Comment by water-data-dude

Water policy isn't as simple as you might think. Dams aren't a magical fix, they cause a lot of issues (like crashing the salmon populations, etc.). They're expensive to build and maintain, and the water you store in a big reservoir doesn't magically stay in place - you lose a lot to evaporation and you lose a lot that ends up going into the groundwater system. A much bigger part of the problem is western water law, where water rights are assigned based on prior appropriation and are lost if they aren't exercised. That leads to a lot of bullshit, like people growing very water hungry crops (alfalfa, rice) in the middle of the desert.

The reason we don't build like the people who first came to California did isn't because we're stupid, it's because we've learned a lot of lessons the hard way. If you're interested in some of the history I'd recommend Cadillac Desert, which is about western water in general, but which focuses a lot on California (including the machinations that the movie China Town was based on).