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Global water resources affected by human interventions and climate change

  1. Dominik Wisseri,j
  1. aDepartment of Hydrology, Norwegian Water Resources and Energy Directorate, NO-0301 Oslo, Norway;
  2. bPotsdam Institute for Climate Research, 14473 Potsdam, Germany;
  3. cInternational Livestock Research Institute, Nairobi 00100, Kenya;
  4. dEarth System Science and Climate Change Group, Wageningen University and Research Centre, 6700 AA Wageningen, The Netherlands;
  5. eCenter for Environmental Systems Research, University of Kassel, 34109 Kassel, Germany;
  6. fCenter for Global Environmental Research, National Institute for Environmental Studies, Tsukuba 305-8506, Japan;
  7. gMax Planck Institute for Meteorology, 20146 Hamburg, Germany;
  8. hCivil Engineering Department, City College of New York, New York, NY 10031;
  9. iDepartment of Physical Geography, Utrecht University, 3584 CD Utrecht, The Netherlands; and
  10. jCenter for Development Research, University of Bonn, 53113 Bonn, Germany

  1. Edited by Katja Frieler, Potsdam Institute for Climate Impact Research, Potsdam, Germany, and accepted by the Editorial Board August 5, 2013 (received for review January 30, 2013)

Significance

Humans alter the water cycle by constructing dams and through water withdrawals. Climate change is expected to additionally affect water supply and demand. Here, model analyses of climate change and direct human impacts on the terrestrial water cycle are presented. The results indicate that the impact of man-made reservoirs and water withdrawals on the long-term global terrestrial water balance is small. However, in some river basins, impacts of human interventions are significant. In parts of Asia and the United States, the effects of human interventions exceed the impacts expected for moderate levels of global warming. This study also identifies areas where irrigation water is currently scarce, and where increases in irrigation water scarcity are projected.

Abstract

Humans directly change the dynamics of the water cycle through dams constructed for water storage, and through water withdrawals for industrial, agricultural, or domestic purposes. Climate change is expected to additionally affect water supply and demand. Here, analyses of climate change and direct human impacts on the terrestrial water cycle are presented and compared using a multimodel approach. Seven global hydrological models have been forced with multiple climate projections, and with and without taking into account impacts of human interventions such as dams and water withdrawals on the hydrological cycle. Model results are analyzed for different levels of global warming, allowing for analyses in line with temperature targets for climate change mitigation. The results indicate that direct human impacts on the water cycle in some regions, e.g., parts of Asia and in the western United States, are of the same order of magnitude, or even exceed impacts to be expected for moderate levels of global warming (+2 K). Despite some spread in model projections, irrigation water consumption is generally projected to increase with higher global mean temperatures. Irrigation water scarcity is particularly large in parts of southern and eastern Asia, and is expected to become even larger in the future.

Footnotes

  • ↵1To whom correspondence should be addressed. E-mail: ingjerd.haddeland{at}nve.no.

  • Author contributions: I.H., J.H., F.L., and J.S. designed research; I.H., J.H., H.B., S.E., M.F., N.H., M.K., Y.M., T.S., Z.D.T., Y.W., and D.W. performed research; I.H. and J.H. analyzed data; and I.H., J.H., H.B., S.E., M.F., N.H., M.K., F.L., Y.M., J.S., T.S., Z.D.T., Y.W., and D.W. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission. K.F. is a guest editor invited by the Editorial Board.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1222475110/-/DCSupplemental.

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