WE LIVE IN A CITY THAT HAS TRIED TO CEMENT ITS rivers out of existence, thinks it’s a desert but isn’t, has two rainy seasons and acts shocked every time it rains, has drained its wetlands but loves rain-forest vegetation. And the most notorious scandal in the city’s history involved building an aqueduct.

If Los Angeles has heretofore approached the subject of water with insistent lunacy — as well as greed, power mongering and a will to environmental devastation — then watershed management is fast ushering in a new era of sanity. We’re admitting, at long last, that we live in a place with water, and are revolutionizing the way we move the water through this city. And moving water around badly and unfairly is implicated in more of L.A.’s Big Troubles than one might imagine. Watershed management: It’s a ho-hum phrase, but these two simple words promise as much for the quality of life in L.A. as any movement I can think of.

It’s still mostly in the planning stages. But since the early 1990s, watershed management has rocketed from a radical-sounding dream among farseeing environmentalists to the widely agreed-upon Way We Should Do Things in L.A. In 2000, the L.A. County Department of Public Works — our gods of infrastructure, and former concrete lovers of America — moved 25 of its engineers into a new Watershed Management Division, which now has 45-plus engineers working away within it. It’s practically a party: DPW has been collaborating with the water agencies, city governments, state conservancies, North East Trees, the Watershed Council, and pretty much every single other relevant public and private player to design new management plans for the watersheds of the L.A. and San Gabriel rivers as well as the smaller watersheds of Malibu, Topanga, Ballona and Dominguez creeks — a.k.a. the river basin in which we built L.A.

To appreciate why you should love these DPW engineers, you have to watch water move through L.A. now — via the flood-control system, built in the 1940s and ’50s, which drastically re-routed water through the basin. First, contrary to public opinion, water does fall out of the sky here: In wet years, it’s enough to meet half or more of L.A.’s water needs. This rainfall hits ground that is now 60 percent hard pavement, which drains the water into storm sewers that rush it as fast as possible into concrete-lined river channels that speed the water to the Pacific Ocean. We then purchase rain that falls on Northern California, Wyoming and Colorado, and import it at great expense 250 to 350 miles by aqueduct.

Call it aqua-psychosis. Call it "watering the ocean." The old system has spawned about 15 dozen problems. It wastes water — well, duh. While it does contain floods, it dramatically increases the flood volume in the rivers! It pollutes the rivers and the bay: A stew of hundreds of everyday toxics (oil, pesticides, bits of asbestos brake lining, to name a few) washes off roads and driveways into the storm drains. It erodes the Southland’s beaches and depletes the soils: The walled-in rivers can’t deposit nutrients or sand. The concrete channels erase wetlands and wildlife habitat. They turn L.A.’s obvious sites for parks and greenbelts into no man’s lands that break apart rather than connect communities. This brainiac system also makes water and green spaces prerogatives of the rich. And it pisses off the rest of the West. To put it in a sentence, watering the ocean is tied tightly to L.A.’s notorious water imperialism, absence of park space, and environmental ruin as well as to failures of community and to social injustices.

NOW WATCH HOW WATER IN L.A. COULD AND should move from sky to ground to tap. Watershed management harnesses the hydrology of the watershed — the flowing of water from mountains through the L.A. basin to the sea — rather than declaring war on it. First, you capture rain where it falls — using strategies such as backyard cisterns, porous pavement, and road and gutter designs to direct water toward soft ground, as well as restored wetlands, a great many more parks and just plain more trees. Second, you either use the rainwater on-site, for example to water gardens, or let it drain back into the aquifer. Filtering water through soils neutralizes toxins. And finally, once you’ve captured a hefty share of the storm water, you use diversion lakes and concrete channels where necessary to control flooding during the heaviest rains.

And voilà. You minimize flooding and maximize water supplies and quality. You get parks, wetlands, wildlife habitat, clean flowing rivers, clean beaches and bays, and low-cost clean water all over the place. The river corridors can be greenbelts with bikeways that connect the city. The trees and added parks will help clean the air, too — and no places in L.A. suffer worse air than the poorer communities that are the most park-deprived.

The transition to watershed management will be more of a 40-to-50-year voilà, however, since at the moment, the riverside lands we need for wetlands and diversion lakes are full of industry, and a sea of pavement slants the wrong way. You can’t cart the dynamite and jackhammers to the L.A. River until you’ve built enough lakes and wetlands and re-slanted enough pavement to capture the rainfall — unless you want to be able to swim laps on most of our freeways. Right now, TreePeople, a pioneer influence on DPW, is using an ingenious economic model for a sustainable L.A. to test modifications to houses and yards to capture water, and is working with schools to convert asphalt blacktops to soft ground. The major watershed-management players are starting up wetlands projects in places ranging from the Tujunga Wash and Sepulveda basin to Taylor Yard downtown, to the Headworks across from Griffith Park, to a string of sites in Southeast L.A. from South Gate to Long Beach. The same crowd has been scouting sites up and down the rivers that could be available now or in the future for parks, lakes and wetlands. If you want to see the first chunk of concrete fly, camp out on the banks of the Arroyo Seco, where the abundance of existing green space has given watershed management a head start. And in the most ambitious project of all, our heroes at DPW have scrapped plans to install a $42 million storm-drain system in Sun Valley — in the Northeast San Fernando Valley — and have set out instead to use the area to test and showcase the principles of watershed management.

We forget or deny at our own peril that we live inside natural systems. Managing those systems badly — inequitably, unsustainably — has been a sure route for all American cities to failures of health, economics and community. L.A., we know, likes to take other cities’ mistakes to extremes. But we’re just as bold with our fixes, and one of my two deep beliefs about this new era of watershed management is that it could summon other cities to get on the bus.