Sinking poses severe risk to infrastructure, may lead to groundwater contamination
Mexico City, the heavily populated capital of Mexico, is sinking at an alarming and nearly irreversible rate, according to a recent study.
The city is sinking as groundwater drilling over centuries has caused the clay the city sits on to become dry, crack and compress. This poses a severe risk to infrastructure and water security for millions of city residents, the study said as quoted by Sciencealert.com.
The cracks in the clay may allow rain and spring water running off from the surrounding area to flow through and contaminate ground water with sewerage, it added.
The study, titled “Over a Century of Sinking in Mexico City: No Hope for Significant Elevation and Storage Capacity Recovery,” was published in the journal JGR Solid Earth on March 30.
"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," said the study.
An aquitard is a region that restricts groundwater flowing from one aquifer to another.
Scientists first noticed Mexico City was sinking in the early 1900s, at a rate of roughly 8cm a year. The rate had increased to 29cm a year by 1958, at which point the amount of groundwater that could be drawn from wells in the city was limited.
Although the measure was thought to have brought the sinking rate back down to less than 9cm per year, data in the new study has found that the downtown area of Mexico City has been sinking at a consistent rate of 40cm a year.