1. Implemented groundwater module (gwflow) into SWAT+ for four watersheds with different unique hydrologic features across the United States.

2. Presented methods for sensitivity analysis, uncertainty analysis and parameter estimation for coupled models.

3. Sensitivity analysis for streamflow and groundwater head conducted using Morris method.

4. Uncertainty analysis and parameter estimation performed using an iterative ensemble smoother within the PEST framework.

This opinion paper reflects on the risks of overusing groundwater savings to supply permanent water use requirements. Using novel data recently developed for Chile, we reveal how groundwater is being overused, causing ecological and socioeconomic impacts and concealing a Day Zero scenario. Our argument underscores the need for reformed water allocation rules and sustainable management, shifting from a perception of groundwater as an unlimited source to a finite and vital one.