San Luis Obispo County Water Resources

Public Works Department


Los Osos Valley Groundwater Basin Non-Adjudicated "Fringe Areas"


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The Los Osos Valley Groundwater Basin, DWR Bulletin 118 Basin No. 3-08, is bounded on the north by Park Ridge, on the south by Irish Hills, on the west by Morro Bay, and on the east by a drainage divide separating Los Osos Valley from San Luis Valley. The Los Osos Basin, as defined by DWR, is located in San Luis Obispo County and covers 6,990 acres (10.9 square miles).


In 2015, the State legislature approved a new groundwater management law known as the Sustainable Groundwater Management Act (SGMA). SGMA requires that high and medium priority basins comply with the new law, with certain exceptions for listed adjudicated basins. DWR categorized the Los Osos Valley Groundwater Basin as a high priority basin and designated the basin to be in a “condition of critical overdraft”. SGMA does not apply to the portion of the Los Osos basin that is at issue in the litigation (“adjudicated area”) provided that certain requirements are met by the Los Osos Basin Management Committee. However, there are “fringe areas” outside of the adjudicated area, but within the State-determined basin boundaries that must comply with the new groundwater management requirements. These “fringe areas” are referred to as the Eastern Valley Area and the Southern Beach Area. The maps below show both the adjudicated areas exempt from SGMA, and the fringe areas that are subject to SGMA.



Interactive Map of Los Osos Basin

Welcome to the SGMA Interactive Data Viewer for the Los Osos Basin! This is an interactive mapping system to help you to navigate around the Los Osos Basin by panning, zooming, or searching for a specific parcel or street address. There are different map layers that can be shown and superimposed in this interactive mapping system such as boundaries of groundwater basins, cities, roads, SGMA eligible entities, and others by checking the layer names indicated on the left panel layer menu. To search and locate a specific APN or street address on the map:


1. Enter either the nine-digit parcel number (APN) including hyphens or the complete street address in the “Search...” bar on the upper right hand corner of the map screen and then click on the search button to locate it. The APN or street address that you just entered will appear on the left panel and a location marker will show up on the map to identify the location.

2. Click on the APN or street address name shown on the left panel layer menu will zoom in to the specified location for a close-up look


Click here to open the Interactive Map of Los Osos Groundwater Basin in a new window




Current News, Information, and Upcoming Meetings



The Los Osos Basin Fringe Areas – County of San Luis Obispo Groundwater Sustainability Agency (GSA) is submitting an initial notification to the California Department of Water Resources (DWR) of the GSA’s decision to explore boundary modification(s) for the Los Osos Valley Groundwater Basin (Bulletin 118 Basin No. 3-08; “Los Osos Basin”). A majority of the Los Osos Valley Groundwater Basin is subject to the adjudication stipulated in 2015; however, there are multiple “fringe areas” in the Los Osos Basin located outside of the adjudicated area. All three non-adjudicated “fringe areas” within the County of San Luis Obispo will be considered for the basin boundary modification request.


    County Public Workshop - SGMA and Basin Boundary Modification Request (BBMR)

    Wednesday, July 27, 2017


    Approval to explore basin boundary modification for the Los Osos Valley Groundwater Basin

    Tuesday, March 6, 2018


    Los Osos Basin “Fringe Areas” – Public Workshop

    Monday, March 26, 2018


    County Board of Supervisors Hearing

    Tuesday June, 5 2018


    The County provides updates on SGMA and BBMR at the Los Osos Basin Management Committee (BMC) meetings, please visit the BMC

    website here for additional meeting information.


For the DWR public process regarding the basin boundary modification, please visit the DWR Basin Boundary Modifications website here.


Commenting Process:

Please click here to view information regarding the County/State public commenting process.


Upcoming Meeting:



More Information

For more information on the Sustainable Groundwater Management Act, please visit the County SGMA website.



How to Get Involved?

  • Check back to see current news, information, and upcoming meetings.
  • Attend upcoming meetings.
  • Sign up for the SGMA Mailing List here.
  • Contact Information:
    • County - Cathy Martin

      (805) 781-5275


Los Osos Valley Groundwater Basin Documents and Reports


Los Osos Valley Groundwater Basin Fringe Areas Characterization


Los Osos Basin BBMR


Please send all written comments to Cathy Martin, Water Resources Engineer, at The comment period will end April 10, 2018


SGMA Mailing List

Please select from the following list(s):


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