GP’s statement you quoted is entirely inaccurate. The natural state of California’s Central Valley is a wetland, which is how settlers found it in the 1800s, full of swamps, fish, deer, and lakes. And then they set to the work of draining all of the swamps so they could grow things there. It’s an unnatural desertification, and if the dams and waterworks were removed, it would return to the marshland. Even now, the rice grown near Sacramento is grown in land that is periodically flooded by the river.