Do you mean to say that dry lake beds indicate a lack of rain?
Cute. I mean to say that currently populated areas -- the Los Angeles Basin, Las Vegas, Phoenix and the rest of the Southwest -- are subject to severe periodic 200 to 1,000-year or longer droughts, not the brief alternating dry and wet spells of historical record. That knowledge has been around for generations. These guys give the impression they discovered it. It's nice they added a few new data points but the references to AGW make me think their "study" is not the least bit objective.