A key resource that Los Angeles has relied upon to balance its imported water supply portfolio is local groundwater. Over the last five years local groundwater has provided approximately 12% of the total water supply for Los Angeles, and historically has provided up to 23% of the city’s total supply in drought years. In recent years, contamination issues have impacted the LADWP’s ability to fully utilize its groundwater entitlements. In response to contamination issues and declining groundwater levels, the LADWP has proactively cooperated with other agencies to improve the overall health of our groundwater basins.

    The City of Los Angeles owns water rights in the San Fernando, Sylmar, Eagle Rock, Central, and West Coast Basins. Combined, these water rights total approximately 109,809 acre-feet per year (AFY). An acre-foot of water is the amount of water that would cover an acre of land one-foot deep or approximately one-third of a million gallons. Water rights in the Upper Los Angeles River Area (ULARA) which comprises of San Fernando, Eagle Rock and Sylmar basins total approximately 91,000 AFY. Water rights in the Central and West Coast Basin are 17,236 AFY and 1,503 AFY, respectively. Additionally, the LADWP may have the right to recapture a portion of the water returned to the Verdugo Basin as a result of imported water being utilized in that basin. However, the LADWP has never attempted to exercise this right. Neither does the LADWP exercise its pumping rights in the West Coast Basin at this time due to deterioration of wells and localized water quality issues. The chart below summarizes the city’s annual local groundwater entitlements by basin.

    Graphic depicting total annual groundwater entitlement: 500 acre feet (AF) for Eagle Rock, 1503 AF for West Coast, 3570 AF for Sylmar, 17,236 AF for Central, and 87,000 AF for San Fernando.
    Total : 109,809 AFY. AFY = Acre Feet per Year.

    LADWP optimizes groundwater production from the basins by utilizing conjunctive use. Conjunctive use of surface water and groundwater consists of combining the use of both resources to optimize the water supply/demand balance, thereby improving the overall availability and reliability of water. The timing of groundwater extractions can be used to meet varying demands, and surface water can be stored in groundwater basins during normal and wet years for extraction in dry years. Conjunctive use of Los Angeles’s local groundwater supplies and imported water supplies from the Los Angeles Aqueduct and/or Metropolitan Water District (MWD) is used each year by pumping annual groundwater entitlements from April to October when the highest water-demand occurs.

    Additionally, the LADWP stores imported water during wet and normal years so groundwater production can be increased during dry years. However, recent multiple years of below normal precipitation and groundwater contamination have limited the amount of recharge occurring and the LADWP’s ability to pump.

    Furthermore, conjunctive use enables the LADWP to purchase and store in-lieu MWD replenishment supplies at a reduced unit cost, when available. While providing a cost benefit, this in-lieu storage of groundwater allows the groundwater basins to be recharged by reducing the pumping duration within the basins.

    Groundwater Production

    On average, about 89% of the City’s groundwater supply was extracted from ULARA groundwater basins, while the Central Basin provided 11%. No production has occurred in the West Coast Basin since 1980.

    ULARA – San Fernando, Sylmar, Eagle Rock Basins

    LADWP has eight major well fields within the SFB containing 115 wells. These include the Tujunga, Rinaldi-Toluca, North Hollywood West Branch, North Hollywood East Branch, Erwin, Verdugo, Whitnall, and Pollock Well Fields. These wells were generally installed over a period spanning from 1924 to 1991, with the most recent installations being the Rinaldi-Toluca Well Field in 1988, and the Tujunga Well Field in 1991. Currently, Sylmar Basin has two wells in operation and Eagle Rock Basin has no groundwater production even though the LADWP has the right to extract the safe yield from the basin. Groundwater monitoring wells are being installed in the Sylmar Basin to evaluate the condition of groundwater in the area.

    Groundwater Monitoring Wells Installation at El Dorado Avenue
    Groundwater Production Wells Installation in Sylmar

    Central & West Coast Basins

    Two LADWP facilities provide groundwater supplies in the Central Basin: the Manhattan Wells and the 99th Street Wells. The active Manhattan Wells were installed between 1928 and 1974, and have a production capacity of 7 cubic feet per second (cfs). Wells at the 99th Street location were installed between 1974 and 2002, and have a production capacity of  6.1cfs. Both Central Basin wellfields are being rehabilitated in an effort to maximize their production capacity. LADWP has not been able to pump its water entitlement from the West Coast Basin for many years due to localized groundwater contamination issues and deterioration of the wells at the Lomita Wellfield.

    Groundwater Production Well Installation at Manhattan Well Field

    Groundwater Management

    LADWP’s Groundwater Management Program will be gradually increasing its capital investments, primarily focusing on projects that increase groundwater recharge and well production as well as improve groundwater quality in the SFB. The LADWP is investigating opportunities for increased storage of groundwater in the local basins to create a cost-effective, environmentally-friendly reserve of water resources in cases of extreme drought or other emergencies.

    Water quality issues have reduced our available groundwater supply requiring the LADWP to expedite studies and projects to restore lost groundwater production. While the LADWP has experienced groundwater quality challenges, the groundwater management efforts that the LADWP has undertaken have resulted in all groundwater delivered to customers meeting or exceeding all water quality regulations. As part of its regulatory compliance efforts, the LADWP works with the California Department of Public Health (CDPH) to perform water quality testing on production and monitoring wells. More information on groundwater remediation.

    LADWP conducts nearly 250,000 field and laboratory tests on more than 25,000 samples collected throughout the year for hundreds of different chemicals such as arsenic, chromium, lead, and disinfection by-products to ensure that all water sources are well within safe levels before we serve the water to our customers.

    Every well that is pumped to supply water to the City of Los Angeles is actively monitored by the LADWP as required by CDPH. LADWP’s groundwater monitoring program is comprised of several distinct components, including:

    • Monitoring of general minerals annually;
    • Monitoring of metals, coliform bacteria, inorganics, volatile organic compounds (VOCs) and unregulated compounds such as vanadium, and boron annually, quarterly, or monthly, depending on the level of contamination found in each well;
    • Monitoring of radiological and synthetic organic compounds (SOCs) every three years; and
    • Monitoring of asbestos every nine years.

    Monitoring for all contaminants is performed at entry points into the distribution system in close proximity to where the water is being pumped from the wells. If water quality problems are detected, the well source is immediately isolated and retested. LADWP pumps only from wells that can produce a safe quality of water for its customers.

    LADWP has established operating goals for trichloroethylene (TCE), tetrachloroethylene (PCE), nitrates, perchlorate, and total chromium that are more stringent than the maximum contaminant levels (MCLs) permitted by Federal or State regulations. These stricter operational goals provide an additional safety margin from these contaminants for our customers.

    TCE and PCE compounds are commonly used in industries requiring metal degreasing. PCE is also used in dry cleaning and automotive repair industries.

    Nitrate is a concern because of its acute effect of impeding the uptake of oxygen to the blood. Infants (who are in the earliest stages of development) are most sensitive to the effects of nitrates. The current standard for nitrate is 45 parts per million (ppm). A single exceedance of the nitrate standard is classified as an acute violation requiring immediate public notification. Treatment for nitrates may eventually become necessary for affected Los Angeles groundwater supplies.

    In October 2007, a MCL was adopted for perchlorate of 6 parts per billion (ppb). Perchlorate is an inorganic compound that is most commonly used in the manufacture of rocket fuels, munitions, and fireworks. In addition to its detection in groundwater, the compound was also been detected in Colorado River Aqueduct water, but not in recent years.

    Chromium is discussed within the Emerging Contaminants of Concern subsection below.


    The City of Los Angeles encompasses an area of 465 square miles with a population of over 4 million residents and an annual average water consumption of approximately 215 billion gallons (or 660,000 acre-feet). Local groundwater provides approximately 11% to 15% of the total water supply for Los Angeles, and has provided up to 30% of the total supply in drought years. Los Angeles has water rights to the San Fernando, Central, Sylmar, West Coast, Eagle Rock, and Verdugo Basins. The San Fernando Basin accounts for over 80% of the City’s total local water rights.

    Located in the highly urbanized areas of Los Angeles County, the basins have been contaminated to varying degrees during the past 70 years. Contamination is primarily due to improper storage and handling of chemicals such as chlorinated solvents. Chlorinated solvents were heavily used in the aircraft manufacturing industry dating back to World War II through the Cold War, and account for the majority of the Los Angeles’ groundwater contamination. Other sources of groundwater contamination can be attributed to improper storage, handling, and/or containment of harmful/hazardous materials by commercial activities associated with automobile and equipment repair, automobile recycling, unlined landfills, dry cleaners, paint shops, chrome plating, textile manufacturing, fuel storage and dispensing, and chemical manufacturing. Waste from past dairy, agricultural and residential use of chemical fertilizer and septic systems have also contributed to the contamination of the groundwater in Los Angeles.

    Environmental regulations enacted since 1970's along with more stringent enforcement of these regulations have significantly reduced the potential for improper handling or release of these harmful chemicals and have greatly reduced the risk of further contamination of soil and groundwater.


    Chlorinated solvents (primarily trichloroethene (TCE), tetrachloroethylene (PCE) and carbon tetrachloride), 1-4 diethyleneoxide (dioxane), hexavalent chromium, perchlorate, nitrates, and n-nitrosodimethylamine (NDMA) have been detected in the Los Angeles’ groundwater ranging from low to extremely high concentrations. High concentrations have been detected adjacent to the sources of contamination. The four plume maps below illustrate the extent of the TCE, PCE, chromium, and nitrate contaminations that have impacted Los Angeles’ groundwater pumping activities from the San Fernando Basin.

    The United States and California Environmental Protection Agencies are addressing several of the contamination source sites resulting in limited groundwater cleanup by the responsible parties. Unfortunately once the contamination moves down in the soil column and reaches the groundwater, the contamination spreads rapidly. At that point, it becomes extremely difficult and costly to treat and cleanup contaminants from the groundwater.

    Los Angeles has 115 groundwater production wells in the San Fernando Basin and today approximately half are unusable due to contamination. The loss of so many wells means Los Angeles is unable to pump its adjudicated groundwater rights. At the current rate of migration of these contamination plumes, Los Angeles would virtually be unable to utilize the majority of its local groundwater from the San Fernando Basin within the next 5 to 9 years.


    Given the extent of the contamination and the growing scarcity of available water, the only viable solution is to cleanup and treat groundwater to meet Los Angeles’ water demand. That is why the LADWP is embarking on an ambitious and capital intensive plan to cleanup and treat the groundwater in the San Fernando Basin. The plan may involve construction and operation of a number of large and small groundwater treatment facilities to remove and cleanup 107,000 to 123,000 acre feet of contaminated groundwater per year in the San Fernando Basin. These facilities could cost $600 to $900 million. LADWP is planning to have these facilities in-place and operational by mid-2022 subject to securing the necessary funding and approvals. These proposed facilities will restore Los Angeles’ historic groundwater pumping capacity from the San Fernando Basin at a reasonable cost and provide a reliable local source of high quality water to Los Angeles’ residents and businesses well into the foreseeable future.

    Chromium Plume Map
    Nitrate Plume Map
    PCE Plume Map
    TCE Plume Map
    Groundwater: A vital water resource for Los Angeles
    San Fernando Groundwater Basin Fact Sheet

    Updated August 26, 2015

    LADWP manages emerging contaminants on many levels:

    1. By encouraging the development of standardized testing to enable early detection, and supporting the regulatory framework by providing early occurrence data,
    2. By advocating good science and a balanced approach to risk assessment,
    3. By seeking to gain a risk perspective with other existing contaminants to manage the emerging contaminants in the absence of regulations,
    4. By supporting early interpretation of emerging contaminants in collaboration with research and regulatory agencies, and
    5. By supporting the research to develop cost-effective treatment for the removal and management of these emerging contaminants.

    An example of how the LADWP manages an emerging contaminant is chromium VI (commonly known as hexavalent chromium). Hexavalent chromium does not have an enforceable drinking water standard at this time. However, hexavalent chromium is included in the State total chromium standard of 50 ppb. CDPH is expected to establish a drinking water standard for the compound in the near future. Chromium is a heavy metal that has been used in industry for various purposes including electroplating, leather tanning, and textile manufacturing, as well as controlling biofilm formation in cooling towers. LADWP began low level monitoring of hexavalent chromium long before monitoring was required by regulators. LADWP supported new health-effects research needed to support risk assessment, and advocated a balanced approach to risk management. LADWP funded research to develop new treatment technologies to reduce hexavalent chromium to lower detection levels.

    Most recent among emerging contaminants are “pharmaceutically active compounds and personal care products” known collectively as PPCPs that are finding their way into rivers, lakes and waterways from urbanized areas. There are concerns about the occurrence and effects of endocrine disrupters, hormone-shifting compounds, and pharmaceuticals. As technology now allows us to detect compounds down to the parts per trillion levels, some of these compounds are now being detected. The risk assessment field is finding it difficult to keep pace with advances in analytical technology. The question requiring investigation is “Do these contaminants pose a health risk at these low levels?”. LADWP will continue to proactively manage emerging contaminants through early monitoring and utilization of a balanced approach to risk management.

    To ensure supply reliability, the LADWP has initiated a number of fast-tracked and ambitious undertakings to restore its lost groundwater production in the SFB and other basins. These undertakings will also prepare the LADWP to safely manage and extract water from future groundwater recharge efforts. For details on groundwater remediation measures, go to Projects & Initiatives.

    Map of wells equipped with data loggers in the San Fernando basin.


    Project Background

    LADWP provides a reliable and high quality water to over four million residents and businesses in the City of Los Angeles. Local groundwater supply accounts for approximately 11 percent of the City of Los Angeles’ annual water supply of approximately 660,000 acre-feet. The San Fernando Basin (SFB) accounts for over 80 percent of the City’s groundwater supply and offers the greatest future potential for groundwater storage and related-use opportunities.

    The SFB is overseen by a Court-appointed Watermaster, who in collaboration with the area water agencies including the LADWP, gathers and reports on data regarding water supply, groundwater extractions, groundwater levels, change in storage, imported water use, recharge operations, water quality, and other pertinent information. The Watermaster relies on accurate groundwater level measurements to monitor the supply levels in the SFB. For more information, please visit the Watermaster website at http://ularawatermaster.com/.

    Currently, the LADWP obtains these measurements manually on a monthly or quarterly basis. The information obtained from these manual measurements only provides the LADWP and the Watermaster with a snap shot of the groundwater levels. Automating the groundwater level measurements will help the LADWP and the Watermaster in obtaining continuous data with greater efficiency and lower cost. The continuous data will enable the LADWP and the Watermaster to better understand the dynamic nature of the groundwater fluctuations and its potential impacts on our water gathering activities. LADWP has also secured a grant funding from the State of California to offset the cost of purchasing and installing these automated groundwater level measuring devices (also unknown as electronic data loggers) to help reduce the overall cost to our customers.

    Scope of Project

    The scope of the project is to install electronic data loggers in approximately 115 existing monitoring wells in the vicinity of groundwater pumping wells and spreading grounds in the SFB. Installation of the data loggers began in March 2011. The installation of these electronic data loggers typical takes approximately one hour.


    The purpose of installing electronic data loggers is to facilitate better groundwater management through collection of continuous water level information.

    Electronic Data Logger

    An electronic data logger is a device with built-in sensor that can record water levels. It is a “cigar-shaped” device measuring approximately one inch in diameter and approximately nine inches in length. It is powered by an internal battery with data storage capacity. Electronic data logger sensors are placed into groundwater monitoring wells connected to a data cable to enable water level data to be collected electronically via a hand held device.


    LADWP has received a grant funding of approximately $250,000 from the State of California Department of Water Resources with an in-kind cost share commitment of approximately $127,000 from the LADWP.


    The project will enhance operation and management of the SFB through a better understanding of basin dynamics including:

    1. assessment of groundwater contours and groundwater gradients;
    2. more accurate estimation of groundwater storage;
    3. better calibration of current flow models;
    4. data correlation between pumping, spreading, and water levels;
    5. better planning and operation of existing extraction and spreading facilities; and
    6. immediate downloading to the SFB database along with facilitated dissemination of the data to other agencies and interested parties. 

    The project will also provide significant cumulative operational cost savings and efficiencies.

    LADWP Contact Information

    If you have any questions, please contact Mr. Hadi Jonny at (213) 367-0905 or Fatema Akhter at (213) 367-0904.

    November 17, 2011

    For information regarding the Groundwater System Improvement Study (GSIS), or the groundwater monitoring well to be constructed in your neighborhood, click here.