Thursday, April 25, 2013

Probably Just a Coincidence

In the winter, some of us who live along the Front Range of the Rockies (roughly from Casper, Wyoming as far south as Pueblo, Colorado) keep an eye on the mountain snow pack.  That's the water that's going to caught in the reservoirs for use next summer.  A month ago, we were looking at a pretty lean snow pack.  Multiple late-season storms have eased the situation somewhat in parts of the mountains.  Some of the drainages (there's a reason Colorado is sometimes known as the "Mother of Rivers") in the northern part of the state are now above 100% of the 30-year average for the date and all of them are above 90%.  In contrast, the southern drainages, and the southwestern part of the state in particular are in much worse shape.  The Upper Rio Grande is at only 68%; we're not going to be sending much water to New Mexico and Texas this year.  Texas is already busy fighting over water with its neighbors.  The Supreme Court heard a case between Oklahoma and Texas this week.  Earlier this year, Texas filed another Supreme Court case against New Mexico.

This division of Colorado into a relatively wet north and a quite dry south reminded me of another map I had reviewed lately.  This map of North America is taken from the U.S. Global Change Research Program's draft 2013 report to Congress.  This figure shows changes in winter and spring precipitation for later this century under a continued high CO2 emissions scenario (you should be able to "View Image" or similar in your browser to see a larger image).  Blue-green colors indicate increased precipitation, brown shades decreased precipitation, with darker colors indicating greater changes.  Colorado sits roughly in the area where the changes come together -- increased precipitation in the north, decreased in the south, the same sort of pattern that we're seeing in this year's snow pack.

The similarity of the maps is probably just a coincidence.

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