Department of Water Resources Home

Media Contacts:

Ted Thomas
Chief, Media & Public Information
Work: (916) 653-9712
Cell: (916) 798-1701

Elizabeth Scott
Information Officer
Work: (916) 653-9515
Cell: (916) 712-3904

Well Information

Groundwater Basics

WellAs a private well owner, it is important to recognize that you are responsible for ensuring the quantity and quality of your own water supply. A basic understanding of the nature and occurrence of groundwater, provided by materials found at the links below, can assist you in this quest.

DWR provides basic information on groundwater in this eight-page fact sheet.

The Groundwater Foundation web page provides basic information on groundwater hydrology and groundwater protection, as well as a useful glossary of terms.

Groundwater occurs throughout California, in a number of different geologic settings. Much of the State's groundwater occurs in large alluvial basins. DWR's Bulletin 118 provides locations and information on the State's major groundwater basins.

In rural areas, however, many well owners obtain their water supply from groundwater that occurs in fractured igneous, metamorphic, and sedimentary rocks. A DWR fact sheet provides information on the occurrence of groundwater in fractured rocks.

The depth of groundwater fluctuates in response to natural seasonal and long-term fluctuations in recharge, as well as to manmade variations caused by pumping. DWR collects water level data, generally semi-annually, from numerous wells to document these changes. Water level information for your area may be available at DWR's Groundwater Level Home Page. In order to best use this information, you should understand the State Well Numbering System.

Water Well Basics

Although some groundwater users may be served by springs, the vast majority of users are served by a water well. Proper construction, maintenance and destruction of water wells is necessary to not only provide a reliable water supply, but also to protect the groundwater resource. Section 231 of the California Water Code requires DWR to develop well standards to protect groundwater quality. Common questions on the well standards are answered in Water Facts, Number 5.

Most counties, and some cities have adopted ordinances to protect groundwater quality. These ordinances generally require permits to be issued before a well can be drilled or modified. You can find contact information for your local well permitting agency here.

When a well is constructed, modified or destroyed, the law requires that the drilling contractor submit a Well Completion Report to DWR. As the well owner, you should obtain a copy of this report from your drilling contractor.

If it becomes necessary for you to deepen your existing well, drill a new well, or destroy a well on your property, there are some important things to know. The California Business and Professions Code requires that, "No person shall undertake to dig, bore, or drill a water well, cathodic protection well, groundwater monitoring well, or geothermal heat exchange well, to deepen or reperforate such a well, or to abandon or destroy such a well, unless the person responsible for that construction, alteration, destruction, or abandonment possesses a C-57 Water Well Contractor's License." The California Contractors State License Board web page can be checked to find out whether a contractor is licensed and the status of a license, as well as providing information on hiring a contractor.

Water Quality

While the quantity of water may be a well owners primary concern, water quality should be an ongoing concern as well. Unlike public water supplies, there is no state or federal agency that ensures the quality of water from an individual domestic well. The American Groundwater Trust offers recommendations for well testing.Facet

You may collect a sample on your own, or you may wish to hire a professional to conduct the sampling for you. In any case, the analysis should be conducted by a laboratory certified by the California Department of Health Services, which provides a list of certified laboratories.

Once you have obtained analytical results from the laboratory, the standards that have been set for public water systems can be a useful reference for interpreting your own water quality. Maximum contaminant levels are set by the California Department of Health Services; there are national drinking water standards set by the U.S. EPA as well.

If you have a water quality problem with your well, it may be possible to treat the water to improve its quality. High bacterial concentrations may be controlled by disinfecting the well. High concentrations of inorganic and organic compounds may be treated with a number of devices. DHS offers a listing of certified treatment devices.

For More Information

If you need more information on groundwater, please visit the Groundwater web site.