Almaden Dam and Reservoir

Almaden Reservoir is one of Santa Clara County's six original reservoirs, built in 1935, and is one of 10 current reservoirs operated by the Santa Clara Valley Water District. Able to store 1,590-acre feet of water, the reservoir, located 12 mile south of San Jose, produces about 4 percent of the district's local water supply and also provides water for groundwater recharge.

Its accompanying earth fill dam stands 110-feet tall with a crest of about 500-feet. Subject to safety regulations by the State Division of Safety and Dams (DSOD), Almaden Dam is currently considered a high-hazard dam due to the number of people who live in the potential flood zone downstream and the extensive amount of damage that a flood could cause in case of a dam breach.

The seismic project

In 2000, the water district launched the Almaden Dam Improvements Project to address sediment accumulation at the dam's intake structure and correct aging outlet works infrastructure. In 2005, a seismic stability evaluation for the dam halted the planning phase and while the findings in 2012 indicated the embankment is stable, the dam will still require work to ensure its long term reliability. The project, currently in design phase, will:

• Modify or construct a new intake structure to meet DSOD regulatory standards.
• Reconfigure the spillway as the result of potential findings from the reservoir's future probable maximum flood investigation.
• Correct ongoing operation and maintenance issues to aging hydraulic lines, valves and energy dissipaters.

In 2016, Valley Water's Board of Directors approved a consultant amendment to perform improvements to the Almaden-Calero Canal in addition to the already approved consultant agreement for improvements at the Almaden Dam. However, project improvements are on hold until Valley Water completes improvements at the Anderson, Calero and Guadalupe dams. 

For more information, contact Public Information Representative Tony Mercado at 408-630-2342 or at [email protected]. 

Inundation maps
Inundation Map of Hypothetical Fair Weather Failure of Almaden Dam (2019) (Weather Failure index map)
Inundation Map of Hypothetical Inflow Design Flood Failure of Almaden Dam (2019) (Flood Failure index map)