A Change of Paradigm in Water Sciences at the Turn of the Century?

A definition of the meaning of "paradigm" is given, followed by a specification of "change of paradigm" in the sense of modern theory of science. It is shown that the presently valid paradigm for planning of environmental and water resources systems is no longer sufficient. The requirements of today's society lead to the postulation of a new paradigm. A trial is made to define such a new planning paradigm with the aid of the formulation of four criteria. These new criteria are: (1) sustainable development; (2) ecological quality; (3) consideration of macroscale systems and effects; and (4) planning in view of changes in natural and socioeconomic systems. The meaning of these new criteria is specified and research activities in those fields are briefly discussed, which may lead-partially-to the formulation of new planning techniques and tools, which are still missing at present.