“Reason is the first casualty in a drought”*…
n 1878, without benefit of the Landsat program, GPS or Google, and just a decade after the creation of the National Weather Service, John Wesley Powell first advanced the idea that the climatic boundary between the United States’ humid East and arid West lay along a line “about midway in the Great Plains” — almost exactly 100 degrees longitude west of the prime meridian in Greenwich, England. This line, the 100th meridian, runs from pole to pole and cuts through six U.S. states, forming a partial boundary between Oklahoma and Texas. The 100th meridian also corresponds roughly to the 600-meter elevation contour as the land rises from the Great Plains toward the Rockies.
In his 1878 “Report on the Lands of the Arid Region of the United States,” Powell identified the “arid region” as the land west of the 51-centimeter-per-year rainfall line, which closely tracked the 100th meridian. This amount of rainfall per year is about the minimum that permits farming without irrigation, and it also greatly influences the types of crops that can be grown. The line Powell noted as dividing the arid and humid sections of the continent has become known as the “effective” 100th meridian.
Powell’s original goal in describing the effective 100th meridian as a dividing line was to persuade the federal government to bear in mind the greater aridity when planning for settlement and development in the western territories, which would be very different than in the moisture-rich east…
Today, the 100th meridian is still considered a climatic boundary line, but that will likely change in the coming decades: The 51-centimeter rainfall line is gradually moving east due to climate change, according to recent research…
The very middle of the U.S. is becoming increasing drier, with what are sure to be huge consequences: “Dividing line: The past, present and future of the 100th Meridian.”
* Marc Reisner, Cadillac Desert: The American West and Its Disappearing Water
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As we ponder parching, we might send environmentally-unfriendly birthday greetings to C. Montgomery Burns; he was (fictionally) born on this date in 1893. A recurring character in the animated television series The Simpsons (voiced initially by Christopher Collins, and currently by Harry Shearer), he is the evil, devious, greedy, and fabulously wealthy owner of the Springfield Nuclear Power Plant and, by extension, Homer Simpson’s boss.
“Excellent.”
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