Mexico City sinking as aquifer exhausted

[Judi Lynn]

Mexico City sinking as aquifer exhausted

Extended periods of drought in the future could make the problem worse.

By Brooks Hays | Dec. 11, 2014 at 2:14 PM

MEXICO CITY, Dec. 11 (UPI) -- As Mexico City continues to pull water from the aquifer below, its ground is sinking. The process is called subsidence. Now, the city's subsidence can be visualized from the perspective of low Earth orbit.
The European Space Agency has created an ariel composite image -- compiled using satellite imagery collected between October 3 and December 2 -- showing the city's rate of subsidence. Some areas of the city are sinking as much as one inch per month.

The subsidence that results from groundwater extraction is a problem all over the world, but is especially dramatic in Mexico City. The aquifer has been under increasing pressure over the last several decades as the city's population has skyrocketed. Additionally, the city is mostly constructed atop layers of clay and highly permeable sand and gravel -- the type of ground most liable to collapse as water is pulled out.

While subsidence has been stabilized in the city center, many parts of the metropolitan area, as evidenced by ESA's new map, continue to shrink. Some parts have sunk more than 30 feet during the last century.

More:
http://www.upi.com/Science_News/2014/12/11/Mexico-City-sinking-as-aquifer-exhausted/9531418321604/#ixzz3LcYhKwL7

[TlalocW]

1. In the 90s, I remember seeing two photos

Of the same thing in Mexico City - of a simple water pump coming out of the ground - the kind where you pull up on a lever and water comes out. In the first picture taken in the 50/60s when it was just put in, the pump was 2 feet off the ground like it should be. In the second picture, taken in the 80/90s, the pump was now ten feet in the air - the ground had sunk around it revealing more of the pipe it was connected to that once had been underground. It was a stark example of what's happening.

TlalocW

[Judi Lynn]

2. That IS a shocking example, absolutely no doubt. I've never seen that happen to one of those pumps.

Sickening.

Can't imagine what people must feel who can see this going on right where they live.

Thank you, TlalocW.

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