Versatile Uses of the Entropy Concept in Water Resources

The concept of entropy, which originated in classical thermodynamics, has found versatile uses in hydrology and water resources. The investigations in one group of applications basically rely on the concept of “thermodynamic entropy”, where problems associated with river morphology and river hydraulics are handled by a rather non-probabilistic approach. The second group of studies use the concept of “informational entropy” within a probabilistic context to define uncertainties in hydrologic variables, hydrologic systems and their models, and parameters of probability distribution functions. Although it has a very short history in hydrology and water resources, informational entropy has found a wider range of applications in this field, as compared to the thermodynamic entropy. The presented paper discusses the versatile uses of informational entropy in water resources, summarizing the progress obtained so far in developing the concept into a widely accepted technique. Besides the already covered areas of application, new fields where entropy can be used effectively are proposed to cover basically problems in environmental engineering. In view of current research results, the merits and limitations using entropy in water resources engineering problems are discussed, followed by the conclusion that there is a definite need for further investigations so that entropy becomes a principal technique in hydrology and water resources.