Mexico City officials exploring new aquifer they hope can resolve capital's water problem

People gather for a ceremony to unveil an aquifer found by an exploratory well in Mexico City, Wednesday, Jan. 23, 2013. City authorities announced the discovery of an aquifer more than a mile below ground that could provide enough water for at least some of the metropolitan area's 20 million residents but warned that many feasibility studies remain to be done. (AP Photo/Dario Lopez-Mills) (The Associated Press)

A city worker stands next to large tubes as he watches a ceremony unveiling an exploratory well into a recently found aquifer in Mexico City, Wednesday, Jan. 23, 2013. City authorities announced the discovery of an aquifer more than a mile below ground that could provide enough water for at least some of the metropolitan area's 20 million residents but warned that many feasibility studies remain to be done. (AP Photo/Dario Lopez-Mills) (The Associated Press)

Mexico City's Mayor Miguel Angel Mancera, behind right, and General Director of Mexico's National Water Commission David Korenfeld Federman, behind center, watch geologist Federico Mooser take a drink of water from an exploratory well that discovered an aquifer in Mexico City,Wednesday, Jan. 23, 2013. City authorities announced the discovery of an aquifer more than a mile below ground that could provide enough water for at least some of the metropolitan area's 20 million residents but warned that many feasibility studies remain to be done. (AP Photo/Dario Lopez-Mills) (The Associated Press)

Mexico City officials are launching a new, deep-drilling effort to tap into what may be a new aquifer about 6,560 feet (2,000 meters) underground.

The Mexican capital is built on the spongy soil of a former lake bed. So much water has been extracted from shallow near-surface wells that the city is sinking.

Mexico City Mayor Miguel Angel Mancera visited the new drilling site Wednesday. He says more drilling is needed to explore the deep limestone strata and determine how much water is there.

The city also has to pump in water from outside sources to supply more than 21 million people living in the greater metropolitan area.

Paradoxically, the city is also plagued by periodic flooding because it sits in a mountain-ringed valley with no natural outlet.