It turns out that they run a patch of wetlands in Corona—actually in Riverside County—just behind the Prado Dam, at the base of the Santa Ana River. In 1992, they converted a series of duck-hunting ponds into an ecosystem that further treats wastewater that has been already treated three times.
This is nature's most natural filtration system—with a few pumps and pipes added.
These ponds remove ~30 tons of nitrate a month, plus other pollutants like sex hormones and pharmaceuticals, residual traces of which end up getting urinated into the toilet. (Do not flush your unwanted pills down the toilet, please!)
They are not only functional, but pretty...
...and create a great habitat for various types of wildlife...
...as well as a number of birds.
These aren't natural wetlands, of course.
In fact, they're the largest manmade wetlands in Southern California.
Part of the maintenance of the wetlands includes removing non-native invasive vegetation, planting native species...
...and rotating the ponds so they're not all working at the same time.
It's become a precious area for conservation of threatened species, so it's not open to the public.
Fortunately, OCWD conducts occasional bird-watching tours in the spring.
And oddly, duck hunting is still allowed here.
Although it looks tranquil, the adjacent shooting range regularly erupts in gunfire, making the visit a bit unnerving (apparently only to people—the birds seem to have gotten used to it).
The Prado Dam is actually a project of the U.S. Army Corps of Engineers, a branch of the military devoted to working on national security from an environmental perspective.
Often that means employing measures to control floods—including 700 dams in U.S. states and territories, and the LA River. Lots of civilians work with army officers to help make that happen.
The Prado Dam releases floodwaters incrementally, so Orange County doesn't get too much water flow all at once.
There are some nice flowers here, too—including jimson, which is usually referred to as a weed, but at least it's native.
The problem with non-native, invasive species of plants is that usually they require a much higher water load than the natives—and they're aggressive, which means they use up all the water available (which isn't much), and overtake the area, killing the water-starved native plants.
Typically invasive plants—like Arundo donax—don't provide a natural food source, because they can't be eaten by native species.
Fortunately the bird life seems to be thriving there, with barn owl chicks fledgling in boxes, almost ready to leave their nests.
There are some actual natural nests built up in the trees. Environmental stewards plant native mule fat trees at the wetlands, but there are lots of other trees as well.
In a grove of willow trees, we were surrounded by so much white puffy cottony stuff that it looked like it was snowing.
We also encountered a huge stinging nettle grove with gigantic leaves. Stinging nettle—which does sting upon skin contact—is abundant throughout the wetlands, and its numbers are increasing.
Conservation efforts also include protecting the Santa Ana Sucker Fish, a now-threatened species of fish that used to thrive in the Santa Ana River watershed.
Some years, the Prado Wetlands see an active nesting season, while other years they don't—and it's not necessarily dependent on how bad the drought is. At one point or another, in addition to the barn owls, you're likely to spot box owls, Great Blue Herons, and even endangered species like the Southwestern Willow Flycatcher and the least Bell's Vireo—the latter of which is particularly protected and monitored.
A big part of this is trapping the cowbirds that parasitize the nests of this small, migratory songbird. The female cowbirds literally go into the nests of vireos (and other songbirds too) and lay their own eggs in there to let the unsuspecting host raise it as their own. They don't even bother building nests of their own—ever!
Sometimes they'll knock one of the host's eggs out of the next to make room for their own. If they don't do that at first, sometimes they'll keep an eye on their intruder egg, and if it's threatened or removed for some reason, the cowbird will destroy the host's eggs. And sometimes if the vireo spots the intruding egg, it will abandon its nest—even with its own eggs still in it, drastically reducing their population.
So traps are set up with male cowbirds (the dark ones) inside to lure the females (the brown ones) in through a narrow opening at the top. It's easy enough for the girls to get in, but nearly impossible for them to escape, so they are trapped in there until they meet their gruesome fate—destruction.
And then, of course, there are the ducks. But the sanctioned hunting helps control the population of the waterfowl, at least.
Prado is lesser-known than some of the other area wetlands, but it's super-weird and fascinating—and if you can manage to get on a tour, your small group will have the place all to yourselves.
Photo Essay: Wastewater in the Time of Drought
Basking in the Gloom at Bolsa Chica Wetlands
Photo Essay: Hansen Dam, from Floods to Drought