I was just going to recommend this book myself. Before reading it, I had no idea how long some of these aqueducts are and how many dams had been built nationwide (and why) - now when I fly I can't help but trace water paths and look for dams. It's a great look in to how cities in the arid southwest can exist and just how close some could be to non-existence.

EDIT: This article does a decent job touching on the scale of the water projects in California. Cadillac Desert provides a decent look into that scale on a national level (though, admittedly, most of the mind blowing information revolves around California).