The south fork of Lake Oroville, California’s second largest reservoir, in September 2014. Photo by Kelly M. Grow/California Department of Water Resources

By Jay Lund

California’s ongoing drought will continue to break records and grab headlines, but it is unlikely to be especially rare from a water policy and management perspective.

Estimates of the current drought’s rarity range from once in 15 years to once in 1,200 years (Griffin and Anchukaitis 2014), depending on the region and indicators used (precipitation, stream runoff, soil moisture or snowpack). In the Middle Ages, large parts of California had droughts far worse than this one, some lasting more than a century (Stine 1994). The probability of California experiencing a once in 1,200-year drought during a short human lifetime is extremely low.

The chance that this dry period is a “new normal” is probably small. Many parts of Australia are paying for expensive desalination plants…