Severe land subsidence due to groundwater extraction may occur in multiaquifer systems where highly compressible aquitards are present. The highly compressible nature of the aquitards leads to nonlinear consolidation where groundwater flow parameters are stress-dependent. The case is further complicated by the heterogeneity of the hydrogeologic and geotechnical properties of the aquitards. We will illustrate the effect of realistic vertical heterogeneity of hydrogeologic and geotechnical parameters on the consolidation of highly compressible aquitards by means of one-dimensional Monte Carlo numerical simulations. Then we will present an algorithm to model these heterogeneous systems coupling the nonlinear groundwater flow and consolidation model with a data assimilation method based on ensemble Kalman filter. The approach allows to accurately estimate total settlement, the vertical distribution of stress-dependent variables and parameters and a measure of the uncertainty associated to those estimates. We will illustrate the approach with synthetic examples. Ongoing work is devoted to simulating land subsidence in a site in Mexico City.
Dr. Eric Morales-Casique is Senior Researcher in Subsurface Hydrology in the Institute of Geology of the Universidad Nacional Autónoma de México (UNAM). His research focuses on groundwater hydrology and mathematical and numerical modeling of groundwater flow and solute transport, particularly in the effect of heterogeneity and spatial variability of hydrogeologic parameters on our ability to model groundwater flow and solute transport processes. He is also interested in groundwater related problems in Mexico City, such as land subsidence due to intensive groundwater pumping; he has also collaborated in a subsurface exploration program in this city by means of five wells up to 2000 m depth. Morales-Casique is an alumnus (PHD Hydrology) of the Department of Hydrology and Atmospheric Sciences, University of Arizona.