Space and time scales are fundamental for both scientific and operational hydrology issues. The question of how different scales interact and how we can transport results from one scale to another is basic to hydrological understanding and strategically important for decision-making.

Two questions dominate water resources management: how much remains for the future? and what is the response to environmental stresses? To answer them, a proper grasp of the interactions at different scales between the atmosphere, lithosphere, hydrosphere and biosphere, and their relations to agricultural, urban and industrial activities is needed.

Financial support for the preparation of this publication from Schlumberger Water Services is gratefully appreciated.
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