LOS ANGELES – During the storms that swept through California from Feb. 26-March 2, the U.S. Army Corps of Engineers assisted local agencies maximize their ground water recharge.
“USACE understands the seriousness of this drought,” said Brig. Gen. David Turner, commander of the Corps’ South Pacific Division. “I’ve spoken with California’s Emergency Management Agency Director and his message is clear: ‘Every drop of water counts.’”
The reservoirs the Corps owns and operates in Southern California have flood risk management as their primary purpose. Three dams, including Prado and Whittier Narrows, have a secondary purpose to regulate releases in order to minimize the discharge of water to the Pacific Ocean, as long as it does not interfere with or diminish the primary objective of flood risk reduction.
Modifications to those releases that the Corps instituted during the recent rain had a significant beneficial impact.
“We activated our Reservoir Operations Center in response to the series of storms,” said Col. Kim Colloton, commander of the Corps’ Los Angeles District. “As a result, we were able to contribute to local ground water recharge by providing nearly 22,000 acre-feet of water at a rate that the local downstream agencies could spread into their groundwater recharge basins.”
A acre-foot, defined as the volume of one acre of surface area to a depth of one foot, is equal to 325,851 gallons. That is enough water to fill nearly 8,000 bathtubs.
Recognizing the severe drought situation in California, the Corps requested and received approval to modify its operations for potential additional water conservation at Prado and Whittier Narrows dams during these storms. The deviations allowed an additional 1,325 acre-feet of water at Whittier Narrows Dam and an additional 10,500 acre-feet of water at Prado.
Ned Araujo, chief of the District’s Reservoir Regulation Section, explains the procedural changes.
“Over the past three years, we’ve worked closely with our partners to capture nearly all of the rain water that flowed into the basins for water conservation at Prado Dam and Whittier Narrows Dam,” he said. “Even though the area did not receive the amount of rain anticipated, we prepared to temporarily increase the water conservation storage at Prado Dam by 114 percent and at Whittier Narrows Dam by 52 percent. We were able to assist our partners convert storm water runoff into groundwater by capturing all the rain water from this storm.”
The procedural changes at the end of the flood season provided for temporary increased storage availability for water supply to downstream water agencies.
“During the rainfall event that began at the end of February, Prado Dam allowed for the capture of 10,000 acre-feet of storm water,” wrote Michael Markus, the general manager for the Orange County Water District, to Colloton. “Absent the capture at Prado Dam, this water would have flowed to the ocean and not been available to replenish Orange County's water supplies. The 10,000 acre-feet of water captured at Prado Dam for recharge into the Orange County Groundwater Basin is enough water to supply 80,000 people for a year.”