If every house in the southwest saved its rainwater off the roof, this problem would not exist.
What rainwater?
You mean in illegal rain barrels?
It does rain. Many areas like this get deluges, most of which runs out to sea. Building dams allows dry areas to be fruitful, but if that isn’t enough, even private citizens saving their rain water can make a difference.
During this drought, there have been lots of stories about flooding from rain water in LA.