Irvine Lake

Water Storage at Irvine Lake

Since it was originally constructed in 1933, the primary purpose of Irvine Lake (Santiago Creek Reservoir) is to store water for the benefit of the surrounding communities – initially to provide irrigation water for local farms, and more recently to satisfy water demands primarily for urban needs. Irvine Ranch Water District (IRWD) utilizes water from Irvine Lake for two purposes: 1) as a source of water for non-drinking purposes, such as irrigation for avocado orchards, and 2) as a source of water for the Baker Water Treatment Plant which creates drinking water for an estimated 85,000 homes in Orange County. Serrano Water District (SWD), a co-owner of Irvine Lake with IRWD, also uses water from Irvine Lake to provide treated drinking water to its customers in the City of Villa Park and some parts of the City of Orange.

Both IRWD and SWD balance the benefits of storing water in Irvine Lake to ensure customers have a reliable supply of water with minimizing evaporation of water from the Lake. When the water level in Irvine Lake is high, the rate of evaporation increases dramatically with the increased surface area of water. One other key consideration for managing water levels in the Lake is preserving the ability to capture rainwater from the surrounding hills that will flow into Irvine Lake. Capturing this fresh water in Irvine Lake at no cost to both agencies can help reduce the cost of providing drinking water to customers.

Water Quality at Irvine Lake

As a source of drinking and recycled water, water quality at Irvine Lake is important. Rainwater runoff from the local watershed fills the lake. In order to ensure water quality remains high and supports uses, IRWD conducts extensive routine monitoring of the lake. The Irvine Lake watershed is also subject to sanitary surveys every 5-years to determine if there are any threats to water quality present in the watershed. The most recent survey was completed in 2019, and it found that the local watershed is predominantly rural with the primary threats to water quality from wildfires and septic systems.

During years with less rainfall, IRWD and Serrano Water District add imported water to Irvine Lake purchased from the Metropolitan Water District of Southern California (MWD). MWD provides drinking water to communities throughout Southern California, and they conduct extensive monitoring of federal and state regulated constituents as well as many additional water quality parameters. Water quality data from all drinking water sources used by IRWD are reported on in our annual Water Quality Report.

Fishing at Irvine Lake

While Irvine Lake remains primarily a water resource facility, limited shoreline fishing is back, resuming Aug. 17, 2019. For details on fishing, please contact the County of Orange (OC Parks).

At IRWD, we support recreation in Orange County and take pride in offering opportunities for our customers to explore the outdoors and learn about their environment. However IRWD has no ownership of Irvine Lake recreation, and operates the lake first and foremost as a water storage reservoir. Irvine Lake recreation is the responsibility of the owners of the “Irvine Lake Recreation Rights.” Those rights are shared between the following entities:

• The Irvine Company/County of Orange: 75%
• Serrano Water District: 25%

Fishing and boating had been allowed at Irvine Lake in the past, but public access was closed for three years starting in July 2016. The return of shoreline fishing in 2019 has been made possible by an agreement executed by the County, Serrano Water District, and IRWD. Click here to see the agreement.