Mexico City sinking at unstoppable rate
After centuries of water drainage from underground aquifers, the lake bed on which this city sits has grown increasingly dry, causing the clay sheets to compress and crack at a largely unstoppable rate, E. Havazli, H. Fattahi, E. Cabral‐Cano, and D. Solano‐Rojas write.
Not only does this put infrastructure at risk, it also threatens water security for millions of people.
Despite putting an end to groundwater drilling in the 1950s, 115 years of leveling data and 24 years of GPS data has found the city is continuing to drop at roughly the same rate.
In the northeast sector of the city - an area that is still not yet urbanized and where sinking rates have so far gone undetected - researchers have found the land is depressing at a rate of up to 50 centimeters a year.
"Even if water levels were to be raised, there is no hope for recovering the great majority of the lost elevation and the lost storage capacity of the aquitard," the authors write. An aquitard is a region that restricts groundwater flowing from one aquifer to another.
Using modern data, researchers now estimate the clay sheets underneath Mexico City could ultimately compress by 30 percent, and while that won't happen for another 150 years or so, there's little we can do to stop it.
Today, the upper clay of the city is already 17 percent compacted, and the authors say these changes are "almost fully irreversible." ■