Global assessment of water challenges under uncertainty in water scarcity projections


Water scarcity, a critical environmental issue worldwide, has primarily been driven by a significant increase in water extractions during the last century. In the coming decades, climate and societal changes are projected to further exacerbate water scarcity in many regions worldwide. Today, a major issue for the ongoing policy debate is to identify interventions able to address water scarcity challenges in the presence of large uncertainties. Here, we take a probabilistic approach to assess global water scarcity projections following feasible combinations of shared socioeconomic pathways and representative concentration pathways for the first half of the twenty-first century. We identify—alongside trends in median water scarcity—changes in the uncertainty range of anticipated water scarcity conditions. Our results show that median water scarcity and the associated range of uncertainty are generally increasing worldwide, including many major river basins. On the basis of these results, we develop a general decision-making framework to enhance policymaking by identifying four representative clusters of specific water policy challenges and needs.

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Fig. 1: Median and IQR derived from the multi-model, multi-scenario ensemble of 45 global, decadal water scarcity projections.
Fig. 2: Relative importance of each source of uncertainty within the 2046–2055 period.
Fig. 3: Basin averages of decade-to-decade change of the uncertainty distribution and the relative importance of different uncertainty sources.
Fig. 4: Identifying areas of low, medium and high water policy challenges.

Data availability

The WFaS data that support the findings of this study are available from the corresponding author upon request.


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The authors acknowledge the Global Environment Facility (GEF) for funding the development of this research as a part of the ‘Integrated Solutions for Water, Energy, and Land (ISWEL)’ project (GEF Contract Agreement: 6993), and the support of the United Nations Industrial Development Organization. The Water Futures and Solutions Initiative (WFaS) was launched by the International Institute for Applied Systems Analysis, UNESCO/UN-Water, the World Water Council, the International Water Association and the Ministry of Land, Infrastructure and Transport of the Republic of Korea, and has been supported by the government of Norway, the Asian Development Bank and the Austrian Development Agency. More than 35 organizations contribute to the scientific project team, and an additional 25 organizations are represented in stakeholder groups. Furthermore, WFaS relies on numerous databases compiled and made available by many more organizations, which are referred to in this paper. The research described in this paper would not have been possible without the collaboration of all of these organizations in the WFaS Project Team. The WFaS data are available upon request.

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P.G., T.K. and Y.W. designed the study and the associated analysis. P.G. performed all computations. Y.S. preprocessed the data. Y.W., T.K., Y.S., P.B., S.T., G.F., R.B. and S.L. designed the water scenarios. P.G., T.K., J.M., T.S. and Y.W. wrote the manuscript. All authors commented on the manuscript.

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Correspondence to P. Greve.

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Greve, P., Kahil, T., Mochizuki, J. et al. Global assessment of water challenges under uncertainty in water scarcity projections. Nat Sustain 1, 486–494 (2018).

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