Uncertainty in model estimates of global groundwater depth
Date
2024
Authors
Reinecke, Robert
Gnann, Sebastian
Stein, Lina
Bierkens, Marc
de Graaf, Inge
Gleeson, Tom
Essink, Gualbert Oude
Sutanudjaja, Edwin H
Ruz Vargas, Claudia
Verkaik, Jarno
Journal Title
Journal ISSN
Volume Title
Publisher
Environmental Research Letters
Abstract
Knowing the depth at which groundwater can be found below the land surface is critical for understanding its potential accessibility by ecosystems and society. Uncertainty in global scale water table depth (WTD) limits our ability to assess groundwater’s role in a water cycle altered by changing climate, land cover, and human water use. Global groundwater models offer a top–down pathway to gain this knowledge, but their uncertainty is currently poorly quantified. Here, we investigate four global groundwater models and reveal steady-state WTD disagreements of more than 100 m for one-third of the global land area. We find that model estimates of land areas with shallow groundwater at <10 m depth vary from 10% to 71% (mean of 23%). This uncertainty directly translates into subsequent assessments, as land areas with potential groundwater accessibility for forests, population, and areas equipped for irrigation, differ substantially depending on the chosen model. We explore reasons for these differences and find that contrary to observations, 3 out of 4 models show deeper water tables in humid than in arid climates and greatly overestimate how strongly topographic slope controls WTD. These results highlight substantial uncertainty associated with any global-scale groundwater analysis, which should be considered and ultimately reduced.
Description
Keywords
groundwater, global models, uncertainty
Citation
Reinecke, R., Gnann, S., Stein, L., Bierkens, M., De Graaf, I., Gleeson, T., Essink, G. O., Sutanudjaja, E. H., Vargas, C. R., Verkaik, J., & Wagener, T. (2024). Uncertainty in model estimates of global groundwater depth. Environmental Research Letters, 19(11), 114066. https://doi.org/10.1088/1748-9326/ad8587