Water Supply FAQs

Where does San Jose Water's supply come from?


This water is pumped from over 100 wells that draw water from the Santa Clara Groundwater Basin. Groundwater accounts for approximately 40% of our supply.

Imported surface water

Imported surface water is provided by the Santa Clara Valley Water District (SCVWD), our wholesale supplier. Surface water imported from the Sacramento-San Joaquin Delta and purchased from the Santa Clara Valley Water district accounts for approximately 50% of our supply. A majority of this water originates as Sierra snowmelt and travels through the state and federal water projects before treatment at SCVWD's three water treatment plants. A smaller portion is impounded in local reservoirs in Santa Clara County. More information about the imported water supply and treatment can be found on the SCVWD website.

Local mountain surface water

Collected on our watershed in the Santa Cruz Mountains, we treat it at our two water treatment plants. Local surface water accounts for approximately 10% of our supply.

What is the difference between groundwater and surface water?

Surface water comes from lakes and rivers while groundwater is pumped from wells. Wells extract water from underground layers of sand, gravel or porous rock called aquifers.

Groundwater generally has a higher mineral content than surface water but requires less treatment. To control bacteria, all surface water is filtered and disinfected with chlorine and/or chloramines at modern water treatment plants before it is distributed to customers. Groundwater pumped from our deep wells is largely free of bacteria. The wells require disinfection primarily to prevent the growth of bacteria in the pipes and tanks of our water distribution system. Both groundwater and surface water sources are of excellent quality and are regularly tested to ensure compliance with safe drinking water standards.

What type of water am I primarily receiving?

The San Jose Water service area and water supply sources map indicates only the predominant source of water in your area. Because these sources are often blended together in the distribution system, you may receive different sources from day to day as customer usage changes. If you need more specific information about your source of supply, please call us at (408) 279-7900.