Former Southern Nevada water chief Pat Mulroy explains that, while Las Vegas is an easy rhetorical landing spot because it is right next door to Lake Mead, the dropping Colorado River reservoir is a basin wide issue:

What we are experiencing is not a Las Vegas problem — it is truly a regional problem that encompasses an area responsible for 27 percent of the country’s gross domestic product.

The entire piece is worth reading, and the comment thread is actually pretty good.