Thick clouds veiled the peaks of the San Gabriel Mountains. Not far away, just south of East Riverside Drive in Ontario, water gushed into an earthen basin the size of 10 football fields.
It had washed up there from the rain-filled gutters of East Merion Drive, Doral Court and South Grove Avenue. Most parts of Southern California would have shunted the storm runoff to the sea as fast as they could.
But here, on the southwestern edge of San Bernardino County, a local utility hoarded it, letting it sink into the earth and into the future drinking supplies of the Inland Empire.
The simple act defied a century of Southern California tradition.
Ever since cold Sierra meltwater first tumbled into the San Fernando Valley from the Los Angeles Aqueduct, the Southland has been addicted to water from someplace else.
But as the big straws that carry that water hundreds of miles from the Eastern Sierra, Colorado River and Northern California all shrivel under long-term environmental forces, water managers are shifting their gaze homeward, toward sources that Martha Davis calls "overlooked, mistreated or underutilized."
Davis is executive manager of water policy for the Inland Empire Utilities Agency, a district at the forefront of the emerging local-is-good movement. About 70% of the agency's water comes from its own backyard: a patchwork of dairies, industrial parks and planned communities overlying the big Chino Groundwater Basin.
In Los Angeles, local sources make up less than 15% of the city supply. The Southern California region overall gets more than half its water from afar. In a typical year, the L.A. Basin sends the equivalent of three-quarters of Los Angeles' annual water demand into the ocean in the form of runoff and treated wastewater.
"We're going to have to live within our means," says Richard Atwater, chief executive of the Inland Empire agency. "Do you really want to wait until we all go over a cliff?"
Davis, 55, and Atwater, 57, are at first glance an unlikely management team.
Atwater grew up in Long Beach, wears white button-down collar shirts and spent a decade working for the U.S. Bureau of Reclamation and the Metropolitan Water District of Southern California -- powerful agencies that move water around California and the West as though it were a railroad box car.
As an MWD official in the late 1980s, he helped kill a state water board proposal to cut water shipments from Northern California for environmental reasons, decrying the plan as a recipe for drought "forever" in the Southland.
Davis grew up in Marin County and worked for Greenpeace after college.
For much of the 1980s and '90s, she headed the small but tenacious Mono Lake Committee, which took on L.A.'s mighty water brokers and won, eventually forcing the city to give up much of its water from the ecologically fragile Mono Basin on the edge of the Eastern Sierra.
A state lawmaker once described her as "a baby-faced killer" who possessed the endearing looks of a cocker spaniel and the jaw hold of a pit bull.
When Atwater left the MWD in 1990 to become general manager of two water districts in Los Angeles County, their interests converged. He was developing recycled water -- a.k.a cleansed sewage -- to inject into coastal aquifers as a seawater barrier.
Davis' group, meanwhile, was exploring water recycling as a way for Los Angeles to make up for its Mono losses. The two wound up working together to pursue federal funding and Atwater came out in support of the "Save Mono Lake" campaign.
When Atwater was hired to run the Inland Empire agency in 1999, he called Davis -- though she had never envisioned herself as a water utility executive. "Heavens no!" Davis exclaims.
Since then, she's learned it's easier to tell public agencies what to do than to do it herself from the executive suite.
"Particularly when you're on the outside looking in, you say, 'Why aren't you doing this? Isn't this obvious?' " she says. "But to put together the combination of resources, engineering design, political support -- that's very complicated. Very doable but very complicated."
In early February, days of storms had filled the 25-foot-deep catchment south of East Riverside Drive, where rainwater began to seep into the sand and gravel at a rate of a quarter-foot a day, starting a years-long, subterranean journey to the utility's well fields a few miles south.
By the time it arrives, it will have mingled with natural drainage from the San Gabriel foothills, as well as treated wastewater, other storm runoff and some imported water the district uses to help replenish the aquifer.
At the wells, pumps suck the brew into desalting plants that strip out contaminants, including the nitrates and salts left by a century of farming. From there, the purified water goes to the bathrooms and kitchens of Chino, Norco, Ontario and Chino Hills.