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Overestimation of past and future increases in global river flow by Earth system models

Nature Geoscience (2026)Cite this article

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Abstract

Reliable quantification of global water-cycle components, such as river flow and land evapotranspiration, remains a major challenge. Here we refine estimates of global water partitioning by combining outputs from multiple Earth system models with river flow observations from 50 large basins, applying the emergent constraint approach. Between 1980 and 2014, global river flow was (39.1 ± 5.4) × 103 km3 yr−1, with a river flow-to-precipitation ratio of 0.35 ± 0.03, both lower than previous estimates. Land evapotranspiration reached (73.4 ± 6.2) × 103 km3 yr−1. Under climate change, we project global river flow to rise by 7.8 ± 5.5 mm per year per degree of warming. This estimate, refined through the emergent constraint method, is 9.3% lower than the ensemble mean of Earth system models and reduces inter-model uncertainty by 66%. By integrating river flow observations, we provide more accurate historical estimates and strengthen future projections of global water-cycle components.

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Fig. 1: Global runoff and its EC.
Fig. 2: Partitioning of the global water cycle using the EC approach.
Fig. 3: Changes in global water-cycle components under climate change.

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Data availability

Data used in the EC method for partitioning of global water-cycle components are stored at https://doi.org/10.5281/zenodo.11096334 (ref. 78). Source data are provided with this paper.

Code availability

The code generating figures is available from figshare (https://doi.org/10.6084/m9.figshare.30164416) (ref. 79).

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Acknowledgements

Y.Z. acknowledges financial support from the National Natural Science Foundation of China (grants 42330506 and 42361144709) and the Talent Program of the Ministry of Science and Technology of China. D.K. acknowledges financial support from the National Natural Science Foundation of China (grant 42430610). T.W. acknowledges 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). G.B., T.W. and F.H.S.C. acknowledge support from the PIFI outstanding international team project by the Chinese Academy of Sciences. We thank the following agencies and persons for sharing or providing streamflow data used for this study: the Global Runoff Data Centre, A. Dai, Service d’observation des ressources en eaux du bassin de l’Amazone, Agência Nacional de Águas, Ministry of Water Resources of the People’s Republic of China, the Arctic Great Rivers Observatory (https://arcticgreatrivers.org/), Peterson’s dataset, Mekong River Commission (https://portal.mrcmekong.org/home) and India Water Resources Information System. We thank H. Müller Schmied for providing WaterGAP model simulation outputs. We also thank P. Döll and H. Shiogama for their comments and suggestions.

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Authors and Affiliations

  1. Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China

    Yongqiang Zhang, Haoshan Wei, Ning Ma, Jing Tian, Congcong Li, Longhao Wang, Xingcai Liu, Xuanze Zhang & Changming Liu

  2. Institute of Hydraulic and Water Resources Engineering, Technische Universität Wien, Vienna, Austria

    Günter Blöschl

  3. University of Chinese Academy of Sciences, Beijing, China

    Haoshan Wei & Longhao Wang

  4. Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan, China

    Dongdong Kong

  5. Institute of Environmental Science and Geography, University of Potsdam, Potsdam, Germany

    Thorsten Wagener

  6. State Key Laboratory of Water Resources and Hydropower Engineering Sciences, Wuhan University, Wuhan, China

    Jun Xia

  7. CSIRO Environment, Canberra, Australian Capital Territory, Australia

    Francis H. S. Chiew & Hongxing Zheng

  8. Pacific Northwest National Laboratory, Richland, WA, USA

    L. Ruby Leung

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  1. Yongqiang Zhang
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  2. Günter Blöschl
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Contributions

Y.Z. designed this study, conducted most of the data analysis, prepared most of the figures and wrote the first draft. T.W., G.B. and F.H.S.C. provided critical insights into the data analysis. H.W., N.M. and C. Li collated streamflow datasets. D.K. collated CMIP6 and evapotranspiration datasets. X.L. proceeded with the WaterGAP model dataset. L.W. contributed to the global water-cycle diagram and figure optimization. All authors contributed to discussion, text revisions and result interpretations.

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Correspondence to Yongqiang Zhang.

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Zhang, Y., Blöschl, G., Wei, H. et al. Overestimation of past and future increases in global river flow by Earth system models. Nat. Geosci. (2026). https://doi.org/10.1038/s41561-025-01897-9

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