Supply Stewardship

Water Delivery System

The San Gabriel Valley Municipal Water District delivery system is the Devil Canyon-Azusa pipeline, which was constructed in 1972 to deliver water from the State Water Project to the Main San Gabriel Basin. The pipeline (highlighted in red on the map below) is about 38 miles long and runs west from the Devil Canyon Power Plant in the San Bernardino Mountains to the San Gabriel Canyon Spreading Grounds in Azusa.

The pipeline is gravity fed and has three pressure reducing stations in Glendora, La Verne, and Fontana to control the speed of water. The diameter of the pipeline ranges from 30 inches to more than 4 feet around, starting at Devil Canyon. The pipeline’s capacity is 55cfs (cubic feet per second) which is the equivalent of 27,450 gallons per minute. In the map below, the red line represents the approximate route of the pipeline.

The system allows the District to provide reliable supplemental water for the communities of Alhambra, Azusa, Monterey Park, and Sierra Madre.

Main San Gabriel Basin

The Main San Gabriel Basin is a large groundwater basin replenished by stream runoff from the adjacent mountains and hills, by rainfall directly on the surface of the valley floor, subsurface inflow from the Raymond and Puente basins, and irrigation runoff. The illustration below simulates how water is fed, captured and stored below ground. Imported water from the State Water Project is also used to replenish the Main Basin, which serves as a natural storage reservoir. The surface area of the Basin is about 167 square miles and the freshwater storage capacity is estimated to be about 8.6 million acre-feet.

In addition to SGVMWD, two other municipal wholesale water districts import water to the Basin and are responsible for providing replacement water for overproduction: Upper San Gabriel Valley Municipal Water District (Upper District), and Three Valleys Municipal Water District (TVMWD).

The Main San Gabriel Basin Watermaster, a nine-person board appointed by the Los Angeles County Superior Court, administers and enforces the provisions of court judgments which established water rights and the responsibility for efficient management of the quantity and quality of the Basin’s ground water. The watermaster is charged with:

  • Managing and controlling withdrawals and replenishment;
  • Determining the annual operating safe yield;
  • Raising replenishment revenue through assessments;
  • Acquiring and spreading untreated imported water for groundwater replenishment;
  • Coordinating efforts to preserve and restore the quality of the basin’s groundwater;
  • Assisting with enforcement of water quality regulations in the basin;
  • Collecting data from agencies on production, water quality, etc.;
  • Preparing an annual report.

Dams & Reservoirs

In the San Gabriel Valley, the Los Angeles County Department of Public Works operates an extensive system of dams, debris basins, reservoirs and flood control channels not only to protect San Gabriel Valley residents from flooding, but they also act as water conservation facilities, trapping runoff and allowing it to slowly seep into the groundwater basin.

The dams and reservoirs that control the flow of the San Gabriel River and the Rio Hondo include:

A. Cogswell Reservoir on the west fork of the San Gabriel River;

B. San Gabriel Reservoir at the confluence of the west and east forks of the San Gabriel River;

C. Morris Reservoir near the mouth of the San Gabriel Canyon;

Spreading Grounds

Imported water for groundwater replenishment is delivered through flood control channels and diverted into spreading grounds through Main Basin Watermaster’s agreement with the Los Angeles County Department of Public Works (DPW). Water from SGVMWD’s pipeline is delivered to the spreading grounds where it percolates to recharge the San Gabriel Basin. This water can be pumped and used at a later time.

Baldwin Park Key Well

The Baldwin Park Key Well is located in the central portion of the San Gabriel Valley within the City of Baldwin Park and is a widely accepted indicator of water elevations throughout the Main San Gabriel Basin. Groundwater levels have dipped considerably since 2011. For information on local water supply conditions and key well levels, visit


San Gabriel Canyon Spreading Grounds in Azusa


State Water Project Map

State Water Project

The San Gabriel Valley Municipal Water District is one of 29 local water agencies that hold long-term contracts with the California Department of Water Resources for supplies from the State Water Project (SWP). The District uses the water to replenish groundwater in the San Gabriel Valley for future use. In return, SGVMWD and other State Water Project Contractors help pay for the bond used to construct the SWP, as well as its operation and maintenance.

The SWP moves water from Lake Oroville in Northern California and through the Sacramento-San Joaquin Delta to Southern California, supporting millions of residents, businesses and farms. The District entered into a contract with DWR in 1962 for the delivery of 25,000 acre-feet of water per year from the State Water Project (SWP). In 1964, the contract was amended to allow for 28,800 acre-feet. The actual allocations each year for contractors depend on supply conditions such as rainfall, snowpack, and the amount of water in storage, as well as operational constraints for fish and wildlife protection, water quality, and environmental and legal restrictions.

The long-term sustainability of imported water deliveries has been a concern for many years in California, with a variety of proposals to achieve dual goals of water sustainability and preservation of the delicate Sacramento-San Joaquin Delta eco-system. The Department of Water Resources (DWR) supports the Delta Conveyance Project, which would build a tunnel under the Delta to improve supply reliability. In November 2020, the SGVMWD Board approved the use of $2.68 million to assist with environmental planning for the Delta Conveyance Project.


Left: Sacramento-San Joaquin River Delta | Right: California Aqueduct

State Water Contractors

SGVMWD is a member of the State Water Contractors (SWC), an association of public water agencies working together to protect the environment and public health and promote water conservation and water use efficiency.

By promoting reliable State Water Project supplies, the SWC is committed to:

  • Promoting science-based decision making
  • Promoting sound fiscal management of the SWP
  • Maintaining the operational integrity of the SWP
  • Assuring an affordable and reliable electrical supply for the SWP

SWC invests more than $2 million annually to implement a science and research program, collaborating with its partners in academia, government, non-profit and the private sectors on research and programs that will spur future policymaking and improved water management practices throughout California.

Urban Water Management Plan

 2020 Urban Water Management Plan

The Urban Water Management Planning Act requires every “urban water supplier[1]” to prepare and adopt an Urban Water Management Plan (UWMP) and Water Shortage Contingency Plan (WSCP) every five years. The UWMP is a planning document and a source document to direct urban water suppliers to evaluate and compare their water supply and reliability to their existing water conservation efforts.

On June 24, 2021 the final 2020 Urban Water Management Plan was adopted by the Board of Directors of the San Gabriel Valley Municipal Water District.

[1] Section 10617 of the Urban Water Management Planning Act states, “Urban Water Supplier” means a supplier, either publicly or privately owned, providing water for municipal purposes either directly or indirectly to more than 3,000 customers or supplying more than 3,000 acre-feet of water annually.

Sustainability Solutions

SGVMWD is dedicated to the protection of natural resources and sustainable operations. As part of our sustainability efforts, we use water moving through the system to generate clean energy.

The District’s hydroelectric power plant in San Dimas is located along our Devil Canyon-Azusa Pipeline, which delivers water from the State Water Project to the Main San Gabriel Basin. Built in 1985 as part of the District’s green energy initiative, a turbine generator is powered by water flowing in the pipeline. The 1.05-megawatt generator has the capacity to produce enough electricity for approximately 500 homes each year. The revenue the Water District receives through energy sales helps to offset operating costs and stabilizes rates for our customers.