Mexico City's Sinking Lands

TL;DR

Mexico City sinks 35–50 cm per year because centuries of groundwater pumping from ancient lakebed clay soils causes irreversible compression.

Key Points

• 1.Mexico City sits on a drained ancient lakebed. The Basin of Mexico once held five interconnected lakes; Lake Texcoco alone spanned 7,800 sq km but now covers just 16 sq km after deliberate drainage over centuries.
• 2.The Aztec city of Tenochtitlán was built on a lake island. Founded in the 1320s–1340s, it reached 200,000 residents and used sophisticated water engineering including the Nezahualcoyotl dyke, which the Spanish later destroyed.
• 3.Spanish colonization dismantled flood defenses, triggering catastrophic flooding. The 1629 flood killed an estimated 30,000 people and left Mexico City underwater for five years after drainage gates were controversially closed.
• 4.Groundwater pumping began in 1847 and directly causes the sinking. By 1886 there were over 1,000 shallow wells; removing water from clay-rich lakebed soils causes them to compress up to 25–30% of their original volume.
• 5.Subsidence rates peaked at 46 cm/year in some downtown areas. Despite engineers proving the link to pumping by the 1920s, a 1947 pumping restriction was widely ignored due to economic and industrial interests.
• 6.Infrastructure across the city is severely damaged by uneven sinking. The Grand Drainage Canal's flow actually reversed from subsidence, requiring a new exit tunnel in 1960; the city also loses 40% of its water to leaks and breaks.
• 7.Even a full stop to pumping today won't halt the sinking. Estimates suggest subsidence will continue for another 150 years and up to 30 more meters as the lakebed keeps compressing, while 58–70% of water supply still comes from the ground.