The Irvine sub-basin is located within the OCWD boundary; however, the Lake Forest area sub- basin is outside of the OCWD boundary. A. Orange County Groundwater Basin The Basin covers approximately 350 square miles bordered by Chino Hills to the north, the Santa Ana Mountains to the northeast and Pacific Ocean to the southwest. Measured recharge consists of water artificially recharged at OCWD’s forebay recharge facilities and water injected at the Talbert Barrier and on the Orange County side of the Alamitos Barrier. Groundwater conditions in the Basin are influenced by the natural hydrologic conditions of rainfall, groundwater seepage and stream flow. Incidental recharge accounts for a significant amount of the Basin’s producible yield including precipitation and subsurface inflow. The production from the main Basin in FY 2025 was approximately 302,000 AF. IRWD produces most of its groundwater from the main portion of the Basin.
IRWD Groundwater Production
Historically, IRWD received nearly all water supplies from imported sources. To alleviate the dependency on imported water, IRWD first began to develop a series of local wells in 1979. Most of the potable groundwater supply to IRWD is produced from the Dyer Road Well Field (DRWF) located in the City of Santa Ana, which is connected to IRWD's potable distribution system. The DRWF consists of 16 wells pumping from the clear water zone of the Basin and two wells (with tinted-water treatment facilities) pumping from the deep, tinted-water zone of the Basin. The tinted-water portion of the DRWF is also referred to as the Deep Aquifer Treatment System or DATS. Under Agreement, IRWD can produce up to 28,000 AF per year consisting of 20,000 AF of clear groundwater and an additional 8,000 AF of “matching” clear groundwater, provided that a minimum of 8,000 AF of tinted groundwater is pumped from the deep aquifer zone. IRWD also owns and operates a groundwater production well in the City of Orange which can serve up to 3,200 AFY of demands within IRWD’s Orange Park Acres service area and north Irvine. In 2012, IRWD constructed and now operates the Wells 21 and 22 Desalter in the City of Tustin which removes total dissolved solids (TDS) and nitrates for potable use. Annual yield from Wells 21 and 22 currently averages around 2,400 AFY and can be up to 6,400 AFY.
A. Irvine Sub-Basin Pumping
IRWD also produces water from the Irvine sub-basin, which forms the southern-most portion of the Basin. This sub-basin has a perennial groundwater yield estimated at 13,000 AF. The Irvine Company (TIC), the major landowner in IRWD, historically pumped agricultural water from the Irvine sub-basin. By agreement between TIC and IRWD, TIC production capacity, wells and other facilities and all the company’s water rights were transferred from TIC to IRWD and IRWD assumed production from the sub-basin. The groundwater in this sub-basin is generally higher in total dissolved solids, tint, and nitrates. IRWD constructed the Irvine Desalter Project (IDP) to treat some of the water produced for
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IRWD – 2025 Urban Water Management Plan
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