If you try to imagine what a dystopian future would look like, you might conjure up aliens invading Earth, or robots overpowering humans. But according to author Seamus McGraw, the problems of the future are more down-to-earth than some may imagine. In his book, “A Thirsty Land: The Making Of An American Water Crisis,” McGraw writes about how water scarcity in Texas could turn into a crisis that affects all Americans. And it could happen sooner rather than later.