Irvine Lake is expected to undergo a major drawdown beginning in fall 2026 as Irvine Ranch Water District prepares for the Santiago Creek Dam Improvement Project. Major dam construction is expected to begin in summer 2027 and continue through approximately 2030.
The work is much more than a renovation of the recreational areas around Irvine Lake. Santiago Creek Dam, which forms the lake, is more than 90 years old, and the project will replace major components of the dam, strengthen the earthen embankment and improve seismic safety and water-storage reliability.
When Is Irvine Lake Closing?
Irvine Ranch Water District is completing site-preparation work in 2026, and Orange County Water District reported that IRWD plans to begin draining Irvine Lake in fall 2026 in preparation for the Santiago Creek Dam project.
IRWD documents describe modifications to the existing outlet tower that will allow the lake to be drained as low as possible before the main dam contractor mobilizes. For that reason, it is more accurate to describe the upcoming work as a major drawdown rather than assume that every part of Irvine Lake will become completely dry.
As of September 2026, shoreline fishing remains available at Irvine Lake on Fridays through Sundays. A specific final date for public fishing has not yet been announced on the official project page. Visitors should check current conditions before making a trip.
See our Irvine Lake guide for current fishing hours, rules, parking, maps and visitor information.
How Long Will the Irvine Lake Project Take?
IRWD currently expects major construction to begin in summer 2027, with the project estimated to be completed in 2030. Orange County Water District has described the dam construction as spanning four dry seasons and reported that water will not be retained behind the dam during that work.
- 2026: Site preparation and advance construction activities.
- Fall 2026: Planned Irvine Lake drawdown begins.
- Summer 2027: Major Santiago Creek Dam construction is expected to begin.
- 2027–2030: Major dam construction period.
- 2030: Current estimated project completion.
Why Is Irvine Lake Being Drained?
The drawdown is necessary so crews can complete the Santiago Creek Dam improvements safely. The dam was originally constructed in 1933, creating Irvine Lake. IRWD began a comprehensive assessment of the dam in 2017.
According to IRWD, the engineered earthen dam remains operational but could be made safer. The assessment also determined that the existing outlet tower and spillway are reaching the end of their useful lives and should be replaced and upgraded to modern seismic and dam-safety standards.
What Work Will Be Done at Santiago Creek Dam?
The Santiago Creek Dam Improvement Project includes several major improvements:
- Replace the existing outlet tower that controls water entering and leaving Irvine Lake.
- Construct a new spillway designed to current seismic and safety standards.
- Strengthen the earthen dam embankment.
- Improve control of water flowing into and out of the reservoir.
- Restore reservoir storage capacity.
- Improve long-term seismic performance, dam safety and water reliability.
Advance work also includes modifications to the outlet tower, a temporary water line along Blue Diamond Haul Road, an isolation valve for the Irvine Lake Pipeline, demolition of the former dam keeper’s residence and removal of a floating boat dock along the lake’s western shoreline.
Why Irvine Lake Is Important to Orange County
Irvine Lake is best known locally for fishing, but recreation is not its primary purpose. The reservoir stores water for surrounding Orange County communities and supplies water used by the Baker and Howiler treatment plants. IRWD says those facilities collectively provide water to approximately 85,000 homes in Central and Southern Orange County.
The project is also intended to restore additional reservoir capacity, allowing Irvine Lake to capture more local rainwater and helping reduce dependence on imported water.
What Does the Project Mean for Villa Park?
Irvine Lake has a direct connection to Villa Park’s water supply. Serrano Water District, which serves Villa Park and a small portion of Orange, owned 25% of Irvine Lake for more than 90 years. On January 15, 2025, Serrano transferred its ownership of Irvine Lake and Santiago Creek Dam to Irvine Ranch Water District.
Serrano Water District continues to use local surface water stored in Irvine Lake as part of its water supply. The ownership transfer was made in exchange for a new backup water-supply connection between Serrano and IRWD, providing another connection to the regional water system.
Will Irvine Lake Fishing Close?
The planned drawdown and dam construction are expected to affect recreation at Irvine Lake. However, an official final fishing date and detailed recreation closure schedule have not yet been announced. Shoreline fishing is currently managed by OC Parks, while IRWD manages the reservoir and dam project.
Because the construction schedule and lake conditions can change, anglers should check the OC Parks Irvine Lake page for fishing access and the IRWD Santiago Creek Dam Improvement Project for construction updates.
Will Irvine Lake Reopen?
The project is intended to keep Santiago Creek Dam and Irvine Lake operating safely for decades to come, not permanently eliminate the reservoir. IRWD has described the improvements as preparing the facility for another 100 years of operation.
What has not yet been announced is a specific date for the return of shoreline fishing or what recreational access will look like after construction. Those details should become clearer as the project progresses.
Irvine Lake Project Updates
We will update this page as IRWD and OC Parks release additional information about the Irvine Lake drawdown, fishing closure, construction schedule and reopening. For general lake information, maps and current fishing rules, visit our Irvine Lake fishing and visitor guide.