Central and West Coast Basin

Central Basin
The Central Basin underlies the cities of Artesia, Bellflower, Cerritos, Compton, Downey, Huntington Park, Lakewood, Los Angeles, Long Beach, Montebello, Paramount, Pico Rivera, Norwalk, Santa Fe Springs, Signal Hill, South Gate, Vernon and Whittier, as well as portions of unincorporated Los Angeles County.  The Central Basin has a total storage capacity of 13.8 million acre feet, with 1.1 million acre feet unused; and 330 thousand acre feet available for storage.

Safe yield in the basin is 125,805 acre feet per year. However, allowable annual pumping is 217,000 AF per year, with the Water Replenishment District of Southern California (WRD) being the agency that ensures enough replenishment water is delivered to make up any difference between safe yield and extractions. WRD has authority to replenish the basin, using imported and recycled water provided by the County Sanitation Districts of Los Angeles County.  WRD determines the amount of supplemental recharge required, while the Los Angeles County Department of Public Works (LACDPW) is responsible for groundwater recharge at the Montebello Forebay Spreading Grounds under a permit issued by the Los Angeles Regional Water Quality Control Board (RWQCB).

In December of 2013, Los Angeles Superior Court granted a motion by WRD, Long Beach, Los Angeles, Lakewood and other parties to amend the Central Basin Judgment to establish a legal framework for the storage and extraction of stored water in the Central Basin. The legal framework permits a groundwater pumper with adjudicated rights to store water (e.g. through stormwater infiltration) and subsequently extract that stored water without the extraction counting against its water rights and without having to pay the Replenishment Assessment, provided regular monitoring is performed to determine the actual amount of recharged water, among other provisions.

Another potential opportunity includes cooperative projects between two or more parties to the Central Basin Judgment may participate in a groundwater recharge project by sharing common costs and benefits, and hence can share, on a proportional basis, the additional extraction rights produced.  Water rights gained from a project of this type likely would not be subject to the replenishment assessment upon extraction.

West Coast Basin
The West Coast Basin overlies the cities of El Segundo, Manhattan Beach, Hermosa Beach, Torrance, Inglewood, Hawthorne, Gardena, Lomita, Carson, and Long Beach, and portions of unincorporated Los Angeles County.  The West Coast Basin has a total storage capacity of 6.5 million acre feet, of which 1.1 million acre feet are unused; and 120 thousand acre feet are available for storage (MWD, 2007).  Most of the West Coast Basin is confined; therefore, there have not been many locations identified for surface spreading. Thus, recharge is only feasible through injection.  In addition, brackish water located inland of the West Coast Basin barrier may limit the ability to store and extract water in some parts of the basin.  In recent years, the Brewer and Goldsworthy Desalters have increased the ability to use this part of the West Coast Basin.

 

Notes on Groundwater Contamination: Although groundwater basins currently offer the most storage space available, many cannot be used because of contamination.  Therefore, any water infiltrated or injected into these basins would become contaminated as well. This contamination can last decades and the stored water must be remediated before it can be placed to beneficial use. Remediation is a time-intensive process that involves determining responsibility before groundwater remediation can begin.  There are also technical obstacles to groundwater remediation efforts, including multiple pollutants and contamination across more than one aquifer zone. Cleanup goals may evolve over time as new pollutants are identified, and target concentrations change based on new information about the risk and effects of pollutants.  Although local examples exist, it can be extraordinarily difficult to find end uses for the treated water.  Even though pumped and treated water is a valuable resource, agencies often lack the coordination or legal means to successfully bring this water to beneficial use.  These problems are further complicated by the fact that several regulatory agencies have jurisdiction, and their regulatory requirements are often inconsistent.

REFERENCES
Atwater, R., 2011. History of Groundwater Conjunctive Use in Southern California. Presentation to the Managed Aquifer Recharge Symposium, January 2011.

Metropolitan Water District, 2007. Groundwater Assessment Study—Chapter IV: Groundwater Basins Report. Report number 1308, September 2007. Accessed October 23, 2013.

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