Entropy: Uncertainty in Hydrology and Nature

This thesis presents a review of literature related to the concept of entropy. Its aim is to offer an introduction of the meaning and applications of entropy to a hydrological engineering audience. Furthermore, it discusses some common misconceptions surrounding the concept of entropy, the most important being the identification of entropy with “disorder”. Entropy and related concepts from probability theory, information theory and thermodynamics are defined. In parallel with the definitions, the history of and the technological, scientific and philosophical motivations for the concepts of interest are presented. The main concepts in focus are the second law of thermodynamics; thermodynamic and information-theoretic entropy; entropy production rate and the maximization thereof; statistical inference based on the principle of maximum entropy. The thesis presents examples of applications of entropy from the area of hydrology, specifically from hydrometeorology and stochastic hydrology; from other natural sciences, specifically from the theory of self-organizing systems with examples of such systems, and from the Earth-System science; and from engineering, specifically an application of measurement system configuration optimization. The thesis discusses at various sections philosophical questions regarding the concept of entropy.