No one ever knows how long a drought will be when it starts.
I thought about this a lot when I was a kid. My mom had come out to New Mexico as a teenager to work on archaeological digs. Years later when I was a child, her interest in the past shaped family vacations. We often visited the abandoned ruins of places where people once built homes, farmed, and then disappeared. Some were in cliffs. Some were multi-story mud buildings rising from the valley floor not far from Phoneix. Chaco Canyon in New Mexico was particularly memorable. Tree rings, carbon dating, evidence of deforestation told the story of those civilizations learning to thrive, expanding, deteriorating the resource base, and then collapsing when some unpredictable event like a long drought struck.
The Nation last year ran an article about the possibility that Phoenix, where I spent much of my childhood, could become uninhabitable in the not too distant future. ( http://www.thenation.com/article/173346/could-phoenix-soon-become-uninhabitable#) The article notes the dramatic decline in the aquifers in Arizona, the heavy dependence on unreliable imported water, and the exponential increase in acreage of upland forests burned in recent decades. Several of those trends helped prompt my parents to move here from Arizona in the mid 1990s. They were living in an upland forest near Prescott. Their wells combined produced less than a gallon a minute. And it was getting more difficult to rake up pine needles and control fire hazard.
So now we are here in California at the start of 2014 in very dry conditions. Back to those tree rings at the archaeological sites. In the last 1,000 years or so, there have been droughts in the American West that lasted decades. So what happens when a major city like Phoenix becomes uninhabitable? Do we welcome the refugees? And how long can California offer food and drink to its millions if the drought stretches on?