Letter | Published:

Terrestrial water fluxes dominated by transpiration

Nature volume 496, pages 347350 (18 April 2013) | Download Citation

Abstract

Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km3 per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth’s continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km3 of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates6. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.

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Acknowledgements

We thank T. W. D. Edwards, T. Gleeson and M. C. Molles Jr for comments on the manuscript, and are grateful to O. Kwiecien, D. G. Miralles, B. K. Nyarko, K. Yoshimura and F. Yuan for providing access to isotope and gridded data sets. Support for this work was provided by a graduate fellowship awarded to S.J. by the Caswell Silver Foundation through the University of New Mexico.

Author information

Affiliations

  1. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA

    • Scott Jasechko
    • , Zachary D. Sharp
    •  & Peter J. Fawcett
  2. Alberta Innovates – Technology Futures, Vancouver Island Technology Park, Victoria, British Columbia V8Z 7X8, Canada

    • John J. Gibson
    • , S. Jean Birks
    •  & Yi Yi
  3. Department of Geography, University of Victoria, Victoria, British Columbia V8W 3R4, Canada

    • John J. Gibson
    •  & Yi Yi
  4. Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

    • S. Jean Birks

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Contributions

S.J. designed the study, compiled each data set, did the geographic information system and remote sensing work, developed the equations, did the water balance and carbon flux calculations, and wrote the paper. Z.D.S., J.J.G., S.J.B., Y.Y. and P.J.F. discussed the results, commented on the manuscript and contributed to text.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Scott Jasechko.

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    Supplementary Information

    This file contains Supplementary Text, Supplementary Figures 1-6 Supplementary Tables 1-6 and Supplementary References.

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    Supplementary Data

    This file contains a tabulated dataset of δ18O and δ2H values (V-SMOW standard reference) for large lakes.

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https://doi.org/10.1038/nature11983

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