High water remains in the basin Aug. 21 at Whittier Narrows Dam in Pico Rivera, California, the day after Tropical Storm Hilary made landfall. Although the primary purpose of this and other Corps dams is flood-risk management, about 75 percent of stormwater runoff — an estimated 7,000 acre-feet, valued at $7 million — passed through Whittier Narrows Dam and was captured downstream for groundwater recharge by the Los Angeles County Public Works.