The present volume contains the edited proceedings of the International Workshop on New Uncertainty Concepts in Hydrology and Water Resources, held in Madralin near Warsaw, Poland from 24 to 26 September 1990. It was organized under the auspices of the Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland, and the International Commission on Water Resources Systems (ICWRS) – a body within the International Association of Hydrological Sciences (IAHS). The Organization and Programme Committee for the Workshop consisted of the following individuals: Professor Lars Gottschalk (Norway/ ICWRS/IAHS), Professor Zdzislaw Kaczmarek (Poland/IIASA), Professor Janusz Kindler (Poland), Professor Zbigniew W. Kundzewicz (Poland), who acted as the Secretary, Professor Uri Shamir (Israel/ICWRS/IAHS) and Professor Witold Strupczewski (Poland).

The Workshop was a continuation of series of meetings organized under the aegis of the International Commission of Water Resources Systems (ICWRS) within the IAHS. This series of meetings was initiated by the former ICWRS President, Professor Mike Hamlin in Birmingham, 1984. Last Workshop of similar character was organized by the ICWRS Secretary, Professor Lars Gottschalk in Oslo (1989).

The Workshop was primarily devoted to recent methods of representation of uncertainty in hydrology and water resources. This embraces newly introduced methods and approaches that, albeit not new, have raised considerable recent interest. In the menu of topics tackled at the Workshop were, among others, such diverse items, as fractals, risk and reliability-related criteria, fuzzy sets, pattern recognition, random fields, time series, outliers detection, nonparametric methods, etc.