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Megadrought in south western USA

  1. Oct 8, 2016 #1


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  2. jcsd
  3. Oct 8, 2016 #2


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    ScienceDaily seems to sensationalize science news, but I believe there is a general consensus that the Western US, and perhaps particularly the SW US, will see diminished precipitation during this century. We certainly see a lot less snow in the mountains in Cascades and Sierra Nevada ranges.

    California and Oregon monthly precipitation - http://www.cnrfc.noaa.gov/rainfall_data.php#monthly


    Colorado climate (2003) - dated material

    http://climatetrends.colostate.edu/ [Broken] - more recent - but specific data hard to locate.
    http://climate.colostate.edu/~drought/ - current analysis

    US drought situation - http://www.ncdc.noaa.gov/sotc/drought/201608
    Last edited by a moderator: May 8, 2017
  4. Oct 8, 2016 #3
    This is the source of the megadrought story: http://advances.sciencemag.org/content/2/10/e1600873

    Relative impacts of mitigation, temperature, and precipitation on 21st-century megadrought risk in the American Southwest

    In the late '90s started focusing on global water issues and, living in the western US, looked closely at changing climate patterns there and that effect on water reserves . Even with a couple years of good snowpacks in the Sierra Nevada, the recharge of the water into the total system will not be enough to take California out of its drought. What isn't seen by looking at surface water is that aquifers aren't being recharged. That's bad for the people who draw on them. What's bad for the plants is that rainfall isn't recharging the soil. Just before this last Big Sur fire, I was monitoring soil moisture in the area. Since 2002, rainfall hasn't been sufficient to wet the soil deeper than a few inches. In the past it was the cumulative effect of successive winter storms that wetted the soil to below the root zone. Now, many oaks and pines that were identified as water-stressed back then are dead. I haven't quite figured out what is happening in Arizona, where I live half the time. There is sufficient rainfall to keep drought-resistant native shrubs alive, but I've lost a few trees on my property. Ironically (to me) is that the humidity has increased so that moss is growing in shaded areas of the arroyos. The long term weather that defines climate zones is unstable and in the end, given the current climate models, it appears that the desert/arid climate zone is expanding in the Southwest. This is a rough and crude summary of what we've come up with in the Global Environmental Focus Group of the American Geophysical Union.
  5. Dec 13, 2016 #4


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    For the globe, this seems to be the definitive history of the last thirty years.

    Source: Hao, Z. et al. Global integrated drought monitoring and prediction system. Nature, Scientific Data 1, Article number: 140001 (2014) doi:10.1038/sdata.2014.1

    "Fraction of global land areas under D0 to D4 drought severity levels"

    "Fraction of the global land in D0 (abnormally dry), D1 (moderate), D2 (severe), D3 (extreme), and D4 (exceptional) drought condition (Data: Standardized Precipitation Index data derived from MERRA-Land). "
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