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.