Irvine Lake, Orange County’s largest freshwater reservoir, began lowering its water levels on the 26th of the month. This measure is a preparatory step for anticipated El Niño winter storms and for scheduled repairs to the aging Santiago Creek dam.
The Irvine Ranch Water District (IRWD), which manages the reservoir, plans to reduce the lake's water elevation from approximately 738 feet above sea level to 720 feet. This adjustment will leave only about 300 acre-feet of water in the lake. The reservoir is slated for complete emptying next summer to allow for construction work on the dam structure.
According to the water district, the primary purpose of this significant water level reduction is to create additional space within the reservoir to accommodate heavy rainfall. This action is deemed necessary to protect the safety of residents located downstream from the dam. Established in 1933, Irvine Lake serves as a vital resource, supplying drinking water to an estimated 900,000 people across Orange County, in addition to its historical role as a popular fishing destination.
A safety assessment conducted in 2017 identified that major facilities of the Santiago Creek dam had reached the end of their operational lifespan. This assessment concluded that these components required replacement to ensure compliance with current seismic and safety standards. The upcoming construction project is specifically designed to replace both the intake tower and the spillway facilities, with the ultimate goal of restoring the reservoir's full water storage capacity.
The entirety of the dam repair project is anticipated to span a period of five years. Throughout this construction phase, Irvine Lake will remain completely empty, impacting its recreational and water storage functions.
In response to the planned drainage, fishing enthusiasts have vocalized a demand for a comprehensive rescue and relocation plan. Their concern centers on protecting various fish species, including sturgeon and blue catfish, which have been stocked in the lake. The Irvine Ranch Water District has stated that it is actively engaged in discussions with the California Department of Fish and Wildlife, along with relevant experts, to formulate appropriate countermeasures. The IRWD also anticipates that fishing activities will be able to resume once the extensive construction work on the dam is successfully completed.
