Preprints
https://doi.org/10.5194/gmd-2024-131
https://doi.org/10.5194/gmd-2024-131
Submitted as: model description paper
 | 
18 Jul 2024
Submitted as: model description paper |  | 18 Jul 2024
Status: a revised version of this preprint is currently under review for the journal GMD.

The Water Table Model (WTM) v2.0.1: Coupled groundwater and dynamic lake modelling

Kerry L. Callaghan, Andrew D. Wickert, Richard Barnes, and Jacqueline Austermann

Abstract. Ice-free land comprises 26 % of Earth’s surface and holds liquid waters that delineate ecosystems, affect global geochemical cycling, and modulate sea level. However, we currently lack capacity to simulate and predict these terrestrial water changes over the full range of relevant spatial (watershed to global) and temporal (monthly to millennial) scales. To address this gap in knowledge, we present the Water Table Model (WTM), which comprises coupled components to compute dynamic lake and groundwater levels. The groundwater component solves the 2D horizontal groundwater-flow equation by using non-linear equation solvers in the C++ PETSc library. The dynamic lakes component makes use of the Fill-Spill-Merge (FSM) algorithm to move surface water into lakes, where it may evaporate or affect groundwater flow. To demonstrate the continental scale capabilities of the WTM, we simulate steady-state climate-driven present-day and Last Glacial Maximum (LGM: 21,000 calendar years before present) water table for the North American continent. At the LGM, North America stored 6.0 cm sea-level equivalent (SLE) more water in lakes and groundwater than in the climate-driven present-day scenario. We then advance the simulation transiently from 21–16 ka, in which lake volume remains approximately constant but groundwater storage drops by 4.5 cm SLE due to reduced precipitation. Open-source code for the WTM is available on Github and Zenodo.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Kerry L. Callaghan, Andrew D. Wickert, Richard Barnes, and Jacqueline Austermann

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2024-131', Anonymous Referee #1, 29 Jul 2024
    • RC2: 'Reply on RC1', Anonymous Referee #1, 29 Jul 2024
    • RC3: 'Reply on RC1', Anonymous Referee #1, 22 Aug 2024
  • RC4: 'Comment on gmd-2024-131', Reed Maxwell, 31 Aug 2024
  • RC5: 'Comment on gmd-2024-131', Anonymous Referee #3, 12 Sep 2024
  • AC1: 'Response to reviewer comments', Kerry Callaghan, 02 Nov 2024
Kerry L. Callaghan, Andrew D. Wickert, Richard Barnes, and Jacqueline Austermann

Model code and software

Water Table Model Kerry L. Callaghan, Richard Barnes, and Andrew D. Wickert https://github.com/KCallaghan/WTM

Kerry L. Callaghan, Andrew D. Wickert, Richard Barnes, and Jacqueline Austermann

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Short summary
We present the Water Table Model (WTM), which simulates groundwater and lake levels at continental scales over millennia. Our simulations show that North America held more ground- and lake-water at the Last Glacial Maximum than in the present day – enough to lower sea level by 6 cm. We also simulate the changing water table from 21,000 to 16,000 years ago, finding that groundwater storage decreased following reduced precipitation in the model inputs. Open-source WTM code is available on Github.