Groundwater in Los Angeles
Groundwater use in California has historically been unregulated. Los Angeles County is one exception, with seven adjudicated groundwater basins where pumping rights are established and overseen by court-appointed groundwater masters. Groundwater rights were collectively allocated to those who could show a record of pumping through the legally negotiated adjudications. Rights are codified and can be leased or transferred. This has resulted in a system with over 300 rights holders throughout L.A. County today, overseen by groundwater masters who manage pumping levels to ensure safe yield.
For groundwater supplies to match annual pumping allowances, natural groundwater recharge from rainfall is supplemented from many sources, including imported water from the Metropolitan Water District, captured stormwater from L.A. County water agencies, and recycled water. Water for recharge also comes through conservation. The established system of groundwater rights, however, limits the volume of water that parties can store. Adjudicated pumping and storage rights have been fixed for decades. Future challenges will likely necessitate changes to the historic allocation of groundwater rights as cities, municipal water districts, and utilities seek flexibility to store more water in groundwater basins to meet water shortages during droughts.
Groundwater rights vary greatly throughout the county. Retailers along the coast are generally less reliant on groundwater, while upper basin retailers in the Main San Gabriel and Raymond basins receive significant groundwater supplies.
The complex and polycentric governance structure has successfully adapted to changes over time. But past achievements do not guarantee future successes in the face of water scarcity and population growth. With less reliable imported water supplies, groundwater basins must be used even more for short- and long-term water storage. Retailers with access to more groundwater rights, storage capacity, and imported water will be better positioned to store water in wet periods for later pumping. Given these differences, some areas will find it harder to achieve local reliance and increase drought resilience than others. Equitable access to groundwater throughout the county will likely require reallocating some rights. Market trades such as leasing or selling rights can help efficiently redistribute rights, while re-adjudications will also be necessary for communities less able to pay market prices for long-term groundwater access.
Our analysis of the seven adjudicated basins indicates a trend toward greater control or regulation of groundwater rights by public institutions, as well as a consolidation in the number of rights held by larger parties. Many agencies are examining possibilities for greater water recycling and stormwater capture to augment recharge sources. Larger institutions, such as municipalities and special districts will likely drive this process and induce broader system changes. Such agencies are most capable of building the large, capital-intensive projects for capture and recycling. However, they may not have sufficient groundwater rights for storing water. As a first step, groundwater managers can facilitate long-term plans for excess groundwater basin capacity that offer utilities and agencies opportunities to store recycled or captured water for later use.
