Quantitative mapping of groundwater depletion at the water management scale using a combined GRACE/InSAR approach

In order to illustrate the GRACE/InSAR combination procedure, we present a case study in Central Mexico, where groundwater depletion of ~ 5000 Million Cubic Meters per year (MCM/yr) is reported by the water governance agencies and is well documented in the scientific literature. However, in this region, not all GRACE solutions provide reasonable groundwater depletion estimates. Using two of them, an inversion is performed to focus the groundwater-related GRACE signal over different mass distribution maps. Several mass distributions are tested, including two from InSAR-derived aquifer compaction mapping. The results show that the regions of Mexico City and Bajio, an agricultural and industrial corridor 250 km North of Mexico City, are the main contributors to the regional groundwater depletion. The mass distribution map produced directly from InSAR leads to results closer to official groundwater budgets than the others tested.