This paper assesses the ability of global water systems, resolved at 282 large river basins or Assessment Sub Regions (ASRs), to the meet water requirements over the coming decades under integrated projections of socioeconomic growth and climate change. The argues that for many developing nations, water-demand increases due to population growth and economic activity have a much stronger effect on water stress than climate change. The paper concludes that uncertain regional climate change can play a secondary role to either exacerbate or dampen the increase in water stress due to socioeconomic growth.