What is an artesian well?

An artesian well may sound like a fancy place to get your water, but it’s really nothing more than a well tapping groundwater that is under pressure. In some artesian wells, the pressure is high enough that a pump isn’t needed to bring water to the surface. These wells are known as flowing artesian wells.

Artesian wells occur naturally over large areas of the Santa Clara Valley, and flowing artesian wells have been observed since the 1850s. When pressures in groundwater aquifers are high, old lost wells may begin flowing freely at the land surface. This wastes water and can create nuisance conditions. Recent wet winters and low groundwater pumping are causing higher pressures in artesian aquifers. This is causing more old wells to start flowing and leading to more frequent discoveries of old abandoned wells.

Whether they are flowing or not, the problem with abandoned wells is they can provide a way for contaminants to move into groundwater or between groundwater aquifers. That’s why they’re not allowed by state law or Valley Water ordinance.

Groundwater is a key source of water for Santa Clara County – our groundwater basins can hold more water than all 10 of our surface water reservoirs combined – and Valley Water works hard to protect the quality of this water that is so important to life in our county.

All wells that are no longer in use must be properly destroyed to avoid groundwater contamination. Artesian wells are the responsibility of the property owner where the well is found.

If you see a lot of water on the ground, how do you know if it’s coming from an artesian well?

Things to look for:

  • Water at the land surface with no known source: it’s not leaking from pipes; it’s not from shallow groundwater (usually found in low spots on freeways, during excavation or in basements, etc.); and it’s not from a spring (typically found on or at the base of a hill slope);
  • There may be bubbles in the water;
  • You actually see water emanating from a well.

If you suspect an artesian or abandoned well on your property or elsewhere, contact your water provider first to rule out leaking pipelines. If it’s truly an abandoned well, Valley Water can help guide you in taking the steps necessary to get the well properly destroyed and help us protect the groundwater basin.

For more information, please contact Valley Water’s Well Ordinance Program at (408) 630-2660.


  1. Thank you for explaining that all wells that are no longer in service must be correctly destroyed to prevent groundwater contamination. The old in my grandparent’s house is no longer working, but they want to have it checked to see if there’s a way to fix it. I better advise them to hire an expert well drilling service near their place to provide them with options applicable for their well.


  2. Thanks for helping me understand that groundwater would usually be filled with more than ten surface water reservoirs can have. I guess that kind of source would be a good option for us if it is possible on the piece of land we moved into. We definitely need to have another source to save money in the long run, and we also need to have pump repair services once we have that kind of equipment to provide our needs to ensure that it will work in the long run.


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