A lakebed that keeps compressing
Much of Mexico City sits on the former bed of Lake Texcoco and other lakes in a high basin. The lake water is gone, but the soft sediments left behind are still there: layers of clay that hold water and behave more like a compressed sponge than solid rock.
As the city draws groundwater from underground aquifers, pressure in those water-bearing layers falls. The clay above them gradually squeezes together, pushing water out and reducing the soil’s volume. That compaction is difficult to reverse, even if pumping later slows. The weight of buildings adds pressure, but the changing groundwater conditions are a major driver of the ongoing settlement.
The ground does not sink evenly
Different parts of the basin contain different sediments and experience different levels of groundwater withdrawal. As a result, the city settles unevenly. One street may drop more than a nearby block, putting strain on buildings, roads, water pipes and other buried infrastructure. A structure can tilt or crack not simply because the whole city is moving, but because its supports are moving at different rates.
The changes also affect drainage. Mexico City already has to move stormwater and wastewater out of a basin with little natural outlet. When sections of the ground settle at different rates, canals, pipes and other drainage routes can lose some of their intended slope, making water management harder.
A visible city, a shifting foundation
The sinking is not just a geological curiosity beneath the pavement. It can gradually reshape the elevations that streets and infrastructure were built to follow. In a city built on a drained lakebed, keeping those systems working means adapting to a surface that continues to change—sometimes subtly from year to year, but persistently beneath everyday life.
