Understanding each other's models: a standard representation of 16 global water models to support intercomparison, improvement, and communication

  • Global water models (GWMs) simulate the terrestrial water cycle, on the global scale, and are used to assess the impacts of climate change on freshwater systems. GWMs are developed within different modeling frameworks and consider different underlying hydrological processes, leading to varied model structures. Furthermore, the equations used to describe various processes take different forms and are generally accessible only from within the individual model codes. These factors have hindered a holistic and detailed understanding of how different models operate, yet such an understanding is crucial for explaining the results of model evaluation studies, understanding inter-model differences in their simulations, and identifying areas for future model development. This study provides a comprehensive overview of how state-of-the-art GWMs are designed. We analyze water storage compartments, water flows, and human water use sectors included in 16 GWMs that provide simulations for the Inter-Sectoral Impact Model Intercomparison Project phase 2b (ISIMIP2b). We develop a standard writing style for the model equations to further enhance model improvement, intercomparison, and communication. In this study, WaterGAP2 used the highest number of water storage compartments, 11, and CWatM used 10 compartments. Seven models used six compartments, while three models (JULES-W1, Mac-PDM.20, and VIC) used the lowest number, three compartments. WaterGAP2 simulates five human water use sectors, while four models (CLM4.5, CLM5.0, LPJmL, and MPIHM) simulate only water used by humans for the irrigation sector. We conclude that even though hydrologic processes are often based on similar equations, in the end, these equations have been adjusted or have used different values for specific parameters or specific variables. Our results highlight that the predictive uncertainty of GWMs can be reduced through improvements of the existing hydrologic processes, implementation of new processes in the models, and high-quality input data.

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Author:Camelia-Eliza TelteuORCiD, Hannes Müller SchmiedORCiDGND, Wim ThieryORCiDGND, Guoyong Leng, Peter BurekORCiDGND, Xingcai LiuORCiD, Julien Eric Stanislas BoulangeORCiD, Lauren Seaby AndersenORCiD, Manolis GrillakisORCiD, Simon N. GoslingORCiDGND, Yusuke Satoh, Oldrich RakovecORCiD, Tobias StackeORCiD, Jinfeng ChangORCiD, Niko WandersORCiD, Harsh Lovekumar Shah, Tim TrautmannORCiD, Ganquan MaoORCiD, Naota HanasakiORCiD, Aristeidis KoutroulisORCiD, Yadu PokhrelORCiDGND, Luis Eduardo Samaniego EguigurenORCiDGND, Yoshihide WadaORCiDGND, Vimal MishraORCiD, Junguo LiuORCiD, Petra DöllORCiDGND, Fang Zhao, Anne GädekeORCiD, Sam S. RabinORCiD, Florian HerzORCiDGND
Parent Title (English):Geoscientific model development discussions
Place of publication:Katlenburg-Lindau
Document Type:Article
Date of Publication (online):2021/01/08
Date of first Publication:2021/01/08
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2023/05/25
Page Number:56
First Page:1
Last Page:56
Begutachteter Artikel erschienen in: Geoscientific model development, 14.2021, Nr. 6, S. 3843–3878, doi: 10.5194/gmd-14-3843-2021
Code availability: Information on the availability of source code for the models featured in this article can be found in the Table 12
Correspondence to: Camelia-Eliza Telteu (telteu@em.uni-frankfurt.de)
Institutes:Geowissenschaften / Geographie / Geographie
Fachübergreifende Einrichtungen / Biodiversität und Klima Forschungszentrum (BiK-F)
Dewey Decimal Classification:9 Geschichte und Geografie / 91 Geografie, Reisen / 910 Geografie, Reisen
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International