Well Inventory Database

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DPR maintains the well inventory database (WIDB) of wells sampled for pesticides by DPR and other agencies. In an effort to make water quality data more easily accessible, the database is available online. This database includes information about the well, the study name, the sampling agency, sample date, analysis date, analyzing laboratory, chemical analyzed, concentration reported, reporting limit, analytical method notes, legal agricultural use determination (point or non-point source determination), and the year the record was included in the database. Testing done for other water parameters (i.e. pH, salt, calcium) is not included in the database. There are over two million records in the database.

For well owner confidentiality, this database does not include the exact well location or the owners name and address; the location of each well is randomized within a public lands survey system section. The WIDB data and well locations are listed by county, the county-meridian-township-range and section (CMTRS), the unique well key assigned to all wells in the WIDB, and a randomized latitude and longitude based on the CMTRS of the well.

WIDB data separated by county in CSV file format from August 1977 to December 31, 2019.

Alameda Alpine Amador Butte Calaveras
Colusa Contra Costa Del Norte El Dorado Fresno
Glenn Humboldt Imperial Inyo Kern
Kings Lake Lassen Los Angeles Madera
Marin Mariposa Mendocino Merced Modoc
Mono Monterey Napa Nevada Orange
Placer Plumas Riverside Sacramento San Benito
San Bernardino San Diego San Francisco San Joaquin San Luis Obispo
San Mateo Santa Barbara Santa Clara Santa Cruz Shasta
Sierra Siskiyou Solano Sonoma Stanislaus
Sutter Tehama Trinity Tulare Tuolumne
Ventura Yolo Yuba    

Note about excluded data

Some records in the database are questionable and were excluded due to the following:

  • 1. Point Source Contamination due to pesticide spills near the wellhead, missing backflow protection devices, poor well construction, or monitoring wells surrounding pesticide application test-plot fields.
  • 2. Probable Laboratory/Sampling Agency reporting errors where DPR was unable to confirm or deny the validity of data submitted from outside agencies.

This affected 1,018 reported detections and the excluded data are available on request.

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