This reminds me of the science fiction novel The Water Knife by Paolo Bacigalupi. From the Amazon description:
"In the near future, the Colorado River has dwindled to a trickle. Detective, assassin, and spy, Angel Velasquez “cuts” water for the Southern Nevada Water Authority, ensuring that its lush arcology developments can bloom in Las Vegas. When rumors of a game-changing water source surface in Phoenix, Angel is sent south, hunting for answers that seem to evaporate as the heat index soars and the landscape becomes more and more oppressive."
