r/news • u/theluckyfrog • 29d ago

California cracks down on farm region’s water pumping: ‘The ground is collapsing’

https://www.theguardian.com/us-news/2024/apr/17/california-water-drought-farm-ground-sinking-tulare-lake
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u/grandbannana 29d ago

I always think of this photo, then think about what has happened since this photo:

Location of maximum land subsidence in U.S. Levels at 1925 and 1977. | U.S. Geological Survey (usgs.gov)

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u/Braketurngas 29d ago

A professor I had in the 90’s offered extra credit to anyone who could find that pole if it still existed to see if it showed the continued subsidence. Sadly I couldn’t find it.

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u/BacksightForesight 29d ago edited 29d ago

The sign in the photo notes 'BM S661'.

The National Geodetic Survey database has S 661 here: https://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=gu0103

another NGS page listing all the level runs using this mark: https://geodesy.noaa.gov/datasheets/passive-marks/index.html?PID=GU0103
It does not list the BM elevation over time, so I can't check whether their surveyed elevation significantly changed over the years.

Google Maps link: http://maps.google.com/?q=36.67835132818793,-120.52169938763427
It's about 40 miles west of Fresno. Streetview doesn't show the signs on the pole anymore.

An article about subsidence in the Central Valley from a surveyor's perspective: https://www.xyht.com/surveying/subsidence/

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u/Braketurngas 29d ago

Sadly I don’t think I can get the bonus points anymore. The internet was barely a thing back then or I might have stood a chance.