Sunday, 19 April 2015

How Severe Is California's Drought Really?

The drought is breaking records and forcing Californians to make hard decisions. But understanding its severity is a complicated process that yields gloomy results.

A visitor walks near the receding waters at Folsom Lake in January.

Robert Galbraith / Reuters

In California, April really is the cruelest month.

At a time when the Golden State's reservoirs should be brimming and the snowpack deep, much of California is instead parched and dry. Gov. Jerry Brown has announced historic mandatory water restrictions on urban areas, and some are wondering if people and business are about to start fleeing.

But understanding the true severity of California's drought is harder to pin down and depends a lot on how it's defined, according to scientists who spoke with BuzzFeed News. To understand what's going on it's easiest to break the drought down into two very general categories: First, how much water California has in an absolute sense, and second, how much California needs for all of its people.

You may have heard that the current drought is California's worst in 1,200 years. That oft-cited figure comes from a paper by Daniel Griffin, of the University of Minnesota, and Kevin Anchukaitis, of the Woods Hole Oceanic Institution.

In conversations with BuzzFeed News, both researchers explained that they came to that conclusion after studying tree ring samples, as well as using what's known as the Palmer Drought Severity Index, or PDSI. Basically the PDSI measures soil moisture as it compares to what is "normal" for a particular place.

Daniel Griffin collects a tree-ring sample from a dead tree, which can be used to extend the tree-ring record back in time up to 700 years.

Courtesy Dan Griffin and Kevin Anchukaitis. / Via

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