Friday, January 6, 2012

Dry Times in California

Vermont has finally picked up a little bit of snow, but California is not faring as well.  After a relatively wet start to fall in at least southern California, conditions have become extremely dry across the entire state.



(Above map from the Western Regional Climate Center)





Rainfall in southern California is rather fickle.  In Los Angeles over the last 100 years, yearly precipitation (as measured from July 1 to June 30) has ranged from over 35 inches- around the average precipitation of Portland, Oregon... to around 4 inches - which is around the average precipitation of Las Vegas, Nevada.  There have been Decembers in southern California with little or no precipitation.  Besides, the few storms in the last 60 days (mostly in November) actually targeted extreme southern California, mostly missing the northern part of the state.  Northern California, on the other hand, generally picks up more reliable winter precipitation and this shortage is rather extreme.  The mountains of northern California - the Sierras, the Klamath Mountains, the Trinity Alps, and the Mount Shasta area - provide most of the drinking and irrigation water for the state.  We've got a lot of catching up to do if we are to pick up average snowfall in these areas!


(National Weather Service image, as posted on Weather West blog)

The reason for the dry conditions in California as well as the lack of snow in much of the rest of the US appears to be a rare and extremely amplified jet stream position - the opposite of an equally extreme jet stream pattern that occurred last year and brought heavy snow to most of the same areas.  As mentioned in this same article, last year's extreme jet stream layout may have been associated with a lack of Arctic sea ice - whereas this year's jet stream may be more related to activity associated with the sun - but no one knows for sure.

While some disasters, like hurricanes, tornados, and earthquakes, are clearly acts of nature, droughts are a bit more complex.  People are ready to declare a drought any time there is not as much water as people want.  In truth, California and the rest of the US Southwest suffer more from a water shortage than a drought.  As seen in the graph in that link, the main issue is increasing demand, rather than decreasing supply.  There is no evidence that average precipitation in California is decreasing - stories of springs drying up and creeks that used to flow and are now dry are very likely true, but are due to watershed degradation and groundwater extraction rather than decreases in precipitation.  A few years back I talked to an expert on California's pre-colonization climate, and he told me something terrifying - California is actually experiencing much wetter weather than it has over the last few thousand years.  There is evidence that extremely severe droughts have impacted the area in the last few thousand years.  Were one of these droughts to occur today, life as we know it in California would end.  At best, there would be very dramatic lifestyle changes, and at worst the area would descend into immediate depopulation, a dust-bowl type scenario and probably civil unrest or perhaps even war.

The worst case scenario hopefully won't happen in our lifetimes, but between natural climate variability and changes caused by humans (both to the climate and to watersheds), it makes sense to prepare now for times of sparsity ahead.  If you live in the area, the single best thing you can do is GET RID OF YOUR LAWN and other thirsty plants in your landscaping.  Lawns will probably vanish from most of California in the next couple of decades anyway.  Removing some or all of your lawn and replacing it with native plants or non-invasive cacti and succulents will save an amazing amount of water.  Or, replace your lawn with a vegetable garden.  You'll need to water it more than native plants or cacti, but you will be taking a bit of the burden off of the food system that also requires a lot of water.  Local parks can retain their lawns for sports and picnics, ideally using reclaimed water.

If you have a pool you don't use much, consider getting rid of it, or at least putting a cover on it.  Evaporation from pools also wastes a lot of water.  Instead, visit a community pool or go to the beach!

Also, don't forget that rain barrels and cisterns can collect a huge amount of water, even during dry winters.  Depending on what your roof is made of the water may not be usable for irrigating food crops, but it's great for keeping other landscape plants alive.

And, hope for the best - a soggy, snowy remainder of the winter!  There is some evidence that the persistent climate pattern of the past few months may be changing, which could bring more precipitation to California (and possibly extreme cold to Vermont) after the next 10 days or so.  But, long range forecasts are iffy, and it may not happen.  We'll see.

2 comments:

  1. Very informative post. Thank you for sharing.

    ReplyDelete
  2. I appreciate your post. Valuable advices indeed.

    ReplyDelete