By Dexter Roberts, with Huang Zhe in Beijing

While the struggle to secure supplies of petroleum has long ranked as a top global concern, another scarce commodity is now taking center stage. Countries rich and poor are facing up to the tremendous challenge of ensuring adequate and safe supplies of water for their people, industries, and agriculture.

Decades of urbanization and industrialization have driven soaring demand for water in populous countries such as India and China. Now, new challenges ranging from civil wars to climate change are intensifying the problem in water-strapped and poor nations such as Sudan, Pakistan, and the Maldives. Richer countries, too, are hardly immune: Israel, Kuwait, and other desert nations struggle to meet their water needs.

Click ahead to see the some of the world's most water-challenged countries:

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