Monday, November 28, 2016

Is The California Drought The Worst in 1200 Years?

For the past few years, California has been going through a record drought.  Every year there is hopes that the drought will end with a particularly wet season, only to have hopes dashed by increased drought statewide.  The California drought has a lot of people worried.  First, roughly 25% of the total food in the United States comes from California.  In addition, the amount of moisture being taken from ground water reserves has caused some areas of California to entirely require water from outside their area.  With a great deal of water going towards maintaining agriculture, rivers, streams, and lakes are at record lows threatening native species that depend on the waters for survival. 

All of this only begins to scratch the surface of the problems that California is currently faced with thanks to this drought.  With one in eight US residents living in California, what effects California will affect everyone else.  So, is the current California drought the worst seen in 1200 years?  Lets take a look at what research exists and get to the bottom of just how bad this drought really is.

How Do We Know The Drought Is Bad?

From 2012 to the present time, California has been going through a severe drought.  When comparing California now to records of rainfall dating back a century, the most recent drought can be considered severe.  While droughts are rare, they do happen.  This begs the question of how unusual this event is?  Simply put, it is quite unusual.  According to a letter published in the Geophysical Research Letters, there are several ways to measure the overall effects of this drought when compared to past events.  Two particularly important ways that this can be measured are through moisture rates in the soil as well as tree ring chronologies that can be carefully studied to see when droughts like this have occurred in the past.

Two Techniques For Measuring The Severity Of The Drought

When carefully examining the amount of moisture in the soil, viewing past records of soil moisture reveals a common trend in California.  In particular, having periods of time where the average rate of precipitation matches what has been seen now is not uncommon.  Two or even three-year droughts have happened in the past.  However, with the 3rd year having so little soil moisture, this particular drought has not been seen for at least millennia.  Every additional year of continued drought will make it that much more rare.  While measuring the accumulated moisture deficits provide an excellent way to look at this problem, it does not reveal the entire picture.  For that, the examination of tree rings is required. 

So what can tree rings tell us?  Well, as it turns out, the yearly growth of trees are reflected in the atmospheric conditions that they are exposed to during that time, including moisture and rainfall.  With this in mind, we can look at a cross section of a very old tree to see if rainfall has ever led to a pattern of growth where the growth rings are very close together.  When examining the effects of rainfall on tree ring growth now, we see that there have been times in the past where similar growth patterns have been found.  While this drought is extreme, it is not outside the general range of natural variability found in sampling.

Where Does That Leave Us?

Simply put, the drought that California is experiencing right now is extremely rare and quite severe to the economy and lifestyle of California residents.  In addition to putting in danger crop yields, the price of food may rise nationwide as a result of this continued drought.  As it continues, the state may be forced to take even more dramatic action in response to the severe water shortage currently affecting the state.  While not the worst in 1200 years by itself, what makes it significantly worse then anything since is that it is paired with record high temperatures.

Is There An End In Sight To The California Drought?

As a society, US residents and California citizens are exceptionally good at holding out.  The question that we end up asking however is whether or not there is an end to this drought some time in the future.  With California coming off a particularly moist century, rainfall is predicted to be less then what was assumed normal in the years to come.  In addition, given how rare this drought is, it is hard to tell whether or not it is going to end any time soon.  What available research exists is split on the issue, leaving the average citizen to hope for the best as the government takes steps to plan for the worst.  Until then we are left to wait and see.

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