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About Us

The Six Basins
The Six Basins are a group of adjacent groundwater basins, located just south of the San Gabriel Mountains in eastern Los Angeles and western San Bernardino Counties. Groundwater is pumped from the Six Basins primarily by public water-supply agencies and mutual water companies that supply water for municipal uses.

The main source of groundwater replenishment to the Six Basins is surface-water runoff from precipitation that falls on the San Gabriel Mountains and recharges at spreading grounds located along the foot of the mountain range—predominantly at the San Antonio Spreading Grounds. The water-supply agencies also use imported surface water from the Metropolitan Water District of Southern California for direct uses and for artificial recharge at the spreading grounds.

The pumping and storage rights for the Six Basins were adjudicated in 1998 through a stipulated judgment  titled “Southern California Water Company vs. City of La Verne, et al.” in the Superior Court of California for the County of Los Angeles (Case No. KC029152).  The Judgment prescribes a physical solution for the coordinated management of the Six Basins with the objective that the parties to the Judgment can reliably pump their respective rights and maximize the beneficial use of groundwater. The Judgment also established the Six Basins Watermaster to implement the physical solution. The Court maintains continuing jurisdiction over the Judgment. 
The Judgment is the current groundwater management plan for the Six Basins.  The main components of the Judgment include the establishment of:
  • a Safe Yield of 19,300 acre-feet per year (acre-ft/yr) of annual groundwater pumping
  • an Operating Safe Yield (OSY) that is determined annually by the Watermaster, which is based on the Safe Yield and the current and expected recharge, pumping, and groundwater levels
  • the allocation of base annual production rights to the individual Watermaster parties
  • Carryover Rights which allow up to 25 percent of unused production rights to be carried over to the subsequent operating year
  • the rules and methods for “replacing” groundwater pumped in excess of a party’s share of the OSY
  • the rules and responsibilities for the continued replenishment of the Six Basins with native surface water from the San Gabriel Mountains
  • monitoring and mitigation measures to protect against the threat of rising groundwater
  • guidelines for entering into Storage and Recovery Agreements
  • the governance structure and rules to conduct and fund Watermaster actions and activities
The Watermaster is a committee of representatives of the parties to the Judgment.  The Watermaster convenes monthly to conduct its business and prepares an annual budget and assessment to fund its operations and activities.   The Watermaster maintains this website for the purpose of disseminating important documents and data to the Parties, other stakeholders, and the interested public, such as meeting agendas and minutes, production and water-level elevation data, guiding documents, Watermaster forms.
In 2012, the Watermaster parties collectively agreed to enhance the management of the Six Basins beyond the execution of the Judgment, and began development of a Strategic Plan for the Six Basins (Strategic Plan).  The objective of the Strategic Plan is develop a water-resources management program that sustains and enhances the water supplies available to the Six Basins in a cost-effective manner and in accordance with the Judgment.  The development of the Strategic Plan is in progress.