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Water Supply


AMWC obtains all of its water from two distinct yet interrelated groundwater sources - the Salinas River Underflow and the Atascadero  Groundwater Basin. Water from these sources resides in the tiny spaces between sands and gravels until it is pumped to the surface by AMWC's wells. These sands and gravels act as natural filters, resulting in water that is clean and clear. Shallow wells (70' - 100') pump water from the Salinas River Underflow, while deeper wells (300' - 500') pump from the Atascadero Groundwater Basin. 

Diagram of goundwater geology

Private Wells


In 1913, AMWC was deeded all water rights within its service area to hold in trust for its shareholders. As trustee, AMWC has the authority and responsibility to manage these groundwater resources. AMWC has a policy that restricts the drilling and use of private wells within its service area. AMWC's intent is to protect the groundwater resources of the shareholders and provide for the equitable distribution of these resources. AMWC allows the drilling and use of some private wells in those areas where the wells are not likely to have significant impacts on the groundwater resources of AMWC. AMWC prohibits the drilling and use of new wells in areas that overlie the Atascadero Sub-basin, the alluvial deposits of the Salinas River, or other areas that could significantly impact the quantity, quality, or recharge of groundwater.

Refer to Board Policy

Nacimiento Water Project


The Nacimiento Water Project (NWP) regional raw water transmission facility delivers water from Lake Nacimiento to communities in San Luis Obispo County. The NWP includes 45 miles of pipeline ranging from 12 inches to 36 inches in diameter, an intake structure at Nacimiento Lake, three pump stations ranging from 1,200 horsepower (hp) to 3,500 hp, and three water storage tanks ranging from 300,000 gallons to 850,000 gallons. The NWP is designed to deliver 15,750 acre-feet of water per year (AFY). Atascadero Mutual Water Company (AMWC) has contracted for 2,000 AFY, which will significantly improve its ability to meet the current and future water needs of its shareholders. One acre-foot of water is approximately 326,000 gallons. The County of San Luis Obispo was the lead agency for the $176.1 million NWP. In 2004, AMWC entered into a Delivery Entitlement Contract with the County for participation in the project, with AMWC’s share of the project costs being approximately $39 million to be paid over 30 years. Other agencies currently participating in the project are the City of Paso Robles, Templeton Community Services District, and the City of San Luis Obispo. The project has already had a large effect on connection fees and water rates paid by AMWC’s shareholders. Construction on the project is complete, and AMWC began taking deliveries of water in the summer of 2012.

The NWP is owned, managed, and operated by San Luis Obispo Flood Control and Water Conservation District. For more information, visit 

Urban Water Management Plan

A Conservation Plan for Our Finite Water Resources

AMWC looks ahead to efficiently plan for your future water supply. The 2015 Urban Water Management Plan (draft) provides an overview of water supply sources, conservation measures, programs, and incentives to ensure the wise and beneficial use of your water resources.

For further questions about the plan, which is updated every five years as part of the California Water Code, please contact

2020 Urban Water Management Plan [pdf]

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