Groundwater Deficit and Land Subsidence in the Lerma-Santiago-Pacifico Watershed, Mexico
In this project, gravimetric data from GRACE satellites, radar data from Radarsat-2, and field data are combined and interpreted. The study aims to evaluate: (1) the deficit at the scales of major cities (Toluca, Aguascalientes, Guadalajara, Querétaro, Morelia, León, and Celaya); (2) the consequences of this deficit: land subsidence and surface deformation; and (3) the accumulated impacts of the local deficits on the hydrogeological dynamics of the watershed.
GRACE data have been generated since 2002, measuring large scale gravimetric variations. Total water storage variations are extracted from these data, resulting in a combination of four signals: (1) unsaturated soil water storage; (2) surface water storage; (3) snowpack water storage; and (4) groundwater storage. A proper estimation of these parameters allows the user to extract the remaining parameter. In this study, groundwater storage variation are extracted and interpreted along with field and InSAR data.
InSAR techniques allow a complete monitoring of the land surface deformations over the watershed. Results can be interpreted along with lithology and water extraction data. A numerical model combined with a subsidence module can be calibrated using results of land subsidence gradient maps from InSAR. Nowadays, new PS-InSAR techniques of land subsidence monitoring are evolving toward a better understanding of spatial and temporal variations of soil surface, allowing a better estimation of underlying hydrogeological processes.
In this session techniques, principles, and limitations are presented, as well as the first results on the evaluation of the groundwater storage variations and mapping of land subsidence over the watershed.