Uncertainty in model estimates of global groundwater depth

Robert Reinecke*, Sebastian Gnann, Lina Stein, Marc Bierkens, Inge de Graaf, Tom Gleeson, Gualbert Oude Essink, Edwin H. Sutanudjaja, Claudia Ruz Vargas, Jarno Verkaik, Thorsten Wagener

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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.

Original languageEnglish
Article number114066
Number of pages12
JournalEnvironmental Research Letters
Volume19
Issue number11
DOIs
Publication statusPublished - 1 Nov 2024

Bibliographical note

Publisher Copyright:
© 2024 The Author(s). Published by IOP Publishing Ltd.

Funding

RR, SJG, LS, and TW acknowledge support from the Alexander von Humboldt Foundation in the framework of the Alexander von Humboldt Professorship endowed by the German Federal Ministry of Education and Research (BMBF). We thank Ying Fan Reinfelder for her helpful remarks on an early draft.

FundersFunder number
Alexander von Humboldt-Stiftunghttp://dx.doi.org/10.13039/100005156
Alexander von Humboldt Foundation
German Federal Ministry of Education and Research (BMBF)

    Keywords

    • global models
    • groundwater
    • uncertainty

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