Land subsidence in Mexico City: New insights from field data and numerical modeling

Abstract

Water supply to Mexico City relies mainly on groundwater from a regional aquifer overlain by highly compressible lacustrine sediments. Intensive pumping has originated land subsidence, threatening water supply and damaging urban infrastructure. A research site where the thickness of the aquitard reaches 100 m, was instrumented with piezometers, benchmarks and extensometers and monitored for 10 years. Data are analyzed to understand the main drivers and quantify their contribution to the process of land subsidence in Mexico City. Total settlement amounted to 3.661 m, at an average rate of 0.314 m/year. Increase in total stress due to new infrastructure built near the site (a highway) at the start of the monitoring period amounts for 35% of the observed total settlement; this deformation takes place from 0 to 36 m within the aquitard, where pore pressure maintained a hydrostatic distribution. Our analysis shows that the main driver for land subsidence is groundwater pumping from the regional aquifer as most of the deformation due to consolidation (2.128 m) was registered below a depth of 82 m. Since the thickness of the aquitard at the research site is 100 m, numerical simulation shows that most of this deformation most probably takes place at interbedded compressible lenses within the regional aquifer. Future modeling efforts in Mexico City need to consider this process.