Jay Lund, Director, UC Davis Watershed Sciences Institute
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 built when a severe drought was misinterpreted as a new normal. If this drought is as unusual as once in 1,200 years, then why pay heed beyond just getting through it? We are unlikely to see the likes of it again.
The obsession over El Niño and the California drought masks the reality that the atmospheric condition is poorly correlated with stream flows in Northern California, where 75 percent of the state’s water supply originates.
East Coast news media should keep this perspective: Every summer California has a drought far drier and longer than the eastern U.S. has ever seen. This explains California’s extensive water and irrigation infrastructure (and why people move to California).