Water is a key natural resource, the modelling and management of which is made complex by its inherent spatial unevenness and temporal variability. Stochastic modelling and forecasting cannot at present adequately represent the characteristics of hydrological regimes, nor analyze the influence of water on processes that arise in biological systems and those involving hydrological, geophysical and other processes. This book presents discussions of new stochastic modelling approaches against the requirement of sustainable development in an environment that is changing due to human influence. A major challenge is to consider the effects of a changing climate and ecological impacts when developing modelling and risk assessment procedures in support of river basin management.