The rivers frequently flooded their banks, a life-giving pulse that created sprawling riverside cienegas, or fertile wetlands; braided and beaver-dammed channels; meandering oxbows; and bosques — riparian habitats with towering cottonwoods, mesquite and willows. This lush, wet Arizona landscape, combined with the searing heat of the Sonoran Desert, gave rise to a vast array of insects, fish and wildlife, including apex predators such as Mexican wolves, grizzly bears, jaguars and cougars, which prowled the river corridors.
The confluence now is a very different place, its richness long diminished. A massive mountain of orange- and dun-colored smelter tailings, left from the days of copper and lead processing and riddled with arsenic, towers where the two rivers meet. Water rarely flows there, with an occasional summer downpour delivering an ephemeral trickle.
On a recent visit, only a few brown, stagnant pools remained. In one, hundreds of small fish gasped for oxygen. An egret that had been feeding on the fish flew off. The plop of a bull frog, an invasive species, echoed in the hot, still air.