Groundwater deficits occur in several areas of Central Mexico, where water resource assessment is limited by the availability and reliability of field data. In this context, GRACE and InSAR are used to remotely assess groundwater storage loss in one of Mexico's most important watersheds in terms of size and economic activity: the Lerma‐Santiago‐Pacifico (LSP). In situ data and Land Surface Models are used to subtract soil moisture and surface water storage changes from the total water storage change measured by GRACE satellites. As a result, groundwater mass change time‐series are obtained for a 12 years period. ALOS‐PALSAR images acquired from 2007 to 2011 were processed using the SBAS‐InSAR algorithm to reveal areas subject to ground motion related to groundwater over‐exploitation. In the perspective of providing guidance for groundwater management, GRACE and InSAR observations are compared with official water budgets and field observations. InSAR‐derived subsidence mapping generally agrees well with official water budgets, and shows that deficits occur mainly in cities and irrigated agricultural areas. GRACE does not entirely detect the significant groundwater losses largely reported by official water budgets, literature and InSAR observations. The difference is interpreted as returns of wastewater to the groundwater flow systems, which limits the watershed scale groundwater depletion but suggests major impacts on groundwater quality. This phenomenon is enhanced by ground fracturing as noticed in the field. Studying the fate of the extracted groundwater is essential when comparing GRACE data with higher resolution observations, and particularly in the perspective of further InSAR/GRACE combination in hydrogeology.

As a result of global climate change, glacial melt occurs worldwide. Major impacts are expected on the dynamics of aquifers and rivers in and downstream of mountain ranges. This study aims at quantifying the melt water input fluxes into the watersheds draining the Canadian Rocky Mountains and improving our knowledge about the fate of meltwater within the hydrological cycle. To this end, we use (1) time‐variable gravity data from GRACE satellites that is decomposed into water storage change; (2) an ensemble of glacier information: in situ observations, geodetic measurements, and a mass balance model and (3) in situ surface water and groundwater level observations. The glacier mass balance model estimates a total ice mass change of ~43 Gt for the period 2002‐2015, corresponding to an average of ‐3,056 (±2,275) MCM/yr. 78% of the meltwater total flows West of the continental divide (to the Pacific Ocean), while 22% flows East of the continental divide (to the Arctic Ocean and Hudson Bay). However, the GRACE‐derived total water storage increases, suggesting that groundwater storage compensates for the glacial melt with an increase of 3,976 (± 2,819) MCM/yr. A plausible explanation is that meltwater is not immediately flowing down in rivers but rather stored locally in aquifers. This hypothesis is supported by in situ river base flow observations, showing base flow increase in basins draining the ice melt, mostly west of the continental divide. Direct in situ evidences such as well water level time‐series are not sufficiently available to fully support this hypothesis.