Why "California's Driest Year on Record" is less serious (and more) than you're hearing
January 12, 2014
As January 2014 dawned, California residents were greeted with a collection of terrifying headlines about the lack of rain the state received in 2013. The Weather Channel posted a national story titled "Record Driest Year in California, Parts of Oregon". The San Francisco Chronicle warned "After dry spell, get ready for water restrictions" while the LA Times editorialized "LA's driest year: Time to shut off the lawn sprinklers for good". The Huffington Post plays it straight "2013 Is California's Driest Year On Record" while the Wall Street Journal reported "California Stretched by Worsening Drought". A map published by the NOAA showed nearly all of California under some water stress, while a large swath (inconveniently centered around Paso Robles) was under "Extreme Drought":
The data from our weather station at Tablas Creek bears this out. In all of 2013, we received 3.71 inches of rain. That's just 13% of what we consider our normal rainfall of 28 inches, and easily the least in a calendar year since we started keeping records in 1997. The story in areas east of us is worse: the weather station at J. Lohr, in the Paso Robles Estrella River heartland, totaled just 1.93 inches in 2013.
Why it's not as bleak as it seems
So, why is this story not as bleak as it looks? It all looks much worse because of how the rain we've received the last two winters falls on the calendar. The rainy season in California doesn't follow the yearly calendar; it starts in November and goes through April. This season largely corresponds to winter, when agricultural crops like grapevines are dormant. A grapevine doesn't care whether the rainfall arrives early or late in the dormant season; it's not going to start using that water until it sprouts in the spring. So looking at how much rain fell between January 2013 and April 2013 (some 2.35 inches at Tablas Creek) and ignoring the fact that November and December 2012 were unusually wet (11.74 inches) gives a false picture of both what last winter was like and what the growing conditions are now.
Similarly, the winter of 2011-12 was characterized by late rain: more than two-thirds of the 15 inches of rain that we received that winter came in 2012. Between the late rain that winter and the early rain the following winter, it looks like 2012 was an about average rainfall year, with just under 23 inches of rain out here, when in fact both the winters of 2011-2012 and 2012-2013 provided roughly half of normall rainfall.
So, while a headline like "13% of annual rainfall" makes for good copy, the situation on the ground is more nuanced. We've had two consecutive low-rainfall but hardly bone-dry winters in the books, and we're in the middle of what looks like another dry --maybe even very dry -- winter. That's plenty bad enough, but not unprecedented.
Why it may be worse than it seems
So why is the situation worse than it seems? We're not sure whether our historical norms are still what we should expect on average. We're in our 15th winter since 1999-2000, and in those winters, we've only seen four seasons with above-average rainfall (2004-05, 2005-06, 2009-10, and 2010-11). Two others (1999-2000 and 2007-2008) saw more or less average rainfall. That leaves nine years with 60% or less of normal rainfall, raising the question of what normal rainfall actually is for us now.
Most models of climate change suggest that rising global temperatures will result in drier conditions in the American southwest, including California. The EPA's Climate Change Center concludes that "human-induced climate change will likely result in more frequent and more severe droughts" in the our area. Both the EPA's low-emission and high-emission models project for significant declines in California precipitation over the 21st century:
Drought is by nature a cyclical phenomenon. But whether the current three-year dry pattern breaks this spring, next year, or later (and we're definitely hoping for sooner than later) it seems inevitable that we're entering a period where even relatively wet areas like ours will suffer more frequent and more prolonged periods of low rainfall, with all the attendant stresses on ground water supplies and growing tensions between agriculture, housing and recreation.
What to do?
How a vineyard is developed determines to a great extent the amount of water it needs each year to remain healthy and productive. The more closely spaced grapevines are, the more support they will need each year. This suggests that the old-school California vineyards planted before widespread irrigation are a model worth studying. These vineyards were planted at very low density by modern standards, often as much as 12 feet by 12 feet apart (rather than the current norm of 3 feet by 8 feet). We've been planting recent blocks -- such as our head-trained, dry-farmed "Scruffy Hill" block, pictured below -- using this old-fashioned vine density, and are cautiously optimistic about the results. Sure, we're not going to get 4 tons per acre, but that's not what we want anyway. We're seeing acceptable yields (2 to 2.5 tons per acre) and excellent vine health without irrigation over the last two dry years.
Other vineyard techniques that we've been using and expect to see more widely adopted in coming years include deep ripping of the soils before the rainy season, to encourage water to penetrate rather than run off, switching from more frequent but shorter-duration irrigation to less-frequent but longer-duration irrigation to encourage deeper root growth and better vine self-sufficiency, and greater exploration of higher-vigor, deeper-rooting rootstocks instead of the lower-vigor, more shallow-rooting rootstocks that are the most common today.
Even if "California's Driest Year on Record" is a bit of a statistical fluke, it's clear that it's dry here and likely to get drier. Anyone who is not planning now for that future is courting disaster.