Orange County’s largest freshwater lake is set to remain empty for five years as local water managers prepare to drain Irvine Lake for major safety repairs to a 93-year-old dam. The 750-acre reservoir was created in 1933 after the Santiago Creek Dam was built. The Irvine Ranch Water District will lower the lake’s water level from 735 feet to about 720 feet, according to reporting by SFGATE. This will reduce the amount of stored water from 2,800 acre-feet to just 300 acre-feet.
It will begin a gradual drawdown this month. The remaining water will stay in the lake until next summer. Contractors will then drain the basin completely to begin structural repairs on the aging dam. he five-year construction plan aims to improve aging infrastructure, address safety risks identified by regulators, and increase the lake’s long-term water storage capacity.
However, crews will repeatedly lower the stored water back to 300 acre-feet before draining the lake completely next summer.
Local water managers said lowering the lake is also necessary to prepare for expected winter weather. “Drawing down the lake’s levels ahead of El Niño will ensure we have enough space in the reservoir to accommodate major storms and keep the downstream community safe,” Fabris told SFGATE. “Ultimately, one of the benefits of the Santiago Creek Dam Improvement project is that it will allow us to take advantage of future big storms and capture more rainwater, adding to the community’s water supply,” Fabris noted.
The drawdown schedule takes seasonal weather preparations and long-term construction plans into account. John Fabris, spokesperson for the Irvine Ranch Water District, explained the plan in an email statement cited by SFGATE. Fabris added that winter rainfall could temporarily raise the lake’s water level in the coming months.