The future adequacy of freshwater resources is difÞcult to assess, owing to a
complex and rapidly changing geography of water supply and use. Numerical
experiments combining climate model outputs, water budgets, and socioeconomic information along digitized river networks demonstrate that (i) a large proportion of the worldÕs population is currently experiencing water stress and (ii) rising water demands greatly outweigh greenhouse warming in deÞning the state of global water systems to 2025. Consideration of direct human impacts on global water supply remains a poorly articulated but potentially important facet of the larger global change question.