Water users throughout the western United States have faced supply problems from the conception of modern civilization. Today, climate change, population growth, and declining water quality combine with the age-old problem of finding sufficient water resources in a region with a largely arid climate. Climate change in particular poses a significant threat to the sustainability of water supplies in the western United States (the West). Casting aside all debate about who and what is responsible for climate change, the public and water utilities alike must be prepared to address its effects on water supplies.