Tuesday, April 10, 2007

How Dry Is It?

It is very dry, and it is about the become drier.

The US Drought Monitor says we are in an extreme drought in southern California. You may wonder, just how bad is it?
  • The National Weather Service has a page full of Precipitation Data links.
  • You can go directly to the water year 2007 page. ("The water year starts on Oct 1 and ends on Sept 30." Wow! Precipitation follows the Federal Fiscal Year calendar.)
It is bad; LAX has received only 2.16 inches of rain so far in this water year. We typically don't get much more in the late spring and summer. Remember the skewness of the rainfall distribution I mentioned before? Even though we have received 18% as much rainfall as an average year, we are at more than that compared to a median year. There are simply more dry years than wet years. The relatively few extremely wet years make the average rainfall substantially higher than the median rainfall.

In fact, the western US may be heading to a permanent drought. The LA Times has a good story about this. What if the climatology that the water treaties were based upon water data from an anomalously wet period? Now that we have a more complete climatology, we know that more water has been promised than typically falls.

"This is a situation that is going to cause water wars," said Kevin Trenberth, a scientist at the National Center for Atmospheric Research in Boulder, Colo.

"If there's not enough water to meet everybody's allocation, how do you divide it up?"

The story is even bleaker. Many parts of the west have been supplementing rainfall by pumping water from the Oglala aquifer. According to the USGS, this ancient water, stored up over a period of hundreds of thousands of years, is being depleted at a rapid rate, especially in Texas and Kansas. Water in storage in Texas was down by 27% between the 1940s and the year 2000.

Depletion is especially severe in the Lubbock, Texas area. What is the water used for? To grow cotton in the desert, possibly to make T-shirts that no one really needs.

Fashion Incubator has been blogging about sustainable fashion. As usual, her reasoning is sound and backed up with data.

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