the reservoir,[4] and provides fishing[5] ("catch-and-release"), picnicking, and hiking activities. Boating, water-skiing and jet-skiing are permitted in the reservoir.

Risk of dam failure[edit]

The 235-foot high earthen Leroy Anderson Dam sits on Cochrane Road, east of Morgan Hill, and along the Calaveras Fault, which runs from Hollister to Milpitas. It holds 90,000 acre feet (110,000,000 m3) of water when full: more than the other nine reservoirs in the county combined.

In January, 2009, a preliminary routine seismic study suggested a small chance that a high-magnitude earthquake (6.6 with the dam at the epicenter, or 7.2 up to a mile away) could result in flooding in Morgan Hill and up to as far away as San Jose. In response, the Santa Clara Valley Water District (SCVWD) lowered the water level to 74% capacity and announced further analysis of the situation, which could possibly result in retrofitting the dam if necessary.[6] Updated findings in October, 2010 indicated that the dam could fail if a magnitude 7.25 earthquake occurred within 2 kilometers of the dam, potentially releasing a wall of water 35 feet high into downtown Morgan Hill in 14 minutes, and 8 feet deep into San Jose within three hours.[7] In response SCVWD has lowered the water to 54% full, which is 60 feet below the dam crest.[8]

In July 2011 the Santa Clara Valley Water District issued a report stating that the seismic stability study on Anderson Dam was completed. The storage restriction that has been in place since October 2010 was adjusted, allowing 12 additional feet of storage which measures 68 percent of the dam's capacity, up from 57 percent. The water district has initiated a capital project for a seismic retrofit by the end of 2018. The operating restriction will remain in place until the project is completed.[9] According to the SCVWD, remediation of the problem will cost as much as $100 million.[7]

See also[edit]


  1. ^ Santa Clara Valley Water District. "Anderson Reservoir". Retrieved 2009-01-06. 
  2. ^ Santa Clara Valley Water District (2009-01-05). "Frequently Asked Questions: Anderson Reservoir". Retrieved 2009-01-06. 
  3. ^ U.S. Geological Survey Geographic Names Information System: Anderson Lake
  4. ^ Santa Clara County Parks: Anderson Lake
  5. ^ Santa Clara County Parks: Fishing Guidelines
  6. ^ Rogers, Paul (January 5, 2009). "New study shows massive earthquake could cause Anderson Dam to fail". San Jose Mercury News. 
  7. ^ a b Sandra Gonzales (2010-10-13). "Study: Santa Clara County's Anderson Dam at risk of collapse in major earthquake". San Jose Mercury News. Retrieved 2010-10-29. 
  8. ^ Marty Grimes (2010-10-13). Preliminary findings indicate Anderson Dam needs seismic retrofit (Report). Santa Clara Valley Water District. Archived from the original on 12 November 2010. Retrieved 2010-10-29.
  9. ^ Marty Grimes (2011-07-06). Final Anderson Dam seismic study concludes that storage restrictions can be modified but dam must be retrofitted (Report). Santa Clara Valley Water District. Retrieved 2011-07-26.